Nd isotopic features in the western subarctic Pacific Ocean

Radiogenic Nd isotopic signatures in the Pacific Ocean reflect the weathering of volcanic rocks such as New Guinea, Hawaii and Fiji Islands. Kamchatka Peninsula and Aleutian Islands are also possible radiogenic sources of Nd in the subarctic region. North Pacific Intermediate water (NPIW) is generated in the western North Pacific and delivers the Nd signal from surface to intermediate depths. We present the meridional distribution of Nd isotopic composition from 30°N to 52°N along the 165°W transect. Seawater samples were collected by CTD-CMS during R/V Hakuho-Maru KH-11-7 research cruise (GEOTRACES-Japan). Dissolved Nd was preconcentrated from 10L of filtered seawater by Fe-hydroxide co-precipitation, and then chemically purified by standard ion-exchange chromatography. After isolation of Nd from Sm by Ln resin, Nd isotopic composition was measured by TIMS. Radiogenic Nd isotopic signature was observed at intermediate and deep waters at higher latitude than 30°N. Especially, more radiogenic Nd isotopic composition was observed at σθ = 27.0 -27.4 corresponding to lower NPIW, relative to that in the upper NPIW (σθ = 26.6 -27.0). Nd isotopic composition is a possible proxy for the intermediate water in the western subarctic Pacific.