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Sample records for southwestern greenland implications

  1. Identifying potential Greenland halibut spawning areas and nursery grounds off East and South-western Greenland and its management implications

    NASA Astrophysics Data System (ADS)

    Gundersen, A. C.; Kennedy, J.; Woll, A.; Fossen, I.; Boje, J.

    2013-01-01

    Spawning and nursery grounds are poorly described for the West Nordic stock of Greenland halibut (Reinhardtius hippoglossoides) and the entire stock is assumed to originate from a common spawning ground southwest of Iceland. Greenland halibut with hydrated eggs in their ovary were caught during a gillnet survey in 1995 in Greenland waters. This suggests that the spawning areas for the West Nordic stock are not limited to the previously described area southwest of Iceland. Further this paper provides information on distribution of immature Greenland halibut in the fjords of East Greenland. The densities in Tasilaq area suggest that this area may be part of a nursery area in the West-Nordic management unit. However, the importance of this area to the stock is currently unknown. The results have potential implications for the management of the West Nordic Greenland halibut as the management seems to comprise of several stocks, or perhaps a meta-population.

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

    PubMed

    Nagy, B; Zumberge, J E; Nagy, L A

    1975-03-01

    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.

  3. 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

  4. 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

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

    PubMed

    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

  6. Age of the Ørkendalen moraines, Kangerlussuaq, Greenland: constraints on the extent of the southwestern margin of the Greenland Ice Sheet during the Holocene

    NASA Astrophysics Data System (ADS)

    Levy, Laura B.; Kelly, Meredith A.; Howley, Jennifer A.; Virginia, Ross A.

    2012-10-01

    Although Greenland ice core records register relatively stable Holocene climate conditions, the lower elevation margins of the Greenland Ice Sheet (GrIS) experienced significant Holocene fluctuations. These fluctuations include ice sheet recession during the Holocene Thermal Maximum (9-5 ka) and advance during the Little Ice Age (LIA; ˜A.D. 1350-1880). Determining the extent and timing of these fluctuations is important for understanding the response of the GrIS to interglacial climate conditions both warmer and colder than at present and for developing accurate ice sheet models. Sets of moraines marking past extents of the southwestern GrIS margin occur in the Kangerlussuaq region. We focus on the Ørkendalen moraines, a prominent moraine set located within 2 km of the modern ice margin and just outboard of the LIA moraines. We present the first 10Be ages of the Ørkendalen moraines indicating they were deposited at 6.8 ± 0.3 ka. The geomorphic relationship between the Ørkendalen and LIA moraines indicates that the ice sheet margin was inboard of its Ørkendalen extent between ˜6.8 ka and the culmination of the LIA. The age of the Ørkendalen moraines provides an important constraint on the extent of the southwestern GrIS during the middle Holocene.

  7. 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.

  8. Spatial and temporal variability of lake ontogeny in south-western Greenland

    NASA Astrophysics Data System (ADS)

    Law, A. C.; Anderson, N. J.; McGowan, S.

    2015-10-01

    Holocene palaeolimnological records of diatoms and β carotene (a proxy for aquatic production) from four lakes in the low Arctic region of south-western Greenland were used to investigate the role of climate on lake ontogeny. Two of the lakes are located in the maritime, coastal region near Sisimiut and two inland close to the head of Kangerlussuaq fjord, where there is a more continental climate. Diatom records from the four lakes (AT1, AT4, SS1381, SS8) had similar long-term ontogeny trends, independent of climatic setting and the changes are interpreted as responses to first order weathering controls on catchment/lake chemistry. Short-term excursions from these broad trends occurred in one coastal site (AT4) caused by intense erosion of the steep catchment, and at inland sites where temporary hydrological closure and lake level decline occurred during the mid-Holocene (˜8000 - 5000 cal a BP). Algal production (as β carotene) was more closely and consistently correlated with climatic changes; it peaked during the mid-Holocene, the warmest period of the Holocene, at all sites and there were transient increases in production in inland lakes during the Medieval Climate Anomaly and Little Ice Age because of fertilization through increased aeolian dust deposition. A synthesis of seven palaeolimnological records from this region identified that only the mid-Holocene was correlated with diatom stratigraphic zones and there was considerable among-site variability in later Holocene lake response to climate forcing in this area. Comparable long-term trends in species assemblage turnover (DCA/CA axis 1 scores) clearly demonstrate that lakes have predictable ontogeny trends in this region, characterised by maximum alkalinity and nutrient availability in the first few millennia followed by progressive oligotrophication and alkalinity loss. However, individual lake and catchment characteristics (lake morphology, catchment geomorphology), when modified by climatic change

  9. Subpixel variability of MODIS albedo retrievals and its importance for ice sheet surface melting in southwestern Greenland's ablation zone

    NASA Astrophysics Data System (ADS)

    Moustafa, S.; Rennermalm, A. K.; Roman, M. O.; Koenig, L.; Smith, L. C.; Schaaf, C.; Wang, Z.; Mioduszewski, J.

    2013-12-01

    On the Greenland ice sheet, albedo declined across 70% of its surface since 2000, with the greatest reduction in the lower 600 m of the southwestern ablation zone. Because albedo plays a prominent role in the ice sheet surface energy balance, its decline has resulted in near doubling of meltwater production. To characterize ice sheet albedo, Moderate Imaging Spectrometer (MODIS) surface albedo products are typically used. However, it is unclear how the spatial variability of albedo within a MODIS pixel influences surface melting and whether it can be considered a linear function of albedo. In this study, high spatiotemporal resolution measurements of spectral albedo and ice sheet surface ablation were collected along a ~ 1.3 km transect during June 2013 within the Akuliarusiarsuup Kuua (AK) River watershed in southwest Greenland. Spectral measurements were made at 325-1075 nm using a Analytical Spectral Devices (ASD) spectroradiometer, fitted with a Remote Cosine Receptor (RCR). In situ albedo measurements are compared with the daily MODIS albedo product (MCD43A) to analyze how space, time, surface heterogeneity, atmospheric conditions, and solar zenith angle geometry govern albedo at different scales. Finally, analysis of sub-pixel albedo and ablation reveal its importance on meltwater production in the lower parts of the ice sheet margin.

  10. 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

  11. Rapid last-deglacial thinning and retreat of the marine-terminating southwestern Greenland ice sheet

    NASA Astrophysics Data System (ADS)

    Winsor, Kelsey; Carlson, Anders E.; Caffee, Marc W.; Rood, Dylan H.

    2015-09-01

    Marine-terminating outlet glaciers are a major source of modern ice loss from the Greenland Ice Sheet (GrIS), but their role in GrIS retreat during the last deglaciation is not well constrained. Here, we develop deglacial outlet glacier retreat chronologies for four regions in southwest and south Greenland to improve understanding of spatial variations in centennial- to millennial-scale ice loss under a warming climate. We calculate 10Be surface exposure ages of boulders located in fjords near the towns of Qaqortoq, Paamiut, Nuuk, and Sisimiut. Our northernmost study site, Sisimiut, deglaciated earliest at ∼18 ka to ∼15 ka with an average thinning rate of 0.1-0.3 m yr-1. Inland retreat from Sisimiut to the modern ice margin took ∼7 ka at an average retreat rate of 15-20 m yr-1. A 10Be-dated moraine ∼25 km from the modern GrIS margin deposited at ∼8 ka suggests a possible ice-margin still-stand, but this does not change overall retreat rates. After retreat from the small coastal Sisimiut fjords, the GrIS margin was mainly land-terminating in this region. In contrast, earliest exposure occurred at ∼12 ka near Qaqortoq, and 11-10 ka near Nuuk and Paamiut, with ice thinning at rates of 0.2-0.3 m yr-1 to instantaneous within measurement uncertainty. Ice retreat inland through the extensive Nuuk, Paamiut, and Qaqortoq fjord systems to near modern ice margins occurred in <1 ka, resulting in minimum retreat rates of 25-65 m yr-1 and maximum retreat rates of ∼95 m yr-1 to instantaneous within the uncertainty of our measurements. This rapid thinning and retreat of marine-terminating southwest GrIS margins is contemporaneous with an incursion of relatively warm ocean waters into the Labrador Sea and toward the southwest Greenland coast, suggesting that a warming ocean may have contributed to the more rapid retreat of marine GrIS termini in the Nuuk, Paamiut, and Qaqortoq fjord systems relative to the slower ice retreat inland from Sisimiut. Our results highlight

  12. Multi-modal albedo distributions in the ablation area of the southwestern Greenland Ice Sheet

    NASA Astrophysics Data System (ADS)

    Moustafa, S. E.; Rennermalm, A. K.; Smith, L. C.; Miller, M. A.; Mioduszewski, J. R.; Koenig, L. S.; Hom, M. G.; Shuman, C. A.

    2015-05-01

    Surface albedo is a key variable controlling solar radiation absorbed at the Greenland Ice Sheet (GrIS) surface and, thus, meltwater production. Recent decline in surface albedo over the GrIS has been linked to enhanced snow grain metamorphic rates, earlier snowmelt, and amplified melt-albedo feedback from atmospheric warming. However, the importance of distinct surface types on ablation area albedo and meltwater production is still relatively unknown. In this study, we analyze albedo and ablation rates using in situ and remotely sensed data. Observations include (1) a new high-quality in situ spectral albedo data set collected with an Analytical Spectral Devices Inc. spectroradiometer measuring at 325-1075 nm along a 1.25 km transect during 3 days in June 2013; (2) broadband albedo at two automatic weather stations; and (3) daily MODerate Resolution Imaging Spectroradiometer (MODIS) albedo (MOD10A1) between 31 May and 30 August 2012 and 2013. We find that seasonal ablation area albedos in 2013 have a bimodal distribution, with snow and ice facies characterizing the two peaks. Our results show that a shift from a distribution dominated by high to low albedos corresponds to an observed melt rate increase of 51.5% (between 10-14 July and 20-24 July 2013). In contrast, melt rate variability caused by albedo changes before and after this shift was much lower and varied between ~10 and 30% in the melting season. Ablation area albedos in 2012 exhibited a more complex multimodal distribution, reflecting a transition from light to dark-dominated surface, as well as sensitivity to the so called "dark-band" region in southwest Greenland. In addition to a darkening surface from ice crystal growth, our findings demonstrate that seasonal changes in GrIS ablation area albedos are controlled by changes in the fractional coverage of snow, bare ice, and impurity-rich surface types. Thus, seasonal variability in ablation area albedos appears to be regulated primarily as a function

  13. Bimodal albedo distributions in the ablation zone of the southwestern Greenland Ice Sheet

    NASA Astrophysics Data System (ADS)

    Moustafa, S. E.; Rennermalm, A. K.; Smith, L. C.; Miller, M. A.; Mioduszewski, J. R.

    2014-09-01

    Surface albedo is a key variable controlling solar radiation absorbed at the Greenland Ice Sheet (GrIS) surface, and thus, meltwater production. Recent decline in surface albedo over the GrIS has been linked to enhanced snow grain metamorphic rates and amplified ice-albedo feedback from atmospheric warming. However, the importance of distinct surface types on ablation zone albedo and meltwater production is still relatively unknown, and excluded in surface mass balance models. In this study, we analyze albedo and ablation rates using in situ and remotely-sensed data. Observations include: (1) a new high-quality in situ spectral albedo dataset collected with an Analytical Spectral Devices (ASD) spectroradiometer measuring at 325-1075 nm, along a 1.25 km transect during three days in June 2013; (2) broadband albedo at two automatic weather stations; and (3) daily MODerate Resolution Imaging Spectroradiometer (MODIS) albedo (MOD10A1) between 31 May and 30 August. We find that seasonal ablation zone albedos have a bimodal distribution, with two alternate states. This suggests that an abrupt switch from high to low albedo can be triggered by a modest melt event, resulting in amplified surface ablation rates. Our results show that such a shift corresponds to an observed melt rate percent difference increase of 51.6% during peak melt season (between 10-14 and 20-24 July 2013). Furthermore, our findings demonstrate that seasonal changes in GrIS ablation zone albedo are not exclusively a function of a darkening surface from ice crystal growth, but rather are controlled by changes in the fractional coverage of snow, bare ice, and impurity-rich surface types. As the climate continues to warm, regional climate models should consider the seasonal evolution of ice surface types in Greenland's ablation zone to improve projections of mass loss contributions to sea level rise.

  14. Bimodal Albedo Distributions in the Ablation Zone of the Southwestern Greenland Ice Sheet

    NASA Astrophysics Data System (ADS)

    Moustafa, S.; Rennermalm, A. K.; Smith, L. C.; Miller, M. A.; Mioduszewski, J.; Koenig, L.

    2014-12-01

    Surface albedo is a key variable controlling solar radiation absorbed at the Greenland Ice Sheet (GrIS) surface, and thus meltwater production. Recent decline in surface albedo over the GrIS has been linked to enhanced snow grain metamorphic rates and amplified ice-albedo feedback from atmospheric warming. However, the importance of distinct surface types on ablation zone albedo and meltwater production is still relatively unknown, and excluded in surface mass balance models. In this study, we analyze albedo and ablation rates (m d-1) using in situ and remotely-sensed data. Observations include: 1) a new high-quality in situ spectral albedo dataset collected with an Analytical Spectral Devices (ASD) spectroradiometer measuring at 325-1075 nm, along a 1.25 km transect during three days in June 2013; 2) broadband albedo at two automatic weather stations; and 3) daily MODerate Resolution Imaging Spectroradiometer (MODIS) albedo (MOD10A1) between 31 May and 30 August. We find that seasonal ablation zone albedos have a bimodal distribution, with two alternate states. This suggests that an abrupt switch from high to low albedo can be triggered by a modest melt event, resulting in amplified ablation rates. Our results show that such a shift corresponds to an observed melt rate percent difference increase of 51.6% during peak melt season (between 10-14 July and 20-24 July, 2013). Furthermore, our findings demonstrate that seasonal changes in GrIS ablation zone albedo are not exclusively a function of a darkening surface from ice crystal growth, but rather are controlled by changes in the fractional coverage of snow, bare ice, and impurity-rich surface types. As the climate continues to warm, regional climate models should consider the seasonal evolution of ice surface types in Greenland's ablation zone to improve projections of mass loss contributions to sea level rise.

  15. Efficient removal of meltwater runoff through supraglacial streams and rivers on the southwestern Greenland Ice Sheet

    NASA Astrophysics Data System (ADS)

    Smith, L. C.; Yang, K.; Pitcher, L. H.; Overstreet, B. T.; Rennermalm, A. K.; Chu, V. W.; Ryan, J.; Hubbard, A.; Cooper, M. G.; Tedesco, M.; Mote, T. L.; Young, K.; Behar, A.

    2015-12-01

    Supraglacial streams and rivers flowing on the Greenland Ice Sheet have received little physical study. We present remotely sensed (UAV, WorldView) and in situ (Acoustic Doppler Current Profiler, Lagrangian drifters) measurements of supraglacial river drainage pattern, hydraulic properties, and discharge in the Kangerlussuaq region. This area of the ice sheet is characterized by large, well-organized supraglacial stream/river networks that efficiently drain the ice surface with minimal retention of surface water, with river moulins being the the dominant physical mechanism by which surface meltwater enters the ice sheet. An intensive 2015 field campaign acquired novel datasets of watershed extent, drainage pattern, ablation rate, albedo and discharge for a ~70 km2 mid-elevation ice catchment ("Rio Behar"), including a continuous 72-hour record of discharge and water temperature in a supraglacial river upstream of its terminal moulin. We conclude that this area of the ice sheet is efficiently drained by supraglacial stream/river networks, that ice-surface DEMs alone cannot fully describe supraglacial drainage and its connection to subglacial systems; and that in situ measurements of supraglacial river discharge offer a unique opportunity to test runoff predictions of regional climate models.

  16. Greenland ice sheet albedo feedback: mass balance implications

    NASA Astrophysics Data System (ADS)

    Box, J. E.; Tedesco, M.; Fettweis, X.; Hall, D. K.; Steffen, K.; Stroeve, J. C.

    2012-12-01

    Greenland ice sheet mass loss has accelerated responding to combined glacier discharge and surface melt water runoff increases. During summer, absorbed solar energy, modulated at the surface primarily by albedo, is the dominant factor governing surface melt variability in the ablation area. NASA MODIS data spanning 13 summers (2000 - 2012), indicate that mid-summer (July) ice sheet albedo declined by 0.064 from a value of 0.752 in the early 2000s. The ice sheet accordingly absorbed 100 EJ more solar energy for the month of July in 2012 than in the early 2000s. This additional energy flux during summer doubled melt rates in the ice sheet ablation area during the observation period. Abnormally strong anticyclonic circulation, associated with a persistent summer North Atlantic Oscillation extreme 2007-2012, enabled 3 amplifying mechanisms to maximize the albedo feedback: 1) increased warm (south) air advection along the western ice sheet increased surface sensible heating that in turn enhanced snow grain metamorphic rates, further reducing albedo; 2) increased surface downward shortwave flux, leading to more surface heating and further albedo reduction; and 3) reduced snowfall rates sustained low albedo, maximizing surface solar heating, progressively lowering albedo over multiple years. The summer net infrared and solar radiation for the high elevation accumulation area reached positive values during this period, contributing to an abrupt melt area increase in 2012. A number of factors make it reasonable to expect more melt episodes covering 100% of the ice sheet area in coming years: 1) the past 13 y of increasing surface air temperatures have eroded snowpack 'cold content', preconditioning the ice sheet for earlier melt onset. Less heat is required to bring the surface to melting; 2) Greenland temperatures, have lagged the N Hemisphere average in the 2000s, need to increase further for Greenland to be in phase with the N Hemisphere average. 3) Arctic amplification

  17. Fram Strait Ice Export during the Nineteenth and Twentieth Centuries Reconstructed from a Multiyear Sea Ice Index from Southwestern Greenland.

    NASA Astrophysics Data System (ADS)

    Schmith, Torben; Hansen, Carsten

    2003-08-01

    Historical observations of multiyear ice, called `storis,' in the southwest Greenland waters exist from the period 1820-2000, obtained from ship logbooks and ice charts. It is argued that this ice originates in the Arctic Ocean and has traveled via the Fram Strait, southward along the Greenland coast in the East Greenland Current, and around the southern tip of Greenland. Therefore, it is hypothesized that these observations can be used as `proxies' for reconstructing the Fram Strait ice export on an annual basis. An index describing the storis extent is extracted from the observations and a linear statistical model formulated relating this index to the Fram Strait ice export. The model is calibrated using ice export values from a hindcast study with a coupled ocean-ice model over the period 1949-98. Subsequently, the model is used to reconstruct the Fram Strait annual ice export in the period 1820-2000. The model has significant skill, calculated on independent data.Based on this reconstruction, it is discussed how time periods with large and small ice export on multidecadal timescales coincide with time periods of cold and warm North Atlantic sea surface temperatures reported by others. This implies that trend studies based on satellite observations should be regarded with some care, since the time period of satellite observations, the last decades, where a particularly strong negative trend is observed in the ice export, is preceded by a time period with a positive trend. The occurrence of `great salinity anomalies' (GSAs) is also connected to the multidecadal variability. The GSAs observed in Greenland waters around 1968-70 and 1980-82 both occurred when the general level of ice export was high. Prior to these there was a long period with generally low ice export and no GSAs, but during an epoch around the turn of the nineteenth century several GSAs occurred. Finally, it is found that the correlation between the Fram Strait ice export and the North Atlantic

  18. New Aerogeophysical Results from the Arctic Ocean, north of Greenland: Implications for Late Cretaceous rifting

    NASA Astrophysics Data System (ADS)

    Døssing, Arne; Hopper, John; Olesen, Arne; Halpenny, John

    2013-04-01

    against the Lincoln Sea/Greenland plate. Our results provide important geometrical constraints for Late Cretaceous plate reconstructions of the Arctic and have important implications for understanding the earlier Cretaceous and possibly Jurassic episodes of seafloor spreading around the Arctic.

  19. Cyanotoxins in arctic lakes of southwestern Greenland and the potential for toxin transfer within-lake and across the aquatic-terrestrial boundary

    NASA Astrophysics Data System (ADS)

    Trout-Haney, J. V.; Cottingham, K. L.

    2015-12-01

    Arctic lakes are often characterized as low-resource environments in which the autotrophic community is limited by factors such as nutrients, temperature, and light. Studies of cyanotoxins have traditionally focused on nutrient-rich lakes with conspicuous blooms, however toxigenic cyanobacteria are confined to neither high nutrient environments nor planktonic taxa. We quantified the occurrence of cyanotoxins across 19 arctic lakes of varying size and depth in the Kangerlussuaq region of southwestern Greenland. Whole lake water microcystins (MC) were detected in all lakes and ranged from low (<5 ng/L) to moderate (>100 ng/L) concentrations. Benthic colonial cyanobacteria of the genus Nostoc are a prominent feature of certain lakes in this region, with estimated densities ranging between 500 and >500,000 colonies per lake. MC were present in the tissue of Nostoc colonies (95% CI, 1638.9 - 3237.6 pg MC (g wet weight)-1) and were actively released by colonies into surrounding water in laboratory trials. These results highlight the potential importance of toxic benthic cyanobacteria in lake ecosystems. Further, we investigated the transfer of these cyanotoxins to other organisms in the lake as well as several mechanisms (i.e., emerging insects, aerosols) that may influence the movement of toxins into the terrestrial ecosystem. The presence and movement of cyanotoxins in the coupled terrestrial-aquatic ecosystem demonstrate that high-latitude lakes can support toxigenic cyanobacteria, and that we may be underestimating the potential for these systems to develop high levels of toxicity in the future.

  20. 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.

  1. 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

  2. 'Uncertainty explosion' in 21st century Greenland temperature change - implications for sea level rise

    NASA Astrophysics Data System (ADS)

    Kodra, E. A.; Ganguly, A. R.

    2011-12-01

    Sea level rise is one of the most important consequences of anthropogenic climate change, carrying potentially catastrophic implications for coastal populations and ecosystems, and simultaneously one of the most uncertain. Greenland's ice sheet is considered a critical tipping point in the earth's system, where a mean temperature rise of more than 3 degrees Celsius may lead to unrecoverable ice sheet melt and hence sea level rise. However, assigning likelihood to such a tipping point is a difficult task, involving the consideration of many factors. An 'uncertainty explosion' representation of Greenland temperature change is developed here by considering step-by-step accumulation of uncertainty as factors are integrated which are progressively difficult to quantify. Factors considered include uncertainty related to structural differences in global climate models, initial condition runs, methods for assigning credibility to climate models, fossil fuel emissions trajectories, polar amplification of global average warming, and equilibrium climate sensitivity. Results suggest that exceeding the tipping point of 3 degrees change appears to be highly plausible. More broadly, strictly quantitative uncertainty characterization methods may fail to broadcast the true state of uncertainty and the degree of ignorance that is not captured by state-of-the-art numerical models, and thus such methods may understate or completely ignore high risk but low probability runaway warming and hence sea level rise. This work poses implications not only for sea level rise but for many other tasks involving uncertainty characterization, as well. Next steps may involve evaluating the cascade of uncertainty as sequential steps of sea level rise are considered in a similar, extended framework.

  3. Peregrinations of the Greenland Ice Sheet divide in the last glacial cycle: implications for central Greenland ice cores

    NASA Astrophysics Data System (ADS)

    Marshall, Shawn J.; Cuffey, Kurt M.

    2000-06-01

    The superb quality of the climate chronology archived in the Summit, Greenland ice cores (GRIP, GISP2) testifies that the Greenland Ice Sheet divide has been generally stable through the last glacial cycle. The ice sheet has experienced a broad range of paleoclimate conditions, ice sheet margin configurations, and internal dynamical adjustments in glacial-interglacial transitions, however. It is unlikely that the Summit region escaped shifts in ice divide position, geometry, elevation, and flow characteristics. Details of this dynamical history are important to several aspects of ice core studies. The magnitudes of pure and simple shearing, reconstruction of vertical ice velocity, the explicit location of the ice divide, and the divide 'residence time' at different locations are all of interest in interpretation of climatic variables and physical properties of ice in the ice cores. We apply a three-dimensional, thermomechanical ice sheet model to examine the evolution of these dynamical variables over the last 160 kyr in central Greenland. While a high-elevation ice dome is present in the Summit region throughout the simulation, ice divide migrations of up to 150 km are predicted. All points in the vicinity of the Summit ice cores, including the modern divide, have been subject to flowline shifts and variable, non-zero shear deformation during the adjustment from glacial to Holocene conditions, from ca. 10 ka to the present. Modelled divide peregrinations and strain rate history are consistent with the observed disturbance of deep ice in the GRIP and GISP2 ice cores, which has muddled paleoclimate reconstructions for the last interglacial (Eemian) period in Greenland. Dynamical excursions are also evident north of the modern summit, where the NGRIP ice core is currently being drilled [Dahl-Jensen et al., J. Glaciol. 43 (1997) 300-306]. However, the prevailing flow direction and deformation regime at the NGRIP site are much more stable than those at GRIP and GISP2

  4. 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.

  5. 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

  6. Basin development and structure of the area covered by Tertiary basalts, offshore central West Greenland - implications of subvolcanic plays

    SciTech Connect

    Whittaker, R.C.; Bate, K.J.; Chalmers, J.A. )

    1996-01-01

    The West Greenland shelf area between 68[degrees] and 72[degrees] is covered by Lower Tertiary basalts and has so far proved difficult to explore seismically compared to the offshore basins farther north (Melville Bay) and south (southern West Greenland). A first seismic and geological interpretation of the basalt area has lead to a better understanding of the tectonic events during the Tertiary and their implications for hydrocarbon exploration. After a period of extension accompanied by basalt volcanic in the Paleocene, a period of transpression occurred related to sea-floor spreading in the Labrador Sea and Baffin Bay. The crests of the anticlines formed were then eroded and transgressive marine sediments infilled the irregular topography and formed a number of restricted basins. Strike-slip faulting continued throughout the Eocene. Ongoing geophysical studies, including acquisition of additional seismic data in 1995, are aimed at improving seismic resolution beneath the basalts and deter- mining the structure and nature of the underlying sedimentary section. It has been possible, locally, to interpret horizons beneath the Paleocene volcanics where a thick sedimentary section is inferred to be present. The geological development of this succession has to be extrapolated from offshore southern West Greenland and the nearby onshore Nuussuaq basin. Active exploration including drilling started in the onshore basin in 1995 after the discovery of hydrocarbons in basalts at the surface and in shallow wells. The most promising play concept is subbasaltic reservoir sandstones with a mid- Cretaceous marine or a Paleocene deltaic oil-prone source rock. A possible post - basaltic play has also been identified and several large structural leads have been identified by mapping the Top Paleocene Volcanics horizon.

  7. Basin development and structure of the area covered by Tertiary basalts, offshore central West Greenland - implications of subvolcanic plays

    SciTech Connect

    Whittaker, R.C.; Bate, K.J.; Chalmers, J.A.

    1996-12-31

    The West Greenland shelf area between 68{degrees} and 72{degrees} is covered by Lower Tertiary basalts and has so far proved difficult to explore seismically compared to the offshore basins farther north (Melville Bay) and south (southern West Greenland). A first seismic and geological interpretation of the basalt area has lead to a better understanding of the tectonic events during the Tertiary and their implications for hydrocarbon exploration. After a period of extension accompanied by basalt volcanic in the Paleocene, a period of transpression occurred related to sea-floor spreading in the Labrador Sea and Baffin Bay. The crests of the anticlines formed were then eroded and transgressive marine sediments infilled the irregular topography and formed a number of restricted basins. Strike-slip faulting continued throughout the Eocene. Ongoing geophysical studies, including acquisition of additional seismic data in 1995, are aimed at improving seismic resolution beneath the basalts and deter- mining the structure and nature of the underlying sedimentary section. It has been possible, locally, to interpret horizons beneath the Paleocene volcanics where a thick sedimentary section is inferred to be present. The geological development of this succession has to be extrapolated from offshore southern West Greenland and the nearby onshore Nuussuaq basin. Active exploration including drilling started in the onshore basin in 1995 after the discovery of hydrocarbons in basalts at the surface and in shallow wells. The most promising play concept is subbasaltic reservoir sandstones with a mid- Cretaceous marine or a Paleocene deltaic oil-prone source rock. A possible post - basaltic play has also been identified and several large structural leads have been identified by mapping the Top Paleocene Volcanics horizon.

  8. 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.

  9. Fram Strait ice export during the 19th and 20th centuries reconstructed from a multi-year sea-ice index from Southwestern Greenland

    NASA Astrophysics Data System (ADS)

    Schmith, T.; Hansen, C.

    2003-04-01

    Historical observations of multi-year ice, called 'Storis', in the Southwest Greenland waters exist from the period 1820-2000, obtained from ships logbooks and ice charts. It is argued that this ice originates in the Arctic Ocean and has travelled via the Fram Strait, southward along the Greenland coast in the East Greenland Current and around the southern tip of Greenland. Therefore, it is hypothesised that these observations can be used as 'proxies' for reconstructing the Fram Strait ice export on an annual basis. An index describing the Storis extent is extracted from the observations and a linear statistical model formulated relating this index to the Fram Strait ice export. The model is calibrated using ice export values from a hindcast study with a coupled ocean-ice model over the period 1949-1998. Subsequently, the model is used to reconstruct the Fram Strait annual ice export in the period 1820-2000. The model has significant skill, calculated on independent data. Based on this reconstruction, it is discussed how time periods with large and small ice export on multidecadal time scale coincide with time periods of cold and warm North Atlantic sea surface temperatures reported by others. This implies that trend studies based on satellite observations should be regarded with some care, since the time period of satellite observations, the last decades, where a particularly strong negative trend is observed in the ice export is preceded by a time period with a positive trend. The occurrence of 'Great salinity anomalies' (GSA's) are also connected to the multidecadal variability. The GSA's observed in Greenland waters around 1968-1970 and 1980-1982 both occurred when the general level of ice export was high. Prior to these there was a long period with generally low ice export and no GSA's but during an epoch around the turn of the 19th century several GSA's occurred. Finally, it is found that the correlation between the Fram Strait ice export and the NAO index

  10. Implications of increased surface melt under global warming scenarios: Greenland ice-sheet simulations

    NASA Astrophysics Data System (ADS)

    Parizek, B. R.; Alley, R. B.

    2003-04-01

    The Greenland Ice Sheet represents ~10% (by volume) of the cryosphere and ~7 meters of sea-level equivalence. Citing the inherent stability offered by the long glaciological timescales involved in classical ice-sheet dynamics, the elevation of the bedrock on which the ice sheet is perched, and the extremely cold inland surface temperatures, numerical studies on the future of this ice sheet under various global-warming scenarios have all but dismissed the potential for substantial dynamic changes in the next millennium. Unlike for the setting of the West Antarctic Ice Sheet, there were simply no foreseen mechanisms for rapid switches in Greenland's prevailing ice-flow regime. Recently, field observations near the Swiss Camp in west-central Greenland may have offered the essential link between surface temperatures and ice dynamics at and below the equilibrium line that may require the ice sheet to ``listen'' to climate far more closely than previously envisioned by model parameterizations. Zwally et al. (2002) documented correlation between increased ice velocity and increased surface melt (as parameterized by positive degree days (PDD)). They argued that surface water is piped directly to the bed with little delay, causing increased basal-water pressures and basal-sliding velocities. Using the PSU/UofC thermomechanical flowline model, numerous simulations are being conducted to test a wide variety of parameter spaces that link surface melt with a new sliding law under several global warming scenarios. Initial comparisons to the EISMINT Level 3 global-warming benchmark illustrate an enhanced sensitivity of the ice sheet to surface warming resulting in higher ablation rates, thinning of the margin, and a reduction in ice volume that all lead to a positive contribution to global sea-level rise.

