A preserved landscape discovered beneath the Antarctic ice cap | Polarjournal
This is what Antarctica must have looked like before a dome of ice covered the continent. Valleys, trees, animals and a landscape reminiscent of Snowdonia in north-west Wales. Image : Pixabay

A preserved landscape has recently been discovered beneath the East Antarctic ice sheet. A discovery that could help us understand how the ice sheet was formed and how it could evolve under conditions of global warming.

A vast landscape of once verdant hills and valleys, with two deep fjords and several rivers. This is the discovery made by a team of scientists in a study published last October in Nature Communications. Using radio-echo sounding (RES) technology, this team of British and American researchers discovered an area 32,000 km2 in size, larger than Belgium, and unseen for several millions years.

The fact that it was found intact – in other words, not eroded by the ice sheet – suggests that the climatic changes that led to the cooling and subsequent creation of the East Antarctic Ice Sheet (EAIS) 34 million years ago were rapid. “The landscape was formed by rivers prior to ice sheet build-up but later modified by local glaciation before being dissected by outlet glaciers at the margin of a restricted ice sheet.”, the authors state in their article, highlighting the fact that it is rare to discover preserved landscapes that have recorded past glacial conditions. This makes it possible to establish the history of the ice sheet.

According to Stewart Jamieson, Professor in the Department of Geography at Durham University and lead author of the study, the landscape would have resisted the retreat of ice during ancient warming periods such as the Pliocene, 3 to 4.5 million years ago.

The area identified by the scientists is referred to as “Highland A” in this representation of the topography of the Antarctic continent. Under more than 2,000 meters of ice, the area in question is located in Wilkes Land, in the southeastern part of the continent. Image: Stewart Jamieson, Durham University / AFP

To obtain these results, the researchers used radio-echo sounding. This technology involves flying over a given area while sending radio waves through the ice. The echoes are then analyzed to determine the topography. However, this procedure would be difficult to achieve on the scale of the vast white continent. To complete their data, the group of researchers used existing satellite images of this eastern part of Antarctica.

These images, combined with data obtained from the radio-echo sounding, have revealed a landscape which, according to the researchers, offers similar characteristics to Snowdonia in Wales.

A landscape that could find itself exposed, and therefore threatened, by the global warming we are currently experiencing: “Given that modern atmospheric CO2 and temperature conditions have reached levels unprecedented since the Pliocene, we are now on course to develop atmospheric conditions similar to those that prevailed between 34 and 14 Ma (ca. 3–7 °C warmer than present), with CO2 conditions reaching above 500 ppm between now and 2100 under continued fossil fuel burning.”, point out the authors, for whom the EAIS could retreat sufficiently to reveal these ancient landscapes if global warming continues.

However, exposing this landscape to the open air will take time, as it lies hundreds of kilometers inland from the ice edge.

Covered by a thick ice sheet, the Antarctic continent is still poorly understood. The discovery of this preserved landscape, along with recent discoveries of buried mountains and a subglacial lake, provides a better understanding of how the EAIS formed, and to what extent it expanded and retreated in response to past climates. Invaluable information for understanding how the ice cap might react to global warming in the future.

Link to the study : Jamieson, S.S.R., Ross, N., Paxman, G.J.G. et al. An ancient river landscape preserved beneath the East Antarctic Ice Sheet. Nat Commun 14, 6507 (2023). https://doi.org/10.1038/s41467-023-42152-2

Mirjana Binggeli, PolarJournal

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