| 1. |
- Shakhova, Natalia, et al.
(författare)
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The East Siberian Arctic Shelf : towards further assessment of permafrost-related methane fluxes and role of sea ice
- 2015
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Ingår i: Philosophical Transactions. Series A. - : The Royal Society. - 1364-503X .- 1471-2962. ; 373:2052
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Tidskriftsartikel (refereegranskat)abstract
- Sustained release of methane (CH4) to the atmosphere from thawing Arctic permafrost may be a positive and significant feedback to climate warming. Atmospheric venting of CH4 from the East Siberian Arctic Shelf (ESAS) was recently reported to be on par with flux from the Arctic tundra; however, the future scale of these releases remains unclear. Here, based on results of our latest observations, we show that CH4 emissions from this shelf are likely to be determined by the state of subsea permafrost degradation. We observed CH4 emissions from two previously understudied areas of the ESAS: the outer shelf, where subsea permafrost is predicted to be discontinuous or mostly degraded due to long submergence by seawater, and the near shore area, where deep/open taliks presumably form due to combined heating effects of seawater, river run-off, geothermal flux and pre-existing thermokarst. CH4 emissions from these areas emerge from largely thawed sediments via strong flare-like ebullition, producing fluxes that are orders of magnitude greater than fluxes observed in background areas underlain by largely frozen sediments. We suggest that progression of subsea permafrost thawing and decrease in ice extent could result in a significant increase in CH4 emissions from the ESAS.
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| 2. |
- Semiletov, Igor, et al.
(författare)
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Acidification of East Siberian Arctic Shelf waters through addition of freshwater and terrestrial carbon
- 2016
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Ingår i: Nature Geoscience. - : Springer Science and Business Media LLC. - 1752-0894 .- 1752-0908. ; 9, s. 361-365
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Tidskriftsartikel (refereegranskat)abstract
- Ocean acidification affects marine ecosystems and carbon cycling, and is considered a direct effect of anthropogenic carbon dioxide uptake from the atmosphere. Accumulation of atmospheric CO2 in ocean surface waters is predicted to make the ocean twice as acidic by the end of this century. The Arctic Ocean is particularly sensitive to ocean acidification because more CO2 can dissolve in cold water. Here we present observations of the chemical and physical characteristics of East Siberian Arctic Shelf waters from 1999, 2000–2005, 2008 and 2011, and find extreme aragonite undersaturation that reflects acidity levels in excess of those projected in this region for 2100. Dissolved inorganic carbon isotopic data and Markov chain Monte Carlo simulations of water sources using salinity and delO-18 data suggest that the persistent acidification is driven by the degradation of terrestrial organic matter and discharge of Arctic river water with elevated CO2 concentrations, rather than by uptake of atmospheric CO2. We suggest that East Siberian Arctic Shelf waters may become more acidic if thawing permafrost leads to enhanced terrestrial organic carbon inputs and if freshwater additions continue to increase, which may affect their efficiency as a source of CO2.
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| 3. |
- Shakhova, Natalia, et al.
(författare)
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Current rates and mechanisms of subsea permafrost degradation in the East Siberian Arctic Shelf
- 2017
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 8
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Tidskriftsartikel (refereegranskat)abstract
- The rates of subsea permafrost degradation and occurrence of gas-migration pathways are key factors controlling the East Siberian Arctic Shelf (ESAS) methane (CH4) emissions, yet these factors still require assessment. It is thought that after inundation, permafrost-degradation rates would decrease over time and submerged thaw-lake taliks would freeze; therefore, no CH4 release would occur for millennia. Here we present results of the first comprehensive scientific re-drilling to show that subsea permafrost in the near-shore zone of the ESAS has a downward movement of the ice-bonded permafrost table of similar to 14 cm year(-1) over the past 31-32 years. Our data reveal polygonal thermokarst patterns on the seafloor and gas-migration associated with submerged taliks, ice scouring and pockmarks. Knowing the rate and mechanisms of subsea permafrost degradation is a prerequisite to meaningful predictions of near-future CH4 release in the Arctic.
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| 4. |
- 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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| 5. |
- Dudarev, Oleg, et al.
