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Sample records for disko west greenland

  1. Seismic architecture and evolution of the Disko Bay trough-mouth fan, central West Greenland margin

    NASA Astrophysics Data System (ADS)

    Hofmann, Julia C.; Knutz, Paul C.; Nielsen, Tove; Kuijpers, Antoon

    2016-09-01

    The present study is the first to document the large-scale glacigenic evolution of a West Greenland trough-mouth fan (TMF) system, i.e. the Disko Bay TMF, from onset of shelf-based glaciation to present. We have constrained the paleo-ice sheet configuration in the Disko Bay region and determine the controlling factors of ice-stream development using 2D- and 3D-seismic reflection data, seabed bathymetry and stratigraphic information from two exploration wells. This has revealed three stages of the Disko Bay TMF development. The early stage, probably of Pliocene-early Pleistocene age, marks the onset of a central depocentre located below the modern mid-shelf and constructed by sediment progradation delivered through at least two erosive pathways related to fast-flowing, grounded ice. At that time, ice-stream routing in the Disko Bay shelf region was strongly controlled by the pre-glacial topography and structural boundaries associated with fracture zones and deep-seated faults. During the middle evolutionary stage, the focus of deposition shifted from the mid-shelf to two elongate areas fringing the outer margin. The marginal depocentres were not only related to glacial processes but also alongslope deposition by contour currents, which may have developed as a consequence of basin subsidence surrounding the Davis Strait High and the Kangerluk Structure. The late stage of TMF development, presumably representing the late Pleistocene to Holocene, is characterized by the marginal depocentres becoming less significant and sediment aggradation occurring over wide parts of the mid-outer shelf, while features of subglacial erosion are generally absent. In contrast to the inferred fast-flowing ice streams of the early-middle evolutionary stages, this points to the existence of a rather thin and "lightly" grounded ice sheet, i.e. at the threshold of floatation. The "lightly" grounded ice sheet scenario, applying to the late Pleistocene interval of the Disko Bay TMF, was

  2. Seismic stratigraphic architecture of the Disko Bay trough-mouth fan system, West Greenland

    NASA Astrophysics Data System (ADS)

    Hofmann, Julia C.; Knutz, Paul C.

    2015-04-01

    Spatial and temporal changes of the Greenland Ice Sheet on the continental shelf bordering Baffin Bay remain poorly constrained. Then as now, fast-flowing ice streams and outlet glaciers have played a key role for the mass balance and stability of polar ice sheets. Despite their significance for Greenland Ice Sheet dynamics and evolution, our understanding of their long-term behaviour is limited. The central West Greenland margin is characterized by a broad continental shelf where a series of troughs extend from fjords to the shelf margin, acting as focal points for trough-mouth fan (TMF) accummulations. The sea-ward bulging morphology and abrupt shelf-break of these major depositional systems is generated by prograding depocentres that formed during glacial maxima when ice streams reached the shelf edge, delivering large amounts of subglacial sediment onto the continental slope (Ó Cofaigh et al., 2013). The aim of this study is to unravel the seismic stratigraphic architecture and depositional processes of the Disko Bay TMF, aerially the largest single sedimentary system in West Greenland, using 2D and 3D seismic reflection data, seabed bathymetry and stratigraphic information from exploration well Hellefisk-1. The south-west Disko Bay is intersected by a deep, narrow trough, Egedesminde Dyb, which extends towards the southwest and links to the shallower and broader cross-shelf Disko Trough (maximum water depths of > 1000 m and a trough length of c. 370 km). Another trough-like depression (trough length of c. 120 km) in the northern part of the TMF, indicating a previous position of the ice stream, can be distinguished on the seabed topographic map and the seismic images. The Disko Bay TMF itself extends from the shelf edge down to the abyssal plain (abyssal floor depths of 2000 m) of the southern Baffin Bay. Based on seismic stratigraphic configurations relating to reflection terminations, erosive patterns and seismic facies (Mitchum et al., 1977), the TMF

  3. Seafloor geomorphology and glacimarine sedimentation associated with fast-flowing ice sheet outlet glaciers in Disko Bay, West Greenland

    NASA Astrophysics Data System (ADS)

    Streuff, Katharina; Ó Cofaigh, Colm; Hogan, Kelly; Jennings, Anne; Lloyd, Jeremy M.; Noormets, Riko; Nielsen, Tove; Kuijpers, Antoon; Dowdeswell, Julian A.; Weinrebe, Wilhelm

    2017-08-01

    Fast-flowing outlet glaciers currently drain the Greenland Ice Sheet (GIS), delivering ice, meltwater and debris to the fjords around Greenland. Although such glaciers strongly affect the ice sheet's mass balance, their glacimarine processes and associated products are still poorly understood. This study provides a detailed analysis of lithological and geophysical data from Disko Bay and the Vaigat Strait in central West Greenland. Disko Bay is strongly influenced by Jakobshavn Isbræ, Greenland's fastest-flowing glacier, which currently drains ∼7% of the ice sheet. Streamlined glacial landforms record the former flow of an expanded Jakobshavn Isbræ and adjacent GIS outlets through Disko Bay and the Vaigat Strait towards the continental shelf. Thirteen vibrocores contain a complex set of lithofacies including diamict, stratified mud, interbedded mud and sand, and bioturbated mud deposited by (1) suspension settling from meltwater plumes and the water column, (2) sediment gravity flows, and (3) iceberg rafting and ploughing. The importance of meltwater-related processes to glacimarine sedimentation in West Greenland fjords and bays is emphasised by the abundance of mud preserved in the cores. Radiocarbon dates constrain the position of the ice margin during deglaciation, and suggest that Jakobshavn Isbræ had retreated into central Disko Bay before 10.6 cal ka BP and to beyond Isfjeldsbanken by 7.6-7.1 cal ka BP. Sediment accumulation rates were up to 1.7 cm a-1 for ice-proximal glacimarine mud, and ∼0.007-0.05 cm a-1 for overlying distal sediments. In addition to elucidating the deglacial retreat history of Jakobshavn Isbræ, our findings show that the glacimarine sedimentary processes in West Greenland are similar to those in East Greenland, and that variability in such processes is more a function of time and glacier proximity than of geographic location and associated climatic regime.

  4. Surface exposure dating of Little Ice Age ice cap advances on Disko Island, West Greenland

    NASA Astrophysics Data System (ADS)

    Lane, Timothy; Jomelli, Vincent; Rinterknecht, Vincent; Brunstein, Daniel; Schimmelpfennig, Irene; Swingedouw, Didier; Favier, Vincent; Masson-Delmotte, Valerie

    2015-04-01

    Little Ice Age (LIA: 1200-1920 AD) glacier advances in Greenland often form the most extensive positions of Greenland Ice Sheet (GrIS) ice cap and margins since the Early Holocene. Across Greenland these advances are commonly represented by un-vegetated moraines, usually within 1-5 km of the present ice margin. However, chronological constraints on glacier advances during this period are sparse, meaning that GrIS and ice cap behavior and advance/retreat chronology remains poorly understood during this period. At present the majority of ages are based on historical accounts, ice core data, and radiocarbon ages from proglacial threshold lakes. However, developments in the accuracy and precision of surface exposure methods allow dating of LIA moraine boulders, permitting an opportunity to better understand of ice dynamics during this period. Geomorphological mapping and surface exposure dating (36Cl) were used to interpret moraine deposits from the Lyngmarksbræen on Disko Island, West Greenland. A Positive Degree Day (PDD) model was used to estimate Equilibrium Line Altitude (ELA) and mass balance changes for two distinct paleo-glacial extents. Three moraines (M1, M2, and M3) were mapped in the field, and sampled for 36Cl surface exposure dating. The outermost moraine (M1) was of clearly different morphology to the inner moraines, and present only in small fragments. M2 and M3 were distinct arcuate termino-lateral moraines within 50 m of one another, 1.5 km from the present ice margin. The weighted average of four 36Cl ages from M1 returned an early Holocene age of 8.4 ± 0.6 ka. M2 (four samples) returned an age of 0.57 ± 0.04 ka (1441 AD) and M3 (four samples) returned an age of 0.28 ± 0.02 ka (1732 AD). These surface exposure ages represent the first robustly dated Greenlandic ice cap moraine sequence from the LIA. The two periods of ice cap advance and marginal stabilisation are similar to recorded periods of LIA GrIS advance in west Greenland, constrained

  5. Deglaciation of a major palaeo-ice stream in Disko Trough, West Greenland

    NASA Astrophysics Data System (ADS)

    Hogan, Kelly A.; Ó Cofaigh, Colm; Jennings, Anne E.; Dowdeswell, Julian A.; Hiemstra, John F.

    2016-09-01

    Recent work has confirmed that grounded ice reached the shelf break in central West Greenland during the Last Glacial Maximum (LGM). Here we use a combination of marine sediment-core data, including glacimarine lithofacies and IRD proxy records, and geomorphological and acoustic facies evidence to examine the nature of and controls on the retreat of a major outlet of the western sector of the Greenland Ice Sheet (GrIS) across the shelf. Retreat of this outlet, which contained the ancestral Jakobshavns Isbræ ice stream, from the outer shelf in Disko Trough was rapid and progressed predominantly through iceberg calving, however, minor pauses in retreat (tens of years) occurred on the middle shelf at a trough narrowing forming subtle grounding-zone wedges. By 12.1 cal kyr BP ice had retreated to a basalt escarpment and shallow banks on the inner continental shelf, where it was pinned and stabilised for at least 100 years. During this time the ice margin appears to have formed a calving bay over the trough and melting became an important mechanism of ice-mass loss. Fine-grained sediments (muds) were deposited alternately with IRD-rich sediments (diamictons) forming a characteristic deglacial lithofacies that may be related to seasonal climatic cycles. High influxes of subglacial meltwater, emanating from the nearby ice margins, deposited muddy sediments during the warmer summer months whereas winters were dominated by iceberg calving leading to the deposition of the diamictons. This is the first example of this glacimarine lithofacies from a continental-shelf setting and we suggest that the calving-bay configuration of the ice margin, plus the switching between calving and melting as ablation mechanisms, facilitated its deposition by channelling meltwater and icebergs through the inner trough. The occurrence of a major stillstand on the inner shelf in Disko Trough demonstrates that the ice-dynamical response to local topography was a crucial control on the behaviour

  6. Plant and vegetation dynamics on Disko Island, west Greenland: snapshots separated by over 40 years.

    PubMed

    Callaghan, Terry V; Christensen, Torben R; Jantze, Elin J

    2011-09-01

    We report on a revisit in 2009 to sites where vegetation was recorded in 1967 and 1970 on Disko Island, West Greenland. Re-sampling of the same clones of the grass Phleum alpinum after 39 years showed complete stability in biometrics but dramatic earlier onset of various phenological stages that were not related to changes in population density. In a fell-field community, there was a net species loss, but in a herb-slope community, species losses balanced those that were gained. The type of species establishing and increasing in frequency and/or cover abundance at the fell-field site, particularly prostrate dwarf shrubs, indicates a possible start of a shift towards a heath, rather than a fell-field community. At the herb-slope site, those species that established or increased markedly in frequency and/or cover abundance indicate a change to drier conditions. This is confirmed both by the decrease in abundance of Alchemilla glomerulans and Epilobium hornemanii, and the drying of a nearby pond. The causes of these changes are unknown, although mean annual temperature has risen since 1984.

  7. Surface and sub-surface multi-proxy reconstruction of middle to late Holocene palaeoceanographic changes in Disko Bugt, West Greenland

    NASA Astrophysics Data System (ADS)

    Moros, Matthias; Lloyd, Jeremy M.; Perner, Kerstin; Krawczyk, Diana; Blanz, Thomas; de Vernal, Anne; Ouellet-Bernier, Marie-Michele; Kuijpers, Antoon; Jennings, Anne E.; Witkowski, Andrzej; Schneider, Ralph; Jansen, Eystein

    2016-01-01

    We present new surface water proxy records of meltwater production (alkenone derived), relative sea surface temperature (diatom, alkenones) and sea ice (diatoms) changes from the Disko Bugt area off central West Greenland. We combine these new surface water reconstructions with published proxy records (benthic foraminifera - bottom water proxy; dinocyst assemblages - surface water proxy), along with atmospheric temperature from Greenland ice core and Greenland lake records. This multi-proxy approach allows us to reconstruct centennial scale middle to late Holocene palaeoenvironmental evolution of Disko Bugt and the Western Greenland coastal region with more detail than previously available. Combining surface and bottom water proxies identifies the coupling between ocean circulation (West Greenland Current conditions), the atmosphere and the Greenland Ice Sheet. Centennial to millennial scale changes in the wider North Atlantic region were accompanied by variations in the West Greenland Current (WGC). During periods of relatively warm WGC, increased surface air temperature over western Greenland led to ice sheet retreat and significant meltwater flux. In contrast, during periods of cold WGC, atmospheric cooling resulted in glacier advances. We also identify potential linkages between the palaeoceanography of the Disko Bugt region and key changes in the history of human occupation. Cooler oceanographic conditions at 3.5 ka BP support the view that the Saqqaq culture left Disko Bugt due to deteriorating climatic conditions. The cause of the disappearance of the Dorset culture is unclear, but the new data presented here indicate that it may be linked to a significant increase in meltwater flux, which caused cold and unstable coastal conditions at ca. 2 ka BP. The subsequent settlement of the Norse occurred at the same time as climatic amelioration during the Medieval Climate Anomaly and their disappearance may be related to harsher conditions at the beginning of the

  8. Investigating a newly discovered firn aquifer on Disko Ice Cap, west Greenland: Insights from ground observations, remote sensing, and modeling

    NASA Astrophysics Data System (ADS)

    Trusel, L. D.; Das, S. B.; Smith, B.; Kuipers Munneke, P.; Evans, M. J.; Frey, K. E.; Osman, M.; York, A.

    2015-12-01

    Expanding and intensifying surface melt have accelerated contributions from Greenland to global sea level rise in recent decades. Yet, important questions remain regarding the evolution and eventual fate of this meltwater over time and space, a fact underscored by recent observations of expansive aquifers within the Greenland Ice Sheet firn. In April 2015 we observed liquid water retained at depth in an ice cap on Disko Island, central west Greenland. Two adjacent ~20 m firn/ice cores were collected before intercepting a layer saturated with liquid water as evident by water drainage from our cores. Borehole temperature profiling confirms increasing temperature with depth, revealing 0°C isothermal firn below ~10 m depth. Detailed physical stratigraphic analyses conducted on these cores allow us to assess firn properties and their small scale (< 1m) spatial heterogeneity. Notably, multiple, thick (>1 m) and likely impermeable refrozen melt horizons exist above the inferred aquifer surface, raising questions about processes of aquifer formation. To discern the spatial character of the observed firn liquid water and melt stratigraphy, we utilize ground penetrating radar collected in 2014, as well as airborne radar data collected through NASA Operation IceBridge in 2012 and 12 days prior to our field observations in 2015. Glaciochemical analyses on our ice cores reveal preservation of an annual signal allowing derivation of net snow accumulation rates. Combined with surface mass balance modeled by RACMO2.3 and melt assessed via microwave remote sensing, we investigate the recently prevailing climatic and glaciological conditions on Disko. This work will provide new insights into mechanisms of firn aquifer formation and sustenance more broadly, as well as the representation of aquifers in existing radar observations and firn models.

  9. Identifying potential seasonal and historical drivers of marine-terminating glacier retreat in Disko and Uummannaq Bays, West Greenland

    NASA Astrophysics Data System (ADS)

    York, A.; Frey, K. E.; Das, S. B.

    2015-12-01

    The variability in outlet glacier termini positions is an important indicator of overall glacier health and the net effects of ice-ocean-atmosphere interactions. Glacier margins fluctuate on both seasonal and interannual time scales and satellite imagery provides a critical spatially- and temporally-extensive resource for monitoring glacier behavior. Outlet glaciers have generally been retreating globally over recent decades, but the magnitude of seasonal variation, overall retreat, and foremost drivers have proven unique to each glacier. The outlet glaciers in central West Greenland are generally experiencing the same regional atmospheric forcing, yet previous studies have shown varying magnitudes of retreat over the last forty years. In this study, we utilize Landsat imagery between the years 1985 and 2014 to digitize a time series of glacier front positions of 18 marine-terminating outlet glaciers in the Disko and Uummannaq Bay regions of West Greenland. We examine potential drivers of trends in outlet glacier retreat through satellite observations of adjacent sea ice concentrations and sea surface temperatures. Additionally, reanalysis data and long-term automatic weather station measurements are investigated to contextualize the role of atmospheric drivers at both a regional and local scale. Results indicate retreat of all glaciers in the region over the study period and no indication of a south to north trend in magnitude of retreat on either a seasonal or long-term scale. The 11 glaciers in Uummannaq Bay retreated between 25 m and 3.5 km, an average of 1.22 ± 1.20 km over the entire study period. The retreat of 7 glaciers in Disko Bay ranged from 181 m to 2.3 km, an average of 1.0 ± 0.78 km over the period. Although the mean terminus retreat rate between the two bays is comparable, there remains a wide range of total retreat amounts among the glaciers. We investigate the degree of seasonal variation in terminus position as an indicator of longer

  10. Palynology of the late Holocene in Disko Bugt, West Greenland: evidence for centennial variability in sea-surface conditions.

    NASA Astrophysics Data System (ADS)

    Allan, Estelle; de Vernal, Anne; Matthias, Moros; Marie-Michèle, Ouellet-Bernier

    2016-04-01

    The palynological analyses of a sediment core collected in Disko Bay (core 343310; 68° 38,861'N, 53° 49,493'W) provide a dinocyst record of the last 1500 years with 5-30 year time resolution and thus permit reconstruction of changes in surface water, including sea-ice cover, temperature and salinity. Dinocyst assemblages are characterized by high taxonomic diversity (18 taxa) with dominance of Islandinium minutum, Pentapharsodinium dalei, Brigantedinium spp. and Islandinium? cezare and by very high concentrations (>105 cysts.cm-3) leading to calculate fluxes of the order of (>104 cysts.cm-2.years-1). The modern analogue technique (MAT) was applied to dinocyst assemblages to quantitatively reconstruct paleo-sea-surface conditions. The seasonal sea ice cover shows large amplitude variations from 2 to 8 months.yr-1(sea ice coverage >50%), with maxima at 1050-1300 AD, 1400-1500 AD, 1550-1600 AD and 1770-1800 AD, which reflect episodic cooling during the last millennium. In the overall record, sea ice cover and salinity variation are correlated with increase sea ice extent corresponding with decrease salinity and vice versa, which suggests strong linkages between the regional freshwater/meltwater budget and winter sea ice. Relationship between sea ice cover and the North Atlantic Oscillation (NAO) is also possible. The increased sea ice being associated with dominant NAO+ mode can be linked with change of the regional properties of the West Greenland Current, the marked by lower influence of warm and saline Atlantic waters relative to an increase influence of the polar and low salinity in Arctic waters from East Greenland Current under NAO+ situation.

  11. Past sea-level data from Lakse Bugt, Disko Island, West Greenland from ground-penetrating radar data

    NASA Astrophysics Data System (ADS)

    Souza, Priscila E.; Nielsen, Lars; Kroon, Aart; Clemmensen, Lars B.

    2016-04-01

    Beach-ridge deposits have been used as sea-level indicators in numerous studies from temperate coastal regions. However, their present surface morphology in artic regions may not accurately correspond to past sea-level, because subsequent surface erosion, solifluction processes and/or later sediment deposition may have altered the surface significantly. The internal structure of these beach ridges, however, is often well-preserved and thus constitutes an important key to reconstruction of past sea levels as seen elsewhere. In the present study, high-resolution reflection GPR data and high-precision topographic data were collected at Lakse Bugt (Disko Island, West Greenland) using a shielded 250 MHz antennae system and a RTK-Trimble R8 DGPS, respectively. Three transects were collected across a sequence of fossil, raised beach ridge deposits, and two transects were obtained across modern beach deposits at the shoreline of the mesotidal regime. Along all radar profiles we observed downlap reflection points, which we interpret to represent the boundary between sediments deposited on the beachface and sediments deposited in the upper shoreface regime. Both the upper shoreface and the beachface deposits exhibit reflection patterns dipping in the seaward direction. The beachface deposits show the strongest dip. At or just below the downlap points strong diffractions are often observed indicating the presence of a layer containing stones. These stones are large enough to generate significant signal scattering. At the present day beach a sharp transition defined by the presence of large stones is observed near the low tide water level: cobbles characterize the seaside, while the land side is characterized by sand and gravel. Therefore, it seems reasonable to conclude that downlap points observed in the GPR data serve as indicators of past low-tide levels (at the time of deposition). The downlap points show a consistent offset with respect to present surface topography

  12. Modelling near field regional uplift patterns in West Greenland/Disko Bay with plane-Earth finite element models.

    NASA Astrophysics Data System (ADS)

    Meldgaard, Asger; Nielsen, Lars; Iaffaldano, Giampiero

    2017-04-01

    Relative sea level data, primarily obtained through isolation basin analysis in western Greenland and on Disko Island, indicates asynchronous rates of uplift during the Early Holocene with larger rates of uplift in southern Disko Bay compared to the northern part of the bay. Similar short-wavelength variations can be inferred from the Holocene marine limit as observations on the north and south side of Disko Island differ by as much as 60 m. While global isostatic adjustment models are needed to account for far field contributions to the relative sea level and for the calculation of accurate ocean functions, they are generally not suited for a detailed analysis of the short-wavelength uplift patterns observed close to present ice margins. This is in part due to the excessive computational cost required for sufficient resolution, and because these models generally ignore regional lateral heterogeneities in mantle and lithosphere rheology. To mitigate this problem, we perform sensitivity tests to investigate the effects of near field loading on a regional plane-Earth finite element model of the lithosphere and mantle of the Disko Bay area, where the global isostatic uplift chronology is well documented. By loading the model area through detailed regional ocean function and ice models, and by including a high resolution topography model of the area, we seek to assess the isostatic rebound generated by surface processes with wavelengths similar to those of the observed rebound signal. We also investigate possible effects of varying lithosphere and mantle rheology, which may play an important role in explaining the rebound signal. We use the abundance of relative sea level curves obtained in the region primarily through isolation basin analysis on Disko Island to constrain the parameters of the Earth model.

  13. Centennial scale variations of surface ocean in the Disko Bugt, west Greenland

    NASA Astrophysics Data System (ADS)

    Allan, Estelle; de Vernal, Anne; Henry, Maryse; Faurschou Knudsen, Mads; Moros, Matthias; Ouellet-Bernier, Marie-Michèle; Ribeiro, Sofia

    2017-04-01

    Palynological analyses of the sediment core MSM343310 from Disko Bugt document decadal-centennial variations of surface waters during the last 3600 years. The dinocyst assemblages dominated by Islandinium minutum, Brigantedinium spp., Islandinium? cezare and the cyst of Pentapharsodinium dalei indicate large seasonal gradients of temperature due to stratified surface waters. The high dinocysts concentrations (>105 cysts/cm3) and fluxes (>104 cysts/cm2year1) correspond to an extremely high productivity. The application of the modern analogue technique to dinocyst assemblages indicates centennial scale variation of sea-surface salinity in phase with fluctuation of the ∂18O in the Camp Century ice core, thus highlighting the importance of ocean/atmosphere exchanges on regional proxy-climate records. The seasonal sea ice cover also records large amplitude variations, with a main change of regime at about 500 AD, from winter only sea ice of about 2 months/year to more unstable conditions marked by successive cooling pulses with up to 8 months/year of ice coverage.

  14. Impact of changing ice cover on pelagic productivity and food web structure in Disko Bay, West Greenland: a dynamic model approach

    NASA Astrophysics Data System (ADS)

    Hansen, Anja Skjoldborg; Nielsen, Torkel Gissel; Levinsen, Henrik; Madsen, Siz D.; Thingstad, T. Frede; Hansen, Benni Winding

    2003-01-01

    A rise in global temperatures could potentially lead to less ice in the Arctic, including a reduction in the ice-covered period. The consequence of a changing ice cover on the food web structure and production in Disko Bay, Western Greenland, is analysed through application of a dynamical model for the planktonic food web. The model is successfully calibrated and tested for sensitivity, using a detailed data set for 1996-1997. Model scenarios are (1) extended ice cover and (2) no ice. These scenarios are compared to model runs with measured ice cover in two normal years. In the extended ice scenario, assuming unchanged copepod behaviour, copepods are starving or feeding in the ice/water interface from the time they ascend to the surface layer from over-wintering depths until the ice break-up in June. The total annual primary production reaches the same level as it does in the average year, but copepod ingestion and, as a consequence, vertical carbon export is reduced by app. 40%. In the ice-free situation, an early diatom bloom is initiated by stratification of the water in March, before the copepods ascend. The diatom bloom is grazed upon by protozooplankton, which reach a high biomass before the copepods ascend in April. Annual primary production increases by 52% while copepod ingestion and vertical loss of carbon is reduced by 57%. This study illustrates how a change in the ice cover in Arctic areas can potentially create a mismatch between spring primary production and copepod grazers. The result may be a planktonic food web dominated by protozooplankton, resulting in lower export of organic material out of the photic zone despite increased primary productivity, or alternatively lead to changes in species composition or behaviour.

  15. Formation of native iron in sediment-contaminated magma: I. A. case study of the Hanekammen Complex on Disko Island, West Greenland

    SciTech Connect

    Ulff-Moller, F. )

    1990-01-01

    For the first time a compositional range of native iron bodies is described in a cogenetic series of sediment-contaminated volcanic rocks from the Tertiary West Greenland Basalt Province. The iron-bearing rocks occur in a high-level composite intrusion, the Hanekammen Complex. Reaction between a tholeiitic parent magma with >11% MgO and carbonaceous Al{sub 2}O{sub 3}-rich shale took place in a reservoir >3 km below the paleosurface and created magmatic layering with basaltic magma overlain by less dense andesitic magma. The contaminated rock series bears a strong imprint of assimilation but very little fractional crystallization, which implies that the two processes were not intimately coupled in the present in basalt and andesite form a general trend, defined by Co versus Ni concentrations, that reflects the degree of assimilation, the amount of immiscible sulfide liquid, and the degree of reduction (in order of decreasing importance). The zoning of single iron grains reflects the dynamics of their growth and, to some extent, subsequent homogenization and reaction with magma. Weakly zoned iron spherules in viscous andesite were formed and remained in situ, whereas iron grains in basalt settled through the layered magma and developed strong zoning. All iron types contain Co-rich domains (<1 mm in diameter); their conservation implies a residence time for the iron at magmatic temperatures on the order of a month or less before the emplacement in the subvolcanic intrusions.

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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

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

  17. An eddy covariance derived annual carbon budget for an arctic terrestrial ecosystem (Disko, Greenland)

    NASA Astrophysics Data System (ADS)

    McConnell, Alistair; Lund, Magnus; Friborg, Thomas

    2016-04-01

    Ecosystems with underlying permafrost cover nearly 25% of the ice-free land area in the northern hemisphere and store almost half of the global soil carbon. Future climate changes are predicted to have the most pronounced effect in northern latitudes. These Arctic ecosystems are therefore subject to dramatic changes following thawing of permafrost, glacial retreat, and coastal erosion. The most dramatic effect of permafrost thawing is the accelerated decomposition and potential mobilization of organic matter stored in the permafrost. This will impact global climate through the mobilization of carbon and nitrogen accompanied by release of greenhouses gases, including carbon dioxide. This study presents the initial findings and first full annual carbon (CO2) budget, derived from eddy covariance measurements, for an Arctic landscape in West Greenland. The study site, a terrestrial Arctic maritime climate, is located at Østerlien, near Qeqertarsuaq, on the southern coast of Disko Island in central West Greenland (69° 15' N, 53° 34' W) within the transition zone from continuous to discontinuous permafrost. The mean annual air temperature is -5 C and the annual precipitation as rain is 150-200 mm. Arctic ecosystem feedback mechanisms and processes interact on micro, local and regional scales. This is further complicated by several potential feedback mechanisms likely to occur in permafrost-affected ecosystems, involving the interactions of microorganisms, vegetation and soil. The eddy covariance method allows us to interrogate the processes and drivers of land-atmosphere carbon exchange at extremely high temporary frequency (10 Hz), providing landscape-scale measurements of CO2, H2O and heat fluxes for the site, which are processed to derive daily, monthly and now, annual carbon fluxes. We discuss the scientific methodology, challenges, and analysis, as well as the practical and logistic challenges of working in the Arctic, and present an annual carbon budget

  18. Decadal-resolution early Holocene temperature and precipitation reconstruction near Disko Bugt, western Greenland

    NASA Astrophysics Data System (ADS)

    Thomas, E. K.; Castañeda, I. S.; Briner, J. P.; Schweinsberg, A.; Nguyen, K.; Salacup, J. M.

    2015-12-01

    Quantifying ice sheet responses to climate change is critical for predicting sea level rise in a warming world. In particular, increased precipitation may play an important role in offsetting ice sheet mass balance losses caused by rising temperatures. Past intervals of rapid climate change on human-relevant timescales provide natural experiments for quantifying ice sheet response to temperature and precipitation. During the early Holocene, western Greenland Ice Sheet retreat in the Disko Bugt region was punctuated by rapid and dramatic advances, likely in response to abrupt climate changes at 9.3 and 8.2 ka. The character of early Holocene decadal-scale temperature and precipitation changes in western Greenland remains unknown, however, so direct comparison of climate and ice sheet reconstructions currently is not possible. Leaf wax hydrogen isotopes reflect temperature and precipitation changes in the Arctic. We will present a decadal-resolution multiproxy record of early Holocene terrestrial temperature and precipitation using leaf wax hydrogen isotopes and other organic and inorganic proxies from a well-dated lake sediment sequence in the Disko Bugt region of western Greenland.

  19. Biodegradation of crude oil in Arctic subsurface water from the Disko Bay (Greenland) is limited.

    PubMed

    Scheibye, Katrine; Christensen, Jan H; Johnsen, Anders R

    2017-04-01

    Biological degradation is the main process for oil degradation in a subsurface oil plume. There is, however, little information on the biodegradation potential of Arctic, marine subsurface environments. We therefore investigated oil biodegradation in microcosms at 2 °C containing Arctic subsurface seawater from the Disko Bay (Greenland) and crude oil at three concentrations of 2.5-10 mg/L. Within 71 days, the total petroleum hydrocarbon concentration decreased only by 18 ± 18% for an initial concentration of 5 mg/L. The saturated alkanes nC13-nC30 and the isoprenoids iC18-iC21 were biodegraded at all concentrations indicating a substantial potential for biodegradation of these compound classes. Polycyclic aromatic compounds (PACs) disappeared from the oil phase, but dissolution was the main process of removal. Analysis of diagnostic ratios indicated almost no PAC biodegradation except for the C1-naphthalenes. To conclude, the marine subsurface microorganisms from the Disko Bay had the potential for biodegradation of n-alkanes and isoprenoids while the metabolically complex and toxic PACs and their alkylated homologs remained almost unchanged.

  20. Assessing Methanesulfonate as a Proxy for Sea Ice Concentration Using Firn Cores from the Disko Bay Region of Greenland

    NASA Astrophysics Data System (ADS)

    Thadhani, E.; Fernandopulle, G. C.; Rhodes, C. T.; Galls, D.; Bingham, M.

    2016-12-01

    The Jakobshavn Glacier, responsible for draining upwards of 7% of the Greenland Ice Sheet (GIS) into Disko Bay, has experienced terminal retreat in recent decades. High sea ice concentrations have been heavily implicated in the blocking of glacier calving, thereby reducing glacial retreat. However, the satellite imagery used to evaluate levels of sea ice only spans the past few decades, thus establishing the necessity for a valid proxy to generate records father into the past. Methanesulfonate (MSA) is an oxidation product of dimethyl sulfide (DMS), a chemical released by phytoplankton. As phytoplankton population increases with decreased sea ice concentration, MSA concentrations should shift directly with the phytoplankton population and inversely with sea ice concentration.The objective of this study was to evaluate MSA as a natural proxy for sea ice variability.Two meters of firn core were drilled from an ice cap on the Nuussuaq Peninsula, near Disko Bay in April 2014. The core was processed into 3 cm resolution samples for measurement of oxygen isotope ratios by cavity ring down spectroscopy and MSA concentrations by ion chromatography. Sea Ice concentrations at three locations around Disko Bay were calculated using IDRISI software (a GIS) and satellite imagery. Peaks in the oxygen isotope ratio, which has stable seasonal variation with maximum levels in warmer months, were correlated with the likewise seasonal peaks in the percent of the grid uncovered by sea ice (Figure 1). With these corresponding peaks, Taylor series approximation allowed each sample depth to be dated. We subsequently compared MSA concentrations to sea ice concentrations at known dates for three different potential source areas around Disko Bay within 25km by 25km grids. In the grid below Disko Island, peaks in MSA and the inverse of sea ice concentration occurred simultaneously (Figure 2, r=0.4). The parallel peaks in MSA, oxygen isotope and inverse sea ice concentration indicate the

  1. Multibeam Bathymetry Surveys in Fjords and Coastal Areas of West-Greenland

    NASA Astrophysics Data System (ADS)

    Weinrebe, W.; Kuijpers, A.; Klaucke, I.; Fink, M.

    2009-12-01

    High-resolution bathymetric maps are not available for many of the sparsely populated fjords in West-Greenland as those areas are remote and difficult to navigate. During a recent (2007) cruise of RV Maria S. Merian large coastal areas of West-Greenland including some of these fjords were mapped in detail with multibeam bathymetry, among them many parts which never had been investigated before. The surveys covered the Godthabfjord, Nordre Stroemfjord, Disko Bay, Vaigat, Uumannaq-Fjord and the Marmorilik area. The data acquired by a Kongsberg EM120 deep water multibeam and a Kongsberg EM1002 shallow water multibeam system were of very good quality. In summer 2008 the survey in the Disko Bay area was extended far into the Ilulissat Icefjord using a local boat and a portable Seabeam 1180 multibeam system. The seafloor in these areas is intensively shaped by glacial processes which create characteristic submarine landforms. Revealing the morphology helps to understand these processes, high-resolution bathymetry displays the relief and morphology of the seafloor. In particular, rims and sills which may mark ancient ice margins have been identified in the bathymetry. Multibeam mapping was continued also during transits off the coast in the Davis Strait. Here areas sculptured intensively by iceberg plough marks were found. Several distinct patterns of directions can be identified which probably represent different phases of drift. The water depth here is generally greater than 240 m documenting rather deep going icebergs.

  2. Quantitative reconstruction of Holocene sea ice and sea surface temperature off West Greenland from the first regional diatom data set

    NASA Astrophysics Data System (ADS)

    Krawczyk, D. W.; Witkowski, A.; Moros, M.; Lloyd, J. M.; Høyer, J. L.; Miettinen, A.; Kuijpers, A.

    2017-01-01

    Holocene oceanographic conditions in Disko Bay, West Greenland, were reconstructed from high-resolution diatom records derived from two marine sediment cores. A modern data set composed of 35 dated surface sediment samples collected along the West Greenland coast accompanied by remote sensing data was used to develop a diatom transfer function to reconstruct April sea ice concentration (SIC) supported by July sea surface temperature (SST) in the area. Our quantitative reconstruction shows that oceanographic changes recorded throughout the last 11,000 years reflect seasonal interplay between spring (April SIC) and summer (July SST) conditions. Our records show clear correlation with climate patterns identified from ice core data from GISP2 and Agassiz-Renland for the early to middle Holocene. The early Holocene deglaciation of western Greenland Ice Sheet was characterized in Disko Bay by initial strong centennial-scale fluctuations in April SIC with amplitude of over 40%, followed by high April SIC and July SST. These conditions correspond to a general warming of the climate in the Northern Hemisphere. A decrease in April SIC and July SST was recorded during the Holocene Thermal Optimum reflecting more stable spring-summer conditions in Disko Bay. During the late Holocene, high April SIC characterized the Medieval Climate Anomaly, while high July SST prevailed during the Little Ice Age, supporting previously identified antiphase relationship between surface waters in West Greenland and climate in NW Europe. This antiphase pattern might reflect seasonal variations in regional oceanographic conditions and large-scale fluctuations within the North Atlantic Oscillation and Atlantic Meridional Overturning Circulation.

  3. Reconstructing the late Holocene expansion of mountain ice caps in west-central Greenland

    NASA Astrophysics Data System (ADS)

    Briner, J. P.; Schweinsberg, A.; Miller, G. H.; Bennike, O.; Lifton, N. A.

    2013-12-01

    The retreat of glaciers is one of the most profound visual manifestations of global warming. Yet without the longer-term context of glacier history, the magnitude of retreat observed today is less meaningful. We are reconstructing the late Holocene history of mountain ice caps in west-central Greenland to determine: 1) the precedence of their current size, 2) the pattern of Neoglaciation across the northwestern North Atlantic, and 3) how their record of Neoglaciation compares with that of the adjacent Greenland Ice Sheet. Our chronology is built on radiocarbon ages from in situ surface moss emerging from receding ice cap margins. We assert that the moss died during ice cap expansion across tundra surfaces, and has since been entombed beneath non-erosive ice cap sectors that we strategically target. Although this project is in its beginning stages, two initial radiocarbon ages from in situ moss that recently were exposed in front of Lyngmarksbræen, a plateau ice cap on southern Disko island, are 3580-3700 and 3450-3570 cal yr BP. The moss became ice free sometime during the summer in which they were collected, and historical imagery shows the sites are tens of meters behind the ice margin in August 23, 2004. The radiocarbon ages indicate that Lyngmarksbræen has not been as small as it is today since ~3500 yr ago. Other age constraints on Neoglaciation from the Disko Bugt region are similar to the ages we obtained here: reworked marine fauna in Greenland Ice Sheet moraines indicate ice sheet growth at this time, and relative sea level records indicate that landscape submergence (due to ice sheet growth) initiated around this time. Furthermore, ice cap melt records demonstrate that ice caps in this sector of the Arctic are melting more today than they have in the past 4000 years. Additional ages from multiple ice cap margins on Disko island, the Nuussuaq peninsula and various locations in the Uummannaq region will be presented. This dataset of ice cap expansion in

  4. Ocean forcing of Ice Sheet retreat in central west Greenland from LGM to the early Holocene

    NASA Astrophysics Data System (ADS)

    Jennings, Anne E.; Andrews, John T.; Ó Cofaigh, Colm; Onge, Guillaume St.; Sheldon, Christina; Belt, Simon T.; Cabedo-Sanz, Patricia; Hillaire-Marcel, Claude

    2017-08-01

    Three radiocarbon dated sediment cores from trough mouth fans on the central west Greenland continental slope were studied to determine the timing and processes of Greenland Ice Sheet (GIS) retreat from the shelf edge during the last deglaciation and to test the role of ocean forcing (i.e. warm ocean water) thereon. Analyses of lithofacies, quantitative x-ray diffraction mineralogy, benthic foraminiferal assemblages, the sea-ice biomarker IP25, and δ18 O of the planktonic foraminifera Neogloboquadrina pachyderma sinistral from sediments in the interval from 17.5-10.8 cal ka BP provide consistent evidence for ocean and ice sheet interactions during central west Greenland (CWG) deglaciation. The Disko and Uummannaq ice streams both retreated from the shelf edge after the last glacial maximum (LGM) under the influence of subsurface, warm Atlantic Water. The warm subsurface water was limited to depths below the ice stream grounding lines during the LGM, when the GIS terminated as a floating ice shelf in a sea-ice covered Baffin Bay. The deeper Uummannaq ice stream retreated first (ca. 17.1 cal ka BP), while the shallower Disko ice stream retreated at ca. 16.2 cal ka BP. The grounding lines were protected from accelerating mass loss (calving) by a buttressing ice shelf and by landward shallowing bathymetry on the outer shelf. Calving retreat was delayed until ca. 15.3 cal ka BP in the Uummannaq Trough and until 15.1 cal ka BP in the Disko Trough, during another interval of ocean warming. Instabilities in the Laurentide, Innuitian and Greenland ice sheets with outlets draining into northern Baffin Bay periodically released cold, fresh water that enhanced sea ice formation and slowed GIS melt. During the Younger Dryas, the CWG records document strong cooling, lack of GIS meltwater, and an increase in iceberg rafted material from northern Baffin Bay. The ice sheet remained in the cross-shelf troughs until the early Holocene, when it retreated rapidly by calving and strong

  5. Mantle wedge involvement in the petrogenesis of Archaean grey gneisses in West Greenland

    NASA Astrophysics Data System (ADS)

    Steenfelt, Agnete; Garde, Adam A.; Moyen, Jean-François

    2005-01-01

    The Archaean crust in West Greenland is dominated by grey orthogneiss complexes formed in periods of crustal accretion at around 3.8, 3.6, 3.2, 3.0-2.9 and 2.8-2.7 Ga. The majority of the gneisses have tonalite-trondhjemite-granodiorite (TTG) compositions, while subordinate quartz-dioritic and dioritic gneisses have calc-alkaline compositions. The major and trace element chemistry of gneiss samples has been compiled from three large regions representing different terranes and ages in southern and central West Greenland, the Godthåbsfjord, Fiskefjord and Disko Bugt regions. The TTG gneisses are typical for their kind and show little variation, except marked Sr enrichment in the Fiskefjord area and slight Cr enrichment in a unit within the Disko Bugt region. Thus, while most of the crust has probably formed from magmas derived by slab melting, local involvement of mantle-derived components is suggested. Most of the diorites have geochemical signatures compatible with mantle-derived parental magmas, i.e., elevated Mg, Cr and flat chondrite-normalised REE patterns. A group of quartz-diorite and diorite samples from the Fiskefjord region exhibits marked enrichment in Sr, Ba, P, K and REE, combined with steep REE patterns. A similar but much more pronounced enrichment in the same elements characterises Palaeoproterozoic subduction-related monzodiorites within the Nagssugtoqidian orogen, as well as carbonatites and carbonatitic lamprophyres within the same part of West Greenland. We argue that the parental magmas of the enriched diorites are derived by partial melting from regions within the mantle that have been metasomatised by carbonatite-related material, e.g., in the form of carbonate-apatite-phlogopite veins. Alternatively, ascending slab melts may have reacted with carbonatite-metasomatised mantle. Carbonatitic carbonates have high Sr and Ba, and carbonatitic apatite has high P 2O 5 and very steep REE spectra. Adding such a component to a peridotite-derived magma

  6. 3D-seismic observations of Late Pleistocene glacial dynamics on the central West Greenland margin

    NASA Astrophysics Data System (ADS)

    Hofmann, Julia; Knutz, Paul; Cofaigh, Colm Ó.

    2016-04-01

    suggesting the transition between grounded ice and a glacimarine setting. The back-stepping scarps are suggestive of slide scars that were created as a result of mass movement induced by instabilities along the NW slope. The buried section contains morphologies indicating an asymmetric feature with a steeper side facing south. It comprises a thickness of c. 100 m and a length of c. 28 km. The detailed surface observations and seismic geometries suggest that the northern area represents a relict grounding-zone wedge (GZW). The wedge is covered by stratified deposits suggesting that it was at least occasionally submarine after its formation and may have served as pinning-point for floating ice shelves during periods of the Late TMF Stage. Important implications of the study are the intermittent development of floating ice shelves during the course of the Late Stage of TMF development and the presence of shelf-edge terminating grounded Late Weichselian ice outside of the troughs. Hofmann, J.C., Knutz, P.C., Nielsen, T., Kuijpers, A., submitted. Seismic architecture and evolution of the Disko Bay trough-mouth fan, central West Greenland margin. Quaternary Science Reviews.

  7. The multifaceted West Greenland passive margin

    NASA Astrophysics Data System (ADS)

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

    2013-04-01

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

  8. Holocene RSL variation on southwestern Disko Island (Greenland): an interpretation based on GPR data, topography and luminescence dating

    NASA Astrophysics Data System (ADS)

    Emerich Souza, P.; Nielsen, L.; Kroon, A.; Murray, A. S.; Sohbati, R.; Clemmensen, L. B.

    2016-12-01

    We investigate RSL variations during the Holocene in Lakse Bugt by assessing topography, internal structure, and luminescence ages of fossil beach ridges and the modern beach. Lakse Bugt (Bay) lies on the southwestern coast of Disko Island in a meso-tidal regime and a mild wave climate. Beach ridges are widespread over the marine terrace, extending from 40 above sea level (masl). The most recent ridges terminate either at the beach or at the coastal sandy cliffs 8 masl immediately behind the modern beach. These ridges are covered mainly by rounded boulders; the terrain surfaces of the swales have clearly been deformed by freezing and thawing processes, in contrast to those of the ridge crests, which are relatively smooth.High-resolution reflection GPR data and high-resolution topographical data were collected along cross-shore transects using a shielded 250 MHz antennae system and a DGPS system, respectively. Sediment samples were collected along these transects from holes 0.5 m deep using light-proof plastic tubes, and dated using standard optically stimulated luminescence (OSL) techniques on sand-sized quartz grains.Beach profiles show that current berms lie much above the high tide range, and therefore they must have been formed under conditions more energetic than usual. Additionally, the low-tide level is well-marked by a sharp transition of sediment grain size: cobbles occur on the upper shoreface, whereas the foreshore is sandy. Seaward downlap reflection points were identified in the internal structure of all beach ridges. Radar reflections are strongly scattered at or just below the downlap points, indicating the transition to a deeper layer with coarser material. Therefore, we suggest that in this location the radar downlap points correspond to low-tide level at the time of deposition. Preliminary luminesce dating for samples collected 9 masl indicates that they were deposited in the late Holocene (4 to 2 ka ago); based on ridge separation, this suggests

  9. Marine sediments in Disko Trough reveal meltwater-influenced sedimentation during ice-stream retreat

    NASA Astrophysics Data System (ADS)

    Hogan, Kelly A.; Cofaigh, Colm Ó.; Jennings, Anne E.; Dowdeswell, Julian A.

    2015-04-01

    Marine geophysical data from middle and outer Disko Trough, West Greenland reveal thick (more than ten metres) acoustically-laminated, fine-grained sediments between subglacial tills at their base and post-glacial marine sediments at the seafloor. These sediments are interpreted as a transitional facies deposited as ice retreated from the trough during deglaciation. New sediment-core records indicate that these units were likely deposited by meltwater plumes emanating from a nearby grounded-ice margin, probably during stillstands in ice retreat. The retreat of ice in the trough may have been stabilised at a narrowing in DiskoTrough on the mid-shelf, as well as at the basalt escarpment south of Disko Island. Such thicknesses of deglacial or "transitional" glacimarine sediments are relatively unusual on high-latitude continental shelves and indicate a significant meltwater production in central West Greenland during deglaciation. This is consistent with the seafloor landforms in the inner and middle parts of the trough that include channels and moats around bedrock protrusions that look to have been eroded by water. IRD counts from the cores indicate that iceberg rafting also occurred during this transitional phase but that this signal was diluted by the fine-grained transitional sediments. Once ice had withdrawn from the area and sedimentation was hemipelagic in nature the IRD signal was less diluted.

  10. Buoyant Currents West and East of Greenland

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

  11. New insights into West Greenland ice sheet/stream dynamics during the last glacial cycle.

    NASA Astrophysics Data System (ADS)

    Roberts, David; Lane, Tim; Rea, Brice; Cofaigh, Colm O.; Jamieson, Stewart; Vieli, Andreas; Rodes, Angel

    2015-04-01

    Onshore and offshore geomorphological mapping and deglacial chronologies from West Greenland constrain the nature and magnitude of ice advance and decay of the Greenland Ice Sheet (GrIS) during the last glacial cycle. Several ice stream troughs are known to have fed ice to the shelf edge during the last glacial cycle. Their offshore expression suggests that many were coalescent systems fed by smaller outlet glaciers and ice streams onshore but their central flow pathways were also controlled by geology and preglacial topography. The bed morphology of these large ice streams shows they operated over soft, deforming beds with drumlins, mega-scale glacial lineations and grounding zone wedges marking an offshore transition from predominant areal scour onshore. Records of offshore deglacial chronology remain sparse but the Uummannaq and Disko Bugt ice stream corridors are now well constrained. The Uummannaq ice stream (UIS) completely deglaciated from the continental shelf between 14.8 ka and 11.0 ka in response to rising air temperatures, increasing JJA solar radiation and sea-level rise, but temporary standstills and the asynchronous retreat history of its feeder zones suggest that topography/bathymetry strongly modulated retreat rates as ice became 'locked' back into the coastal fjord system. Initial reconstructions of behaviour UIS discounted an oceanic role in early deglaciation and favoured retreat from the mid-shelf and inner-shelf prior to the Younger Dryas but both these concepts remain under investigation. In Disko Bugt, Jakobshavn Isbrae deglaciated later than the UIS and remained on the outer shelf during the Younger Dyras stadial (12.8 - 11.7 cal. kyrs BP) only reaching in the inner coast fjords at approximately 10.0 ka. The later deglaciation of the Disko system (despite similar external forcing mechanisms) was controlled by regional topographic/bathymetric contrasts in their respective trough morphologies. This hypothesis is supported by recent model

  12. Towards multi-decadal to multi-millennial ice core records from coastal west Greenland ice caps

    NASA Astrophysics Data System (ADS)

    Das, Sarah B.; Osman, Matthew B.; Trusel, Luke D.; McConnell, Joseph R.; Smith, Ben E.; Evans, Matthew J.; Frey, Karen E.; Arienzo, Monica; Chellman, Nathan

    2017-04-01

    The Arctic region, and Greenland in particular, is undergoing dramatic change as characterized by atmospheric warming, decreasing sea ice, shifting ocean circulation patterns, and rapid ice sheet mass loss, but longer records are needed to put these changes into context. Ice core records from the Greenland ice sheet have yielded invaluable insight into past climate change both regionally and globally, and provided important constraints on past surface mass balance more directly, but these ice cores are most often from the interior ice sheet accumulation zone, at high altitude and hundreds of kilometers from the coast. Coastal ice caps, situated around the margins of Greenland, have the potential to provide novel high-resolution records of local and regional maritime climate and sea surface conditions, as well as contemporaneous glaciological changes (such as accumulation and surface melt history). But obtaining these records is extremely challenging. Most of these ice caps are unexplored, and thus their thickness, age, stratigraphy, and utility as sites of new and unique paleoclimate records is largely unknown. Access is severely limited due to their high altitude, steep relief, small surface area, and inclement weather. Furthermore, their relatively low elevation and marine moderated climate can contribute to significant surface melting and degradation of the ice stratigraphy. We recently targeted areas near the Disko Bay region of central west Greenland where maritime ice caps are prevalent but unsampled, as potential sites for new multi-decadal to multi-millennial ice core records. In 2014 & 2015 we identified two promising ice caps, one on Disko Island (1250 m. asl) and one on Nuussuaq Peninsula (1980 m. asl) based on airborne and ground-based geophysical observations and physical and glaciochemical stratigraphy from shallow firn cores. In spring 2015 we collected ice cores at both sites using the Badger-Eclipse electromechanical drill, transported by a medley

  13. Molecular diversity patterns among various phytoplankton size-fractions in West Greenland in late summer

    NASA Astrophysics Data System (ADS)

    Elferink, Stephanie; Neuhaus, Stefan; Wohlrab, Sylke; Toebe, Kerstin; Voß, Daniela; Gottschling, Marc; Lundholm, Nina; Krock, Bernd; Koch, Boris P.; Zielinski, Oliver; Cembella, Allan; John, Uwe

    2017-03-01

    Arctic regions have experienced pronounced biological and biophysical transformations as a result of global change processes over the last several decades. Current hypotheses propose an elevated impact of those environmental changes on the biodiversity, community composition and metabolic processes of species. The effects on ecosystem function and services, particularly when invasive or toxigenic harmful species become dominant, can be expressed over a wide range of temporal and spatial scales in plankton communities. Our study focused on the comparison of molecular biodiversity of three size-fractions (micro-, nano-, picoplankton) in the coastal pelagic zone of West Greenland and their association with environmental parameters. Molecular diversity was assessed via parallel amplicon sequencing the 28S rRNA hypervariable D1/D2 region. We showed that biodiversity distribution within the area of Uummannaq Fjord, Vaigat Strait and Disko Bay differed markedly within and among size-fractions. In general, we observed a higher diversity within the picoplankton size fraction compared to the nano- and microplankton. In multidimensional scaling analysis, community composition of all three size fractions correlated with cell size, silicate and phosphate, chlorophyll a (chl a) and dinophysistoxin (DTX). Individually, each size fraction community composition also correlated with other different environmental parameters, i.e. temperature and nitrate. We observed a more homogeneous community of the picoplankton across all stations compared to the larger size classes, despite different prevailing environmental conditions of the sampling areas. This suggests that habitat niche occupation for larger-celled species may lead to higher functional trait plasticity expressed as an enhanced range of phenotypes, whereas smaller organisms may compensate for lower potential plasticity with higher diversity. The presence of recently identified toxigenic harmful algal bloom (HAB) species (such

  14. 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.

  15. Using Coastal Ice Cap Records to Investigate Maritime Climate and Ice Sheet Processes in West Greenland

    NASA Astrophysics Data System (ADS)

    Das, S. B.; Evans, M. J.; Frey, K. E.; Osman, M. B.; Smith, B. E.; Stevens, L. A.; Trusel, L. D.; York, A.; Bingham, M.

    2014-12-01

    Recent changes, including outlet glacier retreat and speedup, and increased rates of surface melting, have dramatically increased the Greenland ice sheet contribution to sea-level rise over the past few decades. Increasingly studies point towards the influence of coupled ocean-ice processes in modulating Greenland ice sheet mass balance and glacier behavior in response to climate change, but many of these studies are limited to the past few years to decades, restricting our ability to understand these ocean-ice relationships over longer time periods. Ice core records have the potential to provide unique, high-resolution records of interest (e.g. accumulation and melt variability, as well as contemporaneous proxy records of regional air temperature and sea surface conditions), but suitable Greenland ice sheet coring regions are often located far inland (>200 km) from many maritime regions of interest. In this study we focus on new records from previously unstudied maritime ice caps (10-30 km from the coast) to reconstruct past environmental conditions in the Disko, Ummannaq and Baffin Bay regions. Here we present results from our recent 2014 field investigation of three high altitude ice caps (1300-2000 m) on Disko Island and the Nuussuaq Peninsula, as well as complementary results from two sites in the western ice sheet accumulation zone. Geophysical observations provide constraints on ice thickness, layering, and ice flow. Physical and chemical stratigraphic observations from snow pits and shallow firn cores are used to reconstruct recent accumulation rate and melt variability, as well as to develop and test environmental proxy relationships over the satellite era. Multi-century records from longer coastal ice cores, to be drilled in 2015, will contribute a key missing component to the existing observational record documenting ice, ocean and atmospheric changes in this region over a time period of dramatic change in Greenland ice sheet behavior (retreat and

  16. Force balance along Isunnguata Sermia, west Greenland

    NASA Astrophysics Data System (ADS)

    Meierbachtol, Toby; Harper, Joel; Johnson, Jesse

    2016-09-01

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

  17. The impact of local topography on glacial geomorphological records in West Greenland

    NASA Astrophysics Data System (ADS)

    Adamson, Kathryn; Lane, Tim

    2015-04-01

    The Holocene glacial record of Lyngmarksbræen, an ice cap in West Greenland, has been used to explore the impacts of local topography on landform generation and preservation. It is well-established that glacial response to regional climate drivers may be locally modulated by local-scale topography, but there has been little systematic investigation of its impacts on the geomorphological record. Establishing the relative influence of regional and local-scale drivers on landform development is important as it will allow us to make more robust reconstructions of past ice dynamics. Detailed geomorphological analysis of seven outlet valleys from Lyngmarksbræen, Disko Island has been undertaken. Satellite imagery and field mapping have been used to explore the topographic variations of neighbouring valleys, and the resulting geomorphological record. Comparisons between valleys are made on the basis of existing morphostratigraphic correlations (Ingólfsson, 1990) and recent surface exposure ages (Lane et al., In prep), which indicate that the majority of the landforms were deposited during the Little Ice Age (LIA). The valleys draining Lyngmarksbræen vary considerably in terms of geometry, landform characteristics (type, size, location), and ice extent (Holocene to present day). This allows us to explore geomorphological dynamics in contrasting, but geographically proximal, settings. During the LIA, ice extended up to 3 km beyond the present ice margins. In all outlets, glacial landforms are confined to the radial valleys and there is only limited evidence of deposition in the larger trunk valleys. To the north and east of Lyngmarksbræen, large latero-frontal moraines are well-preserved and often impound small proglacial lakes. In the west, the LIA and present day ice margins are more diffuse, and there is evidence of ice-cored moraine, kettle holes, and buried ice. To the south of the ice cap, landform preservation is limited. We discuss the extent to which these

  18. The diel cycle of water vapor in west Greenland

    NASA Astrophysics Data System (ADS)

    Kopec, B. G.; Lauder, A. M.; Posmentier, E. S.; Feng, X.

