Durham research: the impact of melting ice sheets

By Cameron Scott

The climate emergency is already posing existential threats to ecosystems and societies across the globe, a threat only increased by the continued use of fossil fuels that unlock catastrophic feedback mechanisms. Exponential warming of the Antarctic ice sheets is a critical example, and the danger is easy to understand. White sheet ice is an excellent reflector of sunlight, but when rising global temperatures causes ice to melt there is less to act as a protective mirror. Heat that would have otherwise been reflected now remains on Earth, further raising global temperatures and accelerating the decline of the ice sheets. The vanishing of the ice sheets will raise global sea levels, threatening to inundate many coastal areas.

However, recent research (conducted by the Geography Department of Durham University and published in Nature) has shown that the amount of sea level rise may still be within our hands to control. If humanity is able to remain under the upper limit of two degrees of global warming set by the 2015 Paris Climate Agreement, then the melting of the East Antarctic Ice Sheet (EAIS) is likely to add less than half a metre to global sea levels by 2500. By analysing the effects of previous periods of warming on the ice sheet and combining the results of the computer simulations from previous studies, Durham’s researchers were able to predict that if emissions are significantly cut now then the EAIS may only contribute 2cm to sea levels by the end of the century – significantly less than that predicted to be caused by the ice on Greenland or West Antarctica. However, should greenhouse gas emissions remain high until 2100, the melting of the EAIS could cause up to half a metre in sea level rise. If emissions remain high beyond the end of the century, between two and five metres could be added to global sea levels. Research published in Nature Communications in 2021 estimated that there are currently 267 million people living in coastal zones that are less than two metres above sea level with the number expected to grow to 410 million by 2100. The danger posed by melting sea ice is therefore evident.

The climate crisis is anthropogenic in cause and will be anthropic in effect

Rising sea levels are not the only result of melting sea ice. Fossil fuel usage results in a greater concentration of CO2 in the air, which is then absorbed into the ocean and results in the acidification of the seas. In water distant from melting sea ice, the natural alkalinity of the sea counteracts this acidification; but in water near the ice sheets the ice melt flows into the ocean and dilutes it. This reduces the ocean’s ability to resist acidification and leads to a rapid lowering of the water’s pH. The biochemistry of seaweed would need to adapt to live in such acidic environs and this change would likely propagate all the way up the food chain. Wei-Jun Cai, a marine chemist at the University of Delaware and a co-author of a Science article into the acidification caused by melting ice, stated while speaking to The Guardian: “We are far from knowing what the cost is for biological systems. We don’t know what organisms could be affected.”

What is clear is that ocean acidification has already been shown to pose a threat to coral reefs around the world. An increased acidity reduces the concentration of the carbonate ions necessary to grow new coral. Coral reefs are a rich home for a diverse ecosystem of marine life and the risk posed by ocean acidification is a serious threat. When combined with the bleaching of corals due to rising ocean temperatures, the prospects seem bleak.

Consequently, the Durham research is particularly potent. If it is within our power to prevent the worst melting of sheet ice and reduce the devastating effects of rising sea levels and ocean acidification, it is humanity’s responsibility to try. The climate crisis is anthropogenic in cause and will be anthropic in effect. Keeping the world below the two degrees of warming targeted with the Paris Agreement remains absolutely crucial.

Image credit: Anders Jildén via Unsplash

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