Vertical cycling of Cu and Ni in the western North and Equatorial Pacific

Abstract

Vertical profiles of Cu and Ni were determined at 5 stations in the western North Pacific and in the western equatorial Pacific. Cu concentrations are 1–4 nmol/kg at a depth of 1 km, and increase gradually with depth to 4–5 nmol/kg at 4 km. The Cu vertical profiles indicate that Cu is scavenged in the intermediate water. Ni concentrations are 7–10 nmol/kg at a depth of 1 km and about 10 nmol/kg at 2–3 km depth, and then decrease gradually toward the bottom. The convex profiles indicate that Ni is regenerated in the intermediate-deep water. By applying a one-dimensional advection and diffusion model, the mean Cu removal rate is calculated to be 8 μ mol-Cu/m 2 yr between 1–4 km water in the North Pacific. The mean renewal time of dissolved Cu in the deep North Pacific water is about 500 yr. The mean regeneration rate of Ni in the deep North Pacific water is 6 μ mol-Ni/m 2 yr. The mean renewal time is about 600 yr.