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  • 1
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    The SPLASH Action Group – Towards standardized sampling strategies in permafrost science (2020)
    In:  EPIC3Advances in Polar Science, 31(3), pp. 153-155, ISSN: 1674-9928
    Details
    Publication Date: 2020-09-14
    Description: The Action Group called ‘Standardized methods across Permafrost Landscapes: from Arctic Soils to Hydrosystems’ (SPLASH) is a community-driven effort aiming to provide a suite of standardized field strategies for sampling mineral and organic components in soils, sediments, and water across permafrost landscapes. This unified approach will allow data from different landscape interfaces, field locations and seasons to be shared and compared, thus improving our understanding of the processes occurring during lateral transport in circumpolar Arctic watersheds.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 2
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    Lateral and vertical organic matter dynamics in an Arctic lagoon system (2020)
    In:  EPIC3Arctic Change 2020, Online, 2020-12-07-2020-12-10
    Details
    Publication Date: 2021-02-14
    Description: Increasing warming causes severe environmental changes in the Arctic coastal zone such as longer open water periods and rising sea levels. These processes intensify the erosion of permafrost coasts and lateral transport of sediment and organic matter (OM). Lagoons play a particularly important role in the transfer process of terrestrial OM but have been rarely investigated in the Arctic. Here, we studied a lagoon system along the Arctic Yukon coast to better understand the lateral pathways of OM from land to sea and its deposition dynamics over time. We sampled terrestrial, lagoon and marine sediment to track OM along a land-lagoon-ocean transect and took short cores to assess OM deposition dynamics. Samples were analysed for total organic carbon and nitrogen (TOC, TN), stable carbon and nitrogen isotopes (δ13C, δ15N), as well as grain size and surface area. We further analysed the shoreline change rates of the lagoon from 1950s to 2018 and coupled it to sedimentation rates derived from 210Pb/137Cs dating. Turbidity was estimated in the lagoon surface water using Landsat imagery for the main wind directions. Our results show that OC concentrations significantly decrease along the land-lagoon-ocean transect. Currents potentially removed large portions of eroded OM, especially under easterly winds, which is indicated by elevated SPM concentrations. In contrast, OM can get buried quickly, which is indicated by high OM contents in deeper lagoon sediments. Coastal erosion rates in the lagoon increased drastically since the 1970s and correspond with increasing sedimentation rates, suggesting a direct relation of environmental forcing and OM deposition dynamics in the lagoon. We conclude that lagoons are a crucial transfer zone between land and ocean, which can substantially influence OM pathways. Under current environmental change scenarios in the Arctic, the role of lagoons may get more important as gateways of OM from land to sea.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev
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  • 3
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    Landscape-related ground ice variability on the Yukon coastal plain inferred from computed tomography and potential implications on lateral permafrost carbon release (2020)
    In:  EPIC3Arctic Change 2020, Online, 2020-12-07-2020-12-10
    Details
    Publication Date: 2021-02-14
    Description: Warming in the Arctic causes strong environmental changes with permafrost degradation being among the most striking effects. Active layer deepening and permafrost erosion can result in the mobilization and lateral transport of organic carbon (OC), which potentially alters carbon cycles in the Arctic substantially. Although the understanding of ground ice contents and permafrost OC release is improving, still little is known of permafrost OC release rates, lateral transport pathways and its driving mechanisms on a landscape scale. In this study we investigate ground ice characteristics and OC composition of the most dominant landscape units of the Yukon coastal plain. In total, 12 permafrost cores were taken from moraine, lacustrine, fluvial and glaciofluvial deposits with a SIPRE corer. Ground ice and sediment contents were analysed using computed tomography and k-means classification. Active layer and upper permafrost were subsampled to analyse OC contents and isotopes of bulk material and a leaching-incubation experiment was conducted with active layer and permafrost sediments to assess potential dissolved OC export and degradation rates. Preliminary results show that ground ice contents vary significantly between landscape units. Ground ice contents in permafrost average 72.4 vol.-% with highest contents in moraines (78.3 vol.-%) and lowest contents in fluvial deposits (53.2 vol.-%). We expect highest dissolved OC leaching and loss rates from permafrost in contrast to active layer and from fluvial and lacustrine deposits, as they simply contain more OC. Yet, lateral OC transport is more likely for landscapes with a topographic gradient such as ground ice-rich moraines. We conclude that due to the high ground ice contents on the Yukon coastal plain, substantial changes of the permafrost landscape will occur under current warming trends. This will include subsidence, abrupt erosion, changes in hydrology and OC degradation processes, which will differ between landscape units.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev
