The authors data assimilation method recently developed is presented and tested together with the ocean circulation model. It is shown that the method is able to assimilate data. It produces analyses closer to observations and also has several advantages in comparison with the traditional data assimilation schemes, for instance, with the Ensemble Optimal Interpolation scheme (EnOI). It provides a better forecast and requires less computational consumptions.

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.

Analyses of ocean tides are based on the separation of the tidal signal into constituents with different periodicities. We prepare a constituents list for the operational usage of a tidal prediction method called Harmonic Representation of Inequalities. A frequency analysis is applied to data from 111 tide gauges. The new list consists of 39 entries. This are four constituents less than previously used. Comparisons with observations suggest that it leads to slightly improved tidal predictions.

There is a unresolved paradox about the merging of two like-signed oceanic mesoscale eddies. Using two typical observations, we clarified that only the mass, total circulation and angular momentum are conserved, if the orbital angular momentum relative to mass center, which was previously overlooked, is taken into account as the eddies rotated around the mass center before merging. The eddy kinetical energy reduced due to fusion, but the eddy potential energy increased.

After 2007 ²³⁰Th decreased significantly in the central Amundsen Basin, this decrease is accompanied by a circulation change, indicated by changes in salinity. Ventilation of waters is most likely not the reason for the observed depletion in ²³⁰Th, atmospherically derived tracers do not reveal an increase in ventilation rate, it is suggested that these interior waters have undergone enhanced scavenging of Th during transit from the Fram Strait and the Barents Sea to the central Amundsen Basin.

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.

Nitric oxide (NO) could be produced by nitrite photolysis, the rates from dissolved nitrite in artificial seawater showed increasing trends with decreasing pH, increasing temperatures and increasing salinity. However, NO photoproduction from the natural seawater samples did not show correlations with pH, water temperature and salinity as well as dissolved nitrite concentrations in the western tropical North Pacific Ocean (WNTP). And there were other NO loss process in the surface layer of WNTP.

The North Sea became much less clear during the 20^th 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 20^th 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 20^th Century. This can explain the majority of the observed long-term decline in water clarity.

A model downscaling approach is used for investigating the effects of sea-level rise (SLR) on local tides. Results indicate that SLR induces larger increases in tidal amplitude and stronger nonlinear tidal distortion in the bay compared to the adjacent shelf sea. SLR can also change shallow-water tidal asymmetry and influence the direction and magnitude of residual sediment transport. The model downscaling approach is widely applicable for local SLR projections in estuaries and coastal bays.

Based on the closed link with ENSO and IOD, the concept of the Pacific-Indian Ocean associated mode (PIOAM) is proposed. When studying the influence of SSTA in the Pacific and Indian oceans on weather and climate, the Pacific and Indian oceans should be considered as unified. Since the PIOAM is so important, how well do current climate models simulate it? The outputs from the climate system models for the CMIP5 were used for this research, from which we aim to provide a more complete evaluation.

During 2017 Austral winter, an ice-free area surrounded by the winter sea ice called open ocean polynya appeared in the Lazarev Sea, Antarctica. A layer between 80–180 m depth storage energy from summer months characterizing the vertical structure of the water column. Mixing processes drives the exchange of energy in the water column. This exchange of energy contribute to the open-ocean polynya preconditioning.

Ocean forecasting systems predict ocean water level, but the accuracy of predictions varies as a function of the forecast lead time and the dynamics causing water level variability. This study investigates the accuracy of predictions of tidal water levels in the AMSEAS forecast system, with emphasis on the small (roughly 5 cm) fluctuations associated with the baroclinic tide. To be useful, data from future satellites will require accurate forecasts; their accuracy is quantified in this study.

A new methodology, named as IBR, is developed to estimate the response of the coastal ocean to meteorological forcing. The response is taken as the combination of the static response calculated using inverted barometer formula and the dynamic response estimated using multivariable linear regression. The analysed results in the Bohai Bay indicate that the adjusted sea levels are related more to the regional wind than to the local wind and the IBR is a feasible and relatively effective method.

Convection deeper than 1,300 m persisted in the Irminger Sea during four consecutive winters (2015–2018). The 2015 deep convection was favored by exceptional atmospheric forcing. The 2016–2018 deep convection, which occurred under averaged atmospheric forcing, was favored by the preconditioning of the water column thanks to the cooling of the layer 200–800 m and the freshening of the layer 1,200 m–1,400 m.

This work investigates the seasonal variations in the major tidal constituents in the Bohai Bay. The M₂ tidal amplitude and phase reach maximum in summer and minimum in winter, while the frequencies of the S₂ and K₁ tidal amplitudes and phases and the O₁ tidal phase are semi-annual. The results of numerical experiments indicate that the seasonality of stratification and vertical eddy viscosity coefficient induce seasonal variations in the major tidal phases and amplitudes, respectively.

Using simulated "signal" of Sea Surface Height Anomalies (SSHA) where the phase speed of the dominant mode is known a-priory, 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.

Diatoms are a group of phytoplankton species responsible for ~20% 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. Here we synthesize OA experiments with natural communities and found: Diatoms are more likely to be positively than negatively affected by OA but there will be winners/losers within communities. This has important implications for the ecosystem services they provide

The FluxEngine is an open source software toolbox designed to allow the easy calculation of air-sea gas fluxes. This manuscript 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 order to provide an aid for the interpretation of observations of the formation, the structure and the dynamics of submesoscale patterns, a numerical model is applied in a double-offline nested setup to a subarea of the Baltic Sea. A model with 500-m horizontal resolution is nested into an existing operational model in order to create a realistic mesoscale environment. Turbulent patterns with horizontal scales < 1 km are resolved by a second nest with 100-m resolution.

This work presents high-resolution simulations of a coupled regional model in the Mediterranean basin. The used approach allows assessing the role of ocean feedbacks in the downscaled climate. Our results show good skills in simulating present climate; the model's robustness introduces improvements in reproducing physical processes at local scales. Our climate projections reveal that by the end of the 21st century the Mediterranean Sea will be warmer and saltier, although not in a homogeneous way.

The Galápagos Archipelago and Marine Reserve is among the world's most iconic wildlife refuges. Yet, plastic litter is now found even in this remote island archipelago. It is unclear where this plastic originates from. In this study, we show that remote coastal sources of plastic pollution are fairly localized and limited to South and Central American coastlines. Identifying how plastic ends up in the Galápagos aids integrated management opportunities to reduce plastic pollution.

The work presented is part of a bigger wave energy 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.

This study presents a detailed spatial structure and temporal variability of the deep circulation under enhanced mixing in the South China Sea (SCS) based on eddy-resolving model simulations verified by continuous current-meter observations and enables us to investigate sensitivity to distribution of mixing. Comparing the northern shelf of the SCS with the Luzon Strait, deep circulation in the SCS is more sensitive to the large vertical mixing parameters in the Zhongsha Island Chain area.

This work investigates the variabilities of the barrier layer thickness (BLT) in the tropical Indian Ocean with the Simple Ocean Data Assimilation version 3 ocean reanalysis data. Our results show that the seasonal variation of the BLT is in relation to the changes of thermocline and sea surface salinity. In terms of the interannual time scale, BLT presents a clear seasonal phase-locking dominated by different drivers during the Indian Dipole and El Niño South Oscillation events.