Development of Improved Space Sampling Strategies for Ocean Chemical Properties:
Total Carbon Dioxide and Dissolved Nitrate

Catherine Goyet
Woods Hole Oceanographic Institution
Woods Hole, Massachusetts 02543 USA

Daniel Davis
Monterey Bay Aquarium Research Institute
Pacific Grove, California 93950 USA

Edward T. Peltzer
Woods Hole Oceanographic Institutiton
Woods Hole, Massachusetts 02543 USA

Peter G. Brewer
Monterey Bay Aquarium Research Institute
Pacific Grove, California 93950 USA

Geophysical Research Letters (1995) 22: 945-948.

Received: 24 January 1994.
Revised: 8 July 1994.
Accepted: 19 August 1994.
Published: 15 April 1995.

ABSTRACT

Large-scale ocean observing programs such as the Joint Global Ocean Flux (JGOFS) and the World Ocean Circulation Experiment (WOCE) must face the problem of designing an adequate sampling strategy. For ocean chemical variables, the goals and observing technologies are quite different from ocean physical variables (temperature, salinity, pressure). We have recently acquired data on the ocean CO2 properties on WOCE cruises P16c and P17c that are sufficiently dense to test for sampling redundancy. We use linear and quadratic interpolation methods on the sampled field to investigate what is the minimum number of samples required to define the deep ocean total inorganic carbon (TCO2) field within the limits of experimental accuracy (± 4 µmol/kg). Within the limits of current measurements, these lines were oversampled in the deep ocean. Should the precision of the measurement be improved, then a denser sampling pattern may be desirable in the future. This approach rationalizes the efficient use of resources for field work and for estimating gridded TCO2 fields needed to constrain geochemical models.

Acknowledgements

We thank Ms. Sally Hacker for measuring TCO2 during WOCE cruise P17c and chief scientists Jim Swift and Mizuki Tsuchiya. This work has been supported by Department of Energy grant DE-FG02-ER60980, the David and Lucile Packard Foundation, and the National Aeronautic and Space Administration grant NAGW-2431. This is contribution number 8754 of the Woods Hole Oceanographic Institution.

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