Current Results

Sedimentary and geochemical characteristics of two small permafrost-dominated Arctic river deltas in northern Alaska

Matthias Fuchs, Guido Grosse, Benjamin M. Jones, Jens Strauss, Carson A. Baughman, Donald A. Walker

Arktos (2018) 4: 20.

Abstract: Arctic river deltas are highly dynamic environments in the northern circumpolar permafrost region that are affected by fluvial, coastal, and permafrost-thaw processes. They are characterized by thick sediment deposits containing large but poorly constrained amounts of frozen organic carbon and nitrogen. This study presents new data on soil organic carbon and nitrogen storage as well as accumulation rates from the Ikpikpuk and Fish Creek river deltas, two small, permafrost-dominated arctic river deltas on the Arctic Coastal Plain of northern Alaska. A soil organic carbon storage of 42.4 kg C m-2 and 37.9 kg C m-2 and soil nitrogen storage of 2.1 kg N m-2 and 2.0 kg N m-2 was found for the first two meters of soil for the Ikpikpuk and Fish Creek river delta, respectively. While the upper meter of soil contains 3.57 Tg C, substantial amounts of carbon (3.09 Tg C or 46%) are also stored within the second meter of soil (100 – 200 cm) in the two deltas. An increasing and inhomogeneous distribution of C with depth is indicative of the dominance of deltaic depositional rather than soil forming processes for soil organic carbon storage. Largely mid- to late Holocene radiocarbon dates in our cores suggest different carbon accumulation rates for the two deltas for the last 2000 years. Rates up to 28 g C m-2 yr-1 for the Ikpikpuk river delta are about twice as high as the Fish Creek river delta. With this study, we highlight the importance of including these highly dynamic permafrost environments in future permafrost carbon estimations.

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Carbon and nitrogen pools in thermokarst-affected permafrost landscapes in Arctic Siberia

Matthias Fuchs, Guido Grosse, Jens Strauss, Frank Günther, Mikhail Grigoriev, Georgy M. Maximov, Gustaf Hugelius

Biogeosciences, 15, 953-971, 2018
DOI: 10.5194/bg-15-953-2018

Summary: Ice-rich yedoma-dominated landscapes store considerable amounts of organic carbon (C) and nitrogen (N) and are vulnerable to degradation under climate warming. We investigate the C and N pools in two thermokarst-affected yedoma landscapes – on Sobo-Sise Island and on Bykovsky Peninsula in the north of eastern Siberia. Soil cores up to 3 m depth were collected along geomorphic gradients and analysed for organic C and N contents. A high vertical sampling density in the profiles allowed the calculation of C and N stocks for short soil column intervals and enhanced understanding of within-core parameter variability. Profile-level C and N stocks were scaled to the landscape level based on landform classifications from 5 m resolution, multispectral RapidEye satellite imagery.

Mean landscape C and N storage in the first metre of soil for Sobo-Sise Island is estimated to be 20.2 kg C m−2 and 1.8 kg N m−2 and for Bykovsky Peninsula 25.9 kg C m−2 and 2.2 kg N m−2. Radiocarbon dating demonstrates the Holocene age of thermokarst basin deposits but also suggests the presence of thick Holocene-age cover layers which can reach up to 2 m on top of intact yedoma landforms. Reconstructed sedimentation rates of 0.10–0.57 mm yr−1 suggest sustained mineral soil accumulation across all investigated landforms. Both yedoma and thermokarst landforms are characterized by limited accumulation of organic soil layers (peat).
We further estimate that an active layer deepening of about 100 cm will increase organic C availability in a seasonally thawed state in the two study areas by  ∼  5.8 Tg (13.2 kg C m−2). Our study demonstrates the importance of increasing the number of C and N storage inventories in ice-rich yedoma and thermokarst environments in order to account for high variability of permafrost and thermokarst environments in pan-permafrost soil C and N pool estimates.

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Deep Yedoma permafrost: A synthesis of depositional characteristics and carbon vulnerability

Jens Strauss, Lutz Schirrmeister, Guido Grosse, Daniel Fortier, Gustaf Hugelius, Christian Knoblauch, Vladimir Romanovsky, Christina Schädel, Thomas Schneider von Deimling, Edward A. G. Schuur, Denis Shmelev, Mathias Ulrich, Alexandra Veremeeva

