ratio, R. R was found to be highly variable at full resolution, with a wide 33 range of surface elevations possible at tightly constrained drafts. Averaging over larger circular 34 patches collapsed the observed relation onto the modelled relation as patch size increased. A 35 significant positive snow thickness bias (R lower than isostacy would predict) with respect to the 36 measured 30 cm mean snow thickness was observed over level ice. Separating the deformed ice 37 regions, using their surface roughness characteristics, showed these to be negatively biased (R 38 higher than isostacy would predict), attributed to the significantly more extensive nature of the 39 deformed features underwater than above. This was especially the case over a large first-year 40 pressure ridge, which had significantly more volume than surface measurements would predict. 41 Averaging over footprints corresponding to satellite altimeter instruments showed ICESat-1 and 2 42 to slightly underestimate the R figure over these data, due to averaging within a footprint, while 43 Cryosat 2's reported 'minimum-within-a-footprint' characteristic may significantly overestimate R 44 over mixed ice types. The importance of in situ measurements to constrain the isostatic relation is 45 clearly demonstrated.
2012ThomasTGRS:
Motion Tracking of Discontinuous Sea Ice
Authors: Thomas, M. V., C. Kambhamettu, C. Geiger
Reference: IEEE Transactions on Geoscience and Remote Sensing, Manuscript: TGRS-2010-00277.R2
Comments: Preprint forthcoming
Keywords: Cryosphere, image analysis, high resolution, motion analysis, Fourier theory, discontinuity identification, inpainting.
Funding: Major funding from NSF with many acknowledgments (ASF, NOAA, NIC, CIS, UAF)
Abstract: The purpose of this paper is two-fold: (1) To develop a high-resolution sea ice motion tracking system at the geo-spatial mesoscale (1 km2 - 100 km2), and (2) To propose an algorithm that measures motion at close proximity to discontinuous regions. Our motion tracking system computes differential motion at a resolution of around 400 m, which is the highest resolution
possible within the constraints of geo-location accuracy. To validate the accuracy of the motion tracking system four studies
are presented. The first study measures the accuracy of the system against displacements measured from in situ GPS buoys
deployed at the SEDNA and SHEBA experiments. The estimates are found to be statistically comparable with the ground truth
GPS measurements, with an average error of 361.9 m and 600.6 m for the SEDNA and SHEBA experiments, respectively.
The second study compares the motion tracking system to displacements measured by the RGPS. The measurements indicate
a precision error of 75.7 m between the two motion tracking systems. The third study uses intensity warping of
randomly sampled measurements to measure the improvement in using discontinuous motion tracking. A one-tailed Wilcoxon
Signed Rank test is used to evaluate these measurements at =0.01. The results from this study indicate that the anisotropic
extension produces significantly smaller errors at discontinuous locations (W = 4240; p < 0:001). The fourth study compares
the displacements measured by the anisotropic extension against manual measurements, which indicate an average reduction of
the error by 50 m at discontinuities.
2012HutchingsIGS:
Spatial and temporal characterization of sea ice deformation
Authors: Jennifer K. Hutchings, Andrew Roberts, Cathleen A. Geiger,
Jacqueline Richter-Menge,
Reference: in press, Annals of Glaciology special issue on sea ice processing and biogeophysical connections.
Comments: Preprint Forthcoming
Keywords: sea ice, deformation, fractal dimension, power spectra
Funding: Major funding from NSF with many acknowledgments (UW-APL, US NAVY - ASL, ISSI, MPS)
Abstract: In late-March 2007 an array of GPS ice drifters was deployed in the Beaufort Sea as part of the Sea Ice Experiment: Dynamic Nature of the Arctic (SEDNA) experiment. The drifters were deployed in an array designed to resolve four, nested spatial scales of sea
ice deformation, from 10 km to 140 km, with the arrays maintaining appropriate shape for strain-rate calculation until mid-June. In this paper we test whether sea ice deformation displays fractal properties in the vicinity of SEDNA. We identify that deformation time series have different spectral properties depending on the spatial scale. At the scales around 100 km deformation is a red-noise process, indicating the importance of the ice pack surface forcing in determining the deformation rate of sea ice at this scale. At smaller scales the
deformation becomes an increasingly whiter process (it has pink noise properties), which suggests an increasing role of dissipative processes at smaller scales. At spatial scales between 10 to 100 km, and sub-daily scales, there is no deformation coherence across scales, coherence
only becomes apparent at longer scales greater than 100 km. The lack of coherence at small scales aids in understanding previous observations where correlation between 10 km regions adjacent to each other varied widely, with correlation coefficients between -0.3 and 1. This
suggests it is not appropriate to think of sea ice as having a de-correlation length scale for deformation. We find that lead scale observations of deformation are required when estimating ice growth in leads and ridging time-series. For the two SEDNA arrays, we find
coherence between 140 km and 20km scale deformation up to periods of 16 days. This suggests sea ice deformation displays coherent deformation between 100 km scale to the scale of the Beaufort Sea (of order 1000 km), over synoptic time periods (daily to weekly time scales).
Organization of leads at synoptic and larger scales is an emergent feature of the deformation field that is caused by the smooth variation of surface forcing (wind) on the ice pack.
2011DeLibertyDSRII
Estimating the annual cycle of sea ice thickness and volume in the Ross Sea
Authors: DeLiberty (UD), Geiger (UD), Ackley (UTSA), Worby (Antarctic CRC), VanWoert (NSF)
Reference: Deep Sea Research II: Topical Studies in Oceanography, Antarctic Sea Ice Research during the International Polar Year
2007-2009, vol 58, Issue 9-10, May 2011, Pages 1250-1260.
Comments: Publication Link
Keywords: Antarctic Sea Ice thickness distribution, sea ice volume, thickness variability, sea ice mass balance
Funding: NSF, NOAA
Abstract: Antarctic sea ice thickness and concentration derived from satellite-based ice charts are compared to contemporaneous ship-based estimates of the same parameters collected in the Ross Sea between 130°W and 160°E from 1995 to 2001. Thickness variability on the scale of individual ice chart polygons (tens of kilometers) is found to be compatible with WMO thickness ranges except in areas with high concentration of ridging. Reasonable agreement is also found for integrated results on the regional scale (<1% excluding complications with ridging and very thick ice but 20% difference when including extremes). Recognizing the natural limits associated with ridging and heavily rafted ice, we proceed to focus on the resolved ice chart ice typing cataloging from 1995-1998. We therefore use the weekly ice charts to assess annual cycle and interannual changes in the sea ice thickness and volume of the Ross Sea region. Compared to extent and area, sea ice thickness and volume lag between 2 to 10 weeks during all growth seasons and decay seasons in 1996 and 1998. We postulate, therefore, that ice thickening processes evolve somewhat independent of sea ice extent. Thickness variability is found to be more sensitive than extent/area to climate events during the 1996 La Nina and 1997/98 El Nino episodes. These results contradict some existing model studies which show that sea ice thickness and extent co-vary. Hence, this first observational result demonstrates the importance of measured ice thickness which responds distinctly different from extent in response to dynamic and thermodynamic processes.
2008HutchingsEOS:
Role of ice dynamics in the sea ice mass balance
Authors: J. Hutchings, C. Geiger, A. Roberts, J. Richter-Menge, M. Doble, R. Forsberg, K. Giles, C. Haas, S. Hendriks, C.
Khambhamettu, S. Laxon, T. Martin, M. Pruis, M. Thomas, P. Wadhams, J. Zwally
Reference: EOS, Vol. 89, No. 50, 9 December.
Comments: Publication Link
Keywords: Arctic Sea Ice thickness distribution, sea ice mass balance, sea ice dynamics
Funding: Major Funding from US NSF and EU Damocles
2008WorbyJGR:
The thickness distribution of Antarctic sea ice
Authors: Worby, A. P., C. A. Geiger, M. J. Paget, M. L. Van Woert, S. F. Ackley, and T. L. DeLiberty
Reference: J. Geophys. Res. VOL. 113, C05S92, doi:10.1029/2007JC004254, 2008
Comments: Publication Link
Keywords: Antarctic Sea Ice thickness distribution, sea ice thickness variability, sea ice observations, ship-based
observations
Funding: NSF, NOAA, Australian Government
Abstract: Ship-based observations are used to describe regional and seasonal changes in the thickness distribution and characteristics of sea ice and snow cover thickness around Antarctica. The data set comprises 23,373 observations collected over more than 2 decades of activity and has been compiled as part of the Scientific Committee on Antarctic Research (SCAR) Antarctic Sea Ice Processes and Climate (ASPeCt) program. The results show the seasonal progression of the ice thickness distribution for six regions around the continent together with statistics on the mean thickness, surface ridging, snow cover, and local variability for each region and season. A simple ridge model is used to calculate the total ice thickness from the observations of level ice and surface topography, to provide a best estimate of the total ice mass, including the ridged component. The long-term mean and standard deviation of total sea ice thickness (including ridges) is reported as 0.87 ± 0.91 m, which is 40% greater than the mean level ice thickness of 0.62 m. Analysis of the structure function along north/south and east/west transects revealed lag distances over which sea ice thickness decorrelates to be of the order of 100–300 km, which we use as a basis for presenting near-continuous maps of sea ice and snow cover thickness plotted on a 2.50 x 5.00 grid.
2008GeigerDSRII:
Springtime ice motion in the western Antarctic peninsula region
Authors: C. A. Geiger and D. K. Perovich
Reference: Deep-Sea Research II, Vol. 55, Nos. 3-4, 338-350, (U.S. GLOBEC contribution number 515)
Comments: Publication Link
Keywords: Ice, Sea Ice, Kinematics, Inertial Oscillations, Biological Coupling
Funding: NSF - Office of Polar Programs; GPS buoys
Abstract: Oscillatory motion of sea ice is examined using two ice drifting buoys separated by one degree latitude around 66°S during the winter to spring transition in the Marguerite Bay region west of the Antarctic Peninsula . The buoys’ motion exhibits spectrally distinct periods
(12.87 ± 0.04 and 13.03 ± 0.04 hours, respectively) despite highly correlated motion between them (r2 is 0.62 and 0.81 for u and v,
respectively). The periods shift with latitude and nearly match the local inertial periods (13.00 and 13.10, respectively). The oscillations are
further examined with respect to the kinematics involved in the breakup process of sea ice. These include hourly resolved manifestation of circular
trajectories, semi-circular oscillations with compressed trajectory cusps, and “accordion-like” compressions along straight line trajectories.
Oscillations are found in all trajectory types over the lifetime of both buoys (several months). Traditional circular and semi-circular oscillations
are particularly prominent during two episodes, one of which is preceded by strong wind events and a substantial decrease in ice thickness and
concentration. These episodes combine with seasonally warming temperatures to break up and melt the sea ice cover. We discuss potential relationships between the degradation of the ice pack during spring breakup and the increase in energy at near-inertial frequencies including a non-linear cascade of energy within the ice from the low frequencies (commensurate with storms and fortnightly tides) to semi-diurnal frequencies. We further comment on the implications this type of high-frequency motion has on local biological ecosystems. Specifically we find that sea ice semi-diurnal oscillations are at their peak during the final decay of sea ice just before springtime primary productivity begins. Hence the oscillatory motion of sea ice not only serves as an effective mixing agent within the ice-ocean mixed layer, but also serves as an effective seeding platform for distributing phyto- and zooplankton that have over-wintered within and around the ice floes.
