Ocean tides and mean sea level (MSL) can show correlations of short-term variability in addition to the long-term trends, which may combine to increase total water levels at multiple timescales. Such changes may have implications for short-term high-water events such as nuisance flooding. This work analyses the variability in tides in the Hong Kong region to find that small changes in MSL may amplify tidal changes in Hong Kong, suggesting a strong sensitivity of water levels in the region.

We analyse how surface drifters separate after being released as pairs or triplets in close proximity to wind farms. There is some tentative evidence that these drifters experience turbulent flows arising from an interaction between tidal currents and wind turbine towers. However, more comprehensive studies would be needed to clearly distinguish such wind-farm-related effects from the effects of turbulence that naturally occurs in a complex coastal environment.

In a large-scale analysis, the spread of disinfection by-products from oxidative ballast water treatment is investigated, with a focus on Southeast Asia where major ports are located. Halogenated compounds such as bromoform (CHBr₃) are produced in the ballast water and, once emitted into the environment, can participate in ozone depletion. Anthropogenic bromoform is rapidly emitted into the atmosphere and can locally double around large ports. A large-scale impact cannot be found.

The bottom topography of the Baltic Sea is analysed using the digital depth model from the European Marine Observation and Data Network (EMODnet) published in 2018. Analyses include depth distribution vs. area and seafloor depth variation on a kilometre scale. The limits for the Baltic Sea and analysed sub-basins are from HELCOM. EMODnet is compared with the previously most widely used depth model and the area of deep water exchange between the Bothnian Sea and the Northern Baltic Proper.

In this paper we present a gas equilibrator that can be used to equilibrate gases continuously or in discrete samples from seawater into a carrier gas. The headspace is analysed by a commercially available proton-transfer-reaction mass spectrometer. This allows for the measurement of a broad range of dissolved gases up to a very high solubility in seawater. The main advantage of this equilibrator is its unique design and ease of reproducibility.

Mesoscale eddies are ubiquitous swirling flow patterns in the open ocean with diameters of around 100 km. They transport a huge amount of heat and material and are therefore key elements of the “weather” of the ocean. Using satellite-based ocean surface elevation, we found that the combined global effect of all mesoscale eddies can be treated as a single strong “super-vortex”. This finding can be helpful to estimate the energy budget of ocean regions where only sparse field data are available.

The northern Gulf of Mexico is characterized by complex estuary–shelf–ocean interactions. We developed a 3-D model to represent these interactions. The model is validated with observational data and used to examine the remote influence of Mississippi–Atchafalaya freshwater discharge on Texas coastal systems. Numerical experiments reveal that the remote influence varies greatly under different wind conditions, suggesting great control from the shelf circulations on estuarine dynamics.

After 10 years of research and development, validated analysis and forecasts of the main parameters of the Mediterranean Sea biogeochemistry (e.g. phytoplankton, nutrients, oxygen, pH, carbon fluxes) at high spatial and temporal resolution are provided in the frame of the EU Copernicus Marine Environment Monitoring Service. Along with a traditional skill performance assessment, novel metrics exploiting the Biogeochemical Argo floats data are designed to estimate the forecasts uncertainty.

The assimilation of satellite SST data into ocean models is complex. The temperature of the thin uppermost layer that is measured by satellites may differ from the much thicker upper layer used in numerical models, leading to biased results. This paper shows how canonical correlation analysis can be used to generate observation operators from existing datasets of model states and corresponding observation values. This type of operator can correct for near-surface effects when assimilating SST.

This work uses high-resolution ocean model data to quantify the sinking of waters in the subpolar North Atlantic. The largest amount of sinking is found at the depth of maximum AMOC at 45° N below the mixed layer depth, and 90 % of the sinking occurs near the boundaries in the first 250 km off the shelf. The characteristics of the sinking (total amount, seasonal variability, and vertical structure) vary largely according to the region considered, revealing a complex picture for the sinking.

Methane seepage from the seafloor west of Svalbard was investigated with a fast-response membrane inlet laser spectrometer. The acquired data were in good agreement with traditional sparse discrete water sampling, subsequent gas chromatography, and with a new 2-D model based on echo-sounder data. However, the acquired high-resolution data revealed unprecedented details of the methane distribution, which highlights the need for high-resolution measurements for future climate studies.

The ocean emits the gases carbonyl sulfide (OCS) and carbon disulfide (CS₂), which affect our climate. The goal of this study was to quantify the rates at which both gases are produced in the eastern tropical South Pacific (ETSP), one of the most productive oceanic regions worldwide. Both gases are produced by reactions triggered by sunlight, but we found that the amount produced depends on different factors. Our results improve numerical models to predict oceanic concentrations of both gases.

This study investigates the resolving capabilities of the DUACS gridded products delivered through the CMEMS catalogue. Our method is based on the noise-to-signal ratio approach. While altimeter along-track data resolve scales on the order of a few tens of kilometers, we found that the merging of these along-track data into continuous maps in time and space leads to effective resolution ranging from ~ 800 km wavelength at the Equator to 100 km wavelength at high latitude.

The Copernicus Marine Service (CMEMS) provides oceanographic products and services. Using a mesoscale eddy tracker, we evaluate the performance of three CMEMS model products in the western Mediterranean. Performance testing provides valuable feedback to the model developers. The eddy tracker allows us to construct 3-D eddy composites for each model in the Alboran Sea gyres. Comparison of the composites with data from Argo floats highlights the importance of data assimilation for these models.

A new high-resolution ocean model at 1.5 km has replaced the 7 km system for delivering short-term forecasts of the North-West European Shelf seas. The products (temperature, salinity, currents, and sea surface height) are available on the Copernicus Marine Service catalogue. This study focuses on the high-resolution impact on the quality of the products delivered to the users. Results show that the high-resolution model is better at resolving the variability of the physical variables.

Diatoms are a group of phytoplankton species responsible for ~ 25 % of primary production on Earth. Ocean acidification (OA) could influence diatoms but the key question is if they become more or less important within marine food webs. We synthesize OA experiments with natural communities and found that diatoms are more likely to be positively than negatively affected by high CO² and larger species may profit in particular. This has important implications for ecosystem services diatoms provide.