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 Polynya (NOW)
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 BP. A
thick-billed murre (Uria lomvia) colony on Appat (Saunders Island) in the mouth of the
Wolstenholme Fjord started 5650 cal BP. Both species provide
marine-derived nutrients (MDNs) that fertilize 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, decrease over time, and were about
2-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 ratios 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 stable-water isotopic record 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-center, dry-out, and
polygon-high-center 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, thus
indirectly following the Holocene climate trends.
Recent Peat Accumulation Rates in Zoige Peatlands, Eastern Tibet, Inferred by 210Pb and 137Cs Radiometric Techniques
