NASA's Earth Observing System (EOS) satellite Aqua, launched on May 4, is dedicated to advancing our
understanding of the Earth's water cycle. The National Space Development Agency of Japan's (NASDA's)
Advanced Microwave Scanning Radiometer - EOS (AMSR-E) is one of six key Earth-observing instruments
on board Aqua and has recently been used to obtain images of the sea ice covers of both polar
regions, showing their changes from the June 2-4 period to the July 21-22 period.
In these images, white indicates the area of sea ice cover and gray indicates land. Because of the
time period covered (late spring to summer in the Northern Hemisphere; late fall to winter in the
Southern Hemisphere), the area of the ice cover in the Arctic region is decreasing while the area
of ice cover in the Antarctic region is increasing, a fact captured very well in the AMSR-E images.
Annually, sea ice cover in the Arctic tends to decrease from March through September, then to
increase, while sea ice cover in the Antarctic tends to increase from February through September,
then to decrease. The presence of sea ice in the polar regions influences the balance of global heat
and radiation, as it restricts heat exchanges between the ocean and atmosphere and reflects much of
the solar radiation that reaches it.
These satellite-based maps show sea ice concentration in the Arctic and Antarctic during September 2008 and February 2009, the months of the sea ice maximums and minimums in the respective hemispheres.