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Sample records for southwestern greenland implications

  1. Abiotic, Graphitic Microstructures in Micaceous Metaquartzite about 3760 Million Years Old from Southwestern Greenland: Implications for Early Precambrian Microfossils

    PubMed Central

    Nagy, Bartholomew; Zumberge, John E.; Nagy, Lois Anne

    1975-01-01

    An Early Precambrian micaceous metaquartzite subjected to low to moderate metamorphism in the Isua area of Southwestern Greenland was derived from the erosion of preexisting rocks which were probably sialic in composition. This metaquartzite may have been formed before the emergence of life. It contains globular particles of graphite arranged in narrow veins or along foliation or bedding planes. This rock contains no organic compounds besides traces of methane and no biologically significant elements associated with the graphite microstructures. Reaction of primitive methane with ferric oxides appears to have oxidized the methane to the vein graphite and reduced the ferric oxides to ferrous-ferric oxide (magnetite). The graphitic microstructures are likely to be abiotic in origin, although a biological origin is not impossible. Somewhat younger microstructures found in other locations on earth have often been described as microfossils; this origin should be reexamined on the basis of the above mentioned conclusions. Images PMID:16592229

  2. Chromophoric Dissolved Organic Matter in Southwestern Greenland Lakes

    NASA Astrophysics Data System (ADS)

    Osburn, C. L.; Giles, M. E.; Underwood, G. J. C.

    2014-12-01

    Dissolved organic matter (DOM) is an important property of Arctic lake ecosystems, originating from allochthonous inputs from catchments and autochthonous production by plankton in the water column. Little is known about the quality of DOM in Arctic lakes that lack substantial inputs from catchments and such lakes are abundant in southwestern Greenland. Colored dissolved organic matter (CDOM), the fraction that absorbs ultraviolet (UV) and visible light, is the controlling factor for the optical properties of many surface waters and as well informs on the quality of DOM. We examined the quality of CDOM in 21 lakes in southwestern Greenland, from the ice sheet to the coast, as part of a larger study examining the role of DOM in regulating microbial communities in these lakes. DOM was size fractioned and absorbance and fluorescence was measured on each size fraction, as well as on bulk DOM. The specific ultraviolet absorbance (SUVA) at 254 nm (SUVA254), computed by normalizing absorption (a254) to dissolved organic carbon (DOC) concentration, provided an estimate of the aromatic carbon content of DOM. SUVA values were generally <2, indicating low aromatic content. Parallel factor analysis (PARAFAC) of CDOM fluorescence was used to determine the relative abundance of allochthonous and autochthonous DOM in all size fractions. Younger lakes near the ice sheet and lakes near the coast had lower amounts of CDOM and appeared more microbial in quality. However, lakes centrally located between the ice sheet and the coast had the highest CDOM concentrations and exhibited strong humic fluorescence. Overall distinct differences in CDOM quality were observed between lake locations and among DOM size fractions.

  3. Presence of the Cyanotoxin Microcystin in Arctic Lakes of Southwestern Greenland

    PubMed Central

    Trout-Haney, Jessica V.; Wood, Zachary T.; Cottingham, Kathryn L.

    2016-01-01

    Cyanobacteria and their toxins have received significant attention in eutrophic temperate and tropical systems where conspicuous blooms of certain planktonic taxa release toxins into fresh water, threatening its potability and safe use for recreation. Although toxigenic cyanobacteria are not confined to high nutrient environments, bloom-forming species, or planktonic taxa, these other situations are studied les often studied. For example, toxin production in picoplankton and benthic cyanobacteria—the predominant photoautotrophs found in polar lakes—is poorly understood. We quantified the occurrence of microcystin (MC, a hepatotoxic cyanotoxin) across 18 Arctic lakes in southwestern Greenland. All of the focal lakes contained detectable levels of MC, with concentrations ranging from 5 ng·L−1 to >400 ng·L−1 during summer, 2013–2015. These concentrations are orders of magnitude lower than many eutrophic systems, yet the median lake MC concentration in Greenland (57 ng·L−1) was still 6.5 times higher than the median summer MC toxicity observed across 50 New Hampshire lakes between 1998 and 2008 (8.7 ng·L−1). The presence of cyanotoxins in these Greenlandic lakes demonstrates that high latitude lakes can support toxigenic cyanobacteria, and suggests that we may be underestimating the potential for these systems to develop high levels of cyanotoxins in the future. PMID:27589801

  4. Recent warming at Summit, Greenland: Global context and implications

    NASA Astrophysics Data System (ADS)

    McGrath, Daniel; Colgan, William; Bayou, Nicolas; Muto, Atsuhiro; Steffen, Konrad

    2013-05-01

    at Summit, Greenland suggest that the annual mean near-surface air temperature increased at 0.09 ± 0.01°C/a over the 1982-2011 climatology period. This rate of warming, six times the global average, places Summit in the 99th percentile of all globally observed warming trends over this period. The rate of warming at Summit is increasing over time. During the instrumental period (1987-2011), warming has been greatest in the winter season, although the implications of summer warming are more acute. The annual maximum elevation of the equilibrium line and dry snow line has risen at 44 and 35 m/a over the past 15 and 18 years, respectively. Extrapolation of this observed trend now suggests, with 95% confidence intervals, that the dry snow facies of the Greenland Ice Sheet will inevitably transition to percolation facies. There is a 50% probability of this transition occurring by 2025.

  5. Soil development as limiting factor for shrub expansion in southwestern Greenland

    NASA Astrophysics Data System (ADS)

    Caviezel, Chatrina; Hunziker, Matthias; Zoller, Oliver; Wüthrich, Christoph; Kuhn, Nikolaus J.

    2014-05-01

    Southern Greenland currently experiences an increase in summer temperatures and a prolonged growing season (Masson-Delmotte et al. 2012), resulting in an increased shrub cover at the boreal - tundra border ecotone (Normand et al. 2013). These findings suggest the beginning of a greener Greenland in which tundra vegetation is transformed to a boreal woody flora. However, vegetation at borderline ecotones is influenced by further ecologic factors than just temperature. In this study, the ecologic conditions at a selection of sites along an elevation gradient near Igaliku in southern Greenland were examined to identify potential factors limiting the expansion of woody vegetation apart from temperature. The sites differ in elevation, topography, shrub density and soil parent material. The three study sites comprise i) well established birch shrubs growing between 50 and 180 m a.s.l., where the parent material origins from the Julianehab granite (Brooks 2012); ii) extended shrub patches at about 250 m a.s.l., where the parent material consists of Gardar Sandstones and Lavas (Brooks 2012) and iii) restricted shrub patches at an elevation of 250 m a.s.l., where the soil parent material originates from the Gardar intrusions (Brooks 2012). The extent of the shrub areas, topography and soil moisture were mapped, additionally soil samples were analyzed for C-and N-content, texture including coarse fraction and pH and used as soil development indicators. Our results show that the topographic setting regulates the existence or absence of soil while the soil parent material is an important limiting factor for soil moisture. According to these findings, we suggest that a high proportion of areas where temperature increase would allow the increase of shrub cover is not suitable for a woody flora. Brooks, Kent. 2012. "A Tale of Two Intrusions—where Familiar Rock Names No Longer Suffice." Geology Today 28 (1): 13-19. doi:10.1111/j.1365-2451.2012.00815.x. Masson-Delmotte, V., D

  6. Real-time measurements of CH4 and CO2 flux and del13C from a proglacial wetland in southwestern Greenland.

    NASA Astrophysics Data System (ADS)

    Stern, J. C.; White, J. R.; Pratt, L. M.; Thompson, H. A.

    2015-12-01

    Arctic permafrost environments represent a large repository of stored carbon that may be mobilized as global temperatures increase, providing a substrate for microbial CH4 production. Proglacial wetlands and lakes are important targets of study to better understand how rapidly changing landscapes affected by climate warming adapt their carbon cycling. Recent advances in portable laser spectrometry have enabled rapid in situ measurements of not only greenhouse gas fluxes, but also del13C compositions of these gases. Here we use a Picarro CH4 and CO2 isotope analyzer to continuously measure CH4 and CO2 flux in situ for comparison to static closed chamber measurements where samples are collected at discrete time intervals and returned to the laboratory for analysis. Real-time, in situ analysis also allowed simple light/dark experiments to be performed on chambers containing different vegetation. In addition, this instrument can be used to measure concentration and del13C of both dissolved CH4 and CO­­2 in lake waters when appropriate gas stripped methods are used. We present data for CH4 and CO2 flux and del13C of emitted and dissolved gases from permafrost-affected wetlands and lakes associated with proglacial landscapes in southwestern Greenland near the Russell Glacier.

  7. Ocean Melting Greenland (OMG) bathymetric survey of northwest Greenland and implications for the recent evolution of its glaciers

    NASA Astrophysics Data System (ADS)

    Wood, M.; Rignot, E. J.; Willis, J. K.; Fenty, I. G.

    2015-12-01

    Oceans Melting Greenland (OMG) is a five-year Earth Ventures Suborbital Mission funded by NASA to investigate the role of the oceans in ice loss around the margins of the Greenland Ice Sheet, which includes measurements of seafloor bathymetry from multibeam surveys and airborne gravity, glacier surface elevation from high-frequency radar interferometry, and temperature/salinity/depth from vessels and airborne-dropped probes. Here, we describe the results of the 2016 bathymetry survey of northwest Greenland that took place in the summer of 2015: july 22-August 19 and Sept 2-Sept 16 spanning from Ilulissat to Thule AFB in north Greenland, and to be complemented by a survey of southeast Greenland in 2016. We deployed a multibeam Reson 7160 with 512 beams installed on the hull of the Cape Race vessel, with enhanced capabilities for fjord wall and ice face mapping. The survey tracks were optimized based on the IBCAO3 database, recent cruises, airborne gravity data collected by NASA Operation IceBridge which indicated the presence of troughs, bed topography mapped inland using a mass conservation approach, the spatial distribution of ice discharge to locate the largest outlets and maximizing the number of major fjords sampled during the survey, with the goal to identify all troughs that are major pathways for subsurface ocean heat, and constrain as many glacier ice front thickness as permitted by time and the practicality of navigating the ice-choked fjords. The data reveal many deep, U-shaped, submarine valleys connected to the glaciers, intercut with sills and over deepened in narrower passages where former glaciers and ice streams merged into larger units; as well as fjords ending in shallow plateaus with glaciers in retreated positions. The presence of warm, salty water of Atlantic origin (AW) in the fjords is documented using CTD. Some glaciers sit on shallow plateaus in cold, fresh polar waters (PW) at the end of deep fjords, while others are deeper and standing in

  8. The crust and upper mantle of central East Greenland - implications for continental accretion and rift evolution

    NASA Astrophysics Data System (ADS)

    Schiffer, Christian; Balling, Niels; Ebbing, Jörg; Holm Jacobsen, Bo; Bom Nielsen, Søren

    2016-04-01

    .B., 2015. The East Greenland Caledonides - teleseismic signature, gravity and isostasy. Geophysical Journal International, 203, 1400-1418. 2) Schiffer, C., Stephenson, R.A., Petersen, K.D., Nielsen, S.B., Jacobsen, B.H., Balling, N. and Macdonald, D.I.M., 2015. A sub-crustal piercing point for North Atlantic reconstructions and tectonic implications. Geology, 43, 1087-1090.

  9. Causes of Greenland temperature variability over the past 4000 yr: implications for northern hemispheric temperature changes

    NASA Astrophysics Data System (ADS)

    Kobashi, T.; Goto-Azuma, K.; Box, J. E.; Gao, C.-C.; Nakaegawa, T.

    2013-10-01

    Precise understanding of Greenland temperature variability is important in two ways. First, Greenland ice sheet melting associated with rising temperature is a major global sea level forcing, potentially affecting large populations in coming centuries. Second, Greenland temperatures are highly affected by North Atlantic Oscillation/Arctic Oscillation (NAO/AO) and Atlantic multidecadal oscillation (AMO). In our earlier study, we found that Greenland temperature deviated negatively (positively) from northern hemispheric (NH) temperature trend during stronger (weaker) solar activity owing to changes in atmospheric/oceanic changes (e.g. NAO/AO) over the past 800 yr (Kobashi et al., 2013). Therefore, a precise Greenland temperature record can provide important constraints on the past atmospheric/oceanic circulation in the region and beyond. Here, we investigated Greenland temperature variability over the past 4000 yr reconstructed from argon and nitrogen isotopes from trapped air in a GISP2 ice core, using a one-dimensional energy balance model with orbital, solar, volcanic, greenhouse gas, and aerosol forcings. The modelled northern Northern Hemisphere (NH) temperature exhibits a cooling trend over the past 4000 yr as observed for the reconstructed Greenland temperature through decreasing annual average insolation. With consideration of the negative influence of solar variability, the modelled and observed Greenland temperatures agree with correlation coefficients of r = 0.34-0.36 (p = 0.1-0.04) in 21 yr running means (RMs) and r = 0.38-0.45 (p = 0.1-0.05) on a centennial timescale (101 yr RMs). Thus, the model can explain 14 to 20% of variance of the observed Greenland temperature in multidecadal to centennial timescales with a 90-96% confidence interval, suggesting that a weak but persistent negative solar influence on Greenland temperature continued over the past 4000 yr. Then, we estimated the distribution of multidecadal NH and northern high-latitude temperatures

  10. Age and archaeological implications of Xitle volcano, southwestern Basin of Mexico-City

    NASA Astrophysics Data System (ADS)

    Siebe, C.

    2000-12-01

    The Pedregal lavas are fresh, well-exposed basaltic flows erupted from the Xitle scoria-and-cinder cone in the southwestern part of the Basin of Mexico. These lavas cover an area of 70 km 2 and were emplaced over pyramids and other buildings (e.g. Cuicuilco and Copilco archaeological sites). Today, a part of Mexico-City (including the National University) is built on the flows. Initial strombolian activity produced an ash fallout layer, which was immediately followed by effusive emplacement of lava flows. The Xitle cone grew on the north-facing slope of Ajusco volcano, and lava flowed down to the N-NE until it reached the basin floor. More than 30 radiocarbon dates have been obtained by several workers on charcoal samples from beneath the lava, and several ages for the eruption have been proposed from these dates. Most dated samples were not directly produced by Xitle's eruption but instead are artifacts of human activity that predates the eruption. Thus, these ages (mostly about 2000 BP) are older than the eruption. A new age of 1670±35 years BP (AD 245-315) obtained on charcoal samples collected just beneath the lavas is favored for the Xitle eruption. These samples originated by ignition of vegetation during the emplacement of hot scoriaceous tephra. The new age is within the Classic period of Mesoamerican archaeology, whereas the earlier reported ages are at the end of the Preclassic. The new age carries important implications for the timing of population shifts within the Basin of Mexico.

  11. Submarine end moraines on the continental shelf off NE Greenland - Implications for Lateglacial dynamics

    NASA Astrophysics Data System (ADS)

    Winkelmann, Daniel; Jokat, Wilfried; Jensen, Laura; Schenke, Hans-Werner

    2010-05-01

    Favourable sea-ice conditions gave way to an acoustic survey offshore NE Greenland during RV Polarstern ARK-XXIV/3 leg in 2009. The acquired data set clearly depicts sediment ridges in an area of app. 18 × 9 km. The ridges are found in water depths between 270 and 350 m. The sediment ridges are 2.5-9 km long, 50-250 m wide and 5-25 m high. In profile, most of these ridges are characterized by steep slopes towards Northwest and gentle slopes towards Southeast. Their internal structure, imaged by parametric echo-sounding data, shows that they are positive sedimentation features rather than erosive remnant structures. Arcuate shape, joint orientation and position on a basal till are indicative for end moraines. Because they are positioned within the Westwind Trough on a basal till that extends further east, we consider these ridges end moraines of the Westwind ice stream reported by Evans et al. (2009), Marine geophysical evidence for former expansion and flow of the Greenland Ice Sheet across the north-east Greenland continental shelf. Journal of Quaternary Science (2008), doi: 10.1002/jqs.1231.). Based on our hydro-acoustic data, we interpret these end moraines to be formed by short-lived re-advances during an overall recession of the ice margin. However, they could also be deposited during halts of the grounding line (comparable to De Geer moraines) though their morphological characteristics are slightly different from most published De Geer moraines. The ages for the moraine deposition can be inferred from a thin sedimentary drape indicating timing between Lateglacial and early Holocene. This set of end moraines is direct evidence for a dynamic behaviour of the marine-based ice stream during the last deglaciation on the NE Greenland shelf.

  12. Present-day kinematics of the Rivera plate and implications for tectonics in southwestern Mexico

    NASA Technical Reports Server (NTRS)

    Demets, Charles; Stein, Seth

    1990-01-01

    A model for the present-day motion of the Rivera plate relative to the North America, Cocos, and Pacific plates is derived using new data from the Pacific-Rivera rise and Rivera transform fault, together with new estimates of Pacific-Rivera motions. The results are combined with the closure-consistent NUVEL-1 global plate motion model of DeMets et al. (1990) to examine present-day deformation in southwestern Mexico. The analysis addresses several questions raised in previous studies of the Rivera plate. Namely, do plate motion data from the northern East Pacific rise require a distinct Rivera plate? Do plate kinematic data require the subduction of the Rivera plate along the seismically quiescent Acapulco trench? If so, what does the predicted subduction rate imply about the earthquake recurrence interval in the Jalisco region of southwestern Mexico?

  13. Observations of Pronounced Greenland Ice Sheet Firn Warming and Implications for Runoff Production

    NASA Technical Reports Server (NTRS)

    Polashenski, Chris; Courville, Zoe; Benson, Carl; Wagner, Anna; Chen, Justin; Wong, Gifford; Hawley, Robert; Hall, Dorothy

    2014-01-01

    Field measurements of shallow borehole temperatures in firn across the northern Greenland ice sheet are collected during May 2013. Sites first measured in 19521955 are revisited, showing long-term trends in firn temperature. Results indicate a pattern of substantial firn warming (up to +5.7C) at midlevel elevations (1400-2500 m) and little temperature change at high elevations (2500 m). We find that latent heat transport into the firn due to meltwater percolation drives the observed warming. Modeling shows that heat is stored at depth for several years, and energy delivered from consecutive melt events accumulates in the firn. The observed warming is likely not yet in equilibrium with recent melt production rates but captures the progression of sites in the percolation facies toward net runoff production.

  14. Fluid-deposited graphite and its geobiological implications in early Archean gneiss from Akilia, Greenland.

    PubMed

    Lepland, A; van Zuilen, M A; Philippot, P

    2011-01-01

    Graphite, interpreted as altered bioorganic matter in an early Archean, ca. 3.83-Ga-old quartz-amphibole-pyroxene gneiss on Akilia Island, Greenland, has previously been claimed to be the earliest trace of life on Earth. Our petrographic and Raman spectroscopy data from this gneiss reveal the occurrence of graphitic material with the structure of nano-crystalline to crystalline graphite in trails and clusters of CO₂, CH₄ and H₂O bearing fluid inclusions. Irregular particles of graphitic material without a fluid phase, representing decrepitated fluid inclusions are common in such trails too, but occur also as dispersed individual or clustered particles. The occurrence of graphitic material associated with carbonic fluid inclusions is consistent with an abiologic, fluid deposited origin during a poly-metamorphic history. The evidence for fluid-deposited graphitic material greatly complicates any claim about remnants of early life in the Akilia rock.

  15. Implications of Farmers' Propensity to Discontinue Adoption of Downy-Mildew Resistant Maize and Improved Cowpea Varieties for Extension Education in Southwestern Nigeria

    ERIC Educational Resources Information Center

    Oladele, O. I.; Adekoya, A. E.

    2006-01-01

    This paper examines the implications of farmers' propensity to discontinue the adoption of agricultural technologies in southwestern Nigeria. This is predicated on the fact that extension education process should be proactive in addressing farmers in order to sustain the adoption process. Empirical studies looking at diffusion processes from an…

  16. Implications of high species turnover on the south-western Australian sandplains

    PubMed Central

    Gibson, Neil; Prober, Suzanne; Meissner, Rachel; van Leeuwen, Stephen

    2017-01-01

    Species turnover and its components related to replacement and nestedness form a significant element of diversity that is historically poorly accounted for in conservation planning. To inform biodiversity conservation and contribute to a broader understanding of patterns in species turnover, we undertook a floristic survey of 160 plots along an 870 km transect across oligotrophic sandplains, extending from the mesic south coast to the arid interior of south-western Australia. A nested survey design was employed to sample distances along the transect as evenly as possible. Species turnover was correlated with geographic distance at both regional and local scales, consistent with dispersal limitation being a significant driver of species turnover. When controlled for species richness, species replacement was found to be the dominant component of species turnover and was uniformly high across the transect, uncorrelated with either climatic or edaphic factors. This high replacement rate, well documented in the mega-diverse south-west, appears to also be a consistent feature of arid zone vegetation systems despite a decrease in overall species richness. Species turnover increased rapidly with increasing extent along the transect reaching an asymptote at ca. 50 km. These findings are consistent with earlier work in sandplain and mallee vegetation in the south-west and suggests reserve based conservation strategies are unlikely to be practicable in the south-western Australia sandplains when communities are defined by species incidence rather than dominance. PMID:28245232

  17. Comparing dust flux records from the Subarctic North Pacific and Greenland: Implications for atmospheric transport to Greenland and for the application of dust as a chronostratigraphic tool

    NASA Astrophysics Data System (ADS)

    Serno, Sascha; Winckler, Gisela; Anderson, Robert F.; Maier, Edith; Ren, Haojia; Gersonde, Rainer; Haug, Gerald H.

    2015-06-01

    We present a new record of eolian dust flux to the western Subarctic North Pacific (SNP) covering the past 27,000 years based on a core from the Detroit Seamount. Comparing the SNP dust record to the North Greenland Ice Core Project (NGRIP) ice core record shows significant differences in the amplitude of dust changes to the two regions during the last deglaciation, while the timing of abrupt changes is synchronous. If dust deposition in the SNP faithfully records its mobilization in East Asian source regions, then the difference in the relative amplitude must reflect climate-related changes in atmospheric dust transport to Greenland. Based on the synchronicity in the timing of dust changes in the SNP and Greenland, we tie abrupt deglacial transitions in the 230Th-normalized 4He flux record to corresponding transitions in the well-dated NGRIP dust flux record to provide a new chronostratigraphic technique for marine sediments from the SNP. Results from this technique are complemented by radiocarbon dating, which allows us to independently constrain radiocarbon paleoreservoir ages. We find paleoreservoir ages of 745 ± 140 years at 11,653 year B.P., 680 ± 228 years at 14,630 year B.P., and 790 ± 498 years at 23,290 year B.P. Our reconstructed paleoreservoir ages are consistent with modern surface water reservoir ages in the western SNP. Good temporal synchronicity between eolian dust records from the Subantarctic Atlantic and equatorial Pacific and the ice core record from Antarctica supports the reliability of the proposed dust tuning method to be used more widely in other global ocean regions.

  18. Arctic chlorine monoxide observations during spring 1993 over Thule, Greenland, and implications for ozone depletion

    NASA Technical Reports Server (NTRS)

    Shindell, D. T.; Reeves, J. M.; Emmons, L. K.; De Zafra, R. L.

    1994-01-01

    We have determined the vertical distribution of chlorine monoxide (ClO), from measurements of pressure-broadened molecular-emission spectra made over Thule, Greenland, during the 1993 Arctic spring. The measurements show a weak lower stratospheric layer of chlorine monoxide inside the vortex in late February, which was, however, significantly greater in mixing ratio than that seen in observations we made in the spring of 1992. ClO was also observed in much smaller quantities in early to mid-March 1993 when Thule was outside the vortex. The amount of ClO within the vortex was severely reduced by the time it returned over Thule in late March. This reduction occurred several weeks earlier relative to the winter solstice than the decline of ClO inside the Antarctic vortex in 1993. The enhanced Arctic lower stratospheric layer seen in late February 1993 at a nearly equivalent photochemical period, and beyond. We have calculated daily ozone loss rates, due primarily to the dimer chlorine catalytic cycle, from both sets of measurements. The vertical integral of the Arctic daily percentage ozone loss when the largest ClO levels were present, at the end of February, is found to be approximately one quarter of that in the Antarctic at a photochemical period only 1 week later. The relative weakness of daily ozone depletion, combined with the early disappearance of ClO in the Arctic, suggests that hemispheric dilution by ozone-poor air from within the Arctic vortex is unlikely to be sufficient to explain the historically extreme loss of midlatitude northern hemisphere ozone which began in 1992 and persisted throughout 1993.

  19. Distribution and characteristics of overdeepenings beneath the Greenland and Antarctic ice sheets and their glaciological implications

    NASA Astrophysics Data System (ADS)

    Swift, Darrel; Patton, Henry; Livingstone, Stephen; Jones, Andrew; Clark, Chris; Cook, Simon

    2016-04-01

    Understanding of overdeepening origin and glaciological significance is limited by an absence of quantitative empirical studies. To address this shortcoming, we have mapped the distribution of closed-topographic depressions (i.e. potential overdeepenings) beneath the Antarctic and Greenland ice sheets using automated GIS techniques, and have analysed the resulting database of overdeepening characteristics. The morphologies of a subset of mapped depressions that pass strict quality criteria indicate that overdeepening growth is generally allometric and that topographic confinement of ice flow enhances overdeepening depth. However, we infer that deepening slows with overdeepening age because (a) overdeepening depth is skewed towards shallow values - typically 200 to 300 m; and (b) overdeepening adverse slope steepness declines with overdeepening planform size. Analysis of overdeepening surface ice gradient to bed gradient ratio (the SB ratio) and surface ice velocity shows that velocities are highest for overdeepenings with SB ratios of ~ -1 to -1.5. Further, this ratio is close to the preferred range of SB ratio values exhibited by the dataset. This indicates that ice flow velocity and erosion potential are modulated by the changing efficiency of subglacial drainage and sediment transport that occurs as an overdeepening grows. This is presumed to encourage sediment deposition on the adverse slope, whilst overdeepening enlargement by headward growth (e.g. quarrying) is able to continue, and this presumption is supported by analysis of overdeepening long-profiles, which indicates that overdeepenings are typically asymmetric, with the deepest point skewed toward the overdeepening head. Our observations lead to the conclusion that overdeepening formation enhances ice sheet flow and that thinning during retreat, which will produce even greater negative SB ratios, should result a slowing or stabilisation of ice sheet flow.

  20. Arctic chlorine monoxide observations during spring 1993 over Thule, Greenland, and implications for ozone depletion

    NASA Astrophysics Data System (ADS)

    Shindell, D. T.; Reeves, J. M.; Emmons, L. K.; de Zafra, R. L.

    1994-12-01

    We have determined the vertical distribution of chlorine monoxide (ClO), from measurements of pressure-broadened molecular-emission spectra made over Thule, Greenland, during the 1993 Arctic spring. The measurements show a weak lower stratospheric layer of chlorine monoxide inside the vortex in late February, which was, however, significantly greater in mixing ratio than that seen in observations we made in the spring of 1992. ClO was also observed in much smaller quantities in early to mid-March 1993 when Thule was outside the vortex. The amount of ClO within the vortex was severely reduced by the time it returned over Thule in late March. This reduction occurred several weeks earlier relative to the winter solstice than the decline of ClO inside the Antarctic vortex in 1993. The enhanced Arctic lower stratospheric layer seen in late February 1993 had a peak mixing ratio of about 0.5 parts per billion by volume (ppbv), slightly less than a factor of 3 smaller than that observed in the Antarctic in 1993 at a nearly equivalent photochemical period, and beyond. We have calculated daily ozone loss rates, due primarily to the dimer chlorine catalytic cycle, from both sets of measurements. The vertical integral of the Arctic daily percentage ozone loss when the largest ClO levels were present, at the end of February, is found to be approximately one quarter of that in the Antarctic at a photochemical period only 1 week later. The relative weakness of daily ozone depletion, combined with the early disappearance of ClO in the Arctic, suggests that hemispheric dilution by ozone-poor air from within the Arctic vortex is unlikely to be sufficient to explain the historically extreme loss of midlatitude northern hemisphere ozone which began in 1992 and persisted throughout 1993.

  1. Implications of ground-deformation measurements across earth fissures in subsidence areas in the southwestern USA

    USGS Publications Warehouse

    Holzer, Thomas L.

    2010-01-01

    Ground deformation was monitored at earth fissures in areas of land subsidence induced by groundwater extraction in the southwestern United States. The ground deformation is consistent with the mechanism that fissures are caused by horizontal strains generated by bending of overburden in response to localized differential compaction. Subsidence profiles indicated that localized differential subsidence occurred across the fissures and that maximum convex-upward curvature was at the fissure. The overall shape of the profile stayed similar with time, and maximum curvature remained stationary at the fissure. Horizontal displacements were largest near the fissure, and generally were small to negligible away from the fissure. Maximum tensile horizontal strains were at the fissure and coincided with maximum curvature in the subsidence profiles. Horizontal tensile strain continued to accumulate at fissures after they formed with rates of opening ranging from 30 to 120 microstrain/year at fissures in Arizona.

  2. Geophysical framework of the southwestern Nevada volcanic field and hydrogeologic implications

    USGS Publications Warehouse

    Grauch, V.J.; Sawyer, David A.; Fridrich, Chris J.; Hudson, Mark R.

    1999-01-01

    Gravity and magnetic data, when integrated with other geophysical, geological, and rock-property data, provide a regional framework to view the subsurface geology in the southwestern Nevada volcanic field. The region has been loosely divided into six domains based on structural style and overall geophysical character. For each domain, the subsurface tectonic and magmatic features that have been inferred or interpreted from previous geophysical work has been reviewed. Where possible, abrupt changes in geophysical fields as evidence for potential structural lithologic control on ground-water flow has been noted. Inferred lithology is used to suggest associated hydrogeologic units in the subsurface. The resulting framework provides a basis for investigators to develop hypotheses from regional ground-water pathways where no drill-hole information exists.

  3. Tamarix as habitat for birds: Implications for riparian restoration in the Southwestern United States

    USGS Publications Warehouse

    Sogge, M.K.; Sferra, S.J.; Paxton, E.H.

    2008-01-01

    Exotic vegetation has become a major habitat component in many ecosystems around the world, sometimes dramatically changing the vegetation community structure and composition. In the southwestern United States, riparian ecosystems are undergoing major changes in part due to the establishment and spread of the exotic Tamarix (saltcedar, tamarisk). There are concerns about the suitability of Tamarix as habitat for birds. Although Tamarix habitats tend to support fewer species and individuals than native habitats, Arizona Breeding Bird Atlas data and Birds of North America accounts show that 49 species use Tamarix as breeding habitat. Importantly, the relative use of Tamarix and its quality as habitat vary substantially by geographic location and bird species. Few studies have examined how breeding in Tamarix actually affects bird survivorship and productivity; recent research on Southwestern Willow Flycatchers has found no negative effects from breeding in Tamarix habitats. Therefore, the ecological benefits and costs of Tamarix control are difficult to predict and are likely to be species specific and site specific. Given the likelihood that high-quality native riparian vegetation will not develop at all Tamarix control sites, restoration projects that remove Tamarix but do not assure replacement by high-quality native habitat have the potential to reduce the net riparian habitat value for some local or regional bird populations. Therefore, an assessment of potential negative impacts is important in deciding if exotic control should be conducted. In addition, measurable project objectives, appropriate control and restoration techniques, and robust monitoring are all critical to effective restoration planning and execution. ?? 2008 Society for Ecological Restoration International.

  4. Detrital mineral chronology of the Uinta Mountain Group: Implications for the Grenville flood in southwestern Laurentia

    USGS Publications Warehouse

    Mueller, P.A.; Foster, D.A.; Mogk, D.W.; Wooden, J.L.; Kamenov, George D.; Vogl, J.J.

    2007-01-01

    Numerous studies have shown that large quantities of Grenville-age detritus dominate Neo-proterozoic to Cambrian arenites in southwest Laurentia (southwestern United States). U-Pb ages and Hf isotopic compositions of zircons and 40Ar/39Ar ages of white mica from clastic sedimentary rocks of the Neoproterozoic Uinta Mountain Group also indicate significant Mesoproterozoic detritus mixed with a variably abundant Archean component. Zircons with ages representative of the Paleoproterozoic basement in the eastern Uinta Mountains or the younger Paleoproterozoic rocks of the adjacent Yavapai-Mazatzal terranes were not observed. A limited range of initial ??Hf (???90% between -3 and +3) for Mesoproterozoic zircons suggests derivation from a source region (or regions) characterized by mixing between juvenile and reworked older crust during Grenville orogenesis. The enriched Grenville-age basement proposed to underlie much of southeastern North America may be this source based on similarities of Hf isotopic data from Mesoproterozoic zircons in Mississippi River sand and available paleocurrent data. If so, then disruption of this supply in the Cambrian may be related to Iapetan rifting and, perhaps, the separation of the Precordillera terrane from Laurentia. ?? 2007 The Geological Society of America.

  5. Climate model performance and its implications for future glacier mass balance in southwestern Canada

    NASA Astrophysics Data System (ADS)

    Radic, V.; Anslow, F. S.; Jarosch, A.; Reuten, C.; Clarke, G. K.

    2009-12-01

    The aim of this study is to model the 21st century mass balance of all glaciers in southwestern Canada and northern Washington State, applying the climate scenarios of General Circulation Models (GCMs). Prior to projecting future mass balance the performance of 22 GCMs from the Coupled Model Intercomparison Project (CMIP3) archive is analyzed in comparison with North American Regional Reanalysis (NARR) over the overlapping period (1980-1999). Two different approaches are used for this analysis: (1) statistical metrics such as root-mean-square errors computed for several climate variables and (2) Self-Organizing Maps (SOMs) for deriving climatic patterns and comparing their frequency of occurrence in GCMs vs NARR. Based on the average of the relative errors over all climate variables considered, some models appear to perform substantially better than others. However, the ranking of the models strongly depends on the choice of validation approaches. The 21st century scenarios from validated GCMs are statistically downscaled using a variant of ‘weather typing’ that links the patterns of general atmospheric circulation with the patterns of regional mass balance fields, both derived from the SOM algorithm. Results confirm the dominant role of warmer climate as a driver for large glacier mass loss in the region. The range of projections associated with the choice of GCM is large, with enhanced future warming and more mass loss simulated when the better performing GCMs are used.

  6. Rehabilitation of a debris-flow prone mountain stream in southwestern China - Strategies, effects and implications

    NASA Astrophysics Data System (ADS)

    Yu, Guo-an; Huang, He Qing; Wang, Zhaoyin; Brierley, Gary; Zhang, Kang

    2012-01-01

    SummaryRehabilitation of Shengou Creek, a small, steep mountain stream in southwestern China that is prone to debris flows, started more than 30 years ago through an integrated program of engineering applications (check dams and guiding dikes), biological measures (reforestation), and social measures (reducing human disturbance). Small and medium-sized check dams and guiding dikes were constructed on key upper and middle sections of the creek to stabilize hillslopes and channel bed. Meanwhile, Leucaena leucocephala, a drought-tolerant, fast-growing, and highly adaptive plant species, was introduced to promote vegetation recovery in the watershed. The collective community structure of tree, shrub, and herb assemblages in the artificial L. leucocephala forest, which developed after 7 years, enhanced soil structure and drastically reduced soil erosion on hillslopes. Cultivation of steep land was strictly controlled in the basin, and some inhabitants were encouraged to move from upstream areas to downstream towns to reduce disturbance. These integrated measures reduced sediment supply from both hillslopes and upstream channels, preventing sediment-related hazards. The development of natural streambed resistance structures (mainly step-pool systems) and luxuriant riparian vegetation aided channel stability, diversity of stream habitat, and ecological maintenance in the creek. These findings are compared with Jiangjia and Xiaobaini Ravines, two adjacent non-rehabilitated debris-flow streams which have climate and geomorphologic conditions similar to Shengou Creek. Habitat diversity indices, taxa richness, biodiversity, and bio-community indices are much higher in Shengou Creek relative to Jiangjia and Xiaobaini Ravines, attesting to the effectiveness of rehabilitation measures.

  7. Geophysical framework of the southwestern Nevada volcanic field and hydrogeologic implications

    SciTech Connect

    Grauch, V.J.S.; Sawyer, D.A.; Fridrich, C.J.; Hudson, M.R.

    2000-06-08

    Gravity and magnetic data, when integrated with other geophysical, geological, and rock-property data, provide a regional framework to view the subsurface geology in the southwestern Nevada volcanic field. The authors have loosely divided the region into six domains based on structural style and overall geophysical character. For each domain, they review the subsurface tectonic and magmatic features that have been inferred or interpreted from previous geophysical work. Where possible, they note abrupt changes in geophysical fields as evidence for potential structural or lithologic control on ground-water flow. They use inferred lithology to suggest associated hydrogeologic units in the subsurface. The resulting framework provides a basis for investigators to develop hypotheses for regional ground-water pathways where no drill-hole information exists. The authors discuss subsurface features in the northwestern part of the Nevada Test Site and west of the Nevada Test Site in more detail to address potential controls on regional ground-water flow away from areas of underground nuclear-weapons testing at Pahute Mesa. Subsurface features of hydrogeologic importance in these areas are (1) the resurgent intrusion below Timber Mountain, (2) a NNE-trending fault system coinciding with western margins of the Silent Canyon and Timber Mountain caldera complexes, (3) a north-striking, buried fault east of Oasis Mountain extending for 15 km, which they call the Hogback fault, and (4) an east-striking transverse fault or accommodation zone that, in part, bounds Oasis Valley basin on the south, which they call the Hot Springs fault. In addition, there is no geophysical nor geologic evidence for a substantial change in subsurface physical properties within a corridor extending from the northwestern corner of the Rainier Mesa caldera to Oasis Valley basin (east of Oasis Valley discharge area). This observation supports the hypothesis of other investigators that regional ground water

  8. The Neoproterozoic and Paleozoic tectonostratigraphic evolution of Southwestern Mongolia and implications for crustal growth in Asia

    NASA Astrophysics Data System (ADS)

    Macdonald, F. A.; Bold, U.; Buchwaldt, R.; Smith, E. F.

    2013-12-01

    Neoproterozoic and Paleozoic strata on the Zavkhan Terrane of southwestern Mongolia contain unique geochemical and paleontological records that have become central to our understanding of this pivital era of Earth history. Here we present sedimentological, stratigraphic, structural, geochemical, and geochronological data that provide context for these records, and for the tectonic evolution of the Central Asian Orogenic Belt (CAOB). The CAOB is commonly cited as the largest region of Phanerozoic crustal growth on Earth, yet the tectonic evolution of this region is poorly constrained. In contrast to previous studies that depicted a back-arc basin setting for deposition of Neoproterozoic strata in Mongolia, we propose that the Zavkhan Terrane is a segment of a ribbon continent, which formed through collapse of an extensive ca. 811-802 Ma continental arc system on the Tarim margin of Rodinia, associated with the subduction of a mid-ocean ridge at around 800 Ma. Extension is recorded by emplacement of mafic dike swarms, normal faulting, growth fault deposition of more than 500m of cobble conglomerates and the eruption of ignimbrites in the Zavkhan Volcanics. As the Zavkhan Terrane detached, an additional succession of coarse siliciclastic strata was deposited in the Khasagtin suite, followed by passive margin sedimentation consisting of limestone and glacial deposits of the Tsagaan Olom Group on an isolated carbonate platform. Detrital zircon in the glacigenic Maikhan Ul Formation constrain its age to younger than 730 Ma. Chemostratigraphy in the overlying Tayshir Formation further suggests that the Maikhan Ul diamictite is correlative with the ca. 717-662 Ma Sturtian glacial epoch. By the time limestone of the overlying Tayshir Formation was deposited, arc volcanism had been inactive for over 100 Myrs. After rifting, the Proterozoic terranes of Mongolia formed an isolated ribbon continent that was mantled with passive margin carbonate platform sedimentation through

  9. Further paleomagnetic results for lower Permian basalts of the Baoshan Terrane, southwestern China, and paleogeographic implications

    NASA Astrophysics Data System (ADS)

    Xu, Yingchao; Yang, Zhenyu; Tong, Ya-Bo; Wang, Heng; Gao, Liang; An, Chunzhi

    2015-05-01

    The Baoshan Terrane of southwestern China is considered to have been part of the Cimmerian block during the late Paleozoic; consequently, knowledge of its paleoposition and geological evolution can provide constraints on the Permian breakup of northern East Gondwana. Therefore, we conducted paleomagnetic and rockmagnetic studies on lower Permian basalts from four localities in the Baoshan Terrane. The basalts hold a stable characteristic remanent magnetization (ChRM) at high temperatures (300-680 °C) that is carried by magnetite, maghemite, and hematite with both pseudo-single and multiple domains. To test the reliability of data from these volcanic rocks, we analyzed the geomagnetic secular variation (GSV) and reliability of both the present data and previous paleomagnetic data. The results from 23 sites yield a single reversed polarity directed downwards to the southwest, giving a site-mean direction of Dg/Ig = 156.7°/56.6° (kg = 8.0, α95 = 11.4°) before tilt correction, and Ds/Is = 218.3°/60.1° (ks = 14.1, α95 = 8.4°) after tilt correction. The result passed the fold test, but the GSV was able to be averaged out in only two sections. All available data were examined section-by-section using the angular dispersion (SB) of virtual geomagnetic poles (VGPs) to ensure that the GSV was completely averaged out. Because the dispersion in declinations is likely to have been affectedby subsequent tectonic deformation, the paleosecular variation (PSV) could not be evaluated from all the data amassed from different sections, and the PSV was able to be removed from only four (combined) sections. A small-circle fit of these VGPs gives an averaged paleocolatitude of 51.9° ± 3.7° (N = 31 sites) centered on 24°N, 99°E. The result indicates that the sampled area of the Baoshan Terrane was located at a latitude of 38°S ± 3.7° during the late early Permian. A comparison of this result with early Permian data from Gondwanan blocks suggests that the Baoshan Terrane

  10. Spatial and temporal oxygen isotope variability in northern Greenland - implications for a new climate record over the past millennium

    NASA Astrophysics Data System (ADS)

    Weißbach, S.; Wegner, A.; Opel, T.; Oerter, H.; Vinther, B. M.; Kipfstuhl, S.

    2016-02-01

    We present for the first time all 12 δ18O records obtained from ice cores drilled in the framework of the North Greenland Traverse (NGT) between 1993 and 1995 in northern Greenland. The cores cover an area of 680 km × 317 km, 10 % of the Greenland ice sheet. Depending on core length (100-175 m) and accumulation rate (90-200 kg m-2 a-1) the single records reflect an isotope-temperature history over the last 500-1100 years. Lowest δ18O mean values occur north of the summit and east of the main divide as a consequence of Greenland's topography. In general, ice cores drilled on the main ice divide show different results than those drilled east of the main ice divide that might be influenced by secondary regional moisture sources. A stack of all NGT records and the NGRIP record is presented with improved signal-to-noise ratio. Compared to single records, this stack represents the mean δ18O signal for northern Greenland that is interpreted as proxy for temperature. Our northern Greenland δ18O stack indicates distinctly enriched δ18O values during medieval times, about AD 1420 ± 20 and from AD 1870 onwards. The period between AD 1420 and AD 1850 has depleted δ18O values compared to the average for the entire millennium and represents the Little Ice Age. The δ18O values of the 20th century are comparable to the medieval period but are lower than that about AD 1420.

  11. Diet and environment of a mid-Pliocene fauna from southwestern Himalaya: Paleo-elevation implications

    NASA Astrophysics Data System (ADS)

    Wang, Yang; Xu, Yingfeng; Khawaja, Sofia; Passey, Benjamin H.; Zhang, Chunfu; Wang, Xiaoming; Li, Qiang; Tseng, Zhijie J.; Takeuchi, Gary T.; Deng, Tao; Xie, Guangpu

    2013-08-01

    A mid-Pliocene fauna (4.2-3.1 Ma) was recently uncovered in the Zanda (Zhada) Basin in the southwestern Himalaya, at an elevation of about 4200 m above sea level. These fossil materials provide a unique window for examining the linkage among tectonic, climatic and biotic changes. Here we report the results from isotopic analyses of this fauna and of modern herbivores and waters as well as paleo-temperature estimates from the Zanda Basin. The δ13C values of enamel samples from modern wild Tibetan asses, and domesticated horses, cows and goats in the area are -9.4±1.8‰, which indicate a diet comprising predominantly of C3 plants and are consistent with the current dominance of C3 vegetation in the region. The enamel-δ13C values of the fossil horses, rhinos, deer, and bovids are -9.6±0.8‰, indicating that these ancient mammals, like modern herbivores in the area, also fed primarily on C3 vegetation and lived in an environment dominated by C3 plants. The lack of significant C4 plants in the basin suggests that the area had reached high elevations (>2.5 km) by at least the mid-Pliocene. Taking into account the changes in the δ13C of atmospheric CO2 in the past, the enamel-δ13C values suggest that the average modern-equivalent δ13C value of C3 vegetation in the Zanda Basin in the mid-Pliocene was ∼1-2‰ lower than that of the C3 biomass in the basin today. This would imply a reduction in annual precipitation by about 200-400 mm in the area since then (assuming that the modern C3 δ13C-precipitation relationship applied to the past). Consistent with this inference from the δ13C data, the enamel-δ18O data show a significant shift to higher values after the mid-Pliocene, which also suggests a shift in climate to much drier conditions after ∼4-3 Ma. Paleo-temperature estimates derived from a fossil bone-based oxygen isotope temperature proxy as well as the carbonate clumped isotope thermometer for the mid-Pliocene Zanda Basin are higher than the present

  12. Post-Gondwana geomorphic evolution of southwestern Africa: Implications for hte controls on landscape development from observations and numerical experiments

    NASA Technical Reports Server (NTRS)

    Gilchrist, Alan R.; Kooi, Henk; Beaumont, Christopher

    1994-01-01

    The relationship between morphology and surficial geology is used to quantify the denudation that has occurred across southwestern Africa sicne the fragmentation of Gondwana during the Early Mesozoic. Two main points emerge. Signficant denudation, of the order of kilometers, is widespread except in the Kalahari region of the continental interior. The denudation is systematically distributed so that the continental exterior catchment, draining directly to the Cape basin, is denuded to a greater depth than the interior catchment inland of the Great Escarpment. The analysis also implies tha the majority of the denudation occurred before the beginning of the Cenozoic for both teh exerior and interior catchments. Existing models of landscape development are reviewed, and implications of the denudation chronology are incorporated into a revised conceptual model. This revision implies tha thte primary effect of rifting on the subsequent landscape evolution is that it generates two distinct drainage regimes. A marginal upwarp, or rift flank uplift, separates rejuvenated rivers that drain into the subsiding rift from rivers in the continetal interior that are deflected but not rejuvenated. The two catchments evolve independently unless they are integrated by breaching of hte marginal upwarp. If this occurs, the exterior baselevel is communicated to the interior catchment that is denuded accordingly. Denudation rates generally decrease as the margin evolves, and this decrease is reinforced by the exposure of substrate that is resistant to denudation and/or a change to a more arid climate. The observations do not reveal a particular style of smaller-scale landscape evolution, sucha s escarpment retreat, that is responsible for the differential denudation across the region. It is proposed that numerical model experiments, which reflect the observational insights at the large scale, may identify the smaller-scale controls on escarpment development if the model and natural

  13. Petrogenesis and tectonic implications of Permian post-collisional granitoids in the Chinese southwestern Tianshan, NW China

    NASA Astrophysics Data System (ADS)

    Xia, Bin; Zhang, Lifei; Zhang, Lu

    2016-11-01

    Permian porphyritic granite and leucogranite from the Kekesu and Muzhaerte Valleys in the southwestern (SW) Tianshan orogenic belt, NW China have been studied to decipher their petrogenesis and tectonic implications. For porphyritic granite in the Kekesu Valley, in situ LA-ICPMS zircon U-Pb dating yields crystallization ages of 295-291 Ma. The granite is a high potassic calc-alkaline, slightly peraluminous type, enriched in large ion lithosphere elements (LILE) and light rare earth elements (LREE), but depleted in high field strength elements (HFSE). Zircon Hf isotopic analysis (zircon εHf(t) of -5.8 to -0.2, two-stage Hf model ages of 1323-1680 Ma) and Ti-in-zircon thermometry, which yields crystallization temperatures of 744-749 °C, indicate the parent magma was likely formed by partial melting of a Mesoproterozoic crustal source. By contrast, leucogranite in the Kekesu valley yields crystallization ages of 274-267 Ma. It contains muscovite and garnet, has high silicon and potassium, and is strongly peraluminous. Multiple inherited zircon cores and low zircon crystallization temperatures (687-701 °C), combined with negative zircon εHf(t) values (-7.0 to -4.0), indicate its parent magma was sourced from supracrustal metasedimentary rocks by muscovite-breakdown partial melting. In the Muzhaerte Valley, porphyritic granite has similar major and trace elements characteristics to the Kekesu porphyritic granite. However, its higher zircon εHf(t) values (-0.9 to +3.8) and corresponding lower two-stage Hf model ages (1070-1367 Ma) indicate that the parent magma likely included an input from a more juvenile mantle source. Ti-in-zircon thermometry gives lower crystallization temperature of ∼705 °C. The intrusive relationships between the Permian granitoids and Paleozoic arc plutons, and the LP-HT and (U)HP metamorphic belts, combined with geochronological studies, suggest that these Permian granitoids were generated in a post-collisional environment. It is

  14. Absolute calibration of the Greenland time scale: implications for Antarctic time scales and for Δ 14C

    NASA Astrophysics Data System (ADS)

    Shackleton, N. J.; Fairbanks, R. G.; Chiu, Tzu-chien; Parrenin, F.

    2004-07-01

    We propose a new age scale for the two ice cores (GRIP and GISP2) that were drilled at Greenland summit, based on accelerator mass spectrometry 14C dating of foraminifera in core MD95-2042 (Paleoceanography 15 (2000) 565), calibrated by means of recently obtained paired 14C and 230Th measurements on pristine corals (Marine radiocarbon calibration curve spanning 10,500 to 50,000 years BP (thousand years before present) Based on paired 230Th/ 234U/ 238U and 14C dates on Pristine Corals Geological Society of America Bulletin, 2003, submitted for publication). The record of core MD95-2042 can be correlated very precisely to the Greenland ice cores. Between 30 and 40 ka BP our scale is 1.4 ka older than the GRIP SS09sea time scale (Journal of Quaternary Science 16 (2001) 299). At the older end of Marine Isotope Stage 3 we use published 230Th dates from speleothems to calibrate the record. Using this scale we show a Δ 14C record that is broadly consistent with the modelled record (Earth Planet. Sci. Lett. 200 (2002) 177) and with the data of Hughen et al. (Science 303 (2004) 202), but not consistent with the high values obtained by Beck et al. (Science 292 (2001) 2453) or by Voelker et al. (Radiocarbon 40 (1998) 517). We show how a set of age scales for the Antarctic ice cores can be derived that are both fully consistent with the Greenland scale, and glaciologically reasonable.

  15. Nuuk, Greenland

    NASA Technical Reports Server (NTRS)

    2008-01-01

    Nuuk (or Gadthab) is the capital and largest city of Greenland. It is located at the mouth of the Nuup Kangerlua inlet on the west coast of Greenland. It has a population of about 15,000. The site has a long history of different inhabitation: first by the Inuit people around 2000 B.C., later by Viking explorers in the 10th century. Inuit and Vikings lived together for about 500 years until about 1500, when human habitation suddenly stopped, most likely due to change in climate and vegetation.

    The image was acquired August 2, 2004, covers an area of 22.7 x 26 km, and is located at 64.2 degrees north latitude, 51.8 degrees west longitude.

    The U.S. science team is located at NASA's Jet Propulsion Laboratory, Pasadena, Calif. The Terra mission is part of NASA's Science Mission Directorate.

  16. The Weichselian (Würmian) Pleniglacial chronology of the Nussloch loess section/Germany revisited. Implications for the matching of pedosedimentary units with Greenland stadial and interstadial periods.

    NASA Astrophysics Data System (ADS)

    Kadereit, A.; Kind, C.-J.; Wagner, G. A.

    2012-04-01

    The loess section of Nussloch in SW-Germany is a key profile for the reconstruction of the terrestrial palaeoenvironment of central Europe for the time of the Weichselian (Würmian) Pleniglacial (e.g. Antoine et al., 2009). In this period, the earliest modern humans invaded SW-Germany as documented in unique cultural remains from karst caves of the Swabian Jura (e.g. Conard et al., 2009). The Nussloch profile includes a Middle Pleniglacial Cambisol remain (Lohne Soil), which serves as an important loess marker horizon throughout Europe. Greenland interstadial (GIS) 8 was hitherto regarded as the likely period of soil formation for the Lohne Soil and a suite of partly soliflucted Cryosols in the hanging wall is interpreted to represent warm climate excursions of the Upper Pleniglacial period, starting with GIS8 or GIS7 (e.g. Antoine et al., 2001, 2009; Rousseau et al., 2011). However, revaluation of available chronometric data from Nussloch suggests (GIS7 to) GIS5 as the likely period of soil formation for the Lohne Soil. GIS8 is documented by deposits from thermokarst dynamics, stratigraphically several units below the marker soil. Consequences of a revised chronology for correlations of Pleniglacial Cryosols below and above the Lohne Soil with Greenland interstadials are discussed. The implications are important for European loess research as the Nussloch section serves as a reference base throughout Europe. The revised chronology suggests also that the Lohne Soil postdates the immigration of the earliest modern humans in SW-Germany and central Europe. This finding is in contrast to the earlier age-model for the Nussloch site.

  17. Three-dimensional velocity structure of crust and upper mantle in southwestern China and its tectonic implications

    USGS Publications Warehouse

    Wang, Chun-Yong; Chan, W.W.; Mooney, W.D.

    2003-01-01

    Using P and S arrival times from 4625 local and regional earthquakes recorded at 174 seismic stations and associated geophysical investigations, this paper presents a three-dimensional crustal and upper mantle velocity structure of southwestern China (21??-34??N, 97??-105??E). Southwestern China lies in the transition zone between the uplifted Tibetan plateau to the west and the Yangtze continental platform to the east. In the upper crust a positive velocity anomaly exists in the Sichuan Basin, whereas a large-scale negative velocity anomaly exists in the western Sichuan Plateau, consistent with the upper crustal structure under the southern Tibetan plateau. The boundary between these two anomaly zones is the Longmen Shan Fault. The negative velocity anomalies at 50-km depth in the Tengchong volcanic area and the Panxi tectonic zone appear to be associated with temperature and composition variations in the upper mantle. The Red River Fault is the boundary between the positive and negative velocity anomalies at 50-km depth. The overall features of the crustal and the upper mantle structures in southwestern China are a low average velocity, large crustal thickness variations, the existence of a high-conductivity layer in the crust or/and upper mantle, and a high heat flow value. All these features are closely related to the collision between the Indian and the Asian plates.

  18. Distribution and characteristics of overdeepenings beneath the Greenland and Antarctic ice sheets: Implications for overdeepening origin and evolution

    NASA Astrophysics Data System (ADS)

    Patton, H.; Swift, D. A.; Clark, C. D.; Livingstone, S. J.; Cook, S. J.

    2016-09-01

    Glacier bed overdeepenings are ubiquitous in glacier systems and likely exert significant influence on ice dynamics, subglacial hydrology, and ice stability. Understanding of overdeepening formation and evolution has been hampered by an absence of quantitative empirical studies of their distribution and morphology, with process insights having been drawn largely from theoretical or numerical studies. To address this shortcoming, we first map the distribution of potential overdeepenings beneath the Antarctic and Greenland ice sheets using a GIS-based algorithm that identifies closed-contours in the bed topography and then describe and analyse the characteristics and metrics of a subset of overdeepenings that pass further quality control criteria. Overdeepenings are found to be widespread, but are particularly associated with areas of topographically laterally constrained ice flow, notably near the ice sheet margins where outlet systems follow deeply incised troughs. Overdeepenings also occur in regions of topographically unconstrained ice flow (for example, beneath the Siple Coast ice streams and on the Greenland continental shelf). Metrics indicate that overdeepening growth is generally allometric and that topographic confinement of ice flow in general enhances overdeepening depth. However, overdeepening depth is skewed towards shallow values - typically 200-300 m - indicating that the rate of deepening slows with overdeepening age. This is reflected in a decline in adverse slope steepness with increasing overdeepening planform size. Finally, overdeepening long-profiles are found to support headward quarrying as the primary factor in overdeepening development. These observations support proposed negative feedbacks related to hydrology and sediment transport that stabilise overdeepening growth through sedimentation on the adverse slope but permit continued overdeepening planform enlargement by processes of headward erosion.

  19. Modeling Subglacial Meltwater Plumes across Greenland's Outlet Glaciers: Implications for Ice-Ocean Coupling in a Warming Climate

    NASA Astrophysics Data System (ADS)

    Carroll, D.; Sutherland, D.; Moon, T. A.; Hudson, B.; Noel, B.; Felikson, D.; Catania, G. A.; Nash, J. D.; Shroyer, E.; Bartholomaus, T.; Stearns, L. A.; van den Broeke, M.

    2015-12-01

    Meltwater accumulated on the Greenland Ice Sheet (GrIS) drains to glacier beds, often discharging into outlet glacier fjords hundreds of meters below sea level. The injection of buoyant meltwater at depth drives a turbulent plume that entrains warm bottom water as it rises along the ice face, resulting in increased submarine melt rates. Recent studies have used remotely sensed data to identify distinct seasonal flow patterns in GrIS outlet glacier dynamics, suggesting some glaciers are especially sensitive to changes at the terminus. However, we currently lack an understanding of the corresponding regional patterns in near-glacier circulation that are a first-order control on submarine melt rates and indirectly modulate the resultant estuarine exchange flow and mixing of fjord waters. In this study, we use a buoyant plume model combined with a synthesis of shipboard hydrography, moored observations, estimates of subglacial discharge, and remotely sensed data on glacier characteristics, to provide an estimate of plume properties across GrIS outlet glaciers in both time and space. We validate our model results with detailed ice-ocean measurements from neighboring outlet glacier fjords in Uummannaq Bay, west Greenland. Model and observations agree that strongly stratified fjords with deep outlet glaciers result in warm, subsurface plumes, while shallow fjords result in surface-intensified plumes that retain their cold meltwater signature. We compare these results to a high-resolution ocean model to provide an estimate of submarine melt rates during peak summer discharge. One advantage of our approach is the rapid characterization of distinct plume regimes across GrIS outlet glacier parameter space. Finally, we compare these plume regimes with characteristics of glacier behavior (ice velocity, surface elevation, terminus position), over decadal and seasonal time-scales. This comparison allows us to investigate which outlet glacier systems might be more sensitive to

  20. Implication of azelaic acid in a Greenland Ice Core for oceanic and atmospheric changes in high latitudes

    NASA Astrophysics Data System (ADS)

    Kawamura, K.; Yokoyama, K.; Fujii, Y.; Watanabe, O.

    A Greenland ice core (450 years) has been studied for low molecular weight dicarboxylic acids (C2-C10) using a capillary gas chromatography and mass spectrometer. Their molecular distribution generally showed a predominance of succinic acid (C4) followed by oxalic (C2), malonic (C3), glutaric (C5), adipic (C6), and azelaic (C9) acids. Azelaic acid, that is a specific photochemical reaction product of biogenic unsaturated fatty acids, gave a characteristic historical trend in the ice core; i.e., the concentrations are relatively low during late 16th to 19th century (Little Ice Age) but become very high in late 19th to 20th century (warmer periods) with a large peak in 1940s AD. Lower concentrations of azelaic acid may have been caused by a depressed emission of unsaturated fatty acids from seawater microlayers due to enhanced sea ice coverage during Little Ice Age. Inversely, increased concentrations of azelaic acid in late 19th to 20th century are likely interpreted by an enhanced sea-to-air emission of the precursor unsaturated fatty acids due to a retreat of sea ice and/or by the enhanced production due to a potentially increased oxidizing capability of the atmosphere.

  1. Moisture Flux Convergence in Regional and Global Climate Models: Implications for Droughts in the Southwestern United States Under Climate Change

    SciTech Connect

    Gao, Yanhong; Leung, Lai-Yung R.; Salathe, E.; Dominguez, Francina; Nijssen, Bart; Lettenmaier, D. P.

    2012-05-10

    The water cycle of the southwestern United States (SW) is dominated by winter storms that maintain a positive annual net precipitation. Analysis of the control and future climate from four pairs of regional and global climate models (RCMs and GCMs) shows that the RCMs simulate a higher fraction of transient eddy moisture fluxes because the hydrodynamic instabilities associated with flow over complex terrain are better resolved. Under global warming, this enables the RCMs to capture the response of transient eddies to increased atmospheric stability that allows more moisture to converge on the windward side of the mountains by blocking. As a result, RCMs simulate enhanced transient eddy moisture convergence in the SW compared to GCMs, although both robustly simulate drying due to enhanced moisture divergence by the divergent mean flow in a warmer climate. This enhanced convergence leads to reduced susceptibility to hydrological change in the RCMs compared to GCMs.

  2. Metamorphism of the ca. 3800 Ma supracrustal rocks at Isua, West Greenland: implications for early Archaean crustal evolution

    NASA Astrophysics Data System (ADS)

    Boak, Jeremy L.; Dymek, Robert F.

    1982-06-01

    A detailed mineralogical and petrological study has been carried out on samples from two clastic metasedimentary lithologies from the ˜ 3800 Ma Isua Supracrustal Belt, West Greenland. Semipelitic to pelitic "garnet-biotite schist" contains the limiting AKFM assemblage: muscovite-biotite-garnet-staurolite (+ quartz + plagioclase + ilmenite), whereas "muscovite-biotite gneiss", derived from felsic volcanogenic graywacke, locally contains kyanite (+ quartz+ plagioclase + Ca-, Mn-rich garnet). Temperatures calculated from Fe-Mg partitioning between coexisting garnet- biotite indicate equilibration for garnet coresat T ˜550°C, and ˜460°C for garnet rims. We interpret the higher T as a minimum estimate for prograde regional metamorphism which we argue occurred before 3600 Ma, whereas the lower T reflects later retrogression as indicated by the development of chlorite ± sericite in many samples. The presence of kyanite as the stable aluminosilicate polymorph, combined with phase assemblage data, indicate P ˜5 kbar during prograde metamorphism, and a depthof burial of at least 15 km. The Isua supracrustals are the oldest comprehensively dated rocks on Earth, and the metamorphic mineral assemblages reported here constitute the earliest direct record of thermal regimes in Archaean crust. Therefore, characterization of the metamorphic history of the Isua region places an important constraint on models of early Earth history. Our data and observations indicate that prograde regional metamorphism at Isua occurred at conditions which are considered "normal" for an orogenic system, with a metamorphic thermal gradient ˜35°C/km. Moreover, our results contraindicate the universal occurrence of "thin" Archaean crust and excessively "steep" crustal thermal gradients as proposed by some investigators. Such conclusion appears at odds with estimates for higher terrestrial heat production during the early Archaean, but can be resolved by appealing to more rapid convection and

  3. Implications of Climate Change for Bird Conservation in the Southwestern U.S. under Three Alternative Futures.

    PubMed

    Friggens, Megan M; Finch, Deborah M

    2015-01-01

    Future expected changes in climate and human activity threaten many riparian habitats, particularly in the southwestern U.S. Using Maximum Entropy (MaxEnt3.3.3) modeling, we characterized habitat relationships and generated spatial predictions of habitat suitability for the Lucy's warbler (Oreothlypis luciae), the Southwestern willow flycatcher (Empidonax traillii extimus) and the Western yellow-billed cuckoo (Coccyzus americanus). Our goal was to provide site- and species-specific information that can be used by managers to identify areas for habitat conservation and/or restoration along the Rio Grande in New Mexico. We created models of suitable habitat for each species based on collection and survey samples and climate, biophysical, and vegetation data. We projected habitat suitability under future climates by applying these models to conditions generated from three climate models for 2030, 2060 and 2090. By comparing current and future distributions, we identified how habitats are likely to change as a result of changing climate and the consequences of those changes for these bird species. We also examined whether land ownership of high value sites shifts under changing climate conditions. Habitat suitability models performed well. Biophysical characteristics were more important that climate conditions for predicting habitat suitability with distance to water being the single most important predictor. Climate, though less important, was still influential and led to declines of suitable habitat of more than 60% by 2090. For all species, suitable habitat tended to shrink over time within the study area leaving a few core areas of high importance. Overall, climate changes will increase habitat fragmentation and reduce breeding habitat patch size. The best strategy for conserving bird species within the Rio Grande will include measures to maintain and restore critical habitat refugia. This study provides an example of a presence-only habitat model that can be used

  4. Implications of Climate Change for Bird Conservation in the Southwestern U.S. under Three Alternative Futures

    PubMed Central

    Friggens, Megan M.; Finch, Deborah M.

    2015-01-01

    Future expected changes in climate and human activity threaten many riparian habitats, particularly in the southwestern U.S. Using Maximum Entropy (MaxEnt3.3.3) modeling, we characterized habitat relationships and generated spatial predictions of habitat suitability for the Lucy’s warbler (Oreothlypis luciae), the Southwestern willow flycatcher (Empidonax traillii extimus) and the Western yellow-billed cuckoo (Coccyzus americanus). Our goal was to provide site- and species-specific information that can be used by managers to identify areas for habitat conservation and/or restoration along the Rio Grande in New Mexico. We created models of suitable habitat for each species based on collection and survey samples and climate, biophysical, and vegetation data. We projected habitat suitability under future climates by applying these models to conditions generated from three climate models for 2030, 2060 and 2090. By comparing current and future distributions, we identified how habitats are likely to change as a result of changing climate and the consequences of those changes for these bird species. We also examined whether land ownership of high value sites shifts under changing climate conditions. Habitat suitability models performed well. Biophysical characteristics were more important that climate conditions for predicting habitat suitability with distance to water being the single most important predictor. Climate, though less important, was still influential and led to declines of suitable habitat of more than 60% by 2090. For all species, suitable habitat tended to shrink over time within the study area leaving a few core areas of high importance. Overall, climate changes will increase habitat fragmentation and reduce breeding habitat patch size. The best strategy for conserving bird species within the Rio Grande will include measures to maintain and restore critical habitat refugia. This study provides an example of a presence-only habitat model that can be

  5. Local tomography and focal mechanisms in the south-western Alps: Comparison of methods and tectonic implications

    NASA Astrophysics Data System (ADS)

    Nicole, Béthoux; Christian, Sue; Anne, Paul; Jean, Virieux; Julien, Fréchet; François, Thouvenot; Marco, Cattaneo

    2007-03-01

    We investigate how focal solutions and hypocenter locations may depend on the ray tracing algorithm and the strategy of velocity inversion. Using arrival times from a temporary seismological network in the south-western Alps, a local earthquake tomography has been performed by Paul et al. [Paul, A., Cattaneo, M., Thouvenot, F., Spallarossa, D., Béthoux, N., and Fréchet, J., 2001. A three-dimensional crustal velocity model of the south-western Alps from local earthquake tomography. J. Geophys. Res. 106, 19367-19390.] with the method developed by Thurber [Thurber, C.H., 1993. Local earthquake tomography: velocity and Vp/Vs-Theory, in Seismic Tomography: Theory and practice, Iyer, H.M., and Irahara eds., Chapman and Hall, New York, 563-583.]. Another inversion of the same data set is performed here using a different tomography code relying on a shooting paraxial method and cubic interpolation of velocities. The resulting images display the same main features, although Thurber's code appears to be more robust in regions with scarce ray coverage and strong velocity contrasts. Concerning hypocenter location in Piemont units, one major result is the concentration of hypocenters at the boundary between the mantle wedge of the Ivrea body and the European crust. Forty-six focal mechanisms are shown that were computed using both the take-off angles in the minimum 1-D model and in the 3-D velocity structures resulting from the two inversions. The sets of focal solutions are very similar, proving the reliability and the coherency of the focal solutions. The widespread extension in the core of the western Alps is confirmed whereas a few compressive solutions are found east of the Piemont units. These results constrain the sharp change of stress tensor and evidence a decoupling of strain beneath the east of Dora Maira massif up to beneath the north of Argentera massif. On a geodynamical point of view seismicity and focal mechanism distribution are compatible with the present

  6. Age of the Dawson Arkose, southwestern Air Force Academy, Colorado, and implications for the uplift history of the Front Range

    SciTech Connect

    Kluth, C.F.; Nelson, S.N. )

    1988-01-01

    An angular unconformity within the synorogenic Dawson Arkose (Late Cretaceous-Eocene) is preserved and exposed in areas south of Denver, Colorado, along the eastern side of the Front Range uplift. In the southwestern part of the Air Force Academy, the basal Dawson is concordant with the underlying Laramie and Fox Hills formations and dips 72-84{degree} eastward. Above an intraformational angular unconformity, younger units of the Dawson dip 24{degree}-46{degree} eastward. Smaller angular unconformities (10{degree}{plus minus}), and beds with gradually decreasing dip occur higher in the Dawson section. Rocks above the largest unconformity contain a rich palynomorph assemblage of Late Maestrichtain age. These data indicate that approximately 30{degree}-40{degree}, and possibly as much as approximately 70{degree}, of tilting of the underlying rocks occurred during the Late Maestrichtian (66-70 Ma). It is also possible that approximately 30{degree}-40{degree} of the tilting of the Late Cretaceous rocks occurred between latest Maestrichtian and Eocene (approximately 45 Ma). These results suggest that the transition from a tectonically quiet marine environment to a non-marine, tectonically active condition took place rapidly, probably within a few million years. When combined with published data, the authors study indicates that the Front Range has different tectonic histories on its eastern and its western side, and that the deformation is diachronous along the strike of the eastern side of the Front Range.

  7. Mimomys savini size evolution in the Early Pleistocene of south-western Europe and possible biochronological implications

    NASA Astrophysics Data System (ADS)

    Lozano-Fernández, Iván; Cuenca-Bescós, Gloria; Blain, Hugues-Alexandre; López-García, Juan Manuel; Agustí, Jordi

    2013-09-01

    Over the course of their evolutionary history, some species of mammals have undergone variations in size, with a general trend towards increased morphometry. This effect can be seen very clearly in the fossil record of rodents because their high rate of reproduction that generates a high fossil record, which allows this phenomenon to be studied in detail. Furthermore, the rapid geographic distribution of rodents means that their evolution can be studied on a continental scale. If a relationship can be established between the size of individuals and their chronology, and the trend that governs a species' increase in size can be determined, then the chronologies of different sites can be estimated based on the size of the individuals of that species recovered at those particular sites. The correlation between morphometric data of micromammal fossils and age was already used by other authors. This article studies the rate at which the length of the first lower molar (m1) of Mimomys savini (a species of Palearctic arvicoline present in Europe between approximately 1.8 and 0.6 Ma ago) increased over the course of its evolution in Iberian Peninsula (south-western Europe). Because this increase in length occurred at a constant rate, a direct relationship can be established between average length of m1 and chronology, which allows us to set numerical dates to Pleistocene sites containing Mimomys savini remains.

  8. Knowledge, attitudes and practices of traceability among livestock traders in south-western Nigeria: implications for sustainable livestock industry.

    PubMed

    Adesokan, Hezekiah K; Ocheja, Samuel E

    2014-01-01

    Livestock diseases and other animal health events are a threat to achieving sustainable livestock industry. The knowledge of trace-back and the practice of providing feedback on diseases encountered in slaughtered animals from the abattoir to the farm can help limit the spread as well as manage potential future incidents of such diseases. We assessed the knowledge, attitudes and practices of 200 willing livestock traders on traceability in Bodija Municipal Abattoir, south-western Nigeria. The results reveal that the majority of these traders had poor knowledge (79.5 %) and practices (74.0 %) of traceability, though 89.5 % demonstrated good attitudes. While 22.9 % knew that traceability could be an effective means to control diseases, only a lower proportion (9.0 %) knew the health status of the animals being purchased. Though 29.0 % reported the diseases encountered in their animals during slaughter to the farm, only 9.5 % followed up to ensure the farmers take steps at preventing further occurrence of the reported diseases. While age (p = 0.000; 0.014) and education (p = 0.000; 0.000) were both significant for good knowledge and attitudes, frequency of condemned cases (p = 0.000) and length of years in the trade (p = 0.004) were, respectively, significant for good knowledge and attitudes with none associated with practice. These poor levels of knowledge and practices of traceability are a threat to sustainable livestock industry, food security and human health; hence, there is an urgent need to institute national feedback mechanism on slaughtered animals in order to strengthen interventions against diseases at farm levels.

  9. Greenland Ice Sheet retreat during the Eemian

    NASA Astrophysics Data System (ADS)

    van de Berg, W. J.; Helsen, M. M.; van de Wal, R. S. W.; van den Broeke, M. R.; Oerlemans, J.

    2012-04-01

    from the rapid retreat in southwestern Greenland.

  10. Sea ice and primary production proxies in surface sediments from a High Arctic Greenland fjord: Spatial distribution and implications for palaeoenvironmental studies.

    PubMed

    Ribeiro, Sofia; Sejr, Mikael K; Limoges, Audrey; Heikkilä, Maija; Andersen, Thorbjørn Joest; Tallberg, Petra; Weckström, Kaarina; Husum, Katrine; Forwick, Matthias; Dalsgaard, Tage; Massé, Guillaume; Seidenkrantz, Marit-Solveig; Rysgaard, Søren

    2017-02-01

    In order to establish a baseline for proxy-based reconstructions for the Young Sound-Tyrolerfjord system (Northeast Greenland), we analysed the spatial distribution of primary production and sea ice proxies in surface sediments from the fjord, against monitoring data from the Greenland Ecosystem Monitoring Programme. Clear spatial gradients in organic carbon and biogenic silica contents reflected marine influence, nutrient availability and river-induced turbidity, in good agreement with in situ measurements. The sea ice proxy IP25 was detected at all sites but at low concentrations, indicating that IP25 records from fjords need to be carefully considered and not directly compared to marine settings. The sea ice-associated biomarker HBI III revealed an open-water signature, with highest concentrations near the mid-July ice edge. This proxy evaluation is an important step towards reliable palaeoenvironmental reconstructions that will, ultimately, contribute to better predictions for this High Arctic ecosystem in a warming climate.

  11. Setting a chronology for the basal ice at Dye-3 and GRIP: Implications for the long-term stability of the Greenland Ice Sheet

    NASA Astrophysics Data System (ADS)

    Yau, Audrey M.; Bender, Michael L.; Blunier, Thomas; Jouzel, Jean

    2016-10-01

    The long-term stability of the Greenland Ice Sheet (GIS) is an important issue in our understanding of the climate system. Limited data suggest that the northern and southern sections extend well back into the Pleistocene, but most age constraints do not definitively date the ice. Here, we re-examine the GRIP and Dye-3 ice cores to provide direct ice core observations as to whether the GIS survived previous interglacials known to be warmer (˜130 ka) or longer (˜430 ka) than the present interglacial. We present geochemical analyses of the basal ice from Dye-3 (1991-2035 m) and GRIP (3020-3026 m) that characterize and date the ice. We analyzed the elemental and isotopic composition of O2, N2, and Ar, of trapped air in these two cores to assess the origin of trapped gases in silty ice. Dating of the trapped air was then achieved by measuring the paleoatmospheric δ40Ar/38Ar and the 17O anomaly (17Δ) of O2. The resulting age is a lower limit because the trapped air may be contaminated with crustal radiogenic 40Ar. The oldest average age of replicates measured at various depths is 970 ± 140 ka for the GRIP ice core and 400 ka ± 170 ka for Dye-3. 17Δ data from Dye-3 also argue strongly that basal ice in this core predates the Eemian. This confirms that the Greenland Ice Sheet did not completely melt at Southern Greenland during the last interglacial, nor did it completely melt at Summit Greenland during the unusually long interglacial ˜430 kyr before present.

  12. Aponogeton pollen from the Cretaceous and Paleogene of North America and West Greenland: Implications for the origin and palaeobiogeography of the genus☆

    PubMed Central

    Grímsson, Friðgeir; Zetter, Reinhard; Halbritter, Heidemarie; Grimm, Guido W.

    2014-01-01

    The fossil record of Aponogeton (Aponogetonaceae) is scarce and the few reported macrofossil findings are in need of taxonomic revision. Aponogeton pollen is highly diagnostic and when studied with light microscopy (LM) and scanning electron microscopy (SEM) it cannot be confused with any other pollen types. The fossil Aponogeton pollen described here represent the first reliable Cretaceous and Eocene records of this genus worldwide. Today, Aponogeton is confined to the tropics and subtropics of the Old World, but the new fossil records show that during the late Cretaceous and early Cenozoic it was thriving in North America and Greenland. The late Cretaceous pollen record provides important data for future phylogenetic and phylogeographic studies focusing on basal monocots, especially the Alismatales. The Eocene pollen morphotypes from North America and Greenland differ in morphology from each other and also from the older Late Cretaceous North American pollen morphotype, indicating evolutionary trends and diversification within the genus over that time period. The presence of Aponogeton in the fossil record of North America and Greenland calls for a reconsideration of all previous ideas about the biogeographic history of the family. PMID:24926107

  13. Aponogeton pollen from the Cretaceous and Paleogene of North America and West Greenland: Implications for the origin and palaeobiogeography of the genus.

    PubMed

    Grímsson, Friðgeir; Zetter, Reinhard; Halbritter, Heidemarie; Grimm, Guido W

    2014-01-01

    The fossil record of Aponogeton (Aponogetonaceae) is scarce and the few reported macrofossil findings are in need of taxonomic revision. Aponogeton pollen is highly diagnostic and when studied with light microscopy (LM) and scanning electron microscopy (SEM) it cannot be confused with any other pollen types. The fossil Aponogeton pollen described here represent the first reliable Cretaceous and Eocene records of this genus worldwide. Today, Aponogeton is confined to the tropics and subtropics of the Old World, but the new fossil records show that during the late Cretaceous and early Cenozoic it was thriving in North America and Greenland. The late Cretaceous pollen record provides important data for future phylogenetic and phylogeographic studies focusing on basal monocots, especially the Alismatales. The Eocene pollen morphotypes from North America and Greenland differ in morphology from each other and also from the older Late Cretaceous North American pollen morphotype, indicating evolutionary trends and diversification within the genus over that time period. The presence of Aponogeton in the fossil record of North America and Greenland calls for a reconsideration of all previous ideas about the biogeographic history of the family.

  14. Recent changes in North West Greenland climate documented by NEEM shallow ice core data and simulations, and implications for past temperature reconstructions

    NASA Astrophysics Data System (ADS)

    Masson-Delmotte, V.; Steen-Larsen, H. C.

