The carbonate system in the North Sea: Sensitivity and model validation

Abstract

The ocean plays an important role in regulating the climate, acting as a sink for carbon dioxide, perturbing the carbonate system and resulting in a slow decrease of seawater pH. Understanding the dynamics of the carbonate system in shelf sea regions is necessary to evaluate the impact of Ocean Acidification (OA) in these societally important ecosystems. Complex hydrodynamic and ecosystem coupled models provide a method of capturing the significant heterogeneity of these areas. However rigorous validation is essential to properly assess the reliability of such models. The coupled model POLCOMS-ERSEM has been implemented in the North Western European shelf with a new parameterization for alkalinity explicitly accounting for riverine inputs and the influence of biological processes. The model has been validated in a like with like comparison with North Sea data from the CANOBA dataset. The model shows good to reasonable agreement for the principal variables, physical (temperature and salinity), biogeochemical (nutrients) and carbonate system (dissolved inorganic carbon and total alkalinity), but simulation of the derived variables, pH and pCO 2 , are not yet fully satisfactory. This high uncertainty is attributed mostly to riverine forcing and primary production. This study suggests that the model is a useful tool to provide information on Ocean Acidification scenarios, but uncertainty on pH and pCO 2 needs to be reduced, particularly when impacts of OA on ecosystem functions are included in the model systems.

A general framework for aquatic biogeochemical models

“…To demonstrate the portability of biogeochemical models coded in FABM, we present simulation results obtained with two reference models included in FABM: a model for carbonate chemistry (Artioli et al, 2012), and a simple nutrient-phytoplanktonzooplankton-detritus (NPZD) model, originally developed by Fennel and Neumann (1996) and modified by Burchard et al (2005). These two models are coupled: the carbonate model maintains pools of dissolved inorganic carbon and (optionally) alkalinity, and the NPZD model interacts with the inorganic carbon pool by consuming and producing CO 2 .…”

The assessment of a global marine ecosystem model on the basis of emergent properties and ecosystem function: a case study with ERSEM

“…The dissolved inorganic carbon (DIC) cycle in the model is described in Artioli et al (2012). There are no explicit limitations of the upper or lower limits of inorganic nitrogen, phosphorus or silicon in the model.…”

Socio-economic Impacts—Fisheries

“…However, variability and uncertainties are considerable due to riverine inputs, biologically-driven processes and geochemical interactions between the water column and sea-bottom sediments (Blackford and Gilbert 2007;Artioli et al 2012). Under a high CO 2 emission scenario, model outputs indicate that much of the North Sea seafloor is likely to become undersaturated with regard to aragonite (a form of calcium carbonate used by some marine organisms to build their shells or skeletons) during late winter/early spring by 2100 (Artioli et al 2012).…”

“…However, variability and uncertainties are considerable due to riverine inputs, biologically-driven processes and geochemical interactions between the water column and sea-bottom sediments (Blackford and Gilbert 2007;Artioli et al 2012). Under a high CO 2 emission scenario, model outputs indicate that much of the North Sea seafloor is likely to become undersaturated with regard to aragonite (a form of calcium carbonate used by some marine organisms to build their shells or skeletons) during late winter/early spring by 2100 (Artioli et al 2012). Ocean acidification may have direct and indirect impacts on the recruitment, growth and survival of exploited species (Fabry et al 2008;Llopiz et al 2014) and some species may become more vulnerable to ocean acidification with increases in temperature (Hale et al 2011).…”