Ocean Variability in the Southernmost Philippine Sea
Yuji Kashino (Japan Marine Science and Technology Center, 2-15 Natsushima Yokosuka, 237-0061, Japan, e-mail: kashinoy@jamstec.go.jp),
Hidetoshi Watanabe (Sanyo Techno Marine Inc., 1-3-7 Nihonbashi Horidome Chuo-ku, Tokyo, 103-0012, Japan),
Bambang Herunadi (Badan Pengkajian Dan Penerapan Teknologi, Jl.M.H. Thamrin 8, Jakarta, 10340, Indonesia),
Michio Aoyama (Meteorological Research Institute, 1-1 Nagamine Tsukuba, Ibaraki, 305-0052, Japan),
Djoko Hartoryo (Badan Pengkajian Dan Penerapan Teknologi), and
Akio Ishida (Japan Marine Science and Technology Center)
Abstract
Current variability in the southernmost Philippine Sea is investigated using direct current and hvdrographic measurements, and numerical results from JAMSTEC Eddy-resolving General Circulation Model (JEGCM).
Results from moorings deployed at the southwestern boundary of the Philippine Sea show that 50-day oscillations occur in this region. Seasonal change of the current was also seen in the mooring results; it is consistent with those from hydrographic observations conducted in the Philippine Sea during boreal winter and summer, and it is perhaps due to the movement of the Halmahera Eddy.
Similar results are also obtained from the JEGCM. For example, oscillations are appeared in the southernmost Philippine and Celebes Seas in the model results although its frequency is a little different from observations. The seasonal current pattern change in the southernmost Philippine Sea from the model result is also consistent with observations.
1. Introduction
In the southernmost Philippine Sea, there is the Pacific entrance of the Indonesian Throughflow, which source water is supplied by the complicated Pacific low-latitude western boundary currents (Figuer 1). Since the Indonesian Throughflow, which is a part of "The Great Ocean Conveyer" [Broecker, 1991], probably has some roles in the global thermohaline circulation, it has been investigated by many oceanographers. At first, Wyrtki [1961] showed its zero-order description using historical data in and around the Indonesian Sea. After then, some observational study such as WEPOCS [e.g., Lukas et al., 1991], US-PRC [e.g., Toole et al., 1990] and Arlindo [e.g., Ilahude and Gordon, 1996] were conducted in this region, however, its description is still unclear due to limited observation data.
In order to clarify the characteristics of the Indonesian Throughflow, Japan Marine Science and Technology Center conducted the observations using R/V Kaiyo from 1992 to 1996 collaborating with Badan Pengkajian Dan Penerapan Teknologi (Indonesia) in the southernmost Philippine Sea. In this paper, we focus the ocean variability in the Philippine Sea, which is probably related to that of the Indonesian Throughflow using these observational results.
