An iceberg off the coast of Greenland.
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Without serious emission reductions, melting ice sheets in Greenland and Antarctica could lead to an additional 44 centimeters of sea level rise by 2100. This is shown by an international collaboration between NASA and more than sixty ice, ocean and climate scientists, which the Vrije Universiteit Brussel (VUB) also participated in. .
The international research team studied two climate scenarios of the UN Climate Panel (IPCC): one with a further increase in CO2 emissions and another in which the Paris Climate Agreement is followed and thus emissions are significantly reduced.
‘This is a big step forward in order to be able to better inform the IPCC.’
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-‘The strength of this project is that for the first time almost all existing ice sheet models have performed the same experiments under the same climate scenarios,’ explains glaciologist Philippe Huybrechts from the VUB. ‘In this way we can form a better picture of the uncertainty. This is a big step forward to better inform the IPCC. ‘
A first group of scientists selected the most reliable climate models for the polar regions, which were then used as input for the ice sheet models. Another group calculated how higher ocean temperatures could lead to melting under the ice shelves and more glacial calving. The VUB team performed calculations with their ice sheet models for both ice sheets.
Greenland
In a scenario with high emissions, the scientists determined that meltwater from the Greenland ice sheet would lead to an additional sea level rise of an average of 9 centimeters by 2100, within a uncertainty interval of 5 centimeters.
In the lower emissions scenario, the loss of the ice sheet would raise the global sea level by about 3 centimeters, with an uncertainty of plus or minus 1.5 centimeters. This rise comes on top of the 6 millimeter sea level rise that has been inevitable as a result of global warming since the start of the industrial revolution.
Antarctica
The team also analyzed the Antarctic Ice Sheet, which is much more unpredictable. In West Antarctica, warm ocean currents melt the bottoms of large floating ice shelves. But the massive East Antarctic ice sheet may even gain mass as warmer temperatures cause more snowfall.
In West Antarctica, warm ocean currents melt the bottoms of large floating ice shelves.
The results here point to a wider range of possibilities: from a rise in sea level of 30 centimeters to even a fall of 8 centimeters. The regional projections show the greatest impact in West Antarctica, with sea levels rising to 18 centimeters by 2100 in the hottest conditions.
Worst case
For both ice sheets together, the projections come to 0 to 20 centimeters for a low emission scenario and –4 to +44 centimeters for a high emission scenario.
So far the measured emission values are very close to the most pessimistic emission scenario of the UN.
“The observations of the last 40 years are close to and even slightly above the upper limit of the model results for the high emission scenario,” says Philippe Huybrechts. “If greenhouse gas emissions are not reduced quickly, the sea level rise risks being close to the maximum as shown by the study.”
The study was published Thursday in a special edition of the journal The Cryosphere.
