Characterization of the East China Sea Continental Shelf Circulation Northeast of Taiwan Surrounding Mien-Hua Canyon

Abstract

Submarine canyons have a proven and direct influence on continental shelf circulation and flow dynamics, especially in relation to western boundary currents. There are two key circulation features northeast of Taiwan on the East China Sea continental shelf: (1) the cold dome, a cyclonic feature that appears primarily in summer and is associated with upwelling, and (2) Kuroshio intrusions onto the continental shelf in the vicinity of Mien-Hua Canyon. This paper is a descriptive physical oceanography study with a focus on characterizing the circulation patterns northeast of Taiwan surrounding Mien-Hua Canyon, closely correlating these patterns with the migration of the Kuroshio and its variability and intrusions onto the southern East China Sea continental shelf, leading to the formation of the cold dome. The Institute of Oceanography at the National Taiwan University and WHOI executed a joint international field survey at Mien-Hua Canyon aiming to improve the understanding of canyon flow dynamics between the East China Sea continental shelf northeast of Taiwan and the Kuroshio as the North Pacific Gyre westward boundary current. This joint oceanographic expedition expands on previous joint US/Taiwan physical oceanographic and ocean acoustic studies in the China Seas dating back to ASIAEX in the South China Sea during 2000-2001 and QPE in the East China Sea during 2008-2009. The strengthening and weakening of Kuroshio transport and intensity northeast of Taiwan is closely correlated to the timescales of mesoscale westward propagating eddies arriving to the East Taiwan Channel. When a canyon has a Rossby number ~1 or Rossby radius equivalent to the width of the canyon in a region of left-bounded flow, induced cyclonic flow will experience an upwelling regime within the canyon system with dominant upwelling located at the downstream canyon rim vertically constrained by Rossby Height. Observational analysis of canyon bottom-moored ADCPs and vertical temperature arrays supports previous theory on submarine canyon dynamics on a continental shelf. Satellite sea surface temperature and absolute dynamic topography observations render the formation of a cold dome northeast of Taiwan coincident with this joint oceanographic survey.