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  • 1
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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
    Details
    Publication Date: 2016-06-03
    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 and total soil organic carbon (POC and TOC). 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 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.
    Print ISSN: 0886-6236
    Electronic ISSN: 1944-9224
    Topics: Biology , Chemistry and Pharmacology , Geography , Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 2
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    Vegetation composition and shrub extent on the Yukon coast, Canada, are strongly linked to ice-wedge polygon degradation (2016)
    Norwegian Polar Institute
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    Publication Date: 2016-06-18
    Description: Changing environmental and geomorphological conditions are resulting in vegetation change in ice-wedge polygons in Arctic tundra. However, we do not yet know how microscale vegetation patterns relate to individual environmental and geomorphological parameters. This work aims at examining these relations in polygonal terrain. We analysed composition and cover of vascular plant taxa and surface height, active layer depth, soil temperature, carbon and nitrogen content, pH and electrical conductivity in four polygon mires located on the Yukon coast. We found that vascular plant species composition and cover correlates best with relative surface height. Ridges of low-centred polygons and raised centres of high-centred polygons support the growth of mesic and wetland species (e.g., Betula glandulosa , Salix pulchra , S. reticulata , Rubus chamaemorus , various ericaceous dwarf shrubs, Eriophorum vaginatum , Poa arctica ). Wetland and aquatic plant species (e.g., E. angustifolium , Carex aquatilis , C. chordorrhiza , Pedicularis sudetica ) grow in low-lying centres of polygons and in troughs between polygons. We also found a relationship between vascular plant species composition and substrate characteristics such as pH, electrical conductivity and total organic carbon, although the individual influence of these parameters could not be determined because of their correlation with relative surface height. Our findings stress the regulatory role of microtopography and substrate in vegetation dynamics of polygonal terrain. Ongoing warming in this region will lead to changes to polygonal terrain through permafrost degradation and subsequent conversion of low-centred into high-centred polygons. Our results indicate that shrubs, particularly Betula glandulosa and heath species, have the potential to expand most. Keywords: Ice-wedge polygon mires; western Canadian Arctic; modern vegetation; microtopography; permafrost. (Published: 17 June 2016) To access the supplementary material for this article, please see the supplementary files in the column to the right (under Article Tools). Citation: Polar Research 2016, 35 , 27489, http://dx.doi.org/10.3402/polar.v35.27489
    Print ISSN: 0800-0395
    Electronic ISSN: 1751-8369
    Topics: Geography , Geosciences
    Published by Norwegian Polar Institute
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  • 3
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    Variability in transport of terrigenous material on the shelves and the deep Arctic Ocean during the Holocene (2015)
    Norwegian Polar Institute
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    Publication Date: 2015-12-10
    Description: Arctic coastal zones serve as a sensitive filter for terrigenous matter input onto the shelves via river discharge and coastal erosion. This material is further distributed across the Arctic by ocean currents and sea ice. The coastal regions are particularly vulnerable to changes related to recent climate change. We compiled a pan-Arctic review that looks into the changing Holocene sources, transport processes and sinks of terrigenous sediment in the Arctic Ocean. Existing palaeoceanographic studies demonstrate how climate warming and the disappearance of ice sheets during the early Holocene initiated eustatic sea-level rise that greatly modified the physiography of the Arctic Ocean. Sedimentation rates over the shelves and slopes were much greater during periods of rapid sea-level rise in the early and middle Holocene, as a result of the relative distance to the terrestrial sediment sources. However, estimates of suspended sediment delivery through major Arctic rivers do not indicate enhanced delivery during this time, which suggests enhanced rates of coastal erosion. The increased supply of terrigenous material to the outer shelves and deep Arctic Ocean in the early and middle Holocene might serve as analogous to forecast changes in the future Arctic. Keywords: Arctic; riverine input; coastal erosion; land–ocean interaction; Holocene. (Published: 9 December 2015) To access the supplementary material for this article, please see supplementary files in the column to the right (under Article Tools). Citation: Polar Research 2015, 34 , 24964, http://dx.doi.org/10.3402/polar.v34.24964
    Print ISSN: 0800-0395
    Electronic ISSN: 1751-8369
    Topics: Geography , Geosciences
    Published by Norwegian Polar Institute
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  • 4
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    Mechanistic investigations in α-hydroxycarbonyls reduction by BH4- (2012)
    Wiley
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    Publication Date: 2012-06-19
    Description: BH 4 - , a well-known and widely used reducing agent for carbonyl compounds, has been reported to have the ability to participate in dihydrogen bonding, an interaction with applications in catalysis, stereoselectivity and crystal engineering. Specifically, α-hydroxycarbonyls are activated for reduction by dihydrogen bonding that occurs between BH 4 - and hydroxyl group. We explored the effect of the interaction on the mechanism of these reactions by examining their activation parameters. We found that dihydrogen bonding activates α-hydroxycyclopentanone for reduction with NBu 4 BH 4 by lowering the activation enthalpy by 6.6 kcal/mol. While the activation entropy is a significant component of the barrier, the changes resulting from the occurrence of dihydrogen bonding are manifested predominantly in the enthalpy term. Computational studies suggest that, while internal hydrogen bonding is allowed by the flexibility of the carbon backbone, that interaction is outweighed by dihydrogen bonding once BH 4 - is present in the system. Experimentally, a red shift of the hydroxyl frequency is observed upon addition of BH 4 - to the reaction mixture, suggesting a dihydrogen bonding interaction. The flexibility of the substrate's skeleton or the selectivity of the hydride sites in BH 4 - does not account for the lack of directing effect of the dihydrogen bonding. When a substrate with a rigid naphthalene backbone moiety, 2-hydroxyacenaphthylen-1(2H)-one, is reduced, the stereochemical outcome is very similar to the one corresponding to the α-hydroxycyclopentanone. Copyright © 2012 John Wiley & Sons, Ltd. Dihydrogen bonding between BH 4 - and hydroxyl group of α-hydroxycyclopentanone, evidenced by a red shift of the hydroxyl frequency, activates α-hydroxycyclopentanone for reduction with NBu 4 BH 4 by lowering the activation enthalpy by 6.6 kcal/mol. While the activation entropy is a significant component of the barrier, the changes due to dihydrogen bonding are manifested predominantly in the enthalpy term. The rigidity of the substrate or the selectivity of the hydride sites in BH 4 - does not have an effect on the stereochemical outcome.
