This NASA Earth Observatory image obtained July 27, 2012, shows a massive ice island as it broke free of the Petermann Glacier in northwestern Greenland. (Jesse Allen and Robert Simmon/NASA Earth Observatory via AFP) This story has been updated. New York City has plenty to worry about from sea level rise. But according to a new study by NASA researchers, it should worry specifically about two major glacier systems in Greenland’s northeast and northwest — but not so much about other parts of the vast northern ice sheet. The research draws on a curious and counterintuitive insight that sea level researchers have emphasized in recent years: As ocean levels rise around the globe, they will not do so evenly. Rather, because of the enormous scale of the ice masses that are melting and feeding the oceans, there will be gravitational effects and even subtle effects on the crust and […]