NDP-110 (2023)

NCEI Accession 0279118 Data and Documentation Files

A novel sea surface partial pressure of carbon dioxide (pCO2) data product for the global coastal ocean resolving trends over the 1982-2020 period (NCEI Accession 0279118)

Alizée Roobaert^1,2, Pierre Regnier¹, Peter Landschützer², Goulven G. Laruelle¹

Prepared by Alex Kozyr³

¹Department of Geosciences, Environment & Society-BGEOSYS, Université Libre de Bruxelles, Belgium
²Flanders Marine Institute (VLIZ), Ostend, Belgium
³National Centers for Environmental Information, National Oceanic and Atmospheric Administration, 1315 East-West Highway, Silver Spring, MD 20910-3282

Abstract

This dataset contains continuous monthly maps of sea surface partial pressure of CO₂ (pCO₂) in the coastal ocean from 1982 to 2020. This product is an updated version of the coastal product of Laruelle et al. (2017) and has been created using a 2-step Self Organizing Maps (SOM) and Feed Forward Network (FFN) method and uses ~ 18 million direct observations from the latest release of the Surface Ocean CO₂ database (SOCATv2022, Bakker et al., 2014, 2022). In a first step, the global coastal ocean is divided into 10 biogeochemical provinces using SOM, which group regions with similar environmental properties. Then, for each province, the FFN algorithm reconstructs nonlinear relationships between a set of environmental variables (e.g., sea surface temperature, salinity...) and the observed pCO₂. These relationships are then used to perform the spatiotemporal pCO₂ extrapolation in regions and time periods where data are lacking. The output consists of continuous monthly pCO₂ maps for the coastal ocean, with a spatial resolution of 0.25°, covering the 1982-2020 period. Additionally, this new coastal pCO2 product is used to generate a new coastal air-sea CO₂ exchange (FCO2) product for each grid cell at the monthly time scale from 1982 to 2020 using the following equation: FCO2=k∙K0∙∆pCO2∙(1-ice) where FCO2 represents the coastal air-sea CO₂ exchange (in mol C m-2 yr-1). By convention a positive FCO₂ value corresponds to a CO₂ source for the atmosphere. ∆pCO₂ represents the difference between the oceanic pCO₂ and the atmospheric pCO₂ (in atm). K0 (mol C m-3 atm-1) represents the CO₂ solubility in sea water which is a function of SST and SSS following the equation of Weiss et al. (1974). k represents the gas exchange transfer velocity (m yr-1) which is a function of the second moment of the wind speed and is calculated using the equation of Ho et al. (2011) and the Schmidt number based on the equation of Wanninkhof et al. (2014). The sea-ice coverage is represented by the term ice and has no units.

Please cite this data set as:

Roobaert, Alizée; Regnier, Pierre; Landschützer, Peter; Laruelle, Goulven G. (2023). A novel sea surface partial pressure of carbon dioxide (pCO2) data product for the global coastal ocean resolving trends over the 1982-2020 period (NCEI Accession 0279118). NOAA National Centers for Environmental Information. Dataset. https://doi.org/10.25921/4sde-p068.

Content:

ULB-SOM-FFN-coastalv2.nc

The netcdf file contains:

• lat: latitude in degrees North (89.875°S – 89.875°N with 0.25° resolution).
• lon: longitude in degrees East (179.875°W-179.875°E with 0.25° resolution).
• time: time in seconds since 2000-01-01-00:00 (monthly resolution).
• fco2: air-sea CO2 flux density (FCO2, in mol C m-2 yr-1).
• pco2: sea surface partial pressure of CO2 (pCO2, in μatm).
• dpco2: delta pCO2 (ΔpCO2, in μatm) calculated as the CO2 partial pressure difference between atmosphere and the raw surface ocean partial pressure and used to calculate the air-sea CO2 exchange. The atmospheric pCO2 is calculated from the dry air mixing ratio of CO2 (xCO2) provided by the NOAA Marine Boundary Layer reference product (https://www.esrl.noaa.gov/gmd/ccgg/mbl/) assuming 100 % humidity at the air-sea interface (following calculation specified in Dickson et al., 2007) and using the NCEP reanalysis total pressure at sea level (Kalnay et al., 1996).
• mask: coastal mask defined as "global coastal mask that excludes estuaries and inland water bodies while its outer limit is set 300 km away from the shoreline leading to a total surface area of 77 million km²" (see Laruelle et al., 2017).
• surface: surface area (in km²).
• k: gas exchange transfer velocity (k, in m yr-1, 0.251*wind_speed_second_moment*((sc./660)^(-0.5))*87.6581277).
• sol: CO2 solubility (K0, in mol m-3 atm-1). K0 is calculated using the equation of Weiss et al. (2007) with the monthly means of the daily NOAA OI SST V2 (Reynolds et al., 2007) and of the daily Hadley center EN4 SSS (Good et al., 2013).
• ice: sea-ice coverage (ice, no units) calculated as the monthly mean of the daily 0.25° dataset of Reynolds et al. (2007).
• wind_speed_second_moment: second moment of the wind speed (in m2 yr-2) from the global atmospheric reanalysis ERA-interim wind product (Dee et al., 2011).
• sc: schmidt number (no units).
	

Reference:

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Bakker, D. C., Alin, S. R., Becker, M., Bittig, H. C., Castaño-Primo, R., Feely, R. A., ... & Wilson, D. (2022). Surface Ocean CO2 Atlas Database Version 2022 (SOCATv2022) (NCEI Accession 0253659).
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