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Sample records for glacial trees recovered

  1. Interannual physiological responses of glacial trees to changes in atmospheric [CO2] since the Last Glacial Maximum

    NASA Astrophysics Data System (ADS)

    Gerhart, L. M.; Harris, J. M.; Ward, J. K.

    2009-12-01

    During the Last Glacial Maximum, atmospheric [CO2] were as low as 180 ppm and have currently risen to a modern value of 385 ppm as a result of fossil fuel combustion and deforestation. In order to understand how changing [CO2] influenced the physiology of trees over the last 50,000 years, we analyzed carbon isotope ratios of individual tree rings from juniper wood specimens from the Rancho La Brea tar pits in southern California and kauri wood specimens from peat bogs in New Zealand (North Island). Modern trees from different altitudes were compared to account for changes in precipitation and temperature through time in order to isolate the effects of changing [CO2]. We hypothesized that over the last 50,000 years, the ratio of ci (intracellular [CO2]) to ca (atmospheric [CO2]) would be maintained within each species. Consequently, ci values would be significantly lower in glacial trees due to lower ca levels during the LGM. In addition, we hypothesized that low [CO2] (which does not vary between years during the LGM) dominated tree physiology during the LGM as evidenced by low levels of inter-annual variation in ci/ca ratios relative to modern trees (which are known to respond to high frequency variation in water and temperature between years). In both kauri and juniper trees, mean ci/ca values remained constant throughout 50,000 years despite major climatic and [CO2] changes, indicating that there is a long-term physiological set point in these species. Limitations on the ci values of glacial junipers suggest that 90 ppm CO2 represents a survival compensation point for this species. In addition, glacial trees showed very low inter-annual variation in ci/ca values compared to modern trees. This suggests that glacial tree physiology may have been dominated by low CO2 that was constant between years, whereas modern trees may be dominated by climatic factors that vary substantially between years. Consequently, while each species maintained mean ci/ca values over time

  2. Glacial refugia and modern genetic diversity of 22 western North American tree species

    PubMed Central

    Roberts, David R.; Hamann, Andreas

    2015-01-01

    North American tree species, subspecies and genetic varieties have primarily evolved in a landscape of extensive continental ice and restricted temperate climate environments. Here, we reconstruct the refugial history of western North American trees since the last glacial maximum using species distribution models, validated against 3571 palaeoecological records. We investigate how modern subspecies structure and genetic diversity corresponds to modelled glacial refugia, based on a meta-analysis of allelic richness and expected heterozygosity for 473 populations of 22 tree species. We find that species with strong genetic differentiation into subspecies had widespread and large glacial refugia, whereas species with restricted refugia show no differentiation among populations and little genetic diversity, despite being common over a wide range of environments today. In addition, a strong relationship between allelic richness and the size of modelled glacial refugia (r2 = 0.55) suggest that population bottlenecks during glacial periods had a pronounced effect on the presence of rare alleles. PMID:25761711

  3. Cryptic or mystic? Glacial tree refugia in northern Europe.

    PubMed

    Tzedakis, P C; Emerson, B C; Hewitt, G M

    2013-12-01

    Here, we examine the evidence for tree refugia in northern Europe during the Late Pleniglacial (LPG) interval of maximum tree-range contraction. Our review highlights the often equivocal nature of genetic data and a tendency to overestimate potential tree distributions due to warm climate-model bias, and also reveals a convergence of macrofossil and pollen evidence. What emerges is the absence of temperate trees north of 45°N and a west-east (W-E) asymmetry in boreal tree distribution, with a treeless Western Europe north of 46°N, while restricted boreal populations persisted in Eastern Europe up to 49°N, and higher latitudes east of the Fennoscandian ice-sheet. These results have implications for current thinking on European genetic diversity patterns, species migration capacity, and conservation strategies.

  4. Tree ring and glacial records of Holocene climate change, northern Gulf of Alaska region

    NASA Astrophysics Data System (ADS)

    Barclay, David J.

    1998-11-01

    Tree-ring cross-dates of glacially overrun trees at eight sites around western Prince William Sound show ice margins advanced in the early (late 12th through 13th centuries AD) and middle (17th to early 18th centuries) Little Ice Age. Tree-ring dates of 22 moraines at 13 glaciers in the same region indicate an early period of moraine stabilization in the early 18th century. This overlaps with the second period of glaciers overrunning trees and marks culmination of this middle Little Ice Age advance. Moraine stabilization on nine of the study forefields in the latter 19th century delineates a third interval of Little Ice Age glacial expansion. These intervals of land-terminating glacier advance are synchronous with other tree-ring dated glacial histories from around the northern Gulf of Alaska, suggesting common climatic forcing across this region. Ring-widths in a 1119-year long tree-ring-width chronology developed from subfossil and living trees on glacial forefields around western Prince William Sound are primarily controlled by May through July temperatures of the growth year. Multi-decadal length warm periods in western Prince William Sound during the past 750 years were centered on 1300, 1440, 1730 and 1950 AD. Major cool periods were centered on 1400, 1660 and 1870 AD. Surficial mapping and 52 radiocarbon ages enable reconstruction of the Holocene glacial history of Yakutat Bay and Russell Fiord. Following an early to middle Holocene non-glacial interval, Hubbard Glacier began an advance at ~5600 cal. BP that culminated between ~4300 and 3474 cal. BP. Retreat by ~3200 cal. BP preceded readvance to Holocene maxima in Yakutat Bay and Russell Fiord at ~725 cal. BP (1225 cal. AD). The Hubbard ice margin in Yakutat Bay retreated by 1245 cal. AD, and was behind its modern position by 1791 AD. Ice from the Brabazon Range kept the Russell Fiord glacier lobe at its maximum until retreat during the late 18th and 19th centuries AD. The extent and timing of specific

  5. The RECAP ice core - recovering a full Glacial record from Eastern Greenland

    NASA Astrophysics Data System (ADS)

    Vinther, Bo

    2016-04-01

    During May-June 2015 the 584m an international team drilled the RECAP (REnland ice CAp Project) ice core to bedrock on the Renland ice cap in Eastern Greenland. The exact drill site selection was determined from a detailed radio echo sounding (RES) grid, that had been measured from the ice cap surface right before drilling operations began. The RES data suggested that the ice cap internal layers are horizontal almost right down to the bed at the selected site, and that ice from the Glacial period was present some 30-50m above bedrock. The RES results have now been confirmed by measurements on the RECAP core that shows the entire Glacial being nicely preserved in the 20m section indicated by the RES measurements. The RECAP core thus yields the first undisturbed ice core record from Eastern Greenland covering the last Glacial, a marked improvement compared to the landmark 1988 Renland ice core that was disturbed by ice flow features both during the mid-Holocene and especially during Marine Isotope Stages 4 and 5.

  6. Variations in tree cover in North America since the last glacial maximum

    NASA Astrophysics Data System (ADS)

    Williams, John W.

    2003-01-01

    Accurate reconstructions of late-Quaternary land-cover change are needed to better understand past interactions of the terrestrial biosphere with other components of the earth system. This paper presents a sequence of reconstructed needleleaved and broadleaved tree-cover densities for North America since the last glacial maximum, generated from fossil-pollen data and present-day tree-cover estimates derived from the Advanced Very High Resolution Radiometer (AVHRR). For this study, a refined form of the modern analog technique was developed, called the hierarchical analog technique, which can constrain paleoenvironmental properties even for fossil-pollen assemblages without close analogs in the modern-pollen record. Pollen taxa from samples that are compositionally unlike any modern-pollen samples are regrouped into plant functional categories based upon phenology, life form, leaf shape, and climatic tolerances, and the analog analysis rerun. Reclassifying individual pollen taxa into broader functional categories enables analogs to be found when no compositional analogs exist, but at a cost of increased uncertainties in the analog estimates. Tests of the hierarchical analog technique shows that it accurately reconstructs present-day tree-cover densities. The median standard deviation for each individual estimate is <10%. Tree-cover densities during the last glacial maximum were low relative to present, and have increased since. Lower-than-present tree-cover densities at the last glacial maximum were likely due to a combination of low temperatures, low precipitation, and low atmospheric CO 2 concentrations. By 14 ka, broadleaved tree-cover densities had begun to rise in the southeastern US and needleleaved forests grew in the western US, southeastern US, and as a belt along the southern margin of the Laurentide Ice Sheet. By the mid-Holocene, the northern and western needleleaved forests had joined. Needleleaved and broadleaved tree densities continued to increase

  7. Comparison of oil recovered from tea tree leaf by ethanol extraction and steam distillation.

    PubMed

    Baker, G R; Lowe, R F; Southwell, I A

    2000-09-01

    Two methods for the determination of oil and oil major components from tea tree (Melaleuca alternifolia) leaf are quantitatively compared. A microwave assisted ethanol extraction and a 2-h hydrodistillation technique were used on both dry and fresh leaf from a low and a high oil concentration tree. There was no significant difference between dry and fresh leaf. The distillation technique recovered 88% and 82% of the extractable oil for the low and high concentration material, respectively. For both samples this distilled oil was composed of lower absolute amounts of sesquiterpenoids and marginally lower amounts of monoterpenoids. Extending the distillation to 6 h increased the sesquiterpenoid recovery but this resulted in a reduction in both the absolute and relative amounts of the oxygenated monoterpenoids, terpinen-4-ol and 1,8-cineole.

  8. High-resolution study of Late Glacial and Early Holocene vegetation and tree line changes in the Southern Carpathian Mountains

    NASA Astrophysics Data System (ADS)

    Magyari, E.; Jakab, G.; Braun, M.; Buczkó, K.; Bálint, M.

    2009-04-01

    The Retezat Massif of the S Carpathian Mountains abounds in glacial lakes, mainly above 1900 m a.s.l., just above the present day tree limit formed by Picea abies and Pinus cembra in the northern slopes. For the reconstruction of Late Glacial and Early Holocene vegetation and tree line changes in this mountain, two lakes were selected: Taul dintre Brazi (1740 m a.s.l.) and Lake Gales (1990 m a.s.l.). Sediments obtained from these lakes extend back to the Late Glacial, and so provide us an exceptional opportunity to study 1) when trees were first established locally around the lower lake following glacial retreat and 2) what tree and shrub species were present and replaced each other in the Late Glacial and early postglacial forests in response to the high-amplitude climatic fluctuation, and in case of the Early Holocene, the high-amplitude climatic amelioration. Pollen, conifer stomata and plant macrofossils were studied from both lake sediments at approximately 100 years resolution. Sediment chronologies were based on multiple AMS radiocarbon dates. Preliminary results from this study show that Pinus mugo, Pinus cembra, Picea abies and Betula nana appeared very early during the lateglacial interstadial, ca. 14,500 cal yr BP followed by Larix decidua around 14,200 cal yr BP. Pinus cembra gained dominance in the Latglacial interstadial forest and survived locally during the Younger Dryas reversal unlike Picea abies. Another important result was the reconstruction of the Early Holocene forest composition around the lower lake that proved much more species rich than the present-day forest; Picea abies grew together with Larix decidua, Pinus mugo, Pinus cembra, Alnus viridis, Juniperus, Betula nana and Betula pubescens during the Early Holocene, furthermore the stomatal record suggested that conifer species were evenly distributed around the lake. In light of our data, the position of the Early Holocene tree line reached 1990 m a.s.l. by ca. 10,700 cal yr BP (i

  9. A late glacial record of ice-sheet dynamics and melt supply recovered in the sediments of IODP Expedition 347 in the Baltic Sea

    NASA Astrophysics Data System (ADS)

    Passchier, Sandra; Jensen, Jørn Bo; Kenzler, Michael; Johnson, Sean; Andrén, Thomas; Barker Jørgensen, Bo

    2015-04-01

    Modern observations of increased surface ablation, meltwater routing to the bed, and increases in glacial speeds point to feedbacks between ice-sheet dynamics, melt supply, and subglacial discharge. Paleorecords have the potential to explore the decadal to centennial variability of these systems, but until recently such records were short and discontinuous in ice-proximal settings and underutilized for this specific purpose. The Integrated Ocean Drilling Program Expedition 347 in the Baltic Sea recovered annually laminated sediments that document the dynamics of the Scandinavian Ice Sheet. Hydraulic piston cores recovered from Sites M0060, M0063, M0064, and M0065 allow us to reconstruct a nearly complete record of ca. 6000 years in ice retreat history at annual to decadal resolution between ca. 17 and 11ka. The late glacial successions of these four IODP drillsites comprise of a till or proglacial fluvioglacial sediment overlain by variable thicknesses of well-laminated deglacial successions within several high-recovery holes. As the Scandinavian Ice Sheet retreated from the western Baltic Sea, and to the North, the ice-sheet's grounding line migrated across the four sites and deposited overlapping sections of high-resolution ice-proximal to ice-distal successions. Laser particle size results from Sites M0060 and M0063, and inspection of line-scan images, show shifts in sedimentary facies and lithologies that were not recognized during initial visual core description. For example, at Site M0060 in the Kattegat, ice-rafting fluxes in silty clays decrease upward and are negligible in the overlying varved succession. These characteristics are interpreted as ice retreat within a calving bay environment from ca. 17ka onward, followed by distal glacial marine deposition from sediment plumes governed by meltwater discharge. Moreover, at Site M0063 in the Baltic Sea, laser particle size distributions record an abrupt shift from interlaminated clayey silt to laminated clay

  10. Multiple glacial refugia for cool-temperate deciduous trees in northern East Asia: the Mongolian oak as a case study.

    PubMed

    Zeng, Yan-Fei; Wang, Wen-Ting; Liao, Wan-Jin; Wang, Hong-Fang; Zhang, Da-Yong

    2015-11-01

    In East Asia, temperate forests are predicted to have retracted southward to c. 30° N during the last glacial maximum (LGM) based on fossil pollen data, whereas phylogeographic studies have often suggested glacial in situ survival of cool-temperate deciduous trees in their modern northern ranges. Here we report a study of the genetic diversity and structure of 29 natural Mongolian oak (Quercus mongolica) populations using 19 nuclear simple sequence repeat (nSSR) loci and four chloroplast DNA fragments. Bayesian clustering analysis with nSSRs revealed five groups, which were inferred by approximate Bayesian computation (ABC) to have diverged in multiple refugia through multiple glacial-interglacial cycles. Analysis of chloroplast DNA variation revealed four lineages that were largely but incompletely geographically disjunct. Ecological niche modelling (ENMs) indicated a southward range shift of the oak's distribution at the LGM, although high suitability scores were also evident in the Changbai Mts. (Northeast China), the Korean Peninsula, areas surrounding the Bohai Sea, and along the coast of the Russian Far East. In addition, endemic chloroplast DNA haplotypes and nuclear lineages occurred in high-latitude northern areas where the ENM predicted no suitable habitat. The combined evidence from nuclear and chloroplast DNA, and the results of the ENM clearly demonstrate that multiple northern refugia, including cryptic ones, were maintained across the current distributional range of the Mongolian oak during the LGM or earlier glacial periods. Though spatially limited, postglacial expansions from these refugia have led to a pattern of decreased genetic diversity with increasing latitude.

  11. Phylogenetic assemblage structure of North American trees is more strongly shaped by glacial-interglacial climate variability in gymnosperms than in angiosperms.

    PubMed

    Ma, Ziyu; Sandel, Brody; Svenning, Jens-Christian

    2016-05-01

    How fast does biodiversity respond to climate change? The relationship of past and current climate with phylogenetic assemblage structure helps us to understand this question. Studies of angiosperm tree diversity in North America have already suggested effects of current water-energy balance and tropical niche conservatism. However, the role of glacial-interglacial climate variability remains to be determined, and little is known about any of these relationships for gymnosperms. Moreover, phylogenetic endemism, the concentration of unique lineages in restricted ranges, may also be related to glacial-interglacial climate variability and needs more attention. We used a refined phylogeny of both angiosperms and gymnosperms to map phylogenetic diversity, clustering and endemism of North American trees in 100-km grid cells, and climate change velocity since Last Glacial Maximum together with postglacial accessibility to recolonization to quantify glacial-interglacial climate variability. We found: (1) Current climate is the dominant factor explaining the overall patterns, with more clustered angiosperm assemblages toward lower temperature, consistent with tropical niche conservatism. (2) Long-term climate stability is associated with higher angiosperm endemism, while higher postglacial accessibility is linked to to more phylogenetic clustering and endemism in gymnosperms. (3) Factors linked to glacial-interglacial climate change have stronger effects on gymnosperms than on angiosperms. These results suggest that paleoclimate legacies supplement current climate in shaping phylogenetic patterns in North American trees, and especially so for gymnosperms.

  12. Linking dominant Hawaiian tree species to understory development in recovering pastures via impacts on soils and litter

    USGS Publications Warehouse

    Yelenik, Stephanie G.

    2017-01-01

    Large areas of tropical forest have been cleared and planted with exotic grass species for use as cattle pasture. These often remain persistent grasslands after grazer removal, which is problematic for restoring native forest communities. It is often hoped that remnant and/or planted trees can jump-start forest succession; however, there is little mechanistic information on how different canopy species affect community trajectories. To investigate this, I surveyed understory communities, exotic grass biomass, standing litter pools, and soil properties under two dominant canopy trees—Metrosideros polymorpha (‘ōhi‘a) and Acacia koa (koa)—in recovering Hawaiian forests. I then used structural equation models (SEMs) to elucidate direct and indirect effects of trees on native understory. Native understory communities developed under ‘ōhi‘a, which had larger standing litter pools, lower soil nitrogen, and lower exotic grass biomass than koa. This pattern was variable, potentially due to historical site differences and/or distance to intact forest. Koa, in contrast, showed little understory development. Instead, data suggest that increased soil nitrogen under koa leads to high grass biomass that stalls native recruitment. SEMs suggested that indirect effects of trees via litter and soils were as or more important than direct effects for determining native cover. It is suggested that diverse plantings which incorporate species that have high carbon to nitrogen ratios may help ameliorate the negative indirect effects of koa on natural understory regeneration.

  13. Recovering more than tree cover: herbivores and herbivory in a restored tropical dry forest.

    PubMed

    Juan-Baeza, Iris; Martínez-Garza, Cristina; Del-Val, Ek

    2015-01-01

    Intense and chronic disturbance may arrest natural succession, reduce environmental quality and lead to ecological interaction losses. Where natural succession does not occur, ecological restoration aims to accelerate this process. While plant establishment and diversity is promoted by restoration, few studies have evaluated the effect of restoration activities on ecological processes and animal diversity. This study assessed herbivory and lepidopteran diversity associated with two pioneer tree species growing in 4-year-old experimental restoration plots in a tropical dry forest at Sierra de Huautla, in Morelos, Mexico. The study was carried out during the rainy season of 2010 (July-October) in eleven 50 x 50 m plots in three different habitats: cattle-excluded, cattle-excluded with restoration plantings, and cattle grazing plots. At the beginning of the rainy season, 10 juveniles of Heliocarpus pallidus (Malvaceae) and Ipomoea pauciflora (Convolvulaceae) were selected in each plot (N = 110 trees). Herbivory was measured in 10 leaves per plant at the end of the rainy season. To evaluate richness and abundance of lepidopteran larvae, all plants were surveyed monthly. Herbivory was similar among habitats and I. pauciflora showed a higher percentage of herbivory. A total of 868 lepidopteran larvae from 65 morphospecies were recorded. The family with the highest number of morphospecies (9 sp.) was Geometridae, while the most abundant family was Saturnidae, with 427 individuals. Lepidopteran richness and abundance were significantly higher in H. pallidus than in I. pauciflora. Lepidopteran richness was significantly higher in the cattle-excluded plots, while abundance was significantly higher in the non-excluded plots. After four years of cattle exclusion and the establishment of plantings, lepidopteran richness increased 20 -fold in the excluded plots compared to the disturbed areas, whereas herbivory levels were equally high in both restored and disturbed sites

  14. Recovering More than Tree Cover: Herbivores and Herbivory in a Restored Tropical Dry Forest

    PubMed Central

    2015-01-01

    Intense and chronic disturbance may arrest natural succession, reduce environmental quality and lead to ecological interaction losses. Where natural succession does not occur, ecological restoration aims to accelerate this process. While plant establishment and diversity is promoted by restoration, few studies have evaluated the effect of restoration activities on ecological processes and animal diversity. This study assessed herbivory and lepidopteran diversity associated with two pioneer tree species growing in 4-year-old experimental restoration plots in a tropical dry forest at Sierra de Huautla, in Morelos, Mexico. The study was carried out during the rainy season of 2010 (July-October) in eleven 50 x 50 m plots in three different habitats: cattle-excluded, cattle-excluded with restoration plantings, and cattle grazing plots. At the beginning of the rainy season, 10 juveniles of Heliocarpus pallidus (Malvaceae) and Ipomoea pauciflora (Convolvulaceae) were selected in each plot (N = 110 trees). Herbivory was measured in 10 leaves per plant at the end of the rainy season. To evaluate richness and abundance of lepidopteran larvae, all plants were surveyed monthly. Herbivory was similar among habitats and I. pauciflora showed a higher percentage of herbivory. A total of 868 lepidopteran larvae from 65 morphospecies were recorded. The family with the highest number of morphospecies (9 sp.) was Geometridae, while the most abundant family was Saturnidae, with 427 individuals. Lepidopteran richness and abundance were significantly higher in H. pallidus than in I. pauciflora. Lepidopteran richness was significantly higher in the cattle-excluded plots, while abundance was significantly higher in the non-excluded plots. After four years of cattle exclusion and the establishment of plantings, lepidopteran richness increased 20 –fold in the excluded plots compared to the disturbed areas, whereas herbivory levels were equally high in both restored and disturbed sites

  15. Will the US economy recover in 2010? A minimal spanning tree study

    NASA Astrophysics Data System (ADS)

    Zhang, Yiting; Lee, Gladys Hui Ting; Wong, Jian Cheng; Kok, Jun Liang; Prusty, Manamohan; Cheong, Siew Ann

    2011-06-01

    We calculated the cross correlations between the half-hourly times series of the ten Dow Jones US economic sectors over the period February 2000 to August 2008, the two-year intervals 2002-2003, 2004-2005, 2008-2009, and also over 11 segments within the present financial crisis, to construct minimal spanning trees (MSTs) of the US economy at the sector level. In all MSTs, a core-fringe structure is found, with consumer goods, consumer services, and the industrials consistently making up the core, and basic materials, oil & gas, healthcare, telecommunications, and utilities residing predominantly on the fringe. More importantly, we find that the MSTs can be classified into two distinct, statistically robust, topologies: (i) star-like, with the industrials at the center, associated with low-volatility economic growth; and (ii) chain-like, associated with high-volatility economic crisis. Finally, we present statistical evidence, based on the emergence of a star-like MST in Sep 2009, and the MST staying robustly star-like throughout the Greek Debt Crisis, that the US economy is on track to a recovery.

  16. A coupled phylogeographical and species distribution modelling approach recovers the demographical history of a Neotropical seasonally dry forest tree species.

    PubMed

    Collevatti, Rosane G; Terribile, Levi Carina; Lima-Ribeiro, Matheus S; Nabout, João C; de Oliveira, Guilherme; Rangel, Thiago F; Rabelo, Suelen G; Diniz-Filho, Jose A F

    2012-12-01

    We investigated here the demographical history of Tabebuia impetiginosa (Bignoniaceae) to understand the dynamics of the disjunct geographical distribution of South American seasonally dry forests (SDFs), based on coupling an ensemble approach encompassing hindcasting species distribution modelling and statistical phylogeographical analysis. We sampled 17 populations (280 individuals) in central Brazil and analysed the polymorphisms at chloroplast (trnS-trnG, psbA-trnH, and ycf6-trnC intergenic spacers) and nuclear (ITS nrDNA) genomes. Phylogenetic analyses based on median-joining network showed no haplotype sharing among population but strong evidence of incomplete lineage sorting. Coalescent analyses showed historical constant populations size, negligible gene flow among populations, and an ancient time to most recent common ancestor dated from ~4.7 ± 1.1 Myr BP. Most divergences dated from the Lower Pleistocene, and no signal of important population size reduction was found in coalescent tree and tests of demographical expansion. Demographical scenarios were built based on past geographical range dynamic models, using two a priori biogeographical hypotheses ('Pleistocene Arc' and 'Amazonian SDF expansion') and on two additional hypotheses suggested by the palaeodistribution modelling built with several algorithms for distribution modelling and palaeoclimatic data. The simulation of these demographical scenarios showed that the pattern of diversity found so far for T. impetiginosa is in consonance with a palaeodistribution expansion during the last glacial maximum (LGM, 21 kyr BP), strongly suggesting that the current disjunct distribution of T. impetiginosa in SDFs may represent a climatic relict of a once more wide distribution.

  17. Larix decidua δ(18)O tree-ring cellulose mainly reflects the isotopic signature of winter snow in a high-altitude glacial valley of the European Alps.

    PubMed

    Leonelli, Giovanni; Battipaglia, Giovanna; Cherubini, Paolo; Saurer, Matthias; Siegwolf, Rolf T W; Maugeri, Maurizio; Stenni, Barbara; Fusco, Stella; Maggi, Valter; Pelfini, Manuela

    2017-02-01

    We analyzed the chronologies of cellulose stable isotopes (δ(13)C and δ(18)O) and tree-ring widths from European larch (Larix decidua) in a high-altitude site (2190ma.s.l.) at the bottom of a glacial valley in the Italian Alps, and investigated their dependence on monthly meteorological variables and δ(18)O precipitation values. The δ(18)O of tree-ring cellulose appears to be strongly driven by the δ(18)O of winter snowfall (November to March), which suggests that larch trees mostly use the snow-melt water of the previous winter during the growing season. This water, which also comes from the slope streams and from the underground flow of nearby steep slopes, infiltrates the soil in the valley bottom. The tree-ring cellulose δ(18)O values were also found to be influenced by the August precipitation δ(18)O and mean temperature. The associated regression model shows that the δ(18)O chronology from the tree rings explains up to 34% of the variance in the winter precipitation δ(18)O record, demonstrating the potential for reconstructing the δ(18)O isotopic composition of past winter precipitation in the study region. Unlike most other tree-ring studies that focus on growing season signals, in our study the summer signal was small and the winter signal dominant due to the special conditions of the glacial valley. Site topography, geomorphology and soil characteristics in particular influence the stable isotope signal in tree-ring cellulose.

  18. Diversity of culturable bacteria recovered from Pico Bolívar's glacial and subglacial environments, at 4950 m, in Venezuelan tropical Andes.

    PubMed

    Rondón, Johnma; Gómez, Wileidy; Ball, María M; Melfo, Alejandra; Rengifo, Marcos; Balcázar, Wilvis; Dávila-Vera, Delsy; Balza-Quintero, Alirio; Mendoza-Briceño, Rosa Virginia; Yarzábal, Luis Andrés

    2016-11-01

    Even though tropical glaciers are retreating rapidly and many will disappear in the next few years, their microbial diversity remains to be studied in depth. In this paper we report on the biodiversity of the culturable fraction of bacteria colonizing Pico Bolívar's glacier ice and subglacial meltwaters, at ∼4950 m in the Venezuelan Andean Mountains. Microbial cells of diverse morphologies and exhibiting uncompromised membranes were present at densities ranging from 1.5 × 10(4) to 4.7 × 10(4) cells/mL in glacier ice and from 4.1 × 10(5) to 9.6 × 10(5) cells/mL in subglacial meltwater. Of 89 pure isolates recovered from the samples, the majority were eurypsychrophilic or stenopsychrophilic, according to their temperature range of growth. Following analysis of their 16S rDNA nucleotidic sequence, 54 pure isolates were assigned to 23 phylotypes distributed within 4 different phyla or classes: Beta- and Gammaproteobacteria, Actinobacteria, and Bacteroidetes. Actinobacteria dominated the culturable fraction of glacier ice samples, whereas Proteobacteria were dominant in subglacial meltwater samples. Chloramphenicol and ampicillin resistance was exhibited by 73.07% and 65.38%, respectively, of the subglacial isolates, and nearly 35% of them were multiresistant. Considering the fast rate at which tropical glaciers are melting, this study confirms the urgent need to study the microbial communities immured in such environments.

  19. Evapotranspiration is Less Variable Than Tree Transpiration as Well-Drained Boreal Forests Recover From Wildfires Over 150 years

    NASA Astrophysics Data System (ADS)

    Ewers, B. E.; Litvak, M.; Bond-Lamberty, B.; Goulden, M. L.; Gower, S. T.

    2006-12-01

    Recent work on the boreal forest has produced mixed results regarding the impact of changing fire frequencies on the carbon cycle and even less is known about interactions with the water and energy cycles. The objective of this study was to quantify the impact of forest succession following wildfires on evapotranspiration from boreal black spruce forests. In five stands ranging from 13 to 152 years old, we quantified evapotranspiration using eddy covariance and stand transpiration using sap flux measurements. Previous work from these stands had shown that stand transpiration was dependent on tree species and stand age and that below canopy temperatures were inversely correlated with tree leaf area index. Recent work has shown that bryophyte leaf area generally increases with stand age. Thus, we hypothesized that 1) evapotranspiration would be a combination of measured transpiration and the linear influence of bryophyte leaf area, and 2) length of growing season measured by the onset and end of tree transpiration would be inversely correlated with tree leaf area. Growing season evapotranspiration changed significantly with stand age with daily averages of 1.7, 1.8, 2.1, 1.8 and 2.0 mm per day from the 13, 21, 38, 72, and 152 year old stands respectively. However, stand evapotranspiration was much less variable with stand age than tree transpiration or bryophyte leaf area rejecting our first hypothesis. Tests of our second hypothesis were mixed because tree leaf area index was strongly correlated to onset of spring transpiration but weakly correlated to end of transpiration in the fall. Spring transpiration was delayed up to seven days in the two oldest stands with leaf area indices above 6.0 m2 m-2 compared to the 13 year-old stand with leaf area index of 0.6 m2 m-2. Bryophyte leaf area index alone was not sufficient to explain the difference between measured stand transpiration and evapotranspiration. We are exploring errors in eddy covariance and stand

  20. Extending glacial refugia for a European tree: genetic markers show that Iberian populations of white elm are native relicts and not introductions

    PubMed Central

    Fuentes-Utrilla, P; Venturas, M; Hollingsworth, P M; Squirrell, J; Collada, C; Stone, G N; Gil, L

    2014-01-01

    Conservation policies usually focus on in situ protection of native populations, a priority that requires accurate assessment of population status. Distinction between native and introduced status can be particularly difficult (and at the same time, is most important) for species whose natural habitat has become both rare and highly fragmented. Here, we address the status of the white elm (Ulmus laevis Pallas), a European riparian tree species whose populations have been fragmented by human activity and is protected wherever it is considered native. Small populations of this species are located in Iberia, where they are unprotected because they are considered introductions due to their rarity. However, Iberia and neighbouring regions in southwestern France have been shown to support discrete glacial refuge populations of many European trees, and the possibility remains that Iberian white elms are native relicts. We used chloroplast RFLPs and nuclear microsatellites to establish the relationship between populations in Iberia and the Central European core distribution. Bayesian approaches revealed significant spatial structure across populations. Those in Iberia and southwestern France shared alleles absent from Central Europe, and showed spatial population structure within Iberia common in recognized native taxa. Iberian populations show a demographic signature of ancient population bottlenecks, while those in Central European show a signature of recent population bottlenecks. These patterns are not consistent with historical introduction of white elm to Iberia, and instead strongly support native status, arguing for immediate implementation of conservation measures for white elm populations in Spain and contiguous areas of southern France. PMID:24022495

  1. Trees

    ERIC Educational Resources Information Center

    Al-Khaja, Nawal

    2007-01-01

    This is a thematic lesson plan for young learners about palm trees and the importance of taking care of them. The two part lesson teaches listening, reading and speaking skills. The lesson includes parts of a tree; the modal auxiliary, can; dialogues and a role play activity.

  2. Trees

    NASA Astrophysics Data System (ADS)

    Epstein, Henri

    2016-11-01

    An algebraic formalism, developed with V. Glaser and R. Stora for the study of the generalized retarded functions of quantum field theory, is used to prove a factorization theorem which provides a complete description of the generalized retarded functions associated with any tree graph. Integrating over the variables associated to internal vertices to obtain the perturbative generalized retarded functions for interacting fields arising from such graphs is shown to be possible for a large category of space-times.

  3. Neoendemic ground beetles and private tree haplotypes: two independent proxies attest a moderate last glacial maximum summer temperature depression of 3-4 °C for the southern Tibetan Plateau

    NASA Astrophysics Data System (ADS)

    Schmidt, Joachim; Opgenoorth, Lars; Martens, Jochen; Miehe, Georg

    2011-07-01

    Previous findings regarding the Last Glacial Maximum LGM summer temperature depression (maxΔT in July) on the Tibetan Plateau varied over a large range (between 0 and 9 °C). Geologic proxies usually provided higher values than palynological data. Because of this wide temperature range, it was hitherto impossible to reconstruct the glacial environment of the Tibetan Plateau. Here, we present for the first time data indicating that local neoendemics of modern species groups are promising proxies for assessing the LGM temperature depression in Tibet. We used biogeographical and phylogenetic data from small, wingless edaphous ground beetles of the genus Trechus, and from private juniper tree haplotypes. The derived values of the maxΔT in July ranged between 3 and 4 °C. Our data support previous findings that were based on palynological data. At the same time, our data are spatially more specific as they are not bound to specific archives. Our study shows that the use of modern endemics enables a detailed mapping of local LGM conditions in High Asia. A prerequisite for this is an extensive biogeographical and phylogenetic exploration of the area and the inclusion of additional endemic taxa and evolutionary lines.

  4. Glacial history of Tranquilo glacier (Central Patagonia) since the Last Glacial Maximum through to the present.

    NASA Astrophysics Data System (ADS)

    Sagredo, E. A.; Araya, P. S.; Schaefer, J. M.; Kaplan, M. R.; Kelly, M. A.; Lowell, T. V.; Aravena, J. C.

    2014-12-01

    Deciphering the timing and the inter-hemispheric phasing of former glacial fluctuations is critical for understanding the mechanisms and climate signals underlying these glacial events. Here, we present a detailed chronology of glacial fluctuations for Río Tranquilo glacier (47°S), since the LGM, including up to the present. Río Tranquilo is a small glacial valley located on the northern flank of Monte San Lorenzo, an isolated granitic massif, ~70 km to the east of the southern limit of the Northern Patagonian Icefield. Although Mt. San Lorenzo is located on the leeward side of the Andes, it is one of the most glacierized mountains in the region, with an ice surface area of ~140 km2. Geomorphic evidence suggests that during past episodes of climate change several small glaciers that today occupy the headwalls of Río Tranquilo valley expanded and coalesced, depositing a series of moraines complexes along the flanks and bottom of the valley. We used two independent dating techniques to constrain the age of the glacial history of the area. 10Be surface exposure ages from boulders located atop moraine ridges reveal that Río Tranquilo valley underwent glacial expansion/stabilization during at least the LGM (late LGM?), Late glacial (ACR and Younger Dryas) and Mid-Holocene. Within the Mid-Holocene limits, tree-ring based chronology indicates that Río Tranquilo glacier expanded during the Late Holocene as well. Our results are the first detailed chronology of glacial fluctuations from a single valley glacier, spanning the entire period from the (end of the) LGM up to the present, in southern South America. By identifying different glacial episodes within a single alpine valley, this study provides baseline data for studying the relative magnitude of the climate events responsible for these glacial events.

  5. Glacial integrative modelling.

    PubMed

    Ganopolski, Andrey

    2003-09-15

    Understanding the mechanisms of past climate changes requires modelling of the complex interaction between all major components of the Earth system: atmosphere, ocean, cryosphere, lithosphere and biosphere. This paper reviews attempts at such an integrative approach to modelling climate changes during the glacial age. In particular, the roles of different factors in shaping glacial climate are compared based on the results of simulations with an Earth-system model of intermediate complexity, CLIMBER-2. It is shown that ice sheets, changes in atmospheric compositions, vegetation cover, and reorganization of the ocean thermohaline circulation play important roles in glacial climate changes. Another example of this approach is the modelling of two major types of abrupt glacial climate changes: Dansgaard-Oeschger and Heinrich events. Our results corroborate some of the early proposed mechanisms, which relate abrupt climate changes to the internal instability of the ocean thermohaline circulation and ice sheets. At the same time, it is shown that realistic representation of the temporal evolution of the palaeoclimatic background is crucial to simulate observed features of the glacial abrupt climate changes.

  6. The taphonomy of human remains in a glacial environment.

    PubMed

    Pilloud, Marin A; Megyesi, Mary S; Truffer, Martin; Congram, Derek

    2016-04-01

    A glacial environment is a unique setting that can alter human remains in characteristic ways. This study describes glacial dynamics and how glaciers can be understood as taphonomic agents. Using a case study of human remains recovered from Colony Glacier, Alaska, a glacial taphonomic signature is outlined that includes: (1) movement of remains, (2) dispersal of remains, (3) altered bone margins, (4) splitting of skeletal elements, and (5) extensive soft tissue preservation and adipocere formation. As global glacier area is declining in the current climate, there is the potential for more materials of archaeological and medicolegal significance to be exposed. It is therefore important for the forensic anthropologist to have an idea of the taphonomy in this setting and to be able to differentiate glacial effects from other taphonomic agents.

  7. Glacial Geology of Wisconsin.

    ERIC Educational Resources Information Center

    Madison Public Schools, WI.

    This publication is a teacher's resource and guidebook for the presentation of the three filmstrips in the "Glacial Geology of Wisconsin" series. The first filmstrip is subtitled, "Evidence of the Glaciers," the second "How the Glaciers Reshaped the Landscape," and the third "Fossils of the Ice Age."…

  8. Bacterial recovery from ancient glacial ice.

    PubMed

    Christner, Brent C; Mosley-Thompson, Ellen; Thompson, Lonnie G; Reeve, John N

    2003-05-01

    Ice that forms the bottom 18 m of a 308 m ice core drilled from the Guliya ice cap on the Qinghan-Tibetan plateau in Western China is over 750000 years old and is the oldest glacial ice known to date. Fourteen bacterial isolates have been recovered from samples of this ice from approximately 296 m below the surface (mbs). Based on 16S rDNA sequences, these are members of the alpha- and beta-proteobacterial, actinobacterial and low-G + C Gram-positive bacterial lineages. 16S rDNA molecules have also been amplified directly, cloned and sequenced from the ice-core melt water. These originated from Pseudomonas and Acinetobacter gamma-proteobacterial species. These results demonstrate that bacteria can be recovered from water ice that has frozen for time periods relevant to biological survival through terrestrial ice ages or during interplanetary transport.

  9. PALEOCLIMATE: Glacial Climate Instability.

    PubMed

    Labeyrie, L

    2000-12-08

    Throughout the last glacial period, rapid climatic changes called Dansgaard-Oeschger (D-O) events occurred in the Northern Hemisphere. As Labeyrie discusses in his Perspective, these events are ideal targets for testing our understanding of climate change and developing climatic change models. Important steps toward understanding D-O events, particularly regarding the role of the low latitudes, are now reported by Hughen et al. and Peterson et al.

  10. Glacial atmospheric phosphorus deposition

    NASA Astrophysics Data System (ADS)

    Kjær, Helle Astrid; Dallmayr, Remi; Gabrieli, Jacopo; Goto-Azuma, Kumiko; Hirabayashi, Motohiro; Svensson, Anders; Vallelonga, Paul

    2016-04-01

    Phosphorus in the atmosphere is poorly studied and thus not much is known about atmospheric phosphorus and phosphate transport and deposition changes over time, though it is well known that phosphorus can be a source of long-range nutrient transport, e.g. Saharan dust transported to the tropical forests of Brazil. In glacial times it has been speculated that transport of phosphorus from exposed shelves would increase the ocean productivity by wash out. However whether the exposed shelf would also increase the atmospheric load to more remote places has not been investigated. Polar ice cores offer a unique opportunity to study the atmospheric transport of aerosols on various timescales, from glacial-interglacial periods to recent anthropogenic influences. We have for the first time determined the atmospheric transport of phosphorus to the Arctic by means of ice core analysis. Both total and dissolved reactive phosphorus were measured to investigate current and past atmospheric transport of phosphorus to the Arctic. Results show that glacial cold stadials had increased atmospheric total phosphorus mass loads of 70 times higher than in the past century, while DRP was only increased by a factor of 14. In the recent period we find evidence of a phosphorus increase over the past 50 yrs in ice cores close to human occupation likely correlated to forest fires. References: Kjær, Helle Astrid, et al. "Continuous flow analysis method for determination of dissolved reactive phosphorus in ice cores." Environmental science & technology 47.21 (2013): 12325-12332. Kjær, Helle Astrid, et al. "Greenland ice cores constrain glacial atmospheric fluxes of phosphorus." Journal of Geophysical Research: Atmospheres120.20 (2015).

  11. PROCESS OF RECOVERING URANIUM

    DOEpatents

    Carter, J.M.; Larson, C.E.

    1958-10-01

    A process is presented for recovering uranium values from calutron deposits. The process consists in treating such deposits to produce an oxidlzed acidic solution containing uranium together with the following imparities: Cu, Fe, Cr, Ni, Mn, Zn. The uranium is recovered from such an impurity-bearing solution by adjusting the pH of the solution to the range 1.5 to 3.0 and then treating the solution with hydrogen peroxide. This results in the precipitation of uranium peroxide which is substantially free of the metal impurities in the solution. The peroxide precipitate is then separated from the solution, washed, and calcined to produce uranium trioxide.

  12. Glacial curvilineations: gradual or catastrophic origin?

    NASA Astrophysics Data System (ADS)

    Clark, Chris; Livingstone, Stephen

    2016-04-01

    Glacial curvilineations (GCLs) are enigmatic landforms that have recently been discovered in Poland (Lesemann et al., 2010, 2014). They comprise parallel sets of sinuous ridges separated by troughs that are found in tunnel valleys and replicate the morphology and pattern of the valley sides. The sedimentology for some has been reported to indicate that the sediment composition relates to a pre-GCL phase. So far just one theory for their formation exists - erosion by longitudinal-vortices within high-energy subglacial meltwater flows (Lesemann et al., 2010). Here, we provide an alternative hypothesis for their formation developed from observations of GCLs found along the southern sector of the Laurentide Ice Sheet. In all cases GCLs were found associated with tunnel valley widenings or hollows and occur as distinct parallel sets that mimic each other in terms of nicks and cusps. Using analogies from tree-rings and coral growth we take such mimicry as indicating either incremental growth or development from a template over time. Although without a strong physical explanation we find it much less likely that a series of parallel water channels would maintain such strong mimicry. We instead suggest that subglacial thawing of frozen ground in association with discrete water bodies (tunnel valleys or subglacial lakes) resulted in retrogressive bank failure, possibly along a glide plane provided by a frozen surface. References: Lesemann, J.-E., Piotrowski, J. a, Wysota, W., 2010. "Glacial curvilineations": New glacial landforms produced by longitudinal vortices in subglacial meltwater flows. Geomorphology 120, 153-161. Lesemann, J.-E., Piotrowski, J. a, Wysota, W., 2014. Genesis of the "glacial curvilineation" landscape by meltwater processes under the former Scandinavian Ice Sheet, Poland. Sediment. Geol. 312, 1-18.

  13. Categorizing ideas about trees: a tree of trees.

    PubMed

    Fisler, Marie; Lecointre, Guillaume

    2013-01-01

    The aim of this study is to explore whether matrices and MP trees used to produce systematic categories of organisms could be useful to produce categories of ideas in history of science. We study the history of the use of trees in systematics to represent the diversity of life from 1766 to 1991. We apply to those ideas a method inspired from coding homologous parts of organisms. We discretize conceptual parts of ideas, writings and drawings about trees contained in 41 main writings; we detect shared parts among authors and code them into a 91-characters matrix and use a tree representation to show who shares what with whom. In other words, we propose a hierarchical representation of the shared ideas about trees among authors: this produces a "tree of trees." Then, we categorize schools of tree-representations. Classical schools like "cladists" and "pheneticists" are recovered but others are not: "gradists" are separated into two blocks, one of them being called here "grade theoreticians." We propose new interesting categories like the "buffonian school," the "metaphoricians," and those using "strictly genealogical classifications." We consider that networks are not useful to represent shared ideas at the present step of the study. A cladogram is made for showing who is sharing what with whom, but also heterobathmy and homoplasy of characters. The present cladogram is not modelling processes of transmission of ideas about trees, and here it is mostly used to test for proximity of ideas of the same age and for categorization.

  14. Recovering plant biodiversity

    PubMed Central

    2011-01-01

    Studying recovering plant biodiversity on Mount Pinatubo may provide valuable insights that improve our understanding of recovery of other ecosystems following disturbances of all types. Ongoing sheet and rill erosion coupled with mass waste events in the unstable pyroclastic flow deposits persist, effectively re-setting primary succession at micro-landscape scale without affecting habitat level diversity. Spatial factors and micro-habitat diversity may exert more control over continued succession as the riparian systems become more deeply dissected and complex. The number of taxa within functional groups and conservation concerns are botanical issues that deserve further research. PMID:22019638

  15. Somma-Vesuvius ground deformation over the last glacial cycle

    NASA Astrophysics Data System (ADS)

    Marturano, Aldo; Aiello, Giuseppe; Barra, Diana

    2013-04-01

    Vertical ground movements at Somma-Vesuvius during the last glacial cycle have been inferred from micropalaeontological and petrochemical analyses of rock samples from boreholes drilled at the archaeological sites of Herculaneum and Pompeii as well as on the apron of the volcano and the adjacent Sebeto and Sarno Valleys. Opposing movements occurred during the periods preceding and following the Last Glacial Maximum (LGM). The uplift began 20 ka ago with marine deposits rising several tens of metres up to 25 m a.s.l., recovering previous subsidence which occurred during the Late glacial period, suggesting a strict connection between volcano-tectonic and glacial cycles. Here we present the analysis of deposits predating the LGM, which confirms subsidence of the Campanian Plain where Mt. Somma-Vesuvius is located, shows variable surface loading effects and highlights the volcano-tectonic stages experienced by the volcano. The self-balancing mechanism of the volcanic system, evolving towards an explosive, subaerial activity 60 ka ago, is testified to by a large ground oscillation in phase with sea level change during the last glacial cycle.

  16. Process for recovering uranium

    DOEpatents

    MacWood, G. E.; Wilder, C. D.; Altman, D.

    1959-03-24

    A process useful in recovering uranium from deposits on stainless steel liner surfaces of calutrons is presented. The deposit is removed from the stainless steel surface by washing with aqueous nitric acid. The solution obtained containing uranium, chromium, nickel, copper, and iron is treated with an excess of ammonium hydroxide to precipitnte the uranium, iron, and chromium and convert the nickel and copper to soluble ammonio complexions. The precipitated material is removed, dried and treated with carbon tetrachloride at an elevated temperature of about 500 to 600 deg C to form a vapor mixture of UCl/ sub 4/, UCl/sub 5/, FeCl/sub 3/, and CrCl/sub 4/. The UCl/sub 4/ is separated from this vapor mixture by selective fractional condensation at a temperature of about 500 to 400 deg C.

  17. PROCESS FOR RECOVERING URANIUM

    DOEpatents

    MacWood, G.E.; Wilder, C.D.; Altman, D.

    1959-03-24

    A process is described for recovering uranium from deposits on stainless steel liner surfaces of calutrons. The deposit is removed from the stainless steel surface by washing with aqueous nitric acid. The solution obtained containing uranium, chromium, nickels copper, and iron is treated with excess of ammonium hydroxide to precipitatc the uranium, irons and chromium and convert thc nickel and copper to soluble ammonia complexions. The precipitated material is removed, dried, and treated with carbon tetrachloride at an elevated temperature of about 500 to 600 deg C to form a vapor mixture of UCl/sub 4/, UCl/sub 5/, FeCl/ sub 3/, and CrCl/sub 4/. The UCl/sub 4/ is separated from this vapor mixture by selective fractional condensation at a temprrature of about 300 to400 deg C.

  18. METHOD OF RECOVERING THORIUM

    DOEpatents

    Fisher, R.W.

    1957-12-10

    A method is described for recovering thorium from impurities found in a slag containing thorium and said impurities, comprising leaching a composition containing thorium with water, removing the water solution, treating the residue with hydrochloric acid, separating the solution from the insoluble residue, adjusting its acidity to 1 to 3 normal, adding oxalic acid, and thereafter separating the precipitated thorium oxalate digesting the residue from the hydrochloric acid treatment with a strong solution of sodium hydroxide at an elevated temperature, removing said solution and treating the insoluble residue with hydrochloric acid, separating the solution from the insoluble residue, adjusting the acidity of this solution to 1 to 3 normal, adding nitric acid to oxidize the iron present, adding oxalic acid and thereafter separating the thorium oxalate thus precipitated.

  19. Effect of low glacial atmospheric CO{sub 2} on tropical African montane vegetation

    SciTech Connect

    Jolly, D.; Haxeltine, A.

    1997-05-02

    Estimates of glacial-interglacial climate change in tropical Africa have varied widely. Results from a process-based vegetation model show how montane vegetation in East Africa shifts with changes in both carbon dioxide concentration and climate. For the last glacial maximum, the change in atmospheric carbon dioxide concentration alone could explain the observed replacement of tropical montane forest by a scrub biome. This result implies that estimates of the last glacial maximum tropical cooling based on tree-line shifts must be revised. 30 refs., 2 figs.

  20. Recover bromine on site

    SciTech Connect

    Schubert, P.; Mahajan, S.; Beatty, R.D.; Rostrup-Nielsen, T.; Schubert, D.W.; Lu, Phat Tan

    1993-04-01

    Chemists have long recognized the importance of recovering bromine from waste streams, and attempts to do so catalytically date back more than 50 years. Although the early interest in bromine recovery was driven primarily by economics, increased environmental pressures are providing additional incentives to recycle this element. As the acceptability of discharging wastes into the environment decreases, the cost of doing so increases, creating a need for alternative handling. The authors interest in waste bromine recovery was driven by both economic and environmental factors. In their evaluation of a research program that included a bromination step as part of a synthesis process, Catalytica researchers found that the process would be feasible commercially only if the waste HBr produced were recycled on site to bromine. A nonbromine route was eventually adopted for this particular research program, but the need for an economical and environmentally sound process for recycling HBr to bromine was recognized. The development of this process became a project in its own right. This process eliminates the need to form and ship aqueous sodium bromide offsite. It converts the waste HBr directly to bromine by catalytic oxidation.

  1. PROCESS OF RECOVERING URANIUM

    DOEpatents

    Kilner, S.B.

    1959-12-29

    A method is presented for separating and recovering uranium from a complex mixure of impurities. The uranium is dissolved to produce an aqueous acidic solution including various impurities. In accordance with one method, with the uranium in the uranyl state, hydrogen cyanide is introduced into the solution to complex the impurities. Subsequently, ammonia is added to the solution to precipitate the uraniunn as ammonium diuranate away from the impurities in the solution. Alternatively, the uranium is precipitated by adding an alkaline metal hydroxide. In accordance with the second method, the uranium is reduced to the uranous state in the solution. The reduced solution is then treated with solid alkali metal cyanide sufficient to render the solution about 0.1 to 1.0 N in cyanide ions whereat cyanide complex ions of the metal impurities are produced and the uranium is simultaneously precipituted as uranous hydroxide. Alternatively, hydrogen cyanide may be added to the reduced solution and the uranium precipitated subsequently by adding ammonium hydroxide or an alkali metal hydroxide. Other refinements of the method are also disclosed.

  2. The last glacial maximum

    USGS Publications Warehouse

    Clark, P.U.; Dyke, A.S.; Shakun, J.D.; Carlson, A.E.; Clark, J.; Wohlfarth, B.; Mitrovica, J.X.; Hostetler, S.W.; McCabe, A.M.

    2009-01-01

    We used 5704 14C, 10Be, and 3He ages that span the interval from 10,000 to 50,000 years ago (10 to 50 ka) to constrain the timing of the Last Glacial Maximum (LGM) in terms of global ice-sheet and mountain-glacier extent. Growth of the ice sheets to their maximum positions occurred between 33.0 and 26.5 ka in response to climate forcing from decreases in northern summer insolation, tropical Pacific sea surface temperatures, and atmospheric CO2. Nearly all ice sheets were at their LGM positions from 26.5 ka to 19 to 20 ka, corresponding to minima in these forcings. The onset of Northern Hemisphere deglaciation 19 to 20 ka was induced by an increase in northern summer insolation, providing the source for an abrupt rise in sea level. The onset of deglaciation of the West Antarctic Ice Sheet occurred between 14 and 15 ka, consistent with evidence that this was the primary source for an abrupt rise in sea level ???14.5 ka.

  3. The role of meltwater in glacial processes

    NASA Astrophysics Data System (ADS)

    Eyles, Nick

    2006-08-01

    Water plays a dominant role in many glacial processes and the erosional, depositional and climatic significance of meltwaters and associated fluvioglacial processes cannot be overemphasized. At its maximum extent c. 20,000 years ago, the volume of the Laurentide ice sheet was 33 × 10 6 km 3 (about the same as the volume of all ice present today on planet Earth). The bulk of this was released as water in little more than 10,000 years. Pulses of meltwater flowing to the Atlantic Ocean from large ice dammed lakes altered thermohaline circulation of the world's oceans and global climate. One such discharge event via Hudson Bay at 8200 years BP released 160,000 km 3 of water in 12 months. Global sea levels recovered from glacial maximum low stands reached at about 20,000 years ago at an average rate of 15 m per thousand years but estimates of shorter term rates suggest as much as 20 m sea level rise in 1000 years and for short periods, rates as high as 4 m per hundred years. Meltwaters played a key role in lubricating ice sheet motion (and thus areal abrasion) across the inner portions of the ice sheet where it slid over rigid crystalline bedrock of the Canadian Shield. The recharge of meltwater into the ice sheets bed was instrumental in generating poorly sorted diamict sediments (till) by sliding-induced shearing and deformation of overpressured sediment and soft rock. The transformation of overpressured till into hyperconcentrated slurries in subglacial channels may have generated a highly effective erosional tool for selective overdeepening and sculpting of bedrock substrates. Some workers credit catastrophic subglacial 'megafloods' with the formation of drumlins and flutes on till surfaces. Subglacial melt river systems were instrumental in reworking large volumes of glaciclastic sediment to marine basins; it has been estimated that less than 6% of the total volume of glaciclastic sediment produced during the Pleistocene remains on land. Fluvioglacial and

  4. Categorizing Ideas about Trees: A Tree of Trees

    PubMed Central

    Fisler, Marie; Lecointre, Guillaume

    2013-01-01

    The aim of this study is to explore whether matrices and MP trees used to produce systematic categories of organisms could be useful to produce categories of ideas in history of science. We study the history of the use of trees in systematics to represent the diversity of life from 1766 to 1991. We apply to those ideas a method inspired from coding homologous parts of organisms. We discretize conceptual parts of ideas, writings and drawings about trees contained in 41 main writings; we detect shared parts among authors and code them into a 91-characters matrix and use a tree representation to show who shares what with whom. In other words, we propose a hierarchical representation of the shared ideas about trees among authors: this produces a “tree of trees.” Then, we categorize schools of tree-representations. Classical schools like “cladists” and “pheneticists” are recovered but others are not: “gradists” are separated into two blocks, one of them being called here “grade theoreticians.” We propose new interesting categories like the “buffonian school,” the “metaphoricians,” and those using “strictly genealogical classifications.” We consider that networks are not useful to represent shared ideas at the present step of the study. A cladogram is made for showing who is sharing what with whom, but also heterobathmy and homoplasy of characters. The present cladogram is not modelling processes of transmission of ideas about trees, and here it is mostly used to test for proximity of ideas of the same age and for categorization. PMID:23950877

  5. Pre-glacial, Early Glacial, and Ice Sheet Stratigraphy Cored During NBP1402, Sabrina Coast, East Antarctic Margin

    NASA Astrophysics Data System (ADS)

    Domack, E. W.; Gulick, S. P. S.; Fernandez-Vasquez, R. A.; Frederick, B.; Lavoie, C.; Leventer, A.; Shevenell, A.; Saustrup, S., Sr.; Bohaty, S. M.; Sangiorgi, F.

    2014-12-01

    Western Wilkes Land provides an unusual setting with regard to passive margin subsidence and exposure of Cenozoic sedimentary units across the continental shelf, due to the unique rift to drift history off of the Australian-Antarctic Discordance and subsequent deep glacial erosion of the evolved continental shelf. The first factor has provided extensive accommodation space for the preservation of stratigraphic sequences that in turn represent critical periods in the climate evolution of Antarctica. Glacial erosion has then provided access to this stratigraphy that is usually inaccessible to all but deep drilling programs. Such stratigraphies are well exposed to within cm of the seafloor off the Sabrina Coast. Cruise NBP1402 investigated this region via a combination of multi-channel seismic imaging and innovative, strategic coring. The geophysical data imaged the geologic evolution of the margin, which exhibits a continuum from non-glacial, partly glaciated, to fully glaciated depo- and erosional systems. Based on the seismic stratigraphy, we collected dredges and one barrel Jumbo Piston Cores (JPCs) across areas of outcropping strata imaged seismically, a unique strategy that allowed us to identify and sample specific reflectors. The stratigraphically deepest coring targeted sections for which the seismic character suggested a pre-glacial context, with non-glaciated continental margin sequences including deltas. Coring recovered dark organic rich siltstones and sandy mudstones, and a large concretion whose center contained a cm-sized plant fossil. In addition, the sediments contain a fossil snail. These fossils provide a glimpse into the pre-glacial terrestrial environment in Antarctica. Overlying this section, coring recovered similar dark siltstones with a 20 cm thick horizon with abundant large angular clasts of variable lithology, interpreted to be ice-rafted debris and indicative of early glacial ice in Antarctica. Finally, JPCs targeting a younger part of

  6. Sub-glacial volcanic eruptions

    USGS Publications Warehouse

    White, Donald Edward

    1956-01-01

    The literature on sub-glacial volcanic eruptions and the related flood phenomena has been reviewed as a minor part of the larger problem of convective and conductive heat transfer from intrusive magma. (See Lovering, 1955, for a review of the extensive literature on this subject.) This summary of data on sub-glacial eruptions is part of a program that the U.S. Geological Survey is conducting in connection with its Investigations of Geologic Processes project on behalf of the Division of Research, U.S. Atomic Energy Commission.

  7. Millennial climatic fluctuations are key to the structure of last glacial ecosystems.

    PubMed

    Huntley, Brian; Allen, Judy R M; Collingham, Yvonne C; Hickler, Thomas; Lister, Adrian M; Singarayer, Joy; Stuart, Anthony J; Sykes, Martin T; Valdes, Paul J

    2013-01-01

    Whereas fossil evidence indicates extensive treeless vegetation and diverse grazing megafauna in Europe and northern Asia during the last glacial, experiments combining vegetation models and climate models have to-date simulated widespread persistence of trees. Resolving this conflict is key to understanding both last glacial ecosystems and extinction of most of the mega-herbivores. Using a dynamic vegetation model (DVM) we explored the implications of the differing climatic conditions generated by a general circulation model (GCM) in "normal" and "hosing" experiments. Whilst the former approximate interstadial conditions, the latter, designed to mimic Heinrich Events, approximate stadial conditions. The "hosing" experiments gave simulated European vegetation much closer in composition to that inferred from fossil evidence than did the "normal" experiments. Given the short duration of interstadials, and the rate at which forest cover expanded during the late-glacial and early Holocene, our results demonstrate the importance of millennial variability in determining the character of last glacial ecosystems.

  8. Extraterrestrial accretion and glacial cycles

    NASA Technical Reports Server (NTRS)

    Muller, R. A.

    1994-01-01

    We propose that the approx. 100-k.y. cycle seen in terrestrial glaciation is due to changes in meteor flux that come from changes in the Earth's orbit. This model can explain a 70-k.y. 'anomalous' period in climate data and the apparent discrepancy between present extraterrestrial fluxes and those in oceanic sediments. It can be tested by measuring Ir densities in sediments and ice during glacials and interglacials.

  9. Personality in recovered depressed elderly.

    PubMed

    Schneider, L S; Zemansky, M F; Bender, M; Sloane, R B

    1992-01-01

    Personality traits in euthymic elderly subjects with and without past histories of major depressive episodes were assessed using the Structured Clinical Interview for DSM-III-R and the Social Adjustment Scale-SR. Recovered depressed subjects were characterized by significantly more personality traits from DSM-III-R Clusters B and C than controls, and they exhibited differences in social adjustment, as well. Subjects who have recovered from depressive episodes may show significant differences in personality and social adjustment that might represent residua of past depression, a trait characteristic, or a risk factor for recurrence.

  10. A new record of post-glacial sedimentation in a glacial trough, offshore sub-Antarctic South Georgia

    NASA Astrophysics Data System (ADS)

    Meisel, Ove; Graham, Alastair; Kuhn, Gerhard

    2014-05-01

    Past studies of South Georgia's climatic history were constrained to land-based sedimentary records, such as peat bogs and coastal lakes, or to terrestrial geomorphology, such as terminal moraines. Hence, the current state of knowledge on past climatic changes in South Georgia is characterised by a complete absence of records from sedimentary marine archives in the fjords or coastal embayments of the region. This study comprises detailed examination of one of the first marine sediment cores recovered on its northeastern shelf in Royal Bay Glacial Trough. Alongside the analysis of new acoustic sub-bottom data, it is the first work to deliver extensive insight into South Georgia's post-glacial climatic history from a marine perspective. The glacial troughs on the South Georgia shelf radiate from the coast towards the shelf edge and represent major sediment traps as they form the only key large-scale depressions in the shelf bathymetry. Sedimentary records, covering a period since at least the Last Glacial Maximum, are thought likely to be recorded in most of them. The sediment core of this study covers sedimentation dated from a maximum of 15,346 ± 492 cal. yr BP until the present day. Physical core parameters indicate a major change in climatic conditions around 14,000 cal. yr BP, the time of the Antarctic Cold Reversal. Holocene climate variabilities are also recorded in the trough infill. The acoustic data show a major change in sedimentation and a pronounced unconformity at the core site, which appears to have had a widespread effect over a large area of the shelf. The origin of the unconformity remains unclear, though several hypotheses, including bottom-current erosion, glacial overriding and earthquake activity, are proposed and discussed. Another important finding at the core site is the presence of methane-derived authigenic carbonates. They form either as secondary precipitates in the subsurface or syndepositional at the seafloor as individual minerals or

  11. Robust 3D Quantification of Glacial Landforms: A Use of Idealised Drumlins in a Real DEM

    NASA Astrophysics Data System (ADS)

    Hillier, J. K.; Smith, M. S.

    2012-04-01

    (-Fm60) removing clutter (e.g. trees and buildings) to estimate a terrain model (DTM) before processing improves ɛh dramatically to 0.412. Mean height (hin) of 6.8 m is then much better recovered at 7.1±0.3 (2σ), as opposed to 12.5 ± 0.6 (2σ) before decluttering. So, guidelines proposed to best quantify mapped glacial landforms are to i) declutter before ii) removing heights within the drumlin, then iii) interpolating to estimate a basal surface using Delauney triangulation. Mapping landforms' outlines from DTMs is not recommended since outlines are shifted by the distortions they contain, inducing errors. The 'synthetic' DEMs used have been demonstrated to be statistically valid, reliably representing reality. So, the optimal isolation method will now be used to assess the drumlins and their populations in the study area. Synthetic DEMs could be readily created to assess a variety of other landforms and other areas.

  12. Humid glacials, arid interglacials? Results from a multiproxy study of the loess-paleosol sequence Crvenka, Serbia

    NASA Astrophysics Data System (ADS)

    Zech, R.; Zech, M.; Markovic, S.; Huang, Y.

    2012-04-01

    The loess-paleosol sequences in the Carpathian Basin, southeast Europe, are up to tens of meters thick and provide valuable archives for paleoenvironmental and -climate change over several glacial-interglacial cycles. The Crvenka section spans the full last glacial cycle and is used in this multi-proxy study to reconstruct past climate conditions. Crvenka features the characteristic pattern in terms of grain size and weathering intensity, i.e. finer grain sizes and more intensive weathering in the paleosols compared to the glacial loess units. The analysis of plant-derived long-chain n-alkanes as molecular biomarkers for past vegetation indicates the presence of trees during glacials, which is consistent with other e.g. macrofossil findings and the notion that parts of southeast Europe served as tree-refugia. However, virtually tree-less grass steppes are reconstructed for the Eemian, the last interglacial. More humid conditions during glacials and more arid conditions during interglacials would be in good agreement with lake-level reconstructions from the Dead Sea, but they seem to be at odds with traditional interpretations of pollen and stable isotope records for the Mediterranean region. In order to further contribute to this issue, we performed compound-specific D/H analyses on the most abundant alkanes C29 and C31, which should mainly record past changes in the isotopic composition of precipitation. The absence of a clear signal towards more depleted values during glacials shows that the temperature-effect is not dominant and probably offset by a strong source-effect, namely the enrichment of the Mediterranean sea water during glacials. This very same source effect may generally need to be taken into account when interpreting terrestrial isotope records in the Mediterranean, which implies that more positive values during glacials may not necessarily indicate an amount-effect and more arid conditions.

  13. Dendroclimatic trend and glacial fluctuations in the Central Italian Alps

    NASA Astrophysics Data System (ADS)

    Pelfini, M.; Santilli, M.; D Agata, C.; Diolaiuti, G.; Smiraglia, C.

    2003-04-01

    In the Alpine environment, one of the main limiting factors for tree growth is the thermal conditions of the vegetative season. The conifers at high altitude, if not subject to others disturbs, such as geomorphological processes or biological interferences, undergo a development, from which the width of annual rings depends. Five chronologies few centuries long, obtained for the species Larix decidua Mill. and Pinus cembra L. from different valleys of the Central Italian Alps (Alpisella, Valfurva, Gavia and Solda) in proximity of timberline (2000-2550 m of altitude), were analysed and their climatic signal gained; this last one was then related to the recent glacial fluctuations. The chronologies are the averages of many dendrochronological indicized curves obtained from dominant trees with regular growth and extended from 13th-17th century up to the present. The time intervals of the chronologies are the following ones: Pinus cembra: 1752-1999 for Valfurva; 1607-1999 for Gavia; 1593-1999 for Val Solda. With regard to Larix decidua: 1252-1998 for Val Solda; 1784-2001 for Alpisella. The good correspondence between the various chronologies allows to consider them representative of the climatic regional signal. In order to evidence climatic evolution, linear trends based on running mean with period of 11 years have been constructed. Those curves have been compared between them and then overlapped and mediated in order to obtain a climatic signal of regional value that excludes eventual local anomalies. Finally, the growth variations in the chronologies have been compared to known alpine climatic variations and glacial fluctuations. In particular time-distance curves (curves of cumulated frontal variations) of some glaciers from the Ortles-Cevedale Group were utilized. The periods of tree rings growth rate reduction appear well correlated to glacial advancing phases of the Little Ice Age and of the following phases. In particular, growth rate reductions are observable

  14. Recovering Zinc From Discarded Tires

    NASA Technical Reports Server (NTRS)

    Du Fresne, E. R.

    1984-01-01

    Zinc sulfate monohydrate sold at profit. Shredded tire material steeped in three sulfuric acid baths to extract zinc. Final product removed by evaporating part of solution until product crystallizes out. Recovered as zinc sulfate monohydrate and sold as fertilizer or for general use.

  15. PROCESS OF RECOVERING ALKALI METALS

    DOEpatents

    Wolkoff, J.

    1961-08-15

    A process is described of recovering alkali metal vapor by sorption on activated alumina, activated carbon, dehydrated zeolite, activated magnesia, or Fuller's earth preheated above the vaporization temperature of the alkali metal and subsequent desorption by heating the solvent under vacuum. (AEC)

  16. Recovering entanglement by local operations

    SciTech Connect

    D’Arrigo, A.; Lo Franco, R.; Benenti, G.; Paladino, E.; Falci, G.

    2014-11-15

    We investigate the phenomenon of bipartite entanglement revivals under purely local operations in systems subject to local and independent classical noise sources. We explain this apparent paradox in the physical ensemble description of the system state by introducing the concept of “hidden” entanglement, which indicates the amount of entanglement that cannot be exploited due to the lack of classical information on the system. For this reason this part of entanglement can be recovered without the action of non-local operations or back-transfer process. For two noninteracting qubits under a low-frequency stochastic noise, we show that entanglement can be recovered by local pulses only. We also discuss how hidden entanglement may provide new insights about entanglement revivals in non-Markovian dynamics.

