Storm surge a growing menace as sea levels rise

Beth Daley in the Boston Globe: The large waves, storm surge, and flooding that Hurricane Earl will spawn as it strikes Massachusetts tonight comes with an added dollop of trouble: sea level rise. Very gradual, and in some cases accelerating, rises in sea level off our coast over the last century will boost the height of Earl’s storm surge — expected to be 1 to 4 feet — meaning the wall of water will be able to travel that much farther inland and over higher elevations to flood basements, streets, and other low-lying areas.

Although scientists agree that sea level rise contributes to flooding during severe storms, exactly how much can be hard to determine because coastal flooding depends on tides, winds, and topography. Sea levels can also vary by several feet from one region to another, and even from season to season, because of ocean circulation and other factors.

Sea level is rising, scientists say, largely because of a global warming double punch: higher ocean temperatures that expand the volume of water and melting glaciers that add water to the sea. So future hurricanes are likely to cause more widespread flooding.

“Sea level rise is fairly insidious and one of those things that we think is in the background and not in our lifetime or our children’s lifetime, but it keeps adding up,’’ said Greg Berman, coastal processes specialist with Woods Hole Sea Grant and Cape Cod Cooperative Extension. He said sea level rise in the last century has coincided with the mass migration of people to live near the coast, and although “we drew a line in the sand where the sea should stop, it’s not listening to us.’’…

A dune on Cape Cod, near Provincetown, shot by Daniel Schwen, Wikimedia Commons, under the Creative Commons Attribution-Share Alike 2.5 Generic license