    2014-12-01

    Stack records of accumulation, d18O and deuterium excess were produced from up to 4 shallow ice cores at NEEM (North-West Greenland), spanning 1724-2007 and updated to 2011 using pit water stable isotope data. Signal-to-noise ratio is high for d18O (1.3) and accumulation (1.2) but is low for deuterium excess (0.4). No long-term trend is observed in the accumulation record. By contrast, NEEM d18O shows multi-decadal increasing trends in the late 19th century and since the 1980s. Decadal d18O and accumulation variability is in phase with Atlantic Multi-decadal Oscillation indices, and enhanced at the beginning of the 19th century. Large-scale spatial coherency is detected between NEEM and other Greenland ice core and temperature records, strongest for North-West Greenland d18O and summer South-West coastal temperature instrumental records. The strength of correlations with the North Atlantic Oscillation is smaller than in central or south Greenland. The strongest positive d18O values are recorded at NEEM in 2010, followed by 1928, while maximum accumulation occurs in 1933. The coldest/driest decades are depicted at NEEM in 1815-1825 and 1836-1836. The spatial structure of these warm/ wet years and cold/dry decades is investigated using all available Greenland ice cores. During the period 1958-2011, the NEEM accumulation and d18O records are highly correlated with simulated precipitation, temperature and d18O from simulations performed with MAR, LMDZiso and ECHAM5iso atmospheric models, nudged to atmospheric reanalyses. Model-data agreement is better using ERA reanalyses than NCEP/NCAR and 20CR ones. Model performance is poor for deuterium excess. Gridded temperature reconstructions, instrumental data and model outputs at NEEM are used to estimate the d18O-temperature relationship for the strong warming period in 1979-2007. The estimated slope of this relationship is 1.1±0.2‰ per °C, about twice larger than previously used to estimate last interglacial temperature

  15. Greenland Ice Flow

    NASA Video Gallery

    Greenland looks like a big pile of snow seen from space using a regular camera. But satellite radar interferometry helps us detect the motion of ice beneath the snow. Ice starts flowing from the fl...

  16. Flying Low over Southeast Greenland

    NASA Video Gallery

    Few of us ever get to see Greenland's glaciers from 500 meters above the ice. But in this video — recorded on April 9,2013 in southeast Greenland using a cockpit camera installed and operated by ...

  17. Record of volcanism since 7000 B. C. from the GISP2 Greenland ice core and implications for the volcano-climate system

    SciTech Connect

    Zielinski, G.A.; Mayewski, P.A.; Meeker, L.D.; Whitlow, S.; Twickler, M.S.; Morrison, M. ); Meese, D.A.; Gow, A.J. ); Alley, R.B. )

    1994-05-13

    Sulfate concentrations from continuous biyearly sampling of the GISP2 Greenland ice core provide a record of potential climate-forcing volcanism since 7000 B.C. Although 85 percent of the events recorded over the last 2000 years were matched to documented volcanic eruptions, only about 30 percent of the events from 1 to 7000 B.C. were matched to such events. Several historic eruptions may have been greater sulfur producers than previously thought. There are three times as many events from 5000 to 7000 B.C. as over the last two millennia with sulfate deposition equal to or up to five times that of the largest known historical eruptions. The increased volcanism in the early Holocene may have contributed to climatic cooling.

  18. Record of Volcanism Since 7000 B.C. from the GISP2 Greenland Ice Core and Implications for the Volcano-Climate System.

    PubMed

    Zielinski, G A; Mayewski, P A; Meeker, L D; Whitlow, S; Twickler, M S; Morrison, M; Meese, D A; Gow, A J; Alley, R B

    1994-05-13

    Sulfate concentrations from continuous biyearly sampling of the GISP2 Greenland ice core provide a record of potential climate-forcing volcanism since 7000 B.C. Although 85 percent of the events recorded over the last 2000 years were matched to documented volcanic eruptions, only about 30 percent of the events from 1 to 7000 B.C. were matched to such events. Several historic eruptions may have been greater sulfur producers than previously thought. There are three times as many events from 5000 to 7000 B.C. as over the last two millennia with sulfate deposition equal to or up to five times that of the largest known historical eruptions. This increased volcanism in the early Holocene may have contributed to climatic cooling.

  19. Glaciers of Greenland

    USGS Publications Warehouse

    Williams, Richard S.; Ferrigno, Jane G.

    1995-01-01

    Landsat imagery, combined with aerial photography, sketch maps, and diagrams, is used as the basis for a description of the geography, climatology, and glaciology, including mass balance, variation, and hazards, of the Greenland ice sheet and local ice caps and glaciers. The Greenland ice sheet, with an estimated area of 1,736,095+/-100 km2 and volume of 2,600,000 km3, is the second largest glacier on the planet and the largest relict of the Ice Age in the Northern Hemisphere. Greenland also has 48,599+/-100 km2 of local ice caps and other types of glaciers in coastal areas and islands beyond the margin of the ice sheet.

  20. Episodic speleothem deposition in Ireland during the late Quaternary; implications for Greenland ice core chronology and British-Irish Ice Sheet dynamics

    NASA Astrophysics Data System (ADS)

    McDermott, Frank; Fankhauser, Adelheid

    2016-04-01

    In shallow caves, episodes of speleothem deposition during the late Quaternary, constrained by U-series dates, provide unequivocal evidence for periods of climate amelioration (presence of liquid water, elevated soil pCO2). U-series data for speleothems from several cave systems in Ireland (Crag, Ballynamintra and Marble Arch) provide clear evidence for episodic speleothem deposition, ranging in age from Marine Isotope Stage (MIS) 7 to the Last Glacial Termination. Speleothem deposition and non-depositional phases within these caves are particularly sensitive to regional-scale climatic conditions, reflecting Ireland's mid-latitudinal, Atlantic margin location. Currently, the earliest dated speleothems from the region are sparsely preserved and thin MIS 7 and MIS 5 flowstones from Ballynamintra and Crag caves respectively. Relatively short-lived depositional phases also occurred at Crag cave during MIS4 and MIS3 and are coeval with the Greenland Interstadials (GI), supporting the recently modified GICC05 Greenland ice core chronology (Buizert et al., 2015), and new providing evidence for synchronous or nearly-synchronous climate amelioration in the N. hemisphere mid- and high-latitudes during the GI events. On the other hand, there is strong evidence that conditions at Crag cave site during stadials and the Heinrich stadials were not conducive to speleothem deposition. Episodes of non-deposition occur synchronously in several speleothems from Crag cave, providing independent constraints on the timing of Heinrich stadials HS-6 to HS-2. The new data also provide independent new insights into the behaviour of the British Irish Ice Sheet (BIIS) during MIS2. In this regard, the presence of a short depositional pulse at 23.35 ± 0.1 ka at Crag cave coincides precisely with the weak and short-lived GI2.2 event within MIS 2, suggesting a dynamic BIIS margin. Simple conductive thermal models for the propagation of surface air temperatures through the limestone karst

  1. Average sedimentary rock rare Earth element patterns and crustal evolution: Some observations and implications from the 3800 Ma ISUA supracrustal belt, West Greenland

    NASA Technical Reports Server (NTRS)

    Dymek, R. F.; Boak, J. L.; Gromet, L. P.

    1983-01-01

    Rare earth element (REE) data is given on a set of clastic metasediments from the 3800 Ma Isua Supracrustal belt, West Greenland. Each of two units from the same sedimentary sequence has a distinctive REE pattern, but the average of these rocks bears a very strong resemblance to the REE pattern for the North American Shale Composite (NASC), and departs considerably from previous estimates of REE patterns in Archaean sediments. The possibility that the source area for the Isua sediments resembled that of the NASC is regarded as highly unlikely. However, REE patterns like that in the NASC may be produced by sedimentary recycling of material yielding patterns such as are found at Isua. The results lead to the following tentative conclusions: (1) The REE patterns for Isua Seq. B MBG indicate the existence of crustal materials with fractionated REE and negative Eu anomalies at 3800 Ma, (2) The average Seq. B REE pattern resembles that of the North American Shale Composite (NASC), (3) If the Seq. B average is truly representative of its crustal sources, then this early crust could have been extensively differentiated. In this regard, a proper understanding of the NASC pattern, and its relationship to post-Archaean crustal REE reservoirs, is essential, (4) The Isua results may represent a local effect.

  2. Provenance and tectonic setting of the Paleo- to Mesoproterozoic Dongchuan Group in the southwestern Yangtze Block, South China: Implication for the breakup of the supercontinent Columbia

    NASA Astrophysics Data System (ADS)

    Wang, Wei; Zhou, Mei-Fu

    2014-01-01

    The Paleoproterozoic to Mesoproterozoic (1742-1503 Ma) Dongchuan Group in the southwestern Yangtze Block is a rift-related sedimentary sequence that was associated with the breakup of the supercontinent Columbia and is particularly important for the possible linkage between the Yangtze Block and other continents in Columbia. The Dongchuan Group consists of the Yinmin, Luoxue, Etouchang and Luzhijiang formations from the base upward. Sandstones from the Yinmin Formation are mainly arkose containing dominant K-feldspar with subordinate plagioclase and quartz. Abundant feldspar and high Qm/Q ratios (0.94-1) are indicative of plutonic sources. These sandstones have high La/Sc (3.06 to 4.32), low Sc/Th (0.74 to 1.15) and Co/Th (0.85 to 1.52) and highly evolved Nd isotopes (εNd(t) = - 6.2 to - 8.2), consistent with an old, felsic igneous source. Detrital zircons of this formation have two major age groups at 2602-2887 Ma and 2224-2392 Ma. Siltstones of the Etouchang Formation have detrital zircons with a prominent age peak at ~ 2560 Ma and several subordinate peaks at ~ 2180 Ma, ~ 2100 Ma and ~ 1900 Ma. They have high Sc/Th (1.00-7.08), Co/Th (0.13 to 6.31) and εNd(t) (- 2.1 to - 6.7), significantly different from the Yinmin Formation. The Yinmin Formation is interpreted to deposit during the initial stage of extensional rifting receiving detritus of granites and TTG mainly from uplifted shoulder. The Etouchang Formation more likely formed in a passive margin with sedimentary material largely from cratonic sources. Paleoproterozoic to Mesoproterozoic rift basins in the southwestern Yangtze Block, north Australia and northwestern Laurentia have remarkably similar provenance and tectonic setting in their lower part (1742-1596 Ma), but significantly different since the onset of the Etouchang Formation (ca. 1596 Ma). Therefore, the southwestern Yangtze Block was likely connected with the north Australia and northwestern Laurentia in Columbia and drifted away from these

  3. Mesoproterozoic rapakivi granites of the Rondonia Tin Province, southwestern border of the Amazonian craton, Brazil-I. Reconnaissance U-Pb geochronology and regional implications

    USGS Publications Warehouse

    Bettencourt, Jorge S.; Tosdal, R.M.; Leite, W.B.; Payolla, B.L.

    1999-01-01

    Rapakivi granites and associated mafic and ultramafic rocks in the Rondonia Tin Province, southwestern Amazonian craton, Brazil were emplaced during six discrete episodes of magmatism between ca 1600 and 970 Ma. The seven rapakivi granite suites emplaced at this time were the Serra da Providencia Intrusive Suite (U-Pb ages between 1606 and 1532 Ma); Santo Antonio Intrusive Suite (U-Pb age 1406 Ma); Teotonio Intrusive Suite (U-Pb age 1387 Ma); Alto Candeias Intrusive Suite (U-Pb ages between 1346 and 1338 Ma); Sao Lourenco-Caripunas Intrusive Suite (U-Pb ages between 1314 and 1309 Ma); Santa Clara Intrusive Suite (U-Pb ages between 1082 and 1074 Ma); and Younger Granites of Rondonia (U-Pb ages between 998 and 974 Ma). The Serra da Providencia Intrusive Suite intruded the Paleoproterozoic (1.80 to 1.70 Ga) Rio Negro-Juruena crust whereas the other suites were emplaced into the 1.50 to 1.30 Ga Rondonia-San Ignacio crust. Their intrusion was contemporaneous with orogenic activity in other parts of the southwestern Amazonian craton, except for the oldest, Serra da Providencia Intrusive Suite. Orogenic events coeval with emplacement of the Serra da Providencia Intrusive Suite are not clearly recognized in the region. The Santo Antonio, Teotonio, Alto Candeias and Sao Lourenco-Caripunas Intrusive Suites are interpreted to represent extensional anorogenic magmatism associated with the terminal stages of the Rondonian-San Ignacio orogeny. At least the Sao Lourenco-Caripunas rapakivi granites and coeval intra-continental rift sedimentary rocks may, in contrast, represent the products of extensional tectonics and rifting preceding the Sunsas/Aguapei orogeny (1.25 to 1.0 Ga). The two youngest rapakivi suites, the Santa Clara Intrusive Suite and Younger Granites of Rondonia, seemingly represent inboard magmatism in the Rondonian-San Ignacio Province during a younger episode of reworking in the Rio Negro-Juruena Province during the waning stages of the collisional 1.1 to 1.0 Ga

  4. Isotopic, geochemical, and temporal characterization of Proterozoic basement rocks in the Quitovac region, northwestern Sonora, Mexico: Implications for the reconstruction of the southwestern margin of Laurentia

    USGS Publications Warehouse

    Iriondo, A.; Premo, W.R.; Martinez-Torres, L. M.; Budahn, J.R.; Atkinson, W.W.; Siems, D.F.; Guaras-Gonzalez, B.

    2004-01-01

    A detailed geochemical characterization of 19 representative Proterozoic basement rocks in the Quitovac region in northwestern Sonora, Mexico, has identified two distinct Paleoproterozoic basement blocks that coincide spatially with the previously proposed Caborca and "North America" blocks. New U-Pb zircon geochronology revises their age ranges, the Caborca (1.78-1.69 Ga) and "North America" (1.71-1.66 Ga) blocks at Quitovac, and precludes a simple age differentiation between them. In addition, Grenvillian-age granitoids (ca. 1.1 Ga), spatially associated with the Caborca block have been identified at Quitovac. Nd isotopes and major- and trace-element geochemistry support the distinction of these Paleoproterozoic blocks. Granitoids of the "North America" block are characterized by depleted ??Nd values (3.4-3.9) and younger Nd model ages (1800-1740 Ma) and have lower K2O, Y, Rb, Ba, Th, REE, and Fe/Mg values than coeval rocks of the Caborca block. The Caborca block granitoids are likewise characterized by slightly less depleted ??Nd (0.6-2.6) and older Nd model ages (2070-1880 Ma). Despite the subtle differences, granitoids from both the Caborca and "North America" blocks exhibit island arc-like affinities. We propose that the Proterozoic basement rocks from the Quitovac region are an extension of the Proterozoic crustal provinces in the southwestern United States. Specifically, rocks of the Caborca block exhibit an affinity to rocks of either the Yavapai province or the Mojave-Yavapai transition zone, whereas rocks of the "North America" block have signatures similar to those of the Mazatzal province or possibly the Yavapai province of Arizona. The new isotopic ages and geochemical data do not support the existence of the Late Jurassic Mojave-Sonora megashear at Quitovac, as originally proposed. However, the Quitovac region accounts only for a small fraction of the Proterozoic basement in Sonora, so these findings do not eliminate the possibility of a megashear

  5. Scientific Collaboration Along the Trinational Frontier of Brazil-Bolivia-Peru: Implications for Regional Land-Use in the MAP Region of Southwestern Amazonia

    NASA Astrophysics Data System (ADS)

    Brown, I.

    2002-12-01

    High-speed road systems are connecting southwestern Amazonia (~1.5 million km2) to Pacific and Atlantic ports as well as providing greater access to Brazilian, Bolivian and Peruvian urban markets. Coupled with this increased accessibility are ambitious governmental plans to expand production of timber, non-timber forest products, and beef, all of which are likely to modify human migrations in the region. The heart of southwestern Amazonia lies in the trinational frontier region of Madre de Dios Department/Peru, eastern Acre State/Brazil and Pando Department/Bolivia (MAP region: ~200,000 km2, ~500,000 inhabitants). The MAP region composes a global hot spot of terrestrial biodiversity and has become an axis of integration for the three countries. Faced with rapid change in socioeconomic trends, regional environmental scientists and professionals have promoted collaborative projects to analyze land use trends and their forcing functions and to supply these results to local and regional societies. In addition, they have begun to develop a regional scientific community that bridges different nationalities and specialties. The projects are both international - as they involve three countries - and local/regional as they involve institutions that are within a radius of 300 km of the border. In the past two years, LBA-sponsored activities have helped bring over 100 professionals together in the region in five MAP-oriented workshops. The research results are now influencing public policy and are being incorporated into the regional school systems with the objective of maximizing the benefits and minimizing the adverse impacts of the changing socio-economic trends on land-use and development in the MAP region.

  6. Geological analysis of aeromagnetic data from southwestern Alaska: implications for exploration in the area of the Pebble porphyry Cu-Au-Mo deposit

    USGS Publications Warehouse

    Anderson, Eric D.; Hitzman, Murray W.; Monecke, Thomas; Bedrosian, Paul A.; Shah, Anjana K.; Kelley, Karen D.

    2013-01-01

    Aeromagnetic data are used to better understand the geology and mineral resources near the Late Cretaceous Pebble porphyry Cu-Au-Mo deposit in southwestern Alaska. The reduced-to-pole (RTP) transformation of regional-scale aeromagnetic data shows that the Pebble deposit is within a cluster of magnetic anomaly highs. Similar to Pebble, the Iliamna, Kijik, and Neacola porphyry copper occurrences are in magnetic highs that trend northeast along the crustal-scale Lake Clark fault. A high-amplitude, short- to moderate-wavelength anomaly is centered over the Kemuk occurrence, an Alaska-type ultramafic complex. Similar anomalies are found west and north of Kemuk. A moderate-amplitude, moderate-wavelength magnetic low surrounded by a moderate-amplitude, short-wavelength magnetic high is associated with the gold-bearing Shotgun intrusive complex. The RTP transformation of the district-scale aeromagnetic data acquired over Pebble permits differentiation of a variety of Jurassic to Tertiary magmatic rock suites. Jurassic-Cretaceous basalt and gabbro units and Late Cretaceous biotite pyroxenite and granodiorite rocks produce magnetic highs. Tertiary basalt units also produce magnetic highs, but appear to be volumetrically minor. Eocene monzonite units have associated magnetic lows. The RTP data do not suggest a magnetite-rich hydrothermal system at the Pebble deposit. The 10-km upward continuation transformation of the regional-scale data shows a linear northeast trend of magnetic anomaly highs. These anomalies are spatially correlated with Late Cretaceous igneous rocks and in the Pebble district are centered over the granodiorite rocks genetically related to porphyry copper systems. The spacing of these anomalies is similar to patterns shown by the numerous porphyry copper deposits in northern Chile. These anomalies are interpreted to reflect a Late Cretaceous magmatic arc that is favorable for additional discoveries of Late Cretaceous porphyry copper systems in southwestern

  7. Recent changes in north-west Greenland climate documented by NEEM shallow ice core data and simulations, and implications for past-temperature reconstructions

    NASA Astrophysics Data System (ADS)

    Masson-Delmotte, V.; Steen-Larsen, H. C.; Ortega, P.; Swingedouw, D.; Popp, T.; Vinther, B. M.; Oerter, H.; Sveinbjornsdottir, A. E.; Gudlaugsdottir, H.; Box, J. E.; Falourd, S.; Fettweis, X.; Gallée, H.; Garnier, E.; Gkinis, V.; Jouzel, J.; Landais, A.; Minster, B.; Paradis, N.; Orsi, A.; Risi, C.; Werner, M.; White, J. W. C.

    2015-08-01

    Combined records of snow accumulation rate, δ18O and deuterium excess were produced from several shallow ice cores and snow pits at NEEM (North Greenland Eemian Ice Drilling), covering the period from 1724 to 2007. They are used to investigate recent climate variability and characterise the isotope-temperature relationship. We find that NEEM records are only weakly affected by inter-annual changes in the North Atlantic Oscillation. Decadal δ18O and accumulation variability is related to North Atlantic sea surface temperature and is enhanced at the beginning of the 19th century. No long-term trend is observed in the accumulation record. By contrast, NEEM δ18O shows multidecadal increasing trends in the late 19th century and since the 1980s. The strongest annual positive δ18O values are recorded at NEEM in 1928 and 2010, while maximum accumulation occurs in 1933. The last decade is the most enriched in δ18O (warmest), while the 11-year periods with the strongest depletion (coldest) are depicted at NEEM in 1815-1825 and 1836-1846, which are also the driest 11-year periods. The NEEM accumulation and δ18O records are strongly correlated with outputs from atmospheric models, nudged to atmospheric reanalyses. Best performance is observed for ERA reanalyses. Gridded temperature reconstructions, instrumental data and model outputs at NEEM are used to estimate the multidecadal accumulation-temperature and δ18O-temperature relationships for the strong warming period in 1979-2007. The accumulation sensitivity to temperature is estimated at 11 ± 2 % °C-1 and the δ18O-temperature slope at 1.1 ± 0.2 ‰ °C-1, about twice as large as previously used to estimate last interglacial temperature change from the bottom part of the NEEM deep ice core.

  8. Recent changes in north-west Greenland climate documented by NEEM shallow ice core data and simulations, and implications for past temperature reconstructions

    NASA Astrophysics Data System (ADS)

    Masson-Delmotte, V.; Steen-Larsen, H. C.; Ortega, P.; Swingedouw, D.; Popp, T.; Vinther, B. M.; Oerter, H.; Sveinbjornsdottir, A. E.; Gudlaugsdottir, H.; Box, J. E.; Falourd, S.; Fettweis, X.; Gallée, H.; Garnier, E.; Jouzel, J.; Landais, A.; Minster, B.; Paradis, N.; Orsi, A.; Risi, C.; Werner, M.; White, J. W. C.

    2015-01-01

    Combined records of snow accumulation rate, δ18O and deuterium excess were produced from several shallow ice cores and snow pits at NEEM (north-west Greenland), covering the period from 1724 to 2007. They are used to investigate recent climate variability and characterize the isotope-temperature relationship. We find that NEEM records are only weakly affected by inter-annual changes in the North Atlantic Oscillation. Decadal δ18O and accumulation variability is related to North Atlantic SST, and enhanced at the beginning of the 19th century. No long-term trend is observed in the accumulation record. By contrast, NEEM δ18O shows multi-decadal increasing trends in the late 19th century and since the 1980s. The strongest annual positive δ18O anomaly values are recorded at NEEM in 1928 and 2010, while maximum accumulation occurs in 1933. The last decade is the most enriched in δ18O (warmest), while the 11-year periods with the strongest depletion (coldest) are depicted at NEEM in 1815-1825 and 1836-1846, which are also the driest 11-year periods. The NEEM accumulation and δ18O records are strongly correlated with outputs from atmospheric models, nudged to atmospheric reanalyses. Best performance is observed for ERA reanalyses. Gridded temperature reconstructions, instrumental data and model outputs at NEEM are used to estimate the multi-decadal accumulation-temperature and δ18O-temperature relationships for the strong warming period in 1979-2007. The accumulation sensitivity to temperature is estimated at 11 ± 2% °C-1 and the δ18O-temperature slope at 1.1 ± 0.2‰ °C-1, about twice larger than previously used to estimate last interglacial temperature change from the bottom part of the NEEM deep ice core.

  9. Greenland ice sheet melting during the last interglacial

    NASA Astrophysics Data System (ADS)

    Langebroek, Petra M.; Nisancioglu, Kerim H.

    2016-04-01

    During the last interglacial period (LIG) peak temperatures over Greenland were several degrees warmer than today. The Greenland ice sheet (GIS) retreated causing a global sea-level rise in the order of several meters. Large uncertainties still exist in the exact amount of melt and on the source location of this melt. Here we examine the GIS response to LIG temperature and precipitation patterns using the SICOPOLIS ice sheet model. The LIG climate was simulated by forcing the Norwegian Earth System Model (NorESM) with the appropriate greenhouse gases and orbital settings. The resulting LIG ice volume evolution strongly depends on the chosen value of uncertain model parameters for the ice sheet (e.g. basal sliding parameter, PDD factors, and atmospheric temperature lapse rate). We reduce the uncertainty by evaluating an ensemble of model results against present-day observations of ice sheet size, elevation and stability, together with paleo information from deep ice cores. We find a maximum GIS reduction equivalent to 0.8 to 2.2m of global sea-level rise. In this model set-up most of the melting occurs in southwestern Greenland.

  10. Mineralogy and composition of Archean Crust, Greenland: A pilot study

    NASA Technical Reports Server (NTRS)

    Goetz, Alexander F. H.; Curtiss, Brian

    1989-01-01

    The Portable Instant Display and Analysis Spectrometer (PIDAS) was taken to southwestern Greenland to investigate in situ the potential application of AVIRIS to estimate the mineralogy and composition of rocks exposed in Archean terranes. The goal was to determine the feasibility of using a high spectral resolution scanner to find and study pristine rocks, those that have not been altered by subsequent deformation and metamorphism. The application of AVIRIS data to the problems in Greenland is logical. However, before a costly deployment of the U-2 aircraft to Greenland is proposed, this study was undertaken to acquire the spectral data necessary to verify that mineralogical mapping in the environmental conditions found there is possible. Although field conditions were far from favorable, all of the major objectives of the study were addressed. One of the major concerns was that lichens would obscure the rock surfaces. It was found that the spectral signature of the lichens was distinct from the underlying rocks. Thus, a spectrum of a rock outcrop, with its partial cover of lichens, can be un-mixed into rock and lichen components. The data acquired during the course of this study supports the conclusion that areas of pristine Archean crust can be differentiated from that which has experienced low grade alteration associated with Proterizoic faulting.

  11. An mtDNA analysis in ancient Basque populations: implications for haplogroup V as a marker for a major paleolithic expansion from southwestern europe.

    PubMed Central

    Izagirre, N; de la Rúa, C

    1999-01-01

    mtDNA sequence variation was studied in 121 dental samples from four Basque prehistoric sites, by high-resolution RFLP analysis. The results of this study are corroborated by (1) parallel analysis of 92 bone samples, (2) the use of controls during extraction and amplification, and (3) typing by both positive and negative restriction of the linked sites that characterize each haplogroup. The absence of haplogroup V in the prehistoric samples analyzed conflicts with the hypothesis proposed by Torroni et al., in which haplogroup V is considered as an mtDNA marker for a major Paleolithic population expansion from southwestern Europe, occurring approximately 10,000-15,000 years before the present (YBP). Our samples from the Basque Country provide a valuable tool for checking the previous hypothesis, which is based on genetic data from present-day populations. In light of the available data, the most realistic scenario to explain the origin and distribution of haplogroup V suggests that the mutation defining that haplogroup (4577 NlaIII) appeared at a time when the effective population size was small enough to allow genetic drift to act-and that such drift is responsible for the heterogeneity observed in Basques, with regard to the frequency of haplogroup V (0%-20%). This is compatible with the attributed date for the origin of that mutation (10,000-15, 000 YBP), because during the postglacial period (the Mesolithic, approximately 11,000 YBP) there was a major demographic change in the Basque Country, which minimized the effect of genetic drift. This interpretation does not rely on migratory movements to explain the distribution of haplogroup V in present-day Indo-European populations. PMID:10364533

  12. Geochemistry and isotopic composition of the Guerrero Terrane (western Mexico): implications for the tectono-magmatic evolution of southwestern North America during the Late Mesozoic

    NASA Astrophysics Data System (ADS)

    Mendoza, O. T.; Suastegui, M. G.

    2000-10-01

    The composite Guerrero Terrane of western Mexico records much of the magmatic evolution of southwestern North America during Late Mesozoic time. The Guerrero includes three distinctive subterranes characterized by unique stratigraphic records, structural evolutions, and geochemical and isotopic features that strongly suggest they evolved independently. The eastern Teloloapan Subterrane represents an evolved intra-oceanic island arc of Hauterivian to Cenomanian age, which includes a high-K calc-alkaline magmatic suite. The central Arcelia-Palmar Chico Subterrane represents a primitive island arc-marginal basin system of Albian to Cenomanian age, consisting of an oceanic suite and a tholeiitic arc suite. The western Zihuatanejo-Huetamo Subterrane comprises three components that represent an evolved island arc-marginal basin-subduction complex system of Late Jurassic (?) -Early Cretaceous age built on a previously deformed basement. The Zihuatanejo Sequence includes a thick high-K calc-alkaline magmatic suite. The Las Ollas Complex consists of tectonic slices containing exotic blocks of arc affinity affected by high-pressure/low-temperature metamorphism included in a sheared matrix. The Huetamo Sequence consists mainly of volcanic-arc derived sedimentary rocks, including large pebbles of tholeiitic, calc-alkaline, and shoshonitic lavas. These sequences are unconformably underlain by the Arteaga Complex, which represents the subvolcanic basement. On the basis of available geology, geochemistry, geochronology, and isotopic data, we suggest that Late Mesozoic volcanism along the western margin of southern North America developed in broadly contemporaneous but different intra-oceanic island arcs that constitute a complex fossil arc-trench system similar to the present-day western Pacific island arc system.

  13. Age and zircon inheritance of eastern Blue Ridge plutons, southwestern North Carolina and northeastern Georgia, with implications for magma history and evolution of the southern Appalachian origin

    SciTech Connect

    Miller, C.F.; Hatcher, R.D. Jr.; Ayers, J.C.; Coath, C.D.; Harrison, T.M.

    2000-02-01

    High-resolution ion microprobe analysis of zircon has provided ages for previously undated plutons of the high-grade eastern Blue Ridge of northeastern Georgia and southwestern North Carolina. These data, together with backscattered electron imaging, reveal the presence of nearly ubiquitous inherited cores of highly variable age and magmatic rims that have experienced variable Pb loss, thus making interpretation of conventional U-Pb analyses very difficult. Ion probe rim analyses indicate that the plutons were emplaced during both the mod-Ordovician and mid-Devonian. Zircons from all intrusions have predominantly 1.0 to 1.25 Ga cores (Grenvillian). In addition, both Devonian and Ordovician plutons have smaller populations of Late Proterozoic-early Paleozoic (0.5--0.75 Ga), Middle Proterozoic (1.4 Ga), and Late Archean (2.6--2.9 Ga) cores. The ubiquitous, round cores and thick magmatic rims suggest significant resorption and then protracted growth within the melts. Zircon saturation temperatures based on whole-rock ({approximately}melt) Zr concentrations are lower than expected for magma generation (710--760 C). Zirconium concentrations may not reflect saturation at maximum temperature, if melting was very rapid (<{approximately}10{sup 5} yrs), or if zircon cores represent grains that were shielded from melt inside host grains for much of the magmatic history. Ages of magmatic and inherited zones of zircon from the plutons demonstrate that similar crust underlay the eastern Blue Ridge during both Taconian and Acadian orogenies, that there was no single episode of voluminous magmatism, and that metamorphism and deformation began before 470 Ma and continued after 370 Ma. These plutons do not constitute a significant convergence-related arc, though it is possible that they represent a displaced part of an arc that lies primarily to the east (in the Inner Piedmont?).

  14. An mtDNA analysis in ancient Basque populations: implications for haplogroup V as a marker for a major paleolithic expansion from southwestern europe.

    PubMed

    Izagirre, N; de la Rúa, C

    1999-07-01

    mtDNA sequence variation was studied in 121 dental samples from four Basque prehistoric sites, by high-resolution RFLP analysis. The results of this study are corroborated by (1) parallel analysis of 92 bone samples, (2) the use of controls during extraction and amplification, and (3) typing by both positive and negative restriction of the linked sites that characterize each haplogroup. The absence of haplogroup V in the prehistoric samples analyzed conflicts with the hypothesis proposed by Torroni et al., in which haplogroup V is considered as an mtDNA marker for a major Paleolithic population expansion from southwestern Europe, occurring approximately 10,000-15,000 years before the present (YBP). Our samples from the Basque Country provide a valuable tool for checking the previous hypothesis, which is based on genetic data from present-day populations. In light of the available data, the most realistic scenario to explain the origin and distribution of haplogroup V suggests that the mutation defining that haplogroup (4577 NlaIII) appeared at a time when the effective population size was small enough to allow genetic drift to act-and that such drift is responsible for the heterogeneity observed in Basques, with regard to the frequency of haplogroup V (0%-20%). This is compatible with the attributed date for the origin of that mutation (10,000-15, 000 YBP), because during the postglacial period (the Mesolithic, approximately 11,000 YBP) there was a major demographic change in the Basque Country, which minimized the effect of genetic drift. This interpretation does not rely on migratory movements to explain the distribution of haplogroup V in present-day Indo-European populations.

  15. Adventure Learning @ Greenland

    NASA Astrophysics Data System (ADS)

    Miller, B. G.; Cox, C. J.; Hougham, J.; Walden, V. P.; Eitel, K.; Albano, A.

    2013-12-01

    Teaching the general public and K-12 communities about scientific research has taken on greater importance as climate change increasingly impacts the world we live in. Science researchers and the educational community have a widening responsibility to produce and deliver curriculum and content that is timely, scientifically sound and engaging. To address this challenge, in the summer of 2012 the Adventure Learning @ Greenland (AL@GL) project, a United States' National Science Foundation (NSF) funded initiative, used hands-on and web-based climate science experiences for high school students to promote climate and science literacy. This presentation will report on an innovative approach to education and outreach for environmental science research known as Adventure Learning (AL). The purpose of AL@GL was to engage high school students in the US, and in Greenland, in atmospheric research that is being conducted in the Arctic to enhance climate and science literacy. Climate and science literacy was explored via three fundamental concepts: radiation, the greenhouse effect, and climate vs. weather. Over the course of the project, students in each location engaged in activities and conducted experiments through the use of scientific instrumentation. Students were taught science research principles associated with an atmospheric observatory at Summit Station, Greenland with the objective of connecting climate science in the Arctic to student's local environments. Summit Station is located on the Greenland Ice Sheet [72°N, 38°W, 3200 m] and was the primary location of interest. Approximately 35 students at multiple locations in Idaho, USA, and Greenland participated in the hybrid learning environments as part of this project. The AL@GL project engaged students in an inquiry-based curriculum with content that highlighted a cutting-edge geophysical research initiative at Summit: the Integrated Characterization of Energy, Clouds, Atmospheric state, and Precipitation at

  16. Greenland's Biggest Losers

    NASA Astrophysics Data System (ADS)

    Box, J. E.; Hubbard, A.; Howat, I. M.; Csatho, B. M.; Decker, D. T.; Bates, R.; Tulaczyk, S. M.

    2010-12-01

    On 4 August, 2010, 275 square km of the front of the floating Petermann Glacier, far northwest Greenland, broke away. The glacier effectively retreated 15 km. Petermann has retreated 21 km since year 2000. Consulting available imagery, publications, and maps spanning the past century, we conclude that this is a retreat to a minimum extent in the observational record. This glacier is not the only ice are loser in Greenland. GRACE observations verify the concern of increased mass budget deficit. Retreat is ongoing at the 110 km wide Humboldt glacier and at the 23 km wide Zachariae ice stream. Humboldt, Zachariae, and Petermann (16 km wide) are among a handful of large marine-terminating outlets that have bedrock trenches that lead inland below sea level to the thick, interior reservoir of the ice sheet. Sleeping giants are awakening. Our area change survey of the 35 widest Greenland outlets indicates an annual marine-terminating glacier area loss rate in excess of 130 sq km per year. Here, we evaluate in this context the mechanisms for marine-terminating glacier retreat, dynamical responses to calving, and the apparent climate forcings. The work thus consults a suite of data sets, including: long-term meteorological station records; satellite-derived sea and land surface temperatures; satellite-derived sea ice extent; regional climate model output; oceanographic casts; time lapse cameras, surface elevation change, and tidal records. Cumulative area change at Greenland’s glacier top 5 “losers”. 2010 areas are measured ~1 month prior to the end of summer melt when the survey usually is made . We do not expect 2010 area changes to be much different using the future data. If anything, we expect the losses to be larger. Click here for a full resolution graphic.

  17. Greenland Glacier Albedo Variability

    NASA Technical Reports Server (NTRS)

    2004-01-01

    The program for Arctic Regional Climate Assessment (PARCA) is a NASA-funded project with the prime goal of addressing the mass balance of the Greenland ice sheet. Since the formal initiation of the program in 1995, there has been a significant improvement in the estimates of the mass balance of the ice sheet. Results from this program reveal that the high-elevation regions of the ice sheet are approximately in balance, but the margins are thinning. Laser surveys reveal significant thinning along 70 percent of the ice sheet periphery below 2000 m elevations, and in at least one outlet glacier, Kangerdlugssuaq in southeast Greenland, thinning has been as much as 10 m/yr. This study examines the albedo variability in four outlet glaciers to help separate out the relative contributions of surface melting versus ice dynamics to the recent mass balance changes. Analysis of AVHRR Polar Pathfinder albedo shows that at the Petermann and Jakobshavn glaciers, there has been a negative trend in albedo at the glacier terminus from 1981 to 2000, whereas the Stor+strommen and Kangerdlugssuaq glaciers show slightly positive trends in albedo. These findings are consistent with recent observations of melt extent from passive microwave data which show more melt on the western side of Greenland and slightly less on the eastern side. Significance of albedo trends will depend on where and when the albedo changes occur. Since the majority of surface melt occurs in the shallow sloping western margin of the ice sheet where the shortwave radiation dominates the energy balance in summer (e.g. Jakobshavn region) this region will be more sensitive to changes in albedo than in regions where this is not the case. Near the Jakobshavn glacier, even larger changes in albedo have been observed, with decreases as much as 20 percent per decade.

  18. Exploring the Care Relationship between Grandparents/Older Carers and Children Infected with HIV in South-Western Uganda: Implications for Care for Both the Children and Their Older Carers

    PubMed Central

    Rutakumwa, Rwamahe; Zalwango, Flavia; Richards, Esther; Seeley, Janet

    2015-01-01

    The care of children orphaned by HIV/AIDS in sub-Saharan Africa is often undertaken by grandparents, yet little is known about the care relationship between grandparent and grandchild. Our aim was to examine this relationship to understand the needs and responsibilities of both the HIV positive child and older carer and the nature of the relationship, and to assess the implications for care for the children and the older carers. A qualitative study was conducted with 40 purposively sampled children (13–17 years) and their older carers (50 years and above). Participants were recruited from two clinics in south-western Uganda. Up to three semi-structured interviews were held with each participant. Data were analysed using a thematic framework approach. We found that the care relationship was mostly reciprocal: HIV positive children depended on carers for basic and health needs and carers counted on the children for performing tedious household tasks. The relationship was also characterised by challenges, sometimes causing tension between child and carer. We conclude that: (1) interventions targeting HIV positive children need to also address the needs of older carers, and (2) carers and children would benefit from psychosocial support and social protection. PMID:25689350

  19. Petrography and detrital zircon study of late Carboniferous sequences in the southwestern North China Craton: Implications for the regional tectonic evolution and bauxite genesis

    NASA Astrophysics Data System (ADS)

    Cai, Shuhui; Wang, Qingfei; Liu, Xuefei; Feng, Yuewen; Zhang, Ying

    2015-02-01

    The North China Craton (NCC) has been flanked by the North Qilian and North Qinling arc-accretionary belts to the south and southwest since ∼400 Ma. The part of the NCC to the east of the Alax terrane (E-NCC) experienced a long sedimentary hiatus and tectonic quiescence between the Middle Ordovician and the late Carboniferous. The northern margin of the E-NCC was reactivated and uplifted with contemporaneous volcanism during the late Carboniferous, an event that partly induced the transformation of the E-NCC from an erosional platform to a continental sedimentary basin. However, the factors controlling this transformation are still not fully understood. A series of sedimentary rocks overlying Ordovician carbonates in the southwestern E-NCC contains a lower iron-oxide layer and an upper phyllosilicate layer. Detrital zircons from different parts of the profile, from the base to the top of the two layers, have similar U-Pb ages. These zircons have a minimum age of ca. 300 Ma and a prominent peak at ca. 450 Ma, with subordinate peaks at ca. 1000 and 2500 Ma. The near-identical minimum age for the two layers suggests they were semi-simultaneously deposited in the late Carboniferous after the long hiatus in sedimentation. Detrital zircons with ages of ∼450 Ma have initial Hf isotopic compositions that vary from large negative to elevated positive. These data, together with the trace element compositions of these zircons, indicate that these minerals formed in a continental arc environment. Samples from the upper sedimentary layer contain mica group minerals that are weakly buckled and fractured, and have weathered to form clay minerals, including chlorite and illite. This suggests that the protolith of this sedimentary layer was dominated by mica schist or mica-bearing granitoid that most likely located near the adjoined part between the North Qilian and North Qinling arc-accretionary belts. Detrital zircons with the youngest ages (ca. 300 Ma) were considered to

  20. Distribution and Mobilization of Arsenic in the Ganges plain sedimentary deposits of South-western Bangladesh; implications from field and laboratory observations

    NASA Astrophysics Data System (ADS)

    Rahman, M.; Mano, A.; Udo, K.; Ishibashi, Y.; Han, Y.

    2011-12-01

    The variation of arsenic concentration depending on sediment size and its depositional age in a variety of sediments extracted from four As contaminated sites of the southwestern Bangladesh were studied to elucidate the aquifer geological parameters that controls the vertical As distribution and mobilization in the sediment-water interface. It was found that sediment size, reactive surface area, relative depositional age and presence of other carrier minerals having higher affinity to adsorb As, may greatly dominate the arsenic accumulation. Sorption of As onto sediment surfaces was found to vary based on the variation of the particle diameters (2 to 250 μm), which eventually reflects the role of geological materials in controlling the As distribution in various depositional layers. Medium sands commonly found in the deeper aquifer (~150m), being older in age (> 7000 yrs BP) and having relatively larger diameter (φ~250 μm) were found to contain relatively low amount of As (0.8 μg/g) whereas higher As (5 to 25 μg/g) was identified noticeably in the recently deposited and reasonably younger (100 to 1000 yrs BP) sediment particles including clay and finer sands that commonly have moderately smaller diameter (φ~2 to 90 μm). These observations were supported strongly by the findings obtained from the laboratory batch adsorption tests conducted with those sediments. Presence of As was also observed to be greatly dependent on the availability of its carrier minerals particularly Fe and Al oxide/hydroxide along the aquifer depths. Clay particles with relatively moderate Fe and Al oxide minerals was found to adsorb as much as 70 μg/g As whereas medium sand with less Fe and Al oxide minerals were noticed to capture only 4 μg/g of As in the batch adsorption test. In laboratory leaching test, significant amount of As (12 μg/g) coupled with Fe (4.8 mg/g) were found to be leached out from the shallower brown clay by using sodium bicarbonate (pH~9) as the leaching agent

  1. Oxytetracycline and penicillin-G residues in cattle slaughtered in south-western Nigeria: implications for livestock disease management and public health.

    PubMed

    Adesokan, Hezekiah K; Agada, Charity A; Adetunji, Victoria O; Akanbi, Ibikunle M

    2013-01-01

    After the discovery of indiscriminate antibiotic use in ready-for-slaughter cattle in south-western Nigeria, 90 tissue samples from randomly selected slaughtered cattle were evaluated for oxytetracycline and penicillin-G residues using high performance liquid chromatography and the data analysed by one-way Analysis of variance (ANOVA). The findings revealed residues of oxytetracycline (kidney: 9.47 µ/kg ± 3.24 µ/kg; liver: 12.73 µ/kg ± 4.39 µ/kg; muscle: 16.17 µ/kg ± 5.52 µ/kg) and penicillin-G (kidney: 6.27 µ/kg ± 2.46 µ/kg; liver: 8.5 µ/kg ± 2.80 µ/kg; muscle: 11.67 µ/kg ± 2.94 µ/kg) in all tissues screened. Significantly high levels (oxytetracycline: F = 16.77; penicillin-G: F = 29.38) were, however, found in muscles, followed by liver and then kidney – findings confirming recent antibiotic administration to the animals before slaughter. The dietary intakes through the tissues screened were 0.024% (oxytetracycline) and 0.017% (penicillin-G) of the acceptable daily intake (ADI). Although the concentrations in the tissues screened were below the maximum residue limits despite recent administration of these antibiotics before slaughter, the lower concentrations are suggestive of the probable low dosages often administered by those involved in indiscriminate use of antibiotics. This therefore raises serious concerns for the livestock industry as well as human health, given the resultant emergence and spread of resistant strains of bacterial pathogens that could ensue from prolonged use of low dosages of antibiotics. Additionally, the lower concentrations of the daily intakes notwithstanding, the plausible exposure to these antibiotics from other food sources is a cause for concern. Since antimicrobial misuse and its consequent effects are not just a problem limited to Nigeria but also a concern in sub-Saharan Africa, the need for national and international stakeholder intervention is emphasised.

  2. Greenland Sea observations

    SciTech Connect

    Gudmandsen, P.; Mortensen, H.B.; Pedersen, L.T.; Skriver, H.; Minnett, P.

    1992-12-31

    ERS-1 SAR data have been acquired over the Greenland Sea and Fram Strait during two periods, the Ice Phase of three-day repeat cycle from January to March 1992 and a one-month period in the 35-day repeat cycle from 16 July to 15 August 1992. Most data became available by way of the Broadband Data Dissemination System, i.e. with a spatial resolution of about 100 m. With these data various algorithms have been tested to derive sea ice parameters such as ice extent, ice concentration and ice displacement. In the latter period data were collected to support the activities of a research vessel in the area mainly related to the large polynyas that form east and north of Greenland. The formation of polynyas could clearly be outlined but also other phenomena were observed related to the influence of wind streets and gravity waves associated with the atmospheric boundary layer. The data will have to be studied further including full-resolution data to substantiate the conclusions arrived at.

  3. 'Death ... more desirable than life'? The human skeletal record and toxicological implications of ancient copper mining and smelting in Wadi Faynan, southwestern Jordan.

    PubMed

    Grattan, John; Huxley, Steven; Abu Karaki, Lotus; Toland, Harry; Gilbertson, David; Pyatt, Brian; al Saad, Ziad

    2002-07-01

    Skeletal material from 36 people, dating from the early Christian era, who lived by or worked in the notorious Roman copper mines of Phaeno, were analysed to determine their exposure to copper and lead. We demonstrate that many of the bones analysed had a substantially higher concentration of these cations than modern individuals exposed to metals through industrial processes. Health, toxicological and environmental implications of these data are reviewed.

  4. Paleoenvironmental implications of concentration and 13C/ 12C ratios of Fe(CO 3)OH in goethite from a mid-latitude Cenomanian laterite in southwestern Minnesota

    NASA Astrophysics Data System (ADS)

    Feng, Weimin; Yapp, Crayton J.

    2009-05-01

    A mid-Cretaceous (˜95 Ma) laterite in southwestern Minnesota contains pisolites that consist primarily of gibbsite, quartz, and kaolinite with smaller amounts of goethite (α-FeOOH) and hematite. The presence of minor berthierine (an Fe(II) sheet silicate) suggests that this Cenomanian laterite experienced some degree of low temperature reductive diagenesis during its burial history. The prospects for extracting useful paleoenvironmental information from the pisolitic goethite were explored by studying measured mole fraction (X m) and δ 13Cm values of the Fe(CO 3)OH component in solid solution in the goethite using the method of incremental vacuum dehydration-decarbonation. Data arrays that occupy distinctly different domains in plots of δ 13Cm vs. 1/ Xm suggest the existence of two generations of goethite in the pisolites. The apparently younger generation of goethite ("generation 2") evolves CO 2 at 170 °C, while the older generation ("generation 1") evolves CO 2 at 220 °C. The distribution of the data suggests that generation 2 goethite is a proxy for mixing of CO 2 from three distinct CO 2 sources in an oxidative environment which post-dated the reductive diagenesis. The small amount of generation 1 goethite seems to have persisted through the reductive diagenesis, and nine of the generation 1 goethite data appear to define a proxy, two-endmember, soil CO 2 mixing line. Such two-component mixing is consistent with expectations for a highly evolved, carbonate-free laterite (i.e., the pre-diagenetic Cenomanian weathering system). The δ 13Cm values of these nine data points range from -23.1‰ to -13.7‰, whereas Xm values range from 0.0007 to 0.0222. Linear regression of these nine data yields a slope of 0.0064, which corresponds to an ancient tropospheric CO 2 concentration of about 1900 ppmV. Isotopic data from pisolitic kaolinite indicate a paleotemperature of about 24 °C at a paleolatitude of ˜40°N. This is substantially warmer than modern

  5. Upper Paleozoic mafic and intermediate volcanic rocks of the Mount Pleasant caldera associated with the Sn-W deposit in southwestern New Brunswick (Canada): Petrogenesis and metallogenic implications

    NASA Astrophysics Data System (ADS)

    Dostal, Jaroslav; Jutras, Pierre

    2016-10-01

    Upper Paleozoic ( 365 Ma) mafic and intermediate volcanic rocks of the Piskahegan Group constitute a subordinate part of the Mount Pleasant caldera, which is associated with a significant polymetallic deposit (tungsten-molybdenum-bismuth zones 33 Mt ore with 0.21% W, 0.1% Mo and 0.08% Bi and tin-indium zones 4.8 Mt with 0.82% Sn and 129 g/t In) in southwestern New Brunswick (Canada). The epicontinental caldera complex formed during the opening of the late Paleozoic Maritimes Basin in the northern Appalachians. The mafic and intermediate rocks make up two compositionally distinct associations. The first association includes evolved rift-related continental tholeiitic basalts, and the second association comprises calc-alkaline andesites, although both associations were emplaced penecontemporaneously. The basalts have low Mg# 0.34-0.40, smooth chondrite-normalized REE patterns with (La/Yb)n 5-6, primitive mantle-normalized trace element patterns without noticeable negative Nb-Ta anomalies, and their ɛNd(T) ranges from + 2.5 to + 2.2. The basalts were generated by partial melting of a transition zone between spinel and garnet mantle peridotite at a depth of 70-90 km. The calc-alkaline andesites of the second association have chondrite-normalized REE patterns that are more fractionated, with (La/Yb)n 7-8.5, but without significant negative Eu anomalies. Compared to the basaltic rocks, they have lower ɛNd(T) values, ranging from + 0.5 to + 1.9, and their mantle-normalized trace element plots show negative Nb-Ta anomalies. The ɛNd(T) values display negative correlations with indicators of crustal contamination, such as Th/La, Th/Nb and SiO2. The andesitic rocks are interpreted to have formed by assimilation-fractional crystallization processes, which resulted in the contamination of a precursor basaltic magma with crustal material. The parent basaltic magma for both suites underwent a different evolution. The tholeiitic basalts experienced shallow-seated fractional

  6. Paleo-Mesoproterozoic arc-accretion along the southwestern margin of the Amazonian craton: The Juruena accretionary orogen and possible implications for Columbia supercontinent

    NASA Astrophysics Data System (ADS)

    Scandolara, J. E.; Correa, R. T.; Fuck, R. A.; Souza, V. S.; Rodrigues, J. B.; Ribeiro, P. S. E.; Frasca, A. A. S.; Saboia, A. M.; Lacerda Filho, J. V.

    2017-01-01

    The southwestern portion of the Amazonian craton, between the Ventuari-Tapajós province and the Andean chain, has been ascribed to a succession of orogenic events from 1.81 to 0.95 Ga, culminating with widespread anorogenic magmatism. Southwestward of the Serra do Cachimbo graben occurs the Juruena accretionary orogenic belt (ca. 1.81-1.51 Ga), previously included in the Rio Negro-Juruena and Rondonian/San Ignácio geocronological provinces or Rondônia-Juruena geologic province. The Juruena orogen proposed here includes the Jamari and Juruena tectonostratigraphic terranes, products of convergence which culminated in the soft collision of the Paraguá protocraton and the Tapajós-Parima arc system (Tapajós Province) ca. 1.69-1.63 Ga ago. Geophysical, geochemical, petrological and geochronological data and systematic geological mapping suggest that the convergent event resulted in a single orogenic system with two continental margin arcs, namely the Jamari and Juruena arcs. Modern geological and tectonic approaches, combined with aerogeophysics data, enable to interpreting this wide region of the Amazonian craton as a Paleoproterozoic orogen with well defined petrotectonic units and tectonoestructural framework. The Juruena orogen is an E-W trending belt, about 1100 km long and 350 km wide, inflecting to NW-SE, in Mato Grosso, Amazonas and Rondonia, Brazil. The general direction of the belt, its inflections and internal geometric and kinematic aspects of its macrostructures do not corroborate the general NW-SE trend of the originally proposed geocronological provinces. The Juruena accretionary orogen has been the site of repeated reactivation with renewed basin formation, magmatism and orogeny during the Mesoproterozoic and the early Neoproterozoic. U-Pb and whole-rock Sm-Nd ages, Ar-Ar and Rb-Sr mineral ages suggest that the older high grade tectonometamorphic events in the Juruena accretionary orogen took place between 1.69 and 1.63 Ga, defining the metamorphic

  7. Modelling Greenland Outlet Glaciers

    NASA Technical Reports Server (NTRS)

    vanderVeen, Cornelis; Abdalati, Waleed (Technical Monitor)

    2001-01-01

    The objective of this project was to develop simple yet realistic models of Greenland outlet glaciers to better understand ongoing changes and to identify possible causes for these changes. Several approaches can be taken to evaluate the interaction between climate forcing and ice dynamics, and the consequent ice-sheet response, which may involve changes in flow style. To evaluate the icesheet response to mass-balance forcing, Van der Veen (Journal of Geophysical Research, in press) makes the assumption that this response can be considered a perturbation on the reference state and may be evaluated separately from how this reference state evolves over time. Mass-balance forcing has an immediate effect on the ice sheet. Initially, the rate of thickness change as compared to the reference state equals the perturbation in snowfall or ablation. If the forcing persists, the ice sheet responds dynamically, adjusting the rate at which ice is evacuated from the interior to the margins, to achieve a new equilibrium. For large ice sheets, this dynamic adjustment may last for thousands of years, with the magnitude of change decreasing steadily over time as a new equilibrium is approached. This response can be described using kinematic wave theory. This theory, modified to pertain to Greenland drainage basins, was used to evaluate possible ice-sheet responses to perturbations in surface mass balance. The reference state is defined based on measurements along the central flowline of Petermann Glacier in north-west Greenland, and perturbations on this state considered. The advantage of this approach is that the particulars of the dynamical flow regime need not be explicitly known but are incorporated through the parameterization of the reference ice flux or longitudinal velocity profile. The results of the kinematic wave model indicate that significant rates of thickness change can occur immediately after the prescribed change in surface mass balance but adjustments in flow

  8. The deep accumulation of 10Be at Utsira, southwestern Norway: Implications for cosmogenic nuclide exposure dating in peripheral ice sheet landscapes

    NASA Astrophysics Data System (ADS)

    Briner, Jason P.; Goehring, Brent M.; Mangerud, Jan; Svendsen, John Inge

    2016-09-01

    Cosmogenic nuclide exposure dating is a widely used method for constraining past ice sheet histories. We scrutinize a recently published data set of cosmogenic 10Be data from erratic boulders in Norway used to constrain the deglaciation of the western Scandinavian Ice Sheet to 20 ka. Our model of the 10Be inventory in glacial surfaces leads us to conclude that the chronology may be afflicted by the deep subsurface accumulation of 10Be during long-lasting ice-free periods that resulted in 10Be ages >10% too old. We suggest that the majority of the dated erratic boulders contain a uniform level of inherited muon-produced 10Be and were derived from bedrock depths >2.5 m and most likely ~4 m. The implication of our finding is that for landscapes that experience long ice-free periods between brief maximum glacial phases, glacial erosion of >5 m is required to remove detectable traces of inherited 10Be.

  9. Cultural adaptation, compounding vulnerabilities and conjunctures in Norse Greenland.

    PubMed

    Dugmore, Andrew J; McGovern, Thomas H; Vésteinsson, Orri; Arneborg, Jette; Streeter, Richard; Keller, Christian

    2012-03-06

    Norse Greenland has been seen as a classic case of maladaptation by an inflexible temperate zone society extending into the arctic and collapse driven by climate change. This paper, however, recognizes the successful arctic adaptation achieved in Norse Greenland and argues that, although climate change had impacts, the end of Norse settlement can only be truly understood as a complex socioenvironmental system that includes local and interregional interactions operating at different geographic and temporal scales and recognizes the cultural limits to adaptation of traditional ecological knowledge. This paper is not focused on a single discovery and its implications, an approach that can encourage monocausal and environmentally deterministic emphasis to explanation, but it is the product of sustained international interdisciplinary investigations in Greenland and the rest of the North Atlantic. It is based on data acquisitions, reinterpretation of established knowledge, and a somewhat different philosophical approach to the question of collapse. We argue that the Norse Greenlanders created a flexible and successful subsistence system that responded effectively to major environmental challenges but probably fell victim to a combination of conjunctures of large-scale historic processes and vulnerabilities created by their successful prior response to climate change. Their failure was an inability to anticipate an unknowable future, an inability to broaden their traditional ecological knowledge base, and a case of being too specialized, too small, and too isolated to be able to capitalize on and compete in the new protoworld system extending into the North Atlantic in the early 15th century.

  10. Cultural adaptation, compounding vulnerabilities and conjunctures in Norse Greenland

    PubMed Central

    Dugmore, Andrew J.; McGovern, Thomas H.; Vésteinsson, Orri; Arneborg, Jette; Streeter, Richard; Keller, Christian

    2012-01-01

    Norse Greenland has been seen as a classic case of maladaptation by an inflexible temperate zone society extending into the arctic and collapse driven by climate change. This paper, however, recognizes the successful arctic adaptation achieved in Norse Greenland and argues that, although climate change had impacts, the end of Norse settlement can only be truly understood as a complex socioenvironmental system that includes local and interregional interactions operating at different geographic and temporal scales and recognizes the cultural limits to adaptation of traditional ecological knowledge. This paper is not focused on a single discovery and its implications, an approach that can encourage monocausal and environmentally deterministic emphasis to explanation, but it is the product of sustained international interdisciplinary investigations in Greenland and the rest of the North Atlantic. It is based on data acquisitions, reinterpretation of established knowledge, and a somewhat different philosophical approach to the question of collapse. We argue that the Norse Greenlanders created a flexible and successful subsistence system that responded effectively to major environmental challenges but probably fell victim to a combination of conjunctures of large-scale historic processes and vulnerabilities created by their successful prior response to climate change. Their failure was an inability to anticipate an unknowable future, an inability to broaden their traditional ecological knowledge base, and a case of being too specialized, too small, and too isolated to be able to capitalize on and compete in the new protoworld system extending into the North Atlantic in the early 15th century. PMID:22371594

  11. Surface-atmosphere decoupling limits accumulation at Summit, Greenland.

    PubMed

    Berkelhammer, Max; Noone, David C; Steen-Larsen, Hans Christian; Bailey, Adriana; Cox, Christopher J; O'Neill, Michael S; Schneider, David; Steffen, Konrad; White, James W C

    2016-04-01

    Despite rapid melting in the coastal regions of the Greenland Ice Sheet, a significant area (~40%) of the ice sheet rarely experiences surface melting. In these regions, the controls on annual accumulation are poorly constrained owing to surface conditions (for example, surface clouds, blowing snow, and surface inversions), which render moisture flux estimates from myriad approaches (that is, eddy covariance, remote sensing, and direct observations) highly uncertain. Accumulation is partially determined by the temperature dependence of saturation vapor pressure, which influences the maximum humidity of air parcels reaching the ice sheet interior. However, independent proxies for surface temperature and accumulation from ice cores show that the response of accumulation to temperature is variable and not generally consistent with a purely thermodynamic control. Using three years of stable water vapor isotope profiles from a high altitude site on the Greenland Ice Sheet, we show that as the boundary layer becomes increasingly stable, a decoupling between the ice sheet and atmosphere occurs. The limited interaction between the ice sheet surface and free tropospheric air reduces the capacity for surface condensation to achieve the rate set by the humidity of the air parcels reaching interior Greenland. The isolation of the surface also acts to recycle sublimated moisture by recondensing it onto fog particles, which returns the moisture back to the surface through gravitational settling. The observations highlight a unique mechanism by which ice sheet mass is conserved, which has implications for understanding both past and future changes in accumulation rate and the isotopic signal in ice cores from Greenland.

  12. The prevalence of seasonal affective disorder (SAD) in Greenland is related to latitude.

    PubMed

    Kegel, Mogens; Dam, Henrik; Ali, Fatuma; Bjerregaard, Peter

    2009-01-01

    The aim of this study was to determine the prevalence of seasonal affective disorder (SAD) in Greenlanders and Danes living at four different latitudes in Greenland. A Seasonal Pattern Assessment Questionnaire (SPAQ) was mailed to 6021 men and women between the ages of 18 and 59 years living in four different municipalities in Greenland. The recipients were randomly selected from the National Population Register. Approximately 9% of the respondents met the criteria for SAD, and the incidence of SAD varied between a southern municipality and three northern municipalities. The prevalence of SAD was particularly high in northern municipalities. No significant difference was found in the prevalence of SAD between Greenlanders and Danes. The results are comparable with other population studies that have reported a high prevalence of SAD in arctic areas. The clinical implications of our findings and the possibilities for introducing light therapy should be assessed in future studies.

  13. Utility of imaging spectrometry for lithologic mapping in Greenland

    NASA Technical Reports Server (NTRS)

    Rivard, Benoit; Arvidson, Raymond E.

    1992-01-01

    Landsat Thematic Mapper (TM) multispectral image data and field-based spectral reflectance measurements for a portion of the island of Storo, southwestern Greenland, were used to evaluate the potential of imaging spectrometry for lithologic mapping in arctic terrains. TM data allow mapping of tundra vegetation that typically covers moraines at lower elevations, and lichen-covered bedrock exposed at higher elevations. However, the ubiquitous lichen cover, combined with the limited spectral and radiometric capabilities of TM, severely hamper mapping of the amphibolite, anorthosite, gneiss, and granite outcrops on the island. Diagnostic mineral signatures can be discerned from high spectral and radiometric resolution observations, because lichen cover is patchy at mineral and outcrop scales. Results imply that high resolution imaging spectrometer data (e.g., from the HIRIS sensor to fly on the Earth Observing System), detailed field work, and application of subpixel mixing models will dramatically improve the ability to identify and map bedrock in similar terrains.

  14. 10Be measurements in bedrock constrain erosion beneath the Greenland Ice Sheet margin

    NASA Astrophysics Data System (ADS)

    Young, Nicolás. E.; Briner, Jason P.; Maurer, Josh; Schaefer, Joerg M.

    2016-11-01

    Glacial erosion is a key process driving landscape evolution, but it remains unclear what factors dictate the rate at which subglacial erosion occurs. Moreover, estimates of subglacial erosion that do not rely on sediment flux techniques are rare. Here, we present in situ 10Be measurements from bedrock surfaces in western Greenland with well-constrained ice-cover histories to quantify the erosion rate beneath the Greenland Ice Sheet margin during historical times. We calculate an abrasion rate of 0.72 ± 0.35 mm yr-1 and a likely total basin-wide erosion rate (abrasion + quarrying) of 1-1.8 mm yr-1, which are at least 1 order of magnitude higher than typical subglacial erosion rates in other polar landscapes. A compilation of published 10Be data suggests that the southwestern Greenland Ice Sheet acts as a particularly effective erosional agent within the broader Baffin Bay-Greenland region over millennial to glacial-interglacial timescales, suggestive of a basal ice sheet thermal regime controlled by regional climate.

  15. Seasonal variability of the warm Atlantic water layer in the vicinity of the Greenland shelf break

    NASA Astrophysics Data System (ADS)

    Grist, Jeremy P.; Josey, Simon A.; Boehme, Lars; Meredith, Michael P.; Laidre, Kristin L.; Heide-Jørgensen, Mads Peter; Kovacs, Kit M.; Lydersen, Christian; Davidson, Fraser J. M.; Stenson, Garry B.; Hammill, Mike O.; Marsh, Robert; Coward, Andrew C.

    2014-12-01

    The warmest water reaching the east and west coast of Greenland is found between 200 and 600 m. While important for melting Greenland's outlet glaciers, limited winter observations of this layer prohibit determination of its seasonality. To address this, temperature data from Argo profiling floats, a range of sources within the World Ocean Database, and unprecedented coverage from marine-mammal borne sensors have been analyzed for the period 2002-2011. A significant seasonal range in temperature (~1-2°C) is found in the warm layer, in contrast to most of the surrounding ocean. The phase of the seasonal cycle exhibits considerable spatial variability, with the warmest water found near the eastern and southwestern shelf break toward the end of the calendar year. High-resolution ocean model trajectory analysis suggests the timing of the arrival of the year's warmest water is a function of advection time from the subduction site in the Irminger Basin.

  16. Southwestern desert resources

    USGS Publications Warehouse

    Halvorson, William L.; van Riper, Charles; Schwalbe, Cecil R.

    2010-01-01

    The southwestern deserts stretch from southeastern California to west Texas and then south to central Mexico. The landscape of this region is known as basin and range topography featuring to "sky islands" of forest rising from the desert lowlands which creates a uniquely diverse ecology. The region is further complicated by an international border, where governments have caused difficulties for many animal populations. This book puts a spotlight on individual research projects which are specific examples of work being done in the area and when they are all brought together, to shed a general light of understanding the biological and cultural resources of this vast region so that those same resources can be managed as effectively and efficiently as possible. The intent is to show that collaborative efforts among federal, state agency, university, and private sector researchers working with land managers, provides better science and better management than when scientists and land managers work independently.

  17. Brief communication: Getting Greenland's glaciers right - a new data set of all official Greenlandic glacier names

    NASA Astrophysics Data System (ADS)

    Bjørk, A. A.; Kruse, L. M.; Michaelsen, P. B.

    2015-12-01

    Place names in Greenland can be difficult to get right, as they are a mix of Greenlandic, Danish, and other foreign languages. In addition, orthographies have changed over time. With this new data set, we give the researcher working with Greenlandic glaciers the proper tool to find the correct name for glaciers and ice caps in Greenland and to locate glaciers described in the historic literature with the old Greenlandic orthography. The data set contains information on the names of 733 glaciers, 285 originating from the Greenland Ice Sheet (GrIS) and 448 from local glaciers and ice caps (LGICs).

  18. North Atlantic warming and the retreat of Greenland's outlet glaciers.

    PubMed

    Straneo, Fiammetta; Heimbach, Patrick

    2013-12-05

    Mass loss from the Greenland ice sheet quadrupled over the past two decades, contributing a quarter of the observed global sea-level rise. Increased submarine melting is thought to have triggered the retreat of Greenland's outlet glaciers, which is partly responsible for the ice loss. However, the chain of events and physical processes remain elusive. Recent evidence suggests that an anomalous inflow of subtropical waters driven by atmospheric changes, multidecadal natural ocean variability and a long-term increase in the North Atlantic's upper ocean heat content since the 1950s all contributed to a warming of the subpolar North Atlantic. This led, in conjunction with increased runoff, to enhanced submarine glacier melting. Future climate projections raise the potential for continued increases in warming and ice-mass loss, with implications for sea level and climate.

  19. Desert Voices: Southwestern Children's Literature.

    ERIC Educational Resources Information Center

    Polette, Keith

    1997-01-01

    Examines three books with different ways of writing about the desert. Discusses: "Here Is the Southwestern Desert" by Madeline Dunphy, "The Desert Is My Mother" by Pat Mora, and "The Desert Mermaid" by Alberto Blanco. (PA)

  20. Paleohydrology of Southwestern Texas

    NASA Astrophysics Data System (ADS)

    Kochel, R. Craig; Baker, Victor R.; Patton, Peter C.

    1982-08-01

    Current statistical methods may be unable to accurately predict recurrence intervals of rare, large-magnitude floods, especially in semiarid regions having positively skewed annual flood distributions, great hydrologic variability, and widely spaced gaging stations. Current approaches rely on historical data, but catastrophic floods may have recurrence intervals far greater than the length of historical records. In the lower Pecos and Devils Rivers of southwestern Texas, paleoflood discharge and frequency estimates are extended over 10,000 years by the study of slack-water flood sediments. Slack-water deposits are typically fine-grained sand and silt that accumulate during floods in areas where current velocity is reduced, i.e., in back-flooded tributary mouths, channel expansions, downstream from bedrock spurs and/or slump blocks, and in shallow caves along bedrock walls. Radiocarbon dating of organic detritus in slack-water deposits establishes the flood chronology while paleoflood discharges can be estimated by slope-area techniques. Paleoflood information extracted from slack-water sediments can greatly extend flood records. These floods may be weighted like historical data in log Pearson type 3 calculations of flood frequency. Our morphostratigraphic approach combines recorded data with geomorphic evidence to derive estimates of flood frequency. This technique offers an inexpensive and rapid way to assess catastrophic flood risk.

  1. Seasonal Evolution of Supra-glacial Lakes Across the Greenland Ice Sheet

    NASA Astrophysics Data System (ADS)

    Sundal, A.; Shepherd, A.; Nienow, P.; Palmer, S.; Hanna, E.

    2008-12-01

    We used 268 MODIS satellite images spanning the melt seasons 2003 and 2005-2007 to investigate the seasonal evolution of supra-glacial lakes in three different regions of the Greenland ice sheet. Lake area estimates were obtained by developing an automated classification method for their identification based on 250 m resolution MODIS surface reflectance images. Our dataset reveal widespread supra-glacial lake formation and drainage across the Greenland ice sheet, with a 2-3 weeks delay in the evolution of total supra-glacial lake area in the northern study areas compared to the south-western study area. The onset of lake growth varies by up to one month inter-annually, and lakes form and drain at progressively higher altitudes during the melt season. The annual peak in total lake area is positively correlated with modelled annual runoff across all study areas. Our results indicate that, in a warmer climate, supra-glacial lakes on the surface of the Greenland ice sheet can be expected to form earlier in the melt season and at higher altitudes than is presently the case. In consequence, the area and time period over which connections between the ice sheet surface and base may be established (Das et al 2008) will increase, potentially increasing the rate of ice sheet discharge and its sea level contribution (Zwally et al 2002). Das, S., Joughin, M., Behn, M., Howat, I., King, M., Lizarralde, D., Bhatia, M., 2008. Fracture propagation to the base of the Greenland Ice Sheet during supra-glacial lake drainage, Science, 5877, p.778-781. Zwally, H.J., Abdalati, W., Herring, T., Larson, K., Saba, J., Steffen, K., 2002. Surface Melt-Induced Acceleration of Greenland Ice-Sheet Flow, Science, 297, p.218-221.

  2. Selenium status in Greenland Inuit.

    PubMed

    Hansen, Jens C; Deutch, Bente; Pedersen, Henning Sloth

    2004-09-20

    In Greenland, the human intake of selenium has always been relatively high and is closely connected to intake of the traditional food of marine origin. Analyses of historic and present day human and animal hair samples have indicated that the selenium level in the marine environment has been constant over time, while the levels in humans have declined corresponding to a decrease in intake of traditional food. The Inuit population in Greenland is in dietary transition where western-style food will increasingly dominate. As a consequence, the ample supply of selenium may not be sustained in the future. We report here the selenium status in three Greenlandic population groups, Ittoqqortoormiit and Tasiilaq on the east coast and Uummannaq on the west coast. Mean whole blood concentrations ranged from 178 microg/l in Tasiilaq men to 488 microg/l in Uummannaq men. Plasma concentrations ranged from 79 microg/l in Tasiilaq women to 113 microg/l in Uummannaq men. With increasing Se concentrations in whole blood, the plasma concentrations increased but tended to stabilise a level approximately 140 microg/l. Selenium blood levels were highly significantly correlated with long chain marine fatty acids. Dietary survey and food composition data from the west coast showed that whale skin, muktuk, is the main source of Se followed by birds, seal meat and organs, and fish. Terrestrial animals contributed only insignificantly to the selenium intake. In West Greenland, daily Se intake (235 microg/day) was estimated by dietary survey; it corresponded well with a calculated intake (220 microg/day) based on the mean blood concentration.

  3. Surface-atmosphere decoupling limits accumulation at Summit, Greenland

    PubMed Central

    Berkelhammer, Max; Noone, David C.; Steen-Larsen, Hans Christian; Bailey, Adriana; Cox, Christopher J.; O’Neill, Michael S.; Schneider, David; Steffen, Konrad; White, James W. C.

    2016-01-01

    Despite rapid melting in the coastal regions of the Greenland Ice Sheet, a significant area (~40%) of the ice sheet rarely experiences surface melting. In these regions, the controls on annual accumulation are poorly constrained owing to surface conditions (for example, surface clouds, blowing snow, and surface inversions), which render moisture flux estimates from myriad approaches (that is, eddy covariance, remote sensing, and direct observations) highly uncertain. Accumulation is partially determined by the temperature dependence of saturation vapor pressure, which influences the maximum humidity of air parcels reaching the ice sheet interior. However, independent proxies for surface temperature and accumulation from ice cores show that the response of accumulation to temperature is variable and not generally consistent with a purely thermodynamic control. Using three years of stable water vapor isotope profiles from a high altitude site on the Greenland Ice Sheet, we show that as the boundary layer becomes increasingly stable, a decoupling between the ice sheet and atmosphere occurs. The limited interaction between the ice sheet surface and free tropospheric air reduces the capacity for surface condensation to achieve the rate set by the humidity of the air parcels reaching interior Greenland. The isolation of the surface also acts to recycle sublimated moisture by recondensing it onto fog particles, which returns the moisture back to the surface through gravitational settling. The observations highlight a unique mechanism by which ice sheet mass is conserved, which has implications for understanding both past and future changes in accumulation rate and the isotopic signal in ice cores from Greenland. PMID:27386509

  4. A synthesis of the basal thermal state of the Greenland Ice Sheet

    USGS Publications Warehouse

    MacGregor, Joseph A; Fahnestock, Mark A; Catania, Ginny A; Aschwanden, Andy; Clow, Gary D.; Colgan, William T.; Gogineni, Prasad S.; Morlighem, Mathieu; Nowicki, Sophie M .J.; Paden, John D; Price, Stephen F.; Seroussi, Helene

    2016-01-01

    The basal thermal state of an ice sheet (frozen or thawed) is an important control upon its evolution, dynamics and response to external forcings. However, this state can only be observed directly within sparse boreholes or inferred conclusively from the presence of subglacial lakes. Here we synthesize spatially extensive inferences of the basal thermal state of the Greenland Ice Sheet to better constrain this state. Existing inferences include outputs from the eight thermomechanical ice-flow models included in the SeaRISE effort. New remote-sensing inferences of the basal thermal state are derived from Holocene radiostratigraphy, modern surface velocity and MODIS imagery. Both thermomechanical modeling and remote inferences generally agree that the Northeast Greenland Ice Stream and large portions of the southwestern ice-drainage systems are thawed at the bed, whereas the bed beneath the central ice divides, particularly their west-facing slopes, is frozen. Elsewhere, there is poor agreement regarding the basal thermal state. Both models and remote inferences rarely represent the borehole-observed basal thermal state accurately near NorthGRIP and DYE-3. This synthesis identifies a large portion of the Greenland Ice Sheet (about one third by area) where additional observations would most improve knowledge of its overall basal thermal state.

  5. A synthesis of the basal thermal state of the Greenland Ice Sheet.

    PubMed

    MacGregor, Joseph A; Fahnestock, Mark A; Catania, Ginny A; Aschwanden, Andy; Clow, Gary D; Colgan, William T; Gogineni, S Prasad; Morlighem, Mathieu; Nowicki, Sophie M J; Paden, John D; Price, Stephen F; Seroussi, Hélène

    2016-08-10

    The basal thermal state of an ice sheet (frozen or thawed) is an important control upon its evolution, dynamics and response to external forcings. However, this state can only be observed directly within sparse boreholes or inferred conclusively from the presence of subglacial lakes. Here we synthesize spatially extensive inferences of the basal thermal state of the Greenland Ice Sheet to better constrain this state. Existing inferences include outputs from the eight thermomechanical ice-flow models included in the SeaRISE effort. New remote-sensing inferences of the basal thermal state are derived from Holocene radiostratigraphy, modern surface velocity and MODIS imagery. Both thermomechanical modeling and remote inferences generally agree that the Northeast Greenland Ice Stream and large portions of the southwestern ice-drainage systems are thawed at the bed, whereas the bed beneath the central ice divides, particularly their west-facing slopes, is frozen. Elsewhere, there is poor agreement regarding the basal thermal state. Both models and remote inferences rarely represent the borehole-observed basal thermal state accurately near NorthGRIP and DYE-3. This synthesis identifies a large portion of the Greenland Ice Sheet (about one third by area) where additional observations would most improve knowledge of its overall basal thermal state.

  6. IceBridge Radar as a Tool for Understanding Accumulation Variability throughout the Western Greenland Ice Sheet

    NASA Astrophysics Data System (ADS)

    Lewis, G.; Hawley, R. L.; Osterberg, E. C.; Marshall, H. P.

    2015-12-01

    Understanding the mass balance of the Greenland Ice Sheet (GIS) in a warming climate is of critical interest to scientists and the general public in the context of future sea-level rise. The mass balance of the GIS has been increasingly negative over recent decades, with a conservative estimate of ice sheet mass loss of 2000 Gt yr-1 over the 1988-2014 period. Snow accumulation, the critical input to surface mass balance, varies through time and regionally around Greenland and from the coast to interior, but is constrained by relatively few observations. An improved understanding of temporal and spatial snow accumulation variability will thus reduce uncertainties in GIS mass balance models and sea-level rise projections. Here we quantify spatial and temporal variations in snow accumulation in central and southwest Greenland using data from NASA's Operation IceBridge Accumulation Radar. We estimate depth-density and depth-age relationships using a Herron-Langway density model and Nye flow model, which are iteratively calculated at 50 km intervals along each radar line. We then trace isochrones to calculate spatial and temporal variability in average snow accumulation along several flight paths throughout central and southwestern Greenland. Depth-density, depth-age, and snow accumulation calculations are calibrated at Summit using data from the GISP2, Katie, and SM07C ice cores. Accumulation results will be verified by a series of snow pits, shallow firn cores, and ice-penetrating radar profiles collected on the Greenland Traverse for Accumulation and Climate Studies (GreenTrACS) through southwest Greenland during spring 2016 and 2017.

