Ice-nucleating particles over the Labrador Sea during the M-Phase campaigns

• Main Author: Gallagher, Martin
• Format: Conference Object
• Language: unknown
• Published: 2024
• Subjects: Greenland; Labrador Sea; Sea ice
• Online Access: https://research.manchester.ac.uk/en/publications/267630c6-5471-42a7-a3b2-3d60b09508dc; https://doi.org/10.5194/egusphere-egu24-9453

As the Earth warms, it is important to understand how a change in the ice:water ratio in mixed-phase clouds influences the cloud-phase feedback; a cooling effect caused by the change in albedo of the cloud. Ice-nucleating particles (INPs), aerosols that can trigger the freezing of liquid cloud droplets via heterogeneous nucleation, may regulate this cooling process by maintaining the ice contents in clouds, hence it is necessary to identify the types, sources, and concentrations of INPs to determine their contribution and better represent this in models. We undertook ship and aircraft-based INP measurement campaign in the Labrador Sea region, which features clouds that are susceptible to the effect of INPs, in 2022: (i) a cruise on the RRS Discovery, as part of a joint SEANA/M-Phase project in May-June, and (ii) a flight campaign on the FAAM BAe-146 aircraft as part of the M-Phase project in October-November that focused on northwesterly cold air outbreak (CAO) cloud systems. During the SEANA/M-Phase ship cruise, real-time measurements of INP concentrations were taken using a Portable Ice Nucleation Experiment (PINE) expansion chamber alongside offline filter-based measurements and bulk seawater measurements. Preliminary results suggest that high INP concentrations correlated with air masses that had passed over the exposed (i.e. not snow- or ice-covered) coastline of Greenland, while lower concentrations correlated with air masses that had passed over the sea ice. These results suggest a high-latitude source of INPs not currently accounted for in models, the study of which could be crucial in understanding their influence on clouds in a changing climate. Offline filter-based INP measurements during the FAAM aircraft campaign showed highly reproducible INP concentrations during CAO events (0.05 INP L−1 at −15 °C), with both much higher and much lower concentrations during non-CAO days. Further analysis will include further processing of the campaign data, including aerosol size distributions together with ...