Changes To Soil And Sedimentary Organic Matter Composition With Permafrost Active Layer Detachments In A Canadian High Arctic Watershed
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Changes To Soil And Sedimentary Organic Matter Composition With Permafrost Active Layer Detachments In A Canadian High Arctic Watershed
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Author : David Michael Grewer
language : en
Publisher:
Release Date : 2017
Changes To Soil And Sedimentary Organic Matter Composition With Permafrost Active Layer Detachments In A Canadian High Arctic Watershed written by David Michael Grewer and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2017 with categories.
The vast reservoir of organic matter (OM) locked up in Arctic permafrost may become vulnerable to degradation with increased thawing. In recent years, higher than average Arctic temperatures have increased the frequency of abrupt permafrost thawing events. On sloped terrain, deeper seasonal thawing of permafrost soils can initiate landslide-like events called active layer detachments (ALDs) which can release large amounts of previously unavailable carbon into the surrounding environment. Once exposed, more easily degraded permafrost-derived OM may be transported and mineralized through hydrological networks, altering biogeochemical cycles both locally and globally. It is therefore important to investigate the environmental fate of permafrost-derived OM following release by ALDs. Several complementary methods were used to investigate soil and sedimentary OM composition from an ALD-impacted High Arctic watershed, including: biomarker analyses via gas chromatography-mass spectrometry (solvent extractable compounds, base hydrolysable products, CuO oxidation products, phospholipid fatty acids), solid-state 13C nuclear magnetic resonance (NMR) spectroscopy, and radiocarbon analysis using accelerator mass spectrometry. Samples collected from the watershed represented three distinct environments: soils, fluvial sediments, and lacustrine sediments. Soil OM composition of depth profiles from upslope and downslope regions of the disturbance were compared. Lower amounts of labile OM upslope, suggesting increased erosion, contrasted with higher amounts downslope indicative of the accumulation of OM. Additionally, labile OM observed in subterranean soil downslope indicates storage of more easily degraded material in deep permafrost. Fluvial sedimentary OM composition downstream of the disturbance was investigated to characterize potential shifts in OM composition resulting from ALD inputs. In addition, downstream translocation of ALD inputs over time was determined when comparing samples from 2011, 2013, and 2014. OM composition in areas along the river receiving ALD inputs also shifted from permafrost-derived biomarkers toward more contemporary aquatic-derived inputs over time. OM composition from recent lacustrine sediments contained older, more persistent compounds suggesting that the labile OM released by ALDs likely undergoes degradation before reaching the lake. Overall, this thesis reveals the ongoing shifts in the OM composition of ALD-impacted Arctic landscapes and contributes to the growing body of evidence suggesting enhanced losses of labile permafrost-derived carbon with future warming and climate change.
Organic Matter Sources Transformations And Fates In Northern High Latitude Regions On The Forefront Of Climate Change
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Author : Megan Irene Behnke
language : en
Publisher:
Release Date : 2022
Organic Matter Sources Transformations And Fates In Northern High Latitude Regions On The Forefront Of Climate Change written by Megan Irene Behnke and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2022 with Chemical oceanography categories.
