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

Are we cooling?

After a cool Arctic summer, sea ice at the North Pole has recovered somewhat from last year’s record low extent. While this is a welcome pause in the downward trend of sea ice extent, some are taking it a step further and hailing this rebound as evidence that the Arctic is no longer warming. But does the recent uptick mean that we have entered a period of global cooling? NSIDC scientists point out why we shouldn’t be reading too much into one summer of less sea ice decline. Continue reading

Core of climate history

Lou and the Ice Core Drill

Scientists take ice core samples in cold, windy, and forbidding environments. After drilling through solid ice to retrieve a core, initial measurements are taken before it is sent away for more in-depth analysis and storage. Photo credit: NSIDC courtesy Ted Scambos and Rob Bauer

People have asked how scientists know that today’s climate situation is unusual. Hasn’t the Earth undergone many cold and warm cycles before? Could this just be another? Buried in the world’s ice sheets is a long story of climate on Earth–and the contribution of atmospheric CO2 to warming or cooling. Scientists can access a unique and detailed look at the history of the Earth’s atmosphere through ice cores and start to understand the recent climate in context of past ones. Continue reading

Are Arctic cyclones chewing up sea ice?

Satellite image of the 2012 Arctic cyclone

This satellite image of the Great Arctic Cyclone was taken on August 7, 2012 when the center of the storm rolled into the middle of the Arctic Ocean. (Courtesy LANCE/NASA GSFC)

The Big One

The Great Arctic Cyclone of 2012 lifted out of Siberia on August 2nd, swirling in a counter-clockwise rotation up into the Arctic. As one of the most extreme Arctic cyclones ever recorded, its consumption of an already low sea ice extent raised many concerns. Now Arctic cyclones are garnering attention, but is all the hype warranted?

“People seem to have this thought that all this storminess is unusual,” said Mark Serreze, an Arctic climatologist and center director at NSIDC. “Well it’s not. It simply isn’t. Summer is the time for cyclones.” Arctic summers are not calm. In fact, the months of August and September see a maximum amount of cyclonic activity. Not every summer is very stormy, but overall, the Arctic is the Arctic for a reason. Continue reading

Are scientists conservative about sea ice?

The U.S. Coast Guard Cutter Healy encountered only small patches of sea ice in the Chukchi Sea when this photograph was taken on July 20, 2011. (Courtesy NASA Goddard Space Flight Center)

The U.S. Coast Guard Cutter Healy encountered only small patches of sea ice in the Chukchi Sea when this photograph was taken on July 20, 2011. (Courtesy NASA Goddard Space Flight Center)

Guest post by Walt Meier, NSIDC Scientist

Arctic sea ice set a record minimum extent in September 2012, far below the previous record low in 2007. Summer extents have been far lower than average for the last decade, with several record or near-record years. Looking at the numbers, one is tempted to think that the Arctic Ocean may reach nearly sea ice-free conditions within just a few years. But most expert analyses indicate that we’re likely at least a couple decades away from seeing a blue Arctic Ocean during the summer.

Continue reading