| 1. |
- Winiger, Patrik, et al.
(författare)
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Source apportionment of circum-Arctic atmospheric black carbon from isotopes and modeling
- 2019
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Ingår i: Science Advances. - : American Association for the Advancement of Science (AAAS). - 2375-2548. ; 5:2
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Tidskriftsartikel (refereegranskat)abstract
- Black carbon (BC) contributes to Arctic climate warming, yet source attributions are inaccurate due to lacking observational constraints and uncertainties in emission inventories. Year-round, isotope-constrained observations reveal strong seasonal variations in BC sources with a consistent and synchronous pattern at all Arctic sites. These sources were dominated by emissions from fossil fuel combustion in the winter and by biomass burning in the summer. The annual mean source of BC to the circum-Arctic was 39 +/- 10% from biomass burning. Comparison of transport-model predictions with the observations showed good agreement for BC concentrations, with larger discrepancies for (fossil/biomass burning) sources. The accuracy of simulated BC concentration, but not of origin, points to misallocations of emissions in the emission inventories. The consistency in seasonal source contributions of BC throughout the Arctic provides strong justification for targeted emission reductions to limit the impact of BC on climate warming in the Arctic and beyond.
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| 2. |
- Charkin, Alexander N., et al.
(författare)
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Discovery and characterization of submarine groundwater discharge in the Siberian Arctic seas : a case study in the Buor-Khaya Gulf, Laptev Sea
- 2017
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Ingår i: The Cryosphere. - : Copernicus GmbH. - 1994-0416 .- 1994-0424. ; 11:5, s. 2305-2327
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Tidskriftsartikel (refereegranskat)abstract
- It has been suggested that increasing terrestrial water discharge to the Arctic Ocean may partly occur as submarine groundwater discharge (SGD), yet there are no direct observations of this phenomenon in the Arctic shelf seas. This study tests the hypothesis that SGD does exist in the Siberian Arctic Shelf seas, but its dynamics may be largely controlled by complicated geocryological conditions such as permafrost. The field-observational approach in the southeastern Laptev Sea used a combination of hydrological (temperature, salinity), geological (bottom sediment drilling, geoelectric surveys), and geochemical (Ra-224, Ra-223, Ra-228, and Ra-226) techniques. Active SGD was documented in the vicinity of the Lena River delta with two different operational modes. In the first system, groundwater discharges through tectonogenic permafrost talik zones was registered in both winter and summer. The second SGD mechanism was cryogenic squeezing out of brine and water-soluble salts detected on the periphery of ice hummocks in the winter. The proposed mechanisms of groundwater transport and discharge in the Arctic land-shelf system is elaborated. Through salinity vs. Ra-224 and Ra-224/Ra-223 diagrams, the three main SGD-influenced water masses were identified and their end-member composition was constrained. Based on simple mass-balance box models, discharge rates at sites in the submarine permafrost talik zone were 1.7 x 10(6) m(3) d(-1) or 19.9 m(3) s(-1), which is much higher than the April discharge of the Yana River. Further studies should apply these techniques on a broader scale with the objective of elucidating the relative importance of the SGD transport vector relative to surface freshwater discharge for both water balance and aquatic components such as dissolved organic carbon, carbon dioxide, methane, and nutrients.
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| 3. |
- Charkin, A. N., et al.