2008ThomasCRST:
High resolution (400m) Motion Characterization of Sea Ice using ERS-1 SAR Imagery
Authors: Thomas, M. V., C. A. Geiger, and C. Kambhamettu
Reference: Cold Regions Science and Technology, Elsevier, Guest Editors: Mary Albert and Cathleen Geiger with Guest Editorial, Volume 52, Issue 2, April, Pages 207-223
Comments: Publication Link
Keywords: Ice, Sea Ice, SAR, Kinematics, Remote Sensing, GPS Buoys
Funding: initially supported by research grants from NSF (OPP-9818645) and ONR (N00014-02-1-0244 and N00014-03-1-0045); Imagery
from © ESA ERS-1
Abstract: Using Synthetic Aperture Radar (SAR) images from ERS-1, we render high resolution motion fields of sea ice using a
multi-resolution processing system. The results are provided at a 400 m resolution, which is an order of magnitude greater than the standard SAR
motion products (5-10 km). An error propagation experiment shows a standard deviation of 1.3% day-1 for the noise in invariant shear
resulting from position uncertainties and processing techniques. We use this noise level to determine a significant lower threshold when identifying
shear zone discontinuities. As example, a 24-day sequence of images is processed using this system to examine the development and evolution of a
shear zone. This evolution is in response to the topographic steering caused by ocean circulation and wind forcing along a continental shelf break.
In addition, we adapt the Line Integral Convolution (LIC) to depict flow patterns present in the motion field. Collectively, these motion products
provide valuable descriptions of the non-rigid dynamics taking place within the sea ice. Our goal is to complement the existing RADARSAT Geophysical
Processing System (RGPS) motion products and aid in the validation and further development of the most progressive ``lead-resolving'' sea ice models
currently available. This form of sea ice visualization is important for understanding air-ice-sea momentum transfer processes that transcend through small-scale to large-scale fracture events with application to ship navigation.
2008AndreasBLM:
Identifying Nonstationarity in Turbulence Series
Authors: Andreas, E. L., C. A. Geiger, G. Treviño, K. Claffey
Reference: Boundary-Layer Meteorology, vol. 127, 37–56, DOI 10.1007/s10546-007-9252-z, 2008
Comments: Publication Link
Keywords: Atmospheric surface layer, Integral scale; Nonstationarity, Time-dependent memory method (TDM method); Time series
analysis
Funding: US Army
Abstract: Because of rapid forcing by varying cloud and sky conditions, turbulence time series collected in the atmospheric surface layer over land may often be nonstationary. The meteorological community, however, has no consensus definition of what nonstationarity is and, thus, no consensus method of how to identify it. This study, therefore, adopts definitions for first-order and second-order stationarity taken from the time series analysis literature and implements new analysis techniques and probabilistic tests to quantify first-order and second-order nonstationarity. First-order nonstationarity manifests as a change in the series mean; second-order nonstationarity, as a change in the variance. The analysis identifies nonstationarity in surface-level turbulent temperature and water vapor series collected during two sample days with solar forcing influenced by cirrus and cirrostratus clouds, but that nonstationarity is not as severe as expected despite the rapid thermal forcing by these clouds. On the other hand, even with negligible cloud forcing, both sample days exhibited severe nonstationarity at night.
2005GeigerJGR:
Coincident buoy- and SAR-derived surface fluxes in the western Weddell Sea during Ice Station Weddell 1992
Authors: C. A. Geiger and M. R. Drinkwater
Reference: Journal of Geophysical Research, vol. 110, C04002, doi: 10.1029/2003JC002112
Comments: Publication Link
Keywords: Ice, Sea Ice, Kinematics, Remote Sensing, Data Synthesis, Climate
Funding: NSF OPP9818645 and NASA Code Y 665-21-02 and 621-21-02; Imagery from © ESA ERS-1
Abstract: We examine sea ice kinematics relevant to surface fluxes using ERS-1 SAR images coincident with buoys in the western Weddell
Sea in austral autumn of 1992. Careful matching of temporal and spatial scales shows that buoy- and SAR-derived velocity differ in RMSE by 0.6 cm
s-1 and 7.80 degrees in magnitude and direction, respectively. These values represent agreements of 91.3% and 92.7%, respectively, and
correspond to instrument uncertainties. Scaling analysis shows shear matching best at the smallest scales (=5 km), while divergence is better
represented at scales of 40 km and larger. Sensitivity to error propagation shows lower agreement for divergence (47.4%; RMSE = 7.46 x
10-8 s-1), but we find these results sufficient for integrated surface flux comparisons. Using a toy model, we test the effects of aliasing in surface flux determination. The results show that variability associated with storms, ocean tides, inertial oscillations, and other
high-frequency forcing affects integrated sea ice growth rates along this continental slope location. Integrated salt and new ice production rates
computed from buoys are found to be two times larger than those computed from ERS-1 SAR motion products. We show that these differences in salt and
ice production rates result primarily from inadequate temporal resolution of heat flux variability and sea ice divergence. Comparison with other
studies shows that the problem is widespread, thereby impacting the modeling of sea ice mass balance and variability. The small-scale processes cited here have significant ramifications for larger scales and the global thermohaline circulation.
2001AckleyIGS:
The Ronne Polynya of 1997-98: Observations of air-ice-ocean interaction
Authors: S. F. Ackley, C. A. Geiger, J. C. King, E. C. Hunke, and J. Comiso
Reference: Annals of Glaciology, Vol. 33,425-429, 2001.
Comments:
Publication Link
Keywords: Ice, Sea Ice, Air-Ice-Sea Interaction
Funding: NSF OPP9818645 and NASA Code Y 665-21-02 and 621-21-02; Imagery from © ESA ERS-1
Abstract: The Ronne Polynya formed in the Weddell Sea during the period November 1997 to February 1998 to an extent not seen previously
in the twenty-five years of all-weather satellite observations. The vessel HMS Endurance traversed the polynya region and took sea ice, physical
oceanographic, and meteorological measurements during January and early February 1998. These observations, together with satellite imagery and
weather records, were analyzed to determine the causes of the anomolous condition observed and to provide comparisons for numerical modeling
experiments. The polynya area, analyzed from satellite imagery, showed a linear, nearly constant, increase with time from mid-November 1997 through
February 1998. It had a maximum open water area of 3x105 km2 and extended 500 km north of the Ronne Ice Shelf (at
76oS) to 70oS. The ice and snow structure of floes at the northern edge of the polynya showed the ice there had formed in the
previous mid to late winter (October 1997 or earlier) and had been advected there either from the eastern Weddell Sea or from the front of the Ronne
Ice Shelf. Analysis of the wind fields showed anomalous spring-summer wind fields in the polynya year, with a strong southerly to southwesterly
component compared to the mean easterly winds typical of summer conditions. These southerly wind conditions, both in magnitude and direction,
therefore account for the drift of ice northward. The predominant summer easterly winds usually fill the southern Weddell Sea with ice from the east, and the high albedo surfaces reflect the solar radiation, preventing warming of the surface ocean waters and consequent sea ice melt. Instead, high
incident solar radiation from November 1997 to February 1998 was absorbed by the open water, rather than being reflected, thereby both melting ice
and preventing ice formation, and thereby sustaining the polynya. We conclude that open water-albedo feedback is necessary to allow the observed
polynya formation, since similar drift conditions prevail in winter (arising from southerly winds also) and usually result in extensive new ice
formation in front of the Ronne Ice Shelf. The strong southerly winds therefore have quite opposing seasonal effects, leading to high ice production
in winter as usually found, and extensive open water if they occur in spring and summer, as seen in this atypical event in 1997-98. In this case, the atypical southerly winds are believed to be associated with an ENSO-induced atmospheric circulation pattern.
2000GeigerJGR:
Large-scale comparison between buoy and SSM/I drift and deformation in the Eurasian Basin during winter 1992-1993
Authors: C. A. Geiger, Y. Zhao, A. K. Liu, and S. M. Häkkinen
Reference: Journal of Geophysical Research 105, C2, 3357-3368, 2000
Comments: Publication Link
Keywords: Ice, Sea Ice, Kinematics, satellite remote sensing
Funding: USRA NAS-5-32484 and NASA Polar Programs
Abstract: A method for comparing sea ice velocity, divergence and shear at the large-scale between buoys and SSM/I is presented. For
initial testing, the method is applied in the Eurasian Basin because of its relatively simple circulation dominated by the wind. Using 8 ARGOS buoys, 11 strain-rate arrays 100 to 600 km in size are constructed. Daily 100 km resolution sea ice motion derived from SSM/I 85 GHz brightness temperatures is sampled 100 to 1000 km from the center of the buoy arrays. Over this range of possible scales, a minimum RMS difference for deformation is used to identify an optimal inclusion radius of 600 km corresponding to a length scale of 1000 km. This length scale is typical of local storms confirming a strong connection between wind and observed sea ice motion. Based on all 11 arrays, an average RMS difference of 2.48 ± 0.05 cm s-1 for velocity vector and 8.8 ± 0.9 x 10-8 s-1 using all 4 deformation components (d ui /d xj) is found at the optimal inclusion radius corresponding to average correlation coefficients of 0.896 ± 0.002 and 0.729 ± 0.030, respectively. RMS differences are found to scale with the temporal and spatial uncertainties of the SSM/I suggesting that even better results can be achieved with higher
resolution instruments.
2000HäkkinenJGR:
Simulated low-frequency modes of circulation in the Arctic Ocean
Authors: S. M. Häkkinen and C.A. Geiger
Reference: Journal of Geophysical Research, 105, C3, 6549-6564, 2000
Comments: Publication Link
Keywords: Ice, Sea Ice, Numerical Modeling, NAO, AO, Great Salinity Anomaly
Funding: NAS-5-32484 and NASA Polar Programs
Abstract: The variability of the Arctic circulation is investigated for a 43 year period (1951-1993) from a coupled ice-ocean model.
Empirical orthogonal function (EOF) analysis shows that the variability of the sea surface height (SSH) and vertically integrated transport is
organized so that in the leading mode the whole Arctic operates as a single gyre. The mode is associated with the Arctic Oscillation (AO)
[Thompson and Wallace, 1998], and it explains over 70% of the variance in the vertically integrated transport and 25% of the SSH
variability. The physical interpretation of this mode is derived to arise from its close connection to the Atlantic inflow to the Arctic. The
mode shows a major shift toward cyclonic circulation in the end of the 1980s which is associated with a large multiyear pulse of Atlantic water
to the Arctic. Thus this event appears as the likely initiation of the Atlantic layer warming observed during the recent years [Carmack et
al., 1995]. Overall, the first mode shows strong decadal variability as reported by Proshutinsky and Johnson [1997]. The second mode of
the oceanic circulation, which explains 9% of the variance in the transport, contains two gyres with opposing cyclonicity in the Eurasia and Canada
basins. It projects onto the North Atlantic Oscillation (NAO) pattern and displays a 14 year cycle which is known to exist in the midlatitude North Atlantic surface temperatures [Deser and Blackmon, 1993]. A further examination reveals that this mode describes the variability of the flow through the Barents Sea, which is modulated by the water mass modification due to the local heat flux variability. The apparent NAO connection is provided by a simultaneous correlation between the time series of this second mode and the leading heat flux mode in the North Atlantic which is associated with NAO.
1998ZhaoJAMSTS:
Arctic sea ice motion from wavelet analysis of SSM/I data
Authors: Y. Zhao, A. K. Liu, and C. A. Geiger
Reference: IEEE J. Adv. Mar. Sci. Tech. Soci., 4, No. 2, 313-322, 1998
Comments: Publication Link
Keywords: Ice, Sea Ice, Wavelet Analysis, Kinematics, Satellite Remote Sensing
Funding: NASA NSCAT Project
Abstract: Wavelet analysis of DMSP (Defense Meteorological Satellite Program) SSM/I (Special Sensor Microwave/Imager) 85 GHz data from
October of 1992 to March of 1993 is used to obtain daily sea ice drift information for the Arctic region. The derived maps of sea ice drift
provide both improved spatial coverage over the existing array of Arctic Ocean buoys and better temporal resolution over techniques utilizing
satellite data from SAR (Synthetic Aperture Radar). Comparisons of the derived ice velocities from SSM/I with ice velocities derived from the
wavelet analysis of SSM/I are suitable for validation of the ice velocities derived from an ice-ocean interaction model and for data assimilation
input to a model. For demonstration purposes, the ice velocities from SSM/I are compared with the ice velocities derived from a coupled Arctic
ice-ocean system with the comparison revealing the similarities of the general circulation patterns and significant ice velocity differences between
the two. These results indicate where the model results need to be improved; with the expectation that the data assimilation of the model with ice
velocities derived from SSM/I data would improve the model results. This wavelet analysis procedure is robust and can make a major contribution to
the understanding of ice motion over large areas at relatively high temporal resolutions and would help to improve our current knowledge of sea ice
drift and related processes through the data assimilation of ice-ocean numerical modeling.
