Authors: C.A. Geiger, M. V. Thomas, and C. Kambhamettu
Book 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: Preprint (pdf) available (436
KB).
Keywords: Ice, Sea Ice, Kinematics, Thickness
Funded by: 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.
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
Book reference: Ice Mass Balance
Buoy: An Instrument to Measure and Attribute Changes in Ice Thickness,
in book 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: Preprint (pdf) available
Keywords: Ice, Sea Ice, Thickness, Thermodynamics
Funded by: 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.
Impact of temporal-spatio resolution on sea-ice
drift and deformation
Authors: C.A. Geiger
and M.R. Drinkwater
Book 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: Preprint (pdf) available (~1MB).
Keywords: Ice, Sea Ice, Kinematics, Satellite
Remote Sensing
Funded by: 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.
Authors: C.A. Geiger,
S.F. Ackley, and W. D. Hibler III
Book reference: Antarctic Sea Ice Processes, Interactions and Variability
AGU Antarctic
Research Series 74, 141-160, 1998
Comments: Reprint
Keywords: Ice, Sea Ice,
Kinematics, Argos Buoys
Funded by: 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.
Springtime ice motion in the western
Antarctic peninsula region
Authors: C.A. Geiger
and D. K. Perovich
Journal reference: Deep-Sea
Research, Southern Globec Special Issue
Comments: Reprint ,
Southern Globec Contribution #515
Keywords: Ice, Sea Ice,
Kinematics, Inertial Oscillations, Biological Coupling
Funded by: 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.
High resolution (400m) Motion
Characterization of Sea Ice using ERS-1 SAR Imagery
Authors: Thomas, M. V., C.A. Geiger, and C. Kambhamettu
Journal reference: Cold Regions
Science and Technology, Elsevier, Guest Editors: Mary Albert and Cathleen Geiger with Guest Editorial
.
Comments: Reprint
Keywords: Ice, Sea Ice, SAR, Kinematics, Remote Sensing, GPS Buoys
Funded
by: 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.
Identifying Nonstationarity
in Turbulence Series
Authors: Andreas, E. L., C. A. Geiger, G. Treviño,
K. Claffey
Journal reference: Boundary-Layer Meteorology, 127:37–56, DOI
10.1007/s10546-007-9252-z, 2008
Comments: Reprint
Keywords: Atmospheric surface
layer, Integral scale; Nonstationarity,
Time-dependent memory method (TDM method); Time series analysis
Funded by: 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.
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
Journal reference: Journal of Geophysical Research
Comments: Reprint
Keywords: Ice, Sea Ice, Kinematics, Remote Sensing, Data Synthesis, Climate
Funded by: 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.
Authors: S.F. Ackley, C.A. Geiger, J.C. King, E.C. Hunke, and J. Comiso
Journal
reference: Annals of Glaciology, Volume 33, 425-429, 2001.
Comments: Reprint
Keywords: Ice, Sea Ice, Air-Ice-Sea Interaction
Partially
Funded by: NSF Polar Programs Grant No. OPP-9818645
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.
Authors: C.A. Geiger, Y. Zhao, A. K. Liu, and S. M. Häkkinen
Journal
reference: Journal of Geophysical Research 105, C2, 3357-3368, 2000
Comments: Preprint
Keywords: Ice, Sea Ice, Kinematics, satellite remote sensing
Funded
by: 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
(ð ui /ð 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.
Authors: S. M. Häkkinen
and C.A. Geiger
Journal
reference: Journal of Geophysical Research 105, C3, 6549-6564, 2000
Comments: Reprint
Keywords: Ice, Sea Ice, Numerical Modeling, NAO, AO, Great Salinity Anomaly, EOFs
Funded
by: USRA 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.
Authors: Y. Zhao, A. K. Liu, and C.A. Geiger
Journal
reference: J. Adv. Mar. Sci. Tech. Soci., 4, No. 2, 313-322, 1998
Comments: Reprint
Keywords: Ice, Sea Ice, Wavelet Analysis, Kinematics, Satellite
Remote Sensing
Funded by: 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.
Authors: C.A. Geiger, W. D. Hibler III
and S.F. Ackley
Journal
reference: Journal of Geophysical Research (Special Issue on Sea Ice Mechanics) 103, C10, 21893-21914, 1998
Comments: Reprint
Keywords: Ice, Sea Ice, Kinematics, Numerical Model Validation, Argos Buoys
Funded
by: 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.