    Print ISSN: 0894-3230
    Electronic ISSN: 1099-1395
    Topics: Chemistry and Pharmacology , Physics
    Published by Wiley
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  • 5
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    Origin and characteristics of massive ground ice on Herschel Island (western Canadian Arctic) as revealed by stable water isotope and Hydrochemical signatures (2011)
    Wiley
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    Publication Date: 2011-02-11
    Description: Herschel Island in the southern Beaufort Sea is a push moraine at the northwestern-most limit of the Laurentide Ice Sheet. Stable water isotope (δ 18 O, δD) and hydrochemical studies were applied to two tabular massive ground ice bodies to unravel their genetic origin. Buried glacier ice or basal regelation ice was encountered beneath an ice-rich diamicton with strong glaciotectonic deformation structures. The massive ice isotopic composition was highly depleted in heavy isotopes (mean δ 18 O: −33‰; mean δD: −258‰), suggesting full-glacial conditions during ice formation. Other massive ice of unknown origin with a very large δ 18 O range (from −39 to −21‰) was found adjacent to large, striated boulders. A clear freezing slope was present with progressive depletion in heavy isotopes towards the centre of the ice body. Fractionation must have taken place during closed-system freezing, possibly of a glacial meltwater pond. Both massive ground ice bodies exhibited a mixed ion composition suggestive of terrestrial waters with a marine influence. Hydrochemical signatures resemble the Herschel Island sediments that are derived from near-shore marine deposits upthrust by the Laurentide ice. A prolonged contact between water feeding the ice bodies and the surrounding sediment is therefore inferred. Copyright © 2011 John Wiley & Sons, Ltd.
    Print ISSN: 1045-6740
    Electronic ISSN: 1099-1530
    Topics: Geography , Geosciences
    Published by Wiley
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  • 6
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    Relation between planimetric and volumetric measurements of permafrost coast erosion: a case study from Herschel Island, western Canadian Arctic (2016)
    Norwegian Polar Institute
    Details
    Publication Date: 2016-09-24
    Description: Ice-rich permafrost coasts often undergo rapid erosion, which results in land loss and release of considerable amounts of sediment, organic carbon and nutrients, impacting the near-shore ecosystems. Because of the lack of volumetric erosion data, Arctic coastal erosion studies typically report on planimetric erosion. Our aim is to explore the relationship between planimetric and volumetric coastal erosion measurements and to update the coastal erosion rates on Herschel Island in the Canadian Arctic. We used high-resolution digital elevation models to compute sediment release and compare volumetric data to planimetric estimations of coastline movements digitized from satellite imagery. Our results show that volumetric erosion is locally less variable and likely corresponds better with environmental forcing than planimetric erosion. Average sediment release volumes are in the same range as sediment release volumes calculated from coastline movements combined with cliff height. However, the differences between these estimates are significant for small coastal sections. We attribute the differences between planimetric and volumetric coastal erosion measurements to mass wasting, which is abundant along the coasts of Herschel Island. The average recorded coastline retreat on Herschel Island was 0.68 m a −1 for the period 2000–2011. Erosion rates increased by more than 50% in comparison with the period 1970–2000, which is in accordance with a recently observed increase along the Alaskan Beaufort Sea. The estimated annual sediment release was 28.2 m 3 m −1 with resulting fluxes of 590 kg C m −1 and 104 kg N m −1 . Keywords: Coastal erosion; LiDAR; carbon fluxes; mass wasting; landslides; digital elevation model. (Published: 23 September 2016) To access the supplementary material for this article, please see Supplementary files under Article Tools online. Citation: Polar Research 2016, 35 , 30313, http://dx.doi.org/10.3402/polar.v35.30313
    Print ISSN: 0800-0395
    Electronic ISSN: 1751-8369
    Topics: Geography , Geosciences
    Published by Norwegian Polar Institute
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  • 7
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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
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    Publication Date: 2018-01-25
    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 m 2 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/m 3 , 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 × 10 3 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.
    Print ISSN: 0148-0227
    Topics: Biology , Geosciences
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 8
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    Collapsing Arctic coastlines (2017)
    Springer Nature
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    Publication Date: 2017-01-05
    Description: A holistic and transdisciplinary approach is urgently required to investigate the physical and socio-economic impacts of collapsing coastlines in the Arctic nearshore zone. Nature Climate Change 7 6 doi: 10.1038/nclimate3188
    Print ISSN: 1758-678X
    Electronic ISSN: 1758-6798
    Topics: Geosciences
    Published by Springer Nature
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