NASA’s Satellite Measures Microwaves to Map Arctic Sea Ice

Last week we reported the end of the 2010 Arctic sea ice melt season, as declared by the National Snow and Ice Data Center (NSIDC)  and also that this year reached the third-lowest sea ice minimum ever recorded by satellites. Of course, it makes sense that ice melts during the Arctic summer, when days are longer (up to 24 hours long, in fact) and temperatures are warmer in the Northern Hemisphere. Although some melting is expected, the warm season in the Arctic isn’t enough to melt all of the ice that accumulates over the dark, frigid colder winter. However, over the past 30 years, more and more ice has been melting, indicating that ocean and atmospheric temperatures are climbing in the Arctic.  

Aqua satellite image of Arctic sea ice as of September 3, 2010, when the extent of the ice was still shrinking.

Figuring out exactly how much ice there is and how much of it is melting seems like a daunting task, however, given that Arctic sea ice is so vast, averaging over 3 million square miles? 

One of NASA’s Earth Observing System satellites, Aqua, is perfectly equipped to help with that tough task. One of Aqua’s six sensors, known as the Advanced Microwave Scanning Radiometer (AMSR-E), actually measures the microwaves that radiate from the Earth’s surface, and can detect the boundary between ice and water in the Arctic with good precision. Everything on the planet, including you and me, emits microwave radiation, but the wavelength of the rays is different for each type of object. It turns out that the difference in microwaves from the solid (ice) and liquid forms of water are different enough that a sensitive satellite detector like AMSR-E can see the change. Measuring microwaves turns out to be pretty handy for measuring the ice boundary because the radiation can be detected through clouds and in the dark.

For more stunning satellite images, check out NASA’s Earth Observatory.