Top PDF Review of Survey activities 2013: Katabatic winds and piteraq storms: observations from the Greenland ice sheet

Review of Survey activities 2013: Katabatic winds and piteraq storms: observations from the Greenland ice sheet

Review of Survey activities 2013: Katabatic winds and piteraq storms: observations from the Greenland ice sheet

Greenland, this suggests that the near-surface atmosphere is commonly less buoyant (denser) at higher elevations than air at lower elevations. In a free atmosphere such a density difer- ence over a few vertical kilometres would trigger an immedi- ate adjustment through convection. Over the large horizontal scale of the Greenland ice sheet, the actual density gradients are roughly two orders of magnitude smaller, which adds in- signiicantly to the force balance. Figure 2B illustrates that during winter, the high elevation interior of the ice sheet cools more than lower elevation regions near the margin. As a re- sult, the shallow (c. 100 m thick) stable atmospheric boundary layer that blankets the ice sheet attains an even larger tempera- ture deicit compared to the free atmosphere at high elevation in winter. he larger this temperature deicit relative to the free atmosphere, the larger the density diference relative to the free atmosphere, and thus the larger the gravitational ac- celeration of the shallow boundary layer. his katabatic force increases linearly with increasing surface slope.
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Review of Survey activities 2014: Observed melt-season snowpack evolution on the Greenland ice sheet

Review of Survey activities 2014: Observed melt-season snowpack evolution on the Greenland ice sheet

Due to recent warm and record-warm summers in Green- land (Nghiem et al. 2012), the melt of the ice-sheet surface and the subsequent runof are increasing (Shepherd et al. 2012). About 84% of the mass loss from the Greenland ice sheet between 2009 and 2012 resulted from increased sur- face runof (Enderlin et al. 2014). h e largest melt occurs in the ablation zone, the low marginal area of the ice sheet (Van As et al. 2014), where melt exceeds wintertime accumulation and bare ice is thus exposed during each melt season. In the higher regions of the ice sheet (i.e. the accumulation area), melt is limited and the snow cover persists throughout the year. It is in the vast latter area that models struggle to calcu- late certain mass l uxes with accuracy. A better understand- ing of processes such as meltwater percolation and refreezing in snow and i rn is crucial for more accurate Greenland ice- sheet mass-budget estimates (Van Angelen et al. 2013).
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Review of Survey activities 2015: Regional climate-model performance in Greenland firn derived from in situ observations

Review of Survey activities 2015: Regional climate-model performance in Greenland firn derived from in situ observations

Recent record-warm summers in Greenland (Khan et al. 2015) have started affecting the higher regions of the ice sheet (i.e. the accumulation area), where increased melt has altered the properties of firn (i.e. multi-year snow). At high altitudes, meltwater percolates in the porous snow and firn, where it re- freezes. The result is mass conservation, as the refrozen melt- water is essentially stored (Harper et al. 2012). However, in some regions increased meltwater refreezing in shallow firn has created thick ice layers. These ice layers act as a lid, and can inhibit meltwater percolation to greater depths, causing it to run off instead (Machguth et al. 2016). Meltwater at the surface also results in more absorbed sunlight, and hence increased melt in the accumulation area (Charalampidis et al. 2015). These relatively poorly understood processes are important for ice-sheet mass-budget projections.
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Review of Survey activities 2012: Darkening of the Greenland ice sheet due to the melt-albedo feedback observed at PROMICE weather stations

Review of Survey activities 2012: Darkening of the Greenland ice sheet due to the melt-albedo feedback observed at PROMICE weather stations

In the wake of several record-breaking warm summers – increasing surface melt rate and extent (Nghiem et al. 2012) – interest in Greenland’s surface mass balance has increased (Tedesco et al. 2013). Observations of net ablation at PROM- ICE stations provided in situ confirmation of extreme mass- loss events in 2010 (Fausto et al. 2012) and 2012, primarily documented by other workers through satellite data. In this paper, we present atmospheric temperatures and surface solar reflectivity (known as albedo) of the Greenland ice sheet in the PROMICE period. Albedo modulates the absorption of solar radiation, which is the primary source of melt energy. It is reported to be decreasing in Greenland in recent years (Box et al. 2012), causing the monitoring of albedo variability to be increasingly important. Air temperatures, besides being strongly correlated to surface melt rates, affect surface albedo by controlling the rate of snow-grain metamorphism and the fraction of summer precipitation falling as rain versus snow. To elucidate the so-called melt-albedo feedback, whereby increased melt darkens the ice sheet and further enhances
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Review of Survey activities 2013: Earthquake swarms in Greenland

