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Dittmann A.,University of Innsbruck | Schlosser E.,University of Innsbruck | Schlosser E.,Austrian Polar Research Institute | Masson-Delmotte V.,French Climate and Environment Sciences Laboratory | And 4 more authors.
Atmospheric Chemistry and Physics | Year: 2016

A unique set of 1-year precipitation and stable water isotope measurements from the Japanese Antarctic station, Dome Fuji, has been used to study the impact of the synoptic situation and the precipitation origin on the isotopic composition of precipitation on the Antarctic Plateau. The Antarctic Mesoscale Prediction System (AMPS) archive data are used to analyse the synoptic situations that cause precipitation. These situations are investigated and divided into five categories. The most common weather situation during a precipitation event is an upper-level ridge that extends onto the Antarctic Plateau and causes strong northerly advection from the ocean. Most precipitation events are associated with an increase in temperature and wind speed, and a local maximum of λ 18O. During the measurement period, 21 synoptically caused precipitation events caused 60% of the total annual precipitation, whereas the remaining 40% were predominantly attributed to diamond dust. By combining the synoptic analyses with 5-day back-trajectories, the moisture source regions for precipitation events were estimated. An average source region around a latitude of 55°S was found. The atmospheric conditions in the source region were used as initial conditions for running a Rayleigh-type isotopic model in order to reproduce the measured isotopic composition of fresh snow and to investigate the influence of the precipitation source region on the isotope ratios. The model represents the measured annual cycle of λ 18O and the second-order isotopic parameter deuterium excess reasonably well, but yields on average too little fractionation along the transport/cooling path. While simulations with an isotopic general circulation model (GCM) (ECHAM5-wiso) for Dome Fuji are on average closer to the observations, this model cannot reproduce the annual cycle of deuterium excess. In the event-based analysis, no evidence of a correlation of the measured deuterium excess with the latitude of the moisture source region or the corresponding conditions was identified. Contrary to the assumption used for decades in ice core studies, a more northerly moisture source does not necessarily mean a larger temperature difference between source area and deposition site, thus a more depleted precipitation in heavy isotopes with a higher deuterium excess. © Author(s) 2016.

Muller A.L.,University of Vienna | Muller A.L.,Austrian Polar Research Institute | De Rezende J.R.,University of Aarhus | De Rezende J.R.,Northumbria University | And 7 more authors.
ISME Journal | Year: 2014

Microbial biogeography is influenced by the combined effects of passive dispersal and environmental selection, but the contribution of either factor can be difficult to discern. As thermophilic bacteria cannot grow in the cold seabed, their inactive spores are not subject to environmental selection. We therefore conducted a global experimental survey using thermophilic endospores that are passively deposited by sedimentation to the cold seafloor as tracers to study the effect of dispersal by ocean currents on the biogeography of marine microorganisms. Our analysis of 81 different marine sediments from around the world identified 146 species-level 16S rRNA phylotypes of endospore-forming, thermophilic Firmicutes. Phylotypes showed various patterns of spatial distribution in the world oceans and were dispersal-limited to different degrees. Co-occurrence of several phylotypes in locations separated by great distances (west of Svalbard, the Baltic Sea and the Gulf of California) demonstrated a widespread but not ubiquitous distribution. In contrast, Arctic regions with water masses that are relatively isolated from global ocean circulation (Baffin Bay and east of Svalbard) were characterized by low phylotype richness and different compositions of phylotypes. The observed distribution pattern of thermophilic endospores in marine sediments suggests that the impact of passive dispersal on marine microbial biogeography is controlled by the connectivity of local water masses to ocean circulation. © 2014 International Society for Microbial Ecology. All rights reserved.

