Biologically Mediated Aerosol Precursor Emissions and Secondary Aerosol Formation along the Antarctic Ice Edge
EMILY FRANKLIN, Caleb Mynard, Joel Alroe, Marc Mallet, Ruhi Humphries, Robert Strzepek, Erin Dunne, CSIRO Environment
Abstract Number: 267
Working Group: Remote and Regional Atmospheric Aerosol
Abstract
Volatile organic compounds (VOCs) produced by the interactions of phytoplankton, bacteria, and other members of the marine microbiome play a critical role in the formation of secondary marine aerosol over the ocean. This secondary aerosol material is known to play a critical role in cloud formation in the pristine marine atmosphere. The complex feedback loops between rapidly changing ocean conditions, marine microbiology, associated VOC emissions, and cloud formation over the ocean are incompletely understood and significantly contribute to climate model uncertainties. As part of the Multidisciplinary Investigations of the Southern Ocean (MISO) voyage, the Australian Research Vessel Investigator spent 19 days traversing the biologically productive Antarctic ice edge between 150 and 113 º E between 13 January and 1 February 2024. During the voyage, a suite of research-grade instrumentation was deployed to characterize VOC concentrations, aerosol size distributions, and aerosol composition. Preliminary results point towards particle formation and growth events characterized by rapid depletion of elevated atmospheric dimethyl sulfide (DMS) concentrations and increases in sulfate aerosol and semivolatile organosulfur concentrations. In addition to the ambient measurements, two sets of multi-day mesocosm experiments were conducted, in which natural ice-edge water with its complete microbial community was transferred into two 1,000 L tanks designed with isolated, low-oxidant headspaces. In each experiment, one tank was fertilized with iron while the other was maintained as a control. Preliminary results of the mesocosm studies indicate biologically-mediated changes in the relative distribution of marine organosulfur emissions between DMS and other species, particularly methanethiol (MeSH), as well as light-dependent emissions of isoprene. Together, these observations and experiments advance our mechanistic understanding of the complex feedback loops connecting ocean, aerosol, cloud, and climate.