Product information Product name OceanSODA-ETHZ-v2 SOCOM-style name OSETHZv2-NN Product version v2024r01 Coverage 1982-01-01 — 2022-12-31 Global ice free ocean Resolution 8-day 0.25° x 0.25° Contact nicolas.gruber@env.ethz.ch OR luke.gregor@usys.ethz.ch Variables Each netCDF contains only one variable. The metadata also has a start and end time as well as min/max lat/lon.The information about the settings used in PyCO2SYS is also included in each file's metadata. Folder Variable name Units Description fgco2 FCO2MBL mmol m−2 day−1 Sea-air CO2 flux computed using Marine Boundary Layer xCO2 fgco2CT FCO2CT mmol m−2 day−1 Sea-air CO2 flux computed using CarbonTracker xCO2 fgco2_global globally integrated FCO2 PgC yr−1 Surface — atmosphere ocean fugacity of CO2 dfco2 ΔfCO2 μatm Surface — atmosphere ocean fugacity of CO2 sfco2 fCO2sea μatm Surface ocean fugacity of CO2 sfco2_uncert fCO2sea uncertainty μatm Uncertainty of surface ocean fugacity of CO2 based on 5.7 ⨉ ensemble spread kw kw cm hr−1 Gas transfer velocity sol K0 mol L−1 atm−1 Solubility of CO2 in seawater ice ice fraction Sea-ice fraction File structure The file naming structure is __OceanSODAETHZv2.2024rXX.nc. Data are grouped by decade, with each file being about 800 MB. Not all files contain the same number of years (e.g., 1982-1989). The size for each variable (1982-2022) is between 2.5 and 3.5 GB. Product description This dataset contains a global gridded dataset of sea-air carbon dioxide fluxes (FCO2) for subseasonal to decadal studies. The product is available from 1982 through 2022 and is at an 8-daily by 0.25° by 0.25° resolution. FCO2 is calculated using the bulk formulation of flux: (fCO2sea−fCO2atm) ⋅ kw ⋅ K0 ⋅ (1−ice) where (fCO2sea − fCO2atm) is the sea-air difference in fugacity of carbon dioxide, kw is the gas transfer velocity, K0 is the solubility of CO2 in seawater, and ice is the sea-ice fraction. The surface ocean fugacity of carbon dioxide (fCO2sea) is calculated using the surface Ocean Carbon dioxide Neural Network (OceanCarbNN). This two-step approach first estimates an 8-day climatology of fCO2sea based on climatological drivers. The second step uses the output of the first step as a prior estimate of fCO2sea which is then adjusted to a time-varying product. An important novelty of this method is that the first step uses Gradient Boosted Trees (low bias, low variance, but unable to extrapolate) while the second step uses Neural Networks (able to extrapolate, but higher variance). We use 35 ensemble members to make these estimates. The average of the ensemble members is used as the final estimate of fCO2sea. Further, the standard deviation of the ensemble members can be scaled (× 5.7) to be used as an analog of the uncertainty. The atmospheric fugacity of carbon dioxide (fCO2atm) is calculated using the NOAA Marine Boundary Layer (MBL) product OR the NOAA CarbonTracker 2022 product (CT), ERA5 sea level pressure. kw is calculated using the Wanninkhof (2014) formulation, but we adjust the coefficient of gas transfer for the ERA5 wind reanalysis product (0.274) so that the global mean kw = 16.5 cm/hr. K0 is calculated using the Weiss (1974) formulation.