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Abstract Analysis of dissolved oxygen (O₂) in the Arctic's surface ocean provides insights into gas transfer between the atmosphere‐ice‐ocean system, water mass dynamics, and biogeochemical processes. In the Arctic Ocean's Canada Basin mixed layer, higher O₂concentrations are generally observed under sea ice compared to open water regions. Annual cycles of O₂and O₂saturation, increasing from summer through spring and then sharply declining to late summer, are tightly linked to sea ice cover. The primary fluxes that influence seasonal variability of O₂are modeled and compared to Ice‐Tethered Profiler O₂observations to understand the relative role of each flux in the annual cycle. Findings suggest that sea ice melt/growth dominates seasonal variations in mixed layer O₂, with minor contributions from vertical entrainment and atmospheric exchange. While the influence of biological activity on O₂variability cannot be directly assessed, indirect evidence suggests relatively minor contributions, although with significant uncertainty. Past studies show that O₂molecules are expelled from sea ice during brine rejection; sea ice cover can then inhibit air‐sea gas exchange resulting in winter mixed layers that are super‐saturated. Decreasing mixed layer O₂concentrations and saturation levels are observed during winter months between 2007 and 2019 in the Canada Basin. Only a minor portion of the decreasing trend in wintertime O₂can be attributed to decreased solubility. This suggests the O₂decline may be linked to more efficient air‐sea exchange associated with increased open water areas in the winter sea ice pack that are not necessarily detectable via satellite observations. 

Abstract: These time-series of pCO2, pH, Temperature, Dissolved Oxygen, Photosynthetically active radiation (PAR) were collected on moorings deployed as part of the Beaufort Gyre Observing System. SAMI-CO2 and SAMI-pH sensors were secured in a stainless steel strong-back and deployed at ~35 m depth at each deployment site. Three moorings were used in this study: Mooring-A (75o 0.0072’ N, 150o 0.0075’ W), Mooring-B (78o 0.352’ N, 149o 57.066’ W, Mooring-D (74o 0.1940’ N, 140o 0.0073’ W). These data were accompanied by ADCP data and profiler data (McLane, MMP) collected by Rick Krishfield et al. (WHOI). See http://www.whoi.edu/page.do?pid=66559 for more information about the mooring locations and for access to additional mooring data. 

Abstract: These data were collected on the CCGS (Canadian Coast Guard) Louis St. Laurent during BGOS (Beaufort Gyre Observing System) research cruises in 2012-2014 and 2016-2025 in the Beaufort Sea area. They are underway pCO2 (Partial pressure of carbon dioxide) data collected using an equilibrator-infrared method (SUPER CO2 system from Sunburst Sensors). Ancillary data for calculation of air-sea CO fluxes include temperature, salinity, atmospheric CO2, wind speed, and gas transfer velocity (calculated from Wanninkhof et al. (2009). Fluxes are not corrected for fractional ice-coverage. The specific goal of the study is to continue to operate an Arctic Observing Network (AON) for the measurement of the partial pressure of CO2 (pCO2), pH, and dissolved O2 (DO) focused on the surface waters of the Arctic Ocean (specifically, the Canada Basin). These data were collected on the CCGS (Canadian Coast Guard) Louis St. Laurent during a BGOS (Beaufort Gyre Observing System) research cruise in the Beaufort Sea area. It is underway pCO2 (partial pressure of carbon dioxide) data collected using an equilibrator-infrared method (SUPER CO2 system from Sunburst Sensors). Ancillary data for calculation of air-sea CO2 fluxes include temperature, salinity, atmospheric CO2. 

