Melting ice sheets alone risk 38cm sea level rise by 2100, Nasa says

If greenhouse gas emissions continue rising at the same rate, Greenland and Antarctica’s ice sheets could together contribute more than 38cm of global sea level rise, a Nasa-led study has found.

The team also warns that this rise is beyond the amount that has already been set in motion by the Earth’s warming climate.

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

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

But 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 would also be a significant contributor to sea level rise.

In the high emissions scenario, they found that the Greenland ice sheet would lead to an additional global sea level rise of about 9cm by 2100. In the lower emissions scenario, the loss from the ice sheet would raise global sea level by about 3cm.

This is beyond what is already destined to be lost from the ice sheet due to warming temperatures between pre-industrial times and now.

Ice loss from the Antarctic ice sheet was found to be 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 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 Helene Seroussi, an ice scientist at Nasa’s Jet Propulsion Laboratory in Southern California.

“With these new results, we can focus our efforts in the correct direction and know what needs to be worked on to continue improving the projections.”

Meltwater from ice sheets contributes about a third of the total global sea level rise. The new results tally with a report from the Intergovernmental Panel on Climate Change, which projected that Greenland would contribute 8-27cm to global sea level rise between 2000-2100 and Antarctica could contribute 3-28cm.

“It took over six years of workshops and teleconferences with scientists from around the world working on ice sheet, atmosphere, and ocean modelling to build a community that was able to ultimately improve our sea level rise projections,” said project leader and ice scientist Sophie Nowicki, now at the University at Buffalo and formerly at Nasa Goddard.

“The reason it worked is because the polar community is small, and we’re all very keen on getting this problem of future sea level right. We need to know these numbers.

“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 and how much the ice sheets contribute is really dependent on what the climate will do.”

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