Climate change is dramatically altering the global carbon cycle. The warming caused by climate change is approximately twice the global average in Arctic and contiguous northern high-latitude regions, which are thus especially susceptible to ecosystem shifts (e.g. permafrost thaw, wetland drying/wetting cycle exacerbation). Rivers process and transport organic matter (OM) from land where warming is destabilizing previously stabilized carbon stocks to the ocean. This dissertation examines how fluvial OM in northern high latitudes responds to climate change, and how the fate of such OM may influence the global carbon cycle. Specifically, it focuses on how the source and processing of dissolved and particulate organic matter (DOM and POM) interact to dictate OM fate. To do so, Fourier-transform ion cyclotron resonance mass spectrometry, carbon isotopes ([capital delta]14C, [small delta]13C), and data on OM concentrations and carbon to nitrogen (C:N) ratios are used. Across the pan-Arctic (Chapters 2 and 3) and northeast Pacific coastal temperate rainforest (NPCTR; Chapters 4 and 5), sources appear to influence the fate of DOM (Chapters 2, 4, and 5) and POM (Chapter 3). Both landscape-scale factors like permafrost or agricultural extent (Chapters 2 and 3) and watershed slope and wetland extent (Chapters 3, 4, and 5), as well as specific source types like tree canopy or bark and soil layer (Chapters 4 and 5) impact OM molecular, isotopic, and elemental compositions and thus processing. Further, seasonality varies between the pan-Arctic watershed (Chapters 2 and 3) and the NPCTR (Chapters 4 and 5), leading to differential timing of the strongest terrestrial carbon source impacts on the system.In large pan-Arctic rivers, spring freshet contains DOM primarily sourced from terrestrial material but also includes a latent high-energy subsidy that explains the historical paradox of freshet DOM's bulk terrestrial composition but apparent high biolability. Winter riverine DOM is mostly sourced from old, microbially degraded groundwater DOM. This work uncovered a stable core Arctic riverine fingerprint (CARF) present in all samples from six years. The CARF may contribute to a carbon sink of aged DOM that appears to persist in the global ocean. Further, this dissertation uses a decade of compositional data on POM to untangle multiple allochthonous and autochthonous pan-Arctic and watershed-specific POM endmembers sourced from literature (for the full list of literature values used in endmembers, see supplementary file "Table B5.csv"). The three tracers used (C:N ratio, [small delta]13C, and [capital delta]14C) appear to reveal a substantial, previously overlooked aquatic biomass signal in POM (~53% of the annual pan-Arctic POM flux which averages 4391 Gg/y of exported particulate organic carbon). Splitting soil endmember values into shallow and deep soil pools (mean [plus or minus] standard deviation: -228 [plus or minus] 211 volume -492 [plus or minus] 173%) rather than the less representative traditional active layer and permafrost categories (-300 ± 236 volume -441 ± 215‰) also improved endmember resolution. In the NPCTR, dissolved organic carbon concentrations as high as 167 mgCL-1 were found in tree DOM (which proved highly biolabile in this study; >50%). Since the NPCTR is hypermaritime, tree DOM fluxes may be substantial. Condensed aromatic formulae comprised as much as 38% relative abundance of spruce and hemlock bark leachate DOM. Coniferous trees could thus be major condensed aromatic sources. Soil wetness determined DOM composition and response to microbial processing. Source-specific marker formulae were discovered in multiple soil and tree sources, and though the majority were consumed during bioincubations certain marker formulae persisted. All of these source-specific marker formulae (of which >90% were from spruce stemflow) were then located downstream in the watershed demonstrating that tree DOM may escape biodegradation. Summertime in the NPCTR yields the most terrestrial DOM, which then appears to degrade during the colder, wetter, fall-spring period. Despite these seasonal trends two metrics of fresh terrestrial DOM contribution (marker formulae and modified aromaticity index) did not show any significant relationships with hydrologic or temperature variables. Antecedent conditions (rather than precipitation alone) thus seems to control molecular terrestrial connectivity. Climate change is modifying both the sources and seasons that this dissertation shows to influence DOM composition and fate in northern regions. Increasing precipitation intensity in the NPCTR may tighten land-ocean linkages, while warming, permafrost thaw, and increasing CO2 concentrations could enhance allochthonous and autochthonous POM fluxes and the contribution of old, microbially processed, stable DOM to the Arctic Ocean. This work shows that an improved understanding of current controls on OM composition and fate will be necessary to predict future changes in northern high-latitude ecosystem carbon cycling and its role in furthering global climate change.
Permafrost Soils
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Author : Rosa Margesin
language : en
Publisher: Springer Science & Business Media
Release Date : 2008-10-31
Permafrost Soils written by Rosa Margesin and has been published by Springer Science & Business Media this book supported file pdf, txt, epub, kindle and other format this book has been release on 2008-10-31 with Science categories.
Most of the Earth’s biosphere is characterized by low temperatures. Vast areas (>20%) of the soil ecosystem are permanently frozen or are unfrozen for only a few weeks in summer. Permafrost regions occur at high latitudes and also at high ele- tions; a significant part of the global permafrost area is represented by mountains. Permafrost soils are of global interest, since a significant increase in temperature is predicted for polar regions. Global warming will have a great impact on these soils, especially in northern regions, since they contain large amounts of organic carbon and act as carbon sinks, and a temperature increase will result in a release of carbon into the atmosphere. Additionally, the intensified release of the clima- relevant tracer gas methane represents a potential environmental harzard. Significant numbers of viable microorganisms, including bacteria, archaea, p- totrophic cyanobacteria and green algae, fungi and protozoa, are present in per- frost, and the characteristics of these microorganisms reflect the unique and extreme conditions of the permafrost environment. Remarkably, these microorg- isms have been reported to be metabolically active at subzero temperatures, even down to ?20°C.
