This study analyses physical and biogeochemical data collected in the East Australian Current (EAC) to understand variability in the nutrient-poor surface waters. The distribution of nutrients in the water column is influenced by seasonal flow and the EAC's position. An inshore EAC has a deeper nutricline and lower nutrient concentrations compared to an offshore EAC position. This has implications for the marine ecosystems along the coastline.

Ocean circulations include small-scale processes like transport through sub-mesoscale eddies and turbulence by internal wave breaking. Knowledge is lacking on the interaction between the different processes. In deep, weakly stratified waters, continuous spectral slopes are observed that extend from sub-mesoscales across the internal wave band to the turbulence range. Such correspondence is suggested as being a potential feedback mechanism stabilizing large-scale ocean circulations.

Water isotopes in the ocean trace the freshwater exchanges between the ocean, the atmosphere, and the cryosphere and are used to investigate processes of the hydrological cycle. We illustrate offsets in seawater isotopic composition between different datasets that are larger than the expected variability that one often wants to explore. This highlights the need to share seawater isotopic composition samples dedicated to specific intercomparison of data produced in different laboratories.

The East Siberian Sea has nearly 80 % of the subsea permafrost worldwide. The cold layer with a temperature around −1.5 ºC above the seafloor prevents heat transporting from above to melt permafrost and release methane from sediments. However, we observed a warming trend at the seafloor caused by wave-induced vertical mixing in the shelf. The intensified mixing can transport enormous heat downward, leading to warming of more than 3 °C at the bottom, putting the subsea permafrost at high risk.

Climate change impacts the ocean carbon cycle, demanding methods to monitor ocean carbon uptake. We developed a machine learning tool applied to a global ocean biogeochemistry model to identify and track marine carbon biomes both seasonally and from 1958 to 2018. Distinct carbon biomes with varied ocean dynamics were detected. Changes in biome coverage revealed responses to seasonal and long-term shifts, offering insights into the impacts of climate change.

Seemingly interconnected beaches are often separated by human-made obstacles and natural divergence areas of sediment flux. We decompose the sedimentary shores of the Gulf of Riga into five naturally almost isolated compartments based on the analysis of wave-driven sediment flux. The western, southern, and eastern shores have quite different and fragmented sediment transport regimes. The transport rates along different shore segments show extensive interannual variations but no explicit trends.

Submarine canyons are topographic features found along the continental slope worldwide. Here we use numerical simulations to study how a submarine canyon influences the circulation near the coast when winds moving poleward influence the region. Our results show that submarine canyons modify the circulation near the coast, causing strong velocities perpendicular to the coast. These changes can trap particles inside the canyon, an important mechanism to explain its role as a biological hotspot.

The west African coastal region sustains highly productive fisheries and marine ecosystems influenced by sea surface temperature. We use oceanic models to show that the freshwater input from land to ocean strengthens a surface northward (southward) coastal current north (south) of the Congo River mouth, promoting a transfer of cooler (warmer) waters to north (south) of the Congo discharge location. We highlight the significant impact of river discharge on ocean temperatures and circulation.

This study provides the first assessment of decadal changes in the whole phytoplankton community, addressed by flow cytometry, in the highly productive waters of the Strait of Dover. A significant surface seawater temperature increase of 1°C, associated with an important change in the nutrient concentration and balance, has triggered a change in the phytoplankton communities, characterized by a higher total abundance and an increasing proportion of the smallest cells (picroeukaryotes and picocyanobacteria).

The Weddell Sea Bottom Water gravity current transports dense water from the continental shelf to the deep sea and is crucial for the formation of new deep-sea water. Building on vertical profiles and time series measured in the northwestern Weddell Sea, we apply three methods to distinguish turbulence caused by internal waves from that by other sources. We find that in the upper part of the gravity current, internal waves are important for the mixing of less dense water down into the current.