Measurement Report: A comparison of ice-nucleating particle and cloud condensation nuclei sources and properties during autumn at contrasting marine and terrestrial locations

Ice-nucleating particles (INPs) are an important class of aerosols found worldwide that have far-reaching but poorly quantified climate feedback mechanisms through interaction with clouds and impacts on precipitation. These particles can have highly variable physicochemical properties in the atmosphere, and it is vital to measure their concentration and interconnection with other ambient aerosol populations at a wide variety of sites to comprehensively understand aerosol-cloud interactions in the atmosphere. Toward this aim, we have measured INP concentrations at two contrasting sites, one in the Southern Great Plains (SGP) region of the United States with a substantial terrestrially influenced aerosol population, and one in the Eastern North Atlantic Ocean (ENA) with a primarily marine-influenced aerosol population. These measurements were made at a high time resolution for at least 45 days at each site. From our ENA data, a singular relationship between cloud condensation nuclei (CCN) and INPs was found, suggesting that INPs and CCN originated from the same population of aerosols and potentially the same source. Backward air mass trajectories reveal a strong marine influence at ENA with most air masses originating over the Atlantic Ocean, but analysis of particle chemistry suggested an additional mineral dust INP source at ENA that did not contain large quantities of organic material. This relationship between CCN and INPs was not seen at SGP, and in fact has never been detected before, suggesting that the aerosol particles collected at ENA may represent a unique class of marine aerosols that contain both mineral dust and organics internally mixed in the aerosols and that are capable of acting as both CCN and INPs.