scholarly journals Simultaneous disintegration of outlet glaciers in Porpoise Bay (Wilkes Land), East Antarctica, driven by sea ice break-up

2017 ◽  
Vol 11 (1) ◽  
pp. 427-442 ◽  
Author(s):  
Bertie W. J. Miles ◽  
Chris R. Stokes ◽  
Stewart S. R. Jamieson
Keyword(s):  
Sea Ice ◽  
East Antarctica ◽  
High Temporal Resolution ◽  
Ice Flow ◽  
Envisat Asar ◽  
Glacier Terminus ◽  
Wilkes Land ◽  
Break Up ◽  
Atmospheric Circulation Anomalies ◽  
Landfast Sea Ice

Abstract. The floating ice shelves and glacier tongues which fringe the Antarctic continent are important because they help buttress ice flow from the ice sheet interior. Dynamic feedbacks associated with glacier calving have the potential to reduce buttressing and subsequently increase ice flow into the ocean. However, there are few high temporal resolution studies on glacier calving, especially in East Antarctica. Here we use ENVISAT ASAR wide swath mode imagery to investigate monthly glacier terminus change across six marine-terminating outlet glaciers in Porpoise Bay (76° S, 128° E), Wilkes Land (East Antarctica), between November 2002 and March 2012. This reveals a large near-simultaneous calving event in January 2007, resulting in a total of  ∼  2900 km2 of ice being removed from glacier tongues. We also observe the start of a similar large near-simultaneous calving event in March 2016. Our observations suggest that both of these large calving events are driven by the break-up of the multi-year sea ice which usually occupies Porpoise Bay. However, these break-up events appear to have been driven by contrasting mechanisms. We link the 2007 sea ice break-up to atmospheric circulation anomalies in December 2005 weakening the multi-year sea ice through a combination of surface melt and a change in wind direction prior to its eventual break-up in January 2007. In contrast, the 2016 break-up event is linked to the terminus of Holmes (West) Glacier pushing the multi-year sea ice further into the open ocean, making the sea ice more vulnerable to break-up. In the context of predicted future warming and the sensitivity of sea ice to changes in climate, our results highlight the importance of interactions between landfast sea ice and glacier tongue stability in East Antarctica.

scholarly journals Simultaneous disintegration of outlet glaciers in Porpoise Bay (Wilkes Land), East Antarctica, and the long-term speed-up of Holmes Glacier

2016 ◽  
Author(s):  
B. W. J. Miles ◽  
C. R. Stokes ◽  
S. S. R. Jamieson
Keyword(s):  
Sea Ice ◽  
East Antarctica ◽  
High Temporal Resolution ◽  
Ice Flow ◽  
Outlet Glacier ◽  
Ice Shelves ◽  
Glacier Terminus ◽  
Wilkes Land ◽  
Speed Up

Abstract. The floating ice shelves and glacier tongues which fringe the Antarctic continent are important because they help buttress ice flow from the ice sheet interior. Dynamic feedbacks associated with glacier calving have the potential to reduce buttressing and subsequently increase ice flow into the ocean. However, there are few high temporal resolution studies on glacier calving, especially in East Antarctica. Here we use remote sensing to investigate monthly glacier terminus change across six marine-terminating outlet glaciers in Porpoise Bay (−76° S, 128° E), Wilkes Land (East Antarctica), between November 2002 and March 2012. This reveals a large simultaneous calving event in January 2007, resulting in a total of ~ 2900 km2 of ice being removed from glacier tongues. Our observations suggest that sea-ice must be removed from glacier termini for any form of calving to take place, and we link this major calving event to a rapid break-up of the multi-year sea-ice which usually occupies Porpoise Bay. Using sea-ice concentrations as a proxy for glacier calving, and by analysing available satellite imagery stretching back to 1963, we reconstruct the long-term calving activity of the largest glacier in Porpoise Bay: Holmes (West) Glacier. This reveals that its present-day velocity (~ 1450 m a−1) is approximately 50 % faster than between 1963 and 1973 (~ 900 m a−1). We also observed the start of a large calving event in Porpoise Bay in March 2016 that is consistent with our reconstructions of the periodicity of major calving events. These results highlight the importance of sea-ice in modulating outlet glacier calving and velocity in East Antarctica.

scholarly journals Recent variations in the terminus position, ice velocity and surface elevation of Langhovde Glacier, East Antarctica

