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Narrator: The polar ice caps have been shrinking in summer and expanding in winter for millions of years. But in the last three decades, the Arctic sea ice at the end of each summer's melt has been getting steadily smaller. The decline was already alarming but in 2007 when the sea ice melt shattered the previous record by almost 25% researchers at NASA's Goddard Space Flight Center wondered is this an anomaly or part of an even more alarming trend?
Josefino Comiso: We've had low ice cover since 1998 in the Artic. And what that means is that we have more open water in the region. More open water, you're getting more solar evergy into the system. So the Arctic Ocean has actually been warming up.
Narrator: As the Ice melts, less light energy is reflected back into space, and more of the Sun's energy is absorbed into the ocean which fuels further melting. In March 2008, the ice cap rebounded to a near normal winter level. But much of this ice was thin, single year ice and after a record rate of melting in the month of August the ice shrank to its second smallest extent on record.
Comiso: If it keeps on going, then the potential is that you lose the perenial ice altogether. Then we'll have a blue ocean in the Arctic. Now if the ocean becomes blue, there'll be a lot of environmental impacts. There are a lot of ecological impacts.
Narrator: Comiso says the 30 years of satellite data we have on the Arctic sea ice suggest that it's not likely to recover. As a scientist, he is intrigued by the trends, but personally he worries about the planet's future.
Comiso: Well, it makes me feel sad. A lot of things can happen. In terms of... the impacts to the environment, the impacts to the ecosystem, and not just in the Arctic, but for the whole Earth. And the ocean is such a big part of the climate system and you perturb it a little bit a you're going to change the climate of the world.
Narrator: One result of such global climate change has already begun to emerge at the other end of the Earth. Summer sea ice minima in the southern hemisphere have not been declining. As warmer ocean water promotes evaporation, which creates more snow to feed the Antarctic ice fields. NASA scientists are using a suite of satellites to study sea ice in both poles, trying to better understand how a complex set of phenomenon, such as cloud cover, reflectivity, the thickness of the ice, weather patterns like La Nina and El Nino, and ocean temperature effect the trends we see today.
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