T95 Harmony and Discord: Exploring the Interplay of Climate and Tectonics in Central Asia

Monday, 23 September 2024
8:00 AM - 12:00 PM
304A

MID-PLEISTOCENE LINKS BETWEEN ASIAN DUST, TIBETAN GLACIERS, AND PACIFIC IRON FERTILIZATION

Paper number: T95-3
Program: Technical Sessions
Time: 8:35 AM – 8:50 AM

Authors

  • Jinbo Zan Presenting Author
    Chinese Academy of Sciences, Beijing, Beijing
  • Barbara A. Maher
    Centre for Environmental Magnetism & Palaeomagnetism, Lancaster Environment Centre, University of Lancaster, Lancaster
  • Toshitsugu Yamazaki
    Atmosphere and Ocean Research Institute, The University of Tokyo, Kashiwa 277-8564, Japan, Tokyo
  • Xiaomin Fang
    Chinese Academy of Sciences, Beijing
  • Wenxia Han
    School of Resource and Environmental Sciences, Linyi University, Linyi
  • Jian Kang
    Chinese Academy of Sciences, Beijing, Beijing
  • Zhe Hu
    Chinese Academy of Sciences, Beijing, Beijing

Abstract

Increasing Asian dust fluxes, associated with late Cenozoic cooling and intensified glaciations, are conventionally thought to drive iron fertilization of phytoplankton productivity in the North Pacific, contributing to ocean carbon storage and drawdown of atmospheric CO2. During the early Pleistocene glaciations, however, productivity remained low despite higher Asian dust fluxes, only displaying glacial stage increases after the mid-Pleistocene climate transition (~800 ka B.P.). We solve this paradox by analyzing an Asian dust sequence, spanning the last 3.6 My, from the Tarim Basin, identifying a major switch in the iron composition of the dust at ~800 ka, associated with expansion of Tibetan glaciers and enhanced production of freshly ground rock minerals. This compositional shift in the Asian dust was recorded synchronously in the downwind, deep sea sediments of the central North Pacific. The switch from desert dust, containing stable, highly oxidized iron, to glacial dust, richer in reactive reduced iron, coincided with increased populations of silica-producing phytoplankton in the equatorial North Pacific and increased primary productivity in more northerly locations, such as the South China Sea. We calculate that potentially bioavailable Fe2+ flux to the North Pacific was more than doubled after the switch to glacially- sourced dust. These findings indicate a positive feedback between Tibetan glaciations, glaciogenic production of dust with enhanced iron bioavailability, and changes in North Pacific iron fertilization. Notably, this strengthened link between climate and eolian dust coincided with the mid-Pleistocene transition to increased storage of C in the glacial North Pacific and more intense northern hemisphere glaciations.

Geological Society of America Abstracts with Programs. Vol. 56, No. 5

doi: 10.1130/abs/2024AM-403834

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