Solute sources and geochemical processes in Subglacial Lake Whillans, West Antarctica

Subglacial Lake Whillans (SLW), West Antarctica, located beneath 800 m of ice is an active component of the subglacial hydrological network. The fill and drain behavior of SLW leads to long (years - decades) water residence times. Here, we present the aqueous geochemistry of the SLW water column and porewaters from a 36 cm sediment core. Stable isotopes indicate that the water is primarily sourced from basal-ice melt with a minor contribution from seawater that reaches a maximum of ~ 6% in porewater at the bottom of the sediment core. Silicate weathering products dominate the crustal (non-seawater) component of lake and porewater solutes, and there is evidence for cation exchange processes with the clay-rich lake sediments. The crustal solute component ranges from 6 meq L-1 in lake waters to 17 meq L-1 in the deepest porewaters. The porewater profiles of the major dissolved ions indicate a more concentrated solute source at depth (>36 cm). The combination of significant seawater and crustal components to SLW lake and sediment porewaters in concert with ion-exchange processes result in a weathering regime that contrasts with other subglacial systems. The results also indicate cycling of marine water sourced from the sediments back to the ocean during lake drainage events.