  11. North America-Greenland-Eurasian relative motions: implications for circum-arctic tectonic reconstructions

    SciTech Connect

    Rowley, D.B.; Lottes, A.L.; Ziegler, A.M.

    1985-02-01

    The Mesozoic-Cenozoic tectonic evolution of the Circum-Arctic region is based on constraints imposed by (1) relative motion histories of the three major plates (North America, Greenland, and Eurasia) and a number of smaller pieces, and (2) distribution and age of sutures, accretionary prisms, volcanic arcs, fold-thrust belts, stretched continental crust, strike-slip faults, and ocean floor. The authors conclude that: (1) North America and Eurasia remained relatively fixed to each other until the latest Cretaceous-Paleocene opening of the Labrador Sea-Baffin Bay and Greenland-Norwegian and Eurasian basins (earlier convergence between North America and Eurasia in the Bering Sea region shown on many reconstructions are artifacts of incorrect plate reconstructions); (2) the North Slope-Seward-Chukotka block has constituted an isthmus connection between North America and northeast Asia since at least the middle Paleozoic and did not rotate away from the Canadian Arctic; (3) the Canada basin opened behind a clockwise-rotating Alpha Cordillera-Mendeleyev ridge arc during the Early to middle Cretaceous and consumed older, Paleozoic(.) Makarov basin ocean floor (the Chukchi cap is a detached continental fragment derived from the Beaufort Sea; the North Slope Arctic margin is a left-lateral transform fault associated with the opening of the Canada basin); and (4) the Nares Strait fault has a net relative displacement of approximately 25 km, but actual motion between Greenland and northern Ellesmere was about 250 km of strongly transpressive motion that resulted in the Eurekan and Svalbardian orogenies.

  12. Metasomatic origin of quartz-pyroxene rock, Akilia, Greenland, and implications for Earth's earliest life.

    PubMed

    Fedo, Christopher M; Whitehouse, Martin J

    2002-05-24

    A quartz-pyroxene rock interpreted as a banded iron formation (BIF) from the island of Akilia, southwest Greenland, contains (13)C-depleted graphite that has been claimed as evidence for the oldest (>3850 million years ago) life on Earth. Field relationships on Akilia document multiple intense deformation events that have resulted in parallel transposition of Early Archean rocks and significant boudinage, the tails of which commonly form the banding in the quartz-pyroxene rock. Geochemical data possess distinct characteristics consistent with an ultramafic igneous, not BIF, protolith for this lithology and the adjacent schists. Later metasomatic silica and iron introduction have merely resulted in a rock that superficially resembles a BIF. An ultramafic igneous origin invalidates claims that the carbon isotopic composition of graphite inclusions represents evidence for life at the time of crystallization.

  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. PMID:21070588

  15. 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.

  16. 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?

  17. 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…

  18. Measured basal water pressure variability of the western Greenland Ice Sheet: Implications for hydraulic potential

    NASA Astrophysics Data System (ADS)

    Wright, Patrick J.; Harper, Joel T.; Humphrey, Neil F.; Meierbachtol, Toby W.

    2016-06-01

    The gradient of the hydraulic potential field at the ice-bedrock interface beneath the Greenland Ice Sheet (GrIS) dictates the routing and energetics of subglacial water, thereby influencing drainage system characteristics and sliding dynamics. In the ablation zone of the GrIS, variable water pressure due to an active subglacial drainage system and basal topography with high relief potentially interact to drive unknown spatial patterns and temporal changes in the hydraulic potential field. Here we present a suite of water pressure measurements collected in 13 boreholes along a 46 km transect on the western GrIS to investigate the role of spatial and temporal basal water pressure adjustments in hydraulic potential gradient dynamics. All borehole sites show pressures with similar seasonality, having relatively steady and high values during winter, variable and irregular behavior during spring and fall, and diurnal cycles that can persist for multiple weeks during the peak melt season. Despite much higher variability during the melt season, the median pressure of the summer period is nearly the same as the median pressure of the winter period. However, time variability of water pressure due to basal drainage processes can force changes in the magnitude and orientation of the hydraulic potential field over diurnal periods. We find that the basal water pressure across the transect generally mimics the ice thickness field but with superimposed large pressure gradients that develop at shorter scales within the basal drainage system. This leads to a complex hydraulic potential field across regions of similar ice thickness.

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

    2015-06-01

    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 between 74 to 80° N, 36 to 49° W and 2000 to 3200 m a.s.l. The cores cover an area of 680 km × 317 km, ~200 000 km2 or 10 % of the area of Greenland. Depending on core length (100-175 m) and accumulation rate (90-200 kg m-2 a-1) the records reflect an isotope-temperature history over the last 500-1100 years. The δ18O signal in northern Greenland is influenced by temperature, accumulation and the topography of the North Greenland ice sheet between 72 and 80° N. About 12 % of the variability can be attributed to the position of the single drill sites in relation to the ice sheet topography. Lowest δ18O mean values occur north of summit and east of the main divide. 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 12 NGT records and the NGRIP record is presented with improved signal-to-noise ratio. This stack represents the mean δ18O signal for northern Greenland that is interpreted as proxy for temperature. Our northern Greenland δ18O stack indicates isotopically enriched periods compared to their average during medieval times, about 1420 ± 20 AD and from 1870 AD onwards. The period between 1420 AD and 1850 AD was isotopically depleted compared to the average for the entire millennium and represents the Little Ice Age. The 20th century has isotopic values higher than the 1000 years mean and is comparable to the medieval period but lower than about 1420 AD.

  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. 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.

  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. Lipid compounds in speleothem calcite from southwestern Oregon: Composition, sources and paleoenvironmental implications

    NASA Astrophysics Data System (ADS)

    Rushdi, A. I.; Clark, P. U.; Ersek, V.; Simoneit, B. R.; Mix, A. C.; Cheng, H.; Edwards, R.

    2011-12-01

    Speleothem calcite from the Oregon Caves National Monument, southwestern Oregon was analyzed to determine the occurrence, concentrations, distribution, and sources of aliphatic lipid compounds preserved in the calcite. Concentrations of the total lipid compounds range from 0.5 to 12.9 μg g-1. They increase at times of low speleothem growth rate, suggesting dilution, whereas the apparent accumulation rate of lipid compounds tends to be highest during times of fastest speleothem growth rate. Such increased accumulation generally corresponds to times of warm (interglacial) climate, suggesting either a greater source of organic materials during interglacial times and/or greater efficiency of compound capture during more rapid calcite growth. Aliphatic lipid compounds include homologous n-alkanoic acids (0.3-7.8 μg g-1), n-alkanols (0.4-1.1 μg g-1) and methyl n-alkanoates (0.5-9.6 μg g-1) and sterols (0.1-2.7 μg g-1). Minor amounts of branched methyl n-alkanoates and dimethyl n-alkanedioates are also present. The presence of methyl n-alkanoates as major compounds is likely due to the esterification reactions of free fatty acids in alkaline dripping cave waters. The major sources of the aliphatic lipids are from higher plants and microbial residues derived from the soil zone above the cave systems as indicated by the distribution patterns and the geochemical parameters and indices. The contribution of microbial inputs ranges from 42 to 90% of the total lipid compounds and increase during warm climates. The lipid compounds in speleothem calcite are well-preserved and could be used as biomarkers for paleoenvironmental study.

  8. 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

  9. Thermochronologic limits on Late Cenozoic denudation of Fiordland, southwestern New Zealand: implications for subduction initiation

    NASA Astrophysics Data System (ADS)

    House, M.; Kamp, P. J.; Gurnis, M.; Sutherland, R.

    2001-12-01

    New (U-Th)/He and fission track ages in apatites from Fiordland, southwestern New Zealand, provide insight into the spatial and temporal patterns of crustal uplift and exhumation that accompanied the transition between subduction and transform motion across this section of the Pacific plate boundary during Late Cenozoic times. Preliminary helium and fission track ages in apatites (AHE and AFT, respectively) indicate that much of the Fiordland region cooled through temperatures of ~110-70 C during Late Miocene-Early Pliocene times. Early Pliocene AFT and AHE ages from a constant elevation transect collected at sea level along Doubtful Sound are similar to AFT and AHE ages from a lake-level transect along the shores of Lake Te Anau. Another sea-level transect collected in southwesternmost Fiordland along Dusky Sound yielded Middle and Late Miocene AFT and AHE ages. AHE and AFT ages from two vertical profiles (one in western Doubtful Sound and one at Lake Hauroko in southeastern Fiordland) have similar slopes, corresponding to exhumation rates of 0.2-0.3 km/my. However, the profiles are offset slightly so that cooling ages from western Doubtful Sound are approx 5 m.y. younger than those from Lake Hauroko. Oligocene and older AFT and AHE ages from several localities in eastern Fiordland serve to delimit the extent of recent crustal uplift and exhumation to regions to the west of the Moonlight, Hollyford and Hauroko fault zones. We speculate that the abundance of Middle Miocene and younger cooling ages from Fiordland reflects regional uplift and exhumation resulting from changing plate motion and subduction initiation to the south. A Late Cenozoic geothermal gradient of 30 C/km and a surface temperature of 5 C imply that AFT and AHE ages correspond to the removal of approx 3.5 km and 2.2 km of material, respectively. This age and magnitude of denudation is consistent with estimates of Fiordland uplift based on provenance studies in the Halfway Formation to the north, as

  10. 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

  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. An integrated geophysical investigation of Greenland's tectonic history

    NASA Astrophysics Data System (ADS)

    Roman, Daniel Robert

    A new model for the crustal evolution of the Labrador Sea region of southwestern Greenland (58.7--61.9°N and 48--53°W) was developed from gravity-derived Moho estimates and lithologic and geologic features interpreted from correlative geopotential anomalies, and recent seismic surveys [Chian and Louden, 1994; Chian et al., 1995a, Chian et al., 1995b; Chalmers and Laursen, 1995]. Previous kinematic models [Srivastava, 1978; Srivastava and Tapscott, 1986; Roest and Srivastava, 1989] suggested that the opening of the Labrador Sea caused a counterclockwise rotation of Greenland from ca. 92 to 36 Ma as a part of the opening of the North Atlantic Ocean. These models were based on interpretation of a 150 km wide zone of crust off of the coasts of Greenland and Labrador as oceanic crust with continuous magnetic isochrons through anomaly 33. The structural implications of the gravity-derived Moho and crustal density models challenge this interpretation. Instead, this region is interpreted a combination of rifted-continental and transitional crust. The correlation analysis of free-air gravity and magnetic anomalies determined that rocks within this 150 km zone were more characteristic of rifted-continental or transitional crust, and this was further supported by the results of seismic surveys [Chian and Louden, 1994; Chian et al., 1995a; 1995b; Chalmers and Laursen, 19951. The linear magnetic anomalies interpreted as isochrons 31 and 33 by Roest and Srivastava [1995] were interpreted as serpentinization along the crustal rupture and delamination surfaces or along the base of regional-scale half-grabens. The revised model postulates that the rotational opening of the Canada Basin from 135 to 118 Ma induced a counterclockwise rotation of Greenland, which extended and thinned the Archean crust between Greenland and Labrador. This weakened crust was thus well disposed to rifting when the North Atlantic rift system propagated northward into the region at about 90 Ma. Slow

  13. Climatic Trends in the Triassic to Early Jurassic Lacustrine Succession of East Greenland: Implications for Correlation in the North Atlantic Region

    NASA Astrophysics Data System (ADS)

    Andrews, Steven

    2013-04-01

    The Triassic continental successions of the North Atlantic region are poorly age constrained and therefore regional correlation is problematic. Climatic trends offer potential as the basis of regional correlation. The Triassic of East Greenland lies in the northern continuation of the northern North Sea Rift and, following reconstruction, aligns with the Viking Graben. This position, between the northern North Sea, Norwegian Sea and the Barents Shelf successions, means it is key in constructing regional correlations and understanding both tectonic and climatic evolution throughout the Triassic of the North Atlantic region. Detailed sedimentological study of exceptional exposures through the largely lacustrine Mid-Late Triassic succession of East Greenland has provided the basis for a palaeoclimatic reconstruction. This has highlighted the occurrence of significant periods of increased aridity during the Late Ladinian and the Late Carnian which bracket the more humid conditions of the Early Carnian (the 'Carnian Pluvial Event'). Following the Late Carnian arid phase a gradual cooling through the Late Triassic and Early Jurassic is recorded. Comparisons and correlations are made with Triassic successions throughout the North Atlantic. Understanding climatic trends and the response of sedimentary systems to these has important implications for the construction of facies models and therefore the prediction of both reservoir and seal distribution in the prospective North Atlantic petroleum provinces.

  14. Relative sea-level change, Kjove Land, Scoresby Sund, East Greenland: Implications for seasonality in Younger Dryas time

    NASA Astrophysics Data System (ADS)

    Hall, B.; Baroni, C.; Denton, G.; Kelly, M. A.; Lowell, T.

    2008-12-01

    The age of the Milne Land Stade (MLS) moraines in the Scoresby Sund region of East Greenland is key for testing the hypothesis that strong seasonality marked abrupt cooling events, such as the Younger Dryas, registered in Greenland ice cores. The relevant chronology is based on 69 radiocarbon dates of shells from raised beaches and deltas related to marine inundation and isostatic rebound that accompanied glacier retreat from the moraines. Taken together, these dates form the basis for a relative sea-level curve that shows very high rates of emergence typical of recently deglaciated regions. Upward extrapolation of this curve suggests that the marine limit (134 m a.s.l.) dates to about 12,400 cal yr B.P. The shorelines that mark the marine limit lie within areas that were ice-covered when the glaciers were at the outer limit of the MLS advance; hence, the moraines that form the outer limit must antedate 12,400 cal yr B.P. and probably are from earliest Younger Dryas or Allerød time. At Holger Danskes Briller, an inner moraine grades to a massive ice-contact delta, now at 101 m a.s.l., which is dated to 11,000-11,300 cal yr B.P. The age of the outer MLS moraines, along with constraints on the maximum possible Younger Dryas ice extent and snowline lowering are consistent with the idea that East Greenland climate experienced strong seasonality during Younger Dryas time.

  15. Constraining MODIS snow albedo at large solar zenith angles: Implications for the surface energy budget in Greenland

    NASA Astrophysics Data System (ADS)

    Wang, Xianwei; Zender, Charles S.

    2010-11-01

    An understanding of the surface albedo of high latitudes is crucial for climate change studies. MODIS albedo retrievals flagged as high-quality compare well with in situ Greenland Climate Network (GC-Net) measurements but cover too small an area to fully characterize Greenland's albedo in nonsummer months. In contrast, poor quality MODIS retrievals provide adequate spatiotemporal coverage, but are not recommended for use at large solar zenith angles (SZAs) where they have a systematic low bias. We introduce an empirical adjustment to the poor quality data based on high-quality reference albedos and constrained by GC-Net data and theory, and use the adjusted data to improve estimates and fill in gaps of the year-round, Greenland-wide, albedo and surface energy budget. For observations made with SZAs between 55° and 75°, the mean differences (MODIS minus GC-Net) between our adjusted MODIS albedo and GC-Net measurements are -0.02 and -0.03 at Saddle and Summit, respectively, compared to -0.05 and -0.08 between the unadjusted MODIS albedo and GC-Net measurements. The adjusted MODIS snow albedos are usually between 0.75 and 0.87 over dry snow when SZA is larger than 55°, and they reduce unrealistic seasonal and meridional trends associated with MODIS retrievals at large SZA, defined as SZA > 55° and 70°, respectively, for low- and high-quality retrievals. The impact of the adjusted albedo on the surface energy budget, relative to the unadjusted albedo from all MODIS data, is smallest (-0.7 ± 0.1W/m2) in June, and largest (-6.2 ± 0.9 W/m2) in September for the black-sky albedo (BSA). The mean annual absorbed solar radiation (ASR) reduction by the adjusted MODIS albedo in Greenland from 2003 to 2005 is 3.1 ± 0.2 and 4.3 ± 0.2 W/m2 for BSA and white-sky albedo (WSA), respectively, about 8.0 ± 0.5% and 10.8 ± 0.4% of ASR based on the raw BSA and WSA. The ASR reduction by the adjusted blue-sky (actual) albedo is between 2.9 and 4.5 W/m2, enough to annually melt 27

  16. 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

  17. 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.

  18. Crustal structure of the Innuitian region of Arctic Canada and Greenland from gravity modelling: implications for the Palaeogene Eurekan orogen

    NASA Astrophysics Data System (ADS)

    Oakey, Gordon N.; Stephenson, Randell

    2008-06-01

    New gravity observations collected over Ellesmere Island and Axel Heiberg Island have been integrated with existing Canadian and Danish data sets to produce a comprehensive regional compilation over the Innuitian Region of the Canadian and Greenland High Arctic. This compilation has provided quantitative assessment of the geometry of the plate boundary between northern Greenland and Ellesmere Island and crustal structures across the Cretaceous-Palaeogene Eurekan Orogen. A large amplitude linear gravity low-Nares Strait Gravity Low (NSGL) (<-160 mGal)-extends obliquely across Nares Strait from northern Greenland to Ellesmere Island. This feature closely correlates with the distribution of the Palaeozoic Franklinian Margin sequences and is cross-cut by the Cenozoic Eurekan Frontal Thrust (EFT), which represents the mappable western limit of the undeformed Greenland Plate associated with the Eurekan Orogen. Newly identified linear gravity features occur north of the NSGL: the Hazen Plateau Gravity High (HPGH), corresponding with the low-lying topography of the Hazen Trough and the Grantland Gravity Low (GGL), over the elevated topography of the Grantland Uplift. Gravity models for profiles crossing the NSGL, the HPGH and the GGL indicate that the long-wavelength component of the gravity anomalies is produced by systematic variations in Moho depth. Although significant Eurekan-age thrusting and thickening of low-density Palaeozoic strata is observed on Ellesmere Island, locally contributing to the mass-deficit generating the NSGL, equivalent strata on Greenland are undeformed. The NSGL is interpreted to be primarily the signature of the remnant (Early Palaeozoic) margin with the downwards flexure of the crust beneath a northwards thickening sedimentary wedge rather than purely the result of crustal thickening from the Eurekan Orogeny. Digital bathymetry and sediment thickness data were used to determine a residual `crustal' gravity field, which in turn was used to

  19. 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.

  20. 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

  1. 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.

  2. Depositional setting and paleogeographic implications of earth's oldest supracrustal rocks, the >3.7 Ga Isua Greenstone belt, West Greenland

    NASA Astrophysics Data System (ADS)

    Fedo, Christopher M.; Myers, John S.; Appel, Peter W. U.

    2001-06-01

    New structural and stratigraphic mapping in the Isua greenstone belt, West Greenland has revealed that the exposed lithologic succession is quite different to that depicted in earlier studies. The key to a better understanding of the stratigraphy has been the recognition of intense strain and metasomatic effects combined with ductile fault structures that segment the belt into a number of tectonic slices. In some of these slices, deformation and metasomatism are somewhat lower than in surrounding slices (though still significant), which permit the recognition of primary depositional features that may be used to compare with lithologies from elsewhere in the belt. The belt is dominated by amphibolite that in a number of places show well-defined pillows. Pillow breccias and basaltic debris flows also occur within this package. Strongly recrystallized ultramafic bodies that occur in the belt are interpreted as intrusions or komatiitic flows. The most common sedimentary rock type is chert/banded iron-formation. These lithologies have been strongly affected by brittle and ductile deformation in combination with coarse recrystallization. Siliciclastic detrital rocks such as conglomerate and sandstone are much less common in the belt, and where present, have intrabasinally derived sources. Highly deformed quartzo-feldspathic schist crops out in a number of places in the belt and most likely has multiple origins. Previously these schists have been considered to be felsic volcaniclastic rocks, though recent mapping, and geochemical, and isotopic studies support the hypothesis that at least some of these schists are highy deformed and carbonated tonalitic gneiss sheets or replaced pillow-lava successions. Carbonate rocks in the belt are now considered to be mostly, or entirely, replacement in origin, where metasomatizing fluids have particularly utilized amphibolite-chert contacts; additionally, some carbonate may represent the products of early sea-floor alteration. We

  3. 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

  4. Autosomal recessive diseases among the Athabaskans of the southwestern United States: recent advances and implications for the future.

    PubMed

    Erickson, Robert P

    2009-11-01

    Genetic and linguistic data suggest that the Na-Dene, of which the Athabaskans are the largest group, are part of a later immigration into the Americas than the first Amerind immigration. Whether a second and third immigration can be separated seems unlikely but continued cross-Bering Strait exchanges may have masked what was a greater separation in the past. The movement of tribes into Siberia appears to have involved a genetic bottleneck leading to at least one disease allele shared by Eskimo/Aleuts and Navajos and a second possibly shared by the Navajo and a Siberian population, but not the same Siberian population that share deep linguistic affinities with the Navajo. A second bottleneck appears to have occurred with the migration of Athabaskans from Northwest North America to the Southwestern United States along the Rocky Mountains. This bottleneck is reflected in several rare recessive diseases shared by the Navajo and Apache. Finally, the Navajo were captured and imprisoned under conditions which led to severe population loss. This, and the "hiding away" of a small number of Navajos in what is now the Western portion of the reservation, led to a Navajo-specific bottleneck(s) resulting in an increased frequency of several rare recessive diseases among the Navajo. Prejudice against human genetic research is high among the Southwestern Athabaskans but attempts to bridge the gap are now occurring. The involvement of Navajo scientists in this process is especially encouraging. PMID:19842189

  5. 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.

  6. 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

  7. 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

  8. 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

  9. Decadal slowdown of a land-terminating sector of the Greenland Ice Sheet during sustained climate warming - implications for wider ice sheet hydrology-dynamics coupling

    NASA Astrophysics Data System (ADS)

    Nienow, P. W.; Tedstone, A. J.; Gourmelen, N.; Dehecq, A.; Goldberg, D. N.; Hanna, E.

    2015-12-01

    The relationship between surface melting and ice motion will affect how the Greenland Ice Sheet (GrIS) responds to climate and the structure of the subglacial drainage system may be crucial in controlling how changing melt-rates impact ice motion. Ice sheet motion varies over seasonal time-scales in response to varying surface meltwater inputs to the ice-sheet bed which lubricate the ice-bed interface, resulting in periods of faster ice motion. However, the impact of hydro-dynamic coupling on ice motion over decadal timescales remains poorly constrained. Here we utilise remotely-sensed optical Landsat imagery to generate a record of annual motion spanning three decades extending back to 1985. Our observations cover an ˜8000 km2 area along ˜170 km of predominantly land-terminating margin of the west GrIS, and extend ˜50 km inland to 1100 m asl. We find that that annual ice motion was 12% slower in 2007-2014 compared to 1985-1994, despite a corresponding 50% increase in surface meltwater production. Less than 1/3 of the observed slowdown can be explained by a reduction in internal deformation caused by marginal ice sheet thinning, and we therefore hypothesise that increases in subglacial drainage efficiency, associated with sustained larger melt volumes, have reduced basal lubrication resulting in slower ice flow. Our findings suggest that hydro-dynamic coupling in this section of the ablation zone resulted in net ice motion slowdown over decadal timescales — not speedup as previously postulated. Increases in meltwater production from projected climate warming may therefore further reduce the motion of land-terminating margins of the ice-sheet indicating such margins are more resilient to the dynamic impacts of enhanced meltwater production than previously thought. The implications of these observations for wider ice sheet hydrology-dynamics coupling are considered.

  10. 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

  11. Response of aridland trees to artificial summer rains: Implications for climate change in the southwestern U.S.

    SciTech Connect

    Williams, D.G.; Ehleringer, J.

    1995-09-01

    The Arizona monsoon in the southwestern U.S. brings summertime precipitation to a region where water most limits primary productivity. Woodland species in southern Utah were given 25 mm of artificial rain in late July and mid September, 1994, to evaluate inter and intraspecific responses to monsoon precipitation. {delta}D of xylem water and predawn water potential increased following irrigation for Juniperus osteosperma and Pinus edulis indicating that these species have active surface roots during the monsoon season. The capacity of these trees to respond to irrigation, however, was greater in September than in July. Either high soil temperature limits root function in July or surface root growth over August promotes greater response in September. Quercus gambelii, a common associate within these woodlands, did not respond to the irrigations, demonstrating its reliance on deeper roots through the growing season. Future shifts in the seasonality of precipitation might, therefore, have differential effects on these woodland species leading to vegetation change. Interactions between changes in temperature and the seasonality of precipitation, however, need to be considered when predicting these responses.

  12. Characterization of the Monument Hill fault system and implications for the active tectonics of the Red Rock Valley, Southwestern Montana

    NASA Astrophysics Data System (ADS)

    Regalla, Christine A.; Anastasio, David J.; Pazzaglia, Frank J.

    2007-08-01

    New geologic mapping, morphologic fault scarp modeling, and geomorphic metrics in the Red Rock Valley, southwestern Montana, help characterize the Quaternary history of the virtually unstudied Monument Hill fault and tectonics of the youthful and seismically active Red Rock graben. Two generations of Pleistocene surface ruptures are preserved along the Monument Hill fault. Similarity in rupture ages along multiple strands, determined from offset alluvial surfaces and morphologic modeling, suggest earthquake clusters at 22-32 ka and possibly >160 ka. Quaternary activity along the Monument Hill fault is also reflected in elongate drainage basins and channel profiles with anomalously steep reaches coincident with mapped faults. An anticlinal accommodation zone at Kidd accommodates a change in fault polarity between the en echelon Monument Hill and Red Rock faults and a northward decrease in extension within the Red Rock graben. The unique rupture histories of the Monument Hill and Red Rock faults, however, suggest the systems are not seismogenically linked and that the accommodation zone serves as a rupture barrier. The geometry, interconnectivity, and kinematics of faults in the Red Rock Valley may represent a snapshot of the early stages of extension applicable to the evolution of other Northern Basin and Range grabens.

  13. 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.

  14. Analysis of FMR1 (CGG)n alleles and FRAXA microsatellite haplotypes in the population of Greenland: implications for the population of the New World from Asia.

    PubMed

    Larsen, L A; Armstrong, J S; Grønskov, K; Hjalgrim, H; Brøndum-Nielsen, K; Hasholt, L; Nørgaard-Pedersen, B; Vuust, J

    1999-01-01

    The fragile X syndrome is caused by the expansion of a polymorphic (CGG)n tract in the promoter region of the FMR1 gene. Apparently the incidence of fragile X syndrome is rare in the population of Greenland. In order to examine population-related factors involved in stability of the (CGG)n sequence, DNA samples obtained randomly from the Greenlandic population were analysed for size and AGG interspersion pattern of the FMR1 (CGG)n region and associated DXS548-FRAXAC1 haplotypes. In addition a large Greenland family with unstable transmission in the premutation range was analysed. The (CGG)n allele sizes in the Greenland population showed a narrow distribution similar to that reported for Asian populations. DNA sequencing of alleles with 36 CGG repeats revealed an AGG(CGG)6 insertion previously reported exclusively in Asian populations and a high frequency of alleles with a (CGG)10AGG(CGG)9AGG(CGG)9 or (CGG)9AGG(CGG)9AGG(CGG)6AGG(CGG)9 sequence pattern was found. Thus the data confirm the Asian origin of the Greenlandic (Eskimo) population and indicates that some (CGG)n alleles have remained stable for 15-30,000 years, since the population of the New World arrived from Asia via the Bering Strait. PMID:10573009

  15. 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.

  16. Coeval fluctuations of the Greenland Ice Sheet and a local ice cap during the Younger Dryas: implications for late-glacial climate

    NASA Astrophysics Data System (ADS)

    Levy, Laura; Kelly, Meredith; Lowell, Tom; Hall, Brenda; Howley, Jennifer; Smith, Colby

    2016-04-01

    Although the Younger Dryas (YD) has been recorded in ice cores atop the Greenland Ice Sheet, past glacier extents on Greenland dating to the YD are rare. In part, this is due to much of the Greenland Ice Sheet being located offshore until early Holocene time. The Scoresby Sund region (~71°N, 26°W) of central East Greenland, however, is one of only a few locations where the margins of the Greenland Ice Sheet and glaciers independent of the ice sheet were located at least partially on land by late-glacial time. In this region, two distinct sets of moraines, known as the inner and outer Milne Land Stade moraines, have been defined and mark a significant readvance or stillstand during deglaciation from the last glacial maximum. Previous work has dated these moraines to late-glacial and early Holocene time. We present a new 10Be chronology on fluctuations of both the Greenland Ice Sheet and the adjacent Milne Land ice cap from the type locality of the Milne Land Stade moraines in Milne Land. 10Be ages of boulders on bedrock distal to the inner Milne Land Stade moraines range from 12.3 to 11.5 ka and indicate that both ice masses retreated during the YD, likely in response to rising summer temperatures. Since Greenland ice-cores register cold mean annual temperatures throughout the YD, these ice-marginal data support climate conditions characterized by strong seasonality. The mean ages (± 1σ uncertainty) of the inner Milne Land Stade moraines date to 11.4 ± 0.8 ka (Greenland Ice Sheet) and 11.4 ± 0.6 ka (ice cap) indicating that they were formed during Preboreal time or at the end of the YD. Based on these coeval moraine ages, we suggest that both ice masses responded to climate conditions acting on the ice margins, specifically ablation. Moreover, our data show that the ice sheet responded sensitively (i.e., on the same time scale as a small ice cap) to late-glacial and early Holocene climate conditions.

  17. 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.

  18. 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.

  19. 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

  20. 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. PMID:24926107

  1. 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

  2. Siderophile and chalcophile metal variations in Tertiary picrites and basalts from West Greenland with implications for the sulphide saturation history of continental flood basalt magmas

    NASA Astrophysics Data System (ADS)

    Keays, Reid R.; Lightfoot, Peter C.

    2007-04-01

    Sixty-five million year old continental flood basalts crop out on Qeqertarssuaq Island and the Nuussuaq Peninsula in West Greenland, and they include ˜1,000 m of picritic lavas and discrete 10- to 50-m-thick members of highly contaminated basalts. On Qeqertarssuaq, the lavas are allocated to the Vaîgat and Maligât Formations of which the former includes the Naujánguit member, which consists of picrites with 7-29 wt% MgO, 80-1,400 ppm Ni, 5.7-9.4 ppb Pt and 4.2-12.9 ppb Pd. The Naujánguit member contains two horizons of contaminated basalts, the Asûk and Kûgánguaq, which have elevated SiO2 (52-58 wt%) and low to moderate MgO (7.5-12.8 wt%). These lavas are broadly characterized by low Cu and Ni abundances (average, 40 ppm Ni and 45 ppm Cu) and very low Pt (0.16-0.63 ppb) and Pd (0.13-0.68 ppb) abundances, and in the case of the Asûk, they contain shale xenoliths and droplets of native iron and troilite. The contaminated basalts from Nuussuaq, the B0 to B4 members, are also usually Ni-, Cu-, and platinum-group elements (PGE)-depleted. The geochemical signatures (especially the ratios of incompatible trace elements such as Th/Nb) of all of the contaminated basalts from Qeqertarssuaq and some of those from Nuussuaq record what appears to be a chemical contribution from deltaic shales that lie immediately below the lavas. This suggests that the contamination of the magmas occurred during the migration of the magmas through plumbing systems developed in sedimentary rocks, and hence, at a high crustal level. Nickel, Cu, and PGE depletion together with geochemical signatures produced by crustal contamination are also a feature of Siberian Trap basalts from the Noril’sk region. These basalts belong to the 0- to 500-m thick, ˜5,000- to 10,000-km3 Nadezhdinsky Formation, which is centered in the Noril’sk Region. A major difference between Siberia and West Greenland is that PGE depletion in the Nadezhdinsky Formation samples with the lowest Cu and Ni contents is

  3. 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...

