Two studies carried out with an underwater robot provide new information about the worrying loss of icy mass
On all continents, scientists study the mechanisms of melting on high-mountain glaciers, as well as in Greenland, the Arctic, and Antarctica. They analyze the rate at which they break, their evolution in the coming decades and their possible consequences for the rise in sea level. In this context, one of the greatest sources of uncertainty is found in the Antarctic region, which for a long time has remained relatively stable despite global warming, but which has been giving multiple alarm signals in recent years.
Two studies published this Wednesday in Natureexplore the dynamics that occur under Antarctic glaciers and their possible contribution to the rise in the level of the oceans. These works have focused on the glaciar Thwaitesin the western part of the continent, one of the fastest changing ice-ocean systems.
According to the authors, the rapid retreat experienced by this frozen mass is driven by hitherto unknown dynamics; Specifically, new observations made at the intersection of the ocean and the glacier show that melting in cracks and crevices is much more significant than previously thought. Thus, the Thwaites Glacier (with an extension similar to that of Great Britain) continues to recede, even when no mass losses are observed on the surface (for example, spectacular calving of icebergs).
The papers describe how a layer of cold water between the bottom of the ice shelf and the underlying ocean slows the rate of melting in the flat parts of the shelf. Specifically, observations show that although melting has increased in the submerged part, the rate at which it does so is slower than many computer models currently estimate. On the other hand, the authors were surprised to see that the melting modeled a staggered topography at the bottom of the platform and that in these areas, as well as in the cracks, it is producing a more significant loss than previously thought.
“These results are surprising, but the situation of the glacier is still very problematic,” confirms Peter Davis, of the British Antarctic Survey Service (BAS), lead author of one of the studies of Nature. “When the ice shelf and the glacier are in equilibrium, the amount of ice lost from the continent is stable with respect to the amount that disappears due to melting and calving of icebergs. What we have observed is that, despite the small amounts of melting that are being seen on the surface, there is still a rapid retreat of the glacierwhich means it doesn’t take much to get it unbalanced.”
field observations
The new data was collected under the MELT project, a collaboration between the United States and the United Kingdom. The scientists carried out observations at the line where the glacier meets the ocean, with the aim of better understanding how the ice and the sea interact. In Antarctica much of the frozen mass is below the water level and it is susceptible to rapid and irreversible loss of ice which, as the authors stress, could raise global sea level by more than half a metre.
The British team made oceanic measurements through a 600 meter deep borehole, carried out using a hot water drill. Those measurements were compared to melt rate observations taken at five other points under the ice-water shelf. On the other hand, their American counterparts at Cornell University they deployed a robot called Icefin by that hole created with the drill.
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Human remains appear on the Monte Perdido glacier due to melting ice
Human remains appear on the Monte Perdido glacier due to melting ice
The rover is designed to access areas that were previously nearly impossible to explore, and its observations of the seafloor and surrounding ice have uncovered stairs and terraces in the ice base, as well as rapidly growing crevasses. The thaw is especially relevant in those cracks, since water is channeled through them and the heat and salt can in turn widen the fissures. It is this dynamic that worries the authors, because it can be a significant factor in a rapid loss of mass as the main cracks progress through the platform.
“New ways of looking at the glacier allow us to understand that what matters in these ‘warm’ areas of Antarctica is not just how much is melting, but how and where,” says Britney Schmidt, an associate professor at Cornell University and lead author of the second study. “We see cracks and terraces in many glaciers that are getting hot, like the Thwaites; warm water is entering the crevasses, helping to wear down the glacier at its weakest points.”
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