Surfactants’ global regulation of CO2 fluxes across the air-sea interface

The sea surface microlayer (SML) refers to the uppermost millimeter of the ocean surface that is in direct contact with the atmosphere. It has physicochemical and biological properties that are distinct from the underlying water and its properties determine air-sea exchange of momentum, mass and energy. Gas transfer velocity is mostly determined by wind forcing, where gas transfer is enhanced at low to moderate wind speeds. However, biological and pollutant enrichment of the SML with surfactants reduces gas transfer by suppressing turbulence and damping waves. Local impacts from surfactants can be significant, reducing air-sea gas transfer by single to double-digit percentages at moderate wind speeds.

I calculate a timeseries of contemporary global air-sea CO₂ fluxes using FluxEngine, adjusting the calculation for the presence of biological surfactants. Surfactant suppression of air-sea gas transfer is estimated as a function of total organic carbon concentration, which is in turn estimated using global satellite products of particulate and dissolved organic carbon. Results will be compared to previous regional estimates of surfactant regulation of CO₂ fluxes. This approach will produce a novel global estimate of biological surfactants’ regulation of CO₂ fluxes across the air-sea interface, supporting further work isolating pollutants’ role in regulation of gas transfer.