Preformed and regenerated phosphate in ocean general circulation models: can right total concentrations be wrong?
- 1GEOMAR, Helmholtz-Zentrum für Ozeanforschung Kiel, Düsternbrooker Weg 20, 24105 Kiel, Germany
- 2Centre IRD de Bretagne – BP70 – 29280 Plouzane, France
- 3AOS Program, Princeton University, Forrestal Campus, P.O. Box CN710, Princeton, NJ 08544–0710, USA
- 4Laboratoire des Sciences du Climat et de l'Environnement, Orme des Merisiers, CE Saclay, 91191 Gif sur Yvette, France
- 5Department of Earth and Planetary Science, McGill University, Montreal, QC, Canada
- 6CSIRO Marine and Atmosphere Research, Hobart, TAS, Australia
- 7Department of Earth System Science, University of California, Irvine, CA 92697, USA
- 8Max-Planck-Institut für Meteorologie, Bundesstrasse 53, 20146 Hamburg, Germany
Abstract. Phosphate distributions simulated by seven state-of-the-art biogeochemical ocean circulation models are evaluated against observations of global ocean nutrient distributions. The biogeochemical models exhibit different structural complexities, ranging from simple nutrient-restoring to multi-nutrient NPZD type models. We evaluate the simulations using the observed volume distribution of phosphate. The errors in these simulated volume class distributions are significantly larger when preformed phosphate (or regenerated phosphate) rather than total phosphate is considered. Our analysis reveals that models can achieve similarly good fits to observed total phosphate distributions for a~very different partitioning into preformed and regenerated nutrient components. This has implications for the strength and potential climate sensitivity of the simulated biological carbon pump. We suggest complementing the use of total nutrient distributions for assessing model skill by an evaluation of the respective preformed and regenerated nutrient components.