Minimal extent of summer sea ice in the Arctic, in 2018, tied for the sixth-lowest record ever seen – ScienceDaily

Arctic sea ice, the cape of frozen seawater covering most of the Arctic Ocean and surrounding seas in winter, follows seasonal patterns of growth and degradation. It thickens and spreads in the fall and in the winter and thins in the spring and summer. However, in recent decades, rising temperatures have resulted in a significant decrease in the extent of Arctic sea ice, with particularly rapid decreases in the minimum summer range. Declining Arctic ice cover can ultimately affect the weather conditions of the planet and the circulation of the oceans.

"The minimum of this year is relatively high compared to the record low level recorded in 2012, but it is still small compared to what it was in the 1970s, 1980s and even 1990s," said Claire Parkinson, a scientist experienced in climate change. at NASA's Goddard Space Flight Center in Greenbelt, Maryland.

Parkinson and his colleague Nick DiGirolamo have calculated that since the late 1970s, the extent of Arctic sea ice has declined by about 54,000 square kilometers (21,000 square miles) each year. This is equivalent to losing a piece of sea ice the size of Maryland and New Jersey combined each year for four decades.

This summer, weather conditions in the Arctic were mixed, with some regions experiencing warmer than average temperatures and rapid melting and other regions remaining colder than normal, resulting persistent sea ice patches. However, the minimum extent of pack ice in 2018 is 629,000 square miles (1.63 million square kilometers) below the average of the 1981-2010 annual minimum extensions.

One of the most unusual features of this year's melt season was the reopening of a polynya-like hole in the pack ice north of Greenland, where usually the oldest sea ice resides and the thickest in the Arctic. In February of this year, a similar opening appeared in the same area, attracting the attention of ice floe scientists all over the world. The first appearance of the hole raised concerns that the area could become vulnerable if the thicker ice cover was replaced by thinner ice when the exposed seawater refrozen. NASA's Operation IceBridge mission surveyed the region in March, finding that the ice was actually thinner and therefore more likely to be repelled by winds and ocean currents.

"This summer, the combination of thin ice and warm southerly winds has broken and melted sea ice in the region, opening up the hole," said Melinda Webster, researcher on the sea ice at Goddard. "This opening is important for several reasons: for starters, the newly exposed water absorbs sunlight and heats the ocean, which affects the rate of growth of the pack ice in the following autumn. fleets that rely on thicker, snow-covered sea ice for calving and hunting.

Measurements of sea ice thickness, an important additional factor in determining changes in ice cover mass and volume, were much less complete than measurements of extent and distribution ice during the last four decades. With the successful launch of Ice, Cloud and Land Elevation Satellite-2, or ICESat-2, NASA, on September 15, scientists will be able to use data from the spacecraft's advanced laser altimeter to create detailed maps of the thickness of the sea ice. in the Arctic and Antarctic.

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