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A study published in Nature Climate Change looks at the future increase of Antarctic ice-shelf melting.
Professor John Moore, Arctic Centre, University of Lapland, Finland, said:
“This work is a very thorough study of how the standard IPCC scenarios impact the water driving melt under the vulnerable ice shelves in the Amundsen Sea sector of Antarctica.
“IPCC AR6 WG2 note that there is no plausible scenario to limit temperature rises to 1.5C, and that these will lead to tipping points such as the collapse of the most vulnerable parts of the West Antarctic ice sheet. So, this work confirms that, and earlier work that also from nearly a decade ago (Favier et al., 2014; Rignot et al., 2014, Joughin et al., 2014) that these glaciers may have passed the tipping point.
“Clearly the planetary stewardship failure of humanity to mitigate emissions strongly enough now means hard choices between accepting serious migration pressures, and irreversible loss of coastal ecosystems mainly in the Global South, or taking a more active responsibility for climate and the critical elements of the system.
“It concentrates attention on radial approaches to limiting temperature rises such as by solar radiation management. But the glaciers may have already lost too much buttressing for direct climate control, then a targeted approach such as preventing access of the deep warmer water with a removable flexible barrier (articles published this year in PNAS Nexus, Keefer et al., 2023; Wolovick et al. 2023). Thereby lowering the melt rates and stopping thinning of the most vulnerable ice shelves.”
References:
Favier L, et al. 2014. Retreat of Pine Island Glacier controlled by marine ice-sheet instability. Nat Clim Change. 4(2):117–121.
Joughin I, Smith BE, Medley B. 2014. Marine ice sheet collapse potentially underway for the Thwaites Glacier Basin, West Antarctica. Science. 344(6185):735–738.
Rignot E, Mouginot J, Morlighem M, Seroussi H, Scheuchl B. 2014. Widespread, rapid grounding line retreat of Pine Island, Thwaites, Smith and Kohler glaciers, West Antarctica from 1992 to 2011. Geophys Res Lett. 41(10):3502–3509.
Wolovick, M., J.C. Moore, B. Keefer, 2023The potential for stabilizing Amundsen Sea glaciers via underwater Curtains, PNAS Nexus, 2, 4, pgad103, https://doi.org/10.1093/pnasnexus/pgad103
Keefer, B. M. Wolovick J.C. Moore 2023 Feasibility of Ice Sheet Conservation Using Seabed Anchored Curtains PNAS Nexus, 2, 3 pgad053pgad053, 10.1093/pnasnexus/pgad053
Professor Jonathan Bamber, School of Geographical Sciences, University of Bristol, said:
“This is a unique and valuable study that implies that ocean warming is effectively baked into a particularly important sector of the Southern Ocean for ice sheet dynamics. Their results suggest that irrespective of any future emission pathways, this sector, called the Amundsen Sea, will experience enhanced warming on the continental shelf, which will in turn erode the ice shelves that buttress the inland ice. This part of West Antarctica contains sufficient ice to raise global sea level by more than a metre so it’s important to understand how it will evolve in the future.
“Their analysis is based on a single ocean model and driven by the output of a single general circulation model. Models can vary significantly in their regional and local trends and it would be useful to see to what extent different model set ups reproduce the pattern of ocean warming they find. It’s also important to note that this study is looking at changes in ocean temperatures and not directly at how this will affect discharge of ice from West Antarctica. The headline of the press release is therefore a bit misleading and it when it comes to sea level rise, the most important factor is the rate rather than the commitment as it is the former that determines whether adaptation is possible. The latter is interesting but if it’s over, say, multiple millennia then it may not be the most pressing issue driving adaptation and mitigation policy.”
Professor Andrew Shepherd, Head of Department of Geography and Environment at Northumbria, Director of the NERC Centre for Polar Observation and Modelling, said:
“While the author’s conclusion about the inevitability of West Antarctic Ice Sheet collapse is pessimistic, sticking to 1.5 degrees C of global warming buys us 50 years on the extreme scenario RCP8.5 and even 20 years on sticking to 2 degrees C. This could make all the difference to coastal planners, and so is not to be sniffed at. It’s vitally important that these ocean forcing trajectories are translated into projections of ice sheet losses so that we know what sea level rise to expect.”
Dr Tiago Segabinazzi Dotto, Senior Research Scientist at the National Oceanography Centre, said:
“This study brings new information by suggesting that the mitigation policies are limited to reducing the ocean warming in coastal regions of the Amundsen Sea, putting the main ice shelves of the region at risk for future projections.
“It is likely that we passed a tipping point to avoid the instability of the West Antarctic Ice Sheet (WAIS). This work fits with existing evidence that suggests that the collapse of ice shelves in the Amundsen Sea is imminent, such as the Thwaites Ice Shelf – vastly studied within the International Thwaites Glacier Collaboration project. However, the pace of this collapse is still uncertain – it can happen in decades for some specific ice shelves or centuries.
“The conclusions of the work are based on a single model and need to be treated carefully since different models and even ensembles of the same model can give different responses. The time limitation of observational measurements in the Amundsen Sea prevents a clear understanding of the model outputs compared with the real ocean and its similarity with the reality. However, the fact that the local atmospheric forcing has a role in driving the warming of the ocean and that the study also supports the hypothesis that the intensification of a bottom intensified current brings more warm water to the continental shelf, which agrees with previous studies in the region, gives confidence that this study needs to be taken in consideration for policymakers.”
Professor Alberto Naveira Garabato, Professor in Physical Oceanography at the University of Southampton, said:
“This is a sobering piece of research. It illustrates how our past choices have likely committed us to substantial melting of the West Antarctic Ice Sheet and its consequent sea level rise – to which we will inevitably have to adapt as a society over coming decades and centuries. However, it should also serve as a wake up call. We can still save the rest of the Antarctic Ice Sheet, containing about ten times as many metres of sea level rise, if we learn from our past inaction and start reducing greenhouse gas emissions now.”
“This new study suggests that future rapid and accelerating sea level rise is not an “if question” but a “how fast question”. This regardless of what we do now: melting of the West Antarctic Ice Sheet will increase in coming decades and centuries under every mitigation scenarios. Increased Antarctic ice melting will not only accelerate sea level rise, but will also disrupt major ocean currents that regulate global climate (https://www.nature.com/articles/s41586-023-05762-w). While we are likely committed to sea level rise from West Antarctica, we can still act and reduce carbon emissions to limit melting in other areas of Antarctica (https://www.nature.com/articles/s41586-022-04946-0). Particularly important will be the future of East Antarctica, where about 90% of the Antarctic ice is stored.”
‘Unavoidable future increase in West Antarctic ice-shelf melting over the twenty-first century’ by Kaitlin A. Naughten et al. was published in Nature Climate Change at 16:00 UK time on Monday 23 October.
DOI: 10.1038/s41558-023-01818-x
Declared interests
Professor Moore: No conflicts of interest.
Professor Bamber: Funded by the ERC, EC and German BMBF but has no competing interests.
Prof Garabato: No conflicts of interest.
Dr Silvano: No conflicts of interest.
For all other experts, no reply to our request for DOIs was received.