Coastal ocean and shelf-sea biogeochemical cycling of trace elements and isotopes: Lessons learned from GEOTRACES

Matthew A. Charette, Phoebe J. Lam, Maeve C. Lohan, Eun Young Kwon, Vanessa Hatje, Catherine Jeandel, Alan M. Shiller, Gregory A. Cutter, Alex Thomas, Philip W. Boyd, William B. Homoky, Angela Milne, Helmuth Thomas, Per S. Andersson, Don Porcelli, Takahiro Tanaka, Walter Geibert, Frank Dehairs, Jordi Garcia-Orellana

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28 Citations (Scopus)

Abstract

© 2016 The Author(s) Published by the Royal Society. All rights reserved. Continental shelves and shelf seas play a central role in the global carbon cycle. However, their importance with respect to trace element and isotope (TEI) inputs to ocean basins is less well understood. Here, we present major findings on shelf TEI biogeochemistry from the GEOTRACES programme as well as a proof of concept for a new method to estimate shelf TEI fluxes. The case studies focus on advances in our understanding of TEI cycling in the Arctic, transformations within a major river estuary (Amazon), shelf sediment micronutrient fluxes and basin-scale estimates of submarine groundwater discharge. The proposed shelf flux tracer is 228-radium (T1/2 = 5.75 yr), which is continuously supplied to the shelf from coastal aquifers, sediment porewater exchange and rivers. Model-derived shelf 228Ra fluxes are combined with TEI/228Ra ratios to quantify ocean TEI fluxes from the western North Atlantic margin. The results from this new approach agree well with previous estimates for shelf Co, Fe, Mn and Zn inputs and exceed published estimates of atmospheric deposition by factors of approximately 3-23. Lastly, recommendations are made for additional GEOTRACES process studies and coastal margin-focused section cruises that will help refine the model and provide better insight on the mechanisms driving shelf-derived TEI fluxes to the ocean. This article is part of the themed issue 'Biological and climatic impacts of ocean trace element chemistry'.
Original languageEnglish
Article number20160076
JournalPhilosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences
Volume374
Issue number2081
DOIs
Publication statusPublished - 28 Nov 2016

Keywords

  • Continental shelf
  • GEOTRACES
  • Isotopes
  • Radium
  • Trace Elements

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    Charette, M. A., Lam, P. J., Lohan, M. C., Kwon, E. Y., Hatje, V., Jeandel, C., Shiller, A. M., Cutter, G. A., Thomas, A., Boyd, P. W., Homoky, W. B., Milne, A., Thomas, H., Andersson, P. S., Porcelli, D., Tanaka, T., Geibert, W., Dehairs, F., & Garcia-Orellana, J. (2016). Coastal ocean and shelf-sea biogeochemical cycling of trace elements and isotopes: Lessons learned from GEOTRACES. Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, 374(2081), [20160076]. https://doi.org/10.1098/rsta.2016.0076