Replacement Times of a Spectrum of Elements in the North Atlantic Based on Thorium Supply

Christopher T. Hayes, Robert F. Anderson, Hai Cheng, Tim M. Conway, R. Lawrence Edwards, Martin Q. Fleisher, Peng Ho, Kuo Fang Huang, Seth G. John, William M. Landing, Susan H. Little, Yanbin Lu, Peter L. Morton, S. Bradley Moran, Laura F. Robinson, Rachel U. Shelley, Alan M. Shiller, Xin Yuan Zheng

Research output: Contribution to journalArticlepeer-review

15 Scopus citations

Abstract

The measurable supply of 232Th to the ocean can be used to derive the supply of other elements, which is more difficult to quantify directly. The measured inventory of an element divided by the derived supply yields a replacement time estimate, which in special circumstances is related to a residence time. As a proof of concept, Th-based supply rates imply a range in the replacement times of the rare earth elements in the North Atlantic that is consistent with the chemical reactivity of rare earth elements related to their ionic charge density. Similar estimates of replacement times for the bioactive trace elements (Fe, Mn, Zn, Cd, Cu, and Co), ranging from <5 years to >50,000 years, demonstrate the broad range of elemental reactivity in the ocean. Here we discuss how variations in source composition, fractional solubility ratios, or noncontinental sources, such as hydrothermal vents, lead to uncertainties in Th-based replacement time estimates. We show that the constraints on oceanic replacement time provided by the Th-based calculations are broadly applicable in predicting how elements are distributed in the ocean and for some elements, such as Fe, may inform us on how the carbon cycle may be impacted by trace element supply and removal.

Original languageEnglish (US)
Pages (from-to)1294-1311
Number of pages18
JournalGlobal Biogeochemical Cycles
Volume32
Issue number9
DOIs
StatePublished - Sep 2018

Bibliographical note

Funding Information:
This study grew out of a synthesis workshop at the Lamont-Doherty Earth Observatory of Columbia University in August 2016, with financial support from the GEOTRACES Project Office (U.S. NSF 1536294) and the Ocean Carbon and Biogeochemistry Program. The U.S. National Science Foundation supported all of the analytical work on GA03: Th isotope work at Columbia University, the University of Minnesota, and the Woods Hole Oceanographic Institution (NSF OCE-0927064, OCE-0926860, and OCE-0927754); REE work at the University of Southern Mississippi (NSF OCE-0927951); and aerosol work at the Florida State University (NSF OCE-0752832, OCE-0929919, and OCE-1132766). A portion of this work was performed at the National High Magnetic Field Laboratory, which is supported by National Science Foundation Cooperative Agreement DMR-1157490 and the State of Florida. The lead author acknowledges support from a start-up grant from the University of Southern Mississippi. This manuscript benefited from comments made by participants at the 2017 Gordon Research Conference on Chemical Oceanography at Colby-Sawyer College and formal reviews by the Associate Editor, Gideon Henderson, and one anonymous reviewer. GA03 data used in this study are accessible through the Biological and Chemical Oceanography Data Management Office (http://data.bco-dmo.org/jg/dir/BCO/GEOTRACES/NorthAtlanticTransect/). Basin-averaged North Atlantic data are available in the supporting information.

Funding Information:
This study grew out of a synthesis workshop at the Lamont-Doherty Earth Observatory of Columbia University in August 2016, with financial support from the GEOTRACES Project Office (U.S. NSF 1536294) and the Ocean Carbon and Biogeochemistry Program. The U.S. National Science Foundation supported all of the analytical work on GA03: Th isotope work at Columbia University, the University of Minnesota, and the Woods Hole Oceanographic Institution (NSF OCE-0927064, OCE-0926860, and OCE-0927754); REE work at the University of Southern Mississippi (NSF OCE-0927951); and aerosol work at the Florida State University (NSF OCE- 0752832, OCE-0929919, and OCE- 1132766). A portion of this work was performed at the National High Magnetic Field Laboratory, which is supported by National Science Foundation Cooperative Agreement DMR-1157490 and the State of Florida. The lead author acknowledges support from a start-up grant from the University of Southern Mississippi. This manuscript benefited from comments made by participants at the 2017 Gordon Research Conference on Chemical Oceanography at Colby-Sawyer College and formal reviews by the Associate Editor, Gideon Henderson, and one anonymous reviewer. GA03 data used in this study are accessible through the Biological and Chemical Oceanography Data Management Office (http://data.bco-dmo.org/jg/dir/ BCO/GEOTRACES/NorthAtlantic Transect/). Basin-averaged North Atlantic data are available in the supporting information.

Publisher Copyright:
©2018. American Geophysical Union. All Rights Reserved.

Keywords

  • GEOTRACES
  • geochemistry
  • residence times
  • trace metals

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