Recent publication : Oxygen budget of the north-western Mediterranean deep- convection region.

Caroline Ulses, Claude Estournel, Marine Fourrier, Laurent Coppola, Faycal Kessouri, Dominique Lefevre, Patrick Marsaleix; 2021 Biogeosciences 18(3):937-960 DOI:10.5194/bg-18-937-2021

The north-western Mediterranean deep convection plays a crucial role in the general circulation and biogeochemical cycles of the Mediterranean Sea. The DEWEX (DEnse Water EXperiment) project aimed to better understand this role through an intensive observation platform combined with a modelling framework. We developed a three-dimensional coupled physical and biogeochemical model to estimate the cycling and budget of dissolved oxygen in the entire north-western Mediterranean deep-convection area over the period September 2012 to September 2013. After showing that the simulated dissolved oxygen concentrations are in a good agreement with the in situ data collected from research cruises and Argo floats, we analyse the seasonal cycle of the air–sea oxygen exchanges, as well as physical and biogeochemical oxygen fluxes, and we estimate an annual oxygen budget. Our study indicates that the annual air-to-sea fluxes in the deep-convection area amounted to 20 molm-2yr-1. A total of 88 % of the annual uptake of atmospheric oxygen, i.e. 18 mol m−2, occurred during the intense vertical mixing period. The model shows that an amount of 27 mol m−2 of oxygen, injected at the sea surface and produced through photosynthesis, was transferred under the euphotic layer, mainly during deep convection. An amount of 20 mol m−2 of oxygen was then gradually exported in the aphotic layers to the south and west of the western basin, notably, through the spreading of dense waters recently formed. The decline in the deep-convection intensity in this region predicted by the end of the century in recent projections may have important consequences on the overall uptake of atmospheric oxygen in the Mediterranean Sea and on the oxygen exchanges with the Atlantic Ocean, which appear necessary to better quantify in the context of the expansion of low-oxygen zones.

Modeled (a) wind velocity (m s −1 ), (b) mixed-layer depth (m) (dark grey lines represent 500, 1000 and 1500 isocontours and light grey line the contour of the deep-convection area), (c) oxygen saturation anomaly (%) at the surface and (d) air-to-sea oxygen flux (mmol m −2 d −1 ), averaged over the 2013 deep-convection period (15 January-8 March; 15-24 March).

More news

News

Recent publication : Influence of winds, geostrophy and typhoons on the seasonal variability of the circulation in the Gulf of Tonkin: A high-resolution 3D regional modeling study

Violaine Piton, Marine Herrmann, Patrick Marsaleix, Thomas Duhaut, Trin Bich Ngoc, Manh Cuong Tran, Kipp Shearman, Sylvain Ouillon; Regional Studies in Marine Science 45(6):101849 ; DOI:10.1016/j.rsma.2021.101849 The present study explores the seasonal variability of the circulation in the Gulf of Tonkin (GoT) and associated water fluxes, and identifies the driving physical processes of this circulation. […]

News

Dynamics of the North Balearic Front

Dynamics of the North Balearic Front during an autumn tramontane and mistral storm: air–sea coupling processes and stratification budget diagnostic  The North Balearic Front forms the southern branch of the cyclonic gyre in the northwestern Mediterranean Sea. Its dynamics exhibit significant seasonal variability. During autumn, the front spreads northward during the calm wind periods and […]

03.04.2019

News

3D phase-resolved wave modelling with a non-hydrostatic ocean circulation model

SIROCCO developers derived a phase-resolved wave model from an ocean circulation model SYMPHONIE for the purpose of studying wave-current effects in nearshore zones. One challenge is to adapt the circulation model to the specificities of wave physics. This mainly concerns the consideration of non-hydrostatic effects and the parametrization of wave breaking. The non-hydrostatic pressure is […]

Search