  4. Supraglacial Streams on the Greenland Ice Sheet Delineated from Combined Spectral-Shape Information in High Resolution Satellite Imagery

    NASA Astrophysics Data System (ADS)

    Yang, K.; Smith, L. C.

    2012-12-01

    Supraglacial meltwater streams and lakes that form each summer across large expanses of the Greenland Ice Sheet (GrIS) ablation zone have global implications for sea level rise yet remain one of the least-studied hydrologic systems on Earth. Remote sensing of supraglacial streams is challenging owing to their narrow width (~1 - 30 m), and proximity to other features having similar visible/NIR reflectance (lakes and slush) or shape (dry stream channels, crevasses, and fractures). This presentation presents a new, automated "spectral-shape" procedure for delineating actively flowing streams in high-resolution satellite imagery, utilizing both spectral and pattern information. First, a modified Normalized Difference Water Index adapted for ice (NDWIice) enhances the spectral contrast between open water and drier snow/ice surfaces. Next, three NDWIice thresholds are used to mask deep-water lakes and discern open water from slush, in concert with a multi-points fast marching method to rejoin resulting stream fragments. Comparison of this procedure with manual digitization for six WorldView-2 images in southwestern Greenland demonstrates its value for detecting actively flowing supraglacial streams, especially in slushy areas where classification performance improves dramatically versus simple threshold methods. While a simple threshold approach is satisfactory for areas known to be slush-free, the procedure outlined here enables comprehensive stream mapping across the GrIS ablation zone, regardless of slush conditions and/or the presence of similarly shaped glaciological features.

  5. Linking petrology and seismology of the southwest Greenland lithosphere

    NASA Astrophysics Data System (ADS)

    Lesher, C. E.; Vestergaard, C.; Brown, E.; Schutt, D.

    2015-12-01

    Mantle xenoliths from late-Proterozoic diamond-bearing kimberlitic dikes in the Kangerlussuaq, Sarfartoq and Maniitsoq areas of southwestern Greenland provide constraints on the composition and thermal state of lithospheric mantle beneath Greenland to depths of ~200 km [1]. Similarly, surface wave tomography studies carried out as part of the GLATIS project use a range of Rayleigh wave periods sensitive to structures at a similar depth interval within southwestern Greenland lithospheric mantle [2]. Here we link petrologic and seismologic constraints on the mantle lithosphere beneath Greenland utilizing methods of [3] that show that inferred chemical and mineralogical stratification inferred from petrology, showing mantle peridotite transitioning from garnet-free harzburgite to garnet lherzolite between ~70 and 180 km, cannot readily be resolved with fundamental mode Rayleigh waves. On the other hand, comparing phase velocities predicted from xenolith compositions, mineralogy and last equilibration temperatures and pressures, defining the continental geotherm during late-Proterozoic time, with those for the present-day mantle lithosphere suggest significant cooling of the cratonic mantle to a modern geotherm characterized by a heat flux of 30 mW/m2 and average crustal heat production of 0.3 mW/m3 [4]. These preliminary findings point to the weak dependence of shear wave velocities on mantle peridotite composition and mineralogy, and further illustrate its strong temperature dependence. Comparison of ancient and modern continental geotherms made possible by combining petrologic and seismological data, as shown here for southwest Greenland, provide additional constraints on secular cooling of cratonic regions linked to large-scale tectonic processes. [1] Bizzarro et al., 2003, CMP, 146; Sand et al., Lithos, 112. [2] Darbyshire et al., 2004, GJI, 158. [3] Schutt and Lesher, 2006, JGR, 111. [4] Meirerbachtol et al., 2015, JGR/ES, 120.

  6. Large-scale gravity anomaly in northern Norway: tectonic implications of shallow or deep source depth and a possible conjugate in northeast Greenland

    NASA Astrophysics Data System (ADS)

    Gradmann, Sofie; Ebbing, Jörg

    2015-12-01

    A prominent gravity and geoid low lies just south of the Lofoten peninsula in northern Norway, partly coinciding with the location of Proterozoic granites of the Transscandinavian Igneous Belt and being offset by ca. 100 km to the highest topography of northern Norway. The study area extends both onshore and offshore and lies at the transition between Archaean and Proterozoic lithosphere. The Palaeoproterozoic basement has been overthrusted by the Palaeozoic nappes of the Caledonian orogen and now forms the passive margin of the NE Atlantic. We investigate the gravity anomaly performing combined 3-D geophysical-petrological forward modelling of the lithosphere and sublithospheric upper mantle using the interactive modelling program LitMod3D. We include variations in thickness and composition of the lithospheric mantle in order to include the effects on the rifted margin adjoining the Baltic craton. We compare three possible origins of the anomaly: (i) a low-density upper crust, representing the northward extension of the Transscandinavian Igneous Belt, (ii) a lower crustal source formed by a Moho depression and (iii) a thick, depleted lithospheric mantle of possibly Archaean origin. A similar, yet wider and stronger gravity anomaly is found on the conjugate margin in northeastern Greenland. A shallow crustal source is most consistent with the geophysical data sets. A respective source of the granitic belt, however, is difficult to reconcile with the regional geology both in Fennoscandia and Greenland. An additional contribution form a deeper source is suggested.

  7. 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 ...

  8. An early Holocene Greenland whale from Melville Bugt, Greenland

    NASA Astrophysics Data System (ADS)

    Bennike, Ole

    2008-01-01

    Radiocarbon age determination of a Greenland whale ( Balaena mysticetus) vertebra from Melville Bugt in northwestern Greenland yields an age of 9259-8989 cal yr BP. The margin of the Greenland Ice Sheet in Melville Bugt was situated behind its AD 1950-2000 position in the early Holocene, at a similar position to that being reached following rapid retreat in recent years. Such an early deglaciation of areas close to the Greenland Ice Sheet is unusual. This probably reflects the unique glaciological setting resulting from the narrow fringe of ice-free islands and peninsulas and offshore waters with deep areas that characterize this part of Greenland. The timing of Greenland Ice Sheet retreat to its present margin varies significantly around Greenland.

  9. 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.

  10. 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

  11. Q Fever in Greenland

    PubMed Central

    Svendsen, Claus Bo; Christensen, Jens Jørgen; Bundgaard, Henning; Vindfeld, Lars; Christiansen, Claus Bohn; Kemp, Michael; Villumsen, Steen

    2010-01-01

    We report a patient with Q fever endocarditis in a settlement in eastern Greenland (Isortoq, Ammassalik area). Likely animal sources include sled dogs and seals. Q fever may be underdiagnosed in Arctic areas but may also represent an emerging infection. PMID:20202433

  12. 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.

  13. Carbon-isotope stratigraphy of the Lower Ordovician succession in Northeast Greenland: Implications for correlations with St. George Group in western Newfoundland (Canada) and beyond

    NASA Astrophysics Data System (ADS)

    Azmy, Karem; Stouge, Svend; Christiansen, Jørgen L.; Harper, Dave A. T.; Knight, Ian; Boyce, Douglas

    2010-03-01

    The Lower Ordovician sequence on the Ella Ø Island in Northeast (N-E) Greenland is a thick shallow marine platform carbonate sequence (˜ 1415 m thick) and constitutes the major part of the Kong Oscar Fjord Group. It consists, from bottom to top, of the Antiklinalbugt, Septembersø, and Cape Weber formations, which are believed to be respectively coeval with the Watts Bight, Boat Harbour, and Catoche formations of the St. George Group in western Newfoundland, Canada. Samples were collected from outcrops at high-resolution intervals and micritic materials were extracted by microdrilling after screening their petrographic and geochemical criteria to evaluate the degree of preservation. The δ13C and δ18O values of well preserved micrite microsamples range from -5.2‰ to 0.5‰ (VPDB) and from -10.3‰ to-6.5‰ (VPDB), respectively. The δ13C carb profile of the sequence reveals few negative shifts, which vary between ˜ 2 and 4.7‰ and are associated with unconformities/disconformities, thus reflecting the effect of significant sea-level changes. The δ13C shifts can be correlated with counterparts on the St. George Group and also on the global Lower Ordovician δ13C profiles around the early Tremadoc (˜ 2.3‰) and late Tremadoc-early Arenig (˜ 4.7‰).

  14. Tectonic events in Greenland

    NASA Astrophysics Data System (ADS)

    Dahl-Jensen, T.; Voss, P.; Larsen, T.; Pinna, L.

    2012-12-01

    In Greenland a station separation of around 400km mean that many earthquakes are only detected on one or two stations. The development of the seismic monitoring have gone from having only three seismic stations in Greenland up to the late 1990'ies, till today where there are 18 permanent stations. All stations are equipped with broadband sensors and all of the permanent stations transmit data in real time. The recent major improvement of the seismic monitoring is performed by the Greenland ice sheet monitoring network (GLISN, http://glisn.info). The primary goal of GLISN is to provide broadband seismic data for the detection of glacial earthquakes. GLISN is now fully implemented with Iridium real time data transfer is in operation at five stations. In the Ammassalik region in Southeast Greenland, where small earthquakes often are felt, data from a temporary additional station has been utilized for a study covering 9 months in 2008/9. In this period 62 local earthquakes have been analyzed and re-located. Some of the events had formerly been located from distant stations by using a universal earth model. The result of this localization was a scattered distribution of the events in the region. The locations have now been improved by using a local earth model along with phase readings from two local stations not previously included; ANG in Tasiilaq and ISOG in Isortoq. From relocating the events two zones with a higher degree of seismicity than in the rest of the region are observed. The first zone is located by felsic intrusions. The second zone is at the boundary between the Archaean Craton and the Ammasalik region where reworked Archaean gneisses are dominating the geology. During the analysis it was observed that the additional information from the local stations are of great importance for the result. Active broad band stations in Greenland

  15. Atmospheric polybrominated diphenyl ethers (PBDEs) and Pb isotopes at a remote site in Southwestern China: implications for monsoon-associated transport.

    PubMed

    Xu, Yue; Zhang, Gan; Li, Jun; Liu, Xiang; Li, Xiangdong

    2011-10-01

    A 13-month sampling campaign was conducted at a remote site in southwestern China from October, 2005 to December, 2006. An integrated approach with lead isotopes and air back trajectory analysis was used to investigate the monsoon-associated atmospheric transport of PBDEs in tropical/subtropical Asia regions. The air concentration of PBDEs ranged from 1.6 to 57.5 pgm(-3) (15.9±12.0 pgm(-3)), comparable to reported levels at other remote sites in the world. BDE-209, followed by BDE-47 and -99 dominated the PBDE compositions, indicating a mixed deca- and penta-BDE source. Air mass back trajectory analysis revealed that the major potential source regions of BDE-47 and -99 could be southern China and Thailand, while those of BDE-209 are widely distributed in industrialized and urbanized areas in tropical Asia. The different lead isotope compositions of aerosols between trajectory clusters further substantiated the observation that the South Asian monsoon from spring to summer could penetrate deep into southwestern China, and facilitate long-range transport of airborne pollutants from South Asia.

  16. 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.

  17. 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.

  18. 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

  19. 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

  20. 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

  1. Gravity in Greenland

    SciTech Connect

    Hughes, R.J.; Goldman, T.; Nieto, M.M.

    1988-01-01

    Preliminary results of the test of the Newtonian Law of Gravitation conducted by Ander et al., in a borehole in the Greenland ice-cap were reported at this meeting. In this paper we consider the interpretations of these results in terms of a non-Newtonian component of gravity, and compare them with the results of other geophysical inverse-square law tests. 8 refs.

  2. 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

  3. 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.

  4. Atuarfitsialak: Greenland's Cultural Compatible Reform

    ERIC Educational Resources Information Center

    Wyatt, Tasha R.

    2012-01-01

    In 2002, Greenlandic reform leaders launched a comprehensive, nation-wide reform to create culturally compatible education. Greenland's reform work spans the entire educational system and includes preschool through higher education. To assist their efforts, reform leaders adopted the Standards for Effective Pedagogy developed at the Center for…

  5. The East Greenland Current studied with CFCs and released sulphur hexafluoride

    NASA Astrophysics Data System (ADS)

    Olsson, K. Anders; Jeansson, Emil; Tanhua, Toste; Gascard, Jean-Claude

    2005-03-01

    The distribution and evolution of water masses along the East Greenland Current (EGC) from south of the Fram Strait to the Denmark Strait were investigated using chlorofluorocarbons (CFCs) and the released tracer sulphur hexafluoride (SF 6) together with hydrographic data. Water masses contributing to the Denmark Strait overflow, and to some extent also contributions to the Iceland-Scotland overflow, are discussed from observations in 1999. Special emphasis is put on the advection and mixing of Greenland Sea Arctic Intermediate Water (GSAIW), which could be effectively traced thanks to the release of sulphur hexafluoride in the Greenland Sea Gyre in 1996. By means of the dispersion of the tracer, Greenland Sea Arctic Intermediate Water was followed down to the Denmark Strait Sill as well as close to the Faroe-Shetland Channel. The results indicate that this water mass can contribute to both overflows within 3 years from leaving the Greenland Sea. The transformation of Greenland Sea Arctic Intermediate Water was dominated by water from the Arctic Ocean, especially by isopycnal mixing with upper Polar Deep Water (uPDW) but, to a less extent, also by Canadian Basin Deep Water. A mixture of Greenland Sea Arctic Intermediate Water and upper Polar Deep Water was lifted 500 m on its way through southwestern Iceland Sea, to a depth shallow enough to let it reach the sill of the Denmark Strait from where it can be incorporated in the densest layer of the overflow. The observations show contributions to the Denmark Strait overflow from both the East Greenland Current and the Iceland Sea.

  6. SeaWinds - Greenland

    NASA Technical Reports Server (NTRS)

    1999-01-01

    The frequent coverage provided by NASA's SeaWinds instrument on the QuikScat satellite provides unprecedented capability to monitor daily and seasonal changes in the key melt zones of Greenland, which is covered with a thick ice sheet that resulted from snow accumulating over tens of thousands of years. The thickness of the snow layers reveals details about the past global climate, and comparing snow accumulation and snow melting can provide insight into climate change and global warming. In particular, the extent of summer melting of snow in Greenland is considered a sensitive indicator of global change.

    Earlier scatterometer data has suggested that Greenland has experienced significantly more melting in recent years. This figure compares the melting observed over 15 days during July 1999 in Greenland. The red areas around the central blue and white areas are the main melt zones and have lower radar back scatter because of water on the surface that saturates the surface snow. As the days warm up, the melt extent dramatically increases. Comparing this data with computer models and past scatterometer data will help scientists evaluate the inter-annual variability of the melting as a step toward understanding potential climate change.

    The world's large ice sheets in Greenland and Antarctica act as vast storehouses of freshwater. Summer season melting releases large quantities of freshwater into the ocean, and year-to-year variations can have a significant impact on global sea level. Furthermore, long-term changes in the patterns and extent of melting on the large ice sheets reflect the effects of climate variability; thus Greenland is considered a sensitive indicator of global warming.

    Satellite microwave radars are extremely sensitive to melting and can provide the only effective means of accurately measuring the year-round picture of the extent and variability in ice sheet melting. Daily mean images were produced from QuikScat data collected over the

  7. 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.

  8. 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.

  9. MTA-B or not to be? Recycled bifaces and shifting hunting strategies at Le Moustier and their implication for the late Middle Palaeolithic in southwestern France.

    PubMed

    Gravina, Brad; Discamps, Emmanuel

    2015-07-01

    Explaining late Middle Palaeolithic industrial variability remains a topic of great interest for researchers focusing on aspects of Neanderthal behavioural complexity and the so-called Middle-to-Upper Paleolithic 'transition.' Several sites in southwestern France figure prominently in these discussions, including the eponymous site of Le Moustier (Dordogne, France), one of the 'key' sequences used in larger anthropological models. Here we present a re-assessment of this important site based on a technological and taphonomic re-evaluation of previously studied collections combined with an analysis of unpublished archaeological material, which includes both lithic and faunal components. Our study produces a very different interpretation of the 'classic' Le Moustier sequence, challenging previous cultural attributions in a way that significantly impacts current debates surrounding the proposed Mousterian of Acheulean Tradition (MTA)--Châtelperronian affiliation. This new interpretation highlights independent changes in lithic technology and subsistence strategies that were previously undetected as well as a novel aspect of Neanderthal raw material use. Finally, we discuss how this new vision has important ramifications for broader issues connected to the definition of late Mousterian techno-complexes, such as the MTA, and the identification of relationships between technology, subsistence, and mobility strategies. PMID:25976251

  10. Detrital mode, mineralogy and geochemistry of the Sidi Aïch Formation (Early Cretaceous) in central and southwestern Tunisia: Implications for provenance, tectonic setting and paleoenvironment

    NASA Astrophysics Data System (ADS)

    Gallala, Wissem; Gaied, Mohamed Essghaier; Montacer, Mabrouk

    2009-03-01

    The chemical and mineralogical composition of the Sidi Aïch Formation sandstones in central and southwestern Tunisia has been investigated in order to infer the provenance and tectonic setting, as well as to appraise the influence of weathering. The sixteen studied samples are mainly composed of quartz, feldspar, kaolinite and/or illite. Sidi Aïch sandstones are mainly arkosic, potassic feldspar-rich and immature. Much of the feldspar was transformed to kaolinite. Concerning the relation between sandstone detrital composition and their depositional setting, the Sidi Aïch Formation sandstone in the major studied localities, probably accumulated in relatively proximal small basins within the continental interior. However, for the Khanguet El Ouara study site, sandstones may have been deposited in a foreland basin which received recycled sediments from an adjacent orogenic belt. The source area may have included quartzose sedimentary rocks. The dominance of quartz and enrichment in immobile elements suggest that the depositional basins were associated with a passive margin. The petrography and geochemistry reflect a stable continental margin and sediments were derived from granitic and pegmatitic sources located in the southern parts of the Gafsa basin. High values for the chemical index of alteration (CIA) indicate that recycling processes might have been important. Particularly high CIA values in the Garet Hadid locality indicate more intense chemical alteration, either due to weathering processes or tectonic control.

  11. 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

  12. 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.

  13. 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

  14. 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.

  15. 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?).

  16. Crustal structure beneath Eastern Greenland

    NASA Astrophysics Data System (ADS)

    Reiche, S.; Thybo, H.; Kaip, G.; Skjoth Bruun, A.; Reid, I.; Chemia, Z.; Greschke, B.

    2011-12-01

    The conjugate Atlantic passive margins of western Norway and eastern Greenland are characterized by the presence of coast-parallel mountain ranges with peak elevations of more than 3.5 km close to Scoresby Sund in Eastern Greenland. Knowledge about crustal thickness and composition below these mountain belts is needed for assessing the isostatic balance of the crust and to gain insight into possible links between crustal composition, rifting history and present-day topography of the North Atlantic Region. However, the acquisition of geophysical data onshore Greenland is logistically complicated by the presence of an up to 4 km thick ice sheet, permanently covering the largest part of the land mass. Hence previous seismic surveys have only been carried out offshore and near the coast of Greenland, where little information about the continental part of the crust could be gained. To get insight into crustal thickness and composition below the Greenland ice sheet, the TopoGreenland project collects the first ever seismic data onshore Greenland. Wide-angle data was acquired along an EW-trending profile, extending 350 km inland from the approximate edge of the stable ice cap near Scoresby Sund. Data is recorded by 350 Reftek Texan receivers for 10 equidistant shot points along the profile. We use forward ray tracing modelling to construct a two-dimensional velocity model from the observed travel times. These results show the first images of the subsurface velocity structure beneath the Greenland ice sheet and provide a link between the composition of the crust and the present-day topography of Greenland.

  17. 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.

  18. 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

  19. Greenland meltwater experiments

    NASA Astrophysics Data System (ADS)

    Olsen, S. M.; Schmith, T.

    2012-04-01

    We explore the climatic response to additional Greenland Ice Sheet melting in the EC-EARTH coupled climate model. As reference runs, we use an ensemble of two simulations from 1850 to present with historic forcing. For each of these we pick the years 1935,1950 and 1965, respectively as initial conditions for perturbed experiments with an additional freshwater forcing of 0.1 Sv distributed uniformly around Greenland , a plausible value in the upper end of future Greenland ice sheet melt estimates. We find give no evidence for abrupt transitions associated with tipping points in the Atlantic overturning circulation and mid-latitude heat transport. In fact, modelled decline in overturning in response to the additional forcing does not project onto a comparable reduction in the mid latitude (36N) ocean heat transport. This result points to an ongoing watermass transformation in the subpolar region and Arctic Mediterranean as a whole and a continued thermal mode of operation of the overturning. At the northern boundary of the subpolar region (60N) the response in overturning shows a contrasting increase in intensity along with an increase in heat transport. Whereas the latter may be expected as a result of freshwater capping and subsurface warming in the subpolar region, the increased overturning at 60N is more difficult to explain. In order to assess this in more detail we have quantified the individual thermohaline exchange components of light and dense water masses across the Greenland-Scotland Ridge. We find that the intensified overturning at 60N is reflected in increased transports of light Atlantic Water to the Nordic Seas. However, the vertical, thermohalinie overturning loop is not equally strengthened. On the contrary, we model a decline in the denser parts of the outflow, the overflows in the Denmark Strait and Faroe Bank Channel and a strong increase in the polar outflow in the Denmark Strait. We observe a gradual transition from a vertical mode of operation

  20. Cenozoic Motion of Greenland - Overlaps and Seaways

    NASA Astrophysics Data System (ADS)

    Lawver, L. A.; Norton, I. O.; Gahagan, L.

    2014-12-01

    Using the seafloor magnetic anomalies found in the Labrador Sea, North Atlantic and Eurasian basin to constrain the Cenozoic motion of Greenland, we have produced a new model for the tectonic evolution of the region. The aeromagnetic data collected by the Naval Research Lab [Brozena et al., 2003] in the Eurasian Basin and Canadian data from the Labrador Sea have been re-evaluated using new gridding algorithms and profile modeling using ModMag (Mendel et al., 2005). As a consequence, we have changed the published correlations, mostly prior to Chron C6 [19.05 Ma]. Presently published seafloor magnetic anomalies from the Labrador Sea assume that seafloor spreading ceased at C13 [33.06 Ma] but such an assumption produces an unacceptable overlap of Kronprins Christian Land of northeast Greenland with Svalbard, up to 140 km of overlap in some models. Our new model does not need any "unacceptable" overlap but does produce a slight amount of Eocene compression on Svalbard as is found on land there. Our model allows for an Early Eocene seaway between Ellesmere Island and northwest Greenland that may have connected the Labrador Sea through Baffin Bay and ultimately to the nascent Eurasian Basin, although its depth or even its essential existence is unknowable. During the Miocene, there is no room for a deepwater seaway in Fram Strait until at least the very end of the Early Miocene and perhaps not until Middle Miocene. Brozena, J. and six others, 2003. New aerogeophysical study of the Eurasia Basin and Lomonosov Ridge: Implications for basin development. Geology 31, 825-828. Mendel, V., M. Munschy and D.Sauter, 2005, MODMAG, a MATLAB program to model marine magnetic anomalies, Comp. Geosci., 31, .589-597

  1. 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

  2. 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

  3. 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.

  4. Greenland to gather more exploration data

    SciTech Connect

    Not Available

    1991-01-28

    Danish authorities are taking steps to make more exploration data available on Greenland in advance of a possible West Greenland shelf licensing round in 1993. Seismic data acquisition and other studies continue toward more fully evaluating Greenland's oil and gas potential. Geological Survey of Greenland (GGU), Copenhagen, Denmark, is processing 2,041 line miles of reflection seismic data shot on the West Greenland shelf in August and September of 1990. Sixty-fold stacks and migrations will be obtained. Total field magnetic data were also recorded during the survey, known as project Syd Vest Seis. Early work is under way to kick off the multicompany Kanumas seismic acquisition project, proposed in 1986, during 1991. Meanwhile, the Mineral Resources Administration for Greenland (MRA), Copenhagen, the Danish and Greenland governments aim to sweeten Greenland's exploration regulations prior to making areas available.

  5. 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.

  6. 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

  7. 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.

  8. The Greenland Telescope

    NASA Astrophysics Data System (ADS)

    Grimes, Paul; Blundell, Raymond

    2012-09-01

    In the spring of 2010, the Academia Sinica Institute of Astronomy and Astrophysics, and the Smithsonian Astrophysical Observatory, acquired the ALMA North America prototype antenna - a state-of-the-art 12-m diameter dish designed for submillimeter astronomy. Together with the MIT-Haystack Observatory and the National Radio Astronomy Observatory, the plan is to retrofit this antenna for cold-weather operation and equip it with a suite of instruments designed for a variety of scientific experiments and observations. The primary scientific goal is to image the shadow of the Super-Massive Black Hole in M87 in order to test Einstein’s theory of relativity under extreme gravity. This requires the highest angular resolution, which can only be achieved by linking this antenna with others already in place to form a telescope almost the size of the Earth. We are therefore developing plans to install this antenna at the peak of the Greenland ice-sheet. This location will produce an equivalent North-South separation of almost 9,000 km when linked to the ALMA telescope in Northern Chile, and an East-West separation of about 6,000 km when linked to SAO and ASIAA’s Submillimeter Array on Mauna Kea, Hawaii, and will provide an angular resolution almost 1000 times higher than that of the most powerful optical telescopes. Given the quality of the atmosphere at the proposed telescope location, we also plan to make observations in the atmospheric windows at 1.3 and 1.5 THz. We will present plans to retrofit the telescope for cold-weather operation, and discuss potential instrumentation and projected time-line.

  9. 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).

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

    PubMed

    Straneo, Fiammetta; Heimbach, Patrick

    2013-12-01

    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.

  11. The Pedagogical Situation in Greenland.

    ERIC Educational Resources Information Center

    Gunther, Bent

    The history of Greenland's educational activities began in 1721 with the work of a missionary who encouraged the people to learn to read and write. A century later, higher education became available. In 1905, legislation was enacted that served as a milestone of progress for the growth of education. Separation from Denmark, which was leading…

  12. Greenland: More Questions than Answers.

    ERIC Educational Resources Information Center

    Allison, Pete

    1998-01-01

    Journal entries, reflections, and interviews from a phenomenological study indicate the benefits experienced by 70 British youth participating in a six-week Greenland expedition. Themes emerging from the data include reflection on values, life and career plans, friendships and relationships, connectedness to self and society, environmental…

  13. 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.

  14. 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)

  15. 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. PMID:27386509

  16. 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

  17. 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.

  18. Fluctuations of the Greenland Ice Sheet since the last ice age: comparisons of the response of marine and land-terminating ice margins to Holocene climate changes

    NASA Astrophysics Data System (ADS)

    Levy, Laura; Larsen, Nicolaj; Kelly, Meredith; Kjær, Kurt; Bjørk, Anders; Kjeldsen, Kristian; Funder, Svend; Applegate, Patrick; Howley, Jennifer; Virginia, Ross

    2016-04-01

    Fluctuations of the margins of the Greenland Ice Sheet (GrIS) in response to Holocene climate change may be used as a proxy for how they may respond to future climate change. Here, we present records of Holocene fluctuations of the margins of the GrIS in southeastern and southwestern Greenland based on geomorphic mapping and 10Be dating of boulders on moraines and boulders on bedrock. We show that in southeastern Greenland the marine-terminating outlet glaciers retreated from the outer coast between 10.4 and 9.4 ka and responded rapidly to early Holocene warming, retreating up-fjord at a rate of ~70-100 m yr-1. These rates are comparable, or higher than, modern retreat rates of 30-100 m yr-1. In contrast, the terrestrial margin of the GrIS in the Kangerlussuaq region of southwestern Greenland retreated only ~25 m yr-1 throughout the early and middle Holocene. These data indicate that forcings such as warm ocean waters, fjord geometry, fjord bathymetry and ice dynamics are potential mechanisms that caused differences in retreat rates between marine and terrestrial-terminating margins of the ice sheet. Additionally, they show that the margins of the GrIS responded sensitively to Holocene climate change.

  19. 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.

  20. 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.

  1. 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

  2. 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.

  3. Weathering along a periglacial stream, Western Greenland

    NASA Astrophysics Data System (ADS)

    Evans, M.; Beal, S.

    2009-12-01

    Chemical weathering of Ca-Mg silicate minerals followed by marine carbonate precipitation is the fundamental sink for atmospheric CO2 in the long-term carbon cycle. Weathering of silicates along the margins of large ice sheets has been implicated in reducing atmospheric CO2 and impacting global climate despite low temperatures and a lack of significant soil cover; conditions not traditionally considered conducive to high reaction rates. Most glacial weathering studies have focused on valley glacier settings, where high water flux and an abundance of clay to silt sized sediments speed the breakdown of silicate minerals. However, little is known about these processes in the marginal zones of the Greenland Ice Sheet (GIS), where recent warming and accelerated melt may lead to profound shifts in hydrology and biogeochemistry. Continued melting should increase water flux and eventually expose additional margin land-surface. It is unclear however if these changing conditions will lead to increased chemical denudation along the margin. An examination of the current weathering regime along the GIS margin is necessary to better constrain estimates of the impacts of changing conditions on future chemical weathering fluxes and related CO2 drawdown. Water, suspended load, and bedload samples were collected in July 2008 along a 6 km stretch of stream exiting the western side of the Greenland Ice Sheet. Waters and sediments were analyzed for major ions, alkalinity and Sr isotopes to determine the character and extent of weathering. Major ion concentrations in the stream waters are very low (0-45 μM HCO3- and 2-26 μM for individual salts) with significant dilution by superglacial ice melt. There are no systematic down-stream trends in ion concentrations. Silicate-derived ions make up most of the stream alkalinity indicating little to no carbonate weathering. K+ contributes up to 40% of the cation load and K+/Σcation ratios in streams far exceed those in bedload samples. This

  4. Crustal structure beneath Central-Eastern Greenland

    NASA Astrophysics Data System (ADS)

    Reiche, S.; Thybo, H.; Reid, I.; Shulgin, A.

    2012-04-01

    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. Previous seismic surveys have only been carried out offshore and near the coast of Greenland, where little information about the continental part of the crust could be gained. Aiming to improve our understanding about crustal thickness and composition below the Greenland ice cap, the TopoGreenland project was initiated to collect the first ever controlled source seismic data onshore Greenland. Wide-angle seismic data were acquired along an EW-trending profile, extending 310 km inland from the approximate edge of the stable ice cap near Scoresby Sund across the centre of the ice cap. In total, 348 Reftek Texan receivers recorded high-quality data from 8 equidistant shot points along the profile. Based on forward ray tracing modelling, a two-dimensional velocity model provides the first insight into the velocity structure beneath the Greenland ice sheet. Modelling results indicate a decrease of crustal thickness from 50 km below the centre of Greenland to 42 km in the eastern part of the profile. Relatively high lower crustal velocities (Vp 6.8 - 7.3) in the western part of the model may be related to past collisional tectonic events or to the passage of the Iceland mantle plume.

