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Sept. 27 (UPI) -- Satellite observations suggest the Arctic's sea ice reached its summertime minimum extent on Sept. 19, and then again four days later on Sept. 23. On those dates, the sea ice surface area totaled 1.77 million square miles -- the sixth lowest summertime minimum extent in modern history, tied with 2008 and 2010.
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"This year's minimum is relatively high compared to the record low extent we saw in 2012, but it is still low compared to what it used to be in the 1970s, 1980s and even the 1990s," Claire Parkinson, a climate change senior scientist at NASA's Goddard Space Flight Center, said in a news release.
Every year, ice in the Arctic Ocean grows through the winter months, reaching a maximum in early spring, and then shrinks through summer months, reaching a minimum in early autumn. Satellites and aerial surveys help scientists keep track of the maximum and minimum extents.
Data collected over the last several decades suggests both the Arctic's minimum and maximum sea ice extents are getting smaller over time. Several studies have shown climate change to be having an outsized impact on Earth's poles.
The Arctic experienced a mix of unusually warm and cool weather this summer, leading to intense melting in some regions and the persistence of ice in others.
Scientists were surprised to observe melting at the center of a region of old, thick ice north of Greenland. Aerial surveys conducted earlier suggest the historically thick region of sea ice was thinning.
When ice melts and refreezes, thinning in the process, it can become more susceptible to warmth and air and currents, enabling the transfer of heat to previously insulated regions of Arctic ice.
Earlier this year, scientists found evidence that thermal energy had penetrated deep into the Arctic interior of a period of several decades.
The same pattern -- melting and thinning magnifying the impacts of warm air and water -- appears to be happening throughout the Arctic, across both short and long timeframes.
"This summer, the combination of thin ice and southerly warm winds helped break up and melt the sea ice in the region, reopening the hole," said Melinda Webster, a sea ice researcher at Goddard. "This opening matters for several reasons; for starters, the newly exposed water absorbs sunlight and warms up the ocean, which affects how quickly sea ice will grow in the following autumn. It also affects the local ecosystem; for example, it impacts seal and polar bear populations that rely on thicker, snow-covered sea ice for denning and hunting."
Earlier this month, NASA launched the agency's newest ICE mission satellite, ICESat-2. Scientists hope the probe's more precise laser-based ice measuring system will help them better understand sea ice loss in Arctic.
"We're losing more and more sea ice every year and we don't know why," Tom Wagner, ICESat-2 program scientist, told UPI.