2014 ◽  
Vol 26 (6) ◽  
pp. 636-645 ◽  
Author(s):  
Takehiro Fukuda ◽  
Shin Sugiyama ◽  
Takanobu Sawagaki ◽  
Kazuki Nakamura
Keyword(s):  
Sea Ice ◽  
Flow Velocity ◽  
Stable Condition ◽  
Field Measurements ◽  
East Antarctica ◽  
Surface Elevation ◽  
Ice Flow ◽  
Glacier Terminus ◽  
Ice Conditions ◽  
Ice Velocity

AbstractTo improve the understanding of the mechanism driving recent changes in outlet glaciers in East Antarctica, we measured changes in the terminus position, ice flow velocity and surface elevation of the Langhovde Glacier located on the Sôya Coast. From satellite images from 2000–12 and field measurements taken in 2012 the glacier terminus position and flow velocity showed little change between 2003 and 2007. After this quiescent period, the glacier progressively advanced by 380 m and the flow velocity increased near the calving front by 10 m a-1 from 2007–10. No significant change was observed in surface elevation during the study period. The changes in the terminus position and flow velocity imply a reduction in the calving rate from 93 m a-1 (2003–07) to 16 m a-1 (2007–10). This suggests that calving was inhibited by stable sea ice conditions in the ocean. Theses results indicate that the Langhovde Glacier was in a relatively stable condition during the study period, and its terminus position was controlled by the rate of calving under the influence of sea ice conditions.

scholarly journals Pan–ice-sheet glacier terminus change in East Antarctica reveals sensitivity of Wilkes Land to sea-ice changes

2016 ◽  
Vol 2 (5) ◽  
pp. e1501350 ◽  
Author(s):  
Bertie W. J. Miles ◽  
Chris R. Stokes ◽  
Stewart S. R. Jamieson
Keyword(s):  
Sea Ice ◽  
Drainage Basin ◽  
Ice Sheet ◽  
East Antarctica ◽  
Position Change ◽  
Outlet Glacier ◽  
Ocean Stratification ◽  
Glacier Terminus ◽  
Warm Deep Water ◽  
Wilkes Land

The dynamics of ocean-terminating outlet glaciers are an important component of ice-sheet mass balance. Using satellite imagery for the past 40 years, we compile an approximately decadal record of outlet-glacier terminus position change around the entire East Antarctic Ice Sheet (EAIS) marine margin. We find that most outlet glaciers retreated during the period 1974–1990, before switching to advance in every drainage basin during the two most recent periods, 1990–2000 and 2000–2012. The only exception to this trend was in Wilkes Land, where the majority of glaciers (74%) retreated between 2000 and 2012. We hypothesize that this anomalous retreat is linked to a reduction in sea ice and associated impacts on ocean stratification, which increases the incursion of warm deep water toward glacier termini. Because Wilkes Land overlies a large marine basin, it raises the possibility of a future sea level contribution from this sector of East Antarctica.

scholarly journals Formation, flow and break-up of ephemeral ice mélange at LeConte Glacier and Bay, Alaska

2020 ◽  
Vol 66 (258) ◽  
pp. 577-590
Author(s):  
Jason M. Amundson ◽  
Christian Kienholz ◽  
Alexander O. Hager ◽  
Rebecca H. Jackson ◽  
Roman J. Motyka ◽  
...  
Keyword(s):  
Sea Ice ◽  
Glacier Retreat ◽  
Glacier Terminus ◽  
Glacier Runoff ◽  
Oceanographic Data ◽  
Break Up ◽  
Frontal Ablation

AbstractIce mélange has been postulated to impact glacier and fjord dynamics through a variety of mechanical and thermodynamic couplings. However, observations of these interactions are very limited. Here, we report on glaciological and oceanographic data that were collected from 2016 to 2017 at LeConte Glacier and Bay, Alaska, and serendipitously captured the formation, flow and break-up of ephemeral ice mélange. Sea ice formed overnight in mid-February. Over the subsequent week, the sea ice and icebergs were compacted by the advancing glacier terminus, after which the ice mélange flowed quasi-statically. The presence of ice mélange coincided with the lowest glacier velocities and frontal ablation rates in our record. In early April, increasing glacier runoff and the formation of a sub-ice-mélange plume began to melt and pull apart the ice mélange. The plume, outgoing tides and large calving events contributed to its break-up, which took place over a week and occurred in pulses. Unlike observations from elsewhere, the loss of ice mélange integrity did not coincide with the onset of seasonal glacier retreat. Our observations provide a challenge to ice mélange models aimed at quantifying the mechanical and thermodynamic couplings between ice mélange, glaciers and fjords.

