scholarly journals Estimates of Ocean Currents Using a Labrador Sea Ice Model

1983 ◽  
Vol 4 ◽  
pp. 141-146
Author(s):  
T. E. Keliher ◽  
J. S. Foley
Keyword(s):  
Current Data ◽  
Ocean Current ◽  
Labrador Sea ◽  
Data Set ◽  
Model Simulations ◽  
Pack Ice ◽  
Ice Drift ◽  
Ice Concentration ◽  
Fast Ice ◽  
Ice Model

Efforts to develop a dynamical model of Labrador pack ice have been hampered by a lack of input data, especially ocean current data. This work reports the results of approaching this problem in another way, where model simulations are used as a basis for adjusting the input currents to obtain agreement with ice drift data. The ice drift data comes from a period in February 1977 when a ship was fast in the northern Labrador pack. Unfortunately, the ship experienced navigation problems and the direct current observations were suspect. The model simulations bear this out indicating that it would have been very unlikely that the observed currents along with the other forcing terms could lead to the observed ice drift. A climatological current data set gave better agreement and was slightly modified to give the best agreement. This improved data set was used for a short sensitivity test of the rheological specifications of the model. It was found that the ice drift tracks were not very sensitive to the linear viscous stress law but were more sensitive to the parameterization used to reduce ice velocities in areas of high ice concentration and fast ice. Further plans are to use a model with a more realistic rheological component in order to assess its importance in estimating currents.

scholarly journals Estimates of Ocean Currents Using a Labrador Sea Ice Model

1983 ◽  
Vol 4 ◽  
pp. 141-146 ◽  
Author(s):  
T. E. Keliher ◽  
J. S. Foley
Keyword(s):  
Current Data ◽  
Ocean Current ◽  
Labrador Sea ◽  
Data Set ◽  
Model Simulations ◽  
Pack Ice ◽  
Ice Drift ◽  
Ice Concentration ◽  
Fast Ice ◽  
Ice Model

Efforts to develop a dynamical model of Labrador pack ice have been hampered by a lack of input data, especially ocean current data. This work reports the results of approaching this problem in another way, where model simulations are used as a basis for adjusting the input currents to obtain agreement with ice drift data. The ice drift data comes from a period in February 1977 when a ship was fast in the northern Labrador pack. Unfortunately, the ship experienced navigation problems and the direct current observations were suspect. The model simulations bear this out indicating that it would have been very unlikely that the observed currents along with the other forcing terms could lead to the observed ice drift. A climatological current data set gave better agreement and was slightly modified to give the best agreement. This improved data set was used for a short sensitivity test of the rheological specifications of the model. It was found that the ice drift tracks were not very sensitive to the linear viscous stress law but were more sensitive to the parameterization used to reduce ice velocities in areas of high ice concentration and fast ice. Further plans are to use a model with a more realistic rheological component in order to assess its importance in estimating currents.

scholarly journals Studies of the Movement of Coastal Sea Ice Near Prudhoe Bay, Alaska, U.S.A.

1977 ◽  
Vol 19 (81) ◽  
pp. 533-546 ◽  
Author(s):  
W. F. Weeks ◽  
A. Kovacs ◽  
S. J. Mock ◽  
W. B. Tucker ◽  
W. D. Hibler ◽  
...  
Keyword(s):  
Prediction Models ◽  
Stress Transfer ◽  
Short Term ◽  
Laser Measurements ◽  
A Value ◽  
Pack Ice ◽  
Ice Drift ◽  
Coastal Sea ◽  
Fast Ice ◽  
Prudhoe Bay

Abstract During March-May 1976, a combination of laser and radar ranging systems was used to study the motion of both the fast ice and the pack ice near Narwhal and Cross Islands, two barrier islands located 16 and 21 km offshore in the vicinity of Prudhoe Bay, Alaska. Laser measurements of targets on the fast ice near Narwhal Island indicate small net displacements of approximately 1 m over the period of study (71 d) with short-term displacements of up to 40 cm occurring over 3 d periods. The main motion was outward normal to the coast and was believed to be the result of thermal expansion of the ice. The radar records of fast-ice sites farther offshore show a systematic increase in the standard deviation of the displacements as measured parallel to the coast, reaching a value of ±6.6 m at 31 km. The farthest fast-ice sites show short-term displacements of up to 12 m. There are also trends in the records that are believed to be the result of the general warming of the fast ice with time. Radar targets located on the pack ice showed large short-term displacements (up to 2.7 km) but negligible net ice drift along the coast. There was no significant correlation between the movement of the pack and the local wind, suggesting that coastal ice prediction models can only succeed if handled as part of a regional model which incorporates stress transfer through the pack. The apparent fast-ice-pack-ice boundary in the study area was located in 30-35 m of water.

