Seen from Space 2006
Variation of sea ice cover in the Antarctic Ocean
Figure 1 presents an animated movie of the yearly transition of sea ice in the Antarctic Ocean. The movie is composed of pictures captured by the JAXA's microwave instrument AMSR-E aboard NASA's Aqua satellite. The figure illustrates the observed sea ice in the white area in the center, the land in gray, and the sea surface in blue. The yearly sea-ice extent in the Antarctic Ocean experiences its greatest decrease in March (autumn in the southern hemisphere), unlike the Arctic Ocean ice, which decreases in September.
The figure indicates that the sea-ice cover of this year has a round shape, whereas the shape and position of the past sea-ice cover have varied significantly depending on the year. Recent sea-ice observations by satellite indicate continued reduction of the extent of sea ice in the Arctic Ocean. In contrast, the extent of sea ice in the Antarctic Ocean does not exhibit such an explicit decreasing trend. Rather, snow depth over the sea-ice cover in the Antarctic Ocean has increased recently, and the sea ice extent also has expanded gradually but continuously. Why does sea ice behave so differently in the two polar regions? Until now, no one has clarified the reason for the conflicting behavior. However, researchers believe that, as the climate of the Earth becomes warmer, sea ice itself floating on the ocean melts easier while the precipitation (snow fall) rate increases. The faint increase trend of the Antarctic sea ice extent is considered to balance the climate system of the Earth, which is believed to be getting warmer year by year, demonstrating the complexity and difficulty of understanding the formation of the climate system. JAXA will continue to monitor these climatic trends by using Earth-observation satellites.
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