Satellite Data Causes Scientists Concern Over Declining Arctic Ice

According to NASA, researchers from the National Snow and Ice Data Center (NSIDC), part of the University of Colorado at Boulder, and NASA scientists have been observing the declining Arctic sea ice cover since 1979 when the earliest measurements were taken.

New questions about the interactions of sea ice, ocean temperature and atmospheric temperature have arisen pursuant to the sudden speed-up of sea ice decline. Also unknown is what the decline will mean for the future of Earth's northern polar region. According to NSIDC, melting Arctic sea ice has shrunk to a 29-year low, significantly below the minimum set in 2005, according to preliminary figures

NASA developed passive microwave sensors to provide the first views of the extent and concentration of sea ice from satellites in space. In 2002, NASA launched an advanced microwave instrument--the Advanced Microwave Scanning Radiometer aboard the Aqua satellite -- that provides a view of sea ice dynamics in greater detail than has ever been seen before.

The Advanced Microwave Scanning Radiometer (AMSR-E) is a high-resolution passive microwave Instrument. AMSR-E provides a remarkably clear view of sea ice dynamics in greater detail than has ever been seen before. The data from AMSR-E is used to study the unique movements of sea ice from season to season. Researchers also use this information to study polar bear habitats. AMSR-E is a joint project of NASA and the National Space Development Agency of Japan.

In 2003, NASA launched ICESat spacecraft (Ice, Cloud, and land Elevation Satellite). Its primary goal is to determine how much the melting Arctic ice sheets are contributing to sea-level rise. In addition, ICESat permits the collection of data enabling scientists to make estimates of sea ice thickness with unprecedented detail.

ICESat's capabilities are important because previous instrumentation only maps sea ice in two dimensions. This limitation makes it difficult to find out how the thickness of the ice contributes to the change in the total volume of the ice.

NASA scientists have made extensive remarks on the data collected by the battery of satellites continuously surveying the polar regions. Several statements follow:

"Because Arctic ice cover varies so much year to year, it can be dangerous to look at any one year and draw too much of a conclusion from it," said Waleed Abdalati, head of NASA Goddard Space Flight Center's Cryospheric Sciences Branch. "But this year, the amount of ice is so far below that of previous years that it really is cause for concern. The trend in decreasing ice cover seems to be getting stronger and stronger as time goes on."

"The decline in the amount of thick ice that survives the summer melt season this year is quite remarkable," said Josefino C. Comiso, senior scientist at NASA's Goddard Space Flight Center, Greenbelt, Md. "The extent of this 'perennial' sea ice and the area it covers are both nearly 38 percent lower than average. Compared to the record low in 2005, the extent and area are 24 percent and nearly 26 percent lower this year, respectively."

"The rapid trend of the perennial ice previously reported in 2002 appears now to be in an accelerated mode," Comiso further observed.

Comiso believes that the accelerating decline in sea ice may be due to changes in climate brought on by the lack of sea ice itself. "When there is less sea ice in the summer, the Arctic Ocean [itself] receives more heat. The warmer water makes it harder for the ice to recover in the winter, and, therefore, there is a higher likelihood that sea ice will retreat farther during the summer. This process repeats itself year after year," Comiso said.

"The longer this process continues, the less likely recovery becomes," Abdalati believes. "The implications on global climate are not well known, but they have the potential to be quite large, since the Arctic ice cover exhibits a tremendous influence on our climate. It really is imperative that we try to understand the interactions between the ice, ocean and atmosphere. And satellites hold the key to developing this understanding."

"What we need to truly understand the interaction of the ice, ocean and atmosphere in the Arctic is sea ice thickness information," said Abdalati. "The new capability we have with ICESat is expected to be extended into the next decade based on recent recommendations by the National Research Council for a follow-on mission. Ultimately, like the 29-year record we have now of sea ice cover, a long-term ice thickness record will help scientists understand these complex interactions and what the changes in the ice cover will mean to the ecology of the Arctic and to life on Earth.

Animated images showing the extent of decline of Arctic sea ice are available as movies on the NASA Web site.

"'Remarkable' Drop in Arctic Sea Ice Raises Questions," NASA.