Eddie Gonzales Jr. – MessageToEagle.com – Antarctica’s Ross Ice Shelf – the world’s largest ice shelf – is melting 10 times faster than expected due to solar heating of the surrounding ocean, researchers say.
The Ross Ice Shelf plays an important role in the region by stabilizing the West Antarctic ice sheet by blocking the ice which flows into it from some of the world’s largest glaciers.
The Ross Polynya where solar heat is absorbed by the ocean. The vertical wall of the ice front stretches a distance of 600 km. Credit: Poul Christoffersen
During several years, an international team of scientists observed who how the north-west sector of this vast ice shelf interacts with the ocean beneath it. They found that this process is taking place due to inflowing warm water.
Using instruments deployed through a 260 metre-deep borehole, the team measured temperature, salinity, melt rates and ocean currents in the cavity under the ice.
“The stability of ice shelves is generally thought to be related to their exposure to warm deep ocean water, but we’ve found that solar heated surface water also plays a crucial role in melting ice shelves,” said first author Dr. Craig Stewart from the National Institute of Water and Atmospheric Research (NIWA) in New Zealand, who conducted the work while a Ph.D. student at the University of Cambridge.
“Previous studies have shown that when ice shelves collapse, the feeding glaciers can speed up by a factor or two or three,” said co-author Dr. Poul Christoffersen from Cambridge’s Scott Polar Research Institute, in a press release.
“The difference here is the sheer size of Ross Ice Shelf, which over one hundred times larger than the ice shelves we’ve already seen disappear.”
Dr. Stewart and Dr. Christoffersen traveled more than 1000 km by snowmobile in order to measure ice thicknesses and map basal melt rates. Data from the instruments showed that solar heated surface water flows into the cavity under the ice shelf near Ross Island, causing melt rates to nearly triple during the summer months.
The melting is affected by a large area of open ocean in front of the ice shelf that is empty of sea ice due to strong offshore winds. This area, known as the Ross Sea Polynya, absorbs solar heat quickly in summer and this solar heat source is clearly influencing melting in the ice shelf cavity.
“Climate change is likely to result in less sea ice, and higher surface ocean temperatures in the Ross Sea, suggesting that melt rates in this region will increase in the future,” said Stewart.
While the Ross Ice Shelf is considered to be relatively stable, the new findings show that it may be more vulnerable than thought so far.