Changes To Modern And Aged Dissolved Organic Matter Inputs Into The Kolyma River
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Author : Jennifer A. Rogers
language : en
Publisher:
Release Date : 2020
Changes To Modern And Aged Dissolved Organic Matter Inputs Into The Kolyma River written by Jennifer A. Rogers and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2020 with Aquaculture categories.
Climate change is radically altering the Arctic. These alterations are expected to have immense and cascading implications on the carbon cycling of the region. In particular, our interest lies in the Kolyma River (KR) as it is the largest Arctic watershed entirely lined below with continuous organic-rich permafrost and is equally subject to shrubification. On one hand, it appears that permafrost is predicted to thaw with the potential to release large quantities of ancient organic carbon. On the other hand, nutrient liberation, increased moisture, and warming allow vegetation to colonize more effectively increasing modern sources of organic carbon. The decomposition of permafrost soil organic matter has been postulated to release permafrost-derived dissolved organic matter (DOM) into stream and riverine networks that is exceptionally old and aliphatic in nature. We aimed to improve the evaluation of permafrost dissolved organic carbon (DOC) inputs and fate by implementing ramped pyrolysis oxidation (RPO) and isotopic analysis coupled with ultrahigh-resolution mass spectrometry. Bioincubation analyses were fundamental in replicating the transformations that occur to DOM during riverine transport. We found that highly aliphatic molecular formulae identified in undegraded permafrost DOM contrasts with the comparatively aliphatic-poor composition of KR DOM, suggesting that limited quantities of undegraded permafrost DOM are present in the KR. RPO radiocarbon analysis of KR DOC fractions exhibited no "hidden" aged component indicative of permafrost influence. Consistent with radiocarbon results, thermostability analysis indicated limited biodegraded permafrost DOC in the KR. A mixing model allowed us to estimate permafrost inputs to the KR DOC. Ultimately, our findings highlight that export of modern terrestrial DOM is currently overwhelming any permafrost DOM signature in the KR. This emphasizes the important ramifications of vegetation changes on the composition and biolability of transported DOM in this region with increasing shrubs dominance over herbaceous vegetation and bare ground. To investigate this, we subjected leachates of representative vegetation and soils both to biodegradation incubations and analysis using ultrahigh-resolution mass spectrometry. Biolability was seen to primarily be driven by lower relative abundances of highly unsaturated and phenolic compounds and higher relative abundances of aliphatic compounds and an overall low nominal oxidation state of carbon. In particular, DOC derived from shrubs has a lower biolability when compared to non-woody vegetation, containing on average nearly half as much %BDOC. This indicates that this DOC may persist in the water column which may have large implications as we continue attempts to quantify a permafrost DOC flux. It may be that studies will need to appraise the role vegetation cover plays in altering the age and composition of DOM of a region before investigating inputs of aged sources.
Dissolved Organic Matter In Arctic Watersheds And Coastal Waters
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Author : Craig Thomas Connolly
language : en
Publisher:
Release Date : 2019
Dissolved Organic Matter In Arctic Watersheds And Coastal Waters written by Craig Thomas Connolly and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2019 with categories.
