Gravitational potential energy sinks/sources in the oceans

Gravitational Potential Energy (GPE) is lost during convective adjustment. Using climatological datasets, the annual mean GPE loss due to convective adjustment in the world oceans is estimated as 0.11TW. GPE conversion from the mean state to eddies is also estimated, using the commonly accepted Gent-McWilliams scheme. Our estimate is that about 1.7TW is converted from mean state into eddy GPE. The known sources of GPE are: wind stress work on the geostrophic current (1.3TW, but it is unclear how much of this energy can be converted into GPE) and tidal dissipation rate in the deep ocean (0.9TW, corresponding to 0.18TW after conversion through mixing), near-inertial gravity waves (0.7TW, corresponding to 0.14TW after conversion through mixing), and gravitational GPE generated by geothermal heating (0.05TW). This indicates a large imbalance in the GPE balance in the oceans. It is speculated that there might be large source of GPE that has not been counted in the current estimates. For the current climate setting, a large amount of heat is lost in the North Atlantic. As a result, the mixed layer penetrates deep and the amount of GPE loss due to convective adjustment is large. In addition, conversion through the baroclinic instability is relatively strong in the North Atlantic. In order to maintain the balance of heat and GPE, northward transport of heat and GPE is required.