Seasonality of Dissolved Organic Carbon Exchange across Gibraltar Strait

XX Seminario Ibérico de Química Marina SIQUIMAR 2020, Barcelona (Spain), 1st-3rd July 2020.

Exchange of mass, heat and dissolved materials across the Strait of Gibraltar are fundamental to understand the hydrography, circulation and biogeochemistry of the Mediterranean Sea and the North Atlantic Ocean (Huertas et al., 2012; Schneider et al., 2014; Barbosa et al., 2015). Here we focus on the exchange of dissolved organic carbon (DOC) across the strait. A marked bimodal distribution is observed, with exchange minima around 5 109 g C d–1 in late June and late October and maxima around 15 109 g C d–1 in mid April and late August. This temporal pattern is mainly due to seasonal variation of the DOC gradient between the Atlantic surface water (ASW, salinity < 37.5) that enters the Mediterranean Sea and the opposite-flowing Mediterranean Overflow Water (MOW, salinity > 37.5) (Huertas et al., 2012). This gradient is primarily controlled by the different seasonal cycles followed by the concentration of DOC in the two layers. Seasonal variability at the strait is not only autochthonous but caused by biogeochemical processes occurring during the transits of ASW and MOW to the Gibraltar strait too. Water exchange across the strait also varies seasonally, from a maximum of 0.90 Sv by early April and a minimum of 0.75 Sv by mid August (Sammartino et al., 2015), having a secondary impact on the variability of DOC fluxes. The annual average DOC exchange across the Strait of Gibraltar, 4.2 ± 1.5 1012 g C y–1, represents 55% of the external DOC inputs and supports 32% of the net heterotrophy of the Mediterranean Sea

Funding for this work was provided by the EU through projects SESAME (FP6-036949 GOCE), CARBOCHANGE (FP7-264879) and PERSEUS (FP7-287600) and by the Spanish Ministry of Education and Sciences (CTM2006-28141-E/MAR

Peer reviewed