Review of Survey activities 2013: Earthquake swarms in Greenland

Seismographs have been continuously operating in Green- land since 1927 (Hjelme 1996). Originally the instruments were large, diicult to install and labour intensive to main- tain. It was only possible to operate a few stations in Green- land. his changed with the development of digital instru- ments, and during the last decade a network of 20 digital broadband seismographs with real-time data transmission has been installed in Greenland (Fig. 1). his massive un- dertaking is a result of the international collaboration in the Greenland Ice Sheet Monitoring Network (GLISN) project with funding from around the world (Dahl-Jensen et al. 2010). he latest seismological station was installed in Upernavik in 2013 by the Korean Polar Research Institute (see UPNV Fig. 1).
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SOCIAL ECONOMY – A FORM OF INCLUSION AND OF ''REACTIVATING'' OF LABOR IN THE CONTEXT OF THE CURRENT CRISIS

SOCIAL ECONOMY – A FORM OF INCLUSION AND OF ''REACTIVATING'' OF LABOR IN THE CONTEXT OF THE CURRENT CRISIS

The cultivating, through different social policies, especially through the ideologization of the values , of the contempt for the real, productive work represents a major problem. Only one country in the world set the objective – within the constitution – to not spend more

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Review of Survey Activities 2005: The Tikiusaaq carbonatite: a new Mesozoic intrusive complex in southern West Greenland

Review of Survey Activities 2005: The Tikiusaaq carbonatite: a new Mesozoic intrusive complex in southern West Greenland

The large and well-exposed bodies of alkaline rocks and carbonatites in the Gardar Province were discovered already in the early 1800s (Ussing 1912), while less conspicuous bod- ies were discovered much later during geological mapping and mineral exploration. Many alkaline rock bodies, particu- larly dykes, are difficult to identify in the field because they weather more extensively than the country rock gneisses and form vegetated depressions in the landscape. However, their distinct chemistry and mineralogy render alkaline rocks iden- tifiable in geochemical and geophysical survey data. Thus, the Sarfartôq carbonatite complex was discovered during regional airborne gamma-spectrometric surveying owing to its elevated uranium and thorium contents (Secher 1986).
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Surface mass budget and meltwater discharge from the Kangerlussuaq sector of the Greenland ice sheet during record-warm year 2010

Surface mass budget and meltwater discharge from the Kangerlussuaq sector of the Greenland ice sheet during record-warm year 2010

tours perpendicularly starting at the pro-glacial watersheds, which we preferred over e.g. standard software tools that have proven to perform poorly over smooth surfaces with a low aspect ratio such as an ice sheet. As van de Wal and Russell (1994) already concluded, a large uncertainty in meltwater run-off estimates remains due to missing information on the exact extent of the drainage area. Our glacier surface catchment

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Review of Survey activities 2006: A multi-disciplinary study of Phanerozoic landscape development in West Greenland

Review of Survey activities 2006: A multi-disciplinary study of Phanerozoic landscape development in West Greenland

