Talk about good news-bad news: A new study finds that sea level isn't rising in the Chesapeake Bay as fast as it is elsewhere, but the region's land is sinking so rapidly it more than makes up for it.
After reviewing satellite measurements and tide gauge data, researchers at the Virginia Institute of Marine Science concluded that absolute sea level is rising only about 1.8 millimeters a year in the bay - less than a tenth of an inch. That's just a little more than half the annual average sea-level rise of 3.1 millimeters that the Intergovernmental Panel on Climate Change figured is happening globally.
But tide gauges from Baltimore to Norfolk show relative sea-level rise of 2.9 to 5.8 millimeters a year - more than is seen anywhere else along the East Coast. The difference must reflect local land subsidence, the VIMS scientists say. The bay region is gradually sinking because of shifts in land resulting from the melting of polar ice caps after the last Ice Age, a comet striking near the mouth of the bay millions of years ago, recent local ground-water withdrawals and other factors.
Overall, the study confirms what scientists have been saying for some time, that land subsidence accounts for about half the sea level rise seen in the Chesapeake. The research, lead by VIMS' John Boon, was underwritten by the Army Corps of Engineers Norfolk District and reviewed by the National Oceanic and Atmospheric Administration and by the Maryland Geological Survey.
The scientists say from the data they analyzed they couldn't tell for sure whether sea level rise in the bay is accelerating, as global-warming models predict it will worldwide. But the bad news, they note, is that the bay's already rapid relative sea-level rise shows no signs of letting up.
(Bay Bridge from Sandy Point State Park. 2009 Baltimore Sun photo by Jed Kirschbaum)