Synopsis of the ECCO Central Production Global Ocean and Sea-Ice State Estimate, Version 4 Release 4
ECCO Consortium, Ichiro Fukumori, Ou Wang, Ian Fenty, Gaël Forget, Patrick Heimbach, Rui M. Ponte
Abstract
This note provides a brief synopsis of ECCO Version 4 Release 4 (R4), an updated edition to<br> the global ocean state estimate described by Forget et al. (2015b, 2016) and Fukumori et al.<br> (2017). Release 4 is available at https://ecco.jpl.nasa.gov/drive/files/Version4/Release4.<br> As of this writing, Version 4 represents the latest ocean state estimate of the Consortium for<br> Estimating the Circulation and Climate of the Ocean (ECCO) (Wunsch et al., 2009; Wunsch and<br> Heimbach, 2013) that synthesizes nearly all modern observations with an ocean circulation<br> model (MITgcm, originally described by Marshall et al., 1997) into coherent, physically<br> consistent descriptions of the ocean’s time-evolving state covering the era of satellite altimetry.<br> Among its characteristics, Version 4 (Forget et al., 2015b; Release 1 [R1]) is the first multidecadal<br> ECCO estimate (1992-2011) that is truly global, including the Arctic Ocean. Unlike<br> previous versions, the model uses a nonlinear free surface formulation and real freshwater flux<br> boundary condition, permitting a more accurate simulation of sea level change. In addition to<br> estimating forcing and initial conditions as done in earlier analyses, the Version 4 estimate also<br> adjusts the model’s mixing parameters that enables an improved fit to observations (Forget et al.,<br> 2015a). The Version 4 synthesis also incorporates a diffusion operator in evaluating model-data<br> misfits (Forget and Ponte, 2015) and controls (Weaver and Courtier, 2001), accounting for some<br> of the spatial correlation that exist among these elements.