1998GeigerJGR:
Modeled vs. observed drift and deformation in the western Weddell Sea during 1992
Authors: C.A. Geiger, W. D. Hibler III and S.F. Ackley
Reference: Journal of Geophysical Research (Special Issue on Sea Ice Mechanics), 103, C10, 21893-21914, 1998
Comments: Publication Link
Keywords: Ice, Sea Ice, Kinematics, Numerical Model Validation, Argos Buoys
Funding: NSF (DPP-9203470); ONR (N0014-93-1-1221); and USRA NAS-5-32484
Abstract: Statistical comparisons between numerical sea ice models and an observed large-scale strain array in the western Weddell Sea
during 1992 are used to evaluate the performance of three of the more generally utilized sea ice rheology formulations. Results show that sea ice
velocity is reproduced with relatively high accuracy (90% coherence, >80% normalized cross correlation) in models having high-quality
atmospheric forcing fields(e.g., the European Centre for Medium-Range Weather Forecasts). On the other hand, temporal and spatial variability of the
velocity field, as exemplified by progressive vector plots and ice deformation, respectively, are reproduced less accurately (coherence and
normalized cross correlation <50%). In terms of model sensitivity, this means that deformation and temporal variability are more discriminating in terms of elucidating specifics about the constitutive relation and mechanical properties of sea ice on a large scale. For example, inclusion of both compressive and shear stresses is important in attaining a proper probability distribution of deformation relative to observations. Additional analysis shows that adjustments to specific model parameters improve the model results for either drift or selected deformation components, but no best solution could be found, given the models examined here. Results suggest that inclusion of more physically based processes, such as sub-daily
tidal and inertial oscillations, reconsideration of the boundary layer formulation, and consideration of anisotropy, may be necessary to include in
next-generation sea ice models, especially those that are intended for coupling with high-resolution (eddy resolving) ocean models.
1997GeigerIGS:
Year-round pack ice in the Weddell Sea: Sensitivity to atmospheric and oceanic forcing
Authors: C.A. Geiger, S.F. Ackley, and W. D. Hibler III
Reference: Annals of Glaciology, 25, 269-275, 1997
Comments: Publication Link
Keywords: Ice, Sea Ice, Numerical Modeling, Sensitivity Studies, Thermodynamics
Funding: NSF (OPP-9024809 and DPP-9203470); ONR (N0014-93-1-1221)
Abstract: Using a dynamic-thermodynamic numerical sea-ice model, external oceanic and atmospheric forcing on sea ice in the Weddell Sea
are examined to identify physical processes associated with the seasonal cycle of pack ice, and to identify further the parameters that coupled
models need to consider in predicting the response of the pack ice to climate and ocean circulation changes. In agreement with earlier studies, the
primary influence on the winter ice-edge maximum extent is air temperature. Ocean heat flux has more impact on the minimum ice-edge extent and in
reducing pack-ice thickness, especially in the eastern Weddell Sea. Low relative humidity enhances ice growth in thin ice and open-water regions,
producing a more realistic ice edge along the coastal areas of the western Weddell Sea where dry continental air has an impact. The modeled extent of the Weddell Summer pack is equally sensitive to ocean heat flux and atmospheric relative humidity variations with the more dynamic responses being from the atmosphere. Since the atmospheric regime in the eastern Weddell is dominated by marine intrusions from lower latitudes, with high humidity already, it is unlikely that either the moisture transport could be further raised or that it could be significantly lowered because of its distance from the continent (the lower humidity source). Ocean heat-transport variability is shown to lead to overall ice thinning in the model response and is a known feature of the actual system, as evidenced by the occurrence of the Weddell Polynya in the mid 1970s.
Book Chapters
2010HuffmanEDU:
Chapter 2: Tips and Tricks in the Classroom
Authors: Huffman, L., J. Baeseman, K. Timm, J. Warburton,
with contributions from M. Albert, M. H. Almeida, P. Azinhaga, R. Bindschadler, P. Dionísio, R. Frisch-Gleason,
C. Geiger, C. Hamilton, T. Haste, J. Hubbard, M. Jeffries, L. Murphy, M. M. Passas , M. Prevenas, M. Raymond,
R. Salmon, F. Silva, C. Teixeira, K. Tolstein, B. Trummel, J. Xavier, S. Zicus
Reference: in book – Polar Science and Global Climate: An International Resource for Education and Outreach.
B. Kaiser (ed), Pearson, London, 129-141, 2010.
Comments: For more information contact the British Antarctic Survey, POC: Melissa Deets at ipyipo@bas.ac.uk
Keywords: Education, Polar Science, Global Climate, Classroom Tips
Funding: US NSF International Polar Year
2007GeigerIWASIT:
SAR motion products: Tools for monitoring changes in sea ice mass balance and thickness distribution
Authors: C. A. Geiger, M. V. Thomas, and C. Kambhamettu
Reference: SAR motion products: Tools for monitoring changes in sea ice mass balance and thickness distribution, in book Arctic Sea Ice Thickness, Proceedings from the International Workshop on Arctic Sea Ice Thickness (IWASIT)Rungsted Kyst, Denmark, 8-9 Nov 2005, 64-73, Elsevier Publishing.
Comments: Publication Link
Keywords: Ice, Sea Ice, Kinematics, Thickness
Funding: NASA grant NNH05AB76I, Imagery from © CSA RADARSAT-1
Abstract: Sea ice is a discontinuous non-rigid material when viewed from microwave SAR imagery at scales of tens of kilometers. The discontinuous motion and behavior of sea ice has a definitive impact on its thickness distribution. Techniques for resolving sea ice discontinuities are demonstrated as contributions toward an integrated Arctic Observing Network.
2007RichterMengeIWASIT:
Ice Mass Balance Buoy: An Instrument to Measure and Attribute Changes in Ice Thickness
Authors: Richter-Menge, J.A., D. K. Perovich, C.A. Geiger, B. C. Elder, K. Claffey
Reference: in Arctic Sea Ice Thickness, Proceedings from the International Workshop on Arctic Sea Ice Thickness (IWASIT), Rungsted Kyst, Denmark, 8-9 Nov 2005, 24-29. Elsevier Publishing.
Comments: Publication Link
Keywords: Ice, Sea Ice, Thickness, Thermodynamics
Funding: NOAA, NSF, ONR
Abstract: We have developed the Ice Mass Balance buoy (IMB) in response to the need for monitoring changes in the thickness of the Arctic sea ice cover. The IMB is an autonomous, ice-based system. IMB buoys provide a time series of ice mass balance, snow accumulation and ablation, internal ice and snow temperature fields, temporally averaged estimates of ocean heat flux, sea level pressure (SLP), surface air temperature (SAT), and ice drift. The most unique feature of the IMB is that it also allows us to determine whether changes in the thickness of the ice occur at the top or bottom of the ice cover. This information provides important insight on the driving sources behind the change and is necessary for extending the results from these individual sites to a broader region. The value of the IMB is further enhanced when it is coupled with other tools.
2001GeigerIUTAM
Impact of temporal-spatio resolution on sea-ice drift and deformation
Authors: C. A. Geiger and M. R. Drinkwater
Reference: IUTAM Symposium on Scaling Laws in Ice Mechanics and Dynamics, (eds.) J. P. Dempsey and H. H. Shen, Kluwer Academic Publishers , Netherlands, 407-416, 2001.
Comments: Publication Link
Keywords: Ice, Sea Ice, Kinematics, Satellite Remote Sensing
Funding: NSF OPP9818645 and NASA Code Y 665-21-02 and 621-21-02
Abstract: Crafting a zero-mean Gaussian noise numerical experiment, we examine the relationship between the temporal-spatio resolution of any given instrument and the impact that resolution window has on the propagation of error associated with the computation of sea-ice position, velocity, and deformation. These results are characterized through a fitted curve model describing agreement between two data sets (a pure signal and a noise corrupted signal) as a function of time sampling and spatial uncertainty. Using two example instruments (SAR and SSM/I), we demonstrate how this method can be applied to a variety of instruments to estimate the precision of motion vector products given an instrument's chosen temporal and spatial resolution. Relevance to future satellite designs and preprocessing of current data sets is also discussed.
1998GeigerARS
Sea-ice drift and deformation processes from field measurements in the western Weddell Sea during 1992
Authors: C.A. Geiger, S.F. Ackley, and W. D. Hibler III
Reference: Antarctic Sea Ice Processes, Interactions and Variability, AGU Antarctic Research Series 74, 141-160, 1998.
Comments: Publication Link
Keywords: Ice, Sea Ice, Kinematics, Argos Buoys
Funding: NSF (OPP-9024809 and DPP-9203470); ONR (N0014-93-1-1221); and USRA NAS-5-32484
Abstract: Data from Ice Station Weddell (ISW) during 1992 are used to examine sea ice drift and deformation activity to identify relevant external forces responsible for driving specific sea ice processes. Power spectra results from wind, sea ice, and ocean current measurements together with deformation analysis of sea ice reveal the following. First, the drift of sea ice in the western Weddell region is a low frequency (<1 cycle/day) dynamic process driven primarily by low frequency forcing in the form of moderate steady ocean currents and intermittent strong winds from high energy storm activity. Second, higher frequencies, specifically diurnal and semi-diurnal tidal/inertial oscillation frequencies, are the main contributors to sea ice deformation in this region. Shear deformation has large high and low frequency components, with elongation (normal deformation) oriented parallel to the shelf break being the main form of deformation at low frequencies. The observed higher frequency processes are driven by 12 and 24 hour ocean oscillations (2 and 1 cycles/day, respectively) with a 12 hour peak contributing the most to the total shear activity and the 24 hour peak contributing more to the solid body rotation (vorticity) of ice on scales as large or larger than the ISW array (150 km). East to west rising ocean bottom topography of the continental slope is also believed to play a major role in the directional preference of both observed ice drift and deformation in this region. Ice drift and deformation seem particularly sensitive to the forcing caused by topographic change as enhanced by ocean currents.
Thesis Work
1996GeigerDartmouth:
Investigation of dynamic sea ice processes in the Weddell Sea during 1992
Authors: C. A. Geiger
Reference: Thayer School of Engineering Doctor of Philosophy Thesis, 384 pgs., 1996
Comments: Publication Link
Keywords: Ice, Sea Ice, Kinematics, Numerical Modeling, Remote Sensing
Funding: NSF (OPP-9024809 DPP-9203470), ONR (N0014-93-1-1221), CRREL (5-36686.140), Thayer (255402.140 420048.140)
Abstract: Through a series of case studies, signal processing, and statistical tools, analysis of dynamic sea-ice processes of drift, deformation, and ice pack expansion and decay are investigated for the Weddell Sea region during 1992. Cavitating fluid (CAV) and viscous-plastic (VP) models are the most widely used ice models in sea ice, ocean, and climate communities. Examination of these and observations are presented in order to identify the external (air/ocean) and internal (ice) forces that affect specific processes. Inconsistencies between processes in models and observations are isolated and examined with suggestions given for the next generation of ice models. Key findings are as follows. Observationally, from ISW 1992, ice velocity in western Weddell is found to be driven by low frequency forcing (longer than one day), while sub-daily frequencies drive ice deformation. In the models, annual expansion during winter months is dominated by air temperature at the ice edge and storms in the interior where sensible/latent heat fluxes are large, especially in leads. Coupled with this is divergent advection towards open water regimes which works to expand the ice pack. Thermodynamic processes dominate ice edge retreat in summer, specifically daily /sub-daily thermal variations, relative humidity/latent heat, and ocean heat flux. Interior thickness and deformation are respectively more sensitive than ice edge extent and velocity. Relative humidity and ocean heat flux are critical climatological variables having their greatest impact near the Antarctic Peninsula. Increased ocean heat flux reduces overall thickness with little effect to the ice edge, leading to catastrophic melting scenarios. Cross-spectral analysis show significant coherence between simulated and 30-hour low pass filter observed velocity and strain-rates. Shear is significantly better modeled than divergence. Suggestions for next generation models include a reformulation of the boundary layer and incorporation of high frequency tidal forcing.
