We investigate the structural changes the Antarctic Slope Front in the southern Weddell Sea experiences in a warming climate by conducting two ocean simulations driven by atmospheric data of different horizontal resolutions. Cross-slope currents associated with a regime shift from a cold to a warm Filchner Trough on the continental shelf temporarily disturb the structure of the slope front and reduce its depth, but the primary reason for a regime shift is the cross-slope density gradient.

During the annual phytoplankton bloom, rates of primary production and carbon export in the Ross Sea, Antarctica, are uncoupled from each other and from oxygen and carbon stocks. These biogeochemical rates support the high-productivity, low-export classification of the region and suggest that environmental factors influence these stocks and rates differently and make projections under future climate change scenarios difficult.

Subantarctic mode water in the South Pacific Ocean is important due to its role in the uptake and transport of anthropogenic heat and carbon. The Subantarctic mode water region can be split into two pools using mixed-layer-depth properties. Sensitivity experiments are used to understand the effects of heating and wind on each pool. It is found that the optimal conditions to form large amounts of Subantarctic mode water in the South Pacific are local cooling and upstream warming combined.

Marine heatwaves are of growing concern around the world. We use a state-of-the-art ensemble of downscaled climate models to project how often heatwaves will occur in the future across northwestern Europe under a high-emission scenario. The projections show that, without emission reductions, heatwaves will occur more than half of the time in the future. We show that the seafloor is expected to experience much more frequent heatwaves than the sea surface in the future.

The Arabian Sea Mini Warm Pool matures in the southeastern Arabian Sea in May, and the influence of the ocean and atmosphere on its formation has been debated for the past 2 decades. Using a coupled numerical model, our study concludes that both oceanic and atmospheric conditions are necessary for its genesis. For instance, in a robust Mini Warm Pool year, the pre-April ocean condition primarily influences its formation, which is further favored by the presence of a wind shadow zone.

The South China Sea is the largest semi-enclosed marginal sea in the western Pacific, featuring unique layered circulation with rotating currents in its upper, middle, and deep layers. This study uses simulations to explore how stronger currents in the upper layer influence circulation across the entire basin. The vorticity analyses show that the enhanced upper currents increase the strength of middle and deep currents, driven by changes in bottom pressure and cross-slope movements.

While preparing a new set of sea level scenarios for the Netherlands, we found out that many climate models overestimate the changes in ocean circulation for the last 30 years. To quantify this effect, we defined three methods that rely on diverse and independent observations: tide gauges, satellite altimetry, temperature and salinity in the ocean, land ice melt, etc. Based on these observations, we define a few methods to select models and discuss their advantages and disadvantages.

We evaluated a deep-learning model, HIDRA2, for predicting sea levels along the Estonian coast and compared it to traditional numerical models. HIDRA2 performed better overall, offering faster forecasts and valuable uncertainty estimates using ensemble predictions.

By providing all weather, global, and real-time observations of sea level, a key variable to constrain ocean analysis and forecasting systems, satellite altimetry has had a profound impact on the development of operational oceanography. This paper provides an overview of the development and evolution of satellite altimetry and operational oceanography over the past 20 years from the launch of Jason-1 in 2001 to the launch of SWOT (Surface Water and Ocean Topography) in 2022.

Mode water is formed annually and sits between the warm surface water and deeper older waters. In the Arabian Sea, it plays a crucial role in regulating ocean heat and oxygen variability by acting as a doorway between the surface and deeper waters. Using observations and models, we show that its formation is primarily driven by atmospheric forcing, though ocean currents, eddies, and biological heating also influence its life cycle. This water mass contributes up to 40 % of the region's oxygen content.

Particle tracking models allow us to explore pathways of floating marine litter, source to sink, between countries. This study shows the influence of seasonality for dispersal in the Bay of Bengal and how ocean current forcing impacts model performance. Most litter beached on the country of origin, but there was a greater spread shown between countries during the post-monsoon period (Oct–Jan). Results will inform future model developments as well as management of marine litter in the region.

This study evaluates various treatments to prevent changes in dissolved inorganic carbon (DIC) during water sample preservation without HgCl₂ addition. We found that combining filtration with benzalkonium chloride (BAC) addition effectively stabilized DIC by inhibiting microbial activity for up to 41 weeks. This procedure provides a practical, environmentally friendly alternative to conventional mercury-disinfected methods, enduring effective water sample preservation in aquatic environments.

Coastal zones are crucial ecological areas, yet our understanding of groundwater–ocean interactions remains limited. Ocean and groundwater models typically operate independently, with ocean models ignoring submarine groundwater discharge and groundwater models viewing the ocean as a static boundary. This separation impedes accurate simulations. By integrating these models, we can capture real-time water flow and salt movement while considering factors such as tides.

Present-day sea level rise is not uniform regionally. For better understanding of regional sea level variations, a classical approach is to compare the observed sea level trend patterns with those of the sum of the contributions. If the regional sea level trend budget is not closed, this allows the detection of errors in the observing systems. Our study shows that the trend budget is not closed in the North Atlantic Ocean and identifies errors in Argo-based salinity data as the main suspect.

Vertical salinity profiles with their highest values at the surface layers – surface saline lakes – have been known to occur in the eastern Mediterranean, where strong evaporation, warm summers, and low winds all contribute to an increase in surface salinity. Our analysis of Argo data from the past 2 decades showed that saline lakes also occur in other regions across the Mediterranean Sea. This poses the question of whether such changes indicate a salinification of the entire basin due to climate change.

The study combines archived surface drifter trajectories along the Equator with a novel extension of Ekman's wind-driven theory to the equatorial β-plane in order to estimate the depth of the equatorial Ekman layer and the speed of upwelling into it. The analysis provides a direct estimate of the depth of the equatorial Ekman layer based on observed drifter trajectories and does not involve the 3D continuity equation, which is only used for estimating the upwelling speed. 

MIOST24 (Multivariate Inversion of Ocean Surface Topography 2024) annual and monthly internal tide (IT) atlases, based on 25 years of altimetry data and an updated wavelength database, are presented for the Indo-Philippine archipelago and the Amazon shelf. The atlases show monthly IT variability and a better correction of IT in altimetry data than with MIOST22 (MIOST 2022) and HRET (High-Resolution Empirical Tide). The results support the development of a global MIOST24.

During the summer of 2022 in the eastern Gulf of Lion (NW Mediterranean), exceptionally warm temperatures were observed down to depths of 30 m, along with massive mortality of benthic species. It has been shown that these deep marine heatwaves are linked to southeasterly wind episodes, which induce deep plunges of surface water overheated by the atmospheric heatwave. These events are rare in summer, but their impact on ecosystems is dramatic and will only increase with climate change.

Since 2010, pelagic Sargassum spp. blooms have increased in several tropical Atlantic regions, causing socioeconomic and ecosystem impacts. Offshore structuration of Sargassum by mesoscale dynamics may influence transport and growth. Sargassum stays afloat, constantly interacting with currents, waves, winds, and mesoscale eddies. We find that anticyclones and cyclones effectively trap Sargassum throughout its propagation, with a greater tendency for cyclones to accumulate Sargassum.