Wissenschaftliche Monitoringkonzepte für die Deutsche Bucht (WIMO) - Abschlussbericht

The state and development of coastal marine systems and an understanding of the interaction of organisms, sea floor, water column, and biochemical and physical processes can only be obtained by a combination of long-term monitoring and modelling approaches of different complexity. A need for the development and evaluation of monitoring strategies is driven by a framework of different European and German regulations. The research project WIMO (Scientific Monitoring Concepts for the German Bight) has developed concepts and methods that aim at a fundamental scientific understanding of marine systems and also meet monitoring requirements of European legislation and regulations like the EU Marine Strategy Framework Directive. In this final report examples of common descriptors of ecosystem state like seabed integrity, eutrophication, and biodiversity are discussed. It has been assessed to what extent established measuring procedures used to survey the characteristics of the sea floor, and newly developed technologies are eligible for governmental monitoring. The significance of integrative modelling for linking and visualising results of measurements and models is illustrated. It is shown how new concepts have been implemented into governmental monitoring in the form of web based data sheets. These insights enable continuous analyses and developments in the future

Copernicus Ocean State Report, issue 6

The 6th issue of the Copernicus OSR incorporates a large range of topics for the blue, white and green ocean for all European regional seas, and the global ocean over 1993–2020 with a special focus on 2020

Impacts of the Assimilation of Satellite Sea Surface Temperature Data on Volume and Heat Budget Estimates for the North Sea

Mechanisms controlling the heat budget of the North Sea are investigated based on a combination of satellite sea surface temperature measurements and numerical model simulations. Lateral heat fluxes across the shelf edge and into the Baltic Sea as well as vertical ocean‐atmosphere heat exchange are considered. A 3‐D variational (3DVAR) data assimilation (DA) scheme is applied, which contains assumed model error correlations that depend on the mixed layer depth derived from a coupled circulation/ocean wave model. The analysis balances pressure gradients introduced by temperature modifications. Significant hydrodynamic model response to DA was found, which should be considered in the heat budget estimations. The observed change of the current velocity field decreases the lateral advective volume/heat exchanges between the North Sea and the Atlantic, yielding an increased heat flux from the Atlantic into the North Sea and more heat flux from the sea to the atmosphere. The largest DA impact on volume/heat transport is in the Norwegian Channel, where the dominant process is Eulerian transport, followed by tidal pumping and wind pumping. Further analysis reveals an acceleration of the along‐shelf current at the northern edge of the North Sea, a decrease in the horizontal pressure gradient from the Atlantic to the North Sea, and a reduction of the Eulerian transport of volume/heat outward the North Sea. Furthermore, the coupling between the circulation model and the wave model has significant impacts on lateral heat advection in the DA run, which is due to the wave impact on the mixed layer depth.Plain Language Summary: Seawater temperature simulations are important for climate change research, fishery management, coastline protection, ecological balance maintenance, and weather predictions. To improve the seawater temperature prediction capability, a data assimilation (DA) scheme is often applied to combine data from measurements, such as from satellites, buoys, and ships, with data provided by climate models that consider circulation, wave, atmosphere, and ice components. For decades, various DA methods have been developed with a focus on implementing sophisticated mathematical techniques. However, few studies have focused on the impacts of DA on physical processes and the secondary effects of DA. We used a model and satellite data to investigate the impacts of sea surface temperature (SST) assimilations on the volume and heat budgets over the North Sea. We found that DA improved SST modeling, thereby modifying the volume and heat budgets between the North Sea and the Atlantic. The largest change occurs at the Norwegian Channel, where the total water/heat transport from the North Sea outward is reduced. Moreover, SST assimilation also changes the air‐sea heat exchange. This study improves our understanding of the relations between model physics and DA.Key Points: Even with balanced pressure gradients there is a significant response of the three‐dimensional model circulation to sea surface temperature (SST) assimilation in the North Sea. Volume transports through the Norwegian Channel are modified by SST assimilation leading to changes in lateral heat advection. Mechanisms controlling the heat budget of the North Sea are different at west, north, and east boundaries.the German Helmholtz Association (HGF)the Federal Ministry of Education and Research (BMBF)Helmholtz Association http://dx.doi.org/10.13039/501100009318Bundesministerium für Bildung und Forschung http://dx.doi.org/10.13039/50110000234

Oxygen dynamics in the Black Sea as seen by Argo profiling floats.

Observations collected in the Black Sea from May 2010 until December 2011 from two Argo floats with oxygen sensors demonstrated the potential of the applied technique to deliver high-quality oxygen data in this oxic/anoxic environment where the oxygen concentration varies from the level of saturation to zero. It was demonstrated that the dynamics of the oxic-anoxic interface was dominated by vigorous mesoscale processes displacing locally anoxic waters up to about 70 m below the sea surface. Alternatively, oxygenation (ventilation) in the coastal zone penetrated down to about 150–200 m. The range of mesoscale variability, which appeared to reach half of the range of climatic trend during the last 50 years, helped to objectively assess the validity of interpretation of historical data. It was proved that the shift of the suboxic zone from isopycnal depth σt = 16.5 to σt = 15.5 during 1960–2010, interrupted by its deepening between 1990 and 2000, was greater than the possible error limit caused by insufficient sampling of mesoscale variability. Furthermore, profiling floats shed a new light into the seasonal variability of the subsurface oxygen maximum. It was also demonstrated that the assumption of isopycnal alignment of oxygen was coarsely applicable to the suboxic layer in both the coastal and interior part of the Black Sea where the isopycnal mixing revealed large temporal and spatial variability. Therefore, deeper understanding of the dynamics of suboxic zone necessitated continuous basin-wide sampling

Coastal observing and forecasting system for the German Bight – estimates of hydrophysical states

A coastal observing system for Northern and Arctic Seas (COSYNA) aims at construction of a long-term observatory for the German part of the North Sea, elements of which will be deployed as prototype modules in Arctic coastal waters. At present a coastal prediction system deployed in the area of the German Bight integrates near real-time measurements with numerical models in a pre-operational way and provides continuously state estimates and forecasts of coastal ocean state. The measurement suite contributing to the pre-operational set up includes in situ time series from stationary stations, a High-Frequency (HF) radar system measuring surface currents, a FerryBox system and remote sensing data from satellites. The forecasting suite includes nested 3-D hydrodynamic models running in a data-assimilation mode, which are forced with up-to-date meteorological forecast data. This paper reviews the present status of the system and its recent upgrades focusing on developments in the field of coastal data assimilation. Model supported data analysis and state estimates are illustrated using HF radar and FerryBox observations as examples. A new method combining radial surface current measurements from a single HF radar with a priori information from a hydrodynamic model is presented, which optimally relates tidal ellipses parameters of the 2-D current field and the M2 phase and magnitude of the radials. The method presents a robust and helpful first step towards the implementation of a more sophisticated assimilation system and demonstrates that even using only radials from one station can substantially benefit state estimates for surface currents. Assimilation of FerryBox data based on an optimal interpolation approach using a Kalman filter with a stationary background covariance matrix derived from a preliminary model run which was validated against remote sensing and in situ data demonstrated the capabilities of the pre-operational system. Data assimilation significantly improved the performance of the model with respect to both SST and SSS and demonstrated a good skill not only in the vicinity of the Ferry track, but also over larger model areas. The examples provided in this study are considered as initial steps in establishing new coastal ocean products enhanced by the integrated COSYNA-observations and numerical modelling