Arctic Sea Ice
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There use to be a time when knowing that polar bears lived at the north pole rather than the south pole made most people experts on Arctic ecology.
You knew, for example, that polar bears enjoyed surfing the ice packs as the Arctic spring and summer sun melted the once solid ice cap that covers the northern most portion of our planet.
You were reassured each year that the broken up ice pack reassembled because, of course, Santa and his reindeers always successfully completed their legendary annual world journey, including a successful North Pole take off and landing.
Ice is still the predominant characteristic of arctic ecology today. However, the text accompanying the Arctic ice story has changed considerably over the past five decades.
A changing climate now means that it is possible that the Arctic Ocean will be ice free by the year 2013. According to the The National Snow and Ice Data Center, the primary scientific body examining the issue, "it could be as early as 2013 or as late as 2100".
The thinning of Arctic Sea Ice is generally attributed to a changing climate. The General Circulation Models (GCMs) used to model climate change have consistently suggested that the greatest impact of climate change will be felt in the polar regions. To date, the changing Arctic ecology fails to falsify the results of the scientific models.
While increasing temperatures in the Arctic region account for some of the ice thinning, the melting is more fully explained by a double causative model that includes increased air temperatures and a changing ocean ecosystem.
Maps provided by the Arctic Climatology Project, a cooperative United States-Russian program, were among the first to illustrate an overall thinning pattern for the polar ice cap.
One set of maps which contrasts ice thickness at a 75 meter depth in the 1950s and in the 1980s shows ice pack density decreases in the potentially most dense ice packs off the coast of Norway and Russia. They also show overall density thinning throughout the entire Arctic Ocean.
Debate exists over the actual amount of sea-ice thinning, however, one scientific estimate, published in the journal, Geophysical Research Letters records an average 1.3 meter (~4 feet) thinning.
Why the thinning? Most scientists attribute the thinning to a weakening of the halocline layer of the Arctic Ocean, which basically is the bottom portion of the top layer of the three layers of water constituting the Arctic Ocean. The halocline layer, defined by its strong salinity, traditionally functioned as a road block, stopping the warmer Atlantic Ocean water (the Atlantic layer= 2nd level of Arctic Ocean) from mixing with and melting the top layer, the ice.
© 2001-2009. Patricia A. Michaels