May 2015 Permafrost Alert
The U.S. Permafrost Association, together with the American Geosciences Institute (AGI), is pleased to provide the following Permafrost Monthly Alerts (PMA). The AGI GeoRef service regularly scans the contents of over 3500 journals in 40 languages from the global geosciences literature, comprised of approximately 345 different sources. In addition to journals, special publications such as papers in proceedings and hard-to-find publications are provided. Each PMA represents a listing of the permafrost-related materials added to GeoRef during the previous month. Where available, a direct link to the publication is included, which provides access to the full document if you or your institution have a current online subscription.
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15049660 Swindles, Graeme T. (University of Leeds, School of Geography, Leeds, United Kingdom); Amesbury, Matthew J.; Turner, T. Edward; Carrivick, Jonathan L.; Woulds, Clare; Raby, Cassandra; Mullan, Donal; Roland, Thomas P.; Galloway, Jennifer M.; Parry, Lauren; Kokfelt, Ulla; Garneau, Michelle; Charman, Dan J. and Holden, Joseph. Evaluating the use of testate amoebae for palaeohydrological reconstruction in permafrost peatlands: Palaeogeography, Palaeoclimatology, Palaeoecology, 424, p. 111-122, illus. incl. 4 tables, charts, sketch map, 85 ref., April 15, 2015.
The melting of high-latitude permafrost peatlands is a major concern due to a potential positive feedback on global climate change. We examine the ecology of testate amoebae in permafrost peatlands, based on sites in Sweden (~ 200 km north of the Arctic Circle). Multivariate statistical analysis confirms that water-table depth and moisture content are the dominant controls on the distribution of testate amoebae, corroborating the results from studies in mid-latitude peatlands. We present a new testate amoeba-based water table transfer function and thoroughly test it for the effects of spatial autocorrelation, clustered sampling design and uneven sampling gradients. We find that the transfer function has good predictive power; the best-performing model is based on tolerance-downweighted weighted averaging with inverse deshrinking (performance statistics with leave-one-out cross validation: R2 = 0.87, RMSEP = 5.25 cm). The new transfer function was applied to a short core from Stordalen mire, and reveals a major shift in peatland ecohydrology coincident with the onset of the Little Ice Age (c. AD 1400). We also applied the model to an independent contemporary dataset from Stordalen and find that it outperforms predictions based on other published transfer functions. The new transfer function will enable paleohydrological reconstruction from permafrost peatlands in Northern Europe, thereby permitting greatly improved understanding of the long-term ecohydrological dynamics of these important carbon stores as well as their responses to recent climate change. Abstract Copyright (2015) Elsevier, B.V.
15047371 Lange, Jens (University of Freiburg, Chair of Hydrology, Freiburg, Germany); Kopp, Benjamin Johannes; Bents, Matthias and Menzel, Lucas. Tracing variability of run-off generation in mountainous permafrost of semi-arid northeastern Mongolia: Hydrological Processes, 29(6), p. 1046-1055, illus. incl. sketch map, 37 ref., March 15, 2015.
The headwaters of mountainous, discontinuous permafrost regions in north-eastern Mongolia are important water resources for the semi-arid country, but little is known about hydrological processes there. Run-off generation on south-facing slopes, which are devoid of permafrost, has so far been neglected and is totally unknown for areas that have been affected by recent forest fires. To fill this knowledge gap, the present study applied artificial tracers on a steppe-vegetated south-facing and on two north-facing slopes, burned and unburned. Combined sprinkling and dye tracer experiments were used to visualize processes of infiltration and water fluxes in the unsaturated zone. On the unburned north-facing slope, rapid and widespread infiltration through a wet organic layer was observed down to the permafrost. On the burned profile, rapid infiltration occurred through a combusted organic and underlying mineral layer. Stained water seeped out at the bottom of both profiles suggesting a general tendency to subsurface stormflow (SSF). Ongoing SSF could directly be studied 24 h after a high-intensity rainfall event on a 55-m hillslope section in the burned forest. Measurements of water temperature proved the role of the permafrost layer as a base horizon for SSF. Repeated tracer injections allowed direct insights into SSF dynamics: A first injection suggested rather slow dispersive subsurface flow paths; whereas 18 h later, a second injection traced a more preferential flow system with 20 times quicker flow velocities. We speculate that these pronounced SSF dynamics are limited to burned slopes where a thermally insulating organic layer is absent. On three south-facing soil profiles, the applied tracer remained in the uppermost 5 cm of a silt-rich mineral soil horizon. No signs of preferential infiltration could be found, which suggested reduced biological activity under a harsh, dry and cold climate. Instead, direct observations, distributed tracers and charcoal samples provided evidence for the occurrence of overland flow. Copyright 2014 John Wiley & Sons, Ltd.
15051582 Li Wangping (Cold and Arid Regions Environmental and Engineering Research Institute, Cryosphere Research Station on Qinghai-Xizang Plateau, Lanzhou, China); Zhao Lin; Wu Xiaodong; Wang Shijie; Sheng Yu; Ping, Chienlu; Zhao Yonghua; Fang Hongbing and Shi Wei. Soil distribution modeling using inductive learning in the eastern part of permafrost regions in Qinghai-Xizang (Tibetan) Plateau: Catena (Giessen), 126, p. 98-104, illus. incl. 3 tables, sketch maps, 43 ref., March 2015. Includes appendices.
Soil-landscape models serve as a basis for understanding the relationships between soils and landscape, and such models also allow us to study soil distribution, and classification. To understand the distribution of soils and landform relationships in permafrost regions, we developed a soil-landscape model by using See5.0 decision tree software in the Wenquan region of Xinghai County, in the eastern part of permafrost regions of Qinghai-Xizang (Tibetan) Plateau (QTP). The model was based on soil pedon data from 2009. Nine environmental factors closely related to permafrost-affected-soil formation were selected as variables for the model: land surface temperature for warm season and cool season, elevation, slope gradient, slope aspect, planform and profile curvatures, wetness index and NDVI. A 5-fold cross-validation method was applied to verify the effectiveness of the soil-landscape model. The model results were consistent with field observations, and the slope was the most strongly correlated factor with soil type of the nine environmental variables. The soils in the modeled area are mainly Ustic Cambosols and Ustic Isohumisols, which cover about 60.0% and 25.6% of the total area, respectively. Gelic cambosols occur mainly in permafrost region, while Ustic isohumosols occur in the transition region between permafrost and seasonally frozen ground. Further studies are required to utilize the soil-landscape model to predict the spatial distribution of soil types over the QTP. Abstract Copyright (2015) Elsevier, B.V.
15053781 Draebing, D. (University of Bonn, Department of Geography, Bonn, Germany); Krautblatter, M. and Dikau, R. Interaction of thermal and mechanical processes in steep permafrost rock walls; a conceptual approach: Geomorphology, 226, p. 226-235, illus. incl. sketch map, 105 ref., December 1, 2014.
Degradation of permafrost rock wall decreases stability and can initiate rock slope instability of all magnitudes. Rock instability is controlled by the balance of shear forces and shear resistances. The sensitivity of slope stability to warming results from a complex interplay of shear forces and resistances. Conductive, convective and advective heat transport processes act to warm, degrade and thaw permafrost in rock walls. On a seasonal scale, snow cover changes are a poorly understood key control of the timing and extent of thawing and permafrost degradation. We identified two potential critical time windows where shear forces might exceed shear resistances of the rock. In early summer combined hydrostatic and cryostatic pressure can cause a peak in shear force exceeding high frozen shear resistance and in autumn fast increasing shear forces can exceed slower increasing shear resistance. On a multiannual system scale, shear resistances change from predominantly rock-mechanically to ice-mechanically controlled. Progressive rock bridge failure results in an increase of sensitivity to warming. Climate change alters snow cover and duration and, hereby, thermal and mechanical processes in the rock wall. Amplified thawing of permafrost will result in higher rock slope instability and rock fall activity. We present a holistic conceptual approach connecting thermal and mechanical processes, validate parts of the model with geophysical and kinematic data and develop future scenarios to enhance understanding on system scale. Abstract Copyright (2014) Elsevier, B.V.
15053742 Goyanes, G. (Universidad de Buenos Aires, Departmento de Ciencias Geológicas, Buenos Aires, Argentina); Vieira, G.; Caselli, A.; Cardoso, M.; Marmy, A.; Santos, F.; Bernardo, I. and Hauck, C. Local influences of geothermal anomalies on permafrost distribution in an active volcanic island (Deception Island, Antarctica): in Permafrost and periglacial research in Antarctica; new results and perspectives (Guglielmin, Mauro, editor; et al.), Geomorphology, 225, p. 57-68, illus. incl. geol. sketch map, 63 ref., November 15, 2014.
