HR: 11:05h
AN: OS32B-04    [Abstracts]
TI: Rare Earth Elements in the North Western Pacific Ocean
AU: Shacat, J A
EM: jshacat@soest.hawaii.edu
AF: Department of Oceanography, 1000 Pope Road University of Hawaii, Honolulu, HI 96822
AU: * De Carlo, E H
EM: edecarlo@soest.hawaii.edu
AF: Department of Oceanography, 1000 Pope Road University of Hawaii, Honolulu, HI 96822
AU: Qiu, B
EM: bo@soest.hawaii.edu
AF: Department of Oceanography, 1000 Pope Road University of Hawaii, Honolulu, HI 96822
AB: Filtered seawater collected from the northwest Pacific Ocean during the IOC 2002 cruise was analyzed for Y and the Rare Earth Elements (YREE) using Flow Injection Analysis Inductively Coupled Plasma Mass Spectrometry (FIA-ICPMS). The highest surface YREE concentrations were observed in the North Pacific Subarctic Gyre near the Kuril Islands and are thought to derive from outflow from the Sea of Okhotsk through the Bussol Strait. The least fractionated Ce anomalies in surface waters, however, were observed in the Kuroshio Extension and Recirculation System, off the coast of Japan. Ce anomalies in surface waters display a weak positive correlation with the modeled dust deposition rates reported by Measures et al. (2005), suggesting the Ce anomaly may serve as a proxy for atmospheric dust deposition to the surface ocean. A novel approach used to calculate a Ce oxidation rate in North Pacific Intermediate Water yielded rates of of 0.23 - 0.35% d-1, within a factor of 2-3 of Ce oxidation rates in the Sargasso Sea (up to ~0.7% d-1) reported by Moffett (1990). Use of REE as geochemical tracers of the water masses was also investigated. Molar ratios of La/Yb, La/Dy and Dy/Yb behave conservatively as a function of potential depth in the open ocean independent of geographic location, although variations in La relative to other YREE near the coast of Japan suggest that excess La is derived locally but quickly scavenged in the subtropical gyre. Variations in the Y/La ratio behave predictably as a function of potential density but vary according to water mass origin, suggesting the Y/La ratio is an unexploited tracer for water mass distribution and origin.
DE: 1065 Major and trace element geochemistry
DE: 4825 Geochemistry
DE: 4866 Sorptive scavenging
DE: 4875 Trace elements (0489)
SC: Ocean Sciences [OS]
MN: Fall Meeting 2005