Climate protection no longer helps: Study: West Antarctica ice shelf can no longer be saved

Climate protection no longer helps
Study: The ice shelf in West Antarctica can no longer be saved

October 23, 2023 at 6:10 pm

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The ice shelf in parts of West Antarctica will melt inexorably and no climate protection measures will help: this is the conclusion of a British study. For this reason, the world must prepare for a significant rise in sea levels.

Even with ambitious climate protection measures, the melting of large ice shelves in West Antarctica can no longer be prevented, according to a study. Warming ocean currents are likely to thin ice shelves — that is, extensions of inland ice floating on water — from below in the Amundsen Sea over the course of the 21st century, a group led by Caitlin Naughton of the British Antarctic Survey writes. In the journal “Climate Change Nature”. Because this ice shelf supports inland glaciers, thinning ice is likely to increase their flow into the sea.

The team and an independent commentator in the magazine advise that it is necessary to prepare for the resulting significant rise in sea levels. Complete melting of the West Antarctica ice sheet would cause sea levels to rise by up to five metres.

However, the study only looked at the evolution of the ice shelf, that is, the outer part of the ice sheet that lies on the sea. While the ice shelf in East Antarctica is stable or partially growing, in West Antarctica it has been thinning for years, mainly due to warming ocean currents. I recently got one The study in the journal “Scientific Progress” They show that the Antarctic ice shelf has lost 7.5 trillion tons of meltwater in 25 years, much of it into the Amundsen Sea, which borders West Antarctica.

Four climate scenarios – from 1.5 degrees to uncontrolled increase

Naughton’s team has now simulated the evolution in this region of the ocean using four different climate scenarios: these ranged from the optimistic scenario in which the Earth warms by a maximum of only 1.5 degrees compared to pre-industrial times, to the extreme scenario. RCP8.5 for uncontrolled climate change.

“All scenarios show a significant and widespread future warming of the Amundsen Sea and increased melting of its ice shelf,” the group says. “Even in the most ambitious scenario, the Amundsen Sea is warming three times faster than in the 20th century.” This warming applies to all four scenarios. The extreme RCP8.5 scenario will only become noticeable in this regard from around 2045.

The reason for this trend lies in the water column, the group wrote, and above all in the so-called thermocline. This layer separates cold water at a depth of 100 to 400 meters from a deeper area containing slightly warmer water. In all climate simulation scenarios, this buffer layer rises, along with a layer of warm water that hollows out the ice shelf below.

The study did not specifically examine the consequences of this on sea levels. But as the ice shelf thins, its supporting function is likely to decline, the research group stresses. This could cause large ice masses left behind, such as the Thwaites or Pine Island Glaciers, to deplete more quickly, causing sea levels to rise.

“Our simulations show a realistic view of the Amundsen Sea,” the team concludes. By 2100, the weather could be up to 2 degrees warmer than before industrialization. “For Antarctic water masses, a two-degree increase is astonishing,” she says.

Poor study

The team also admits there are weaknesses in the study: it does not take into account interactions with changing ice geometry and focuses only on the influence of ocean currents, but not on weather factors. These matters may become more important in the long term. But either way: In the coming centuries, we will have to prepare for a sharp rise in sea levels. The group stresses that climate measures still make sense to keep at least other parts of the Antarctic ice sheet stable.

The study provides the most comprehensive projection of the warming of the Amundsen Sea to date, Taimur Sohail of the University of New South Wales in Sydney wrote in a commentary. “Although the opportunity to prevent the melting of West Antarctica’s ice shelves has likely passed, the actual consequences of climate change on sea levels will depend on a variety of factors.”

For example, the stability of the East Antarctica ice sheet – which is much larger – depends on climate protection measures, and climate fluctuations in this region are also large. However, based on the study, it seems clear that sea level rise is inevitable. Policymakers must now find ways to prepare for the consequences.

“A combination of damage reduction, adaptation and luck.”

Naughton’s research team also emphasizes this: “Limiting the social and economic costs of sea level rise will require a combination of damage reduction, adaptation, and luck.”

Reinhard Droz of the University of Tübingen points out that carbon dioxide emissions in Germany are also driving ice loss in Antarctica. “This process has already begun, and inherent inertia means we cannot stop some of the ice loss, no matter what measures are taken,” says the expert who was not involved in the study. “This does not question the necessity of climate policy, quite the opposite. It is another indication of how serious the changes are and how local action can have a global impact. For better or worse.”