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NASA scientists explain what’s driving the decline in Arctic sea ice

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24.09.2021

September marks the end of the summer sea ice melt season and the Arctic sea ice minimum, when sea ice over the Northern Hemisphere ocean reaches its lowest extent of the year.

For ship captains hoping to navigate across the Arctic, this is typically their best chance to do it, especially in more recent years. Sea ice cover there has dropped by roughly half since the 1980s as a direct result of increased carbon dioxide from human activities.

As NASA scientists, we analyze the causes and consequences of sea ice change. In 2021, the Arctic’s sea ice cover reached its minimum extent on September 16. While it wasn’t a record low, a look back through the melt season offers some insight into the relentless decline of Arctic sea ice in the face of climate change.

In recent years, Arctic sea ice levels have been at their lowest since at least 1850 for the annual mean and in at least 1,000 years for late summer, according to the latest climate assessment from the U.N.’s Intergovernmental Panel on Climate Change. The IPCC concluded that “the Arctic is likely to be practically sea ice free in September at least once before 2050.”

As the Arctic’s bright ice is replaced by a darker open ocean surface, less of the sun’s radiation is reflected back to space, driving additional heating and ice loss. This albedo feedback loop is just one of several reasons why the Arctic is warming about three times faster than the planet as a whole.

The stage for this year’s sea ice minimum was set last winter. The Arctic experienced an anomalous high pressure system and strong clockwise winds, driving the thickest, oldest sea ice of the Central Arctic into the Beaufort Sea, north of Alaska. Sea ice scientists were taking note.

Summer melt began in earnest in May, a month........

© Fast Company


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