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.

scholarly journals Development of glacial lakes and evaluation of related outburst hazard at Adygine glacier complex, Northern Tien Shan

2018 ◽  
Author(s):  
Kristyna Falatkova ◽  
Miroslav Šobr ◽  
Bohumír Janský ◽  
Anton Neureiter ◽  
Wolfgang Schöner
Keyword(s):  
Satellite Image ◽  
Tien Shan ◽  
Glacier Retreat ◽  
Hazard Evaluation ◽  
Glacier Mass Balance ◽  
Mountain Range ◽  
Glacial Lakes ◽  
Glacier Terminus ◽  
Glacier Runoff ◽  
Outburst Hazard

Abstract. Formation and development of glacial lakes in mountain regions is one of the consequences of glacier recession. Such lakes may drain partially or completely when the stability of their dam is disturbed. We presented a case study from Central-Asian mountain range of Tien Shan, a north-oriented tributary valley Adygine, where a glacier retreat resulted in formation of several generations of lakes. The aim of this study was to analyse past development of different types of glacial lakes influenced by the same glacier, to project site's future development, and to evaluate the hazard of individual lakes with an outlook for expected future change. We addressed the problem with a combination of methods, namely bathymetric, geodetic, and geophysical on-site survey, satellite image and DEM analysis, and modelling of glacier runoff evolution. Based on the case of glacial lakes of varied age and type, we demonstrate the significance of glacier ice in lake's development. Lake 3, which is in contact with glacier terminus, has changed rapidly over the last decade, expanding both in area and depth and increasing its volume more than 13 times (7 800 m3 to 106 000 m3). Hydrological connections and routing of glacier meltwater proved to be an important factor as well, since most lakes in the region are drained by subsurface channels. Within the hazard evaluation of lakes, we highlighted the importance of field data which can provide crucial information on lake stability. In our case, the understanding of site's hydrological system and its regime helped to categorise Lake 2 into low outburst hazard, while Lake 1 and Lake 3 were labelled as medium hazard lakes. Further development of the site will be driven mainly by rising air temperature and increasingly negative glacier mass balance. All three scenarios predict a significant glacier area decrease by 2050, specifically leaving 73.2 % (A1B), 62.3 % (A2), and 55.6 % (B1) of the 2012 glacier extent. The glacier retreat will be accompanied by changes in glacier runoff with first peak expected around the year 2020.

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 Exceptional retreat of Novaya Zemlya's marine-terminating outlet glaciers between 2000 and 2013

2017 ◽  
Author(s):  
J. Rachel Carr ◽  
Heather Bell ◽  
Rebecca Killick ◽  
Tom Holt
Keyword(s):  
Sea Ice ◽  
Sea Level Rise ◽  
Sea Level ◽  
Remotely Sensed ◽  
Glacier Retreat ◽  
Remotely Sensed Data ◽  
Novaya Zemlya ◽  
The Past ◽  
Air Temperatures ◽  
The Impact

Abstract. Novaya Zemlya (NVZ) has experienced rapid ice loss and accelerated marine-terminating glacier retreat during the past two decades. However, it is unknown whether this retreat is exceptional longer-term and/or whether it has persisted since 2010. Investigating this is vital, as dynamic thinning may contribute substantially to ice loss from NVZ, but is not currently included in sea level rise predictions. Here, we use remotely sensed data to assess controls on NVZ glacier retreat between the 1973/6 and 2015. Glaciers that terminate into lakes or the ocean receded 3.5 times faster than those that terminate on land. Between 2000 and 2013, retreat rates were significantly higher on marine-terminating outlet glaciers than during the previous 27 years, and we observe widespread slow-down in retreat, and even advance, between 2013 and 2015. There were some common patterns in the timing of glacier retreat, but the magnitude varied between individual glaciers. Rapid retreat between 2000–2013 corresponds to a period of significantly warmer air temperatures and reduced sea ice concentrations, and to changes in the NAO and AMO. We need to assess the impact of this accelerated retreat on dynamic ice losses from NVZ, to accurately quantify its future sea level rise contribution.

scholarly journals Seasonal Food Web Dynamics in the Antarctic Benthos of Tethys Bay (Ross Sea): Implications for Biodiversity Persistence Under Different Seasonal Sea-Ice Coverage

2020 ◽  
Vol 7 ◽  
Author(s):  
Simona Sporta Caputi ◽  
Giulio Careddu ◽  
Edoardo Calizza ◽  
Federico Fiorentino ◽  
Deborah Maccapan ◽  
...  
Keyword(s):  
Sea Ice ◽  
Food Web ◽  
Ross Sea ◽  
Food Web Structure ◽  
Ice Dynamics ◽  
Web Architecture ◽  
Sea Ice Dynamics ◽  
Before And After ◽  
Basal Resources ◽  
Break Up

