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This dataset collects a record of physical and chemical observations made by two uncrewed sailing vehicles (Saildrone 1038 and Saildrone 1039) in the South Indian Ocean during 2022 and 2023. SD1038 collected data near 15°E and between latitudes 35°S and 50°S during July 19-26, 2022. SD1039 made observations within the Subantarctic Zone (37-47°S, 20-45°E) between September 1, 2022 until February 24, 2023. The local atmospheric and surface ocean parameters measured are listed below: -- Atmospheric measurements: temperature, pressure, humidity. -- Seawater measurements: temperature, pressure, conductivity, salinity. -- Carbon measurements: fCO2, xCO2, and pCO2 in atmosphere and seawater. -- Chlorophyll measurements: concentration. -- Oxygen measurements: concentration, saturation, ratio of O2 in water to air. -- Wind measurements: eastward, northward, and downward speed, plus gusts and direction. -- Wave measurements: significant wave height and dominant wave period. -- Irradiation measurements (SD1039 only): longwave, shortwave, and PAR. -- Current velocity measurements (SD1039 only): eastwards, northwards, and upwards, down to 102m. -- CCMP wind estimates (hourly only): collocated to Saildrone time and location. -- Directions of large eddies transitted (SD1039 hourly only): based on AVISO eddy database. Four files included: -- SD1038_1min.nc (SD1038’s raw data at 1-minute timesteps with frequent gaps) -- SD1039_1min.nc (SD1039’s raw data at 1-minute timesteps with frequent gaps) -- SD1038_hrly.nc (SD1038’s hourly-averaged data, plus eddies and CCMP winds) -- SD1039_hrly.nc (SD1039’s hourly-averaged data, plus eddies and CCMP winds) 1-minute files contain the “raw” data, at all times it was collected. Because many variables were only sampled once or a few times an hour, these files include frequent gaps. Hourly files were made from the 1-minute data, averaging whatever data exists within each hour, such that few gaps in the data exist for most variables. 

This dataset includes surface underway chemical, meteorological and physical data collected from Autonomous Surface Vehicle (ASV) Saildrone 1038 (EXPOCODE 316420220616) in the Indian Ocean, Southern Ocean from 2022-06-16 to 2022-07-26. These data include xCO2 SW (wet) - mole fraction of CO2 in air in equilibrium with the seawater at sea surface temperature and measured humidity; H2O SW - Mole fraction of H2O in air from equilibrator; xCO2 Air (wet) - Mole fraction of CO2 in air from airblock, 0.67m (26") above the sea surface at measured humidity; H2O Air - Mole fraction of H2O in air from airblock, 0.67m (26") above the sea surface; Atmospheric pressure at the airblock, 0.67m (26") above the sea surface; Atmospheric pressure at the airblock, 0.67m (26") above the sea surface; Temperature of the Infrared Licor 820 in degrees Celsius; MAPCO2 %O2 - The percent oxygen of the surface seawater divided by the percent oxygen of the atmosphere at 0.67m (26") above the sea surface; Sea Surface Temperature; Sea Surface Salinity; xCO2 SW (dry) - Mole fraction of CO2 in air in equilibrium with the seawater at sea surface temperature (dry air); xCO2 Air (dry) - Mole fraction of CO2 in air at the airblock, 0.67m (26") above the sea surface (dry air); fCO2 SW (sat) - Fugacity of CO2 in air in equilibrium with the seawater at sea surface temperature (100% humidity); fCO2 Air (sat) - Fugacity of CO2 in air at the airblock, 0.67m (26") above the sea surface (100% humidity); dfCO2 - Difference of the fugacity of the CO2 in seawater and the fugacity of the CO2 in air (fCO2 SW - fCO2 Air); pCO2 SW (wet) - Partial Pressure of CO2 in air in equilibrium with the seawater at sea surface temperature (100% humidity); pCO2 Air (wet) - Partial Pressure of CO2 in air at the airblock, 0.67m (26") above the sea surface (100% humidity); dpCO2 - Difference of the partial pressure of CO2 in seawater and air (pCO2 SW - pCO2 Air; pH of Seawater (total scale). The Autonomous Surface Vehicle CO2 (ASVCO2) instruments used to collect these data include Bubble type equilibrator for autonomous carbon dioxide (CO2) measurement, Carbon dioxide (CO2) gas analyzer, Humidity Sensor, and oxygen meter. 