  17. Methods of recovering alkali metals

    DOEpatents

    Krumhansl, James L; Rigali, Mark J

    2014-03-04

    Approaches for alkali metal extraction, sequestration and recovery are described. For example, a method of recovering alkali metals includes providing a CST or CST-like (e.g., small pore zeolite) material. The alkali metal species is scavenged from the liquid mixture by the CST or CST-like material. The alkali metal species is extracted from the CST or CST-like material.

  18. 15 k.y. paleoclimatic and glacial record from northern New Mexico

    NASA Astrophysics Data System (ADS)

    Armour, Jake; Fawcett, Peter J.; Geissman, John W.

    2002-08-01

    The southern Sangre de Cristo Mountains, New Mexico, contain evidence of glacial activity from the late Pleistocene to late Holocene. Sediment cores recovered from an alpine bog (3100 m) trapped behind a Pinedale age moraine, ˜2 km downvalley from a high-elevation cirque, reached glacial-age debris and recovered ˜6 m of lake clays overlain by gyttja. Accelerator mass spectrometry dating, sedimentology, variations in magnetic properties, and organic carbon data reveal six distinct periods of glacial and/or periglacial activity. These include a late Pleistocene Pinedale glacial termination just before 12120 14C yr B.P., a Younger Dryas chron cirque glaciation, an early Neoglacial periglacial event (ca. 4900 14C yr B.P.), a late Holocene cirque glaciation (3700 14C yr B.P.), as well as late Holocene periglacial events at 2800 14C yr B.P. and the Little Ice Age (ca. 120 14C yr B.P.). Cold events in the middle to late Holocene correlate with subtle ice-rafting events in the North Atlantic and records of cold events in North America and Europe and were probably hemispheric in extent.

  19. Differences in Bacterial Diversity and Communities Between Glacial Snow and Glacial Soil on the Chongce Ice Cap, West Kunlun Mountains

    PubMed Central

    Yang, Guang Li; Hou, Shu Gui; Le Baoge, Ri; Li, Zhi Guo; Xu, Hao; Liu, Ya Ping; Du, Wen Tao; Liu, Yong Qin

    2016-01-01

    A detailed understanding of microbial ecology in different supraglacial habitats is important due to the unprecedented speed of glacier retreat. Differences in bacterial diversity and community structure between glacial snow and glacial soil on the Chongce Ice Cap were assessed using 454 pyrosequencing. Based on rarefaction curves, Chao1, ACE, and Shannon indices, we found that bacterial diversity in glacial snow was lower than that in glacial soil. Principal coordinate analysis (PCoA) and heatmap analysis indicated that there were major differences in bacterial communities between glacial snow and glacial soil. Most bacteria were different between the two habitats; however, there were some common bacteria shared between glacial snow and glacial soil. Some rare or functional bacterial resources were also present in the Chongce Ice Cap. These findings provide a preliminary understanding of the shifts in bacterial diversity and communities from glacial snow to glacial soil after the melting and inflow of glacial snow into glacial soil. PMID:27811967

  20. Differences in Bacterial Diversity and Communities Between Glacial Snow and Glacial Soil on the Chongce Ice Cap, West Kunlun Mountains.

    PubMed

    Yang, Guang Li; Hou, Shu Gui; Le Baoge, Ri; Li, Zhi Guo; Xu, Hao; Liu, Ya Ping; Du, Wen Tao; Liu, Yong Qin

    2016-11-04

    A detailed understanding of microbial ecology in different supraglacial habitats is important due to the unprecedented speed of glacier retreat. Differences in bacterial diversity and community structure between glacial snow and glacial soil on the Chongce Ice Cap were assessed using 454 pyrosequencing. Based on rarefaction curves, Chao1, ACE, and Shannon indices, we found that bacterial diversity in glacial snow was lower than that in glacial soil. Principal coordinate analysis (PCoA) and heatmap analysis indicated that there were major differences in bacterial communities between glacial snow and glacial soil. Most bacteria were different between the two habitats; however, there were some common bacteria shared between glacial snow and glacial soil. Some rare or functional bacterial resources were also present in the Chongce Ice Cap. These findings provide a preliminary understanding of the shifts in bacterial diversity and communities from glacial snow to glacial soil after the melting and inflow of glacial snow into glacial soil.

  1. Decadal-scale climate drivers for glacial dynamics in Glacier National Park, Montana, USA

    USGS Publications Warehouse

    Pederson, G.T.; Fagre, D.B.; Gray, S.T.; Graumlich, L.J.

    2004-01-01

    Little Ice Age (14th-19th centuries A.D.) glacial maxima and 20th century retreat have been well documented in Glacier National Park, Montana, USA. However, the influence of regional and Pacific Basin driven climate variability on these events is poorly understood. We use tree-ring reconstructions of North Pacific surface temperature anomalies and summer drought as proxies for winter glacial accumulation and summer ablation, respectively, over the past three centuries. These records show that the 1850's glacial maximum was likely produced by ???70 yrs of cool/wet summers coupled with high snowpack. Post 1850, glacial retreat coincides with an extended period (>50 yr) of summer drought and low snowpack culminating in the exceptional events of 1917 to 1941 when retreat rates for some glaciers exceeded 100 m/yr. This research highlights potential local and ocean-based drivers of glacial dynamics, and difficulties in separating the effects of global climate change from regional expressions of decadal-scale climate variability. Copyright 2004 by the American Geophysical Union.

  2. Obsidian hydration dates glacial loading?

    PubMed

    Friedman, I; Pierce, K L; Obradovich, J D; Long, W D

    1973-05-18

    Three different groups of hydration rinds have been measured on thin sections of obsidian from Obsidian Cliff, Yellowstone National Park, Wyoming. The average thickness of the thickest (oldest) group of hydration rinds is 16.3 micrometers and can be related to the original emplacement of the flow 176,000 years ago (potassium-argon age). In addition to these original surfaces, most thin sections show cracks and surfaces which have average hydration rind thicknesses of 14.5 and 7.9 micrometers. These later two hydration rinds compare closely in thickness with those on obsidian pebbles in the Bull Lake and Pinedale terminal moraines in the West Yellowstone Basin, which are 14 to 15 and 7 to 8 micrometers thick, respectively. The later cracks are thought to have been formed by glacial loading during the Bull Lake and Pinedale glaciations, when an estimated 800 meters of ice covered the Obsidian Cliff flow.

  3. Obsidian hydration dates glacial loading?

    USGS Publications Warehouse

    Friedman, I.; Pierce, K.L.; Obradovich, J.D.; Long, W.D.

    1973-01-01

    Three different groups of hydration rinds have been measured on thin sections of obsidian from Obsidian Cliff, Yellowstone National Park, Wyoming . The average thickness of the thickest (oldest) group of hydration rinds is 16.3 micrometers and can be related to the original emplacement of the flow 176,000 years ago (potassium-argon age). In addition to these original surfaces, most thin sections show cracks and surfaces which have average hydration rind thicknesses of 14.5 and 7.9 micrometers. These later two hydration rinds compare closely in thickness with those on obsidian pebbles in the Bull Lake and Pinedale terminal moraines in the West Yellowstone Basin, which are 14 to 15 and 7 to 8 micrometers thick, respectively. The later cracks are thought to have been formed by glacial loading during the Bull Lake and Pinedale glaciations, when an estimated 800 meters of ice covered the Obsidian Cliff flow.

  4. Talking Trees

    ERIC Educational Resources Information Center

    Tolman, Marvin

    2005-01-01

    Students love outdoor activities and will love them even more when they build confidence in their tree identification and measurement skills. Through these activities, students will learn to identify the major characteristics of trees and discover how the pace--a nonstandard measuring unit--can be used to estimate not only distances but also the…

  5. Process for recovering actinide values

    DOEpatents

    Horwitz, E. Philip; Mason, George W.

    1980-01-01

    A process for rendering actinide values recoverable from sodium carbonate scrub waste solutions containing these and other values along with organic compounds resulting from the radiolytic and hydrolytic degradation of neutral organophosphorous extractants such as tri-n butyl phosphate (TBP) and dihexyl-N,N-diethyl carbamylmethylene phosphonate (DHDECAMP) which have been used in the reprocessing of irradiated nuclear reactor fuels. The scrub waste solution is preferably made acidic with mineral acid, to form a feed solution which is then contacted with a water-immiscible, highly polar organic extractant which selectively extracts the degradation products from the feed solution. The feed solution can then be processed to recover the actinides for storage or recycled back into the high-level waste process stream. The extractant is recycled after stripping the degradation products with a neutral sodium carbonate solution.

  6. Process for recovering acidic gases

    SciTech Connect

    Riggs, O.L. Jr.

    1989-09-26

    This patent describes an improvement in a continuous process for recovering carbon dioxide from a carbon dioxide-rich gas stream. The gas stream is contacted with an aqueous alknolamine solution in an absorption section contained in an absorption zone to produce a carbon dioxide-lean gaseous overhead stream and a carbon dioxide-rich liquid effluent stream. The carbon dioxide-rich effluent stream is heated in a regeneration zone to produce a carbon dioxide-rich gaseous overhead stream and a carbon dioxide-lean liquid effluent stream. The carbon dioxide-lean liquid effluent stream comprising a regenerated aqueous alkanolamine solution. The regenerated aqueous alkanolamine solution is returned to and introduced into the absorption zone.

  7. METHOD OF RECOVERING URANIUM COMPOUNDS

    DOEpatents

    Poirier, R.H.

    1957-10-29

    S>The recovery of uranium compounds which have been adsorbed on anion exchange resins is discussed. The uranium and thorium-containing residues from monazite processed by alkali hydroxide are separated from solution, and leached with an alkali metal carbonate solution, whereby the uranium and thorium hydrorides are dissolved. The carbonate solution is then passed over an anion exchange resin causing the uranium to be adsorbed while the thorium remains in solution. The uranium may be recovered by contacting the uranium-holding resin with an aqueous ammonium carbonate solution whereby the uranium values are eluted from the resin and then heating the eluate whereby carbon dioxide and ammonia are given off, the pH value of the solution is lowered, and the uranium is precipitated.

  8. Record of glacial Lake Missoula floods in glacial Lake Columbia, Washington

    NASA Astrophysics Data System (ADS)

    Hanson, Michelle A.; Clague, John J.

    2016-02-01

    During the last glaciation (marine oxygen isotope stage 2), outburst floods from glacial Lake Missoula deposited diagnostic sediments within glacial Lake Columbia. Two dominant outburst flood lithofacies are present within glacial Lake Columbia deposits: a flood expansion bar facies and a finer-grained hyperpycnite facies. We conclude that the flood sediments have a glacial Lake Missoula source because: (1) current indicators indicate westward flow through the lake, and upvalley flow followed by downvalley flow in tributary valleys; (2) no flood sediments are found north of a certain point; (3) there is a dominance of Belt-Purcell Supergroup clasts in a flood expansion bar; and (4) some of the finer-grained beds have a pink colour, reflective of glacial Lake Missoula lake-bottom sediments. A new radiocarbon age of 13,400 ± 100 14C BP on plant detritus found below 37 flood beds helps constrain the timing of outburst flooding from glacial Lake Missoula.

  9. Recovering Radioactive Materials with OSRP team

    SciTech Connect

    2008-04-30

    The National Nuclear Security Administration sponsors a program, executed by Los Alamos National Laboratory, to recover radioisotopes used by industry and academia and no longer needed. Called the "Offsite Source Recovery Program (OSRP), it has recovered

  10. Recovering Radioactive Materials with OSRP team

    ScienceCinema

    None

    2016-07-12

    The National Nuclear Security Administration sponsors a program, executed by Los Alamos National Laboratory, to recover radioisotopes used by industry and academia and no longer needed. Called the "Offsite Source Recovery Program (OSRP), it has recovered

  11. Fast Vegetational Responses to Late-Glacial Climate Change

    NASA Astrophysics Data System (ADS)

    Williams, J. W.; Post, D. M.; Cwynar, L. C.; Lotter, A. F.; Levesque, A. J.

    2001-12-01

    How rapidly can natural ecosystems respond to rapid climate change? This question can be addressed by studying paired paleoecological and paleoclimatological records spanning the last deglaciation. Between 16 and 10 ka, abrupt climatic oscillations (e.g. Younger Dryas, Gerzensee/Killarney Oscillations) interrupted the general warming trend. Rates of climate change during these events were as fast or faster than projected rates of change for this century. We compiled a dozen high-resolution lacustrine records in North America and Europe with a pollen record and independent climatic proxy, a clear Younger Dryas signal, and good age control. Cross-correlation analysis suggests that vegetation responded rapidly to late-glacial climate change, with significant changes in vegetation composition occurring within the lifespan of individual trees. At all sites, vegetation lagged climate by less than 200 years, and at two-thirds of the sites, the initial vegetational response occurred within 100 years. The finding of rapid vegetational responses is consistent across sites and continents, and is similar to the 100-200 year response times predicted by gap-scale forest models. Likely mechanisms include 1) increased susceptibility of mature trees to disturbances such as fire, wind, and disease, thereby opening up gaps for colonization, 2) the proximity of these sites to late-glacial treeline, where climate may directly control plant population densities and range limits, 3) the presence of herbaceous taxa with short generation times in these plant communities, and 4) rapid migration due to rare long-distance seed dispersals. Our results are consistent with reports that plant ranges are already shifting in response to recent climate change, and suggest that these shifts will persist for the next several centuries. Widespread changes in plant distributions may affect surface-atmosphere interactions and will challenge attempts to manage ecosystems and conserve biodiversity.

  12. Understanding the glacial methane cycle

    NASA Astrophysics Data System (ADS)

    Hopcroft, Peter O.; Valdes, Paul J.; O'Connor, Fiona M.; Kaplan, Jed O.; Beerling, David J.

    2017-02-01

    Atmospheric methane (CH4) varied with climate during the Quaternary, rising from a concentration of 375 p.p.b.v. during the last glacial maximum (LGM) 21,000 years ago, to 680 p.p.b.v. at the beginning of the industrial revolution. However, the causes of this increase remain unclear; proposed hypotheses rely on fluctuations in either the magnitude of CH4 sources or CH4 atmospheric lifetime, or both. Here we use an Earth System model to provide a comprehensive assessment of these competing hypotheses, including estimates of uncertainty. We show that in this model, the global LGM CH4 source was reduced by 28-46%, and the lifetime increased by 2-8%, with a best-estimate LGM CH4 concentration of 463-480 p.p.b.v. Simulating the observed LGM concentration requires a 46-49% reduction in sources, indicating that we cannot reconcile the observed amplitude. This highlights the need for better understanding of the effects of low CO2 and cooler climate on wetlands and other natural CH4 sources.

  13. Understanding the glacial methane cycle

    PubMed Central

    Hopcroft, Peter O.; Valdes, Paul J.; O'Connor, Fiona M.; Kaplan, Jed O.; Beerling, David J.

    2017-01-01

    Atmospheric methane (CH4) varied with climate during the Quaternary, rising from a concentration of 375 p.p.b.v. during the last glacial maximum (LGM) 21,000 years ago, to 680 p.p.b.v. at the beginning of the industrial revolution. However, the causes of this increase remain unclear; proposed hypotheses rely on fluctuations in either the magnitude of CH4 sources or CH4 atmospheric lifetime, or both. Here we use an Earth System model to provide a comprehensive assessment of these competing hypotheses, including estimates of uncertainty. We show that in this model, the global LGM CH4 source was reduced by 28–46%, and the lifetime increased by 2–8%, with a best-estimate LGM CH4 concentration of 463–480 p.p.b.v. Simulating the observed LGM concentration requires a 46–49% reduction in sources, indicating that we cannot reconcile the observed amplitude. This highlights the need for better understanding of the effects of low CO2 and cooler climate on wetlands and other natural CH4 sources. PMID:28220787

  14. Analysis of recent glacial earthquakes in Greenland

    NASA Astrophysics Data System (ADS)

    Olsen, K.; Nettles, M.

    2015-12-01

    Large calving events at Greenland's outlet glaciers produce teleseismically detectable glacial earthquakes. These events are observed in the seismic record for the past 22 years, but the complete catalog of glacial earthquakes still numbers only ~300. The annual occurrence of these long-period events has increased over time, which makes recent years especially valuable in expanding the global dataset. Glacial earthquakes from 1993- 2010 have been analyzed systematically (Tsai and Ekström, 2007; Veitch and Nettles, 2012). Here, we analyze more recent events using the same centroid—single-force (CSF) approach as previous authors, focusing initially on data from 2013. In addition, we perform a focused study of selected events from 2009-2010 to assess the reliability of the force azimuths obtained from such inversions. Recent spatial and temporal patterns of glacial earthquakes in Greenland differ from those in previous years. In 2013, three times as many events occurred on the west coast as on the east, and these events originated predominantly from two glaciers: Jakobshavn Glacier on the west coast and Helheim Glacier on the east. Kangerdlugssuaq Glacier, on the east coast, produced no glacial earthquakes in 2013, though it produced many events in earlier years. Previous CSF results for glacial earthquakes show force azimuths perpendicular to the glacier front during a calving event, with force plunges near horizontal. However, some azimuths indicate forces initially oriented upglacier, while others are oriented downglacier (seaward). We perform a set of experiments on events from 2009 and 2010 and find two acceptable solutions for each glacial earthquake, oriented 180° apart with plunges of opposite sign and centroid times differing by approximately one half of the assumed duration of the earthquake time function. These results suggest the need for a more complex time function to model glacial earthquakes more accurately.

  15. A fresh look at glacial foods

    USGS Publications Warehouse

    Colman, Steven M.

    2002-01-01

    Over the last 20 years, it has become clear that ice ages are characterized by glacial as well as climatic instability on millennial time scales. In his Perspective, Colman highlights two recent papers investigating the role of glacial meltwater and continental drainage in this instability. The results suggest a fundamental instability feedback between ocean circulation and ice sheet dynamics and provides an explanation for why instability was greatest at times of intermediate ice volume.

  16. Nutrient Dynamics in the Glacial Southern Ocean

    NASA Astrophysics Data System (ADS)

    Latimer, J. C.; Filippelli, G. M.

    2004-12-01

    The Southern Ocean (SO) was likely a key contributor to glacial/interglacial climate change resulting from variability either in biogeochemical cycles or ocean stratification and CO2 degassing. Many of the hypotheses to explain the interglacial to glacial difference in atmospheric CO2 suggest that higher glacial dust fluxes led to Fe fertilization of surface waters and increased export production in the SO because the modern-day Southern Ocean is co-limited by both Fe and light availability. Documented Fe sources include upwelled Upper Circumpolar Deep Water, eolian deposition, and melting sea-ice. However, the influence of these sources is variable with latitude and position relative to major frontal zones. Presumably these same Fe sources were important during glacial times albeit at potentially different rates and magnitudes. To examine this effect, we have compared sedimentary Fe fluxes with records of dust deposition. We have found that Fe fluxes are higher than can be explained by eolian deposition, supporting an additional hemipelagic source of Fe to the deep ocean during glacial intervals. Furthermore, different proxies used to evaluate export production and nutrient utilization during glacial intervals yield different and seemingly contradictory results-for example, different studies have concluded that net productivity increased, decreased, and/or remained constant in the SO. Results from phosphorus geochemistry suggest that maxima in export production actually occur at terminations rather than either full glacial or interglacial conditions adding yet another possibility. The focus here will be to try to reconcile the nutrient, export production, and Fe data into a coherent view of nutrient utilization and export production in the glacial SO.

  17. Last Glacial vegetation and climate change in the southern Levant

    NASA Astrophysics Data System (ADS)

    Miebach, Andrea; Chen, Chunzhu; Litt, Thomas

    2015-04-01

    limiting factor for tree growth was precipitation. Consequently, the precipitation gradient was not as strong as today, and semiarid conditions prevailed in the southern Levant during the Last Glacial. Our study will contribute to the overall aim to reconstruct the way of modern humans to Europe and to understand the complex connection between climate and vegetation change in the Eastern Mediterranean.

  18. Subglacial morphology and glacial evolution of the Palmer deep outlet system, Antarctic Peninsula

    NASA Astrophysics Data System (ADS)

    Domack, Eugene; Amblàs, David; Gilbert, Robert; Brachfeld, Stefanie; Camerlenghi, Angelo; Rebesco, Michele; Canals, Miquel; Urgeles, Roger

    2006-04-01

    The Palmer Deep is an erosional, inner-shelf trough located at the convergence of ice flow from three distinct accumulation centers. It served as a funnel for ice flow out across the continental shelf of the Antarctic Peninsula. Swath mapping of 1440 km 2 of seafloor in and adjacent to the Palmer Deep basin defines a large paleo-ice stream that flowed 230 km across the Antarctic Peninsula continental shelf during the Last Glacial Maximum (MIS-2). The unique perspective and detail of the Palmer Deep physiography allow us to recognize several phases of erosion and deposition in the outlet basin. These events are uniquely constrained by two ODP drill cores (sites 1099 and 1098) that together recovered over 150 m of latest Pleistocene and Holocene sediment. We divide this region of the continental shelf into three zones based upon mega- to meso-scale bathymetric features and emphasize that all three were part of one glacial outlet during the most recent period of glaciation. These zones include from inner shelf to outer shelf: the Palmer Deep basin, the Palmer Deep Outlet Sill and the Hugo Island Trough. Specific seafloor features associated with these zones include: relict terraces, sub-glacial lake deltas, channels and levees, debris slopes, spindle and out bed forms, mega-scale glacial lineations, morainal banks, and bank breach points. The origin of many of these features can be linked to the development of a sub-glacial lake basin within the Palmer Deep during or prior to MIS-2, its subsequent drainage, and recession of the Palmer Deep ice stream system. This sub-glacial lake system is reconstructed at the head of a major paleo-ice stream.

  19. Paleoclimate of northern Guatemala during the Last Glacial Cycle

    NASA Astrophysics Data System (ADS)

    Hodell, D. A.; Anselmetti, F.; Ariztegui, D.; Brenner, M.; Curtis, J.; Gilli, A.; Mueller, A.

    2006-12-01

    Lake Peten Itza (zmax = 165 m) in northern Guatemala is the deepest lake in the lowlands of Central America. Annual rainfall averages ~1600 mm and is highly seasonal with over 90% occurring in the months from May to October. As part of an ICDP project, we recovered 1327 m of lake sediment at seven sites using the GLAD800 superbarge. Preliminary research has focused on Site PI-6 at a water depth of 71 m. Three holes were drilled and recovered a complete stratigraphic section to a maximum depth of 75.9 mblf. Radiocarbon dates on terrestrial organic matter display a regular increase in age with depth, and indicate a mean sedimentation rate of ~100 cm per 1000 yrs (1mm/yr). The top 10.8 mcd were deposited during the Holocene and consist primarily of gray carbonate clay with abundant charcoal. The Pleistocene/Holocene boundary at 10.8 mcd is marked by a transition to Holocene clay from underlying, interbedded dense gypsum sand and clay deposited during the Late Glacial period from ~17 to 9.3 kyrs. This transition represents a switch to moist climate during the early Holocene from more arid conditions during the Late Glacial. Arid conditions during the Late Glacial period may coincide with episodic delivery of seasonal meltwater to the Gulf of Mexico (Aharon, 2003, Paleoceanography, 18, 1079). In contrast to the Late Glacial period, the earlier Last Glacial Maximum (LGM), from 23 to 17 kyrs, consists of gray carbonate clay that is very similar to Holocene deposits, suggesting high detrital input and high lake level. This finding contradicts previous results suggesting that the LGM was dry in the Peten lowlands. We speculate that a cold, wet LGM may have been caused by increased winter precipitation when the Laurentide Ice Sheet (LIS) was at its southernmost extent. The mechanism may have been related to increased frequency of polar outbreaks and "Norte" winds, which occasionally bring rain to the Peten today during the dry season. Similar increases in winter

  20. Phytoremediation of 1,4-dioxane-containing recovered groundwater.

    PubMed

    Ferro, Ari M; Kennedy, Jean; LaRue, James C

    2013-01-01

    The results of a pilot-scale phytoremediation study are reported in this paper. Small plots of trees established on a closed municipal waste landfill site were irrigated with recovered groundwater containing 1,4-dioxane (dioxane) and other volatile organic compounds (VOCs). The plots were managed to minimize the leaching of irrigation water, and leaching was quantified by the use of bromide tracer. Results indicated that the dioxane (2.5 microg/L) was effectively removed, probably via phytovolatilization, and that a full-scale phytoremediation system could be used. A system is now in place at the site in which the recovered groundwater can be treated using two different approaches. A physical treatment system (PTS) will be used during the winter months, and a 12 ha phytoremediation system (stands of coniferous trees) will be used during the growing season. The PTS removes VOCs using an air-stripper, and destroys dioxane using a photo-catalytic oxidation process. Treated water will be routed to the local sewer system. The phytoremediation system, located on the landfill, will be irrigated with effluent from the PTS air-stripper containing dioxane. Seasonal use of the phytoremediation system will reduce reliance on the photo-catalytic oxidation process that is extremely energy consumptive and expensive to operate.

  1. Grassland Vegetation in the Southern Great Plains during the Last Glacial Maximum

    NASA Astrophysics Data System (ADS)

    Hall, Stephen A.; Valastro, Salvatore

    1995-09-01

    New pollen records from White Lake in the Southern High Plains and from Friesenhahn Cave on the southeastern Edwards Plateau of Texas indicate that the glacial-age vegetation of the southern Great Plains was a grassland. The High Plains was a treeless Artemisia grassland and the Edwards Plateau, at the south edge of the Great Plains, was a grassland with pinyon pines and deciduous trees in canyons and riparian habitats. The glacial-age grasslands differ from modern shortgrass and tallgrass prairies and may have no modern analog. The dominance of prairie vegetation during the last glacial maximum is compatible with late Pleistocene mammalian faunas and late-glacial grassland pollen records from the region. Earlier interpretations of a pine-spruce forest on the High Plains were based on pollen assemblages that are here shown to have been altered by postdepositional deterioration, resulting in differential preservation of conifer pollen grains. Accordingly, the "Tahoka Pluvial" and other "climatic episodes" defined by High Plains pollen records are abandoned.

  2. Association of Macroposthonia xenoplax and Scutellonema brachyurum with the Peach Tree Short Life Syndrome

    PubMed Central

    Nesmith, W. C.; Zehr, E. I.; Dowler, W. M.

    1981-01-01

    High populations of both Scutellonema brachyurum and Macroposthonia xenoplax were detected in the root zones of peach trees growing at sites where peach tree short life occurred. Both nematodes responded to changes in tree health, with the highest numbers detected under the most vigorous trees; both populations declined as tree vigor declined. Few of either species were detected 6 months after trees died. The nematode populations were inversely correlated with each other. More M. xenoplax were recovered during cool, wet weather, but moisture seems more important than temperature in influencing population levels. Most S. brachyurum were recovered during hot, dry weather. PMID:19300749

  3. Late Glacial to Holocene paleoenvironmental change on the northwestern Pacific seaboard, Kamchatka Peninsula (Russia)

    NASA Astrophysics Data System (ADS)

    Pendea, Ionel Florin; Ponomareva, Vera; Bourgeois, Joanne; Zubrow, Ezra B. W.; Portnyagin, Maxim; Ponkratova, Irina; Harmsen, Hans; Korosec, Gregory

    2017-02-01

    We used a new sedimentary record from a small kettle wetland to reconstruct the Late Glacial and Holocene vegetation and fire history of the Krutoberegovo-Ust Kamchatsk region in eastern Kamchatka Peninsula (Russia). Pollen and charcoal data suggest that the Late Glacial landscape was dominated by a relatively fire-prone Larix forest-tundra during the Greenland Interstadial complex (GI 1) and a subarctic steppe during the Younger Dryas (GS1). The onset of the Holocene is marked by the reappearance of trees (mainly Alnus incana) within a fern and shrub dominated landscape. The Holocene Thermal Maximum (HTM) features shifting vegetational communities dominated by Alnus shrubs, diverse forb species, and locally abundant aquatic plants. The HTM is further defined by the first appearance of stone birch forests (Betula ermanii) - Kamchatka's most abundant modern tree species. The Late Holocene is marked by shifts in forest dynamics and forest-graminoid ratio and the appearance of new non-arboreal taxa such as bayberry (Myrica) and meadow rue (Filipendula). Kamchatka is one of Earth's most active volcanic regions. During the Late Glacial and Holocene, Kamchatka's volcanoes spread large quantities of tephra over the study region. Thirty-four tephra falls have been identified at the site. The events represented by most of these tephra falls have not left evidence of major impacts on the vegetation although some of the thicker tephras caused expansion of grasses (Poaceae) and, at least in one case, forest die-out and increased fire activity.

  4. Sources of glacial moisture in Mesoamerica

    USGS Publications Warehouse

    Bradbury, J.P.

    1997-01-01

    Paleoclimatic records from Mesoamerica document the interplay between Atlantic and Pacific sources of precipitation during the last glacial stage and Holocene. Today, and throughout much of the Holocene, the entire region receives its principal moisture in the summer from an interaction of easterly trade winds with the equatorial calms. Glacial records from sites east of 95?? W in Guatemala, Florida, northern Venezuela and Colombia record dry conditions before 12 ka, however. West of 95?? W, glacial conditions were moister than in the Holocene. For example, pollen and diatom data show that Lake Pa??tzcuaro in the central Mexican highlands was cool, deep and fresh during this time and fossil pinyon needles in packrat middens in Chihuahua, Sonora, Arizona, and Texas indicate cooler glacial climates with increased winter precipitation. Cold Gulf of Mexico sea-surface temperatures and reduced strength of the equatorial calms can explain arid full and late glacial environments east of 95?? W whereas an intensified pattern of winter, westerly air flow dominated hydrologic balances as far south as 20?? N. Overall cooler temperatures may have increased effective moisture levels during dry summer months in both areas. ?? 1997 INQUA/ Elsevier Science Ltd.

  5. Last Glacial loess in the conterminous USA

    USGS Publications Warehouse

    Bettis, E. Arthur; Muhs, Daniel R.; Roberts, Helen M.; Wintle, Ann G.

    2003-01-01

    The conterminous United States contains an extensive and generally well-studied record of Last Glacial loess. The loess occurs in diverse physiographic provinces, and under a wide range of climatic and ecological conditions. Both glacial and non-glacia lloess sources are present, and many properties of the loess vary systematically with distance from loess sources. United States' mid-continent Last Glacial loess is probably the thickest in the world, and our calculated mass accumulation rates (MARs) are as high as 17,500 g/m2/yr at the Bignell Hill locality in Nebraska, and many near-source localities have MARs greater than 1500 g/m2/yr. These MARs are high relative to rates calculated in other loess provinces around the world. Recent models of LastGlacial dust sources fail to predict the extent and magnitude of dust flux from the mid-continent of the United States. A better understanding of linkages between climate, ice sheet behaviour, routing of glacial meltwater, land surface processes beyond the ice margin, and vegetation is needed to improve the predictive capabilities of models simulating dust flux from this region.

  6. Glacial-interglacial organic carbon record from the Makassar Strait, Indonesia: Implications for regional changes in continental vegetation

    USGS Publications Warehouse

    Visser, K.; Thunell, R.; Goni, M.A.

    2004-01-01

    Recent studies convincingly show that climate in the Western Pacific Warm Pool and other equatorial/tropical regions was significantly colder (by ???3-4??C) during glacial periods, prompting a reexamination of the late Pleistocene paleoenvironments of these regions. This study examines changes in continental vegetation during the last two deglaciations (Terminations I and II) using a sediment core (MD9821-62) recovered from the Makassar Strait, Indonesia. Evidence based on the lignin phenol ratios suggests that vegetation on Borneo and other surrounding islands did not significantly change from tropical rainforest during the last two glacial periods relative to subsequent interglacial periods. This supports the hypothesis that the winter monsoon increased in strength during glacial periods, allowing Indonesia to maintain high rainfall despite the cooler conditions. ?? 2003 Elsevier Ltd. All rights reserved.

  7. Audubon Tree Study Program.

    ERIC Educational Resources Information Center

    National Audubon Society, New York, NY.

    Included are an illustrated student reader, "The Story of Trees," a leaders' guide, and a large tree chart with 37 colored pictures. The student reader reviews several aspects of trees: a definition of a tree; where and how trees grow; flowers, pollination and seed production; how trees make their food; how to recognize trees; seasonal changes;…

  8. Glacial stages and post-glacial environmental evolution in the Upper Garonne valley, Central Pyrenees.

    PubMed

    Fernandes, M; Oliva, M; Palma, P; Ruiz-Fernández, J; Lopes, L

    2017-04-15

    The maximum glacial extent in the Central Pyrenees during the Last Glaciation is known to have occurred before the global Last Glacial Maximum, but the succession of cold events afterwards and their impact on the landscape are still relatively unknown. This study focuses on the environmental evolution in the upper valley of the Garonne River since the Last Glaciation. Geomorphological mapping allows analysis of the spatial distribution of inherited and current processes and landforms in the study area. The distribution of glacial records (moraines, till, erratic boulders, glacial thresholds) suggests the existence of four glacial stages, from the maximum expansion to the end of the glaciation. GIS modeling allows quantification of the Equilibrium Line Altitude, extent, thickness and volume of ice in each glacial stage. During the first stage, the Garonne glacier reached 460m in the Loures-Barousse-Barbazan basin, where it formed a piedmont glacier 88km from the head and extended over 960km(2). At a second stage of glacier stabilization during the deglaciation process, the valley glaciers were 12-23km from the head until elevations of 1000-1850m, covering an area of 157km(2). Glaciers during stage three remained isolated in the upper parts of the valley, at heights of 2050-2200m and 2.6-4.5km from the head, with a glacial surface of 16km(2). In stage four, cirque glaciers were formed between 2260m and 2590m, with a length of 0.4-2km and a glacial area of 5.7km(2). Also, the wide range of periglacial, slope, nival and alluvial landforms existing in the formerly glaciated environments allows reconstruction of the post-glacial environmental dynamics in the upper Garonne basin. Today, the highest lands are organized following three elevation belts: subnival (1500-1900m), nival (1900-2300m) and periglacial/cryonival (2300-2800m).

  9. Tree harvesting

    SciTech Connect

    Badger, P.C.

    1995-12-31

    Short rotation intensive culture tree plantations have been a major part of biomass energy concepts since the beginning. One aspect receiving less attention than it deserves is harvesting. This article describes an method of harvesting somewhere between agricultural mowing machines and huge feller-bunchers of the pulpwood and lumber industries.

  10. Recovering Radioactive Materials with ORSP Team

    ScienceCinema

    LANL

    2016-07-12

    The National Nuclear Security Administration sponsors a program, executed by Los Alamos National Laboratory, to recover radioisotopes used by industry and academia and no longer needed. Called the "Offsite Source Recovery Program (OSRP), it has recovered more than 16,000 orphan sources as of 2008.

  11. Impact of CO2 and climate on Last Glacial maximum vegetation - a factor separation

    NASA Astrophysics Data System (ADS)

    Claussen, M.; Selent, K.; Brovkin, V.; Raddatz, T.; Gayler, V.

    2013-06-01

    The factor separation of Stein and Alpert (1993) is applied to simulations with the MPI Earth system model to determine the factors which cause the differences between vegetation patterns in glacial and pre-industrial climate. The factors firstly include differences in the climate, caused by a strong increase in ice masses and the radiative effect of lower greenhouse gas concentrations; secondly, differences in the ecophysiological effect of lower glacial atmospheric CO2 concentrations; and thirdly, the synergy between the pure climate effect and the pure effect of changing physiologically available CO2. It is has been shown that the synergy can be interpreted as a measure of the sensitivity of ecophysiological CO2 effect to climate. The pure climate effect mainly leads to a contraction or a shift in vegetation patterns when comparing simulated glacial and pre-industrial vegetation patterns. Raingreen shrubs benefit from the colder and drier climate. The pure ecophysiological effect of CO2 appears to be stronger than the pure climate effect for many plant functional types - in line with previous simulations. The pure ecophysiological effect of lower CO2 mainly yields a reduction in fractional coverage, a thinning of vegetation and a strong reduction in net primary production. The synergy appears to be as strong as each of the pure contributions locally, but weak on global average for most plant functional types. For tropical evergreen trees, however, the synergy is strong on global average. It diminishes the difference between glacial and pre-industrial coverage of tropical evergreen trees, due to the pure climate effect and the pure ecophysiological CO2 effect, by approximately 50 per cent.

  12. Two middle Pleistocene glacial-interglacial cycles from the Valle Grande, Jemez Mountains, northern New Mexico

    USGS Publications Warehouse

    Fawcett, Peter J.; Heikoop, Jeff; Goff, Fraser; Anderson, R. Scott; Donohoo-Hurley, L.; Geissman, John William; WoldeGabriel, Giday; Allen, Craig D.; Johnson, Catrina M.; Smith, Susan J.; Fessenden-Rahn, Julianna

    2006-01-01

    A long-lived middle Pleistocene lake formed in the Valle Grande, a large moat valley of the Valles caldera in northern New Mexico, when a post-caldera eruption (South Mountain rhyolite) dammed the drainage out of the caldera. The deposits of this lake were cored in May 2004 (GLAD5 project, hole VC-3) and 81 m of mostly lacustrine silty mud were recovered. A tentative chronology has been established for VC-3 with a basal tephra Ar-Ar date of 552 +/- 3 ka, a correlation of major climatic changes in the core with other long Pleistocene records (deep sea oxygen isotope records and long Antarctic ice core records), and the recognition of two geomagnetic field polarity events in the core which can be correlated with globally recognized events. This record spans a critical interval of the middle Pleistocene from MIS 14 (552 ka) to MIS 10 (~360 ka), at which time the lacustrine sediments filled the available accommodation space in the caldera moat. Multiple analyses, including core sedimentology and stratigraphy, sediment density and rock magnetic properties, organic carbon content and carbon isotope ratios, C/N ratios, and pollen content reveal two glacial/interglacial cycles in the core (MIS 14 to MIS 10). This record includes glacial terminations V and VI and complete sections spanning interglacials MIS 13 and MIS 11. In the VC-3 record, both of these interglacials are relatively long compared with the intervening glacials (MIS 14 and MIS 12), and interglacial MIS 13 is significantly muted in amplitude compared with MIS 11. These features are similar to several other mid-Pleistocene records. The glacial terminations are quite abrupt in this record with notable changes in sedimentation, organic carbon content, C/N ratios and watershed vegetation type. Termination V is the largest climate change evident in this part of the middle Pleistocene. The glacial inceptions tend to be more gradual, on the order of a few thousand years.

  13. Abrupt climate and vegetation variability of eastern Anatolia during the last glacial

    NASA Astrophysics Data System (ADS)

    Pickarski, N.; Kwiecien, O.; Langgut, D.; Litt, T.

    2015-11-01

    Detailed analyses of the Lake Van pollen, Ca / K ratio, and stable oxygen isotope record allow the identification of millennial-scale vegetation and environmental changes in eastern Anatolia throughout the last glacial (~ 111.5-11.7 ka BP). The climate of the last glacial was cold and dry, indicated by low arboreal pollen (AP) levels. The driest and coldest period corresponds to Marine Isotope Stage (MIS) 2 (~ 28-14.5 ka BP), which was dominated by highest values of xerophytic steppe vegetation. Our high-resolution multi-proxy record shows rapid expansions and contractions of tree populations that reflect variability in temperature and moisture availability. These rapid vegetation and environmental changes can be related to the stadial-interstadial pattern of Dansgaard-Oeschger (DO) events as recorded in the Greenland ice cores. Periods of reduced moisture availability were characterized by enhanced occurrence of xerophytic species and high terrigenous input from the Lake Van catchment area. Furthermore, the comparison with the marine realm reveals that the complex atmosphere-ocean interaction can be explained by the strength and position of the westerlies, which are responsible for the supply of humidity in eastern Anatolia. Influenced by the diverse topography of the Lake Van catchment, more pronounced DO interstadials (e.g., DO 19, 17-16, 14, 12 and 8) show the strongest expansion of temperate species within the last glacial. However, Heinrich events (HE), characterized by highest concentrations of ice-rafted debris (IRD) in marine sediments, cannot be separated from other DO stadials based on the vegetation composition in eastern Anatolia. In addition, this work is a first attempt to establish a continuous microscopic charcoal record for the last glacial in the Near East. It documents an immediate response to millennial-scale climate and environmental variability and enables us to shed light on the history of fire activity during the last glacial.

  14. Cosmogenic 10Be constraints on Little Ice Age glacial advances in the eastern Tian Shan, China

    NASA Astrophysics Data System (ADS)

    Li, Yanan; Li, Yingkui; Harbor, Jon; Liu, Gengnian; Yi, Chaolu; Caffee, Marc W.

    2016-04-01

    Presumed Little Ice Age (LIA) glacial advances, represented by a set of fresh, sharp-crested, boulder covered and compact moraines a few hundred meters downstream from modern glaciers, have been widely recognized in the Central Asian highlands. However, few studies have constrained the formation ages of these moraines. We report 31 10Be exposure ages from presumed LIA moraines in six glacial valleys in the Urumqi River headwater area and the Haxilegen Pass area of the eastern Tian Shan, China. Our results reveal that the maximum LIA glacial extent occurred mainly around 430 ± 100 yr, a cold and wet period as indicated by proxy data from ice cores, tree rings, and lake sediments in Central Asia. We also dated a later glacial advance to 270 ± 55 yr. However, 10Be exposure ages on several presumed LIA moraines in front of small, thin glaciers are widely scattered and much older than the globally recognized timing of the LIA. Historical topographic maps indicate that most glaciers were more extensive in the early 1960s, and two of our 10Be sample sites were located close to the ice front at that time. Boulders transported by these small and thin glaciers may be reworked from deposits originally formed prior to the LIA glacial advances, producing apparently old and widely scattered exposure ages due to varied nuclide inheritance. Other published ages indicated an earlier LIA advance around 790 ± 300 yr in the easternmost Tian Shan, but in our study area the more extensive advance around 430 ± 100 yr likely reworked or covered deposits from this earlier event.

  15. Late glacial aridity in southern Rocky Mountains

    SciTech Connect

    Davis, O.K.; Pitblado, B.L.

    1995-09-01

    While the slopes of the present-day Colorado Rocky Mountains are characterized by large stands of subalpine and montane conifers, the Rockies of the late glacial looked dramatically different. Specifically, pollen records suggest that during the late glacial, Artemisia and Gramineae predominated throughout the mountains of Colorado. At some point between 11,000 and 10,000 B.P., however, both Artemisia and grasses underwent a dramatic decline, which can be identified in virtually every pollen diagram produced for Colorado mountain sites, including Como Lake (Sangre de Cristo Mountains), Copley Lake and Splains; Gulch (near Crested Butte), Molas Lake (San Juan Mountains), and Redrock Lake (Boulder County). Moreover, the same pattern seems to hold for pollen spectra derived for areas adjacent to Colorado, including at sites in the Chuska Mountains of New Mexico and in eastern Wyoming. The implications of this consistent finding are compelling. The closest modem analogues to the Artemisia- and Gramineae-dominated late-glacial Colorado Rockies are found in the relatively arid northern Great Basin, which suggests that annual precipitation was much lower in the late-glacial southern Rocky Mountains than it was throughout the Holocene.

  16. The latest LGM culmination of the Garda Glacier (Italian Alps) and the onset of glacial termination. Age of glacial collapse and vegetation chronosequence

    NASA Astrophysics Data System (ADS)

    Ravazzi, Cesare; Pini, Roberta; Badino, Federica; De Amicis, Mattia; Londeix, Laurent; Reimer, Paula J.

    2014-12-01

    In the deglacial sequence of the largest end moraine system of the Italian Alps, we focused on the latest culmination of the Last Glacial Maximum, before a sudden downwasting of the piedmontane lobe occupying the modern lake basin. We obtained a robust chronology for this culmination and for the subsequent deglacial history by cross-radiocarbon dating of a proximal fluvioglacial plain and of a deglacial continuous lake sedimentation. We used reworked dinocysts to locate sources of glacial abrasion and to mark the input of glacial meltwater until depletion. The palynological record from postglacial lake sediments provided the first vegetation chronosequence directly reacting to the early Lateglacial withdrawal so far documented in the Alps. Glacier collapse occurred soon after 17.46 ± 0.2 ka cal BP, which is, the Manerba advance culmination. Basin deglaciation of several overdeepened foreland piedmont lakes on southern and northern sides of the Alps appears to be synchronous at millennial scale and near-synchronous with large-scale glacial retreat at global scale. The pioneering succession shows a first afforestation step at a median modeled age of 64 years after deglaciation, while rapid tree growth lagged 7 centuries. Between 16.4 ± 0.16 and 15.5 ± 0.16 ka cal BP, a regressive phase interrupted forest growth marking a Lateglacial phase of continental-dry climate predating GI-1. This event, spanning the most advanced phases of North-Atlantic H1, is consistently radiocarbon-framed at three deglacial lake records so far investigated on the Italian side of the Alps. Relationships with the Gschnitz stadial from the Alpine record of Lateglacial advances are discussed.

  17. Glacial Lake Lind, Wisconsin and Minnesota

    USGS Publications Warehouse

    Johnson, M.D.; Addis, K.L.; Ferber, L.R.; Hemstad, C.B.; Meyer, G.N.; Komai, L.T.

    1999-01-01

    Glacial Lake Lind developed in the pre-late Wisconsinan St. Croix River valley, Minnesota and Wisconsin, and lasted more than 1000 yr during the retreat of the Superior lobe at the end of the Wisconsinan glaciation. Lake Lind sediment consists primarily of red varved silt and clay, but also includes mud-flow deposits, nearshore silt (penecontemporaneously deformed in places), nearshore rippled sand, and deltaic sand. Lake Lind varved red clay is not part of glacial Lake Grantsburg, as suggested by earlier authors, because the red varves are separated from overlying glacial Lake Grantsburg silt and clay by a unit of deltaic and fluvial sand. Furthermore, varve correlations indicate that the base of the red varves is younger to the north, showing that the basin expanded as the Superior lobe retreated and was not a lake basin dammed to the southwest by the advancing Grantsburg sublobe. Varve correlations indicate that the Superior lobe retreated at a rate of about 200 m/yr. Uniform winter-clay thickness throughout most of the varve couplets suggests thermal stratification in the lake with clay trapped in the epilimnion; some clay would exit the lake at the outlet prior to winter freeze. Zones of thicker winter-clay layers, in places associated with mud-flow layers, indicate outlet incision, lake-level fall, and shoreline erosion and resuspension of lake clay. The most likely outlet for glacial Lake Lind was in the southwest part of the lake near the present site of Minneapolis, Minnesota. Nearshore sediment indicates that the lake level of glacial Lake Lind was around 280 m. The elevation of the base of the Lake Lind sediments indicates water depth was 20 to 55 m. Evidence in the southern part of the lake basin suggests that the Superior lobe readvanced at least once during the early stages of glacial Lake Lind. Lake Lind ended not by drainage but by being filled in by prograding deltas and outwash plains composed of sand derived from the retreating Superior lobe. It

  18. Glacial influence on caldera-forming eruptions

    NASA Astrophysics Data System (ADS)

    Geyer, Adelina; Bindeman, Ilya

    2011-04-01

    It has been suggested that deglaciations have influenced volcanism in several areas around the world increasing productivity of mantle melting and eruptions from crustal magma chambers. However, the connection between glaciations and increased volcanism is not straightforward. Investigation of Ar-Ar, U-Pb, and 14C ages of caldera-forming eruptions for the past million years in the glaciated arc of Kamchatka has lead to the observation that the majority of large-volume ignimbrites, which are associated with the morphologically preserved calderas, correspond in time with "maximum glacial" conditions for the past several glacial cycles. In the field, the main proof is related to the fact that glaciated multi-caldera volcanoes hosted thick glacial ice caps. Additional evidence comes from clustering Kamchatka-derived marine ash layers with glacial moraines in DSDP cores. Here we present a set of new results from numerical modelling using the Finite Element Method that investigate how the glacial load dynamic may affect the conditions for ring-fault formation in such glaciated multi-caldera volcanoes. Different scenarios were simulated by varying: (1) the thickness and asymmetric distribution of the existing ice cap, (2) the depth and size of the magmatic reservoir responsible for the subsequent collapse event, (3) the thickness and mechanical properties of the roof rock due to the alteration by hydrothermal fluids, (4) the existence of a deeper and wider magmatic reservoir and (5) possible gravitational failure triggered, in part, by subglacial rock mass build up and hydrothermal alteration. The results obtained indicate that: (1) Any ice cap plays against ring fault formation; (2) Asymmetric distribution of ice may favour the initiation of trap-door type collapse calderas; (3) Glacial erosion of part of volcanic edifice or interglacial edifice failure may facilitate subsequent ring fault formation; (4) hydrothermal system under an ice cap may lead to a quite effective

  19. Surveying Dead Trees and CO2-Induced Stressed Trees Using AVIRIS in the Long Valley Caldera

    NASA Technical Reports Server (NTRS)

    deJong, Steven M.

    1996-01-01

    background of glacial deposits and crystalline rocks. The dead tree areas are located on the flanks of Mammoth Mountain (N:37 deg 37' 45" and W:119 deg 02' 05") at an elevation between 2600 and 3000 meters. The area is covered by an open type of Montane Forest. The dominant tree species are Lodgepole Pine (Pinus contorta), the Red Fir (Abies magnifica) and the Jeffrey Pine (Pinus jeffreyi). The soil surface near Horseshoe Lake is generally fairly bright. The surface is covered by glacial deposits (till) consisting mainly of weathered granitic rocks.

  20. Glacial-marine and glacial-lacustrine sedimentation in Sebago Lake, Maine: Locating the marine limit

    SciTech Connect

    Johnston, R.A.; Kelley, J.T. ); Belknap, D. . Dept. of Geological Sciences)

    1993-03-01

    The marine limit in Maine marks a sea-level highstand at approximately 13 ka. It was inferred to cross Sebago Lake near Frye Island by Thompson and Borns (1985) on the Surficial Geological Map of Maine, dividing the lake into a northern glacial-lacustrine basin and a southern glacial-marine basin. This study examined the accuracy of the mapped marine limit in the lake and the nature of glacial-lacustrine and glacial-marine facies in Maine. Recognition of the marine limit is usually based on mapped shorelines, glacial-marine deltas, and contacts with glacial-marine sediments. This study, in Maine's second largest lake, collected 100 kilometers of side-scan sonar images, 100 kilometers of seismic reflection profiles, and one core. Side-scan sonar records show coarse sand and gravel and extensive boulder fields at an inferred grounding-line position near Frye Island, where the marine limit was drawn. ORE Geopulse seismic reflection profiles reveal a basal draping unit similar to glacial-marine units identified offshore. Later channels cut more than 30 m into the basal stratified unit. In addition, till and a possible glacial-tectonic grounding-line feature were identified. Slumps and possible spring disruptions are found in several locations. The top unit is an onlapping ponded Holocene lacustrine unit. Total sediment is much thicker in the southern basin; the northern basin, >97 m deep, north of the marine limit appears to have been occupied by an ice block. Retrieved sediments include 12 meters of rhythmites. Microfossil identifications and dating will resolve the environments and time of deposition in this core.

  1. Technical Tree Climbing.

    ERIC Educational Resources Information Center

    Jenkins, Peter

    Tree climbing offers a safe, inexpensive adventure sport that can be performed almost anywhere. Using standard procedures practiced in tree surgery or rock climbing, almost any tree can be climbed. Tree climbing provides challenge and adventure as well as a vigorous upper-body workout. Tree Climbers International classifies trees using a system…

  2. Exotic trees.

    PubMed

    Burda, Z; Erdmann, J; Petersson, B; Wattenberg, M

    2003-02-01

    We discuss the scaling properties of free branched polymers. The scaling behavior of the model is classified by the Hausdorff dimensions for the internal geometry, d(L) and d(H), and for the external one, D(L) and D(H). The dimensions d(H) and D(H) characterize the behavior for long distances, while d(L) and D(L) for short distances. We show that the internal Hausdorff dimension is d(L)=2 for generic and scale-free trees, contrary to d(H), which is known to be equal to 2 for generic trees and to vary between 2 and infinity for scale-free trees. We show that the external Hausdorff dimension D(H) is directly related to the internal one as D(H)=alphad(H), where alpha is the stability index of the embedding weights for the nearest-vertex interactions. The index is alpha=2 for weights from the Gaussian domain of attraction and 0

  3. Postglacial trends of hillslope development in two glacially formed mountain valleys in western Norway

    NASA Astrophysics Data System (ADS)

    Laute, K.; Beylich, A. A.

    2012-04-01

    Although rockfall talus slopes occur in all regions where rock weathering products accumulate beneath rock faces and cliffs, they are particularly common in glacially formed mountain landscapes. The retreat of glacier ice from glaciated valleys which have probably experienced oversteepening of rock slopes by glacial erosion causes paraglacial destabilization of the valley sidewalls related to stress-relief, unloading, frost weathering and / or degradation of mountain permafrost. Large areas of the Norwegian fjord landscapes are occupied by hillslopes which are owned by the influences of the glacial inheritance of the last glacial maximum (LGM). This study focuses on Postglacial trends of hillslope development in two glacially formed mountain valleys in western Norway (Erdalen and Bødalen). The research is part of a doctoral thesis, which is integrated in the Norwegian Research Council (NFR) funded SedyMONT-Norway project within the ESF TOPO-EUROPE SedyMONT (Timescales of sediment dynamics, climate and topographic change in mountain landscapes) Programme. The main aspects addressed in this study are: (i) the spatio-temporal variability of denudative slope processes over the Holocene and (ii) the Postglacial modification of the glacial relief. The applied process-based approach includes detailed geomorphological fieldmapping combined with terrestrial laser scans (LIDAR) of slope deposits in order to identify possible deposition processes and their spatial variability, relative dating techniques (tree rings and lichens) to analyze subrecent temporal variations, detailed surface mapping with additional geophysical subsurface investigations to estimated regolith thicknesses as well as CIR- and orthophoto delineation combined with GIS and DEM computing for calculating estimates of average valley-wide rockwall retreat rates. Results show Holocene rockwall retreat rates for the two valleys which are in a comparable range with other estimates of rockwall retreat rates in

  4. Topographic quantitative EEG amplitude in recovered alcoholics.

    PubMed

    Pollock, V E; Schneider, L S; Zemansky, M F; Gleason, R P; Pawluczyk, S

    1992-05-01

    Topographic measures of electroencephalographic (EEG) amplitude were used to compare recovered alcoholics (n = 14) with sex- and age-matched control subjects. Delta, alpha, and beta activity did not distinguish the groups, but regional differences in theta distribution did. Recovered alcoholics showed more uniform distributions of theta amplitudes in bilateral anterior and posterior regions compared with controls. Because a minimum of 5 years had elapsed since the recovered alcoholic subjects fulfilled DSM-III-R criteria for alcohol abuse or dependence, it is unlikely these EEG theta differences reflect the effects of withdrawal.

  5. Calibrating divergence times on species trees versus gene trees: implications for speciation history of Aphelocoma jays.

    PubMed

    McCormack, John E; Heled, Joseph; Delaney, Kathleen S; Peterson, A Townsend; Knowles, L Lacey

    2011-01-01

    Estimates of the timing of divergence are central to testing the underlying causes of speciation. Relaxed molecular clocks and fossil calibration have improved these estimates; however, these advances are implemented in the context of gene trees, which can overestimate divergence times. Here we couple recent innovations for dating speciation events with the analytical power of species trees, where multilocus data are considered in a coalescent context. Divergence times are estimated in the bird genus Aphelocoma to test whether speciation in these jays coincided with mountain uplift or glacial cycles. Gene trees and species trees show general agreement that diversification began in the Miocene amid mountain uplift. However, dates from the multilocus species tree are more recent, occurring predominately in the Pleistocene, consistent with theory that divergence times can be significantly overestimated with gene-tree based approaches that do not correct for genetic divergence that predates speciation. In addition to coalescent stochasticity, Haldane's rule could account for some differences in timing estimates between mitochondrial DNA and nuclear genes. By incorporating a fossil calibration applied to the species tree, in addition to the process of gene lineage coalescence, the present approach provides a more biologically realistic framework for dating speciation events, and hence for testing the links between diversification and specific biogeographic and geologic events.

  6. The vegetation cover of New Zealand at the Last Glacial Maximum

    NASA Astrophysics Data System (ADS)

    Newnham, Rewi; McGlone, Matt; Moar, Neville; Wilmshurst, Janet; Vandergoes, Marcus

    2013-08-01

    A new reconstruction of the vegetation cover for New Zealand at the Last Glacial Maximum (LGM) is presented, based primarily on a database of 66 pollen site records and a more limited range of plant macrofossil and coleopteran records. Extensive forest is evident only from Auckland northwards. Conifer-broadleaf forest similar to that in the region today, but with Agathis australis scarce, persisted in the far north, whilst Nothofagus trees and a range of shrub taxa characterised the more open forests elsewhere in Northland. Survival of Nothofagus-dominated forest in coastal and exposed continental shelf locations to the southwest of Auckland and northwestern South Island is also indicated. Beyond these regions, vegetation cover comprised shrubland- and grassland-dominant communities, with the latter more prominent in eastern areas, to the south and presumably at higher altitudes. Nevertheless the survival of forest trees is indicated unambiguously in most regions apart from the eastern South Island. Thus the concept of 'micro glacial forest refugia' in New Zealand remains supported by this latest glacial vegetation reconstruction and we draw possible parallels with the developing but contentious concept of 'northern cryptic refugia' in Europe. Recent assertions that pollen and beetle reconstructions of the New Zealand LGM vegetation patterns diverge significantly are not supported by this analysis. Rather, the two proxies are readily reconciled if the term 'woody' as indicated by coleoptera is not restricted to tall forest trees but extended to the widespread woody shrub and small tree elements of the New Zealand flora. Regional distinctions in the LGM vegetation reconstruction concur broadly with the contemporary vegetation pattern, suggesting that, along with temperature depression and likely drier growing conditions, a zonal circulation regime with prominent southern westerly winds was important at 21 ka, as it is today. Pollen-climate modelling of the extent of

  7. Automated monitoring of recovered water quality

    NASA Technical Reports Server (NTRS)

    Misselhorn, J. E.; Hartung, W. H.; Witz, S. W.

    1974-01-01

    Laboratory prototype water quality monitoring system provides automatic system for online monitoring of chemical, physical, and bacteriological properties of recovered water and for signaling malfunction in water recovery system. Monitor incorporates whenever possible commercially available sensors suitably modified.

  8. What Makes a Tree a Tree?

    ERIC Educational Resources Information Center

    NatureScope, 1986

    1986-01-01

    Provides: (1) background information on trees, focusing on the parts of trees and how they differ from other plants; (2) eight activities; and (3) ready-to-copy pages dealing with tree identification and tree rings. Activities include objective(s), recommended age level(s), subject area(s), list of materials needed, and procedures. (JN)

  9. METHOD FOR RECOVERING URANIUM FROM OILS

    DOEpatents

    Gooch, L.H.

    1959-07-14

    A method is presented for recovering uranium from hydrocarbon oils, wherein the uranium is principally present as UF/sub 4/. According to the invention, substantially complete removal of the uranium from the hydrocarbon oil may be effected by intimately mixing one part of acetone to about 2 to 12 parts of the hydrocarbon oil containing uranium and separating the resulting cake of uranium from the resulting mixture. The uranium in the cake may be readily recovered by burning to the oxide.

  10. Variations in Glacial Erosion over Multiple Glacial-Interglacial Cycles: A Numerical Modelling Approach

    NASA Astrophysics Data System (ADS)

    Headley, Rachel M.; Ehlers, Todd A.

    2013-04-01

    Mountain topography is constructed through a variety of interacting processes. As one of these processes, glacial erosion plays an important role in the development of landscapes by the formation of distinctive topographic features. Glacial landscape evolution models reproduce many observed features at the orogen scale. Detailed comparisons at the scale of individual valleys holds potential for quantifying the influence of glacial physics in glacial erosion models. Over long timescales (>10,000 yr), glacial erosion has typically been simulated using a modified shallow ice approximation (SIA) approach. In this study, we compare the strengths and weaknesses of shallow ice and high-order, Stokes-flow glacial landscape evolution models. Our emphasis is placed on the patterns and rates of glacial erosion over multiple glacial-interglacial cycles. We present a comparison of two different numerical models for glacial erosion. For both approaches, a modified version of the ICE Cascade model is used to develop and evolve topography. This model calculates hillslope and fluvial erosion and sediment transport, isostasy, temporally variable orographic precipitation, and a range of glaciological processes: glacial mass balance, snow avalanching, basal ice superfreezing, and basal water buoyancy feedback in large overdeepenings. Within this framework, we compare the predicted ice-flow field and erosion patterns using a modified SIA as well as predictions from a nested, thermally-coupled, Stokes-flow model calculated using COMSOL Multiphysics. Simulations are conducted for a range of amplitudes and periodicity in surface temperature change between glacial and interglacial periods. We investigate these simulations, as well as the effects of each model for various initial topographies and with a temperature-dependent ice rheology. In general, both models predict visually similar patterns in sliding velocity, and resulting erosion rates, assuming the erosion rate scales with the

  11. North Atlantic Deep Water Production during the Last Glacial Maximum.

    PubMed

    Howe, Jacob N W; Piotrowski, Alexander M; Noble, Taryn L; Mulitza, Stefan; Chiessi, Cristiano M; Bayon, Germain

    2016-06-03

    Changes in deep ocean ventilation are commonly invoked as the primary cause of lower glacial atmospheric CO2. The water mass structure of the glacial deep Atlantic Ocean and the mechanism by which it may have sequestered carbon remain elusive. Here we present neodymium isotope measurements from cores throughout the Atlantic that reveal glacial-interglacial changes in water mass distributions. These results demonstrate the sustained production of North Atlantic Deep Water under glacial conditions, indicating that southern-sourced waters were not as spatially extensive during the Last Glacial Maximum as previously believed. We demonstrate that the depleted glacial δ(13)C values in the deep Atlantic Ocean cannot be explained solely by water mass source changes. A greater amount of respired carbon, therefore, must have been stored in the abyssal Atlantic during the Last Glacial Maximum. We infer that this was achieved by a sluggish deep overturning cell, comprised of well-mixed northern- and southern-sourced waters.

  12. Relative timing of last glacial maximum and late-glacial events in the central tropical Andes

    NASA Astrophysics Data System (ADS)

    Bromley, Gordon R. M.; Schaefer, Joerg M.; Winckler, Gisela; Hall, Brenda L.; Todd, Claire E.; Rademaker, Kurt M.

    2009-11-01

    Whether or not tropical climate fluctuated in synchrony with global events during the Late Pleistocene is a key problem in climate research. However, the timing of past climate changes in the tropics remains controversial, with a number of recent studies reporting that tropical ice age climate is out of phase with global events. Here, we present geomorphic evidence and an in-situ cosmogenic 3He surface-exposure chronology from Nevado Coropuna, southern Peru, showing that glaciers underwent at least two significant advances during the Late Pleistocene prior to Holocene warming. Comparison of our glacial-geomorphic map at Nevado Coropuna to mid-latitude reconstructions yields a striking similarity between Last Glacial Maximum (LGM) and Late-Glacial sequences in tropical and temperate regions. Exposure ages constraining the maximum and end of the older advance at Nevado Coropuna range between 24.5 and 25.3 ka, and between 16.7 and 21.1 ka, respectively, depending on the cosmogenic production rate scaling model used. Similarly, the mean age of the younger event ranges from 10 to 13 ka. This implies that (1) the LGM and the onset of deglaciation in southern Peru occurred no earlier than at higher latitudes and (2) that a significant Late-Glacial event occurred, most likely prior to the Holocene, coherent with the glacial record from mid and high latitudes. The time elapsed between the end of the LGM and the Late-Glacial event at Nevado Coropuna is independent of scaling model and matches the period between the LGM termination and Late-Glacial reversal in classic mid-latitude records, suggesting that these events in both tropical and temperate regions were in phase.

  13. Ice flow models and glacial erosion over multiple glacial-interglacial cycles

    NASA Astrophysics Data System (ADS)

    Headley, R. M.; Ehlers, T. A.

    2014-06-01

    Mountain topography is constructed through a variety of interacting processes. Over glaciological time scales, even simple representations of glacial-flow physics can reproduce many of the distinctive features formed through glacial erosion. However, detailed comparisons at orogen time and length scales hold potential for quantifying the influence of glacial physics in landscape evolution models. We present a comparison using two different numerical models for glacial flow over single and multiple glaciations, within a modified version of the ICE-Cascade landscape evolution model. This model calculates not only glaciological processes but also hillslope and fluvial erosion and sediment transport, isostasy, and temporally and spatially variable orographic precipitation. We compare the predicted erosion patterns using a modified SIA as well as a nested, 3-D Stokes-flow model calculated using COMSOL Multiphysics. Both glacial-flow models predict different patterns in time-averaged erosion rates. However, these results are sensitive to the climate and the ice temperature. For warmer climates with more sliding, the higher-order model has a larger impact on the erosion rate, with variations of almost an order of magnitude. As the erosion influences the basal topography and the ice deformation affects the ice thickness and extent, the higher-order glacial model can lead to variations in total ice-covered that are greater than 30%, again with larger differences for temperate ice. Over multiple glaciations and long-time scales, these results suggest that consideration of higher-order glacial physics may be necessary, particularly in temperate, mountainous settings.

  14. Ice flow models and glacial erosion over multiple glacial-interglacial cycles

    NASA Astrophysics Data System (ADS)

    Headley, R. M.; Ehlers, T. A.

    2015-03-01

    Mountain topography is constructed through a variety of interacting processes. Over glaciological timescales, even simple representations of glacial-flow physics can reproduce many of the distinctive features formed through glacial erosion. However, detailed comparisons at orogen time and length scales hold potential for quantifying the influence of glacial physics in landscape evolution models. We present a comparison using two different numerical models for glacial flow over single and multiple glaciations, within a modified version of the ICE-Cascade landscape evolution model. This model calculates not only glaciological processes but also hillslope and fluvial erosion and sediment transport, isostasy, and temporally and spatially variable orographic precipitation. We compare the predicted erosion patterns using a modified SIA as well as a nested, 3-D Stokes flow model calculated using COMSOL Multiphysics. Both glacial-flow models predict different patterns in time-averaged erosion rates. However, these results are sensitive to the climate and the ice temperature. For warmer climates with more sliding, the higher-order model yields erosion rates that vary spatially and by almost an order of magnitude from those of the SIA model. As the erosion influences the basal topography and the ice deformation affects the ice thickness and extent, the higher-order glacial model can lead to variations in total ice-covered area that are greater than 30% those of the SIA model, again with larger differences for temperate ice. Over multiple glaciations and long timescales, these results suggest that higher-order glacial physics should be considered, particularly in temperate, mountainous settings.

  15. Quaking aspen productivity recovers after repeated prescribed fire. Forest Service research paper

    SciTech Connect

    Perala, D.A.

    1995-08-01

    Aspen yield may be less after burning slash left by clearcutting, but the study shows that repeated burning may ameliorate growth. Ultimately, aspen yield is determined by conditions that control growth, stockability, and site index. Site index was diminished by the initial burn and did not recover regardless of ensuing history. The response to subsequent burning suggests mitigation of the factors controlling stockability, thought to be related to the water balance. The responsible mechanism is not apparent from these data. Tree growth may follow different trajectories accompanied by more-or-less complementary survival trajectories. Thus stands may eventually converge on the same yield, distributed over different numbers of trees.

  16. Glacial bed forms at Findelengletscher, Zermatt, Switzerland

    NASA Astrophysics Data System (ADS)

    Madella, Andrea; Nyffenegger, Franziska; Schlüchter, Christian

    2013-04-01

    The current glacier meltdown is increasingly unveiling the glacial bed forms produced by the most recent glacial advance of the 1980ies, such as flutes, mega-flutes and drumlins. This is a challenging opportunity to study these morphologies and the processes involved in their formation; in addition, our observation suggests a new question to be answered: why can't any of these features in units belonging to previous glacial advances be recognised? Similar forms could either have been washed away already, or never been built during LGM and since. The most beautiful and evident of the forms under investigation are the flutes and mega-flutes: elongated streamlined ridges of sediments either starting from an obstacle or just sticking out of the basal lodgement till. The way flutes have been initiated and then evolve is still partially unknown, due to their variety in shape, size and material. The glacial forefield at Findelengletscher under investigation deglaciated over the past two years, offers a well-preserved variety of such forms at all scales. Their material (basal lodgement till) is homogeneous and consistent all over the site, as well as their fabric. In addition, this silty sand shows a low plasticity index. These preliminary results support the idea that flutes build up very quickly during repeated seasonal advances in thin ice conditions with retreating trend (Coray, 2007), and that they could be equally easily and rapidly washed away. References: Coray Sandro (2007): Genesis and significance of flutes at Findelengletscher, Valais, Switzerland, Institute of Geological Sciences, University of Bern.

