EGU24-4358, updated on 08 Mar 2024
EGU General Assembly 2024
© Author(s) 2024. This work is distributed under
the Creative Commons Attribution 4.0 License.

Ice-nucleating particles in springtime cold-air outbreaks associated with Arctic haze

Erin Raif1, Sarah Barr1,2, Mark Tarn1, James McQuaid1, Martin Daily1, Steven Abel3, Paul Barrett3, Keith Bower4, Paul Field3, Kenneth Carslaw1, and Benjamin Murray1
Erin Raif et al.
  • 1Institute for Climate and Atmospheric Science, University of Leeds, United Kingdom
  • 2National Centre for Atmospheric Science, University of Leeds, United Kingdom
  • 3Met Office, United Kingdom
  • 4Department of Earth and Environmental Sciences, University of Manchester, United Kingdom

Concentrations of ice-nucleating particles (INPs) were measured in springtime cold-air outbreaks over the Norwegian and Barents Seas using filter samples taken on board the FAAM BAe-146 aircraft. These measurements of INP concentrations were comparable to the highest INP concentrations previously observed in the Arctic and were similar to typical terrestrial midlatitude INP concentrations. This is important because shallow cloud systems such as those in mid- to high-latitude cold-air outbreaks are highly sensitive to INPs and are a highly uncertain contributor to cloud feedbacks. 

To investigate the types of aerosol responsible for this high INP concentration, we used aerosol-size data from underwing optical probes to derive an active site density of the INP samples. By comparing to laboratory derived active site densities of different aerosol types, this suggested that sea spray was unlikely to be a dominant INP type and that there were likely to be strong biological and dust components to the INP population. Scanning electron microscopy with energy-dispersive spectroscopy used on selected filters revealed that sub-micron particles were dominantly sulphates and carbonaceous, while super-micron particles were dominantly mineral dust.

Samples taken above the cloud decks had greater active site densities than those below, and back-trajectory analysis and meteorological conditions suggested a lack of obvious local INP sources. We hypothesise that the high INP concentration is most likely to be associated with aged aerosol that has accumulated over the Arctic (Arctic Haze).  These high INP concentrations imply that these clouds may have a more negative cloud-phase feedback than their Southern Ocean equivalents.

How to cite: Raif, E., Barr, S., Tarn, M., McQuaid, J., Daily, M., Abel, S., Barrett, P., Bower, K., Field, P., Carslaw, K., and Murray, B.: Ice-nucleating particles in springtime cold-air outbreaks associated with Arctic haze, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4358,, 2024.