Physical controls on dissolved inorganic radiocarbon variability in the California Current

Caroline A Masiello,Ellen R.M Druffel,James E Bauer

doi:10.1016/s0967-0645(97)00096-9

Caroline A Masiello, Ellen R.M Druffel + Show 1 more

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https://doi.org/10.1016/s0967-0645(97)00096-9

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Abstract

We present depth profiles of Δ 14C and δ 13C of dissolved inorganic carbon (DIC) at Station M in the Eastern North Pacific. Several seasonal profiles are presented for the time period between 1991 and 1996. Comparison with GEOSECS data clearly shows changes in ocean radiocarbon profiles since 1973. The Δ 14C of DIC shows the most variability at depths of 450, 85, and 25 m, and the lowest variability at depths of 1600 and 2500 m. The largest variability in DIC Δ 14C occurs at 450 m, a depth marked by large fluctuations in the radiocarbon signatures of the source waters. The likely controls of DIC Δ 14C variability are physical changes in the circulation of the California Current System. A simple two-box model is used to show the importance of wind driven mixing at the surface. We discuss the likely effects of mesoscale eddies and ENSO on the DIC Δ 14C values at this site. We also show that remineralization of organic carbon (dissolved or particulate) is not responsible for the variability in the Δ 14C of DIC observed at Station M.

Highlights

The variability of seawater dissolved inorganic carbon (DIC) C is relevant to a number of oceanographic questions
DIC is the precursor of sinking organic material
The highest DIC C values are found at the surface because of the ocean’s contact with the atmosphere

Summary

Introduction

The variability of seawater DIC C is relevant to a number of oceanographic questions. The C signature of DIC in seawater is a useful physical oceanographic tracer. Because of the input of bomb C to the environment by nuclear weapons testing in the late 1950s and early 1960s, C DIC data have been used to address short timescale oceanographic questions, such as equatorial upwelling rates (Quay et al, 1983). Bomb C is a useful tracer of the input rate of fossil fuel The C of DIC is rCeOlevatnot the environment. DIC is the inorganic precursor of all biological material produced in the ocean. DIC is the precursor of sinking organic material. This sinking material provides a rapid pathway between inorganic carbon at the ocean surface (taurpboaotilonins)eaqnudilicbarriubmonwinithocaetamnosspedhiemriecnCtsO(a and influenced by pool stable on geologic human pertime). Data on the radiocarbon variability of the parent DIC pool are necessary to interpret data on the radiocarbon variability of sinking organic material (see, e.g. (Druffel et al., 1996))

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