Authors: C.A. Geiger, S.F.
Ackley, and W. D. Hibler III Author
Names Go Here including in a linked form
Journal
reference: Annals of Glaciology 25, 269-275, 1997
Comments: Reprint
Keywords: Ice, Sea Ice, Numerical Modeling, Sensitivity Studies, Thermodynamics
Funded
by: 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.
Authors: C.A. Geiger
Journal
reference: Thayer School of Engineering Doctor of Philosophy
Thesis, 384 pgs., 1996
Comments: Reprint
Keywords: Ice, Sea Ice, Kinematics, Numerical Modeling, Remote Sensing
Funded
by: 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.
Authors: C.A. Geiger
Reference: University of Bergen Candidatus
scientus Thesis, 100 pgs, July 1990
Comments: Reprint needed
Keywords: Ice, Sea Ice, Polar Physical Oceanography, Deep-Water Formation, Boreas
Basin
Funded
by: 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.
(Cruise 1) (Cruise 2)
Peer Reviewed
Towards estimation of dense disparities from stereo
images containing large textureless regions, (2008):. Accepted to ICPR 2008
Authors: Rohith MV, G. Somanath, C. Kambhamettu, C. A. Geiger
Reference: International Conference on Pattern Recognition, Tampa,
FL, USA 8-12
December, 2008
Comments: Reprint
Keywords: Ice, stereo imaging, disparity
Funded by: 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.
Streamline Regularization for the Estimation of Large
Discontinuous Non-Rigid Motion
Authors: M. V. Thomas, C. A. Geiger, C. Kambhamettu, J. Hutchings, J. A. Richter-Menge, M. Engram
Reference: Annual Conference of Remote
Sensing and Photogrammetry Society,
Newcastle-Upon-Tyne, UK, September, 2007
Comments: Reprint
Keywords: Ice, Sea
Ice, Kinematics, Remote Sensing Techniques
Funded by: NSF ARC-0612105
(SEDNA Project); Imagery from © CSA RADARSAT-1
Abstract:
When
non-rigid motion is estimated under a non-topology preserving deformation, it
has to sometimes contend with the presence of discontinuous structures that are
created due to the dynamics involved. However, under a continuous rheology framework, non-rigid motion can be approximated as
a higher order motion model. In the presence of discontinuities, the models
that work in continuum fail to encapsulate the dynamics, with an increased
estimation error at the discontinuities. In this paper, we propose an algorithm
that can estimate large scale nonrigid motion in the
presence of discontinuous regions. The estimation-regularization framework used
here, utilizes particle streamlines to generate a plausible 0ow 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 T-test which indicated the improvement in the estimation accuracy
through the proposed regularization scheme. .
Vector field characterization in ERS-1 imagery of sea
ice
Authors: M. Thomas, C.A. Geiger, C. Kambhamettu, J. Hutchings, J. A. Richter-Menge, M. Engram
Reference: Annual Conference of Remote
Sensing and Photogrammetry Society, Newcastle-Upon-Tyne, UK,
September, 2007
Comments: Reprint
Keywords: Ice, Sea
Ice, Kinematics, Remote Sensing Techniques
Funded by: NSF ARC-0612105
(SEDNA Project); Imagery from © CSA RADARSAT-1
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.
Vector field characterization in ERS-1 imagery of sea
ice
Authors: M. Thomas, M., C. Kambhamettu,
C. A. Geiger, J. Hutchings, M. Engram
Reference: 15th Annual ACM GIS conference in Seattle, Washington,
November, 2007
Comments: Reprint
Keywords: Ice, Sea
Ice, Kinematics, Remote Sensing Techniques
Funded by: NSF ARC-0612105
(SEDNA Project); Imagery from © CSA RADARSAT-1
Abstract:
This paper
describes the modeling of a near real time geophysical motion analysis system
for the Applied Physics Laboratory Ice Station (APLIS) that was held as part of
the International Polar Year. One of the important aspects of the motion
analysis system was to help scientists plan instrumentation deployments 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.
