September 13, 2013
Expedition Investigates Ice Flow Melt Beneath Remote Antarctic Glacier
[ Watch the Video: Warm Ocean Melting Pine Island Glacier ]
redOrbit Staff & Wire Reports - Your Universe OnlineThe floating ice shelf in a remote region of Antarctica is being melted by warm ocean water, not hot air, an international team of researchers report in the latest edition of the journal Science.
As described in the new study, an expedition to Pine Island Glacier allowed scientists to get an up-close-and-personal look beneath the ice of one of the most difficult to reach sites on the planet.
Once dubbed the “biggest source of uncertainty in global sea level projections” by glaciologists, the processes occurring in this region could affect the fate of millions of people, the researchers explained in a statement.
“Intensive melting under the Pine Island ice shelf, as observed in our study, could potentially lead to the speed up and ultimate break-up of the ice shelf,” said co-author David Holland of New York University (NYU). “That's important, as this ice shelf is currently holding back inland ice, and without that restraining force, the Pine Island catchment basin could further contribute to global sea-level rise.”
Holland and his colleagues studied Pine Island Glacier, a major outlet of the West Antarctic Ice Sheet, because it had rapidly thinned and accelerated over the past several years. Logistically, it has been a difficult destination to reach, as it lies far away from McMurdo base, the usual location of American research in Antarctica, they explained.
Between December 2012 and January 2013, during the southern hemisphere’s summer season, the research team drilled holes in the ice in order to place various instruments. They also used radar to map the ice shelf’s underside, as well as the bottom of the ocean. They discovered that the ice shelf is melting more rapidly from below.
There are multiple causes of this phenomenon. For one thing, the ocean waters are warmer than they have been in the past, and water is capable of transferring a greater amount of heat than air. Also, there is a series of channels beneath the ice shelf, and the floating ice in the channels has enough room to allow ocean water to flow in.
“The water melts some of the ice beneath and cools,” Penn State University, which handled the geophysics of the project, explained in a statement. “If the water remained in the channel, the water would eventually cool to a point where it was not melting much ice, but the channels allow the water to flow out to the open ocean and warmer water to flow in, again melting the ice shelf from beneath.”
“The way the ocean water is melting the ice shelf is a deeply non-uniform way. That's going to be more effective in breaking these ice shelves apart,” added Penn State geosciences professor Sridhar Anandakrishnan. He and his colleagues said that the shelf plugs the channel, but once it is gone, the glacier will move towards the sea at a faster rate, forming more ice shelf while also removing a considerable portion of ice from the glacier in the process.
Floating ice shelves do not cause sea levels to increase when they melt, because once they are in the water, the ice shelves themselves have already contributed to the sea level rise. However, since the majority of Antarctic glaciers are on land, adding new ice shelf material to the floating mass will cause sea level to increase. While Anandakrishnan said that Antarctica is “relatively stable,” he warns that it won’t stay that way forever.
“This is a harbinger of what will happen,” he added. “The Antarctic has been relatively quiet as a contributor to sea rise. What this work shows is that we have been blind to a huge phenomenon, something that will be as big a player in sea level rise in the next century as any other contributor.”
In addition to NYU and Penn State, researchers from the Naval Postgraduate School (NPS) in California, the University of Alaska, NASA and the British Antarctic Survey were involved in the research. The project was funded by NASA, the National Science Foundation (NSF) and the UK’s Natural Environment Research Council.