Different sampling strategies have been assessed in order to evaluate the most efficient configuration for the assimilation of high resolution measurements into a regional ocean model. The results show the capability of the model to ingest both large scale and high resolution observations and the improvement of the forecast fields. In particular, the configurations using eight gliders and the one assimilating CTDs show similar results and the give the best performance among all the simulations

Tide predictions based on tide-gauge observations are not just astronomical tides; they also contain periodic sea level changes due to the weather. Forecasts of total water level during storm surges add the immediate effects of the weather to the astronomical tide prediction and thus risk double-counting these effects. We use a global model to see how much double-counting may affect these forecasts and also how much of the Highest Astronomical Tide may be due to recurrent weather patterns.

A 6-year simulation of the Turkish Straits System is presented. The simulation is performed by a model using unstructured triangular mesh and realistic atmospheric forcing. The dynamics and circulation of the Marmara Sea are analysed and the mean state of the system is discussed on annual averages. Volume fluxes computed throughout the simulation are presented and the response of the model to severe storms is shown. Finally, it was possible to assess the kinetic energy budget in the Marmara Sea.

In South Korea, over 27 % of the population of 75 million live in coastal city areas. Despite the potential threat of sea level rise, there is little knowledge of how sea level has varied in the past and how those variations compare to present day sea level rise. In this study, new methods are proposed to improve the understanding of past sea level around the Korean Peninsula. The degree to which this understanding can inform policy makers about future sea level rise is also explored.

The currents along the West African seaboard are poorly known. Based on a carefully evaluated numerical simulation the present study describes these currents in the sector 8–20°N and the physical processes that drive them. Prevailing northward flow with two intensification periods per year is identified. Both local and distant coastal winds (blowing as far as thousands of kilometers away in the Gulf of Guinea) contribute to the circulation in this sector.

Two types of marine geoid exist with the first type being the average level of sea surface height if the water is at rest (classical definition), and the second type being satellite-determined with the condition that the water is usually not at rest. The associated absolute dynamic ocean topography (DOT) also has two types. Horizontal gradients of the two DOTs are different with the 1st (2nd) type representing the absolute (relative) surface geostrophic currents.

This paper is focused on a new treatment to along-track satellite data so as to improve the processing of information related to the occurrence of extreme values. The main objective is to preserve information concerning the occurrence of short-term extreme events (2-5 days), like cyclones. In this way, the representativeness of these events is enhanced when applying extreme value return analyses. This method allows us to improve our estimation of return periods for risk analyses.

The impact of boreal spring intraseasonal wind bursts on sea surface temperature variability in the eastern tropical Atlantic in 2005 and 2006 is investigated. The cooling events induced by southerly wind bursts are modulated by local and remote forcing. A particularly strong wind event and a strong cooling occurred in mid-May 2005. It appears as a decisive event in the West African monsoon onset. This study emphasizes the need to further document and monitor the South Atlantic region.

We consider the prospects for seasonal forecasts for the North-west European Shelf (NWS) seas. The recent maturation of global seasonal forecast systems and NWS marine reanalyses provide a basis for such forecasts. We assess the potential of three possible approaches: direct use of global forecast fields and empirical and dynamical downscaling. We conclude that there is potential for NWS seasonal forecasts and as an example show a skillful prototype SST forecast for the English Channel.

The Western Valley is one of the passages across the Iceland–Scotland Ridge through which a strong overflow of cold, dense water has been thought to feed the deep limb of the Atlantic Meridional Overturning Circulation (AMOC), but its strength has not been known. Based on a field experiment with instruments moored across the valley, we show that this overflow branch is much weaker than previously thought and that this is because it is suppressed by the warm countercurrent in the upper layers.

Analysing increased ¹³⁷Cs and ¹³⁴Cs / ¹³⁷Cs ratio derived from the Fukushima Nuclear Power Plant accident in the Sea of Japan and its marginal sea, we found a rapid transport process associated with subduction in the subtropical mode water (STMW) formation region and obduction in the north East China Sea. The integrated amount of FNPP1 ¹³⁷Cs entering the Sea of Japan until 2016 was estimated to be 0.21 ± 0.03 PBq, which corresponds to 5.1 (3.4–8.0) % of the total amount of FNPP1 ¹³⁷Cs in the STMW.

A new methodology to reconstruct HF radar velocity fields based on neural networks is developed. Its performance is compared with other methods focusing on the propagation of errors introduced in the reconstruction of the velocity fields through the trajectories, Lagrangian flow structures and residence times. We find that even when a large number of measurements in the HFR velocity field is missing, the Lagrangian techniques still give an accurate description of oceanic transport properties.

Mixing in the ocean is highly variable and it is often difficult to measure the more energetic regions. Here we present the first full-depth turbulence profiles from Cook Strait, New Zealand. This 22 km wide channel between the major islands of New Zealand sustains very fast tidally driven flows. The measurements show that large vertical eddies exist, moving water up and down. This will affect stratification, as well as any biology, as it passes through the strait.

Zooplankton and fishes found below a depth of 200 m may perform a vertical migration to the surface waters. The migration patterns (from 400 m to the surface) of four groups of organisms were studied in the deep (1500 m) eastern Mediterranean (Cretan Sea) for 2.5 years. The lunar cycle, daylight duration, cloudiness and presence of predators and prey explain their migration variability. This phenomenon is important as it constitutes an active transport of organic matter over large distances.

The mean circulation on the poleward side of the oxygen minimum zone is overlain by eddy activity playing an important role in the distribution of water masses and oxygen within the OMZ. The activity of different types of eddies was investigated during their westward propagation from the formation area off Peru/Chile into the open ocean. The focus was on the development of eddies, seasonal conditions during their formation, and the change of water mass properties transported within the eddies.

30 years of BPR data at Drake Passage are used to investigate the Mf, Mm and Mt long-period tides. Amplitudes of Mf and Mt, and all phase lags, vary over the nodal cycle as in the equilibrium tide. Mm amplitude is almost constant, and so inconsistent at 3σ from anticipation due to energetic non-tidal variability. Most findings agree with a modern ocean tide model. BPR records are superior to conventional tide gauge data in this work due to lower proportion of non-tidal variability.

The Northern Current (NC) in the NW Mediterranean Sea is studied by HF radar, glider, vessel survey, wind station, and model. NC variability is dominated by synoptic response to wind events, studied decomposing geostrophic and ageostrophic surface components. The combination of autonomous observing platforms with classical marine surveys provides high-resolution datasets for scientific purposes and practical applications such as the management of marine resources in the Mediterranean Sea.