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The Greenland ice sheet is shrinking due to the greenhouse effect generated by the consumption of fossil fuels. It’s a fate shared by the Antarctic Ice Sheet and glaciers around the world. Now, however, a new study reveals that this reduction is much faster than expected: it travels at the rate of 30 million tons of ice per hour, on average, or 20% more than calculated to date.
The new research, published January 17 in the journal Nature, provides a detailed account of this process already described by scientists, but never measured so completely. “Almost all of Greenland’s glaciers are retreating, no matter how you look at it,” said Chad Greene, a glaciologist at NASA’s Jet Propulsion Laboratory and lead author of the study. “This retreat is happening everywhere and much faster than expected.” The consequences could be far-reaching: the fear is that this additional source of fresh water flowing into the North Atlantic could further accelerate the collapse of the ocean currents that regulate temperatures on both sides of the Atlantic Ocean, with serious consequences for the ‘humanity.
For decades there has been a significant loss of ice from Greenland due to the climate emergency. Techniques used to date – such as measuring the height of the ice sheet or its weight using data derived from the law of gravity – are effective in determining surface losses, which end up in the ocean and raise sea levels. They cannot explain, however, the retreat of that part of the glaciers that is already below sea level in the narrow fjords around the island. In this study, scientists analyzed satellite photos to determine the locations of all Greenland glaciers, month by month, from 1985 to 2022. The team led by Greene used artificial intelligence techniques to map more than 235,000 terminal locations of the glaciers. glaciers over 38 years, with a resolution of 120 meters. The result of the new calculations is that the Greenland ice sheet has lost an area of about 5,000 square kilometers at its margins since 1985, equivalent to a trillion tons of ice. These one trillion marginal losses are in addition to the five trillion overall losses estimated to date.
Estimates of annual losses also increase by a fifth, which were quantified at 221 billion tons of ice. The new study adds another 43 billion tons per year, bringing the total loss to about 30 million tons per hour. Greene’s comment: “If you discharge more fresh water into the North Atlantic Ocean, you will certainly get a weakening of the Amoc”, the Atlantic Meridional Overturning Circulation, or the system of Atlantic currents, of which the Atlantic current is also part Gulf, which transports warm saline water from the Caribbean northwards into the surface layers up to the Arctic Circle, where it cools and sinks, returning towards the south in depth. A growing influx of fresh water, resulting from the accelerated melting of the Greenland ice sheet and other sources, is increasingly choking these flows. The influx of fresh water, less dense, slows down the normal process that leads the heavier salt water to sink into the polar region.
It was already known that Amoc was in very strong decline: in 2021 it had reached its weakest point in the last 1600 years and a team of scientists had identified alarming signs of an imminent collapse. A study last year, led by glaciologist Peter Ditlevsen of the University of Copenhagen, suggested that collapse could occur as early as 2025 in the worst-case scenario and 2050 in the median scenario. “It would be a very, very big change. Amoc hasn’t stopped for 12,000 years,” commented Ditlevsen. The collapse of this current system is one of the climatic turning points that worries scientists most. Now the study led by Greene, just published by Nature, describes an even more worrying situation. The new study states: “There is some concern that any small additional source of fresh water could provide the final push that could trigger a large-scale collapse of the AMOC, upsetting global weather patterns, ecosystems and global food security”.