March 14, 2017
Half of arctic sea ice loss is due to natural variation, study finds
Mountains of scientific evidence have shown the remarkable decrease of Arctic sea ice in recent decades, which has actually outpaced many models of climate change.
A new study published in the journal Nature Climate Change has found a considerable slice of sea ice loss during recent summers was as a result of normal variation in the atmosphere over the Arctic Ocean.Lead study author Qinghua Ding, a climate scientist at the University of California Santa Barbara, said human activities are still the dominant player when it comes to climate change, "but we found that natural variability has helped to accelerate this melting, especially over the past 20 years."
Hotspot over Greenland and Arctic Canada
The study expands on prior work by the same researchers that discovered modifications in the tropical Pacific Ocean have recently produced a "hot spot" over Greenland and Arctic Canada that has increased warming in that area.
The warm spot is a massive area of high-pressure air. The compression of all this air causes it to be warmer, in the same way than a tire warms up as it fills up with more and more air. This warmer air over the Arctic can hold more moisture, and the result is more heat being shipped to the sea ice below.
The new study concentrates explicitly on what this atmospheric flow means for Arctic sea ice in September when the ocean hits its maximum area of open water. To reach their conclusion, researchers designed a new sea ice simulation that showed a change in wind patterns is behind around 60 percent of sea-ice loss in the Arctic Ocean since 1979. Some of this transfer is connected to manmade climate change, but about 30 to 50 percent of the detected sea ice loss since 1979 is as a result of normal shifts in this massive atmospheric pattern.
The researchers said the normal long-term variability is thought to be powered by the tropical Pacific Ocean. Factors in the tropical Pacific set off atmospheric waves that ripple around the globe to produce areas of high and low air pressure.
"The idea that natural or internal variability has contributed substantially to the Arctic sea ice loss is not entirely new," study author Axel Schweiger, a University of Washington polar scientist, said in a news release. "This study provides the mechanism and uses a new approach to illuminate the processes that are responsible for these changes."
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