Paleosols of the Interglacial Climates in Canada

Although paleosols are useful indicators of paleoclimates. it is first necessary to establish the relationships between the northern limits of the various contemporary soils and the pertinent climatic parameters. It is then necessary to determine the age of the various paleosols and, if possible, their northern limits. Comparison of the distribution and northern limits of the contemporary soils with the distribution and northern limits of the analogous paleosols then permits the reconstruction of the paleoenvironments. For the purposes of comparison the mean annual temperature of the Old Crow area during the Pliocene epoch was also determined (about 4°C) even though this was not an interglacial period. It was found that during the pre-lllinoian interglacial periods the central Yukon had a mean annual temperature of about 7°C while during the Sangamonian interglacial period it had a mean annual temperature of about - 3°C. During the Holocene epoch, the current interglacial period, the climate has been similar to or only slightly cooler than that existing during the Sangamonian interglacial period. The fluctuating position of the arctic tree line (and associated forest soils) during the Holocene epoch, however, indicates that the climate has also been fluctuating during this time. The paleoclimatic reconstruction presented in this paper also relies heavily on both diagnostic soil features and the soil development during the various interglacial periods.Pour que les paléosols soient des indicateurs utiles de paléoclimats, on doit d'abord établir les relations entre les limites nordiques des divers sols contemporains et les paramètres climatiques appropriés. On doit ensuite déterminer l'âge des divers paléosols et, si possible, leur limite nordique. La comparaison entre la répartition et la limite nordique des sols contemporains et celles des paléosols analoques permet alors d'effectuer une reconstitution des paléoenvironnements. Pour fins de comparaison ici, la température moyenne annuelle dans la région de Old Crow au cours du Pliocène a également été déterminée (environ 4°C), même s'il ne s'agissait pas d'une période interglaciaire. On a estimé que, durant les périodes interglaciaires pré-illinoiennes. Ie centre du Yukon avait une température moyenne annuelle d'environ 7°C. alors que durant l'interglaciaire du Sangamonien. Ia température était d'environ -3°C. Pendant l'Holocène, c'est-à-dire la période interglaciaire actuelle, le climat a été semblable ou très légèrement plus froid que pendant l'interglaciaire du Sangamonien. La fluctuation de la limite des arbres (et des sols forestiers associés) au cours de l'Holocène montre que le climat a également connu des changements. La reconstitution paléoclimatique présentée repose en outre sur des caractéristiques pédologiques diagnostiques et sur le développement du profil au cours des différentes périodes interglaciaires.Obwohl Palàobôden nutzliche Indikatoren der Palâoklimas sind, ist es nôtig. zuerst die Beziehungen zwischen den nôrdlichen Grenzen der verschiedenen gegenwartigen Bôden und den betreffenden klimatischen Parametern herzustellen. Dann muss das Alter der verschiedenen Palàobôden bestimmt werden und wenn môglich ihre nôrdlichen Grenzen. Der Vergleich der Verteilung und nôrdlichen Grenzen der gegenwartigen Bôden mit denjenigen der analogen Palàobôden erlaubt dann, die Palâoumwelten zu rekonstruieren. Zum Zweck des Vergleichs wurde auch die durchschnittliche Jahrestemperatur in der Gegend von Old Crow wàhrend des Pliozân bestimmt (ungefâhr 4 C), auch wenn dies keine interglaziale Période war. Man fand heraus. dass wàhrend der prà-illinoischen interglazialen Perioden im Zentrum von Yukon eine durchschnittliche Jahrestemperatur von ungefâhr 7°C herrschte, wohingegen es wàhrend des sangamonischen Interglazial eine Jahresdurchschnittstemperatur von ungefâhr - 30C gab. Wàhrend des Holozan, der gegenwartigen interglazialen Epoche, war das Klima àhnlich oder nur leicht kùhler als das, was wàhrend des sangamonischen Interglazial herrschte. Die Fluktuation der arktischen Baumgrenze (und der mit ihr in Verbindung gebrachten Waldbôden) wàhrend des Holozan weist indessen darauf hin. dass das Klima wàhrend dieser Zeit auch fluktuierte. Die in diesem Aufsatz vorgestellte palâoklimatische Rekonstruktion ruht auch in bedeutender Masse sowohl auf diagnostischen Boden-Merkmalen wie auf der Boden-Entwicklung wàhrend der verschiedenen interglazialen Perioden

Pedological Investigations of Pleistocene Glacial Drift Surfaces in the Central Yukon