  17. Low but structured chloroplast diversity in Atherosperma moschatum (Atherospermataceae) suggests bottlenecks in response to the Pleistocene glacials

    PubMed Central

    Worth, James R. P.; Marthick, James R.; Jordan, Gregory J.; Vaillancourt, René E.

    2011-01-01

    Background and Aims The cool temperate rainforests of Australia were much reduced in range during the cold and dry glacial periods, although genetic evidence indicates that two key rainforest species, Nothofagus cunninghamii and Tasmannia lanceolata, survived within multiple locations and underwent only local range expansions at the end of the Last Glacial. To better understand the glacial response of a co-occurring but wind-dispersed and less cold-tolerant rainforest tree species, Atherosperma moschatum, a chloroplast phylogeographic study was undertaken. Methods A total of 3294 bp of chloroplast DNA sequence was obtained for 155 samples collected from across the species' range. Key Results The distribution of six haplotypes observed in A. moschatum was geographically structured with an inferred ancestral haplotype restricted to Tasmania, while three non-overlapping and endemic haplotypes were found on the mainland of south-eastern Australia. Last glacial refugia for A. moschatum are likely to have occurred in at least one location in western Tasmania and in Victoria and within at least two locations in the Great Dividing Range of New South Wales. Nucleotide diversity of A. moschatum was lower (π = 0·00021) than either N. cunninghamii (0·00101) or T. lanceolata (0·00073), and was amongst the lowest recorded for any tree species. Conclusions This study provides evidence for past bottlenecks having impacted the chloroplast diversity of A. moschatum as a result of the species narrower climatic niche during glacials. This hypothesis is supported by the star-like haplotype network and similar estimated rates of chloroplast DNA substitution for A. moschatum and the two more cold tolerant and co-occurring species that have higher chloroplast diversity, N. cunninghamii and T. lanceolata. PMID:21856633

  18. Vegetation responses to climate changes during the penultimate glacial period (marine isotope stage 6) in southern Europe

    NASA Astrophysics Data System (ADS)

    Roucoux, Katy; Margari, V.; Lawson, I. T.; Tzedakis, P. C.

    2010-05-01

    changes in insolation are not translated into high amplitude changes in vegetation and climate at Ioannina. Millennial-scale expansions and contractions of tree populations indicative of oscillations in temperature and moisture availability are recorded but they appear to have been more subdued than their counterparts during the last glacial. This supports the presence of non-linearity in the link between orbital-scale insolation forcing and regional climate.

  19. Late Glacial ice advances in southeast Tibet

    NASA Astrophysics Data System (ADS)

    Strasky, Stefan; Graf, Angela A.; Zhao, Zhizhong; Kubik, Peter W.; Baur, Heinrich; Schlüchter, Christian; Wieler, Rainer

    2009-03-01

    The sensitivity of Tibetan glacial systems to North Atlantic climate forcing is a major issue in palaeoclimatology. In this study, we present surface exposure ages of erratic boulders from a valley system in the Hengduan Mountains, southeastern Tibet, showing evidence of an ice advance during Heinrich event 1. Cosmogenic nuclide analyses ( 10Be and 21Ne) revealed consistent exposure ages, indicating no major periods of burial or pre-exposure. Erosion-corrected (3 mm/ka) 10Be exposure ages range from 13.4 to 16.3 ka. This is in agreement with recalculated exposure ages from the same valley system by [Tschudi, S., Schäfer, J.M., Zhao, Z., Wu, X., Ivy-Ochs, S., Kubik, P.W., Schlüchter, C., 2003. Glacial advances in Tibet during the Younger Dryas? Evidence from cosmogenic 10Be, 26Al, and 21Ne. Journal of Asian Earth Sciences 22, 301-306.]. Thus this indicates that local glaciers advanced in the investigated area as a response to Heinrich event 1 cooling and that periglacial surface adjustments during the Younger Dryas overprinted the glacial morphology, leading to deceptively young exposure ages of certain erratic boulders.

  20. Applications for carbon fibre recovered from composites

    NASA Astrophysics Data System (ADS)

    Pickering; Liu, Z.; Turner, TA; Wong, KH

    2016-07-01

    Commercial operations to recover carbon fibre from waste composites are now developing and as more recovered fibre becomes available new applications for recovered fibre are required. Opportunities to use recovered carbon fibre as a structural reinforcement are considered involving the use of wet lay processes to produce nonwoven mats. Mats with random in-plane fibre orientation can readily be produced using existing commercial processes. However, the fibre volume fraction, and hence the mechanical properties that can be achieved, result in composites with limited mechanical properties. Fibre volume fractions of 40% can be achieved with high moulding pressures of over 100 bar, however, moulding at these pressures results in substantial fibre breakage which reduces the mean fibre length and the properties of the composite manufactured. Nonwoven mats made from aligned, short carbon fibres can achieve higher fibre volume fractions with lower fibre breakage even at high moulding pressure. A process for aligning short fibres is described and a composite of over 60% fibre volume fraction has been manufactured at a pressures up to 100 bar with low fibre breakage. Further developments of the alignment process have been undertaken and a composite of 46% fibre volume fraction has been produced moulded at a pressure of 7 bar in an autoclave, exhibiting good mechanical properties that compete with higher grade materials. This demonstrates the potential for high value applications for recovered carbon fibre by fibre alignment.

  1. The Tree Worker's Manual.

    ERIC Educational Resources Information Center

    Smithyman, S. J.

    This manual is designed to prepare students for entry-level positions as tree care professionals. Addressed in the individual chapters of the guide are the following topics: the tree service industry; clothing, eqiupment, and tools; tree workers; basic tree anatomy; techniques of pruning; procedures for climbing and working in the tree; aerial…

  2. Constraints on the glacial erosion rule

    NASA Astrophysics Data System (ADS)

    Herman, Frédéric

    2016-04-01

    It is thought that glaciers erode their underlying bedrock mainly through abrasion and quarrying. Theories predict erosion to be proportional to ice-sliding velocity raised to some power: ˙e = Kguls (1) where ė is the erosion rate, and Kg a proportionality constant and l an exponent. By implementing such a rule in numerical models, it has been possible to reproduce typical glacial landscape features, such as U-shape valleys, hanging valleys, glacial cirques or fjords. Although there have been great advances in the level of sophistication of these models, for example through the inclusion of high-order ice dynamics and subglacial hydrology, the proportionality constant, and the exponent have remained poorly constrained parameters. Recently, two independent studies in the Antarctic Peninsula and Patagonian Andes (Koppes et al., 2015) and the Franz Josef Glacier, New Zealand (Herman et al., 2015) simultaneously collected erosion rate and ice velocity data to find that erosion depends non-linearly on sliding velocity, and that the exponent on velocity is about 2. Such a nonlinear rule is appealing because it may, in part, explain the observed variations in erosion rates globally. Furthermore, an exponent about 2 closely matches theoretical predictions for abrasion. Although it is tempting to argue that abrasion is the dominant process for fast flowing glaciers like the Franz Josef Glacier, there is a clear need for more data and better quantification for the role of quarrying. Both studies also led to very similar values for the proportionality constant Kg. These new results therefore imply that glacial erosion processes might be better constrained than previously thought. Given that glacial velocity can nowadays be measured and modeled at an unprecedented resolution, it may potentially become possible to use glacial erosion models in a predictive manner. Herman, F. et al. "Erosion by an Alpine glacier." Science 350.6257 (2015): 193-195. Koppes, M. et al. "Observed

  3. Ergonomic analysis jobs in recovered factories.

    PubMed

    Cuenca, Gabriela; Zotta, Gastón

    2012-01-01

    With the advent of the deep economic crisis in Argentina on 2001, the recovery of companies through to the creation of the Cooperatives Working Self-Management or Factories Recovered by its workers was constituted as one of the ways in which the salaried disobeyed the increasing unemployment. When the companies turn into recovered factories they tend to leave of side practices that have been seen like imposed by the previous organization and not understanding them as a primary condition for the execution of his tasks. Safety and ergonomics are two disciplines that are no longer considered relevant to the daily work. Therefore this investigation aims to revalue, undergo semantic to give back to a place in every organization analyzed. This research developed a self-diagnostic tool for working conditions, and the environment, present in the recovered factories.

  4. Mechanical Stimuli Regulate the Allocation of Biomass in Trees: Demonstration with Young Prunus avium Trees

    PubMed Central

    Coutand, Catherine; Dupraz, Christian; Jaouen, Gaëlle; Ploquin, Stéphane; Adam, Boris

    2008-01-01

    Background and Aims Plastic tree-shelters are increasingly used to protect tree seedlings against browsing animals and herbicide drifts. The biomass allocation in young seedlings of deciduous trees is highly disturbed by common plastic tree-shelters, resulting in poor root systems and reduced diameter growth of the trunk. The shelters have been improved by creating chimney-effect ventilation with holes drilled at the bottom, resulting in stimulated trunk diameter growth, but the root deficit has remained unchanged. An experiment was set up to elucidate the mechanisms behind the poor root growth of sheltered Prunus avium trees. Methods Tree seedlings were grown either in natural windy conditions or in tree-shelters. Mechanical wind stimuli were suppressed in ten unsheltered trees by staking. Mechanical stimuli (bending) of the stem were applied in ten sheltered trees using an original mechanical device. Key Results Sheltered trees suffered from poor root growth, but sheltered bent trees largely recovered, showing that mechano-sensing is an important mechanism governing C allocation and the shoot–root balance. The use of a few artificial mechanical stimuli increased the biomass allocation towards the roots, as did natural wind sway. It was demonstrated that there was an acclimation of plants to the imposed strain. Conclusions This study suggests that if mechanical stimuli are used to control plant growth, they should be applied at low frequency in order to be most effective. The impact on the functional equilibrium hypothesis that is used in many tree growth models is discussed. The consequence of the lack of mechanical stimuli should be incorporated in tree growth models when applied to environments protected from the wind (e.g. greenhouses, dense forests). PMID:18448448

  5. Proportion of recovered waterfowl bands reported

    USGS Publications Warehouse

    Geis, A.D.; Atwood, E.L.

    1961-01-01

    Data from the annual mail survey of waterfowl hunters in the United States were used to estimate the total numbers of banded waterfowl that were shot. These estimates were compared with Banding Office records to estimate the proportion of recovered bands that was reported. On the average, about two banded birds were recovered for each one reported. The proportion reported was higher for some areas and for some species than for others. The proportion reported was higher when more of the reports came through employees of conservation agencies.

  6. Solid recovered fuels in the steel industry.

    PubMed

    Kepplinger, Werner L; Tappeiner, Tamara

    2012-04-01

    By using waste materials as alternative fuels in metallurgical plants it is possible to minimize the traditionally used reducing agents, such as coke, coal, oil or natural gas. Moreover, by using waste materials in the metallurgical industry it is feasible to recover these materials as far as possible. This also represents another step towards environmental protection because carbon dioxide emissions can be reduced, if the H(2) content of the waste material is greater in comparison with that of the substituted fuel and the effects of global warming can therefore be reduced. In the present article various solid recovered fuels and their applications in the metallurgical industry are detailed.

  7. Impact of CO2 and climate on Last Glacial Maximum vegetation - a factor separation

    NASA Astrophysics Data System (ADS)

    Claussen, M.; Selent, K.; Brovkin, V.; Raddatz, T.; Gayler, V.

    2012-11-01

    Differences between glacial and pre-industrial potential vegetation patterns can conceptually be attributed to two factors: firstly to differences in the climate, caused by a strong increase in ice masses and the radiative effect of lower greenhouse gas concentrations, and secondly to differences in the ecophysiological effect of lower glacial atmospheric CO2 concentrations. The synergy emerging from these effects when operating simultaneously can be interpreted as sensitivity of the effect of enhancing physiologically available CO2 on shifting vegetation to climate warming. Alternatively and equally valid, it can be viewed as sensitivity of climatically induced vegetation changes to differences in physiologically available CO2. A first complete factor separation based on simulations with the MPI Earth System Model indicates that the pure climate effect mainly leads to a contraction or a shift in vegetation patterns when comparing glacial with pre-industrial simulation vegetation patterns. Globally, a reduction in fractional coverage of most plant functional types is seen - except for raingreen shrubs which strongly benefit from the colder and drier climate. The ecophysiological effect of CO2 appears to be stronger than the pure climate contribution for many plant functional types - in line with previous simulations. The ecophysiological effect of lower CO2 mainly yields a reduction in fractional coverage, a thinning of vegetation and a strong reduction in net primary production. The synergy appears to be as strong as each of the pure contributions locally. For tropical evergreen trees, the synergy appears strong also on global average. Hence this modelling study suggests that for tropical forests, an increase in CO2 has, on average, a stronger ecophysiological effect in warmer climate than in glacial climate. Alternatively, areal differences in tropical forests induced by climate warming can, on average, be expected to be larger with increasing concentration of

  8. Phylogeography and post-glacial recolonization in wolverines (Gulo gulo) from across their circumpolar distribution.

    PubMed

    Zigouris, Joanna; Schaefer, James A; Fortin, Clément; Kyle, Christopher J

    2013-01-01

    Interglacial-glacial cycles of the Quaternary are widely recognized in shaping phylogeographic structure. Patterns from cold adapted species can be especially informative - in particular, uncovering additional glacial refugia, identifying likely recolonization patterns, and increasing our understanding of species' responses to climate change. We investigated phylogenetic structure of the wolverine, a wide-ranging cold adapted carnivore, using a 318 bp of the mitochondrial DNA control region for 983 wolverines (n=209 this study, n=774 from GenBank) from across their full Holarctic distribution. Bayesian phylogenetic tree reconstruction and the distribution of observed pairwise haplotype differences (mismatch distribution) provided evidence of a single rapid population expansion across the wolverine's Holarctic range. Even though molecular evidence corroborated a single refugium, significant subdivisions of population genetic structure (0.01< ΦST <0.99, P<0.05) were detected. Pairwise ΦST estimates separated Scandinavia from Russia and Mongolia, and identified five main divisions within North America - the Central Arctic, a western region, an eastern region consisting of Ontario and Quebec/Labrador, Manitoba, and California. These data are in contrast to the nearly panmictic structure observed in northwestern North America using nuclear microsatellites, but largely support the nuclear DNA separation of contemporary Manitoba and Ontario wolverines from northern populations. Historic samples (c. 1900) from the functionally extirpated eastern population of Quebec/Labrador displayed genetic similarities to contemporary Ontario wolverines. To understand these divergence patterns, four hypotheses were tested using Approximate Bayesian Computation (ABC). The most supported hypothesis was a single Beringia incursion during the last glacial maximum that established the northwestern population, followed by a west-to-east colonization during the Holocene. This pattern is

  9. Additive Similarity Trees

    ERIC Educational Resources Information Center

    Sattath, Shmuel; Tversky, Amos

    1977-01-01

    Tree representations of similarity data are investigated. Hierarchical clustering is critically examined, and a more general procedure, called the additive tree, is presented. The additive tree representation is then compared to multidimensional scaling. (Author/JKS)

  10. North Atlantic Deep Water Production during the Last Glacial Maximum

    PubMed Central

    Howe, Jacob N. W.; Piotrowski, Alexander M.; Noble, Taryn L.; Mulitza, Stefan; Chiessi, Cristiano M.; Bayon, Germain

    2016-01-01

    Changes in deep ocean ventilation are commonly invoked as the primary cause of lower glacial atmospheric CO2. The water mass structure of the glacial deep Atlantic Ocean and the mechanism by which it may have sequestered carbon remain elusive. Here we present neodymium isotope measurements from cores throughout the Atlantic that reveal glacial–interglacial changes in water mass distributions. These results demonstrate the sustained production of North Atlantic Deep Water under glacial conditions, indicating that southern-sourced waters were not as spatially extensive during the Last Glacial Maximum as previously believed. We demonstrate that the depleted glacial δ13C values in the deep Atlantic Ocean cannot be explained solely by water mass source changes. A greater amount of respired carbon, therefore, must have been stored in the abyssal Atlantic during the Last Glacial Maximum. We infer that this was achieved by a sluggish deep overturning cell, comprised of well-mixed northern- and southern-sourced waters. PMID:27256826

  11. Training Tree Transducers

    DTIC Science & Technology

    2004-01-01

    trees (similar to the role played by the finite- state acceptor FSA for strings). We describe the version (equivalent to TSG ( Schabes , 1990)) where...strictly contained in tree sets of tree adjoining gram- mars (Joshi and Schabes , 1997). 4 Extended-LHS Tree Transducers (xR) Section 1 informally described...changes without modifying the training procedure, as long as we stick to tree automata. 10 Related Work Tree substitution grammars or TSG ( Schabes , 1990

  12. 27 CFR 19.393 - Restoration and redenaturation of recovered denatured spirits and recovered articles.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2011-04-01 2011-04-01 false Restoration and redenaturation of recovered denatured spirits and recovered articles. 19.393 Section 19.393 Alcohol, Tobacco Products and Firearms ALCOHOL AND TOBACCO TAX AND TRADE BUREAU, DEPARTMENT OF THE TREASURY...

  13. 27 CFR 19.393 - Restoration and redenaturation of recovered denatured spirits and recovered articles.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2012-04-01 2012-04-01 false Restoration and redenaturation of recovered denatured spirits and recovered articles. 19.393 Section 19.393 Alcohol, Tobacco Products and Firearms ALCOHOL AND TOBACCO TAX AND TRADE BUREAU, DEPARTMENT OF THE TREASURY...

  14. Method and apparatus for recovering waste oil

    SciTech Connect

    Kennedy, A.B.

    1982-09-21

    Oil is recovered from a mixture of oil and water by heating the mixture, adding a de-emulsifier, passing the mixture through a first vibrating screen, adding a surface tension reducer, processing through a hydrocyclone, passing through a second vibrating screen, and separating the oil from water by settling.

  15. Process for recovering filler from polymer

    DOEpatents

    Smith, Maurice L.; Smith, Robert M.

    1978-01-01

    This disclosure relates to a process for recovering filler material from a polymeric matrix by reacting the matrix at an elevated temperature in a gas atmosphere with a controlled oxidizing potential and thereafter separating and cleaning the residue from the reaction mixture.

  16. 27 CFR 17.168 - Recovered spirits.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2012-04-01 2012-04-01 false Recovered spirits. 17.168 Section 17.168 Alcohol, Tobacco Products and Firearms ALCOHOL AND TOBACCO TAX AND TRADE BUREAU, DEPARTMENT... separate alcohol is subject to the registration requirements of 26 U.S.C. 5179 and subpart C of part 29...

  17. Stress Levels of Recovering Drug Addicts.

    ERIC Educational Resources Information Center

    LaMon, Brent C.; Alonzo, Anthony

    It appears that chronic drug use may develop as a means of coping in which individuals use self-medication to produce a more desirable state of being. Because drugs are often used to cope with stress, this study examined stress among recovering male drug addicts (N=23) from an urban substance abuse program by administering a self-report inventory…

  18. Applications for Energy Recovering Free Electron Lasers

    SciTech Connect

    George Neil

    2007-08-01

    The availability of high-power, high-brilliance sources of tunable photons from energy-recovered Free Electron Lasers is opening up whole new fields of application of accelerators in industry. This talk will review some of the ideas that are already being put into production, and some of the newer ideas that are still under development.

  19. Earth's glacial record and its tectonic setting

    NASA Astrophysics Data System (ADS)

    Eyles, N.

    1993-09-01

    Glaciations have occurred episodically at different time intervals and for different durations in Earth's history. Ice covers have formed in a wide range of plate tectonic and structural settings but the bulk of Earth's glacial record can be shown to have been deposited and preserved in basins within extensional settings. In such basins, source area uplift and basin subsidence fulfill the tectonic preconditions for the initiation of glaciation and the accomodation and preservation of glaciclastic sediments. Tectonic setting, in particular subsidence rates, also dictates the type of glaciclastic facies and facies successions that are deposited. Many pre-Pleistocene glaciated basins commonly contain well-defined tectonostratigraphic successions recording the interplay of tectonics and sedimentation; traditional climatostratigraphic approaches involving interpretation in terms of either ice advance/retreat cycles or glacio-eustatic sea-level change require revision. The direct record of continental glaciation in Earth history, in the form of classically-recognised continental glacial landforms and "tillites", is meagre; it is probable that more than 95% of the volume of preserved "glacial" strata are glacially-influenced marine deposits that record delivery of large amounts of glaciclastic sediment to offshore basins. This flux has been partially or completely reworked by "normal" sedimentary processes such that the record of glaciation and climate change is recorded in marine successions and is difficult to decipher. The dominant "glacial" facies in the rock record are subaqueous debris flow diamictites and turbidites recording the selective preservation of poorly-sorted glaciclastic sediment deposited in deep water basins by sediment gravity flows. However, these facies are also typical of many non-glacial settings, especially volcanically-influenced environments; numerous Archean and Proterozoic diamictites, described in the older literature as tillites, have no

  20. Excitation of the earth's rotational axis by recent glacial discharges

    NASA Technical Reports Server (NTRS)

    Gasperini, P.; Sabadini, R.; Yuen, D. A.

    1986-01-01

    The effects of present-day glacial discharges and the growth of the Antarctic ice sheet on exciting the earth's rotational axis are studied. Glacial forcing could cause a maximum change in J2 of about one-third of the observed amount, for the Maxwell rheology and for Burgers' body models with a long-term, lower-mantle viscosity greater than about 10 to the 23rd P. For transient rheologies the amount of excitation due to glacial melting decreases. Polar wander is not much excited by recent glacial melting for the various types of rheologies examined.

  1. Glacial isostatic uplift of the European Alps

    NASA Astrophysics Data System (ADS)

    Mey, Juergen; Scherler, Dirk; Wickert, Andrew D.; Egholm, David L.; Tesauro, Magdala; Schildgen, Taylor F.; Strecker, Manfred R.

    2016-04-01

    Present-day vertical movements of the Earth's surface are mostly due to tectonic deformation, volcanic processes, and crustal loading/unloading. In tectonically stable regions of North America and Scandinavia, vertical movements are almost entirely attributable to glacial isostatic rebound after the melting of the Laurentide and Fennoscandian ice sheets. In contrast, the Pleistocene Alpine icecap grew on a younger mountain belt that formed by collision of the European and African plates, still subject to shortening. Therefore, measured uplift is potentially a composite signal of tectonic shortening and unloading after deglaciation and concomitant erosion. Deciphering the contributions of tectonics and crustal unloading to present-day uplift rates in formerly-glaciated mountain belts is a prerequisite to using uplift data to estimate the viscosity structure of the Earth's mantle, a key variable in geodynamics. We evaluate the post-LGM glacial-isostatic rebound of the Alps following a 4-tiered procedure. First, we estimated the thickness distribution of sedimentary valley fills to create a bedrock map of the entire mountain belt. Second, this map was used as topographic basis for the reconstruction of the Alpine icecap using a numerical ice-flow model. Third, we estimated the equilibrium deflection of the Alpine lithosphere, using the combined loads of ice and sediments with a variable effective elastic thickness. Finally, we used an exponential decay function to infer the residual deflection and the present-day uplift rate for a range of upper mantle viscosities. Our analysis shows that virtually all of the geodetically measured surface uplift in the Swiss and the Austrian Alps can be attributed to glacial unloading and redistribution of sediments, assuming an upper-mantle viscosity lower than that inferred for an old craton (e.g., Fennoscandia), but higher than that for a region with recent crustal thinning (e.g., Basin and Range province).

  2. Slow growth rates of Amazonian trees: consequences for carbon cycling.

    PubMed

    Vieira, Simone; Trumbore, Susan; Camargo, Plinio B; Selhorst, Diogo; Chambers, Jeffrey Q; Higuchi, Niro; Martinelli, Luiz Antonio

    2005-12-20

    Quantifying age structure and tree growth rate of Amazonian forests is essential for understanding their role in the carbon cycle. Here, we use radiocarbon dating and direct measurement of diameter increment to document unexpectedly slow growth rates for trees from three locations spanning the Brazilian Amazon basin. Central Amazon trees, averaging only approximately 1 mm/year diameter increment, grow half as fast as those from areas with more seasonal rainfall to the east and west. Slow growth rates mean that trees can attain great ages; across our sites we estimate 17-50% of trees with diameter >10 cm have ages exceeding 300 years. Whereas a few emergent trees that make up a large portion of the biomass grow faster, small trees that are more abundant grow slowly and attain ages of hundreds of years. The mean age of carbon in living trees (60-110 years) is within the range of or slightly longer than the mean residence time calculated from C inventory divided by annual C allocation to wood growth (40-100 years). Faster C turnover is observed in stands with overall higher rates of diameter increment and a larger fraction of the biomass in large, fast-growing trees. As a consequence, forests can recover biomass relatively quickly after disturbance, whereas recovering species composition may take many centuries. Carbon cycle models that apply a single turnover time for carbon in forest biomass do not account for variations in life strategy and therefore may overestimate the carbon sequestration potential of Amazon forests.

  3. New mechanism proposed for glacial cycles

    NASA Astrophysics Data System (ADS)

    Newman, Alan

    Were the ice ages triggered by an influx of extraterrestrial dust or meteoroids hitting Earth's upper atmosphere? A controversial and still unproven new theory recently described by Muller and MacDonald [1995] in Nature links the 100,000 year glacial cycle with changes in Earth's orbital inclination relative to the plane of the solar system. And, say the theory developers, the only logical mechanism they can find for the connection is increasing amounts of extraterrestrial material entering the atmosphere whenever Earth's orbit sweeps through the solar plane. Climate researchers are just beginning to test the model's predictions.

  4. The vegetation and climate during the Last Glacial Cold Period, northern South Island, New Zealand

    NASA Astrophysics Data System (ADS)

    Callard, S. Louise; Newnham, Rewi M.; Vandergoes, Marcus J.; Alloway, Brent V.; Smith, Carol

    2013-08-01

    Pollen assemblages from Howard Valley, South Island, New Zealand, were used to reconstruct the palaeovegetation and infer past climate during the period ca 38-21 cal. ka, which encompasses the Marine Isotope Stage (MIS) 3/2 transition and Last Glacial Cold Period (LGCP). A glacier occupied the upper Howard Valley during the Last Glacial, whilst extensive glaciofluvial outwash surfaces were constructed in the lower valley. Episodic periods of fluvial aggradation and incision have produced a complex sequence of terraces flanking the main Howard River and its tributaries. Sedimentary sequences from three exposed valley fills, sampled for palynological analysis and radiocarbon dating, consist of a complex vertical and lateral arrangement of coarse textured cobbly sandy gravels interbedded with organic-rich silt deposits. Palynology of these organic-rich horizons was directly compared to an existing beetle record from these same horizons. During late MIS 3 the site was dominated by marshy shrubland vegetation interspersed with mixed beech forest, indicating temperatures ˜2-3 °C cooler than present. Climate cooling began as early as 35.7 cal. ka and coincides with evidence of cooling from other sites in New Zealand, South America and with an Antarctic cooling signature. A three phase vegetation and inferred climate pattern occurs at the site during the LGCP beginning with a transition to an alpine/sub-alpine grassland comparable to communities growing near treeline today marking the change to glacial conditions before 31 cal. ka. A small increase in tree abundance between ca 25.8 and 22.7 cal. ka suggests minor climate amelioration during the mid-LGCP. During this phase, a possible volcanically induced vegetation disruption caused by the deposition of the Kawakawa Tephra at 25 cal. ka is evident in the pollen record. This is followed by a further decline in tree pollen and increase in alpine grassland and herb pollen indicating further deterioration of conditions and a

  5. Geological constraints on Earth system sensitivity to CO2 during glacial and non-glacial times

    NASA Astrophysics Data System (ADS)

    Royer, D. L.; Park, J. J.; Pagani, M.; Beerling, D. J.

    2011-12-01

    Earth system climate sensitivity (ESS) is the long-term (>103 yr) response of global surface temperature to doubled CO2 that integrates fast and slow climate feedbacks. ESS has energy policy implications because global temperatures are not expected to decline appreciably for many centuries, even if anthropogenic greenhouse-gas emissions drop to zero. We report ESS estimates for the last 420 Myr of Earth history of 3 °C or higher during many non-glacial times and ~6-8 °C during glacial times. Analyses include both direct comparison of CO2 and temperature records, and fitting Berner's long-term carbon cycle model GEOCARBSULFvolc to proxy CO2 records while using ESS as a tunable parameter (Park & Royer, 2011, American Journal of Science 311: 1-26). Our ESS estimates are generally higher than climate sensitivities simulated from global climate models for the same ancient periods (~3 °C). Our two-fold amplification during glacial times is probably caused by long-term continental ice-sheet dynamics, a mechanism consistent with other studies. Even for non-glacial times, climate models do not capture the full suite of positive climate feedbacks. These absent feedbacks may be related to clouds, trace greenhouse gases, seasonal snow cover, and/or vegetation, especially in polar regions. Better characterization and quantification of these feedbacks is a priority given the current accumulation of atmospheric greenhouse gases.

  6. Glacial lakes in the Indian Himalayas--from an area-wide glacial lake inventory to on-site and modeling based risk assessment of critical glacial lakes.

    PubMed

    Worni, Raphael; Huggel, Christian; Stoffel, Markus

    2013-12-01

    Glacial lake hazards and glacial lake distributions are investigated in many glaciated regions of the world, but comparably little attention has been given to these topics in the Indian Himalayas. In this study we present a first area-wide glacial lake inventory, including a qualitative classification at 251 glacial lakes >0.01 km(2). Lakes were detected in the five states spanning the Indian Himalayas, and lake distribution pattern and lake characteristics were found to differ significantly between regions. Three glacial lakes, from different geographic and climatic regions within the Indian Himalayas were then selected for a detailed risk assessment. Lake outburst probability, potential outburst magnitudes and associated damage were evaluated on the basis of high-resolution satellite imagery, field assessments and through the use of a dynamic model. The glacial lakes analyzed in the states of Jammu and Kashmir and Himachal Pradesh were found to present moderate risks to downstream villages, whereas the lake in Sikkim severely threatens downstream locations. At the study site in Sikkim, a dam breach could trigger drainage of ca. 16×10(6)m(3) water and generate maximum lake discharge of nearly 7000 m(3) s(-). The identification of critical glacial lakes in the Indian Himalayas and the detailed risk assessments at three specific sites allow prioritizing further investigations and help in the definition of risk reduction actions.

  7. Range persistence during the last glacial maximum: Carex macrocephala was not restricted to glacial refugia.

    PubMed

    King, Matthew G; Horning, Matthew E; Roalson, Eric H

    2009-10-01

    The distribution of many species inhabiting northwestern North America has been heavily influenced by the climatic changes during the late Pleistocene. Several studies have suggested that species were restricted to glacial refugia north and/or south of the continental ice sheet front. It is also hypothesized that the coast of northwestern North America could have been a prime location for glacial refugia because of the lowering of the eustatic sea level and the concomitant rise of the continental shelf because of tectonic rebound. Alternatively, some coastal species distributions and demographics may have been unaffected in the long-term by the last glacial maximum (LGM). We tested the glacial refugium hypothesis on an obligate coastal plant species, Carex macrocephala by sampling 600 individuals from 41 populations with 11 nuclear microsatellite loci and the rpL16 plastid intragenic spacer region. The microsatellite data sets suggest a low level of population differentiation with a standardized G'(ST) = 0.032 and inbreeding was high with an F = 0.969. The homogenization of the populations along the coast was supported by a principal coordinate analysis, amovas and samova analyses. Analyses using the rpL16 data set support the results of the microsatellite analyses, with a low F(ST) of 0.042. Coalescent and mismatch analyses using rpL16 suggest that C. macrocephala has not gone through a significant bottleneck within the past 100,000 years, although a much earlier population expansion was indicated by the mismatch analysis. Carex macrocephala exhibits the characteristics of metapopulation dynamics and on the basis of these results, we concluded that it was not restricted to glacial refugia during the LGM, but that it existed as a large metapopulation.

  8. Tree Tectonics

    NASA Astrophysics Data System (ADS)

    Vogt, Peter R.

    2004-09-01

    Nature often replicates her processes at different scales of space and time in differing media. Here a tree-trunk cross section I am preparing for a dendrochronological display at the Battle Creek Cypress Swamp Nature Sanctuary (Calvert County, Maryland) dried and cracked in a way that replicates practically all the planform features found along the Mid-Oceanic Ridge (see Figure 1). The left-lateral offset of saw marks, contrasting with the right-lateral ``rift'' offset, even illustrates the distinction between transcurrent (strike-slip) and transform faults, the latter only recognized as a geologic feature, by J. Tuzo Wilson, in 1965. However, wood cracking is but one of many examples of natural processes that replicate one or several elements of lithospheric plate tectonics. Many of these examples occur in everyday venues and thus make great teaching aids, ``teachable'' from primary school to university levels. Plate tectonics, the dominant process of Earth geology, also occurs in miniature on the surface of some lava lakes, and as ``ice plate tectonics'' on our frozen seas and lakes. Ice tectonics also happens at larger spatial and temporal scales on the Jovian moons Europa and perhaps Ganymede. Tabletop plate tectonics, in which a molten-paraffin ``asthenosphere'' is surfaced by a skin of congealing wax ``plates,'' first replicated Mid-Oceanic Ridge type seafloor spreading more than three decades ago. A seismologist (J. Brune, personal communication, 2004) discovered wax plate tectonics by casually and serendipitously pulling a stick across a container of molten wax his wife and daughters had used in making candles. Brune and his student D. Oldenburg followed up and mirabile dictu published the results in Science (178, 301-304).

  9. Geothermal activity helps life survive glacial cycles.

    PubMed

    Fraser, Ceridwen I; Terauds, Aleks; Smellie, John; Convey, Peter; Chown, Steven L

    2014-04-15

    Climate change has played a critical role in the evolution and structure of Earth's biodiversity. Geothermal activity, which can maintain ice-free terrain in glaciated regions, provides a tantalizing solution to the question of how diverse life can survive glaciations. No comprehensive assessment of this "geothermal glacial refugia" hypothesis has yet been undertaken, but Antarctica provides a unique setting for doing so. The continent has experienced repeated glaciations that most models indicate blanketed the continent in ice, yet many Antarctic species appear to have evolved in almost total isolation for millions of years, and hence must have persisted in situ throughout. How could terrestrial species have survived extreme glaciation events on the continent? Under a hypothesis of geothermal glacial refugia and subsequent recolonization of nongeothermal regions, we would expect to find greater contemporary diversity close to geothermal sites than in nongeothermal regions, and significant nestedness by distance of this diversity. We used spatial modeling approaches and the most comprehensive, validated terrestrial biodiversity dataset yet created for Antarctica to assess spatial patterns of diversity on the continent. Models clearly support our hypothesis, indicating that geothermally active regions have played a key role in structuring biodiversity patterns in Antarctica. These results provide critical insights into the evolutionary importance of geothermal refugia and the history of Antarctic species.

  10. Geothermal activity helps life survive glacial cycles

    PubMed Central

    Fraser, Ceridwen I.; Terauds, Aleks; Smellie, John; Convey, Peter; Chown, Steven L.

    2014-01-01

    Climate change has played a critical role in the evolution and structure of Earth’s biodiversity. Geothermal activity, which can maintain ice-free terrain in glaciated regions, provides a tantalizing solution to the question of how diverse life can survive glaciations. No comprehensive assessment of this “geothermal glacial refugia” hypothesis has yet been undertaken, but Antarctica provides a unique setting for doing so. The continent has experienced repeated glaciations that most models indicate blanketed the continent in ice, yet many Antarctic species appear to have evolved in almost total isolation for millions of years, and hence must have persisted in situ throughout. How could terrestrial species have survived extreme glaciation events on the continent? Under a hypothesis of geothermal glacial refugia and subsequent recolonization of nongeothermal regions, we would expect to find greater contemporary diversity close to geothermal sites than in nongeothermal regions, and significant nestedness by distance of this diversity. We used spatial modeling approaches and the most comprehensive, validated terrestrial biodiversity dataset yet created for Antarctica to assess spatial patterns of diversity on the continent. Models clearly support our hypothesis, indicating that geothermally active regions have played a key role in structuring biodiversity patterns in Antarctica. These results provide critical insights into the evolutionary importance of geothermal refugia and the history of Antarctic species. PMID:24616489

  11. Interhemispheric Correlation of Late Pleistocene Glacial Events

    NASA Astrophysics Data System (ADS)

    Lowell, T. V.; Heusser, C. J.; Andersen, B. G.; Moreno, P. I.; Hauser, A.; Heusser, L. E.; Schluchter, C.; Marchant, D. R.; Denton, G. H.

    1995-09-01

    A radiocarbon chronology shows that piedmont glacier lobes in the Chilean Andes achieved maxima during the last glaciation at 13,900 to 14,890, 21,000, 23,060, 26,940, 29,600, and >=33,500 carbon-14 years before present (14C yr B.P.) in a cold and wet Subantarctic Parkland environment. The last glaciation ended with massive collapse of ice lobes close to 14,000 14C yr B.P., accompanied by an influx of North Patagonian Rain Forest species. In the Southern Alps of New Zealand, additional glacial maxima are registered at 17,720 14C yr B.P., and at the beginning of the Younger Dryas at 11,050 14C yr B.P. These glacial maxima in mid-latitude mountains rimming the South Pacific were coeval with ice-rafting pulses in the North Atlantic Ocean. Furthermore, the last termination began suddenly and simultaneously in both polar hemispheres before the resumption of the modern mode of deep-water production in the Nordic Seas. Such interhemispheric coupling implies a global atmospheric signal rather than regional climatic changes caused by North Atlantic thermohaline switches or Laurentide ice surges.

  12. Glacial CO2 Cycles: A Composite Scenario

    NASA Astrophysics Data System (ADS)

    Broecker, W. S.

    2015-12-01

    There are three main contributors to the glacial drawdown of atmospheric CO2 content: starvation of the supply of carbon to the ocean-atmosphere reservoir, excess CO2 storage in the deep sea, and surface-ocean cooling. In this talk, I explore a scenario in which all three play significant roles. Key to this scenario is the assumption that deep ocean storage is related to the extent of nutrient stratification of the deep Atlantic. The stronger this stratification, the larger the storage of respiration CO2. Further, it is my contention that the link between Milankovitch insolation cycles and climate is reorganizations of the ocean's thermohaline circulation leading to changes in the deep ocean's CO2 storage. If this is the case, the deep Atlantic d13C record kept in benthic foraminifera shells tells us that deep ocean CO2 storage follows Northern Hemisphere summer insolation cycles and thus lacks the downward ramp so prominent in the records of sea level, benthic 18O and CO2. Rather, the ramp is created by the damping of planetary CO2 emissions during glacial time intervals. As it is premature to present a specific scenario, I provide an example as to how these three contributors might be combined. As their magnitudes and shapes remain largely unconstrained, the intent of this exercise is to provoke creative thinking.

  13. Apparatus for separating and recovering hydrogen isotopes

    DOEpatents

    Heung, Leung K.

    1994-01-01

    An apparatus for recovering hydrogen and separating its isotopes. The apparatus includes a housing bearing at least a fluid inlet and a fluid outlet. A baffle is disposed within the housing, attached thereto by a bracket. A hollow conduit is coiled about the baffle, in spaced relation to the baffle and the housing. The coiled conduit is at least partially filled with a hydride. The hydride can be heated to a high temperature and cooled to a low temperature quickly by circulating a heat transfer fluid in the housing. The spacing between the baffle and the housing maximizes the heat exchange rate between the fluid in the housing and the hydride in the conduit. The apparatus can be used to recover hydrogen isotopes (protium, deuterium and tritium) from gaseous mixtures, or to separate hydrogen isotopes from each other.

  14. Emergency destruction system for recovered chemical munitions

    SciTech Connect

    Shepodd, T.J.; Stofleth, J.H.; Haroldsen, B.L.

    1998-04-01

    At the request of the US Army Project Manager for Non-Stockpile Chemical Materiel, Sandia National Laboratories is developing a transportable system for destroying recovered, explosively configured, chemical warfare munitions. The system uses shaped charges to access the agent and burster followed by chemical neutralization to destroy them. The entire process takes place inside a sealed pressure vessel. In this paper, they review the design, operation, and testing of a prototype system capable of containing up to one pound of explosive.

  15. Method of recovering oil-based fluid

    SciTech Connect

    Brinkley, H.E.

    1993-07-13

    A method is described of recovering oil-based fluid, said method comprising the steps of: applying an oil-based fluid absorbent cloth of man-made fiber to an oil-based fluid, the cloth having at least a portion thereof that is napped so as to raise ends and loops of the man-made fibers and define voids; and absorbing the oil-based fluid into the napped portion of the cloth.

  16. Recovering intrinsic fluorescence by Monte Carlo modeling.

    PubMed

    Müller, Manfred; Hendriks, Benno H W

    2013-02-01

    We present a novel way to recover intrinsic fluorescence in turbid media based on Monte Carlo generated look-up tables and making use of a diffuse reflectance measurement taken at the same location. The method has been validated on various phantoms with known intrinsic fluorescence and is benchmarked against photon-migration methods. This new method combines more flexibility in the probe design with fast reconstruction and showed similar reconstruction accuracy as found in other reconstruction methods.

  17. Recovering selenium from copper refinery slimes

    NASA Astrophysics Data System (ADS)

    Hyvärinen, Olli; Lindroos, Leo; Yllö, Erkki

    1989-07-01

    The selenium contained within copper refinery slimes may be recovered advantageously by roasting at about 600°C. While roasting in air is inefficient, roasting in a sulfating atmosphere enables practically complete selenium recovery. Based on laboratory tests, a new selenium recovery process was adopted at Outokumpu Copper Refinery. In this process, sulfation is achieved by feeding sulfur dioxide and oxygen into the roasting furnace.

  18. The Needs of Trees

    ERIC Educational Resources Information Center

    Boyd, Amy E.; Cooper, Jim

    2004-01-01

    Tree rings can be used not only to look at plant growth, but also to make connections between plant growth and resource availability. In this lesson, students in 2nd-4th grades use role-play to become familiar with basic requirements of trees and how availability of those resources is related to tree ring sizes and tree growth. These concepts can…

  19. Ocean Drilling Program Leg 178 (Antarctic Peninsula): Sedimentology of glacially influenced continental margin topsets and foresets

    USGS Publications Warehouse

    Eyles, N.; Daniels, J.; Osterman, L.E.; Januszczak, N.

    2001-01-01

    Ocean Drilling Program Leg 178 (February-April 1998) drilled two sites (Sites 1097 and 1103) on the outer Antarctic Peninsula Pacific continental shelf. Recovered strata are no older than late Miocene or early Pliocene (<4.6 Ma). Recovery at shallow depths in loosely consolidated and iceberg-turbated bouldery sediment was poor but improved with increasing depth and consolidation to allow description of lithofacies and biofacies and interpretation of depositional environment. Site 1097 lies on the outer shelf within Marguerite Trough which is a major outlet for ice expanding seaward from the Antarctic Peninsula and reached a maximum depth drilled of 436.6 m below the sea floor (mbsf). Seismic stratigraphic data show flat-lying upper strata resting on strata that dip gently seaward. Uppermost strata, to a depth of 150 mbsf, were poorly recovered, but data suggest they consist of diamictites containing reworked and abraded marine microfauna. This interval is interpreted as having been deposited largely as till produced by subglacial cannibalization of marine sediments (deformation till) recording ice sheet expansion across the shelf. Underlying gently dipping strata show massive, stratified and graded diamictite facies with common bioturbation and slump stuctures that are interbedded with laminated and massive mudstones with dropstones. The succession contains a well-preserved in situ marine microfauna typical of open marine and proglacial marine environments. The lower gently dipping succession at Site 1097 is interpreted as a complex of sediment gravity flows formed of poorly sorted glacial debris. Site 1103 was drilled in that part of the continental margin that shows uppermost flat-lying continental shelf topsets overlying steeper dipping slope foresets seaward of a structural mid-shelf high. Drilling reached a depth of 363 mbsf with good recovery in steeply dipping continental slope foreset strata. Foreset strata are dominated by massive and chaotically

  20. Method for recovering metals from waste

    DOEpatents

    Wicks, George G.; Clark, David E.; Schulz, Rebecca L.

    1998-01-01

    A method for recovering metals from metals-containing wastes, and vitrifying the remainder of the wastes for disposal. Metals-containing wastes such as circuit boards, cathode ray tubes, vacuum tubes, transistors and so forth, are broken up and placed in a suitable container. The container is heated by microwaves to a first temperature in the range of approximately 300.degree.-800.degree. C. to combust organic materials in the waste, then heated further to a second temperature in the range of approximately 1,000.degree.-1,550.degree. C. at which temperature glass formers present in the waste will cause it to melt and vitrify. Low-melting-point metals such as tin and aluminum can be recovered after organics combustion is substantially complete. Metals with higher melting points, such as gold, silver and copper, can be recovered from the solidified product or separated from the waste at their respective melting points. Network former-containing materials can be added at the start of the process to assist vitrification.

  1. Method for recovering metals from waste

    DOEpatents

    Wicks, George G.; Clark, David E.; Schulz, Rebecca L.

    2000-01-01

    A method for recovering metals from metals-containing wastes, and vitrifying the remainder of the wastes for disposal. Metals-containing wastes such as circuit boards, cathode ray tubes, vacuum tubes, transistors and so forth, are broken up and placed in a suitable container. The container is heated by microwaves to a first temperature in the range of approximately 300-800.degree. C. to combust organic materials in the waste, then heated further to a second temperature in the range of approximately 1,000-1,550.degree. C. at which temperature glass formers present in the waste will cause it to melt and vitrify. Low-melting-point metals such as tin and aluminum can be recovered after organics combustion is substantially complete. Metals with higher melting points, such as gold, silver and copper, can be recovered from the solidified product or separated from the waste at their respective melting points. Network former-containing materials can be added at the start of the process to assist vitrification.

  2. Method for recovering materials from waste

    DOEpatents

    Wicks, G.G.; Clark, D.E.; Schulz, R.L.

    1994-01-01

    A method for recovering metals from metals-containing wastes, a vitrifying the remainder of the wastes for disposal. Metals-containing wastes such as circuit boards, cathode ray tubes, vacuum tubes, transistors and so forth, are broken up and placed in a suitable container. The container is heated by microwaves to a first temperature in the range of approximately 300--800{degrees}C to combust organic materials in the waste, then heated further to a second temperature in the range of approximately 1000--1550{degrees}C at which temperature glass formers present in the waste will cause it to melt and vitrify. Low-melting-point metals such as tin and aluminum can be recovered after organics combustion is substantially complete. Metals with higher melting points, such as gold, silver and copper, can be recovered from the solidified product or separated from the waste at their respective melting points. Network former-containing materials can be added at the start of the process to assist vitrification.

  3. Method for recovering metals from waste

    DOEpatents

    Wicks, G.G.; Clark, D.E.; Schulz, R.L.

    1998-12-01

    A method is described for recovering metals from metals-containing wastes, and vitrifying the remainder of the wastes for disposal. Metals-containing wastes such as circuit boards, cathode ray tubes, vacuum tubes, transistors and so forth, are broken up and placed in a suitable container. The container is heated by microwaves to a first temperature in the range of approximately 300--800 C to combust organic materials in the waste, then heated further to a second temperature in the range of approximately 1,000--1,550 C at which temperature glass formers present in the waste will cause it to melt and vitrify. Low-melting-point metals such as tin and aluminum can be recovered after organics combustion is substantially complete. Metals with higher melting points, such as gold, silver and copper, can be recovered from the solidified product or separated from the waste at their respective melting points. Network former-containing materials can be added at the start of the process to assist vitrification. 2 figs.

  4. Glacial magnetite dissolution in abyssal NW Pacific sediments - evidence for carbon trapping?

    NASA Astrophysics Data System (ADS)

    Korff, Lucia; von Dobeneck, Tilo; Frederichs, Thomas; Kasten, Sabine; Kuhn, Gerhard; Gersonde, Rainer; Diekmann, Bernhard

    2016-04-01

    The abyssal North Pacific Ocean's large volume, depth, and terminal position on the deep oceanic conveyor make it a candidate site for deep carbon trapping as postulated by climate theory to explain the massive glacial drawdown of atmospheric CO2. As the major basins of the North Pacific have depths of 5500-6500m, far below the modern and glacial Calcite Compensation Depths (CCD), these abyssal sediments are carbonate-free and therefore not suitable for carbonate-based paleoceanographic proxy reconstructions. Instead, paleo-, rock and environmental magnetic methods are generally well applicable to hololytic abyssal muds and clays. In 2009, the international paleoceanographic research cruise SO 202 INOPEX ('Innovative North Pacific Experiment') of the German RV SONNE collected two ocean-spanning EW sediment core transects of the North Pacific and Bering Sea recovering a total of 50 piston and gravity cores from 45 sites. Out of seven here considered abyssal Northwest Pacific piston cores collected at water depths of 5100 to 5700m with mostly coherent shipboard susceptibility logs, the 20.23m long SO202-39-3, retrieved from 5102 m water depth east of northern Shatsky Rise (38°00.70'N, 164°26.78'E), was rated as the stratigraphically most promising record of the entire core transect and selected for detailed paleo- and environmental magnetic, geochemical and sedimentological investigations. This core was dated by correlating its RPI and Ba/Ti records to well-dated reference records and obviously provides a continuous sequence of the past 940 kyrs. The most striking orck magnetic features are coherent magnetite-depleted zones corresponding to glacial periods. In the interglacial sections, detrital, volcanic and even submicron bacterial magnetite fractions are excellently preserved. These alternating magnetite preservation states seem to reflect dramatic oxygenation changes in the deep North Pacific Ocean and hint at large-scale benthic glacial carbon trapping

  5. Timing of advance and basal condition of the Laurentide Ice Sheet during the last glacial maximum in the Richardson Mountains, NWT

    NASA Astrophysics Data System (ADS)

    Lacelle, Denis; Lauriol, Bernard; Zazula, Grant; Ghaleb, Bassam; Utting, Nicholas; Clark, Ian D.

    2013-09-01

    This study presents new ages for the northwest section of the Laurentide Ice Sheet (LIS) glacial chronology from material recovered from two retrogressive thaw slumps exposed in the Richardson Mountains, Northwest Territories, Canada. One study site, located at the maximum glacial limit of the LIS in the Richardson Mountains, had calcite concretions recovered from aufeis buried by glacial till that were dated by U/Th disequilibrium to 18,500 cal yr BP. The second site, located on the Peel Plateau to the east yielded a fossil horse (Equus) mandible that was radiocarbon dated to ca. 19,700 cal yr BP. These ages indicate that the Peel Plateau on the eastern flanks of the Richardson Mountains was glaciated only after 18,500 cal yr BP, which is later than previous models for the global last glacial maximum (LGM). As the LIS retreated the Peel Plateau around 15,000 cal yr BP, following the age of the Tutsieta phase, we conclude that the presence of the northwestern margin of the LIS at its maximum limit was a very short event in the western Canadian Arctic.

  6. Sub-glacial Origin of the Hot Springs Bay Valley hydrothermal System, Akutan, Alaska

    NASA Astrophysics Data System (ADS)

    Stelling, P. L.; Tobin, B.; Knapp, P.

    2015-12-01

    Exploration for geothermal energy in Hot Springs Bay Valley (HSBV) on Akutan Island, Alaska, has revealed a rich hydrothermal history, including what appears to be a stage of peak activity during a significant glacial period. Alteration mineralogy observed in 754 m of drill core recovered from the outflow zone is dominated by chlorite and includes minor smectite clays, a suite of zeolite species and several moderately high-temperature hydrothermal minerals (epidote/clinozoisite, prehnite, adularia and wairakite). The latter minerals each have minimum formation temperatures exceeding 200 oC, and fluid inclusion results in related calcite crystals indicate temperatures of formation to be as high as 275 oC, some 100 oC hotter than the modern boiling point with depth (BPD) curve at that depth (>62 m). In order to maintain liquid temperatures this high, the pressure during mineralization must have been substantially greater (~680 bar), a pressure change equivalent to erosion of ~280 m of rock (ρ=2.5 g/cm3). Although glacial erosion rates are too low (0.034 mm/yr; Bekele et al., 2003) for this amount of erosion to occur in a single glaciation, glacial melting and ablation are substantially more rapid (~100 mm/yr; Bekele et al., 2003; Person et al., 2012). Thus, a more probable scenario than pure erosion is that peak hydrothermal conditions occurred during a large glacial event, with the added pressure from the overlying ice allowing the high temperature minerals to form closer to the ground surface. Subsequent melting of the ice eroded upper tributary valleys and upper levels of the originally smectite-rich alteration assemblage, explaining the paucity of swelling clays in the region. We present mineralogical, fluid inclusion and geochronologic evidence to support these conclusions, and discuss the general implications of sub-glacial hydrothermal system formation and geothermal resource potential. References: Bekele, E., Rostron, B. and Person, M. (2003) Fluid pressure

  7. Quaternary Glacial Mapping in Western Wisconsin Using Soil Survey Information

    ERIC Educational Resources Information Center

    Oehlke, Betsy M.; Dolliver, Holly A. S.

    2011-01-01

    The majority of soils in the western Wisconsin have developed from glacial sediments deposited during the Quaternary Period (2.6 million years before present). In many regions, multiple advances and retreats have left a complex landscape of diverse glacial sediments and landforms. The soils that have developed on these deposits reflect the nature…

  8. Contrasting scaling properties of interglacial and glacial climates

    PubMed Central

    Shao, Zhi-Gang; Ditlevsen, Peter D.

    2016-01-01

    Understanding natural climate variability is essential for assessments of climate change. This is reflected in the scaling properties of climate records. The scaling exponents of the interglacial and the glacial climates are fundamentally different. The Holocene record is monofractal, with a scaling exponent H∼0.7. On the contrary, the glacial record is multifractal, with a significantly higher scaling exponent H∼1.2, indicating a longer persistence time and stronger nonlinearities in the glacial climate. The glacial climate is dominated by the strong multi-millennial Dansgaard–Oeschger (DO) events influencing the long-time correlation. However, by separately analysing the last glacial maximum lacking DO events, here we find the same scaling for that period as for the full glacial period. The unbroken scaling thus indicates that the DO events are part of the natural variability and not externally triggered. At glacial time scales, there is a scale break to a trivial scaling, contrasting the DO events from the similarly saw-tooth-shaped glacial cycles. PMID:26980084

  9. Contrasting scaling properties of interglacial and glacial climates.

    PubMed

    Shao, Zhi-Gang; Ditlevsen, Peter D

    2016-03-16

    Understanding natural climate variability is essential for assessments of climate change. This is reflected in the scaling properties of climate records. The scaling exponents of the interglacial and the glacial climates are fundamentally different. The Holocene record is monofractal, with a scaling exponent H∼0.7. On the contrary, the glacial record is multifractal, with a significantly higher scaling exponent H∼1.2, indicating a longer persistence time and stronger nonlinearities in the glacial climate. The glacial climate is dominated by the strong multi-millennial Dansgaard-Oeschger (DO) events influencing the long-time correlation. However, by separately analysing the last glacial maximum lacking DO events, here we find the same scaling for that period as for the full glacial period. The unbroken scaling thus indicates that the DO events are part of the natural variability and not externally triggered. At glacial time scales, there is a scale break to a trivial scaling, contrasting the DO events from the similarly saw-tooth-shaped glacial cycles.

  10. Hydrogeology of glacial drift, Mesabi Iron Range, northeastern Minnesota

    USGS Publications Warehouse

    Winter, Thomas C.

    1973-01-01

    Practical sustained yield of aquifers in glacial drift is estimated to be as much as 40 million gallons per day from known aquifers. Assuming that the ratio of area underlain by aquifer to total area is constant for the study area (about 20 percent where mapped in detail), as much as 80 million gallons per day could be developed from glacial-drift aquifers.

  11. Tea tree oil.

    PubMed

    Hartford, Orville; Zug, Kathryn A

    2005-09-01

    Tea tree oil is a popular ingredient in many over-the-counter healthcare and cosmetic products. With the explosion of the natural and alternative medicine industry, more and more people are using products containing tea tree oil. This article reviews basic information about tea tree oil and contact allergy, including sources of tea tree oil, chemical composition, potential cross reactions, reported cases of allergic contact dermatitis, allergenic compounds in tea tree oil, practical patch testing information, and preventive measures.

  12. Oxygen isotopic composition of the Mediterranean Sea since the Last Glacial Maximum: constraints from pore water analyses

    NASA Astrophysics Data System (ADS)

    Paul, Hilary A.; Bernasconi, Stefano M.; Schmid, Daniel W.; McKenzie, Judith A.

    2001-09-01

    Interstitial waters recovered from Ocean Drilling Program, Leg 161, site 976 in the western Mediterranean Sea are used in conjunction with a numerical model to constrain the δ 18O of seawater in the basin since the Last Glacial Maximum, including Sapropel Event 1. To resolve the oxygen isotopic composition of the deep Mediterranean, we use a model that couples fluid diffusion with advective transport, thus producing a profile of seawater δ 18O variability that is unaffected by glacial-interglacial variations in marine temperature. Comparing our reconstructed seawater δ 18O to recent determinations of 1.0‰ for the mean ocean change in glacial-interglacial δ 18O due to the expansion of global ice volume, we calculate an additional 0.2‰ increase in Mediterranean δ 18O caused by local evaporative enrichment. This estimate of δ 18O change, due to salinity variability, is smaller than previous studies have proposed and demonstrates that Mediterranean records of foraminiferal calcite δ 18O from the last glacial period include a strong temperature component. Paleotemperatures determined in combination with a stacked record of foraminiferal calcite depict almost 9°C of regional cooling for the Last Glacial Maximum. Model results suggest a decrease of ˜1.1‰ in seawater δ 18O relative to the modern value caused by increased freshwater input and reduced salinity accompanying the formation of the most recent sapropel. The results additionally indicate the existence of isotopically light water circulating down to bottom water depths, at least in the western Mediterranean, supporting the existence of an 'anti-estuarine' thermohaline circulation pattern during Sapropel Event 1.

  13. Evidence for enhanced convection of North Pacific Intermediate Water to the low-latitude Pacific under glacial conditions

    NASA Astrophysics Data System (ADS)

    Max, L.; Rippert, N.; Lembke-Jene, L.; Mackensen, A.; Nürnberg, D.; Tiedemann, R.

    2017-01-01

    We provide high-resolution foraminiferal stable carbon isotope (δ13C) records from the subarctic Pacific and Eastern Equatorial Pacific (EEP) to investigate circulation dynamics between the extratropical and tropical North Pacific during the past 60 kyr. We measured the δ13C composition of the epibenthic foraminiferal species Cibicides lobatulus from a shallow sediment core recovered from the western Bering Sea (SO201-2-101KL; 58°52.52'N, 170°41.45'E; 630 m water depth) to reconstruct past ventilation changes close to the source region of Glacial North Pacific Intermediate Water (GNPIW). Information regarding glacial changes in the δ13C of subthermocline water masses in the EEP is derived from the deep-dwelling planktonic foraminifera Globorotaloides hexagonus at ODP Site 1240 (00°01.31'N, 82°27.76'W; 2921 m water depth). Apparent similarities in the long-term evolution of δ13C between GNPIW, intermediate waters in the eastern tropical North Pacific and subthermocline water masses in the EEP suggest the expansion of relatively 13C-depleted, nutrient-enriched, and northern sourced intermediate waters to the equatorial Pacific under glacial conditions. Further, it appears that additional influence of GNPIW to the tropical Pacific is consistent with changes in nutrient distribution and biological productivity in surface waters of the glacial EEP. Our findings highlight potential links between North Pacific mid-depth circulation changes, nutrient cycling, and biological productivity in the equatorial Pacific under glacial boundary conditions.

  14. Glacial-interglacial vegetation change in the Zambezi catchment

    NASA Astrophysics Data System (ADS)

    Dupont, L. M.; Kuhlmann, H.

    2017-01-01

    Changes in the environment are thought to have had strong impact on human evolution. The pollen record of GeoB9311, retrieved offshore of the Zambezi River mouth, indicates glacial-interglacial changes in the vegetation of southern East Africa with enhanced forests in the coastal area during interglacials, more Afromontane forest and ericaceous bushland during glacials and an increase in mopane woodland during the transitional periods. C4 swamps, probably with papyrus, might have spread during the more humid phases of the glacial, while mangroves responded sensitively to changes in sea level. The spread of open ericaceous bushland and Afromontane forest during glacials is found for most of Southern Africa with the exception of the extreme south and southwest regions. In contrast to the western part of the continent, forest and woodland in East Africa did not completely disappear during the glacial. It seems that on a regional scale climatic perturbations of the vegetation are less severe than in West Africa.

  15. Late Holocene glacial history of the Copper River Delta, coastal south-central Alaska, and controls on valley glacier fluctuations

    NASA Astrophysics Data System (ADS)

    Barclay, David J.; Yager, Elowyn M.; Graves, Jason; Kloczko, Michael; Calkin, Parker E.

    2013-12-01

    Fluctuations of four valley glaciers in coastal south-central Alaska are reconstructed for the past two millennia. Tree-ring crossdates on 216 glacially killed stumps and logs provide the primary age control, and are integrated with glacial stratigraphy, ages of living trees on extant landforms, and historic forefield photographs to constrain former ice margin positions. Sheridan Glacier shows four distinct phases of advance: in the 530s to c.640s in the First Millennium A.D., and the 1240s to 1280s, 1510s to 1700s, and c.1810s to 1860s during the Little Ice Age (LIA). The latter two LIA advances are also recorded on the forefields of nearby Scott, Sherman and Saddlebag glaciers. Comparison of the Sheridan record with other two-millennia long tree-ring constrained valley glacier histories from south-central Alaska and Switzerland shows the same four intervals of advance. These expansions were coeval with decreases in insolation, supporting solar irradiance as the primary pacemaker for centennial-scale fluctuations of mid-latitude valley glaciers prior to the 20th century. Volcanic aerosols, coupled atmospheric-oceanic systems, and local glacier-specific effects may be important to glacier fluctuations as supplemental forcing factors, for causing decadal-scale differences between regions, and as a climatic filter affecting the magnitude of advances.

  16. Glacial isostatic uplift of the European Alps

    PubMed Central

    Mey, Jürgen; Scherler, Dirk; Wickert, Andrew D.; Egholm, David L.; Tesauro, Magdala; Schildgen, Taylor F.; Strecker, Manfred R.

    2016-01-01

    Following the last glacial maximum (LGM), the demise of continental ice sheets induced crustal rebound in tectonically stable regions of North America and Scandinavia that is still ongoing. Unlike the ice sheets, the Alpine ice cap developed in an orogen where the measured uplift is potentially attributed to tectonic shortening, lithospheric delamination and unloading due to deglaciation and erosion. Here we show that ∼90% of the geodetically measured rock uplift in the Alps can be explained by the Earth's viscoelastic response to LGM deglaciation. We modelled rock uplift by reconstructing the Alpine ice cap, while accounting for postglacial erosion, sediment deposition and spatial variations in lithospheric rigidity. Clusters of excessive uplift in the Rhône Valley and in the Eastern Alps delineate regions potentially affected by mantle processes, crustal heterogeneity and active tectonics. Our study shows that even small LGM ice caps can dominate present-day rock uplift in tectonically active regions. PMID:27830704

  17. Measurements of Glacial Isostatic Adjustment in Greenland

    NASA Astrophysics Data System (ADS)

    Khan, Shfaqat Abbas; Bamber, Jonathan; Bevis, Michael; Wahr, John; van dam, Tonie; Wouters, Bert; Willis, Michael

    2015-04-01

    The Greenland GPS network (GNET) was constructed to provide a new means to assess viscoelastic and elastic adjustments driven by past and present-day changes in ice mass. Here we assess existing glacial isostatic adjustments (GIA) models by analysing 1995-present data from 61 continuous GPS receivers located along the edge of the Greenland ice sheet. Since GPS receivers measure both the GIA and elastic signal, we isolate the GIA signal, by removing the elastic adjustments of the crust due to present-day mass loss using high-resolution ice surface elevation change grids derived from satellite and airborne altimetry measurements (ERS1/2, ICESat, ATM, ENVISAT, and CryoSat-2). In general, our observed GIA rates contradict models, suggesting GIA models and hence their ice load history for Greenland are not well constrained.

  18. Quaternary glacial stratigraphy and chronology of Mexico

    NASA Astrophysics Data System (ADS)

    White, Sidney E.

    The volcano Iztaccihuatl in central Mexico was glaciated twice during the middle Pleistocene, once probably in pre-Illinoian (or pre-Bull Lake) time, and once in late Illinoian (or Bull Lake) time. Glaciation during the late Pleistocene was restricted to the late Wisconsin (or Pinedale). A maximum advance and one readvance are recorded in the early part, and one readvance in the latter part. Three or four small neoglacial advances occurred during the Holocene. Two other volcanoes nearby, Ajusco and Malinche, have a partial record of late Pleistocene and Holocene glaciations. Three others, Popocatépetl, Pico de Orizaba, and Nevado de Toluca, have a full Holocene record of three to five glacial advances during Neoglaciation.

  19. Glacial isostatic uplift of the European Alps.

    PubMed

    Mey, Jürgen; Scherler, Dirk; Wickert, Andrew D; Egholm, David L; Tesauro, Magdala; Schildgen, Taylor F; Strecker, Manfred R

    2016-11-10

    Following the last glacial maximum (LGM), the demise of continental ice sheets induced crustal rebound in tectonically stable regions of North America and Scandinavia that is still ongoing. Unlike the ice sheets, the Alpine ice cap developed in an orogen where the measured uplift is potentially attributed to tectonic shortening, lithospheric delamination and unloading due to deglaciation and erosion. Here we show that ∼90% of the geodetically measured rock uplift in the Alps can be explained by the Earth's viscoelastic response to LGM deglaciation. We modelled rock uplift by reconstructing the Alpine ice cap, while accounting for postglacial erosion, sediment deposition and spatial variations in lithospheric rigidity. Clusters of excessive uplift in the Rhône Valley and in the Eastern Alps delineate regions potentially affected by mantle processes, crustal heterogeneity and active tectonics. Our study shows that even small LGM ice caps can dominate present-day rock uplift in tectonically active regions.

  20. Glacial isostatic uplift of the European Alps

    NASA Astrophysics Data System (ADS)

    Mey, Jürgen; Scherler, Dirk; Wickert, Andrew D.; Egholm, David L.; Tesauro, Magdala; Schildgen, Taylor F.; Strecker, Manfred R.

    2016-11-01

    Following the last glacial maximum (LGM), the demise of continental ice sheets induced crustal rebound in tectonically stable regions of North America and Scandinavia that is still ongoing. Unlike the ice sheets, the Alpine ice cap developed in an orogen where the measured uplift is potentially attributed to tectonic shortening, lithospheric delamination and unloading due to deglaciation and erosion. Here we show that ~90% of the geodetically measured rock uplift in the Alps can be explained by the Earth's viscoelastic response to LGM deglaciation. We modelled rock uplift by reconstructing the Alpine ice cap, while accounting for postglacial erosion, sediment deposition and spatial variations in lithospheric rigidity. Clusters of excessive uplift in the Rhône Valley and in the Eastern Alps delineate regions potentially affected by mantle processes, crustal heterogeneity and active tectonics. Our study shows that even small LGM ice caps can dominate present-day rock uplift in tectonically active regions.

  1. Recovering hydrocarbons from hydrocarbon-containing vapors

    DOEpatents

    Mirza, Zia I.; Knell, Everett W.; Winter, Bruce L.

    1980-09-30

    Values are recovered from a hydrocarbon-containing vapor by contacting the vapor with quench liquid consisting essentially of hydrocarbons to form a condensate and a vapor residue, the condensate and quench fluid forming a combined liquid stream. The combined liquid stream is mixed with a viscosity-lowering liquid to form a mixed liquid having a viscosity lower than the viscosity of the combined liquid stream to permit easy handling of the combined liquid stream. The quench liquid is a cooled portion of the mixed liquid. Viscosity-lowering liquid is separated from a portion of the mixed liquid and cycled to form additional mixed liquid.

  2. Recovering the fine structures in solar images

    NASA Technical Reports Server (NTRS)

    Karovska, Margarita; Habbal, S. R.; Golub, L.; Deluca, E.; Hudson, Hugh S.

