Near 5-day nonisostatic response of the Atlantic Ocean to atmospheric surface pressure deduced from sub-surface and bottom pressure measurements

Nonisostatic ocean responses to atmospheric pressure have been observed in tropical regions of the Pacific and Atlantic Oceans at periods near 5 days. Barotropic ocean model simulations coupled to atmospheric forcing predicted that this nonisostatic ocean response is driven not regionally but globally by the Rossby-Haurwitz wave. To date little observational evidence has been provided to support the model simulations, especially at extratropical latitudes. Here we present the basin-scale nature of the nonisostatic response in the Atlantic Ocean near 5-day periods using four historical long-term ( >= 1.5 year) sub-surface and bottom pressure measurements spanning from 16 degrees S to 37 degrees N. Joint analysis of them together with global-gridded atmospheric pressure reveals a basin-scale nonisostatic sea level fluctuation in the North and tropical Atlantic Oceans near 5-day periods with almost uniform phase. It also confirms that the driving force for this near 5-day fluctuation is the westward propagating Rossby-Haurwitz wave.