This project is an airborne field investigation of the physical characteristics of leads in arctic sea ice using a lidar and multi- frequency radiometers to remotely probe the ice surface, as well as of the emission of dimethylsulfide (DMS) from the ocean of its effects on cloud condensation nuclei (CCN), the structure and radiative properties of arctic haze and stratus clouds. The project will make use of an instrumented C-131 aircraft owned by the University of Washington, and will be a component of the Arctic Lead Dynamics Experiment (LEADEX) and the Arctic Gas and Aerosol Sampling Program (AGASP-IV). Although leads, or areas of open water in the sea ice cover, account for only a few percent of the Arctic Ocean, they play a major role in the turbulent transfer of heat to the atmosphere, and in the transfer of volatile biogenic material. This project will concentrate on the flux of oceanic DMS, which is an important contributor to the atmospheric sulfur budget and, through oxidation to sulfur dioxide and sulfates, is a primary source of cloud condensation nuclei in the marine atmosphere. The principal investigator will also study the effect of DMS on arctic haze, which is an atmospheric phenomenon considered to be important in a variety of arctic processes. It affects the radiation budget directly by modifying the albedo and the thermal infra-red flux at cloud top levels, and indirectly through the modulation effect on cloud radiative properties by cloud condensation nuclei. If it can be shown that local Cloud Condensation Nuclei concentrations depend upon DMS emissions, it may be possible to identify a biological control of the arctic marine stratus albedo. It may also be that deposited trace elements from arctic haze contribute significant fluxes of contaminants to sensitive arctic ecosystems.