This study aims at understanding the spatial distribution and characteristics of the frozen and unfrozen terrain in an alluvial fan on Deception Island, which is an active strato-volcano located in the Bransfield Strait (South Shetland Islands) with recent eruptions in 1967, 1969 and 1970. The alluvial fan is dominated by debris-flow, run-off and rock fall processes and permafrost occurs in several parts in the vicinity of anomalous geothermal heat flux. The aim is to assess the ways volcanic activity controls permafrost development and associated geomorphic dynamics using shallow subsurface, surface and air temperature measurements as well as thaw depth and electrical resistivity tomography (ERT) surveys. Results show a temperature increase with depth in the lower part of the fan reaching 13 °C at 0.80 m depth, without the presence of permafrost. The shallow borehole located at this site showed a stable thermal stratification all year-round, with only the upper 0.20 m reacting to meteorological forcing. In the upper part of the alluvial fan and debris cones, c. 100 m from the coast, frozen ground is present at c. 0.70 m depth. There, the shallow borehole shows a good coupling with air temperatures and the thermal regime favours the presence of permafrost. ERT shows the lowest resistivity values in the lower part of the alluvial fan and a highly resistivity zone in the upper sector of the fan and in the debris cones. These large variations in resistivity mark the presence of a saline water wedge from the sea into the fan, reaching frozen ground conditions about 100 m inland. It can be shown that the volcano-hydrothermal activity only inhibits frost development very locally, with frozen ground conditions occurring about 100 m away. Abstract Copyright (2014) Elsevier, B.V.
15053737 Guglielmin, Mauro; Vieira, Goncalo and Harvey, Adrian, editors. Permafrost and periglacial research in Antarctica; new results and perspectives: Geomorphology, 225, 99 p., illus., November 15, 2014. Individual papers are cited separately.
15053741 Guglielmin, Mauro (Insubria University, Department of Theoretical and Applied Sciences, Varese, Italy); Worland, M. Roger; Baio, Fabio and Convey, Peter. Permafrost and snow monitoring at Rothera Point (Adelaide Island, Maritime Antarctica); implications for rock weathering in cryotic conditions: in Permafrost and periglacial research in Antarctica; new results and perspectives (Guglielmin, Mauro, editor; et al.), Geomorphology, 225, p. 47-56, illus. incl. 6 tables, sketch map, 53 ref., November 15, 2014.
In February 2009 a new permafrost borehole was installed close to the British Antarctic Survey Station at Rothera Point, Adelaide Island (67.57195°S 68.12068°W). The borehole is situated at 31 m asl on a granodiorite knob with scattered lichen cover. The spatial variability of snow cover and of ground surface temperature (GST) is characterised through the monitoring of snow depth on 5 stakes positioned around the borehole and with thermistors placed at three different rock surfaces (A, B and C). The borehole temperature is measured by 18 thermistors placed at different depths between 0.3 and 30 m. Snow persistence is very variable both spatially and temporally with snow free days per year ranging from 13 and more than 300, and maximum snow depths varying between 0.03 and 1.42 m. This variability is the main cause of high variability in GST, that ranged between - 3.7 and - 1.5 °C. The net effect of the snow cover is a cooling of the surface. Mean annual GST, mean summer GST, and the degree days of thawing and the n-factor of thawing were always much lower at sensor A where snow persistence and depth were greater than in the other sensor locations. At sensor A the potential freeze-thaw events were negligible (0-3) and the thermal stress was at least 40% less than in the other sensor locations. The zero curtain effect at the rock surface occurred only at surface A, favouring chemical weathering over mechanical action. The active layer thickness (ALT) ranged between 0.76 and 1.40 m. ALT was directly proportional to the mean air temperature in summer, and inversely proportional to the maximum snow depth in autumn. ALT temporal variability was greater than reported at other sites at similar latitude in the Northern Hemisphere, or with the similar mean annual air temperature in Maritime Antarctica, because vegetation and a soil organic horizon are absent at the study site. Zero annual amplitude in temperature was observed at about 16 m depth, where the mean annual temperature is - 3 °C. Permafrost thickness was calculated to range between 112 and 157 m, depending on the heat flow values adopted. The presence of sub-sea permafrost cannot be excluded considering the depth of the shelf around Rothera Point and its glacial history. Abstract Copyright (2014) Elsevier, B.V.
15053473 Onaca, Alexandru L. (West University of Timisoara, Department of Geography, Timisoara, Romania); Urdea, Petru and Ardelean, Adrian C. Internal structure and permafrost characteristics of the rock glaciers of Southern Carpathians (Romania) assessed by geoelectrical soundings and thermal monitoring: Geografiska Annaler. Series A: Physical Geography, 95(3), p. 249-266, illus. incl. sketch maps, 3 tables, sects., 65 ref., September 2013.
Six rock glaciers in the Southern Carpathians have been investigated by means of geoelectrical soundings in order to detect their internal stratigraphy and the existence of frozen sediments. In the case of three relict rock glaciers, the electrical resistivity measurements indicated a typical internal structure. Low resistivity values (<10 kWm) which are typical of unfrozen fine-grained materials were obtained, but high resistivity values (25-240 kWm) measured in the Pietroasa, Iesu and Pietrele rock glaciers denote the presence of sediments cemented by interstitial ice and ice lenses. Based on the moderate resistivity values, the ice content is probably low to medium in the upper portion of these rock glaciers, that is, above 2040 m. At two sites (Pietroasa and Vaiuga rock glaciers), ground surface temperature (GST) evolution was monitored using digital dataloggers. Mean annual ground surface temperature and GST regime throughout the winter were extracted from the recordings and confirmed the probability of permafrost occurrence in Pietroasa rock glacier. In the Iesu and Pietrele rock glaciers, measurements of bottom temperatures of the winter snow cover were performed in March 2012. Considering the thick active layer, the reduced ice content and the presence of scarce vegetation on their surface it could be assumed that the permafrost exists in marginal conditions in the Southern Carpathians. The ground ice in permafrost is produced by the groundwater freezing or by snow banks buried by coarse angular boulders following large rockfalls. Abstract Copyright (2013), Swedish Society for Anthropology and Geography.
15050431 Yu Fan (Chinese Academy of Sciences, Cold and Arid Regions Environmental and Engineering Research Institute, Laboratory of Frozen Soil Engineering, Lanzhou, China); Qi Jilin; Yao Xiaoliang and Liu Yongzhi. In-situ monitoring of settlement at different layers under embankments in permafrost regions on the Qinghai-Tibet Plateau: Engineering Geology, 160, p. 44-53, illus. incl. sects., 4 tables, sketch map, 44 ref., June 27, 2013.
Ground temperature and settlement at different soil layers are monitored at four typical sections of the Qinghai-Tibet Highway (QTH) and one section of a newly built test road (NBTR) in Beilu River basin, for the purpose of extensive investigation on the rather complicated mechanism of embankment settlement owing to several physical and mechanical processes (i.e., settlement sources) taking place in different soil layers in permafrost regions. Combining the ground temperature with borehole drilling exploration, thawing temperatures of the permafrost layers in the five sections are determined, and then characteristics of permafrost degradation are analyzed. Three types of sections are summarized to clarify different settlement sources in different soil layers. On these bases, characteristics of embankment settlement under different geological conditions are analyzed; the influence of the seasonal changes of air temperature on embankment settlement is discussed; since the two sections, one on QTH and the other on NBTR, are both located in Beilu River basin, they are compared with respect to the variation of the main settlement source in the process of permafrost degradation. The results help to understand the mechanism of embankment settlement. Abstract Copyright (2013) Elsevier, B.V.
15054456 Liu Changling (Qingdao Institute of Marine Geology, Laboratory of Gas Hydrate, Qingdao, China); Meng Qingguo; He Xingliang; Li Chengfeng; Ye Yuguang; Lu Zhenquan; Zhu Youhai; Li Yonghong and Liang Jinqiang. Comparison of the characteristics for natural gas hydrate recovered from marine and terrestrial areas in China: Journal of Geochemical Exploration, 152, p. 67-74, illus. incl. 3 tables, sketch map, 55 ref., May 2015.
China has carried out several drilling campaigns for natural gas hydrate both in marine and terrestrial areas and successfully obtained the samples. The marine gas hydrate samples were firstly recovered from Shenhu area in 2007 and then from the Pearl River Mouth basin in 2013 in South China Sea (SCS). The terrestrial gas hydrate samples were recovered from Qilian Mountain permafrost (QMP) in 2009 and 2013, respectively. In this paper, systematic analyses have been carried out on these gas hydrate samples to compare the characteristics of gas hydrates from SCS with those from QMP. The results indicate that the characteristics of occurrence, structure and gas composition are obviously different. Marine gas hydrate from SCS shows different kinds of occurrence and demonstrates a typical structure I (sI), with cage occupancy of more than 99% methane in large cage and 90% in small cage, respectively, corresponding to hydration numbers of approximately 6.0 by thermodynamic calculation. The guest molecules are predominantly methane (> 99%) from biogenic origin produced by CO2 reduction. However, the terrestrial gas hydrates from QMP occur as a thin layer within the cracks of fine-grained sandstones, siltstones and mudstones, showing a possible structure II (sII) hydrate based on its Raman spectra and gas composition. The molecular composition of hydrate-bound gas indicates that CH4 only accounts for ~ 60% of the guests while the others are heavier hydrocarbons (e.g. C2H6, C3H8 and C4H10).The cage occupancy ratio of methane in small and large cage (qS/qL) is around 7.5, suggesting that larger molecules preferentially occupy the large cage of the hydrate. The isotopic analysis shows that hydrate-bound gases in QMP are from thermogenic origin. Abstract Copyright (2015) Elsevier, B.V.