Earth-Science Reviews, 172, September 2017, Pages 75-86, 

Summary: Permafrost is a distinct feature of the terrestrial Arctic and is vulnerable to climate warming. Permafrost degrades in different ways, including deepening of a seasonally unfrozen surface and localized but rapid development of deep thaw features. Pleistocene ice-rich permafrost with syngenetic ice-wedges, termed Yedoma deposits, are widespread in Siberia, Alaska, and Yukon, Canada and may be especially prone to rapid-thaw processes. Freeze-locked organic matter in such deposits can be re-mobilized on short time-scales and contribute to a carbon-cycle climate feedback. Here we synthesize the characteristics and vulnerability of Yedoma deposits by synthesizing studies on the Yedoma origin and the associated organic carbon pool. We suggest that Yedoma deposits accumulated under periglacial weathering, transport, and deposition dynamics in non-glaciated regions during the late Pleistocene until the beginning of late glacial warming. The deposits formed due to a combination of aeolian, colluvial, nival, and alluvial deposition and simultaneous ground ice accumulation. We found up to 130 gigatons organic carbon in Yedoma, parts of which are well-preserved and available for fast decomposition after thaw. Based on incubation experiments, up to 10% of the Yedoma carbon is considered especially decomposable and may be released upon thaw. The substantial amount of ground ice in Yedoma makes it highly vulnerable to disturbances such as thermokarst and thermo-erosion processes. Mobilization of permafrost carbon is expected to increase under future climate warming. Our synthesis results underline the need of accounting for Yedoma carbon stocks in next generation Earth-System-Models for a more complete representation of the permafrost-carbon feedback.

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Landsat-Based Trend Analysis of Lake Dynamics across Northern Permafrost Regions

Ingmar Nitze, Guido Grosse, Benjamin M. Jones, Christopher D. Arp, Mathias Ulrich, Alexander Fedorov, Alexandra Veremeeva

Remote Sensing, 9(7), 640,2017, doi:10.3390/rs9070640

Summary: Lakes are a ubiquitous landscape feature in northern permafrost regions. They have a strong impact on carbon, energy and water fluxes and can be quite responsive to climate change. The monitoring of lake change in northern high latitudes, at a sufficiently accurate spatial and temporal resolution, is crucial for understanding the underlying processes driving lake change. To date, lake change studies in permafrost regions were based on a variety of different sources, image acquisition periods and single snapshots, and localized analysis, which hinders the comparison of different regions. Here, we present a methodology based on machine-learning based classification of robust trends of multi-spectral indices of Landsat data (TM, ETM+, OLI) and object-based lake detection, to analyze and compare the individual, local and regional lake dynamics of four different study sites (Alaska North Slope, Western Alaska, Central Yakutia, Kolyma Lowland) in the northern permafrost zone from 1999 to 2014.

Regional patterns of lake area change on the Alaska North Slope (−0.69%), Western Alaska (−2.82%), and Kolyma Lowland (−0.51%) largely include increases due to thermokarst lake expansion, but more dominant lake area losses due to catastrophic lake drainage events. In contrast, Central Yakutia showed a remarkable increase in lake area of 48.48%, likely resulting from warmer and wetter climate conditions over the latter half of the study period.

Within all study regions, variability in lake dynamics was associated with differences in permafrost characteristics, landscape position (i.e., upland vs. lowland), and surface geology. With the global availability of Landsat data and a consistent methodology for processing the input data derived from robust trends of multi-spectral indices, we demonstrate a transferability, scalability and consistency of lake change analysis within the northern permafrost region.

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Yedoma Ice Complex of the Buor Khaya Peninsula (southern Laptev Sea)

Lutz Schirrmeister, Georg Schwamborn, Pier Paul Overduin, Jens Strauss, Margret C. Fuchs, Mikhail Grigoriev, Irina Yakshina, Janet Rethemeyer, Elisabeth Dietze, and Sebastian Wetterich

Biogeosciences, 14, 1261-1283, 2017 doi:10.5194/bg-14-1261-2017

Summary: In this study, we investigate late Pleistocene permafrost at the western coast of the Buor Khaya Peninsula in the south-central Laptev Sea (Siberia). Two Yedoma exposures and one drill core were studied for cryolithological, geochemical, and geochronological parameters. The deposition of the Yedoma, as revealed by radiocarbon dates of sedimentary organic matter, took place between 54.1 and 30.1 kyr BP. Continued Yedoma deposition until about 14.7 kyr BP is shown by dates from organic matter preserved in ice-wedge ice. For the lowermost and oldest Yedoma part, infrared-stimulated luminescence dates on feldspar show deposition ages between 51.1 ± 4.9 and 44.2 ± 3.6 kyr BP. The cryolithological inventory of the Yedoma IC preserved on the Buor Khaya Peninsula is closely related to the results of other studies, for example, to the west on the Bykovsky Peninsula, where formation time and formation conditions were similar. Due to intense coastal erosion, the biogeochemical signature of the studied Yedoma IC represents the terrestrial end-member, and is closely related to organic matter currently being deposited in the marine realm of the Laptev Sea shelf.


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