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Biogeochemical protocols and diagnostics for the CMIP6 Ocean Model Intercomparison Project (OMIP)

Type of publication Peer-reviewed
Publikationsform Original article (peer-reviewed)
Author Orr James C., Najjar Raymond G., Aumont Olivier, Bopp Laurent, Bullister John L., Danabasoglu Gokhan, Doney Scott C., Dunne John P., Dutay Jean-Claude, Graven Heather, Griffies Stephen M., John Jasmin G., Joos Fortunat, Levin Ingeborg, Lindsay Keith, Matear Richard J., McKinley Galen A., Mouchet Anne, Oschlies Andreas, Romanou Anastasia, Schlitzer Reiner, Tagliabue Alessandro, Tanhua Toste, Yool Andrew,
Project Climate and Environmental Physics: Modeling Global Biogeochemical Cycles in the Earth System (bgcCEP)
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Original article (peer-reviewed)

Journal Geoscientific Model Development
Volume (Issue) 10(6)
Page(s) 2169 - 2199
Title of proceedings Geoscientific Model Development
DOI 10.5194/gmd-10-2169-2017

Open Access

URL http://doi.org/10.5194/gmd-10-2169-2017
Type of Open Access Publisher (Gold Open Access)

Abstract

Abstract. The Ocean Model Intercomparison Project (OMIP) focuses on the physics and biogeochemistry of the ocean component of Earth system models participating in the sixth phase of the Coupled Model Intercomparison Project (CMIP6). OMIP aims to provide standard protocols and diagnostics for ocean models, while offering a forum to promote their common assessment and improvement. It also offers to compare solutions of the same ocean models when forced with reanalysis data (OMIP simulations) vs. when integrated within fully coupled Earth system models (CMIP6). Here we detail simulation protocols and diagnostics for OMIP's biogeochemical and inert chemical tracers. These passive-tracer simulations will be coupled to ocean circulation models, initialized with observational data or output from a model spin-up, and forced by repeating the 1948–2009 surface fluxes of heat, fresh water, and momentum. These so-called OMIP-BGC simulations include three inert chemical tracers (CFC-11, CFC-12, SF6) and biogeochemical tracers (e.g., dissolved inorganic carbon, carbon isotopes, alkalinity, nutrients, and oxygen). Modelers will use their preferred prognostic BGC model but should follow common guidelines for gas exchange and carbonate chemistry. Simulations include both natural and total carbon tracers. The required forced simulation (omip1) will be initialized with gridded observational climatologies. An optional forced simulation (omip1-spunup) will be initialized instead with BGC fields from a long model spin-up, preferably for 2000 years or more, and forced by repeating the same 62-year meteorological forcing. That optional run will also include abiotic tracers of total dissolved inorganic carbon and radiocarbon, CTabio and 14CTabio, to assess deep-ocean ventilation and distinguish the role of physics vs. biology. These simulations will be forced by observed atmospheric histories of the three inert gases and CO2 as well as carbon isotope ratios of CO2. OMIP-BGC simulation protocols are founded on those from previous phases of the Ocean Carbon-Cycle Model Intercomparison Project. They have been merged and updated to reflect improvements concerning gas exchange, carbonate chemistry, and new data for initial conditions and atmospheric gas histories. Code is provided to facilitate their implementation.
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