Abstract
Abstract. Sea salts and halogens in aerosols, frost flowers, and brine play an important role in atmospheric chemistry in polar regions. Simultaneous sampling and observations of frost flowers, brine, and aerosol particles were conducted around Siorapaluk in northwestern Greenland during December 2013 to March 2014. Results show that water-soluble frost flower and brine components are sea-salt components (e.g., Na+, Cl−, Mg2+, K+, Ca2+, Br−, and iodine). Concentration factors of sea-salt components of frost flowers and brine relative to seawater were 1.14–3.67. Sea-salt enrichment of Mg2+, K+, Ca2+, and halogens (Cl−, Br−, and iodine) in frost flowers is associated with sea-salt fractionation by precipitation of mirabilite and hydrohalite. High aerosol number concentrations correspond to the occurrence of higher abundance of sea-salt particles in both coarse and fine modes, and blowing snow and strong winds. Aerosol number concentrations, particularly in coarse mode, are increased considerably by release from the sea-ice surface under strong wind conditions. Sulfate depletion by sea-salt fractionation was found to be limited in sea-salt aerosols because of the presence of non-sea-salt (NSS) SO42−. However, coarse and fine sea-salt particles were found to be rich in Mg. Strong Mg enrichment might be more likely to proceed in fine sea-salt particles. Magnesium-rich sea-salt particles might be released from the surface of snow and slush layer (brine) on sea ice and frost flowers. Mirabilite-like and ikaite-like particles were identified only in aerosol samples collected near new sea-ice areas. From the field evidence and results from earlier studies, we propose and describe sea-salt cycles in seasonal sea-ice areas.
Highlights
Frost flowers on sea ice are ice crystals that contain brine and sea salts
Relationships among Mg2+, K+, Ca2+, and Cl− in frost flowers well matched those in brine
The molar ratios to Cl− were not changed by mirabilite precipitation without Cl− loss by heterogeneous reactions
Summary
Frost flowers on sea ice are ice crystals that contain brine and sea salts. They appear often during winter–spring on the surface of new and young sea ice in polar regions. To elucidate the atmospheric impact of fractionated seasalt particles and their relationship with sea-salt particles in the atmosphere and frost flowers on sea ice, one must ascertain (1) the chemical properties (e.g., concentrations, ratios, and pH) of frost flowers and brine, and (2) the physical and chemical properties of aerosols (e.g., size distribution, components, and mixing states) above seasonal sea ice with frost flowers Despite their importance, simultaneous observations and measurements of aerosols and frost flowers over seasonal ice areas with known frost flower occurrences have not been reported for polar regions, sampling and observations of frost flowers have been conducted in the Arctic (e.g., Alvaraz-Aviles et al, 2008; Douglas et al, 2012) and Antarctic (Rankin and Wolff, 2000; Rankin et al, 2002). Using data from simultaneous measurements and sampling of aerosols, frost flowers, and brine around northwestern Greenland during winter–spring, this study was conducted to elucidate seasalt cycles in seasonal sea-ice areas and related phenomena, such as sea-salt fractionation on the sea-ice surface including frost flowers, brine, and snow, their aging processes, and the release of fractionated sea-salt particles into the atmosphere
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