Muller A.L.,University of Vienna | Muller A.L.,Austrian Polar Research Institute | Kjeldsen K.U.,University of Aarhus | Rattei T.,University of Vienna | And 3 more authors.
ISME Journal | Year: 2015

The energy metabolism of essential microbial guilds in the biogeochemical sulfur cycle is based on a DsrAB-type dissimilatory (bi)sulfite reductase that either catalyzes the reduction of sulfite to sulfide during anaerobic respiration of sulfate, sulfite and organosulfonates, or acts in reverse during sulfur oxidation. Common use of dsrAB as a functional marker showed that dsrAB richness in many environments is dominated by novel sequence variants and collectively represents an extensive, largely uncharted sequence assemblage. Here, we established a comprehensive, manually curated dsrAB/DsrAB database and used it to categorize the known dsrAB diversity, reanalyze the evolutionary history of dsrAB and evaluate the coverage of published dsrAB-targeted primers. Based on a DsrAB consensus phylogeny, we introduce an operational classification system for environmental dsrAB sequences that integrates established taxonomic groups with operational taxonomic units (OTUs) at multiple phylogenetic levels, ranging from DsrAB enzyme families that reflect reductive or oxidative DsrAB types of bacterial or archaeal origin, superclusters, uncultured family-level lineages to species-level OTUs. Environmental dsrAB sequences constituted at least 13 stable family-level lineages without any cultivated representatives, suggesting that major taxa of sulfite/sulfate-reducing microorganisms have not yet been identified. Three of these uncultured lineages occur mainly in marine environments, while specific habitat preferences are not evident for members of the other 10 uncultured lineages. In summary, our publically available dsrAB/DsrAB database, the phylogenetic framework, the multilevel classification system and a set of recommended primers provide a necessary foundation for large-scale dsrAB ecology studies with next-generation sequencing methods. © 2015 International Society for Microbial Ecology.

Bartsch A.,Vienna University of Technology | Bartsch A.,Austrian Polar Research Institute | Kroisleitner C.,Vienna University of Technology | Heim B.,Alfred Wegener Institute for Polar and Marine Research
European Space Agency, (Special Publication) ESA SP | Year: 2016

The ESA DUE Permafrost service has been utilized to produce a pan-arctic database (25km, 2000-2014) comprising Mean Annual Surface Temperature, Annual and summer Amplitude of Surface Temperature, Mean Summer (July-August) Surface Temperature. Surface status (frozen/unfrozen) related products have been also derived from the ESA DUE Permafrost service. This includes the length of unfrozen period, first unfrozen day and first frozen day. In addition, SAR (ENVISAT ASAR GM) statistics as well as topographic parameters have been considered. The circumpolar datasets have been assessed for their redundancy in information content. 12 distinct units could be derived. This paper presents the result of this assessment and formulates recommendations for extensions of the in situ monitoring networks and categorizes the sites by satellite data requirements (specifically Sentinels) with respect to the landscape type and related processes.

Semmens K.A.,Lehigh University | Ramage J.,Lehigh University | Bartsch A.,Vienna University of Technology | Bartsch A.,Austrian Polar Research Institute | Liston G.E.,Colorado State University
Environmental Research Letters | Year: 2013

High latitude drainage basins are experiencing higher average temperatures, earlier snowmelt onset in spring, and an increase in rain on snow (ROS) events in winter, trends that climate models project into the future. Snowmelt-dominated basins are most sensitive to winter temperature increases that influence the frequency of ROS events and the timing and duration of snowmelt, resulting in changes to spring runoff. Of specific interest in this study are early melt events that occur in late winter preceding melt onset in the spring. The study focuses on satellite determination and characterization of these early melt events using the Yukon River Basin (Canada/USA) as a test domain. The timing of these events was estimated using data from passive (Advanced Microwave Scanning Radiometer - EOS (AMSR-E)) and active (SeaWinds on Quick Scatterometer (QuikSCAT)) microwave remote sensors, employing detection algorithms for brightness temperature (AMSR-E) and radar backscatter (QuikSCAT). The satellite detected events were validated with ground station meteorological and hydrological data, and the spatial and temporal variability of the events across the entire river basin was characterized. Possible causative factors for the detected events, including ROS, fog, and positive air temperatures, were determined by comparing the timing of the events to parameters from SnowModel and National Centers for Environmental Prediction North American Regional Reanalysis (NARR) outputs, and weather station data. All melt events coincided with above freezing temperatures, while a limited number corresponded to ROS (determined from SnowModel and ground data) and a majority to fog occurrence (determined from NARR). The results underscore the significant influence that warm air intrusions have on melt in some areas and demonstrate the large temporal and spatial variability over years and regions. The study provides a method for melt detection and a baseline from which to assess future change. © 2013 IOP Publishing Ltd.

