Impacts of Sea Ice Leads on Sea Salt Aerosols in the Arctic: Insights from Observations and Modeling

Description

Sea salt aerosols are a major contributor to total aerosol in the Arctic. The dominant sources of sea salt aerosol in the Arctic during the cold season, when concentrations are at their peak, are still under debate. Recent observations suggest open leads in sea ice may play a dominant role. This source is currently missing from climate models, leading to potentially large biases in simulations of Arctic aerosols, clouds, and radiation and a critical gap in our understanding of future Arctic climate change. We analyze ground-based observations of aerosol chemical composition and properties, combined with satellite-retrieved lead area to assess the impacts of sea ice leads on sea salt aerosol in the Arctic atmosphere. Here we focus on sodium concentrations from three Arctic stations during the period of available lead fraction data from the AMSR-E satellite (November-April, 2002 - 2011). We select high lead fraction and low lead fraction days for each site based on statistical analysis of the lead fraction in a 50- and 100-km radius of each site. We then compare the aerosol sodium concentrations between the high and low lead fraction days. We find statistically significant differences between the sodium concentration distributions that imply the presence of sea ice leads impacts the surrounding concentration of sea salt aerosols. We combine this analysis with windspeed and wind direction data, where available, to further assess lead influence. We also simulate the emissions of sea salt aerosols from sea ice leads in the Arctic using the 3‐D atmospheric chemical transport model GEOS‐Chem for the years 2002-2008. From this, we quantify the impacts on total sea salt aerosol loading and the resulting atmospheric chemistry including bromine and ozone. These results will inform parameterization development of sea ice lead emissions within E3SM.