15053740 Almeida, Ivan C. C. (Instituto Federal Norte de Minas Gerais, Januaria, Brazil); Schaefer, Carlos Ernesto G. R.; Fernandes, Raphael B. A.; Pereira, Thiago T. C.; Nieuwendam, Alexandre and Pereira, Antonio Batista. Active layer thermal regime at different vegetation covers at Lions Rump, King George Island, Maritime Antarctica: in Permafrost and periglacial research in Antarctica; new results and perspectives (Guglielmin, Mauro, editor; et al.), Geomorphology, 225, p. 36-46, illus. incl. 7 tables, sketch map, 35 ref., November 15, 2014.
Climate change impacts the biotic and abiotic components of polar ecosystems, affecting the stability of permafrost, active layer thickness, vegetation, and soil. This paper describes the active layer thermal regimes of two adjacent shallow boreholes, under the same soil but with two different vegetations. The study is location in Lions Rump, at King George Island, Maritime Antarctic, one of the most sensitive regions to climate change, located near the climatic limit of Antarctic permafrost. Both sites are a Turbic Cambic Cryosol formed on andesitic basalt, one under moss vegetation (Andreaea gainii, at 85 m a.s.l.) and another under lichen (Usnea sp., at 86 m a.s.l.), located 10 m apart. Ground temperature at same depths (10, 30 and 80 cm), water content at 80 cm depth and air temperature were recorded hourly between March 2009 and February 2011. The two sites showed significant differences in mean annual ground temperature for all depths. The lichen site showed a higher soil temperature amplitude compared to the moss site, with ground surface (10 cm) showing the highest daily temperature in January 2011 (7.3 °C) and the lowest daily temperature in August (- 16.5 °C). The soil temperature at the lichen site closely followed the air temperature trend. The moss site showed a higher water content at the bottommost layer, consistent with the water-saturated, low landscape position. The observed thermal buffering effect under mosses is primarily associated with higher moisture onsite, but a longer duration of the snowpack (not monitored) may also have influenced the results. Active layer thickness was approximately 150 cm at low-lying moss site, and 120 cm at well-drained lichen site. This allows to classify these soils as Cryosols (WRB) or Gelisols (Soil Taxonomy), with evident turbic features. Abstract Copyright (2014) Elsevier, B.V.
15053744 Michel, Roberto F. M. (Universidade Estadual de Santa Cruz, Ilheus, Brazil); Schaefer, Carlos E. G. R.; López Martínez, Jerónimo; Simas, Felipe N. B.; Haus, Nick W.; Serrano, Enrique and Bockheim, James G. Soils and landforms from Fildes Peninsula and Ardley Island, Maritime Antarctica: in Permafrost and periglacial research in Antarctica; new results and perspectives (Guglielmin, Mauro, editor; et al.), Geomorphology, 225, p. 76-86, illus. incl. 5 tables, geol. sketch map, 63 ref., November 15, 2014.
Fildes Peninsula (F.P.) and Ardley Island (A.I.) are among the first ice-free areas in Maritime Antarctica. Since the last glacial retreat in this part of Antarctica (8000 to 5000 years BP), the landscape in these areas evolved under paraglacial to periglacial conditions, with pedogenesis marked by cryogenic processes. We carried out a detailed soil and geomorphology survey, with full morphological and analytical description for both areas; forty-eight soil profiles representing different landforms were sampled, analyzed and classified according to the U.S. Soil Taxonomy and the World Reference Base for Soil Resources (WRB). Soils are mostly turbic, moderately developed, with podzolization and strong phosphatization (chemical weathering of rock minerals and formation of amorphous Al and Fe minerals) in former ornithogenic sites while in areas with poor vegetation show typical features of cryogenic weathering. Nivation, solifluction, cryoturbation, frost weathering, ablation and surface erosion are widespread. The most represented landform system by surface in Fildes Peninsula is the periglacial one, and 15 different periglacial landforms types have been identified and mapped. These features occupy about 30% of the land surface, in which patterned ground and stone fields are the most common landforms. Other significant landforms as protalus lobes, rock glaciers or debris lobes indicate the extensive presence of permafrost. Soil variability was high, in terms of morphological, physical and chemical properties, due to varying lithic contributions and mixing of different rocks, as well as to different degrees of faunal influence. Three soil taxonomy orders were identified, whereas thirty four individual pedons were differentiated. Fildes Peninsula experiences a south-north gradient from periglacial to paraglacial conditions, and apparently younger soils and landforms are located close to the Collins Glacier. Arenosols/Entisols and Cryosols/Gelisols (frequently cryoturbic) are the most important soil classes; Leptosols/Entisols, Gleysols/Aquents and Cambisols/Inceptisols also occur, all with gelic properties, and with varying faunal influences. Both soil classification systems are adequate to distinguish the local pedogenesis processes. The WRB system is broader, since it was designed to be applied in all Polar Regions; the family classes adopted by the ST were effective in separating soils with important differences with regard to texture and gravel content, all important attributes accounting for the ecological succession and periglacial processes. An altitudinal organization of landforms and processes can be recognized from geomorphological mapping. Periglacial features are dominant above 50 m a.s.l. although are present at lower altitude. Abstract Copyright (2014) Elsevier, B.V.
15053743 Vieira, Goncalo (Universidade de Lisboa, Centre for Geographical Studies, Lisbon, Portugal); Mora, Carla; Pina, Pedro and Schaefer, Carlos E. R. A proxy for snow cover and winter ground surface cooling; mapping Usnea sp. communities using high-resolution remote sensing imagery (Maritime Antarctica): in Permafrost and periglacial research in Antarctica; new results and perspectives (Guglielmin, Mauro, editor; et al.), Geomorphology, 225, p. 69-75, illus. incl. 3 tables, sketch maps, 43 ref., November 15, 2014.
Usnea sp. formations show a spatial distribution coinciding with wind-exposed locations on rock knobs or sedimentary bodies, while they are commonly absent from concave sites. Field collection of georeferenced ground truthing data in the Meseta Norte (Fildes Peninsula, Maritime Antarctica) and the application of supervised classification techniques over a summer high resolution QuickBird satellite scene showed excellent classification accuracy for the different landcover types. The results show that Usnea formation distribution maps are a viable proxy for areas with less snow during the cold season. Such an approach provides input for permafrost and active layer modelling since snow acts as a critical control on ground surface heat balance. Since snow mapping is extremely difficult in Maritime Antarctica our tested approach provides important added-value for empirical-statistical modelling of permafrost distribution. Abstract Copyright (2014) Elsevier, B.V.
15051802 Li Jia (Chinese Academy of Sciences, Xinjiang Institute of Ecology and Geography, Laboratory of Desert and Oasis Ecology, Urumqi, China) and Shi Wenjiao. Effects of alpine swamp wetland change on rainfall season runoff and flood characteristics in the headwater area of the Yangtze River: Catena (Giessen), 127, p. 116-123, illus. incl. 3 tables, sketch maps, 37 ref., April 2015. Includes appendices.
The effects of changes in alpine swamp wetland (ASW) on rainfall season runoff and flood characteristics have not been quantified adequately in the headwater area of the Yangtze River (HYR). To address this, we focus on detecting changes in ASW based on remote sensing data. In particular, we analyzed the effects of ASW on runoff (both runoff and runoff coefficient) and flood characteristics (i.e., peak flow, rising time, duration and flood runoff coefficient) during the rainfall season based on observed runoff and climate data. Our results indicate that the area of ASW decreased by 28.22% and 30.54% at Zhimenda (ZMD) and Tuotuohe (TTH), respectively, from 1975 to 2004. Moreover, 76% and 71% of the decreases at ZMD and TTH, respectively, occurred during the period from 1990 to 2004. Both runoff and the runoff coefficients decreased at ZMD and increased at TTH with decreasing ASW in the rainfall season; we attribute this to the variability in runoff mechanisms. The effects of ASW on runoff and runoff coefficients were more pronounced at ZMD than at TTH. A slightly lower maximum peak flow and a greater frequency of moderate and small peak flows were observed at ZMD. Conversely, maximum peak flow increased and the frequency of maximum and moderate peak flows increased at TTH. Flood events increased at both ZMD and TTH, whereas both the rising time and duration decreased at both sites. Overall, the volume of snowmelt water increased and the ability to conserve water decreased in response to decreased ASW and permafrost were responsible for the observed changes in flood characteristics. Abstract Copyright (2015) Elsevier, B.V.
