Projections of Extreme Sea Level Rise Events along the Northeast Coast of North America

Abstract:

By analyzing long-term tide gauge (TG) records, we find an extreme sea level rise (SLR) event during 2009-10 along the Northeast Coast of North America. Within a two-year period, the coastal sea level north of New York City (NYC) jumped by up to 128 mm. Despite significant year-to-year fluctuation, this magnitude of SLR is unprecedented during the entire history of the TG records. We show that this extreme SLR event is a combined effect of two factors: an observed 30% downturn of the Atlantic meridional overturning circulation (AMOC) from April 2009 to March 2010, and an onshore/alongshore wind stress anomaly associated with the significant negative North Atlantic Oscillation (NAO) index.

During the 21st century, state-of-the-art climate models project an increase in magnitude and frequency of extreme SLR events on the interannual time scale along this densely populated coast. An ensemble of 24 climate models demonstrates that AMOC strength is likely to decrease and extreme negative NAO indices are likely to increase over the next century. Our 2009-10 case study suggests that the combination of these two extreme dynamics causes exceptionally high sea levels from Cape Hatteras to the Southeast Coast of Canada.