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  • 1
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    Coastal Erosion of Permafrost Soils Along the Yukon Coastal Plain and Fluxes of Organic Carbon to the Canadian Beaufort Sea (2018)
    Wiley
    In:  EPIC3Journal of Geophysical Research-Biogeosciences, Wiley, 123(2), pp. 406-422, ISSN: 0148-0227
    Details
    Publication Date: 2018-08-13
    Description: Reducing uncertainties about carbon cycling is important in the Arctic where rapid environmental changes contribute to enhanced mobilization of carbon. Here we quantify soil organic carbon (SOC) contents of permafrost soils along the Yukon Coastal Plain and determine the annual fluxes from coastal erosion. Different terrain units were assessed based on surficial geology, morphology, and ground ice conditions. To account for the volume of wedge ice and massive ice in a unit, SOC contents were reduced by 19% and sediment contents by 16%. The SOC content in a 1 m² column of soil varied according to the height of the bluff, ranging from 30 to 662 kg, with a mean value of 183 kg. Forty‐four per cent of the SOC was within the top 1 m of soil and values varied based on surficial materials, ranging from 30 to 53 kg C/m³, with a mean of 41 kg. Eighty per cent of the shoreline was erosive with a mean annual rate of change of −0.7 m/yr. This resulted in a SOC flux per meter of shoreline of 132 kg C/m/yr, and a total flux for the entire 282 km of the Yukon coast of 35.5 × 10^6 kg C/yr (0.036 Tg C/yr). The mean flux of sediment per meter of shoreline was 5.3 × 103 kg/m/yr, with a total flux of 1,832 × 10^6 kg/yr (1.832 Tg/yr). Sedimentation rates indicate that approximately 13% of the eroded carbon was sequestered in nearshore sediments, where the overwhelming majority of organic carbon was of terrestrial origin.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 2
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    Nearshore zone dynamics determine pathway of organic carbon from eroding permafrost coasts (2020)
    Wiley
    In:  EPIC3Geophysical Research Letters, Wiley, 47, ISSN: 0094-8276
    Details
    Publication Date: 2022-07-04
    Description: Collapse of permafrost coasts delivers large quantities of particulate organic carbon (POC) to arctic coastal areas. With rapidly‐changing environmental conditions, sediment and organic carbon (OC) mobilization and transport pathways are also changing. Here, we assess the sources and sinks of POC in the highly‐dynamic nearshore zone of Herschel Island ‐ Qikiqtaruk (Yukon, Canada). Our results show that POC concentrations sharply decrease, from 15.9 to 0.3 mg L‐1, within the first 100 – 300 meters offshore. Simultaneously, radiocarbon ages of POC drop from 16,400 to 3,600 14C years, indicating rapid settling of old permafrost POC to underlying sediments. This suggests that permafrost OC is, apart from a very narrow resuspension zone (〈5 m water depth), predominantly deposited in nearshore sediments. While long‐term storage of permafrost OC in marine sediments potentially limits biodegradation and its subsequent release as greenhouse gas, resuspension of fine‐grained, OC‐rich sediments in the nearshore zone potentially enhances OC turnover.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , NonPeerReviewed , info:eu-repo/semantics/article
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  • 3
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    Eroding permafrost coasts release low amounts of dissolved organic carbon (DOC) from ground ice into the nearshore zone of the Arctic Ocean (2016)
    Wiley
    In:  EPIC3Global Biogeochemical Cycles, Wiley, 30(7), pp. 1054-1068, ISSN: 0886-6236
    Details
    Publication Date: 2022-08-12
    Description: Ice-rich permafrost coasts in the Arctic are highly sensitive to climate warming and erode at a pace that exceeds the global average. Permafrost coasts deliver vast amounts of organic carbon into the nearshore zone of the Arctic Ocean. Numbers on flux exist for particulate organic carbon (POC) and total or soil organic carbon (TOC, SOC). However, they do not exist for dissolved organic carbon (DOC), which is known to be highly bioavailable. This study aims to estimate DOC stocks in coastal permafrost as well as the annual flux into the ocean. DOC concentrations in ground ice were analyzed along the ice-rich Yukon coast (YC) in the western Canadian Arctic. The annual DOC flux was estimated using available numbers for coast length, cliff height, annual erosion rate, and volumetric ice content in different stratigraphic horizons. Our results showed that DOC concentrations in ground ice range between 0.3 and 347.0 mg L^-1 with an estimated stock of 13.6 ± 3.0 g m^-3 along the YC. An annual DOC flux of 54.9 ± 0.9 Mg yr^-1 was computed. These DOC fluxes are low compared to POC and SOC fluxes from coastal erosion or POC and DOC fluxes from Arctic rivers. We conclude that DOC fluxes from permafrost coasts play a secondary role in the Arctic carbon budget. However, this DOC is assumed to be highly bioavailable. We hypothesize that DOC from coastal erosion is important for ecosystems in the Arctic nearshore zones, particularly in summer when river discharge is low, and in areas where rivers are absent.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , NonPeerReviewed
