PCO2A - Ocean Observatories Initiative

Located at the sea surface, the pCO2 Air-Sea sensor measures the partial pressure of carbon dioxide (pCO2) in both the atmosphere and ocean. The Pro-Oceanus CO2-Pro Atmosphere instrument is comprised of a CO2-Pro that mounts beneath a buoy for water measurements, connected to a NEMA box that is used to take in air from above the buoy. Alternating measurements of pCO2 in air and water made with the same detector ensure a high level of accuracy for reliable calculations of CO2 flux.

The OOI Level 1 Partial Pressure of CO2 in Air and Surface Seawater core data products (PCO2ATM and PCO2SSW) are created by converting the Level 0 CO2 Mole Fractions (XCO2ATM or XCO2SSW, in ppm), into μatm units by using an equation that incorporates the L0 Gas Stream Pressure (PRESAIR, in mbar). The instrument computes the xCO2 value internally by measuring the infrared absorbance level of CO2 and compensating for the measured pressure, temperature, and humidity. The Level 2 flux of CO2 across the air-sea interface (L2 CO2FLUX data product) is computed from in situ measurements of the partial pressures of carbon dioxide in both the surface ocean and the overlying air. The flux is then estimated as proportional to the difference of these partial pressures. The proportionality factor is parameterized using the wind speed, and sea surface temperature and salinity are used to further adjust this factor. See data product specifications (linked below) for computational details.

Data Products

This instrument measures the following data products. Select a data product's name to learn more.

Data Product	Code	DPS
Flux of CO2 from the Ocean into the Atmosphere	CO2FLUX	DPS
Partial Pressure of CO2 in Atmosphere	PCO2ATM	DPS
Partial Pressure of CO2 in Surface Sea Water	PCO2SSW	DPS
PCO2A Gas Stream Pressure	PRESAIR	DPS
CO2 Mole Fraction in Atmosphere	XCO2ATM	DPS
CO2 Mole Fraction in Surface Sea Water	XCO2SSW	DPS

The algorithm code used to generate data products for this instrument is also available in the ion-functions GitHub repository.

Algorithm Code

Instrument Models & Deployed Locations

The OOI includes the following instrument makes and models for this instrument type. Follow the links below to find out where in the OOI this instrument has been deployed. You'll also find quick links for each instrument to Data Explorer, where you can plot and access data.

Class-Series	Make	Model
PCO2AA	Pro-Oceanus	pCO2-pro

The CO2-Pro Atmosphere NEMA box, used to take in air from above the buoy. (Image courtesy Pro-Oceanus; http://www.pro-oceanus.com/co2-pro-atmosphere.php)