MERCATOR OCEAN JOURNA: 
SEPTEMBER 2021 
The lateral open boundaries in the Atlantic Ocean and the 
Baltic Sea play a key role for shelf seas dynamics and the 
distribution of biogeochemical variables. R&D activities are 
assessing the impact of nesting the biogeochemical system 
into the Global Copernicus Marine Service’s biogeochemical 
model, instead of using relaxation toward World Ocean 
Atlas climatological values. In particular, changing the 
boundary condition will allow a better representation 
within reanalysis products of current biogeochemical 
trends in the Atlantic, especially relevant for processes like 
ocean acidification. In addition to updating biogeochemical 
variables currently used at the open ocean boundary, 
the nesting enables the inclusion of realistic boundary 
conditions for phytoplankton biomass and Chlorophyll for 
each phytoplankton functional group, calculated from total 
phytoplankton biomass and Chlorophyll, and SST. Studies 
have also been conducted to improve the nesting at the 
Baltic boundary which influences the salinity in the North 
Sea and Norwegian Coastal Current. Improvements were 
introduced in the latest version of the reanalysis, with 
the use of baroclinic boundary conditions instead of only 
barotropic conditions. Work is ongoing for improving the 
Baltic boundaries also in the forecast system. 
The river forcing plays an important role on the accuracy 
of the products, not limited to the immediate coastal areas. 
The data set for the river runoff and nutrient discharge 
has been improved during the NERC/DEFRA funded Shelf 
Sea Biogeochemistry project. The total annual discharge 
and mean nutrient concentration In the period 1991 to 
2018, compared to the old climatology, shows significant 
interannual variability as well as a trend in phosphorus 
concentration, both of which might affect the product 
quality. For this reason, the decision was made to move 
from using the climatological forcing dataset to using 
the full dataset, which can more precisely represent the 
dynamic behaviour of the coastal areas of the domain. 
This change was implemented in both the latest version 
of the reanalysis and the forecasting system. In an ongoing 
contract exploring hydrological river forcing for the NWS 
MFC, model data from Copernicus Marine Service runoff 
products (LAMBDA Project and European Flood Awareness 
System) were compared to the full and climatologica' 
runoff datasets, and their impacts on NWS models will be 
assessed. 
Multi Model Ensemble products have been developed for the 
Torecast and the Multi Year products, following the work of 
5olbeck et al., (2015). The multi-model ensemble of forecast 
products (MME FC) is a valuable tool for users, revealing 
the temporal and spatial distribution of uncertainties of 
3cean forecast products, and it may yield the best estimate 
ior some physical parameters. Currently, there are eight 
hourly forecast products contributing to the MME FC in the 
NWS for the following parameters: temperature, salinity, 
zurrents and transports (figures on NOOS webpage). A 
sO-Called warning system supports the near-real time 
evaluation of product quality by identifying forecast 
products drifting away from the ensemble. The MME FC is 
under continuous development and supports the activity 
zomparison in overlapping regions: intercomparisons with 
neighbouring MFCs in overlapping areas have already 
been implemented in the MME, e.g., comparison of salt 
transport in the Skagerrak / Kattegat region (NWS and 
BAL MFC products). Like the MME FC, the MME of multi- 
year products (MME MYP) serves as a valuable tool for 
users, revealing the temporal and spatial distribution of 
uncertainties between the ensemble members. Currently 
there are three products providing monthly temperature 
and salinity fields covering the period 1993-2018 (CMEMS 
NWS MFC, GLO MFC, IBI MFC). This product has been 
available as Copernicus Marine Service internal products 
to all other production centrews since July 2020. 
The future development of the NWS system will include 
ensemble products. A preliminary ensemble version of the 
ocean-physics configuration at 7 km resolution, has been 
developed. This prototype ensemble system is meant to 
be a baseline from which to develop ensemble generation 
methods for the shelf-seas forecasting systems, and is 
certainly not in an operational-ready state vet.