Measured properties of the Antarctic ice sheet derived from the SCAR Antarctic digital database

AbstractThe completion of the SCAR Antarctic digital database (ADD) has provided a new basis for statistical calculations for Antarctica: data-sets are available at the scale of the original source material, and generalised to 1:1,000,000, 1:3,000,000, 1:10,000,000, and 1:30,000,000. The new descriptive statistics presented are based on the ADD 1:1,000,000 data-set since this is the largest scale at which source maps provided complete cover of the coastline and ice-free areas. The statistics include the total length and proportions of coastline types and the total area of Antarctica with the proportions of its constituent feature types. The areas of the Ross and Filchner-Ronne ice shelves have also been computed. Whilst the total area of Antarctica has remained static compared with previous studies, the relative proportions of coastline types and constituent feature types within the total area show significant changes. In particular the calculated area of ice-free ground is only approximately one-seventh of that often quoted from previous studies. The changes reported result from improved mapping, reinterpretation of data, and actual changes of coastline.

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A global high-resolution data set of ice sheet topography, cavity geometry and ocean bathymetry

10.5194/essd-2016-3 ◽

2016 ◽

Cited By ~ 4

Author(s):

Janin Schaffer ◽

Ralph Timmermann ◽

Jan Erik Arndt ◽

Steen Savstrup Kristensen ◽

Christoph Mayer ◽

...

Keyword(s):

High Resolution ◽

Continental Shelf ◽

Ice Sheet ◽

The Arctic ◽

Global Ocean ◽

Data Set ◽

Antarctic Ice Sheet ◽

Ice Shelves ◽

Surface Topographies ◽

The Antarctic

Abstract. The ocean plays an important role in modulating the mass balance of the polar ice sheets by interacting with the ice shelves in Antarctica and with the marine-terminating outlet glaciers in Greenland. Given that the flux of warm water onto the continental shelf and into the sub-ice cavities is steered by complex bathymetry, a detailed topography data set is an essential ingredient for models that address ice-ocean interaction. We followed the spirit of the global RTopo-1 data set and compiled consistent maps of global ocean bathymetry, upper and lower ice surface topographies and global surface height on a spherical grid with now 30-arc seconds resolution. We used the General Bathymetric Chart of the Oceans (GEBCO_2014) as the backbone and added the International Bathymetric Chart of the Arctic Ocean version 3 (IBCAOv3) and the International Bathymetric Chart of the Southern Ocean (IBCSO) version 1. While RTopo-1 primarily aimed at a good and consistent representation of the Antarctic ice sheet, ice shelves and sub-ice cavities, RTopo-2 now also contains ice topographies of the Greenland ice sheet and outlet glaciers. In particular, we aimed at a good representation of the fjord and shelf bathymetry surrounding the Greenland continent. We corrected data from earlier gridded products in the areas of Petermann Glacier, Hagen Bræ and Sermilik Fjord assuming that sub-ice and fjord bathymetries roughly follow plausible Last Glacial Maximum ice flow patterns. For the continental shelf off northeast Greenland and the floating ice tongue of Nioghalvfjerdsfjorden Glacier at about 79° N, we incorporated a high-resolution digital bathymetry model considering original multibeam survey data for the region. Radar data for surface topographies of the floating ice tongues of Nioghalvfjerdsfjorden Glacier and Zachariæ Isstrøm have been obtained from the data centers of Technical University of Denmark (DTU), Operation Icebridge (NASA/NSF) and Alfred Wegener Institute (AWI). For the Antarctic ice sheet/ice shelves, RTopo-2 largely relies on the Bedmap-2 product but applies corrections for the geometry of Getz, Abbot and Fimbul ice shelf cavities. The data set is available in full and in regional subsets in NetCDF format from the PANGAEA database at https://doi.pangaea.de/10.1594/PANGAEA.856844.

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A global, high-resolution data set of ice sheet topography, cavity geometry, and ocean bathymetry

Earth System Science Data ◽

10.5194/essd-8-543-2016 ◽

2016 ◽

Vol 8 (2) ◽

pp. 543-557 ◽

Cited By ~ 63

Author(s):

Janin Schaffer ◽

Ralph Timmermann ◽

Jan Erik Arndt ◽

Steen Savstrup Kristensen ◽

Christoph Mayer ◽

...

