The Energetics of Global Thermohaline Circulation and Its Wind Enhancement

Abstract The energy budget of global thermohaline circulation (THC) is numerically investigated using an ocean general circulation model (OGCM) under a realistic configuration. Earlier studies just discuss a globally integrated energy budget. This study intends to draw a comprehensive picture of the global THC by separately calculating the energy budgets for three basins (the Atlantic, Indo-Pacific, and Southern Ocean). The largest mechanical energy source is a kinetic energy (KE) input to the general circulation by wind. Of that, 0.3 TW is converted to gravitational potential energy (GPE), and 80% of the energy conversion occurs in the Southern Ocean. Almost the same quantity of GPE is supplied by vertical mixing. Injected GPE is almost equally dissipated by convective adjustment and the effect of cabbeling, and a large part of that is consumed in the Southern Ocean. A dominant role of the Southern Ocean in the energy balance of THC and importance of the interbasin transport of GPE are found. Then, the enhancement of the meridional overturning circulation in the Atlantic induced by wind in the Southern Ocean is examined. Calculating the energy budget anomaly enables the authors to identify its mechanism as a component of THC.