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  • 4
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    Retrogressive thaw slumps along permafrost coasts transform organic matter before release into the Arctic Ocean (2020)
    In:  EPIC3European Geosciences Union General Assembly, Vienna, Austria, 2020-05-04-2020-05-08
    Details
    Publication Date: 2020-05-28
    Description: Changing environmental conditions in the Arctic have profound impacts on permafrost coasts, which erode at great pace. Although numbers exist on annual carbon and sediment fluxes from coastal erosion, little is known on how terrestrial organic matter (OM) is transformed by thermokarst and –erosional processes on transit from land to sea. Here, we investigated a retrogressive thaw slump (RTS) on Qikiqtaruk - Herschel Island in the western Canadian Arctic. The RTS was classified into an undisturbed, disturbed and nearshore zone and systematically sampled along transects. Collected sediments were analyzed for organic carbon (OC), nitrogen (N), stable carbon isotopes (δ13C-OC) and ammonium. C/N-ratios, δ13C-signatures and ammonium concentrations were used as general indicator for OM degradation. Permafrost sediments from the RTS headwall and mud lobe sediments from the thaw stream outlet were incubated to further assess OM degradation and potential greenhouse gas formation during slumping and upon release into the nearshore zone. Our results show that OM concentrations significantly decrease upon slumping in the disturbed zone with OC and N decreasing by 〉70% and 〉50%, respectively. Whereas δ13C-signatures remain fairly stable, C/N-ratios decrease significantly and ammonium concentrations increase slightly in fresh slumping material. Nearshore sediments have low OM contents and a terrestrial signature comparable to disturbed sites on land. The incubations show that carbon dioxide (CO2) forms quickly from thawing permafrost deposits and mud debris with ~2-3 mg CO2 per gram dry weight being cumulatively produced within two months. We suggest that the initial strong decrease in OM concentration after slumping is caused by a combination of OC degradation, dilution with melted massive ice and immediate offshore transport via the thaw stream. After stabilization in the slump floor, recolonizing vegetation takes up N from the disturbed sediment. Upon release into the nearshore zone, larger portions of OM are directly deposited in marine sediments, where they further degrade or being buried. The incubations indicate that CO2 is rapidly produced upon slumping and potentially continues to form within the nearshore zone that receives eroded material. We conclude that coastal RTS systems profoundly change the characteristic of modern and ancient permafrost terrestrial OM during transit from land to sea - a process which is likely linked to the production of greenhouse gases. Our study provides valuable information on the potential fate of terrestrial OM along eroding permafrost coasts under the trajectory of a warming Arctic.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev
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  • 5
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    Hydrodynamic sorting and degradation of permafrost organic matter in the nearshore zone of Herschel Island (Yukon, Canada) (2020)
    In:  EPIC3Arctic Change Conference, Online, Canada, 2020-12-07-2020-12-10
    Details
    Publication Date: 2021-02-14
    Description: Thermal erosion of permafrost coasts delivers large quantities of organic carbon (OC) to arctic coastal waters. While deposition of permafrost OC in nearshore sediments potentially attenuates the ‘permafrost carbon feedback’, continued resuspension of sediments by waves, storms and currents potentially enhances greenhouse gas production in the nearshore zone. Recent studies, focusing on bulk sediments, suggest that permafrost OC derived from coastal erosion is predominantly deposited in the nearshore zone. However, hydrodynamic gradients in the coastal zone allow sorting processes to strongly influence the OC distribution and fate, which cannot be assessed by using bulk sediment approaches. Here, we study soils and sediments fractionated by density (1.8 g/cm-3 cutoff), separating the organic from