EGU2020-3957
https://doi.org/10.5194/egusphere-egu2020-3957
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Nitrate isotopic constraints on routes of nutrient supply to global ocean pycnocline

Francois Fripiat1,2, Aflredo Martinez-Garcia2, Dario Marconi3, Sarah E. Fawcett4, Daniel M. Sigman3, and Gerald H. Haug2
Francois Fripiat et al.
  • 1Université Libre de Bruxelles, Department of Geosciences, Environment and Society, Belgium (francois.fripiat@ulb.be)
  • 2Max Planck Institute for Chemistry, Germany
  • 3Princeton University, Department of Geosciences, USA
  • 4University of Cape Town, Department of Oceanography, South Africa

The circulation of the ocean plays a fundamental role in restoring the surface nutrients necessary to maintain global ocean biological production. However, our quantitative understanding of the physical mechanisms that return deep-ocean water and nutrients to the upper ocean is currently limited. The nitrate isotopes are investigated here as a new data constraint on the percentage of gross water transport into the global pycnocline that derives from the Southern Ocean as opposed to the deep ocean (which we term the “pycnocline recipe”). Based on a comparison between large-scale observations of nitrate isotopes and the output of a box model, we estimate that the pycnocline recipe is 75 ± 10%; this result implies that ~ 64% of the nutrients supplied to the low latitude pycnocline pass through the Southern Ocean. Our simulations also highlight the shortcomings of a purely advective view of the ocean’s transport of water and nutrients, confirming that mixing with both the deep ocean and the Southern Ocean ventilating area are key to the exchange of water and nutrients between the pycnocline and higher-density deep and polar surface waters. Our calculations support a pure advective-diffusive balance in the deep ocean. In contrast, in the Southern Ocean, our findings provide independent evidence for the importance of air-sea fluxes of momentum and buoyancy in driving the circulation.

How to cite: Fripiat, F., Martinez-Garcia, A., Marconi, D., Fawcett, S. E., Sigman, D. M., and Haug, G. H.: Nitrate isotopic constraints on routes of nutrient supply to global ocean pycnocline, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3957, https://doi.org/10.5194/egusphere-egu2020-3957, 2020

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