Regime shift in high arctic fjord signals the vulnerability of the Arctic’s Last Ice Area

A consequence of the collapse of Arctic ice shelves is the draining and loss of epishelf lakes and their unique ice-dependent ecosystems. Epishelf lakes are formed by meltwater runoff that is dammed behind an ice shelf resulting in a perennial layer of freshwater (or lake), floating directly on seawater. They were once widespread in the Arctic and have been present for thousands of years. After several drainage events across the region, the last epishelf lake in the Canadian Arctic was lost during the collapse of the Milne Ice Shelf in 2020. We assess the range of oceanographic, atmospheric, and cryospheric factors that likely contributed to this major calving event, and analyze an unprecedented record of epishelf lake drainage from an ice-tethered mooring. A decadal time series of water column profiles collected pre- and post-calving shows the abrupt one-way transition from a relatively stable freshwater ecosystem to a marine system. The loss of the Milne Fiord epishelf lake marks the extinction of a rare feature of a colder world and highlights the vulnerability of even the ‘Last Ice Area’ of Arctic sea ice to climate warming.