The role of heating, winds, and topography on sea level changes in the North Atlantic

Abstract

AbstractSeasonal and interannual‐to‐decadal variations of large‐scale altimetric sea surface height (SSH) owing to surface heating and wind forcing in the presence of topography are investigated using simplified models. The dominant forcing mechanisms are time scale dependent. On the seasonal time scale, locally forced thermosteric height explains most of the SSH variance north of 18°N. First‐mode linear long baroclinic Rossby waves forced by changes in the winds and eastern boundary conditions explain most of the variance between 10°N and 15°N and are also important east of Greenland. On interannual‐to‐decadal time scales, local thermosteric height remains important at several locations in the middle and high latitudes. A topographic Sverdrup response explains interannual‐to‐decadal SSH between 53°N and 63°N east of Greenland. Farther south, the linear Rossby wave model explains SSH variations on interannual‐to‐decadal time scales between 30°N and 50°N from mid‐basin to the eastern boundary. Propagation of the eastern boundary condition into the interior dominates the interannual‐to‐decadal SSH signals south of 30°N. The effect from NAO‐related heat flux on SSH is small, but forcing the topographic Sverdrup models with NAO‐regressed winds gives slightly better agreement with the observed SSH in the subpolar gyre on interannual‐to‐decadal time scales than using the full winds.