Lynne D. Talley

Marine dissolved inorganic carbon (DIC _total ) is a key component of the global ocean carbon cycle. Over recent decades, DIC _total has increased due to rising anthropogenic CO ₂ , but the response from the biological carbon pump (BCP), which transfers carbon from the surface to the ocean interior, remains uncertain. Here, we reconstruct global three-dimensional DIC changes from 2004 to 2024 down to 2 km depth and distinguish contributions from anthropogenic, organic matter remineralization, and calcium carbonate cycling. We find that while DIC _total increased throughout the water column, driven primarily by anthropogenic CO ₂ , the global inventory of biologically respired carbon associated with the BCP remained constant. However, this apparent stability masked pronounced regional and vertical redistribution of respired carbon within the ocean interior. In some regions, respired carbon accumulated at shallower depths, reducing its isolation from the atmosphere, whereas in others it was transported deeper, enhancing long-term storage. These contrasting patterns co-vary with changes in ocean stratification and ventilation, indicating that these processes regulate where biologically respired carbon is retained. Although these redistributions did not impact the net global carbon inventory over the study period, they reveal a structural reorganization of the BCP that may influence the ocean’s capacity to sequester carbon under continued climate change.

Future projections of oxygen and water mass age change in the upper Pacific Ocean show a consistent pattern: strong deoxygenation and increased age in the well‐ventilated subtropical gyres, contrasted by weak deoxygenation and younger age in the poorly ventilated tropical oxygen minimum zones. We investigate the underlying dynamics of this pattern by forcing an intermediate‐complexity ocean circulation and biogeochemistry model with globally uniform and regionally‐distinct idealized warming experiments. We find that this meridional contrast in oxygen and age change arises from a slowdown of vertical velocities driven by a combination of Pacific basin and remote Southern Ocean heat forcing. Warming and stratifying the upper Pacific basin compresses the subtropical gyre circulation into a shallower, flatter layer, thereby reducing ventilation along the base of the North Pacific ventilated thermocline. Warming in the mid‐latitude Southern Ocean reduces downwelling locally, but remotely reduces upwelling of old, low‐oxygen water in the Tropical and North Pacific via a Kelvin wave‐mediated adjustment of the circulation. The combination of these two effects drives the “young get older, but old get younger” response of the Pacific thermocline. Continued monitoring of upper ocean oxygen through the Biogeochemical‐Argo float program and improved model representation of mid‐ and high‐latitude ventilation processes are critical to inform how marine ecosystems will adapt to a warmer and more stratified ocean.

The coastal Ocean Data Analysis Product in North America (CODAP-NA, Version 2026) represents a major expansion of coastal ocean carbonate chemistry synthesis for North American continental margins. Compared to CODAP-NA Version 2021, the updated product integrates newly available cruise observations spanning more than four decades, substantially increasing both the spatial and temporal coverage of coastal biogeochemical measurements across North American continental shelves. Observations from multiple research programs have been harmonized into a unified, internally consistent format through standardized quality control procedures, enabling large-scale analyses of ocean carbon cycling and ocean acidification along the North American margins. This version comprises 446 cruises, 31,864 hydrographic profiles, and 195,489 discrete data records covering continental shelf environments from Alaska to Mexico in the west and from Canada to the Caribbean in the east from 1981 to 2024. Fourteen variables (including temperature, salinity, dissolved oxygen, dissolved inorganic carbon, total alkalinity, pH on the Total Scale, carbonate ion, fugacity of carbon dioxide, silicate, phosphate, nitrate, nitrite, nitrate plus nitrite, and ammonium) were subjected to extensive quality control. CODAP-NA Version 2026 is available as a merged data product in CSV, MATLAB, and NetCDF formats (https://doi.org/10.25921/h2ff-9d66) through the NOAA Ocean Carbon and Acidification Data System (OCADS: https://www.ncei.noaa.gov/data/oceans/ncei/ocads/metadata/0315529.html). The original cruise data were archived and are accessible via a summary table at the NCEI Ocean Acidification Data Stewardship repository (https://www.ncei.noaa.gov/access/ocean-carbon-acidification-data-system/synthesis/CODAP-NAv2.html).

Small-scale turbulent mixing in the ocean interior is vital in governing ocean circulation and tracer distributions, and hence global climate. However, the planetary extent of this role and its dependence on the microphysics of mixing remain inadequately understood. Here, we emphasize the variety of spatio-temporal scales on which such interior turbulent mixing can shape the climate system. In addition to its well-established role in facilitating the equilibration of deep branches of ocean circulation on centennial-to-millennial timescales, interior turbulent mixing is a leading determinant of oceanic tracer budgets on timescales as short as sub-annual. We highlight the importance of the co-dependence of vertical (diapycnal) mixing and lateral (isopycnal) stirring in establishing the large-scale impacts of oceanic turbulence. We conclude with a summary of theoretical, observational and computational bottlenecks in the way of a sufficiently accurate representation of mixing in Earth System Models, and discuss emerging opportunities for making progress in these areas.

