A group of scientists is about to embark on an expedition to a lake that has never been seen by human eyes. The lake holds clues about our changing climate and the evolution of life on our planet, but it is hidden beneath thousands of feet of Antarctic ice.

So begins the award-winning documentary The Lake at the Bottom of the World, following the progress of the SALSA Science Team through its campaign to access, characterize and retrieve samples from Mercer Subglacial Lake (SLM), West Antarctica.  SALSA - Subglacial Antarctic Lakes Scientific Access - blended rigorous hypothesis-driven science with discovery, technology development, training, education, and public outreach to bring a heightened understanding of one of life's least touched Earthly habitats: the dark, cold wetlands that underlie much of the West Antarctic Ice Sheet (WAIS). SLM lies beneath 3600 feet of ice of the Mercer Ice Stream, one of the six ice streams that drain from West Antarctica into the Ross Ice Shelf.

This lead award (1543537) supported:  [1] The integration/management of the overall project, comprising five additional awards (1543347, 1543396, 1543405, 1543441, 1543453) and subawards.  We brought together diverse scientists, engineers, and students with a common purpose: elucidate the roles that meltwater, ice flow dynamics and relict organic carbon deposited during past intrusions of the ocean play in shaping the SLM ecosystem and in controlling its contemporary biogeochemical processes;  [2] Coordination with contractors, including the accomplished team of drillers that opened a borehole through the ice into which our sampling devices were deployed, and the engineers obtaining unique under-ice video with their remotely operated submersible;  [3] Scientific studies of SLM geochemistry, characterization of its sediment layers and microfossils, enumeration of microbial cells and viruses, and measurements of biological activity;  [4] Communication with the public via website and social media, PBS Research Learning Modules, short films, and production of the 91-minute documentary by filmmakers embedded within the science team; [5] Training of undergraduate, graduate and postdoctoral researchers in interdisciplinary science and scientific documentary filmmaking; and  [6] Liaising with international collaborators and providing samples to specialized laboratories worldwide.

Numerous scientific publications present SALSA results, while presentations made at national and international scientific conferences largely came from a new generation of polar researchers supported through the SALSA project.  Many detailed results are found associated with the individual SALSA awards; here, we highlight a few notable findings/achievements by the SALSA project as a whole:

Ice surface height variation data from satellites have been validated with GPS positioning, placing the SALSA field work period into the context of a roughly decadal SLM fill/drain cycle.  Sediment cores recovered from SLM display distinct layering at the lake floor interpreted as the product of lake fill/drain cycles.  The observed layering, along with statistical modelling, suggests that SLM has been a persistent feature for 1 - 2 centuries.

The 50-foot deep SLM is only the second subglacial Antarctic lake sampled, and is distinct from previously sampled 7-foot deep Whillans Subglacial Lake (SLW).  SLW is located under the Whillans Ice Stream, which is the neighboring ice stream to Mercer Ice Stream, flowing approximately in parallel. SLW is approximately ~ 60 km from SLM.  Both lakes present evidence of deeper, marine sedimentary influences, but measurements of microbial biomass/activity, methane and other chemical energy sources, such as dissolved organic carbon in SLM are low; while, energy sinks such as dissolved oxygen are high, compared to those in SLW.  Despite these differences, DNA analyses of SLM microbial communities demonstrate greater similarity to those in SLW than from marine sediments at the grounding line downstream from SLW where the grounded ice meets the ocean.  These novel findings imply a network of inter-related microbial populations beneath the ice linked through ice sheet dynamics and the transport of microbes, water, and sediments beneath the WAIS.

Iron, an important micronutrient that supports biological productivity by photosynthetic microorganisms, is typically found in low concentrations in the Southern Ocean. We documented a large export of trace metals including iron via subglacial outflow from SLM into the ocean cavity beneath the Ross Ice Shelf, which in turn is connected to the Southern Ocean.  Our findings suggest that ice sheets need to be included in models/studies assessing the iron fertilization of adjacent marine systems, such as the Southern Ocean through subglacial water discharge.

Stewardship of samples and preservation of the environment that we sampled is a requirement of our research.  Pristine sediment cores collected by SALSA are archived at Oregon State University according to internationally accepted protocols.  Sampling activities utilized state-of-the-art decontamination procedures for microbiologically clean access.  The drilling, sampling, and imaging technologies we used during the SALSA project serve as prototypes for those that may eventually be deployed to penetrate the icy crusts of ocean worlds like Europa and Enceladus in the search for life beyond Earth.

Last Modified: 02/13/2023
Modified by: Mark Skidmore