“Terminal diagnosis” for multi-year Arctic sea ice: Report

We are already well into the risk zone for irreversible damage from continued loss of the planet’s global ice stores, says the report

Total Arctic summer sea ice loss is now inevitable, likely before 2050, concluded the State of the Cryosphere Report 2022, released at COP27 in Sharm El-Sheikh, Egypt. The report emphasised the IPCC Sixth Assessment’s alarming conclusion that even with very low emissions, summer loss of Arctic sea ice will occur at least once.

This past year saw March rains on East Antarctica, with temperatures 40°C above normal; a spike in Greenland surface melt for the first time ever in September; loss of over 5% of glacier ice in the Alps this past summer; and the first documented rise in methane release due to global warming from a permafrost monitoring site. It also saw greater shell damage in parts of the Arctic Ocean, a clear sign of growing acidification. All of these impacts are irreversible on human timescales, the report said.

“The two lowest emissions pathways or scenarios are the only ones with any possibility of preventing these catastrophic events that cannot be reversed in anything less than centuries, to tens of thousands of years. A decision to exceed these limits is a de facto decision to make this happen” said Julie Brigham-Grette, University of Massachusetts Amherst and former chair of the U.S – Polar Research Board.

Growing losses, global impacts 

The report highlighted that the true rate of Arctic warming is three to four times faster than the global average. Arctic sea ice loss drives this cycle, increasing the amount of heat absorbed by the dark surface of the ocean. 

In addition to losing nearly three-quarters of summer sea ice volume since the early 1980s, the Arctic has lost one-third of its entire winter sea ice volume in the past 20 years, mainly due to the loss of thick, multi-year ice. This once-prevalent multi-year ice has been replaced with thinner “seasonal” ice, which melts completely each summer, the report found.

This loss of multi-year sea ice also threatens Arctic marine life. North Water polynya (NOW) is a unique open-water ecosystem surrounded by sea ice between Greenland and Ellesmere Island in Canada. The report warned that vulnerable regions such as NOW may no longer be able to serve as a winter refuge for keystone High Arctic mammals, or as central fishing and hunting ground for Inuit communities in the region as well as commercial fishing activities. According to the report, multiple lines of evidence now show increasing sea ice instability in this sector over the last two decades.

Mentioning more impacts of melting glaciers, the report said that South Asian agriculture is increasingly dependent on freshwater from sources such as glacier melt and snowmelt, both of which are becoming increasingly erratic water sources because of rising temperatures. There’s also a clear link between glacier retreat and the growth of glacial lakes, increasing the risk of glacial lake outburst floods in the Himalaya, the report added.

The report found that sections of the West Antarctic Ice Sheet may collapse even without further emissions, causing more than four metres of additional sea-level rise.  However, the risk can be diminished by meeting Paris Agreement goals.

“Our planet’s melting ice pays no attention to climate pledges and NDCs. It responds only to the level of CO2 and warming in the atmosphere, which shows no sign of pausing. Until our CO2 rise slows, halts and begins to decrease, the ice will continue to respond as it always has: to the only number that really matters,” said Pam Pearson, director, International Cryosphere Climate Initiative.

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