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Dissolved Thorium Isotope Evidence for Export Productivity in the Subtropical North Pacific During the Late Quaternary
Author(s) -
Liu Ruolin,
Wang Maoyu,
Li Weiqiang,
Shi Xuefa,
Chen Tianyu
Publication year - 2020
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2019gl085995
Subject(s) - oceanography , quaternary , glacial period , productivity , geology , deep sea , interglacial , marine isotope stage , ocean gyre , subtropics , environmental science , paleontology , ecology , biology , economics , macroeconomics
The vast area of the North Pacific subtropical gyre (NPSG) makes it an important region in exporting biogenic particles and carbon to the deep ocean. Nevertheless, we remain largely ignorant on its past changes in export productivity, leaving an important gap in the understanding of ocean‐climate interactions during the late Quaternary. Here, we take a novel approach to study the particle export via reconstruction of dissolved 230 Th/ 232 Th based on ferromanganese crusts in deep waters of the NPSG at 3.8‐ and 2.8‐km water depth, respectively. The U‐series data indicate stable growth rates of both samples and a rather small variability of their initial ( 230 Th/ 232 Th) in the last ca. 0.7 Myr. These glacial–interglacial integrated values are only about half of the modern dissolved ( 230 Th/ 232 Th) in the deep NPSG, reflecting increased dust dissolution and also particle scavenging related to ~10–40% higher average export productivity than today.