15047363 Laurin, Jiri (Academy of Sciences of the Czech Republic, Institute of Geophysics, Prague, Czech Republic); Meyers, Stephen R.; Ulicny, David; Jarvis, Ian and Sageman, Bradley B. Axial obliquity control on the greenhouse carbon budget through middle- to high-latitude reservoirs: Paleoceanography, 30(2), p. 133-149, illus. incl. 1 table, 108 ref., February 2015. NSF Grant EAR-0959108.
Carbon sources and sinks are key components of the climate feedback system, yet their response to external forcing remains poorly constrained, particularly for past greenhouse climates. Carbon-isotope data indicate systematic, million-year-scale transfers of carbon between surface reservoirs during and immediately after the Late Cretaceous thermal maximum (peaking in the Cenomanian-Turonian, circa 97-91 million years, Myr, ago). Here we calibrate Albian to Campanian (108-72 Myr ago) high-resolution carbon isotope records with a refined chronology and demonstrate how net transfers between reservoirs are plausibly controlled by ~1 Myr changes in the amplitude of axial obliquity. The amplitude-modulating terms are absent from the frequency domain representation of insolation series and require a nonlinear, cumulative mechanism to become expressed in power spectra of isotope time series. Mass balance modeling suggests that the residence time of carbon in the ocean-atmosphere system is-by itself-insufficient to explain the Myr-scale variability. It is proposed that the astronomical control was imparted by a transient storage of organic matter or methane in quasi-stable reservoirs (wetlands, soils, marginal zones of marine euxinic strata, and potentially permafrost) that responded nonlinearly to obliquity-driven changes in high-latitude insolation and/or meridional insolation gradients. While these reservoirs are probably underrepresented in the geological record due to their quasi-stable character, they might have provided an important control on the dynamics and stability of the greenhouse climate. Abstract Copyright (2015), . American Geophysical Union. All Rights Reserved.
15053739 Fountain, Andrew G. (Portland State University, Department of Geology, Portland, OR); Levy, Joseph S.; Gooseff, Michael N. and Van Horn, David. The McMurdo dry valleys; a landscape on the threshold of change: in Permafrost and periglacial research in Antarctica; new results and perspectives (Guglielmin, Mauro, editor; et al.), Geomorphology, 225, p. 25-35, illus. incl. sketch maps, 73 ref., November 15, 2014.
Field observations of coastal and lowland regions in the McMurdo Dry Valleys suggest they are on the threshold of rapid topographic change, in contrast to the high elevation upland landscape that represents some of the lowest rates of surface change on Earth. A number of landscapes have undergone dramatic and unprecedented landscape changes over the past decade including, the Wright Lower Glacier (Wright Valley) - ablated several tens of meters, the Garwood River (Garwood Valley) has incised > 3 m into massive ice permafrost, smaller streams in Taylor Valley (Crescent, Lawson, and Lost Seal Streams) have experienced extensive down-cutting and/or bank undercutting, and Canada Glacier (Taylor Valley) has formed sheer, > 4 meter deep canyons. The commonality between all these landscape changes appears to be sediment on ice acting as a catalyst for melting, including ice-cement permafrost thaw. We attribute these changes to increasing solar radiation over the past decade despite no significant trend in summer air temperature. To infer possible future landscape changes in the McMurdo Dry Valleys, due to anticipated climate warming, we map 'at risk' landscapes defined as those with buried massive ice in relative warm regions of the valleys. Results show that large regions of the valley bottoms are 'at risk'. Changes in surface topography will trigger important responses in hydrology, geochemistry, and biological community structure and function. Abstract Copyright (2014) Elsevier, B.V.
15053738 Mink, Sandra (Instituto Geológico y Minero de España, Madrid, Spain); López Martínez, Jerónimo; Maestro, Adolfo; Garrote, Julio; Ortega, José A.; Serrano, Enrique; Durán, Juan José and Schmid, Thomas. Insights into deglaciation of the largest ice-free area in the South Shetland Islands (Antarctica) from quantitative analysis of the drainage system: in Permafrost and periglacial research in Antarctica; new results and perspectives (Guglielmin, Mauro, editor; et al.), Geomorphology, 225, p. 4-24, illus. incl. 4 tables, geol. sketch map, 88 ref., November 15, 2014.
A quantitative geomorphic analysis of the drainage system on Byers Peninsula, Livingston Island, has been carried out in order to study the relief evolution, glacial history and possible neotectonic influence on the largest ice-free area of the South Shetlands archipelago. Aerial photographs, SAR data from RADARSAT-2 satellite, field work, a digital elevation model and GIS spatial analysis have been used to identify, map and study the existing drainage basins. A series of morphometric parameters have been studied in 30 selected basins in order to characterize their shape as well as the drainage network. Results in morphometric parameters reveal elongation trends in the shape of basins and a limited hierarchical network, common of a youthful stage of landscape evolution models. Several morphometric indexes (hypsometric integral, hypsometric curves, SL index, transverse topographical drainage basin asymmetry-T-Factor) have been used to study possible controls on drainage development. Results have been discussed in relation to relief and drainage evolution linked to the spatial distribution of lithological units and structural framework. T-Factor shows an apparently disorganized pattern and absence of tectonic influence. However, there are local values of second order basin asymmetry directions and magnitudes, which could reflect a succession of master rills through time, related to the changes in water supply during the deglaciation history of Byers Peninsula. Hypsometric values and curves of basins are also mainly related to a young stage of landscape evolution. Analysis of hypsometric integrals together with T-Factor index has allowed us to establish a possible deglaciation model on Byers Peninsula, which successfully explains the results. Areas of different landscape evolution stage are linked in space and support the hypothesis of local glacial centers during the ice cover retreat process. SL index results do not show the same pattern in results, which could be due to differences between incision and lateral shifting ratios. Quantitative geomorphic analysis indicates that during the deglaciation of Byers Peninsula, at least three areas acted as local glacial centers (NW, central and Rotch Dome area). Changes in index results clearly show a different behavior between two areas; distal areas and proximal areas close to the glacial centers. Morphometric indexes have demonstrated their being useful tools to provide information on the glacial history in recently deglaciated Antarctic areas. Abstract Copyright (2014) Elsevier, B.V.
15053745 Souza, Katia Karoline Delpupo (Universidade Federal de Vicosa, Departamento de Solos, Vicosa, Brazil); Schaefer, Carlos Ernesto G. R.; Simas, Felipe Nogueira Bello; Spinola, Diogo Noses and de Paula, Mayara Daher. Soil formation in Seymour Island, Weddell Sea, Antarctica: in Permafrost and periglacial research in Antarctica; new results and perspectives (Guglielmin, Mauro, editor; et al.), Geomorphology, 225, p. 87-99, illus. incl. 4 tables, sketch map, 58 ref., November 15, 2014.
The Antarctic Peninsula marks the climatic transition between Maritime and Continental Antarctica. Ice-free areas at the western side of the Peninsula (Maritime Antarctica) have been increasingly studied in the last 10 years whereas soils on the eastern coast have been relatively less studied. The objective of the present study is to analyze the properties of soils developed on Seymour Island, in the Weddell sea sector, eastern coast of the Antarctic Peninsula, in order to identify the main factors and processes involved in soil formation under semi-polar desert conditions in this part of Antarctica. Twenty-one pedons were described, sampled and analyzed for their physical, chemical and mineralogical attributes. Most of the soils were classified as Gelisols and Cryosols by the Soil Taxonomy and WRB/FAO, respectively. Three soil groups were found: immature alkaline soils on sandstones and siltstones, acid sulfate and ornithogenic soils. Soils have little cryoturbation and are all affected by salinization with natric and salic characters. Acid sulfate soils are the most weathered soils in Seymour Island. Due to the dry climate, phosphatization is still incipient with P-rich ornithogenic layers with little interaction with the mineral substrate. The Soil Taxonomy and WRB/FAO systems lack adequate classification criteria to classify all soils developed in transitional areas that are affected by a combination of salinization, sulfurization and phosphatization. Abstract Copyright (2014) Elsevier, B.V.
15046000 Kasmer, Ozgu (Ministry of Environment and Urbanization, Ankara, Turkey); Ulusay, Resat and Genis, Melih. Assessments on the stability of natural slopes prone to toe erosion, and man-made historical semi-underground openings carved in soft tuffs at Zelve open-air museum (Cappadocia, Turkey): Engineering Geology, 158, p. 135-158, illus. incl. block diags., sect., 3 tables, sketch maps, 29 ref., May 24, 2013.