    2014-08-01

    We present a study of the dynamics of small-scale (~100 km) atmospheric circulation in west Greenland which is dominated by interactions of marine and continental air masses. Water vapor concentration and isotopic ratios measured continuously over a 25 day period in Kangerlussuaq, Greenland were used to monitor the convergence of easterly katabatic winds and westerly sea breezes that form a front between the dry, isotopically depleted, glacial air mass and the moist, isotopically enriched, marine air mass. During the latter 16 days of the measurement period, an interval with no large-scale synoptic interference, the inland penetration of the sea breeze controlled the largest day-to-day humidity and vapor isotopic variations. Kangerlussuaq experienced sea breezes in the afternoon on 9 days, consistent with the long-term average of such occurrences on 56% of days in July and August. The inland position of the sea breeze front is controlled by the katabatic wind strength, which is stronger during times of reduced cloud coverage and/or higher-pressure gradient between the coast and the Greenland ice sheet. The position and movement of the front will likely respond to changes in the general atmospheric circulation and regional radiation balance resulting from global warming, which will, in turn, impact the local hydrological cycle and ecosystem processes.

  19. Vegetation phenology gradients along the west and east coasts of Greenland from 2001 to 2015.

    PubMed

    Karami, Mojtaba; Hansen, Birger Ulf; Westergaard-Nielsen, Andreas; Abermann, Jakob; Lund, Magnus; Schmidt, Niels Martin; Elberling, Bo

    2017-02-01

    The objective of this paper is to characterize the spatiotemporal variations of vegetation phenology along latitudinal and altitudinal gradients in Greenland, and to examine local and regional climatic drivers. Time-series from the Moderate Resolution Imaging Spectroradiometer (MODIS) were analyzed to obtain various phenological metrics for the period 2001-2015. MODIS-derived land surface temperatures were corrected for the sampling biases caused by cloud cover. Results indicate significant differences between West and East Greenland, in terms of both observed phenology during the study period, as well as the climatic response. The date of the start of season (SOS) was significantly earlier (24 days), length of season longer (25 days), and time-integrated NDVI higher in West Greenland. The sea ice concentration during May was found to have a significant effect on the date of the SOS only in West Greenland, with the strongest linkage detected in mid-western parts of Greenland.

  20. Levels and temporal trends of HCH isomers in ringed seals from West and East Greenland.

    PubMed

    Rigét, Frank; Vorkamp, Katrin; Dietz, Rune; Muir, Derek C G

    2008-08-01

    Levels and temporal trends of the hexachlorocyclohexane isomers alpha-, beta- and gamma-HCH were analysed in blubber of juvenile ringed seals from West Greenland (1994 to 2006) and juvenile and adult ringed seals from East Greenland (1986 to 2006). No significant differences in the concentration levels in the juvenile seals were found between East and West Greenland for any of the three isomers. alpha-HCH concentrations were not significantly different between juvenile and adult ringed seals from East Greenland, whereas beta- and gamma-HCH concentrations were significantly higher in adult ringed seals. alpha- and beta-HCH in Greenland ringed seals were approximately a factor two lower than in the Canadian Arctic, and alpha-HCH was a factor 2-3 higher than in ringed seals from an area east of Svalbard, Norway. Annual decreases in ringed seals from Greenland during the study periods were detected to be 9.1-11.7%, 1.4-3.9% and 6.0-6.4% for alpha-, beta- and gamma-HCH, respectively, being quite similar in both East and West Greenland. Similar levels and trends in East and West Greenland support the general understanding of the pathways of HCH isomers to and in the Arctic.

  1. Divergent parasite faunas in adjacent populations of West Greenland caribou: suggested natural and anthropogenic influences

    USDA-ARS?s Scientific Manuscript database

    Gastrointestinal parasite diversity was characterized for two adjacent populations of west Greenland caribou (Rangifer tarandus groenlandicus) through examinations of abomasa and small intestines of adult and subadult females collected during late winter. Three trichostrongyline (Trichostrongylina: ...

  2. Soil Response to Aeolian Disturbance in West Greenland

    NASA Astrophysics Data System (ADS)

    Heindel, R. C.; Culler, L. E.; Chipman, J. W.; Virginia, R. A.

    2015-12-01

    Arctic soils are a critical ecological resource, yet are increasingly vulnerable to global change. In the Kangerlussuaq region of West Greenland, aeolian disturbance is the greatest threat to soil stability, with strong katabatic winds eroding vegetation and soil down to the underlying glacial till or bedrock. Little is known about what controls the distribution and rate of the aeolian erosion, which initially results in a state change from tundra to a deflated and nearly unvegetated ground. It is unclear if vegetation can eventually reestablish after erosion occurs, potentially aided by the biological soil crust (BSC) that develops within the eroded areas, or if this soil loss is an irreversible change in vegetation and soil carbon (C) and nitrogen (N) cycling. Our analysis of high-resolution satellite imagery shows that across the entire study region, deflated ground covers 22% of the terrestrial landscape. Aeolian erosion occurs more frequently closer to the Greenland Ice Sheet and on S-facing slopes. Using lichenometry, we estimate that erosional fronts move across the landscape at rates of 2.5 cm yr-1, leaving unproductive ground in their wake. The onset of widespread aeolian erosion occurred roughly 700-1000 years ago, pointing toward regional cooling and aridity as the drivers behind erosion. Finally, we consider whether the BSCs can improve soil quality enough to allow for full vegetation regrowth. Preliminary results show that while the BSCs fix atmospheric N and increase C storage, the rate of soil quality recovery is extremely slow. Understanding the thresholds between vegetated tundra and eroded ground is critical for predicting how the Kangerlussuaq landscape will respond to anticipated changes in climate and ice sheet dynamics.

  3. Gyrfalcon diet in central west Greenland during the nestling period

    USGS Publications Warehouse

    Booms, Travis; Fuller, Mark R.

    2003-01-01

    We studied food habits of Gyrfalcons (Falco rusticolus) nesting in central west Greenland in 2000 and 2001 using three sources of data: time-lapse video (3 nests), prey remains (22 nests), and regurgitated pellets (19 nests). These sources provided different information describing the diet during the nesting period. Gyrfalcons relied heavily on Rock Ptarmigan (Lagopus mutus) and arctic hares (Lepus arcticus). Combined, these species contributed 79-91% of the total diet, depending on the data used. Passerines were the third most important group. Prey less common in the diet included waterfowl, arctic fox pups (Alopex lagopus), shorebirds, gulls, alcids, and falcons. All Rock Ptarmigan were adults, and all but one arctic hare were young of the year. Most passerines were fledglings. We observed two diet shifts, first from a preponderance of ptarmigan to hares in mid-June, and second to passerines in late June. The video-monitored Gyrfalcons consumed 94-110 kg of food per nest during the nestling period, higher than previously estimated. Using a combination of video, prey remains, and pellets was important to accurately document Gyrfalcon diet, and we strongly recommend using time-lapse video in future diet studies to identify biases in prey remains and pellet data.

  4. Gyrfalcon diet in central west Greenland during the nesting period

    USGS Publications Warehouse

    Booms, T.L.; Fuller, M.R.

    2003-01-01

    We studied food habits of Gyrfalcons (Falco rusticolus) nesting in central west Greenland in 2000 and 2001 using three sources of data: time-lapse video (3 nests), prey remains (22 nests), and regurgitated pellets (19 nests). These sources provided different information describing the diet during the nesting period. Gyrfalcons relied heavily on Rock Ptarmigan (Lagopus mutus) and arctic hares (Lepus arcticus). Combined, these species contributed 79-91% of the total diet, depending on the data used. Passerines were the third most important group. Prey less common in the diet included waterfowl, arctic fox pups (Alopex lagopus), shorebirds, gulls, alcids, and falcons. All Rock Ptarmigan were adults, and all but one arctic hare were young of the year. Most passerines were fledglings. We observed two diet shifts, first from a preponderance of ptarmigan to hares in mid-June, and second to passerines in late June. The video-monitored Gyrfalcons consumed 94-110 kg of food per nest during the nestling period, higher than previously estimated. Using a combination of video, prey remains, and pellets was important to accurately document Gyrfalcon diet, and we strongly recommend using time-lapse video in future diet studies to identify biases in prey remains and pellet data.

  5. Measurement campaign for wind power potential in west Greenland

    NASA Astrophysics Data System (ADS)

    Rønnow Jakobsen, Kasper

    2013-04-01

    Experiences and results from a wind resource exploring campaign 2003- in west Greenland. Like many other countries, Greenland is trying to reduce its dependency of fossil fuel by implementing renewable energy. The main challenge is that the people live on the coast in scattered settlements, without power infrastructure. Based on this a wind power potential project was established in 2002, funded by the Greenlandic government and the Technical University of Denmark. We present results and experiences of the campaign. 1 Field campaign There were only a few climate stations in or close to settlements and due to their positioning and instrumentation, they were not usable for wind resource estimation. To establish met stations in Arctic areas with complex topography, there are some challenges to face; mast positioning in complex terrain, severe weather conditions, instrumentation, data handling, installation and maintenance budget. The terrain in the ice free and populated part, mainly consists of mountains of different heights and shapes, separated by deep fjords going from the ice cap to the sea. With a generally low wind resource the focus was on the most exposed positions close to the settlements. Data from the nearest existing climate stations was studied for background estimations of predominant wind directions and extreme wind speeds, and based on that the first 10m masts were erected in 2003. 2 Instruments The first installations used standard NRG systems with low cost NRG instruments. For most of the sites this low cost setup did a good job, but there were some problems with the first design, including instrument and boom strains. In subsequent years, the systems were updated several times to be able to operate in the extreme conditions. Different types of instruments, data logger and boom systems were tested to get better data quality and reliability. Today 11 stations with heights ranging from 10-50m are installed and equipped according to the IEC standard

  6. Recent trends in the west Greenland salmon fishery, and implications for Thick-billed Murres

    USGS Publications Warehouse

    Piatt, John F.; Reddin, David G.

    1982-01-01

    In the late 1960s and early 1970s, a high net-mortality of seabirds, particularly Thick-billed Murres (Uria lomvia), was associated with the west Greenland salmon fishery. Since 1972, the domestic fishery has been controlled by quotas and fishery opening dates and non-Greenlandic offshore drift-net fishery was phased out in 1975. These restrictions probably resulted in a substantial decrease in murre net-mortality. However, the Greenlandic fishery has changed considerably since 1972 when seabird bycatch was last examined in detail. Fishing vessels now use monofilament nylon nets almost exclusively; fishing effort has redistributed closer to murre breeding colonies and intensive drift-netting occurs offshore on the continental shelf. These factors, combined with a change in 1981 to a later fishing season have probably resulted in a renewal of significant murre net-morality at west Greenland.

  7. Assessment of Undiscovered Oil and Gas Resources of the West Greenland-East Canada Province, 2008

    USGS Publications Warehouse

    Schenk, Christopher J.; Bird, Kenneth J.; Brown, Philip J.; Charpentier, Ronald R.; Gautier, Donald L.; Houseknecht, David W.; Klett, Timothy R.; Pawlewicz, Mark J.; Shah, Anjana; Tennyson, Marilyn E.

    2008-01-01

    The U.S. Geological Survey (USGS) recently assessed the undiscovered oil and gas potential of the West Greenland?East Canada Province as part of the USGS Circum-Arctic Oil and Gas Resource Appraisal effort. The West Greenland?East Canada Province is essentially the offshore area between west Greenland and east Canada and includes Baffin Bay, Davis Strait, Lancaster Sound, and Nares Strait west of and including Kane Basin. The tectonic evolution of the West Greenland?East Canada Province led to the formation of several major structural domains that are the geologic basis for the five assessment units (AU) defined in this study. The five AUs encompass the entire province. Each AU was assessed in its entirety for undiscovered, technically recoverable (assuming absence of sea ice) oil and gas resources, but the assessment results reported here are only for those portions of each AU that are north of the Arctic Circle, as that latitude defines the area of the Circum-Arctic oil and gas assessment.

  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. The Vaigat Rock Avalanche Laboratory, west-central Greenland

    NASA Astrophysics Data System (ADS)

    Dunning, S.; Rosser, N. J.; Szczucinski, W.; Norman, E. C.; Benjamin, J.; Strzelecki, M.; Long, A. J.; Drewniak, M.

    2013-12-01

    Rock avalanches have unusually high mobility and pose both an immediate hazard, but also produce far-field impacts associated with dam breach, glacier collapse and where they run-out into water, tsunami. Such secondary hazards can often pose higher risks than the original landslide. The prediction of future threats posed by potential rock avalanches is heavily reliant upon understanding of the physics derived from an interpretation of deposits left by previous events, yet drawing comparisons between multiple events is normally challenging as interactions with complex mountainous terrain makes deposits from each event unique. As such numerical models and the interpretation of the underlying physics which govern landslide mobility is commonly case-specific and poorly suited to extrapolation beyond the single events the model is tuned to. Here we present a high-resolution LiDAR and hyperspectral dataset captured across a unique cluster of large rock avalanche source areas and deposits in the Vaigat straight, west central Greenland. Vaigat offers the unprecedented opportunity to model a sample of > 15 rock avalanches of various age sourced from an 80 km coastal escarpment. At Vaigat many of the key variables (topography, geology, post-glacial history) are held constant across all landslides providing the chance to investigate the variations in dynamics and emplacement style related to variable landslide volume, drop-heights, and thinning/spreading over relatively simple, unrestricted run-out zones both onto land and into water. Our data suggest that this region represents excellent preservation of landslide deposits, and hence is well suited to calibrate numerical models of run out dynamics. We use this data to aid the interpretation of deposit morphology, structure lithology and run-out characteristics in more complex settings. Uniquely, we are also able to calibrate our models using a far-field dataset of well-preserved tsunami run-up deposits, resulting from the 21

  10. Levels and spatial and temporal trends of contaminants in Greenland biota: an updated review.

    PubMed

    Riget, F; Dietz, R; Vorkamp, K; Johansen, P; Muir, D

    2004-09-20

    Knowledge of contaminant levels in Greenland biota has increased substantially in recent years, particularly for persistent organic pollutants. This paper reviews and updates knowledge of spatial and temporal trends of Cd, Hg and organochlorines (PCBs, DDTs, HCHs, HCB and chlordane-related compounds) in Greenland terrestrial, freshwater and marine biota. The most comprehensive studies of spatial trends of Cd and Hg in the terrestrial ecosystem concern lichens, with relatively complete coverage, and caribou (Rangifer tarandus), with coverage mainly in different regions of central West Greenland and Southwest Greenland. The Arctic char (Salvelinus alpinus) is the only freshwater organism for which studies of spatial trends of Hg levels have been completed. Information on spatial trends of Cd and Hg in the marine environment is available from studies of fish, seabirds, ringed seals (Phoca hispida) and polar bears (Ursus maritimus). Geographical patterns of Cd and Hg in Greenland biota were not always consistent among different species or different studies. In landlocked Arctic char the concentrations of Hg decreased from south to north. In marine animals levels of Hg tended to be higher in East Greenland than in West Greenland and Cd levels were highest in biota from Disko Island in central West Greenland. The observed regional differences are difficult to explain but in most cases the causes appear to be natural rather than anthropogenic. Only a few time series covering the last 20 years exist for Cd and Hg. The one time series indicating a temporal change is for ringed seals in Northwest Greenland, which shows an increasing trend of Hg and a decreasing trend of Cd since 1984. Whether the changes reflect anthropogenic inputs, seal behaviour or other environmental factors is unknown. The most significant new insights have concerned organochlorines. In general, levels of these compounds were very low in terrestrial biota compared to marine species. Concentrations in

  11. One million years of glaciation and denudation history in west Greenland

    PubMed Central

    Strunk, Astrid; Knudsen, Mads Faurschou; Egholm, David L.; Jansen, John D.; Levy, Laura B.; Jacobsen, Bo H.; Larsen, Nicolaj K.

    2017-01-01

    The influence of major Quaternary climatic changes on growth and decay of the Greenland Ice Sheet, and associated erosional impact on the landscapes, is virtually unknown beyond the last deglaciation. Here we quantify exposure and denudation histories in west Greenland by applying a novel Markov-Chain Monte Carlo modelling approach to all available paired cosmogenic 10Be-26Al bedrock data from Greenland. We find that long-term denudation rates in west Greenland range from >50 m Myr−1 in low-lying areas to ∼2 m Myr−1 at high elevations, hereby quantifying systematic variations in denudation rate among different glacial landforms caused by variations in ice thickness across the landscape. We furthermore show that the present day ice-free areas only were ice covered ca. 45% of the past 1 million years, and even less at high-elevation sites, implying that the Greenland Ice Sheet for much of the time was of similar size or even smaller than today. PMID:28098141

  12. One million years of glaciation and denudation history in west Greenland

    NASA Astrophysics Data System (ADS)

    Strunk, Astrid; Knudsen, Mads Faurschou; Egholm, David L.; Jansen, John D.; Levy, Laura B.; Jacobsen, Bo H.; Larsen, Nicolaj K.

    2017-01-01

    The influence of major Quaternary climatic changes on growth and decay of the Greenland Ice Sheet, and associated erosional impact on the landscapes, is virtually unknown beyond the last deglaciation. Here we quantify exposure and denudation histories in west Greenland by applying a novel Markov-Chain Monte Carlo modelling approach to all available paired cosmogenic 10Be-26Al bedrock data from Greenland. We find that long-term denudation rates in west Greenland range from >50 m Myr-1 in low-lying areas to ~2 m Myr-1 at high elevations, hereby quantifying systematic variations in denudation rate among different glacial landforms caused by variations in ice thickness across the landscape. We furthermore show that the present day ice-free areas only were ice covered ca. 45% of the past 1 million years, and even less at high-elevation sites, implying that the Greenland Ice Sheet for much of the time was of similar size or even smaller than today.

  13. One million years of glaciation and denudation history in west Greenland.

    PubMed

    Strunk, Astrid; Knudsen, Mads Faurschou; Egholm, David L; Jansen, John D; Levy, Laura B; Jacobsen, Bo H; Larsen, Nicolaj K

    2017-01-18

    The influence of major Quaternary climatic changes on growth and decay of the Greenland Ice Sheet, and associated erosional impact on the landscapes, is virtually unknown beyond the last deglaciation. Here we quantify exposure and denudation histories in west Greenland by applying a novel Markov-Chain Monte Carlo modelling approach to all available paired cosmogenic (10)Be-(26)Al bedrock data from Greenland. We find that long-term denudation rates in west Greenland range from >50 m Myr(-1) in low-lying areas to ∼2 m Myr(-1) at high elevations, hereby quantifying systematic variations in denudation rate among different glacial landforms caused by variations in ice thickness across the landscape. We furthermore show that the present day ice-free areas only were ice covered ca. 45% of the past 1 million years, and even less at high-elevation sites, implying that the Greenland Ice Sheet for much of the time was of similar size or even smaller than today.

  14. Abrupt Holocene climate change as an important factor for human migration in West Greenland.

    PubMed

    D'Andrea, William J; Huang, Yongsong; Fritz, Sherilyn C; Anderson, N John

    2011-06-14

    West Greenland has had multiple episodes of human colonization and cultural transitions over the past 4,500 y. However, the explanations for these large-scale human migrations are varied, including climatic factors, resistance to adaptation, economic marginalization, mercantile exploration, and hostile neighborhood interactions. Evaluating the potential role of climate change is complicated by the lack of quantitative paleoclimate reconstructions near settlement areas and by the relative stability of Holocene temperature derived from ice cores atop the Greenland ice sheet. Here we present high-resolution records of temperature over the past 5,600 y based on alkenone unsaturation in sediments of two lakes in West Greenland. We find that major temperature changes in the past 4,500 y occurred abruptly (within decades), and were coeval in timing with the archaeological records of settlement and abandonment of the Saqqaq, Dorset, and Norse cultures, which suggests that abrupt temperature changes profoundly impacted human civilization in the region. Temperature variations in West Greenland display an antiphased relationship to temperature changes in Ireland over centennial to millennial timescales, resembling the interannual to multidecadal temperature seesaw associated with the North Atlantic Oscillation.

  15. Chapter 41: Geology and petroleum potential of the West Greenland-East Canada Province

    USGS Publications Warehouse

    Schenk, C.J.

    2011-01-01

    The US Geological Survey (USGS) assessed the potential for undiscovered oil and gas resources of the West Greenland-East Canada Province as part of the USGS Circum-Arctic Resource Appraisal programme. The province lies in the offshore area between western Greenland and eastern Canada and includes Baffin Bay, Davis Strait, Lancaster Sound and Nares Strait west of and including part of Kane Basin. A series of major tectonic events led to the formation of several distinct structural domains that are the geological basis for defining five assessment units (AU) in the province, all of which are within the Mesozoic-Cenozoic Composite Petroleum System. Potential petroleum source rocks include strata of Ordovician, Lower and Upper Cretaceous, and Palaeogene ages. The five AUs defined for this study - the Eurekan Structures AU, NW Greenland Rifted Margin AU, NE Canada Rifted Margin AU, Baffin Bay Basin AU and the Greater Ungava Fault Zone AU - encompass the entire province and were assessed for undiscovered technically recoverable resources. The mean volumes of undiscovered resources for the West Greenland-East Canada Province are 10.7 ?? 109 barrels of oil, 75 ?? 1012 cubic feet of gas, and 1.7 ?? 109 barrels of natural gas liquids. For the part of the province that is north of the Arctic Circle, the estimated mean volumes of these undiscovered resources are 7.3 ?? 109 barrels of oil, 52 ?? 1012 cubic feet of natural gas, and 1.1 ?? 109 barrels of natural gas liquids. ?? 2011 The Geological Society of London.

  16. Abrupt Holocene climate change as an important factor for human migration in West Greenland

    PubMed Central

    D’Andrea, William J.; Huang, Yongsong; Fritz, Sherilyn C.; Anderson, N. John

    2011-01-01

    West Greenland has had multiple episodes of human colonization and cultural transitions over the past 4,500 y. However, the explanations for these large-scale human migrations are varied, including climatic factors, resistance to adaptation, economic marginalization, mercantile exploration, and hostile neighborhood interactions. Evaluating the potential role of climate change is complicated by the lack of quantitative paleoclimate reconstructions near settlement areas and by the relative stability of Holocene temperature derived from ice cores atop the Greenland ice sheet. Here we present high-resolution records of temperature over the past 5,600 y based on alkenone unsaturation in sediments of two lakes in West Greenland. We find that major temperature changes in the past 4,500 y occurred abruptly (within decades), and were coeval in timing with the archaeological records of settlement and abandonment of the Saqqaq, Dorset, and Norse cultures, which suggests that abrupt temperature changes profoundly impacted human civilization in the region. Temperature variations in West Greenland display an antiphased relationship to temperature changes in Ireland over centennial to millennial timescales, resembling the interannual to multidecadal temperature seesaw associated with the North Atlantic Oscillation. PMID:21628586

  17. 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.

  18. Nuuk, Greenland

    NASA Image and Video Library

    2008-05-23

    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. This image was acquired August 2, 2004 by NASA Terra spacecraft.

  19. Mountain glaciers vs Ice sheet in Greenland - learning from a new monitoring site in West Greenland

    NASA Astrophysics Data System (ADS)

    Abermann, Jakob; van As, Dirk; Wacker, Stefan; Langley, Kirsty

    2017-04-01

    Only 5 out of the 20.000 peripheral glaciers and ice caps surrounding Greenland are currently monitored due to logistical challenges and despite their significance for sea level rise. Large spatial coast-to-icesheet mass and energy balance gradients limit simple upscaling methods from ice-sheet observations, which builds the motivation for this study. We present results from a new mass and energy balance time series at Qasigiannguit glacier (64°09'N; 51°21'W) in Southwest Greenland. Inter-annual variability is discussed and the surface energy balance over two summers is quantified and a ranking of the main drivers performed. We find that short-wave net radiation is by far the most dominant energy source during summer, followed by similar amounts of net longwave radiation and sensible heat, respectively. We then relate these observations to synchronous measurements at similar latitude on an outlet glacier of the ice sheet a mere 100 km away. We find very pronounced horizontal surface mass balance gradients, with generally more positive values closer to the coast. We conclude that despite minor differences of atmospheric parameters (i.e. humidity, radiation, and temperature) the main reason for the strongly different signal is a pronounced winter precipitation gradient that translates in a different duration of ice exposure and through that an albedo gradient. Modelled energy balance gradients converted into mass changes show good agreement to measured surface mass balance gradients and we explore a latitudinal signal of these findings.

  20. Paleoecology and paleoclimatology of a late holocene peat deposit from Braendevinsskaer, Central West Greenland

    SciTech Connect

    Bennike, O. )

    1992-08-01

    The macroscopical plant and animal remains of a nearshore peat deposit in West Greenland are described and documented. The assemblages contain a mixture of limnic, terrestrial, and marine plants and animals. These are divided into four local macrofossil assemblage zones, of which zone 3, ca. A.D. 950 to ca. A.D. 1760, represents a wet phase which is correlated in part with the Little Ice Age.

  1. Paleoceanography and Ice Sheet-Ocean Interactions on the Central West Greenland Margin, LGM through Deglaciation

    NASA Astrophysics Data System (ADS)

    Jennings, A. E.; Andrews, J. T.; Ó Cofaigh, C.; St-Onge, G.; Belt, S. T.; Cabedo-Sanz, P.; Dowdeswell, J. A.

    2014-12-01

    Hemipelagic sediments in several central West Greenland trough mouth fan cores are critical for testing whether an ice shelf covered Baffin Bay during the late LGM and H1 (core HU2008029-12PC) and to investigate the role of ocean warming in initiating and/or sustaining retreat of the Greenland Ice Sheet from the shelf edge (cores JR175-VC29 & -VC46). We use benthic and planktic foram assemblages, IP25 sea ice biomarker, ice-rafted detritus (IRD), lithofacies and quantitative mineralogy to reconstruct paleoceanographic conditions. HU2008029-12PC comprises bioturbated, thin turbidites and hemipelagic sediments with Greenlandic provenance from >19.2 to 16.7 cal ka BP. Abundance spikes of planktic forams provide the radiocarbon dates in this interval and coincide with abundance spikes of benthic foram species indicative of chilled Atlantic Water and episodic marine productivity. IRD and IP25 are rare in this interval. These characteristics are consistent with the ice margin at the shelf edge meeting a heavily sea-ice covered ocean with chilled Atlantic Water at depth, rather than an ice shelf-covered ocean. Initial deglaciation from the West Greenland margin began c. 16.7 ka BP, as recorded by a lithofacies shift from turbidites to bioturbated mud with dispersed IRD and continued presence of Atlantic Water benthic species. After 16.7 ka BP, IP25, large diatoms and benthic forams indicative of sea-ice edge productivity show warming conditions. By 15.2 ka BP Greenlandic IRD and meltwater species, Elphidium excavatum, reflect accelerated ice sheet ablation. By 14.4 ka BP a strong rise in IP25 content, introduction of key Atlantic Water species Cassidulina neoteretis, and IRD spikes rich in detrital carbonate with a northern Baffin Bay provenance provide evidence for increased advection of West Greenland Current, collapse of the LIS ice streams, and formation of an IRD belt along the W. Greenland margin during the Bølling-Allerod and early Holocene warm intervals.

  2. Undercutting of marine-terminating glaciers in West Greenland

    NASA Astrophysics Data System (ADS)

    Rignot, Eric; Fenty, Ian; Xu, Yun; Cai, Cilan; Kemp, Chris

    2015-07-01

    Marine-terminating glaciers control most of Greenland's ice discharge into the ocean, but little is known about the geometry of their frontal regions. Here we use side-looking, multibeam echo sounding observations to reveal that their frontal ice cliffs are grounded deeper below sea level than previously measured and their ice faces are neither vertical nor smooth but often undercut by the ocean and rough. Deep glacier grounding enables contact with subsurface, warm, salty Atlantic waters (AW) which melts ice at rates of meters per day. We detect cavities undercutting the base of the calving faces at the sites of subglacial water (SGW) discharge predicted by a hydrological model. The observed pattern of undercutting is consistent with numerical simulations of ice melt in which buoyant plumes of SGW transport warm AW to the ice faces. Glacier undercutting likely enhances iceberg calving, impacting ice front stability and, in turn, the glacier mass balance.

  3. Crustal structure of the West Greenland margin in North Baffin Bay

    NASA Astrophysics Data System (ADS)

    Damm, V.; Block, M.; Berglar, K.; Ehrhardt, A.; Heyde, I.; Schnabel, M.; Schreckenberger, B.; Altenbernd, T.; Suckro, S.

    2012-04-01

    The tectonic and geodynamic evolution of the Baffin Bay is interpreted to be closely associated with mantle dynamics and plume activity. The initial opening of the Baffin Bay coincides with the volcanic activity along the West Greenland margin between 60.7 and 59.4 Ma (Storey at al., 1998), attributed to the arrival of the Iceland plume beneath Greenland (Lawver and Müller, 1994, Larsen and Saunders, 1998). Rifting in the Baffin Bay is linked to oceanic spreading in the Labrador Sea, but there is no consensus about the nature of the underlying crust in central Baffin Bay. The geodynamic evolution of the Baffin Bay and plate tectonic reconstructions for Greenland relative to North America are still a matter of debate though they are of special importance in the circum-Arctic geodynamic framework. Due to lack of data the plate boundary between the North American plate and the Greenland plate is not well defined and the nature of the continent-ocean transition zone is widely unknown. Evidence indicating that the deep sea area of the Baffin Bay crust is oceanic has been provided by Keen and Barrett (1972) based on seismic refraction data. However, Reid and Jackson (1997) did not find evidence for layered oceanic crust and interpreted the deep part of Baffin Bay as serpentinized mantle material. They suggest that rifting was amagmatic and separation of passive continental margins was comparable to ultra-slow spreading ridges. Linear magnetic anomaly patterns in this region were not clearly identified. The position of the extinct spreading axis was defined by a northwest-trending linear gravity anomaly of central Baffin Bay (Chalmers and Pulvertaft, 2001). Spreading in the Baffin Bay took obviously place in Paleocene and Eocene times in two phases which may be distinguished by a reorientation of the directions of plate motion for Greenland starting about 55 Ma ago (Chalmers and Pulvertaft, 2001). It is not fully explained how a postulated major transform fault

  4. Outbreak of trichinellosis associated with consumption of game meat in West Greenland.

    PubMed

    Møller, Lone Nukâraq; Petersen, Eskild; Kapel, Christian M O; Melbye, Mads; Koch, Anders

    2005-09-05

    The Inuit population of the Arctic has always been at risk of acquiring trichinellosis and severe outbreaks have been recorded in Alaska and Canada. In West Greenland, a number of large outbreaks took place during the 1940s and 1950s; they involved total 420 cases including 37 deaths. Since then only sporadic cases have been reported. Here, we describe an outbreak of infection with Trichinella spp. after consumption of infected meat presumably from walrus or polar bear caught in western Greenland. Six persons who had eaten of the walrus and polar bear meat were two males and four females, age range 6--47 years. Using ELISA and Western blot analysis (Trichinella-specific IgG antibodies against excreted/secreted antigen and synthetic tyvelose antigen, respectively) four of these persons were found to be sero-positive for Trichinella antibodies, with three of these having clinical symptoms compatible with trichinellosis. On re-test, 12--14 months later one of the two sero-negative persons had sero-converted, probably due to a new, unrelated infection. This study demonstrates that acquiring Trichinella from the consumption of marine mammals remains a possibility in Greenland, and that cases may go undetected. Trichinellosis in Greenland can be prevented by the implementation of public health measures.

  5. Mapping faults and intrusions onshore Disko Island by use of Vibroseismic data, shallow marine seismic data and electromagnetic observations

    NASA Astrophysics Data System (ADS)

    Clausen, Ole R.; Nørmark, Egon; Gulbrandsen, Pelle; Sabra, Henrik

    2014-05-01

    The west Greenland margin is characterized by sedimentary basins containing high density of intrusions (dikes and sills) originating from the Cenozoic breakup and separation of Greenland and North American. The magmatic rocks have lately attracted interest due to observations of hydrocarbons associated to the intrusions but here due to the ore potential associated to the same intrusions. In 2000 a marine seismic campaign by GEUS in the coastal areas of West Greenland showed that it is possible to identify magmatic intrusions in the sedimentary succession as well as map normal faults, and that the intrusions are heterogeneous distributed and probably related to the normal faults. The presence of normal faults is known from the regional onshore geological mapping campaigns performed by GEUS. However, the marine seismic data indicate a much more complicated structural pattern than presented in the onshore maps, which is a well-known phenomenon (Marcussen et al., 2002). In 2012 and 2013 seismic data were acquired onshore on the northern coast of Disko as part of a research project funded by Avannaa Resources . The objective was initially to test whether it is possible to acquire data of a quality enabling the observation and mapping of intrusions in the subsurface. Later it was followed by a more extensive survey where it was attempted to map the depth to and geometry of the intrusions. The relatively dense seismic grid onshore -compared to the marine seismic data offshore west Greenland- enable the identification and more important the mapping of several intrusions. They show some of the same characteristics as intrusions observed at e.q. the Norwegian margin of the North Atlantic (Hansen et al., 2004). The preliminary results which integrate both marine and onshore seismic data revise the structural understanding of the area and indicate a close relation between the intrusions and the rift related normal faults. The results are consistent with remote sensing methods

  6. Geologic Assessment of Undiscovered Oil and Gas Resources of the West Greenland-East Canada Province

    USGS Publications Warehouse

    Schenk, Christopher J.

    2010-01-01

    The U.S. Geological Survey (USGS) recently assessed the potential for undiscovered oil and gas resources of the West Greenland-East Canada Province as part of the USGS Circum-Arctic Resource Appraisal program. The province lies in the offshore area between western Greenland and eastern Canada and includes Baffin Bay, Davis Strait, Lancaster Sound, and Nares Strait west of and including part of Kane Basin. A series of major tectonic events led to the formation of several distinct structural domains that are the geologic basis for defining five assessment units (AU) in the province, all of which are within the Mesozoic-Cenozoic Composite Total Petroleum System (TPS). Potential petroleum source rocks within the TPS include strata of Ordovician, Early and Late Cretaceous, and Paleogene ages. The five AUs defined for this study-the Eurekan Structures AU, Northwest Greenland Rifted Margin AU, Northeast Canada Rifted Margin AU, Baffin Bay Basin AU, and the Greater Ungava Fault Zone AU-encompass the entire province and were assessed for undiscovered, technically recoverable resources.

  7. Mapping and classifying the seabed of the West Greenland continental shelf

    NASA Astrophysics Data System (ADS)

    Gougeon, S.; Kemp, K. M.; Blicher, M. E.; Yesson, C.

    2017-03-01

    Marine benthic habitats support a diversity of marine organisms that are both economically and intrinsically valuable. Our knowledge of the distribution of these habitats is largely incomplete, particularly in deeper water and at higher latitudes. The western continental shelf of Greenland is one example of a deep (more than 500 m) Arctic region with limited information available. This study uses an adaptation of the EUNIS seabed classification scheme to document benthic habitats in the region of the West Greenland shrimp trawl fishery from 60°N to 72°N in depths of 61-725 m. More than 2000 images collected at 224 stations between 2011 and 2015 were grouped into 7 habitat classes. A classification model was developed using environmental proxies to make habitat predictions for the entire western shelf (200-700 m below 72°N). The spatial distribution of habitats correlates with temperature and latitude. Muddy sediments appear in northern and colder areas whereas sandy and rocky areas dominate in the south. Southern regions are also warmer and have stronger currents. The Mud habitat is the most widespread, covering around a third of the study area. There is a general pattern that deep channels and basins are dominated by muddy sediments, many of which are fed by glacial sedimentation and outlets from fjords, while shallow banks and shelf have a mix of more complex habitats. This first habitat classification map of the West Greenland shelf will be a useful tool for researchers, management and conservationists.

  8. Runoff simulations from the Greenland ice sheet at Kangerlussuaq from 2006-2007 to 2007/08. West Greenland

    SciTech Connect

    Mernild, Sebastian Haugard; Hasholt, Bent; Van Den Broeke, Michiel; Liston, Glen

    2009-01-01

    This study focuses on runoff from a large sector of the Greenland Ice Sheet (GrIS) - the Kangerlussuaq drainage area, West Greenland - for the runoff observation period 2006/07 to 2007/08. SnowModel, a state-of-the-art snow-evolution modeling system, was used to simulate winter accumulation and summer ablation processes, including runoff. Independent in situ end-of-winter snow depth and high-resolution runoff observations were used for validation of simulated accumulation and ablation processes. Runoff was modeled on both daily and hourly time steps, filling a data gap of runoff exiting part of the GrIS. Using hourly meteorological driving data instead of smoothed daily-averaged data produced more realistic meteorological conditions in relation to snow and melt threshold surface processes, and produced 6-17% higher annual cumulative runoff. The simulated runoff series yielded useful insights into the present conditions of inter-seasonal and inter-annual variability of Kangerlussuaq runoff, and provided an acceptable degree of agreement between simulated and observed runoff. The simulated spatial runoff distributions, in some areas of the GrIS terminus, were as high as 2,750 mm w.eq. of runoff for 2006/07, while only 900 mm w.eq was simulated for 2007/08. The simulated total runoff from Kangerlussuaq was 1.9 km{sup 3} for 2006/07 and 1.2 km{sup 3} for 2007/08, indicating a reduction of 35-40% caused by the climate conditions and changes in the GrIS freshwater storage. The reduction in runoff from 2006/07 to 2007/08 occurred simultaneously with the reduction in the overall pattern of satellite-derived GrIS surface melt from 2007 to 2008.

  9. Sedimentary Record and Morphological Effects of a Landslide-Generated Tsunami in a Polar Region: The 2000 AD Tsunami in Vaigat Strait, West Greenland

    NASA Astrophysics Data System (ADS)

    Szczucinski, W.; Rosser, N. J.; Strzelecki, M. C.; Long, A. J.; Lawrence, T.; Buchwal, A.; Chague-Goff, C.; Woodroffe, S.

    2012-12-01

    To date, the effects of tsunami erosion and deposition have mainly been reported from tropical and temperate climatic zones yet tsunamis are also frequent in polar zones, particularly in fjord settings where they can be generated by landslides. Here we report the geological effects of a landslide-triggered tsunami that occurred on 21st November 2000 in Vaigat, northern Disko Bugt in west Greenland. To characterise the typical features of this tsunami we completed twelve detailed coastal transects in a range of depositional settings: cliff coasts, narrow to moderate width coastal plains, lagoons and a coastal lake. At each setting we completed a detailed map using a laser scanner and DGPS survey. The tsunami deposits were described from closely spaced trenches and, from the lake, by a series of sediment cores . At each setting we examined the sedimentological properties of the deposits, as well as their bulk geochemistry and diatom content. Selected specimens of arctic willow from inundated and non-inundated areas were collected to assess the impact of the event in their growth ring records. Samples of sediments beneath the AD 2000 deposit were studied for 137Cs to confirm the age of the tsunami and to assess the extent of erosion. Offshore sediment samples, modern beach and soils/sediments underlying the AD 2000 tsunami deposits were sampled to determine tsunami deposit sources. The observed tsunami run-up exceeded 20 m next to the tsunami trigger - a rock avalanche at Paatuut - and up to 10 m on the opposite coast of the fjord. The inland inundation distance ranged from several tens of meters to over 300 m. The wave was recorded as far as 180 km away from the source. The tsunami inundated the coast obliquely to the shoreline in all locations studied. The tsunami frequently caused erosion of existing beach ridges whilst erosional niches were formed inland. The tsunami deposits mainly comprise gravels and very coarse sand. They are over 30 cm thick close to the

  10. Characterizing West Greenland ice sheet runoff losses from modeled and measured data

    NASA Astrophysics Data System (ADS)

    Moustafa, S.; Rennermalm, A. K.; Tedesco, M.; Mote, T. L.; Koenig, L.; Smith, L. C.; Hagedorn, B.; Overeem, I.; Sletten, R. S.; Mikkelsen, A. B.; Hasholt, B.; van As, D.; Hall, D. K.

    2016-12-01

    Increased surface meltwater runoff from the Greenland ice sheet (GrIS) accounts for half or more of total mass loss. Despite its importance, modeled meltwater runoff fluxes are poorly constrained, primarily due to a lack of direct in situ observations. Here, we present an inter-comparison of modeled and observed discharge for three drainage basins -Naujat Kuat (Nuuk), Watson, and North River (Thule) - moving from south to north along West Greenland. Modeled runoff outputs are obtained from the surface mass balance Modèle Atmosphérique Régional (MAR), and integrated for several catchment realizations. Our analyses reveal that (1) MAR is overestimating runoff losses for all three catchments and (2) drainage basin delineation can cause great uncertainty in model runoff estimates. This study's findings offers a unique opportunity to examine runoff estimates of surface mass balance models and will inform future development and parameterization of these models.

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

    NASA Astrophysics Data System (ADS)

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

    2004-12-01

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

  12. Paleomagnetism and multi-model stereo photogrammetry of the West Greenland flood volcanic province

    NASA Astrophysics Data System (ADS)

    Riisager, J.; Riisager, P.; Pedersen, A. K.

    2002-12-01

    We present new paleomagnetic and multi-model photogrammetry data from the West Greenland part of the North Atlantic igneous province (NAIP). During fieldwork the paleomagnetic sampling sites were photographed from helicopter with stereoscopic overlap and in colour. The photographs have been set up for multi-model photogrammetry allowing three-dimensional lithological mapping, giving us important information for interpreting the paleomagnetic data in their stratigraphic context. Another advantage of the multi-model photogrammetry coverage is that individual lavas can be traced in three-dimensional space allowing very precise measurements of the attitude of strata (+/-0.5°) to be made for tectonic correction of the paleomagnetic data. The paleomagnetic study is based on a large collection of 586 oriented paleomagnetic drill cores collected from 81 lava flows. All sampled flows carry stable thermoremanent magnetization of reversed polarity. The earliest part of the volcanic sequence (i.e. Vaigat Fm.) is characterized by several consecutive flows recording statistically indistinguishable paleomagnetic field directions. The thickest Vaigat Fm. directional group consists of 37 lava flows (combined thickness 104 meter), which based on photogrammetry and XRF observations we interpret to represent a single flow field (i.e. one eruption consisting of several lavas erupted in a short period of time). If Paleocene paleosecular variation was similar to Holocene variations, the thick directional groups would form within 100 years implying an extreme volcanic activity at the onset of NAIP volcanism on West Greenland. Based on directional groups we obtain a new well-defined paleomagnetic pole for Greenland, which is statistically similar to a recently published NAIP pole from Faroe Islands (Riisager et al., 2002) rotated to Greenland. The corresponding paleolatitude of the central NAIP in Paleocene is ~20° south of the present latitude of the Iceland hotspot, indicating that the

  13. Impact of fine debris on ice melt rates at Russell Glacier, central-west Greenland

    NASA Astrophysics Data System (ADS)

    Carr, Rachel; Linighan, James; Cumming, Alex M. J.

    2017-04-01

    Losses from the Greenland Ice Sheet (GrIS) have increased sharply in recent years, due to accelerated glacier discharge and increased surface melting. In 2012, 99% of the Greenland ice sheet experienced melt, which was exceptional on centennial timescales, but is expected to occur frequently in the future, as climate warms. Ice albedo is a primary control on melt rates and remotely sensed data shows that the GrIS has darkened substantial in recent decades, due to both inorganic and biological material. This has been particularly marked in south- and central-west Greenland and can lead to the development of positive feedbacks. Consequently, it is important to understand the relationship between melt and surface albedo on the GrIS. Here we use a combination of satellite remote sensing and field data to assess the impact of fine debris on melt rates at Russell Glacier, central-west Greenland. Our field data demonstrate that areas with a greater percentage coverage of fine, largely inorganic debris experienced higher melt rates than in areas with a sparse coverage. However, the relationship between melt and debris cover was highly spatially variable. Furthermore, the debris cover evolved substantially over time and we saw marked changes over a period of a few days. Using ASTER imagery, we show that the spatial extent of debris has expanded markedly in this section of the GrIS during the last decade, which could substantially accelerate melting. However, the complex and variable relationship between debris cover and melt rates highlights the need for further research, in order to accurately forecast its impact on GrIS melt rates.

  14. Sm-Nd age of the Fiskenaesset Anorthosite Complex, West Greenland

    NASA Technical Reports Server (NTRS)

    Ashwal, Lewis D.; Goldstein, Steven J.; Jacobsen, Stein B.; Myers, John S.; Kalsbeek, Feiko

    1989-01-01

    A Sm-Nd isotopic study on samples from the Fiskenaesset Anorthosite Complex in West Greenland was conducted to estimate the age of crystallization of the complex. A five-point isochron, including data for whole-rock samples of anorthosite, metagabbro, metaperidotite, and separates of calcic plagioclase and mafic matrix from a coarse megacrystic leucogabbro, corresponds to an age of 2.86 + or - 0.05 Ga, with initial sigma(Nd) of +2.9 + or - 0.4. This implies a relatively short time interval, on the order of 70 Ma, during which anorthosite formation, tonalite emplacement, and high-grade metamorphism took place.

  15. Warble infestations by Hypoderma tarandi (Diptera; Oestridae) recorded for the first time in West Greenland muskoxen☆

    PubMed Central

    Samuelsson, Fredrik; Nejsum, Peter; Raundrup, Katrine; Hansen, Tina Vicky Alstrup; Kapel, Christian Moliin Outzen

    2013-01-01

    In the northern hemisphere, Caribou (Rangifer spp.) populations are known to be infested with the skin-penetrating ectoparasite, Hypoderma tarandi (Diptera; Oestridae). Although regarded as host specific, H. tarandi has been reported from other species, and has become of increasing concern as a zoonosis infecting humans. In February 2012, concurrent with the hunting of muskoxen, we examined carcasses for muscle and tissue parasites, and recorded warble larvae infestations. DNA extracted from samples of larvae was amplified targeting 579 bp of the COI gene, and subsequently sequenced, to be confirmed as H. tarandi. Infestation by oestrid flies has not previously been reported in muskoxen in West Greenland. PMID:24533338

  16. Study of subaqueous melting of Store Glacier, West Greenland using ocean observations and numerical simulations

    NASA Astrophysics Data System (ADS)

    Xu, Y.; Rignot, E. J.; Menemenlis, D.; van den Broeke, M. R.

    2012-12-01

    Ice discharge from the Greenland Ice Sheet is mainly through tidewater glaciers that terminate in the ocean and melt in contact with ocean waters. Subaqueous melting at the calving front is a direct mechanism for mass loss and a potential trigger for glacier acceleration. We present an analysis of oceanographic data collected in the fjord of Store Glacier, West Greenland during August 2010 and 2012. Using these data, we calculate the subaqueous melt rates. Independently, we employ the Massachusetts Institute of Technology general circulation model (MITgcm), modified to include melting at the calving front and outflow of subglacial water to model the ice melt rates of Store Glacier. Previous 2-D sensitivity studies showed that the subaqueous melt rate reaches several meters per day during the summer, increases non-linearly with subglacial runoff and linearly with ocean thermal forcing, and ceases when subglacial discharge is off during winter. We present new 3-D simulations at very high resolution, with measured oceanic temperature/salinity as boundary conditions, and subglacial runoff from the University of Utrecht's Regional Atmospheric Climate Model outputs on different years and seasons. We compare the ocean observations and numerical simulations and discuss the seasonal and inter-annual variations of subaqueous melting. This study helps evaluate the impact of the ocean on the subaqueous melting of Greenland tidewater glaciers and in turn on glacier mass balance. This work was carried out at University of California, Irvine and at the Jet Propulsion Laboratory under contract with NASA Cryosphere Science Program.

  17. Monitoring South-West Greenland's ice sheet melt with ambient seismic noise

    NASA Astrophysics Data System (ADS)

    Mordret, Aurélien; Mikesell, Dylan; Harig, Christopher; Lipovsky, Brad; Prieto, German

    2016-04-01

    The Greenland ice sheet (GIS) accounts for ~ 70% of global ice sheet mass loss and contributes to sea level rise at a rate of 0.7 mm/yr. Therefore, the GIS needs to be carefully monitored. The spaceborne techniques commonly used to monitor the GIS mass balance contain inherent uncertainties. These uncertainties can be reduced by comparing independent datasets and techniques. However, spaceborne methods remain inadequate in the sense that they offer low spatial and/or temporal resolution. This fact highlights the need for other complementary methods to monitor the GIS more accurately and with greater resolution. Here we use a seismic method: the correlation of seismic noise recorded at South-West Greenland seismic stations to show that the GIS seasonal melt produces significant variations of seismic wave speed in the Greenland crust. The amplitudes of the measured velocity variations during 2012-2013 correlate with the total ice plus atmospheric mass variations measured by the GRACE (Gravity Recovery and Climate Experiment) satellite mission. We explain the phase delay between mass maxima and velocity minima ( 50 days) using a non-linear poroelastic model that includes a 55 cm-thick layer of till between the ice sheet and the bedrock. We, thus, interpret the velocity variations as pore pressure variations in the bedrock resulting from the loading and unloading of the overlying glacier and atmosphere. This method provides a new and independent way to monitor in near real-time the first-order state of the GIS, giving new constraints on its evolution and its contribution to the global sea level rise. By increasing the density of seismic stations in the region it will be possible to increase the spatial and temporal resolution of the method and create detailed maps of ice-mass variations across Greenland.

  18. Monitoring South-West Greenland's ice sheet melt with ambient seismic noise

    NASA Astrophysics Data System (ADS)

    Mordret, A.; Mikesell, T. D.; Harig, C.; Lipovsky, B.; Prieto, G. A.

    2015-12-01

    The Greenland ice sheet (GIS) accounts for ~ 70% of global ice sheet mass loss and contributes to sea level rise at a rate of 0.7 mm/yr. Therefore, the GIS needs to be carefully monitored. The spaceborne techniques commonly used to monitor the GIS mass balance contain inherent uncertainties. These uncertainties can be reduced by comparing independent datasets and techniques. However, spaceborne methods remain inadequate in the sense that they offer low spatial and/or temporal resolution. This fact highlights the need for other complimentary methods to monitor the GIS more accurately and with greater resolution. Here we use a seismic method: the correlation of seismic noise recorded at South-West Greenland seismic stations to show that the GIS seasonal melt produces significant variations of seismic wave speed in the Greenland crust. The amplitudes of the measured velocity variations during 2012-2013 correlate with the total ice plus atmospheric mass variations measured by the GRACE (Gravity Recovery and Climate Experiment) satellite mission. We explain the phase delay between mass maxima and velocity minima ( 50 days) using a non-linear poroelastic model that includes a 55 cm-thick layer of till between the ice sheet and the bedrock. We, thus, interpret the velocity variations as pore pressure variations in the bedrock resulting from the loading and unloading of the overlying glacier and atmosphere. This method provides a new and independent way to monitor in near real-time the first-order state of the GIS, giving new constraints on its evolution and its contribution to the global sea level rise. By increasing the density of seismic stations in the region it will be possible to increase the spatial and temporal resolution of the method and create detailed maps of ice-mass variations across Greenland.

  19. 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

  20. Use of Glacial Fronts by Narwhals (Monodon monoceros) in West Greenland

    NASA Astrophysics Data System (ADS)

    Laidre, K. L.

    2015-12-01

    Glacial fronts in Greenland are known to be important summer habitat for narwhals (Monodon monoceros), as freshwater runoff and sediment discharge may aggregate prey at the terminus. We investigated the importance of glacial habitat characteristics in determining narwhal visitation. Narwhals (n=18) were instrumented with satellite transmitters in September 1993-1994 and 2006-2007 in Melville Bay, West Greenland. Daily narwhal locations were interpolated using a correlated random walk based on observed filtered locations and associated positional error. We also compiled a database on physical features of 41 glaciers along the northwest Greenland coast. This covered the entire coastal region with narwhal activity. Parameters included glacier ice velocity (km/yr) from radar satellite data, glacier front advance and retreat, and glacier width (km) at the ice-ocean interface derived using front position data digitized from 20-100m resolution radar image mosaics and Landsat imagery. We also quantified relative volumes and extent of glacial ice discharge, thickness of the glacial ice at the terminus (m), and water depth at the terminus (m) from gravity and airborne radar data, sediment flux from satellite-based analysis, and freshwater runoff from a regional atmospheric climate model (RACMO2.3). We quantified whale visits to glaciers at three distances (5, 7, and 10 km) and conducted proximity analyses on annual and monthly time steps. We estimated 1) narwhal presence or absence, 2) the number of 24 h periods spent at glaciers, and 3) the fraction of study animals that visited each glacier. The use of glacial habitat by narwhals expanded to the north and south between the 1990s (n=9 unique glaciers visited) and the 2000s (n=30 visited), likely due to loss of summer fast ice and later fall freeze-up trends (3.5 weeks later since 1979). We used a generalized linear mixed effects framework to quantify the glacier and fjord habitat characteristics preferred by narwhals.

  1. Snowmelt and runoff modelling of an Arctic hydrological basin in west Greenland

    NASA Astrophysics Data System (ADS)

    Bøggild, C. E.; Knudby, C. J.; Knudsen, M. B.; Starzer, W.

    1999-09-01

    This paper compares the performance of a conceptual modelling system and several physically-based models for predicting runoff in a large hydrological basin, Tasersuaq, in west Greenland. This basin, which is typical of many Greenland basins, is interesting because of the fast hydrological response to changing conditions. Due to the predominance of exposed bedrock surface and only minor occurrence of sediments and organic soils, there is little restraint to run-off, making the treatment of the snowmelt component of primary importance.Presently a conceptual modelling system, HBV, is applied in Greenland and also in most of the arctic regions of Scandinavia for operational forecasting. A general wish to use hydrological models for other purposes, such as to improve data collection and to gain insight into the hydrological processes has promoted interest in the more physically-based hydrological models. In this paper, two degree-day models, the Danish version of the physically-based SHE distributed hydrological modelling system (MIKE SHE) and the conceptual HBV model are compared with a new model that links MIKE SHE and a distributed energy balance model developed for this study, APUT.The HBV model performs the best overall simulation of discharge, which presently makes it most suited for general forecasting. The combination of MIKE SHE and APUT i.e. a physically based modelling system shows promising results by improving the timing of the initiation of spring flood, but does not perform as well throughout the remaining part of the snowmelt season. The modelling study shows that local parameters such as the snow depletion curve, the temporal snow albedo and perhaps also melt water storage need to be more precisely determined from field studies before physically-based modelling can be improved.

  2. Geomicrobiology of subglacial meltwater samples from Store Landgletscher and Russell Glacier, West Greenland

    NASA Astrophysics Data System (ADS)

    Cameron, K. A.; Dieser, M.; Choquette, K.; Christner, B. C.; Hagedorn, B.; Harrold, Z.; Liu, L.; Sletten, R. S.; Junge, K.

    2012-12-01

    The melting of the Greenland Ice Sheet provides direct connections between atmospheric, supraglacial and subglacial environments. The intraglacial hydrological pathways that result are believed to accommodate the microbial colonization of subglacial environments; however, little is known about the abundance, diversity and activity of microorganisms within these niches. The Greenland Ice Sheet (1.7 million square kilometers) and its associated surpaglacial and subglacial ecosystems may contribute significantly to biogeochemical cycling processes. We analyzed subglacial microbial assemblages in subglacial outflows, near Thule and Kangerlussuaq, West Greenland. The investigative approach included correlating microbial diversity, inferred function, abundance, melt water chemistry, O-18 water isotope ratios, alkalinity and sediment load. Using Illumina sequencing, bacterial small subunit ribosomal RNA hypervariable regions have been targeted and amplified from both extracted DNA and reverse transcribed rRNA. Over 3 billion sequence reads have been generated to create a comprehensive diversity profile. Total abundances ranged from 2.24E+04 to 1.58E+06 cells mL-1. In comparison, the total abundance of supraglacial early season snow samples ranged from 3.35E+02 to 2.8E+04 cells mL-1. 65 % of samples incubated with cyano ditoyl tetrazolium chloride (CTC), used to identify actively respiring cells, contained CTC-positive cells. On average, these cells represented 1.9 % of the estimated total abundance (1.86E+02 to 2.19E+03 CTC positive cells mL-1; 1.39E+03 cells mL-1 standard deviation); comparative to those measured in temperate freshwater lakes. The overarching objective of our research is to provide data that indicates the role of microbial communities, associated with ice sheets, in elemental cycling and in the release of biomass and nutrients to the surrounding marine biome.

  3. Helicopter-based Photography for use in SfM over the West Greenland Ablation Zone

    NASA Astrophysics Data System (ADS)

    Mote, T. L.; Tedesco, M.; Astuti, I.; Cotten, D.; Jordan, T.; Rennermalm, A. K.

