scholarly journals Seasonal dynamics of Totten Ice Shelf controlled by sea ice buttressing

2018 ◽  
Author(s):  
Chad A. Greene ◽  
Duncan A. Young ◽  
David E. Gwyther ◽  
Benjamin K. Galton-Fenzi ◽  
Donald D. Blankenship
Keyword(s):  
Sea Ice ◽  
Seasonal Cycle ◽  
Satellite Image ◽  
Climate Forcing ◽  
Surface Velocity ◽  
Ice Shelf ◽  
Ice Velocity ◽  
Glacier Velocity ◽  
Landfast Sea Ice ◽  
Image Pairs

Abstract. Previous studies of Totten Ice Shelf have employed surface velocity measurements to estimate its mass balance and understand its sensitivities to interannual changes in climate forcing. However, displacement measurements acquired over timescales of days to weeks may not accurately characterize long-term flow rates where ice velocity fluctuates with the seasons. Quantifying annual mass budgets or analyzing interannual changes in ice velocity requires knowing when and where observations of glacier velocity could be aliased by subannual variability. Here, we analyze 16 years of velocity data for Totten Ice Shelf, which we generate at subannual resolution by applying feature tracking algorithms to several hundred satellite image pairs. We identify a seasonal cycle characterized by a spring to autumn speedup of more than 100 m yr−1 close to the ice front. The amplitude of the seasonal cycle diminishes with distance from the open ocean, suggesting the presence of a resistive backstress at the ice front that is strongest in winter. Springtime acceleration precedes summer surface melt and is not attributable to thinning from basal melt. We attribute the onset of ice shelf acceleration each spring to the loss of buttressing from the breakup of seasonal landfast sea ice.

scholarly journals Seasonal dynamics of Totten Ice Shelf controlled by sea ice buttressing

2018 ◽  
Vol 12 (9) ◽  
pp. 2869-2882 ◽  
Author(s):  
Chad A. Greene ◽  
Duncan A. Young ◽  
David E. Gwyther ◽  
Benjamin K. Galton-Fenzi ◽  
Donald D. Blankenship
Keyword(s):  
Sea Ice ◽  
Seasonal Cycle ◽  
Satellite Image ◽  
Back Stress ◽  
Surface Velocity ◽  
Ice Shelf ◽  
Ice Velocity ◽  
Glacier Velocity ◽  
Landfast Sea Ice ◽  
Image Pairs

Abstract. Previous studies of Totten Ice Shelf have employed surface velocity measurements to estimate its mass balance and understand its sensitivities to interannual changes in climate forcing. However, displacement measurements acquired over timescales of days to weeks may not accurately characterize long-term flow rates wherein ice velocity fluctuates with the seasons. Quantifying annual mass budgets or analyzing interannual changes in ice velocity requires knowing when and where observations of glacier velocity could be aliased by subannual variability. Here, we analyze 16 years of velocity data for Totten Ice Shelf, which we generate at subannual resolution by applying feature-tracking algorithms to several hundred satellite image pairs. We identify a seasonal cycle characterized by a spring to autumn speedup of more than 100 m yr−1 close to the ice front. The amplitude of the seasonal cycle diminishes with distance from the open ocean, suggesting the presence of a resistive back stress at the ice front that is strongest in winter. Springtime acceleration precedes summer surface melt and is not attributable to thinning from basal melt. We attribute the onset of ice shelf acceleration each spring to the loss of buttressing from the breakup of seasonal landfast sea ice.

scholarly journals Velocity increases at Cook Glacier, East Antarctica linked to ice shelf loss and a subglacial flood event

2018 ◽  
Author(s):  
Bertie W. J. Miles ◽  
Chris R. Stokes ◽  
Stewart S. R. Jamieson
Keyword(s):  
East Antarctica ◽  
Climate Forcing ◽  
Ice Shelf ◽  
Position Change ◽  
Climate Conditions ◽  
Ocean Climate ◽  
Subglacial Lake ◽  
Bathymetric Data ◽  
Front Position ◽  
Landfast Sea Ice

