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Biogeosciences An interactive open-access journal of the European Geosciences Union
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https://doi.org/10.5194/bg-2019-71
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/bg-2019-71
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

Submitted as: research article 10 Apr 2019

Submitted as: research article | 10 Apr 2019

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This discussion paper is a preprint. It is a manuscript under review for the journal Biogeosciences (BG).

Stable isotope signatures of Holocene syngenetic permafrost trace seabird presence in the Thule District (NW Greenland)

Sebastian Wetterich1, Thomas A. Davidson2, Anatoly Bobrov3, Thomas Opel1, Torben Windirsch1, Kasper L. Johansen4, Ivan González-Bergonzoni5, Anders Mosbech4, and Erik Jeppesen2 Sebastian Wetterich et al.
  • 1Alfred Wegener Institute, Helmholtz Center for Polar and Marine Research, Potsdam, Germany
  • 2Department of Bioscience, Arctic Research Centre, Aarhus University, Silkeborg, Denmark
  • 3Department of Soil Science, MoscowState University, Russia
  • 4Department of Bioscience, Arctic Research Centre, Aarhus University, Roskilde, Denmark
  • 5Departamento del Agua, CENUR Litoral Norte, Universidad de la República, Paysandú, Uruguay

Abstract. Holocene permafrost from ice wedge polygons in the vicinity of large seabird breeding colonies in the Thule District, NW Greenland, was drilled to explore the relation between permafrost aggradation and seabird presence. The latter is reliant on the presence of the North Water (NOW) polynya in the northern Baffin Bay. The onset of peat accumulation associated with the arrival of little auks (Alle alle) in a breeding colony at Annikitisoq north of Cape York is radiocarbon-dated to 4400 cal yr BP. A thick-billed murre (Uria lomvia) colony on Appat (Saunders Ø) in the mouth of the Wolstenholme Fjord started 5650 cal yr BP. Both species provide marine-derived nutrients (MDNs) that fertilise vegetation and promote peat growth. The geochemical signature of organic matter left by the birds is traceable in the frozen Holocene peat. The peat accumulation rates at both sites are highest after the onset and decrease over time and were about two-times faster at the little auk site than at the thick-billed murre site. High accumulation rates induce shorter periods of organic matter (OM) decomposition before it enters the perennially frozen state. This is seen in comparably high C / N and less depleted δ13C, pointing to a lower degree of OM decomposition at the little auk site, while the opposite pattern can be discerned at the thick-billed murre site. Peat accumulation rates correspond to δ15N trends, where decreasing accumulation led to increasing depletion in δ15N as seen in the little-auk related data. In contrast, the more decomposed OM of the thick-billed murre site shows almost stable δ15N. Late Holocene wedge ice fed by cold season precipitation was studied at the little auk site and provides the first such stable-water isotopic records from Greenland with mean δ18O of −18.0 ± 0.8 ‰, mean δD of −136.2 ± 5.7 ‰, mean d excess of 7.7 ± 0.7 ‰, and a δ18O-δD slope of 7.27, which is close to those of the modern Thule Meteoric Water Line. The syngenetic ice wedge polygon development is mirrored in testacean records of the little auk site and delineates polygon low-centre, dry-out and polygon-high-centre stages. The syngenetic permafrost formation directly depending on peat growth (controlled by bird activity) falls within the period of Neoglacial cooling and the establishment of the NOW polynya, thus indirectly follows the Holocene climate trends.

Sebastian Wetterich et al.
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Sebastian Wetterich et al.
Sebastian Wetterich et al.
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Short summary
The effects of seabird presence on permafrost peat evolution in NW Greenland were studied by tracing changes in stable C and N isotope composition along the path from bird sources into permafrost peat. The permafrost growth was triggered by organic matter and nutrient input since the neoglacial cooling and concurrent polynya establishment. The study deals with the complex response of biologic and permafrost dynamics to high-Arctic climatic and oceanographic conditions of the late Holocene.
The effects of seabird presence on permafrost peat evolution in NW Greenland were studied by...
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