20% higher than thought; Greenland losing 30mln tonnes of ice an hour

By Al Mayadeen English
Source: The Guardian
18 Jan 2024 09:48

The new melting rate of ice in Greenland is 20% more than what was previously predicted, a new study found.

A group from the Poseidon Expeditions looks over an iceberg in the Scoresby Sund, Thursday, Sept. 7, 2023, in Greenland (AP)

A study has revealed that the Greenland ice cap is losing an average of 30m tonnes of ice an hour due to the climate crisis, which is 20% more than previously assumed.

The Atlantic meridional overturning circulation (Amoc), which is an additional source of freshwater pouring into the North Atlantic and triggering a collapse of the ocean currents, according to scientists, is closer now, and this will have severe repercussions on humanity.

The techniques of measuring the height of the ice sheet or its weight by gravity data are being used in Greenland and have indicated major ice loss from the latter as a result of global heating over the past decades. However, they cannot account for the retreat of glaciers that lie mostly below sea level in the narrow fjords around the island.

At NASA's Jet Propulsion Laboratory in the US, Dr. Chad Greene, who led the research said, “The changes around Greenland are tremendous and they’re happening everywhere – almost every glacier has retreated over the past few decades.” Concerned, he added, “It makes sense that if you dump freshwater onto the North Atlantic Ocean, then you certainly get a weakening of the Amoc, though I don’t have an intuition for how much weakening.”

It is noteworthy that the Amoc is at its weakest in 1,600 years as in 2021, researchers caught warning signs of a near tipping point. This is also expected for a significant part of the Greenland ice sheet itself, which is close to a tipping point of irreversible melting, with ice equivalent to 1-2 meters of sea level rise probably already predicted. A recent study suggested the collapse could happen as soon as 2025 in the worst-case scenario.

Using artificial intelligence techniques to map more than 235,000 glacier end positions over 38 years at a resolution of 120 meters, the study, published in the journal Nature, revealed that the Greenland ice sheet had lost an area of about 5,000 sq km of ice at its margins since 1985, equivalent to a trillion tonnes of ice.

Making the total loss of ice about 30mln tonnes an hour on average, the new study added 43bln tonnes a year to the already existing data of 221bln tonnes of ice lost since 2003.

The scientists said, “There is some concern that any small source of freshwater may serve as a ‘tipping point’ that could trigger a full-scale collapse of the Amoc, disrupting global weather patterns, ecosystems, and global food security. Yet freshwater from the glacier retreat of Greenland is not included in oceanographic models at present.” The Amoc is triggering the slowing of the usual process of heavier salty water sinking due to the influx of less dense freshwater into the sea.

There's still some hope

According to an analysis from Prof. Tim Lenton, at the University of Exeter, UK, “This additional freshwater input to the North Atlantic is a concern, particularly for the formation of deep water in the Labrador and Irminger Seas within the subpolar gyre, as other evidence suggests these are the regions most prone to being tipped into an ‘off’, or collapsed state.”

“That would be like a partial Amoc collapse, but unfolding faster and having profound impacts on the UK, western Europe, parts of North America, and the Sahel region, where the west African monsoon could be severely disrupted,” he said. “Whether this previously unaccounted source is enough freshwater to make a difference depends on how close we are to that subpolar gyre tipping point. Recent models suggest it could be close already at the present level of global warming.”

However, Prof. Andrew Shepherd believes that “although there was a step-change in glacier retreat at the turn of the century, it’s reassuring to see that the pace of ice loss has been steady since then and is still well below the levels needed to disturb the Amoc.”

Not only Greenland

A comprehensive study of all the world's glaciers other than the Greenland and Antarctic ice sheets shows that over half of them will melt by the end of the century, even if the world fulfills its most aggressive global warming target.

The study, published on January 4 in the journal Science, discovered that even with only 1.5°C (2.7 degrees Fahrenheit) of warming above preindustrial levels, 104,000 of the world's more than 215,000 mountain glaciers and ice caps will melt, raising global sea levels by just under 4 inches.

A 1.5°C increase above preindustrial temperatures is currently extremely difficult to avert, implying that such a development may be nearly unstoppable. The outlook worsens with each extra degree of temperature rise.

According to the study, 3°C (5.4 degrees Fahrenheit) of warming would result in the disappearance of more than 70% of the world's glaciers and a 5-inch rise in global sea level. Even though many losses are already baked in, the authors argue that it is still worthwhile to attempt to avert as much warming as possible.