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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. 

Understanding and predicting Arctic change and its impacts on global climate requires broad, sustained observations of the atmosphere-ice-ocean system, yet technological and logistical challenges severely restrict the temporal and spatial scope of observing efforts. Satellite remote sensing provides unprecedented, pan-Arctic measurements of the surface, but complementary in situ observations are required to complete the picture. Over the past few decades, a diverse range of autonomous platforms have been developed to make broad, sustained observations of the ice-free ocean, often with near-real-time data delivery. Though these technologies are well suited to the difficult environmental conditions and remote logistics that complicate Arctic observing, they face a suite of additional challenges, such as limited access to satellite services that make geolocation and communication possible. This paper reviews new platform and sensor developments, adaptations of mature technologies, and approaches for their use, placed within the framework of Arctic Ocean observing needs. 

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. 

This dataset consists of the Surface Ocean CO2 Atlas Version 2022 (SOCATv2022) data product files. 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 2022 has quality-controlled in situ surface ocean fCO2 (fugacity of CO2) measurements on ships, moorings, autonomous and drifting surface platforms for the global oceans and coastal seas from 1957 to 2021. The main synthesis and gridded products contain 33.7 million fCO2 values with an estimated accuracy of better than 5 μatm. A further 6.4 million fCO2 sensor data with an estimated accuracy of 5 to 10 μatm are separately available. During 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, flags 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 in SOCAT versions 3 to 2022. 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 5 to 10 (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. 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. 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 and using SOCAT. Automation of data upload and initial data checks allows annual releases of SOCAT from version 4 onwards. SOCAT is used for quantification of ocean CO2 uptake and ocean acidification and for evaluation of climate models and sensor data. SOCAT products inform the annual Global Carbon Budget since 2013. The annual SOCAT releases by the SOCAT scientific community are a Voluntary Commitment for United Nations Sustainable Development Goal 14.3 (Reduce Ocean Acidification) (#OceanAction20464). More broadly the SOCAT releases contribute to UN SDG 13 (Climate Action) and SDG 14 (Life Below Water), and to the UN Decade of Ocean Science for Sustainable Development. 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 inorganic carbon measurements of the oceans, which provides policy makers with critical information on ocean CO2 uptake in climate negotiations. The need for accurate knowledge of global ocean CO2 uptake and its (future) variation makes sustained funding of in situ surface ocean CO2 observations imperative.