  7. Drought in Southwestern United States

    NASA Technical Reports Server (NTRS)

    2007-01-01

    The southwestern United States pined for water in late March and early April 2007. This image is based on data collected by the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA's Terra satellite from March 22 through April 6, 2007, and it shows the Normalized Difference Vegetation Index, or NDVI, for the period. In this NDVI color scale, green indicates areas of healthier-than-usual vegetation, and only small patches of green appear in this image, near the California-Nevada border and in Utah. Larger areas of below-normal vegetation are more common, especially throughout California. Pale yellow indicates areas with generally average vegetation. Gray areas appear where no data were available, likely due to persistent clouds or snow cover. According to the April 10, 2007, update from the U.S. Drought Monitor, most of the southwestern United Sates, including Utah, Nevada, California, and Arizona, experienced moderate to extreme drought. The hardest hit areas were southeastern California and southwestern Arizona. Writing for the Drought Monitor, David Miskus of the Joint Agricultural Weather Facility reported that March 2007 had been unusually dry for the southwestern United States. While California's and Utah's reservoir storage was only slightly below normal, reservoir storage was well below normal for New Mexico and Arizona. In early April, an international research team published an online paper in Science noting that droughts could become more common for the southwestern United States and northern Mexico, as these areas were already showing signs of drying. Relying on the same computer models used in the Intergovernmental Panel on Climate Change (IPCC) report released in early 2007, the researchers who published in Science concluded that global warming could make droughts more common, not just in the American Southwest, but also in semiarid regions of southern Europe, Mediterranean northern Africa, and the Middle East.

  8. The Greenland gravitational constant experiment.

    NASA Astrophysics Data System (ADS)

    Zumberge, M. A.; Ander, M. E.; Lautzenhiser, T. V.; Parker, R. L.; Aiken, C. L. V.; Gorman, M. R.; Nieto, M. M.; Cooper, A. P. R.; Ferguson, J. F.; Fisher, E.; Greer, J.; Hammer, P.; Hansen, B. L.; McMechan, G. A.; Sasagawa, G. S.; Sidles, C.; Stevenson, J. M.; Wirtz, J.

    1990-09-01

    An Airy-type geophysical experiment was conducted in a 2-km-deep hole in the Greenland ice cap at depths between 213 m and 1673 m to test for possible violations of Newton's inverse square law. Gravity measurements were made at eight depths in 183-m intervals with a LaCoste & Romberg borehole gravity meter. An anomalous variation in gravity totaling 3.87 mGal (3.87x10-5m/s2) in the depth interval of 1460 m was observed. This may be attributed either to a breakdown of Newtonian gravity or to unexpected density variations in the rock below the ice.

  9. The Greenland Ice Mapping Project

    NASA Astrophysics Data System (ADS)

    Joughin, I.; Smith, B.; Howat, I. M.; Moon, T. A.; Scambos, T. A.

    2015-12-01

    Numerous glaciers in Greenland have sped up rapidly and unpredictably during the first part of the 21st Century. We started the Greenland Ice Mapping Project (GIMP) to produce time series of ice velocity for Greenland's major outlet glaciers. We are also producing image time series to document the advance and retreat of glacier calving fronts and other changes in ice-sheet geometry (e.g., shrinking ice caps and ice shelves). When the project began, there was no digital elevation model (DEM) with sufficient accuracy and resolution to terrain-correct the SAR-derived products. Thus, we also produced the 30-m GIMP DEM, which, aside from improving our processing, is an important product in its own right. Although GIMP focuses on time series, complete spatial coverage for initializing ice sheet models also is important. There are insufficient data, however, to map the full ice sheet in any year. There is good RADARSAT coverage for many years in the north, but the C-band data decorrelate too quickly to measure velocity in the high accumulation regions of the southeast. For such regions, ALOS data usually correlate well, but speckle-tracking estimates at L-band are subject to large ionospheric artifacts. Interferometric phase data are far less sensitive to the effect of the ionosphere, but velocity estimates require results from crossing orbits. Thus, to produce a nearly complete mosaic we used data from multiple sensors, beginning with ERS-1/2 data from the mid 1990s. By using a primarily phase-only solution for much of the interior, we have reduced the velocity errors to ~1-3 m/yr. For the faster moving ice-sheet margin where phase data cannot be unwrapped, we used speckle-tracking data. In particular, we have relied on TerraSAR-X for many fast-moving glaciers because the ionosphere far less affects X-band data. This pan-Greenland velocity map as well as many of the time series would not have been possible without an extensive archive of data collected using six

  10. Annual variation of coastal uplift in Greenland as an indicator of variable and accelerating ice mass loss

    NASA Astrophysics Data System (ADS)

    Yang, Qian; Wdowinski, Shimon; Dixon, Timothy H.

    2013-05-01

    Seasonal melting of the coastal part of the Greenland ice sheet is investigated using GPS vertical displacement data from coastal stations, combined with data on atmospheric and ocean temperatures. Using a high pass filter and cubic spline models, we estimate five variables describing seasonal uplift, a proxy for proximal mass loss, including duration of the melt season and the amount of summer uplift. Our analysis shows both temporal and spatial variations of uplift. Southern coastal Greenland experienced anomalously large uplift in summer 2010, implying significant melting that year. However, the northwest coast did not experience significant change in uplift at that time. Our data suggest that a combination of warm summer air temperature and warm sub-surface ocean water temperature drove the large mass losses in 2010. Using the uplift pattern of 2008-2010, and comparing to atmospheric data and ocean water temperature data, we show that warm Irminger Water (IW) exerted significant influence on coastal melting in southeastern, southern and southwestern Greenland, reaching about 69°N in 2010. North of this, IW did not exert significant influence, in effect defining the northward limit of the sub-polar gyre for that year. Thus, short-term variability in the coastal GPS uplift signal can be used to infer an oceanographic parameter that has a critical influence on Greenland ice sheet health.

  11. Variations in Sr and Nd isotopic ratios of mineral particles in cryoconite in western Greenland

    NASA Astrophysics Data System (ADS)

    Nagatsuka, Naoko; Takeuchi, Nozomu; Uetake, Jun; Shimada, Rigen; Onuma, Yukihiko; Tanaka, Sota; Nakano, Takanori

    2016-11-01

    In order to better understand the source of minerals on the dark-colored ice, located in the Greenland ice sheet ablation zone, we analyzed the Sr and Nd isotopic ratios of minerals in cryoconite, which were collected from glaciers in northwest and southwest Greenland. We focused on the following: (i) comparison of the isotopes of minerals in cyroconite with those in sediments from local and distant areas, (ii) regional variations in western Greenland, and (iii) spatial variations across an individual a glacier. The mineral components of the cryoconite showed variable Sr and Nd isotopic ratios (87Sr/86Sr: 0.711335 to 0.742406, ɛNd (0): -33.1 to -22.9), which corresponded to those of the englacial dust and moraine on and around the glaciers but were significantly different from those of the distant deserts that have been considered to be primary sources of mineral dust on the Greenland Ice Sheet. This suggests that the minerals within the cryoconites were mainly derived from local sediments, rather than from distant areas. The Sr ratios in the northwestern region were significantly higher than those in the southwestern region. This is probably due to geological differences in the source areas, such as the surrounding glaciers in each region. The isotopic ratios further varied spatially within a glacier (Qaanaaq and Kangerlussuaq areas), indicating that the silicate minerals on the glaciers were derived not from a single source but from multiple sources, such as englacial dust and wind-blown minerals from the moraine surrounding the glaciers.

  12. Southwest coast of Greenland and Davis Strait

    NASA Technical Reports Server (NTRS)

    2002-01-01

    This true-color image was taken by MODIS as it passed over the southwest coast of Greenland (right) and the Davis Strait (center and left). The Davis Strait connects Baffin Bay to the north and the Labrador Sea to the south, and separates Greenland from Baffin Island, Canada. The Davis Strait is part of the Northwest Passage, a navigable seaway connecting the Atlantic Ocean and the Pacific Ocean. The image shows the prevailing currents in the area, with the warm water of a branch of the North Atlantic Drift flowing northward along the Greenland coast, and the cold, iceberg-filled Labrador Current flowing southward along the Baffin Island coast.

  13. High-resolution passive sampling of dissolved methane in the water column of lakes in Greenland

    NASA Astrophysics Data System (ADS)

    Goldman, A. E.; Cadieux, S. B.; White, J. R.; Pratt, L. M.

    2013-12-01

    Arctic lakes are important participants in the global carbon cycle, releasing methane in a warming climate and contributing to a positive feedback to climate change. In order to yield detailed methane budgets and understand the implications of warming on methane dynamics, high-resolution profiles revealing methane behavior within the water column need to be obtained. Single day sampling using disruptive techniques has the potential to result in biases. In order to obtain high-resolution, undisturbed profiles of methane concentration and isotopic composition, this study evaluates a passive sampling method over a multi-day equilibration period. Selected for this study were two small lakes (<1km2) within a narrow valley stretching between Russells Glacier and Søndre Strømfjord in southwestern Greenland, which are part of an ongoing study of a series of seven lakes. Commercially available, 150 mL, polyethylene Passive Diffusion Bags (PDB's) were deployed in July 2013 for five days at 0.5-meter depth intervals. PDB samples were compared to samples collected with a submersible, electric pump taken immediately before PBD deployment. Preliminary CH4 concentrations and carbon isotopes for one lake were obtained in the field using a Los Gatos Research Methane Carbon Isotope Analyzer. PDB sampling and pump sampling resulted in statistically similar concentrations (R2=0.89), ranging from 0.85 to 135 uM from PDB and 0.74 to 143 uM from pump sampling. In anoxic waters of the lake, where concentrations were high enough to yield robust isotopic results on the LGR MCIA, δ13C were also similar between the two methods, yielding -73‰ from PDB and -74‰ from pump sampling. Further investigation will produce results for a second lake and methane carbon and hydrogen isotopic composition for both lakes. Preliminary results for this passive sampling method are promising. We envision the use of this technique in future studies of dissolved methane and expect that it will provide a

  14. Miocene to Quaternary tectonostratigraphic evolution of the middle section of the Burdur-Fethiye Shear Zone, south-western Turkey: Implications for the wide inter-plate shear zones

    NASA Astrophysics Data System (ADS)

    Elitez, İrem; Yaltırak, Cenk

    2016-10-01

    The Burdur-Fethiye Shear Zone (BFSZ) is a 75- to 90- km wide and 300-km-long transtensional left-lateral shear zone which is located in one of the most tectonically active regions in south-western Turkey. A considerable number of studies suggested contradictory models of the evolution and Neogene stratigraphy of the BFSZ and in most cases, the local river and alluvial fan deposits were mapped together with the lacustrine sediments and assigned a Pliocene age. We present new field data, fault kinematic analyses, and DEM and earthquake data to characterize the tectonic controls and extent of the middle section of the BFSZ including Acıpayam, Çameli and Gölhisar basins. Our field observations revealed two distinct sedimentary sequences that unconformably overlie the pre-Neogene basement. The first sequence begins with middle-upper Miocene meandering- and braided-river sediments of the Gölhisar Formation, which transition upward into lacustrine sediments of the upper Miocene-lower Pliocene İbecik Formation. This sequence is overlain by upper Pliocene-lower Quaternary alluvial fan conglomerates, mudstones and claystones of the Dirmil Formation. The basin deposits located in the middle section of the BFSZ consist of lacustrine sediments of a late Miocene lake that likely evaporated due to the Messinian salinity crisis. Fault kinematic analysis and DEM and earthquake data indicate that the middle BFSZ can be characterized as a heterogeneous left-lateral transtensional shear zone rather than a major fault system. Our findings suggest that the middle section of the BFSZ developed under the influence of progressive counter clockwise rotation of south-western Turkey, the Aegean graben system and the Cyprus and Hellenic arcs since the middle Miocene.

  15. Rich Rogers Flying Over Greenland Icecap

    NASA Video Gallery

    Ihis is a view from the NASA P3 aircraft cockpit as it flies 1000 feet over the Greenland icecap during Operation Icebridge mission, which flies each March-May. The end of video shows an ice camp w...

  16. Greenland's Coast in Holiday Colors

    NASA Technical Reports Server (NTRS)

    2003-01-01

    Vibrant reds, emerald greens, brilliant whites, and pastel blues adorn this view of the area surrounding the Jakobshavn Glacier on the western coast of Greenland. The image is a false-color (near-infrared, green, blue) view acquired by the Multi-angle Imaging SpectroRadiometer's nadir camera. The brightness of vegetation in the near-infrared contributes to the reddish hues; glacial silt gives rise to the green color of the water; and blue-colored melt ponds are visible in the bright white ice. A scattering of small icebergs in Disco Bay adds a touch of glittery sparkle to the scene.

    The large island in the upper left is called Qeqertarsuaq. To the east of this island, and just above image center, is the outlet of the fast-flowing Jakobshavn (or Ilulissat) glacier. Jakobshavn is considered to have the highest iceberg production of all Greenland glaciers and is a major drainage outlet for a large portion of the western side of the ice sheet. Icebergs released from the glacier drift slowly with the ocean currents and pose hazards for shipping along the coast.

    The Multi-angle Imaging SpectroRadiometer views the daylit Earth continuously and the entire globe between 82 degrees north and 82 degrees south latitude is observed every 9 days. These data products were generated from a portion of the imagery acquired on June 18, 2003 during Terra orbit 18615. The image cover an area of about 254 kilometers x 210 kilometers, and use data from blocks 34 to 35 within World Reference System-2 path 10.

    MISR was built and is managed by NASA's Jet Propulsion Laboratory, Pasadena, CA, for NASA's Office of Earth Science, Washington, DC. The Terra satellite is managed by NASA's Goddard Space Flight Center, Greenbelt, MD. JPL is a division of the California Institute of Technology.

  17. The Greenland gravitational constant experiment

    NASA Astrophysics Data System (ADS)

    Ander, Mark E.; Parker, Robert L.; Aiken, Carlos L. V.; Gorman, Michael R.; Nieto, Michael Martin; Cooper, A. Paul R.; Ferguson, John F.; Fisher, Elizabeth; Greer, James; Hammer, Phil; Hansen, B. Lyle; McMechan, George A.; Sasagawa, Glenn S.; Sidles, Cyndi; Stevenson, J. Mark; Wirtz, Jim

    1990-09-01

    An Airy-type geophysical experiment was conducted in a 2-km-deep hole in the Greenland ice cap at depths between 213 m and 1673 m to test for possible violations of Newton's inverse square law. The experiment was done at Dye 3, the location of a Distant Early Warming Line radar dome and the site of the deepest of the Greenland Ice-Sheet Program (GISP) drill holes. Gravity measurements were made at eight depths in 183-m intervals with a LaCoste & Romberg borehole gravity meter. Prior to the experiment the borehole, gravity meter was calibrated with an absolute gravity meter, and the wireline depth-finding system used in the borehole logging was calibrated in a vertical mine-shaft against a laser geodimeter. The density of the ice in the region was calculated from measurements taken from ice cores obtained from earlier drilling observations. Ice penetrating radar was employed in order to correct the gravity data for the topography of the ice-rock interface. Surface gravity observations were made to assess the extent to which density variations in the sub-ice rock could affect the vertical gravity gradient. The locations of the gravity observation points were determined with a combination of GPS recording, first-order leveling, and EDM surveying. An anomalous variation in gravity totaling 3.87 mGal (3.87×10-5 m/s2) in a depth interval of 1460 m was observed. This may be attributed either to a breakdown of Newtonian gravity or to unexpected density variations in the rock below the ice.

  18. Dynamic Controls on Recent Increases in Northwest Greenland Coastal Precipitation

    NASA Astrophysics Data System (ADS)

    Wong, G. J.; Osterberg, E. C.; Hawley, R. L.; Courville, Z.; Ferris, D. G.; Howley, J. A.

    2015-12-01

    Arctic precipitation has been rising over recent decades, with implications for glacier mass balance, sea level rise, and thermohaline circulation via the freshening of the Arctic seas. Coastal instrumental data and proxy records in northwest (NW) Greenland indicate positive summer precipitation trends from 1952-2012 along with a long-term, significant (p < 0.05) summer warming trend. While the observed precipitation increase is likely due in part to Clausius-Clapeyron increases in vapor pressure, the dynamical mechanisms responsible for the increasing trend remain poorly understood. Here we use a 61-year record of precipitation from Thule Air Base in NW Greenland and NCEP/NCAR reanalysis data to identify atmospheric circulation patterns associated with enhanced precipitation in recent decades. We evaluate Thule precipitation-circulation relationships for the warm season (July-October [JASO]; 49% of annual precipitation) and cold season (December-February [DJF]; 20% of annual precipitation). Anomalously high precipitation in DJF and JASO is associated with enhanced southerly flow of warm, moist air and enhanced uplift (omega) in Northern Baffin Bay. Meridional flow in Baffin Bay is strongly correlated with the North Atlantic Oscillation (NAO). We observe enhanced southerly flow, uplift and Thule precipitation during negative NAO conditions in winter and to a weaker extent JASO. Based on this mechanism, the trend (p < 0.10) of declining annual NAO index values since 1981 is consistent with the rising trends in Thule annual precipitation over this interval. We find evidence that a NW Greenland ice core proxy record (2Barrel) has a diminished JASO seasonal bias compared with the coast, and thus a future, longer proxy record collected from the 2Barrel site would be well suited for capturing both summer and winter climate variability.

  19. Supraglacial fluvial landscape evolution on the Greenland Ice Sheet

    NASA Astrophysics Data System (ADS)

    Karlstrom, L.; Yang, K.

    2015-12-01

    In the ablation zone of the Greenland Ice Sheet, melting during the summer drives drainage development in which flow is routed downslope through a network of supgraglacial streams and lakes until it is sequestered by the englacial system or flows off of the glacier. This supraglacial drainage network sets the efficacy by which melt water is transport into the glacier and thus has important implications for coupling between ice sheet sliding and surface melt. Thermal erosion in supraglacial streams is rapid compared to other fluvial environments, raising the possibility that supraglacial topographic evolution is to some extent set by local fluvial incision rather than by underlying bedrock or iceflow. We study a series of supraglacial drainage basins on top of the West Greenland Ice Sheet between 1000-1500 m elevation using a combination of high-resolution images, and concurrent (2 m resolution) DEMs constructed from World View Imagery. Although large-scale topography correlates well with underlying bedrock topography, spectral filtering of the surface also reveals broad, low relief valleys that suggest fluvial modification at all elevations. We extract several hundred supraglacial stream longitudinal profiles per drainage basin, finding many channel segments that are clearly out of equilibrium but also numerous concave up channel segments that are not well correlated with underlying bedrock. These concave up segments have a similar power law exponent, suggesting similarities to equilibrium bedrock and alluvial rivers (although the exponent is different in this setting). We develop a stream-power model to predict equilibrium longitudinal profiles where erosion is due to melting driving by viscous dissipation of heat within streams. We speculate that fluvial erosion driven by viscous dissipation is in part responsible for shaping the Greenland Ice Sheet ablation zone annually, superimposed on long wavelength bedrock control of surface topography and basins.

  20. Southwestern Power Administration Update, October- December 2004

    SciTech Connect

    2004-12-01

    On October 29, 2004, Southwestern and Southwest Power Pool, Inc. (SPP) reached agreement on interim arrangements to be implemented after the October 31, 2004, expiration of the membership agreement between the two parties. According to Jim McDonald, Director of Southwestern’s Division of Customer Service, the interim agreement forged between Southwestern and SPP seeks to minimize impacts to SPP as well as to Southwestern and its customers while Southwestern and SPP work on a seams/coordination agreement to succeed the expired membership agreement.

  1. A new reconstruction of the Paleozoic continental margin of southwestern North America: Implications for the nature and timing of continental truncation and the possible role of the Mojave-Sonora megashear

    USGS Publications Warehouse

    Stevens, C.H.; Stone, P.; Miller, J.S.

    2005-01-01

    Data bearing on interpretations of the Paleozoic and Mesozoic paleogeography of southwestern North America are important for testing the hypothesis that the Paleozoic miogeocline in this region has been tectonically truncated, and if so, for ascertaining the time of the event and the possible role of the Mojave-Sonora megashear. Here, we present an analysis of existing and new data permitting reconstruction of the Paleozoic continental margin of southwestern North America. Significant new and recent information incorporated into this reconstruction includes (1) spatial distribution of Middle to Upper Devonian continental-margin facies belts, (2) positions of other paleogeographically significant sedimentary boundaries on the Paleozoic continental shelf, (3) distribution of Upper Permian through Upper Triassic plutonic rocks, and (4) evidence that the southern Sierra Nevada and western Mojave Desert are underlain by continental crust. After restoring the geology of western Nevada and California along known and inferred strike-slip faults, we find that the Devonian facies belts and pre-Pennsylvanian sedimentary boundaries define an arcuate, generally south-trending continental margin that appears to be truncated on the southwest. A Pennsylvanian basin, a Permian coral belt, and a belt of Upper Permian to Upper Triassic plutons stretching from Sonora, Mexico, into westernmost central Nevada, cut across the older facies belts, suggesting that truncation of the continental margin occurred in the Pennsylvanian. We postulate that the main truncating structure was a left-lateral transform fault zone that extended from the Mojave-Sonora megashear in northwestern Mexico to the Foothills Suture in California. The Caborca block of northwestern Mexico, where Devonian facies belts and pre-Pennsylvanian sedimentary boundaries like those in California have been identified, is interpreted to represent a missing fragment of the continental margin that underwent ???400 km of left

  2. Fire in desert grassland region of the southwestern USA: Where and why

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Fire is an important driver of ecological processes in semiarid systems and serves a vital role in shrub-grass interactions. In desert grasslands of the Southwestern US, the loss of fire has been implicated as a primary cause of shrub encroachment. Where fires can currently be re-introduced and mana...

  3. Crustal Structure in Central-Eastern Greenland

    NASA Astrophysics Data System (ADS)

    Shulgin, A.; Thybo, H.

    2013-12-01

    We present the seismic structure in the interior of Greenland based on the first measurements by the seismic refraction/wide angle reflection method. Previous seismic surveys have only been carried out offshore and near the coast of Greenland, where the crustal structure is affected by oceanic break-up and may not be representative of the interior of the island. Acquisition of geophysical data onshore Greenland is logistically complicated by the presence of an up to 3.4 km thick ice sheet, permanently covering most of the land mass. The seismic data was acquired by a team of six people during a two-month long experiment in summer of 2011 on the ice cap in the interior of central-eastern Greenland. The EW-trending profile extends 310 km inland from the approximate edge of the stable ice cap near Scoresby Sund across the centre of the ice cap. The planned extension of the profile by use of OBSs and air gun shooting in Scoresbysund Fjord to the east coast of Greenland was unfortunately cancelled, because navigation was prevented by ice drift. 350 Reftek Texan receivers recorded high-quality seismic data from 8 equidistant shots along the profile. Explosive charge sizes were 1 ton at the ends and ca. 500 kg along the profile, loaded with about 100 kg at 35-85 m depth in individual boreholes. Two-dimensional velocity model based on forward ray tracing and tomography modelling shows a decrease of crustal thickness from 47 km below the centre of Greenland in the western part to 40 km in the eastern part of the profile. Earlier studies show that crustal thickness further decreases eastward to ca. 30 km below the fjord system, but details of the changes are unknown. Relatively high lower crustal velocities (Vp 6.8 - 7.3) in the western part of the TopoGreenland profile may indicate past collision tectonics or may be related or to the passage of the Iceland mantle plume. The origin of the pronounced circum-Atlantic mountain ranges in Norway and eastern Greenland, which have

  4. Pervasive solar influence on Greenland temperature over the past 4000 years

    NASA Astrophysics Data System (ADS)

    Kobashi, T.; Azuma, K. G.; Box, J. E.; Gao, C.; Nakaegawa, T.

    2013-12-01

    (Hegerl et al., 2011) possibly because of less accurate forcing reconstruction. The weak but pervasive solar influence on Greenland temperature over the past 4000 years provides important implications on current and future Greenland temperatures. Hegerl, G., Luterbacher, J., González-Rouco, F., Tett, S. F., Crowley, T., and Xoplaki, E.: Influence of human and natural forcing on European seasonal temperatures, Nat. Geosci., 4, 99-103, 2011. Kobashi, T., Kawamura, K., Severinghaus, J. P., Barnola, J.-M., Nakaegawa, T., Vinther, B. M., Johnsen, S. J., and Box, J. E.: High variability of Greenland surface temperature over the past 4000 years estimated from trapped air in an ice core, Geophys. Res. Lett., 38, 10.1029/2011GL049444, 2011. Kobashi, T., Shindell, D. T., Kodera, K., Box, J. E., Nakaegawa, T., and Kawamura, K.: On the origin of Greenland temperature anomalies over the past 800 years, Clim. Past, 9, 583-596, 2013.

  5. Validation of supraglacial bathymetry models developed for optical sensors using high-resolution stereo-imagery: Implications for meltwater storage assessments across the ablation region of the Greenland ice sheet.

    NASA Astrophysics Data System (ADS)

    Moussavi, M. S.; Abdalati, W.; Pope, A.; Scambos, T. A.

    2014-12-01

    Supraglacial lakes on the Greenland ice sheet have attracted a great deal of attention in the scientific community with respect to their role in seasonal enhancements of ice flow velocities. Large amounts of meltwater generated at the surface can be efficiently delivered to the base of the ice sheet through hydro-fractured pathways beneath supraglacial lakes, potentially increasing basal sliding velocities. Therefore, assessments of surface meltwater volumes stored in and transported from supraglacial lakes to the englacial and subglacial systems are crucial for better coupling models of ice sheet hydrology and dynamics, particularly in response to a warming climate. Several physically-based and empirical passive remote sensing techniques based on MODIS, ASTER, Landsat measurements have been proposed to derive bathymetric information over supraglacial lakes. While unvalidated, most of the techniques have been calibrated against limited in-situ observations and yet have been applied across large regions of the ablation region. In this study, we investigate the validity of such techniques, specifically developed for MODIS, Landsat and WorldView-2 instruments. To make such an assessment, we calibrate the depth-retrieval models by using water-leaving radiances over lakes captured by a specific sensor early in the melt season, and depth measurements from a high resolution WV-2 DEM over the same lakes when devoid of water. Having applied calibrated models over lakes (validation dataset), we then compare the modeled depths against observations derived from the after-drainage DEM of the area. Our primary study site is located in a portion of the ablation region of the GrIS with its center situated at 67o 18' N, 48o 55' W at approximately 1200 m A.S.L[1]. Initial results from the study specifically point to the capability of WV-2 multispectral measurements in calculating lake depths with a high degree of accuracy (bias< 2% of mean depth) and precision (RMSE< 12% of mean

  6. Solar radiation management geoengineering and the Greenland Ice Sheet

    NASA Astrophysics Data System (ADS)

    Applegate, P. J.; Keller, K.

    2014-12-01

    Several authors have suggested that technologies for modifying the Earth's climate should be developed so that they can be deployed if a climate emergency seems imminent. These technologies are generally called geoengineering, or climate engineering. Solar radiation management is perhaps the most commonly discussed geoengineering technique. It involves lofting reflective particles into the upper atmosphere, in imitation of explosive volcanic eruptions that produce measurable cooling at the Earth's surface. Given that geoengineering is intended to reduce surface air temperatures, some authors suggest that it could be used to prevent sea level rise from ice sheet mass loss. The Greenland Ice Sheet is an obvious target for geoengineering-based efforts to avoid sea level rise, because it is large and vulnerable to surface air temperature increases. To evaluate this possibility, we use a three-dimensional, shallow-ice sheet model (SICOPOLIS; sicopolis.greveweb.net) to examine the ability of geoengineering to reduce sea level contributions from the Greenland Ice Sheet. Although this model is highly simplified, its speed of execution allows us to investigate many different potential geoengineering scenarios, covering tens of thousands of model years (excluding spinup). We examine stylized geoengineering scenarios, including both aggressive, sustained geoengineering and more moderate efforts. We comment on the implications of our model results for the ability of geoengineering to reduce future ice sheet-driven sea level change, and how our results might change if our experiments were repeated with a more sophisticated ice sheet model.

  7. Greenland Flow Dynamics: (De)coding Process Understanding

    NASA Astrophysics Data System (ADS)

    Alley, R. B.; Parizek, B. R.; Anandakrishnan, S.; Applegate, P. J.; Christianson, K. A.; Dixon, T. H.; Holland, D. M.; Holschuh, N.; Keller, K.; Koellner, S. J.; Lampkin, D. J.; Muto, A.; Nicholas, R.; Stevens, N. T.; Voytenko, D.; Walker, R. T.

    2015-12-01

    Extensive modeling informed by the growing body of observational data yields important insights to the controlling processes operating across a range of spatiotemporal scales that have influenced the dynamic variability of the Greenland ice sheet. Pressurized basal lubrication enhances ice flow. This lubricating water is largely produced by basal and/or surface melt. For the North East Greenland Ice Stream, elevated geothermal heat flux (GHF) near its onset helps initiate the streaming flow. We suggest that the elevated GHF is likely caused by melt production and migration due to cyclical loading of the lithosphere over glacial timescales. On sub-seasonal timescales, surface meltwater production and transmission to the subglacial environment can enhance flow for pressurized, distributed hydraulic systems and diminish regional sliding for lower-pressure, channelized systems. However, in a warming climate, this lubricating source occurs across an expanding ablation zone, possibly softening shear margins and triggering basal sliding over previously frozen areas. Yet, the existence of active englacial conduits can lead to a plumbing network that helps preserve ice tongues and limit the loss of important buttressing of outlet glacier flow. Ocean forcing has been implicated in the variability of outlet glacier speeds around the periphery of Greenland. The extent and timescale over which those marginal changes influence inland flow depends on the basal rheology that, on a local scale, also influences the concentration of englacial stresses. Detailed observations of a calving event on Helheim Glacier have helped constrain diagnostic simulations of the pre- and post-calving stress states conducted in hopes of informing improved calving relationships. Furthermore, warm-water-mass variability within Irminger/Atlantic Waters off Greenland may play an important role in the monthly modulation of outlet glacier flow speeds, as has been observed for an ice stream draining into

  8. Amino acids and hydrocarbons approximately 3,800-Myr old in the Isua rocks, southwestern Greenland

    NASA Technical Reports Server (NTRS)

    Nagy, B.; Engel, M. H.; Zumberge, J. E.; Ogino, H.; Chang, S. Y.

    1981-01-01

    Results of an analysis of amino acids and hydrocarbons found in the Isua banded iron formation, which contains the oldest known rocks on earth, are discussed. Similarities are pointed out between the relative amino acid abundances of the Isua rocks and those of lichens found on their surfaces, and a lack of substantial racemization indicated by the low D/L ratios in the 3800-million year old rock samples is noted. Experimental results showing the possibility of amino acid diffusion from lichens into the rocks are presented. Comparisons of the Isua rock amino acid D/L ratios with those reported for samples from other regions indicates that none of the Isua amino acids are older than a few tens of thousands to a few hundred thousand years. Analyses of the saturated hydrocarbons of the Isua samples reveals no odd carbon number preference, which may indicate antiquity, however laboratory experiments have shown that amino acids and aromatic and saturated aliphatic hydrocarbons could not have survived the metamorphic history of the Isua rocks. The evidence presented thus suggests that the amino acids and hydrocarbons found are not of the age of the sediments.

  9. Oceanic transport of surface meltwater from the southern Greenland ice sheet

    NASA Astrophysics Data System (ADS)

    Luo, Hao; Castelao, Renato M.; Rennermalm, Asa K.; Tedesco, Marco; Bracco, Annalisa; Yager, Patricia L.; Mote, Thomas L.

    2016-07-01

    The Greenland ice sheet has undergone accelerating mass losses during recent decades. Freshwater runoff from ice melt can influence fjord circulation and dynamics and the delivery of bioavailable micronutrients to the ocean. It can also have climate implications, because stratification in the adjacent Labrador Sea may influence deep convection and the strength of the Atlantic meridional overturning circulation. Yet, the fate of the meltwater in the ocean remains unclear. Here, we use a high-resolution ocean model to show that only 1-15% of the surface meltwater runoff originating from southwest Greenland is transported westwards. In contrast, up to 50-60% of the meltwater runoff originating from southeast Greenland is transported westwards into the northern Labrador Sea, leading to significant salinity and stratification anomalies far from the coast. Doubling meltwater runoff, as predicted in future climate scenarios, results in a more-than-double increase in anomalies offshore that persists further into the winter. Interannual variability in offshore export of meltwater is tightly related to variability in wind forcing. The new insight that meltwaters originating from the west and east coasts have different fates indicates that future changes in mass loss rates and surface runoff will probably impact the ocean differently, depending on their Greenland origins.

  10. Oceanic Transport of Surface Meltwater from the Southern Greenland Ice Sheet

    NASA Technical Reports Server (NTRS)

    Luo, Hao; Castelao, Renato M.; Rennermalm, Asa K.; Tedesco, Marco; Bracco, Annalisa; Yager, Patricia L.; Mote, Thomas L.

    2016-01-01

    The Greenland ice sheet has undergone accelerating mass losses during recent decades. Freshwater runoff from ice melt can influence fjord circulation and dynamic1 and the delivery of bioavailable micronutrients to the ocean. It can also have climate implications, because stratification in the adjacent Labrador Sea may influence deep convection and the strength of the Atlantic meridional overturning circulation. Yet, the fate of the meltwater in the ocean remains unclear. Here, we use a high-resolution ocean model to show that only 1-15% of the surface meltwater runoff originating from southwest Greenland is transported westwards. In contrast, up to 50-60% of the meltwater runoff originating from southeast Greenland is transported westwards into the northern Labrador Sea, leading to significant salinity and stratification anomalies far from the coast. Doubling meltwater runoff, as predicted in future climate scenarios, results in a more-than-double increase in anomalies offshore that persists further into the winter. Interannual variability in offshore export of meltwater is tightly related to variability in wind forcing. The new insight that meltwaters originating from the west and east coasts have different fates indicates that future changes in mass loss rates and surface runoff will probably impact the ocean differently, depending on their Greenland origins.

  11. Earthshots: Satellite images of environmental change – Petermann Glacier, Greenland

    USGS Publications Warehouse

    Adamson, Thomas

    2016-01-01

    This calving is normal, but it’s worth watching Petermann and other Greenland glaciers closely. Petermann is one of the major marine-terminating glaciers of Greenland. Ice loss from the Greenland Ice Sheet has increased recently. An article in Nature concluded that climate change may cause Petermann and other Greenland glaciers to contribute to sea level rise. Landsat helps glaciologists keep a close eye on this remote but significant glacier.

  12. Clouds enhance Greenland ice sheet meltwater runoff.

    PubMed

    Van Tricht, K; Lhermitte, S; Lenaerts, J T M; Gorodetskaya, I V; L'Ecuyer, T S; Noël, B; van den Broeke, M R; Turner, D D; van Lipzig, N P M

    2016-01-12

    The Greenland ice sheet has become one of the main contributors to global sea level rise, predominantly through increased meltwater runoff. The main drivers of Greenland ice sheet runoff, however, remain poorly understood. Here we show that clouds enhance meltwater runoff by about one-third relative to clear skies, using a unique combination of active satellite observations, climate model data and snow model simulations. This impact results from a cloud radiative effect of 29.5 (±5.2) W m(-2). Contrary to conventional wisdom, however, the Greenland ice sheet responds to this energy through a new pathway by which clouds reduce meltwater refreezing as opposed to increasing surface melt directly, thereby accelerating bare-ice exposure and enhancing meltwater runoff. The high sensitivity of the Greenland ice sheet to both ice-only and liquid-bearing clouds highlights the need for accurate cloud representations in climate models, to better predict future contributions of the Greenland ice sheet to global sea level rise.

  13. Clouds enhance Greenland ice sheet meltwater runoff

    PubMed Central

    Van Tricht, K.; Lhermitte, S.; Lenaerts, J. T. M.; Gorodetskaya, I. V.; L'Ecuyer, T. S.; Noël, B.; van den Broeke, M. R.; Turner, D. D.; van Lipzig, N. P. M.

    2016-01-01

    The Greenland ice sheet has become one of the main contributors to global sea level rise, predominantly through increased meltwater runoff. The main drivers of Greenland ice sheet runoff, however, remain poorly understood. Here we show that clouds enhance meltwater runoff by about one-third relative to clear skies, using a unique combination of active satellite observations, climate model data and snow model simulations. This impact results from a cloud radiative effect of 29.5 (±5.2) W m−2. Contrary to conventional wisdom, however, the Greenland ice sheet responds to this energy through a new pathway by which clouds reduce meltwater refreezing as opposed to increasing surface melt directly, thereby accelerating bare-ice exposure and enhancing meltwater runoff. The high sensitivity of the Greenland ice sheet to both ice-only and liquid-bearing clouds highlights the need for accurate cloud representations in climate models, to better predict future contributions of the Greenland ice sheet to global sea level rise. PMID:26756470

  14. Clouds enhance Greenland ice sheet meltwater runoff

    NASA Astrophysics Data System (ADS)

    Van Tricht, Kristof; Lhermitte, Stef; Lenaerts, Jan T. M.; Gorodetskaya, Irina V.; L'Ecuyer, Tristan S.; Noël, Brice; van den Broeke, Michiel R.; Turner, David D.; van Lipzig, Nicole P. M.

    2016-04-01

    The Greenland ice sheet has become one of the main contributors to global sea level rise, predominantly through increased meltwater runoff. The main drivers of Greenland ice sheet runoff, however, remain poorly understood. Here we show that clouds enhance meltwater runoff by about one-third relative to clear skies, using a unique combination of active satellite observations, climate model data and snow model simulations. This impact results from a cloud radiative effect of 29.5 (±5.2) W m-2. Contrary to conventional wisdom, however, the Greenland ice sheet responds to this energy through a new pathway by which clouds reduce meltwater refreezing as opposed to increasing surface melt directly, thereby accelerating bare-ice exposure and enhancing meltwater runoff. The high sensitivity of the Greenland ice sheet to both ice-only and liquid-bearing clouds highlights the need for accurate cloud representations in climate models, to better predict future contributions of the Greenland ice sheet to global sea level rise.

  15. Evidence for a (15)N positive excursion in terrestrial foodwebs at the Middle to Upper Palaeolithic transition in south-western France: Implications for early modern human palaeodiet and palaeoenvironment.

    PubMed

    Bocherens, Hervé; Drucker, Dorothée G; Madelaine, Stéphane

    2014-04-01

    The Middle to Upper Palaeolithic transition around 35,000 years ago coincides with the replacement of Neanderthals by anatomically modern humans in Europe. Several hypotheses have been suggested to explain this replacement, one of them being the ability of anatomically modern humans to broaden their dietary spectrum beyond the large ungulate prey that Neanderthals consumed exclusively. This scenario is notably based on higher nitrogen-15 amounts in early Upper Palaeolithic anatomically modern human bone collagen compared with late Neanderthals. In this paper, we document a clear increase of nitrogen-15 in bone collagen of terrestrial herbivores during the early Aurignacian associated with anatomically modern humans compared with the stratigraphically older Châtelperronian and late Mousterian fauna associated with Neanderthals. Carnivores such as wolves also exhibit a significant increase in nitrogen-15, which is similar to that documented for early anatomically modern humans compared with Neanderthals in Europe. A shift in nitrogen-15 at the base of the terrestrial foodweb is responsible for such a pattern, with a preserved foodweb structure before and after the Middle to Upper Palaeolithic transition in south-western France. Such an isotopic shift in the terrestrial ecosystem may be due to an increase in aridity during the time of deposition of the early Aurignacian layers. If it occurred across Europe, such a shift in nitrogen-15 in terrestrial foodwebs would be enough to explain the observed isotopic trend between late Neanderthals and early anatomically modern humans, without any significant change in the diet composition at the Middle to Upper Palaeolithic transition.

  16. Sediment fluxes and delta evolution at Tuapaat, Disko Island, Greenland

    NASA Astrophysics Data System (ADS)

    Kroon, A.; Andersen, T. J.; Bendixen, M.

    2013-12-01

    Ice and snow and freezing temperatures have an important influence on the coastal morphodynamics in arctic polar coastal environments. Global climate changes induce many changes along the arctic coasts. Sea-levels are rising due to thermal expansion and due to an increased fresh water flux from the glaciers and land ice masses while ice coverage of the coastal waters decreases and the open water periods in summer extend. On a yearly basis, there is a strong variation over the seasons with open waters and active rivers in summer and ice-covered coastal waters and inactive rivers in winter. The coastal processes by waves and tides are thus often limited to the summer and early fall. On a daily basis, there is also a strong variation in fluvial discharges due to the daily variations in glacier melt with maximum melt in the afternoon and minimum values at night. At the same time, the actual flux of the river to the coastal bay is also influenced by the tidal phase: low tides in the afternoon will probably give the maximum plumes in the coastal waters and high tides in the early morning will reduce the input of sediments to the coastal waters to zero. The southern shore of Disko Island in western Greenland has four deltas: Igpik, Signiffik, Tuappat and Skansen. The sediments of these deltas are a mixture of sand and gravel and they are fed by melting glaciers. The Tuapaat delta is located at the end of a pro-glacial and fluvial valley at about 16 km from the glacier. The shores of the delta are reworked by waves, predominantly from southwestern (largest fetch, over 50 km), southern, and southeastern directions. The environment has a micro- to meso- tidal range with a spring tidal range of 2.7m. The morphologic changes on the delta over the last decades clearly showed an eastward migration of the main delta channel, probably due to wave-driven alongshore processes in the ice-free periods. In this presentation, we focus on quantification of sediment fluxes on the Tuapaat

  17. Airborne Laser Mapping of Greenland

    SciTech Connect

    Krabill, W.B.; Thomas, R.H.; Martin, C.F.; Sonntag, J.G.

    1996-10-01

    The Polar ice sheets contain enough water to raise Earth`s sea level by some 70 m. It is not clear whether changes in these ice sheets are contributing to the current rise. Ice sheet mass balance estimates can be obtained by monitoring the topography of selected Polar regions. The Arctic Ice Mapping (AIM) Project is a continuing program designed to provide a record of the absolute height of representative Arctic ice sheets. Using the Global Positioning System (GPS), aircraft flight lines may be duplicated with sufficient tolerance to provide repeated laser elevation measurements from one year to another. The raw GPS measurements are re-processed post-mission to provide sub-10 cm trajectories for each aircraft flight. This program began in 1991 with a proof-of-concept mission to Greenland. The data from this mission demonstrates 20 cm repeatability, principally due to the limited GPS constellation available. Refinements in all phases of the program (software, law and GPS hardware, and a complete GPS constellation) have yielded 10 cm repeatability in data from subsequent years, which includes probable geophysical change in the surface due to storm events and wind drift. 5 refs., 5 figs., 2 tabs.

  18. Radar measurements of melt zones on the Greenland Ice Sheet

    NASA Technical Reports Server (NTRS)

    Jezek, Kenneth C.; Gogineni, Prasad; Shanableh, M.

    1994-01-01

    Surface-based microwave radar measurements were performed at a location on the western flank of the Greenland Ice Sheet. Here, firn metamorphasis is dominated by seasonal melt, which leads to marked contrasts in the vertical structure of winter and summer firn. This snow regime is also one of the brightest radar targets on Earth with an average backscatter coefficient of 0 dB at 5.3 GHz and an incidence angle of 25 deg. By combining detailed observations of firn physical properties with ranging radar measurements we find that the glaciological mechanism associated with this strong electromagnetic response is summer ice lens formation within the previous winter's snow pack. This observation has important implications for monitoring and understanding changes in ice sheet volume using spaceborne microwave sensors.

  19. Skerrylike mirages and the discovery of greenland.

    PubMed

    Lehn, W H

    2000-07-20

    The Norse discovery of Greenland is associated with the sighting of low barren islands called Gunnbjörn's Skerries, which have never been satisfactorily identified. Here the historical references that connect the skerries to Greenland are reviewed. A mirage of the Greenland coast, arising specifically from optical ducting under a sharp temperature inversion, is used to explain the vision of skerries seen by the Norse mariners. Images from both ducting and uniform inversions are calculated. Under the assumption of a clean Rayleigh atmosphere, sufficient visibility remains to see the skerry image at a distance of 220 km. There is significant circumstantial evidence to indicate that the Norse were familiar with the skerrylike mirage and that they used it to discover new lands.

  20. 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.

  1. Fatal outbreak of botulism in Greenland.

    PubMed

    Hammer, Tóra Hedinsdottir; Jespersen, Sanne; Kanstrup, Jakob; Ballegaard, Vibe Cecilie; Kjerulf, Anne; Gelvan, Allan

    2015-03-01

    Botulism commonly occurs when the anaerobic, gram-positive bacterium Clostridium botulinum, under suitable conditions, produces botulinum neurotoxins. Named A-F, these toxins are the immediate causative agent of the clinical symptoms of symmetrical, descending neurological deficits, including respiratory muscle paralysis. We present five cases of foodborne botulism occurring in Greenland, two with fatal outcome, caused by ingestion of tradionally preserved eider fowl. In the cases of the survivors, antitoxin and supportive care, including mechanical ventilation, were administered. In these cases recovery was complete. Microbiological assays, including toxin neutralization bioassay, demonstrated the presence of neurotoxin E in two survivors. The third survivor was shown by PCR to have the BoNT type E gene in faeces. This is the first report of cases of fatal botulism in Greenland. It underscores the importance of prompt coordinated case management effort in a geographically isolated area such as Greenland.

  2. Late Pliocene deglaciation of Southern Greenland

    NASA Astrophysics Data System (ADS)

    Walczak, M. H.; Carlson, A. E.; Stoner, J. S.; Hatfield, R. G.; Wolhowe, M. D.; Mathias, A.

    2015-12-01

    Predicting the response of the remaining Antarctic and Greenland ice sheets to increasing atmospheric greenhouse gas concentrations is an important goal of climate science. The late Pliocene (3.3-3.0 Ma; formerly the middle Pliocene) may offer a natural quasi-analogue to climate in the upcoming centuries: CO2 levels were ~400 PPM, global surface temperatures were 2-3 degrees higher, and sea level was likely at least 6 m higher than today. Yet little is currently known about the history of the pre-Quaternary Greenland ice sheet. IODP Expedition 303 site U1307 at 2575 m depth on the Eirik Ridge extends back to 3.4 Ma, capturing the late-Pliocene warm period adjacent to the southern Greenland ice sheet. Ice-rafted debris records, interpreted on a paleomagnetic reversal age model, suggest roughly 40 ka cyclicity of between ~5% and ~40% sand. Between ~3.3 and 3.2 Ma there is a significant change in lithology characterized by an abrupt reduction in magnetic susceptibility, during which time the sand fraction remains below 10%. Assuming a magnetite mineralogy, hysteresis ratios support a much finer magnetic assemblage of unique provenance in this interval; Mrs/Ms values of the silt fraction range from ~0.2-0.25, compared to ~0.1 in the sediments above and below. The origin this material will be discussed, although this observation is unambiguously consistent with the disappearance of silt transported from the southern Greenland ice sheet. The lack of Greenlandic source material observed in this interval is unique in the last 3.4 Ma at this location, and may indicate full deglaciation of southern Greenland in the late Pliocene.

  3. Towards Greenland Glaciation: cumulative or abrupt transition?

    NASA Astrophysics Data System (ADS)

    Tan, Ning; Dumas, Christophe; Ladant, Jean-Baptiste; Ramstein, Gilles; Contoux, Camille

    2016-04-01

    During the mid-Pliocene warming period (3-3.3 Ma BP), global annual mean temperature is warmer by 2-3 degree than pre-industrial. Greenland ice sheet volume is supposed to be a 50% reduction compared to nowadays [Haywood et al. 2010]. Around 2.7-2.6 Ma BP, just ~ 500 kyr after the warming peak of mid-Pliocene, there is already full Greenland Glaciation [Lunt et al. 2008]. How does Greenland ice sheet evolve from a half size to a glaciation level during 3 Ma - 2.5 Ma? Data show that there is a decreasing trend of atmospheric CO2 concentration from 3 Ma to 2.5 Ma [Seki et al.2010; Bartoli et al. 2011; Martinez et al. 2015]. However, a recent study [Contoux et al. 2015] suggests that a lowering of CO2 is not sufficient to initiate a perennial glaciation on Greenland and must be combined to low summer insolation, to preserve the ice sheet during insolation maximum, suggesting a cumulative process. In order to diagnose whether the ice sheet build-up is an abrupt event or a cumulative process, we carry on, for the first time, a transient simulation of climate and ice sheet evolutions from 3 Ma to 2.5 Ma. This strategy enables to investigate waxing and waning of the ice sheet during several orbital cycles. To reach this goal, we use a tri-dimensional interpolation method designed by Ladant et al. (2014) which combines the evolution of CO2 concentration, orbital parameters and Greenland ice sheet sizes in an off-line way by interpolating snapshots simulations. Thanks to this new method, we can build a transient like simulation through asynchronous coupling between GCM and ice sheet model. With this method, we may consistently answer the question of the build-up of Greenland: abrupt or cumulative process.

  4. Quaternary vertebrates from Greenland: A review

    NASA Astrophysics Data System (ADS)

    Bennike, Ole

    Remains of fishes, birds and mammals are rarely reported from Quaternary deposits in Greenland. The oldest remains come from Late Pliocene and Early Pleistocene deposits and comprise Atlantic cod, hare, rabbit and ringed seal. Interglacial and interstadial deposits have yielded remains of cod, little auk, collared lemming, ringed seal, reindeer and bowhead whale. Early and Mid-Holocene finds include capelin, polar cod, red fish, sculpin, three-spined stickleback, Lapland longspur, Arctic hare, collared lemming, wolf, walrus, ringed seal, reindeer and bowhead whale. It is considered unlikely that vertebrates could survive in Greenland during the peak of the last glaciation, but many species had probably already immigrated in the Early Holocene.

  5. Alkenone and Isotopic Records of Holocene Climatic and Environmental Change From Laminated West Greenland Lakes

    NASA Astrophysics Data System (ADS)

    D'Andrea, W. J.; Huang, Y.

    2004-12-01

    Long chain alkenones (LCAs) are a key class of biomarkers for paleotemperature reconstructions. These compounds are ubiquitous in ocean sediments, but rare in lake sediments. Here we report the first discovery of LCAs in a downcore profile and surface sediments of five Greenland lakes. The concentrations of LCAs in surface sediments of these lakes are one to two orders of magnitude higher than those reported previously in other lake surface sediments around the world. Alkenones are present in five Greenland lakes with elevated salinity, but absent from five freshwater lakes. The alkenones have exceptionally low \\delta13C values ranging from -40 to -43\\permil, and are depleted by 10 to 15\\permil relative to short-chain fatty acids and sterols within the same samples. These \\delta13C values are the lowest ever reported for alkenones in a natural setting and have important implications for tracing the alkenone producers in lakes. Using the published calibration for lake sediments, the alkenone unsaturation indices in the surface sediments of the Greenland lakes record late spring/early summer temperature when algal blooms occur, suggesting the applicability of lacustrine alkenones as a paleotemperature proxy. LCA unsaturation indices and \\deltaD from sediment cores taken from these Greenland lakes will help elucidate the environmental controls on these sedimentary parameters, and will aid the reconstruction of Holocene climate variability in West Greenland. Ongoing work on the saline lakes includes determining high resolution alkenone unsaturation ratios/abundances and bulk/compound-specific isotopic values from sediment cores, algal culturing, and establishing microbial community structure in the saline lakes using DNA/RNA fingerprinting. Up-to-date results will be presented in the meeting.

  6. The fate of the Greenland Ice Sheet in a geoengineered, high CO2 world

    NASA Astrophysics Data System (ADS)

    Irvine, Peter J.; Lunt, Daniel J.; Stone, Emma J.; Ridgwell, Andy

    2009-10-01

    Solar radiation management (SRM) geoengineering has been proposed as one means of helping avoid the occurrence of dangerous climate change and undesirable state transitions ('tipping points') in the Earth system. The irreversible melting of the Greenland Ice Sheet is a case in point—a state transition that could occur as a result of CO2-driven elevated global temperatures, and one leading to potentially catastrophic sea-level rise. SRM schemes such as the creation of a 'sunshade' or injection of sulfate aerosols into the stratosphere could reduce incoming solar radiation, and in theory balance, in a global mean, the greenhouse warming resulting from elevated concentrations of CO2 in the atmosphere. Previous work has highlighted that a geoengineered world would have: warming towards the poles, cooling in the tropics, and a reduction in the global hydrological cycle, which may have important implications for the Greenland Ice Sheet. Using a fully coupled global climate model in conjunction with an ice sheet model, we assess the consequences for the mass balance of the Greenland Ice Sheet of the reorganization of climate patterns by the combination of high CO2 and geoengineering. We find that Greenland surface temperature and precipitation anomalies, compared to the pre-industrial situation, decrease almost linearly with increasing levels of SRM geoengineering, but that these combine to create a highly non-linear response of the ice sheet. The substantial melting of the Greenland Ice Sheet predicted for four times pre-industrial CO2 levels is prevented in our model with only a partial application of SRM, and hence without having to fully restore the global average temperature back to pre-industrial levels. This suggests that the degree of SRM geoengineering required to mitigate the worst impacts of greenhouse warming, such as sea-level rise, need not be as extensive as generally assumed.

  7. Geochemical and geochronological characteristics of Late Cretaceous to Early Paleocene granitoids in the Tengchong Block, Southwestern China: Implications for crustal anatexis and thickness variations along the eastern Neo-Tethys subduction zone

    NASA Astrophysics Data System (ADS)

    Zhao, Shao-wei; Lai, Shao-cong; Qin, Jiang-feng; Zhu, Ren-Zhi; Wang, Jiang-bo

    2017-01-01

    The Tengchong Block of Southwestern China is key to tracing the eastward subduction of Neo-Tethys and collision between Indian and Asian continents. The block contains a magmatic belt that represents the southeastward continuation of the Gangdese belt, produced by the eastward subduction of eastern Neo-Tethyan oceanic lithosphere. In this paper we present geochemical and geochronological data of Late Cretaceous to Early Paleocene ( 64 Ma) granitic rocks of the Guyong and Husa batholiths in the Tengchong Block. These can be subdivided into high-silica peraluminous granites and low-silica metaluminous granodiorites, and all belong to the high-K calc-alkaline series, are enriched in LILE, and depleted in HFSE. The Guyong granitoids have high initial Sr ratios of 0.706511-0.711753, negative εNd(t) values of - 9.2 to - 11.6, two-stage model ages of 1.39-1.55 Ga, and Pb isotopic compositions that indicate a crustal affinity. The Husa granodiorites also have high initial Sr ratios of 0.716496, negative εNd(t) value of - 16.5, two-stage model age of 1.89 Ga, variable εHf(t) values of 3.4 to - 18.1 and Pb isotopic compositions similar to lower crustal values. These geochemical and isotopic data indicate that the Guyong granitoids were likely derived from partial melting of ancient crustal metapelite or mixed pelite-greywacke sources, while the Husa granodiorites were derived from the partial melting of lower crustal mixed sources involving metasedimentary and metaigneous rocks. To understand the thermal state and architecture of the Late Cretaceous to Early Paleocene magmatic arc crust, the crust-derived intermediate to acidic igneous rocks of the southern-central Lhasa and Tengchong blocks and eastern Himalayan syntaxis are compared. We infer that partial melting of crust occurred at great depth in the southern Lhasa Block, intermediate depths in the eastern Himalayan syntaxis, and shallow depths in the central Lhasa and Tengchong Block. Sr/Y ratios indicate that the

  8. Southwestern Power Administration annual site environmental report CY 1997

    SciTech Connect

    1998-11-01

    This report provides a synopsis of Southwestern Power Administration`s (Southwestern`s) effectiveness in managing its operations in an environmentally responsible manner. In CY 1997, the Office of Environmental, Safety, and Health was reorganized and incorporated into the Division of Acquisition and Property. The Division of Acquisition, Property, and Environmental Management maintains responsibility for development, oversight, and implementation of environmental programs. Senior Management at Southwestern has taken actions to increase environmental awareness throughout the organization. During CY 1997, (Southwestern) was not involved in any known programs or activities that had adverse impacts on the environment. The 1997 Environmental Appraisal, a portion of Southwestern`s Self-Assessment and Appraisal Program, indicated approximately 90% compliance with Southwestern`s written environmental programs. Southwestern continued to function throughout CY 1997 in an operations and maintenance posture with minor substation projects.

  9. A Climatology of Atmospheric Rivers Potentially Impacting the Boundary Layer over Greenland: 1871-2012

    NASA Astrophysics Data System (ADS)

    Neff, William; Compo, Gilbert P.

    2016-04-01

    Recently, (Neff et al. 2014) examined the 2012 Greenland melt episode and compared it to the last episode in 1889 using the Twentieth Century Reanalysis (Compo et al. 2011), finding similar factors at work. A key factor in 2012 was the presence of an Atmospheric River (AR) that transported warm air from a mid-continent heat wave over the Atlantic Ocean and thence to the west coast of Greenland and then over the Greenland ice sheet (GIS) with a confirming water vapor isotopic signature (Bonne et al. 2015). ARs are thin filaments of high-moisture air occurring at frontal boundaries and represent an efficient poleward transport mechanism for warm moist air (Newell et al. 1992) to the Arctic (Bonne et al. 2015; Neff et al. 2014) and the Antarctic (Gorodetskaya et al. 2014). Some common characteristics of the events in 1889 and 2012, in addition to the expression of poleward transport as an AR, included continental heat anomalies in the trajectory source regions as well as a trough-ridge pattern that focused transport along the west coast of Greenland. The latter consisted of a trough of low-pressure situated to the west, generally over Baffin Island, and a high-pressure ridge to the southeast of Greenland. This type trough-ridge pattern was also implicated in a major rain event in 2011 along the western margin of the Greenland ice sheet in late summer that accelerated the flow of ice into the ocean (Doyle et al. 2015). Although the events of 2012 and 1889 were extreme, the question remains of how frequent are the near-misses of ARs that are likely to have affected lower elevations and/or included increases in moisture over the GIS that would have modified the boundary layer over the high elevations of the GIS. In this presentation we will show an example of the boundary layer modification lifecycle during the 2012 event and then the climatology of events that reveal an increase in such AR events along the west coast of Greenland over the last three decades.

  10. First Younger Dryas moraines in Greenland

    NASA Astrophysics Data System (ADS)

    Funder, Svend; Larsen, Nicolaj K.; Linge, Henriette; Möller, Per; Schomacker, Anders; Fabel, Derek; Kjær, Kurt H.; Xu, Sheng

    2016-04-01

    Over the Greenland ice sheet the Younger Dryas (YD) cold climate oscillation (12.9-11.7 kaBP) began with up to 10°C drop in temperatures and ended with up to 12°C abrupt warming. In the light of the present warming and melting of the ice sheet, and its importance for future climate change, the ice sheet's response to these dramatic changes in the past is of great interest. However, even though much effort has gone into charting YD ice margin behaviour around Greenland in recent years, no clear-cut signal of response to the oscillation has been uncovered. Here we show evidence to suggest that three major outlets from a local ice cap at Greenland's north coast advanced and retreated synchronously during YD. The evidence comprises OSL (optically stimulated luminescence) dates from a marine transgression of the coastal valleys that preceded the advance, and exposure ages from boulders on the moraines, formed by glaciers that overrode the marine sediment. The OSL ages suggest a maximum age of 12.4 ±0.6 kaBP for the marine incursion, and 10 exposure ages on boulders from the three moraines provide an average minimum age of 12.5 ±0.7 kaBP for the moraines, implying that the moraines were formed within the interval 11.8-13.0 kaBP. Elsewhere in Greenland evidence for readvance has been recorded in two areas. Most notably, in the East Greenland fjord zone outlet glaciers over a stretch of 800 km coast advanced through the fjords. In Scoresby Sund, where the moraines form a wide belt, an extensive 14C and exposure dating programme has shown that the readvance here probably culminated before YD, while cessation of moraine formation and rapid retreat from the moraine belt did not commence until c. 11.5 kaBP, but no moraines have so far been dated to YD. Readvance is also seen in Disko Bugt, the largest ice sheet outlet in West Greenland. However, here the advance and retreat of the ice stream took place in mid YD times, and lasted only a few hundred years, while YD in

  11. Characterization of household waste in Greenland

    SciTech Connect

    Eisted, Rasmus; Christensen, Thomas H.

    2011-07-15

    The composition of household waste in Greenland was investigated for the first time. About 2 tonnes of household waste was sampled as every 7th bag collected during 1 week along the scheduled collection routes in Sisimiut, the second largest town in Greenland with about 5400 inhabitants. The collection bags were sorted manually into 10 material fractions. The household waste composition consisted primarily of biowaste (43%) and the combustible fraction (30%), including anything combustible that did not belong to other clean fractions as paper, cardboard and plastic. Paper (8%) (dominated by magazine type paper) and glass (7%) were other important material fractions of the household waste. The remaining approximately 10% constituted of steel (1.5%), aluminum (0.5%), plastic (2.4%), wood (1.0%), non-combustible waste (1.8%) and household hazardous waste (1.2%). The high content of biowaste and the low content of paper make Greenlandic waste much different from Danish household waste. The moisture content, calorific value and chemical composition (55 elements, of which 22 were below detection limits) were determined for each material fraction. These characteristics were similar to what has been found for material fractions in Danish household waste. The chemical composition and the calorific value of the plastic fraction revealed that this fraction was not clean but contained a lot of biowaste. The established waste composition is useful in assessing alternative waste management schemes for household waste in Greenland.

  12. Characterization of household waste in Greenland.

    PubMed

    Eisted, Rasmus; Christensen, Thomas H

    2011-07-01

    The composition of household waste in Greenland was investigated for the first time. About 2tonnes of household waste was sampled as every 7th bag collected during 1 week along the scheduled collection routes in Sisimiut, the second largest town in Greenland with about 5400 inhabitants. The collection bags were sorted manually into 10 material fractions. The household waste composition consisted primarily of biowaste (43%) and the combustible fraction (30%), including anything combustible that did not belong to other clean fractions as paper, cardboard and plastic. Paper (8%) (dominated by magazine type paper) and glass (7%) were other important material fractions of the household waste. The remaining approximately 10% constituted of steel (1.5%), aluminum (0.5%), plastic (2.4%), wood (1.0%), non-combustible waste (1.8%) and household hazardous waste (1.2%). The high content of biowaste and the low content of paper make Greenlandic waste much different from Danish household waste. The moisture content, calorific value and chemical composition (55 elements, of which 22 were below detection limits) were determined for each material fraction. These characteristics were similar to what has been found for material fractions in Danish household waste. The chemical composition and the calorific value of the plastic fraction revealed that this fraction was not clean but contained a lot of biowaste. The established waste composition is useful in assessing alternative waste management schemes for household waste in Greenland.

  13. Greenland's pronounced glacier retreat not irreversible

    NASA Astrophysics Data System (ADS)

    Schultz, Colin

    2012-02-01

    In recent decades, the combined forces of climate warming and short-term variability have forced the massive glaciers that blanket Greenland into retreat, with some scientists worrying that deglaciation could become irreversible. The short history of detailed glacier observations, however, makes pinning the ice loss to either short-term dynamics or long-term change difficult. Research by Young et al. detailing the effects of two bouts of sudden and temporary cooling during an otherwise warm phase in Greenland's climate history could help answer that question by showing just how heavy a hand short-term variability can have in dictating glacier dynamics. Along the western edge of Greenland the massive Jakobshavn Isbræ glacier reaches out to the coast, its outflow dropping icebergs into Baffin Bay during the summer months. Flanking the glacier's tongue are the Tasiussaq and Marrait moraines—piles of rock marking the glacier's former extent. Researchers suspected the moraines were tied to two periods of abrupt cooling that hit Greenland 9300 and 8200 years ago, and that association was reinforced by the authors' radiocarbon and beryllium isotope analyses of the area surrounding the moraines. Beryllium-10 forms when cosmic radiation travels through the atmosphere and strikes the Earth's surface, with surface rock concentrations indicating how long it has been ice-free.

  14. Climate science: The history of Greenland's ice

    NASA Astrophysics Data System (ADS)

    Blard, Pierre-Henri; Leduc, Guillaume; Glasser, Neil

    2016-12-01

    Global sea levels would rise by several metres if the Greenland Ice Sheet melted completely. Two studies have examined its past behaviour in an effort to evaluate its vulnerability in a warming world -- and have come to seemingly conflicting conclusions. Two geochemists and a glaciologist discuss the issues. See Letters p.252 & p.256

  15. The multifaceted West Greenland passive margin

    NASA Astrophysics Data System (ADS)

    Breuer, Sonja; Damm, Volkmar; Block, Martin; Schreckenberger, Bernd; Heyde, Ingo; Nelson, Catherine; Kouwe, Wim

    2013-04-01

    The Baffin Bay located between Greenland and Canada, is the northward extension of the Labrador Sea. The Davis Strait High separates these two marine basins. The evolution of these basins is closely linked, and is as well affiliated to the opening of the North Atlantic Ocean. The opening history started in the Cretaceous with the formation of several terrestrial rift basins with a block-faulted, metamorphic Precambrian basement. The further opening of the Baffin Bay coincides with the volcanic activity (60.9-52.5 Ma) along the West Greenland margin (Storey et al., 1998). The subsequent seafloor spreading in the Baffin Bay is linked to the Labrador Sea by the Ungava Fault Zone (UFZ), which is the most prominent transform fault in this region. Two main problems are still unsolved: 1) There are clear indications for normal seafloor spreading in the Baffin Bay like the seaward dipping reflectors (SDRs) on the Canadian side (Skaarup et al., 2006) and on the Greenland side based on our data. On the other hand, associated magnetic spreading anomalies are not yet discovered in the Baffin Bay or are not formed. These findings may either point to slow or ultraslow spreading or underlying strongly extended continental crust and/or serpentinised mantle. 2) The Greenlandic margin is much wider than the Canadian. In addition, a breakup unconformity can only be traced on the Greenland side and is not reported for the Canadian side. Which process causes this asymmetric margin and differences in shelf width? Is it a result of asymmetric spreading or connected to volcanic activity during breakup processes? In summer 2008, a marine geoscientific expedition (MSM09/03) was conducted with the research vessel "Maria S. Merian" in the Davis Strait and southern Baffin Bay. Approximately 1800 km of multichannel reflection seismic data were acquired. To supplement the database, a subsequent marine geoscientific expedition ARK-XXV/3 with RV POLARSTERN in summer 2010 was conducted. In our

  16. Southwestern Power Administration Annual Report 2011

    SciTech Connect

    2013-04-01

    Dear Secretary Chu: I am pleased to present the financial statements and operating data for Southwestern Power Administration (Southwestern) for Fiscal Year (FY) 2011. In FY 2011, Southwestern delivered over 4.1 billion kilowatt-hours of energy to its wholesale customers in Arkansas, Kansas, Louisiana, Missouri, Oklahoma, and Texas, generating $167 million in revenue. In fulfilling its mission to market and reliably deliver renewable Federal hydroelectric power, Southwestern maintains 1,380 miles of high-voltage transmission lines, substations, and communications sites, contributing to the reliability of the regional and National electric grid. Southwestern also actively partners with the Department of Energy, the U.S. Army Corps of Engineers, Southwestern’s customers, and other Federal power stakeholders to most effectively balance their diverse interests with Southwestern’s mission while continuing to maximize Federal assets to repay the Federal investment in the 24 hydropower facilities within Southwestern’s marketing region. Southwestern is proud of its past successes, and we look forward to continuing to serve the Nation’s energy needs in the future. Sincerely, Christopher M. Turner Administrator

  17. Southwestern Power Administration Annual Report 2012

    SciTech Connect

    2013-09-01

    Dear Secretary Moniz: I am pleased to present the financial statements and operating data for Southwestern Power Administration (Southwestern) for Fiscal Year (FY) 2012. In FY 2012, Southwestern delivered over 4.1 billion kilowatt-hours of energy to its wholesale customers in Arkansas, Kansas, Louisiana, Missouri, Oklahoma, and Texas, generating $195 million in revenue. In fulfilling its mission to market and reliably deliver renewable Federal hydroelectric power, Southwestern maintains 1,380 miles of high-voltage transmission lines, substations, and communications sites, contributing to the reliability of the regional and National electric grid. Southwestern also actively partners with the Department of Energy, the U.S. Army Corps of Engineers, Southwestern’s customers, and other Federal power stakeholders to most effectively balance their diverse interests with Southwestern’s mission while continuing to maximize Federal assets to repay the Federal investment in the 24 hydropower facilities within Southwestern’s marketing region. Southwestern is proud of its past successes, and we look forward to continuing to serve the Nation’s energy needs in the future. Sincerely, Christopher M. Turner Administrator

  18. Southwestern Power Administration Annual Report 2010

    SciTech Connect

    2012-09-01

    Dear Secretary Chu: I am pleased to present the financial statements and operating data for Southwestern Power Administration (Southwestern) for Fiscal Year (FY) 2010. In FY 2010, Southwestern delivered nearly 7.6 billion kilowatt-hours of energy to its wholesale customers in Arkansas, Kansas, Louisiana, Missouri, Texas, and Oklahoma, generating $189 million in revenue. In fulfilling its mission to market and reliably deliver renewable Federal hydroelectric power, Southwestern maintains 1,380 miles of high-voltage transmission lines, substations, and communications sites, contributing to the reliability of the regional and National electric grid. Southwestern also actively partners with the Department of Energy, the U.S. Army Corps of Engineers, Southwestern’s customers, and other Federal power stakeholders to most effectively balance their diverse interests with Southwestern’s mission while continuing to maximize Federal assets to repay the Federal investment in the 24 hydropower facilities within Southwestern’s marketing region. Southwestern is proud of its past successes, and we look forward to continuing to serve the Nation’s energy needs in the future. Sincerely, Christopher M. Turner Administrator

  19. What controls the isotopic composition of Greenland surface snow?

    NASA Astrophysics Data System (ADS)

    Steen-Larsen, H. C.; Masson-Delmotte, V.; Hirabayashi, M.; Winkler, R.; Satow, K.; Prié, F.; Bayou, N.; Brun, E.; Cuffey, K. M.; Dahl-Jensen, D.; Dumont, M.; Guillevic, M.; Kipfstuhl, S.; Landais, A.; Popp, T.; Risi, C.; Steffen, K.; Stenni, B.; Sveinbjörnsdottír, A. E.

    2014-02-01

    Water stable isotopes in Greenland ice core data provide key paleoclimatic information, and have been compared with precipitation isotopic composition simulated by isotopically enabled atmospheric models. However, post-depositional processes linked with snow metamorphism remain poorly documented. For this purpose, monitoring of the isotopic composition (δ18O, δD) of near-surface water vapor, precipitation and samples of the top (0.5 cm) snow surface has been conducted during two summers (2011-2012) at NEEM, NW Greenland. The samples also include a subset of 17O-excess measurements over 4 days, and the measurements span the 2012 Greenland heat wave. Our observations are consistent with calculations assuming isotopic equilibrium between surface snow and water vapor. We observe a strong correlation between near-surface vapor δ18O and air temperature (0.85 ± 0.11‰ °C-1 (R = 0.76) for 2012). The correlation with air temperature is not observed in precipitation data or surface snow data. Deuterium excess (d-excess) is strongly anti-correlated with δ18O with a stronger slope for vapor than for precipitation and snow surface data. During nine 1-5-day periods between precipitation events, our data demonstrate parallel changes of δ18O and d-excess in surface snow and near-surface vapor. The changes in δ18O of the vapor are similar or larger than those of the snow δ18O. It is estimated using the CROCUS snow model that 6 to 20% of the surface snow mass is exchanged with the atmosphere. In our data, the sign of surface snow isotopic changes is not related to the sign or magnitude of sublimation or deposition. Comparisons with atmospheric models show that day-to-day variations in near-surface vapor isotopic composition are driven by synoptic variations and changes in air mass trajectories and distillation histories. We suggest that, in between precipitation events, changes in the surface snow isotopic composition are driven by these changes in near-surface vapor

  20. What controls the isotopic composition of Greenland surface snow?

    NASA Astrophysics Data System (ADS)

    Steen-Larsen, H. C.; Masson-Delmotte, V.; Hirabayashi, M.; Winkler, R.; Satow, K.; Prié, F.; Bayou, N.; Brun, E.; Cuffey, K. M.; Dahl-Jensen, D.; Dumont, M.; Guillevic, M.; Kipfstuhl, J.; Landais, A.; Popp, T.; Risi, C.; Steffen, K.; Stenni, B.; Sveinbjörnsdottír, A.

    2013-10-01

    Water stable isotopes in Greenland ice core data provide key paleoclimatic information, and have been compared with precipitation isotopic composition simulated by isotopically-enabled atmospheric models. However, post-deposition processes linked with snow metamorphism remain poorly documented. For this purpose, a monitoring of the isotopic composition (δ18O, δD) of surface water vapor, precipitation and samples of top (0.5 cm) snow surface has been conducted during two summers (2011-2012) at NEEM, NW Greenland. The measurements also include a subset of 17O-excess measurements over 4 days, and the measurements span the 2012 Greenland heat wave. Our observations are consistent with calculations assuming isotopic equilibrium between surface snow and water vapor. We observe a strong correlation between surface vapor δ18O and air temperature (0.85 ± 0.11 ‰ °C-1 (R = 0.76) for 2012). The correlation with air temperature is not observed in precipitation data or surface snow data. Deuterium excess (d-excess) is strongly anti-correlated with δ18O with a stronger slope for vapor than for precipitation and snow surface data. During nine 1-5 days periods between precipitation events, our data demonstrate parallel changes of δ18O and d-excess in surface snow and surface vapor. The changes in δ18O of the vapor are similar or larger than those of the snow δ18O. It is estimated that 6 to 20% of the surface snow mass is exchanged with the atmosphere using the CROCUS snow model. In our data, the sign of surface snow isotopic changes is not related to the sign or magnitude of sublimation or condensation. Comparisons with atmospheric models show that day-to-day variations in surface vapor isotopic composition are driven by synoptic weather and changes in air mass trajectories and distillation histories. We suggest that, in-between precipitation events, changes in the surface snow isotopic composition are driven by these changes in surface vapor isotopic composition. This

  1. Ocean-Glacier Interactions in Alaska and Comparison to Greenland

    NASA Astrophysics Data System (ADS)

    Motyka, R. J.; Truffer, M.

    2011-12-01

    hydrographic data from Alaskan fjords to Greenland data and evaluate similarities and differences. Studies on Alaskan fjords have implications for understanding land ice - ocean interactions in Greenland as well as elsewhere in the world but much more needs to be learned on how these fjords operate.

  2. Did Dust From the 1930s US Dust Bowl Make it to Greenland?

    NASA Astrophysics Data System (ADS)

    Biscaye, P. E.; Bory, A. J.; Gill, T. E.; Steffensen, J.

    2005-12-01

    The "Dust Bowl" phenomenon during the 1930s in the southwestern United States generated huge amounts of airborne dust with northward and eastward transport of mineral aerosol. Amidst the normal (past 40,000 years) flux of dust from China and Mongolia to the Greenland ice cap, were there any "Dust Bowl" years during which North American dust made significant deposits, or were even detectable? Donarummo et al. (2003) reported a possible instance of Dust-Bowl dust during 1933 from the GISP2 ice core drilled at Summit in central Greenland. Did this occur elsewhere and/or in other years? At the NorthGRIP (75 N; 042 W) ice camp in 2001, we drilled four shallow firn cores (~ 1 m apart and 25.0 m deep) to the level of 1930 firn. We divided the cores into the four periods 1930-1945, 1945-1960, 1960-1980, and 1980-1990, and combined the appropriate intervals of all four cores in order to recover sufficient dust. If the southwestern U.S. dust were to be detected during the primary Dust-Bowl years (1930-1945 interval), we expected to see the signal return to pure East Asian characteristics over the course of the subsequent three periods. The four composite firn samples were melted, the dust extracted in the field by super-centrifugation, and returned to LDEO. Non-destructive XRD analyses for clay mineralogy preceded dissolution, chemical purification and analysis of radiogenic isotope composition (ENd(0) and 87Sr/86Sr) by Thermal Ionization Mass Spectrometry. The results of these analyses were compared to our samples of Chinese and Mongolian desert material, to samples of known Dust-Bowl dust, and to all the samples of ice-core and snow-pit dust from Greenland we had previously analyzed. These comparisons reveal no hint of compositional change from Asian- toward Dust-Bowl characteristics. We conclude that the single possible occurrence of Dust-Bowl dust in 1933 ice reported by Donarummo et al. (2003) did not at all characterize the entire Dust-Bowl era in Greenland. We have

  3. Did Dust From the 1930s US Dust Bowl Make it to Greenland?

    NASA Astrophysics Data System (ADS)

    Biscaye, P. E.; Bory, A. J.; Gill, T. E.; Steffensen, J.

    2004-12-01

    The "Dust Bowl" phenomenon during the 1930s in the southwestern United States generated huge amounts of airborne dust with eastward transport of mineral aerosol. Amidst the normal flux of dust from China and Mongolia to the Greenland ice cap, were there any "Dust Bowl" years during which North American dust made significant deposits, or were even detectable? Donarummo et al. (2003) reported a possible instance of Dust-Bowl dust during 1933 from the GISP2 ice core drilled at Summit in central Greenland. Did this occur elsewhere in other years? At the NorthGRIP (75 N; 042 W) ice camp in 2001, we drilled four shallow firn cores (~ 1 m apart and 25.0 m deep) to the level of 1930 firn. We divided the cores into the four periods 1930-1945, 1945-1960, 1960-1980, and 1980-1990, and combined the appropriate intervals of all four cores in order to recover sufficient dust. If the southwestern U.S. dust were to be detected during the primary Dust-Bowl years (1930-1945 interval), we expected to see the signal return to pure East Asian characteristics over the course of the subsequent three periods. The four composite firn samples were melted, the dust extracted in the field by super-centrifugation, and returned to LDEO. Non-destructive XRD analyses for clay mineralogy preceded dissolution, chemical purification and analysis of radiogenic isotope composition (ƒONd(0) and 87Sr/86Sr) by Thermal Ionization Mass Spectrometry. The results of these analyses were compared to our samples of Chinese and Mongolian desert material, to samples of known Dust-Bowl dust, and to all the samples of ice-core and snow-pit dust from Greenland we had previously analyzed. These comparisons reveal no hint of compositional change from Asian toward Dust-Bowl characteristics. We conclude that the single possible occurrence of Dust-Bowl dust in 1933 ice reported by Donarummo et al. (2003) did not at all characterize the entire Dust-Bowl era in Greenland. We have also previously shown that the

  4. Ice-Free Greenland during the Mid-Pleistocene

    NASA Astrophysics Data System (ADS)

    Schaefer, J. M.; Finkel, R. C.; Caffee, M. W.; Alley, R. B.; Balco, G.; Zimmerman, S. R. H.; Briner, J. P.; Young, N. E.; Schwartz, R.

