Cross-slope variations of dissolved organic carbon in the Gulf of Cadiz, NE Atlantic Ocean (February 1998)

Abstract

Our observations at a traverse of Cadiz in February 1998 indicated dissolved organic carbon (DOC) concentrations ranging from 61 to 89 μM C within the Spanish Shelf Water, from 48 to 64 μM C within the North Atlantic Surface Water, and from 49 to 55 μM C within the North Atlantic Central Water. Moreover, according to temperature and salinity data, the shallow core of the Mediterranean outflow was also identified deeper than 350 m depth with DOC concentrations between 52 and 58 μM C. The data suggest that DOC distribution at the traverse of the Gulf of Cadiz was controlled by outputs of degraded particles transported within along-slope descending shelf waters and also by features of the circulation in the Gulf of Cadiz. An estimate of organic carbon transport suggests that ca 1.34 to 2.68 x 102 mol C s-1 were transported within the shallow core of Mediterranean outflow. This amount of DOC was 2 orders of magnitude less than that calculated within the Mediterranean outflow in the Strait of Gibraltar for the summer and autumn seasons. These processes might partly regulate the biogeochemistry of the shallow core of the Mediterranean outflow along the Iberian coast.