Aerosol production over remote marine areas - A new route

We report on enhanced levels of 3-5nm particles in the remote summer Arctic . Simultaneous increases in particle number occurred in certain size ranges <50Kn. Particles >100nm, marine in origin, were also present. Stable airma sses with at least 4 days residence over the ice, a surface mixed layer <14 0m deep, capped by a temperature inversion and cloud-free stable layer simi lar to 1km in depth excluded a tropospheric source. Instead a surface sourc e was indicated. The most vigorous nucleation was associated with sudden re ductions of humidity (<80%) causing rapid dissipation of fogs. However, par ticles <50nm contained no detectable H2SO4 implying recent formation or gro wth from material other than the acid. It is proposed that the marine parti cles were derived from bubbles bursting on open leads and provided the mate rial for both nucleation and larger particle formation. Nucleation is attri buted to oxidation of an amino acid, L-methionine.