  5. 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.

  6. 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

  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. 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...

  9. Shock melting of K-feldspar and interlacing with cataclastically deformed plagioclase in granitic rocks at Toqqusap Nunaa, southern West Greenland: Implications for the genesis of the Maniitsoq structure

    NASA Astrophysics Data System (ADS)

    Keulen, Nynke; Garde, Adam A.; Jørgart, Tommy

    2015-11-01

    Folded sheets of Mesoarchaean, leucocratic plagioclase-K-feldspar-mesoperthite-bearing granitic rocks in the Toqqusap Nunaa area of the Maniitsoq structure, West Greenland, are characterised by their very fine grain sizes and microstructures without normal igneous or planar/linear tectonic fabrics. Quartz forms equidimensional and branching, ductilely deformed aggregates and bifurcating panels with protrusions, constrictions and chains of ball-shaped grains with healed, radiating intergranular fractures. Plagioclase (An10-20) was cataclastically deformed and comminuted, whereas K-feldspar and mesoperthite are devoid of cataclastic microstructures. K-feldspar forms dispersed, highly irregular grains with numerous cusps and saddles, indicating almost ubiquitous direct (shock) melting of this mineral. It is commonly located along former fractures in plagioclase, resulting in an 'interlaced' feldspar microstructure with contact shapes indicating subsequent melting of plagioclase directly adjacent to K-feldspar. Mesoperthite forms separate, rounded, and irregular grains with protrusions and cusped margins indicating crystallisation from melts. Some mesoperthite grains are texturally and compositionally heterogeneous and contain internal lenses of K-feldspar and/or plagioclase. Other mesoperthite grains comprise coarsened, 'unzipped' areas, presumably due to localised, fluid-controlled dissolution-reprecipitation processes. The ternary feldspar precursor of the mesoperthite is interpreted as having crystallised from variably effectively mixed K-feldspar shock melts and plagioclase contact melts. Direct melting of K-feldspar, but no whole-rock melting, requires shock metamorphism with a short-lived temperature excursion to above the melting temperature of K-feldspar (~ 1300 °C). The presence of three different feldspar species and absence of chemical zonation, magmatic mantling, or metamorphic coronas furthermore hinders interpretations solely by means of endogenic

  10. Holocene climate variability in south-western France

    NASA Astrophysics Data System (ADS)

    Oliveira, D.; Naughton, F.; Trigo, R.; Rodrigues, T.; Jouanneau, J.-M.; Weber, O.

    2012-04-01

    Vegetation and climate changes in western France/northern Spain are documented for the last c. 9000 cal. yr BP in a well dated shelf core, KS05-10, retrieved in the southwestern margin of the Bay of Biscay (Basque country) (43°22'765N, 2°16'744W). The continuous high resolution pollen record shows orbital and suborbital climate fluctuations similar to those noticed for the North Atlantic region and Greenland. A long-term Pinus, Quercus and Corylus forest reduction follows the cooling trend in Greenland and the general decrease of mid-latitude summer insolation until approximately 350 yr cal. BP. Within the millennial scale variability, the southwestern Bay of Biscay pollen record shows 6 main phases: The first phase, c. 9000 and 6600 cal. yr BP, is marked by a Pinus and deciduous Quercus forest with Corylus, indicating a humid and temperate climate. During the phase, c. 6600 - 4500 cal. yr BP, the pollen record shows a stable period of rich, mixed Quercus forest. During this interval occurred the establishment of Alnus, Ulmus, Tilia, Fraxinus excelsior-type and Fagus trees and the reduction of Pinus forest. This vegetation assemblage probably indicates an increase in moisture in relatively mild conditions. Fagus became continuously present in the region after c. 4500 c. cal. yr BP in agreement with what have been noticed by continental pollen sequences. An important contraction of Pinus, deciduous Quercus and Corylus forest occur after c. 3600 cal. yr BP. This evolution is contemporaneous to the maximum expansion of Fagus and the increase of heaths, which may be linked to a weakening of seasonality and more humid summer conditions. A strong forest reduction, involving all trees except pine, and a marked spread of herbaceous plants took place after c. 1400 cal. years BP. The presence of Juglans, Cerealia type and Castanea after c. 550 cal. yr BP and the re-expansion of Pinus after c. 350 cal. yr BP testify the increasing role played by the human activity in the

  11. 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.

  12. 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.

  13. 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.

  14. Correlation of stratigraphy, structure, metamorphism and intrusion in the Caledonian allochthons of East Greenland and Svalbard

    NASA Astrophysics Data System (ADS)

    Gee, David G.

    2014-05-01

    migmatization and associated granite intrusion. In northeastern Greenland, the Hager Berg Allochthon, and overlying nearly 20 km thick Neoproterozoic and Early Paleozoic succession, was emplaced hot, at least 150 km westwards during the mid to late Silurian (perhaps Devonian) over the underlying Niggli Spids Complex and the latter, notably lacking the Silurian granites, was thrust at least a further 100 km westwards over the partly allochthonous Laurentian basement and its Cambro-Ordovician cover. Emplacement of the Caledonian allochthons in northeastern Greenland continued during Devonian deposition of the overlying Old Red Sandstone successions. Although the Svalbard Caledonides are disrupted by at least three major N-trending, orogen-parallel fault-zones, with vertical displacements of several kilometres and, locally, some clear evidence of sinistral strike-slip movements and orogen-parallel extension, there can be little doubt that the overall Caledonian structure of the archipelago, as in northeast Greenland, is dominated by long-transported allochthons. Those authors favoring strike-slip displacements of thousands of kilometers for the assembly of Svalbard's Caledonian "terranes" need to explain how these movements can be accommodated within the Baltica-Laurentia collisional framework. However, subordinate sinistral strike-slip displacements are necessary to explain the juxtaposition of the allochthons of northeast Greenland affinities with the co-called "Southwestern Terrane" of westernmost Spitsbergen. The latter shares some of the characteristics of the Pearya Terrane of northernmost Canada (Ellesmere Island). Tectonic extrusion, as in the Himalaya- Tibet Orogen, provides a suitable analogue.

  15. 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

  16. 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.

  17. 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

  18. 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.

  19. 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.

  20. 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.

  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. 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.

  3. 8. VIEW OF EL PASO AND SOUTHWESTERN RAILROAD BRIDGE, PIER ...

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

    8. VIEW OF EL PASO AND SOUTHWESTERN RAILROAD BRIDGE, PIER BETWEEN EAST APPROACH AND RAILROAD, LOOKING NORTH. - El Paso & Southwestern Railroad Rio Grande Bridge, Spanning Rio Grande at Southwestern Railroad, El Paso, El Paso County, TX

  4. 7. VIEW OF EL PASO AND SOUTHWESTERN RAILROAD BRIDGE, PIER ...

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

    7. VIEW OF EL PASO AND SOUTHWESTERN RAILROAD BRIDGE, PIER BETWEEN HIGHWAY AND RAILROAD, LOOKING NORTH. - El Paso & Southwestern Railroad Rio Grande Bridge, Spanning Rio Grande at Southwestern Railroad, El Paso, El Paso County, TX

  5. 4. GENERAL VIEW OF EL PASO AND SOUTHWESTERN RAILROAD BRIDGE, ...

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

    4. GENERAL VIEW OF EL PASO AND SOUTHWESTERN RAILROAD BRIDGE, RAILROAD SPAN, LOOKING NORTH. - El Paso & Southwestern Railroad Rio Grande Bridge, Spanning Rio Grande at Southwestern Railroad, El Paso, El Paso County, TX

  6. 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...

  7. 21 CFR 102.57 - Greenland turbot (Reinhardtius hippoglossoides).

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 2 2010-04-01 2010-04-01 false Greenland turbot (Reinhardtius hippoglossoides... for Specific Nonstandardized Foods § 102.57 Greenland turbot (Reinhardtius hippoglossoides). “Greenland turbot” is the common or usual name of the food fish Reinhardtius hippoglossoides, a species...

  8. 21 CFR 102.57 - Greenland turbot (Reinhardtius hippoglossoides).

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 2 2014-04-01 2014-04-01 false Greenland turbot (Reinhardtius hippoglossoides... for Specific Nonstandardized Foods § 102.57 Greenland turbot (Reinhardtius hippoglossoides). “Greenland turbot” is the common or usual name of the food fish Reinhardtius hippoglossoides, a species...

  9. 21 CFR 102.57 - Greenland turbot (Reinhardtius hippoglossoides).

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 2 2012-04-01 2012-04-01 false Greenland turbot (Reinhardtius hippoglossoides... for Specific Nonstandardized Foods § 102.57 Greenland turbot (Reinhardtius hippoglossoides). “Greenland turbot” is the common or usual name of the food fish Reinhardtius hippoglossoides, a species...

  10. 21 CFR 102.57 - Greenland turbot (Reinhardtius hippoglossoides).

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 2 2013-04-01 2013-04-01 false Greenland turbot (Reinhardtius hippoglossoides... for Specific Nonstandardized Foods § 102.57 Greenland turbot (Reinhardtius hippoglossoides). “Greenland turbot” is the common or usual name of the food fish Reinhardtius hippoglossoides, a species...

  11. Geochemistry of anorthositic differentiated sills in the Archean (~ 2970 Ma) Fiskenæsset Complex, SW Greenland: Implications for parental magma compositions, geodynamic setting, and secular heat flow in arcs

    NASA Astrophysics Data System (ADS)

    Polat, Ali; Fryer, Brian J.; Appel, Peter W. U.; Kalvig, Per; Kerrich, Robert; Dilek, Yildirim; Yang, Zhaoping

    2011-04-01

    The Fiskenæsset Complex, SW Greenland, is one of the best preserved layered Archean intrusions in the world, consisting of an association of ca. 550-meter-thick anorthosite, leucogabbro, gabbro, and ultramafic rocks (dunite, peridotite, pyroxenite, and hornblendite). Despite poly-phase deformation and amphibolite to granulite facies metamorphism, primary cumulate textures and igneous layering are well-preserved in the complex. This study reports new major and trace element data for three variably thick (1 to 5 m) differentiated (dunite, through peridotite, pyroxenite, gabbro leucogabbro, to anorthosite) sequences (Sequences 1, 2 and 3) in the Sinarssuk area of the Fiskenæsset region. On several variation diagrams, samples from these sequences plot along a well-defined liquid line of descent, consistent with in situ fractional crystallization. The average chemical compositions of these sequences are used to constrain their approximate parental magma compositions. Petrographic observations and geochemical data suggest that Sequences 2 and 3 solidified from evolved magmas that underwent olivine fractionation prior to their intrusion. In contrast, Sequence 1 appears to have been derived from a near-primary parental magma (SiO 2 = 43 wt.%, MgO = 20 wt.%, Al 2O 3 = 16 wt.%, CaO = 9.3 wt.%, Ni = 840 ppm, Mg-number = 80). The trace element patterns of this parental magma are comparable to those of Phanerozoic boninites, consistent with a supra-subduction zone geodynamic setting. If the relative thickness of ultramafic layers, the sum of dunite, peridotite and pyroxenite layers, in differentiated sequences is taken as an analog for the original complex emplaced into Archean oceanic crust, the Fiskenæsset Complex might have had a minimum thickness of 1000 m, with a 500 m thick ultramafic unit at the bottom. The thickness of the ultramafic unit in the preserved complex is less than 50 m, suggesting that more than 90% of the original ultramafic unit was either delaminated

  12. Polar continental margins: Studies off East Greenland

    NASA Astrophysics Data System (ADS)

    Mienert, J.; Thiede, J.; Kenyon, N. H.; Hollender, F.-J.

    The passive continental margin off east Greenland has been shaped by tectonic and sedimentary processes, and typical physiographic patterns have evolved over the past few million years under the influence of the late Cenozoic Northern Hemisphere glaciations. The Greenland ice shield has been particularly affected.GLORIA (Geological Long Range Inclined Asdic), the Institute of Oceanographic Sciences' (IOS) long-range, side-scan sonar, was used on a 1992 RV Livonia cruise to map large-scale changes in sedimentary patterns along the east Greenland continental margin. The overall objective of this research program was to determine the variety of large-scale seafloor processes to improve our understanding of the interaction between ice sheets, current regimes, and sedimentary processes. In cooperation with IOS and the RV Livonia, a high-quality set of seafloor data has been produced. GLORIA'S first survey of east Greenland's continental margin covered several 1000- × 50-km-wide swaths (Figure 1) and yielded an impressive sidescan sonar image of the complete Greenland Basin and margin (about 250,000 km2). A mosaic of the data was made at a scale of 1:375,000. The base map was prepared with a polar stereographic projection having a standard parallel of 71°.

  13. 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.

  14. 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.

  15. 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.

  16. Clouds enhance Greenland ice sheet meltwater runoff

    NASA Astrophysics Data System (ADS)

    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.

  17. 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

  18. 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.

  19. 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.

  20. Sucrase deficiency in Greenland. Incidence and genetic aspects.

    PubMed

    Gudmand-Høyer, E; Fenger, H J; Kern-Hansen, P; Madsen, P R

    1987-01-01

    The disaccharidase activities in small-intestinal surgical biopsy specimens from 97 Greenlanders were investigated. Five of the patients, or 5%, had sucrase deficiency. The diagnosis, sucrose malabsorption, was established by sucrose tolerance tests. In all parts of the world other than the arctic regions sucrase deficiency is a rare condition. The patients were divided into three separate groups in accordance with their sucrase activity. The middle group was considered to be heterozygote carriers of the sucrase-deficient gene. The number of people in the group corresponded to the theoretical number of heterozygotes in accordance with the Hardy-Weinberg equation, suggesting that sucrase deficiency is recessively inherited in a simple Mendelian fashion. Four of the five patients with sucrase deficiency had deficiency of lactase as well. The nutritional implications are discussed. PMID:3563408

  1. Greenland unveils terms for offshore licenses

    SciTech Connect

    Not Available

    1992-04-20

    This paper reports that Greenland has spelled out terms for its first round of offshore licensing. The action off western Greenland could lead to the first oil and gas exploration there since an unsuccessful campaign in the 1970s. The Mineral Resources Administration (MRA) for Greenland pegged exploration license terms on 133 blocks, all south of the 66th parallel, at 10 years with options for 2 year extensions to a maximum of 6 more years. The license can cover as many as six blocks. In the first 3 year period companies will have only a seismic obligation of 1,588 km per six blocks. For the second 3 year period there will be a one well obligation and one well in each subsequent 2 year periods.

  2. 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.

  3. Lead Sources in Human Diet in Greenland

    PubMed Central

    Bjerregaard, Peter; Johansen, Poul; Mulvad, Gert; Pedersen, Henning Sloth; Hansen, Jens C.

    2004-01-01

    Although blood lead levels have declined in Greenland, they are still elevated despite the fact that lead levels in the Greenland environment are very low. Fragments of lead shot in game birds have been suggested as an important source of dietary exposure, and meals of sea birds, particularly eider, contain high concentrations of lead. In a cross-sectional population survey in Greenland in 1993–1994, blood lead adjusted for age and sex was found to be associated with the reported consumption of sea birds. Participants reporting less than weekly intake of sea birds had blood lead concentrations of approximately 75 μg/L, whereas those who reported eating sea birds several times a week had concentrations of approximately 110 μg/L, and those who reported daily intake had concentrations of 170 μg/L (p = 0.01). Blood lead was not associated with dietary exposure to other local or imported food items. PMID:15531433

  4. 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.

  5. 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.

  6. 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. PMID:24630359

  7. 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.

  8. Provenance, volcanic record, and tectonic setting of the Paleozoic Ventania Fold Belt and the Claromecó Foreland Basin: Implications on sedimentation and volcanism along the southwestern Gondwana margin

    NASA Astrophysics Data System (ADS)

    Alessandretti, Luciano; Philipp, Ruy Paulo; Chemale, Farid; Brückmann, Matheus Philipe; Zvirtes, Gustavo; Matté, Vinícius; Ramos, Victor A.

    2013-11-01

    This study focuses on the provenance, volcanic record, and tectonic setting of the Paleozoic Ventania System, a geologic province which comprises the Cambro-Devonian Ventania Fold Belt and the adjoining Permo-Carboniferous Claromecó Foreland Basin, located inboard the deformation front. The Ventania Fold Belt is formed of the Curamalal and Ventana groups, which are composed mainly of mature quartzites that were unconformably deposited on igneous and metamorphic basement. The Pillahuincó Group is exposed as part of the Claromecó Basin and it has lithological and structural features totally distinct from the lowermost groups. This group is composed of immature arkoses and subarkoses with intercalated tuff horizons, unconformably overlaying the quartzites and associated with glacial-marine deposits of the lower Late Carboniferous to Early Permian section. The petrography, as well as major and trace elements (including rare earth elements) support that the Ventania quartzites were derived from cratonic sources and deposited in a passive margin environment. For the Pillahuincó Group, we suggest a transition between rocks derived from and deposited in a passive margin environment to those with geochemical and petrographical signatures indicative of an active continental margin provenance. LA-MC-ICP-MS analysis performed on euhedral and prismatic zircon grains of the tuffs revealed an age of 284 ± 15 Ma. The geochemical fingerprints and geochronological data of the tuffs found in the Claromecó Basin support the presence of an active and widespread Lower Permian pyroclastic activity in southwestern Gondwana, which is interpreted as part of the Choiyoi Volcanic Province in Argentina and Chile.

  9. 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.

  10. 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.

  11. 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

  12. Ellesmere Island (Canada) and Northern Greenland

    NASA Technical Reports Server (NTRS)

    2002-01-01

    In late July, our planet.s northernmost land masses appear to finally be responding to the warmth of Northern Hemisphere summer. Ellesmere Island, Canada, (top left) and northern Greenland (right) have decided kick off their snowy winter garments in this true-color Moderate Resolution Imaging Spectroradiometer (MODIS) image from July 3, 200. Bare brown soils are exposed along the coasts of the still frozen (but thawing!) Arctic waters. Several large, permanent ice caps and glaciers will remain on Ellesmere Island year-round, and Greenland does little more than remove her mittens, but thinning, blue ice is showing up in the many fjords and inlets in the rocky coastlines, showing that temperatures are on the rise. The Nares Strait, which separates the two land masses, still has a way to go before a passage opens up between Baffin Bay to the south and the Artic Ocean to the north. Although Ellesmere Island appears to be 'higher' or farther north than Greenland, that is simply a result of the way the high-latitude scene was projected into an image. To better picture the terrain, imagine that you took a printed copy of the rectangular image and rolled it into a cylinder along its northeast-southwest axis. If you held that cylinder straight up in front of you, you would find that Peary Land, Greenland (right of center), is actually the more northern terrain. In fact Peary Land is the northernmost point on land on the Earth.

  13. 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.

  14. The Greenland Ice Sheet Monitoring Network (GLISN)

    NASA Astrophysics Data System (ADS)

    Anderson, K. R.; Beaudoin, B. C.; Butler, R.; Clinton, J. F.; Dahl-Jensen, T.; Ekstrom, G.; Giardini, D.; Govoni, A.; Hanka, W.; Kanao, M.; Larsen, T.; Lasocki, S.; McCormack, D. A.; Mykkeltveit, S.; Nettles, M.; Agostinetti, N. P.; Stutzmann, E.; Tsuboi, S.; Voss, P.

    2010-12-01

    The GreenLand Ice Sheet monitoring Network (GLISN) is an international, broadband seismic capability for Greenland, being installed and implemented through the collaboration of Denmark, Canada, Germany, Italy, Japan, Norway, Poland, Switzerland, and USA. GLISN is a real-time sensor array of seismic stations to enhance and upgrade the performance of the sparse Greenland seismic infrastructure for detecting, locating, and characterizing glacial earthquakes and other cryo-seismic phenomena, and contributing to our understanding of Ice Sheet dynamics. Complementing data from satellites, geodesy, and other sources, and in concert with these technologies, GLISN will provide a powerful tool for detecting change, and will advance new frontiers of research in the glacial systems; the underlying geological and geophysical processes affecting the Greenland Ice Sheet; interactions between oceans, climate, and the cryosphere; and other multidisciplinary areas of interest to geoscience and climate dynamics. The glacial processes that induce seismic events (internal deformation, sliding at the base, disintegration at the calving front, drainage of supra-glacial lakes) are all integral to the overall dynamics of glaciers, and seismic observations of glaciers therefore provide a quantitative means for monitoring changes in their behavior over time. Long-term seismic monitoring of the Greenland Ice Sheet will contribute to identifying possible unsuspected mechanisms and metrics relevant to ice sheet collapse, and will provide new constraints on Ice Sheet dynamic processes and their potential roles in sea-level rise during the coming decades. GLISN will provide a new, fiducial reference network in and around Greenland for monitoring these phenomena in real-time, and for the broad seismological study of Earth and earthquakes. The 2010 summer field season saw the installation or upgrade of 9 stations in the GLISN network. Sites visited under the GLISN project include Station Nord (NOR

  15. TopoGreenland: crustal structure in central-eastern Greenland along a new refraction profile

    NASA Astrophysics Data System (ADS)

    Shulgin, Alexey; Thybo, Hans; Field Team TopoGreenland

    2013-04-01

    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 in 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 center 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 canceled, 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 125 kg at 35-85 m depth in individual boreholes. Two-dimensional velocity model based on tomographic inversion and forward ray tracing modeling shows a decrease of crustal thickness from 47 km below the center 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

  16. 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.

  17. 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

  18. 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

  19. Modern solar maximum forced late twentieth century Greenland cooling

    NASA Astrophysics Data System (ADS)

    Kobashi, T.; Box, J. E.; Vinther, B. M.; Goto-Azuma, K.; Blunier, T.; White, J. W. C.; Nakaegawa, T.; Andresen, C. S.

    2015-07-01

    The abrupt Northern Hemispheric warming at the end of the twentieth century has been attributed to an enhanced greenhouse effect. Yet Greenland and surrounding subpolar North Atlantic remained anomalously cold in 1970s to early 1990s. Here we reconstructed robust Greenland temperature records (North Greenland Ice Core Project and Greenland Ice Sheet Project 2) over the past 2100 years using argon and nitrogen isotopes in air trapped within ice cores and show that this cold anomaly was part of a recursive pattern of antiphase Greenland temperature responses to solar variability with a possible multidecadal lag. We hypothesize that high solar activity during the modern solar maximum (approximately 1950s-1980s) resulted in a cooling over Greenland and surrounding subpolar North Atlantic through the slowdown of Atlantic Meridional Overturning Circulation with atmospheric feedback processes.

  20. 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

  1. 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

  2. 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

  3. Characterizing the variability in precipitation-bearing storms over Central Greenland during the last glacial period

    NASA Astrophysics Data System (ADS)

    Winstrup, Mai; Svensson, Anders M.; Rasmussen, Sune O.; Ditlevsen, Peter; Kipfstuhl, Sepp; Steig, Eric J.

    2013-04-01

    A few ice core records are of sufficiently high resolution that they are able to record individual weather events. In this study, we are looking into one of these, namely the visual stratigraphy of the NGRIP ice core record from Central Greenland. We consider the evidence these data contains on variability in past precipitation-bearing storm tracks over Central Greenland during the rapid climatic changes of the last glacial. This information has implications for the variability of past circulation patterns in the North Atlantic region and their governing climate mechanisms. From the NGRIP ice core, Central Greenland, very detailed images of the visual stratigraphy in the core has been obtained. For the ice deposited during the last glacial period, the images show a clear banding of small-scale layers with a range of thicknesses. These layers are believed to be the result of individual precipitation events, which can be distinguished due to differences in their impurity concentrations. This assumption is justified by a qualitative comparison of contemporary Central Greenland weather data to the layering in early Holocene visual stratigraphy data. In combination with an accurate layer-counted chronology for the NGRIP ice core, the data allows us to look into the variability of past storminess over Central Greenland. This variability is quantified in terms of the changes in frequency and intensity of precipitation-bearing storms over the warm and cold phases of the last glacial period. Preliminary investigations show that whereas the average amount of precipitation per storm event is relatively constant with climate, the frequency of storms is changing significantly: A considerably larger number of precipitating storms per year are reaching the NGRIP drill site, Central Greenland, during the interstadials. On the other hand, inter-annual variability in the frequency of major storm occurrences is observed to be largest during the cold periods. We hypothesize that the

  4. 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

  5. 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.

  6. Greenland opens more offshore, land acreage to exploration

    SciTech Connect

    Not Available

    1992-01-13

    Greenland's Mineral Resources Administration (MRA) plans a series of licensing rounds off western Greenland. Meanwhile, the MRA has declared the Jameson Land basin of east central Greenland as open acreage. Greenland Geological Survey (GGU), Copenhagen, has prepared a report on the geographical conditions, logistics, exploration history, and geological development of Jameson Land. The article emphasizes source and reservoir rocks, conceptual play types with six seismic examples, and thermal history with basin modeling. It also includes two interpreted regional seismic lines, a geological and an aeromagnetic map, depth structure, and isopach maps of selected formations.

  7. 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.

  8. Complex Greenland outlet glacier flow captured.

    PubMed

    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

  9. 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.

  10. 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

  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

    2016-02-01

    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. PMID:26912699

  12. 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.

  13. 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.

  14. 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.

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

    DOE PAGESBeta

    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,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

  16. 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.

  17. 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...

  18. Staking Out the Public Interest in the Merger between Pacific Telesis and Southwestern Bell Corporation. A White Paper.

    ERIC Educational Resources Information Center

    Valdez, Armando; And Others

    This white paper informs Californians of the implications of the possible merger of Pacific Telesis and Southwestern Bell Corporation, under consideration by the California Public Utilities Commission (CPUC). The decision will determine the future direction and character of telecommunications in California. Only a small number of Californians are…

  19. 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

  20. Lomonosov Ridge off Greenland (LOMROG) 2007

    NASA Astrophysics Data System (ADS)

    Marcussen, C.; Jakobsson, M.

    2007-12-01

    The Lomonosov Ridge off Greenland was the primary focus for the LOMROG expedition. This part of the Arctic is virtually unexplored as difficult sea ice conditions have made it inaccessible for surface vessels. With Swedish icebreaker /Oden/ supported by new Russian nuclear icebreaker /50 Let Pobedy/, LOMROG managed to reach the southern most tip of the Lomonosov Ridge off Greenland to carry out multibeam mapping, subbottom and seismic reflection profiling, gravity measurements, geological coring and oceanographic station work. The LOMROG expedition is a Swedish/Danish collaboration project with participating scientists also from Canada, Finland, and USA. The data collection was made for the purpose of studying paleoceanography/oceanography, glacial history and the tectonic evolution of the of the Arctic Ocean as well as for Denmark's Continental Shelf Project under the United Nations Convention on the Law of the Sea Article 76. One of the reasons for targeting the ice-infested area north of Greenland was that it likely holds answers to key questions regarding the glacial history of the Arctic Ocean, such as whether immense ice shelves existed in the Arctic Ocean during past glacial periods./ /Previous expeditions with /Oden/ in 1996 and the US nuclear submarine /Hawkbill/ in 1999, have demonstrated the occurrence of ice grounding down to 1000 m present water depth at about 87°N 145°E on the Lomonosov Ridge crest. If this ice grounding event resulted from a much debated, but supposedly coherent and large floating ice shelf, the Lomonosov Ridge north of Greenland must also be scoured. To test the hypothesis of a huge Arctic Ocean ice shelf LOMROG mapped the areas of the Lomonosov Ridge north of Greenland using the new EM120 multibeam bathymetry and SBP120 subbottom profiling system installed on the /Oden/ during the spring of 2007. Glacial erosion was indeed found at water depth shallower than approximately 800 m and two sediment cores retrieved from the glacially

  1. 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

  2. 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...

  3. 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.

  4. 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.

  5. Accumulation rates in Northwest Greenland from continuous GPR profiling along the Greenland Inland Traverse

    NASA Astrophysics Data System (ADS)

    Hawley, R. L.; Courville, Z.; Kehrl, L. M.; Lutz, E.; Osterberg, E. C.; Overly, T. B.; Wong, G. J.

    2012-12-01

    Snow accumulation is one of the fundamental parameters governing the mass balance of the Greenland Ice Sheet. While many point measurements of accumulation exist from shallow and deep ice cores, there are few spatially extensive and continuous records of accumulation in Greenland, particularly in the northwest quadrant. In April and May 2011, the Greenland Inland Traverse traveled via tractor train from Thule Air Base in northwest Greenland to Summit Station, at the center of the ice sheet. The science team on the traverse collected both point and profile measurements along the route. Kinematic GPS and 400 MHz GPR profiles provide geolocated subsurface stratigraphy. Density measurements from snowpits and shallow cores on the profile allow us to determine the true depth of radar reflecting horizons, commonly interpreted to be isochrons. We use three ice cores collected at the beginning, the end, and roughly the middle of the route to date horizons. We traced strong reflecting horizons along the entire route. From the combination of dated, traced horizons, density measurements, and position measurements, we determine accumulation rates continuously along the traverse route. We find our traverse route begins in a high-accumulation area, and accumulation decreases as we cross to the east side of the summit ridge. Accumulation then climbs again as we approach summit (directly on the summit ridge). We compare our accumulation rates with previous studies, both measurements (traverse and point measurements) and models.

  6. Northeastern Exterior, Northwestern Exterior, & Southwestern Exterior Elevations, Northeastern Interior, ...

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

    Northeastern Exterior, Northwestern Exterior, & Southwestern Exterior Elevations, Northeastern Interior, Southeastern Interior, & Southwestern Interior Elevations, Floor Plan, and Eastern Corner Detail - Manatoc Reservation, Vale Edge Adirondack, 1075 Truxell Road, Peninsula, Summit County, OH

  7. The East Greenland Ridge - a continental sliver along the Greenland Fracture Zone

    NASA Astrophysics Data System (ADS)

    Gerlings, Joanna; Funck, Thomas; Castro, Carlos F.; Hopper, John R.

    2014-05-01

    The East Greenland Ridge (EGR), situated along the Greenland Fracture Zone in the northern part of the Greenland-Norwegian Sea, is a NW-SE trending 250-km-long and up to 50-km-wide bathymetric high that separates the Greenland Basin in the south from the Boreas Basin in the north. Previous seismic work established that the EGR is primarily continental in nature. Detailed swath bathymetric data revealed a complex internal structure of the ridge with two main overstepping ridge segments. These segments were not adequately covered by the GEUS2002NEG seismic survey as the detailed structure was not known at that time. The crustal affinity of the northwestern, landward-most ridge segment, and how it is attached to the Northeast Greenland continental shelf, remained unclear. The GEUS-EAGER2011 survey was designed to address these issues and to provide further constraints on the structural development of the EGR. During the GEUS-EAGER2011 survey, additional seismic refraction and reflection data were acquired on the EGR and the Northeast Greenland shelf. The data set consists of two strike lines covering the seaward-most part of the Northeast Greenland shelf and the landward-most part of the EGR, and one cross line extending from the Boreas Basin, across the ridge and into the Greenland Basin. A total of 15 ocean bottom seismometers and 46 sonobuoys were deployed along the three seismic refraction lines. P-wave velocity models for the crust and upper mantle were derived by forward and inverse modelling of the travel times of the observed seismic phases using the raytracing algorithm RAYINVR. Seismic reflection data, coinciding with the seismic refraction data were used to guide the modelling of the sedimentary layers down to basement. The velocity models confirm that the crust has a continental nature along both ridge segments with a velocity structure that significantly differs from that of normal oceanic crust. The models also show that the crust of the EGR is linked to

  8. 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.

