Emissions to add 15 inches to global sea-level rise by 2100: NASA-led study

Washington: Greenland and Antarctica's ice sheets could together contribute more than 38 centimetres to global sea level rise by 2100, if greenhouse gas emissions continue, according to a study led by NASA.

The findings are in line with projections in the Intergovernmental Panel on Climate Change's (IPCC) 2019 Special Report on Oceans and the Cryosphere or portions of Earth's surface where water is in solid form, NASA said.

Meltwater from ice sheets contribute about a third of the total global sea level rise, it said. The IPCC report projected that Greenland would contribute 8 to 27 cm to global sea level rise between 2000-2100 and Antarctica could contribute 3 to 28 cm, according to the US space agency.

The findings, published in the journal The Cryosphere, come from the Ice Sheet Model Intercomparison Project (ISMIP6) led by NASA's Goddard Space Flight Center.

"One of the biggest uncertainties when it comes to how much sea level will rise in the future is how much the ice sheets will contribute," said project leader and ice scientist Sophie Nowicki, now at the University at Buffalo in the US, and formerly at NASA Goddard.

"The strength of ISMIP6 was to bring together most of the ice sheet modelling groups around the world, and then connect with other communities of ocean and atmospheric modelers as well, to better understand what could happen to the ice sheets," said Heiko Goelzer, who led the Greenland ice sheet ISMIP6 effort while at Utrecht University in the Netherlands.

With warming air temperatures melting the surface of the ice sheet, and warming ocean temperatures causing ocean-terminating glaciers to retreat, Greenland's ice sheet is a significant contributor to sea level rise, the researchers said.

The ISMIP6 team investigated two different scenarios the IPCC has set for future climate to predict sea level rise between 2015 and 2100: one with carbon emissions increasing rapidly and another with lower emissions.

In the high emissions scenario, they found that the Greenland ice sheet would lead to an additional global sea level rise of about 3.5 inches (9 cm) by 2100.

In the lower emissions scenario, the loss from the ice sheet would raise global sea level by about 1.3 inches (3 cm). This is beyond what is already destined from the ice sheet loss due to warming temperatures between pre-industrial times and now, the researchers said.

Previous studies have estimated that 'locked in' contribution to global sea level rise by 2100 to be about a quarter-inch (6 millimetres) for the Greenland ice sheet, they said.

The ISMIP6 team also analysed the Antarctic ice sheet to understand how much ice melt from future climate change would add to sea level rise, beyond what recent warming temperatures have already put in motion, the researchers said.

Ice loss from the Antarctic ice sheet is more difficult to predict: In the west, warm ocean currents erode the bottom of large floating ice shelves, causing loss; while the vast East Antarctic ice sheet can gain mass, as warmer temperatures cause increased snowfall, they added.

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