Cover

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pp. 1-1

Title Page, Copyright

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pp. 2-5

Contents

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pp. v-vi

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Abstract

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pp. vii-8

By observing simultaneous changes in the concentration and 13C/12C ratio of dissolved inorganic carbon (DIC) in seawater over the annual carbon cycle it is possible to distinguish physical and biological processes that govern this cycle in near-surface waters. We report an analysis of monthly data from 1983 through 1989 at Station S ...

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Acknowledgments

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pp. viii-9

We are grateful to the staff of the Bermuda Biological Station for Research, Inc.: to the director, Anthony Knap, and to Timothy Jickels, Rachael Sherriff-Dow, and Anthony Michaels for their continuing assistance in providing water samples and for their many helpful discussions regarding both the field work and the interpretation of the data. ...

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1. Introduction

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pp. 1-2

Physical and biogeochemical processes act together in controlling the carbon balance in the upper ocean. The international oceanic sciences community recently made remarkable progress toward establishing details of this marine carbon cycle based on results from the ongoing Joint Global Ocean Flux Study time series stations in the subtropical North Atlantic ...

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2. Processes Controlling the Carbon Balance in the Upper Ocean

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pp. 3-8

We begin by discussing the processes of both biological and physicochemical origin that influence the balance of DIC in the upper ocean with special emphasis on their effects on the stable isotopic ratio of DIC, expressed by the reduced ratio: ...

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3. Constraining Carbon Budgets by Concurrent Measurements of DIC and 13δ

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pp. 9-10

To demonstrate how concurrent measurements of DIC and its isotopic ratio 13δ constrain carbon budgets we now develop the following budget equations to be used in our later analysis. ...

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4. Seasonal Observations

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pp. 11-12

The data utilized in this seasonal study are derived from water samples collected at Station S near the northern edge of the Sargasso Sea. Station S is located at 32° 10' N, 64" 30' W, about 21 km southeast of Bermuda within the recirculation region of the North Atlantic anticyclonic subtropical gyre (Worthington 1976, 93). ...

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5. Harmonic Fitting

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pp. 13-14

Isotopic data show considerable scatter, much of which reflects occasions when the data at 1 m and 10 m are not in good agreement. To reduce the influence of this scatter, data that differ between these depths by more than 0.05% on the same date were excluded from the fit, even though these data may reflect real differences ...

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6. Description of the Seasonal Model

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pp. 15-22

We have chosen a three-box model, presented schematically in Figure 6, to represent the seasonal cycle of carbon in the ocean near Bermuda. The middle box represents the mixed layer (ml) which lies in direct contact with the air-sea interface. It is overlain by an atmospheric box (atm) and directly underlain by a box representing the water in the "submixed layer" (Ib, for "layer below"). ...

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7. Results of the Seasonal Model

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pp. 23-26

The rates of change in the salinity-normalized DIC concentration calculated by the model over the course of the annual cycle, are shown in Figure 9 individually for gas exchange, vertical turbulent diffusive transport, vertical entrainment, and net biological exchange. ...

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8. Discussion

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pp. 27-34

The seasonally varying fluxes of carbon predicted for the waters near Bermuda by our model are all influenced to some degree by uncertainties in the relationships used for the calculations. After identifying uncertainties in estimating each flux, we challenge the plausibilities of these relationships by means of sensitivity tests. ...

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9. Summary and Conclusions

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pp. 35-38

The seasonal cycle of DIC in the surface waters near Bermuda is only partially a result of biological processes. To determine the rate at which DIC is converted to organic carbon via photosynthesis and is regenerated by oxidation of organic matter, observed changes in DIC must first be corrected to account for transport processes that alter the DIC concentration, ...

References

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pp. 39-48

Appendix A: Formulas for the Seasonal Model

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pp. 49-56

Appendix B: Three-Dimensional Global Ocean Tracer Transport Model of Bacastow and Maier-Reimer (1991)

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pp. 57-58

Appendix C: Sensitivity Tests

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pp. 59-62

Tables

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pp. 63-79

Figures

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pp. 80-96

Back Cover

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pp. 106-106