Ocean mixing in the Arctic Ocean cools and freshens the Atlantic and Pacific-origin waters by mixing them with surrounding waters, which has major implications on global scale as the Arctic Ocean is a main sink for heat and salt. We investigate the drivers of ocean mixing north of Svalbard, in the Atlantic sector of the Arctic, based on observations collected during two research cruises in summer and fall 2018 as part of the Nansen Legacy project.

Changes in ocean temperature may affect vertical density stratification, which may hamper turbulent exchange and thus nutrient availability for phytoplankton growth. To quantify varying physical conditions, we sampled the upper 500 m along 17 ± 5° W between [30, 62]° N in summer. From south to north, temperature decreased with stratification while turbulence and nutrient fluxes remained constant, likely due to internal waves breaking and little affected by the physical process of global warming.

A Seaglider was deployed for 8 months in the Norwegian Sea mounting an oxygen and for the first time a CO₂ optode and a chlorophyll fluorescence sensor. The oxygen and CO₂ data were used to assess the spatial and temporal variability and calculate the net community production, N(O₂) and N(C_T). The dataset was used to calculate net community production from inventory changes, air-sea flux, and entrainment.

We conducted an underway measurement of O₂/Ar using membrane inlet mass spectrometry and estimated net community production (NCP) in the South China Sea (SCS) in both summer and autumn. We found that nutrient, especially nitrogen, is the dominant factor affecting primary production in the SCS. In the summer survey, we observed the rapid response of the ecosystem to the episodic nutrient supply induced by eddies. This is the first report on NCP estimation based on O₂/Ar data in the SCS.

As we warm our planet, oceans expand, ice on land melts and sea levels are rising. On century time scales, we find that sea level response to warming can be characterized by a single metric: the transient sea level sensitivity. Historical sea level exhibits substantially higher sensitivity than model-based estimates such as those analysed in authoritative climate assessments. This implies that recent projections could well underestimate the likely sea level rise by the end of this century.

The Maud Rise Polynya is a hole in the sea-ice surrounding Antarctica that occurs during winter. It appeared in the 1970s and in 2016 and 2017. Our study concludes that heat and salt accumulation around 1000 m depth are likely to be important for polynya formation. The heat is mixed upward to the surface where it is able to melt the sea-ice and thereby creating a polynya. How often the polynya forms, depends largely on the variation in time of the heat and salt accumulation.

Acoustic and satellite observations of ship wakes show that ships can mix the water column down to 30 m depth, and that a temperature signature of the wake can last for tens of km. The temporal and spatial scales of the wake imply that intensive ship traffic have the potential to affect the natural exchange of nutrient and gases in the surface layer of the ocean. Thus, ship-induced mixing should be considered when estimating environmental impact from shipping in areas with intense ship traffic.

We systematically estimated the vertical displacement of thermocline affected by mesoscale eddies using global, 17-year spanning Argo dataset in combination with satellite altimetry. Thermocline is deeper in anticyclones, shallower in cyclones. Eddies induce the largest thermocline displacement in spring especially along strong western boundaries. This displacement is linearly correlated with eddy radius and amplitude. And the effect of eddies with opposite polarity on thermocline is asymmetric.

In this paper, we applied FVCOM to perform the numerical simulation of salinity in Liao River estuary waters, with consideration of effects of river discharge cutoff and shoreline variation. Decrease in runoff was demonstrated to significantly increase the mean salinity values of the estuary. The shoreline change caused by the port construction was observed to have an obvious influence on salinity distribution patterns, with the mean salinity value increased in wetland waters near the port.

Dense waters sinking by Antarctica and in the North Atlantic control global ocean currents and carbon storage. We need to know how these change with climate change, so we need accurate climate models. Here we show that dense water sinking in the latest models is better than in the previous ones, but there still is too much water sinking, too deep, too often. This impacts how well models represent the deep ocean density and the deep currents, globally. We also suggest ways to improve the models.

Mesoscale datasets are used to study coastal gradients in the marine climate and oceanography south of Cape Town. Building on past work, satellite and ocean/atmosphere reanalysis are used to gain new insights on the mean structure, circulation and meteorological features. HYCOM v3 hindcasts represent a coastward reduction of mixing that enhances stratification and productivity in False Bay during summer.

