Anthropogenic carbon inventory in the Gulf of Cádiz

Abstract

16 17The North Atlantic is the most important sink for atmospheric CO 2 although there still 18 remain uncertainties about the total amount stored by this region and the contribution of 19 the anthropogenic CO 2 (C ANT ) that is exchanged between the Mediterranean Sea and the 20 Atlantic Ocean. During the P 3 A 2 cruise performed in October 2008 throughout the 21 oceanic area covered by the Gulf of Cádiz and the Strait of Gibraltar, which channelizes 22 the water exchange between the Atlantic and the Mediterranean, extensive 23 measurements of the carbon system parameters (pH, total alkalinity and total inorganic 24 carbon) and others related (dissolved oxygen and nutrients) were carried out to analyse 25 their distribution in the area. In order to study the C ANT spatial variability, three 26 observational methods for C ANT concentration assessment (φC T º, ∆C* and TrOCA) 27 were applied. The three water masses identified in the area, North Atlantic Central 28Water (NACW), North Atlantic Deep Water (NADW) and Mediterranean Outflow 29Water (MOW), were shown to contain different C ANT concentration. NADW exhibited 30 the lowest C ANT levels whereas NACW was the most C ANT enriched. Data also indicate 31 a net import of C ANT from the Atlantic towards the Mediterranean through Gibraltar. 32

Increase of dissolved inorganic carbon and decrease in pH in near-surface waters in the Mediterranean Sea during the past two decades

“…To estimate it, several empirical methods have been developed. Flecha et al (2012) computed the anthropogenic carbon inventory in the Gulf of Cadiz. They used observations made during a cruise in October 2008 throughout the oceanic area covered by the Gulf of Cadiz and the Strait of Gibraltar to estimate C ant with three methods, which are C* (Gruber et al, 1996), TrOCA (Touratier and Goyet, 2004;Touratier et al, 2007) and ϕC 0 T (Vázquez-Rodríguez et al, 2009).…”

Physical forcing and physical/biochemical variability of the Mediterranean Sea: a review of unresolved issues and directions for future research

“…Lateral exchanges of carbon to surrounding seas are significant (e.g., Ait-Ameur and Goyet, 2006;Huertas et al, 2009;Schneider et al, 2010;Flecha et al, 2012) well constrained, similar to different methods for calculating C ant in the Mediterranean Overflow Water (MOW), which lead to different magnitudes and even direction of the net flux through the Strait of Gibraltar. In particular, it seems that the TrOCA method overestimates the C ant concentration in the MOW, leading to too large an export of C ant from the Mediterranean to the Atlantic.…”

Palaeohydrological changes over the last 50 ky in the central Gulf of Cadiz: complex forcing mechanisms mixing multi-scale processes

“…In this context, the North Atlantic is the major contributor to atmospheric CO 2 sequestration (Sabine et al, 2004;Takahashi et al, 2009), especially in high latitudes, even if uncertainties remain in the calculated amount stored by coastal regions (e.g. Flecha et al, 2012). Disregarding abiotic processes, CO 2 storage evolution is itself substantially governed by continental and marine primary producers through biological carbon fixing, export and fossilization.…”

“…The central Gulf of Cadiz is a place of low present-day marine productivity, with a moderate ability to store CO 2 and CH 4 (e.g. Huertas et al, 2006Huertas et al, , 2009Flecha et al, 2012). However, this might not have been the case in the past due to the potential migration of proximal productive centres (e.g.…”