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NOAA reports continuing Arctic warming Report card for 2017 emphasizes a new normal of reduced sea ice cover and shorter snow seasons despite near average temperatures Alan Bailey Petroleum News
Although Arctic air temperatures last summer and fall were cooler than in recent years, long-term indicators continue to point to a “new normal” for the Arctic, with air temperatures rising at double the global rate, declining sea-ice cover, a declining extent and duration of snow cover, and the declining mass of glaciers and the Greenland ice sheet, according to the National Oceanic and Atmospheric Administration’s Arctic Report Card for 2017.
“Arctic conditions in 2017 provide an excellent example of the need to assess observations in the context of longer-term records,” the report card says. “After a very warm Arctic-wide autumn 2016, spring and summer 2017 had near average air temperatures relative to the 1981-2010 climatology.”
The relatively cool conditions led to a rebound in the extent of the snow cover in May and June in Eurasia, the slowing of the rate of loss of sea ice, and a below-average extent of the melt of the Greenland ice sheet, the report card says. The spring snow cover extent over Eurasia was the second highest on record since 1967, the minimum sea ice extent in September was up a bit relative to the last couple of years, and the extent of the summer Greenland ice sheet melt was the lowest since 1996.
Long term trend But the report card cautioned against using last summer’s cool conditions as evidence that there may be some relaxation in the overall warming of the Arctic. In the longer term, surface temperatures in the Arctic Ocean are increasing, causing sea ice to form later in the fall. Onshore, temperatures in the permafrost have also been rising, the report card says.
“Arctic paleo-reconstructions, which extend back millions of years, indicate that the magnitude and pace of the 21st century sea-ice decline and surface ocean warming is unprecedented in at least the last 1,500 years and likely much longer,” the report card says.
The consequence of the long term warming has been an increase in the biological productivity in the Arctic Ocean, a factor that impacts the web of marine life. And, on land, vegetation is expanding, with impacts on hydrology, on the cycling of carbon and nutrients, on the surface energy balance, and on plant eating wildlife and domestic animals.
“The unprecedented rate and global reach of these changes highlight the pressing need to prepare for and adapt to the new Arctic, enabled by more effective and timely communication of observations to scientists, policymaker and residents,” the report card says.
Warm in Alaska and NW Canada Despite relatively cool conditions across much of the Arctic during the summer of 2017, Alaska and northwestern Canada saw above average surface air temperatures, with some locations in interior Alaska experiencing their warmest conditions on record for July.
And in August 2017 surface sea temperatures in parts of the Barents and Chukchi seas reached levels 4 C higher than the 1982 to 2010 mean for that month. These surface temperatures, set mainly by the absorption of solar radiation, are impacted by a number of factors, including the distribution of sea ice and cloud cover, the report card says.
Sea ice conditions March 2017 saw the lowest winter maximum sea ice extent since satellite observations began in 1979. Then, following the relatively cool conditions that persisted through the summer, the September minimum ice extent was the eighth lowest on record. However, this extent remained consistent with a long-term downward trend of 13.2 percent per decade. And the high surface temperatures in the Chukchi and Barents seas in August delayed fall sea ice formation in these regions. Moreover, the proportion of thicker and more durable multiyear ice in the overall Arctic ice pack has been falling steadily, with the amount of ice at least four years old dwindling to particularly low levels
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