The Zelve Open-Air Museum, consisting of three valleys, is one of the oldest historical semi-underground settlements in the Cappadocia Region of Turkey which was designated as a World Heritage Site in 1985 by UNESCO. Particularly in the first valley, there are a lot of underground openings of different sizes carved in a soft tuff next to the valley cliffs used for cliff settlement in the past and several antique churches with some geo-engineering problems. In addition, steep natural slopes in this valley are prone to toe erosion resulting in stability problems. In this study, it is aimed to investigate engineering characteristics of the surrounding tuff and factors affecting them, and to assess the effect of rate of toe erosion on the stability of steep valley slopes and structural stability of some selected typical underground openings with large spans subjected to spalling. For these purposes, some observational, experimental and numerical modelling studies were conducted. Experimental results indicate that strength and deformability properties of the weak tuff surrounding the openings drastically reduce when it becomes wet or saturated. This situation suggests that possibility of occurrence of failures is expected to be higher in rainy seasons due to increase in water content of the tuff. Experimental results also suggest that spalling commonly observed in the valley is related with freezing-thawing and wetting-drying cycles in nature and that the process of freezing and thawing accelerates further the degradation of the rock. The long-term measurements at selected locations suggest that erosion in the tuff is important, which increases particularly in winter and spring seasons and results in the loss of support accelerating the occurrence of further slope failures. The 2-D numerical solutions indicate that no significant change in shear and tensile stresses in steep valley slopes prone to toe erosion would be expected after 100 years. However, the solutions obtained from the 500- and 1000-year scenarios suggest that failure zones due to the tensile stresses would develop in the form of slabs with thicknesses of 50-60 cm and 90-100 cm, respectively, which would break off from the slope and fall down. The results from 3-D numerical solutions indicate that failure (yield) zone resulting from tensile stresses around the semi-underground openings will develop parallel to the sidewalls. These results confirm the observed spalling of the tuff in the form of slabs parallel to the walls of the openings. Abstract Copyright (2013) Elsevier, B.V.
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15046286 Finger, R. (University of Alaska Fairbanks, Biology and Wildlife, Fairbanks, AK); Euskirchen, E. S. and Turetsky, M. Effects of permafrost thaw on nitrogen availability and plant nitrogen acquisition in Interior Alaska [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract GC52B-02, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.
The degradation of ice-rich permafrost, which covers a large portion of Interior Alaska, typically leads to thermokarst and increases in soil saturation. As a result, conifer peat plateaus degrade and are often replaced by wet collapse scar bogs. This state change results in profound changes in regional hydrology, biogeochemical cycling, and plant community composition. Preliminary data suggest that permafrost thaw can increase surface soil inorganic nitrogen (IN) concentrations but it is still unknown whether these changes in nutrient availability are short-lived (pulse releases) and whether or not they impact collapse scar vegetation composition or productivity, particularly as collapse scars undergo succession with time-after-thaw. Therefore we are currently examining changes in plant community composition, N availability and plant N acquisition along three thermokarst gradients in Interior Alaska. Each gradient is comprised of a forested permafrost peat plateau, adjacent ecotones experiencing active permafrost degradation (including a collapsing forest canopy and a saturated moat), and a collapse scar bog where permafrost has completely degraded. We predicted that IN concentrations would be highest along the active thaw margin, and lowest in the peat plateau. We also predicted that IN concentrations would be positively related to shifts in vegetation community composition, nutrient use efficiency (NUE) and tissue 15N concentrations. Preliminary results have shown that IN concentrations increase in newer collapse scar features as well as with thaw depth. Our data also show a shift from feather moss and ericaceous shrub-dominate understories in the permafrost plateau to Sphagnum and sedge dominated thaw ecotone and bog communities. Further successional development of the collapse scar bog results in the reintroduction of small evergreen and deciduous shrubs as the peat mat develops. Over time, collapse scar succession and peat accumulation appears to lead to progressive N limitations, resulting in the dominance of plants with higher NUE. This likely has implications for plant litter quality, and could inhibit decomposition processes. We are collecting additional data to compare species-level NUE and nutrient resorption efficiency. We also will measure d15N of aboveground plant organs, roots, soil, and pore water to explore sources of plant N, which we expect will influenced rooting depth as permafrost thaws as well as differences in mycorrhizal associations along our thaw gradient. Because thawing permafrost soils are anticipated to mobilize large amounts of N from soils, our results will improve our understanding of how permafrost thaw influences vegetation and soil N pools, soil N availability, and plant nutrition.
15048983 Rogger, M. (Vienna University of Technology, Institute of Hydraulic Engineering and Water Resources Management, Vienna, Austria); Chirico, G.; Hausmann, Helmut; Krainer, Karl; Brückl, E. and Bloeschl, G. Alpine permafrost systems under change [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract H23J-03, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.
The thawing of alpine permafrost in a warmer climate may alter the runoff regime of high alpine catchments. We present a case study where detailed geophysical and geological field investigations were performed in a 5 km2 large catchment in Western Austria to assess its main hydrogeological settings. Ground-penetrating radar data, seismic refraction measurements and ground-surface-temperature data were employed to map the spatial permafrost distribution and depth of the permafrost table and the bedrock interface. The results for different types of unconsolidated sediments were then translated into five sets of flow path concepts in the presence and absence of permafrost. These concepts were then used to set up a rainfall-runoff model and simulate the runoff response of the catchment for scenarios with and without permafrost. The simulations indicate that the complete thawing of permafrost will increase the catchment storage capacity which will reduce the flood peaks by up to 20% and increase runoff during recession by about 15%. The reduction of extreme events is important since it may also affect flood events in downstream catchments. The study highlights the importance of interdisciplinary work between hydrology, geophysics and geology which can greatly help to improve the understanding of subsurface processes.
15050684 Rowland, J. C. (Los Alamos National Laboratory, Los Alamos, NM); Gangodagamage, C.; Crosby, B. T.; Pope, P. A.; Brumby, S. P. and Wilson, C. J. Sensitivity of permafrost dominated river and stream banks to climate change [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract H41B-1234, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.
River systems in permafrost environments may be particularly sensitive to climate-induced changes in hydrology, water temperature, and air temperatures. In these systems, the rate of bank erosion may be significantly influenced by the presence of permafrost and the rate the permafrost thaw. Using analysis of remote sensing imagery and field studies, we attempt quantification of the spatial and temporal patterns of river bank erosion to understand the controls on river planform dynamics in permafrost settings. The rate that river banks erode in permafrost settings represents a balance between the rate at which bank material may thaw and become mobile and the rate at which mobile material may be transported away from the river bank. Along steep banks in large river systems with a significant discharge throughout the open water season, such at the Yukon River, fine-grained (silt and sand) sediments may be removed as quickly as they are thawed. In these systems, the maximum rate of bank retreat is effectively thermally limited and may be sensitive to climate changes that increase the rate of permafrost thaw, such as water and air (to a lesser degree) temperature increases. In contrast, in smaller river systems, like the Selawik River in northwest Alaska, highly seasonal discharge, heterogeneous floodplain deposits, and bank vegetation all lead to significant variability in the spatial and temporal rates of bank erosion. At one riverbank site monitored between 2010 and 2012, yearly retreat rates varied from 0 m/yr to 5 m/yr (the long term average measured from aerial photos and satellite imagery). However, in the year with a retreat of 5 m the erosion occurred over a 5-day time period corresponding to peak snow melt discharges. The year with no observable bank retreat followed a winter season with very little snow pack and reduced spring discharge. These observations suggest that in small systems with highly seasonal flows, small changes in river hydrographs, such as changes in the duration of peak flows by a few days, have the potential to significantly change riverbank erosion rates. In the Selawik, spring bank erosion often leads to bank undercutting that produces large mats of tundra vegetation that drape or fall onto the bank face. It appears that these vegetation mats may protect the banks from further erosion over the course of the summer, even during discharge events with stages close to those observed during snow melt. At locations where the vegetation mats do not re-freeze to the bank face, spring ice out appears to remove the prior season's mats thereby exposing the banks to fresh erosion. Mats that become frozen within the winter ice cover may be carried away with the ice, while mats higher on the bank or attached to the surface tundra may be abraded by ice rafts carried in the flow. Hydrological changes that affect the timing and magnitude of spring ice out flows may also alter this erosional dynamic with the riparian vegetation. Our observations suggest that the response of river planform dynamics to climate-induced changes in arctic freshwater systems may be quite complex and exhibit significant spatial and temporal heterogeneity.
15050587 Schuur, E. A. (University of Florida, Gainesville, FL); Natali, S.; Bracho, R. G.; Coe, K. K.; Crummer, K. G.; Krapek, J.; Pegoraro, E.; Pries, C.; Salmon, V. and Webb, E. The impact of permafrost carbon loss on the carbon balance of an experimentally warmed tundra ecosystem [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract EP11A-02, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.