This dataset includes surface underway chemical, meteorological and physical data collected from Autonomous Surface Vehicle (ASV) Saildrone 1039 (EXPOCODE 316420220901) in the Indian Ocean, Southern Ocean from 2022-09-01 to 2023-04-27. These data include xCO2 SW (wet) - mole fraction of CO2 in air in equilibrium with the seawater at sea surface temperature and measured humidity; H2O SW - Mole fraction of H2O in air from equilibrator; xCO2 Air (wet) - Mole fraction of CO2 in air from airblock, 0.67m (26") above the sea surface at measured humidity; H2O Air - Mole fraction of H2O in air from airblock, 0.67m (26") above the sea surface; Atmospheric pressure at the airblock, 0.67m (26") above the sea surface; Atmospheric pressure at the airblock, 0.67m (26") above the sea surface; Temperature of the Infrared Licor 820 in degrees Celsius; MAPCO2 %O2 - The percent oxygen of the surface seawater divided by the percent oxygen of the atmosphere at 0.67m (26") above the sea surface; Sea Surface Temperature; Sea Surface Salinity; xCO2 SW (dry) - Mole fraction of CO2 in air in equilibrium with the seawater at sea surface temperature (dry air); xCO2 Air (dry) - Mole fraction of CO2 in air at the airblock, 0.67m (26") above the sea surface (dry air); fCO2 SW (sat) - Fugacity of CO2 in air in equilibrium with the seawater at sea surface temperature (100% humidity); fCO2 Air (sat) - Fugacity of CO2 in air at the airblock, 0.67m (26") above the sea surface (100% humidity); dfCO2 - Difference of the fugacity of the CO2 in seawater and the fugacity of the CO2 in air (fCO2 SW - fCO2 Air); pCO2 SW (wet) - Partial Pressure of CO2 in air in equilibrium with the seawater at sea surface temperature (100% humidity); pCO2 Air (wet) - Partial Pressure of CO2 in air at the airblock, 0.67m (26") above the sea surface (100% humidity); dpCO2 - Difference of the partial pressure of CO2 in seawater and air (pCO2 SW - pCO2 Air; pH of Seawater (total scale). The Autonomous Surface Vehicle CO2 (ASVCO2) instruments used to collect these data include Bubble type equilibrator for autonomous carbon dioxide (CO2) measurement, Carbon dioxide (CO2) gas analyzer, Humidity Sensor, and oxygen meter. 

Abstract Ocean heat content (OHC) is key to estimating the energy imbalance of the earth system. Over the past two decades, an increasing number of OHC studies were conducted using oceanic objective analysis (OA) products. Here we perform an intercomparison of OHC from eight OA products with a focus on their robust features and significant differences over the Argo period (2005-2019), when the most reliable global scale oceanic measurements are available. For the global ocean, robust warming in the upper 2000 m is confirmed. The 0-300 m layer shows the highest warming rate but is heavily modulated by interannual variability, particularly the El Niño–Southern Oscillation. The 300-700 m and 700-2000 m layers, on the other hand, show unabated warming. Regionally, the Southern Ocean and mid-latitude North Atlantic show a substantial OHC increase, and the subpolar North Atlantic displays an OHC decrease. A few apparent differences in OHC among the examined OA products were identified. In particular, temporal means of a few OA products that incorporated other ocean measurements besides Argo show a global-scale cooling difference, which is likely related to the baseline climatology fields used to generate those products. Large differences also appear in the interannual variability in the Southern Ocean and in the long-term trends in the subpolar North Atlantic. These differences remind us of the possibility of product-dependent conclusions on OHC variations. Caution is therefore warranted when using merely one OA product to conduct OHC studies, particularly in regions and on timescales that display significant differences. 

Abstract Salinity is one of the fundamental ocean state variables and has been used to infer important information about climate change and variability. Previous studies have found inconsistent salinity variations in various objective ocean analyses that are based on the Argo measurements. However, as far as we are aware, a comprehensive assessment of those inconsistencies, as well as robust spatial and temporal features of salinity variability among the Argo-based products, has not been conducted. Here we compare and evaluate ocean salinity variability from five objective ocean analyses that are solely or primarily based on Argo measurements for their overlapping period from 2005 to 2015. We examine the salinity variability at the sea surface and within two depth intervals (0–700 and 700–2000 m). Our results show that the climatological mean is generally consistent among all examined products, although regional discrepancies are evident in the subsurface ocean. The time evolution, vertical structure, and leading EOF modes of salinity variations show good agreement among most of the examined products, indicating that a number of robust features of the salinity variability can be obtained by examining gridded Argo products. However, significant discrepancies in these variations exist, particularly in the subsurface North Atlantic and Southern Oceans. Also, despite the increasing number of Argo floats deployed in the ocean, the discrepancies were not significantly reduced over time. Our analyses, particularly those of the discrepancies between products, can serve as a useful reference for utilizing and improving the existing objective ocean analyses that are based on Argo measurements.