alaurent101/ROMS_OAE: ROMS biogeochemical model with alkalinity addition (multiple feedstocks)

This release provides the code used in Laurent et al (2025, https://doi.org/10.5194/egusphere-2025-3361). It includes the ROMS code (v3.9, https://github.com/myroms/roms/) used by Ohashi et al (2024, https://doi.org/10.5194/gmd-17-8697-2024) with a biogeochemical model that includes the capability for alkalinity addition for marine CO2 removal (mCDR). The biogeochemical model is based on the Fennel module in ROMS that is simplified to improve computational efficiency for studying the carbonate system in the context of alkalinity enhancement. The model state variables are alkalinity (TA), dissolved inorganic carbon (DIC) and oxygen (O2). The main differences with the Fennel module are the removal of state variables for nutrients (NO3, PO4, NH4) and particulate organic matter (phytoplankton, zooplankton, small and large detritus) and their replacement with parameterizations. New tracers were added for dTA and dDIC, which represent the added alkalinity and the resulting increase in DIC, respectively. The model includes a point source for feedstock addition that can be set constant or to vary with time using a forcing file. Since the feedstock is often partly in particulate form (delivered as a slurry), three additional tracers TAp1, TAp2 and TAp3 are added to represent the particulate phase of up to three types of feedstock, which dissolve into dTA and sink at specified rates. The model supports multiple concomitant releases at various locations. A description of the model and the model equations are available in Laurent et al (2025, https://doi.org/10.5194/egusphere-2025-3361).