Map surfaces ice sheet’s underbelly

U. TEXAS-AUSTIN (US) — A high-resolution map uses ice-penetrating radar to reveal some of the largest fjords on Earth at the Aurora Subglacial Basin in East Antarctica.

The map is expected to help scientists improve simulations of the past and future of the Antarctic ice sheet and predict its potential impact on global sea levels.

Because the immense ice-buried lowland lies kilometers below sea level, seawater could penetrate beneath the ice, causing portions of the ice sheet to collapse and float off to sea.

Indeed, the new research shows that it has been significantly smaller in the past.

“We knew almost nothing about what was going on, or could go on, under this part of the ice sheet and now we’ve opened it up and made it real,” says Duncan Young, research scientist at the University of Texas-Austin and lead author on the study, which appears in this week’s Nature.

“We chose to focus on the Aurora Subglacial Basin because it may represent the weak underbelly of the East Antarctic Ice Sheet, the largest remaining body of ice and potential source of sea-level rise on Earth,” says Donald Blankenship, principal investigator for the ICECAP project, a multinational collaboration using airborne geophysical instruments to study the ice sheet.

Previous work based on ocean sediments and computer models indicates the East Antarctic Ice Sheet grew and shrank widely and frequently, from about 34 to 14 million years ago, causing sea level to fluctuate by 200 feet.

Since then, it has been comparatively stable, causing sea-level fluctuations of less than 50 feet.

The new map reveals vast channels cut through mountain ranges by ancient glaciers that mark the edge of the ice sheet at different times in the past, sometimes hundreds of kilometers from its current edge.

“We’re seeing what the ice sheet looked like at a time when Earth was much warmer than today,” Young says. “Back then it was very dynamic, with significant surface melting. Recently, the ice sheet has been better behaved.”

However, recent lowering of major glaciers near the edge detected by satellites has raised concerns about this sector of Antarctica.

Past configurations of the ice sheet give a sense of how it might look in the future, although it is not expected to shrink as dramatically in the next 100 years.

But even a small change could have a significant effect on sea level.

Scientists will next use the map to forecast how the ice sheet will evolve in the future and how it might affect sea level.

Funding was provided by the National Science Foundation NASA, the Natural Environment Research Council, the Australian Antarctic Division, the G. Unger Vetlesen Foundation, the Antarctic Climate and Ecosystems CRC and The University of Texas at Austin’s Jackson School of Geosciences.

Topographic map of Aurora Subglacial Basin.

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