Determining food web architecture and its seasonal cycles is a precondition for making predictions about Antarctic marine biodiversity under varying climate change scenarios. However, few scientific data concerning Antarctic food web structure, the species playing key roles in web stability and the community responses to changes in sea-ice dynamics are available. Based on C and N stable isotope analysis, we describe Antarctic benthic food webs and the diet of species occurring in shallow waters (Tethys Bay, Ross Sea) before and after seasonal sea-ice break-up. We hypothesized that the increased availability of primary producers (sympagic algae) following sea-ice break-up affects the diet of species and thus food web architecture. Basal resources had distinct isotopic signatures that did not change after sea-ice break-up, enabling a robust description of consumer diets based on Bayesian mixing models. Sympagic algae had the highest δ13C (∼−14‰) and red macroalgae the lowest (∼−37‰). Consumer isotopic niches and signatures changed after sea-ice break-up, reflecting the values of sympagic algae. Differences in food web topology were also observed. The number of taxa and the number of links per taxon were higher before the thaw than after it. After sea-ice break-up, sympagic inputs allowed consumers to specialize on abundant resources at lower trophic levels. Foraging optimization by consumers led to a simpler food web, with lower potential competition and shorter food chains. However, basal resources and Antarctic species such as the bivalve Adamussium colbecki and the sea-urchin Sterechinus neumayeri were central and highly connected both before and after the sea-ice break-up, thus playing key roles in interconnecting species and compartments in the web. Any disturbance affecting these species is expected to have cascading effects on the entire food web. The seasonal break-up of sea ice in Antarctica ensures the availability of resources that are limiting for coastal communities for the rest of the year. Identification of species playing a key role in regulating food web structure in relation to seasonal sea-ice dynamics, which are expected to change with global warming, is central to understanding how these communities will respond to climate change.

scholarly journals Seasonal changes in Arctic sea-ice morphology

2001 ◽  
Vol 33 ◽  
pp. 171-176 ◽  
Author(s):  
Donald K. Perovich ◽  
Jacqueline A. Richter-Menge ◽  
Walter B. Tucker
Keyword(s):  
Sea Ice ◽  
Heat Budget ◽  
Open Water ◽  
Ice Cover ◽  
Arctic Sea Ice ◽  
The Arctic ◽  
Ice Surface ◽  
Arctic Sea ◽  
Dynamic Forcing ◽  
Break Up

AbstractThe morphology of the Arctic sea-ice cover undergoes large changes over an annual cycle. These changes have a significant impact on the heat budget of the ice cover, primarily by affecting the distribution of the solar radiation absorbed in the ice-ocean system. In spring, the ice is snow-covered and ridges are the prominent features. The pack consists of large angular floes, with a small amount of open water contained primarily in linear leads. By the end of summer the ice cover has undergone a major transformation. The snow cover is gone, many of the ridges have been reduced to hummocks and the ice surface is mottled with melt ponds. One surface characteristic that changes little during the summer is the appearance of the bare ice, which remains white despite significant melting. The large floes have broken into a mosaic of smaller, rounded floes surrounded by a lace of open water. Interestingly, this break-up occurs during summer when the dynamic forcing and the internal ice stress are small During the Surface Heat Budget of the Arctic Ocean (SHEBA) field experiment we had an opportunity to observe the break-up process both on a small scale from the ice surface, and on a larger scale via aerial photographs. Floe break-up resulted in large part from thermal deterioration of the ice. The large floes of spring are riddled with cracks and leads that formed and froze during fall, winter and spring. These features melt open during summer, weakening the ice so that modest dynamic forcing can break apart the large floes into many fragments. Associated with this break-up is an increase in the number of floes, a decrease in the size of floes, an increase in floe perimeter and an increase in the area of open water.

Western Canadian Arctic Ringed Seal Organic Contaminant Trends in Relation to Sea Ice Break-Up

2012 ◽  
Vol 46 (8) ◽  
pp. 4427-4433 ◽  
Author(s):  
A. Gaden ◽  
Steve H. Ferguson ◽  
L. Harwood ◽  
H. Melling ◽  
J. Alikamik ◽  
...  
Keyword(s):  
Sea Ice ◽  
Canadian Arctic ◽  
Ringed Seal ◽  
Organic Contaminant ◽  
Break Up

Application of Satellite Remote Sensing Techniques to Quantify Terminus and Ice Mélange Behavior at Helheim Glacier, East Greenland

2014 ◽  
Vol 48 (5) ◽  
pp. 81-91 ◽  
Author(s):  
Steve Foga ◽  
Leigh A. Stearns ◽  
C.J. van der Veen
Keyword(s):  
Remote Sensing ◽  
Sea Ice ◽  
East Greenland ◽  
Object Based Image Analysis ◽  
Glacier Terminus ◽  
Object Based ◽  
Radar Imagery ◽  
Iceberg Calving ◽  
Calving Rate ◽  
Remote Sensing Techniques

