AAAR 37th Annual Conference October 14 - October 18, 2019 Oregon Convention Center Portland, Oregon, USA
Abstract View
Comparison of Antarctic and Arctic Seasonal Cycles of Aerosol Chemical Components
LYNN RUSSELL, Amanda Frossard, Patricia Quinn, Sangeeta Sharma, Richard Leaitch, Dan Lubin, Scripps Institution of Oceanography
Abstract Number: 845 Working Group: Remote and Regional Atmospheric Aerosol
Abstract In this study, we compare the Antarctic and Arctic seasonal cycle of aerosol chemical components. The distribution of aerosol particles in the Antarctic is characterized by its unique location and surrounding ocean (which largely isolates it from the sources present in other continents), its near-complete coverage by ice and snow (which eliminates most local dust and terrestrial biological particle sources), and its near-absence of human activities (which minimizes the emissions from combustion, cooking, and other human activities). The lack of orographic features in the Southern Ocean surrounding Antarctica supports the midlatitude westerlies, effectively overriding substantial transport of continental emissions into the Antarctic region. The result is that aerosol concentrations reflect the seasonal trends of ocean phytoplankton (sulfate), seabirds (organic), and wind-driven sea spray (salt).
The highest sulfate and organic mass concentrations in the annual cycles in the Arctic at both Barrow and Alert show the well-known springtime haze that results from transport from the northern mid-latitudes. The overall low concentrations of submicron mass concentration are otherwise a common feature of the Arctic and Antarctic. The spring sulfate mass concentrations exceed summer and winter by a factor of more than 2, obscuring the smaller differences between summer and winter seasons. The Barrow and Alert measurements both show higher salt in winter, which likely tracks with winds but could be either from transported sea spray or frost flowers or possibly blowing snow. The prevalence of nearby new sea ice and the depletion of Na relative to Cl are consistent with frost flowers being a main contribution. Another interesting difference is the relative amount of sulfate to organic, which is nearly 1:1 in summer at AWARE and Barrow, but it exceeds 2:1 at Alert, especially in early spring. The higher organic and sulfate mass concentration in summer in Antarctica is coincident with higher concentrations of CCN at supersaturations of 0.1% and 1%. This correlation means that the biogenic sulfate and organic sources may well both contribute significantly to summertime CCN concentrations. The relationship between biogenic sulfate and organic means that both can have an effect on cloud droplet number concentrations, potentially decreasing cloud drop effective radius and shortwave reflection.