Lake Mercer is a subglacial lake in Westarctica covered by a sheet of ice 1,067 meters (3,501 feet) thick; the water below is hydraulically active, with water replacement times on the order of a decade from the Ross Sea.
Lake Mercer is identified as high risk for a collapse of the West Antarctic Ice Sheet caused by global warming. Studies suggest that Mercer Lake as well as other subglacial lakes appear to be linked, with drainage events in one reservoir causing filling and follow-on drainage in adjacent lakes.
Helen Amanda Fricker from the Scripps Institution of Oceanography discovered subglacial Lake Mercer by accident in 2007, while using satellite radar soundings to search for the grounding line of a glacier. On 28 December 2018, the Subglacial Antarctic Lakes Scientific Access (SALSA) team, where Fricker serves on the executive committee of the project, announced they had reached Mercer Lake after two days of melting their way through 1,067 m (3,501 ft) of ice with a high-pressure hot-water drill.
Discovery of ancient life
A preliminary report states that ancient carcasses of crustaceans and a tardigrade were isolated from the sediment samples. The lake water samples contains enough oxygen to support aquatic animals, and bacteria are present with a density of at least 10,000 cells per milliliter. Other ancient organisms retrieved from the sediments include shells of diatoms (a photosynthetic algae) and thread-like plants or fungi. How the crustaceans and tardigrade reached Lake Mercer is a matter of debate, but the scientists suspect that the gradual uplift of the continent transformed shallow ocean bays into isolated lakes. The team will attempt to establish the age of the animal remains using radiocarbon dating, and will also try to sequence DNA from crustaceans to find out whether they belong to marine or freshwater species.
The sediment cores will also be analyzed by geobiologists to study how relic organic matter deposited during marine incursions influences contemporary biodiversity and carbon cycling.