Flux of CO₂ Between Ocean and Atmosphere

Understanding air-sea gas exchange is important for improving storm forecasting and climate-change models, as well as for estimating the exchange of carbon between the upper and deep ocean. The datasets highlighted in this nugget showcase three different regimes of air-sea flux of CO₂. The OOI Coastal Endurance Array represents a coastal upwelling area where during times of upwelling, CO₂-rich deep water reaches the surface where it is outgassed into the atmosphere. The outgassing of upwelled water is then followed by a period of net intake of CO₂ due to increased primary production from the nutrients upwelled with the CO₂. The OOI Coastal Pioneer Array, off the coast of New England, in contrast, is not an upwelling zone, but is an area of high productivity. As phytoplankton blooms occur, particularly in the winter/spring time period, there is a net flux of CO₂ into the ocean. During the summer months as the surface water warms, the water can no longer hold as much CO₂ and there is a small (relative to the upwelling) net outgassing. The cold, productive waters of the OOI Global Argentine Basin Array are a net sink for CO₂ year round.

pCO₂ Air-Sea instruments are located on surface buoys with one probe in the air and one probe in the water to measure the partial pressure of CO₂ in both the atmosphere and the ocean. From these measurements, CO₂ flux from the ocean to the atmosphere can be calculated to determine which locations and time periods the ocean is a source vs a sink of CO₂.

Calculating air-sea gas exchange depends on the saturation of the gas in the water and wind speed. For example, the more saturated the water is with CO₂ and the faster the wind is blowing across the water, the higher the flux of CO₂ out of the water. Solubility of a gas in seawater is determined by the temperature and salinity of that water. Wind speed data used in this calculation are from meteorological sensors located on the tower of each surface buoy. For more information on how to calculate CO₂ flux, check out the Data Product Specification document. Note, positive values indicate flux from the ocean into the atmosphere.

Data included in the below graphs and csv files represent CO₂ flux data calculated through these measures. Data provided in the csv file only includes the CO₂ data and does not include the meteorological data used in the calculations. However, the CO₂ flux calculation instructions in the Python code does include instructions for pulling the necessary meteorological data to make the calculations. Additionally, corresponding meteorological data can accessed on OOINet (Endurance, Pioneer, Argentine) and Data Review Pages (Endurance, Pioneer, Argentine).