This study targets high-resolution, diatom-specific sedimentary ancient DNA using a DNA metabarcoding approach. Diatom DNA has been preserved with substantial taxonomic richness in the eastern Fram Strait over the past 30 000 years with taxonomic composition being dominated by cold-water and sea-ice-associated diatoms. Taxonomic reorganisations took place after the Last Glacial Maximum and after the Younger Dryas. Peak proportions of pennate diatoms might indicate past sea-ice presence.

Currents are high-speed continuous ocean flows. In general, currents accelerate surface waves. However, studies are performed at normal wind speeds only, with few studies at extremely high wind speeds. We investigate the effects of current on surface waves at extremely high wind speeds and use three wind-wave tanks to demonstrate surface waves and currents. As a result, at extremely high wind speeds, a similar acceleration effect is observed as under the conditions of normal wind speeds.

Extreme water levels are often created by several drivers with different properties. For example, the contribution from the water volume of the Baltic Sea follows a Gaussian distribution, but storm surges represent a Poisson process. We show that wave set-up heights (the third major component of high water levels) usually follow an exponential distribution and thus also represent a Poisson process. However, at some locations set-up heights better match an inverse Gaussian (Wald) distribution.

AMOC variability controls climate and is driven by wind and buoyancy forcing in the Atlantic. Density changes there are expected to connect to tropical regions. We develop methods to identify boundary density profiles at 26° N which relate to the AMOC. We found that density anomalies propagate equatorward along the western boundary, eastward along the Equator and then poleward up the eastern boundary with 2 years lag between boundaries. Record lengths of more than 26 years are required.

Ekman's (1905) solution for how wind affects ocean surface currents is revisited and extended analytically for a piecewise-constant profile of vertical diffusion. This allows a comprehensive understanding of how the surface current deflection angle relative to the wind direction varies with the profile of vertical diffusion.

Based on a well-validated ocean circulation model, we found that near-inertial oscillations (NIOs) and near-inertial kinetic energy (KEni) varied distinctly during forcing and relaxation stages of tropical cyclone (TC) forcing, and the horizontal and vertical transport of KEni was largely modulated by the velocity and vorticity of the jet in the semi-enclosed South China Sea (SCS). This study enriches our understanding of the spatial–temporal variability of NIOs in the frequently TC-affected SCS.

On ice-affected coasts, obtaining year-long sea level records for traditional tidal predictions is difficult. We evaluate the complete tidal species modulation with tidal constant corrections (CTSM+TCC) method for predicting tides at the "mixed, mainly diurnal" Jang Bogo Antarctic Research Station in the Ross Sea, Antarctica, using short in situ records plus longer records from the nearby "diurnal" Cape Roberts. The method succeeded in using data from periods with above-average tidal ranges.

A kilometre-scale coupled ocean–atmosphere simulation is used to study the impact of a medicane on the oceanic upper layer. The processes responsible for the surface cooling are comparable to those of weak tropical cyclones. The oceanic response is influenced by the dynamics of the central Mediterranean. In particular, a cyclonic eddy leads to weaker cooling. Heavy rain occuring early in the event creates a salinity barrier layer, reinforcing the effects of the surface fluxes on the cooling.

Very little is currently known about the activities and emissions of private leisure boats. To change this, a new model was created (BEAM). The model was used for the Baltic Sea to estimate leisure boat emissions, also considering antifouling paint leach. When compared to commercial shipping, the modeled leisure boat emissions were seen to be surprisingly large for some pollutant species, and these emissions were heavily concentrated on coastal inhabited areas during summer and early autumn.

This study provides for the first time estimates of sea level anomalies very close to the coastline based on high-resolution retracked altimetry data, as well as corresponding sea level trends, over a 14-year time span. This new information has so far not been provided by standard altimetry data.

Global inorganic and organic nutrient deposition fields are coupled to PISCES to investigate their effect on ocean biogeochemistry. Pre-industrial deposition fluxes are lower compared to the present day, resulting in lower oceanic productivity. Future changes result in a modest decrease in the nutrients put into the global ocean. This work provides a first assessment of the atmospheric organic nutrients' contribution, highlighting the importance of their representation in biogeochemistry models.

The dynamical balance of the Antarctic Circumpolar Current and its implications on the functioning of the world ocean are not fully understood and poorly represented in global circulation models. In this study, the sensitivities of an idealized Southern Ocean (SO) storm track are explored with a set of eddy-rich numerical simulations. We show that the classical partition between barotropic and baroclinic modes is sensitive to current–topography interactions in the mesoscale range of 10–100 km.

The high-resolution ocean models ROMS and FESOM configured for the Fram Strait reveal very energetic ocean conditions there. The two main currents meander strongly and shed circular currents of water, called eddies. Our analysis shows that this region is characterised by small and short-lived eddies (on average around a 5 km radius and 10 d lifetime). Both models agree on eddy properties and show similar patterns of baroclinic and barotropic instability of the West Spitsbergen Current.

This article accounted for the change in sediment supply in the central Yellow Sea since the last deglaciation. Sediment sources were distinguished based on the integration of clay mineralogical and geochemical data such as trace elements and Sr and Nd isotopes. The core 11YS-PCL14 was divided into four units and showed clear vertical variations according to sediment supply and sea level change.

Diel vertical migration (DVM) of zooplankton is the largest nonhuman migration on the Earth. DVM in the eastern Beaufort Sea was assessed using a 2-year-long time series of currents and acoustic signal from a bottom-anchored oceanographic mooring. Our results show that DVM is deviated by the (i) seasonal and interannual variability in sea ice and (ii) wind-driven water dynamics. We also observed the midnight-sun DVM during summer 2004, a signal masked by suspended particles in summer 2005.

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 timescale, BLT presents a clear seasonal phase locking dominated by different drivers during the Indian Dipole and El Niño–Southern Oscillation events.

Data assimilation is the most comprehensive strategy to estimate the biogeochemical state of the ocean. Here, surface Chl a data are daily assimilated into a 24-member NEMO–PISCES ensemble configuration to implement a complete 4D assimilation system. Results show the assimilation increases the skills of the ensemble, though a regional diagnosis suggests that the description of model and observation uncertainties needs to be refined according to the biogeochemical characteristics of each region.

A large percentage of global ocean plastic enters the Indian Ocean through rivers, but the fate of these plastics is generally unknown. In this paper, we use computer simulations to show that floating plastics beach and end up on coastlines throughout the Indian Ocean. Coastlines where a lot of plastic enters the ocean are heavily affected by beaching plastic, but plastics can also beach far from the source on remote islands and countries that contribute little plastic pollution of their own.