Abstract. Cook Glacier drains a large proportion of the Wilkes Subglacial Basin in East Antarctica, a region thought to be vulnerable to marine ice sheet instability and with potential to make a significant contribution to sea-level. Despite its importance, there have been very few observations of its longer-term behaviour (e.g. of velocity or changes at its ice front). Here we use a variety of satellite imagery to produce a time-series of ice-front position change from 1947–2017 and ice velocity from 1973–2017. Cook Glacier has two distinct outlets (termed East and West) and we observe the near-complete loss of the Cook West Ice Shelf at some time between 1973 and 1989. This was associated with a doubling of the velocity of Cook West glacier, which may also be linked to previously published reports of inland thinning. The loss of the Cook West Ice Shelf is surprising given that the present-day ocean-climate conditions in the region are not typically associated with catastrophic ice shelf loss. However, we speculate that a more intense ocean-climate forcing in the mid-20th century may have been important in forcing its collapse. Since the loss of the Cook West Ice Shelf, the presence of landfast sea-ice and mélange in the newly formed embayment appears to be important in stabilising the glacier front and enabling periodic advances. We also observe a short-lived increase in velocity of Cook East between 2006 and 2007 which we link to the drainage of subglacial Lake Cook. Taken together, these observations suggest that the velocity, and hence discharge, of Cook Glacier is highly sensitive to changes at its terminus but a more detailed process-based analysis of this potentially vulnerable region requires further oceanic and bathymetric data.

scholarly journals Ice platelets below Weddell Sea landfast sea ice

2015 ◽  
Vol 56 (69) ◽  
pp. 175-190 ◽  
Author(s):  
Mario Hoppmann ◽  
Marcel Nicolaus ◽  
Stephan Paul ◽  
Priska A. Hunkeler ◽  
Günther Heinemann ◽  
...  
Keyword(s):  
Sea Ice ◽  
Volume Fraction ◽  
Weddell Sea ◽  
Ice Shelf ◽  
Platelet Volume ◽  
Local Maxima ◽  
Model Studies ◽  
Warm Surface Water ◽  
Fast Ice ◽  
Landfast Sea Ice

AbstractBasal melt of ice shelves may lead to an accumulation of disc-shaped ice platelets underneath nearby sea ice, to form a sub-ice platelet layer. Here we present the seasonal cycle of sea ice attached to the Ekström Ice Shelf, Antarctica, and the underlying platelet layer in 2012. Ice platelets emerged from the cavity and interacted with the fast-ice cover of Atka Bay as early as June. Episodic accumulations throughout winter and spring led to an average platelet-layer thickness of 4 m by December 2012, with local maxima of up to 10 m. The additional buoyancy partly prevented surface flooding and snow-ice formation, despite a thick snow cover. Subsequent thinning of the platelet layer from December onwards was associated with an inflow of warm surface water. The combination of model studies with observed fast-ice thickness revealed an average ice-volume fraction in the platelet layer of 0.25 ± 0.1. We found that nearly half of the combined solid sea-ice and ice-platelet volume in this area is generated by heat transfer to the ocean rather than to the atmosphere. The total ice-platelet volume underlying Atka Bay fast ice was equivalent to more than one-fifth of the annual basal melt volume under the Ekström Ice Shelf.

scholarly journals Modelling landfast sea ice and its influence on ocean-ice interactions in the area of the Totten Glacier, East Antarctica

2021 ◽  
Author(s):  
Guillian Van Achter ◽  
Thierry Fichefet ◽  
Hugues Goosse ◽  
Charles Pelletier ◽  
Jean Sterlin ◽  
...  
Keyword(s):  
Sea Ice ◽  
Climate Models ◽  
Mixed Layer Depth ◽  
Global Climate Models ◽  
East Antarctica ◽  
Ice Shelf ◽  
Sea Ice Extent ◽  
Coastal Polynya ◽  
Landfast Sea Ice ◽  
The Impact

<p>The Totten Glacier in East Antarctica is of major climate interest because of the large fluctuation of its grounding line and of its potential vulnerability to climate change. The ocean above the continental shelf in front of the Totten ice shelf exhibits large extents of landfast sea ice with low interannual variability. Landfast sea ice is mostly not or sole crudely represented in current climate models. These models are potentially omitting or misrepresenting important effects related to this type of sea ice, such as its influence on coastal polynya locations. Yet, the impact of the landfast sea<br>ice on the ocean – ice shelf interactions is poorly understood. Using a series of high-resolution, regional NEMO-LIM-based experiments including an<br>explicit treatment of ocean – ice shelf interactions over the years 2001-2010, we simulate a realistic landfast sea ice extent in the area of Totten Glacier<br>through a combination of a sea ice tensile strength parameterisation and a grounded iceberg representation. We show that the presence of landfast sea<br>ice impacts seriously both the location of coastal polynyas and the ocean mixed layer depth along the coast, in addition to favouring the intrusion of<br>mixed Circumpolar Deep Water into the ice shelf cavities. Depending on the local bathymetry and the landfast sea ice distribution, landfast sea ice affects ice shelf cavities in different ways, either by increasing the ice melt (+28% for the Moscow University ice shelf) or by reducing its seasonal cycle<br>(+10% in March-May for the Totten ice shelf). This highlights the importance of including an accurate landfast sea ice representation in regional and<br>eventually global climate models</p>

scholarly journals Seasonal control of Petermann Gletscher ice-shelf melt by the ocean's response to sea-ice cover in Nares Strait

