ESTIMATE OF SURFACE PCO2, IN THE GULF OF CALIFORNIA FROM UNDERWAY PH MEASUREMENTS AND SATELLITE IMAGERY

The feasibility of estimating the partial pressure of CO2 (PCO2) from underway measurements of sea-surface temperature, pH, salinity and spe cific alkalinity was tested in the Gulf of California; PCO2 was also e stimated from satellite-obtained sea-surface temperature (SST) by appl ying the pH-temperature relationship of the underway data to the image ry. The pH and PCO2 values were correlated with the major thermal feat ures of the area studied. At the southern, warmer end of the gulf, est imated PCO2 values are approximately 30 to 40 mu atm above an expected surface equilibrium value of ca, 356 mu atm. Maximum PCO2 values of a bout 550 mu atm were found in the region of the midriff islands. For t he 700-km transect, positive correlations were found between pH, in si tu measured temperature (IST) and SST. For the warm zone, there was al so a negative correlation between satellite-derived pigment (logP) and pH and temperature. LogP did not correlate with the other variables i n the cold zone. The feasibility of using ''ships of opportunity'' to monitor pH and surface temperature as part of a world-wide PCO2 monito ring program is discussed.