scholarly journals On simulating high-frequency variability in Antarctic sea-ice dynamics models

1998 ◽  
Vol 27 ◽  
pp. 443-448 ◽  
Author(s):  
W. D. Hibler III ◽  
Petra Heil ◽  
Victoria I. Lytle
Keyword(s):  
Boundary Layer ◽  
Sea Ice ◽  
High Frequency ◽  
Ice Dynamics ◽  
Antarctic Sea Ice ◽  
Sea Ice Dynamics ◽  
Ice Drift ◽  
Dynamics Models ◽  
The Antarctic ◽  
Ocean Boundary

Due to frequent and intense storm systems moving across the Antarctic sea ice, ice drift and deformation fluctuate substantially. Observations of drilling buoys show inertial power to be a substantial component of ice drift and deformation. Because the inertial period at high latitudes is close to tidal periods, this peak can be amplified due to resonance. in practice, the energy dissipation by ice interaction plays a significant role in dampening out this inertial energy. in present sea-ice dynamics models both with and without ice interaction, this inertial motion is overdamped due to the underestimation of coupling to the ocean boundary layer. To develop a more consistent treatment of ice drift under fluctuating wind fields, we consider here a vertically integrated formulation of the ice-ocean boundary-layer system that incorporates a more realistic treatment of the upper ocean. Under steady wind conditions this model reduces to the normal water-drag formulation used in most sea-ice dynamics models. Simulations using this “imbedded” model are analyzed to elucidate the role of ice interaction in the Antarctic ice-pack in modifying the high-frequency motion and inducing deformation which in turn significantly impact ice-thickness characteristics. The simulations demonstrate that in an interacting ice field in the presence of kinematic waves inertial imbedding can lead to oscillations in ice concentration of up to ~10% open water. These variations are similar in magnitude to observed deformation fluctuations in tide-free regions.

Simulation of Sea Ice Dynamics During AIDJEX

1977 ◽  
Vol 99 (3) ◽  
pp. 491-497 ◽  
Author(s):  
R. S. Pritchard ◽  
M. D. Coon ◽  
M. G. McPhee
Keyword(s):  
Boundary Layer ◽  
Sea Ice ◽  
The Arctic ◽  
Ice Dynamics ◽  
Ice Surface ◽  
Sea Ice Dynamics ◽  
Pack Ice ◽  
Ice Drift ◽  
Ice Conditions ◽  
Arctic Ice

A mathematical model is used to simulate sea ice conditions observed during May 15–25, 1975 as part of the Arctic Ice Dynamics Joint Experiment. Calculated motions and forces within the region are compared with observed values. Ice velocity and tractions exerted on the upper and lower ice surface compare well with observed values. Results of another calculation using different boundary layer parameters help assess the effect of boundary layer models on the computed ice drift. The calculated strain field does not compare with observed strains well enough to allow prediction of stress in the pack ice. Several sources of error have been identified for future study.

scholarly journals Sea-ice dynamics in the Weddell Sea in winter

1991 ◽  
Vol 15 ◽  
pp. 9-16 ◽  
Author(s):  
Heinrich Hoeber
Keyword(s):  
Sea Ice ◽  
Bulk Viscosity ◽  
Current Data ◽  
Weddell Sea ◽  
Small Scale ◽  
Ice Dynamics ◽  
Sea Ice Dynamics ◽  
Momentum Budget ◽  
Ice Drift

Observations of ice drift received from an array of ARGOS buoys drifting in the Weddell Sea in winter 1986 are described. Wind and current data are also available, permitting derivation of the complete momentum budget including the internal ice stress computed as residuum. It is shown that the variability of forcing both of the atmosphere and of the ocean is large, and that internal ice stress is not negligible; monthly vector averages amount to about half of the wind and water stresses. Coefficients of shear and bulk viscosity are derived according to Hibler's model of ice rheology; they turn out to be negative occasionally, in particular when small-scale forcing of the atmosphere is large.

scholarly journals Brief communication: lack of agreement in remote sensing detection of cyclonic drift caused by Atlantic weather in Antarctic sea ice

