Publications des scientifiques de l'IRD

Maes Christophe, O'Kane T. (2014). Seasonal variations of the upper ocean salinity stratification in the Tropics. Journal of Geophysical Research. Oceans, 119 (3), p. 1706-1722. ISSN 2169-9275.

Titre du document
Seasonal variations of the upper ocean salinity stratification in the Tropics
Année de publication
2014
Type de document
Article référencé dans le Web of Science WOS:000333816100011
Auteurs
Maes Christophe, O'Kane T.
Source
Journal of Geophysical Research. Oceans, 2014, 119 (3), p. 1706-1722 ISSN 2169-9275
In comparison to the deep ocean, the upper mixed layer is a region typically characterized by substantial vertical gradients in water properties. Within the Tropics, the rich variability in the vertical shapes and forms that these structures can assume through variation in the atmospheric forcing results in a differential effect in terms of the temperature and salinity stratification. Rather than focusing on the strong halocline above the thermocline, commonly referred to as the salinity barrier layer, the present study takes into account the respective thermal and saline dependencies in the Brunt-V€ais€al€a frequency (N2) in order to isolate the specific role of the salinity stratification in the layers above the main pycnocline. We examine daily vertical profiles of temperature and salinity from an ocean reanalysis over the period 2001–2007. We find significant seasonal variations in the Brunt-V€ais€al€a frequency profiles are limited to the upper 300 m depth. Based on this, we determine the ocean salinity stratification (OSS) to be defined as the stabilizing effect (positive values) due to the haline part of N2 averaged over the upper 300 m. In many regions of the tropics, the OSS contributes 40–50% to N2 as compared to the thermal stratification and, in some specific regions, exceeds it for a few months of the seasonal cycle. Away from the tropics, for example, near the centers of action of the subtropical gyres, there are regions characterized by the permanent absence of OSS. In other regions previously characterized with salinity barrier layers, the OSS obviously shares some common variations; however, we show that where temperature and salinity are mixed over the same depth, the salinity stratification can be significant. In addition, relationships between the OSS and the sea surface salinity are shown to be well defined and quasilinear in the tropics, providing some indication that in the future, analyses that consider both satellite surface salinity measurements at the surface and vertical profiles at depth will result in a better determination of the role of the salinity stratification in climate prediction systems.
Plan de classement
Climatologie / Météorologie [032CLIMET]
Descripteurs
INTERACTION OCEAN ATMOSPHERE ; SALINITE ; STRATIFICATION ; TEMPERATURE DE SURFACE ; METHODE D'ANALYSE ; PROFIL VERTICAL ; VARIATION SAISONNIERE
Description Géographique
ZONE TROPICALE
Localisation
Fonds IRD [F B010061581]
Identifiant IRD
fdi:010061581
Contact