On Thin Ice

NASAs new satellite will give scientists their best picture yet of how much and how fast seas will rise

- Amy Thompson ​​​​​​​

WHEN HURRICANE FLORENCE STRUCK THE U.S. last month, rain and wind weren’t the only causes of damage. Rising seas contributed to storm surges that reached nearly 20 feet in some estuaries. In the past 20 years, sea levels have risen about 3 millimeters per year, which has had an effect on coastal flooding. How much more will the seas rise in coming decades?

The North and South poles are a good place to look for an answer. Melting ice in Greenland and Antarctica is a big cause of rising seas; Greenland has enough ice to raise sea levels by 21 feet. Loss of ice at the North Pole could shut down the Gulf Stream, plunging Northern Europe and Scandinavia into a deep freeze—a scenario depicted in the 2004 sci-fi movie The Day After Tomorrow. “It wouldn’t happen as dramatically as in the movie,” says physicist Thorsten Markus, who studies polar ice at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “But that is basically the idea. If the circulation shuts down, everything changes dramatically.”