テイチャク ヒョウイキ ノ パドル オヨビ カイホウ スイメン ナイブ ノ スイシツ ト ソレガ カイヨウ ニ アタエル エイキョウ ニ ツイテ

夏季のリュツォ・ホルム湾の定着氷域内に形成されるパドル及び開放水面の環境について,観測を行ったので報告する.パドルのような小さな開口部は,定着氷とほぼ同じ厚さの淡水に近い低塩分水で満たされていた.この低塩分水は定着氷の融氷水が溜まったものと考えられる.定着氷が大きく消失せず天候も平穏であれば,パドルにたまった融氷水は下層へ拡散せず,定着氷下の海水を低塩分化させない.また開口部内の表層水の水温は下層の海水温より高く,特に2005年1月下旬にラングホブデ・袋浦で観測された水温は最高4°C であった.このように定着氷域における夏季の海洋表層の水温・塩分分布は変化に富んでいる.Summer environments in puddles and open waters formed in the fast ice area near Syowa Station, Antarctica were observed. Small open waters formed in the fast ice were filled with low saline water. Low saline water was supplied by melting sea ice and snow. If fast ice is not broken up by rough weather, melt water masses will stay stably in open water surrounded by fast ice. Consequently, this melt water will not dilute the surface sea water located under the fast ice. On the other hand, the water temperature of melt water was higher than underlying saline water. Especially, a maximum temperature of 4°C was observed in Hukuro Ura, Langhovde in late January 2005. Thus, structure of water temperature and salinity of summer open waters formed in the fast ice area have been rich in change

JARE ニヨル カイヒョウ モニタリング ニ ムケテ -コクサイ ヒョウジュン ニ モトヅク カンソク テジュン ノ カンリャクカ ト ソノ カツヨウ レイ-

日本南極地域観測隊(JARE)用の船不海氷目視観測のプロトコルを提案した.ASPeCt(Antarctic Sea ice Processes and Climate)のプロトコルを簡略化したもので,海氷の定量化に必要なものに絞ったものである.このプロトコルに従って,第46次隊から目視観測を開始した.流氷域での観測では,沿岸に近づくにつれて氷厚・変形氷の割合とも大きくなり,海氷の体積が著しく大きくなることが示された.継続した目視観測データの蓄積は,南極沿岸流氷域の海氷(特にその厚さ)の気候値・年々変動を知る不で貴重なものとなる.A protocol for ship-based visual observation of sea ice is proposed for the Japanese Antarctic Research Expedition (JARE). The protocol is a simplified version of the ASPeCt protocol, used for extracting quantitative information on sea ice. The ship-based visual observations started from JARE-46. In the pack ice region, ice thickness, ratio of deformed ice, and total ice volume increased toward the coast. Continuous monitoring of sea ice, particularly its thickness, by ship-based observation is effective for obtaining information on climatology and interannual variation of sea ice in the coastal pack ice region

2004-05ネン カキ ノ オングルカイキョウ テイチャクヒョウカ ニオケル ショクブツ プランクトン ト エイヨウエン ノ ジケイレツ ヘンカ

弱光環境の定着氷下で高濃度のクロロフィルaが存在する要因を明らかにするため,2004-05年夏季にオングル海峡にて海洋観測を行った. 観測されたクロロフィルa濃度は,これまで報告された値より小さく,最大で7.6 mg/m3であった.しかし,観測期間中の表層の硝酸塩,リン酸塩の減少量は大きく,定着氷下の一次生産は活発であったと考えられる.一方,定着氷下の流向及び流速は,概ね北向きに平均4.4 cm/sの流れが存在した.それゆえオングル海峡の定着氷下の水塊は,8日間前には約30 km南方の海域に存在したと考えられる.リュツォ・ホルム湾宗谷海岸の定着氷は,オングル海峡周辺より融解が早く,海中光量が増加して植物プランクトンの増殖できる環境が早く整う. したがってオングル海峡の定着氷下で観測される多量の植物プランクトンは,宗谷海岸沖の開水面域・薄氷域で増殖し,海流に乗って輸送され存在する可能性が考えられる.Time series oceanographic observation was carried out in Ongul Strait during the austral summer of 2004/05 in order to clarify the reason why dense chlorophyll a can exist under fast ice where the light condition is unfavorable for ordinary phytoplankton. Chlorophyll a concentration observed in this study was smaller than that previously reported, and the maximum was 7.6 mg/m3. However, the decrease of nitrate and phosphate concentration in surface water during the observation period was large, and primary production under the fast ice seemed to be active. At the same time, a northward surface current of 4.4 cm/s was observed under the fast ice. Therefore, the water mass in Ongul Strait is believed to have been about 30 km south of the strait 8 days earlier. The fast ice in the Sôya coastal area in southeastern Lützow-Holm Bay melts earlier than that around Ongul Strait. Underwater light intensity increases and a favorable condition for multiplication of phytoplankton exists in early summer. Consequently, it is believed that the high biomass of phytoplankton observed under fast ice in the Ongul Strait increased in open water and under thin ice in the southern area (off the Sôya Coast area) and was transported northward by the current

Water characteristics in puddles and open waters in the fast ice area and its influence to marine environment

Summer environments in puddles and open waters formed in the fast ice area near Syowa Station, Antarctica were observed. Small open waters formed in the fast ice were filled with low saline water. Low saline water was supplied by melting sea ice and snow. If fast ice is not broken up by rough weather, melt water masses will stay stably in open water surrounded by fast ice. Consequently, this melt water will not dilute the surface sea water located under the fast ice. On the other hand, the water temperature of melt water was higher than underlying saline water. Especially, a maximum temperature of 4°C was observed in Hukuro Ura, Langhovde in late January 2005. Thus, structure of water temperature and salinity of summer open waters formed in the fast ice area have been rich in change

Sea-ice monitoring by ship-based visual observation during JARE ―Simplification of observation method based on the ASPeCt protocol―

A protocol for ship-based visual observation of sea ice is proposed for the Japanese Antarctic Research Expedition (JARE). The protocol is a simplified version of the ASPeCt protocol, used for extracting quantitative information on sea ice. The ship-based visual observations started from JARE-46. In the pack ice region, ice thickness, ratio of deformed ice, and total ice volume increased toward the coast. Continuous monitoring of sea ice, particularly its thickness, by ship-based observation is effective for obtaining information on climatology and interannual variation of sea ice in the coastal pack ice region

Temporal changes of phytoplankton and nutrients under the fast ice in the Ongul Strait during the austral summer of 2004/05

Time series oceanographic observation was carried out in Ongul Strait during the austral summer of 2004/05 in order to clarify the reason why dense chlorophyll a can exist under fast ice where the light condition is unfavorable for ordinary phytoplankton. Chlorophyll a concentration observed in this study was smaller than that previously reported, and the maximum was 7.6 mg/m3. However, the decrease of nitrate and phosphate concentration in surface water during the observation period was large, and primary production under the fast ice seemed to be active. At the same time, a northward surface current of 4.4 cm/s was observed under the fast ice. Therefore, the water mass in Ongul Strait is believed to have been about 30 km south of the strait 8 days earlier. The fast ice in the Sôya coastal area in southeastern Lützow-Holm Bay melts earlier than that around Ongul Strait. Underwater light intensity increases and a favorable condition for multiplication of phytoplankton exists in early summer. Consequently, it is believed that the high biomass of phytoplankton observed under fast ice in the Ongul Strait increased in open water and under thin ice in the southern area (off the Sôya Coast area) and was transported northward by the current