The effect of wind and thermohaline forcing on a warmpool variability and a circulation in the western equatorial Pacific and the eastern Indian ocean.
Kei Muneyama(A) Shoichiro Nakamoto(AB)
(A)Japan Marine Science and Technology Centre.
(B)Earth Science and Technology Organization
1. Introduction
Warmpool dynamics in the western equatorial Pacific has been one of the most interesting issues for years in the oceanography in its interrelations to the global climate variabilities (TOGA Programme (1))
El Nino and oceanic variabilities in the western Pacific are one of such examples. Recently Yasunari and Seki, (1992) (2)suggested that El Nino was strongly related with the variability of Asian monsoon. Lukas et.ali(3) and Kashino et.al.(4) showed the watermass distribution in the western equatorial Pacific ocean that involves with the global ocean conveyor belt circulation.
Although recent oceanic expeditions has provided many insight about ocean circulation, complex oceanic and atmospheric interaction processes in the equatorial Pacific region require further quantification in terms of statistical emsemble nature of oceanic variables for understanding of its dynamics, examination of conceptual models as well as validation of general circulation models. Required observations may include ocean currents, heat fluxes and ocean mixed layer structure variation in space and in time.. The goal of Jamstec proposed ocean- atmosphere observation buoy project is described in a report. (5) In this paper we will explain one of the objectives of the buoy project, that is to provide data-set to understand a maintaining mechanism of the warmpool and to understand how it is related to the variabilities of the Indian ocean, in conjunction with model study and validation with a coupled mixed layer-isopycnal Ocean General Circulation Model (OPYC). The proposed positions of the buoy network is presented (6) and shown in Fig.1.
2. The western equatorial Pacific
Atmospheric convection in the warm pool region is strong in winter and an atmospheric circulation there reverses its direction between winter and summer. A numerical simulation using a global mixed layer-isopycnal ocean general circulation model (OPYC) mimics a salinity distribution in the first layer (surface mixed layer)(Fig.2) and subsurface layers around 100m to 250m depth.
The figure indicates that the high salinity water has its source at the subtropical southern hemisphere. This high salinity water marked by35% is transported westward at subsurface. While the surface of warmpool region and the western equatorial intermediate water region are less saline (Bingham and Lukas,1995(7)) the high salinity water intrudes into the second to the fifth layers of the model warm pool region around l00m to 250m depth along a northern coast of New Guinea island through Vitiaz strait (Fig.3) . The high salinity water mass in this region was also supported by observations (Tsuchiya et.al., 1989 (8)). It is interesting to note that the path for the high salinity water originated in the southern hemisphere is located above the flow of AAIW low salinity path. We believe that a high salinity tongue in this western equatorial Pacific is an extension of tropical water originated in the
