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Tracer and observationally-derived constraints on horizontal and diapycnal diffusivities in ocean models
  • +6
  • David Trossman,
  • Caitlin Whalen,
  • Thomas Haine,
  • Amy Waterhouse,
  • Arash Bigdeli,
  • An Nguyen,
  • Matthew Mazloff,
  • Patrick Heimbach,
  • Robin Kovach
David Trossman
University of Texas-Austin, Oden Institute for Computational Engineering and Sciences, University of Texas-Austin, Oden Institute for Computational Engineering and Sciences, University of Texas-Austin, Oden Institute for Computational Engineering and Sciences, University of Texas-Austin, Oden Institute for Computational Engineering and Sciences

Corresponding Author:[email protected]

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Caitlin Whalen
University of Washington, Applied Physics Laboratory, University of Washington, Applied Physics Laboratory, University of Washington, Applied Physics Laboratory, University of Washington, Applied Physics Laboratory
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Thomas Haine
Johns Hopkins University, Department of Earth and Planetary Sciences, Johns Hopkins University, Department of Earth and Planetary Sciences, Johns Hopkins University, Department of Earth and Planetary Sciences, Johns Hopkins University, Department of Earth and Planetary Sciences
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Amy Waterhouse
Scripps Institution of Oceanography, Scripps Institution of Oceanography, Scripps Institution of Oceanography, Scripps Institution of Oceanography
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Arash Bigdeli
University of Texas-Austin, Oden Institute for Computational Engineering and Sciences, University of Texas-Austin, Oden Institute for Computational Engineering and Sciences, University of Texas-Austin, Oden Institute for Computational Engineering and Sciences, University of Texas-Austin, Oden Institute for Computational Engineering and Sciences
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An Nguyen
University of Texas-Austin, Oden Institute for Computational Engineering and Sciences, University of Texas-Austin, Oden Institute for Computational Engineering and Sciences, University of Texas-Austin, Oden Institute for Computational Engineering and Sciences, University of Texas-Austin, Oden Institute for Computational Engineering and Sciences
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Matthew Mazloff
University of California San Diego Scripps Institution of Oceanography, University of California San Diego Scripps Institution of Oceanography, University of California San Diego Scripps Institution of Oceanography, University of California San Diego Scripps Institution of Oceanography
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Patrick Heimbach
University of Texas-Austin, Oden Institute for Computational Engineering and Sciences, Jackson School of Geosciences & Institute for Geophysics, University of Texas-Austin, Oden Institute for Computational Engineering and Sciences, Jackson School of Geosciences & Institute for Geophysics, University of Texas-Austin, Oden Institute for Computational Engineering and Sciences, Jackson School of Geosciences & Institute for Geophysics, University of Texas-Austin, Oden Institute for Computational Engineering and Sciences, Jackson School of Geosciences & Institute for Geophysics
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Robin Kovach
SSAI, SSAI, SSAI
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Abstract

Mixing parameters can be inaccurate in ocean data assimilation systems, even if there is close agreement between observations and mixing parameters in the same modeling system when data are not assimilated. To address this, we investigate whether there are additional observations that can be assimilated by ocean modeling systems to improve their representation of mixing parameters and thereby gain knowledge of the global ocean’s mixing parameters. Observationally-derived diapycnal diffusivities–using a strain-based parameterization of finescale hydrographic structure–are included in the Estimating the Circulation & Climate of the Ocean (ECCO) framework and the GEOS-5 coupled Earth system model to test if adding observational diffusivities can reduce model biases. We find that adjusting ECCO-estimated and GEOS-5-calculated diapycnal diffusivity profiles toward profiles derived from Argo floats using the finescale parameterization improves agreement with independent diapycnal diffusivity profiles inferred from microstructure data. Additionally, for the GEOS-5 hindcast, agreement with observed mixed layer depths and temperature/salinity/stratification (i.e., hydrographic) fields improves. Dynamic adjustments arise when we make this substitution in GEOS-5, causing the model’s hydrographic changes. Adjoint model-based sensitivity analyses suggest that the assimilation of dissolved oxygen concentrations in future ECCO assimilation efforts would improve estimates of the diapycnal diffusivity field. Observationally-derived products for horizontal mixing need to be validated before conclusions can be drawn about them through similar analyses.