Atlantic water masses are particularly interesting, not only regionally, but also for the global ocean, due to the vital status of the Atlantic Meridional Overturning Circulation in the global climate. This study presents quantitative assessments of water mass age characteristics and ventilation time scales through an analysis using the transient tracers chlorofluorocarbon‑12 (CFC‑12), sulfur hexafluoride (SF6), and argon‑39 (39Ar). The age analysis reveals significant basin‑scale asymmetries, with western basins exhibiting younger ages compared to eastern counterparts. This integrated age framework provides novel insights into water mass ventilation dynamics and their biogeochemical implications through quantitative characterization of temporal‑spatial age distributions across different oceanographic provinces.

This paper in the Ocean Science Jubilee Special Issue is a multidisciplinary review of silicon in the ocean (and in fact also in the earth system). It presents "everything you ever wanted to know about silicates but were afraid to ask". In addition to its scientific excellence and thoroughness as a review, it is also noteworthy for being entirely conceived and written by a group of early career researchers who decided to work together on this topic. We commend their initiative!

This is an important contribution to the science surrounding the Atlantic Meridional Overturning Circulation (known as AMOC), in particular with regard to observations and methods. This work may have strategic relevance for planning observations in the future. It also represents an interesting effort at incorporating artificial intelligence (AI) technology into obtaining optimal results from observational data analysis.

This 'review and perspectives' paper, recently accepted in the Jubilee Special Issue of Ocean Science, provides an authoritative overview of the role of mixing in estuarine circulation. It gives valuable guidance to good and up-to-date practice in estuarine modelling. It will be a valuable resource for anyone wanting to know the state of the art in understanding physical processes in estuaries.

Oxygen is fundamental to ocean biogeochemical processes, with deoxygenation potentially reducing biodiversity, and disrupting biogeochemical cycles. This paper develops and implements a new inverse method to decompose oxygen change into its constituent parts by linking each process to concomitant changes in temperature and dissolved inorganic carbon (DIC). They apply this method to a GO-SHIP repeated section of the North Atlantic Ocean. They find that alterations in remineralisation, either local or upstream, are responsible for up to half of the total oxygen decrease seen in the upper 2000 m between 1992 and 2015. This method could be repeated on any dataset, observations or model, that includes temperature, DIC, and oxygen concentration data.

Tide gauges have been critical sources for sea level research, enabling the development of tidal theory and an understanding of local variations that occur across the global oceans. Tides play important roles in a variety of oceanographic and geodetic applications; characterizing their spatial variability is valuable for applications ranging from fishing to flood risk management. Coastal characteristics of ocean tides are presented based on 3,591 high-frequency tide gauge observations. The analysis shows that 125 out of 237 long-time series show statistically significant trends in one or more tide constituents. Particularly the novel results on tidal high-water durations and tidal trends are of interest. The paper provides a global summary of a number of tidal characteristic quantities that will be useful for tide experts but also for the greater oceanographic community, in particular sea level researchers, providing insights crucial for a wide range of biogeochemical processes. It also presents insights that can be useful for local communities. This paper, along with its accompanying data, could become an important reference in the field.

The paper contributes to our knowledge of the impact of marine heat waves on ecosystems, a subject that is topical and that we know little of. The impact on coccolithophores is important for carbon uptake. The impact of MHW more generally on algal blooms is also important for higher trophic levels, the wider ecosystem, and for commercial interests such as aquaculture. The study gives useful confirmation that the environmental ranges defined by O’Brien et al for coccolithophore blooms do seem to apply even in these anomalous MHW conditions and in two separate regions.

The study introduces an innovative method for estimating meridional heat transport (MHT) across latitudes. By combining diverse oceanographic approaches, including remote sensing (gravimetry, altimetry), in-situ observations, and advanced statistical modeling, the study bridges several domains of ocean science. It opens the door for things such as an improved estimation of ocean heat content, surface fluxes, sea level variability, currents and enhanced error characterization in satellite observations. The new method could serve as the foundation for alternative estimates of both MHT and the Atlantic Meriodional Circulation (AMOC) that do not depend on costly, geographically limited in-situ observing arrays, which is especially beneficial if it allows the AMOC to be observed across a range of latitudes.