Hottest half-year on record sinks Arctic ice to new lows

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An image of Arctic sea ice captured from 1,500 feet during an Operation IceBridge mission(Credit: NASA/Goddard/Operation IceBridge)

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Last month, scientists reported an earlier-than-normal annual melting of Arctic sea ice, and now NASA researchers taking further stock of the situation are providing a clearer picture of how fast it is shrinking and the reasons why. As Earth sweats through its hottest six-month period on record, analysis of the same timeframe has revealed record-breaking shrinking of Arctic sea ice, with total coverage at the height of the melting season now 40 percent less than in the late 1970s.

The US National Oceanic and Atmospheric Administration (NOAA) has today revealed data showing 2016 had the hottest June on record, topping last year's record-breaking June by 0.04° F (0.02° C) and the 20th century average by 1.62° F (0.9° C). June marked the 14th consecutive month such a title has been claimed and makes January-June of 2016 the planet's hottest half-year period on record.

"While the El Niño event in the tropical Pacific this (Northern Hemisphere) winter gave a boost to global temperatures from October onwards, it is the underlying trend which is producing these record numbers," says Gavin Schmidt, director at NASA's Goddard Institute for Space Studies.

Temperatures are rising across the globe, but scientists say that the warmth in the Arctic has been especially profound, as they report exceptionally low snow cover in the Northern Hemisphere and premature seasonal melting of sea ice along with the Greenland ice sheet.

"It has been a record year so far for global temperatures, but the record high temperatures in the Arctic over the past six months have been even more extreme," says Walt Meier, a sea ice scientist at NASA's Goddard Space Flight Center. "This warmth as well as unusual weather patterns have led to the record low sea ice extents so far this year."

Of the first six months of 2016, five of those saw the lowest levels of Arctic sea ice for those respective months since records began in 1979. March was the exception, but logged the second smallest ice coverage for that particular month. Arctic sea ice is generally at its lowest in September, and the team says that levels at this point in the cycle have been declining by 13.4 percent per decade.

NASA has been conducting flyovers of the Arctic sea ice for eight years through Operation IceBridge, a mission designed to collect data on changes in sea ice shape and size. But this year the scientists have a slightly different focus: the pools of water known as melt pond that form on the ice in spring and summer.

Recent research has shown these gatherings of melted ice can serve as a good predictor of the seasonal low-points as they reduce the ability of the sea ice to reflect solar radiation, which has the effect of accelerating overall shrinkage. By mapping how many there are and how big and deep they go, NASA hopes to learn more about how they might be helping shape the future of the region.

"Although there have been previous airborne campaigns in the Arctic, no one has ever mapped the large-scale depth of melt ponds on sea ice using remote sensing data," says Nathan Kurtz, IceBridge's project scientist and a sea ice researcher at NASA's Goddard Space Flight Center in Greenbelt, Maryland. "The information we'll collect is going to show how much water is retained in melt ponds and what kind of topography is needed on the sea ice to constrain them, which will help improve melt pond models."

The video below gives an overview of the recent climate and sea ice trends.

Source: NASA

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