Marine ice nucleating particle (INP) emissions are an important source of uncertainty in modelling cloud dynamics and radiation balance over oceans, yet we know little about which aerosols nucleate ice, their numbers or seasonality. INP concentrations from measured oceanic regions are typically low, but include some intriguing reports of high levels occurring above upwelling convergence regions with high biological productivity. Mesocosm experiments at the Center for Aerosol Impacts on the Climate and the Environment simulate, under controlled conditions, the complex microbial successions that occur during marine phytoplankton blooms. During two diverse mesocosm experiments we measured the concentrations and characteristics of INPs in sea-spray aerosol generated using two bubble bursting processes (plunging water or wave crashing). INPs in aerosol were measured and collected in real-time using the Colorado State University’s continuous flow diffusion chamber (CFDC), and on filters using an immersion freezing technique. To characterize the INPs as biological entities (eg, bacteria or viruses) or their byproducts (eg, ice nucleating monolayers of aliphatics), tests included H2O2 oxidation, heat treatment, size filtration, and PCR for ice nucleation active bacteria. Direct measurements of INP identities was achieved via transmission electron microscopy and micro-Raman spectroscopy analyses of ice crystal residuals collected downstream of the CFDC. Highest numbers of INPs emitted were observed 3-5 days after peak bloom chlorophyll concentrations, subsiding again over the following several days. In the wave flume, flocs of organic, ice nucleation active “marine snow” sedimented after the blooms. These results suggest that the chemistry of oceanic life processes are a complex and dynamic modifier of organic marine INP emissions.

Characteristics of ice nucleating particles in seawater and sea spray aerosol produced during laboratory phytoplankton blooms

251st National Meeting (2016)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.