Emissions could add 38cm to sea level rise by 2100

If greenhouse gas emissions continue apace, Greenland and Antarctica's melting ice sheets could together contribute more than 38 centimetre of global sea level rise by 2100, says a NASA-led study.

Results from this study that brought together more than 60 ice, ocean and atmosphere scientists from three dozen international institutions are in line with projections in the Intergovernmental Panel on Climate Change's (IPCC) 2019 Special Report on Oceans and the Cryosphere.

Meltwater from ice sheets contribute about a third of the total global sea level rise.

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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.

These new results, published in a special issue of the journal The Cryosphere, come from the Ice Sheet Model Intercomparison Project (ISMIP6) led by NASA's Goddard Space Flight Center in Greenbelt, Maryland.

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.

"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, and formerly at NASA Goddard.

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"And how much the ice sheets contribute is really dependent on what the climate will do."

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 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.

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

In the lower emissions scenario, the loss from the ice sheet would raise global sea level by about 3 cm.

The 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.

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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.

The results point to a greater range of possibilities, from ice sheet change that decreases sea level by 7.8 cm, to increasing it by 30 cm by 2100, with different climate scenarios and climate model inputs.

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The regional projections show the greatest loss in West Antarctica, responsible for up to 18 cm of sea level rise by 2100 in the warmest conditions, according to the research.

"The Amundsen Sea region in West Antarctica and Wilkes Land in East Antarctica are the two regions most sensitive to warming ocean temperatures and changing currents, and will continue to lose large amounts of ice," said Heeleene Seroussi, an ice scientist at NASA's Jet Propulsion Laboratory in Southern California.