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29 June 2017

20,000-year-old Sub-glacial Lakes Discovered under West Antarctic Ice Sheet

Antarctica remains a land of many mysteries, with countless new discoveries emerging each year which have the potential to change how we think about the Earth’s last true wilderness, and how it affects the planet as a whole. In one such recent breakthrough, a team comprised of researchers from the British Antarctic Survey (BAS), the Alfred Wegener Institute, the University of Utrecht, the Lamont-Doherty Earth Observatory, and the Universities of Bremen and Leipzig, has confirmed the presence of ancient sub-glacial lakes beneath what was once part of the West Antarctic Ice Sheet.

The German icebreaker RV Polarstern takes sediment samples from the Amundsen Sea   - Img: James Smith/BAS
Making use of sophisticated geochemical techniques to analyse sediment cores from the sea-floor of Pine Island Bay, the team were able to ascertain that the lakes existed during the last glacial period approximately 20,000 years ago when the ice sheet was both thicker and more widespread. Several sub-glacial lakes have been confirmed to have at one point existed in the area, with the largest being approximately the size of Loch Lomond which itself has an area of around 71km².

The importance of this data stems from the fact that such lakes are not purely a remnant of the past; hundreds of sub-glacial lakes are known to exist to this day, trapped under the modern Antarctic Ice Sheet. These lakes are believed to not only hold their own unique ecosystem full of undiscovered life forms, but also have an effect upon the flow of the ice above them due to the movement of water from one lake to another. However while gaining an understanding of such features is undeniably important, these lakes are difficult to access and by extension difficult to study, and that’s where the ancient lakes prove their usefulness to the scientific field.

Instead of drilling through the ice sheet to reach the modern lakes still remaining, a process which carries with it considerable technological challenges, the team instead sampled sediment from the floor of ‘palaeo’ lakes long since expired. The sediment samples were collected during expeditions to the Amundsen Sea aboard the German icebreaker RV Polarstern in 2006 and 2010.

Lead author Dr Gerhard Kuhn, of the Alfred Wegener Institute, said of the study, “We retrieved these unique cores from valleys on the ocean floor that were situated under the Antarctic Ice Sheet in the Earth’s past. The ice there has now dramatically retreated, which allowed us to sample the lake sediments from the ship.”

The team confirmed that these sediments did in fact come from a sub-glacial freshwater lake due to the extremely low chloride content found in the lower parts of some cores.

Author Dr Claus-Dieter Hillenbrand, of the British Antarctic Survey, also commented, “The really satisfying aspect of our project is that it confirms previous predictions based on acoustic surveys of the sea-floor which showed deep basins and meltwater channels eroded into hard rock. This suggested that palaeo-subglacial lakes existed in the past but now we’ve proved it.”

It is hoped that the data gleamed from the study of past sub-glacial lakes may help researchers to understand the properties of their modern day equivalents without the need for heavily-invasive and potentially disruptive techniques.

Dr James Smith, also from British Antarctic Survey, explains, “Now that we’ve developed techniques to identify palaeo-subglacial lake sediments in the geological record we can learn more about the properties of these unique systems. Obviously it is unlikely that we will be able to address the ‘did life exist in these lakes’ question but our new knowledge can help refine sampling strategies before we drill into existing sub-glacial lakes.”

Sam Bonson

Sam is an aspiring novelist with a passion for fantasy and crime thrillers. He is currently working as a content writer, journalist & editor in an attempt to expand his horizons.