Arctic sea ice narrowed in 2007 and has not recovered

Picture taken on May 20, 2021. Ice is receding from an ice cap glacier and fjords near Kangerlussuaq, Greenland. / Saul Loeb / AFP

Science | glaciology

This change is further evidence of the lasting impacts of climate change

Elena Martin Lopez

Starting in 2007, the Arctic sea ice became thinner and more uniform. Since then, the fraction of thick, deformed ice - that which accumulates and persists in the ocean for several consecutive years, more resilient than younger sea ice - has roughly halved, and has not recovered to date. . This is underlined by a
study published this Wednesday in the journal 'Nature'.

To reach this conclusion, the authors used continuous, direct measurements of ice thickness across ocean moorings from the Fram Strait Arctic Outbound Observatory, which has been monitoring sea ice and ocean properties since 1990. The results show a drastic change from 2007, characterized by a reduction of thick ice (more than 4 meters thick), by more than 50%, and the increase of thinner and more uniform ice.

This change came after an Arctic-wide reduction in sea ice residence time - the average length of time sea ice stays in the ocean before melting or being carried elsewhere by current - between 2005 and 2007. Specifically, this was reduced from 4.3 to 2.7 years. The residence time of sea ice can vary due to several factors: air and water temperature, wind speed and direction, and ocean circulation.

Impact on the ecosystem

"These findings show the long-lasting impacts of climate change on Arctic sea ice, suggesting that the change in sea ice thickness was a result of increased ocean heat in ice-forming areas. Thinner, more uniform sea ice may affect ocean mixing, and consequently ocean ecosystems, below the ice," the researchers warn.

Thick ice is important to the global climate and Arctic ecosystem for several reasons: it helps regulate ocean and air temperatures, and it provides a hunting and feeding platform for Arctic wildlife such as polar bears and seals. By contrast, melting sea ice does not contribute to sea level rise because it forms from the seawater on which it floats, not like land ice, which releases previously trapped water into the ocean when it melts. the earth.

This information is published days after the
Antarctic sea ice to hit record lows in February 2023, continuing a decade-long decline and reaching “its lowest extent in the 45-year satellite data record”, said Samantha Burgess, Deputy Director of the Copernicus Climate Change Service (C3S). ).