Coastal Sea Level from the Mid-Atlantic United States to Canada - What Causes the Interannual Variability in this “Hotspot” of Sea Level Rise?

Magdalena Andres, Physical Oceanography


2013 COI Funded Project


While average global sea level is rising, this rise in not uniformly distributed along all coasts.  One region of particular interest stretches along the coast of the mid-Atlantic United States to Canada.  The coastal sea level here is observed to rise at a rate three times faster than the global rate of sea level rise.  Projecting future sea levels for this region requires an understanding of physical processes occurring at different spatial and temporal scales.  Though the stakes are high – both in economic terms and human terms – accurately predicting how the regional sea level will respond to global climate changes is challenging.  Perhaps because the stakes are so high, the issue has become political, with legislators in North Carolina, for example, passing Bill 819 that sets how rates of sea level change are defined for regulatory purposes.  Where economics and nature collide, as they do on the matter of regional sea level rise, science is critical for informing the policy debate.

Existing theories suggest that the enhanced rate of sea level rise along the Middle Atlantic Bight results from changes in large-scale ocean circulation in the Atlantic Meridional Overturning Circulation or the Gulf Stream.  Implicit in these theories, is that sea level variability over the shelves and along the coast is remotely forced.  Comparison of tide gauge data, satellite altimetry and wind stress turns this paradigm on its head.  The preliminary analysis suggests that year-to year variations in coastal sea levels along the Middle Atlantic Bight, the Gulf of Maine and the Scotian Shelf are directly driven by the winds blowing over the continental shelf.  Furthermore, this regional variability may cause changes in the shelf/slope circulation that influence the position of the Gulf Stream.

This proposal aims to examine sea level along the eastern seaboard of the United States and Canada to establish to what extent the region’s interannual changes in sea level are forced locally versus remotely.  It is anticipated that the analysis, which will use existing observational data sets, will lead to publishable results and will provide the foundation for a NASA proposal to examine the interaction and feedbacks of the shelf with the open ocean.  This study also has the potential to make connections to ongoing observational programs including Line W, the upcoming Pioneer Array and the Oleander Program.