Journal cover Journal topic
Geoscientific Model Development An interactive open-access journal of the European Geosciences Union
Geosci. Model Dev., 8, 3071-3104, 2015
http://www.geosci-model-dev.net/8/3071/2015/
doi:10.5194/gmd-8-3071-2015
© Author(s) 2015. This work is distributed
under the Creative Commons Attribution 3.0 License.
Model description paper
06 Oct 2015
ECCO version 4: an integrated framework for non-linear inverse modeling and global ocean state estimation
G. Forget1, J.-M. Campin1, P. Heimbach1,2,3, C. N. Hill1, R. M. Ponte4, and C. Wunsch5 1Dept. of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
2Institute for Computational Engineering and Sciences, The University of Texas at Austin, Austin, TX 78712, USA
3Jackson School of Geosciences, The University of Texas at Austin, Austin, TX 78712, USA
4Atmospheric and Environmental Research, Inc., Lexington, MA 02421, USA
5Dept. of Earth and Planetary Sciences, Harvard University, Cambridge, MA 02139, USA
Abstract. This paper presents the ECCO v4 non-linear inverse modeling framework and its baseline solution for the evolving ocean state over the period 1992–2011. Both components are publicly available and subjected to regular, automated regression tests. The modeling framework includes sets of global conformal grids, a global model setup, implementations of data constraints and control parameters, an interface to algorithmic differentiation, as well as a grid-independent, fully capable Matlab toolbox. The baseline ECCO v4 solution is a dynamically consistent ocean state estimate without unidentified sources of heat and buoyancy, which any interested user will be able to reproduce accurately. The solution is an acceptable fit to most data and has been found to be physically plausible in many respects, as documented here and in related publications. Users are being provided with capabilities to assess model–data misfits for themselves. The synergy between modeling and data synthesis is asserted through the joint presentation of the modeling framework and the state estimate. In particular, the inverse estimate of parameterized physics was instrumental in improving the fit to the observed hydrography, and becomes an integral part of the ocean model setup available for general use. More generally, a first assessment of the relative importance of external, parametric and structural model errors is presented. Parametric and external model uncertainties appear to be of comparable importance and dominate over structural model uncertainty. The results generally underline the importance of including turbulent transport parameters in the inverse problem.

Citation: Forget, G., Campin, J.-M., Heimbach, P., Hill, C. N., Ponte, R. M., and Wunsch, C.: ECCO version 4: an integrated framework for non-linear inverse modeling and global ocean state estimation, Geosci. Model Dev., 8, 3071-3104, doi:10.5194/gmd-8-3071-2015, 2015.
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Short summary
The ECCO v4 non-linear inverse modeling framework and its reference solution are made publicly available. The inverse estimate of ocean physics and atmospheric forcing yields a dynamically consistent and global state estimate without unidentified sources of heat and salt that closely fits in situ and satellite data. Any user can reproduce it accurately. Parametric and external model uncertainties are of comparable magnitudes and generally exceed structural model uncertainties.
The ECCO v4 non-linear inverse modeling framework and its reference solution are made publicly...
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