(författare)
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Seasonal and interannual variability of sedimentation and organic matter distribution in the Buor-Khaya Gulf : the primary recipient of input from Lena River and coastal erosion in the southeast Laptev Sea
- 2011
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Ingår i: Biogeosciences. - : Copernicus GmbH. - 1726-4170 .- 1726-4189. ; 8:9, s. 2581-2594
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Tidskriftsartikel (refereegranskat)abstract
- Climate warming is amplified in the land-sea system of the East Siberian Arctic, which also holds large pools of vulnerable carbon in permafrost. This coastal area is strongly influenced by sediment and carbon transport from both its large rivers and extensive erosion of Pleistocene permafrost along its coastline. This study is investigating the coastal fate of the sediment and organic carbon delivered to the Buor-Khaya Gulf, which is the first recipient of the overwhelming fluvial discharge from the Lena River and is additionally receiving large input from extensive erosion of the coastal ice-complex (permafrost a. k.a. Yedoma; loess soil with high organic carbon content). Both water column suspended particulate matter (SPM) and surface sediments were sampled at about 250 oceanographic stations in the Gulf in this multi-year effort, including one winter campaign, and analyzed for the distribution and sorting of sediment size, organic carbon content, and stable carbon isotope signals. The composition of the surface sediment suggests an overwhelmingly terrestrial contribution from both river and coastal erosion. The objective of this paper is to improve our understanding of the seasonal (i.e., winter vs summer) and interannual variability of these coastal sedimentation processes and the dynamics of organic carbon (OC) distribution in both the water column SPM and the surface sediments of the Buor-Khaya Gulf. Based on data collected during several years in the period 2000-2008, two different sedimentation regimes were revealed for the Buor-Khaya Gulf, the relative importance of each at a given time depend on hydrometeorological conditions, the Lena River water discharge and sea-ice regime: Type 1 erosion-accumulation and Type 2 accumulation. The Type 1 erosion-accumulation sedimentation regime is typical (2000-2006) for the ice-free period of the year (here considered in detail for August 2005). Under such conditions terrigenous sources of SPM and particulate organic carbon (POC) stem predominantly from river discharge, thermal erosion of coastal ice-complex and remobilized bottom sediments. The Type 2 accumulation sedimentation regime develops under ice-covered conditions, and only occasionally during the ice-free period (August 2008). In Type 2 winter, combined terrigenous and marine-biogenic SPM and POC sources are dominating due to relatively low overall terrigenous input (April 2007). In Type 2 summer, river alluvium becomes the major SPM and POC source (August 2008). The water column SPM and POC loadings vary by more than a factor of two between the two regimes. This study underscores the necessity of multi-year investigations to better understand the functioning of the primary recipient of terrestrially expulsed matter in the East Siberian Arctic.
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| 4. |
- Semiletov, I. P., et al.
(författare)
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Carbon transport by the Lena River from its headwaters to the Arctic Ocean, with emphasis on fluvial input of terrestrial particulate organic carbon vs. carbon transport by coastal erosion
- 2011
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Ingår i: Biogeosciences. - : Copernicus GmbH. - 1726-4170 .- 1726-4189. ; 8:9, s. 2407-2426
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Tidskriftsartikel (refereegranskat)abstract
- The Lena River integrates biogeochemical signals from its vast drainage basin, and the integrated signal reaches far out over the Arctic Ocean. Transformation of riverine organic carbon (OC) into mineral carbon, and mineral carbon into the organic form in the Lena River watershed, can be considered to be quasi-steady-state processes. An increase in Lena discharge exerts opposite effects on total organic (TOC) and total inorganic (TCO(2)) carbon: TOC concentration increases, while TCO(2) concentration decreases. Significant inter-annual variability in mean values of TCO(2), TOC, and their sum (total carbon, TC) has been found. This variability is determined by changes in land hydrology which cause differences in the Lena River discharge. There is a negative correlation in the Lena River between TC in September and its mean discharge in August; a time shift of about one month is required for water to travel from Yakutsk to the Laptev Sea. Total carbon entering the sea with the Lena discharge is estimated to be almost 10 Tg C yr(-1). The annual Lena River discharge of particulate organic carbon (POC) can be as high as 0.38 Tg (moderate to high estimate). If we instead accept Lisytsin's (1994) statement that 85-95% of total particulate matter (PM) (and POC) precipitates on the marginal filter, then only about 0.03-0.04 Tg of Lena River POC reaches the Laptev Sea. The Lena's POC export would then be two orders of magnitude less than the annual input of eroded terrestrial carbon onto the shelf of the Laptev and East Siberian seas, which is estimated to be about 4 Tg. Observations support the hypothesis of a dominant role for coastal erosion (Semiletov, 1999a, b) in East Siberian Arctic Shelf (ESAS) sedimentation and the dynamics of the carbon/carbonate system. The Lena River is characterized by relatively high concentrations of the primary greenhouse gases, dissolved carbon dioxide (CO(2)) and methane (CH(4)). During all seasons the river is supersaturated in CO(2) compared to the atmosphere, by up to 1.5-2 fold in summer, and 4-5 fold in winter. This results in a significant CO(2) supersaturation in the adjacent coastal sea. Localized areas of dissolved CH(4) along the Lena River and in the Lena delta channels may reach 100 nM, but the CH(4) concentration decreases to 5-20nM towards the sea, which suggests that riverborne export of CH(4) plays but a minor role in determining the ESAS CH(4) budget in coastal waters. Instead, the seabed appears to be the source that provides most of the CH(4) to the Arctic Ocean.
