AMM15: a new high-resolution NEMO configuration for operational simulation of the European north-west shelf

This paper describes the next-generation ocean forecast model for the European north-west shelf, which will become the basis of operational forecasts in 2018. This new system will provide a step change in resolution and therefore our ability to represent small-scale processes. The new model has a resolution of 1.5 km compared with a grid spacing of 7 km in the current operational system. AMM15 (Atlantic Margin Model, 1.5 km) is introduced as a new regional configuration of NEMO v3.6. Here we describe the technical details behind this configuration, with modifications appropriate for the new high-resolution domain. Results from a 30-year non-assimilative run using the AMM15 domain demonstrate the ability of this model to represent the mean state and variability of the region. Overall, there is an improvement in the representation of the mean state across the region, suggesting similar improvements may be seen in the future operational system. However, the reduction in seasonal bias is greater off-shelf than on-shelf. In the North Sea, biases are largely unchanged. Since there has been no change to the vertical resolution or parameterization schemes, performance improvements are not expected in regions where stratification is dominated by vertical processes rather than advection. This highlights the fact that increased horizontal resolution will not lead to domain-wide improvements. Further work is needed to target bias reduction across the north-west shelf region

Ocean sprawl facilitates dispersal and connectivity of protected species

Highly connected networks generally improve resilience in complex systems. We present a novel application of this paradigm and investigated the potential for anthropogenic structures in the ocean to enhance connectivity of a protected species threatened by human pressures and climate change. Biophysical dispersal models of a protected coral species simulated potential connectivity between oil and gas installations across the North Sea but also metapopulation outcomes for naturally occurring corals downstream. Network analyses illustrated how just a single generation of virtual larvae released from these installations could create a highly connected anthropogenic system, with larvae becoming competent to settle over a range of natural deep-sea, shelf and fjord coral ecosystems including a marine protected area. These results provide the first study showing that a system of anthropogenic structures can have international conservation significance by creating ecologically connected networks and by acting as stepping stones for cross-border interconnection to natural populations

Circulation changes in the Eastern Mediterranean sea over the past 23,000 years inferred from authigenic Nd isotopic ratios

The Eastern Mediterranean Sea (EMS) is a key region to study circulation change because of its own thermohaline circulation. In this study, we focused on intermediate/deep water circulation since the Last Glacial Maximum (LGM) including the sapropel S1 period. Two cores from the Levantine Sea and the Strait of Sicily, respectively, collected at 1,780 m and 771 m water depth, were studied using Nd-143/Nd-144 (epsilon(Nd)) of foraminiferal tests and leachates as well as benthic foraminiferal stable isotopes (delta C-13, delta O-18). This approach allowed the determination of variations in (1) the North Atlantic water contribution to the Mediterranean basin, (2) water exchanges at the Strait of Sicily, and (3) the influence of the Nile River over the last 23,000 years. During the LGM, high benthic foraminiferal delta C-13 values indicate well-ventilated intermediate and deep waters in the EMS. The epsilon(Nd) values were more radiogenic than at present, reflecting a smaller contribution of unradiogenic North Atlantic waters to the EMS due to reduced exchange at the Strait of Sicily. The sluggish circulation in the EMS initiated during deglaciation was further enhanced by increased Nile River freshwater inputs between 15 ka BP and the S1 period. Partial dissolution of Nile River particles contributed to an increase in EMS epsilon(Nd). The large epsilon(Nd) gradient between the EMS and the Western Mediterranean Sea observed during LGM and S1 suggests that each basin had a distinct circulation mode. Decreasing epsilon(Nd) values at the Strait of Sicily after S1 reflected improved water exchange between both basins, leading to the modern circulation pattern

LE PORTEFEUILLE D'INDICATEURS DE SURVEILLANCE DES OCÉANS DU CMEMS POUR LES EAUX DE L'IBERIAN BISCAY IRISH (IBI) : VARIABLES ESSENTIELLES SURVEILLÉES DE MANIÈRE OPÉRATIONNELLE ET PERSPECTIVES D'AVENIR

