On the annual variability of Antarctic aerosol size distributions at Halley research station

Research output: Contribution to journalArticle

Authors

  • Thomas Lachlan-Cope
  • Neil Brough
  • Anna E. Jones
  • Angelo Lupi
  • Young Jun Yoon
  • Aki Virkkula
  • Manuel Dall'Osto

Colleges, School and Institutes

External organisations

  • Department of Environmental Sciences/Center of Excellence in Environmental Studies, King Abdulaziz University
  • British Antarctic Survey, NERC, High Cross, Madingley Rd, Cambridge, CB3 0ET, UK
  • Institute of Polar Sciences (ISP), National Research Council (CNR), via P. Gobetti 101, 40129 Bologna, Italy
  • Institute for Atmospheric and Earth System Research, University of Helsinki, 00014 Helsinki, Finland
  • Korea Polar Research Institute
  • Institute of Marine Sciences, ICM-CSIC, Passeig Marítim de la Barceloneta, 37-49. E-08003, Barcelona, Spain

Abstract

The Southern Ocean and Antarctic region currently best represent one of the few places left on our planet with conditions similar to the preindustrial age. Currently, climate models have a low ability to simulate conditions forming the aerosol baseline; a major uncertainty comes from the lack of understanding of aerosol size distributions and their dynamics. Contrasting studies stress that primary sea salt aerosol can contribute significantly to the aerosol population, challenging the concept of climate biogenic regulation by new particle formation (NPF) from dimethyl sulfide marine emissions.We present a statistical cluster analysis of the physical characteristics of particle size distributions (PSDs) collected at Halley (Antarctica) for the year 2015 (89 % data coverage; 6–209 nm size range; daily size resolution). By applying the Hartigan–Wong k-mean method we find eight clusters describing the entire aerosol population. Three clusters show pristine average low particle number concentrations (< 121–179 cm−3) with three main modes (30, 75–95 and 135–160 nm) and represent 57 % of the annual PSD (up to 89 %–100 % during winter and 34 %–65 % during summer based on monthly averages). Nucleation and Aitken mode PSD clusters dominate summer months (September–January, 59 %–90 %), whereas a clear bimodal distribution (43 and 134 nm, respectively; Hoppel minimum at mode 75 nm) is seen only during the December–April period (6 %–21 %). Major findings of the current work include: (1) NPF and growth events originate from both the sea ice marginal zone and the Antarctic plateau, strongly suggesting multiple vertical origins, including the marine boundary layer and free troposphere; (2) very low particle number concentrations are detected for a substantial part of the year (57 %), including summer (34 %–65 %), suggesting that the strong annual aerosol concentration cycle is driven by a short temporal interval of strong NPF events; (3) a unique pristine aerosol cluster is seen with a bimodal size distribution (75 and 160 nm, respectively), strongly associated with high wind speed and possibly associated with blowing snow and sea spray sea salt, dominating the winter aerosol population (34 %–54 %). A brief comparison with two other stations (Dome C – Concordia – and King Sejong Station) during the year 2015 (240 d overlap) shows that the dynamics of aerosol number concentrations and distributions are more complex than the simple sulfate–sea-spray binary combination, and it is likely that an array of additional chemical components and processes drive the aerosol population. A conceptual illustration is proposed indicating the various atmospheric processes related to the Antarctic aerosols, with particular emphasis on the origin of new particle formation and growth.

Details

Original languageEnglish
Pages (from-to)4461-4476
Number of pages16
JournalAtmospheric Chemistry and Physics
Volume20
Issue number7
Publication statusPublished - 17 Apr 2020

ASJC Scopus subject areas