The variability of surface radiation fluxes over landfast sea ice near Zhongshan station, east Antarctica during austral spring

2017 ◽  
Vol 12 (8) ◽  
pp. 860-877 ◽  
Author(s):  
Lejiang Yu ◽  
Qinghua Yang ◽  
Mingyu Zhou ◽  
Donald H. Lenschow ◽  
Xianqiao Wang ◽  
...  
Keyword(s):  
Sea Ice ◽  
East Antarctica ◽  
Surface Radiation ◽  
Austral Spring ◽  
Zhongshan Station ◽  
Radiation Fluxes ◽  
Landfast Sea Ice

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>

Observation and thermodynamic modeling of the influence of snow cover on landfast sea ice thickness in Prydz Bay, East Antarctica

2020 ◽  
Author(s):  
Jiechen Zhao ◽  
Bin Cheng ◽  
Timo Vihma ◽  
Qinghua Yang ◽  
Fengming Hui ◽  
...  
Keyword(s):  
Sea Ice ◽  
Snow Cover ◽  
Annual Cycle ◽  
Snow Depth ◽  
Snow Accumulation ◽  
East Antarctica ◽  
Prydz Bay ◽  
Ice Thickness ◽  
Sea Ice Thickness ◽  
Landfast Sea Ice

<p>The observed snow depth and ice thickness on landfast sea ice in Prydz Bay, East Antarctica, were used to determine the role of snow in (a) the annual cycle of sea ice thickness at a fixed location (SIP) where snow usually blows away after snowfall and (b) early summer sea ice thickness within the transportation route surveys (TRS) domain farther from coast, where annual snow accumulation is substantial. The annual mean snow depth and maximum ice thickness had a negative relationship (r = −0.58, p < 0.05) at SIP, indicating a primary insulation effect of snow on ice thickness. However, in the TRS domain, this effect was negligible because snow contributes to ice thickness. A one-dimensional thermodynamic sea ice model, forced by local weather observations, reproduced the annual cycle of ice thickness at SIP well. During the freeze season, the modeled maximum difference of ice thickness using different snowfall scenarios ranged from 0.53–0.61 m. Snow cover delayed ice surface and ice bottom melting by 45 and 24 days, respectively. The modeled snow ice and superimposed ice accounted for 4–23% and 5–8% of the total maximum ice thickness on an annual basis in the case of initial ice thickness ranging from 0.05–2 m, respectively.</p>

Hydrological and Kinematic Precursors of Iceberg Calving at Petermann Glacier in Northern Greenland Observed High-temporal Resolution Sentinel-2 Images

2020 ◽  
Author(s):  
Daan Li ◽  
Liming Jiang
Keyword(s):  
Remote Sensing ◽  
High Resolution ◽  
Sea Ice ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Flow Speed ◽  
High Temporal Resolution ◽  
Backscatter Coefficient ◽  
Ice Flow ◽  
Iceberg Calving

<p>   The Greenland ice sheet is currently contributing to global sea level at an approximate rate of 0.8 mm/yr. Ice mass loss of Greenland is primarily due to both thinning and retreat of outlet glaciers. For enhanced calving events, detail dynamics characteristics of hydrological and kinematic precursors and underlying mechanisms which control the development of ice calving remain poorly understood, especially in the absence of high-resolution remote sensing observations. On July 26 2017, a calving event took place along a pre-existing rift in Petermann glacier, northern Greenland, which removed partly of the glacier tongue and formed a tabular iceberg 5 km long. In this study, we used high-temporal satellite remote sensing data to detect changes in ice-flow speed, melt ponds and ice mélange during May and July. These hydrological and kinematic dynamics derived from Sentinel-1/2 satellite images with sub-weekly acquisition repeat cycles can be utilized as retreat precursors to characterize the detailed calving process. Moreover, the stress field and analytical damage solution were calculated by coupling the remote sensing observations with SSA ice sheet model to explain the dynamics mechanism. Our preliminary results show that the ice speed in dense observation reached to 30 m/d on the eve of the calving, which is roughly 10 times quicker than usual ice velocity. Additionally, there exited obviously abnormal stress distribution in crack region. And the landfast sea ice and ice mélange transformed into open water that the  backscatter coefficient decreased to 28 dB. The extent of melt pond reached the peak about 30 square kilometers coverage in duration month of calving event. It is inferred that this calving event of Petermann glacier may be related to weakening of sea ice and ice mélange lost the buttressing for ice glacier terminate, tributary glacier extrusion, related with meltwater infiltrated crevasses. Therefore, dense remote sensing observations and numerical modeling in ice flow system make it possible for early waring and projecting glacier calving in the future.</p><p>Key words: Iceberg Calving Precursors, Petermann Glacier, High Resolution Remote Sensing, SSA modeling</p>

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