Journal
GEOMORPHOLOGY
Volume 303, Issue -, Pages 504-523Publisher
ELSEVIER SCIENCE BV
DOI: 10.1016/j.geomorph.2017.11.003
Keywords
Holocene landscape history; Ground ice; NE Greenland; Carbon sink
Funding
- EC [282700]
- University Centre in Svalbard, UNIS
- Center for Permafrost, CENPERM at University of Copenhagen
- Danish National Research Foundation [CENPERM DNRF100]
- Nordic Center of Excellence, DEFROST 'Biogeochemistry in a changing cryosphere depicting ecosystem-climate feedbacks as affected by changes in permafrost, snow and ice distribution' - Nordic Research Council [23001]
- Perma-Nordnet [43082]
- Norden as part of (Nordic Ministerial Council) Arctic collaboration program
- Center for Permafrost (CENPERM), Copenhagen
- University Centre in Svalbard (UNIS)
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In High Arctic northern Greenland, future responses to climatic changes are poorly understood on a landscape scale. Here, we present a study of the geomorphology and cryostratigraphy in the Zackenberg Valley in NE Greenland (74 degrees N) containing a geomorphological map and a simplified geocryological map, combined with analyses of 13 permafrost cores and two exposures. Cores from a solifluction sheet, alluvial fans, and an emerged delta were studied with regards to cryostructures, ice and total carbon contents, grain size distribution, and pore water electrical conductivity; and the samples were AMS C-14 dated. The near-surface permafrost on slopes and alluvial fans is ice rich, as opposed to the ice-poor epigenetic permafrost in the emerged delta. Ground ice and carbon distribution are closely linked to sediment transport processes, which largely depend on lithology and topography. Holocene alluvial fans on the lowermost hillslopes, covering 12% of the study area, represent paleoenvironmental archives. During the contrasting climates of the Holocene, the alluvial fans continued to aggrade - through the warmer early Holocene Optimum, the colder late Holocene, and the following climate warming - and by 0.45 mm a(-1), on average. This is caused by three factors: sedimentation, ground ice aggradation, and vegetation growth and is reflected by AMS C-14 dating and continuously alternating cryostructures. Highly variable sedimentation rates in space and time at the alluvial fans have been detected. This is also reflected by alternating lenticular and microlenticular cryostructures indicating syngenetic permafrost aggradation during sedimentation with suspended and organic-matrix cryostructures indicating quasi-syngenetic permafrost aggradation in response to vegetation growth in periods with reduced or no sedimentation. Over time, this causes organic matter to become buried, indicating that alluvial fans represent effective carbon sinks that have previously been overlooked. (C) 2017 Elsevier B.V. All rights reserved.
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