Antarctica researchers have become alarmed by a new finding that shows sub-glacial lakes under the ic of the Thwaites glacier are draining a significant amount of meltwater 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. These phenomena are not included in current climate models.
Along with Pine Island glacier, Thwaites will eventually collapse due to our warming climate and take West Antarctica's entirety with it. Extreme melting is driven by warm ocean water and at the last interglacial caused a sea-level rise of three feet in ocean temperatures less than 2C. As the Proceedings of the National Acadamy of Sciences of the United States write in their study on the significance of this temperature ‘We present a multiproxy record that implies a loss of the West Antarctic Ice Sheet during the Last Interglacial (129,000 to 116,000 y ago), associated with ocean warming and the release of greenhouse gas methane from marine sediments. Our ice sheet modeling predicts that Antarctica may have contributed several meters to global sea level at this time, suggesting that this ice sheet lies close to a “tipping point” under projected warming.’
The European Space Agency notes ‘Water routing models suggest the lakes are part of a vast meltwater system underlying the Antarctic ice sheet.’ (Emphasis mine)
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.
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.
Climate News Network writes that Heat from factories and car exhausts must go somewhere. A surprising amount is now sunk in the remote Antarctic depths.
LONDON, 28 October, 2020 − Thanks to global heating, a vital part of the Southern Ocean is warming at a rate five times faster than the average for the Blue Planet as a whole, in the far Antarctic depths: 2000 metres or more below the surface of the Weddell Sea.
It is happening because at that depth the Weddell Sea has absorbed five times as much atmospheric heat − fuelled by greenhouse gas emissions from human fossil fuel combustion − as the average for the rest of the ocean. But what happens out of sight and far below the surface may not stay invisible. The Weddell Sea is where vast volumes of water circulate.
The fear is that such dramatic warming at depth could end up weakening a powerful current that encircles Antarctica, according to a new study in the Journal of Climate.
New Scientist writes on how atmospheric rivers are melting sea ice in the Weddell Sea.
Rivers of warm air transported across the atmosphere have been found to play a major role in the creation of vast openings in Antarctic sea ice.
Storms are known to help trigger the openings, known as polynyas, which in the past have expanded to tens of thousands or even hundreds of thousands of square kilometres. But despite the world’s most powerful storms being a regular fixture in the Southern Ocean around Antarctica, they don’t on their own explain why the polynyas form at some times and not at others.
Now, Diana Francis at Khalifa University in Abu Dhabi, United Arab Emirates, and her colleagues think they have the answer. Combing satellite records and climate data, they looked at major polynya events in the Weddell Sea on the Antarctic coast in 1973 and 2017.
They found that flows of heat and water vapour in the sky, known as atmospheric rivers, travelled huge distances, in one case moving from the south-eastern coast of South America down to the Weddell Sea in 2017. During September that year, one river increased air temperatures in the Weddell Sea by 10°C.