Antarctica researchers have become alarmed by a new finding that shows sub-glacial lakes under the Thwaites glacier are draining a significant amount of water to the bedrock under miles thick with ice. Once the lake water reaches the bedrock, it lubricates the glacier enough to create frictional heat at the bed while possibly absorbing additional heat from the West Antarctic Rift System, which is responsible for volcanic activity in the area. Tectonic activity is almost impossible to determine as a source of heat at the bedrock. Still, along with frictional heat, it would melt the ice above the bedrock enough to provide entry for warm ocean water upwelling to further weaken the fragile glacier from below. The satellite data obtained on subglacial lake repeated drainage is another worrisome sign that the glacier will speed up its flow and raise sea levels worldwide.
Thwaites, along with Pine Island glaciers, will eventually collapse due to our warming climate and take West Antarctica’s entirety with it. Extreme melting is driven by warm ocean water caused a sea-level rise of three feet in ocean temperatures less than 2C.
Lily Roberts writes in the Glacier Hub blog published by the Earth Institute at Columbia University.
A new study has found that a network of lakes underneath a major Antarctic glacier underwent large drainage events in 2013 and in 2017. After completely emptying in 2013, the lakes regained volume over four years, only to empty again — this time faster and with more water discharged — in 2017. This was the first time repeat drainage and recharge of subglacial lakes under Thwaites Glacier has been recorded. Recent improvements in satellite instrumentation permit these precise measurements of the movement of water two kilometers below the permanent ice surface.
The presence of meltwater at the bed of the glacier lubricates the base and reduces friction between the rock and ice, preconditioning the glacier above to slide over the slippery surface more easily and flow faster toward the ocean. The velocity of the glacier directly influences its rate of mass loss and accordingly, sea level rise contribution. This study highlights yet another mechanism weakening Antarctica’s ice. Another concern is that the study’s results suggest that previous modelled estimates of melting at the bed have been substantially underestimated.
Thwaites Glacier is world-renowned for its importance in regulating Antarctic ice loss. It is known to be one of the fastest-changing glaciers in the region, transporting vast amounts of ice from the interior of the enormous West Antarctic Ice Sheet out to the sea. Scientists have been monitoring Thwaites Glacier for over two decades and have recognized it as one of the first glaciers to respond significantly to climate change. This critical glacier also accounts for a major proportion of Antarctica’s contribution to global sea level rise.
— Stef Lhermitte (@StefLhermitte) June 23, 2020
The results from the study found that four lakes that drained in 2013 were also involved in the 2017 event. George Malczyk, a glaciologist at the University of Edinburgh and the study’s lead author, told GlacierHub that “what is interesting about this second drainage event is how different it is from the first, with a much faster transfer of water and increased discharge. Our observations highlight that there were potentially significant modifications to the subglacial system between these two events.” This is intriguing because large changes occurred over a short time scale — once again highlighting the rapid ability of the Antarctic ice sheet to respond to change.
“What takes place under the ice sheet is critical to how it responds to changes in the atmosphere and ocean around Antarctica, and yet it is hidden from view by kilometres of ice, which makes it very difficult to observe,” explains Noel Gourmelen, also from the University of Edinburgh, study co-author and experienced researcher in Antarctic glaciology. He went on to add that the movements of water give key information about the kind of environment and hydrology network that is present beneath the glacier — information which is needed when trying to project the role of Thwaites Glacier in Antarctic contribution to sea level rise.