the mineral-associated fraction, and size (63 µm), separating sand-associated from silt and clay-associated OC. We sampled sediments along a transect from an active retrogressive thaw slump at the coast of Herschel Island - Qikiqtaruk (Yukon, Canada), to the nearshore zone, towards an offshore sedimentary basin. Each sediment fraction was analysed for its elemental content (TOC, TN), carbon isotope signature (δ13C, Δ14C), molecular biomarkers (n-alkanes, n-alkanoic acids, lignin phenols, cutin acids), and mineral surface area. Preliminary data show that the OC partitioning between the sediment fractions changes considerably over the transect, suggesting that hydrodynamic sorting processes take place. Additionally, the OC characteristics of the fractions are significantly different from each other. For example, the low-density organic fraction shows a slightly less degraded signal than the high-density silt- and clay-associated OC fraction in several molecular biomarker proxies, and has a higher average TOC/TN ratio (24 ±3 versus 12 ±2). We aim to disentangle sorting processes and degradation mechanisms of permafrost OC along this transect of fractionated soils and sediments in the nearshore zone, and give new insights into pathway of this material upon erosion.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev
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  • 6
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    Molecular and radiocarbon constraints on sources and degradation of terrestrial organic carbon along the Kolyma paleoriver transect, East Siberian Sea (2010)
    Copernicus Publications on behalf of the European Geosciences Union
    Details
    Publication Date: 2022-05-25
    Description: © The Authors, 2010. This article is distributed under the terms of the Creative Commons Attribution 3.0 License. The definitive version was published in Biogeosciences 7 (2010): 3153-3166, doi:10.5194/bg-7-3153-2010.
    Description: Climate warming in northeastern Siberia may induce thaw-mobilization of the organic carbon (OC) now held in permafrost. This study investigated the composition of terrestrial OC exported to Arctic coastal waters to both obtain a natural integration of terrestrial permafrost OC release and to further understand the fate of released carbon in the extensive Siberian Shelf Seas. Application of a variety of elemental, molecular and isotopic (δ13C and Δ14C) analyses of both surface water suspended particulate matter and underlying surface sediments along a 500 km transect from Kolyma River mouth to the mid-shelf of the East Siberian Sea yielded information on the sources, degradation status and transport processes of thaw-mobilized soil OC. A three end-member dual-carbon-isotopic mixing model was applied to deduce the relative contributions from riverine, coastal erosion and marine sources. The mixing model was solved numerically using Monte Carlo simulations to obtain a fair representation of the uncertainties of both end-member composition and the end results. Riverine OC contributions to sediment OC decrease with increasing distance offshore (35±15 to 13±9%), whereas coastal erosion OC exhibits a constantly high contribution (51±11 to 60±12%) and marine OC increases offshore (9±7 to 36±10%). We attribute the remarkably strong imprint of OC from coastal erosion, extending up to ~500 km from the coast, to efficient offshoreward transport in these shallow waters presumably through both the benthic boundary layer and ice-rafting. There are also indications of simultaneous selective preservation of erosion OC compared to riverine OC. Molecular degradation proxies and radiocarbon contents indicated a degraded but young (Δ14C ca. −60‰ or ca. 500 14C years) terrestrial OC pool in surface water particulate matter, underlain by a less degraded but old (Δ14C ca. −500‰ or ca. 5500 14C years) terrestrial OC pool in bottom sediments. We suggest that the terrestrial OC fraction in surface water particulate matter is mainly derived from surface soil and recent vegetation fluvially released as buoyant organic-rich aggregates (e.g., humics), which are subjected to extensive processing during coastal transport. In contrast, terrestrial OC in the underlying sediments is postulated to originate predominantly from erosion of mineral-rich Pleistocene coasts (i.e., yedoma) and inland mineral soils. Sorptive association of this organic matter with mineral particles protects the OC from remineralization and also promotes rapid settling (ballasting) of the OC. Our findings corroborate recent studies by indicating that different Arctic surface soil OC pools exhibit distinguishing susceptibilities to degradation in coastal waters. Consequently, the general postulation of a positive feedback to global warming from degradation of permafrost carbon may be both attenuated (by reburial of one portion) and geographically displaced (degradation of released terrestrial permafrost OC far out over the Arctic shelf seas).
