Can variability in the subarctic North Atlantic plankton bloom be detected in the properties of ambient marine aerosol?

Ocean phytoplankton productivity is an integral part of many Earth system processes. It drives the exchange of CO₂ between the ocean and atmosphere and forms the basis for ocean food webs. In addition to the impacts of plankton productivity on ocean ecosystems, it has been hypothesized to lead to the emission of high levels of aerosol-forming compounds that can affect cloud formation and alter Earth's radiation budget. One approach for improved understandings of the linkages between ocean ecosystems and aerosol properties is to make simultaneous ocean and aerosol measurements in an ocean region with seasonally varying plankton blooms and a minimally polluted overlying atmosphere. The subarctic North Atlantic is such a region. It hosts the largest annual phytoplankton bloom in the global ocean with a large spatial and seasonal variability in plankton biomass and composition. In addition, periods of low aerosol number concentrations associated with unpolluted air masses allow for the detection of any potential impacts of the bloom on aerosol properties. Several field campaigns have been conducted in the North Atlantic during the past decade focused on links between the bloom and marine aerosols. These include the second Western Atlantic Climate Study (WACS-2) and four North Atlantic Aerosols and Marine Ecosystem Study cruises (NAAMES-1, NAAMES-2, NAAMES-3, NAAMES-4). The timing of the experiments was designed to allow for coverage of all seasons to assess how changes in the state of the bloom might impact ocean-derived aerosol properties. Observations of ambient aerosol properties sampled during these 5 cruises will be presented. The analysis is limited to clean marine conditions as defined by low Radon (a tracer of continental air masses) (< 500 mBq m^-3), low total particle number concentration (< 500 cm^-3), and HYSPLIT back trajectories. The aerosol properties used in the analysis include unheated and heated (230°) number and volume size distributions, CCN activity, and aerosol composition. We find that detectable changes in the properties of ocean-derived aerosols in response to seasonal changes in the bloom state are limited to biogenic non-sea salt sulfate aerosol.