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  • 4
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    Rapid CO2 release from eroding permafrost in seawater (2019)
    Wiley
    In:  EPIC3Geophysical Research Letters, Wiley, 46, ISSN: 0094-8276
    Details
    Publication Date: 2022-08-12
    Description: Permafrost is thawing extensively due to climate warming. When permafrost thaws, previously frozen organic carbon (OC) is converted into carbon dioxide (CO2) or methane, leading to further warming. This process is included in models as gradual deepening of the seasonal non‐frozen layer. Yet, models neglect abrupt OC mobilization along rapidly eroding Arctic coastlines. We mimicked erosion in an experiment by incubating permafrost with seawater for an average Arctic open‐water season. We found that CO2 production from permafrost OC is as efficient in seawater as without. For each gram (dry weight) of eroding permafrost, up to 4.3 ± 1.0 mg CO2 will be released and 6.2 ± 1.2% of initial OC mineralized at 4 °C. Our results indicate that potentially large amounts of CO2 are produced along eroding permafrost coastlines, onshore and within nearshore waters. We conclude that coastal erosion could play an important role in carbon cycling and the climate system.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , NonPeerReviewed , info:eu-repo/semantics/article
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  • 5
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    Ice wedge polygon stability on steep slopes in West Greenland related to temperature and moisture dynamics of the active layer (2023)
    Wiley
    In:  EPIC3Permafrost and Periglacial Processes, Wiley, 34(2), pp. 194-207, ISSN: 1045-6740
    Details
    Publication Date: 2023-08-28
    Description: Ice wedge polygons on steep slopes have generally been described as being covered by periglacial sediments and, typically, the active layer on slopes becomes mobile during thaw periods, which can lead to solifluction. In West Greenland close to the ice margin, however, the active layer and ice wedge polygons are stable despite their occurrence on steep slopes with inclinations of ≥30°. We conducted a soil survey (including sampling for soil analyses and radiocarbon dating) in the Umimmalissuaq valley and installed a field station ~4 km east of the current ice margin to monitor soil temperature and water tension at depths of 10, 20 and 35 cm of the active layer on a steep, north-facing slope in the middle of an ice wedge polygon from 2009 to 2015. Thawing and freezing periods lasted between 2 and 3 months and the active layer was usually completely frozen from November to April. We observed simultaneous and complete water saturation at all three depths of the active layer in one summer for 1 day. The amount of water in the active layer apparently was not enough to trigger solifluction during the summer thaw, even at slope inclinations above 30°. In addition, the dense shrub tundra absorbs most of the water during periods between thawing and freezing, which further stabilizes the slope. This process, together with the dry and continental climate caused by katabatic winds combined with no or limited frost heave, plays a crucial role in determining the stability of these slopes and can explain the presence of large-scale stable ice wedge polygon networks in organic matter-rich permafrost, which is about 5,000 years old. This study underlines the importance of soil hydrodynamics and local climate regime for landscape stability and differing intensities of solifluction processes in areas with strong geomorphological gradients and rising air temperatures.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 6
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    Northeast Siberian Permafrost Ice-Wedge Stable Isotopes Depict Pronounced Last Glacial Maximum Winter Cooling (2021)
    Wiley
    In:  EPIC3Geophysical Research Letters, Wiley, 48(7), pp. e2020GL092087-e2020GL092087, ISSN: 0094-8276
    Details
    Publication Date: 2024-04-20
    Description: Stable isotopes (δ18O, δD) of wedge ice hold potential to reconstruct past winter climate conditions. Here, we present records of the marine isotope stages (MIS) 3 and 2 including the last Glacial maximum (LGM) from Bol’shoy Lyakhovsky Island (NE Siberia). MIS 3 wedge ice dated from 52 to 40 Kyr b2k varies between −32 and −29‰ in δ18O. Colder LGM conditions are implied by δ18O of −37‰ around 25 Kyr b2k. Similar Deuterium excess values indicate comparable moisture sources during MIS 3 and MIS 2. Regional LGM climate reconstructions depend on the seasonal resolution of the proxies and model simulations. Our wedge-ice record reflects coldest winters during global minima in atmospheric CO2 and sea level. The extreme LGM winter cooling is not represented in model projections of global LGM climate where West Beringia shows noticeably little cooling or even warming in mean annual temperatures compared to the late Holocene.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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