The SLA data from Jason-2 have been reprocessed and extended towards the coast of the Red Sea. The new extended data at the coast are more consistent with the CTD-derived geostrophic currents (GCs). The GCs in summer flow southward over the Red Sea except along the east coast. In winter, the flow is northward for the entire Red Sea except for a small southward flow near the central coast. This flow is modified by the presence of cyclonic and anticyclonic eddies.

We revisit the sources for the upper limb of the overturning circulation in the South Atlantic by tracking fluid particles in a high-resolution ocean model. Our results suggest that the upper limb’s transport is dominantly supplied by waters with Indian Ocean origin, but the contribution of waters with Pacific origin is substantially larger than previously estimated with coarse-resolution models. Yet, a large part of upper limb waters obtains thermohaline properties within the South Atlantic.

This modelling study aimed to recreate the Agulhas Current transport proxy within a regional HYCOM simulation of the Agulhas Current system, attempting to test the validity of the underlying assumptions on which the satellite-altimeter proxy was based. Results showed that the proxy is sensitive to subsurface variability in the model but that the proxy remained robust regarding the time periods needed to build a sufficient linear relationship between transport and sea surface height slope.

Decadal variability in Caspian Sea water properties (temperature, salinity, density) is investigated using a numerical modeling approach. The paper illustrates the sea response to global climate change, including abrupt surface-level variations and the strengthening of water stratification. Water exchange between the three Caspian basins (northern, middle and southern) is demonstrated to play an important role in the formation of the sea 3-D circulation.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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).