  9. 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

  10. First results from Acoustic Doppler Current Profiler measurements of meltwater flux in a large supraglacial river in western Greenland compared with downstream proglacial river outflow

    NASA Astrophysics Data System (ADS)

    Pitcher, L. H.; Smith, L. C.; Overstreet, B. T.; Chu, V. W.; Rennermalm, A. K.; Cooper, M. G.; Gleason, C. J.; Yang, K.

    2015-12-01

    A vast network of seasonally evolving, thermally eroding supraglacial rivers on the southwestern Greenland Ice Sheet (GrIS) is the preeminent transporter of meltwater across this area of the ablation zone. Supraglacial rivers are important for estimating surface water storage and transport into moulins and into the en-, sub-, and proglacial environments. Yet, little is known about their role in the GrIS cryo-hydrologic system. To that end, supraglacial river discharge in a large river, the "Rio Behar" (67.05°, -49.02°; ~75 km from the Kangerlussuaq International Airport), was measured in situ over 300 times: approximately four times per hour over three consecutive days from July 19 - 22, 2015. The Rio Behar drains a ~ 70 km2 ice catchment and enters a large moulin in the Watson River land-ice watershed in western Greenland. River discharge was measured using a Sontek M9 Acoustic Doppler Current Profiler. Each profile records water temperature, depth-integrated velocity, channel width and channel bathymetry. This novel dataset can be used to assess diurnal variations in river discharge, slope, velocity, stream power, and channel incision in order to enhance process-level understanding of GrIS meltwater routing, storage and transport. Future work will compare supraglacial river discharge in the Rio Behar with in situ estimates of proglacial river outflow upstream of the Watson River bridge in Kangerlussuaq, Greenland.

  11. Continuous broadband seismic observation on the Greenland Ice Sheet under Greenland Ice Sheet monitoring Network

    NASA Astrophysics Data System (ADS)

    Tsuboi, Seiji; Kanao, Masaki; Tono, Yoko; Himeno, Tetsuto; Toyokuni, Genti; Childs, Dean; Dahl-Jensen, Trine; anderson, Kent

    2013-04-01

    We have installed the ice sheet broadband seismograph station, called ICE-S (DK.ICESG) in June 2011, in collaboration with IRIS Polar Services under the GreenLand Ice Sheet monitoring Network (GLISN), which is a new, international, broadband seismic capability for Greenland being implemented through the collaboration between Denmark, Canada, France, Germany, Italy, Japan, Norway, Poland, Switzerland, and the USA. The primary purpose of GLISN project is to define the fine structure and detailed mechanisms of glacial earthquakes within the Greenland Ice Sheet. These glacial earthquakes in the magnitude range 4.6-5.1 may be modeled as a large glacial ice mass sliding downhill several meters on its basal surface over duration of 30 to 60 seconds. Glacial earthquakes have been observed at seismic stations within Greenland (Larsen et al, 2006), but the coverage was very sparse and a broadband, real-time seismic network was needed to be installed throughout Greenland's Ice Sheet and perimeter. The National Institute for Polar Research and Japan Agency for Marine-Earth Science and Technology are members of GLISN project and we have started to operate ICESG station since 2011. The station is equipped with a CMG-3T broadband seismometer and a Quanterra Q330 data logger. We have visited the station again in May, 2012 and successfully retrieved one year of continuous records from the broadband seismometer and updated the telemetry system to eventually allow real time monitoring of the station. ICESG station is now daily sending 1 Hz continuous data over the iridium satellite system using RUDICS. The observed three component seismograms demonstrate that the quality of this ice sheet station is good enough to record not only local earthquakes around Greeland but also teleseismic earthquakes. We could record three component broadband seismograms for April 11, 2012 Off the west coast of Northern Sumatra earthquake (Mw8.6). These seismograms show high signal to noise ratio

  12. Eocene ostracoda from Oshosun formation Southwestern Nigeria

    NASA Astrophysics Data System (ADS)

    Okosun, E. A.

    A biostratigraphic study of the phosphate-bearing Oshosun Formation in southwestern Nigeria (eastern Dahomey Embayment) gave ostracos which are diagnostic for the Eocene. The ostracod assemblage contains the early to middle Eocene zonal index Costa dahomeyi. The majority of the species are common to the phosphatic sequence in the western Dahomey Embayment. This paleontologic evidence, and the association of clay and shale with the phosphate occurrences in different parts of the basin, suggest that the phosphatic beds were deposited in the Dahomey Embayment under similar paleoenvironmental conditions. Phosphatic sedimentation in southwestern Nigeria is inferred to have occurred during an early to early middle Eocene minor marine transgression.

  13. 25 CFR 38.15 - Southwestern Indian Polytechnic Institute.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 25 Indians 1 2010-04-01 2010-04-01 false Southwestern Indian Polytechnic Institute. 38.15 Section 38.15 Indians BUREAU OF INDIAN AFFAIRS, DEPARTMENT OF THE INTERIOR EDUCATION EDUCATION PERSONNEL § 38.15 Southwestern Indian Polytechnic Institute. (a) The Southwestern Indian Polytechnic Institute...

  14. 25 CFR 38.15 - Southwestern Indian Polytechnic Institute.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 25 Indians 1 2011-04-01 2011-04-01 false Southwestern Indian Polytechnic Institute. 38.15 Section 38.15 Indians BUREAU OF INDIAN AFFAIRS, DEPARTMENT OF THE INTERIOR EDUCATION EDUCATION PERSONNEL § 38.15 Southwestern Indian Polytechnic Institute. (a) The Southwestern Indian Polytechnic Institute...

  15. Clouds enhance Greenland ice sheet mass loss

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

    Clouds have a profound influence on both the Arctic and global climate, while they still represent one of the key uncertainties in climate models, limiting the fidelity of future climate projections. The potentially important role of thin liquid-containing clouds over Greenland in enhancing ice sheet melt has recently gained interest, yet current research is spatially and temporally limited, focusing on particular events, and their large scale impact on the surface mass balance remains unknown. We used a combination of satellite remote sensing (CloudSat - CALIPSO), ground-based observations and climate model (RACMO) data to show that liquid-containing clouds warm the Greenland ice sheet 94% of the time. High surface reflectivity (albedo) for shortwave radiation reduces the cloud shortwave cooling effect on the absorbed fluxes, while not influencing the absorption of longwave radiation. Cloud warming over the ice sheet therefore dominates year-round. Only when albedo values drop below ~0.6 in the coastal areas during summer, the cooling effect starts to overcome the warming effect. The year-round excess of energy due to the presence of liquid-containing clouds has an extensive influence on the mass balance of the ice sheet. Simulations using the SNOWPACK snow model showed not only a strong influence of these liquid-containing clouds on melt increase, but also on the increased sublimation mass loss. Simulations with the Community Earth System Climate Model for the end of the 21st century (2080-2099) show that Greenland clouds contain more liquid water path and less ice water path. This implies that cloud radiative forcing will be further enhanced in the future. Our results therefore urge the need for improving cloud microphysics in climate models, to improve future projections of ice sheet mass balance and global sea level rise.

  16. 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

  17. 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.

  18. 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

  19. 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

  20. 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

  1. Firn Densification and Meltwater Runoff in Western Greenland

    NASA Astrophysics Data System (ADS)

    Harper, J. T.; Humphrey, N. F.; Pfeffer, W. T.; Brown, J. M.; West, D.; Bradford, J. H.

    2009-12-01

    implications for understanding the mass balance and surface elevation changes of the Greenland Ice Sheet.

  2. Mental disorders in the Greenlandic population. A register study.

    PubMed

    Lynge, I; Mortensen, P B; Munk-Jørgensen, P

    1999-07-01

    In a register study of all psychiatric first hospitalizations (1974-93) of persons born and resident in Greenland rates for all admissions as well as for the separate diagnostic groups, hierarchically organized, were compared with corresponding figures for the population in Denmark. Relative mortality rates for the psychiatric patients compared with the general population were computed for the Greenlandic and Danish populations respectively. No significant differences in the total pattern of hospitalization was found, but Greenlandic men 15-24 years old and Greenlandic women 25-34 years old had significantly higher and older age groups lower first admission rates than Danish men and women, respectively. The rates for affective psychoses were low especially among men in Greenland, whereas the rates for schizophrenia among men were comparatively high. The relative mortality risk compared to the general population was much higher among Danish than Greenlandic psychiatric patients, especially regarding suicide. A probable explanation for that is that the suicide rate in the Green-landic general population is very high.

  3. Media Makes the Message at Southwestern Life

    ERIC Educational Resources Information Center

    Brosseau, Beth

    1974-01-01

    The new J. Carlton Smith Educational Center, training center of Southwestern Life Insurance Company, Dallas, Texas, utilizes a 3,600 square feet facility and employs a wide range of methods to make life underwriting training fast and interesting. Multimedia instruction is the key to their effective educational programs. (MW)

  4. Variability in the East Greenland Current

    NASA Astrophysics Data System (ADS)

    Holfort, J.; Meincke, J.; Mortensen, J.

    2003-04-01

    The East Greenland Current (EGC) carries different water masses along the eastern coast of Greenland to the south. Denmark Strait overflow water (DSOW) is a mixture of these southward flowing water masses. The Polar Water part (liquid and ice) is the main oceanic fresh water source for the North Atlantic. Changes in the composition of the EGC can therefore have considerable impact also on the larger scale (e.g. the global thermohaline circulation). We will give a picture of the variability of the water mass characteristics of the EGC based on oceanic data and discuss possible effect onto the DSOW. For the shorter term variability the main data sources are recent hydrographic data; and temperature, salinity and current data from a mooring array across the EGC at 75°N. The mooring data spans 2 years (9/2000-9/2002) for deep bottom part and 1 year (9/2001-9/2002) for the upper water column. For longer term (>2 years) variability the main source are historical and recent hydrografic data.

  5. Anthropogenic carbon in the East Greenland Current

    NASA Astrophysics Data System (ADS)

    Jutterström, Sara; Jeansson, Emil

    2008-07-01

    Sections of dissolved inorganic anthropogenic carbon ( CTanthro) based on 2002 data in the East Greenland Current (EGC) are presented. The CTanthro has been estimated using a model based on optimum multiparameter analysis with predefined source water types. Values of CTanthro have been assigned to the source water types through age estimations based on the transit time distribution (TTD) technique. The validity of this approach is discussed and compared to other methods. The results indicated that the EGC had rather high levels of CTanthro in the whole water column, and the anthropogenic signal of the different source areas were detected along the southward transit. We estimated an annual transport of CTanthro with the Denmark Strait overflow ( σθ > 27.8 kg m -3) of ∼0.036 ± 0.005 Gt C y -1. The mean CTanthro concentration in this density range was ∼30 μmol kg -1. The main contribution was from Atlantic derived waters, the Polar Intermediate Water and the Greenland Sea Arctic Intermediate Water.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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

  14. 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

  15. 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

  16. The impact of snow nitrate photolysis on boundary layer chemistry and the recycling and redistribution of reactive nitrogen across Antarctica and Greenland in a global chemical transport model

    NASA Astrophysics Data System (ADS)

    Zatko, Maria; Geng, Lei; Alexander, Becky; Sofen, Eric; Klein, Katarina

    2016-03-01

    The formation and recycling of reactive nitrogen (NO, NO2, HONO) at the air-snow interface has implications for air quality and the oxidation capacity of the atmosphere in snow-covered regions. Nitrate (NO3-) photolysis in snow provides a source of oxidants (e.g., hydroxyl radical) and oxidant precursors (e.g., nitrogen oxides) to the overlying boundary layer, and alters the concentration and isotopic (e.g., δ15N) signature of NO3- preserved in ice cores. We have incorporated an idealized snowpack with a NO3- photolysis parameterization into a global chemical transport model (Goddard Earth Observing System (GEOS) Chemistry model, GEOS-Chem) to examine the implications of snow NO3- photolysis for boundary layer chemistry, the recycling and redistribution of reactive nitrogen, and the preservation of ice-core NO3- in ice cores across Antarctica and Greenland, where observations of these parameters over large spatial scales are difficult to obtain. A major goal of this study is to examine the influence of meteorological parameters and chemical, optical, and physical snow properties on the magnitudes and spatial patterns of snow-sourced NOx fluxes and the recycling and redistribution of reactive nitrogen across Antarctica and Greenland. Snow-sourced NOx fluxes are most influenced by temperature-dependent quantum yields of NO3- photolysis, photolabile NO3- concentrations in snow, and concentrations of light-absorbing impurities (LAIs) in snow. Despite very different assumptions about snowpack properties, the range of model-calculated snow-sourced NOx fluxes are similar in Greenland (0.5-11 × 108 molec cm-2 s-1) and Antarctica (0.01-6.4 × 108 molec cm-2 s-1) due to the opposing effects of higher concentrations of both photolabile NO3- and LAIs in Greenland compared to Antarctica. Despite the similarity in snow-sourced NOx fluxes, these fluxes lead to smaller factor increases in mean austral summer boundary layer mixing ratios of total nitrate (HNO3+ NO3-), NOx, OH

  17. 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

  18. 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.

  19. 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.

  20. Pathways of warm water to the Northeast Greenland outlet glaciers

    NASA Astrophysics Data System (ADS)

    Schaffer, Janin; Timmermann, Ralph; Kanzow, Torsten; Arndt, Jan Erik; Mayer, Christoph; Schauer, Ursula

    2015-04-01

    The ocean plays an important role in modulating the mass balance of the Greenland Ice Sheet by delivering heat to the marine-terminating outlet glaciers surrounding the Greenland coast. The warming and accumulation of Atlantic Water in the subpolar North Atlantic has been suggested to be a potential driver of the glaciers' retreat over the last decades. The shelf regions thus play a critical role for the transport of Atlantic Water towards the glaciers, but also for the transfer of freshwater towards the deep ocean. A key region for the mass balance of the Greenland Ice Sheet is the Northeast Greenland Ice Stream. This large ice stream drains the second-largest basin of the Greenland Ice Sheet and feeds three outlet glaciers. The largest one is Nioghalvfjerdsfjorden (79°N-Glacier) featuring an 80 km long floating ice tongue. Both the ocean circulation on the continental shelf off Northeast Greenland and the circulation in the cavity below the ice tongue are weakly constrained so far. In order to study the relevant processes of glacier-ocean interaction we combine observations and model work. Here we focus on historic and recent hydrographic observations and on the complex bathymetry in the Northeast Greenland shelf region, which is thought to steer the flux of warm Atlantic water onto the continental shelf and into the sub-ice cavity beneath the 79°N-Glacier. We present a new global topography data set, RTopo-2, which includes the most recent surveys on the Northeast Greenland continental shelf and provides a detailed bathymetry for all around Greenland. In addition, RTopo-2 contains ice and bedrock surface topographies for Greenland and Antarctica. Based on the updated ocean bathymetry and a variety of hydrographic observations we show the water mass distribution on the continental shelf off Northeast Greenland. These maps enable us to discuss possible supply pathways of warm modified Atlantic waters on the continental shelf and thus potential ways of heat

  1. 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

  2. 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

  3. 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.

  4. Arctic Warming, Greenland Melt and Moulins

    NASA Astrophysics Data System (ADS)

    Steffen, K.; Huff, R.; Behar, A.

    2007-12-01

    Air temperatures on the Greenland ice sheet have increased by 4 deg. C since 1991. The ice sheet melt area increased by 30% for the western part between 1979-2006, with record melt years in 1987, 1991, 1998, 2002, 2005, and possibly the most extreme melt year in 2007. The increasing trend in the total area of melting bare ice is unmistakable at 13% per year, significant at a probability of 0.99. Hence, the bare ice region, the wet snow region, and the equilibrium line altitude have moved further inland and resulting in increased melt water flux towards the coast. Warm and extended air temperatures are to blame for 1.5 m water equivalent surface reduction at the long-term equilibrium line altitude, 1100 m elevation at 70 deg. N during summer 2007. Increase in ice velocity in the ablation region and the concurrent increase in melt water suggests that water penetrates to great depth through moulins and cracks, lubricating the bottom of the ice sheet. New insight was gained of subsurface hydrologic channels and cavities using new instrumentation and a video system during the melt peak in August 2007. Volume and geometry of a 100 m deep moulin were mapped with a rotating laser, and photographs with digital cameras. Sub-glacial hydrologic channels were investigated and filmed using a tethered, autonomous system, several hundred meters into the ice. These new results will be discussed in view of the rapid increase in melt area and mass loss of the Greenland ice sheet due to increasing air temperatures.

  5. 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

  6. 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

  7. 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

  8. 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

  9. Crustal Structure in Central-Eastern Greenland: TOPOGREENLAND Refraction Profile

    NASA Astrophysics Data System (ADS)

    Shulgin, A. A.; Thybo, H.

    2013-05-01

    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

  10. 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

  11. 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.

  12. 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

  13. 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.

  14. 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.

  15. Language Policy and Language Planning after the Establishment of the Home Rule in Greenland.

    ERIC Educational Resources Information Center

    Moller, Aquigssiaq

    1988-01-01

    Discusses the progress made and problems still surrounding Greenland's Home Rule Act which established the roles of Greenlandic and Danish in the instructional arena, covering attempts to make Greenlandic the native language while also encouraging bilingualism through mastery of Danish. (Author/CB)

  16. 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.

  17. 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. PMID:17412920

  18. Spatial variability of snow physical properties across northwestern Greenland

    NASA Astrophysics Data System (ADS)

    Courville, Z.; Polashenski, C.; Dibb, J. E.; Domine, F.

    2013-12-01

    In the late spring and early summer of 2013, researchers on the SAGE (Sunlight Absorption on the Greenland ice sheet Experiment) Traverse, embarked on a 4000 km ground traverse across northwestern Greenland in an attempt to quantify spatial variability of snow chemistry, snow physical properties, and snow reflectance. The field team targeted sites first visited by Carl Benson during his series of traverses from 1952 to 1955 as part of his pioneering work to characterize the Greenland Ice Sheet. This route now represents a rapidly changing and variable area of Greenland, as the route passes through several of the ice sheet facies first delimited by Benson. Along the traverse, the SAGE field team made ground-based albedo measurements using a hand-held spectroradiometer and collected snow physical property samples to determine snow specific surface area (SSA) from shallow, 2m pits. In addition, snow density and stratigraphy were measured. Snow layers in the near-surface and at the previous season's melt layer were targeted for sampling. Here we present preliminary snow physical property results from the upper portion of the snow pits and relate these to surface albedo data collected over the route. Further measurements of snow properties in the 2012 melt layer will be analyzed to assess the potential role of snow chemical (see Dibb et al. for a discussion of chemical analysis) and physical property driven albedo feedbacks could have played in contributing to that event. Route of 2013 SAGE Traverse in northwestern Greenland.

  19. 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

  20. 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.

  1. 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.

  2. 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.

  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. PMID:22043659

  4. Contaminants in two West Greenland caribou populations.

    PubMed

    Gamberg, Mary; Cuyler, Christine; Wang, Xiaowa

    2016-06-01

    Two caribou populations in West Greenland were sampled and the kidneys, liver and muscle analyzed for contaminants, including aluminum, arsenic, cadmium, copper, lead, mercury, selenium and zinc. Although close in proximity, the two populations are topographically separated by an ice cap, which creates different climates and vegetation types in each region. Contaminant levels reflected the differing diets of the two caribou populations. To the south in the wetter lichen-rich region, caribou had significantly more aluminum, arsenic, cadmium, lead, mercury, selenium and zinc, likely due to atmospheric deposition on lichens. To the north in the dry desert steppe where grasses predominate, caribou had higher levels of copper. Cows collected in late winter had significantly less hepatic copper, lead and mercury if pregnant, indicating placental transfer of these elements. Our results suggest that hepatic copper levels <200 μg g(-1) dry weight may result in copper depletion in pregnant cows and hepatic mercury concentrations above 0.5 μg g(-1) dry weight may negatively affect fertility in caribou cows. Hepatic mercury levels were negatively correlated with cow body weight, suggesting an adverse effect on body condition. Element concentrations found in tissues from these caribou are not considered to be of a health concern for those consuming this traditional food. PMID:26956180

  5. Permanent GPS and crustal deformation in Greenland

    NASA Astrophysics Data System (ADS)

    Khan, S. A.

    2003-12-01

    The National Survey and Cadastre - Denmark (KMS) is responsible for the geodetic definition of the reference network in Greenland. Permanent GPS plays an important role in the monitoring and maintenance of the geodetic network. Furthermore, KMS supports the international GPS infrastructure and research by supporting IGS. In October 1998 KMS has established a permanent GPS station THU2 at Thule Airbase. Besides THU2 the old permanent station THU1 is also running. The Thule stations are important because they are two of the few northernmost stations in the IGS network. THU2 has been operating since March 1999, and it is now a high quality and high performance station contributing to the IGS Low-Earth Orbiters (LEO) network. Besides the GPS stations in Thule, KMS is also running a permanent GPS station SCOB in Scoresbysund, which was established in August 1997, and in October 2001 a permanent station QAQ1 was established in Qaqortoq. This station is registered at IGS. Furthermore, University of Colorado operates the IGS station Kellyville near Kangerlussuaq and a station in Kulusuk. Using the BERNESE software, we have calculated daily baseline solutions between the GPS sites. The time series of the 3D crustal movements are analyzed due to post glacial rebound, plate tectonic and seasonal deformations (e.g. atmosphere loading). In addition, we have used the GIPSY OASIS II software to obtain similar time series. The results are compared with modeled estimates of the glacial rebound.

  6. Hydrocarbon prospects offshore southern West Greenland

    SciTech Connect

    Chalmers, J.A.; Dahl-Jensen, T.; Bate, K.J.; Whittaker, R.C. )

    1996-01-01

    Interpretation of regional seismic data acquired in the 1990s together with a re-appraisal of the wells drilled in the 1970s has lead to an appreciation that the southern West Greenland Basin is underexplored and may contain large quantities of hydrocarbons. The regional structure and stratigraphy of the basin has been worked out. An early phase of extension, probably in the Early Cretaceous, was followed by a thermal subsidence phase in the Late Cretaceous during which thick mudstones were deposited. Renewed extension and strike-slip faulting associated with the onset of sea-floor spreading in the Labrador Sea in the Early Tertiary lead to the formation of large structures capable of trapping large quantities of hydrocarbons. Flat spots have been identified in several prospects in the Fylla Structural Complex, which is presently open for licensing, and other large structural traps exist on the Kang[cflx a]miut Ridge and in the Ikermiut area. Stratigraphic traps exist in a large syn-rift fan of mid-Cretaceous age and in Lower Tertiary basin-floor fans. All of these after structures are found in an area with an [open quotes]open-door[close quotes] licensing policy.

  7. Hydrocarbon prospects offshore southern West Greenland

    SciTech Connect

    Chalmers, J.A.; Dahl-Jensen, T.; Bate, K.J.; Whittaker, R.C.

    1996-12-31

    Interpretation of regional seismic data acquired in the 1990s together with a re-appraisal of the wells drilled in the 1970s has lead to an appreciation that the southern West Greenland Basin is underexplored and may contain large quantities of hydrocarbons. The regional structure and stratigraphy of the basin has been worked out. An early phase of extension, probably in the Early Cretaceous, was followed by a thermal subsidence phase in the Late Cretaceous during which thick mudstones were deposited. Renewed extension and strike-slip faulting associated with the onset of sea-floor spreading in the Labrador Sea in the Early Tertiary lead to the formation of large structures capable of trapping large quantities of hydrocarbons. Flat spots have been identified in several prospects in the Fylla Structural Complex, which is presently open for licensing, and other large structural traps exist on the Kang{cflx a}miut Ridge and in the Ikermiut area. Stratigraphic traps exist in a large syn-rift fan of mid-Cretaceous age and in Lower Tertiary basin-floor fans. All of these after structures are found in an area with an {open_quotes}open-door{close_quotes} licensing policy.

  8. 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

  9. Biology of the Greenland shark Somniosus microcephalus.

    PubMed

    MacNeil, M A; McMeans, B C; Hussey, N E; Vecsei, P; Svavarsson, J; Kovacs, K M; Lydersen, C; Treble, M A; Skomal, G B; Ramsey, M; Fisk, A T

    2012-04-01

    Greenland shark Somniosus microcephalus is a potentially important yet poorly studied cold-water species inhabiting the North Atlantic and Arctic Oceans. Broad-scale changes in the Arctic ecosystem as a consequence of climate change have led to increased attention on trophic dynamics and the role of potential apex predators such as S. microcephalus in the structure of Arctic marine food webs. Although Nordic and Inuit populations have caught S. microcephalus for centuries, the species is of limited commercial interest among modern industrial fisheries. Here, the limited historical information available on S. microcephalus occurrence and ecology is reviewed and new catch, biological and life-history information from the Arctic and North Atlantic Ocean region is provided. Given the considerable by-catch rates in high North Atlantic Ocean latitudes it is suggested that S. microcephalus is an abundant predator that plays an important, yet unrecognized, role in Arctic marine ecosystems. Slow growth and large pup sizes, however, may make S. microcephalus vulnerable to increased fishing pressure in a warming Arctic environment.

  10. Contaminants in two West Greenland caribou populations.

    PubMed

    Gamberg, Mary; Cuyler, Christine; Wang, Xiaowa

    2016-06-01

    Two caribou populations in West Greenland were sampled and the kidneys, liver and muscle analyzed for contaminants, including aluminum, arsenic, cadmium, copper, lead, mercury, selenium and zinc. Although close in proximity, the two populations are topographically separated by an ice cap, which creates different climates and vegetation types in each region. Contaminant levels reflected the differing diets of the two caribou populations. To the south in the wetter lichen-rich region, caribou had significantly more aluminum, arsenic, cadmium, lead, mercury, selenium and zinc, likely due to atmospheric deposition on lichens. To the north in the dry desert steppe where grasses predominate, caribou had higher levels of copper. Cows collected in late winter had significantly less hepatic copper, lead and mercury if pregnant, indicating placental transfer of these elements. Our results suggest that hepatic copper levels <200 μg g(-1) dry weight may result in copper depletion in pregnant cows and hepatic mercury concentrations above 0.5 μg g(-1) dry weight may negatively affect fertility in caribou cows. Hepatic mercury levels were negatively correlated with cow body weight, suggesting an adverse effect on body condition. Element concentrations found in tissues from these caribou are not considered to be of a health concern for those consuming this traditional food.

  11. The rare Chrysopidae (Neuroptera) of southwestern Europe

    NASA Astrophysics Data System (ADS)

    Canard, Michel; Letardi, Agostino; Thierry, Dominique

    2007-05-01

    Quantitative surveys of the chrysopid fauna from southwestern Europe, namely the Iberian and Italian peninsulas, France south of 46° N, and the west-Mediterranean Islands, were analysed. A total of 56 species of Chrysopidae were reported, of which three species were abundant. These, Chrysoperla carnea (Stephens, 1836) sensu lato, Dichochrysa prasina (Burmeister, 1839) and D. flavifrons (Brauer, 1850), comprised a large percentage of the specimens. For the rarer species, comments are made on their distributions, the enhanced geographic range of exotic ones, and on levels of endemism and stenotopy.

  12. 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.

  13. 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.

  14. 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. PMID:25061208

  15. Evidence for slab material under Greenland and links to Cretaceous High Arctic magmatism

    NASA Astrophysics Data System (ADS)

    Shephard, G. E.; Trønnes, R. G.; Spakman, W.; Panet, I.; Gaina, C.

    2016-04-01

    Understanding the evolution of extinct ocean basins through time and space demands the integration of surface kinematics and mantle dynamics. We explore the existence, origin, and implications of a proposed oceanic slab burial ground under Greenland through a comparison of seismic tomography, slab sinking rates, regional plate reconstructions, and satellite-derived gravity gradients. Our preferred interpretation stipulates that anomalous, fast seismic velocities at 1000-1600 km depth imaged in independent global tomographic models, coupled with gravity gradient perturbations, represent paleo-Arctic oceanic slabs that subducted in the Mesozoic. We suggest a novel connection between slab-related arc mantle and geochemical signatures in some of the tholeiitic and mildly alkaline magmas of the Cretaceous High Arctic Large Igneous Province in the Sverdrup Basin. However, continental crustal contributions are noted in these evolved basaltic rocks. The integration of independent, yet complementary, data sets provides insight into present-day mantle structure, magmatic events, and relict oceans.

  16. 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…

  17. 75 FR 52527 - Southwestern Power Administration; Notice of Filing

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-08-26

    .... 714, 73 FR 57515 (Oct. 3, 2008), FERC Stats. & Regs ] 31,276 (2008) (Order No. 714). \\2\\ 18 CFR 35.28... 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...

  18. 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...

  19. 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...

  20. 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...

  1. 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...

  2. 77 FR 3766 - Southwestern Gas Storage Technical Conference

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-01-25

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF ENERGY Federal Energy Regulatory Commission Southwestern Gas Storage Technical Conference Notice of Public Conference On... interested parties to discuss issues related to natural gas storage development in the southwestern...

  3. Gestational diabetes mellitus in Greenland: a national study of prevalence and testing efficacy

    PubMed Central

    Pedersen, Michael Lynge; Olesen, Jesper; Jørgensen, Marit Eika; Damm, Peter

    2016-01-01

    Background Within the last 20 years, the prevalence of gestational diabetes mellitus (GDM) has been reported to be increasing worldwide in correlation with ethnic and geographic variations. The actual prevalence of GDM throughout all of Greenland remains unknown. Objective The aim of this study was to estimate the prevalence of GDM among Greenlanders and non-Greenlanders living in Greenland and to estimate the efficacy of testing for GDM. Design This study was performed as an observational, cross-sectional study including all women with permanent address in Greenland who had given birth to a singleton during 2014. The prevalence of GDM was calculated as the proportion of all pregnant women tested with a 75-g 2-h glucose tolerance test who had a 2-h capillary whole-blood glucose value of 8.5 mmol/l or above. Testing efficacy was calculated as the proportion of women who fulfilled the testing criteria who were actually tested in Greenland in 2014. Results A total of 794 women (727 Greenlanders and 67 non-Greenlanders) were included in the study. The prevalence of GDM among tested women was 3.3% (confidence interval, CI: 0.9–5.6) among Greenlanders and 12.5% (CI: 0–25.7) among non-Greenlanders, corresponding, respectively, to 1.0% (CI: 0.3–1.3) and 4.5% (CI: 0–9.4) of all singleton pregnancies in Greenland in 2014. The overall testing efficacy was 69.0% among all eligible residents of Greenland and 85.1% among eligible residents in the capital city, Nuuk. Conclusion In conclusion, the prevalence of GDM seems quite low in Greenland. Although diagnostic testing activity has improved within the last 6 years, still around one-third of all pregnant women in all Greenland fulfilling the testing criteria were not tested. Universal testing for GDM may be needed to improve testing of GDM in Greenland. PMID:27562574

  4. 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

  5. Observation and modeling of surface ozone over Greenland

    SciTech Connect

    Kiilsholm, I.S.; Mikkelsen, I.S.; Rasmussen, A.; Sorensen, J.H.

