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Find out which glacier could put your city under water

Glaciers melting in Greenland would cause sea levels in Los Angeles to rise more than those in Alaska, according to new research from NASA’s Jet Propulsion Lab.

Glaciers melting in Greenland would cause sea levels in Los Angeles to rise more than those in Alaska, according to new research from NASA’s Jet Propulsion Lab.

That sounds counterintuitive, but earth’s oceans aren’t like a bathtub with a single waterline. When glaciers melt, they disproportionately affect sea level rise in certain parts of the world, while other coastlines don’t see the ocean rise much at all. In fact, the closer a city is to a huge chunk of ice that slides off land into the ocean, the more that city’s sea level will drop.

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That’s what a new study, written by NASA researchers Eric Larour, Erik Ivins, and Surendra Adhikari and published Thursday in the journal Science Advances, suggests. If ice sheets in the northeastern part of Greenland melt, for example, they would cause sea level to rise in New York. Those same glaciers, however, would cause sea level to drop in Reykjavik, Iceland.

The study includes an interactive tool that shows how sea level rise from different glaciers will affect 293 cities around the world. The redder the glacier on the map, the more that ice will affect sea level in a city; blue glaciers indicate a sea level drop.

READ: 3 reasons to worry about that huge iceberg that broke off Antarctica

“Our approach here was to flip the situation around. Most scientists, when they compute the shape of the ocean, they’re sitting on the ice, and when it melts they figure out its global effect,” Eric Larour, the lead developer on the project with NASA Jet Propulsion Laboratory, told VICE News. “We did the opposite. We’re in the coastal city, and we compute the changes as they affect the city.”

The study uses three factors to figure out how glacial melt will affect sea level rise:

  • Gravity: A big and dense enough iceberg creates gravitational field, so when one slides off land and into the ocean, it actually attracts the water around it. This is “the most important effect by far,” Larour said.
  • Land expansion: The earth expands when a massive iceberg slides off of land, much like a foam mattress would when someone gets out of bed. As land expands, it takes up more space in the water and causes sea level to rise.
  • The Earth’s rotation: Enormous ice sheets are so massive that when they melt, they affect the way the earth spins on its axis, which, in turn, changes water distribution across the globe.

The researchers hope that this study will help cities plan for the effect of climate change.

“Right now most city planners mostly use global mean sea level,” or the average amount that sea levels will rise globally, Larour told VICE News. “With this tool, they can go one step further.”