Lake Mercer Update: An Unprecedented Window into Subglacial Lake Draining

Lake Mercer Science Updates

Mercer Subglacial Lake is a hydraulically active lake that lies more 1000m beneath the Whillans Ice Plain, a fast moving section of the West Antarctic Ice Sheet. GPS stations have been installed at the Mercer Subglacial Lake site for over a decade and, with the return of the sun to power their batteries, have recently powered back on from their winter hiatus. Initial data acquired during October are showing that the lake may be entering draining phase of its multi-year fill-drain cycle. Since about the middle of July, the lake surface appears to have dropped at a rate of about 3 cm per day (inferred to be just under 50 m3/s (1750 cfs) of water draining out of the lake). This presents SALSA with an unprecedented window into the process of subglacial lake draining.

In the words of one of SALSA’s glaciologists Matthew Siegfried, “We just hit the jackpot: given the huge amount of lead time needed to execute a project like this, the odds of actually exploring a lake during a rapid drainage event are incredibly slim. This is going to be really exciting stuff.”

Lake Mercer GPS Station
SALSA Geophysics Researcher Matthew Siegfried servicing a GPS station at the Lake Mercer drill site with help from grad student Susheel Adusumilli in November 2017.

Sampling the water column of this lake during a draining phase will allow scientists to examine biogeophysical processes providing us with new insights into the linkages between the dynamics of lake drainage on ice flow, sediments, chemistry, and organisms in the lake, says John Priscu, SALSA Chief Scientist.  The surface geophysics team, led by Siegfried, is currently at McMurdo Station in Antarctica and about to embark on an electromagnetic survey aimed at mapping subglacial water, including lake depth and possible outflow channels, in the month before the drilling at Lake Mercer begins.  Helen Fricker, lead-PI of the surface geophysics team and SALSA ExComm, is excited at the prospect of detecting the subglacial outflow of the lake with electromagnetics, and also in making new radar measurements to determine how much of the height-change signal on the lake surface is due to lake volume change.

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