    2015-12-01

    In the face of accelerated ice sheet contribution to sea level rise, in part fueled by rapid thinning and retreat of marine terminating outlet glaciers, it remains uncertain how the Greenland Ice Sheet (GrIS) will adjust to a warming Arctic, declining sea ice and related changing precipitation patterns. This is concerning, given that future sea level rise is strongly dependent on the GrIS's response to Arctic change. The scientific community is currently torn between a model of a dynamic GrIS that becomes greatly reduced during interglacials and a model where the GrIS is relatively stable, even through interglacials that were warmer than today. We review the paleo-stability of the GrIS and discuss the implications for GrIS predictions. Based on new cosmogenic data from the bedrock core drilled underneath the GISP2 ice core, we present the case that Greenland might have been free of ice at least once during the Pleistocene, highlighting its vulnerability. An immediate climate driver for the GrIS collapse is not evident from the existing paleo-climate database, motivating re-intensified research of physical mechanisms to melt the GrIS. We discuss a few preliminary climate scenarios that might have contributed to this dramatic ice-sheet collapse. On the shorter time-scale, we present tentative strategies how to investigate the stability of the GrIS during the Holocene Climate Optimum, a period of arguable-warmer-than today temperatures. Finally, we summarize the value of the paleo-data for predictions of the GrIS stability.

  5. Quaternary deposits in southwestern Afghanistan

    USGS Publications Warehouse

    Smith, G.I.

    1974-01-01

    Geologic evidence in the closed Seistan Basin of southwestern Afghanistan and adjacent parts of Iran and Pakistan indicates that a lake as much as 65,000 sq km in size occupied this closed depression during Pleistocene time. The deposits consist mostly of lacustrine silt and clay and have a maximum observed thickness of about 250 m. A layer of alluvial gravels overlies the sequence. The deposits are probably early or middle Pleistocene in age; they are old enough to have sustained nearly 300 m of erosion over large areas but are not faulted or detectably folded in the central part of the basin although they are upwarped along the west edge of the basin. Sand dunes cover extensive areas of the basin. Dune orientation shows that the strong surface winds enter the basin blowing toward the south-southeast and then are deflected to the east, apparently as a response to mountains bordering the basin on its south side. The Gawdezereh, a large deflation depression, may be a result of an augmented excavation ability of winds that oc urs where turbulence is created along a zone of deflection. ?? 1974.

  6. Greenland Ice Sheet Today: A daily look at surface melt of the Greenland ice sheet

    NASA Astrophysics Data System (ADS)

    Leslie, S. R.; Gergely, K. L.; Beitler, J.; Scambos, T. A.; Stroeve, J. C.

    2013-12-01

    An increase in the surface melt of the Greenland ice sheet in recent decades signals the waning of the ice sheet in a changing climate. The unprecedented intense surface melt of the ice sheet in 2012 prompted NASA and NSIDC to launch Greenland Ice Sheet Today, a Web site that offers daily updated satellite data and periodic scientific analysis on surface melting of the Greenland ice sheet. Near-real-time melt data are derived from an algorithm that estimates melt and is applied to DMSP SSMIS brightness temperatures gridded to a 25km EASE-Grid. These data are then used to generate a daily melt image, a cumulative melt days image, and a daily melt graph. Contextual background information on ice sheets as well as scientific discussions about the status of the Greenland ice sheet are posted periodically. Greenland Ice Sheet Today serves to keep a wide range of user communities informed about a crucial part of the Earth's cryosphere and here we examine the development of and reactions to the Web site.

  7. Building sustained partnerships in Greenland through shared science

    NASA Astrophysics Data System (ADS)

    Culler, L. E.; Albert, M. R.; Ayres, M. P.; Grenoble, L. A.; Virginia, R. A.

    2013-12-01

    Greenland is a hotspot for polar environmental change research due to rapidly changing physical and ecological conditions. Hundreds of international scientists visit the island each year to carry out research on diverse topics ranging from atmospheric chemistry to ice sheet dynamics to Arctic ecology. Despite the strong links between scientific, social, and political issues of rapid environmental change in Greenland, communication with residents of Greenland is often neglected by researchers. Reasons include language barriers, difficulties identifying pathways for communication, balancing research and outreach with limited resources, and limited social and cultural knowledge about Greenland by scientists. Dartmouth College has a legacy of work in the Polar Regions. In recent years, a National Science Foundation (NSF) Integrative Graduate Education and Research Traineeship (IGERT) in Polar Environmental Change funded training for 25 Ph.D. students in the Ecology, Earth Science, and Engineering graduate programs at Dartmouth. An overarching goal of this program is science communication between these disciplines and to diverse audiences, including communicating about rapid environmental change with students, residents, and the government of Greenland. Students and faculty in IGERT have been involved in the process of engaging with and sustaining partnerships in Greenland that support shared cultural and educational experiences. We have done this in three ways. First, a key component of our program has been hosting students from Ilisimatusarfik (the University of Greenland). Since 2009, five Greenlandic students have come to Dartmouth and formed personal connections with Dartmouth students while introducing their Greenlandic culture and language (Kalaallisut). Second, we have used our resources to extend our visits to Greenland, which has allowed time to engage with the community in several ways, including sharing our science via oral and poster presentations at Katuaq

  8. Satellite Gravity Measurements Confirm Accelerated Melting of Greenland Ice Sheet

    NASA Astrophysics Data System (ADS)

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

    2006-09-01

    Using time-variable gravity measurements from the Gravity Recovery and Climate Experiment (GRACE) satellite mission, we estimate ice mass changes over Greenland during the period April 2002 to November 2005. After correcting for the effects of spatial filtering and limited resolution of GRACE data, the estimated total ice melting rate over Greenland is -239 +/- 23 cubic kilometers per year, mostly from East Greenland. This estimate agrees remarkably well with a recent assessment of -224 +/- 41 cubic kilometers per year, based on satellite radar interferometry data. GRACE estimates in southeast Greenland suggest accelerated melting since the summer of 2004, consistent with the latest remote sensing measurements.

  9. Biophysical influences on the spatial distribution of fire in the desert grassland region of the southwestern USA

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Context: Fire is an important driver of ecological processes in semiarid systems and serves a vital role in shrub-grass interactions. In desert grasslands of the Southwestern US, the loss of fire has been implicated as a primary cause of shrub encroachment. Where fires can currently be re-introduced...

  10. Petroleum geology of southwestern Ohio

    SciTech Connect

    Sitler, G.

    1987-09-01

    Approximately 250 wells have been drilled in the 22-county area comprising southwestern Ohio. Despite numerous shows from various zones, no sustained commercial production has been established. Live oil and gas shows have been reported from surface exposures of outcropping Silurian carbonates down to, and including, the Cambrian Mount Simon Sandstone. Several wells have been completed and actually produced hydrocarbons for a short period, but were subsequently abandoned. Despite the lack of established production, the area holds considerable promise as a potential oil and natural gas producing region. Gravity, magnetics, seismic, surface and source rock geochemistry, linear trace analysis, and subsurface computer mapping have all been used to study the structure, stratigraphy, and petroleum geology of the area. Basement geology is complex and has affected sedimentation patterns in the overlying Cambrian rocks. The Grenville-Central Province contact is present in the area and exhibits faulting, mineralization, and possibly plutonism. The Cambrian and Ordovician stratigraphy in the area is relatively simple, with clastics at the base, carbonates in the middle, and a thick shale capping the sequence. Several major facies changes are evident within the section. Structural geology is also fairly simple. However, local discontinuities are apparent and include Precambrian doming and faulting, reactivated faulting, and Knox unconformable surfaces. Potential reservoirs in the area include the Utica Shale, Trenton Limestone, St. Peter Sandstone, Rose Run sandstone, Knox dolomites, Kerbel sandstone, Eau Claire Sandstone, and Mount Simon Sandstone. Favorable source rock geochemistry and the abundance of hydrocarbon shows suggest favorable source rocks to be present. Many different types of traps have been observed.

  11. Holocene deceleration of the Greenland Ice Sheet.

    PubMed

    MacGregor, Joseph A; Colgan, William T; Fahnestock, Mark A; Morlighem, Mathieu; Catania, Ginny A; Paden, John D; Gogineni, S Prasad

    2016-02-05

    Recent peripheral thinning of the Greenland Ice Sheet is partly offset by interior thickening and is overprinted on its poorly constrained Holocene evolution. On the basis of the ice sheet's radiostratigraphy, ice flow in its interior is slower now than the average speed over the past nine millennia. Generally higher Holocene accumulation rates relative to modern estimates can only partially explain this millennial-scale deceleration. The ice sheet's dynamic response to the decreasing proportion of softer ice from the last glacial period and the deglacial collapse of the ice bridge across Nares Strait also contributed to this pattern. Thus, recent interior thickening of the Greenland Ice Sheet is partly an ongoing dynamic response to the last deglaciation that is large enough to affect interpretation of its mass balance from altimetry.

  12. Holocene deceleration of the Greenland Ice Sheet

    NASA Astrophysics Data System (ADS)

    MacGregor, Joseph A.; Colgan, William T.; Fahnestock, Mark A.; Morlighem, Mathieu; Catania, Ginny A.; Paden, John D.; Gogineni, S. Prasad

    2016-02-01

    Recent peripheral thinning of the Greenland Ice Sheet is partly offset by interior thickening and is overprinted on its poorly constrained Holocene evolution. On the basis of the ice sheet’s radiostratigraphy, ice flow in its interior is slower now than the average speed over the past nine millennia. Generally higher Holocene accumulation rates relative to modern estimates can only partially explain this millennial-scale deceleration. The ice sheet’s dynamic response to the decreasing proportion of softer ice from the last glacial period and the deglacial collapse of the ice bridge across Nares Strait also contributed to this pattern. Thus, recent interior thickening of the Greenland Ice Sheet is partly an ongoing dynamic response to the last deglaciation that is large enough to affect interpretation of its mass balance from altimetry.

  13. Complex Greenland outlet glacier flow captured

    PubMed Central

    Aschwanden, Andy; Fahnestock, Mark A.; Truffer, Martin

    2016-01-01

    The Greenland Ice Sheet is losing mass at an accelerating rate due to increased surface melt and flow acceleration in outlet glaciers. Quantifying future dynamic contributions to sea level requires accurate portrayal of outlet glaciers in ice sheet simulations, but to date poor knowledge of subglacial topography and limited model resolution have prevented reproduction of complex spatial patterns of outlet flow. Here we combine a high-resolution ice-sheet model coupled to uniformly applied models of subglacial hydrology and basal sliding, and a new subglacial topography data set to simulate the flow of the Greenland Ice Sheet. Flow patterns of many outlet glaciers are well captured, illustrating fundamental commonalities in outlet glacier flow and highlighting the importance of efforts to map subglacial topography. Success in reproducing present day flow patterns shows the potential for prognostic modelling of ice sheets without the need for spatially varying parameters with uncertain time evolution. PMID:26830316

  14. Secret Science: Exploring Cold War Greenland

    NASA Astrophysics Data System (ADS)

    Harper, K.

    2013-12-01

    During the early Cold War - from the immediate postwar period through the 1960s - the United States military carried out extensive scientific studies and pursued technological developments in Greenland. With few exceptions, most of these were classified - sometimes because new scientific knowledge was born classified, but mostly because the reasons behind the scientific explorations were. Meteorological and climatological, ionospheric, glaciological, seismological, and geological studies were among the geophysical undertakings carried out by military and civilian scientists--some in collaboration with the Danish government, and some carried out without their knowledge. This poster will present some of the results of the Exploring Greenland Project that is coming to a conclusion at Denmark's Aarhus University.

  15. Results from the Sunlight Absorption on the Greenland Ice Sheet Experiment (SAGE)

    NASA Astrophysics Data System (ADS)

    Polashenski, C.; Dibb, J. E.; Flanner, M.; Courville, Z.; Chen, J.

    2014-12-01

    MODIS observations indicate that albedo of the Greenland ice sheet (GIS) has been declining since 2001, with important implications for energy balance and surface melt. The SAGE project seeks to understand the relative roles played by grain size changes, black carbon (BC), dust, and surface melt in decreasing the albedo of the high elevation areas of the GIS. Traverses were conducted in 2013 and 2014, sampling a total of 67 snow pits across much of northwestern Greenland to characterize snow microphysics and the deposition of absorbing impurities over the prior 1-2 annual cycles, with particular attention paid to sampling the 2012 melt layer. Results show elevated biomass burning derived BC levels in summer 2012 and elevated dust concentrations in spring 2013 at some sites, both particularly in the central areas of the ice sheet. Observations and modeling results indicate, however, that the albedo impact of these modest enhancements in impurity concentrations was very minimal (<<1%) in the dry snow environment. Grain metamorphosis in dry snow and surface wetting/grain growth occurring when melt extends to higher elevations appear to be the most important processes controlling albedo change across the high elevations of the Greenland ice sheet.

  16. Measured and modelled absolute gravity in Greenland

    NASA Astrophysics Data System (ADS)

    Nielsen, E.; Forsberg, R.; Strykowski, G.

    2012-12-01

    Present day changes in the ice volume in glaciated areas like Greenland will change the load on the Earth and to this change the lithosphere will respond elastically. The Earth also responds to changes in the ice volume over a millennial time scale. This response is due to the viscous properties of the mantle and is known as Glaical Isostatic Adjustment (GIA). Both signals are present in GPS and absolute gravity (AG) measurements and they will give an uncertainty in mass balance estimates calculated from these data types. It is possible to separate the two signals if both gravity and Global Positioning System (GPS) time series are available. DTU Space acquired an A10 absolute gravimeter in 2008. One purpose of this instrument is to establish AG time series in Greenland and the first measurements were conducted in 2009. Since then are 18 different Greenland GPS Network (GNET) stations visited and six of these are visited more then once. The gravity signal consists of three signals; the elastic signal, the viscous signal and the direct attraction from the ice masses. All of these signals can be modelled using various techniques. The viscous signal is modelled by solving the Sea Level Equation with an appropriate ice history and Earth model. The free code SELEN is used for this. The elastic signal is modelled as a convolution of the elastic Greens function for gravity and a model of present day ice mass changes. The direct attraction is the same as the Newtonian attraction and is calculated as this. Here we will present the preliminary results of the AG measurements in Greenland. We will also present modelled estimates of the direct attraction, the elastic and the viscous signals.

  17. Greenland Meltwater and Arctic Circulation Regimes

    NASA Astrophysics Data System (ADS)

    Dukhovskoy, D. S.; Proshutinsky, A. Y.; Timmermans, M. L.; Myers, P. G.; Platov, G.

    2015-12-01

    Between 1948 and 1996, wind-driven components of ice drift and surface ocean currents experienced a well-pronounced decadal variability alternating between anticyclonic and cyclonic circulation regimes. During cyclonic regimes, low sea level atmospheric pressure dominated over the Arctic Ocean driving sea ice and the upper ocean clockwise; the Arctic atmosphere was relatively warm and humid and freshwater flux from the Arctic Ocean toward the sub-Arctic seas was intensified. During anticylonic circulation regimes, high sea level pressure dominated over the Arctic driving sea ice and ocean counter-clockwise; the atmosphere was cold and dry and the freshwater flux from the Arctic to the sub-Arctic seas was reduced. Since 1997, however, the Arctic system has been dominated by an anticyclonic circulation regime with a set of environmental parameters that are atypical for these regimes. Of essential importance is to discern the causes and consequences of the apparent break-down in the natural decadal variability of the Arctic climate system, and specifically: Why has the well-pronounced decadal variability observed in the 20th century been replaced by relatively weak interannual changes under anticyclonic circulation regime conditions in the 21st century? We discuss a hypothesis explaining the causes and mechanisms regulating the intensity and duration of Arctic circulation regimes, and speculate how changes in freshwater fluxes from Greenland impact environmental conditions and interrupt their decadal variability. In order to test this hypothesis, numerical experiments with several FAMOS (Forum for Arctic Modeling & Observational Synthesis) ice-ocean coupled models have been conducted. In these experiments, Greenland melt freshwater is tracked by passive tracers being constantly released along the Greenland coast. Propagation pathways and time scales of Greenland meltwater within the sub-Arctic seas are discussed.

  18. Generating synthetic fjord bathymetry for coastal Greenland

    NASA Astrophysics Data System (ADS)

    Williams, Christopher N.; Cornford, Stephen L.; Jordan, Thomas M.; Dowdeswell, Julian A.; Siegert, Martin J.; Clark, Christopher D.; Swift, Darrel A.; Sole, Andrew; Fenty, Ian; Bamber, Jonathan L.

    2017-02-01

    Bed topography is a critical boundary for the numerical modelling of ice sheets and ice-ocean interactions. A persistent issue with existing topography products for the bed of the Greenland Ice Sheet and surrounding sea floor is the poor representation of coastal bathymetry, especially in regions of floating ice and near the grounding line. Sparse data coverage, and the resultant coarse resolution at the ice-ocean boundary, poses issues in our ability to model ice flow advance and retreat from the present position. In addition, as fjord bathymetry is known to exert strong control on ocean circulation and ice-ocean forcing, the lack of bed data leads to an inability to model these processes adequately. Since the release of the last complete Greenland bed topography-bathymetry product, new observational bathymetry data have become available. These data can be used to constrain bathymetry, but many fjords remain completely unsampled and therefore poorly resolved. Here, as part of the development of the next generation of Greenland bed topography products, we present a new method for constraining the bathymetry of fjord systems in regions where data coverage is sparse. For these cases, we generate synthetic fjord geometries using a method conditioned by surveys of terrestrial glacial valleys as well as existing sinuous feature interpolation schemes. Our approach enables the capture of the general bathymetry profile of a fjord in north-west Greenland close to Cape York, when compared to observational data. We validate our synthetic approach by demonstrating reduced overestimation of depths compared to past attempts to constrain fjord bathymetry. We also present an analysis of the spectral characteristics of fjord centrelines using recently acquired bathymetric observations, demonstrating how a stochastic model of fjord bathymetry could be parameterised and used to create different realisations.

  19. Holocene thinning of the Greenland ice sheet.

    PubMed

    Vinther, B M; Buchardt, S L; Clausen, H B; Dahl-Jensen, D; Johnsen, S J; Fisher, D A; Koerner, R M; Raynaud, D; Lipenkov, V; Andersen, K K; Blunier, T; Rasmussen, S O; Steffensen, J P; Svensson, A M

    2009-09-17

    On entering an era of global warming, the stability of the Greenland ice sheet (GIS) is an important concern, especially in the light of new evidence of rapidly changing flow and melt conditions at the GIS margins. Studying the response of the GIS to past climatic change may help to advance our understanding of GIS dynamics. The previous interpretation of evidence from stable isotopes (delta(18)O) in water from GIS ice cores was that Holocene climate variability on the GIS differed spatially and that a consistent Holocene climate optimum-the unusually warm period from about 9,000 to 6,000 years ago found in many northern-latitude palaeoclimate records-did not exist. Here we extract both the Greenland Holocene temperature history and the evolution of GIS surface elevation at four GIS locations. We achieve this by comparing delta(18)O from GIS ice cores with delta(18)O from ice cores from small marginal icecaps. Contrary to the earlier interpretation of delta(18)O evidence from ice cores, our new temperature history reveals a pronounced Holocene climatic optimum in Greenland coinciding with maximum thinning near the GIS margins. Our delta(18)O-based results are corroborated by the air content of ice cores, a proxy for surface elevation. State-of-the-art ice sheet models are generally found to be underestimating the extent and changes in GIS elevation and area; our findings may help to improve the ability of models to reproduce the GIS response to Holocene climate.

  20. 75 FR 52527 - Southwestern Power Administration; Notice of Filing

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-08-26

    ... From the Federal Register Online via the Government Publishing Office ] DEPARTMENT OF ENERGY Federal Energy Regulatory Commission Southwestern Power Administration; Notice of Filing August 19, 2010. Take notice that on August 17, 2010, the Department of Energy, Southwestern Power...

  1. Jaguar critical habitat designation causes concern for Southwestern ranchers

    USGS Publications Warehouse

    Svancara, Colleen; Lien, Aaron M.; Vanasco, Wendy T.; Laura Lopez-Hoffman,; Ruyle, George B.

    2015-01-01

    The designation of jaguar critical habitat in April 2014 in southern Arizona and southwestern New Mexico created concern for livestock ranchers in the region. We interviewed ranchers to understand their concerns with the jaguar critical habitat designation and their attitudes toward jaguars, wildlife conservation, and resource management in general. Ranchers we interviewed were concerned about direct impacts of designated critical habitat on ranching, as well as possible alternative agendas of critical habitat advocates and issues specific to the borderlands region. The ranchers were less concerned about the presence of jaguars but were more concerned about possible limiting effects of the Endangered Species Act (ESA), distrust of government entities, and litigious environmental groups. To maximize effectiveness, government agencies should work to foster trust in the ranching community, be cognizant of sensitive issues specific to the region that may challenge endangered species conservation goals, recognize the opportunity to work with ranchers for endangered species management, and provide outreach about implications of the ESA.

  2. Prescription drug abuse among prisoners in rural Southwestern Virginia.

    PubMed

    Wunsch, Martha J; Nakamoto, Kent; Goswami, Anil; Schnoll, Sidney H

    2007-01-01

    Non-medical use of prescription medications is on the rise across the U.S., particularly in rural areas. In this study of 233 prisoners and probationers in southwestern Virginia, we add to an emerging profile of individuals abusing prescription medications. In this retrospective review of 2000-2004 augmented Addiction Severity Index data, those abusing prescription medications reported increased illicit drug and alcohol abuse, poly-drug abuse, psychiatric problems, and arrests for property crimes. Forty percent reported abuse of OxyContin, a drug implicated in a number of deaths in this region. Compared to non-users, OxyContin users were younger, more likely to be female, and more likely to abuse benzodiazepines, methadone, cocaine, and heroin. Longevity of abuse of these other drugs belies suggestions that OxyContin was acting as a "gateway" drug leading naïve users into addiction and risk of death.

  3. Changes in the firn structure of the western Greenland Ice Sheet caused by recent warming

    DOE PAGES

    de la Peña, S.; Howat, I. M.; Nienow, P. W.; ...

    2015-06-11

    Atmospheric warming over the Greenland Ice Sheet during the last 2 decades has increased the amount of surface meltwater production, resulting in the migration of melt and percolation regimes to higher altitudes and an increase in the amount of ice content from refrozen meltwater found in the firn above the superimposed ice zone. Here we present field and airborne radar observations of buried ice layers within the near-surface (0–20 m) firn in western Greenland, obtained from campaigns between 1998 and 2014. We find a sharp increase in firn-ice content in the form of thick widespread layers in the percolation zone,more » which decreases the capacity of the firn to store meltwater. The estimated total annual ice content retained in the near-surface firn in areas with positive surface mass balance west of the ice divide in Greenland reached a maximum of 74 ± 25 Gt in 2012, compared to the 1958–1999 average of 13 ± 2 Gt, while the percolation zone area more than doubled between 2003 and 2012. Increased melt and column densification resulted in surface lowering averaging –0.80 ± 0.39 m yr⁻¹ between 1800 and 2800 m in the accumulation zone of western Greenland. Since 2007, modeled annual melt and refreezing rates in the percolation zone at elevations below 2100 m surpass the annual snowfall from the previous year, implying that mass gain in the region is retained after melt in the form of refrozen meltwater. If current melt trends over high elevation regions continue, subsequent changes in firn structure will have implications for the hydrology of the ice sheet and related abrupt seasonal densification could become increasingly significant for altimetry-derived ice sheet mass balance estimates.« less

  4. Changes in the firn structure of the western Greenland Ice Sheet caused by recent warming

    SciTech Connect

    de la Peña, S.; Howat, I. M.; Nienow, P. W.; van den Broeke, M. R.; Mosley-Thompson, E.; Price, S. F.; Mair, D.; Noël, B.; Sole, A. J.

    2015-06-11

    Atmospheric warming over the Greenland Ice Sheet during the last 2 decades has increased the amount of surface meltwater production, resulting in the migration of melt and percolation regimes to higher altitudes and an increase in the amount of ice content from refrozen meltwater found in the firn above the superimposed ice zone. Here we present field and airborne radar observations of buried ice layers within the near-surface (0–20 m) firn in western Greenland, obtained from campaigns between 1998 and 2014. We find a sharp increase in firn-ice content in the form of thick widespread layers in the percolation zone, which decreases the capacity of the firn to store meltwater. The estimated total annual ice content retained in the near-surface firn in areas with positive surface mass balance west of the ice divide in Greenland reached a maximum of 74 ± 25 Gt in 2012, compared to the 1958–1999 average of 13 ± 2 Gt, while the percolation zone area more than doubled between 2003 and 2012. Increased melt and column densification resulted in surface lowering averaging –0.80 ± 0.39 m yr⁻¹ between 1800 and 2800 m in the accumulation zone of western Greenland. Since 2007, modeled annual melt and refreezing rates in the percolation zone at elevations below 2100 m surpass the annual snowfall from the previous year, implying that mass gain in the region is retained after melt in the form of refrozen meltwater. If current melt trends over high elevation regions continue, subsequent changes in firn structure will have implications for the hydrology of the ice sheet and related abrupt seasonal densification could become increasingly significant for altimetry-derived ice sheet mass balance estimates.

  5. Seasonal Greenland Ice Sheet ice flow variations in regions of differing bed and surface topography

    NASA Astrophysics Data System (ADS)

    Sole, A. J.; Livingstone, S. J.; Rippin, D. M.; Hill, J.; McMillan, M.; Quincey, D. J.

    2015-12-01

    The contribution of the Greenland Ice Sheet (GrIS) to future sea-level rise is uncertain. Observations reveal the important role of basal water in controlling ice-flow to the ice sheet margin. In Greenland, drainage of large volumes of surface meltwater to the ice sheet bed through moulins and hydrofracture beneath surface lakes dominates the subglacial hydrological system and provides an efficient means of moving mass and heat through the ice sheet. Ice surface and bed topography influence where meltwater can access the bed, and the nature of its subsequent flow beneath the ice. However, no systematic investigation into the influence of topographic variability on Greenland hydrology and dynamics exists. Thus, physical processes controlling storage and drainage of surface and basal meltwater, and the way these affect ice flow are not comprehensively understood. This presents a critical obstacle in efforts to predict the future evolution of the GrIS. Here we present high-resolution satellite mapping of the ice-surface drainage network (e.g. lakes, channels and moulins) and measurements of seasonal variations in ice flow in south west Greenland. The region is comprised of three distinct subglacial terrains which vary in terms of the amplitude and wavelength and thus the degree to which basal topography is reflected in the ice sheet surface. We find that the distribution of surface hydrological features is related to the transfer of bed topography to the ice sheet surface. For example, in areas of thinner ice and high bed relief, moulins occur more frequently and are more uniformly dispersed, indicating a more distributed influx of surface-derived meltwater to the ice sheet bed. We investigate the implications of such spatial variations in surface hydrology on seasonal ice flow rates.

  6. Changes in the firn structure of the western Greenland Ice Sheet caused by recent warming

    NASA Astrophysics Data System (ADS)

    de la Peña, S.; Howat, I. M.; Nienow, P. W.; van den Broeke, M. R.; Mosley-Thompson, E.; Price, S. F.; Mair, D.; Noël, B.; Sole, A. J.

    2015-06-01

    Atmospheric warming over the Greenland Ice Sheet during the last 2 decades has increased the amount of surface meltwater production, resulting in the migration of melt and percolation regimes to higher altitudes and an increase in the amount of ice content from refrozen meltwater found in the firn above the superimposed ice zone. Here we present field and airborne radar observations of buried ice layers within the near-surface (0-20 m) firn in western Greenland, obtained from campaigns between 1998 and 2014. We find a sharp increase in firn-ice content in the form of thick widespread layers in the percolation zone, which decreases the capacity of the firn to store meltwater. The estimated total annual ice content retained in the near-surface firn in areas with positive surface mass balance west of the ice divide in Greenland reached a maximum of 74 ± 25 Gt in 2012, compared to the 1958-1999 average of 13 ± 2 Gt, while the percolation zone area more than doubled between 2003 and 2012. Increased melt and column densification resulted in surface lowering averaging -0.80 ± 0.39 m yr-1 between 1800 and 2800 m in the accumulation zone of western Greenland. Since 2007, modeled annual melt and refreezing rates in the percolation zone at elevations below 2100 m surpass the annual snowfall from the previous year, implying that mass gain in the region is retained after melt in the form of refrozen meltwater. If current melt trends over high elevation regions continue, subsequent changes in firn structure will have implications for the hydrology of the ice sheet and related abrupt seasonal densification could become increasingly significant for altimetry-derived ice sheet mass balance estimates.

  7. Changes in the firn structure of the Greenland Ice Sheet caused by recent warming

    NASA Astrophysics Data System (ADS)

    de la Peña, S.; Howat, I. M.; Nienow, P. W.; van den Broeke, M. R.; Mosley-Thompson, E.; Price, S. F.; Mair, D.; Noël, B.; Sole, A. J.

    2015-01-01

    Atmospheric warming over the Greenland Ice Sheet during the last two decades has increased the amount of surface meltwater production, resulting in the migration of melt and percolation regimes to higher altitudes and an increase in the amount of solid ice from refrozen meltwater found in the firn above the equilibrium line. Here we present observations of near-surface (0-20 m) firn conditions in western Greenland obtained from campaigns between 1998 and 2014. We find a sharp increase in firn ice content in the form of thick widespread layers in the percolation zone, which decreases the capacity of the firn to store meltwater. The estimated total annual ice content retained in the firn in areas with positive surface mass balance west of the ice divide in Greenland reached a maximum of 74 ± 25 Gt in 2012, compared to the 1958-1999 average of 13 ± 2 Gt, while the percolation zone area more than doubled between 2003 and 2012. Increased melt and column densification resulted in surface lowering averaging -0.80 ± 0.39 m yr-1 between 1800 and 2800 m in the accumulation zone of western Greenland. Since 2007, annual melt and refreezing rates in the percolation zone at elevations below 2100 m surpass the annual snowfall from the previous year, implying that mass gain in the region is now in the form of refrozen meltwater. If current melt trends over high elevation regions continue, subsequent changes in firn structure will have implications for the hydrology of the ice sheet and related abrupt seasonal densification could become increasingly significant for altimetry-derived ice sheet mass balance estimates.

  8. Uncertainty of GIA models across the Greenland

    NASA Astrophysics Data System (ADS)

    Ruggieri, Gabriella

    2013-04-01

    In the last years various remote sensing techniques have been employed to estimate the current mass balance of the Greenland ice sheet (GIS). In this regards GRACE, laser and radar altimetry observations, employed to constrain the mass balance, consider the glacial isostatic adjustment (GIA) a source of noise. Several GIA models have been elaborated for the Greenland but they differ from each other for mantle viscosity profile and for time history of ice melting. In this work we use the well know ICE-5G (VM2) ice model by Peltier (2004) and two others alternative scenarios of ice melting, ANU05 by Lambeck et al. (1998) and the new regional ice model HUY2 by Simpson et al. (2009) in order to asses the amplitude of the uncertainty related to the GIA predictions. In particular we focus on rates of vertical displacement field, sea surface variations and sea-level change at regional scale. The GIA predictions are estimated using an improved version of SELEN code that solve the sea-level equation for a spherical self-gravitating, incompressible and viscoelastic Earth structure. GIA uncertainty shows a highly variable geographic distribution across the Greenland. Considering the spatial pattern of the GIA predictions related to the three ice models, the western sector of the Greenland Ice Sheets (GrIS) between Thule and Upernavik and around the area of Paamiut, show good agreement while the northeast portion of the Greenland is characterized by a large discrepancy of the GIA predictions inferred by the ice models tested in this work. These differences are ultimately the consequence of the different sets of global relative sea level data and modern geodetic observations used by the authors to constrain the model parameters. Finally GPS Network project (GNET), recently installed around the periphery of the GrIS, are used as a tool to discuss the discrepancies among the GIA models. Comparing the geodetic analysis recently available, appears that among the GPS sites the

  9. Towards Greenland Glaciation: Cumulative or Abrupt Transition?

    NASA Astrophysics Data System (ADS)

    Tan, N.; Ramstein, G.; Contoux, C.; Ladant, J. B.; Dumas, C.; Donnadieu, Y.

    2014-12-01

    The insolation evolution [Laskar 2004] from 4 to 2.5 Ma depicts a series of three summer solstice insolation minima between 2.7 and 2.6 Ma, but there are other more important summer solstice minima notably around 3.82 and 3.05 Ma. On such a time span of more than 1 Ma, data shows that there are variations in the evolution of atmospheric CO2 concentration with a local maximum around 3 Ma [Seki et al.2010; Bartoli et al. 2011], before a decrease between 3 and 2.6 Ma. The latter, suggesting an abrupt ice sheet inception around 2.7 Ma, has been shown to be a major culprit for the full Greenland Glaciation [Lunt et al. 2008]. However, a recent study [Contoux et al. 2014, in review] suggests that a lowering of CO2 is not sufficient to initiate a glaciation on Greenland and must be combined to low summer insolation, with surviving ice during insolation maximum, suggesting a cumulative process in the first place, which could further lead to full glaciation at 2.7 Ma. Through a new tri-dimensional interpolation method implemented within the asynchronous coupling between an atmosphere ocean general circulation model (IPSL-CM5A) and an ice sheet model (GRISLI), we investigate the transient evolution of Greenland ice sheet during the Pliocene to diagnose whether the ice sheet inception is an abrupt event or rather a cumulative process, involving waxing and waning of the ice sheet during several orbital cycles. ReferencesBartoli, G., Hönisch, B., & Zeebe, R. E. (2011). Atmospheric CO2 decline during the Pliocene intensification of Northern Hemisphere glaciations. Paleoceanography, 26(4). Contoux C, Dumas C, Ramstein G, Jost A, Dolan A. M. (2014) Modelling Greenland Ice sheet inception and sustainability during the late Pliocene. (in review for Earth and Planetary Science Letters.).Laskar, J., Robutel, P., Joutel, F., Gastineau, M., Correia, A. C. M., & Levrard, B. (2004). A long-term numerical solution for the insolation quantities of the Earth. Astronomy & Astrophysics, 428

  10. A Coupled Ocean-Iceberg Model Over The 20th Century: Iceberg Flux At 48°N As A Proxy For Greenland Iceberg Discharge

    NASA Astrophysics Data System (ADS)

    Bigg, G. R.; Wilton, D.; Hanna, E.

    2013-12-01

    Grant R. Bigg1 , David J. Wilton1 and Edward Hanna1 1Department of Geography, The University of Sheffield, Sheffield, S10 2TN We have used a coupled ocean-iceberg model, the Fine Resolution Greenland and Labrador ocean model [1], to study the variation in, and trajectory of, icebergs over the twentieth century, focusing particularly on Greenland and surrounding areas. The model is forced with daily heat, freshwater and wind fluxes derived from the Twentieth Century Reanalysis Project [2]. We use the observed iceberg flux at 48°N off Newfoundland (I48N) from 1900 to 2008 [3] to assess the iceberg component of the model. Model I48N is calculated with both a variable and constant annual calving rate. The results show that ocean and atmosphere changes alone do not account for the variation in observed I48N and suggests that this series can be used as a proxy for iceberg discharge from west Greenland tidewater glaciers. The implication of this proxy is that there is significant interannual variability in Greenland iceberg discharge over the whole twentieth century. Our model results suggest that in the early decades of the twentieth century I48N was dominated by icebergs originating from south Greenland (below latitude 65°N) with west Greenland becoming the main source of I48N from the late 1930s onwards. Modeled icebergs from the east of Greenland very rarely reach 48°N. We also present results from the ocean model showing the variation of ocean transport fluxes over the course of the twentieth and early twenty first century. References 1. M. R. Wadley, and G. R. Bigg, (2002), Q. J. R. Meteorol. Soc., 128, 2187-2203 2. G. P. Compo, et al. (2011), Q. J. R. Meteorol. Soc., 137, 1-28 3. D. L. Murphy (2011) http://www.navcen.uscg.gov/?pageName=IIPIcebergCounts

  11. Greenland surface albedo changes 1981-2012 from satellite observations

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Significant melt over Greenland has been observed during the last several decades associated with extreme warming events over the northern Atlantic Ocean. An analysis of surface albedo change over Greenland is presented, using a 32-year consistent satellite albedo product from the Global Land Surfac...

  12. Brief communication "The aerophotogrammetric map of Greenland ice masses"

    NASA Astrophysics Data System (ADS)

    Citterio, M.; Ahlstrøm, A. P.

    2013-03-01

    The PROMICE (Programme for Monitoring of the Greenland Ice Sheet) aerophotogrammetric map of Greenland ice masses is the first high resolution dataset documenting the mid-1980s areal extent of the Greenland Ice Sheet and all the local glaciers and ice caps. The total glacierized area excluding nunataks was 1 804 638 km2 ± 2178 km2, of which 88 083 ± 1240 km2 belonged to local glaciers and ice caps (GIC) substantially independent from the Greenland Ice Sheet. This new result of GIC glacierized area is higher than most previous estimates, 81% greater than Weng's (1995) measurements, but is in line with contemporary findings based on independent data sources. A comparison between our map and the recently released Rastner et al. (2012) inventory and GIMP (Greenland Ice Mapping Project) Ice-Cover Mask (Howat and Negrete, 2013) shows potential for change-assessment studies.

  13. Greenland during the last interglacial: the relative importance of insolation and oceanic changes

    NASA Astrophysics Data System (ADS)

    Pedersen, Rasmus A.; Langen, Peter L.; Vinther, Bo M.

    2016-09-01

    Insolation changes during the Eemian (the last interglacial period, 129 000-116 000 years before present) resulted in warmer than present conditions in the Arctic region. The NEEM ice core record suggests warming of 8 ± 4 K in northwestern Greenland based on stable water isotopes. Here we use general circulation model experiments to investigate the causes of the Eemian warming in Greenland. Simulations of the atmospheric response to combinations of Eemian insolation and preindustrial oceanic conditions and vice versa are used to disentangle the impacts of the insolation change and the related changes in sea surface temperatures and sea ice conditions. The changed oceanic conditions cause warming throughout the year, prolonging the impact of the summertime insolation increase. Consequently, the oceanic conditions cause an annual mean warming of 2 K at the NEEM site, whereas the insolation alone causes an insignificant change. Taking the precipitation changes into account, however, the insolation and oceanic changes cause more comparable increases in the precipitation-weighted temperature, implying that both contributions are important for the ice core record at the NEEM site. The simulated Eemian precipitation-weighted warming of 2.4 K at the NEEM site is low compared to the ice core reconstruction, partially due to missing feedbacks related to ice sheet changes and an extensive sea ice cover. Surface mass balance calculations with an energy balance model further indicate that the combination of temperature and precipitation anomalies leads to potential mass loss in the north and southwestern parts of the ice sheet. The oceanic conditions favor increased accumulation in the southeast, while the insolation appears to be the dominant cause of the expected ice sheet reduction. Consequently, the Eemian is not a suitable analogue for future ice sheet changes.

  14. Quaternary evolution and ice sheet history of contrasting landscapes in Uummannaq and Sukkertoppen, western Greenland

    NASA Astrophysics Data System (ADS)

    Beel, C. R.; Lifton, N. A.; Briner, J. P.; Goehring, B. M.

    2016-10-01

    Constraining the history of the Greenland Ice Sheet (GIS) is important for improving our understanding of ice sheet dynamics and landscape evolution processes. We analyzed in situ cosmogenic 10Be and 26Al in 26 rock samples from two high-elevation landscapes adjacent to the GIS, minimally eroded by past glaciations and of differing character in Uummannaq (n = 16) and Sukkertoppen (n = 10), western Greenland. The Uummannaq region is characterized by a marine embayment with islands and peninsulas, where the margin of the GIS is marine-based, whereas the Sukkertoppen landscape resides within the wide terrestrial fringe outboard of the land-terminating portion of the southwestern GIS margin. We targeted landscapes for sampling with highly weathered surfaces adjacent to cold-based portions of extant ice caps (indicated by preservation of fragile, dead vegetation emerging from beneath retreating ice margins). Paired isotope results require differing surface histories between the two areas. Many surfaces in the Uummannaq region have minimum exposure durations up to ca. 300 kyr, but with no significant burial. Most surfaces in the Sukkertoppen region, however, yield complex exposure histories with minimum cumulative exposure durations up to ca. 100 kyr and minimum cumulative burial durations up to ca. 400 kyr, yielding minimum total surface histories of up to 500 ka. These findings suggest that parts of the Uummannaq landscape may have been continuously exposed throughout much of the middle and late Quaternary. On the other hand, the high-altitude surfaces in the Sukkertoppen region were largely preserved beneath minimally-erosive, cold-based ice during the same period. Data from the Uummannaq region thus stand in contrast not only to the Sukkertoppen region, but also to other sites surrounding Baffin Bay reported in previous studies. We hypothesize that surfaces in the Uummannaq region may have remained as nunataks above the Last Glacial Maximum (LGM) ice sheet surface

  15. Cosmogenic 26Al/10Be surface production ratio in Greenland

    NASA Astrophysics Data System (ADS)

    Corbett, Lee B.; Bierman, Paul R.; Rood, Dylan H.; Caffee, Marc W.; Lifton, Nathaniel A.; Woodruff, Thomas E.

    2017-02-01

    The assumed value for the cosmogenic 26Al/10Be surface production rate ratio in quartz is an important parameter for studies investigating the burial or subaerial erosion of long-lived surfaces and sediments. Recent models and data suggest that the production ratio is spatially variable and may be greater than originally thought. Here we present measured 26Al/10Be ratios for 24 continuously exposed bedrock and boulder surfaces spanning 61-77°N in Greenland. Empirical measurements, such as ours, include nuclides produced predominately by neutron-induced spallation with percent-level contributions by muon interactions. The slope of a York regression line fit to our data is 7.3 ± 0.3 (1σ), suggesting that the 26Al/10Be surface production ratio exceeds the commonly used value of 6.75, at least in the Arctic. A higher 26Al/10Be production ratio has implications for multinuclide cosmogenic isotope studies because it results in greater modeled burial durations and erosion rates.

  16. Growth of Greenland ice sheet - Measurement

    NASA Technical Reports Server (NTRS)

    Zwally, H. Jay; Bindschadler, Robert A.; Marsh, James G.; Brenner, Anita C.; Major, Judy A.

    1989-01-01

    Measurements of ice-sheet elevation change by satellite altimetry show that the Greenland surface elevation south of 72 deg north latitude is increasing. The vertical velocity of the surface is 0.20 + or - 0.06 meters/year from measured changes in surface elevations at 5906 intersections between Geosat paths in 1985 and Seasat in 1978, and 0.28 + or - 0.02 meters/year from 256,694 intersections of Geosat paths during a 548-day period of 1985 to 1986.

  17. North Greenland's Ice Shelves and Ocean Warming

    NASA Astrophysics Data System (ADS)

    Muenchow, A.; Schauer, U.; Padman, L.; Melling, H.; Fricker, H. A.

    2014-12-01

    Rapid disintegration of ice shelves (the floating extensions of marine-terminating glaciers) can lead to increasing ice discharge, thinning upstream ice sheets, rising sea level. Pine Island Glacier, Antarctica, and Jacobshavn Isbrae, Greenland, provide prominent examples of these processes which evolve at decadal time scales. We here focus on three glacier systems north of 78 N in Greenland, each of which discharges more than 10 Gt per year of ice and had an extensive ice shelf a decade ago; Petermann Gletscher (PG), Niogshalvfjerdsfjorden (79N), and Zachariae Isstrom (ZI). We summarize and discuss direct observations of ocean and glacier properties for these systems as they have evolved in the northwest (PG) and northeast (79N and ZI) of Greenland over the last two decades. We use a combination of modern and historical snapshots of ocean temperature and salinity (PG, 79N, ZI), moored observations in Nares Strait (PG), and snapshots of temperature and velocity fields on the broad continental shelf off northeast Greenland (79N, ZI) collected between 1993 and 2014. Ocean warming adjacent to PG has been small relative to the ocean warming adjacent to 79N and ZI; however, ZI lost its entire ice shelf during the last decade while 79N, less than 70 km to the north of ZI, remained stable. In contrast, PG has thinned by about 10 m/y just prior to shedding two ice islands representing almost half its ice shelf area or a fifth by volume. At PG advective ice flux divergence explains about half of the dominantly basal melting while response to non-steady external forcing explains the other half. The observations at PG,79N, and ZI suggest that remotely sensed ambient surface ocean temperatures are poor proxies to explain ice shelf thinning and retreat. We posit that local dynamics of the subsurface ocean heat flux matters most. Ocean heat must first be delivered over the sill into the fjord and then within the ice shelf cavity to the base of the shelf near the grounding line

  18. The recent warming trend in North Greenland

    NASA Astrophysics Data System (ADS)

    Orsi, Anais; Kawamura, Kenji; Masson-Delmotte, Valerie; Landais, Amaelle; Severinghaus, Jeff

    2015-04-01

    The arctic is the fastest warming region on Earth, but it is also one where there is little historical data. Although summer warming causes melt, the annual temperature trend is dominated by the winter and fall season, which are much less well documented. In addition, the instrumental record relies principally on coastal weather stations, and there are very few direct temperature observations in the interior dating back more than 30 years, especially in North Greenland, where the current warming trend is the largest. Here, we present a temperature reconstruction from NEEM (51°W, 77°N), in North Greenland, for the last 100 years, which allows us to put the recent trend in the context of the longer term climate. We use a combination of two independent proxies to reconstruct the temperature history at NEEM: borehole temperature and inert gas isotope measurements in the firn. Borehole temperature takes advantage of the low temperature diffusivity of the snow and ice, which allows the temperature history to be preserved in the ice for several centuries. Temperature gradients in the firn (old snow above the ice) influence the gas isotopic composition: thermal fractionation causes heavy isotopes to concentrate on the cold end of the firn column. We measured the isotopes of inert gases (N2, Ar and Kr), which have a constant atmospheric composition through time, and use the thermal fractionation signal as an additional constraint on the temperature history at the site. We find that NEEM has been warming by 0.86±0.22°C/decade over the past 30 years, from -28.55±0.29°C for the 1900-1970 average to -26.77±0.16°C for the 2000-2010 average. The warming rate at NEEM is similar to that of Greenland Summit, and confirms the large warming trends in North Greenland (polar amplification) and high altitude sites (tropospheric rather than surface warming). Water isotopes show that the recent past has not met the level of the 1928 anomaly; but the average of the past 30 years has

  19. Towards Introducing a Geocoding Information System for Greenland

    NASA Astrophysics Data System (ADS)

    Siksnans, J.; Pirupshvarre, Hans R.; Lind, M.; Mioc, D.; Anton, F.

    2011-08-01

    Currently, addressing practices in Greenland do not support geocoding. Addressing points on a map by geographic coordinates is vital for emergency services such as police and ambulance for avoiding ambiguities in finding incident locations (Government of Greenland, 2010) Therefore, it is necessary to investigate the current addressing practices in Greenland. Asiaq (Asiaq, 2011) is a public enterprise of the Government of Greenland which holds three separate databases regards addressing and place references: - list of locality names (towns, villages, farms), - technical base maps (including road center lines not connected with names, and buildings), - the NIN registry (The Land Use Register of Greenland - holds information on the land allotments and buildings in Greenland). The main problem is that these data sets are not interconnected, thus making it impossible to address a point in a map with geographic coordinates in a standardized way. The possible solutions suffer from the fact that Greenland has a scattered habitation pattern and the generalization of the address assignment schema is a difficult task. A schema would be developed according to the characteristics of the settlement pattern, e.g. cities, remote locations and place names. The aim is to propose an ontology for a common postal address system for Greenland. The main part of the research is dedicated to the current system and user requirement engineering. This allowed us to design a conceptual database model which corresponds to the user requirements, and implement a small scale prototype. Furthermore, our research includes resemblance findings in Danish and Greenland's addressing practices, data dictionary for establishing Greenland addressing system's logical model and enhanced entity relationship diagram. This initial prototype of the Greenland addressing system could be used to evaluate and build the full architecture of the addressing information system for Greenland. Using software engineering

  20. Exceptional summer warming leads to contrasting outcomes for methane cycling in small Arctic lakes of Greenland

    NASA Astrophysics Data System (ADS)

    Cadieux, Sarah B.; White, Jeffrey R.; Pratt, Lisa M.

    2017-02-01

    In thermally stratified lakes, the greatest annual methane emissions typically occur during thermal overturn events. In July of 2012, Greenland experienced significant warming that resulted in substantial melting of the Greenland Ice Sheet and enhanced runoff events. This unusual climate phenomenon provided an opportunity to examine the effects of short-term natural heating on lake thermal structure and methane dynamics and compare these observations with those from the following year, when temperatures were normal. Here, we focus on methane concentrations within the water column of five adjacent small lakes on the ice-free margin of southwestern Greenland under open-water and ice-covered conditions from 2012-2014. Enhanced warming of the epilimnion in the lakes under open-water conditions in 2012 led to strong thermal stability and the development of anoxic hypolimnia in each of the lakes. As a result, during open-water conditions, mean dissolved methane concentrations in the water column were significantly (p < 0.0001) greater in 2012 than in 2013. In all of the lakes, mean methane concentrations under ice-covered conditions were significantly (p < 0.0001) greater than under open-water conditions, suggesting spring overturn is currently the largest annual methane flux to the atmosphere. As the climate continues to warm, shorter ice cover durations are expected, which may reduce the winter inventory of methane and lead to a decrease in total methane flux during ice melt. Under open-water conditions, greater heat income and warming of lake surface waters will lead to increased thermal stratification and hypolimnetic anoxia, which will consequently result in increased water column inventories of methane. This stored methane will be susceptible to emissions during fall overturn, which may result in a shift in greatest annual efflux of methane from spring melt to fall overturn. The results of this study suggest that interannual variation in ground-level air

  1. The PolarSEEDS project: communicating Greenland melting through visualization and sonification

    NASA Astrophysics Data System (ADS)

    Tedesco, M.; Perl, J.; Saltz, I.; Ham, E.

    2013-12-01

    During fall of 2011 a group of faculty at the City College of New York from the Science and Art Divisions drafted a concept for a project about communicating results from his research concerning the melting of the Greenland ice sheet through 'unconventional' venues, such as Visual Arts and Music. The opportunity to build a team and perform a project came to reality when the City College of New York (CCNY) called for the City SEED call proposal (therefore the name POLARSEEDS). The call was looking to fund innovative interdisciplinary work that could create connections among different disciplines within CCNY. The faculty members of the project were affiliated with the Dept. of Earth and Atmospheric Sciences (Tedesco), the Music Dept. and the Sonic Arts Center (Perl) and Art Dept. (Saltz and Ham). The PolarSEEDS project involved also six students at graduate and master level from the three departments. The project culminated in an exhibition at CCNY in which soundscapes obtained from sounds recorded during fieldwork in Greenland were combined with sonifications of the outputs of a climate model used to study melting in Greenland to generate ambient sounds. At the exhibit, many sonifications of the model outputs were available at computer stations together with the explanation of the different approaches undertaken to generate them. Large aerial photos of supraglacial streams and lakes over Greenland were exhibited together with infographics addressing some of the causes and implications of melting. Videos showing either footage of melting features or the impact of albedo on melting (through ad hoc experiments carried out in laboratory and filmed for the exhibit) were also exhibited. Lastly, the visitors had the opportunity to play an interactive web game developed for the project in which they had to balance the amount of clouds, solar radiation, rain and snow to keep the Greenland ice sheet from melting completely and flood New York City. In my presentation, I will

  2. Late Holocene expansion of Istorvet ice cap, Liverpool Land, east Greenland

    NASA Astrophysics Data System (ADS)

    Lowell, Thomas V.; Hall, Brenda L.; Kelly, Meredith A.; Bennike, Ole; Lusas, Amanda R.; Honsaker, William; Smith, Colby A.; Levy, Laura B.; Travis, Scott; Denton, George H.

    2013-03-01

    The Greenland Ice Sheet is undergoing dynamic changes that will have global implications if they continue into the future. In this regard, an understanding of how the ice sheet responded to past climate changes affords a baseline for anticipating future behavior. Small, independent ice caps adjacent to the Greenland Ice Sheet (hereinafter called "local ice caps") are sensitive indicators of the response of Greenland ice-marginal zones to climate change. Therefore, we reconstructed late Holocene ice-marginal fluctuations of the local Istorvet ice cap in east Greenland, using radiocarbon dates of subfossil plants, 10Be dates of surface boulders, and analyses of sediment cores from both threshold and control lakes. During the last termination, the Istorvet ice cap had retreated close to its maximum Holocene position by ˜11,730 cal yr BP. Radiocarbon dates of subfossil plants exposed by recent recession of the ice margin indicate that the Istorvet cap was smaller than at present from AD 200 to AD 1025. Sediments from a threshold lake show no glacial input until the ice cap advanced to within 365 m of its Holocene maximum position by ˜AD 1150. Thereafter the ice cap remained at or close to this position until at least AD 1660. The timing of this, the most extensive of the Holocene, expansion is similar to that recorded at some glaciers in the Alps and in southern Alaska. However, in contrast to these other regions, the expansion in east Greenland at AD 1150 appears to have been very close to, if not at, a maximum Holocene value. Comparison of the Istorvet ice-cap fluctuations with Holocene glacier extents in Southern Hemisphere middle-to-high latitude locations on the Antarctic Peninsula and in the Andes and the Southern Alps suggests an out-of-phase relationship. If correct, this pattern supports the hypothesis that a bipolar see-saw of oceanic and/or atmospheric circulation during the Holocene produced asynchronous glacier response at some localities in the two

  3. Three Millennia of Southwestern North American Dustiness and Future Implications.

    PubMed

    Routson, Cody C; Overpeck, Jonathan T; Woodhouse, Connie A; Kenney, William F

    2016-01-01

    Two sediment records of dust deposition from Fish Lake, in southern Colorado, offer a new perspective on southwest United States (Southwest) aridity and dustiness over the last ~3000 years. Micro scanning X-ray fluorescence and grain size analysis provide separate measures of wind-deposited dust in the lake sediment. Together these new records confirm anomalous dustiness in the 19th and 20th centuries, associated with recent land disturbance, drought, and livestock grazing. Before significant anthropogenic influences, changes in drought frequency and aridity also generated atmospheric dust loading. Medieval times were associated with high levels of dustiness, coincident with widespread aridity. These records indicate the Southwest is naturally prone to dustiness. As global and regional temperatures rise and the Southwest shifts toward a more arid landscape, the Southwest will likely become dustier, driving negative impacts on snowpack and water availability, as well as human health.

  4. Three Millennia of Southwestern North American Dustiness and Future Implications

    PubMed Central

    Routson, Cody C.; Overpeck, Jonathan T.; Woodhouse, Connie A.; Kenney, William F.

    2016-01-01

    Two sediment records of dust deposition from Fish Lake, in southern Colorado, offer a new perspective on southwest United States (Southwest) aridity and dustiness over the last ~3000 years. Micro scanning X-ray fluorescence and grain size analysis provide separate measures of wind-deposited dust in the lake sediment. Together these new records confirm anomalous dustiness in the 19th and 20th centuries, associated with recent land disturbance, drought, and livestock grazing. Before significant anthropogenic influences, changes in drought frequency and aridity also generated atmospheric dust loading. Medieval times were associated with high levels of dustiness, coincident with widespread aridity. These records indicate the Southwest is naturally prone to dustiness. As global and regional temperatures rise and the Southwest shifts toward a more arid landscape, the Southwest will likely become dustier, driving negative impacts on snowpack and water availability, as well as human health. PMID:26886350

  5. Hydrologically Induced Basal Slip Triggers Greenland Supraglacial Lake Drainages

    NASA Astrophysics Data System (ADS)

    Stevens, L. A.; Behn, M. D.; McGuire, J. J.; Das, S. B.; Joughin, I. R.; Herring, T.; Shean, D. E.; King, M. A.

    2014-12-01

    We investigate what triggers the rapid drainage of a large supraglacial lake on the western margin of the Greenland Ice Sheet using a Network Inversion Filter (NIF) (Segall and Matthews, 1997) to invert a dense local network of GPS observations over three summers (2011-2013). The NIF is used to determine the spatiotemporal variability in ice sheet behavior (1) prior to lake drainage, and in response to (2) vertical hydro-fracture crack propagation and closure, (3) the opening of a horizontal cavity at the ice-sheet bed that accommodates the rapid injection of melt-water, and (4) extra basal slip due to enhanced lubrication. The NIF also allows us to infer the distribution of melt-water at the ice-sheet bed before, during, and after drainage. Our data show that the opening and propagation of each summer's lake-draining hydro-fracture is preceded by a local stress perturbation associated with ice sheet uplift and enhanced slip above pre-drainage background velocities. Within <1 day after the onset of each precursor, a vertical crack propagates through the lake basin and the lake drains rapidly (<5 hours). The NIF shows that the precursors are not associated with slow propagation of the lake draining hydrofracture, but rather pre-existing crevasses and/or moulins, which allow substantial amounts of melt-water to reach the bed and activate enhanced basal slip up to a day before hydro-fracture crack initiation. Identification of these precursors combined with the fact that drainages are observed to occur across a range of lake volumes and geometries, suggests that lakes do not spontaneously hydro-fracture once they surpass a specific threshold despite the numerous healed hydro-fracture cracks present within the lake basin from the prior years' drainage events. These results have implications for rapid drainage of supraglacial lakes in less crevassed, interior regions of the Greenland Ice Sheet, as well as the rapid collapse of Antarctic ice shelves through melt pond

  6. Robots could assist scientists working in Greenland

    NASA Astrophysics Data System (ADS)

    Showstack, Randy

    2011-07-01

    GREENLAND—Tom Lane and Suk Joon Lee, recent graduates of Dartmouth University's Thayer School of Engineering, in Hanover, N. H., are standing outside in the frigid cold testing an autonomous robot that could help with scientific research and logistics in harsh polar environments. This summer, Lane, Lee, and others are at Summit Station, a U.S. National Science Foundation (NSF)-sponsored scientific research station in Greenland, fine-tuning a battery-powered Yeti robot as part of a team working on the NSF-funded Cool Robot project. The station, also known as Summit Camp, is located on the highest point of the Greenland Ice Sheet (72°N, 38°W, 3200 meters above sea level) near the middle of the island. It is a proving ground this season for putting the approximately 68-kilogram, 1-cubic-meter robot through its paces, including improving Yeti's mobility capabilities and field-testing the robot. (See the electronic supplement to this Eos issue for a video of Yeti in action (http://www.agu.org/eos_elec/).) During field-testing, plans call for the robot to collect data on elevation and snow surface characteristics, including accumulation. In addition, the robot will collect black carbon and elemental carbon particulate matter air samples around Summit Camp's power generator to help study carbon dispersion over snow.

  7. Toxaphene in the aquatic environment of Greenland.

    PubMed

    Vorkamp, Katrin; Rigét, Frank F; Dietz, Rune

    2015-05-01

    The octa- and nonachlorinated bornanes (toxaphene) CHBs 26, 40, 41, 44, 50 and 62 were analysed in Arctic char (Salvelinus alpinus), shorthorn sculpin (Myoxocephalus scorpius), ringed seal (Pusa hispida) and black guillemot eggs (Cepphus grylle) from Greenland. Despite their high trophic level, ringed seals had the lowest concentrations of these species, with a Σ6Toxaphene median concentration of 13-20 ng/g lipid weight (lw), suggesting metabolisation. The congener composition also suggests transformation of nona- to octachlorinated congeners. Black guillemot eggs had the highest concentrations (Σ6Toxaphene median concentration of 971 ng/g lw). Although concentrations were higher in East than in West Greenland differences were smaller than for other persistent organic pollutants. In a circumpolar context, toxaphene had the highest concentrations in the Canadian Arctic. Time trend analyses showed significant decreases for black guillemot eggs and juvenile ringed seals, with annual rates of -5 to -7% for Σ6Toxaphene. The decreases were generally steepest for CHBs 40, 41 and 44.

  8. Instrument for Analysis of Greenland's Glacier Mills

    NASA Technical Reports Server (NTRS)

    Behar, Alberto E.; Matthews, Jaret B.; Tran, Hung B.; Steffen, Konrad; McGrath, Dan; Phillips, Thomas; Elliot, Andrew; OHern, Sean; Lutz, Colin; Martin, Sujita; Wang, Henry

    2010-01-01

    A new instrument is used to study the inner workings of Greenland s glacier mills by riding the currents inside a glacier s moulin. The West Greenland Moulin Explorer instrument was deployed into a tubular shaft to autonomously record temperature, pressure, 3D acceleration, and location. It is built with a slightly positive buoyancy in order to assist in recovery. The unit is made up of several components. A 3-axis MEMS (microelectromechanical systems) accelerometer with 0.001-g resolution forms the base of the unit. A pressure transducer is added that is capable of withstanding 500 psi (=3.4 MPa), and surviving down to -40 C. An Iridium modem sends out data every 10 minutes. The location is traced by a GPS (Global Positioning System) unit. This GPS unit is also used for recovery after the mission. Power is provided by a high-capacity lithium thionyl chloride D-sized battery. The accelerometer is housed inside a cylindrical, foot-long (=30 cm) polyvinyl chloride (PVC) shell sealed at each end with acrylic. The pressure transducer is attached to one of these lids and a MEMS accelerometer to the other, recording 100 samples per second per axis.

  9. Buoyant Currents West and East of Greenland

    NASA Astrophysics Data System (ADS)

    Aksenov, Y.; Bacon, S.; Nurser, G.; Coward, A.

    2014-12-01

    Low salinity buoyant polar waters exit the Arctic Ocean into the Nordic Seas and the North Atlantic, affecting deep convection in the Nordic and Labrador Seas with potential impacts on the meridional overturning circulation. The pathways of the polar water in Davis Strait, Fram Strait and then to the south are well documented by observations and model simulations. In contrast, measurements upstream of Fram Strait are too sparse to allow us to explain what causes the outflows to exit either west or east of Greenland or to attribute the variability in the Arctic outflows to atmospheric or oceanic mechanisms. Two high-resolution global ocean general circulation models (OGCM), NEMO-ORCA025, of ~12 km resolution, and NEMO-ORCA12, of ~4 km resolution, have been used to examine the dynamics and seasonal variability of the outflow west and east of Greenland. Montgomery potential analysis is used to investigate the dynamics of the currents in the area. The model results suggest wind as a driving mechanism for the seasonal variability of the ocean circulation in the area.

  10. Pathways of Petermann Glacier meltwater, Greenland

    NASA Astrophysics Data System (ADS)

    Heuzé, Céline; Wåhlin, Anna; Johnson, Helen; Münchow, Andreas

    2016-04-01

    Radar and satellite observations suggest that the floating ice shelf of Petermann Glacier loses up to 80% of its mass through basal melting, caused by the intrusion of warm Atlantic Water into the fjord and under the ice shelf. The fate of Petermann's glacial meltwater is still largely unknown. It is investigated here, using hydrographic observations collected during a research cruise on board I/B Oden in August 2015. Two methods are used to detect the meltwater from Petermann: a mathematical one that provides the concentration of ice shelf meltwater, and a geometrical one to distinguish the meltwater from Petermann and the meltwater from other ice shelves. The meltwater from Petermann mostly circulates on the north side of the fjord. At the sill, 0.5 mSv of meltwater leave the fjord, mostly on the northeastern side between 100 and 350 m depth, but also in the central channel, albeit with a lesser concentration. Meltwater from Petermann is found in all the casts in Hall Basin, notably north of the sill by Greenland coast. The geometrical method reveals that the casts closest to the Canadian side mostly contain meltwater from other, unidentified glaciers. As Atlantic Water warms up, it is key to monitor Greenland melting glaciers and track their meltwater to properly assess their impact on the ocean circulation and sea level rise.

  11. Central Greenland Holocene Deuterium Excess Variability

    NASA Astrophysics Data System (ADS)

    Masson-Delmotte, V.; Jouzel, J.; Falourd, S.; Cattani, O.; Dahl-Jensen, D.; Johnsen, S.; Sveinbjornsdottir, A. E.; White, J. W. C.

    Water stable isotopes (oxygen 18 and deuterium) have been measured along the Holocene part of two deep ice cores from central Greenland, GRIP and North GRIP. Theoretical studies have shown that the second-order isotopic parameter, the deu- terium excess (d=dD-8d18O), is an indicator of climatic changes at the oceanic mois- ture source reflecting at least partly changes in sea-surface-temperature. The two deu- terium excess records from GRIP and North GRIP show a long term increasing trend already observed in Antarctic deep ice cores and related to changes in the Earth's obliquity during the Holocene : an decreased obliquity is associated with a larger low to high latitude annual mean insolation gradient, warmer tropics, colder poles, and a more intense atmospheric transport from the tropics to the poles, resulting in a higher moisture source temperature and higher deuterium excess values. Superimposed onto this long term trend, central Greenland deuterium excess records also exhibit small abrupt events (8.2 ka BP and 4.5 ka BP) and a high frequency variability.

  12. Greenland Ice Core: Geophysics, Geochemistry, and the Environment

    NASA Astrophysics Data System (ADS)

    Langway, C. C., Jr.; Oeschger, H.; Dansgaard, W.

    The Greenland Ice Sheet Program (GISP) is already recognized as a major achievement in glaciology. GISP support came from the Swiss National Science Foundation, the Danish Commission for Scientific Research in Greenland and the United States National Science Foundation. And with the spirit, drive, and ability of Hans Oeschger, Willi Dansgaard and Chester Langway, GISP was planned, undertaken and successfully concluded. The results presented here demonstrate the significance of the climatic record stored in ice sheets and reemphasizes the need for additional deep ice cores from Greenland and Antarctica.

  13. Winter Camp: A Blog from the Greenland Summit, Part II

    NASA Technical Reports Server (NTRS)

    Koenig, Lora

    2009-01-01

    An earlier issue presents the first half of the author's experience living and working at the National Science Foundation's (NSF) Greenland Summit Camp. The author is a remote-sensing glaciologist at NASA s Goddard Space Flight Center. She took measurements that will be used to validate data collected by NASA s Aqua, Terra, and Ice, Clouds, and land Elevation Satellite (ICESat) satellites with ground-truth measurements of the Greenland Ice Sheet she made at Summit Camp from November 2008-February 2009. This article presents excerpts from the second half of her stay and work at the Greenland Summit.

  14. Comparison of magnetic activity in Greenland and Nordic countries

    NASA Astrophysics Data System (ADS)

    Peitso, P.; Tanskanen, E. I.; Stolle, C.; Berthou Lauritsen, N.; Matzka, J.

    2014-04-01

    We will examine geomagnetic activity from Greenland and IMAGE magnetic observations. Geomagnetic activity maps for the Greenland and IMAGE magnetic field measurements will be produced. The maps will be produced separately for the different months where the seasonal variation will be examined. We will compare geomagnetic conditions during winter and summer separately to examine in detail the differences and similarities. The Greenland magnetic field measurements will be used to estimate the geomagnetic field variation between Svalbard and northernmost tip of Norway, where we lack magnetic measurements due to the Arctic Ocean.

  15. SIMPL/AVIRIS-NG Greenland 2015: Flight Report

    NASA Technical Reports Server (NTRS)

    Brunt, Kelly M.; Neumann, Thomas A.; Markus, Thorsten

    2015-01-01

    In August 2015, NASA conducted a two-­aircraft, coordinated campaign based out of Thule Air Base, Greenland, in support of Ice, Cloud, and land Elevation Satellite-2 (ICESat-2) algorithm development. The survey targeted the Greenland Ice Sheet and sea ice in the Arctic Ocean during the summer melt season. The survey was conducted with a photon-counting laser altimeter in one aircraft and an imaging spectrometer in the second aircraft. Ultimately, the mission, SIMPL/AVIRIS-NG Greenland 2015, conducted nine coordinated science flights, for a total of 37 flight hours over the ice sheet and sea ice.

  16. Physical Properties of the Ice Cover of the Greenland Sea.

    DTIC Science & Technology

    1982-11-01

    DA-A13 i PHYSICAL PROPERTIES OF THE ICE COVER OF THE GREENLAND 1/1 I SEAMU COLD REGIONS RESEARCH AND ENGINEERING LAB USI FE HANOVER NH N F REEKS NOV...I PERIOD COVERED PHYSICAL PROPERTIES OF THE ICE COVER OF THE GREENLAND SEA S. PERFORMING ORG. REPORT NUMBER 7. AUTHOR(e) S. CONTRACT OR GRANT NUMBER...NOTES 19. KEY WORDS (Continue on revere aide if neceaary and identify by block number) Greenland Ice Ice properties Sea ice SABSTRACT (Vntmm em reverse

  17. Greenland Ice Sheet Program. 1979. Phase 1. Casing Operation.

    DTIC Science & Technology

    1980-06-01

    A-l0-1119 699 COLD. REGIONS RESEARCH AND ENGINEERING LAS HANOVER NH F/6 8/12 GREENLAND ICE SHEET PROGRAM. 1979. PHASE 1. CASING OPERATION. (U) JNAB J...Thermal drills Drills Glac iology Greenland 124 AnRACr (cimEaeu m reverse ssNnouiesaw ad Middfr by block nmber) )A modified CHREL thermal drill was used at...DYE-3 in Greenland to drill a 8.T5-in.-diamneter hole 251 ft deep for the installation of a steel casing. This activity was accomplished by a drill

  18. Crustal structure of the Central-Eastern Greenland: results from the TopoGreenland refraction profile

    NASA Astrophysics Data System (ADS)

    Shulgin, Alexey; Thybo, Hans

    2014-05-01

    Until present, seismic surveys have only been carried out offshore and near the coasts of Greenland, where the crustal structure is affected by oceanic break-up. We present the deep seismic structure of the crust of the interior of Greenland, based on the new and the only existing so far seismic refraction/wide-angle reflection profile. The seismic data was acquired by a team of six people during a two-month long experiment in summer of 2011 on the ice cap in the interior of central-eastern Greenland. The presence of an up to 3.4 km thick ice sheet, permanently covering most of the land mass, made acquisition of geophysical data logistically complicated. The profile extends 310 km inland in E-W direction from the approximate edge of the stable ice cap near the Scoresby Sund across the center of the ice cap. 350 Reftek Texan receivers recorded high-quality seismic data from 8 equidistant shots along the profile. Explosive charge sizes were 1 ton at the ends and ca. 500 kg along the profile, loaded with about 125 kg at 35-85 m depth in individual boreholes. Given that the data acquisition was affected by the thick ice sheet, we questioned the quality of seismic records in such experiment setup. We have developed an automatic routine to check the amplitudes and spectra of the selected seismic phases and to check the differences/challenges in making seismic experiments on ice and the effects of ice on data interpretation. Using tomographic inversion and forward ray tracing modelling we have obtained the two-dimensional velocity model down to a 50 km depth. The model shows a decrease of crustal thickness from 47 km below the centre of Greenland in the western part of the profile to 40 km in its eastern part. Relatively high lower crustal velocities (Vp 6.8 - 7.3 km/s) in the western part of the TopoGreenland profile may result from past collision tectonics or, alternatively, may be related to the speculated passage of the Iceland mantle plume. Comparison of our results

  19. Radiation Climatology of the Greenland Ice Sheet Derived from Greenland Climate Network Data

    NASA Technical Reports Server (NTRS)

    Steffen, Konrad; Box, Jason

    2003-01-01

    The magnitude of shortwave and longwave dative fluxes are critical to surface energy balance variations over the Greenland ice sheet, affecting many aspects of its climate, including melt rates, the nature of low-level temperature inversions, the katabatic wind regime and buoyant stability of the atmosphere. Nevertheless, reliable measurements of the radiative fluxes over the ice sheet are few in number, and have been of limited duration and areal distribution (e.g. Ambach, 1960; 1963, Konzelmann et al., 1994, Harding et al., 1995, Van den Broeke, 1996). Hourly GC-Net radiation flux measurements spanning 1995-2001 period have been used to produce a monthly dataset of surface radiation balance components. The measurements are distributed widely across Greenland and incorporate multiple sensors

  20. Southwestern Power Administration Annual Report 2008

    SciTech Connect

    2010-12-01

    Dear Secretary Chu, I am pleased to present the financial statements and operating data for Southwestern Power Administration (Southwestern) for Fiscal Year (FY) 2008. In FY 2008, Southwestern delivered over 7.3 billion kilowatt-hours of energy to its wholesale customers – nearly 31% more than average due to numerous record rainfall amounts in the southwest region. These record amounts produced revenues which exceeded the average annual revenue requirement by nearly $20 million and resulted in over $200 million in economic benefits to the region. Yet even as Southwestern exceeded its goals of marketing and delivering Federal hydroelectric power to our customers, we stayed focused on safety, security, and reliability. For example, we maintained our nearly 1,400 miles of high-voltage transmission lines, substations, and communications sites while achieving a Recordable Accident Frequency Rate of 0.0, a record that reflects Southwestern’s safety achievement of no recordable injuries for every 200,000 hours worked. We kept our rights-of-way secure from vegetation and other obstacles, work that not only supports our mission but also promotes reliability of the regional and National grid. We exceeded all North American Electric Reliability Corporation (NERC) Control Performance Standards (CPS- 1 and CPS-2), and maintained regulation and reserve obligations and reactive reserve margins to ensure the reliability of the bulk electric system, even during extended periods of restricted hydro operations due to unusually high project inflows. Finally, we continued our partnerships with the Department of Energy, the U.S. Army Corps of Engineers, our customers, and other Federal power stakeholders, partnerships that are vital to our continued success in marketing and delivering carbon-free, renewable, and domestically produced energy to our customers and to the Nation. Sincerely, Jon Worthington Administrator

  1. Haptophyte alga from Greenland lakes offers unprecedented opportunity to decipher alkenone biosynthetic pathways and functionality

    NASA Astrophysics Data System (ADS)

    Theroux, S.; Amaral-Zettler, L.; Huang, Y.

    2009-12-01

    The alkenone unsaturation index is an invaluable tool for paleoclimate reconstructions—however, the physiological mechanism governing alkenone production remains unknown. We have identified and isolated a novel species of Haptophyte alga that produces anomalously high concentrations of alkenone lipids during a spring bloom period in southwestern Greenland lakes. We have confirmed that the extant blooming haptophyte ribosomal RNA (rRNA) gene sequences match those found in sediments dating back 6000 yrs. This species comprises a unique clade within the Isochrysidales, and forms macroscopic colonies during its bloom period, the only time when alkenone lipids are produced. Alkenones sampled in situ through the water column demonstrate a temperature-dependent control on unsaturation. Under nutrient-enriched ex situ culture conditions the alga discontinues alkenone biosynthesis. This finding is consistent with reported enhancement of alkenone production in Emiliania huxleyi under nutrient-deplete conditions. Extensive manipulation of culture conditions and simulation of bloom-period lake water conditions enables us to identify environmental triggers of alkenone production. In parallel with the culturing work, RNA samples taken before and during the lake bloom event also allow for a metatranscriptomic analysis to assay the genes involved in alkenone production. In combination, these samples give us a unique opportunity for annotating gene transcripts up- and down-regulated during alkenone biosynthesis. Identification of genes involved in alkenone biosynthesis will enable functional gene-based phylogenetic comparisons among Haptophtye algae, improving our understanding of the evolution of alkenone biosynthesis and the alkenone’s role in cellular function.

  2. Southwestern Willow Flycatcher Breeding Site and Territory Summary - 2006

    USGS Publications Warehouse

    Durst, Scott L.; Sogge, Mark K.; Stump, Shay D.; Williams, Sartor O.; Kus, Barbara E.; Sferra, Susan J.

    2007-01-01

    Introduction The Southwestern Willow Flycatcher (Empidonax traillii extimus) is an endangered bird that breeds only in dense riparian habitats in six southwestern states (southern California, extreme southern Nevada, southern Utah, southwestern Colorado, Arizona, and New Mexico). Since 1993, hundreds of Southwestern Willow Flycatcher surveys have been conducted each year, and many new flycatcher breeding sites located. This document synthesizes information on all known Southwestern Willow Flycatcher breeding sites. This rangewide data synthesis was designed to meet these objectives: * identify all known Southwestern Willow Flycatcher breeding sites, and * assemble data on population size, location, habitat, and other information for all breeding sites, for as many years as possible, from 1993 through 2006. This report provides data summaries in terms of the number of flycatcher sites and the number of territories.

  3. The first glacier inventory for entire Greenland

    NASA Astrophysics Data System (ADS)

    Rastner, P.; Bolch, T.; Mölg, N.; Le Bris, R.; Paul, F.

    2012-04-01

    Detailed glacier data is becoming more and more important in the last decades to solve several research issues. One of the most prominent questions in this regard is the potential contribution of glaciers and icecaps (GIC) to global sea-level rise. Primarily, estimates are uncertain due to the globally still incomplete information about glacier location and size, as well as large uncertainties in future climate scenarios. Recent studies that calculate global sea-level rise from GIC have developed simplified approaches using information from glacier inventories or gridded data sets and a range of different global climate models and emission scenarios. However, for several strongly glacierized regions very rough assumptions about the ice distribution have to be made and an urgent demand for a globally complete glacier inventory is expressed. The GIC on Greenland are one of the regions with lacking information. Within the EU FP7 project ice2sea we mapped the GIC on Greenland using Landsat TM/ETM+ imagery acquired around the year 2000, along with an additional dataset in the North (DCW - Digital Chart of the World). A digital elevation model (DEM) with 90 m resolution (GIMP DEM) was used to derive drainage divides and henceforth topographic parameters for each entity. A major challenge in this regard is the application of a consistent strategy to separate the local GIC from the ice sheet. For this purpose we have defined different levels of connectivity (CL) of the local GIC with the ice sheet: CL0: Not connected. CL1: Connected but separable (either with drainage divides in the accumulation region or in touch only - and thus separable - in the ablation region). CL2: Connected but non-separable (the local GIC contribute to the flow of an ice sheet outlet in the ablation area). Up to now close to 12'000 GIC (only CL0 and CL1) with a total area of about 129'000 km2 have been mapped considering only entities larger than 0.1 km2. The area of the ice sheet itself is

  4. Mapping Greenland's mass loss in space and time.

    PubMed

    Harig, Christopher; Simons, Frederik J

    2012-12-04

    The melting of polar ice sheets is a major contributor to global sea-level rise. Early estimates of the mass lost from the Greenland ice cap, based on satellite gravity data collected by the Gravity Recovery and Climate Experiment, have widely varied. Although the continentally and decadally averaged estimated trends have now more or less converged, to this date, there has been little clarity on the detailed spatial distribution of Greenland's mass loss and how the geographical pattern has varied on relatively shorter time scales. Here, we present a spatially and temporally resolved estimation of the ice mass change over Greenland between April of 2002 and August of 2011. Although the total mass loss trend has remained linear, actively changing areas of mass loss were concentrated on the southeastern and northwestern coasts, with ice mass in the center of Greenland steadily increasing over the decade.

