‘Zeespiegelstijging kan dubbel zo hoog worden’

9 mei 2016 – Een weinig opbeurend bericht komt van een publicatie in Nature: de zeespiegelstijging zou tegen het einde van deze eeuw dubbel zo hoog kunnen zijn als tot nu toe voorspeld. 

Uit een bericht van The Washington Post over het onderzoek
‘(…) The startling findings paint a far grimmer picture than current consensus predictions, which have suggested that seas could rise by just under a meter at most by the year 2100. Those estimates relied on the notion that expanding ocean waters and the melting of relatively small glaciers would fuel the majority of sea level rise, rather than the massive ice sheets of Greenland and Antarctica. The projection “nearly doubles” prior estimates of sea level rise, which had relied on a “minimal contribution from Antarctica,” said Rob DeConto of University of Massachusetts, Amherst, who authored the study with  David Pollard of Penn State University. (…)’

Uit Nature
‘(…) Robert DeConto and David Pollard use a newly improved numerical ice-sheet model calibrated to Pliocene and Last Interglacial sea-level estimates to develop projections of Antarctica’s evolution over the next five centuries, driven by a range of greenhouse gas scenarios. The modelling shows that the Antarctic ice sheet has the potential to contribute between almost nothing, to contributing more than a metre of sea-level rise by 2100 and more than 15 metres by 2500. The startling high-end estimate arises from unabated emissions and previously underappreciated mechanisms: ice-fracturing by surface meltwater and collapse of large ice cliffs. The low end shows that a scenario of strong climate mitigation can radically reduce societal exposure to higher sea levels. (…)
Polar temperatures over the last several million years have, at times, been slightly warmer than today, yet global mean sea level has been 6–9 metres higher as recently as the Last Interglacial (130,000 to 115,000 years ago) and possibly higher during the Pliocene epoch (about three million years ago). In both cases the Antarctic ice sheet has been implicated as the primary contributor, hinting at its future vulnerability. Here we use a model coupling ice sheet and climate dynamics—including previously underappreciated processes linking atmospheric warming with hydrofracturing of buttressing ice shelves and structural collapse of marine-terminating ice cliffs—that is calibrated against Pliocene and Last Interglacial sea-level estimates and applied to future greenhouse gas emission scenarios. Antarctica has the potential to contributmore than a metre of sea-level rise by 2100 and more than 15 metres by 2500, if emissions continue unabated. In this case atmospheric warming will soon become the dominant driver of ice loss, but prolonged ocean warming will delaits recovery for thousands of years. (…)’

The Washington Post, 30 maart 2016: Scientists nearly double sea level rise projections for 2100, because of Antarctica
Nature, 31 maart 2016, Contribution of Antarctica to past anfuture sea-level rise

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