Geomorphology. Three different palaeosurfaces in the Pre - cam brian basement have been identified in West Greenland, viz. a surface formed by deep weathering and stripping of the weathering mantle (etch surface, ES), and an upper and lower planation surface (UPS and LPS; Bonow 2005; Bonow et al. 2006a, b). The ES is characterised by distinct hills (Fig. 2A) and re ceived its final shape in part prior to the deposition of Upper Cretaceous deltaic sediments and in part prior to the extrusion of Palaeogene basalts (Fig. 2B). The ES can mainly be identified at low elevations and close to cover rocks (Figs 1, 2C). The UPS has low relative relief compared to the ES (Fig. 2D) and must be younger as it cuts across both mid- Eocene basalts and the etch surface. The UPS forms the sum- mits of differentially tilted, fault-bounded tectonic blocks. A planation surface cannot be formed as an inclined plain because any tilt would cause valleys to incise and the relief to rejuvenate towards the baselevel (Bonow et al. 2006b, fig. 6). The LPS was formed in response to lowered baselevel (uplift) and became incised into the UPS (Fig. 2E). Furthermore, summits of distinct hill complexes above the UPS (Fig. 2F)
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Review of Survey Activities 2005: Using zircon geochronology to resolve the Archaean geology of southern West Greenland

Review of Survey Activities 2005: Using zircon geochronology to resolve the Archaean geology of southern West Greenland

Until recently, in situ U-Pb zircon geochronology could be carried out only using ion microprobes, requiring lengthy analysis times of c. 20 minutes. However, new developments in laser ablation inductively coupled plasma mass spectrometer technologies have resulted in zircon geochronology tech- niques that are much faster, simpler, cheaper, and more pre- cise than before (e.g. Frei et al. 2006, this volume). Analyses approaching the precision obtained via ion microprobe can now be undertaken in 2–4 minutes using instruments such as the 213 nm laser ablation (LA) system coupled with Element2 sector-field inductively coupled plasma mass spec- trometer (SF-ICP-MS) housed at the Geological Survey of Denmark and Greenland (GEUS). The up to tenfold decrease in analytical time means that zircon geochronology can now be used in a much wider range of studies.
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Simultaneous Determination Of Adjusted Ranks Of Sample Observations And Their Sums And Products

Simultaneous Determination Of Adjusted Ranks Of Sample Observations And Their Sums And Products

Sometimes one may have a sample drawn from a population that may be a measurement on as low as the ordinal scales that are not necessarily continuous or even numeric. Research interest is in using ranks instead of raw scores in statistical analyses. In this case one may have to first assign ranks to each of the observations before further analyses. A problem that often arises is how to systematically assign ranks to these data without having to arrange them in any order, either from the smallest to the largest or from the largest to the smallest. It is acknowledged that several methods exist for generating rank sums, products, sums of squares and breaking of ties between sample observations in their rankings (Gibbons J. D. 1973; Hollander and Wolfe, 1999; Siegel Sidney, 1956; Oyeka et al, 2014) adopting different approaches. We, in this paper, propose to develop a statistical method along the line of Oyeka et al (2013) to help in systematically assigning ranks to a sample of observations without first arranging them in any order. We also develop a statistical method for the estimation of the sums of squares and products of ranks in the presence of tied observations in which some or all the observations are tied and therefore assigned mean ranks.
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<i>Brief Communication</i> "Expansion of meltwater lakes on the Greenland Ice Sheet"

<i>Brief Communication</i> "Expansion of meltwater lakes on the Greenland Ice Sheet"

Figure 2 shows the elevation of the uppermost 0.1 km 2 of lake area for each study area grouped by region, which fol- lows the edge of lake extent while providing some spatial and temporal smoothing. We also calculated the elevations for the uppermost 0.05 and 0.2 km 2 lake areas, but varying this parameter only shifts the curves, respectively, up and down, without substantially changing temporal variability. For areas with data in the 1970s and 1980s, we observe little change in lake elevation before the year 2000. Since 2000, however, all study areas have undergone an increase in lake elevation on the order of hundreds of meters and tens of km inland. Among the largest observed change is above the out- let glacier Jakobshavn Isbrœ (area E in Fig. 2), where lakes now extend to near 1900 m, approximately 30 km further in- land than before 2000 (Figs. 1 and 2). Areas to the south now have lakes extending well above 2000 m elevation.
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Review of Survey activities 2004: Greenstone belts in the central Godthåbsfjord region, southern West Greenland

