2017OSCMICREINPM

Macquarie Island Cloud and Radiation Experiment (MICRE): Ice Nucleating Particle Measurements

1 March 2017 - 31 March 2018

Lead Scientist: Paul DeMott

Observatory: OSC , MCQ

Biological processes in seawater and the sea surface microlayer lead to ice nucleating particle (INP) production in sea spray aerosol (SSA) emissions. Laboratory and some field data indicate that these SSA INPs represent a distinctly different and much less effective INP population in comparison to long range transported desert dust. Over the Southern Ocean (SO), far from land sources, these SSA INPs may dominate in the marine boundary layer, and may thereby influence overlying supercooled cloud properties. In this way, marine INPs may affect cloud phase and lifetime in this sensitive climatic region. A variety of international measurement efforts will be focused in the SO region between now and Spring 2018. The particular effort in this project involves at least twice-weekly collections of filters over a full annual cycle during the Macquarie Island Cloud and Radiation Experiment (MICRE) deployment that includes DOE-ARM, Australian Antarctic Division and Australian Bureau of Meteorology instrumentation for aerosol, cloud, and radiative transfer measurements. Filters collected from March 2017 to March 2018 will be returned frozen and post-processed to determine the temperature spectrum of the concentrations of INPs active via the immersion freezing mechanism across the temperature regime from 0 to -27°C. Additional analyses (thermal, chemical) will be used to discern the microbial and biomolecular organic versus inorganic contributions to INP populations, data of potential use in constraining and revising emission models for organic aerosols and INPs. Portions of samples will be archived frozen for future analyses, such as genetic analyses of biological community diversity in aerosols. Results will provide the first ever annual cycle of marine boundary layer INP characteristics for a fixed site in the SO region, and will therefore be valuable for use in modeling the impacts of marine boundary layer aerosols on climate and radiation via aerosol-indirect effects on the widespread mixed phase clouds present over the SO region.