Keyword(s):

High Resolution ◽

Continental Shelf ◽

Ice Sheet ◽

The Arctic ◽

Global Ocean ◽

Data Set ◽

Antarctic Ice Sheet ◽

Ice Shelves ◽

Surface Topographies ◽

The Antarctic

Abstract. The ocean plays an important role in modulating the mass balance of the polar ice sheets by interacting with the ice shelves in Antarctica and with the marine-terminating outlet glaciers in Greenland. Given that the flux of warm water onto the continental shelf and into the sub-ice cavities is steered by complex bathymetry, a detailed topography data set is an essential ingredient for models that address ice–ocean interaction. We followed the spirit of the global RTopo-1 data set and compiled consistent maps of global ocean bathymetry, upper and lower ice surface topographies, and global surface height on a spherical grid with now 30 arcsec grid spacing. For this new data set, called RTopo-2, we used the General Bathymetric Chart of the Oceans (GEBCO_2014) as the backbone and added the International Bathymetric Chart of the Arctic Ocean version 3 (IBCAOv3) and the International Bathymetric Chart of the Southern Ocean (IBCSO) version 1. While RTopo-1 primarily aimed at a good and consistent representation of the Antarctic ice sheet, ice shelves, and sub-ice cavities, RTopo-2 now also contains ice topographies of the Greenland ice sheet and outlet glaciers. In particular, we aimed at a good representation of the fjord and shelf bathymetry surrounding the Greenland continent. We modified data from earlier gridded products in the areas of Petermann Glacier, Hagen Bræ, and Sermilik Fjord, assuming that sub-ice and fjord bathymetries roughly follow plausible Last Glacial Maximum ice flow patterns. For the continental shelf off Northeast Greenland and the floating ice tongue of Nioghalvfjerdsfjorden Glacier at about 79° N, we incorporated a high-resolution digital bathymetry model considering original multibeam survey data for the region. Radar data for surface topographies of the floating ice tongues of Nioghalvfjerdsfjorden Glacier and Zachariæ Isstrøm have been obtained from the data centres of Technical University of Denmark (DTU), Operation Icebridge (NASA/NSF), and Alfred Wegener Institute (AWI). For the Antarctic ice sheet/ice shelves, RTopo-2 largely relies on the Bedmap-2 product but applies corrections for the geometry of Getz, Abbot, and Fimbul ice shelf cavities. The data set is available in full and in regional subsets in NetCDF format from the PANGAEA database at doi:10.1594/PANGAEA.856844.

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A gridded data set of upper-ocean hydrographic properties in the Weddell Gyre obtained by objective mapping of Argo float measurements

Earth System Science Data ◽

10.5194/essd-8-15-2016 ◽

2016 ◽

Vol 8 (1) ◽

pp. 15-40 ◽

Cited By ~ 13

Author(s):

K. A. Reeve ◽

O. Boebel ◽

T. Kanzow ◽

V. Strass ◽

G. Rohardt ◽

...

Keyword(s):

Data Availability ◽

Global Ocean ◽

Data Sets ◽

Data Set ◽

Ice Shelves ◽

Argo Float ◽

Weddell Gyre ◽

Mass Properties ◽

Composite Maps ◽

The Antarctic

Abstract. The Weddell Gyre plays a crucial role in the modification of climate by advecting heat poleward to the Antarctic ice shelves and by regulating the density of water masses that feed the lowest limb of the global ocean overturning circulation. However, our understanding of Weddell Gyre water mass properties is limited to regions of data availability, primarily along the Prime Meridian. The aim of this paper is to provide a data set of the upper water column properties of the entire Weddell Gyre. Objective mapping was applied to Argo float data in order to produce spatially gridded, time-composite maps of temperature and salinity for fixed pressure levels ranging from 50 to 2000 dbar, as well as temperature, salinity and pressure at the level of the sub-surface temperature maximum. While the data are currently too limited to incorporate time into the gridded structure, the data are extensive enough to produce maps of the entire region across three time-composite periods (2001–2005, 2006–2009 and 2010–2013), which can be used to determine how representative conclusions drawn from data collected along general RV transect lines are on a gyre scale perspective. The work presented here represents the technical prerequisite for addressing climatological research questions in forthcoming studies. The data sets are available in netCDF format at doi:10.1594/PANGAEA.842876.

