As greenhouse gas emissions continue to rise, researchers are looking at a source of even more carbon emissions: thawing permafrost. A warming Arctic may cause significant amounts of dead, organic material currently frozen in permafrost to thaw out and decay, releasing more carbon into the atmosphere. How exactly does permafrost store carbon? And what are the consequences if the permafrost thaws?
If gardening in icy Greenland sounds unbelievable, think again. A chef in Kangerlussuaq has started growing tomatoes, peppers, herbs, and even strawberries for his restaurant, and Greenland’s potato production doubled between 2008 and 2012. These agricultural feats would have been impossible only a hundred years ago. The Arctic has been warming over the past several decades at a rate twice as fast as the rest of the globe. As the region warms, several teams of scientists have been tracking changes in Arctic vegetation, trying to see if higher temperatures mean more green. Continue reading
In spite of the massive blizzards that have slammed parts of the northeastern United States, much of the country is experiencing a pronounced lack of snow. And where there is snow, it is less than usual. It follows a very low snow year from the previous season, causing people to worry if low snowfall is the new normal.
A previous Icelights post, Arctic sea ice and U.S. weather, discussed possible causes behind the changes in winter weather, trying to see if there are correlations to larger climate changes. Researchers like Jennifer Francis of Rutgers University are exploring the possibility that declining sea ice in the Arctic is altering atmospheric temperatures and weakening the jet stream. This change may shift the Northern Hemisphere storm track, leaving some places unusually snowy, or leaving normally snowy locations dry. Can a few good blizzards help reverse the snow drought across parts of the United States? Or is this string of dry winters yet another symptom of climate change? Continue reading
September 2012 was a record-setting month for both of Earth’s poles, but for different reasons: sea ice in the Arctic fell to a record low minimum extent after a summer of melting while Antarctic sea ice froze to a record high extent during the South Pole winter. Is record Antarctic sea ice canceling out the losses in Arctic ice? And does the record in the south mean that Antarctica is not warming?
Warming at the South Pole
Polar scientists say no on both counts. Ted Scambos, lead scientist at NSIDC, said, “These systems are not directly connected, and they certainly don’t offset each other. The climate and ocean processes that control summer Arctic ice extent are completely different from the ones that drive the Antarctic.” Data records indicate warming at both poles, but Antarctica’s geography is forcing warming to show in different ways than it does in the Arctic. “Antarctica’s trend is not nearly as large or as clear as the Arctic’s,” Scambos said.
Antarctica is a vast and largely ice-bound landmass, and the effects of warming are more complicated for scientists to sort out. The East Antarctic Ice Sheet has remained fairly stable, but air temperatures over the Antarctic Peninsula and the West Antarctic Ice Sheet are rising. Along the Peninsula, warmer air has increased surface melting, and several large ice shelves along the Peninsula have disintegrated dramatically after particularly warm summer periods.
In spite of warmer air, the climate of rest of the West Antarctic Ice Sheet remains colder than the Peninsula, so the rise in temperatures has not led to much summertime melting. There, the main culprit is warmer ocean currents. New ocean circulation patterns are bringing much warmer water to the ice edges along the coast. This is rapidly thinning the thickest glaciers at their base, and causing them to speed up. Consequently, glaciers in West Antarctica are also losing ice, in much larger amounts than glaciers along the Peninsula.
Wind, weather, and ozone
Yet warming is only part of the story. Changes in Antarctica’s winter sea ice are due more to changes in the winds that encircle the continent and, strangely enough, in the ozone layer above it. “The winds that blow around the continent have gotten stronger,” Scambos said. “And an added effect is the ozone hole, which also changes winds in the far south.” This seasonal hole forms over Antarctica each winter. Normally, ozone absorbs sunlight and warms the atmosphere. The current lack of ozone leaves a much colder air mass above Antarctica. While this may sound ideal for ice formation, it can sometimes have the opposite effect on sea ice. When warmer air from the north mixes with stubbornly cold air over Antarctica, the resulting turbulence generates stronger winds. During winter, stronger winds often blow the ice northward, away from the continent, creating a larger overall extent. These winds shifts are also behind the new patterns of ocean circulation that is warming glaciers at the edges of the West Antarctic Ice Sheet
For now, however, most of Antarctica remains a very cold place, and it has not yet reached the critical threshold beyond which melting further amplifies changes. “Both the Arctic and Antarctic systems are being driven in new directions by human-caused changes. At this point, the side effects for the Antarctic are outweighing the effect of warming,” Scambos said.
For more information on see the differences between Arctic and Antarctic sea ice, see this previous Icelights post: Sea ice down under: Antarctic ice and climate
For a more in-depth explanation of this year’s polar ice conditions, see Poles apart: A record-breaking summer and winter.
To view maps of Arctic and Antarctic sea ice derived from satellite data, see the NSIDC Sea Ice Index.
Satellite observations since 1979 show that sea ice melted to its lowest extent in the satellite record, during August 2012 . As of this post date, the ice continues to melt, with two to three weeks left before the days shorten enough for the ice extent to begin to expand through the winter. Readers often write to us asking what such records really mean. How far from normal is this year’s record low, and how do scientists decide what is normal? Continue reading