29 Aug 2022
29 Aug 2022

Improving the thermocline calculation over the global ocean

Emmanuel Romero1, Leonardo Tenorio-Fernandez2, Esther Portela3,4, Jorge Montes-Aréchiga5, and Laura Sánchez-Velasco1 Emmanuel Romero et al.
  • 1Instituto Politécnico Nacional–Centro Interdisciplinario de Ciencias Marinas (IPN-CICIMAR), Departamento de Oceanología, Av. IPN s/n, La Paz, B.C.S., 23096, México
  • 2CONACyT-Instituto Politécnico Nacional-Centro Interdisciplinario de Ciencias Marinas (IPN-CICIMAR), Av. IPN s/n, La Paz, B.C.S, 23096, México
  • 3Institute for Marine and Antarctic Studies, University of Tasmania, Hobart 7001, Australia
  • 4Univ. Brest, Laboratoire d’Océanographie Physique et Spatiale, CNRS, IRD, Ifremer, Plouzané, France
  • 5Universidad de Guadalajara, Departamento de Física, Gral. Marcelino García Barragán 1421, Olímpica, 44430 Guadalajara, Jal, México

Abstract. According to the typical thermal structure of the ocean, the water column can be divided into three layers: the mixing layer, the thermocline and the deep layer. In this study, we provide a new methodology, based on a function adjustment on the temperature profile, to locate the minimum and maximum depths of the thermocline, and therefore its thickness, to separate the water column into layers. We first validated our methodology by comparing the mixed layer depth obtained with the method proposed here with that of two previous studies. Since we found a very good agreement between the three methods we used the function adjustment to compute the monthly climatologies of the mixed layer depth, the maximum depth of the thermocline and the thermocline thickness, throughout the ocean. We also provide an assessment of the regions of the ocean where our adjustment is valid, and consequently the regions 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 and the major contribution of salinity to stratification. This assessment highlights the limitations of the existing methods to accurately determine the mixed layer depth and the thermocline in oceanic regions that are particularly turbulent as the Southern Ocean and the northern North Atlantic, among others. The method proposed here has shown to be robust and easy to apply, and it can be used in both local and global studies.

Emmanuel Romero et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2022-788', Anonymous Referee #1, 29 Nov 2022
  • RC2: 'Comment on egusphere-2022-788', Anonymous Referee #2, 01 Feb 2023

Emmanuel Romero et al.

Emmanuel Romero et al.


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Short summary
We provide a new methodology based on a function fit to locate the thermocline over the global ocean. Using this methodology, global monthly climatologies of mixed layer depth, maximum thermocline depth, and thermocline thickness were calculated from Argo data. Our method reveals the limitations of existing methods to accurately locate the mixed layer depth in turbulent oceanic regions.