Filling and draining of meltwater lakes that form on the surface of glaciers during summer periods and under the influence of global warming, leads to the bending of the floating Antarctic ice shelf, which potentially threatens its stability and may provoke a more rapid and sharp rise in the level of the World Ocean.
The existence of surface waters on ice shelves has long been known. More than 100 years ago, members of the Ernest Shackleton team recorded them and plotted on the Nansen shelf map, about 300 kilometers from the McMurdo shelf, where we conducted our research. In addition, satellite images show a wide distribution of meltwater over the past ten years, forming every Antarctic summer on many floating glaciers.
-Ian Willis, co-author of the study from the Polar Research Institute. Scott (UK)
Most of the Antarctic continent is covered with an ice sheet, which is up to four kilometers thick and contains enough ice to raise the level of the World Ocean by 58 meters. For most of the year, almost all over the continent, the air temperature is well below zero. About 75 percent of the shield is bordered by ice shelves, which are up to one kilometer thick. Their main part is hidden under the water, but a few tens of meters still protrude above it, and in the summer months, when the air temperature rises above the freezing water level, the surface of these white rocks begins to melt.
It is not yet known to what extent the forming lakes can destabilize the ice shelf, especially during warm periods, when their formation is significant. If the slope of the floating glacier is sufficiently steep, water can drain from it, forming rivers, which mitigates any potential threat to its integrity. But what if the lake lingers for a long time?
Danger arises if water accumulates in hollows on a glacier, forming large lakes. Extra weight will put pressure on its surface, causing the glacier to sink more and more into the sea. Around the edge of the lake, it will curve upward, and then, when the water drains, it will return to its original position. It is this filling and drainage of the lakes that leads to permanent vertical bends of the ice shelf, and if enough stress arises, faults can occur.
-Alison Banwell, lead author of the study from the Polar Research Institute
The results demonstrate the link between melting the surface and weakening the Antarctic shelves and support the idea that the collapse of the Larsen glacier in 2002 off the coast of the Antarctic Peninsula could be triggered, at least in part, by the large amount of melt water formed in response to atmospheric warming. As the climate continues to change, more and more ice shelves may become its victims over the next century.
The team hopes that their work will inspire researchers to search for evidence of the bend and destruction of other ice shelves around Antarctica. In addition, the findings of scientists will help in the development of scale models of the ice sheet, which will be used to predict the stability of the ice shelves in the future, as they act as a “protective screen”, preventing the rapid flow of ice behind them into the ocean.
Threats to the glaciers of Antarctica
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