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Antarctic ice sheet response to upper-bound scenarios

10.5194/egusphere-egu21-11823 ◽

2021 ◽

Author(s):

Sainan Sun ◽

Frank Pattyn

Keyword(s):

Sea Level Rise ◽

Sea Level ◽

Upper Bound ◽

Ice Sheet ◽

Climate Forcing ◽

Ice Shelf ◽

Antarctic Ice Sheet ◽

Ice Shelves ◽

Basal Sliding ◽

The Antarctic

Mass loss of the Antarctic ice sheet contributes the largest uncertainty of future sea-level rise projections. Ice-sheet model predictions are limited by uncertainties in climate forcing and poor understanding of processes such as ice viscosity. The Antarctic BUttressing Model Intercomparison Project (ABUMIP) has investigated the 'end-member' scenario, i.e., a total and sustained removal of buttressing from all Antarctic ice shelves, which can be regarded as the upper-bound physical possible, but implausible contribution of sea-level rise due to ice-shelf loss. In this study, we add successive layers of &#8216;realism&#8217; to the ABUMIP scenario by considering sustained regional ice-shelf collapse and by introducing ice-shelf regrowth after collapse with the inclusion of ice-sheet and ice-shelf damage (Sun et al., 2017). Ice shelf regrowth has the ability to stabilize grounding lines, while ice shelf damage may reinforce ice loss. In combination with uncertainties from basal sliding and ice rheology, a more realistic physical upperbound to ice loss is sought. Results are compared in the light of other proposed mechanisms, such as MICI due to ice cliff collapse.

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Driving Forces of Circum-Antarctic Glacier and Ice Shelf Front Retreat over the Last Two Decades

10.5194/tc-2020-224 ◽

2020 ◽

Cited By ~ 1

Author(s):

Celia A. Baumhoer ◽

Andreas J. Dietz ◽

Christof Kneisel ◽

Heiko Paeth ◽

Claudia Kuenzer

Keyword(s):

Sea Ice ◽

Surface Temperature ◽

Sea Surface Temperature ◽

Air Temperature ◽

Environmental Variables ◽

Sea Surface ◽

Ice Shelf ◽

Antarctic Ice Sheet ◽

Ice Shelves ◽

The Antarctic

Abstract. The safety band of Antarctica consisting of floating glacier tongues and ice shelves buttresses ice discharge of the Antarctic Ice Sheet. Recent disintegration events of ice shelves and glacier retreat indicate a weakening of this important safety band. Predicting calving front retreat is a real challenge due to complex ice dynamics in a data-scarce environment being unique for each ice shelf and glacier. We explore to what extent easy to access remote sensing and modelling data can help to define environmental conditions leading to calving front retreat. For the first time, we present a circum-Antarctic record of glacier and ice shelf front retreat over the last two decades in combination with environmental variables such as air temperature, sea ice days, snowmelt, sea surface temperature and wind direction. We find that the Antarctic ice sheet area shrank 29,618 ± 29 km2 in extent between 1997–2008 and gained an area of 7,108 ± 144.4 km2 between 2009 and 2018. Retreat concentrated along the Antarctic Peninsula and West Antarctica including the biggest ice shelves Ross and Ronne. Glacier and ice shelf retreat comes along with one or several changes in environmental variables. Decreasing sea ice days, intense snow melt, weakening easterlies and relative changes in sea surface temperature were identified as enabling factors for retreat. In contrast, relative increases in air temperature did not correlate with calving front retreat. To better understand drivers of glacier and ice shelf retreat it is of high importance to analyse the magnitude of basal melt through the intrusion of warm Circumpolar Deep Water (CDW) driven by strengthening westerlies and to further assess surface hydrology processes such as meltwater ponding, runoff and lake drainage.

