Total organic carbon distribution and budget through the Strait of Gibraltar in April 1998

Abstract

In order to investigate total organic carbon TOC exchange through the Strait of Gibraltar, samples were taken along two Ž. Ž. sections from the western Gulf of Cadiz and eastern Western Alboran Sea entrances of the Strait and at the middle of thé Strait in April 1998. TOC was measured by using a high-temperature catalytic oxidation method. The results referenced here are based on a three-layer model of water mass exchange through the Strait, which includes the Atlantic inflow, Mediterranean outflow and an interface layer in between. All layers were characterised by a decrease of TOC concentrations from the Gulf of Cadiz to the Western Alboran Sea: from 60-79 to 59-66 mM C in the Atlantic inflow and from 40-60 tó 38-52 mM C in the Mediterranean waters, respectively. TOC concentrations in the modified North Atlantic Central Water Ž. varied from 43 to 55 mM C. Intermediate TOC values were measured in the interface layer 43-60 mM C. TOC concentrations increased from the middle of the Strait towards continents indicating a contribution of organic carbon of photosynthetic origin along Spain and Morocco coasts or TOC accumulation due to upwelling in the northeastern part of the Strait. Our results indicate that the short-term variability caused by the tide greatly impacts the TOC distribution, particularly in the Gulf of Cadiz. The TOC input from the Atlantic Ocean to the Mediterranean Sea through the Strait of Gibraltar varieś 4 4 y 1 Ž 12 12 y 1. from 0.9 = 10 to 1.0 = 10 mol C s or 0.28 = 10 to 0.35 = 10 mol C year , respectively. This estimate suggests that the TOC inflow and outflow through the Strait of Gibraltar are two and three orders of magnitude higher than reported via the Turkish Straits and Mediterranean River inputs.

New insights on the mineralization of dissolved organic matter in central, intermediate, and deep water masses of the northeast North Atlantic

“…Finally, regarding the LDW, our archetypal concentration, 44.1 6 0.5 mmol kg 21 , was 3.6 mmol kg 21 above the DOC of Antarctic bottom water (AABW) reported by Carlson et al (2010), but note that whereas the archetypal depth of our LDW was 3700 6 159 10 24 Pa, the average depth of AABW was 5019 10 24 Pa. Regarding the archetypal DOC concentration of MW, 47.3 6 0.7 mmol kg 21 , it was significantly lower than the expected concentration of 48.8-49.3 mmol kg 21 obtained when mixing the Mediterranean overflow water (MOW) of the Strait of Gibraltar (45-46 mmol kg 21 ; Dafner et al 2001) with the SPMW (50.5 6 0.6 mmol kg 21 ; Fig. 4a) in a MOW : SPMW proportion of 0.25-0.34 to form the MW (Rogerson et al 2012).…”

The N:Si:P molar ratio in the Strait of Gibraltar

“…[7] The study area and the hydrographic conditions found in the Strait of Gibraltar in April 1998 have been already described in greater detail [Dafner et al, 2001]. The Redfield molar ratios based on individual nutrient concentrations ( Figure 2, second line) suggest that the N:Si:P ratios in the Atlantic water at the western entrance of the Strait are lower than the classical Redfield ratio.…”

“…Samples were also taken at few meters from the bottom. A detailed description of the depth profiles and bottled sampling are shown in Dafner et al [2001].…”

Plankton in the open Mediterranean Sea: a review

“…Clearly, inputs from the atmosphere and land contribute not only nutrients to support primary production but also reduced, potentially respirable carbon. To complete the picture, we should also consider the net DOC input through Gibraltar, which is in the order of 0.3×10 12 mol C y −1 (Dafner et al, 2001). Inputs from the Black Sea would amount to 10% of those entering through Gibraltar (Sempéré et al, 2002), but a significant part of them are likely processed within the Aegean Sea, thus not affecting the overall picture.…”