Recent  

Ocean and atmosphere dynamics redistribute heat and freshwater, which drives regional sea level changes. This study reports on the east-to-west propagation of sea level anomalies in the subpolar North Atlantic, mainly associated with advection by the mean flow – an important component of the leading mode of interannual sea level variability in the region. This variability mainly results from oceanic advection and air-sea heat fluxes, whose relative contributions are space- and time-dependent.

More and more studies indicate that the Open Ocean can be a significant source of methane, the second greenhouse gas after CO₂. Our study in the North subtropical Atlantic Ocean shows that a significant part of the methane flux to the atmosphere is related to cyanobacteria, a ubiquitous phytoplankton, that produce methane as part of their metabolic activity. This study is a response to the lack of data on the role of the oceans on the methane budget in the context of the climate change.

The south-eastern Bay of Biscay is an accumulation zone for marine litter. Yet, the transport and fate of riverine litter in the coastal area is poorly understood. We resolve this by studying litter buoyancy and transport, based on high-frequency radar observations and Lagrangian simulations. We show large seasonal and regional differences between items behaviour, particularly in summer when highly buoyant litter beach faster, and Gipuzkoa and Pyrénées-Atlantiques regions are mostly affected.

Three deep water masses pass the southern exit of the Labrador Sea. Usually they are defined by explicit density intervals linked to the formation region. We evaluate this relation in an ocean model by backtracking the paths the water follows for 40 years. 48 % densify without contact to the atmosphere. 24 % densify in contact with the atmosphere and 19 % come from the Nordic Seas. All three contribute to a similar density interval with very weak specific formation location characteristics.

In the Western Tropical South Atlantic, coastward currents spread oceanic cnidarians over the continental shelf. While both costal and oceanic communities co-occur in scenarios of higher runoff and weaker boundary current intensity, oceanic species dominate almost the entire shelf during the dry season characterized by stronger currents. Meanwhile, offshore, when the mixed-layer, the enhanced primary productivity supports larger populations of planktonic cnidarians.

Surface flow fields of the global oceans are dominated by so called mesoscale (50–300 km) eddies. They drift usually westward with a speed of a few km/day, transport mass, temperature, chlorophyll, debris, etc. Several methods are developed to identify and track eddies based on satellite measurements, some of them is computationally very demanding. Here we extend to global scale a recently proposed simple procedure which gives a quick coarse-grained statistics of mesoscale vortex properties.

River engineering measures strongly changed tidal dynamics in the Weser estuary. We studied the effect on saltwater intrusion with numerical models. Our analysis shows that a deepening of the navigation channel causes saltwater to intrude further into the Weser estuary. This effect is mostly outweighed by the natural variability of river discharge. In the study, it proved essential to recalibrate individual hindcast models due to different resolutions of underlying bathymetrical data.

Seasonal variability of the M₂ ocean tide can be detected at many ports. The physical mechanisms underlying seasonality, in broadest terms, are astronomical, frictional/advective interactions, and climate processes. Some of these induce annual modulations, some semiannual, in amplitude, phase, or both. This note reviews how this occurs and gives an example from each broad category. Phase conventions and their relationship to causal mechanisms, as well as nomenclature, are also addressed.

We use machine learning to analyze the long-term variation of the surface currents in the Eastern Mediterranean, precisely in the Levantine Sea. We decompose the circulation into groups based on their physical characteristics, then analyze their spatial and temporal variability. We show that most structures of the Levantine Sea are becoming more energetic with time, even though those of the western part remain the most dominant due to the complex bathymetry and the strong currents.

The hydrological evolution of deep water carried within the lower limb of the Atlantic Meridional Overturning Circulation (AMOC) is analysed from a combination of ship-based and Deep-Argo data gathered between 2015 and 2018. In our study, we show that its evolution through a main fracture zone of the Reykjanes Ridge have a large impact on the lower limb of the AMOC in compensating fresh inputs of dense water from the interior of the Irminger Sea.

Quantifying the spatial-temporal water level dynamics is essential for water resources management in estuaries. In this study, we propose a simple yet powerful regression model to examine the influence of the world’s largest dam, the Three Gorges Dam (TGD), on the spatial-temporal water level dynamics within the Yangtze River estuary. The presented method is particularly useful for determining scientific strategies for sustainable water resources management in dam-controlled estuaries worldwide.

In a context of climate change, having sea level data all along the coast is essential. However, tide gauges yield pointwise observations and satellite altimetry has limitations at the coast. We present a method that, learning from a several-years model output and using tide gauge observations only, is able to reconstruct sea level all along the coast. The accuracy of the reconstruction has been validated against independent observations and proved to be better than that of satellite altimetry.

Observations of the eastern subpolar North Atlantic in the 2010s show exceptional freshening and cooling of the upper ocean, peaking in 2016 with the lowest salinities recorded for 120 years. Using output from a high-resolution hindcast model simulation, we propose that the primary cause is reduced surface cooling in the Labrador Sea, leading to increased outflow of relatively fresh and cold water in the upper ocean and so to freshening and cooling of the eastern subpolar North Atlantic.

Two-year mooring observations show the evolution of temperature, salinity, and currents in the northern Barents Sea. Inflow of Atlantic Water from the north in autumn/winter was the main driver of the seasonal cycle in the ocean. Winds modulated the inflow on shorter timescales. The upper ocean state reflected how much sea ice had previously melted in the area. The import of ocean water and sea ice from adjacent regions play a key role in the complex air-ice-ocean interplay.

This study explores the variability of water mass transformation within the Weddell Gyre (WG). The WG is the largest source of Antarctic Bottom Water (AABW). Changes to our climate can modify the mechanisms that transform waters to become AABW. In this study, we computed water mass transformation volume budgets by using three ocean models and a mathematical framework developed by Walin. Out of the three models, we found one to be most useful in studying the interannual variability of AABW.

The circulation patterns of surface water over the northern Gulf of Cadiz are described based on hourly High Frequency Radar data from 2016 to 2020. It is revealed the presence of a persistent current that follows the continental shelf slope eastward while near the coast, currents generally have balanced (eastward-westward) direction. In summer cross-shelf transport is promoted when westward coastal counter currents recirculate offshore at the western region and merge with the slope current.

Tides affect the marine carbonate chemistry within a coastal polynya neighbouring the Ekström Ice Shelf by movement of seawater with different CO₂ content. The result is that the coastal polynya in the summer can cycle between being a sink and a source of CO₂ several times a day. We encourage consideration of tides when collecting measurements in polar coastal regions to account for variability and to avoid over- or underestimations of CO₂ exchange between the atmosphere and ocean.

The sea ice bridge usually forms during winter in Nares Strait and prevents ice to drift south. However, this bridge has recently become unstable, and in this study we investigate the role of oceanic heat flux in this decline. Using satellite data, we identify areas where sea ice is relatively thin and further attribute those areas to the heat fluxes from the warm subsurface water masses. We also discuss the potential role of such impact on the ice bridge instability and the earlier break up.