GISS Lunch Seminar Speaker: Hannah M. Horowitz (UIUC) Topic: Chemistry and climate feedbacks of sea salt aerosol emissions: From the subtropics to the poles Sea salt aerosols influence climate by directly scattering radiation and serving as cloud condensation nuclei. While a natural aerosol source, sea salt emissions are influenced by climate change. This occurs both through dependencies on sea surface temperatures and windspeed on a global scale, and in polar regions, sea ice cover and properties influence additional emissions processes including from sea ice leads, or cracks in sea ice, and blowing saline snow. Sea salt aerosols are also the largest source of tropospheric reactive halogens globally, which play a key role in the atmosphere’s oxidative potential and the chemistry of mercury, ozone, methane, and other aerosol species like nitrates, leading to additional feedbacks on pollution and climate. Here I will present recent work in our group simulating the impacts of sea salt aerosol emissions 1) from sea ice leads in the Arctic; 2) for Marine Cloud Brightening climate intervention; and 3) over the Benguela upwelling system off the coast of Southern Africa along with other marine aerosols. For each, we develop and apply the GEOS-Chem 3-D atmospheric chemical transport model. To simulate emissions from Arctic sea ice leads in particular, we also have incorporated satellite retrievals of sea ice lead fractions from AMSR-E and MODIS into our parameterizations. Our results will inform the relative importance of different emissions processes with respect to sea salt and total aerosol in the Arctic and over the Benguela and how this has changed under recent climate change, as well as the unintended feedbacks of intentional sea salt aerosol emissions for Marine Cloud Brightening on pollutants and greenhouse gases.