Minimum extent of sea ice in summer and Arctic for 2018 tied for sixth lowest record

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. The shrinking of the Arctic sea ice can ultimately affect the weather conditions of the planet and the circulation of the oceans.

"This year's minimum is relatively high compared to the record level recorded in 2012, but it remains low compared to what it was in the 1970s, 1980s and even the 1990s," said Claire Parkinson, Senior Scientist of 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 has been the reopening of a polynya-like hole in the pack ice in northern Greenland, where the oldest and thickest sea ice in Canada is usually found. '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 would become vulnerable if the original, thicker ice cover was replaced by finer ice as the exposed seawater returned. NASA's Operation IceBridge surveyed the region in March, finding that the ice was indeed thinner and therefore more likely to be driven by ocean winds and currents.

"This summer, the combination of thin ice and warm southerly winds has broken up and melted sea ice in the area, which has opened up the hole," said Melinda Webster, sea ice researcher at Goddard. "This openness counts for several reasons; for starters, the newly exposed water absorbs sunlight and warms the ocean, which affects the speed with which sea ice will grow in the following fall. It also affects the local ecosystem; for example, it affects populations of polar seals and bears that depend 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. Now, with the successful launch on September 15 of satellite-2 on NASA's ice, clouds and land, or ICESat-2, scientists will be able to use advanced laser altimeter data from the Spacecraft to create detailed maps of the thickness of sea ice. In the Arctic and Antarctic.

Source: The NASA