[1] Observations of aerosol constituents and acidic gases in the Antarctic area were carried out at Syowa (39.58°E, 69.00°S) in 1997 and1998 and Dome Fuji stations (39.62°E, 77.37°S) in 1997. Sea-salt concentrations decreased to background levels in the summer at both Syowa (Na + , 4 nmol m À3 ) and Dome Fuji (Na + , $0.44 nmol m À3 on average). During the winter, blizzard and strong wind may cause an increase of sea-salt particles at Syowa, whereas long-range transport from the boundary layer at midlatitudes and coastal Antarctic regions may contribute significantly to the increase in sea-salt particles observed at Dome Fuji. Particulate Cl À and Br À are liberated preferentially from sea-salt particles at Syowa and Dome Fuji in the summer. The molar ratio of Cl À /Na + and Br À /Na + at Syowa decreased to $0.5 and %0, respectively, in summer. At Dome Fuji more Cl À tend to be liberated from sea-salt particles thorough heterogeneous NO 3 À formation. The concentrations of gaseous chlorine species (mostly HCl) and bromine species ranged from 0.2 to 5.3 nmol m À3 and below detection limit (BDL) to 1.5 nmol m À3 , respectively, corresponding to sea-salt modification. In the present study, SO 4 2À depletion due to mirabilite formation was observed not only at Syowa but also at Dome Fuji. This evidence suggests that SO 4 2À depletion might occur through sublimation on snow surfaces in addition to seawater freezing. At Syowa, sea-salt fractionation relating to Mg 2+ , K + , and Ca 2+ was also observed mostly under strong wind conditions.

Abstract.To better understand the spatio-temporal variability of the glaciological environment in Dronning Maud Land (DML), East Antarctica, a 2800-km-long Japanese-Swedish traverse was carried out. The route includes ice divides between two ice-coring sites at Dome Fuji and EPICA DML. We determined the surface mass balance (SMB) averaged over various time scales in the late Holocene based on studies of snow pits and firn cores, in addition to radar data. We find that the large-scale distribution of the SMB depends on the surface elevation and continentality, and that the SMB differs between the windward and leeward sides of ice divides for strong-wind events. We suggest that the SMB is highly influenced by interactions between the large-scale surface topography of ice divides and the wind field of strong-wind events that are often associated with high-precipitation events. Local variations in the SMB are governed by the local surface topography, which is influenced by the bedrock topography. In the eastern part of DML, the accumulation rate in the second half of the 20th century is found to be higher by ∼15 % Correspondence to: S. Fujita (sfujita@nipr.ac.jp) than averages over longer periods of 722 a or 7.9 ka before AD 2008. A similar increasing trend has been reported for many inland plateau sites in Antarctica with the exception of several sites on the leeward side of the ice divides.

During our aerosol measurement program at Syowa Station, Antarctica, in 2004–2007, some low‐visibility (haze) phenomena were observed during winter–spring under conditions with low winds and without drifting snow and fog. During “Antarctic haze” phenomena, the number concentration of aerosol particles and black carbon concentration increased by 1 to 2 orders higher relative to background conditions at Syowa Station, whereas surface O3 concentration dropped simultaneously, especially after polar sunrise. Chemical analysis showed that major aerosol constituents in the haze phenomena were sea salt (e.g., Na+, Cl−). Trajectory analysis and the Navy Aerosol Analysis and Prediction System model showed that plumes from biomass burning in South America and southern Africa were transported to Syowa Station, on the Antarctic coast, because of the eastward (occasionally westward) approach of cyclones in the Southern Ocean and subsequent poleward flow. This poleward flow from midlatitudes of the plume and injection of sea‐salt particles during the transport might engender Antarctic haze phenomena at Syowa Station. Differences of O3 concentration between the background and the haze conditions tended to be larger in spring (after polar sunrise) than in winter. Enhancement of sea‐salt particles in the haze events can serve important roles in providing additional sources of reactive halogen species.

Tethered balloon-borne aerosol measurements were conducted at Syowa Station, Antarctica, during the 46th Japanese Antarctic expedition (2005–2006). Direct aerosol sampling was operated from near the surface to the lower free troposphere (approximately 2500 m) using a balloon-borne aerosol impactor. Individual aerosol particles were analyzed using a scanning electron microscope equipped with an energy dispersive X-ray spectrometer. Seasonal and vertical features of aerosol constituents and their mixing states were investigated. Results show that sulfate particles were predominant in the boundary layer and lower free troposphere in summer, whereas sea-salt particles were predominant during winter through spring. Minerals, MgSO₄, and sulfate containing K were identified as minor aerosol constituents in both boundary layer and free troposphere over Syowa Station. Although sea-salt particles were predominant during winter through spring, the relative abundance of sulfate particles increased in the boundary layer when air masses fell from the free troposphere over the Antarctic coast and continent. Sea-salt particles were modified considerably through heterogeneous reactions with SO₄²⁻ CH₃SO₃⁻ and their precursors during summer, and were modified slightly through heterogeneous reactions with NO₃⁻ and its precursors. During winter through spring, sea-salt modification was insignificant, particularly in the cases of high relative abundance of sea-salt particles and higher number concentrations. In August, NO₃⁻ and its precursors contributed greatly to sea-salt modification over Syowa Station. Because of the occurrence of sea-salt fractionation on sea ice, Mg-rich sea-salt particles were identified during the months of April through November. In contrast, Mg-free sea-salt particles and slightly Mg-rich sea-salt particles coexisted in the lower troposphere during summer. Thereby, Mg separation can proceed by sea-salt fractionation during summer in Antarctic regions