A study uncovers how East Antarctica's ice sheet collapsed rapidly around 9,000 years ago due to warm ocean currents. This event triggered a self-reinforcing feedback loop that spread ice loss across the continent. The findings highlight potential instabilities in modern Antarctic ice under climate change.
New research published in Nature Geoscience details a major retreat of the East Antarctic Ice Sheet (EAIS) about 9,000 years ago. Led by Professor Yusuke Suganuma of the National Institute of Polar Research (NIPR) and the Graduate University for Advanced Studies (SOKENDAI), the team found that warm Circumpolar Deep Water (CDW) surged into Lützow-Holm Bay, causing floating ice shelves to collapse. This loss of support accelerated inland ice flow toward the sea, creating a "cascading positive feedback" where melting in one area hastened it elsewhere via ocean currents.
To reconstruct this event, researchers analyzed marine sediment cores from Lützow-Holm Bay near Japan's Syowa Station along the Sôya Coast. Samples came from Japanese Antarctic Research Expeditions (JARE) spanning 1980 to 2023, including recent work from the icebreaker Shirase. Using sedimentological, micropaleontological, geochemical analyses, and beryllium isotope ratios (10Be/9Be), they dated the collapse to the early Holocene, when global temperatures were higher than during the last Ice Age.
Climate and ocean circulation models explained the warm water surge: meltwater from regions like the Ross Ice Shelf freshened the Southern Ocean surface, strengthening vertical stratification. This allowed deeper warm water to reach East Antarctica's shelf more easily, reinforcing the melting cycle. The East Antarctic Ice Sheet holds over half of Earth's freshwater, and similar processes are observed today in West Antarctica, such as at Thwaites and Pine Island glaciers.
The international collaboration involved over 30 institutions, including the Geological Survey of Japan (AIST), Japan Agency for Marine-Earth Science and Technology (JAMSTEC), University of Tokyo, and partners from New Zealand and Spain. Professor Suganuma stated: "This study provides essential data and modeling evidence that will facilitate more accurate predictions of future Antarctic ice-sheet behavior. The cascading feedbacks identified in this study serve to underscore the notion that minor regional alterations can potentially engender global ramifications."
These insights suggest that Antarctic ice retreat can amplify through oceanic connections, offering clues to future sea-level rise.