    1994-01-01

    Several examples of the capability of the blind iterative deconvolution (BID) technique to recover the real point spread function, when limited a priori information is available about its characteristics. To demonstrate the potential of image post-processing for probing the fine scale and temporal variability of the solar atmosphere, the BID technique is applied to different samples of solar observations from space. The BID technique was originally proposed for correction of the effects of atmospheric turbulence on optical images. The processed images provide a detailed view of the spatial structure of the solar atmosphere at different heights in regions with different large-scale magnetic field structures.

  3. Recovering valuable metals from recycled photovoltaic modules.

    PubMed

    Yi, Youn Kyu; Kim, Hyun Soo; Tran, Tam; Hong, Sung Kil; Kim, Myong Jun

    2014-07-01

    Recovering valuable metals such as Si, Ag, Cu, and Al has become a pressing issue as end-of-life photovoltaic modules need to be recycled in the near future to meet legislative requirements in most countries. Of major interest is the recovery and recycling of high-purity silicon (> 99.9%) for the production of wafers and semiconductors. The value of Si in crystalline-type photovoltaic modules is estimated to be -$95/kW at the 2012 metal price. At the current installed capacity of 30 GW/yr, the metal value in the PV modules represents valuable resources that should be recovered in the future. The recycling of end-of-life photovoltaic modules would supply > 88,000 and 207,000 tpa Si by 2040 and 2050, respectively. This represents more than 50% of the required Si for module fabrication. Experimental testwork on crystalline Si modules could recover a > 99.98%-grade Si product by HNO3/NaOH leaching to remove Al, Ag, and Ti and other metal ions from the doped Si. A further pyrometallurgical smelting at 1520 degrees C using CaO-CaF2-SiO2 slag mixture to scavenge the residual metals after acid leaching could finally produce > 99.998%-grade Si. A process based on HNO3/NaOH leaching and subsequent smelting is proposed for recycling Si from rejected or recycled photovoltaic modules. Implications: The photovoltaic industry is considering options of recycling PV modules to recover metals such as Si, Ag, Cu, Al, and others used in the manufacturing of the PV cells. This is to retain its "green" image and to comply with current legislations in several countries. An evaluation of potential resources made available from PV wastes and the technologies used for processing these materials is therefore of significant importance to the industry. Of interest are the costs of processing and the potential revenues gained from recycling, which should determine the viability of economic recycling of PV modules in the future.

  4. Used float shoe recovered and tested

    SciTech Connect

    Colvard, R.L.

    1986-02-01

    A cement float valve has been recovered after it was circulated through and cemented downhole. It was retrieved by coring as part of an investigation into a cementing failure. The float equipment was then analyzed for downhole performance. This is believed to be the first instance of intact recovery of full-scale cementing hardware after it has been cemented in place. In this instance, the valve performed as designed. Flash set proved to be the probable cause of job failure. This article documents the job and includes photographs of the used float shoe and its components.

  5. Dissolved organic matter export in glacial and non-glacial streams along the Gulf of Alaska

    NASA Astrophysics Data System (ADS)

    Hood, E. W.; Scott, D.; Jeffery, A.; Schreiber, S.; Heavner, M.; Edwards, R.; D'Amore, D. V.; Fellman, J.

    2009-12-01

    The Gulf of Alaska drainage basin contains more than 75,000 km2 of glaciers, many of which are rapidly thinning and receding. We are using a paired watershed approach to evaluate how changes in glacier ecosystems will impact the export dissolved organic matter (DOM) into the Gulf of Alaska. Our primary study watersheds, Lemon Creek and Montana Creek, are similar in size, bedrock lithology and elevation range and extend from near sea level to the margin or interior of the Juneau Icefield. Lemon Creek has a glacial coverage of ~60%, while Montana Creek is free of glacier ice. Our goal is to evaluate seasonal differences in the quantity, chemical character and reactivity of DOM being exported from these watersheds to downstream near-shore marine ecosystems. In addition, we are monitoring a variety of physical parameters that influence instream DOM metabolism in both watersheds. Our initial results from the 2009 runoff season indicate that concentrations of dissolved organic carbon (DOC) are substantially higher in the non-glacial watershed. However, fluorescence analyses indicate that DOM from the glacier watershed has a higher protein and lower humic material content compared to DOM from the non-glacial watershed. After the spring snowmelt season, physical parameters between the two watersheds diverged, with higher streamflow and turbidity as well as colder water temperatures in the glacial watershed. Although our previous yield calculations show significantly higher DOC fluxes from the forested watershed, our results here suggest that glacier watersheds may be an important source of labile carbon to the near shore marine ecosystem. The contrast in the physical habitat between the two rivers (e.g glacier stream = cold, low light penetration, unstable substrate) supports the hypothesis that that in-stream DOM processing is limited within glacier dominated rivers, therefore delivering a higher percentage of labile DOM downstream.

  6. Numerical simulation of Glacial Isostatic Adjustment

    NASA Astrophysics Data System (ADS)

    Miglio, E.

    2015-12-01

    In the Earth's crust, stress can be subdivided into tectonic background stress, overburden pressure, and pore-fluid pressure. The superposition of the first two and the variation of the third part are key factors in controlling movement along faults. Furthermore, stresses due to sedimentation and erosion contribute to the total stress field. In deglaciated regions, an additional stress must be considered: the rebound stress, which is related to rebounding of the crust and mantle after deglaciation. During the growth of a continental ice sheet, the lithosphere under the iceload is deformed and the removal of the ice load during deglaciation initiates a rebound process. The uplift is well known in formerly glaciated areas, e.g.North America and Scandinavia, and in currently deglaciating areas, e.g.Alaska, Antarctica, and Greenland. The whole process of subsiding and uplifting during the growth and melting of an iceload and all related phenomena is known as glacial isostatic adjustment. During the process of glaciation, the surface of the lithosphere is depressed underneath the ice load and compressional flexural stresses are induced in the upper lithosphere, whereas the bottom of the lithosphere experiences extensional flexural stresses; an additional vertical stress due to the ice load is present and it decreases to zero during deglaciation. During rebound, flexural stresses relax slowly. These stresses are able to change the original stress directions and regime.In this work we aim to study the effect of the GIA process in the context of petroleum engineering. The main aspect we will focus on is the mathematical and numerical modeling of the GIA including thermal effects. We plan also to include a preliminary study of the effect of the glacial erosion. All these phenomena are of paramount importance in petroleum engineering: for example some reservoir have been depleted due to tilting caused by both GIA, erosion and thermal effects.

  7. Glacial onset predated Late Ordovician climate cooling

    NASA Astrophysics Data System (ADS)

    Pohl, Alexandre; Donnadieu, Yannick; Le Hir, Guillaume; Ladant, Jean-Baptiste; Dumas, Christophe; Alvarez-Solas, Jorge; Vandenbroucke, Thijs R. A.

    2016-06-01

    The Ordovician glaciation represents the acme of one of only three major icehouse periods in Earth's Phanerozoic history and is notorious for setting the scene for one of the "big five" mass extinction events. Nevertheless, the mechanisms that drove ice sheet growth remain poorly understood and the final extent of the ice sheet crudely constrained. Here using an Earth system model with an innovative coupling method between ocean, atmosphere, and land ice accounting for climate and ice sheet feedback processes, we report simulations portraying for the first time the detailed evolution of the Ordovician ice sheet. We show that the emergence of the ice sheet happened in two discrete phases. In a counterintuitive sequence of events, the continental ice sheet appeared suddenly in a warm climate. Only during the second act, and set against a background of decreasing atmospheric CO2, followed steeply dropping temperatures and extending sea ice. The comparison with abundant sedimentological, geochemical, and micropaleontological data suggests that glacial onset may have occurred as early as the Middle Ordovician Darriwilian, in agreement with recent studies reporting third-order glacioeustatic cycles during the same period. The second step in ice sheet growth, typified by a sudden drop in tropical sea surface temperatures by ˜8°C and the further extension of a single, continental-scale ice sheet over Gondwana, marked the onset of the Hirnantian glacial maximum. By suggesting the presence of an ice sheet over Gondwana throughout most of the Middle and Late Ordovician, our models embrace the emerging paradigm of an "early Paleozoic Ice Age."

  8. Fault-Tree Compiler

    NASA Technical Reports Server (NTRS)

    Butler, Ricky W.; Boerschlein, David P.

    1993-01-01

    Fault-Tree Compiler (FTC) program, is software tool used to calculate probability of top event in fault tree. Gates of five different types allowed in fault tree: AND, OR, EXCLUSIVE OR, INVERT, and M OF N. High-level input language easy to understand and use. In addition, program supports hierarchical fault-tree definition feature, which simplifies tree-description process and reduces execution time. Set of programs created forming basis for reliability-analysis workstation: SURE, ASSIST, PAWS/STEM, and FTC fault-tree tool (LAR-14586). Written in PASCAL, ANSI-compliant C language, and FORTRAN 77. Other versions available upon request.

  9. PROCESS OF RECOVERING URANIUM FROM ITS ORES

    DOEpatents

    Galvanek, P. Jr.

    1959-02-24

    A process is presented for recovering uranium from its ores. The crushed ore is mixed with 5 to 10% of sulfuric acid and added water to about 5 to 30% of the weight of the ore. This pugged material is cured for 2 to 3 hours at 100 to 110 deg C and then cooled. The cooled mass is nitrate-conditioned by mixing with a solution equivalent to 35 pounds of ammunium nitrate and 300 pounds of water per ton of ore. The resulting pulp containing 70% or more solids is treated by upflow percolation with a 5% solution of tributyl phosphate in kerosene at a rate equivalent to a residence time of about one hour to extract the solubilized uranium. The uranium is recovered from the pregnant organic liquid by counter-current washing with water. The organic extractant may be recycled. The uranium is removed from the water solution by treating with ammonia to precipitate ammonium diuranate. The filtrate from the last step may be recycled for the nitrate-conditioning treatment.

  10. Process for recovering organic vapors from air

    DOEpatents

    Baker, Richard W.

    1985-01-01

    A process for recovering and concentrating organic vapor from a feed stream of air having an organic vapor content of no more than 20,000 ppm by volume. A thin semipermeable membrane is provided which has a feed side and a permeate side, a selectivity for organic vapor over air of at least 50, as measured by the ratio of organic vapor permeability to nitrogen permeability, and a permeability of organic vapor of at least 3.times.10.sup.-7 cm.sup.3 (STP) cm/cm.sup.2 sec.cm Hg. The feed stream is passed across the feed side of the thin semipermeable membrane while providing a pressure on the permeate side which is lower than the feed side by creating a partial vacuum on the permeate side so that organic vapor passes preferentially through the membrane to form an organic vapor depleted air stream on the feed side and an organic vapor enriched stream on the permeate side. The organic vapor which has passed through the membrane is compressed and condensed to recover the vapor as a liquid.

  11. When will the Antarctic Ozone Hole Recover?

    NASA Technical Reports Server (NTRS)

    Newman, Paul A.; Nash, Eric R.; Kawa, S. Randolph; Montzka, Steve

    2006-01-01

    The Antarctic ozone hole develops each year and culminates by early Spring. Antarctic ozone values have been monitored since 1979 using satellite observations from the .TOMS instrument. The severity of the hole has been assessed from TOMS using the minimum total ozone value from the October monthly mean (depth of the hole) and by calculating the average size during the September-October period. Ozone is mainly destroyed by halogen catalytic cycles, and these losses are modulated by temperature variations in the collar of the polar lower stratospheric vortex. In this presentation, we show the relationships of halogens and temperature to, both the size and depth of the hole. Because atmospheric halogen levels are responding to international agreements that limit or phase out production, the amount of halogens in the stratosphere should decrease over the next few decades. Using projections of halogen levels combined with age-of-air estimates, we find that the ozone hole is recovering at an extremely slow rate and that large ozone holes will regularly recur over the next 2 decades. The ozone hole will begin to show first signs of recovery in about 2023, and the hole will fully recover to pre-1980 levels in approximately 2070. This 2070 recovery is 20 years later than recent projections.

  12. When Will the Antarctic Ozone Hole Recover?

    NASA Technical Reports Server (NTRS)

    Newman, Paul A.; Nash, Eric R.; Kawa, S. Randolph; Montzka, Steve

    2005-01-01

    The Antarctic ozone hole develops each year and culminates by early Spring. Antarctic ozone values have been monitored since 1979 using satellite observations from the TOMS instrument. The severity of the hole has been assessed from TOMS using the minimum total ozone value from the October monthly mean (depth of the hole) and by calculating the average size during the September-October period. Ozone is mainly destroyed by halogen catalytic cycles, and these losses are modulated by temperature variations in the collar of the polar lower stratospheric vortex. In this presentation, we show the relationships of halogens and temperature to both the size and depth of the hole. Because atmospheric halogen levels are responding to international agreements that limit or phase out production, the amount of halogens in the stratosphere should decrease over the next few decades. Using projections of halogen levels combined with age-of-air estimates, we find that the ozone hole is recovering at an extremely slow rate and that large ozone holes will regularly recur over the next 2 decades. We will show estimates of both when the ozone hole will begin to show first signs of recovery, and when the hole will fully recover to pre-1980 levels.

  13. Examining differences between recovered and declining endangered species

    USGS Publications Warehouse

    Abbitt, R.J.F.; Michael, Scott J.

    2001-01-01

    Between 1973 and 1999, 43 species in the United States were reclassified from endangered to threatened or removed entirely from the Endangered Species List. Of these, 23 were identified as recovered. In 1999 the U.S. Fish and Wildlife Service (USFWS) published a list of 33 additional species for possible reclassification and/or delisting. We initiated this study to examine why some endangered species recover but others continue to decline and to identify differences in management activities between these two groups. We defined recovered/recovering species as previously recovered species and the additional recovered/recovering species listed by the USFWS. We defined declining species as those identified as declining in the most recent USFWS Report to Congress. Information on recovered/recovering and declining species was gathered from relevant literature, recovery plans, U.S. Federal Register documents, and individuals responsible for the recovery management of each species. We used this information to examine (1) the percentage of current and historic range covered by management activities; (2) threats affecting the species; (3) population sizes at the time of listing; (4) current versus historic range size; and (5) percentage of recovery management objectives completed. Although few statistical analyses provided significant results, those that did suggest the following differences between recovered/recovering and declining species: (1) recovered/recovering species face threats that are easier to address; (2) recovered/recovering species occupy a greater percentage of their historic range; and (3) recovered/recovering species have a greater percentage of their recovery management objectives completed. Those species with threats easier to address and that occupy a greater percentage of their historic range are recovered/recovering. In contrast, declining species face threats more difficult to address and occupy significantly less of their historic range. If this

  14. Carbon pools recover more quickly than plant biodiversity in tropical secondary forests

    PubMed Central

    Martin, Philip A.; Newton, Adrian C.; Bullock, James M.

    2013-01-01

    Although increasing efforts are being made to restore tropical forests, little information is available regarding the time scales required for carbon and plant biodiversity to recover to the values associated with undisturbed forests. To address this knowledge gap, we carried out a meta-analysis comparing data from more than 600 secondary tropical forest sites with nearby undisturbed reference forests. Above-ground biomass approached equivalence to reference values within 80 years since last disturbance, whereas below-ground biomass took longer to recover. Soil carbon content showed little relationship with time since disturbance. Tree species richness recovered after about 50 years. By contrast, epiphyte richness did not reach equivalence to undisturbed forests. The proportion of undisturbed forest trees and epiphyte species found in secondary forests was low and changed little over time. Our results indicate that carbon pools and biodiversity show different recovery rates under passive, secondary succession and that colonization by undisturbed forest plant species is slow. Initiatives such as the Convention on Biological Diversity and REDD+ should therefore encourage active management to help to achieve their aims of restoring both carbon and biodiversity in tropical forests. PMID:24197410

  15. Variations in glacial and interglacial marine conditions over the last two glacial cycles off northern Greenland

    NASA Astrophysics Data System (ADS)

    Löwemark, Ludvig; Chao, Weng-Si; Gyllencreutz, Richard; Hanebuth, Till J. J.; Chiu, Pin-Yao; Yang, Tien-Nan; Su, Chih-Chieh; Chuang, Chih-Kai; León Dominguez, Dora Carolina; Jakobsson, Martin

    2016-09-01

    Five sediment cores from the Lomonosov Ridge and the Morris Jesup Rise north of Greenland show the history of sea-ice coverage and primary productivity over the last two glacial cycles. Variations in Manganese content, benthic and planktonic foraminifera, bioturbation, and trace fossil diversity are interpreted to reflect differences in sea-ice cover and sediment depositional conditions between the identified interglacials. Marine Isotope Stage (MIS) 1 and MIS 2 are represented by thin (<<5 cm) sediment units while the preceding interglacial MIS 5 and glacial MIS 6 are characterized by thick (10-20 cm) deposits. Foraminiferal abundances and bioturbation suggest that MIS 1 was generally characterized by severe sea-ice conditions north of Greenland while MIS 5 appears to have been considerably warmer with more open water, higher primary productivity, and higher sedimentation rates. Strengthened flow of Atlantic water along the northern continental shelf of Greenland rather than development of local polynyas is here suggested as a likely cause for the relatively warmer marine conditions during MIS 5 compared to MIS 1. The cores also suggest distinct differences between the glacial intervals MIS 2 and MIS 6. While MIS 6 is distinguished by a relatively thick sediment unit poor in foraminifera and with low Mn values, MIS 2 is practically missing. We speculate that this could be the effect from a paleocrystic sea-ice cover north of Greenland during MIS 2 that prevented sediment delivery from sea ice and icebergs. In contrast, the thick sequence deposited during MIS 6 indicates a longer glacial period with dynamic intervals characterized by huge drifting icebergs delivering ice rafted debris (IRD). A drastic shift from thinner sedimentary cycles where interglacial sediment parameters indicate more severe sea-ice conditions gave way to larger amplitude cycles with more open water indicators was observed around the boundary between MIS 7/8. This shift is in agreement with a

  16. High-resolution Geophysical Mapping of Submarine Glacial Landforms

    NASA Astrophysics Data System (ADS)

    Jakobsson, M.; Dowdeswell, J. A.; Canals, M.; Todd, B. J.; Dowdeswell, E. K.; Hogan, K. A.; Mayer, L. A.

    2014-12-01

    Glacial landforms are generated from the activity of glaciers and display spatial dimensions ranging from below one meter up to tens of kilometers. Glacial landforms are used as diagnostic features of past activity of ice sheets and glaciers; they are specifically important in the field of palaeoglaciology. Mapping of submarine glacial landforms is largely dependent on geophysical survey methods capable of imaging the seafloor and sub-bottom through the water column. Full "global" seafloor mapping coverage, equivalent to what exists for land elevation, is to-date only achieved by the powerful method of deriving bathymetry from altimeters on satellites like GEOSAT and ERS-1. The lateral resolution of satellite derived bathymetry is, however, limited by the footprint of the satellite and the need to average out local wave and wind effects resulting in values of around 15 km. Consequently, mapping submarine glacial landforms requires for the most part higher resolution than is achievable by satellite derived bathymetry. The most widely-used methods for mapping submarine glacial landforms are based on echo-sounding principles. This presentation shows how the evolution of marine geophysical mapping techniques, in particular the advent of side-scan and multibeam bathymetric sonars, has made it possible to study submarine glacial landforms in unprecedented detail. Examples are shown from the Atlas of Submarine Glacial Landforms: Modern, Quaternary and Ancient, which will be published in late 2015 in the Memoir Series of the Geological Society of London.

  17. Glacial and periglacial buzzsaws: fitting mechanisms to metaphors

    NASA Astrophysics Data System (ADS)

    Hall, Adrian M.; Kleman, Johan

    2014-03-01

    The buzzsaw hypothesis refers to the potential for glacial and periglacial processes to rapidly denude mountains at and above glacier Equilibrium Line Altitudes (ELAs), irrespective of uplift rates, rock type or pre-existing topography. Here the appropriateness of the buzzsaw metaphor is examined alongside questions of the links between glacial erosion and ELAs, and whether the glacial system can produce low-relief surfaces or limit summit heights. Plateau fragments in mountains on both active orogens and passive margins that have been cited as products of glacial and periglacial buzzsaw erosion instead generally represent dissected remnants of largely inherited, pre-glacial relief. Summit heights may correlate with ELAs but no causal link need be implied as summit erosion rates are low, cirque headwalls may not directly abut summits and, on passive margins, cirques are cut into pre-existing mountain topography. Any simple links between ELAs and glacial erosion break down on passive margins due to topographic forcing of ice-sheet growth, and to the km-scale vertical swaths through which ELAs have shifted through the Quaternary. Glaciers destroy rather than create low-relief rock surfaces through the innate tendency for ice flow to be faster, thicker and warmer along valleys. The glacial buzzsaw cuts down.

  18. New method for assessing the potential hazardousness of glacial lakes in the Cordillera Blanca, Peru

    NASA Astrophysics Data System (ADS)

    Emmer, A.; Vilímek, V.

    2014-02-01

    This paper presents a new and easily repeatable objective method for assessing the potential hazardousness of glacial lakes within the Peruvian region of Cordillera Blanca (excluding ice-dammed lakes, which do not reach significant volumes in this region). The presented method was designed to meet four basic principles, which we considered as being crucial. These are: (a) principle of regional focus; (b) principle of objectivity; (c) principle of repeatability; and (d) principle of multiple results. Potential hazardousness is assessed based on a combination of decision trees for clarity and numerical calculation for objectivity. A total of seventeen assessed characteristics are used, of which seven have yet to be used in this context before. Also, several ratios and calculations are defined for the first time. We assume that it is not relevant to represent the overall potential hazardousness of a particular lake by one result (number), thus the potential hazardousness is described in the presented method by five separate results (representing five different glacial lake outburst flood scenarios). These are potentials for: (a) dam overtopping resulting from a dynamic slope movement into the lake; (b) dam overtopping following the flood wave originating in a lake situated upstream; (c) dam failure resulting from a dynamic slope movement into the lake; (d) dam failure following the flood wave originating in a lake situated upstream; and (e) dam failure following a heavy earthquake. All of these potentials theoretically range from 0 to 1. The presented method was verified on the basis of assessing the pre-flood conditions of seven lakes which have produced ten glacial lake outburst floods in the past and ten lakes which have not. A comparison of these results showed that the presented method successfully identifies the potentially hazardous lakes.

  19. Associated terrestrial and marine fossils in the late-glacial Presumpscot Formation, southern Maine, USA, and the marine reservoir effect on radiocarbon ages

    USGS Publications Warehouse

    Thompson, W.B.; Griggs, C.B.; Miller, N.G.; Nelson, R.E.; Weddle, T.K.; Kilian, T.M.

    2011-01-01

    Excavations in the late-glacial Presumpscot Formation at Portland, Maine, uncovered tree remains and other terrestrial organics associated with marine invertebrate shells in a landslide deposit. Buds of Populus balsamifera (balsam poplar) occurred with twigs of Picea glauca (white spruce) in the Presumpscot clay. Tree rings in Picea logs indicate that the trees all died during winter dormancy in the same year. Ring widths show patterns of variation indicating responses to environmental changes. Fossil mosses and insects represent a variety of species and wet to dry microsites. The late-glacial environment at the site was similar to that of today's Maine coast. Radiocarbon ages of 14 tree samples are 11,907??31 to 11,650??5014C yr BP. Wiggle matching of dated tree-ring segments to radiocarbon calibration data sets dates the landslide occurrence at ca. 13,520+95/??20calyr BP. Ages of shells juxtaposed with the logs are 12,850??6514C yr BP (Mytilus edulis) and 12,800??5514C yr BP (Balanus sp.), indicating a marine reservoir age of about 1000yr. Using this value to correct previously published radiocarbon ages reduces the discrepancy between the Maine deglaciation chronology and the varve-based chronology elsewhere in New England. ?? 2011 University of Washington.

  20. Evidence of late glacial paleoseismicity from submarine landslide deposits within Lac Dasserat, northwestern Quebec, Canada

    NASA Astrophysics Data System (ADS)

    Brooks, Gregory R.

    2016-09-01

    An integrated seismo- and chronostratigraphic investigation at Lac Dasserat, northwestern Quebec, identified 74 separate failures within eight event horizons. Horizons E and B, and H and G have strong or moderately-strong multi-landslide signatures, respectively, composed of 11-23 failures, while horizons F, D, C, and A have minor landslide signatures consisting of a single or pair of deposit(s). Cores collected at six sites recovered glacial Lake Ojibway varve deposits that are interbedded with the event horizons. The correlation of the varves to the regional Timiskaming varve series allowed varve ages or ranges of varve ages to be determined for the event horizons. Horizons H, G, E, and B are interpreted to be evidence of paleoearthquakes with differing levels of interpretative confidence, based on the relative strength of the multi-landslide signatures, the correlation to other disturbed deposits of similar age in the region, and the lack or possibility of alternative aseismic mechanisms. The four interpreted paleoearthquakes occurred between 9770 ± 200 and 8470 ± 200 cal yr BP, when glacial Lake Ojibway was impounded behind the Laurentide Ice Sheet during deglaciation. They probably represent an elevated period of seismicity at deglaciation that was driven by crustal unloading.

  1. Early local last glacial maximum in the tropical Andes.

    PubMed

    Smith, Jacqueline A; Seltzer, Geoffrey O; Farber, Daniel L; Rodbell, Donald T; Finkel, Robert C

    2005-04-29

    The local last glacial maximum in the tropical Andes was earlier and less extensive than previously thought, based on 106 cosmogenic ages (from beryllium-10 dating) from moraines in Peru and Bolivia. Glaciers reached their greatest extent in the last glacial cycle approximately 34,000 years before the present and were retreating by approximately 21,000 years before the present, implying that tropical controls on ice volumes were asynchronous with those in the Northern Hemisphere. Our estimates of snowline depression reflect about half the temperature change indicated by previous widely cited figures, which helps resolve the discrepancy between estimates of terrestrial and marine temperature depression during the last glacial cycle.

  2. Isotopic evidence for reduced productivity in the glacial Southern Ocean

    SciTech Connect

    Shemesh, A. ); Macko, S.A. ); Charles, C.D. ); Rau, G.H. )

    1993-10-15

    Records of carbon and nitrogen isotopes in biogenic silica and carbon isotopes in planktonic foraminifera from deep-sea sediment cores from the Southern Ocean reveal that the primary production during the last glacial maximum was lower than Holocene productivity. These observations conflict with the hypothesis that the low atmospheric carbon dioxide concentrations were introduced by an increase in the efficiency of the high-latitude biological pump. Instead, different oceanic sectors may have had high glacial productivity, or alternative mechanisms that do not involve the biological pump must be considered as the primary cause of the low glacial atmospheric carbon dioxide concentrations.

  3. Probability of moraine survival in a succession of glacial advances.

    USGS Publications Warehouse

    Gibbons, A.B.; Megeath, J.D.; Pierce, K.L.

    1984-01-01

    Emplacement of glacial moraines normally results in obliteration of older moraines deposited by less extensive glacial advances, a process we call 'obliterative overlap'. Assuming randomness and obliterative overlap, after 10 glacial episodes the most likely number of surviving moraines is only three. The record of the Pleistocene is in agreement with the probability analysis: the 10 glaciations during the past 0.9 Myr inferred from the deep-sea record resulted in moraine sequences in which only two or three different-aged moraine belts can generally be distinguished. -from Authors

  4. Evolution of tree nutrition.

    PubMed

    Raven, John A; Andrews, Mitchell

    2010-09-01

    Using a broad definition of trees, the evolutionary origins of trees in a nutritional context is considered using data from the fossil record and molecular phylogeny. Trees are first known from the Late Devonian about 380 million years ago, originated polyphyletically at the pteridophyte grade of organization; the earliest gymnosperms were trees, and trees are polyphyletic in the angiosperms. Nutrient transporters, assimilatory pathways, homoiohydry (cuticle, intercellular gas spaces, stomata, endohydric water transport systems including xylem and phloem-like tissue) and arbuscular mycorrhizas preceded the origin of trees. Nutritional innovations that began uniquely in trees were the seed habit and, certainly (but not necessarily uniquely) in trees, ectomycorrhizas, cyanobacterial, actinorhizal and rhizobial (Parasponia, some legumes) diazotrophic symbioses and cluster roots.

  5. Tree Classification Software

    NASA Technical Reports Server (NTRS)

    Buntine, Wray

    1993-01-01

    This paper introduces the IND Tree Package to prospective users. IND does supervised learning using classification trees. This learning task is a basic tool used in the development of diagnosis, monitoring and expert systems. The IND Tree Package was developed as part of a NASA project to semi-automate the development of data analysis and modelling algorithms using artificial intelligence techniques. The IND Tree Package integrates features from CART and C4 with newer Bayesian and minimum encoding methods for growing classification trees and graphs. The IND Tree Package also provides an experimental control suite on top. The newer features give improved probability estimates often required in diagnostic and screening tasks. The package comes with a manual, Unix 'man' entries, and a guide to tree methods and research. The IND Tree Package is implemented in C under Unix and was beta-tested at university and commercial research laboratories in the United States.

  6. Fine Dissection of Human Mitochondrial DNA Haplogroup HV Lineages Reveals Paleolithic Signatures from European Glacial Refugia

    PubMed Central

    Sarno, Stefania; Sevini, Federica; Vianello, Dario; Tamm, Erika; Metspalu, Ene; van Oven, Mannis; Hübner, Alexander; Sazzini, Marco; Franceschi, Claudio; Pettener, Davide; Luiselli, Donata

    2015-01-01

    Genetic signatures from the Paleolithic inhabitants of Eurasia can be traced from the early divergent mitochondrial DNA lineages still present in contemporary human populations. Previous studies already suggested a pre-Neolithic diffusion of mitochondrial haplogroup HV*(xH,V) lineages, a relatively rare class of mtDNA types that includes parallel branches mainly distributed across Europe and West Asia with a certain degree of structure. Up till now, variation within haplogroup HV was addressed mainly by analyzing sequence data from the mtDNA control region, except for specific sub-branches, such as HV4 or the widely distributed haplogroups H and V. In this study, we present a revised HV topology based on full mtDNA genome data, and we include a comprehensive dataset consisting of 316 complete mtDNA sequences including 60 new samples from the Italian peninsula, a previously underrepresented geographic area. We highlight points of instability in the particular topology of this haplogroup, reconstructed with BEAST-generated trees and networks. We also confirm a major lineage expansion that probably followed the Late Glacial Maximum and preceded Neolithic population movements. We finally observe that Italy harbors a reservoir of mtDNA diversity, with deep-rooting HV lineages often related to sequences present in the Caucasus and the Middle East. The resulting hypothesis of a glacial refugium in Southern Italy has implications for the understanding of late Paleolithic population movements and is discussed within the archaeological cultural shifts occurred over the entire continent. PMID:26640946

  7. Large Scale Anthropogenic Reduction of Forest Cover in Last Glacial Maximum Europe

    PubMed Central

    Pfeiffer, Mirjam; Kolen, Jan C. A.; Davis, Basil A. S.

    2016-01-01

    Reconstructions of the vegetation of Europe during the Last Glacial Maximum (LGM) are an enigma. Pollen-based analyses have suggested that Europe was largely covered by steppe and tundra, and forests persisted only in small refugia. Climate-vegetation model simulations on the other hand have consistently suggested that broad areas of Europe would have been suitable for forest, even in the depths of the last glaciation. Here we reconcile models with data by demonstrating that the highly mobile groups of hunter-gatherers that inhabited Europe at the LGM could have substantially reduced forest cover through the ignition of wildfires. Similar to hunter-gatherers of the more recent past, Upper Paleolithic humans were masters of the use of fire, and preferred inhabiting semi-open landscapes to facilitate foraging, hunting and travel. Incorporating human agency into a dynamic vegetation-fire model and simulating forest cover shows that even small increases in wildfire frequency over natural background levels resulted in large changes in the forested area of Europe, in part because trees were already stressed by low atmospheric CO2 concentrations and the cold, dry, and highly variable climate. Our results suggest that the impact of humans on the glacial landscape of Europe may be one of the earliest large-scale anthropogenic modifications of the earth system. PMID:27902716

  8. Historical distribution of Sundaland’s Dipterocarp rainforests at Quaternary glacial maxima

    PubMed Central

    Cannon, Charles H.; Hijmans, Robert J.; Piessens, Thomas; Saw, Leng Guan; van Welzen, Peter C.; Slik, J. W. Ferry

    2014-01-01

    The extent of Dipterocarp rainforests on the emergent Sundaland landmass in Southeast Asia during Quaternary glaciations remains a key question. A better understanding of the biogeographic history of Sundaland could help explain current patterns of biodiversity and support the development of effective forest conservation strategies. Dipterocarpaceae trees dominate the rainforests of Sundaland, and their distributions serve as a proxy for rainforest extent. We used species distribution models (SDMs) of 317 Dipterocarp species to estimate the geographic extent of appropriate climatic conditions for rainforest on Sundaland at the last glacial maximum (LGM). The SDMs suggest that the climate of central Sundaland at the LGM was suitable to sustain Dipterocarp rainforest, and that the presence of a previously suggested transequatorial savannah corridor at that time is unlikely. Our findings are supported by palynologic evidence, dynamic vegetation models, extant mammal and termite communities, vascular plant fatty acid stable isotopic compositions, and stable carbon isotopic compositions of cave guano profiles. Although Dipterocarp species richness was generally lower at the LGM, areas of high species richness were mostly found off the current islands and on the emergent Sunda Shelf, indicating substantial species migration and mixing during the transitions between the Quaternary glacial maxima and warm periods such as the present. PMID:25385612

  9. Large Scale Anthropogenic Reduction of Forest Cover in Last Glacial Maximum Europe.

    PubMed

    Kaplan, Jed O; Pfeiffer, Mirjam; Kolen, Jan C A; Davis, Basil A S

    2016-01-01

    Reconstructions of the vegetation of Europe during the Last Glacial Maximum (LGM) are an enigma. Pollen-based analyses have suggested that Europe was largely covered by steppe and tundra, and forests persisted only in small refugia. Climate-vegetation model simulations on the other hand have consistently suggested that broad areas of Europe would have been suitable for forest, even in the depths of the last glaciation. Here we reconcile models with data by demonstrating that the highly mobile groups of hunter-gatherers that inhabited Europe at the LGM could have substantially reduced forest cover through the ignition of wildfires. Similar to hunter-gatherers of the more recent past, Upper Paleolithic humans were masters of the use of fire, and preferred inhabiting semi-open landscapes to facilitate foraging, hunting and travel. Incorporating human agency into a dynamic vegetation-fire model and simulating forest cover shows that even small increases in wildfire frequency over natural background levels resulted in large changes in the forested area of Europe, in part because trees were already stressed by low atmospheric CO2 concentrations and the cold, dry, and highly variable climate. Our results suggest that the impact of humans on the glacial landscape of Europe may be one of the earliest large-scale anthropogenic modifications of the earth system.

  10. Assessing the persistence of millennial-scale oscillations during the penultimate glacial phase in southern Europe

    NASA Astrophysics Data System (ADS)

    Wilson, Graham; Frogley, Mick; Jones, Tim; Leng, Melanie

    2016-04-01

    There is growing evidence that millennial-scale climate oscillations are a pervasive feature of glacial intervals. During the last glaciation (Marine Isotope Stage (MIS) 2-4), incursions of cold water into the North Atlantic appeared to coincide with abrupt reductions in southern European tree populations (Tzedakis et al., 2004: Geology 32, 109-112), suggesting down-stream impacts on continental temperature and hydroclimate. Ice-rafting into the North Atlantic during the penultimate glacial (MIS 6) is thought to be less extensive than at times during MIS 2-4, perhaps resulting in more subdued climate oscillations. Published pollen data from Lake Ioannina core I-284 (Epirus, NW Greece) suggest pronounced oscillations in tree population extent during early MIS 6 (185-155 ka), followed by much-reduced tree populations and subdued oscillations throughout late MIS 6 (155-135 ka) (Roucoux et al., 2011: Journal of Quaternary Science 26, 616-626). Previous studies of the diatom and isotope records from the MIS 7/6, 6/5e and 2/1 transitions, and from MIS 5e and 1 in Lake Ioannina core I-284 demonstrate the sensitivity of these proxies to changes in regional climate. Here we apply a combined diatom and stable isotope (carbon and oxygen) approach to evaluate the influence of millennial-scale oscillations on southern Europe hydroclimate during MIS 6. The new isotope data from Lake Ioannina core I-284 demonstrates higher precipitation / evaporation (P/E) ratios between c. 178 and 164 ka, associated with peak insolation during MIS 6e, and episodes of planktonic diatom expansion likely reflecting the interstadials of the 6e complex. Close correspondence between diatom planktonic frequencies, arboreal pollen and regional sea-surface temperatures together provide strong evidence for millennial-scale oscillations in regional precipitation at times during the early‒mid MIS 6. The isotope data suggest overall cooler and drier conditions during the mid-late MIS 6, consistent with

  11. PROCESSES OF RECOVERING URANIUM FROM A CALUTRON

    DOEpatents

    Baird, D.O.; Zumwalt, L.R.

    1958-07-15

    An improved process is described for recovering the residue of a uranium compound which has been subjected to treatment in a calutron, from the parts of the calutron disposed in the source region upon which the residue is deposited. The process may be utilized when the uranium compound adheres to a surface containing metals of the group consisting of copper, iron, chromium, and nickel. The steps comprise washing the surface with an aqueous acidic oxidizing solvent for the uranium whereby there is obtained an acidic aqueous Solution containing uranium as uranyl ions and metals of said group as impurities, treating the acidic solution with sodium acetate in the presenee of added sodium nitrate to precipitate the uranium as sodium uranyl acetate away from the impurities in the solution, and separating the sodium uranyl acetate from the solution.

  12. BACKUP -- Recovering from incremental tape backups

    NASA Astrophysics Data System (ADS)

    Allan, P. M.

    The importance of making regular backups of your disks in well known, but it can be very frustrating to have a head crash and then discover that you cannot recover from your backups because the manuals do not tell you what to do. The DEC documentation covers most possibilities, but not the case where a removable pack is copied to a new pack, the new pack is then used as the current pack, and incremental backups to tape are then made. This situation is a fairly common one when you have two or more removable disk drives. This note covers backup and recovery in general terms, and details exactly what to do in the above mentioned case.

  13. Apparatus to recover tritium from tritiated molecules

    DOEpatents

    Swansiger, William A.

    1988-01-01

    An apparatus for recovering tritium from tritiated compounds is provided, including a preheater for heating tritiated water and other co-injected tritiated compounds to temperatures of about 600.degree. C. and a reactor charged with a mixture of uranium and uranium dioxide for receiving the preheated mixture. The reactor vessel is preferably stainless steel of sufficient mass so as to function as a heat sink preventing the reactor side walls from approaching high temperatures. A disposable copper liner extends between the reaction chamber and stainless steel outer vessel to prevent alloying of the uranium with the outer vessel. The uranium dioxide functions as an insulating material and heat sink preventing the reactor side walls from attaining reaction temperatures to thereby minimize tritium permeation rates. The uranium dioxide also functions as a diluent to allow for volumetric expansion of the uranium as it is converted to uranium dioxide.

  14. Recovering Velocity Distributions Via Penalized Likelihood

    NASA Astrophysics Data System (ADS)

    Merritt, David

    1997-07-01

    Line-of-sight velocity distributions are crucial for unravelling the dynamics of hot stellar systems. We present a new formalism based on penalized likelihood for deriving such distributions from kinematical data, and evaluate the performance of two algorithms that extract N(V) from absorption-line spectra and from sets of individual velocities. Both algorithms are superior to existing ones in that the solutions are nearly unbiased even when the data are so poor that a great deal of smoothing is required. In addition, the discrete-velocity algorithm is able to remove a known distribution of measurement errors from the estimate of N(V). The formalism is used to recover the velocity distribution of stars in five fields near the center of the globular cluster omega Centauri.

  15. Illumination Under Trees

    SciTech Connect

    Max, N

    2002-08-19

    This paper is a survey of the author's work on illumination and shadows under trees, including the effects of sky illumination, sun penumbras, scattering in a misty atmosphere below the trees, and multiple scattering and transmission between leaves. It also describes a hierarchical image-based rendering method for trees.

  16. The Wish Tree Project

    ERIC Educational Resources Information Center

    Brooks, Sarah DeWitt

    2010-01-01

    This article describes the author's experience in implementing a Wish Tree project in her school in an effort to bring the school community together with a positive art-making experience during a potentially stressful time. The concept of a wish tree is simple: plant a tree; provide tags and pencils for writing wishes; and encourage everyone to…

  17. Diary of a Tree.

    ERIC Educational Resources Information Center

    Srulowitz, Frances

    1992-01-01

    Describes an activity to develop students' skills of observation and recordkeeping by studying the growth of a tree's leaves during the spring. Children monitor the growth of 11 tress over a 2-month period, draw pictures of the tree at different stages of growth, and write diaries of the tree's growth. (MDH)

  18. Minnesota's Forest Trees. Revised.

    ERIC Educational Resources Information Center

    Miles, William R.; Fuller, Bruce L.

    This bulletin describes 46 of the more common trees found in Minnesota's forests and windbreaks. The bulletin contains two tree keys, a summer key and a winter key, to help the reader identify these trees. Besides the two keys, the bulletin includes an introduction, instructions for key use, illustrations of leaf characteristics and twig…

  19. Winter Birch Trees

    ERIC Educational Resources Information Center

    Sweeney, Debra; Rounds, Judy

    2011-01-01

    Trees are great inspiration for artists. Many art teachers find themselves inspired and maybe somewhat obsessed with the natural beauty and elegance of the lofty tree, and how it changes through the seasons. One such tree that grows in several regions and always looks magnificent, regardless of the time of year, is the birch. In this article, the…

  20. What happened to the coal forests during Pennsylvanian glacial phases?

    SciTech Connect

    Falcon-Lang, H.J.; Dimichele, W.A.

    2010-09-15

    Sequence stratigraphic analysis of Pennsylvanian coal-bearing strata suggests that glacial-interglacial fluctuations at high latitudes drove cyclic changes in tropical biomes. A literature review of plant assemblages in this paleoclimatic context suggests that coal forests dominated during humid interglacial phases, but were replaced by seasonally dry vegetation during glacial phases. After each glacial event, coal forests reassembled with largely the same species composition. This remarkable stasis implies that coal-forest refugia existed across the equatorial landscape during glacial phases, expanding to repopulate lowlands during and following deglaciation. One possibility is that refugia comprised small pockets of wetland forest strung out along valleys at some sites, but data are currently insufficient to test this hypothesis. The model presented here, if accepted, dramatically alters our understanding of the coal forests and helps explain aspects of their dynamics.

  1. A novel tree structure based watermarking algorithm

    NASA Astrophysics Data System (ADS)

    Lin, Qiwei; Feng, Gui

    2008-03-01

    In this paper, we propose a new blind watermarking algorithm for images which is based on tree structure. The algorithm embeds the watermark in wavelet transform domain, and the embedding positions are determined by significant coefficients wavelets tree(SCWT) structure, which has the same idea with the embedded zero-tree wavelet (EZW) compression technique. According to EZW concepts, we obtain coefficients that are related to each other by a tree structure. This relationship among the wavelet coefficients allows our technique to embed more watermark data. If the watermarked image is attacked such that the set of significant coefficients is changed, the tree structure allows the correlation-based watermark detector to recover synchronously. The algorithm also uses a visual adaptive scheme to insert the watermark to minimize watermark perceptibility. In addition to the watermark, a template is inserted into the watermarked image at the same time. The template contains synchronization information, allowing the detector to determine the geometric transformations type applied to the watermarked image. Experimental results show that the proposed watermarking algorithm is robust against most signal processing attacks, such as JPEG compression, median filtering, sharpening and rotating. And it is also an adaptive method which shows a good performance to find the best areas to insert a stronger watermark.

  2. Enigmatic sediment ridges in the German Bight - glacial vs post-glacial morphologies?

    NASA Astrophysics Data System (ADS)

    Unnithan, Vikram; Pio Rossi, Angelo; Praeg, Daniel

    2014-05-01

    The German Wadden Sea extends over 1000 km from the Dutch coast to that of Sweden and consists of a long chain of barrier islands and ephemeral sand banks punctuated by estuaries and rivers. The sedimentary environment is currently shaped and characterised by storm surges, high tidal and wave energy levels. However, this part of the North Sea has been repeatedly covered by continental ice sheets, and it remains unclear how glacial to interglacial sedimentary processes may have influenced seabed morphology in the region. The study area is situated approximately 70 km north of Cuxhaven, and 5 km due east of the islands of Helgoland and Dune. It covers an approximate area of 5 km square with water depths ranging from 50 m in the south to about 20 m in the north. High resolution multibeam (Simrad EM710) and parametric echosounder (Innomar SES2000) data were acquired during graduate and undergraduate teaching excursions on the RV Heincke in Spring 2010 (HE-324) and 2011 (HE-349). The seabed swath bathymetric data reveal distinctive linear seabed ridges. The ridges trend NNW-SSE, are 1-5 m in height, have wavelengths on the order of 100 m and crest lengths ranging from 100-2500 m. The ridge crests are broadly anastomosing. They bifurcate towards the north to form more subdued structures, while they converge and disappear to the south. Profiles across the ridges show an asymmetric structure, with steeper slopes trending west in the western part of the study area but trending east in the eastern part. These enigmatic sedimentary structures have not been previously mapped in the Wadden Sea, and their origin remains uncertain. Possible interpretations to be tested include sub-crop structural control on seabed morphology, relict glacial or glaciofluvial landforms and post-glacial marine bedforms linked to processes of sediment redistribution.

  3. Distributed Contour Trees

    SciTech Connect

    Morozov, Dmitriy; Weber, Gunther H.

    2014-03-31

    Topological techniques provide robust tools for data analysis. They are used, for example, for feature extraction, for data de-noising, and for comparison of data sets. This chapter concerns contour trees, a topological descriptor that records the connectivity of the isosurfaces of scalar functions. These trees are fundamental to analysis and visualization of physical phenomena modeled by real-valued measurements. We study the parallel analysis of contour trees. After describing a particular representation of a contour tree, called local{global representation, we illustrate how di erent problems that rely on contour trees can be solved in parallel with minimal communication.

  4. Oceanographic gradients and seabird prey community dynamics in glacial fjords

    USGS Publications Warehouse

    Arimitsu, Mayumi L.; Piatt, John F.; Madison, Erica N.; Conaway, Jeff; Hillgruber, N.

    2012-01-01

    Glacial fjord habitats are undergoing rapid change as a result of contemporary global warming, yet little is known about how glaciers influence marine ecosystems. These ecosystems provide important feeding, breeding and rearing grounds for a wide variety of marine organisms, including seabirds of management concern. To characterize ocean conditions and marine food webs near tidewater glaciers, we conducted monthly surveys of oceanographic variables, plankton, fish and seabirds in Kenai Fjords, Alaska, from June to August of 2007 and 2008. We also measured tidal current velocities near glacial features. We found high sediment load from glacial river runoff played a major role in structuring the fjord marine ecosystem. Submerged moraines (sills) isolated cool, fresh, stratified and silt-laden inner fjord habitats from oceanic influence. Near tidewater glaciers, surface layers of turbid glacial runoff limited availability of light to phytoplankton, but macrozooplankton were abundant in surface waters, perhaps due to the absence of a photic cue for diel migration. Fish and zooplankton community structure varied along an increasing temperature gradient throughout the summer. Acoustic measurements indicated that low density patches of fish and zooplankton were available in the surface waters near glacial river outflows. This is the foraging habitat occupied most by Kittlitz's murrelet (Brachyramphus brevirostris), a rare seabird that appears to be specialized for life in glacially influenced environments. Kittlitz's murrelets were associated with floating glacial ice, and they were more likely to occur near glaciers, in deeper water, and in areas with high acoustic backscatter. Kittlitz's murrelet at-sea distribution was limited to areas influenced by turbid glacial outflows, and where prey was concentrated near the surface in waters with low light penetration. Tidewater glaciers impart unique hydrographic characteristics that influence marine plankton and fish

  5. Greenland ice cores constrain glacial atmospheric fluxes of phosphorus

    NASA Astrophysics Data System (ADS)

    Kjær, Helle Astrid; Dallmayr, Remi; Gabrieli, Jacopo; Goto-Azuma, Kumiko; Hirabayashi, Motohiro; Svensson, Anders; Vallelonga, Paul

    2015-10-01

    Phosphorus is a limiting nutrient for primary productivity, but little is known about past atmospheric fluxes to the open ocean. In this study, phosphate and phosphorus concentrations have been determined in the North Greenland Eemian Ice Drilling Project ice core for selected periods during the last glacial. Phosphate was determined continuously by using a molybdenum blue spectroscopic absorption method and discretely using an ion chromatograph. Total P was determined discretely using an inductively coupled plasma sector field mass spectrometer. For the last glacial period, we found concentrations of between 3 and 62 nM PO43- and 7 and 929 nM P. We find glacial atmospheric fluxes of phosphorus to Greenland were 4 to 11 times higher than in the past century, with the highest input during the cold glacial stadials (GS). Changes in P and PO43- fluxes between mild glacial interstadials (GI) and GS correlate positively with dust variability. The soluble fraction of P is larger in the mild GIs as compared to the dust-rich GSs. For the very high phosphate and phosphorus loads during the Last Glacial Maximum, the relationship between phosphate and dust is weaker than in GIs and milder GSs, suggesting either secondary phosphate sources or multiple dust sources. Based on crustal abundances, we find that dust inputs are sufficient to account for all P deposited during all periods investigated except the Last Glacial Maximum. During the glacial, sea salts contributed 10-3 nM P, while land biogenic emissions were a minor source of P.

  6. Early Circum-Arctic Glacial Decay Following the Last Glacial Maximum?

    NASA Astrophysics Data System (ADS)

    Snow, T.; Alonso-Garcia, M.; Flower, B. P.; Shevenell, A.; Roehl, U.; Goddard, E.

    2012-12-01

    Recent rapid warming, glacial retreat, and sea ice reduction observed in the Arctic suggest extreme regional environmental sensitivity to ongoing anthropogenic climate change. To place these recent environmental changes in context and better understand the forcings and feedbacks involved in Arctic climate change, regional studies of past intervals of rapid warming are required. Paleoceanographic studies from the high-latitude North Atlantic indicate close relationships between meltwater discharges from circum-Arctic ice sheets, perturbations of Atlantic Meridional Overturning Circulation (AMOC), and global climate variations on sub-orbital timescales during the Late Quaternary. During the last glacial-interglacial transition (25-10 ka), when atmospheric temperatures over Greenland warmed 10-15°C and the AMOC experienced millennial-scale variability, low-resolution stable isotope studies from Fram Strait sediment cores indicate that the circum-Arctic ice sheets began to melt earlier than lower latitude Northern Hemisphere ice sheets, discharging their meltwater into the high latitude North Atlantic. Fram Strait, located at the gateway between the Atlantic and Arctic Oceans, is the only region where Arctic meltwater can exchange with the world oceans on both glacial and interglacial timescales. Thus, high-resolution paleoceanographic studies of Fram Strait sediments are critically required for understanding changes in Arctic meltwater flux to the North Atlantic on sub-orbital timescales. Here we present the first high-resolution (<100 yr) multi-proxy dataset from Fram Strait (ODP Site 986; 77°20.43'N, 9°04.66'E; water depth: 2063 m) to assess the timing of circum-Arctic ice sheet decay since the Last Glacial Maximum. Foraminiferal isotopic and elemental, scanning X-Ray Fluorescence, and ice-rafted debris records are used to isolate Arctic meltwater and iceberg discharge signals. Sharp increases in productivity and changes in water mass ventilation are inferred

  7. Growth of a Pine Tree

    ERIC Educational Resources Information Center

    Rollinson, Susan Wells

    2012-01-01

    The growth of a pine tree is examined by preparing "tree cookies" (cross-sectional disks) between whorls of branches. The use of Christmas trees allows the tree cookies to be obtained with inexpensive, commonly available tools. Students use the tree cookies to investigate the annual growth of the tree and how it corresponds to the number of whorls…

  8. Holocene and Late Glacial varved sediments from Czechowskie Lake (Poland)

    NASA Astrophysics Data System (ADS)

    Ott, Florian; Brauer, Achim; Słowiński, Michał; Dulski, Peter; Plessen, Birgit; Blaszkiewicz, Miroslaw

    2013-04-01

    Annual laminated (varved) sediment records are essential for detailed paleoclimate and environmental reconstructions as they function as a natural memory beyond instrumental datasets. In order to determine Holocene inter-annual and decadal-scale variability we investigated varved Lake Czechowskie (53°52' N/ 18°14' E, 108 m asl.), northern Poland. During two coring campaigns in 2009 and 2012 we recovered several long and short cores with the longest core reaching 14.5 m. Based on correlation with a biostratigraphically and tephrochronologically dated neighboring paleolake sediment record (Trzechowskie mire) the record extends back in to the Late Glacial. Lake Czechowskie is well suited for climate reconstruction as varves are almost entirely well (88 %) or poorly (5%) preserved. Only 7 % of the sediment profile are non-varved. Detailed investigations have been carried out for the last 2000 years of the sediment profile applying micro-facies analyses combined with X-ray fluorescence element scanning (µ-XRF) at 200 µm resolution and carbon and nitrogen analyses (TOC, TC, TN) at five-varveresolution. The chronology has been established by a multiple dating approach with 137Cs (for the last ca. 50 years), AMS 14C on plant macro remains (back to 2800 cal BP) and varve counting. Varve formation and preservation ceases at the beginning of the 20th century whereas the younger sediments are again faintly varved. Micro-facies analyses reveal that the sediment consists of biogenic calcite varves with intercalated diatom rich layers. Three distinct 100 to 200 years long periods of up to threefold thicker varves (approx. 1.4 to 5.0 mm/year) are predominantly caused by an increase in the diatom sub-layers and indicate distinct short-term climatic and environmental fluctuations. Possible reasons for these changes that occurred abruptly with only few years are either changes in lake water circulation or in nutrient supply to the lake. This study is a contribution to the Virtual

  9. Rapid loss of glacial ice reveals stream community assembly processes

    PubMed Central

    Brown, Lee E; Milner, Alexander M

    2012-01-01

    Glacial retreat creates new habitat which is colonized and developed by plants and animals during the process of primary succession. While there has been much debate about the relative role of deterministic and stochastic processes during terrestrial succession, evidence from freshwater ecosystems remains minimal and a general consensus is lacking. Using a unique 27 years record of community assembly following glacial recession in southeast Alaska, we demonstrate significant change in the trait composition of stream invertebrate communities as catchment glacial cover decreased from ∼70% to zero. Functional diversity increased significantly as glacier cover decreased and taxonomic richness increased. Null modelling approaches led to a key finding that niche filtering processes were dominant when glacial cover was extensive, reflecting water temperature and dispersal constraints. Thereafter the community shifted towards co-occurrence of stochastic and deterministic assembly processes. A further novel discovery was that intrinsic functional redundancy developed throughout the study, particularly because new colonizers possessed similar traits to taxa already present. Rapid glacial retreat is occurring in Arctic and alpine environments worldwide and the assembly processes observed in this study provide new fundamental insights into how glacially influenced stream ecosystems will respond. The findings support tolerance as a key primary successional mechanism in this system, and have broader value for developing our understanding of how biological communities in river ecosystems assemble or restructure in response to environmental change.

  10. 32 CFR 245.26 - Aircraft being recovered.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 32 National Defense 2 2014-07-01 2014-07-01 false Aircraft being recovered. 245.26 Section 245.26... Traffic Under ESCAT § 245.26 Aircraft being recovered. Aircraft being recovered will be expedited to home or an alternate base. Search and Rescue aircraft may be expedited on their missions. Such...

  11. 32 CFR 245.26 - Aircraft being recovered.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 32 National Defense 2 2010-07-01 2010-07-01 false Aircraft being recovered. 245.26 Section 245.26... Traffic Under ESCAT § 245.26 Aircraft being recovered. Aircraft being recovered will be expedited to home or an alternate base. Search and Rescue aircraft may be expedited on their missions. Such...

  12. 32 CFR 245.26 - Aircraft being recovered.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 32 National Defense 2 2012-07-01 2012-07-01 false Aircraft being recovered. 245.26 Section 245.26... Traffic Under ESCAT § 245.26 Aircraft being recovered. Aircraft being recovered will be expedited to home or an alternate base. Search and Rescue aircraft may be expedited on their missions. Such...

  13. 32 CFR 245.26 - Aircraft being recovered.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 32 National Defense 2 2013-07-01 2013-07-01 false Aircraft being recovered. 245.26 Section 245.26... Traffic Under ESCAT § 245.26 Aircraft being recovered. Aircraft being recovered will be expedited to home or an alternate base. Search and Rescue aircraft may be expedited on their missions. Such...

  14. 32 CFR 245.26 - Aircraft being recovered.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 32 National Defense 2 2011-07-01 2011-07-01 false Aircraft being recovered. 245.26 Section 245.26... Traffic Under ESCAT § 245.26 Aircraft being recovered. Aircraft being recovered will be expedited to home or an alternate base. Search and Rescue aircraft may be expedited on their missions. Such...

  15. 40 CFR 721.4600 - Recovered metal hydroxide.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Recovered metal hydroxide. 721.4600... Substances § 721.4600 Recovered metal hydroxide. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as a recovered metal hydroxide (PMN...

  16. 40 CFR 721.4600 - Recovered metal hydroxide.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Recovered metal hydroxide. 721.4600... Substances § 721.4600 Recovered metal hydroxide. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as a recovered metal hydroxide (PMN...

  17. 40 CFR 721.4600 - Recovered metal hydroxide.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Recovered metal hydroxide. 721.4600... Substances § 721.4600 Recovered metal hydroxide. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as a recovered metal hydroxide (PMN...

  18. 40 CFR 721.4600 - Recovered metal hydroxide.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Recovered metal hydroxide. 721.4600... Substances § 721.4600 Recovered metal hydroxide. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as a recovered metal hydroxide (PMN...

  19. 40 CFR 721.4600 - Recovered metal hydroxide.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Recovered metal hydroxide. 721.4600... Substances § 721.4600 Recovered metal hydroxide. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as a recovered metal hydroxide (PMN...

  20. [Structural recovering in Andean successional forests from Porce (Antioquia, Colombia)].

    PubMed

    Yepes, Adriana P; del Valle, Jorge I; Jaramillo, Sandra L; Orrego, Sergio A

    2010-03-01

    Places subjected to natural or human disturbance can recover forest through an ecological process called secondary succession. Tropical succession is affected by factors such as disturbances, distance from original forest, surface configuration and local climate. These factors determine the composition of species and the time trend of the succession itself. We studied succession in soils used for cattle ranching over various decades in the Porce Region of Colombia (Andean Colombian forests). A set of twenty five permanent plots was measured, including nine plots (20 x 50 m) in primary forests and sixteen (20 x 25 m) in secondary forests. All trees with diameter > or =1.0 cm were measured. We analyzed stem density, basal area, above-ground biomass and species richness, in a successional process of ca. 43 years, and in primary forests. The secondary forests' age was estimated in previous studies, using radiocarbon dating, aerial photographs and a high-resolution satellite image analysis (7 to >43 years). In total, 1,143 and 1,766 stems were measured in primary and secondary forests, respectively. Basal area (5.7 to 85.4 m2 ha(-1)), above-ground biomass (19.1 to 1,011.5 t ha(-1)) and species richness (4 to 69) directly increased with site age, while steam density decreased (3,180 to 590). Diametric distributions were "J-inverted" for primary forests and even-aged size-class structures for secondary forests. Three species of palms were abundant and exclusive in old secondary forests and primary forests: Oenocarpus mapora, Euterpe precatoria and Oenocarpus bataua. These palms happened in cohorts after forest disturbances. Secondary forest structure was 40% in more than 43 years of forest succession and indicate that many factors are interacting and affecting the forests succession in the area (e.g. agriculture, cattle ranching, mining, etc.).

  1. Glacial Landforms, how distorted is our view of them?

    NASA Astrophysics Data System (ADS)

    Smith, Mike J.; Hillier, John K.

    2014-05-01

    Concurrent with the dramatic resurgence in geomorphological mapping over the last decade there has been a progression towards finding more objective, and sometimes automated, techniques and procedures for mapping. Yet manual, interpretive, techniques remain effective and commonly used. By definition manual mapping is subjective and it is therefore important that criteria are developed, and agreed upon, in order to facilitate inter-comparability of mapped outputs and assess the reliability of these data. To this end we have compared glacial geomorphological mapping by different interpreters. An EGU funded workshop was attended by 24 academics, ranging from undergraduates to faculty. All had an interest in geomorphological mapping, but there was a mix of expertise, from those with many years experience in mapping from satellite imagery and DEMs, to those with almost no background. In order to robustly compare mapping by individuals, a real landscape containing statistically representative 'synthetic' drumlins (Hillier and Smith, 2012) was utilised. To create these synthetic DEMs, observed drumlins were removed from a measured DEM and replaced by elongate 3D Gaussian ones of equivalent dimensions positioned randomly with respect to the 'noise' (e.g. trees) and regional trends (e.g. hills). Five variations were generated, each containing 173 drumlins (known a priori), and for each DEM mappers asked to map the outline, ridge crest and highpoint of each identifiable drumlin prior to the workshop. In total 20,760 landforms were presented to the 24 mappers and 11,687 were mapped, of which 8,288 were coincident. Drumlins mapped per individual ranged from 198 to 989 out of 865 present. Overall 'accuracy' (i.e. ncoincident/ntotal) was 40%, however the 'reliability' of mapping (i.e. ncoincident/nmapped) ranged from 41% to 100% depending upon the mapper. This presentation summarises the results of the mapping, gives insights into the drivers of accuracy (e.g. experience

  2. Evolutionary history of a widespread tree species Acer mono in East Asia

    PubMed Central

    Guo, Xi-Di; Wang, Hong-Fang; Bao, Lei; Wang, Tian-Ming; Bai, Wei-Ning; Ye, Jun-Wei; Ge, Jian-Ping

    2014-01-01

    East Asia has the most diverse temperate flora in the world primarily due to the lack of Pleistocene glaciation and the geographic heterogeneity. Although increasing phylogeography studies in this region provided more proofs in this issue, discrepancies and uncertainty still exist, especially in northern temperate deciduous broad-leaved and coniferous mixed forest region (II). And a widespread plant species could reduce the complexity to infer the relationship between diversity and physiographical pattern. Hence, we studied the evolution history of a widespread temperate tree, Acer mono, populations in region II and the influence of physiographic patterns on intraspecific genetic diversity. Analyses of chloroplast sequences and nuclear microsatellites indicated high levels of genetic diversity. The diversity distribution was spatially heterogeneous and a latitudinal cline existed in both markers. The spatial distribution pattern between genetic diversity within A. mono and the diversity at species level was generally consistent. Western subtropical evergreen broad-leaved forest subregion (IVb) had a unique ancient chloroplast clade (CP3) and a nuclear gene pool (GP5) with dominance indicating the critical role of this area in species diversification. Genetic data and ecological niche model results both suggested that populations in region II disappeared during the last glacial maximum (LGM) and recovered from south of Changbai Mt. and the Korean Peninsula. Two distribution centers were likely during the LGM, one in the north edge of warm temperate deciduous broad-leaved forest region (III) and another in the south edge of region III. This was reflected by the genetic pattern with two spatially independent genetic groups. This study highlights the key role of region III in sustaining genetic diversity in the northern range and connecting diversity between southern and northern range. We elucidated the diversity relationship between vegetation regions which could

  3. Paleomonsoonal Precipitation and Hydroclimate Variability from Glacial to Interglacial Climates in the Southwest: The Stoneman Lake, Arizona Record

    NASA Astrophysics Data System (ADS)

    Garcia, D.; Fawcett, P. J.; Anderson, R. S.; Sharp, Z. D.

    2015-12-01

    Oxygen isotope values from diatom silica have been used to determine past hydrological conditions in a variety of settings including differentiating summer monsoonal paleoprecipitation from winter frontal paleoprecipitation in the American southwest. Lacustrine cores from the Valles Caldera, New Mexico, show a distinct change in silica oxygen isotope values from glacial to interglacial as a switch from a purely winter frontal precipitation during the glacial to a mix of winter frontal and summer monsoonal precipitation during the interglacial. A relatively large (ca. 20‰) and rapid increase in δ18O following the glacial termination implies an abrupt onset of the North American monsoon. We plan to elaborate on this research to see if this is true elsewhere in the southwest. Two lacustrine sediment cores (70 m deep and 30 m deep respectively) were recovered from Stoneman Lake, northern Arizona in October of 2014. With these cores we plan to determine regional hydroclimate variability between the Pleistocene-Holocene glacial transition ca. 14 ka. Oxygen isotope analysis from diatom silica will allow us to determine past sources of precipitation to the basin (Gulf of Mexico vs North Pacific), and paleoprecipitation variability. In conjunction with other proxies, we can determine if the onset of paleomonsoonal precipitation in central Arizona occurs immediately after the glacial termination as in NM, or if there is some component of monsoonal precipitation during the late glacial period. Diatom sampling was performed at approximately every 50 cm. To purify the diatoms, the samples are chemically and physically separated. The step wise fluorination and laser ablation technique are then applied to remove water & hydroxyl groups and to extract O2 & SiF4 respectively.If results from the Stoneman Lake core are similar to that of the Valles Caldera core, we should expect to see a nearly 20‰ increase in δ18Olake water. This would suggest a: 1) collapse of the summer

  4. Method for recovering metal from waste stream

    SciTech Connect

    Greenberg, B.

    1991-09-10

    This patent describes a method for recovering metal from a waste stream to render the waste stream suitable for discharge. It comprises passing a waste stream comprised of heavy metal salts in dilute solution into a cathode chamber of an anion exchange membrane delineated electrolytic cell, wherein the metals are selected from the group having a standard reduction potential more negative than that of hydrogen in the electromotive force series and the heavy metal ion concentration of the solution is less than about 10,000 parts per million of dissolved material; subjecting the waste stream to high current density electrolysis at up to about 25 volts to enhance the controlled regular formation of a noncompressible metal hydrous oxide crystalline precipitate in the cathode chamber; separating the precipitate from the waste stream; and splitting the clarified liquid waste stream so that a portion of the clarified liquid waste stream is discharged and a portion is returned downstream for commingling with the metal ion-containing waste stream for further treatment.

  5. Neoproterozoic Glacial Extremes: How Plausible is the

    NASA Astrophysics Data System (ADS)

    Peltier, W. R.

    2004-05-01

    The suggestion that the glaciation events of the Neoproterozoic could have been global in extent, so-called "snowball" glaciations, during which the oceans were entirely covered by sea ice and the continents by massive continental ice sheets, is an idea tha is recurrent in the geological and climate dynamics literature. It is an idea that haa both critics and defenders but concensus concerning it's plausiblity has yet to emerge. Previous work on this problem has led to the suggestion that a more likely scenario than the "hard snowball" is one in which open water continues to persist at the equator, thus enabling biological evolution into the Cambrian to proceed, perhaps stimulated by the transition from the cold conditions of the Neoproterozoic to the warm condition of the Cambrian, thus leading to the Cambrian "explosion of life". We will discuss recent extensions of our previous efforts to model the extreme climate of the Neoproterozoic, using both the University of Toronto Glacial Systems Model and the NCAR Community Climate System Model. With an appropriate choice for the albedo of sea ice, the former model conntinues to deliver hysteresis in the surface temperature vs. CO2 concentration space when solar luminosity is reduced by 6% below modern, and thus continues to suggest the existence of the previously hypothesized "CO2 attractor". We argue here that the system could be locked onto this attractor by the strong "out of equilibrium" effects of the carbon cycle recently discussed by Rothman et al. (PNAS, 2003). The open water solution is confirmed as the preferred mode of the system by the detailed CCSM integrations that we have performed.

  6. Preformed Nitrate in the Glacial North Atlantic

    NASA Astrophysics Data System (ADS)

    Homola, K.; Spivack, A. J.; D'Hondt, S.; Estes, E. R.; Insua, T. L.; McKinley, C. C.; Murray, R. W.; Pockalny, R. A.; Robinson, R. S.; Sauvage, J.

