As ice sheets on Greenland and Antarctica melt, which cities are most liable to flood? NASA scientists have built a new simulation to help coastal planners find answers.
Scientists know where meltwater will enter the ocean, but a combination of factors determining where that excess water will end up is more complicated.
The new simulation analyzes the planet's spin rate and gravitational field to more accurately predict how meltwater will be redistributed globally -- revealing where sea levels will rise most dramatically.
Scientists and coastal planners can use the simulation to determine which glaciers and meltwater drainage systems will affect their risk of flooding most directly.
Researchers described their forecasting tool in the journal Science Advances.
"As cities and countries attempt to build plans to mitigate flooding, they have to be thinking about 100 years in the future and they want to assess risk in the same way that insurance companies do," Erik Ivins, senior scientist at NASA's Jet Propulsion Laboratory, told BBC.
The simulation suggests New York will be most directly affected by melting in the northern and eastern portions of Greenland's ice sheet. London will be most directly impacted by meltwater spilling off Greenland's northeastern coast.
In the Southern Hemisphere, the city of Sydney is likely to be most affected by melting on the northern half of Antarctica.
The distribution of water in the oceans -- including meltwater -- is dictated by Earth's gravity and rotation. As ice melts, the gravitational pull of the ice sheet is diminished. The shrinking ice sheets allow the compressed land beneath to expand, altering the local gravity fields.
The wobbly spin of the Earth also affects water distribution. As masses shift as a result of melting ice and expanding land, the nature of Earth's wobble and spin is affected. By analyzing these factors, scientists can estimate where additional meltwater will end up over time.
"We can compute the exact sensitivity -- for a specific town -- of a sea level to every ice mass in the world," lead researcher Eric Larour said. "This gives you an idea, for your own city, of which glaciers, ice sheets and ice caps are of specific importance."
Related research efforts are focusing on predicting which portions of the ice sheets on Greenland and Antarctica are most vulnerable in order to provide the simulation with the most accurate forecasts.
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