Arctic Ocean sea ice melted faster last month than it has in any previous June since satellite measurements began 30 years ago, continuing a pattern that could see a new record retreat by summer's end, according to North America's main ice-monitoring research centre.
The U.S. National Snow and Ice Data Centre, the Colorado-based institute that tracks the annual cycle of winter ice buildup and summer thaw, says in its latest report that June's rapid melt — which followed a similar record-setting retreat in May — means the polar ice cover remained on pace to shrink more than it did in 2007, when an unprecedented loss of ice first prompted scientists to raise alarms about the Arctic as a harbinger of global climate change.
"Arctic air temperatures were higher than normal, and Arctic sea ice continued to decline at a fast pace" last month, the centre said in its July 6 report, adding that June also "saw the return of the Arctic dipole anomaly, an atmospheric pressure pattern that contributed to the record sea ice loss in 2007."
The sharp overall decrease in Arctic ice was driven partly by an extensive melt in Hudson Bay, which normally retains significant amounts of ice into July but is virtually clear this year, the NSIDC stated.
At the same time, the "Nares Strait ice arch" between Ellesmere Island and Greenland, which normally blocks the southward flow of thicker ice from the central Arctic Ocean, disappeared in May — similar to what happened in 2007 — and could allow an above-average discharge of older ice into warmer waters, the centre noted.
"Weather conditions, atmospheric patterns, and cloud cover over the next month will play a major role in determining whether the 2010 sea ice decline tracks at a level similar to 2007," the report stated. "It would not be surprising to see the rate of ice loss slow in coming weeks as the melt process starts to encounter thicker, second and third year ice in the central Arctic Ocean. Loss of ice has already slowed in the Beaufort and Chukchi seas due to the tongue of thicker, older ice in the region."
Last week, for the first time since early May, the trend line for 2010's rapid ice melt leveled out just enough to intersect with the 2007 trend line on NSIDC's daily satellite graphing of total Arctic ice extent.
The U.S. centre was instrumental in alerting the world in 2007 to that year's unprecedented summer melt of Arctic sea ice, from 14 million square kilometres at the end of the winter to about 4.3 million square kilometres by September 2007.
The past two summers have shown modest recoveries in ice extent to a late-summer minimum of about 4.7 million square kilometres (2008) and 5.4 million square kilometres (2009), still the second- and third-lowest extents since satellite measurements began in 1979.
The Colorado centre's experts and most other ice-monitoring researchers around the world — including the federal Canadian Ice Service — recently predicted another significant meltdown this summer, but not a record-setting one exceeding the historic retreat of 2007.
While many scientists expect virtually ice-free summers to occur in the Arctic in the coming decades — with some forecasting clear sailing within a few years — scientists continue to probe the reasons for the recent pattern of ice loss, its significance in long-term climate history and the immediate implications of a reduced polar cap, including the "feedback" risk of decreased sunlight reflection and even greater ocean warming.
Meanwhile, Canada and other northern nations — anticipating an increasingly ice-free polar realm and more Arctic ship traffic — are rushing to implement new transport and environmental regulations, bolster international search-and-rescue protocols and prepare for increased Arctic oil and gas development.
Last week, the world's largest association of maritime cargo carriers raised concerns about the Canadian government's July 1 implementation of a new, mandatory Arctic ship-tracking system for most foreign and domestic vessels travelling through Canada's northern waters.