2021 ◽  
Author(s):  
Wayne de Jager ◽  
Marcello Vichi
Keyword(s):  
Remote Sensing ◽  
Sea Ice ◽  
Alternative Methods ◽  
Polar Regions ◽  
Sea Ice Concentration ◽  
Sea Ice Extent ◽  
Ice Dynamics ◽  
Antarctic Sea Ice ◽  
Ice Drift ◽  
The Impact

Abstract. Sea-ice extent variability, a measure based on satellite-derived sea ice concentration measurements, has traditionally been used as an essential climate variable to evaluate the impact of climate change on polar regions. However, concentration- based measurements of ice variability do not allow to discriminate the relative contributions made by thermodynamic and dynamic processes, prompting the need to use sea-ice drift products and develop alternative methods to quantify changes in sea ice dynamics that would indicate trends in Antarctic ice characteristics. Here, we present a new method to automate the detection of rotational drift features in Antarctic sea ice at daily timescales using currently available remote sensing ice motion products from EUMETSAT OSI SAF. Results show that there is a large discrepancy in the detection of cyclonic drift features between products, both in terms of intensity and year-to-year distributions, thus diminishing the confidence at which ice drift variability can be further analysed. Product comparisons showed that there was good agreement in detecting anticyclonic drift, and cyclonic drift features were measured to be 1.5–2.2 times more intense than anticyclonic features. The most intense features were detected by the merged product, suggesting that the processing chain used for this product could be injecting additional rotational momentum into the resultant drift vectors. We conclude that it is therefore necessary to better understand why the products lack agreement before further trend analysis of these drift features and their climatic significance can be assessed.

scholarly journals Unexpectedly high ultrafine aerosol concentrations above East Antarctic sea ice

2016 ◽  
Vol 16 (4) ◽  
pp. 2185-2206 ◽  
Author(s):  
R. S. Humphries ◽  
A. R. Klekociuk ◽  
R. Schofield ◽  
M. Keywood ◽  
J. Ward ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Southern Ocean ◽  
Sea Ice ◽  
Radiative Forcing ◽  
Free Troposphere ◽  
Radiative Balance ◽  
Air Masses ◽  
Antarctic Sea Ice ◽  
Ocean Region ◽  
The Antarctic

Abstract. Better characterisation of aerosol processes in pristine, natural environments, such as Antarctica, have recently been shown to lead to the largest reduction in uncertainties in our understanding of radiative forcing. Our understanding of aerosols in the Antarctic region is currently based on measurements that are often limited to boundary layer air masses at spatially sparse coastal and continental research stations, with only a handful of studies in the vast sea-ice region. In this paper, the first observational study of sub-micron aerosols in the East Antarctic sea ice region is presented. Measurements were conducted aboard the icebreaker Aurora Australis in spring 2012 and found that boundary layer condensation nuclei (CN3) concentrations exhibited a five-fold increase moving across the polar front, with mean polar cell concentrations of 1130 cm−3 – higher than any observed elsewhere in the Antarctic and Southern Ocean region. The absence of evidence for aerosol growth suggested that nucleation was unlikely to be local. Air parcel trajectories indicated significant influence from the free troposphere above the Antarctic continent, implicating this as the likely nucleation region for surface aerosol, a similar conclusion to previous Antarctic aerosol studies. The highest aerosol concentrations were found to correlate with low-pressure systems, suggesting that the passage of cyclones provided an accelerated pathway, delivering air masses quickly from the free troposphere to the surface. After descent from the Antarctic free troposphere, trajectories suggest that sea-ice boundary layer air masses travelled equatorward into the low-albedo Southern Ocean region, transporting with them emissions and these aerosol nuclei which, after growth, may potentially impact on the region's radiative balance. The high aerosol concentrations and their transport pathways described here, could help reduce the discrepancy currently present between simulations and observations of cloud and aerosol over the Southern Ocean.

scholarly journals Estimating instantaneous sea-ice dynamics from space using the bi-static radar measurements of Earth Explorer 10 candidate Harmony