    Description: The ISSS-08 program was supported by the Knut and Alice Wallenberg Foundation, Headquarters of the Far Eastern Branch of the Russian Academy of Sciences, the Swedish Research Council (VR Contract No. 621-2004-4039 and 621-2007-4631), the US National Oceanic and Atmospheric Administration (Siberian Shelf Study), the Russian Foundation of Basic Research (08-05-13572, 08-05-00191-a, and 07-05-00050a), the Swedish Polar Research Secretariat, the Arctic Co-Op Program of the Nordic Council of Ministers (331080-70219) and the National Science Foundation (OPP ARC 0909546). O¨ . G. also acknowledges financial support as an Academy Research Fellow from the Swedish Royal Academy of Sciences, L. S. a Marie Curie grant (contract no. PIEF-GA-2008-220424), T. E. an NSF grant (ARC-0909377) and A. A. support from the Knut and Alice Wallenberg Foundation.
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 7
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    The Expedition to the Peel River in 2019: Fluvial Transport Across a Permafrost Landscape (2020)
    Alfred Wegener Institute for Polar and Marine Research
    In:  EPIC3Berichte zur Polar- und Meeresforschung = Reports on polar and marine research, Bremerhaven, Alfred Wegener Institute for Polar and Marine Research, 743, 40 p., ISSN: 1866-3192
    Details
    Publication Date: 2020-05-19
    Repository Name: EPIC Alfred Wegener Institut
    Type: "Berichte zur Polar- und Meeresforschung" , notRev
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  • 8
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    Differential mobilization of terrestrial carbon pools in Eurasian Arctic river basins (2013)
    Details
    Publication Date: 2022-05-26
    Description: Author Posting. © The Author(s), 2013. This is the author's version of the work. It is posted here by permission of National Academy of Sciences for personal use, not for redistribution. The definitive version was published in Proceedings of the National Academy of Sciences of the United States of America 110 (2013): 14168–14173, doi:10.1073/pnas.1307031110.
    Description: Mobilization of Arctic permafrost carbon is expected to increase with warming-induced thawing. However, this effect is challenging to assess due to the diverse processes controlling the release of various organic carbon (OC) pools from heterogeneous Arctic landscapes. Here, by radiocarbon dating various terrestrial OC components in fluvially- and coastally-integrated estuarine sediments, we present a unique framework for deconvoluting the contrasting mobilization mechanisms of surface versus deep (permafrost) carbon pools across the climosequence of the Eurasian Arctic. Vascular-plant-derived lignin phenol 14C contents reveal significant inputs of young carbon from surface sources whose delivery is dominantly controlled by river runoff. In contrast, plant wax lipids predominantly trace ancient (permafrost) OC that is preferentially mobilized from discontinuous permafrost regions where hydrological conduits penetrate deeper into soils and thermokarst erosion occurs more frequently. As river runoff has significantly increased across the Eurasian Arctic in recent decades, we estimate from an isotopic mixing model that, in tandem with an increased transfer of young surface carbon, the proportion of mobilized terrestrial OC accounted for by ancient carbon has increased by 3-6% between 1985-2004. These findings suggest that, while partly masked by surface-carbon export, climate-change-induced mobilization of old permafrost carbon is well under way in the Arctic.