Ivy D.J.,Massachusetts Institute of Technology | Solomon S.,Massachusetts Institute of Technology | Rieder H.E.,University of Graz | Rieder H.E.,Austrian Polar Research Institute
Journal of Climate | Year: 2016

Radiative and dynamical heating rates control stratospheric temperatures. In this study, radiative temperature trends due to ozone depletion and increasing well-mixed greenhouse gases from 1980 to 2000 in the polar stratosphere are directly evaluated, and the dynamical contributions to temperature trends are estimated as the residual between the observed and radiative trends. The radiative trends are obtained from a seasonally evolving fixed dynamical heating calculation with the Parallel Offline Radiative Transfer model using four different ozone datasets, which provide estimates of observed ozone changes. In the spring and summer seasons, ozone depletion leads to radiative cooling in the lower stratosphere in the Arctic and Antarctic. In Arctic summer there is weak wave driving, and the radiative cooling due to ozone depletion is the dominant driver of observed trends. In late winter and early spring, dynamics dominate the changes in Arctic temperatures. In austral spring and summer in the Antarctic, strong dynamical warming throughout the mid- to lower stratosphere acts to weaken the strong radiative cooling associated with the Antarctic ozone hole and is indicative of a strengthening of the Brewer-Dobson circulation. This dynamical warming is a significant term in the thermal budget over much of the Antarctic summer stratosphere, including in regions where strong radiative cooling due to ozone depletion can still lead to net cooling despite dynamical terms. Quantifying the contributions of changes in radiation and dynamics to stratospheric temperature trends is important for understanding how anthropogenic forcings have affected the historical trends and necessary for projecting the future. © 2016 American Meteorological Society.

Tveit A.T.,University of Tromsø | Urich T.,University of Vienna | Urich T.,Austrian Polar Research Institute | Svenning M.M.,University of Tromsø
Applied and Environmental Microbiology | Year: 2014

Recent advances in meta-omics and particularly metatranscriptomic approaches have enabled detailed studies of the structure and function of microbial communities in many ecosystems. Molecular analyses of peat soils, ecosystems important to the global carbon balance, are still challenging due to the presence of coextracted substances that inhibit enzymes used in downstream applications. We sampled layers at different depths from two high-Arctic peat soils in Svalbard for metatranscriptome preparation. Here we show that enzyme inhibition in the preparation of metatranscriptomic libraries can be circumvented by linear amplification of diluted template RNA. A comparative analysis of mRNA-enriched and nonenriched metatranscriptomes showed that mRNA enrichment resulted in a 2-fold increase in the relative abundance of mRNA but biased the relative distribution of mRNA. The relative abundance of transcripts for cellulose degradation decreased with depth, while the transcripts for hemicellulose debranching increased, indicating that the polysaccharide composition of the peat was different in the deeper and older layers. Taxonomic annotation revealed that Actinobacteria and Bacteroidetes were the dominating polysaccharide decomposers. The relative abundances of 16S rRNA and mRNA transcripts of methanogenic Archaea increased substantially with depth. Acetoclastic methanogenesis was the dominating pathway, followed by methanogenesis from formate. The relative abundances of 16S rRNA and mRNA assigned to the methanotrophic Methylococcaceae, primarily Methylobacter, increased with depth. In conclusion, linear amplification of total RNA and deep sequencing constituted the preferred method for metatranscriptomic preparation to enable high-resolution functional and taxonomic analyses of the active microbiota in Arctic peat soil. © 2014, American Society for Microbiology.

