Antarctica’s role in the climate system is propagated largely through changes in its ice cover. The scale of this connection ranges from seasonal variations in sea-ice extent and sub-ice shelf melting that affect planetary albedo dynamics, atmospheric and oceanic circulation, and ocean productivity, to decadal and long-term changes in ice sheet volume that affect global sea levels. While Antarctica’s important role in the dynamic linkages of the earth system is now recognized, many of the details remain poorly understood.
Ice sheets and sea levelGlobal sea level is modulated by ice sheet mass balance through two competing processes: the addition of mass through the long-term storage of precipitation falling as snow, and the removal of mass through the slower release of water back into the ocean by ice flow which results in melting and iceberg calving along the edges of the ice sheet. Climate variability has an effect on both processes. The longer-term effect relates to ice flow. A much shorter-term fluctuation in ice sheet mass (and volume) occurs when there is a change in accumulation rate. This short-term response is relevant to investigations of present-day sea level rise, as discussed by the 2007 IPCC report. In other words, the Antarctic ice sheet might be undergoing a long-term decrease in volume as the ice flow adjusts to climate change at the end of the last ice age, superimposed on a short-term increase in volume due to recent changes in accumulation rate. The net effect of these two responses is incompletely known, and improving our understanding is a key objective of this project.
Our limited understanding of climate and ice sheet conditions in East Antarctica is partly due to inadequate sampling of characteristics and processes that contain a great deal of spatial and temporal variability. Local spatial variability in accumulation occurs as a result of subtle changes in surface slope that affect the interaction between air flow and snow deposition. Larger scale spatial variability is due to atmospheric circulation patterns and the position of storm tracks. Circulation changes can affect the position of storm tracks and lead to temporal variability in precipitation and temperature. Because most of the precipitation in Antarctica is delivered by cyclones, which usually do not penetrate very far inland, it is likely that significant changes in accumulation will be observed in coastal areas first. Some progress is now being made using atmospheric models to understand this temporal and spatial variability in Antarctic accumulation, but a carefully planned program of ice core collection is still necessary to provide the data needed to calibrate such models.
|Above: Traverse route overlaid on a Radarsat SAR mosaic of East Antarctica. Side panels illustrate (A) locations of prior and planned traverses, (B) decadal temperature trend for 1958-2002, (C) dH/dt, 1992-2002, and (D) snow accumulation rates. The box in each panel indicates the region of the proposed traverses.|
Prior studiesDronning Maud Land (in East Antarctica) has been one of the least scientifically explored parts of Antarctica. The South Pole–Queen Maud Land Expedition (1964-68) traversed in a saw-tooth pattern between the South Pole and 76 º S, 7 º E. Japanese expeditions have collected glaciological data since the launch of the Enderby Land Glaciological Observation Program in 1969, which resulted in the publication of a glaciological folio covering the ice sheet sector between 15 º -55 º E that extends from the coast to 80 º S. To the north and west of Troll station, data are available from two early expeditions that originated from Maudheim and Norway stations. Ice cores were collected in western DML by several Swedish Antarctic Research Program (SWEDARP) expeditions and an ITASE traverse conducted by SWEDARP. Our work will represent a major addition to the existing data from this region.
Traverse fieldworkFieldwork conducted during the two traverses will include:
- collection of intermediate-depth (~90 m deep) ice cores and shallow (~30 m) firn cores;
- near-surface in situ sampling of chemical and isotopic composition;
- continuous profiling of ice thickness and stratigraphy in the upper ice sheet between ice core sites using several radar systems;
- studies of the physical properties of the surface and near-surface firn;
- the deployment of Automatic Weather Stations;
- studies of ice dynamics at ice core sites and along the traverse routes; and
- physically-based modeling of snow-atmosphere processes and interactions.
- investigation of the recently discovered ‘Recovery Lakes’ using a range of geophysical instrumentation
Connection to larger framework
Our objectives contribute directly to the “Vision for the International Polar Year” (NRC 2004), by providing an assessment of polar environmental change through studies of the past environment and the creation of baseline data sets. Our work directly contributes to the study of environmental change and the linked traverses in East Antarctica mentioned in “International Polar Year 2007-2008: Report of the Implementation Workshop (NRC, 2005). This research addresses the International Council for Science (ICSU) “IPY Framework for the International Polar Year” (ICSU, 2004) Theme 1, contributing findings from East Antarctica to determine the present environmental status in the polar regions; Theme 2, quantifying and understanding past and future environmental change in the polar regions; and Theme 4, examining characteristics of the surface of East Antarctica for frontiers of science. This project is a part of the Trans-Antarctic Scientific Traverse Expeditions – Ice Divide of East Antarctica (TASTE-IDEA), and the International Partners in Ice Coring Sciences (IPICS), both highly international endeavors that have ISCU-WMO endorsement for the International Polar Year 2007-2008.