Wintertime Arctic Ocean sea water properties and primary marine aerosol concentrations

J Zábori,J Ström,G De Leeuw,E D Nilsson,R Krejci,A M L Ekman,E M Mårtensson

doi:10.5194/acp-12-10405-2012

Abstract

Abstract. Sea spray aerosols are an important part of the climate system through their direct and indirect effects. Due to the diminishing sea ice, the Arctic Ocean is one of the most rapidly changing sea spray aerosol source areas. However, the influence of these changes on primary particle production is not known. In laboratory experiments we examined the influence of Arctic Ocean water temperature, salinity, and oxygen saturation on primary particle concentration characteristics. Sea water temperature was identified as the most important of these parameters. A strong decrease in sea spray aerosol production with increasing water temperature was observed for water temperatures between −1°C and 9°C. Aerosol number concentrations decreased from at least 1400 cm−3 to 350 cm−3. In general, the aerosol number size distribution exhibited a robust shape with one mode close to dry diameter Dp 0.2 μm with approximately 45% of particles at smaller sizes. Changes in sea water temperature did not result in pronounced change of the shape of the aerosol size distribution, only in the magnitude of the concentrations. Our experiments indicate that changes in aerosol emissions are most likely linked to changes of the physical properties of sea water at low temperatures. The observed strong dependence of sea spray aerosol concentrations on sea water temperature, with a large fraction of the emitted particles in the typical cloud condensation nuclei size range, provide strong arguments for a more careful consideration of this effect in climate models.

Highlights

Sea spray aerosols (SSA) represent the largest natural aerosol source on Earth by mass flux
Using real Arctic sea water in laboratory experiments, we focus on analyzing the microphysical properties, including number concentration and number size distribution, of the aerosol particles emitted from the sea water surface by bubble bursting
The influence of water temperature, salinity, and oxygen saturation on sea spray aerosol emissions from winter Arctic Ocean sea water was studied by means of laboratory experiments at Ny-Alesund, Svalbard

Summary

Introduction

Sea spray aerosols (SSA) represent the largest natural aerosol source on Earth by mass flux. SSA are aerosol particles produced at the ocean surface from breaking waves and consist of sea salt mixed with other species, in particular organic matter (de Leeuw et al, 2011). The aerosol particles have a substantial impact on the radiative balance of the Earth through scattering of incident solar radiation and as a source of cloud condensation nuclei (CCN). Different model estimates of the global annual mean clear sky direct radiative forcing due to sea salt range between −0.6 W m−2 and −5.03 W m−2 (compilation of results in Ma et al, 2008). Using a cloud-parcel model, the same authors estimated an increase of cloud droplet concentrations between 15 % and more than 100 % due to the increase in organic matter.

Methods

Results

Discussion

Conclusion