Arctic warming is already affecting the movement of freshwater and dissolved organic matter (DOM) from watersheds to the coastal ocean in the Arctic. Improved understanding of DOM in freshwater sources and linkages to DOM characteristics in Arctic coastal waters is needed to assess responses to and feedbacks with climate change. This work focuses on DOM characteristics that couple watershed and coastal systems in the Arctic, with specific considerations of river and groundwater inputs to lagoon ecosystems along the eastern Alaska Beaufort Sea coast. We found that spring and summer river-borne concentrations of dissolved organic carbon and nitrogen (DOC and DON) are strongly linked to variations in watershed slope and soil organic matter coverage across space and scale in the Arctic. The quantities and composition of DOM in lagoons of the eastern Alaska Beaufort Sea coast vary markedly between seasons. Specifically, lagoons experience a shift from high to low DOC and DON concentrations between the late spring sea ice break-up and winter ice-covered periods, but these concentrations are more variable during the summer open water period. Distinct seasonal transitions in ice coverage, runoff from land, and water exchange with the Beaufort Sea strongly influence the availability of lagoon DOM. During the summer, concentrations of DOC and DON in supra-permafrost groundwater (SPGW) inputs to lagoons are much higher than those found in local rivers and lagoons. Late-summer fluxes of SPGW DOM to the northern Alaska coastline are substantial and may be the principal source of DOM to lagoons without river inputs. This SPGW DOM is sourced from readily leachable organic matter in surface soils and deeper soil horizons that likely extend into thawing permafrost. SPGW DOM contains aromatic carbon compounds that are largely resistant to microbial degradation on the order of days to months. While nearby river and lagoon water DOM has a similar composition and degradability, SPGW contains a portion of bioavailable and reactive DOM that is not present in river and lagoon waters. Inputs of SPGW DOM provide a potentially important source of energy for lagoon food webs along the Alaskan Beaufort Sea coast during the late summer
Methanogen Community And Activity In Canadian High Arctic Soils In Response To Global Warming
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Author : Jennifer Allan
language : en
Publisher:
Release Date : 2013
Methanogen Community And Activity In Canadian High Arctic Soils In Response To Global Warming written by Jennifer Allan and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2013 with categories.
"Recent modeling indicates that up to 90 % of the top 3 m of Arctic permafrost will melt by 2090 as a result of climate change. This thawing is predicted to expand anaerobic environments and provide previously frozen carbon stores for microbial decomposition. This may favour methanogen production of methane (CH4), a greenhouse gas (GHG) 25 times more potent than carbon dioxide (CO2). This study examined the effects of increased temperatures and substrates on Archaeal and methanogenic abundance, activity and diversity in active layer and permafrost soils from Axel Heiberg Island in the Canadian high Arctic. This was completed through in situ measurements and two permafrost microcosms experiments. The first microcosm experiment was unamended at 4 and 15° C, and the second was amended with the 13C-labelled substrates: acetate, methanol and CO2, at 4 and 22° C. The activity of methanogens was determined by the anaerobic production of CO2 and CH4, and their diversity and abundance were determined by 454 pyrosequencing of the Archaeal 16S rRNA gene and qPCR of the methanogen mcrA gene. In addition, DNA stable isotope probing (SIP) determined the active community in the 70 cm 22°C CO2 microcosm sample. The production of CO2 in situ and in unamended microcosms correlated with organic matter and temperature but only increased with temperature in acetate-amended microcosms. The production of CH4 correlated with the combined effects of substrate and temperature, being highest with CO2 amendment. The Nitrososphaerales were the most abundant Archaeal order, averaging 88 % of total 454 pyrosequencing reads. The abundance and diversity of methanogens increased with depth, from 1 % of total Archaeal reads at 30 cm to 11 % at 70 cm, likely due to the increased anaerobicity. All of the methanogen orders were detected, but the most abundant were Methanomicrobiales and Methanococcales. The Methanomicrobiales also accounted for the highest increase in methanogens, from 9.5 % in the unamended core to 39.5 % in the 70 cm 4°C CO2 sample. However, this was not associated with an increase in CH4 production. The Methanopyrales were the only active order detected by DNA-SIP in the 70 cm 22°C CO2 sample, and correlated with the CH4 production in all 70 cm samples. Therefore, despite their low abundance, the Methanopyrales may play an important functional role in the production of CH4 in these high arctic polygon soils. As permafrost thaws, microbial decomposition of carbon stores is expected to increase the release CO2. Our results indicate that this increase in CO2 may promote the production of CH4 from Canadian high Arctic polygon soils." --
Dissolved Organic Matter Discharge In The Six Largest Arctic Rivers Chemical Composition And Seasonal Variability
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Author : Amanda J. Rinehart
language : en
Publisher:
Release Date : 2010
Dissolved Organic Matter Discharge In The Six Largest Arctic Rivers Chemical Composition And Seasonal Variability written by Amanda J. Rinehart and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2010 with categories.