2017 ◽  
Vol 63 (238) ◽  
pp. 324-330 ◽  
Author(s):  
E. L. SHROYER ◽  
L. PADMAN ◽  
R. M. SAMELSON ◽  
A. MÜNCHOW ◽  
L. A. STEARNS
Keyword(s):  
Sea Ice ◽  
Mass Loss ◽  
Ocean Circulation ◽  
Greenland Ice Sheet ◽  
Ice Shelf ◽  
Near Surface ◽  
Eastern Side ◽  
Nares Strait ◽  
Landfast Sea Ice ◽  
Basal Melting

AbstractPetermann Gletscher drains ~4% of the Greenland ice sheet (GrIS) area, with ~80% of its mass loss occurring by basal melting of its ice shelf. We use a high-resolution coupled ocean and sea-ice model with a thermodynamic glacial ice shelf to diagnose ocean-controlled seasonality in basal melting of the Petermann ice shelf. Basal melt rates increase by ~20% in summer due to a seasonal shift in ocean circulation within Nares Strait that is associated with the transition from landfast sea ice to mobile sea ice. Under landfast ice, cold near-surface waters are maintained on the eastern side of the strait and within Petermann Fjord, reducing basal melt and insulating the ice shelf. Under mobile sea ice, warm waters are upwelled on the eastern side of the strait and, mediated by local instabilities and eddies, enter Petermann Fjord, enhancing basal melt down to depths of 200 m. The transition between these states occurs rapidly, and seasonal changes within Nares Strait are conveyed into the fjord within the same season. These results suggest that long-term changes in the length of the landfast sea-ice season will substantially alter the structure of Petermann ice shelf and its contribution to GrIS mass loss.

scholarly journals Survey and Mapping of Recent Ice Shelf Changes and Landfast Sea Ice Growth Along the North Coast of Ellesmere Island, NWT, Canada

1986 ◽  
Vol 8 ◽  
pp. 96-99 ◽  
Author(s):  
M.O. Jeffries ◽  
H.V. Serson
Keyword(s):  
Sea Ice ◽  
Ellesmere Island ◽  
North Coast ◽  
Ice Shelf ◽  
Negative Mass ◽  
Ice Shelves ◽  
The North ◽  
Landfast Ice ◽  
Melt Water ◽  
Landfast Sea Ice

Ground and aerial surveys along the north coast of Ellesmere Island confirm that a considerable area of shelf ice remains, although it is not as extensive as it once was due to periodic ice island calvings. However, the lost ice shelf is quickly replaced by landfast sea ice. The sea ice often persists for many years and thickens sufficiently to be considered as the restoration of former ice shelf. The landfast ice quickly assumes an undulating topography, similar to the ice shelves, the development of which is encouraged by melt water and wind action. Even under the present conditions of negative mass balance, the sea ice reaches considerable, undeformed thicknesses. The thick sea ice forming today could be the precursor of an expansion of the ice shelves.

scholarly journals SEASONAL COMPARISON OF VELOCITY OF THE EASTERN TRIBUTARY GLACIERS, AMERY ICE SHELF, ANTARCTICA, USING SAR OFFSET TRACKING

2019 ◽  
Vol IV-2/W5 ◽  
pp. 595-600
Author(s):  
S. D. Jawak ◽  
S. Kumar ◽  
A. J. Luis ◽  
P. H. Pandit ◽  
S. F. Wankhede ◽  
...  
Keyword(s):  
Primary Objective ◽  
Velocity Estimation ◽  
East Antarctica ◽  
Surface Velocity ◽  
Ice Shelf ◽  
Ice Shelves ◽  
Tracking Method ◽  
Amery Ice Shelf ◽  
Glacier Velocity ◽  
Offset Tracking

