A model set-up for future scenario simulations in the northwest European shelf

Abstract

<p>A coupled physical-ecosystem modelling set-up is designed in the framework of GCOAST (Geesthacht Coupled cOAstal model SysTem) to study the ecosystem in the NorthWest European shelf (NWES). Physical model NEMO (Nucleus for European Modelling of the Ocean) is coupled with ECOSMO (ECOSystem MOdel). ECOSMO is a NPDZ (Nutrients, Phytoplankton, Detritus, Zooplankton) model that simulates 3 phytoplankton groups and 3 nutrient cycles. The domain includes Baltic Sea- North Sea and northeast part of Atlantic Ocean bearing ~3.6 km resolution. Physical model forcings include temperature & salinity from WOA data, tides from OTIS and wind from ERA5 datasets, whereas for ecosystem, nutrients (from WOA), and river nutrient load. Unique characteristics to the domain are low-saline brackish water, longer water-cycle memory, and sea ice coverage in the Baltic Sea. The North Sea is relatively saline with shallower depths. This domain extends to eastern North Atlantic that encloses a broader shelf-slope region. Anthropogenic drivers like, river nutrient loads, wind turbines, trawling, shipping, etc constantly modify the coastal waters of the domain. This motivates us to study the region for hindcast and future scenario simulations. Initial experiments are conducted for studying the skill of the set-up. Model validation metrics showed that the simulation has skill in matching a large data set of in situ observations (from ICES and HELCOM datasets) for ecosystem and physical variables. Time series validation of temperature, salinity, and nutrients shows the seasonality and the general characteristics of the ecosystem. The model set-up reproduces cyanobacterial blooms in Baltic Sea; higher primary and secondary production at the shelf-slope, Norwegian trench, and coastal regions of North Sea; tidal mixing fronts in the North Sea, etc. Planned experiments are a hindcast (1992-2017) and Representative Concentration Pathway (RCP8.5) simulation (1992-2050).</p>