Why is there so much Antarctic sea ice?


Photograph from a ship traveling through Antarctic sea ice

Even during the Antarctic summer, heavy sea ice conditions are not uncommon. This photograph of sea ice was taken from the British icebreaker, HMS Protector, on its way to assist a Norwegian cruise ship that had become stuck in sea ice in January 2013.
–Credit: Royal Navy Media Archive (http://www.flickr.com/photos/rn_topten/8443836559/in/set-72157632684027667)

In late December 2013, the Russian research vessel, Akademik Shokalskiy, became trapped in thick sea ice off the coast of Antarctica. After several research vessels and icebreakers attempted rescue, the 52 passengers were evacuated. Soon after, one of the rescue ships also became stuck in the ice. However, conditions eased and both icebound ships safely churned out to open water.

Research in polar regions is inherently risky, and these events show how easily weather and ice conditions can disrupt research missions and travel during the already short Antarctic summer. But why was there so much sea ice around Antarctica to begin with, and why was it so thick? Antarctic sea ice is ruled by very different systems than Arctic sea ice. The reasons behind this increase are complex, and several recent studies show that scientists are still trying to understand them. Continue reading

What is the polar vortex?

Photograph of Chicago during the 2014 polar vortex

This view of Chicago was taken from Diversey Harbor on January 7, 2014, when a trough of the Northern Hemisphere polar vortex looped south across the United States, putting much of the country in a deep freeze. Credit: Edward Stojakovic (Creative Commons, http://creativecommons.org/licenses/by/2.0/)

Guest post by Mark Serreze, NSIDC Director and Professor, Department of Geography, University of Colorado Boulder

Lately there has been much talk about extreme cold weather in the United States and its connection to the polar vortex. Just what is the polar vortex, and how does it affect the lower latitudes? We asked Mark Serreze, NSIDC Director and a specialist in Arctic climatology, to provide an explanation. Here is his response:

A vortex is a region within a fluid where the flow is mostly a rotational motion around a given axis. The Earth’s atmosphere, while a gas, nevertheless behaves broadly as a fluid. The polar vortex is the region of the atmosphere that contains the hemisphere’s cold air, rotating from west to east. In the Northern Hemisphere, the axis of the rotation is generally located in the Arctic. There is also a polar vortex in the Southern Hemisphere, in which the axis of rotation is around the Antarctic continent. This post discusses the Northern Hemisphere polar vortex, recognizing that the same basic processes work in the Southern Hemisphere. Continue reading

What can stall a glacier?

Much talk surrounds the deterioration of glaciers and ice sheets—particularly, how they are thinning and losing mass with global warming; but the mechanisms are complicated and scientists want to know more about their flow. The Antarctic ice sheet, in particular, piques interest because it contains enough fresh water to raise sea levels 60 meters (200 feet), if it were to melt completely. So how does the ground beneath the ice influence mobility? When and how does the ice sheet stall? When does it accelerate? And how does this ebb and flow contribute to global sea level rise? Continue reading