The Impact of Sea Spray on the Air-Sea Transport of Heat, Water Vapor, and Gases During a North Atlantic Gale

An investigation of a North Atlantic gale south of Iceland in June 1998 revealed anomalous air-sea fluxes of heat, water vapour, and gases. Underway salinity measurements from the RRS Discovery (as part of the NERC-ACSOE campaign) suggested that the production and evaporation of sea spray were very large and may have dominated the interfacial latent heat flux during the height of the gale. The magnitude of the spray evaporative flux is constrained with a simple data assimilation scheme using the measured underway salinity with a series of upper ocean boundary layer models. Outgassing from the upper ocean, estimated by comparing chemical profiles measured before and after the gale, indicated that there was significant coupling between the atmospheric and oceanic boundary layers. Different gasses had different outgassing characteristics. The extent of outgassing may have depended on the way that the chemical species were destroyed in the overlying atmosphere. The physical and chemical observations are interpreted with a coupled ocean/atmosphere model that combines an upper ocean one dimensional model with a microphysical aerosol model in the lowermost 10 m of the atmosphere. A chemical module is combined within the atmospheric box model to allow the chemical processing of molecules in both the gas and aerosol phases. The results reveal a significant impact of sea spray on the transport of heat and gasses in the upper ocean and lower atmosphere during the gale.