Multi-year gradient measurements of sea spray fluxes over the Baltic Sea and the North Atlantic Ocean

Abstract. Ship-based measurements of sea spray aerosol (SSA) gradient fluxes in the size range 0.5–47 µm diameter were conducted between 2009–2017 in both the Baltic Sea and the North Atlantic Ocean. Measured total SSA fluxes varied between 8.9⸱10³ ± 6.8⸱10⁵ m^-2 s^-1 for the Baltic Sea, and 1.0⸱10⁴ ± 10⁵ m^-2 s^-1. for the Atlantic Ocean. The analysis uncovered a significant decrease (by a factor of 2.2 in wind speed range 10.5 m s^-1–14.5 m s^-1) in SSA fluxes with chlorophyll-a (Chl-a) concentration higher than 3.5 mg m^-3 in the Baltic Sea area. We found statistically significant correlations for both regions of interest between SSA fluxes and various environmental factors including wind speed, wind acceleration, wave age, significant wave height, and wave Reynolds number. Using these factors, we developed separate parameterizations and compared them with previous studies. Additionally, in both measurement regions we observed weak correlations between SSA fluxes and air and water temperature, as well as atmospheric stability. Comparing the Baltic Sea and North Atlantic, we noted distinct emission behaviours, with higher emissions in the Baltic Sea at low wave age values compared to the Atlantic Ocean. This study represents the first comparative analysis of SSA flux measurements using the same methodology in these contrasting marine environments.