Thursday, November 2, 2017

Massive Polynya in Antarctica

An hole in the sea ice as large as lake superior has opened in Antarctica. This is called a "polynya" and scientists have observed them before. This hole is unusual because of it great size. It has a diameter of about 30,000 square miles.

The first time scientists spotted something like this was in the 1970’s, but the opening disappeared for several decades before appearing again.

The blue curves represent the ice edge, and the polynya is the dark open water within the ice pack. Image: MODIS-Aqua via NASA Worldview; sea ice contours from AMSR2 ASI via University of Bremen

A polynya forms when water that is above freezing moves from the lower depths of the ocean to the surface. Heat transfers from the warmer water to the ice, melting it, and preventing new ice from forming. This type of polynya is called a "sensible heat" polynya. The ocean itself provides the heat needed to melt the ice. Sensible-heat polynyas usually form in mid-ocean areas, far from coasts or other barriers.

Polynyas are important as a source of heat and moisture in the atmosphere. This has an effect on the climate of the region. Polynyas also provide access between the ocean and atmosphere for a variety of animals, including seals and penguins. The overturning ocean water in a polynya brings nutrients to the surface, like phytoplankton, microscopic plant-like organisms that are a food source for marine life. During the summer, Antarctic polynyas are one of the most biologically productive regions in the world's oceans.

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