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Seasonal/Interannual Variations of the Indonesian Throughflow and the Eastern Indian Ocean

 

Yukio Masumoto (Department of Earth and Planetary Physics, Graduate School of Science, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.

Also at Frontier Research System for Global Change, Institute for Global Change Research, 1-2-1 Shibaura, Minato-ku, Tokyo, 105-6791 Japan)

e-mail: masumoto@geoph.s.u-tokyo.ac.jp

 

ABSTRACT

 

Seasonal and interannual variations of the Indonesian throughflow and the eastern Indian Ocean are investigated by use of an Indo-Pacific Ocean General Circulation Model forced by wind stresses derived from ERS satellites. Simulated seasonal variations of the throughflow are qualitatively consistent with other model results and the observations; large transport occurs during boreal late summer and fall season and weak transport appears in winter and spring with clear semiannual signals. Interannual variation in the simulated throughflow is also consistent with the observations and the other models. Analyses of the relation between the throughflow transport and the dynamic height field suggest that the meridional pressure gradient both at the entrance and at the exit of the Indonesian archipelago seems to play important roles to determine the throughflow magnitude.

 

1. Introduction

 

Despite the importance of the Indonesian throughflow from the Pacific to the Indian Ocean on the global thermohaline circulation and the regional circulations around the western Pacific and the eastern Indian Oceans, little has been known on the processes regulating the magnitude of the throughflow. This is due partly to the sparseness of the observed evidences both in time and in spaces, which makes it difficult to understand quantitatively the mean throughflow transport and the variations in it. From the numerical modeling point of view, simulations of the flow through the Indonesian archipelago are also hard task because of the complex geometry and the existence of the very narrow passages through which the swift current flows. It is obvious that both observations and modeling studies are necessary for further understanding of the throughflow mechanisms.

This paper describes preliminary results on seasonal and interannual variations of the Indonesian throughflow simulated in an Indo-Pacific basin ocean general circulation model (OGCM), in which the complex geometry in the archipelago is moderately represented. The model used in the present study is briefly introduced in section 2. Section 3 shows the simulated transport variations of the throughflow, and the relationship between the variability of the throughflow and the dynamic height variations in the Indonesian archipelago and the surrounding regions is examined in section 4.

 

 

 

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