A vast hole has re-opened in Antarctica, and it could have something to teach us about climate change.
Some 40 years after satellites observed a wintertime gap in the ice of the Weddell Sea near the Antarctic Peninsula, the phenomenon has returned; and it comprises an area larger than Maryland.
At this time of year, the area is usually coated in thick ice. So the appearance of the hole—or polynya, as this type of phenomenon is called—is of interest to climate scientists and other observers.
"For us this ice-free area is an important new data point which we can use to validate our climate models," said Dr. Torge Martin, meteorologist and climate modeler at the GEOMAR Helmholtz Center for Ocean Research Kiel.
Martin says that the re-appearance of the hole at this time confirms the center's previous calculations; GEOMAR has posited a model that explains the polynya as part of natural climate processes.
"The Southern Ocean is strongly stratified. A very cold but relatively fresh water layer covers a much warmer and saltier water mass, thus acting as an insulating layer," Prof. Dr. Mojib Latif, head of the Research Division at GEOMAR, told the site.
Sometimes, the layer of warm water can then melt the ice. "This is like opening a pressure relief valve—the ocean then releases a surplus of heat to the atmosphere for several consecutive winters until the heat reservoir is exhausted," Latif said.
What is not fully known, however, is how climate change might affect this process. Some American scientists think that this polynya will never re-appear, as melting ice and more precipitation in the air separates the surface ice sheet from deeper layers of water.
But some models suggest that's wrong. The reappearance of the hole will bring new data to help solve the quandary.
And, Latif said, understanding the relationship between climate change and this kind of natural phenomenon can help scientists understand the climate system more broadly.
"Global warming is not a linear process and happens on top of internal variability inherent to the climate system. The better we understand these natural processes, the better we can identify the anthropogenic impact on the climate system," Latif said.
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