UC San Diego

Tropospheric marine aerosol presence in the western Antarctic is coupled to physical and biological processes. These aerosols may be biogenic, formed from the activity of primary producers, and can be associated with seasonal dynamics of sea ice melt and phytoplankton blooms. These aerosols may also influence local environments of polar regions by absorbing and scattering solar radiation and by initiating cloud formation. To study tropospheric marine aerosol in the remote marine Bellingshausen Sea environment, we used a specialized instrument onboard the NASA Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) capable of detecting the presence of aerosols at altitudes close to the sea surface. We termed this measurement marine aerosol optical depth (MAOD). To further support these observations, we also examined coarse-mode aerosol optical depth (AODC), often used as a proxy for sea spray aerosol (SSA). We used MAOD and AODC to examine trends in marine tropospheric aerosol and undertook a multi-year remote sensing analysis in the Bellingshausen Sea from 2006-2018.

Across open ocean to coastal regions, daily fluctuations in nighttime and daytime winds, respectively, drove increasing MAOD and AODC. MAOD depicted strong correlations with wind speed across the open ocean and weak correlations in coastal regions, suggesting that daily fluxes in wind speed drive the production of SSA. In the open ocean, we further observed that warmer SST enhanced AODC and the associated production of SSA, supporting prior studies. We also observed seasonal increases in MAOD alongside a seasonal increase in chl-a and the melt of sea ice; these patterns suggest that biological activity of primary producers likely contributed towards magnitudes of marine tropospheric aerosol. This work is also the first to distinguish a late winter to early spring temporal MAOD signal, likely tied to an aerosol source from either venting of biogenic aerosol from breaks in sea ice or to the production of SSA resulting from pulses in wind speed. Our work extends upon previous findings of marine aerosol in polar environments and more fully characterizes interactions during polar winter.