Vector field characterization in ERS-1 imagery of sea
ice
Authors: M. Thomas, C.A. Geiger, and C. Kambhamettu
Reference: 8th IEEE Workshop on Applications of Computer Vision, Feb
21-22, 2007
Comments: Preprint
Keywords: Ice, Sea Ice, Kinematics, Remote Sensing Techniques
Funded by: NSF OPP0612527; Imagery from © ESA ERS-1
Abstract:
When tackling large vector fields, it
is essential to be able to locate critical points, also know as coherent
structures, in the flow. These points are equivalent to the feature points in
an image, whereby the type and location of these coherent structures can be
used to describe the entire flow field. In this paper, we attempt to enhance the
characterization of the flow field of sea ice estimated from satellite imagery
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.
Vector field characterization in ERS-1 imagery of sea
ice
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: Preprint
Keywords: Boundary Layer, Atmospheric Processes, nonstationary processes, Monin-Obuhkov
similarity, Field Measurements
Funded by: 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.
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., 2006
Comments: Publications\2006AMS.Andreas.Geiger.pdf, http://ams.confex.com/ams/Annual2006/techprogram/paper_99718.htm
Keywords: Boundary Layer, Atmospheric Processes, nonstationary
processes, Monin-Obuhkov similarity, Field
Measurements
Funded by: 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.
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: Preprint
Keywords: Ice, Sea Ice, Kinematics, Remote Sensing
Funded by: 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.
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: Preprint, http://vims.cis.udel.edu/sea ice
Keywords: Ice, Sea Ice, Kinematics, Remote Sensing
Funded by: 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
Reconstruction
of snow and ice surfaces using multiple view vision techniques, (2008):, Proceedings of the 65th Eastern Snow Conference,
Authors: G. Somanath, R. MV, C., Geiger, C. Kambhamettu
Reference: Proceedings of the 65th Eastern Snow Conference Fairlee, VT, USA.
May, 2008.
Comments: Preprint
Keywords: sea ice, topography, surface mapping, surface reconstruction, computer
vision, stereo
Funded by: 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.
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 (cdrom).
Comments: Preprint,
Keywords: Ice, Sea Ice, GIS, Antarctic, thickness, mass balance
Funded by: 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.
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: Preprint, http://www.esri.com/uc
Keywords: Ice, Sea Ice, GIS, Antarctic, thickness, mass balance
Funded by: 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.
Sea ice
Thickness in the Ross Sea
Authors: DeLiberty,
T. L., B. A. Schellenberg, C.A. Geiger, A. P. Worby,
M. Van Woert
Reference: Illustrated paper, American
Associate of Geographers meeting, March 5-9, 2003.
Comments: NEED REF
Keywords: Ice,
Sea Ice, GIS, thickness, mass balance
Funded by: NSF OPP-0088040
Abstract:
NEED
info from TRACY
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: Preprint
Keywords: Ice, Sea Ice, GIS, ASPeCt, ship
observations, thickness, mass balance
Funded by: FIND THIS
Abstract:
FIND
THIS
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: Poster presentation given at AMS meeting. Preprint of extended abstract (PDF ~213KB)
Keywords: Ice, Sea Ice, Thickness, Concentration, Mass Balance, Climatology
Funded by: 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.
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: Reprint.
Keywords: Ice, Sea Ice, Remote Sensing; Polar
Regions; Heat, Mass, Momentum Transfer and Fluxes
Funded by: 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.
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: Reprint needed here More
information on the International Arctic Buoy Program. Refereed journal paper: Geiger, Zhao, Liu, and Häkkinen,
2000.
Keywords: Ice, Sea Ice, Kinematics
Funded by: 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).
Authors: C.A. Geiger
Reference: Proceedings from Workshop on Polar Processes in Global Climate.
13-15, November 1996, Cancun,
Mexico, AMS
publication, 122-125, 1997
Comments: Reprint needed here More information on the American Meteorological Society
Keywords: Ice, Sea Ice, Climate Variability, Processes, Model
Validation
Funded by: 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, 1998a, and 1998b) will be used here to illustrate the
current level of understanding of the response of these four monitoring
parameters to external forcing.
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: Reprint needed here. Refereed journal paper: Geiger, Ackley, and Hibler
(1998). Part of Ph.D. thesis: Geiger (1996)
Keywords: Ice, Sea Ice, Kinematics, Argos Buoys
Funded by: 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.
