A new variable for estimating total heat content anomalies of the global oceans and its applications

A new variable defined by sum of absolute positive and negative heat content anomalies (HCA) categorized by depth levels, in-situ temperature and salinity, respectively, is used to estimate the “total” HCA of the global oceans. In comparison of commonly used net HCA, the new variable (the absolute HCA hereafter) represents the strength of thermal perturbations in the global oceans, whereas the net HCA represents how much heat the ocean gains or loses. In this study, the absolute HCA has two applicatons. First, it provides a rough estimations of “total” thermal perturbations and further makes it possible to evaluate the relative contributions of the reversible adiabatic and irreversible diabatic processes in the global oceans. The results show that in the global oceans only a small portion of the thermal perturbations is diabatic, and the rest of signals are adiabatic in nature. Thus, adiabatic motions induced by wind stress play a dominant role in driving thermal perturbations in the global oceans. Second, it examine the global thermal perturbations from different angles, revealing the important role of the polar region, such as the Southern Ocean, in regulating thermal perturbations associated with water mass formation.