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Descriptive Statistics and Cross-National Comparisons of Arctic Power Projection

Perils of Plenty ◽

10.1093/oso/9780190078249.003.0004 ◽

2020 ◽

pp. 56-80

Author(s):

Jonathan N. Markowitz

Keyword(s):

Descriptive Statistics ◽

The Arctic ◽

Military Force ◽

Data Sets ◽

Data Set ◽

Power Projection ◽

Resource Rents ◽

Before And After ◽

Military Activity ◽

Events Data

Chapter 4 employs data from three new data sets, the Arctic Military Activity Events Data Set, the Arctic Bases Data Set, and the Icebreaker and Ice-Hardened Warships Data Set. These new data enable a systematic comparison of each state’s Arctic military forces and deployments before and after the 2007 climate shock. The data offer a corrective to both sensationalist media accounts that suggest that all states are scrambling to fight over Arctic resources and those who downplay real changes in states’ Arctic military capabilities and presence. Confirming Rent-Addition’s Theory’s predictions, the descriptive statistical comparisons reveal that the states that were most economically dependent on resource rents, Norway and Russia, were the most willing to back their claims by projecting military force to disputed areas and investing in Arctic bases, ice-hardened warships, and icebreakers.

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Modelling the long-term response of the Antarctic ice sheet to global warming

Annals of Glaciology ◽

10.3189/1998aog27-1-161-168 ◽

1998 ◽

Vol 27 ◽

pp. 161-168 ◽

Cited By ~ 29

Author(s):

Roland C. Warner ◽

W.Κ. Budd

Keyword(s):

Global Warming ◽

Mass Loss ◽

Ice Sheet ◽

Ice Shelf ◽

Antarctic Ice Sheet ◽

Ice Shelves ◽

Basal Melting ◽

The Antarctic ◽

Term Response

The primary effects of global warming on the Antarctic ice sheet can involve increases in surface melt for limited areas at lower elevations, increases in net accumulation, and increased basal melting under floating ice. For moderate global wanning, resulting in ocean temperature increases of a few °C, the large- increase in basal melting can become the dominant factor in the long-term response of the ice sheet. The results from ice-sheet modelling show that the increased basal melt rates lead to a reduction of the ice shelves, increased strain rates and flow at the grounding lines, then thinning and floating of the marine ice sheets, with consequential further basal melting. The mass loss from basal melting is counteracted to some extent by the increased accumulation, but in the long term the area of ice cover decreases, particularly in West Antarctica, and the mass loss can dominate. The ice-sheet ice-shelf model of Budd and others (1994) with 20 km resolution has been modified and used to carry out a number of sensitivity studies of the long-term response of the ice sheet to prescribed amounts of global warming. The changes in the ice sheet are computed out to near-equilibrium, but most of the changes take place with in the first lew thousand years. For a global mean temperature increase of 3°C with an ice-shelf basal melt rate of 5 m a−1 the ice shelves disappear with in the first few hundred years, and the marine-based parts of the ice sheet thin and retreat. By 2000 years the West Antarctic region is reduced to a number of small, isolated ice caps based on the bedrock regions which are near or above sea level. This allows the warmer surface ocean water to circulate through the archipelago in summer, causing a large change to the local climate of the region.

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The Southern Ocean and its interaction with the Antarctic Ice Sheet

Science ◽

10.1126/science.aaz5491 ◽

2020 ◽

Vol 367 (6484) ◽

pp. 1326-1330

Author(s):

David M. Holland ◽

Keith W. Nicholls ◽

Aurora Basinski

Keyword(s):

Southern Ocean ◽

Ocean Circulation ◽

Thermal Structure ◽

Ice Sheet ◽

Major Influence ◽

Antarctic Ice Sheet ◽

Ice Shelves ◽

Air Temperatures ◽

The Antarctic ◽

Circulation Changes

The Southern Ocean exerts a major influence on the mass balance of the Antarctic Ice Sheet, either indirectly, by its influence on air temperatures and winds, or directly, mostly through its effects on ice shelves. How much melting the ocean causes depends on the temperature of the water, which in turn is controlled by the combination of the thermal structure of the surrounding ocean and local ocean circulation, which in turn is determined largely by winds and bathymetry. As climate warms and atmospheric circulation changes, there will be follow-on changes in the ocean circulation and temperature. These consequences will affect the pace of mass loss of the Antarctic Ice Sheet.

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Impact of transient increases in atmospheric CO2 on the accumulation and mass balance of the Antarctic ice sheet

Annals of Glaciology ◽

10.1017/s0260305500013938 ◽

1997 ◽

Vol 25 ◽

pp. 137-144 ◽

Cited By ~ 6

Author(s):

Siobhan P. O’Farrell ◽

John L. McGregor ◽

Leon D. Rotstayn ◽

William F. Budd ◽

Christopher Zweck ◽

...

