Evidence of Subglacial Brine Inflow and Wind-Induced Mixing from High Resolution Temperature Measurements in Lake Bonney, Antarctica

• Main Author: Lawrence, Jade
• Format: Text
• Language: unknown
• Published: LSU Digital Commons 2017
• Subjects: limnology; McMurdo Dry Valleys; Antarctica; Lake Bonney; Geology; Hydrology; Blood Falls; Bonney; Lobe Lake; Taylor Glacier; Antarc*
• Online Access: https://digitalcommons.lsu.edu/gradschool_theses/4343; https://doi.org/10.31390/gradschool_theses.4343; https://digitalcommons.lsu.edu/context/gradschool_theses/article/5348/viewcontent/lawrence_thesis.pdf

Hypersaline brine beneath Taylor Glacier enters proglacial West Lobe Lake Bonney (WLB) subglacially as well as from Blood Falls, a surface discharge point at the Taylor Glacier terminus. The brine strongly influences the water column of WLB. Because of the extremely high salinities below the chemocline in WLB, density is determined almost entirely by salinity and temperature can be used as a passive tracer. Cold brine intrusions enter WLB at the glacier face and intrude in to the water column at the depth of neutral buoyancy, where they can be identified by anomalously cold temperatures at that depth. This study is the first to definitively identify subglacial brine intrusions in WLB, since the absence of an open water moat in the winter prevents brine entry from the surface at Blood Falls. High resolution thermistors and CTDs deployed year-round beneath the perennial ice cover demonstrate that brine intrusions can influence the thermal stratification of the water column near the glacier terminus for the majority of the year, and that the effects diminish with distance from the glacier terminus. High volumes of brine inflow alter the density stratification of the water column at the depth of the intrusion and cause turbulent mixing near the glacier terminus. High resolution measurements also reveal internal water movements associated with katabatic wind events, a novel finding that challenges long held assumptions about the stability of the WLB water column. The long term records of Blood Falls flow and of temperature anomalies in WLB indicate that brine release from the subglacial system has been a persistent feature in the region for decades, with implications for the geochemistry and biology of WLB.