In 2007, scientists observed a loss of massive amounts of thick, multilayer sea ice, contributing to the record-low extent of Arctic sea ice that year. This raised the concern that the Arctic could be on the edge of a significant transition toward a seasonal ice cover.
Record Drop in Arctic Sea Ice
June through September 2007 brought record sea ice melt in the Arctic region, well below the previous record set in September 2005. According to the National Snow and Ice Data Center (NSIDC), the sea ice extent dropped to 1.59 million square miles (4.13 million square kilometers) on September 16, 2007. It was 38% below average and 24% below the record set in 2005.
Since the beginning of the satellite record, the monthly average extent of Arctic sea ice has shown a decline in every season and every region. The drop of perennial sea ice was faster than the decline of the ice cover as a whole, indicating a shift towards less multiyear ice and more first-year ice, thus showing a thinner ice pack.
Switch Gear Mechanism
New research by an international team of scientists reveals the reason behind the Arctic sea ice loss trend since 2007. Their study indicates that more substantial declines in sea ice could occur when an atmospheric phenomenon called Arctic dipole reverses itself in its recurring cycle. Their analysis also helps explain the influence of North Atlantic water on the Arctic Ocean climate.
Led by Professor Igor Polyakov of the University of Alaska Fairbanks College of Natural Science and Mathematics, the scientists made a multidisciplinary study of what is going on in the Arctic and beyond. Their research includes the ocean, ice, atmosphere, changing continents, and changing biology in response to climate change.
The team relied on a pool of information such as direct instrumental observations, reanalysis products, and satellite data that goes back several decades. It was revealed that the Arctic dipole alternates in an approximately 15-year cycle and that the system could be at the end of the present regime.
In the present positive regime of the Arctic dipole, which was believed to have been in place since 2007, high pressure centered over the Canadian region of the Arctic and produced clockwise winds. Meanwhile, low pressure is centered over the Siberian Arctic and involves counterclockwise winds.
After investigating the oceanic responses to the wind pattern since 2007, the team discovered decreased flow from the Atlantic Ocean into the Arctic Ocean through the Fram Strait east of Greenland. Increased Atlantic flow into the Barents Sea north of Norway and west of Russia was also found. These alternating changes in the Fram Strait and the Barents Sea were referred to as "switchgear mechanism" that resulted from the Arctic dipole regimes.
From 2007 to 2021, freshwater had a slow movement, which helped slow down the overall loss of sea ice in the Arctic compared to 1992 through 2006. As the depth of the freshwater layer increased, it became too thick and stable to mix with the heavier saltwater below. The thick freshwater layer also prevents the warmer saltwater from melting sea ice from the bottom.
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