Carbon dioxide in surface ocean waters: 3. Measurements on Lusiad Expedition 1962-1963

Abstract

Direct measurements of carbon dioxide in equatorial surface waters during Lusiad Expedition, 1962–1963, indicate that high concentration relative to atmospheric CO2 is associated with eastward-flowing equatorial undercurrents in the Indian and Atlantic oceans. In the tropical Indian Ocean the measurements are sufficient to construct the areal distribution during two seasons. A broad band of high CO2 occurs during the northeast monsoon but not during the southwest monsoon. An undercurrent is observed only during the former period. Adjacent to the equatorial zone the CO2 concentration is generally lower than equilibrium with the atmosphere in all oceans. In the South Indian Ocean the concentration rises sharply southward on approaching the northern limit of the antarctic circumpolar current. In the western North Pacific Ocean the concentration attains very low values in the east-flowing extension of the Kuroshio Current. In general, low concentration in surface waters exists when rapid cooling occurs and when withdrawal of CO2 by marine organisms exceeds replenishment by physical transport; high concentration exists when rapid warming occurs and when upwelling or vertical mixing supplies more CO2 than can be withdrawn by plants or can escape to the atmosphere.