scholarly journals Studies of the Movement of Coastal Sea Ice Near Prudhoe Bay, Alaska, U.S.A.

1977 ◽  
Vol 19 (81) ◽  
pp. 533-546
Author(s):  
W. F. Weeks ◽  
A. Kovacs ◽  
S. J. Mock ◽  
W. B. Tucker ◽  
W. D. Hibler ◽  
...  
Keyword(s):  
Prediction Models ◽  
Stress Transfer ◽  
Short Term ◽  
Laser Measurements ◽  
A Value ◽  
Pack Ice ◽  
Ice Drift ◽  
Coastal Sea ◽  
Fast Ice ◽  
Prudhoe Bay

AbstractDuring March-May 1976, a combination of laser and radar ranging systems was used to study the motion of both the fast ice and the pack ice near Narwhal and Cross Islands, two barrier islands located 16 and 21 km offshore in the vicinity of Prudhoe Bay, Alaska. Laser measurements of targets on the fast ice near Narwhal Island indicate small net displacements of approximately 1 m over the period of study (71 d) with short-term displacements of up to 40 cm occurring over 3 d periods. The main motion was outward normal to the coast and was believed to be the result of thermal expansion of the ice. The radar records of fast-ice sites farther offshore show a systematic increase in the standard deviation of the displacements as measured parallel to the coast, reaching a value of ±6.6 m at 31 km. The farthest fast-ice sites show short-term displacements of up to 12 m. There are also trends in the records that are believed to be the result of the general warming of the fast ice with time.Radar targets located on the pack ice showed large short-term displacements (up to 2.7 km) but negligible net ice drift along the coast. There was no significant correlation between the movement of the pack and the local wind, suggesting that coastal ice prediction models can only succeed if handled as part of a regional model which incorporates stress transfer through the pack. The apparent fast-ice-pack-ice boundary in the study area was located in 30-35 m of water.

scholarly journals Estimation of sea ice parameters from sea ice model with assimilated ice concentration and SST

2018 ◽  
Vol 12 (12) ◽  
pp. 3949-3965 ◽  
Author(s):  
Siva Prasad ◽  
Igor Zakharov ◽  
Peter McGuire ◽  
Desmond Power ◽  
Martin Richard
Keyword(s):  
Sea Ice ◽  
Remote Sensing Data ◽  
Labrador Sea ◽  
Ice Thickness ◽  
Ridge Height ◽  
Ocean Salinity ◽  
Ice Concentration ◽  
The Difference ◽  
Interpolation Analysis ◽  
Ice Model

Abstract. A multi-category numerical sea ice model CICE was used along with data assimilation to derive sea ice parameters in the region of Baffin Bay and Labrador Sea. The assimilation of ice concentration was performed using the data derived from the Advanced Microwave Scanning Radiometer (AMSR-E and AMSR2). The model uses a mixed-layer slab ocean parameterization to compute the sea surface temperature (SST) and thereby to compute the freezing and melting potential of ice. The data from Advanced Very High Resolution Radiometer (AVHRR-only optimum interpolation analysis) were used to assimilate SST. The modelled ice parameters including concentration, ice thickness, freeboard and keel depth were compared with parameters estimated from remote-sensing data. The ice thickness estimated from the model was compared with the measurements derived from Soil Moisture Ocean Salinity – Microwave Imaging Radiometer using Aperture Synthesis (SMOS–MIRAS). The model freeboard estimates were compared with the freeboard measurements derived from CryoSat2. The ice concentration, thickness and freeboard estimates from the model assimilated with both ice concentration and SST were found to be within the uncertainty in the observation except during March. The model-estimated draft was compared with the measurements from an upward-looking sonar (ULS) deployed in the Labrador Sea (near Makkovik Bank). The difference between modelled draft and ULS measurements estimated from the model was found to be within 10 cm. The keel depth measurements from the ULS instruments were compared to the estimates from the model to retrieve a relationship between the ridge height and keel depth.

