Atmosphere-Ocean Feedback From Wind-Driven Sea Spray Aerosol Production

Geophysical Earth Letters (2021)

Atmosphere-Ocean Feedback From Wind-Driven Sea Spray Aerosol Production

Atmospheric aerosols can have a cooling influence on Earth’s climate by scattering sunlight and seeding cloud formation. Over oceans, aerosols often contain a high fraction of sea spray, and their abundance is strongly dependent on wind speed. High wind speeds cause wave breaking and bubble bursting, which emit sea spray aerosol (SSA). Previously SSA has been shown to have a cooling influence on surface climate. We show that when we artificially enhance SSA emissions in a coupled Earth system model that about half of the cooling influence is offset by the ocean response; more SSA emitted from the ocean leads to surface cooling, and therefore wind speeds weaken and produce less SSA. This is particularly important over the Southern Ocean which is the windiest region on Earth year-round. We show that, in a climate model, the strength of the feedback depends on how SSA emission is represented by the model. Therefore in a warmer, windier climate, simulating SSA accurately will be critical for understanding natural versus human influences on climate.