    2015-12-01

    Results of low-elevation high-resolution aerial photography from a helicopter are reported for a supraglacial watershed in West Greenland. Data were collected at the end of July 2015 over a supraglacial watershed terminating in the Kangerlussuaq region of Greenland and following the Utrecht University K-Transect of meteorological stations. The aerial photography reported here were complementary observations used to support hyperspectral measurements of albedo, discussed in the Greenland Ice sheet hydrology session of this AGU Fall meeting. A compact digital camera was installed inside a pod mounted on the side of the helicopter together with gyroscopes and accelerometers that were used to estimate the relative orientation. Continuous video was collected on 19 and 21 July flights, and frames extracted from the videos are used to create a series of aerial photos. Individual geo-located aerial photos were also taken on a 24 July flight. We demonstrate that by maintaining a constant flight elevation and a near constant ground speed, a helicopter with a mounted camera can produce 3-D structure of the ablation zone of the ice sheet at unprecedented spatial resolution of the order of 5 - 10 cm. By setting the intervalometer on the camera to 2 seconds, the images obtained provide sufficient overlap (>60%) for digital image alignment, even at a flight elevation of ~170m. As a result, very accurate point matching between photographs can be achieved and an extremely dense RGB encoded point cloud can be extracted. Overlapping images provide a series of stereopairs that can be used to create point cloud data consisting of 3 position and 3 color variables, X, Y, Z, R, G, and B. This point cloud is then used to create orthophotos or large scale digital elevation models, thus accurately displaying ice structure. The geo-referenced images provide a ground spatial resolution of approximately 6 cm, permitting analysis of detailed features, such as cryoconite holes, evolving small

  4. Fjord circulation promotes significant glacier-wide submarine melting at a west Greenland tidewater glacier

    NASA Astrophysics Data System (ADS)

    Slater, Donald A.; Straneo, Fiamma; Das, Sarah B.; Nienow, Peter W.

    2017-04-01

    In recent decades, rapid change at Greenland's marine-terminating glaciers has significantly impacted the contribution of the ice sheet to sea level. While these changes have been widely linked to a warming of the ocean around Greenland, process understanding linking ocean forcing to glacier response, for example by submarine melting, remains at an early stage. The most rapid submarine melting likely occurs where buoyant plumes, initiated by subglacial discharge, rise up tidewater glacier calving fronts. Plumes have therefore received much attention, yet a plume typically occupies only a small fraction of the submerged calving front area. Thus melting within the plume itself may be a small contributor to the front-wide melting experienced by the glacier. A plume may however promote melting over a much larger area by inducing a fjord-scale circulation which, by increasing water velocities at the ice/ocean interface, can give rise to increased melting over the entire glacier face. Here we address this fjord-scale, plume-driven circulation and its impact on submarine melting by combining observations collected within 100 m of marine-terminating Saqqarliup Sermia in west Greenland with high-resolution fjord modelling using the MITgcm. Both field data and modelling show that water from the main plume flows away from the glacier as a subsurface jet, and that entrainment into this jet generates regions of fjord water recirculating back towards the glacier. The modelling further suggests that these recirculations drive elevated across-glacier water motion thereby promoting significant submarine melting over the full 4 km-width of the calving front, resulting in total melt volumes which substantially exceed those generated directly by the relatively narrow plume. Our results highlight the value of combining detailed field observations with modelling and demonstrate how the secondary fjord circulation generated by plumes may play a significant role in driving submarine

  5. Rise in central west Greenland surface melt unprecedented over the last three centuries

    NASA Astrophysics Data System (ADS)

    Trusel, Luke; Das, Sarah; Osman, Matthew; Evans, Matthew; Smith, Ben; McConnell, Joe; Noël, Brice; van den Broeke, Michiel

    2017-04-01

    Greenland Ice Sheet surface melting has intensified and expanded over the last several decades and is now a leading component of ice sheet mass loss. Here, we constrain the multi-century temporal evolution of surface melt across central west Greenland by quantifying layers of refrozen melt within well-dated firn and ice cores collected in 2014 and 2015, as well as from a core collected in 2004. We find significant agreement among ice core, satellite, and regional climate model melt datasets over recent decades, confirming the fidelity of the ice core melt stratigraphy as a reliable record of past variability in the magnitude of surface melt. We also find a significant correlation between the melt records derived from our new 100-m GC-2015 core (2436 m.a.s.l.) and the older (2004) 150-m D5 core (2472 m.a.s.l.) located 50 km to the southeast. This agreement demonstrates the robustness of the ice core-derived melt histories and the potential for reconstructing regional melt evolution from a single site, despite local variability in melt percolation and refreeze processes. Our array of upper percolation zone cores reveals that although the overall frequency of melt at these sites has not increased, the intensification of melt over the last three decades is unprecedented within at least the last 365 years. Utilizing the regional climate model RACMO 2.3, we show that this melt intensification is a nonlinear response to warming summer air temperatures, thus underscoring the heightened sensitivity of this sector of Greenland to further climate warming. Finally, we examine spatial correlations between the ice core melt records and modeled melt fields across the ice sheet to assess the broader representation of each ice core record. This analysis reveals wide-ranging significant correlations, including to modeled meltwater runoff. As such, our ice core melt records may furthermore offer unique, observationally-constrained insights into past variability in ice sheet mass loss.

  6. Temporal trends of mercury in marine biota of west and northwest Greenland.

    PubMed

    Rigét, Frank; Dietz, Rune; Born, Erik W; Sonne, Christian; Hobson, Keith A

    2007-01-01

    Temporal trends in mercury concentrations ([Hg]) during the last two to three decades were determined in liver of shorthorn sculpin, ringed seal and Atlantic walrus from northwest Greenland (NWG, 77 degrees N) and in liver of shorthorn sculpin and ringed seal from central west Greenland (CWG, 69 degrees N) during the last decade. Stable-nitrogen (delta(15)N) and carbon (delta(13)C) isotope values were determined in muscle of ringed seals to provide insight into potential trophic level changes through time. Log-linear regressions on annual median [Hg] did not reveal any temporal trend in shorthorn sculpin from CWG and NWG and walrus from NWG. In ringed seals from NWG, an increase in [Hg] of 7.8% per year was observed. When based on delta(15)N-adjusted [Hg] this rate increased to 8.5% but was still non-significant. In ringed seal from CWG no trend was found in [Hg] during the period 1994-2004. However, during the last part of the period (1999-2004) the [Hg] increased significantly. Including tissue delta(15)N values as a covariate had a marked effect on these results. The annual changes in delta(15)N-adjusted [Hg] was estimated to -5.0% for the whole period and 2.2% during the last 5 years compared to -1.3% and 12.4%, respectively, for the non-adjusted [Hg].

  7. The early archaean crustal history of West Greenland as recorded by detrital zircons

    NASA Technical Reports Server (NTRS)

    Kinny, P. D.; Compston, W.; Mcgregor, V. R.

    1988-01-01

    The isotope systematics of some of the oldest samples on Earth from both Greenland and Australia was discussed. The antiquity was confirmed of the 4.1 to 4.2 Ga zircons from Western Australia; the model Lu-Hf age of these zircons, as measured with the ANU ion probe is 4.14 + or - 0.24 Ga, although the oldest preserved rock units there are anorthosites with a Lu-Hf model age of about 3.73 Ga. U-Pb ion probe ages of detrital zircons ranging between 2.87 and 3.89 Ga from an Akilia association quartzite was reported, whose age of deposition is probably around 3.8 Ga. It was argued that the younger age in this range are discordant because of late Pb-loss, probably associated with a high grade metamorphic event at about 3.6 Ga. It was also argued that the earliest crust in West Greenland and elsewhere is about 3.9 Ga, but in some places, such as Western Australia, crustal evolution took place much earlier, perhaps starting as far back as 4.3 Ga. This would account for the presence in that terrane of abundant K rich granitoid, the paucity of tonalitic and trondhjemitic materials, and the existence of Eu anomalies in early Archean sediments.

  8. Using reflection seismics to identify and monitor the basal conditions of Russell Glacier South West Greenland.

    NASA Astrophysics Data System (ADS)

    Hofstede, Coen; Kleiner, Thomas; Bondzio, Johannes; Eisen, Olaf; Wilhelms, Frank; Bohleber, Pascal; Fritzsche, Diedrich; Hubbard, Alun

    2015-04-01

    Russell Glacier is a land terminating glacier in South West Greenland. Survey site SHR lies at several kilometers from the terminus and is closely monitored. In recent years in Summer months, site SHR has seen unusual high ice velocities of up to 400m/a which have been linked to increased Summer melt. To capture the probably changing basal conditions of Russell Glacier at SHR we carried out two seismic surveys at site SHR, one in September 2013 at the end of the melt season and one in May 2014 at the start of the melt season. The seismic data were recorded using a 300m snow streamer and explosives. The data reveal an ice thickness of about 550m and 30 to 40m thick accreted subglacial sediments with varying degrees of water saturation in both ice and sediment. We speculate the increased ice velocity is caused by sediments that become temporarily liquefied in the Summer months.

  9. High basal melt rates observed on Store Glacier, West Greenland, using phase-sensitive FMCW radar

    NASA Astrophysics Data System (ADS)

    Young, T. J.; Christoffersen, P.; Nicholls, K. W.; Lok, L. B.; Doyle, S. H.; Hubbard, B. P.; Stewart, C.; Hofstede, C. M.; Bougamont, M. H.; Todd, J.; Brennan, P. V.; Hubbard, A.

    2016-12-01

    The Greenland ice sheet is losing mass, and is currently contributing 1 mm/year to global sea level rise. The large majority of these changes can be attributed to the recent acceleration in flow of marine-terminating outlet glaciers within the last several decades. Such fast ice flow is characterised by ice deformation, as well as basal motion. However, there are few direct observations of either of these contributing mechanisms due to the difficulty of accessing the subglacial environment. In particular, although basal melt rates have been measured on ice shelves for decades, there exist almost no equivalent observations for grounded ice sheets. We present the first time series of directly-measured rates of basal melting at the bed of Store Glacier, a major outlet glacier flowing into Uummannaq Fjord in West Greenland. The measurements were obtained using a phase-sensitive, frequency modulated continuous wave (FMCW) radar system installed 30 km upflow of the calving terminus at a location where the surface velocity of the glacier is 700 m/year. Radar data were recorded every 4 hours from 26 July to 11 December 2014. The same site was used to instrument 610-m-deep boreholes drilled to the bed as part of the Subglacial Access and Fast Ice research Experiment (SAFIRE). With internal and basal reflector ranges captured at high spatial (millimetre) and temporal (hourly) resolutions, we obtained a unique, 6-month-long time series of ice deformation and basal melting coincident with englacial and subglacial borehole measurements. Here, we report sustained basal melting of 3 m/year during winter, and maxima of 20 m/year during summer when basal motion is enhanced by surface water delivered to the bed. The lower, but more constant rate of winter basal melting is likely to be driven by frictional heat generated from basal sliding. These discoveries indicate that basal melting beneath Greenland's fast flowing outlet glaciers is considerably higher than basal melting reported

  10. Significance of the late Archaean granulite facies terrain boundaries, Southern West Greenland

    NASA Technical Reports Server (NTRS)

    Friend, C. R. L.; Nutman, A. P.; Mcgregor, V. R.

    1988-01-01

    Three distinct episodes and occurrences of granulite metamorphism in West Greenland are described: (1) the oldest fragmentary granulites occur within the 3.6-Ga Amitsoq gneisses and appear to have formed 200 Ma after the continental crust in which they lie (Spatially associated rapakivi granites have zircon cores as old as 3.8 Ga, but Rb-Sr, whole-rock Pb-Pb, and all other systems give 3.6 Ga, so these granulites apparently represent a later metamorphic event); (2) 3.0-Ga granulites of the Nordlandet Peninsula NW of Godthaab, developed immediately after crustal formation in hot, dry conditions, are carbonate-free, associated with voluminous tonalite, and formed at peak metamorphic conditions of 800 C and 7 to 8 kbar (Synmetamorphic trondhjemite abounds and the activity of H2O has been indicated by Pilar to have varied greatly); and (3) 2.8-Ga granulites south of Godthaab, lie to the south of retrogressed amphibolite terranes. Prograde amphibolite-granulite transitions are clearly preserved only locally at the southern end of this block, near Bjornesund, south of Fiskenaesset. Progressively deeper parts of the crust are exposed from south to north as a major thrust fault is approached. Characteristic big hornblende pegmatites, which outcrop close to the thrust in the east, have been formed by replacement of orthopyroxene. Comparable features were not seen in South Indian granulites. It was concluded that no one mechanism accounts for the origin of all granulites in West Greenland. Various processes have interacted in different ways, and what happened in individual areas must be worked out by considering all possible processes.

  11. The use of electromagnetic induction methods for establishing quantitative permafrost models in West Greenland

    NASA Astrophysics Data System (ADS)

    Ingeman-Nielsen, Thomas; Brandt, Inooraq

    2010-05-01

    The sedimentary settings at West Greenlandic town and infrastructural development sites are dominated by fine-grained marine deposits of late to post glacial origin. Prior to permafrost formation, these materials were leached by percolating precipitation, resulting in depletion of salts. Present day permafrost in these deposits is therefore very ice-rich with ice contents approaching 50-70% vol. in some areas. Such formations are of great concern in building and construction projects in Greenland, as they loose strength and bearing capacity upon thaw. It is therefore of both technical and economical interest to develop methods to precisely investigate and determine parameters such as ice-content and depth to bedrock in these areas. In terms of geophysical methods for near surface investigations, traditional methods such as Electrical Resistivity Tomography (ERT) and Refraction Seismics (RS) have generally been applied with success. The Georadar method usually fails due to very limited penetration depth in the fine-grained materials, and Electromagnetic Induction (EMI) methods are seldom applicable for quantitative interpretation due to the very high resistivities causing low induced currents and thus small secondary fields. Nevertheless, in some areas of Greenland the marine sequence was exposed relatively late, and as a result the sediments may not be completely leached of salts. In such cases, layers with pore water salinity approaching that of sea water, may be present below an upper layer of very ice rich permafrost. The saline pore water causes a freezing-point depression which results in technically unfrozen sediments at permafrost temperatures around -3 °C. Traditional ERT and VES measurements are severely affected by equivalency problems in these settings, practically prohibiting reasonable quantitative interpretation without constraining information. Such prior information may be obtained of course from boreholes, but equipment capable of drilling

  12. Investigations on soil organic carbon stocks and active layer thickness in West Greenland

    NASA Astrophysics Data System (ADS)

    Gries, Philipp; Wagner, Julia; Kandolf, Lorenz; Henkner, Jessica; Kühn, Peter; Scholten, Thomas; Schmidt, Karsten

    2017-04-01

    The soil organic carbon (SOC) pool in the first 300 cm of arctic soils includes about 50 % of the estimated global terrestrial belowground organic carbon, which makes about 1024 Pg C and up to 496 Pg within the upper permafrost one meter. Being a sensible ecosystem, the Arctic is sensitive to climate change. Hence, thawing of permafrost-affected soils to greater depth and for longer periods increases the release of CO2 and CH4 to the atmosphere, which queries soils as an important carbon pool. Especially in arctic environments, sparse soil data and limited knowledge of soil processes cause underestimation of SOC stocks. Due to different regional climatic conditions, changing soil-environmental conditions result in varying soil organic carbon contents in Greenland. In West Greenland, coastal oceanic conditions turn into continental climate at the ice margin showing less precipitation, higher insolation and increasing permafrost thickness. The objectives of this study are (i) to determine SOC stocks and active layer thickness (ALT), (ii) to identify main environmental factors influencing SOC stocks and ALT, and (iii) to specify differences of SOC stocks, ALT and influencing factors induced by a climatic trend in West Greenland. Respecting different climatic conditions, one study area is situated next to the ice margin in the Kangerlussuaq area and the second one is located near Sisimiut at the coast. Both study areas (2 km2) are representative for each region and have similar environmental settings. Soil samples were taken from depth increments (0-25, 25-50, 50-100, and 100-200 cm) at 80 sampling locations in each study area. Additionally, we addressed soil moisture content (TDR-measurements), ALT, and soil horizons, vegetation (types, coverage), and terrain characteristics (aspect, geomorphology) at each sampling point. As a preliminary result, at the coast the average SOC stock is 13.1 kg/m2 in the upper 25 cm and about 35.9 kg/m2 in the first 200 cm. The amount of

  13. Ice-dammed lake drainage in west Greenland: Drainage pattern and implications on ice flow and bedrock motion

    NASA Astrophysics Data System (ADS)

    Kjeldsen, Kristian K.; Khan, Shfaqat A.; Bjørk, Anders A.; Nielsen, Karina; Mouginot, Jeremie

    2017-07-01

    Ice-dammed lakes drain frequently in Greenland, but the impacts of these events differ between sites. Here we study the quasi-cyclic behavior of the 40 km2 Lake Tininnilik in west Greenland and its impact on ice flow and crustal deformation. Data reveal rapid drainage of 1.83 ± 0.17 km3 of water in less than 7 days in 2010, leading to a speedup of the damming glacier, and an instantaneous modeled elastic bedrock uplift of 18.6 ± 0.1 mm confirmed by an independent lakeside GPS record. Since ice-dammed lakes are common on Greenland, our results highlight the importance of including other sources of surface loading in addition to ice mass change, when assessing glacial isostatic adjustment or elastic rebound using geodetic data. Moreover, the results illustrates a linkage between subglacial discharge and ice surface velocity, important for assessing ice flux, and thus mass balance, in a future warming climate.

  14. A synthesis of the ongoing seasonal work in a west Greenland tidewater outlet glacier fjord, Godthåbsfjord

    NASA Astrophysics Data System (ADS)

    Mortensen, J.; Bendtsen, J.; Rysgaard, S.

    2015-12-01

    The coastal waters off west Greenland is subjected to significant temperature fluctuations which might affect the mass loss from local tidewater outlet glaciers from the Greenland Ice Sheet in different ways. We present a comprehensive hydrographic data set from a west Greenland fjord, Godthåbsfjord, a fjord in contact with the Greenland Ice Sheet through tidewater outlet glaciers. We analyze with respect to water masses, dynamics, seasonal and interannual hydrographic variability. Through seasonal observations of hydrographic and moored observations we recognize a seasonal pattern in the fjords circulation system, where an intermediate baroclinic circulation mode driven by tidal currents at the fjord entrance is associated as an important local heat source for the fjord. Four distinct circulation modes are observed in the fjord of which all can contribute to glacial ice melt. In water observation of a subglacial plume core will be presented and discussed with respect to vertical distribution of water masses and local heat budget in the fjord. The example of the extreme case of subglacial plume will be discussed (ice-dammed lake drainage).

  15. Spacing and physical habitat selection patterns by peregrine falcons in central West Greenland

    USGS Publications Warehouse

    Wightman, C.; Fuller, Mark R.

    2005-01-01

    We examined nest-site spacing and selection of nesting cliffs by Peregrine Falcons (Falco peregrinus) in central West Greenland. Our sample included 67 nesting cliffs that were occupied at least once between 1972 and 1999 and 38 cliffs with no known history of Peregrine Falcon occupancy. We measured 29 eyrie, cliff, and topographical features at each occupied nesting cliff and unused cliff in 1998a??1999 and used them to model the probability of peregrines occupying a cliff for a breeding attempt. Nearest-neighbor distance was significantly greater than both nearest-cliff distance and nearest-occupied distance (the distance between an occupied cliff and one occupied at least once, 1972a??1999). Thus, spacing among occupied cliffs was probably the most important factor limiting nesting-cliff availability, and, ultimately, peregrine nesting densities. Although some unused cliffs were unavailable in a given year because of peregrine spacing behavior, physical characteristics apparently made some cliffs unsuitable, regardless of availability. We confirmed the importance of several features common to descriptions of peregrine nesting habitat and found that peregrines occupied tall nesting cliffs with open views. They chose nesting cliffs with eyrie ledges that provided a moderate degree of overhang protection and that were inaccessible to ground predators. Overall, we concluded that certain features of a cliff were important in determining its suitability as a nest site, but within a given breeding season there also must be sufficient spacing between neighboring falcon pairs. Our habitat model and information on spacing requirements may be applicable to other areas of Greenland and the Arctic, and can be used to test the generalities about features of Peregrine Falcon nesting cliffs throughout the species' widespread distribution.

  16. Multi-decadal and seasonal variability of dust observations in West Greenland.

    NASA Astrophysics Data System (ADS)

    Bullard, Joanna E.; Mockford, Tom

    2017-04-01

    Since the early 1900s expedition records from west Greenland have reported local dust storms. The Kangerlussuaq region, near the inland ice, is dry (mean annual precipitation <160 mm) with, on average, 150 snow-free days per year. The main local dust sources are active, proglacial outwash plains although reworking of loess deposits may also be important. This paper presents an analysis of 70-years of dust storm observations (1945-2015) based on WMO weather codes 6 (dust haze), 7 (raised dust or sand) and 9 (distant or past dust storm) and associated wind data. The 70-year average number of dust observations days is 5 per year but variable ranging from 0 observations to 23 observations in 1985. Over the past 7 decades the number of dust days has increased from <30 in 1945-54 to >75 in 1995-2004 and 2005-2015. The seasonality of dust observations has remained consistent throughout most of the period. Dust days occur all year round but are most frequent in May-June and September-October and are associated with minimum snow cover and glacial meltwater-driven sediment supply to the outwash plains during spring and fall flood events. Wind regime is bimodal dominated by katabatic winds from the northeast, which are strongest and most frequent during winter months (Nov-Jan), with less frequent, southwesterly winds generated by Atlantic storms mostly confined to spring (May, June). The southwesterly winds are those most likely to transport dust onto the Greenland ice sheet.

  17. Basin-Wide Mass Balance of Jakobshavn Isbræ (West Greenland) during 1880-2100

    NASA Astrophysics Data System (ADS)

    Muresan, I. S.; Khan, S. A.; Aschwanden, A.; Langen, P. L.; Khroulev, C.; Box, J. E.; Kjaer, K. H.

    2015-12-01

    Greenland's main outlet glaciers have more than doubled their contribution to global sea-level rise over the past decade through acceleration of ice discharge. Jakobshavn Isbræ (JI) in west Greenland is the largest outlet glacier in terms of drainage area.Here we use a 3-D modeling approach to study the mechanisms controlling dynamic changes at the terminus of JI over a period of 220 years. Over 100 simulations are performed with different sets of parameters where the calving fronts and the grounding lines are free to evolve in time under atmospheric and oceanic forcing. We find that the thinning and the retreat that starts at the calving front and then propagates upstream is mostly controlled by a loss of resistive stresses at the terminus through glacier dynamics induced calving rather than by changes in oceanic temperatures. Three major accelerations are identified in 1928, 1998 and in the summer of 2003. The acceleration which started in 1928 slowly faded by 1948, while the accelerations in 1998 and 2003 sustain the high velocities observed at JI in the last decade. Further, we find that under atmospheric RCP 4.5 and RCP 8.5 forcing (no RCP ocean forcing included), an increase in ocean temperatures of just 0.7 °C (relative to 1880-2012) is enough to trigger a collapse of the JI's southern tributary by 2050 which further destabilizes JI and unleashes a major glacial collapse of ~25 km. JI's contribution to SLR is found to be ~2.8 mm (~1014 Gt) for the period 1880 to 2014, from which the contribution between 1997 to 2014 represents 27 %. By the end of the century contributions to SLR as high as ~11 mm (~4000 Gt under RCP 8.5 and almost 300% increase relative to 1880-2014) can be expected from Jakobshavn Isbræ only. Our choice of ice sheet model comprises the Parallel Ice Sheet Model (PISM).

  18. Variability of subglacial discharge recorded with thermal infrared timelapse of a tidewater glacier, West Greenland

    NASA Astrophysics Data System (ADS)

    Byers, L. C.; Stearns, L. A.; Brunsell, N. A.; Catania, G. A.; Fried, M.; Bartholomaus, T.; Felikson, D.; Sutherland, D.; Carroll, D.; Shroyer, E.; Nash, J. D.; Walker, R. T.; Finnegan, D. C.; LeWinter, A.

    2015-12-01

    Subglacial hydrology and the dynamics therein are important modulators of ice flow in the Greenland Ice Sheet. At tidewater outlet glaciers the characteristics of proglacial discharge affect fjord circulation, sediment deposition, submarine melt rates, and iceberg calving. Information about the spatio-temporal variability of discharge is limited by the challenges of in situ data collection at tidewater glaciers. Here, we present summertime measurements of subglacial discharge variability using a thermal infrared (7.5μm to 13μm) camera and intervalometer at Kangerlussuup Sermia (KS), a ~4km wide outlet glacier in the Uummannaq Bay region of West Greenland (71.46 N, 51.43 W). KS has an advantageous geometry for this investigation because of its shallow grounding zone and well-entrenched subglacial hydrologic system. In tandem, these characteristics promote buoyant freshwater to rise to the fjord surface from discrete outlets at the glacier's base. We investigate the timing of plume activity at these outlets and discuss potential controls on outlet switching. Raw camera measurements cannot be accurately converted to surface temperature without correcting for environmental variables and scene geometry, both of which are time-evolving during data acquisition. Our processing methodology relies on a variety of existing techniques -- image segmentation, ray casting, atmospheric radiative transfer modeling, Monte Carlo simulations -- and a variety of ancillary data products -- satellite imagery, atmospheric reanalysis, meteorologic and hydrologic measurements -- to produce the final results. What is gained is an unprecedented view into interactions between the cryosphere, hydrosphere, and atmosphere that control the dynamic and sensitive terminus region of a tidewater outlet glacier.

  19. Modelled and observed present-day state of the Jakobshavn Isbræ, west Greenland

    NASA Astrophysics Data System (ADS)

    Khan, S. A.; Muresan, I. S.; Aschwanden, A.; Khroulev, C.

    2014-12-01

    Jakobshavn Isbræ located in west Greenland drains approximately 7.5 % of the area of the Greenland ice sheet (GrIS). Understanding its sensitivity to climatic forcing is critical for assessing mass balance of the GrIS. Here we use a high-resolution, three dimensional and time-dependent regional outlet glacier model developed as part of the Parallel Ice Sheet Model (PISM) forced by climatology datasets from RACMO2 to model present-day state of Jakobshavn Isbræ. Our choice of modelling consists of a forward integration in time (hindcasting) for 1990-2012 with monthly climatic forcing. To assess the modeled mass change, we use observed ice volume change from airborne and satellite laser altimetry from ATM, ICESat, and LVIS during 1997-2013 and convert to mass change. However, the airborne and satellite measurements are conducted few times per year, and may provide yearly mass loss rates only. To assess weekly to monthly scale mass variability, we use measurements of bedrock displacement from permanent GPS sites during 2005-2013. The GPS data provide daily to monthly scale estimates of bedrock displacements caused by the earth's elastic response to ice mass change from Jakobshavn Isbræ. Additionally, we assess modeled ice velocities (and velocity changes) with observed velocities obtained from measurements of ice motion by satellite interferometric synthetic-aperture radar (InSAR) data from the RADARSAT-1 satellite.Our results show good agreement between modeled and observed mass change and velocity change from weekly to long-term timespan. Both model and observations show huge mass loss anomalies in 2010 and 2012 caused by enhanced melting during summer months.

  20. The Holocene sedimentary history of the Kangerlussuaq Fjord-valley fill, West Greenland

    NASA Astrophysics Data System (ADS)

    Storms, Joep E. A.; de Winter, Ilja L.; Overeem, Irina; Drijkoningen, Guy G.; Lykke-Andersen, Holger

    2012-03-01

    West Greenland has been intensively studied to reconstruct and better understand past relative sea level changes and deglacial history. This study extends these efforts by linking sea level and deglacial history to the sedimentary infill successions of Kangerlussuaq Fjord and associated landward valleys. Based on published and new land- and sea-based geophysical data, radiocarbon dates and geological observations we have characterized the infill and reconstructed the sedimentation history during the Holocene. Based on a revised sea level curve and data presented in this paper we defined three depositional phases. Phase I (>7000 yr BP) is represented by dominant glaciomarine deposition associated with a tide-water glacier system. As the Greenland Ice Sheet (GIS) continued to retreat it became land based. During phase II (7000-1500 yr BP) two separate depocenters formed. Keglen delta depocenter arose from a temporary stabilization phase of the GIS and prograded rapidly over the glaciomarine deposits of Phase I. Further inland, proglacial lake formation and subsequent sedimentary infill associated with the ongoing GIS retreat is represents the second depocenter. The Watson River connected both depocenters by a flood plain which transferred sediment from the GIS to the Keglen delta. Ongoing sea level fall due to glacio-isostastic uplift combined with a gradually cooler and dryer climate resulted in terrace formation along the Watson River flood plain. Around 4000 yr BP, the GIS margin reached its most landward location and began to advance to its present location. The final phase (Phase III; <1500 yr BP) is represented by a stabilized GIS position and a relative sea level rise which led to aggrading conditions near the present-day delta plain of Watson River. Simultaneously, subaqueous channels were formed at the delta front by hyperpycnal flows associated with jökulhlaup events.

  1. A 3D Full-Stokes Calving Model Applied to a West Greenland Outlet Glacier

    NASA Astrophysics Data System (ADS)

    Todd, Joe; Christoffersen, Poul; Zwinger, Thomas; Råback, Peter; Chauché, Nolwenn; Hubbard, Alun; Toberg, Nick; Luckman, Adrian; Benn, Doug; Slater, Donald; Cowton, Tom

    2017-04-01

    Iceberg calving from outlet glaciers accounts for around half of all mass loss from both the Greenland and Antarctic ice sheets. The diverse nature of calving and its complex links to both internal dynamics and external climate make it challenging to incorporate into models of glaciers and ice sheets. Consequently, calving represents one of the most significant uncertainties in predictions of future sea level rise. Here, we present results from a new 3D full-Stokes calving model developed in Elmer/Ice and applied to Store Glacier, the second largest outlet glacier in West Greenland. The calving model implements the crevasse depth criterion, which states that calving occurs when surface and basal crevasses penetrate the full thickness of the glacier. The model also implements a new 3D rediscretization approach and a time-evolution scheme which allow the calving front to evolve realistically through time. We use the model to test Store's sensitivity to two seasonal environmental processes believed to significantly influence calving: submarine melt undercutting and ice mélange buttressing. Store Glacier discharges 13.9 km3 of ice annually, and this calving rate shows a strong seasonal trend. We aim to reproduce this seasonal trend by forcing the model with present day levels of submarine melting and ice mélange buttressing. Sensitivity to changes in these frontal processes was also investigated, by forcing the model with a) increased submarine melt rates acting over longer periods of time and b) decreased mélange buttressing force acting over a reduced period. The model displays a range of observed calving behaviour and provides a good match to the observed seasonal evolution of the Store's terminus. The results indicate that ice mélange is the primary driver of the observed seasonal advance of the terminus and the associated seasonal variation in calving rate. The model also demonstrates a significant influence from submarine melting on calving rate. The results

  2. 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

  3. 13C-Depleted carbon microparticles in >3700-Ma sea-floor sedimentary rocks from west greenland

    PubMed

    Rosing

    1999-01-29

    Turbiditic and pelagic sedimentary rocks from the Isua supracrustal belt in west Greenland [more than 3700 million years ago (Ma)] contain reduced carbon that is likely biogenic. The carbon is present as 2- to 5-micrometer graphite globules and has an isotopic composition of delta13C that is about -19 per mil (Pee Dee belemnite standard). These data and the mode of occurrence indicate that the reduced carbon represents biogenic detritus, which was perhaps derived from planktonic organisms.

  4. Arctic Outflow West Of Greenland: Nine Years Of Volume And Freshwater Transports From Observations In Davis Strait

    NASA Astrophysics Data System (ADS)

    Curry, B.; Lee, C.; Petrie, B.; Moritz, R. E.; Kwok, R.

    2014-12-01

    Recent Arctic changes suggest alterations in the export of freshwater from the Arctic to the North Atlantic, with conceivable impacts on the Atlantic Meridional Overturning circulation. Approximately 50% of the Arctic outflow exits west of Greenland, traveling through the Canadian Arctic Archipelago (CAA) and into Baffin Bay before crossing Davis Strait. The CAA outflow contributes over 50% of the net southward freshwater outflow through Davis Strait. The remainder is deeper outflow from Baffin Bay, flow from the West Greenland Current and runoff from West Greenland and CAA glaciers. Since September 2004, an observational program in Davis Strait has quantified volume and freshwater transport variability. The year-round program includes velocity, temperature and salinity measurements from 15 moorings spanning the full width (330 km) of the strait accompanied by autonomous Seagliders surveys (average profile separation = 4 km) and autumn ship-based hydrographic sections. Over the shallow Baffin Island and West Greenland shelves, moored instrumentation provides temperature and salinity measurements near the ice-ocean interface. From 2004-2013, the average net volume and liquid freshwater transports are -1.6 ± 0.2 Sv, -94 ± 7 mSv, respectively (salinity referenced to 34.8 and negative indicates southward transport); sea ice contributes an additional -10 ± 1 mSv. Over this period, volume and liquid freshwater transports show significant interannual variability and no clear trends, but a comparison with reanalyzed 1987-90 data indicate a roughly 40% decrease in net southward liquid volume transport and a corresponding an almost 30% decrease in freshwater transport. Connections between the Arctic are also captured, e.g., a unique yearlong Davis Strait freshening event starting September 2009 that was likely driven by an earlier freshening (January 2009 - April/May 2010) in the Canadian Arctic. The Davis Strait autumn 2009 salinity minimum was fresher (by about 0

  5. The origin of decoupled Hf-Nd isotope compositions in Eoarchean rocks from southern West Greenland

    NASA Astrophysics Data System (ADS)

    Hoffmann, J. Elis; Münker, Carsten; Polat, Ali; Rosing, Minik T.; Schulz, Toni

    2011-11-01

    Radiogenic isotope compositions of Hf and Nd are typically coupled in Phanerozoic and Proterozoic mafic rocks due to a similar behaviour of Lu-Hf and Sm-Nd during mantle melting. Eoarchean rocks, for instance those from southern West Greenland, exhibit an apparent decoupling of Hf and Nd isotope compositions. This apparent decoupling may either indicate metamorphic disturbance or, alternatively, mirror early differentiation processes in the silicate Earth. To evaluate the issue, we performed combined measurements of Hf-Nd isotope compositions together with major and trace element concentrations for well preserved >3720 to >3800 Ma old tholeiitic metabasalts and gabbros from the ˜3700 Ma and ˜3800 Ma old terranes of the Isua Supracrustal Belt, southern West Greenland. In contrast to younger mafic rocks, calculated initial ɛHf-ɛNd values of the Isua tholeiites show similar spreads and are both near chondritic to strongly depleted (-0.7 to +6.3 and -0.8 to +4.4, respectively), also in contrast to previously reported more depleted signatures in nearby boninite-like metabasalts of the Garbenschiefer unit. An evaluation of alteration effects based on preserved major and trace element arrays reveals pristine magmatic trends and therefore the measured isotope compositions indeed in most cases characterize contrasting Eoarchean mantle sources. In accord with this view, compositions of the Isua metabasalts yield Eoarchean regression ages in Sm-Nd and Lu-Hf isochron spaces, overlapping with emplacement ages inferred from crosscutting relationships with tonalites. Lutetium-Hf systematics of the Isua metabasalts studied here, yield clear isochron relationships. For both terranes, there is some scatter in Sm-Nd space, indicating early disturbance of the Sm-Nd system close in time to the extrusion ages, possibly by seafloor alteration. Trace element compositions of the metabasalts indicate an arc setting and a strong source overprint by melt-like subduction components. It is

  6. Modelling of subglacial hydrological development during a rapid lake drainage event, West Greenland

    NASA Astrophysics Data System (ADS)

    Dow, C. F.; Kulessa, B.; Pimentel, S.; Tsai, V. C.; Doyle, S. H.; Rutt, I. C.; Jones, G. A.; Booth, A. D.; Hubbard, A.

    2012-12-01

    We present results from a local-scale model of subglacial hydrological development during a rapid lake drainage event on the Russell Glacier catchment in West Greenland. Previous models applied to rapid lake drainage events include a turbulent radial model (Tsai and Rice, 2010) and a 1-D flowband model (Pimentel and Flowers, 2011). Both models have limitations for application to lake drainage events. For the former, the radial extent of water flow is restricted to several ice thicknesses and no provision is made for the development of basal channels. For the latter model, the input of water directly from the lake to the bed without modulation by englacial flow, together with the fact that lateral basal flux is neglected, causes unrealistic subglacial pressure levels. To resolve these limitations, we link the two models together, thus allowing both local radial flux and downstream development of a coupled efficient and distributed drainage system. Our model is constrained by inputs from fieldwork completed in summer 2010 at a rapid lake drainage site in the land-terminating region of West Greenland. Passive seismic records indicate the region of basal water injection. Reflection seismic amplitude vs. angle (AVA) surveys allow analysis of the basal material characteristics. Lake drainage rate and differential GPS vertical and horizontal motion records are used as constraints for our model outputs. Our preliminary results suggest that large basal channels do not necessarily form during the rapid drainage of supraglacial lakes. A lack of an efficient drainage system has an impact on the local ice dynamics and the treatment of lake drainage events in larger-scale dynamic models. References: Pimentel, S and Flowers, G. (2011). A numerical study of hydrologically driven glacier dynamics and subglacial flooding, Proceedings of the Royal Society A: Mathematical, Physical and Engineering Science, 467 (2126): doi: 10.1098/rspa.2010.0211. Tsai, V.C. and Rice, J.R. (2010). A

  7. Two years of Irminger Ring observations offshore of the West Greenland Shelf

    NASA Astrophysics Data System (ADS)

    Femke de Jong, M.; Bower, Amy S.; Furey, Heather; Lilly, Jonathan M.

    2013-04-01

    Anti-cyclonic eddies, called Irminger Rings, shed from the boundary current along the west coast of Greenland, transport warm and saline Irminger Current water into the interior Labrador Sea. The transport of heat and salt by Irminger Rings into the relatively fresh and cold Labrador Sea is thought to be important in the restratification of the basin after convection. However, since there are few observations, recent estimates of the importance of Irminger Rings are mostly based on models. This study shows new data from a mooring deployed offshore of the west Greenland shelf near the local maximum of eddy kinetic energy associated with the shedding of Irminger Rings. The mooring was deployed between September 2007 and September 2009. It recorded the hydrographic properties and current velocities of the water column, thus obtaining a time series of passing Irminger Rings. During the 2 year mooring deployment 12 eddies fitting the description of an Irminger Ring were observed to pass the mooring location. The Irminger Ring core properties show a seasonal cycle in temperature and salinity with a range of about 2°C and 0.05 psu, with maxima observed in late fall. This results in larger heat and salt contribution estimates compared to observations in literature, which were either taken earlier in the year or further downstream sampling older modified Irminger Rings. Some inter-annual variability was also observed. Most of the 12 Irminger Rings described here were observed during the first year. The decrease in the number of observed eddies during the second year of deployment appears to be due to a change in boundary current strength, as determined from satellite altimetry and surveys of the AR7W section. The resulting change in the circulation pattern was evident in the current meter records at the mooring site. More information about the seasonal to inter-annual variability is needed to fully understand the exchange between the boundary current and the interior

  8. Divergent parasite faunas in adjacent populations of west Greenland caribou: Natural and anthropogenic influences on diversity☆

    PubMed Central

    Steele, Jillian; Orsel, Karin; Cuyler, Christine; Hoberg, Eric P.; Schmidt, Niels M.; Kutz, Susan J.

    2013-01-01

    Gastrointestinal parasite diversity was characterised for two adjacent populations of west Greenland caribou (Rangifer tarandus groenlandicus) through examinations of abomasa and small intestines collected from adult and subadult females during late winter. Three trichostrongyline (Trichostrongylina: Nematoda) species were identified from the abomasa, although none were recovered from the small intestines, with faunal composition differing between the caribou populations. In caribou from Kangerlussuaq-Sisimiut, Marshallagia marshalli and Teladorsagia boreoarcticus were highly prevalent at 100% and 94.1%, respectively. In contrast, Ostertagia gruehneri was found at 100% prevalence in Akia-Maniitsoq caribou, and was the only abomasal parasite species present in that population. We hypothesise that parasite faunal differences between the populations are a consequence of parasite loss during caribou colonisation of the region approximately 4000–7000 years ago, followed by a more recent spill-over of parasites from muskoxen (Ovibos moschatus wardi) and semi-domesticated Norwegian reindeer (Rangifer tarandus tarandus) introduced to Kangerlussuaq-Sisimiut and Akia-Maniitsoq regions, respectively, in the 20th century. PMID:24533335

  9. Use of glacial fronts by narwhals (Monodon monoceros) in West Greenland.

    PubMed

    Laidre, Kristin L; Moon, Twila; Hauser, Donna D W; McGovern, Richard; Heide-Jørgensen, Mads Peter; Dietz, Rune; Hudson, Ben

    2016-10-01

    Glacial fronts are important summer habitat for narwhals (Monodon monoceros); however, no studies have quantified which glacial properties attract whales. We investigated the importance of glacial habitats using telemetry data from n = 15 whales tagged in September of 1993, 1994, 2006 and 2007 in Melville Bay, West Greenland. For 41 marine-terminating glaciers, we estimated (i) narwhal presence/absence, (ii) number of 24 h periods spent at glaciers and (iii) the fraction of narwhals that visited each glacier (at 5, 7 and 10 km) in autumn. We also compiled data on glacier width, ice thickness, ice velocity, front advance/retreat, area and extent of iceberg discharge, bathymetry, subglacial freshwater run-off and sediment flux. Narwhal use of glacial habitats expanded in the 2000s probably due to reduced summer fast ice and later autumn freeze-up. Using a generalized multivariate framework, glacier ice front thickness (vertical height in the water column) was a significant covariate in all models. A negative relationship with glacier velocity was included in several models and glacier front width was a significant predictor in the 2000s. Results suggest narwhals prefer glaciers with potential for higher ambient freshwater melt over glaciers with silt-laden discharge. This may represent a preference for summer freshwater habitat, similar to other Arctic monodontids. © 2016 The Author(s).

  10. Biogeochemical data from terrestrial and aquatic ecosystems in a periglacial catchment, West Greenland

    NASA Astrophysics Data System (ADS)

    Lindborg, Tobias; Rydberg, Johan; Tröjbom, Mats; Berglund, Sten; Johansson, Emma; Löfgren, Anders; Saetre, Peter; Nordén, Sara; Sohlenius, Gustav; Andersson, Eva; Petrone, Johannes; Borgiel, Micke; Kautsky, Ulrik; Laudon, Hjalmar

    2016-09-01

    Global warming is expected to be most pronounced in the Arctic where permafrost thaw and release of old carbon may provide an important feedback mechanism to the climate system. To better understand and predict climate effects and feedbacks on the cycling of elements within and between ecosystems in northern latitude landscapes, a thorough understanding of the processes related to transport and cycling of elements is required. A fundamental requirement to reach a better process understanding is to have access to high-quality empirical data on chemical concentrations and biotic properties for a wide range of ecosystem domains and functional units (abiotic and biotic pools). The aim of this study is therefore to make one of the most extensive field data sets from a periglacial catchment readily available that can be used both to describe present-day periglacial processes and to improve predictions of the future. Here we present the sampling and analytical methods, field and laboratory equipment and the resulting biogeochemical data from a state-of-the-art whole-ecosystem investigation of the terrestrial and aquatic parts of a lake catchment in the Kangerlussuaq region, West Greenland. This data set allows for the calculation of whole-ecosystem mass balance budgets for a long list of elements, including carbon, nutrients and major and trace metals. The data set is freely available and can be downloaded from PANGAEA: doi:10.1594/PANGAEA.860961.

  11. Use of glacial fronts by narwhals (Monodon monoceros) in West Greenland

    PubMed Central

    Moon, Twila; Hauser, Donna D. W.; McGovern, Richard; Heide-Jørgensen, Mads Peter; Dietz, Rune; Hudson, Ben

    2016-01-01

    Glacial fronts are important summer habitat for narwhals (Monodon monoceros); however, no studies have quantified which glacial properties attract whales. We investigated the importance of glacial habitats using telemetry data from n = 15 whales tagged in September of 1993, 1994, 2006 and 2007 in Melville Bay, West Greenland. For 41 marine-terminating glaciers, we estimated (i) narwhal presence/absence, (ii) number of 24 h periods spent at glaciers and (iii) the fraction of narwhals that visited each glacier (at 5, 7 and 10 km) in autumn. We also compiled data on glacier width, ice thickness, ice velocity, front advance/retreat, area and extent of iceberg discharge, bathymetry, subglacial freshwater run-off and sediment flux. Narwhal use of glacial habitats expanded in the 2000s probably due to reduced summer fast ice and later autumn freeze-up. Using a generalized multivariate framework, glacier ice front thickness (vertical height in the water column) was a significant covariate in all models. A negative relationship with glacier velocity was included in several models and glacier front width was a significant predictor in the 2000s. Results suggest narwhals prefer glaciers with potential for higher ambient freshwater melt over glaciers with silt-laden discharge. This may represent a preference for summer freshwater habitat, similar to other Arctic monodontids. PMID:27784729

  12. Lu-Hf total-rock age for the Amitsoq gneisses, West Greenland

    NASA Technical Reports Server (NTRS)

    Pettingill, H. S.; Patchett, P. J.

    1981-01-01

    Lu-Hf total-rock data for the Amitsoq gneisses of West Greenland yield an age of 3.55 + or - 0.22 billion years, based on the decay constant for Lu-176 of 1.96 x 10 to the -11th/year, and an initial Hf-176/Hf-177 ratio of 0.280482 + or - 33. The result is in good agreement with Rb-Sr total-rock and U-Pb zircon ages. In spite of severe metamorphism of the area at 2.9 billion years, zircons from two of the samples have remained on the total-rock line, and define points close to the initial Hf ratio. The initial Hf-176/Hf-177 lies close to a chondritic Hf isotopic evolution curve from 4.55 billion years to present. This is consistent with the igneous precursors to the Amitsoq gneisses having been derived from the mantle at or shortly before 3.6 billion years. Anomalous relationships between Hf concentration and the Lu-176/Hf-177 ratio may suggest that trace element abundances in the Amitsoq gneisses are partly controlled by processes related to metamorphism.

  13. Gyrfalcon feeding behavior during the nestling period in central west Greenland

    USGS Publications Warehouse

    Booms, Travis; Fuller, Mark R.

    2003-01-01

    We studied gyrfalcon (Falco rusticolus) food delivery and feeding behavior during the nestling period in central West Greenland during the 2000 and 2001 field seasons. We used time-lapse video cameras installed at three nests to record 2677.25 hours of nestling video. Ptarmigan delivered to nests were usually plucked prior to delivery and included the breast and superior thoracic vertebrae. Arctic hare leverets were rarely plucked and often delivered in parts. The most commonly delivered leveret part was the hind legs attached to the lower back. Passerines were rarely plucked and usually delivered whole. After feeding the young, adults removed 20.9% of prey items from the nest, which included items both with and without obvious muscle still attached. Prey delivery rates were similar among nests and increased as nestlings aged. Prey delivery frequency peaked in the morning and evening, with a distinct lull in the late evening and early morning hours. Male and female adults delivered a similar number of prey, though males typically delivered smaller prey than females. Gyrfalcons cached and re-delivered at least 9.1% of all items delivered, and one item was cached and retrieved three times.

  14. A new Eimeria species (Protozoa: Eimeriidae) from caribou in Ameralik, West Greenland.

    PubMed

    Skirnisson, K; Cuyler, C

    2016-04-01

    Fecal samples of 11 calves shot in the Ameralik area, West Greenland, in August-September 2014 were examined for coccidian parasites. The calves belonged to a population of interbreeding indigenous caribou Rangifer tarandus groenlandicus and feral semi-domestic Norwegian reindeer Rangifer tarandus tarandus. Two coccidian species were found: Eimeria rangiferis and a coccidium that was identified and described as a new species. The latter's sporulated oocyst is spherical or slightly subspherical. Average size is 25.6 × 24.8 μm. The oocyst has two distinct walls. Wall thickness is ∼1.4 μm. The unicolored outer wall is brown, the inner wall is dark gray. The oocysts contain a small polar granule but are devoid of a microphyle. The oocysts enclose four ovoid-shaped sporocysts with a rounded end opposite to the Stieda body. The average size of sporocysts is 15.2 × 7.8 μm. Sporocysts contain a granular sporocyst residuum that forms a spherical cluster between the sporocysts, one large refractile body is present in each sporozoite. The spherical form easily distinguishes oocysts of the new species from the seven previously described eimerid species in R. tarandus. This is the first eimerid described as a new species to the sciences from caribou in the Nearctic.

  15. 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

  16. Meltwater flux and runoff modeling in the abalation area of jakobshavn Isbrae, West Greenland

    SciTech Connect

    Mernild, Sebastian Haugard; Chylek, Petr; Liston, Glen; Steffen, Konrad

    2009-01-01

    The temporal variability in surface snow and glacier melt flux and runoff were investigated for the ablation area of lakobshavn Isbrae, West Greenland. High-resolution meteorological observations both on and outside the Greenland Ice Sheet (GrIS) were used as model input. Realistic descriptions of snow accumulation, snow and glacier-ice melt, and runoff are essential to understand trends in ice sheet surface properties and processes. SnowModel, a physically based, spatially distributed meteorological and snow-evolution modeling system was used to simulate the temporal variability of lakobshavn Isbrre accumulation and ablation processes for 2000/01-2006/07. Winter snow-depth observations and MODIS satellite-derived summer melt observations were used for model validation of accumulation and ablation. Simulations agreed well with observed values. Simulated annual surface melt varied from as low as 3.83 x 10{sup 9} m{sup 3} (2001/02) to as high as 8.64 x 10{sup 9} m{sup 3} (2004/05). Modeled surface melt occurred at elevations reaching 1,870 m a.s.l. for 2004/05, while the equilibrium line altitude (ELA) fluctuated from 990 to 1,210 m a.s.l. during the simulation period. The SnowModel meltwater retention and refreezing routines considerably reduce the amount of meltwater available as ice sheet runoff; without these routines the lakobshavn surface runoff would be overestimated by an average of 80%. From September/October through May/June no runoff events were simulated. The modeled interannual runoff variability varied from 1.81 x 10{sup 9} m{sup 3} (2001/02) to 5.21 x 10{sup 9} m{sup 3} (2004/05), yielding a cumulative runoff at the Jakobshavn glacier terminus of {approx}2.25 m w.eq. to {approx}4.5 m w.eq., respectively. The average modeled lakobshavn runoff of {approx}3.4 km{sup 3} y{sup -1} was merged with previous estimates of Jakobshavn ice discharge to quantify the freshwater flux to Illulissat Icefiord. For both runoff and ice discharge the average trends are

  17. Paleomagnetism of large igneous provinces: case-study from West Greenland, North Atlantic igneous province

    NASA Astrophysics Data System (ADS)

    Riisager, Janna; Riisager, Peter; Pedersen, Asger Ken

    2003-09-01

    We present new paleomagnetic and multi-model stereo photogrammetry data from lava sequences in the West Greenland part of the North Atlantic igneous province (NAIP). The joint analyses of paleomagnetic and photogrammetric data yield a well-defined paleomagnetic pole located at Lat=73.6°N, Long=160.5°E ( N=44, α95=6.2°, K=13.1; age ˜61-55 Ma), which is statistically indistinguishable from a pole recently obtained for the Eurasian part of the NAIP on Faroe Islands [Riisager et al., Earth Planet. Sci. Lett. 201 (2002) 261-276]. Combining the two datasets we obtain a joint NAIP paleomagnetic pole in Greenland coordinates: Lat=71.1°N, Long=161.1°E ( N=87, α95=4.3°, K=13.6; age ˜61-54 Ma). The results presented here represent the first study in which photogrammetry profiles were photographed at the exact same locations where paleomagnetic fieldwork was carried out, and a direct flow-to-flow comparison of the two datasets is possible. Photogrammetry is shown to be particularly useful because of (i) highly precise dip/strike measurements and (ii) detailed 'field observations' that can be made in the laboratory. Highly precise determination of the structural attitude of well-exposed Kanisut Mb lava sequences demonstrates that their apparently reliable in-field dip/strike measurements typically are up to ˜6° wrong. Erroneous dip/strike readings are particularly problematic as they offset paleomagnetic poles without affecting their confidence limits. Perhaps more important for large igneous provinces is the recognition of a variable temporal relationship between consecutive lava flows. We demonstrate how correct interpretation of paleosecular variation, facilitated by the detailed photogrammetry analysis, is crucial for the rapidly emplaced Vaigat Formation lavas. Inaccurate tectonic correction, non-averaged paleosecular variation and unrecognized excursional directions may, perhaps, explain why coeval paleomagnetic poles from large igneous provinces are often

  18. Modeling the West Antarctic and Greenland ice sheets: New dynamic, thermodynamic, and isostatic insights

    NASA Astrophysics Data System (ADS)

    Parizek, Byron R.

    Numerical simulations indicate that the apparent long-term persistence and short-term variability of the Ross ice streams in West Antarctica are tied to regional thermal conditions and local basal lubrication. Modelling results suggest that the flux of latent heat in a throughgoing hydrologic system fed by melt beneath thick inland ice maintains the lubrication of the ice streams despite their tendency to freeze to the bed, and would allow additional thinning and grounding-line retreat. However, the efficiency of basal water distribution may be a constraint on the system. Because local thermal deficits promote basal freeze-on (especially on topographic highs), observed short-term variability is likely to persist. Furthermore, simulations indicate that the ice streams have experienced only small deglacial thickness changes and are thinning more rapidly than their beds are rising isostatically. Thickness changes of O (100)m are modelled at the modern grounding line through the last glacial cycle. Coupled ice and bedrock models indicate isostatic rebound is raising the ice sheet at the modern grounding line faster than the rising sea level is submerging it. While, in and of itself, this could potentially lead to a grounding-line re-advance, ice flow is modelled to respond to recent changes in temperature, accumulation rate, and basal processes more rapidly than it does to bedrock-elevation and/or sea-level fluctuations. Future projections of the Greenland ice sheet indicate a faster contribution to sea-level rise in a warming world than previously believed, based on numerical modelling using a parameterization of recent results showing surface-meltwater lubrication of Greenland ice flow (Zwally et al., 2002). Numerous simulations were conducted to test a wide range of parameter space linking surface melt with a new sliding law based on Zwally et al. data under different global warming scenarios. Comparisons to reconstructions generated with a traditional sliding

  19. Modeling of Ice Flow and Internal Layers Along a Flow Line Through Swiss Camp in West Greenland

    NASA Technical Reports Server (NTRS)

    Wang, W. L.; Zwally, H. Jay; Abdalati, W.; Luo, S.; Koblinsky, Chester J. (Technical Monitor)

    2001-01-01

    An anisotropic ice flow line model is applied to a flow line through Swiss Camp (69.57 N, 49.28 W) in West Greenland to estimate the dates of internal layers detected by Radio-Echo Sounding measurements. The effect of an anisotropic ice fabric on ice flow is incorporated into the steady state flow line model. The stress-strain rate relationship for anisotropic ice is characterized by an enhancement factor based on the laboratory observations of ice deformation under combined compression and shear stresses. By using present-day data of accumulation rate, surface temperature, surface elevation and ice thickness along the flow line as model inputs, a very close agreement is found between the isochrones generated from the model and the observed internal layers with confirmed dates. The results indicate that this part of Greenland ice sheet is primarily in steady state.

  20. Larval outbreaks in West Greenland: Instant and subsequent effects on tundra ecosystem productivity and CO2 exchange.

    PubMed

    Lund, Magnus; Raundrup, Katrine; Westergaard-Nielsen, Andreas; López-Blanco, Efrén; Nymand, Josephine; Aastrup, Peter

    2017-02-01

    Insect outbreaks can have important consequences for tundra ecosystems. In this study, we synthesise available information on outbreaks of larvae of the noctuid moth Eurois occulta in Greenland. Based on an extensive dataset from a monitoring programme in Kobbefjord, West Greenland, we demonstrate effects of a larval outbreak in 2011 on vegetation productivity and CO2 exchange. We estimate a decreased carbon (C) sink strength in the order of 118-143 g C m(-2), corresponding to 1210-1470 tonnes C at the Kobbefjord catchment scale. The decreased C sink was, however, counteracted the following years by increased primary production, probably facilitated by the larval outbreak increasing nutrient turnover rates. Furthermore, we demonstrate for the first time in tundra ecosystems, the potential for using remote sensing to detect and map insect outbreak events.

  1. Estimating ice-melange properties with repeat UAV surveys over Store Glacier, West Greenland

    NASA Astrophysics Data System (ADS)

    Toberg, Nick; Ryan, Johnny; Christoffersen, Poul; Snooke, Neal; Todd, Joe; Hubbard, Alun

    2016-04-01

    In the past decade, tidewater outlet glaciers of the Greenland ice sheet (GrIS) have thinned and retreated when compared to the 1980s when the ice sheet was in a state of dynamic balance. With a growing amount of ice discharged into the sea by tidewater glaciers as well as more ice melting on the surface, the Greenland Ice Sheet has become the single largest cryospheric source of global sea level rise. Today, the ice sheet causes sea level rise of 1 mm per year, highlighting the need to understand the ice sheet's response to climate change. Atmospheric warming will inevitably continue to increase surface meltwater production, but the dynamic response, which includes hundreds of fast-flowing tidewater glaciers, is largely unknown. To develop new understanding of ice sheet dynamics, we investigated the mechanism whereby icebergs break off tidewater glaciers and form a proglacial ice melange. This melange is rigid in winter when sea ice and friction along the sidewalls of the fjord, or even at the sea floor, hold it together. The result is a resistive force, which reduces the rate of iceberg calving when the ice melange is rigid and is lost when the melange disappears in the summer. From early May to late July 2014, we launched unmanned aerial vehicles (UAVs) from a basecamp on a bluff overlooking the calving front of Store Glacier, a 5 km wide tidewater glacier flowing into Uummannaq Fjord in West Greenland. The Skywalker X8 UAVs had a wing-span of 2.1m and a payload containing a high resolution camera, an autopilot system and a GPS data logger. We generated almost 70,000 georeferenced images during 63 sorties over the glacier during a 10 week field season starting 13 May 2014. The images were used to construct orhorectified mosaics and digital elevation models of the proglacial melange with Photoscan structure-from-motion software. The imagery and the DEMs were analysed statistically to understand the spatial characteristics of the ice melange. By combining the

  2. The Archean geology of the Godthabsfjord Region, southern west Greenland (includes excursion guide)

    NASA Technical Reports Server (NTRS)

    Mcgregor, V. R.; Nutman, A. P.; Friend, C. R. L.

