The influence of short-term wind variability on air-sea CO2 exchange

Abstract

Quantifying the regional and global exchange of CO2 between the ocean and atmosphere requires knowledge of the factors that affect CO2 gas transfer (e.g., wind speed) and the air-sea difference in partial pressure of CO2 (ρCO2). A major uncertainty is the effect of short-term variability on air-sea CO2 flux. Using high sampling frequency wind speed and ρCO2 data collected during deployments of the autonomous CARbon Interface OCean Atmosphere (CARIOCA) buoy, we compare CO2 fluxes at different sampling frequency of wind speed (i.e., hourly versus daily averaged). Air-sea CO2 flux was up to three times greater if high frequency wind data was used rather than daily average values. This difference arises from the non-linear relationship between wind speed and CO2 gas transfer coefficient, and a better representation of wind distribution at a higher frequency (i.e., hourly) of sampling. This finding has significant implications for determining regional and global air-sea CO2 fluxes, and understanding of the global carbon cycle.