Journal cover Journal topic
Biogeosciences An interactive open-access journal of the European Geosciences Union
Journal topic
Volume 10, issue 9
Biogeosciences, 10, 6019–6028, 2013
https://doi.org/10.5194/bg-10-6019-2013
© Author(s) 2013. This work is distributed under
the Creative Commons Attribution 3.0 License.
Biogeosciences, 10, 6019–6028, 2013
https://doi.org/10.5194/bg-10-6019-2013
© Author(s) 2013. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 12 Sep 2013

Research article | 12 Sep 2013

Late Holocene variations in Pacific surface circulation and biogeochemistry inferred from proteinaceous deep-sea corals

T. P. Guilderson1,2, M. D. McCarthy2, R. B. Dunbar3, A. Englebrecht1, and E. B. Roark3,* T. P. Guilderson et al.
  • 1Center for Accelerator Mass Spectrometry, Lawrence Livermore National Laboratory, Livermore, CA, USA
  • 2Institute of Marine Sciences and Department of Ocean Sciences, University of California, Santa Cruz, CA, USA
  • 3Department of Environmental Earth System Science, Stanford University, Stanford, CA, USA
  • *now at: Department of Geography, Texas A&M University, College Station, TX, USA

Abstract. δ15N and δ13C data obtained from samples of proteinaceous deep-sea corals collected from the North Pacific Subtropical Gyre (Hawaiian Archipelago) and the central equatorial Pacific (Line Islands) document multidecadal to century-scale variability in the isotopic composition of surface-produced particulate organic matter exported to the deep sea. Comparison of the δ13C data, where Line Islands samples are 0.6‰ more positive than the Hawaiian samples, supports the contention that the North Pacific Subtropical Gyre is more efficient than the tropical upwelling system at trapping and/or recycling nutrients within the mixed layer. δ15N values from the Line Islands samples are also more positive than those from the central gyre, and within the Hawaiian samples there is a gradient with more positive δ15N values in samples from the main Hawaiian Islands versus the French Frigate Shoals in the Northwestern Hawaiian Islands. The gradient in the Hawaiian samples likely reflects the relative importance of algal acquisition of metabolic N via dissolved seawater nitrate uptake versus nitrogen fixation. The Hawaiian sample set also exhibits a strong decrease in δ15N values from the mid-Holocene to present. We hypothesize that this decrease is most likely the result of decreasing trade winds, and possibly a commensurate decrease in entrainment of more positive δ15N-NO3 subthermocline water masses.

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