    1986-01-01

    The part of the West Greenland Archean gneiss complex centered around Godthabsfjord and extending from Isukasia in the north to south Faeringehavn is studied. Extensive outcrops of 3800 to 3400 Ma rocks can provide some direct evidence of conditions and processes that operated on the Earth in the early Archean. However, the ways in which primary characteristics have been modified by later deformation, metamorphism, and chemical changes are first taken into account. The rocks exposed are the products of two major phases of accretion of continental crust, at 3800 to 3700 Ma and 3100 to 29 Ma. The main features of these two accretion phases are similar, but careful study of the least modified rocks may reveal differences related to changes in the Earth in the intervening period. The combination of excellent exposure over an extensive area, relatively detailed geological mapping of much of the region, and a considerable volume of isotopic and other geochemical data gives special insights into processes that operated at moderately deep levels of the crust in the Archean. Of particular interest is the effect of late Archean granulite facies metamorphism on early Archean rocks, especially the extent to which isotope systems were disturbed. Similar processes may well have partly or wholly destroyed evidence of more ancient components of other high grade terrains. This account does not attempt to be an exhaustive review of all work carried out on the geology of the region. Rather, it attempts to summarize aspects of the geology and some interest in the context of early crustal genesis.

  3. Influence of the Little Ice Age on the biological structure of lakes in South West Greenland

    NASA Astrophysics Data System (ADS)

    McGowan, S.; Hogan, E. J.; Jones, V.; Anderson, N. J.; Simpson, G.

    2013-12-01

    Arctic lakes are considered to be particularly sensitive to environmental change, with biological remains in lake sediment records being interpreted as reflecting climate forcing. However the influence that differences in catchment properties and lake morphometries have on the sedimentary record is rarely considered. We investigated sediment cores from three lakes located close to the inland ice sheet margin in the Kangerlussuaq area of South West Greenland but within a few kilometres of one another. This regional replication allowed for direct comparisons of biological change in lakes exposed to identical environmental pressures (cooling, increased wind speeds) over the past c.2000 years. Sedimentary pigments were used as a proxy for whole-lake production and to investigate differences in phytoplankton community structure whilst fossil diatom assemblages were studied to determine differences in ecological responses during this time. We noted several major effects of the Little Ice Age cooling (LIA, c. 1400-1850AD). The organic content of sediments in all three lakes declined, and this effect was most pronounced in lakes closest to the inland ice sheet margin, which suggests that aeolian inputs derived from the glacial outwash plains (sandurs), and wind-scouring of the thin catchment soils by strong katabatic winds associated with the regional cooling might have both contributed to this sedimentary change. During the LIA total algal production (as indicated by chlorophyll and carotenoid pigments) was lower in all three lakes, most likely because of extended ice-cover and shorter growing seasons, and the ratio of planktonic: benthic diatom taxa increased, possibly because of lower light availability or fertilization from loess material. Despite this coherence in lake response to the LIA, diatom community composition changes in individual lakes differed, reflecting individual lake morphometry and catchment characteristics. These findings highlight the importance of

  4. Fatty Acid Composition of Muscle, Adipose Tissue and Liver from Muskoxen (Ovibos moschatus) Living in West Greenland

    PubMed Central

    Alves, Susana P.; Raundrup, Katrine; Cabo, Ângelo; Bessa, Rui J. B.; Almeida, André M.

    2015-01-01

    Information about lipid content and fatty acid (FA) composition of muskoxen (Ovibos moschatos) edible tissues is very limited in comparison to other meat sources. Thus, this work aims to present the first in-depth characterization of the FA profile of meat, subcutaneous adipose tissue and liver of muskoxen living in West Greenland. Furthermore, we aim to evaluate the effect of sex in the FA composition of these edible tissues. Samples from muscle (Longissimus dorsi), subcutaneous adipose tissue and liver were collected from female and male muskoxen, which were delivered at the butchery in Kangerlussuaq (West Greenland) during the winter hunting season. The lipid content of muscle, adipose tissue and liver averaged 284, 846 and 173 mg/g of dry tissue, respectively. This large lipid contents confirms that in late winter, when forage availability is scarce, muskoxen from West Greenland still have high fat reserves, demonstrating that they are well adapted to seasonal feed restriction. A detailed characterization of FA and dimethylacetal composition of muskoxen muscle, subcutaneous adipose tissue and liver showed that there are little differences on FA composition between sexes. Nevertheless, the 18:1cis-9 was the most abundant FA in muscle and adipose tissue, reaching 43% of total FA in muscle. The high content of 18:1cis-9 suggests that it can be selectively stored in muskoxen tissues. Regarding the nutritional composition of muskoxen edible tissues, they are not a good source of polyunsaturated FA; however, they may contribute to a higher fat intake. Information about the FA composition of muskoxen meat and liver is scarce, so this work can contribute to the characterization of the nutritional fat properties of muskoxen edible tissues and can be also useful to update food composition databases. PMID:26678792

  5. Origin of cratonic lithospheric mantle roots: A geochemical study of peridotites from the North Atlantic Craton, West Greenland

    NASA Astrophysics Data System (ADS)

    Wittig, N.; Pearson, D. G.; Webb, M.; Ottley, C. J.; Irvine, G. J.; Kopylova, M.; Jensen, S. M.; Nowell, G. M.

    2008-09-01

    A critical examination of the extent to which geodynamic information on the initial mantle depletion and accretion event(s) is preserved in kimberlite-borne cratonic SCLM peridotite xenoliths is attempted by using new major and trace element data of whole-rock peridotites ( n = 55) sampled across the North Atlantic Craton (NAC; West Greenland). We also present additional whole-rock trace element data of mantle xenoliths from Somerset Island, the Slave and Kaapvaal cratons for comparison. Peridotites comprising the West Greenland SCLM are distinctly more olivine-rich and orthopyroxene-poor than most other cratonic peridotites, in particular those from the Kaapvaal craton. The West Greenland peridotites have higher Mg/Si but lower Al/Si, Al 2O 3 and CaO than cratonic mantle from the Kaapvaal Craton. We suggest that the more orthopyroxene depleted, harzburgite to dunite character of the NAC peridotites reflects more of the original melting history than peridotites from other cratons and in that sense may be more typical of cratonic lithosphere compositions prior to extensive modification. Despite this, some modal and cryptic metasomatism has clearly taken place in the West Greenland lithosphere. The insensitivity of major elements to pressure of melting at high degrees of melt extraction combined with the ease with which these elements may be changed by modal metasomatism mean that we cannot confidently constrain the depth of melting of peridotites using this approach. Mildly incompatible trace elements offer much more promise in terms of providing geodynamic information about the original Archean melting regime. The very low, systematically varying heavy REE abundances in NAC whole-rock peridotites and in peridotites from all other cratons where high-quality data are available provide ubiquitous evidence for a shallow melting regime in the absence of, or to the exhaustion of garnet. This finding explicitly excludes large extents of deep (iso- and polybaric) melting

  6. A novel multispectral glacier mapping method and its performance in Greenland

    NASA Astrophysics Data System (ADS)

    Citterio, M.; Fausto, R. S.; Ahlstrom, A. P.; Andersen, S. B.

    2014-12-01

    Multispectral land surface classification methods are widely used for mapping glacier outlines. Significant post-classification manual editing is typically required, and mapping glacier outlines over larger regions remains a rather labour intensive task. In this contribution we introduce a novel method for mapping glacier outlines from multispectral satellite imagery, requiring only minor manual editing.Over the last decade GLIMS (Global Land Ice Measurements from Space) improved the availability of glacier outlines, and in 2012 the Randolph Glacier Inventory (RGI) attained global coverage by compiling existing and new data sources in the wake of the Fifth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC AR5). With the launch of Landsat 8 in 2013 and the upcoming ESA (European Space Agency) Sentinel 2 missions, the availability of multispectral imagery may grow faster than our ability to process it into timely and reliable glacier outline products. Improved automatic classification methods would enable a full exploitation of these new data sources.We outline the theoretical basis of the proposed classification algorithm, provide a step by step walk-through from raw imagery to finished ice cover grids and vector glacier outlines, and evaluate the performance of the new method in mapping the outlines of glaciers, ice caps and the Greenland Ice Sheet from Landsat 8 OLI imagery. The classification output is compared against manually digitized ice margin positions, the RGI vectors, and the PROMICE (Programme for Monitoring of the Greenland Ice Sheet) aerophotogrammetric map of Greenland ice masses over a sector of the Disko Island surge cluster in West Greenland, the Qassimiut ice sheet lobe in South Greenland, and the A.P. Olsen ice cap in NE Greenland.

  7. Variability in the timing of the late Holocene maximum extent of the southwest Greenland Ice Sheet

    NASA Astrophysics Data System (ADS)

    Carlson, A. E.; Winsor, K.; Ullman, D. J.; Murray, D. S.; Rood, D. H.; Axford, Y.

    2011-12-01

    Boreal summer climate generally cooled across the mid to late Holocene, driving growth of the Greenland Ice Sheet. The timing of maximum late Holocene Greenland Ice Sheet extent is usually assigned to the Little Ice Age (LIA), although earlier more extensive Neoglacial advances may have occurred. Here we present new 10-Be surface exposure ages from erratic boulders on bedrock just outside of historical moraines deposited during the LIA near Kangerlussuaq, Paamiut and Narsarsuaq in southwest Greenland to date when ice was more extensive than during the LIA. A more extensive Neoglacial advance at ~2 ka was previously proposed near Kangerlussuaq. Our cosmogenic dates just outside the historical moraine at Kangerlussuaq indicate, however, that ice has been within its historical limit since 6.8±0.1 ka (n=6, 1 std. error), which is similar to recently published age constraints further north in the Disko Bugt region of west Greenland. Near Narsarsuaq in south Greenland, cosmogenic boulder dates indicate that at 1.2±0.2 ka (n=4, 1 std. error), the outlet glacier Kiagtût sermiat was ~200 m thicker than its historical limit. The timing of thicker ice near Narsarsuaq is likely concurrent with an ~8 km advance the same outlet glacier relative to the modern ice margin previously inferred from one minimum limiting radiocarbon date of 1.2±0.1 ka (1σ). Cosmogenic dates from near Paamiut in southwest Greenland and additional Narsarsuaq dates are forthcoming. The timing of ice thinning and retreat near Narsarsuaq beginning at ~1.2 ka is concurrent with a switch from the dominance of Arctic- to Atlantic-sourced water masses within southern Greenland fjords, inferred from changes in fjord faunal assemblages. Modern switches in the source of fjord waters are related to variations in the North Atlantic Oscillation (NAO), with a switch from a positive to a negative phase causing the incursion of relatively warm Irminger Current waters around southern Greenland. We hypothesize that

  8. Automated Ground-based Time-lapse Camera Monitoring of West Greenland ice sheet outlet Glaciers: Challenges and Solutions

    NASA Astrophysics Data System (ADS)

    Ahn, Y.; Box, J. E.; Balog, J.; Lewinter, A.

    2008-12-01

    Monitoring Greenland outlet glaciers using remotely sensed data has drawn a great attention in earth science communities for decades and time series analysis of sensory data has provided important variability information of glacier flow by detecting speed and thickness changes, tracking features and acquiring model input. Thanks to advancements of commercial digital camera technology and increased solid state storage, we activated automatic ground-based time-lapse camera stations with high spatial/temporal resolution in west Greenland outlet and collected one-hour interval data continuous for more than one year at some but not all sites. We believe that important information of ice dynamics are contained in these data and that terrestrial mono-/stereo-photogrammetry can provide theoretical/practical fundamentals in data processing along with digital image processing techniques. Time-lapse images over periods in west Greenland indicate various phenomenon. Problematic is rain, snow, fog, shadows, freezing of water on camera enclosure window, image over-exposure, camera motion, sensor platform drift, and fox chewing of instrument cables, and the pecking of plastic window by ravens. Other problems include: feature identification, camera orientation, image registration, feature matching in image pairs, and feature tracking. Another obstacle is that non-metric digital camera contains large distortion to be compensated for precise photogrammetric use. Further, a massive number of images need to be processed in a way that is sufficiently computationally efficient. We meet these challenges by 1) identifying problems in possible photogrammetric processes, 2) categorizing them based on feasibility, and 3) clarifying limitation and alternatives, while emphasizing displacement computation and analyzing regional/temporal variability. We experiment with mono and stereo photogrammetric techniques in the aide of automatic correlation matching for efficiently handling the enormous

  9. Accumulation of organotin compounds and mercury in harbour porpoises (Phocoena phocoena) from the Danish waters and West Greenland.

    PubMed

    Strand, Jakob; Larsen, Martin M; Lockyer, Christina

    2005-11-01

    The concentrations of butyltin (summation operatorBT=TBT+DBT+MBT) and mercury (Hg) were determined in the liver of 35 harbour porpoises (Phocoena phocoena), which were found dead along the coastlines or caught as by-catch in the Danish North Sea and the Inner Danish waters. In addition, three harbour porpoises hunted in West Greenland were analysed. High levels of butyltin and mercury, within the range of 68-4605 mg BT/kg ww and 0.22-92 mg Hg/kg ww, were found in the liver of the Danish harbour porpoises and both substances tend to accumulate with age. The levels in the harbour porpoise from West Greenland were 2.0-18 mg BT/kg ww and 6.3-6.9 mg Hg/kg ww, respectively. The concentrations of butyltin and mercury were both found to be higher in stranded than in by-caught harbour porpoises but only the butyltin concentration was significantly higher in stranded porpoises in the age group 1-5 years. These substances are suspected of inducing adverse effects on immune and endocrine systems in mammals and they may thereby pose a threat to the animals. This study suggests that organotin compounds are also important, when assessing the risks of contaminants on the health and viability of harbour porpoises in Danish waters.

  10. Modeling experiments on the deceleration and reactivation of Kangerlussuup Sermusa, West Greenland

    NASA Astrophysics Data System (ADS)

    Rezvanbehbahani, S.; Stearns, L. A.; van der Veen, C. J.; Catania, G. A.

    2015-12-01

    Seasonal variations in outlet glacier velocity due to basal sliding are well-documented and typically involve acceleration early in the melt season due to enhanced sliding as a result of inefficient drainage of surface water reaching the bed. However, velocity observations from Kangerlussuup Sermusa (KS) in West Greenland contradict this pattern. Instead, ice velocity at KS shows no significant change in early spring compared with the previous winter. This sluggish response of the glacier to spring melt is often followed by an extreme, and short-lived, deceleration. For example, in August 2010, the lower 20 km of the trunk decelerated from about 1600 m a-1 to less than 250 m a-1; this event was followed by a rapid reactivation back to the previous velocity in less than 60 days. Available records since 2006 show that the sequence of steady spring velocity, followed by summer deceleration, and rapid fall reactivation occurs annually; however, the magnitudes of deceleration vary. In this regard, the response of KS to regional environmental forcings is unique compared to its neighboring glaciers. In this study, we investigate whether the unique behavior of KS can be explained by the interaction between changes in basal conditions and the local geometry of the glacier. We model the glacier flow by solving full-Stokes equations using the finite element method in the open-source FEniCS framework. Assuming isothermal ice within the lower trunk, we run experiments on the mechanical properties and boundary conditions of the glacier. These experiments include spatio-temporal changes in basal slipperiness, periodic melt-water influx to the bed, and ice viscosity variations due to changes in melt-water supply to the bed. We also conduct sensitivity analyses on the glacier flow with different ice geometries (e.g. thickness and surface slope) to investigate conditions under which we can produce the unique seasonal behavior of KS. Finally, we assess the impact of the combination

  11. Regime Change of Ice Draft in Nares Strait to the West of Greenland 2003 to 2009

    NASA Astrophysics Data System (ADS)

    Ryan, P. A.; Muenchow, A.; Huntley, H.

    2014-12-01

    The last of remaining multi-year ice exits the Arctic Ocean via Nares Strait to the west of northern Greenland. Measuring ice draft and velocity directly, we maintained moored sensors in Nares Strait from 2003 through 2009. Two ice profiling sonars measured acoustic travel times from about 100-m depth to the bottom of the sea ice. Estimates of ice draft result, if vertically averaged density, speed of sound, and depth of the sensor are known. We use concurrently measured temperature, salinity, and pressure at nearby mooring locations for those properties at daily time scales. Sensitivity tests reveal that our ice draft estimates are accurate to within 0.1 m. With ice drafts sampled at 15 second intervals, we construct ice draft probability density functions to define ice categories and to compare these at inter-annual and seasonal time sales. Categories are open water (no ice), thin ice (< 0.5 m), first year ice (0.5- 2 m; FYI), multi year ice (>2 m; MYI). FYI dominated the ice draft distribution from 2003 to 2006 when it was observed about half of the time. It diminished to ~20% from 2006 to 2009 when much FYI was replaced by a combination of thin ice and MYI. We interpret this finding as a transition towards a more dynamic and advective ice regime in Nares Strait. At seasonal time scales we found the largest ice drafts always during the period prior to prolonged periods of zero ice velocity, that is, the onset of landfast ice conditions. The duration of this landfast season reduced from more than 180 days per year on average for the 2003-06 period to less than 20 days per year on average for the 2006-09 period. Implications on ice flux are profound as the transition from landfast to mobile ice conditions enhances both local wind forcing, local ice formation (thin ice), and ice export. We emphasize that this transition precedes the record setting Arctic ice minimum in the summer of 2007.

  12. Processes and timescales of melt metasomatism in the continental lower crust of West Greenland

    NASA Astrophysics Data System (ADS)

    Smit, Matthijs; Waight, Tod; Nielsen, Troels

    2017-04-01

    The lower continental crust is infiltrated by mantle-derived melts that are at extreme chemical disequilibrium with this reservoir. The chemical effect, and the degree and extent of melt infiltration within the lower crust are important parameters to investigating the role of this process in modifying local and regional crustal composition. However, in spite of ground-breaking contributions in this field, the processes of melt metasomatism within the lower crust are not entirely clear. Challenges lie in obtaining primary petrological, geochemical and chronological information from deep crustal rocks that are difficult to sample and are often repeatedly recrystallized and chemically modified. In this study, we investigated mafic granulite xenoliths from the crustal root of the Archean North Atlantic Craton (Sarfartôq location) and the adjoining Paleoproterozoic Nagssugtôqidian Orogen (Sisimiut location), West Greenland. These rocks were chosen because: 1) they are xenolith and hence are unaffected by tectonic overprinting, 2) they show a rich petrological record of melt infiltration formed in the run up to their scavenging by the host aillikite magmas, 3) they represent two locations with similar crustal composition and architecture, but different underlying lithospheric mantle enabling teasing-out of the role of melt-mantle interaction. We used various imaging techniques and in-situ chemical analysis by electron-probe micro-analyzer to characterize the different melt pockets within the samples, their textural relationships, as well as their composition. In addition, we performed thermometry and multi-method speedometry (Fe-in-rutile, majors-in-garnet) to assess the conditions and duration of melt infiltration for melts of different texture and composition. The primary granular assemblage of the xenoliths has been infiltrated by three different types of melts, each of which is found in grain boundaries, melt-corroded cracks, and voids formed by melt

  13. Measuring short term velocity changes of Kangilerngata Sermia, west Greenland using a Gamma Portable Radar Interferometer

    NASA Astrophysics Data System (ADS)

    Kane, E.; Rignot, E. J.; Mouginot, J.; Li, X.; Millan, R.; Fahnestock, M. A.; Nakayama, Y.; Scheuchl, B.

    2016-12-01

    Kangilerngata Sermia, west Greenland, is a 4 km wide marine terminating glacier that experienced rapid retreat from 2005-2010, withdrawing from a stabilizing sill at 150 m depth to its current state, grounded 350 m below sea level. The ice front retreated 2.3 km over a 5 year period with ice speeds increasing to 3x the average rate as the front retreated into deeper water. With a bed that is continuously 200-450 m below sea level for 30 km upstream, this glacier might continue to retreat rapidly for decades to come. We conducted a 16-day field campaign in July 2016 aimed to increase the temporal resolution of ice flow velocity measurements during the peak calving season by using a Gamma Portable Radar Interferometer (GPRI) deployed at 100m elevation about 3 km from the glacier front, scanning the glacier every 3 minutes. In addition we conducted an hydrography survey, collecting a set of 11 CTDs (conductivity, temperature, depth plus dissolved oxygen) about 1 km from the calving front, to estimate the amount of ice melted by the ocean. We compare these results to simulations of ice melt of a calving face using the MITgcm ocean model to help evaluate the model results on one glacier. With the GPRI we form a time series of radar images that show the dynamics of the ocean surface in front of the glacier as a result of wind, sub-glacial water discharge and calving events. We form time series of radar interferograms to analyze the time evolution of glacier speed, especially in relation to calving events, both small and large. Velocity records are used to detect changes in speed, prior, during and post-calving and to determine how long these changes persisted. These results are then analyzed in relation to bed topography (mapped with multi-beam) and tidal cycle. We also compare our results with TerraSAR-X ice velocity maps. We conclude on the impacts of calving events on short-term ice dynamics and implications for the future of this glacier. This work was preformed at

  14. Measurements of supraglacial lake drainage and surface streams over West Greenland and effects on ice dynamics

    NASA Astrophysics Data System (ADS)

    Tedesco, M.; Willis, I. C.; Alexander, P. M.; Banwell, A. F.

    2011-12-01

    During the summer of 2011 we measured the filling and draining of two surface lakes in the Paakitsoq region of the West Greenland Ice Sheet (49.79 W, 69.57 N), together with the level of streams flowing into the basins feeding the lakes. We also used GPS to record the horizontal and vertical movement of the ice sheet surface at five locations surrounding the lakes for a two week period (overlapping the draining of the two lakes). In this talk we report results concerning the processes of lake filling and draining between the two lakes. 'Lake Half Moon', with a smaller catchment area, filled slowly at a steady rate over several days, then drained gradually over a 24 hour period as an existing moulin located outside the bottom of the lake became active; the lake level continued to drop very slowly over the remaining week as the surface stream leading from the lake to the moulin incised. 'Lake Ponting', with the larger catchment area, filled more rapidly and at an accelerating rate as depressions upstream of the lake filled with water, overflowed and delivered increasing volumes of water to the lake. Lake Ponting drained by hydrofracture following a particularly rapid rise in water level, generating a new ~ 800m long extensional crevasse on the ice sheet surface. The entire ~ 3 x 106 m3 lake drained within a few hours. For the Lake Pointing, we show, for the first time, a movie of the lake draining, showing many features that we observed right after its drainage. The rate of lake level lowering during the drainage varied; initially moderately rapid while the fractures formed and accommodated the water, then exceptionally rapid as the fractures reached the bed allowing the lake to drain completely. The analysis of the GPS data suggest that the different styles of lake draining affect the vertical and horizontal movement of the ice sheet in different ways. We also anticipate that the effect of the draining of Lake Ponting was affecting the GPS sensors in a different

  15. Accessory Mineral Records of Early Earth Crust-Mantle Systematics: an Example From West Greenland

    NASA Astrophysics Data System (ADS)

    Storey, C. D.; Hawkesworth, C. J.

    2008-12-01

    Conditions for the formation and the nature of Earth's early crust are enigmatic due to poor preservation. Before c.4 Ga the only archives are detrital minerals eroded from earlier crust, such as the Jack Hills zircons in western Australia, or extinct isotope systematics. Zircons are particularly powerful since they retain precise records of their ages of crystallisation, and the Lu-Hf radiogenic isotope and O stable isotope systematics of the reservoir from which they crystallised. In principle, this allows insight into the nature of the crust, the mantle reservoir from which the melt was extracted and any reworked material incorporated into that melt. We have used in situ methods to measure U-Pb, O and Lu-Hf within single zircon crystals from tonalitic gneisses from West Greenland in the vicinity of the Isua Supracrustal Belt. They have little disturbed ages of c.3.8 Ga, mantle-like O isotope signatures and Lu-Hf isotope signatures that lie on the CHUR evolution line at 3.8 Ga. These samples have previously been subjected to Pb isotope feldspar and 142Nd whole rock analysis and have helped constrain models in which early differentiation of a proto-crust must have occurred. The CHUR-like Lu-Hf signature, along with mantle-like O signature from these zircons suggests juvenile melt production at 3.8 Ga from undifferentiated mantle, yet the other isotope systems preclude this possibility. Alternatively, this is further strong evidence for a heterogeneous mantle in the early Earth. Whilst zircons afford insight into the nature of the early crust and mantle, it is through the Sm-Nd system that the mantle has traditionally been viewed. Titanite often contains several thousand ppm Nd, making it amenable to precise analysis, and is a common accessory phase. It has a reasonably high closure temperature for Pb and O, and it can retain cores with older ages and distinct REE chemistry. It is often the main accessory phase alongside zircon, and it is the main carrier of Nd

  16. Parasites as biological tags to track an ontogenetic shift in the feeding behaviour of Gadus morhua off West and East Greenland.

    PubMed

    Münster, Julian; Klimpel, Sven; Fock, Heino O; MacKenzie, Ken; Kuhn, Thomas

    2015-07-01

    Parasites, being an integral part of every ecosystem and trophically transmitted along the food webs, can provide detailed insights into the structure of food webs and can close the information gap between short-term stomach content analyses and long-term fish otolith analyses. They are useful for tracking ontogenetic shifts in the host's diet, the occurrence of specific organisms or migratory behaviour of their hosts, even in inaccessible environments. In the present study, stomach content analyses and parasitological examinations were performed on 70 Atlantic cod Gadus morhua, one of the most important high-level predators of small fish in the North Atlantic, caught during one research vessel cruise from West and East Greenlandic waters. Analyses revealed significant differences in fish size with higher values for East Greenland (average total length (TL) of 50.5 cm) compared to West Greenland (average TL of 33.3 cm). Clear differences were also present in prey and parasite composition. Crustacea was the main food source for all fish (IRI = 10082.70), while the importance of teleosts increased with fish size. With a prevalence of 85 % in West Greenland and 100 % in East Greenland, Nematoda were the most abundant parasite group. The results indicate an ontogenetic shift in the diet, which are discussed in the context of the common distribution theory, stock dynamics and migratory behaviour.

  17. Hydrogeochemistry of Groundwater as Part of the Greenland Analogue Project in an Area of Continuous Permafrost Adjacent to the Greenland Ice Sheet, Kangerlussuaq, West Greenland

    NASA Astrophysics Data System (ADS)

    Henkemans, E.; Frape, S.; Ruskeeniemi, T.; Claesson-Liljedahl, L.; Lehtinen, A.; Annable, W. K.

    2011-12-01

    Studying groundwater in areas of continuous permafrost is often limited to studies of springs and open pingos (eg. Pollard et al. 1999 and Allen et al. 1976). Boreholes in such locations are expensive, risky and logistically challenging (eg. Stotler et al. 2011) resulting in a limited understanding of the interaction between continental scale ice sheets and groundwater. Continental ice sheet models are often coupled to groundwater flow systems; however, there is a lack of modern field data with which to compare the results of models and their treatment of groundwater flow systems under the influence of glaciation. The Greenland Analogue Project (GAP) aims to eliminate some of the uncertainties in modeling ice sheets by using the Greenland ice sheet as a modern analogue for past glaciations. Since 2009, 3 boreholes have been drilled, 2 of which contain sampling systems. DH-GAP01 is a 191 m deep borehole drilled at an angle into a talik and has been sampled and studied since 2009. DH-GAP04 is a 632 m deep, angled borehole that intersects the groundwater flow system directly beneath Isunguata Sermia and is producing preliminary groundwater samples. Additional information on groundwater in the Kangerlussuaq area comes from a spring located directly in front of the Leverett ice lobe. Geochemical and isotopic (δ18O, δ2H, δ37Cl, 87Sr/86Sr, and δ34S and δ18O of SO4) tools are used to interpret geochemical processes acting on groundwaters and provide insight into groundwater flow. Analyses of δ18O and δ2H in groundwaters from DH-GAP01 show the borehole waters fall along the Global Meteoric Water Line (GMWL). Evaporation is an important process affecting the δ18O-δ2H of surface waters in the region causing lakes to plot along a local evaporation line (Leng and Anderson, 2003). The waters from the Leverett spring plot to the right of the GMWL as possibly a mixture of groundwater and surface evaporated fluids. However, both the waters from DH-GAP01 and the Leverett

  18. Simulating Ice-Flow and Calving on Store Glacier, West Greenland, with a 3D Full Stokes Model

    NASA Astrophysics Data System (ADS)

    Todd, J.; Christoffersen, P.; Zwinger, T.; Luckman, A. J.; Benn, D.

    2015-12-01

    The mass balance and long-term stability of the ice sheets in Greenland and Antarctica depend heavily on the dynamics of their ice-ocean margins. Iceberg calving accounts for the majority of the net annual loss of ice in Antarctica and around half of that from Greenland. Furthermore, climate driven changes to dynamics at these calving margins can be transmitted far inland. Thus, predicting future sea level contribution from the cryosphere requires an improved understanding of calving, and the processes which link it to climate and ice-sheet flow. We present results from a new 3D calving model coupled to a full-Stokes, time evolving glacier dynamic model, implemented for Store Glacier, a 5-km-wide calving glacier in the Uummannaq region of West Greenland, which flows at a rate of 20 m/day at its terminus. The model is developed using the open source finite element package Elmer/Ice, with the criterion that calving occurs when surface and basal crevasses meet. Crevasses open in response to tensile stresses near the terminus and water pressure at the bed. When the model was applied in 2D for the central flowline of Store Glacier, we found that basal topography exerts overarching control on the long term position of the calving front, while ice mélange buttressing allows the seasonal extension of a floating tongue, which collapses in early summer. New results emerging from implementation of calving in a 3D model indicate significant spatial heterogeneity in calving dynamics because the northern half of the terminus is grounded whereas the southern half is floating. This contrasting setting affects calving dynamics, further underlining the importance of geometry and basal topography, and suggesting that lower dimensional calving models may miss important aspects of calving dynamics. Our results also suggest that implementing grounding line dynamics is important for modelling calving, even for glaciers which are, for the most part, firmly grounded.

  19. Variations of the glacio-marine air mass front in West Greenland through water vapor isotopes

    NASA Astrophysics Data System (ADS)

    Kopec, B. G.; Lauder, A. M.; Posmentier, E. S.; Feng, X.

    2012-12-01

    While the isotopic distribution of precipitation has been widely used for research in hydrology, paleoclimatology, and ecology for decades, intensive isotopic studies of atmospheric water vapor has only recently been made possible by spectral-based technology. New instrumentation based on this technology opens up many opportunities to investigate short-term atmospheric dynamics involving the water cycle and moisture transport. We deployed a Los Gatos Water Vapor Isotope Analyzer (WVIA) at Kangerlussuaq, Greenland from July 21 to August 15, and measured the water vapor concentration and its isotopic ratios continuously at 10s intervals. A Danish Meteorological Institute site is located about 1 km from the site of the deployment, and meteorological data is collected at 30 min intervals. During the observation period, the vapor concentration of the ambient air ranges from 5608.4 to 11189.4 ppm; dD and d18O range from -254.5 to -177.7 ‰ and -34.2 to -23.2 ‰, respectively. The vapor content (dew point) and the isotopic ratios are both strongly controlled by the wind direction. The easterly winds are associated with dry, isotopically depleted air masses formed over the glacier, while westerly winds are associated with moist and isotopically enriched air masses from the marine/fjord surface. This region typically experiences katabatic winds off of the ice sheet to the east. However, during some afternoons, the wind shifts 180 degrees, blowing off the fjord to the west. This wind switch marks the onset of a sea breeze, and significant isotopic enrichment results. Enrichment in deuterium is up to 60 ‰ with a mean of 15‰, and oxygen-18 is enriched by 3‰ on average and up to 8 ‰. Other afternoons have no change in wind, and only small changes in humidity and vapor isotopic ratios. The humidity and isotopic variations suggest the local atmosphere circulation is dominated by relatively high-pressure systems above the cold glaciers and cool sea surface, and diurnal

  20. A modeling study of the effect of runoff variability on the effective pressure beneath Russell Glacier, West Greenland

    NASA Astrophysics Data System (ADS)

    Fleurian, Basile; Morlighem, Mathieu; Seroussi, Helene; Rignot, Eric; Broeke, Michiel R.; Kuipers Munneke, Peter; Mouginot, Jeremie; Smeets, Paul C. J. P.; Tedstone, Andrew J.

    2016-10-01

    Basal sliding is a main control on glacier flow primarily driven by water pressure at the glacier base. The ongoing increase in surface melting of the Greenland Ice Sheet warrants an examination of its impact on basal water pressure and in turn on basal sliding. Here we examine the case of Russell Glacier, in West Greenland, where an extensive set of observations has been collected. These observations suggest that the recent increase in melt has had an equivocal impact on the annual velocity, with stable flow on the lower part of the drainage basin but accelerated flow above the Equilibrium Line Altitude (ELA). These distinct behaviors have been attributed to different evolutions of the subglacial draining system during and after the melt season. Here we use a high-resolution subglacial hydrological model forced by reconstructed surface runoff for the period 2008 to 2012 to investigate the cause of these distinct behaviors. We find that the increase in meltwater production at low elevation yields a more efficient drainage system compatible with the observed stagnation of the mean annual flow below the ELA. At higher elevation, the model indicates that the drainage system is mostly inefficient and is therefore strongly sensitive to an increase in meltwater availability, which is consistent with the observed increase in ice velocity.

  1. Analysis of Arctic outflows west and east of Greenland in an eddying global sea ice-ocean model

    NASA Astrophysics Data System (ADS)

    Aksenov, Yevgeny; Bacon, Sheldon; Regan, Heather; Nurser, George; Coward, Andrew

    2014-05-01

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

  2. Modelling calving front dynamics using a level-set method: application to Jakobshavn Isbræ, West Greenland

    NASA Astrophysics Data System (ADS)

    Bondzio, Johannes H.; Seroussi, Hélène; Morlighem, Mathieu; Kleiner, Thomas; Rückamp, Martin; Humbert, Angelika; Larour, Eric Y.

    2016-03-01

    Calving is a major mechanism of ice discharge of the Antarctic and Greenland ice sheets, and a change in calving front position affects the entire stress regime of marine terminating glaciers. The representation of calving front dynamics in a 2-D or 3-D ice sheet model remains non-trivial. Here, we present the theoretical and technical framework for a level-set method, an implicit boundary tracking scheme, which we implement into the Ice Sheet System Model (ISSM). This scheme allows us to study the dynamic response of a drainage basin to user-defined calving rates. We apply the method to Jakobshavn Isbræ, a major marine terminating outlet glacier of the West Greenland Ice Sheet. The model robustly reproduces the high sensitivity of the glacier to calving, and we find that enhanced calving triggers significant acceleration of the ice stream. Upstream acceleration is sustained through a combination of mechanisms. However, both lateral stress and ice influx stabilize the ice stream. This study provides new insights into the ongoing changes occurring at Jakobshavn Isbræ and emphasizes that the incorporation of moving boundaries and dynamic lateral effects, not captured in flow-line models, is key for realistic model projections of sea level rise on centennial timescales.

  3. Longitudinal Inter-Comparison of Modeled and Measured West Greenland Ice Sheet Meltwater Runoff Losses (2004-2014)

    NASA Astrophysics Data System (ADS)

    Moustafa, S.; Rennermalm, A. K.; Tedesco, M.; Mote, T. L.; Koenig, L.; Smith, L. C.; Hagedorn, B.; Overeem, I.; Sletten, R. S.; Mikkelsen, A. B.; Hasholt, B.; Hall, D. K.

    2015-12-01

    Increased surface meltwater runoff, that exits the Greenland ice sheet (GrIS) margin via supra-, en-, and sub-glacial drainage networks into fjords, pro-glacial lakes and rivers, accounts for half or more of total mass loss. Despite its importance, modeled meltwater runoff fluxes are poorly constrained, primarily due to a lack of direct in situ observations. Here, we present the first ever longitudinal (north-south) inter-comparison of a multi-year dataset (2004-2014) of discharge for four drainage basins - Watson, Akuliarusiarsuup Kuua, Naujat Kuat, and North Rivers - along West Greenland. These in situ hydrologic measurements are compared with modeled runoff output from Modèle Atmosphérique Régional (MAR) regional climate model, and the performance of the model is examined. An analysis of the relationship between modeled and actual ice sheet runoff patterns is assessed, and provides insight into the model's ability to capture inter-annual and intra-annual variability, spatiotemporal patterns, and extreme melt events. This study's findings will inform future development and parameterization of ice sheet surface mass balance models.

  4. Bathymetry data reveal glaciers vulnerable to ice-ocean interaction in Uummannaq and Vaigat glacial fjords, west Greenland

    NASA Astrophysics Data System (ADS)

    Rignot, E.; Fenty, I.; Xu, Y.; Cai, C.; Velicogna, I.; Cofaigh, C. Ó.; Dowdeswell, J. A.; Weinrebe, W.; Catania, G.; Duncan, D.

    2016-03-01

    Marine-terminating glaciers play a critical role in controlling Greenland's ice sheet mass balance. Their frontal margins interact vigorously with the ocean, but our understanding of this interaction is limited, in part, by a lack of bathymetry data. Here we present a multibeam echo sounding survey of 14 glacial fjords in the Uummannaq and Vaigat fjords, west Greenland, which extends from the continental shelf to the glacier fronts. The data reveal valleys with shallow sills, overdeepenings (>1300 m) from glacial erosion, and seafloor depths 100-1000 m deeper than in existing charts. Where fjords are deep enough, we detect the pervasive presence of warm, salty Atlantic Water (AW) (>2.5°C) with high melt potential, but we also find numerous glaciers grounded on shallow (<200 m) sills, standing in cold (<1°C) waters in otherwise deep fjords, i.e., with reduced melt potential. Bathymetric observations extending to the glacier fronts are critical to understand the glacier evolution.

  5. The metamorphic record of subduction-accretion processes in the Neoarchaean: the Nuuk region, southern West Greenland.

    NASA Astrophysics Data System (ADS)

    Dziggel, Annika; Kolb, Jochen

    2013-04-01

    The Nuuk region of southern West Greenland exposes an exceptionally well preserved section through Archaean mid- to lower continental crust, and therefore provides a natural laboratory to study the tectonic processes in the Archaean. The area mainly consists of amphibolite to granulite facies TTG gneisses, narrow supracrustal belts, and minor late-tectonic granites. It is made up of several distinct terranes, including, from NW to SE, the Færingehavn, Tre Brødre, and Tasiusarsuaq terranes. Extensive high-grade metamorphism and a clockwise PT evolution of the Færingehavn terrane in the Neoarchaean (2.72-2.71 Ga) have been interpreted as a result of crustal thickening and thrusting of the Tasiusarsuaq terrane on top of the Tre Brødre and Færingehavn terranes (Nutman and Friend, 2007). Prior to final collision, the Tasiusarsuaq terrane (the upper plate in a plate tectonic model) underwent a prolonged period of compressive deformation between 2.8 and 2.72 Ga (Kolb et al., 2012). The structural evolution was associated with near-isobaric cooling from medium-pressure granulite facies conditions of ca. 850°C and 7.5 kbar to amphibolite facies conditions of ca. 700°C and 6.5-7 kbar (Dziggel et al., 2012). Despite this long period of crustal convergence, there is no evidence for exhumation and/or loading, pointing to a rheologically weak and unstable Archaean crust perhaps due to low density differences and ongoing melt extraction. Rocks of the structurally underlying Færingehavn terrane record a distinctly different metamorphic evolution. Although generally more strongly retrogressed, relict higher-pressure mineral assemblages in mafic granulites and felsic gneisses record conditions of > 8-9 kbar and >= 750°C, indicating burial to depths of at least 30 km along an apparent geothermal gradient of 20-25°C/km. The peak of metamorphism was followed by isothermal decompression at ca. 2.715 Ga (Nutman and Friend, 2007), indicating rapid exhumation of lower crustal

  6. Impairment of cellular immunity in west Greenland sledge dogs (Canis familiaris) dietary exposed to polluted minke whale (Balaenoptera acutorostrata) blubber.

    PubMed

    Sonne, Christian; Dietz, Rune; Larsen, Hans J S; Loft, Klaus Earl; Kirkegaard, Maja; Letcher, Robert J; Shahmiri, Soheila; Móller, Per

    2006-03-15

    Minke whale (Balaenoptera acutorostrata) blubber is rich in organohalogen contaminants, mercury, and n-3 fatty acids. In the present study we show that a daily intake of 50-200 g of minke whale blubber causes an impairment of the nonspecific and specific cellular immune system in the West Greenland sledge dog (Canis familiaris). Immune reactions were measured by mitogen (PHA, Con A) and antigen (KLH) intradermal testing, and as the study used exposure levels similar to those of Inuits and polar bears (Ursus maritimus), it is reasonable to infer that Inuits and polar bears suffer from similar decreased resistance to diseases. It is speculated that food sources are depleted by thinning sea ice due to climate change and that more research should assess the forecasted rise in additive immunopathy effects in polar bears. Additionally, our study suggests that the fatty acid composition may be of importance when investigating combined immunotoxic effects of contaminated food resources in future Inuit and polar bear studies.

  7. The newly discovered Jurassic Tikiusaaq carbonatite-aillikite occurrence, West Greenland, and some remarks on carbonatite-kimberlite relationships

    NASA Astrophysics Data System (ADS)

    Tappe, Sebastian; Steenfelt, Agnete; Heaman, Larry M.; Simonetti, Antonio

    2009-11-01

    We discuss mineral chemistry data and report ten high-precision U-Pb (zircon, baddeleyite, pyrochlore, and perovskite) and Rb-Sr phlogopite ages for the newly discovered Tikiusaaq carbonatite intrusion and associated ultramafic dykes from the North Atlantic craton, West Greenland. At Tikiusaaq, massive dolomite-calcite carbonatite sheets intruded an 2 × 3 km area along a ductile shear zone between ca. 158 and 155 Ma. The accompanying carbonatite and carbonate-rich ultramafic silicate dykes were emplaced between ca. 165 and 157 Ma in close proximity to this carbonatite centre utilizing pre-existing brittle fractures. The deep volatile-rich magmatism at Tikiusaaq forms part of a larger Jurassic alkaline province in southern West Greenland and represents the earliest manifestation of rifting processes related to the opening of the Mesozoic-Cenozoic Labrador Sea Basin. Although the ultramafic silicate dykes macroscopically resemble hypabyssal kimberlites, they are identified as kimzeyite-bearing monticellite aillikites (carbonate-rich ultramafic lamprophyres) using a modern mineralogical-genetic classification. The overlapping emplacement ages of the carbonatite sheets and aillikite dykes, along with the carbonate-rich nature of the latter, suggest a genetic relationship between these magma types. The aillikites carry garnet peridotite xenoliths and have mineralogical characteristics of primitive magmas such as highly forsteritic olivine (up to Fo 90 mol%) and Cr-rich spinel (up to 46 wt.% Cr 2O 3) microphenocrysts; whereas the carbonatite sheets reveal a higher degree of differentiation such as Fe-rich dolomite compositions (up to 9 wt.% FeO). The initial findings reported here from Tikiusaaq suggest that a link between these magma types by an increasing degree of partial melting of a common carbonated upper mantle peridotite source region, as commonly envisaged for the compositionally similar Sarfartoq complex, is untenable. Rather, proto-aillikite magma may be

  8. The effect of long range nitrogen deposition on nutrient limitation of phytoplankton growth in lakes in South West Greenland

    NASA Astrophysics Data System (ADS)

    Hogan, E. J.; Mcgowan, S.; Anderson, N. J.

    2011-12-01

    There is growing evidence of ecological change in Arctic lakes. The majority of this evidence comes from lake sediment records which suggest that the composition of algal communities has changed, and that algal productivity has increased in the past 150 years. This change has commonly been attributed to a change in climate. However, such interpretation often ignores other drivers of change such as long range nitrogen (N) deposition, which has been shown to occur over a similar period of time. The region of South West Greenland is typical of much of the Arctic in terms of lake density, precipitation patterns and vegetation. It also provides a unique opportunity to investigate long range N deposition as a possible driver of ecological change as it has not experienced rapid 20th century warming which has been observed elsewhere in the Arctic. There is also evidence from ice core records that long range N deposition has increased in Greenland during the past 150 years. The effect of N deposition on nutrient limitation of phytoplankton growth was investigated in 20 freshwater lakes situated in 3 study regions in South West Greenland. The three regions span a gradient of increasing precipitation (and predicted N deposition) from the inland ice sheet margin to the coast. Nutrient limitation was investigated 3 times between August 2010 and July 2011, allowing both seasonal and regional differences to be explored. Phytoplankton growth was assessed over 14 days following in vivo fluorescence of sub-surface water samples treated with one of six nutrient additions: control (no addition), P (6 μM NaH2PO4), NH4+ (90 μM NH4Cl), NO3- (90 μM NaNO3), P + NH4+ (final concentrations as before), P + NO3- (final concentrations as before). A clear response to nutrient addition was found in 95 % of all bioassays, and of these, co-nutrient limitation was most commonly recorded (70 %). Regardless of region, phytoplankton growth appeared to show a seasonal change in nutrient limitation

  9. Identifying and assessing the role of warm air advection (Atmospheric Rivers) along the west coast of Greenland comparing various reanalyses for the period 2000-2012

    NASA Astrophysics Data System (ADS)

    Neff, William; Shupe, Matthew; Compo, Gilbert P.

    2017-04-01

    Neff et al. (2014) examined the 2012 summer Greenland melt episode and compared it to the last episode in 1889 using the Twentieth Century Reanalysis (20CR, Compo et al. 2011). A key factor in both 2012 and 1889 was the presence of an Atmospheric River (AR) that transported warm air over the Atlantic Ocean and thence to the west coast of Greenland. 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). The cases in 1889 and 2012 share a similar synoptic situation with lows just south and/or west of Baffin Island and highs to the southeast of Greenland. Although the details in the position of the moisture plumes are different, they both produce an anomaly in integrated water vapor (IWV) just off the southwest coast of Greenland suggesting this location as a key diagnostic location for potential AR impact on west Greenland. As part of a long-term goal to assess the frequency of such events that affect the surface energy budget of Greenland back to 1871 using the 20CR, we have compared in more detail transport signatures using 20CR, ERA-I, and NCEP-NCAR reanalyses for the period 2000-2012. In particular, we used reanalysis data at 50oW, 60oN, which lies just off the southwest coast of Greenland. These data included wind speed and direction, integrated precipitable water vapor (IWV), and specific humidity (q) at 850 hPa (which is a nominal height for the southerly coastal jet identified in previous AR events (Neff et al. 2014).) We found substantial agreement in the various reanalyses in terms of wind direction and speed distributions. We found IWV spatial distributions during southerly wind speed and IWV maxima that range from "blobs" to well-organized transport events. Using compositing techniques we also have examined the subsequence evolution of

  10. A 1200-year high-resolution sedimentary record in Holsteinsborg Dyb on the West Greenland shelf: foraminiferal and diatom indication of oceanographic changes

    NASA Astrophysics Data System (ADS)

    Reng Erbs-Hansen, Dorthe; Luise Knudsen, Karen; Ambrosius Underbjerg, Jens; Sha, Longbin; Jiang, Hui; Lykke-Andersen, Holger; Joest Andersen, Thorbjørn; Heinemeier, Jan; Símonarson, Leifur A.; Eiríksson, Jón

    2010-05-01

    A deep buried valley, crossing the West Greenland continental shelf from the town of Sisimiut towards the southwest, appears to have been repeatedly eroded and subsequently filled up by a series of Quaternary deposits. Two gravity cores (GA306-GC3 and GA306-GC4; 435 cm and 501 cm long) were obtained during the Galathea 3 expedition in 2006, at water depths of 425 and 445 m, respectively. Each of the cores is supplemented with a boxcore, covering the top part of the record. Age models for the two cores, established by the help of radiocarbon dating, combined with lead-210 dating for the younger parts, show that 7000 cal. years are represented at core site GA306-GC3 and 1200 cal. years at GA306-GC4. The present water masses along the West Greenland coast are dominated by two components. Closest to the shore, the East Greenland Current component brings water of Polar origin northward along the West Greenland Coast. This water is diluted by run-off water from the various fjord systems on its way, and the current turns westward towards Canada at around 65-66 degrees N. Atlantic Water masses, representing a current component originating from Irminger Water and the North Atlantic Current, is found below and to the west of the Polar Water component of the West Greenland Current. This water mass can be traced all the way along West Greenland to Thule in the north. Our core sites are located in the present "Irminger Mode Water" with temperature around 4 degrees C and salinity around 34.9 PSU. The foraminiferal and diatom assemblages in the sedimentary record at the GA306-GC4 site show that there have been considerable changes in the oceanography during the last 1200 years. The time interval between AD 715 and 840 is characterised by relatively strong bottom water currents and probably stratification of the water column. Between AD 840 and 1290, corresponding in time to the Medieval Warm Period (MWP), there is foraminiferal indication of reduced bottom current speed and

  11. Investigating near-glacier circulation and plume theory with high-resolution fjord surveys in West Greenland

    NASA Astrophysics Data System (ADS)

    Jackson, R. H.; Nash, J. D.; Shroyer, E.; Sutherland, D.; Fried, M.; Catania, G. A.; Carroll, D.; Bartholomaus, T. C.; Stearns, L. A.

    2016-12-01

    The plumes that emanate from Greenland's glaciers are hotspots of mixing between meltwater and ambient fjord waters. The dynamics of these plumes affect both submarine melting of glacier termini and the dilution of freshwater as it is exported into the ocean. Modeling studies often rely on buoyant plume theory to represent the circulation and mixing at the ocean/ice interface. However, a dearth of measurements in the near-glacier region has left open many questions about glacial plumes, entrainment, and the applicability of idealized plume theory to these environments. Here, we present near-glacier ocean surveys from Kangerdlugssuaq Sermerssua in central West Greenland in three consecutive summers (2013-2015). High-resolution measurements of velocity and water properties were collected by ship, by surface drifters, and by a remotely operated surface vessel - all focusing on the region within 2 km of the glacier terminus. These novel measurements of the 3D circulation capture a persistent near-surface plume, along with its time-evolution over a tidal cycle and between different summers. Concurrent multibeam sonar measurements of the submarine terminus morphology show that the plume emerges from a large undercut subglacial channel outlet. Plume theory, when applied with this fjord's stratification and any flux of subglacial discharge, cannot match the observed plume's volume flux and water properties. The discrepancy between our observations and plume theory suggests that there is enhanced entrainment at depth that is not adequately represented in plume theory. The details of this entrainment have important consequences for submarine melt rates, terminus morphology, and fjord circulation.

  12. 10Be dating reveals early-middle Holocene age of the Drygalski Moraines in central West Greenland

    NASA Astrophysics Data System (ADS)

    Cronauer, Sandra L.; Briner, Jason P.; Kelley, Samuel E.; Zimmerman, Susan R. H.; Morlighem, Mathieu

    2016-09-01

    We reconstruct the history of the Greenland Ice Sheet margin on the Nuussuaq Peninsula in central West Greenland through the Holocene using lake sediment analysis and cosmogenic 10Be exposure dating of the prominent Drygalski Moraines. Erratics perched on bedrock outboard of the Drygalski Moraines constrain local deglaciation to ∼9.9 ± 0.6 ka (n = 2). Three Drygalski Moraine crests yield mean 10Be ages of 8.6 ± 0.4 ka (n = 2), 8.5 ± 0.2 ka (n = 3), and 7.6 ± 0.1 ka (n = 2) from outer to inner. Perched erratics between the inner two moraines average 7.8 ± 0.1 ka (n = 2) and are consistent with the moraine ages. Sediments from a proglacial lake with a catchment area extending an estimated 2 km beneath (inland of) the present ice sheet terminus constrain an ice sheet minimum extent from 5.4 ka to 0.6 ka. The moraine chronology paired with the lake sediment stratigraphy reveals that the ice margin likely remained within ∼2 km of its present position from ∼9.9 to 5.4 ka. This unexpected early Holocene stability, preceded by rapid ice retreat and followed by minimum ice extent between ∼5.4 and 0.6 ka, contrasts with many records of early Holocene warmth and the Northern Hemisphere summer insolation maximum. We suggest ice margin stability may instead be tied to adjacent ocean temperatures, which reached an optimum in the middle Holocene.

  13. 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.

  14. 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.

  15. Northern Greenland

    NASA Image and Video Library

    2008-09-16

    The northernmost land in the world is located in Pearyland, Greenland, at a latitude of 83 degrees, 39.6 minutes. This is a land of permanent snows, glaciers, and 24-hours of daylight during the summer months. The ASTER image was acquired May 17, 2003, covers an area of 47.9 x 42.1 km, and is located at 83.6 degrees north latitude, 33.4 degrees west longitude. http://photojournal.jpl.nasa.gov/catalog/PIA11169

  16. Tidewater dynamics at Store Glacier, West Greenland from daily repeat UAV surveys

    NASA Astrophysics Data System (ADS)

    Ryan, Jonathan; Hubbard, Alun; Toberg, Nick; Box, Jason; Todd, Joe; Christoffersen, Poul; Neal, Snooke

    2017-04-01

    A significant component of the Greenland ice sheet's mass wasteage to sea level rise is attributed to the acceleration and dynamic thinning at its tidewater margins. To improve understanding of the rapid mass loss processes occurring at large tidewater glaciers, we conducted a suite of daily repeat aerial surveys across the terminus of Store Glacier, a large outlet draining the western Greenland Ice Sheet, from May to July 2014 (https://www.youtube.com/watch?v=-y8kauAVAfE). The unmanned aerial vehicles (UAVs) were equipped with digital cameras, which, in combination with onboard GPS, enabled production of high spatial resolution orthophotos and digital elevation models (DEMs) using standard structure-from-motion techniques. These data provide insight into the short-term dynamics of Store Glacier surrounding the break-up of the sea-ice mélange that occurred between 4 and 7 June. Feature tracking of the orthophotos reveals that mean speed of the terminus is 16 - 18 m per day, which was independently verified against a high temporal resolution time-series derived from an expendable/telemetric GPS deployed at the terminus. Differencing the surface area of successive orthophotos enable quantification of daily calving rates, which significantly increase just after melange break-up. Likewise, by differencing bulk freeboard volume of icebergs through time we could also constrain the magnitude and variation of submarine melt. We calculate a mean submarine melt rate of 0.18 m per day throughout the spring period with relatively little supraglacial runoff and no active meltwater plumes to stimulate fjord circulation and upwelling of deeper, warmer water masses. Finally, we relate calving rates to the zonation and depth of water-filled crevasses, which were prominent across parts of the terminus from June onwards.

  17. Modelling the dynamic response of Jakobshavn Isbræ, West Greenland, to calving rate perturbations

    NASA Astrophysics Data System (ADS)

    Bondzio, J. H.; Seroussi, H.; Morlighem, M.; Kleiner, T.; Rückamp, M.; Humbert, A.; Larour, E.

    2015-10-01

    Calving is a major means of ice discharge of the Antarctic and Greenland Ice Sheets. The breaking off of icebergs changes the ice front configuration of marine terminating glaciers, which affects the stress regime of their upstream areas. Recent observations show the close correlation between the ice front position and the behaviour of many outlet glaciers. However, modelling of a glacier subject to calving poses various challenges. No universal calving rate parametrisation is known, and tracking of a moving ice front and the related boundary conditions in two or three spatial dimensions is non-trivial. Here, we present the theoretical and technical framework for a Level-Set Method, an implicit boundary tracking scheme, which we implemented into the Ice Sheet System Model (ISSM). The scheme allows us to study the dynamic response of a drainage basin to user-defined front ablation rates. We apply the method in a suite of experiments to Jakobshavn Isbræ, a major marine terminating outlet glacier of the western Greenland Ice Sheet. The model robustly reproduces the high sensitivity of the glacier to frontal ablation in form of calving. We find that enhanced calving is able to trigger significant acceleration of the ice stream. Upstream acceleration is sustained through a combination of various feedback mechanisms. However, lateral stress and ice influx into the trough are able to stabilise the ice stream. This study contributes to the present discussion on causes and effects of the continued changes occurring at Jakobshavn Isbræ, and emphasises that the incorporation of seasonal calving and dynamic lateral effects is key for realistic model projections of future global sea level rise on centennial time scales.