1990GeigerBergen:
An assessment of convective processes relevant to deep water formation in the Boreas Basin
Authors: C. A. Geiger
Reference: University of Bergen Candidatus scientus Thesis, 108 pgs, July 1990
Comments: Publication Link
Keywords: Convection, Chimney, Chimnies, Chimneys, Ice, Sea Ice, Polar Physical Oceanography, Deep-Water Formation, Boreas Basin
Funding: ONR Polar Programs - MIZEX
Abstract: Two types of mesoscale 10 to 30 km upper ocean chimnies were found in the Boreas Basin during two experiments in 1987 and 1989 using a 2.5 km resolution undulating Seasoar and 5 to 10 km resolution CTD sections. The upper ocean chimneys were located along the Polar and Arctic Fronts. The warm upper ocean chimney type is a homogeneous upper layer region of LAIW extending from the surface to at least 460m. This upper ocean chimney type was seen in several areas along the Arctic Front but only in 1987. The cold upper ocean chimney is a homogeneous upper layer region of TDW extending from the surface to at least 600m. This upper ocean chimney type was observed just west of the Hovgaard Seamount in an area with a complex cyclonic circulation in 1989. Cooling, freezing, and heat flux estimates indicate that the cold upper ocean chimney has a higher likelihood of producing new deep water than the warm upper ocean chimney due to the difference in compressibility between the warm saline LAIW in the warm upper ocean chimney and the cold less saline TDW in the cold upper ocean chimney. Surface cooling and freezing combined with meanders and eddies along the fronts appear to be two of the chief mechanisms responsible for the development of these two chimney types.
Proceedings and Conference Papers
Peer Reviewed
2010MvISVC:
Modified region growing for stereo of slant and textureless surfaces
Authors: Rohith MV (UD: CIS), Gowri Somanath (UD: CIS), Chandra Kambhamettu (UD: CIS), Cathleen Geiger (UD: Geography), Dave Finnegan (CRREL)
Reference: International Symposium on Visual Computing (ISVC - Highly peer-reviewed conference publication)), G. Bebis et al. (Eds.): ISVC 2010, Part I, LNCS 6453, pp. 666-677, Springer-Verlag Berlin Heidelberg.
Comments: Publication Link. See VIMS at http://vims.cis.udel.edu/ for algorithm.
Keywords: stereo, ice, topography, computer vision, photogrammetry, algorithm
Funding: Supported through the US National Science Foundation
Abstract: In this paper, we present an algorithm for estimating disparity
for images containing large textureless regions. We propose a fast
and efficient region growing algorithm for estimating the stereo disparity.
Though we present results on ice images, the algorithm can be easily used
for other applications. We modify the first-best region growing algorithm
using relaxed uniqueness constraints and matching for sub-pixel values
and slant surfaces. We provide an efficient method for matching multiple
windows using a linear transform. We estimate the parameters required
by the algorithm automatically based on initial correspondences. Our
method was tested on synthetic, benchmark and real outdoor data. We
quantitatively demonstrated that our method performs well in all three
cases.
2010HutchingsSNAME:
On the Spatial and Temporal Characterization of Motion Induced Sea Ice Internal Stress
Authors: Hutchings, J. K., C. A. Geiger, A. Roberts, J. Richter-Menge and B. Elder
Reference: proceedings from ICETECH10, International Conference and Exhibition on Performance of Ships and Structures in Ice (www.icetech10.org) by SNAME, 20-23 Sep, Anchorage, AK, paper no. 166, 8 pages.
Comments: Publication Link
Keywords: sea ice, Beaufort Sea, deformation,
stress measurement, scaling relationship
Funding: Major Funding provided by the US National Science Foundation
Abstract: In April 2007 an array of buoys was deployed in the Beaufort Sea with one aim (among others) of examining the relationship between internal ice stress and ice pack strain-rate or deformation. Here we present preliminary analysis of stress data from this experiment. This analysis is discussed in the context of strain-rate analysis that has been performed previously. In order to identify ice motion induced stress from stress measurements recorded at a point in the ice pack, we first need to remove the thermal stress signal from the measurement time series. We introduce a conceptual model of thermal stresses to support a method of extracting ice motion induced stress from stress buoy data. The model will require independent verification, which we outline, however is useful for understanding our results. In this paper we focus on spectral and scaling analysis of ice motion induced stresses, and compare these to similar analysis of sea ice strain-rate. By comparing spectral properties of stress and divergence we estimate that dynamic stress events (such as ridge building) may be felt at a stress sensor up to 45km from the site of deformation. Ice motion induced stresses demonstrate fractal scaling properties, and are anti-persistent. This echoes similar results that have been identified for sea ice strain rate across spatial scales from 10 to 1000 km. Ice motion induced stress and sea ice strain rate can not be described by Gaussian statistics, and have “fat tailed” probability distribution functions. These findings provide insight into how to model risk of large deformation, with large ice motion induced stress, events impacting any given place in the Arctic ice pack.
2010GeigerIAHR:
A Case Study Testing the Impact of Scale on Arctic Sea Ice Thickness Distribution
Authors: Geiger, C. A., J. Richter-Menge, T. Deliberty, B. Elder, J. Hutchings, A. Lawson,
J. Rodrigues, N. Toberg, and P. Wadhams
Reference: Proceedings of 20th IAHR International Symposium on Ice held in Lahti, Finland, June 14 to 18, 2010, 15 pages.
Comments: Publication Link
Keywords: submarine sonar, sea ice draft, sea ice thickness distribution, uncertainties, Beaufort Sea
Funding: Major Funding provided by US National Science Foundation and EU Damocles Project for International Polar Year (IPY)
Abstract: We examine the variability of sea ice thickness distribution from the 20 km x 20 km nested UK submarine survey taken on 18 March 2007 in the Beaufort Sea. The survey is centered about a U.S. Navy ice camp. From 1-7 April 2007, two weeks later, a ground survey team measured the snow and ice thickness within a 2 km circle of the ice camp during an NSF-sponsored science program. Because sea ice drifts, the ice camp was additionally equipped with a GPS buoy to provide a Lagrangian reference reporting position continuously from 15 March to 15 April. Results include a draft-to-thickness conversion ratio of 1.27 (including snow load effects) using a statistical mode matching algorithm. We find a mean of 2.99m for the ground survey and 3.07 ± 0.21m (average and range) for 2 km incremental scales of the submarine survey relative to the camp. When truncating all submarine survey subsets to the 8m limit of the ground survey, we find even closer agreement (2.95 ± 0.20m). The range of mean thicknesses over all scales is less than instrument uncertainties. This leads to the conclusion that the mean thickness is nearly scale invariant in support of modeling assumptions using a continuum approach with grid cell resolutions from 2 – 20 km. The largest differences between scales are variations in relative amounts of deformed ice with level-to-slightly deformed first-year ice dominating near the camp. Beyond the camp, we find increased proportions of new ice, associated deformation, and deformation of thick first-year and multi-year ice categories. The result is an increased skewing, broadening, and flattening of the thickness distribution away from the strong narrow peak found close to the camp. Hence while the mean thickness is does not change over these scales, the thickness distribution does, and this difference may have a fundamental impact on modeling calculations, especially heat fluxes, material behavior, momentum fluxes, and certainly local biogeochemical interactions.
2009MvICPR:
Stereo analysis of low textured regions with application towards sea-ice reconstruction
Authors: Rohith MV, G. Somanath, C. Kambhamettu, C. A. Geiger
Reference: International Conference on Pattern Recognition, July 13-16, 2009, Las Vegas, USA.
Comments: Publication Link
Keywords: stereo, Sea ice, textureless regions, Entropy
segmentation, Belief propagation
Funding: NSF-OPP 0636726
Abstract: Images with large areas of low texture pose significant challenge to stereo algorithms. We propose a novel
segmentation based stereo scheme tuned to handle such scenes. We combine entropy based filtering and two levels of
belief propagation to create an algorithm that can handle a scene with very little color variation. We test the performance
of our method on standard stereo evaluation and find that it outperforms comparable algorithms. We also present results
on dataset containing images of a frozen river and find that the algorithm produces good disparity estimates.
2008ThomasPhDShowcase:
Mapping of Large Scale Discontinuous Motion of Sea Ice
Authors: Thomas, M., C. Kambhamettu, C. A. Geiger
Reference: Ph.D. showcase at the ACM SIGSPATIAL International Conference on Advances in Geographic Information Systems (ACM GIS), Santorini, Greece, May, 2008.
Comments: Publication Link
Keywords: Design, Algorithms, Measurement, Performance, sea ice, motion tracking
Funding: Major funding provided through US National Science Foundation
Abstract: In this work, we attempt to extend the body of knowledge on
sea ice motion tracking in two specific directions. The first direction is the development of a computationally efficient,
high resolution motion tracking system with a resolution of 400m, which is an order of magnitude greater than the currently
available standard data products (3 - 5km). Validation of this method using GPS measurements shows an average
error that is less than 0.06cm/s. The second direction is the development of objective analysis technique to handle
motion at close proximity to discontinuities. The goal of this second direction is to identify and track discontinuous
features such as cracks, leads, ridges and other material damage zones. These developments allow motion to be estimated
at a high resolution in a robust manner (validated against various noise models). With the observed changes in
global climate, sparked by variations in the sea ice thickness and extent, our long term goal is to use this system to merge
the “temporally rich”GPS measurements with the “spatially rich” measurements from satellite images.
2008MvICPR:
Towards estimation of dense disparities from stereo images containing large textureless regions
Authors: Rohith MV, G. Somanath, C. Kambhamettu, C. A. Geiger
Reference: International Conference on Pattern Recognition, Tampa, FL, USA 8-12 December, 2008
Comments: Publication Link
Keywords: Ice, stereo imaging, disparity
Funding: NSF-OPP 0636726
Abstract: Stereo algorithms for structure reconstruction demand accurate disparities with low mismatch errors and false positives. Mismatch errors in large textureless regions force most accurate algorithms to be sparse, with disparities known only in textured regions. We propose a novel method which uses characteristics of the multi-valued disparity to segregate image regions into unambiguous, occluded but textured and regions with low color variation. The disparity in the unambiguous region is calculated using stable matching with local disparity filtering. The disparity is interpolated into other regions by diffusion using unstructured triangulation and method of finite elements for rapid convergence. The boundary conditions for each of the region are appropriately modified so that accurate discontinuities in the disparity are preserved. Through experiments, a comparison of our method to existing methods reveals that this algorithm indeed performs significantly better in producing dense accurate disparities.
2008ThomasIAPR
Streamline Regularization for Large Discontinuous Motion of Sea Ice
Authors: Thomas, M., C. A. Geiger, P. Kannan, and C. Kambhamettu
Reference: Proceedings of the 5th IAPR Workshop on Pattern Recognition in Remote Sensing (in conjunction with ICPR), Tampa, Florida, December, 2008.
Comments: Publication Link
Keywords: computer vision, algorithms, sea ice, motion tracking, streamline, in-painting
Funding: Major funding provided through US National Science Foundation
Abstract: Non-rigid motion has to sometimes contend with the presence of discontinuous structures when it is estimated
under a non-topology preserving deformation. In this paper, we propose an algorithm that estimates large
scale non-rigid motion in the presence of these discontinuous structures. We have developed a streamline regularization
framework that uses particle streamlines to compute a plausible flow at discontinuities, thereby enabling
us to predict the motion more accurately. To quantitatively validate the accuracy of our results, we
applied the Wilcoxon Signed Rank Test, which shows an improvement in estimation accuracy using our proposed scheme.
