Also, despite being exposed to freezing chilly winds during the last month, this polynya has continued to persist, which means whatever force caused the hole to form is strong enough to keep it from refreezing. The last time this kind of large ice-free area in the Weddell Sea of the Antarctic Peninsula was observed in mid 1970s. It's odd for one very good reason: while most polynyas occur near coastlines, the Weddell is far inland and relatively sheltered from the violent winds and turbulent seas that generally cause them. An enormous hole in the sea ice just opened up for no apparent reason, and researchers are at a loss as to why it might've happened. The polynya was observed in the same region in the 1970's, then disappeared and appeared on a few weeks back past year. In an otherwise thick layer of sea ice, still frozen from the Antarctic winter, the hole is an aberration.
As the researchers note, often area of open sea surrounded by ice, known as polynyas, formed relatively close to the border of the ice and the sea. Instead, the Weddel Polynya can be pinned to water stratification in the Southern Ocean, according to scientists at the GEOMAR Helmholtz Centre for Ocean Research who closely following its development. In certain conditions, however, the warm water can rise to the surface, melting the ice.
'The Southern Ocean is strongly stratified, ' says Professor Dr Mojib Latif, head of the Research Division at GEOMAR. While it wasn't seen for decades after 1976, it reappeared in August a year ago.More news: No NAFTA Better Than Bad Deal, Say Business Leaders
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"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", Prof.
Is climate change the cause? The cold surface layer is shown in blue, with warm water indicataed in red. The polynyas opened in the winter from 1974 to 1976. "The better we understand these natural processes, the better we can identify the anthropogenic impact on the climate system", Latif said.