scholarly journals Some Results from a Linear-Viscous Model of the Arctic Ice Cover

1979 ◽  
Vol 22 (87) ◽  
pp. 293-304 ◽  
Author(s):  
W. D. Hibler ◽  
W. B. Tucker
Keyword(s):  
Local Stress ◽  
Ice Cover ◽  
Current Data ◽  
The Arctic ◽  
Ocean Current ◽  
Drift Model ◽  
Time Period ◽  
Ice Drift ◽  
Non Local ◽  
Arctic Ice

AbstractIn order to assess the effect of non-local stress transferral through the ice cover empirically, a linear viscous model (employing both bulk and shear viscosities) is used to predict drift-rates for one Soviet and two U.S. drifting stations over the time period May 1962 to April 1964. The predictions, based on available atmospheric pressure and ocean-current data, are compared to free-drift results and to observed values. The empirical viscosity values giving the best fit to observations show a pronounced seasonal variation that correlates well with the growth rate of thin ice. Drift predictions, especially long-term net drift results, show drift magnitudes and turning angles to be simulated significantly better by a viscous model than by a free-drift model. The effects of steady currents are shown to be small for velocities averaged over days but significant for averages over years.

scholarly journals Some Results from a Linear-Viscous Model of the Arctic Ice Cover

1979 ◽  
Vol 22 (87) ◽  
pp. 293-304 ◽  
Author(s):  
W. D. Hibler ◽  
W. B. Tucker
Keyword(s):  
Local Stress ◽  
Ice Cover ◽  
Current Data ◽  
The Arctic ◽  
Ocean Current ◽  
Drift Model ◽  
Time Period ◽  
Ice Drift ◽  
Non Local ◽  
Arctic Ice

AbstractIn order to assess the effect of non-local stress transferral through the ice cover empirically, a linear viscous model (employing both bulk and shear viscosities) is used to predict drift-rates for one Soviet and two U.S. drifting stations over the time period May 1962 to April 1964. The predictions, based on available atmospheric pressure and ocean-current data, are compared to free-drift results and to observed values. The empirical viscosity values giving the best fit to observations show a pronounced seasonal variation that correlates well with the growth rate of thin ice. Drift predictions, especially long-term net drift results, show drift magnitudes and turning angles to be simulated significantly better by a viscous model than by a free-drift model. The effects of steady currents are shown to be small for velocities averaged over days but significant for averages over years.

Impact of the Mertz Glacier Tongue calving on the emergence of polynyas in the d'Urville Trough, East Antarctica

2020 ◽  
Author(s):  
Lucile Ricard ◽  
Marie-Noelle Houssais ◽  
Christophe Herbaut ◽  
Alexander Fraser ◽  
Rob Massom ◽  
...  
Keyword(s):  
Sea Ice ◽  
Microwave Remote Sensing ◽  
Sea Ice Concentration ◽  
Glacier Tongue ◽  
Pack Ice ◽  
Ice Concentration ◽  
Ice Conditions ◽  
Fast Ice ◽  
Ice Production ◽  
The Impact

<p> </p><p><br>Passive microwave remote sensing observations and atmospheric data are used to characterize the impact of the Mertz Glacier Tongue (MGT) calving in February 2010 on the sea ice conditions in the D’Urville Trough, East Antarctic shelf (139°E-141°E). The main objective is to determine if conditions for dense shelf water production in this area were possibly influenced by the calving. In particular, we look for the existence of winter polynyas capable of sustaining significant sea ice production, a prerequisite for the formation of dense, saline waters. We show that polynyas in the D'Urville area are part of a complex icescape made of fast ice and drifting pack ice. The seasonal evolution of this icescape has been profoundly modified with the calving of the MGT and opening of new polynyas. Pre-calving and post-calving sea ice concentrations are analyzed to identify major patterns of variability. Examination of the fast ice distribution and atmospheric forcing helps to develop a scenario for the formation of low sea ice concentration regions and their relation to the sea ice fluxes, supporting the conclusion that the role of the Adelie Bank as a barrier to the drift ice may have strengthened after the calving.</p>

scholarly journals Atmosphere–Sea Ice Interactions during a Cyclone Passage Investigated by Using Model Simulations and Measurements