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| 5. |
- Vonk, J. E., et al.
(författare)
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Activation of old carbon by erosion of coastal and subsea permafrost in Arctic Siberia
- 2012
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 489:7414, s. 137-140
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Tidskriftsartikel (refereegranskat)abstract
- The future trajectory of greenhouse gas concentrations depends on interactions between climate and the biogeosphere(1,2). Thawing of Arctic permafrost could release significant amounts of carbon into the atmosphere in this century(3). Ancient Ice Complex deposits outcropping along the similar to 7,000-kilometre-long coastline of the East Siberian Arctic Shelf (ESAS)(4,5), and associated shallow subsea permafrost(6,7), are two large pools of permafrost carbon(8), yet their vulnerabilities towards thawing and decomposition are largely unknown(9-11). Recent Arctic warming is stronger than has been predicted by several degrees, and is particularly pronounced over the coastal ESAS region(12,13). There is thus a pressing need to improve our understanding of the links between permafrost carbon and climate in this relatively inaccessible region. Here we show that extensive release of carbon from these Ice Complex deposits dominates (57 +/- 2 per cent) the sedimentary carbon budget of the ESAS, the world's largest continental shelf, overwhelming the marine and topsoil terrestrial components. Inverse modelling of the dual-carbon isotope composition of organic carbon accumulating in ESAS surface sediments, using Monte Carlo simulations to account for uncertainties, suggests that 44 +/- 10 teragrams of old carbon is activated annually from Ice Complex permafrost, an order of magnitude more than has been suggested by previous studies(14). We estimate that about two-thirds (66 +/- 16 per cent) of this old carbon escapes to the atmosphere as carbon dioxide, with the remainder being re-buried in shelf sediments. Thermal collapse and erosion of these carbon-rich Pleistocene coastline and seafloor deposits may accelerate with Arctic amplification of climate warming(2,13).
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| 6. |
- Sanchez-Garcia, Laura, et al.
(författare)
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Characterisation of Three Regimes of Collapsing Arctic Ice Complex Deposits on the SE Laptev Sea Coast using Biomarkers and Dual Carbon Isotopes
- 2014
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Ingår i: Permafrost and Periglacial Processes. - : Wiley. - 1045-6740 .- 1099-1530. ; 25:3, s. 172-183
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Tidskriftsartikel (refereegranskat)abstract
- Arctic amplification of climate warming is intensifying the thaw and coastal erosion of the widespread and carbon-rich Siberian Ice Complex Deposits (ICD). Despite the potential for altering long-term carbon dynamics in the Arctic, the susceptibility of organic carbon (OC) to degradation as the ICD thaw is poorly characterised. This study identifies signs of OC degradation in three Siberian ICD regimes of coastal erosion through elemental, isotopic and molecular analyses. The degree of erosion appears to determine the extent of degradation. The moisture-limited and beach-protected ICD bluff near Buor-Khaya Cape, characterised by thermokarst mounds (baydzherakhs), represents a dormant regime with limited ongoing degradation. Conversely, the more exposed ICD scarps on eroding riverbanks (Olenek Channel, Lena Delta) and coastal slopes (Muostakh Island) showed more pronounced signs of ongoing OC decay. Different parameters suggest that degradation can partially explain the shift of the OC signature with C-14 age in the thawing ICD. Exposure time, degree of erosion, slope gradient and moisture conditions appear to be key factors determining the degradation propensity of OC in exposed ICD. These field results document the lability of OC in ICD upon thaw and illustrate the potential for transferring old OC into the rapidly cycling atmosphere-biosphere carbon pools.
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