(författare)
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East Siberian Sea : Interannual heterogeneity of the suspended particulate matter and its biogeochemical signature
- 2022
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Ingår i: Progress in Oceanography. - : Elsevier BV. - 0079-6611 .- 1873-4472. ; 208
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Forskningsöversikt (refereegranskat)abstract
- The East Siberian Sea (ESS) is the largest, shallowest and most icebound Arctic marginal sea. It receives substantial input of terrigenous material and climate-vulnerable old organic carbon from both coastal erosion and rivers draining the extensive permafrost-covered watersheds. This study focuses on the interannual variability and spatial distribution of suspended particulate matter (SPM) in the surface and bottom waters of the ESS during the ice-free period in 2000, 2003, 2004, 2005 and 2008. We report on the composition and variability of particulate organic carbon (POC), total nitrogen (TN), POC/TN ratios, carbon and nitrogen isotopes (δ13C, δ15N) and provide estimates of the contribution of terrestrial organic carbon (terrOC) based on the δ13C isotopic values.The results show that interannual SPM distribution and elemental-isotopic characteristics of POC differ significantly between the western biogeochemical province (WBP; West of 165oE) and the eastern biogeochemical province (EBP; East of 165oE) of the ESS. The SPM mean concentration in the WBP is almost an order of magnitude higher than in the EBP. From west-to-east of the ESS, SPM tends to become more depleted in δ15N, while the δ13C becomes isotopically heavier. This trend can be explained by a shift in organic matter sources from terrigenous origin (erosion of the coastal ice complex and riverine POC) to becoming dominantly from marine plankton.The maximum contribution of terrOC to POC reached 99% in parts of the WBP, but accounts for as low as 1% in parts of the EBP. At the same time, the type of atmospheric circulation and its associated regime of both water circulation and ice transport control a displacement of the semi-stable biogeochemical border between WBP and EBP to the east or to the west if compared to its long-term average position near 165oE. Our multi-year investigation provides a robust observational basis for better understanding of the transport and fate of terrigenous material upon entering the ESS shelf waters. Our results also provide deeper insights into the interaction in the land-shelf sea system of the largest shelf sea system of the World Ocean, the East Siberian Arctic Shelf system.
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| 6. |
- Karlsson, Emma, 1980-, et al.
(författare)
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Contrasting sources of dissolved and particulate organic matter along 62N-72N in the Siberian-Arctic Lena River
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The Lena River transports large amounts of sediment and dissolved organic matter to the shallow Laptev Sea, where it may be subject to degradation and potential release of OC. We studied organic matter collected in summer 2008, along a 1450 km section of the Lena River, from near Yakutsk at 62°N to the deltaic region at 72°N, to better understand potential in-river processing of the terrestrial particulate and dissolved fractions in the river surface water.Carbon isotopes (δ13C and Δ14C) and plant wax lipid markers combine to reveal two distinct OC pools with different behavior in the river. The molar OC/TN ratios for POC were low (6-13) which suggests contribution from (freshwater) plankton, but most of the POC was of old age (770-4500 14C years) which rather suggests a pre-aged origin - perhaps from erosion of riverbank permafrost material. Much in contrast, COC was young (20-440 14C years) and displayed a high OC/TN composition (23-56) with a steady δ13C signal along the river course (-26.7 to -27.7). There was an apparent absence of ice complex deposit permafrost (mineral soil/yedoma OC) in the COC fraction, and only small contributions to POC. The COC signal suggest contribution from contemporary plant detritus/surface soil OC. It seems as if pre-aged permafrost OC, potentially from riverbank erosion, partitions into the particulate pool and almost not at all to the DOC/COC pool.Degradation markers indicate a highly degraded COC lipid pool and a less degraded POC - the n-alkane carbon preference index (CPI, C24-C34) was 1.0-1.3 for COC and 1.2-4.9 (on average 3.3) for POC.Taken together DOC/COC and POC have clearly different terrestrial sources and different fates on its way to the shelf waters. Previously freeze-locked old permafrost OC remobilizes into the Lena River in particulate form which (at least temporarily) escapes degradation as it follows the river course seawards in a less degraded state.
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| 7. |
- Karlsson, Emma, et al.