    2015-12-01

    Atmospheric CO2 abundances are highly correlated with global temperature variations over the past 800,000 years. Consequently, understanding the feedbacks between climate and CO2 is important for predictions of future climate. Leading hypotheses to explain this feedback invoke changes in ocean biology, circulation, chemistry, and/or gas exchange rates to trap CO2 in the deep ocean, thereby reducing the greenhouse effect of CO2 in the atmosphere. To test these hypotheses, we use sediment pore water profiles of dissolved nitrate and oxygen to reconstruct paleo-preformed nitrate concentrations at two deep-water sites in the western North Atlantic (23°N 57°W, 5557 m water depth; 30°N 58°W, 5367 m water depth). Preformed nitrate increases down-core to 22.7 μM (25.6 m core depth) at the northern site, and to 28.5 μM (27.8 m core depth) at the southern site. The large preformed nitrate gradient between these sites reveals a paleo-boundary between a southern water source high in preformed nitrate and a northern water source with lower concentrations, similar to today's ocean. However, the boundary between these water masses occurs north of where their modern counterparts meet, indicating that Antarctic Bottom Water (AABW) extended farther north during the Last Glacial Maximum (LGM). In addition, the southern source had a higher preformed nitrate concentration than today's AABW (25 μM), contradicting hypotheses that nutrient utilization was more efficient in the Southern Ocean deep-water formation regions during the LGM. Comparison to our previous Pacific data reveals that the average preformed nitrate concentration of the deep ocean was slightly higher during the LGM than today. This result implies that the CO2-climate feedback was not principally due to more efficient nitrate utilization.

  7. Geochemical Weathering in Glacial and Proglacial Environments

    NASA Astrophysics Data System (ADS)

    Tranter, M.

    2003-12-01

    It seems counterintuitive that chemical erosion in glaciated regions proceeds at rates comparable to those of temperate catchments with comparable specific runoff (Anderson et al., 1997). All the usual factors that are associated with elevated rates of chemical weathering ( Drever, 1988, 1994), such as water, soil, and vegetation, are either entirely absent or absent for much of the year. For example, glaciated regions are largely frozen for significant periods each year, the residence time of liquid water in the catchment is low ( Knight, 1999), there are thin, skeletal soils at best, and vegetation is either absent or limited ( French, 1997). Other chapters in this volume have highlighted how these factors are important in other, more temperate and tropical environments. Even so, chemical erosion rates in glaciated terrain are usually near to or greater than the continental average ( Sharp et al., 1995; Wadham et al., 1997; Hodson et al., 2000). This is because glaciated catchments usually have high specific runoff, there are high concentrations of freshly comminuted rock flour, which is typically silt sized and coated with microparticles, and adsorbed organic matter or surface precipitates that may hinder water-rock interactions are largely absent ( Tranter, 1982). In short, the rapid flow of water over fine-grained, recently crushed, reactive mineral surfaces maximizes both the potential rates of chemical weathering and chemical erosion.A range of both lab- and field-based studies of glacial chemical weathering have been undertaken, mainly on the smaller glaciers of Continental Europe (e.g., Brown et al., 1993a, b), Svalbard (e.g., Hodson et al., 2002), and North America (e.g., Anderson et al., 2000). The field-based studies typically generate hydrographs of glacier runoff, which show a characteristic diurnal cycle during summer in low latitudes ( Figure 1), and more subdued diurnal cycles at high latitudes (Figure 2 and Figure 3). The concentration of ions in

  8. "Pleistocene Park" - A Glacial Ecosystem in a Warming World

    NASA Astrophysics Data System (ADS)

    Zimov, N.; Zimov, S. A.

    2011-12-01

    Most people if asked what association they have to the phrase - ice age, will answer - "Mammoth". But mammoths are not only big wooly elephants which went extinct in the beginning of Holocene. They were also part of a great ecosystem, the Northern Steppe or Mammoth Ecosystem, which was the world's largest ecosystem for hundreds thousand of years. This ecosystem, with extremely high rates of biocycling, could maintain animal densities which can be hardly found anywhere in the modern world. Northern steppe played an important role in shaping the glacial climate of the planet. High albedo grasslands reflected a much bigger portion of sun heat back to the atmosphere. Cold soils and permafrost served as sinks of carbon, helping to keep greenhouse gas concentration in the atmosphere at low levels. In the beginning of Holocene, simultaneously with wave of human expansion, an extinction wave took place. Tens of megafauna species became extinct at that time worldwide, while ones that resisted the extinction substantially dropped in numbers. The Northern Steppe ecosystem became imbalanced. Without large numbers of herbivores grazing and trampling the pasture, trees, shrubs and moss invaded grasslands. Within just a few hundreds years the mammoth ecosystem was gone, replaced by much lower productivity ecosystems. Already 14 thousand year ago, by simply increasing hunting pressure, humans managed to dramatically change Earth's appearance. We propose that by artificially maintaining a high animal density and diversity on a limited territory for extended period of time, it will be possible to reverse the shift, reestablishing the productive Northern Steppe ecosystem. Moss, shrubs and tree sprouts are not able to resist grazing pressure so they will be quickly replaced by grasses and herbs. Animals digesting all aboveground biomass would accelerate nutrition cycling and consequently increase bioproductivity. Higher bioproductivity would increase evapotranspiration, keeping soils

  9. Aspects of conducting site investigations in glacial terrain

    SciTech Connect

    Schilling, K.E. )

    1993-03-01

    Much of northern US is mantled by Pleistocene glacial drift consisting of heterogeneous deposits of fine to coarse-textured sediments. Hazardous waste site investigations in glacial settings can often present unique design and implementation considerations. Complex glacial stratigraphy encountered during drilling activities demands flexibility built into work plans to allow for field decisions based on field conditions. Continuous cores should be collected from boreholes on a routine basis for stratigraphic purposes with particular importance assigned to field identification of relative permeabilities of stratigraphic units. Selection of appropriate field screening methodology should be based on site conditions. Utilization of open borehole groundwater sampling is recommended for fine-textured glacial settings where soil gas and well point sampling are ineffective. Installation of boreholes allows for collection of stratigraphic information and enables more surface area exposed beneath the water table for groundwater recharge and sampling. Water level determinations can be made on open boreholes for an initial assessment of the horizontal direction of groundwater flow. Placement of screens for monitoring wells should be based on field determination of likely groundwater flow paths. Nested wells are necessary to define the vertical groundwater flow system at most sites. Evaluation of the vertical flow system can often dominate site investigations in fine-textured glacial terrain. Two case studies from Iowa illustrate the usefulness of incorporating the above considerations in planning and implementing in fine-textured glacial sediments. Field investigations utilizing open borehole groundwater sampling successfully delineated site glacial geology and hydrogeology for determination of the nature and extent of groundwater contamination and better located the horizontal and vertical placement of monitoring wells.

  10. Quantum decision tree classifier

    NASA Astrophysics Data System (ADS)

    Lu, Songfeng; Braunstein, Samuel L.

    2013-11-01

    We study the quantum version of a decision tree classifier to fill the gap between quantum computation and machine learning. The quantum entropy impurity criterion which is used to determine which node should be split is presented in the paper. By using the quantum fidelity measure between two quantum states, we cluster the training data into subclasses so that the quantum decision tree can manipulate quantum states. We also propose algorithms constructing the quantum decision tree and searching for a target class over the tree for a new quantum object.

  11. Fragmentation of random trees

    NASA Astrophysics Data System (ADS)

    Kalay, Ziya; Ben-Naim, Eli

    2015-03-01

    We investigate the fragmentation of a random recursive tree by repeated removal of nodes, resulting in a forest of disjoint trees. The initial tree is generated by sequentially attaching new nodes to randomly chosen existing nodes until the tree contains N nodes. As nodes are removed, one at a time, the tree dissolves into an ensemble of separate trees, namely a forest. We study the statistical properties of trees and nodes in this heterogeneous forest. In the limit N --> ∞ , we find that the system is characterized by a single parameter: the fraction of remaining nodes m. We obtain analytically the size density ϕs of trees of size s, which has a power-law tail ϕs ~s-α , with exponent α = 1 + 1 / m . Therefore, the tail becomes steeper as further nodes are removed, producing an unusual scaling exponent that increases continuously with time. Furthermore, we investigate the fragment size distribution in a growing tree, where nodes are added as well as removed, and find that the distribution for this case is much narrower.

  12. arb_tree_32

    SciTech Connect

    Bavykin, Sergey; Alferov, Oleg

    2006-08-01

    The purpose of this program is to generate probes specific for the group of sequences that belong to a given phylogenetic node. For each node of the input tree, this program selects probes that are positive for all sequences that belong to this node and negative for all that doesn't. The program uses condensed tree for probe representation to save computer memory. As a result of calculation, the program prints lists for each node from the tree. Input file formats: FASTA for sequence database and ARB tree for phylogenetic organization of nodes. Output file format: text file.

  13. Efficiency of Nuclear and Mitochondrial Markers Recovering and Supporting Known Amniote Groups

    PubMed Central

    Lambret-Frotté, Julia; Perini, Fernando Araújo; de Moraes Russo, Claudia Augusta

    2012-01-01

    We have analysed the efficiency of all mitochondrial protein coding genes and six nuclear markers (Adora3, Adrb2, Bdnf, Irbp, Rag2 and Vwf) in reconstructing and statistically supporting known amniote groups (murines, rodents, primates, eutherians, metatherians, therians). The efficiencies of maximum likelihood, Bayesian inference, maximum parsimony, neighbor-joining and UPGMA were also evaluated, by assessing the number of correct and incorrect recovered groupings. In addition, we have compared support values using the conservative bootstrap test and the Bayesian posterior probabilities. First, no correlation was observed between gene size and marker efficiency in recovering or supporting correct nodes. As expected, tree-building methods performed similarly, even UPGMA that, in some cases, outperformed other most extensively used methods. Bayesian posterior probabilities tend to show much higher support values than the conservative bootstrap test, for correct and incorrect nodes. Our results also suggest that nuclear markers do not necessarily show a better performance than mitochondrial genes. The so-called dependency among mitochondrial markers was not observed comparing genome performances. Finally, the amniote groups with lowest recovery rates were therians and rodents, despite the morphological support for their monophyletic status. We suggest that, regardless of the tree-building method, a few carefully selected genes are able to unfold a detailed and robust scenario of phylogenetic hypotheses, particularly if taxon sampling is increased. PMID:23032608

  14. Obliquity pacing of the late Pleistocene glacial terminations.

    PubMed

    Huybers, Peter; Wunsch, Carl

    2005-03-24

    The 100,000-year timescale in the glacial/interglacial cycles of the late Pleistocene epoch (the past approximately 700,000 years) is commonly attributed to control by variations in the Earth's orbit. This hypothesis has inspired models that depend on the Earth's obliquity (approximately 40,000 yr; approximately 40 kyr), orbital eccentricity (approximately 100 kyr) and precessional (approximately 20 kyr) fluctuations, with the emphasis usually on eccentricity and precessional forcing. According to a contrasting hypothesis, the glacial cycles arise primarily because of random internal climate variability. Taking these two perspectives together, there are currently more than thirty different models of the seven late-Pleistocene glacial cycles. Here we present a statistical test of the orbital forcing hypothesis, focusing on the rapid deglaciation events known as terminations. According to our analysis, the null hypothesis that glacial terminations are independent of obliquity can be rejected at the 5% significance level, whereas the corresponding null hypotheses for eccentricity and precession cannot be rejected. The simplest inference consistent with the test results is that the ice sheets terminated every second or third obliquity cycle at times of high obliquity, similar to the original proposal by Milankovitch. We also present simple stochastic and deterministic models that describe the timing of the late-Pleistocene glacial terminations purely in terms of obliquity forcing.

  15. Glacial ocean circulation and stratification explained by reduced atmospheric temperature.

    PubMed

    Jansen, Malte F

    2017-01-03

    Earth's climate has undergone dramatic shifts between glacial and interglacial time periods, with high-latitude temperature changes on the order of 5-10 °C. These climatic shifts have been associated with major rearrangements in the deep ocean circulation and stratification, which have likely played an important role in the observed atmospheric carbon dioxide swings by affecting the partitioning of carbon between the atmosphere and the ocean. The mechanisms by which the deep ocean circulation changed, however, are still unclear and represent a major challenge to our understanding of glacial climates. This study shows that various inferred changes in the deep ocean circulation and stratification between glacial and interglacial climates can be interpreted as a direct consequence of atmospheric temperature differences. Colder atmospheric temperatures lead to increased sea ice cover and formation rate around Antarctica. The associated enhanced brine rejection leads to a strongly increased deep ocean stratification, consistent with high abyssal salinities inferred for the last glacial maximum. The increased stratification goes together with a weakening and shoaling of the interhemispheric overturning circulation, again consistent with proxy evidence for the last glacial. The shallower interhemispheric overturning circulation makes room for slowly moving water of Antarctic origin, which explains the observed middepth radiocarbon age maximum and may play an important role in ocean carbon storage.

  16. Glacial ocean circulation and stratification explained by reduced atmospheric temperature

    NASA Astrophysics Data System (ADS)

    Jansen, Malte F.

    2017-01-01

    Earth’s climate has undergone dramatic shifts between glacial and interglacial time periods, with high-latitude temperature changes on the order of 5–10 °C. These climatic shifts have been associated with major rearrangements in the deep ocean circulation and stratification, which have likely played an important role in the observed atmospheric carbon dioxide swings by affecting the partitioning of carbon between the atmosphere and the ocean. The mechanisms by which the deep ocean circulation changed, however, are still unclear and represent a major challenge to our understanding of glacial climates. This study shows that various inferred changes in the deep ocean circulation and stratification between glacial and interglacial climates can be interpreted as a direct consequence of atmospheric temperature differences. Colder atmospheric temperatures lead to increased sea ice cover and formation rate around Antarctica. The associated enhanced brine rejection leads to a strongly increased deep ocean stratification, consistent with high abyssal salinities inferred for the last glacial maximum. The increased stratification goes together with a weakening and shoaling of the interhemispheric overturning circulation, again consistent with proxy evidence for the last glacial. The shallower interhemispheric overturning circulation makes room for slowly moving water of Antarctic origin, which explains the observed middepth radiocarbon age maximum and may play an important role in ocean carbon storage.

  17. Reconciling Glacial Snow Lines With Tropical Sea Surface Temperatures

    NASA Astrophysics Data System (ADS)

    Lorenz, S. J.; Lohmann, G.

    Reconstructions of tropical snow lines during the last glacial maximum (LGM) 21,000 years ago are incompatible with the sea surface temperature (SST) reconstructions of the CLIMAP project, when assuming present day atmospheric lapse rates (e.g. Pe- teet and Rind 1985). Since proxy data for the vertical structure of the atmosphere during glacial times do not exist, numerical experiments with an atmospheric gen- eral circulation model for glacial and interglacial climates have been performed. Our model experiments reveal that slightly cooler tropical SSTs relative to the ones by CLIMAP (1981) are sufficient to simulate proper glacial freezing temperature levels. The depression of tropical snow lines in our LGM experiment can be attributed to two effects: Less moisture content provides an increased environmental lapse rate in the free atmosphere. This effect is strongest in the tropical middle troposphere where we observe an additional two degrees cooling. Secondly, the surface temperature near tropical glaciers is further cooled by a longer duration of snow cover. Our model result provides a consistent view of the last glacial maximum climate with much colder tem- peratures than today in the tropical mountains in concordance with moderate lowering of tropical SSTs.

  18. Evaluating Object-Based Image Analysis on Glacial Micromorphology

    NASA Astrophysics Data System (ADS)

    Chin, K. S.; Sjogren, D. B.

    2007-12-01

    Micromorphology has recently been applied more in analyzing glacial sediments at a microscopic level. It provides additional information and details that may help to explain glacial processes in areas where macro- scale observations cannot yield sufficient information. However, the process of interpreting thin sections has been very subjective, and reaching general consensus about glacial processes is difficult. Remote sensing technology is increasingly helpful in the development and advancement of many sciences; the concepts that lie behind the technology in object cognition used in other fields, such as landscape ecology, can be applied to micromorphology. Similar to what has been done to landscape ecology in the past, automating the process of interpreting objects in glacial sediments may potentially simplify and decrease the subjectivity of the process. Definiens Professional 5 is an object-based image analysis program that imitates human cognitive methods; it is used in this study to identify objects apart from background matrices in multiple thin section images of glacial sediments. The program's initial results proved that more work was needed to be done for better results, but overall the software produced promising results. The method is repeatable and continues to generate consistent results with no bias or ambiguity, so the application of this method to micromorphology and other areas alike will be valuable.

  19. Glacial geology of the Hellas region on Mars

    NASA Technical Reports Server (NTRS)

    Kargel, Jeffrey S.; Strom, Robert G.; Johnson, Natasha

    1991-01-01

    A glacial geologic interpretation was recently presented for Argyre, which is herein extended to Hellas. This glacial event is believed to constitute an important link in a global cryohydric epoch of Middle Amazonian age. At glacial maximum, ice apparently extended far beyond the regions of Argyre and Hellas, and formed what is termed as the Austral Ice Sheet, an agglomeration of several ice domes and lobes including the Hellas Lobe. It is concluded that Hellas was apparently heavily glaciated. Also glaciation was young by Martian standards (Middle Amazonian), and ancient by terrestrial standards. Glaciation appears to have occurred during the same period that other areas on Mars were experiencing glaciation and periglacial activity. Glaciation seems to have occurred as a geological brief epoch of intense geomorphic activity in an era characterized by long periods of relative inactivity.

  20. Tectonic control on the persistence of glacially sculpted topography.

    PubMed

    Prasicek, Günther; Larsen, Isaac J; Montgomery, David R

    2015-08-14

    One of the most fundamental insights for understanding how landscapes evolve is based on determining the extent to which topography was shaped by glaciers or by rivers. More than 10(4) years after the last major glaciation the topography of mountain ranges worldwide remains dominated by characteristic glacial landforms such as U-shaped valleys, but an understanding of the persistence of such landforms is lacking. Here we use digital topographic data to analyse valley shapes at sites worldwide to demonstrate that the persistence of U-shaped valleys is controlled by the erosional response to tectonic forcing. Our findings indicate that glacial topography in Earth's most rapidly uplifting mountain ranges is rapidly replaced by fluvial topography and hence valley forms do not reflect the cumulative action of multiple glacial periods, implying that the classic physiographic signature of glaciated landscapes is best expressed in, and indeed limited by, the extent of relatively low-uplift terrain.

  1. Tectonic control on the persistence of glacially sculpted topography

    PubMed Central

    Prasicek, Günther; Larsen, Isaac J.; Montgomery, David R.

    2015-01-01

    One of the most fundamental insights for understanding how landscapes evolve is based on determining the extent to which topography was shaped by glaciers or by rivers. More than 104 years after the last major glaciation the topography of mountain ranges worldwide remains dominated by characteristic glacial landforms such as U-shaped valleys, but an understanding of the persistence of such landforms is lacking. Here we use digital topographic data to analyse valley shapes at sites worldwide to demonstrate that the persistence of U-shaped valleys is controlled by the erosional response to tectonic forcing. Our findings indicate that glacial topography in Earth's most rapidly uplifting mountain ranges is rapidly replaced by fluvial topography and hence valley forms do not reflect the cumulative action of multiple glacial periods, implying that the classic physiographic signature of glaciated landscapes is best expressed in, and indeed limited by, the extent of relatively low-uplift terrain. PMID:26271245

  2. GLOF, Glacial Lake Mapping an ESA DUE Innovator 2 Project

    NASA Astrophysics Data System (ADS)

    Wiesmann, Andreas; Strozzi, Tazio; Kaab, Andreas

    2010-12-01

    Glacier lake outbursts have repeatedly been the cause of major fatal events and damage in, for instance, the Himalayas, Central Asia, Andes, Caucasus, and the European Alps. The related hazards may even currently increase due to climate change as glaciers worldwide retreat and leave under certain circumstances glacier lakes behind. As a particularly far-reaching glacier- related hazard, glacier lake outburst floods may have devastating impact on populated areas that are located far downstream of the source area. Glacial lakes are often located in inaccessible areas, or can only be accessed with a substantial effort and cost to investigate their condition. While e.g. in Switzerland a network is setup to monitor glacier changes and help prevent glacial hazards, large and inaccessible areas e.g. in the Pamir and Himalayan mountains cannot be easily monitored from ground and air. Spaceborne remote sensing data are therefore a valuable and important information source to collect information on glacial lakes in these areas.

  3. Tree nut oils

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The major tree nuts include almonds, Brazil nuts, cashew nuts, hazelnuts, macadamia nuts, pecans, pine nuts, pistachio nuts, and walnuts. Tree nut oils are appreciated in food applications because of their flavors and are generally more expensive than other gourmet oils. Research during the last de...

  4. Trees Are Terrific!

    ERIC Educational Resources Information Center

    Braus, Judy, Ed.

    1992-01-01

    Ranger Rick's NatureScope is a creative education series dedicated to inspiring in children an understanding and appreciation of the natural world while developing the skills they will need to make responsible decisions about the environment. Contents are organized into the following sections: (1) "What Makes a Tree a Tree?," including…

  5. CSI for Trees

    ERIC Educational Resources Information Center

    Rubino, Darrin L.; Hanson, Deborah

    2009-01-01

    The circles and patterns in a tree's stem tell a story, but that story can be a mystery. Interpreting the story of tree rings provides a way to heighten the natural curiosity of students and help them gain insight into the interaction of elements in the environment. It also represents a wonderful opportunity to incorporate the nature of science.…

  6. The Flame Tree

    ERIC Educational Resources Information Center

    Lewis, Richard

    2004-01-01

    Lewis's own experiences living in Indonesia are fertile ground for telling "a ripping good story," one found in "The Flame Tree." He hopes people will enjoy the tale and appreciate the differences of an unfamiliar culture. The excerpt from "The Flame Tree" will reel readers in quickly.

  7. Fragmentation of random trees

    NASA Astrophysics Data System (ADS)

    Kalay, Z.; Ben-Naim, E.

    2015-01-01

    We study fragmentation of a random recursive tree into a forest by repeated removal of nodes. The initial tree consists of N nodes and it is generated by sequential addition of nodes with each new node attaching to a randomly-selected existing node. As nodes are removed from the tree, one at a time, the tree dissolves into an ensemble of separate trees, namely, a forest. We study statistical properties of trees and nodes in this heterogeneous forest, and find that the fraction of remaining nodes m characterizes the system in the limit N\\to ∞ . We obtain analytically the size density {{φ }s} of trees of size s. The size density has power-law tail {{φ }s}˜ {{s}-α } with exponent α =1+\\frac{1}{m}. Therefore, the tail becomes steeper as further nodes are removed, and the fragmentation process is unusual in that exponent α increases continuously with time. We also extend our analysis to the case where nodes are added as well as removed, and obtain the asymptotic size density for growing trees.

  8. Trees for Mother Earth.

    ERIC Educational Resources Information Center

    Greer, Sandy

    1993-01-01

    Describes Trees for Mother Earth, a program in which secondary students raise funds to buy fruit trees to plant during visits to the Navajo Reservation. Benefits include developing feelings of self-worth among participants, promoting cultural exchange and understanding, and encouraging self-sufficiency among the Navajo. (LP)

  9. Reclamation: what about trees

    SciTech Connect

    Kolar, C.A.; Ashby, W.C.

    1982-07-01

    A five-year research programme was started in 1978 in the Botany Department of Southern Illinois University to evaluate the effect of reclamation practices on tree survival and growth. The project was initiated as a direct result of reports from Illinois and Indiana of tree-planting failures on mined lands reclaimed to current regulation standards.

  10. Structural Equation Model Trees

    ERIC Educational Resources Information Center

    Brandmaier, Andreas M.; von Oertzen, Timo; McArdle, John J.; Lindenberger, Ulman

    2013-01-01

    In the behavioral and social sciences, structural equation models (SEMs) have become widely accepted as a modeling tool for the relation between latent and observed variables. SEMs can be seen as a unification of several multivariate analysis techniques. SEM Trees combine the strengths of SEMs and the decision tree paradigm by building tree…

  11. Trees in Our Lives.

    ERIC Educational Resources Information Center

    NatureScope, 1986

    1986-01-01

    Provides: (1) background information on how trees have influenced human history and how trees affect people today; (2) four activities dealing with these topics; and (3) a ready-to-copy page related to paper and plastics. Activities include an objective, recommended age level(s), subject area(s), list of materials needed, and procedures. (JN)

  12. Dependency Tree Annotation Software

    DTIC Science & Technology

    2015-11-01

    Features 5 Distribution List 12 iv List of Figures Fig. 1 Manually created dependency tree for the sentence, “The little cat ate the pie...with a dependency relation label. Fig. 1 Manually created dependency tree for the sentence, “The little cat ate the pie” The user can easily

  13. Is rate of glacial retreat accelerated in Indian Himalaya? (Invited)

    NASA Astrophysics Data System (ADS)

    Kulkarni, A. V.

    2013-12-01

    The Himalaya has one of the largest concentration of glaciers and rivers like Indus, Ganga and Bramhputra originate from this region. The snow and glacier melt is an important source of water for these rivers. However, this source of water may get affected in the near future due to changes in the cryosphere. Therefore, retreat of Himalayan glaciers are discussed extensively in scientific and public forums in India. Conventionally health of glaciers is assessed using changes in glacial length, as it is widely measured. However changes in glacial length and loss in areal extent near terminus needs to be interpreted carefully, as these changes can be influenced by numerous terrain and climatically sensitive parameters. The terrain parameters which can influence glacial retreat are slope, area altitude distribution, debris cover and orientation. In addition, climatically sensitive parameters like mass balance, glacial lakes and black carbon can also influence glacier retreat. These multiple influences can produce a complex pattern of glacial retreat. In this paper long-term glacier retreat in three river basins in the Indian Himalaya as Tista, Baspa and Parbati will be discussed. These basins are located in different climatically sensitive regions and each basin has unique dominant process of mass wasting. In addition to terrain parameters, influence of process like formation and expansion of moraine dammed lakes in Tista basin, deposition of black carbon on accumulation area in Baspa basin and debris cover in Parbati basin will also be discussed. This will provide understanding on varying influence of different mass wasting processes on glacial retreat during last five decades in the Indian Himalaya.

  14. Productivity of the glacial ocean: Discussion of the iron hypothesis

    SciTech Connect

    Berger, W.H. ); Wefer, G. )

    1991-12-01

    An increase in the productivity of the glacial-age Southern Ocean has been postulated to explain the decrease in pCO{sub 2} of the atmosphere observed in ice cores. A plausible mechanism has been proposed elsewhere that productivity is limited by the availability of Fe in this region and that the greater supply of eolian dust during glacial time removed this limit. Recently published evidence from cores from the Southern Ocean suggests that in fact there was no change in productivity in the assumed manner. Glacial-age productivity was indeed greatly increased in the equatorial Pacific and in the eastern boundary upwelling systems. The cause, presumably, was the mechanical action of glacial-age winds rather than a greater supply of Fe. However, a role of increased supply of micronutrients from the continents in the increase of equatorial productivity during glacial time cannot be excluded. Such enhancement from increased supply of dust would have the interesting corollary of more efficient export transfer to depth, possibly contributing to nutrient depletion in glacial-age, deep intermediate waters. There is some indication, as well, of a general decrease in nutrient content in the tropical thermocline in the western Pacific during the last several million years, a depletion that may have been fostered by increasing supply of dust from emerging Asian highlands. Alternative explanations are available. The case for Fe as a major modifier of productivity and biogenic sedimentation on geological time scales cannot be made in the absence of criteria diagnostic for Fe supply as opposed to stirring and upwelling.

  15. Geometric dependency of Tibetan lakes on glacial runoff

    NASA Astrophysics Data System (ADS)

    Phan, V. H.; Lindenbergh, R. C.; Menenti, M.

    2013-10-01

    The Tibetan Plateau is an essential source of water for Southeast Asia. The runoff from its ~34 000 glaciers, which occupy an area of ~50 000 km2, feeds Tibetan lakes and major Asian rivers like the Indus and Brahmaputra. Reported glacial shrinkage likely has an impact on the runoff. Unfortunately, accurate quantification of glacial changes is difficult over the high-relief Tibetan Plateau. However, it has recently been shown that it is possible to directly assess water level changes of a significant number of the ~900 Tibetan lakes with an area over 1 km2. This paper exploits different remote sensing products to create drainage links between Tibetan glaciers, lakes and rivers. The results allow us to differentiate between lakes with and without outlet. In addition, we introduce the notion of geometric dependency of a lake on glacial runoff, defined as the ratio between the total area of glaciers draining into a lake and the total area of the lake catchment. We determined these dependencies for all ~900 sufficiently large Tibetan lakes. To do so, we combined three remote sensing products: the CAREERI glacier mask product, a lake mask product based on the MODIS MOD44W water product and the HydroSHEDS river network product derived from Shuttle Radar Topography Mission (SRTM) elevation data. Using a drainage network analysis, we determined all drainage links between glaciers and lakes. The results show that 25.3% of the total glacier area directly drains into one of 244 Tibetan lakes. The results also give the geometric dependency of each lake on glacial runoff. For example, there are ten lakes with direct glacial runoff from at least 240 km2 of glacier. Three case studies, including one of the well-studied Nam Tso Lake, demonstrate how the geometric dependency of a lake on glacial runoff can be directly linked to hydrological processes.

  16. Geometric dependency of Tibetan lakes on glacial runoff

    NASA Astrophysics Data System (ADS)

    Phan, V. H.; Lindenbergh, R. C.; Menenti, M.

    2013-01-01

    The Tibetan plateau is an essential source of water for South-East Asia. The run-off from its ~ 34 000 glaciers, which occupy an area of ~ 50 000 km2, feed Tibetan lakes and major Asian rivers like Indus and Brahmaputra. Reported glacial shrinkage likely has its impact on the run-off. Unfortunately, accurate quantification of glacial changes is difficult over the high relief Tibetan plateau. However, it has been recently shown that it is possible to directly assess water level changes of a significant part of the ~ 900 Tibetan lakes greater than one square kilometer. This paper exploits different remote sensing products to explicitly create links between Tibetan glaciers, lakes and rivers. The results allow us first to differentiate between lakes with and without outlet. In addition, we introduce the notion of geometric dependency of a lake on glacial runoff, defined as the ratio between the total area of glaciers draining into a lake and the area of the catchment of the lake. These dependencies are determined for all ~ 900 Tibetan lakes. To obtain these results, we combine the so-called CAREERI glacier mask, a lake mask based on the MODIS MOD44W water product and the HydroSHEDS river network product derived from SRTM elevation data. Based on a drainage network analysis, all drainage links between glaciers and lakes are determined. The results show that 25.3% of the total glacier area directly drains into one of 244 Tibetan lakes. The results also give the geometric dependency of each lake on glacial runoff. For example, there are 10~lakes with direct glacial runoff from at least 240 km2 of glacier. Three case studies, including one over the well-studied Nam Tso, demonstrate how the geometric dependency of a lake on glacial runoff can be directly linked to hydrological processes.

  17. Noble Gas Signatures in Greenland - Tracing Glacial Meltwater Sources

    NASA Astrophysics Data System (ADS)

    Niu, Y.; Castro, M. C.; Hall, C. M.; Aciego, S.; Stevenson, E. I.; Arendt, C. A.

    2014-12-01

    This study is meant to explore the information noble gases can provide in glacial environments with respect to glacial meltwater sources, relative source contributions, water residence times, and spatial location where this glacial meltwater originates in the ice sheet. Ultimately, we seek to improve our understanding on the dynamics of these massive ice sheets, critical for the major role they play on climate change. This is possible due to the conservative nature of noble gases and temperature dependency of their concentrations in water in equilibrium with the atmosphere (ASW) allowing for calculation of noble gas temperatures (NGTs) and, under certain assumptions, estimation of the altitude at which glacial meltwater originated. In addition, crustally produced isotopes such as He accumulate in water over time, allowing for estimation of water residence times. Glacial meltwater samples were collected and analyzed for noble gas concentrations and isotopic ratios at five different locations in southern Greenland, between sea level and 1221 m. All samples are enriched in He with respect to ASW and are depleted in all other noble gases. Two patterns are apparent. The first one presents a relative Ar enrichment with respect to Ne, Kr, and Xe, a pattern first observed in high-altitude springs in the Galápagos Islands. The second one displays a mass-dependent pattern, a pattern first observed in Michigan rainwater samples. Most samples point to equilibration temperatures at ~0°C and altitudes between 1000 m and 2000 m, values which are consistent with both temperatures and elevations in Greenland. He concentrations vary between 1.1 and 7 times that of ASW and suggest glacial meltwater ages between ~170 and 1150 yrs, a result which is consistent with a preliminary tritium analysis. He isotopes point to surface (precipitation as snow and rainfall) contributions for most samples between ~60% and 90% with a ~10% - 40% crustal contribution from groundwater.

  18. Ever deeper phylogeographies: trees retain the genetic imprint of Tertiary plate tectonics.

    PubMed

    Hampe, Arndt; Petit, Rémy J

    2007-12-01

    Changes in species distributions after the last glacial maximum (c. 18 000 years bp) are beginning to be understood, but information diminishes quickly as one moves further back in time. In this issue of Molecular Ecology, Magri et al. (2007) present the fascinating case of a Mediterranean tree species whose populations preserve the genetic imprints of plate tectonic events that took place between 25 million years and 15 million years ago. The study provides a unique insight into the pace of evolution of trees, which, despite interspecific gene flow, can retain a cohesive species identity over timescales long enough to allow the diversification of entire plant and animal genera.

  19. Glacial modification of granite tors in the Cairngorms, Scotland

    USGS Publications Warehouse

    Hall, A.M.; Phillips, W.M.

    2006-01-01

    A range of evidence indicates that many granite tors in the Cairngorms have been modified by the flow of glacier ice during the Pleistocene. Comparisons with SW England and the use of a space-time transformation across 38 tor groups in the Cairngorms allow a model to be developed for progressive glacial modification. Tors with deeply etched surfaces and no, or limited, block removal imply an absence of significant glacial modification. The removal of superstructure and blocks, locally forming boulder trains, and the progressive reduction of tors to stumps and basal slabs represent the more advanced stages of modification. Recognition of some slabs as tor stumps from which glacial erosion has removed all superstructure allows the original distribution of tors to be reconstructed for large areas of the Cairngorms. Unmodified tors require covers of non-erosive, cold-based ice during all of the cold stages of the Middle and Late Pleistocene. Deformation beneath cold-based glacier ice is capable of the removal of blocks but advanced glacial modification requires former wet-based glacier ice. The depth of glacial erosion at former tor sites remains limited largely to the partial or total elimination of the upstanding tor form. Cosmogenic nuclide exposure ages (Phillips et al., 2006) together with data from weathering pit depths (Hall and Phillips, 2006), from the surfaces of tors and large erratic blocks require that the glacial entrainment of blocks from tors occurred in Marine Isotope Stages (MIS) 4-2, 6 and, probably, at least one earlier phase. The occurrence of glacially modified tors on or close to, the main summits of the Cairngorms requires full ice cover over the mountains during these Stages. Evidence from the Cairngorms indicates that tor morphology can be regarded as an important indicator of former ice cover in many formerly glaciated areas, particularly where other evidence of ice cover is sparse. Recognition of the glacial modification of tors is important

  20. The role of ocean-atmosphere reorganizations in glacial cycles

    NASA Astrophysics Data System (ADS)

    Broecker, Wallace S.; Denton, George H.

    A case is made that glacial-to-interglacial transitions involve major reorganizations of the ocean-atmosphere system. Such reorganizations constitute jumps between stable modes of operation which cause changes in the greenhouse gas content and albedo of the atmosphere. Only in this way can the rapidity of glacial terminations, the hemispheric synchroneity and symmetry of mountain glaciation, and the large polar air temperature and dustiness variations be accounted for. If these reorganizations are driven in some fashion by orbitally induced seasonal insolation changes, then the connection between insolation and climate is most likely through impacts of fresh water transport on the ocean's salinity distribution.

  1. The role of ocean-atmosphere reorganizations is glacial cycles

    NASA Astrophysics Data System (ADS)

    Broecker, Wallace S.; Denton, George H.

    1989-10-01

    A case is made that glacial-to-interglacial transitions involve major reorganizations of the ocean-atmosphere system. Such reorganizations constitute jumps between stable modes of operation which cause changes in the greenhouse gas content and albedo of the atmosphere. Only in this way can the rapidity of glacial terminations, the hemispheric synchroneity and symmetry of mountain glaciation, and the large polar air temperature and dustiness variations be accounted for. If these reorganizations are driven in some fashion by orbitally induced seasonal insolation changes, then the connection between insolation and climate is most likely through impacts of fresh water transport on the ocean's salinity distribution.

  2. The last glacial-Holocene transition in southern Chile.

    PubMed

    Bennett, K D; Haberle, S G; Lumley, S H

    2000-10-13

    Warming at the last glacial termination in the North Atlantic region was interrupted by a period of renewed glacial activity during the Younger Dryas chronozone (YDC). The underlying mechanism of this cooling remains elusive, but hypotheses turn on whether it was a global or a North Atlantic phenomenon. Chronological, sedimentological, and palaeoecological records from sediments of small lakes in oceanic southern Chile demonstrate that there was no YDC cooling in southern Chile. It is therefore likely that there was little or no cooling in southern Pacific surface waters and hence that YDC cooling in the North Atlantic was a regional, rather than global, phenomenon.

  3. Project Learning Tree (Corporate Propaganda Tree).

    ERIC Educational Resources Information Center

    Mayer, Mike

    This document contains a critical analysis of Project Learning Tree (PLT). PLT was developed and distributed in the mid-1970s. It consists of 2 activity guides, one for grades K-6 with 89 activities and another for grades 7-12 with 88 activities. The program also provides free workshops for teachers and others. The analysis of PLT includes the…

  4. An Assessment of Glacial Contributions to Lake Dynamics across the Tibetan Plateau since the Late Pleistocene

    NASA Astrophysics Data System (ADS)

    Sheng, Y.

    2014-12-01

    The Tibetan Plateau is one of the world's most vulnerable areas to global warming, and is home of the world's largest group of mountain glaciers and high-altitude lakes. These lakes in general have shrunk significantly since the late Pleistocene, and are currently continuing to experience changes in their distribution and inundation area. In the meantime, Tibetan glaciers have also gone through dramatic changes as evidenced by paleo glacial relics and recent accelerated melting. The paper provides a regional-scale systematic assessment of both paleo and contemporary lake changes across the plateau using geo-spatial information and optically stimulated luminescence (OSL) dating technologies. Using high-resolution satellite imagery of the plateau together with topographic data, this research recovered paleo lake extents for hundreds of contemporary lakes with visible paleo shore relics and estimated the amount of paleo lake shrinkage at regional scales. Both the basin-based water mass balance analysis using glacier/lake sizes and OSL dating of paleo shores suggest that paleo glaciers played a crucial role in the observed paleo lake shrinkage. Recent ~40 year lake dynamics was monitored by tracking thousands of Tibetan lakes using hundreds of satellite images. The results reveal that the overall total lake area has increased by ~26% between 1976 and 2009. The detected lake dynamics exhibit a strong spatial pattern generally but with local variations. The climate change and its regional glacier variations explain the general trend and the regional patterns of lake dynamics, respectively. The glacier mass monitored by GRACE satellites suggests a thinning trend over the past 12 years in the south while a gaining along the northern rim of the plateau. Basin-based analysis identifies glacial impacts on lake dynamics and explains many local variations. It can be concluded that glaciers play an important role in detected paleo as well as recent lake changes, and will

  5. Deepwater redox changes in the southern Okinawa Trough since the last glacial maximum

    NASA Astrophysics Data System (ADS)

    Dou, Yanguang; Yang, Shouye; Li, Chao; Shi, Xuefa; Liu, Jihua; Bi, Lei

    2015-06-01

    In this study, rare earth element (REE) was treated as a paleo-redox proxy to investigate the changes of depositional environment in the southern Okinawa Trough since the last glacial maximum. The acid-leachable fraction (leachate) of the sediments recovered from the ODP Site 1202B is dominated by biogenic and authigenic components while detrital contamination is minor. The significant enrichment of middle REE suggests a large contribution from authigenic Mn oxyhydroxides and cerium (Ce) anomaly can indicate deepwater redox change. The REE parameters including Ce anomaly in the leachate exhibit remarkable and abrupt changes in the early Holocene (∼9.5 ka) and during LGM (∼20 ka). An increase of Ce anomaly at 28-22 ka implies the suboxic deepwater condition probably caused by increased primary productivity. Weak positive Ce anomalies during the last glacial maximum and deglaciation suggest an oxic depositional environment responding to the enhanced deepwater ventilation with the advection of the North Pacific Intermediate Water and/or South China Sea Intermediate Water into the trough. A decrease of Ce anomaly in the early Holocene might be caused by the intrusion and strengthening of the Kuroshio Current in the trough that enhanced the water stratification and induced a gradual development of suboxic depositional condition. Furthermore, an abrupt change of chemical composition at ca. 4 ka probably indicates a decrease of dissolved oxygen in deepwater and a weakening of ventilation in the Okinawa Trough. This study suggests that REE proxy can provide new insights into the linkage among surface current, deepwater circulation and sediment record in the continental margin where terrigenous input dominates.

  6. Last Glacial - Present Glacial Activity in East Greenland Fjords Inferred from Swath Bathymetry and High-Resolution Seismic Data

    NASA Astrophysics Data System (ADS)

    Forwick, M.; Laberg, J. S.; Husum, K.; Olsen, I. L.

    2014-12-01

    Swath bathymetry and high-resolution penetration echo sounder (chirp) data from fjords and sounds between Kong Oscars Fjord and Bredefjord, East Greenland, reveal glacial landforms and sedimentary processes that can be used to infer glacial activity from the last glacial to the present. Relatively straight, linear features oriented parallel to the fjord axes, as well as beyond the mouths of some fjords, are interpreted to be glacial lineations providing evidence of fast-flowing grounded ice draining the eastern parts of the Greenland Ice Sheet during the last glacial. In some areas, the glacial lineations are the only preserved glacigenic landfjorms (e.g. beyond the mouth of Bredefjord). However, in other areas, they are covered with multiple transverse ridges interpreted to be small terminal moraines (e.g. in Youngsund). Whereas the absence of such moraines is suggested to represent a rapid ice retreat due to lift-up and disintegration during parts of the deglaciation, their presence reflects that multiple halts and/or re-advances interrupted the retreat. Acoustically stratified sediment sequences dominate the fjord-fill stratigraphies (up to 180 ms two-way travel time). These deposits are suggested to reflect repeatedly changing lithological compositions in a glacimarine environment where deposition mainly occurred from suspension fall-out, in addition to ice rafting from icebergs calving off from tidewater glaciers, and sea ice. The stratified deposits form often relatively uniform drapes indicating that the tidewater glaciers were mainly located near the fjord heads since the last deglaciation. However, acoustically transparent bodies with irregular geometries, intercalated within the stratified deposits, occur in some of the inner fjords. These are suggested to be glacigenic sediment wedges (debris-flow lobes) that formed during relatively recent advances of tidewater glaciers (e.g. in Nordfjord and Moskusoksefjord).

  7. Morphologic Map of Glacial and Periglacial Features in the Northwestern Argyre Basin, Mars

    NASA Astrophysics Data System (ADS)

    Raack, J.; Hiesinger, H.; Reiss, D.

    2010-03-01

    We produced a morphological map of the northwestern rim of the Argyre Basin with focus on glacial and periglacial features. We report on features such as gullies, pingo-like forms and glacial remnants which are observed.

  8. Glacial landforms of the southern Ungava Bay region (Canada): implications for the late-glacial dynamics and the damming of glacial Lake Naskaupi

    NASA Astrophysics Data System (ADS)

    Dube-Loubert, Hugo; Roy, Martin

    2014-05-01

    The Laurentide ice sheet played an important role in the late Pleistocene climate, notably through discharges of icebergs and meltwater. In this context, the Ungava Bay region in northern Quebec-Labrador appears particularly important, especially during the last deglaciation when the retreating ice margin dammed major river valleys, creating large proglacial lakes (e.g., McLean, aux Feuilles). The history of these lakes is closely related to the temporal evolution of the Labrador-Quebec ice dome. There are, however, large uncertainties regarding the position of its ice divide system through time, thereby limiting our understanding of the history of these glacial lakes. Here we focus on glacial and deglacial landforms present in the George River valley, south of Ungava Bay, in order to bring additional constraints on the late-glacial ice dynamics of this region, which also comprised glacial Lake Naskaupi. This work is based on surficial mapping using aerial photos and satellite imagery, combined with extensive fieldwork and sediment sampling. Our investigation showed significant differences in the distribution of glacial landforms across the region. The area east of the George River is characterized by well-developed Naskaupi shorelines while the elevated terrains show a succession of geomorphological features indicative of cold-based ice or ice with low basal velocities. In the easternmost part of this sector, ice flow directional data indicate that the ice was flowing towards ENE, against the regional slope. Eskers show paleocurrent directions indicating a general ice retreat from east to west. In the western part of this sector, near the George River valley, eskers are absent and the region is covered by felsenmeer and ground moraine that likely reflect the presence of a residual ice mass that was no longer dynamic. The presence of a stagnant ice represents the best mechanism to explain the formation of glacial lakes in the George River valley and its main

  9. Tree-ring analysis of ancient baldcypress trees and subfossil wood

    NASA Astrophysics Data System (ADS)

    Stahle, David W.; Burnette, Dorian J.; Villanueva, Jose; Cerano, Julian; Fye, Falko K.; Griffin, R. Daniel; Cleaveland, Malcolm K.; Stahle, Daniel K.; Edmondson, Jesse R.; Wolff, Kathryn P.

    2012-02-01

    Ancient baldcypress trees found in wetland and riverine environments have been used to develop a network of exactly dated annual ring-width chronologies extending from the southeastern United States, across Mexico, and into western Guatemala. These chronologies are sensitive to growing season precipitation in spite of frequently flooded site conditions, and have been used to reconstruct moisture levels the southeastern United States and Mexico for over 1000 years. The El Nino/Southern Oscillation (ENSO) is a major influence on the climate reconstructions derived from these baldcypress chronologies, especially in Mexico where some of the most extreme reconstructed droughts occurred during El Nino events. In the Southeast, the ENSO influence on climate and tree growth changes sign from spring to summer, and this change in dynamical forcing is recorded by sub-seasonal chronologies of earlywood and latewood width. Most existing baldcypress chronologies have been extended with tree-ring data from "subfossil" wood recovered from surface and submerged deposits. Well-preserved subfossil logs have also been recovered in quantity from buried deposits of great age, and may permit development of long continuously dated Holocene chronologies and discontinuous "floating" Pleistocene chronologies. The extensive subfossil baldcypress swamp discovered 6 m below the streets of Washington D.C. was overrun by a transgression of the Potomac estuary, possibly during the previous super interglacial (marine OIS 5e), and provides direct evidence for one potential impact of unmitigated anthropogenic warming and sea level rise.

  10. The Influence of Glacial Ice Sheets on Atlantic Meridional Overturning Circulation Through Atmospheric Circulation Change under Glacial Climate

    NASA Astrophysics Data System (ADS)

    Sherriff-Tadano, S.; Abe-Ouchi, A.; Yoshimori, M.; Oka, A.; Chan, W. L.

    2014-12-01

    It is well known that glacial ice sheets (Laurentide, Fennoscandian and Antarctic ice sheets) exert a large influence on the climate including the atmospheric circulation. Moreover, recent climate modeling studies suggest that glacial ice sheets have a large impact on the Atlantic meridional overturning circulation (AMOC). However, the process by which the ice sheets impact on the AMOC is not yet fully understood. On the other hand, recent studies showed that surface wind changes play a crucial role on changes to the AMOC under glacial climate. Therefore, in this study, we investigate in detail, the process by which the ice sheet modifies the AMOC through surface wind change. Here we conduct numerical experiments using an atmospheric general circulation model (AGCM) and an ocean general circulation model (OGCM) separately. Our method consists of 2 steps. First, from AGCM experiments, we evaluate the effect of glacial ice sheets on the surface wind. Second, from OGCM experiments, we evaluate the influence of the wind stress change on the AMOC by applying the surface wind change as a boundary condition, while leaving other boundary conditions (surface heat and water fluxes) unchanged. In addition, we conduct several sensitivity experiments. Using the AGCM, we explore individual ice sheet effect, ice sheet topography effect and albedo effect on surface wind change. Moreover, using the OGCM, we change the surface wind gradually or apply the surface wind change only at a specific region in order to explore the wind change effect in detail. We find that glacial ice sheets largely intensify the AMOC by surface wind change under glacial climate. Compare to other regions, it reveals that the wind change at the North Atlantic (NA) is a key region. There, the northern glacial ice sheet topography intensifies the Icelandic Low and anti-cyclonic circulation over the Laurentide ice sheet. However, this wind effect is effective only when the NA is not widely covered by sea ice

  11. Do post-glacial river valleys in northern New England store mill-dam legacy sediments?

    NASA Astrophysics Data System (ADS)

    Strouse, S.; Snyder, N. P.

    2010-12-01

    Dam-influenced floodplain morphology has not been studied extensively in post-glacial rivers with high densities of colonial-era milldams. Fluvial restoration in the eastern U.S. often focuses on understanding the natural, or pre-Colonial, floodplain processes. Recent work by Walter and Merritts (2008) in the piedmont of the U.S. Mid-Atlantic region suggests milldams significantly impact sedimentation by creating surfaces composed of post-dam legacy sediment that are often abandoned by the river and function as fill terraces. This work has not yet been tested in a post-glacial environment. I analyze channel morphology and sedimentation patterns upstream of two breached dams on the Sheepscot River in Mid-Coastal Maine using lidar digital elevation models, historical aerial photographs, radiocarbon dating, and hydraulic modeling. In the past several decades, observable channel morphologic changes occurred at the two study sites: Maxcy’s Mills dam (built in 1809, it was 4-m high and breached in the late 1950s), and at Head Tide dam (built in the 1760s, it is 6-m high and was partially breached in 1952). The Sheepscot River is one of Maine’s eight rivers with native anadromous Atlantic salmon populations. Because Atlantic salmon are a federally listed endangered species, understanding the existence and transport of legacy sediment has become an important component of habitat restoration efforts in the region. The goal of this investigation is to determine the extent of legacy sediment in order to better understand how historical dam sites affect morphology and sediment transport in a post-glacial, low-gradient river system. Field and remote sensing analyses indicate that surfaces (up to 2-m high) composed of mud and sand function as floodplains 1.5-2.5 km upstream of both former dam sites. Preliminary analysis of seven radiocarbon dates from pieces of tree bark sampled from the stratigraphy (58-187 cm below the surface) of the two study sites suggest at least 1.8 m

  12. Phylogenetic trees in bioinformatics

    SciTech Connect

    Burr, Tom L

    2008-01-01

    Genetic data is often used to infer evolutionary relationships among a collection of viruses, bacteria, animal or plant species, or other operational taxonomic units (OTU). A phylogenetic tree depicts such relationships and provides a visual representation of the estimated branching order of the OTUs. Tree estimation is unique for several reasons, including: the types of data used to represent each OTU; the use ofprobabilistic nucleotide substitution models; the inference goals involving both tree topology and branch length, and the huge number of possible trees for a given sample of a very modest number of OTUs, which implies that fmding the best tree(s) to describe the genetic data for each OTU is computationally demanding. Bioinformatics is too large a field to review here. We focus on that aspect of bioinformatics that includes study of similarities in genetic data from multiple OTUs. Although research questions are diverse, a common underlying challenge is to estimate the evolutionary history of the OTUs. Therefore, this paper reviews the role of phylogenetic tree estimation in bioinformatics, available methods and software, and identifies areas for additional research and development.

  13. Lazy decision trees

    SciTech Connect

    Friedman, J.H.; Yun, Yeogirl; Kohavi, R.

    1996-12-31

    Lazy learning algorithms, exemplified by nearest-neighbor algorithms, do not induce a concise hypothesis from a given training set; the inductive process is delayed until a test instance is given. Algorithms for constructing decision trees, such as C4.5, ID3, and CART create a single {open_quotes}best{close_quotes} decision tree during the training phase, and this tree is then used to classify test instances. The tests at the nodes of the constructed tree are good on average, but there may be better tests for classifying a specific instance. We propose a lazy decision tree algorithm-LazyDT-that conceptually constructs the {open_quotes}best{close_quote} decision tree for each test instance. In practice, only a path needs to be constructed, and a caching scheme makes the algorithm fast. The algorithm is robust with respect to missing values without resorting to the complicated methods usually seen in induction of decision trees. Experiments on real and artificial problems are presented.

  14. 26 CFR 1.1336-1 - Basis of recovered property.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ....1336-1 Internal Revenue INTERNAL REVENUE SERVICE, DEPARTMENT OF THE TREASURY (CONTINUED) INCOME TAX (CONTINUED) INCOME TAXES War Loss Recoveries § 1.1336-1 Basis of recovered property. (a) General rule. (1... considered the fair market value of such recovered property upon the date of its recovery with the...

  15. 26 CFR 1.1336-1 - Basis of recovered property.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ....1336-1 Internal Revenue INTERNAL REVENUE SERVICE, DEPARTMENT OF THE TREASURY (CONTINUED) INCOME TAX (CONTINUED) INCOME TAXES (CONTINUED) War Loss Recoveries § 1.1336-1 Basis of recovered property. (a) General... property is considered the fair market value of such recovered property upon the date of its recovery...

  16. 26 CFR 1.1336-1 - Basis of recovered property.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ....1336-1 Internal Revenue INTERNAL REVENUE SERVICE, DEPARTMENT OF THE TREASURY (CONTINUED) INCOME TAX (CONTINUED) INCOME TAXES (CONTINUED) War Loss Recoveries § 1.1336-1 Basis of recovered property. (a) General... property is considered the fair market value of such recovered property upon the date of its recovery...

  17. 26 CFR 1.1336-1 - Basis of recovered property.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ....1336-1 Internal Revenue INTERNAL REVENUE SERVICE, DEPARTMENT OF THE TREASURY (CONTINUED) INCOME TAX (CONTINUED) INCOME TAXES (CONTINUED) War Loss Recoveries § 1.1336-1 Basis of recovered property. (a) General... property is considered the fair market value of such recovered property upon the date of its recovery...

  18. 26 CFR 1.1336-1 - Basis of recovered property.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ....1336-1 Internal Revenue INTERNAL REVENUE SERVICE, DEPARTMENT OF THE TREASURY (CONTINUED) INCOME TAX (CONTINUED) INCOME TAXES (CONTINUED) War Loss Recoveries § 1.1336-1 Basis of recovered property. (a) General... property is considered the fair market value of such recovered property upon the date of its recovery...

  19. Phosphorus distribution in a soil fertilized with recovered manure phosphates

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Phosphorus (P) can be recovered in a concentrated form from livestock manure and poultry litter. A greenhouse study was conducted to evaluate the short-term leaching potential and plant availability of P from recovered P materials from liquid pig manure (SRP) and broiler litter (LRP) in a characteri...

  20. The 14 Worst Myths about Recovered Mental Patients.

    ERIC Educational Resources Information Center

    National Inst. of Mental Health (DHHS), Rockville, MD.

    Fourteen myths about recovered mental patients are discussed in this pamphlet. The myths are introduced in a true/false checklist. Famous recovered victims of mental illness are cited, most notably Abraham Lincoln. Three vignettes concerning non-famous people and the rebuffs they faced as they attempted to become self-sufficient are presented.…

  1. Fertilizing cotton with P recovered from swine wastewater

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A new treatment technology has been developed to recover soluble P from waste on swine (Sus scrofa domesticus) farms. Our objective was to compare this recovered P to triple superphosphate and broiler litter for soil availability, leaching, and cotton (Gossypium hirsutum L.) plant P concentration. A...

  2. 48 CFR 245.607-2 - Recovering precious metals.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 48 Federal Acquisition Regulations System 3 2010-10-01 2010-10-01 false Recovering precious metals... Disposal of Contractor Inventory 245.607-2 Recovering precious metals. (b) Precious metals are silver, gold... office with disposition instructions for certain categories of precious metals-bearing...

  3. 48 CFR 945.607-2 - Recovering precious metals.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 48 Federal Acquisition Regulations System 5 2010-10-01 2010-10-01 false Recovering precious metals... Recovering precious metals. (b) Contractors generating contractor inventory containing precious metals shall... the DOE precious metals pool. This includes all precious metals in any form, including shapes,...

  4. 48 CFR 945.607-2 - Recovering precious metals.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 48 Federal Acquisition Regulations System 5 2011-10-01 2011-10-01 false Recovering precious metals... Recovering precious metals. (b) Contractors generating contractor inventory containing precious metals shall... the DOE precious metals pool. This includes all precious metals in any form, including shapes,...

  5. 48 CFR 945.607-2 - Recovering precious metals.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 48 Federal Acquisition Regulations System 5 2012-10-01 2012-10-01 false Recovering precious metals... Recovering precious metals. (b) Contractors generating contractor inventory containing precious metals shall... the DOE precious metals pool. This includes all precious metals in any form, including shapes,...

  6. Learning classification trees

    NASA Technical Reports Server (NTRS)

    Buntine, Wray

    1991-01-01

    Algorithms for learning classification trees have had successes in artificial intelligence and statistics over many years. How a tree learning algorithm can be derived from Bayesian decision theory is outlined. This introduces Bayesian techniques for splitting, smoothing, and tree averaging. The splitting rule turns out to be similar to Quinlan's information gain splitting rule, while smoothing and averaging replace pruning. Comparative experiments with reimplementations of a minimum encoding approach, Quinlan's C4 and Breiman et al. Cart show the full Bayesian algorithm is consistently as good, or more accurate than these other approaches though at a computational price.

  7. The gravity apple tree

    NASA Astrophysics Data System (ADS)

    Espinosa Aldama, Mariana

    2015-04-01

    The gravity apple tree is a genealogical tree of the gravitation theories developed during the past century. The graphic representation is full of information such as guides in heuristic principles, names of main proponents, dates and references for original articles (See under Supplementary Data for the graphic representation). This visual presentation and its particular classification allows a quick synthetic view for a plurality of theories, many of them well validated in the Solar System domain. Its diachronic structure organizes information in a shape of a tree following similarities through a formal concept analysis. It can be used for educational purposes or as a tool for philosophical discussion.

  8. Evolutionary tree reconstruction

    NASA Technical Reports Server (NTRS)

    Cheeseman, Peter; Kanefsky, Bob

    1990-01-01

    It is described how Minimum Description Length (MDL) can be applied to the problem of DNA and protein evolutionary tree reconstruction. If there is a set of mutations that transform a common ancestor into a set of the known sequences, and this description is shorter than the information to encode the known sequences directly, then strong evidence for an evolutionary relationship has been found. A heuristic algorithm is described that searches for the simplest tree (smallest MDL) that finds close to optimal trees on the test data. Various ways of extending the MDL theory to more complex evolutionary relationships are discussed.

  9. Hydrostratigraphy of Tree Island Cores from Water Conservation Area 3

    USGS Publications Warehouse

    McNeill, Donald F.; Cunningham, Kevin J.

    2003-01-01

    Cores and borehole-geophysical logs collected on and around two tree islands in Water Conservation Area 3 have been examined to develop a stratigraphic framework for these ecosystems. Especially important is the potential for the exchange of ground water and surface water within these features. The hydrostratigraphic results from this study document the lithologic nature of the foundation of the tree islands, the distribution of porous intervals, the potential for paleotopographic influence on their formation, and the importance of low-permeability, subaerial-exposure horizons on the vertical exchange of ground water and surface water. Figure 1. Location of Tree Islands 3AS3 and 3BS1. [larger image] Results from this hydrostratigraphic study indicate that subtle differences occur in lithofacies and topography between the on-island and off-island subsurface geologic records. Specifics are described herein. Firstly, at both tree-island sites, the top of the limestone bedrock is slightly elevated beneath the head of the tree islands relative to the off-island core sites and the tail of the tree islands, which suggests that bedrock 'highs' acted as 'seeds' for the development of the tree islands of this study and possibly many others. Secondly, examination of the recovered core and the caliper logs tentatively suggest that the elevated limestone beneath the tree islands may have a preferentially more porous framework relative to limestone beneath the adjacent areas, possibly providing a ground-water-to-surface-water connection that sustains the tree island system. Finally, because the elevation of the top of the limestone bedrock at the head of Tree Island 3AS3 is slightly higher than the surrounding upper surface of the peat, and because the wetland peats have a lower hydraulic conductivity than the limestone bedrock (Miami Limestone and Fort Thompson Formation), it is possible that there is a head difference between surface water of the wetlands and the ground water

  10. Chinaberry tree (Melia azedarach) poisoning in dog: a case report.

    PubMed

    Ferreiro, D; Orozco, J P; Mirón, C; Real, T; Hernández-Moreno, D; Soler, F; Pérez-López, M

    2010-02-01

    This article describes a case of Chinaberry tree poisoning diagnosed in a dog. The initial clinical signs were variable and included tremors (muscular seizures) and a moderate limp in the dog's back leg, which evolved to a more severe condition in the following hours. Abdominal radiographic evaluation was requested, and abundant small, foreign, radio-dense bodies were detected, which were associated with Chinaberry tree fruits after surgical extraction. Adequate treatment was established, and the patient recovered completely. In addition, we compare clinical and gross postmortem findings in other similar cases reported in the literature. There is a general lack of information of such poisoning in pets.

  11. Survival of Listeria innocua in rainbow trout protein recovered by isoelectric solubilization and precipitation with acetic and citric acids.

    PubMed

    Otto, R A; Paker, I; Bane, L; Beamer, S; Jaczynski, J; Matak, K E

    2011-08-01

    During mechanical fish processing, a substantial amount of protein is discarded as by-products. Isoelectric solubilization and precipitation (ISP) is a process that uses extreme pH shifts to solubilize and precipitate protein from by-products to recover previously discarded protein. Typically, strong acids are used for pH reduction, but these acids do not have a pasteurization effect (6 log reduction) on bacterial load; therefore, organic acids were used during ISP processing to test the impact on Listeria innocua concentrations. Headed and gutted rainbow trout (Oncorhynchus mykiss) were inoculated with L. innocua, homogenized, and brought to the target pH with granular citric acid (pH 2.0 and 2.5) or glacial acetic acid (pH 3.0 and 3.5). Proteins were solubilized for 10 min at 4°C, and insoluble components (e.g., skin and insoluble protein) were removed by centrifugation. The remaining solution was pH shifted to the protein isoelectric point (pH 5.5) with sodium hydroxide, and precipitated protein was separated from the water. Microbial cells for each component (proteins, insolubles, and water) were enumerated on modified Oxford agar (MOX) and tryptic soy agar with 6% yeast extract (TSAYE). The sums of the surviving cells from each component were compared with the initial inoculum levels. No significant differences were observed between results obtained from TSAYE and from MOX (P > 0.05). Significant reductions in microbial populations were detected, regardless of pH or acid type (P < 0.05). The greatest reduction was at pH 3.0 with glacial acetic acid, resulting in a mean reduction of 6.41 log CFU/g in the recovered protein and 5.88 log CFU/g in the combined components. These results demonstrate the antimicrobial potential of organic acids in ISP processing.

  12. Glacial Influences on Solar Radiation in a Subarctic Sea.

    EPA Science Inventory

    Understanding macroscale processes controlling solar radia­tion in marine systems will be important in interpreting the potential effects of global change from increasing ultraviolet radiation (UV) and glacial retreat. This study provides the first quantitative assessment of UV i...

  13. Terrestrial glacial eskers: Analogs for Martian sinuous ridges

    NASA Technical Reports Server (NTRS)

    Kargel, Jeffrey S.; Strom, Roger G.

    1991-01-01

    A glacial model was introduced last year for the Argyre region, a concept which is now extended, and which was recently integrated with a Global Hydrologic Model incorporating many other aspects of Martian geology. Despite wide agreement that the Martian ridges strongly resemble glacial eskers, this hypothesis has been presented with great equivocation due to a perceived lack of other glacial landforms. Quite to the contrary, it is shown that the Martian ridges actually do occur in logical ordered sequences with many other types of characteristically glacial appearing landforms. Herein, the esker hypothesis is further supported in isolation from considerations of regional landform assemblages. It is concluded that Martian sinuous ridges are similar in every respect to terrestrial eskers: scale, morphology, planimetric pattern, and associations with other probable glaciogenic landforms. It is found that the esker hypothesis is well supported. Eskers are glaciofluvial structures, and owe their existence to large scale melting of stagnant temporate glaciers. Thus, eskers are indicators of an ameliorating climatic regime after a protracted episode of cold, humid conditions.

  14. Glacial melting: an overlooked threat to Antarctic krill

    NASA Astrophysics Data System (ADS)

    Fuentes, Verónica; Alurralde, Gastón; Meyer, Bettina; Aguirre, Gastón E.; Canepa, Antonio; Wölfl, Anne-Cathrin; Hass, H. Christian; Williams, Gabriela N.; Schloss, Irene R.

    2016-06-01

    Strandings of marine animals are relatively common in marine systems. However, the underlying mechanisms are poorly understood. We observed mass strandings of krill in Antarctica that appeared to be linked to the presence of glacial meltwater. Climate-induced glacial meltwater leads to an increased occurrence of suspended particles in the sea, which is known to affect the physiology of aquatic organisms. Here, we study the effect of suspended inorganic particles on krill in relation to krill mortality events observed in Potter Cove, Antarctica, between 2003 and 2012. The experimental results showed that large quantities of lithogenic particles affected krill feeding, absorption capacity and performance after only 24 h of exposure. Negative effects were related to both the threshold concentrations and the size of the suspended particles. Analysis of the stomach contents of stranded krill showed large quantities of large particles ( > 106 μm3), which were most likely mobilized by glacial meltwater. Ongoing climate-induced glacial melting may impact the coastal ecosystems of Antarctica that rely on krill.

  15. Ecology of invasive Melilotus alba on Alaskan glacial river floodplains

    Technology Transfer Automated Retrieval System (TEKTRAN)

    White sweetclover has recently invaded glacial river floodplains in Alaska. We sampled vegetation and measured environmental variables along transects located along the Nenana, Matanuska, and Stikine Rivers to describe plant communities and to determine the effects of white sweetclover on other plan...

  16. Glacial melting: an overlooked threat to Antarctic krill

    PubMed Central

    Fuentes, Verónica; Alurralde, Gastón; Meyer, Bettina; Aguirre, Gastón E.; Canepa, Antonio; Wölfl, Anne-Cathrin; Hass, H. Christian; Williams, Gabriela N.; Schloss, Irene R.

    2016-01-01

    Strandings of marine animals are relatively common in marine systems. However, the underlying mechanisms are poorly understood. We observed mass strandings of krill in Antarctica that appeared to be linked to the presence of glacial meltwater. Climate-induced glacial meltwater leads to an increased occurrence of suspended particles in the sea, which is known to affect the physiology of aquatic organisms. Here, we study the effect of suspended inorganic particles on krill in relation to krill mortality events observed in Potter Cove, Antarctica, between 2003 and 2012. The experimental results showed that large quantities of lithogenic particles affected krill feeding, absorption capacity and performance after only 24 h of exposure. Negative effects were related to both the threshold concentrations and the size of the suspended particles. Analysis of the stomach contents of stranded krill showed large quantities of large particles ( > 106 μm3), which were most likely mobilized by glacial meltwater. Ongoing climate-induced glacial melting may impact the coastal ecosystems of Antarctica that rely on krill. PMID:27250339

  17. Volcanic fire and glacial ice: Mount Rogers National Recreation Area

    USGS Publications Warehouse

    ,; ,

    2007-01-01

    In addition to containing the highest point in Virginia (Mount Rogers, elevation 5,729 feet), the Mount Rogers National Recreation Area (NRA) of the Jefferson National Forest is a window on the history of ancient volcanic eruptions and glacial movement.

  18. Obliquity Control On Southern Hemisphere Climate During The Last Glacial

    PubMed Central

    Fogwill, C.J.; Turney, C.S.M.; Hutchinson, D.K.; Taschetto, A.S.; England, M.H.

    2015-01-01

    Recent paleoclimate reconstructions have challenged the traditional view that Northern Hemisphere insolation and associated feedbacks drove synchronous global climate and ice-sheet volume during the last glacial cycle. Here we focus on the response of the Patagonian Ice Sheet, and demonstrate that its maximum expansion culminated at 28,400 ± 500 years before present (28.4 ± 0.5 ka), more than 5,000 years before the minima in 65°N summer insolation and the formally-defined Last Glacial Maximum (LGM) at 21,000 ± 2,000 years before present. To investigate the potential drivers of this early LGM (eLGM), we simulate the effects of orbital changes using a suite of climate models incorporating prescribed and evolving sea-ice anomalies. Our analyses suggest that Antarctic sea-ice expansion at 28.5 ka altered the location and intensity of the Southern Hemisphere storm track, triggering regional cooling over Patagonia of 5°C that extends across the wider mid-southern latitudes. In contrast, at the LGM, continued sea-ice expansion reduced regional temperature and precipitation further, effectively starving the ice sheet and resulting in reduced glacial expansion. Our findings highlight the dominant role that orbital changes can play in driving Southern Hemisphere glacial climate via the sensitivity of mid-latitude regions to changes in Antarctic sea-ice extent. PMID:26115344

  19. Glacial isostatic stress shadowing by the Antarctic ice sheet

    NASA Technical Reports Server (NTRS)

    Ivins, E. R.; James, T. S.; Klemann, V.

