Estimating Contributions of Potential Sea Salt Aerosol Sources to the Arctic Using Satellite Data

Abstract:

The Arctic is undergoing rapid climate change, including in sea ice. Aerosol particles can alter climate by reflecting sunlight in summer and forming clouds that trap heat at the surface in winter. The dominant sources of observed sea salt aerosol during the cold season in the Arctic are currently debated. Field measurements near Utqiaġvik, Alaska suggest cracks in the sea ice, or “leads”, through which sea spray can release salt may be important. In Antarctica, recent field campaigns have observed salty snow on young sea ice blown into the air by high winds, but it is not clear whether conditions in the Arctic are as favorable We use satellite observations to estimate the potential contribution of leads and blowing snow on first-year sea ice to sea salt aerosol emissions in the Arctic. We calculate the area of sea ice leads from the Integrated Climate Data Center lead area fractions, derived from AMSR-E passive microwave brightness temperatures. For the area of first-year sea ice, we combine MEaSUREs sea ice age (derived from SSM/I, SSMIS, SMMR, AMSR-E, and AVHRR satellite data) with monthly sea ice concentration climatologies determined from SMMR and SSM/I-SSMIS data. In addition, we estimate the area of snow-covered first-year sea ice by combining these results with SMMR and SSM/I-SSMIS snow cover data. We analyze and compare the spatial and temporal patterns of monthly-mean lead area and (snow-covered) first-year sea ice area in the Arctic from 2002 – 2011, when both datasets are available. From this analysis, we determine the maximum potential contribution of each source to sea salt aerosol emissions in different sectors and months, as well as temporal trends. This work will inform further development of Earth system models, which are currently missing these sources of sea salt aerosol, in order to better represent Arctic aerosol and climate.