  18. Tidewater Dynamics at Store Glacier, West Greenland from Daily Repeat UAV Survey

    NASA Astrophysics Data System (ADS)

    Hubbard, A., II; Ryan, J.; Toberg, N.; Todd, J.; Christoffersen, P.; Snooke, N.; Box, J. E.

    2015-12-01

    A significant component of the Greenland ice sheet's mass wasteage to sea level rise is attributed to the acceleration and dynamic thinning at its tidewater margins. To improve understanding of the rapid mass loss processes occurring at large tidewater glaciers, we conducted a suite of daily repeat aerial surveys across the terminus of Store Glacier, a large outlet draining the western Greenland Ice Sheet, from May to July 2014 (https://www.youtube.com/watch?v=-y8kauAVAfE). A suite flock of Unmanned Aerial Vehicles (UAVs) were equipped with digital cameras, which, in combination with onboard GPS, enabled production of high spatial resolution orthophotos and digital elevation models (DEMs) using standard structure-from-motion techniques. These data provide insight into the short-term dynamics of Store Glacier surrounding the break-up of the sea-ice mélange that occurred between 4 and 7 June. Feature tracking of the orthophotos reveals that mean speed of the terminus is 16 - 18 md-1, which was independently verified against a high temporal resolution time-series derived from an expendable/telemetric GPS deployed at the terminus. Differencing the surface area of successive orthophotos enable quantification of daily calving rates, which significantly increase just after melange break-up. Likewise, by differencing bulk freeboard volume of icebergs through time we could also constrain the magnitude and variation of submarine melt. We calculate a mean submarine melt rate of 0.18 md-1 throughout the spring period with relatively little supraglacial runoff and no active meltwater plumes to stimulate fjord circulation and upwelling of deeper, warmer water masses. Finally, we relate calving rates to the zonation and depth of water-filled crevasses, which were prominent across parts of the terminus from June onwards.

  19. Subglacial Meltwater Drainage at Paakitsoq, West Greenland: Insights From a Distributed, Physically Based Numerical Model

    NASA Astrophysics Data System (ADS)

    Long, S. M.; Willis, I.; Arnold, N.; Ahlstrom, A. P.

    2008-12-01

    Recent results indicate that surface melting influences the dynamics of the Greenland Ice Sheet margin through meltwater input to a subglacial drainage system, but the hydrological characteristics of this drainage system and the degree to which variations in subglacial water pressure enhance or impede ice flow remain uncertain. Investigating the hydrology of this relatively inaccessible subglacial system requires a numerical modeling approach in which spatial and temporal variations in subglacial water pressures are calculated in response to the main controlling variables (subglacial drainage system structure and morphology and surface water inputs). We present the preliminary findings of such a study for the Paakitsoq region of W. Greenland, north of Jakobshavn Isbrae. Recent airborne radar data are used to construct surface and bed DEMs of the region from which patterns of subglacial hydraulic potential are derived. These are used to define the subglacial drainage system structure (the location, alignment and interconnection of major drainage pathways). Water flow along these pathways is modeled using a component of the United States Environmental Protection Agency's Storm Water Management Model (SWMM) modified to allow for enlargement and closure of ice walled channels (cf. Arnold et al., Hydrol. Processes, 12, 1998). We assess the model's ability to deal with two types of input: rapid lake drainage events, and diurnally varying melt inputs calculated from a degree-day model. We perform sensitivity tests to determine the effects of model parameters on modeled channel cross-sectional area, water pressure and subglacial flow. Finally, we simulate drainage beneath the ice sheet for a summer melt season and compare the results with measured proglacial stream discharges. Preliminary results suggest that channelized flow is only possible close to the ice sheet margin where ice is thin and water inputs are large. Distributed drainage is predicted beneath thicker inland

  20. Rerouting of subglacial water flow between neighboring glaciers in West Greenland

    NASA Astrophysics Data System (ADS)

    Chu, Winnie; Creyts, Timothy T.; Bell, Robin E.

    2016-05-01

    Investigations of the Greenland ice sheet's subglacial hydrological system show that the connectivity of different regions of the system influences how the glacier velocity responds to variations in surface melting. Here we examine whether subglacial water flow paths can be rerouted beneath three outlet glaciers in the ablation zone of western Greenland. We use Lamont-Doherty and Center for Remote Sensing of Ice Sheets of University of Kansas (CReSIS) ice-penetrating radar data to create a new ice thickness map. We then use a simple subglacial water flow model to examine whether flow paths can be rerouted and identify the topographic conditions that are sensitive to subglacial rerouting. By varying water pressures within an observationally constrained range, we show that moderate changes in pressure can cause flow paths to reroute and exchange water from one subglacial catchment to another. Flow across subglacial overdeepenings is particularly sensitive to rerouting. These areas have low hydraulic gradients driving flow, so subtle water pressure variations have a strong influence on water flow direction. Based on correlations between water flow paths and ice velocity changes, we infer that water piracy between neighboring catchments can result in a different spatial pattern of hydrologically induced ice velocity speedup depending on the amount and timing of surface melt. The potential for subglacial water to reroute across different catchments suggests that multiple hydrographs from neighboring glaciers are likely necessary to accurately ascertain melt budgets from proglacial point measurements. The relationship between surface runoff, ice dynamics, and proglacial discharge can be altered by rerouting of subglacial water flow within and across outlet glaciers.

  1. Subglacial Meltwater Drainage at Paakitsoq, West Greenland: Insights from a Distributed, Physically Based Numerical Model

    NASA Astrophysics Data System (ADS)

    Banwell, Alison; Willis, Ian; Arnold, Neil; Ahlstrom, Andreas

    2010-05-01

    Recent studies indicate that surface meltwater is reaching the bed of the Greenland Ice Sheet (GrIS) and modulating glacier sliding rates at the ice sheet margin. However, the hydrological characteristics of this drainage system and the degree to which variations in subglacial water pressure enhance or impede ice flow remain uncertain. As the subglacial hydrological system beneath the GrIS is physically inaccessible and beyond the resolution of geophysical imaging techniques, numerical models are an important tool for investigating the stability of plausible hydrological systems. We present preliminary results of a numerical model that investigates theoretically-constructed hydrological systems of the Paakitsoq region of W. Greenland, north of Jakobshavn Isbrae. Subglacial drainage system structures (the location, alignment and interconnection of major drainage channels) are defined from patterns of subglacial hydrological potential derived from surface and bed DEMs. Discharge and hydraulic head within subglacial channels are modelled using a component of the US EPA Storm Water Management Model (SWMM), modified to allow for enlargement and closure of ice walled channels (Arnold et al., Hydrol. Processes, 12, 1998). We assess the model's ability to deal with two types of input: rapid lake drainage events; and diurnally varying melt inputs calculated from a degree-day model. We perform sensitivity tests to determine the effects of individual model parameters on modelled channel cross-sectional area, water pressure and subglacial flow. Finally, we simulate drainage beneath the ice sheet for a summer melt season and compare the results with measured proglacial stream discharges. Through a recent code modification allowing subglacial water pressures to reach values in excess of ice overburden pressures, we find that consistently high inland subglacial water pressures assist with keeping marginal conduits full and counteract the effects of creep closure, allowing

  2. Modeling of ocean-induced ice melt rates of five west Greenland glaciers over the past two decades

    NASA Astrophysics Data System (ADS)

    Rignot, E.; Xu, Y.; Menemenlis, D.; Mouginot, J.; Scheuchl, B.; Li, X.; Morlighem, M.; Seroussi, H.; den Broeke, M. van; Fenty, I.; Cai, C.; An, L.; Fleurian, B. de

    2016-06-01

    High-resolution, three-dimensional simulations from the Massachusetts Institute of Technology general circulation model ocean model are used to calculate the subaqueous melt rate of the calving faces of Umiamako, Rinks, Kangerdlugssup, Store, and Kangilerngata glaciers, west Greenland, from 1992 to 2015. Model forcing is from monthly reconstructions of ocean state and ice sheet runoff. Results are analyzed in combination with observations of bathymetry, bed elevation, ice front retreat, and glacier speed. We calculate that subaqueous melt rates are 2-3 times larger in summer compared to winter and doubled in magnitude since the 1990s due to enhanced subglacial runoff and 1.6 ± 0.3°C warmer ocean temperature. Umiamako and Kangilerngata retreated rapidly in the 2000s when subaqueous melt rates exceeded the calving rates and ice front retreated to deeper bed elevation. In contrast, Store, Kangerdlugssup, and Rinks have remained stable because their subaqueous melt rates are 3-4 times lower than their calving rates, i.e., the glaciers are dominated by calving processes.

  3. Epidemiological study of viral hepatitis types A, B, C, D and E among Inuits in West Greenland.

    PubMed

    Langer, B C; Frösner, G G; von Brunn, A

    1997-09-01

    A descriptive study was performed to evaluate the relative frequencies and molecular epidemiological features of viral hepatitis types A to E among the Inuit population in West Greenland. Serum samples were collected from 503 Inuits (186 males and 317 females; mean age 35 years; range 7-79 years) and were tested for markers of viral hepatitis infection. The hepatitis A prevalence averaged 54%, with a significant rise from 9% to 50% between the second and third decade of life. As for hepatitis B, 42% of the total study population showed serological evidence of current or past hepatitis B virus (HBV) infection and 7% were hepatitis B surface antigen (HBsAg) carriers. Among the carriers, 6% were also positive for hepatitis B e antigen (HBeAg), and HBV DNA could be detected in 49% of carriers by polymerase chain reaction. Typing of the HBV isolates revealed genomic group D in 83% (serotype ayw2) and group A in 17% (serotype adw 2). Less than 1% of the study population had antibodies to the hepatitis C virus. None were positive for HCV RNA. Serological evidence of hepatitis D infection was found in 7% of those with hepatitis B helper virus infection markers and in 40% of the HBsAg carriers. As for hepatitis E, 3% of the Inuits showed reactivity in an enzyme immunoassay that detected hepatitis E virus antibody. HEV RNA could not be detected.

  4. Multi-Year Elevation Changes Near the West Margin of the Greenland Ice Sheet from Satellite Radar Altimetry

    NASA Technical Reports Server (NTRS)

    Lingle, Craig S.; Brenner, Anita C.; Zwally, H. Jay; DiMarzio, John P.

    1991-01-01

    Mean changes in the surface elevation near the west margin of the Greenland ice sheet are measured using Seasat altimetry and altimetry from the Geosat Exact Repeat Mission (ERM). The Seasat data extend from early July through early October 1978. The ERM data extend from winter 1986-87 through fall 1988. Both seasonal and multi-year changes are measured using altimetry referenced to GEM T2 orbits. The possible effects of orbit error are minimized by adjusting the orbits into a common ocean surface. Seasonal mean changes in the surface height are recognizable during the Geosat ERM. The multi-year measurements indicate the surface was lower by 0.4 +/- 0.4 m on average in late summer 1987 than in late summer 1978. The surface was lower by 0.2 +/- 0.5 m on average in late summer 1988 than in late summer 1978. As a control case, the computations art also carried out using altimetry referenced to orbits not adjusted into a common ocean surface.

  5. Multi-year elevation changes near the west margin of the Greenland ice sheet from satellite radar altimetry

    SciTech Connect

    Lingle, C.S.; Brenner, A.C.; Zwally, H.J.; DiMarzio, J.P.

    1992-03-01

    Mean changes in the surface elevation near the west margin of the Greenland ice sheet are measured using Seasat altimetry and altimetry from the Geosat Exact Repeat Mission (ERM). The Seasat data extend from early July through early October 1978. The ERM data extend from winter 1986-87 through fall 1988. Both seasonal and multi-year changes are measured using altimetry referenced to GEM T2 orbits. The possible effects of orbit error are minimized by adjusting the orbits into a common ocean surface. Seasonal mean changes in the surface height are recognizable during the Geosat ERM. The multi-year measurements indicate the surface was lower by 0.4 +/- 0.4 m on average in late summer 1987 than in late summer 1978. The surface was lower by 0.2 +/- 0.5 m on average in late summer 1988 than in late summer 1978. As a control case, the computations are also carried out using altimetry referenced to orbits not adjusted into a common ocean surface.

  6. Applying foraminiferal stratigraphy as a biomarker for heavy metal contamination and mining impact in a fiord in West Greenland.

    PubMed

    Elberling, Bo; Knudsen, Karen Luise; Kristensen, Peter H; Asmund, Gert

    2003-04-01

    Sulphidic mine waste disposed in marine environments constitutes an environmental risk to aquatic life due to potential uptake and accumulation of heavy metals in biota. Fiord sediments near the former Black Angel Mine in West Greenland are contaminated by lead and zinc as a result of submarine tailings disposal in 1973-1990. In 1999 cores were taken up to 10 km away from the disposal area. Analyses include heavy metals, radiochemical dating (210Pb) and high-resolution foraminiferal stratigraphy. The mining operation resulted in significant changes in the assemblage composition. In addition, up to 20% of the Melonis barleeanus population found in sediment deposited during nearby tailings disposal was deformed compared to a natural background of less than 5%. Throughout cores representing the last 100 years of sedimentation, the total numbers and frequency of morphological abnormalities among M. barleeanus revealed some correlation with heavy metals concentrations (up to r2 = 79%). We conclude that abnormalities among foraminifera may represent a useful biomarker for evaluating trends in the biological impact resulting of submarine tailings disposal as well as long-term environmental impact and subsequent recovery.

  7. Trans-generational and neonatal humoral immune responses in West Greenland sledge dogs (Canis familiaris) exposed to organohalogenated environmental contaminants.

    PubMed

    Sonne, Christian; Larsen, Hans Jørgen S; Kirkegaard, Maja; Letcher, Robert J; Dietz, Rune

    2010-11-01

    Previous investigations in the Arctic have suggested OHC (organohalogen contaminant) induced immune toxic effects on e.g. polar bears (Ursus maritimus). We therefore studied the dietary impact from minke whale blubber (Balaenoptera acutorostrata), rich in polyunsaturated fatty acids and OHCs, on the humoral immunity of 7 captive West Greenland sledge dog (Canis familiaris) bitches and their 4 pups constituting a sentinel model species for polar bears. A control group was composed of 8 bitches and their 5 pups all fed pork (Suis scrofa) fat. The study included serum IgG measurements (bitches and pups) and specific immune responses towards tetanus toxoid (bitches) and diphtheria toxoid (pups) as well as influenza virus (pups). The analyses showed that IgG concentrations were non-significantly lowest in exposed bitches and pups (t-test: all p>0.05). In addition, significant lower antibody response was detected in exposed pups immunized with influenza virus at age 3 months (t-test: both p<0.05). No clear group differences were found for tetanus toxoid in bitches and diphtheria toxoid in pups. The results suggest that the humoral immune system of sledge dogs may be suppressed by the dietary blubber composition of OHCs and polyunsaturated fatty acids while a larger follow-up study is recommended in order to investigate this relationship further.

  8. Recognition of > or = 3850 Ma water-lain sediments in West Greenland and their significance for the early Archaean Earth

    NASA Technical Reports Server (NTRS)

    Nutman, A. P.; Mojzsis, S. J.; Friend, C. R.; Bada, J. L. (Principal Investigator)

    1997-01-01

    A layered body of amphibolite, banded iron formation (BIF), and ultramafic rocks from the island of Akilia, southern West Greenland, is cut by a quartz-dioritic sheet from which SHRIMP zircon 206Pb/207Pb weighted mean ages of 3865 +/- 11 Ma and 3840 +/- 8 Ma (2 sigma) can be calculated by different approaches. Three other methods of assessing the zircon data yield ages of >3830 Ma. The BIFs are interpreted as water-lain sediments, which with a minimum age of approximately 3850 Ma, are the oldest sediments yet documented. These rocks provide proof that by approximately 3850 Ma (1) there was a hydrosphere, supporting the chemical sedimentation of BIF, and that not all water was stored in hydrous minerals, and (2) that conditions satisfying the stability of liquid water imply surface temperatures were similar to present. Carbon isotope data of graphitic microdomains in apatite from the Akilia island BIF are consistent with a bio-organic origin (Mojzsis et al. 1996), extending the record of life on Earth to >3850 Ma. Life and surface water by approximately 3850 Ma provide constraints on either the energetics or termination of the late meteoritic bombardment event (suggested from the lunar cratering record) on Earth.

  9. Recognition of > or = 3850 Ma water-lain sediments in West Greenland and their significance for the early Archaean Earth.

    PubMed

    Nutman, A P; Mojzsis, S J; Friend, C R

    1997-01-01

    A layered body of amphibolite, banded iron formation (BIF), and ultramafic rocks from the island of Akilia, southern West Greenland, is cut by a quartz-dioritic sheet from which SHRIMP zircon 206Pb/207Pb weighted mean ages of 3865 +/- 11 Ma and 3840 +/- 8 Ma (2 sigma) can be calculated by different approaches. Three other methods of assessing the zircon data yield ages of >3830 Ma. The BIFs are interpreted as water-lain sediments, which with a minimum age of approximately 3850 Ma, are the oldest sediments yet documented. These rocks provide proof that by approximately 3850 Ma (1) there was a hydrosphere, supporting the chemical sedimentation of BIF, and that not all water was stored in hydrous minerals, and (2) that conditions satisfying the stability of liquid water imply surface temperatures were similar to present. Carbon isotope data of graphitic microdomains in apatite from the Akilia island BIF are consistent with a bio-organic origin (Mojzsis et al. 1996), extending the record of life on Earth to >3850 Ma. Life and surface water by approximately 3850 Ma provide constraints on either the energetics or termination of the late meteoritic bombardment event (suggested from the lunar cratering record) on Earth.

  10. Recognition of > or = 3850 Ma water-lain sediments in West Greenland and their significance for the early Archaean Earth

    NASA Technical Reports Server (NTRS)

    Nutman, A. P.; Mojzsis, S. J.; Friend, C. R.; Bada, J. L. (Principal Investigator)

    1997-01-01

    A layered body of amphibolite, banded iron formation (BIF), and ultramafic rocks from the island of Akilia, southern West Greenland, is cut by a quartz-dioritic sheet from which SHRIMP zircon 206Pb/207Pb weighted mean ages of 3865 +/- 11 Ma and 3840 +/- 8 Ma (2 sigma) can be calculated by different approaches. Three other methods of assessing the zircon data yield ages of >3830 Ma. The BIFs are interpreted as water-lain sediments, which with a minimum age of approximately 3850 Ma, are the oldest sediments yet documented. These rocks provide proof that by approximately 3850 Ma (1) there was a hydrosphere, supporting the chemical sedimentation of BIF, and that not all water was stored in hydrous minerals, and (2) that conditions satisfying the stability of liquid water imply surface temperatures were similar to present. Carbon isotope data of graphitic microdomains in apatite from the Akilia island BIF are consistent with a bio-organic origin (Mojzsis et al. 1996), extending the record of life on Earth to >3850 Ma. Life and surface water by approximately 3850 Ma provide constraints on either the energetics or termination of the late meteoritic bombardment event (suggested from the lunar cratering record) on Earth.

  11. Influence of habitat heterogeneity on distribution, occupancy patterns, and productivity of breeding peregrine falcons in central west Greenland

    USGS Publications Warehouse

    Wightman, C.; Fuller, Mark R.

    2006-01-01

    We used occupancy and productivity data collected at 67 cliffs used for nesting from 1972 to 1999 to assess patterns of distribution and nest-site selection in an increasing population of Peregrine Falcons (Falco peregrinus) in central West Greenland. Peregrine Falcons breeding at traditionally occupied cliffs used for nesting had significantly lower variation in productivity and thus these cliffs were better quality sites. This indicates that Peregrine Falcons occupied cliffs according to a pattern of despotic distribution. Falcons breeding at cliffs that were consistently occupied during the breeding season had higher average productivity and lower variation in productivity than falcons at inconsistently occupied cliffs, and thus consistent occupancy also was indicative of cliff quality. Features of high quality habitat included tall cliffs, greater change in elevation from the lowest point within 3 km of the cliff to the cliff top (elevation gain), and protection from weather on the eyrie ledge. Spacing of suitable and occupied cliffs also was an important feature, and the best cliffs generally were more isolated. Increased spacing was likely a mechanism for reducing intraspecific competition. Our results suggest that Peregrine Falcons use a resource defense strategy to compete for better quality habitats and may use spacing and physical features of a nest site to identify good quality breeding habitat.

  12. Influence of habitat heterogeneity on distribution, occupancy patterns, and productivity of breeding peregrine falcons in central West Greenland

    USGS Publications Warehouse

    Wightman, C.S.; Fuller, M.R.

    2006-01-01

    We used occupancy and productivity data collected at 67 cliffs used for nesting from 1972 to 1999 to assess patterns of distribution and nest-site selection in an increasing population of Peregrine Falcons (Falco peregrinus) in central West Greenland. Peregrine Falcons breeding at traditionally occupied cliffs used for nesting had significantly lower variation in productivity and thus these cliffs were better quality sites. This indicates that Peregrine Falcons occupied cliffs according to a pattern of despotic distribution. Falcons breeding at cliffs that were consistently occupied during the breeding season had higher average productivity and lower variation in productivity than falcons at inconsistently occupied cliffs, and thus consistent occupancy also was indicative of cliff quality. Features of high quality habitat included tall cliffs, greater change in elevation from the lowest point within 3 km of the cliff to the cliff top (elevation gain), and protection from weather on the eyrie ledge. Spacing of suitable and occupied cliffs also was an important feature, and the best cliffs generally were more isolated. Increased spacing was likely a mechanism for reducing intraspecific competition. Our results suggest that Peregrine Falcons use a resource defense strategy to compete for better quality habitats and may use spacing and physical features of a nest site to identify good quality breeding habitat. ?? The Cooper Ornithological Society 2006.

  13. Comparison of remote sensing reflectance from above-water and in-water measurements west of Greenland, Labrador Sea, Denmark Strait, and west of Iceland.

    PubMed

    Garaba, Shungudzemwoyo P; Zielinski, Oliver

    2013-07-01

    The need to obtain ocean color essential climate variables (OC-ECVs) using hyperspectral technology has gained increased interest in recent years. Assessing ocean color on a large scale in high latitude environments using satellite remote sensing is constrained by polar environmental conditions. Nevertheless, on a small scale we can assess ocean color using above-water and in-water remote sensing. Unfortunately, above-water remote sensing can only determine apparent optical properties leaving the sea surface and is susceptible to near surface environmental conditions for example sky and sunglint. Consequently, we have to rely on accurate in-water remote sensing as it can provide both synoptic inherent and apparent optical properties of seawater. We use normalized water leaving radiance LWN or the equivalent remote sensing reflectance RRS from 27 stations to compare the differences in above-water and in-water OC-ECVs. Analysis of above-water and in-water RRS spectra provided very good match-ups (R2 > 0.97, MSE < 1.8*10(-7)) for all stations. The unbiased percent differences (UPD) between above-water and in-water approaches were determined at common OC-ECVs spectral bands (410, 440, 490, 510 and 555) nm and the classic band ratio (490/555) nm. The spectral average UPD ranged (5 - 110) % and band ratio UPD ranged (0 - 12) %, the latter showing that the 5% uncertainty threshold for ocean color radiometric products is attainable. UPD analysis of these stations West of Greenland, Labrador Sea, Denmark Strait and West of Iceland also suggests that the differences observed are likely a result of environmental and instrumental perturbations.

  14. Adjacent fjords and glaciers respond differently to ice sheet surface melt in West Greenland

    NASA Astrophysics Data System (ADS)

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

    2016-12-01

    Neighboring tidewater glaciers often exhibit asynchronous dynamic behavior, despite relatively uniform regional atmospheric and oceanic forcings. This variability may be controlled by a combination of local factors, including glacier and fjord geometry, fjord heat content and circulation, and glacier surface melt. In order to characterize and understand contrasts in adjacent tidewater glacier and fjord dynamics, we made coincident ice-ocean-atmosphere observations at high temporal resolution (minutes to weeks) within a 10,000 km^2 area near Uummannaq, Greenland. Water column velocity, temperature and salinity measurements reveal systematic differences in neighboring fjords that imply contrasting circulation patterns. The observed ocean velocity and hydrography, combined with numerical modeling, suggest that subglacial discharge plays a major role in setting fjord conditions. In addition, satellite remote sensing of seasonal ice flow speed and terminus position reveal both speedup and slow-down in response to melt, as well as differences in calving style among the neighboring glaciers. Glacier force budgets and modeling also point toward subglacial discharge as a key factor in glacier behavior. For the studied region, individual glacier and fjord geometry modulate subglacial discharge, which leads to contrasts in both fjord and glacier dynamics.

  15. Spatio-temporal Variability in the Glacier-Ocean Boundary in Central West Greenland

    NASA Astrophysics Data System (ADS)

    Catania, G. A.; Fried, M.; Bartholomaus, T.; Peters, D.; Felikson, D.; Carroll, D.; Sutherland, D.; Stearns, L. A.; Shroyer, E.; Nash, J. D.

    2015-12-01

    Outlet glacier termini represent the boundary between ice and ocean systems. As such, spatio-termporal differences in terminus shape and position may be indicative of how the ice and ocean systems interact. We examine over 40 years of remote-sensing imagery collected by multiple satellites to characterize the termini of 15 outlet glaciers in Central Western Greenland with unprecedented detail. Our record consists of an average of ~300 terminus observations per glacier; during the last 5 years, we average ~20 observations per year. We find that many glaciers in this region initiated retreat around 1998, coincident with retreat further south at Jakobshavn Isbræ, although the rate and duration of retreat varies from glacier-to-glacier. We explore variations in retreat rate and extent by examining individual fjord geometries, namely changes in fjord width and depth from available ship-based sounding observations. We also explore variations in retreat rate by examining spatial variations in surface melt-induced terminus ablation using a buoyant plume model coupled with field observations. Finally, we identify glaciers in the region that did not undergo significant retreat and examine the balance of forces that may be responsible for their stability.

  16. Transformation of landforms and sediments in the periglacial setting of West Greenland

    NASA Astrophysics Data System (ADS)

    Česnulevičius, Algimantas; Šeirienė, Vaida

    2009-06-01

    The article deals with the cryogenic processes taking place in the terminal zone of the recessing glacier of SW Greenland, which modify the sediment layers and transform the landforms. The sediment horizons were examined in natural outcrops and in trenches. Structural analysis of periglacial sediments in the slopes has shown that subdued evaporation and shallow permafrost favour the development of cryoturbations. In relief declensions, the formation of polygonal surfaces is predetermined by shallow beds of magmatic rocks, permafrost and especially slow evaporation during short warm seasons. Aeolian processes are most active in the valleys sculptured by glaciofluvial flows where cold arid winds blow out or rework inequigranular deposits. Dust is blown out by wind erosion, whereas the coarse-grained material is transported by creeping or saltation. Sand ripple and embryo dune terrains are widespread in glaciofluvial valleys. Wind erosion processes forming pebble-boulder deflation pavements take place in relief declensions. Outcrops sized 10-60 m2 and niches develop in the hill slopes. Diatoms indicate that sedimentation in small closed basins took place under cold, oligotrophic, acidophilous conditions.

  17. A Fully Automated Supraglacial lake area and volume Tracking ("FAST") algorithm: development and application using MODIS imagery of West Greenland

    NASA Astrophysics Data System (ADS)

    Williamson, Andrew; Arnold, Neil; Banwell, Alison; Willis, Ian

    2017-04-01

    Supraglacial lakes (SGLs) on the Greenland Ice Sheet (GrIS) influence ice dynamics if draining rapidly by hydrofracture, which can occur in under 24 hours. MODerate-resolution Imaging Spectroradiometer (MODIS) data are often used to investigate SGLs, including calculating SGL area changes through time, but no existing work presents a method that tracks changes in individual (and total) SGL volume in MODIS imagery over a melt season. Here, we present such a method. First, we tested three automated approaches to derive SGL areas from MODIS imagery by comparing calculated areas for the Paakitsoq and Store Glacier regions in West Greenland with areas derived from Landsat-8 (LS8) images. Second, we applied a physically-based depth-calculation algorithm to the pixels within the SGL boundaries from the best performing method, and validated the resultant depths with those calculated using the same method applied to LS8 imagery. Our results indicated that SGL areas are most accurately generated using dynamic thresholding of MODIS band 1 (red) with a 0.640 threshold value. Calculated SGL area, depth and volume values from MODIS were closely comparable to those derived from LS8. The best performing area- and depth-detection methods were then incorporated into a Fully Automated SGL Tracking ("FAST") algorithm that tracks individual SGLs between successive MODIS images. It identified 43 (Paakitsoq) and 19 (Store Glacier) rapidly draining SGLs during 2014, representing 21% and 15% of the respective total SGL populations, including some clusters of rapidly draining SGLs. We found no relationship between the water volumes contained within these rapidly draining SGLs and the ice thicknesses beneath them, indicating that a critical water volume linearly related to ice thickness cannot explain the incidence of rapid drainage. The FAST algorithm, which we believe to be the most comprehensive SGL tracking algorithm developed to date, has the potential to investigate statistical

  18. Changing surface-atmosphere energy exchange and refreezing capacity of the lower accumulation area, West Greenland

    NASA Astrophysics Data System (ADS)

    Charalampidis, C.; van As, D.; Box, J. E.; van den Broeke, M. R.; Colgan, W. T.; Doyle, S. H.; Hubbard, A. L.; MacFerrin, M.; Machguth, H.; Smeets, C. J. P. P.

    2015-11-01

    We present 5 years (2009-2013) of automatic weather station measurements from the lower accumulation area (1840 m a.s.l. - above sea level) of the Greenland ice sheet in the Kangerlussuaq region. Here, the summers of 2010 and 2012 were both exceptionally warm, but only 2012 resulted in a strongly negative surface mass budget (SMB) and surface meltwater run-off. The observed run-off was due to a large ice fraction in the upper 10 m of firn that prevented meltwater from percolating to available pore volume below. Analysis reveals an anomalously low 2012 summer-averaged albedo of 0.71 (typically ~ 0.78), as meltwater was present at the ice sheet surface. Consequently, during the 2012 melt season, the ice sheet surface absorbed 28 % (213 MJ m-2) more solar radiation than the average of all other years. A surface energy balance model is used to evaluate the seasonal and interannual variability of all surface energy fluxes. The model reproduces the observed melt rates as well as the SMB for each season. A sensitivity analysis reveals that 71 % of the additional solar radiation in 2012 was used for melt, corresponding to 36 % (0.64 m) of the 2012 surface lowering. The remaining 64 % (1.14 m) of surface lowering resulted from high atmospheric temperatures, up to a +2.6 °C daily average, indicating that 2012 would have been a negative SMB year at this site even without the melt-albedo feedback. Longer time series of SMB, regional temperature, and remotely sensed albedo (MODIS) show that 2012 was the first strongly negative SMB year, with the lowest albedo, at this elevation on record. The warm conditions of recent years have resulted in enhanced melt and reduction of the refreezing capacity in the lower accumulation area. If high temperatures continue, the current lower accumulation area will turn into a region with superimposed ice in coming years.

  19. Preliminary results from hot-water drilling and borehole instrumentation on Store Glacier, West Greenland

    NASA Astrophysics Data System (ADS)

    Doyle, S. H.; Christoffersen, P.; Hubbard, B. P.; Young, T. J.; Hofstede, C. M.; Box, J.; Todd, J.; Bougamont, M. H.; Hubbard, A.

    2015-12-01

    As part of the Subglacial Access and Fast Ice Research Experiment (SAFIRE) pressurised hot water was used to drill four 603-616 m-long boreholes to the bed of the Greenland Ice Sheet at a site located 30 km from the calving front of fast-flowing, marine-terminating Store Glacier (70° N, ~1000 m elevation). Despite the boreholes freezing within hours, 4 wired sensor strings were successfully deployed in three of the boreholes. These included a thermistor string to obtain the englacial temperature profile installed in the same borehole as a string of tilt sensors to measure borehole deformation, and two sets of water pressure, electrical conductivity and turbidity sensors installed just above the bed in separate, adjacent boreholes. The boreholes made a strong hydrological connection to the bed during drilling, draining rapidly to ~80 m below the ice surface. The connection of subsequent boreholes was observed as a perturbation in water pressure and temperature recorded in neighbouring boreholes, indicating an effective hydrological sub- or en-glacial connection between them. The sensors, which were all connected to loggers at the surface by cables, operated for between ~30 and 80+ days before indications suggest that the cables stretched and then snapped - with the lowermost sensors failing first. The records obtained from these sensors reveal (i) high and increasing water pressure varying diurnally close to overburden albeit of a small magnitude (~ 0.3 m H2O), (ii) a minimum extrapolated englacial temperature of -21°C with above-freezing temperatures at the bed, and (iv) high rates of internal deformation and strain increasing towards the bed as evinced by increasing tilt with depth. These borehole observations are complemented by GPS measurements of ice motion, meteorological data, and seismic and radar surveys.

  20. Local and synoptic controls on rapid supraglacial lake drainage in West Greenland

    NASA Astrophysics Data System (ADS)

    Williamson, Andrew; Banwell, Alison; Arnold, Neil; Willis, Ian

    2016-04-01

    Many supraglacial lakes within the ablation zone of the Greenland Ice Sheet (GrIS) are known to drain rapidly (in <1 day) in the mid- to late melt season, delivering large meltwater pulses to the subglacial drainage system, thus affecting basal water pressures and ice-sheet dynamics. Although it is now generally recognised that rapid lake drainage is caused by hydrofracture, the precise controls on hydrofracture initiation remain poorly understood: they may be linked to a local critical water-volume threshold, or they may be associated with synoptic-scale factors, such as ice thickness, driving stresses, ice velocities and strain rates. A combination of the local water-volume threshold and one or more synoptic-scale factors may explain the overall patterns of rapid lake drainage, but this requires verification using targeted field- and remotely-based studies that cover large areas of the GrIS and span long timescales. Here, we investigate a range of potential controls on rapid supraglacial lake drainage in the land-terminating Paakitsoq region of the ice sheet, northeast of Jakobshavn Isbræ, for the 2014 melt season. We have analysed daily 250-m Moderate Resolution Imaging Spectroradiometer (MODIS) imagery in order to calculate lake areas, depths and volumes, and have developed an automatic lake-tracking algorithm to determine the dates on which all rapid lake drainage events occur. For each rapidly draining lake, the water volumes immediately prior to drainage are compared with other local factors, notably lake-filling rate and ice thickness, and with a variety of synoptic-scale features, such as slope angles, driving stresses, surface velocities, surface strain rates and the incidence of nearby lake-drainage events. We present the outcomes of our statistical analysis to elicit the statistically significant controls on hydrofracture beneath supraglacial lakes.

  1. Changing Surface-Atmosphere Energy Exchange and Refreezing Capacity of the Lower Accumulation Area, West Greenland

    NASA Astrophysics Data System (ADS)

    Charalampidis, C.; van As, D.; Machguth, H.; Smeets, P.; van den Broeke, M. R.; Box, J. E.

    2014-12-01

    We present five years (2009-2013) of automatic weather station (AWS) data from the lower accumulation area (1840 m above sea level) of the Kangerlussuaq region, western Greenland ice sheet. The summers of 2010 and 2012 were both exceptionally warm, but only 2012 resulted in negative surface mass budget (SMB) and surface runoff. The observed runoff was due to a large ice fraction in the upper 10 m of firn that prevented melt water from percolating to available pore space below. Analysis of the in situ data reveals a relatively low 2012 summer albedo of ~0.7 as melt water was present at the surface. Consequently, during the 2012 melt season the surface absorbed 30% (213 MJ m-2) more solar radiation than in 2010. We drive a surface energy balance model with the AWS data to evaluate the seasonal and interannual variability of all surface energy fluxes. The model is able to reproduce the observed melt rates as well as the SMB for each season. While the drive for melt is solar radiation, year-to-year differences are controlled by terrestrial radiation, apart from 2012 when solar radiation dominated melt. Sensitivity tests reveal that 72% of the excess solar energy in 2012 was used for melt, corresponding to 40% (0.67 m) of the 2012 surface ablation. The remaining ablation (0.99 m) was primarily due to the relatively high atmospheric temperatures up to +2.6 °C daily average, indicating that 2012 would have been a negative SMB year in the lower accumulation area even without the melt-albedo feedback. Longer time series of SMB, regional temperature and remotely sensed albedo (MODIS) suggest that 2012 was the first negative SMB year with the lowest albedo at this elevation on record. The warming conditions of the last years resulted in enhanced melt and reduction of the refreezing capacity of the lower accumulation area. If the warming continues the lower accumulation area will be transformed into superimposed ice.

  2. Ocean properties, ice-ocean interactions, and calving front morphology at two major west Greenland glaciers

    NASA Astrophysics Data System (ADS)

    Chauché, N.; Hubbard, A.; Gascard, J.-C.; Box, J. E.; Bates, R.; Koppes, M.; Sole, A.; Patton, H.

    2013-11-01

    Warm sub-polar mode water (SPMW) has been identified as a primary driver of mass loss of marine terminating glaciers draining the Greenland Ice Sheet (GrIS) yet, the specific mechanisms by which SPMW interacts with these tidewater termini remain uncertain. We present oceanographic data from Rink Glacier (RG) and Store Glacier (SG) fjords, two major marine outlets draining the western sector of the GrIS into Baffin Bay over the contrasting melt-seasons of 2009 and 2010. Submarine melting occurs wherever ice is in direct contact with warmer water and the consistent presence of 2.8 °C SPMW adjacent to both ice fronts below 400 m throughout all surveys indicates that melting is maintained by a combination of molecular diffusion and large scale, weak convection, diffusional (hereafter called ubiquitous) melting. At shallower depths (50-200 m), cold, brine-enriched water (BEW) formed over winter appears to persist into the summer thereby buffering this melt by thermal insulation. Our surveys reveal four main modes of glacier-ocean interaction, governed by water depth and the rate of glacier runoff water (GRW) injected into the fjord. Deeper than 200 m, submarine melt is the only process observed, regardless of the intensity of GRW or the depth of injection. However, between the surface and 200 m depth, three further distinct modes are observed governed by the GRW discharge. When GRW is weak (≲1000 m3 s-1), upward motion of the water adjacent to the glacier front is subdued, weak forced or free convection plus diffusional submarine melting dominates at depth, and seaward outflow of melt water occurs from the glacier toe to the base of the insulating BEW. During medium intensity GRW (∼1500 m3 s-1), mixing with SPMW yields deep mixed runoff water (DMRW), which rises as a buoyant plume and intensifies local submarine melting (enhanced buoyancy-driven melting). In this case, DMRW typically attains hydrostatic equilibrium and flows seaward at an intermediate depth of

  3. Volume and Freshwater Flux to the West of Greenland: Nares Strait from 2003 to 2009

    NASA Astrophysics Data System (ADS)

    Muenchow, A.; Melling, H.

    2014-12-01

    Nares Strait is a 30-40 km wide channel between northern Greenland and Canada where we collected time series observation of velocity, subsurface pressure, and salinity from 2003 to 2009 to quantify volume and freshwater flux. Direct sub-surface observations are augmented by ice velocity and dynamical constraints to interpolate observations to the surface. Measurements indicate a mean volume flux of 1.0 +/- 0.08 Sv (Sv=10^6 m^3/s) and a mean freshwater flux of 62 mSv from the Arctic Ocean through Nares Strait to the south. About 20% of the volume and 50% of the freshwater flux reside in the top 30-m of the water column. Flux variability peaks at a 20-day time scale and correlates strongly with along-channel pressure gradients which explain more than 80% of the flux variance. Seasonal volume flux variations have an amplitude of about 0.1 Sv and a phase that result in maximal and minimal southward transports in March and November, respectively. Ice cover is usually land-fast in March and mobile in November suggesting that the frictional dynamics in a surface layer under the ice are secondary in importance to the along-channel pressure gradient that peaks in early spring with high sea level in the Arctic and low sea level in the more southerly Baffin Bay. Observed changes in the duration of land-fast ice conditions impact ocean stratification and flux through Nares Strait. For example, volume and freshwater fluxes increased by 50% and 100% in years when the ice was mobile almost year-round from 2006 through 2010 as compared to the 2003 to 2006 period when the ice was not mobile for more than 6 month per year on average. Local winds explain almost 50% of the variance during the 2007 to 2009 period of year-round mobile ice when a southern ice arch did not form. This ice arch returned to southern Nares Strait in 2011 resulting in long periods of land-fast ice cover and, we hypothesize, reduced ocean flux.

  4. Atmospheric concentrations of organochlorine pesticides, polybrominated diphenyl ethers and polychloronaphthalenes in Nuuk, South-West Greenland

    NASA Astrophysics Data System (ADS)

    Bossi, Rossana; Skov, Henrik; Vorkamp, Katrin; Christensen, Jesper; Rastogi, Suresh C.; Egeløv, Axel; Petersen, Dorthe

    Atmospheric concentrations of organochlorine pesticides (OCs), polybrominated diphenyl ethers (PBDEs) and polychloronaphthalenes (PCNs) were measured for the first time in Nuuk, Greenland in 2004 and 2005. The annual mean concentrations of the measured OCs were: α-HCH 20.2 pg m -3, γ-HCH (lindane) 5.1 pg m -3, endosulfan 4.8 pg m -3 and dieldrin 1.9 pg m -3. Concentrations of Σ-chlordanes, DDEs and heptachlor epoxide were generally similar and lower than those of α-HCH and γ-HCH. The concentrations of most chlorinated pesticides did not show any clear seasonal variation, with the exception of γ-HCH, which had maximum concentration in August in both years. The average annual mean for ΣPBDEs was 1.14 ± 0.81 pg m -3. The predominant congeners measured in Nuuk were BDE-47 and BDE-99 followed by BDE-100, -153 and -28, indicating the use of penta-BDE technical products as the main source. A clear seasonal variation of PBDE concentrations was observed with maximum concentrations occurring in the summer months. The ΣPCNs concentrations ranged between 0.062 and 0.258 pg m -3 with an annual mean concentration of 0.161 ± 0.004 pg m -3. The PCNs profile was dominated by the tetra-PCNs (74% of the annual mean) and the penta-PCNs (18% of the annual mean). A seasonal trend for ΣPCNs was not observed. Atmospheric concentrations of the investigated compounds were correlated with temperature and anthropogenic CO in order to obtain information about their transport pattern. Positive correlations were found between CO and chlordanes, p, p'-DDE and trifluralin, while a negative correlation was found for γ-HCH. A significant correlation with temperature variations was found for dieldrin, heptachlor epoxide, α-HCH, γ-HCH, BDE-47, BDE-99 and tetra-PCNs, which indicates that re-emission of these compounds from previously contaminated surfaces as an important factor for the observed variations in concentrations.

  5. 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

  6. Mesoarchean melting and Neoarchean to Paleoproterozoic metasomatism during the formation of the cratonic mantle keel beneath West Greenland

    NASA Astrophysics Data System (ADS)

    van Acken, D.; Luguet, A.; Pearson, D. G.; Nowell, G. M.; Fonseca, R. O. C.; Nagel, T. J.; Schulz, T.

    2017-04-01

    Highly siderophile element (HSE) concentration and 187Os/188Os isotopic heterogeneity has been observed on various scales in the Earth's mantle. Interaction of residual mantle peridotite with infiltrating melts has been suggested to overprint primary bulk rock HSE signatures originating from partial melting, contributing to the heterogeneity seen in the global peridotite database. Here we present a detailed study of harzburgitic xenolith 474527 from the Kangerlussuaq suite, West Greenland, coupling the Re-Os isotope geochemistry with petrography of both base metal sulfides (BMS) and silicates to assess the impact of overprint induced by melt-rock reaction on the Re-Os isotope system. Garnet harzburgite sample 474527 shows considerable heterogeneity in the composition of its major phases, most notably olivine and Cr-rich garnet, suggesting formation through multiple stages of partial melting and subsequent metasomatic events. The major BMS phases show a fairly homogeneous pentlandite-rich composition typical for BMS formed via metasomatic reaction, whereas the 187Os/188Os compositions determined for 17 of these BMS are extremely heterogeneous ranging between 0.1037 and 0.1981. Analyses by LA-ICP-MS reveal at least two populations of BMS grains characterized by contrasting HSE patterns. One type of pattern is strongly enriched in the more compatible HSE Os, Ir, and Ru over the typically incompatible Pt, Pd, and Re, while the other type shows moderate enrichment of the more incompatible HSE and has overall lower compatible HSE/incompatible HSE composition. The small-scale heterogeneity observed in these BMS highlights the need for caution when utilizing the Re-Os system to date mantle events, as even depleted harzburgite samples such as 474527 are likely to have experienced a complex history of metasomatic overprinting, with uncertain effects on the HSE.

  7. 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

  8. Changes in ice geometry and supraglacial hydrology, Sermeq Avannarleq ablation zone, West Greenland

    NASA Astrophysics Data System (ADS)

    McLamb, W. S.; Colgan, W.; Phillips, T. P.; Abdalati, W.; Steffen, K.; Motyka, R. J.; Rajaram, H.

    2010-12-01

    distribution. We also manually extracted major supraglacial lakes from both the 1985 map and 2009 imagery. No significant difference was found in lake locations or area distribution over the study interval. From this we hypothesize that despite an increase in melt water production, Sermeq Avannarleq’s supraglacial lakes have experienced an acceleration in their filling and draining cycle over the study period. Generally, the high rates of thinning (reaching a maximum of 5.79 ± 1.29 m/a) are too great to be explained by surface balance and along-flow ice flux alone. We suggest that an increase in across-flow ice flux, associated with the acceleration of Jakobshavn Isbrae to the south, has resulted in significant dynamic thinning. The observations of marginal recession of land-terminating ice and a thinning and steepening of the ablation zone are also consistent with model predictions the Greenland Ice Sheet’s dynamic response to a warming climate.

  9. Northern Greenland

    NASA Technical Reports Server (NTRS)

    2008-01-01

    The northernmost land in the world is located in Pearyland, Greenland, at a latitude of 83 degrees, 39.6 minutes. This is a land of permanent snows, glaciers, and 24-hours of daylight during the summer months. The ASTER image was acquired May 17, 2003, covers an area of 47.9 x 42.1 km, and is located at 83.6 degrees north latitude, 33.4 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.

  10. Oceanic Mixing Processes in Disko Bay-Ilulissat Icefjord System: Can We Quantify the Heat Loss from the Atlantic Water Layer?

    NASA Astrophysics Data System (ADS)

    Djoumna, G.; Holland, D. M.

    2014-12-01

    Ilulissat Icefjord (IIF) has been the site of few hydrographic observations. Recent hydrographic data from Disko Bay (DB) showed a significant warming from the below of the cold Polar Water entering DB from the mid-to-late 19901990s onward, and the sill at the fjord mouth prevented the modified West Greenland Irminger Waters (WGIW) to fill the IIF basin. Here we identify and attempt to quantify the fluxes associated with the small-scale processes that contribute to the upward diapycnal fluxes of heat, salt and from the modified WGIW to the surface-mixed layer using five years of summer data (2009 - 2013). The interaction between the WGIW and Egedesminde Dyb trough cutting across the continental shelf from the shelf break into DB creates the cold/warm layering of water masses which contribute to the formation of double diffusive thermohaline staircases. We found evidence of thermohaline staircase consists of series of sharp interfaces across which both TT and SS increase with depth separated by thick well-defined convective layers. We hypothesize that the warming of the PW layer in DB may have been caused by the upward heat fluxes from the AW driven double diffusive convection. Vertical heat fluxes estimated from laboratory-based flux laws for the diffusive regime of double diffusive convection were up to 0.20.2Wm-2^{-2}. The other major player responsible for the Atlantic water heat loss is shear instabilities in the internal wave and tides generated by barotropic tidal flow over the Egedesminde Dyb trough, the continental shelf and across the sill at the entrance of IIF. Using moored pressure data, we found that the fjord could be described as a wave-fjord during neap tide and turns into a tidal jet-fjord during spring tide, therefore a weak nonlinear response due to supercritical conditions with flow separation over the sill and a linear baroclinic tidal response due to the deeper right side of the sill could be expected. We found enhanced eddy diffusivity K

  11. Shoreline changes and its impact on activities in the coastal zone in Greenland

    NASA Astrophysics Data System (ADS)

    Kroon, A.; Bendixen, M.; Elberling, B.

    2015-12-01

    Almost all coastal environments in Greenland are developed in high-relief areas, along fjords, or hard-rock cliffs. The sedimentary shores often fringe these areas and a large number of small deltas (areal delta surface < 10 km2) exists. The sediments mostly originate from rivers that are fed by melting glaciers or drain pro-glacial and fluvial valleys. There is also active reworking at the present shorelines of sedimentary deposits of glacial, peri-glacial and deltaic origin that were formed during and after the last glaciation of the coastal plain.Arctic coastal processes are not only affected by waves, tides and currents, but to a large extend by freezing temperatures, ice and snow. There is a seasonal variation with open waters and active rivers in summer and ice-covered coastal waters and frozen rivers in winter. The coastal processes by waves and tides are thus often limited to summer and early fall. Nowadays, global climate changes induce many changes along the arctic coasts. Global sea-levels are rising due to thermal expansion and an increased fresh water flux from the glaciers and land ice masses, while ice coverage of the coastal waters decreases and the open water periods in summer extend. However, it is still unknown if the extra input of fluvial sediments can cope with increased erosion rates at the shores. Besides, the rate of actual sea-level rise in West Greenland is probably less than the local rate of isostatic uplift, leading to local relative sea level fall.The focus in this presentation is on shoreline changes and its impact on two coastal environments in Greenland: the Young Sound area (fjord environment in North-East Greenland), and the southern shore of Disko Island (open sea embayment in West Greenland). These coastal environments exhibit a wide variety of coastal landforms like deltas, spits, barriers, etc. The coastal landforms were mapped and aerial images, orthogonal photos, and satellite images were used to digitize successive

  12. Seasonal and regional variability in dissolved and particulate iron fluxes via glacial runoff along the West Greenland coast

    NASA Astrophysics Data System (ADS)

    Choquette, K.; Hagedorn, B.; Sletten, R. S.; Harrold, Z.; Liu, L.; Dieser, M.; Cameron, K. A.; Christner, B. C.; Junge, K.

    2012-12-01

    Subglacial weathering, due to biogeochemical and physical weathering processes, can affect the chemical evolution of subglacial waters and release dissolved and particulate iron via glacial runoff. Iron is a growth limiting nutrient and plays a critical role in the biogeochemical cycles of coastal and marine waters. More recently, dissolved and colloidal iron derived from subglacial sources have been considered an important contributor of Fe fluxes to the ocean; however, their dependency on lithology, grain size, and microbial activity is not well understood. This study characterizes the solute chemistry, in particular iron mineralogy and dissolved iron concentrations, released from beneath the Greenland Ice Sheet (GrIS), from two locations along the West Greenland coast, Thule (76°N, 68°W) and Kangerlussuaq (67°N, 50°W). We hypothesize that the subglacial lithology has a control on Fe fluxes from the GrIS to coastal and marine systems. The underlying bedrock in Thule is the Precambrian Dundas and Narssarssuk sedimentary formations which include sandstone, siltstone, and shale. The bedrock in Kangerlussuaq is dominated by Archean granodioritic gneiss and amphibolite within the Nagssugtoqidian Orogen. Supra and subglacial meltwater samples were collected directly in front of the Ice Sheet over an entire melt season in 2011 (North River, Thule) and 2012 (Akuliarusiarsuup Kuua River, Kangerlussuaq). In situ parameters such as temperature, pH, dissolved oxygen, and electrical conductivity were recorded in order to interpret meltwater chemistry. Dissolved Fe(II) and Fe(III) species were fixed immediately and analyzed within 24 hours after sampling in the field laboratory using a spectrophotometer and 10 cm cell. Total dissolved iron (FeT) of different size fractions (<0.22 and <0.05 μm) of iron were determined back in the home laboratory using reaction cell ICP MS. Preliminary results demonstrate that subglacial meltwater of North River has average Fe

  13. High-resolution, terrestrial radar velocity observations and model results reveal a strong bed at stable, tidewater Rink Isbræ, West Greenland

    NASA Astrophysics Data System (ADS)

    Bartholomaus, T. C.; Walker, R. T.; Stearns, L. A.; Fahnestock, M. A.; Cassotto, R.; Catania, G. A.; Felikson, D.; Fried, M.; Sutherland, D.; Nash, J. D.; Shroyer, E.

    2015-12-01

    At tidewater Rink Isbræ, on the central west coast of Greenland, satellite observations reveal that glacier velocities and terminus positions have remained stable, while the lowest 25 km have thinned 30 m since 1985. Over this same time period, other tidewater glaciers in central west Greenland have retreated, thinned and accelerated. Here we present field observations and model results to show that the flow of Rink Isbræ is resisted by unusually high basal shear stresses. Terrestrial radar interferometry (TRI) observations over 9 days in summer 2014 demonstrate weak velocity response to 4 km wide, full thickness calving events. Velocities at the terminus change by +/- 10% in response to rising and falling tides within a partial-width, 2.5-km-long floating ice tongue; however these tidal perturbations damp out within 2 km of the grounding line. Inversions for basal shear stress and force balance analyses together show that basal shear stresses in excess of 300 kPa support the majority of the driving stress at thick, steep Rink Isbræ. These observational and modeling results tell a consistent story in which a strong bed may limit the unstable tidewater glacier retreats observed elsewhere. Rink Isbræ has an erosion resistant quartzite bed with low fracture density. We hypothesize that this geology may play a major role in the bed strength.

  14. Seasonal Variation and Controls on Subglacial Riverine CO2 Concentrations From a Small Catchment, West Greenland Ice Sheet

    NASA Astrophysics Data System (ADS)

    Andrews, G.; Jacobson, A. D.

    2015-12-01

    Previous research has suggested that subglacial discharge from the Greenland Ice Sheet (GrIS) may have the potential to be a significant source of CO2 to the atmosphere in a warming world (Ryu and Jacobson, 2011). To trace the flux, sources of, and controls on subglacial CO2, we sampled the Akuliarusiarsuup Kuua River subglacial portal, which receives water from the Isunnguata and Russell Glaciers, west GrIS, six times throughout June - August, 2014. Additionally, we sampled two nearby supraglacial streams. We present preliminary data on pCO2 values, DIC and DOC concentrations, major cation and anion concentrations, δ13CDIC isotopes, as well as ∆14C-DIC and -DOCisotopes. Waters emerging from the subglacial portal are 2 - 2.5x supersaturated in CO2 with respect to atmospheric equilibrium. pCO2 values rise from ~700 to 1000ppm between June and July then return to ~700ppm in August. Although subglacial pCO2 and ∆14CDIC values vary, throughout the summer they exhibit similar trends as contemporaneous supraglacial stream values, suggesting that subglacial CO2 is at least partially derived from supraglacial meltwater which has accessed the ice sheet base through moulins and crevasses. δ13CDIC isotopes of supraglacial streams are highly depleted (-24‰), suggesting that CO2 is sourced from microbial respiration of surficial organic carbon. Subglacial portal δ13CDIC isotopes are also relatively depleted (-17‰) but are sufficiently different relative to supraglacial streams so as to require an additional δ13CDIC enriched source. A strong correlation (R2 = 0.89, n= 6) between subglacial Ca+Mg concentrations and alkalinity (≈ HCO3) suggests that the additional source of DIC to these waters is dissolution of carbonate. Finally, the correlation (R2 = 0.55, n = 6) between subglacial pCO2 and ∆14CDOC values suggest that one control on variable CO2 concentrations throughout the melt season is the age, and presumably, the lability, of organic carbon available to

  15. Plate Tectonics at 3.8-3.7 Ga: Field Evidence from the Isua Accretionary Complex, Southern West Greenland.

    PubMed

    Komiya; Maruyama; Masuda; Nohda; Hayashi; Okamoto

    1999-09-01

    A 1&rcolon;5000 scale mapping was performed in the Isukasia area of the ca. 3.8-Ga Isua supracrustal belt, southern West Greenland. The mapped area is divided into three units bounded by low-angle thrusts: the Northern, Middle, and Southern Units. The Southern Unit, the best exposed, is composed of 14 subunits (horses) with similar lithostratigraphy, bound by layer-parallel thrusts. Duplex structures are widespread in the Isua belt and vary in scale from a few meters to kilometers. Duplexing proceeded from south to north and is well documented in the relationship between link- and roof-thrusts. The reconstructed lithostratigraphy of each horse reveals a simple pattern, in ascending order, of greenstone with low-K tholeiitic composition with or without pillow lava structures, chert/banded iron-formation, and turbidites. The cherts and underlying low-K tholeiites do not contain continent- or arc-derived material. The lithostratigraphy is quite similar to Phanerozoic "oceanic plate stratigraphy," except for the abundance of mafic material in the turbidites. The evidence of duplex structures and oceanic plate stratigraphy indicates that the Isua supracrustal belt is the oldest accretionary complex in the world. The dominantly mafic turbidite composition suggests that the accretionary complex was formed in an intraoceanic environment comparable to the present-day western Pacific Ocean. The duplex polarity suggests that an older accretionary complex should occur to the south of the Isua complex. Moreover, the presence of seawater (documented by a thick, pillow, lava unit at the bottom of oceanic plate stratigraphy) indicates that the surface temperature was less than ca. 100 degrees C in the Early Archean. The oceanic geotherm for the Early Archean lithosphere as a function of age was calculated based on a model of transient half-space cooling at given parameters of surface and mantle temperatures of 100 degrees and 1450 degrees C, respectively, suggesting that the

  16. Ice-Ocean Interactions to the North-West of Greenland: Glaciers, Straits, Ice Bridges, and the Rossby Radius (Invited)

    NASA Astrophysics Data System (ADS)

    Muenchow, A.; Falkner, K. K.; Melling, H.; Johnson, H. L.; Huntley, H. S.; Ryan, P.; Friends Of Petermann

    2010-12-01

    Petermann Glacier at 81 N latitude is a major outlet glacier adjacent to Nares Strait. It terminates in a long (70 km), narrow (16 km) and thin (50 m) floating tongue and has a grounding line more than 500 m below sea level. A calving event in 2010 reduced the floating area by 25% and produced a single 240 km2 ice island currently moving south in Nares Strait where it will likely interact with island to potentially create a temporary polynya in Nares Strait. The 2010 calving from Petermann Glacier contributes <10% to its mass balance as more than 80% is lost due to basal melting by the ocean. Hence the largely unexplored physics at the ice-ocean interface determine how a changing climate impacts this outlet glacier. Conducting exploratory surveys inside Petermann Fjord in 2003, 2007, and 2009, we find a 1100 m deep fjord connected to Nares Strait via a sill at 350-450 m depth. The fjord receives about 3 times the amount of heat required for the basal melt rates. Furthermore, limited data and analytical modeling suggests a 3-dimensional circulation over the upper 300-m of the water column with a coastally trapped buoyant outflow. We integrate these findings with more complete oceanic time series data from an array moored in Nares Strait from 2003 through 2009 near 80.5 N. In the past Nares Strait and Petermann Fjord were covered by land fast sea ice during the 9-10 month long winter season. Archeological and remotely sensed records indicate that an ice bridge formed regularly at the southern end of Nares Strait creating the North-Water polynya near 79 N latitude. Since 2006 this ice bridge has largely failed to form, leading, perhaps, to the occasional formation of a secondary ice bridge 300 km to the north where Nares Strait connects to the Arctic Ocean. However, this ice bridge appears to form for shorter periods only. Consequently Arctic sea ice can now exit the Arctic in winter via pathways to the west of Greenland all year. We speculate that this changed ocean

  17. Ice Sheet Meltwater Impacts on Biological Productivity in High-Latitude Coastal Zones - Observations and Model Results for West Antarctica and Southwest Greenland

    NASA Astrophysics Data System (ADS)

    Yager, P. L.; Oliver, H.; Sherrell, R. M.; Stammerjohn, S. E.; St-Laurent, P.; Hofmann, E. E.; Mote, T. L.; Castelao, R. M.; Rennermalm, A. K.; Tedesco, M.; Arrigo, K. R.