The role of plankton communities in important environmental issues is an active research question. Large amounts of plankton images collected using modern devices call for automated analysis methods. We consider classification of phytoplanktons using compact convolutional neural networks allowing fast model training. We analyse the confused classes and their practical implications to aquatic research. We show that good accuracy can be obtained with a limited amount of unbalanced training data.

The rate of change in the marine environment along the south coast of South Africa (32–37 S, 20–30 E) is studied using reanalysis observations 1900-2015 and coupled ensemble model projections 1980–2100. Although sea surface temperatures off-shore are warming rapidly, a trend toward easterly winds and stronger shelf-edge currents have intensified near-shore upwelling (-.03 °C/yr) and contribute to a drier climate.

Ash from the Calbuco 2015 eruption spread across northern Patagonia, the SE Pacific and SW Atlantic Oceans. In the Pacific, a phytoplankton bloom corresponded closely to the volcanic ash plume, suggesting that ash fertilized this region of the ocean. No such fertilization was found in the Atlantic where nutrients plaussibly supplied by ash were likely already in excess of phytoplankton demand. In Patagonia, the May bloom was more intense than usual, but the mechanistic link to ash less clear.

Coastal trapped waves (CTWs) are very long shallow water waves that propagate along the continental shelves of most major ocean basins. Their general properties are known but can be easily modified by changes in the coastline or other factors through a process known as scattering. Scattering is not well understood but can cause high surface velocities. For the first time, we directly observe CTW scattering using a simple mathematical technique that can be easily applied to other coastlines.

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

The Atlantic Meridional Overturning Circulation (AMOC) is an important component of the climate system. Understanding its structure and variability is a key priority for many scientists. Here, we present the first estimate of AMOC variations for the tropical South Atlantic – from the TRACOS array at 11° S. Over the observed period, the AMOC is dominated by seasonal variability. We investigate the respective mechanisms with an ocean model and find different wind-forced waves to play a big role.

Internal tides can have a signature of several cm at the ocean surface and need to be corrected from altimeter measurements. This paper presents a detailed validation of several internal tides models using existing satellite altimeter databases. The analysis focuses on the main diurnal and semi-diurnal tidal constituents. Results show the interest of the methodology proposed, the quality of the internal tide models tested and their positive contribution for estimating an accurate sea level.

Diel vertical migration (DVM) of zooplankton is the largest non-human migration on the Earth. DVM in the eastern Beaufort Sea was assessed using a two-year-long time series of currents and acoustic signal from the bottom-anchored oceanographic mooring. Our results show that DVM is deviated by the (i) seasonal and inter-annual 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.

The ocean is a turbulent system, full of meandering currents and fronts of various scales. These processes can influence the distribution of microscopic algae or phytoplankton by upwelling deep, nutrient-rich waters to the sunlit surface or by actively gathering and accumulating them. Our results suggest that at surface, salinity is the main conditioning factor for phytoplankton distribution. However, at the subsurface, oceanic currents influence the phytoplankton distribution the most.

We investigated the long-term changes of the principal tidal component M₂ over the North Atlantic coasts, from 1846 to 2018. We analysed 9 tide gauges. We found that M₂ variations are consistent at all the stations in the North East Atlantic, whereas some discrepancies appear in the North West Atlantic. The similarity between the North Atlantic Oscillation and M₂ variations in the North East Atlantic suggests a possible influence of the large-scale atmospheric circulation on the tide.

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.

The coastal East China Sea (ECS) is a highly productive system characterized of multiple spatial and temporal scale, in which physical, biogeochemical and ecological processes strongly interact. A coupled model system was implemented to a high resolution coastal ECS. The model was capable to reproduce main temporal and spatial features for phytoplankton and nutrients. This work could form a significant basis for future work, e.g. the response of biogeochemical flux to physical mechanism.

From the global escape of light gases (H, ammonia, water vapour) to space, the global water loss could not be estimated. Therefore the ancient and recent sea levels and volumes were used to estimate the disappearance of water from the Earth. Earlier high sea levels with decreasing fluctuations indicate water loss long before man existed. Highest sea level was referred to as the Infant Sea with an estimated volume that could have been by 26 % more voluminous than it is today.