<p><strong>Abstract.</strong> Antarctica and Greenland are two major Earth’s continental ice shelves which play an important role in influencing Earth’s energy balance through their high albedo. The ice sheets comprise of grounded ice or the continental glaciers and their associated ice shelves. Surface velocity is an important parameter that needs to be monitored to understand the glacier dynamics. Marine terminating glaciers have higher velocity than land terminating glaciers. Therefore, ice shelves are generally observed to have higher velocity as compared to continental glaciers. The focus of this study is Amery ice shelf (AIS) which is the third largest ice shelf located in east Antarctica terminating into the Prydz Bay on the eastern Antarctica. The surface ice-flow velocity of AIS is very high compared to its surrounding glaciers which flows at a rate of 1400&amp;thinsp;m&amp;thinsp;a<sup>&amp;minus;1</sup> and drains about 8% of the Antarctic ice sheet. AIS is fed by different glaciers and ice streams at the head, as well as from the western and eastern side of the ice shelf before it terminates into the ocean. The primary objective of this study was to compute velocity of the eastern tributary glaciers of AIS using SAR from Sentinel-1 data. The secondary objective was to compare the winter and summer velocities of the glaciers for 2017&amp;ndash;2018. The offset tracking method has been applied to the ground range detected (GRD) product obtained from Sentinel-1 satellite. This method is suitable for regions with higher glacier velocity where interferometry is generally affected by the loss of coherence. The offset tracking method works by tracking the features on the basis of another feature and calculates the offset between the two features in the images. Two tributary glaciers near the Clemence massif and another glacier near the Pickering Nunatak feed into this ice shelf from the eastern glacial basin region that drains ice from the American Highland, east Antarctica. The glaciers near the Clemence massif showed low annual velocity which ranged from 100&amp;thinsp;m&amp;thinsp;a<sup>&amp;minus;1</sup> at the head to &amp;sim;300&amp;thinsp;m&amp;thinsp;a<sup>&amp;minus;1</sup> near the end of the glacier, where it merges with AIS. The glaciers flowing near the Pickering Nunatak exhibited moderate velocity ranging from 150&amp;thinsp;m&amp;thinsp;a<sup>&amp;minus;1</sup> at its head and reaching up to 450&amp;thinsp;m&amp;thinsp;a<sup>&amp;minus;1</sup> near the tongue. The summer velocity (March 2018) was observed to be higher than the velocity in winter (July 2017) and the difference between the summer and the winter velocities was found to be between 50&amp;thinsp;m&amp;thinsp;a<sup>&amp;minus;1</sup> and 130&amp;thinsp;m&amp;thinsp;a<sup>&amp;minus;1</sup>. The results for the velocity were obtained at 120&amp;thinsp;m resolution and were compared with the previous MEaSUREs (Making Earth System Data Records for Use in Research Environments) yearly velocity at 450&amp;thinsp;m and 1&amp;thinsp;km resolution provided by National Snow and Ice Data Center portal. The results were evaluated using statistical measure- bias and the accuracy was derived using the root mean square error. The bias did not exceed 20&amp;thinsp;m&amp;thinsp;a<sup>&amp;minus;1</sup> for the three glaciers and the accuracy was observed to be more than 85% for most of the regions. The accuracy of the results suggests that the offset tracking technique is useful for future velocity estimation in the regions of high glacier velocity.</p>

scholarly journals Seasonality of sea ice controls interannual variability of summertime Ω<sub>A</sub> at the ice shelf in the Eastern Weddell Sea – an ocean acidification sensitivity study

2015 ◽  
Vol 12 (2) ◽  
pp. 1653-1687 ◽  
Author(s):  
A. Weeber ◽  
S. Swart ◽  
P. M. S. Monteiro
Keyword(s):  
Surface Water ◽  
Sea Ice ◽  
Primary Production ◽  
Interannual Variability ◽  
Mixed Layer ◽  
Seasonal Cycle ◽  
Weddell Sea ◽  
Ice Shelf ◽  
Saturation State ◽  
Anthropogenic Co2

