Strange Tides on the East Coast

As anyone who has seen the marsh around high tide lately can tell you, Charleston has been experiencing some extremely high tides.  Tides are running between six inches and two feet above their normal levels.  At first it was the entire east coast, but now it seems to be centered more on the mid-Atlantic states, especially Virginia.

Scientists are perplexed with the variation they’ve been seeing.  They say that it has come on too fast to be anything involving melting ice sheets.  The popular opinion right now is that it is mainly caused by a combination of Northeast winds over the ocean and a reduction in the ocean current running from Florida up the coast (not the Gulf Stream, but a prevailing near-shore current mainly caused by Southwest trade-winds).  The winds haven’t been particularly strong, just persistent.  

So, what is causing the winds?  Bill Chameides posted on the Duke University site that it could be a result of a phenomenon known as the North Atlantic Oscillation (NAO).  The NAO is a smaller cousin of the ENSO (El Nino/Southern Oscillation).  Essentially, its a periodic shift in wind patterns that can cause a sloshing back and forth of the entire ocean.

One hole in this theory is that the NAO has not been particularly intense.  Another theory (similar in affect, really) is that rising sea levels are causing changes in global atmospheric circulation.  According to this theory, the sea levels will not rise uniformly around the entire world, but will in effect slosh back and forth as they rise.

Many questions still remain such as how long will it last?  Is this a very temporary anomaly, is it the beginning a longer trend, or is this just a taste of things to come when the sea levels rise?  One thing for sure is that we don’t need a storm surge from a hurricane coming ashore during a freak high tide (or anytime, really).  As for how it will affect our commercial fishing seasons, no one knows.  There are different portions of the marsh being exposed to tide and current as well as some portions that are spending more time under water.  This is sure to effect our oyster seasons, but good or bad?  Who knows?

For more information, check out NOAA’s news, alerts, and up to the minute tidal information here.  You can also read more about it here and here.