Under the ice flows a river
Antarctic ice shrouds the continent's geology. With the help of technology, however, secrets are being wrested from it again and again: for example, a river as long as the Thames.
Under the ice of Antarctica there is not only bare rock: Science has known about Lake Vostok for decades, for example, and other lakes have already been discovered. They are probably fed and partly connected by a dense network of flowing waters. Martin Siegert from Imperial College in London and his team now report in "Nature Geoscience" on a previously unknown river that is roughly the length of the Thames and drains an area the size of France and Germany together. . The team discovered the river, which is at least 460 kilometres long, using airborne radar surveys that penetrate the ice. Siegert and co then used the data to model the hydrology of the ice sheet. The team focused on a largely inaccessible and little-explored area that encompasses the ice of both the East and West Antarctic Ice Sheets and extends to the Weddell Sea. The river empties into the sea there under the ice shelf.
Compared to rivers like the Rhine, relatively small amounts of water flow into the ocean: according to calculations, it is about 86 400 cubic metres per hour. This corresponds to just under a tenth of the Rhine at Cologne at normal water level. However, the water has so far come exclusively from the base of the glacier, where friction and high pressure liquefy the ice - in contrast to Greenland, for example, where summer melt water also penetrates from the surface through so-called glacier mills into the depths, where it can collect. In Antarctica, however, the maximum temperatures are not yet sufficient for this, even in summer in large parts of the continent.
This could change with the advent of a new ice age.
However, this could change with continued global warming: The existence of large rivers would then have to be taken into account when predicting the possible consequences of climate change in the region. If, for example, summers become warm enough to cause a corresponding surface melt, this meltwater could reach the river systems under the ice, at least in parts of Antarctica, and strengthen them. One possible consequence would then be that the affected glaciers would flow faster, increasing ice loss at the South Pole.
The river water could also stir up warm water in the ocean and push it against the ice shelf, causing it to thaw more from below. "From satellite measurements we know which regions of Antarctica are losing ice and how much, but we don't necessarily know why. This discovery could be a missing building block for our models. We could be severely underestimating the rate at which the system is melting if we don't take into account the influence of these river systems," says co-author Christine Dow of the University of Waterloo. "The fact that such a large system could remain undiscovered at all until now shows how much we still have to learn about the continent."
Spectrum of Science
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