The behaviour of nickel, copper, zinc, and cadmium in the subarctic Pacific Ocean: East–West differences

Abstract Nickel (Ni), copper (Cu), zinc (Zn), and cadmium (Cd) are trace metals classified as nutrient-type elements in the oceans. This study reports the full-depth distribution of dissolved (d) Ni, Cu, Zn, and Cd during the 2017 GEOTRACES Japan KH-17-3 cruise, aiming to augment the knowledge of chemical oceanography of the nutrient-type elements and highlight the east–west differences in the subarctic Pacific Ocean. The linear relationship of dCd and PO 4 reflects a concurrent influence of ocean circulation and biogeochemical cycling. For the other metals, the dM/PO 4 ratios reflect preferential uptake by phytoplankton, fluvial inputs, reversible scavenging, and release from the bottom. The east–west differences in the dM/PO 4 ratios suggest supplies of Ni and Cu from marginal seas and the North American continent. East–west gradient of the dZn/PO 4 ratio shows severer depletion of dZn in the surface water of the eastern subarctic Pacific, which is consistent with previous research. We calculate the enrichment factor ( EF ) that is the dM/dAl ratio normalised with the M/Al ratio in the crust for dNi, dCu, dZn, and dCd. The EF values are substantially high in the central part of the Subarctic Gyre, implying the presence of anthropogenic atmospheric input via the westerly wind.