Tornado Science, Facts and History
Sea ice coverage over the Arctic has reached its lowest point for the year, coming in second only to 2007 for the lowest ice extent recorded since 1979, scientists announced Tuesday.
The latest low was recorded on Sept. 12, when the region's sea ice extent dropped to 1.74 million square miles (4.52 million square kilometers). This appears to be the low point for the year, as ice has started to reform in response to autumn cooling in the Arctic, according to the National Snow and Ice Data Center (NSIDC), which monitors sea ice extent.
The 2008 minimum is the second-lowest recorded since 1979, when satellite coverage began, and is 0.86 million square miles (2.24 million square kilometers) below the 1979 to 2000 average minimum.
The record minimum came on Sept. 16, 2007, when sea ice extent was reduced to an estimated 1.65 million square miles (4.28 million square kilometers) — 9.4 percent lower than this year's estimated minimum.
Though the ice did not melt this year to a record low, it is further evidence of the overall downward trend in sea ice extent in recent decades, the NSIDC said in a statement. Arctic sea ice has also been thinning, as older, thicker ice melts away and the ice that reforms each winter is thinner perennial sea ice that melts away again in the summer. Scientists attribute this trend to the rise of global temperatures caused by the increase of greenhouse gases in Earth's atmosphere.
The pattern of ice melt this year was different than in 2007. This year did not have the substantial ice loss in the central Arctic, north of the Chukchi and East Siberian Seas. However, 2008 did see greater loss in the Beaufort, Laptev and Greenland Seas.
Both years saw the opening of the shallow Amundsen's Northwest Passage, but the deeper Parry's Channel of the Northwest Passage did not quite open in 2008.
This year saw another opening though: the Northern Sea Route, the passage through the Arctic Ocean along the coast of Siberia.
While the Sept. 12 minimum appears to be the minimum for the entire year, further melting could occur later. In 2005, for example, the ice extent appeared to reach a minimum in early September, but the ice contracted later in the season, creating a new minimum.
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