Abstract: The ocean absorbs one quarter of the global CO2 emissions from human activity. The community-led Surface Ocean CO2 Atlas (www.socat.info) is key for the quantification of ocean CO2 uptake and its variation, now and in the future. SOCAT version 2025 has quality-controlled in situ surface ocean fCO2 (fugacity of CO2) measurements on ships, moorings, sailing yachts, autonomous and drifting surface platforms for the global ocean and coastal seas from 1957 to 2025. The main SOCAT synthesis and gridded products contain fCO2 values with an estimated accuracy of better than 5 μatm. Sensor fCO2 data with an estimated accuracy of better than 10 μatm are separately available. During secondary quality control, marine scientists assign a flag to each data set, as well as WOCE flags of 2 (good), 3 (questionable) or 4 (bad) to individual fCO2 values. Data sets are assigned flags of A and B for an estimated accuracy of better than 2 μatm, flag of C (and D) for an accuracy of better than 5 μatm and a flag of E for an accuracy of better than 10 μatm. Bakker et al. (2016) describe the quality control criteria used from SOCAT version 3 onward. SOCAT quality control cookbooks provide quality control updates (www.socat.info), with (Gkritzalis et al., 2024) used for version 2025. Quality control comments for individual data sets can be accessed via the SOCAT Data Set Viewer (www.socat.info). All data sets, where data quality has been deemed acceptable, have been made public. The main SOCAT synthesis files and the gridded products contain all data sets with an estimated accuracy of better than 5 µatm (data set flags of A to D) and fCO2 values with a WOCE flag of 2. Access to data sets with an estimated accuracy of better than 10 µatm (flag of E) and fCO2 values with flags of 3 and 4 is via additional data products and the Data Set Viewer (Table 8 in Bakker et al., 2016). SOCAT publishes a global gridded product with a 1° longitude by 1° latitude resolution without gap filling. A second product with a higher resolution of 0.25° longitude by 0.25° latitude is available for the coastal seas. The gridded products contain all data sets with an estimated accuracy of better than 5 µatm (data set flags of A to D) and fCO2 values with a WOCE flag of 2. Gridded products are available monthly, per year and per decade. Two powerful, interactive, online viewers, the Data Set Viewer and the Gridded Data Viewer (www.socat.info), enable investigation of the SOCAT synthesis and gridded data products. SOCAT data products can be downloaded. Matlab code is available for reading these files. Ocean Data View also provides access to the SOCAT data products (www.socat.info). SOCAT data products are discoverable, accessible and citable. The SOCAT Data Use Statement (www.socat.info) asks users to generously acknowledge the contribution of SOCAT scientists by invitation to co-authorship, especially for data providers in regional studies, and/or reference to relevant scientific articles. It also asks users to cite the relevant SOCAT data set, the relevant methods paper(s), and to use acknowledgement text (https://socat.info/index.php/citing-socat/). The SOCAT website (www.socat.info) provides a single access point for online viewers, downloadable data sets, the Data Use Statement, a list of contributors and an overview of scientific publications on SOCAT and using SOCAT. Automation of data upload and initial data checks have allowed annual releases of SOCAT from version 4 onwards. Automation of metadata upload is ongoing. SOCAT is used for quantification of ocean CO2 uptake and ocean acidification and for evaluation of earth system models and sensor data. SOCAT products inform on ocean CO2 uptake in the annual Global Carbon Budget since 2013. SOCAT is a key element of the World Meteorological Organization’s (WMO) Global Greenhouse Gas Watch (G3W) program and is a key resource for Copernicus’ evaluations. The annual SOCAT releases by the SOCAT scientific community contribute to United Nations (UN) Sustainable Development Goal (SDG) 13 and SDG 14 (Life Below Water), and to the UN Decade of Ocean Science for Sustainable Development. However, since 2022 SOCAT critically relies on support provided by the Pacific Marine Environmental Laboratory of the National Oceanic and Atmospheric Administration in the US. This has been sufficient to keep the basic operation running, however this limited support has resulted in SOCAT data architecture not being updated, leading to a system with limited resilience that is highly vulnerable to external factors. Hundreds of peer-reviewed scientific publications and high-impact reports cite SOCAT. The SOCAT community-led synthesis product is a key step in the value chain based on in situ surface ocean carbon measurements, which provides policy makers with critical information on ocean CO2 uptake for policy makers. The need for accurate knowledge of global ocean CO2 uptake and its (future) variation makes sustained funding of in situ surface ocean CO2 observations and their synthesis imperative. 

Ocean Acidification (OA) is negatively affecting the physiological processes of marine organisms, altering biogeochemical cycles, and changing chemical equilibria throughout the world’s oceans. It is difficult to measure pH broadly, in large part because accurate pH measurement technology is expensive, bulky, and requires technical training. Here, we present the development and evaluation of a hand-held, affordable, field-durable, and easy-to-use pH instrument, named the pHyter, which is controlled through a smartphone app. We determine the accuracy of pH measurements using the pHyter by comparison with benchtop spectrophotometric seawater pH measurements, measurement of a certified pH standard, and comparison with a proven in situ instrument, the iSAMI-pH. These results show a pHyter pH measurement accuracy of ±0.046 pH or better, which is on par with interlaboratory seawater pH measurement comparison experiments. We also demonstrate the pHyter’s ability to conduct both temporal and spatial studies of coastal ecosystems by presenting data from a coral reef and a bay, in which the pHyter was used from a kayak. These studies showcase the instrument’s portability, applicability, and potential to be used for community science, STEM education, and outreach, with the goal of empowering people around the world to measure pH in their own backyards. 

