Scientific access into Mercer Subglacial Lake: Scientific objectives, drilling operations and initial observations

Abstract

The Subglacial Antarctic Lakes Scientific Access (SALSA) Project accessed Mercer Subglacial Lake using environmentally clean hot-water drilling to examine interactions among ice, water, sediment, rock, microbes and carbon reservoirs within the lake water column and underlying sediments. A ∼0.4 m diameter borehole was melted through 1087 m of ice and maintained over ∼10 days, allowing observation of ice properties and collection of water and sediment with various tools. Over this period, SALSA collected: 60 L of lake water and 10 L of deep borehole water; microbes >0.2 m in diameter from in situ filtration of ∼100 L of lake water; 10 multicores 0.32-0.49 m long; 1.0 and 1.76 m long gravity cores; three conductivity-temperature-depth profiles of borehole and lake water; five discrete depth current meter measurements in the lake and images of ice, the lake water-ice interface and lake sediments. Temperature and conductivity data showed the hydrodynamic character of water mixing between the borehole and lake after entry. Models simulating melting of the ∼6 m thick basal accreted ice layer imply that debris fall-out through the ∼15 m water column to the lake sediments from borehole melting had little effect on the stratigraphy of surficial sediment cores.