Ship-based measurements of ice nuclei concentrations over the Arctic, Atlantic, Pacific and Southern Ocean

• Main Authors: Welti, André, Bigg, E. Keith, DeMott, Paul J., Gong, Xianda, Hartmann, Markus, Harvey, Mike, Henning, Silvia, Herenz, Paul, Hill, Thomas C. J., Hornblow, Blake, Leck, Caroline, Löffler, Mareike, McCluskey, Christina S., Rauker, Anne Marie, Schmale, Julia, Tatzelt, Christian, Pinxteren, Manuela, Stratmann, Frank
• Format: Text
• Language: English
• Published: 2020
• Subjects: Arctic; Pacific; Southern Ocean; Antarc*; Antarctica
• Online Access: https://doi.org/10.5194/acp-2020-466; https://www.atmos-chem-phys-discuss.net/acp-2020-466/

Ambient concentrations of ice-forming particles measured during ship expeditions are collected and summarized with the aim of establishing a spatial distribution and variability of ice nuclei in oceanic regions. The presented data from literature and previously unpublished data from over 23 months of ship-based measurements stretch from the Arctic to the Southern Ocean and include a circumnavigation of Antarctica. In comparison to continental observations, ship-based measurements of ambient ice nuclei show one to two order of magnitude lower mean concentrations. To quantify the geographical variability in oceanic areas, the concentration range of potential ice nuclei in different climate zones is analysed by meridionally dividing the expedition tracks into: tropical, temperate and polar climate zones. We find that concentrations of ice nuclei in these meridional zones follow temperature spectra with similar slope, but vary in absolute concentration. Typically, the frequency with which specific concentrations of ice nuclei are observed at a certain temperature follows a log-normal distribution. A consequence of the log-normal distribution is that the mean concentration is higher than the most frequently measured concentration. Finally, the potential contribution of ship exhaust to the measured ice nuclei concentration on board of research-vessels is analysed as function of temperature. We find a sharp onset of the influence at approximately −36 °C, but none at warmer temperatures that could bias ship-based measurements.