Review of Survey activities 2004: Greenstone belts in the central Godthåbsfjord region, southern West Greenland

variably calc-silicate banded with rare pillow structures pre- served in areas of low strain (Fig. 2). Schists of intermediate composition also preserve angular clasts of inferred volcanic origin in areas of low strain. Thin packages of layered metasedimentary and metavolcanic rocks are seen at Store Malene, Sermitsiaq and south-east Bjørneøen (Fig. 1) and commonly contain tourmaline-rich layers; in some cases they define refolded folds. They have been interpreted as strata- bound syngenetic deposits, closely associated with the tung- sten mineral scheelite (CaWSO 4 ; Appel & Garde 1987).
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Review of Survey activities 2015: Palaeovalleys at the basal unconformity of the Palaeoproterozoic Karrat Group, West Greenland

Review of Survey activities 2015: Palaeovalleys at the basal unconformity of the Palaeoproterozoic Karrat Group, West Greenland

A ternary diagram (Fig. 5) discriminates the signatures of the base-metal mineralisation hosted by carbonate rocks of the Mârmorilik or Qaarsukassak formations, and of the rusty-weathering horizons hosted by the Nûkavsak Forma- tion. The latter are dominated by pyrite or pyrrhotite and lack significant amounts of base metals (Fig. 5). Due to the effects of weathering, resulting in gossanous horizons, compositions of the sulphides in exposed rocks can depart from pyrite and become enriched in iron and depleted in sulphur. The former have variable amounts of iron sulphide, but can also have significant sphalerite or galena contents. The two samples closest to the metal corner were collected at the previously established ‘Discovery’ and ‘South Lakes Glacier’ occurrences, samples 569813 and 569807, respec- tively. A third sample (569816, Fig. 5) was collected c. 10 km to the north-west (Fig. 2) where mineralisation was not previously seen. Although the absolute base-metal content of this sample is not high, it is elevated relative to sulphur (akin to the tenor concept in nickel exploration). Its pres- ence supports potential correlation with the Mârmorilik Formation and the proposed continuation of the Qaarsu- kassak Formation, hosting base-metal mineralisation, to the north-western limb of the wide anticline of the cross section shown in Fig. 2.
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Melting trends over the Greenland ice sheet (1958–2009) from spaceborne microwave data and regional climate models

Melting trends over the Greenland ice sheet (1958–2009) from spaceborne microwave data and regional climate models

In this study, we analyze results from two Regional Cli- mate Models (RCMs) in conjunction with those obtained from spaceborne microwave brightness temperatures to study surface and near-surface melt variability over the GrIS since 1979 and extend the analysis back to 1958. The RCMs used in this study are MAR (for Mod`ele Atmosph´erique R´egional), described by Gall´ee and Schayes (1994) and Fettweis (2007) and RACMO2, described by Ettema et al. (2009). Both RCMs are fully coupled with an energy balance-based snow model allowing feedbacks between the surface and the atmosphere. The models have been forced at the boundaries by the re-analyses of the European Cen- tre for Medium-Range Weather Forecasts (ECMWF) since September 1957. Both models have demonstrated their abil- ity to reliably simulate the GrIS SMB since 1958 (Ettema et al., 2009; Fettweis et al., 2011). Moreover, the MAR model was already satisfactorily compared with passive microwave- derived observations (Fettweis et al., 2005, 2007) and was used to improve the microwave-based algorithm developed by Abdalati and Steffen (2001) for retrieving melt extent (Fettweis et al., 2006). Combining results from modeling and measurement tools (e.g., satellite data) would provide an ideal framework to overcome some of the intrinsic limita- tions/uncertainties of each tool considered separately. A ma- jor outcome of this study is a first assessment of the potential assimilation of melt detection from spaceborne microwave data into the RCMs, with the ultimate scope of reducing un- certainties in model-based Surface Mass Balance (SMB) es- timates.
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The Greenland ice sheet: modelling the surface mass balance from GCM output with a new statistical downscaling technique

The Greenland ice sheet: modelling the surface mass balance from GCM output with a new statistical downscaling technique

plays a major role in Crocus, triggering earlier seasonal snow surface melting and the reappearance of below-the-surface old ice in summer. The latter explains the greater decrease of RCP8.5 Crocus snowmelt (Fig. 11c) and SMB (Fig. 11d) projections for the 21st and 22nd century relative to CNRM-CM5.1 modelling. However, the further contin- uous snowfall augmentation eventually leads to a rise in the average GrIS snow albedo

