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Arctic continues dramatic warming trend NOAA annual report card points to rising temperatures, shrinking sea ice, increasing ocean acidification, melting of Greenland ice ALAN BAILEY Petroleum News
The National Oceanic and Atmospheric Administration’s Arctic Report Card for 2016 highlights persistent warming in the Arctic region with the sea ice cover continuing to shrink as temperatures rise. On land, the Greenland ice sheet is melting. Atmospheric carbon dioxide that dissolves in the sea water is pushing up levels of ocean acidification.
NOAA has published its Arctic Report Card annually since 2006, as a vehicle for publishing peer-reviewed, concise and reliable environmental information for the Arctic region.
Rising air temperatures The report says that Arctic air temperatures have been rising at double the overall global rate. The average surface air temperature over land north of 60 degrees north latitude between October 2015 and September 2016 was 2 C higher than the 1981 to 2010 baseline and by far the highest since observational records began in 1900. The average temperature has increased 3.5 C over that time period. Winter air temperatures greatly exceeded previous record levels, with January temperatures more than 8 C above normal at some locations, the report says.
However, air temperatures over the Arctic Ocean in the summer of 2016 were relatively low, a situation that slowed the rate of summer sea ice loss. Thus, despite a record low winter maximum sea ice extent in March, the minimum extent reached in September tied for the second lowest on record rather than setting a new record for the minimum. But, given the multi-year warming trend, the sea ice cover continues to be relatively young and thin. The proportion of multi-year ice relative to first-year ice in March has shrunk from 45 percent in 1985 to 22 percent in 2016.
Warming ocean The retreat of sea ice is exposing more of the sea surface to solar radiation, thus causing upper ocean and sea surface temperatures to rise through much of the Arctic Ocean and the adjacent seas, the report says. The Chukchi Sea, off Alaska, and eastern Baffin Bay, off west Greenland, have seen the fastest rates of warming, with warming trends of around 0.5 C per decade since 1982. In August 2016 the surface sea temperatures in regions of the Barents Sea and the Chukchi Sea, and off the east and west coasts of Greenland, were up to 5 C higher than the 1982 to 2010 average.
The decline of sea ice cover, by exposing more of the sea surface to sunlight, is also causing an increase in biological productivity in the sea water. The only exceptions to this trend are in the North American Arctic and the Sea of Okhotsk, the report says.
However, the Arctic seas, with relatively cool water temperatures and the prevalence of processes such as the freezing and melting of sea ice, are also particularly susceptible to acidification from the dissolving of carbon dioxide from the atmosphere. Relatively small amounts of human-derived carbon dioxide in the Arctic atmosphere can trigger significant chemical changes not observed in other regions, the report says. Current data demonstrates that shallow waters over Arctic marine shelves are experiencing prolonged ocean acidification effects. With these waters then being transported off the shelves to greater depths, the corrosive impacts of acidification have been extending deeper into the Arctic basin in recent decades, the report says.
Greenland ice sheet melting On land, the Greenland ice sheet has continued to melt, especially in the sheet’s southwest and northeast regions. In 2016 the melt season lasted longer than usual by up to 40 days, the report says.
The Arctic snow cover extent has also dropped significantly since satellite observations began in 1967 and in particular since 2005. April and May of 2016 saw a new record low for the North American Arctic. The drop in snow cover appears to result both from rising air temperatures and a lower mass of pre-melt snow, the report suggests.
Other impacts of rising Arctic temperatures include the increasing greenness of the tundra and the thawing of the permafrost. And, although an extended Arctic growing season results in an increased uptake of carbon from the atmosphere, that effect is more than offset by carbon loss in the winter, as carbon dioxide and methane escape from permafrost areas. Changes in the Arctic tundra are also causing changes in the distribution of Arctic fauna, with evidence of poleward shifts of small mammals such as Arctic shrews.
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