2008ThomasICPR
Vector Field Resampling using Local Streamline Approximation
Authors: M. Thomas, C. Kambhamettu, C. A. Geiger
Reference: Proceedings of the 8th IEEE Workshop on Applications of Computer Vision,
Proceedings of the 19th International Conference on Pattern Recognition (ICPR), Tampa, Florida, December, 2008.
Comments: Publication Link
Keywords: computer vision, algorithms, sea ice, motion tracking, streamline, in-painting
Funding: Major funding provided through US National Science Foundation
Abstract: In this paper, we propose an algorithm to resample coarse vector fields in order to obtain vector fields of a
higher density. Unlike the typical linear interpolation scheme, our algorithm attempts to identify streamline characteristics in the flow field, and uses local polynomial parameterization of the flow to perform interpolation. Quantitative validation of the streamline oriented algorithm indicate that the Mean Square Error of the flow field obtained is more accurate than those obtained by bilinear interpolation schemes.
2007ThomasACM
Near-real time motion analysis for APLIS 2007: A systems modeling perspective
Authors: Thomas, M., C. Kambhamettu, C. A. Geiger, J. Hutchings and M. Engram
Reference: Proceedings of the 15th ACM International Symposium on Advances in Geographic Information Systems (in cooperation with SIGMETRICS), Seattle, November, 2007.
Comments: Publication Link
Keywords: Design, Algorithms, Measurement, Performance, sea ice, motion tracking, Software Engineering, Image Processing And Computer Vision, Physical Sciences And Engineering
Funding: Major funding provided through US National Science Foundation
Abstract: This paper describes the modeling of a near real time geophysical motion analysis system for the Applied Physics
Laboratory Ice Station (APLIS'07) that was held as part of the International Polar Year (IPY 2007-2009). One of the
important aspects of the motion analysis system was to help field scientists to plan instrumentation based on the large scale dynamics taking place in the scene. This required that the data flow architecture be simultaneously efficient and
accurate. Therefore, in order to provide for an efficient and robust method of analysis, the system was designed within
the Unified Modeling Language framework and developed as modules that could be easily scaled to subsequent stages
of research. This design-development framework helped in the successful use of the product for ground instrumentation
deployment.
2007ThomasRSPSoc
Near-real time estimation of sea ice deformation and its application at the APLIS Ice Camp 2007
Authors: Thomas, M., C. A. Geiger, C. Kambhamettu, J. Hutchings, and M. Engram
Reference: Proceedings of the Annual Conference of the Remote Sensing and Photogrammetry Society,
Newcastle-Upon-Tyne, UK, September, 2007.
Comments: Publication Link
Keywords: sea ice, IPY, APLIS 2007, SEDNA, RADARSAT, SAR, buoys, motion estimation, discontinuity identification, line
integral convolution, near-real time processing
Funding: Major funding provided through US National Science Foundation
Abstract: A near-real time sea ice motion tracking system was developed and tested as a part of APLIS’07 Ice Camp activities under the SEDNA project. This system was used as a logistical aid to determine optimal locations for deploying 12 GPS (strain-rate) buoys and 5 stress buoys. Critical elements essential for a nominal system design are presented in the discussion based on the operational experiences
learned under field conditions.
2007ThomasWACV
Vector field characterization in ERS-1 imagery of sea-ice
Authors: Thomas, M., C. A. Geiger and C. Kambhamettu
Reference: Proceedings of the 8th Workshop on Applications of Computer Vision (WACV), Austin, February, 2007.
Comments: Publication Link
Keywords: sea ice, motion estimation, ERS-1, discontinuity identification
Funding: Major funding provided through US National Science Foundation
Abstract: The non rigid motion of sea ice is an essential component when describing global climatology models. With the availability of sequential ERS-1 satellite imagery, we estimate high resolution motion and describe the differential characteristics
of motion. This characterization is subsequently used to locate critical points, also known as coherent structures,
in the flow, thereby reducing the large vector field into a collection of important feature points which essentially
describe the flow pattern. In this paper, we build on previous work in an attempt to enhance the characterization
of the flow field via visualization and quantification of these coherent structures. We show that the statistical quantification
of these structures can provide a greater clarity in our understanding of the physical dynamics taking place within the sea ice.
2007ThomasISPRS
High Resolution Motion Estimation of sea ice using an Implicit Quad-Tree Approach"
Authors: Thomas, M., C. A. Geiger and C. Kambhamettu
Reference: Proceedings of the ISPRS Workshop on High-Resolution Earth Imaging for Geospatial Information, Hannover, Germany, 2-5 June, 2007.
Comments: Publication Link
Keywords: RADARSAT, motion estimation, Quadtree decomposition, phase correlation, line integral convolution
Funding: Major funding provided through US National Science Foundation
Abstract: In this paper we estimate the motion between time-lagged Synthetic Aperture Radar (SAR) image pairs via an implicit quad-tree scheme. The algorithm provides a means to estimate motion at a spatial resolution that is an order of magnitude greater than the
currently available data products. Since the motion is extracted from the image data iteratively, the estimated field provides an accurate
picture of the underlying discontinuous motion. Experimental tests indicate that the algorithm is also computationally efficient. This is
extremely valuable when attempting to localize leads and ridges that are created in sea ice.
2007AndreasAMS:
Identifying nonstationarity in the atmospheric surface layer
Authors: Andreas, E. L, C.A. Geiger, G. Treviño, and K. J. Claffey
Reference: 21st Conference, Hydrology, San Antonio, TX, 14–18 January 2007, American Meteorological Society, 2007
Comments: Publication Link
Keywords: Boundary Layer, Atmospheric Processes, nonstationary processes, Monin-Obuhkov similarity, Field Measurements
Funding: U.S. Army 611102T2400
Abstract: Results from a field study, application of a Time Dependent Memory Method (TDMM), and statistical tests are used to identify nonstationary events in wind and temperature flux measurements over an early spring field location. Results show that nonstationarity may explain a wide range in Monin-Obukhov similarity functions that apply to stable stratification.
2006AndreasAMS:
Rapid forcing of the surface and near-surface atmosphere
Authors: Andreas, E. L, C. A. Geiger, K. J. Claffey, G. Treviño, and C. C. Ryerson
Reference: 10th Symposium on Integrated Observing and Assimilation Systems for the Atmosphere, Oceans and Land Surface, Atlanta, GA, 29 January–2 February 2006, American Meteorological Society, CD-ROM 4.2, 12 pp., 2006e
Comments: Publication Link
Keywords: Boundary Layer, Atmospheric Processes, nonstationary processes, Monin-Obuhkov similarity, Field Measurements
Funding: U.S. Army 611102T2400
Abstract: Results from a field study, application of a Time Dependent Memory Method (TDMM), and statistical tests are used to identify nonstationary events in wind and temperature flux measurements over an early spring field location.
2006ThomasPOAC:
Mesoscale sea ice features derived from discontinuous nonrigid motion SAR products
Authors: Thomas, M. V., C.A. Geiger, and C. Kambhamettu
Reference: Proc. 18th Int. Conf. on Port and Ocean Eng. Under Arctic Conditions, Vol. 3, 1011-1020, 2004.
Comments: Publication Link
Keywords: Ice, Sea Ice, Kinematics, Remote Sensing
Funding: initially supported by research grants from NSF (OPP-9818645) and ONR (N00014-02-1-0244 and N00014-03-1-0045); Imagery from © ESA ERS-1
Abstract: We have learned that standard techniques in computer vision can not be directly applied to SAR-derived sea ice motion products because of multiple discontinuities with varying orientations and scales. Additionally discontinuities intersect, undergo deformations, and appear as unique image regional textures in remote sensing products. We therefore find it imperative to identify the discontinuities before computing deformation. Our motion analysis system performs in a coarse-to-fine hierarchy where we build on our earlier works of 1) information propagation between scales and 2) nonrigid motion analysis. The basic strategy is to determine translational motion between image pairs in a coarse-to-fine hierarchy, followed by local linear deformation, and finally local non-linear nonrigid deformation. This paper describes a method for the robust estimation of the global translational motion followed by a piecewise local linear motion to a resolution of 400 m. In addition to this high resolution vector field, the results also include a discontinuity map identified from the correlation and velocity field gradients.
2004ThomasIEEEworkshop:
Discontinuous Non-Rigid Motion Analysis of Sea Ice using C-Band Synthetic Aperture Radar Satellite Imagery
Authors: Thomas, M. V., C. A. Geiger, and C. Kambhamettu
Reference: IEEE Workshop on Articulated and Nonrigid Motion (ANM) (In conjunction with CVPR'04), held June 27, 2004 in Washington, D.C., 9 pages, 2004.
Comments: Publication Link
Keywords: Ice, Sea Ice, Kinematics, Remote Sensing
Funding: initially supported by research grants from NSF (OPP-9818645) and ONR (N00014-02-1-0244 and N00014-03-1-0045); Imagery from © ESA ERS-1
Abstract: Sea ice motion consists of complex non-rigid motions involving continuous, piecewise-continuous, and discrete particle motion. Techniques for estimating non-rigid motion of sea ice from pairs of satellite images (generally spaced three to four days apart) are still in the developmental stages. For interior Arctic and Antarctic pack ice, the continuum assumption begins to fail below the 5 km scale with evidence of discontinuities already revealed in models and remote sensing products in the form of abrupt changes in differential velocity magnitude and direction of the differential velocity. Using a hierarchical multi-resolution phase correlation method and profiting from known limitations of cross correlation methods, we incorporate the identification of discontinuities into our motion estimation algorithm, thereby descending below the continuum threshold to examine the phenomenon of discontinuous non-rigid motion of sea ice.
Non-Peer Reviewed
2008SomanathESC:
Reconstruction of snow and ice surfaces using multiple view vision techniques
Authors: G. Somanath, R. MV, C., Geiger, C. Kambhamettu
Reference: Proceedings of the 65th Eastern Snow Conference Fairlee, VT, USA. May, 2008.
Comments: Publication Link
Keywords: sea ice, topography, surface mapping, surface reconstruction, computer vision, stereo
Funding: NSF-OPP 0636726
Abstract: In this paper we describe a vision system for reconstructing the relative structure of snow and ice surfaces. This effort is one step toward the long-term goal of rendering absolute scale topography. The target application is mapping of sea ice topography from transiting ships for monitoring sea ice mass balance. Images of snow and ice scenes pose difficulties in image analysis due to low contrast and the presence of large areas with low color variation. Since this is a less studied area in computer vision, our first goal is to obtain a candidate data set, evaluate different camera configurations, and develop algorithms to process the data. For simplicity, we chose the imaging of river ice as a surrogate for sea ice because of its accessibility. Multiple views of a scene were obtained using a variable zoom camera (15-300mm) mounted on a pan-tilt unit which moved along a 1m baseline. Data were collected at seven locations from heights of 2-100m and viewing angles of 5-45 degrees. The range of heights and angles are intended to simulate views from an icebreaker ship or sea ice camp. The same locations were imaged under various weather and illumination conditions.
2005DeLibertyAMS:
Temporal and Regional Variations of Sea Ice Thickness in the Ross Sea During 1995 and 1998
Authors: DeLiberty, T. L. and C. A. Geiger
Reference: Proceedings of the 8th Conference on Polar Meteorology and Oceanography, San Diego, CA. January 10-14, 2005. Paper 9.5
Comments: Publication Link
Keywords: Ice, Sea Ice, GIS, Antarctic, thickness, mass balance
Funding: NSF OPP-0088040 and the National Oceanic and Atmospheric Administration/National Ice Center (DG133E-03-SE-1055, DG133E-02-SE-0699)
Abstract: This paper focuses on the temporal and spatial variability of sea ice extent and thickness in the Ross Sea during 1995 and 1998. This analysis is being used to establish a framework for creating a Southern Hemisphere sea ice thickness climatology, and enabling the detection of any trends in the distribution of Antarctic sea ice thickness. Analysis of this type is underway for the 4-year time period from 1995 through 1998 and for the other regional seas in the Southern Ocean. A GIS web site is under development for online visualization and distribution of the in situ sea ice observations from the ASPECT program and satellite-derived NIC weekly ice charts. This GIS web application is being built using the new ESRI ArcGIS Server to display thickness estimates and their respective uncertainties, along with spatial and temporal queries to view and subset time periods and geographic areas of interest. The goal is to provide a database for studying sea ice thickness variability and validating climate models.