  5. Permian of Norwegian-Greenland sea margins: future exploration target

    SciTech Connect

    Surlyk, F.; Hurst, J.M.; Piasecki, S.; Rolle, F.; Stemmerik, L.; Thomsen, E.; Wrang, P.

    1984-09-01

    Oil and gas exploration in the northern North Sea and the southern Norwegian shelf has mainy been concentrated on Jurassic and younger reservoirs with Late Jurassic black shale source rocks. New onshore investigations in Jameson Land, central East Greenland, suggest that the Permian of the Norwegian-Greenland Sea margins contains relatively thick sequences of potential oil source rocks interbedded with carbonate reefs. The East Greenland, Upper Permian marine basin is exposed over a length of 400 km (250 mi) from Jameson Land in the south to Wollaston Forland in the north, parallel with the continental margin. The Upper Permian black shale is relatively thick, widely distributed, has a high organic carbon content, and a favorable kerogen type. Consequently, the possibilities for a Permian play in the northern part of the Norwegian shelf and along parts of the Norwegian-Greenland Sea margins are worth evaluating.

  6. Greenland Expeditions by Alfred Wegener - A photographic window to past

    NASA Astrophysics Data System (ADS)

    Leitner, M.; Tschürtz, S.; Kirchengast, G.; Kranzelbinder, H.; Prügger, B.; Krause, R. A.; Kalliokoski, M.; Thórhallsdóttir, E.

    2012-04-01

    On several expeditions to Greenland, Alfred Wegener (1880-1930) took pictures on glass plates from landscapes and glaciers, the expedition equipment, the people and animals taking part on the expeditions as well as physical phenomena as dust storm, clouds or spherical light phenomena. Chronologically the plates show the Danmark Expedition 1906-1908, the crossing of Greenland expedition with stop in Iceland 1912-1913, and the German Greenland Expedition 1929-1930. Until the tragic end of the expedition in 1930, Wegener was professor at the University of Graz, and such a stock of about 300 glass plates stayed there. The aim of our work is to digitize all plates for further studies. We present a first selection of Wegener's Greenland expedition pictures. For those made at Iceland in 1912 we will present a comparison of the past with pictures from the same viewing point made in 2011.

  7. High export of dissolved silica from the Greenland Ice Sheet

    NASA Astrophysics Data System (ADS)

    Meire, L.; Meire, P.; Struyf, E.; Krawczyk, D. W.; Arendt, K. E.; Yde, J. C.; Juul Pedersen, T.; Hopwood, M. J.; Rysgaard, S.; Meysman, F. J. R.

    2016-09-01

    Silica is an essential element for marine life and plays a key role in the biogeochemistry of the ocean. Glacial activity stimulates rock weathering, generating dissolved silica that is exported to coastal areas along with meltwater. The magnitude of the dissolved silica export from large glacial areas such as the Greenland Ice Sheet is presently poorly quantified and not accounted for in global budgets. Here we present data from two fjord systems adjacent to the Greenland Ice Sheet which reveal a large export of dissolved silica by glacial meltwater relative to other macronutrients. Upscaled to the entire Greenland Ice Sheet, the export of dissolved silica equals 22 ± 10 Gmol Si yr-1. When the silicate-rich meltwater mixes with upwelled deep water, either inside or outside Greenland's fjords, primary production takes place at increased silicate to nitrate ratios. This likely stimulates the growth of diatoms relative to other phytoplankton groups.

  8. Southwestern Power Administration Annual Report 2007

    SciTech Connect

    2008-01-01

    “Renewable energy” isn’t just a catchphrase at Southwestern Power Administration (Southwestern). It describes the hydroelectric energy we market, and the energy that Southwestern’s employees bring to work every day, constantly challenging themselves to become more eff ective and effi cient in providing aff ordable, environmentally clean power to the American people. As Southwestern’s new Administrator, I have had the opportunity to view our operations from a fresh perspective, and I’m proud to share with you how a focus on continual improvement has been evident in accomplishments throughout the agency during fi scal year (FY) 2007. When the North American Electric Reliability Corporation (NERC) implemented new reliability standards, we met applicable implementation dates and exceeded NERC’s control performance standards throughout the year. When tasked with reducing the agency’s carbon footprint, we found ways to achieve an 8.7% reduction in energy intensity from last year without impacting our operational capabilities. And when faced with record-breaking infl ows into the reservoir projects from which we market power, we capitalized on the opportunity to provide customers with signifi cant quantities of supplemental energy. Our supplemental sales this year not only saved customers over $122 million, but increased Southwestern’s revenues -- a huge win-win for Southwestern’s ratepayers and the Nation’s taxpayers alike. Southwestern is proud of its role in protecting National and economic security by contributing to the diverse supply of domestically produced energy, operating and maintaining a safe and reliable transmission system, and ensuring good stewardship of our Nation’s water resources and environment. In FY 2007, Southwestern continued to repay all power costs to the American taxpayers by marketing and delivering approximately 5.6 billion kilowatthours of hydropower at cost-based rates to customers in our six-state region. This energy

  9. Reconstruction of the past 2000 years of ocean and glacier variability in Sermilik Fjord, SE Greenland, based on sediment archives

    NASA Astrophysics Data System (ADS)

    Stoican, Andreea; Andresen, Camilla; Seidenkrantz, Marit-Solveig; Kjaer, Kurt; Kuijpers, Antoon; Massé, Guillaume; Weckström, Kaarina

    2013-04-01

    Glaciomarine sediments represent valuable archives of climate and glacier variability in the arctic environment. Especially the fjords along Greenland's east coast represent a dynamic and complicated system, influenced by regional ocean circulation, local currents and by glacier terminations. Therefore, they represent appropriate locations for sedimentary core studies in order to detect the relative glacier and ocean variability. The aim of this project is to reconstruct the past 2000 years of glacier and ocean variability in Sermilik fjord, SE Greenland, into which Helheim glacier terminates. This is done by analysing two sedimentary cores (ER11 and ER07) and hereby reconstruct fluctuations in marine-terminating outlet glacier dynamics (including iceberg and to a lesser extent melt water production) and the interaction with oceanographic changes. The oceanographic variability is reconstructed on the basis of benthic and planktonic foraminiferal analysis and the content of the biomarker IP25 and these proxies are interpreted to reflect changes in the inflow of the warm Irminger Current and polar waters in association with the East Greenland Current. Interestingly, studies show that the onset of the Little Ice Age was characterised by intensified inflow of Irminger Current water masses to the Southeastern and Southwestern shelves of Greenland and that these may be associated with a contracted subpolar gyre. At the same time, the EGC Polar Water transport also intensified leading to a stratified water column on the shelf and this may have favoured entrainment of warm subsurface IC waters. Alternatively, the relatively warm rim of the eastern subpolar gyre may have promoted intense submarine melting of extended outlet glaciers at this time, producing enhanced melt water outflow which favoured estuarine circulation processes maintaining the inflow of IC water masses. Thus the aim of this study is to investigate in detail the circulation of these LIA warm waters from

  10. Changes in the velocity structure of the Greenland Ice Sheet.

    PubMed

    Rignot, Eric; Kanagaratnam, Pannir

    2006-02-17

    Using satellite radar interferometry observations of Greenland, we detected widespread glacier acceleration below 66 degrees north between 1996 and 2000, which rapidly expanded to 70 degrees north in 2005. Accelerated ice discharge in the west and particularly in the east doubled the ice sheet mass deficit in the last decade from 90 to 220 cubic kilometers per year. As more glaciers accelerate farther north, the contribution of Greenland to sea-level rise will continue to increase.

  11. Climate Change and Baleen Whale Trophic Cascades in Greenland

    DTIC Science & Technology

    2008-01-01

    species in West Greenland. We use a multidisciplinary approach by combining observations of foraging ecology and phenology collected by satellite and...feeding in each site and the phenology of the use of the focal areas. These data are related to long-term physical and biological monitoring program...in Nuuk Fjord and on the coast of West Greenland, where long-term fishery data are collected to quantify seasonal and inter-annual variations in the

  12. Distinct patterns of seasonal Greenland glacier velocity.

    PubMed

    Moon, Twila; Joughin, Ian; Smith, Ben; van den Broeke, Michiel R; van de Berg, Willem Jan; Noël, Brice; Usher, Mika

    2014-10-28

    Predicting Greenland Ice Sheet mass loss due to ice dynamics requires a complete understanding of spatiotemporal velocity fluctuations and related control mechanisms. We present a 5 year record of seasonal velocity measurements for 55 marine-terminating glaciers distributed around the ice sheet margin, along with ice-front position and runoff data sets for each glacier. Among glaciers with substantial speed variations, we find three distinct seasonal velocity patterns. One pattern indicates relatively high glacier sensitivity to ice-front position. The other two patterns are more prevalent and appear to be meltwater controlled. These patterns reveal differences in which some subglacial systems likely transition seasonally from inefficient, distributed hydrologic networks to efficient, channelized drainage, while others do not. The difference may be determined by meltwater availability, which in some regions may be influenced by perennial firn aquifers. Our results highlight the need to understand subglacial meltwater availability on an ice sheet-wide scale to predict future dynamic changes.

  13. Growth of Greenland ice sheet - Interpretation

    NASA Technical Reports Server (NTRS)

    Zwally, H. Jay

    1989-01-01

    An observed 0.23 m/year thickening of the Greenland ice sheet indicates a 25 percent to 45 percent excess ice accumulation over the amount required to balance the outward ice flow. The implied global sea-level depletion is 0.2 to 0.4 mm/year, depending on whether the thickening is only recent (5 to 10 years) or longer term (less than 100 years). If there is a similar imbalance in the northern 60 percent of the ice-sheet area, the depletion is 0.35 to 0.7 mm/year. Increasing ice thickness suggests that the precipitation is higher than the long-term average; higher precipitation may be a characteristic of warmer climates in polar regions.

  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. Drivers of River Water Temperature Space-time Variability in Northeast Greenland

    NASA Astrophysics Data System (ADS)

    Hannah, D. M.; Docherty, C.; Milner, A.

    2015-12-01

    Water temperature plays an important role in stream ecosystem functioning; however, water temperature dynamics in high Arctic environments have received relatively little attention. Given that global climate is predicted to change most at high latitudes, it is vital we broaden our knowledge of space-time variability in Arctic river temperature to understand controlling processes and potential consequences of climate change. To address this gap, our research aims: (1) to characterise seasonal and diel patterns of variability over three summer and two winter seasons with contrasting hydrometeorological conditions, (2) to unravel the key drivers influencing thermal regimes and (3) to place these results in the context of other snow/ glacier-melt dominated environments. Fieldwork was undertaken in July-September 2013, 2014 and 2015 close to the Zackenberg Research Station in Northeast Greenland - an area of continuous permafrost with a mean July air temperature of 6 °C. Five streams were chosen that drain different water source contributions (glacier melt, snow melt, groundwater). Data were collected at 30 minute intervals using micro-dataloggers. Air temperature data were collected within 7km by the Greenland Survey. Weather conditions were highly variable between field campaigns, with 2013 experiencing below average, and 2014 and 2015 above average, snowfall. Summer water temperatures appear to be high in comparison to some Arctic streams in Alaska and in Svalbard. Winter snowfall extent decreases stream water temperature; and water temperature increases with atmospheric exposure time (distance from source) - illustrating the intertwined controls of water and heat fluxes. These Greenland streams are most strongly influenced by snowmelt, but groundwater contributions could increase with a changing climate due to increased active layer thickness, which may result in increased river temperature with implications for aquatic biodiversity and ecosystem functioning.

  16. Cenozoic uplift on the West Greenland margin: active sedimentary basins in quiet Archean terranes.

    NASA Astrophysics Data System (ADS)

    Jess, Scott; Stephenson, Randell; Brown, Roderick

    2016-04-01

    The North Atlantic is believed by some authors to have experienced tectonically induced uplift within the Cenozoic. Examination of evidence, onshore and offshore, has been interpreted to imply the presence of kilometre scale uplift across the margins of the Barents Sea, North Sea, Baffin Bay and Greenland Sea. Development of topography on the West Greenland margin (Baffin Bay), in particular, has been subject to much discussion and dispute. A series of low temperature thermochronological (AFT and AHe) studies onshore and interpretation of seismic architecture offshore have suggested uplift of the entire margin totalling ~3km. However, challenges to this work and recent analysis on the opposing margin (Baffin Island) have raised questions about the validity of this interpretation. The present work reviews and remodels the thermochronological data from onshore West Greenland with the aim of re-evaluating our understanding of the margin's history. New concepts within the discipline, such as effect of radiation damage on Helium diffusivity, contemporary modelling approaches and denudational mapping are all utilised to investigate alternative interpretations to this margins complex post rift evolution. In contrast to earlier studies our new approach indicates slow protracted cooling across much of the region; however, reworked sedimentary samples taken from the Cretaceous Nuussuaq Basin display periods of rapid reheating and cooling. These new models suggest the Nuussuaq Basin experienced a tectonically active Cenozoic, while the surrounding Archean basement remained quiet. Faults located within the basin appear to have been reactivated during the Palaeocene and Eocene, a period of well-documented inversion events throughout the North Atlantic, and may have resulted in subaerial kilometre scale uplift. This interpretation of the margin's evolution has wider implications for the treatment of low temperature thermochronological data and the geological history of the North

  17. Levels and trends of radioactive contaminants in the Greenland environment.

    PubMed

    Dahlgaard, Henning; Eriksson, Mats; Nielsen, Sven P; Joensen, Hans Pauli

    2004-09-20

    Levels of radioactive contaminants in various Greenland environments have been assessed during 1999-2001. The source of 137Cs, 90Sr and (239,240)Pu in terrestrial and fresh water environments is mainly global fallout. In addition, the Chernobyl accident gave a small contribution of 137Cs. Reindeer and lamb contain the largest observed 137Cs concentrations in the terrestrial environment--up to 80 Bq kg(-1) fresh weight have been observed in reindeer. Due to special environmental conditions, 137Cs is transferred to landlocked Arctic char with extremely high efficiency in South Greenland leading to concentrations up to 100 Bq kg(-1) fresh weight. In these cases very long ecological half-lives are seen. Concentrations of 99Tc, 137Cs and 90Sr in seawater and in marine biota decrease in the order North-East Greenland and the coastal East Greenland current > South-West Greenland > Central West Greenland and North-West Greenland > Irmiger Sea-Faroe Islands. The general large-scale oceanic circulation combined with European coastal discharges and previous contamination of the Arctic Ocean causes this. As the same tendency is seen for the persistent organic pollutants (POPs) DDT and PCB in marine biota, it is suggested that long-distance oceanic transport by coastal currents is a significant pathway also for POPs in the Greenland marine environment. The peak 99Tc discharge from Sellafield 1994-1995 has only been slightly visible in the present survey year 2000. The concentrations are expected to increase in the future, especially in East Greenland. The Bylot Sound at the Thule Airbase (Pituffik) in North-West Greenland was contaminated with plutonium and enriched uranium in a weapons accident in 1968. Biological activity has mixed accident plutonium efficiently into the new sediments resulting in continued high surface sediment concentrations three decades after the accident. Transfer of plutonium to benthic biota is low--and lower than observed in the Irish Sea. This is

  18. Role of Greenland meltwater in the changing Arctic

    NASA Astrophysics Data System (ADS)

    Dukhovskoy, Dmitry; Proshutinsky, Andrey; Timmermans, Mary-Louise; Myers, Paul; Platov, Gennady; Bamber, Jonathan; Curry, Beth; Somavilla, Raquel

    2016-04-01

    Observational data show that the Arctic ocean-ice-atmosphere system has been changing over the last two decades. Arctic change is manifest in the atypical behavior of the climate indices in the 21st century. Before the 2000s, these indices characterized the quasi-decadal variability of the Arctic climate related to different circulation regimes. Between 1948 and 1996, the Arctic atmospheric circulation alternated between anticyclonic circulation regimes and cyclonic circulation regimes with a period of 10-15 years. Since 1997, however, the Arctic has been dominated by an anticyclonic regime. Previous studies indicate that in the 20th century, freshwater and heat exchange between the Arctic Ocean and the sub-Arctic seas were self-regulated and their interactions were realized via quasi-decadal climate oscillations. What physical processes in the Arctic Ocean - sub-Arctic ocean-ice-atmosphere system are responsible for the observed changes in Arctic climate variability? The presented work is motivated by our hypothesis that in the 21st century, these quasi-decadal oscillations have been interrupted as a result of an additional freshwater source associated with Greenland Ice Sheet melt. Accelerating since the early 1990s, the Greenland Ice Sheet mass loss exerts a significant impact on thermohaline processes in the sub-Arctic seas. Surplus Greenland freshwater, the amount of which is about a third of the freshwater volume fluxed into the region during the 1970s Great Salinity Anomaly event, can spread and accumulate in the sub-Arctic seas influencing convective processes there. It is not clear, however, whether Greenland freshwater can propagate into the interior convective regions in the Labrador Sea and the Nordic Seas. In order to investigate the fate and pathways of Greenland freshwater in the sub-Arctic seas and to determine how and at what rate Greenland freshwater propagates into the convective regions, several numerical experiments using a passive tracer to

  19. Instrumentation for single-dish observations with The Greenland Telescope

    NASA Astrophysics Data System (ADS)

    Grimes, Paul K.; Asada, K.; Blundell, R.; Burgos, R.; Chang, H.-H.; Chen, M. T.; Goldie, D.; Groppi, C.; Han, C. C.; Ho, P. T. P.; Huang, Y. D.; Inoue, M.; Kubo, D.; Koch, P.; Leech, J.; de Lera Acedo, E.; Martin-Cocher, P.; Nishioka, H.; Nakamura, M.; Matsushita, S.; Paine, S. N.; Patel, N.; Raffin, P.; Snow, W.; Sridharan, T. K.; Srinivasan, R.; Thomas, C. N.; Tong, E.; Wang, M.-J.; Wheeler, C.; Withington, S.; Yassin, G.; Zeng, L.-Z.

    2014-07-01

    The Greenland Telescope project will deploy and operate a 12m sub-millimeter telescope at the highest point of the Greenland i e sheet. The Greenland Telescope project is a joint venture between the Smithsonian As- trophysical Observatory (SAO) and the Academia Sinica Institute of Astronomy and Astrophysics (ASIAA). In this paper we discuss the concepts, specifications, and science goals of the instruments being developed for single-dish observations with the Greenland Telescope, and the coupling optics required to couple both them and the mm-VLBI receivers to antenna. The project will outfit the ALMA North America prototype antenna for Arctic operations and deploy it to Summit Station,1 a NSF operated Arctic station at 3,100m above MSL on the Greenland I e Sheet. This site is exceptionally dry, and promises to be an excellent site for sub-millimeter astronomical observations. The main science goal of the Greenland Telescope is to carry out millimeter VLBI observations alongside other telescopes in Europe and the Americas, with the aim of resolving the event horizon of the super-massive black hole at the enter of M87. The Greenland Telescope will also be outfitted for single-dish observations from the millimeter-wave to Tera-hertz bands. In this paper we will discuss the proposed instruments that are currently in development for the Greenland Telescope - 350 GHz and 650 GHz heterodyne array receivers; 1.4 THz HEB array receivers and a W-band bolometric spectrometer. SAO is leading the development of two heterodyne array instruments for the Greenland Telescope, a 48- pixel, 325-375 GHz SIS array receiver, and a 4 pixel, 1.4 THz HEB array receiver. A key science goal for these instruments is the mapping of ortho and para H2D+ in old protostellar ores, as well as general mapping of CO and other transitions in molecular louds. An 8-pixel prototype module for the 350 GHz array is currently being built for laboratory and operational testing on the Greenland Telescope

  20. Model Projections of an Imminent Transition to a More Arid Climate in Southwestern North America

    NASA Astrophysics Data System (ADS)

    Seager, Richard; Ting, Mingfang; Held, Isaac; Kushnir, Yochanan; Lu, Jian; Vecchi, Gabriel; Huang, Huei-Ping; Harnik, Nili; Leetmaa, Ants; Lau, Ngar-Cheung; Li, Cuihua; Velez, Jennifer; Naik, Naomi

    2007-05-01

    How anthropogenic climate change will affect hydroclimate in the arid regions of southwestern North America has implications for the allocation of water resources and the course of regional development. Here we show that there is a broad consensus among climate models that this region will dry in the 21st century and that the transition to a more arid climate should already be under way. If these models are correct, the levels of aridity of the recent multiyear drought or the Dust Bowl and the 1950s droughts will become the new climatology of the American Southwest within a time frame of years to decades.

  1. Model projections of an imminent transition to a more arid climate in southwestern North America.

    PubMed

    Seager, Richard; Ting, Mingfang; Held, Isaac; Kushnir, Yochanan; Lu, Jian; Vecchi, Gabriel; Huang, Huei-Ping; Harnik, Nili; Leetmaa, Ants; Lau, Ngar-Cheung; Li, Cuihua; Velez, Jennifer; Naik, Naomi

    2007-05-25

    How anthropogenic climate change will affect hydroclimate in the arid regions of southwestern North America has implications for the allocation of water resources and the course of regional development. Here we show that there is a broad consensus among climate models that this region will dry in the 21st century and that the transition to a more arid climate should already be under way. If these models are correct, the levels of aridity of the recent multiyear drought or the Dust Bowl and the 1950s droughts will become the new climatology of the American Southwest within a time frame of years to decades.

  2. (abstract) Geological Tour of Southwestern Mexico

    NASA Technical Reports Server (NTRS)

    Adams, Steven L.; Lang, Harold R.

    1993-01-01

    Nineteen Landsat Themic Mapper quarter scenes, coregistered at 28.5 m spatial resolution with three arc second digital topographic data, were used to create a movie, simulating a flight over the Guerrero and Mixteco terrains of southwestern Mexico. The flight path was chosen to elucidate important structural, stratigraphic, and geomorphic features. The video, available in VHS format, is a 360 second animation consisting of 10 800 total frames. The simulated velocity during three 120 second flight segments of the video is approximately 37 000 km per hour, traversing approximately 1 000 km on the ground.

  3. Monitoring Fires in Southwestern Amazonia Rain Forests

    NASA Astrophysics Data System (ADS)

    Brown, I. Foster; Schroeder, Wilfrid; Setzer, Alberto; de Los Rios Maldonado, Monica; Pantoja, Nara; Duarte, Alejandro; Marengo, Jose

    2006-06-01

    From mid-July to mid-October 2005, an environmental disaster unfolded in the trinational region of Madre de Dios, Peru; Acre, Brazil; and Pando, Bolivia (the MAP region), in southwestern Amazonia. A prolonged dry season and human-initiated fires resulted in smoke pollution affecting more than 400,000 persons, fire damage to over 300,000 hectares of rain forest, and over US$50 million of direct economic losses. Indicators suggest that anomalous drought conditions could occur again this year.

  4. The instrumental climate history of southwestern Colorado

    SciTech Connect

    Doesken, N.J.; McKee, T.B.

    1995-09-01

    Instrumental observations of the climate of southwestern Colorado date back to about 1880. Climatic conditions since the late 19th century will be described with emphasis on temperatures, temperature ranges and observed precipitation. Typical seasonal patterns of temperature and precipitation will be shown, and variations and apparent trends over time will be discussed. Drought characteristics will be described based on a standardized precipitation index developed for Colorado. Finally, brief comments on the challenge of collecting accurate and consistent long-term data will be given.

  5. Unusual phytoplankton bloom phenology in the northern Greenland Sea during 2010

    NASA Astrophysics Data System (ADS)

    Qu, Bo; Gabric, Albert J.; Lu, Zhifeng; Li, Hehe; Zhao, Li

    2016-12-01

    Arctic marine ecosystems are disproportionately impacted by global warming. Sea ice plays an important role in the regional climate system and the loss of perennial sea ice has diverse ecological implications. Here we investigate the causes of an unusually early and strong phytoplankton bloom in the northern Greenland Sea (20°W-10°E, 75°N-80°N) during the 2010 season. In order to better understand the anomalous bloom in 2010, we examine the correlation between satellite-derived biomass and several possible environmental factors for the period 2003-2012. Results show that the timing of sea ice melt played an important role in promoting the growth of phytoplankton. Multivariate lagged regression analysis shows that phytoplankton biomass (CHL) is correlated with ice concentration (ICE) and ice melting, as well as sea surface temperature (SST) and photosynthetically active radiation (PAR). During 2010, the spring peak in biomass came much earlier and achieved a higher value than most other years in the satellite archive record, which was due to earlier and more extensive sea ice melt in that year. Relative lower SST and PAR in spring and early summer in year 2010 associated with a persistent negative North Atlantic Oscillation (NAO) index were possible drivers of the bloom. Wind direction changed from the southeast to southwest direction in spring, possibly transporting nutrient enriched melt runoff from glaciers on Greenland and other sources from the south to northern coastal regions.

  6. Reconstruction of Greenland and Antarctica Mass Changes Prior to the GRACE Mission

    NASA Astrophysics Data System (ADS)

    Nerem, R. Steven; Talpe, Matthieu; Pilinski, Emily; Lemoine, Frank G.; Chinn, Douglas S.

    2013-04-01

    Low order coefficients of the gravity field can be determined using conventional satellite tracking data such satellite laser ranging (SLR) and DORIS, a method that extends the gravitational data record across multiple decades. More recently, the Gravity Recovery and Climate Experiment (GRACE) mission has contributed monthly solutions of the gravity field to degree and order 60, which have led to fundamental advances in our knowledge of changes in the distribution of water across the planet. In particular, GRACE has provided new insight into mass changes in Greenland and Antarctica. The objective of this work is to extend mass change data beyond the ten years of the GRACE mission using SLR data that both predates the GRACE mission and is expected to continue beyond it. This work uses a technique to fuse the two data sets by applying empirical orthogonal function (EOF) analysis to the GRACE data to isolate the temporal variability and spatial maps associated with the critical modes of mass change. The EOF modes are then reconstructed using the conventional tracking data allowing for a comparison of reconstructed EOF modes and GRACE data products. We will show results from reconstructing Greenland and Antarctica mass changes during the GRACE mission (to validate the technique) as well as prior to the launch of the GRACE mission in 2002. The technique also has important implications for bridging potential gaps between the GRACE and GRACE Follow On missions.

  7. Recent Changes in the Greenland Ice Sheet as Seen from Space

    NASA Technical Reports Server (NTRS)

    Hall, Dorothy K.

    2011-01-01

    Many changes in the Greenland Ice Sheet have been reported in the recent scientific literature and have been attributed to various responses of the ice sheet due to regional (and global) warming. Because melting of the ice sheet would contribute approximately 7 m to sea-level rise, the lives and habitat of hundreds of millions of people worldwide would be directly and indirectly affected if continued ice-sheet melting occurs. As mean-annual global temperatures have increased, there has been an increasing focus on studying the Greenland Ice Sheet using available satellite data, and numerous expeditions have been undertaken. Regional "clear-sky" surface temperature increases since the early 1980s in the Arctic, measured using Advanced Very High Resolution Radiometer (AVHRR) infrared data, range from 0.57+/-0.02 C to 0.72+/-0.10 C per decade. Arctic warming has important implications for ice-sheet mass balance because much of the periphery of the Greenland Ice Sheet is already near O C during the melt season, and is thus vulnerable to more extensive melting if temperatures continue to increase. An increase in melting of the ice sheet would accelerate sea-level rise, an issue of increasing concern to billions of people worldwide. The surface temperature of the ice sheet has been studied in even greater detail using Moderate-Resolution Imaging Spectroradiometer (MODIS) data in the six individual drainage basins as well as for the ice sheet as a whole. Surface temperature trends in the decade of the 2000s have not been strong, according to the MODIS measurements. In addition to surface-temperature increases over the last few decades as measured by AVHRR, other changes have been observed such as accelerated movement of many of Greenland's outlet glaciers and sudden draining of supraglacial lakes. Decreasing mass of the ice sheet since (at least) 2002 has been measured using Gravity Recovery and Climate Experiment (GRACE) data, along with an build-up of ice at the higher

  8. Transformational Leadership and Teacher Motivation in Southwestern Arizona High Schools

    ERIC Educational Resources Information Center

    Reynolds, Catherine L.

    2009-01-01

    The purpose of this study was to explore the relationship between transformational leadership and teacher motivation in Southwestern Arizona high schools. Teachers in a school district in Southwestern Arizona comprised of high schools were surveyed using two instruments, Leithwood and Jantzi's (1998) The Leadership and Management of Schools in…

  9. 78 FR 64494 - Southwestern Power Administration; Notice of Filing

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-10-29

    ... Energy Regulatory Commission Southwestern Power Administration; Notice of Filing Take notice that on...), confirmed, approved, and placed in effect on an interim basis in Rate Order SWPA- 67, Southwestern Power Administration annual rate for the sale of power and energy from the Rayburn Project to the Sam Rayburn...

  10. 77 FR 65679 - Southwestern Power Administration; Notice of Filing

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-10-30

    ... Energy Regulatory Commission Southwestern Power Administration; Notice of Filing Take notice that on..., Southwestern Power Administration annual rate for the sale of power and energy from the Willis Project to the Sam Rayburn Municipal Power Agency. Any person desiring to intervene or to protest this filing...

  11. 78 FR 64494 - Southwestern Power Administration; Notice of Filing

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-10-29

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF ENERGY Federal Energy Regulatory Commission Southwestern Power Administration; Notice of Filing Take notice that on...), confirmed, approved, and placed in effect on an interim basis in Rate Order SWPA- 66, Southwestern...

  12. 77 FR 5247 - Southwestern Power Administration; Notice of Filing

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-02-02

    ... Energy Regulatory Commission Southwestern Power Administration; Notice of Filing Take notice that on... in Rate Order SWPA-63, Southwestern Power Administration Integrated System Rates, Rate Schedule P-11, Wholesale Rates for Hydro Peaking Power, Rate Schedule NFTS-11, Wholesale Rates for Non-Federal...

  13. 77 FR 3766 - Southwestern Gas Storage Technical Conference

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-01-25

    ... interested parties to discuss issues related to natural gas storage development in the southwestern United... Energy Regulatory Commission Southwestern Gas Storage Technical Conference Notice of Public Conference On... interests associated with storage development. In addition, staff has reached out to other...

  14. How warm was Greenland during the last interglacial period?

    NASA Astrophysics Data System (ADS)

    Landais, Amaelle; Masson-Delmotte, Valérie; Capron, Emilie; Langebroek, Petra M.; Bakker, Pepijn; Stone, Emma J.; Merz, Niklaus; Raible, Christoph C.; Fischer, Hubertus; Orsi, Anaïs; Prié, Frédéric; Vinther, Bo; Dahl-Jensen, Dorthe

    2016-09-01

    The last interglacial period (LIG, ˜ 129-116 thousand years ago) provides the most recent case study of multimillennial polar warming above the preindustrial level and a response of the Greenland and Antarctic ice sheets to this warming, as well as a test bed for climate and ice sheet models. Past changes in Greenland ice sheet thickness and surface temperature during this period were recently derived from the North Greenland Eemian Ice Drilling (NEEM) ice core records, northwest Greenland. The NEEM paradox has emerged from an estimated large local warming above the preindustrial level (7.5 ± 1.8 °C at the deposition site 126 kyr ago without correction for any overall ice sheet altitude changes between the LIG and the preindustrial period) based on water isotopes, together with limited local ice thinning, suggesting more resilience of the real Greenland ice sheet than shown in some ice sheet models. Here, we provide an independent assessment of the average LIG Greenland surface warming using ice core air isotopic composition (δ15N) and relationships between accumulation rate and temperature. The LIG surface temperature at the upstream NEEM deposition site without ice sheet altitude correction is estimated to be warmer by +8.5 ± 2.5 °C compared to the preindustrial period. This temperature estimate is consistent with the 7.5 ± 1.8 °C warming initially determined from NEEM water isotopes but at the upper end of the preindustrial period to LIG temperature difference of +5.2 ± 2.3 °C obtained at the NGRIP (North Greenland Ice Core Project) site by the same method. Climate simulations performed with present-day ice sheet topography lead in general to a warming smaller than reconstructed, but sensitivity tests show that larger amplitudes (up to 5 °C) are produced in response to prescribed changes in sea ice extent and ice sheet topography.

  15. Development of a Climate-Data Record (CDR) of the Surface Temperature of the Greenland Ice Sheet

    NASA Technical Reports Server (NTRS)

    Hall, Dorthy K.; Comiso, Josefino C.; Shuman, Christopher A.; DiGirolamo, Nicolo E.; Stock, Larry V.

    2010-01-01

    Regional "clear sky" surface temperature increases since the early 1980s in the Arctic, measured using Advanced Very High Resolution Radiometer (AVHRR) infrared data, range from 0.57+/-0.02 deg C to 72+/-0.10 deg C per decade. Arctic warming has important implications for ice-sheet mass balance because much of the periphery of the Greenland Ice Sheet is already near 0 deg C during the melt season, and is thus vulnerable to rapid melting if temperatures continue to increase. An increase in melting of the ice sheet would accelerate sea-level rise, an issue affecting potentially billions of people worldwide. To quantify the ice-surface temperature (IST) of the Greenland Ice Sheet, and to provide an IST dataset of Greenland for modelers that provides uncertainties, we are developing a climate-data record (CDR) of daily "clear-sky" IST of the Greenland Ice Sheet, from 1982 to the present using AVHRR (1982 - present) and Moderate-Resolution Imaging Spectroradiometer (MODIS) data (2000 - present) at a resolution of approximately 5 km. Known issues being addressed in the production of the CDR are: time-series bias caused by cloud cover (surface temperatures can be different under clouds vs. clear areas) and cross-calibration in the overlap period between AVHRR instruments, and between AVHRR and MODIS instruments. Because of uncertainties, mainly due to clouds, time-series of satellite IST do not necessarily correspond with actual surface temperatures. The CDR will be validated by comparing results with automatic-weather station data and with satellite-derived surface-temperature products and biases will be calculated.

  16. On the Origins of the Recent Greenland Melt in the US 2012 Heat Wave

    NASA Astrophysics Data System (ADS)

    Neff, W. D.; Shupe, M.; Ralph, F. M.; Compo, G.; Turner, D. D.

    2012-12-01

    present in June and July 1889 during positive anomalies in surface temperatures over this two-month period. During one such event on 30 July 1889, a strong trough-ridge pattern had set up, potentially bringing warm southerly flow from the eastern US to Greenland. One of the unique features of the most recent event was prolonged drought and high temperatures over North America during the spring and summer of 2012 - an implication being that having a persistent source of unusually warm air over North America, coupled with a relatively rare, and short-lived negative anomaly in the AO created almost perfect conditions for the warming of Greenland above the freezing point. This is one example of how an extreme event that appears to be part of the general picture of a warming Arctic may in fact have its origins in the mid-latitudes.

  17. The sea bottom temperature offshore southwestern Taiwan

    NASA Astrophysics Data System (ADS)

    Chiang, H.; Shyu, C.; Peng, Y.; Chang, H.; Chen, S.; Chung, S.; Wang, Y.

    2012-12-01

    The sea bottom temperature (SBT) is important to apply to the heat flow estimation by BSR. Also the SBT may response the fluid migration near subsurface. Here we present 150 measurements of SBT offshore southwestern Taiwan where abundant gas hydrates has been evaluated. The SBT data were acquired by the heat probe with high resolution up to 0.0001°C. Thermal gradients were determined from several temperature sensors installed in different depth in the heat probe and then the SBT could be calculated by extrapolation. The results show that the SBT are between 2.23 and 10.14°C in water depth within the range of 409 to 3248 meters. Basically, the SBT is inversely hyperbolic proportional to the water depth for those 132 measurements the water depth are shallower than 2650 meters. The product of SBT and water depth has an average of 4419 m-°C and a standard deviation of 402 m-°C. However the SBT of others 18 measurements in the deep water region are scattered without any significant trend. Some measurements near mud diapirs in the shallow water have high anomaly SBT. It is suggested that the fluid from deep underground may migrate along the fractures or faults related to the movements of the mud volume.; The sea bottom temperature offshore southwestern Taiwan

  18. Tobacco Use Among Southwestern Alaska Native People

    PubMed Central

    Renner, Caroline C.

    2013-01-01

    Introduction: We examined the characteristics, attitudes, beliefs, and exposure to tobacco products in a cohort of rural dwelling Alaska Native (AN) people. Methods: We conducted a study of 400 of AN adult tobacco users and nonusers living in Southwestern Alaska. Questionnaires covered variables such as demographics, tobacco-use history, current tobacco use and dependence scales, general health status, attitudes and beliefs about tobacco, and quitting history. Results: The study population smoked 7.8 cigarettes per day compared with 16.8 on average for the U.S. population: a significant proportion of the population engaged in dual use of cigarettes and smokeless tobacco products. Over one third (40.9%), first tried tobacco at age 11 or younger. The mean measures of tobacco addiction (e.g., Fagerstrom Test for Nicotine Dependence, Severson Scale of Smokeless Tobacco Dependence) scores were lower compared with other U.S. populations. Conclusions: Very high tobacco-use prevalence, dual product use, and early tobacco use are observed in Southwestern AN people. Unexpectedly these did not appear to be correlated with heavier individual tobacco use or higher levels of addiction in this population. PMID:22949573

  19. Effect of microorganism on Greenland ice sheet surface temperature change

    NASA Astrophysics Data System (ADS)

    Shimada, R.; Takeuchi, N.; Aoki, T.

    2012-12-01

    Greenland ice sheet holds approximately 10% of the fresh water on earth. If it melts all, sea level rises about 7.2meter. It is reported that mass of Greenland ice sheet is decreasing with temperature rising of climate change. Melting of the coastal area is particularly noticeable. It is established that 4 to 23% of the sea level rising from 1993 to 2005 is caused by the melting of Greenland ice sheet. In 2010, amount of melting per year became the largest than the past. However many climate models aren't able to simulate the recent melting of snow and ice in the Arctic including Greenland. One of the possible causes is albedo reduction of snow and ice surface by light absorbing snow impurities such as black carbon and dust and by glacial microorganisms. But there are few researches for effect of glacial microorganism in wide area. So it is important to clarify the impact of glacial microorganisms in wide area. The purpose of this study is to clarify the effect of microorganism on Greenland ice sheet surface temperature change using satellite images of visible, near infrared and thermal infrared wavelength range and observation carried out in northwestern Greenland. We use MODIS Land Surface Temperature Product as ice sheet surface temperature. It estimates land surface temperature based on split window method using thermal infrared bands. MODIS data is bound to cover the whole of Greenland, and calculated the ratio of the temperature change per year. Analysis period is from December 2002 to November 2010. Results of calculating Greenland ice sheet surface temperature change using the MODIS data, our analysis shows that it is upward trend in the whole region. We find a striking upward trend in northern and western part of Greenland. The rate is 0.33±0.03 degree Celsius per a year from 47.5°W to 49°W. While in the coastal area from 49°W to 50.7°W, the rate is 0.26±0.06 degree Celsius per a year. This large upward trend area is the same area as dark region

  20. Resolving bathymetry from airborne gravity along Greenland fjords

    NASA Astrophysics Data System (ADS)

    Boghosian, Alexandra; Tinto, Kirsty; Cochran, James R.; Porter, David; Elieff, Stefan; Burton, Bethany L.; Bell, Robin E.

    2015-12-01

    Recent glacier mass loss in Greenland has been attributed to encroaching warming waters, but knowledge of fjord bathymetry is required to investigate this mechanism. The bathymetry in many Greenland fjords is unmapped and difficult to measure. From 2010 to 2012, National Aeronautics and Space Administration's Operation IceBridge collected a unique set of airborne gravity, magnetic, radar, and lidar data along the major outlet glaciers and fjords in Greenland. We applied a consistent technique using the IceBridge gravity data to create 90 bathymetric profiles along 54 Greenland fjords. We also used this technique to recover subice topography where warm or crevassed ice prevents the radar system from imaging the bed. Here we discuss our methodology, basic assumptions and error analysis. We present the new bathymetry data and discuss observations in six major regions of Greenland covered by IceBridge. The gravity models provide a total of 1950 line kilometers of bathymetry, 875 line kilometers of subice topography, and 12 new grounding line depths.

  1. Resolving bathymetry from airborne gravity along Greenland fjords

    USGS Publications Warehouse

    Boghosian, Alexandra; Tinto, Kirsty; Cochran, James R.; Porter, David; Elieff, Stefan; Burton, Bethany; Bell, Robin E.

    2015-01-01

    Recent glacier mass loss in Greenland has been attributed to encroaching warming waters, but knowledge of fjord bathymetry is required to investigate this mechanism. The bathymetry in many Greenland fjords is unmapped and difficult to measure. From 2010 to 2012, National Aeronautics and Space Administration's Operation IceBridge collected a unique set of airborne gravity, magnetic, radar, and lidar data along the major outlet glaciers and fjords in Greenland. We applied a consistent technique using the IceBridge gravity data to create 90 bathymetric profiles along 54 Greenland fjords. We also used this technique to recover subice topography where warm or crevassed ice prevents the radar system from imaging the bed. Here we discuss our methodology, basic assumptions and error analysis. We present the new bathymetry data and discuss observations in six major regions of Greenland covered by IceBridge. The gravity models provide a total of 1950 line kilometers of bathymetry, 875 line kilometers of subice topography, and 12 new grounding line depths.

  2. How warm was Greenland during the last interglacial period?

    NASA Astrophysics Data System (ADS)

    Landais, Amaelle; Masson-Delmotte, Valérie; Capron, Emilie; Langenbroeck, Petra; Bakker, Pepijn; Stone, Emma; Fischer, Hubertus; Vinther, Bo; Dahl-Jensen, Dorthe

    2016-04-01

    The last interglacial period (LIG, ~129-116 thousand years ago) provides the most recent evidence for the response of Greenland and Antarctic ice sheets to polar warming above pre-industrial level, and a valuable test bed for ice sheet models. Key constraints on past changes in both ice sheet topography and surface temperature are derived from Greenland ice cores. The large warming estimated from the recent NEEM ice core drilled in northwest Greenland (8 ±4°C above pre-industrial) together with the evidence for limited local ice thinning have led to the "NEEM paradox", suggesting more stability of the ice sheet than simulated by ice flow models in response to such large warming. Here, we provide a new assessment of the LIG warming using ice core air isotopic composition (d15N) together with available relationships for Greenland between accumulation rate and temperature. The temperature at the upstream NEEM deposition site is estimated to be between -20°C to -24°C which is consistent with the 8±4°C warming relative to pre-industrial previously determined from water isotopic records measured on the NEEM ice, although we feel the lower end of this range to be more likely. Moreover, we show that under such warm temperature, melting of snow probably led to a significant firn shrinking by 15 m. We show that confirmation of this high temperature range for the LIG in Greenland is difficult to reconcile with climate modeling experiments

  3. Exploring Greenland: science and technology in Cold War settings.

    PubMed

    Heymann, Matthias; Knudsen, Henrik; Lolck, Maiken L; Nielsen, Henry; Nielsen, Kristian H; Ries, Christopher J

    2010-01-01

    This paper explores a vacant spot in the Cold War history of science: the development of research activities in the physical environmental sciences and in nuclear science and technology in Greenland. In the post-war period, scientific exploration of the polar areas became a strategically important element in American and Soviet defence policy. Particularly geophysical fields like meteorology, geology, seismology, oceanography, and others profited greatly from military interest. While Denmark maintained formal sovereignty over Greenland, research activities were strongly dominated by U.S. military interests. This paper sets out to summarize the limited current state of knowledge about activities in the environmental physical sciences in Greenland and their entanglement with military, geopolitical, and colonial interests of both the USA and Denmark. We describe geophysical research in the Cold War in Greenland as a multidimensional colonial endeavour. In a period of decolonization after World War II, Greenland, being a Danish colony, became additionally colonized by the American military. Concurrently, in a period of emerging scientific internationalism, the U.S. military "colonized" geophysical research in the Arctic, which increasingly became subject to military directions, culture, and rules.

  4. Modeling deep convection in the Greenland Sea

    NASA Technical Reports Server (NTRS)

    Hakkinen, S.; Mellor, G. L.; Kantha, L. H.

    1992-01-01

    The development of deep convective events in the high-latitude ocean is studied using a three-dimensional, coupled ice-ocean model. Oceanic mixing is described according to the level 2.5 turbulence closure scheme in which convection occurs in a continuous way, i.e., convective adjustment is not invoked. The model is forced by strong winds and surface cooling. Strong upwelling at the multilyear ice edge and consequent entrainment of warm Atlantic waters into the mixed layer is produced by winds parallel to the ice edge. Concomitant cooling drives deep convection and produces chimneylike structures. Inclusion of a barotropic mean flow over topography to the model provides important preconditioning and selects the location of deep convection. The most efficient preconditioning occurs at locations where the flow ascends a slope. In a stratified environment similar to the Greenland Sea with a 12 m/s wind the model simulations show that localized deep convection takes place after about 10 days to depths of 1000 m.

  5. Greenland ice sheet mass balance: a review.

    PubMed

    Khan, Shfaqat A; Aschwanden, Andy; Bjørk, Anders A; Wahr, John; Kjeldsen, Kristian K; Kjær, Kurt H

    2015-04-01

    Over the past quarter of a century the Arctic has warmed more than any other region on Earth, causing a profound impact on the Greenland ice sheet (GrIS) and its contribution to the rise in global sea level. The loss of ice can be partitioned into processes related to surface mass balance and to ice discharge, which are forced by internal or external (atmospheric/oceanic/basal) fluctuations. Regardless of the measurement method, observations over the last two decades show an increase in ice loss rate, associated with speeding up of glaciers and enhanced melting. However, both ice discharge and melt-induced mass losses exhibit rapid short-term fluctuations that, when extrapolated into the future, could yield erroneous long-term trends. In this paper we review the GrIS mass loss over more than a century by combining satellite altimetry, airborne altimetry, interferometry, aerial photographs and gravimetry data sets together with modelling studies. We revisit the mass loss of different sectors and show that they manifest quite different sensitivities to atmospheric and oceanic forcing. In addition, we discuss recent progress in constructing coupled ice-ocean-atmosphere models required to project realistic future sea-level changes.

  6. Force balance along Isunnguata Sermia, west Greenland

    NASA Astrophysics Data System (ADS)

    Meierbachtol, Toby; Harper, Joel; Johnson, Jesse

    2016-09-01

    Ice flows when gravity acts on gradients in surface elevation, producing driving stresses. In the Isunnguata Sermia and Russel Glacier catchments of western Greenland, a 50% decline in driving stress along a flow line is juxtaposed with increasing surface flow speed. Here, these circumstances are investigated using modern observational data sources and an analysis of the balance of forces. Stress gradients in the ice mass and basal drag which resist the local driving stress are computed in order to investigate the underlying processes influencing the velocity and stress regimes. Our results show that the largest resistive stress gradients along the flowline result from increasing surface velocity. However, the longitudinal coupling stresses fail to exceed 15 kPa, or 20% of the local driving stress. Consequently, computed basal drag declines in proportion to the driving stress. In the absence of significant resistive stress gradients, other mechanisms are therefore necessary to explain the observed velocity increase despite declining driving stress. In the study area, the observed velocity - driving stress feature occurs at the long-term mean position of the equilibrium line of surface mass balance. We hypothesize that this position approximates the inland limit where surface meltwater penetrates the bed, and that the increased surface velocity reflects enhanced basal motion associated with seasonal meltwater perturbations.

  7. Distinct patterns of seasonal Greenland glacier velocity

    PubMed Central

    Moon, Twila; Joughin, Ian; Smith, Ben; van den Broeke, Michiel R; van de Berg, Willem Jan; Noël, Brice; Usher, Mika

    2014-01-01

    Predicting Greenland Ice Sheet mass loss due to ice dynamics requires a complete understanding of spatiotemporal velocity fluctuations and related control mechanisms. We present a 5 year record of seasonal velocity measurements for 55 marine-terminating glaciers distributed around the ice sheet margin, along with ice-front position and runoff data sets for each glacier. Among glaciers with substantial speed variations, we find three distinct seasonal velocity patterns. One pattern indicates relatively high glacier sensitivity to ice-front position. The other two patterns are more prevalent and appear to be meltwater controlled. These patterns reveal differences in which some subglacial systems likely transition seasonally from inefficient, distributed hydrologic networks to efficient, channelized drainage, while others do not. The difference may be determined by meltwater availability, which in some regions may be influenced by perennial firn aquifers. Our results highlight the need to understand subglacial meltwater availability on an ice sheet-wide scale to predict future dynamic changes. Key Points First multi-region seasonal velocity measurements show regional differences Seasonal velocity fluctuations on most glaciers appear meltwater controlled Seasonal development of efficient subglacial drainage geographically divided PMID:25821275

  8. What influences climate and glacier change in southwestern China?

    NASA Astrophysics Data System (ADS)

    Yasunari, Teppei J.

    2011-12-01

    The subject of climate change in the Tibetan Plateau (TP) and Himalayas has taken on increasing importance because of the availability of water resources from their mountain glaciers (Immerzeel et al 2010). Many of the glaciers over these regions have been retreating, while some are advancing and stable (Yao et al 2004, Scherler et al 2011). Other studies report that some glaciers in the Himalayas show acceleration of their shrinkage (e.g., Fujita and Nuimura 2011). However, the causes of glacier melting are still difficult to grasp because of the complexity of climatic change and its influence on glacier issues. Despite this, it is vital that we pursue further study to enable future predictions of glacier changes. The paper entitled 'Climate and glacier change in southwestern China during the past several decades' by Li et al (2011) provided carefully analyzed, quality controlled, long-term data on atmospheric temperature and precipitation during the period 1961-2008. The data were obtained from 111 Chinese stations. The researchers performed systematic analyses of temperature and precipitation over the whole southwestern Chinese domain. They discussed those changes in terms of other meteorological components such as atmospheric circulation patterns, radiation and altitude difference, and then showed how these factors could contribute to climate and glacier changes in the region. Air temperature and precipitation are strongly associated with glacier mass balance because of heat balance and the addition of mass when it snows. Temperature warming trends over many places in southwestern China were unequivocally dominant in all seasons and at higher altitudes. This indicates that the heat contribution to the glaciers has been increasing. On the other hand, precipitation has a wider variability in time and space. It is more difficult to clearly understand the effect of precipitation on the climate and glacier melting characteristics in the whole of southwestern China

  9. Paleoclimate. Synchronization of North Pacific and Greenland climates preceded abrupt deglacial warming.

    PubMed

    Praetorius, Summer K; Mix, Alan C

    2014-07-25

    Some proposed mechanisms for transmission of major climate change events between the North Pacific and North Atlantic predict opposing patterns of variations; others suggest synchronization. Resolving this conflict has implications for regulation of poleward heat transport and global climate change. New multidecadal-resolution foraminiferal oxygen isotope records from the Gulf of Alaska (GOA) reveal sudden shifts between intervals of synchroneity and asynchroneity with the North Greenland Ice Core Project (NGRIP) δ(18)O record over the past 18,000 years. Synchronization of these regions occurred 15,500 to 11,000 years ago, just prior to and throughout the most abrupt climate transitions of the last 20,000 years, suggesting that dynamic coupling of North Pacific and North Atlantic climates may lead to critical transitions in Earth's climate system.

  10. Greenland Ice Sheet: High-Elevation Balance and Peripheral Thinning.

    PubMed

    Krabill; Abdalati; Frederick; Manizade; Martin; Sonntag; Swift; Thomas; Wright; Yungel

    2000-07-21

    Aircraft laser-altimeter surveys over northern Greenland in 1994 and 1999 have been coupled with previously reported data from southern Greenland to analyze the recent mass-balance of the Greenland Ice Sheet. Above 2000 meters elevation, the ice sheet is in balance on average but has some regions of local thickening or thinning. Thinning predominates at lower elevations, with rates exceeding 1 meter per year close to the coast. Interpolation of our results between flight lines indicates a net loss of about 51 cubic kilometers of ice per year from the entire ice sheet, sufficient to raise sea level by 0.13 millimeter per year-approximately 7% of the observed rise.

  11. Subglacial lake drainage detected beneath the Greenland ice sheet

    PubMed Central

    Palmer, Steven; McMillan, Malcolm; Morlighem, Mathieu

    2015-01-01

    The contribution of the Greenland ice sheet to sea-level rise has accelerated in recent decades. Subglacial lake drainage events can induce an ice sheet dynamic response—a process that has been observed in Antarctica, but not yet in Greenland, where the presence of subglacial lakes has only recently been discovered. Here we investigate the water flow paths from a subglacial lake, which drained beneath the Greenland ice sheet in 2011. Our observations suggest that the lake was fed by surface meltwater flowing down a nearby moulin, and that the draining water reached the ice margin via a subglacial tunnel. Interferometric synthetic aperture radar-derived measurements of ice surface motion acquired in 1995 suggest that a similar event may have occurred 16 years earlier, and we propose that, as the climate warms, increasing volumes of surface meltwater routed to the bed will cause such events to become more common in the future. PMID:26450175

  12. Subglacial lake drainage detected beneath the Greenland ice sheet.

    PubMed

    Palmer, Steven; McMillan, Malcolm; Morlighem, Mathieu

    2015-10-09

    The contribution of the Greenland ice sheet to sea-level rise has accelerated in recent decades. Subglacial lake drainage events can induce an ice sheet dynamic response--a process that has been observed in Antarctica, but not yet in Greenland, where the presence of subglacial lakes has only recently been discovered. Here we investigate the water flow paths from a subglacial lake, which drained beneath the Greenland ice sheet in 2011. Our observations suggest that the lake was fed by surface meltwater flowing down a nearby moulin, and that the draining water reached the ice margin via a subglacial tunnel. Interferometric synthetic aperture radar-derived measurements of ice surface motion acquired in 1995 suggest that a similar event may have occurred 16 years earlier, and we propose that, as the climate warms, increasing volumes of surface meltwater routed to the bed will cause such events to become more common in the future.

  13. Greenland temperature response to climate forcing during the last deglaciation.

    PubMed

    Buizert, Christo; Gkinis, Vasileios; Severinghaus, Jeffrey P; He, Feng; Lecavalier, Benoit S; Kindler, Philippe; Leuenberger, Markus; Carlson, Anders E; Vinther, Bo; Masson-Delmotte, Valérie; White, James W C; Liu, Zhengyu; Otto-Bliesner, Bette; Brook, Edward J

    2014-09-05

    Greenland ice core water isotopic composition (δ(18)O) provides detailed evidence for abrupt climate changes but is by itself insufficient for quantitative reconstruction of past temperatures and their spatial patterns. We investigate Greenland temperature evolution during the last deglaciation using independent reconstructions from three ice cores and simulations with a coupled ocean-atmosphere climate model. Contrary to the traditional δ(18)O interpretation, the Younger Dryas period was 4.5° ± 2°C warmer than the Oldest Dryas, due to increased carbon dioxide forcing and summer insolation. The magnitude of abrupt temperature changes is larger in central Greenland (9° to 14°C) than in the northwest (5° to 9°C), fingerprinting a North Atlantic origin. Simulated changes in temperature seasonality closely track changes in the Atlantic overturning strength and support the hypothesis that abrupt climate change is mostly a winter phenomenon.

  14. Deformation Studies of NEEM, Greenland Basal Folded Ice

    NASA Astrophysics Data System (ADS)

    Keegan, K.; Dahl-Jensen, D.; Montagnat, M.; Weikusat, I.

    2015-12-01

    Deep Greenland ice cores and airborne radio echo sounding (RES) images have recently revealed that basal ice flow of the Greenland Ice Sheet is very unstable. In many locations, a basal layer of disturbed ice is observed. At the NEEM, Greenland site this folding occurs at the boundary between the Eemian and glacial ice regimes, indicating that differences in physical properties of the ice play a role in the disturbance. Past work in metallurgy and ice suggests that impurity content controls grain evolution and therefore deformation. We hypothesize that the differences in ice flow seen deep in the NEEM ice core are controlled by differences in the impurity content of the ice layers. Here we present results of fabric, grain size, impurity content, and deformation studies from samples above and below this unstable boundary in the ice sheet.

  15. Sparteine oxidation polymorphism in Greenlanders living in Denmark.

    PubMed Central

    Brøsen, K

    1986-01-01

    Sparteine oxidation appeared to be polymorphic in 185 healthy Greenlanders living in Denmark. Six subjects (3.2%) were phenotyped as poor metabolizers (PM) and 179 subjects as extensive metabolizers (EM). The metabolic ratio (MR) between sparteine and 2- + 5-dehydrosparteine in a 12 h urine sample ranged from 0.06-3.12 in EM and from 30-480 in PM. The excretion of dehydrosparteines accounted for less than 2.2% of the dose in PM and ranged from 5.6%-63% in EM. The urinary recovery (% of dose) of sparteine, 2-dehydrosparteine and total sparteine + dehydrosparteines was lower in Greenlander EM than in Danish EM (Brøsen et al., 1985). Incomplete urine collection in a substantial proportion of the Greenlanders could explain these discrepancies. PMID:3768256

  16. Greenland ice mass balance estimation from GRACE: a reexamination

    NASA Astrophysics Data System (ADS)

    Jensen, L.; Eicker, A.; Kusche, J.

    2011-12-01

    In recent years there have been several studies using GRACE satellite data to investigate the melting of the Greenland ice sheet. The results of the different investigations vary considerably. In this study, monthly GRACE solutions calculated by the Institute of Geodesy and Geoinformation of the University Bonn (ITG-GRACE2010 solutions) are evaluated to obtain a new estimate for the mass balance of the Greenland ice sheet including the corresponding error estimate. One of the major issues when dealing with the mass variations in Greenland is the leakage problem. In the contribution at hand, leakage-in effects caused by external mass variations are adressed by estimating a regional adjustment of the applied ocean model. The approach assumes time-invariant spatial patterns of ocean mass variations to be correctly reproduced in the circulation model but their time-variable amplitudes to be improvable. New amplitudes are determined by comparison to the GRACE observations in a least-squares estimation process. Leakage-out can be compensated for by rescaling the ice mass changes with a constant factor. In addition to a simple technique, a more complex approach developed by Baur et al. (2009) is applied in this investigation to obtain the rescaling factor. Besides mass variations in the area of Greenland also mass variations in an extended area around Greenland are taken into account in this procedure. A further important aspect is the problem of signal separation, especially separating the ice mass variations from mass trends caused by glacial isostatic adjustment (GIA). A comparison of different GIA models shows why this is one of the major sources of uncertainty when trying to determine the Greenland ice mass balance. The possibility to improve GIA modelling using geodetic data is therefore another aspect which will be discussed on the poster. The results of the new ice mass balance estimate from GRACE will be compared to the results obtained from alternative

  17. Evolution of the elevated passive margin of northwest Greenland

    NASA Astrophysics Data System (ADS)

    Spiegel, Cornelia; Reiter, Wolfgang; Lisker, Frank; Damm, Volkmar

    2015-04-01

    The geomorphic evolution of high-standing passive continental margins is still controversially discussed. This is particularly true for the elevated margins of Greenland. They have alternatively been explained by resulting from prolonged very slow erosion following Paleozoic orogeny, resulting from rifting and opening of ocean basins adjacent to the Greenland continental margins, or as young geomorphic features only formed during the Cenozoic. This study focuses on the northwestern margin of Greenland, north of the Melville Bugt at the northern end of Baffin Bay, using a combination of apatite fission track and (U-Th-Sm)/He thermochronology. Opening and formation of oceanic crust of Baffin Bay took place during the Late Cretaceous. The study area is also situated at the southern termination of the postulated Wegener Fault, a controversially discussed large-scale strike-slip fault system supposedly active during the Paleogene, which has been described as one of the last problems of global plate tectonic reconstructions. Our data show that several normal faults dissecting the northwest Greenland margin were active during or after the Cretaceous, presumably related to extension associated with the opening of Baffin Bay. Also, our data show a clear - although not very pronounced - cooling signal at the end of the Cretaceous, which we interpret as reflecting initial formation of an elevated margin during and after continental breakup. Margin formation was followed by subsidence, with maximum burial at c. 30 Ma, again followed by a period of relatively rapid exhumation associated with net denudation of 2 - 3 km. This post-30 Ma denudation period may be related to tectonic activity associated with ongoing northward movement of Greenland, or to climatic changes such as early glaciation of the Arctic realm. In any case, our data imply that the present morphologic expression of the northwest Greenland margin results from young Cenozoic processes unrelated to earlier

  18. Leakage of the Greenland Ice Sheet through accelerated ice flow

    NASA Astrophysics Data System (ADS)

    Rignot, E.

    2005-12-01

    A map of coastal velocities of the Greenland ice sheet was produced from Radarsat-1 acquired during the background mission of 2000 and combined with radio echo sounding data to estimate the ice discharge from the ice sheet. On individual glaciers, ice discharge was compared with snow input from the interior and melt above the flux gate to determine the glacier mass balance. Time series of velocities on several glaciers at different latitudes reveal seasonal fluctuations of only 7-8 percent so that winter velocities are only 2 percent less than the yearly mean. The results show the northern Greenland glaciers to be close to balance yet losing mass. No change in ice flow is detected on Petermann, 79north and Zachariae Isstrom in 2000-2004. East Greenland glaciers are in balance and flowing steadily north of Kangerdlussuaq, but Kangerdlussuaq, Helheim and all the southeastern glaciers are thinning dramatically. All these glaciers accelerated, Kangerdlussuaq in 2000, Helheim prior to 2004, and southeast Greenland glaciers accelerated 10 to 50 percent in 2000-2004. Glacier acceleration is generally brutal, probably once the glacier reached a threshold, and sustained. In the northwest, most glaciers are largely out of balance. Jakobshavn accelerated significantly in 2002, and glaciers in its immediate vicinity accelerated more than 50 percent in 2000-2004. Less is known about southwest Greenland glaciers due to a lack of ice thickness data but the glaciers have accelerated there as well and are likely to be strongly out of balance despite thickening of the interior. Overall, I estimate the mass balance of the Greenland ice sheet to be about -80 +/-10 cubic km of ice per year in 2000 and -110 +/-15 cubic km of ice per year in 2004, i.e. more negative than based on partial altimetry surveys of the outlet glaciers. As climate continues to warm, more glaciers will accelerate, and the mass balance will become increasingly negative, regardless of the evolution of the ice sheet

  19. Vanadium and Other Elements in Greenland Ice Cores

    DTIC Science & Technology

    1976-07-01

    Photograph by C’.C. Langway , Jr.) :1 CRREL Report 76-24 Vanadium and other elements in Greenland ice cores M.M. Herron, C.C. Langway , Jr., H.V. Weiss...Chemistry, San Diego State University; by Dr. C.C. Langway , Jr., Chairman of the Department of Geological Sciences, State University of New. York at Buffalo...the use of such commercial products. ij! 𔃼y\\ .j =3 VANADIUM AND OTHER ELEMENTS IN GREENLAND ICE CORES M.M. Herron;C.C. Langway , Jr., H.V.,Weiss, J

  20. Control and monitoring software for the Greenland Telescope

    NASA Astrophysics Data System (ADS)

    Patel, Nimesh A.; Nishioka, Hiroaki; Huang, Chih-Wei Locutus

    2016-08-01

    The Greenland Telescope (GLT) is a 12m diameter antenna that is being developed from the ALMA North America prototype antenna, for VLBI observations and single-dish science approaching THz, at the Summit station in Greenland. The GLT is a collaboration between the Smithsonian Astrophysical Observatory and the Academia Sinica Institute of Astronomy and Astrophysics. We describe the control and monitoring software that is being developed for GLT. The present version of the software is ready for the initial tests of the antenna at Thule, including optical and radio pointing calibration, holography, and VLBI observations at 230 GHz.

  1. Surface Drifters Track the Fate of Greenland Ice Sheet Meltwater

    NASA Astrophysics Data System (ADS)

    Hauri, Claudine; Truffer, Martin; Winsor, Peter; Lennert, Kunuk

    2014-07-01

    Understanding the fate and influence of glacial meltwater in heavily ice-covered fjord systems has proven difficult because previous measurement platforms were con­strained to deeper water to keep instrumentation safe from drifting icebergs. Now, using novel, satellite-tracked devices that can with­ stand multiple collisions with ice blocks (see Figure 1) without incurring much damage, scientists have obtained new and detailed data about the role of Greenland Ice Sheet meltwater and its trajectories through God­thåbsfjord in western Greenland.

  2. Smoking as a determinant of high organochlorine levels in Greenland.

    PubMed

    Deutch, Bente; Pedersen, Henning Sloth; Jørgensen, Eva C Bonefeld; Hansen, Jens C

    2003-01-01

    The authors investigated the accumulation of organochlorines among smoking and nonsmoking Inuit hunters (n = 48) in Uummanaq, Greenland, a population with high dietary exposure to persistent organic pollutants (POPs). Human plasma organochlorine levels were positively correlated with age, marine diet, and smoking or plasma cotinine in multiple linear-regression models (p < 0.001). Body mass index was inversely correlated with organochlorine accumulation, independent of smoking status. These findings confirm that the source of POPs among the Inuit in Greenland is diet, but smoking is an important determinant of POP bioaccumulation. Smoking cessation may provide a means to lower the body burden of POPs.

  3. North and northeast Greenland ice discharge from satellite radar interferometry

    SciTech Connect

    Rignot, E.J.; Gogineni, S.P.; Krabill, W.B.

    1997-05-09

    Ice discharge from north and northeast Greenland calculated from satellite radar interferometry data of 14 outlet glaciers is 3.5 times that estimated from iceberg production. The satellite estimates, obtained at the grounding line of the outlet glaciers, differ from those obtained at the glacier front, because basal melting is extensive at the underside of the floating glacier sections. The results suggest that the north and northeast parts of the Greenland ice sheet may be thinning and contributing positively to sea-level rise. 24 refs., 3 figs., 1 tab.

  4. Operation of a Radar Altimeter over the Greenland Ice Sheet

    NASA Technical Reports Server (NTRS)

    Grund, Matthew D.

    1996-01-01

    This thesis presents documentation for the Advanced Application Flight Experiment (AAFE) pulse compression radar altimeter and its role in the NASA Multisensor Airborne Altimetry Experiment over Greenland in 1993. The AAFE Altimeter is a Ku-band microwave radar which has demonstrated 14 centimeter range precision in operation over arctic ice. Recent repairs and improvements were required to make the Greenland missions possible. Transmitter, receiver and software modifications, as well as the integration of a GPS receiver are thoroughly documented. Procedures for installation, and operation of the radar are described. Finally, suggestions are made for further system improvements.

  5. Environmental Assessment for power marketing policy for Southwestern Power Administration

    SciTech Connect

    Not Available

    1993-12-01

    Southwestern Power Administration (Southwestern) needs to renew expiring power sales contracts with new term (10 year) sales contracts. The existing contracts have been in place for several years and many will expire over the next ten years. Southwestern completed an Environmental Assessment on the existing power allocation in June, 1979 (a copy of the EA is attached), and there are no proposed additions of any major new generation resources, service to discrete major new loads, or major changes in operating parameters, beyond those included in the existing power allocation. Impacts from a no action plan, proposed alternative, and market power for less than 10 years are described.

  6. Late glacial and Holocene history of the Greenland Ice Sheet margin, Nunatarssuaq, Northwestern Greenland

    NASA Astrophysics Data System (ADS)

    Farnsworth, L. B.; Kelly, M. A.; Axford, Y.; Bromley, G. R.; Osterberg, E. C.; Howley, J. A.; Zimmerman, S. R. H.; Jackson, M. S.; Lasher, G. E.; McFarlin, J. M.

    2015-12-01

    Defining the late glacial and Holocene fluctuations of the Greenland Ice Sheet (GrIS) margin, particularly during periods that were as warm or warmer than present, provides a longer-term perspective on present ice margin fluctuations and informs how the GrIS may respond to future climate conditions. We focus on mapping and dating past GrIS extents in the Nunatarssuaq region of northwestern Greenland. During the summer of 2014, we conducted geomorphic mapping and collected rock samples for 10Be surface exposure dating as well as subfossil plant samples for 14C dating. We also obtained sediment cores from an ice-proximal lake. Preliminary 10Be ages of boulders deposited during deglaciation of the GrIS subsequent to the Last Glacial Maximum range from ~30-15 ka. The apparently older ages of some samples indicate the presence of 10Be inherited from prior periods of exposure. These ages suggest deglaciation occurred by ~15 ka however further data are needed to test this hypothesis. Subfossil plants exposed at the GrIS margin on shear planes date to ~ 4.6-4.8 cal. ka BP and indicate less extensive ice during middle Holocene time. Additional radiocarbon ages from in situ subfossil plants on a nunatak date to ~3.1 cal. ka BP. Geomorphic mapping of glacial landforms near Nordsø, a large proglacial lake, including grounding lines, moraines, paleo-shorelines, and deltas, indicate the existence of a higher lake level that resulted from a more extensive GrIS margin likely during Holocene time. A fresh drift limit, characterized by unweathered, lichen-free clasts approximately 30-50 m distal to the modern GrIS margin, is estimated to be late Holocene in age. 10Be dating of samples from these geomorphic features is in progress. Radiocarbon ages of subfossil plants exposed by recent retreat of the GrIS margin suggest that the GrIS was at or behind its present location at AD ~1650-1800 and ~1816-1889. Results thus far indicate that the GrIS margin in northwestern Greenland

  7. A new bed elevation dataset for Greenland

    NASA Astrophysics Data System (ADS)

    Griggs, J. A.; Bamber, J. L.; Hurkmans, R. T. W. L.; Dowdesewell, J. A.; Gogineni, S. P.; Howat, I.; Mouginot, J.; Paden, J.; Palmer, S.; Rignot, E.; Steinhage, D.

    2012-11-01

    We present a new bed elevation dataset for Greenland derived from a combination of multiple airborne ice thickness surveys undertaken between the 1970s and 2011. Around 344 000 line kilometres of airborne data were used, with the majority of this having been collected since the year 2000, when the last comprehensive compilation was undertaken. The airborne data were combined with satellite-derived elevations for non glaciated terrain to produce a consistent bed digital elevation model (DEM) over the entire island including across the glaciated/ice free boundary. The DEM was extended to the continental margin with the aid of bathymetric data, primarily from a compilation for the Arctic. Ice shelf thickness was determined where a floating tongue exists, in particular in the north. The across-track spacing between flight lines warranted interpolation at 1 km postings near the ice sheet margin and 2.5 km in the interior. Grids of ice surface elevation, error estimates for the DEM, ice thickness and data sampling density were also produced alongside a mask of land/ocean/grounded ice/floating ice. Errors in bed elevation range from a minimum of ±6 m to about ±200 m, as a function of distance from an observation and local topographic variability. A comparison with the compilation published in 2001 highlights the improvement in resolution afforded by the new data sets, particularly along the ice sheet margin, where ice velocity is highest and changes most marked. We use the new bed and surface DEMs to calculate the hydraulic potential for subglacial flow and present the large scale pattern of water routing. We estimate that the volume of ice included in our land/ice mask would raise eustatic sea level by 7.36 m, excluding any solid earth effects that would take place during ice sheet decay.

  8. A new bed elevation dataset for Greenland

    NASA Astrophysics Data System (ADS)

    Bamber, J. L.; Griggs, J. A.; Hurkmans, R. T. W. L.; Dowdeswell, J. A.; Gogineni, S. P.; Howat, I.; Mouginot, J.; Paden, J.; Palmer, S.; Rignot, E.; Steinhage, D.

    2013-03-01

    We present a new bed elevation dataset for Greenland derived from a combination of multiple airborne ice thickness surveys undertaken between the 1970s and 2012. Around 420 000 line kilometres of airborne data were used, with roughly 70% of this having been collected since the year 2000, when the last comprehensive compilation was undertaken. The airborne data were combined with satellite-derived elevations for non-glaciated terrain to produce a consistent bed digital elevation model (DEM) over the entire island including across the glaciated-ice free boundary. The DEM was extended to the continental margin with the aid of bathymetric data, primarily from a compilation for the Arctic. Ice thickness was determined where an ice shelf exists from a combination of surface elevation and radar soundings. The across-track spacing between flight lines warranted interpolation at 1 km postings for significant sectors of the ice sheet. Grids of ice surface elevation, error estimates for the DEM, ice thickness and data sampling density were also produced alongside a mask of land/ocean/grounded ice/floating ice. Errors in bed elevation range from a minimum of ±10 m to about ±300 m, as a function of distance from an observation and local topographic variability. A comparison with the compilation published in 2001 highlights the improvement in resolution afforded by the new datasets, particularly along the ice sheet margin, where ice velocity is highest and changes in ice dynamics most marked. We estimate that the volume of ice included in our land-ice mask would raise mean sea level by 7.36 m, excluding any solid earth effects that would take place during ice sheet decay.

  9. Collaborating with the local community of Kullorsuaq, Greenland to obtain high-quality hydrographic measurements near Alison Glacier

    NASA Astrophysics Data System (ADS)

    Porter, D. F.; Turrin, M.; Tinto, K. J.; Giulivi, C. F.; Cochran, J. R.; Bell, R. E.

    2014-12-01

    Warming ocean waters around Greenland have been implicated, along with warmer air temperatures, in the rapid increase of melt of the tidewater glaciers that drain the ice sheet. Most available regional oceanographic measurements have been collected during the summer seasons and are concentrated near the largest and most accessible glaciers. In order to gain a more comprehensive picture of the changing environment around the entirety of Greenland, more fjords, especially in the north, must be sampled. In July 2014, we travelled to Kullorsuaq in Northwest Greenland in order to foster a partnership with the local community to obtain new hydrographic data from CTD casts near Alison Glacier (74.6N, 57W). The terminus of this glacier abruptly retreated 10 km between 2000 and 2006. Although adequate observations from that time period are unavailable, our recently collected temperature and salinity data suggests that the deep water near Alison is similar to the waters further south, where near-synchronous ocean warming and glacial acceleration has been documented. Over the course of two sampling days, a hand-operated winch from a small boat was used to make standard CTD casts in front of Alison Glacier. We find evidence of glacial and mélange melt and the signature of both Polar and Atlantic Water masses at depth. Along-fjord casts illustrate how the ocean waters are modified as they circulate in and out of the fjord and the interaction of this water with the melting glacial front. At 500m depths, ocean temperatures are about 3°C above the in-situ freezing point of seawater, suggesting a possible influence of warm ocean waters on the mass loss of Alison Glacier. Using NASA Operation IceBridge and satellite altimetry data, we relate our new hydrographic data to the observed recent changes in Alison Glacier. An additional important result is that this short field campaign uncovered the possibility of working with local Greenlandic communities to aid scientists in both

  10. Measurements of snow grain hydroxyl radical at Summit, Greenland

    NASA Astrophysics Data System (ADS)

    Anastasio, C.; Galbavy, E.; Hutterli, M.; Friel, D.; Bales, R.

    2004-12-01

    Sunlit snowpacks release a number of volatile organic compounds (VOCs) such as formaldehyde and other carbonyls, carboxylic acids, alkenes, and alkyl halides. It has been hypothesized that this flux of VOCs to the overlying atmosphere is in part due to reactions of hydroxyl radical (OH) with snowgrain organic matter. Recent laboratory measurements by Grannas et al. support this idea by showing that the photolysis of polar snow releases formaldehyde, and that this release is enhanced by the addition of nitrate, a photochemical source of OH. In addition to its effects on organic chemistry, OH is probably also important in other snowpack reactions such as the oxidation of halides to form volatile, reactive gaseous halogens. However, the possible role of OH in these reactions has not been quantified. To begin to address the importance of OH in snowpack chemistry, we have measured the photochemical formation of hydroxyl radicals on snow grains at Summit, Greenland during the spring and summer. Measurements were made using a chemical probe technique where benzoate is added to the snow sample in order to scavenge OH and convert it into p-hydroxybenzoate, which is measured by HPLC. We found that OH is formed on snow grains during both seasons and that the rate of formation in the summer was more than an order of magnitude greater than the typical springtime value. Expressed on a bulk (melted) snow volume basis, the average summer value was approximately 200 nM/hr. Assuming that this reactivity occurs within a snowgrain "quasi-liquid layer" (QLL) that represents approximately 0.001% of the bulk liquid volume, rates of OH photoformation in the QLL are on the order of 10 mM/hr. The possible implications of this enormous rate of OH formation for snowpack chemistry (e.g., for VOC release) will be discussed. We have also examined the relative importance of nitrate and hydrogen peroxide as sources of photoformed OH on snow grains at Summit. Based on quantum yields determined in

  11. Bone foreshafts from a clovis burial in southwestern montana.

    PubMed

    Lahren, L; Bonnichsen, R

    1974-10-11

    Formal and functional analyses of bone artifacts from a Clovis burial in southwestern Montana suggest that they were constructed to serve as (detachable or nondetachable) foreshafts for attaching fluted projectile points to lance shafts.

  12. 7. DETAIL VIEW OF SOUTHWESTERN CORNER OF BRIDGE AND FOUNDATION, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    7. DETAIL VIEW OF SOUTHWESTERN CORNER OF BRIDGE AND FOUNDATION, SHOWING TRACES OF CONCRETE POURING DURING CONSTRUCTION AND EMBEDDED IRON HARDWARE ON OUTER FACE OF PARAPET. FACING NORTHEAST - Brevard Bridge, Spanning Westland Run at Ullom Road, Export, Washington County, PA

  13. Greenland ice sheet motion insensitive to exceptional meltwater forcing.

    PubMed

    Tedstone, Andrew J; Nienow, Peter W; Sole, Andrew J; Mair, Douglas W F; Cowton, Thomas R; Bartholomew, Ian D; King, Matt A

    2013-12-03

    Changes to the dynamics of the Greenland ice sheet can be forced by various mechanisms including surface-melt-induced ice acceleration and oceanic forcing of marine-terminating glaciers. We use observations of ice motion to examine the surface melt-induced dynamic response of a land-terminating outlet glacier in southwest Greenland to the exceptional melting observed in 2012. During summer, meltwater generated on the Greenland ice sheet surface accesses the ice sheet bed, lubricating basal motion and resulting in periods of faster ice flow. However, the net impact of varying meltwater volumes upon seasonal and annual ice flow, and thus sea level rise, remains unclear. We show that two extreme melt events (98.6% of the Greenland ice sheet surface experienced melting on July 12, the most significant melt event since 1889, and 79.2% on July 29) and summer ice sheet runoff ~3.9 σ above the 1958-2011 mean resulted in enhanced summer ice motion relative to the average melt year of 2009. However, despite record summer melting, subsequent reduced winter ice motion resulted in 6% less net annual ice motion in 2012 than in 2009. Our findings suggest that surface melt-induced acceleration of land-terminating regions of the ice sheet will remain insignificant even under extreme melting scenarios.

