A group of scientists collected from the United States, United Kingdom and Australia, have taken a look below the Aurora Subglacial Basin in the East Antarctic Ice Sheet and found some of the largest fjords on Earth.
The fjords – an often long and narrow valley that has been carved out by the movement of a glacier – are some of the largest ever found on Earth, and provide important insights for scientists hoping to understand the history of ice in Antarctica, as well as providing important data for computer modellers who are hoping to better simulate the past and future of the Antarctic ice sheet, and its potential impact on the global sea level.
“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,” said Duncan Young, research scientist at The University of Texas at Austin’s Institute for Geophysics and lead author on the study, which appears in this week’s journal 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,” said Donald Blankenship, principal investigator for the ICECAP project, a multinational collaboration using airborne geophysical instruments to study the ice sheet.
One of the greatest fears for the Aurora Subglacial Basin was due to the fact that it lies several kilometres below sea level. Scientists feared that seawater could penetrate beneath the ice, which would cause certain portions of the ice sheet to detach and float away, eventually melting and increasing the global sea levels.
In fact, the current data has already shown that the ice sheet has been significantly smaller in the past. Together with previous work on ocean sediments and computer models, the East Antarctic Ice Sheet has grown and shrunk rapidly and frequently from about 34 to 14 million years ago, causing massive fluctuations in the sea level by up to 200 feet.
However, over the past 14 million years, the ice sheet has been comparatively stable, causing fluctuations in the sea levels by up to 50 feet.
The new map – which was created by flying an upgraded World War II-era DC-3 aircraft with a suite of geophysical instruments including an ice-penetrating radar over the area for three field seasons – shows that glaciers cut massive fjords through the mountain ranges which lie below the ice sheet, and mark the edge of the ice sheet at different times in the past. At some points, these edges lie several hundreds of kilometres from the current edge of the ice sheet.
“We’re seeing what the ice sheet looked like at a time when Earth was much warmer than today,” said Young. “Back then it was very dynamic, with significant surface melting. Recently, the ice sheet has been better behaved.”