Deep beneath Antarctica’s vast ice sheet, networks of subglacial lakes can suddenly drain, releasing enormous volumes of freshwater into the ocean. New research reveals this process triggers a powerful and previously underappreciated mechanism that significantly accelerates the melting of floating ice shelves from below. By creating turbulent plumes of freshwater that draw warmer, deep ocean water up to the ice, these drainage events can destabilize some of the world's most critical glaciers and threaten to increase the rate of global sea-level rise.
The process goes far beyond simply lubricating the base of a glacier. Instead, it initiates a chain reaction in the ocean cavity beneath the ice shelf, directly attacking the glacier at its most vulnerable point. A 2013 event at West Antarctica's Thwaites Glacier, a region of particular concern for its potential contribution to sea-level rise, has provided scientists with a clear case study of how this hidden plumbing system can have outsized effects on the ice sheet's stability.
A Case Study: The 2013 Thwaites Glacier Drainage
In early 2013, scientists observed a dramatic change beneath the Thwaites Glacier. According to a study published in Nature Communications, an extensive, connected system of seven subglacial lakes, located as far as 408 kilometers inland from the glacier's edge, began to drain. Using high-resolution satellite data from missions including the European Space Agency’s CryoSat, researchers tracked changes in the ice surface elevation to reveal the scale of the event. The lakes released approximately seven cubic kilometers of freshwater—a volume comparable to Scotland’s Loch Ness—into the Amundsen Sea over a short period.
This massive discharge of freshwater occurred at the glacier's grounding line, the critical boundary where the ice sheet lifts off the bedrock and begins to float. For Thwaites, this discharge point is located at a depth of roughly one kilometer below sea level. The event provided researchers from the International Thwaites Glacier Collaboration and other institutions with a unique opportunity to pair satellite observations with ocean modeling to uncover the precise consequences of such a large-scale freshwater release.
