[A-CG47] 海洋と大気の波動・渦・循環の力学

[ACG47-18] 強非線形順圧チャネルモデルにおける偏西風に逆らう西向き周極流の形成メカニズム

*松田 拓朗¹、久保川 厚¹、三寺 史夫²、尾形 友道³ (1.北海道大学地球環境科学研究院、2.北海道大学低温科学研究所、3.海洋研究開発機構)

キーワード：順圧チャネルモデル、非線形性、順圧不安定、渦運動量輸送

Recent studies have indicated that even in stratified reentrant channel models, barotropic dynamics play a role in the adjustment of form stress. However, research addressing nonlinear barotropic dynamics has primarily focused on cases without external forcing or with very low seafloor topography. The impact of nonlinearities on barotropic dynamics in the presence of wind forcing and sufficiently large seamounts has not been sufficiently explored. In this study, we conduct numerical experiments using a barotropic reentrant channel forced by westerly winds to investigate the relationship between nonlinearity and circumpolar transport. In the weakly nonlinear regime, the circumpolar transport is eastward, with only a slight modification due to inertial effects. In contrast, in the strongly nonlinear regime, the circumpolar transport is westward, opposing the westerlies. We demonstrate that eddy radiation resulting from barotropic instability accelerates the mean flow westward during the initial stage of spin-up, forming a westward circumpolar current. Once the westward circumpolar current is established, it is sustained by the inertial effect of western boundary currents.