2005 ◽  
Vol 133 (12) ◽  
pp. 3678-3692 ◽  
Author(s):  
S. Dierer ◽  
K. H. Schlünzen ◽  
G. Birnbaum ◽  
B. Brümmer ◽  
G. Müller
Keyword(s):  
Sea Ice ◽  
Ice Cover ◽  
Polar Regions ◽  
Atmospheric Parameters ◽  
Sea Ice Concentration ◽  
Ice Drift ◽  
Ice Concentration ◽  
Simulated Wind ◽  
Stream Model ◽  
Ice Model

Abstract A high-resolution atmosphere–sea ice model is used to investigate the interactions between cyclones and sea ice cover in polar regions. For this purpose, a cyclone passage observed during the 1999 Fram Strait Cyclone Experiment (FRAMZY) is simulated for two consecutive days. The results of the coupled mesoscale transport and stream model–mesoscale sea ice model (METRAS–MESIM) are compared with aircraft and ice drift measurements. With the exception of temperature, all atmospheric parameters are well simulated. Main reasons for discrepancies were found in large differences between the measurements and the forcing data taken from the results of the regional model (REMO). In addition, advection was slightly wrong as a result of a 17° deviation in wind directions. The altogether well simulated wind field is interactively used to force the sea ice model MESIM; results agree well with drift buoy measurements. Average deviations of simulated and measured ice drift are smaller than 8° for direction and smaller than 3.7 cm s−1 for speed, which is less than 10% of the average speed. The simulated ratio between ice drift and wind velocity increases slightly during cyclone passage from 2.6% to 2.9%, a tendency also known from observations. During a 36-h period, the simulated sea ice concentration locally decreases up to 20% in accordance with measurements. A neglect of changing sea ice cover causes a decrease of the heat flux to the atmosphere from 53 to 12 W m−2. The values correspond to averages over the evaluation region (approximately 228 000 km2) and period (36 h). Temperature and humidity are decreased by 2 K and 0.2 g kg−1, respectively, over the ice-covered region. In contrast, the effect on pressure and wind remains small, probably because the cyclone does not move in the vicinity of the ice edge.

scholarly journals The distribution and formative processes of latent-heat polynyas in East Antarctica

1998 ◽  
Vol 27 ◽  
pp. 420-426 ◽  
Author(s):  
R. A. Massom ◽  
P.T. Harris ◽  
Kelvin J. Michael ◽  
M.J. Potter
Keyword(s):  
Open Water ◽  
East Antarctica ◽  
Emperor Penguin ◽  
Spatial And Temporal Variability ◽  
Areal Extent ◽  
Study Region ◽  
Pack Ice ◽  
Ice Concentration ◽  
Fast Ice ◽  
Microwave Imager

A study of polynya characteristics in East Antarctica was undertaken using ice concentrations derived from special sensor microwave/imager data for the period July 1987-August 1994. The areas of polynyas were defined as having an ice concentration ≤75%. The analysis revealed a total of 28 coastal polynyas within the study region. The spatial and temporal variability in areal extent was quantified. The timing of mean maximum areal extent varied from June to October. The bathymetry and wind regime at each polynya site was examined to gauge the relative importance of these parameters in polynya formation and maintenance. In 20 locations, shallow banks and shoals form grounding zones for icebergs and anchoring sites for fast ice, which form barriers to the predominantly westward drift of the pack ice; elsewhere north-south coastal protrusions or alignments form similar barriers. The subsequent removal of newly formed sea ice from the lee of such barriers by katabatic and synoptic winds maintains areas of reduced ice concentration and open water. Very few coastal polynyas are attributed solely to katabatic outflow. The combined influence of bathymetry, topography and winds is responsible for the characteristics of the majority of polynyas. Many were considered to be marginal, characterised by occasional periods when the ice concentration falls below 75%. An analysis of annual winter totals of areas with ice concentrations < 75% shows no trends in total polynya areal extent over the period 1987-94. Known locations of emperor penguin (Aptenodytes forsteri) rookeries were also found to be associated with the locations of coastal polynyas.

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