Approximately 1700 billion tons of soil carbon are stored in the northern circumpolar permafrost zone, more than twice as much carbon than currently contained in the atmosphere. Permafrost thaw, and the microbial decomposition of previously frozen organic carbon, is considered one of the most likely positive feedbacks from terrestrial ecosystems to the atmosphere in a warmer world. Yet, the rate and form of release is highly uncertain but crucial for predicting the strength and timing of this carbon cycle feedback this century and beyond. Here we report results from five years of an ecosystem warming manipulation --the Carbon in Permafrost Experimental Heating Research (CiPEHR) project--where we increased air and soil temperature, and degraded the surface permafrost. We used snow fences coupled with spring snow removal to increase deep soil temperatures and thaw depth (soil warming) and open top chambers to increase growing season air temperatures (air warming). We showed that experimental warming that caused permafrost degradation led to a two-fold increase in net C uptake by the ecosystem during the growing season, in line with decadal trends of 'greening' tundra across the region. This response increased through the first three years of the experiment and then maintained an elevated level in year four, even though thaw depth continued to increase. Warming also enhanced growing season and winter respiration, which entirely offset growing season C gains. These results highlight the importance of winter processes in determining whether tundra acts as a C source or sink, and demonstrate the potential magnitude of C release from the permafrost zone that might be expected in a warmer climate. Furthermore, this initial response to warming quantifies the vulnerability of organic C stored in near surface permafrost to temperature change, and corresponds to the initial stages of permafrost degradation observed from a thaw gradient at the same location.
15054194 Walker, Jesse (Louisiana State University, Department of Geography, Baton Rouge, LA) and McGraw, Molly. Tapped lakes as sediment traps in an Arctic delta: in Sediment dynamics from the summit to the sea (Xu, Y. Jun, editor; et al.), IAHS-AISH Publication, 367, p. 407-412, illus. incl. 1 table, 9 ref., 2014. Meeting: Sediment dynamics from the summit to the sea, Dec. 11-14, 2014, New Orleans.
Lakes within the Colville River delta in northern Alaska, USA, vary in size from small ponds created by ice-wedge growth to thaw lakes that are as much as three kilometres long and ten metres deep. As the river migrates, lake edges are breached and the lakes are drained. Such lake tapping is aided by permafrost thaw and ice wedge melt and, in the case of the larger lakes, by wave action within them. Once a lake is tapped, it drains rapidly creating a deep scour hole at its entrance and from then on it is subject to the varying stages and discharge of the river. During flooding, when the river is transporting its largest amount of sediment, the tapped lakes become settling basins and rapidly fill. The Colville River delta has lakes in all stages from freshly breached to those that are now being destroyed by channel migration.
15049461 Loisel, Julie (University of California Los Angeles, Institute of the Environment and Sustainability, Los Angeles, CA); Yu, Zicheng; Beilman, David W. and Kaiser, Karl. Biochemical, geochemical, and paleoecological analyses of a newly discovered peatland on the western Antarctic Peninsula [abstr.]: in Geological Society of America, 2014 annual meeting & exposition, Abstracts with Programs - Geological Society of America, 46(6), p. 581, 2014. Meeting: Geological Society of America, 2014 annual meeting & exposition, Oct. 19-22, 2014, Vancouver, BC, Canada.
Peat-forming ecosystems along the West Antarctic Peninsula (WAP) have been receiving lots of attention from scientists and the media recently. These moss-dominated terrestrial ecosystems can be cored and potentially used as high-resolution, high-quality archives for late-Holocene climatic conditions, thereby providing new insights on the southern hemisphere recent climate history. So far, these Antarctic studies have focused on 'dry' permafrost mossbanks. However, during our field expedition in February 2014, we discovered two 'wet' peatlands that had formed in rocky depressions near Vernadsky Station (65°14' S, 64°15' W). The similarity between these peatlands and those found in the northern hemisphere is striking, and the rarity of these systems along the WAP is intriguing. These peatlands may represent a transition from aerobic mossbanks to anaerobic/waterlogged peatlands, which would be an important ecosystem transformation along the WAP that could be promoted in a warmer and wetter climate. We present a high-resolution, multi-proxy record of ecosystem development and environmental conditions for Rasmussen peatland. To our knowledge, this peatland is the very first one to be described and analyzed along the WAP. Carbon isotope measurements and biochemical analyses (e.g., amino acids, carbohydrates, lignin phenols) are being performed, in addition to routine analyses including carbon and nitrogen content, organic and inorganic matter content, and plant macrofossil analysis. The peatland has a high organic matter content (> 90% dry weight) and distinct changes in peat properties were visually described on the basis of color and texture. Preliminary biochemical results are promising, as the signature of each Antarctic plant functional type (e.g., algae, vascular, moss, fungi, lichen) can be distinguished. These modern plant signatures will be used to reconstruct past vegetation assemblages downcore. Decomposition indicators such as carbohydrate yields, acid:aldehyde ratios of lignin phenols, and hydroxyproline yields will be determined to better understand the extent of peat decay that has occurred at this site, particularly in relation to the recent warming. Overall, this study of a newly discovered peatland offers insight regarding Antarctic paleoclimate using a new approach.
15053969 McDermott, Kyle J. (University of North Carolina at Wilmington, Department of Geography and Geology, Wilmington, NC); Hawkes, Andrea D.; Donnelly, Jeffrey P.; Sullivan, Richard M.; Maio, Christopher V.; Toomey, Michael R. and Madsen, Stephanie M. Reconstructing high-latitude storm events from a fjord in Newfoundland [abstr.]: in Geological Society of America, 2014 annual meeting & exposition, Abstracts with Programs - Geological Society of America, 46(6), p. 750, 2014. Meeting: Geological Society of America, 2014 annual meeting & exposition, Oct. 19-22, 2014, Vancouver, BC, Canada.
The Arctic is highly susceptible and vulnerable to changes in climate, directly impacted by albedo and heat flux. High latitudinal storms may be influenced by changes in upper and lower tropospheric temperature gradients, sea ice extent and an increase of latent heat release. Atmospheric moisture variations may also play a significant role in influencing the frequency and intensity of these storms. Arctic regions seasonally impacted by sea-ice are at risk from extended summer periods, increasing ice retreat and enhancing permafrost thawing. This extended summer warm period may subject the coastal zone to prolonged exposure possibly leading to enhanced coastal erosion. This project reconstructs the frequency of storm events from a fjord in northern Newfoundland using an 800-cm core spanning 0 to 10,000 yrs BP. Fjord sedimentation is dominantly composed of dark gray silt punctuated by coarser anomalies in grain size distribution signifying abrupt depositional events, most likely storms. The temporal occurrence of these storm-induced deposits will be compared with regional climate records in hopes of providing insight into high latitude storm dynamics. Storm frequency will be compared to warming (decreased temperature gradient, decreased seasonal sea ice, increased fetch and increased transport) and cooling (increased temperature gradient, increased seasonal sea ice, decreased fetch and decreased transport) events documented in the geologic record. Storminess periodicity between ocean basins will be compared to gain insight into the feedbacks between climate change and high latitudinal storminess. A Recent multi-decadal increase/decrease in regional storm frequency may be indicative of future changes likely to impact high latitudes in the coming decades to centuries.
15049358 Roberts, Jennifer A. (University of Kansas, Geology, Lawrence, KS); Gray, Neil D.; McCann, Clare; Christgen, Beate; Edwards, Stephen and Graham, David W. The role of phosphorus cycling and soil mineralogy in defining methanotroph ecology in Arctic soils [abstr.]: in Geological Society of America, 2014 annual meeting & exposition, Abstracts with Programs - Geological Society of America, 46(6), p. 27, 2014. Meeting: Geological Society of America, 2014 annual meeting & exposition, Oct. 19-22, 2014, Vancouver, BC, Canada.
A large portion of the World's terrestrial organic carbon is stored in Arctic permafrost soils and permafrost warming in these regions is leading to increasing fluxes of CH4 (methane), a potent greenhouse gas, to the atmosphere. As patterns of CH4 release from Arctic soils change there is an urgent need to better understand the basis of in situ CH4 production by methanogens and oxidation rates and patterns by methanotrophs; the main biological mechanism for CH4 consumption. To identify environmental controls on such releases, we characterized soil geochemistry and microbial community conditions in 13 near-surface Arctic soils collected across Kongsfjorden, Svalbard. Surveys of methane flux vary by five orders of magnitude across sites and do not correlate to methanotroph abundance. Instead bacterial and Type I methanotroph gene abundances co-vary with soil phosphorous (P) concentrations. Soils in this region are organic-rich and their mineral components derived from weathering of metamorphic silicates and carbonates, which contain apatite in their primary mineralogy. They are rich in clay minerals (smectite, kaolinite, and illite) and mix-valence iron oxyhydroxides derived from mica schists and variably enriched authigenic carbonates that exhibit methanogenic signatures based on 13C isotopic analyses. These soils do not contain detectable apatite nor other phosphate minerals, but instead P is sorbed to clay and iron minerals and its occurrence is pH dependent. Native methanotroph communities appear to be P-limited and respond to P addition with increases in biomass and CH4 consumption. These data, taken in their entirety, suggest that phosphorus abundance and cycling in Arctic soils critically impact biological mediation of CH4 flux by native methanotrophs and therefore, methane flux is likely to increase in these areas as thawing continues.
