The U.S. Northeast Biogeochemistry Ecosystem Model (NeBEM) was developed based on the modified version of the European Regional Seas Ecosystem Model (ERSEM). NeBEM was applied to examine the ocean acidification (OA) in Massachusetts Bay (Mass Bay) through one- and three-dimensional (1-D and 3-D) experiments. This paper focuses on the 1-D investigation made at the outer and inner bay sites, aiming to a) demonstrate NeBEM’s capability of simulating the observed seasonal cycles for the OA-related variables under near-actual physical conditions, especially pCO2 and pH in shallow and deep areas of the Mass Bay, and b) examine the sensitivity of the model performance to parameterizations and evaluate the various algorithms to calculate dissolved inorganic carbon (DIC), total alkalinity (TA), pCO2, and pH in ERSEM. Model skill assessments were done for physical and biogeochemical variables, and the mechanisms driving the changes in DIC and TA were discussed. Experiment results show that the 1-D NeBEM was robust enough to capture seasonal and interannual variability of nutrients, dissolved oxygen (DO), and chlorophyll a, pCO2, and pH at the deep outer bay site, where the surface meteorological forcing dominantly drove the ecosystem. However, it failed at the shallow inner bay site due to an inadequate characterization of river discharge-induced advection. Calculating pCO2 and pH via diagnostic, prognostic, and semi-diagnostic TA algorithms suggests that the semi-diagnostic method performed better to resolve the observed seasonal variation of pCO2 and has the highest correlation and most minor root mean square error, although all three methods show an insignificant difference in pH simulation. The semi-diagnostic algorithm was also compared with the data-fitting-based BGC+/BGC+* model and T/S-fitting methods. The performances of all three empirical models rely substantially on their calibration set. In this region, NeBEM showed the change in TA (even though underestimated due to 1-D limitation) was dominantly modulated by nitrification and net community production (NCP), while the benthic remineralization was not a significant driver. NCP primarily controlled the change in DIC, and the atmospheric CO2 loading played as the first-order contributor compared to NCP.
Wang L., Chen C., Salisbury J., Beardsley R. & Motyka J., 2024. Modeling of ocean acidification in the Massachusetts Bay and Boston Harbor: 1-D experiments. SSRN. Article (subscription required).
