Hidden from view by ice kilometres thick, there is a vast network of lakes and streams under the Antarctic ice sheet. Using a decade of altimetry data from European Space Agency’s (ESA) CryoSat satellite, researchers at the University of Edinburgh, including a scientist with the PROPHET project of the International Thwaites Glacier Collaboration (ITGC), have made an unexpected discovery about how lakes beneath Thwaites Glacier drain and recharge in quick succession.
Meltwater beneath the ice arises from frictional heating as the ice flows over the bedrock, as well as from geothermal heat coming from below the bedrock. Measurements of geothermal heat flux beneath the ice are particularly difficult to obtain and there are large differences between the various recent estimates. It is important that our knowledge of the distribution of meltwater and the geothermal heat flux is improved because both factors influence the speed the ice flows into the ocean.
While subglacial meltwater is hidden from view by kilometres-thick ice, its movement beneath the ice causes tiny movements on the surface of the ice, which, remarkably, can be detected and monitored from space.
A study published in the journal Geophysical Research Letters in December 2020 describes how a decade of radar altimetry observations have revealed a network of four subglacial lakes under Thwaites Glacier, which drained and recharged in two events observed within that time period. By comparing the rates to modelled estimates, the team found that previous models underestimated the rate of basal melting by 150%. This finding will help glaciologists reassess models and improve predictions of how the ice sheet might behave in the future.
Thwaites Glacier was the topic of my most recent Yale Climate Connections video, see below.
Prior to Helen A Fricker’s paper in 2007 we believed the lakes to be totally static. Over time more and more subglacial lakes were found to be active. Now we find that they are more active than previously believed and by a big margin.
The geothermal aspect has me worried in that it could be used as a denialist talking point. (That was one reason I didn’t like that one of the EIS time-lapse glaciers was on Iceland, as geothermal activity there has a significant influence on glacial behavior.)