2004DeLibertyESRI:
Examining Sea Ice in the Southern Ocean Using ArcGIS
Authors: DeLiberty, T. L., C.A. Geiger and M. D. Lemcke
Reference: Proceedings of the 2004 ESRI International User Conference, August 9-13, 2004, 12 pp., San Diego, CA, 2004
Comments: Publication Link
Keywords: Ice, Sea Ice, GIS, Antarctic, thickness, mass balance
Funding: NSF OPP-0088040 and the National Oceanic and Atmospheric Administration/National Ice Center (DG133E-03-SE-1055, DG133E-02-SE-0699)
Abstract: A National Science Foundation (NSF) project is underway with researchers at the University of Delaware , the Australian Antarctic Division, the National Ice Center (NIC) and Clarkson University to evaluate two datasets - in situ (point) sea-ice thickness observations and weekly ice charts (polygon). The goal is to ascertain their quality for use in monitoring sea-ice thickness and mass balance changes in the Southern Ocean. Sea-ice thickness calculations from both datasets are temporally joined with spatially averaged in situ observations matching their respective NIC ice chart using ArcGIS’s field calculator, attribute query, spatial join and dissolve tools. The uncertainties of total ice thickness for both in situ observations and NIC ice charts are propagated through individual calculations and GIS tools. A composite product of the two datasets and their error estimates is being developed for monitoring sea-ice thickness, mass balance and validation fields for climate modeling. ArcGIS is used for the analysis of sea-ice conditions over the 1995-2000 period of study by visually and quantitatively examining the spatial extent of sea-ice and the variability of sea ice thickness for selected weeks during 1995 and 1998. The 3D Analyst extension also provides a means for displaying sea-ice thickness fields by draping the errors over the thickness estimates.
2002WorbyIAHR:
Circumpolar sea ice thickness maps for the Antarctic
Authors: Worby, A.P., C.A. Geiger, T.L. DeLiberty and B.A. Schellenberg
Reference: International Association for Hydraulic Engineering and Research 16th International Symposium on Ice, Dunedin, New Zealand, Dec 2-6, 2002
Comments: Publication Link
Keywords: Ice, Sea Ice, GIS, ASPeCt, ship observations, thickness, mass balance
Funding: Antarctic CRC, Hobart, Tasmania; US NSF Polar Programs Grant No. OPP-0088040
2002SchellenbergAMS:
Investigation of seasonal sea-ice thickness variability in the Ross Sea
Authors: B. A. Schellenberg, T. L. DeLiberty, C. A. Geiger, J. Silberman, and A. P. Worby
Reference: 13th Symposium on Global and Climate Variations, American Meterological Society,Orlando, Florida, January 13-17, 130-132, 2002.
Comments: Publication Link
Keywords: Ice, Sea Ice, Thickness, Concentration, Mass Balance, Climatology
Funding: NSF Polar Programs Grant No. OPP-0088040
Abstract: Antarctic sea ice is an important feature of the global climate system as it affects ocean-atmosphere interaction in the Southern Ocean. The mass balance of sea ice is a product of its areal extent and thickness. Of these two, thickness is the least known. Since 1995, the National Ice Center (NIC) has been classifying and cataloguing the "stages-of-development" of sea-ic based on a subset of the World Meteorological Organization (WMO) sea-ice classification standards. This classification scheme is used as an areal proxy for ice thickness. However, to date, no systematic effort has been undertaken to validate or test this proxy information against in-situ measurements. The first goal of this project is to make use of approximately 11,000 ship-based thickness observations obtained through ASPeCt under SCAR to compare with the NIC proxy charts. Sea-ice charts of the Ross Sea are believed to be the most accurate because of the extensive aircraft reconnaissance coverage there. Hence, the Ross Sea has been selected as the first region for comparison of these two data sets with the goal of ascertaining the quality of these data in climate studies. With the quality of the charts ascertained, the second goal is to quantify how much seasonal variability can be seen using the NIC charts.
1999DrinkwaterOCEANOBS:
Quantifying surface fluxes in the ice-covered polar oceans using satellite microwave remote sensing data
Authors: M. R. Drinkwater, R. Kwok, C. A. Geiger, J. A. Maslanik, C. W. Fowler, and W. J. Emery
Reference: In Proc. OCEANOBS '99: An International Conference on The Ocean Observing System for Climate, Volume 1, San Raphael, France, 18 - 22 October, 1999, Centre National D'Etudes Spatiales, 18 avenue Edouard Belin, 31401 Toulouse Cedex 4, France, 1999.
Comments: Publication Link
Keywords: Ice, Sea Ice, Remote Sensing; Polar Regions; Heat, Mass, Momentum Transfer and Fluxes
Funding: NASA Code Y 665-21-02, 621-2102, and 622-82-31 (MRD); and NSF OPP-9818645 (CAG), WCRP IABP program
Abstract: Satellite passive microwave sea-ice concentration data of 20 or more years in extent have become an important proxy for climate variability. More recently, in the 1990's there data have been exploited in conjunction with fine resolution satellite image datasets originating from ERS-1/2, and RADARSAT Synthetic Aperture Radar (SAR), and new medium resolution ERS-1/2 and NSCAT radar scatterometer instrument data. New technologies in image data processing and sea-ice tracking developed from these efforts are generating fresh insight into the dynamics and evolution of the Arctic and Southern Ocean ice covers. These approaches have matured to the point where estimates of salt and freshwater exports can be made, as well as assessments of the impact that these have upon the thermohaline circulation.
1998GeigerIABP:
Preliminary findings between buoy and satellite drift and deformation from October 1992 to March 1993
Authors: C. A. Geiger, Y. Zhao, and A. K. Liu
Reference: Proceedings from International Arctic Buoy Program, Aug 3-4, 1998, pgs 17-18, July, 1999.
Comments: Publication Link
Keywords: Ice, Sea Ice, Kinematics
Funding: NASA Polar Programs
Abstract: The development of a wavelet technique by Liu et al (1997) provides daily high spatial resolution sea-ice motion. These new sea-ice motion fields hold great promise toward understanding sea-ice processes. However, their spatial and temporal resolutions are different from that of the more traditional buoy data. It is important to understand these differences particularly when examining the differential drift, or deformation, which is responsible for the creation of open water and in terms of developing merged buoy-satellite data products for input into numerical models. Using the 85 GHz channel from the SSM/I from the period of October 1992 to March 1993, daily velocity fields are constructed via a 2D Mexican hat wavelet transform (Liu et al., 1998) to track features at a spatial scale on the order of 25 km. The daily ice motion fields are constructed from the tracked features with displacements computed relative to a 4-day sliding window such that motion of features two days prior to and two days following a given day are used to determine velocity. The 4-day sliding window works as an effective filter to smooth out noise incurred by the SSM/I sampling. The resultant velocities of specific features are block averaged to the 100km resolution SSM/I grid. A case study in the Eurasian basin is chosen using seven buoys from IABP to determine compatible spatial and temporal scales needed to compare buoy and SSM/I derived motion products. The comparison is made in a Lagrangian reference relative to the center of the drifting buoy array using the statistical methods described in Geiger et al (1998).
1997GeigerAMS:
Importance of sea ice for validating global climate model
Authors: C. A. Geiger
Reference: orkshop on Polar Processes in Global Climate. 13-15, November 1996, Cancun, Mexico, AMS publication, 122-125, 1997
Comments: Publication Link
Keywords: Ice, Sea Ice, Climate Variability, Processes, Model Validation
Funding: AMS, NASA, and NSF
Abstract: Sea ice has served as both a monitoring platform and sensitivity parameter of polar climate since the time of Fridtjof Nansen. However, using sea-ice characteristics to monitor climate variability implies a certain level of understanding of sea-ice physics. This level of understanding must be sufficient to accurately reproduce the four major sea-ice variables in current day large-scale numerical models, namely: sea-ice thickness, compactness/extent, velocity, and deformation. These variables need to be understood both in terms of mean regional quantities and accompanying temporal-spatio variability at scales suitable for climate monitoring. Examples from some recent work in the Weddell Sea region by Geiger (1996), Geiger et al., (1997) will be used here to illustrate the current level of understanding of the response of these four monitoring parameters to external forcing.
1994GeigerSavonlinna:
Results from a large scale strain array in western Weddell Sea during 1992
Authors: C.A. Geiger, S.F. Ackley, and W. D. Hibler III
Reference: Evening Sessions of the Summer School on Physics of Ice-Covered Seas, Savonlinna, Finland, 6-17 June 1994, edited by Timo Vihma, Report Series in Geophysics, No 28. University of Helsinki, Department of Geophysics, Helsinki, pgs. 47-50, 1994
Comments: Publication Link
Keywords: Ice, Sea Ice, Kinematics, Argos Buoys
Funding: NSF Polar Programs
Abstract: Data collected from Ice Station Weddell during 1992 in the western Weddell Sea are used to estimate large-scale drift velocity and strain-rates of sea ice. Using power spectra and strain-rate analyses, it is possible to show that the velocity, or general drift, of the sea-ice pack is driven primarily by low frequency forcing (i.e., greater than one day periods). Contrary to this, higher frequencies, specifically oceanic tidal frequencies, appear to be the main source driving the strain-rates which occur in this region.
Published Technical Reports and Data Archives
2010GeigerSFOS:
Coincident Airborne-Ground EM and Drill Hole Data from 1-km-scale SEDNA survey lines
Authors: SEDNA Team, APLIS'07, POC on Data: C. A. Geiger
Reference: http://dw.sfos.uaf.edu/sedna
Comments: Data archive located at UAF with mirror site at NSIDC
Keywords: electromagnetic induction (EM), sea ice thickness, coincident measurements, Cal/Val
Funding: Major Support from US National Science Foundation and EU Damocles
Abstract: Analysis product of coincident raw data products from coincident Airborne and Ground EM measurements
from six 1-km long sea ice thickness calibration lines. Data collection in Beaufort Sea April 2007 at start of International Polar Year 2007-2009. Ground EM collected every 5m while Airborne EM collected every 3-4m and interpolated to 5m to match Ground EM. Calibration of Ground data with drill hole data also included. See peer-reviewed paper 2012GeigerJGR for details when using this archive.
2006HoltNASA:
Cryospheric Advanced Sensor: A Spaceborne Microwave Sensor for Sea Ice Thickness and Snow Cover Characteristics
Authors: Ben Holt and Kyle McDonald – JPL, Don Perovich, Matthew Sturm, and C.A. Geiger – CRREL
Reference: NASA ESTO Instrument Incubator Program Final Report, JPL Publication, 2006. CAS SCIENCE TASK, FINAL REPORT 2007.
Comments: Contact Ben Holt at JPL (benjamin.m.holt@jpl.nasa.gov) for Final Report.
Keywords: Ice, Sea Ice, Snow, Thickness
Funding: NASA
2006GeigerCRREL:
Propagation of Uncertainites in Sea Ice Thickness Calculations from Basin-Scale Operational Observations
Authors: C.A. Geiger
Reference: ERDC/CRREL Technical Report TR-06-16, September 2006, 39 pp.