Cryospheric Advanced Sensor: A Spaceborne
Microwave Sensor for Sea Ice Thickness and Snow Cover Characteristics
Authors: Team Participants : 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: Preprint
goes here
Keywords: Ice, Sea Ice, Snow, thickness
F unded by: NASA
Abstract:
Need
this from Ben. E-mail sent
Abstract:
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: Reprint
Keywords: Ice, Sea Ice, thickness, mass balance, GIS, ASPeCt
Funded by: 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.
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
Funded by: NSF Office of Polar Programs, NOAA, ONR
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.
Authors: W. D. Hibler III, C.A. Geiger, and X. Song
Report no: 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
Funded by: 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}
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
Report no: University of Bergen Report, 40 pp., June 1989
Comments: Edited by C.A. Geiger. For more information see the website
about the Geophysical Institute or e-mail .
Keywords: Physical Oceanography, Fjordal Dynamics
Funded by: 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.
(Cruise Information)
Authors: Johannessen, O.M., T.Olaussen,
Lasse Pettersson , J. A. Johannessen
, P. Haugen, K. Kloster , S. Sandven , L. Hansen, C.A. Geiger
Report no: NRSC Special Report 1, December 1988
Comments: For additional information see the website of the Nansen Remote Sensing Center or contact researchers for data tapes and report
copies.
Keywords: Physical Oceanography, ADCP Velocity Profiler, Remote Sensing, Toxic
Algal Bloom
(Cruise Information)
Authors: C.A. Geiger, S.Sandven,
J.Johannessen, O.M. Johannessen,
I.Moen
Report no: NRSC Technical Report 17, 176pp., October 1988
Comments: For additional information contact researchers at the Nansen 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
Funded by: 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.
(Cruise Information)
Authors: C.A. Geiger Report no: NRSC Internal
Technical Report, 8pp., May 1988
Comments: For additional information contact Stein Sandven at the Nansen Remote Sensing Center for the code.
Keywords: Physical Oceanography, Computer Software Package
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.
Authors: S. Sandven, , Z. Kovacs, C.A. Geiger, T.Olaussen,
and O.M.Johannessen
Report no: NRSC Technical Report 13, 243pp., April 1988
Comments: For additional information contact researchers at the Nansen 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
Funded by: 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.
(Cruise Information)
Authors: H. Røyset
and P.E.Bjerke 1982 Updated by C.A. Geiger 1987
Report no: NRSC Internal Technical Report, 42pp., October 1987
Comments: For additional information contact Stein Sandven at the Nansen Remote Sensing Center.
Keywords: Physical Oceanography, Data Processing Software, Hydrographic Data
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 recalibration 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.
Authors: S. Sandven,, C.A. Geiger, J.A. Johannessen, and O.M. Johannessen
Report no: NRSC Technical Report 3, 207pp., October 12, 1987
Comments: For additional information contact researchers at the Nansen 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
Funded by: 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 udner 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.
(Cruise Information)
Authors: C.A. Geiger, S.Sandven, and O.M.Johannessen
Report no: NRSC Technical Report 1 , 73pp., January 1987
Comments: For additional information contact researchers at the Nansen 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
Funded by: 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
and 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 stardard 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 pertainent
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.
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.
Report no: NRSC Internal Technical Report August 29, 1986
Comments: For additional information contact researchers at the Nansen 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
(Cruise Information)
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
Report no: NRSC and Geophysical Institute, Avd. A., UiB. 28pp., May 21, 1986
Comments: For additional information contact researchers at the Nansen Remote
Sensing Center where the research and all data tapes were stored.
Keywords: Physical Oceanography, ADCP, Ocean Current, Norwegian Coastal
Current, Coastal Oceanography
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 (available soon)
• 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.
(Cruise Information)
Authors: C.A. Geiger, edited by Lois Wood
Journal reference: Directions, Thayer Publication THAY 5.2M1193TMD/ETP,
8 No. 1, 58-61, 1993
Comments: If you would like to contact the editor or her assistant , they will be glad to
provide further assistance.
Keywords: Thayer, Dartmouth, Engineering Magazine
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 thourghts 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.
Modified November 2006; maintained by cag.