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Researchers at NASA have created a new model of sea level rise, allowing them to predict with incredible accuracy which major cities will be affected when any one region of ice melts. The researchers hope the new tool could be used to pre-empt disasters and be used by future city planners.
Publishing their results in Science Advances they show, for example, if the north-west part of the Greenland ice sheet melts then London is likely to be affected by sea level rise, while if the entire northern and eastern parts of the sheet melted, it will be New York that is flooded.
This latest model is more comprehensive than most, as it includes a whole host of key processes, such as Earth’s spin and gravity, that many would not necessarily think about when considering how melting ice sheets cause the sea level to rise.
The melting of the polar ice caps is often viewed in simplistic terms, like ice cubes melting in a glass of water. But we know that in reality, this is not the case. Contrary to what you might think, the sea does not rise at the same level around the planet, meaning that some coastal cities are likely to be affected by flooding before others.
As the Earth spins, it wobbles slightly. This wobble is affected by the mass of objects on the surface, such as the polar ice caps. Last year, scientists at NASA detailed how the annual melting of the Arctic is enough to influence this wobble as the distribution of mass on the surface changes. If portions of ice that never usually melt, such as the sheets covering Greenland, disappeared, the wobble would once again be altered, and this, in turn, would redistribute this water unevenly around the planet.
But the researchers have also modeled the effect that gravity has on the distribution of the water when the ice melts. Amazingly, some of the ice sheets, again such as the ones that cover Greenland, are so massive they produce their own gravity.
“These [ice sheets] are huge masses that exert an attraction on the ocean,” Dr Eric Larour, lead developer on this project at NASA's Jet Propulsion Laboratory, told the BBC. “When the ice shrinks, that attraction diminishes – and the sea will move away from that mass.” As the ice melts, it also means that the rock beneath it that it had been pushing down on rises slightly, once again influencing where that water goes.
They hope that town and city planners, as well as those already living in these places, can use the tool to help guard them against future flooding.