    1996-12-31

    DMI initiated continuous measurements of surface ozone concentration in Greenland during spring 1994 as apart of the ARCTOC project (ARCtic Tropospheric Ozone Chemistry). The ARCTOC project is partially financed by EU, and is coordinated by the Institute for Environmental Physics, University of Heidelberg. The objectives are to investigate the mechanism causing sudden arctic tropospheric ozone loss, spatial extent and possible consequences of the phenomenon. The observation sites in Greenland are Thule (76{degrees} 31{prime} N, 68{degrees} 50{prime} W), Sondre Stromfjord (67{degrees} 00{prime} N, 50{degrees} 48{prime}W) and Scoresbysund (70{degrees} 29{prime}N, 21{degrees} 58{prime} W). The instruments are photometric ozone analyzers. Preliminary results show that the air parcels with low ozone values have spent four days or more in the boundary layer and have recently passed the strait between Canada and Greenland.

  6. 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.

  7. 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

    2014-09-01

    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. PMID:25190795

  8. 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

    2014-09-01

    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.

  9. Y-chromosome STR haplotypes in males from Greenland.

    PubMed

    Hallenberg, Charlotte; Tomas, Carmen; Simonsen, Bo; Morling, Niels

    2009-09-01

    A total of 272 males from Greenland were typed for 11 Y-chromosome STRs DYS19, DYS385a/b, DYS389-I, DYS389-II, DYS390, DYS391, DYS392, DYS393, DYS437, DYS438 and DYS439 with the PowerPlex Y System (Promega). A total of 146 different haplotypes were observed and the haplotype diversity was 0.9887. The number of haplotypes seen once was 108 and the most common haplotype was observed in 12 males. A significant F(ST) value was observed (F(ST)=0.012, P<0.00001) when comparing the population of 15 locations in Greenland assigned to 7 groups. The significance could mainly be attributed to the subpopulation of males from Tasiilaq (East of Greenland). The R(ST) value was not statistically significant (R(ST)=0.016, P=0.15). PMID:19647703

  10. Paleofluvial mega-canyon beneath the central Greenland ice sheet.

    PubMed

    Bamber, Jonathan L; Siegert, Martin J; Griggs, Jennifer A; Marshall, Shawn J; Spada, Giorgio

    2013-08-30

    Subglacial topography plays an important role in modulating the distribution and flow of basal water. Where topography predates ice sheet inception, it can also reveal insights into former tectonic and geomorphological processes. Although such associations are known in Antarctica, little consideration has been given to them in Greenland, partly because much of the ice sheet bed is thought to be relatively flat and smooth. Here, we present evidence from ice-penetrating radar data for a 750-km-long subglacial canyon in northern Greenland that is likely to have influenced basal water flow from the ice sheet interior to the margin. We suggest that the mega-canyon predates ice sheet inception and will have influenced basal hydrology in Greenland over past glacial cycles. PMID:23990558

  11. Paleofluvial mega-canyon beneath the central Greenland ice sheet.

    PubMed

    Bamber, Jonathan L; Siegert, Martin J; Griggs, Jennifer A; Marshall, Shawn J; Spada, Giorgio

    2013-08-30

    Subglacial topography plays an important role in modulating the distribution and flow of basal water. Where topography predates ice sheet inception, it can also reveal insights into former tectonic and geomorphological processes. Although such associations are known in Antarctica, little consideration has been given to them in Greenland, partly because much of the ice sheet bed is thought to be relatively flat and smooth. Here, we present evidence from ice-penetrating radar data for a 750-km-long subglacial canyon in northern Greenland that is likely to have influenced basal water flow from the ice sheet interior to the margin. We suggest that the mega-canyon predates ice sheet inception and will have influenced basal hydrology in Greenland over past glacial cycles.

  12. Technical Note: Semi-automated effective width extraction from time-lapse RGB imagery of a remote, braided Greenlandic river

    NASA Astrophysics Data System (ADS)

    Gleason, C. J.; Smith, L. C.; Finnegan, D. C.; LeWinter, A. L.; Pitcher, L. H.; Chu, V. W.

    2015-06-01

    River systems in remote environments are often challenging to monitor and understand where traditional gauging apparatus are difficult to install or where safety concerns prohibit field measurements. In such cases, remote sensing, especially terrestrial time-lapse imaging platforms, offer a means to better understand these fluvial systems. One such environment is found at the proglacial Isortoq River in southwestern Greenland, a river with a constantly shifting floodplain and remote Arctic location that make gauging and in situ measurements all but impossible. In order to derive relevant hydraulic parameters for this river, two true color (RGB) cameras were installed in July 2011, and these cameras collected over 10 000 half hourly time-lapse images of the river by September of 2012. Existing approaches for extracting hydraulic parameters from RGB imagery require manual or supervised classification of images into water and non-water areas, a task that was impractical for the volume of data in this study. As such, automated image filters were developed that removed images with environmental obstacles (e.g., shadows, sun glint, snow) from the processing stream. Further image filtering was accomplished via a novel automated histogram similarity filtering process. This similarity filtering allowed successful (mean accuracy 79.6 %) supervised classification of filtered images from training data collected from just 10 % of those images. Effective width, a hydraulic parameter highly correlated with discharge in braided rivers, was extracted from these classified images, producing a hydrograph proxy for the Isortoq River between 2011 and 2012. This hydrograph proxy shows agreement with historic flooding observed in other parts of Greenland in July 2012 and offers promise that the imaging platform and processing methodology presented here will be useful for future monitoring studies of remote rivers.

  13. Alcohol in Greenland 1951–2010: consumption, mortality, prices

    PubMed Central

    Aage, Hans

    2012-01-01

    Background Fluctuations in alcohol consumption in Greenland have been extreme since alcohol became available to the Greenland Inuit in the 1950s, increasing from low levels in the 1950s to very high levels in the 1980s – about twice as high as alcohol consumption in Denmark. Since then, consumption has declined, and current consumption is slightly below alcohol consumption in Denmark, while alcohol prices are far above Danish prices. Objective Description of historical trends and possible causal connections of alcohol prices, alcohol consumption and alcohol-related mortality in Greenland 1951–2010 as a background for the evaluation of the impact of various types of policy. Design Time series for Greenland 1951–2010 for alcohol prices, consumption and mortality are compiled, and variation and correlations are discussed in relation to various policies aimed at limiting alcohol consumption. Corresponding time series for Denmark 1906–2010 are presented for comparison. Results The trends in alcohol prices and consumption followed each other rather closely until the 1990s in Greenland and the 1980s in Denmark. At this time, consumption stabilised while prices decreased further, but the effect of prices upon consumption is strong, also in recent years. A trend in Greenlandic mortality similar to consumption is discernible, but not significant. Among alcohol-related deaths cirrhosis of the liver is less prevalent whilst accidents are more prevalent than in Denmark. Conclusions The effect of alcohol excise taxes and rationing upon consumption is evident. The stabilisation and subsequent decline in consumption since the mid-1990s, while alcohol prices decreased persistently, does not preclude continued effects of prices. On the contrary, price effects have been neutralised by other stronger causes. Whether these are government anti-alcohol campaigns or a cultural change is not clear. PMID:23256091

  14. Processes affecting the CO2 concentrations measured in Greenland ice

    NASA Astrophysics Data System (ADS)

    Anklin, Martin; Barnola, Jean-Marc; Schwander, Jakob; Stauffer, Bernhard; Raynaud, Dominique

    1995-09-01

    Detailed CO2 measurements on ice cores from Greenland and Antarctica show different mean CO2 concentrations for samples at the same gas age. The deviation between Antarctic and Greenland CO2 records raises up to 20 ppmv during the last millennium. Based on the present knowledge of the global carbon cycle we can exclude such a high mean interhemispheric difference of the CO2 concentration between high northern and southern latitudes. Diffusive mixing of the air in the firn smoothes out short term variations of the atmospheric CO2 Concentration. Nevertheless, we observe short term CO2 variations in Greenland ice in the range of 10 20 ppmv, which cannot represent atmospheric CO2 variations. Due to the low temperature at Summit, meltlayers can be excluded for most of the ice and they cannot account for the frequent anomalous short term CO2 variations and the elevated mean CO2 concentration in the Greenland ice. In this work we give some clues, that in situ production of CO2 in Greenland ice could build up excess CO2 after pore close of. Possible chemical reactions are the oxidation of organic carbon and the reaction between acidity and carbonate. We conclude that the carbonate-acidity reaction is the most probable process to explain the excess CO2 in the bubbles. The reaction could take place in very small liquid-like veins in cold ice, where the mobility of impurities is higher than in the ice lattice. At present, there exists no technique to measure the carbonate concentration in the ice directly. However, a comparison of CO2 analyses performed with a dry- and a wet-extraction technique allows to estimate the carbonate content of the ice. This estimate indicates a carbonate concentration in Greenland ice of about 0.4±0.2µmol/l and a much lower concentration in Antarctic ice.

  15. Acoustic mapping of the Ilulissat Ice Fjord mouth, West Greenland

    NASA Astrophysics Data System (ADS)

    Schumann, Kai; Völker, David; Weinrebe, Wilhelm R.

    2012-04-01

    A ship-based acoustic mapping campaign was conducted at the exit of Ilulissat Ice Fjord of West Greenland and in the sedimentary basin of Disko Bay west of the fjord mouth. Submarine landscape and sediment distribution patterns represented by five acoustic facies types represent glaciomarine sediment facies types that are related to variations in the past position and relative motion of the glacier front. Asymmetric ridges on the shelf that form a curved entity and a large sill at the fjord mouth represent moraines that depict at least two relatively stable positions of the ice front in the Disko Bay and at the fjord mouth. Comparable ice-end features are not observed seaward of the East Greenland Kangerdlugssuaq Glacier, although both glaciers are comparable in their latitudinal position, present size and present role for the ice discharge from the Inland Ice sheet. Apparently, the retreat of the Greenland Inland Ice after the last maximum expansion was a more discontinuous process on the West Greenland Shelf than on the East Greenland Shelf. The Iceberg Bank, a prominent sill at the fjord exit appears to play an important role for the sedimentation after the retreat of the ice front from the shelf was completed. The retreat of the glacier behind the Iceberg Bank into the inner fjord is marked by a reorganization of sediment delivery in Disko Bay, as most of the till is now deposited within the fjord. Two linear clusters of pockmarks in the center of the sedimentary basin seem to be linked to methane release due to dissociation of gas hydrates, a process driven by fast crustal uplift of the Greenland Shelf. The orientation of these clusters appears to reflect a migration path that is defined by a buried structure which we could not resolve.

  16. 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

  17. 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

  18. 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.

  19. 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.

  20. 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.

  1. 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

  2. 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

  3. Lithospheric flexure across an extremely stretched and detached transform margin: Example from the East Greenland Ridge and Greenland FZ in the Norwegian-Greenland Sea.

    NASA Astrophysics Data System (ADS)

    Døssing, A.; Watts, A. B.

    2009-04-01

    The 250 km long East Greenland Ridge (EGR) is located along the Greenland Fracture Zone (GFZ), which is part of a first-order plate tectonic feature in the Norwegian-Greenland Sea that formed when Eocene seafloor spreading was translated along the De Geer megashear region between Greenland and Svalbard to the Arctic Ocean. The EGR rises abruptly about 250 km west from the Mohns-Knipovich Ridge axis in Chron 13 (33.3 Ma) crust and continues to Chron 24 (54.4 Ma) crust. Results of recently acquired wide-angle and MCS seismic data have shown that the EGR and an adjacent faulted basin province to the north of the ridge represent a continental sliver detached from the incipient NE Greenland and SW Barents Sea margins. Crustal thicknesses were found to be around 10 km (Døssing et al., 2008). The EGR-GFZ tectonic setting can therefore be rendered as an extremely stretched transform margin. A strong asymmetry is observed across the GFZ going from south to north with (i) a long wave-length downwards deflection of the oceanic crust, (ii) a steep southern flank of the EGR reaching more than 4 km above the predicted lithospheric thermal contraction level, and (iii) a gentle northern flank of the ridge dipping towards the faulted basin province. Hence, the ridge resembles the characteristics of other anomalously shallow, FZ parallel, transverse ridges. We propose a model in which flexural response of the lithosphere to normal faulting is responsible for the formation of the ridge. Interpretations of three, ~250 km long, seismic profiles normal to the GFZ are used to model the across-strike basement geometry. The results indicate that the observed lithospheric flexure was formed due to ~20 km extension normal to the GFZ along low-angle faults. Ref: Døssing, A., T. Dahl-Jensen, H. Thybo, R. Mjelde, and Y. Nishimura (2008), East Greenland Ridge in the North Atlantic Ocean: An integrated geophysical study of a continental sliver in a boundary transform fault setting, J. Geophys

  4. 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

  5. Long offset seismic reflection data and the crustal structure of the NE Greenland Margin

    NASA Astrophysics Data System (ADS)

    Granath, J. W.; Whittaker, R. C.; Dinkelman, M. G.

    2011-12-01

    crust. The data show a 9 km thick sedimentary sequence in the southern parts of the DB and TB where the Danmarkshavn Ridge (DR) intervenes. Both basins are interpreted to include a thick Mesozoic section. Older Palaeozoic sediments are also thought to be present in the DB and subcrop along the DR, which forms a prominent structural high separating the two basins. Connections between the two basins around the DR to the north indicate at least Cretaceous if not older sediments occur in the TB. These new data have important implications for reconstructions of the plate relationships between Greenland and Eurasia and for the understanding of the role of the Mesozoic to Cenozoic intra-continental De Geer Megashear.

  6. Greenland Ice Sheet Surface Elevation at Summit, Greenland: 2007-2013

    NASA Astrophysics Data System (ADS)

    Lutz, E.; Hawley, R. L.; Herring, T.

    2013-12-01

    Quantifying surface elevation change is essential for ice sheet mass balance estimates. We assessed surface elevation and elevation change of the Greenland Ice Sheet at a range of spatial scales using six years of monthly GPS surveys conducted near Summit between 8/2007 and 3/2013. The ~11 km route consists of 15 transects that run parallel and orthogonal to IceSat's groundtrack 412 and includes 121 repeat locations spatially distributed along the route (Figure 1). Horizontal velocities and velocity gradients derived from base station and transect positions agree closely with previous studies. At the survey scale, no significant linear elevation trend is evident over the study period. However, local- and transect-scale time series revealed significant elevation increases of 1--2 cm per year in the central and southern regions of the survey that spatially and temporally may correlate with wind transport events from Summit station. This finding illustrates how sample scale (e.g., density, location and extent) affects surface elevation estimates critical to remote sensing validation and mass balance estimation. Spectral time series analysis showed that the expected annual elevation cycle was dwarfed by a two-year periodicity that dominated nearly all time series. The elevation maximum of Winter 2012-2013 fell short of the expected elevation peak, possibly due to accelerated compaction forced by high temperatures in the preceding Summer of 2012. We also highlight spatial comparisons with elevation products from three NASA altimeters, including the Airborne Topographic Mapper (ATM), the Land, Vegetation, and Ice Sensor (LVIS), and the Multiple Altimeter Beam Experiment Lidar (MABEL). This unique long-term GPS dataset is valuable for assessing ice sheet elevation change at a range of spatial-temporal scales, and for validating remote sensing products. With continued effort this survey will provide invaluable ground-based observations linking ICESat, IceBridge and ICESat

  7. Southwestern Power Administration site environmental report for calendar year 1993

    SciTech Connect

    Not Available

    1994-06-01

    During CY 93, Southwestern was not involved in any programs that had a direct effect on the environment, involving endangered species, protection of wetlands, or increased electromagnetic radiation. Southwestern continued to function throughout the year in an operations and maintenance posture with minor substation projects. Southwestern received an environmental management audit by the Department of Energy`s Office of Environmental Audit (EH-24), during CY 1992. The purpose of the audit was to give Southwestern, DOE headquarters, and the Secretary an indication of the status of Southwestern management`s effectiveness in discharging its duties in an environmentally responsible manner. The audit identified 17 findings. An action plan was developed and remediation of the findings has been accomplished. Several strengths were identified during the audit with regard to the environmental programs at Southwestern. Most importantly, senior management at Southwestern has taken actions to increase environmental awareness throughout the organization which is evidenced by the creation of the Environmental, Safety, Health, and Security Office.

  8. Lidar observations of the Pinatubo aerosol layer at Thule, Greenland

    SciTech Connect

    Di Girolamo, P.; Cacciani, M.; Sarra, A. di; Fiocco, G.; Fua, D. )

    1994-06-22

    This paper summarizes lidar measurements from Thule Greenland made during EASOE. The lidar was able to track aerosols, primarily of volcanic origin, through the winter. Above 18 km the aerosol content was strongly dependent upon the location of the vortex, and did not show a substantial increase until the vortex broke up.

  9. 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

  10. 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.

  11. The extreme melt across the Greenland ice sheet in 2012

    NASA Astrophysics Data System (ADS)

    Nghiem, S. V.; Hall, D. K.; Mote, T. L.; Tedesco, M.; Albert, M. R.; Keegan, K.; Shuman, C. A.; DiGirolamo, N. E.; Neumann, G.

    2012-10-01

    The discovery of the 2012 extreme melt event across almost the entire surface of the Greenland ice sheet is presented. Data from three different satellite sensors - including the Oceansat-2 scatterometer, the Moderate-resolution Imaging Spectroradiometer, and the Special Sensor Microwave Imager/Sounder - are combined to obtain composite melt maps, representing the most complete melt conditions detectable across the ice sheet. Satellite observations reveal that melt occurred at or near the surface of the Greenland ice sheet across 98.6% of its entire extent on 12 July 2012, including the usually cold polar areas at high altitudes like Summit in the dry snow facies of the ice sheet. This melt event coincided with an anomalous ridge of warm air that became stagnant over Greenland. As seen in melt occurrences from multiple ice core records at Summit reported in the published literature, such a melt event is rare with the last significant one occurring in 1889 and the next previous one around seven centuries earlier in the Medieval Warm Period. Given its rarity, the 2012 extreme melt across Greenland provides an exceptional opportunity for new studies in broad interdisciplinary geophysical research.

  12. Project CAP. Boston Mountains Educational Cooperative, Greenland, Arkansas.

    ERIC Educational Resources Information Center

    Hamilton, Jack A.; Leffler, Jeanne

    This description of career education activities in Greenland, Arkansas, was prepared as part of a study conducted to identify evaluated, exemplary career education activities which represent the best of the current career education programs and practices referred to in Public Law 93-380. (See CE 018 212 for the final report of this study.) This…

  13. Supporting an Externally Developed Model of Education in Greenland

    ERIC Educational Resources Information Center

    Wyatt, Tasha R.

    2010-01-01

    This study investigated the adaptation process of an externally developed model of reform in Greenland's educational system. Under investigation was how reform leaders responded to the needs of the community after implementing an educational model developed in the United States by researchers at the Center for Research on Education, Diversity, and…

  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. 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.

  16. Antarctic climate signature in the Greenland ice core record

    PubMed Central

    Barker, Stephen; Knorr, Gregor

    2007-01-01

    A numerical algorithm is applied to the Greenland Ice Sheet Project 2 (GISP2) dust record from Greenland to remove the abrupt changes in dust flux associated with the Dansgaard–Oeschger (D–O) oscillations of the last glacial period. The procedure is based on the assumption that the rapid changes in dust are associated with large-scale changes in atmospheric transport and implies that D–O oscillations (in terms of their atmospheric imprint) are more symmetric in form than can be inferred from Greenland temperature records. After removal of the abrupt shifts the residual, dejumped dust record is found to match Antarctic climate variability with a temporal lag of several hundred years. It is argued that such variability may reflect changes in the source region of Greenland dust (thought to be the deserts of eastern Asia). Other records from this region and more globally also reveal Antarctic-style variability and suggest that this signal is globally pervasive. This provides the potential basis for suggesting a more important role for gradual changes in triggering more abrupt transitions in the climate system. PMID:17954910

  17. 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.

  18. 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

    2013-12-01

    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 ~3.9 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.

  19. 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.

  20. Greenlandic Microbiomes and Greenhouse Gas Emissions

    NASA Astrophysics Data System (ADS)

    Jacobsen, C. S.; Nielsen, M. S.; Priemé, A.; Holben, W. E.; Stibal, M.; Morales, S.; Bælum, J.; Elberling, B.; Kuhry, P.; Hugelius, G.

    2014-12-01

    Thawing permafrost and the resulting mineralization of previously frozen organic carbon (C) and nitrogen (N) are considered important future feedbacks from terrestrial ecosystems to the atmosphere. We characterized two contrasting permafrost cores as well as 21 top permafrost cores from Zackenberg in High-Arctic Greenland which is a site characterized by progressive permafrost thawing of more than 1 cm y-1 since 1996. Samples have been analyzed for total C and N content, dissolved C and N as well as the potential production of carbon dioxide, methane and nitrous oxide in an incubation experiment. 10 days after the thawing was initiated, rRNA from selected samples were extracted, transformed into cDNA and cloned to obtain an overview of the most abundant active bacterial populations in the incubation experiment. A total of 697 clones were successfully sequenced, yielding 21 unique OTUs. Despite the relatively high coverage values the diversity of bacteria in the samples was low (with a maximum Shannon-Wiener diversity index of 2.1). Firmicutes (6 OTUs, 45-77% of clones) and Gammaproteobacteria (5 OTUs, 19-47% of clones) were the dominant groups in the samples, with Betaproteobacteria (4 OTUs), Actinobacteria (4 OTUs), Alphaproteobacteria (1 OTU) and Bacteroidetes (1 OTU) being less dominant. These characterizations revealed that those bacteria that are able to quickly colonize the thawing permafrost are mainly related to three groups of bacterial clones: Lysinibacillus; Pseudomonas and Clostridium. Quantification of functional genes related to soil nitrogen transformation were performed both on the DNA and on the mRNA level using primers specific for genes involved in production of nitrous oxide (nirS, nirK) and consumption of nitrous oxide (nosZ). This showed that the genes were found in most soils, but that they only were expressed at a low level. We further measured the rates of nitrous oxide release from the soils and found that these were not clearly related to

  1. Modeled variations of precipitation over the Greenland Ice Sheet

    SciTech Connect

    Bromwich, D.H.; Robasky, F.M.; Bolzan, J.F. ); Keen, R.A.

    1993-07-01

    A parameterization of the synoptic activity at 500 hPa and a simple orographic scheme are used to model the spatial and temporal variations of precipitation over the Greenland Ice Sheet for 1963-88 from information from the National Meteorological Center (NMC). Most major spatial characteristics of the observed accumulation distribution are reproduced. The modeled time-averaged total precipitation amount over Greenland is within the range of values determined by other investigators from surface-based observations. A downward trend in simulated ice sheet precipitation over the 26 years is found, supported by a number of lines of evidence. This negative precipitation trend would mean that the Greenland Ice Sheet, depending on its 1963 mass balance state, has over the 1963-88 period either decreased its negative, or increased its positive, contribution to recently observed global sea level rise. Superimposed on the declining simulated precipitation rate for the entire ice sheet is a pronounced 3-5-yr periodicity. This is prominent in the observed and modeled precipitation time series from Summit, Greenland. This cycle shows some aspects in common with the Southern Oscillation. Some deficiencies in the NMC analyses were highlighted by this work. A large jump in simulated precipitation amounts at Summit around 1962, which is not verified by accumulation data, is inferred to be due to an artificial increase in cyclonic activity at 500 hPa associated with the NMC change from manual to numerical analyses. The activity of the storm track along the west coast of Greenland appears to be anomalously low in the NMC analyses, perhaps due to mesoscale cyclogenesis that is not resolved by the NMC analysis scheme. 71 refs., 21 figs., 1 tab.

  2. 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

  3. Moho, LAB and crustal velocities underneath central-eastern Greenland

    NASA Astrophysics Data System (ADS)

    Kraft, H. A.; Thybo, H.

    2014-12-01

    Major parts of Greenland are covered with up to 3.4 km of ice. Due to logistical challenges connected to the ice only very sparse geophysical information is available. We present here results of the TopoGreenland project, which forms the first regional seismic experiment conducted on the Greenlandic ice shield. Our objective is to gain detailed information about the lithospheric structure and to connect it with topographic features, the recent substantial uplift and the earlier history of rifting and break-up in the region. We focus on a 200 km x 600 km large area in central-eastern Greenland, where 22 broadband seismometers were installed between June 2009 and May 2012. 10 of those were operating on the ice cap, 12 on bedrock. 16 of the stations were installed along a 600 km long profile at 70°N, from Scorsbysund to the centre of the ice cap. The remaining 6 stations covered a 200 km wide area north of this profile. In addition data from 6 permanent and long-term stations from the GLISN network were integrated. Here we present models from P- and S- receiver function (PRF, SRF) calculations and Rayleigh wave tomography. The RF calculations were used to map Moho and LAB depths and to have well constrained input parameters for the tomography. From the Rayleigh wave tomography we then obtain models for crustal shear-velocities. The PRF for the stations on the ice cap show multiples with very high amplitudes from within the ice, why we decided to derive Moho and LAB depths for those stations from SRF. The results will be compared with a seismic refraction profile acquired in the same region and then linked to topographic features like the uplift of the mountain chain in East Greenland.

  4. 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.

  5. Relation between the occurence of major glaciations of Antarctica and Greenland and the atmospheric CO2: a modelling approach

    NASA Astrophysics Data System (ADS)

    Bonelli, S.; Ramstein, G.; Donnadieu, Y.; Dumas, C.; Ritz, C.; Waldman, R.

    2009-12-01

    The main purpose of the studies presented here is to investigate the relationship between the occurrence of major glaciations of Antarctica and Greenland and the atmospheric CO_2 through modelling approach. We use a Climate Model of Intermediate Complexity^1 coupled with two ice sheet models GRISLI^2 for Antarctica ice sheet and GREMLINS^3 for Greenland. Our study focuses on the two extremities of Cenozoic(Palaeocene / Eocene glaciation of Antarctica 34My BP) and Pliocene (3My) glaciation of Greenland. Using such a tool enable to explore the different forcing factors (CO_2 , insolation, tectonics) and more interestingly to capture the CO2 threshold that corresponds to ice sheet build-up. Our results compare well with CO_2 reconstructions for instance from Pagani M., 2005^4 for Paleocene / Eocene and with Kürschner, W.^5 for glaciation of Greenland. Moreover, these results^6 are in good agreement with previous studies of Antarctica glaciation^7,8, and with the recent study of D. Lunt^9 for Greenland. Major finding is that CO_2 decrease is indeed the basic tempo for explaining ice sheet, but the real value of CO_2 which will trigger the onset of glaciation are deeply modulated by changes in paleogeography, tectonic, ocean dynamics and insolation. 1. Bonelli S., Charbit S., Kageyama M., Woillez M.N., Ramstein G., Dumas C., Quiquet A., 2009. Investigating the evolution of major Northern Hemisphere ice sheets during the last glacial-interglacial cycle.Clim. Past 5, 329-345 2. Ritz, C., Rommelaere, V., and Dumas, C.: Modeling the evolution of Antarctic ice sheet over the last 420,000 years: Implications for altitude changes in the Vostok region, J. Geophys. Res.-Atmos., 106(D23), 31943¿31964, 2001 3. Ritz, C., Fabre, A., and Letreguilly, A.: Sensitivity of a Greenland ice sheet model to ice flow and ablation parameters: consequences for the evolution through the last climatic cycle, Clim. Dynam., (13), 11¿24, 1997. 4. Pagani, M., J. C. Zachos, et al. (2005). "Marked

  6. 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.

  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. 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

  9. 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

  10. 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

  11. A Geomorphological Analysis of the Cenozoic Rejuvenation of the Southwestern Norwegian 'Passive' Margin

    NASA Astrophysics Data System (ADS)

    McDermott, Jeni; Redfield, Tim; Terje Osmundsen, Per; Arnhold, Chad; Conrad, Dan

    2015-04-01

    Although the Norwegian and Greenland rifted margins underwent Early Paleocene breakup, the southwestern Norwegian continental margin exhibits 2 to 3 km-high, sharply asymmetric seaward-facing escarpments and a 250+ km long topographic displacement gradient, a morphology not consistent with simple margin evolution models that predict subsidence and cooling as the dominate processes in tectonically-quiescent regions. Such atypical margins present a paradox: How is high, rugged topography along rifted margins maintained for tens to hundreds of millions of years after the cessation of extension? Recent work indicates the offshore crustal thinning gradient, a measure of the length from the continental escarpment to the location of the maximum crustal thickness, may play a controlling role: where the gradient is sharp the topography is most elevated; where gentle, the escarpments are lower. Although controversy remains, it is generally accepted, based on offshore geophysical data and onshore geomorphology, thermochronology, and structural geology, that the southwestern Norwegian escarpment has undergone topographic rejuvenation during the Cenozoic. Although several mechanistic models invoking various contributions of active tectonism have been proposed, from remnant topography recently carved by extensive glaciation to active uplift along large-scale onshore margin-parallel faults, the rejuvenating mechanism has not been resolved. Non-glacial components of rock column uplift may possibly be occurring today: tectonic control of major drainage patterns has been proposed and recent work in the Møre-Trøndelag Fault Complex provides compelling evidence for discrete fault-bound tectonic blocks with unique exhumation histories. We are seeking to constrain the primary mode of Cenozoic deformation along the western Norwegian continental rifted margin by utilizing a tiered approach with distinct but complementary techniques encompassing tectonic geomorphology, structural geology

  12. Greenland ice cores tell tales on the extent of the Greenland Ice Sheet during the warm climate Eemian period 130.000 - 115.000 years BP.

    NASA Astrophysics Data System (ADS)

    Dahl-Jensen, D.

    2012-12-01

    A new Greenland ice core has been drilled. The first results from the NEEM ice core are presented and then combined with the results from the other deep ice cores from the Greenland Ice Sheet. All the ice cores drilled though the Greenland ice sheets have been analyzed and the results show that all the ice cores contain ice from the last interglacial, the Eemian, near the base. Is it thus clear that the Greenland Ice Sheet did exist 124.000 years ago in the previous warm climate period where it was more than 5 deg C warmer over Greenland. The difference between the Eemian and the Holocene stable oxygen isotope values have been combined with an ice sheet flow model constrained by the ice core results and internal radio echo sounding layers to estimate the volume of the Greenland Ice Sheet 124.000 years ago. The results show that South Greenland has not been ice free during the Eemian period and that the sea level contribution from the Greenland Ice Sheet has been 2.0 +-0.5 m.

  13. 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

  14. Reconstructing thermal properties of firn at Summit, Greenland from a temperature profile

    NASA Astrophysics Data System (ADS)

    Giese, A. L.; Hawley, R. L.

    2013-12-01

    Thermodynamic properties of firn are important factors when considering energy balance and temperature-dependent physical processes in the near-surface of glaciers. Of particular interest is thermal diffusivity, which can take a range of values and which governs both the temperature gradient and its evolution through time. Given that temperature is a well-established driver of firn densification, a better understanding of heat transfer will permit greater accuracy in the compaction models essential for interpreting inter-annual and seasonal ice surface elevation changes detected by airborne and satellite altimetry. Due to its dependence on microstructure, diffusivity can vary significantly by location. Rather than directly measuring diffusivity or one of its proxies (e.g. density, hardness, shear strength), this study inverts the heat equation to reconstruct diffusivity values. This is a less logistically-intensive approach which circumvents many of the challenges associated with imperfect proxies and snow metamorphism during measurement. Hourly records (May 2004 - July 2008) from 8 thermistors placed in the top 10 m at Summit, Greenland provide temperature values for Summit's firn, which is broadly representative of firn across the ice sheet's dry snow zone. In this study, we use both physical analysis and a finite-difference numerical model to determine a diffusivity magnitude and gradient; we find that diffusivity of Summit firn falls in the lower end of the range expected from local density and temperature conditions alone (i.e. 15 - 36 m^2/a for firn at -30C). Further, we assess the utility of our modeling approach, explore the validity of assuming bulk conductive heat transfer when modeling temperature changes in non-homogeneous firn, and investigate the implications of a low-end diffusivity value for surface compaction modeling in Greenland.

