Rate of Work Done by Atmospheric Pressure on the Ocean General Circulation and Tides

Abstract

Quantitative analysis of the energetics of the ocean is crucial for understanding its circulation and mixing. The power input by fluctuations in atmospheric pressure pa resulting from the S1 and S2 air tides and the stochastic continuum is analyzed here, with a focus on globally integrated, time-mean values. Results are based on available 1° ? 1° near-global pa and sea level fields and are intended as mainly order-of-magnitude estimates. The rate of work done on the radiational and gravitational components of the S2 ocean tide is estimated at 14 and ?60 GW, respectively, mostly occurring at low latitudes. The net extraction of energy at a rate of ?46 GW is about 10% of available estimates of the work rates by gravity on the S2 tide. For the mainly radiational S1 tide, the power input by pa is much weaker (0.25 GW). Based on daily mean quantities, the stochastic pa continuum contributes ?3 GW to the nontidal circulation, with substantial power input being associated with the pa-driven dynamic response in the Southern Ocean at submonthly time scales. Missing contributions from nontidal variability at the shortest periods (≤ 2 days) may be substantial, but the rate of work done by pa on the general circulation is likely to remain < 1% of the available wind input estimates. The importance of pa effects when considering local, time-variable energetics remains a possibility, however.