Future projections of oxygen and water mass age change in the upper Pacific Ocean show a consistent pattern: strong deoxygenation and increased age in the well-ventilated subtropical gyres, contrasted by weak deoxygenation and younger age in the poorly ventilated tropical oxygen minimum zones. We investigate the underlying dynamics of this pattern by forcing an intermediate-complexity ocean circulation and biogeochemistry model with globally uniform and regionally-distinct idealized warming experiments. We find that this meridional contrast in oxygen and age change arises from a slowdown of vertical velocities driven by a combination of Pacific basin and remote Southern Ocean heat forcing. Warming and stratifying the upper Pacific basin compresses the subtropical gyre circulation into a shallower, flatter layer, thereby reducing ventilation along the base of the North Pacific ventilated thermocline. On the other hand, warming in Southern Ocean water mass formation regions decreases age and increases oxygen in the tropical and North Pacific by reducing upwelling of old waters from depth via a wave-mediated adjustment. The combination of these two effects drives the “young get older, but old get younger” response of the Pacific thermocline. Continued observing and improved modeling of the spatial patterns of ocean deoxygenation is key to informing how marine ecosystems will adapt to a warmer and more stratified ocean.

Antarctica InSync is a global effort to synchronise research across Antarctica and the Southern Ocean, connecting ice, ocean, land, climate, and life to protect this vital region. This roadmap paper introduces the scientific and technological motivation and action plan to build an international programme for a coordinated field season in Antarctica and its surrounding seas. It lays out the international collaboration that is required to realise an ambitious action plan and the opportunities for the science community to address important scientific themes that identify current knowledge gaps. In the spirit of the Antarctic Treaty Consultative Meeting (ATCM), the planned scientific action mandates free data exchange, facilitates international collaboration, and derives expert scientific advice together with the Scientific Committee on Antarctic Research (SCAR). Aligned with challenges of the United Nation Ocean and Cryosphere Decades, we plan a shared global effort to better understand the role of Antarctica and its surrounding ocean for our global futures, building on decades of achievements in polar and ocean science. As a milestone leading up to the next International Polar Year in 2032/33 (IPY5), the ambition is to achieve a new level of cooperation, with opportunities for the next generation of polar scientists around the world by enhancing practices in sharing of ideas, infrastructure and information.

Antarctica InSync is a global effort to synchronise research across Antarctica and the Southern Ocean, connecting ice, ocean, land, climate, and life to protect this vital region. This roadmap paper introduces the scientific and technological motivation and action plan to build an international programme for a coordinated field season in Antarctica and its surrounding seas. It lays out the international collaboration that is required to realise an ambitious action plan and the opportunities for the science community to address important scientific themes that identify current knowledge gaps. In the spirit of the Antarctic Treaty Consultative Meeting (ATCM), the planned scientific action mandates free data exchange, facilitates international collaboration, and derives expert scientific advice together with the Scientific Committee on Antarctic Research (SCAR). Aligned with challenges of the United Nation Ocean and Cryosphere Decades, we plan a shared global effort to better understand the role of Antarctica and its surrounding ocean for our global futures, building on decades of achievements in polar and ocean science. As a milestone leading up to the next International Polar Year in 2032/33 (IPY5), the ambition is to achieve a new level of cooperation, with opportunities for the next generation of polar scientists around the world by enhancing practices in sharing of ideas, infrastructure and information.

Theme 1 addresses the Southern Ocean’s (south of 30°S) critical role in regulating Earth’s climate through circulation patterns that mediate global exchanges of heat, carbon, freshwater, and nutrients. The region has absorbed over 70% of anthropogenic heat and has contributed to about 40% of the global ocean uptake of human-emitted carbon dioxide (CO₂) while also controlling ice shelf stability and sea level rise. However, fundamental gaps in year-round observations, particularly during austral autumn, winter, and spring, severely limit our understanding of these processes and their responses to rapid climate change. This white paper establishes key knowledge gaps and high-priority recommendations that are tractable within the InSync timeframe through coordinated program execution with strong engagement from national operators and funding agencies. Critical needs include seasonal observations of the marginal ice zone where carbon, heat and nutrient-rich waters upwell, year-round continental shelf measurements where dense water formation and ice-ocean interactions occur, standardized air-sea flux measurements, and strategic monitoring of regional choke points. Success requires international resource sharing, coordinated deployments, and sustained commitment to both process studies and long-term monitoring.

Southern Ocean mode waters act as a major sink for both anthropogenic heat and carbon, yet the mechanistic understanding of their variability remains incomplete. We use observation-based data to examine an oceanic pathway that begins at the Indonesian Throughflow (ITF), extends through the South Equatorial Current and Agulhas Current, and ultimately encircles the Southern Ocean via the Antarctic Circumpolar Current (ACC). Our analysis reveals that interannual temperature–salinity variations observed in the ITF region propagate into the Southern Ocean along this pathway, taking approximately 3 years to propagate from the Indonesian Archipelago to the Agulhas Retroflection region. Lagrangian particle tracking reveals that both Agulhas Current waters and waters from the Atlantic and further poleward shape the temperature–salinity characteristics of ACC waters in the western Indian Ocean, although the relative contributions of these oceanic pathways and atmospheric forcings have yet to be quantified. In the western Indian Ocean, mixed-layer depth (MLD) and Subantarctic Mode Water (SAMW) volume and temperature–salinity properties all show strong quasi-biennial variability. These anomalies are advected eastward with the ACC as vertically coherent structures extending over the top 1000 m, reemerging in the eastern Indian Ocean approximately 1 year later, reaching the southeast Pacific in 4–5 years and further to the east of Drake Passage a year afterward. The propagation speed of these anomalies is around 40°–55° longitude per year along the ACC, or equivalently 0.15–0.2 m s ⁻¹ , matching the advective speed of water particles driven by mean geostrophic currents in the ACC. In specific years, the eastward advection of anomalies can complete a full circumpolar circuit around the Southern Ocean.