Distinct soil morphologies associated with three different ages of Quaternary glacial deposits are characterized and subsequently named. Properties which provide a basis for distinguishing these in the field include solum depth, B horizon colour, clay skin development, coarse fragment weathering and periglacial features. A strong relationship is evident between the clay content at depth and the age of soil. Low values of Na pyrophosphate-extractable Fe and Al confirm the absence of any active podzol-forming processes even within the reddest (5YR, 2.5YR) soil horizons. Wounded Moose paleosols are the preserved soils observed on pre-Reid Glaciation (.2-1.2 Ma) deposits which show strong paleoargillic horizon development with red colours, high clay content, and common periglacial modification. Diversion Creek paleosols are the preserved soils found on Reid (80-120 ka) glacial deposits which show moderate paleoargillic horizon development and resemble the contemporary Gray Luvisols of the mid and southern boreal forest regions of Canada. Stewart soils are the weakly developed Brunisols formed on stable landform surfaces of McConnell (14-30 ka) glacial deposits. The Wounded Moose and Diversion Creek paleosols, while found commonly in local areas, occupy only a small proportion of the regional landscape.On a dégagé les caractéristiques des sols (auxquels on a attribué des noms) dont les morphologies distinctes correspondent à trois épisodes de dépôts glaciaires du Quaternaire. Les propriétés pédologiques qui permettent de faire les distinctions sur le terrain sont la profondeur du solum, Ia couleur de l'horizon B, le développement des pellicules argileuses, l'altération des éléments grossiers et les caractéristiques périglaciaires. On constate qu'il existe une forte relation entre la teneur en argile en profondeur et l'âge du sol. Les bas taux de Fe et Al extractibles au pyrophosphate par le sodium démontrent l'absence de processus de formation de podzol, même dans les horizons les plus rouges (5YR, 2,5YR). Les paléosols de Wounded Moose sont les sols conservés que l'on peut observer sur les dépôts de la pré-glaciation de Reed (0,2-1,2 Ma) et qui montrent un fort développement de l'horizon enrichi d'argile à cause des couleurs rouges, de la haute teneur en argile et des modifications périglaciaires courantes. Les paléosols de Diversion Creek sont les sols conservés que l'on peut observer sur les dépôts de la glaciation de Reed (8000-12 000 ans) qui montrent un développement moyen de l'horizon enrichi d'argile et qui ressemblent aux luvisols actuels de Gray que l'on trouve dans le sud et le centre des forêts boréales du Canada. Les sols de Stewart sont des brunisols peu développés formés sur les reliefs stables mis en place par les dépôts de la glaciation de McConnell (14 000-30 000 ans). Les paléosols de Wounded Moose et de Diversion Creek, bien que courants à l'échelle locale, n'occupent qu'une faible partie du territoire.Unterschiedliche Bodenmorphologien werden auf drei verschiedene Episoden glazialer Ablagerungen im Quaternâr bezogen, cha-rakterisiert und anschlieBend benannt. Die Eigenschaften, welche eine Basis zur Unterscheidung dieser bei der Feldforschung liefern, sind die Tiefe des Solum, die Farbe des B-Horizonts, die Entwicklung der Lehm-Oberflàche, die Verwitterung grober Fragmente und die periglazialen Charakteristika. Es besteht offensichtlich eine enge Beziehung zwischen dem Lehm-Gehalt in der Tiefe und dem Alter des Erdreichs. Niedrige Werte von mittels Na Pyrophosphat herauslôsbarem Fe und Al bestàtigen das Fehlen jeglicher aktiver Podsol bildender Prozesse, selbst innerhalb der rôtesten Erd-Horizonte (5 YR, 2.5 YR). Die Paleosols von Wounded Moose sind die auf den Ablagerungen der Vor-Reid-Vereisung (.2-1.2 Ma) erhaltenen Bôden, welche eine starke Entwicklung des paleolehmigen Horizonts aufweisen, mit roten Farben, hohem Lehmgehalt und der ùblichen periglazialen Verànderung. Diversion Creek Paleobôden sind die auf glazialen Ablagerungen von Reid (80-120 ka) vorgefundenen erhaltenen Bôden, welche eine gemàBigte, paleolehmige Horizont-Entwicklung aufweisen und den gegenwàrtigen Luvisols von Gray âhneln, die man in der Mitte und im Sùden der nôrdlichen Waldgebiete von Kanada findet. Die Bôden von Stewart sind schwach entwickelte Brunisols, die sich auf den festen Oberflâchen-reliefs der glazialen Ablagerungen von McConnell (14-30 ka) gebildet haben. Die Paleobôden von Wounded Moose und Diversion Creek nehmen nur einen kleinen Teil der regionalen Landschaft ein, obwohl sie auf ôrtlichem Niveau allgemein zu finden sind

