Denis Volkov, University of Miami/NOAA, USA


The North Atlantic Sea Surface Height Tripole: Its Relation to the Meridional Overturning Circulation and Impact on Coastal Sea Level


Regional sea level changes can deviate significantly from the global average change, which is largely the result of the spatial redistribution of heat and freshwater by ocean circulation. The latter is often simplified by a zonal integral of meridional velocities known as the Meridional Overturning Circulation (MOC). A tripole mode of the ocean gyre-scale sea surface height (SSH) variability has been identified in the North Atlantic, with the subtropical band varying out-of-phase with the tropical and subpolar bands. This mode is largely driven by the large-scale heat divergence related to the Atlantic MOC (AMOC) and the low-frequency North Atlantic Oscillation (NAO). During a positive/negative NAO state, the stronger/weaker AMOC is associated with the weaker/stronger southward upper mid-ocean transport (between the Bahamas and Africa). This leads to heat convergence/divergence and, therefore, an increase/decrease of thermosteric sea level in the subtropical/tropical band of the tripole. The tripole-related thermosteric signals translate to coastal sea level changes along the western and eastern boundaries of the subtropical North Atlantic. Specifically, the tripole explains up to 80% of the interannual sea level variance south of Cape Hatteras and in the Gulf of Mexico. Along the eastern boundary, the tripole-related signals can extend up to the Strait of Gibraltar and impact the Mediterranean Sea level. 


Monday May 8, 11:15


Rossbysalen C609, Arrhenius laboratory, Svante Arrhenius väg 16C, 6th floor