A preliminary model study of the large‐scale seasonal cycle in bottom pressure over the global ocean

Output from the primitive equation model of Semtner and Chervin [1992] is used to examine the seasonal cycle in bottom pressure p b over the global ocean. Effects of the volume-conserving formulation of the model on the calculation of p b are considered. The estimated seasonal, large-scale p b signals have amplitudes ranging from less than 1 cm over most of the deep ocean to several centimeters over shallow, boundary regions. Variability generally increases toward the western sides of the basins and is also larger in some Southern Ocean regions. An oscillation between subtropical and higher latitudes in the North Pacific is clear. Comparison with barotropic simulations indicates that, on basin scales, seasonal p b variability is related to barotropic dynamics and the seasonal cycle in Ekman pumping and results from a small, net residual in mass divergence from the balance between Ekman and Sverdrup flows.

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