  14. 34 First Callisto solar burst spectrometer station in Greenland

    NASA Astrophysics Data System (ADS)

    Monstein, Christian

    2016-04-01

    In mid of March 2016 a new long wavelength station in Greenland was set into operation. It is a dual circular polarization, frequency agile solar radio burst spectrometer based on two Callisto spectrometers and the Long Wavelength Array antenna. During the commissioning phase several nice radio burst observations proved that the system works as expected.

  15. 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".

  16. Greenland ice sheet motion insensitive to exceptional meltwater forcing

    PubMed Central

    Tedstone, Andrew J.; Nienow, Peter W.; Sole, Andrew J.; Mair, Douglas W. F.; Cowton, Thomas R.; Bartholomew, Ian D.; King, Matt A.

    2013-01-01

    Changes to the dynamics of the Greenland ice sheet can be forced by various mechanisms including surface-melt–induced ice acceleration and oceanic forcing of marine-terminating glaciers. We use observations of ice motion to examine the surface melt–induced dynamic response of a land-terminating outlet glacier in southwest Greenland to the exceptional melting observed in 2012. During summer, meltwater generated on the Greenland ice sheet surface accesses the ice sheet bed, lubricating basal motion and resulting in periods of faster ice flow. However, the net impact of varying meltwater volumes upon seasonal and annual ice flow, and thus sea level rise, remains unclear. We show that two extreme melt events (98.6% of the Greenland ice sheet surface experienced melting on July 12, the most significant melt event since 1889, and 79.2% on July 29) and summer ice sheet runoff ∼3.9σ above the 1958–2011 mean resulted in enhanced summer ice motion relative to the average melt year of 2009. However, despite record summer melting, subsequent reduced winter ice motion resulted in 6% less net annual ice motion in 2012 than in 2009. Our findings suggest that surface melt–induced acceleration of land-terminating regions of the ice sheet will remain insignificant even under extreme melting scenarios. PMID:24248343

  17. Assessment of Glacial Isostatic Adjustment in Greenland using GPS

    NASA Astrophysics Data System (ADS)

    Khan, S. A.; Bevis, M. G.; Sasgen, I.; van Dam, T. M.; Wahr, J. M.; Wouters, B.; Bamber, J. L.; Willis, M. J.; Knudsen, P.; Helm, V.; Kuipers Munneke, P.; Muresan, I. S.

    2015-12-01

    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) predictions by analysing 1995-2015 data from 61 continuous GPS receivers located along the margin of the Greenland ice sheet. Since GPS receivers measure both the GIA and elastic signals, we isolate GIA, by removing the elastic adjustments of the lithosphere due to present-day mass changes using high-resolution fields of ice surface elevation change derived from satellite and airborne altimetry measurements (ERS1/2, ICESat, ATM, ENVISAT, and CryoSat-2). For most GPS stations, our observed GIA rates contradict GIA predictions; particularly, we find huge uplift rates in southeast Greenland of up to 14 mm/yr while models predict rates of 0-2 mm/yr. Our results suggest possible improvements of GIA predictions, and hence of the poorly constrained ice load history and Earth structure models for Greenland.

  18. A high-resolution record of Greenland mass balance

    NASA Astrophysics Data System (ADS)

    McMillan, Malcolm; Leeson, Amber; Shepherd, Andrew; Briggs, Kate; Armitage, Thomas W. K.; Hogg, Anna; Kuipers Munneke, Peter; Broeke, Michiel; Noël, Brice; Berg, Willem Jan; Ligtenberg, Stefan; Horwath, Martin; Groh, Andreas; Muir, Alan; Gilbert, Lin

    2016-07-01

    We map recent Greenland Ice Sheet elevation change at high spatial (5 km) and temporal (monthly) resolution using CryoSat-2 altimetry. After correcting for the impact of changing snowpack properties associated with unprecedented surface melting in 2012, we find good agreement (3 cm/yr bias) with airborne measurements. With the aid of regional climate and firn modeling, we compute high spatial and temporal resolution records of Greenland mass evolution, which correlate (R = 0.96) with monthly satellite gravimetry and reveal glacier dynamic imbalance. During 2011-2014, Greenland mass loss averaged 269 ± 51 Gt/yr. Atmospherically driven losses were widespread, with surface melt variability driving large fluctuations in the annual mass deficit. Terminus regions of five dynamically thinning glaciers, which constitute less than 1% of Greenland's area, contributed more than 12% of the net ice loss. This high-resolution record demonstrates that mass deficits extending over small spatial and temporal scales have made a relatively large contribution to recent ice sheet imbalance.

  19. Ground penetrating radar (GPR) measurements at Mittivakkat Gletscher, Southeast Greenland

    NASA Astrophysics Data System (ADS)

    Clement Yde, Jacob; Løland, Ronny; Ruud, Henry; Mernild, Sebastian H.; Riger-Kusk, Mette; de Villiers, Simon; Tvis Knudsen, N.; Malmros, Jeppe K.

    2014-05-01

    Here, we present ground penetrating radar (GPR) measurements conducted on the surface of Mittivakkat Gletscher in Southeast Greenland (the only long-term mass balance observed glacier in Greenland) and estimate the change in ice volume over an 18 year period. Between a previous direct volume survey in 1994 and the new GPR survey in 2012, the glacier has changed its volume from 2.02 ± 0.10 to 1.50 ± 0.08 km3 while the study area has decreased from 17.6 to 15.8 km2. These results are in accordance with the cumulative mass loss observed by long-term mass balance measurements (1995/1996 - 2011/2012) at Mittivakkat Gletscher and confirms that the glacier is in severe climatic disequilibrium (AAR = 0.17). The observed volume-area scaling exponent γ and coefficient c are outside the range of global scaling parameters, but are sensitive to small uncertainties. As Mittivakkat Gletscher is generally considered as representative of glaciers in Southeast Greenland, these findings could indicate that a regional volume-area scaling approach would provide a more accurate total glacier volume estimate for Greenland than using parameters given by global scaling relationships.

  20. The Wegener Memorial Expedition to the Greenland Caledonides

    NASA Astrophysics Data System (ADS)

    Stüwe, Kurt; Piller, Werner

    2014-05-01

    2012 marked the 100 anniversary of the publication of Alfred Wegeners book: 'Die Entstehung der Kontinente' - which is often hailed as the discovery of continental drift theory in the advent of plate tectonics. Wegener was later appointed as professor for geophysics at the University of Graz in Austria - in part for this discovery. He held this position until his death in Greenland in 1930. In honor of the hundredth anniversary of the 1912 milestone publication, the University of Graz in Austria stages an expedition to Greenland in the spirit of Alfred Wegener, supported by the Austrian Academy of Sciences. The expedition aims predominantly to unravel secrets of the Caledonides of Northeastern Greenland using an extensive sampling program to some of the least explored corners of the orogenic belt. Particular emphasis will be placed on the Hager Bjerg allochthon and its relationship to the hanging wall and footwall units. The expedition will use the unparalleled flexibility of small aircraft that will be piloted by experienced Alaskan bush pilots and brought to Greenland from Alaska for this purpose.

  1. Crustal structure of southwestern Saudi Arabia

    USGS Publications Warehouse

    Gettings, M.E.; Blank, H.R.; Mooney, W.D.; Healy, J.H.

    1983-01-01

    The southwestern Arabian Shield is composed of uplifted Proterozoic metamorphic and plutonic rocks. The Shield is bordered on the southwest by Cenozoic sedimentary and igneous rocks of the Red Sea paar and on the east by the Arabian Platform, an area of basin sedimentation throughout Phanerozoic time. The Shield appears to have been formed by successive episodes of island arc volcanism and sea-floor spreading, followed by several cycles of compressive tectonism and metamorphism. An interpretation and synthesis of a deep-refraction seismic profile from the Riyadh area to the Farasan Islands, and regional gravity, aeromagnetic, heat flow, and surface geologic data have yielded a self-consistent regional-scale model of the crust and upper mantle for this area. The model consists of two 20 km-thick layers of crust with an average compressional wave velocity in the upper crust of about 6.3 km/s and an average velocity in the lower. crust of about 7.0 km/s. This crust thins abruptly to less than 20 km near the southwestern end of the profile where Precambrian outcrops abut the Cenozoic rocks and to 8 km beneath the Farasan Islands. The data over the coastal plain and Red Sea shelf areas are fit satisfactorily by an oceanic crustal model. A major lateral velocity inhomogeneity in the crust is inferred about 25 km northeast of Sabhah and is supported by surface geologic evidence. The major velocity discontinuities occur at about the same depth across the entire Shield and are interpreted to indicate horizontal metamorphic stratification of the Precambrian crust. Several lateral inhomogenities in both the upper and lower .crust of the . Shield are interpreted, to indicate bulk compositional variations. The subcrustal portion of the model is composed of a hot, low-density lithosphere beneath the Red Sea which is systematically cooler and denser to the northeast. This model provides a mechanism which explains the observed topographic uplift, regional gravity pattern, heat

  2. Seasonal changes in Fe along a glaciated Greenlandic fjord.

    NASA Astrophysics Data System (ADS)

    Hopwood, Mark; Connelly, Douglas; Arendt, Kristine; Juul-Pedersen, Thomas; Stinchcombe, Mark; Meire, Lorenz; Esposito, Mario; Krishna, Ram

    2016-03-01

    Greenland's ice sheet is the second largest on Earth, and is under threat from a warming Arctic climate. An increase in freshwater discharge from Greenland has the potential to strongly influence the composition of adjacent water masses with the largest impact on marine ecosystems likely to be found within the glaciated fjords. Here we demonstrate that physical and chemical estuarine processes within a large Greenlandic fjord are critical factors in determining the fate of meltwater derived nutrients and particles, especially for non-conservative elements such as Fe. Concentrations of Fe and macronutrients in surface waters along Godthåbsfjord, a southwest Greenlandic fjord with freshwater input from 6 glaciers, changed markedly between the onset and peak of the meltwater season due to the development of a thin (<10 m), outflowing, low-salinity surface layer. Dissolved (<0.2 µm) Fe concentrations in meltwater entering Godthåbsfjord (200 nM), in freshly melted glacial ice (mean 38 nM) and in surface waters close to a land terminating glacial system (80 nM) all indicated high Fe inputs into the fjord in summer. Total dissolvable (unfiltered at pH <2.0) Fe was similarly high with concentrations always in excess of 100 nM throughout the fjord and reaching up to 5.0 µM close to glacial outflows in summer. Yet, despite the large seasonal freshwater influx into the fjord, Fe concentrations near the fjord mouth in the out-flowing surface layer were similar in summer to those measured before the meltwater season. Furthermore, turbidity profiles indicated that sub-glacial particulate Fe inputs may not actually mix into the outflowing surface layer of this fjord. Emphasis has previously been placed on the possibility of increased Fe export from Greenland as meltwater fluxes increase. Here we suggest that in-fjord processes may be effective at removing Fe from surface waters before it can be exported to coastal seas.

  3. Radiostratigraphy and age structure of the Greenland Ice Sheet.

    PubMed

    MacGregor, Joseph A; Fahnestock, Mark A; Catania, Ginny A; Paden, John D; Prasad Gogineni, S; Young, S Keith; Rybarski, Susan C; Mabrey, Alexandria N; Wagman, Benjamin M; Morlighem, Mathieu

    2015-02-01

    Several decades of ice-penetrating radar surveys of the Greenland and Antarctic ice sheets have observed numerous widespread internal reflections. Analysis of this radiostratigraphy has produced valuable insights into ice sheet dynamics and motivates additional mapping of these reflections. Here we present a comprehensive deep radiostratigraphy of the Greenland Ice Sheet from airborne deep ice-penetrating radar data collected over Greenland by The University of Kansas between 1993 and 2013. To map this radiostratigraphy efficiently, we developed new techniques for predicting reflection slope from the phase recorded by coherent radars. When integrated along track, these slope fields predict the radiostratigraphy and simplify semiautomatic reflection tracing. Core-intersecting reflections were dated using synchronized depth-age relationships for six deep ice cores. Additional reflections were dated by matching reflections between transects and by extending reflection-inferred depth-age relationships using the local effective vertical strain rate. The oldest reflections, dating to the Eemian period, are found mostly in the northern part of the ice sheet. Within the onset regions of several fast-flowing outlet glaciers and ice streams, reflections typically do not conform to the bed topography. Disrupted radiostratigraphy is also observed in a region north of the Northeast Greenland Ice Stream that is not presently flowing rapidly. Dated reflections are used to generate a gridded age volume for most of the ice sheet and also to determine the depths of key climate transitions that were not observed directly. This radiostratigraphy provides a new constraint on the dynamics and history of the Greenland Ice Sheet.

  4. Radiostratigraphy and age structure of the Greenland Ice Sheet

    PubMed Central

    MacGregor, Joseph A; Fahnestock, Mark A; Catania, Ginny A; Paden, John D; Prasad Gogineni, S; Young, S Keith; Rybarski, Susan C; Mabrey, Alexandria N; Wagman, Benjamin M; Morlighem, Mathieu

    2015-01-01

    Several decades of ice-penetrating radar surveys of the Greenland and Antarctic ice sheets have observed numerous widespread internal reflections. Analysis of this radiostratigraphy has produced valuable insights into ice sheet dynamics and motivates additional mapping of these reflections. Here we present a comprehensive deep radiostratigraphy of the Greenland Ice Sheet from airborne deep ice-penetrating radar data collected over Greenland by The University of Kansas between 1993 and 2013. To map this radiostratigraphy efficiently, we developed new techniques for predicting reflection slope from the phase recorded by coherent radars. When integrated along track, these slope fields predict the radiostratigraphy and simplify semiautomatic reflection tracing. Core-intersecting reflections were dated using synchronized depth-age relationships for six deep ice cores. Additional reflections were dated by matching reflections between transects and by extending reflection-inferred depth-age relationships using the local effective vertical strain rate. The oldest reflections, dating to the Eemian period, are found mostly in the northern part of the ice sheet. Within the onset regions of several fast-flowing outlet glaciers and ice streams, reflections typically do not conform to the bed topography. Disrupted radiostratigraphy is also observed in a region north of the Northeast Greenland Ice Stream that is not presently flowing rapidly. Dated reflections are used to generate a gridded age volume for most of the ice sheet and also to determine the depths of key climate transitions that were not observed directly. This radiostratigraphy provides a new constraint on the dynamics and history of the Greenland Ice Sheet. Key Points Phase information predicts reflection slope and simplifies reflection tracing Reflections can be dated away from ice cores using a simple ice flow model Radiostratigraphy is often disrupted near the onset of fast ice flow PMID:26213664

  5. Muscle plasticity of Inuit sled dogs in Greenland.

    PubMed

    Gerth, Nadine; Sum, Steffen; Jackson, Sue; Starck, J Matthias

    2009-04-01

    This study examined flexible adjustments of skeletal muscle size, fiber structure, and capillarization in Inuit sled dogs responding to seasonal changes in temperature, exercise and food supply. Inuit dogs pull sleds in winter and are fed regularly throughout this working season. In summer, they remain chained to rocks without exercise, receiving food intermittently and often fasting for several days. We studied two dog teams in Northern Greenland (Qaanaaq) where dogs are still draught animals vital to Inuit hunters, and one dog team in Western Greenland (Qeqertarsuaq) where this traditional role has been lost. Northern Greenland dogs receive more and higher quality food than those in Western Greenland. We used ultrasonography for repeated muscle size measurements on the same individuals, and transmission electron microscopy on micro-biopsies for summer-winter comparisons of muscle histology, also within individuals. At both study sites, dogs' muscles were significantly thinner in summer than in winter - atrophy attributable to reduced fiber diameter. Sarcomeres from West Greenland dogs showed serious myofilament depletion and expansion of the sarcoplasmatic space between myofibrils during summer. At both study sites, summer samples showed fewer interfibrillar and subsarcolemmal mitochondria, and fewer lipid droplets between myofibrils, than did winter samples. In summer, capillary density was higher and inter-capillary distance smaller than in winter, but the capillary-to-fiber-ratio and number of capillaries associated with single myofibers were constant. Increased capillary density was probably a by-product of differential tissue responses to condition changes rather than a functional adaptation, because thinning of muscle fibers in summer was not accompanied by reduction in the capillary network. Thus, skeletal muscle of Inuit dogs responds flexibly to changes in functional demands. This flexibility is based on differential changes in functional components

  6. Greenland coastal air temperatures linked to Baffin Bay and Greenland Sea ice conditions during autumn through regional blocking patterns

    NASA Astrophysics Data System (ADS)

    Ballinger, Thomas J.; Hanna, Edward; Hall, Richard J.; Miller, Jeffrey; Ribergaard, Mads H.; Høyer, Jacob L.

    2017-03-01

    Variations in sea ice freeze onset and regional sea surface temperatures (SSTs) in Baffin Bay and Greenland Sea are linked to autumn surface air temperatures (SATs) around coastal Greenland through 500 hPa blocking patterns, 1979-2014. We find strong, statistically significant correlations between Baffin Bay freeze onset and SSTs and SATs across the western and southernmost coastal areas, while weaker and fewer significant correlations are found between eastern SATs, SSTs, and freeze periods observed in the neighboring Greenland Sea. Autumn Greenland Blocking Index values and the incidence of meridional circulation patterns have increased over the modern sea ice monitoring era. Increased anticyclonic blocking patterns promote poleward transport of warm air from lower latitudes and local warm air advection onshore from ocean-atmosphere sensible heat exchange through ice-free or thin ice-covered seas bordering the coastal stations. Temperature composites by years of extreme late freeze conditions, occurring since 2006 in Baffin Bay, reveal positive monthly SAT departures that often exceed 1 standard deviation from the 1981-2010 climate normal over coastal areas that exhibit a similar spatial pattern as the peak correlations.

  7. Mycobacterium tuberculosis outbreak strain of Danish origin spreading at worrying rates among greenland-born persons in Denmark and Greenland.

    PubMed

    Lillebaek, T; Andersen, A B; Rasmussen, E M; Kamper-Jørgensen, Z; Pedersen, M K; Bjorn-Mortensen, K; Ladefoged, K; Thomsen, V O

    2013-12-01

    Transmission of Mycobacterium tuberculosis continues at high rates among Greenland-born persons in Greenland and Denmark, with 203 and 450 notified cases per 10(5) population, respectively, in the year 2010. Here, we document that the predominant M. tuberculosis outbreak strain C2/1112-15 of Danish origin has been transmitted to Greenland-born persons in Denmark and subsequently to Greenland, where it is spreading at worrying rates and adding to the already heavy tuberculosis burden in this population group. It is now clear that the C2/1112-15 strain is able to gain new territories using a new population group as the "vehicle." Thus, it might have the ability to spread even further, considering the potential clinical consequences of strain diversity such as that seen in the widely spread Beijing genotype. The introduction of the predominant M. tuberculosis outbreak strain C2/1112-15 into the Arctic circumpolar region is a worrying tendency which deserves attention. We need to monitor whether this strain already has, or will, spread to other countries.

  8. Ice stream retreat following the LGM and onset of the west Greenland current in Uummannaq Trough, west Greenland

    NASA Astrophysics Data System (ADS)

    Sheldon, Christina; Jennings, Anne; Andrews, John T.; Ó Cofaigh, Colm; Hogan, Kelly; Dowdeswell, Julian A.; Seidenkrantz, Marit-Solveig

    2016-09-01

    The deglacial history and oceanography of Uummannaq Trough, central West Greenland continental shelf, was investigated using foraminiferal, sedimentological, and bathymetric records together with a radiocarbon chronology, providing a timeline for the retreat of glacial ice after the Last Glacial Maximum (LGM). To map ice stream retreat, data were collected from cores from the outer (JR175-VC45 and JR175-VC43) and inner (JR175-VC42) Uummannaq Trough. A large ice stream, fed by confluent glaciers draining the interior of the Greenland Ice Sheet, extended across the outer shelf during the LGM and was in retreat by 15.0 cal kyr BP. Foraminiferal data indicate that the 'warm' West Greenland Current (WGC) was established prior to 14.0 cal kyr BP, which is the hitherto earliest record of Atlantic Water found on the West Greenland shelf. For each of the cores, foraminifera indicate that ice sheet retreat was followed quickly by incursion of the WGC, suggesting that the warm water may have enhanced ice retreat. Prior to the Younger Dryas cold event, the radiocarbon chronology indicates that the ice sheet retreated to the mid-shelf, where it subsequently stabilised and formed a large grounding-zone wedge (GZW). After the Younger Dryas, around 11.5 cal kyr BP, the ice retreated rapidly from the GZW and into the fjords.

  9. Cretaceous rocks from southwestern Montana to southwestern Minnesota, northern Rocky Mountains, and Great Plains

    USGS Publications Warehouse

    Dyman, T.S.; Cobban, W.A.; Fox, J.E.; Hammond, R.H.; Nichols, D.J.; Perry, W.J.; Porter, K.W.; Rice, D.D.; Setterholm, D.R.; Shurr, G.W.; Tysdal, R.G.; Haley, J.C.; Campen, E.B.

    1994-01-01

    In Montana, Wyoming, North and South Dakota, and Minnesota, Cretaceous strata are preserved in the asymmetric Western Interior foreland basin. More than 5,200 m (17,000 ft) of Cretaceous strata are present in southwestern Montana, less than 300 m (1,000 ft) in eastern South Dakota. The asymmetry resulted from varying rates of subsidence due to tectonic and sediment loading. The strata consist primarily of sandstone, siltstone, mudstone, and shale. Conglomerate is locally abundant along the western margin, whereas carbonate is present in most areas of the eastern shelf. Sediment was deposited in both marine and nonmarine environments as the shoreline fluctuated during major tectonic and eustatic cycles.A discussion of Cretaceous strata from southwestern to east-central Montana, the Black Hills, eastern South Dakota, and southwestern Minnesota shows regional stratigraphy and facies relations, sequence, boundaries, and biostratigraphic and radiometric correlations. The thick Cretaceous strata in southwestern Montana typify nonmarine facies of the rapidly subsiding westernmost part of the basin. These strata include more than 3,000 m (10,000 ft) of synorogenic conglomerate of the Upper Cretaceous part of the Beaverhead Group. West of the Madison Range, sequence boundaries bracket the Kootenai (Aptian and Albian), the Blackleaf (Albian and Cenomanian), and the Frontier Formations (Cenomanian and Turonian); sequence boundaries are difficult to recognize because the rocks are dominantly non-marine. Cretaceous strata in east-central Montana (about 1,371 m; 4,500 ft thick) lie at the approximate depositional axis of the basin and are mostly marine terrigenous rocks. Chert-pebble zones in these rocks reflect stratigraphic breaks that may correlate with sequence boundaries to the east and west. Cretaceous rocks of the Black Hills region consist of a predominantly marine clastic sequence averaging approximately 1,524 m (5,000 ft) thick. The Cretaceous System in eastern South

  10. Orogenic gold mineralisation hosted by Archaean basement rocks at Sortekap, Kangerlussuaq area, East Greenland

    NASA Astrophysics Data System (ADS)

    Holwell, D. A.; Jenkin, G. R. T.; Butterworth, K. G.; Abraham-James, T.; Boyce, A. J.

    2013-04-01

    Paleogene mafic intrusions. The identification of this occurrence of orogenic-style Au mineralisation has implications for exploration in the underexplored area of east Greenland between 62 and 69° N, where other, similar supracrustal units are known to be present.

  11. Reconstructing the history of major Greenland glaciers since the Little Ice Age

    NASA Astrophysics Data System (ADS)

    Csatho, B. M.; Schenk, A. F.; van der Veen, C. J.; Stearns, L.; Babonis, G. S.

    2008-12-01

    The Greenland Ice Sheet may have been responsible for rapid sea level rise during the last interglacial period and recent studies indicate that it is likely to make a faster contribution to sea-level rise than previously believed. Rapid thinning and velocity increase has been observed on most major outlet glaciers with terminus retreat that might lead to increased discharge from the interior and consequent further thinning and retreat. Potentially, such behavior could have serious implications for global sea level. However, the current thinning may simply be a manifestation of longer-term behavior of the ice sheet as it responds to the general warming following the Little Ice Age (LIA). Although Greenland outlet glaciers have been comprehensively monitored since the 1980s, studies of long-term changes mostly rely on records of the calving front position. Such records can be misleading because the glacier terminus, particularly if it is afloat, can either advance or retreat as ice further upstream thins and accelerates. To assess whether recent trends deviate from longer-term behavior, we examined three rapidly thinning and retreating outlet glaciers, Jakobshavn Isbrae in west, Kangerdlussuaq Glacier in east and Petermann Glacier in northwest Greenland. Glacier surface and trimline elevations, as well as terminus positions were measured using historical photographs and declassified satellite imagery acquired between the 1940s and 1985. These results were combined with data from historical records, ground surveys, airborne laser altimetry, satellite observations and field mapping of lateral moraines and trimlines, to reconstruct the history of changes since the (LIA) up to the present. We identified several episodes of rapid thinning and ice shelf break-up, including thinning episodes that occurred when the calving front was stationary. Coastal weather station data are used to assess the influence of air temperatures and intensity of surface melting, and to isolate

  12. The Subglacial Access and Fast Ice Research Experiment - SAFIRE - on Store Glacier, West Greenland

    NASA Astrophysics Data System (ADS)

    Christoffersen, P.; Hubbard, B. P.; Doyle, S. H.; Young, T. J.; Hofstede, C. M.; Bougamont, M. H.; Todd, J.; Toberg, N.; Nicholls, K. W.; Box, J.; Walter, J. I.; Hubbard, A.

    2015-12-01

    Marine-terminating outlet glaciers drain 90 percent of the Greenland Ice Sheet and are responsible for about half of the ice sheet's net annual mass loss, which currently raises global sea level by 1 mm per year. The basal controls on these fast-flowing glaciers are, however, poorly understood, with the implication that numerical ice sheet models needed to predict future dynamic ice loss from Greenland relies on uncertain and often untested basal parameterizations. The Subglacial Access and Fast Ice Research Experiment - SAFIRE - is addressing this paucity of observational constraints by drilling to the bed of Store Glacier, a fast-flowing outlet glacier terminating in Uummannaq Fjord, West Greenland. In 2014, we gained access to the bed in four boreholes drilled to depths of 603-616 m near the center of the glacier, 30 km inland from the calving terminus where ice flows at a rate of 700 m/year. A seismic survey showed the glacier bed to consist of water-saturated, soft sediment. The water level in all four boreholes nevertheless dropped rapidly to 80 m below the ice surface when the drill connected with a basal water system, indicating effective drainage over a sedimentary bed. We were able to install wired sensor strings at the bed (water pressure, temperature, electrical conductivity and turbidity) and within the glacier (temperature and tilt) in three boreholes. The sensors operated for up to 80+ days before cables stretched and ultimately snapped due to high internal strain. The data collected during this sensor deployment show ice as cold as -21 degrees Celcius; yet, temperature of water in the basal water system was persistently above the local freezing point. With diurnal variations detected in several sensor records, we hypothesise that surface water lubricates the ice flow while also warming basal ice. The fast basal motion of Store Glacier not only occurs by basal sliding, but from high rates of concentrated strain in the bottom third of the glacier

  13. How much can Greenland melt? An upper bound on mass loss from the Greenland Ice Sheet through surface melting

    NASA Astrophysics Data System (ADS)

    Liu, X.; Bassis, J. N.

    2015-12-01

    With observations showing accelerated mass loss from the Greenland Ice Sheet due to surface melt, the Greenland Ice Sheet is becoming one of the most significant contributors to sea level rise. The contribution of the Greenland Ice Sheet o sea level rise is likely to accelerate in the coming decade and centuries as atmospheric temperatures continue to rise, potentially triggering ever larger surface melt rates. However, at present considerable uncertainty remains in projecting the contribution to sea level of the Greenland Ice Sheet both due to uncertainty in atmospheric forcing and the ice sheet response to climate forcing. Here we seek an upper bound on the contribution of surface melt from the Greenland to sea level rise in the coming century using a surface energy balance model coupled to an englacial model. We use IPCC Representative Concentration Pathways (RCP8.5, RCP6, RCP4.5, RCP2.6) climate scenarios from an ensemble of global climate models in our simulations to project the maximum rate of ice volume loss and related sea-level rise associated with surface melting. To estimate the upper bound, we assume the Greenland Ice Sheet is perpetually covered in thick clouds, which maximize longwave radiation to the ice sheet. We further assume that deposition of black carbon darkens the ice substantially turning it nearly black, substantially reducing its albedo. Although assuming that all melt water not stored in the snow/firn is instantaneously transported off the ice sheet increases mass loss in the short term, refreezing of retained water warms the ice and may lead to more melt in the long term. Hence we examine both assumptions and use the scenario that leads to the most surface melt by 2100. Preliminary models results suggest that under the most aggressive climate forcing, surface melt from the Greenland Ice Sheet contributes ~1 m to sea level by the year 2100. This is a significant contribution and ignores dynamic effects. We also examined a lower bound

  14. Southwestern USA Drought over Multiple Millennia

    NASA Astrophysics Data System (ADS)

    Salzer, M. W.; Kipfmueller, K. F.

    2014-12-01

    Severe to extreme drought conditions currently exist across much of the American West. There is increasing concern that climate change may be worsening droughts in the West and particularly the Southwest. Thus, it is important to understand the role of natural variability and to place current conditions in a long-term context. We present a tree-ring derived reconstruction of regional-scale precipitation for the Southwestern USA over several millennia. A network of 48 tree-ring chronologies from California, Nevada, Utah, Arizona, New Mexico, and Colorado was used. All of the chronologies are at least 1,000 years long. The network was subjected to data reduction through PCA and a "nested" multiple linear regression reconstruction approach. The regression model was able to capture 72% of the variance in September-August precipitation over the last 1,000 years and 53% of the variance over the first millennium of the Common Era. Variance captured and spatial coverage further declined back in time as the shorter chronologies dropped out of the model, eventually reaching 24% of variance captured at 3250 BC. Results show regional droughts on decadal- to multi-decadal scales have been prominent and persistent phenomena in the region over the last several millennia. Anthropogenic warming is likely to exacerbate the effects of future droughts on human and other biotic populations.

  15. Early Cambrian hydrocarbon potential in Southwestern Ohio

    SciTech Connect

    Sfara, R.M.; Benjamin, H.R.; Wolfe, P.J.

    1995-09-01

    A sedimentary basin, inferred to be of Early Cambrian age, has been recently identified in southwestern Ohio. A well drilled into this basin in 1926 penetrated 404 m of sedimentary rocks below the Middle Cambrian Mount Simon Sandstone. This is the only well in Ohio to have penetrated limestone below the Mt. Simon Sandstone. Since 1992 Wright State University has gathered about 35 km of seismic data in this area. The seismic data suggest that these strata dip south into a large basin. The seismic character of the limestone interval at the well extends to a thickness of at least 1000 m. In addition, material underlying the limestone has reflection characteristics similar to the Late Proterozoic Middle Run Sandstone that exists about 40 km to the southwest. The surface on which Mount Simon Sandstone was deposited appears to be a mature karst surface and there was a natural gas show at this horizon. An oil show existed in an 8 m thick arkose within the limestone. All of the limestone encountered in the well was rich in organic material. Since there were gas and oil shows in the old well and the material appears younger than the Middle Run Sandstone, we feel this basin has hydrocarbon production potential.

  16. Cambrian trilobites with Siberian affinities, southwestern Alaska

    SciTech Connect

    Palmer, A.R.; Egbert, R.M.; Sullivan, R.; Knoth, J.S.

    1985-02-01

    Cambrian trilobites occur in two levels (about 7 m apart) in the core of a large, complex anticlinal structure in the area between the Taylor Mountains and the Hoholitna River in southwestern Alaska. The lower collection contains Erbia, Macannaia (a species close to Soviet forms described as Pagetia ferox Lermontova), two species of Kootenia (including one perhaps cospecific with forms from the central Brooks range), and several species of ptychoparioid trilobites. It is clear that biogeographic affinities are with the transitional facies of the eastern Siberian platform and the south Siberian foldbelt. In Soviet terms, the age of the collection falls in a disputed interval called latest Early Cambrian (Tojonian) by some authors, and earliest Middle Cambrian (Amgan) by others. In North American terms, Macannaia is known only from early Middle Cambrian beds. The younger collection contains abundant agnostids, a variety of conocoryphids, Paradoxides, and several species of ptychoparioid trilobites. This is an assemblage of undoubted late Middle Cambrian age, comparable to faunas described from the Maya State of the Siberian platform and the Paradoxides paradoxissimus Stage of the Baltic region. Both faunas are from ocean-facing or outer shelf environments. None of the key non-agnostid or non-pagetiid elements have been seen previously in deposits of Cambrian North America.

  17. Southwestern Pine Forests Likely to Disappear

    ScienceCinema

    McDowell, Nathan

    2016-07-12

    A new study, led by Los Alamos National Laboratory's Nathan McDowell, suggests that widespread loss of a major forest type, the pine-juniper woodlands of the Southwestern U.S., could be wiped out by the end of this century due to climate change, and that conifers throughout much of the Northern Hemisphere may be on a similar trajectory. New results, reported in the journal Nature Climate Change, suggest that global models may underestimate predictions of forest death. McDowell and his large international team strove to provide the missing pieces of understanding tree death at three levels: plant, regional and global. The team rigorously developed and evaluated multiple process-based and empirical models against experimental results, and then compared these models to results from global vegetation models to examine independent simulations. They discovered that the global models simulated mortality throughout the Northern Hemisphere that was of similar magnitude, but much broader spatial scale, as the evaluated ecosystem models predicted for in the Southwest.

  18. Genetic diversity of Ascaris in southwestern Uganda.

    PubMed

    Betson, Martha; Nejsum, Peter; Llewellyn-Hughes, Julia; Griffin, Claire; Atuhaire, Aaron; Arinaitwe, Moses; Adriko, Moses; Ruggiana, Andrew; Turyakira, Grace; Kabatereine, Narcis B; Stothard, J Russell

    2012-02-01

    Despite the common occurrence of ascariasis in southwestern Uganda, helminth control in the region has been limited. To gain further insights into the genetic diversity of Ascaris in this area, a parasitological survey in mothers (n=41) and children (n=74) living in two villages, Habutobere and Musezero, was carried out. Adult Ascaris worms were collected from infected individuals by chemo-expulsion using pyrantel pamoate treatment. Genetic diversity within these worms was assessed by inspection of DNA sequence variation in a mitochondrial marker and length polymorphism at microsatellite loci. Overall prevalence of ascariasis was 42.5% in mothers and 30.4% in their children and a total of 98 worms was examined from 18 hosts. Sequence analysis of a portion of the mitochondrial cytochrome c oxidase subunit 1 gene revealed 19 different haplotypes, 13 of which had not been previously encountered. Microsatellite analysis using eight loci provided evidence for high gene flow between worm populations from the two villages but comparing these worms with others obtained in a prior study on Unguja, Zanzibar, confirmed little genetic exchange and mixing of worm populations between the two areas. By adding to our understanding of the genetic diversity of Ascaris in Africa, this study provides useful information for monitoring changes in parasite population structure in the face of ongoing and future control.

  19. Southwestern Pine Forests Likely to Disappear

    SciTech Connect

    McDowell, Nathan

    2015-12-21

    A new study, led by Los Alamos National Laboratory's Nathan McDowell, suggests that widespread loss of a major forest type, the pine-juniper woodlands of the Southwestern U.S., could be wiped out by the end of this century due to climate change, and that conifers throughout much of the Northern Hemisphere may be on a similar trajectory. New results, reported in the journal Nature Climate Change, suggest that global models may underestimate predictions of forest death. McDowell and his large international team strove to provide the missing pieces of understanding tree death at three levels: plant, regional and global. The team rigorously developed and evaluated multiple process-based and empirical models against experimental results, and then compared these models to results from global vegetation models to examine independent simulations. They discovered that the global models simulated mortality throughout the Northern Hemisphere that was of similar magnitude, but much broader spatial scale, as the evaluated ecosystem models predicted for in the Southwest.

  20. Miocene uplift of the NE Greenland margin linked to plate tectonics: Seismic evidence from the Greenland Fracture Zone, NE Atlantic.

    NASA Astrophysics Data System (ADS)

    Døssing, Arne; Japsen, Peter; Watts, Anthony; Nielsen, Tove; Jokat, Wilfried; Thybo, Hans

    2016-04-01

    Tectonic models predict that, following breakup, rift margins undergo only decaying thermal subsidence during their post-rift evolution. However, post-breakup stratigraphy beneath the NE Atlantic shelves shows evidence of regional-scale unconformities, commonly cited as outer margin responses to inner margin episodic uplift, including the formation of coastal mountains. The origin of these events remains enigmatic. We present a seismic reflection study from the Greenland Fracture Zone - East Greenland Ridge (GFZ-EGR) and the NE Greenland shelf. We document a regional intra-Miocene seismic unconformity (IMU), which marks the termination of syn-rift deposition in the deep-sea basins and onset of: (i) thermo-mechanical coupling across the GFZ, (ii) basin compression, and (iii) contourite deposition, north of the EGR. The onset of coupling across the GFZ is constrained by results of 2-D flexural backstripping. We explain the thermo-mechanical coupling and the deposition of contourites by the formation of a continuous plate boundary along the Mohns and Knipovich ridges, leading to an accelerated widening of the Fram Strait. We demonstrate that the IMU event is linked to onset of uplift and massive shelf-progradation on the NE Greenland margin. Given an estimated middle-to-late Miocene (~15-10 Ma) age of the IMU, we speculate that the event is synchronous with uplift of the East and West Greenland margins. The correlation between margin uplift and plate-motion changes further indicates that the uplift was triggered by plate tectonic forces, induced perhaps by a change in the Iceland plume (a hot pulse) and/or by changes in intra-plate stresses related to global tectonics.

  1. Miocene uplift of the NE Greenland margin linked to plate tectonics: Seismic evidence from the Greenland Fracture Zone, NE Atlantic

    NASA Astrophysics Data System (ADS)

    Døssing, Arne; Japsen, Peter; Watts, Anthony B.; Nielsen, Tove; Jokat, Wilfried; Thybo, Hans; Dahl-Jensen, Trine

    2016-02-01

    Tectonic models predict that following breakup, rift margins undergo only decaying thermal subsidence during their postrift evolution. However, postbreakup stratigraphy beneath the NE Atlantic shelves shows evidence of regional-scale unconformities, commonly cited as outer margin responses to inner margin episodic uplift, including the formation of coastal mountains. The origin of these events remains enigmatic. We present a seismic reflection study from the Greenland Fracture Zone-East Greenland Ridge (GFZ-EGR) and the NE Greenland shelf. We document a regional intra-Miocene seismic unconformity (IMU), which marks the termination of synrift deposition in the deep-sea basins and onset of (i) thermomechanical coupling across the GFZ, (ii) basin compression, and (iii) contourite deposition, north of the EGR. The onset of coupling across the GFZ is constrained by results of 2-D flexural backstripping. We explain the thermomechanical coupling and the deposition of contourites by the formation of a continuous plate boundary along the Mohns and Knipovich ridges, leading to an accelerated widening of the Fram Strait. We demonstrate that the IMU event is linked to onset of uplift and massive shelf progradation on the NE Greenland margin. Given an estimated middle to late Miocene (~15-10 Ma) age of the IMU, we speculate that the event is synchronous with uplift of the east and west Greenland margins. The correlation between margin uplift and plate motion changes further indicates that the uplift was triggered by plate tectonic forces, induced perhaps by a change in the Iceland plume (a hot pulse) and/or by changes in intraplate stresses related to global tectonics.

  2. Atmosphere-Snowpack NOx Exchange: Measurements at Summit, Greenland and Process-Scale Modeling

    NASA Astrophysics Data System (ADS)

    Murray, Keenan; Ganzeveld, Laurens; Kramer, Louisa; Doskey, Paul; Helmig, Detlev; Seok, Brian; Van Dam, Brie

    2013-04-01

    Atmosphere-Snowpack NOx Exchange: Measurements at Summit, Greenland and Process-Scale Modeling Keenan A. Murray, Laurens Ganzeveld, Louisa J. Kramer, Paul V. Doskey, Detlev Helmig, Brian Seok, Brie Van Dam Snowpack over glacial ice is a reservoir for reactive nitrogen gases. During the sunlit season, NOx is generated in the interstitial air of snowpack through photolysis of nitrate (NO3-) in snow. Gradients in NOx mixing ratios between snowpack interstitial air and the overlying atmosphere regulate transfer of NOx to/from snowpack and affect the atmospheric O3 budget, oxidation capacity and, consequently, climate. To better understand the dynamics in cryosphere-atmosphere exchange of NOx we have collected 2 years of meteorological and chemical data at Summit, Greenland. Profiles of NO, NO2 and O3 mixing ratios were measured in interstitial air at several depths in the snowpack and at 2 levels above the snow surface. NOx emissions are episodic, with large NOx events occurring in early spring during high wind speed events (10-20 mph) that elevate NOx levels to ~500 pptv to depths of 2.5 meters into the snowpack. The poster will present measurements of NO, NO2, O3, wind, and irradiance for a high NOx event in the snowpack during the 2008-2010 period. Analysis of these observations will be based upon the application of a 1-D process-scale model of the atmosphere-snowpack exchange of NOx, which includes representations of the snowpack chemistry of reactive nitrogen, peroxides, and small hydrocarbon species. A more highly parameterized version of the process-scale model is currently being developed for inclusion in a global-scale model to assess the implications of climate change on cryosphere-atmosphere NOx and Ox exchange. We will present a first comparison of the predicated NOx and O3 profiles and fluxes from the process-scale/parameterized models, respectively, to observed measurements.

  3. Joint Science Education Project: Learning about polar science in Greenland

    NASA Astrophysics Data System (ADS)

    Foshee Reed, Lynn

    2014-05-01

    The Joint Science Education Project (JSEP) is a successful summer science and culture opportunity in which students and teachers from the United States, Denmark, and Greenland come together to learn about the research conducted in Greenland and the logistics involved in supporting the research. They conduct experiments first-hand and participate in inquiry-based educational activities alongside scientists and graduate students at a variety of locations in and around Kangerlussuaq, Greenland, and on the top of the ice sheet at Summit Station. The Joint Committee, a high-level forum involving the Greenlandic, Danish and U.S. governments, established the Joint Science Education Project in 2007, as a collaborative diplomatic effort during the International Polar Year to: • Educate and inspire the next generation of polar scientists; • Build strong networks of students and teachers among the three countries; and • Provide an opportunity to practice language and communication skills Since its inception, JSEP has had 82 student and 22 teacher participants and has involved numerous scientists and field researchers. The JSEP format has evolved over the years into its current state, which consists of two field-based subprograms on site in Greenland: the Greenland-led Kangerlussuaq Science Field School and the U.S.-led Arctic Science Education Week. All travel, transportation, accommodations, and meals are provided to the participants at no cost. During the 2013 Kangerlussuaq Science Field School, students and teachers gathered data in a biodiversity study, created and set geo- and EarthCaches, calculated glacial discharge at a melt-water stream and river, examined microbes and tested for chemical differences in a variety of lakes, measured ablation at the edge of the Greenland Ice Sheet, and learned about fossils, plants, animals, minerals and rocks of Greenland. In addition, the students planned and led cultural nights, sharing food, games, stories, and traditions of

  4. High-resolution Greenland ice core data show abrupt climate change happens in few years.

    PubMed

    Steffensen, Jørgen Peder; Andersen, Katrine K; Bigler, Matthias; Clausen, Henrik B; Dahl-Jensen, Dorthe; Fischer, Hubertus; Goto-Azuma, Kumiko; Hansson, Margareta; Johnsen, Sigfús J; Jouzel, Jean; Masson-Delmotte, Valérie; Popp, Trevor; Rasmussen, Sune O; Röthlisberger, Regine; Ruth, Urs; Stauffer, Bernhard; Siggaard-Andersen, Marie-Louise; Sveinbjörnsdóttir, Arny E; Svensson, Anders; White, James W C

    2008-08-01

    The last two abrupt warmings at the onset of our present warm interglacial period, interrupted by the Younger Dryas cooling event, were investigated at high temporal resolution from the North Greenland Ice Core Project ice core. The deuterium excess, a proxy of Greenland precipitation moisture source, switched mode within 1 to 3 years over these transitions and initiated a more gradual change (over 50 years) of the Greenland air temperature, as recorded by stable water isotopes. The onsets of both abrupt Greenland warmings were slightly preceded by decreasing Greenland dust deposition, reflecting the wetting of Asian deserts. A northern shift of the Intertropical Convergence Zone could be the trigger of these abrupt shifts of Northern Hemisphere atmospheric circulation, resulting in changes of 2 to 4 kelvin in Greenland moisture source temperature from one year to the next.

  5. Sexual and reproductive health in Greenland: evaluation of implementing sexual peer-to-peer education in Greenland (the SexInuk project)

    PubMed Central

    Homøe, Anne-Sophie; Knudsen, Ane-Kersti Skaarup; Nielsen, Sigrid Brisson; Grynnerup, Anna Garcia-Alix

    2015-01-01

    Background For decades, the rates of sexually transmitted infections (STIs), such as gonorrhoea, chlamydia and syphilis, have increased in Greenland, especially within the young age groups (15–29 years). From 2006 to 2013, the number of abortions has been consistent with approximately 800–900 abortions per year in Greenland, which is nearly as high as the total number of births during the same period. Previous studies in Greenland have reported that knowledge about sexual health is important, both as prevention and as facilitator to stop the increasing rates of STIs. A peer-to-peer education programme about sexual health requires adaption to cultural values and acceptance among the population and government in order to be sustainable. Objective Formative evaluation of a voluntary project (SexInuk), in relation to peer-to-peer education with focus on sexual health. Two workshops were conducted in Nuuk, Greenland, to recruit Greenlandic students. Design Qualitative design with focus group interviews (FGIs) to collect qualitative feedback on feasibility and implementation of the project. Supplemented with a brief questionnaire regarding personal information (gender, age, education) and questions about the educational elements in the SexInuk project. Eight Greenlandic students, who had completed one or two workshops, were enrolled. Results The FGIs showed an overall consensus regarding the need for improving sexual health education in Greenland. The participants requested more voluntary educators, to secure sustainability. The articulation of taboo topics in the Greenlandic society appeared very important. The participants suggested more awareness by promoting the project. Conclusion Cultural values and language directions were important elements in the FGIs. To our knowledge, voluntary work regarding peer-to-peer education and sexual health has not been structurally evaluated in Greenland before. To achieve sustainability, the project needs educators and financial

  6. Initialization of a full-Stokes finite element model of the Greenland ice-sheet using inverse methods

    NASA Astrophysics Data System (ADS)

    Gillet-Chaulet, F.; Gagliardini, O.; Nodet, M.; Ritz, C.; Durand, G.; Zwinger, T.; Seddik, H.; Greve, R.

    2010-12-01

    About a third of the current sea level rise is attributed to the release of Greenland and Antarctic ice, and their respective contribution is continuously increasing since the first diagnostic of the acceleration of their coastal outlet glaciers, a decade ago. Due to their related societal implications, good scenario of the ice sheets evolutions are needed to constrain the sea level rise forecast in the coming centuries. The quality of the model predictions depend primary on the good description of the physical processes involved and on a good initial state reproducing the main present observations (geometry, surface velocities and ideally the trend in elevation change). We model ice dynamics on the whole Greenland ice sheet using the full-Stokes finite element code Elmer. The finite element mesh is generated using the anisotropic mesh adaptation tool YAMS, and shows a high density around the major ice streams. For the initial state, we use an iterative procedure to compute the ice velocities, the temperature field, and the basal sliding coefficient field. The basal sliding coefficient is obtained with an inverse method by minimizing a cost function that measures the misfit between the present day surface velocities and the modelled surface velocities. We use two inverse methods for this: an inverse Robin problem recently proposed by Arthern and Gudmundsson (J. Glaciol. 2010), and a control method taking advantage of the fact that the Stokes equations are self adjoint in the particular case of a Newtonian rheology. From the initial states obtained by these two methods, we run transient simulations to evaluate the impact of the initial state of the Greenland ice sheet onto its related contribution to sea level rise for the next centuries.

  7. Age of Magmatism and Eurekan Deformation in North Greenland

    NASA Astrophysics Data System (ADS)

    Tegner, Christian; Storey, Michael; Holm, Paul M.; Thorarinsson, Sigurjon; Knudsen, Mads F.

    2014-05-01

    The alpine mountains of Northernmost Greenland are composed of Phanerozoic sediments and volcanic rocks that make up a broadly East-West striking orogenic belt. The major components include: 1) Cambrian-Devonian sediments deposited in the Franklinian Basin; 2) Ellesmerian (365-345 Ma) deformation of these sediments into a fold belt; 3) renewed extension and deposition of Carboniferous-Cretaceous sediments and Cretaceous-Paleogene volcanic rocks of the Kap Washington Group; and 4) Eurekan deformation of sediments and volcanic rocks. We present results of 40Ar-39Ar, U-Pb and Rb-Sr dating of volcanic rocks of the Kap Washington Group. This volcanic succesion is part of the High Arctic Large Igneous Province, exceeds 5 km in thickness, and is composed of bimodal alkaline flows, agglomerates and ignimbrites including peralkaline compositions typical of continental rifts such as the East African Rift. Based on zircon U-Pb and amphibole 40Ar-39Ar ages most volcanics were emplaced at 71-68 Ma, but activity continued down to 61 Ma. A thermal resetting age of 49-47 Ma is also identified in 40Ar-39Ar whole-rock data for trachyte flows. Patch perthite feldspars and coeval resetting of Rb-Sr isotopes by hydrothermal fluids provide further support for thermal overprinting, interpreted as a result of Eurekan compressional tectonism. It is striking that North Greenland volcanism terminated at about the same time (c. 61 Ma) as magmatism in the North Atlantic Large Igneous Province began. We suggest that this was a corollary of a change from extensional to compressional tectonism in the High Arctic. In the period when Greenland moved together with Eurasia (>60 Ma), the separation from North America resulted in rift-related alkaline magmatism in the High Arctic. When Greenland subsequently moved as a separate plate (60-35 Ma), overlapping spreading on both sides pushed it northwards and volcanism in the High Arctic stopped due to compression. Evaluation of plate kinematic models

  8. South-western African climate depends on Antarctic sea ice

    NASA Astrophysics Data System (ADS)

    Stuut, J.-B. W.; Crosta, X.; van der Borg, K.; Schneider, R. R.

    2003-04-01

    The typical Fynbos vegetation of the Cape region of South-western Africa is brought about by the local Mediterranean (winter rainfall) climate and its associated sharp seasonal contrasts, especially in precipitation. This biome is bordered by hyper-arid deserts which may rapidly expand in response to future global warming, such as during the last warm period 125.000 years ago. It is therefore essential to understand the mechanisms that drive the winter rainfall in such a restricted area. We relate variations in South-western African humidity to changes in Antarctic sea-ice extent. New records of Antarctic sea-ice extent compared to existing palaeoclimate records of South-western Africa reveal a coherent signal during the last 50 kyr BP, with enhanced continental humidity and trade-wind intensity during periods of increased sea-ice presence. We propose that greater glacial Antarctic sea-ice extent causes a Northward shift of oceanic and atmospheric frontal zones, thereby increasing latitudinal temperature and pressure gradients, leading to enhanced trade-wind intensities. In addition, the equatorward shift and increased intensity of the Southern Westerlies causes an expansion of the winter-rain region and increased precipitation in South-western Africa. This relationship implies enhanced desertification in South-western Africa in response to retreating sea-ice edge in the Atlantic sector of the Southern Ocean if global warming continues.

  9. Assessing the recent droughts in Southwestern China using satellite gravimetry

    NASA Astrophysics Data System (ADS)

    Tang, Jingshi; Liu, Lin

    Heavy droughts have frequently struck Southwestern China in recent years. A major consequence of these droughts is the loss of terrestrial water storage (TWS) which affects agriculture, civil life and industry production and results in serious social and economic losses. The satellite gravimetry has been proved an effective way to estimate hydrological variations over the globe, and we use the monthly gravity solutions from the Gravity Recovery And Climate Experiment (GRACE) satellite mission and extract the hydrological variations from the regional gravity signal. Here we show that the recent heavy droughts in Southwestern China have caused observable nonseasonal gravity changes in the monthly GRACE solutions. Two heavy droughts in 09/2009-05/2010 and 08/2011-01/2012 have resulted in significant TWS depletion up to hundreds of gigatons in Southwestern China. It is found that the latter drought in 2011-2012 is the most severe one in Southwestern China over the decade, hitting large areas and causing heavy TWS depletion. Affected by the recent droughts, the GRACE estimate shows a gradual decrease in the regional TWS during the recent 4 years in Southwestern China with a nominal rate of -13.3±7.5 mm/yr, which indicates the severity of the TWS depletion in this area.

  10. Bilharziasis survey in south-western Asia*

    PubMed Central

    Abdel Azim, M.; Gismann, Anne

    1956-01-01

    This paper describes a limited survey of bilharziasis and its vectors carried out during 1950 and 1951 in some countries of south-western Asia. Lack of time and of full facilities prevented the survey from being as comprehensive and systematic as would have been wished, but enough data were obtained to provide a general estimate of the situation. Information already available from the literature was supplemented by collecting unpublished records, questioning the inhabitants, examining random samples of stools and urine, and investigating rivers, wells, and springs. Bilharziasis haematobia is already heavily endemic in the irrigated areas of Iraq and is also present, in comparatively smaller foci, in northern Syria, Israel, and Sa'udi Arabia. In the opinion of the senior author (M. A. A.), the envisaged extension of irrigation is likely to create a serious health problem in Mesopotamia and to introduce the disease into the Jordan region unless the spread of the molluscan vector, Bulinus sp., is checked. Intensification of infection and further spread are possible in Israel and in the Syrian Jezire, while the remainder of Syria and Lebanon are not considered to be endangered. Bilharziasis mansoni is widespread in the fertile areas of Sa'udi Arabia and also occurs in one minor focus in Israel. The industrialization of Sa'udi Arabia which is planned to exploit its oil resources, with its inevitable concentration of population, equally presents a danger in the intensification of bilharziasis. It is considered that, unless prompt measures are undertaken to break the link between the agricultural and industrial expansion and the spread of the disease, the debilitation of large groups of the population and the economic loss which may well result over most of the inhabited parts of the area discussed will be significant. ImagesFIG. 1 PMID:13342925

  11. Lengthening Spring Season in Southwestern North America

    NASA Astrophysics Data System (ADS)

    Gutzler, D. S.

    2014-12-01

    Climate is changing rapidly in southwestern North America during the Spring season, a critically important transition season in terms of hydrology, ecosystem dynamics, and water resource management. Major rivers are snow-fed in mountainous headwaters but then flow through a monsoonal region with a Summer precipitation maximum; Spring is the dry season in between snowmelt and monsoon onset and is the principal wildfire season in the Southwest. Evaporation during the warm, dry Spring represents a major hydrologic loss in the surface water budget and is a principal cause of projections of significant decreases in post-snowmelt streamflow, during the first half of the growing season when demand for surface water for irrigated agriculture is highest. As temperatures increase, snowpack is expected to decrease and melt earlier, leading to a smaller and earlier peak in snowmelt runoff. Recent climate model projections suggest that monsoon onset should occur later in the year, delaying the summer rainy season. Each of these effects contributes to projections of a lengthening Spring season, at both the beginning and end of Spring. A longer, warmer Spring season is associated with significant surface drying and increased wildfire risk in the 21st Century across the Southwest. So far changes are observed at the beginning of spring in terms of temperature (increasing) and snowpack (decreasing). Detection of other changes, including metrics of the end of spring, has not been easy, in part due to the huge natural variability of precipitation that affects hydrologic variables in conjunction with temperature. This presentation describes efforts to diagnose and document observed changes in the transitions into and out of the Spring dry season in the Southwest, in variables such as temperature, snowmelt date, timing and magnitude of streamflow, and monsoon onset date.

  12. Diachronous retreat of the Greenland ice sheet during the last deglaciation

    NASA Astrophysics Data System (ADS)

    Sinclair, G.; Carlson, A. E.; Mix, A. C.; Lecavalier, B. S.; Milne, G.; Mathias, A.; Buizert, C.; DeConto, R.

    2016-08-01

    The last deglaciation is the most recent interval of large-scale climate change that drove the Greenland ice sheet from continental shelf to within its present extent. Here, we use a database of 645 published 10Be ages from Greenland to document the spatial and temporal patterns of retreat of the Greenland ice sheet during the last deglaciation. Following initial retreat of its marine margins, most land-based deglaciation occurred in Greenland following the end of the Younger Dryas cold period (12.9-11.7 ka). However, deglaciation in east Greenland peaked significantly earlier (13.0-11.5 ka) than that in south Greenland (11.0-10 ka) or west Greenland (10.5-7.0 ka). The terrestrial deglaciation of east and south Greenland coincide with adjacent ocean warming. 14C ages and a recent ice-sheet model reconstruction do not capture this progression of terrestrial deglacial ages from east to west Greenland, showing deglaciation occurring later than observed in 10Be ages. This model-data misfit likely reflects the absence of realistic ice-ocean interactions. We suggest that oceanic changes may have played an important role in driving the spatial-temporal ice-retreat pattern evident in the 10Be data.

  13. Potential Climatic Effects on the Greenland Ice Sheet

    NASA Technical Reports Server (NTRS)

    Bindschadler, R. A.

    1984-01-01

    The Greenland Ice Sheet covers an area of 1,720,000 sq. km and contains approximately 2,600,000 cu km of ice. Most of the ice sheet receives an excess of snow accumulation over the amount of ice lost to wind, meltwater run-off or other ablative processes. The majority of mass loss occurs at the margin of the ice sheet as either surface melt, which flows into the sea or calving of icebergs from the tongues of outlet glaciers. Many estimates of these processes were published. An average of five published estimates is summarized. If these estimates are correct, then the Greenland Ice Sheet is in approximate equilibrium and contributes 490 cu km/a of fresh water to the North Atlantic and Arctic Oceans. Climate effects, ice sheet flow, and application of remote sensing to tracking of the ice sheet are discussed.

  14. Deformation of Eemian and Glacial ice at NEEM, Greenland

    NASA Astrophysics Data System (ADS)

    Keegan, Kaitlin; Dahl-Jensen, Dorthe; Montagnat, Maurine; Weikusat, Ilka; Kipfstuhl, Sepp

    2015-04-01

    New findings from deep Greenland ice cores and airborne radio echo sounding (RES) images show that basal ice flow is very unstable, and a basal layer of disturbed ice is often observed. At NEEM, Greenland this folding occurs at the boundary between the Eemian and glacial ice regimes, suggesting that differences in physical properties of the ice play a role in the disturbance. Past work in metallurgy (Burke, 1957) and ice (Hammer et al., 1978; Langway et al., 1988; Dahl-Jensen et al., 1997), suggests that impurity content controls grain evolution, and therefore deformation, which we hypothesize to be analogous to the differences in ice flow seen deep in the NEEM ice core. Here we present results of fabric, grain size, impurity content, and deformation studies from samples above and below this unstable boundary in the ice sheet.

  15. Large Fluctuations in Speed on Jakobshavn Isbrae, Greenland

    NASA Technical Reports Server (NTRS)

    Joughin, Ian; Abdalati, Waleed; Fahnestock, Mark

    2003-01-01

    We have assembled an 18-year velocity record for Jakobshavn Isbrae, Greenland. From a 1985 speed of approx. 7000 m/yr, the glacier had slowed by approx. 1000 m/ yr in 1992, which coincided with independently observed thickening in the early 1990s . The glacier then sped up by approx. 4000 m/yr between 1997 and 2000, during which time other measurements show rapid thinning . From 2000 to 2003, the glacier s floating ice tongue almost entirely disintegrated, as speed increased to 12,600 m/yr. If the retreat of the ice tongue caused the acceleration, then similar losses of floating ice tongues since the Little Ice Age may explain the current rapid thinning observed for many of Greenland s outlet glaciers.

  16. SAGE: A tool for time-series analysis of Greenland

    NASA Astrophysics Data System (ADS)

    Duerr, R. E.; Gallaher, D. W.; Khalsa, S. S.; Lewis, S.

    2011-12-01

    The National Snow and Ice Data Center (NSIDC) has developed an operational tool for analysis. This production tool is known as "Services for the Analysis of the Greenland Environment" (SAGE). Using an integrated workspace approach, a researcher has the ability to find relevant data and perform various analysis functions on the data, as well as retrieve the data and analysis results. While there continues to be compelling observational evidence for increased surface melting and rapid thinning along the margins of the Greenland ice sheet, there are still uncertainties with respect to estimates of mass balance of Greenland's ice sheet as a whole. To better understand the dynamics of these issues, it is important for scientists to have access to a variety of datasets from multiple sources, and to be able to integrate and analyze the data. SAGE provides data from various sources, such as AMSR-E and AVHRR datasets, which can be analyzed individually through various time-series plots and aggregation functions; or they can be analyzed together with scatterplots or overlaid time-series plots to provide quick and useful results to support various research products. The application is available at http://nsidc.org/data/sage/. SAGE was built on top of NSIDC's existing Searchlight engine. The SAGE interface gives users access to much of NSIDC's relevant Greenland raster data holdings, as well as data from outside sources. Additionally, various web services provide access for other clients to utilize the functionality that the SAGE interface provides. Combined, these methods of accessing the tool allow scientists the ability to devote more of their time to their research, and less on trying to find and retrieve the data they need.

  17. Services for the Analysis of the Greenland Environment (SAGE)

    NASA Astrophysics Data System (ADS)

    Lewis, S.; Gallaher, D. W.; Khalsa, S. S.; Duerr, R. E.

    2010-12-01

    While there continues to be compelling observational evidence for increased surface melting and rapid thinning along the margins of the Greenland ice sheet, there are still uncertainties with respect to estimates of mass balance of Greenland's ice sheet as a whole. To better understand the dynamics of these issues, it is important for scientists to have access to a variety of datasets from multiple sources, and to be able to integrate and analyze the data. To address this need, the National Snow and Ice Data Center (NSIDC) has the Services for the Analysis of the Greenland Environment (SAGE). Using an integrated workspace approach, a researcher has the ability to find relevant data and perform various analysis functions on the data, as well as retrieve the data and analysis results. Data from various sources, such as AMSR-E and AVHRR datasets, can be analyzed individually through various time-series plots and aggregation functions; or they can be analyzed together with scatterplots or overlaid time-series plots to provide quick and useful results to support various research products. Built on top of NSIDC's Searchlight engine, the SAGE interface gives users access to much of NSIDC's relevant Greenland raster data holdings, as well as data from several outside sources. Additionally, various web services provide access for other clients to utilize the functionality that the SAGE interface provides. Combined, these methods of accessing the tool allow scientists the ability to devote more of their time to their research, and less on trying to find and retrieve the data they need.

  18. The Nitrate Content of Greenland Ice and Solar Activity

    NASA Astrophysics Data System (ADS)

    Kocharov, G. E.; Kudryavtsev, I. V.; Ogurtsov, M. G.; Sonninen, E.; Jungner, H.

    2000-12-01

    Past solar activity is studied based on analysis of data on the nitrate content of Greenland ice in the period from 1576 1991. Hundred-year (over the entire period) and quasi-five-year (in the middle of the 18th century) variations in the nitrate content are detected. These reflect the secular solar-activity cycle and cyclicity in the flare activity of the Sun.

  19. Ice Core Records of Recent Northwest Greenland Climate

    NASA Astrophysics Data System (ADS)

    Osterberg, E. C.; Wong, G. J.; Ferris, D.; Lutz, E.; Howley, J. A.; Kelly, M. A.; Axford, Y.; Hawley, R. L.

    2014-12-01

    Meteorological station data from NW Greenland indicate a 3oC temperature rise since 1990, with most of the warming occurring in fall and winter. According to remote sensing data, the NW Greenland ice sheet (GIS) and coastal ice caps are responding with ice mass loss and margin retreat, but the cryosphere's response to previous climate variability is poorly constrained in this region. We are developing multi-proxy records (lake sediment cores, ice cores, glacial geologic data, glaciological models) of Holocene climate change and cryospheric response in NW Greenland to improve projections of future ice loss and sea level rise in a warming climate. As part of our efforts to develop a millennial-length ice core paleoclimate record from the Thule region, we collected and analyzed snow pit samples and short firn cores (up to 21 m) from the coastal region of the GIS (2Barrel site; 76.9317o N, 63.1467o W, 1685 m el.) and the summit of North Ice Cap (76.938o N, 67.671o W, 1273 m el.) in 2011, 2012 and 2014. The 2Barrel ice core record has statistically significant relationships with regional spring and fall Baffin Bay sea ice extent, summertime temperature, and annual precipitation. Here we evaluate relationships between the 2014 North Ice Cap firn core glaciochemical record and climate variability from regional instrumental stations and reanalysis datasets. We compare the coastal North Ice Cap record to more inland records from 2Barrel, Camp Century and NEEM to evaluate spatial and elevational gradients in recent NW Greenland climate change.

  20. Lively Earthquake Activity in North-Eastern Greenland

    NASA Astrophysics Data System (ADS)

    Larsen, Tine B.; Dahl-Jensen, Trine; Voss, Peter H.

    2016-04-01

    The seismograph at the Danish military outpost, Station Nord (NOR) in North East Greenland, records many regional/local earthquakes every day. Most of these events originate at the Arctic plate boundary between the Eurasian and the North American plates. The plate boundary has a particularly active segment approximately 200 km from the seismograph. Additionally we find a seismically very active region 20-30 km from NOR on the Kronprins Christian Land peninsula. The BB seismograph at NOR was installed in 2002 and later upgraded with real-time telemetry as part of the GLISN-project. Since late 2013 data from NOR have been included in routine processing at GEUS. Phase readings on some of the older data, primarily 2002-2003, have been carried out previously in connection with other projects. As a result, phase readings for more than 6000 local events, recorded exclusively at NOR, were found in the GEUS data base. During the years 2004 to 2007 four locations were occupied by temporary BB seismographs on the North coast of Greenland as part of the Law of the Sea preparatory work. Data from these stations have not previously been analyzed for local and regional events. In this study we combine the recordings from NOR with phase readings from the temporary seismographs in Northern Greenland. The local events on Kronprins Christian Land range in magnitude from less than 2 to a 4.8 event widely recorded in the region and felt by the personnel at Station Nord on August 30, 2005. Station Nord is located in the seismically most active region of Greenland.

  1. Climate Change and Baleen Whale Trophic Cascades in Greenland

    DTIC Science & Technology

    2009-09-30

    approach by combining observations of movements, foraging ecology and phenology collected by satellite and archival telemetry with intensive and...whale species in West Greenland. We use a multidisciplinary approach by combining observations of movements, foraging ecology and phenology collected...including the time individuals spend feeding in each site and the phenology of the use of the focal areas. These data are related to long-term physical

  2. Climate Change and Baleen Whale Trophic Cascades in Greenland

    DTIC Science & Technology

    2012-03-19

    approach by combining observations of movements, foraging ecology and phenology collected by satellite and archival telemetry with intensive and localized... phenology of the use of the focal areas. These data were related to long-term physical and biological monitoring program in Nuuk Fjord and on the coast...of West Greenland, where long-term fishery data are collected to quantify seasonal and inter-annual variations in the biological and geophysical

  3. Climate Change and Baleen Whale Trophic Cascades in Greenland

    DTIC Science & Technology

    2010-01-01

    species in West Greenland. We use a multidisciplinary approach by combining observations of movements, foraging ecology and phenology collected by...along the coast using probabilistic spatial techniques, including the time individuals spend feeding in each site and the phenology of the use of...where long-term fishery data are collected to quantify seasonal and inter-annual variations in the biological and geophysical properties of the marine

  4. Prevalence and genotype identification of Toxoplasma gondii in wild animals from southwestern Spain.

    PubMed

    Calero-Bernal, Rafael; Saugar, José M; Frontera, Eva; Pérez-Martín, Juan E; Habela, Miguel A; Serrano, Francisco J; Reina, David; Fuentes, Isabel

    2015-01-01

    We used PCR to detect Toxoplasma gondii in the principal game species in southwestern Spain. We detected T. gondii in 32.2% of animals tested. Prevalences varied from 14.7% in wild boar (Sus scrofa) to 51.2% in red fox (Vulpes vulpes). The most prevalent genotype was type II (50.0%), followed by type III (20.6%) and type I (5.9%). Mixed infections (11.8%) were detected in wild boar (types I+III) and red fox (types II+III). Polymorphic strains (11.8%) were detected in several species. The high prevalence and the genetic variability shown could have implications for infection of farm animals and humans.

  5. FATAL CASE OF STREPTOCOCCUS SUIS INFECTION IN A YOUNG WILD BOAR (SUS SCROFA) FROM SOUTHWESTERN SPAIN.

    PubMed

    Risco, David; Fernández-Llario, Pedro; Cuesta, Jesús M; García-Jiménez, Waldo L; Gonçalves, Pilar; Martínez, Remigio; García, Alfredo; Rosales, Rubén; Gómez, Luis; de Mendoza, Javier Hermoso

    2015-06-01

    Streptococcus suis is a recognized pathogen that may cause important diseases in pigs and humans. This microorganism has been repeatedly isolated from wild boar (Sus scrofa). However, its health implications for this wild species are still unknown. This article reports a detailed description of a fatal case of septicemia by S. suis affecting a young wild boar. The affected animal, about 15 days old, was found near death and exhibiting neurologic signs at a wild boar estate in southwestern Spain. Postmortem examination showed generalized congestion, brain hemorrhages and lobular pneumonia. Histopathological evaluation demonstrated the presence of meningitis and encephalitis with marked congestion and suppurative bronchopneumonia. Streptococcus suis serotype 2 isolates exhibiting important virulence factors (extracellular factor, muramidase-released protein, and suylisin) were isolated from the affected animal. This study confirms the presence of potentially virulent and zoonotic strains of S. suis in wild boar from Spain.

  6. Repeated probing of Southwestern blots using alkaline phosphatase stripping.

    PubMed

    Jia, Yinshan; Jiang, Daifeng; Jarrett, Harry W

    2010-11-05

    Southwestern blotting is when a DNA sequence is used to probe DNA-binding proteins on an electrophoretic gel blot. It would be highly desirable to be able to probe a blot repeatedly with different DNA sequences. Alkaline phosphatase can remove 5'-phosphoryl groups from DNA and radiolabeled 5'-(32)P-DNA probes are commonly used in Southwestern blotting. Here is shown that once probed, the radioisotope signal on the blot can be effectively removed by brief digestion with alkaline phosphatase, and the blot can then be repeatedly probed at least six times with different DNA probes. This exceeds the repetitions possible with another commonly used method using SDS. The technique can be used with either one-dimensional or multi-dimensional Southwestern blots and does not have a large effect on the phosphorylation state of the blotted proteins. An alternative method using T4 polynucleotide kinase stripping is also introduced but was less well characterized.

  7. The Greenland Telescope (GLT): antenna status and future plans

    NASA Astrophysics Data System (ADS)

    Raffin, Philippe; Algaba-Marcosa, Juan Carlos; Asada, Keiichi; Blundell, Raymond; Burgos, Roberto; Chang, Chih-Cheng; Chen, Ming-Tang; Christensen, Robert; Grimes, Paul K.; Han, C. C.; Ho, Paul T. P.; Huang, Yau-De; Inoue, Makoto; Koch, Patrick M.; Kubo, Derek; Leiker, Steve; Liu, Ching-Tang; Martin-Cocher, Pierre; Matsushita, Satoki; Nakamura, Masanori; Nishioka, Hiroaki; Nystrom, George; Paine, Scott N.; Patel, Nimesh A.; Pradel, Nicolas; Pu, Hung-Yi; Shen, H.-Y.; Snow, William; Sridharan, Tirupati K.; Srinivasan, Ranjani; Tong, Edward; Wang, Jackie

    2014-07-01

    The ALMA North America Prototype Antenna was awarded to the Smithsonian Astrophysical Observatory (SAO) in 2011. SAO and the Academia Sinica Institute of Astronomy and Astrophysics (ASIAA), SAO's main partner for this project, are working jointly to relocate the antenna to Greenland to carry out millimeter and submillimeter VLBI observations. This paper presents the work carried out on upgrading the antenna to enable operation in the Arctic climate by the GLT Team to make this challenging project possible, with an emphasis on the unexpected telescope components that had to be either redesigned or changed. Five-years of inactivity, with the antenna laying idle in the desert of New Mexico, coupled with the extreme weather conditions of the selected site in Greenland have it necessary to significantly refurbish the antenna. We found that many components did need to be replaced, such as the antenna support cone, the azimuth bearing, the carbon fiber quadrupod, the hexapod, the HVAC, the tiltmeters, the antenna electronic enclosures housing servo and other drive components, and the cables. We selected Vertex, the original antenna manufacturer, for the main design work, which is in progress. The next coming months will see the major antenna components and subsystems shipped to a site of the US East Coast for test-fitting the major antenna components, which have been retrofitted. The following step will be to ship the components to Greenland to carry out VLBI

  8. Factors Controlling Methane in Arctic Lakes of Southwest Greenland

    PubMed Central

    2016-01-01

    We surveyed 15 lakes during the growing season of 2014 in Arctic lakes of southwest Greenland to determine which factors influence methane concentrations in these systems. Methane averaged 2.5 μmol L-1 in lakes, but varied a great deal across the landscape with lakes on older landscapes farther from the ice sheet margin having some of the highest values of methane reported in lakes in the northern hemisphere (125 μmol L-1). The most important factors influencing methane in Greenland lakes included ionic composition (SO4, Na, Cl) and chlorophyll a in the water column. DOC concentrations were also related to methane, but the short length of the study likely underestimated the influence and timing of DOC on methane concentrations in the region. Atmospheric methane concentrations are increasing globally, with freshwater ecosystems in northern latitudes continuing to serve as potentially large sources in the future. Much less is known about how freshwater lakes in Greenland fit in the global methane budget compared to other, more well-studied areas of the Arctic, hence our work provides essential data for a more complete view of this rapidly changing region. PMID:27454863

  9. Spatial variation in energy exchange across coastal environments in Greenland

    NASA Astrophysics Data System (ADS)

    Lund, M.; Abermann, J.; Citterio, M.; Hansen, B. U.; Larsen, S. H.; Stiegler, C.; Sørensen, L. L.; van As, D.

    2015-12-01

    The surface energy partitioning in Arctic terrestrial and marine areas is a crucial process, regulating snow, glacier ice and sea ice melt, and permafrost thaw, as well as modulating Earth's climate on both local, regional, and eventually, global scales. The Arctic region has warmed approximately twice as much as the global average, due to a number of feedback mechanisms related to energy partitioning, most importantly the snow and ice-albedo feedback. However, direct measurements of surface energy budgets in the Arctic are scarce, especially for the cold and dark winter period and over transects going from the ice sheet and glaciers to the sea. This study aims to describe annual cycles of the surface energy budget from various surface types in Arctic Greenland; e.g. glacier, snow, wet and dry tundra and sea ice, based on data from a number of measurement locations across coastal Greenland related to the Greenland Ecosystem Monitoring (GEM) program, including Station Nord/Kronprins Christians Land, Zackenberg/Daneborg, Disko, Qaanaq, Nuuk/Kobbefjord and Upernaviarsuk. Based on the available time series, we will analyze the sensitivity of the energy balance partitioning to variations in meteorological conditions (temperature, cloudiness, precipitation). Such analysis would allow for a quantification of the spatial variation in the energy exchange in aforementioned Arctic environments. Furthermore, this study will identify uncertainties and knowledge gaps in Arctic energy budgets and related climate feedback effects.

  10. Self-inhibiting growth of the Greenland Ice Sheet

    NASA Astrophysics Data System (ADS)

    Langen, P. L.; Solgaard, A. M.; Hvidberg, C. S.

    2012-04-01

    The build-up of the Greenland Ice Sheet from ice free conditions is studied in an ice sheet model (ISM) driven by fields from an atmospheric general circulation model (GCM). Experiments where the two are coupled offline are performed and augmented by one where an intermediate ice sheet configuration, taken as a snap shot during the regrowth in the ISM, is coupled back to the GCM. It is found that several open questions regarding reversibility or irreversibility of a disintegration of the Greenland Ice Sheet may be reconciled with these experiments. Running the ISM with GCM fields corresponding to a present day ice sheet configuration leads to regrowth, while considerations of the GCM's snow accumulation in an ice free run point to irreversibility. Forcing the ISM with the GCM fields corresponding to the ice free state leads to extensive regrowth which, however, is halted when an intermediate recoupling step is included. This inhibition of further growth is believed to be due to a Föhn effect of moist air parcels being lifted over the intermediate ice sheet and arriving in the Greenland interior with high temperatures.

  11. Unmanned Aircraft System (UAS) Assessment of Melt Lakes in Greenland

    NASA Astrophysics Data System (ADS)

    Adler, J.; Steffen, K.

    2007-12-01

    The objective of this August 2007 week-long test campaign was to assess the viability of supraglacial lake depths with high-resolution hyperspectral measurements. The knowledge of melt lake depth is essential in determining the volume of water which forms on top of glacial surfaces during the annual melt season. The assessment of melt water volume is a crucial input parameter for modeling the Greenland ice sheet dynamics. UAS operations were flown out of western Greenland. Preliminary results from five hyperspectral data cubes are presented, indicating that supraglacial water depths can be determined from low altitude, high-resolution hyperspectral imaging. The pixel resolution of the hyperspectral sensor is 0.2 meters at an altitude of 300 meters above the ice surface; this provides accuracy that is two orders of magnitude better than imagery obtained by the MODIS sensor or other similar satellite-based methods. Further, a UAS-based hyperspectral approach enables the measurement of supraglacial lake depths under most cloud cover conditions. The capabilities of three UAS types (Manta, Silver Fox, and electric Silver Fox) flight tested in Greenland are discussed. Also, we present future field planning (2008 and 2009) to measure supraglacial lake depths with hyperspectral imagery in conjunction with a green laser altimeter.

  12. Laser altimetry reveals complex pattern of Greenland Ice Sheet dynamics.

    PubMed

    Csatho, Beata M; Schenk, Anton F; van der Veen, Cornelis J; Babonis, Gregory; Duncan, Kyle; Rezvanbehbahani, Soroush; van den Broeke, Michiel R; Simonsen, Sebastian B; Nagarajan, Sudhagar; van Angelen, Jan H

    2014-12-30

    We present a new record of ice thickness change, reconstructed at nearly 100,000 sites on the Greenland Ice Sheet (GrIS) from laser altimetry measurements spanning the period 1993-2012, partitioned into changes due to surface mass balance (SMB) and ice dynamics. We estimate a mean annual GrIS mass loss of 243 ± 18 Gt ⋅ y(-1), equivalent to 0.68 mm ⋅ y(-1) sea level rise (SLR) for 2003-2009. Dynamic thinning contributed 48%, with the largest rates occurring in 2004-2006, followed by a gradual decrease balanced by accelerating SMB loss. The spatial pattern of dynamic mass loss changed over this time as dynamic thinning rapidly decreased in southeast Greenland but slowly increased in the southwest, north, and northeast regions. Most outlet glaciers have been thinning during the last two decades, interrupted by episodes of decreasing thinning or even thickening. Dynamics of the major outlet glaciers dominated the mass loss from larger drainage basins, and simultaneous changes over distances up to 500 km are detected, indicating climate control. However, the intricate spatiotemporal pattern of dynamic thickness change suggests that, regardless of the forcing responsible for initial glacier acceleration and thinning, the response of individual glaciers is modulated by local conditions. Recent projections of dynamic contributions from the entire GrIS to SLR have been based on the extrapolation of four major outlet glaciers. Considering the observed complexity, we question how well these four glaciers represent all of Greenland's outlet glaciers.

