Calcite dust and the atmospheric supply of Nd to the Japan Sea

Andrew D. Jacobson*, Chris Holmden

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

17 Scopus citations

Abstract

We report neodymium concentrations and isotope ratios (εNd) measured in the carbonate and silicate fractions of Chinese loess. The goal of the study is to investigate if the atmospheric supply of dissolved calcite dust to the oceans influences the cycling of Nd in seawater. We primarily focus on the Japan Sea, because it receives large quantities of dust from eastern Asia, and it has a known Nd isotope composition and a simple hydrologic budget. A steady-state atmospheric transport model is used to calculate the flux of soluble Nd delivered to the Japan Sea surface by the wet deposition of dissolved calcite dust. This information is then incorporated in a steady-state two-box model in order to evaluate controls on dissolved εNd values as well as to calculate the residence time of Nd in seawater. On average, calcite in fresh Chinese loess contains ∼150 nmol of Nd g-1 with an εNd of -8.6. The atmospheric input of dissolved calcite to the Japan Sea surface is 7.4 × 1012 g yr-1, which corresponds to a dissolved Nd flux of 1.1 × 1018 pmol yr-1. This flux represents the largest input of Nd to the basin, and it is required to produce the εNd composition of Japan Sea waters. Approximately 65% of the Nd flowing from the Japan Sea surface into the western North Pacific originates directly from the input of dissolved calcite dust. Downwelling surface water and the remineralization of settling particles containing Nd scavenged from surface water contribute ∼77% of the Nd in the Japan Sea deep, which indicates that ∼50% of the deep Nd originates from calcite dust. The εNd composition of deep water is balanced by a benthic flux, but the input is a factor of ∼10 lower than the calcite dust flux and accounts for only ∼23% of the deep Nd. Surface and deep waters in the Japan Sea have Nd residence times, with respect to particle scavenging, of ∼14 and 530 yr, respectively. These findings reveal that the atmospheric supply of dissolved calcite dust to the Japan Sea is a more important component of the marine Nd cycle in this basin than previously recognized.

Original languageEnglish (US)
Pages (from-to)418-430
Number of pages13
JournalEarth and Planetary Science Letters
Volume244
Issue number1-2
DOIs
StatePublished - Apr 15 2006

Keywords

  • Carbonate weathering
  • Chinese Loess Plateau
  • Dust
  • Isotopes
  • Nd
  • Seawater geochemistry

ASJC Scopus subject areas

  • Geophysics
  • Geochemistry and Petrology
  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science

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