International audienceThe CMEMS Iberian-Biscay-Ireland Monitoring and Forecasting Center (IBI-MFC) currently provides a variety of OMIs oriented to monitor the main oceanographic processes taking place in this regional domain. Among the OMIs currently delivered by IBI-MFC, it is worth mentioning (i) the coastal upwelling index focused on the African-Iberian coast, (ii) the indicator of Mediterranean Outflow Water variability and (iii) diverse indicators of extreme events of temperature or wave height. Currently, IBIMFC efforts are concentrated on designing bloom phenology indicators derived from chlorophyll anomalies detected within IBI regional seas.The present work aims to provide a general overview of the IBI-MFC OMIs operationally provided nowadays and further insight into the routine OMI update strategy, as well as main conclusions from them. Finally, ongoing developments of novel upcoming OMIs for the IBI region are also introduced.Le centre de surveillance et de prévision CMEMS Iberian-Biscay-Ireland (IBI-MFC) fournit actuellement une variété d'OMIs orientés vers la surveillance des principaux processus océanographiques ayant lieu dans ce domaine régional. Parmi les OMIs actuellement fournis par l'IBI-MFC, il convient de mentionner (i) l'indice d'upwelling côtier centré sur la côte africaine-ibérique, (ii) l'indicateur de variabilité des eaux de sortie de la Méditerranée et (iii) divers indicateurs d'événements extrêmes de température ou de hauteur de vague. Actuellement, les efforts de l'IBIMFC se concentrent sur la conception d'indicateurs de la phénologie des fleurs d'eau dérivés des anomalies de chlorophylle détectées dans les mers régionales de l'IBI.Le présent travail vise à fournir une vue d'ensemble des OMIs IBI-MFC fournis de manière opérationnelle aujourd'hui et un aperçu de la stratégie de mise à jour de routine des OMIs, ainsi que les principales conclusions qui en découlent. Enfin, les développements en cours des nouveaux OMIs à venir pour la région IBI sont également présentés

LE SERVICE OPÉRATIONNEL CMEMS IBI-MFC AUJOURD'HUI : EXAMEN DES PRINCIPALES RÉALISATIONS AU COURS DE LA PHASE DE SERVICE DE COPERNICUS-1 (2015-2021)

International audienceThe CMEMS IBI-MFC (Iberia-Biscay-Ireland Monitoring & Forecasting Centre) delivers daily ocean model forecasts, analysis and reanalysis of different physical and biogeochemical parameters for the Atlantic façade, supporting all kind of marine applications. Along Copernicus-1, this IBI operational service has continuously evolved, upgrading both its forecast capabilities (in 2015, only a circulation forecast in place; today, 3 operational services, including waves and biogeochemical forecasts) and its multi-Year production (covering altimetric era with ocean and wave reanalysis products, together with a non-assimilative biogeochemical hindcast). The main IBIMFC operational achievements and product upgrades are here reviewed. An overview of main IBI service milestones, in terms of both operational production (with inclusion of new variables, increase of product resolution and temporal frequency, extension of forecast horizons and reanalysis coverages) and product quality enhancement is provided. The IBI model applications are routinely validated through meaningful skill scores and a wide range of statistical metrics computed to quantitatively assess the quality and reliability of these model solutions. The CMEMS IBI-MFC delivers today a reliable operational service, meeting user needs for a widespread end-user community (with strong IBI-ROOS connections and marked by a high number of ‘regular’ operational users linked to downstream services). The IBI-MFC service is expected to be upgraded, already in a Copernicus-2 context, and major guidelines of the roadmap are here outlined

Assessment of tidal range changes in the North Sea from 1958 to 2014

We document an exceptional large‐spatial scale case of changes in tidal range in the North Sea, featuring pronounced trends between ‐2.3 mm/yr at tide gauges in the UK and up to 7 mm/yr in the German Bight between 1958 and 2014. These changes are spatially heterogeneous and driven by a superposition of local and large‐scale processes within the basin. We use principal component analysis to separate large‐scale signals appearing coherently over multiple stations from rather localized changes. We identify two leading principal components (PCs) that explain about 69% of tidal range changes in the entire North Sea including the divergent trend pattern along UK and German coastlines that reflects movement of the region's semidiurnal amphidromic areas. By applying numerical and statistical analyses, we can assign a baroclinic (PC1) and a barotropic large‐scale signal (PC2), explaining a large part of the overall variance. A comparison between PC2 and tide gauge records along the European Atlantic coast, Iceland and Canada shows significant correlations on time scales of less than 2 years, which points to an external and basin‐wide forcing mechanism. By contrast, PC1 dominates in the southern North Sea and originates, at least in part, from stratification changes in nearby shallow waters. In particular, from an analysis of observed density profiles, we suggest that an increased strength and duration of the summer pycnocline has stabilized the water column against turbulent dissipation and allowed for higher tidal elevations at the coast