2021 ◽  
Vol 15 (7) ◽  
pp. 3101-3118
Author(s):  
Marcel Kleinherenbrink ◽  
Anton Korosov ◽  
Thomas Newman ◽  
Andreas Theodosiou ◽  
Alexander S. Komarov ◽  
...  
Keyword(s):  
Sea Ice ◽  
High Temporal Resolution ◽  
Wave Spectra ◽  
Two Dimensional ◽  
Ice Dynamics ◽  
Sea Ice Dynamics ◽  
Ice Drift ◽  
Sea Ice Drift ◽  
Radar Measurements ◽  
Cross Track

Abstract. This article describes the observation techniques and suggests processing methods to estimate dynamical sea-ice parameters from data of the Earth Explorer 10 candidate Harmony. The two Harmony satellites will fly in a reconfigurable formation with Sentinel-1D. Both will be equipped with a multi-angle thermal infrared sensor and a passive radar receiver, which receives the reflected Sentinel-1D signals using two antennas. During the lifetime of the mission, two different formations will be flown. In the stereo formation, the Harmony satellites will fly approximately 300 km in front and behind Sentinel-1, which allows for the estimation of instantaneous sea-ice drift vectors. We demonstrate that the addition of instantaneous sea-ice drift estimates on top of the daily integrated values from feature tracking have benefits in terms of interpretation, sampling and resolution. The wide-swath instantaneous drift observations of Harmony also help to put high-temporal-resolution instantaneous buoy observations into a spatial context. Additionally, it allows for the extraction of deformation parameters, such as shear and divergence. As a result, Harmony's data will help to improve sea-ice statistics and parametrizations to constrain sea-ice models. In the cross-track interferometry (XTI) mode, Harmony's satellites will fly in close formation with an XTI baseline to be able to estimate surface elevations. This will allow for improved estimates of sea-ice volume and also enables the retrieval of full, two-dimensional swell-wave spectra in sea-ice-covered regions without any gaps. In stereo formation, the line-of-sight diversity allows the inference of swell properties in both directions using traditional velocity bunching approaches. In XTI mode, Harmony's phase differences are only sensitive to the ground-range direction swell. To fully recover two-dimensional swell-wave spectra, a synergy between XTI height spectra and intensity spectra is required. If selected, the Harmony mission will be launched in 2028.

scholarly journals Pack-Ice Drift off East Antarctica and some Implications

1989 ◽  
Vol 12 ◽  
pp. 1-8 ◽  
Author(s):  
Allison Ian
Keyword(s):  
Sea Ice ◽  
Bottom Topography ◽  
Regional Climate ◽  
Qualitative Assessment ◽  
Ocean Bottom ◽  
Ice Dynamics ◽  
Antarctic Sea Ice ◽  
Ice Drift ◽  
Region Data ◽  
Autumn And Winter

Three satellite-tracked data buoys were deployed between 70° and 80°E south of 65°S in February-March 1985. These buoys were subsequently trapped within the expanding seasonal sea ice and drifted with the ice. The buoys measured air temperature and pressure, and water temperatures to 100 m depth. Data from the buoys are used to describe the ice drift and environment within the winter sea-ice zone in this region, both north and south of the Antarctic Divergence. Additional preliminary data from a further six buoys deployed in the same area in March 1987 are also presented. Besides providing information on the broad-scale drift of the ice in the Prydz Bay region, data from the buoys have shown: (i) the important role that ice drift plays in determining the autumn and winter expansion of Antarctic sea ice; (ii) the highly mobile nature of the ice, even hundreds of kilometres from the ice edge; (iii) the role that ocean-bottom topography has in determining ice drift over the continental shelf; and (iv) the modifying influence that an ice cover has on regional climate. A qualitative assessment is made of the relative importance of the major forces driving the ice, although the data are insufficient for a detailed study of the ice dynamics.