    2005-01-01

    Numerous examples of fault slip that offset late Quaternary glacial deposits and bedrock polish support the idea that the glacial loading cycle causes earthquakes in the upper crust. A semianalytical scheme is presented for quantifying glacial and postglacial lithospheric fault reactivation using contemporary rock fracture prediction methods. It extends previous studies by considering differential Mogi-von Mises stresses, in addition to those resulting from a Coulomb analysis. The approach utilizes gravitational viscoelastodynamic theory and explores the relationships between ice mass history and regional seismicity and faulting in a segment of East Antarctica containing the great Antarctic Plate (Balleny Island) earthquake of 25 March 1998 (Mw 8.1). Predictions of the failure stress fields within the seismogenic crust are generated for differing assumptions about background stress orientation, mantle viscosity, lithospheric thickness, and possible late Holocene deglaciation for the D91 Antarctic ice sheet history. Similar stress fracture fields are predicted by Mogi-von Mises and Coulomb theory, thus validating previous rebound Coulomb analysis. A thick lithosphere, of the order of 150-240 km, augments stress shadowing by a late melting (middle-late Holocene) coastal East Antarctic ice complex and could cause present-day earthquakes many hundreds of kilometers seaward of the former Last Glacial Maximum grounding line.

  20. Alaskan mountain glacial melting observed by satellite gravimetry

    NASA Astrophysics Data System (ADS)

    Chen, J. L.; Tapley, B. D.; Wilson, C. R.

    2006-08-01

    We use satellite gravity measurements from the Gravity Recovery and Climate Experiment (GRACE) as an indication of mass change to study potential long-term mountain glacial melting in southern Alaska and West Canada. The first 3.5 yr of GRACE monthly gravity data, spanning April 2002-November 2005, show a prominent glacial melting trend in the mountain regions around the Gulf of Alaska (GOA). GRACE-observed surface mass changes correlate remarkably well with available mass balance data at Gulkana and Wolverine, two benchmark glaciers of the U.S. Geological Survey (USGS), although the GRACE signals are smaller in magnitude. In addition, terrestrial water storage (TWS) changes estimated from an advanced land surface model show significant mass loss in this region during the same period. After correcting for the leakage errors and removing TWS contributions using model estimates, we conclude that GRACE-observed glacial melting in the GOA mountain region is equivalent to ˜ - 101 ± 22 km 3/yr, which agrees quite well with the assessment of ˜ - 96 ± 35 km 3/yr based on airborne laser altimetry data, and is consistent with an earlier estimate based on the first 2 yr of GRACE data. This study demonstrates the significant potentials of satellite gravity measurements for monitoring mountain glacial melting and regional climate change.

  1. Obliquity Control On Southern Hemisphere Climate During The Last Glacial.

    PubMed

    Fogwill, C J; Turney, C S M; Hutchinson, D K; Taschetto, A S; England, M H

    2015-06-26

    Recent paleoclimate reconstructions have challenged the traditional view that Northern Hemisphere insolation and associated feedbacks drove synchronous global climate and ice-sheet volume during the last glacial cycle. Here we focus on the response of the Patagonian Ice Sheet, and demonstrate that its maximum expansion culminated at 28,400 ± 500 years before present (28.4 ± 0.5 ka), more than 5,000 years before the minima in 65 °N summer insolation and the formally-defined Last Glacial Maximum (LGM) at 21,000 ± 2,000 years before present. To investigate the potential drivers of this early LGM (eLGM), we simulate the effects of orbital changes using a suite of climate models incorporating prescribed and evolving sea-ice anomalies. Our analyses suggest that Antarctic sea-ice expansion at 28.5 ka altered the location and intensity of the Southern Hemisphere storm track, triggering regional cooling over Patagonia of 5 °C that extends across the wider mid-southern latitudes. In contrast, at the LGM, continued sea-ice expansion reduced regional temperature and precipitation further, effectively starving the ice sheet and resulting in reduced glacial expansion. Our findings highlight the dominant role that orbital changes can play in driving Southern Hemisphere glacial climate via the sensitivity of mid-latitude regions to changes in Antarctic sea-ice extent.

  2. Sulfur/Carbonate Springs and Life in Glacial Ice

    NASA Technical Reports Server (NTRS)

    Allen, C. C.; Grasby, S.; Longazo, T.

    2001-01-01

    Glacial springs are useful analogs to channels and seeps issuing from frozen strata on Mars. Mineralized water can move through, and discharge from, solid ice. This water, even near freezing, can support microbial life and bring it to the surface. Additional information is contained in the original extended abstract.

  3. Oxygen-isotope variations in post-glacial Lake Ontario

    NASA Astrophysics Data System (ADS)

    Hladyniuk, Ryan; Longstaffe, Fred J.

    2016-02-01

    The role of glacial meltwater input to the Atlantic Ocean in triggering the Younger Dryas (YD) cooling event has been the subject of controversy in recent literature. Lake Ontario is ideally situated to test for possible meltwater passage from upstream glacial lakes and the Laurentide Ice Sheet (LIS) to the Atlantic Ocean via the lower Great Lakes. Here, we use the oxygen-isotope compositions of ostracode valves and clam shells from three Lake Ontario sediment cores to identify glacial meltwater contributions to ancient Lake Ontario since the retreat of the LIS (∼16,500 cal [13,300 14C] BP). Differences in mineralogy and sediment grain size are also used to identify changes in the hydrologic regime. The average lakewater δ18O of -17.5‰ (determined from ostracode compositions) indicates a significant contribution from glacial meltwater. Upon LIS retreat from the St. Lawrence lowlands, ancient Lake Ontario (glacial Lake Iroquois) lakewater δ18O increased to -12‰ largely because of the loss of low-18O glacial meltwater input. A subsequent decrease in lakewater δ18O (from -12 to -14‰), accompanied by a median sediment grain size increase to 9 μm, indicates that post-glacial Lake Ontario received a final pulse of meltwater (∼13,000-12,500 cal [11,100-10,500 14C] BP) before the onset of hydrologic closure. This meltwater pulse, which is also recorded in a previously reported brief freshening of the neighbouring Champlain Valley (Cronin et al., 2012), may have contributed to a weakening of thermohaline circulation in the Atlantic Ocean. After 12,900 cal [11,020 14C] BP, the meltwater presence in the Ontario basin continued to inhibit entry of Champlain seawater into early Lake Ontario. Opening of the North Bay outlet diverted upper Great Lakes water from the lower Great Lakes causing a period (12,300-8300 cal [10,400-7500 14C] BP) of hydrologic closure in Lake Ontario (Anderson and Lewis, 2012). This change is demarcated by a shift to higher δ18Olakewater

  4. Large spatial variations in glacial erosion detected with detrital thermochronology

    NASA Astrophysics Data System (ADS)

    Ehlers, T. A.; Stock, G. M.; Farley, K. A.; Densmore, M. S.; Rushlow, C.

    2008-12-01

    Studies of drainage basin erosion and landform evolution are often limited by not knowing where sediment is sourced from and how climate change influences catchment erosion. Detrital thermochronometer cooling ages collected from Quaternary glacial moraines and modern river sediments provide a promising tool to address these problems. We present an application of detrital thermochronology to quantify spatial variations in alpine glacial erosion during the Last Glacial Maximum (LGM). Results are compared to the distribution of recent erosion recorded in samples from modern river sediments. The elevation dependence of detrital apatite (U-Th)/He (AHe) ages is used as a sediment tracer to track the elevations where glacially eroded sediment is produced from bedrock. We measured ~204 AHe single grain ages from three moraines located between 2.3 and 3.7 km elevation in the Lone Pine catchment, Sierra Nevada, California. Ages from the lowest elevation moraine were measured on fine (<250 um) and coarse (>250 um) grained fractions of the sample to assess potential variations in sediment supply from different erosional processes. Measured AHe age probability density functions (PDFs) were compared with predicted PDFs, calculated by convolving bedrock age-elevation relationships with catchment hypsometries clipped at different elevations to reflect variable source elevations of sediment. Statistical comparison of the PDFs using a Monte Carlo approach and Kuiper test are used to evaluate the spatial distribution of erosion in the catchments. Results from the lowest elevation moraine indicate sediment is produced from the lower ~50-70% of catchment elevations at the 95% confidence level, indicating erosion near the base and sides of the glacier proportionally outweigh erosion from higher elevation head wall retreat and rock fall onto the glacier. Furthermore, grain-age distributions from the fine and coarse grain fractions are virtually indistinguishable, suggesting either both

  5. Trees of trees: an approach to comparing multiple alternative phylogenies.

    PubMed

    Nye, Tom M W

    2008-10-01

    Phylogenetic analysis very commonly produces several alternative trees for a given fixed set of taxa. For example, different sets of orthologous genes may be analyzed, or the analysis may sample from a distribution of probable trees. This article describes an approach to comparing and visualizing multiple alternative phylogenies via the idea of a "tree of trees" or "meta-tree." A meta-tree clusters phylogenies with similar topologies together in the same way that a phylogeny clusters species with similar DNA sequences. Leaf nodes on a meta-tree correspond to the original set of phylogenies given by some analysis, whereas interior nodes correspond to certain consensus topologies. The construction of meta-trees is motivated by analogy with construction of a most parsimonious tree for DNA data, but instead of using DNA letters, in a meta-tree the characters are partitions or splits of the set of taxa. An efficient algorithm for meta-tree construction is described that makes use of a known relationship between the majority consensus and parsimony in terms of gain and loss of splits. To illustrate these ideas meta-trees are constructed for two datasets: a set of gene trees for species of yeast and trees from a bootstrap analysis of a set of gene trees in ray-finned fish. A software tool for constructing meta-trees and comparing alternative phylogenies is available online, and the source code can be obtained from the author.

  6. Glacial geology, glacial recession, proglacial lakes, and postglacial environments, Fishers Island, New York

    SciTech Connect

    Sirkin, L. ); Funk, R.E. . Anthropological Survey)

    1993-03-01

    The Fishers Island Moraine, a complex of three parallel ice margin depositional trends, forms the west-central segment of a major recessional moraine of the Connecticut-Rhode Island Lobe of the late Wisconsinan glacier. As such, the moraine links the Orient Point Moraine of eastern Long Island and the Charlestown Moraine of western Rhode Island and marks a prominent recessional ice margin. The moraine is correlative with the Roanoke Point Moraine of the Connecticut Lobe of northeastern Long Island. Pollen stratigraphy of >13,180 ka bog sediments begins early in the spruce (A) pollen zone with evidence of a cold, late-glacial climate. The pine (B) pollen zone, beginning prior to 11,145 ka, and the oak (C) pollen zone, dating from about 9,000 ka with hickory and hemlock subzones, are well represented. However, after about 2,000 ka, the stratigraphic record in the bog sections is missing in most cases due to peat harvesting. Pollen spectra from several archeological sites fall within the late oak pollen zone, well within the land clearing interval with evidence of hardwood forests and locally holly and cedar. Evidence of cultigens in the pollen record is sparse. Marine deposits over fresh water bog and proglacial lake sediments show that some coastal bogs were drowned by sea level rise.

  7. Negligible glacial-interglacial variation in continental chemical weathering rates.

    PubMed

    Foster, Gavin L; Vance, Derek

    2006-12-14

    Chemical weathering of the continents is central to the regulation of atmospheric carbon dioxide concentrations, and hence global climate. On million-year timescales silicate weathering leads to the draw-down of carbon dioxide, and on millennial timescales chemical weathering affects the calcium carbonate saturation state of the oceans and hence their uptake of carbon dioxide. However, variations in chemical weathering rates over glacial-interglacial cycles remain uncertain. During glacial periods, cold and dry conditions reduce the rate of chemical weathering, but intense physical weathering and the exposure of carbonates on continental shelves due to low sea levels may increase this rate. Here we present high-resolution records of the lead isotope composition of ferromanganese crusts from the North Atlantic Ocean that cover the past 550,000 years. Combining these records with a simple quantitative model of changes in the lead isotope composition of the deep North Atlantic Ocean in response to chemical weathering, we find that chemical weathering rates were two to three times lower in the glaciated interior of the North Atlantic Region during glacial periods than during the intervening interglacial periods. This decrease roughly balances the increase in chemical weathering caused by the exposure of continental shelves, indicating that chemical weathering rates remained relatively constant on glacial-interglacial timescales. On timescales of more than a million years, however, we suggest that enhanced weathering of silicate glacial sediments during interglacial periods results in a net draw-down of atmospheric carbon dioxide, creating a positive feedback on global climate that, once initiated, promotes cooling and further glaciation.

  8. Tree-bank grammars

    SciTech Connect

    Charniak, E.

    1996-12-31

    By a {open_quotes}tree-bank grammar{close_quotes} we mean a context-free grammar created by reading the production rules directly from hand-parsed sentences in a tree bank. Common wisdom has it that such grammars do not perform well, though we know of no published data on the issue. The primary purpose of this paper is to show that the common wisdom is wrong. In particular, we present results on a tree-bank grammar based on the Penn Wall Street Journal tree bank. To the best of our knowledge, this grammar outperforms all other non-word-based statistical parsers/grammars on this corpus. That is, it outperforms parsers that consider the input as a string of tags and ignore the actual words of the corpus.

  9. Leonardo's Tree Theory.

    ERIC Educational Resources Information Center

    Werner, Suzanne K.

    2003-01-01

    Describes a series of activities exploring Leonardo da Vinci's tree theory that are designed to strengthen 8th grade students' data collection and problem solving skills in physical science classes. (KHR)

  10. Tea tree oil.

    PubMed

    Larson, David; Jacob, Sharon E

    2012-01-01

    Tea tree oil is an increasingly popular ingredient in a variety of household and cosmetic products, including shampoos, massage oils, skin and nail creams, and laundry detergents. Known for its potential antiseptic properties, it has been shown to be active against a variety of bacteria, fungi, viruses, and mites. The oil is extracted from the leaves of the tea tree via steam distillation. This essential oil possesses a sharp camphoraceous odor followed by a menthol-like cooling sensation. Most commonly an ingredient in topical products, it is used at a concentration of 5% to 10%. Even at this concentration, it has been reported to induce contact sensitization and allergic contact dermatitis reactions. In 1999, tea tree oil was added to the North American Contact Dermatitis Group screening panel. The latest prevalence rates suggest that 1.4% of patients referred for patch testing had a positive reaction to tea tree oil.

  11. Generalized constructive tree weights

    SciTech Connect

    Rivasseau, Vincent E-mail: adrian.tanasa@ens-lyon.org; Tanasa, Adrian E-mail: adrian.tanasa@ens-lyon.org

    2014-04-15

    The Loop Vertex Expansion (LVE) is a quantum field theory (QFT) method which explicitly computes the Borel sum of Feynman perturbation series. This LVE relies in a crucial way on symmetric tree weights which define a measure on the set of spanning trees of any connected graph. In this paper we generalize this method by defining new tree weights. They depend on the choice of a partition of a set of vertices of the graph, and when the partition is non-trivial, they are no longer symmetric under permutation of vertices. Nevertheless we prove they have the required positivity property to lead to a convergent LVE; in fact we formulate this positivity property precisely for the first time. Our generalized tree weights are inspired by the Brydges-Battle-Federbush work on cluster expansions and could be particularly suited to the computation of connected functions in QFT. Several concrete examples are explicitly given.

  12. Glacial vicariance in Eurasia: mitochondrial DNA evidence from Scots pine for a complex heritage involving genetically distinct refugia at mid-northern latitudes and in Asia Minor

    PubMed Central

    Naydenov, Krassimir; Senneville, Sauphie; Beaulieu, Jean; Tremblay, Francine; Bousquet, Jean

    2007-01-01

    Background At the last glacial maximum, Fennoscandia was covered by an ice sheet while the tundra occupied most of the rest of northern Eurasia. More or less disjunct refugial populations of plants were dispersed in southern Europe, often trapped between mountain ranges and seas. Genetic and paleobotanical evidences indicate that these populations have contributed much to Holocene recolonization of more northern latitudes. Less supportive evidence has been found for the existence of glacial populations located closer to the ice margin. Scots pine (Pinus sylvestris L.) is a nordic conifer with a wide natural range covering much of Eurasia. Fractures in its extant genetic structure might be indicative of glacial vicariance and how different refugia contributed to the current distribution at the continental level. The population structure of Scots pine was investigated on much of its Eurasian natural range using maternally inherited mitochondrial DNA polymorphisms. Results A novel polymorphic region of the Scots pine mitochondrial genome has been identified, the intron 1 of nad7, with three variants caused by insertions-deletions. From 986 trees distributed among 54 populations, four distinct multi-locus mitochondrial haplotypes (mitotypes) were detected based on the three nad7 intron 1 haplotypes and two previously reported size variants for nad1 intron B/C. Population differentiation was high (GST = 0.657) and the distribution of the mitotypes was geographically highly structured, suggesting at least four genetically distinct ancestral lineages. A cosmopolitan lineage was widely distributed in much of Europe throughout eastern Asia. A previously reported lineage limited to the Iberian Peninsula was confirmed. A new geographically restricted lineage was found confined to Asia Minor. A new lineage was restricted to more northern latitudes in northeastern Europe and the Baltic region. Conclusion The contribution of the various ancestral lineages to the current

  13. Thriving in the Cold: Glacial Expansion and Post-Glacial Contraction of a Temperate Terrestrial Salamander (Plethodon serratus)

    PubMed Central

    Newman, Catherine E.; Austin, Christopher C.

    2015-01-01

    The dynamic geologic history of the southeastern United States has played a major role in shaping the geographic distributions of amphibians in the region. In the phylogeographic literature, the predominant pattern of distribution shifts through time of temperate species is one of contraction during glacial maxima and persistence in refugia. However, the diverse biology and ecology of amphibian species suggest that a “one-size-fits-all” model may be inappropriate. Nearly 10% of amphibian species in the region have a current distribution comprised of multiple disjunct, restricted areas that resemble the shape of Pleistocene refugia identified for other temperate taxa in the literature. Here, we apply genetics and spatially explicit climate analyses to test the hypothesis that the disjunct regions of these species ranges are climatic refugia for species that were more broadly distributed during glacial maxima. We use the salamander Plethodon serratus as a model, as its range consists of four disjunct regions in the Southeast. Phylogenetic results show that P. serratus is comprised of multiple genetic lineages, and the four regions are not reciprocally monophyletic. The Appalachian salamanders form a clade sister to all other P. serratus. Niche and paleodistribution modeling results suggest that P. serratus expanded from the Appalachians during the cooler Last Glacial Maximum and has since been restricted to its current disjunct distribution by a warming climate. These data reject the universal applicability of the glacial contraction model to temperate taxa and reiterate the importance of considering the natural history of individual species. PMID:26132077

  14. Thriving in the Cold: Glacial Expansion and Post-Glacial Contraction of a Temperate Terrestrial Salamander (Plethodon serratus).

    PubMed

    Newman, Catherine E; Austin, Christopher C

    2015-01-01

    The dynamic geologic history of the southeastern United States has played a major role in shaping the geographic distributions of amphibians in the region. In the phylogeographic literature, the predominant pattern of distribution shifts through time of temperate species is one of contraction during glacial maxima and persistence in refugia. However, the diverse biology and ecology of amphibian species suggest that a "one-size-fits-all" model may be inappropriate. Nearly 10% of amphibian species in the region have a current distribution comprised of multiple disjunct, restricted areas that resemble the shape of Pleistocene refugia identified for other temperate taxa in the literature. Here, we apply genetics and spatially explicit climate analyses to test the hypothesis that the disjunct regions of these species ranges are climatic refugia for species that were more broadly distributed during glacial maxima. We use the salamander Plethodon serratus as a model, as its range consists of four disjunct regions in the Southeast. Phylogenetic results show that P. serratus is comprised of multiple genetic lineages, and the four regions are not reciprocally monophyletic. The Appalachian salamanders form a clade sister to all other P. serratus. Niche and paleodistribution modeling results suggest that P. serratus expanded from the Appalachians during the cooler Last Glacial Maximum and has since been restricted to its current disjunct distribution by a warming climate. These data reject the universal applicability of the glacial contraction model to temperate taxa and reiterate the importance of considering the natural history of individual species.

  15. Tree Topology Estimation

    PubMed Central

    Estrada, Rolando; Tomasi, Carlo; Schmidler, Scott C.; Farsiu, Sina

    2015-01-01

    Tree-like structures are fundamental in nature, and it is often useful to reconstruct the topology of a tree—what connects to what—from a two-dimensional image of it. However, the projected branches often cross in the image: the tree projects to a planar graph, and the inverse problem of reconstructing the topology of the tree from that of the graph is ill-posed. We regularize this problem with a generative, parametric tree-growth model. Under this model, reconstruction is possible in linear time if one knows the direction of each edge in the graph—which edge endpoint is closer to the root of the tree—but becomes NP-hard if the directions are not known. For the latter case, we present a heuristic search algorithm to estimate the most likely topology of a rooted, three-dimensional tree from a single two-dimensional image. Experimental results on retinal vessel, plant root, and synthetic tree datasets show that our methodology is both accurate and efficient. PMID:26353004

  16. Stem compression reversibly reduces phloem transport in Pinus sylvestris trees.

    PubMed

    Henriksson, Nils; Tarvainen, Lasse; Lim, Hyungwoo; Tor-Ngern, Pantana; Palmroth, Sari; Oren, Ram; Marshall, John; Näsholm, Torgny

    2015-10-01

    Manipulating tree belowground carbon (C) transport enables investigation of the ecological and physiological roles of tree roots and their associated mycorrhizal fungi, as well as a range of other soil organisms and processes. Girdling remains the most reliable method for manipulating this flux and it has been used in numerous studies. However, girdling is destructive and irreversible. Belowground C transport is mediated by phloem tissue, pressurized through the high osmotic potential resulting from its high content of soluble sugars. We speculated that phloem transport may be reversibly blocked through the application of an external pressure on tree stems. Thus, we here introduce a technique based on compression of the phloem, which interrupts belowground flow of assimilates, but allows trees to recover when the external pressure is removed. Metal clamps were wrapped around the stems and tightened to achieve a pressure theoretically sufficient to collapse the phloem tissue, thereby aiming to block transport. The compression's performance was tested in two field experiments: a (13)C canopy labelling study conducted on small Scots pine (Pinus sylvestris L.) trees [2-3 m tall, 3-7 cm diameter at breast height (DBH)] and a larger study involving mature pines (∼15 m tall, 15-25 cm DBH) where stem respiration, phloem and root carbohydrate contents, and soil CO2 efflux were measured. The compression's effectiveness was demonstrated by the successful blockage of (13)C transport. Stem compression doubled stem respiration above treatment, reduced soil CO2 efflux by 34% and reduced phloem sucrose content by 50% compared with control trees. Stem respiration and soil CO2 efflux returned to normal within 3 weeks after pressure release, and (13)C labelling revealed recovery of phloem function the following year. Thus, we show that belowground phloem C transport can be reduced by compression, and we also demonstrate that trees recover after treatment, resuming C

  17. Anatomy of the Pythagoras' Tree

    ERIC Educational Resources Information Center

    Teia, Luis

    2016-01-01

    The architecture of nature can be seen at play in a tree: no two are alike. The Pythagoras' tree behaves just as a "tree" in that the root plus the same movement repeated over and over again grows from a seed, to a plant, to a tree. In human life, this movement is termed cell division. With triples, this movement is a geometrical and…

  18. How Trees Can Save Energy.

    ERIC Educational Resources Information Center

    Fazio, James R., Ed.

    1991-01-01

    This document might easily have been called "How To Use Trees To Save Energy". It presents the energy saving advantages of landscaping the home and community with trees. The discussion includes: (1) landscaping advice to obtain the benefits of tree shade; (2) the heat island phenomenon in cities; (3) how and where to properly plant trees for…

  19. State Trees and Arbor Days.

    ERIC Educational Resources Information Center

    Forest Service (USDA), Washington, DC.

    Provides information on state trees for each of the 50 states and the District of Columbia. Includes for each state: (1) year in which state tree was chosen; (2) common and scientific names of the tree; (3) arbor day observance; (4) address of state forester; and (5) drawings of the tree, leaf, and fruit or cone. (JN)

  20. New method for assessing the susceptibility of glacial lakes to outburst floods in the Cordillera Blanca, Peru

    NASA Astrophysics Data System (ADS)

    Emmer, A.; Vilímek, V.

    2014-09-01

    This paper presents a new and easily repeatable method for assessing the susceptibility of glacial lakes to outburst floods (GLOFs) within the Peruvian region of the Cordillera Blanca. The presented method was designed to: (a) be repeatable (from the point of view of the demands on input data), (b) be reproducible (to provide an instructive guide for different assessors), (c) provide multiple results for different GLOF scenarios and (d) be regionally focused on the lakes of the Cordillera Blanca. Based on the input data gained from remotely sensed images and digital terrain models/topographical maps, the susceptibility of glacial lakes to outburst floods is assessed using a combination of decision trees for clarity and numerical calculation for repeatability and reproducibility. A total of seventeen assessed characteristics are used, of which seven have not been used in this context before. Also, several ratios and calculations are defined for the first time. We assume that it is not relevant to represent the overall susceptibility of a particular lake to outburst floods by one result (number), thus it is described in the presented method by five separate results (representing five different GLOF scenarios). These are potentials for (a) dam overtopping resulting from a fast slope movement into the lake, (b) dam overtopping following the flood wave originating in a lake situated upstream, (c) dam failure resulting from a fast slope movement into the lake, (d) dam failure following the flood wave originating in a lake situated upstream and (e) dam failure following a strong earthquake. All of these potentials include two or three components and theoretically range from 0 to 1. The presented method was verified on the basis of assessing the pre-flood conditions of seven lakes which have produced ten glacial lake outburst floods in the past and ten lakes which have not. A comparison of these results showed that the presented method successfully identified lakes

  1. Recovering Bi and Sb from electrolyte in copper electrorefining

    NASA Astrophysics Data System (ADS)

    Ando, K.; Tsuchida, N.

    1997-12-01

    The separation of antimony and bismuth in copper electrorefining is somewhat difficult and costly. An ion-exchange technique for the removal of the metals from the electrolyte has been practiced recently, although the metals recovered require further processing. Sumitomo Metal Mining has developed a process to recover antimony and bismuth directly from the eluant by an electrowinning process using a mixture of sulfuric acid and sodium chloride as an eluant for the desorption from the resin. The content of bismuth in the antimony metal recovered by this process was less than 0.2%, while the content of antimony in the bismuth metal was less than 0.4%.

  2. Proportion of recovered goose and brant bands that are reported

    USGS Publications Warehouse

    Martinson, R.K.; McCann, J.A.

    1966-01-01

    A few more than one-third of the goose and brant bands recovered by hunters were reported to the Bird Banding Laboratory (a rate of 0.361) during the 1962-64 hunting seasons. We calculated this band-reporting rate by comparing the estimated number of goose and brant bands recovered by hunters, based on a mail questionnaire survey, with the number of bands actually reported to the Bird Banding Laboratory. This band-reporting rate is probably representative only of the 1962-65 period. It is likely that, in earlier years, a greater proportion (perhaps about 0.60) of recovered goose and brant bands were reported.

  3. A first 10Be cosmogenic glacial chronology from the High Atlas, Morocco, during the last glacial cycle.

    NASA Astrophysics Data System (ADS)

    Fink, David; Hughes, Philip; Fenton, Cassie

    2014-05-01

    Glacial geomorphological mapping, 10Be cosmogenic exposure ages of 21 erratics from cirque-valley systems and paleo-glacier climate modelling in the High Atlas Mountains, Morocco (31.1° N, 7.9° W), provides new and novel insights as to the history and evolution of the largest desert region on Earth. The Atlas Mountains display evidence of extensive and multiple Late Pleistocene glaciations whose extent is significantly larger than that recognised by previous workers. The largest glaciers formed in the Toubkal massif where we find 3 distinct phases of glacial advances within the last glacial cycle. The oldest moraines occurring at the lowest elevations have yielded eight 10Be ages ranging from 30 to 88 ka. Six of eight samples from moraines at intermediate elevations gave ages of 19 to 25 ka (2 outliers) which correlates well with the global Last Glacial Maximum (ca. 26-21 ka) and the last termination during marine isotope stage 2. Five erratics from the youngest and most elevated moraines yielded a suite of normally distributed exposure ages from 11 to 13 ka which supports a correlation with the northern hemisphere Younger Dryas (12.9-11.7 ka). The glacial record of the High Atlas effectively reflects moisture supply to the north-western Sahara Desert and can provide an indication of shifts between arid and pluvial conditions. The plaeo equilibrium line altitudes (ELA) of these three glacier phases was more than 1000 m lower than the predicted ELA based on today's temperatures. Glacier-climate modelling indicates that for each of these glacier phases climate was not only significantly cooler than today, but also much wetter. The new evidence on the extent, timing and palaeoclimatic significance of glaciations in this region has major implications for understanding moisture transfer between the North Atlantic Ocean and the Sahara Desert during Pleistocene cold stages.

  4. Quaternary glacial and post-glacial depositional history associated with the Green Bay lobe, east-central Wisconsin

    SciTech Connect

    Thieme, L.D.; Smith, G.L. . Dept. of Geology)

    1993-03-01

    Multiple layers of peat and wood fragments indicate that Quaternary glaciation of the east-central region of Wisconsin was punctuated by at least two interglacial periods. Till, outwash, and glaciolacustrine deposits suggest that deposition took place in alternating glacial and non-glacial environments due to oscillations in the position of the Green Bay Lobe terminus. The data for this study consists of 36 auger borings, 70 geologic logs and 100 well-construction reports from water wells. Nine vibracores were taken at the northern margin of Lake Winnebago in order to document in detail the post-glacial history of Glacial Lake Oshkosh/Lake Winnebago. Local bedrock consists of limestones and dolomites of the Middle Ordovician Sinnipee Group. Bedrock elevations range from 211--237 m; bedding dips regionally to the southeast at 1--2 degrees. Bedrock is overlain by a 3--13 m-thick layer of alternating red clay and gray silty-clay (basal Kewaunee Formation ) perhaps deposited in a proglacial lake. These sediments are overlain by apeat/wood layer indicating marsh deposition. This peat/wood layer is overlain by more proglacial lake sediment, 3--10 m of gray brown clay to silty-clay. A second peat/wood layer overlies the gray/brown sediment and may correlate with the Two Creeks buried forest bed. The uppermost unit consists of 2--3 m red silty-clay till (Middle Inlet Member of the Kewaunee Formation). Along the northern margin of present-day Lake Winnebago, red silty-clay is overlain by silty-sand deposited by Glacial Lake Oshkosh. Future work includes obtaining radiocarbon dates from buried peat/wood layers to verify these tentative correlations between east-central Wisconsin and the Lake Michigan Basin.

  5. Genetic Signals of Demographic Expansion in Downy Woodpecker (Picoides pubescens) after the Last North American Glacial Maximum

    PubMed Central

    Pulgarín-R, Paulo C.; Burg, Theresa M.

    2012-01-01

    The glacial cycles of the Pleistocene have been recognized as important, large-scale historical processes that strongly influenced the demographic patterns and genetic structure of many species. Here we present evidence of a postglacial expansion for the Downy Woodpecker (Picoides pubescens), a common member of the forest bird communities in North America with a continental distribution. DNA sequences from the mitochondrial tRNA-Lys, and ATPase 6 and 8 genes, and microsatellite data from seven variable loci were combined with a species distribution model (SDM) to infer possible historical scenarios for this species after the last glacial maximum. Analyses of Downy Woodpeckers from 23 geographic areas suggested little differentiation, shallow genealogical relationships, and limited population structure across the species’ range. Microsatellites, which have higher resolution and are able to detect recent differences, revealed two geographic groups where populations along the eastern edge of the Rocky Mountains (Montana, Utah, Colorado, and southern Alberta) were genetically isolated from the rest of the sampled populations. Mitochondrial DNA, an important marker to detect historical patterns, recovered only one group. However, populations in Idaho and southeast BC contained high haplotype diversity and, in general were characterized by the absence of the most common mtDNA haplotype. The SDM suggested several areas in the southern US as containing suitable Downy Woodpecker habitat during the LGM. The lack of considerable geographic structure and the starburst haplotype network, combined with several population genetic tests, suggest a scenario of demographic expansion during the last part of Pleistocene and early Holocene. PMID:22792306

  6. Saharan Wind Regimes Traced by the Sr-Nd Isotopic Composition of Subtropical Atlantic Sediments: Last Glacial Maximum vs Today

    NASA Astrophysics Data System (ADS)

    Grousset, F. E.; Parra, M.; Bory, A.; Martinez, P.; Bertrand, P.; Shimmield, G.; Ellam, R. M.

    New Nd-Sr isotopic data on the <30 μm lithic particles of surface and Last Glacial Maximum sediments recovered along the African margin between the Equator and the Gibraltar Strait are presented in combination with grain-size measurements. This <30 μm size fraction allows us to eliminate any hemipelagic contribution that could occur in the coarser fractions. In the eolian fraction, both Sr and Nd isotopic tracers reveal the same major northwestern origin (Mauritania, Mali, southern Algeria and Morocco). The Archaean formations of the western Saharan shield could be the source of the very unradiogenic ratios observed here. The more southern regions (Senegal, Guinea) act only as secondary sources. A similar pattern is observed for the LGM. Lithic particles are mostly transported by both Trade and Saharan Air Layer (SAL) winds, along an approximate NE-SW axis; this main feature matches the 'southern plume', characterizing the dust transport observed during winter. No significant latitudinal shift of the belt winds is observed between the LGM and today. At the LGM, however, dust fluxes were 2-4 times higher than today, leading to a more 'Archaean-type' imprint in the deposits. We do not observe any clear relationship between the latitudinal variability of the upwelling systems identified in this region at the LGM and the location of the major wind systems. Both enhanced aridity on the continent and increased wind speed probably occurred together over western tropical Africa during the Last Glacial period.

  7. Genetic signals of demographic expansion in Downy Woodpecker (Picoides pubescens) after the last North American glacial maximum.

    PubMed

    Pulgarín-R, Paulo C; Burg, Theresa M

    2012-01-01

    The glacial cycles of the Pleistocene have been recognized as important, large-scale historical processes that strongly influenced the demographic patterns and genetic structure of many species. Here we present evidence of a postglacial expansion for the Downy Woodpecker (Picoides pubescens), a common member of the forest bird communities in North America with a continental distribution. DNA sequences from the mitochondrial tRNA-Lys, and ATPase 6 and 8 genes, and microsatellite data from seven variable loci were combined with a species distribution model (SDM) to infer possible historical scenarios for this species after the last glacial maximum. Analyses of Downy Woodpeckers from 23 geographic areas suggested little differentiation, shallow genealogical relationships, and limited population structure across the species' range. Microsatellites, which have higher resolution and are able to detect recent differences, revealed two geographic groups where populations along the eastern edge of the Rocky Mountains (Montana, Utah, Colorado, and southern Alberta) were genetically isolated from the rest of the sampled populations. Mitochondrial DNA, an important marker to detect historical patterns, recovered only one group. However, populations in Idaho and southeast BC contained high haplotype diversity and, in general were characterized by the absence of the most common mtDNA haplotype. The SDM suggested several areas in the southern US as containing suitable Downy Woodpecker habitat during the LGM. The lack of considerable geographic structure and the starburst haplotype network, combined with several population genetic tests, suggest a scenario of demographic expansion during the last part of Pleistocene and early Holocene.

  8. Simulation and understanding the nature of Quaternary glacial cycles

    NASA Astrophysics Data System (ADS)

    Ganopolski, A.; Calov, R.

    2012-04-01

    Although it is generally accepted that, as postulated by the Milankovitch theory, Earth's orbital variations play an important role in Quaternary climate dynamics, the mechanism of glacial cycles still remains poorly understood. Among remaining scientific challenges are an understanding of the nature of 100 kyr cycles that dominated global ice volume and climate variability over the late part of Quaternary and the causes of the transition from the "40 kyr world" to the "100 kyr world" around one million years ago. Using the Earth system model of intermediate complexity CLIMBER-2, we demonstrate that both strong 100 kyr periodicity in the ice volume variations and the timing of glacial terminations during past 800 kyr can be successfully simulated as direct, strong nonlinear responses of the climate-cryosphere system to orbital forcing alone. We show that the sharp 100 kyr peak in the power spectrum of ice volume results from the phase locking of the long glacial cycles to the corresponding eccentricity cycles. Variations in obliquity and CO2 concentration are not required to simulate strong 100 kyr cyclicity if the atmospheric CO2 concentration stays below its typical interglacial value. The existence of long glacial cycles is primarily attributed to the North American ice sheet and it requires the presence of a large continental area with exposed rocks. In case when the continents are completely covered by a thick sediment layer, for the realistic range of CO2 concentrations (180-300 ppm), the long glacial cycles can not be simulated. In the experiment with fixed CO2 concentration, ice volume variations contain both strong precessional and obliquity cycles, which apparently is in odd with empirical data that suggest complete dominance of the obliquity cycle. However, in the experiments with interactive carbon cycle, simulated obliquity component becomes much stronger, especially, in the deep ocean temperature. This is explained by the direct and indirect (via the

  9. The Glacial BuzzSaw, Isostasy, and Global Crustal Models

    NASA Astrophysics Data System (ADS)

    Levander, A.; Oncken, O.; Niu, F.

    2015-12-01

    The glacial buzzsaw hypothesis predicts that maximum elevations in orogens at high latitudes are depressed relative to temperate latitudes, as maximum elevation and hypsography of glaciated orogens are functions of the glacial equilibrium line altitude (ELA) and the modern and last glacial maximum (LGM) snowlines. As a consequence crustal thickness, density, or both must change with increasing latitude to maintain isostatic balance. For Airy compensation crustal thickness should decrease toward polar latitudes, whereas for Pratt compensation crustal densities should increase. For similar convergence rates, higher latitude orogens should have higher grade, and presumably higher density rocks in the crustal column due to more efficient glacial erosion. We have examined a number of global and regional crustal models to see if these predictions appear in the models. Crustal thickness is straightforward to examine, crustal density less so. The different crustal models generally agree with one another, but do show some major differences. We used a standard tectonic classification scheme of the crust for data selection. The globally averaged orogens show crustal thicknesses that decrease toward high latitudes, almost reflecting topography, in both the individual crustal models and the models averaged together. The most convincing is the western hemisphere cordillera, where elevations and crustal thicknesses decrease toward the poles, and also toward lower latitudes (the equatorial minimum is at ~12oN). The elevation differences and Airy prediction of crustal thickness changes are in reasonable agreement in the North American Cordillera, but in South America the observed crustal thickness change is larger than the Airy prediction. The Alpine-Himalayan chain shows similar trends, however the strike of the chain makes interpretation ambiguous. We also examined cratons with ice sheets during the last glacial period to see if continental glaciation also thins the crust toward

  10. Glacially induced stresses in sedimentary rocks of northern Poland

    NASA Astrophysics Data System (ADS)

    Trzeciak, Maciej; Dąbrowski, Marcin

    2016-04-01

    During the Pleistocene large continental ice sheets developed in Scandinavia and North America. Ice-loading caused bending of the lithosphere and outward flow in the mantle. Glacial loading is one of the most prominent tectono-mechanical event in the geological history of northern Poland. The Pomeranian region was subjected several times to a load equivalent of more than 1 km of rocks, which led to severe increase in both vertical and horizontal stresses in the upper crustal rocks. During deglaciation a rapid decrease in vertical stress is observed, which leads to destabilization of the crust - most recent postglacial faults scarps in northern Sweden indicate glacially induced earthquakes of magnitude ~Mw8. The presence of the ice-sheet altered as well the near-surface thermal structure - thermal gradient inversion is still observable in NW Poland. The glacially related processes might have left an important mark in the sedimentary cover of northern Poland, especially with regard to fracture reopening, changes in stress state, and damage development. In the present study, we model lithospheric bending caused by glacial load, but our point of interest lies in the overlying sediments. Typical glacial isostatic studies model the response of (visco-) elastic lithosphere over viscoelastic or viscous asthenosphere subjected to external loads. In our model, we introduce viscoelastic sedimentary layers at the top of this stack and examine the stress relaxation patterns therein. As a case study for our modelling, we used geological profiles from northern Poland, near locality of Wejherowo, which are considered to have unconventional gas potential. The Paleozoic profile of this area is dominated by almost 1 km thick Silurian-Ordovician shale deposits, which are interbedded with thin and strong limestone layers. This sequence is underlain by Cambrian shales and sandstones, and finally at ~3 km depth - Precambrian crystalline rocks. Above the Silurian there are approximately

  11. Pleistocene glacial evolution of Fuentes Carrionas (Cantabrian Range, NW Spain)

    NASA Astrophysics Data System (ADS)

    Pellitero, Ramon

    2014-05-01

    Fuentes Carrionas is a massif situated at the N of Spain, between Castilla y Leon and Cantabria regions. It is the second highest mountain massif of the Cantabrian Range after Picos de Europa, with peaks over 2500 m.a.s.l. and valleys well over 1000 m.a.s.l. Fuentes Carrionas was glaciated during Quaternary, and even during the Holocene and as far as Little Ice Age the presence of glaciers, or at least permafrost is controversial. Results from glacial geomorphology analysis of Fuentes Carrionas Massif are presented. Based on the interpretation of glacial landforms, glacial evolution since the Last Glacial Maximum until Pleistocene deglaciation is described. Four different glacial equilibrium phases are identified, the last one divided into two pulsations. Deglaciation process took place between 36 ka BP and 11 ka BP. Local Last Glacial Maximum is dated back to 36-38 ka. BP, therefore earlier than LGM. Glaciers reached 15 km. long and occupied valleys down to 1250 m.a.s.l. during this phase. By European LGM (20-18 ka.BP) glaciers had substantially retreated to fronts about 1700 m.a.s.l. A final stage with two marked pulsations shows only small glaciers located at cirques above 2000 m.a.s.l. and, finally, only small cirque glaciers at North and Northeast orientation above 2200 m.a.s.l. Both these phases have been correlated to Oldest and Younger Dryas, although no dates have been done yet. A palaeoenvironmental reconstruction is proposed, based on ELA (Equilibrium Line Altitude) rise. ELA has been calculated with the AAR method and 0.67 ratio. This reconstruction shows that temperatures ranged between 9°C and 10°C lower than present ones at the end of Pleistocene, depending on a precipitations variation between 30% higher and 20% lower than current ones. Further research will focus on these retreat phases, especially on Younger Dryas identification and reconstruction for this site and the rest of Cantabrian Range.

  12. Microbial Succession in Glacial Foreland Soils of the Canadian Subarctic

    NASA Astrophysics Data System (ADS)

    Kazemi, S.; Lanoil, B. D.

    2014-12-01

    The Canadian arctic has experienced increasing temperatures over the past century leading to heightened rate of glacial retreat. Glacial retreat leads to subsequent exposure of foreland soils to atmospheric conditions, thus creating a sequence of change in these ecosystems. Microbes are critical for soil development and nutrient dynamics in glacial systems as they are the primary colonizers of these soils and have been demonstrated to play a role in geochemical weathering and nutrient cycling beneath the glacier. Although viable microbial communities exist beneath glaciers and are known to be important for the glacial ecosystem, the impact of glacial retreat on these communities and development of the resulting foreland ecosystem is not well understood. Here, we investigate how microbial communities respond to changing conditions brought on by glacial retreat and whether a pattern of succession, such as those found in well characterized plant systems, occurs along a soil foreland in these microbial communities. We hypothesis that time since deglaciation is the major determinant of structure and composition of microbial assemblages. To test this, soil samples were collected along two glacier forelands, Trapridge Glacier and Duke River Glacier, located in Kluane National Park, Yukon Territory. Chronosequence dating of satellite images using geographic information system software revealed sampling sites have been ice-free from ~30 years to over 60 years. Soil chemistry analysis of major nutrients revealed no change in chemical parameters along the chronosequence, suggesting that presence of microbes after exposure from subglacial environments does not significantly alter soil characteristics in the timeframe observed. Furthermore, next-generation IonTorrentTM sequencing performed on soil samples revealed over five million sequencing reads, suggesting prominent microbial presence within these soils. Further analysis on sequencing data is needed to establish the

  13. Early Brain Stimulation May Help Stroke Survivors Recover Language Function

    MedlinePlus

    ... Making News on Heart.org Learn More Early brain stimulation may help stroke survivors recover language function ... org and strokeassociation.org Related Images Infographic - Thiel-Brain Stimulation copyright American Heart Association Download (311.8 ...

  14. 48 CFR 52.223-4 - Recovered Material Certification.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 1976 (42 U.S.C. 6962(c)(3)(A)(i)), the offeror certifies, by signing this offer, that the percentage of....223-4 Recovered Material Certification. As prescribed in 23.406(c), insert the following...

  15. 48 CFR 52.223-4 - Recovered Material Certification.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 1976 (42 U.S.C. 6962(c)(3)(A)(i)), the offeror certifies, by signing this offer, that the percentage of....223-4 Recovered Material Certification. As prescribed in 23.406(c), insert the following...

  16. Improving CO2 Efficiency for Recovering Oil in Heterogeneous Reservoirs

    SciTech Connect

    Grigg, Reid B.; Svec, Robert K.

    2003-03-10

    The work strived to improve industry understanding of CO2 flooding mechanisms with the ultimate goal of economically recovering more of the U.S. oil reserves. The principle interests are in the related fields of mobility control and injectivity.

  17. Why Some Kids Take Longer to Recover from Brain Injury

    MedlinePlus

    ... Why Some Kids Take Longer to Recover From Brain Injury Scans reveal white-matter decline after some ... 15, 2017 WEDNESDAY, March 15, 2017 (HealthDay News) -- Brain scans may reveal which children will take longer ...

  18. Analysis of ``soft`` recovered shaped charge jet particles

    SciTech Connect

    Lassila, D.H.; Nikkel, D.J. Jr.; Kershaw, R.P.; Walters, W.P.

    1996-04-01

    A shaped charge with an 81 mm diameter, 42{degree} apex angle oxygen-free high-conductivity (OFHC) copper conical liner was fired into a ``soft`` recovery bunker to allow metallurgical examination of recovered jet particles and the slug. The initial weight of the copper liner was 245 g, of which 184 g was recovered. The number of jet particles recovered was 37 (approximately 63% of the particles formed by the charge). Extensive metallurgical analyses were performed on the recovered slug and jet particles. The microstructural features associated with voids, e.g., dendritic grain growth, clearly indicate that the regions in the vicinity of the centerline of the slug and jet particles were melted. In this work the authors present calculations of jet temperature as a function of constitutive behavior. In order to predict melt in the center region of the jet they find it necessary to scale flow stress with a pressure dependent shear modulus.

  19. Glacial landscape evolution on Hall Peninsula, Baffin Island, since the Last Glacial Maximum: insights into switching glacial dynamics and thermo-mechanical conditions

    NASA Astrophysics Data System (ADS)

    Johnson, C. L.; Ross, M.

    2012-12-01

    Ice cover in north central Hall Peninsula, Baffin Island has evolved from full Laurentide Ice Sheet (LIS) cover during the Last Glacial Maximum (LGM) to a thin ice cap that now covers about 800 km2 in the northeast sector. The exposed subglacial landscape consists of contrasting geomorphological zones which allude to complex spatial and temporal changes in basal ice dynamics and thermal regime since LGM. We used satellite imagery, field observations, a large till geochemical database, and terrestrial cosmogenic isotopes to get new insights into subglacial erosion intensity, ice flow dynamics, and glacial history. Fields of streamlined bedrock-cored ridges (e.g. drumlins) have been mapped and their elongation ratios calculated. The density of bedrock-controlled lakes, which has traditionally been used as a proxy for subglacial erosion intensity on Baffin Island, has been re-examined using modern GIS techniques. This work has revealed a mosaic of glacial terrain zones each consisting of characteristics that are distinct from the other zones. Five glacial terrain zones (GTZ) have been recognized. One zone (GTZ 1) is characterized by a broad flowset of northeast trending streamlined hills and parallel paleo-flow indicators. It also has the highest streamlined hill density, longest elongation ratios, and the highest lake density of the study area. This northeast flowset is crosscut locally by ice flow indicators that converge into troughs that now form a series of fjords. Landforms and ice flow indicators of this younger system (GTZ 2) are traced inland showing propagation of the channelized system into this portion of the LIS. The central area of the peninsula contains a zone of thicker till and rolling topography (GTZ 3) as well as a zone consisting of southeast trending features and associated perpendicular moraines (GTZ 4). The modern ice cap and its past extension form the last zone (GTZ 5). The preservation of the northeast system (GTZ 1) outside of the

  20. On the gravity and geoid effects of glacial isostatic adjustment in Fennoscandia - a short note

    NASA Astrophysics Data System (ADS)

    Sjöberg, L. E.

    2016-02-01

    Many geoscientists argue that there is a gravity low of 10-30 mGal in Fennoscandia as a remaining fingerprint of the last ice age and load, both vanished about 10 kyr ago. However, the extraction of the gravity signal related with Glacial Isostatic Adjustment (GIA) is complicated by the fact that the total gravity field is caused by many significant density distributions in the Earth. Here we recall a methodology originating with A. Bjerhammar 35 years ago, that emphasizes that the present land uplift phenomenon mainly occurs in the region thatwas covered by the ice cap, and it is highly correlated with the spectral window of degrees 10-22 of the global gravity field, whose lower limit fairly well corresponds to the wavelength that agrees with the size of the region. This implies that, although in principle the GIA is a global phenomenon, the geoid and gravity lows as well as the land upheaval in Fennoscandia are typically regional phenomena that cannot be seen in a global correlation study as it is blurred by many irrelevant gravity signals. It is suggested that a regional multi-regression analysis with a band-limited spectral gravity signal as the observable, a method tested already 2 decades ago, can absorb possible significant disturbing signals, e.g. from topographic and crustal depth variations, and thereby recover the GIA signal.

  1. On the gravity and geoid effects of glacial isostatic adjustment in Fennoscandia - a short note

    NASA Astrophysics Data System (ADS)

    Sjöberg, L. E.

    2015-12-01

    Many geoscientists argue that there is a gravity low of 10-30 mGal in Fennoscandia as a remaining fingerprint of the last ice age and load, both vanished about 10 kyr ago. However, the extraction of the gravity signal related with Glacial Isostatic Adjustment (GIA) is complicated by the fact that the total gravity field is caused by many significant density distributions in the Earth. Here we recall a methodology originating with A. Bjerhammar 35 years ago, that emphasizes that the present land uplift phenomenon mainly occurs in the region thatwas covered by the ice cap, and it is highly correlated with the spectral window of degrees 10-22 of the global gravity field, whose lower limit fairly well corresponds to the wavelength that agrees with the size of the region. This implies that, although in principle the GIA is a global phenomenon, the geoid and gravity lows as well as the land upheaval in Fennoscandia are typically regional phenomena that cannot be seen in a global correlation study as it is blurred by many irrelevant gravity signals. It is suggested that a regional multi-regression analysis with a band-limited spectral gravity signal as the observable, a method tested already 2 decades ago, can absorb possible significant disturbing signals, e.g. from topographic and crustal depth variations, and thereby recover the GIA signal.

  2. Reinforcement Learning Trees.

    PubMed

    Zhu, Ruoqing; Zeng, Donglin; Kosorok, Michael R

    In this paper, we introduce a new type of tree-based method, reinforcement learning trees (RLT), which exhibits significantly improved performance over traditional methods such as random forests (Breiman, 2001) under high-dimensional settings. The innovations are three-fold. First, the new method implements reinforcement learning at each selection of a splitting variable during the tree construction processes. By splitting on the variable that brings the greatest future improvement in later splits, rather than choosing the one with largest marginal effect from the immediate split, the constructed tree utilizes the available samples in a more efficient way. Moreover, such an approach enables linear combination cuts at little extra computational cost. Second, we propose a variable muting procedure that progressively eliminates noise variables during the construction of each individual tree. The muting procedure also takes advantage of reinforcement learning and prevents noise variables from being considered in the search for splitting rules, so that towards terminal nodes, where the sample size is small, the splitting rules are still constructed from only strong variables. Last, we investigate asymptotic properties of the proposed method under basic assumptions and discuss rationale in general settings.

  3. Reinforcement Learning Trees

    PubMed Central

    Zhu, Ruoqing; Zeng, Donglin; Kosorok, Michael R.

    2015-01-01

    In this paper, we introduce a new type of tree-based method, reinforcement learning trees (RLT), which exhibits significantly improved performance over traditional methods such as random forests (Breiman, 2001) under high-dimensional settings. The innovations are three-fold. First, the new method implements reinforcement learning at each selection of a splitting variable during the tree construction processes. By splitting on the variable that brings the greatest future improvement in later splits, rather than choosing the one with largest marginal effect from the immediate split, the constructed tree utilizes the available samples in a more efficient way. Moreover, such an approach enables linear combination cuts at little extra computational cost. Second, we propose a variable muting procedure that progressively eliminates noise variables during the construction of each individual tree. The muting procedure also takes advantage of reinforcement learning and prevents noise variables from being considered in the search for splitting rules, so that towards terminal nodes, where the sample size is small, the splitting rules are still constructed from only strong variables. Last, we investigate asymptotic properties of the proposed method under basic assumptions and discuss rationale in general settings. PMID:26903687

  4. Palaeogeographic regulation of glacial events during the Cretaceous supergreenhouse

    NASA Astrophysics Data System (ADS)

    Ladant, Jean-Baptiste; Donnadieu, Yannick

    2016-09-01

    The historical view of a uniformly warm Cretaceous is being increasingly challenged by the accumulation of new data hinting at the possibility of glacial events, even during the Cenomanian-Turonian (~95 Myr ago), the warmest interval of the Cretaceous. Here we show that the palaeogeography typifying the Cenomanian-Turonian renders the Earth System resilient to glaciation with no perennial ice accumulation occurring under prescribed CO2 levels as low as 420 p.p.m. Conversely, late Aptian (~115 Myr ago) and Maastrichtian (~70 Myr ago) continental configurations set the stage for cooler climatic conditions, favouring possible inception of Antarctic ice sheets under CO2 concentrations, respectively, about 400 and 300 p.p.m. higher than for the Cenomanian-Turonian. Our simulations notably emphasize that palaeogeography can crucially impact global climate by modulating the CO2 threshold for ice sheet inception and make the possibility of glacial events during the Cenomanian-Turonian unlikely.

  5. Glacial cycles drive variations in the production of oceanic crust.

    PubMed

    Crowley, John W; Katz, Richard F; Huybers, Peter; Langmuir, Charles H; Park, Sung-Hyun

    2015-03-13

    Glacial cycles redistribute water between oceans and continents, causing pressure changes in the upper mantle, with consequences for the melting of Earth's interior. Using Plio-Pleistocene sea-level variations as a forcing function, theoretical models of mid-ocean ridge dynamics that include melt transport predict temporal variations in crustal thickness of hundreds of meters. New bathymetry from the Australian-Antarctic ridge shows statistically significant spectral energy near the Milankovitch periods of 23, 41, and 100 thousand years, which is consistent with model predictions. These results suggest that abyssal hills, one of the most common bathymetric features on Earth, record the magmatic response to changes in sea level. The models and data support a link between glacial cycles at the surface and mantle melting at depth, recorded in the bathymetric fabric of the sea floor.

  6. Hemispheric sea ice distribution sets the glacial tempo

    NASA Astrophysics Data System (ADS)

    Lee, Jung-Eun; Shen, Aaron; Fox-Kemper, Baylor; Ming, Yi

    2017-01-01

    The proxy record of global temperature shows that the dominant periodicity of the glacial cycle shifts from 40 kyr (obliquity) to 100 kyr (eccentricity) about a million years ago. Using climate model simulations, here we show that the pace of the glacial cycle depends on the pattern of hemispheric sea ice growth. In a cold climate the sea ice grows asymmetrically between two hemispheres under changes to Earth's orbital precession, because sea ice growth potential outside of the Arctic Circle is limited. This difference in hemispheric sea ice growth leads to an asymmetry in absorbed solar energy for the two hemispheres, particularly when eccentricity is high, even if the annual average insolation is similar. In a warmer climate, the hemispheric asymmetry of the sea ice decreases as mean Arctic and Antarctic sea ice decreases, diminishing the precession and eccentricity signals and explaining the dominant obliquity signal (40 kyr) before the mid-Pleistocene transition.

  7. Sedimentary architecture of the Amundsen Sea Embayment shelf, West Antarctica, from pre-glacial to glacial processes

    NASA Astrophysics Data System (ADS)

    Gohl, Karsten; Uenzelmann-Neben, Gabriele; Hillenbrand, Claus-Dieter; Larter, Robert; Nitsche, Frank

    2013-04-01

    Studies of the sedimentary architecture and characteristics of Antarctic shelves provide clues of past ice sheet advance-retreat cycles and help improve constraints for paleo-ice dynamic models since early glacial periods. A first seismostratigraphic analysis of the Amundsen Sea Embayment shelf and slope of West Antarctica reveals insights into the structural architecture of the continental margin and shows stages of sediment deposition, erosion and transport history from pre-glacial times to early glaciation and to the most recent glacial periods. The shelf geometry consists of a large pre- and syn-rift basin in the middle shelf region between outcropping basement of the inner shelf and basement ridges and highs beneath the outer shelf. A middle shelf sub-basin exists which may have formed as a result of motion along an early West Antarctic Rift System branch. At least 4 km of pre-glacial strata has been eroded from the present inner shelf and coastal hinterland by ice sheet advances since the onset of glaciation. Some of the eroded sediments were deposited as a progradational wedge extending the outer shelf by 25 to 65 km oceanward of the pre-glacial shelf-break. Comparing the observed seismic characteristics with those of other Antarctic shelf sequences, we assign an Early Cretaceous age for bottom sedimentary unit ASS-1, a Late Cretaceous to Oligocene age for unit ASS-2, an Early to Mid-Miocene age for unit ASS-3, a Mid-Miocene age for unit ASS-4, a Late Miocene to Early Pliocene age for unit ASS-5, and a Pliocene to Pleistocene age for the top unit ASS-6. The survival of buried grounding zone wedges in the upper part of unit ASS-5 of the outer shelf is consistent with the onset of a long warming phase and a retreated ice sheet in the early Pliocene as observed for the Ross Sea shelf and reconstructed from paleo-ice sheet models. Our data also reveal that the paleo-ice flow paths of the central Pine Island Trough system have remained stationary across the

  8. Mercury fluxes out of glacial and non-glacial streams, as determined by continuous measurements of turbidity and CDOM

    NASA Astrophysics Data System (ADS)

    Vermilyea, A.; Nagorski, S. A.; Lamborg, C. H.; Scott, D.; Hood, E. W.

    2011-12-01

    Glaciers and icefields along the Alaskan coast contribute nearly half of the freshwater discharge to the Gulf of Alaska and can play an important role in near-shore marine ecosystems. In southeastern Alaska, glaciers are rapidly thinning and retreating and are being replaced by temperate forests and wetlands. This ongoing landscape evolution is altering the sensitivity of coastal watersheds to atmospheric Hg inputs. The influence of glacial runoff with high suspended sediment loads on in-stream mercury fluxes and dynamics is poorly understood. In contrast, numerous studies have shown that streams with large contributions from wetlands typically carry high dissolved organic matter (DOM) and filtered methylmercury (FMHg) loads. This study compares and contrasts the mercury concentrations, fluxes, partitioning, and speciation in two coastal watersheds in southeastern Alaska. The two watersheds are separated by only 23 km and are relatively similar in area, however one is heavily glaciated (Lemon Creek) and one is dominated by temperate forest and wetlands (Peterson Creek). Grab samples for unfiltered total mercury (UTHg), particulate total mercury (PTHg), filtered total mercury (FTHg), and FMHg were taken during three, 4-day sampling periods within the glacial melt season (May-Sept) while continuously monitoring in-situ chromophoric dissolved organic matter (CDOM) fluorescence and stream turbidity. While UTHg concentration-discharge relationships were poor (R2=0.38-0.55) in both streams, flux estimates for UTHg were greatly improved using CDOM fluorescence (R2=0.82) for Peterson Creek, and turbidity (R2=0.81) for Lemon Creek. UTHg concentrations were consistently greater in Peterson Creek (factor of 1.7-2.3); however, the watershed area normalized UTHg flux was 3-6 times greater in glacial Lemon Creek than Peterson Creek across all time periods. In Peterson Creek, the majority of the UTHg was in the filtered phase, whereas in Lemon Creek the majority of the mercury

  9. Late-glacial vegetation and climate at the Manis Mastodon site, Olympic Peninsula, Washington

    NASA Astrophysics Data System (ADS)

    Petersen, Kenneth L.; Mehringer, Peter J.; Gustafson, Carl E.

    1983-09-01

    As the late Wisconsin Cordilleran Ice Sheet retreated, sediment accumulated in shallow depressions at the Manis Mastodon Archaeological site on the Olympic Peninsula, near Sequim, Washington. Pollen, plant macrofossils, and bones of mastodon, caribou, and bison occur within the lower 47 cm of these deposits. The fossil pollen and seed assemblages indicate persistence for 1000 yr (11,000-12,000 yr B.P.) of an herb-and-shrub-dominated landscape at a time when forest species appear elsewhere in Washington and in adjacent British Columbia. At present, Sequim is near the northern coastal limits of both Cactaceae and Ceratophyllum. Mean annual precipitation is 42.7 cm and summer temperatures average 15°-16°C in July. The absence of coniferous trees and the presence of cactus and Ceratophyllum in late-glacial sediments are explained by a regional climate that was drier and at least as warm as today. These conditions persisted in the rain shadow of the Olympic Mountains until at least 11,000 yr B.P.

  10. The influence of Pleistocene glacial refugia on tawny owl genetic diversity and phylogeography in western Europe.

    PubMed

    Brito, Patrícia H

    2005-09-01

    The glacial refugia hypothesis indicates that during the height of the Pleistocene glaciations the temperate species that are today widespread in western Europe must have survived in small and climatically favourable areas located in the southern peninsulas of Iberia, Italy and Balkans. One such species is the tawny owl, a relatively sedentary, nonmigratory bird presently distributed throughout Europe. It is a tree-nesting species closely associated with deciduous and mixed coniferous woodlands. In this study I used control region mtDNA sequences from 187 individuals distributed among 14 populations to determine whether current genetic patterns in tawny owl populations were consistent with postglacial expansion from peninsular refugia. European, North African and Asian tawny owls were found to represent three distinct lineages, where North Africa is the sister clade to all European owls. Within Europe, I found three well-supported clades that correspond to each of the three allopatric refugia. Expansion patterns indicate that owls from the Balkan refugium repopulated most of northern Europe, while expansion out of Iberia and Italy had only regional effects leading to admixture in France. Estimates of population divergence times between refugia populations are roughly similar, but one order of magnitude smaller between Greece and northern Europe. Based on a wide range of mutation rates and generation times, divergence between refugia appears to date to the Pleistocene.

  11. Late-Glacial to Early Holocene Climate Changes from a Central Appalachians Pollen and Macrofossil Record

    NASA Technical Reports Server (NTRS)

    Kneller, Margaret; Peteet, Dorothy

    1997-01-01

    A Late-glacial to early Holocene record of pollen, plant macrofossils and charcoal, based on two cores, is presented for Browns Pond in the central Appalachians of Virginia. An AMS radiocarbon chronology defines the timing of moist and cold excursions, superimposed upon the overall warming trend from 14,200 to 7,500 C-14 yr B.P. This site shows cold, moist conditions from approximately 14,200 to 12,700 C-14 yr B.P., with warming at 12,730, 11,280 and 10,050 C-14 yr B.P. A decrease in deciduous broad-leaved tree taxa and Pinus strobus (haploxylon) pollen, simultaneous with a re-expansion of Abies denotes a brief, cold reversal from 12,260 to 12,200 C-14 yr B.P. A second cold reversal, inferred from increases in montane conifers, is centered at 7,500 C-14 yr B.P. The cold reversals at Browns Pond may be synchronous with climate change in Greenland, and northwestern Europe. Warming at 11,280 C-14 yr B.P. shows the complexity of regional climate responses during the Younger Dryas chronozone.

  12. Reconstructions of the 14C cosmogenic isotope content from natural archives after the last glacial termination

    NASA Astrophysics Data System (ADS)

    Kudryavtsev, I. V.; Volobuev, D. M.; Dergachev, V. A.; Nagovitsyn, Yu. A.; Ogurtsov, M. G.

    2016-12-01

    Data on the content of the 14C cosmogenic isotope in tree rings, which were obtained as a result of laboratory measurements, are often used when solar activity (SA) is reconstructed for previous epochs, in which direct observations are absent. However, these data contain information not only about SA variations but also about changes in the Earth climatic parameters, such as the global temperature and the CO2 content in the Earth's atmosphere. The effect of these variations on the 14C isotope content in different natural reservoirs after the last glacial termination to the middle of the Holocene is considered. The global temperature and the CO2 content increased on this time interval. In this case the 14C absolute content in the atmosphere increased on this time interval, even though the 14C to 12C isotope concentration ratio (as described by the Δ14C parameter) decreased. These variations in the radiocarbon absolute content can be caused by its redistribution between natural reservoirs. It has been indicated that such a redistribution is possible only when the rate of carbon exchange between the ocean and atmosphere depends on temperature. The values of the corresponding temperature coefficient for the 17-10 ka BC time interval, which make it possible to describe the carbon redistribution between the ocean and atmosphere, have been obtained.

  13. Climate, CO2, and the history of North American grasses since the Last Glacial Maximum.

    PubMed

    Cotton, Jennifer M; Cerling, Thure E; Hoppe, Kathryn A; Mosier, Thomas M; Still, Christopher J

    2016-03-01

    The spread of C4 grasses in the late Neogene is one of the most important ecological transitions of the Cenozoic, but the primary driver of this global expansion is widely debated. We use the stable carbon isotopic composition (δ(13)C) of bison and mammoth tissues as a proxy for the relative abundance of C3 and C4 vegetation in their grazing habitat to determine climatic and atmospheric CO2 controls on C4 grass distributions from the Last Glacial Maximum (LGM) to the present. We predict the spatial variability of grass δ(13)C in North America using a mean of three different methods of classification and regression tree (CART) machine learning techniques and nine climatic variables. We show that growing season precipitation and temperature are the strongest predictors of all single climate variables. We apply this CART analysis to high-resolution gridded climate data and Coupled Model Intercomparison Project (CMIP5) mean paleoclimate model outputs to produce predictive isotope landscape models ("isoscapes") for the current, mid-Holocene, and LGM average δ(13)C of grass-dominated areas across North America. From the LGM to the present, C4 grass abundances substantially increased in the Great Plains despite concurrent increases in atmospheric CO2. These results suggest that changes in growing season precipitation rather than atmospheric CO2 were critically important in the Neogene expansion of C4 grasses.

  14. Climate, CO2, and the history of North American grasses since the Last Glacial Maximum

    PubMed Central

    Cotton, Jennifer M.; Cerling, Thure E.; Hoppe, Kathryn A.; Mosier, Thomas M.; Still, Christopher J.

    2016-01-01

    The spread of C4 grasses in the late Neogene is one of the most important ecological transitions of the Cenozoic, but the primary driver of this global expansion is widely debated. We use the stable carbon isotopic composition (δ13C) of bison and mammoth tissues as a proxy for the relative abundance of C3 and C4 vegetation in their grazing habitat to determine climatic and atmospheric CO2 controls on C4 grass distributions from the Last Glacial Maximum (LGM) to the present. We predict the spatial variability of grass δ13C in North America using a mean of three different methods of classification and regression tree (CART) machine learning techniques and nine climatic variables. We show that growing season precipitation and temperature are the strongest predictors of all single climate variables. We apply this CART analysis to high-resolution gridded climate data and Coupled Model Intercomparison Project (CMIP5) mean paleoclimate model outputs to produce predictive isotope landscape models (“isoscapes”) for the current, mid-Holocene, and LGM average δ13C of grass-dominated areas across North America. From the LGM to the present, C4 grass abundances substantially increased in the Great Plains despite concurrent increases in atmospheric CO2. These results suggest that changes in growing season precipitation rather than atmospheric CO2 were critically important in the Neogene expansion of C4 grasses. PMID:27051865

  15. Requirements for extracting mantle viscosity from glacial isostatic adjustment

    NASA Astrophysics Data System (ADS)

    Cathles, L. M.

