We assess storm surges in the Baltic Sea and how they are represented in a regional climate model. We show how well different model formulations agree with each other and how this model uncertainty relates to observational uncertainty. With an ensemble of model solutions that represent today's climate, we show that this uncertainty is of the same size as the observational uncertainty. The second part of this study compares climate uncertainty with scenario uncertainty and natural variability.

We use a model of the Caribbean Sea to study how coastal upwelling along Venezuela impacts the evolution of energetic anticyclonic eddies. We show that the anticyclones grow by the advection of the cold upwelling filaments. These filaments increase the density gradient and vertical shear of the anticyclones. Furthermore, we show that stronger upwelling results in stronger eddies, while model simulations with weaker upwelling contain weaker eddies.

Internal tides are subsurface waves generated by tidal flows over ocean ridges. When they break they create turbulence that drives an upward flux of nutrients from the deep ocean to the nutrient-poor photic zone. Measuring internal tides is problematic because oceanographic moorings are often fished-out by commercial trawlers. We show that autonomous ocean gliders and acoustic Doppler current profilers can be used together to accurately measure the amount of energy carried by internal tides.

The main goals are to study the performance of gridded SST datasets in coastal waters by comparing to homogenized in situ SST records. In recognizing that local data may reflect local effects, we focus on the dominant EOFs of the in situ SSTs and localized gridded datasets, examining patterns, variabilities, and trends. We conclude that gridded datasets need improvement in the pre-satellite era by reexamining in detail archives of local SST records in many data-sparse regions.

In this paper we present wave buoy measurements from the Finnish archipelago. The properties of the waves inside the archipelago differed from waves in the open sea because of the sheltering effect of the islands. In the archipelago the highest single wave was, on average, only 1.58 times the significant wave height, which is lower than what is predicted by previous research. A more robust way to calculate the wave frequency in the complex archipelago conditions was proposed.

As part of the Copernicus Marine Environment Monitoring Service, an operational ocean forecasting system monitors the ocean dynamics and marine ecosystems of the European waters. This paper assesses the performance of the key biogeochemical variables (oxygen, nutrients, Chl a, primary production) using a 7-year pre-operational qualification simulation (2010–2016). The simulation can be used to better understand the current state, the changes and the health of European marine ecosystems.

The work presented is part of the SWERM project on Swedish wave energy resource mapping. The project aims to generate and combine different layers of information for the Swedish Exclusive Economic Zone in order to identify the most suitable areas for wave energy conversion. This paper presents the results for the mean sea level variation layer. For the case study considered, the most suitable sites where to deploy WEC parks are found in the Gotland basins and in the Bothnian Sea.

The Persian Gulf Water and Red Sea Water are salty and dense waters recirculating in the Gulf of Oman and the Gulf of Aden, in the form of small features. We study the life cycle of intense and small vortices and their impact on the spread of Persian Gulf Water and Red Sea Water by using idealized numerical simulations. Small vortices are generated along the continental slopes, drift away, merge and form larger vortices. They can travel across the domain and participate in the tracer diffusion.

The unresolved paradox about the merging of two anticyclonic mesoscale eddies is studied. While the conservation laws of mass and total circulation were satisfied, the conservation of AM required inclusion of the orbital AM. Both the conservation of circulation and the orbital AM were overlooked in previous theoretical studies. The eddy kinetic energy decreased due to fusion, but the eddy potential energy increased. This behaves like a large-scale energy pump in inverse energy cascades.

In this work, 25 years of daily satellite data on absolute dynamic topography (ADT) show that before 2002 Caribbean Water (CW) was less intrusive inside the Gulf of Mexico (GoM). Our results suggests that from 2003 onward, larger volumes of oligotrophic waters from the Caribbean Sea have invaded the western GoM and reduced mean surface Chl a concentrations. A direct comparison between the 1998–2002 and 2009–2014 periods indicates that the Chl a concentration has decreased significantly.

This research considers the physical environmental factors that underpin changes in ocean productivity over the shelf of South Africa, where coastal upwelling occurs next to a warm current. Statistical analysis of model assimilated data show that salinity and wind play prominent roles in changes of chlorophyll content, with possible consequences for the coastal fishery.

Using simulated signal of sea surface height anomalies (SSHA) where the phase speed of the dominant mode is known a priori, we demonstrate that four of the common methods employed in estimating the propagation speed of SSHA do not identify the correct input mode. This finding explains the lack of progress made in recent years in bridging the gap between the "too fast" Rossby wave phase speed observations by satellites and the phase speed in the highly accurate linear trapped wave theory.

