Two papers distributed in Nature this week call into uncertainty ongoing forecasts of unavoidable Antarctic ice sheet collapse. The first paper proposes that continued collapse of Antarctic sheets into the sea, brought about by rising worldwide temperatures and dissolving ice racks, might not largely affect ocean level ascent.
This implies prominent and questionable forecasts from 2016, which guaranteed that this sort of bluff collapse could add in excess of a meter to rising seas by 2100, may be substantially over-estimated.
SThe study took a gander at ice losses three-million-years ago, 125,000 years ago, and over the last 25 years in more detail and found that unstable ice-cliff collapses aren’t needed to reproduce sea level rises in the past. Removing this mechanism from the model, they predict that there is only a five percent chance that the Antarctic contribution to sea level rise will exceed 39 cm by 2100 – much lower than the previous predictions of over a metre.
Dr. Tamsin Edwards, Lecturer in Physical Geography at King’s College London, who led the work, explains: “Unstable ice-cliffs in Antarctica were proposed as a cause of the unstoppable collapse of large parts of the ice sheet in the past. They were, therefore, also predicted to cause rapidly rising seas with global warming in our near future. But we’ve re-analysed the data and found this isn’t the case.”
“We’ve shown that ice-cliff instability doesn’t appear to be an essential mechanism in reproducing past sea level changes and so this suggests ‘the jury’s still out’ when it comes to including it in future predictions. Even if we do include ice-cliff instability, our more thorough assessment shows that the most likely contribution to sea level rise would be less than half a meter by 2100.”
Professor Tony Payne, a co-author on the paper and professor in Bristol’s School of Geographical Sciences, commented: “This is a significant step forward in efforts to reconcile recent estimates of future sea level rise and will of great use in the upcoming Intergovernmental Panel on Climate Change assessment of the impacts of future climate change.”
“It is also a useful reminder of the caution required in using geological data to constrain future sea level rise.”
In a second paper, scientists found that current climate models do not consider the full effect of melting ice sheets in Greenland and Antarctica.
Both papers concur that the in all probability Antarctic contribution to ocean level rise will associate with 14 – 15 centimeters under states of high greenhouse gases concentrations.