Abstract. Increasing anthropogenic CO2 is decreasing surface water aragonite saturation state (ΩA), a growing concern for calcifying Euthecosome pteropods and its wider impact on Antarctic ecosystems. However, our understanding of the seasonal cycle and interannual variability of this vulnerable ecosystem remains limited. This study examines surface water ΩA from four consecutive summers in the Eastern Weddell Gyre (EWG) ice shelf region, and investigates the drivers and the role played by the seasonal cycle in the interannual variability of ΩA. Interannual variability in the seasonal phasing and the rate of summer sea ice thaw was found to be the primary factor explaining interannual variability in surface water ΩA. In "optimal" summers when summer sea ice thaw began in late November/early December (2008/2009 and 2010/2011), the summertime increase in ΩA was found to be 1.02, approximately double that from summers when sea ice thaw was delayed to late December (2009/2010 and 2011/2012). We propose that the two critical climate (physical-biogeochemical) sensitivities for ΩA are the timing and the rate of sea ice thaw, which has a direct impact on the mixed layer and the resulting onset and persistence of phytoplankton blooms. The strength of summertime carbonate saturation depends on seasonal changes of sea ice, stratification and primary production. The sensitivity of surface water biogeochemistry in this region to interannual changes in mixed layer – sea ice processes, suggests that future trends in climate and the seasonal cycle of sea ice, combined with rapidly increasing anthropogenic CO2 will likely be a concern for the Antarctic ice shelf ecosystem within the next few decades. If in the future, primary production is reduced and CO2 increased, our results suggest that in the EWG summertime surface water aragonite undersaturation will emerge by the middle of this century.

scholarly journals Velocity increases at Cook Glacier, East Antarctica, linked to ice shelf loss and a subglacial flood event

2018 ◽  
Vol 12 (10) ◽  
pp. 3123-3136 ◽  
Author(s):  
Bertie W. J. Miles ◽  
Chris R. Stokes ◽  
Stewart S. R. Jamieson
Keyword(s):  
East Antarctica ◽  
Climate Forcing ◽  
Ice Shelf ◽  
Position Change ◽  
Climate Conditions ◽  
Ocean Climate ◽  
Subglacial Lake ◽  
Bathymetric Data ◽  
Front Position ◽  
Landfast Sea Ice

Abstract. Cook Glacier drains a large proportion of the Wilkes Subglacial Basin in East Antarctica, a region thought to be vulnerable to marine ice sheet instability and with potential to make a significant contribution to sea level. Despite its importance, there have been very few observations of its longer-term behaviour (e.g. of velocity or changes at its ice front). Here we use a variety of satellite imagery to produce a time series of ice front position change from 1947 to 2017 and ice velocity from 1973 to 2017. Cook Glacier has two distinct outlets (termed East and West), and we observe the near-complete loss of the Cook West Ice Shelf at some time between 1973 and 1989. This was associated with a doubling of the velocity of Cook West Glacier, which may also be linked to previously published reports of inland thinning. The loss of the Cook West Ice Shelf is surprising given that the present-day ocean climate conditions in the region are not typically associated with catastrophic ice shelf loss. However, we speculate that a more intense ocean climate forcing in the mid-20th century may have been important in forcing its collapse. Since the loss of the Cook West Ice Shelf, the presence of landfast sea ice and mélange in the newly formed embayment appears to be important in stabilizing the glacier front and enabling periodic advances. We also show that the last calving event at the larger Cook East Ice Shelf resulted in the retreat of its ice front into a dynamically important portion of the ice shelf and observe a short-lived increase in velocity of Cook East between 2006 and 2007, which we link to the drainage of subglacial Lake Cook. Taken together, these observations suggest that the velocity, and hence discharge, of Cook Glacier is highly sensitive to changes at its terminus, but a more detailed process-based analysis of this potentially vulnerable region requires further oceanic and bathymetric data.

scholarly journals Survey and Mapping of Recent Ice Shelf Changes and Landfast Sea Ice Growth Along the North Coast of Ellesmere Island, NWT, Canada

1986 ◽  
Vol 8 ◽  
pp. 96-99 ◽  
Author(s):  
M.O. Jeffries ◽  
H.V. Serson
Keyword(s):  
Sea Ice ◽  
Ellesmere Island ◽  
North Coast ◽  
Ice Shelf ◽  
Negative Mass ◽  
Ice Shelves ◽  
The North ◽  
Landfast Ice ◽  
Melt Water ◽  
Landfast Sea Ice

Ground and aerial surveys along the north coast of Ellesmere Island confirm that a considerable area of shelf ice remains, although it is not as extensive as it once was due to periodic ice island calvings. However, the lost ice shelf is quickly replaced by landfast sea ice. The sea ice often persists for many years and thickens sufficiently to be considered as the restoration of former ice shelf. The landfast ice quickly assumes an undulating topography, similar to the ice shelves, the development of which is encouraged by melt water and wind action. Even under the present conditions of negative mass balance, the sea ice reaches considerable, undeformed thicknesses. The thick sea ice forming today could be the precursor of an expansion of the ice shelves.

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