  15. 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.

  16. 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.

  17. A new Munidopsis species (Galatheoidea, Munidopsidae) from the Southwestern Atlantic.

    PubMed

    Cardoso, Irene A; Serejo, Cristiana S; Rodrigues, Celso

    2014-01-01

    Six Munidopsis species are recorded to the Southwestern Atlantic: M. barbarae; M. erinacea; M. nitida; M. sigsbei; M. riveroi and M. transtridens. Herein a new Munidopsis species from Southwestern Atlantic is described: Munidopsis trindadensis sp.nov., was sampled off Trindade Island (Espírito Santo, Brazil) at 360 m depth and differs from all six species previously recorded in this region by the telson with seven plates.

  18. 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

  19. Natural variability of Greenland climate, vegetation, and ice volume during the past million years.

    PubMed

    de Vernal, Anne; Hillaire-Marcel, Claude

    2008-06-20

    The response of the Greenland ice sheet to global warming is a source of concern notably because of its potential contribution to changes in the sea level. We demonstrated the natural vulnerability of the ice sheet by using pollen records from marine sediment off southwest Greenland that indicate important changes of the vegetation in Greenland over the past million years. The vegetation that developed over southern Greenland during the last interglacial period is consistent with model experiments, suggesting a reduced volume of the Greenland ice sheet. Abundant spruce pollen indicates that boreal coniferous forest developed some 400,000 years ago during the "warm" interval of marine isotope stage 11, providing a time frame for the development and decline of boreal ecosystems over a nearly ice-free Greenland. PMID:18566284

  20. 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

  1. A new frontier province offshore northwest Greenland: Structure, basin development, and petroleum potential of the Melville Bay area

    SciTech Connect

    Whittaker, R.C.; Hamann, N.E.

    1997-06-01

    In the Melville Bay area, offshore northwest Greenland, very large structures and sedimentary basins, which were predicted many years ago on the basis of magnetic and gravity data, have been confirmed by a recent reconnaissance seismic survey, with implications that are encouraging for petroleum exploration in the area. The Melville Bay area flanks a small ocean basin in Baffin Bay that is thought to have formed by oblique sea-floor spreading in the Eocene. There are two major, coast-parallel basins in the area. The inner basin, the Melville Bay Graben, is essentially a half graben with a maximum thickness of sediments exceeding 13 km. A complex fault-controlled ridge system separates this basin from the outer Kivioq Basin in which up to 7 km of sediments have accumulated. By analogy with onshore geology in the surrounding areas and well data from the continental shelves off southern west Greenland and Labrador to the south, it is expected that the first phase of rifting and sedimentation took place in the Early-middle Cretaceous, while a second phase of rifting took place in the latest Cretaceous and early Paleocene. Later, compression and inversion affected the northern part of the area, leading to the formation of large anticlinal structures. The existence of large tilted fault blocks and inversion anticlines provides grounds for anticipating the presence of large structural traps. Synrift sandstones and deeper water fans are expected to provide potential reservoirs, and correlatives of oil-prone source rocks known from the lower part of the upper Cenomanian-lower Maastrichtian Kanguk Formation in the Canadian Arctic may also have oil source properties in the Melville Bay area. Recent discoveries of live oil in the uppermost Cretaceous and lower Tertiary of onshore central west Greenland provide proof that oil has been generated in the region.

  2. 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.

  3. 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

  4. 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

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. Paleocene sequence stratigraphy of southwestern Alabama

    SciTech Connect

    Mancini, E.A.; Tew, B.H.

    1988-09-01

    In southwestern Alabama, the Paleocene consists of about 1300 ft (396 m) of marginal marine and marine terrigenous and carbonate sediments. Based on regional stratigraphic, sedimentologic, and paleontologic data, up to seven unconformity-bounded depositional sequences resulting from relative changes in coastal onlap during the Paleocene are recognized in these strata. These sequences are, in ascending order, the TP1.1a, comprised of the Pine Barren Member of the Clayton Formation; the TP1.1b, comprised of the Turritella rock beds of the Pine Barren and the McBryde Limestone Member of the Clayton Formation, and the clays and marls of the lower member of the Porters Creek Formation; the TP1.2, comprised of the cross-bedded sands of the lower member and the Matthews Landing Marl Member of the Porters Creek Formation, and Oak Hill Member of the Naheola Formation; the TP1.3, comprised of the Coal Bluff Marl Member of the Naheola Formation; the TP2.1, comprised of the Gravel Creek Sand, Ostrea thirsae beds, and Grampian Hills Members of the Nanafalia Formation, and the lower beds of the Tuscahoma Sand; the TP2.2, comprised of the Greggs Landing Marl Member and the middle beds of the Tuscahoma Sand; and the TP2.3, comprised of the Bells Landing Marl Member and the upper beds of the Tuscahoma Sand.

  10. 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.

  11. The Changing Albedo of the Greenland Ice Sheet

    NASA Astrophysics Data System (ADS)

    Human, J. M.; Box, J. E.

    2009-12-01

    The study evaluates Greenland ice sheet surface albedo sensitivity to surface melt intensity, air pollution, and precipitation using data from the MODIS and MOPITT sensors operating on the NASA Terra satellite 2000-2009. Precipitation rates are simulated by the Polar WRF climate model running in data assimilation mode. Statistical regression facilitates ranking the relative importance of each of the albedo forcings in space and time. Further, quantitative estimates of the albedo sensitivity to its forcing factors are made, for the first time and over the observed inter-annual range. The work investigates regional patterns in detail to quantify melt water production associated with absorbed solar radiation variability. In-situ records are used to evaluate the cloud radiative effect as another important factor of absorbed solar radiation and ice melt. Insight into Greenland ice sheet melt-precipitation-pollution-albedo feedback is gained, key in better understanding the mass balance response of the ice sheet to future climate change.

  12. A Comparison of Geoid Undulations for West Central Greenland

    NASA Technical Reports Server (NTRS)

    Roman, Daniel R.; Csatho, Beata; Jezek, Kenneth C.; Thomas, Robert H.; Krabill, William B.; vonFrese, Ralph R. B.; Forsberg, Rene

    1997-01-01

    The accuracy of a new local gravity field model, GEOID94A, is examined at a site on the western Greenland ice sheet. The model, developed by the Danish National Survey and Cadastre, incorporates several new gravity data sets including an extensive amount of airborne gravity data. Model-derived geoid undulations were compared to independently determined undulations found by differencing the elevations from Global Positioning System controlled airborne laser altimetry and optical leveling surveys. Differences between the two sets of undulations were less than +/- 6 cm RMS. The comparison improved (+/- 5 cm RMS) when GEOID94A undulations were adjusted by local gravity observations also acquired at the site. Our comparisons demonstrate that GEOID94A adequately models the long to intermediate wavelengths of the gravity field. We conclude that GEOID94A constitutes a reliable reference model for studies of Greenland's gravity field.

  13. Conditioning instabilities of the Greenland Sea. Master's thesis

    SciTech Connect

    Olson, J.M.

    1992-09-01

    This is an examination of the open ocean deep water formation process of the Greenland Sea and how it is effected by the depth dependent thermal expansion coefficient. It is hypothesized that free convection associated with parcel instability is possible because of the increase in the thermal expansion coefficient with pressure in conjunction with requisite ambient temperature and salinity profiles. Based on the depth dependence of the thermal expansion coefficient, a neutral profile model for parcel instability was formulated and the effects on mixed layer dynamics were investigated. in situ profiles for the wintertime Greenland Sea were examined for potential parcel instabilities. It was shown that only small surface salinity increases associated with freezing could lead to deep penetrative convection. Finally, an analysis was performed for regions of low stability using climatology from the Levitus data set to determine regions most likely for deep convection.

  14. Greenland precipitation estimates from the atmospheric moisture budget

    SciTech Connect

    Robasky, F.M.; Bromwich, D.H.

    1994-11-15

    Eight radiosonde stations surrounding Greenland at an average separation of 750 km are used to compute the atmospheric moisture budget. Radiosonde data were available from 1963-89, but were not used for 1963-79 due to insufficient data coverage which likely resulted in a major underestimation of large moisture inflow events. There is a mean annual inflow of moisture to the atmospheric volume over Greenland through its southeast and southwest sectors, and outflow to the northeast. Moisture convergences, equivalent to precipitation minus evaporation, yield an areal average of 32 cm yr{sup {minus}1} of water equivalent; they also show high inter- and intra-annual agreement with earlier modeled precipitation estimates found by the authors and serve as further confirmation of their modeling results. The time-averaged eddy component accounts for 90% of the total moisture convergence, reflecting the dominant contribution of precipitation from synoptic-scale cyclones. 20 refs., 5 figs.

  15. RadarSAT And Snow Characteristics At Greenland Summit

    NASA Astrophysics Data System (ADS)

    Manninen, Terhikki; Lahtinen, Panu; Anttila, Kati; Riihela, Aku

    2013-12-01

    The RASCALS (Radiation, Snow Characteristics and Albedo at Summit) campaign [1] was carried out at the Greenland Summit camp research station during June - July 2010. The collection of surface roughness, dielectric constant and density profiles of snow were carried out concurrently with snow albedo and bidirectional reflectance distribution function (BRDF) measurements. Polarimetric interferometry of Radarsat-2 quad pol fine beam images is used to study the snow surface anisotropy at Summit, Greenland. Various methods of determining the polarimetric coherence are tested and the results are compared with the in situ surface roughness results, which show a clear anisotropy varying with time. In addition, surface backscattering modelling is used to check the fraction of the surface backscattering.

  16. 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.

  17. Past temperatures directly from the greenland ice sheet

    PubMed

    Dahl-Jensen; Mosegaard; Gundestrup; Clow; Johnsen; Hansen; Balling

    1998-10-01

    A Monte Carlo inverse method has been used on the temperature profiles measured down through the Greenland Ice Core Project (GRIP) borehole, at the summit of the Greenland Ice Sheet, and the Dye 3 borehole 865 kilometers farther south. The result is a 50, 000-year-long temperature history at GRIP and a 7000-year history at Dye 3. The Last Glacial Maximum, the Climatic Optimum, the Medieval Warmth, the Little Ice Age, and a warm period at 1930 A.D. are resolved from the GRIP reconstruction with the amplitudes -23 kelvin, +2.5 kelvin, +1 kelvin, -1 kelvin, and +0.5 kelvin, respectively. The Dye 3 temperature is similar to the GRIP history but has an amplitude 1.5 times larger, indicating higher climatic variability there. The calculated terrestrial heat flow density from the GRIP inversion is 51.3 milliwatts per square meter. PMID:9765146

  18. Paleofluvial landscape inheritance for Jakobshavn Isbræ catchment, Greenland

    NASA Astrophysics Data System (ADS)

    Cooper, M. A.; Michaelides, K.; Siegert, M. J.; Bamber, J. L.

    2016-06-01

    Subglacial topography exerts strong controls on glacier dynamics, influencing the orientation and velocity of ice flow, as well as modulating the distribution of basal waters and sediment. Bed geometry can also provide a long-term record of geomorphic processes, allowing insight into landscape evolution, the origin of which may predate ice sheet inception. Here we present evidence from ice-penetrating radar data for a large dendritic drainage network, radiating inland from Jakobshavn Isbræ, Greenland's largest outlet glacier. The size of the drainage basin is ˜450,000 km2 and accounts for about 20% of the total land area of Greenland. Topographic and basin morphometric analyses of an isostatically uplifted (ice-free) bedrock topography suggests that this catchment predates ice sheet initiation and has likely been instrumental in controlling the location and form of the Jakobshavn ice stream, and ice flow from the deep interior to the margin, now and over several glacial cycles.

  19. 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.

  20. Micrometeorite pre-solar diamonds from Greenland cryoconite?

    NASA Technical Reports Server (NTRS)

    Yates, P. D.

    1993-01-01

    An acid-resistant residue prepared from Greenland cryoconite has been investigated to determine whether the micrometeorite component within the cryoconite contains pre-solar material analogous to that found in primitive chondritic meteorites. The residue has been analyzed for carbon content and stable isotopic comparison, by electron probe micro-analysis (EPMA) for major element chemistry and then by a combination of X-ray diffraction (XRD) and transmission electron microscopy (TEM) to elucidate the structure of any constituent mineral phases. The cryoconite sample, which was collected ca. 25 km inland of the ice margin at the latitude of Sondre Stromfjord on the west coast of Greenland, was processed following procedures used on bulk meteorite samples for the isolation of pre-solar dust components.

  1. Black carbon concentration in a Greenland Dye-3 ice core

    SciTech Connect

    Chylek, P.; Johnson, B.; Wu, Hong )

    1992-10-01

    We have determined the black carbon concentration in Greenland Dye-3 ice core samples covering the time period from about 3380 to 100 years before present. The average concentration found is 1.53 microg of black carbon per 1 kg of ice. We have found significantly lower black carbon concentrations during the time period from 750 to 100 years before present connected possibly with the Little Ice Age and corresponding changes in atmospheric general circulation patterns and black carbon sources. 18 refs.

  2. The East Greenland Coastal Current: Structure, variability, and forcing

    NASA Astrophysics Data System (ADS)

    Sutherland, David A.; Pickart, Robert S.

    2008-07-01

    The subtidal circulation of the southeast Greenland shelf is described using a set of high-resolution hydrographic and velocity transects occupied in summer 2004. The main feature is the East Greenland Coastal Current (EGCC), a low-salinity, high-velocity jet with a wedge-shaped hydrographic structure characteristic of other surface buoyancy-driven currents. The EGCC was observed along the entire Greenland shelf south of Denmark Strait, while the transect north of the strait showed only a weak shelf flow. This observation, in conjunction with water mass considerations and other supporting evidence, suggests that the EGCC is an inner branch of the East Greenland Current (EGC) that forms south of Denmark Strait. It is argued that bathymetric steering is the most likely reason why the EGC apparently bifurcates at this location. Repeat sections occupied at Cape Farewell between 1997 and 2004 show that the alongshelf wind stress can have an influence on the structure and strength of the EGCC and EGC on timescales of 2-3 days. Accounting for the wind-induced effects, the volume transport of the combined EGCC/EGC system is roughly constant (∼2 Sv) over the study domain, from 68°N to Cape Farewell near 60°N. The corresponding freshwater transport increases by roughly 60% over this distance (59-96 mSv, referenced to a salinity of 34.8). This trend is consistent with a simple freshwater budget of the EGCC/EGC system that accounts for meltwater runoff, melting sea-ice and icebergs, and net precipitation minus evaporation.

  3. 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.

  4. 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.

  5. 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.

  6. Pre-LGM ice dynamics of the Greenland Ice Sheet in Uummannaq Fjord West Greenland, revealed by blockfields, tors and till mantled surfaces

    NASA Astrophysics Data System (ADS)

    Rea, Brice; Roberts, David; Lane, Tim; Rhodés, Angel; Schnabel, Christoph

    2013-04-01

    The future response of the Greenland Ice Sheet has been the focus of much recent modelling work but in order to fully understand the dynamics of this ice mass it is also imperative that the past behaviour of the ice sheet is understood. Indeed it is only through successful hindcasts of past ice geometries and dynamics that confidence in predictions can be achieved. In most glaciated environments determining ice dynamics prior to the Last Glacial Maximum (LGM) and subsequent deglaciation are non-trivial. They rely on fortuitous preservation, more restricted ice cover at LGM than previously or protective cold based ice cover. Here results are presented from hypsometric surfaces in the Uummannaq Fjord region of West Greenland which can provide constrains on the dynamics of ice cover prior to and including the LGM. Uummanaq Fjord is a classic landscape of selective linear erosion containing deeply incised troughs juxtaposed with high elevation plateau where relief approaches 3 km in places. Excavations were made in a number of summit blockfields with samples collected. Results from a morphometric landscape analyses a presented, using both landscape hypsometry and an elevation-range slope-map approach to identify hypsometric surfaces. The hypsometric surfaces are divided into those which are now denuded and classified as regions of areal scour, those with a blockfield cover and areas which are still ice covered. A number of sites have been visited and excavations were made into blockfields. Data are presented indicating minimum depths, granulometry and mineralogy of blockfields which allowed a further subdivision into allochthonous and autochotonous blockfields. Samples were also collected for cosmogenic nuclide exposure analyses and indicate that blockfield boulders and tors exhibit ages extending significantly beyond the LGM. Based on equilibrium profile reconstructions of the LGM ice sheet (constrained by onshore and offshore geomorphology and cosmogenic and 14C ages

  7. Inferring ammonium and sulfate aerosol concentrations using laser particle counters and condensation nuclei counters at summit, Greenland

    SciTech Connect

    Kuhns, H.; Davidson, C.; Bergin, M.

    1995-12-31

    Atmospheric measurements have been conducted in central Greenland over the last 10 years in connection with ice core research. While the primary objective of this research is to facilitate the quantitative interpretation of ice cores, interesting findings are being made in the field of Arctic air chemistry. In recent years, aerosol filters were run simultaneously with laser particle counters (LPC`s) and condensation nuclei counters (CNC`s). The LPC`s used in the this study count particles with diameters greater than 0.5 {mu}m, while the CNC`s count particles larger than approximately 0.01 {mu}m. Results from summertime aerosol sampling at Summit, Greenland are presented from the 1994 field season. Excellent agreement is observed between LPC data and particulate ammonium and sulfate. The correlation between ammonium and LPC data is r=0.88. Of all of the ionic species measured on the filters, the CNC results are in best agreement with MSA. The correlation for CNC and MSA is r=0.58. The relationship between the real-time particle sensor data and the aerosol chemistry has significant implications. The link between MSA and CNC supports the theory that marine biological activity enhances the production of cloud condensation nuclei. Also, this technique shows promise for remote sensing applications since once calibrated, the real time particle count data could be used to infer high temporal resolution aerosol chemistry.

  8. 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. PMID:25101837

  9. 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.

  10. 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

  11. Large fluctuations in speed on Greenland's Jakobshavn Isbrae glacier.

    PubMed

    Joughin, Ian; Abdalati, Waleed; Fahnestock, Mark

    2004-12-01

    It is important to understand recent changes in the velocity of Greenland glaciers because the mass balance of the Greenland Ice Sheet is partly determined by the flow rates of these outlets. Jakobshavn Isbrae is Greenland's largest outlet glacier, draining about 6.5 per cent of the ice-sheet area, and it has been surveyed repeatedly since 1991 (ref. 2). Here we use remote sensing data to measure the velocity of Jakobshavn Isbrae between 1992 and 2003. We detect large variability of the velocity over time, including a slowing down from 6,700 m yr(-1) in 1985 to 5,700 m yr(-1) in 1992, and a subsequent speeding up to 9,400 m yr(-1) by 2000 and 12,600 m yr(-1) in 2003. These changes are consistent with earlier evidence for thickening of the glacier in the early 1990s and rapid thinning thereafter. Our observations indicate that fast-flowing glaciers can significantly alter ice discharge at sub-decadal timescales, with at least a potential to respond rapidly to a changing climate. PMID:15577906

  12. 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

  13. Coastal Greenland air temperature extremes 1890-2010

    NASA Astrophysics Data System (ADS)

    Mernild, Sebastian H.; Hanna, Edward; Cappelen, John

    2013-04-01

    We use observed air temperature data series from fourteen meteorological stations in coastal Greenland (located all around the Greenland Ice Sheet (GrIS)) for 1960-2010, where long-term records for five of the stations extend back to 1890, to illustrate the annual and monthly temporal and spatial distribution of temperature extremes. We find that the 2000s (2001-2010) had the highest number of mean annual air temperature (MAAT) warm extremes, and the 1890s (1891-1900) the highest number of cold extremes. For the 2000s the number of warm extremes was significantly higher by around 50% than the number in the 1940s (the Early Twentieth Century Warm Period): the decade with the second highest occurrence of MAAT warm extremes. Since 1960, based on MAAT the number of cold extremes has decreased on the decadal timescale, while warm extremes have increased leading to a higher occurrence of extremes (cold plus warm extremes): an almost similar pattern occurred on mean monthly and on monthly mean daily maximum and minimum scales. Further, a division of Greenland into east and west sectors shows that the occurrence of cold (warm) extremes was more pronounced in the East than in the West in the 1960s and 1970s (mid-1980s to the 2000s).

  14. Continental ice in Greenland during the Eocene and Oligocene

    NASA Astrophysics Data System (ADS)

    Eldrett, James S.; Harding, Ian C.; Wilson, Paul A.; Butler, Emily; Roberts, Andrew P.

    2007-03-01

    The Eocene and Oligocene epochs (~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 30million 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 20million years earlier than previously documented, at a time when temperatures and atmospheric carbon dioxide concentrations were substantially higher.

  15. Factors Controlling Methane in Arctic Lakes of Southwest Greenland.

    PubMed

    Northington, Robert M; Saros, Jasmine E

    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.

  16. Unexpected Melt at Summit, Greenland: Its Potential Legacy

    NASA Astrophysics Data System (ADS)

    Albert, M. R.

    2012-12-01

    Summit, Greenland is a high altitude cold site where snow on the ice sheet rarely melts; it was the site where the GISP2 ice core was drilled almost two decades ago. In July 2012, unusual meteorological events caused the surface snow at Summit to experience a very rare true melt event. The melt period was short-lived, and subfreezing temperatures soon turned the melt into an ice layer. Modern satellite-born sensing technologies provided the first opportunity to witness and confirm that indeed the melt was very widespread over most of the surface of the Greenland Ice Sheet. Many tens of meters beneath the firn surface at Summit is the next significantly thick ice layer, dating to 1889; this layer also has been identified at a number of other sites in Greenland. The 2012 melt at Summit provided an unusual opportunity to investigate the way in which the melt alters the properties of the snow at this site. Measurements of the nature of the melt at Summit in 2012 and its impact on stratigraphy, density, permeability, and grain size are presented. Insights from the observations we made in July 2012 and comparisons with characteristics of the 1889 ice layer from Summit are employed in a description of the potential impacts of refrozen melt layers on polar snow and firn processes in the dry snow zones of ice sheets. The potential legacy that the 2012 ice layer may imprint on future ice core records is discussed.

  17. First Characterization of Avian Influenza Viruses from Greenland 2014.

    PubMed

    Hartby, Christina Marie; Krog, Jesper Schak; Merkel, Flemming; Holm, Elisabeth; Larsen, Lars Erik; Hjulsager, Charlotte Kristiane

    2016-05-01

    In late February 2014, unusually high numbers of wild thick-billed murres (Uria lomvia) were found dead on the coast of South Greenland. To investigate the cause of death, 45 birds were submitted for laboratory examination in Denmark. Avian influenza viruses (AIVs) with subtypes H11N2 and low pathogenic H5N1 were detected in some of the birds. Characterization of the viruses by full genome sequencing revealed that all the gene segments belonged to the North American lineage of AIVs. The seemingly sparse and mixed subtype occurrence of low pathogenic AIVs in these birds, in addition to the emaciated appearance of the birds, suggests that the murre die-off was due to malnutrition as a result of sparse food availability or inclement weather. Here we present the first characterization of AIVs isolated in Greenland, and our results support the idea that wild birds in Greenland may be involved in the movement of AIV between North America and Europe.

  18. 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.

  19. Factors Controlling Methane in Arctic Lakes of Southwest Greenland.

    PubMed

    Northington, Robert M; Saros, Jasmine E

    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

  20. 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

  1. Tributyltin accumulation and effects in marine molluscs from West Greenland.

    PubMed

    Strand, Jakob; Asmund, Gert

    2003-01-01

    The levels of the antifouling agent tributyltin (TBT) and its breakdown products in bivalves were investigated in 1999-2000 at six areas along the west coast of Greenland with focus on locations inside and outside harbours. In addition female gastropods were examined for the development of TBT-induced masculine characteristics in form of imposex or intersex. The highest TBT concentration, 254 ng x g(-1) ww, was found in the bivalve Mytilus edulis sampled inside Nuuk harbour, but significant TBT concentrations were also present in bivalves from the other harbour areas. Only low levels of TBT were detected in bivalves sampled outside the harbours and in several of the samples the TBT level was below the detection limit. The examination of neogastropods like Buccinum revealed that imposex development occurred in all the harbours. In contrast, imposex was not found in any neogastropods sampled outside the harbour areas. However, the value of marine neogastropods as indicators of TBT contamination in West Greenland seems limited, because of large species diversity and the difficulties in sampling enough specimens at least with the current sampling strategy. No effects, which could be related to TBT contamination, were found in the most abundant tidal gastropod in West Greenland, Littorina saxatilis.

  2. Continental ice in Greenland during the Eocene and Oligocene.

    PubMed

    Eldrett, James S; Harding, Ian C; Wilson, Paul A; Butler, Emily; Roberts, Andrew P

    2007-03-01

    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.

  3. 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.

  4. Arctic coastal zone mapping: Evolution of sedimentary coasts in Greenland

    NASA Astrophysics Data System (ADS)

    Bendixen, M.; Kroon, A.

    2015-12-01

    Climate change threatens many of the coastal areas all over the world. In the Arctic, the warming happens at a rate which is three times faster than the global average increasing the pressure on the coast. Arctic coasts differ from coasts in lower latitude in terms of the natural conditions prevailing, i.e. sea-ice, permafrost, and thermal erosion. These factors are likely to change with an increasing temperature, and thereby the erodibility of the shores and the erosivity of the coastal processes are changing. The majority of studies on arctic coasts focus on tundra coasts. Here, there is a general increase of coastal erosion rates over the last decades. However, the arctic coastal areas of Greenland differ; they are often close to hard rock protrusions and are characterized by large differences in geomorphology, erodibility of sediments, and erosivity by coastal processes. Sedimentary coasts in Greenland are only sporadically investigated, and it is thus difficult to predict the impact of climate changes in these areas. With this work we focus on sedimentary coasts in Greenland and present shoreline analysis of two sedimentary coastal sites. We show how the position of the shoreline has changed since the 1930'ies and we address the responsible factors controlling this evolution. The hotspots of coastal change are all located near delta mouths and the detected changes are coupled to dominating process occurring here.

  5. 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.

  6. Greenland supraglacial rivers and the extreme 2012 melt season

    NASA Astrophysics Data System (ADS)

    Smith, L. C.; Rennermalm, A. K.; Legleiter, C. J.; Behar, A. E.; Chu, V. W.; Forster, R. R.; Gleason, C. J.; Moustafa, S.; Overstreet, B. T.; Pitcher, L. H.; Tedesco, M.; Yang, K.

    2012-12-01

    July 2012 was an extreme melt period for the Greenland ice sheet, affecting up to ~97% of its surface and producing severe proglacial flooding and destruction of an important bridge at Kangerlussuaq. This presentation summarizes collaborative, multi-institutional research to study the production, storages and fluxes of Greenland ice sheet meltwater in supraglacial streams, rivers and lakes that form on the ice surface and emerge as proglacial braided rivers downstream at its edge. The 2012 field season focused on supraglacial river hydraulics, with unprecedented measurements of flow velocity, bathymetric depth, surface slope, hydraulic roughness coefficient, and water-column optical attenuation and spectral characteristics, acquired using telemetered river drifters, Acoustic Doppler Current Profiler (ADCP), an unmanned drone boat, and traditional field surveys. Field sites span ~520 to 1600 m elevation and range from the ice terminus up to ~85 km into the ice sheet interior. These new datasets are especially valuable for scale-up and calibration of remotely sensed observations owing to targeted acquisitions of WorldView-2 and ASTER visible/NIR satellite imagery made contemporaneously with the field measurements. Preliminary analysis indicates that Greenland supraglacial rivers represent major, high-flux pathways for meltwater transport, with flow velocities and hydraulic characteristics quite extraordinary as compared with terrestrial rivers.

  7. Evidence of Meltwater Retention within the Greenland Ice Sheet

    NASA Astrophysics Data System (ADS)

    Rennermalm, A. K.; Smith, L. C.; Chu, V. W.; Box, J. E.; Forster, R. R.; van den Broeke, M. R.

    2012-12-01

    Greenland ice sheet water release, and the magnitude of sub- and englacial storage, firn densification, internal refreezing and other hydrologic processes that delay or reduce true water export to the global ocean remain poorly understood. This problem is compounded by scant hydrometerological measurements. Here, ice sheet surface meltwater runoff and proglacial river discharge determined between 2008 and 2010 for three sites near Kangerlussuaq, western Greenland were used to establish the water budget for a small ice sheet watershed. The water budget could not be closed in the three years, even when uncertainty ranges were considered. Instead, between 12% and 53% of ice sheet surface runoff is retained within the catchment each melt year (time between onset of ice sheet runoff in two consecutive years) most likely in en- and subglacial storages. Evidence suggests that while some holdover summer meltwater may escape during the cold-season, this water volume is too small to close the budget. Thus, this study indicates that the Greenland ice sheet cryo-hydrologic system may remain active year round, and that meltwater may be retained in the pro glacial area, internally, or in firn layers for prolonged time periods before release to the ocean.

  8. 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.

  9. 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

  10. 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.

  11. 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.

  12. 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

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

    NASA Astrophysics Data System (ADS)

    Buizert, C.; Gkinis, V.; Severinghaus, J. P.; He, F.; Lecavalier, B.; Kindler, P.; Leuenberger, M.; Carlson, A. E.; Vinther, B.; White, J. W.; Liu, Z.; Otto-Bliesner, B. L.; Brook, E.

    2013-12-01

    Much of the regional and global climate variability during the last glacial termination (19-11 ka BP) can be explained as the superposition of two distinct modes (1, 2); a spatially uniform increase in global temperature correlated with greenhouse gas forcing, and a redistribution of heat associated with variability in the Atlantic meridional overturning circulation (AMOC) strength. The latter mode is expressed most clearly in the abrupt climate shifts recorded in the precipitation isotopic composition (δ18O) of Greenland ice cores, which are now widely used as a template for abrupt change in the northern hemisphere. Greenland δ18O is influenced by many factors, including source temperature, moisture transport and origin, and precipitation seasonality, complicating reconstruction of past temperatures. Here we use three non-δ18O temperature reconstructions from three ice cores and a general circulation model (GCM) to elucidate the (often abrupt) Greenland surface temperature response to external (insolation) and internal (CO2, AMOC, ice topography) climate forcings during the last termination. Our reconstructions are based on δ15N (NEEM, GISP2) and water isotope diffusion (NGRIP), both of which depend on physical processes in the firn column. The GCM and our reconstructions show excellent agreement on several key features. First, we find that the Younger Dryas (YD) period was 4-6oC warmer than the Oldest Dryas (OD) period in response to increased summer insolation and CO2 forcing. By contrast, δ18O-based reconstrucions from Greenland summit suggest the YD to be the colder of the two periods. Our finding is consistent with non-ice core NH proxy reconstructions, as well as with East Greenland deglacial moraine sequences that suggest only a modest glacial re-advance during the YD. Second, the YD-OD temperature difference shows a polar amplification signal, with warming being greatest at the northernmost NEEM site. By isolating different forcings in the GCM, we

  14. 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

  15. 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

  16. Earlier onset of the spring fine dust season in the southwestern United States

    NASA Astrophysics Data System (ADS)

    Hand, J. L.; White, W. H.; Gebhart, K. A.; Hyslop, N. P.; Gill, T. E.; Schichtel, B. A.

