Dissolved gas dynamics in perennially ice-covered Lake Fryxell, Antarctica

Abstract

We use the concentrations of noble gases (He, Ne, and Ar), helium isotopes, and tritium to characterize the mechanisms and rates of ventilation for Lake Fryxell, Antarctica, as well as the physical processes controlling dissolved gases. The upper oxic zone is ventilated on timescales of several decades. The anoxic bottom waters are weakly ventilated, with a turnover time of ~3,800 years. In the upper euphotic zone, helium and neon are greatly undersaturated with respect to solubility equilibrium with the atmosphere, whereas argon is greatly supersaturated owing to equilibrium partitioning of the gases between ice, water, and air inclusions in the ice. In the bottom waters, the inert dissolved gas concentrations may be remnants of a near-desiccation event that occurred ~2,000 years B.P., consistent with current paleoclimatic theories.