15050637 Bendixen, M. (University of Copenhagen, Copenhagen, Denmark); Kroon, A. and Nielsen, L. Coastal changes in sedimentary environments on Disko Island, western Greenland [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract EP13A-0860, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.
Global climate change affects Arctic coasts. A rising sea level, increasing fresh water fluxes from glaciers, and decreasing sea-ice extent increase the pressure on the sedimentary areas in these high-latitude regions. In Arctic coastal environments, permafrost, sea-ice, and fluvial input from glacial melt water have an impact in controlling the evolution of the coast. In this study we present the results of annual to decadal coastal changes (rates of change in shoreline positions) along the southern Disko Island in Greenland. These changes are detected and quantified using rectified aerial photos and satellite images. The oldest images used are from the 1940's and the most recent one was 2012. Additional field-measurements are made to identify the responsible processes that cause the coastal development in more detail. The southern coast of Disko Island includes two distinct sedimentary deltas: Skansen and Tuapaat. They consist of sandy, gravelly, and pebbly material. Lagoons, spits, and beaches are present on these deltas and our analyses reveal that these characteristic coastal features have undergone significant morphological changes within the last 60 years: The identified changes within the deltas show a migration of the delta mouths over more than 400 m in an eastward direction, and thus closure of the former inlets. These rapid coastal responses are probably caused by a combination of a shift in channel lobe on the delta plain after 1985, combined with a predominant wave-driven alongshore sediment transport to the east. The shift in delta channels is often recognized as the main responsible agent in controlling the evolution of the sedimentary sites.
15053623 Bianchi, T. S. (University of Florida, Department of Geological Sciences, Gainesville, FL); Schreiner, K. M.; Rosenheim, B. E. and Allison, M. Particulate organic carbon transport and burial in the Colville River delta, Beaufort Sea, Alaska [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract H34A-06, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.
Terrestrial particulate organic carbon (tPOC) delivery to nearshore deltaic regions is an important mechanism of OC storage and burial, and river deltas and continental margins worldwide account for approximately 90% of the carbon burial in the ocean. The Arctic Ocean has the greatest percentage of continental shelf area as a proportion of total ocean basin area of any of the world's oceans, and receives freshwater and sediment from numerous large river systems. Increasing warming in the Arctic is leading to an acceleration of the hydrologic cycle, warming and breakdown of permafrost, and broad shifts in vegetation. All of these changes are likely to affect the delivery and burial of tPOC in nearshore regions. However, to date, most studies of tPOC delivery from North America to the Arctic Ocean have focused on large Arctic rivers like the Mackenzie and Yukon, and a significant portion of the watersheds of those rivers lie in sub-Arctic latitudes, indicating that their tPOC delivery is likely not representative of the high Arctic tundra. This study focuses on tPOC delivery by the Colville River, the largest North American river (in terms of both freshwater delivery and sediment load) with a watershed that does not include sub-Arctic latitudes. Sediment samples from the river delta and nearby Simpson's Lagoon were taken in August of 2010 and subsequently fractionated by density, in order to study the delivery of both discrete and sediment-sorbed tPOC. Samples were analyzed for stable carbon isotopes, bulk radiocarbon, terrestrial biomarkers (including lignin-phenols and non-lignin phenols, specifically those that are indicative of peat input), and aquatic biomarkers (algal pigments), and additionally a subset of the samples were analyzed by ramped pyrolysis-14C. Results show that tPOC delivery is concentrated near the river mouth sourced from coastal plain tundra, with additional delivery of tPOC from peat released into the lagoon from the seaward limit of the tundra by coastal erosion. Ramped pyrolysis-14C analysis also shows a clear differentiation between tPOC delivered by the river (which contains high amounts of vegetation-sourced lignin phenols and soil-sourced lignin phenols showing high levels of degradation) and tPOC delivered by coastal retreat in the lagoon (containing high amounts of peat-sourced lignin phenols showing lower amounts of degradation). Older ages north of the delta are affiliated with the least dense fractions, whereas the opposite is true in the lagoon sediments east of the delta. These results are the first to combine biomarker and ramped pyrolysis-14C analyses in an Arctic setting, and the first to combine biomarker and ramped pyrolysis-14C analyses on density-fractionated coastal sediments.
15050683 Lenters, J. D. (LimnoTech, Ann Arbor, MI); George, C.; Carroll, G.; Potter, B. L.; Hinkel, K. M.; Arp, C. D. and Frey, K. E. Long-term variations in ice formation and breakup dates for a thermokarst lake in Barrow, Alaska; climatic drivers and hydrologic impacts [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract H41B-1233, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.
More than one fourth of the world's lakes are located in the Arctic, where climate change is known to be occurring at a rapid pace. Many of these lakes are located in regions of continuous or discontinuous permafrost, and the Arctic Coastal Plain (ACP) of northern Alaska has an especially high density of thermokarst lakes. Roughly 40% of the ACP landscape is comprised of lakes or drained lake basins, highlighting the need for long-term lake monitoring through programs such as the Arctic Observing Network (AON). In recognition of this, a collaborative project was begun in 2012 to establish a "Circum-Arctic Lakes Observation Network (CALON)," which includes extensive monitoring of nearly 60 lakes on the ACP. CALON team members have also interacted with local residents in Arctic communities to identify additional sources of information on thermokarst lakes. One such community is Barrow, Alaska, where long-term observations of ice formation and breakup dates for an inland lake (Isatkoak Lagoon) have been made since 1987. The lake ice record shows a clear trend toward later freeze dates (~7.7 days per decade) and earlier breakup dates (~3.4 days per decade), with an overall decline in ice duration of about 28 days over the 25-year period (1987-2012). Similar delays in freeze-up dates since 1999 (~5 days per decade) have also been noted for a local fishing site (Ikroagvik Lake), based on the ability to access the lake in autumn to set and retrieve fishnets. Combined with local meteorological data, trends in snowmelt dates, and recent summertime energy balance data from the primary CALON study lake in Barrow, we investigate the various climatic drivers of the observed decline in lake ice duration, as well as the impact of the prolonged ice-free season on Arctic lake hydrology.
15050681 Lougheed, V. (University of Texas, El Paso, Biological Sciences, El Paso, TX); Contreras, G.; Andresen, C. G.; Miller, N. A. and Reyes, F. R. Increasing dissolved organic carbon (DOC) in Arctic tundra ponds over the past 40 years [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract H41B-1230, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.
With a warming Arctic, permafrost is expected to thaw and active layer depth to increase, thus releasing organic material and nutrients into aquatic environments; however, there are few long-term datasets with which to test these predictions in aquatic ecosystems. The Arctic tundra ponds at the International Biological Program (IBP) site in Barrow, Alaska, studied for the first time in the 1970s, represent one of the very few locations in the Arctic where long-term data are available on freshwater ecosystem structure and function. The objective of this study was to determine whether Dissolved Organic Carbon (DOC) concentrations in Arctic tundra ponds had changed over time, how changes in thaw depth and temperature have impacted DOC quantity, and what the consequences of any changes have been for aquatic ecosystems. Over the summers of 2010-13 we collected water samples and measured thaw depth from 5 IBP ponds and compared these with data from the 1970s. Ponds were 2°C warmer and thaw depth was up to 19cm deeper in the 2000s as compared to the 1970s. Release of organic (e.g. DOC) and inorganic compounds (e.g.nitrogen) from formerly frozen organic ground into the ponds was associated with the increased thaw depth. For example, DOC was significantly higher in 2009-2012 compared to the 1970s; this was most notable later in the growing season. Similarly, incubations experiments indicate a steady rise in DOC released from permafrost with warming. DOC is likely a relatively conservative tracer of permafrost thaw in aquatic systems, and thus was a better predictor of increased phytoplankton levels than inorganic nutrients. This study will add to our understanding of the changes that warmer temperatures and altered aquatic environments bring to the Arctic and the consequences for carbon budgets in northern latitudes.
15050590 Rich, V. I. (University of Queensland, Australian Centre for Ecogenomics, Brisbane, Queensl., Australia); McCalley, C. K.; Woodcroft, B. J.; Kim, E.; Hodgkins, S. B.; Tfaily, M. M.; Wehr, R. A.; Logan, T.; Jones, R.; Mondav, R.; Hurst, G.; Verberkmoes, N.; Li, C.; Frolking, S. E.; Crill, P. M.; Chanton, J.; Saleska, S. R. and Tyson, G. W. A systems approach to understanding subarctic critical zone changes in a warming climate [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract EP11A-05, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.