    2016-04-01

    Particulate matter (PM)2.5 dust concentrations (mineral particles with aerodynamic diameters less than 2.5 µm) typically peak in spring and early summer at rural and remote sites across the southwestern United States. Trend analyses indicate that springtime regional mean PM2.5 dust concentrations have increased from 1995 to 2014, especially in March (5.4% yr-1, p < 0.01). This increase reflects an earlier onset of the spring dust season across the Southwest by 1 to 2 weeks over the 20 year time period. March dust concentrations were strongly correlated with the Pacific Decadal Oscillation index (r = -0.65, p < 0.01), which was mostly in its negative phase from 2007 to 2014, during which the region was drier, windier, and less vegetated. The positive spring trend and its association with large-scale climate variability have several important implications for visibility, particulate matter, health effects, and the hydrologic cycle in the region.

  17. 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. PMID:26056897

  18. 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.

  19. 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

  20. 78 FR 46332 - Golden Spread Electric Cooperative, Inc. v. Southwestern Public Service Company; Notice of Complaint

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-07-31

    ... Energy Regulatory Commission Golden Spread Electric Cooperative, Inc. v. Southwestern Public Service.... (Golden Spread or Complainant) filed a formal complaint against Southwestern Public Service Company (SPS... Energy Open Access Tariff applicable to pricing of transmission service over the facilities of...

  1. 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.

  2. 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.

  3. Aspects of Development of the Greenland School Seen in Relation to Changed Social Conditions.

    ERIC Educational Resources Information Center

    Berthelsen, Christian

    1981-01-01

    This translation from the "Yearbook of Danish School History" is a report on the changes in Greenland's educational system resulting from economic development and political changes. Special attention is devoted to the problem of converting from the Greenland language to Danish. (AM)

  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. 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…

  6. 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

  7. 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

  8. 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.

  9. 40 CFR 81.125 - Southwestern Oklahoma 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 Oklahoma Intrastate Air... 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...

  10. 40 CFR 81.125 - Southwestern Oklahoma 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 Oklahoma Intrastate Air... 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...

  11. 40 CFR 81.125 - Southwestern Oklahoma 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 Oklahoma Intrastate Air... 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...

  12. 40 CFR 81.125 - Southwestern Oklahoma 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 Oklahoma Intrastate Air... 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...

  13. 40 CFR 81.125 - Southwestern Oklahoma 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 Oklahoma Intrastate Air... 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...

  14. 75 FR 70616 - Prevailing Rate Systems; Redefinition of the Madison, WI, and Southwestern Wisconsin Appropriated...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-11-18

    ... areas. The proposed rule would redefine Adams and Waushara Counties, WI, from the Southwestern Wisconsin... would redefine Adams and Waushara Counties, WI, from the Southwestern Wisconsin wage area to the Madison... industrial establishments. Adams County is currently defined to the Southwestern Wisconsin area...

  15. 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...

  16. 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...

  17. 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...

  18. 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...

  19. 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...

  20. 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.

  1. 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.

  2. 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

  3. Comparison of 2013 and 2012 Greenland Ice Sheet Surface Melt and Associated Mechanisms

    NASA Astrophysics Data System (ADS)

    Chen, Zhiqiang; Liu, Jiping

    2016-04-01

    We examine the characteristics of the Greenland Ice Sheet surface melt in summer 2013 and compare the results with 2012. The atmospheric dynamic and thermodynamic differences between these two cases and their impacts on the Greenland Ice Sheet surface melt are also examined. Results show that the maximum surface melt extent is only 44% in 2013, which is far less than 97% in 2012. The averaged extent and duration of the surface melt in 2013 are close to the climatology. The summer atmospheric circulation anomalies in 2013 are nearly opposite to those observed in 2012. Greenland and the surrounding areas show anomalously low pressure, particularly a negative height at 500-hPa, which leads to a more zonal pattern than that in 2012. The corresponding anomalous cyclonic circulation in the north and south areas of Greenland is favorable for advecting cold Arctic air to Greenland. Moreover, the surface downward radiation pattern in 2013 is oriented in a southwest-northeast direction over Greenland, which differs from the north-south distribution in 2012. The net downward radiation is small due to the cancellation of downward shortwave and longwave components in 2013. However, downward shortwave dominates from the distribution perspective, leading to an insignificant impact on surface temperatures over Greenland. The combination of dynamic effects of atmospheric circulation and thermodynamic effects of the radiation budget contribute to the surface melt of the Greenland Ice Sheet. We further find that a positive feedback between the variability in the extent of summer Arctic sea ice and melt area of the summer Greenland ice sheet, which affects the Greenland ice sheet mass balance.

  4. 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

  5. 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.

  6. 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.

  7. 2011 the first complete glacier inventory for Eastern Greenland

    NASA Astrophysics Data System (ADS)

    Rastner, P.; Bolch, T.; Paul, F.

    2011-12-01

    Meltwater from glaciers and icecaps (GIC) provide a significant contribution to global sea-level rise, but estimates are uncertain due to the globally still incomplete information about glacier location and size, as well as large uncertainties in current Global Climate Models (GCMs). Recent studies that calculate global sea-level rise from GIC have developed simplified approaches using information from glacier inventories or gridded data sets and different GCMs. 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 data is expressed. The GIC on Greenland are one of these regions. Within the "EU-funded" project ice2sea we map the Eastern part of Greenland using Landsat ETM imagery acquired around the year 2000 and the ASTER GDEM to derive topographic parameters and drainage divides. Up to now more than 5500 GIC with a total area of about 26.000 square km have been mapped between 62 degrees and 80 degrees N considering only glaciers with an area larger than 0.1 square km that have no direct connection to the ice sheet. The largest valley glaciers are often debris covered, whereas smaller and mountain glaciers are often shaded due to the steep topography. Seasonal snow hiding the real glacier perimeter is a problem in some of the scenes that can only be solved by using scenes with better snow conditions. The artifacts in the GDEM are locally rather severe, but for the GIC considered for this inventory they were manageable. A comparison with the outline of the Greenland ice sheet as used in current models revealed that along the eastern coast a considerable amount of the local GIC is included in the extent of the ice sheet.

  8. Pre-breakup age of East Greenland Ridge strata

    NASA Astrophysics Data System (ADS)

    Nielsen, Tove; Bjerager, Morten; Lindström, Sofie; Nøhr-Hansen, Henrik; Lander Rasmussen, Tine

    2014-05-01

    The East Greenland Ridge (EGR) is a submarine elevation that juts out from the Northeast Greenland shelf, separating the modern Boreas Basin in north from the Greenland Basin in south. The EGR strikes roughly northwest-southeast and lies almost perpendicular to the Mohns Spreading Ridge and sub-parallel to the Knipovich Spreading Ridge. The EGR is about 320 km long and includes several en-echelon elongated crests. The flanks on either side of the EGR are generally high and steep, with escarpments exposing outcropping sub-strata. The EGR has been characterized as a continental sliver. However, this is based on analysis of seismic data only, while no direct evidence has hitherto been published to strengthen this interpretation. In 2012, two up-slope transects on the northeastern lower flank of the EGR were dredged by GEUS and UiT in order to obtain in-situ samples of the outcropping strata. Subsequent work by GEUS on the dredged samples was concentrated on lithological description and age determination of selected rock samples. The selected samples were either fresh and angular, or too soft to have survived long transport, and therefore interpreted to be in-situ or near in-situ (local and limited transported) and representative for the geology of the EGR. Some rock samples of greenish grey, slightly sandy mudstones were dated by palynological analysis to be of Late Triassic (Carnian) age, i.e. to pre-date the onset of seafloor spreading in this part of the Northeast Atlantic Ocean by more than 150 ma years. Notably, no basalts were dredged, which further supports the interpretation that the strata overlying the basement of the EGR is composed of pre-breakup sediments, and thus strengthen the characterization of the EGR as a continental sliver.

  9. Holocene climate changes in southern Greenland: evidence from lake sediments

    NASA Astrophysics Data System (ADS)

    Andresen, Camilla S.; Björck, Svante; Bennike, Ole; Bond, Gerard

    2004-12-01

    A Holocene lake sediment record is presented from Lake N14 situated on Angissoq Island 15 km off the main coast of southern Greenland. The palaeoclimatic development has been interpreted on the basis of flux and percentage content of biogenic silica, clastic material, organic material and sulphur as well as sedimentation rate, moss content and magnetic susceptibility. A total of 43 radiocarbon dates has ensured a reliable chronology. It is argued that varying sediment composition mainly reflects changing precipitation. By analogy with the present meteorological conditions in southern Greenland, Holocene climate development is inferred. Between 11 550 and 9300 cal. yr BP temperature and precipitation increase markedly, but this period is climatically unstable. From 9300 yr BP conditions become more stable and a Holocene climatic optimum, characterised by warm and humid conditions, is observed from 8000 to 5000 cal. yr BP. From 4700 cal. yr BP the first signs of a climatic deterioration are observed, and from 3700 cal. yr BP the climate has become more dry and cold. Superimposed on the climatic long-term trend is climate variability on a centennial time-scale that increases in amplitude after 3700 cal. yrBP. A climatic scenario related to the strength and position of the Greenland high-pressure cell and the Iceland low-pressure cell is proposed to explain the Holocene centennial climate variability. A comparison of the Lake N14 record with a terrestrial as well as a marine record from the eastern North Atlantic Ocean suggests that the centennial climate variability was uniform over large areas at certain times. Copyright

  10. The peopling of Greenland: further insights from the analysis of genetic diversity using autosomal and X-chromosomal markers.

    PubMed

    Pereira, Vania; Tomas, Carmen; Sanchez, Juan J; Syndercombe-Court, Denise; Amorim, António; Gusmão, Leonor; Prata, Maria João; Morling, Niels

    2015-02-01

    The peopling of Greenland has a complex history shaped by population migrations, isolation and genetic drift. The Greenlanders present a genetic heritage with components of European and Inuit groups; previous studies using uniparentally inherited markers in Greenlanders have reported evidence of a sex-biased, admixed genetic background. This work further explores the genetics of the Greenlanders by analysing autosomal and X-chromosomal data to obtain deeper insights into the factors that shaped the genetic diversity in Greenlanders. Fourteen Greenlandic subsamples from multiple geographical settlements were compared to assess the level of genetic substructure in the Greenlandic population. The results showed low levels of genetic diversity in all sets of the genetic markers studied, together with an increased number of X-chromosomal loci in linkage disequilibrium in relation to the Danish population. In the broader context of worldwide populations, Greenlanders are remarkably different from most populations, but they are genetically closer to some Inuit groups from Alaska. Admixture analyses identified an Inuit component in the Greenlandic population of approximately 80%. The sub-populations of Ammassalik and Nanortalik are the least diverse, presenting the lowest levels of European admixture. Isolation-by-distance analyses showed that only 16% of the genetic substructure of Greenlanders is most likely to be explained by geographic barriers. We suggest that genetic drift and a differentiated settlement history around the island explain most of the genetic substructure of the population in Greenland.

  11. 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.

  12. Improving Estimates of Cloud Radiative Forcing over Greenland

    NASA Astrophysics Data System (ADS)

    Wang, W.; Zender, C. S.

    2014-12-01

    Multiple driving mechanisms conspire to increase melt extent and extreme melt events frequency in the Arctic: changing heat transport, shortwave radiation (SW), and longwave radiation (LW). Cloud Radiative Forcing (CRF) of Greenland's surface is amplified by a dry atmosphere and by albedo feedback, making its contribution to surface melt even more variable in time and space. Unfortunately accurate cloud observations and thus CRF estimates are hindered by Greenland's remoteness, harsh conditions, and low contrast between surface and cloud reflectance. In this study, cloud observations from satellites and reanalyses are ingested into and evaluated within a column radiative transfer model. An improved CRF dataset is obtained by correcting systematic discrepancies derived from sensitivity experiments. First, we compare the surface radiation budgets from the Column Radiation Model (CRM) driven by different cloud datasets, with surface observations from Greenland Climate Network (GC-Net). In clear skies, CRM-estimated surface radiation driven by water vapor profiles from both AIRS and MODIS during May-Sept 2010-2012 are similar, stable, and reliable. For example, although AIRS water vapor path exceeds MODIS by 1.4 kg/m2 on a daily average, the overall absolute difference in downwelling SW is < 4 W/m2. CRM estimates are within 20 W/m2 range of GC-Net downwelling SW. After calibrating CRM in clear skies, the remaining differences between CRM and observed surface radiation are primarily attributable to differences in cloud observations. We estimate CRF using cloud products from MODIS and from MERRA. The SW radiative forcing of thin clouds is mainly controlled by cloud water path (CWP). As CWP increases from near 0 to 200 g/m2, the net surface SW drops from over 100 W/m2 to 30 W/m2 almost linearly, beyond which it becomes relatively insensitive to CWP. The LW is dominated by cloud height. For clouds at all altitudes, the lower the clouds, the greater the LW forcing. By

  13. Modeling ice front Dynamics of Greenland outlet glaciers using ISSM

    NASA Astrophysics Data System (ADS)

    Morlighem, M.; Bondzio, J. H.; Seroussi, H. L.; Rignot, E. J.

    2015-12-01

    The recent increase in the rate of mass loss from the Greenland Ice Sheet is primarily due to the acceleration and thinning of outlet glaciers along the coast. This acceleration is a dynamic response to the retreat of calving fronts, which leads to a loss in resistive stresses. These processes need to be included in ice sheet models in order to be able to accurately reproduce current trends in mass loss, and in the long term reduce the uncertainty in the contribution of ice sheets to sea level rise. Today, the vast majority of ice sheet models that include moving boundaries are one dimensional flow line and vertical flow band models, that are not adapted to the complex geometries of Greenland outlet glaciers, as they do not accurately capture changes in lateral stresses. Here, we use the level set method to track moving boundaries within a 2D plane view model of the Ice Sheet System Model (ISSM), and investigate the sensitivity of Store Glacier, in western Greenland, to the amount of melting occurring at its calving front. We explore different calving laws and obtain the best results with a new simple calving law adapted from von Mises yield criterion. We show that the ocean circulation near the front and the amount of runoff are able to trigger ice front advance and retreat depending on the amount of melting that they produce at the calving face, but the bed topography controls the stable positions of the ice front. The modeled calving front of Store Glacier, for which we have quality bed topography and sea floor bathymetry data, is particularly stable because of the presence of a large sill at the glacier terminus. If the ice front detaches from this stabilizing sill due to larger amounts of melting at the front or due to large calving events, the glacier front starts to retreat as the bed deepens inland, until it finds another stabilizing feature in the bed topography. The new bed topography maps based on mass conservation make it possible to model more

  14. Rapid changes in ice discharge from Greenland outlet glaciers.

    PubMed

    Howat, Ian M; Joughin, Ian; Scambos, Ted A

    2007-03-16

    Using satellite-derived surface elevation and velocity data, we found major short-term variations in recent ice discharge and mass loss at two of Greenland's largest outlet glaciers. Their combined rate of mass loss doubled in less than a year in 2004 and then decreased in 2006 to near the previous rates, likely as a result of fast re-equilibration of calving-front geometry after retreat. Total mass loss is a fraction of concurrent gravity-derived estimates, pointing to an alternative source of loss and the need for high-resolution observations of outlet dynamics and glacier geometry for sea-level rise predictions.

  15. Airborne ICESat-2 simulator (MABEL) results from Greenland

    NASA Astrophysics Data System (ADS)

    Neumann, T.; Markus, T.; Brunt, K. M.; Walsh, K.; Hancock, D.; Cook, W. B.; Brenner, A. C.; Csatho, B. M.; De Marco, E.

    2012-12-01

    The Ice, Cloud, and land Elevation Satellite-2 (ICESat-2) is a next-generation laser altimeter designed to continue key observations of sea ice freeboard, ice sheet elevation change, vegetation canopy height, earth surface elevation and sea surface heights. Scheduled for launch in mid-2016, ICESat-2 will collect data between 88 degrees north and south using a high-repetition rate (10 kHz) laser operating at 532nm, and using a photon-counting detection strategy. Our airborne simulator, the Multiple Altimeter Beam Experimental Lidar (MABEL) uses a similar photon-counting measurement strategy, operates at 532nm (16 beams) and 1064 nm (8 beams) to collect similar data to what we expect for ICESat-2. The comparison between frequencies allows for studies of possible penetration of green light into water or snow. MABEL collects more spatially-dense data than ICESat-2 (2cm along-track vs. 70 cm along track for ICESat-2, and has a smaller footprint than ICESat-2 (2m nominal diameter vs. 10m nominal diameter for ICESat-2) requiring geometric and radiometric scaling to relate MABEL data to simulate ICESat-2 data. We based MABEL out of Keflavik, Iceland during April 2012, and collected ~ 100 hours of data from 20km altitude over a variety of targets. MABEL collected sea ice data over the Nares Strait, and off the east coast of Greenland, the later flight in coordination with NASA's Operation IceBridge, which collected ATM data along the same track within 90 minutes of MABEL data collection. MABEL flew a variety of lines over Greenland in the southwest, Jakobshavn region, and over the ice sheet interior, including 4 hours of coincident data with Operation IceBridge in southwest Greenland. MABEL flew a number of calibration sites, including corner cubes in Svalbard, Summit Station (where a GPS survey of the surface elevation was collected within an hour of our overflight), and well-surveyed targets in Iceland and western Greenland. In this presentation, we present an overview of

  16. 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.

  17. 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.

  18. 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.

  19. 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.…

  20. 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

  1. 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...

  2. 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

  3. 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…

  4. Paleozoic vertical movements in Um Bogma area, southwestern Sinai

    SciTech Connect

    Beyth, M.

    1981-01-01

    The Wadi Khaboba-Gebel Nukhul high, in the Um Bogma area of southwestern Sinai, underwent a small-scale uplift-subsidence cycle during the Paleozoic. The trend of this structure is close to and almost parallel with the Suez rift, indicating that the young rift is related to older structures.

  5. Sphaeroma terebrans: A Threat to the Mangroves of Southwestern Florida.

    PubMed

    Rehm, A; Humm, H J

    1973-10-12

    Sphaeroma terebrans, a wood-boring isopod, is destroying the prop roots of red mangroves along the southwestern coast of Florida to such an extent that the Ten Thousand Islands and mangrove fringes of the mainland are steadily shrinking. Mangroves of the Florida Keys apparently are free of this wood borer.

  6. 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.

  7. 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

  8. 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

  9. 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

  10. 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.

  11. Observational data from the Programme for Monitoring of the Greenland Ice Sheet (PROMICE)

    NASA Astrophysics Data System (ADS)

    Andersen, S. B.; Ahlstrom, A. P.; Andersen, M. L.; Box, J. E.; Citterio, M.; Fausto, R. S.; van As, D.; Forsberg, R.; Skourup, H.; Sandberg, L.; Kristensen, S. S.; Petersen, D.

    2013-12-01

    Climate change in the Arctic has resulted in accelerated mass loss from the Greenland Ice Sheet. The shortage of observations on the Greenland ice sheet infers large uncertainties in estimates of the ice mass loss and in predicting the contribution to sea level rise. For this reason the Programme for Monitoring of the Greenland Ice Sheet (PROMICE) was established in 2007. The aim of the programme is to quantify the mass loss of the Greenland ice sheet and track changes in the extent of the glaciers, ice caps and ice sheet margin. Within PROMICE data sets from several activities are collected. These include: A network of currently 19 automatic weather stations on the margin of the Greenland ice sheet measuring ice ablation and snow fall as well as meteorological parameters. Airborne surveys, yielding surface elevation and ice depth along the entire margin of the Greenland ice sheet. Mapping of all Greenland ice masses, based on the highest detail aero-photogrammetric maps produced from mid-80's aerial photographs. Real-time data from the PROMICE automatic weather station network is shown in at the PROMICE web site www.promice.org and the data is freely available for download. Data from the airborne surveys and mapping activities will also become freely available. Data from PROMICE also contribute to the website www.polarportal.org which is a new Danish web site for providing updated information on the arctic cryosphere to the public.

  12. 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.

  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. 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

  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. Uncovering the genetic history of the present-day Greenlandic population.

    PubMed

    Moltke, Ida; Fumagalli, Matteo; Korneliussen, Thorfinn S; Crawford, Jacob E; Bjerregaard, Peter; Jørgensen, Marit E; Grarup, Niels; Gulløv, Hans Christian; Linneberg, Allan; Pedersen, Oluf; Hansen, Torben; Nielsen, Rasmus; Albrechtsen, Anders

    2015-01-01

    Because of past limitations in samples and genotyping technologies, important questions about the history of the present-day Greenlandic population remain unanswered. In an effort to answer these questions and in general investigate the genetic history of the Greenlandic population, we analyzed ∼200,000 SNPs from more than 10% of the adult Greenlandic population (n = 4,674). We found that recent gene flow from Europe has had a substantial impact on the population: more than 80% of the Greenlanders have some European ancestry (on average ∼25% of their genome). However, we also found that the amount of recent European gene flow varies across Greenland and is far smaller in the more historically isolated areas in the north and east and in the small villages in the south. Furthermore, we found that there is substantial population structure in the Inuit genetic component of the Greenlanders and that individuals from the east, west, and north can be distinguished from each other. Moreover, the genetic differences in the Inuit ancestry are consistent with a single colonization wave of the island from north to west to south to east. Although it has been speculated that there has been historical admixture between the Norse Vikings who lived in Greenland for a limited period ∼600-1,000 years ago and the Inuit, we found no evidence supporting this hypothesis. Similarly, we found no evidence supporting a previously hypothesized admixture event between the Inuit in East Greenland and the Dorset people, who lived in Greenland before the Inuit.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. Surface mass balance of Greenland mountain glaciers and ice caps

    NASA Astrophysics Data System (ADS)

    Benson, R. J.; Box, J. E.; Bromwich, D. H.; Wahr, J. M.

    2009-12-01

    Mountain glaciers and ice caps contribute roughly half of eustatic sea-level rise. Greenland has thousands of small mountain glaciers and several ice caps > 1000 sq. km that have not been included in previous mass balance calculations. To include small glaciers and ice caps in our study, we use Polar WRF, a next-generation regional climate data assimilation model is run at grid resolution less than 10 km. WRF provides surface mass balance data at sufficiently high resolution to resolve not only the narrow ice sheet ablation zone, but provides information useful in downscaling melt and accumulation rates on mountain glaciers and ice caps. In this study, we refine Polar WRF to simulate a realistic surface energy budget. Surface melting is calculated in-line from surface energy budget closure. Blowing snow sublimation is computed in-line. Melt water re-freeze is calculated using a revised scheme. Our results are compared with NASA's Gravity Recovery and Climate Experiment (GRACE) and associated error is calculated on a regional and local scale with validation from automated weather stations (AWS), snow pits and ice core data from various regions along the Greenland ice sheet.

  4. Greenland ice sheet melt from MODIS and associated atmospheric variability

    PubMed Central

    Häkkinen, Sirpa; Hall, Dorothy K; Shuman, Christopher A; Worthen, Denise L; DiGirolamo, Nicolo E

    2014-01-01

    Daily June-July melt fraction variations over the Greenland ice sheet (GIS) derived from the Moderate Resolution Imaging Spectroradiometer (MODIS) (2000–2013) are associated with atmospheric blocking forming an omega-shape ridge over the GIS at 500 hPa height. Blocking activity with a range of time scales, from synoptic waves breaking poleward (<5 days) to full-fledged blocks (≥5 days), brings warm subtropical air masses over the GIS controlling daily surface temperatures and melt. The temperature anomaly of these subtropical air mass intrusions is also important for melting. Based on the years with the greatest melt (2002 and 2012) during the MODIS era, the area-average temperature anomaly of 2 standard deviations above the 14 year June-July mean results in a melt fraction of 40% or more. Though the summer of 2007 had the most blocking days, atmospheric temperature anomalies were too small to instigate extreme melting. Key Points Short-term atmospheric blocking over Greenland contributes to melt episodes Associated temperature anomalies are equally important for the melt Duration and strength of blocking events contribute to surface melt intensity PMID:25821277

  5. Hydraulic geometry of Greenland Ice Sheet supraglacial streams

    NASA Astrophysics Data System (ADS)

    Chu, V. W.; Smith, L. C.; Rennermalm, A. K.; Forster, R. R.; Gleason, C. J.; Pitcher, L. H.; Moustafa, S.; Overstreet, B. T.; Legleiter, C. J.; Behar, A. E.; Tedesco, M.; Yang, K.

    2012-12-01

    Increasing surface melting on the Greenland ice sheet and rising sea level have heightened the need for understanding the complex pathways transporting meltwater from the ice sheet surface to the ice edge and the ocean. Supraglacial streams are abundant throughout the ablation zone, transporting large volumes of meltwater into moulins and the ice edge, yet these streams remain poorly studied. Here we present a study of supraglacial stream hydraulics and geometry in the ablation zone of western Greenland during summer 2012. We measured flow width, depth, velocity, and water surface slope at different elevations and stream network types at five locations in a 70 km transect spanning the ice edge at 500 m to 1420 m elevation. This transect includes two highly sampled catchments in very different environments, one at 500 m and one at 875 m elevation. Our data show that stream width is correlated with width-depth ratios, providing possibilities for extrapolating depths from high-resolution satellite imagery. Furthermore, we explore using average stream velocities and thalweg depths to determine discharge and provide confidence intervals to these calculations by utilizing over 30 full cross-sectional profiles of flow width, depth, velocity, and discharge. These relationships may be useful for scaling up to larger supraglacial rivers and estimating ablation zone meltwater fluxes at other ice sheet locations using high-resolution satellite imagery.

  6. Elevation Change of the Southern Greenland Ice Sheet: Update

    NASA Technical Reports Server (NTRS)

    Davis, C. H.; Kluever, C. A.; Haines, B. J.

    1999-01-01

    The overall focus of our research is to document long-term elevation change of the Greenland ice sheet using satellite altimeter data. In addition, we are investigating seasonal and interannual variations in the ice-sheet elevations to place the long-term measurements in context. Specific objectives of this research include: 1) Developing new techniques to significantly improve the accuracy of elevation-change estimates derived from satellite altimetry. 2) Measuring the elevation change of the Greenland ice sheet over a 10-year time period using Seasat (1978) and Geosat GM (1985-86) and Geosat ERM (1986-88) altimeter data. 3) Quantifying seasonal/interannual variations in the elevation-change estimates using the continuous time series of surface elevations from the Geosat GM and ERM datasets. 4) Extending the long-term elevation change analysis to two decades by incorporating data from the ERS-1/2 missions (1991-99) and, if available, the Geosat-Follow On (GFO) mission (1998-??).

  7. Thresholds for Greenland Ice Sheet Variability on Orbital and Longer Timescales

    NASA Astrophysics Data System (ADS)

    Koenig, S. J.; Deconto, R.; Pollard, D.

    2009-12-01

    Significant built-up of ice caps on Greenland and beyond is believed to have begun in the Pliocene (5.33 - 2.58Ma). The ice sheet has likely been highly dynamic, and paced by Milankovitch orbital parameters. In addition to orbital forcing, (declining) atmospheric carbon dioxide concentrations (pCO2 [ppmv]) has been noted for playing a crucial role in the onset of glaciations in both hemispheres. On the other hand, internal forcings and feedbacks, related to surface characteristics can affect climatic and cryospheric evolution via their role in regional-global energy balance. The timing, likely locations of glacial onset, and variability of the ice sheet on Greenland remain largely uncertain. To determine the inherent thresholds for collapse and (re-)growth of the Greenland ice sheet on glacial-interglacial timescales, the combination of all these forcings have to be taken into account. Here, we show the results of a sensitivity study exploring the inception threshold for the onset and regrowth of the Greenland ice sheet by combining sets of orbital parameters, CO2 levels, and vegetation types over Greenland. Interglacial to glacial transitions are modeled using boundary conditions representative of Pliocene and late Pleistocene. We use the latest (2008) version of the GENESIS GCM Version 3.0 asynchronously coupled to a standard thermomechanical ice-sheet model. The paleoclimate simulations use both modern and ice-free isostatically equilibrated Greenland topography with modern and cold boreal summer orbits (116ka), and a range of pCO2 levels between 200 and 400. Prescribed Greenland vegetation types include tundra, bare ground, best guess interglacial vegetation and evergreen needleleaf trees. We additionally use interactive vegetation simulations to test the dynamic response of vegetation under the prescribed orbits and pCO2. We find that orbits and pCO2 levels pace the timing of glacial inception on Greenland, however, the applied vegetation changes over ice

  8. 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

  9. 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.

  10. 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

  11. 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.

  12. Hyperspectral and photogrammetric helicopter-based measurements over western Greenland

    NASA Astrophysics Data System (ADS)

    Tedesco, M.; Mote, T. L.; Smith, L. C.; Rennermalm, A. K.; Lampkin, D. J.

    2015-12-01

    We discuss the setup and results of an experiment aimed at collecting helicopter-based hyperspectral and photogrammetry measurements over the western Greenland ice sheet (GrIS) for studying the evolution of surface albedo and surface hydrological features. Data were collected during three days at the end of July 2015 concurrently with in-situ hydrological measurements of runoff and discharge of a supraglacial stream (Rio Behar) and along the K-transect up to an elevation of ~ 1500 m a.s.l. Hyperspectral measurements of incoming and outgoing radiation collected at a radiometric resolution of 10 nm were acquired in conjunction with geo-located images by means of a digital camera mounted on the same platform. Gyroscopes and 3-D accelerometers were also used to estimate the relative orientation of the sensors collecting the incoming and outgoing solar radiation. To our knowledge, despite their importance, it is the first time that such measurements have been collected over the Greenland ice sheet from an airborne platform. The sensors were installed inside a pod that was specifically modified for our purpose. The impact of the helicopter on the recorded incoming radiation was characterized by collecting measurements in the absence and presence of the helicopter when the rotors were either off or on. Moreover, the effect of the relative position of the helicopter with respect to the sun's position was also quantified by ad-hoc maneuvers during take off and landing with the helicopter spinning around the main rotor axis. The geo-referenced images collected by our instrument provide an unprecedented ground spatial resolution of ~ 6 cm, hence allowing us to study the spatial distribution of surface hydrological features, such as cryoconite holes, small order streams and cracks developing into larger moulins. Such images were also used to evaluate the application of RGB data to estimate streams and lakes surface area and depths. Our helicopter-based hyperspectral and

  13. 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

  14. Global Warming and Glaciers Melting at Fjords in Greenland

    NASA Astrophysics Data System (ADS)

    Coelho, Pablo

    2015-04-01

    This paper presents a discussion on the validation or not of a likely paradigm about the melting of polar glaciers and their direct impact on increasing ocean levels. Physico-chemical properties of ocean waters, as well as anomalies in the thermal behavior of water are used as providers of this discussion using fjords of Greenland as study area. This text seeks to infer the relationship between the most recent developments in global warming, specifically dealing with the melting of glaciers located in fjords in the eastern part of Greenland, increasing the water temperature in ocean currents and changes in se