fCO sub(2) variability at the CARIACO tropical coastal upwelling time series station

Monthly seawater pH and alkalinity measurements were collected between January 1996 and December 2000 at 10 degree 30'N, 64 degree 40'W as part of the CARIACO (CArbon Retention In A Colored Ocean) oceanographic time series. One key objective of CARIACO is to study temporal variability in Total CO sub(2) (TCO sub(2)) concentrations and CO sub(2) fugacity (fCO sub(2)) at this tropical coastal wind-driven upwelling site. Between 1996 and 2000, the difference between atmospheric and surface ocean CO sub(2) concentrations ranged from about -64.3 to +62.3 mu atm. Physical and biochemical factors, specifically upwelling, temperature, primary production, and TCO sub(2) concentrations interacted to control temporal variations in fCO sub(2). Air-sea CO sub(2) fluxes were typically depressed (0 to +10 mmol C m super(-) super(2) day super(-) super(1)) in the first few months of the year during upwelling. Fluxes were higher during June-November (+10 to 20 mmol C m super(-) super(2) day super(-) super(1)). Fluxes were generally independent of the slight changes in salinity normally seen at the station, but low positive flux values were seen in the second half of 1999 during a period of anomalously heavy rains and land-derived runoff. During the 5 years of monthly data examined, only two episodes of negative air-sea CO sub(2) flux were observed. These occurred during short but intense upwelling events in March 1997 (-10 mmol C m super(-) super(2) day super(-) super(1)) and March 1998 (-50 mmol C m super(-) super(2) day super(-) super(1)). Therefore, the Cariaco Basin generally acted as a source of CO sub(2) to the atmosphere in spite of primary productivity in excess of between 300 and 600 g C m super(-) super(2) year super(-) super(1). ar super(-) super(1).