The New York Times has a frightening overview of the latest science on sea level rise -- specifically, the threat it poses to the United States. The consensus is that, yes, the U.S. is at risk; the East Coast in particular. But surprisingly, it's not just rising tides that we have to watch out for -- it's sinking land. From the Times:
Scientists say the East Coast will be hit harder for many reasons, but among the most important is that even as the seawater rises, the land in this part of the world is sinking. And that goes back to the last ice age, which peaked some 20,000 years ago.
As a massive ice sheet, more than a mile thick, grew over what are now Canada and the northern reaches of the United States, the weight of it depressed the crust of the earth. Areas away from the ice sheet bulged upward in response, as though somebody had stepped on one edge of a balloon, causing the other side to pop up. Now that the ice sheet has melted, the ground that was directly beneath it is rising, and the peripheral bulge is falling.
Some degree of sinking is going on all the way from southern Maine to northern Florida, and it manifests itself as an apparent rising of the sea.
Certain points, scientists say, are affected more severely than others:
Perhaps the weirdest factor of all pertains to Norfolk, Va., and points nearby. What is now the Tidewater region of Virginia was slammed by a meteor about 35 million years ago — a collision so violent it may have killed nearly everything on the East Coast and sent tsunami waves crashing against the Blue Ridge Mountains. The meteor impact disturbed and weakened the sediments across a 50-mile zone. Norfolk is at the edge of that zone, and some scientists think the ancient cataclysm may be one reason it is sinking especially fast, though others doubt it is much of a factor.
Coastal flooding has already become such a severe problem that Norfolk is spending millions to raise streets and improve drainage. Truly protecting the city could cost as much as $1 billion, money that Norfolk officials say they do not have. Norfolk’s mayor, Paul Fraim, made headlines a couple of years ago by acknowledging that some areas might eventually have to be abandoned.
Regardless of the cause, scientists appear convinced that the flooding and coastline damage is happening now, and on a rapid time scale: as in, faster than new homeowners could hope to pay off their mortgage.