Tveit A.T.,University of Tromsø | Urich T.,University of Vienna | Urich T.,Austrian Polar Research Institute | Frenzel P.,Max Planck Institute for Terrestrial Microbiology | Svenning M.M.,University of Tromsø
Proceedings of the National Academy of Sciences of the United States of America | Year: 2015

Arctic permafrost soils store large amounts of soil organic carbon (SOC) that could be released into the atmosphere as methane (CH4) in a future warmer climate. How warming affects the complex microbial network decomposing SOC is not understood. We studied CH4 production of Arctic peat soil microbiota in anoxic microcosms over a temperature gradient from 1 to 30 °C, combining metatranscriptomic, metagenomic, and targeted metabolic profiling. The CH4 production rate at 4 ° C was 25% of that at 25 °C and increased rapidly with temperature, driven by fast adaptations of microbial community structure, metabolic network of SOC decomposition, and trophic interactions. Below 7 °C, syntrophic propionate oxidation was the rate-limiting step for CH4 production; above this threshold temperature, polysaccharide hydrolysis became rate limiting. This change was associated with a shift within the functional guild for syntrophic propionate oxidation, with Firmicutes being replaced by Bacteroidetes. Correspondingly, there was a shift from the formate- and H2-using Methanobacteriales to Methanomicrobiales and from the acetotrophic Methanosarcinaceae to Methanosaetaceae. Methanogenesis from methylamines, probably stemming from degradation of bacterial cells, became more important with increasing temperature and corresponded with an increased relative abundance of predatory protists of the phylum Cercozoa. We concluded that Arctic peat microbiota responds rapidly to increased temperatures by modulating metabolic and trophic interactions so that CH4 is always highly produced: The microbial community adapts through taxonomic shifts, and cascade effects of substrate availability cause replacement of functional guilds and functional changes within taxa.

Mayer M.,University of Vienna | Mayer M.,Austrian Polar Research Institute | Haimberger L.,University of Vienna | Haimberger L.,Austrian Polar Research Institute | And 3 more authors.
Geophysical Research Letters | Year: 2016

Various observation- and reanalysis-based estimates of sea ice mass and ocean heat content trends imply that the energy imbalance of the Arctic climate system was similar [1.0 (0.9,1.2) Wm−2] to the global ocean average during the 2000–2015 period. Most of this extra heat warmed the ocean, and a comparatively small fraction went into sea ice melt. Poleward energy transports and radiation contributed to this energy increase at varying strengths. On a seasonal scale, stronger radiative energy input during summer associated with the ice-albedo feedback enhances seasonal oceanic heat uptake and sea ice melt. In return, lower sea ice extent and higher sea surface temperatures lead to enhanced heat release from the ocean during fall. This weakens meridional temperature gradients, consequently reducing atmospheric energy transports into the polar cap. The seasonal cycle of the Arctic energy budget is thus amplified, whereas the Arctic's long-term energy imbalance is close to the global mean. ©2016. The Authors.

PubMed | University of South Bohemia, University of Vienna, University of Bergen, University of Stockholm and 3 more.
Type: | Journal: Scientific reports | Year: 2016

Arctic ecosystems are warming rapidly, which is expected to promote soil organic matter (SOM) decomposition. In addition to the direct warming effect, decomposition can also be indirectly stimulated via increased plant productivity and plant-soil C allocation, and this so called priming effect might significantly alter the ecosystem C balance. In this study, we provide first mechanistic insights into the susceptibility of SOM decomposition in arctic permafrost soils to priming. By comparing 119 soils from four locations across the Siberian Arctic that cover all horizons of active layer and upper permafrost, we found that an increased availability of plant-derived organic C particularly stimulated decomposition in subsoil horizons where most of the arctic soil carbon is located. Considering the 1,035 Pg of arctic soil carbon, such an additional stimulation of decomposition beyond the direct temperature effect can accelerate net ecosystem C losses, and amplify the positive feedback to global warming.

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