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Seminar

Nd isotopic composition in the oceans

2019-04-01 73

Time:16:00-17:00  4th April 2019

VenueLecture Hall (221), Building No.16,Weijin Campus, Tianjin University

Speaker:Dr. Hiroshi Amakawa (Japan Agency for Marine-Earth Science Technology)

Dr Hiroshi Amakawa is a senior research scientist of Japan Agency for Marine-Earth Science Technology (JAMSTEC).  He defended his PhD at University of Tokyo in 1992 and joined JAMSTEC in 2014 after research experiences in Atmosphere and Ocean Research Institute, The University of Tokyo (1992-2011) and National Taiwan University (2011-2014).  His research interests include: (1) Neodymium isotopic composition: geochemical cycle of Nd, tracing water mass in the past and present, estimating mantle derived Nd fluxes; (2) Strontium isotopic composition: geochemical cycle of Sr, tracing migratory behavior of fish using otolith Sr isotopic composition.

Abstract

The neodymium (Nd) isotopic composition, which is recognized as a “quasi-conservative” tracer for water masses in the oceans, is widely utilized for present and past oceanic circulation studies. With the start of the international GEOTRACES, which aims to reveal the distributions of elements and their isotopic compositions in oceans, the amount of seawater Nd isotopic data increased dramatically. However, few seawater data are available for some oceanic regions, especially in the Indian Ocean. In this talk, I will report three full depth profiles of Nd concentration and isotopic composition from the western Indian Ocean south of the equator, and the Indian sector of the Southern Ocean with the aim of characterizing the water mass structure and ocean circulation patterns in these regions.

Due to recent progress in the use of remotely operated vehicles (ROVs), we are able to collect appropriate Fe-Mn crust samples for geochemical study by allowing in-situ monitoring of water depth and crust occurrence. I will report Nd isotopic composition of the surface layers of ferromanganese crust samples collected from the Takuyo-Daigo Seamount located at the northwest Pacific Ocean with special emphasis on comparison with Nd isotopic composition of ambient seawater.