VARIABILITY OF THE DELTA-C-13 OF DISSOLVED INORGANIC CARBON AT A SITE IN THE NORTH PACIFIC-OCEAN

We present a depth profile of deltaC-13-DIC (dissolved inorganic carbon) and a time-series of surface water deltaC-13-DIC from seawater samples collected at a single site during the Eve cruise in the North Pacific in June of 1987. Our deep water results confirm those reported by KROOPNICK (1985) for GEOSECS Station 213 (10-degrees west of Eve site). We observed a small but significant decrease in the deltaC-13 of DIC in the upper 500 m of the water column over 13 years since the GEOSECS survey. This is likely due, at least in part, to the input of additional fossil fuel-derived CO2 to the upper ocean. We observed a significant change in surface water deltaC-13 over a short time period (2 days) that was the result of a change in the shallow surface water mass. This change emphasizes the need for caution when conducting seasonal studies.