Researchers discovered a new process that contributes to ice shelf melting in West Antarctica, where adjacent ice shelves can cause instability to those shelves downstream. It is a dangerous wild card for world coastlines and stable civilization.
The University of East Anglia researchers also discovered a small gyre in Pine Island Bay, part of the Amundsen Sea Embayment. The studied gyre is a vortex of complicated ocean currents adjacent to the Thwaites Ice Shelf that can impact the amount of glacial meltwater flowing beneath. "The glacial meltwater mixes with saltwater when the ocean melts the base of ice shelves and can form a buoyant layer of water warmer than the surrounding waters. This lighter, relatively fresher, and warmer water brings heat that melts the base of the Thwaites Ice Shelf."
The phenomenon is what analysts now refer to as a deep red code alert. The ice shelf's collapse will mean that the inland ice, lubricated at the bed with geothermal heat and friction from grinding the bedrock, can empty with a two-foot sea level rise and up to sixteen feet if the entire W Antarctica goes down with it. As you know, Thwaites is the cork that holds back the land ice.
Most of this warming was driven by waters with a high volume of glacial meltwater originating from the Pine Island Ice Shelf, further east, flowing into the area beneath the Thwaites Ice Shelf.
The glacial meltwater mixes with saltwater when the ocean melts the base of ice shelves and can form a buoyant layer of water that is warmer than the surrounding waters. This lighter, relatively fresher and warmer water brings heat that melts the base of the Thwaites Ice Shelf.
Lead author Dr Tiago Dotto, of the Centre for Ocean and Atmospheric Sciences at UEA, said: “We have identified another process that could impact the stability of ice shelves, revealing the importance of local ocean circulation and sea-ice.
“Circumpolar Deep Water, a warm variety of Antarctic waters, is a key player in melting the base of ice shelves. However, in this study, we show that a great amount of heat at shallow layers beneath one ice shelf can be provided by waters originating from other melting ice shelves nearby.
“Therefore, what happens to one ice shelf, can impact the adjacent ice shelf, and so on.
This process is important for regions of high ice shelf melting such as the Amundsen Sea because one ice shelf sits next to the other, and the export of heat from one ice shelf can reach the next one through the ocean circulation.”
Dr Dotto added: “These atmosphere-sea-ice-ocean interactions are important because they can prolong warm periods beneath ice shelves by allowing warm and meltwater-enriched water to enter adjacent ice-shelf cavities.
“Gyres potentially existing in other regions around Antarctica may also cause a greater number of ice shelves to be prone to intense basal melting associated with prolonged warm conditions, and as a result further contribute to global sea-level rise.”
ASL is like a permanent hurricane and swirls off the coast of West Antarctica, affecting wind and sea ice, both of which are critical for the stability of the ice cliffs.
The Amundsen Sea Low (ASL) is a dominant feature of the atmospheric circulation in the Southern Ocean. Variations in this low-pressure center influence wind over the Antarctic sea ice, which can cause anomalies in sea ice transport and ice concentration. However, because the location of the low and the sea ice cover differ seasonally, the influence of ASL variability on sea ice differs by region and season. Additionally, the sea ice can exhibit a lagged response to the ASL, resulting in sea ice anomalies many months following variations in the ASL.
Our hypothesis relies on the fact that sea-ice coverage considerably dampens the wind stress over the ocean surface. Polar ocean gyres tend to weaken during periods of extensive sea-ice coverage and less mobile sea-ice (e.g., refs. 32,33,34,35,36.). Moreover, a gyre not only weakens under the presence of high concentrations of landfast-ice but may also reverse its direction from clockwise to anticlockwise depending on the strength and the angle between the wind direction and the sea-ice edge33. A change in the gyre direction could warm the ice-shelf cavities even faster than the simple spin-down suggested in this work because it could lift the isopycnals further up beneath the ice shelf and bring deeper warm waters upwards.
Prolonged periods of weaker gyres lead to warmer conditions within ice-shelf cavities. Consequently, more glacial meltwater may be exported from one ice-shelf cavity to another. The meltwater imported from adjacent cavities suggests that ice shelves are coupled systems connected through the coastal circulation15,19. In this sense, what happens under one ice shelf greatly influences what happens under the ice shelves further downstream in the coastal current. Therefore, models should assess the meltwater pathways from adjacent ice shelves and their consequences at the ice-ocean boundary to better simulate the fate of the Antarctic ice shelves, at least in shelf regions such as the Amundsen Sea where rapidly thinning ice shelves releasing considerable freshwater into the ocean are geographically connected (e.g., ref. 21.).
It is important to note that the British Antarctic Survey has arrived at Thwaites. Perhaps we will get a clearer picture of what is going on. We can safely rule out 2022 as the year Antarctica crumbles, but 2023 could see lots of adverse action when El Nino likely returns.
NASA science notes that El Niño episodes affect the Weddell and Ross Seas. "These areas are considered critical sources of cold and dense bottom water influencing global ocean circulation. The most vital links were observed in the Amundsen, Bellingshausen, and Weddell Seas of the west Antarctic. Within these sectors, higher sea level pressure, warmer air temperature, and warmer sea surface temperature are generally associated with the El Niño phase".Between now and 2100, the rain in Antarctica is projected to become more frequent and more intense, according to the new research. In total, we could be looking at an increase in rainfall of around 240 percent across the continent.
That will have an impact on the inhabitants of the icy wilderness – including emperor and Adélie penguin chicks, whose feathers aren't waterproof. When wet weather is followed by cold and windy weather, these chicks can freeze to death.
"We expect not only more frequent rain events but also more intense rain events," says atmospheric physicist Étienne Vignon from Sorbonne University in France.
Snow is much more common than rain in Antarctica, but it's difficult to measure precipitation.
Antarctica is classed as a desert, and even snow falls rarely. This is partially due to a lack of weather fronts making it to the continent, and partially due to the very dry air. Rain falls mostly around the coast, with the eastern coast estimated to get around 4 days of rainfall per year, and the northwestern peninsula more than 50 days.