(författare)
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Different sources and degradation state of dissolved, particulate, and sedimentary organic matter along the Eurasian Arctic coastal margin
- 2016
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Ingår i: Global Biogeochemical Cycles. - 0886-6236 .- 1944-9224. ; 30:6, s. 898-919
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Tidskriftsartikel (refereegranskat)abstract
- Thawing Arctic permafrost causes massive fluvial and erosional releases of dissolved and particulate organic carbon (DOC and POC) to coastal waters. Here we investigate how different sources and degradation of remobilized terrestrial carbon may affect large-scale carbon cycling, by comparing molecular and dual-isotope composition of waterborne high molecular weight DOC (>1kD, aka colloidal OC), POC, and sedimentary OC (SOC) across the East Siberian Arctic Shelves. Lignin phenol fingerprints demonstrate a longitudinal trend in relative contribution of terrestrial sources to coastal OC. Wax lipids and cutins were not detected in colloidal organic carbon (COC), in contrast to POC and SOC, suggesting that different terrestrial carbon pools partition into different aquatic carrier phases. The C-14 signal suggests overwhelmingly contemporary sources for COC, while POC and SOC are dominated by old C from Ice Complex Deposit (ICD) permafrost. Monte Carlo source apportionment (C-13, C-14) constrained that COC was dominated by terrestrial OC from topsoil permafrost (65%) and marine plankton (25%) with smaller contribution ICD and other older permafrost stocks (9%). This distribution is likely a result of inherent compositional matrix differences, possibly driven by organomineral associations. Modern OC found suspended in the surface water may be more exposed to degradation, in contrast to older OC that preferentially settles to the seafloor where it may be degraded on a longer timescale. The different sources which partition into DOC, POC, and SOC appear to have vastly different fates along the Eurasian Arctic coastal margin and may possibly respond on different timescales to climate change.
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| 8. |
- Karlsson, Emma, 1980-, et al.
(författare)
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Different sources and degradation state of dissolved, particulate and sedimentary organic matter along the Eurasian Arctic coastal margin
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Thawing of permafrost in the Eurasian Arctic causes massive fluvial and erosional releases of both dissolved and particulate organic carbon (DOC and POC) to coastal waters. Here we investigate how different sources and extent of degradation of remobilized terrestrial carbon pools imprint on major recipient carbon pools and thereby affect large-scale carbon cycling. The molecular and dual-isotope composition is compared with source end-member composition in waterborne high-molecular weight DOC (>1kD, a.k.a. colloidal OC), POC and in sedimentary OC (SOC) along coastal Kara, Laptev and East Siberian Seas.The lignin phenol fingerprint demonstrates a clear geospatial trend in the relative contribution of different terrestrial sources to coastal OC in going from the west to the east. The wax lipids and cutins were much less abundant in the COC compared to in the POC and SOC compartment, suggesting that different terrestrial carbon pools partition into different aquatic carrier phases. The Δ14C signal suggests that the COC is overwhelmingly derived from contemporary carbon sources. Furthermore, degradation proxies based on terrestrial lignin phenol biomarkers suggest a highly degraded COC composition. Monte Carlo based source apportionment simulations of the δ13C/Δ14C composition constrained that the COC is dominated by terrestrial OC from topsoil permafrost (65%) and marine plankton (25%) with smaller contribution from Ice Complex Deposit (ICD) and other older stocks of permafrost carbon (9%). This contrasts starkly to the POC and especially the SOC compartment, which are dominated by old C from ICD-OC permafrost.These results combine with other recent studies to suggest a pattern along the East Siberian Arctic margin of SOC being constantly older yet less degraded than water column POC. This study also extends this perspective spatially along the Eurasian Arctic seaboard and also to the large COC (HMW DOC) pool, which is even younger yet even more degraded than the POC. An implication is that DOC and POC pools need to be treated separately in assessments of effects on the large-scale carbon cycle (and climate feedback) of old carbon released from thawing permafrost to aquatic receptors across the Eurasian Arctic coast.
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| 9. |
- Pipko, Irina, et al.
