1. The potential influence of marine biological activity on ice nuclei concentrations over the Southern Ocean Susannah Burrows 1,2 with contributions from: C. Hoose 3, U. Pöschl 2, M. G. Lawrence 2,4 1 – Pacific Northwest National Laboratory 2 – Max Planck Institute for Chemistry 3 – Karlsruhe Institute of Technology 4 – Institute for Advanced Sustainability Studies Burrows, S. M., Hoose, C., Pöschl, U., and Lawrence, M. G.: Ice nuclei in marine air: biogenic particles or dust?, Atmos. Chem. Phys., 13, 245-267, doi:10.5194/acp-13-245-2013, 2013.

2. Do biological / biogenic particles matter for ice nuclei (IN) populations? Globally, the most-important and best-studied ice nuclei are dust (and soot), BUT: Some biological / biogenic particles are more efficient IN than dust, particularly at warmer temperatures. Might induce freezing earlier, changing cloud development Emerging picture: a possible role for biological / biogenic particles as IN under certain conditions: Possible role of organic / biological material in enhancing IN activity of dust (Schnell and Vali, 1972; Pratt et al., 2009; Conen et al., 2011, others) Pristine, biologically active continental environments in absence of dust (“green ocean”) (Prenni et al., 2009) Warm, low-altitude mixed-phase clouds (Spracklen and Heald, 2013) Marine environments? (Bigg, 1973; Schnell and Vali, 1976; Burrows et al., ACP, 2013, Knopf et al., 2012, others) 2

3. Measurements of IN concentrations in marine air

4. IN concentrations compared to Chl-a distribution 4 In situ data: Bigg, 1973; Chlorophyll: MODIS climatology Chl-a in µg m -3 B73 IN counts (different color scale) Schnell and Vali (1976): Possible marine biological source of IN? Burrows et al., ACP, 2013

5. Marine biological IN estimate 5 Satellite data: proxies for marine biological activity (POC, Chl-a) Model parameterization: Sea spray emissions Intermediate result from simulations: Particulate organic matter in sea spray In situ data: IN concentration in marine plankton bloom Result: IN estimate in sea spray Comparison with filter measurements and estimated dust IN concentrations Satellite: POC Burrows et al., ACP, 2013 Comparison at -15°C (from B73)

6. Simulated POM concentrations 15 Burrows et al. (2013) Vignati et al. (2010) Particulate organic matter (POM), μg m -3 Burrows et al., ACP, 2013

7. Comparison of proposed marine biological IN distribution with estimated dust IN distribution Burrows et al., ACP, 2013

8. Upper bound: BIO-IN ∙ 10 {or dust IN ∕ 10 } Marine biological IN: percent contribution to total simulated IN (total = dust + marine biological) - compared at -15°C - in MBL - annual mean 8 Burrows et al., ACP, 2013 UPPER BEST

9. Moving sea spray chemistry forward Empirical parameterizations  semi-mechanistic Chl-a (correlated)  surfactants (causal) Extrapolate from blooms  Account for different chemistry in gyres 9 Burrows et al., ACPD, 2014 Gantt et al., 2011 Burrows et al., ACPD, 2014