A new study finds that the East Antarctic ice sheet experienced massive retreat about 9,000 years ago, driven by a strong feedback loop formed by the interaction of ice melt and ocean currents. By analyzing marine sediment cores and geological survey data from Luzholm Bay, a research team composed of the National Polar Research Institute of Japan and several international institutions confirmed that large amounts of warm deep water flowed to the East Antarctic coast, causing ice shelves to collapse. After the ice shelf breaks up, inland ice flows faster toward the ocean, further pushing the ice sheet back.
Research shows that the melting of the Antarctic ice sheet is not only limited to a certain area, but can also spread to other areas due to the linkage of ocean currents, forming a "cascading positive feedback" phenomenon. That is, melting in one area will accelerate the retreat of ice in other areas. This mechanism helps scientists understand the short-term instability of the Antarctic ice sheet.
The team used beryllium isotope analysis and various geochemical methods to reconstruct the historical changes in the regional environment. The results show that about 9,000 years ago, the inflow of Circumpolar Warm Deep Water (CDW) in Antarctica was significantly enhanced, and the floating ice shelves collapsed, resulting in accelerated inflow of inland ice.
Simulation results show that meltwater from other areas of Antarctica (such as the Ross Ice Shelf) will also be transferred to East Antarctica through ocean currents. This effect enhances the stratification of ocean water and reduces the upward mixing of cold water, making it easier for warm deep water to flow to the continental shelf, inducing further ice sheet melting. The result is a self-reinforcing loop: Meltwater enhances stratification, promoting warm water intrusion and triggering more melting.
This study provides strong evidence for widespread, self-reinforcing melting of the Antarctic ice sheet. Although the above events occurred during the Holocene warm period 9,000 years ago, similar physical mechanisms are also applicable to the current global warming environment. Modern observations have documented that parts of West Antarctica, such as Thwaites and Pine Island glaciers, are rapidly retreating as warm, deep water erodes the bottom. If a similar feedback mechanism is occurring, local melting has the potential to accelerate overall ice sheet loss and significantly push up global sea levels.
This study combines the efforts of more than 30 institutions and uses sedimentary rock analysis, cosmogenic nuclide dating and climate-ocean modeling methods to recreate the complex interaction between the East Antarctic ice sheet and the ocean current system. Professor Yusuke Suganuma, the leader of the study, said: "This study provides important data and modeling foundations to help more accurately predict changes in the Antarctic ice sheet in the future. The cascade feedback mechanism discovered in the study shows that local environmental changes may trigger global impacts."
Compiled from /ScitechDaily