Arctic sea ice narrowed in 2007 and has not recovered

Starting in 2007, 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 resistant than younger sea ice – has been reduced by approximately half, and has not recovered to date. . This is emphasized by a study published this Wednesday in the magazine ‘Nature’.

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

This change followed an Arctic-wide reduction in sea ice residence time – the average period that sea ice remains in the ocean before melting or being transported 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 can affect ocean mixing, and consequently ocean ecosystems, beneath the ice,” the researchers warn.

Thick ice is important to the global climate and the 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. On the contrary, the melting of sea ice does not contribute to the rise in sea level, since it is formed from the sea water on which it floats, not like land ice, which when melting releases water that was previously trapped in the ocean into the ocean. the earth.

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

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