Sea levels are rising worldwide and many coastal communities will soon begin planning — if they haven’t already — for the need to relocate and deal with the encroaching sea waters. However, sea level rise is not just the result of the polar ice caps melting, as Chesapeake Bay is in the midst of finding out.
New research from researchers at the Virginia Institute of Marine Sciences (VIMS) has found that while the sea level rise in the area around Chesapeake Bay is about half that of the global average, the subsidence in the area more than makes up for it.
The distinction is between absolute sea level, which is the measure of the volume and mass of ocean water, and relative sea level, which is the level of the ocean when measured against the land.
When measuring Chesapeake Bay against the absolute sea level, there might be cause for relief, with data from NOAA satellites showing that the sea level is rising at a rate of about 1.8 millimetres per year (half of the global average of 3.1 millimetres per year).
However the VIMS study shows, based on detailed analyses of simultaneous 35-year records from 10 tide gauges between Norfolk and Baltimore that the relative sea level rise in Chesapeake Bay ranges from 2.91 millimetres to 5.80 millimetres per year. When you spread that out over a century, the sea level could rise anywhere between one and two feet.
The mid-Atlantic region is slowly sinking thanks to land movements associated with melting of the polar ice caps since the last Ice Age, faulting associated with the Chesapeake Bay Impact Crater, local groundwater withdrawals, and numerous other factors.
Unfortunately, for the locals of Chesapeake Bay, there is no data to suggest that the subsidence rates in their part of the world are likely to change in the future.