  13. Unusual radar echoes from the Greenland ice sheet

    NASA Technical Reports Server (NTRS)

    Rignot, E. J.; Vanzyl, J. J.; Ostro, S. J.; Jezek, K. C.

    1993-01-01

    In June 1991, the NASA/Jet Propulsion Laboratory airborne synthetic-aperture radar (AIRSAR) instrument collected the first calibrated data set of multifrequency, polarimetric, radar observations of the Greenland ice sheet. At the time of the AIRSAR overflight, ground teams recorded the snow and firn (old snow) stratigraphy, grain size, density, and temperature at ice camps in three of the four snow zones identified by glaciologists to characterize four different degrees of summer melting of the Greenland ice sheet. The four snow zones are: (1) the dry-snow zone, at high elevation, where melting rarely occurs; (2) the percolation zone, where summer melting generates water that percolates down through the cold, porous, dry snow and then refreezes in place to form massive layers and pipes of solid ice; (3) the soaked-snow zone where melting saturates the snow with liquid water and forms standing lakes; and (4) the ablation zone, at the lowest elevations, where melting is vigorous enough to remove the seasonal snow cover and ablate the glacier ice. There is interest in mapping the spatial extent and temporal variability of these different snow zones repeatedly by using remote sensing techniques. The objectives of the 1991 experiment were to study changes in radar scattering properties across the different melting zones of the Greenland ice sheet, and relate the radar properties of the ice sheet to the snow and firn physical properties via relevant scattering mechanisms. Here, we present an analysis of the unusual radar echoes measured from the percolation zone.

  14. Greenland Ice Sheet flow response to runoff variability

    NASA Astrophysics Data System (ADS)

    Stevens, Laura A.; Behn, Mark D.; Das, Sarah B.; Joughin, Ian; Noël, Brice P. Y.; Broeke, Michiel R.; Herring, Thomas

    2016-11-01

    We use observations of ice sheet surface motion from a Global Positioning System network operating from 2006 to 2014 around North Lake in west Greenland to investigate the dynamical response of the Greenland Ice Sheet's ablation area to interannual variability in surface melting. We find no statistically significant relationship between runoff season characteristics and ice flow velocities within a given year or season. Over the 7 year time series, annual velocities at North Lake decrease at an average rate of -0.9 ± 1.1 m yr-2, consistent with the negative trend in annual velocities observed in neighboring regions over recent decades. We find that net runoff integrated over several preceding years has a negative correlation with annual velocities, similar to findings from the two other available decadal records of ice velocity in western Greenland. However, we argue that this correlation is not necessarily evidence for a direct hydrologic mechanism acting on the timescale of multiple years but could be a statistical construct. Finally, we stress that neither the decadal slowdown trend nor the negative correlation between velocity and integrated runoff is predicted by current ice-sheet models, underscoring that these models do not yet capture all the relevant feedbacks between runoff and ice dynamics needed to predict long-term trends in ice sheet flow.

  15. The diel cycle of water vapor in west Greenland

    NASA Astrophysics Data System (ADS)

    Kopec, B. G.; Lauder, A. M.; Posmentier, E. S.; Feng, X.

    2014-08-01

    We present a study of the dynamics of small-scale (~100 km) atmospheric circulation in west Greenland which is dominated by interactions of marine and continental air masses. Water vapor concentration and isotopic ratios measured continuously over a 25 day period in Kangerlussuaq, Greenland were used to monitor the convergence of easterly katabatic winds and westerly sea breezes that form a front between the dry, isotopically depleted, glacial air mass and the moist, isotopically enriched, marine air mass. During the latter 16 days of the measurement period, an interval with no large-scale synoptic interference, the inland penetration of the sea breeze controlled the largest day-to-day humidity and vapor isotopic variations. Kangerlussuaq experienced sea breezes in the afternoon on 9 days, consistent with the long-term average of such occurrences on 56% of days in July and August. The inland position of the sea breeze front is controlled by the katabatic wind strength, which is stronger during times of reduced cloud coverage and/or higher-pressure gradient between the coast and the Greenland ice sheet. The position and movement of the front will likely respond to changes in the general atmospheric circulation and regional radiation balance resulting from global warming, which will, in turn, impact the local hydrological cycle and ecosystem processes.

  16. Radar attenuation and temperature within the Greenland Ice Sheet

    USGS Publications Warehouse

    MacGregor, Joseph A; Li, Jilu; Paden, John D; Catania, Ginny A; Clow, Gary D.; Fahnestock, Mark A; Gogineni, Prasad S.; Grimm, Robert E.; Morlighem, Mathieu; Nandi, Soumyaroop; Seroussi, Helene; Stillman, David E

    2015-01-01

    The flow of ice is temperature-dependent, but direct measurements of englacial temperature are sparse. The dielectric attenuation of radio waves through ice is also temperature-dependent, and radar sounding of ice sheets is sensitive to this attenuation. Here we estimate depth-averaged radar-attenuation rates within the Greenland Ice Sheet from airborne radar-sounding data and its associated radiostratigraphy. Using existing empirical relationships between temperature, chemistry, and radar attenuation, we then infer the depth-averaged englacial temperature. The dated radiostratigraphy permits a correction for the confounding effect of spatially varying ice chemistry. Where radar transects intersect boreholes, radar-inferred temperature is consistently higher than that measured directly. We attribute this discrepancy to the poorly recognized frequency dependence of the radar-attenuation rate and correct for this effect empirically, resulting in a robust relationship between radar-inferred and borehole-measured depth-averaged temperature. Radar-inferred englacial temperature is often lower than modern surface temperature and that of a steady state ice-sheet model, particularly in southern Greenland. This pattern suggests that past changes in surface boundary conditions (temperature and accumulation rate) affect the ice sheet's present temperature structure over a much larger area than previously recognized. This radar-inferred temperature structure provides a new constraint for thermomechanical models of the Greenland Ice Sheet.

  17. Continental ice in Greenland during the Eocene and Oligocene.

    PubMed

    Eldrett, James S; Harding, Ian C; Wilson, Paul A; Butler, Emily; Roberts, Andrew P

    2007-03-08

    The Eocene and Oligocene epochs (approximately 55 to 23 million years ago) comprise a critical phase in Earth history. An array of geological records supported by climate modelling indicates a profound shift in global climate during this interval, from a state that was largely free of polar ice caps to one in which ice sheets on Antarctica approached their modern size. However, the early glaciation history of the Northern Hemisphere is a subject of controversy. Here we report stratigraphically extensive ice-rafted debris, including macroscopic dropstones, in late Eocene to early Oligocene sediments from the Norwegian-Greenland Sea that were deposited between about 38 and 30 million years ago. Our data indicate sediment rafting by glacial ice, rather than sea ice, and point to East Greenland as the likely source. Records of this type from one site alone cannot be used to determine the extent of ice involved. However, our data suggest the existence of (at least) isolated glaciers on Greenland about 20 million years earlier than previously documented, at a time when temperatures and atmospheric carbon dioxide concentrations were substantially higher.

  18. Investigations of The Stable Boundary Layer At Summit, Greenland

    NASA Astrophysics Data System (ADS)

    Ohmura, A.

    The investigation of the exchange processes in the stable atmospheric boundary layer has been hampered by lack of clean experimental data and by the separate treatment of radiative transfer and the turbulent heat transport. An experimental site was chosen at Summit, Greenland which is the highest point in the middle of the Greenland ice sheet. The site is located in the permanently dry snow zone the Greenland. The site is horizontal and very homogeneous with almost unlimited fetch. The atmospheric profiles both for the conventional scalar values and vertical fluxes are measured with a 50 m meteorological tower. The tower is also equipped by three radiation stations; one at the ground, the other at 50 m level; and the third mounted on a vertically mo- bile elevator to measure the divergence. A sensitive micro-barometer is installed at the foot of the tower for the observation of the pressure fluctuations which are caused by internal waves. The tower experiments are augmented by a wind-profiler and ra- diosonde observations to reach higher altitudes. Considerations on a length-scale as well as dimensionless gradients in a stable boundary layer will be presented. The site at Summit offers a very wide range of stability. In addition of extremely stable strat- ification at night and in winter as envisaged, extremely strong instability is found to prevail between 10 and 15 O'clock local time in summer, as net radiation at Summit turns strongly positive.

  19. NGRIP methane record and its relation to Greenland temperature

    NASA Astrophysics Data System (ADS)

    Baumgartner, Matthias; Kindler, Philippe; Eicher, Olivier; Schilt, Adrian; Schwander, Jakob; Spahni, Renato; Capron, Emilie; Chappellaz, Jérôme; Landais, Amaelle; Leuenberger, Markus; Fischer, Hubertus; Stocker, Thomas F.

    2013-04-01

    During the last glacial cycle, Greenland temperature showed many rapid temperature variations, the so called Dansgaard-Oeschger (DO) events. The past atmospheric methane concentration closely follows these temperature variations, which implies that the warmings recorded in Greenland were probably hemispheric in extent. Here, we present 931 new methane measurements along the North Greenland Ice Core Project (NGRIP) ice core. We therefore substantially extend and complete the NGRIP methane record from Termination 1 back to the end of the last interglacial period in high resolution. We relate the amplitudes of the methane increases associated with DO events to the amplitudes of the temperature increases derived from stable nitrogen isotope (δ15N) measurements, which have been performed along the same ice core (see poster by P. Kindler). We find the sensitivity to oscillate between 5 and 20 ppbv/°C with the approximate frequency of the precessional cycle. A remarkable high sensitivity of 26 ppbv/°C is reached during Termination 1. Conservative analysis of the timing of the fast methane and temperature increases reveals significant lags of the methane increases for the DO events 5, 9, 10, 11, 13, and 15.

  20. Field metabolic rate and PCB adipose tissue deposition efficiency in East Greenland polar bears derived from contaminant monitoring data.

    PubMed

    Pavlova, Viola; Nabe-Nielsen, Jacob; Dietz, Rune; Svenning, Jens-Christian; Vorkamp, Katrin; Rigét, Frank Farsø; Sonne, Christian; Letcher, Robert J; Grimm, Volker

    2014-01-01

    Climate change will increasingly affect the natural habitat and diet of polar bears (Ursus maritimus). Understanding the energetic needs of polar bears is therefore important. We developed a theoretical method for estimating polar bear food consumption based on using the highly recalcitrant polychlorinated biphenyl (PCB) congener, 2,2',4,4',55-hexaCB (CB153) in bear adipose tissue as an indicator of food intake. By comparing the CB153 tissue concentrations in wild polar bears with estimates from a purposely designed individual-based model, we identified the possible combinations of field metabolic rates (FMR) and CB153 deposition efficiencies in East Greenland polar bears. Our simulations indicate that if 30% of the CB153 consumed by polar bear individuals were deposited into their adipose tissue, the corresponding FMR would be only two times the basal metabolic rate. In contrast, if the modelled CB153 deposition efficiency were 10%, adult polar bears would require six times more energy than that needed to cover basal metabolism. This is considerably higher than what has been assumed for polar bears in previous studies though it is similar to FMRs found in other marine mammals. An implication of this result is that even relatively small reductions in future feeding opportunities could impact the survival of East Greenland polar bears.

  1. Field Metabolic Rate and PCB Adipose Tissue Deposition Efficiency in East Greenland Polar Bears Derived from Contaminant Monitoring Data

    PubMed Central

    Pavlova, Viola; Nabe-Nielsen, Jacob; Dietz, Rune; Svenning, Jens-Christian; Vorkamp, Katrin; Rigét, Frank Farsø; Sonne, Christian; Letcher, Robert J.; Grimm, Volker

    2014-01-01

    Climate change will increasingly affect the natural habitat and diet of polar bears (Ursus maritimus). Understanding the energetic needs of polar bears is therefore important. We developed a theoretical method for estimating polar bear food consumption based on using the highly recalcitrant polychlorinated biphenyl (PCB) congener, 2,2′,4,4′,55-hexaCB (CB153) in bear adipose tissue as an indicator of food intake. By comparing the CB153 tissue concentrations in wild polar bears with estimates from a purposely designed individual-based model, we identified the possible combinations of field metabolic rates (FMR) and CB153 deposition efficiencies in East Greenland polar bears. Our simulations indicate that if 30% of the CB153 consumed by polar bear individuals were deposited into their adipose tissue, the corresponding FMR would be only two times the basal metabolic rate. In contrast, if the modelled CB153 deposition efficiency were 10%, adult polar bears would require six times more energy than that needed to cover basal metabolism. This is considerably higher than what has been assumed for polar bears in previous studies though it is similar to FMRs found in other marine mammals. An implication of this result is that even relatively small reductions in future feeding opportunities could impact the survival of East Greenland polar bears. PMID:25101837

  2. Observed runoff, jokulhlaups and suspended sediment load from the Greenland ice at Kangerlussuaq, West Greenland, 2007 and 2008

    SciTech Connect

    Mernild, Sebastian Haugard; Hasholt, Bent

    2009-01-01

    This study fills the gap in hydrologic measurements of runoff exiting a part of the Greenland Ice Sheet (GrIS), the Kangerlussuaq drainage area, West Greenland. The observations are of value for obtaining knowledge about the terrestrial freshwater and sediment output from part of the GrIS and the strip of land between the GrIS and the ocean, in the context of varying ice sheet surface melt and influx entering the ocean. High-resolution stage, discharge and suspended sediment load show a decrease in runoff of {approx} 25% and in sediment load of {approx} 40% from 2007 to 2008 in response to a decrease in the summer accumulated number of positive degree days. During the 2007 and 2008 runoff season, joekulhlaups are observed at Kangerlussuaq, drained from an ice-dammed lake at the margin of the GrIS.

  3. Seven Global Goals. 2013 annual report, Southwestern Power Administration

    SciTech Connect

    none,

    2014-09-01

    For over 70 years, Southwestern has marketed and delivered reliable, renewable, and affordable hydropower, partnering with Federal power stakeholders and others in the industry to make sure the lights stay on. This kind of effective, efficient, and cost conscious operation is made possible only by hard work and dedication. Southwestern employees work individually and as a team to meet seven comprehensive agency goals that touch on all aspects of the agency’s operations. Dubbed the “Seven Global Goals” by Administrator Chris Turner, these objectives identify specific, measurable targets that support Southwestern’s mission and reinforce its responsibilities toward its customers and the Nation.

  4. Cryo-life habitability on a polythermal glacier in Greenland

    NASA Astrophysics Data System (ADS)

    Lutz, S.; Anesio, A. M.; Benning, L. G.

    2012-12-01

    Modern surface glacial ice and snow are extreme environments at the edge of Earth's biosphere and potential sites of biosignatures in future planetary missions. The primary colonization of snow and ice is an important biogeological scenario with clear implications for the life detection on other icy planets [1]. Hence, knowledge of the adaptations and survival strategies adopted by extremophiles - cryophiles - in terrestrial cryogenic environments is vital for our ability to process data from future planetary missions. Despite it being one of the most extreme habitats on Earth, glacial ice and snow fields are colonised by a plethora of organisms including snow algae, bacteria, fungi, protozoa, rotifers and even invertebrates [2]. Although low in number and diversity compared to other habitats, snow and ice algae are a major primary producer in glacial settings [3,4]. Their life cycle influences the structure and diversity of neighbouring microbial communities [5] and they produce a suite of complex molecules to protect themselves against cold [6], UV [7], or nutrient deficiency [8]. However, these adaptations are poorly understood and we know very little about the complexity of the biological inventory contained within snow and ice environments. We have been investigating the potential of carbon fluxes from snow to ice, cryoconites and runoff water on the polythermal Mittivakkat glacier in SE Greenland and the effect of cell retention at the glacial surface on the albedo. The complementary microbiological and geochemical characteristics have been characterized at a suite of sampling sites in the ablation, superimposed and accumulation zone of the glacier. Results from photosynthesis and respiration measurements (e.g., snow fields, cryoconites, glacial outflow, clean snow) show that snow and ice surfaces have the potential to accumulate algal cells which become an important source of organic carbon for cryoconites. The accumulation of cells at the glacial surface

  5. Floods of December 1966 in southwestern Utah

    USGS Publications Warehouse

    Butler, Elmer; Mundorff, J.C.

    1970-01-01

    Severe floods occurred in parts of southwestern Utah on December 5-6, 1966, as a result of precipitation of about 1 inch to more than 12 inches during December 3-6. The flood on the Virgin River was the greatest since the first settlers arrived in 1860. The peak discharge of the Virgin River at Virgin, Utah, was 22,830 cubic feet per second on December 6; this exceeded the previous maximum discharge of 13,500 cubic feet per second on March 3, 1938, and September 17, 1961, and probably has a recurrence interval of 100 years. At eight other gage sites in the flood area, the peak discharge in December 1966 was the highest of record; the recurrence intervals of some of the peak discharges may be 100 years. The flood peaks were generally of short duration and most streams receded to near base flow within 24 hours. The dissolved-solids content was significantly lower in the Virgin River at Virgin than at St. George, about 25 miles downstream; the water was of the calcium sulfate type at both sites. Data for the Santa Clara River above Winsor Dam and the Santa Clara River near Santa Clara show a significant increase in dissolved solids between the two sites. The water above Winsor Dam was of the calcium bicarbonate type, and the water near Santa Clara was of the calcium bicarbonate sulfate type. The suspended-sediment discharge, during the period December 5-8, 1966, at Santa Clara River above Winsor Dam, near Santa Clara was about foyer times greater than all the suspended-sediment discharge during the preceding 3 years ; the suspended-sediment discharge of the Virgin River at Virgin was greater during the 4-day period than during any one of the preceding 3 years. Nearly all the flood damage in the area occurred in the Virgin River basin. According to the Soil Conservation Service, total damage in the Dixie Soil Conservation District in Washington County was about $835,000; 60 percent of the damage was caused by floodwater and 40 percent by deposited sediment.

  6. Hydrogeology of the Markagunt Plateau, Southwestern Utah

    USGS Publications Warehouse

    Spangler, Lawrence E.

    2010-01-01

    The Markagunt Plateau, in southwestern Utah, lies at an altitude of about 9,500 feet and is capped primarily by Quaternary-age basalt that overlies Eocene-age freshwater limestone of the Claron Formation. Over large parts of the Markagunt Plateau, dissolution of the Claron limestone and subsequent collapse of the overlying basalt have produced a terrain characterized by sinkholes as much as 1,000 feet across and 100 feet deep. Numerous large springs discharge from the basalt and underlying limestone on the plateau, including Mammoth Spring, one of the largest springs in Utah, with a discharge that can exceed 300 cubic feet per second. Discharge from Mammoth Spring is from the Claron Formation; however, recharge to the spring largely takes place by both focused and diffuse infiltration through the basalt that caps the limestone. Results of dye tracing to Mammoth Spring indicate that recharge originates largely southwest of the spring outside of the Mammoth Creek watershed, as well as from losing reaches along Mammoth Creek. Maximum groundwater travel time to the spring from dye-tracer tests during the snowmelt runoff period was about 1 week. Specific conductance and water temperature data from the spring show an inverse relation to discharge during snowmelt runoff and rainfall events, also indicating short groundwater residence times. Results of major-ion analyses for samples collected from Mammoth and other springs on the plateau indicate calcium-bicarbonate type water containing low (less than 200 mg/L) dissolved-solids concentrations. Investigations in the Navajo Lake area along the southern margin of the plateau have shown that water losing to sinkholes bifurcates and discharges to both Cascade and Duck Creek Springs, which subsequently flow into the Virgin and Sevier River basins, respectively. Groundwater travel times to these springs, on the basis of dye tracing, were about 8.5 and 53 hours, respectively. Similarly, groundwater travel time from Duck Creek

  7. 40 CFR 81.125 - Southwestern Oklahoma Intrastate Air Quality Control Region.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... Air Quality Control Regions § 81.125 Southwestern Oklahoma Intrastate Air Quality Control Region. The Southwestern Oklahoma Intrastate Air Quality Control Region consists of the territorial area encompassed by the... 40 Protection of Environment 17 2010-07-01 2010-07-01 false Southwestern Oklahoma Intrastate...

  8. 40 CFR 81.241 - Southwestern Mountains-Augustine Plains Intrastate Air Quality Control Region.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 17 2010-07-01 2010-07-01 false Southwestern Mountains-Augustine... PLANNING PURPOSES Designation of Air Quality Control Regions § 81.241 Southwestern Mountains-Augustine Plains Intrastate Air Quality Control Region. The Southwestern Mountains-Augustine Plains Intrastate...

  9. The energy behind the power. Southwestern Power Administration 1994 annual report

    SciTech Connect

    1994-12-31

    This is the Southwestern Power Administration 1994 annual report. The topics of the report include a letter to the secretary; an overview including the mission statement, a description of the Southwestern Federal Power System, financial statement, performance measurements, national performance review; year in review, summary of results, financial and statistical data and the Southwestern Power Administration Organization.

  10. 40 CFR 81.241 - Southwestern Mountains-Augustine Plains Intrastate Air Quality Control Region.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 17 2011-07-01 2011-07-01 false Southwestern Mountains-Augustine... PLANNING PURPOSES Designation of Air Quality Control Regions § 81.241 Southwestern Mountains-Augustine Plains Intrastate Air Quality Control Region. The Southwestern Mountains-Augustine Plains Intrastate...

  11. 40 CFR 81.241 - Southwestern Mountains-Augustine Plains Intrastate Air Quality Control Region.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 18 2013-07-01 2013-07-01 false Southwestern Mountains-Augustine... PLANNING PURPOSES Designation of Air Quality Control Regions § 81.241 Southwestern Mountains-Augustine Plains Intrastate Air Quality Control Region. The Southwestern Mountains-Augustine Plains Intrastate...

  12. 40 CFR 81.241 - Southwestern Mountains-Augustine Plains Intrastate Air Quality Control Region.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 18 2014-07-01 2014-07-01 false Southwestern Mountains-Augustine... PLANNING PURPOSES Designation of Air Quality Control Regions § 81.241 Southwestern Mountains-Augustine Plains Intrastate Air Quality Control Region. The Southwestern Mountains-Augustine Plains Intrastate...

  13. 40 CFR 81.241 - Southwestern Mountains-Augustine Plains Intrastate Air Quality Control Region.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 18 2012-07-01 2012-07-01 false Southwestern Mountains-Augustine... PLANNING PURPOSES Designation of Air Quality Control Regions § 81.241 Southwestern Mountains-Augustine Plains Intrastate Air Quality Control Region. The Southwestern Mountains-Augustine Plains Intrastate...

  14. 77 FR 30437 - Proposed Amendment of Air Traffic Service Routes; Southwestern United States

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-05-23

    ... Routes; Southwestern United States AGENCY: Federal Aviation Administration (FAA), DOT. ACTION: Notice of... Federal Register proposing to amend various Air Traffic Service Routes in the Southwestern United States...; Southwestern United States as published in the Federal Register of April 23, 2010 (77 FR 24156) FR Doc....

  15. Crossing the Technology Adoption Chasm: Implications for DoD

    DTIC Science & Technology

    2008-06-30

    elli= cowpea varieties for extension education in Southwestern Nigeria. The Journal of Agricultural Education and Extension, 12(3), 195-200. O’Rourke...Adekoya, A.E. (2006). Implication of farmers’ propensity to discontinue adoption of downey-mildew resistant maize and improved cowpea varieties for... Cowpea (Farmer) Feedback Provision (-) Marketability Varieties Input Availability (+) Dependent Variable = De-adoption of Cowpea

  16. Late-Holocene Fluctuations of the Greenland Ice Sheet: Insights from a south Greenland threshold lake

    NASA Astrophysics Data System (ADS)

    Sinclair, G.; Carlson, A. E.; Reilly, B.

    2015-12-01

    Several centennial-scale climate fluctuations during the late-Holocene make it an ideal test case for examining the effects of climate change on sea level at societally-relevant timescales. Across much of the Arctic, glaciers and ice sheets reached their maximum late-Holocene extent during the Little Ice Age (LIA, 1400-1900 C.E.), approximately coincident with the global temperature minima observed during this time. However, ongoing work suggests the south Greenland Ice Sheet (sGrIS) may have behaved differently during the late-Holocene, with several outlet glaciers retreating, rather than advancing, during the LIA, possibly due to regional warming in the region different from the Arctic trend. The Qassimiut lobe, a low-lying piedmont-like extension of the sGrIS, may be especially sensitive to late-Holocene climate changes. Geomorphic evidence outboard of Naujaat Sermia, an outlet glacier draining the Qassimiut lobe, suggests three distinct periods of land exposure. We hypothesize these occurred during the last deglacial period, after an advance from near or behind the present margin during the Neoglacial, and during warming following the Little Ice Age in the last 1-2 centuries. Here, we present data from threshold lake cores immediately outboard of the presumed Neoglacial moraine. A sharp contact divides glacial sands and silts from organic gyttja, indicating glacial retreat from the moraine and subsequent meltwater diversion. The contact is accompanied by several geochemical changes, including increased Fe/Ti ratios, increased Br, and decreased Si and K, indicating a switch from more clastic to organic sedimentation. Radiocarbon ages from eight macrofossils immediately above this contact are calibrated to 1350-1950 C.E., suggesting the ice sheet may have retreated from its late-Holocene maximum during the Little Ice Age, but the wide range in ages suggests reworking of organic material may be significant in this region.

  17. Organotropism of persistent organic pollutants and heavy metals in the Greenland shark Somniosus microcephalus in NE Greenland.

    PubMed

    Corsolini, Simonetta; Ancora, Stefania; Bianchi, Nicola; Mariotti, Giacomo; Leonzio, Claudio; Christiansen, Jørgen S

    2014-10-15

    The Greenland shark Somniosus microcephalus is an opportunistic feeder, a top predator, and a very long-lived species. The brain, liver, red and white muscle, gonads, fat, skin, pancreas, and spleen of Greenland sharks from NE Greenland fjords were analysed for PCBs, PCDDs/DFs, PBDEs; DDT isomers; HCH isomers; dieldrin; endrin; HCB; Cd, Hg, Pb, and Se. PCBs (2.01-103 ng/g wet wt) and PBDEs (7.9-3050 pg/g wet wt) were detected in most of the samples. PCDDs/DFs showed high values when detected. DDTs, HCB and HCHs were only detected in some tissues. The ΣTEQ was 5.76 pg/g in muscle. Cadmium mainly accumulated in the pancreas and liver (19.6 and 10.7 mg/kg dry wt, respectively); mercury in red muscle (4.10-6.91 mg/kg dry wt); selenium in the pancreas (3.57 mg/kg dry wt) and spleen (1.95 mg/kg dry wt); lead in the skin (0.358 mg/kgd ry wt). The selenium-mercury ratio in the liver was also evaluated.

  18. Has dynamic thinning switched off in south-east Greenland?

    NASA Astrophysics Data System (ADS)

    Murray, T.; Scharrer, K.; James, T.; Luckman, A.; Selmes, N.; Cook, S.; Hughes, A.; Cordero Llana, L.; Booth, A.; McGovern, J.; Rutt, I.

    2008-12-01

    Following a relatively stable period during the 1990s, dramatic changes have been reported for many tidewater outlets in SE Greenland. Some of the most important results come from measurements using the GRACE (Gravity Recovery and Climate Experiment) mission (1, 2). These data clearly identified the SE of the Greenland Ice Sheet (GrIS) as having the highest rates of mass loss. Two of the major outlet glaciers in this area, Helheim and Kangerdlugssuaq accelerated by about 100% and 40%, respectively, and their calving fronts retreated by several km (3, 4). Retreat and acceleration occurred in two phases during summer 2003 and 2005 at Helheim, and in a single period between late 2004 and early 2005 at Kangerdlugssuaq. Further south, widespread glacier acceleration between 1996 and 2005 affected most of the outlet glaciers, and Greenland's mass loss doubled in the period (5). Increased discharge due to thinning in the marginal areas, coupled to rapid changes in ice dynamics and synchronous retreat of calving front positions, led to speculations that the GrIS had crossed a "tipping point" induced by global warming. However, subsequent studies in summer 2006 showed that Helheim and Kangerdlugssuaq had simultaneously slowed down again and thinning stopped (6). In summer 2007, we collected lidar data over Helheim and Kangerdlugssuaq flown by the NERC Airborne Research and Survey Facility. Data collected were single swaths over mountain areas, as well as centerline profiles. In cooperation with NASA Goddard Space Flight Center, we conducted a similar but extended campaign in 2008, collecting lidar and radar data for the 16 largest outlet glaciers in SE Greenland, targeting the full extent of the major GRACE anomaly. We used lidar swaths from bedrock as ground-control for extracting DEMs from ASTER satellite images covering the period with major changes in 2004 to 2006, and compared them to lidar and SPOT 5 DEMs to produce the most recent volume change and velocity estimates

  19. Has dynamic thinning switched off in south-east Greenland?

    NASA Astrophysics Data System (ADS)

    Murray, T.; Scharrer, K.; James, T. D.; Dye, S. R.; Hanna, E.; Booth, A. D.; Selmes, N.; Luckman, A.; Hughes, A. L. C.; Huybrechts, P.

    2009-04-01

    Following a relatively stable period during the 1990's, dramatic changes have been reported for many tidewater outlets in the south-eastern part of the Greenland Ice Sheet (GrIS). Results from measurements using the GRACE (Gravity Recovery and Climate Experiment) mission clearly identified the south-eastern part of the GrIS as having the highest rates of mass loss (1, 2). Two of the major outlet glaciers in this area, Helheim and Kangerdlugssuaq, accelerated by about 100 percent and 40 percent, respectively, and their calving fronts retreated by several km (3). Retreat and acceleration occurred in two phases during summer 2003 and 2005 at Helheim, and in a single period between late 2004 and early 2005 at Kangerdlugssuaq. Further south widespread glacier acceleration between 1996 and 2005 affected most of the outlet glaciers (4). In all Greenland's mass loss was calculated to have doubled in the period (4). Increased discharge due to thinning in the marginal areas, coupled to rapid changes in ice dynamics and synchronous retreat of their calving front positions, led to speculations that the GrIS had crossed a "tipping point" induced by global warming. However, subsequent studies showed that during summer 2006 Helheim and Kangerlugssuaq had simultaneously slowed down and their thinning had stopped. Because variability in the ice sheet's mass loss results mostly from the SE Greenland sector, further understanding of the nature, distribution, and controls of dynamic change in this region is essential. In order to examine the extent of the dynamic changes and to identify their cause we used satellite data to measure glacier surface elevation and calving front positions of 24 outlets of 14 major tidewater terminating glaciers, as well as speeds of 9 outlets in SE Greenland. We concentrate on the region where the GRACE data show highest rates of mass change and our data cover the period during and after the cessation of fast flow and thinning at Helheim and

  20. Holocene history of North Ice Cap, northwestern Greenland

    NASA Astrophysics Data System (ADS)

    Corbett, L. B.; Kelly, M. A.; Osterberg, E. C.; Axford, Y.; Bigl, M.; Roy, E. P.; Thompson, J. T.

    2013-12-01

    Although much research has focused on the past extents of the Greenland Ice Sheet, less is known about the smaller ice caps on Greenland and how they have evolved over time. These small ice caps respond sensitively to summer temperatures and, to a lesser extent, winter precipitation, and provide valuable information about climatic conditions along the Greenland Ice Sheet margins. Here, we investigate the Holocene history of North Ice Cap (76°55'N 68°00'W), located in the Nunatarssuaq region near Thule, northwest Greenland. Our results are based on glacial geomorphic mapping, 10Be dating, and analyses of sediment cores from a glacially fed lake. Fresh, unweathered and unvegetated boulders comprise moraines and drift that mark an extent of North Ice Cap ~25 m outboard of the present ice margin. It is likely that these deposits were formed during late Holocene time and we are currently employing 10Be surface exposure dating to examine this hypothesis. Just outboard of the fresh moraines and drift, boulders and bedrock show significant weathering and are covered with lichen. Based on glacial geomorphic mapping and detailed site investigations, including stone counts, we suggest that the weathered boulders and bedrock were once covered by erosive Greenland Ice Sheet flow from southeast to northwest over the Nunatarssuaq region. Five 10Be ages from the more weathered landscape only 100-200 m outboard of the modern North Ice Cap margin are 52 and 53 ka (bedrock) and 16, 23, and 31 ka (boulders). These ages indicate that recent ice cover has likely been cold-based and non-erosive, failing to remove inherited cosmogenic nuclides from previous periods of exposure, although the youngest boulder may provide a maximum limiting deglaciation age. Sediment cores collected from Delta Sø, a glacially-fed lake ~1.5 km outside of the modern North Ice Cap margin, contain 130 cm of finely laminated sediments overlying coarse sands and glacial till. Radiocarbon ages from just above

  1. 78 FR 54591 - Fisheries of the Exclusive Economic Zone Off Alaska; Greenland Turbot in the Bering Sea and...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-09-05

    ... Economic Zone Off Alaska; Greenland Turbot in the Bering Sea and Aleutian Islands Management Area AGENCY... Greenland turbot in the Bering Sea subarea of the Bering Sea and Aleutian Islands Management Area (BSAI). This action is necessary to fully use the 2013 initial total allowable catch (ITAC) of Greenland...

  2. The origin of jarosite associated with a gossan on Archean gneiss in Southwest Greenland

    NASA Astrophysics Data System (ADS)

    Peng, Y.; Pratt, L. M.; Young, S. A.; Cadieux, S. B.; White, J. R.

    2013-12-01

    The mineral Jarosite [KFe3(SO4)2(OH)6] since its discovery, by Opportunity rover at Meridiani Planum on Mars, has been the subject of intense geochemical and environmental study over the last 5-10 years. Jarosite requires highly acidic, K-enriched, and oxidizing aqueous conditions for formation. Stable isotopes of O, H, and S of jarosite have the ability to record the temperatures of formation, environments of deposition, fluids, and fluid/atmospheric interactions. Therefore, the origin of jarosite is important for understanding present and past environmental conditions on Mars. Unfortunately, the origin of jarosite on Mars remains unclear. Jarosite is commonly found on Earth in the weathering zones of pyrite-bearing ore deposits, near-surface playa sediments in acid-saline lakes, or epithermal environments and hot springs. Here, we report the occurrence of jarosite in association with a gossan overlying weathered Archean gneiss and Paleoproterozoic mafic dikes at the ice-free margin of southwestern Greenland. In our 2012 field campaign, we excavated soil pits to a depth of 40 cm with a high vertical sampling resolution. No visible pyrite was found in the nearby outcroppings of gneiss in the field. XRD data show that all samples were composed of anorthite, quartz, albite, jarosite, muscovite, and microcline. Jarosite was the only sulfur-bearing mineral identified by XRD, with abundance of jarosite increasing with depth (up to 8.4 wt. %) in the soil pits. Water soluble and acid soluble sulfate were sequentially extracted using 10% NaCl and 2N HCl solutions, respectively. Pyrite was then subsequently extracted from insoluble residues by a chromium reduction method. The average abundance of water soluble sulfate, acid soluble sulfate, and pyrite were 100 ppm, 7 wt. %, and 10 ppm, respectively. The δ34S values of water soluble sulfate, acid soluble sulfate, and pyrite range from -0.7‰ to 3.1‰ (average= 1.5‰), -1.2 to 1.5‰ (average= 0.7‰), and 0.3‰ to 6.7

  3. Levels and temporal trends of HCH isomers in ringed seals from West and East Greenland.

    PubMed

    Rigét, Frank; Vorkamp, Katrin; Dietz, Rune; Muir, Derek C G

    2008-08-01

    Levels and temporal trends of the hexachlorocyclohexane isomers alpha-, beta- and gamma-HCH were analysed in blubber of juvenile ringed seals from West Greenland (1994 to 2006) and juvenile and adult ringed seals from East Greenland (1986 to 2006). No significant differences in the concentration levels in the juvenile seals were found between East and West Greenland for any of the three isomers. alpha-HCH concentrations were not significantly different between juvenile and adult ringed seals from East Greenland, whereas beta- and gamma-HCH concentrations were significantly higher in adult ringed seals. alpha- and beta-HCH in Greenland ringed seals were approximately a factor two lower than in the Canadian Arctic, and alpha-HCH was a factor 2-3 higher than in ringed seals from an area east of Svalbard, Norway. Annual decreases in ringed seals from Greenland during the study periods were detected to be 9.1-11.7%, 1.4-3.9% and 6.0-6.4% for alpha-, beta- and gamma-HCH, respectively, being quite similar in both East and West Greenland. Similar levels and trends in East and West Greenland support the general understanding of the pathways of HCH isomers to and in the Arctic.

  4. Addressing Systemic Oppression in Greenland's Preschools: The Adaptation of a Coaching Model

    ERIC Educational Resources Information Center

    Wyatt, Tasha R.; Lyberth, Naussunguaq

    2011-01-01

    For most of the last two centuries, Native Greenlandic teachers had been left out of the decision-making process regarding effective education for Greenlandic students. Rather, Danish education and church officials, living in Denmark, made important pedagogical and curricular decisions with little to no input from local teachers (Jakobsen, 1999).…

  5. Arctic Ocean UNCLOS Article 76 Work for Greenland Starts on Land

    NASA Astrophysics Data System (ADS)

    Dahl-Jensen, T.; Marcussen, C.; Jackson, R.; Voss, P.

    2005-12-01

    One of the most lonely and desolate stretches of coastline on the planet has become the target for UNCLOS article 76 related research. The Danish Continental Shelf Project has launched a work program to investigate the possibilities for Greenland to claim an area outside the 200 nm limit in the Arctic Ocean. The role of the Lomonosov Ridge as a Natural Prolongation of Greenland/Canada is an important issue, and in order to better evaluate the connection between Greenland and the Lomonosov Ridge the nature of not only the ridge but also of Northern Greenland is the target of deep crustal investigations. The North Greenland Fold belt covers the ice-free part of North Greenland and continues west in the Canadian Arctic. The foldbelt was formed during the Ellesmerian orogeny, where sediments from the Franklinian Basin where compressed and deformed. The deep structure of basin and its subsequent closure are broadly unknown. Three broad band earthquake seismological stations where installed in North Greenland to supplement the existing stations at Alert (Canada) and Station Nord to the east, and the first data was available summer 2005. Crustal thickness data from these first results are presented. Plans for the spring 2006 consist of wide-angle acquisition on the sea ice from the Greenland-Canadian mainland out onto the Lomonosov Ridge, a joint Danish - Canadian project with a 400 km long profile over difficult ice conditions, 18 tons of explosives, three helicopters, a Twin Otter and about 30 participants.

  6. On the Origin of Multidecadal to Centennial Greenland Temperature Anomalies Over the Past 800 yr

    NASA Technical Reports Server (NTRS)

    Kobashi, T.; Shindell, D. T.; Kodera, K.; Box, J. E.; Nakaegawa, T.; Kawamura, K.

    2013-01-01

    The surface temperature of the Greenland ice sheet is among the most important climate variables for assessing how climate change may impact human societies due to its association with sea level rise. However, the causes of multidecadal-to-centennial temperature changes in Greenland temperatures are not well understood, largely owing to short observational records. To examine these, we calculated the Greenland temperature anomalies (GTA[G-NH]) over the past 800 yr by subtracting the standardized northern hemispheric (NH) temperature from the standardized Greenland temperature. This decomposes the Greenland temperature variation into background climate (NH); polar amplification; and regional variability (GTA[G-NH]). The central Greenland polar amplification factor as expressed by the variance ratio Greenland/NH is 2.6 over the past 161 yr, and 3.3-4.2 over the past 800 yr. The GTA[G-NH] explains 31-35%of the variation of Greenland temperature in the multidecadal-to-centennial time scale over the past 800 yr. We found that the GTA[G-NH] has been influenced by solar-induced changes in atmospheric circulation patterns such as those produced by the North Atlantic Oscillation/Arctic Oscillation (NAO/AO). Climate modeling and proxy temperature records indicate that the anomaly is also likely linked to solar-paced changes in the Atlantic meridional overturning circulation (AMOC) and associated changes in northward oceanic heat transport.

  7. L3 English Acquisition in Denmark and Greenland: Gender-Related Tendencies

    ERIC Educational Resources Information Center

    Spellerberg, Stine Marie

    2011-01-01

    This paper presents findings of gender-related tendencies found in a study of factors influential in third language acquisition of English in Denmark and Greenland. A survey consisting of a questionnaire and an English test was carried out amongst pupils in their last year of compulsory schooling in Copenhagen, Denmark, and Nuuk, Greenland. In…

  8. First record of Taenia ovis krabbei muscle cysts in muskoxen from Greenland.

    PubMed

    Raundrup, Katrine; Al-Sabi, Mohammad Nafi Solaiman; Kapel, Christian Moliin Outzen

    2012-03-23

    A first record of Taenia ovis krabbei muscle cysts in a muskoxen (Ovibos moschatus) from the Kangerlussuaq population in West Greenland suggests that introduced muskoxen now contributes to the transmission of this parasite in addition to previous observations from caribou (Rangifer tarandus). Muskoxen and caribou are the only wild ungulates in Greenland.

  9. On the origin of multidecadal to centennial Greenland temperature anomalies over the past 800 yr

    NASA Astrophysics Data System (ADS)

    Kobashi, T.; Shindell, D. T.; Kodera, K.; Box, J. E.; Nakaegawa, T.; Kawamura, K.

    2013-03-01

    The surface temperature of the Greenland ice sheet is among the most important climate variables for assessing how climate change may impact human societies due to its association with sea level rise. However, the causes of multidecadal-to-centennial temperature changes in Greenland temperatures are not well understood, largely owing to short observational records. To examine these, we calculated the Greenland temperature anomalies (GTA[G-NH]) over the past 800 yr by subtracting the standardized northern hemispheric (NH) temperature from the standardized Greenland temperature. This decomposes the Greenland temperature variation into background climate (NH); polar amplification; and regional variability (GTA[G-NH]). The central Greenland polar amplification factor as expressed by the variance ratio Greenland/NH is 2.6 over the past 161 yr, and 3.3-4.2 over the past 800 yr. The GTA[G-NH] explains 31-35% of the variation of Greenland temperature in the multidecadal-to-centennial time scale over the past 800 yr. We found that the GTA[G-NH] has been influenced by solar-induced changes in atmospheric circulation patterns such as those produced by the North Atlantic Oscillation/Arctic Oscillation (NAO/AO). Climate modeling and proxy temperature records indicate that the anomaly is also likely linked to solar-paced changes in the Atlantic meridional overturning circulation (AMOC) and associated changes in northward oceanic heat transport.

  10. A climate-data record of the “clear-sky” surface temperature of the Greenland Ice Sheet (Invited)

    NASA Astrophysics Data System (ADS)

    Hall, D. K.; Comiso, J. C.; Digirolamo, N. E.; Stock, L. V.; Riggs, G. A.; Shuman, C. A.

    2009-12-01

    We are developing a climate-data record (CDR) of daily “clear-sky” ice-surface temperature (IST) of the Greenland Ice Sheet, from 1982 to the present using Advanced Very High Resolution Radiometer (AVHRR) (1982 - present) and Moderate-Resolution Imaging Spectroradiometer (MODIS) data (2000 - present) at a resolution of approximately 5 km. The CDR will be continued in the National Polar-orbiting Operational Environmental Satellite System Visible/Infrared Imager Radiometer Suite era. Two algorithms remain under consideration. One algorithm under consideration is based on the split-window technique used in the Polar Pathfinder dataset (Fowler et al., 2000 & 2007). Another algorithm under consideration, developed by Comiso (2006), uses a single channel of AVHRR data (channel 4) in conjunction with meteorological-station data to account for atmospheric effects and drift between AVHRR instruments. Known issues being addressed in the production of the CDR are: time-series bias caused by cloud cover (surface temperatures can be different under clouds vs. clear areas) and cross-calibration in the overlap period between AVHRR instruments, and between AVHRR and MODIS instruments. Because of uncertainties, mainly due to clouds (Stroeve & Steffen, 1998; Wang and Key, 2005; Hall et al., 2008 and Koenig and Hall, submitted), time-series of satellite IST do not necessarily correspond to actual surface temperatures. The CDR will be validated by comparing results with automatic-weather station (AWS) data and with satellite-derived surface-temperature products. Regional “clear-sky” surface temperature increases in the Arctic, measured from AVHRR infrared data, range from 0.57±0.02 deg C (Wang and Key, 2005) to 0.72±0.10 deg C (Comiso, 2006) per decade since the early 1980s. Arctic warming has important implications for ice-sheet mass balance because much of the periphery of the Greenland Ice Sheet is already near 0 deg C during the melt season, and is thus vulnerable to

  11. DRAINED-FIELD AGRICULTURE IN SOUTHWESTERN TLAXCALA, MEXICO.

    DTIC Science & Technology

    This study examines the land and water management problems of Tlaxcala , concentrating on the southwestern portion of the state which lies at the...deposition on basin floor soils, the Tlaxcala farmers practice sophisticated land conservation and reclamation techniques, using a minimum of equipment. In

  12. SOUTHWESTERN CORNER OF SECTION 1, WITH (L TO R) BIVOUAC ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    SOUTHWESTERN CORNER OF SECTION 1, WITH (L TO R) BIVOUAC OF THE DEAD TABLET, INVERTED CANNON AND UNION WOMAN’S RELIEF CORPS #44 MONUMENT IN FOREGROUND. VIEW TO NORTHEAST. - Crown Hill Cemetery, Crown Hill National Cemetery, 700 West Thirty-eighth Street, Indianapolis, Marion County, IN

  13. Wildlife Reservoir for Hepatitis E Virus, Southwestern France

    PubMed Central

    Lhomme, Sebastien; Top, Sokunthea; Bertagnoli, Stephane; Dubois, Martine; Guerin, Jean-Luc

    2015-01-01

    Pigs are a reservoir for hepatitis E virus (HEV). To determine the relative contribution of game to the risk for human HEV infection in southwestern France, we tested wildlife samples. HEV RNA was in 3.3% of wildlife livers, indicating that in this region, eating game meat is as risky as eating pork. PMID:26079541

  14. 2014 annual site environmental report, Southwestern Power Administration

    SciTech Connect

    none,

    2014-12-31

    Southwestern Power Administration’s Annual Site Environmental Report (ASER) serves as the chief reporting mechanism for site environmental performance information within the Department of Energy and as a valuable resource for shared and collaborative environmental protection and performance information to Agency stakeholders and members of the public living near Southwestern Power Administration’s (Southwestern) facilities and transmission line rights-of-ways. This ASER meets the requirements of Department of Energy (DOE) Order 231.B. Southwestern’s key environmental involvement includes an emphasis on the protection of ecological resources which is effectively accomplished through environmental program elements such as protecting water resources, generation of clean hydropower energy, oil spill prevention practices, elimination of green-house gas emissions, and comprehensive project reviews to ensure the protection of living organisms, migratory birds, Federally threatened or endangered species, and historic or cultural resources. Southwestern continues to actively minimize effects to natural resources and strive for continual improvement in the area of environmental compliance and sustainability while achieving the agency mission to market and deliver Federal hydroelectric power.

  15. Treatment for Juveniles Who Sexually Offend in a Southwestern State

    ERIC Educational Resources Information Center

    Ikomi, Philip A.; Harris-Wyatt, Georgetta; Doucet, Geraldine; Rodney, H. Elaine

    2009-01-01

    A 25-item questionnaire was mailed to sex offender treatment providers from counties with 60 or more reported juvenile sex offenders in a Southwestern state to determine the most effective treatment for juvenile sex offenders. Results indicated that cognitive behavioral therapy was the most successful reported approach to treatment with an average…

  16. Listenership of Radio Agricultural Broadcasts in Southwestern Nigeria

    ERIC Educational Resources Information Center

    Emmanuel, Adekoya Adegbenga; Olabode, Badiru Idris

    2012-01-01

    Agricultural broadcasts on radio play a major role in agricultural extension and rural development in Nigeria due to the low ratio of extension agents in relation to the farming population. The broadcasts have been on air for some time and therefore there is a need to investigate their acceptance among the rural dwellers in Southwestern Nigeria.…

  17. Native American Student Resiliency within Southwestern Tribal Colleges

    ERIC Educational Resources Information Center

    Peralez, Elizabeth

    2014-01-01

    The purpose of this study was to explore the degree to which Native American culture impacts the resiliency of Native American students earning degrees at three tribal colleges in the southwestern part of the United States. This study was a qualitative case study that was based on the following research question: "How does Native American…

  18. Guanophilic fungi in three caves of southwestern Puerto Rico

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Fifty species of guanophilic (bat guano-loving) fungi were isolated from field-collected samples within three caves in south-western Puerto Rico; most were mitosporic fungi (23 species). The caves studied were Cueva La Tuna (Cabo Rojo), Cueva de Malano (Sistema de Los Chorros, San Germán), and Cuev...

  19. Characterizing supraglacial meltwater channel hydraulics on the Greenland Ice Sheet from in situ observations

    USGS Publications Warehouse

    Gleason, Colin J.; Smith, Laurence C.; Chu, Vena W.; Legleiter, Carl; Pitcher, Lincoln H.; Overstreet, Brandon T.; Rennermalm, Asa K.; Forster, Richard R.; Yang, Kang

    2016-01-01

    Supraglacial rivers on the Greenland ice sheet (GrIS) transport large volumes of surface meltwater toward the ocean, yet have received relatively little direct research. This study presents field observations of channel width, depth, velocity, and water surface slope for nine supraglacial channels on the southwestern GrIS collected between 23 July and 20 August, 2012. Field sites are located up to 74 km inland and span 494-1485 m elevation, and contain measured discharges larger than any previous in situ study: from 0.006 to 23.12 m3/s in channels 0.20 to 20.62 m wide. All channels were deeply incised with near vertical banks, and hydraulic geometry results indicate that supraglacial channels primarily accommodate greater discharges by increasing velocity. Smaller streams had steeper water surface slopes (0.74-8.83%) than typical in terrestrial settings, yielding correspondingly high velocities (0.40-2.60 m/s) and Froude numbers (0.45-3.11) with supercritical flow observed in 54% of measurements. Derived Manning's n values were larger and more variable than anticipated from channels of uniform substrate, ranging from 0.009 to 0.154 with a mean value of 0.035 +/- 0.027 despite the absence of sediment, debris, or other roughness elements. Ubiquitous micro-depressions in shallow sections of the channel bed may explain some of these roughness values. However, we find that other, unobserved sources of flow resistance likely contributed to these elevated n values: future work should explicitly consider additional sources of flow resistance beyond bed roughness in supraglacial channels. We conclude that hydraulic modelling for these channels must allow for both sub- and supercritical flow, and most importantly must refrain from assuming that all ice-substrate channels exhibit similar hydraulic behavior, especially for Froude numbers and Manning's n. Finally, this study highlights that further theoretical and empirical work on supraglacial channel hydraulics is

  20. Vegetation phenology gradients along the west and east coasts of Greenland from 2001 to 2015.

    PubMed

    Karami, Mojtaba; Hansen, Birger Ulf; Westergaard-Nielsen, Andreas; Abermann, Jakob; Lund, Magnus; Schmidt, Niels Martin; Elberling, Bo

    2017-02-01

    The objective of this paper is to characterize the spatiotemporal variations of vegetation phenology along latitudinal and altitudinal gradients in Greenland, and to examine local and regional climatic drivers. Time-series from the Moderate Resolution Imaging Spectroradiometer (MODIS) were analyzed to obtain various phenological metrics for the period 2001-2015. MODIS-derived land surface temperatures were corrected for the sampling biases caused by cloud cover. Results indicate significant differences between West and East Greenland, in terms of both observed phenology during the study period, as well as the climatic response. The date of the start of season (SOS) was significantly earlier (24 days), length of season longer (25 days), and time-integrated NDVI higher in West Greenland. The sea ice concentration during May was found to have a significant effect on the date of the SOS only in West Greenland, with the strongest linkage detected in mid-western parts of Greenland.

  1. Investigating the past and recent δ18O-accumulation relationship seen in Greenland ice cores

    NASA Astrophysics Data System (ADS)

    Buchardt, S. L.; Clausen, H. B.; Vinther, B. M.; Dahl-Jensen, D.

    2012-08-01

    Decadal means of δ18O and accumulation rates from 52 ice core sites in Greenland are presented. The accumulation rates are derived from annual layers determined in the δ18O curve. Investigation of the δ18O-accumulation relationship across the ice divide reveals a significant Foehn effect with anticorrelation of δ18O and accumulation on the lee side of the divide in Southern Greenland, while no effect is seen in Central Greenland. Furthermore, the sensitivity of accumulation rate to changes in temperature is found to be smaller in Northern Greenland than in the central and southern parts. Four sites in the data set contain sufficient recent data that the period of observed temperature rise from the 1990's and onwards can be investigated. All four sites are located close to the ice divide in Northern Greenland and while three sites show increased temperatures, none show evidence of increased accumulation.

  2. Inter-annual and geographical variations in the extent of bare ice and dark ice on the Greenland ice sheet derived from MODIS satellite images

    NASA Astrophysics Data System (ADS)

    Shimada, Rigen; Takeuchi, Nozomu; Aoki, Teruo

    2016-04-01

    Areas of dark ice have appeared on the Greenland ice sheet every summer in recent years. These are likely to have a great impact on the mass balance of the ice sheet because of their low albedo. We report annual and geographical variations in the bare ice and dark ice areas that appeared on the Greenland Ice Sheet from 2000 to 2014 by using MODIS satellite images. The July monthly mean of the extent of bare ice showed a positive trend over these 15 years, and large annual variability ranging from 89,975 km2 to 279,075 km2, 5% and 16% of the entire ice sheet, respectively. The extent of dark ice also showed a positive trend and varied annually, ranging from 3,575 km2 to 26,975 km2, 4% and 10% of the bare ice extent. These areas are geographically varied, and their expansion is the greatest on the western side, particularly the southwestern side of the ice sheet. The bare ice extent correlates strongly with the monthly mean air temperature in July, suggesting that the extent was determined by snow melt. The dark ice extent also correlates with the air temperature; however, the correlation is weaker. The dark ice extent further correlates negatively with solar radiation. This suggests that the extent of dark ice is not only controlled by snow melt on the ice, but also by changes in the surface structures of the bare ice surface, such as cryoconite holes, which are associated with impurities appearing on the ice surface.

  3. Discussion of “Deglacial paleoclimate in the southwestern United States: an abrupt 18.6 cold event and evidence for a North Atlantic forcing of Termination I” by M.S. Lachniet, Y. Asmerom and V. Polyak

    USGS Publications Warehouse

    Winograd, Isaac J.

    2012-01-01

    Utilizing a stable isotopic time series obtained from a speleothem (PC-1), which grew between 20.1 and 15.6 ka, Lachniet, Asmeron and Polyak (2011; hereafter LAP) present evidence for a significant cold event in the southern Great Basin at 18.6 ka, a finding that we accept. Supplementing this short record with a literature review, they go on to claim, as their central thesis, that the paleoclimate of the southwestern US was driven by “the transmission of atmospheric anomalies to the southwest…that coincided with deglacial climate changes in Greenland and the North Atlantic region”, not by a “dominant Pacific Ocean SST control” as suggested by SST time series off California and by the Devils Hole δ18O time series from the southern Great Basin. We do not find their central thesis supportable.

  4. Southwestern Power Administration Annual Report 2004-2006

    SciTech Connect

    2006-01-01

    Confidence Commitment Cooperation These are words that spring to mind regarding Southwestern Power Administration’s performance during fiscal years (FY) 2004-2006 By offering innovative, customer-oriented service, working to improve system reliability and efficiency, and partnering with customers and other Federal power stakeholders, Southwestern has certainly exhibited all three of these qualities during these challenging yet productive years In fact, our cooperative working relationships were critical to our success during the severe and widespread drought conditions which prevailed throughout Southwestern’s marketing area for much of 2005-2006 When we proposed a temporary energy deferral program, our customers came on board by voluntarily taking less Federal hydropower than they were entitled to, enabling us to preserve system storage and fulfill our contract obligations during the crucial summer months of 2006 The U S Army Corps of Engineers (Corps) also helped improve our drought situation by allowing Southwestern more operational flexibility on a regional level Despite the challenges this critical drought period presented, Southwestern remained committed to fulfilling our mission and strategic goals From FY 2004 through FY 2006, we marketed and delivered all available Federal hydropower while meeting and even exceeding the reliability standards of the North American Electric Reliability Corporation (NERC) Our Power Operations Training Center in Springfield, Missouri, was cited as an “Example of Excellence” during a NERC readiness audit in October 2006; and as we have every year since NERC began measuring, Southwestern far exceeded the accepted NERC compliance ratings for power system operations reliability Our commitment to excellence and accountability has kept our repayment goals on target as well Revenues were sufficient to repay all annual expenses and the required principal investment in the Federal hydropower facilities Furthermore, the original

  5. Physiologically based pharmacokinetic modeling of POPs in Greenlanders.

    PubMed

    Sonne, Christian; Gustavson, Kim; Rigét, Frank F; Dietz, Rune; Krüger, Tanja; Bonefeld-Jørgensen, Eva C

    2014-03-01

    Human exposure to persistent organic pollutants (POPs) and the potential health impact in the Arctic far from the emission sources have been highlighted in numerous studies. As a supplement to human POP biomonitoring studies, a physiologically based pharmacokinetic (PBPK) model was set up to estimate the fate of POPs in Greenlandic Inuit's liver, blood, muscle and adipose tissue following long-term exposure to traditional Greenlandic diet. The PBPK model described metabolism, excretion and POP accumulation on the basis of their physicochemical properties and metabolic rates in the organisms. Basic correlations between chemically analyzed blood POP concentrations and calculated daily POP intake from food questionnaire of 118 middle age (18-35years) Greenlandic Inuits from four cities in West Greenland (Qaanaaq: n=40; Qeqertarsuaq: n=36; Nuuk: n=20; Narsaq: n=22) taken during 2003 to 2006 were analyzed. The dietary items included were polar bear, caribou, musk oxen, several marine species such as whales, seals, bird and fish as well as imported food. The contaminant concentrations of the dietary items as well as their chemical properties, uptake, biotransformation and excretion allowed us to estimate the POP concentration in liver, blood, muscle and adipose tissue following long-term exposure to the traditional Greenlandic diet using the PBPK model. Significant correlations were found between chemically analyzed POP blood concentrations and calculated daily intake of POPs for Qeqertarsuaq, Nuuk and Narsaq Inuit but not for the northernmost settlement Qaanaaq, probably because the highest blood POP level was found in this district which might mask the interview-based POP calculations. Despite the large variation in circulating blood POP concentrations, the PBPK model predicted blood concentrations of a factor 2-3 within the actual measured values. Moreover, the PBPK model showed that estimated blood POP concentration increased significantly after consumption of meals

  6. Melting beneath Greenland outlet glaciers and ice streams

    NASA Astrophysics Data System (ADS)

    Alexander, David; Perrette, Mahé; Beckmann, Johanna

    2015-04-01

    Basal melting of fast-flowing Greenland outlet glaciers and ice streams due to frictional heating at the ice-bed interface contributes significantly to total glacier mass balance and subglacial meltwater flux, yet modelling this basal melt process in Greenland has received minimal research attention. A one-dimensional dynamic ice-flow model is calibrated to the present day longitudinal profiles of 10 major Greenland outlet glaciers and ice streams (including the Jakobshavn Isbrae, Petermann Glacier and Helheim Glacier) and is validated against published ice flow and surface elevation measurements. Along each longitudinal profile, basal melt is calculated as a function of ice flow velocity and basal shear stress. The basal shear stress is dependent on the effective pressure (difference between ice overburden pressure and water pressure), basal roughness and a sliding parametrization. Model output indicates that where outlet glaciers and ice streams terminate into the ocean with either a small floating ice tongue or no floating tongue whatsoever, the proportion of basal melt to total melt (surface, basal and submarine melt) is 5-10% (e.g. Jakobshavn Isbrae; Daugaard-Jensen Glacier). This proportion is, however, negligible where larger ice tongues lose mass mostly by submarine melt (~1%; e.g. Nioghalvfjerdsfjorden Glacier). Modelled basal melt is highest immediately upvalley of the grounding line, with contributions typically up to 20-40% of the total melt for slippery beds and up to 30-70% for resistant beds. Additionally, modelled grounding line and calving front migration inland for all outlet glaciers and ice streams of hundreds of metres to several kilometres occurs. Including basal melt due to frictional heating in outlet glacier and ice stream models is important for more accurately modelling mass balance and subglacial meltwater flux, and therefore, more accurately modelling outlet glacier and ice stream dynamics and responses to future climate change.

  7. Holocene Climate Change in Arctic Canada and Greenland

    NASA Astrophysics Data System (ADS)

    Briner, J. P.; McKay, N.; Axford, Y.; Bennike, O.; Bradley, R. S.; de Vernal, A.; Fisher, D. A.; Francus, P.; Fréchette, B.; Gajewski, K. J.; Jennings, A. E.; Kaufman, D. S.; Miller, G. H.; Rouston, C.; Wagner, B.

    2015-12-01

    We summarize the spatial and temporal pattern of climate change through the Holocene in Arctic Canada and Greenland. Our synthesis includes 47 records from a recent database of highly resolved, quantitative Holocene climate records from the Arctic (Sundqvist et al., 2014). We plot the temperature histories represented by the records in the database and compare them with paleoclimate information based on 53 additional records. Combined, the records include a variety of climate proxy types that range from ice (ice cores), land (lake and peat sequences) and marine (ocean sediment cores and coastal sediments) environments. The temperature-sensitive records indicate more consistent and earlier Holocene warmth in the north and east, and a more diffuse and later Holocene thermal maximum in the south and west. Principal components analysis reveals two dominant Holocene trends, one with early Holocene warmth followed by cooling in the middle Holocene, the other with a broader period of warmth in the middle Holocene followed by cooling in the late Holocene. The temperature decrease from the warmest to the coolest portions of the Holocene is 3.0±1.0°C on average (n=11 records). The Greenland Ice Sheet retracted to its minimum extent between 5 and 3 ka, consistent with many sites from around Greenland depicting a switch from warm to cool conditions around that time. The spatial pattern of temperature change through the Holocene was likely driven by the decrease in northern latitude summer insolation through the Holocene, the varied influence of waning ice sheets in the early Holocene, and the variable influx of Atlantic Water into the study region.

  8. Greenland's mass balance observed by GRACE between 2003-2008

    NASA Astrophysics Data System (ADS)

    Wouters, B.; Schrama, E.

    2009-04-01

    The Gravity Recovery and Climate Experiment (GRACE) satellites have been providing the scientific community with a quasi-continuous record of the Earth's gravity field over the last 6 years. Due to its global coverage, it offers an excellent tool to study mass changes over large regions. Among others, GRACE has lead to a leap in our understanding of the mass balance of Greenland ice sheet, which was indirectly known until a few years ago. In this presentation, we demonstrate how the GRACE observations can be used to monitor changes in Greenland's mass distribution on a regional scale. Over the period of 2003-2008, the ice sheet lost annually approximately 210 cubic kilometers of ice on average, contributing 0.5 mm per year to global mean sea level. According to (Rignot,2008) this value is unprecedented in the last 50 years suggesting a significant impact of global warming on the Greenland's ice volume. A forward modeling technique significantly helps to identify the hydrologic basins where the melt occurs. As a result we now know from the GRACE data that the main melting signal occurs during summer along the southeastern coast, although spreading to the northwest, with most pronounced changes so far occurring in 2007. Although 2008 was not a record year in terms of total mass lost, it may be called exceptional in terms of the spatial pattern of the summer losses, which mainly took place in the high North, consistent with surface melt observations and regional climate model results. Largest mass losses are observed in the regions surroundig the Humboldt Glacier and Zachariae Isstrom, two glaciers that have been reported to have retreated significantly in 2008.

  9. Airborne Hyperspectral Imaging of Supraglacial Lakes in Greenland's Ablation Zone

    NASA Astrophysics Data System (ADS)

    Adler, J.; Behar, A. E.; Jacobson, N. T.

    2010-12-01

    In 2010 an airborne instrument was assembled to image supraglacial lakes near the Jakobshavn Isbrae of the Greenland Ice Sheet. The instrument was designed to fly on a helicopter, and consists of a hyperspectral imager, a GPS/inertial measurement unit (GPS/IMU), and a data-logging computer. A series of narrow visible optical channels ~13nm wide, such as found in a hyperspectral imager, are theorized to be useful in determining the depths of supraglacial lakes using techniques based on the Beer-Lambert-Bouguer Law. During June, several supraglacial lakes were selected for study each day, based upon MODIS imagery taken during the previous week. Flying over a given lake, several track lines were flown to image both shallow and deep sections of the lake, imaging the full range of depth for future algorithm development. The telescoping instrument mount was constructed to allow the sensor package to be deployed from a helicopter in-flight, with an unobstructed downward-facing field of view. The GPS/IMU records the pointing orientation, altitude, and geographical coordinates of the imager to the data-logger, in order to allow post-flight geo-referencing of the raw hyperspectral imagery. With this geo-referenced spectrum data, a depth map for a given lake can be calculated through reference to a water absorptivity model. This risk-reduction expedition to fly a helicopter-borne hyperspectral imager over the supraglacial lakes of Greenland was a success. The instrument mount for the imager worked as designed, and no vibration issues were encountered. As a result, we have confidence in the instrument platform's performance during future surveys of Greenland's supraglacial lakes. The hyperspectral imager, data acquisition computer, and geo-referencing services are provided by Resonon, Inc. of Bozeman, MT, and the GPS/IMU is manufactured by Cloudcap Technology of Hood River, OR.

  10. P wave velocity structure beneath Greenland using teleseismic events

    NASA Astrophysics Data System (ADS)

    Park, Y.; Lee, W.; Yoo, H.

    2013-12-01

    A three-dimensional P-wave velocity model was inverted with 3032 ray paths from 416 events observed on the GLISN network from 2009 to 2013. The relative travel times were computed with respect to the IASP91 global reference model using the multi-channel cross correlation method (MCCC) by VanDecar and Crosson {, 1990 #1}. Our model space was parameterized laterally with 1°×1° from 55°N to 85°N in latitude and from 20°W to 80°W in longitude. This high latitude model space causes spatial distortion in the model parameters on the spherical coordinate for the teleseismic body wave tomography. To minimize a distortion in the model parameters the spherical coordinate system was rotated as the referent stations SUMG and SCO, located on the middle of Greenland, to equator, and all stations and seismic events were converted to this new coordinate system. All ray paths were computed by a three dimensional ray tracing algorithm developed with pseudobending technique and Snell's law {Zhao, 1992 #1}, and travel times were corrected by ice and crustal thicknesses for each observed station as well. Our inverted model shows a broad low velocity anomaly ( -1.5%) in the mid-eastern parts of Greenland, which is connected to the low velocity anomaly beneath Iceland. Another low velocity anomaly was observed below 300km in the middle of Greenland where the Icelandic mantle plume was located in 60Ma. P wave velocity anomaly depth slices from 150 km to 400 km on the rotated coordinate from the center of Green land to the equator.

  11. Holocene climate change in Arctic Canada and Greenland

    NASA Astrophysics Data System (ADS)

    Briner, Jason P.; McKay, Nicholas P.; Axford, Yarrow; Bennike, Ole; Bradley, Raymond S.; de Vernal, Anne; Fisher, David; Francus, Pierre; Fréchette, Bianca; Gajewski, Konrad; Jennings, Anne; Kaufman, Darrell S.; Miller, Gifford; Rouston, Cody; Wagner, Bernd

    2016-09-01

    This synthesis paper summarizes published proxy climate evidence showing the spatial and temporal pattern of climate change through the Holocene in Arctic Canada and Greenland. Our synthesis includes 47 records from a recently published database of highly resolved Holocene paleoclimate time series from the Arctic (Sundqvist et al., 2014). We analyze the temperature histories represented by the database and compare them with paleoclimate and environmental information from 54 additional published records, mostly from datasets that did not fit the selection criteria for the Arctic Holocene database. Combined, we review evidence from a variety of proxy archives including glaciers (ice cores and glacial geomorphology), lake sediments, peat sequences, and coastal and deep-marine sediments. The temperature-sensitive records indicate more consistent and earlier Holocene warmth in the north and east, and a more diffuse and later Holocene thermal maximum in the south and west. Principal components analysis reveals two dominant Holocene trends, one with early Holocene warmth followed by cooling in the middle Holocene, the other with a broader period of warmth in the middle Holocene followed by cooling in the late Holocene. The temperature decrease from the warmest to the coolest portions of the Holocene is 3.0 ± 1.0 °C on average (n = 11 sites). The Greenland Ice Sheet retracted to its minimum extent between 5 and 3 ka, consistent with many sites from around Greenland depicting a switch from warm to cool conditions around that time. The spatial pattern of temperature change through the Holocene was likely driven by the decrease in northern latitude summer insolation through the Holocene, the varied influence of waning ice sheets in the early Holocene, and the variable influx of Atlantic Water into the study region.

  12. Surface energy budget responses to radiative forcing at Summit, Greenland

    NASA Astrophysics Data System (ADS)

    Miller, Nathaniel B.; Shupe, Matthew D.; Cox, Christopher J.; Noone, David; Persson, P. Ola G.; Steffen, Konrad

    2017-02-01

    Greenland Ice Sheet surface temperatures are controlled by an exchange of energy at the surface, which includes radiative, turbulent, and ground heat fluxes. Data collected by multiple projects are leveraged to calculate all surface energy budget (SEB) terms at Summit, Greenland, for the full annual cycle from July 2013 to June 2014 and extend to longer periods for the radiative and turbulent SEB terms. Radiative fluxes are measured directly by a suite of broadband radiometers. Turbulent sensible heat flux is estimated via the bulk aerodynamic and eddy correlation methods, and the turbulent latent heat flux is calculated via a two-level approach using measurements at 10 and 2 m. The subsurface heat flux is calculated using a string of thermistors buried in the snow pack. Extensive quality-control data processing produced a data set in which all terms of the SEB are present 75 % of the full annual cycle, despite the harsh conditions. By including a storage term for a near-surface layer, the SEB is balanced in this data set to within the aggregated uncertainties for the individual terms. November and August case studies illustrate that surface radiative forcing is driven by synoptically forced cloud characteristics, especially by low-level, liquid-bearing clouds. The annual cycle and seasonal diurnal cycles of all SEB components indicate that the non-radiative terms are anticorrelated to changes in the total radiative flux and are hence responding to cloud radiative forcing. Generally, the non-radiative SEB terms and the upwelling longwave radiation component compensate for changes in downwelling radiation, although exact partitioning of energy in the response terms varies with season and near-surface characteristics such as stability and moisture availability. Substantial surface warming from low-level clouds typically leads to a change from a very stable to a weakly stable near-surface regime with no solar radiation or from a weakly stable to neutral

  13. Contrasting response of South Greenland glaciers to recent climatic change

    SciTech Connect

    Warren, C.R.; Glasser, N.F. )

    1992-05-01

    A unique geographical configuration of glaciers exists in the Narsarsuaq district of South Greenland. Two large outlet glaciers divide into seven distributaries, such that each glacier system has land-terminating, tidewater-calving, and fresh-water-calving termini. Despite a similar climatic regime, these seven glaciers have exhibited strongly contrasting terminal behavior in historical time, as shown by historical records, aerial photographs, and fieldwork in 1989. The behavior of the calving glaciers cannot be accounted for with reference solely to climatic parameters. The combination of iceberg calving dynamics and topographic control has partially decoupled them from climatic forcing such that their oscillations relate more closely to glaciodynamic than glacioclimatic factors.

  14. Determining Greenland Ice Sheet Accumulation Rates from Radar Remote Sensing

    NASA Technical Reports Server (NTRS)

    Jezek, Kenneth C.

    2001-01-01

    An important component of NASA's Program for Arctic Regional Climate Assessment (PARCA) is a mass balance investigation of the Greenland Ice Sheet. The mass balance is calculated by taking the difference between the snow accumulation and the ice discharge of the ice sheet. Uncertainties in this calculation include the snow accumulation rate, which has traditionally been determined by interpolating data from ice core samples taken throughout the ice sheet. The sparse data associated with ice cores, coupled with the high spatial and temporal resolution provided by remote sensing, have motivated scientists to investigate relationships between accumulation rate and microwave observations.

  15. The Greenland Telescope: antenna retrofit status and future plans

    NASA Astrophysics Data System (ADS)

    Raffin, Philippe; Ho, Paul T. P.; Asada, Keiichi; Blundell, Raymond; Bower, Geoffrey C.; Burgos, Roberto; Chang, Chih-Cheng; Chen, Ming-Tang; Christensen, Robert; Chu, You-Hua; Grimes, Paul K.; Han, C. C.; Huang, Chih-Wei L.; Huang, Yau-De; Hsieh, Fang-Chia; Inoue, Makoto; Koch, Patrick M.; Kubo, Derek; Leiker, Steve; Lin, Lupin; Liu, Ching-Tang; Lo, Shih-Hsiang; Martin-Cocher, Pierre; Matsushita, Satoki; Nakamura, Masanori; Meyer-Zhao, Zheng; Nishioka, Hiroaki; Norton, Tim; Nystrom, George; Paine, Scott N.; Patel, Nimesh A.; Pu, Hung-Yi; Snow, William; Sridharan, T. K.; Srinivasan, Ranjani; Wang, Jackie

    2016-07-01

    Since the ALMA North America Prototype Antenna was awarded to the Smithsonian Astrophysical Observatory (SAO), SAO and the Academia Sinica Institute of Astronomy and Astrophysics (ASIAA) are working jointly to relocate the antenna to Greenland. This paper shows the status of the antenna retrofit and the work carried out after the recommissioning and subsequent disassembly of the antenna at the VLA has taken place. The next coming months will see the start of the antenna reassembly at Thule Air Base. These activities are expected to last until the fall of 2017 when commissioning should take place. In parallel, design, fabrication and testing of the last components are taking place in Taiwan.

  16. Understanding Recent Mass Balance Changes of the Greenland Ice Sheet

    NASA Technical Reports Server (NTRS)

    vanderVeen, Cornelius

    2003-01-01

    The ultimate goal of this project is to better understand the current transfer of mass between the Greenland Ice Sheet, the world's oceans and the atmosphere, and to identify processes controlling the rate of this transfer, to be able to predict with greater confidence future contributions to global sea level rise. During the first year of this project, we focused on establishing longer-term records of change of selected outlet glaciers, reevaluation of mass input to the ice sheet and analysis of climate records derived from ice cores, and modeling meltwater production and runoff from the margins of the ice sheet.

  17. Fine scale features of stable flows over Greenland

    NASA Astrophysics Data System (ADS)

    Orr, A.; Hunt, J.; Light, M.; Hanna, E.; Cappelen, J.

    2003-04-01

    The atmospheric flows and processes over Greenland occur on many length scales. Flow over and around Greenland is affected by (i) the large and very steep elevation change between the coastal margins and the central plateau (3km), (ii) the combination of very rough surfaces (roughness length zo ˜ 1-10m) and jagged mountains around the coasts, (iii) the strong katabatic flows from the plateau down to the coasts (˜ 100km), (iv) the presence of the semi-permanent Icelandic Low (˜ 1000km), and (v) air-sea-ice interaction processes. Here and in other coastal flows there are extremely sharp gradients in roughness and elevation. These result in local scale phenomena that have long been observed, for example, coastal wind jets, but as they occur on kilometer length scales, they are only described by mesoscale models when they are run with fine resolution (e.g. Capon 2002). But these local scale phenomena can have large scale climate effects, e.g. drag, wind waves, upwelling, cyclogenesis, air-sea-ice interaction, etc. Hunt et al. (2002) investigated the low-level flow response of atmospheric westerly winds over southern Greenland using idealised and numerical modelling. To further understand Greenland's critical climate processes the low-level flow response to easterly, southerly, and northerly atmospheric winds, and a fast moving front passing over the southern tip, are investigated. At a horizontal resolution of 12km, certain broad features (e.g. wind-jets) are well captured by the numerical model and consistent with aspects of the idealised 2-layer model (Hunt et al. 2002) for typical mesoscale atmospheric flows with variations in surface roughness, elevation, and heating. Further understanding is enabled by comparison with observations. An important development is to show how katabatic winds can combine with and be deflected by synoptic winds in regions of barrier jets and in wake jets. (This agreed with field data.) Our studies should help define the magnitudes and

  18. Greenland Ice sheet mass balance from satellite and airborne altimetry

    NASA Astrophysics Data System (ADS)

    Khan, S. A.; Bevis, M. G.; Wahr, J. M.; Wouters, B.; Sasgen, I.; van Dam, T. M.; van den Broeke, M. R.; Hanna, E.; Huybrechts, P.; Kjaer, K.; Korsgaard, N. J.; Bjork, A. A.; Kjeldsen, K. K.

