The physical limnology of a permanently ice‐covered and chemically stratified Antarctic lake using high resolution spatial data from an autonomous underwater vehicle

Abstract

AbstractWe used an Environmentally Non‐Disturbing Under‐ice Robotic ANtarctic Explorer to make measurements of conductivity and temperature in Lake Bonney, a chemically stratified, permanently ice‐covered Antarctic lake that abuts Taylor Glacier, an outlet glacier from the Polar Plateau. The lake is divided into two lobes – East Lobe Bonney (ELB) and West Lobe Bonney (WLB), each with unique temperature and salinity profiles. Most of our data were collected in November 2009 from WLB to examine the influence of the Taylor Glacier on the structure of the water column. Temperatures adjacent to the glacier face between 20 m and 22 m were 3°C colder than in the rest of WLB, due to latent heat transfer associated with melting of the submerged glacier face and inflow of cold brines that originate beneath the glacier. Melting of the glacier face into the salinity gradient below the chemocline generates a series of nearly horizontal intrusions into WLB that were previously documented in profiles measured with 3 cm vertical resolution in 1990–1991. WLB and ELB are connected by a narrow channel through which water can be exchanged over a shallow sill that controls the position of the chemocline in WLB. A complex exchange flow appears to exist through the narrows, driven by horizontal density gradients and melting at the glacier face. Superimposed on the exchange is a net west‐to‐east flow generated by the higher volume of meltwater inflows to WLB. Both of these processes can be expected to be enhanced in the future as more meltwater is produced.