Strong intrusions of the Northern Mediterranean Current on the eastern Gulf of Lion: insights from in-situ observations and high resolution numerical modelling - Aix-Marseille Université Access content directly
Journal Articles Ocean Dynamics Year : 2016

Strong intrusions of the Northern Mediterranean Current on the eastern Gulf of Lion: insights from in-situ observations and high resolution numerical modelling

Nicolas Barrier
Anne Petrenko
Yann Ourmieres

Abstract

The Northern Mediterranean Current is the return branch of the cyclonic circulation of the northwestern Mediterranean Sea. Because of geostrophic constraints, this warm and oligotrophic current is forced to flow westward along the continental slope of the Gulf of Lion. But, occasionally, it penetrates on the shelf and strongly impacts the local biogeochemistry and in turn the primary production. By combining in situ observations and high-resolution modelling, it is shown that intrusions on the eastern part of the gulf are mainly forced by easterly or northwesterly wind events, through physical mechanisms that are very different in nature. Easterlies induce a piling of water along the Gulf of Lion coast that drives, through geostrophy, an alongshore shelf-intruding current. This intrusive current occurs independently of the stratification and is concomitant with the wind forcing. On the other hand, intrusions due to northwesterlies only occur during stratified conditions and are related to the development of upwellings along the Gulf of Lion coasts. When the upwelling develops, a northwestward alongshore pressure force balances the Coriolis force associated with the onshore flow at depth. When the winds drop, the upwelling relaxes and the onshore flow weakens. Consequently, the Coriolis force no longer counterbalances the pressure force that ultimately dominates the momentum balance, causing the displacement of the Northern Current on the Gulf of Lion shelf approximately 1 day after the wind relaxation. This time lag between the northwesterlies decrease and the intrusions permits to anticipate possible changes in the biogeochemistry of the Gulf of Lion.
Fichier principal
Vignette du fichier
paper_nbarrier.pdf (5.09 Mo) Télécharger le fichier
Origin Files produced by the author(s)
Loading...

Dates and versions

hal-01436127 , version 1 (16-01-2017)

Identifiers

Cite

Nicolas Barrier, Anne Petrenko, Yann Ourmieres. Strong intrusions of the Northern Mediterranean Current on the eastern Gulf of Lion: insights from in-situ observations and high resolution numerical modelling. Ocean Dynamics, 2016, 66 (3), pp.313-327. ⟨10.1007/s10236-016-0921-7⟩. ⟨hal-01436127⟩
292 View
492 Download

Altmetric

Share

Gmail Mastodon Facebook X LinkedIn More