    2013-12-01

    Ice loss from the Greenland Ice Sheet (GrIS) is dominated by loss in the marginal areas. Dynamic induced ice loss and its associated ice surface lowering is often largest close to the glacier calving front and may vary from rates of tens of meters per years to a few meters per year over relatively short distances. Hence, high spatial resolution data are required to accurately estimate volume changes. Here, we estimate ice volume change rate of the Greenland ice sheet using data from Ice, Cloud and land Elevation Satellite (ICESat) laser altimeter during 2003-2009 and CryoSat-2 data during 2010-2012. To improve the volume change estimate we supplement the ICESat and CryoSat data with altimeter surveys from NASA's Airborne Topographic Mapper (ATM) during 2003-2012 and NASA's Land, Vegetation and Ice Sensor (LVIS) during 2007-2012. The Airborne data are mainly concentrated along the ice margin and therefore significantly improve the estimate of the total volume change. Furthermore, we divide the GrIS into six major drainage basins and provide volume loss estimates during 2003-2006, 2006-2009 and 2009-2012 for each basin and separate between melt induced and dynamic ice loss. In order to separate dynamic ice loss from melt processes, we use SMB values from the Regional Atmospheric Climate Model (RACMO2) and SMB values from a positive degree day runoff retention model (Janssens & Huybrechts 2000, Hanna et al. 2011 JGR, updated for this study). Our results show increasing SMB ice loss over the last decade, while dynamic ice loss increased during 2003-2009, but has since been decreasing. Finally, we assess the estimated mass loss using GPS observations from stations located along the edge of the GrIS and measurements from the Gravity Recovery and Climate Experiment (GRACE) satellite gravity mission. Hanna, E., et al. (2011), Greenland Ice Sheet surface mass balance 1870 to 2010 based on Twentieth Century Reanalysis, and links with global climate forcing, J. Geophys. Res

  19. Statistical Corrections of HIRLAM and HARMONIE Forecasts for Greenland

    NASA Astrophysics Data System (ADS)

    Mahura, Alexander; Petersen, Claus; Amstrup, Bjarne; Sass, Bent

    2015-04-01

    Numerical Weather Prediction (NWP) for northern regions, and especially, in the Arctic is very complex due to multiple factors. Complexity of physical processes and interactions is not so well studied compared to other geographical regions and first of all, because of limited observational network. Model verification results show that forecasts have larger errors compared to other regions of the world. As a possible solution, statistical corrections to forecasts can be applied. Such corrections can be based on analysis of long-term time-series of meteorological observations and forecasts. The developed method is based on using forecasted meteorological parameters (2m air, dew point, and surface temperatures as well as 10m wind speed) and observations covering only a pre-historical period (ranging from 3 to 30 days). The singular value decomposition method is applied for faster calculations. Then, further improvement/adjustment of forecasts is based on generated statistics of forecasted meteorological parameters. For Greenland, DMI operationally runs two NWP models - HIRLAM (HIgh Resolution Limited Area Model) and HARMONIE (Hirlam Aladin Regional/Meso-scale Operational NWP In Europe). The 1st model (HIRLAM-K05, at 5 km horizontal resolution; runs at 00, 06, 12, and 18 UTC) is run over the entire territory of Greenland. The 2nd model (HARMONIE-GLB, at 2.5 km horizontal resolution; runs at 03, 09, 15, and 21 UTC) is run over the southern (most populated) part of Greenland. The operationalized procedure for statistical correction of the air temperature and wind speed forecasts has been implemented for both models outputs covering forecast lengths up to 48 hours. The procedure includes extraction of observational and model forecast data, assigning data to forecast lengths, calculation of statistical correction to selected meteorological parameters, evaluation of model performance (before vs. after correction applied) for current and previous days with decision-making on

  20. MIS 3 Climate Variability Revealed by Two Stalagmites from Northern and South-Western Romania

    NASA Astrophysics Data System (ADS)

    Dragusin, V.; Hoffmann, D.; Onac, B. P.; Isverceanu, E.

    2011-12-01

    We present two stable isotope records of climate variability from stalagmites in northern (#1152 from Pestera Izvorul Tausoarelor, Rodna Mountains) and south-western (#POM1 from Pestera Ascunsa, Mehedinti Mountains) Romania. Both cave entrances are located at over 1000 m asl in areas covered by mature beech forests, in continental temperate climate. Superimposed on the present-day climatic conditions are two different climate influences: Atlantic in the north and sub-mediterranean in the south-west. Both stalagmites were dated by means of uranium series on a Thermo Neptune MC-ICP-MS at Centro Nacional de Investigacion sobre la Evolucion Humana (Burgos, Spain) and samples for stable O and C stable isotopes were analysed on a Thermo Delta V IRMS at the Stable Isotope Laboratory, University of South Florida. For the stable isotopes profile, stalagmite 1152 was sampled at an average interval of 100 years , whereas POM1 was sampled at a 30 years interval. The two stalagmites reveal differences in isotopic signature response to climatic variability. When the POM1 δ18O profile is compared to the NGRIP δ18O, a lower variability of its values is evident. Even so, we are still able to distinguish structures similar to Greenland Interstadials (GIs) 7 and 8, the latter being composed of two distinct units. The stalagmite 1152 δ18O profile shows less variability although some of the peaks in the values could be correlated to GIs 4 through 12. The absolute values of these two records vary around an average of -7.5%, very close to the typical Holocene values from this part of Europe. This may point to an enhanced Mediterranean circulation towards the north during MIS 3. In return, the δ13C values of the two stalagmites are very different and point to large differences in the activity of plants and soil organisms. POM1 values, averaging -5 to -6%, indicate a C4 type vegetation in the area above the cave, that could belong to alpine meadows. This may document a lowering of the

  1. The experiences of female spouses of survivors of acute myocardial infarction: a pilot study of Lebanese-born women in south-western Sydney, Australia.

    PubMed

    Daly, J; Jackson, D; Davidson, P M; Wade, V; Chin, C; Brimelow, V

    1998-12-01

    Lebanese migrants form a significant proportion of the population in southwestern Sydney (SWS), and in New South Wales, Australia. This pilot study was undertaken in south-western Sydney, a rapidly expanding and socioeconomically disadvantaged region, to explore the experiences of English speaking women of Lebanese origin whose spouses had recently experienced an acute myocardial infarction (AMI). Semi-structured interviews were conducted with seven Lebanese-born women at 2- and 4-week intervals, following the discharge of their husbands from hospital. Qualitative analysis of narrative text revealed four distinct themes. These were: struggle to resolve distress; intensive monitoring of the AMI survivor; searching for avenues of support; and reflecting on the future. Study findings are discussed in relation to the literature. Implications for nursing practice and research are drawn from study findings.

  2. Southwestern Power Administration Combined Financial Statements, 2006-2009

    SciTech Connect

    2009-09-01

    We have audited the accompanying combined balance sheets of the Southwestern Federal Power System (SWFPS), as of September 30, 2009, 2008, 2007, and 2006, and the related combined statements of revenues and expenses, changes in capitalization, and cash flows for the years then ended. As described in note 1(a), the combined financial statement presentation includes the hydroelectric generation functions of another Federal agency (hereinafter referred to as the generating agency), for which Southwestern Power Administration (Southwestern) markets and transmits power. These combined financial statements are the responsibility of the management of Southwestern and the generating agency. Our responsibility is to express an opinion on these combined financial statements based on our audits. We conducted our audits in accordance with auditing standards generally accepted in the United States of America. Those standards require that we plan and perform the audits to obtain reasonable assurance about whether the combined financial statements are free of material misstatement. An audit includes consideration of internal control over financial reporting as a basis for designing audit procedures that are appropriate in the circumstances, but not for the purpose of expressing an opinion on the effectiveness of Southwestern and the generating agency’s internal control over financial reporting. Accordingly, we express no such opinion. An audit also includes examining, on a test basis, evidence supporting the amounts and disclosures in the combined financial statements, assessing the accounting principles used and significant estimates made by management, as well as evaluating the overall combined financial statement presentation. We believe that our audits provide a reasonable basis for our opinion. In our opinion, the combined financial statements referred to above present fairly, in all material respects, the respective financial position of the Southwestern Federal Power

  3. Data on influence of atmospheric rivers on vegetation productivity and fire patterns in the southwestern US

    USGS Publications Warehouse

    Albano, Christine M.; Dettinger, Michael; Soulard, Christopher E.

    2016-01-01

    In the southwestern US, the meteorological phenomenon known as atmospheric rivers (ARs) has gained increasing attention due to its strong connections to floods, snowpacks and water supplies in the West Coast states. Relatively less is known about the ecological implications of ARs, particularly in the interior Southwest, where AR storms are less common. To address this gap, we compared a chronology of AR landfalls on the west coast between 1989-2011 and between 25-42.5ºN, to annual metrics of the Normalized Difference Vegetation Index (NDVI; an indicator of vegetation productivity) and daily-resolution precipitation data to assess influences of AR-fed winter precipitation on vegetation productivity across the southwestern US. We mapped correlations between winter AR precipitation during landfalling ARs and 1) annual maximum NDVI and 2) area burned by large wildfires summarized by ecoregion during the same year as the landfalls and during the following year. The data produced by this study include four sets of eight raster grids (total = 32 grids) representing Spearman Rank correlation coefficients for four types of comparisons across eight different latitudinal bands. Each dataset is named according to the comparison type and latitude of AR landfall. The four types of comparisons (with corresponding filenames indicated in parentheses) include: 1) annual winter atmospheric river precipitation vs. total annual winter precipitation (AR_WinterPrecip), 2) annual winter atmospheric river precipitation vs. annual maximum NDVI (AR_NDVI), 3) spatially-averaged annual winter atmospheric river precipitation vs. area burned by wildfire during the same year by Level IV ecoregion (AR_Fire_SameYear), and 4) spatially-averaged annual winter atmospheric river precipitation vs. area burned by wildfire with a 1-year lag by Level IV ecoregion (AR_Fire_OneYearLag). The eight landfall latitudes are indicated in filenames as follows: 25N, 27_5N, 30N, 32_5N, 35N, 37_5_N, 40N, 42_5N.

  4. First report of Toxoplasma gondii seroprevalence in peafowls in Yunnan Province, Southwestern China

    PubMed Central

    2012-01-01

    Background Toxoplasma gondii is an intracellular protozoan parasite infecting almost all warm-blooded animals, including birds, with a worldwide distribution. Surveys of T. gondii infection in wild birds have been reported extensively in the world, but little is known of T. gondii infection in peafowls worldwide. This study was performed to determine the seroprevalence of T. gondii infection in peafowls in Yunnan Province, southwestern China. Methods Sera from 277 peafowls, including 272 blue peafowls (Pavo cristatus) and 5 green peafowls (Pavo muticus) originated from two geographic areas in Yunnan Province were assayed for T. gondii antibodies using the modified agglutination test (MAT). Results Specific T. gondii antibodies were detected in 35 of 277 (12.64%) peafowls (MAT titer ≥ 1:5). Seropositive birds were found in both species, 33 in 272 blue peafowls and 2 in 5 green peafowls. There was no significant difference in T. gondii seroprevalence between the adolescent birds (6.74%) and the adult birds (6.67%) (P > 0.05). The geographical origins of peafowls was found to be highly associated with T. gondii infection in the present study, a statistically significant difference in T. gondii seropositivity was observed between peafowls from Kunming (31.08%) and those from Xishuangbanna Dai Autonomous Prefecture (5.91%) (OR = 10.956, 95% CI = 1.632-73.545, P = 0.014). Statistical analyses showed that there were no significant interactions between ages and geographical origins of peafowls (P > 0.05). Conclusions The results of the present survey indicated that infection of peafowls with T. gondii is widespread in Yunnan Province, which has significant public health concerns and implications for prevention and control of toxoplamosis in this province. To our knowledge, this is the first seroprevalence report of T. gondii infection in China’s southwestern Yunnan Province. PMID:22992281

  5. Influence of atmospheric rivers on vegetation productivity and fire patterns in the southwestern U.S.

    USGS Publications Warehouse

    Albano, Christine M.; Dettinger, Michael; Soulard, Christopher E.

    2017-01-01

    In the southwestern U.S., the meteorological phenomenon known as atmospheric rivers (ARs) has gained increasing attention due to its strong connections to floods, snowpacks, and water supplies in the West Coast states. Relatively less is known about the ecological implications of ARs, particularly in the interior Southwest, where AR storms are less common. To address this gap, we compared a chronology of AR landfalls on the west coast between 1989 and 2011 and between 25°N and 42.5°N to annual metrics of the normalized difference vegetation index (NDVI; an indicator of vegetation productivity) and daily resolution precipitation data to assess influences of AR-fed winter precipitation on vegetation productivity across the southwestern U.S. We mapped correlations between winter AR precipitation during landfalling ARs and (1) annual maximum NDVI and (2) area burned by large wildfires summarized by ecoregion during the same year as the landfalls and during the following year. Interannual variations of AR precipitation strongly influenced both NDVI and area burned by wildfire in some dryland ecoregions. The influence of ARs on dryland vegetation varied significantly depending on the latitude of landfall, with those ARs making landfall below 35°N latitude more strongly influencing these systems, and with effects observed as far as 1300 km from the landfall location. As climatologists' understanding of the synoptic patterns associated with the occurrence of ARs continues to evolve, an increased understanding of how AR landfalls, in aggregate, influence vegetation productivity and associated wildfire activity in dryland ecosystems may provide opportunities to better predict ecological responses to climate and climate change.

  6. Holocene environmental evolution of the SE Greenland Shelf North and South of the Denmark Strait: Irminger and East Greenland current interactions

    NASA Astrophysics Data System (ADS)

    Jennings, A.; Andrews, J.; Wilson, L.

    2011-04-01

    Holocene climatic and paleoceanographic development of the SE Greenland Shelf is studied from cores MD99-2317 and MD99-2322, at sites north and south of the Denmark Strait, respectively. Lithofacies, IRD counts, calcium carbonate percentages, benthic and planktic foraminiferal assemblages and oxygen isotope analyses, and summer SSTs reveal significant climate variations in the Holocene driven by declining solar insolation and its interaction with waning continental ice sheets, and changing atmospheric pressure patterns. Large changes in the East Greenland and Irminger Currents and the Greenland Ice Sheet are manifested as a 4-part division of the Holocene. An early Holocene cold interval dominated by melting of the Greenland Ice Sheet and Polar Front retreat extends from 11.8 to 9.5 cal kyr BP. A cold interval from 9.5 to 8.1 cal kyr BP involved episodic cooling of the Irminger Current resulting from the last phases of Laurentide Ice Sheet deglaciation and delayed the Holocene optimum off East Greenland by 3 kyr relative to peak summer solar insolation, which likely helped to limit the early Holocene melting of the Greenland Ice Sheet. The period 8.1-3.5 cal kyr BP represents a climatic optimum interval of maximum Greenland Ice Sheet retreat and strong Irminger Current inflow to the Denmark Strait. Between 6.8 and 3.5 cal kyr BP, the Irminger Current penetrated further North into the Nordic Seas than has been observed in recent decades. This signal is consistent with diminished northerly winds, a weaker Greenland High and contracted subpolar gyre. By 5 cal kyr BP, periods of increased Polar Water and decreasing salinity in the Irminger Current suggest a transition toward expansion of the subpolar gyre and increased Polar Water in the EGC. The Neoglacial interval from 3.5 to 0.2 cal kyr BP was cold and variable with increased freshwater forcing from the Arctic Ocean, advance of the Greenland Ice Sheet and southward advance of the Polar Front. Enhanced northerly

  7. The Greenland ice sheet perennial firn aquifer: characteristics, extent and evolution obtained from airborne remote sensing

    NASA Astrophysics Data System (ADS)

    Miège, C.; Forster, R. R.; Koenig, L.; Brucker, L.; Box, J. E.; Burgess, E. W.

    2013-12-01

    The presence of a perennial firn aquifer (PFA) was identified April 2011, in the southeast part of the Greenland ice sheet, from firn-core drilling, surface- and airborne-radar. The PFA is a component of the ice sheet hydrology and corresponds to a liquid water saturated firn aquifer, which persists over the winter without freezing. The average depth of the top of the aquifer is ~20 m below the surface, and is guided by surface topography, following surface undulations, similar to an unconfined aquifer observed in other groundwater aquifer systems. We use a combination of 400 MHz ground-based radar and the 600 to 900 MHz Accumulation Radar on board NASA's airborne Operation IceBridge (OIB) to identify and map PFA extent and evolution between 2011 and 2013. Here, we present an ice-sheet wide mapping of the PFA, including the 2013 field campaign with detailed ground-based radar grids near the firn core site drilled in April 2013 (PFA-13, 66.18°N, 39.04°W and 1563 m). At the PFA-13 location, OIB Accumulation Radar and ground-based radar data were acquired along the same track within two weeks in both 2011 and 2013, offering a unique comparison dataset. This dataset is used to analyze the three year (2011-2013) evolution of PFA top depth, i.e. stored meltwater volume, in areas where radar transects are repeated from one year to the next. This evolution suggests possible horizontal flow of this stored meltwater toward the ice-sheet margins but must be confirmed by further field investigations. In addition, we derive surface slope from latest digital elevation model available for Southeast Greenland and use this slope as parameter to interpolate the PFA top in the area between ground radar transects and airborne radar flight lines. This slope interpolation would aim to improve PFA water volume/extent estimations for areas without airborne radar coverage. The fate of this stored meltwater is currently unknown, even if flow is suggested and drainage into nearby crevasses

  8. Conjugate volcanic rifted margins, spreading and micro-continent: Lessons from the Norwegian-Greenland Sea

    NASA Astrophysics Data System (ADS)

    Gernigon, L.; Blischke, A.; Nasuti, A.; Sand, M.

    2014-12-01

    We have acquired and processed new aeromagnetic data that covers the entire Norway Basin oceanic spreading system located between the Møre volcanic rifted margin and its (intermediate) conjugate system, the Jan Mayen microcontinent (JMMC). The new compilation allows us to revisit its entire structure and spreading evolution from the Early Eocene breakup to the Late Oligocene abortion of the Aegir Ridge. We here discuss the dynamics of conjugate volcanic (rifted) margin formation and reconstruct the subsequent spreading evolution of the Norway Basin until its abortion. We have estimated a new set of Euler poles of rotation for the Norway Basin derived from more than 88,000 km of new magnetic profiles. The new compilation confirms that a fan-shaped spreading evolution of the Norway Basin was particularly active before the cessation of seafloor spreading and abortion of the Aegir Ridge. The Norway Basin shows a more complex system of micro-plates and asymmetric segments locally affected by episodic ridge jumps. The new observations have implications for the syn- and post-breakup stratigraphic and rifted-margin tectonic development of the JMMC and its conjugate margins. In particular, an important Mid-Eocene geodynamic event at around magnetic chron C21r is recognized in the Norway Basin. This event coincides with the onset of diking and rifting between the proto-JMMC and the East Greenland margin, leading to a second phase of breakup in the Norwegian-Greenland Sea ~26 My later in the Oligocene. Restored in its pre-breakup configuration, the new surveys also allow us to discuss further the tectonic and crustal evolution of the conjugate volcanic rifted margins and associated transform and oblique segments. The applicability of magma-poor concepts, off Norway, for example, remains questionable for us. The significant amount of breakup magmatism, the huge amount of pre-breakup sag sedimentation and the presence of thinned and preserved continental crust without the

  9. Response of a Coupled Ocean-Atmosphere Model to Greenland Ice Melting

    NASA Astrophysics Data System (ADS)

    Stammer, D.; Agarwal, N.; Herrmann, P.; Köhl, A.; Mechoso, C. R.

    2011-09-01

    We investigate the transient response of the global coupled ocean-atmosphere system to enhanced freshwater forcing representative of melting of the Greenland ice sheets. A 50-year long simulation by a coupled atmosphere-ocean general circulation model (CGCM) is compared with another of the same length in which Greenland melting is prescribed. To highlight the importance of coupled atmosphere-ocean processes, the CGCM results are compared with those of two other experiments carried out with the oceanic general circulation model (OGCM). In one of these OGCM experiments, the prescribed surface fluxes of heat, momentum and freshwater correspond to the unperturbed simulation by the CGCM; in the other experiment, Greenland melting is added to the freshwater flux. The responses by the CGCM and OGCM to the Greenland melting have similar patterns in the Atlantic, albeit the former having five times larger amplitudes in sea surface height anomalies. The CGCM shows likewise stronger variability in all state variables in all ocean basins because the impact of Greenland melting is quickly communicated to all ocean basins via atmospheric bridges. We conclude that the response of the global climate to Greenland ice melting is highly dependent on coupled atmosphere-ocean processes. These lead to reduced latent heat flux into the atmosphere and an associated increase in net freshwater flux into the ocean, especially in the subpolar North Atlantic. The combined result is a stronger response of the coupled system to Greenland ice sheet melting.

  10. Influence of the Latitudinal Temperature Gradient on Soil Dust Concentration and Deposition in Greenland

    NASA Technical Reports Server (NTRS)

    Tegen, Ina; Rind, David

    2000-01-01

    To investigate the effects of changes in the latitudinal temperature gradient and the global mean temperature on dust concentration in the Northern Hemisphere, experiments with the GISS GCM (Goddard Institute for Space Studies General Circulation Model) are performed. The dust concentration over Greenland is calculated from sources in central and eastern Asia, which are integrated on-line in the model. The results show that an increase in the latitudinal temperature gradient increases both the Asian dust source strength and the concentration over Greenland. The source increase is the result of increased surface winds, and to a minor extent, the increase in Greenland dust is also associated with increased northward transport. Cooling the climate in addition to this increased gradient leads to a decrease in precipitation scavenging, which helps produce a further (slight) increase in Greenland dust in this experiment. Reducing the latitudinal gradient reduces the surface wind and hence the dust source, with a subsequent reduction in Greenland dust concentrations. Warming the climate in addition to this reduced gradient leads to a further reduction in Greenland dust due to enhanced precipitation scavenging. These results can be used to evaluate the relationship of Greenland ice core temperature changes to changes in the latitudinal and global temperatures.

  11. Substantial contribution to sea-level rise during the last interglacial from the Greenland ice sheet

    PubMed

    Cuffey; Marshall

    2000-04-06

    During the last interglacial period (the Eemian), global sea level was at least three metres, and probably more than five metres, higher than at present. Complete melting of either the West Antarctic ice sheet or the Greenland ice sheet would today raise sea levels by 6-7 metres. But the high sea levels during the last interglacial period have been proposed to result mainly from disintegration of the West Antarctic ice sheet, with model studies attributing only 1-2 m of sea-level rise to meltwater from Greenland. This result was considered consistent with ice core evidence, although earlier work had suggested a much reduced Greenland ice sheet during the last interglacial period. Here we reconsider the Eemian evolution of the Greenland ice sheet by combining numerical modelling with insights obtained from recent central Greenland ice-core analyses. Our results suggest that the Greenland ice sheet was considerably smaller and steeper during the Eemian, and plausibly contributed 4-5.5 m to the sea-level highstand during that period. We conclude that the high sea level during the last interglacial period most probably included a large contribution from Greenland meltwater and therefore should not be interpreted as evidence for a significant reduction of the West Antarctic ice sheet.

  12. Melting at the base of the Greenland ice sheet explained by Iceland hotspot history

    NASA Astrophysics Data System (ADS)

    Rogozhina, Irina; Petrunin, Alexey G.; Vaughan, Alan P. M.; Steinberger, Bernhard; Johnson, Jesse V.; Kaban, Mikhail K.; Calov, Reinhard; Rickers, Florian; Thomas, Maik; Koulakov, Ivan

    2016-05-01

    Ice-penetrating radar and ice core drilling have shown that large parts of the north-central Greenland ice sheet are melting from below. It has been argued that basal ice melt is due to the anomalously high geothermal flux that has also influenced the development of the longest ice stream in Greenland. Here we estimate the geothermal flux beneath the Greenland ice sheet and identify a 1,200-km-long and 400-km-wide geothermal anomaly beneath the thick ice cover. We suggest that this anomaly explains the observed melting of the ice sheet’s base, which drives the vigorous subglacial hydrology and controls the position of the head of the enigmatic 750-km-long northeastern Greenland ice stream. Our combined analysis of independent seismic, gravity and tectonic data implies that the geothermal anomaly, which crosses Greenland from west to east, was formed by Greenland’s passage over the Iceland mantle plume between roughly 80 and 35 million years ago. We conclude that the complexity of the present-day subglacial hydrology and dynamic features of the north-central Greenland ice sheet originated in tectonic events that pre-date the onset of glaciation in Greenland by many tens of millions of years.

  13. Hepatitis B prevalence and incidence in Greenland: a population-based cohort study.

    PubMed

    Børresen, Malene Landbo; Andersson, Mikael; Wohlfahrt, Jan; Melbye, Mads; Biggar, Robert J; Ladefoged, Karin; Panum, Inge; Koch, Anders

    2015-03-15

    Greenland remains a highly endemic area for hepatitis B virus (HBV) infection. This is in sharp contrast to other modern societies, such as Denmark. To address this discrepancy, we investigated the natural history of HBV infection in Greenland by estimating the age-specific incidence of HBV infection, the proportion of chronic carriers, and the rates of hepatitis B surface antigen seroclearance. In total, 8,879 Greenlanders (16% of the population) from population-based surveys conducted in 1987 and 1998 were followed through March 2010. Data on HBV status were supplemented by HBV test results from all available HBV registries in Greenland to determine changes in HBV status over time. Incidence rates of HBV infection and hepatitis B surface antigen seroclearance were estimated after taking into account interval censoring. The incidence of HBV infection in 5-14-year-old subjects was less than 1 per 100 person-years and peaked at 5 per 100 person-years in persons 15-24 years of age. Overall, 17.5% of persons infected in adulthood were estimated to become chronic carriers. HBV is primarily transmitted in adolescence and adulthood in Greenland. In contrast to what is observed in most other populations, HBV-infected adults in Greenland have a high risk of progressing to chronic HBV carriage. This phenomenon might explain how the high rate of infection is maintained in Greenland.

  14. Influence of the Latitudinal Temperature Gradient on Soil Dust Concentration and Deposition in Greenland

    NASA Technical Reports Server (NTRS)

    Tegen, Ina; Rind, David

    2000-01-01

    To investigate the effects of changes in the latitudinal temperature gradient and the global mean temperature on dust concentration in the Northern Hemisphere, experiments with the Goddard Institute for Space Studies General Circulation Model (GISS GCM) are performed. The dust concentration over Greenland is calculated from sources in central and eastern Asia, which are integrated on-line in the model. The results show that an increase in the latitudinal temperature gradient increases both the Asian dust source strength and the concentration over Greenland. The source increase is the result of increased surface winds, and to a minor extent, the increase in Greenland dust is also associated with increased northward transport. Cooling the climate in addition to this increased gradient leads to a decrease in precipitation scavenging, which helps produce a further (slight) increase in Greenland dust in this experiment. Reducing the latitudinal gradient reduces the surface wind and hence the dust source, with a subsequent reduction in Greenland dust concentrations. Warming the climate in addition to this reduced gradient leads to a further reduction in Greenland dust due to enhanced precipitation scavenging. These results can be used to evaluate the relationship of Greenland ice core temperature changes to changes in the latitudinal and global temperatures.

  15. The impact of buffer strips and stream-side grazing on small mammals in southwestern Wisconsin

    USGS Publications Warehouse

    Chapman, Erik W.; Ribic, C.A.

    2002-01-01

    The practice of continuously grazing cattle along streams has caused extensive degradation of riparian habitats. Buffer strips and managed intensive rotational grazing (MIRG) have been proposed to protect and restore stream ecosystems in Wisconsin. However, the ecological implications of a switch from traditional livestock management to MIRG or buffer strip establishment have not been investigated. Differences in small mammal communities associated with riparian areas on continuously grazed and MIRG pastures, as well as vegetative buffer strips adjacent to row crops, were investigated in southwestern Wisconsin during May-September 1997 and 1998. More species (mean of 6-7) were found on the buffer sites than on the pasture sites (mean of 2-5). Total small mammal abundance on buffer sites was greater than on the pastures as well: there were 3-5 times as many animals on the buffer sites compared to the pasture sites, depending on year. There were no differences in species richness or total abundance between MIRG and continuously grazed pastures in either year. Total small mammal abundance was greater near the stream than away from the stream, regardless of farm management practice but there were no differences in species richness. Buffer strips appear to support a particularly rich and abundant small mammal community. Although results did not detect a difference in small mammal use between pasture types, farm-wide implications of a conversion from continuous to MIRG styles of grazing may benefit small mammals indirectly by causing an increase in the prevalence of pasture in the agricultural landscape.

  16. Development of a Climate-Data Record of the Surface Temperature of the Greenland Ice Sheet (Invited)

    NASA Astrophysics Data System (ADS)

    Hall, D. K.; Comiso, J. C.; Digirolamo, N. E.; Shuman, C. A.

    2010-12-01

    To quantify the ice-surface temperature (IST) we are developing a climate-data record (CDR) of monthly IST of the Greenland ice sheet, from 1982 to the present using Advanced Very High Resolution Radiometer (AVHRR) and Moderate-Resolution Imaging Spectroradiometer (MODIS) data at 5-km resolution. “Clear-sky” surface temperature increases have been measured from the early 1980s to the early 2000s in the Arctic using AVHRR data, showing increases ranging from 0.57±0.02 (Wang and Key, 2005) to 0.72±0.10 deg C per decade (Comiso, 2006). Arctic warming has implications for ice-sheet mass balance because much of the periphery of the ice sheet is near 0 deg C in the melt season and is thus vulnerable to more extensive melting (Hanna et al., 2008). The algorithm used for this work has a long history of measuring IST in the Arctic with AVHRR (Key and Haefliger, 1992). The data are currently available from 1981 to 2004 in the AVHRR Polar Pathfinder (APP) dataset (Fowler et al., 2000). J. Key/NOAA modified the AVHRR algorithm for use with MODIS (Hall et al., 2004). The MODIS algorithm is now being processed over Greenland. Issues being addressed in the production of the CDR are: time-series bias caused by cloud cover, and cross-calibration between AVHRR and MODIS instruments. Because of uncertainties, time series of satellite ISTs do not necessarily correspond with actual surface temperatures. The CDR will be validated by comparing results with in-situ (see Koenig and Hall, in press) and automatic-weather station data (e.g., Shuman et al., 2001). References Comiso, J. C., 2006: Arctic warming signals from satellite observations, Weather, 61(3): 70- 76. Fowler, C. et al., 2000: updated 2007. AVHRR Polar Pathfinder Twice-daily 5 km EASE-Grid Composites V003, [used dates from 2000 - 2004], Boulder, CO: NSIDC. Digital media. Hall, D.K., J.Key, K.A. Casey, G.A. Riggs and D. J. Cavalieri, 2004: Sea ice surface temperature product from the Moderate-Resolution Imaging

  17. Greenland supraglacial lake drainages triggered by hydrologically induced basal slip.

    PubMed

    Stevens, Laura A; Behn, Mark D; McGuire, Jeffrey J; Das, Sarah B; Joughin, Ian; Herring, Thomas; Shean, David E; King, Matt A

    2015-06-04

    Water-driven fracture propagation beneath supraglacial lakes rapidly transports large volumes of surface meltwater to the base of the Greenland Ice Sheet. These drainage events drive transient ice-sheet acceleration and establish conduits for additional surface-to-bed meltwater transport for the remainder of the melt season. Although it is well established that cracks must remain water-filled to propagate to the bed, the precise mechanisms that initiate hydro-fracture events beneath lakes are unknown. Here we show that, for a lake on the western Greenland Ice Sheet, drainage events are preceded by a 6-12 hour period of ice-sheet uplift and/or enhanced basal slip. Our observations from a dense Global Positioning System (GPS) network allow us to determine the distribution of meltwater at the ice-sheet bed before, during, and after three rapid drainages in 2011-2013, each of which generates tensile stresses that promote hydro-fracture beneath the lake. We hypothesize that these precursors are associated with the introduction of meltwater to the bed through neighbouring moulin systems (vertical conduits connecting the surface and base of the ice sheet). Our results imply that as lakes form in less crevassed, interior regions of the ice sheet, where water at the bed is currently less pervasive, the creation of new surface-to-bed conduits caused by lake-draining hydro-fractures may be limited.

  18. Variations of algal communities cause darkening of a Greenland glacier.

    PubMed

    Lutz, Stefanie; Anesio, Alexandre M; Jorge Villar, Susana E; Benning, Liane G

    2014-08-01

    We have assessed the microbial ecology on the surface of Mittivakkat glacier in SE-Greenland during the exceptional high melting season in July 2012 when the so far most extreme melting rate for the Greenland Ice Sheet has been recorded. By employing a complementary and multi-disciplinary field sampling and analytical approach, we quantified the dramatic changes in the different microbial surface habitats (green snow, red snow, biofilms, grey ice, cryoconite holes). The observed clear change in dominant algal community and their rapidly changing cryo-organic adaptation inventory was linked to the high melting rate. The changes in carbon and nutrient fluxes between different microbial pools (from snow to ice, cryoconite holes and glacial forefronts) revealed that snow and ice algae dominate the net primary production at the onset of melting, and that they have the potential to support the cryoconite hole communities as carbon and nutrient sources. A large proportion of algal cells is retained on the glacial surface and temporal and spatial changes in pigmentation contribute to the darkening of the snow and ice surfaces. This implies that the fast, melt-induced algal growth has a high albedo reduction potential, and this may lead to a positive feedback speeding up melting processes.

  19. Determining Greenland Ice Sheet Accumulation Rates from Radar Remote Sensing

    NASA Technical Reports Server (NTRS)

    Jezek, Kenneth C.

    2002-01-01

    An important component of NASA's Program for Arctic Regional Climate Assessment (PARCA) is a mass balance investigation of the Greenland Ice Sheet. The mass balance is calculated by taking the difference between the areally Integrated snow accumulation and the net ice discharge of the ice sheet. Uncertainties in this calculation Include the snow accumulation rate, which has traditionally been determined by interpolating data from ice core samples taken from isolated spots across the ice sheet. The sparse data associated with ice cores juxtaposed against the high spatial and temporal resolution provided by remote sensing , has motivated scientists to investigate relationships between accumulation rate and microwave observations as an option for obtaining spatially contiguous estimates. The objective of this PARCA continuation proposal was to complete an estimate of surface accumulation rate on the Greenland Ice Sheet derived from C-band radar backscatter data compiled in the ERS-1 SAR mosaic of data acquired during, September-November, 1992. An empirical equation, based on elevation and latitude, is used to determine the mean annual temperature. We examine the influence of accumulation rate, and mean annual temperature on C-band radar backscatter using a forward model, which incorporates snow metamorphosis and radar backscatter components. Our model is run over a range of accumulation and temperature conditions. Based on the model results, we generate a look-up table, which uniquely maps the measured radar backscatter, and mean annual temperature to accumulation rate. Our results compare favorably with in situ accumulation rate measurements falling within our study area.

  20. Moulin distribution and formation on the southwest Greenland ice sheet

    NASA Astrophysics Data System (ADS)

    Chu, V. W.; Smith, L. C.; Gleason, C. J.; Yang, K.; Poinar, K.; Joughin, I.; Pitcher, L. H.

    2015-12-01

    River moulins represent a significant connection between surface meltwater generated on the Greenland ice sheet and subglacial drainage networks, where increased meltwater can enhance ice sliding dynamics. In this study, a new high-resolution moulin map is created from WorldView-1/2 imagery acquired during the 2012 record melt year for a 12,500 km2 area near Russell Glacier in southwest Greenland. A total of 1,236 moulins are mapped and categorized as being located: in crevasse fields, along a single ice fracture, within drained lake basins, or having no visible formation mechanism. We find the presence of moulins up to 1787 m elevation, with 11% of moulins found above 1600 m elevation: higher than previously mapped moulins and where glaciological theory suggests few moulins should form. Our study observes moulins in both extensional and compressional ice flow regimes (28% of moulins are found in areas of high extensional strain rate >0.005 yr-1), suggesting that strain rates are not a strong indicator of the likelihood for moulin formation. Overall, moulin density tends to increase with higher bed elevation, thinner ice, lower surface slope, higher velocity, and higher strain rate. In sum, moulins are most common in crevassed, thinner ice near the ice sheet edge, but significant quantities also develop at high elevations. This indicates that future inland expansion of melting may create hydrologic connections between the surface and the bed at higher elevations than previously thought.

  1. Self-inhibiting growth of the Greenland Ice Sheet

    NASA Astrophysics Data System (ADS)

    Langen, P. L.; Solgaard, A. M.; Hvidberg, C. S.

    2012-06-01

    The build-up of the Greenland Ice Sheet (GrIS) from ice-free conditions is studied in an ice sheet model (ISM) driven by fields from an atmospheric general circulation model (GCM) to demonstrate the importance of coupling between the two components. Experiments where the two are coupled off-line are augmented by one where an intermediate ice sheet configuration is coupled back to the GCM. Forcing the ISM with GCM fields corresponding to the ice-free state leads to extensive regrowth which, however, is halted when the intermediate recoupling step is included. This inhibition of further growth is due to a Föhn effect of moist air parcels being lifted over the intermediate ice sheet and arriving in the low-lying Greenland interior with high temperatures. This demonstrates that two-way coupling between the atmosphere and the ice sheet is essential for understanding the dynamics and that large scale conditions cooler than those of today may be necessary for the GrIS to regrow to the present volume.

  2. Surface elevation contours of Greenland and Antarctic ice sheets

    NASA Technical Reports Server (NTRS)

    Zwally, H. J.; Bindschadler, R. A.; Brenner, A. C.; Martin, T. V.; Thomas, R. H.

    1983-01-01

    Preliminary results from Seasat radar altimetry over Antarctica north of 72 deg S and Greenland south of 72 deg N are presented. Surface elevations of the ice sheets, obtained from computer retracking of the radar altimeter waveforms, are contoured at 50-m intervals for Greenland and at 100-m intervals for Antarctica. Elevation differences at orbital crossover points are analyzed to obtain a precision of 1.9 m; this figure is partly determined by radial errors of approximately 1.0 m in orbital determination and partly by noise due to ice surface irregularities. Adjustment of the radial components of the orbits to minimize the differences in elevations at crossovers over a small, relatively flat region reduces the rms difference to 0.25 m, which is indicative of the optimum precision obtainable over the ice sheets. However, the precision degrades as the slope of the surface or amplitude of the undulations increases, yielding an overall precision of + or - 1.6 m.

  3. Glaciological reconstruction of Holocene ice margins in northwestern Greenland

    NASA Astrophysics Data System (ADS)

    Birkel, S. D.; Osterberg, E. C.; Kelly, M. A.; Axford, Y.

    2014-12-01

    The past few decades of climate warming have brought overall margin retreat to the Greenland Ice Sheet. In order to place recent and projected changes in context, we are undertaking a collaborative field-modeling study that aims to reconstruct the Holocene history of ice-margin fluctuation near Thule (~76.5°N, 68.7°W), and also along the North Ice Cap (NIC) in the Nunatarssuaq region (~76.7°N, 67.4°W). Fieldwork reported by Kelly et al. (2013) reveals that ice in the study areas was less extensive than at present ca. 4700 (GIS) and ca. 880 (NIC) cal. years BP, presumably in response to a warmer climate. We are now exploring Holocene ice-climate coupling using the University of Maine Ice Sheet Model (UMISM). Our approach is to first test what imposed climate anomalies can afford steady state ice margins in accord with field data. A second test encompasses transient simulation of the Holocene, with climate boundary conditions supplied by existing paleo runs of the Community Climate System Model version 4 (CCSM4), and a climate forcing signal derived from Greenland ice cores. In both cases, the full ice sheet is simulated at 10 km resolution with nested domains at 0.5 km for the study areas. UMISM experiments are underway, and results will be reported at the meeting.

  4. Polyfluoroalkyl compounds in the East Greenland Arctic Ocean.

    PubMed

    Busch, Jan; Ahrens, Lutz; Xie, Zhiyong; Sturm, Renate; Ebinghaus, Ralf

    2010-06-01

    Polyfluoroalkyl compounds (PFCs) can be found ubiquitously in the marine environment. The transport of PFCs to remote locations is assumed to be by direct transport via oceanic water currents or indirectly via atmospheric transport of volatile precursor compounds. This study investigates the influence of ocean currents and atmospheric transport to the East Greenland Arctic Ocean (67.5-80.4 degrees N). In this study, 38 water samples were collected in the Arctic summer in 2009 and analyzed by liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS/MS). Concentrations of three PFC classes could be quantified (i.e., perfluoroalkyl carboxylic acids (PFCAs), perfluoroalkyl sulfonates (PFSAs) and perfluoroalkyl sulfonamides) predominantly in a low pg L(-1) range. Dominating compounds were PFOSA and PFOA with mean concentrations of 61 pg L(-1) and 51 pg L(-1), respectively. Statistically significant higher concentrations for PFOSA and PFHxA in the samples taken north of 75 degrees N indicate an atmospheric influence on the concentrations found in the water samples. Significant differences in concentrations of PFHxS, PFHxA, PFHpA and PFOA for samples taken in coastal areas indicate an influence from the Greenlandic mainland.

  5. Greenland's Elastic and Viscoelastic Adjustments to Ice Mass Changes

    NASA Astrophysics Data System (ADS)

    Bevis, M. G.; Khan, S. A.; Brown, A.; Willis, M. J.; Sasgen, I.

    2014-12-01

    We present the latest geodetic time series from the Greenland GPS Network (GNET), assess the relative importance of instantanous elastic and delayed viscoelastic adjustments to the crustal displacement field, and discuss the complementary nature of GNET's and GRACE's sensing of ice mass changes. Clearly the most robust and best informed inversions for modern ice mass changes will utilize the GNET displacement history, GRACE's mass fields, and ice surface height changes derived from repeat altimetry and repeat optical DEMs. These inversions will also be guided by measured changes in ice flow rates, surface mass balance estimates from numerical weather models, and models of glacial isostatic adjustment. Designing an optimal inverse method requires us to asses and exploit the strengths of each class of observation in order to offset the main weaknesses in the others. GPS and GRACE are the only techniques that directly sense ice mass changes, and we present an analysis of accerations in both time series which demonstrates that GNET senses the lateral variability of ice mass accelerations in SE Greenland with much better resolution than does GRACE. When an optimal model for modern ice mass changes is achieved, and the associated elastic adjustments are subtracted from the GPS displacements, the residual displacements can be used to characterize visoelastic adjusments. These should promote an improved 'PGR correction' for GRACE.

  6. Greenland supraglacial lake drainages triggered by hydrologically induced basal slip

    NASA Astrophysics Data System (ADS)

    Stevens, Laura A.; Behn, Mark D.; McGuire, Jeffrey J.; Das, Sarah B.; Joughin, Ian; Herring, Thomas; Shean, David E.; King, Matt A.

    2015-06-01

    Water-driven fracture propagation beneath supraglacial lakes rapidly transports large volumes of surface meltwater to the base of the Greenland Ice Sheet. These drainage events drive transient ice-sheet acceleration and establish conduits for additional surface-to-bed meltwater transport for the remainder of the melt season. Although it is well established that cracks must remain water-filled to propagate to the bed, the precise mechanisms that initiate hydro-fracture events beneath lakes are unknown. Here we show that, for a lake on the western Greenland Ice Sheet, drainage events are preceded by a 6-12 hour period of ice-sheet uplift and/or enhanced basal slip. Our observations from a dense Global Positioning System (GPS) network allow us to determine the distribution of meltwater at the ice-sheet bed before, during, and after three rapid drainages in 2011-2013, each of which generates tensile stresses that promote hydro-fracture beneath the lake. We hypothesize that these precursors are associated with the introduction of meltwater to the bed through neighbouring moulin systems (vertical conduits connecting the surface and base of the ice sheet). Our results imply that as lakes form in less crevassed, interior regions of the ice sheet, where water at the bed is currently less pervasive, the creation of new surface-to-bed conduits caused by lake-draining hydro-fractures may be limited.

  7. Archean metamorphic sequence and surfaces, Kangerdlugssuaq Fjord, East Greenland

    NASA Technical Reports Server (NTRS)

    Kays, M. A.

    1986-01-01

    The characteristics of Archean metamorphic surfaces and fabrics of a mapped sequence of rocks older than about 3000 Ma provide information basic to an understanding of the structural evolution and metamorphic history in Kangerdlugssuaq Fjord, east Greenland. This information and the additional results of petrologic and geochemical studies have culminated in an extended chronology of Archean plutonic, metamorphic, and tectonic events. The basis for the chronology is considered, especially the nature of the metamorphic fabrics and surfaces in the Archean sequence. The surfaces, which are planar mineral parageneses, may prove to be mappable outside Kangerdlugssuaq Fjord, and if so, will be helpful in extending the events that they represent to other Archean sequences in east Greenland. The surfaces will become especially important reference planes if the absolute ages of their metamorphic assemblages can be determined in at least one location where strain was low subsequent to their recrystallization. Once an isochron is obtained, the dynamothermal age of the regionally identifiable metamorphic surface is determined everywhere it can be mapped.

  8. Documenting Melting Features of the Greenland Ice Sheet

    NASA Astrophysics Data System (ADS)

    Tedesco, M.

    2011-12-01

    There is an increasing interest in studying the Greenland Ice Sheet, its hydrology and dynamics over the short term and longer term because of the potential impact of a warming Arctic. Major studies concern about whether increased surface melting will lead to changes in production of supraglacial lakes and subglacial water pressures and hence , potentially, rates of ice movement. In this talk I will show movies recorded over the past three years form fieldwork activities carried out over the West Greenland ice sheet. In particular, I will project and comment movies concerning surface streams and supraglacial lakes, as the one at http://www.youtube.com/watch?v=QbuFphwJn4c. I will discuss the importance of observing such phenomena and how the recorded videos can be used to summarize scientific studies and communicate the relevance of scientific findings. I will also show, for the first time, the video of the drainage of a supraglacial lake, an event during which a lake ~ 6 m deep and ~ 1 km drained in ~ 1.5 hours. This section of the movie is under development as video material was collected during our latest expedition in June 2011.

  9. Moulin density controls drainage development beneath the Greenland ice sheet

    NASA Astrophysics Data System (ADS)

    Banwell, Alison; Hewitt, Ian; Willis, Ian; Arnold, Neil

    2016-12-01

    Uncertainty remains about how the surface hydrology of the Greenland ice sheet influences its subglacial drainage system, affecting basal water pressures and ice velocities, particularly over intraseasonal and interseasonal timescales. Here we apply a high spatial (200 m) and temporal (1 h) resolution subglacial hydrological model to a marginal (extending 25 km inland), land-terminating, 200 km2 domain in the Paakitsoq region, West Greenland. The model is based on that by Hewitt (2013) but adapted for use with both real topographic boundary conditions and calibrated modeled water inputs. The inputs consist of moulin hydrographs, calculated by a surface routing and lake-filling/draining model, which is forced with distributed runoff from a surface energy-balance model. Results suggest that the areal density of lake-bottom moulins and their timing of opening during the melt season strongly affects subglacial drainage system development. A higher moulin density causes an earlier onset of subglacial channelization (i.e., water transport through channels rather than the distributed sheet), which becomes relatively widespread across the bed, whereas a lower moulin density results in a later onset of channelization that becomes less widespread across the bed. In turn, moulin density has a strong control on spatial and temporal variations in subglacial water pressures, which will influence basal sliding rates, and thus ice motion. The density of active surface-to-bed connections should be considered alongside surface melt intensity and extent in future predictions of the ice sheet's dynamics.

  10. Effectiveness of the Targeted Hepatitis B Vaccination Program in Greenland

    PubMed Central

    Koch, Anders; Biggar, Robert J.; Ladefoged, Karin; Melbye, Mads; Wohlfahrt, Jan; Krause, Tyra Grove

    2012-01-01

    Objectives. To evaluate the effectiveness of the hepatitis B virus (HBV) vaccination program in Greenland, which targets children born to mothers who are positive for HBV surface antigen (HBsAg), we determined vaccination coverage, levels of postvaccination antibodies, and frequency of breakthrough infections in at-risk children. Methods. We conducted a population-based retrospective cohort study with data from nationwide registries. We identified all children born to HBsAg-positive mothers from 1992 to 2007 and collected data on their HBV vaccination status. In 2008 to 2010, we tested the children for HBV core antibody, HBsAg, and anti-HBsAg antibody (HBsAb). Results. Of 4050 pregnant women, 3.2% were HBsAg positive. Of 207 children born to these women, 20% received no vaccinations, and only 58% received at least 3 vaccinations. At follow-up, HBsAb levels in vaccinated children were much lower than expected, and 8 (6%) of 140 at-risk children had breakthrough infections, with 4 chronically infected (persistently HBsAg positive). Conclusions. The prevention program targeting children at risk for HBV in Greenland is ineffective. HBV vaccination should be included in the universal childhood vaccination program, and postvaccination HBsAb levels should be monitored. PMID:21940914

  11. Survival of female northern pintails wintering in southwestern Louisiana

    USGS Publications Warehouse

    Cox, R.R.; Afton, A.D.; Pace, R. M.

    1998-01-01

    The North American breeding population of northern pintails (Anas acuta) has reached previously unprecedented low numbers 4 times since 1983. Because pintails show high fidelity to wintering areas, regional survival estimates and identification of factors influencing survival are needed to guide management of wintering pintails. We used raidiotelemetry to estimate survival rates of female pintails wintering in southwestern Lousiaina. We tested for variation in survival and hunting mortality rates in realtiaon to age (immature or adult), winter (1990-91, 1991-92, 1992-93), time period (prehunting season, first hunting season, time between split hunting seasons, second hunting season, posthunting season), body condition (body mass when released, adjusted for body size), and region (southwestern Louisiana or elsewhere on the Texas-Louisiana Gulf Coast or Mississippi Alluvial Valley).

  12. Toxic Trichodesmium bloom occurrence in the southwestern South Atlantic Ocean.

    PubMed

    Sacilotto Detoni, Amália Maria; Costa, Luiza Dy Fonseca; Pacheco, Lucas Abrão; Yunes, João Sarkis

    2016-02-01

    Harmful Trichodesmium blooms have been reported on the continental slope of the southwestern South Atlantic Ocean; we sampled six such blooms. The highest saxitoxin concentration was observed where the number of colonies was proportionally greater relative to the total density of trichomes. Trichodesmium blooms are harmful to shrimp larvae and may lead to plankton community mortality. This study is the first record of neurotoxic blooms in the open waters of the South Atlantic.

  13. Lichens from Simeonof Wilderness, Shumagin Island, Southwestern Alaska

    USGS Publications Warehouse

    Talbot, Stephen S.; Talbot, Sandra L.; Thomson, J.W.; Daniels, F.J.A.; Schofield, W.B.

    2002-01-01

    One hundred eighty-eight taxa of lichens are reported from Simeonof Island in the Shumagin Islands of southwestern Alaska. Wide-ranging arctic-alpine and boreal species dominate the lichens; a coastal element is moderately represented, while amphi-Beringian species form a minor element. The lichen component of Empetrum nigrum dwarf shrub heath, the dominant vegetation type, was analyzed to identify the most frequently occurring lichens within this community.

  14. Uranium-Bearing Carbonaceous Nodules of Southwestern Oklahoma

    USGS Publications Warehouse

    Hill, James Wilcott

    1956-01-01

    Uranium-bearing carbonaceous nodules have been found along the north flank of the Wichita uplift in southwestern Oklahoma. The carbonaceous nodules are black, hard, and predominantly nodular shaped. One specimen, by analyses, was found to contain approximately 42 percent carbon and 3 percent hydrogen. The uranium, vanadium, cobalt, arsenic, nickel, lead and iron contents each range between 1 and 10 percent. It is concluded that the carbonaceous nodules are epigenetic and that the organic and inorganic constituents were derived from, mobile soluttons.

  15. Extended megadroughts in the southwestern United States during Pleistocene interglacials

    USGS Publications Warehouse

    Fawcett, P.J.; Werne, J.P.; Anderson, R. Scott; Heikoop, J.M.; Brown, E.T.; Berke, M.A.; Smith, S.J.; Goff, F.; Donohoo-Hurley, L.; Cisneros-Dozal, L. M.; Schouten, S.; Damste, J.S.S.; Huang, Y.; Toney, J.; Fessenden, J.; Woldegabriel, G.; Atudorei, V.; Geissman, J.W.; Allen, C.D.

    2011-01-01

    The potential for increased drought frequency and severity linked to anthropogenic climate change in the semi-arid regions of the southwestern United States (US) is a serious concern. Multi-year droughts during the instrumental period and decadal-length droughts of the past two millennia were shorter and climatically different from the future permanent, dust-bowl-like-megadrought conditions, lasting decades to a century, that are predicted as a consequence of warming. So far, it has been unclear whether or not such megadroughts occurred in the southwestern US, and, if so, with what regularity and intensity. Here we show that periods of aridity lasting centuries to millennia occurred in the southwestern US during mid-Pleistocene interglacials. Using molecular palaeotemperature proxies to reconstruct the mean annual temperature (MAT) in mid-Pleistocene lacustrine sediment from the Valles Caldera, New Mexico, we found that the driest conditions occurred during the warmest phases of interglacials, when the MAT was comparable to or higher than the modern MAT. A collapse of drought-tolerant C 4 plant communities during these warm, dry intervals indicates a significant reduction in summer precipitation, possibly in response to a poleward migration of the subtropical dry zone. Three MAT cycles-1/42-C in amplitude occurred within Marine Isotope Stage (MIS) 11 and seem to correspond to the muted precessional cycles within this interglacial. In comparison with MIS 11, MIS 13 experienced higher precessional-cycle amplitudes, larger variations in MAT (4-6??C) and a longer period of extended warmth, suggesting that local insolation variations were important to interglacial climatic variability in the southwestern US. Comparison of the early MIS 11 climate record with the Holocene record shows many similarities and implies that, in the absence of anthropogenic forcing, the region should be entering a cooler and wetter phase. ?? 2011 Macmillan Publishers Limited. All rights

  16. Extended megadroughts in the southwestern United States during Pleistocene interglacials.

    PubMed

    Fawcett, Peter J; Werne, Josef P; Anderson, R Scott; Heikoop, Jeffrey M; Brown, Erik T; Berke, Melissa A; Smith, Susan J; Goff, Fraser; Donohoo-Hurley, Linda; Cisneros-Dozal, Luz M; Schouten, Stefan; Sinninghe Damsté, Jaap S; Huang, Yongsong; Toney, Jaime; Fessenden, Julianna; WoldeGabriel, Giday; Atudorei, Viorel; Geissman, John W; Allen, Craig D

    2011-02-24

    The potential for increased drought frequency and severity linked to anthropogenic climate change in the semi-arid regions of the southwestern United States (US) is a serious concern. Multi-year droughts during the instrumental period and decadal-length droughts of the past two millennia were shorter and climatically different from the future permanent, 'dust-bowl-like' megadrought conditions, lasting decades to a century, that are predicted as a consequence of warming. So far, it has been unclear whether or not such megadroughts occurred in the southwestern US, and, if so, with what regularity and intensity. Here we show that periods of aridity lasting centuries to millennia occurred in the southwestern US during mid-Pleistocene interglacials. Using molecular palaeotemperature proxies to reconstruct the mean annual temperature (MAT) in mid-Pleistocene lacustrine sediment from the Valles Caldera, New Mexico, we found that the driest conditions occurred during the warmest phases of interglacials, when the MAT was comparable to or higher than the modern MAT. A collapse of drought-tolerant C(4) plant communities during these warm, dry intervals indicates a significant reduction in summer precipitation, possibly in response to a poleward migration of the subtropical dry zone. Three MAT cycles ∼2 °C in amplitude occurred within Marine Isotope Stage (MIS) 11 and seem to correspond to the muted precessional cycles within this interglacial. In comparison with MIS 11, MIS 13 experienced higher precessional-cycle amplitudes, larger variations in MAT (4-6 °C) and a longer period of extended warmth, suggesting that local insolation variations were important to interglacial climatic variability in the southwestern US. Comparison of the early MIS 11 climate record with the Holocene record shows many similarities and implies that, in the absence of anthropogenic forcing, the region should be entering a cooler and wetter phase.

  17. Development of saline seeps in Southwestern United States

    USGS Publications Warehouse

    Johnson, Kenneth S.; ,

    1994-01-01

    Saline seeps are an increasingly serious problem in semi-arid regions of the southwestern United States. They result when excessive recharge of the shallow ground water in soils raises the water table locally to within one meter of the land surface, and the salinity of the shallow water is increased through evaporation. In this connection, a comprehensive study is being undertaken in Oklahoma and Texas to determine the geologic setting, hydrology, soils, land use, and history of saline-seep development.

  18. Extreme drought event of 2009/2010 over southwestern China

    NASA Astrophysics Data System (ADS)

    Yang, Jing; Gong, Daoyi; Wang, Wenshan; Hu, Miao; Mao, Rui

    2012-02-01

    The extreme drought of 2009/2010 over southwestern China is the driest event with the lowest percentage rainfall anomaly and the longest non-rain days during winter season (October-February) in the past 50 years, and also the severest one with the lowest percentage rainfall anomaly at the same period since 1880. The drought domain is characterized with anomalous warming and drying in the mid-lower troposphere as well as an evident anomalous subsidence. The favorable circulation anomalies for this drought are associated with the following two factors. One is the strongest negative-phase Arctic Oscillation during 2009/2010 winter that accompanies with a weakened Middle East Jet Stream (MEJS), the cyclonic anomaly over Arabian Sea (AS), the anticyclonic anomaly over Tibet and the cyclonic anomaly over Lake Baikal. The weakened MEJS, the AS cyclonic anomaly and the Tibet anticyclonic anomaly weaken the Southern Branch Trough (SBT) that directly decreases the moisture transport toward the southwestern China; the cyclonic anomaly over the Lake Baikal causes a deepened and westward shifted East Asian Major Trough (EAT) so that dry cold air behind the EAT easily invades down to southwestern China. The AS cyclonic anomaly favors the westward extension of Western Pacific Subtropical High (WPSH). The westward extension of WPSH is also associated with the second factor that is the El Nino Modoki event during 2009/2010 autumn-winter. The intensification and westward extension of WPSH enhance the local subsidence, weaken the SBT and exacerbate this drought.

  19. Digital Atlas of the Upper Washita River Basin, Southwestern Oklahoma

    USGS Publications Warehouse

    Becker, Carol J.; Masoner, Jason R.; Scott, Jonathon C.

    2008-01-01

    Numerous types of environmental data have been collected in the upper Washita River basin in southwestern Oklahoma. However, to date these data have not been compiled into a format that can be comprehensively queried for the purpose of evaluating the effects of various conservation practices implemented to reduce agricultural runoff and erosion in parts of the upper Washita River basin. This U.S. Geological Survey publication, 'Digital atlas of the upper Washita River basin, southwestern Oklahoma' was created to assist with environmental analysis. This atlas contains 30 spatial data sets that can be used in environmental assessment and decision making for the upper Washita River basin. This digital atlas includes U.S. Geological Survey sampling sites and associated water-quality, biological, water-level, and streamflow data collected from 1903 to 2005. The data were retrieved from the U.S. Geological Survey National Water Information System database on September 29, 2005. Data sets are from the Geology, Geography, and Water disciplines of the U.S. Geological Survey and cover parts of Beckham, Caddo, Canadian, Comanche, Custer, Dewey, Grady, Kiowa, and Washita Counties in southwestern Oklahoma. A bibliography of past reports from the U.S. Geological Survey and other State and Federal agencies from 1949 to 2004 is included in the atlas. Additionally, reports by Becker (2001), Martin (2002), Fairchild and others (2004), and Miller and Stanley (2005) are provided in electronic format.

  20. The impact of ice layers on gas transport through firn at the North Greenland Eemian Ice Drilling (NEEM) site, Greenland

    NASA Astrophysics Data System (ADS)

    Keegan, K.; Albert, M. R.; Baker, I.

    2014-10-01

    Typically, gas transport through firn is modeled in the context of an idealized firn column. However, in natural firn, imperfections are present, which can alter transport dynamics and therefore reduce the accuracy of reconstructed climate records. For example, ice layers have been found in several firn cores collected in the polar regions. Here, we examined the effects of two ice layers found in a NEEM, Greenland firn core on gas transport through the firn. These ice layers were found to have permeability values of 3.0 and 4.0 × 10-10 m2, and are therefore not impermeable layers. However, the shallower ice layer was found to be significantly less permeable than the surrounding firn, and can therefore retard gas transport. Large closed bubbles were found in the deeper ice layer, which will have an altered gas composition than that expected because they were closed near the surface after the water phase was present. The bubbles in this layer represent 12% of the expected closed porosity of this firn layer after the firn-ice transition depth is reached, and will therefore bias the future ice core gas record. The permeability and thickness of the ice layers at the North Greenland Eemian Ice Drilling (NEEM) site suggest that they do not disrupt the firn-air concentration profiles and that they do not need to be accounted for in gas transport models at NEEM.

  1. Current and future darkening of the Greenland ice sheet

    NASA Astrophysics Data System (ADS)

    Tedesco, Marco; Stroeve, Julienne; Fettweis, Xavier; Warren, Stephen; Doherty, Sarah; Noble, Erik; Alexander, Patrick

    2015-04-01

    Surface melting over the Greenland ice sheet (GIS) promotes snow grains growth, reducing albedo and further enhancing melting through the increased amount of absorbed solar radiation. Using a combination of remote sensing data and outputs of a regional climate model, we show that albedo over the GIS decreased significantly from 1996 to 2012. Further, we show that most of this darkening can be accounted for by enhanced snow grain growth and the expansion of areas where bare ice is exposed, both of which are driven by increases in snow warming. An analysis of the impact of light-absorbing impurities on albedo trends detected from spaceborne measurements was inconclusive because the estimated impact for concentrations of impurities of order of magnitude found in Greenland is within the albedo uncertainty retrievable from space-based instruments. However, neither models nor observations show an increase in pollutants (black carbon and associated organics) in the atmosphere over the GIS in this time period. Additionally, we could not identify trends in the number of fires over North America and Russia, assumed to be among the sources of soot for Greenland. We did find that a 'dark band' of tilted ice plays a crucial role in decreasing albedo along the west margin, and there is some indication that dust deposition to the GIS may be decreasing albedo in this region but this is not conclusive. In addition to looking at the direct impact of impurities on albedo, we estimated the impact of impurities on albedo via their influence on grain growth and found it is relatively small (~ 1- 2 %), though more sophisticated analysis needs to be carried out. Projections obtained under different warming scenarios consistently point to a continued darkening, with anomalies in albedo driven solely by the effects of climate warming of as much as -0.12 along the west margin of the GIS by the end of this century (with respect to year 2000). Projected darkening is likely underestimated

  2. Working With Greenlandic Fishermen: A New Approach to Citizen Science

    NASA Astrophysics Data System (ADS)

    Turrin, M.; Porter, D. F.; Greve, S.

    2014-12-01

    'Leveraging Local Knowledge to Measure Greenland Fjords' is a science project designed with local knowledge sharing and data collection at its core. Citizen Science can take many different forms but in each instance it incorporates active participation of the general public in science research through integrating outreach, instruction, information gathering and data exchange. The strongest projects focus on two-way information exchange with both the citizen scientist and the professional scientist learning when they share their knowledge. Working in cooperation with both teachers and fishermen in a small local community in northwest Greenland, we collected novel oceanographic measurements from a small 5 m fishing boat in the local fjord. We established connections with the local school for developing education initiatives, sharing maps and other resources, and worked through the teachers to connect with the village residents. We hosted a community meeting to provide a forum for a two-way information exchange with the science team providing background on the research project and the local residents providing both narrative information on local environmental change over the last one to three decades, and more quantitative and immediately useful information on fjord depths, iceberg flow directions and timing of seasonal ice break up and move out. The local fishermen were intimately familiar with the local environment, having intrinsically collected data on fjord depth from their regular lowering of fishing line to catch Greenlandic halibut, a benthic fish. For our first trip they worked with us locating the deep and shallow parts of the fjord from many seasons of watching icebergs ground on the shallow shoals, and showed us how to navigate into the ice packed glacial front through the dense ice mélange. The local community interest in the project and in learning how to use the equipment we had brought encouraged us to discuss a long-term data gathering relationship

  3. Mapping Snow Grain Size over Greenland from MODIS

    NASA Technical Reports Server (NTRS)

    Lyapustin, Alexei; Tedesco, Marco; Wang, Yujie; Kokhanovsky, Alexander

    2008-01-01

    This paper presents a new automatic algorithm to derive optical snow grain size (SGS) at 1 km resolution using Moderate Resolution Imaging Spectroradiometer (MODIS) measurements. Differently from previous approaches, snow grains are not assumed to be spherical but a fractal approach is used to account for their irregular shape. The retrieval is conceptually based on an analytical asymptotic radiative transfer model which predicts spectral bidirectional snow reflectance as a function of the grain size and ice absorption. The analytical form of solution leads to an explicit and fast retrieval algorithm. The time series analysis of derived SGS shows a good sensitivity to snow metamorphism, including melting and snow precipitation events. Preprocessing is performed by a Multi-Angle Implementation of Atmospheric Correction (MAIAC) algorithm, which includes gridding MODIS data to 1 km resolution, water vapor retrieval, cloud masking and an atmospheric correction. MAIAC cloud mask (CM) is a new algorithm based on a time series of gridded MODIS measurements and an image-based rather than pixel-based processing. Extensive processing of MODIS TERRA data over Greenland shows a robust performance of CM algorithm in discrimination of clouds over bright snow and ice. As part of the validation analysis, SGS derived from MODIS over selected sites in 2004 was compared to the microwave brightness temperature measurements of SSM\\I radiometer, which is sensitive to the amount of liquid water in the snowpack. The comparison showed a good qualitative agreement, with both datasets detecting two main periods of snowmelt. Additionally, MODIS SGS was compared with predictions of the snow model CROCUS driven by measurements of the automatic whether stations of the Greenland Climate Network. We found that CROCUS grain size is on average a factor of two larger than MODIS-derived SGS. Overall, the agreement between CROCUS and MODIS results was satisfactory, in particular before and during the

  4. Multibeam Mapping of Remote Fjords in Southeast-Greenland

    NASA Astrophysics Data System (ADS)

    Weinrebe, W.; Kjaer, K. H.; Kjeldsen, K. K.; Bjork, A. A.

    2015-12-01

    The fjords of Southeast-Greenland are among the most remote areas of the Northern Hemisphere. Access to this area is hampered by a broad belt of sea ice floating along the East-Greenland coast from North to South. Consequently, the majority of those fjords have never been surveyed in detail until now. During an expedition by the Center of GeoGenetics of the University of Copenhagen in summer of 2014 we were able to map the Skjoldungen Fjord system with multibeam bathymetry. The topsail schooner ACTIV, built 1951 as a cargo ship to supply remote settlements in Greenland was chosen for the expedition. Though a vintage vessel, the ACTIV was well suited to cross the belt of sea ice and to cruise the ice covered fjords. A portable ELAC-Seabeam 1050 multibeam system was temporarily installed on the vessel. The two transducer of the system were mounted at the lower end of a 6 m long pole attached outboard at port side to the hull of the vessel. Though the installation was quite demanding without any winches or cranes, the construction was sufficiently stable and easy to manage throughout the entire cruise. Nearly the entire fjord system, leaving only a small gap of 5 km at the innermost part and small stripes close to the shorelines could be surveyed during the cruise. For the first time, a comprehensive map of Skjoldungen Fjord is now available. The map displays water depths from close to zero up to 800 m, the deepest part along a stretch of about 10 km in the Southwest. The bathymetry of the northern fjord is remarkably different from the southern fjord: the southern fjord features an outer deep part showing water depths between 500 m and 800 m and a shallow inner part with depths less than 300 m and a prominent sill in between. The northern fjord shows a more gradual increase of water depths from 200 m in the inner part to 600 m at the entrance.

  5. Sonification of cryoconite landscapes over the Greenland ice sheet

    NASA Astrophysics Data System (ADS)

    Tedesco, M.

    2015-12-01

    Sonification is the use of non-speech audio to convey information. In sonification, several elements can be altered, modified or manipulated to change the perception of the sound, and in turn, the perception of the information being transmitted. For example, an increase or decrease in pitch, tempo and amplitude can be used to convey the information but this can also happen by varying other less commonly used components. One of the advantages of using sonification lies in the temporal, spatial, amplitude, and frequency resolution that offer complementary and supplementary possibilities with respect to visualization techniques. Two years ago, the outcomes of the PolarSEEDS project (www.polaseeds.org), consisting of sonification of time series of albedo, melting and surface temperature over the Greenland ice sheet, were presented in this very same session. The work that I will discuss in this presentation builds on the PolarSEEDS experience, focusing on the fascinating microcosm of cryoconite. Cryoconite is a unique and extremely fascinating form of glacial cover consisting of aggregated rock dust, inorganic and detrital organic matter, and active microbial colonies. It can be seen as 'living stones', with this ecosystem containing the only form of life that is sustained on the majestic surface of the Greenland ice sheet. Microbes are, indeed, the catalyst for cryoconite formation and growth. The cryoconite constituents radiate metabolic heat promoting glacier hole development, melt water formation, and decreasing glacier surface albedo. Lower albedos cause a positive feedback that further contributes to glacier ablation. Despite their importance, cryoconite systems are poorly studied and little is known about their evolution. In the talk, I will first present and discuss previous sonification projects whose main focus was on the polar regions; then, I will present new sonifications based on data quantifying the distribution and evolution of cryoconite over the west

  6. Only 5 southern Greenland shelf edge glaciations since the early Pliocene

    PubMed Central

    Nielsen, Tove; Kuijpers, Antoon

    2013-01-01

    Much uncertainty exists about the history of the Greenland Ice Sheet (GIS), particularly as to the frequency of extreme shelf edge glaciations. Because the last glaciation removed most of the record of earlier GIS extent on land and shelf exploration of the older GIS glacial record requires the use of deeper marine archives. Here we present seismic evidence for the frequency of extreme shelf edge glaciations offshore southwest Greenland. Our findings reveal that since the GIS formation only 5 glaciations were characterized by an ice sheet covering the entire shelf of southern Greenland. We estimate an age of around 4.5 million years (my) for the oldest episode and found that such extreme GIS expansions may have occur here only 3 times within the past c. 1.5 my. We thus conclude that the first large shelf edge glaciation of southern Greenland did occur prior to the Pliocene warmth epoch. PMID:23698710

  7. Hinge-line Migration of Petermann Gletscher, North Greenland, Detected Using Satellite Radar Interferometry

    NASA Technical Reports Server (NTRS)

    Rignot, Eric

    1998-01-01

    The synthetic-aperture radar interferometry technique is used to detect the migration of the limit of tidal flexing, or hinge line, of the floating ice tongue of Petermann Gletscher, a major outlet glacier of north Greenland.

  8. Ice Flow in the Humboldt, Petermann, and Ryder Glaciers, North Greenland

    NASA Technical Reports Server (NTRS)

    Joughin, I.; Fahnestock, M.; Kwok, R.; Gogineni, P.; Allen, C.

    1998-01-01

    Radar Interferometry, ice-penetrating radar profiles, and an elevation model are used to determine the catchment area, rates of ice discharge, and approximate states of balance for three large outlet glaciers in northeast Greenland.

  9. Comparing Norse animal husbandry practices: paleoethnobotanical analyses from Iceland and Greenland.

    PubMed

    Ross, Julie M; Zutter, Cynthia

    2007-01-01

    The popular view of the Norse settlement across the North Atlantic describes colonies with similar subsistence practices being established from the Faroe Islands in the west to L'Anse aux Meadows in the east. The importance of plant resources to the Norse animal husbandry strategies implemented by settlers upon arrival are not well established, nor are the changes these strategies underwent, eventually resulting in different cultural solutions to varying environmental and social factors. This paper compares archaeobotanical samples from two Icelandic archaeological sites, Svalbarð and Gjögur, and one Greenlandic site, Gården Under Sandet (GUS). Results of this comparison suggest that heathland shrubs were an important fodder resource for caprines in both Iceland and Greenland while apophytes ("weedy taxa") were part of the cattle fodder in Greenland. Further, the results indicate that mucking out of cattle barns to provide fertilizer was likely practiced at the GUS site in the Western Norse settlement of Greenland.

  10. Aerial photographs reveal late-20th-century dynamic ice loss in northwestern Greenland.

    PubMed

    Kjær, Kurt H; Khan, Shfaqat A; Korsgaard, Niels J; Wahr, John; Bamber, Jonathan L; Hurkmans, Ruud; van den Broeke, Michiel; Timm, Lars H; Kjeldsen, Kristian K; Bjørk, Anders A; Larsen, Nicolaj K; Jørgensen, Lars Tyge; Færch-Jensen, Anders; Willerslev, Eske

    2012-08-03

    Global warming is predicted to have a profound impact on the Greenland Ice Sheet and its contribution to global sea-level rise. Recent mass loss in the northwest of Greenland has been substantial. Using aerial photographs, we produced digital elevation models and extended the time record of recent observed marginal dynamic thinning back to the mid-1980s. We reveal two independent dynamic ice loss events on the northwestern Greenland Ice Sheet margin: from 1985 to 1993 and 2005 to 2010, which were separated by limited mass changes. Our results suggest that the ice mass changes in this sector were primarily caused by short-lived dynamic ice loss events rather than changes in the surface mass balance. This finding challenges predictions about the future response of the Greenland Ice Sheet to increasing global temperatures.

  11. Divergent parasite faunas in adjacent populations of West Greenland caribou: suggested natural and anthropogenic influences

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Gastrointestinal parasite diversity was characterized for two adjacent populations of west Greenland caribou (Rangifer tarandus groenlandicus) through examinations of abomasa and small intestines of adult and subadult females collected during late winter. Three trichostrongyline (Trichostrongylina: ...

  12. Native Language Dictionaries and Grammars of Alaska, Northern Canada, and Greenland.

    ERIC Educational Resources Information Center

    Goniwiecha, Mark C.; Hales, David A.

    1988-01-01

    Describes recent political and social activities aimed at preserving the culture of Native Americans in Alaska, Northern Canada, and Greenland. An annotated bibliography of sources for the Eskimo Aleut, Tsimshian, Haida, Athabascan (Athapascan), Eyak and Tlingit languages is provided. (CLB)

  13. Greenland Ice Sheet glacier motion and ice loss: New understanding of ice sheet behavior through remote sensing

    NASA Astrophysics Data System (ADS)

    Moon, T. A.; Fahnestock, M. A.; Scambos, T.; Joughin, I.

    2015-12-01

    Ice loss from the Greenland Ice Sheet makes up roughly a third of current sea level rise, also generating substantial local and regional freshwater fluxes. Containing more than 6 meters of sea level rise equivalent in ice, Greenland has the potential to contribute much more to rising ocean levels and freshening water in the future. Understanding the dynamics of the ice sheet, particularly the behavior of fast flowing coastal outlet glaciers, is critical to improving predictions of future ice sheet change and associated impacts. Combining velocity, glacier ice front, sea ice, and ice sheet surface melt data, we made several important advances in characterizing and understanding seasonal glacier behavior and the processes driving change: 1) seasonal velocity patterns fall into at least 3 distinct patterns, 2) these seasonal velocity patterns likely indicate differences in glacier responsiveness to ocean versus subglacial hydrologic processes, and 3) in some regions seasonal versus multi-year velocity changes appear most strongly influenced by different environmental factors. Further progress was previously hampered by limits in measurement resolution across space and time. To address this challenge, we are creating a new - and continuously growing - ice velocity dataset from Landsat 8 imagery. This data stream supports comprehensive global measurements of ice flow, providing a leap in our understanding of ice sheet motion across space and time. We offer a high-level discussion of our research findings and an introduction to the new Landsat 8-enabled data stream. Our results and measurement capabilities deliver critical new knowledge about ice sheet behavior and interaction with ocean and climate factors. These advances, in turn, have important implications for other elements of Earth system research, including climate, oceanography, and biology.

  14. A Climate-Data Record (CDR) of the "Clear-Sky" Surface Temperature of the Greenland Ice Sheet

    NASA Technical Reports Server (NTRS)

    Hall, Dorothy K.; Comiso, Josefino C.; DiGirolamo, Nocolo E.; Shuman, Christopher A.

    2011-01-01

    We have developed a climate-data record (CDR) of "clear-sky" ice-surface temperature (IST) of the Greenland Ice Sheet using Moderate-Resolution Imaging Spectroradiometer (MODIS) data. The CDR provides daily and monthly-mean IST from March 2000 through December 2010 on a polar stereographic projection at a resolution of 6.25 km. The CDR is amenable to extension into the future using Visible/Infrared Imager Radiometer Suite (VIIRS) data. Regional "clear-sky" surface temperature increases since the early 1980s in the Arctic, measured using Advanced Very High Resolution Radiometer (AVHRR) infrared data, range from 0.57 +/- 0.02 to 0.72 +/- 0.1 c per decade. Arctic warming has important implications for ice-sheet mass balance because much of the periphery of the Greenland Ice Sheet is already near O C during the melt season, and is thus vulnerable to rapid melting if temperatures continue to increase. An increase in melting of the ice sheet would accelerate sea-level rise, an issue affecting potentially billions of people worldwide. The IST CDR will provide a convenient data set for modelers and for climatologists to track changes of the surface temperature of the ice sheet as a whole and of the individual drainage basins on the ice sheet. The daily and monthly maps will provide information on surface melt as well as "clear-sky" temperature. The CDR will be further validated by comparing results with automatic-weather station data and with satellite-derived surface-temperature products.

  15. A Climate-Data Record (CDR) of the "Clear Sky" Surface Temperature of the Greenland Ice Sheet

    NASA Technical Reports Server (NTRS)

    Hall, Dorothy K.; Comiso, J. C.; DiGirolamo, N. E.; Shuman, C. A.

    2011-01-01

    To quantify the ice-surface temperature (IST) we are developing a climate-data record (CDR) of monthly IST of the Greenland ice sheet, from 1982 to the present using Advanced Very High Resolution Radiometer (AVHRR) and Moderate-Resolution Imaging Spectroradiometer (MODIS) data at 5-km resolution. "Clear-sky" surface temperature increases have been measured from the early 1980s to the early 2000s in the Arctic using AVHRR data, showing increases ranging from 0.57-0.02 (Wang and Key, 2005) to 0.72 0.10 deg C per decade (Comiso, 2006). Arctic warming has implications for ice-sheet mass balance because much of the periphery of the ice sheet is near 0 deg C in the melt season and is thus vulnerable to more extensive melting (Hanna et al., 2008). The algorithm used for this work has a long history of measuring IST in the Arctic with AVHRR (Key and Haefliger, 1992). The data are currently available from 1981 to 2004 in the AVHRR Polar Pathfinder (APP) dataset (Fowler et al., 2000). J. Key1NOAA modified the AVHRR algorithm for use with MODIS (Hall et al., 2004). The MODIS algorithm is now being processed over Greenland. Issues being addressed in the production of the CDR are: time-series bias caused by cloud cover, and cross-calibration between AVHRR and MODIS instruments. Because of uncertainties, time series of satellite ISTs do not necessarily correspond with actual surface temperatures. The CDR will be validated by comparing results with in-situ (see Koenig and Hall, in press) and automatic-weather station data (e.g., Shuman et al., 2001).

  16. Trends of perfluorochemicals in Greenland ringed seals and polar bears: indications of shifts to decreasing trends.

    PubMed

    Rigét, Frank; Bossi, Rossana; Sonne, Christian; Vorkamp, Katrin; Dietz, Rune

    2013-11-01

    Time-series of perfluorinated alkylated substances (PFASs) in East Greenland polar bears and East and West Greenland ringed seals were updated in order to deduce whether a response to the major reduction in perfluoroalkyl production in the early 2000s had occurred. Previous studies had documented an exponential increase of perfluorooctane sulphonate (PFOS) in liver tissue from both species. In the present study, PFOS was still the far most dominant compound constituting 92% (West Gr