Control of salinity on the mixed layer depth in the world ocean: 1. General description

Abstract

[1] Using instantaneous temperature and salinity profiles, including recent Argo data, a global ocean climatology of monthly mean properties of the ''barrier layer'' (BL) phenomenon is constructed. This climatology is based on the individual analysis of instantaneous profiles in contrast with previous large-scale climatologies derived from gridded fields. This ensures a more accurate description of the BL phenomenon. We distinguish three types of regions: BLs are quasi-permanent in the equatorial and western tropical Atlantic and Pacific, the Bay of Bengal, the eastern equatorial Indian Ocean, the Labrador Sea, and parts of the Arctic and Southern Ocean. In the northern subpolar basins, the southern Indian Ocean, and the Arabian Sea, BLs are rather seasonal. Finally, BLs are typically never detected between 25°and 45°latitude in each basin. Away from the deep tropics, the analysis reveals strong similarities between the two hemispheres and the three oceans regarding BL seasonality and formation mechanisms. Temperature inversions below the mixed layer are often associated with BLs. Their typical amplitude, depth, and seasonality are described here for the first time at global scale. We suggest that this global product could be used as a reference for future studies and to validate the representation of upper oceanic layers by general circulation models.

Ocean barrier layers’ effect on tropical cyclone intensification

“…In addition, data from several Argo floats (AOML float numbers 4900754, 4900755, 4900800, and 4900572), obtained from http://www.usgodae.org/argo/, are used to examine the sub-surface hydrographic conditions near Omar's path. BLT climatology data, obtained from http://www.lodyc.jussieu.fr/~cdblod/blt.html (30), are used to depict the hurricane season averaged BLT in Fig. 2A.…”

“…Calculations. BLT is defined as ILD minus MLD (30) and can exist if it is at least 10 m in magnitude. Model-simulated TC locations are tracked using a wellestablished TC tracking algorithm (32).…”

Argo profiles variability of barrier layer in the tropical Indian Ocean and its relationship with the Indian Ocean Dipole

“…[4] Seasonal evolution of the BL in the eastern tropical Indian Ocean has been investigated [Wyrtki, 1971;Eriksen, 1979;Sprintall and Tomczak, 1992;Godfrey et al, 1999;Masson et al, 2002;Qu and Meyers, 2005;de Boyer Montégut et al, 2007]. It is believed that the BL formation in the eastern basin is linked to the freshwater input in the near-surface layer from rainfall and river runoff [Sprintall and Tomczak, 1992], and is also forced by the equatorial waves and the Wyrtki Jet [Masson et al, 2002].…”

Comparison of mixed layer depth and barrier layer thickness for the Indian Ocean using two different climatologies

“…Past studies have categorized the vertical structure of upper ocean as three layers instead of two, namely (1) well mixed layer (where temperature and salinity are well mixed), (2) intermediate layer or the barrier layer (BL; which prevail in between the mixed layer and thermocline), and (3) deep stratified ocean (Lukas and Lindstrom, 1991;de Boyer et al, 2007). In this context, presence of BL can have significant impact on mixed layer dynamics and heat budget within the MLD (Sprintall and Tomczak, 1992).…”