What Forcing Mechanisms Affect the Co-variability of Interannual Sea Level Variations Between the Northeast and Southeast Coasts of the United States?
Event: 2023 Ocean Surface Topography Science Team Meeting
Session: Science I: Understanding and Quantifying Regional and Global Sea Level Budgets
Presentation type: Type Oral
Contribution: PDF file
Altimetry measurements suggest that interannual sea level variations between the Northeast and Southeast Coasts of the United States (U.S.) separated by Cape Hatteras are significantly less correlated than those within the respective sectors. This behavior is reproduced by the Estimating the Circulation and Climate of the Ocean (ECCO) ocean state estimate. We investigate forcing mechanisms affecting the co-variability of interannual sea-level variations at Nantucket and Charleston, as two representative locations for the U.S. Northeast and Southeast Coasts, by using an adjoint sensitivity analysis of sea-level reconstruction and decomposition in ECCO’s framework. This method is more rigorous than correlation-based methods to determine causal mechanisms for a quantity of interest (interannual sea-level variations here) by wind stress and buoyancy forcing from different regions. Onshore wind stress north of Cape Hatteras and buoyancy forcing, especially that from the subpolar North Atlantic, both cause interannual sea-level variations to co-vary between Nantucket and Charleston. Offshore wind stress contributes much more to interannual sea-level variation at Charleston than to that at Nantucket and has larger contribution than onshore wind stress for Charleston. Offshore wind stress is the major factor causing incoherent interannual sea-level variations between Nantucket and Charleston. Buoyancy forcing south of Charleston, including the Florida shelf, the Gulf of Mexico, and the Caribbean Sea, can have noticeable contribution to Charleston sea-level variations, but not to Nantucket. But such buoyancy forcing contribution is much smaller than that of offshore wind stress in causing the incoherence of interannual sea-level variations between the Northeast and Southeast Coasts of the United States.