Climate change is dramatically altering the subarctic and Arctic Critical Zone. Permafrost, which currently holds approximately one third of global soil carbon in a relatively unavailable form, is predicted to be virtually eliminated by the end of the century. One endpoint for permafrost habitat thaw is wetlands, which are a major source of the microbially-produced greenhouse gas methane. This creates a potentially large positive feedback to climate change. Our team is using a systems approach spanning diverse geochemical (high-resolution greenhouse gas isofluxes and soil/peat geochemistry) and molecular (16S rRNA gene amplicon, metagenomic and metaproteomic sequencing) measurements to track parallel changes in carbon cycling and in situ microbiology across a natural permafrost thaw gradient. Thaw at this site results in a three-stage habitat shift from ericaceous shrubs, to peat moss, to sedges, concomitant with a substantial increase in methane emissions. Isotopically, emitted methane shifts along the thaw gradient away from hydrogenotrophic methane production, in parallel with the appearance of acetoclastic methanogens in the microbial community. Community data have also revealed the presence of a novel, highly-active methanogen from the euryarchaeal lineage Rice Cluster-II, dubbed Candidatus Methanoflorens stordalenmirensis. Its 'species' is present in numerous other global wetland datasets, has the genomic capacity (inferred from its population genome) for hydrogenotrophic methanogenesis, and was the highest environmental correlate of emitted methane's isotopic signature. In situ community global protein expression profiles (i.e. metaproteomes) revealed that it strongly expresses its hydrogentrophic methanogensis genes, and that methanogenesis is a dominant signal in the overall community proteome. As we generate a portrait of how thaw impacts this major subarctic critical zone habitat, we are working with ecosystem process modelers to integrate new understandings into prognostic models of climate change feedbacks.
15048946 Risser, Rebecca (University of Alaska Fairbanks, Fairbanks, AK); Harms, Tamara and Jones, Jay. Spatial heterogeneity in biogeochemical transport on Arctic hill slopes [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract H23F-1341, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.
Water tracks, saturated regions of the hill slope in permafrosted Arctic catchments, likely deliver the majority of water entering streams in these regions, and may play a central role in delivery of nutrients. Fate of dissolved nutrients and carbon as they are transported in water tracks has a substantial effect on stream ecosystems, as water tracks may cover up to 35% of the catchment land area. Water tracks are distinguished from adjacent areas of the hillslope by higher rates of hydrologic transport, greater woody biomass, and increased pools of nutrients. Substantial spatial heterogeneity within and between water tracks may influence their role in transfer of materials between the terrestrial and aquatic landscape. We examined spatial variability of hydrologic and chemical characteristics within and between water tracks in the Kuparuk Basin of northern Alaska to increase understanding of the factors influencing nutrient export from arctic catchments. We studied a sedge-dominated water track with perennial surface water flow with shrub-dominated water tracks containing intermittent surface flow. Nominal transit times of water in the perennial site was 5 hours, compared to 15.5 h in an ephemeral track over a 50 meter reach, indicating substantial variation in water residence time and opportunity for biogeochemical reaction across sites. We evaluated spatial heterogeneity in biogeochemical characteristics within 25-m reaches at each site with a grain size of 10 m. Dissolved CH4 concentration was elevated above atmospheric equilibrium only at the perennial water track, where CH4 concentration varied by more than 15-fold within the water track, indicating hot spots of anaerobic microbial activity. Dissolved CO2 concentration was 9 times greater on average at the perennial water track, compared to the ephemeral site, suggesting that continuous water flow supports more rapid microbial activity. CO2 concentration was also more variable in the perennial water track, with a CV of 64% compared to 11% in an ephemeral water track. Despite spatial heterogeneity in dissolved gas concentrations within the perennial site, NH4+ concentration in surface and soil water was less variable, with a CV of 38%. In contrast, NH4+ concentration was more variable (CV=41%) than dissolved gases within the ephemeral site, and mean concentration was 2 times greater than at the perennial site, suggesting less active biological retention of nitrogen at the ephemeral site. These differences in dissolved gases and nutrient concentrations among water tracks indicate that nutrient processing during hydrologic transport on hill slopes varies across the catchment, which will likely result in spatially heterogeneous responses of elemental cycles in response to permafrost loss.
15053622 Tank, S. E. (York University, Geography, Toronto, ON, Canada); Kokelj, S. V.; Raymond, P. A.; Striegl, R. G.; McClelland, J. W.; Holmes, R. M. and Spencer, R. G. Seasonality and long term trends in dissolved carbon export from large rivers to the Arctic Ocean, and potential effects on coastal ocean acidification [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract H34A-05, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.
Large Arctic rivers show marked seasonality in constituent flux as a result of variations in flowpath throughout the yearly cycle. Here, we use measurements collected from the mouths of the six largest rivers draining to the Arctic Ocean to explore seasonal variation in dissolved inorganic and dissolved organic carbon (DIC, DOC) flux, and the effect of this flux on nearshore ocean processes. This work uses data from the Yukon and Mackenzie Rivers in North America, and the Kolyma, Lena, Yenisey, and Ob' in Siberia. Mean monthly concentrations of riverine DIC vary synchronously across all rivers, peaking under ice and reaching a low point immediately after the spring freshet. Monthly climatologies for DIC, in addition to similarly constructed climatologies for Ca2+, show that the input of riverwater universally causes aragonite to be undersaturated in riverine-influenced nearshore regions, with an effect that is greater for the Siberian coast than for western North America, and greater in the spring-winter than in the late summer and fall. Because seasonal trends and geographic variation in DOC concentration are opposite to that for DIC in these large rivers, degradation of DOC to CO2 in the nearshore Arctic should accentuate seasonal and spatial patterns in aragonite undersaturation in Arctic coastal regions. Datasets that extend DIC and DOC concentration measurements back to the early 1970's (DIC) and early 1980's (DOC) near the mouth of the Mackenzie River in the western Canadian Arctic indicate that the summertime concentration and flux of these constituents has been increasing over time in this region. While evidence from other regions of the pan-Arctic, and data gathered from smaller sub-catchment studies indicate that this trend is not universal for DOC, there is growing evidence for a consistent increase in summertime DIC flux across both time and gradients of decreasing permafrost extent. These changes, in turn, could have broad implications for both nearshore processes and the larger Arctic carbon cycle. Understanding how riverine dissolved carbon flux is changing in northern regions as a result of variations in hydrologic seasonality and flowpath will greatly aid our understanding of global change across broad spatial scales in the north.
15050678 Young, J. M. (University of Alaska, Fairbanks, International Arctic Research Center, Fairbanks, AK) and Bolton, W. R. Tree water use may significantly impact boreal hydrology [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract H41B-1225, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.
The ecohydrology of boreal forest ecosystems of Interior Alaska is not well understood largely because of challenges posed by the presence of discontinuous permafrost. Near-surface permafrost results in storage-dominated systems with cold, poorly drained soils, and slow growing, low statured coniferous trees (Picea mariana) or CDE's. The transition to permafrost-free areas can occur over a few meters and is accompanied by a vegetation community dominated by large deciduous trees (Populus sp. and Betula sp.) or DDE's. Typically, areas with permafrost are on north facing slopes and valley bottoms, and areas without permafrost are south facing. In Alaska's boreal forest, the permafrost is very warm and vulnerable to the effects of climate change. Once permafrost begins to thaw, the vegetation community shifts from coniferous to deciduous dominated. Streamflow in watersheds with a larger permafrost distribution tends to be higher and more responsive to precipitation events than in watersheds with low permafrost distribution. In fact, precipitation events in the low permafrost areas do not infiltrate past the rooting zone of the deciduous trees (~5-40 cm). This suggests that the deciduous trees may remove water from the system via uptake and transpiration. We focus on how vegetation water use affects boreal forest hydrology in areas of discontinuous permafrost. Specifically, we ask: what are the patterns of vegetation water use in areas with and without permafrost? This study focuses on the CDE and DDE systems. Our research sites are established on low and high locations on each aspect (south facing DDE, north facing CDE) to capture the variability associated with the different hillside drainage properties. At each of the four sites during the growing season, we measured various aspects of plant water use dynamics, including water flux, water content, water sources, depth of water uptake in the soil, and water stress. We use a Bayesian framework to analyze the data. We found that, compared to the coniferous trees, the deciduous trees have higher transpiration rates, lower water stress, higher water content, and use rain-derived water during the summer and snowmelt water prior to leaf out. The amount of water taken up and fluxed by deciduous trees is greater at the high site than the low site. The deciduous trees take up nearly 40% of snowmelt water prior to leaf-out. The low water use rates of the coniferous trees suggests that they play a very small role in the boreal water cycle, resulting in more water remaining in the watershed, which eventually moves into the stream. Conversely, the very high water use of the deciduous trees suggests they have a big effect on the boreal water cycle because they remove water from the system and transpire it to the atmosphere. This suggests that if the climate warms as expected, there may be a profound shift in the boreal forest ecohydrology. This transpiration model is integrated into a storage-based hydrologic model to better understand the relationships between vegetation, permafrost, water and climate in the boreal forest ecosystem.
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