Antarctic RINGS – Surveying the Antarctic Ice Sheet Margin | Polarjournal
For the radar measurements, larger aircraft capable of covering greater distances must be used in addition to Twin Otter and Basler aircraft. Photo: Kenichi Matsuoka

The Antarctic Ice Sheet, which is kilometers thick in places, covers the White Continent almost completely and hardly gives any idea of the structures that lie hidden beneath it. The BEDMAP1 and later BEDMAP2 datasets published by the British Antarctic Survey, which shows much more detail, have provided a glimpse of bedrock topography since 2001 and 2013, respectively. Scientists, however, need more accurate data from the edges of the Antarctic Ice Sheet to better estimate ice discharge and the contribution to sea level rise today and in the future. To fill this gap, a new comprehensive dataset will be collected from aircraft over the next few years – carried out by the “Antarctic RINGS” action group, which was set up specifically for the project.

Just over a year ago, the Scientific Committee on Antarctic Research (SCAR) established the Antarctic RINGS Action Group with the main goal of providing more accurate and complete data on bed topography to reliably assess ice outflows throughout Antarctica. For this, it is necessary to make measurements in three rings along the ice sheet margin: (1) in a primary ring above the ice sheet baseline where the ice meets the ocean and begins to float; (2) in a seaward ring; and (3) in a landward ring. Several different instruments will be used in the research, including radar, gravity and Lidar devices.

In conjunction with satellite data, the new dataset can also be used to detect mass input from snowfall, which is currently estimated only with regional climate models. The accuracy of ice sheet models is also improved by the new data.

The grounding line, where land ice meets the ocean and begins to float, is retreating in many regions in Antarctica. Topography also plays a role. Therefore, the measurements are performed in three rings parallel to the grounding line. Graphic: National Snow and Ice Data Center, NASA

The topography of the subsurface beneath the ice sheet affects both the dynamics of ice flow (velocity, direction, and discharge rate) and the vulnerability of glaciers and ice shelves to current changes in the atmosphere and ocean. This makes it all the more urgent to fill the knowledge gap on nearshore topography, as current predictions of future ice loss in Antarctica are mostly linked to grounding line retreat triggered by ocean processes.

Floating ice shelves occupy most, nearly three-quarters, of the edge of the Antarctic Ice Sheet. If glacier ice flows over the grounding line to the ice shelf, it contributes directly to sea level rise. Accurate measurements of ice thickness and flow velocity at the grounding line are therefore necessary for quantifying ice flow from the ice shelf to the ocean.

It is not yet possible to record the topography of the Antarctic bedrock by satellite, so measurements will be made by airborne radar, as was done for the first two data sets, BEDMAP1 and BEDMAP2. In addition, offshore measurements are carried out by research vessels and unmanned underwater vehicles.

The animation shows the topography of bedrock beneath the Antarctic ice sheet using the BEDMAP2 dataset and the improved resolution compared to BEDMAP1. Video: Nasa

The large-scale project will be realized through international, pan-Antarctic collaboration that integrates existing and new technical and logistical capabilities from numerous countries, including the United Kingdom, Norway, Italy, Denmark, the United States, Australia, China, and Germany.

Currently, the Action Group is still in the planning stages and will lead an initial workshop later this month to discuss scientific priorities, survey requirements and other items. At the same time, a number of international projects are already underway to conduct the first data collections in the 2023/2024 Antarctic field season.

Julia Hager, PolarJournal

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