Assessment of the Skill of Coupled Physical–Biogeochemical Models in the NW Mediterranean

Abstract

Numerical modeling is a key tool to complement the current physical and biogeochemical observational datasets. It is essential for understanding the role of oceanographic processes on marine food webs and producing climate change projections of variables affecting key ecosystem functions. In this work, we evaluate the horizontal and vertical patterns of four state-of-the-art coupled physical-biogeochemical models, three of them already published. Two of the models include data assimilation, physical and/or biological, and two do not. Simulations are compared to the most exhaustive dataset of in situ observations in the North Western Mediterranean, built ad hoc for this work, comprising gliders and conventional CTD surveys and complemented with satellite observations. The analyses are performed both in the whole domain and in four subregions (Catalan Shelf, Ebro Delta, Mallorca Channel, and Ibiza Channel), characterized by a priori divergent primary production dynamics and driving mechanisms. Overall, existing models offer a reasonable representation of physical processes including stratification, surface temperature, and surface currents, but it is shown that relatively small differences among them can lead to large differences in the response of biogeochemical variables. Our results show that all models are able to reproduce the main seasonal patterns of primary production both at the upper layer and at the deep chlorophyll maximum (DCM), as well as the differential behavior of the four subregions. However, there are significant discrepancies in the local variability of the intensity of the winter mixing, phytoplankton blooms, or the intensity and depth of the DCM. All model runs show markedly contrasting patterns of interannual phytoplankton biomass in all four subregions. This lack of robustness should dissuade end users from using them to fill gaps in time series observations without assessing their appropriateness. Finally, we discuss the usability of these models for different applications in marine ecology, including fishery oceanography.

Acidification, deoxygenation, and nutrient and biomass declines in a warming Mediterranean Sea

“…These considerations emphasize the importance of providing eddy-resolving future projections of the Mediterranean Sea biogeochemistry under different emission scenarios. In fact, although observational and modeling studies have been already carried out in the recent period to assess the importance of the mesoscale dynamics for the physical and biogeochemical states of limited areas of the Mediterranean Sea (e.g., Hermann et al, 2008;Moutin and Prieur, 2012;Guyennon et al, 2015;Ramirez-Romero et al, 2020), long-term eddy-resolving biogeochemical projections under different emission scenarios have not yet, to the best of the authors' knowledge, been analyzed for this region. Such projections might be used in future studies specifically focused on the analysis of climate change impacts on specific organisms, habitats and/or local areas.…”

Influence of Thermal Regimes on the Relationship between Parasitic Load and Body Condition in European Sardine along the Catalan Coast

“…In the NW Mediterranean, primary production is determined by the strong vertical mixing and contribution of fluvial nutrient loads [24]. Considerable differences in seawater temperature are reported in this area [25]. Therefore, due to its environmental heterogeneity and particular hydrographical feature, it is of primary interest to study the life history traits of sardine in this area, as well as its parasite infection.…”

Net primary production annual maxima in the North Atlantic projected to shift in the 21st century

“…PISCES has been used and validated in a number of settings (Ramirez-romero et al, 2020;Gutknecht et al, 2019;Kwiatkowski et al, 2018). Skyllas et al (2019) showed a good agreement between EC-Earth3-CC and temperature, salinity, and nutrients and chlorophyll a observations in an offline ocean-only version of NEMO-PISCES, for a northsouth (29-63°N) transect in the northwest Atlantic.…”