Comments: Publication Link
Keywords: Ice, Sea Ice, thickness, mass balance, GIS, ASPeCt
Funding: OPP-0088040
Abstract: Sea ice serves as a natural flux monitor of the global heat balance. This capability is attributed to the unique location of sea ice at the interface of the world’s two largest circulation systems—the air and ocean. The increased awareness of warming in the polar region has precipitated increased efforts to measure sea ice thickness as an index for global heat changes. This increased awareness has brought with it the development of several new prototype in situ, telemetry, and satellite remote sensing instruments. Each of these provides a means for measuring part or all of the frozen material at the air–sea interface, but each comes with considerable limitations. The integration of these measurements into basin-scale objective analysis fields will serve as important input for global climate models, much like current-day weather forecasting systems and the El-Niño monitoring system. As the various thickness monitoring tools begin to develop, it is critical that standards be established to record the quality of these data. This report addresses the data quality issues by examining a robust method for tracking uncertainties in measurements. The data sets considered are the two existing operational basin-scale systems: ship-based observations and satellite composite analysis. Illustrative examples are included.
2006DalyArmy:
Estimating Water Content in Snow: A Practical Guide for Measuring, Recording, and Reporting on Snow
Authors: Daly, S. F., J. Hardy, C. Vuyovich, C. Geiger, and M. Albert
Reference: Prepared for Central Command, US Army, Khandahar, February 14, 2006.
Comments: Contact Steve Daly of CRREL for more information.
Keywords: Snow measurements, steep terrain
Funding: US Army
2004JrmCRREL:
CRREL Sea ice dynamics program: Stress and deformation data from the western Arctic Basin
Authors: Richter-Menge, J. A., C. A. Geiger, B. Elder, K. Claffey, and N. Mulherin
Reference: CD-ROM Version 2.4., May 2004
Comments: Further updates at
http://www.crrel.usace.army.mil/sid/SeaIceDynamics/index.htm
Keywords: Ice, Sea Ice, dynamics, kinematics, buoys, stress
Funding: NOAA, NSF, NASA
Abstract: This CD and follow up web pages describe the study of dynamic forces and stress in the ice pack; forces that can lead to the development of ridges and leads. At spatial scales of 10-300 km sea ice consists of a collection of plates with differential motion that takes place along the edges of these plates. It is equivalent to the oceanographic mesoscale (10-100 km) which is rich in high energy dissipation processes such as eddies and other geostrophic density-driven processes. At this scale, differential sea ice motion plays an analogous dissipative role resulting in the development of features such as leads, slip lines, cracks, and pressure ridges. Within the sea ice community there is, at present, no formal definition of this scale. For most sea ice models small-scale discontinuous behavior is accounted for by a plastic yield curve in an average description suitable for a continuum modeling approach. Within the literature definitions of discontinuous behavior such as linear kinematic features (LKF's) and piece-wise rigid motion and aggregate scale are beginning to emerge. From a human perspective, when navigating in polar waters or maintaining offshore structures, sea-ice discontinuities are either useful conduits (leads) or impediments (ridges). Thus, mobility at the human scale is affected by changes in discontinuities of the sea-ice pack. These discontinuities are also fundamental regulators of heat, mass, and momentum transfer at the air-sea interface of one of the world's most sensitive climatic regions.
1995HiblerCanada:
Ice rheology modifications for the Canadian regional ice forecasting model
Authors: W. D. Hibler III, C.A. Geiger, and X. Song
Reference: KM149-4-P074/01-SS, 74 pp., August 1995
Comments: Prepared for Canadian Ice Services Environment, Ottawa, Canada. Dr. Venkata Neralla - Project Coordinator
Keywords: Ice, Sea Ice, Numerical Modeling
Funding: Canadian Ice Services Environment KM149-4-P074/01-SS
Abstract: Sea ice drift and deformation are significantly affected by internal ice stress. The effect of ice stress is most pronounced in winter when observations of Arctic buoy drift (Colony, 1990) show considerable stoppage of the ice motion despite relatively high wind speeds. Another characteristic observational feature is a consistent long term divergence in the ice pack. Recent work by Hibler and Ip (1995) and Ip (1993) has shown that the way in which plastic rheology is modeled can significantly affect predicted buoy drift. However, while these modifications were examined in a Basin wide context by Ip (1993) they have not been examined within the context of a regional ice forecasting model. Moveover, there are a number of issues that were raised by these studies that have not yet been examined within any context. For this purpose a study was proposed in December 1994 to the Ice Centre of Environment Canada. This report describes the results from that study and contains recommendations for modification to the Canadian Ice Forecasting model. In the following sections we first outline the theory for different rheologies and rheology "creep" closures and discuss the numerical solutions, forcing fields, and grids used for this investigation. In the subsequent result sections we examine the effect of the different rheology creep closures and type of rheology on buoy drift. Viscous-plastic subroutine plast.f included.
1989AsplinUiB:
Student Cruise, January 24-30, 1989 Sandsfjord System in Ryfylke
Authors: L. Asplin, G. Brostrøm, A.Evjen, C. Geiger, B.Gustavson, N.Holt, L.Johansson, T.Løyning, J.Mattsson, K.A.Mork, J.Nilsson, H. Pettersson, P.Samuel, E.Sørgård, P. Väänänen
Reference: University of Bergen Report, Edited by C.A. Geiger, 40 pp., June 1989
Comments: For more information visit the Geophysical Institute at the University of Bergen.
Keywords: Physical Oceanography, Fjordal Dynamics
Funding: Nordisk Kollegium
Abstract: The following report is a summary of a student investigation undertaken in the Sandsfjord area of Ryfylke in Norway. The project was part of the graduate program in oceanography offered at the University of Bergen and in association with the Nordisk Kollegium for Fysisk Oseanografi. The purpose of the investigation was for students to gain hands-on experience in oceanographic field work which included the planning, execution, data processing, and write-up of an oceanographic cruise. The investigation began with a one day preparation on the 24th of January in Bergen. This included lectures on the theoretical background, instrumentation, and the proposed cruise schedule. This was followed by a one day transition to the research area, 4 days of investigation (26th to 29th of January) and a 1 day transit back to Bergen (30th) aboard the Håkon Mosby. The major highlights of the study were outlined at the end of the cruise and each of the 5 participating institutes selected one specific aspect of the study to analyze. An intensive summary meeting was then held at Finse, Norway from the 10th to the 12th of April during which time each institute presented the different aspects of the cruise including instrument accuracy, data processing, and resultant observations. The presentations were followed by intensive discussions on data interpretation and proposed report format for presenting the results. A rough draft was written up at the Geophysical Insitute in Bergen and sent for approval and revision to each of the participating institutes. The final version was then sent to each student and representatives of the Nordisk Kollegium for Fysisk Oseanografi. Participating Institutions: Copenhagen University, University of Oslo, University of Bergen, Gutenberg University, Helsinki University.
1988JohannessenNERSC:
The Toxic Algal Bloom in May 1988
Authors: Johannessen, O. M., T. Olaussen, L. Pettersson , J. A. Johannessen , P. Haugen, K. Kloster , S. Sandven , L. Hansen, C. A. Geiger
Reference: NERSC Special Report 1, December 1988
Comments: For information visit the Nansen Environmental and Remote Sensing Center
Keywords: Physical Oceanography, ADCP Velocity Profiler, Remote Sensing, Toxic Algal Bloom
Funding: Country of Norway
1988GeigerNERSC1:
Seasoar Data Report from Håkon Mosby during Winter MIZEX 1987
Authors: C. A. Geiger, S. Sandven, J. Johannessen, O. M. Johannessen, I. Moen
Reference: NERSC Technical Report 17, 176pp., October 1988
Comments: For additional information contact researchers at the Nansen Environmental and Remote Sensing Center where the research and all data tapes were stored or contact the National Snow and Ice Data Center (NSIDC) in Boulder, Colorado where the data tapes and reports are archived. Part of master's thesis: Geiger (1990)
Keywords: Physical Oceanography, Coastal Oceanography, Eddy Tracking, Seasoar/CTD
Funding: ONR Polar Programs - MIZEX
Abstract: The Winter MIZEX experiment of 1987 was conducted in the Fram Strait/Greenland Sea region and in the Barents Sea. During the period from March 25 to April 11, the University of Bergen's research vessel, the Håkon Mosby, participated in the experiment. Among other activities, the Håkon Mosby made a total of 42 Seasoar sections totally approximately 950 stations. The following report presents the preliminary results of this data in the form of ship's track, TS diagrams, and vertical sections.
1988GeigerNERSC2:
HORIZON: A Horizontal Velocity Plotting Program for the ADCP
Authors: C. A. Geiger
Reference: NERSC Internal Technical Report, 8pp., May 1988
Comments: For additional information contact Stein Sandven at the Nansen Environmental and Remote Sensing Center for the code.
Keywords: Physical Oceanography, Computer Software Package
Funding: NERSC Funding
Abstract: The program HORIZON is designed to run at intermittent periods between transects or anytime after data has been processed by the ADCP program RT1136J. It's main purpose is to process preliminary results while onboard ship as a rough estimate for real-time analysis during the field work operation. It is also designed to spare many a graduate students' eyes and fingers from the tediousness of hand drawing velocity vector arrows.
1988SandvenNERSC:
MIZEX 87: CTD Data Report from Polar Circle
Authors: S. Sandven, Z. Kovacs, C. A. Geiger, T. Olaussen, and O. M. Johannessen
Reference: NRSC Technical Report 13, 243pp., April 1988
Comments: For additional information contact researchers at the Nansen Environmental and Remote Sensing Center where the research and all data tapes were stored or contact the National Snow and Ice Data Center (NSIDC) in Boulder, Colorado where the data tapes and reports are archived. Part of master's thesis: Geiger (1990)
Keywords: Polar Physical Oceanography, Hydrographic Data, Fram Strait
Funding: ONR Polar Programs - MIZEX
Abstract: During the Winter MIZEX experiment of 1987, a total of 206 CTD stations were taken aboard the icebreaker POLAR CIRCLE. Most of the data were obtained in areas with 3-5 m thick ice, and the depth of the CTD casts varied from 150m to 3000m. This report presents these data in the form of station tables, T-S diagrams, station profiles, and vertical sections.
1987RoysetNERSC:
User's Reference Manual for The CTD Data Processing Program Package
Authors: H. Røyset and P. E. Bjerke 1982 Updated by C.A. Geiger 1987
Reference: NRSC Internal Technical Report, 42pp., October 1987
Comments: For additional information contact Stein Sandven at the Nansen Environmental and Remote Sensing Center
Keywords: Physical Oceanography, Data Processing Software, Hydrographic Data
Funding: UiB Funding
Abstract: The following report serves as a user's guide to anyone processing CTD data at the Geophysical Institute at the University of Bergen. The manual is an update of the documentation made by Halvor Røyset and Per Erik Bjerke in November 1982 - "User's Reference Manual". It contains the programs used in the "User's Reference Manual" in updated form and includes all additional programs developed from 1982 to the present. The program package is based on data from the Neil Brown Instrument Mark III CTD system which is a digital conductivity, temperature, pressure microprofiling system that measures at a rate of 31.25 complete scans per second with a sensor response of 30ms. The digital data from the underwater unit is transmitted via an armored cable using frequency shift keyed modulation. These are decoded in a deck unit, displayed and transferred to a minicomputer for further processing and logging on digital tape. These data tapes are further processed ashore as described in this report. The user's guide is divided into two sections. Section I entails a brief description of how the obtained data is actually averaged into the 2m interval CTD format by use of the MEANS program. It also includes a description of the data format and an explanation of calibration and re-calibration procedures needed for raw data processing. Section II is divided into three sections covering the various types of processing available. These include 1) data modification or current CTD data (calibration), 2) programs producing printouts, and 3) plotting programs.