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Heat sources within the Greenland Ice Sheet: dissipation, temperate paleo-firn and cryo-hydrologic warming

Heat sources within the Greenland Ice Sheet: dissipation, temperate paleo-firn and cryo-hydrologic warming

For measurements close to the surface, sets of two ther- mistor strings were deployed in two boreholes at site FOXX, and in one borehole at site GULL. Each string consisted of an 18-core cable with 9 NTC thermistors (Fenwal 135-103FAG- J01) that were shielded from pressure and moisture, and for which individual calibration curves were determined in a cal- ibration bath at six to eight reference temperatures in the range of −17.5 to 10 ◦ C with a digital multi-meter. Refer- ence thermistors, calibrated to an absolute accuracy of 20 mK by the Swiss Federal Office of Metrology, were used to de- termine the bath temperature. The maximum difference be- tween reference temperatures and the calibration curve was 40 mK. In the field, resistances were measured with a full bridge circuit logged by a Campbell CR-1000 data logger, and occasional readings with a digital multi-meter over the course of 2 years. With the setup described above, the abso- lute accuracy of all measured temperatures is estimated to be better than 70 mK.
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Review of Survey activities 2009: Zircon record of the igneous and metamorphic history of the Fiskenæsset anorthosite complex in southern West Greenland

Review of Survey activities 2009: Zircon record of the igneous and metamorphic history of the Fiskenæsset anorthosite complex in southern West Greenland

For U/Pb zircon age determination we selected sample GGU 508216, which consists of hornblenditic dyke material and the surrounding anorthosite rock. The sample was crushed, sieved, and washed on a Wilfley table. The zircons were hand-picked from the heavy mineral fraction, mounted in epoxy resin and polished. Age determination was carried out by laser ablation inductively coupled mass spectrometry us- ing an Element2 and NewWave 213 nm UV-laser system at GEUS following the procedures described in Frei & Gerdes (2009). The results are shown in Fig. 2.
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The comparison of the structure and microhardness of the tool steel C90 and HS 6-5-2 remelted with the electric arc

The comparison of the structure and microhardness of the tool steel C90 and HS 6-5-2 remelted with the electric arc

The samples were remelted on the surface with the electric arc with the use of the FALTIG 315AC/DC apparatus. The single remelting was applied. The treatment parameters were used: amperage of the electric arc I = 100 A, speed of the electrode movement v=200 mm/min. As the plasma formative gas, the argon was used. The treatment has been conducted at the depart- ment of Foundry and Welding of Rzeszow University of Tech- nology. After the remelting, there has been the conventional tempering done 1x1 hour in a temperature of 200°C for the steel C90 and 2x2 hours in the temperature of 560 °C for the steel HS 6- 5-2. Parameters of tempering (temperature, time and multiplicity) of the tested steels were selected according to the standard PN-EN ISO 4957:2002U. The microhardeness measurements were made with the Hanemanna objective mph 100. The load used was 0,064 N, the operating time of the load was 10 s. Metallographic tests were conducted on the optical microscope - Neophot 2 and Tesla BS-340 electronic scanning microscope.
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Simulating the Greenland ice sheet under present-day and palaeo constraints including a new discharge parameterization

Simulating the Greenland ice sheet under present-day and palaeo constraints including a new discharge parameterization

Khroulev, C., Larour, E., Levermann, A., Lipscomb, W. H., Martin, M. A., Morlighem, M., Parizek, B. R., Pollard, D., Price, S. F., Ren, D. D., Rignot, E., Saito, F., Sato, T., Seddik, H., Seroussi, H., Takahashi, K., Walker, R., and Wang, W. L.: Insights into spatial sensitivities of ice mass response to environmental change from the SeaRISE ice sheet modeling project II: Greenland, Geophys. Res. Lett., 118, 1025–1044, doi:10.1002/jgrf.20076, 2013. 1153

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