JGOFS - Seasonal Study of Carbon Chemistry in the Eastern Equatorial Pacific

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The equatorial Pacific represents a significant portion of the ocean/atmosphere CO2 system and is the largest regional source for CO2 to the atmosphere. The sensitivity of the processes controlling pCO2 to climatic forcing is attested to by the impact of the ENSO cycles on the sea surface pCO2, and by the apparent change in equatorial production during the last glacial period. A central goal of JGOFS Equatorial Pacific Process Study is to elucidate the links between the physical circulation and the biological and chemical processes that control the surface ocean pCO2. A crucial part of this program must be to measure the pCO2 in conjunction with the other chemical and biological measurements. pCO2, total CO2, and alkalinity of the upper ocean will be measured using proven and standard methods, on the two "survey" upper ocean JGOFS cruises. Measurement of pCO2 directly, as opposed to calculating pCO2 from other measurements, is necessary to accurately calculate air-sea fluxes. The variation of total CO2 and alkalinity will constrain the dynamics of organic carbon and calcite, respectively. The carbonate chemistry data will be incorporated into a detailed physical circulation model of the equatorial Pacific, to address questions of thermocline ventilation and the effect of nutrient utilization efficiency on atmospheric pCO2.