Scripts used in paper Multi-year Seasonal Trends in Sea Ice, Chlorophyll Concentration, and Marine Aerosol Optical Depth in the Bellingshausen Sea

These scripts are authored by S. Dasarathy. You can find more information by clicking the manuscript link above! Please feel free to reach out to me at srdasara@ucsd.edu, and by checking out my blog-post series on this study here!

Plain Language Summary:
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) and examined MAOD from 2006-2018. We found that the presence of aerosol increases alongside blooms of phytoplankton and sea ice melt, as predicted from prior studies, suggesting a biological source. We also find an increase in aerosol that may be linked to degassing of biogenic aerosol or seasonal increases in wind speed, which may indicate the presence of sea spray or sea salt. This work enriches our knowledge of the interwoven relationship between the surface ocean and the overlying atmosphere in this region of our planet.

Scientific Abstract:
This study presents seasonal trends in marine tropospheric aerosol arising from the interplay between physical and biological processes in the Western Antarctic Peninsula. Remote sensing-based studies focused on aerosol distribution and links to chlorophyll-a concentration and sea ice predominantly use passive sensor retrievals of aerosol optical properties. However, these data are subject to cloud presence, signal uncertainties, and lack of retrievals in high latitude wintertime. To address these concerns, we have developed a method of quantifying tropospheric marine aerosol with the NASA Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO), which we term marine aerosol optical depth (MAOD). MAOD may be retrieved in nighttime conditions of high-latitude winter and is devoid of cloud contamination, thereby advancing upon prior aerosol optical depth (AOD) measurements linked with biogenic aerosol. To examine trends in tropospheric marine aerosol, we undertook a multi-year remote sensing analysis in the Bellingshausen Sea from 2006-2018. A seasonal increase in MAOD was observed alongside a seasonal increase in chl-a and sea ice melt, suggesting a biogenic component to aerosol presence. To the best of our knowledge, this study is also the first to further 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 sea spray/salt aerosol resulting from pulses in wind speed. Our work extends upon previous findings of AOD in polar environments and now more fully characterizes interactions during polar winter.