This study is an attempt to validate the quality of a global temperature and salinity dataset by estimating the effects of measurement errors on the estimated ocean variability. The study shows that the effects of the measurement errors decrease during the quality control process and are almost null for the delayed-time-mode quality-controlled dataset.

The North Sea became much less clear during the 20th century, with potential consequences for primary production. This study analyses the hypothesis that changes in wave regime were a key driver of this change. We hindcast bed shear stress over the 20th century using a long-term wave reanalysis. Shear stress increased by over 20 % in large parts of the southern and central North Sea during the 20th century. An increase of this magnitude would have caused a large decline in water clarity.

Observations of ocean currents within the first meter of the surface are made using a large number of ocean drifters of two different draft depths (0–5 and 0–60 cm). We deconstruct the total drifter velocities using an estimate of the regional circulation and a modeled Stokes drift velocity to calculate the purely wind-driven component of each drifter type. We reveal that the wind-driven velocities rotate to the right of the wind, while also decreasing, with depth.

Data from three campaigns were combined to look at the enrichment of gel particles, which act as a large source of organic matter transport, in the sea surface microlayer. Additionally, depth profiles showed that the vertical distribution in the upper 2 m of the ocean can be both homogeneously and heterogeneously mixed. This highlights the importance of depth for measurements when studying enrichment and the complexity of the near-surface environment.

In December 2002 and January 2003 satellite observations of chlorophyll showed a wavelike pattern with a wavelength of about 750 km south-west of the Cape Verde Peninsula. Such a pattern suggests the existence of a locally generated Rossby wave which slowly propagated westward. To verify this hypothesis a numerical study based on a simple model has been conducted. The numerical results are completed by an analytical study which evaluates the potential impact of the coastline shape.

Spiral streaks or spirals are a common feature on satellite images of the sea surface. Spirals are overwhelmingly cyclonic: they wind anticlockwise in the Northern Hemisphere. Based on a regional circulation model with very high resolution we concluded that submesoscale cyclonic eddies differ from anticyclonic eddies in three ways favoring the formation of spirals: they can be characterized by (a) higher angular velocity, (b) more pronounced differential rotation and (c) negative helicity.

FluxEngine is an open-source software toolbox designed to allow for the easy and accurate calculation of air–sea gas fluxes. This article describes new functionality and capabilities, which include the ability to calculate fluxes for nitrous oxide and methane, optimisation for running FluxEngine on a stand-alone desktop computer, and extensive new features to support the in situ measurement community. Four research case studies are used to demonstrate these new features.

In this study we investigated the variability of the Arctic Front (AF), an important biologically productive region in the Norwegian Sea, using a suite of satellite data, atmospheric reanalysis and a regional coupled ocean–sea ice data assimilation system. We show evidence of the two-way interaction between the atmosphere and the ocean at the AF. The North Atlantic Oscillation is found to influence the strength of the AF and may have a profound influence on the region's biological productivity.

Deep-sea connectivity research is scarce but needed for understanding marine population dynamics and dispersal of animal early-life stages. Here, we modeled near-bottom particle drifts along a continental margin crossed by submarine canyons. The bottom current impacting particle drifts is influenced by uneven topographic structures like submarine canyons. Thus, models with a good representation of the bottom geomorphological structures contribute to improving the deep-sea larval drift modeling.

This study is dedicated to tidally induced dynamics in the Sylt-Rømø Bight with a focus on the non-linear component. The tidal residual circulation and asymmetric tidal cycles largely define the circulation pattern, transport and accumulation of sediment, and the distribution of bedforms. The newly obtained high-quality bathymetric data supported the use of high-resolution grids (up to 2 m in the intertidal zone) and elaboration of the details of tidal energy transformation in the domain.

We measured the transfer of 12 gases between air and sea at very high wind speeds in two different wind-wave tank labs with fresh water, simulated seawater and seawater. We separated the transfer across the water surface from the transfer through the surface of bubbles. At high winds, the transfer through the free water surface increases very strongly and bubbles become important but only for gases which are very weakly soluble in water. On the ocean, bubbles might be important at lower winds.

We present a first direct comparison of nonidentical versus identical twin approaches for an ocean data assimilation system. We show that the identical twin approach overestimates the value of assimilating satellite observations and undervalues the benefit of assimilating temperature and salinity profiles. Misleading assessments such as undervaluing the impact of observational assets are problematic and can lead to misguided decisions on balancing investments among different observing assets.