    Description: The ISSS program is supported by the Knut and Alice Wallenberg Foundation, the Far Eastern Branch of the Russian Academy of Sciences, the Swedish Research Council, the US National Oceanic and Atmospheric Administration, the Russian Foundation of Basic Research, the Swedish Polar Research Secretariat and the Nordic Council of Ministers (Arctic Co-Op and TRI-DEFROST programs). Ö.G. acknowledges an Academy Research Fellow grant from the Swedish Royal Academy of Sciences. Grants OCE-9907129, OCE-0137005, and OCE-0526268 from the US National Science Foundation (NSF), the Stanley Watson Chair for Excellence in Oceanography (to T.I.E.) and ETH Zürich enabled this research. J.E.V. thanks support from NWO-Rubicon (#825.10.022). B.E.v.D thanks support from the UK NERC (NE/I024798/1). X.F. thanks WHOI for a postdoctoral scholar fellowship and for postdoctoral support from ETH Zürich.
    Description: 2014-01-01
    Keywords: Fluvial mobilization ; Compound-specific 14C ; Hydrogeographic control
    Repository Name: Woods Hole Open Access Server
    Type: Preprint
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  • 9
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    Branched glycerol dialkyl glycerol tetraethers in Arctic lake sediments : sources and implications for paleothermometry at high latitudes (2014)
    John Wiley & Sons
    Details
    Publication Date: 2022-05-26
    Description: Author Posting. © American Geophysical Union, 2014. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Biogeosciences 119 (2014): 1738–1754, doi:10.1002/2014JG002639.
    Description: Branched glycerol dialkyl glycerol tetraethers (brGDGTs) are analyzed in different lakes of the Mackenzie (Canadian Arctic) and Kolyma (Siberian Arctic) River basins to evaluate their sources and the implications for brGDGT-based paleothermometry in high-latitude lakes. The comparison of brGDGT distributions and concentrations in the lakes with those in river suspended particulate matter, riverbank sediments, and permafrost material indicates that brGDGTs in Arctic lake sediments have mixed sources. In contrast to global observations, distributional offsets between brGDGTs in Arctic lakes and elsewhere in the catchment are minor, likely due to the extreme seasonality and short window of biological production at high latitudes. Consequently, both soil- and lake-calibrated brGDGT-based temperature proxies return sensible temperature estimates, even though the mean air temperature (MAT) in the Arctic is below the calibration range. The original soil-calibrated MBT-CBT (methylation of branched tetraethers–cyclisation of branched tetraethers) proxy generates MATs similar to those in the studied river basins, whereas using the recently revised MBT′-CBT calibration overestimates MAT. The application of the two global lake calibrations, generating summer air temperatures (SAT) and MAT, respectively, illustrates the influence of seasonality on the production of brGDGTs in lakes, as the latter overestimates actual MAT, whereas the SAT-based lake calibration accounts for this influence and consequently returns more accurate temperatures. Our results in principle support the application of brGDGT-based temperature proxies in high-latitude lakes in order to obtain long-term paleotemperature records for the Arctic, although the calibration and associated transfer function have to be selected with care.
    Description: his work has been supported by an ETH Fellowship (FEL-36 11-1) and NWO Veni grant (863.13.016) to F.P., NWO Rubicon (825.10.022) and Veni (863.12.004) grants to J.E.V., as well as financial support from U.S. NSF (Polaris project 1044610 and Arctic-GRO 0732522 and 1107774), and the WHOI Arctic Research Initiative.
    Description: 2015-02-28
    Keywords: Branched GDGTs ; MBT-CBT proxy ; Permafrost ; Arctic lakes ; Soil ; Yedoma
    Repository Name: Woods Hole Open Access Server
    Type: Article
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    Format: application/vnd.ms-excel
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