AbstractIceberg calving is an efficient mechanism for ice mass loss, and rapidly calving glaciers are often considered to be inherently unstable. However, the physical controls on calving are not well understood. Recent studies hypothesize that the presence of a rigid ice mélange (composed of icebergs, bergy bits, and sea ice) can reduce iceberg calving by providing “backstress” to the terminus. To test this hypothesis we use remote sensing techniques to construct a time series model of calving rate and size and composition of the adjacent ice mélange. We describe a semi-automated routine for expediting the digitization process and illustrate the methods for Helheim Glacier, East Greenland, using 2008 data. Ice velocities of the glacier terminus and ice mélange are derived with feature-tracking software applied to radar imagery, which is successfully tracked year-round. Object-based image analysis (OBIA) is used to inventory icebergs and sea ice within the ice mélange. We find that the model successfully identifies the calving rate and ice mélange response trends associated with seasonal increases in terminus retreat and advance and shows seasonal trends of ice mélange potentially providing seasonal backstress on the glacier terminus.

scholarly journals Glacier meltwater and runoff modelling, Keqicar Baqi glacier,southwestern Tien Shan, China

2007 ◽  
Vol 53 (180) ◽  
pp. 91-98 ◽  
Author(s):  
Yong Zhang ◽  
Shiyin Liu ◽  
Yongjian Ding
Keyword(s):  
Free Surface ◽  
Climate Model ◽  
Regional Climate ◽  
Climate Scenario ◽  
Tien Shan ◽  
Glacier Meltwater ◽  
Glacier Terminus ◽  
Glacier Runoff ◽  
Linear Reservoir ◽  
Projected Changes

AbstractMeltwater and runoff from Keqicar Baqi glacier, a large glacier in the southwestern Tien Shan, northwestern China, are simulated using a modified degree-day model including potential clear- sky direct solar radiation, coupled with a linear reservoir model for the period 1 July to 12 September 2003. There is good agreement between modelled and measured meltwater at ablation stakes and between simulated and observed runoff at the glacier terminus. A reconstruction of glacier meltwater and runoff from an assumed debris-free surface during the study period shows that the effect of the debris layer on glacier meltwater generation crucially affects glacier runoff. The model is also used to calculate glacier runoff given the climate scenario resulting from a doubling of CO2 as projected by the ReCM2 regional climate model. The projected changes in temperature and precipitation vary from 0 to 2.7°C and from 0 to 25%, respectively. Results indicate that glacier runoff increases linearly with temperature over these ranges whether or not the debris layer is taken into consideration. The effect of change in temperature is much more noticeable than that for change in precipitation. Due to the debris layer predominantly covering (and insulating) the ablation area, the response of glacier runoff is less sensitive to temperature increase with a debris-covered surface than with a debris-free surface. Glacier runoff is also markedly reduced when a reduced glacier area is prescribed in the +2.7°C scenario.

scholarly journals A simple parametrization of mélange buttressing for calving glaciers

2021 ◽  
Vol 15 (2) ◽  
pp. 531-545
Author(s):  
Tanja Schlemm ◽  
Anders Levermann
Keyword(s):  
Sea Ice ◽  
Upper Bound ◽  
Ice Sheets ◽  
Analytical Modelling ◽  
Glacier Terminus

Abstract. Both ice sheets in Greenland and Antarctica are discharging ice into the ocean. In many regions along the coast of the ice sheets, the icebergs calve into a bay. If the addition of icebergs through calving is faster than their transport out of the embayment, the icebergs will be frozen into a mélange with surrounding sea ice in winter. In this case, the buttressing effect of the ice mélange can be considerably stronger than any buttressing by mere sea ice would be. This in turn stabilizes the glacier terminus and leads to a reduction in calving rates. Here we propose a simple parametrization of ice mélange buttressing which leads to an upper bound on calving rates and can be used in numerical and analytical modelling.

scholarly journals Impacts of a lengthening open water season on Alaskan coastal communities

2017 ◽  
Author(s):  
Rebecca J. Rolph ◽  
Andrew R. Mahoney ◽  
John Walsh ◽  
Philip A. Loring
Keyword(s):  
Sea Ice ◽  
Open Water ◽  
Severity Index ◽  
Economic Benefits ◽  
Coastal Communities ◽  
Sea Ice Concentration ◽  
Subsistence Hunting ◽  
Break Up ◽  
Indirect Impacts ◽  
The Impact

Abstract. It is often remarked that Arctic coastal communities are on the frontlines of the impacts related to the rapidly diminishing ice pack. These impacts can have direct effects on communities, such as reduced access to subsistence hunting species, or increased wave height and coastal erosion. There are also indirect effects driven by external socioeconomic systems, such as increased maritime activity, which may provide local economic benefits while increasing potential for disruption to subsistence activities. Here, we use the Historical Sea Ice Atlas (HSIA) dataset to assess the potential direct and indirect impacts from sea ice change for selected Alaska communities. The HSIA provides sea ice concentration for the Bering, Chukchi and Beaufort Seas on a 0.25-degree grid for the period 1953–2013. We estimate the timing of freeze-up and break-up, which is reported by local residents to be of critical importance for subsistence hunting activities and food security. We calculate the open water season length and extend the existing timeseries of the Barnett Severity Index (BSI), which assesses the impact of ice conditions on maritime traffic destined for the Beaufort Sea. We find consistent trends toward later freeze-up and earlier break-up, leading to a lengthened open water period. In Utqiavik (formerly Barrow), there is evidence of a navigational regime change in the 1990s when the pack ice edge started to routinely retreat beyond this most northern community.

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