Semiannual Variability of Mid–depth Zonal Currents along 5°N in the Eastern Indian Ocean: Characteristics and Causes

Ke Huang1, Dongxiao Wang2, Weiqing Han3, Ming Feng4, Gengxin Chen1, Weiqiang Wang5, Ju Chen6 and Jian Li7, (1)State Key Laboratory of Tropical Oceanography, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, China, (2)Sun Yet-sen University, Guangzhou, China, (3)University of Colorado Boulder, Department of Atmospheric and Oceanic Sciences, Boulder, United States, (4)CSIRO, Environment, Crawley, Western Australia, Australia, (5)South China Sea Institute of Oceanology, Chinese Academy of Sciences, State Key Laboratory of Tropical Oceanography, Guangzhou 510301, China, (6)SCSIO South China Sea Institute of Oceanology, Chinese Acaademy of Sciences, Guangzhou, China, (7)SCSIO South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, China
Abstract:
Four–year (2014–2017) zonal current data observed by a mooring at (5°N, 90.5°E) in the eastern Indian Ocean show strong semiannual cycle in the mid–depth (~1,200m) with distinct vertical structure. This pronounced mid–depth semiannual variability however is inconsistent with the local wind forcing, which shows a predominant annual cycle. The underlying causes for this unique mid–depth variability along 5°N were elucidated with the addition of a reanalysis product and a continuously stratified linear ocean model. The results suggest that the observed seasonal variability in the mid–depth zonal flow at 5°N is primarily caused by the boundary–reflected Rossby waves forced by the remote semiannual winds along the equator. Contribution from the locally wind–forced Rossby waves is much less.
Back to: Toward an Improved Understanding of Indian Ocean Dynamics and Its Role in the Monsoon III Posters