Keyword(s):

Sea Level Rise ◽

Sea Level ◽

Ice Sheet ◽

Coupled Model ◽

Negative Contribution ◽

Antarctic Ice Sheet ◽

Ice Shelves ◽

Basal Melting ◽

Main Effects ◽

The Antarctic

The response of the Antarctic ice sheet to climate change over the next 500 years is calculated using the output of a transient-coupled ocean-atmosphere simulation assuming the atmospheric CO2value increases up to three times present levels. The main effects on the ice sheet on this time-scale include increasing rates of accumulation, minimal surface melting, and basal melting of ice shelves. A semi-Lagrangian transport scheme for moisture was used to improve the model’s ability to represent realistic rates of accumulation under present-day conditions, and thereby increase confidence in the anomalies calculated under a warmer climate. The response of the Antarctic ice sheet to the warming is increased accumulation inland, offset by loss from basal melting from the floating ice, and increased ice flow near the grounding line. The preliminary results of this study show that the change to the ice-sheet balance for the transient-coupled model forcing amounted to a minimal sea-level contribution in the next century, but a net positive sea-level rise of 0.21 m by 500 years. This new result supercedes earlier results that showed the Antarctic ice sheet made a net negative contribution to sea-level rise over the next century. However, the amplitude of the sea-level rise is still dominated In the much larger contributions expected from thermal expansion of the ocean of 0.25 m for 100 years and 1.00 m for 500 years.

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Recent glacial advance in the western Weddell Sea Sector driven by anomalous sea ice circulation

10.5194/egusphere-egu2020-7801 ◽

2020 ◽

Author(s):

Frazer Christie ◽

Toby Benham ◽

Julian Dowdeswell

Keyword(s):

Sea Ice ◽

Antarctic Peninsula ◽

Ice Sheet ◽

Weddell Sea ◽

Landsat 8 ◽

Ice Shelf ◽

Total Contribution ◽

Antarctic Ice Sheet ◽

Ice Shelves ◽

The Antarctic

The Antarctic Peninsula is one of the most rapidly warming regions on Earth. There, the recent destabilization of the Larsen A and B ice shelves has been directly attributed to this warming, in concert with anomalous changes in ocean circulation. Having rapidly accelerated and retreated following the demise of Larsen A and B, the inland glaciers once feeding these ice shelves now form a significant proportion of Antarctica&#8217;s total contribution to global sea-level rise, and have become an exemplar for the fate of the wider Antarctic Ice Sheet under a changing climate. Together with other indicators of glaciological instability observable from satellites, abrupt pre-collapse changes in ice shelf terminus position are believed to have presaged the imminent disintegration of Larsen A and B, which necessitates the need for routine, close observation of this sector in order to accurately forecast the future stability of the Antarctic Peninsula Ice Sheet. To date, however, detailed records of ice terminus position along this region of Antarctica only span the observational period c.1950 to 2008, despite several significant changes to the coastline over the last decade, including the calving of giant iceberg A-68a from Larsen C Ice Shelf in 2017.Here, we present high-resolution, annual records of ice terminus change along the entire western Weddell Sea Sector, extending southwards from the former Larsen A Ice Shelf on the eastern Antarctic Peninsula to the periphery of Filchner Ice Shelf. Terminus positions were recovered primarily from Sentinel-1a/b, TerraSAR-X and ALOS-PALSAR SAR imagery acquired over the period 2009-2019, and were supplemented with Sentinel-2a/b, Landsat 7 ETM+ and Landsat 8 OLI optical imagery across regions of complex terrain.Confounding Antarctic Ice Sheet-wide trends of increased glacial recession and mass loss over the long-term satellite era, we detect glaciological advance along 83% of the ice shelves fringing the eastern Antarctic Peninsula between 2009 and 2019. With the exception of SCAR Inlet, where the advance of its terminus position is attributable to long-lasting ice dynamical processes following the disintegration of Larsen B, this phenomenon lies in close agreement with recent observations of unchanged or arrested rates of ice flow and thinning along the coastline. Global climate reanalysis and satellite passive-microwave records reveal that this spatially homogenous advance can be attributed to an enhanced buttressing effect imparted on the eastern Antarctic Peninsula&#8217;s ice shelves, governed primarily by regional-scale increases in the delivery and concentration of sea ice proximal to the coastline.

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