A key part of the world’s largest ice shelf is melting 10 times faster than previously estimated.
Solar heating of the oceans, which the study’s authors called a “frequently overlooked process,” was a major factor driving the unexpectedly high melt rate under Antarctica’s Ross Ice Shelf, which extends for hundreds of miles over the Southern Ocean, covering about the same area as France.
During the summer, the Sun warms surface water in the region, which then downwells underneath the shelf and exposes it to higher temperatures.
“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 lead author Craig Stewart, a marine physicist at the National Institute of Water and Atmospheric Research (NIWA) in New Zealand, in a statement.
The Ross Ice Shelf slows the drainage of inland glaciers into the oceans, so its long-term stability is important. If the shelf were to collapse, rapid acceleration of Antarctic glacial melt could cause the global sea level rise to rise by several meters.
Fortunately, scientists don’t think the Ross Ice Shelf is in any immediate danger of collapse or serious erosion. But nonetheless, their study revealed that melt rates at the Ross Sea Polynya, a region located at the northwest edge of the shelf, are an order of magnitude above the shelf-wide average.
To get a sense of the conditions inside this frozen structure, Stewart’s team accumulated four years of observations at various locations on the shelf. The researchers used radar to probe the density of the shelf and traveled hundreds of miles across the ice to retrieve data from disparate locations. They also collected temperature, salinity, and melt rate measurements from a sensor deployed in the ocean under the shelf.
Solar heating and ice melt has implications for projecting the future stability of the Ross Ice Shelf, because it shows that the structure is more vulnerable to surface water temperatures than originally thought.
“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,” Stewart said.
Even if the Ross Ice Shelf’s stability isn’t at immediate risk, the new study demonstrates that critical parts of it could become more vulnerable over the coming decades, emphasizing the need to keep tabs on this gigantic frozen terrain.