(författare)
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The spatial and interannual dynamics of the surface water carbonate system and air–sea CO2 fluxes in the outer shelf and slope of the Eurasian Arctic Ocean
- 2017
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Ingår i: Ocean Science. - : Copernicus GmbH. - 1812-0784 .- 1812-0792. ; 13, s. 997-1016
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Tidskriftsartikel (refereegranskat)abstract
- The Arctic is undergoing dramatic changes which cover the entire range of natural processes, from extreme increases in the temperatures of air, soil, and water, to changes in the cryosphere, the biodiversity of Arctic waters, and land vegetation. Small changes in the largest marine carbon pool, the dissolved inorganic carbon pool, can have a profound impact on the carbon dioxide (CO2) flux between the ocean and the atmosphere, and the feedback of this flux to climate. Knowledge of relevant processes in the Arctic seas improves the evaluation and projection of carbon cycle dynamics under current conditions of rapid climate change. Investigation of the CO2 system in the outer shelf and continental slope waters of the Eurasian Arctic seas (the Barents, Kara, Laptev, and East Siberian seas) during 2006, 2007, and 2009 revealed a general trend in the surface water partial pressure of CO2 (pCO2) distribution, which manifested as an increase in pCO2 values eastward. The existence of this trend was defined by different oceanographic and biogeochemical regimes in the western and eastern parts of the study area; the trend is likely increasing due to a combination of factors determined by contemporary change in the Arctic climate, each change in turn evoking a series of synergistic effects. A high-resolution in situ investigation of the carbonate system parameters of the four Arctic seas was carried out in the warm season of 2007; this year was characterized by the next-to-lowest historic sea-ice extent in the Arctic Ocean, on satellite record, to that date. The study showed the different responses of the seawater carbonate system to the environment changes in the western vs. the eastern Eurasian Arctic seas. The large, open, highly productive water area in the northern Barents Sea enhances atmospheric CO2 uptake. In contrast, the uptake of CO2 was strongly weakened in the outer shelf and slope waters of the East Siberian Arctic seas under the 2007 environmental conditions. The surface seawater appears in equilibrium or slightly supersaturated by CO2 relative to atmosphere because of the increasing influence of river runoff and its input of terrestrial organic matter that mineralizes, in combination with the high surface water temperature during sea-ice-free conditions. This investigation shows the importance of processes that vary on small scales, both in time and space, for estimating the air–sea exchange of CO2. It stresses the need for high-resolution coverage of ocean observations as well as time series. Furthermore, time series must include multi-year studies in the dynamic regions of the Arctic Ocean during these times of environmental change.
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| 10. |
- Vonk, Jorien E., et al.
(författare)
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Preferential burial of permafrost-derived organic carbon in Siberian-Arctic shelf waters
- 2014
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Ingår i: Journal of Geophysical Research Oceans. - 2169-9275. ; 119:12, s. 8410-8421
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Tidskriftsartikel (refereegranskat)abstract
- The rapidly changing East Siberian Arctic Shelf (ESAS) receives large amounts of terrestrial organic carbon (OC) from coastal erosion and Russian-Arctic rivers. Climate warming increases thawing of coastal Ice Complex Deposits (ICD) and can change both the amount of released OC, as well as its propensity to be converted to greenhouse gases (fueling further global warming) or to be buried in coastal sediments. This study aimed to unravel the susceptibility to degradation, and transport and dispersal patterns of OC delivered to the ESAS. Bulk and molecular radiocarbon analyses on surface particulate matter (PM), sinking PM and underlying surface sediments illustrate the active release of old OC from coastal permafrost. Molecular tracers for recalcitrant soil OC showed ages of 3.4-13 C-14-ky in surface PM and 5.5-18 C-14-ky in surface sediments. The age difference of these markers between surface PM and surface sediments is larger (i) in regions with low OC accumulation rates, suggesting a weaker exchange between water column and sediments, and (ii) with increasing distance from the Lena River, suggesting preferential settling of fluvially derived old OC nearshore. A dual-carbon end-member mixing model showed that (i) contemporary terrestrial OC is dispersed mainly by horizontal transport while being subject to active degradation, (ii) marine OC is most affected by vertical transport and also actively degraded in the water column, and (iii) OC from ICD settles rapidly and dominates surface sediments. Preferential burial of ICD-OC released into ESAS coastal waters might therefore lower the suggested carbon cycle climate feedback from thawing ICD permafrost.
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