What is under Greenland’s ice?

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We have been watching surface melting of the Greenland Ice Sheet (see Greenland Ice Sheet Today) as one sign of climate change. Covering some 656,000 square miles and ranging from 1 to 2 miles thick, this mass of ice is often considered a bellwether for change in the Arctic. But there is still much to know about what goes on beneath its surface. Recently, scientists were surprised to find evidence of soil underneath the Greenland Ice Sheet. Why is it there? And what does it reveal about the history of the ice sheet? Continue reading

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

Is declining sea ice changing the atmosphere?

Although Arctic sea ice extent did not set a low record this year, it’s still clear that there is less sea ice than there used to be. Scientists are keeping a close eye not only on the dwindling ice, but also on the ripple effect its loss might have on the rest of the Arctic environment. A big question involves the exchange of heat between ocean and air—and the weather patterns that result.  What does current research say about how floating ice—or the lack of it—might be changing the Arctic atmosphere? Continue reading

Celebrating 35 years of sea ice satellite data

Image of Arctic sea ice derived from SMMR data

This image is derived from the Scanning Multichannel Microwave Radiometer (SMMR), and shows Arctic Ocean sea ice extent in August 1985. Purple and red show greater ice coverage, while greens and blues indicate less ice. The black circle over the pole indicates no data—SMMR took observations very close to, but not directly over, the pole. Image credit: NSIDC

Polar scientists are celebrating an anniversary of sorts. Thirty-five years ago, sea ice research took a great leap forward. On October 26, 1978, the Scanning Multichannel Microwave Radiometer (SMMR) beamed its first data records back down to Earth. The instrument, pronounced simmer, was capable of mapping global sea ice concentration and extent, giving scientists a more comprehensive look at Arctic and Antarctic sea ice. Thanks to SMMR and its successor remote sensing instruments, scientists now have a long and detailed record of sea ice that helps them understand how sea ice works, and how it is changing. Continue reading