The winter air-water CO2 net flux is not significant in the Gulf of California to the north of 30°N

It has been reported that in the Gulf of California tidal energy dissipates at great rates from the region of the midrift islands to the north, with practically no dissipation in the central and southern regions of the gulf. It has also been reported that due to this energy dissipation, in places like Canal de Ballenas, strong water column mixing produces greater CO2 partial pressure (pCO(2)) in the surface seawater than in the atmosphere, even during summer. This causes the sea to be a source of CO2 to the atmosphere. We characterized the spatial distribution of surface pH and pCO(2), under "winter" conditions, in order to explore the possibility of the role of the northern Gulf of California (NGC), north of 30 degrees N, as a source of CO2 to the atmosphere. Our results do not support the hypothesis of a significant air-water CO2 flux in the NGC. Mean surface pCO(2) during winter 1996 was 355 mu atm, with a standard error (s n(-0.5)) of 5 mu atm. This mean was not significantly different from the atmospheric value, at 95% confidence level. Thus, the NGC acts neither as a source nor a sink of CO2.