Tuesday 23 August 2005

P1
1550-1710 hours

215
Water properties in the Halmahera eddy region observed from TRITON buoys
and hydrographic surveys
Atmadipoera, Agus¹, Kuroda, Yoshifumi², Pariwono, John¹, Purwandani, Andri³
1 Bogor Agricultural University, Indonesia
2 Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Yokosuka, Japan
3 Agency for Application and Assessment of Technology (BPPT), Indonesia
Author email: atmadipoeras@yahoo.com
Changes of water properties associated with the development of the Halmahera eddy (HE) in the westernmost equatorial Pacific, in the confluence of northern and southern hemisphere waters, are described by combining the data from TRITON buoys, hydrographic surveys and satellite altimeters. These data show the HE has two distinct phases. One is a weak phase, observed during October 2001 cruise when the inflow of the New Guinea Coastal Current (NGCC) and Undercurrent (NGCUC) was weak, and South Pacific Tropical Water (SPTW) was not carried into the HE region. During the weak phase, the Mindanao Current (MC) was also weak and flowed directly into the region. A small clockwise circulation, recognizable as the HE, was formed, but only North Pacific Tropical Water (NPTW) occupies the area. The second phase observed during the July 2002 cruise, reveals the MC to be remarkably strong and the NGCC/NGCUC also enhanced. These currents merged north of the equator and formed the large strong HE, with the salinity front between the SPTW and NPTW was found farther near 5°N and the SPTW dominating the HE. The time series of dynamic height, 20°C isotherm depth and salinity on the potential density 24.5 kg/m3 indicated that the HE has large perturbation in the intraseasonal time scale of 35-70 days period. The satellite sea surface height anomalies were consistent with in situ data.

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