JpGU-AGU Joint Meeting 2017

講演情報

[JJ]Eveningポスター発表

セッション記号 A (大気水圏科学) » A-CG 大気水圏科学複合領域・一般

[A-CG52] [JJ] 植物プランクトン増殖に関わる海洋-大気間の生物地球化学

2017年5月25日(木) 15:30 〜 16:45 ポスター会場 (国際展示場 7ホール)

[ACG52-P02] Fine- and micro-scale observations in the Oyashio in winter

*田中 雄大1安田 一郎1後藤 恭敬1西岡 純2 (1.東京大学大気海洋研究所、2.北海道大学低温科学研究所)

キーワード:乱流混合、親潮

During the R/V Hakuho-maru cruise in Mar. 2015, fine- and microstructure measurements in the Oyashio water were conducted using a CTD/LADCP and vertical microstructure profiler in order to know the spatial variability of wintertime turbulence field, which has not been reported so far at this area. At a station off the shelf break, whose bottom depth is about 530 m, one-day repeated observations were also conducted to know the temporal variability of turbulence intensity.
The energy dissipation rate, ε, was patchily elevated to O(10-8) [W/kg] and was typically O(10-10 - 10-9) [W/kg] in the upper 400 m depth (less dense than 27.0 σθ) across the Oyashio. Off the shelf break, where the one-day observation was conducted, strong turbulence with ε = O(10-7) [W/kg] and = O(10-3 - 10-2) [m2/s] was observed at around 60 - 70 m depth (26.4 σθ), and ε = O(10-8) [W/kg] and = O(10-3) [m2/s] at around 350 m depth (26.7 σθ) corresponding to the period of isopycnal heaving of about 50m. This strong mixing around 26.4 σθ (26.7 σθ) was enhanced when the along-isobath (down-sill) flow and its associated shear was strengthened. Harmonic analysis shows that the diurnal tidal flow was large in the upper 50 m, while the mean and semi-diurnal flow were also important at around 26.7 σθ suggesting that the tidal flow may impact on the turbulence field at this place.