Variation of dimethylsulfide mixing ratio over the Southern Ocean from 36°S to 70°S

AbstractAtmospheric dimethylsulfide (DMS) was measured to investigate the variation in its concentration over sea ice free oceans and sea ice regions of the Southern Ocean, using a proton transfer reaction-mass spectrometer (PTR-MS) on board the icebreaker Shirase from 1 December 2009 to 16 March 2010. In general, DMS concentrations over sea ice regions were very low compared with those over the sea ice free ocean. However, abrupt increases in DMS concentrations occurred over sea ice regions while the ship was moving and crushing the sea ice. Undoubtedly, the elevated DMS concentrations were caused by large DMS emissions from gaps in the ice made by the ship. During the period when Shirase had anchored off Syowa Station (69°00.4′S, 39°35.3′E), Antarctica, DMS concentrations were not detected. At this time, the surrounding sea of East Ongul island, on which Syowa Station is located, was completely covered with multi-year fast ice. Sea ice probably inhibits DMS emission from the ocean to the atmosphere. In addition, there was no evidence that chlorophyll a concentration in the sea water or wind speed above the sea surface affect atmospheric DMS concentrations over the sea ice free ocean regions

Aerosol nucleation observed in JARE51

第2回極域科学シンポジウム　共通セッション「海氷圏の生物地球化学」 11月16日（水） 統計数理研究所 3階リフレッシュフロ

シラセ トウサイ ヨウ コンテナ ジッケンシツ ノ ガイヨウ

2009年に就航した新「しらせ」には,改造した20 ftコンテナを船上実験室として搭載するスペースが確保された.第51次日本南極地域観測隊では,このコンテナ実験室の内部に大気中の硫化ジメチル濃度を測定するためのプロトン移動反応質量分析計を収納し,観測を実施した.本稿では,コンテナ実験室の概要と今後改良すべき点等について報告する.A portable laboratory, made from a modified 20 feet-long cargo container,was newly installed on the observation deck of the RV Shirase on her maiden voyage to the Antarctic during 2009-2010. The laboratory was used to measure the concentrations of volatile organic compounds (e.g., dimethyle sulfides) in samples of air collected from above the sea and the sea ice, using a proton transfer reaction-mass spectrometer (PTR-MS). This paper describes the laboratory and notes several problems to be overcome in terms of its use

船舶搭載型全天カメラと雲底高度計観測データ解析による雲の特徴

第6回極域科学シンポジウム[OM] 極域気水圏11月16日（月）　国立極地研究所１階交流アトリウ

SULFUR COMPOUNDS OF PHYTOPLANKTON ORIGIN IN THE ATMOSPHERIC BOUNDARY-LAYER

A box model was made to understand how dimethylsulfide (DMS or CH_3SCH_3), released from the ocean surface to the atmosphere, contributes to produce background aerosol particles over the open ocean. Dimethylsulfide undergoes a photooxidation reaction with OH radical during the daytime, but with NO_3 radical during nighttime. This reaction has two pathways : hydrogen abstraction and OH addition to the sulfur atom. The oxidation of DMS produces sulfur dioxide (SO_2) and methanesulfonic acid (MSA or CH_3SO_3H) as intermediate products, and non-sea-salt sulfate (nss-SO_4^) as an end product. We considered the reaction processes in detail to obtain quantitatively the concentrations of SO_2,MSA and nss-SO_4^. The calculated concentrations are consistent with the observed values. It is concluded that DMS is a dominant source of aerosol particles included nss-SO_4^ in the marine atmosphere. The calculation indicates that most nss-SO_4^ must be produced by heterogeneous reactions of SO_2 through cloud droplets. Other processes, MSA oxidation and homogeneous SO_2 oxidation, are inefficient in producing abundant nss-SO_4^

Direct measurements of DMS flux from Antarctic fast sea ice to the atmosphere by a chamber technique

We present the first direct measurements of dimethylsulfide (DMS) emissions from Antarctic sea ice to the atmosphere during the seasonal warming period obtained using a chamber technique. Estimated DMS fluxes measured over the snow and superimposed ice (ice formed by the freezing of snow meltwater) were from 0.1 to 0.3 μmol m−2 d−1. The DMS fluxes measured directly over the sea‐ice slush layer after removal of the snow and superimposed ice, ranged from 0.1 to 5.3 μmol m−2 d−1, were large compared to those measured over the snow and superimposed ice. The DMS concentrations in slush water ranged from 1.0 to 103.7 nM. The DMS fluxes increased with increasing DMS concentrations in slush water. Our results indicate that the potential DMS flux measured over the slush layer occurred originally from the slush layer, and was dependent on the DMS concentrations in slush water. However, snow accumulation and the formation of superimposed ice over the slush layer significantly blocks the diffusion of DMS to the atmosphere, with the result that DMS tends to accumulate in the slush layer although the removal process of DMS by photolysis reaction can modify the DMS flux from the slush layer. Hence, the slush layer has the potential to release the DMS to the atmosphere and ocean when the snow and superimposed ice melts

Report on a portable laboratory, made from a modified cargo container, aboard the RV Shirase during the 2009-2010 Antarctic cruise of the 51st Japanese Antarctic Research Expedition (JARE-51)

A portable laboratory, made from a modified 20 feet-long cargo container,was newly installed on the observation deck of the RV Shirase on her maiden voyage to the Antarctic during 2009-2010. The laboratory was used to measure the concentrations of volatile organic compounds (e.g., dimethyle sulfides) in samples of air collected from above the sea and the sea ice, using a proton transfer reaction-mass spectrometer (PTR-MS). This paper describes the laboratory and notes several problems to be overcome in terms of its use