The permafrost carbon inventory on the Tibetan Plateau : a new evaluation using deep sediment cores

Acknowledgements We are grateful for Dr. Jens Strauss and the other two anonymous reviewers for their insightful comments on an earlier version of this MS, and appreciate members of the IBCAS Sampling Campaign Teams for their assistance in field investigation. This work was supported by the National Basic Research Program of China on Global Change (2014CB954001 and 2015CB954201), National Natural Science Foundation of China (31322011 and 41371213), and the Thousand Young Talents Program.Peer reviewedPostprin

Controls on the composition and lability of dissolved organic matter in Siberia's Kolyma River basin

High-latitude northern rivers export globally significant quantities of dissolved organic carbon (DOC) to the Arctic Ocean. Climate change, and its associated impacts on hydrology and potential mobilization of ancient organic matter from permafrost, is likely to modify the flux, composition, and thus biogeochemical cycling and fate of exported DOC in the Arctic. This study examined DOC concentration and the composition of dissolved organic matter (DOM) across the hydrograph in Siberia's Kolyma River, with a particular focus on the spring freshet period when the majority of the annual DOC load is exported. The composition of DOM within the Kolyma basin was characterized using absorbance-derived measurements (absorbance coefficienta330, specific UV absorbance (SUVA254), and spectral slope ratio SR) and fluorescence spectroscopy (fluorescence index and excitation-emission matrices (EEMs)), including parallel factor analyses of EEMs. Increased surface runoff during the spring freshet led to DOM optical properties indicative of terrestrial soil inputs with high humic-like fluorescence, SUVA254, and low SRand fluorescence index (FI). Under-ice waters, in contrast, displayed opposing trends in optical properties representing less aromatic, lower molecular weight DOM. We demonstrate that substantial losses of DOC can occur via biological (∼30% over 28 days) and photochemical pathways (>29% over 14 days), particularly in samples collected during the spring freshet. The emerging view is therefore that of a more dynamic and labile carbon pool than previously thought, where DOM composition plays a fundamental role in controlling the fate and removal of DOC at a pan-Arctic scale

Drivers of Holocene palsa distribution in North America

Palsas and peat plateaus are climatically sensitive landforms in permafrost peatlands. Climate envelope models have previously related palsa/peat plateau distributions in Europe to modern climate, but similar bioclimatic modelling has not been attempted for North America. Recent climate change has rendered many palsas/peat plateaus in this region, and their valuable carbon stores, vulnerable. We fitted a binary logistic regression model to predict palsa/peat plateau presence for North America by relating the distribution of 352 extant landforms to gridded modern climate data. Our model accurately classified 85.3% of grid cells that contain observed palsas/peat plateaus and 77.1% of grid cells without observed palsas/peat plateaus. The model indicates that modern North American palsas/peat plateaus are supported by cold, dry climates with large seasonal temperature ranges and mild growing seasons. We used palaeoclimate simulations from a general circulation model to simulate Holocene distributions of palsas/peat plateaus at 500-year intervals. We constrained these outputs with timings of peat initiation, deglaciation, and postglacial drainage across the continent. Our palaeoclimate simulations indicate that this climate envelope remained stationary in western North America throughout the Holocene, but further east it migrated northwards during 11.5–6.0 ka BP. However, palsa extents in eastern North America were restricted from following this moving climate envelope by late deglaciation, drainage and peat initiation. We validated our Holocene simulations against available palaeoecological records and whilst they agree that permafrost peatlands aggraded earliest in western North America, our simulations contest previous suggestions that late permafrost aggradation in central Canada was climatically-driven

Effects of permafrost aggradation on peat properties as determined from a pan-arctic synthesis of plant macrofossils