Interfacial generation of internal waves and turbulent heat flux due to enhanced inertial motion for deformed sea-ice floe: Preliminary results from MOSAiC expedition

2021 ◽  
Author(s):  
Yusuke Kawaguchi ◽  
Zoe Koenig ◽  
Mario Hoppman ◽  
Daiki Nomura ◽  
Mats Granskog ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Heat Flux ◽  
Sea Ice ◽  
Internal Waves ◽  
Inertial Motion ◽  
Eddy Heat Flux ◽  
Ice Drift ◽  
Ice Floes ◽  
Ocean Boundary ◽  
Perennial Ice

<p>Sea-ice drift becomes most energetic at last moment in summer when refreezing is about to onset. Perennial ice floes, surviving over all seasons, tend to experience a number of deformation events over yearlong drift, with uneven distribution in thickness. Deformed ice floes protrude tall keels into water of ice-ocean boundary, and then stir it up. Consequently, combination of fast ice drift and deformation-experienced perennial ice could be a primary source of momentum/thermal energy for upper waters through propagation of internal waves. In this study, during MOSAiC expedition, we attempted to perform direct observation of wave generation in ice-ocean boundary layer underneath a drifting ice floe in the central Arctic Ocean. Time series of turbulent signals, represented by Reynolds stress <u'w'> and eddy heat flux <w'T'>, were obtained by an eddy covariance system (ECS), coupling a high-frequency (34 Hz) single-point current meter and a temperature sensor. Vertical/temporal properties of near-inertial waves were obtained by a downward-looking ADCP, collocated with ECS on the same ice floe. At same time, a triangle of high-precision GPS systems tracked ice movement to represent mean drift speed, rotation and deformation about the same floe seamlessly in time. Preliminary analyses of those combined data suggested that pronounced signals of inertial motion occurred in early September of 2020 as sheer ice keels dragged underlying waters, stratified by accumulation of melt water. It then allowed occurrence of near-inertial internal waves that tend to be trapped within the interfacial boundary layer, located within top 20 m. At the conference, we will present latest and quantitative knowledges from the MOSAiC expedition.</p>

Farewell to IceBridge: 10 years of polar sea ice remote sensing

2020 ◽  
Author(s):  
Linette Boisvert ◽  
Joseph MacGregor ◽  
Brooke Medley ◽  
Nathan Kurtz ◽  
Ron Kwok ◽  
...  
Keyword(s):  
Sea Ice ◽  
The Arctic ◽  
Ice Thickness ◽  
Sea Ice Thickness ◽  
Antarctic Sea Ice ◽  
Ice Drift ◽  
Laser Altimeters ◽  
Sea Ice Drift ◽  
To Come ◽  
The Antarctic

<p>NASA’s Operation IceBridge (OIB) was a multi-year, multi-platform, airborne mission which took place between 2009-2019. OIB was designed and implemented to continue monitoring the changing sea ice and ice sheets in both the Arctic and Antarctic by ‘bridging the gap’ between NASA’s ICESat (2003–2009) and ICESat-2 (launched September 2018) satellite missions. OIB’s instrument suite most often consisted of laser altimeters, radar sounders, gravimeters and multi-spectral imagers. These instruments were selected to study polar sea ice thickness, ice sheet elevation, snow and ice thickness, surface temperature and bathymetry. With the launch of ICESat-2, the final year of OIB consisted of three campaigns designed to under fly the satellite: 1) the end of the Arctic growth season (spring), 2) during the Arctic summer to capture many different types of melting surfaces, and 3) the Antarctic spring to cover an entirely new area of East Antarctica. Over this ten-year period a coherent picture of Arctic and Antarctic sea ice and snow thickness and other properties have been produced and monitored. Specifically, OIB has changed the community’s perspective of snow on sea ice in the Arctic. Over the decade, OIB has also been used to validate other satellite altimeter missions like ESA’s CryoSat-2. Since the launch of ICESat-2, coincident OIB under flights with the satellite were crucial for measuring sea ice properties. With sea ice constantly in motion, and the differences in OIB aircraft and ICESat-2 ground speed, there can substantial drift in the sea ice pack over the same ground track distance being measured.Therefore, we had to design and implement sea ice drift trajectories based on low level winds measured from the aircraft in flight, adjusting our plane’s path accordingly so we could measure the same sea ice as ICESat-2. This was implemented in both the Antarctic 2018 and Arctic 2019 campaigns successfully. Specifically, the Spring Arctic 2019 campaign allowed for validation of ICESat-2 freeboards with OIB ATM freeboards proving invaluable to the success of ICESat-2 and the future of sea ice research to come from these missions.</p><p> </p>

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