Providing constraints on Antarctic Subglacial Environments using Observations of Active Subglacial Lakes from Satellite Radar Altimetry

Abstract

<p>Subglacial water at the base of the ice sheet has been shown to impact ice flow and its discharge into the ocean – which modifies ocean properties and melt rates of fringing ice shelves. Subglacial water, generated from frictional heating and geothermal heat flux, collects in hydrological sinks which store and release water in episodic events. These events, interpreted as water moving in and out of active lakes, have a signature at the surface of the ice sheet which can be detected and quantified by satellite altimetry. By quantifying the volume of water involved in these active events, it is possible to obtain insight into processes otherwise hidden from view. In particular, observing the gain in volume following a drainage event provides constraints on hydrological recharge rates, subglacial water fluxes, and processes leading to basal melt water production. Such a method was applied to the inventory of Antarctic active subglacial lakes using CryoSat’s radar altimeter observations over the 2010-2020 period. Out of 136 known lakes, 13 lakes show clear signs of recharge during the observation period. From these we can extract recharge rates, which act as a lower bound on subglacial melt production. These rates are compared against rates of recharge derived by routing modelled subglacial melt production across the Antarctic Ice Sheet. We demonstrate that, for connected subglacial lake networks, satellite observations can provide a robust validation dataset for sub-glacial melt models. Our results show that, at a local level, estimates of melt water flux is highly dependent on the routing method chosen. We also highlight subglacial lakes where observed rates of recharge are too high to be explained by our current knowledge of the bed and of processes responsible for subglacial melting rates.</p>