The vulnerability of the Arctic to climate change has been realized due to disproportionately large increases in surface air temperatures which are not uniformly distributed over the seasonal cycle. Effects of this temperature shift are widespread in the Arctic but likely include changes to the hydrological cycle and permafrost thaw, which have implications for the mobilization of organic carbon into rivers. The focus of this research was to describe the seasonal variability of the chemical composition of dissolved organic matter (DOM) in the six largest Arctic rivers (Yukon, Mackenzie, Ob, Yenisei, Lena and Kolyma) using optical properties (UV-Vis Absorbance and Fluorescence) and lignin phenol analysis. We also investigated differences between rivers and how watershed characteristics influence DOM composition. Dissolved organic carbon (DOC) concentrations followed the hydrograph with highest concentrations measured during peak river flow. The chemical composition of peak-flow DOM indicates a dominance of freshly leached material with elevated aromaticity, larger molecular weight, and elevated lignin yields relative to base-flow DOM. During peak flow, soils in the watershed are still frozen and snowmelt water follows a lateral flow path to the river channels. As the soils thaw, surface water penetrates deeper into the soil horizons leading to lower DOC concentrations and likely altered composition of DOM due to sorption and microbial degradation processes. The six rivers studied here shared a similar seasonal pattern and chemical composition. There were, however, large differences between rivers in terms of total carbon discharge reflecting the differences in watershed characteristics such as climate, catchment size, river discharge, soil types, and permafrost distribution. The large rivers (Lena, Yenisei), with a greater proportion of permafrost, exported the greatest amount of carbon. The Kolyma and Mackenzie exported the smallest amount of carbon annually, however, the discharge weighted mean DOC concentration was almost 2-fold higher in the Kolyma, again, indicating the importance of continuous permafrost. The quality and quantity of DOM mobilized into Arctic rivers appears to depend on the relative importance of surface run-off and extent of soil percolation. The relative importance of these is ultimately determined by watershed characteristics.
Ground Ice Content And Geochemistry Of Active Layer And Permafrost In Northwestern Arctic Canada
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Author : Marielle Fontaine
language : en
Publisher:
Release Date : 2015
Ground Ice Content And Geochemistry Of Active Layer And Permafrost In Northwestern Arctic Canada written by Marielle Fontaine and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2015 with University of Ottawa theses categories.
This study aimed to contribute to baseline knowledge of permafrost geochemistry within the uppermost 3-4 m of permafrost at 8 sites on the Peel Plateau and east of the Mackenzie Delta, NWT (67-68oN). The following variables were measured: gravimetric water content (GWC), pore water conductivity (PWC), leachate conductivity (LC), dissolved ions by ICP-AES (i.e. Ca, SO4, Mg, Fe, K, Na, Mn, Cl), organic carbon content (calculated by linear regression from organic matter content), as well as inorganic carbon content (obtained from loss on ignition analysis). PWC was positively correlated to GWC and values were generally at least 5 times less than LC values, likely underestimating total dissolved solutes using the former method. LC increased with depth to reach maximum values below the paleo thaw unconformity (>10 mS/cm). Carbon content typically remained low throughout the cores with the exception of samples associated to the shallow-rooted vegetation cover at the ground surface. Results showed that the active layer, relict active layer and the permafrost below the thaw unconformity can be divided into three statistically significant layers. PCA results indicated some spatial patterns with increasing LC values at greater depth, suggesting that layer geochemical profiles reflect varying degrees of soil chemical weathering processes since the early Holocene.
Permafrost North American Contribution To The Second International Conference
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Author :
language : en
Publisher: National Academies
Release Date : 1973-01-01
Permafrost North American Contribution To The Second International Conference written by and has been published by National Academies this book supported file pdf, txt, epub, kindle and other format this book has been release on 1973-01-01 with Frozen ground categories.
Permafrost Hydrology
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Author : Ming-ko Woo
language : en
Publisher: Springer Science & Business Media
Release Date : 2012-04-14
Permafrost Hydrology written by Ming-ko Woo and has been published by Springer Science & Business Media this book supported file pdf, txt, epub, kindle and other format this book has been release on 2012-04-14 with Science categories.
Permafrost Hydrology systematically elucidates the roles of seasonally and perennially frozen ground on the distribution, storage and flow of water. Cold regions of the World are subject to mounting development which significantly affects the physical environment. Climate change, natural or human-induced, reinforces the impacts. Knowledge of surface and ground water processes operating in permafrost terrain is fundamental to planning, management and conservation. This book is an indispensable reference for libraries and researchers, an information source for practitioners, and a valuable text for training the next generations of cold region scientists and engineers.