Antarctica is known for its vast ice masses that are capable of raising global sea levels by several meters. A team of experts from European research institutes recently conducted the first systematic stability inspection of the ice sheet’s current state. Their analysis revealed that the ice sheet in West Antarctica is not yet experiencing irreversible, self-reinforcing retreat, but global warming so far could still trigger the gradual loss of ice over the next hundreds to thousands of years.

“With more and more ice being lost in Antarctica over the last years, concerns have been raised whether a tipping point has already been crossed and an irreversible, long-term collapse of the West Antarctic Ice Sheet has already been initiated,” explains Ronja Reese from the Potsdam Institute for Climate Impact Research (PIK) and the Northumbria University, Newcastle. “The results of our studies deliver two messages: First, while a number of glaciers in Antarctica are retreating at the moment, we find no indication of irreversible, self-reinforcing retreat yet, which is reassuring. However, our calculations also clearly indicate that an onset of an irreversible retreat of the ice sheet in West Antarctica is possible if the current state of the climate is sustained.”

The primary cause of ice loss in West Antarctica is the relatively warm ocean water that amplifies melting beneath the ice shelves. These ice shelves are the floating extensions of the grounded ice sheet. The melting of these ice shelves can enhance ice loss by speeding up the dropped sections of the ice sheet. Therefore, the Antarctic margin, with its grounding lines, which is the zone where the grounded and the floating ice are connected, is a crucial indicator of ice sheet health. An accelerated retreat of the grounding lines could indicate an imminent collapse of major marine regions of West Antarctica's ice sheet, particularly those parts of the ice sheet that are grounded below sea level.

Evolving over 10,000 years, triggered today: irreversible ice-loss and sea-level rise

Researchers used advanced ice sheet supercomputer models to conduct a comprehensive study on the irreversible retreat of marine sectors of the Antarctic ice sheet. They also ran simulations to predict how the ice sheet would evolve over the next 10,000 years under current conditions. The results of these hypothetical experiments suggest that certain marine regions of West Antarctica's ice sheet could be irreversibly collapsing even without additional warming beyond what we have already experienced today. The authors found that collapse occurs in their simulations at the earliest in 300 to 500 years from now, under current climate forcing, and a full collapse could take centuries to millennia.

“The thing with sea-level rise from Antarctica is not that changes would happen overnight as an immediate threat to coastal communities. The process of melting would happen over hundreds or thousands of years. However, the cause could be human actions today, as they have the power to trigger and commit a future of 10,000 years to several meters of global sea-level rise. And stronger warming in the future would even speed up this process,” Julius Garbe from PIK stresses. Changes in ice discharge from Antarctica remain one of the greatest uncertainties in future projections of global sea-level rise. “The Antarctic ice is our ultimate heritage of the past, millions of years old and often coined ‘eternal’ ice. But our work shows: that while current ice loss may still be reversible, a destabilization of marine sectors of the ice sheet could initiate a long-term ice loss that is slow but certain. Climate change today could already be enough to tip the scales, that is concerning. Yet, with West Antarctica not destabilized yet there is still a chance to mitigate at least some of the risk by ambitious climate action,” Ricarda Winkelmann from PIK concludes.

Despite the stability inspection for West Antarctica showing that the marine ice sheet is not destabilized yet, the evidence suggests that it is on a path to tipping. This is a worrying sign for the future of our planet, as the destabilization of the ice sheet could have a devastating effect on the environment and the global climate. We must take action now to prevent this from happening, or else we risk facing the consequences of our inaction in the future.

Communities must plan to reduce the risks of extreme weather patterns and record-high temperatures.

Since April 2023, the average global sea surface temperature has been abnormally high and increasing. By August, temperatures in the northern hemisphere ocean reached a record 25°C.

This rapidly warming trend, fuelled by the climate crisis, has manifested as a series of marine heatwaves — periods of unusually warm sea temperatures that can last weeks, months, or even years — across the northern and southern hemispheres.

Marine heatwaves are becoming more frequent, stronger, and longer-lasting. In some areas around the UK and Ireland, surface waters in June–July were 4–5°C above what is usually recorded at this time of the year. Temperatures are also soaring off the coast of Florida and into the Gulf of Mexico, extending across the tropical Pacific, around Japan, and off the coasts of Ecuador and Peru.

Marine heatwaves disrupt, threaten, and damage ecosystems. They are particularly dangerous for temperature-sensitive marine organisms that live in cool waters, such as kelps, invertebrates, and fishes, and organisms that cannot move, such as corals. Many species may be susceptible to disease or mortality, with knock-on effects.

Such events also affect local communities, who suffer economic losses from fisheries and aquaculture impacts.

This makes the concurrent onset of a strong El Niño -- a climate phenomenon that is typically associated with a rise in global temperatures -- particularly worrying. El Niño is a major climate phenomenon that comprises a warm phase (El Niño), a cool phase (La Niña), and a neutral phase. El Niño has the most widespread impact on sea surface temperatures globally. These switch, irregularly, every few years. The combination of marine heatwaves and strong El Niño are particularly worrying.

Earlier in 2023 conditions in the tropical Pacific began to reverse and El Niño appears to be developing. This is likely to increase to the end of the year and possibly next year and is poised to trigger major marine heatwaves.

With impending El Niño conditions with long-term warming trends, it is vital to monitor and help develop plans to reduce risk to wildlife and economies.

In a recent article, researchers are urging decision-makers in marine and coastal biodiversity conservation, fishing, aquaculture, and tourism industries to set out a strategy to reduce risk before, during, and after the event. They also set out four main priorities:

• Identify threatened regions

Historical data can show what areas suffered marine heatwaves during previous El Niños and suggest where future events are likely to occur.

• Improve forecasts and warnings

Developing new predictive supercomputer models and improving the accuracy of current systems is crucial for local biodiversity efforts as well as the fishing, aquaculture, and tourism industries.

• Plan local responses

Seasonal early warning systems should be developed to inform conservation agencies, fishing and aquaculture industries, and the public. Some industries like aquaculture and fisheries may need to change or adapt practices before and during predicted heatwaves.

• Monitor impacts of warmer waters

To better understand ecological responses to extreme warming events, researchers should scale up monitoring efforts to understand more about the physical and biological conditions of a region before a heatwave occurs.

Scientists say that unfortunately, the climate crisis may eventually cause the ocean to reach a permanent heatwave state, and some regions may no longer support certain species and ecosystems.

Postdoctoral Research Assistant Dr Katie Smith from the Marine Biological Association (MBA) who co-authored the paper said: “Marine heatwaves are occurring with increasing regularity and it is crucial that we work towards predicting their impacts and implementing adaptive strategies to reduce the consequences of these events.

Regardless of whether marine heatwaves are exacerbated this year by an El Niño event, preparations to soften their impacts will help marine ecosystems and the industries that rely on them, offering them an opportunity to adjust or transform.”

According to scientists, we must take action now to prepare for stronger marine heat waves in the future. To achieve this, we need to reduce greenhouse gas emissions, improve ocean health, and increase our resilience to climate change. As individuals, we can play our part by reducing our carbon footprint, conserving energy, and supporting policies that protect our oceans and the planet. By taking these steps, we can ensure that future generations have a healthy and thriving marine environment.