Using 13C/12C Measurements to Trace the Ocean Carbon Cycle and Anthropogenic CO2 Uptake in the Subtropical Ocean

University Of Washington, Seattle WA

Investigators

Abstract

ABSTRACT OCE-9911913 The ocean is a major sink for CO2 produced by human activities, yet there are few sites where the oceanic CO2 increase is being measured at regular intervals over a long enough time to be detectable. Quantifying the increase in dissolved inorganic carbon (DIC) concentrations at these time series sites caused by uptake of anthropogenic CO2 is complicated by the natural variability in the DIC budget caused by changes in physical forcing and biological productivity. Measurements of 13C/12C at the Hawaii Ocean Time Series (HOTS) site have been shown to provide a unique fingerprint of the primary processes affecting DIC concentrations in the surface ocean and an excellent proxy for tracking the increase in DIC due to uptake of anthropogenic CO2. Since 1995, the rate of increase in DICs (DIC normalized to constant salinity) and decrease in d13C-DIC has doubled relative to values obtained between 1990-1995. The PI proposes to continue making monthly profiles of 13C/12C and DIC at the HOTS site to determine whether the accelerated DICs increase and d13C-DIC decrease continues. In addition, the proponent also will measure the horizontal gradients of DIC and d13C-DIC of surface waters in the vicinity of HOTS to determine how much of the interannual increase in surface DICs at HOTS can be explained by changes in the advection of water masses and rates of biological carbon export versus uptake of anthropogenic CO2.