    2015-12-01

    Surface mass balance observations and models confirm that both the west Antarctic and Greenland Ice Sheets have undergone accelerating ice mass losses during the past decade. These losses enhance freshwater discharge to the ocean and have important implications for ocean circulation and sea level, but they can also impact marine ecosystems and carbon cycling. High-latitude primary productivity is limited by light or nutrients (or both), and phytoplankton access to these limiting factors can be altered by freshwater additions. Mechanisms for delivering meltwater to the ocean are complex and depend in part on whether the melt occurs at the ice-atmosphere or ice-ocean interface. Marine-terminus glaciers may generate buoyant plumes at depth, similar to upwelling whereas runoff from glacial termini on land will behave more like a riverine point source at the ocean surface. Here, we present preliminary results from two ongoing efforts to understand these impacts: one from the Amundsen Sea Polynya (ASP) in west Antarctica (NSF-funded INSPIRE), and another from NASA-IDS Ice Sheet Impact Study in coastal Greenland. Field observations from the Amundsen Sea Polynya International Research Expedition (ASPIRE) showed how the enormous phytoplankton bloom in the central ASP depends on an iron supply from the Dotson Ice Shelf (DIS). This outcome implied a three-dimensional pathway for iron, from the DIS cavity to the euphotic zone of the ASP bloom region located 20-100 km offshore. Such a pathway differs from the traditional one-dimensional view, where nutrients are injected into the euphotic zone by vertical mixing. Mesoscale structures and eddies may play a central role. A ROMS model is used to investigate key physical and biogeochemical processes in the ASP region. A similar effort is underway to investigate the fate of extreme melt from Greenland and its impact on primary productivity. In coastal Greenland, meltwater is modeled as surface runoff and the resulting shallower

  18. Improving the timing of middle Holocene retreat and late Holocene advance of Jakobshavn Isbrae, Greenland

    NASA Astrophysics Data System (ADS)

    Briner, J. P.; Stewart, H. A.; Young, N. E.; Csatho, B.; Axford, Y.

    2009-04-01

    The Greenland Ice Sheet is undergoing dramatic change. How the ice sheet continues to respond to climate change has important ramifications for global climate and sea level rise, but the observation-based record of ice sheet change is extremely short. We use glacial-geologic techniques to determine the behavior of the Greenland Ice Sheet over longer timescales. In particular, we focus on the Holocene history of Jakobshavn Isbrae, one of the key ice streams on Greenland that is responsible for disproportionate mass loss of the Greenland Ice Sheet. Radiocarbon ages from basal lake sediments and 10Be exposure ages of bedrock spanning from the present ice margin to Disko Bugt, ~50 km west, reveal rapid deglaciation between ~8 and ~7 ka. After ~7 ka, the ice margin continued to retreat inland behind its present position. Although it is difficult to reconstruct how far inland the ice margin retreated, the Little Ice Age advance reworked marine bivalves that date from 2.2 to 6.1 ka (Weidick and Bennike, 2007). The bivalve ages indicate that the ice margin was behind its Little Ice Age position between ~6 and ~2 ka, and that its Neoglacial advance post-dates ~2 ka. We improve the timing of the Neoglacial advance of Jakobshavn Isbrae by collecting sediment cores from lakes that are beyond the Little Ice Age margin but close enough to receive ice sheet meltwater during the Little Ice Age advance. The sediments in these "threshold" lakes contain distinct units of varved sediments (representing a proglacial environment) that sharply overlie gyttja (representing a non-glacial environment). Four radiocarbon ages of the sedimentary contacts from three different lake sites range from 530±10 to 370±60 cal yr BP (1410-1640 AD), and reveal when Jakobshavn Isbrae neared its maximum Little Ice Age margin. Furthermore, the lake sediments reveal that between early Holocene deglaciation and the Little Ice Age, Jakobshavn Isbrae never spilled into these lake basins, indicating that the

  19. Increasing Freshwater Runoff and Tidal Action Influences on Spatial Mixing Patterns in Søndre Strømfjord, West Greenland

    NASA Astrophysics Data System (ADS)

    Smiley, C. R.; Kamenos, N.; Hoey, T.; Cottier, F.; Ellam, R. M.

    2014-12-01

    Greenland Ice Sheet melt has the potential to affect global sea levels and the strength of the thermohaline circulation (THC). Investigating spatial mixing patterns of seawater in Greenlandic fjords can help reveal characteristics of changes in runoff from the GrIS; for example higher runoff may be associated with lower salinity within GrIS fjords, which can be recorded by palaeoenvironmental proxies (Kamenos et al 2012). The Kangerlussuaq Drainage Basin mirrors melt patterns of the whole GrIS and drains into Søndre Strømfjord, a 170km long fjord on the west coast of Greenland. Temperature and salinity profiles to 40m depth were obtained at 11 stations along Søndre Strømfjord during the 2014 melt season. Each station was sampled twice once at high KDB runoff and once at low KDB runoff. With increasing freshwater runoff, salinity decreases by 1.65 - 2.91 at each station over a 7 hour time period. Higher salinities occur at low run-off. In addition, with increasing run-off, the disparity between surface and deeper water (30m) becomes greater with a 19.3 difference between the surface and 30m. With higher KDB runoff temperature increases by 0.47oC - 2.34oC. This information will be integrated with oxygen and deuterium isotope patterns to pinpoint the exact source of the runoff causing salinity reductions. Our data show a relationship between KDB runoff and salinity of Søndre Strømfjord, data that will enable further calibration of marine proxies of GrIS melt.

  20. The tholeiite-TTG connection during Eoarchean crust formation in Isua, southern West Greenland: the role of subduction processes

    NASA Astrophysics Data System (ADS)

    Hoffmann, J. E.; Münker, C.; Nagel, T. J.; Næraa, T.; Polat, A.; Rosing, M. T.

    2012-04-01

    The processes and the geodynamic settings that generated Earth's oldest parts of continental crust are still a matter of debate. A pertinent issue is the genetic relationship between the tonalite-trondhjemite-granodiorite (TTG) suite and the mafic fragments that are found as inclusions within this felsic crust. Here we propose a coherent model for the geodynamic evolution of the oldest (3.65 to 3.85 Ga) continental crust in southern West Greenland. Within the Isua Supracrustal Belt, the best preserved and largest fragment of mafic Eoarchean crust worldwide, tholeiitic and boninite-like amphibolites dominate the sequence, both yielding trace element patterns consistent with a subduction-related origin. The tholeiites yield correlated trace element variations in Nb/Th, La/Yb, Gd/Yb, Zr/Nb, in agreement with a subduction zone setting where a depleted mantle source is overprinted by melt-like slab components (Hoffmann et al., 2011a). Boninite-like rocks in Isua are derived from ultradepleted sources with epsHf(3720) of up to ca. +12.9 (Hoffmann et al., 2010). Petrological phase equilibrium modeling combined with trace element modeling suggests a relationship between the typical Isua arc tholeiites and the TTGs (Nagel et al., 2012). Notably, Hf-Nd isotope signatures between the two lithologies overlap (epsHf(t) = -0.7 to +2.5; epsNd(t) = -0.8 to +4.4), both showing the characteristic decoupling of initial Hf-Nd isotope compositions. Systematically elevated 142Nd anomalies of tholeiites and TTGs are also in agreement with a related origin of both rock types (e.g., Caro et al., 2006). Trace element modeling shows that the Isua TTGs likely formed by melting of thickened mafic arc crust with tholeiite compositions (Hoffmann et al., 2011b) and that the decoupled Hf-Nd signature is likely an inherited feature from melting of the tholeiites. This is also underlined by new Hf and O in zircon data from TTGs in the area (Næraa et al., submitted) that indicate melting of a

  1. Ancient graphite in the Eoarchean quartz-pyroxene rocks from Akilia in southern West Greenland I: Petrographic and spectroscopic characterization

    NASA Astrophysics Data System (ADS)

    Papineau, Dominic; De Gregorio, Bradley T.; Cody, George D.; Fries, Marc D.; Mojzsis, Stephen J.; Steele, Andrew; Stroud, Rhonda M.; Fogel, Marilyn L.

    2010-10-01

    Because all known Eoarchean (>3.65 Ga) volcano-sedimentary terranes are locked in granitoid gneiss complexes that have experienced high degrees of metamorphism and deformation, the origin and mode of preservation of carbonaceous material in the oldest metasedimentary rocks remain a subject of vigorous debate. To determine the biogenicity of carbon in graphite in such rocks, carbonaceous material must be demonstrably indigenous and its composition should be consistent with thermally altered biogenic carbon as well as inconsistent with abiogenic carbon. Here we report the petrological and spectroscopic characteristics of carbonaceous material, typically associated with individual apatite grains, but also with various other minerals including calcite, in a >3.83 Ga granulite-facies ferruginous quartz-pyroxene unit (Qp rock) from the island of Akilia in southern West Greenland. In thin sections of the fine-grained parts of Akilia Qp rock sample G91-26, mapped apatites were found to be associated with graphite in about 20% of the occurrences. Raman spectra of this carbonaceous material had strong G-band and small D-band absorptions indicative of crystalline graphite. Three apatite-associated graphites were found to contain curled graphite structures, identified by an anomalously intense second-order D-band (or 2D-band) Raman mode. These structures are similar to graphite whiskers or cones documented to form at high temperatures. Raman spectra of apatite-associated graphite were consistent with formation at temperatures calculated to be between 635 and 830 °C, which are consistent with granulite-facies metamorphic conditions. Three graphite targets extracted by focused ion beam (FIB) methods contained thin graphite coatings on apatite grains rather than inclusions sensu stricto as inferred from transmitted light microscopy and Raman spectroscopy. TEM analyses of graphite in these FIB sections showed a (0 0 0 2) interplanar spacing between 3.41 and 3.64 Å for apatite

  2. Qassiarsuk, Greenland

    NASA Image and Video Library

    2016-09-16

    The first Norse settlement of Greenland was at Brattahlid (now Qassiarsuk), which yielded a radiocarbon date of about 1000. According to the sagas, it was also in the year 1000 that Leif Erikson left the settlement to explore the regions around Vinland, which is generally assumed to be Newfoundland. Norse settlements at their height had an estimated population of a few thousand. After 450 years, the settlements were all abandoned. Causes include: cumulative environmental damage; gradual climate change; conflicts with hostile neighbors; and loss of contact and support from Europe. The image was acquired June 13, 2016, covers an area of 30.9 by 27.7 km, and is located at 61.1 degrees north, 45.5 degrees west. http://photojournal.jpl.nasa.gov/catalog/PIA20996

  3. Strontium and neodymium isotopic variations in early Archean gneisses affected by middle to late Archean high-grade metamorphic processes: West Greenland and Labrador

    NASA Technical Reports Server (NTRS)

    Collerson, K. D.; Mcculloch, M. T.; Bridgwater, D.; Mcgregor, V. R.; Nutman, A. P.

    1986-01-01

    Relicts of continental crust formed more than 3400 Ma ago are preserved fortuitously in most cratons. The cratons provide the most direct information about crust and mantle evolutionary processes during the first billion years of Earth history. In view of their polymetamorphic character, these terrains are commonly affected by subsequent tectonothermal events. Hence, their isotope systematics may be severely disturbed as a result of bulk chemical change or local isotopic homogenization. This leads to equivocal age and source information for different components within these terrains. The Sr and Nd isotopic data are presented for early Archean gneisses from the North Atlantic Craton in west Greenland and northern Labrador which were affected by younger metamorphic events.

  4. Increasing freshwater runoff and tidal action influences on spatial mixing patterns in Søndre Strømfjord, West Greenland.

    NASA Astrophysics Data System (ADS)

    Smiley, Crystal; Kamenos, Nick; Hoey, Trevor; Cottier, Finlo; Ellam, Rob

    2015-04-01

    Greenland Ice Sheet melt has the potential to affect global sea levels and the strength of the thermohaline circulation (THC). Investigating spatial mixing patterns of seawater in Greenlandic fjords can help reveal characteristics of changes in runoff from the GrIS; for example higher runoff may be associated with lower salinity within GrIS fjords, which can be recorded by palaeoenvironmental proxies (Kamenos et al 2012). The Kangerlussuaq Drainage Basin mirrors melt patterns of the whole GrIS and drains into Søndre Strømfjord, a 170km long fjord on the west coast of Greenland. Temperature and salinity profiles to 40m depth were obtained at 11 stations along Søndre Strømfjord during the 2014 melt season. Each station was sampled twice once at high KDB runoff and once at low KDB runoff. With increasing freshwater runoff, salinity decreased by 1.65 - 2.91 and temperature increased by 0.47oC- 2.34oC at each station over a 7 hour time period. Higher salinities occurred at low run-off. In addition, with increasing run-off, the disparity between surface and deeper water (30m) salinity became greater with a 19.3 difference between the surface and 30m. This information was integrated with oxygen and deuterium isotopic signatures collected at 10 m depth from each station to pinpoint the exact source of the runoff causing salinity reductions. With increasing freshwater runoff, the chemistry of the fjord exhibits an enrichment of the heavier isotope. δ18Ovsmow values enrich by 7.40 permil while δDvsmow enrich 53.26 permil. Our data shows a relationship between KDB runoff, salinity, and oxygen, hydrogen isotopic chemistry of Søndre Strømfjord, data that will enable further calibration of marine proxies of GrIS melt. References Kamenos, N.A, Hoey, T.B, Nienow, P., Fallick, A.E., & Claverie, T., 2012: Reconstructing Greenland Ice Sheet runoff using coralline algae; Geological Society of America, Geology, doi: 10.1130/G33405.1

  5. Fagaceae pollen from the early Cenozoic of West Greenland: revisiting Engler's and Chaney's Arcto-Tertiary hypotheses.

    PubMed

    Grímsson, Friðgeir; Zetter, Reinhard; Grimm, Guido W; Pedersen, Gunver Krarup; Pedersen, Asger Ken; Denk, Thomas

    In this paper we document Fagaceae pollen from the Eocene of western Greenland. The pollen record suggests a remarkable diversity of the family in the early Cenozoic of Greenland. Extinct Fagaceae pollen types include Eotrigonobalanus, which extends at least back to the Paleocene, and two ancestral pollen types with affinities to the Eurasian Quercus Group Ilex and the western North American Quercus Group Protobalanus. In addition, modern lineages of Fagaceae are unambiguously represented by pollen of Fagus, Quercus Group Lobatae/Quercus, and three Castaneoideae pollen types. These findings corroborate earlier findings from Axel Heiberg Island that Fagaceae were a dominant element at high latitudes during the early Cenozoic. Comparison with coeval or older mid-latitude records of modern lineages of Fagaceae shows that modern lineages found in western Greenland and Axel Heiberg likely originated at lower latitudes. Further examples comprise (possibly) Acer, Aesculus, Alnus, Ulmus, and others. Thus, before fossils belonging to modern northern temperate lineages will have been recovered from older (early Eocene, Paleocene) strata from high latitudes, Engler's hypothesis of an Arctic origin of the modern temperate woody flora of Eurasia, termed 'Arcto-Tertiary Element', and later modification by R. W. Chaney and H. D. Mai ('Arcto-Tertiary Geoflora') needs to be modified.

  6. The speed and timing of climate change: Detailed ice core stable isotope records from NorthGRIP, Greenland and Mt. Moulton, West Antarctica

    NASA Astrophysics Data System (ADS)

    Popp, Trevor J.

    Objective projections of future climate change require a detailed understanding of the natural variability and behavior of the climate system observed in the past. This dissertation endeavors to characterize the speed and timing of past climate changes on both orbital and extremely abrupt time scales from new high-resolution stable isotope time series from ice cores collected at NorthGRIP in Greenland and Mt. Moulton in West Antarctica. Greenland ice cores are uniquely suited for study of abrupt climate events because relatively high snow accumulation rates allow single years to be identified well into the last glacial period. Deuterium (deltaD) and deuterium excess time series at near annual resolution or better across the three major abrupt transitions of the last glacial termination are examined from the precisely dated NGRIP ice core. These records have been synchronized to within a few years or less to similar isotopic series developed from the GISP2 ice core which was collected 320 km SSE of the NGRIP site. 300-500 year time intervals were examined in detail at the end of the Younger Dryas (YD, 11.7 ka), the beginning of the YD (12.9 ka), and at the onset of Bolling (14.7 ka). Transition timing, duration and amplitudes were determined for each transition at both sites via a statistical ramp fitting approach. At each transition a complete mode shift between two climate states recorded by deltaD or excess, or both, was detected in as little as a single year with one exception at the cooling at the onset of the YD at GISP2. NGRIP and GISP2 share much common variance, sometimes in remarkable detail, in the timing and evolution of the climate transitions. Complete mode shifts in excess were synchronous to within a year or better between NGRIP and GISP2 for the two cold-to-warm transitions and represent a significant regional reorganization of atmospheric circulation delivering moisture from lower latitude source regions to the high latitudes of Greenland. At the

  7. Decoupling of Hf-Nd isotope ratios in early Archean rocks from southern West Greenland - primary or secondary disturbance?

    NASA Astrophysics Data System (ADS)

    Hoffmann, J.; Munker, C.; Polat, A.; Rosing, M.

    2010-12-01

    In contrast to the strongly coupled behaviour of the Lu-Hf and Sm-Nd systems in Phanerozoic and Proterozoic rocks, early Archean rocks, e.g. those from SW-Greenland, exhibit an apparent decoupling of both systems [e.g., 1]. This apparent decoupling may either indicate metamorphic disturbance or, alternatively, mirror early differentiation processes such as magma ocean crystallisation involving cumulate segregation [1]. To evaluate the issue, we performed combined measurements of Hf-Nd isotope compositions together with major and trace element measurements for well preserved >3.72 to >3.80 Ga old tholeiitic metabasalts and gabbros from the inner western part and the southwestern unit of the Isua Supracrustal Belt, SW-Greenland. A careful evaluation of alteration based on major and trace elements reveals pristine magmatic trends, and therefore near chondritic to moderately depleted initial ɛHf values of -0.2-+2.7 and initial ɛNd values of 0.0-+3.0 indeed most likely characterize the early Archean mantle sources. These values confirm a decoupling of the Hf-Nd systematics, but are in marked contrast to more depleted signatures in nearby boninite-like metabasalts of the Garbenschiefer unit [2]. In Sm-Nd and Lu-Hf isochron space, the Isua metabasalts yield early Archean ages, in agreement with emplacement ages inferred from crosscutting relationships with tonalites. Trace element compositions of the metabasalts indicate a source overprint by subduction components. It is likely, that the source overprint may have caused partial decoupling of ɛHf-ɛNd values, due to selective addition of Nd as in modern subduction settings. In this case, the most radiogenic initial ɛNd and ɛHf isotope values characterize the most depleted mantle sources, and less radiogenic values might reflect addition of more enriched subduction components. A comparison of our data with Hf-Nd isotope data from the literature for early Archean rocks from Greenland reveals an overlap in initial Hf

  8. The Subglacial Access and Fast Ice Research Experiment (SAFIRE): 1. Programme of investigation on Store Glacier, West Greenland

    NASA Astrophysics Data System (ADS)

    Christoffersen, Poul; Hubbard, Bryn; Bougamont, Marion; Doyle, Samuel; Young, Tun Jan; Hofstede, Coen; Nicholls, Keith; Todd, Joe; Box, Jason; Ryan, Johnny; Toberg, Nick; Walter, Jacob; Hubbard, Alun

    2015-04-01

    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 almost 1 mm per year. Understanding the processes that drive the fast flow of these glaciers is crucial because a growing body of evidence points to a strong, but spatially varied and often complex, response to oceanographic as well as atmospheric forcing. While the bed of glaciers elsewhere is known to strongly influence the flow of ice, no observations have ever been made at the bed of a marine-terminating glacier in Greenland. The flow of ice in numerical models of the Greenland Ice Sheet consequently rely on untested basal parameterisations, which form a likely and potentially significant source of error in the prediction of sea level rise over the coming decades and century. The Subglacial Access and Fast Ice Research Experiment (SAFIRE) is addressing this paucity of observational constraints by gaining access to the bed of Store Glacier, a marine-terminating outlet of the Greenland Ice Sheet which has a drainage basin of 35,000 square kilometres and terminates in Uummannaq Fjord. In 2014, the SAFIRE programme drilled four boreholes in a region where ice flows at a rate of 700 m per year and where a seismic survey revealed a bed consisting of soft sediment. (See joint abstract by Hofstede et al. for details.) The boreholes were 603-616 m deep and direct access to the bed was confirmed by a clear hydrological connectivity with a basal water system. (See joint abstract by Doyle et al. for details.) With sensors deployed englacially (temperature and tilt) and at the bed (water pressure, turbidity, electrical conductivity), the SAFIRE will inform the ratio of internal ice deformation and basal slip, vertical strain, ice temperature, and fluctuations in water pressure linked to supraglacial lake drainage as well as diurnal drainage into moulins. In 2015, we plan to

  9. Seasonal and Intra-Seasonal Variability of Surface Streams Over the West Greenland Ice Sheet from High Resolution Satellite Optical Data.

    NASA Astrophysics Data System (ADS)

    Brown, M. G.; Tedesco, M.

    2014-12-01

    The surface hydrology of the Greenland ice sheet plays a crucial role on surface energy and mass balance, as well as on the englacial and sub-glacial environments. The spatial distribution of these surface streams is poorly understood and their temporal variability is (to our knowledge) unknown. One of the reasons for the lack of knowledge on the temporal variability of such streams is related to the historical unavailability of satellite data that could spatially resolve the presence and associated properties of the streams. In recent years, however, multi-spectral commercial satellite data in the visible and infra-red bands have been made available to the scientific community. These newly accessible data sets are provided at spatial resolutions of the order of 1-2 meters, therefore, allowing to perform accurate spatial and temporal analysis of surface streams (and small lakes and ponds that cannot be resolved with sensors such as MODIS or LANDSAT). In this study, we report results concerning the seasonal and intra-seasonal variability of surface streams over a selected area on the west Greenland ice sheet. Using a combination of ENVI® and ArcGIS® software packages applied to multispectral high resolution imagery from World View 2 and Quickbird satellites, surface streams are identified through multiple approaches (either based on unsupervised classifications, band combinations, band ratio thresholds, or digitization) and vector maps of the surface hydrology network were created. Stream networks created during one melting season (at three different stages of the season) were compared and discussed as well as the networks mapped between two consecutive years for proximate dates.

  10. Seasonal and Intra-Seasonal Variability of Surface Streams over the West Greenland Ice Sheet from High Resolution Satellite Optical Data.

    NASA Astrophysics Data System (ADS)

    Brown, Michael G.; Tedesco, Marco

    2015-04-01

    The surface hydrology of the Greenland ice sheet plays a crucial role on surface energy and mass balance, as well as on the en-glacial and sub-glacial environments. The spatial distribution of these surface streams is poorly understood and their temporal variability is (to our knowledge) unknown. One of the reasons for the lack of knowledge on the temporal variability of such streams is related to the historical unavailability of satellite data that could spatially resolve the presence and associated properties of the streams. In recent years, however, multi-spectral commercial satellite data in the visible and infra-red bands have been made available to the scientific community. These newly accessible data sets are provided at spatial resolutions of the order of 1-2 meters, therefore, allowing to perform accurate spatial and temporal analysis of surface streams (and small lakes and ponds that cannot be resolved with sensors such as MODIS or LANDSAT). In this study, we report results concerning the seasonal and intra-seasonal variability of surface streams over a selected area on the west Greenland ice sheet. Using ArcGIS® software applied to multispectral high resolution imagery from World View 2 and Quickbird satellites, surface streams were identified through band math, threshold classifications, and morphological operations. Raster and vector maps of the surface hydrology network were created. Stream networks created during multiple melt seasons (at several different stages of the season) were compared and discussed as well as the networks mapped between consecutive years for proximate dates.

  11. A review of structural patterns and melting processes in the Archean craton of West Greenland: Evidence for crustal growth at convergent plate margins as opposed to non-uniformitarian models

    NASA Astrophysics Data System (ADS)

    Polat, Ali; Wang, Lu; Appel, Peter W. U.

    2015-11-01

    The Archean craton of West Greenland consists of many fault-bounded Eoarchean to Neoarchean tectonic terranes (crustal blocks). These tectonic terranes are composed mainly of tonalite-trondhjemite-granodiorite (TTG) gneisses, granitic gneisses, metavolcanic-dominated supracrustal belts, layered anorthositic complexes, and late- to post-tectonic granites. Rock assemblages and geochemical signatures in these terranes suggest that they represent fragments of dismembered oceanic island arcs, consisting mainly of TTG plutons, tholeiitic to calc-alkaline basalts, boninites, picrites, and cumulate layers of ultramafic rocks, gabbros, leucogabbros and anorthosites, with minor sedimentary rocks. The structural characteristics of the terrane boundaries are consistent with the assembly of these island arcs through modern style of horizontal tectonics, suggesting that the Archean craton of West Greenland grew at convergent plate margins. Several supracrustal belts that occur at or near the terrane boundaries are interpreted as relict accretionary prisms. The terranes display fold and thrust structures and contain numerous 10 cm to 20 m wide bifurcating, ductile shear zones that are characterized by a variety of structures including transposed and redistributed isoclinal folds. Geometrically these structures are similar to those occurring on regional scales, suggesting that the Archean craton of West Greenland can be interpreted as a continental scale accretionary complex, such as the Paleozoic Altaids. Melting of metavolcanic rocks during tectonic thickening in the arcs played an important role in the generation of TTGs. Non-uniformitarian models proposed for the origin of Archean terranes have no analogs in the geologic record and are inconsistent with structural, lithological, petrological and geochemical data collected from Archean terranes over the last four decades. The style of deformation and generation of felsic rocks on outcrop scales in the Archean craton of West

  12. Long-term change of a small ice cap in Greenland: a dynamic perspective from numerical flow modelling

    NASA Astrophysics Data System (ADS)

    Vieli, A.; Adamson, K.; Lane, T. P.

    2016-12-01

    Small ice caps at the periphery of the Greenland ice sheet are often close to the limit of existence and therefore respond far more sensitively to climate change than the land-margin of the neighboring ice sheet. However, their past evolution and dynamic behavior is poorly understood and their use as climate indicators therefore remains limited. We here aim to provide a long-term reconstruction of Lyngmarksbreen, a small (32km2) ice cap on Disko Island in West Greenland, from the pre-little ice age (LIA, starting at about 1200 AD) to present. We use a 2-dim. time-dependent numerical flow model (SIA) in combination with geomorphological mapping, exposure dating and historical observations to simulate its long-term evolution. We specifically focus on retreat since the LIA, which is well constrained by geomorphological length records of several small outlet glaciers and data from local and regional climate stations (Qeqertassuaq and Ilulisat). We also explore aspects related to flow dynamics and find that the dynamic state of this ice cap is far from being balanced and is highly sensitive to the surface elevation mass balance feedback resulting in an asynchronous response of the different outlets. This sensitivity can partly be explained by low surface slopes and a very limited elevation extent of the ice cap. Our investigations further suggest that redistribution of snow through wind-drift is strongly affecting the surface mass balance and hence the evolution of the ice cap. Over the last century the ice cap almost continuously retreated and today almost no accumulation area remains. As a consequence, this ice cap will likely vanish within the next few decades.

  13. Long-term evolution of a small ice cap in Greenland: a dynamic perspective from numerical flow modelling

    NASA Astrophysics Data System (ADS)

    Vieli, Andreas; Lane, Timothy; Adamson, Kathryn

    2017-04-01

    Small ice caps at the periphery of the Greenland ice sheet are often close to the limit of existence and are therefore expected to respond more sensitively to climate change than the land-margin of the neighboring ice sheet. However, their past evolution and dynamic behavior is poorly understood and their use as climate indicators therefore remains so far limited. We here aim to provide a long-term dynamic reconstruction of Lyngmarksbraeen, a small (32km2) ice cap on Disko Island in West Greenland, with a particular focus on the little ice age (LIA, since 1200AD). We use a 2-dim. time-dependent numerical flow model (SIA) and a PDD-mass balance model in combination with historical observations, geomorphological mapping and exposure dating to simulate its long-term evolution and dynamic behaviour. We specifically focus on retreat since the LIA, which is well constrained by geomorphological evidence and historical maps and length records of several small outlet glaciers and data from local and regional climate stations (Qeqertarssuaq and Ilulisat). We also explore aspects related to flow dynamics and find that the dynamic state of this ice cap is, at any time, far from being balanced and is highly sensitive to the surface elevation mass balance feedback and results in an asynchronous response of the different outlets and hysteresis-type behaviour. The modelling is able to reproduce the observed LIA-extent and the almost continuous retreat over the last hundred years well. It further indicates that the ice cap was already dynamically inert since the 1960s. Today, the ice cap has lost almost its entire accumulation area and even without any further warming in the future, the ice cap is expected to vanish within a couple of decades.

  14. Temporal trends of selected POPs and the potential influence of climate variability in a Greenland ringed seal population.

    PubMed

    Rigét, Frank; Vorkamp, Katrin; Hobson, Keith A; Muir, Derek C G; Dietz, Rune

    2013-09-01

    Temporal trends of selected POPs (PCB-52 and 153, p,p'-DDE, HCB, α- and β-HCH) in blubber of ringed seals (Pusa hispida) collected from the early 1990s to 2010 from central West Greenland were studied. In this period, the climate of Greenland warmed and the influences of climate indices such as winter sea-ice coverage (November-May), the number of sea-ice days during winter in Disko Bay, water temperature and salinity at Fyllas Banke during the preceding summer and the Arctic Oscillation Index (AOI) during the preceding winter on concentrations of selected POPs were evaluated using multiple regressions and an information-theoretic approach. Biological co-variables such as age, sex and trophic position (as determined by δ(15)N analysis) of seals were also evaluated. Decreasing levels of the selected POPs were found in all cases and with the highest rate for α-HCH (-10.5% annually) and the lowest rate for β-HCH (-1.9% annually). Sex and age were found to have strong predictive power in the case of PCB-52 and trophic position in the case of p,p'-DDE. Among the climate indices the strongest predictive power was found for the number of sea-ice days in the case of PCB-52, the AOI winter index in the case of α-HCH and salinity at Fyllas Banke during the preceding summer in the case of β-HCH. The present study documents the need for including both biological variables and climate variability parameters in temporal trend studies of POPs in Arctic biota.

  15. The Subglacial Access and Fast Ice Research Experiment (SAFIRE): 2. High magnitude englacial strain detected with autonomous phase-sensitive FMCW radar on Store Glacier, West Greenland

    NASA Astrophysics Data System (ADS)

    Young, Tun Jan; Christoffersen, Poul; Nicholls, Keith; Bun Lok, Lai; Doyle, Samuel; Hubbard, Bryn; Stewart, Craig; Hofstede, Coen; Bougamont, Marion; Todd, Joseph; Brennan, Paul; Hubbard, Alun

    2016-04-01

    Fast-flowing outlet glaciers terminating in the sea drain 90% of the Greenland Ice Sheet. It is well-known that these glaciers flow rapidly due to fast basal motion, but its contributing processes and mechanisms are, however, poorly understood. In particular, there is a paucity of data to quantify the extent to which basal sliding and internal ice deformation by viscous creep contribute to the fast motion of Greenland outlet glaciers. To study these processes, we installed a network of global positioning system (GPS) receivers around an autonomous phase-sensitive radio-echo sounder (ApRES) capable of imaging internal reflectors and the glacier bed. The ApRES system, including antennas, were custom-designed to monitor and image ice sheets and ice shelves in monostatic and multiple-input multiple-output (MIMO) modes. Specifically, the system transmits a frequency-modulated continuous-wave (FMCW) that increases linearly from 200 to 400 MHz over a period of 1 second. We installed this system 30 km up-flow of the tidewater terminus of Store Glacier, which flows into Uummannaq Fjord in West Greenland, and data were recorded every hour from 06 May to 16 July 2014 and every 4 hours from 26 July to 11 December 2014. The same site was used to instrument 600 m deep boreholes drilled to the bed as part of the SAFIRE research programme. With range and reflector distances captured at high temporal (hourly) and spatial (millimetre) resolutions, we obtained a unique, 6-month-long time series of strain through the vertical ice column at the drill site where tilt was independently recorded in a borehole. Our results show variable, but persistently high vertical strain. In the upper three-fourths of the ice column, we have calculated strain rates on the order of a few percent per year, and the strain regime curiously shifts from vertical thinning in winter to vertical thickening at the onset of summer melt. In the basal ice layer we observed high-magnitude vertical strain rates on

  16. Pb isotopes as tracers of mining-related Pb in lichens, seaweed and mussels near a former Pb-Zn mine in West Greenland.

    PubMed

    Søndergaard, Jens; Asmund, Gert; Johansen, Poul; Elberling, Bo

    2010-05-01

    Identification of mining-related contaminants is important in order to assess the spreading of contaminants from mining as well as for site remediation purposes. This study focuses on lead (Pb) contamination in biota near the abandoned 'Black Angel Mine' in West Greenland in the period 1988-2008. Stable Pb isotope ratios and total Pb concentrations were determined in lichens, seaweed and mussels as well as in marine sediments. The results show that natural background Pb ((207)Pb/(206)Pb: 0.704-0.767) and Pb originating from the mine ore ((207)Pb/(206)Pb: 0.955) have distinct isotopic fingerprints. Total Pb in lichens, seaweed, and mussels was measured at values up to 633, 19 and 1536 mg kg(-1) dry weight, respectively, and is shown to be a mixture of natural Pb and ore-Pb. This enables quantification of mining-related Pb and shows that application of Pb isotope data is a valuable tool for monitoring mining pollution.

  17. Long-term response of an arctic fiord system to lead-zinc mining and submarine disposal of mine waste (Maarmorilik, West Greenland).

    PubMed

    Søndergaard, Jens; Asmund, Gert; Johansen, Poul; Rigét, Frank

    2011-06-01

    Contamination by lead (Pb) and zinc (Zn) was studied in seawater, sediments, seaweeds and blue mussels near the former Black Angel Pb-Zn Mine in Maarmorilik, West Greenland. The mine operated during the period 1973-90 when mine waste (tailings and later waste rock) was discharged directly into the sea. Metal concentrations peaked during the mining period and Pb and Zn in seawater within the discharge area were measured up to 440 and 790 μg L⁻¹, respectively. Pb in fiord sediments, seaweeds and blue mussels just outside the discharge area were measured in concentrations up to 190, 84 and 2650 and Zn up to 300, 360 and 1190 μg g⁻¹ dry wt., respectively. Within the discharge area, seawater metal concentrations (especially Pb) decreased abruptly after mine closure. Metals concentrations in sediments and biota, however, decreased more slowly and two decades after mine closure seaweeds and blue mussels were still contaminated 12 km from the mine. Copyright © 2011 Elsevier Ltd. All rights reserved.

  18. 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.

  19. Deciphering the Ecology of Key Diatom Taxa to Understand Climate-Induced Changes in West Greenland Lakes over the Holocene

    NASA Astrophysics Data System (ADS)

    Saros, J. E.; Northington, R.; Malik, H.; Anderson, N. J.

    2014-12-01

    Paleolimnological records from southwest Greenland reveal that diatom communities have not changed in a similar way to other regions of the Arctic, and in general, do not show synchronous change across this area. There are a number of cases in which lakes in close proximity to each other show opposite community changes over the Holocene. These changes in diatom fossil profiles have been difficult to interpret due to a lack of explicit ecological information for key species. The objective of this project is to decipher the ecology of key diatom species that are abundant across these paleolimnological records. We hypothesize that climate-driven changes in nutrients and water column stability (via its effects on light availability) are key factors shaping diatom community structure in these lakes. We assessed the requirements of particular taxa for nutrients and light through comparative lake sampling and resource bioassays. A whole-lake manipulation in which water column stability was reduced through enhanced water circulation was also conducted to assess the response of key taxa to this change. We found that the relative abundances of key diatom taxa are under complex control by the interactive effects of nutrients and light. We discuss how these results will enhance interpretation of climate-induced changes in Arctic lakes in this region.

  20. Colonization history and clonal richness of asexual Daphnia in periglacial habitats of contrasting age in West Greenland.

    PubMed

    Haileselasie, Tsegazeabe H; Mergeay, Joachim; Weider, Lawrence J; Jeppesen, Erik; De Meester, Luc

    2016-07-01

    Due to climate change, Arctic ice sheets are retreating. This leads to the formation of numerous new periglacial ponds and lakes, which are being colonized by planktonic organisms such as the water flea Daphnia. This system provides unique opportunities to test genotype colonization dynamics and the genetic assemblage of populations. Here, we studied clonal richness of the Daphnia pulex species complex in novel periglacial habitats created by glacial retreat in the Jakobshavn Isbrae area of western Greenland. Along a 10 km transect, we surveyed 73 periglacial habitats out of which 61 were colonized by Daphnia pulex. Hence, for our analysis, we used 21 ponds and 40 lakes in two clusters of habitats differing in age (estimated <50 years vs. >150 years). We tested the expectation that genetic diversity would be low in recently formed (i.e. young), small habitats, but would increase with increasing age and size. We identified a total of 42 genetically distinct clones belonging to two obligately asexual species of the D. pulex species complex: D. middendorffiana and the much more abundant D. pulicaria. While regional clonal richness was high, most clones were rare: 16 clones were restricted to a single habitat and the five most widespread clones accounted for 68% of all individuals sampled. On average, 3·2 clones (range: 1-12) coexisted in a given pond or lake. There was no relationship between clonal richness and habitat size when we controlled for habitat age. Whereas clonal richness was statistically higher in the cluster of older habitats when compared with the cluster of younger ponds and lakes, most young habitats were colonized by multiple genotypes. Our data suggest that newly formed (periglacial) ponds and lakes are colonized within decades by multiple genotypes via multiple colonization events, even in the smallest of our study systems (4 m(2) ). © 2016 The Authors. Journal of Animal Ecology © 2016 British Ecological Society.

  1. Phytoplankton Productivity in an Arctic Fjord (West Greenland): Estimating Electron Requirements for Carbon Fixation and Oxygen Production

    PubMed Central

    Hancke, Kasper; Dalsgaard, Tage; Sejr, Mikael Kristian; Markager, Stiig; Glud, Ronnie Nøhr

    2015-01-01

    Accurate quantification of pelagic primary production is essential for quantifying the marine carbon turnover and the energy supply to the food web. Knowing the electron requirement (Κ) for carbon (C) fixation (ΚC) and oxygen (O2) production (ΚO2), variable fluorescence has the potential to quantify primary production in microalgae, and hereby increasing spatial and temporal resolution of measurements compared to traditional methods. Here we quantify ΚC and ΚO2 through measures of Pulse Amplitude Modulated (PAM) fluorometry, C fixation and O2 production in an Arctic fjord (Godthåbsfjorden, W Greenland). Through short- (2h) and long-term (24h) experiments, rates of electron transfer (ETRPSII), C fixation and/or O2 production were quantified and compared. Absolute rates of ETR were derived by accounting for Photosystem II light absorption and spectral light composition. Two-hour incubations revealed a linear relationship between ETRPSII and gross 14C fixation (R2 = 0.81) during light-limited photosynthesis, giving a ΚC of 7.6 ± 0.6 (mean ± S.E.) mol é (mol C)−1. Diel net rates also demonstrated a linear relationship between ETRPSII and C fixation giving a ΚC of 11.2 ± 1.3 mol é (mol C)−1 (R2 = 0.86). For net O2 production the electron requirement was lower than for net C fixation giving 6.5 ± 0.9 mol é (mol O2)−1 (R2 = 0.94). This, however, still is an electron requirement 1.6 times higher than the theoretical minimum for O2 production [i.e. 4 mol é (mol O2)−1]. The discrepancy is explained by respiratory activity and non-photochemical electron requirements and the variability is discussed. In conclusion, the bio-optical method and derived electron requirement support conversion of ETR to units of C or O2, paving the road for improved spatial and temporal resolution of primary production estimates. PMID:26218096

  2. Phytoplankton Productivity in an Arctic Fjord (West Greenland): Estimating Electron Requirements for Carbon Fixation and Oxygen Production.

    PubMed

    Hancke, Kasper; Dalsgaard, Tage; Sejr, Mikael Kristian; Markager, Stiig; Glud, Ronnie Nøhr

    2015-01-01

    Accurate quantification of pelagic primary production is essential for quantifying the marine carbon turnover and the energy supply to the food web. Knowing the electron requirement (Κ) for carbon (C) fixation (ΚC) and oxygen (O2) production (ΚO2), variable fluorescence has the potential to quantify primary production in microalgae, and hereby increasing spatial and temporal resolution of measurements compared to traditional methods. Here we quantify ΚC and ΚO2 through measures of Pulse Amplitude Modulated (PAM) fluorometry, C fixation and O2 production in an Arctic fjord (Godthåbsfjorden, W Greenland). Through short- (2h) and long-term (24h) experiments, rates of electron transfer (ETRPSII), C fixation and/or O2 production were quantified and compared. Absolute rates of ETR were derived by accounting for Photosystem II light absorption and spectral light composition. Two-hour incubations revealed a linear relationship between ETRPSII and gross 14C fixation (R2 = 0.81) during light-limited photosynthesis, giving a ΚC of 7.6 ± 0.6 (mean ± S.E.) mol é (mol C)-1. Diel net rates also demonstrated a linear relationship between ETRPSII and C fixation giving a ΚC of 11.2 ± 1.3 mol é (mol C)-1 (R2 = 0.86). For net O2 production the electron requirement was lower than for net C fixation giving 6.5 ± 0.9 mol é (mol O2)-1 (R2 = 0.94). This, however, still is an electron requirement 1.6 times higher than the theoretical minimum for O2 production [i.e. 4 mol é (mol O2)-1]. The discrepancy is explained by respiratory activity and non-photochemical electron requirements and the variability is discussed. In conclusion, the bio-optical method and derived electron requirement support conversion of ETR to units of C or O2, paving the road for improved spatial and temporal resolution of primary production estimates.

  3. Evaluation of the use of common sculpin (Myoxocephalus scorpius) organ histology as bioindicator for element exposure in the fjord of the mining area Maarmorilik, West Greenland

    SciTech Connect

    Sonne, Christian; Bach, Lis; Søndergaard, Jens; Rigét, Frank F.; Dietz, Rune; Mosbech, Anders; Leifsson, Pall S.; Gustavson, Kim

    2014-08-15

    The former Black Angel lead–zinc mine in Maarmorilik, West Greenland, is a historic example of how mining activity may result in a significant impact on the surrounding fjord system in terms of elevated concentrations of especially lead (Pb) and zinc (Zn) in seawater, sediments and surrounding biota. In order to shed light on the present contamination and possible effects in the fjord we initiated a range of studies including a pilot study on gill and liver morphology of common sculpins (Myoxocephalus scorpius) around Maarmorilik. Sculpins were caught and sampled at five different stations known to represent a gradient of Pb concentrations. Fish livers from all specimens were analyzed for relevant elements in the area: Fe, Zn, As, Cu, Se, Cd, Pb, Ag, Hg, Co and Ni. Lead, As and Hg showed significant differences among the five stations. For 20% of the sculpins, Hg concentrations were in the range of lowest observed effect dose (LOED) of 0.1–0.5 μg/g ww for toxic threshold on reproduction and subclinical endpoints. Likewise LOEDs for tissue lesions, LOEDs for biochemistry, growth, survival and reproduction were exceeded for Cd (0.42–1.8 μg/g ww) and for As (11.6 μg/g ww) in 28% and 85% of the sculpins, respectively. Similar to this, the no observed effect dose (NOED) for biochemistry was exceeded for Pb (0.32 μg/g ww) and for growth, mortality and reproduction for Zn (60–68 μg/g ww) in 33% and 24% of the sculpins, respectively. For all sculpins, females were significantly larger than males and for five of the elements (Fe, Co, Ni, Cu, Se) females had higher concentrations. The chronic lesions observed in liver (mononuclear cell infiltrates, necrosis, vacuolar hepatocytes, portal fibrosis, bile duct hyperplasia, active melanomacrophage centers) and gills (fusion and edema of secondary lamellae, laminar telangiectasis, mononuclear cell infiltrates, blebs) were similar to those in the literature studies for both wild and laboratory exposed sculpins and

  4. Jökulhlaup (ice-dammed lake outburst flood) impact within a valley-confined sandur subject to backwater conditions, Kangerlussuaq, West Greenland

    NASA Astrophysics Data System (ADS)

    Russell, Andrew J.

    2009-03-01

    This paper examines the controls on the morphology and sedimentology of a valley-confined proglacial outwash plain or 'sandur' in West Greenland subject to glacial outburst floods (jökulhlaups). Jökulhlaup flow conditions observed during a recent (1987) flood are linked to sandur sedimentology and morphological change. Backwater effects over the distal sandur resulted in a reduction of stream power despite increasing discharge. Bar units were typically large. Bar front advance of 60 m during 1987 jökulhlaup occurred prior to waning stage bar dissection by chute channels. Channel change was confined to the distal sandur, due to the greater erodibility of the finer-grained bars. A temporary zone of sediment storage prevailed at the transition between free flowing and ponded flood waters until flood powers increased during waning flood stage as backwater effects were removed. Extension of pre-existing high-relief amplitude bars within the distal sandur records sedimentation related to at least eight jökulhlaups, whilst lower-relief amplitude, proximal sandur sediments provide a composite record of the last high stage jökulhlaup flows. Backwater conditions during jökulhlaups have increased the rapidity of spatial variation of grain sizes and fluvial facies types. Complex, within-event, sediment reworking and routing is generated by the onset and break up of backwater effects. The role of local topography is therefore crucial when interpreting the sedimentary record of former proglacial channels potentially subject to jökulhlaups. This study may prove useful in identifying the presence of flood cycles within palaeo-fluvial systems in both formerly glaciated and non glaciated areas.

  5. Trends of lead and zinc in resident and transplanted Flavocetraria nivalis lichens near a former lead-zinc mine in West Greenland.

    PubMed

    Søndergaard, Jens; Johansen, Poul; Asmund, Gert; Rigét, Frank

    2011-09-01

    This study investigated spatial and temporal trends of lead (Pb) and zinc (Zn) in resident and transplanted Flavocetraria nivalis lichens near the former Black Angel Mine in Maarmorilik, West Greenland. The objectives of the study were to evaluate resident and transplanted lichens for monitoring dust contamination and investigate trends in mine-related dust contamination near the mine. The mine operated between 1973 and 1990 and lichens were regularly sampled between 1986 and 2009. When the mine operated, elevated concentrations of Pb, Zn and other elements were observed in resident lichens up to 35 km from Maarmorilik. In the period after mine closure, Pb and Zn concentrations in resident lichens decreased with 1-11% and 0-6% per year, respectively. From 1996 to 2009, lichens were transplanted into the study area from an uncontaminated site and collected the following year. After 1 year, transplanted lichens showed elevated concentrations of Pb and Zn but contained consistently less Pb and Zn compared to resident lichens (24±23% and 63±37%, respectively). During the most recent sampling in 2009, transplanted lichens still showed significantly elevated Pb concentrations (up to a factor 270) within a distance of 20 km from Maarmorilik. Zinc concentrations were only significantly elevated at sites within 5 km from the mine. Time-series regression analyses showed no significant decreases in Pb and Zn in transplanted lichens at any of the sites during the period 1996-2009. In conclusion, our study showed that resident F. nivalis lichens could not be used to evaluate the recent annual dust contamination in Maarmorilik. Lichen transplants, however, were considered adequate for assessing spatial and temporal trends in Pb and Zn contamination from recently deposited dust. The continuous dispersal of contaminated dust in Maarmorilik almost 20 years after mine closure reveals a slow recovery from mining contamination in this arctic area. Copyright © 2011 Elsevier B.V. All

  6. Photobiology of sea ice algae during initial spring growth in Kangerlussuaq, West Greenland: insights from imaging variable chlorophyll fluorescence of ice cores.

    PubMed

    Hawes, Ian; Lund-Hansen, Lars Chresten; Sorrell, Brian K; Nielsen, Morten Holtegaard; Borzák, Réka; Buss, Inge

    2012-06-01

    We undertook a series of measurements of photophysiological parameters of sea ice algae over 12 days of early spring growth in a West Greenland Fjord, by variable chlorophyll fluorescence imaging. Imaging of the ice-water interface showed the development of ice algae in 0.3-0.4 mm wide brine channels between laminar ice crystals in the lower 4-6 mm of the ice, with a several-fold spatial variation in inferred biomass on cm scales. The maximum quantum yield of photosynthesis, F(v) /F(m), was initially low (~0.1), though this increased rapidly to ~0.5 by day 6. Day 6 also saw the onset of biomass increase, the cessation of ice growth and the time at which brine had reached <50 psu and >-2 °C. We interpret this as indicating that the establishment of stable brine channels at close to ambient salinity was required to trigger photosynthetically active populations. Maximum relative electron transport rate (rETR(max)), saturation irradiance (E(k)) and photosynthetic efficiency (α) had also stabilised by day 6 at 5-6 relative units, ~30 μmol photons m⁻² s⁻¹ and 0.4-0.5 μmol photons m⁻²s⁻¹, respectively. E(k) was consistent with under-ice irradiance, which peaked at a similar value, confirming that daytime irradiance was adequate to facilitate photosynthetic activity throughout the study period. Photosynthetic parameters showed no substantial differences with depth within the ice, nor variation between cores or brine channels suggesting that during this early phase of ice algal growth cells were unaffected by gradients of environmental conditions within the ice. Variable chlorophyll fluorescence imaging offers a tool to determine how this situation may change over time and as brine channels and algal populations evolve.

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

    NASA Astrophysics Data System (ADS)

    Masson-Delmotte, V.; Steen-Larsen, H. C.; Ortega, P.; Swingedouw, D.; Popp, T.; Vinther, B. M.; Oerter, H.; Sveinbjornsdottir, A. E.; Gudlaugsdottir, H.; Box, J. E.; Falourd, S.; Fettweis, X.; Gallée, H.; Garnier, E.; 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.

  8. A 1700 Year Record of Oceanic Influence on Jakobshavn Isbræ calving Activity Based on Marine Sediment Cores from Disko Bay

    NASA Astrophysics Data System (ADS)

    Wangner, D. J.; Andresen, C. S.; Jennings, A. E.; Knudsen, M. F.; Vermassen, F.; Dyke, L. M.; Kjaer, K. H.; Kokfelt, U.

    2016-12-01

    The Greenland Ice Sheet has experienced significant mass loss in recent years. A substantial component of this is attributable to the retreat of marine-terminating outlet glaciers; these lost mass through increased calving and meltwater discharge. Jakobshavn Isbræ is the most productive marine-terminating glacier in Greenland, yet relatively little is known about its history. Instrumental observations of local climatic conditions only cover the last 140 years. Similarly, reliable observations of glacier changes are mainly limited to the past 40 years. Consequently, assessing the importance of recent glaciological changes is challenging. Three marine sediment cores were collected from locations near the mouth of Jakobshavn Isfjord in Disko Bay. These cores were analyzed to reconstruct changes in glacier behavior in response to past climatic and oceanographic changes; this provides context against which to assess the significance of recent changes. The sediments deposited at this site reflect oceanographic and climatic changes as well as ice discharge from Jakobshavn Isbræ. Preliminary radiocarbon dating of plant material indicates that the cores cover a time span of 1700 years. High-resolution grain size analyses, X-Ray, XRF, and magnetic susceptibility measurements show a clear change in the sedimentation regime and a distinct decrease in ice-rafted debris (IRD) at around 80 cm sediment depth. Additional dating will constrain the timing of this sedimentation change, but we tentatively date it to sometime between 500 and 900 years ago. Interestingly, we also note a marked multi-decadal variability in the proxy glacier calving record. Further analyses of grain size and additional proxies like foraminifera assemblage and biomarkers will allow us to link changes in the sedimentation regime to climatic and/or oceanographic changes.

  9. New Perspectives on Long Run-out Rock Avalanches: A Dynamic Analysis of 20 Events in the Vaigat Strait, West Greenland

    NASA Astrophysics Data System (ADS)

    Benjamin, J.; Rosser, N. J.; Dunning, S.; Hardy, R. J.; Karim, K.; Szczucinski, W.; Norman, E. C.; Strzelecki, M.; Drewniak, M.

    2014-12-01

    Risk assessments of the threat posed by rock avalanches rely upon numerical modelling of potential run-out and spreading, and are contingent upon a thorough understanding of the flow dynamics inferred from deposits left by previous events. Few records exist of multiple rock avalanches with boundary conditions sufficiently consistent to develop a set of more generalised rules for behaviour across events. A unique cluster of 20 large (3 x 106 - 94 x 106 m3) rock avalanche deposits along the Vaigat Strait, West Greenland, offers a unique opportunity to model a large sample of adjacent events sourced from a stretch of coastal mountains of relatively uniform geology and structure. Our simulations of these events were performed using VolcFlow, a geophysical mass flow code developed to simulate volcanic debris avalanches. Rheological calibration of the model was performed using a well-constrained event at Paatuut (AD 2000). The best-fit simulation assumes a constant retarding stress with a collisional stress coefficient (T0 = 250 kPa, ξ = 0.01), and simulates run-out to within ±0.3% of that observed. Despite being widely used to simulate rock avalanche propagation, other models, that assume either a Coulomb frictional or a Voellmy rheology, failed to reproduce the observed event characteristics and deposit distribution at Paatuut. We applied this calibration to 19 other events, simulating rock avalanche motion across 3D terrain of varying levels of complexity. Our findings illustrate the utility and sensitivity of modelling a single rock avalanche satisfactorily as a function of rheology, alongside the validity of applying the same parameters elsewhere, even within similar boundary conditions. VolcFlow can plausibly account for the observed morphology of a series of deposits emplaced by events of different types, although its performance is sensitive to a range of topographic and geometric factors. These exercises show encouraging results in the model's ability to

  10. Spatial variation in energy exchange across coastal environments in Greenland

    NASA Astrophysics Data System (ADS)

    Lund, M.; Abermann, J.; Citterio, M.; Hansen, B. U.; Larsen, S. H.; Stiegler, C.; Sørensen, L. L.; van As, D.

