Abstract. A Lagrangian tracer study was performed on the west Florida shelf in April 1996 using deliberately injected trace gases. Although such studies have been performed previously, this work is the first where the deliberate tracers, in conjunction with carbon system parameters, are used to quantify changes in water column carbon inventories due to air-sea exchange and net community metabolism. The horizontal dispersion and the gas transfer velocity were determined over a period of 2 weeks from the change in both the concentrations and the concentration ratio of the two injected trace gases, sulfur hexafluoride (SF6) and helium-3 (3He). The second moment of the patch grew to 1.6 x 103 km 2 over a period of 11 days. The gas transfer

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[1] Dissolved organic carbon (DOC), nitrogen (DON), and phosphorus (DOP) were measured monthly at the CARIACO Time Series station (10 30 0 N, 64 40 0 W) in the southeastern Caribbean Sea between 2005 and 2012. Marked seasonal variability in DOC concentrations was observed, with lower values (~66 mM) in the upper water column (<75 m) during the upwelling season (December-April) due to the injection of cool, DOC-impoverished Subtropical Underwater from the Caribbean Sea. During the rainy season (May-November) waters were stratified and upper layer DOC concentrations increased to~71 mM. Interannual variability in surface (1 m) concentrations of DOC was also observed in response to the variable strength in upwelling and stratification that the Cariaco Basin experienced. DON and DOP showed no such seasonality. At depths >350 m, DOC concentrations were 56 AE 4.7 mM, roughly 10 mM higher than those in the Caribbean Sea over the same depth range. DON and DOP showed similar vertical profiles to that of DOC, with higher concentrations (6.8 AE 1.2 mM N and 0.15 AE0.09 mM P) in the upper water column and invariant, lower concentrations at depth (4.8 AE 1.6 mM N and 0.10 AE 0.08 mM P). Wind-driven advection of surface DOC out of the Cariaco Basin was estimated to support a net export~15 Gmol C yr À1 into the Caribbean Sea; this rate is comparable to the flux of settling particulate organic carbon to depths >275 m within the basin.

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