Eastern Tropical Atlantic Mixed Layer Depth: Assessment of Methods from In Situ Profiles in the Gulf of Guinea from Coastal to High Sea

Type Article
Date 2020-04
Language English
Author(s) N’guessan Benjamin Kouadio1, 2, Kouassi Aka Marcel1, Trokourey Albert2, Toualy Elisée3, Kanga Desiré Kouamé1, 2, Brehmer Patrice4
Affiliation(s) 1 : Centre de Recherches Océanologiques (CRO), Abidjan, Côte d’Ivoire
2 : UFR SSMT, Université Felix Houphouët-Boigny, Laboratoire de Chimie-Physique, Abidjan, Côte d’Ivoire
3 : UFR SSMT, Université Felix Houphouët-Boigny, Laboratoire de Physique de l’Atmosphère et de Mécanique des Fluides (LAPA-MF), Abidjan, Côte d’Ivoire
4 : IRD, Univ Brest, CNRS, Ifremer, Lemar, Délégation Régionale IRD Oues, tPlouzané, France
Source Thalassas (0212-5919) (Springer Science and Business Media LLC), 2020-04 , Vol. 36 , N. 1 , P. 201-212
DOI 10.1007/s41208-019-00179-7
Keyword(s) Mixed layer depth, Gulf of Guinea, Atlantic Ocean, Density, Temperature
Abstract

To assess the eastern Atlantic tropical mixed layer depth (MLD) at 4°W in the Gulf of Guinea, water temperature and density profiles from over five hundred historical observational Conductivity – Temperature - Depth (CTD) data were used. These data, obtained from key oceanographic survey databases covering 60 years (1956 to 2016) were used for a numerical and visual determination of the MLD. The numerical approach consists of the use of the algorithms of three methods; while the visual estimation of the MLD were made on both temperature and density profiles. The numerical approaches were evaluated by comparing their results on the determination of tropical MLD with those of the visual inspections by means of statistical and graphical analysis in order to determine the most suitable method for the determination of MLD in the study area. Our results show that the Boyer Montegut density threshold method (potential density) with the constant criterion Δσ = 0.03 kg.m−3 and a reference depth of ten meters is the most appropriate for determining the MLD in the Gulf of Guinea regardless the season. However, in the situation where only temperature profiles are available it is advisable to estimate MLD using the Lorbacher curvative method.

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N’guessan Benjamin Kouadio, Kouassi Aka Marcel, Trokourey Albert, Toualy Elisée, Kanga Desiré Kouamé, Brehmer Patrice (2020). Eastern Tropical Atlantic Mixed Layer Depth: Assessment of Methods from In Situ Profiles in the Gulf of Guinea from Coastal to High Sea. Thalassas, 36(1), 201-212. Publisher's official version : https://doi.org/10.1007/s41208-019-00179-7 , Open Access version : https://archimer.ifremer.fr/doc/00599/71115/