On September 19, Arctic sea ice reached its 2010 minimum, at 4.60 million square kilometers (1.78 million square miles). The National Snow and Ice Data Center (NSIDC) reported that 2010 Arctic sea ice extent was the third-lowest on the satellite record. (The record low, set in 2007, was 4.13 million square kilometers, or 1.59 million square miles.)
The 2010 minimum was part of a larger pattern of overall Arctic sea ice decline dating back to at least the early 1970s.
Arctic Sea Ice Minimum for 2010
The 2010 minimum was part of a larger pattern of overall Arctic sea ice decline dating back to at least the early 1970s.
Arctic Sea Ice Minimum for 2010
At the end of each summer, sea ice in the Arctic reaches its minimum extent for the year. This animation shows the retreat of Arctic sea ice cover from March 31 through September 19, as recorded by the AMSR-E instrument on NASA's Aqua satellite.
This image was compiled using data gathered by NASA's Aqua satellite on Sept. 3, 2010.
Credit: NASA Goddard's Scientific Visualization Studio
Arctic sea ice retreated to its annual minimum extent on Sept. 29, reaching the third-lowest extent in the satellite record.
Sea ice coverage dropped to 4.6 million square kilometers (1.78 million square miles) at its minimum, according to scientists at the National Snow and Ice Data Center. The extent was lower than the 2009 minimum but remained above the record minimums reached in 2007 and 2008.
acquired September 19, 2010 download large sea ice total area graph image (91 KB, PDF)
acquired September 12, 2010
Credit: NASAThis animated graph first tracks the retreat of sea ice, measured in millions of square kilometers, averaged from the start of the satellite record in 1979 through 2000 (white). Next, the graph follows the 2007 extent (green) as it approaches the record minimum. Finally, the graph tracks the decline this year (blue), which reached its minimum on Sept. and ranked as the third-lowest extent in the satellite record.
Credit: NASA/Goddard/Megan Willy
Arctic sea ice behavior was unusual in 2010 in that the sea ice appeared to reach its minimum extent on September 10 and began growing again. Acquired by the Moderate Resolution Imaging Spectroradiometer (MODIS)on NASA’s Terra satellite, the middle and bottom images capture some of that ice growth, occurring in the East Siberian Sea. The middle image is from September 12, and the bottom image is from September 14. New, thin ice appears in the bottom image as rippled sheets, barely lighter than the underlying ocean water. This is probably nilas—thin sheets of ice with an oily or greasy appearance. (See the Earth Observatory Sea Ice feature article to learn more about different types of sea ice.)
After a few days of growth, sea ice declined again until September 19. According to NSIDC scientist Walt Meier, the renewed melting late in the season suggested that sea ice cover was thin and loosely packed. Those conditions make sea ice susceptible not only to melting, but also to disintegration by wind. In early September, NSIDC described large areas ofrotten ice in an advanced state of disintegration.
The minimum sea ice extent in 2010 fits into a long-term pattern of decline, especially in multi-year ice, which persists through the summer melt season and into another winter. Multi-year ice may last for several years, eventually growing up to 4 meters (13 feet) thick.
First-year ice is thinner, saltier, and more vulnerable to melt. NSIDC stated that the 2010 season showed an increase in second- and third-year ice—which might eventually thicken—but the oldest and thickest ice had mostly disappeared from the Arctic.
“A band of thick ice is likely to persist along northern Greenland and northern Canada for some time,” said Ted Scambos, lead scientist at NSIDC. “But in the next 10 to 15 years, there could be substantial open water in the Arctic in the summertime.”
How does the Aqua satellite "see" sea ice? Microwaves. Everything on Earth’s surface -- including people -- emits microwave radiation, the properties of which vary with the emitter, thereby allowing the AMSR-E microwave sensor on Aqua to map the planet.
Ice emits more microwave radiation than water, making regions of the ocean with floating ice appear much brighter than the open ocean to the AMSR-E sensor. This difference allows the satellite to capture a sea ice record year-round, through cloud cover and the months of polar night. Continuous records are important because sea ice is dynamic. Besides melting and freezing, the ice moves with wind and currents which can cause it to split or pile up.
"The data from AMSR-E and other NASA satellites are critical for understanding the coupling between sea ice and the ocean and atmosphere," said Tom Wagner, Cryosphere program manager at NASA Headquarters in Washington. "It’s important for us to understand these connections to improve our predictive models of how the planet will change."
The Arctic sea ice is a major factor in the global climate system. The ice cools the planet by reflecting sunlight back into space. It also helps drive ocean circulation by converting the warm Pacific water that flows into the Arctic into the cold, saltier water that empties into the Atlantic. The sea ice also fundamentally shapes the Arctic; defining the organisms that make up its ecosystem and keeping heat from the ocean from melting the frozen tundra.
In fall 2009, Arctic sea ice reached its minimum extent on about Sept. 12, and was the third lowest since satellite microwave measurements were first made in 1979. Researchers are interested in year-to-year changes, which can be highly variable, so that scientists need many years, even decades, of data to examine long-term trends. Notably, all of the major minimums have occurred in the last decade, consistent with other NASA research, which shows January 2000 to December 2009 was the warmest decade on record.
As the sea ice nears the 2010 minimum later this month, look for images and analysis from NASA and the National Snow and Ice Data Center, in Boulder, Colo.
Ice emits more microwave radiation than water, making regions of the ocean with floating ice appear much brighter than the open ocean to the AMSR-E sensor. This difference allows the satellite to capture a sea ice record year-round, through cloud cover and the months of polar night. Continuous records are important because sea ice is dynamic. Besides melting and freezing, the ice moves with wind and currents which can cause it to split or pile up.
"The data from AMSR-E and other NASA satellites are critical for understanding the coupling between sea ice and the ocean and atmosphere," said Tom Wagner, Cryosphere program manager at NASA Headquarters in Washington. "It’s important for us to understand these connections to improve our predictive models of how the planet will change."
The Arctic sea ice is a major factor in the global climate system. The ice cools the planet by reflecting sunlight back into space. It also helps drive ocean circulation by converting the warm Pacific water that flows into the Arctic into the cold, saltier water that empties into the Atlantic. The sea ice also fundamentally shapes the Arctic; defining the organisms that make up its ecosystem and keeping heat from the ocean from melting the frozen tundra.
In fall 2009, Arctic sea ice reached its minimum extent on about Sept. 12, and was the third lowest since satellite microwave measurements were first made in 1979. Researchers are interested in year-to-year changes, which can be highly variable, so that scientists need many years, even decades, of data to examine long-term trends. Notably, all of the major minimums have occurred in the last decade, consistent with other NASA research, which shows January 2000 to December 2009 was the warmest decade on record.
As the sea ice nears the 2010 minimum later this month, look for images and analysis from NASA and the National Snow and Ice Data Center, in Boulder, Colo.
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