日本地球惑星科学連合2019年大会

講演情報

[J] ポスター発表

セッション記号 M (領域外・複数領域) » M-IS ジョイント

[M-IS14] 南大洋・南極氷床が駆動する全球気候変動

2019年5月27日(月) 17:15 〜 18:30 ポスター会場 (幕張メッセ国際展示場 8ホール)

コンビーナ:関 宰(北海道大学低温科学研究所)、岡 顕(東京大学大気海洋研究所)、植村 立(琉球大学 理学部)、真壁 竜介(国立極地研究所)

[MIS14-P06] 南大洋の季節海氷域における亜表層クロロフィル極大の時系列観測

*影沢 歩友子1佐野 雅美2高尾 信太郎1,2真壁 竜介1,2溝端 浩平3黒沢 則夫4茂木 正人2,3小達 恒夫2 (1.総合研究大学院大学、2.極地研究所、3.東京海洋大学、4.創価大学)

キーワード:亜表層クロロフィル極大、南大洋

A persistent subsurface chlorophyll a maximum (SCM) is often found during the summer-fall season after the ice-edge bloom in the seasonal ice zone of the Southern Ocean, so that SCM would be considered important for biogeochemical cycling through the lower trophic levels. The relevant studies, however, have been qualitative in nature. This study aimed to reveal the dynamics and ecological role of the SCM in the seasonal ice zone.
We carried out Lagrangian observations using a drifter with two time-series sediment traps, an Acoustic Doppler Current Profiler (ADCP) and four sensor flames (Fig. 1). The drifter was deployed at 63.5°S, 110.0°E in January 14th 2019, and 5-day continuous observation was performed. In the vicinity of the drifter, 4 ship-based observations including net sampling and CTD casts were made until the drifter was recovered. Physical environments were measured by CTD, and sea water samples were collected for measurements of chlorophyll a (chl. a) concentration, nutrients, particle organic carbon, dissolved organic carbon, abundance of phytoplankton, micro-zooplankton, bacteria and nano-/pico-phytoplankton. We also conducted an incubation experiment for determining net primary production.
The temperature minimum layer, found between 37 and 52 m depth, decreased from -0.82 ºC to -1.28 ºC during the study period. The maximum chl. a concentration (1.0-2.0 µg/l), comparable to that in typical ice edge blooms, was observed at 40 m depth (Fig. 2). Such a high chl. a concentration might have important roles for food web and for material cycling. We will discuss especially on phytoplankton dynamics showing results of microscopic and chemical analyses.