    2012-04-01

    Extracting mantle viscosity from glacial isostatic adjustment (GIA) data is challenging because it requires a correctly posed rheological model, an accurate description of the ice and water load redistributions that occurred over at least the last glacial cycle, and the ability to interact model predictions with a large amount of observational data. To address sealevel changes, models must be based on an appropriate rheology. Daly focused attention on this critical issue 78 years ago with his down-punching hypothesis. Observing the sympathetic uplift behavior of areas peripheral to continental glacial loads, he suggested a thick lithosphere was required to force this behavior on asthenosphere flow. At the same time Haskell pointed out that deep flow in a constant viscosity Newtonian mantle would produce the observed peripheral bulge behavior without a thick lithosphere. This debate is important today because sealevel changes are particularly impacted by deep mantle viscosity and mantle rheology. Lithosphere and asthenosphere properties are another much discussed topic. The commonly observed substantial short wavelength response requires both a thin (~40 km thick) lithosphere and an asthenosphere ~25 times more fluid than the mantle. Because the manner of local ice removal can affect rebound calculations greatly, it is critical to have accurate ice and water load redistributions. Load redistributions must include changes in the levels of large lakes. Recent studies indicate how important it is to take into account sediment redistribution over the last glacial cycle. Finally, evaluation of the calculated emergence requires the comparison to large amounts of accurate (or at least critically vetted) sea level, emergence, GPS, and other kinds of data. These issues will be discussed and illustrated with some recent calculations.

  16. Glacial History of the Pirrit Hills, West Antarctica

    NASA Astrophysics Data System (ADS)

    Spector, P. E.; Stone, J. O.

    2014-12-01

    We present new ice-thickness constraints from the Pirrit Hills, a small, far-flung group of nunataks located in the Weddell Sector. At the Pirrit Hills, fresh glacial erratics indicate ice levels ~350-450 m above present during the last ice age. The highest erratics have preliminary 10Be exposure ages of ~16 ka, and the ages generally decrease with decreasing elevation, recording the thinning of the ice in the region. Despite the evidence of thicker ice, weathered bedrock extends down to the present ice level, implying prolonged subaerial weathering prior to the last ice age. These features, and the lack of evidence for wet-based glacial erosion, indicate cold-based and non-erosive ice cover. Over the elevation range in which we found glacial erratics, bedrock 10Be, 26Al, and 21Ne concentrations are consistent with modest ice cover, and have exposure ages ranging from ~0.3-1.5 Myr. Around 450 m above the present ice level, bedrock 10Be, 26Al, and 21Ne concentrations increase by a factor of ~4-5 and do not indicate past ice cover. This height coincides with a break in the otherwise steep slopes of the Pirrit Hills, and the bedrock above is more weathered than the bedrock below. This transition marks the height above which ice cover, if it has occurred in the past few million years, has been very rare, brief, and cold-based. This feature may relate to the trimline imprinted on ridges in the Ellsworth Mountains. In both cases, alpine landscapes have been preserved by a polar climate and glacial highstands rising only partway up the mountain flanks.

  17. An Atlas of Submarine Glacial Landforms: Modern, Quaternary and Ancient

    NASA Astrophysics Data System (ADS)

    Jakobsson, M.; Dowdeswell, J. A.; Canals, M.; Todd, B. J.; Dowdeswell, E. K.; Hogan, K. A.

    2014-12-01

    In the past two decades there have been several advances that make the production of an atlas of submarine glacial landforms timely. First is the development of high-resolution imaging technologies; multi-beam echo-sounding or swath bathymetry that allows the detailed mapping of the sea floor at water depths of tens to thousands of metres across continental margins, and 3-D seismic methods that enable the visualisation of palaeo-continental shelves in Quaternary sediments and ancient palaeo-glacial rocks (e.g. Late Ordovician of Northern Africa). A second technological development is that of ice-breaking or ice-strengthened ships that can penetrate deep into the ice-infested waters of the Arctic and Antarctic, to deploy the multibeam systems. A third component is that of relevance - through both the recognition that the polar regions, and especially the Arctic, are particularly sensitive parts of the global environmental system and that these high-latitude margins (both modern and ancient) are likely to contain significant hydrocarbon resources. An enhanced understanding of the sediments and landforms of these fjord-shelf-slope systems is, therefore, of increasing importance to both academics and industry. We are editing an Atlas of Submarine Glacial Landforms that presents a series of individual contributions that describe, discuss and illustrate features on the high-latitude, glacier-influenced sea floor. Contributions are organised in two ways: first, by position on a continental margin - from fjords, through continental shelves to the continental slope and rise; secondly, by scale - as individual landforms and assemblages of landforms. A final section provides discussion of integrated fjord-shelf-slope systems. Over 100 contributions by scientists from many countries contain descriptions and interpretation of swath-bathymetric data from both Arctic and Antarctic margins and use 3D seismic data to investigate ancient glacial landforms. The Atlas will be

  18. Glacial oceanographic contrasts explain phylogeography of Australian bull kelp.

    PubMed

    Fraser, Ceridwen I; Spencer, Hamish G; Waters, Jonathan M

    2009-05-01

    The evolutionary effects of Southern Hemisphere Pleistocene oceanographic conditions - marked by fluctuations in sea levels and water temperatures, and redirected currents - are poorly understood. The southeastern tip of Australia presents an intriguing model system for studying the biological impacts of palaeoceanography. In particular, contrasting oceanographic conditions that existed on eastern vs. western sides of the Bassian Isthmus during Pleistocene glacial periods allow for natural comparisons between putative refugial vs. re-invading populations. Whereas many western Tasmanian marine taxa were likely eliminated by cold subantarctic water during the last glacial period, eastern Tasmanian populations would have persisted in relatively warm temperatures mediated by the ongoing influence of the East Australian Current (EAC). Here we test for the effects of contrasting palaeoceanographic conditions on endemic bull kelp, Durvillaea potatorum, using DNA sequence analysis (COI; rbcL) of more than 100 individuals from 14 localities in southeastern Australia. Phylogenetic reconstructions reveal a deep (maximum divergence 4.7%) genetic split within D. potatorum, corresponding to the 'eastern' and 'western' geographical regions delimited by the Bassian Isthmus, a vicariant barrier during low Pleistocene sea levels. Concordant with the western region's cold glacial conditions, samples from western Tasmania and western Victoria are genetically monomorphic, suggesting postglacial expansion from a mainland refugium. Eastern samples, in contrast, comprise distinct regional haplogroups, suggesting the species persisted in eastern Tasmania throughout recent glacial periods. The deep east-west divergence seems consistent with earlier reports of morphological differences between 'western' and 'eastern' D. potatorum, and it seems likely that these forms represent reproductively isolated species.

  19. Sulfur/Carbonate Springs and Life in Glacial Ice

    NASA Technical Reports Server (NTRS)

    Allen, Carlton; Grasby, Stephen; Longazo, Teresa

    2001-01-01

    Ice in the near subsurface of Mars apparently discharges liquid water on occasion. Cold-tolerant microorganisms are known to exist within terrestrial glacial ice, and may be brought to the surface as a result of melting events. We are investigating a set of springs that deposit sulfur and carbonate minerals, as well as evidence of microbial life, on the surface of a glacier in the Canadian arctic. Additional information is contained in the original extended abstract.

  20. Uncovering the glacial history of the Irish continental shelf (Invited)

    NASA Astrophysics Data System (ADS)

    Dunlop, P.; Benetti, S.; OCofaigh, C.

    2013-12-01

    In 1999 the Irish Government initiated a €32 million survey of its territorial waters known as the Irish National Seabed Survey (INSS). The INSS is amongst the largest marine mapping programmes ever undertaken anywhere in the world and provides high-resolution multibeam, backscatter and seismic data of the seabed around Ireland. These data have been used to provide the first clear evidence for extensive glaciation of the continental shelf west and northwest of Ireland. Streamlined drumlins on the mid to outer shelf record former offshore-directed ice flow towards the shelf edge and show that the ice sheet was grounded in a zone of confluence where ice flowing onto the shelf from northwest Ireland merged with ice flowing across the Malin Shelf from southwest Scotland. The major glacial features on the shelf are well developed nested arcuate moraine systems that mark the position of the ice sheet margin and confirm that the former British Irish Ice Sheet was grounded as far as the shelf edge around 100 km offshore of west Donegal at the last glacial maximum. Distal to the moraines, on the outermost shelf, prominent zones of iceberg plough marks give way to the Barra/Donegal fan and a well developed system of gullies and canyons which incise the continental slope. Since 2008 several scientific cruises have retrieved cores from the shelf and slope to help build a more detailed understanding of glacial events in this region. This presentation will provide an overview of the glacial history of the Irish shelf and will discuss ongoing research programmes that are building on the initial research findings to produce a better understanding of the nature and timing of ice sheet events in this region.

  1. Tectonic stress feedback loop explains U-shaped glacial valleys

    NASA Astrophysics Data System (ADS)

    Schultz, Colin

    2014-03-01

    In the shadow of the Matterhorn, the broad form of the Matter Valley—like so many throughout the Alps—is interrupted by a deep U-shaped glacial trough. Carved into a landscape reflecting millennia of tectonic uplift and river erosion, growing evidence suggests the 100-meter-deep U-shaped groove was produced shortly after a shift toward major cycles of Alpine glaciation almost a million years ago. Subsequent glaciations may have therefore had little effect on the landscape.

  2. Ocean Cooling Pattern at the Last Glacial Maximum

    DOE PAGES

    Zhuang, Kelin; Giardino, John R.

    2012-01-01

    Ocean temperature and ocean heat content change are analyzed based on four PMIP3 model results at the Last Glacial Maximum relative to the prehistorical run. Ocean cooling mostly occurs in the upper 1000 m depth and varies spatially in the tropical and temperate zones. The Atlantic Ocean experiences greater cooling than the rest of the ocean basins. Ocean cooling is closely related to the weakening of meridional overturning circulation and enhanced intrusion of Antarctic Bottom Water into the North Atlantic.

  3. Comparative phylogeography of two North American 'glacial relict' crustaceans.

    PubMed

    Dooh, R T; Adamowicz, S J; Hebert, P D N

    2006-12-01

    The Pleistocene glaciations represent the most recent and dramatic series of habitat changes since the Cretaceous. The impact of these events was particularly acute for aquatic taxa with poor powers of dispersal, but few organisms have evolutionary histories more intimately entwined with the advance and retreat of ice than the 'glacial relicts'. In this study, we used a mitochondrial gene, cytochrome c oxidase subunit I (COI), to examine and compare the phylogeographical structure of two glacial relict crustaceans (Limnocalanus macrurus and members of the Mysis relicta species group) across North America. In both cases, we found a sharp phylogenetic division between populations from inland lakes formed during glacial retreat, and arctic lakes isolated from polar seas via isostatic rebound. However, the depth of this phylogenetic partition varied between taxa. In L. macrurus, nucleotide sequence divergence of 2.2% between these zones is consistent with its current status as a single morphologically variable species, but in Mysis the split occurred among recently described, morphologically conserved species, at a divergence of 8.2%. The disparity in the depth of divergence indicates a history of recurrent freshwater invasions from the arctic seas, in concordance with previous studies of Eurasian glacial relicts. However, we suggest further consideration of a largely overlooked explanation that could account for some of the discrepancies between molecular divergences and glaciation events. Many cladogenetic events could have occurred in arctic seas prior to the transition to inland waters, a possibility supported both by the complex physical and ionic history of arctic seas and by high marine and estuarine lineage diversity in the north.

  4. Floating glacial ice caps in the arctic ocean.

    PubMed

    Broecker, W S

    1975-06-13

    Two arguments are presented, one in favor of the existence of thicker ice in the Arctic Ocean during glacial time, and the other in favor of a full-fledged Arctic ice cap. The first is based on the Greenland air temperature record obtained from isotopic studies of the Camp Century ice core. The second is based on the oxygen isotope record of benthic foraminifera from a deep Pacific Ocean core.

  5. Evidence of strong ocean heating during glacial periods

    NASA Astrophysics Data System (ADS)

    Zimov, S. A.; Zimov, N.

    2013-12-01

    Numerous hypotheses have addressed glacial-interglacial climatic dynamics, but none of them explain the sharp 25C temperature increase in Greenland in the last deglaciation (Cuffey et al. 1995; Dahl-Jensen et al. 1998). These robust data were obtained through analyzing the temperature profile in the Greenland ice sheet where cold from the last glaciation is preserved in the depth of the glacial sheet. We suggest that during glaciations the ocean accumulated energy: interior ocean water heated up to ~20-30C and during deglaciation this energy is released. In the analogy with reconstructing the ice sheet temperature profiles, the most reliable proof of ocean interior warming during the last glaciation is the heat flux profiles in the bottom sediments. In the final reports based on temperature measurements conducted during the DSDP (Deep Sea Drilling Project) it is stated that heat flux in the bottom sediments doesn't vary with depth and consequently there were no substantial temperature changes in the ocean interior during the last glacial cycle, and heat flux on the surface of the ocean bottom is the geothermal heat flux (Erickson et al., 1975, Hyndman et al., 1987). However, we have critically investigated data in all initial reports of all deep sea drilling projects and have noticed that all temperature data show that heat flow decreases strongly with depth (a minimum of 40 mW/m2), i.e. most of the heat flux detected on the surface of the ocean floor is not the geothermal heat flux but remaining heat that bottom sediments release. Sharp shifts in heat flow are seen within boreholes at depths crossing gas hydrate bottom. All this means that during the last glacial period interior water temperature was on 25-30C degrees warmer. Conversely, in isolated seas heat flow in the sediments shows little change with depth.

  6. Glacial Isostatic Adjustment Observed with VLBI and SLR

    NASA Technical Reports Server (NTRS)

    Argus, D.; Peltier, W.; Watkins, M.

    1999-01-01

    In global geodetic solutions vertical rates of site motion are usually estimated relative to the geocenter (center of figure) of the solid earth. The velocity of the geocenter is estimated assuming that the plates are rigid, that the velocities of the plates equal those in NUVEL-1A (DeMets et al. 1990, 1994) and that the uplift, subsidence, and intraplate deformation due to glacial isostatic adjustment is negligible.

  7. Recovery of trees from drought depends on belowground sink control.

    PubMed

    Hagedorn, Frank; Joseph, Jobin; Peter, Martina; Luster, Jörg; Pritsch, Karin; Geppert, Uwe; Kerner, Rene; Molinier, Virginie; Egli, Simon; Schaub, Marcus; Liu, Jian-Feng; Li, Maihe; Sever, Krunoslav; Weiler, Markus; Siegwolf, Rolf T W; Gessler, Arthur; Arend, Matthias

    2016-07-18

    Climate projections predict higher precipitation variability with more frequent dry extremes(1). CO2 assimilation of forests decreases during drought, either by stomatal closure(2) or by direct environmental control of sink tissue activities(3). Ultimately, drought effects on forests depend on the ability of forests to recover, but the mechanisms controlling ecosystem resilience are uncertain(4). Here, we have investigated the effects of drought and drought release on the carbon balances in beech trees by combining CO2 flux measurements, metabolomics and (13)CO2 pulse labelling. During drought, net photosynthesis (AN), soil respiration (RS) and the allocation of recent assimilates below ground were reduced. Carbohydrates accumulated in metabolically resting roots but not in leaves, indicating sink control of the tree carbon balance. After drought release, RS recovered faster than AN and CO2 fluxes exceeded those in continuously watered trees for months. This stimulation was related to greater assimilate allocation to and metabolization in the rhizosphere. These findings show that trees prioritize the investment of assimilates below ground, probably to regain root functions after drought. We propose that root restoration plays a key role in ecosystem resilience to drought, in that the increased sink activity controls the recovery of carbon balances.

  8. Tree nut allergens.

    PubMed

    Roux, Kenneth H; Teuber, Suzanne S; Sathe, Shridhar K

    2003-08-01

    Allergic reactions to tree nuts can be serious and life threatening. Considerable research has been conducted in recent years in an attempt to characterize those allergens that are most responsible for allergy sensitization and triggering. Both native and recombinant nut allergens have been identified and characterized and, for some, the IgE-reactive epitopes described. Some allergens, such as lipid transfer proteins, profilins, and members of the Bet v 1-related family, represent minor constituents in tree nuts. These allergens are frequently cross-reactive with other food and pollen homologues, and are considered panallergens. Others, such as legumins, vicilins, and 2S albumins, represent major seed storage protein constituents of the nuts. The allergenic tree nuts discussed in this review include those most commonly responsible for allergic reactions such as hazelnut, walnut, cashew, and almond as well as those less frequently associated with allergies including pecan, chestnut, Brazil nut, pine nut, macadamia nut, pistachio, coconut, Nangai nut, and acorn.

  9. A wavelet watermarking algorithm based on a tree structure

    NASA Astrophysics Data System (ADS)

    Guitart Pla, Oriol; Lin, Eugene T.; Delp, Edward J., III

    2004-06-01

    We describe a blind watermarking technique for digital images. Our technique constructs an image-dependent watermark in the discrete wavelet transform (DWT) domain and inserts the watermark in the most signifcant coefficients of the image. The watermarked coefficients are determined by using the hierarchical tree structure induced by the DWT, similar in concept to embedded zerotree wavelet (EZW) compression. If the watermarked image is attacked or manipulated such that the set of significant coefficients is changed, the tree structure allows the correlation-based watermark detector to recover synchronization. Our technique also uses a visual adaptive scheme to insert the watermark to minimize watermark perceptibility. The visual adaptive scheme also takes advantage of the tree structure. Finally, a template is inserted into the watermark to provide robustness against geometric attacks. The template detection uses the cross-ratio of four collinear points.

  10. An interhemispheric mechanism for glacial abrupt climate change

    NASA Astrophysics Data System (ADS)

    Banderas, Rubén; Alvarez-Solas, Jorge; Robinson, Alexander; Montoya, Marisa

    2015-05-01

    The last glacial period was punctuated by abrupt climate changes that are widely considered to result from millennial-scale variability of the Atlantic meridional overturning circulation (AMOC). However, the origin of these AMOC reorganizations remains poorly understood. The climatic connection between both hemispheres indicated by proxies suggests that the Southern Ocean (SO) could regulate this variability through changes in winds and atmospheric CO concentration. Here, we investigate this hypothesis using a coupled climate model forced by prescribed CO and SO wind-stress variations. We find that the AMOC exhibits an oscillatory behavior between weak and strong circulation regimes which is ultimately caused by changes in the meridional density gradient of the Atlantic Ocean. The evolution of the simulated climatic patterns matches the amplitude and timing of the largest events that occurred during the last glacial period and their widespread climatic impacts. Our results suggest the existence of an internal interhemispheric oscillation mediated by the bipolar seesaw that could promote glacial abrupt climate changes through variations in atmospheric CO levels, the strength of the SO winds and AMOC reorganizations, and provide an explanation for the pervasive Antarctic-like climate signal found in proxy records worldwide.

  11. Intra-crater glacial processes in central Utopia Planitia, Mars

    NASA Astrophysics Data System (ADS)

    Pearce, Geoffrey; Osinski, Gordon R.; Soare, Richard J.

    2011-03-01

    We describe and interpret a series of previously unidentified glacial-like lobes (34-43°N; 107-125°E) that were discovered as part of a survey of large (D > 5 km) impact craters in Utopia Planitia, one of the great northern plains of Mars. The lobes have characteristics that are consistent with a glacial origin. Evidence includes curvilinearity of form, lineations and ridges, and surface textures that are thought to form by the sublimation of near-surface volatiles. The lobes display morphologies that range from wedge-shaped to near-circular to elongate. The flow directions are towards the northern walls in the case of craters with large single lobes, and in all directions in the case of the largest (D > 30 km) craters. Concentric crater fill is also interspersed within craters of our study region, with such craters having much higher filling rates than those with flow lobes. We suggest that the impact crater population in south-west Utopia Planitia demonstrates a spectrum of glacial modifications, from low levels of filling in the case of craters with elongate lobes at one extreme, to concentric crater fill in highly-filled craters at the other.

  12. Human population dynamics in Europe over the Last Glacial Maximum

    PubMed Central

    Tallavaara, Miikka; Luoto, Miska; Korhonen, Natalia; Järvinen, Heikki; Seppä, Heikki

    2015-01-01

    The severe cooling and the expansion of the ice sheets during the Last Glacial Maximum (LGM), 27,000–19,000 y ago (27–19 ky ago) had a major impact on plant and animal populations, including humans. Changes in human population size and range have affected our genetic evolution, and recent modeling efforts have reaffirmed the importance of population dynamics in cultural and linguistic evolution, as well. However, in the absence of historical records, estimating past population levels has remained difficult. Here we show that it is possible to model spatially explicit human population dynamics from the pre-LGM at 30 ky ago through the LGM to the Late Glacial in Europe by using climate envelope modeling tools and modern ethnographic datasets to construct a population calibration model. The simulated range and size of the human population correspond significantly with spatiotemporal patterns in the archaeological data, suggesting that climate was a major driver of population dynamics 30–13 ky ago. The simulated population size declined from about 330,000 people at 30 ky ago to a minimum of 130,000 people at 23 ky ago. The Late Glacial population growth was fastest during Greenland interstadial 1, and by 13 ky ago, there were almost 410,000 people in Europe. Even during the coldest part of the LGM, the climatically suitable area for human habitation remained unfragmented and covered 36% of Europe. PMID:26100880

  13. Massive remobilization of permafrost carbon during post-glacial warming

    NASA Astrophysics Data System (ADS)

    Tesi, T.; Muschitiello, F.; Smittenberg, R. H.; Jakobsson, M.; Vonk, J. E.; Hill, P.; Andersson, A.; Kirchner, N.; Noormets, R.; Dudarev, O.; Semiletov, I.; Gustafsson, Ö.

    2016-11-01

    Recent hypotheses, based on atmospheric records and models, suggest that permafrost carbon (PF-C) accumulated during the last glaciation may have been an important source for the atmospheric CO2 rise during post-glacial warming. However, direct physical indications for such PF-C release have so far been absent. Here we use the Laptev Sea (Arctic Ocean) as an archive to investigate PF-C destabilization during the last glacial-interglacial period. Our results show evidence for massive supply of PF-C from Siberian soils as a result of severe active layer deepening in response to the warming. Thawing of PF-C must also have brought about an enhanced organic matter respiration and, thus, these findings suggest that PF-C may indeed have been an important source of CO2 across the extensive permafrost domain. The results challenge current paradigms on the post-glacial CO2 rise and, at the same time, serve as a harbinger for possible consequences of the present-day warming of PF-C soils.

  14. Microbial genesis, life and death in glacial ice.

    PubMed

    Price, P Buford

    2009-01-01

    Arguments are given that terrestrial RNA and DNA may have originated in a frozen environment more than 4 billion years ago. Scenarios are developed for atmospheric transport of microbes onto glacial ice, their adaptation to subzero temperatures in the ice, and their incorporation into one of three habitats - liquid veins, mineral grain surfaces, or isolated inside 1 of the crystals that make up polycrystalline ice. The Arrhenius dependence of microbial metabolic rate on temperature is shown to match that required to repair damage owing to spontaneous DNA depurination and amino acid racemization. Even for the oldest glacial ice, microbial lifetime is shown not to be shortened by radiation damage from 238U, 232Th, or 40K in mineral dust in ice, by phage-induced lysis, or by penetrating cosmic radiation. Instead, death of those cells adapted to the hostile conditions in glacial ice is probably due to exhaustion of available nutrients. By contrast, in permafrost microbial death is more likely due to alpha-particle radiation damage from U and Th in the soil and rocks intermixed with ice. For residence times in ice longer than a million years, spore formers may be unable to compete in longevity with vegetative cells that are able to repair DNA damage via survival metabolism.

  15. Human population dynamics in Europe over the Last Glacial Maximum.

    PubMed

    Tallavaara, Miikka; Luoto, Miska; Korhonen, Natalia; Järvinen, Heikki; Seppä, Heikki

    2015-07-07

    The severe cooling and the expansion of the ice sheets during the Last Glacial Maximum (LGM), 27,000-19,000 y ago (27-19 ky ago) had a major impact on plant and animal populations, including humans. Changes in human population size and range have affected our genetic evolution, and recent modeling efforts have reaffirmed the importance of population dynamics in cultural and linguistic evolution, as well. However, in the absence of historical records, estimating past population levels has remained difficult. Here we show that it is possible to model spatially explicit human population dynamics from the pre-LGM at 30 ky ago through the LGM to the Late Glacial in Europe by using climate envelope modeling tools and modern ethnographic datasets to construct a population calibration model. The simulated range and size of the human population correspond significantly with spatiotemporal patterns in the archaeological data, suggesting that climate was a major driver of population dynamics 30-13 ky ago. The simulated population size declined from about 330,000 people at 30 ky ago to a minimum of 130,000 people at 23 ky ago. The Late Glacial population growth was fastest during Greenland interstadial 1, and by 13 ky ago, there were almost 410,000 people in Europe. Even during the coldest part of the LGM, the climatically suitable area for human habitation remained unfragmented and covered 36% of Europe.

  16. The gene tree delusion.

    PubMed

    Springer, Mark S; Gatesy, John

    2016-01-01

    Higher-level relationships among placental mammals are mostly resolved, but several polytomies remain contentious. Song et al. (2012) claimed to have resolved three of these using shortcut coalescence methods (MP-EST, STAR) and further concluded that these methods, which assume no within-locus recombination, are required to unravel deep-level phylogenetic problems that have stymied concatenation. Here, we reanalyze Song et al.'s (2012) data and leverage these re-analyses to explore key issues in systematics including the recombination ratchet, gene tree stoichiometry, the proportion of gene tree incongruence that results from deep coalescence versus other factors, and simulations that compare the performance of coalescence and concatenation methods in species tree estimation. Song et al. (2012) reported an average locus length of 3.1 kb for the 447 protein-coding genes in their phylogenomic dataset, but the true mean length of these loci (start codon to stop codon) is 139.6 kb. Empirical estimates of recombination breakpoints in primates, coupled with consideration of the recombination ratchet, suggest that individual coalescence genes (c-genes) approach ∼12 bp or less for Song et al.'s (2012) dataset, three to four orders of magnitude shorter than the c-genes reported by these authors. This result has general implications for the application of coalescence methods in species tree estimation. We contend that it is illogical to apply coalescence methods to complete protein-coding sequences. Such analyses amalgamate c-genes with different evolutionary histories (i.e., exons separated by >100,000 bp), distort true gene tree stoichiometry that is required for accurate species tree inference, and contradict the central rationale for applying coalescence methods to difficult phylogenetic problems. In addition, Song et al.'s (2012) dataset of 447 genes includes 21 loci with switched taxonomic names, eight duplicated loci, 26 loci with non-homologous sequences that are

  17. A celestial Christmas tree

    NASA Astrophysics Data System (ADS)

    Moore, S.

    2006-12-01

    Having finished decorating your terrestrial Christmas tree this year, you may care to step outside and view a celestial one. Well placed in the December night sky in the often overlooked but very rewarding constellation of Monoceros, NGC 2264, called the Christmas Tree by the American astronomer and writer Leland S. Copeland, lies due south around 1 a.m. in mid-December at an altitude of 50°. The cluster lies amid a vast area of nebulosity, well captured in the image by Gordon Rogers on the cover of this Journal.

  18. How long do U-shaped valleys last? The lifespan of glacial topography set by tectonics.

    NASA Astrophysics Data System (ADS)

    Prasicek, Günther; Larsen, Isaac; Montgomery, David

    2015-04-01

    More than 10 kyr after the last major glaciation the topography of mountain ranges world-wide remains dominated by characteristic glacial landforms such as U-shaped valleys, but the transition from a glacial to a fluvial landscape is poorly constrained and it remains unclear how long glacial morphology persists following deglaciation. The longevity of glacial topography influences glacial extent and erosion in subsequent glaciations and hence the cumulative impact of Pleistocene glacial cycles on the evolution of mountain ranges. We tested whether tectonic forcing and erosional response control the timescale over which glacial topography persists into inter-glacial periods in the western Southern Alps of New Zealand and other mountain ranges worldwide, including the syntaxes of the Himalaya and Taiwan. We quantified the degree of glacial imprint by exploiting the conventional interpretation of V-shaped fluvial and U-shaped glacial valleys. Valley cross sections were automatically extracted from digital terrain models and power-laws were fitted to each cross section to quantify the shape of the valley flanks. A power-law exponent of 1 characterizes the straight valley flanks of a V-shaped cross section and greater exponents are indicative of progressively more U-shaped valleys. Our results show that tectonic forcing is a first-order control on landscape evolution and on the persistence of glacial morphology worldwide. In Earth's most rapidly uplifting mountain ranges the lifespan of glacial topography is on the order of one interglacial period, preventing the development of a cumulative glacial signal. In contrast, in most alpine landscapes more than 100 kyr are required for the transformation from glacial back to fluvial topography and glacial landforms have not or have only partially been erased during the current interglacial. Thus we suggest, emphasizing the influence of glacially preconditioned topography on glacial extent and erosion, that tectonic forcing

  19. Systematically enhanced subarctic Pacific stratification and nutrient utilization during glacials

    NASA Astrophysics Data System (ADS)

    Knudson, K. P.; Ravelo, A. C.

    2015-12-01

    The modern subarctic North Pacific is characterized as a high-nitrate, low-chlorophyll (HNLC) area, but evidence for increased nutrient utilization during the last glacial indicates that this region is highly dynamic. As such, this HNLC area is of particular interest in regard to understanding changes in the biological pump and carbon sequestration and predicting how biogeochemical processes will influence, or be influenced by, future climate change. While it has been suggested that changes in iron supply and/or ocean stratification could explain fluctuations in nutrient utilization and productivity in the subarctic Pacific, short records of nutrient utilization have previously hindered the evaluation of these potential mechanisms over long timescales. Here we present new, high-resolution records of bulk sediment δ15N from 0-1.2 Ma from Integrated Ocean Drilling Program Exp. 323 Site U1342, which are used to calculate Δδ15N (U1342 δ15Nbulk - ODP Site 1012 δ15Nbulk) as a nitrate utilization proxy. The unprecedented length and resolution of this new record allows us, for the first time, to determine orbital-scale systematic behavior in subarctic Pacific nutrient utilization over many glacial/interglacial cycles. Spectral analyses demonstrate that enhanced nutrient utilization was paced by climate on Milankovitch orbital cycles since the Mid-Pleistocene Transition (MPT; ~800 ka). Nitrate utilization maxima is statistically correlated with glacial maxima and enhanced dust/iron availability (represented by existing records of EPICA ice core dust, Southern Pacific Ocean sediment iron, and China loess) but shows low correlation to primary productivity, suggesting that stratification has systematically exerted an important control on subarctic Pacific nutrient utilization since the MPT. These findings imply that the presence of iron helped to change the region into a nitrate-limited, rather than iron-limited, region during glacials and that stratification, which

  20. Climatic Instability and Regional Glacial Advances in the Late Ediacaran

    NASA Astrophysics Data System (ADS)

    Hannah, J. L.; Stein, H. J.; Marolf, N.; Bingen, B.

    2014-12-01

    The Ediacaran Period closed out the environmentally raucous Neoproterozoic Era with the last of multiple glacial events and the first ephemeral glimmer of multicellular life. As such, evolution of Earth's biosphere and the marine environments that nurtured this nascent biota are of particular interest. Because the Ediacaran biota appear in the stratigraphic record just above tillites in many localities, inferences are naturally drawn to link glaciation to bioevolution. Here we review known controls on the timing and extent of the late Ediacaran Gaskier and Varanger glacial events, bolstered by new constraints on the Moelv tillite of South Norway. The elusive mid-Ediacaran glacial strata are poorly dated, patchy in distribution, and relatively limited in thickness. The type Gaskier glaciogenic units in Newfoundland are 582 to 584 Ma, based on U-Pb zircon ages from intercalated ash beds [1]. The Varanger glaciogenic deposits in northern Norway, in contrast, remain only roughly constrained to ca. 630 to 560 Ma. Post-Gaskier negative carbon isotope excursions (CIEs) have been reported from multiple localities in both China and SW United States, suggesting climatic instability in the late Ediacaran. Although most localities lack solid geochronology, paleontologic constraints place the Hongtiegou glacial diamictite and accompanying CIE in the Chaidam Basin, NW China, in the latest Ediacaran, ca. 555 Ma [2]. We previously suggested that the Moelv tillite in south Norway was roughly equivalent to the Gaskier, based on an imprecise Re-Os age of ~560 Ma [3] for the underlying Biri shale. Reanalysis of these data shows that the upper part of the shale section was disturbed by a redox front during the Caledonian orogeny. The undisturbed lower part of the section yields a more precise Model 1 isochron age of 559.5 ± 6.2 Ma, clearly post-dating the Gaskier event well outside analytical uncertainty. These new results bolster arguments that the Gaskier glaciation was not a global

  1. Reconstruction of full glacial environments and summer temperatures from Lago della Costa, a refugial site in Northern Italy

    NASA Astrophysics Data System (ADS)

    Samartin, Stéphanie; Heiri, Oliver; Kaltenrieder, Petra; Kühl, Norbert; Tinner, Willy

    2016-07-01

    Vegetation and climate during the last ice age and the Last Glacial Maximum (LGM, ∼23,000-19,000 cal BP) were considerably different than during the current interglacial (Holocene). Cold climatic conditions and growing ice-sheets during the last glaciation radically reduced forest extent in Europe to a restricted number of so-called ;refugia;, mostly located in the southern part of the continent. On the basis of paleobotanical analyses the Euganian Hills (Colli Euganei) in northeastern Italy have previously been proposed as one of the northernmost refugia of temperate trees (e.g. deciduous Quercus, Tilia, Ulmus, Fraxinus excelsior, Acer, Abies alba, Fagus sylvatica, Carpinus and Castanea) in Europe. In this study we provide the first quantitative, vegetation independent summer air temperature reconstruction for Northern Italy spanning the time ∼31,000-17,000 cal yr BP, which covers the coldest periods of the last glacial, including the LGM and Heinrich stadials 1 to 3. Chironomids preserved in a lake sediment core from Lago della Costa (7m a.s.l.), a small lake at the south-eastern edge of the Euganean Hills, allowed quantitative reconstruction of Full and Late Glacial summer air temperatures using a combined Swiss-Norwegian temperature inference model based on chironomid assemblages from 274 lakes. Chironomid and pollen evidence from Lago della Costa derives from finely stratified autochthonous organic gyttja sediments, which excludes major sediment mixing or reworking. After reconstructing paleo-temperatures, we address the question whether climate conditions were warm enough to permit the local survival of temperate tree species during the LGM and whether local expansions and pollen-inferred contractions of temperate tree taxa coincided with chironomid-inferred climatic changes. Our results suggest that chironomids at Lago della Costa have responded to major climatic fluctuations such as temperature decreases during the LGM and Heinrich stadials. The

  2. The Inference of Gene Trees with Species Trees

    PubMed Central

    Szöllősi, Gergely J.; Tannier, Eric; Daubin, Vincent; Boussau, Bastien

    2015-01-01

    This article reviews the various models that have been used to describe the relationships between gene trees and species trees. Molecular phylogeny has focused mainly on improving models for the reconstruction of gene trees based on sequence alignments. Yet, most phylogeneticists seek to reveal the history of species. Although the histories of genes and species are tightly linked, they are seldom identical, because genes duplicate, are lost or horizontally transferred, and because alleles can coexist in populations for periods that may span several speciation events. Building models describing the relationship between gene and species trees can thus improve the reconstruction of gene trees when a species tree is known, and vice versa. Several approaches have been proposed to solve the problem in one direction or the other, but in general neither gene trees nor species trees are known. Only a few studies have attempted to jointly infer gene trees and species trees. These models account for gene duplication and loss, transfer or incomplete lineage sorting. Some of them consider several types of events together, but none exists currently that considers the full repertoire of processes that generate gene trees along the species tree. Simulations as well as empirical studies on genomic data show that combining gene tree–species tree models with models of sequence evolution improves gene tree reconstruction. In turn, these better gene trees provide a more reliable basis for studying genome evolution or reconstructing ancestral chromosomes and ancestral gene sequences. We predict that gene tree–species tree methods that can deal with genomic data sets will be instrumental to advancing our understanding of genomic evolution. PMID:25070970

  3. Executive dysfunction and autobiographical memory retrieval in recovered depressed women☆

    PubMed Central

    Haddad, Anneke D.M.; Harmer, Catherine J.; Williams, J. Mark G.

    2014-01-01

    Background and objectives Depressed individuals have difficulty remembering specific autobiographical events. These deficits often persist after recovery of mood symptoms, but the mechanisms underlying impaired memory specificity in recovered depressed individuals remain unclear. Here, we sought to examine whether performance on two cognitive measures might be related to deficits in autobiographical memory retrieval in individuals with a history of depression. Methods Twenty-four recovered depressed women (12 with more than one previous episode) and 24 never depressed women completed two cognitive measures (Digit Span and a Number Generation Task) and tests of autobiographical memory recall. Results Overall, the recovered depressed women did not show deficits in autobiographical retrieval. However, those with more than one previous episode had impaired retrieval of categorical autobiographical memories. Moreover, depression history moderated the relationship between Digit Span and retrieval of categoric autobiographical memories such that within the whole recovered depressed group (but not the never depressed group), those with lower Digit Span also had poorer retrieval of categorical autobiographical memories. Limitations Our sample size was small and included only women. Moreover, order effects may have been a significant factor. Conclusions These findings support the notion that working memory is an important factor in impairing autobiographical memory in those who have recovered from depression, but suggest a complex relationship with autobiographical recall. PMID:24374578

  4. Modelling of Gas Hydrate Dissociation During The Glacial-Inter-glacial Cycles, Case Study The Chatham Rise, New Zealand

    NASA Astrophysics Data System (ADS)

    Oluwunmi, P.; Pecher, I. A.; Archer, R.; Moridis, G. J.; Reagan, M. T.

    2015-12-01

    Seafloor depressions covering an area of >20,000 km2 on the Chatham Rise, south east of New Zealand, have been interpreted as pockmarks which are related to past fluid releases. It is proposed that the seafloor depressions were caused by sudden escape of overpressured gas generated by gas hydrate dissociation during glacial sea-level lowering. We are attempting to simulate the evolution of the gas hydrate system through glacial-interglacial cycles in the study area using TOUGH-Hydrate. The Chatham Rise offers a unique opportunity for studying the effect of depressurization from sealevel lowering to gas hydrate systems because it is a bathymetric barrier preventing the Subtropical Front separating subtropical and subantarctic waters from migrating during glacial-interglacial cycles. Hence, bottom-water temperatures can be assumed to remain constant. Recent results from paleoceanographic studies however, indicate that bottom-temperature may have varied locally. These temperature changes may have a more significant effect on the shallow gas hydrate system in the study area than the relatively gradual decrease of pressure associated with sealevel lowering.

  5. Prolonged Soil Frost Affects Hydraulics and Phenology of Apple Trees

    PubMed Central

    Beikircher, Barbara; Mittmann, Claudia; Mayr, Stefan

    2016-01-01

    Restoration of an adequate water supply in spring is a prerequisite for survival of angiosperm trees in temperate regions. Trees must re-establish access to soil water and recover xylem functionality. We thus hypothesized that prolonged soil frost impairs recovery and affects hydraulics and phenology of Malus domestica var. ‘Golden Delicious.’ To test this hypothesis, over two consecutive winters the soil around some trees was insulated to prolong soil frosting, From mid-winter to early summer, the level of native embolism, the water and starch contents of wood, bark and buds were quantified at regular intervals and findings correlated with various phenological parameters, xylogenesis and fine root growth. The findings confirm that prolonged soil frost affects tree hydraulics and phenology but the severity of the effect depends on the climatic conditions. In both study years, percentage loss of hydraulic conductivity (PLC) decreased from about 70% at the end of winter to about 10% in May. Thereby, xylem refilling strongly coincided with a decrease of starch in wood and bark. Also treated trees were able to restore their hydraulic system by May but, in the warm spring of 2012, xylem refilling, the increases in water content and starch depolymerization were delayed. In contrast, in the cold spring of 2013 only small differences between control and treated trees were observed. Prolongation of soil frost also led to a delay in phenology, xylogenesis, and fine root growth. We conclude that reduced water uptake from frozen or cold soils impairs refilling and thus negatively impacts tree hydraulics and growth of apple trees in spring. Under unfavorable circumstances, this may cause severe winter damage or even dieback. PMID:27379146

  6. Prolonged Soil Frost Affects Hydraulics and Phenology of Apple Trees.

    PubMed

    Beikircher, Barbara; Mittmann, Claudia; Mayr, Stefan

    2016-01-01

    Restoration of an adequate water supply in spring is a prerequisite for survival of angiosperm trees in temperate regions. Trees must re-establish access to soil water and recover xylem functionality. We thus hypothesized that prolonged soil frost impairs recovery and affects hydraulics and phenology of Malus domestica var. 'Golden Delicious.' To test this hypothesis, over two consecutive winters the soil around some trees was insulated to prolong soil frosting, From mid-winter to early summer, the level of native embolism, the water and starch contents of wood, bark and buds were quantified at regular intervals and findings correlated with various phenological parameters, xylogenesis and fine root growth. The findings confirm that prolonged soil frost affects tree hydraulics and phenology but the severity of the effect depends on the climatic conditions. In both study years, percentage loss of hydraulic conductivity (PLC) decreased from about 70% at the end of winter to about 10% in May. Thereby, xylem refilling strongly coincided with a decrease of starch in wood and bark. Also treated trees were able to restore their hydraulic system by May but, in the warm spring of 2012, xylem refilling, the increases in water content and starch depolymerization were delayed. In contrast, in the cold spring of 2013 only small differences between control and treated trees were observed. Prolongation of soil frost also led to a delay in phenology, xylogenesis, and fine root growth. We conclude that reduced water uptake from frozen or cold soils impairs refilling and thus negatively impacts tree hydraulics and growth of apple trees in spring. Under unfavorable circumstances, this may cause severe winter damage or even dieback.

  7. A high resolution Late Glacial to Holocene record of climatic and environmental change in the Mediterranean from Lake Ohrid (Macedonia/Albania)

    NASA Astrophysics Data System (ADS)

    Lacey, Jack; Francke, Alexander; Leng, Melanie; Vane, Chris; Wagner, Bernd

    2015-04-01

    Lake Ohrid (Macedonia/Albania) is one of the world's oldest lakes and is renowned for its high degree of biological diversity. It is the target site for the ICDP SCOPSCO (Scientific Collaboration on Past Speciation Conditions in Lake Ohrid) project, an international research initiative to study the links between geology, environment and the evolution of endemic taxa. In 2011 a 10-meter core was recovered from the western shore of Lake Ohrid adjacent to the Lini Peninsula. Here we present high-resolution stable isotope and geochemical data from this core through the Late Glacial to Holocene to reconstruct past climate and hydrology (TIC, δ18Ocalcite, δ13Ccalcite) as well as the terrestrial and aquatic vegetation response to climate (TOC, TOC/N, δ13Corganic, Rock-Eval pyrolysis). The data identify 3 main zones: (1) the Late Glacial-Holocene transition represented by low TIC, TOC and higher isotope values, (2) the early to mid-Holocene characterised by higher TOC, TOC/N and lower δ18Ocalcite, and (3) the late Holocene which shows a marked decrease in TIC and TOC. In general there is an overall trend of increasing δ18Ocalcite from 9 ka to present, suggesting progressive aridification through the Holocene, which is consistent with previous records from Lake Ohrid and the wider Mediterranean region. Several proxies show commensurate excursions that imply the impact of short-term climate oscillations, such as the 8.2 ka event and the Little Ice Age. This is the best-dated and highest resolution archive of Late Glacial and Holocene climate from Lake Ohrid and confirms the overriding influence of the North Atlantic in the north-eastern Mediterranean. The data presented set the context for the SCOPSCO project cores recovered in spring-summer 2013 dating back into the Lower Pleistocene, and will act as a recent calibration to reconstruct climate and hydrology over the entire lake history.

  8. Vegetation, climate and fire-dynamics in East Africa inferred from the Maundi crater pollen record from Mt Kilimanjaro during the last glacial-interglacial cycle

    NASA Astrophysics Data System (ADS)

    Schüler, Lisa; Hemp, Andreas; Zech, Wolfgang; Behling, Hermann

    2012-04-01

    The pollen, charcoal and sedimentological record from the Maundi crater, located at 2780 m elevation on the south-eastern slope of Mt Kilimanjaro, is one of the longest terrestrial records in equatorial East Africa, giving an interesting insight into the vegetation and climate dynamics back to the early last Glacial period. Our sediment record has a reliable chronology until 42 ka BP. An extrapolation of the age-depth model, as well as matching with other palaeo-records from tropical East Africa, suggest a total age of about 90 ka BP at the bottom of the record. During the last Glacial the distribution as well as the composition of the vegetation belts classified as colline savanna, submontane woodland, montane forest, ericaceous belt, and alpine vegetation changed. The early last Glacial is characterized by high amounts of Poaceae and Asteraceae pollen suggesting a climatically dry but stable phase. Based on the absence of pollen grains in samples deposited around 70 ka BP, we assume the occurrence of distinct drought periods. During the pre-LGM (Last Glacial Maximum) a higher taxa diversity of the ericaceous and montane zone is recorded and suggests a spread of forest and shrub vegetation, thus indicating a more humid period. The taxa diversity increases steadily during the recorded time span. The decent of vegetation zones indicate dry and cold conditions during the LGM and seem to have been detrimental for many taxa, especially those of the forest vegetation; however, the early last Glacial seems to have been markedly drier than the LGM. The reappearance of most of the taxa (most importantly Alchemilla, Araliaceae, Dodonea, Hagenia, Ilex, Myrsine, Moraceae, Piperaceae) during the deglacial and Holocene period suggest a shift into humid conditions. An increase in ferns and the decrease in grasses during the Holocene also indicate increasing humidity. Fire played an important role in controlling the development and elevation of the ericaceous zone and the tree

  9. A Universal Phylogenetic Tree.

    ERIC Educational Resources Information Center

    Offner, Susan

    2001-01-01

    Presents a universal phylogenetic tree suitable for use in high school and college-level biology classrooms. Illustrates the antiquity of life and that all life is related, even if it dates back 3.5 billion years. Reflects important evolutionary relationships and provides an exciting way to learn about the history of life. (SAH)

  10. Tree-Ties.

    ERIC Educational Resources Information Center

    Gresczyk, Rick

    Created to help students understand how plants were used for food, for medicine, and for arts and crafts among the Ojibwe (Chippewa) Indians, the game Tree-Ties combines earth and social sciences within a specific culture. The game requires mutual respect, understanding, and agreement to succeed. Sounding like the word "treaties", the…

  11. Christmas Tree Category Manual.

    ERIC Educational Resources Information Center

    Bowman, James S.; Turmel, Jon P.

    This manual provides information needed to meet the standards for pesticide applicator certification. Pests and diseases of christmas tree plantations are identified and discussed. Section one deals with weeds and woody plants and the application, formulation and effects of herbicides in controlling them. Section two discusses specific diseases…

  12. Digging Deeper with Trees.

    ERIC Educational Resources Information Center

    Growing Ideas, 2001

    2001-01-01

    Describes hands-on science areas that focus on trees. A project on leaf pigmentation involves putting crushed leaves in a test tube with solvent acetone to dissolve pigment. In another project, students learn taxonomy by sorting and classifying leaves based on observable characteristics. Includes a language arts connection. (PVD)

  13. Phylogenics & Tree-Thinking

    ERIC Educational Resources Information Center

    Baum, David A.; Offner, Susan

    2008-01-01

    Phylogenetic trees, which are depictions of the inferred evolutionary relationships among a set of species, now permeate almost all branches of biology and are appearing in increasing numbers in biology textbooks. While few state standards explicitly require knowledge of phylogenetics, most require some knowledge of evolutionary biology, and many…

  14. The Sacred Tree.

    ERIC Educational Resources Information Center

    Lethbridge Univ. (Alberta).

    Designed as a text for high school students and adults, this illustrated book presents ethical concepts and teachings of Native societies throughout North America concerning the nature and possibilities of human existence. The final component of a course in self-discovery and development, the book begins with the legend of the "Sacred Tree"…

  15. Glacial interglacial cycles and development of the Afroalpine ecosystem on East African Mountains II. Origins and development of the biotic component

    NASA Astrophysics Data System (ADS)

    Harmsen, R.; Spence, J. R.; Mahaney, W. C.

    The development of the Afroalpine ecosystem as found on a number of isolated mountains in East Africa has a physical component and a biological component which is to a large degree dependent on the physical environment. The origins of the Afroalpine biota are predominantly African-tropical or Palearctic with smaller contributions from South Africa and other more distant sources. Once the ecosystem was established, dispersal from one mountain to others became a main source of increasing complexity. Ecological succession and evolutionary development from simple random assemblages of early invading species on unmodified substrates to complex interactive communities forming a closely integrated biosphere would have been the next stage in the development of the Afroalpine ecosystem. However, glacial interglacial cycles throughout the Pleistocene may have seriously curtailed this process. Detailed on early succession on Neoglacial tills on Mount Kenya supply a reasonable model for the larger scale recolonization of the upper reaches of the mountain following each glacial, and palynological evidence supplies a fairly accurate picture of the lower altitude glacial Afroalpine communities. Yet, our knowledge of the structure of the Afroalpine ecosystem during past glacials and interglacials is far too sketchy to be able to say how severe the effects of the climatic oscillations were on the development and maintenance of the Afroalpine ecosystem. Current conditions indicate a long history (c 2-3 mil yrs) of adaptation to above tree-line conditions for some organisms, but the entire ecosystem is still very young and will probably never be able to reach a successional or evolutionary equilibrium in the unstable climatic conditions of the Afroalpine environment.

  16. An Efficient Algorithm for Gene/Species Trees Parsimonious Reconciliation with Losses, Duplications and Transfers

    NASA Astrophysics Data System (ADS)

    Doyon, Jean-Philippe; Scornavacca, Celine; Gorbunov, K. Yu.; Szöllősi, Gergely J.; Ranwez, Vincent; Berry, Vincent

    Tree reconciliation methods aim at estimating the evolutionary events that cause discrepancy between gene trees and species trees. We provide a discrete computational model that considers duplications, transfers and losses of genes. The model yields a fast and exact algorithm to infer time consistent and most parsimonious reconciliations. Then we study the conditions under which parsimony is able to accurately infer such events. Overall, it performs well even under realistic rates, transfers being in general less accurately recovered than duplications. An implementation is freely available at http://www.atgc-montpellier.fr/MPR.

  17. Linking glacial melting to Late Quaternary sedimentation in climatically sensitive mountainous catchments of the Mount Chlemos compex, Kalavryta, southern Greece

    NASA Astrophysics Data System (ADS)

    Pope, Richard; Hughes, Philip

    2014-05-01

    Compared to the mountainous areas of northern Greece (e.g. Woodward et al., 2008), the influence of deglaciation cycles on sedimentation in mountainous catchments in southern Greece remains poorly understood due to the poor preservation of small moraines and limited opportunities to date glacial and fluvial sediment dynamics fluvial sediments (Pope, unpublished data). Nevertheless, intriguing new insight into links between glacial cycles and sediment transfer/deposition phases in upland catchments have emerged by applying multiple dating techniques to well-preserved multiple generations of moraines and extensive glacio-fluvial fan systems on Mount Chelmos (2355 m a.s.l.). U-series dating of calcites within proximal fan sediments constrain the earliest phase of glacio-fluvial sedimentation to 490 (±21.0)(ka (MIS 12), while OSL dating of fine sands constrains the deposition of extensive medial glacio-fluvial gravels in (valley we walked down through trees) to between 250.99 (±20.67) and 160.82 (±11.08) ka. By comparison, cosmogenic dating of moraine boulders indicates that three generations of well-preserved moraines in the highest cirque areas date to 31-23 ka, 17-16 ka and 12-11.5 ka. OSL dating also provides ages of 18 and 17 (±11.08) for an extensive glacio-fluvial terrace in a major valley draining the southern flanksof Mount Chelmos. The initial Mount Chelmos geochronology suggests that the earliest and middle phases of glacio-fluvial sedimentation are coincident with the Middle Pleistocene glacial stages stages recorded in the Pindus range (Hughes et al, 2006). These include the Skamnellian (MIS 12) and the Vlasian (MIS 6) Stages as well as other cold stage between these (e.g. MIS 8).Evidence of glacio-fluvial outwash in MIS 8 is interesting since evidence for this in the moraine records has remained elusive although is suggested further north in the Balkans (Hughes et al., 2011). The valley moraines and glacio-fluvial terraces (late MIS 2) post-date the

  18. Recovering pointwise values of discontinuous data within spectral accuracy

    NASA Technical Reports Server (NTRS)

    Gottlieb, D.; Tadmor, E.

    1985-01-01

    The pointwise values of a function, f(x), can be accurately recovered either from its spectral or pseudospectral approximations, so that the accuracy solely depends on the local smoothness of f in the neighborhood of the point x. Most notably, given the equidistant function grid values, its intermediate point values are recovered within spectral accuracy, despite the possible presence of discontinuities scattered in the domain. (Recall that the usual spectral convergence rate decelerates otherwise to first order, throughout). To this end, a highly oscillatory smoothing kernel is employed in contrast to the more standard positive unit-mass mollifiers. In particular, post-processing of a stable Fourier method applied to hyperbolic equations with discontinuous data, recovers the exact solution modulo a spectrally small error. Numerical examples are presented.

  19. Presentation video retrieval using automatically recovered slide and spoken text

    NASA Astrophysics Data System (ADS)

    Cooper, Matthew

    2013-03-01

    Video is becoming a prevalent medium for e-learning. Lecture videos contain text information in both the presentation slides and lecturer's speech. This paper examines the relative utility of automatically recovered text from these sources for lecture video retrieval. To extract the visual information, we automatically detect slides within the videos and apply optical character recognition to obtain their text. Automatic speech recognition is used similarly to extract spoken text from the recorded audio. We perform controlled experiments with manually created ground truth for both the slide and spoken text from more than 60 hours of lecture video. We compare the automatically extracted slide and spoken text in terms of accuracy relative to ground truth, overlap with one another, and utility for video retrieval. Results reveal that automatically recovered slide text and spoken text contain different content with varying error profiles. Experiments demonstrate that automatically extracted slide text enables higher precision video retrieval than automatically recovered spoken text.

  20. Method of recovering oil-based fluid and apparatus

    SciTech Connect

    Brinkley, H.E.

    1993-07-20

    A method is described for recovering oil-based fluid from a surface having oil-based fluid thereon comprising the steps of: applying to the oil-based fluid on the surface an oil-based fluid absorbent cloth of man-made fibers, the cloth having at least one napped surface that defines voids therein, the nap being formed of raised ends or loops of the fibers; absorbing, with the cloth, oil-based fluid; feeding the cloth having absorbed oil-based fluid to a means for applying a force to the cloth to recover oil-based fluid; and applying force to the cloth to recover oil-based fluid therefrom using the force applying means.

  1. Isolation and characterization of Cryptococcus neoformans varieties recovered from natural sources in Bogotá, Colombia, and study of ecological conditions in the area.

    PubMed

    Granados, D P; Castañeda, E

    2005-02-01

    Cryptococcus neoformans, the etiological agent of cryptococcosis, has been associated with avian droppings and certain trees in different countries, including Colombia. C neoformans environmental isolates were obtained in urban areas in Bogotá, Colombia, and the strains recovered were phenotypically characterized. Attempts to determine the ecological conditions (micro- and macroclimatic) possibly related to their habitat were also undertaken. Four hundred and eighty samples from bark, soil around trunk bases, and detritus inside hollows of 32 trees were collected in three urban areas during a 5-month period, as well as 89 avian droppings samples from different places. Of plant samples, 6.7% collected from nine tree species yielded C. neoformans var. gattii, serotype B strains in 99% of the cases, and C. neoformans var. grubii, serotype A in 1%. The yeast was more frequently recovered from bark than from soil or detritus inside hollows, and from trees with hollows or rotted wood rather than from trees in which birds nest. C. neoformans was present with higher frequency and density in the rainy season than in the dry season; we found that slightly higher temperature and humidity values of the microhabitat, as compared to those of the environment, favored fungal occurrence, but the phenological state of the tree did not. Of dropping samples, 7.9% yielded C. neoformans strains, all of them C. neoformans var. grubii, serotype A. The yeast was obtained more frequently from dry droppings than from moist ones, but neither the sunlight exposure nor the site of collection of samples was correlated with this occurrence. Population density was significantly higher in droppings than in tree samples. Under laboratory conditions, isolates of different serotype showed similar capsular sizes. Water content and pH ranges were wide and did not show any significant difference between positive and negative samples.

  2. Glacial to paraglacial history and forest recovery in the Oglio glacier system (Italian Alps) between 26 and 15 ka cal BP

    NASA Astrophysics Data System (ADS)

    Ravazzi, Cesare; Badino, Federica; Marsetti, Diego; Patera, Glauco; Reimer, Paula J.

    2012-12-01

    The integrated stratigraphic, radiocarbon and palynological record from an end-moraine system of the Oglio valley glacier (Italian Alps), propagating a lobe upstream in a lateral reach, provided evidence for a complete cycle of glacial advance, culmination and withdrawal during the Last Glacial Maximum and early Lateglacial. The glacier culminated in the end moraine shortly after 25.8 ± 0.8 ka cal BP, and cleared the valley floor 18.3-17.2 ± 0.3 ka cal BP. A primary paraglacial phase is then recorded by fast progradation of the valley floor. As early as 16.7 ± 0.3 ka cal BP, early stabilization of alluvial fans and lake filling promoted expansion of cembran pine. This is an unprecedented evidence of direct tree response to depletion of paraglacial activity during the early Lateglacial, and also documents the cembran pine survival in the mountain belt of the Italian Alps during the last glaciation. Between 16.1 and 14.6 ± 0.5 ka cal BP, debris cones emplacement points to a moisture increase favouring tree Betula and Pinus sylvestris-mugo. A climate perturbation renewed paraglacial activity. According to cosmogenic ages on glacial deposits and AMS radiocarbon ages from lake records in South-Eastern Alps such phase compares favourably with the Gschnitz stadial and with the oscillations recorded at lakes Ragogna, Längsee and Jeserzersee, most probably forced by the latest freshening phases of the Heinrich Event 1. A further sharp pine rise marks the subsequent onset of Bølling interstadial. The chronology of the Oglio glacier compares closely with major piedmont glaciers on the Central and Eastern Alpine forelands. On the other hand, the results of the present study imply a chronostratigraphic re-assessment of the recent geological mapping of the Central Italian Alps.

  3. Timing the last interglacial-glacial transition in glacial sedimentary sequences of the Hudson Bay lowlands (Canada)

    NASA Astrophysics Data System (ADS)

    Roy, M.; Allard, G.; Ghaleb, B.; Lamothe, M.

    2010-12-01

    Paleoclimate records (oxygen isotopes and speleothems) indicate that the onset of the last glacial cycle was characterized by rapid and large-scale growth of continental ice sheets. The timing of the inception of the Laurentide ice sheet (LIS) and its subsequent evolution (extent) remain, however, largely unconstrained. The depositional record of the Hudson Bay Lowlands (HBL) is of particular interest to these issues because this region is located near the former geographic center of the LIS. The presence of nonglacial deposits in HBL glacial sedimentary sequences thus implies drastic changes in ice sheet configuration, but constraining these ice volume changes through absolute dating of nonglacial sediments has been so far inconclusive. Here we use radiocarbon, U-series, and optical stimulated luminescence (OSL) methods to constrain the age of an extensive nonglacial unit containing abundant wood fragments enclosed in compacted clay lying below several meters of glacial deposits along the Nottaway River, in the southeastern sector of the HBL. This region is particularly interesting because it lies near one of the inception centers of the LIS. Radiocarbon dating of a wood fragment yielded a nonfinite 14C age of >55.2 ka, in agreement with similar dating attempts throughout the HBL. Measurements of U and Th concentrations and isotope ratios on fossil wood samples revealed consistent 230Th/U ages, indicating that the wood fragments were subject to a single episode of uranium uptake, with apparently no subsequent disturbance of the geochemical system. Despite mechanical cleaning of the wood outer surfaces, non-authigenic 230Th was found in most samples and correction for this detrital contamination yielded an isochron age of 106.8 (+12.3, -10.3) ka, which represents a minimum age for this unit. The 230Th/U age constraint is nonetheless supported by a series of OSL ages obtained for the overlying fluvial sands, thereby assigning the Nottaway nonglacial unit to the end

  4. Unexpected spontaneous ignition of Late Glacial sediments from the palaeolake Wukenfurche (NE Germany)

    NASA Astrophysics Data System (ADS)

    Dräger, Nadine; Brademann, Brian; Theuerkauf, Martin; Wulf, Sabine; Tjallingii, Rik; Słowiński, Michał; Schlaak, Norbert; Błaszkiewicz, Mirosław; Brauer, Achim

    2015-04-01

    A new finely laminated sediment archive has been recovered from the palaeolake Wukenfurche, NE Germany, comprising the last Glacial to Interglacial transition. The site is located within the Eberswalde ice-marginal valley and south of the terminal moraine that was formed during the Pomeranian phase of the Weichselian glaciation. Two sediment cores were obtained from the presently swampy area in July 2014. From these individual profiles a 14.7 m long continuous composite profile has been compiled by correlation of distinct marker layers. Glacial sand deposits covered by basal peat are found at the base of the cores. A visible volcanic ash layer 6 cm above the transition from basal peat into the overlaying finely laminated lake sediments corresponds most likely to the late Allerød Laacher See Tephra (LST). Preliminary counting on core photographs of the 3.5 m thick package of reddish and black alternating laminae above the LST yields a total of ca. 2500 layer couplets. Further micro-facies analyses on large-scale thin sections will be applied to test if these couplets are of annual origin (i.e. varves). Standard preparation for large-scale thin sections involves freeze-drying (for 48 hours) of 10 cm-long sediment slabs stored in aluminum boxes. Immediately after releasing the vacuum of the freeze-dryer chamber we observed an unexpected spontaneous combustion of the sediment from a particular interval of the profile. The exothermic combustion process lasted for approximately 10 to 20 minutes during which temperatures of up to 350°C have been measured with an infrared camera. Preliminary results suggest that oxidation of iron sulfides contributes to the observed reaction. To our knowledge this is the first time that such spontaneous combustion of lake sediments after freeze-drying has been observed. Details of the combustion process and sediment characteristics will be provided. This study is a contribution to the Virtual Institute of Integrated Climate and Landscape

  5. Are Physical Properties Able to Differentiate Glacial and Interglacial Coral Identity?

    NASA Astrophysics Data System (ADS)

    Lado-Insua, T.; Moran, K.; Anderson, L.; Webster, J. M.; Morgan, S.; Fehr, A.; Lofi, J.; Lukies, V.; Loggia, D.; Iodp Expedition 325 Scientists

    2010-12-01

    The Integrated Ocean Drilling Program Expedition 325 to the Great Barrier Reef provides new information on past sea-level changes and better understanding of mechanisms driving glacial-interglacial cycles. Coral samples recovered during this expedition provide a deeper understanding of coral reef responses to environmental stresses. Inter- and intra-specific differences, growth rates, coral health, symbiotic algae and environmental conditions are all potential causes of differences in the density of coral skeletons and their distribution. Past changes in sea level and temperature can be related not only to isotope ratios but also to the presence of different communities of corals. Density changes in the coral composition can be detected using physical properties such as an increase in the calcium carbonate of a sample. De’ath et al. (2009) reported severe and sudden recent declines in calcification in Porites spp. corals in the Great Barrier Reef in the present that have not been observed over at least the last 400 years, and they attributed the decrease in calcification to changes in sea level, sea surface temperature (SST) and saturation of aragonite in the water column, all of which can limit the capacity of the corals to precipitate calcium carbonate. Variation in Sr/Ca can be related to SST, but different strains of symbiotic algae in the corals’ tissues can also be an important factor affecting skeletal Sr/Ca ratios. Such changes have never been tracked during previous glaciations, but the samples from Expedition 325 give the opportunity to explore their values during and since the last glacial maximum. Physical properties such as gamma ray density, electrical resistivity, and acoustic p-wave velocity can be related to characteristics of the marine sediments that, in turn, are indicative of the depositional environments. We performed a multivariate analysis that relates physical characteristics measured with a multi-sensor core logger (MSCL) and downhole

  6. Chloroplast DNA diversity of the dioecious European tree Ilex aquifolium L. (English holly).

    PubMed

    Rendell, S; Ennos, R A

    2003-10-01

    Variation in the chloroplast genome of Ilex aquifolium (English holly), a dioecious evergreen tree native to south, west and central Europe, was analysed using polymerase chain reaction-restriction fragment length polymorphisms (PCR-RFLPs) and microsatellites. Differentiation between populations was high (GST = 0.595) and evidence for phylogeographical structure was detected (NST = 0.697, significantly higher than GST). Two chloroplast lineages were inferred originating from putative glacial refugia in southern Europe (Iberia, Italy and possibly the Balkans). The GST value was higher than reported for endozoochorous hermaphrodite species and for anemochorous dioecious species investigated over a similar geographical scale. It appears that dioecy has contributed to strong differentiation between refugia and that this has been maintained following postglacial recolonization as a result of limited seed flow. Palynological records for I. aquifolium are poor, thus these results give an important insight into patterns of glacial isolation and postglacial recolonization of this species.

  7. Mechanisms of Recovering Low Cycle Fatigue Damage in Incoloy 901.

    DTIC Science & Technology

    1979-01-01

    Quality at Less Cost," Metals Prog. 106/2, 80-82 (July 1974). 20. D. Raynor and J. M. Silcock, "Strengthening Mechanisms in Gamma -Prime Precipitating...Z AO-A107 255 AIR FORCE INST OF TLCH WRIGHT-PATTERSON AFB OH F/A Il/A MECHANISMS OF RECOVERING LOW CYCLE FATIGUE OAMAGE IN INCOLOY 90-ETC(U) 1979 R E... MECHANISMS OF RECOVERING LOW CYCLE FATIGUE DAMAGE IN INCOLOY 901 Robert E. Schafrik, Capt. USAF (Ph.D.) The Ohio State University, 1979 Professor James A

  8. Susceptible-infected-recovered model with recurrent infection

    NASA Astrophysics Data System (ADS)

    Ruziska, Flávia M.; Tomé, Tânia; de Oliveira, Mário J.

    2017-02-01

    We analyze a stochastic lattice model describing the spreading of a disease among a community composed by susceptible, infected and removed individuals. A susceptible individual becomes infected catalytically. An infected individual may, spontaneously, either become recovered, that is, acquire a permanent immunization, or become again susceptible. The critical properties including the phase diagram is obtained by means of mean-field theories as well as numerical simulations. The model is found to belong to the universality class of dynamic percolation except when the recovering rate vanishes in which case the model belongs to the directed percolation universality class.

  9. The stratotype and facies of the glacial Lower Vendian Nichatka Formation, Chara River basin, Central Siberia

    NASA Astrophysics Data System (ADS)

    Chumakov, N. M.; Kernitskii, V. V.

    2016-07-01

    Sediments of the Nichatka Formation are facially studied and thoroughly described, the sections are correlated, and the subformations are recognized. The formation represents a key stratigraphic unit to reveal the origin of the Central Siberian glacial horizon and to correlate it with glacial horizons in other regions of the world, namely, with the Laplandian Horizon of the Lower Vendian, Nantou and Marino tillites, etc. The Nichatka Formation is correlated with the glacial Bolshoi Patom (Dzhemkukan) Formation of the Vendian reference section at the Ura Uplift. Unlike the latter, it is mainly composed of continental glacial deposits and is marked by a complex facies composition. The glacial origin of the Nichatka Formation is reliably determined on the basis of a set of diagnostic characters. This permits a more complete reconstruction of the Early Vendian depositional environments. In addition to typical basal tillites and marginal moraine deposits, the formation includes glaciolacustrine and fluvioglacial sediments along with aquatillites, allotillites, and the glacial fan, including subaqueous, deposits.

  10. Glacial inception during the late Holocene without carbon emissions from early agriculture: lessons from the stage-19 glacial inception

    NASA Astrophysics Data System (ADS)

    He, F.; Vavrus, S. J.; Kutzbach, J. E.; Ruddiman, W. F.; Tzedakis, P. C.