    2015-12-01

    The surface energy partitioning in Arctic terrestrial and marine areas is a crucial process, regulating snow, glacier ice and sea ice melt, and permafrost thaw, as well as modulating Earth's climate on both local, regional, and eventually, global scales. The Arctic region has warmed approximately twice as much as the global average, due to a number of feedback mechanisms related to energy partitioning, most importantly the snow and ice-albedo feedback. However, direct measurements of surface energy budgets in the Arctic are scarce, especially for the cold and dark winter period and over transects going from the ice sheet and glaciers to the sea. This study aims to describe annual cycles of the surface energy budget from various surface types in Arctic Greenland; e.g. glacier, snow, wet and dry tundra and sea ice, based on data from a number of measurement locations across coastal Greenland related to the Greenland Ecosystem Monitoring (GEM) program, including Station Nord/Kronprins Christians Land, Zackenberg/Daneborg, Disko, Qaanaq, Nuuk/Kobbefjord and Upernaviarsuk. Based on the available time series, we will analyze the sensitivity of the energy balance partitioning to variations in meteorological conditions (temperature, cloudiness, precipitation). Such analysis would allow for a quantification of the spatial variation in the energy exchange in aforementioned Arctic environments. Furthermore, this study will identify uncertainties and knowledge gaps in Arctic energy budgets and related climate feedback effects.

  11. In-situ Measurements of Sedimentary Graphites and Sulfides in Early Archean (>3.7 Ga) Banded Iron-Formations from West Greenland: Biological and Atmospheric Influences

    NASA Astrophysics Data System (ADS)

    Mojzsis, S. J.

    2001-05-01

    might atmospheric and biological evolutionary links be evaluated by studying the carbon and sulfur isotope compositions of ancient sediments? New data reveal well-resolved non-mass-dependent Δ 33S anomalies in an early Archean [3.77-3.83 Ga] banded iron-formation and a metapelite from West Greenland [total range in Δ 33S=+1.10+/-0.07‰ to +1.23+/-0.05‰ , 2σ ] previously analyzed for carbon isotopes. Data from sulfides in a diverse collection of stromatolithic cherts, banded iron-formation and shales of Proterozoic to late Archean age [1.8-3.2 Ga] displayed only mass-dependent [Δ 33S ~0‰ ] sulfur isotope relationships within the precision of the measurements [typically +/-0.06‰ , 2σ ]. Results reveal that non-mass-dependent sulfur isotope anomalies [i.e. Δ 33S>0] are preserved in sulfide phases contained in the oldest known rocks of sedimentary origin. That these rocks contain a record of gas-phase reactions in an early atmosphere would support the interpretation that atmospheric partial pressures of oxygen were low and the effects of UV-photolysis on atmospheric sulfur from a UV-active young Sun were widespread and commonplace on the Archean Earth. This might also be reflected in the long-term [billion-year timescale] changes to the isotope composition of bioorganic carbon. Further studies warrant coupling sulfur, carbon [and nitrogen] measurements in ancient sediments to explore this relationship.

  12. Evaluation of the use of common sculpin (Myoxocephalus scorpius) organ histology as bioindicator for element exposure in the fjord of the mining area Maarmorilik, West Greenland.

    PubMed

    Sonne, Christian; Bach, Lis; Søndergaard, Jens; Rigét, Frank F; Dietz, Rune; Mosbech, Anders; Leifsson, Pall S; Gustavson, Kim

    2014-08-01

    The former Black Angel lead-zinc mine in Maarmorilik, West Greenland, is a historic example of how mining activity may result in a significant impact on the surrounding fjord system in terms of elevated concentrations of especially lead (Pb) and zinc (Zn) in seawater, sediments and surrounding biota. In order to shed light on the present contamination and possible effects in the fjord we initiated a range of studies including a pilot study on gill and liver morphology of common sculpins (Myoxocephalus scorpius) around Maarmorilik. Sculpins were caught and sampled at five different stations known to represent a gradient of Pb concentrations. Fish livers from all specimens were analyzed for relevant elements in the area: Fe, Zn, As, Cu, Se, Cd, Pb, Ag, Hg, Co and Ni. Lead, As and Hg showed significant differences among the five stations. For 20% of the sculpins, Hg concentrations were in the range of lowest observed effect dose (LOED) of 0.1-0.5 μg/g ww for toxic threshold on reproduction and subclinical endpoints. Likewise LOEDs for tissue lesions, LOEDs for biochemistry, growth, survival and reproduction were exceeded for Cd (0.42-1.8 μg/g ww) and for As (11.6 μg/g ww) in 28% and 85% of the sculpins, respectively. Similar to this, the no observed effect dose (NOED) for biochemistry was exceeded for Pb (0.32 μg/g ww) and for growth, mortality and reproduction for Zn (60-68 μg/g ww) in 33% and 24% of the sculpins, respectively. For all sculpins, females were significantly larger than males and for five of the elements (Fe, Co, Ni, Cu, Se) females had higher concentrations. The chronic lesions observed in liver (mononuclear cell infiltrates, necrosis, vacuolar hepatocytes, portal fibrosis, bile duct hyperplasia, active melanomacrophage centers) and gills (fusion and edema of secondary lamellae, laminar telangiectasis, mononuclear cell infiltrates, blebs) were similar to those in the literature studies for both wild and laboratory exposed sculpins and other fish

  13. Karrat REE mineralization on Niaqornakavsak and extension on Umiamako Nuna, West Greenland: mineralogic, geochronologic, and carbon and oxygen isotope constraints on the origin

    NASA Astrophysics Data System (ADS)

    Mott, A.; Bird, D. K.; Grove, M.; Bernstein, S.; Mackay, H.; Rose, N.

    2011-12-01

    The Karrat rare earth element (REE) mineralization is located in the Niaqornakavsak (NIAQ) area of Qeqertarssuaq Island in Greenland (~72°N). A mineralized horizon occurs as a single distinct layer (35-40° dip) within an amphibolite host rock of the Qeqertarssuaq Formation: a member of the Paleoproterozoic Karrat Group sequence. Average Yttrium + REE-oxide (YREEO) concentration is ~1.0 wt. % with concentrations up to 2.59 wt. % over one meter intervals. Eight drill holes across three locations on NIAQ allow for an estimated true thickness of REE enrichment (YREEO ≥ 0.2 wt. %) of 29-38m in the east and central area, and a fault restricted thickness at the site in the west of 16m (at surface) to 28m (at depth). Two distinct metasomatic reaction zones comprise the mineralized horizon and are universal across NIAQ: the upper unit (CCA ~1.5 %YREEO) has a primary mineralogy of calcite + ankerite + fluorite (>50%), grunerite, cummingtonite, magnetite, fergusonite, bastnasite, allanite, and monazite, while the lower unit (BLC) consists of biotite (>50%), calcite, ilmenite, magnetite, allanite, fergusonite, and monazite. An extension of the Karrat REE deposit outcrops 7 km to the east on Umiamako Nuna. Hand samples from Umiamako Nuna similar to CCA (YREEO up to 2.4 wt. %) have been collected, but two exploratory drill holes revealed the majority of the REE enriched zone is comparable to the mineralogy of the incomplete reaction zone around CCA on NIAQ with concentrations of YREEO ranging from 0.5-1.0 wt. % with an estimated thickness of 15m. The mineralization consists of Ca-amphiboles, biotite, calcite, pyrite, albite, and garnet. Enrichment of REE continues to a depth of 60m from vein mineralization. In addition, a secondary occurrence at depth can be found on Umiamako Nuna tens of meters below the primary mineralized horizon, which is characterized by high modal concentrations of calcite, fluorite, and amphiboles. Carbon and oxygen isotope analyses of 145 carbonate

  14. Geodetic long-term studies (1991-2011) in ice dynamics and in mass balance in the Paakitsoq area (West Greenland)

    NASA Astrophysics Data System (ADS)

    Stober, M.; Rawiel, P.; Hepperle, J.

    2012-12-01

    Ice flow velocity, deformation, elevation change and mass balance are essential properties required for modeling ice sheets and correlation with climate change. Since 1991 until 2011 now 11 campaigns had been carried out in order to study ice flow velocity, surface deformation and elevation change respectively mass balance of the inland ice in the Paakitsoq area, West Greenland. It is a long-term project with terrestrial GPS observations of stake networks in two research areas. One area is situated at the Swiss-Camp in an altitude of 1170 m, where the former position of the equilibrium line was supposed. The second research area, called ST2, is located in the flow line in an altitude of 1000 m, and situated close to the automatic weather station JAR1 of the GC-Net. The ST2 network was established in 2004. In 2004, 2005, 2006, 2008 and 2011 here now 5 campaigns have been performed. The results in elevation change very clearly show the increased lowering of the ice surface. At Swiss-Camp we started in the period 1991 until 2002 with -0.25 m/year, in 2002 - 2006 with -0.60 m/year and in 2006 - 2011 with -1.10 m/year. At ST2 in 2004 - 2006 we find a lowering of -0.34 m/year and in 2006 - 2011 of -1.31 m/year. The elevation decrease is directly correlated with altitude. In general, the recent ice thickness loss is more than three times greater than the long-term trend in former years. The elevation changes are converted into mass balance results between the measuring dates. They are compared to meteorological parameters with data from the AWS of the GC-net. Elevation changes are also derived by digital terrain models from the research areas. It is shown that systematic local height change anomalies occur in all years indicating local variations of melting, probably caused by albedo variations. From the horizontal deformation of the stake network the local horizontal strain rates were derived. In connection with the incompressibility condition of ice, the vertical strain

  15. Measuring bioavailable metals using diffusive gradients in thin films (DGT) and transplanted seaweed (Fucus vesiculosus), blue mussels (Mytilus edulis) and sea snails (Littorina saxatilis) suspended from monitoring buoys near a former lead-zinc mine in West Greenland.

    PubMed

    Søndergaard, Jens; Bach, Lis; Gustavson, Kim

    2014-01-15

    Measuring loads of bioavailable metals is important for environmental assessment near mines and other industrial sources. In this study, a setup of monitoring buoys was tested to assess loads of bioavailable metals near a former Pb-Zn mine in West Greenland using transplanted seaweed, mussels and sea snails. In addition, passive DGT samplers were installed. After a 9-day deployment period, concentrations of especially Pb, Zn and Fe in the species were all markedly elevated at the monitoring sites closest to the mine. Lead concentrations in all three species and the DGT-Pb results showed a significant linear correlation. Zinc and Fe concentrations were less correlated indicating that the mechanisms for Zn and Fe accumulation in the three species are more complex. The results show that there is still a significant load of metals from the mine and that such buoys can be an adequate method to assess present loads of bioavailable metals.

  16. 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.

  17. 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

  18. From Arctic greenhouse to icehouse: the Cenozoic development of the West Greenland-Baffin Bay margin and the case for scientific drilling

    NASA Astrophysics Data System (ADS)

    Knutz, Paul; Gregersen, Ulrik; Hopper, John R.; Dybkjær, Karen; Nøhr-Hansen, Henrik; Sheldon, Emma; Huuse, Mads

    2016-04-01

    The long-term evolution of glaciated margins plays an essential role in understanding the driving forces and interactions that determine the build-up and decay of ice sheets. The Greenland continental margin towards Baffin Bay is densely covered by industry seismic data and several exploration wells have been drilled, providing a regional stratigraphic framework for the sedimentary successions. This presentation provides an overview of the major depositional units and stratigraphy of the mid-late Cenozoic (since mid-Eocene), with examples demonstrating the different processes that have formed this margin. A sedimentary succession up to 3.5 km thick, of mid-Eocene to mid-Miocene age (mega-unit D), infills the pronounced ridge-basin structures of the rifted and tectonically inverted margin. The lower part of this interval, presumably late Eocene-Oligocene in age, is interpreted as basin-floor fan deposits, while the upper section, of early-middle Miocene age, is mainly marine mudstone. The basin infilling strata are overlain by a late Miocene-Pliocene succession consisting of two mega-units (B and C), with typical thicknesses of 0.5-1 km. The units are characterised by upslope-climbing sediment waves and along-slope trending sedimentary prisms reminiscent of giant contourite drifts. The borehole data associates the prism accumulations with a deep shelf environment influenced by strong marine currents and nearby fluvial sources. On the slope and in the deep basin of Baffin Bay the late Neogene succession is strongly influenced by mass wasting correlated with erosional scars updip. The uppermost seismic mega-unit (A) is dominated by aggradational wedges and prograding fan deposits displaying depocentres >3 km thick, formed at the terminus of palaeo-ice streams. Borehole information associates this interval with deposition of primarily diamict sediments and suggests a late Pliocene onset of major shelf based glaciations on the NW Greenland margin. The southwest margin

  19. Climate Change and Baleen Whale Trophic Cascades in Greenland

    DTIC Science & Technology

    2008-01-01

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

  20. Selenium status in Greenland Inuit.

    PubMed

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

    2004-09-20

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

  1. Intra- and Inter-Seasonal Supra-glacial Water Variability over the West Greenland Ice Sheet as Estimated from Combining High Resolution Satellite Optical Data and a Digital Elevation Model

    NASA Astrophysics Data System (ADS)

    Brown, M. G.; Tedesco, M.; Smith, L. C.; Rennermalm, A. K.; Yang, K.

    2015-12-01

    The supra-glacial hydrology of the Greenland Ice Sheet (GrIS) plays a crucial role on the surface energy and mass balance budgets of the ice sheet as a whole. The surface hydrology network variability of small streams in the ablation zone of Greenland is poorly understood both spatially and temporally. Using satellites that can spatially resolve the presence and associated properties of small streams, the scientific community is now able to be provided with accurate spatial and temporal analysis of surface hydrology on the ice sheet (that could not have been resolved with other sensors such as those on board MODIS or LANDSAT). In this study we report mapped supra-glacial water networks over a region of the West GrIS (approximately 164 km2) derived from high resolution multispectral satellite imagery from the Quickbird and WorldView - 2 satellites in tandem with a 2 meter stereographic SETSM DEM (digital elevation model). The branching complexity of the identified surface streams is computed from the available DEM as well as the intra- and inter seasonal changes observed in the hydrological system. The stream networks created during the melt season (at several different stages of melting) are compared and discussed as well as the networks mapped between consecutive years for proximate dates. Also, depth and volume estimations for the surface water features identified were extracted via band math algorithms, threshold classifications, and morphological operations. Our results indicate that the higher stream orders have the largest amount of stored surface water per km but the lower stream orders, specifically 1st order with widths of ~ 2 meters, hold more stored surface water overall. We also employ and compare runoff data from the numerical model MAR (Modèle Atmosphérique Régional) to the estimations found using imagery and the DEM.

  2. Seawater-like trace element signatures (REE + Y) of Eoarchaean chemical sedimentary rocks from southern West Greenland, and their corruption during high-grade metamorphism

    NASA Astrophysics Data System (ADS)

    Friend, C. R. L.; Nutman, A. P.; Bennett, V. C.; Norman, M. D.

    2008-02-01

    Modern chemical sediments display a distinctive rare earth element + yttrium (REE + Y) pattern involving depleted LREE, positive La/La*SN, Eu/Eu*SN, and YSN anomalies (SN = shale normalised) that is related to precipitation from circumneutral to high pH waters with solution complexation of the REEs dominated by carbonate ions. This is often interpreted as reflecting precipitation from surface waters (usually marine). The oldest broadly accepted chemical sediments are c. 3,700 Ma amphibolite facies banded iron-formation (BIF) units in the Isua supracrustal belt, Greenland. Isua BIFs, including the BIF international reference material IF-G are generally considered to be seawater precipitates, and display these REE + Y patterns (Bolhar et al. in Earth Planet Sci Lett 222:43 60, 2004). Greenland Eoarchaean BIF metamorphosed up to granulite facies from several localities in the vicinity of Akilia (island), display REE + Y patterns identical to Isua BIF, consistent with an origin by chemical sedimentation from seawater and a paucity of clastic input. Furthermore, the much-debated magnetite-bearing siliceous unit of “earliest life” rocks (sample G91/26) from Akilia has the same REE + Y pattern. This suggests that sample G91/26 is also a chemical sediment, contrary to previous assertions (Bolhar et al. in Earth Planet Sci Lett 222:43 60, 2004), and including suggestions that the Akilia unit containing G91/26 consists entirely of silica-penetrated, metasomatised, mafic rock (Fedo and Whitehouse 2002a). Integration of our trace element data with those of Bolhar et al. (Earth Planet Sci Lett 222:43 60, 2004) demonstrates that Eoarchaean siliceous rocks in Greenland, with ages from 3.6 to 3.85 Ga, have diverse trace element signatures. There are now geographically-dispersed, widespread examples with Isua BIF-like REE + Y signatures, that are interpreted as chemically unaltered, albeit metamorphosed, chemical sediments. Other samples retain remnants of LREE depletion but

  3. The impact of calving front retreat on Jakobshavn Isbræ, West Greenland , using a 3D thermodynamically coupled numerical model

    NASA Astrophysics Data System (ADS)

    Bondzio, J. H.; Seroussi, H. L.; Morlighem, M.; Kleiner, T.; Rückamp, M.; Larour, E. Y.; Humbert, A.

    2016-12-01

    Jakobshavn Isbræ is a major marine terminating outlet glacier of the Greenland Ice Sheet. Since the breakup of its floating ice tongue in the late 1990's, the glacier has been thinning, accelerating and its calving front has been retreating by about 20 km. It is currently a major contributor to global sea level rise. Understanding the processes involved in and driving these changes is important to improve the predictive skills of numerical models and improve estimates of future dynamic ice discharge of the Greenland Ice Sheet. However, the limited amount of observations when the glacier underwent these strong changes does not allow us to fully understand the interplay and significance of the processes involved. Numerical modelling can be used to improve our understanding, but ice flow model studies so far suffered from lacking technical capabilities, poorly constrained input data sets and insufficient computational resources. Here, we use the Ice Sheet System Model (ISSM) to perform, for the first time, a high-resolution, 3D thermodynamically coupled model study of Jakobshavn Isbræ with a dynamically evolving ice front. We perform several sensitivity studies by analyzing the influence of submarine melt, calving and thermal regime on the glacier's thermodynamics to determine the processes that control the response of the glacier to climate change. We find that increased submarine melt significantly contributed to the initial speed-up of the glacier, but that today's flow regime is almost entirely controlled by it's calving front position, which agrees well with observations. The glacier's acceleration causes a substantial increase in internal and basal friction, which increases subglacial melt rates. Sustained higher submarine discharge might increase undercutting of the calving front through melt, leading to higher calving rates even in case of a glacier slow down, creating a potential positive feedback.

  4. 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

  5. The Subglacial Access and Fast Ice Research Experiment (SAFIRE): 2. Preliminary outcomes from hot-water drilling and borehole instrumentation on Store Glacier, West Greenland

    NASA Astrophysics Data System (ADS)

    Doyle, Samuel; Hubbard, Bryn; Christoffersen, Poul; Young, Tun Jan; Hofstede, Coen; Todd, Joe; Bougamont, Marion; Hubbard, Alun

    2015-04-01

    As part of the SAFIRE research programme, pressurised hot water was used to drill four 603-616 m-long boreholes to the bed of the Greenland Ice Sheet at a site located 30 km from the calving front of marine-terminating Store Glacier (70° N, ~1000 m elevation). Despite the boreholes freezing within hours, 4 wired sensor strings were successfully deployed in three of the boreholes. These included a thermistor string to obtain the englacial temperature profile installed in the same borehole as a string of tilt sensors to measure borehole deformation, and two sets of water pressure, electrical conductivity and turbidity sensors installed just above the bed in separate, adjacent boreholes. The boreholes made a strong hydrological connection to the bed during drilling, draining rapidly to ~80 m below the ice surface. The connection of subsequent boreholes was observed as a perturbation in water pressure and temperature recorded in neighbouring boreholes, indicating an effective hydrological sub- or en-glacial connection between them. The short (week long) records obtained from these sensors in summer 2014 tentatively reveal (i) water pressure varying diurnally close to overburden albeit of a small magnitude (~0.3 m H2O), (ii) a minimum extrapolated englacial temperature of -21° C, (iii) and thermistors in the lowest 10 m of the borehole recorded temperatures above the pressure melting point indicating the presence of water. Data loggers were left running and longer records should become available in the near future. Differential drilling and instrument installation depths together with observations of discrete, diurnal turbidity events provisionally suggest the presence of sediment at the bed. These preliminary borehole observations will be complemented by GPS measurements of ice motion, meteorological data, and seismic and radar surveys to be undertaken over the next two years.

  6. 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.

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

    PubMed

    Rignot, Eric; Kanagaratnam, Pannir

    2006-02-17

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

  8. First record of Taenia ovis krabbei muscle cysts in muskoxen from Greenland.

    PubMed

    Raundrup, Katrine; Al-Sabi, Mohammad Nafi Solaiman; Kapel, Christian Moliin Outzen

    2012-03-23

    A first record of Taenia ovis krabbei muscle cysts in a muskoxen (Ovibos moschatus) from the Kangerlussuaq population in West Greenland suggests that introduced muskoxen now contributes to the transmission of this parasite in addition to previous observations from caribou (Rangifer tarandus). Muskoxen and caribou are the only wild ungulates in Greenland.

  9. Provenance of Greenland Ice Sheet icebergs constrained by Ar-Ar radioisotope data from late glacial-early Holocene records

    NASA Astrophysics Data System (ADS)

    Knutz, P. C.; Storey, M.; Kuijpers, A.

    2009-12-01

    Radiogenic Ar-Ar dating of hornblende has been used to constrain the sources of ice-rafted detritus on the southwest Greenland margin and central Davis Strait. Single hornblende grains (total of 248) were picked from sand-size fractions of two marine cores, DA04-31P and TTR462G, covering the early Holocene to late glacial interval including Heinrich events (HE) 1-3. Paleoceanographic analyses of DA04-31P have indicated that the last deglaciation of the southern Greenland Ice Sheet occurred in multiple steps during the early deglacial/HE1, Allerød and early Holocene intervals (Knutz et al., in review). Each of these collapse stages were preceded by upper ocean warming related to enhanced Irminger Current activity. Pre-HE1, Allerød and Holocene hornblende samples show a bimodal signature of late Archean (2.5-3.0 Ga) and early Proterozoic (1.6-2.2 Ga) ages consistent with southern Greenland bedrock sources. In contrast hornblende grains from detrital carbonate HE layers and within the Younger Dryas interval show a dominant early Proterozoic spectrum that is similar to results obtained from the central North Atlantic IRD belt. The early Proterozoic age of Younger Dryas samples from the Davis Strait site and the high amounts of basalt in this core, presumably derived from the Disko-Nussuaq province, suggests that icebergs carrying Archean material from southern Greenland did not enter the Baffin Bay or at least not for this specific time interval. The conclusion of our study is that the Greenland Ice Sheet appears to have been a much larger contributor to non-Heinrich IRD in the North Atlantic than thought previously. P. C. Knutz, H. Ebbesen, S. Christiansen, M.-A. Sicre and A. Kuijpers. Multiple deglaciation steps of the southern Greenland Ice Sheet driven by vigorous Irminger Current: Significance for the Younger Dryas cooling. Submitted to Quaternary Science Reviews.

  10. 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

  11. 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.

  12. Pronounced Warming of the Greenland Ice Sheet

    NASA Astrophysics Data System (ADS)

    Polashenski, C.; Courville, Z.; Benson, C. S.; Wong, G. J.; Hawley, R. L.; Hall, D. K.; Chen, J.

    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, conducted a 4000 km snowmobile traverse across northwest Greenland. One aspect of this study collected field measurements of borehole temperatures across the northern Greenland ice sheet. Sites first measured by Benson in 1953-1955 are re-visited, showing long term trends in ice sheet temperature. Results indicate a pattern of dramatic warming (up to +5-6 C) at mid-level elevations (1400-2500 m) and little temperature change or perhaps slight cooling at high elevations (>2500 m). Compared to coastal West Greenland stations and Arctic-wide temperature reconstructions, which indicate warming trends of 1-1.5 C over the intervening 58-60 years, both results are surprising. Several mechanisms are explored which may account for the rapid warming of mid-altitude ice sheet, including albedo changes and elevated heat transport into the ice due to percolation. The observed ice warming, increasing ice temperature faster than air temperature changes, has serious implications, potentially driving melt facies up the ice sheet faster than would otherwise be expected and priming the ice sheet for greater runoff production.

  13. Greenland Ice Flow

    NASA Image and Video Library

    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...

  14. SeaWinds - Greenland

    NASA Image and Video Library

    2000-05-08

    The frequent coverage provided by NASA SeaWinds instrument on the QuikScat satellite in 1999 provided unprecedented capability to monitor daily and seasonal changes in the key melt zones of Greenland.

  15. Flying Low over Southeast Greenland

    NASA Image and Video Library

    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 ...

  16. Greenland Ice Sheet Mass Balance

    NASA Technical Reports Server (NTRS)

    Reeh, N.

    1984-01-01

    Mass balance equation for glaciers; areal distribution and ice volumes; estimates of actual mass balance; loss by calving of icebergs; hydrological budget for Greenland; and temporal variations of Greenland mass balance are examined.

  17. Hydrothermal-metasomatic and tectono-metamorphic processes in the Isua supracrustal belt (West Greenland): a multi-isotopic investigation of their effects on the earth's oldest oceanic crustal sequence

    NASA Astrophysics Data System (ADS)

    Frei, Robert; Rosing, Minik T.; Waight, Tod E.; Ulfbeck, David G.

    2002-02-01

    Despite superimposed metamorphic overprinting and metasomatic alterations, primary volcanic features remain preserved in low-strain domains of mafic volcanic sequences in the western Isua supracrustal belt (ISB, West Greenland). These basaltic successions represent the hitherto oldest known fragments of oceanic crust on Earth. Early Archean metasomatic fluids, rich in light rare earth elements (LREE), Th, U, Pb, Ba, and alkalies, invaded the supracrustal package and distinctively altered the basaltic sequences. Field relationships, source characteristics traced by Pb isotopes, and geochronological results provide indications that these fluids were genetically related to the emplacement of tonalite sheets into the ISB between 3.81 and 3.74 Ga ago. Subsequent early Archean metamorphism homogenized the mixed primary and metasomatic mineral parageneses of these metavolcanic rocks. Allanite occurs as the most characteristic and critical secondary metasomatic-metamorphic phase and is developed in macroscopically discernible zones of increased metsomatic alteration, even in domains of low strain. Because of its high concentration of LREE, Th, and U, this secondary mineral accounts for much of the disturbances recorded by the Sm-Nd and Th-U-Pb isotope systematics of the pillowed metabasalts. The supracrustal sequences were tectono-metamorphically affected to varying degrees during a late Archean, ˜2.6- to 2.8-Ga-old event, also recognized in the adjacent gneiss terranes of the Isuakasia area. The degree to which bulk rocks were isotopically reequilibrated is directly dependent on the different relative contributions of allanite-hosted parent-daughter elements to the overall whole-rock mass budget of the respective isotope systems. Although low-strained (initially only weakly metasomatized) pillow basalts remained more or less closed with respect to the U-Pb and Rb-Sr systems since ˜3.74 Ga, the Sm-Nd system appears to have been partially opened on a whole-rock scale

  18. Constraints on mantle evolution from 187Os/ 188Os isotopic compositions of Archean ultramafic rocks from southern West Greenland (3.8 Ga) and Western Australia (3.46 Ga)

    NASA Astrophysics Data System (ADS)

    Bennett, Victoria C.; Nutman, Allen P.; Esat, Tezer M.

    2002-07-01

    Initial 187Os/ 188Os isotopic compositions for geochronologically and geologically well -constrained 3.8-Ga spinel peridotites from the Itsaq Gneiss Complex of southern West Greenland and chromite separates from 3.46-Ga komatiites from the Pilbara region of Western Australia have been determined to investigate the osmium isotopic evolution of the early terrestrial mantle. The measured compositions of 187Os/ 188Os(0) = 0.10262 ± 2, from an olivine separate, and 0.10329 ± 3, for a spinel separate from ˜3.8-Ga peridotite G93/42, are the lowest yet reported from any terrestrial sample. The corrections for in situ decay over 3.8 Ga for these low Re/Os phases are minimal and change the isotopic compositions by only 0.5 and 2.2% for the spinel and the olivine, respectively, resulting in 187Os/ 188Os (3.8 Ga) = 0.1021 ± 0.0002 and 0.1009 ± 0.0002, respectively. These data extend direct measurement of Os isotopic compositions to much earlier periods of Earth history than previously documented and provide the best constraints on the Os isotopic composition of the early Archean terrestrial mantle. Analyses of Pilbara chromites yield 3.46-Ga mantle compositions of 0.1042 ± 0.0002 and 0.1051 ± 0.0002. These new data, combined with published initial Os isotopic compositions from late Archean and early Proterozoic samples, are compatible with the mantle, or at least portions of it, evolving from a solar system initially defined by meteorites to a modern composition of 187Os/ 188Os(0) = 0.1296 ± 0.0008 as previously suggested from peridotite xenolith data ( Meisel et al., 2001); the associated 187Re/ 188Os(0) = 0.435 ± 0.005. Thus, chondritic 187Os/ 188Os compositions were a feature of the upper mantle for at least 3.8 billion years, requiring chondritic Re/Os ratios to have been a characteristic of the very early terrestrial mantle. In contrast, nonchondritic initial compositions of some Archean komatiites demonstrate that Os isotopic heterogeneity is an ancient feature

  19. Substantial contribution to sea-level rise during the last interglacial from the Greenland ice sheet

    PubMed

    Cuffey; Marshall

    2000-04-06

    During the last interglacial period (the Eemian), global sea level was at least three metres, and probably more than five metres, higher than at present. Complete melting of either the West Antarctic ice sheet or the Greenland ice sheet would today raise sea levels by 6-7 metres. But the high sea levels during the last interglacial period have been proposed to result mainly from disintegration of the West Antarctic ice sheet, with model studies attributing only 1-2 m of sea-level rise to meltwater from Greenland. This result was considered consistent with ice core evidence, although earlier work had suggested a much reduced Greenland ice sheet during the last interglacial period. Here we reconsider the Eemian evolution of the Greenland ice sheet by combining numerical modelling with insights obtained from recent central Greenland ice-core analyses. Our results suggest that the Greenland ice sheet was considerably smaller and steeper during the Eemian, and plausibly contributed 4-5.5 m to the sea-level highstand during that period. We conclude that the high sea level during the last interglacial period most probably included a large contribution from Greenland meltwater and therefore should not be interpreted as evidence for a significant reduction of the West Antarctic ice sheet.

  20. Nature and tourism in Greenland

    Treesearch

    Berit C. Kaae

    2002-01-01

    This paper provides a short summary on the development of tourism in Greenland, the cultural context, and the protection of the nature resources on which tourism heavily depends. Existing research projects related to tourism in Greenland and the focus of these projects are briefly summarized. In general, most research in Greenland focuses on natural resources, but...

  1. 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.

  2. greenland_summer_campaign

    NASA Image and Video Library

    2015-08-28

    Laurence Smith, chair of geography at University of California, Los Angeles, deploys an autonomous drift boat equipped with several sensors in a meltwater river on the surface of the Greenland ice sheet on July 19, 2015. “Surface melting in Greenland has increased recently, and we lacked a rigorous estimate of the water volumes being produced and their transport,” said Tom Wagner, the cryosphere program scientist at NASA Headquarters in Washington. “NASA funds fieldwork like Smith’s because it helps us to interpret satellite data, and to extrapolate measurements from the local field sites to the larger ice sheet." Credit: NASA/Goddard/Jefferson Beck

  3. Southern tip of Greenland

    NASA Technical Reports Server (NTRS)

    2002-01-01

    Between the Arctic Ocean to the North and the Atlantic to the South, the island of Greenland remains covered in snow and ice throughout the year except for small portions of the coast line that thaw briefly in the summer. This true-color image from November 2, 2001, shows that even the southern tip of Greenland is back to winter, with even the rugged coastline snow-covered once again. About halfway up the western coastline, a phytoplankton bloom is occurring in the Davis Strait, coloring the water blue-green.

  4. Digital Elevation Models of Greenland based on combined radar and laser altimetry as well as high-resolution stereoscopic imagery

    NASA Astrophysics Data System (ADS)

    Levinsen, J. F.; Smith, B. E.; Sandberg Sorensen, L.; Khvorostovsky, K.; Simonsen, S. B.; Forsberg, R.

    2015-12-01

    A number of Digital Elevation Models (DEMs) of Greenland exist, each of which are applicable for different purposes. This study presents two such DEMs: One developed by merging contemporary radar and laser altimeter data, and one derived from high-resolution stereoscopic imagery. All products are made freely available. The former DEM covers the entire Greenland. It is specific to the year 2010, providing it with an advantage over previous models suffering from either a reduced spatial/ temporal data coverage or errors from surface elevation changes (SEC) occurring during data acquisition. Radar data are acquired with Envisat and CryoSat-2, and laser data with the Ice, Cloud, and land Elevation Satellite, the Land, Vegetation, and Ice Sensor, and the Airborne Topographic Mapper. Correcting radar data for errors from slope effects and surface penetration of the echoes, and merging these with laser data, yields a DEM capable of resolving both surface depressions as well as topographic features at higher altitudes. The spatial resolution is 2 x 2 km, making the DEM ideal for application in surface mass balance studies, SEC detection from radar altimetry, or for correcting such data for slope-induced errors. The other DEM is developed in a pilot study building the expertise to map all ice-free parts of Greenland. The work combines WorldView-2 and -3 as well as GeoEye1 imagery from 2014 and 2015 over the Disko, Narsaq, Tassilaq, and Zackenberg regions. The novelty of the work is the determination of the product specifications after elaborate discussions with interested parties from government institutions, the tourist industry, etc. Thus, a 10 m DEM, 1.5 m orthophotos, and vector maps are produced. This opens to the possibility of using orthophotos with up-to-date contour lines or for deriving updated coastlines to aid, e.g., emergency management. This allows for a product development directly in line with the needs of parties with specific interests in Greenland.

  5. 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

  6. Generating synthetic fjord bathymetry for coastal Greenland

    NASA Astrophysics Data System (ADS)

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

    2017-02-01

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

  7. 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

  8. Role of cabbeling in water densification in the Greenland Basin

    NASA Astrophysics Data System (ADS)

    Kasajima, Y.; Johannessen, T.

    2009-07-01

    The effects of cabbeling mixing on water mass modification in the Greenland Sea were explored by hydrographic observations across the Greenland Basin in summer 2006. The neutral surface was chosen as a reference frame, and the strength of cabbeling mixing was quantified by the dianeutral velocity magnitude. Active cabbeling spots were detected with the criterion of the velocity magnitude >1 m/day, and four active cabbeling areas were identified; the west of Bear Island (SB), the Arctic Frontal Zone (AFZ), the central Greenland Sea (CG) and the western Greenland Sea (WG). The most vigorous cabbeling mixing was found at SB, where warm North Atlantic Water (NAW) mixed with cold water from the Barents Sea, inducing a maximum velocity of 7.5 m/day and a maximum density gain of 4.7×10-3 kg/m3. At AFZ and CG, the mixing took place between NAW, modified NAW and Arctic Intermediate Water (AIW), and the density gain at these fronts were 1.5×10-3 kg/m3 (AFZ) and 1.3×10-3 kg/m3 (CG). In the western Greenland Sea, the active cabbeling spots were widely separated and mixing appeared to be rather weak, with a maximum velocity of 2.5 m/day. The mixing source waters at WG were modified NAW, AIW and even denser water, and the density gain in this area was 0.4×10-3 kg/m3. The deepest mixing produced water whose density is equivalent to that of the dense water of the basin, indicating that cabbeling in the western Greenland Sea contributed directly to basin-scale water densification. The water mass modification rate was the highest at AFZ (about 8.0 Sv), suggesting that cabbeling may play an important role in water transformation in the Greenland Basin.

  9. Precipitation over Greenland and its relation to the North Atlantic Oscillation

    NASA Astrophysics Data System (ADS)

    Bromwich, David H.; Chen, Qiu-Shi; Li, Yufang; Cullather, Richard I.

    1999-09-01

    The ω equation method based on an equivalent isobaric geopotential height in σ coordinates has been used to retrieve the precipitation over Greenland. This approach is designed to accurately represent the topographic effects of the Greenland Ice Sheet on atmospheric motion and precipitation. The 11 year mean precipitation from 1985 to 1996 over all of Greenland is 376 mm yr-1, which is close to the long-term mean precipitation of 346 mm yr-1 estimated from glaciological data. The precipitation over all of Greenland shows that the largest value in 1986 is 472 mm yr-1 and the smallest value in 1995 is 309 mm yr-1. The major interannual variability of the atmospheric circulation in the North Atlantic can be represented by the variation of the North Atlantic Oscillation (NAO) index, which is most pronounced during winter. It is found that if the NAO index increases, the total precipitation over Greenland decreases, and vice versa. The correlation coefficient between these two series for 1985-1995 is -0.75. The mean precipitation over southern Greenland, where the majority of precipitation falls, is more closely related to the NAO index in winter, and their correlation coefficient is -0.80. This relationship can be understood from the composite maps of sea level pressure and Greenland precipitation for the high and low index months. During months of high NAO index values, the Icelandic Low is strong. During months of low NAO index values, the monthly mean low is located to the southwest of Greenland over the Labrador Sea. Precipitation amounts over the southeast coast of Greenland are about 100 mm larger during the low NAO index months than the high NAO index months. Precipitation over all of Greenland during the low NAO index months is higher. There are significant downward trends in annual precipitation from 1985-1995 for all of Greenland and its southern and central west coastal regions, amounting to about 3% per year.

  10. 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.

  11. Melting at the base of the Greenland Ice Sheet explained by the Iceland mantle plume 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

    2017-04-01

    Ice-penetrating radar measurements and ice core drilling have shown that large parts of the north-central Greenland Ice Sheet are melting from below. Locally these observational data indicate that an anomalously high geothermal flux is needed to explain the observed basal ice melting. In this study we reconstruct the distribution of geothermal flux in Greenland and identify a large-scale geothermal anomaly beneath the thick ice cover. The anomaly represents a continuous 400-km-wide band of elevated heat flux, crossing Greenland from west to east. Our combined analysis of seismic, gravity and tectonic data links the origin of this anomaly to Greenland's passage over the Iceland mantle plume between roughly 80 and 35 million years ago. Most of the observed subglacial melting as well as previously suggested hydrological networks operating under the ice sheet occur within the anomalous zone. Also the position of the enigmatic 750-km-long northeastern Greenland ice stream is controlled by the enhanced ice deformation and basal sliding induced by the elevated heat flux. This rapid ice flow initiates at the very heart of the reconstructed anomaly, where our study and observations indicate some of the highest rates of basal ice melting in interior Greenland. Our findings suggest that the present-day subglacial hydrology and rapid ice flow of the north-central Greenland Ice Sheet have their origin in tectonic events that predate the onset of Greenland glaciations by many tens of millions of years.

  12. Baffin Bay, Greenland

    NASA Technical Reports Server (NTRS)

    2002-01-01

    Along Greenland's western coast, a small field of glaciers surrounds Baffin Bay. This image was acquired by Landsat 7's Enhanced Thematic Mapper plus (ETM+) sensor on September 3, 2000. This is a false-color composite image made using near-infrared, red, and blue wavelengths. The image has also been sharpened using the sensor's panchromatic band. Image provided by the USGS EROS Data Center Satellite Systems Branch

  13. Modelling Greenland icebergs

    NASA Astrophysics Data System (ADS)

    Marson, Juliana M.; Myers, Paul G.; Hu, Xianmin

    2017-04-01

    The Atlantic Meridional Overturning Circulation (AMOC) is well known for carrying heat from low to high latitudes, moderating local temperatures. Numerical studies have examined the AMOC's variability under the influence of freshwater input to subduction and deep convections sites. However, an important source of freshwater has often been overlooked or misrepresented: icebergs. While liquid runoff decreases the ocean salinity near the coast, icebergs are a gradual and remote source of freshwater - a difference that affects sea ice cover, temperature, and salinity distribution in ocean models. Icebergs originated from the Greenland ice sheet, in particular, can affect the subduction process in Labrador Sea by decreasing surface water density. Our study aims to evaluate the distribution of icebergs originated from Greenland and their contribution to freshwater input in the North Atlantic. To do that, we use an interactive iceberg module coupled with the Nucleus for European Modelling of the Ocean (NEMO v3.4), which will calve icebergs from Greenland according to rates established by Bamber et al. (2012). Details on the distribution and trajectory of icebergs within the model may also be of use for understanding potential navigation threats, as shipping increases in northern waters.

  14. 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

    2015-01-08

    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. Copyright © 2015 The American Society of Human Genetics. Published by Elsevier Inc. All rights reserved.

  15. Climate Change and Baleen Whale Trophic Cascades in Greenland

    DTIC Science & Technology

    2009-09-30

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

  16. Climate Change and Baleen Whale Trophic Cascades in Greenland

    DTIC Science & Technology

    2012-03-19

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

  17. Climate Change and Baleen Whale Trophic Cascades in Greenland

    DTIC Science & Technology

    2010-01-01

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

  18. Trends of perfluorochemicals in Greenland ringed seals and polar bears: indications of shifts to decreasing trends.

    PubMed

    Rigét, Frank; Bossi, Rossana; Sonne, Christian; Vorkamp, Katrin; Dietz, Rune

    2013-11-01

    Time-series of perfluorinated alkylated substances (PFASs) in East Greenland polar bears and East and West Greenland ringed seals were updated in order to deduce whether a response to the major reduction in perfluoroalkyl production in the early 2000s had occurred. Previous studies had documented an exponential increase of perfluorooctane sulphonate (PFOS) in liver tissue from both species. In the present study, PFOS was still the far most dominant compound constituting 92% (West Greenland ringed seals), 88% (East Greenland ringed seals) and 85% (East Greenland polar bears). The PFOS concentrations increased up to 2006 with doubling times of approximately 6 years for the ringed seal populations and 14 years in case of polar bears. Since then a rapid decrease has occurred with clearing half-lives of approximately 1, 2 and 4 years, respectively. In polar bears perfluorohexane sulphonate (PFHxS) and perfluorooctane sulphonamide (PFOSA) also showed decreasing trends in recent years as do perfluorodecanoic acid (PFDA) and perfluoroundecanoic acid (PFUnA). For the West Greenland ringed seal population perfluorooctanoic acid (PFOA), perfluorononanoic acid (PFNA), PFDA and PFUnA peaked in the mid 2000s, whereas PFNA, PFDA and PFUnA in the East Greenland population have been stable or increasing in recent years. The peak of PFASs in Greenland ringed seals and polar bears occurred at a later time than in Canadian seals and polar bears and considerably later than observed in seal species from more southern latitudes. We suggest that this could be explained by the distance to emission hot-spots and differences in long-range transport to the Arctic. Copyright © 2013 Elsevier Ltd. All rights reserved.

  19. Greenland Gains Some, Loses More

    NASA Image and Video Library

    2010-02-19

    NASA GRACE mission has become a key source of knowledge about global ice mass changes. Studies of Greenland using GRACE and other data indicate that between 2000 and 2008 the Greenland ice sheet lost as much as 1,500 gigatons of mass.

  20. 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

  1. 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

  2. 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.

  3. Greenland's Biggest Losers

    NASA Astrophysics Data System (ADS)

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

    2010-12-01

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

  4. 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.

  5. Comparing Norse animal husbandry practices: paleoethnobotanical analyses from Iceland and Greenland.

    PubMed

    Ross, Julie M; Zutter, Cynthia

    2007-01-01

    The popular view of the Norse settlement across the North Atlantic describes colonies with similar subsistence practices being established from the Faroe Islands in the west to L'Anse aux Meadows in the east. The importance of plant resources to the Norse animal husbandry strategies implemented by settlers upon arrival are not well established, nor are the changes these strategies underwent, eventually resulting in different cultural solutions to varying environmental and social factors. This paper compares archaeobotanical samples from two Icelandic archaeological sites, Svalbarð and Gjögur, and one Greenlandic site, Gården Under Sandet (GUS). Results of this comparison suggest that heathland shrubs were an important fodder resource for caprines in both Iceland and Greenland while apophytes ("weedy taxa") were part of the cattle fodder in Greenland. Further, the results indicate that mucking out of cattle barns to provide fertilizer was likely practiced at the GUS site in the Western Norse settlement of Greenland.

  6. 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.

  7. Toxaphene in the aquatic environment of Greenland.

    PubMed

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

    2015-05-01

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

  8. 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.

  9. Toward a Master Chronology for Western Greenland's Fjord Stade Moraines: New 10Be Ages from the Søndre Isortoq Region

    NASA Astrophysics Data System (ADS)

    Lesnek, A.; Briner, J. P.; Schweinsberg, A.; Lifton, N. A.

    2015-12-01

    Reconstructions of Greenland Ice Sheet (GrIS) margin fluctuations during the Holocene place empirical constraints on the extent of the GrIS that can be used as benchmark data for ice-sheet climate models. Here, we reconstruct the early Holocene ice margin history of the Søndre Isortoq region of western Greenland to evaluate the response of the GrIS to Holocene climate change. The moraines in this region are part of an extensive moraine system known as the Fjord Stade moraines, which have been nearly continuously traced throughout western Greenland. These moraines have been directly dated to 9.2 and 8.2 ka in the Disko Bugt region, suggesting that they represent a readvance or stillstand of the GrIS in response to the 9.3 and 8.2 ka abrupt cooling events, respectively. However, because the Fjord Stade moraines have not been directly and precisely dated elsewhere, it is unclear whether the entire western GrIS margin responded to these events or not. To address this issue, we selected boulders from two sites in the Søndre Isortoq region for cosmogenic 10Be exposure dating. In Nunatarssuaq, we sampled eight erratic boulders perched on bedrock beyond and inside of the Fjord Stade moraines. Samples from Qátqatsiaq include nine Fjord Stade moraine boulders and seven erratic boulders that bracket the moraines. We found that the Fjord Stade moraines in the Søndre Isortoq region were abandoned at ~9 ka and that they may be correlated with the outer Fjord Stade moraines in Disko Bugt. If the western GrIS margin did respond to the 9.3 ka cooling event, the later age of ~9 ka at Søndre Isortoq could suggest that land-terminating sectors of the GrIS are less sensitive to centennial-scale climate change than their marine-terminating counterparts. In addition, exposure ages for moraine boulders and boulders inside the moraines are indistinguishable within dating uncertainties, indicating that once initiated, retreat from the Fjord Stade moraines occurred rapidly.

  10. Analysis of recent glacial earthquakes in Greenland

    NASA Astrophysics Data System (ADS)

    Olsen, K.; Nettles, M.

    2015-12-01

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

  11. Greenland Coast in Holiday Colors

    NASA Image and Video Library

    2003-12-23

    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 captured by NASA Terra spacecraft on June 18, 2003.

  12. South Greenland, North Atlantic Ocean

    NASA Image and Video Library

    1992-04-02

    This spectacular north looking view of south Greenland (62.0N, 46.0W) shows numerous indentations along the coastline, many of which contain small settlements. These indentations are fiords carved by glaciers of the last ice age. Even today, ice in the center of Greenland is as much as 10,000 ft. thick and great rivers of ice continuously flow toward the sea, where they melt or break off as icebergs - some of which may be seen floating offshore.

  13. South Greenland, North Atlantic Ocean

    NASA Technical Reports Server (NTRS)

    1992-01-01

    This spectacular north looking view of south Greenland (62.0N, 46.0W) shows numerous indentations along the coastline, many of which contain small settlements. These indentations are fiords carved by glaciers of the last ice age. Even today, ice in the center of Greenland is as much as 10,000 ft. thick and great rivers of ice continuously flow toward the sea, where they melt or break off as icebergs - some of which may be seen floating offshore.

  14. 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

  15. Bathymetry of Greenland Fjords

    NASA Astrophysics Data System (ADS)

    Cochran, J. R.; Boghosian, A.; Tinto, K. J.; Bell, R. E.; Porter, D. F.

    2013-12-01

    Operation IceBridge (OIB) has performed extensive airborne gravity surveys of Greenlandic fjords in order to model their bathymetry. Bathymetry inversions from gravity data provide a model of the fjord bathymetry in areas that are otherwise difficult to survey. We use these gravity surveys along with other OIB datasets to create bathymetry models for fjords surveyed by OIB from 2009-2012. These models allow us to estimate depths to the grounding line in areas with poor radar returns and sill depths and overdeepenings in the fjords. Models have been constructed by combining ice-surface and ice-thickness data from coincident OIB lidar and radar surveys. The inversion of gravity anomalies to bathymetry models is dependent on assumptions of both local and regional variations in geology. Local variations can often be identified with OIB magnetic anomalies. Regional geoid variations produce long-wavelength gravity anomalies that are part of the observed gravity, but not present in the forward modeled gravity over the known bed. This effect varies in magnitude around Greenland. In long fjords, removing the long-wavelength components of the observed anomalies reduces the uncertainties from regional geological variations. The average combined error for absolute model depths varies regionally between 50 m and 200 m. The error budget takes into account the measurement uncertainty of the gravity survey along with sensitivity of the model to regional gravity corrections and the point at which the model is pinned to known bed. Gravity inversions model bathymetry at ~5 km wavelengths, while bed topography onshore is known at a higher resolution from radar surveys. This change of length scale must be taken into account when using bathymetry models to consider grounding line morphology as well as when combining modeled bathymetry with offshore bathymetric data. Models can be improved by pinning to ship surveys of offshore bathymetry. Our dataset has incorporated available offshore

  16. Muscle plasticity of Inuit sled dogs in Greenland.

    PubMed

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

    2009-04-01

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

  17. Population-based comparative epidemiological survey of hepatitis B, D, and C among Inuit migrated to Denmark and in high endemic Greenland.

    PubMed

    Rex, Karsten Fleischer; Krarup, Henrik B; Laurberg, Peter; Andersen, Stig

    2012-06-01

    Infection with hepatitis B virus (HBV) is endemic among Arctic populations where it may have a benign course. However, the relation of HBV to migration to low endemic areas is unknown, as it is for hepatitis D and C, and details on the influence of delta virus at a population level are lacking. Population-based investigation of Greenlanders living in Denmark (n = 136) and in Greenland (n = 441). We tested for HBsAg, anti-HBs, anti-HBc, HBeAg, anti-HBe, HBV-DNA, HBV genotypes, anti-HDV, HDV-RNA, anti-HCV, HCV-Elisa test, HCV-RNA, aspartate aminotransferase, gamma-glutamyl transferase, bilirubin, and albumin, and performed a physical examination. Participation rate was 52/95% in Denmark/Greenland. Half of participants in Denmark had lived more than half of their lives in Denmark, and 54.5% had been exposed to HBV. This was similar to 53% among Greenlanders living in West Greenland (p = 0.76). HBsAg was positive in 4.4% of Greenlanders in Denmark (n = 6), who all were anti-HBe positive and had low viral load. Serological signs of HBV infection associated with having both parents born in Greenland (p = 0.007) and with IV drug use (p = 0.03). We found serological signs of HDV exposure among participants in Denmark/Greenland in 0.7/1.1% (n = 1/5) and HCV exposure in 1.5/0.0% (n = 2/0). Liver biochemistry was elevated in Greenlanders exposed to HDV. Hepatitis B, D, and C occurrences among Greenlanders in Denmark mirrored that of Greenland. Importantly, previously undetected exposure to delta virus associated with elevated liver biochemistry, and the introduction of delta virus is a liability to Greenlanders and to Greenland.

  18. Body feathers as a potential new biomonitoring tool in raptors: a study on organohalogenated contaminants in different feather types and preen oil of West Greenland white-tailed eagles (Haliaeetus albicilla).

    PubMed

    Jaspers, Veerle L B; Rodriguez, Francisco Soler; Boertmann, David; Sonne, Christian; Dietz, Rune; Rasmussen, Lars Maltha; Eens, Marcel; Covaci, Adrian

    2011-11-01

    We investigated the variation in concentrations and profiles of various classes of organohalogenated compounds (OHCs) in different feather types, muscle tissue and preen oil from 15 white-tailed eagle (Haliaeetus albicilla) carcasses from Greenland. The influence of moult patterns and potential external contamination onto the feather surface was examined, while the present study is also the first to investigate the use of body feathers for OHC monitoring. Concentrations of sum polychlorinated biphenyls (PCBs) in feathers from white tailed eagles ranged from 2.3 ng/g in a primary wing feather to 4200 ng/g in body feathers. Using 300 mg of body feathers, almost 50 different OHCs could be quantified and median concentrations in body feathers were 10 fold higher than concentrations in tail feathers (rectrices) or primary wing feathers. Body feathers could be very useful for biomonitoring taking into account their easy sampling, short preparation time and high levels of OHCs. In addition, the effects of confounding variables such as feather size, moult and age are also minimised using body feathers. Correlations with concentrations in muscle tissue and preen oil were high and significant for all feather types (r ranging from 0.81 to 0.87 for sum PCBs). Significant differences in concentrations and profiles of OHCs were found between different primary feathers, indicating that the accumulation of OHCs in feathers varies over the moulting period (maximum three years). Washing of feathers with an organic solvent (acetone) resulted in a significant decrease in the measured concentrations of OHCs in feathers. However, our results indicated that preen oil is probably not the only contributor to the external contamination that can be removed by washing with acetone. Possibly dust and other particles may be of importance and may be sticking to the preened feathers. Rectrices washed only with water showed high and significant correlations with concentrations in muscle and preen

  19. 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.

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

    NASA Astrophysics Data System (ADS)

    Døssing, Arne; Japsen, Peter; Watts, Anthony 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.

  1. Hotspots and key periods of Greenland climate change during the past six decades.

    PubMed

    Abermann, Jakob; Hansen, Birger; Lund, Magnus; Wacker, Stefan; Karami, Mojtaba; Cappelen, John

    2017-02-01

    We investigated air temperature and pressure gradients and their trends for the period 1996-2014 in Greenland and compared these to other periods since 1958. Both latitudinal temperature and pressure gradients were strongest during winter. An overall temperature increase up to 0.15 °C year(-1) was observed for 1996-2014. The strongest warming happened during February at the West coast (up to 0.6 °C year(-1)), weaker but consistent and significant warming occurred during summer months (up to 0.3 °C year(-1)) both in West and East Greenland. Pressure trends on a monthly basis were mainly negative, but largely statistically non-significant. Compared with other time windows in the past six decades, the period 1996-2014 yielded an above-average warming trend. Northeast Greenland and the area around Zackenberg follow the general pattern but are on the lower boundary of observed significant trends in Greenland. We conclude that temperature-driven ecosystem changes as observed in Zackenberg may well be exceeded in other areas of Greenland.

  2. GJB2 (Connexin-26) mutations are not frequent among hearing impaired patients in east Greenland.

    PubMed

    Homøe, Preben; Koch, Anders; Rendtorff, Nanna Dahl; Lodahl, Marianne; Andersen, Ture; Andersen, Stig; Eiberg, Hans; Nielsen, Inge-Merete; Tranebjærg, Lisbeth

    2012-06-01

    Investigate genetic causes of HI among the Inuit populations in the Arctic with a high prevalence of hearing impairment (HI). A cross-sectional survey with population-based controls. Forty-five patients, with sensorineural or mixed HI and an available blood sample for GJB2 sequencing from DNA, were selected from 166 east Greenlanders by specialist audiology examination, including pure-tone air and bone conduction audiometry from 125 Hz to 8000 Hz. Controls were 108 east- and 109 west-Greenlanders. Forty-five patients with HI were included, 24 males and 21 females. Median age was 35 years (range: 5-76). The c.35delG allele frequency was 3.3%. One patient, homozygous for the c.35delG GJB2 mutation, had bilateral congenital profound HI. Another with mixed HI was heterozygous for the same mutation. Three were heterozygous for the p.V27I variant and one was heterozygous for the p.V153I variant. The frequency of the c.35delG mutation in the controls varied between 0.5% in west Greenland to 2.3% in east Greenland. The c.35delG GJB2 mutation occurs in Greenland with low frequency. We conclude the main causes behind the prevalence of HI in this population are chronic otitis media, noise traumas, and/or unidentified genetic causes.

  3. Phenology of Lithothamnion glaciale in mixed fjord conditions: mesocosm experiments provide insight to maerl physiology and distribution in southwestern Greenland.

    NASA Astrophysics Data System (ADS)

    Schoenrock, Kathryn; Baquet, Marion; Kamenos, Nicholas

    2017-04-01

    Maerl are free living coralline algae that are often bedded in the subtidal forming important marine habitats in many regions of the world. Greenland is known to have at least three species of maerl along the coast and extending into some fjord systems. In the Godthåbsfjord region, Lithothamnion glaciale is never found dominating shallow maerl beds as it is further north (Disko bay) and in other regions of the Arctic. To investigate reasons for this maerl physiology was measured in situ over two field seasons and over the year in a mesocosm experiment which manipulated temperature and salinity to represent marine and fjord systems. The results of these measurements show that calcification and photosynthesis (DO production) in L. glaciale as well as another maerl species, Clathromorphum compactum, operate at very low rates and are influenced negatively by low salinity but positively by low temperature throughout the year. Photosynthesis and calcification are not often correlated in these species which is an unusual finding as these two metabolic processes are thought to be coupled. Findings provide natural history background for ecotypes from the Godthåbsfjord region and a baseline for future research in biogeochemistry and ecology.

  4. Kilometer-scale, late Miocene and early Pliocene surface uplift in East Greenland: tectonic forerunners for the build-up of the Greenland Ice Sheet

    NASA Astrophysics Data System (ADS)

    Japsen, Peter; Green, Paul F.; Bonow, Johan M.

