Category Archives: Arctic sea ice

Are we in a snow drought?

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The central and southwestern portions of the United States have experienced drought for the past several years. This photograph was taken in mid-February, 2010. By that point in winter, these rows would normally have been fully covered in snow. Photograph credit: Kristy Johnson (http://www.flickr.com/photos/kayaker1204/4359744393/)

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 →

Industry and ice

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As the Arctic Ocean becomes increasingly ice-free, many countries are eager to tap into previously inaccessible northern resources. Energy companies seek drilling permits for oil and natural gas, and shipping companies hope to ply newly opened sea routes. Given the unpredictable nature of Arctic sea ice, some wonder if operating in the already inhospitable north will be an economically viable effort. Others believe that even if drilling or shipping is not currently viable, the Arctic is changing fast enough that industry in the Arctic is here to stay. Continue reading →

Is stored heat causing Arctic sea ice to freeze later each year?

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Graph showing Arctic sea ice minimum dates from 1979 through 2012, derived from satelite records

This graph shows the yearly trend toward later Arctic sea ice minimum dates, but also illustrates the wide variability from year to year. Credit: NSIDC

A reader recently asked if the date of the annual Arctic sea ice minimum is shifting later each year. And if so, is that shift a sign of heat being stored in the Arctic region?

According to the satellite record, Arctic sea ice generally melts to its minimum annual extent between the first and third week of September, after which ice begins freezing again. In recent decades, the Arctic has been gaining heat: Air, land, and ocean temperatures in the region have been slowly rising, and scientists have noted dramatic reductions in summer sea ice extent, as this heat causes more ice to melt away. But is this heat causing sea ice to form later each fall? Continue reading →

How low is low?

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extent graph

Sea ice extent reached a new record low on August 27, 2012 and continued to decline. The last six years have seen minimum sea ice extents below the two standard deviation range of the data. The graph above shows Arctic sea ice extent as of August 13, 2012, along with daily ice extent data for the previous five years. 2012 is shown in blue, 2011 in orange, 2010 in pink, 2009 in navy, 2008 in purple, and 2007 in green. The gray area around the average line shows the two standard deviation range of the data.

 

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 →

Do satellites sometimes see ice where there isn’t any?

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Readers often ask us, “Why does your sea ice map show sea ice where there is none?” Sometimes our Daily Sea Ice Extent images show sea ice in a particular area, but when readers who live in those areas look out their windows, they see open water—or they even may see ice where our maps show open water. This occurs most frequently along rivers or near coasts. Why does this happen?

Ups and downs of passive microwave

Photograph of Qaanaaq, a small town on the Greenland coast

The rugged coast near Qaanaaq, Greenland, illustrates the challenge to satellite sensors, which must distinguish between land and ocean signals within the same image. Credit: Andy Mahoney|{a href=http://nsidc.org/icelights/files/2012/07/Qaanaaq_coast.jpg}High Resolution Image{/a}

These discrepancies are most often caused by the resolution of the satellite sensor. NSIDC relies on passive microwave sensors to compile daily sea ice maps. These sensors have the advantage of being able to see through the Arctic’s cloudy weather and capture surface data even during long, dark winters, making them ideal for tracking sea ice. The disadvantage, however, is that passive microwave sensors often have low spatial resolution. The sensors collect data in “footprints” that are up to 50 to 70 kilometers (31 to 44 miles) in diameter. Continue reading →