    2013-12-01

    Decreases in orbitally-forced summer insolation along with downward trends in greenhouse gases (GHG) have been precursors to incipient glaciation in the past. In the last several thousand years of the current interglacial, while summer insolation has decreased, there was a reversal of the downward trends in CH4 and CO2 concentration within the Holocene around 5,000 and 7,000 years ago. While the cause of this reversal remains unresolved, a leading hypothesis is Ruddiman's Early Anthropogenic Hypothesis that early agriculture, starting several thousand years ago, caused emissions of GHG large enough to reverse natural downward trends in CO2 and CH4 and kept Earth's climate anomalously warm, with the corollary that this may have prevented incipient glaciation during the late Holocene. Here we use the 1-degree, fully coupled Community Climate System Model version 4 (CCSM4) with climate forcings (orbital parameters and GHG) of a previous glacial inception to investigate whether glacial inception should have occurred prior to the industrial revolution if the concentrations of CH4 and CO2 had followed their natural downward trends throughout the Holocene. Tzedakis et al. [2012] show that for the previous eight interglacials, Stage 11 and Stage 19 are the best analogs of the Holocene because of their low eccentricities, and Stage 19 is a better analog than Stage 11 for the Holocene due to the in-phase relationship between obliquity and precession. Furthermore, their study suggests that 777 ka BP (777,000 years before present) is the timing of glacial inception for Stage 19, based on the occurrence of the earliest bipolar seesaw event associated with glacial melting. Not only do the orbital parameters at 777 ka BP resemble pre-industrial conditions, but the concentrations of CO2 at that time were essentially the same as their expected 'natural' pre-industrial values in the absence of anthropogenic greenhouse emissions. Our multi-millennial coupled CCSM4 simulations show

  11. New Life From Dead Trees

    ERIC Educational Resources Information Center

    DeGraaf, Richard M.

    1978-01-01

    There are numerous bird species that will nest only in dead or dying trees. Current forestry practices include clearing forests of these snags, or dead trees. This practice is driving many species out of the forests. An illustrated example of bird succession in and on a tree is given. (MA)

  12. The Hopi Fruit Tree Book.

    ERIC Educational Resources Information Center

    Nyhuis, Jane

    Referring as often as possible to traditional Hopi practices and to materials readily available on the reservation, the illustrated booklet provides information on the care and maintenance of young fruit trees. An introduction to fruit trees explains the special characteristics of new trees, e.g., grafting, planting pits, and watering. The…

  13. Building up rhetorical structure trees

    SciTech Connect

    Marcu, D.

    1996-12-31

    I use the distinction between the nuclei and the satellites that pertain to discourse relations to introduce a compositionality criterion for discourse trees. I provide a first-order formalization of rhetorical structure trees and, on its basis, I derive an algorithm that constructs all the valid rhetorical trees that can be associated with a given discourse.

  14. The Tree Worker's Manual. [Revised.

    ERIC Educational Resources Information Center

    Lilly, S. J.

    This manual acquaints readers with the general operations of the tree care industry. The manual covers subjects important to a tree worker and serves as a training aid for workers at the entry level as tree care professionals. Each chapter begins with a set of objectives and may include figures, tables, and photographs. Ten chapters are included:…

  15. Our Air: Unfit for Trees.

    ERIC Educational Resources Information Center

    Dochinger, Leon S.

    To help urban, suburban, and rural tree owners know about air pollution's effects on trees and their tolerance and intolerance to pollutants, the USDA Forest Service has prepared this booklet. It answers the following questions about atmospheric pollution: Where does it come from? What can it do to trees? and What can we do about it? In addition,…

  16. Glacial to Holocene climate changes in Easter Island (SE Pacific, 27

    NASA Astrophysics Data System (ADS)

    Sáez, A.; Giralt, S.; Valero-Garcés, B. L.; Moreno, A.; Bao, R.; Pueyo, J. J.; Hernández, A.

    2009-04-01

    Sedimentary architecture and paleoclimate for the last 34 000 cal years BP and human activity during the last 850 years have been reconstructed from the Raraku Lake sediments in Easter Island (SE Pacific, 27°S) using a high-resolution multiproxy study of 8 cores, 36 AMS radiocarbon dates and correlation with previous core studies. The Last Glacial period was characterized by cold and relatively humid conditions between 34 to 28 cal kyr BP. High lake levels and clastic input dominated sedimentation in Raraku Lake and a relatively open forest developed at that time. Between 28 and 17.3 cal kyr BP, including LGM period, colder conditions contributed to a reduction of the tree coverage in the island. The end of Glacial Period occurred at 17.3 cal kyr BP and was characterized by a sharp decrease in lake level conducive to the development of major floods due to the erosion of littoral sediments. The Deglaciation Period (Termination 1) occurred between 17.3 and 12.5 cal kyr BP, characterized by an increase in lake productivity, a decrease in the terrigenous input and a rapid lake level recovery inaugurating a period of intermediate lake levels. During this period, the dominance of algal lamination is interpreted as a warmer climate. The timing and duration of this warming trend in Easter Island broadly agrees with other mid- and low latitude circum South Pacific terrestrial records. The early Holocene was characterized by low lake levels. The lake level dropped during the early Holocene (ca. 9.5 cal kyr BP) and peatbog and shallow lake conditions dominated till mid Holocene, partially caused by the colmatation of the lacustrine basin. During the mid Holocene an intense drought occurred that led to a persistent low water table period, subaerial exposure and erosion of some of the sediments, generating a sedimentary gap in the Raraku sequence, from 4.2 to 0.8 cal kyr BP. The palm deforestation of the Easter Island, attributed to the human colonization at about 850 cal yr

  17. The state and their implication of Himalayan glacial lake changes from satellite observations

    NASA Astrophysics Data System (ADS)

    Nie, Y.; Sheng, Y.; Liu, Q.; Liu, L.; Liu, S.; Zhang, Y.; Song, C.

    2015-12-01

    Glacial lake outburst floods (GLOFs)generally result in catastrophic damages and fatalities. The Himalayas, the world's highest mountains hosting large number of glaciers, have frequently suffered from GLOFs events in the past decades. Climatic warming-induced melting and retreating glaciers make glacial lakes expand obviously and urge the potential risk of GLOFs in Himalayas. However, our knowledge on the state of glacial lakes in the entire Himalayas is still limited. This study conducts a systematically satellite-based inventory to firstly reveal the evolution complex, regional difference and causes of Himalayan glacial lake changes in the whole Himalayas. Hundreds of Landsat images and Google Earth high resolution imagery were employed to extract the extents of glacial lakes at four epochs (circa1990, circa 2000, circa 2005 and circa 2010). Object-oriented mapping method was used to automatically map the lakes. In association with published glacier data (e.g., China Glacier Inventory, Randolph and GLIMS Glacier data), visual inspections and iterative checks for individual lake guarantee the accuracy of our results. This study demonstrates the spatial and topographic distributions, differences, heterogeneity of glacial lake changes and their causes. Our results show that Himalayan glacial lakes present a rapidly expanding state in general. Both disappeared lakes and new-formed lakes were observed, however, pre-existing glacial lakes contributed most to the total areal expansion. Himalayan glacial lakes appeared a clear altitudinal difference between north side and south side of main range. Evolutions of glacial lakes between eastern, western and central Himalaya were different, and the most rapidly expanding areas need to be more concerned. Climatic and geomorphic controls result in the heterogeneity of glacial lake changes. This study will help assess the potential risk of GLOFs and promote the public awareness of glacial disasters in high mountain areas.

  18. Geometric tree kernels: classification of COPD from airway tree geometry.

    PubMed

    Feragen, Aasa; Petersen, Jens; Grimm, Dominik; Dirksen, Asger; Pedersen, Jesper Holst; Borgwardt, Karsten; de Bruijne, Marleen

    2013-01-01

    Methodological contributions: This paper introduces a family of kernels for analyzing (anatomical) trees endowed with vector valued measurements made along the tree. While state-of-the-art graph and tree kernels use combinatorial tree/graph structure with discrete node and edge labels, the kernels presented in this paper can include geometric information such as branch shape, branch radius or other vector valued properties. In addition to being flexible in their ability to model different types of attributes, the presented kernels are computationally efficient and some of them can easily be computed for large datasets (N - 10.000) of trees with 30 - 600 branches. Combining the kernels with standard machine learning tools enables us to analyze the relation between disease and anatomical tree structure and geometry. Experimental results: The kernels are used to compare airway trees segmented from low-dose CT, endowed with branch shape descriptors and airway wall area percentage measurements made along the tree. Using kernelized hypothesis testing we show that the geometric airway trees are significantly differently distributed in patients with Chronic Obstructive Pulmonary Disease (COPD) than in healthy individuals. The geometric tree kernels also give a significant increase in the classification accuracy of COPD from geometric tree structure endowed with airway wall thickness measurements in comparison with state-of-the-art methods, giving further insight into the relationship between airway wall thickness and COPD. Software: Software for computing kernels and statistical tests is available at http://image.diku.dk/aasa/software.php.

  19. Eucalyptus Tree: A Potential Source of Cryptococcus neoformans in Egyptian Environment

    PubMed Central

    Hamza, Dalia; Elhelw, Rehab; Refai, Mohamed

    2016-01-01

    In Egypt, the River Red Gum (Eucalyptus camaldulensis) is a well-known tree and is highly appreciated by the rural and urban dwellers. The role of Eucalyptus trees in the ecology of Cryptococcus neoformans is documented worldwide. The aim of this survey was to show the prevalence of C. neoformans during the flowering season of E. camaldulensis at the Delta region in Egypt. Three hundred and eleven samples out of two hundred Eucalyptus trees, including leaves, flowers, and woody trunks, were collected from four governorates in the Delta region. Thirteen isolates of C. neoformans were recovered from Eucalyptus tree samples (4.2%). Molecular identification of C. neoformans was done by capsular gene specific primer CAP64 and serotype identification was done depending on LAC1 gene. This study represents an update on the ecology of C. neoformans associated with Eucalyptus tree in Egyptian environment. PMID:26884765

  20. Tree Colors: Color Schemes for Tree-Structured Data.

    PubMed

    Tennekes, Martijn; de Jonge, Edwin

    2014-12-01

    We present a method to map tree structures to colors from the Hue-Chroma-Luminance color model, which is known for its well balanced perceptual properties. The Tree Colors method can be tuned with several parameters, whose effect on the resulting color schemes is discussed in detail. We provide a free and open source implementation with sensible parameter defaults. Categorical data are very common in statistical graphics, and often these categories form a classification tree. We evaluate applying Tree Colors to tree structured data with a survey on a large group of users from a national statistical institute. Our user study suggests that Tree Colors are useful, not only for improving node-link diagrams, but also for unveiling tree structure in non-hierarchical visualizations.

  1. Glacial hazards: communicating the science and managing the risk

    NASA Astrophysics Data System (ADS)

    Reynolds, J. M.

    2009-04-01

    The recession of glaciers worldwide has received huge media coverage over the last few years in association with the issue of climate change. Young people at schools and colleges are increasingly aware of the environmental pressures due to ‘global warming'. Yet simultaneously, there appears to be an increasing move away from studying science both at pre-university and undergraduate levels. One of the oft cited reasons is that students cannot see the application of the subjects being taught them. Glacial hazards are one of the most obvious adverse effects of climate change, with many, often poor, communities in remote mountain areas being the most affected by frequently devastating Glacial Lake Outburst Floods (GLOFs). When students are exposed to examples of these hazards and the science behind them, many become enthused by the subject and want to study it further. There has been a huge increase in the number of students selecting projects on glacial hazards as well as a large increase in the number of institutions offering to teach modules on this subject. In an effort to provide a basic visualisation, Peter Kennett has taken the principle of GLOFs and developed a cheap but highly visual demonstration of the potentially devastating effect of melting ice within a moraine leading to subsidence and subsequent dam failure. This is available on www.earthlearningidea.com as ‘Dam burst danger - modelling the collapse of a natural dam in the mountains - and the disaster that might follow'. Furthermore, the methods by which glacial hazards are assessed provide excellent applications of geophysics, geology, geography (physical and Human), engineering, mathematics, and glaciology. By exploring the potential vulnerability of communities downstream, the applications can be extended to include sociology, economics, geopolitics and even psychology. Glacial hazards have been the subject of presentations to the Earth Science Teachers Association (ESTA) in the UK to demonstrate

  2. Caribbean Salinity Variation During the Last Glacial Cycle

    NASA Astrophysics Data System (ADS)

    Schmidt, M. W.; Spero, H. J.; Lea, D. W.

    2003-12-01

    Evaporation exceeds precipitation in the tropical Atlantic, resulting in a net freshwater removal across the Central American Isthmus. Because most of the north Atlantic's subtropical gyre water circulates through the Caribbean before flowing north to sub-polar regions via the Gulf Stream, changes in tropical atmospheric circulation have the potential to affect the salinity and density structure of the entire north Atlantic, thereby influencing glacial-interglacial oscillations in North Atlantic Deep Water (NADW) formation. Here, we combine Mg/Ca measurements (a proxy for the temperature of calcification) and δ 18O analyses of shells from the surface-dwelling foraminifera Globigerinoides ruber s.s. (white var.) from the western Caribbean Colombian Basin at ODP Site 999A (2827m; 4cm/ka sed. rate) and VM28-122 (3623m; 4-10cm/ka sed. rate) to produce the first continuous record of western tropical Atlantic δ 18OSEAWATER (δ 18OSW) during the last 130ka. In order to generate a record for sea surface salinity (SSS) due to regional hydrological change, we removed the δ 18OSW signal due to glacial ice volume variation and normalized the residual to the modern δ 18OSW value for the Colombian Basin (0.8‰ ). The resulting ice volume-free (Δ δ 18OIVF-SW) record shows that Caribbean Δ δ 18OIVF-SW increased by ˜0.5‰ during the Last Glacial Maximum and Marine Isotope Stage 4. Using a modern western Caribbean δ 18OSW:SSS relationship, these enriched δ 18OSW values suggest glacial Caribbean salinities were 2.3 - 2.8‰ higher than modern after removing the influence of ice-volume. Our data supports the hypothesis that the tropics might have been in a state more similar to the modern El Nino mode, characterized by a more southerly position of the ITCZ, during cold phases of the last glacial cycle. Within the resolution of our Δ δ 18OIVF-SW record from VM28-122, elevated glacial Caribbean salinity decreased to modern levels at the onset of the Bolling-Allerod (B

  3. Replicate phylogenies and post-glacial range expansion of the pitcher-plant mosquito, Wyeomyia smithii, in North America.

    PubMed

    Merz, Clayton; Catchen, Julian M; Hanson-Smith, Victor; Emerson, Kevin J; Bradshaw, William E; Holzapfel, Christina M

    2013-01-01

    Herein we tested the repeatability of phylogenetic inference based on high throughput sequencing by increased taxon sampling using our previously published techniques in the pitcher-plant mosquito, Wyeomyia smithii in North America. We sampled 25 natural populations drawn from different localities nearby 21 previous collection localities and used these new data to construct a second, independent phylogeny, expressly to test the reproducibility of phylogenetic patterns. Comparison of trees between the two data sets based on both maximum parsimony and maximum likelihood with Bayesian posterior probabilities showed close correspondence in the grouping of the most southern populations into clear clades. However, discrepancies emerged, particularly in the middle of W. smithii's current range near the previous maximum extent of the Laurentide Ice Sheet, especially concerning the most recent common ancestor to mountain and northern populations. Combining all 46 populations from both studies into a single maximum parsimony tree and taking into account the post-glacial historical biogeography of associated flora provided an improved picture of W. smithii's range expansion in North America. In a more general sense, we propose that extensive taxon sampling, especially in areas of known geological disruption is key to a comprehensive approach to phylogenetics that leads to biologically meaningful phylogenetic inference.

  4. Replicate Phylogenies and Post-Glacial Range Expansion of the Pitcher-Plant Mosquito, Wyeomyia smithii, in North America

    PubMed Central

    Merz, Clayton; Catchen, Julian M.; Hanson-Smith, Victor; Emerson, Kevin J.; Bradshaw, William E.; Holzapfel, Christina M.

    2013-01-01

    Herein we tested the repeatability of phylogenetic inference based on high throughput sequencing by increased taxon sampling using our previously published techniques in the pitcher-plant mosquito, Wyeomyia smithii in North America. We sampled 25 natural populations drawn from different localities nearby 21 previous collection localities and used these new data to construct a second, independent phylogeny, expressly to test the reproducibility of phylogenetic patterns. Comparison of trees between the two data sets based on both maximum parsimony and maximum likelihood with Bayesian posterior probabilities showed close correspondence in the grouping of the most southern populations into clear clades. However, discrepancies emerged, particularly in the middle of W. smithii's current range near the previous maximum extent of the Laurentide Ice Sheet, especially concerning the most recent common ancestor to mountain and northern populations. Combining all 46 populations from both studies into a single maximum parsimony tree and taking into account the post-glacial historical biogeography of associated flora provided an improved picture of W. smithii's range expansion in North America. In a more general sense, we propose that extensive taxon sampling, especially in areas of known geological disruption is key to a comprehensive approach to phylogenetics that leads to biologically meaningful phylogenetic inference. PMID:24039746

  5. Mid-late Pleistocene glacial evolution in the Grove Mountains, East Antarctica, constraints from cosmogenic 10Be surface exposure dating of glacial erratic cobbles

    NASA Astrophysics Data System (ADS)

    Dong, Guocheng; Huang, Feixin; Yi, Chaolu; Liu, Xiaohan; Zhou, Weijian; Caffee, Marc W.

    2016-08-01

    Glacial histories from the East Antarctic Ice Sheet (EAIS) provide keys to understanding correlations between the EAIS and global climate. They are especially helpful in the assessment of global sea level change, and as a means of quantifying the magnitude of past glacial activity and the rate at which ice responded to climate change. Given the significance of EAIS glacial histories, it is imperative that more glacial chronologic data for this region be obtained, especially for the mid-to-late Pleistocene. We report cosmogenic 10Be surface exposure dating results from glacially transported cobbles embedded in blue-ice moraine material at Mount Harding, the Grove Mountains, EAIS. Forty exotic cobbles sampled along two profiles (A and B) on this blue-ice moraine present apparent exposure-ages ranging from 7.2 to 542.2 ka. We explore this scattered dataset by using Principal Component Analysis (PCA) to identify statistically significant trends in the data. We identify a correlation between exposure-age and distance of the cobbles from Mount Harding. In profile A, cobbles further from Mount Harding yield older exposure-ages than those that are relatively close. In profile B, cobbles closer to Mount Harding are found to have relatively older exposure-ages. In term of glacial history we suggest that the direction of ice flow changed during the period from ∼60 to 200 ka, and that multiple glacial fluctuations occurred in the mid-late Pleistocene.

  6. Direct evidence of central European forest refugia during the last glacial period based on mollusc fossils

    NASA Astrophysics Data System (ADS)

    Juřičková, Lucie; Horáčková, Jitka; Ložek, Vojen

    2014-07-01

    Although there is evidence from molecular studies for the existence of central European last glacial refugia for temperate species, there is still a great lack of direct fossil records to confirm this theory. Here we bring such evidence in the form of fossil shells from twenty strictly forest land snail species, which were recorded in radiocarbon-dated late glacial or older mollusc assemblages of nine non-interrupted mollusc successions situated in the Western Carpathians, and one in the Bohemian Massif. We proposed that molluscs survived the last glacial period in central Europe in isolated small patches of broadleaf forest, which we unequivocally demonstrate for two sites of last glacial maximum age.

  7. Beryllium-10 dating of the duration and retreat of the last pinedale glacial sequence

    SciTech Connect

    Gosse, J.C. |; Klein, J.; Evenson, E.B.

    1995-06-02

    Accurate terrestrial glacial chronologies are needed for comparison with the marine record to establish the dynamics of global climate change during transitions from glacial to interglacial regimes. Cosmogenic beryllium-10 measurements in the Wind River Range indicate that the last glacial maximum (marine oxygen isotope stage 2) was achieved there by 21,700 {+-} 700 beryllium-10 years and lasted 5900 years. Ages of a sequence of recessional moraines and striated bedrock surfaces show that the initial deglaciation was rapid and that the entire glacial system retreated 33 kilometers to the cirque basin by 12,100 {+-} 500 beryllium-10 years.

  8. Beryllium-10 dating of the duration and retreat of the last pinedale glacial sequence.

    PubMed

    Gosse, J C; Klein, J; Lawn, B; Middleton, R; Evenson, E B

    1995-06-02

    Accurate terrestrial glacial chronologies are needed for comparison with the marine record to establish the dynamics of global climate change during transitions from glacial to interglacial regimes. Cosmogenic beryllium-10 measurements in the Wind River Range indicate that the last glacial maximum (marine oxygen isotope stage 2) was achieved there by 21,700 +/- 700 beryllium-10 years and lasted 5900 years. Ages of a sequence of recessional moraines and striated bedrock surfaces show that the initial deglaciation was rapid and that the entire glacial system retreated 33 kilometers to the cirque basin by 12,100 +/- 500 beryllium-10 years.

  9. Rate of tree carbon accumulation increases continuously with tree size.

    PubMed

    Stephenson, N L; Das, A J; Condit, R; Russo, S E; Baker, P J; Beckman, N G; Coomes, D A; Lines, E R; Morris, W K; Rüger, N; Alvarez, E; Blundo, C; Bunyavejchewin, S; Chuyong, G; Davies, S J; Duque, A; Ewango, C N; Flores, O; Franklin, J F; Grau, H R; Hao, Z; Harmon, M E; Hubbell, S P; Kenfack, D; Lin, Y; Makana, J-R; Malizia, A; Malizia, L R; Pabst, R J; Pongpattananurak, N; Su, S-H; Sun, I-F; Tan, S; Thomas, D; van Mantgem, P J; Wang, X; Wiser, S K; Zavala, M A

    2014-03-06

    Forests are major components of the global carbon cycle, providing substantial feedback to atmospheric greenhouse gas concentrations. Our ability to understand and predict changes in the forest carbon cycle--particularly net primary productivity and carbon storage--increasingly relies on models that represent biological processes across several scales of biological organization, from tree leaves to forest stands. Yet, despite advances in our understanding of productivity at the scales of leaves and stands, no consensus exists about the nature of productivity at the scale of the individual tree, in part because we lack a broad empirical assessment of whether rates of absolute tree mass growth (and thus carbon accumulation) decrease, remain constant, or increase as trees increase in size and age. Here we present a global analysis of 403 tropical and temperate tree species, showing that for most species mass growth rate increases continuously with tree size. Thus, large, old trees do not act simply as senescent carbon reservoirs but actively fix large amounts of carbon compared to smaller trees; at the extreme, a single big tree can add the same amount of carbon to the forest within a year as is contained in an entire mid-sized tree. The apparent paradoxes of individual tree growth increasing with tree size despite declining leaf-level and stand-level productivity can be explained, respectively, by increases in a tree's total leaf area that outpace declines in productivity per unit of leaf area and, among other factors, age-related reductions in population density. Our results resolve conflicting assumptions about the nature of tree growth, inform efforts to undertand and model forest carbon dynamics, and have additional implications for theories of resource allocation and plant senescence.

  10. Glacial greenhouse-gas fluctuations controlled by ocean circulation changes.

    PubMed

    Schmittner, Andreas; Galbraith, Eric D

    2008-11-20

    Earth's climate and the concentrations of the atmospheric greenhouse gases carbon dioxide (CO(2)) and nitrous oxide (N(2)O) varied strongly on millennial timescales during past glacial periods. Large and rapid warming events in Greenland and the North Atlantic were followed by more gradual cooling, and are highly correlated with fluctuations of N(2)O as recorded in ice cores. Antarctic temperature variations, on the other hand, were smaller and more gradual, showed warming during the Greenland cold phase and cooling while the North Atlantic was warm, and were highly correlated with fluctuations in CO(2). Abrupt changes in the Atlantic meridional overturning circulation (AMOC) have often been invoked to explain the physical characteristics of these Dansgaard-Oeschger climate oscillations, but the mechanisms for the greenhouse-gas variations and their linkage to the AMOC have remained unclear. Here we present simulations with a coupled model of glacial climate and biogeochemical cycles, forced only with changes in the AMOC. The model simultaneously reproduces characteristic features of the Dansgaard-Oeschger temperature, as well as CO(2) and N(2)O fluctuations. Despite significant changes in the land carbon inventory, CO(2) variations on millennial timescales are dominated by slow changes in the deep ocean inventory of biologically sequestered carbon and are correlated with Antarctic temperature and Southern Ocean stratification. In contrast, N(2)O co-varies more rapidly with Greenland temperatures owing to fast adjustments of the thermocline oxygen budget. These results suggest that ocean circulation changes were the primary mechanism that drove glacial CO(2) and N(2)O fluctuations on millennial timescales.

  11. Last Glacial Maximum and deglaciation of the Iberian Central System.

    NASA Astrophysics Data System (ADS)

    Palacios, D.; Andrés, N.; Vieira, G.; Marcos, J.; Vázquez-Selem, L.

    2012-04-01

    The Central System runs E-W across the centre of the Iberian Peninsula and is composed mainly of crystalline rocks. A glacial morphology is well preserved on many of its most important summit areas especially towards the Atlantic. Research has recently been carried out in three of the sierras of this mountain system, with the aim of establishing the absolute chronology of the maximum glacial advance and of the deglaciation in the whole system. The method used is cosmogenic 36Cl surface exposure dating of moraine boulders and glacially polished outcrops. The selected areas are the Sierra de Guadarrama (Palacios et al. 2012) close to Peñalara Peak (40°51'N, 3°57'W; 2428 m), the Sierra de Gredos (Palacios et al. 2011) close to Almanzor Peak (40°14'N, 5°17'W; 2592 m), and the Sierra de la Estrela (Vieira and Palacios, 2010) close to Alto de la Torre summit (40°20'N, 7°34'W; 1993 m). These areas are representative of the whole Central System from west to east. The results are highly homogeneous. Moraines dating from earlier than the last glaciation were not found in any of the sierras. On the contrary, in all cases the oldest moraines from the last glaciation rest on intensely weathered crystalline surfaces. The oldest moraines date from between 31 and 26 ka. In most cases, the deposition of these moraine ridges was followed by minor advances and retreats which left a sequence of ridges very close together, lasting until 18-16 ka. A fast retreat occurred after 16-15 ka, when glaciers completely abandoned the valleys, disappearing in most cases by 13-14 ka. The ice lasted until 11-10 ka, but only in small cirques found on sheltered rock-walls below the highest peaks.

  12. SEM microfabric analysis of glacial varves, Geneseo, N. Y

    SciTech Connect

    Pietraszek, S.R. . Geology Dept.)

    1993-03-01

    A detailed study of the microfabric of Pleistocene varved silty-clay from Geneseo Valley (Geneseo, N.Y.) indicates rapid deposition of sediment in a flocculated state into a glacial lake. Ten varve couplets of a 10 cm thick sample were studied using the Scanning Electron Microscope to determine their microfabric. Each varve ranges from 0.5 cm to 2.0 cm and represents an annual ( ) deposit. Varves consists of a lower light colored, coarse zone of silt and clay, and an upper darker colored, organic fine clayey zone. Graded bedding is observed in each couplet, and random clay particle orientation is dominant throughout a varve, with the exception of the top 0.5 mm of the fine layer. The upper and lower contacts are sharp. Fabric features are instrumental in reconstructing a depositional environment. Microfabric results of the glacial unit indicate that an initial heavy concentration of clay and silt was introduced into the basin in a single pulse during spring runoff. The majority of silt settled together with clay in a flocculated or aggregated state, forming the lower coarse zone of random orientation. As the silt concentration diminished, the clay continued to flocculate and settled as a fine clay aggregate. It is proposed that the settling took place during the spring and summer months. Finally, during the winter months, the sediment surface of the varve was disturbed by nemotode burrows, which reoriented the clay flakes into a zone of preferred fabric. Microfabric analysis of these glacial varves, thus suggests that sediment was rapidly deposited in a flocculated state.

  13. Analysis of glacial and periglacial processes using structure from motion

    NASA Astrophysics Data System (ADS)

    Piermattei, L.; Carturan, L.; de Blasi, F.; Tarolli, P.; Dalla Fontana, G.; Vettore, A.; Pfeifer, N.

    2015-11-01

    Close-range photo-based surface reconstruction from the ground is rapidly emerging as an alternative to lidar (light detection and ranging), which today represents the main survey technique in many fields of geoscience. The recent evolution of photogrammetry, incorporating computer vision algorithms such as Structure from Motion (SfM) and dense image matching such as Multi-View Stereo (MVS), allows the reconstruction of dense 3-D point clouds for the photographed object from a sequence of overlapping images taken with a digital consumer camera. The objective of our work was to test the accuracy of the ground-based SfM-MVS approach in calculating the geodetic mass balance of a 2.1 km2 glacier in the Ortles-Cevedale Group, Eastern Italian Alps. In addition, we investigated the feasibility of using the image-based approach for the detection of the surface displacement rate of a neighbouring active rock glacier. Airborne laser scanning (ALS) data were used as benchmarks to estimate the accuracy of the photogrammetric DTMs and the reliability of the method in this specific application. The glacial and periglacial analyses were performed using both range and image-based surveying techniques, and the results were then compared. The results were encouraging because the SfM-MVS approach enables the reconstruction of high-quality DTMs which provided estimates of glacial and periglacial processes similar to those achievable by ALS. Different resolutions and accuracies were obtained for the glacier and the rock glacier, given the different survey geometries, surface characteristics and areal extents. The analysis of the SfM-MVS DTM quality allowed us to highlight the limitations of the adopted expeditious method in the studied alpine terrain and the potential of this method in the multitemporal study of glacial and periglacial areas.

  14. Linking the Holocene glacial and oceanographic variability in northern Spitsbergen

    NASA Astrophysics Data System (ADS)

    Bartels, Martin; Hebbeln, Dierk

    2015-04-01

    The Svalbard area can be considered as a key region for Arctic heat transfer. The archipelago is located where relatively warm Atlantic Water is reaching further north than at any other Arctic location at similar latitudes. The Holocene variability of Atlantic Water advection is well documented for the western coasts of Spitsbergen whereas records from northern Svalbard are still rare. Here we present a sedimentary record from Woodfjorden in northern Spitsbergen where the influence of Atlantic Water is fading out and glaciers are responding much more sensitive to oceanographic variations than at the western coasts of Spitsbergen. We analyzed the foraminiferal fauna and the distribution of Ice Rafted Debris (IRD) to trace the interplay between the oceanographic and glacial variability, respectively. The appearance of Nonionellina labradorica, a species which is adapted to warm Atlantic Water, shows that the advection of Atlantic-derived water correlates positively with summer insolation. The amount of IRD - increasing during the Allerød interstadial - diminished subsequently with intensifying inflow of Atlantic Water. During the Mid-Holocene, the strong influence of these relative warm water masses concurs with very low IRD values, possibly reflecting the retreat of tidewater glaciers from the coast to a further inland position disconnecting glacier dynamics from the respective marine archives at that time. With declining inflow of Atlantic Water during the late Holocene sea ice expanded, indicated by increased percentages of Islandiella norcrossi. The appearance of this species shows a similar trend as reported for sea-ice biomarkers in the eastern Fram Strait. Thus, variations of Atlantic Water inflow directly affected glacial activity as well as sea-ice coverage. Combining marine and terrestrial proxies enabled us to reconstruct regional (sea-ice) as well as local (glacial expansion) changes over time.

  15. Domestication of a Mesoamerican cultivated fruit tree, Spondias purpurea

    PubMed Central

    Miller, Allison; Schaal, Barbara

    2005-01-01

    Contemporary patterns of genetic variation in crops reflect historical processes associated with domestication, such as the geographic origin(s) of cultivated populations. Although significant progress has been made in identifying several global centers of domestication, few studies have addressed the issue of multiple origins of cultivated plant populations from different geographic regions within a domestication center. This study investigates the domestication history of jocote (Spondias purpurea), a Mesoamerican cultivated fruit tree. Sequences of the chloroplast spacer trnG–trnS were obtained for cultivated and wild S. purpurea trees, two sympatric taxa (Spondias mombin var. mombin and Spondias radlkoferi), and two outgroups (S. mombin var. globosa and Spondias testudinus). A phylogeographic approach was used and statistically significant associations of clades and geographical location were tested with a nested clade analysis. The sequences confirm that wild populations of S. purpurea are the likely progenitors of cultivated jocote trees. This study provides phylogeographic evidence of multiple domestications of this Mesoamerican cultivated fruit tree. Haplotypes detected in S. purpurea trees form two clusters, each of which includes alleles recovered in both cultivated and wild populations from distinct geographic regions. Cultivated S. purpurea populations have fewer unique trnG–trnS alleles than wild populations; however, five haplotypes were absent in the wild. The presence of unique alleles in cultivation may reflect contemporary extinction of the tropical dry forests of Mesoamerica. These data indicate that some agricultural habitats may be functioning as reservoirs of genetic variation in S. purpurea. PMID:16126899

  16. Domestication of a Mesoamerican cultivated fruit tree, Spondias purpurea.

    PubMed

    Miller, Allison; Schaal, Barbara

    2005-09-06

    Contemporary patterns of genetic variation in crops reflect historical processes associated with domestication, such as the geographic origin(s) of cultivated populations. Although significant progress has been made in identifying several global centers of domestication, few studies have addressed the issue of multiple origins of cultivated plant populations from different geographic regions within a domestication center. This study investigates the domestication history of jocote (Spondias purpurea), a Mesoamerican cultivated fruit tree. Sequences of the chloroplast spacer trnG-trnS were obtained for cultivated and wild S. purpurea trees, two sympatric taxa (Spondias mombin var. mombin and Spondias radlkoferi), and two outgroups (S. mombin var. globosa and Spondias testudinus). A phylogeographic approach was used and statistically significant associations of clades and geographical location were tested with a nested clade analysis. The sequences confirm that wild populations of S. purpurea are the likely progenitors of cultivated jocote trees. This study provides phylogeographic evidence of multiple domestications of this Mesoamerican cultivated fruit tree. Haplotypes detected in S. purpurea trees form two clusters, each of which includes alleles recovered in both cultivated and wild populations from distinct geographic regions. Cultivated S. purpurea populations have fewer unique trnG-trnS alleles than wild populations; however, five haplotypes were absent in the wild. The presence of unique alleles in cultivation may reflect contemporary extinction of the tropical dry forests of Mesoamerica. These data indicate that some agricultural habitats may be functioning as reservoirs of genetic variation in S. purpurea.

  17. Metabolic changes in Avena sativa crowns recovering from freezing

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Extensive research has been conducted on cold acclimation and freezing tolerance of fall-sown cereal plants due to their economic importance; however, little has been reported on the biochemical changes occurring over time after the freezing conditions are replaced by conditions favorable for recove...

  18. Silver-palladium braze alloy recovered from masking materials

    NASA Technical Reports Server (NTRS)

    Cierniak, R.; Colman, G.; De Carlo, F.

    1966-01-01

    Method for recovering powdered silver-palladium braze alloy from an acrylic spray binder and rubber masking adhesive used in spray brazing is devised. The process involves agitation and dissolution of masking materials and recovery of suspended precious metal particles on a filter.

  19. Process for recovering niobium from uranium-niobium alloys

    DOEpatents

    Wallace, Steven A.; Creech, Edward T.; Northcutt, Walter G.

    1983-01-01

    Niobium is recovered from scrap uranium-niobium alloy by melting the scrap with tin, solidifying the billet thus formed, heating the billet to combine niobium with tin therein, placing the billet in hydrochloric acid to dissolve the uranium and leave an insoluble residue of niobium stannide, then separating the niobium stannide from the acid.

  20. Process for recovering niobium from uranium-niobium alloys

    DOEpatents

    Wallace, S.A.; Creech, E.T.; Northcutt, W.G.

    1982-09-27

    Niobium is recovered from scrap uranium-niobium alloy by melting the scrap with tin, solidifying the billet thus formed, heating the billet to combine niobium with tin therein, placing the billet in hydrochloric acid to dissolve the uranium and form a precipitate of niobium stannide, then separating the precipitate from the acid.

  1. 33 CFR 385.20 - Restoration Coordination and Verification (RECOVER).

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... activities such as: developing system-wide performance measures; developing and implementing the monitoring... goals and purposes of the Plan; conducting system-wide water quality analyses; developing, refining, and applying system-wide models and tools; and evaluating modifications to the Plan. RECOVER is not a...

  2. 33 CFR 385.20 - Restoration Coordination and Verification (RECOVER).

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... activities such as: developing system-wide performance measures; developing and implementing the monitoring... goals and purposes of the Plan; conducting system-wide water quality analyses; developing, refining, and applying system-wide models and tools; and evaluating modifications to the Plan. RECOVER is not a...

  3. 33 CFR 385.20 - Restoration Coordination and Verification (RECOVER).

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... activities such as: developing system-wide performance measures; developing and implementing the monitoring... goals and purposes of the Plan; conducting system-wide water quality analyses; developing, refining, and applying system-wide models and tools; and evaluating modifications to the Plan. RECOVER is not a...

  4. 27 CFR 20.213 - Reuse of recovered spirits.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2011-04-01 2011-04-01 false Reuse of recovered spirits. 20.213 Section 20.213 Alcohol, Tobacco Products and Firearms ALCOHOL AND TOBACCO TAX AND TRADE BUREAU, DEPARTMENT OF THE TREASURY LIQUORS DISTRIBUTION AND USE OF DENATURED ALCOHOL AND RUM Recovery of...

  5. 27 CFR 20.213 - Reuse of recovered spirits.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2014-04-01 2014-04-01 false Reuse of recovered spirits. 20.213 Section 20.213 Alcohol, Tobacco Products and Firearms ALCOHOL AND TOBACCO TAX AND TRADE BUREAU, DEPARTMENT OF THE TREASURY ALCOHOL DISTRIBUTION AND USE OF DENATURED ALCOHOL AND RUM Recovery of...

  6. 27 CFR 20.213 - Reuse of recovered spirits.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2012-04-01 2012-04-01 false Reuse of recovered spirits. 20.213 Section 20.213 Alcohol, Tobacco Products and Firearms ALCOHOL AND TOBACCO TAX AND TRADE BUREAU, DEPARTMENT OF THE TREASURY LIQUORS DISTRIBUTION AND USE OF DENATURED ALCOHOL AND RUM Recovery of...

  7. Why Are Recovering Substance Abuse Counselors Paid Less?

    ERIC Educational Resources Information Center

    Olmstead, Todd A.; Johnson, J. Aaron; Roman, Paul M.; Sindelar, Jody L.

    2007-01-01

    The goal of this study is to determine why recovering substance abuse counselors are paid less, on average and controlling for other factors, than nonrecovering substance abuse counselors. The data come from the 2002-2003 wave of the National Treatment Center Study and consist of 1,487 full-time counselors from nationally representative samples of…

  8. PACIFIC SALMON: LESSONS LEARNED FOR RECOVERING ATLANTIC SALMON

    EPA Science Inventory

    n evaluation of the history of efforts to reverse the long-term decline of Pacific Salmon provides instructive policy lessons for recovering Atlantic Salmon. From California to southern British Columbia, wild runs of Pacific salmon have universally declined and many have disappe...

  9. Induced Radioactivity in Recovered Skylab Materials. [gamma ray spectra

    NASA Technical Reports Server (NTRS)

    Fishman, G. J.; Meegan, C. A.

    1980-01-01

    Four radioactive isotopes found in aluminum and stainless steel samples from Skylab debris were recovered in Australia. The low-level activity was induced by high-energy protons and neutrons in the space environment. Measurements of the specific activities are given.

  10. Bright, Angry, Recovering Students: Their Value to Colleges.

    ERIC Educational Resources Information Center

    Bratter, Thomas Edward; Parker, Thomas H.

    1994-01-01

    Brings to life a portrait of students who are recovering from psychological troubles, chemical dependencies, and/or instances of physical assault to illustrate how these students can benefit the college/university to which they apply, while also reaping benefits from the institution. (Author/NB)

  11. Phosphorus uptake by potato from fertilizers recovered from anaerobic digestion

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Field experiments were conducted in the Columbia Basin of South Central Washington to assess the yield of potato (Solanum tuberosum) in response to application of phosphorus enriched materials recovered from anaerobic digestion of manure. The treatments were comprised of four rates (0, 56, 112 and ...

  12. Method for recovering hydrocarbons from molten metal halides

    DOEpatents

    Pell, Melvyn B.

    1979-01-01

    In a process for hydrocracking heavy carbonaceous materials by contacting such carbonaceous materials with hydrogen in the presence of a molten metal halide catalyst to produce hydrocarbons having lower molecular weights and thereafter recovering the hydrocarbons so produced from the molten metal halide, an improvement comprising injecting into the spent molten metal halide, a liquid low-boiling hydrocarbon stream is disclosed.

  13. Major Concerns Associated with Recovered Memories of Childhood Abuse.

    ERIC Educational Resources Information Center

    Spray, Kristina J.

    When accusations of child abuse result from false memories, all parties involved suffer. This paper examines some of the issues surrounding recovered memories of childhood abuse. The mechanisms that the mind may employ to deal with traumatic events, such as disassociation and repression, must be further explored through experimental research to…

  14. Habitual Response to Stress in Recovering Adolescent Anorexic Patients

    ERIC Educational Resources Information Center

    Miller, Samantha P.; Erickson, Sarah J.; Branom, Christina; Steiner, Hans

    2009-01-01

    Objective: Although previous research has investigated the stress response in acutely anorexic patients, there is currently little research addressing this response in recovering adolescent anorexic girls. Therefore, this study investigated partially and fully weight-restored anorexic adolescent girls' psychological and physiological response to a…

  15. 27 CFR 20.213 - Reuse of recovered spirits.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2010-04-01 2010-04-01 false Reuse of recovered spirits. 20.213 Section 20.213 Alcohol, Tobacco Products and Firearms ALCOHOL AND TOBACCO TAX AND TRADE BUREAU... beverage or other internal human medicinal use, it may be reused in any approved process without...

  16. Secondary School Experiences of Male Recovering Substance Abusers

    ERIC Educational Resources Information Center

    Maher, Rebecca C.

    2012-01-01

    Problem: Adolescents who begin abusing substances, including alcohol, prescription drugs, and illegal drugs often fail in school suffering life-altering consequences (Cox, Zhang, Johnson, & Bender, 2007). While plentiful research exists on substance abuse, there is a dearth of research on the school experiences of recovering substance abusers.…

  17. Return to Education for Recovering Drug Addicts: The Soilse Project

    ERIC Educational Resources Information Center

    Barter, Eric

    2010-01-01

    This article is an account of a return to education course set up to cater to the needs of recovering heroin addicts in a Dublin rehabilitation project in the summer of 2008. It begins with a brief outline of the HSE Soilse rehabilitation and recovery programme and the rationale for seeking association with the Department of Adult and Community…

  18. Colonizing and Decolonizing Projects of Re/covering Spirituality

    ERIC Educational Resources Information Center

    Rhee, Jeong-eun; Subedi, Binaya

    2014-01-01

    In this postcolonial inquiry, we analyze how spirituality has been simultaneously appropriated/re-covered and re-appropriated/recovered for the purpose of (re)colonizing as well as decolonizing projects. By drawing from discrete yet interconnected literatures of decolonizing, (post)(anti)colonial, Indigenous, and ethnic studies based theories, we…

  19. Auditory Abilities of Speakers Who Persisted, or Recovered, from Stuttering

    ERIC Educational Resources Information Center

    Howell, Peter; Davis, Stephen; Williams, Sheila M.

    2006-01-01

    Objective: The purpose of this study was to see whether participants who persist in their stutter have poorer sensitivity in a backward masking task compared to those participants who recover from their stutter. Design: The auditory sensitivity of 30 children who stutter was tested on absolute threshold, simultaneous masking, backward masking with…

  20. Fault-Tree Compiler Program

    NASA Technical Reports Server (NTRS)

    Butler, Ricky W.; Martensen, Anna L.

    1992-01-01

    FTC, Fault-Tree Compiler program, is reliability-analysis software tool used to calculate probability of top event of fault tree. Five different types of gates allowed in fault tree: AND, OR, EXCLUSIVE OR, INVERT, and M OF N. High-level input language of FTC easy to understand and use. Program supports hierarchical fault-tree-definition feature simplifying process of description of tree and reduces execution time. Solution technique implemented in FORTRAN, and user interface in Pascal. Written to run on DEC VAX computer operating under VMS operating system.

  1. Bathymetry and temperature of some glacial lakes in Wyoming

    PubMed Central

    Leopold, Luna B.

    1980-01-01

    On the west flank of the Wind River Mountains, Wyoming, are several large lakes occupying glacially scoured depressions dammed by terminal moraines. Fremont, Willow, and New Fork Lakes, having maximal depths of 185, 85, and 62 m, respectively, are not only deep, but in 1970-1978 they had no measurable coliform. They have exceptionally low values of total dissolved solids; Fremont Lake has only 12.8 mg/liter, probably the second most dilute large lake in coterminus United States. Summer mixing is restricted to the uppermost 10 m, below which the lakes are essentially isothermal at the maximum density temperature, about 3.9°C. PMID:16592797

  2. Bathymetry and temperature of some glacial lakes in Wyoming.

    PubMed

    Leopold, L B

    1980-04-01

    On the west flank of the Wind River Mountains, Wyoming, are several large lakes occupying glacially scoured depressions dammed by terminal moraines. Fremont, Willow, and New Fork Lakes, having maximal depths of 185, 85, and 62 m, respectively, are not only deep, but in 1970-1978 they had no measurable coliform. They have exceptionally low values of total dissolved solids; Fremont Lake has only 12.8 mg/liter, probably the second most dilute large lake in coterminus United States. Summer mixing is restricted to the uppermost 10 m, below which the lakes are essentially isothermal at the maximum density temperature, about 3.9 degrees C.

  3. Global Value Trees

    PubMed Central

    Zhu, Zhen; Puliga, Michelangelo; Cerina, Federica; Chessa, Alessandro; Riccaboni, Massimo

    2015-01-01

    The fragmentation of production across countries has become an important feature of the globalization in recent decades and is often conceptualized by the term “global value chains” (GVCs). When empirically investigating the GVCs, previous studies are mainly interested in knowing how global the GVCs are rather than how the GVCs look like. From a complex networks perspective, we use the World Input-Output Database (WIOD) to study the evolution of the global production system. We find that the industry-level GVCs are indeed not chain-like but are better characterized by the tree topology. Hence, we compute the global value trees (GVTs) for all the industries available in the WIOD. Moreover, we compute an industry importance measure based on the GVTs and compare it with other network centrality measures. Finally, we discuss some future applications of the GVTs. PMID:25978067

  4. How does tree age influence damage and recovery in forests impacted by freezing rain and snow?

    PubMed

    Zhu, LiRong; Zhou, Ting; Chen, BaoMing; Peng, ShaoLin

    2015-05-01

    The response and recovery mechanisms of forests to damage from freezing rain and snow events are a key topic in forest research and management. However, the relationship between the degree of damage and tree age, i.e., whether seedlings, young trees, or adult trees are most vulnerable, remains unclear and is rarely reported. We investigated the effect of tree age on the degrees of vegetation damage and subsequent recovery in three subtropical forest types-coniferous, mixed, and broad-leaved-in the Tianjing Mountains, South China, after a series of rare icy rain and freezing snow events in 2008. The results showed that damage and recovery rates were both dependent on tree age, with the proportion of damaged vegetation increasing with age (estimated by diameter at breast height, DBH) in all three forest types and gradually plateauing. Significant variation occurred among forest types. Young trees in the coniferous forest were more vulnerable than those in the broad-leaved forest. The type of damage also varied with tree age in different ways in the three forest types. The proportion of young seedlings that were uprooted (the most severe type of damage) was highest in the coniferous forest. In the mixed forest, young trees were significantly more likely to be uprooted than seedlings and adult trees, while in the broad-leaved forest, the proportion of uprooted adult trees was significantly higher than that of seedlings and young trees. There were also differences among forest types in how tree age affected damage recovery. In the coniferous forest, the recovery rate of trees with broken trunks or crowns (DBH > 2.5 cm) increased with tree age. However, in the mixed and broad-leaved forests, no obvious correlation between the recovery rate of trees with broken trunks or crowns and tree age was observed. Trees with severe root damage did not recover; they were uprooted and died. In these forests, vegetation damage and recovery showed tree age dependencies, which varied

  5. Tree Rings: Timekeepers of the Past.

    ERIC Educational Resources Information Center

    Phipps, R. L.; McGowan, J.

    One of a series of general interest publications on science issues, this booklet describes the uses of tree rings in historical and biological recordkeeping. Separate sections cover the following topics: dating of tree rings, dating with tree rings, tree ring formation, tree ring identification, sample collections, tree ring cross dating, tree…

  6. How To Write a Municipal Tree Ordinance.

    ERIC Educational Resources Information Center

    Fazio, James R., Ed.

    1990-01-01

    At the heart of the Tree City USA program are four basic requirements: The community must have the following: (1) a tree board or department; (2) an annual community forestry program with financial provisions for trees and tree care; (3) an annual Arbor Day proclamation and observance; and (4) a tree ordinance. Sections of a model tree ordinance…

  7. Early postglacial appearance of tree species in northern Scandinavia: review and perspective

    NASA Astrophysics Data System (ADS)

    Kullman, Leif

    2008-12-01

    This paper reviews megafossil evidence for the first postglacial records of different tree species in northern Scandinavia. Betula pubescens coll. appeared at the Arctic coast of northern Norway by 16, 900 yr BP. In addition, Betula pubescens (14, 000 yr BP), Pinus sylvestris (11, 700 yr BP) and Picea abies (11, 000 yr BP) existed on early ice- free mountain peaks (nunataks) at different locations in the Scandes during the Lateglacial. Larix sibirica, currently not native to Fennoscandia, and several thermophilous broadleaved tree species were recorded in the earliest part of the Holocene. The conventional interpretation of pollen and macrofossil records from peat and sediment stratigraphies do not consider the occurrence of the species mentioned above that early at these northern and high altitude sites. This very rapid arrival after the local deglaciation implies that the traditional model of far distant glacial refugial areas for tree species has to be challenged. The current results are more compatible with a situation involving scattered "cryptic" refugia quite close to margin of the ice sheet at its full-glacial extension. This fits a more general pattern currently emerging on different continents. In general, "cryptic" refugia should be considered in connection with modelling extinction risks related to modern and possible future "climatic crises".

  8. Insert tree completion system

    SciTech Connect

    Brands, K.W.; Ball, I.G.; Cegielski, E.J.; Gresham, J.S.; Saunders, D.N.

    1982-09-01

    This paper outlines the overall project for development and installation of a low-profile, caisson-installed subsea Christmas tree. After various design studies and laboratory and field tests of key components, a system for installation inside a 30-in. conductor was ordered in July 1978 from Cameron Iron Works Inc. The system is designed to have all critical-pressure-containing components below the mudline and, with the reduced profile (height) above seabed, provides for improved safety of satellite underwater wells from damage by anchors, trawl boards, and even icebergs. In addition to the innovative nature of the tree design, the completion includes improved 3 1/2-in. through flowline (TFL) pumpdown completion equipment with deep set safety valves and a dual detachable packer head for simplified workover capability. The all-hydraulic control system incorporates a new design of sequencing valve for both Christmas tree control and remote flowline connection. A semisubmersible drilling rig was used to initiate the first end flowline connection at the wellhead for subsequent tie-in to the prelaid, surface-towed, all-welded subsea pipeline bundle.

  9. Active flows on trees

    NASA Astrophysics Data System (ADS)

    Forrow, Aden; Woodhouse, Francis G.; Dunkel, Jörn

    2016-11-01

    Coherent, large scale dynamics in many nonequilibrium physical, biological, or information transport networks are driven by small-scale local energy input. We introduce and explore a generic model for compressible active flows on tree networks. In contrast to thermally-driven systems, active friction selects discrete states with only a small number of oscillation modes activated at distinct fixed amplitudes. This state selection can interact with graph topology to produce different localized dynamical time scales in separate regions of large networks. Using perturbation theory, we systematically predict the stationary states of noisy networks. Our analytical predictions agree well with a Bayesian state estimation based on a hidden Markov model applied to simulated time series data on binary trees. While the number of stable states per tree scales exponentially with the number of edges, the mean number of activated modes in each state averages 1 / 4 the number of edges. More broadly, these results suggest that the macroscopic response of active networks, from actin-myosin networks in cells to flow networks in Physarum polycephalum, can be dominated by a few select modes.

  10. Structural regression trees

    SciTech Connect

    Kramer, S.

    1996-12-31

    In many real-world domains the task of machine learning algorithms is to learn a theory for predicting numerical values. In particular several standard test domains used in Inductive Logic Programming (ILP) are concerned with predicting numerical values from examples and relational and mostly non-determinate background knowledge. However, so far no ILP algorithm except one can predict numbers and cope with nondeterminate background knowledge. (The only exception is a covering algorithm called FORS.) In this paper we present Structural Regression Trees (SRT), a new algorithm which can be applied to the above class of problems. SRT integrates the statistical method of regression trees into ILP. It constructs a tree containing a literal (an atomic formula or its negation) or a conjunction of literals in each node, and assigns a numerical value to each leaf. SRT provides more comprehensible results than purely statistical methods, and can be applied to a class of problems most other ILP systems cannot handle. Experiments in several real-world domains demonstrate that the approach is competitive with existing methods, indicating that the advantages are not at the expense of predictive accuracy.

  11. Exact solutions for species tree inference from discordant gene trees.

    PubMed

    Chang, Wen-Chieh; Górecki, Paweł; Eulenstein, Oliver

    2013-10-01

    Phylogenetic analysis has to overcome the grant challenge of inferring accurate species trees from evolutionary histories of gene families (gene trees) that are discordant with the species tree along whose branches they have evolved. Two well studied approaches to cope with this challenge are to solve either biologically informed gene tree parsimony (GTP) problems under gene duplication, gene loss, and deep coalescence, or the classic RF supertree problem that does not rely on any biological model. Despite the potential of these problems to infer credible species trees, they are NP-hard. Therefore, these problems are addressed by heuristics that typically lack any provable accuracy and precision. We describe fast dynamic programming algorithms that solve the GTP problems and the RF supertree problem exactly, and demonstrate that our algorithms can solve instances with data sets consisting of as many as 22 taxa. Extensions of our algorithms can also report the number of all optimal species trees, as well as the trees themselves. To better asses the quality of the resulting species trees that best fit the given gene trees, we also compute the worst case species trees, their numbers, and optimization score for each of the computational problems. Finally, we demonstrate the performance of our exact algorithms using empirical and simulated data sets, and analyze the quality of heuristic solutions for the studied problems by contrasting them with our exact solutions.

  12. Glacial evolution of the Ampato Volcanic Complex (Peru)

    NASA Astrophysics Data System (ADS)

    Alcalá, J.; Palacios, D.; Zamorano, J. J.; Vázquez, L.

    2009-04-01

    Ice masses on the Western range of the Central Andes are a main source of water resources and act as a geoindicator of variations in the climate of the tropics (Mark, 2008). The study of their evolution is of particular interest since they are situated in the transition zone between the tropical and mid-latitude circulation areas of the atmosphere (Zech et al., 2007). The function of this transition area is currently under debate, and understanding it is essential for the development of global climate models (Kull et al, 2008; Mark, 2008). However our understanding of the evolution of glaciers and their paleoclimatic factors for this sector of the Central Andes is still at a very basic level. This paper presents initial results of a study on the glacial evolution of the Ampato volcanic complex (15°24´- 15° 51´ S, 71° 51´ - 73° W; 6288 m a.s.l.) located in the Western Range of the Central Andes in Southern Peru, 70 km NW of the city of Arequipa. The main objectives are to identify the number of glacial phases the complex has undergone using geomorphological criteria to define a time frame for each phase, based on cosmogenic 36Cl dating of a sequence of moraine deposits; and to estimate the glacier Equilibrium Line Altitude (ELA) of each phase. The Ampato volcanic complex is formed by 3 great andesitic stratovolcanoes, the Nevados HualcaHualca-Sabancaya-Ampato, which started forming between the late Miocene and early Quaternary (Bulmer et al., 1999), aligned N-S and with summits covered with glaciers. The Sabancaya volcano is fully active, with its latest eruption occurring in 2001. Glacial landforms were identified and mapped using photointerpretation of vertical aerial photographs from 1955 (1:35,000 scale, National Geographic Institute of Peru), oblique photographs from 1943 (Aerophotographical Service of Peru), and a geo-referenced high-resolution Mrsid satellite image from 2000 (NASA). This cartography was corrected and improved through fieldwork. It was

  13. Rate of tree carbon accumulation increases continuously with tree size

    USGS Publications Warehouse

    Stephenson, N.L.; Das, A.J.; Condit, R.; Russo, S.E.; Baker, P.J.; Beckman, N.G.; Coomes, D.A.; Lines, E.R.; Morris, W.K.; Rüger, N.; Álvarez, E.; Blundo, C.; Bunyavejchewin, S.; Chuyong, G.; Davies, S.J.; Duque, Á.; Ewango, C.N.; Flores, O.; Franklin, J.F.; Grau, H.R.; Hao, Z.; Harmon, M.E.; Hubbell, S.P.; Kenfack, D.; Lin, Y.; Makana, J.-R.; Malizia, A.; Malizia, L.R.; Pabst, R.J.; Pongpattananurak, N.; Su, S.-H.; Sun, I-F.; Tan, S.; Thomas, D.; van Mantgem, P.J.; Wang, X.; Wiser, S.K.; Zavala, M.A.

    2014-01-01

    Forests are major components of the global carbon cycle, providing substantial feedback to atmospheric greenhouse gas concentrations. Our ability to understand and predict changes in the forest carbon cycle—particularly net primary productivity and carbon storage - increasingly relies on models that represent biological processes across several scales of biological organization, from tree leaves to forest stands. Yet, despite advances in our understanding of productivity at the scales of leaves and stands, no consensus exists about the nature of productivity at the scale of the individual tree, in part because we lack a broad empirical assessment of whether rates of absolute tree mass growth (and thus carbon accumulation) decrease, remain constant, or increase as trees increase in size and age. Here we present a global analysis of 403 tropical and temperate tree species, showing that for most species mass growth rate increases continuously with tree size. Thus, large, old trees do not act simply as senescent carbon reservoirs but actively fix large amounts of carbon compared to smaller trees; at the extreme, a single big tree can add the same amount of carbon to the forest within a year as is contained in an entire mid-sized tree. The apparent paradoxes of individual tree growth increasing with tree size despite declining leaf-level and stand-level productivity can be explained, respectively, by increases in a tree’s total leaf area that outpace declines in productivity per unit of leaf area and, among other factors, age-related reductions in population density. Our results resolve conflicting assumptions about the nature of tree growth, inform efforts to understand and model forest carbon dynamics, and have additional implications for theories of resource allocation and plant senescence.

  14. Sensitivity of palaeotidal models of the northwest European shelf seas to glacial isostatic adjustment since the Last Glacial Maximum

    NASA Astrophysics Data System (ADS)

    Ward, Sophie L.; Neill, Simon P.; Scourse, James D.; Bradley, Sarah L.; Uehara, Katsuto

    2016-11-01

    The spatial and temporal distribution of relative sea-level change over the northwest European shelf seas has varied considerably since the Last Glacial Maximum, due to eustatic sea-level rise and a complex isostatic response to deglaciation of both near- and far-field ice sheets. Because of the complex pattern of relative sea level changes, the region is an ideal focus for modelling the impact of significant sea-level change on shelf sea tidal dynamics. Changes in tidal dynamics influence tidal range, the location of tidal mixing fronts, dissipation of tidal energy, shelf sea biogeochemistry and sediment transport pathways. Significant advancements in glacial isostatic adjustment (GIA) modelling of the region have been made in recent years, and earlier palaeotidal models of the northwest European shelf seas were developed using output from less well-constrained GIA models as input to generate palaeobathymetric grids. We use the most up-to-date and well-constrained GIA model for the region as palaeotopographic input for a new high resolution, three-dimensional tidal model (ROMS) of the northwest European shelf seas. With focus on model output for 1 ka time slices from the Last Glacial Maximum (taken as being 21 ka BP) to present day, we demonstrate that spatial and temporal changes in simulated tidal dynamics are very sensitive to relative sea-level distribution. The new high resolution palaeotidal model is considered a significant improvement on previous depth-averaged palaeotidal models, in particular where the outputs are to be used in sediment transport studies, where consideration of the near-bed stress is critical, and for constraining sea level index points.

  15. Pen-reared fulvous tree ducks used in movement studies of wild populations

    USGS Publications Warehouse

    Flickinger, Edward L.; King, K.A.; Heyland, O.

    1973-01-01

    To obtain movement data on wild fulvous tree ducks (Dendrocygna bicolor) 165 immature pen-reared fulvous tree ducks were color-marked and released in three southeast Texas counties in July October 1969/70. Nine (5 percent) of the marked birds were recovered from 3 days to 9 months after release, and an additional 15 birds provided sight records. Many released birds apparently became integrated into the wild population; all of those observed were with wild flocks. Six birds were recovered over 50 miles from the release sites. Four released in late July to mid-September had moved eastward and two went southward in September or later. Five were still in the Texas-Louisiana rice belt (three in late November). The sixth bird was recovered in October in Veracruz, which supports the assumption that U.S. Gulf Coast nesting populations winter in southern Mexico.

  16. Glacial sequence stratigraphy reveal the Weichselian glacial history of the SE sector of the Eurasian Ice Sheet

    NASA Astrophysics Data System (ADS)

    Räsänen, Matti

    2016-04-01

    Reconstructions of the last Weichselian glacial cycle 117,000-11,700 years (kyr) ago propose that S Finland, adjacent Russia and the Baltic countries in the SE sector of the Eurasian Ice Sheet (EIS), were glaciated during the Middle Weichselian time [marine isotope stage (MIS) 4, 71-57 kyr ago] and that this glaciation was preceded in S Finland by an Early Weichselian interstadial (MIS 5c, 105-93 kyr ago) with pine forest. Here glacial sequence stratigraphy (Powell and Cooper 2002) is applied to isolated Late Pleistocene onshore outcrop sections in S Finland. The analysed sedimentary records have traditionally been investigated, interpreted and published separately by different authors without an attempt to a methodologically more systematic survey. By putting new field data and old observations into a regional sequence stratigraphic framework it is shown how previously unnoticed regularities can be found in the lithofacies and fossil successions. It is shown that the proposed Middle Weichselian glaciation or the pine dominated interstadial did not take place at all (Räsänen et al. 2015). The one Late Weichselian glaciation (MIS 2, 29-11 kyr ago) at the SE sector of EIS was preceded in S Finland by a nearly 90 kyr long still poorly known non-glacial period, featuring tundra with permafrost and probably birch forest. The new Middle Weichselian paleoenvironmental scenario revises the configuration and hydrology of the S part of EIS and gives new setting for the evolution of Scandinavian biota. References Powell, R. D., and Cooper, J. M., 2002, A glacial sequence stratigraphic model for temperate, glaciated continental shelves, in Dowdeswell, J. A., and Cofaig, C. Ó. eds., Glacier-Influenced Sedimentation on High-Latitude Continental Margins: The Geological Society of London, London, Geological Society London, Special Publication v. 203, p. 215-244. Räsänen, M.E., Huitti, J.V., Bhattarai, S. Harvey, J. and Huttunen, S. 2015, The SE sector of the Middle

  17. Reintroduced Sumatran orangutans (Pongo abelii): using major food tree species as indicators of habitat suitability.

    PubMed

    Kelle, Doris; Gärtner, Stefanie; Pratje, Peter H; Storch, Ilse

    2014-01-01

    Reintroducing orangutans (Pongo spp.) into the wild requires a suitable, secure habitat. To identify acceptable areas for their reintroduction and define priority conservation sites, we analysed the tree species composition in the Bukit Tigapuluh ecosystem in Jambi, Sumatra. We used this information to determine the distribution patterns of those species that represent an essential part of the diet of reintroduced orangutans. Important orangutan food tree species showed significant differences in composition, frequency and abundance among topographic forest types and recovered selectively logged and unlogged forests. Riparian forests and recovered selectively logged areas offered a vegetation composition and forest structure most suitable for the reintroduction of orangutans and showed numerous important tree species that serve as indicator species, i.e. species growing predominantly or exclusively in a specific forest type. © 2014 S. Karger AG, Basel.

  18. Inverting Glacial Isostatic Adjustment beyond linear viscoelasticity using Burgers rheology

    NASA Astrophysics Data System (ADS)

    Caron, L.; Greff-Lefftz, M.; Fleitout, L.; Metivier, L.; Rouby, H.

    2014-12-01

    In Glacial Isostatic Adjustment (GIA) inverse modeling, the usual assumption for the mantle rheology is the Maxwell model, which exhibits constant viscosity over time. However, mineral physics experiments and post-seismic observations show evidence of a transient component in the deformation of the shallow mantle, with a short-term viscosity lower than the long-term one. In these studies, the resulting rheology is modeled by a Burgers material: such rheology is indeed expected as the mantle is a mixture of materials with different viscosities. We propose to apply this rheology for the whole viscoelastic mantle, and, using a Bayesian MCMC inverse formalism for GIA during the last glacial cycle, study its impact on estimations of viscosity values, elastic thickness of the lithosphere, and ice distribution. To perform this inversion, we use a global dataset of sea level records, the geological constraints of ice-sheet margins, and present-day GPS data as well as satellite gravimetry. Our ambition is to present not only the best fitting model, but also the range of possible solutions (within the explored space of parameters) with their respective probability of explaining the data. Our first results indicate that compared to the Maxwell models, the Burgers models involve a larger lower mantle viscosity and thicker ice over Fennoscandia and Canada.

  19. Glacial Refugium of Pinus pumila (Pall.) Regel in Northeastern Siberia

    SciTech Connect

    Shilo, N A; Lozhkin, A V; Anderson, P M; Brown, T A; Pakhomov, A Y; Solomatkina, T B

    2007-02-10

    One of the most glowing representatives of the Kolyma flora [1], ''Pinus pumila'' (Pall.) Regel (Japanese stone pine), is a typical shrub in larch forests of the northern Okhotsk region, basins of the Kolyma and Indigirka rivers, and high-shrub tundra of the Chukchi Peninsula. It also forms a pine belt in mountains above the forest boundary, which gives way to the grass-underbrush mountain tundra and bald mountains. In the southern Chukchi Peninsula, ''Pinus pumila'' along with ''Duschekia fruticosa'' (Rupr.) Pouzar and ''Betula middendorffii'' Trautv. et C. A. Mey form trailing forests transitional between tundra and taiga [2]. Pinus pumila pollen, usually predominating in subfossil spore-and-pollen spectra of northeastern Siberia, is found as single grains or a subordinate component (up 2-3%, rarely 10%) in spectra of lacustrine deposits formed during the last glacial stage (isotope stage 2) in the Preboreal and Boreal times of the Holocene. Sometimes, its content increases to 15-22% in spectra of lacustrine deposits synchronous to the last glacial stage near the northern coast of the Sea of Okhotsk [3], evidently indicating the proximity of Japanese stone pine thickets.

  20. A study of Glacial Isostatic Adjustment in Greenland

    NASA Astrophysics Data System (ADS)

    Nielsen, Jens Emil; Sandberg Sørensen, Louise; Adalgeirsdottir, Gudfinna; Spada, Giorgio

    2010-05-01

    Glacial isostatic adjustment (GIA) is the viscoelastic response of the Earth caused by changes in ice loads during glaciations and deglaciations. Knowledge of the GIA signal is particularly important in cryospheric applications of satellite gravimetry and altimetry, where the origin of the observed changes must be separated into past and present response. Modeling the present-day GIA signal must include knowledge of both the ice loading history and the Earth's rheology. Neither of these models are well constrained in Greenland, and hence the GIA estimates here are uncertain. In this paper we implement a loading history of the Greenland Ice Sheet derived from the ice sheet model SICOPOLIS, and we study the present-day gravity changes and vertical crustal motion derived from using this ice history. The results are compared with those derived from the widely used ICE-5G ice history. For calculation of present day GIA signal, we assume the Earth's rheology to be a simplified version of the VM2 Earth model. The calculated GIA signal in Greenland, derived from the two ice loading histories are compared with geodetic measurements of vertical crustal motion from GPS time series and with repeated gravity measurements in Greenland. The free code SELEN is used for calculating the effects of the Earth model and different ice loading histories. This study is performed within the Working Group 4 of the ESF COST Action ES0701 "Improved constraints on models of Glacial Isostatic Adjustment".