Modeling study of circulation variability in response to wind and lateral forcing in the China Seas

Abstract

This research aims to investigate the spatial and temporal variability of the circulation in the China Seas (CS), which includes the South China Sea (SCS), the East China Sea (ECS) and the Yellow Sea (YS), under different atmospheric forcings and lateral fluxes. The three-dimensional, high-resolution and well-validated results from China Sea Multi-Scale Ocean Modeling System (CMOMS), which covers entire CS and adjacent Western Pacific Ocean (WPO), are used to conduct the investigation. We examined the interconnecting responses of circulation over the CS to different wind forcing fields derived from global atmospheric models and the associated external transports from the WPO. We found that the oceanic circulations in the China Seas is significantly controlled by the forcing of wind stress curl locally and planetary vorticity influx remotely. In SCS, although the prevailing cyclonic-anticyclonic-cyclonic (CAC) circulation pattern remains largely the same, vertical structure and the long-term variation trend of the CAC circulation varied with different wind forcing. We found that the absence of negative wind stress curl (WSC) patch off Vietnam coastal waters, strengthened overall positive WSC and enhanced CAC circulation in the SCS. Similarly, weakened negative WSC is the coastal waters contributed by the strengthened north-easterly monsoon enhanced upper cyclonic circulation in the ECS. This change of monsoon modified transport and thus the planetary vorticity flux through Taiwan Strait. In the YS, the wind forcing effect on circulation in this semi-closed marginal sea was relatively weak. We also examined the effect of the North Equatorial Current (NEC) on the Kuroshio and thus intrusive flux to the CS. The strengthened NEC accelerated Kuroshio Current (KC), weakened its intrusion or planetary vorticity influx to the CS and thus changed circulations in both SCS and ECS. All these results improve our understanding about the response of oceanic circulation in the CS to internal wind forcing and external intrusive flux from adjacent ocean.

Date of Award	2020
Original language	English
Awarding Institution	The Hong Kong University of Science and Technology