The Earth’s climate is strongly affected by the partitioning of carbon between its mobile reservoirs, primarily between the atmosphere and the ocean. The distribution between the reservoirs is being massively perturbed by human activities, primarily due to fossil fuel emissions, with a range of consequences, including ocean warming and acidification, sea-level rise and coastal erosion, and changes in ocean productivity. These changes directly impact valuable habitats in many coastal regions and threaten the important services the habitats provide to mankind. Among the most productive and diverse systems are coral reefs and vegetated habitats, including saltmarshes, seagrass meadows, and mangroves. Coral reefs are particularly vulnerable to ocean warming and acidification. Vegetated habitats are receiving heightened attention for their ability to sequester carbon, but they are being impacted by land-use change, sea-level rise, and climate change. Overall, coasts play an important, but poorly quantified, role in the global cycling of carbon. Carbon reservoirs on land and in the ocean are connected through the so-called land–ocean aquatic continuum, which includes rivers, estuaries, and the coastal ocean. Terrestrial carbon from soils and rocks enters this continuum via inland water networks and is subject to transformations and exchanges with the atmosphere and sediments during its journey along the aquatic continuum. The expansive permafrost regions, comprised of ground on land and in the seabed that has been frozen for many years, are of increasing concern because they store vast amounts of carbon that is being mobilized due to warming. Quantitative estimates of these transformations and exchanges are relatively uncertain, in large part because the systems are diverse and the fluxes are highly variable in space and time, making observation at the necessary spatial and temporal coverage challenging. But despite their uncertainty, existing estimates point to an important role of these systems in global carbon cycling. 

The goal of the proposed study is to establish an Arctic Observing Network (AON) for sea surface partial pressure of carbon dioxide (pCO2) and pH in the perennially ice-covered portion of the Arctic Ocean. The carbon cycle is of particular concern in the Arctic because it is unknown how carbon sources and sinks will change in response to warming and the reduction of summer sea ice cover, and whether these changes will lead to increased greenhouse gas accumulation in the atmosphere. Furthermore, the penetration of anthropogenic caron dioxide (CO2) into the Arctic Ocean is leading to acidification with potentially serious consequences for organisms. Little is known about pCO2 and the inorganic carbon cycle in the central Arctic Ocean because most measurement programs to date have focused on the Arctic shelves during the accessible summer period. The investigators propose to use an existing component of the Arctic Observing Network, the Ice-Tethered Profilers (ITP), as platforms for deployment of in situ pCO2 and pH sensors. ITPs are automated profiling systems distributed throughout the perennial Arctic ice pack that telemeter data back to shore: 44 ITPs have been deployed since 2004 and the project is currently slated to continue through 2013. In the proposed work, a total of 6 ITPs will be equipped with CO2 sensors and four of these will also have pH sensors. The sensors will be fixed on the ITP cable ~2-4 meters below the ice. Each unit will include additional sensors for dissolved O2, salinity, and photosynthetically available radiation (and in some cases chlorophyll-a fluorescence) and will be capable of making 12 measurements per day for at least one year. These data, available in near real-time on the ITP web site (www.whoi.edu/itp/), will lead to a better understanding of the Arctic Ocean's role in regulating greenhouse gases and how the ecology of the Arctic will change with warming and acidification. The investigators will also engage in outreach programs including public presentations, podcasts, and school visits. A portion of the budget is also dedicated to the development of a climate-change/ocean acidification exhibit to be displayed in the University of Montana's science museum. The exhibit will reside at the museum for three months, then visit over 15 rural and tribal communities annually over a three year period. Undergraduate students will be recruited to assist with the sensor testing and data analysis, gaining a higher level of technical knowledge than possible through a traditional degree program. These data were collected using in situ sensors for the partial pressure of CO2 (pCO2), pH, dissolved oxygen (DO), photosynthetically available radiation (PAR), temperature, salinity and depth. Sensors were deployed at ~6 meter depth on ice-tethered profilers, in collaboration with Woods Hole Oceanographic Institution (Rick Krishfield and John Toole). Data are available at the website http://www.whoi.edu/page.do?pid=20781. 

These data were collected on the CCGS (Canadian Coast Guard) Louis St. Laurent during BGOS (Beaufort Gyre Observing System) research cruises in 2012-2014 and 2016-2021 in the Beaufort Sea area. They are underway pCO2 (Partial pressure of carbon dioxide) data collected using an equilibrator-infrared method (SUPER CO2 system from Sunburst Sensors). Ancillary data for calculation of air-sea CO fluxes include temperature, salinity, atmospheric CO2, wind speed, and gas transfer velocity (calculated from Wanninkhof et al. (2009). Fluxes are not corrected for fractional ice-coverage. The specific goal of the study is to continue to operate an Arctic Observing Network (AON) for the measurement of the partial pressure of CO2 (pCO2), pH, and dissolved O2 (DO) focused on the surface waters of the Arctic Ocean (specifically, the Canada Basin). These data were collected on the CCGS (Canadian Coast Guard) Louis St. Laurent during a BGOS (Beaufort Gyre Observing System) research cruise in the Beaufort Sea area. It is underway pCO2 (partial pressure of carbon dioxide) data collected using an equilibrator-infrared method (SUPER CO2 system from Sunburst Sensors). Ancillary data for calculation of air-sea CO2 fluxes include temperature, salinity, atmospheric CO2.