Export fluxes in the Western Pacific Warm Pool

Abstract

Sediment trap experiments were conducted in order to understand the characteristics of settling particles related to the biological pump in the Western Pacific Warm Pool (WPWP). Mean total mass fluxes of 160.7 and 95.9 mg m-2 day-1 in the hemipelagic region (Sites 1 and 2 in the western WPWP), 13.2 and 25.7 mg m-2 day-1 in the oligotrophic ocean (Sites 4 and 10 in the central WPWP) and 40.1 mg m-2 day-1 in the equatorial upwelling region (Site 3 in the eastern WPWP) were observed. Compared with previous results obtained from the eastern equatorial Pacific, low total mass fluxes with carbonate-dominated and opal-depleted compositions generally characterized the settling particles in the central equatorial Pacific (the central and eastern WPWP). Site 3, located at the western end of the equatorial upwelling, showed the highest concentration of carbonate. The warm, low-density water mass overlay nutrient-rich cold water in the central and eastern WPWP, reducing nutrient supply to the euphotic zone, while the western WPWP was characterized by high productivity with higher biogenic opal content, which was comparable to those in the eastern equatorial Pacific. Due to high precipitation, great relief and tectonically active geography, this region around the Indonesian 'maritime continent' contributes large amounts of water, solutes and sediment to the coastal ocean. Ocean current transport raised lithogenic flux at Sites 1 and 2 during the winter monsoon, which could stimulate biological activity. At Site 3, the organic carbon flux (mg C m-2 day-1) to primary productivity (mg C m-2 day-1) ratios were 1.9 and 1.3% at depths of 1357 and 4363 m, which were higher than those reported at the 140°W equatorial transect. (C) 2000 Elsevier Science Ltd.