The distribution of dissolved cadmium and its isotopes across the subarctic Pacific Ocean
摘要
Cadmium (Cd) is a bioactive trace element with a nutrient-type distribution resembling the macronutrient phosphate (PO4) in the global ocean. At high latitudes, biogeochemical processes generate distinct Cd concentration and isotopic signals in surface waters, which are preserved during formation and advection of high-latitude water masses, exerting a significant control on the deep ocean Cd and dissolved Cd isotope (δ114Cd) distributions. Here, we present the first full depth, cross-basin study of Cd and δ114Cd in the Subarctic Pacific from the Japanese GEOTRACES section GP02, principally along 47˚N. In intermediate and deep waters, δ114Cd values are homogenous (+ 0.24 ± 0.02‰), consistent with previous findings of an isotopically homogenous global deep ocean. However, Cd to PO4 ratios show clear divergences across the 160˚W meridian, representing increased Cd accumulation relative to PO4 in Pacific Deep Water in the east. In surface waters, the relationship between Cd and δ114Cd from the Western Subarctic Gyre can be described by closed-system Rayleigh fractionation, consistent with our understanding of Cd systematics in elevated Cd in surface waters linked to upwelling, high-nutrient low chlorophyll environments. In contrast, in the east, where Cd concentrations are lower, an open-system steady state model is more descriptive.