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SUMMARY:A marine biogenic source of atmospherically relevant ice nucleatin
 g particles - Dr Theo Wilson\, University of Leeds
DTSTART:20160215T141500Z
DTEND:20160215T151500Z
UID:TALK63780@talks.cam.ac.uk
CONTACT:Paul Griffiths
DESCRIPTION:There are limited observations describing marine sources of ic
 e nucleating particles (INPs)\, despite sea spray aerosol being one of the
  dominant sources of atmospheric particles globally. Evidence indicates th
 at some marine aerosol particles act as INPs\, but the source of these par
 ticles is unclear. The sea surface microlayer is enriched in surface activ
 e organic material representative of that found in sub-micron sea-spray ae
 rosol. We show that the sea surface microlayer is enriched in INPs that nu
 cleate ice under conditions pertinent to both high-altitude ice clouds and
  low to mid-altitude mixed-phase clouds. The INPs pass through 0.2 µm por
 e filters\, are heat sensitive and spectroscopic analysis indicates the pr
 esence of material consistent with phytoplankton exudates. Mass spectromet
 ric analysis of solid phase extracted dissolved organic material from micr
 olayer and sub-surface water samples showed that the relative abundance of
  certain ions correlated with microlayer ice nucleation activity. However\
 , these ions were not themselves directly responsible for ice nucleation. 
 We propose that material associated with phytoplankton exudates is a candi
 date for the observed activity of the microlayer samples. We show that lab
 oratory produced exudate from a ubiquitous marine diatom contains INPs des
 pite its separation from diatom cells. Finally we use a parameterisation o
 f our field data to estimate the atmospheric INP contribution from primary
  marine organic emissions using a global model and test the model against 
 existing INP measurements in the remote oceans. We find that biogenic mari
 ne INPs can be dominant in remote marine environments\, such as the Southe
 rn Ocean.
LOCATION:Unilever Lecture Theatre\, Department of Chemistry
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