Sea-surface water heated by the sun causes rapid melting in the Ross ice floe region

Research involving Kiwi scientists has shown that surface seawater, heated by the sun, was a key factor in explaining why the base of part of the Ross Ice Shelf ( RIS) in Antarctica had melted faster than the average.

The results could have major implications for models that attempt to determine the effect that global warming will have on Antarctic ice and sea level rise predictions.

"At the moment, there is a lot of modeling going on to try to understand what might happen in the future," said Niwa's senior marine physics scientist, Mike Williams.

"Some of the scientific research that we have done is not integrated into this type of studies and models, which is what we are really interested in talking about," he said.

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"In fact, integrating this process into future studies is the next step in understanding whether we have a new risky, risky, or controlled mechanism where we do not have to not worry urgently. "

The RIS was about the size of Spain, said Williams. At the front, along the northern edge, where it meets the ocean, it can reach 200 to 250 meters in thickness. This reached 1 to 1.5 km thick at the point where ice covered the earth.

Williams, Niwa's marine physicist, Craig Stewart, and scientists from the University of Cambridge and the British Antarctic Survey studied for several years the northwest corner of the RIS, near the island of Ross , to document its merger. key processes leading him.

They collected data on a mooring under the Ross ice floe with instruments for measuring temperature, salinity, and currents. The mooring also included an acoustic sounder directed upward at the bottom of the ice to measure melting rates.

The mooring was located 7 km from the front of the pack ice and had been installed through a hole drilled in 260 m of ice, with 600 m of ocean under the platform.

The researchers found that melting in the study area was strongly influenced by a seasonal influx of sun-warmed surface water from the Ross Sea polynya – an open water area surrounded by ice.

While the average smelting rate for the entire 500,000 km² of RIS is about 0.1 million per year, it exceeds 1 million in the northwestern sector. Melt rates in the study area were about three times faster in summer than the rest of the year.

Despite this, for the moment, the RIS is considered close to balance. This meant that the amount of ice lost was offset by the ice coming out of Antarctica and the snow falling on the plateau, Williams said.

"The term equilibrium means that everything we lose is about the same as anything we earn." As far as scientists know, this was the case for all RIS, although one of the challenges was a limited number of direct measurements of the merger.

"What's important in this story is that we can not look at things on an annual average – we have to think about what's happening on a seasonal basis," Williams said.

There was a vulnerability to what could be a faster path of change than in other processes where deeper water was coming in and melting the ice.

"Here, we have the opportunity, at the end of the Antarctic winter, that the sun rises to warm the ocean and melt the melt, he drives it to a place where we think that 's. there is what we could call a pin.The island is owned by Ross Island.If it comes off this place, it could then start to retreat, "Williams said.

"This could be a very important process for its impact on the pack ice."

An article on the study, published in Nature Geoscience, said that recent modeling has shown that the rapid fusion identified by the research had an influence on a structurally critical region in which changes in ice thickness could affect the flow velocity ice cream as a whole.

Summer sea ice concentrations in the Ross Sea are expected to decrease by 56% by 2050, and the ice – free period is expected to lengthen, according to the article. Given this, it seemed likely that the melting of the base of the frontal regions of the RIS would increase rapidly.