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.

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.

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 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.

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.

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.

This paper describes the differences between ocean surface winds provided by ERA reanalyses and satellite scatterometer observations. This work is motivated by the widespread use of reanalysis winds for ocean forcing in marine forecasting centers and the application of observations to characterize reanalysis wind errors, which we conjecture are related to deficiencies in the physics of the underlying assimilating model (insufficient wind variability at high spatial and temporal frequencies).

This paper concerns the GlobColour chlorophyll α products disseminated by the Copernicus Marine Environmental Monitoring Service (CMEMS). The strategies for merging and flagging remote-sensing data are discussed. Results are illustrated by comparing the CMEMS GlobColour products provided by ACRI-ST with the OC-CCI/C3S products. This highlights the capability of GlobColour to obtain a better spatial coverage and to ingest the OLCI data in complement with SeaWiFS, MERIS, MODIS and VIIRS sensors.

In the North Atlantic, ocean currents transport warm waters northward in the upper water column, and cold waters southwards at depth. This circulation is here reconstructed from surface data and thermodynamics theory. Its driving role in recent temperature changes (1993–2017) in the North Atlantic is evidenced, and predictions of near-future variability (5 years) are provided and discussed.

OCEAN5 is the fifth generation of the ocean and sea-ice analysis system at ECMWF. It was used for production of historical ocean and sea-ice states from 1979 onwards and is also used for generating real-time ocean and sea-ice states responsible for initializing the operational ECMWF weather forecasting system. This is a valuable data set with broad applications. A description of the OCEAN5 system and an assessment of the historical data set have been documented in this reference paper.

Oceans are modified at the surface by winds and by the exchange of heat with the atmosphere. The effect of changing atmospheric information that is available to drive an ocean model of north-west Europe, which can simulate small-scale details of the ocean state, is tested. We show that simulated temperatures agree better with observations located near the coast around the south-west UK when using data from a high-resolution atmospheric model, and when atmosphere and ocean feedbacks are included.

The paper presents a correlation that can potentially improve the signal obtained from ocean color remote sensing. Results come from a modeling applied to the atmosphere–ocean system in different regions of the southern Baltic, two seasons and two wind speeds, each for nine visible spectral bands. The results show that the variability of the maximum of DoP depends more on seasonal than regional changes and can be explained to a large degree by the seawater absorption-to-attenuation ratio.

Inspired by the known virtue of fish oil to still angry seas, a study has been made on the interaction between wind waves, paddle waves, and airflow in a tank containing a thin fish-oil film. It is rather peculiar that in the wind-only condition the wave field does not grow from the rest condition. This equilibrium was altered by paddle waves. We stress the benefit of experiments with surfactants to disentangle relevant mechanisms involved in the air–sea interaction.

Dissipation of ocean waves due to whitecapping is one of the most important processes that affect generation of gravity waves by wind. Different behavior of traditional approaches used for quantifying whitecapping dissipation under different wave conditions has always been a challenge to choose the most appropriate approach for a given area. The present paper examines the performance of two popular whitecapping approaches incorporated in SWAN during the winter storms along the US east coast.

Simplified 2-D numerical models are typically used for simulating the transport of floating microplastics. This paper demonstrates the impact of vertical mixing on the horizontal transport and fate of microplastics in a bay and therefore the importance of a 3-D approach for accurate modelling of microplastics transport. These results have important implications for the assessment and prediction of pollution hot spots in coastal systems as well as for planning effective clean-up programmes.

Forecasts of ocean temperature, salinity, currents, and sea height can be improved by linking state-of-the-art ocean and wave models, so that they can interact to better represent the real world. We test this approach in an ocean model of north-west Europe which can simulate small-scale details of the ocean state. The intention is to implement the system described in this study for operational use so that improved information can be provided to users of ocean forecast data.

Here we investigate the occurrence of extreme storm surges in the southern German Bight and their associated large-scale forcing mechanisms using climate model simulations covering the last 1000 years. We find that extreme storm surges are characterized by a large internal variability that masks potential links to external climate forcing or background sea level fluctuations; existing estimates of extreme sea levels based on short data records thus fail to account for their full variability.

Diel vertical migration (DVM) is a survival strategy adopted by zooplankton that was investigated in the Corsica Channel using acoustic data from April 2014 to November 2016. The principal aim of the study is to characterize migratory patterns and biomass temporal evolution along the water column. In addition, net samples were taken during summer 2015 at the same location. During the investigated period, zooplankton had a well-defined daily and seasonal cycle, with peaks in late winter.

Retreating sea ice in the Arctic Ocean gives rise to increased naval traffic with shorter navigation distances. Hence, information about the position of the sea ice edge is crucial for safe navigation. In the present study we explore methods for examining the quality of sea ice edge forecasts. We conclude that the forecast quality can be monitored with results from a set of four quantities. We also recommend the use of maps which display discrepancies in the positions of the sea ice edge.

Estuaries are areas where riverine and oceanic waters meet and mix. The exchange flow of an estuary describes the water properties of the inflowing and outflowing water. These can be described by simple bulk values for volume fluxes and salinities. This work focuses on the numerics of one computational method for these values, the Total Exchange Flow. We show that only the so-called dividing salinity method is able to reliably calculate the correct values, even for complex situations.

In this study, we assessed the impacts of the world’s largest dam, the Three Gorges Dam (TGD), on tide–river dynamics and concluded that the strongest impacts occurred during autumn and winter due to the TGD's operation. The results obtained will hopefully enhance our understanding of the impacts of large-scale human interventions on estuarine hydrodynamics and guide effective and sustainable water management in the Yangtze River estuary and other estuaries with substantial freshwater discharge.

The Mediterranean Outflow Water (MOW) is a dense water mass originated in the Gibraltar Straight. The CMEMS IBI ocean reanalysis is used to provide a detailed view of the circulation and mixing processes of MOW near the Iberian and African Continental slopes. This work emphasizes the relevance of the complex bathymetric features defining the circulation and variability processes of MOW in this region.

This work deals with the use of sea surface salinity measurements from space in the context of operational oceanography. The salinity plays an important role in the ocean–atmosphere coupling, especially when an El Niño event occurs in the tropical Pacific. However, it is still difficult to use such data in ocean models due to a large extent to large-scales biases. This study shows that from recent data with a suitable bias correction scheme, it is possible to improve our forecast skill.