Abrupt warming and salinification of intermediate waters interplays with decline of deep convection in the Northwestern Mediterranean Sea

Type Article
Date 2020-12
Language English
Author(s) Margirier Félix1, Testor Pierre1, Heslop Emma2, Mallil Katia1, 3, Bosse Anthony4, Houpert Loïc5, Mortier Laurent6, Bouin Marie-Noëlle7, 8, Coppola Laurent9, D’ortenzio Fabrizio9, Durrieu De Madron Xavier10, Mourre Baptiste11, Prieur Louis9, Raimbault Patrick4, Taillandier Vincent9
Affiliation(s) 1 : CNRS-Sorbonne Universités (UPMC Univ. Pierre et Marie Curie, Paris 06)-CNRS-IRD-MNHN, UMR 7159, Laboratoire d’Océanographie et de Climatologie (LOCEAN), Institut Pierre Simon Laplace (IPSL), 4 place Jussieu, 75005, Paris, France
2 : IOC UNESCO, Paris, France
3 : ENSSMAL, EcosysMarL, 16320, Alger, Algeria
4 : Aix-Marseille Université, Université de Toulon, CNRS, IRD, MIO UM 110, 13288, Marseille, France
5 : National Oceanography Centre, Southampton, UK
6 : ENSTA-Paristech, Laboratoire d’OcéSouthamptonanographie et de Climatologie (LOCEAN), Palaiseau, France
7 : CNRM, Universite de Toulouse, Meteo-France, CNRS, Toulouse, France
8 : Univ. Brest, CNRS, IRD, Ifremer, Laboratoire d’Oceanographie Physique et Spatiale (LOPS), IUEM, 29840, Brest, France
9 : CNRS-Sorbonne Universités (UPMC Univ. Pierre et Marie Curie, Paris 06), UMR 7093, Laboratoire d’Océanographie de Villefranche (LOV), Observatoire Océanologique de Villefranche/mer, Paris, France
10 : CNRS-Université de Perpignan Via Domitia, Centre de Formation et de Recherche sur les Environnements Méditerranéens (CEFREM), Perpignan, France
11 : SOCIB, Balearic Islands Coastal Observing and Forecasting System, Palma de Mallorca, Spain
Source Scientific Reports (2045-2322) (Springer Science and Business Media LLC), 2020-12 , Vol. 10 , N. 1 , P. 20923 (11p.)
DOI 10.1038/s41598-020-77859-5

The Mediterranean Sea is a hotspot for climate change, and recent studies have reported its intense warming and salinification. In this study, we use an outstanding dataset relying mostly on glider endurance lines but also on other platforms to track these trends in the northwestern Mediterranean where deep convection occurs. Thanks to a high spatial coverage and a high temporal resolution over the period 2007–2017, we observed the warming (+0.06 ∘C year−1) and salinification (+0.012 year−1) of Levantine Intermediate Water (LIW) in the Ligurian Sea. These rates are similar to those reported closer to its formation area in the Eastern Mediterranean Sea. Further downstream, in the Gulf of Lion, the intermediate heat and salt content were exported to the deep layers from 2009 to 2013 thanks to deep convection processes. In 2014, a LIW step of +0.3 ∘C and +0.08 in salinity could be observed concomitant with a weak winter convection. Warmer and more saline LIW subsequently accumulated in the northwestern basin in the absence of intense deep convective winters until 2018. Deep stratification below the LIW thus increased, which, together with the air–sea heat fluxes intensity, constrained the depth of convection. A key prognostic indicator of the intensity of deep convective events appears to be the convection depth of the previous year.

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Margirier Félix, Testor Pierre, Heslop Emma, Mallil Katia, Bosse Anthony, Houpert Loïc, Mortier Laurent, Bouin Marie-Noëlle, Coppola Laurent, D’ortenzio Fabrizio, Durrieu De Madron Xavier, Mourre Baptiste, Prieur Louis, Raimbault Patrick, Taillandier Vincent (2020). Abrupt warming and salinification of intermediate waters interplays with decline of deep convection in the Northwestern Mediterranean Sea. Scientific Reports, 10(1), 20923 (11p.). Publisher's official version : https://doi.org/10.1038/s41598-020-77859-5 , Open Access version : https://archimer.ifremer.fr/doc/00663/77507/