Circumpolar Deep Water (CDW) is the main component of the Antarctic Circumpolar Current, and is found several hundred meters deep. Before reaching the continental shelf, its warm waters pass through deep depressions, which lead them into cavities under the Antarctic ice. If the volume of these waters increases between the cavities, they can melt the lower part of the glacier shelf.
“The factors that affect the volume of CDW reaching the continental shelf and the cavities under the ice are quite unknown and are the subject of much ongoing research. It is suspected that they are related to changes in atmospheric circulation patterns, in particular, with the increase in winds from the west ”, Ala Khazendar, from NASA's Jet Propulsion Laboratory and co-author of a study on these waters, told Sinc. they are causing Antarctica's glaciers to melt faster.
The results of this research, published in the journal Nature Communications, support the hypothesis that the amount of warm water below the ice in the Amundsen Sea has increased significantly in the last 16 years.
Scientists studied with data from NASA's Operation IceBridge the behavior of three glaciers in West Antarctica in the Amundsen Sea: The Smith, Pope and Kohler.
Measure ice loss from the bottom of glaciers
This area is home to some of the planet's glaciers that are melting faster. Until now the exact magnitude of the ice loss was not quantified.
To measure the thickness and height of the ice, the scientists used radar instruments and laser altimetry. Radar waves penetrate glaciers to their base, allowing a direct assessment of their lower profiles and how ground lines have changed between 2002 and 2014.
The authors have observed intense and unbalanced melting of glaciers between 2002 and 2009. The Smith, for example, loses 70 meters of ice a year and almost half a kilometer of ice thickness in total. Between 2009 and 2014, the influx of warm water into the Pope and Kohler glaciers has been reduced, leading to less ice loss.
“Recent research work indicates that some of the changes in West Antarctica are already irreversible, in particular the rapid retreat from the land line and the loss of mass from the largest glaciers, such as Thwaites. Several ice shelves on the Antarctic Peninsula, which has one of the fastest rates of global warming in the last 50 years, have collapsed, ”adds Khazendar.
The question now is whether the rest of the glaciers in West Antarctica behave like The Smith or more like Pope and Kohler. But researchers need more information about the bedrock and seafloor, as well as data on ocean circulation and its temperatures, to be able to better predict how much ice from these glaciers will contribute to sea level rise.
Bibliographic reference: Ala Khazendar et al. "Rapid submarine ice melting in the grounding zones of ice shelves in West Antarctica" Nature Communications DOI: 10.1038 / ncomms13243