©2015. American Geophysical Union. All Rights Reserved.This article has been accepted for publication and undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process, which may lead to differences between this version and the Version of Record. Please cite this article as doi: 10.1002/2015JG003061Permafrost dynamics play an important role in high-latitude peatland carbon balance and are key to understanding the future response of soil carbon stocks. Permafrost aggradation can control the magnitude of the carbon feedback in peatlands through effects on peat properties. We compiled peatland plant macrofossil records for the northern permafrost zone (515 cores from 280 sites) and classified samples by vegetation type and environmental class (fen, bog, tundra and boreal permafrost, thawed permafrost). We examined differences in peat properties (bulk density, carbon (C), nitrogen (N) and organic matter content, C/N ratio) and C accumulation rates among vegetation types and environmental classes. Consequences of permafrost aggradation differed between boreal and tundra biomes, including differences in vegetation composition, C/N ratios, and N content. The vegetation composition of tundra permafrost peatlands was similar to permafrost-free fens, while boreal permafrost peatlands more closely resembled permafrost-free bogs. Nitrogen content in boreal permafrost and thawed permafrost peatlands was significantly lower than in permafrost-free bogs despite similar vegetation types (0.9% versus 1.5% N). Median long-term C accumulation rates were higher in fens (23 g C m-2 y-1) than in permafrost-free bogs (18 g C m-2 y-1), and were lowest in boreal permafrost peatlands (14 g C m-2 y-1). The plant macrofossil record demonstrated transitions from fens to bogs to permafrost peatlands, bogs to fens, permafrost aggradation within fens, and permafrost thaw and re-aggradation. Using data synthesis, we've identified predominant peatland successional pathways, changes in vegetation type, peat properties, and C accumulation rates associated with permafrost aggradation.National Science FoundationUSGS Climate and Land-useChange Research and Development ProgramAcademy of FinlandRoyal Swedish Academy of ScienceYmer-80, Knut & Alice Wallenberg and Ahlmann Foundation

Observational constraints on the distribution, seasonality, and environmental predictors of North American boreal methane emissions

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/106685/1/GBC_20128_REVISED_suppinfo.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/106685/2/gbc20128.pd

Vulnerability of high latitude soil organic carbon in North America to disturbance

This synthesis addresses the vulnerability of the North American high-latitude soil organic carbon (SOC) pool to climate change. Disturbances caused by climate warming in arctic, subarctic, and boreal environments can result in significant redistribution of C among major reservoirs with potential global impacts. We divide the current northern high-latitude SOC pools into (1) near-surface soils where SOC is affected by seasonal freeze-thaw processes and changes in moisture status, and (2) deeper permafrost and peatland strata down to several tens of meters depth where SOC is usually not affected by short-term changes. We address key factors (permafrost, vegetation, hydrology, paleoenvironmental history) and processes (C input, storage, decomposition, and output) responsible for the formation of the large high-latitude SOC pool in North America and highlight how climate-related disturbances could alter this pool\u27s character and size. Press disturbances of relatively slow but persistent nature such as top-down thawing of permafrost, and changes in hydrology, microbiological communities, pedological processes, and vegetation types, as well as pulse disturbances of relatively rapid and local nature such as wildfires and thermokarst, could substantially impact SOC stocks. Ongoing climate warming in the North American high-latitude region could result in crossing environmental thresholds, thereby accelerating press disturbances and increasingly triggering pulse disturbances and eventually affecting the C source/sink net character of northern high-latitude soils. Finally, we assess postdisturbance feedbacks, models, and predictions for the northern high-latitude SOC pool, and discuss data and research gaps to be addressed by future research

Low photolability of yedoma permafrost dissolved organic carbon

Vast stores of arctic permafrost carbon that have remained frozen for millennia are thawing, releasing ancient dissolved organic carbon (DOC) to arctic inland waters. Once in arctic waters, DOC can be converted to CO2 and emitted to the atmosphere, accelerating climate change. Sunlight-driven photoreactions oxidize DOC, converting a portion to CO2 and leaving behind a photomodified pool of dissolved organic matter (DOM). Samples from the Kolyma River, its tributaries, and streams draining thawing yedoma permafrost were collected. Irradiation experiments and radiocarbon dating were employed to assess the photolability of ancient permafrost-DOC in natural and laboratory generated samples containing a mix of modern and ancient DOC. Photolabile DOC was always modern, with no measurable photochemical loss of ancient permafrost-DOC. However, optical and ultrahigh resolution mass spectrometric measurements revealed that both modern river DOM and ancient permafrost-DOM were photomodified during the irradiations, converting aromatic compounds to less conjugated compounds. These findings suggest that although sunlight-driven photoreactions do not directly mineralize permafrost-DOC, photomodification of permafrost-DOM chemistry may influence its fate and ecological functions in aquatic systems