Arctic could be past key climate threshold
The Arctic is undergoing a profound, rapid and unmitigated shift into a new climate state, one that is greener, features far less ice, and is a net source of greenhouse gas emissions from melting permafrost, according to a major new assessment of the region.
The consequences of these climate shifts will be felt far outside the Arctic in the form of altered weather patterns, increased greenhouse gas emissions, and rising sea levels from the melting Greenland ice sheet and mountain glaciers.
The findings are contained in the 2019 Arctic Report Card, a major US federal assessment of climate change trends and impacts throughout the region.
Especially noteworthy is the conclusion that the Arctic may have already turned into a net emitter of planet-warming carbon emissions due to thawing permafrost, which would only accelerate global warming.
There has been concern that the approximately 1460 billion to
1600 billion tonnes of organic carbon stored in frozen Arctic soils, which amounts to nearly twice as much greenhouse gas than what is contained in the atmosphere, could be released as the permafrost melts.
The report concludes that permafrost ecosystems could be releasing as much as 1.1 billion to
2.2 billion tonnes of carbon per year – almost as much as the annual emissions of Japan and Russia in 2018, respectively.
The broader Arctic Report Card shows that the region is undergoing extensive changes in the marine environment as well as frozen lands.
Alaska has had its hottest year to date in 2019, with no sea ice visible from the shoreline in Nome as of Monday, which is highly unusual for this time of year.
Meanwhile, Greenland’s vast ice cap is melting faster than expected and will threaten an extra 40 million people with flooding by the end of this century if it is not slowed, the most thorough study to date has revealed.
Summer heatwaves and yearround melting of glaciers mean the rate of ice loss is following the ‘‘high-end climate warming scenario’’ produced by the Intergovernmental Panel on Climate Change (IPCC) says the study, published yesterday in the journal Nature.
The global sea level will rise by an additional 7 centimetres by
2100, on top of the 60cm previously forecast by the IPCC, if Greenland continues to melt at the rate recorded over the past decade. The study says this raises the projection for the number of people affected each year by coastal flooding by the end of the century from 360 million to 400 million.
A team of 89 scientists examined records from 13 satellites and found that Greenland’s rate of ice loss had risen from 33 billion tonnes per year in the
1990s to 254 billion tonnes per year in the past decade.