Variability of the δ13C of dissolved inorganic carbon at a site in the north Pacific Ocean

Ann P Mcnichol,Ellen R.M Druffel

doi:10.1016/0016-7037(92)90402-5

Ann P Mcnichol, Ellen R.M Druffel

Open Access

https://doi.org/10.1016/0016-7037(92)90402-5

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Abstract

We present a depth profile of δ 13 C- DIC (dissolved inorganic carbon) and a time-series of surface water δ 13 C- 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° west of Eve site). We observed a small but significant decrease in the δ 13 C 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 CO 2 to the upper ocean. We observed a significant change in surface water δ 13 C 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.

Highlights

NUMEROUSPROCESSECSONTRIBUTEto the 6 13Csignature of total DIC in seawater
We examined the 613C of DIC in surface seawater at a single site in the north-central Pacific over a 28&y time period
The only temporal change we observed was not related to the warming of the surface waters from late June to early July, but to a change in the water mass that was sampled

Summary

Introduction

NUMEROUSPROCESSECSONTRIBUTEto the 6 13Csignature of total DIC in seawater. Understanding the 6 “C of DIC will provide a further constraint on the carbon cycle in the oceans and help us understand the invasion of fossil fuel CO* into the main thermocline (O-1000 m). It will allow a better understanding of paleorecords of 6 13Cin forams by indicating how short-term changes in 6 13Cin their living environments affect their isotopic signatures. We examined the 613C of DIC in surface seawater at a single site in the north-central Pacific over a 28&y time period. We examined the d “C of DIC in a depth profile to compare these data to those collected during GEOSECS

Results

Discussion

Conclusion