The Eastern Boundary Current is an essential part of the water mass exchange between the subtropical and subpolar North Atlantic. Here, we study the offshore branch of the European Shelf Current (ESC) over the Goban Spur slope area off Ireland. Our analysis is based on current measurements obtained from a multiyear mooring effort, complemented by ship-board observations along a hydrographic section, satellite-derived estimates of absolute dynamic topography with geostrophic currents, and float trajectories. These data serve to quantify the offshore branch of the ESC on intraannual to interannual timescales. From the moored observations, we derive a mean poleward along-slope volume flux of 3.7 +/- 0.7 Sv for the period 2017-2019. Using a multilinear regression model and geostrophic surface velocities, we extend the time series to the period 1993-2019 and obtain a long-term mean transport of 3.2 +/- 0.4 Sv. Both time series show strong variability ranging from -7.5 to 15.7 Sv. The variability is linked to a dynamic eddy field, especially a stationary cyclonic circulation pattern near the mooring array, and meandering of current branches originating from the North Atlantic Current. We find no evidence of a consistent deep boundary current extending from the shelf break to the position of the offshore mooring (4,500 m depth), but confirm a persistent along-slope flow at the shallower slope (1,500 m depth). Geostrophic surface velocities and float trajectories reveal that the offshore branch of the ESC does not follow a clear northward path from the eastern subtropical regions but rather indicate the intermittent character of the flow.

Reliable data are the basis for successful research and scientific publishing. Open data policies assure the availability of publicly financed field measurements to the public, thus to all interested scientists. However, the variety of data sources and the availability or lack of detailed metadata cause a huge effort for each scientist to decide if the data are usable for their own research topic or not. Data end-user communities have different requirements in metadata details and data handling during data processing. For data providing institutes or agencies, these needs are essential to know, if they want to reach a wide range of end-user communities. The Federal Maritime and Hydrographic Agency (BSH, Bundesamt für Seeschifffahrt und Hydrographie, Hamburg, Germany) is collecting a large variety of field data in physical and chemical oceanography, regionally focused on the North Sea, Baltic Sea, and North Atlantic. Data types vary from vertical profiles, time-series, underway measurements as well as real-time or delayed-mode from moored or ship-based instruments. Along other oceanographic data, the BSH provides all physical data via the German Oceanographic Data Center (DOD). It is crucial to aim for a maximum in reliability of the published data to enhance the usage especially in the scientific community. Here, we present our newly established data processing and quality control procedures using agile project management and workflow techniques, and outline their implementation into metadata and accompanied documentation. To enhance the transparency of data quality control, we will apply a detailed quality flag along with the common data quality flag. This detailed quality flag, established by Mayumi Wilms within the research project RAVE Offshore service (research at alpha ventus) enables data end-users to review the result of several individual quality control checks done during processing and thus to identify easily if the data are usable for their research.

Since 2016 a moored observatory is operated at the eastern extension of the “North Atlantic Changes (NOAC)” array at 47°/48°N. This observatory is installed across the shelf break at Goban Spur and consists of two deep-sea moorings that are separated by about 60 km. The aim of this ongoing monitoring program is to quantify the variability and trends in the properties and transport rates of water masses that are advected northwards along the North Atlantic Eastern Boundary and modify the adjacent regions, i.e. the Northwest European Shelf, North Sea, Nordic Seas and Arctic Ocean. Furthermore, the continuous long term time series are essential for a thorough understanding of the circulation system in the eastern North Atlantic and the underlying physical mechanisms that govern its variability. Here, we present results of the analysis of temperature, salinity and current velocity time series from 2016 to 2019. These provide a descriptive view of the complex current structure and variability of water masses on daily to intra- and inter-annual time scales. The most pronounced signal in the variability of temperature and salinity is caused by the presence of Mediterranean Outflow Water located at about 1000 m depth. During the observation period we find significant positive trends in temperature and salinity in the depth range of 500 to 1500 m. The velocity measurements of the onshore mooring show a northeastward directed mean flow following the topography with along-slope variations, while the flow at the offshore mooring position is more unstable with predominantly cross-slope variations. The combination of our observations with float and altimeter data indicates that the presence of eddies and the interaction with the topography seems to play a crucial role for setting the variability of the flow in this region. Finally, we present an approach to evaluate the volume fluxes at the eastern boundary that will add toward an integrated estimate of the strength of the Atlantic Meridional Overturning Circulation at 47°/48°N.

The ICES (International Council for the Exploration of the Sea) Working Group on Oceanic Hydrography (WGOH) was established in the late 1970’s with the aim of gathering experts in physical oceanography to provide regular science-based assessments of the North Atlantic hydrographical condition (basically termohaline fields). From the beginning, the WGOH has relied on repeated long-term in-situ sampling at key sites around the North Atlantic, the Nordic Seas and adjacent shelf seas. An annual Report on Ocean Climate (IROC), produced by the WGOH since the late 1990’s, summarizes trends in regional hydrography and identifies patterns linking these changes across the North Atlantic. Regional analyses are prepared by local experts who are directly involved in the monitoring programs responsible for collecting data presented in the report. An interactive webpage created in 2013 allows users to browse and download data that inform the IROC. Within the last two decades the physical oceanography community has evolved quickly incor- porating technological advances such as autonomous devices into classical in-situ sampling programs. The WGOH has embraced such technological developments without diverting focus from ongoing in-situ long-term monitoring programs. Having longstanding experience synthe- sizing data and expertise from a large number of operational programs spanning an extensive international footprint, the WGOH has a unique perspective to offer the global ocean observing community. Here we discuss how we might foster connections with ICES to benefit the GOOS (Global Ocean Observing System) community.

In diesem Kapitel werden die aktuellen Erkenntnisse bzgl. der vergangenen, derzeitigen und künftigen klimatischen Bedingungen in der Deutschen Bucht zusammengefasst und die Erkenntnisse des 1. Hamburger Klimaberichtes (kurz 1. HKB, von Storch und Claussen 2011) aktualisiert. Das Klima der Metropolregion Hamburg (MRH) wird maßgeblich von den ozeanographischen und meteorologischen Verhältnissen in und über der Nordsee beeinflusst, insbesondere aber von den Verhältnissen in der Deutschen Bucht. Diese grenzt direkt an die Metropolregion und ist auch die seewärtige Begrenzung der Tideelbe (◉ Abb. 4.1).

Six surface drifters (drogued at about 1 m depth) deployed in the inner German Bight (North Sea) were tracked for between 9 and 54 days. Corresponding simulations were conducted offline based on surface currents from two independent models (BSHcmod and TRIM). Inclusion of a direct wind drag (0.6 % of 10 m wind) was needed for successful simulations based on BSHcmod currents archived for a 5 m depth surface layer. Adding 50 % of surface Stokes drift simulated with a third-generation wave model (WAM) was tested as an alternative approach. Results resembled each other during most of the time. Successful simulations based on TRIM surface currents (1 m depth) suggest that both approaches were mainly needed to compensate insufficient vertical resolution of hydrodynamic currents. The study suggests that the main sources of simulation errors were inaccurate Eulerian currents and lacking representation of sub-grid-scale processes. Substantial model errors often occurred under low wind conditions. A lower limit of predictability (about 3–5 km day−1) was estimated from two drifters that were initially spaced 20 km apart but converged quickly and diverged again after having stayed at a distance of 2 km or less for about 10 days. In most cases, errors in simulated 25 h drifter displacements were of similar order of magnitude.