Hysteresis and Dynamics of a Western Boundary Current Flowing by a Gap Forced by Impingement of Mesoscale Eddies

doi:10.1175/2010JPO4489.1

IOCAS-IR > 海洋环流与波动重点实验室

	Hysteresis and Dynamics of a Western Boundary Current Flowing by a Gap Forced by Impingement of Mesoscale Eddies
	Yuan, Dongliang1 ; Wang, Zheng
	2011-05-01
发表期刊	JOURNAL OF PHYSICAL OCEANOGRAPHY
ISSN	0022-3670
卷号	41 期号:5 页码:878-888
文章类型	Article
摘要	Hysteresis of a western boundary current (WBC) flowing by a wide gap of a western boundary and the dynamics of the WBC variations associated with the impingement of mesoscale eddies from the eastern side of the gap are studied using a 1.5-layer reduced-gravity quasigeostrophic ocean model. The study focuses on two issues not covered by existing studies: the effects of finite baroclinic deformation radii and time dependence perturbed by mesoscale eddies. The results of the study show that the hysteresis of the WBC of finite baroclinic deformation radii is not controlled by multiple steady-state balances of the quasigeostrophic vorticity equation. Instead, the hysteresis is controlled by the periodic penetrating and the leaping regimes of the vorticity balance. The regime of the vorticity balance inside the gap is dependent on the history of the WBC evolution, which gives rise to the hysteresis of the WBC path. Numerical experiments have shown that the parameter domain of the hysteresis is not sensitive to the baroclinic deformation radius. However, the domain of the periodic solution, which is determined by the lower Hopf bifurcation of the nonlinear system. is found to be sensitive to the magnitude of the baroclinic deformation radius. The lower Hopf bifurcation from steady penetration to periodic penetration is found to occur at lower Reynolds numbers for larger deformation radii. In general, the lower Hopf bifurcation stays outside the hysteresis domain of the Reynolds number. However, for very small deformation radii, the lower Hopf bifurcation falls inside the hysteresis domain, which results in the transition from the leaping to the penetrating regimes of the WBC to skip the periodic regime and hence the disappearance of the upper Hopf bifurcation.; Hysteresis of a western boundary current (WBC) flowing by a wide gap of a western boundary and the dynamics of the WBC variations associated with the impingement of mesoscale eddies from the eastern side of the gap are studied using a 1.5-layer reduced-gravity quasigeostrophic ocean model. The study focuses on two issues not covered by existing studies: the effects of finite baroclinic deformation radii and time dependence perturbed by mesoscale eddies. The results of the study show that the hysteresis of the WBC of finite baroclinic deformation radii is not controlled by multiple steady-state balances of the quasigeostrophic vorticity equation. Instead, the hysteresis is controlled by the periodic penetrating and the leaping regimes of the vorticity balance. The regime of the vorticity balance inside the gap is dependent on the history of the WBC evolution, which gives rise to the hysteresis of the WBC path. Numerical experiments have shown that the parameter domain of the hysteresis is not sensitive to the baroclinic deformation radius. However, the domain of the periodic solution, which is determined by the lower Hopf bifurcation of the nonlinear system. is found to be sensitive to the magnitude of the baroclinic deformation radius. The lower Hopf bifurcation from steady penetration to periodic penetration is found to occur at lower Reynolds numbers for larger deformation radii. In general, the lower Hopf bifurcation stays outside the hysteresis domain of the Reynolds number. However, for very small deformation radii, the lower Hopf bifurcation falls inside the hysteresis domain, which results in the transition from the leaping to the penetrating regimes of the WBC to skip the periodic regime and hence the disappearance of the upper Hopf bifurcation. Mesoscale eddies approaching the gap from the eastern basin are found to have significant impact on the WBC path inside the gap when the WBC is at a critical state along the hysteresis loop. Cyclonic (anticyclonic) eddies play the role of reducing (enhancing) the inertial advection of vorticity in the vicinity of the gap so that transitions of the WBC path from the leaping (periodic penetrating) to the periodic penetrating (leaping) regimes are induced. In addition. cyclonic eddies are able to induce transitions of the WBC from the periodic penetrating to the leaping regimes through enhancing the meridional advection by its right fling. The transitions are irreversible because of the nonlinear hysteresis and are found to be sensitive to the strength. size, and approaching path of the eddy.
学科领域	Oceanography
DOI	10.1175/2010JPO4489.1
URL	查看原文
收录类别	SCI
语种	英语
WOS记录号	WOS:000291121600003
引用统计	被引频次：59[WOS] [WOS记录] [WOS相关记录]
文献类型	期刊论文
条目标识符	http://ir.qdio.ac.cn/handle/337002/11579
专题	海洋环流与波动重点实验室
作者单位	1.Chinese Acad Sci, Inst Oceanol, Qingdao 266071, Peoples R China 2.Chinese Acad Sci, Key Lab Ocean Circulat & Waves, Qingdao 266071, Peoples R China
第一作者单位	中国科学院海洋研究所
推荐引用方式 GB/T 7714	Yuan, Dongliang,Wang, Zheng. Hysteresis and Dynamics of a Western Boundary Current Flowing by a Gap Forced by Impingement of Mesoscale Eddies[J]. JOURNAL OF PHYSICAL OCEANOGRAPHY,2011,41(5):878-888.
APA	Yuan, Dongliang,&Wang, Zheng.(2011).Hysteresis and Dynamics of a Western Boundary Current Flowing by a Gap Forced by Impingement of Mesoscale Eddies.JOURNAL OF PHYSICAL OCEANOGRAPHY,41(5),878-888.
MLA	Yuan, Dongliang,et al."Hysteresis and Dynamics of a Western Boundary Current Flowing by a Gap Forced by Impingement of Mesoscale Eddies".JOURNAL OF PHYSICAL OCEANOGRAPHY 41.5(2011):878-888.

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