Improving the thermocline calculation over the global ocean

Abstract

According to the typical thermal structure of the ocean, the water column can be divided into three layers: the mixed layer, the thermocline and the deep layer. In this study, we provide a new methodology, based on a function adjustment to the temperature profile, to locate the minimum and maximum depths of the strongest thermocline. We first validated our methodology by comparing the mixed layer depth obtained with the method proposed here with three other methods from previous studies. Since we found a very good agreement between the four methods we used the function adjustment to compute the monthly climatologies of the maximum thermocline depth and the thermocline thickness and strength in the global ocean. We also provide an assessment of the regions of the ocean where our adjustment is valid, i.e., where the thermal structure of the ocean follows the three-layer structure. However, there are ocean regions where the water column cannot be separated into three layers due to the dynamic processes that alter it. This assessment highlights the limitations of the existing methods to accurately determine the mixed layer depth and the thermocline depth in oceanic regions that are particularly turbulent such as the Southern Ocean and the northern North Atlantic, among others. The method proposed here has shown to be robust and easy to apply.