1987SandvenNERSC:
CTD Data Report from the Håkon Mosby during Winter MIZEX March-April 1987
Authors: S. Sandven, C. A. Geiger, J.A. Johannessen, and O.M. Johannessen
Reference: NERSC Technical Report 3, 207pp., October 12, 1987
Comments: For additional information contact researchers at the Nansen Environmental and Remote Sensing Center where the research and all data tapes were stored or contact the National Snow and Ice Data Center (NSIDC) in Boulder, Colorado where the data tapes and reports are archived. Part of master's thesis: Geiger (1990)
Keywords: Physical Oceanography, CTD, Hydrographic Data, Fram Strait, Polar
Funding: ONR Polar Programs - MIZEX
Abstract: The marginal ice zone (MIZ) is the critical region in which polar air masses, ice, and water masses interact with the temperate ocean and climatic systems. the processes that take place there profoundly influence hemispheric climate and have a significant effect on petroleum/mineral exploration and production, naval operations, and commercial fishing. To gain an understanding of these processes sufficient to permit modeling and prediction, a series of field experiments were planned and executed (Johannessen et al., 1983). In 1983, a pilot marginal ice zone experiment was conducted during the summer in the Fram Strait and Greenland Sea (MIZEX Group 1986). The 1983 Fram Strait Experiment was followed in June and July of 1984 by a major multi-national experiment, also in Fram Strait. The purpose of the 1983 and 1984 programs in Fram Strait was to study the mesoscale physical processes by which ice, ocean, and atmosphere interact in the MIZ during the summer months. Extensive research programs were conducted in oceanography, meteorology, acoustics, remote sensing, ice studies, and biology. The major results of this research program are published in Journal of Geophysical Research 1987. As a continuation of the summer MIZEX program, the winter MIZEX 87 was conducted both in the Fram Strait/Greenland Sea region and in the Barents Sea from March 20 to April 10, 1987. The winter MIZ program objectives hinge upon the need to understand the ice/ocean/atmospheric processes responsible for the advance of the winter ice edge, and their effects on acoustics and electromagnetic remote sensing under dramatically different conditions from those during the summer. In this document, we will only report on the CTD oceanography program carried out from the research vessel Håkon Mosby in the open water part of the winter MIZ. Other reports on Seasoar, ADCP, and CTD from the Polar Circle will also be issued. The primary objectives for this winter MIZEX oceanography program are:
1) Investigation of the characteristics of the ice-ocean eddy field including open ocean eddies with respect to space and time scales, energy, generation, propagation, and structural changes, including eddy/eddy interaction and decay.
2) Investigation of the role the ice-ocean eddy field has in heat and mass exchange across the ice edge in order to parameterize this effect in large-scale models.
3) Investigation of the potential role of the MIZ eddy field in upwelling events, on freezing of new ice, and in deep convection of bottom water formation.
4) Provision of time series, at densely spaced locations, of current shear stress values for correlation with MIZ acoustic properties and signatures and of the thermohaline structure for determining sound speed variations.
5) Investigation of the MIZ internal wave field, with emphasis on generation mechanisms associated with the ice field and the interaction between internal waves and ice-ocean eddy fields.
6) Definition of the winter cross-edge velocity and thermohaline structure for comparison with summer measurements.
7) Determination of the role of off-ice advection episodes in the heat, salt, and ice budgets.
1987GeigerNERSC:
AXBT and XBT Temperature Measurements from MIZEX 1983, 1984, and 1985
Authors: C. A. Geiger, S. Sandven, and O. M. Johannessen
Reference: NERSC Technical Report 1, 73pp., January 1987
Comments: For additional information contact researchers at the Nansen Environmental and Remote Sensing Center where the research and all data tapes were stored or contact the National Snow and Ice Data Center (NSIDC) in Boulder, Colorado where the data tapes and reports are archived.
Keywords: Physical Oceanography, Remote Sensing, Temperature Profiles, Fram Strait
Funding: ONR Polar Programs - MIZEX
Abstract: The following data report is a composite of all AXBT (airborne expendable bathythermographs) and XBT (expendable bathythermographs) data collected by the Bergen group during MIZEX 1983 and 1984 and during an airborne pre-winter MIZEX experiment in 1985. The data is comprised of a total of 487 stations set up into 65 sections of which 17 sections are from AXBTs in 1983, 11 from XBTs in 1984, 30 from AXBTs in 1984, and 7 AXBTs from 1985. A brief description of the MIZEX program can be found in the enclosure at the end of this report (MIXEX group 1986). The data were collected by deploying XBT probes from the R/V Håkon Mosby and Kvitbjørn plus AXBT probes from the Norwegian P3 planes. Raw data was obtained on hard copy plots aboard the respective vessels. The plots were then digitized and put onto tapes which were read onto a Sperry 1100 system and formatted into standard CTD form at the University of Bergen. The data set was processed using the CTD package at the Geophysical Institute in Bergen (H. Røyset and P. E. Bjerke, 1982). The results obtained are presented in three parts, one for each year (1983, 1984,1985). Each includes a station position chart and position listing followed by the vertical section profiles for temperature. The plots are standardized with a depth scale set at 25m/0.7cm (0.36m/cm) with a total depth of 500m shown in each profile; depth intervals are marked every 25m. The distance across each section is set at 4km/0.7cm (57m/cm) with intervals marked every 4 km. The initial and final position of each section is listed at the bottom of each plot along with other pertinent information including the date and time. The estimated accuracy of the date is about 1oC. A general outline is given on the following pages which summarize each transect including date, station numbers, section orientation and a comment listing of any deletions or questionable data.
1986JohannessenNERSC:
Seasoar Data Report from the Eddy Tracking Experiment in the Norwegian Coastal Current in Feb-March 1986
Authors: J. A. Johannessen, E.Svendsen, S.Sandven, K.Lygre, and Ø. Skagseth, contrib. from O. M. Johannessen, D. Hunderi, L. Hansen, C.A. Geiger, and B. Hackett.
Reference: NRSC Internal Technical Report August 29, 1986
Comments: For additional information contact researchers at the Nansen Environmental and Remote Sensing Center where the research and all data tapes are stored.
Keywords: Physical Oceanography, Oscillating CTD/Seasoar, Eddy Tracking, Coastal Oceanography, Norwegian Coastal Current
Funding: Many Norwegian Agencies
1986JohannesenNERSC:
Acoustic Doppler Current Profiler Report
Authors: J. A. Johannessen and E.Svendsen with contributions from L. Hansen, C. A. Geiger, D. Hunderi, O. M. Johannessen, S. Sandven, and Harald Svendsen
Reference: NRSC and Geophysical Institute Report, Avd. A., University of Bergen, 28pp., May 21, 1986
Comments: For additional information contact researchers at the Nansen Environmental and Remote Sensing Center where the research and all data tapes were stored.
Keywords: Physical Oceanography, ADCP, Ocean Current, Norwegian Coastal Current, Coastal Oceanography
Funding: Norwegian Oil Companies
Abstract: The main goal of this study was to gain better understanding of mesoscale ocean circulation through a dedicated pilot-study eddy tracking experiment. The specific objectives include:
1) Increased understanding of air-sea interaction in the Norwegian Coastal Current to improve modeling of eddies and wave-current interaction.
2) Obtain three dimensional velocity and hydrographic structure of eddy features.
3) Gain understanding of eddy generation, propagation, and decay
4) Study wave-current (eddy) interaction
5) Study the effect of eddies on SLAR imaging mechanisms
6) Study propagation loss of acoustic signals passing eddies/fronts
7) Study effect of eddies on atmospheric boundary layer conditions
The field experiment was very successful. An extensive interrelated data base, listed below, was obtained using remote sensing and in-situ oceanographic data:
• Remote Sensing Data
• TIROS N satellite IR
• Aero Commander aircraft SLAR
• GEOSAT Altimeter
• In-situ Data
• ADCP onboard Håkon Mosby
• SeaSoar onboard Håkon Mosby
• CTD aboard H.U. Sverdrup
• SST aboard H.U. Sverdrup
• Moored current meters
• Moored wave rider buoys
• Argos drifting buoys with subsurface sail
• Meteorological observations
• Acoustic ray propagation
• Simulation Data
• Rotating tank experiment (video taped)
The following institutes and companies participated and/or supported the experiment with instruments or funding:
Nansen Ocean and Remote Sensing Center, Bergen;
Geophysical Institute, Div. A, University of Bergen;
Defense Research Establishment, Horton;
STATOIL and Norske Shell, Stavanger;
Oceanor, Trondheim;
State Pollution Control Authority, Olso;
Mathematical Institute, University of Oslo;
Fjellanger Widerø e, Oslo;
Weatherforcasting Center for Western Norway, Bergen;
Tromsø Telemetry Station, Tromsø
Christian Michelsens Institute, Bergen;
Norwegian Hydrodynamic Laboratory, Trondheim; and
Marine Research Institute, Bergen.
This data report deals only with the Acoustic Doppler Current Profiler mounted on the University of Bergen Research Vessel Håkon Mosby in December 1985 as funded by STATOIL and Norske Shell, after initiative and proposal from NORSC. The RD Instruments RD-VM0150 Acoustic Doppler Current Profiler (ADCP) System employs the acoustic Doppler technique to remotely measure vertical profiles of horizontal ocean currents from a moving vessel. The ocean current profiles beneath the ship can be measured in up to 128 depth cells (1 to 32 meter thick cells) over a depth of up to 700m dependent on the frequency of the instrument. In areas where the water depth is within the ADCP bottom tracking range (normally 1.5 times the profiling range, ~500m), the sonar also directly measures earth referenced vessel velocity, allowing measurements of absolute current profiles. For applications in water depths greater than the ADCP bottom tracking depth, an optional software/hardware navigation package is available to convert the current profiles measured in the vessel's coordinate system into absolute current profiles, by removing the mean vessel velocity. An HP computer based on the data acquisition system is available to process the current profile, vessel speed, and heading in real-time which together with vessel attitude and position data gives vector averaged current profiles. These profiles displayed in real-time are stored on floppy disks, or 67MB cassette tapes, and may also be dumped on a printer in real-time for further onboard analysis.
Additional Invited Publications
2011GeigerIGS:
Book Review
Authors: Geiger, C. A.
Reference: Book Review of “On Sea Ice” by W. F. Weeks, International Glaciological Society, 57(201), 193-194.
Comments: Publication Link
Keywords: Book Review, On Sea Ice
2010GeigerArgosForum:
Satellite derived motion analysis using Argos ice buoys
Authors: C. A. Geiger
Reference: in ARGOS Forum , Volume 69, pages 6-7.
Comments: Publication Link
Keywords: buoys, remote sensing, IPY, SEDNA, ARGOS
Abstract: The polar extremes, especially the sea ice (frozen sea water) on
polar ocean surfaces, serve as the thermal regulators (air conditioners) of the planet. Argos ice buoys play an important role in
monitoring the dynamics, thickness and extent of sea ice in the Arctic and Antarctic, that are interconnected to recent changes in the global
climate.
1993GeigerDirections:
Life Begins at 2000
Authors: C. A. Geiger
Reference: Directions, Thayer Publication THAY 5.2M1193TMD/ETP, edited by Lois Wood, 8 No. 1, 58-61, 1993
Comments: Publication Link
Keywords: Thayer, Dartmouth, Engineering Magazine, science, engineering, and public policy, cross-disciplinary
Abstract: The commanding goal of General Sylvanus Thayer, founder of Thayer School of Engineering in 1867, is expressed in his own words on the very front of Cummings Hall: "To prepare the most capable and faithful for the most responsible positions and them most difficult service." Students pursuing a doctoral degree in engineering at Thayer School are asked to aspire to General Thayer's ideals through five requirements, which include: 1) several broadly focused fundamental core courses, 2) an oral exam on knowledge of fundamental principles, 3) a written and oral proposal of the Ph.D. research, 4) public defense of an original thesis, and 5) a requirement for almost 10 years (1984 to 1993), the one year seminar course, ENGS 200: Science, Engineering, and Public Policy. Why does Thayer School require this course for its Ph.D. candidates? One premise might be that this course can help couple the student's academic research and individual thoughts with the society through which those thoughts have been molded and to which the developing graduate engineer will someday contribute. We will consider the development of ENGS 200 in context with this hypothesis, and try to determine what the course has contributed over the past nine years to the School's purpose - as expressed by General Thayer and carved in stone on Cummings Hall.