Evidence for Sea Level Rise

The evidence for sea level rise in the Hampton Roads area is from direct measurements of sea level carried out by the Department of Commerce, National Oceanic and Atmospheric Administrations, National Ocean Service. Interestingly, the group that installs and maintains these measuring stations is located in Chesapeake, VA. The key website that summarizes their observations is at http://tidesandcurrents.noaa.gov/sltrends/sltrends.shtml

At this website you can see the real observations and the trends for locations all around the US. Sea level trends measured in our area are at several locations that you can find on the web map.

The trends they have seen are as follows

Mean Trends at local sites
• Sewell's Point 4.44 mm/yr or 1.46 ft per century
• Portsmouth 3.76 mm/yr or 1.23 ft per century
• First Island (fishing pier) of the Chesapeake Bay Bridge Tunnel 6.05 mm/yr or 1.98 ft per century

Why is sea level rising? There are good explanations at http://tidesandcurrents.noaa.gov/sltrends/sltrends.shtml.

In our region here are at least three reasons for this relatively rapid rise.

Reason 1 - The ocean's waters are slowing warming and as they warm they expand: the expansion causes sea level to rise because the volume of water is increasing.

Reason 2 - The last continental glaciation (18,000 years ago) was so heavy it pushed down the land in southern Canada and, like a teeter-tooter, Virginia went up. Now, even long after the glaciers disappeared, southern Canada is rising and coastal Virginia is sinking. The technical term for this is forebulge subsidence. The same thing is happening in England and Holland for example.

Reason 3 - Chesapeake Bolide - There is a very small amount of subsidence in the lower Chesapeake Bay area related to the impact of a meteorite 35 million years ago. The land in that area is subsiding a bit more.