    2015-04-01

    The tectonic origin of late Neogene uplift along NE Atlantic margins has been questioned. Evidence for these movements - such as the recent denudation of mountain ranges and abundant, late Cenozoic coarse sediment near them - has been explained as a result of climate change (Molnar and England, 1990). Identification of the causal relationship between uplift, tectonics and climate deterioration during the late Neogene thus critically depends on defining temporal relation between these events. We have previously argued that the elevated plateaux in East and West Greenland are the result of three tectonic phases of uplift and erosion (Bonow et al., 2014; Japsen et al., 2014). A late Eocene phase of uplift led to formation of a Palaeogene erosion surface near sea level. Uplift of this surface in the late Miocene led to formation of a lower, Neogene surface by incision below the uplifted Palaeogene surface. Finally, a Pliocene phase led to incision of valleys and fjords below the uplifted Neogene surface, resulting in mountain peaks reaching 3.7 km and 2.1 km a.s.l. in East and West Greenland, respectively. Data from West Greenland only provide broad constraints on the timing of the Pliocene phase, and we have not yet been able to define the timing of this phase firmly in the east. Here we present new apatite fission-track data from East Greenland that clearly constrain the timing of late Miocene and early Pliocene events of uplift and exhumation. It is thus clear that the final phase of Cenozoic tectonic uplift preceded the onset of large-scale glaciations in the late Pliocene to Pleistocene. Solgaard et al. (2013) showed that the the build-up of the Greenland Ice Sheet could not initiate in the case of the low-lying and almost flat topography in Greenland prior to the two phases of late Neogene uplift. Furthermore, these results showed that Early Pliocene uplift led to the final formation of the present-day, high coastal mountains in East Greenland that provided

  5. Environmental radioactivity in Greenland in 1974.

    PubMed

    Aarkrog, A; Lippert, J

    1975-07-01

    Measurements of fall-out radioactivity in Greenland in 1974 are reported. Strontium-90 (and Caesium-137 in most cases) was determined in samples of precipitation, sea water, vegetation, animals, and drinking water. Estimates are given of the mean contents of 90Sr and 137Cs in the human diet in Greenland in 1974. Three Greenlanders were measured by wholebody counting.

  6. Phenological Advances and Trophic Consequences in Low- and High-Arctic Greenland

    NASA Astrophysics Data System (ADS)

    Høye, T. T.; Schmidt, N. M.; Forchhammer, M. C.; Bøving, P. S.; Post, E.

    2009-12-01

    Seasonal timing of reproduction (phenology) is highly responsive to global warming, especially in the Arctic. Here, we present a comparative analysis of multi-annual observational data on phenological dynamics across trophic levels from Zackenberg, North-East Greenland (a High Arctic site) and Kangerlussuaq, West Greenland (a Low Arctic site). Both sites have experienced considerable warming and our analyses indicate that rates of change in plant phenological responses may differ between sites, related to different proximal drivers at the two sites. We also present parallel data on interacting organisms (pollinators and mammalian herbivores) to evaluate the risks and effects of trophic mismatch at these two sites.

  7. AirBase - A database of 160,000 aerial photos of Greenland 1930-1980s

    NASA Astrophysics Data System (ADS)

    Korsgaard, Niels; Weng, Willy L.; Kjær, Kurt H.

    2017-04-01

    Beginning in the 1930s Danish survey agencies and US military organizations conducted large-scale aerial photograph surveys of Greenland for mapping purposes (1), eventuating in the recording of more than 160,000 photographs. Glaciological researchers have used this amazing resource of multi-decadal observations of the Greenlandic cryosphere for many decades (e.g. (2), (3), (4)). In recent years this information has been synthesized with modern remote sensing data resulting in a range of published research and data sets ((5), (6), (7), (8)). Today, the historical aerial photographs are stored at the SDFE (Agency for Data Supply and Effiency), the successor agency for the institutions doing the surveying and mapping of Greenland where the material is accessible to researchers and general public alike. The digitized flightline maps and databases necessary for the creation of this data for this work was made available by the SDFE, and it the past and present work with this database we present here. Based on digitized flight line maps, the database contains geocoded metadata such as recording dates, camera and film roll canister, connecting the database with the analog archive material. Past work concentrated on bulk digitization, while the focus of the current work is to improve positional accuracy, completeness, and refinements for web publication. (1) Nielsen, A., Olsen, J. & Weng, W. L. Grønlands opmåling og kortlægning. Landinspektøren 37 (1995). (2) Weidick A. Frontal variations at Upernaviks Isstrøm in the last 100 years. Medd. fra Dansk Geol. Forening. Vol. 14 (1958. (3) Bauer, A., Baussart, M., Carbonnell, M., Kasser, P. Perroud, P. & Renaud, A. Missions aériennes de reconnaissance au Groenland 1957-1958. Observations aériennes et terrestres, exploitation des photographies aériennes, détermination des vitesses des glaciers vêlant dans Disko Bugt et Umanak Fjord. Meddelelser om Grønland 173(3) (1968a. (4) Rignot, E. Box, J.E., Burgess, E. & Hanna, E

  8. Greenland Ice Sheet flow response to runoff variability

    NASA Astrophysics Data System (ADS)

    Stevens, Laura A.; Behn, Mark D.; Das, Sarah B.; Joughin, Ian; Noël, Brice P. Y.; Broeke, Michiel R.; Herring, Thomas

    2016-11-01

    We use observations of ice sheet surface motion from a Global Positioning System network operating from 2006 to 2014 around North Lake in west Greenland to investigate the dynamical response of the Greenland Ice Sheet's ablation area to interannual variability in surface melting. We find no statistically significant relationship between runoff season characteristics and ice flow velocities within a given year or season. Over the 7 year time series, annual velocities at North Lake decrease at an average rate of -0.9 ± 1.1 m yr-2, consistent with the negative trend in annual velocities observed in neighboring regions over recent decades. We find that net runoff integrated over several preceding years has a negative correlation with annual velocities, similar to findings from the two other available decadal records of ice velocity in western Greenland. However, we argue that this correlation is not necessarily evidence for a direct hydrologic mechanism acting on the timescale of multiple years but could be a statistical construct. Finally, we stress that neither the decadal slowdown trend nor the negative correlation between velocity and integrated runoff is predicted by current ice-sheet models, underscoring that these models do not yet capture all the relevant feedbacks between runoff and ice dynamics needed to predict long-term trends in ice sheet flow.

  9. Geographical differences of zinc, cadmium, mercury and selenium in polar bears (Ursus maritimus) from Greenland.

    PubMed

    Dietz, R; Riget, F; Born, E W

    2000-01-17

    Muscle, liver, and kidney tissues from 100 polar bears (Ursus maritimus), caught in the Avanersuaq area, north-west Greenland, and Ittoqqortoormiit area, central-east Greenland, were analysed for zinc, cadmium, mercury and selenium. The zinc concentrations in muscle and liver were higher than in kidney. Mean zinc concentrations ranged from 19.7 to 76.0 micrograms/g (all data are presented as geometric means on a wet wt. basis). The presented cadmium concentrations by area and age groups were all low in muscle and in many cases below the detection limit (range: < 0.015-0.048 microgram/g). Cadmium concentrations were intermediate in liver (range: 0.120-1.98 micrograms/g) and highest in kidney tissue (range: 2.16-28.9 micrograms/g). Mercury was likewise lowest in muscle tissue (range: 0.034-0.191 microgram/g). Mercury concentration ranged quite similarly in liver and kidney tissue (liver range: 2.13-22.0 micrograms/g; kidney range: 2.87-32.0 micrograms/g). The selenium concentration increased from muscle (range: < 0.2-0.452 microgram/g) over liver (range: 1.20-9.80 micrograms/g) to kidney (range: 2.34-13.9 micrograms/g). No age accumulation was found for zinc. A weak increase was found for selenium, whereas cadmium and mercury clearly accumulated with age. An exception was mercury concentrations in muscle tissue, where no clear pattern was observed. Polar bears had significantly lower cadmium concentrations than ringed seals from the same area in all three tissues. Likewise mercury was significantly lower in the muscle tissue of polar bears than in ringed seals, whereas liver and kidney concentrations were higher. Biomagnification factors are provided for different tissues and age groups. Tissue ratios are given for different age groups and metals to enable a rough extrapolation from one tissue to another. Tissue ratios for cadmium, selenium and for mercury vary up to a factor of 6 with age. No significant differences could be detected between the elements analysed in

  10. 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).

  11. 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

  12. Meltwater pathways from marine terminating glaciers of the Greenland ice sheet

    NASA Astrophysics Data System (ADS)

    Gillard, Laura C.; Hu, Xianmin; Myers, Paul G.; Bamber, Jonathan L.

    2016-10-01

    The Greenland ice sheet (GrIS) stores the largest amount of freshwater in the Northern Hemisphere and has been recently losing mass at an increasing rate. An eddy-permitting ocean general circulation model is forced with realistic estimates of freshwater flux from the GrIS. Two approaches are used to track the meltwater and its trajectory in the ocean. We show that freshwater from western and eastern GrIS have markedly different fates, on a decadal time scale. Freshwater from west Greenland predominantly accumulates in Baffin Bay before being exported south down the Labrador shelf. Meanwhile, GrIS freshwater entering the interior of the Labrador Sea, where deep convection occurs, comes predominantly (˜80%) from east Greenland. Therefore, hosing experiments, which generally assume a uniform freshwater flux spatially, will not capture the true hydrographic response and regional impacts. In addition, narrow boundary currents are important for freshwater transport and distribution, requiring simulations with eddy-resolving resolution.

  13. A long-term increase in eggshell thickness of Greenlandic Peregrine Falcons Falco peregrinus tundrius.

    PubMed

    Falk, Knud; Møller, Søren; Mattox, William G

    2006-02-15

    Thickness of eggshell fragments and whole eggs from the Peregrine Falcon Falco peregrinus collected in South and West Greenland between 1972 and 2003 was measured and compared to shell thickness of pre-DDT eggs, also collected in Greenland. Linear regression yields a significant increase in the average thickness of eggshells over the period of 0.19% per year, corresponding to a change in eggshell thinning from 13.9% in 1972 to 7.8% in 2003. Backwards extrapolation of the data, suggests that the Greenlandic Peregrine population probably was never critically affected by DDT-induced eggshell thinning. By sampling eggshell fragments in many nests the spatial and temporal sample distribution was enlarged, allowing the detection of a significant long-term decrease in pollutant-induced eggshell thinning--a trend that could not have been identified if only the rarer whole, addled eggs had been sampled.

  14. Time trend by region of suicides and suicidal thoughts among Greenland Inuit

    PubMed Central

    Bjerregaard, Peter; Larsen, Christina Viskum Lytken

    2015-01-01

    Background Suicides remain a major public health problem in Greenland. Their increase coincides with the modernization since 1950. Serious suicidal thoughts are reported by a significant proportion of participants in countrywide surveys. Objective To analyze the time trend by region of suicides and suicidal thoughts among the Inuit in Greenland. Design Data included the Greenland registry of causes of death for 1970–2011 and 2 cross-sectional health surveys carried out in 1993–1994 and 2005–2010 with 1,580 and 3,102 Inuit participants, respectively. Results Suicide rates were higher among men than women while the prevalence of suicidal thoughts was higher among women. Suicide rates for men and women together increased from 1960 to 1980 and have remained around 100 per 100,000 person-years since then. The regional pattern of time trend for suicide rates varied with an early peak in the capital, a continued increase to very high rates in remote East and North Greenland and a slow increase in villages relative to towns on the West Coast. Suicidal thoughts followed the regional pattern for completed suicides. Especially for women there was a noticeable increasing trend in the villages. The relative risk for suicide was highest among those who reported suicidal thoughts, but most suicides happened outside this high-risk group. Conclusion Suicide rates and the prevalence of suicidal thoughts remain high in Greenland but different regional trends point towards an increased marginalization between towns on the central West Coast, villages and East and North Greenland. Different temporal patterns call for different regional strategies of prevention. PMID:25701279

  15. Time trend by region of suicides and suicidal thoughts among Greenland Inuit.

    PubMed

    Bjerregaard, Peter; Larsen, Christina Viskum Lytken

    2015-01-01

    Suicides remain a major public health problem in Greenland. Their increase coincides with the modernization since 1950. Serious suicidal thoughts are reported by a significant proportion of participants in countrywide surveys. To analyze the time trend by region of suicides and suicidal thoughts among the Inuit in Greenland. Data included the Greenland registry of causes of death for 1970-2011 and 2 cross-sectional health surveys carried out in 1993-1994 and 2005-2010 with 1,580 and 3,102 Inuit participants, respectively. Suicide rates were higher among men than women while the prevalence of suicidal thoughts was higher among women. Suicide rates for men and women together increased from 1960 to 1980 and have remained around 100 per 100,000 person-years since then. The regional pattern of time trend for suicide rates varied with an early peak in the capital, a continued increase to very high rates in remote East and North Greenland and a slow increase in villages relative to towns on the West Coast. Suicidal thoughts followed the regional pattern for completed suicides. Especially for women there was a noticeable increasing trend in the villages. The relative risk for suicide was highest among those who reported suicidal thoughts, but most suicides happened outside this high-risk group. Suicide rates and the prevalence of suicidal thoughts remain high in Greenland but different regional trends point towards an increased marginalization between towns on the central West Coast, villages and East and North Greenland. Different temporal patterns call for different regional strategies of prevention.

  16. The Greenland-Iceland-Faroe Ridge Complex

    NASA Astrophysics Data System (ADS)

    Erlendsson, Ögmundur; Hjartarson, Árni; Blischke, Anett

    2017-04-01

    thick layers of sediments, 8-10 km inside the bathymetric shelf break. Several seamounts were observed on multibeam datasets from the Vesturdjúp Basin West of Iceland, just south of the Greenland - Iceland Ridge at around 1200 m depth. Most of them are cone shaped but ridges and table mountains are also found. These seamounts appear to be much less eroded and younger than the neighbouring ocean floor and might indicate a still active flank or intra plate volcanic zone. Young tectonism with faults, grabens and transverse ridges also characterize the area and most of the volcanic cones are located along fault plans or/and within the grabens of the Vesturdjúp, giving a good example of the complexity of the GIFRC in comparison to simple ocean floor areas.

  17. 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.

  18. Melt anomalies on the Greenland Ice Sheet and large scale modes of atmospheric circulation

    NASA Astrophysics Data System (ADS)

    Huff, Russell

    The relationships between inter annual melt variability in Greenland and large scale atmospheric circulation are explored based on an empirical orthogonal function (EOF) analysis of melt in Greenland derived from passive microwave satellite observations. The first EOF of the melt anomalies was found to be highly representative of the spatial and temporal distribution of melt anomalies accounting for over 34% of the variability and the principal component (PC) time series is 98% correlated with the annual total melt extent time series. The leading melt PC is highly correlated with key features of the large scale atmospheric circulation both in the vicinity of Greenland and regions that are well removed. Some aspects of the atmospheric pressure anomaly fields related to melt in Greenland are congruent with the summer expression of the AO/NAO including the main center of action east of Greenland, however there are features of the melt related anomaly field that are not. During peak melt years there is a decrease in the pressure gradient between the Bearing Sea and more southerly latitudes resulting in a redistribution of the central Arctic low pressure toward the Pacific side of the Arctic basin. This pattern is expressed as a 50% correlation between melt in Greenland and the phase of planetary pressure wave #1 and #2 north of 50° N. The storm tracks related to increased melt in Greenland result in increased summer storm activity to the south and west of Greenland balanced by decreased cyclonic activity to the east and north. Comparison with the NAO related storm track highlights key differences relative to the melt related atmospheric circulation that lead to increased southerly flow directly into Greenland during years with increased melt. The pattern of summer sea ice concentration anomalies linked to the melt PC is remarkably similar to the spatial pattern of recent sea ice decline. The pattern of circulation anomalies associated with increased melt in Greenland

  19. Temporal trends of mercury in Greenland ringed seal populations in a warming climate.

    PubMed

    Rigét, Frank; Dietz, Rune; Hobson, Keith A

    2012-12-01

    Temporal trends of mercury in livers of ringed seals collected from the early 1980s to 2010 from central West, Northwest and central East Greenland were studied. In this period the climate of Greenland warmed and the influences of climate indices such as ice coverage, water temperature and the Atlantic Oscillation Index on mercury concentration were evaluated using multiple regressions and Akaike's Information Criteria (AIC) to determine the most parsimonious models. Biological co-variables such as age, sex and trophic position (as determined by stable isotope analysis) of seals were also evaluated. Increasing levels of mercury in seals were found in Ittoqqortoormiit, central East Greenland, and Avanersuaq, Northwest Greenland, with an annual increase of +10.3 and +2%, respectively. Age was an important co-variable for all three regions and trophic position for two regions. The Atlantic Oscillation Index was also an important explanatory variable for all three regions and was positively associated with mercury concentrations in seals indicating the importance of global climatic processes on ringed seal populations in Greenland.

  20. Mass balance of Greenland from combined GRACE and satellite altimetry inversion

    NASA Astrophysics Data System (ADS)

    Forsberg, Rene; Sandberg Sørensen, Louise; Nilsson, Johan; Simonsen, Sebastian

    2015-04-01

    With 12 years of GRACE satellite data now available, the ice mass loss trend of Greenland are clearly demonstrating ice mass loss in marginal zones of the ice sheets, and increasing mass loss trends in some regions such as the north west marginal zones. Although the GRACE release-5 products have provided a significant increase in resolution, the detailed space-based detection of where the ice sheet is loosing mass needs to come from other sources, notably satellite altimetry from EnviSat, IceSat and CryoSat, which point out the detailed location of areas of change, and - when combined with firn compaction and density models - also can be used to infer mass changes. In the paper we outline results of a novel direct inversion method, where all satellite data can be utilized in a general inverse estimation scheme, and the leakage from neighbouring ice caps minimized. We demonstrate overall mass change results from Greenland and Eastern Canadian Ice Caps 2003-14, highlighting the increasing melt in the marginal zones both in NW and NE Greenland, and highlighting the dynamic nature of the Greenland ice sheet mass loss through the 2012 record melt event, and the 2013 mass gain anomaly. The used data for the Greenland Ice Sheet are provided partly through the ESA Ice Sheets CCI project 2012-17, which will make available long term Essential Climate Variables such as Surface Elevation Changes, Ice Velocity, Mass Balance and Calving Front Locations.

  1. Preliminary screening of perfluorooctane sulfonate (PFOS) and other fluorochemicals in fish, birds and marine mammals from Greenland and the Faroe Islands.

    PubMed

    Bossi, Rossana; Riget, Frank F; Dietz, Rune; Sonne, Christian; Fauser, Patrik; Dam, Maria; Vorkamp, Katrin

    2005-07-01

    Extensive screening analyses of perfluorooctane sulfonate (PFOS) and related perfluorinated compounds in biota samples from all over the world have identified PFOS as a global pollutant and have shown its bioaccumulation into higher trophic levels in the food chain. Perfluorinated compounds have been found in remote areas as the Arctic. In this study a preliminary screening of PFOS and related compounds has been performed in liver samples of fish, birds and marine mammals from Greenland and the Faroe Islands. PFOS was the predominant fluorochemical in the biota analyzed, followed by perfluorooctane sulfonamide (PFOSA). PFOS was found at concentrations above LOQ (10 ng/g wet weight) in 13 out of 16 samples from Greenland and in all samples from the Faroe Islands. The results from Greenland showed a biomagnification of PFOS along the marine food chain (shorthorn sculpin < ringed seal < polar bear). The greatest concentration of PFOS was found in liver of polar bear from east Greenland (mean: 1285 ng/g wet weight, n = 2). The geographical distribution of perfluorinated compounds in Greenland was similar to that of persistent organohalogenated compounds (OHCs), with the highest concentrations in east Greenland, indicating a similar geographical distribution to that of OHCs, with higher concentrations in east Greenland than in west Greenland.

  2. [Rabies in a cat in Greenland].

    PubMed

    Christensen, Laurids Siig; Jacobsen, Keld; Maersk-Møller, Elisabeth

    2008-08-18

    We describe the first case of rabies diagnosed in a cat in Greenland. The cat showed aggressive behaviour one month after the visit of a rabid fox on the premises. Rabies is enzootic in Greenland, the arctic fox being the natural host of rabies virus. Cats are imported in increasing numbers to Greenland and the reported case stresses the need for concern in relation to a hitherto unrecognised risk of exposure to rabies virus and stresses the need to comply with the obligatory anti-rabies vaccination regimes for cats in Greenland.

  3. Environmental radioactivity in Greenland in 1976.

    PubMed

    Aarkrog, A; Lippert, J

    1977-07-01

    Measurements of fall-out radioactivity in Greenland in 1976 are reported. Strontium-90 (and Caesium-137 in most cases) was determined in samples of precipitation, sea water, vegetation, animals, and drinking water. Estimates are given of the mean contents of 90Sr and 137Cs in the human diet in Greenland in 1976.

  4. Temporal and spatial trends of persistent organochlorines in Greenland walrus (Odobenus rosmarus rosmarus).

    PubMed

    Muir, D C; Born, E W; Koczansky, K; Stern, G A

    2000-01-17

    Persistent organochlorines [PCBs, DDT and chlordane related compounds, dieldrin, toxaphene, hexachlorocyclohexane (HCH), chlorobenzenes] were determined in blubber of Atlantic walrus (Odobenus rosmarus rosmarus) in 1978 and 1988 from the Avanersuaq (Thule) region of north-west Greenland and in 1989 from Ittoqqortoormiit (Scoresbysund) in east Greenland. Lowest concentrations of organochlorines (OCs) were found in the samples from the Avanersuaq region while much higher levels of all compounds, except HCH isomers and mono/dichlorobiphenyls (CB5/8), were observed in samples (all males) from Ittoqqortoormiit. Total PCBs (sigma PCB) averaged 246 ng/g (wet wt.) male walrus from Avanersuaq and 2860 ng/g in samples from Ittoqqortoormiit. DDT isomers showed the greatest difference between the two locations, 50 x for p,p'-DDE and 69 x higher for p,p'-DDT. Ittoqqortoormiit walrus showed the pattern of OCs characteristic of seal-eating animals although the consumption of other organisms cannot be ruled out. The higher levels of OCs in east Greenland compared to north-west Greenland animals were consistent with results for polar bears, seals and gulls from the same regions. Principal components analysis showed that the pattern of OCs in Ittoqqortoormiit walrus was very similar to that in walrus from Inukjuaq in east Hudson Bay, which have previously been reported to be seal eaters, and quite distinct from the Avanersuaq walrus. No significant differences in mean concentrations of any OCs were found between male walrus from 1978 and 1988. For females, there were significantly higher levels of CB5/8, trichlorobiphenyls, dieldrin, toxaphene and alpha HCH as well as sigma HCH but not for sigma PCBs or DDT compounds. The data for Greenland walrus from the 1970s and late 1980s provide a baseline for future trend monitoring in walrus.

  5. Greenland Blocking As a Mechanism for Recent Arctic/Mid-Latitude Weather Linkages

    NASA Astrophysics Data System (ADS)

    Overland, J. E.; Hanna, E.; Wang, M.

    2014-12-01

    High-latitude blocking (HLB) located near and west of Greenland and in northeastern Siberia is a process that links Arctic processes to mid-latitude weather. HLB lies north of the jet stream and tends to bifurcate or divert the jet stream southward, rather than providing a complete block to the westerly flow. It is differentiated from mid-latitude blocking located in the central Atlantic to Europe and the western Pacific along eddy-driven jet streams. It is important to identify and understand an increase in recent HLB in early winter during the last five years relative to time series since 1948, even though this length is too short to robustly distinguish the influence of Arctic forcing from random events. In the last five early winters (December-January 2009-10 through 2013-14), two record and four other negative Arctic Oscillation atmospheric circulation index events have been observed, with positive Greenland Blocking Indices (GBI, greater 500 hPa geopotential heights) and increased geopotential thickness west of Greenland. Cold air penetrated into the southeastern United States in December 2009 and 2010 and January 2014 related to amplification in the long-wave upper-level atmospheric wind pattern. Northward air flow over Davis Strait acts as a positive feedback to maintain the Greenland air temperature anomalies. Extreme negative GBI were observed in December 2011-January 2012. Increased thickness associated with positive GBI can be a response to external (local sea ice loss, Greenland surface warming, or even equatorial teleconnections) or internal (advection and orientation of the long wave patterns) processes. A similar blocking feature is observed in Siberia/eastern Asia. A Bayesian approach to an Arctic/mid-latitude weather linkage emphasizes the nearly irresolvable uncertainty surrounding causation of recent major weather events; yet it drives scientific understanding of linkages and potential impacts on seasonal forecasting.

  6. 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.

  7. 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.

  8. Holocene Climate Change in Arctic Canada and Greenland

    NASA Astrophysics Data System (ADS)

    Briner, J. P.; McKay, N.; Axford, Y.; Bennike, O.; Bradley, R. S.; de Vernal, A.; Fisher, D. A.; Francus, P.; Fréchette, B.; Gajewski, K. J.; Jennings, A. E.; Kaufman, D. S.; Miller, G. H.; Rouston, C.; Wagner, B.

    2015-12-01

    We summarize the spatial and temporal pattern of climate change through the Holocene in Arctic Canada and Greenland. Our synthesis includes 47 records from a recent database of highly resolved, quantitative Holocene climate records from the Arctic (Sundqvist et al., 2014). We plot the temperature histories represented by the records in the database and compare them with paleoclimate information based on 53 additional records. Combined, the records include a variety of climate proxy types that range from ice (ice cores), land (lake and peat sequences) and marine (ocean sediment cores and coastal sediments) environments. The temperature-sensitive records indicate more consistent and earlier Holocene warmth in the north and east, and a more diffuse and later Holocene thermal maximum in the south and west. Principal components analysis reveals two dominant Holocene trends, one with early Holocene warmth followed by cooling in the middle Holocene, the other with a broader period of warmth in the middle Holocene followed by cooling in the late Holocene. The temperature decrease from the warmest to the coolest portions of the Holocene is 3.0±1.0°C on average (n=11 records). The Greenland Ice Sheet retracted to its minimum extent between 5 and 3 ka, consistent with many sites from around Greenland depicting a switch from warm to cool conditions around that time. The spatial pattern of temperature change through the Holocene was likely driven by the decrease in northern latitude summer insolation through the Holocene, the varied influence of waning ice sheets in the early Holocene, and the variable influx of Atlantic Water into the study region.

  9. The Greenland gravitational constant experiment.

    NASA Astrophysics Data System (ADS)

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

    1990-09-01

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

  10. 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

  11. Winter warming as an important co-driver for Betula nana growth in western Greenland during the past century

    PubMed Central

    Hollesen, Jørgen; Buchwal, Agata; Rachlewicz, Grzegorz; Hansen, Birger U; Hansen, Marc O; Stecher, Ole; Elberling, Bo

    2015-01-01

    Growing season conditions are widely recognized as the main driver for tundra shrub radial growth, but the effects of winter warming and snow remain an open question. Here, we present a more than 100 years long Betula nana ring-width chronology from Disko Island in western Greenland that demonstrates a highly significant and positive growth response to both summer and winter air temperatures during the past century. The importance of winter temperatures for Betula nana growth is especially pronounced during the periods from 1910–1930 to 1990–2011 that were dominated by significant winter warming. To explain the strong winter importance on growth, we assessed the importance of different environmental factors using site-specific measurements from 1991 to 2011 of soil temperatures, sea ice coverage, precipitation and snow depths. The results show a strong positive growth response to the amount of thawing and growing degree-days as well as to winter and spring soil temperatures. In addition to these direct effects, a strong negative growth response to sea ice extent was identified, indicating a possible link between local sea ice conditions, local climate variations and Betula nana growth rates. Data also reveal a clear shift within the last 20 years from a period with thick snow depths (1991–1996) and a positive effect on Betula nana radial growth, to a period (1997–2011) with generally very shallow snow depths and no significant growth response towards snow. During this period, winter and spring soil temperatures have increased significantly suggesting that the most recent increase in Betula nana radial growth is primarily triggered by warmer winter and spring air temperatures causing earlier snowmelt that allows the soils to drain and warm quicker. The presented results may help to explain the recently observed ‘greening of the Arctic’ which may further accelerate in future years due to both direct and indirect effects of winter warming. PMID:25788025

  12. Documenting Melting Features of the Greenland Ice Sheet

    NASA Astrophysics Data System (ADS)

    Tedesco, M.

    2011-12-01

    There is an increasing interest in studying the Greenland Ice Sheet, its hydrology and dynamics over the short term and longer term because of the potential impact of a warming Arctic. Major studies concern about whether increased surface melting will lead to changes in production of supraglacial lakes and subglacial water pressures and hence , potentially, rates of ice movement. In this talk I will show movies recorded over the past three years form fieldwork activities carried out over the West Greenland ice sheet. In particular, I will project and comment movies concerning surface streams and supraglacial lakes, as the one at http://www.youtube.com/watch?v=QbuFphwJn4c. I will discuss the importance of observing such phenomena and how the recorded videos can be used to summarize scientific studies and communicate the relevance of scientific findings. I will also show, for the first time, the video of the drainage of a supraglacial lake, an event during which a lake ~ 6 m deep and ~ 1 km drained in ~ 1.5 hours. This section of the movie is under development as video material was collected during our latest expedition in June 2011.

  13. Moulin density controls drainage development beneath the Greenland ice sheet

    NASA Astrophysics Data System (ADS)

    Banwell, Alison; Hewitt, Ian; Willis, Ian; Arnold, Neil

    2016-12-01

    Uncertainty remains about how the surface hydrology of the Greenland ice sheet influences its subglacial drainage system, affecting basal water pressures and ice velocities, particularly over intraseasonal and interseasonal timescales. Here we apply a high spatial (200 m) and temporal (1 h) resolution subglacial hydrological model to a marginal (extending 25 km inland), land-terminating, 200 km2 domain in the Paakitsoq region, West Greenland. The model is based on that by Hewitt (2013) but adapted for use with both real topographic boundary conditions and calibrated modeled water inputs. The inputs consist of moulin hydrographs, calculated by a surface routing and lake-filling/draining model, which is forced with distributed runoff from a surface energy-balance model. Results suggest that the areal density of lake-bottom moulins and their timing of opening during the melt season strongly affects subglacial drainage system development. A higher moulin density causes an earlier onset of subglacial channelization (i.e., water transport through channels rather than the distributed sheet), which becomes relatively widespread across the bed, whereas a lower moulin density results in a later onset of channelization that becomes less widespread across the bed. In turn, moulin density has a strong control on spatial and temporal variations in subglacial water pressures, which will influence basal sliding rates, and thus ice motion. The density of active surface-to-bed connections should be considered alongside surface melt intensity and extent in future predictions of the ice sheet's dynamics.

  14. Natural fluctuations of mercury and lead in Greenland lake sediments.

    PubMed

    Lindeberg, Carola; Bindler, Richard; Renberg, Ingemar; Emteryd, Ove; Karlsson, Edvard; Anderson, N John

    2006-01-01

    Given the current scenario of increasing global temperatures, it is valuable to assess the potential influence of changing climate on pollution distribution and deposition. In this study we use long-term sediment records from three lakes (spanning ca. 1000, 4800, and 8000 years, respectively) from the Greenland west coast to assess recent and long-term variations in mercury (Hg) and lead (Pb), including stable Pb isotopes (206Pb and 207Pb), in terms of pollution and climate influences. The temporal trends in sediment deposited from about the mid-19th century and forward are in general agreement with the history of industrial emissions at lower latitudes. Therefore, in recent sediment a possible influence from changing climate is difficult to assess. However, by using deeper sediment layers we show that changes in Greenland climate caused changes in the lake influx of material from regional aeolian activity, which resulted in large fluctuations in Hg and Pb concentrations and 206Pb/207Pb ratios. The aeolian material is primarily derived from glacio-fluvial material with low Hg and Pb concentrations and a different isotopic composition. For one of the lakes, the fluctuations in Hg concentrations (10 to 70 ng g(-1)) prior to the 19th century are equal to the anthropogenic increase in the uppermost layers, suggesting that when studying recent concentrations and time trends of pollution in relatively low-contaminated areas such as the Arctic, the early natural fluctuations must be considered.

  15. Anomalous subglacial heat flow in central Greenland induced by the Iceland plume.

    NASA Astrophysics Data System (ADS)

    Petrunin, Alexey G.; Rogozhina, Irina; Kaban, Mikhail K.; Vaughan, Alan P. M.; Steinberger, Bernhard; Johnson, Jesse; Koulakov, Ivan; Thomas, Maik

    2013-04-01

    3000 m of ice sheet thickness has ensured that central Greenland has kept it geothermal heat flow (GHF) distribution enigmatic. Some few direct ice temperature measurements from deep ice cores reveal a GHF of 50 to 60 mW/m² in the Summit region and this is noticeably above what would be expected for the underlying Early Proterozoic lithosphere. In addition, indirect estimates from zones of rapid basal melting suggest extreme anomalies 15 to 30 times continental background. Subglacial topography indicates caldera like topographic features in the zones hinting at possible volcanic activity in the past [1], and all of these observations combined hint at an anomalous lithospheric structure. Further supporting this comes from new high-resolution P-wave tomography, which shows a strong thermal anomaly in the lithosphere crossing Greenland from east to west [2]. Rock outcrops at the eastern and western end of this zone indicate significant former magmatic activity, older in the east and younger in the west. Additionally, plate modelling studies suggest that the Greenland plate passed over the mantle plume that is currently under Iceland from late Cretaceous to Neogene times, consistent with the evidence from age of magmatism. Evidence of rapid basal melt revealed by ice penetrating radar along the hypocentre of the putative plume track indicates that it continues to affect the Greenland continental geotherm today. We analyse plume-induced thermal disturbance of the present-day lithosphere and their effects on the central Greenland ice sheet by using a novel evolutionary model of the climate-ice-lithosphere-upper mantle system. Our results indicate that mantle plume-induced erosion of the lithosphere has occurred, explaining caldera-type volcanic structures, the GHF anomaly, and requiring dyke intrusion into the crust during the early Cenozoic. The residual thermo-mechanical effect of the mantle plume has raised deep-sourced heat flow by over 25 mW/m² since 60 Ma and

  16. Greenland ice sheet is changing

    NASA Image and Video Library

    2017-09-28

    At 1 p.m. EDT (10 a.m. PDT) on Friday, Aug. 28, NASA's Goddard Space Flight Center in Greenbelt, Maryland, will host a live TV program about agency research into how and why the massive Greenland ice sheet is changing. The event features scientists actively conducting field work in Greenland, along with extensive video footage of their work performed over this summer. Panelists include: Tom Wagner (cryosphere program scientist with NASA's Earth Science Division), Laurence Smith (chair of the University of California, Los Angeles Department of Geography), Mike Bevis (professor of geodynamics at Ohio State University in Columbus), Sophie Nowicki (physical scientist at Goddard), and Josh Willis (JPL). The Friday program will air live on NASA TV and stream online at: www.nasa.gov/nasatv. To ask questions via social media during the televised event, use the hashtag #askNASA. NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Like us on Facebook Find us on Instagram

  17. greenland_summer_campaign_1

    NASA Image and Video Library

    2017-09-28

    Laurence Smith, chair of geography at University of California, Los Angeles, deploys an autonomous drift boat equipped with several sensors in a meltwater river on the surface of the Greenland ice sheet on July 19, 2015. “Surface melting in Greenland has increased recently, and we lacked a rigorous estimate of the water volumes being produced and their transport,” said Tom Wagner, the cryosphere program scientist at NASA Headquarters in Washington. “NASA funds fieldwork like Smith’s because it helps us to interpret satellite data, and to extrapolate measurements from the local field sites to the larger ice sheet." Credit: NASA/Goddard/Jefferson Beck Read more: www.nasa.gov/feature/a-summer-of-nasa-research-on-sea-lev... NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Like us on Facebook Find us on Instagram

  18. Insect-Based Holocene (and Last Interglacial?) Paleothermometry from the E and NW Greenland Ice Sheet Margins: A Fly's-Eye View of Warmth on Greenland

    NASA Astrophysics Data System (ADS)

    Axford, Y.; Bigl, M.; Carrio, C.; Corbett, L. B.; Francis, D. R.; Hall, B. L.; Kelly, M. A.; Levy, L.; Lowell, T. V.; Osterberg, E. C.; Richter, N.; Roy, E.; Schellinger, G. C.

    2011-12-01

    Here we present new paleotemperature reconstructions based upon insect (Chironomidae) assemblages and other proxies from lake sediment cores recovered in east Greenland at ~71° N near Scoresby Sund and in northwest Greenland at ~77° N near Thule/Qaanaaq. In east Greenland, Last Chance Lake (informal name) is a small, non-glacial lake situated ~90 km east of the Greenland Ice Sheet margin. The lake preserves a sedimentary record of the entire Holocene (Levy et al. 2013). Chironomids from Last Chance Lake record cold summer temperatures (and establishment of a cold-climate fauna including abundant Oliveridia and Pseudodiamesa) during the late Holocene, preceded by summer temperatures estimated to have been 3 to 6°C warmer during the first half of the Holocene (when summer insolation forcing was greater than today). In northwest Greenland, Delta Sø and Wax Lips Lake (informal name) both preserve Holocene sediments. Here we discuss the late Holocene chironomid record from Delta Sø, whereas from Wax Lips Lake (a small, non-glacial lake situated ~2 km west of the ice sheet margin) we present a longer sedimentary and biostratigraphic record. The deeper portions of cores from Wax Lips Lake yield pre-Holocene and nonfinite radiocarbon ages, suggesting that this lake preserves sediments predating the Last Glacial Maximum. Abundant chironomids in the pre-glacial sediments appear to record interglacial conditions, and we infer that these sediments may date to the Last Interglacial (Eemian). The preservation of in situ Last Interglacial lacustrine sediments so close to the modern ice sheet margin suggests a minimally erosive glacierization style throughout the last glacial period, like that inferred for other Arctic locales such as on Baffin Island (Briner et al. 2007), ~750 km southwest of our study site. Our study sites are situated nearby key ice core sites (including NEEM, Camp Century, Agassiz and Renland) and very close to the ice sheet margin. These chironomid

  19. Insect-Based Holocene (and Last Interglacial?) Paleothermometry from the E and NW Greenland Ice Sheet Margins: A Fly's-Eye View of Warmth on Greenland

    NASA Astrophysics Data System (ADS)

    Axford, Y.; Bigl, M.; Carrio, C.; Corbett, L. B.; Francis, D. R.; Hall, B. L.; Kelly, M. A.; Levy, L.; Lowell, T. V.; Osterberg, E. C.; Richter, N.; Roy, E.; Schellinger, G. C.

    2013-12-01

    Here we present new paleotemperature reconstructions based upon insect (Chironomidae) assemblages and other proxies from lake sediment cores recovered in east Greenland at ~71° N near Scoresby Sund and in northwest Greenland at ~77° N near Thule/Qaanaaq. In east Greenland, Last Chance Lake (informal name) is a small, non-glacial lake situated ~90 km east of the Greenland Ice Sheet margin. The lake preserves a sedimentary record of the entire Holocene (Levy et al. 2013). Chironomids from Last Chance Lake record cold summer temperatures (and establishment of a cold-climate fauna including abundant Oliveridia and Pseudodiamesa) during the late Holocene, preceded by summer temperatures estimated to have been 3 to 6°C warmer during the first half of the Holocene (when summer insolation forcing was greater than today). In northwest Greenland, Delta Sø and Wax Lips Lake (informal name) both preserve Holocene sediments. Here we discuss the late Holocene chironomid record from Delta Sø, whereas from Wax Lips Lake (a small, non-glacial lake situated ~2 km west of the ice sheet margin) we present a longer sedimentary and biostratigraphic record. The deeper portions of cores from Wax Lips Lake yield pre-Holocene and nonfinite radiocarbon ages, suggesting that this lake preserves sediments predating the Last Glacial Maximum. Abundant chironomids in the pre-glacial sediments appear to record interglacial conditions, and we infer that these sediments may date to the Last Interglacial (Eemian). The preservation of in situ Last Interglacial lacustrine sediments so close to the modern ice sheet margin suggests a minimally erosive glacierization style throughout the last glacial period, like that inferred for other Arctic locales such as on Baffin Island (Briner et al. 2007), ~750 km southwest of our study site. Our study sites are situated nearby key ice core sites (including NEEM, Camp Century, Agassiz and Renland) and very close to the ice sheet margin. These chironomid

  20. 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.

  1. 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.

  2. 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.

  3. Mass balance of Greenland from combined GRACE and satellite altimetry inversion

    NASA Astrophysics Data System (ADS)

    Forsberg, R.; Sandberg Sørensen, L.; Nilsson, J.; Simonsen, S. B.

    2014-12-01

    With 12 years of GRACE satellite data now available, the ice mass loss trend of Greenland are clearly demonstrating ice mass loss in marginal zones of the ice sheets, and increasing mass loss trends in some regions such as the north west marginal zones. Although the GRACE release-5 products have provided a significant increase in resolution, the detailed space-based detection of where the ice sheet is loosing mass needs to come from other sources, notably satellite altimetry from EnviSat, IceSat and CryoSat, which point out the detailed location of areas of change, and - when combined with firn compaction and density models - also can be used to infer mass changes. In the paper we outline results of a novel direct inversion method, where all satellite data can be utilized in a general inverse estimation scheme, and the leakage from neighbouring ice caps minimized. We demonstrate overall mass change results from Greenland and Eastern Canadian Ice Caps 2003-14, highlighting the increasing melt in the marginal zones both in NW and NE Greenland. Most of the used data used are provided by the ESA Ice Sheets CCI project 2012-14, which makes available long term Essential Climate Variables such as Surface Elevation Changes, Ice Velocity and Calving Front Locations for the Greenland ice sheet. In the upcoming 2nd phase of the CCI project, Gravimetric Mass Balance from GRACE will be included as a ECV time series, and a similar CCI project started for Antarctica.

  4. Using ISSM to Simulate the LIA to Present Ice Margin Change at Upernavik Glacier, Greenland

    NASA Astrophysics Data System (ADS)

    Haubner, K.; Larour, E. Y.; Box, J.; Schlegel, N.; Larsen, S. H.; Kjeldsen, K. K.; Kjaer, K. H.

    2015-12-01

    The possibility for rapid melting of the Greenland ice sheet ranks among the most serious societal climate threats. This project puts the rate of contemporary climate change-driven Greenland ice mass change in a temporal context, by simulating the Greenland ice sheet margin throughout the Holocene and comparing the results with past ice margin positions (e.g. Andresen et al., 2014; Bjørk et al., 2012) and records of glacier activity based on fjord sediment strata (Andresen et al. 2012). Here we show first steps to achieve this goal and model the evolution of the Upernavik Isstrøm, a set of marine-terminating glaciers in Northwest Greenland, during the 20thcentury, using the Ice Sheet System Model (ISSM) (Larour et. al 2012). The simulation runs from 1900, shortly after the Little Ice Age (LIA), to year 2013, initialized using trimline data marking the former extent of the ice sheet and forced by a surface mass balance reconstruction after Box (2013). We address uncertainties in ice front positions and thickness by comparing our simulation output with present ice margin positions in the area. Finally, we investigate the possibility of simulating historic changes at ice sheet margins with this finite element ice sheet model. Andresen, C. S., Kjeldsen, K. K., Harden, B., Nørgaard-Pedersen, N. and Kjær, K. H. 2014. Outlet glacier dynamics and bathymetry at Upernavik Isstrøm and Upernavik Isfjord, North-West Greenland. GEUS Bulletin 31 Andresen, C. S., Straneo, F., Ribergaard, M. H., Bjørk, A. A., Andersen, T.J., Kuijpers, A., Nørgaard-Pedersen, N., Kjær, K. H., Schjøth, F., Weckström, K. and Ahlstrøm, A. P. 2012: Rapid response of Helheim Glacier in Greenland to climate variability over the past century. Nature Geoscience 5 Bjørk, A. A., Kjær, K. H., Korsgaard, N. J., Khan, A., S., Kjeldsen, K. K., Andresen, C. S., Box, J. E., Larsen, N. K. and Funder, S. 2012. Historical aerial photographs uncover eighty years of ice-climate interaction in southeast

  5. Chironomids as indicators of climate change: a temperature inference model for Greenland

    NASA Astrophysics Data System (ADS)

    Maddison, Eleanor J.; Long, Antony J.; Woodroffe, Sarah A.; Ranner, P. Helen; Huntley, Brian

    2014-05-01

    Current climate warming is predicted to accelerate melting of the Greenland Ice Sheet and cause global sea level to rise, but there is uncertainty about whether changes will be abrupt or more gradual, and whether the key forcing will be air or ocean temperatures. Examining past ice sheet response to climate change is therefore important, yet only a few quantitative temperature reconstructions exist from the Greenland Ice Sheet margin. Subfossil chironomids are a widely used biological proxy, with modern calibration data-sets used to construct past temperature. Many chironomid-inferred temperature models exist in the northern hemisphere high latitudes, however, no model currently exists for Greenland. Here we present a new model from south-west Greenland which utilises 22 lakes from the Nuup Kangerlua area (samples collected in summer 2011) and 19 lakes from the Kangerlussuaq fjord area (part of a dataset reported in Brodersen and Anderson (2002)). Monthly mean air temperatures were modelled for each lake site from air temperature logger data, collected in 2011-2012 from the Nuup Kangerlua area, and meteorological station temperature data. In the field, lake physical parameters and environmental variables were measured. Collected lake water and sediment samples were analysed in the laboratory. Statistical analysis of air temperature, geographical information, lake water chemistry and contemporary chironomid assemblage data was subsequently undertaken on the 41 lake training set. Mean June air temperature was found to be the main environmental control on the chironomid community, although other factors, including sample depth, conductivity and total nitrogen water content, were also found to be important. Weighted averaging partial least squares (WA-PLS) analysis was used to develop a new mean June air temperature inference model. Analysis indicated that the best model was a two component WA-PLS with r2=0.77, r2boot=0.56 and root mean square error of prediction = 1

  6. 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.

  7. 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.

  8. The summer 2012 Greenland heat wave: monitoring water vapour isotopic composition along an atmospheric river event

    NASA Astrophysics Data System (ADS)

    Bonne, Jean-Louis; Steen-Larsen, Hans Christian; Masson-Delmotte, Valérie; Sodemann, Harald; Lacour, Jean-Lionel; Risi, Camille; Werner, Martin; Clerbaux, Cathy; Fettweis, Xavier

    2014-05-01

    In July 2012, an extreme warm event occurred in Greenland, leading to surface melt over almost all the ice sheet. This event was recorded in the isotopic composition of water vapour measured by the IASI satellite along the transport pathway and at two sites where continuous in situ surface vapour isotopic measurements were conducted, situated at a coastal station of South Greenland (Ivittuut) and further North on top of the ice sheet (NEEM, NW Greenland). These observations allowed us to monitor the isotopic composition of the air mass at different stages of its advection towards Greenland, which can inform on processes along this trajectory, such as cloud properties and moisture sources. In addition, two simulations of this event, using the atmospheric general circulation models LMDZiso and ECHAM5wiso equipped with water stable isotopes and nudged towards large scale wind fields, are investigated. Furthermore, a regional high-resolution model was used to study the moisture transport to Greenland during this event using tagged water tracers of the North Atlantic ocean and coastal land evaporation. Using moisture source diagnostic based on the Lagrangian particle dispersion model Flexpart, we show that this 2012 heat wave event corresponds to moisture sources located over the subtropical Atlantic Ocean, where intense evaporation was caused by dry air masses associated with the US intense summer drought. This moisture was then advected northward along a narrow band, due to a very stationary surface cyclone southwest of Greenland, reached southern Greenland and Ivittuut coastal station on July 9th, travelled along the west coast of Greenland, continued eastwards above the ice sheet and arrived above the NEEM deep drilling camp on July 11th. Surface isotopic observations during the event show larger variations at NEEM than in Ivittuut, strongly reducing the isotopic and deuterium excess latitudinal gradient usually observed between South and North Greenland. This

  9. 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

  10. Interannual variations of the mass balance of the Antarctica and Greenland ice sheets from GRACE

    NASA Astrophysics Data System (ADS)

    Ramillien, G.; Lombard, A.; Cazenave, A.; Ivins, E. R.; Llubes, M.; Remy, F.; Biancale, R.

    2006-09-01

    We propose a new estimate of the mass balance of the West/East Antarctica and Greenland ice sheets from GRACE for the recent period (July 2002-March 2005) and compute the corresponding contribution to the global mean sea level. We use new GRACE geoid solutions provided by the Groupe de Recherche en Géodésie Spatiale (GRGS/CNES), at the resolution of ˜ 400 km and sampled at 10-day interval. In the three regions, significant interannual variations are observed, which we approximate as linear trends over the short time span of analysis. Over Greenland, an apparent total volume loss of 119 +/- 10 cu km/yr water is observed. For the Antarctica ice sheet, a bimodal behaviour is apparent, with volume loss amounting to 88 +/- 10 cu km/yr water in the West, and increase in the East amounting to 72 +/- 20 cu km/yr water. These GRACE results are affected by land hydrology contamination and glacial isostatic adjustment (GIA) of the solid Earth since last deglaciation. We correct for both land hydrology contamination (using a global hydrological model) and GIA using the ICE-4G model for Greenland and the IJ05 model for Antarctica. Corrected for both land hydrology contamination and GIA, GRACE volume rates are - 129 +/- 15 cu km/yr, - 107 +/- 23 cu km/yr and + 67 +/- 28 cu km/yr for Greenland, West Antarctica and East Antarctica respectively. In terms of sea level rise, the GRACE-based ice sheets contributions are + 0.36 +/- 0.04 mm/yr for Greenland, + 0.30 +/- 0.06 mm/yr for West Antarctica and - 0.19 +/- 0.07 for East Antarctica for the time interval of study. The total Antarctica contribution to sea level over this short time span is thus slightly positive (+ 0.11 +/- 0.09 mm/yr). The ice sheets together contribute to a sea level rise of 0.47 +/- 0.1 mm/yr. The results reported here are in qualitative agreement with recent estimates of the mass balance of the ice sheets based on GRACE and with those based upon other remote sensing observations. Due to the very short

  11. Rich Rogers Flying Over Greenland Icecap

    NASA Image and Video Library

    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...

  12. Current and future darkening of the Greenland ice sheet

    NASA Astrophysics Data System (ADS)

    Tedesco, Marco; Stroeve, Julienne; Fettweis, Xavier; Warren, Stephen; Doherty, Sarah; Noble, Erik; Alexander, Patrick

    2015-04-01

    Surface melting over the Greenland ice sheet (GIS) promotes snow grains growth, reducing albedo and further enhancing melting through the increased amount of absorbed solar radiation. Using a combination of remote sensing data and outputs of a regional climate model, we show that albedo over the GIS decreased significantly from 1996 to 2012. Further, we show that most of this darkening can be accounted for by enhanced snow grain growth and the expansion of areas where bare ice is exposed, both of which are driven by increases in snow warming. An analysis of the impact of light-absorbing impurities on albedo trends detected from spaceborne measurements was inconclusive because the estimated impact for concentrations of impurities of order of magnitude found in Greenland is within the albedo uncertainty retrievable from space-based instruments. However, neither models nor observations show an increase in pollutants (black carbon and associated organics) in the atmosphere over the GIS in this time period. Additionally, we could not identify trends in the number of fires over North America and Russia, assumed to be among the sources of soot for Greenland. We did find that a 'dark band' of tilted ice plays a crucial role in decreasing albedo along the west margin, and there is some indication that dust deposition to the GIS may be decreasing albedo in this region but this is not conclusive. In addition to looking at the direct impact of impurities on albedo, we estimated the impact of impurities on albedo via their influence on grain growth and found it is relatively small (~ 1- 2 %), though more sophisticated analysis needs to be carried out. Projections obtained under different warming scenarios consistently point to a continued darkening, with anomalies in albedo driven solely by the effects of climate warming of as much as -0.12 along the west margin of the GIS by the end of this century (with respect to year 2000). Projected darkening is likely underestimated

  13. Earthquake Activity in the North Greenland Region

    NASA Astrophysics Data System (ADS)

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

    2017-04-01

    Many local and regional earthquakes are recorded on a daily basis in northern Greenland. The majority of the earthquakes originate at the Arctic plate boundary between the Eurasian and the North American plates. Particularly active regions away from the plate boundary are found in NE Greenland and in northern Baffin Bay. The seismograph coverage in the region is sparse with the main seismograph stations located at the military outpost, Stations Nord (NOR), the weather station outpost Danmarkshavn (DAG), Thule Airbase (TULEG), and the former ice core drilling camp (NEEM) in the middle of the Greenland ice sheet. Furthermore, data is available from Alert (ALE), Resolute (RES), and other seismographs in northern Canada as well as from a temporary deployment of BroadBand seismographs along the north coast of Greenland from 2004 to 2007. The recorded earthquakes range in magnitude from less than 2 to a 4.8 event, the largest in NE Greenland, and a 5.7 event, the largest recorded in northern Baffin Bay. The larger events are recorded widely in the region allowing for focal mechanisms to be calculated. Only a few existing focal mechanisms for the region can be found in the ISC bulletin. Two in NE Greenland representing primarily normal faulting and one in Baffin Bay resulting from reverse faulting. New calculations of focal mechanisms for the region will be presented as well as improved hypocenters resulting from analysis involving temporary stations and regional stations that are not included in routine processing.

  14. 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.

  15. The Greenland gravitational constant experiment

    NASA Astrophysics Data System (ADS)

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

    1990-09-01

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

  16. Greenland's Coast in Holiday Colors

    NASA Technical Reports Server (NTRS)

    2003-01-01

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

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

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

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

  17. Ice-dammed lake drainage in Greenland and the implications on the surrounding bedrock and ice

    NASA Astrophysics Data System (ADS)

    Kjeldsen, K. K.; Khan, S. A.; Bjork, A. A.; Nielsen, K.

    2016-12-01

    Drainage of ice-dammed lakes is regularly observed along the margin of the Greenland Ice Sheet. However, the speed of the drainage events and implications can vary depending on the size of the lakes and the local settings. Our main focus area is Lake Tinninilik, dammed by Sarqardliup sermia in West Greenland. We use air- and satellite-borne laser- and radar altimetry, supplemented with Landsat imagery, to derive the lake drainage pattern and combine these observations with DEMs from aerial imagery to derive lake volume changes. In 2010 the lake drained within two months and water level dropped by c. 50 m, resulting in drainage of c. 1.53 km3 of water. Here, we assess the implication of drainage on the solid bedrock using Regional ElAstic Rebound calculator (REAR), and on the glacier damming the lake by comparing to altimetry observations.

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

  19. Greenland and Antarctica Ice Sheet Mass Changes and Effects on Global Sea Level

    NASA Astrophysics Data System (ADS)

    Forsberg, Rene; Sørensen, Louise; Simonsen, Sebastian

    2017-01-01

    Thirteen years of GRACE data provide an excellent picture of the current mass changes of Greenland and Antarctica, with mass loss in the GRACE period 2002-2015 amounting to 265 ± 25 GT/year for Greenland (including peripheral ice caps), and 95 ± 50 GT/year for Antarctica, corresponding to 0.72 and 0.26 mm/year average global sea level change. A significant acceleration in mass loss rate is found, especially for Antarctica, while Greenland mass loss, after a corresponding acceleration period, and a record mass loss in the summer of 2012, has seen a slight decrease in short-term mass loss trend. The yearly mass balance estimates, based on point mass inversion methods, have relatively large errors, both due to uncertainties in the glacial isostatic adjustment processes, especially for Antarctica, leakage from unmodelled ocean mass changes, and (for Greenland) difficulties in separating mass signals from the Greenland ice sheet and the adjacent Canadian ice caps. The limited resolution of GRACE affects the uncertainty of total mass loss to a smaller degree; we illustrate the "real" sources of mass changes by including satellite altimetry elevation change results in a joint inversion with GRACE, showing that mass change occurs primarily associated with major outlet glaciers, as well as a narrow coastal band. For Antarctica, the primary changes are associated with the major outlet glaciers in West Antarctica (Pine Island and Thwaites Glacier systems), as well as on the Antarctic Peninsula, where major glacier accelerations have been observed after the 2002 collapse of the Larsen B Ice Shelf.

  20. Relations between Arctic large-scale TEC changes and scintillations over Greenland

    NASA Astrophysics Data System (ADS)

    Durgonics, T.; Hoeg, P.; von Benzon, H. H.

    2014-12-01

    The increasing dependence on GNSS-based methods and technologies for global or regional navigation and communication has raised concerns about the impact of space weather on these systems. Temporal and spatial ionosphere variations caused by driving forces, such as changes in solar radiation, solar wind, and the Earth's magnetic field contribute to errors in satellite navigation positioning and communication systems. In this study we will focus on the impact of space weather in the Arctic region related to total electron content (TEC) and scintillation changes. Measurements from the GNSS network of stations in Greenland are analyzed and geophysical variables such as such as TEC, amplitude scintillation indices (S4), and phase scintillation indices (σϕ), are calculated together with 2D/3D electron density and scintillation maps. For the TEC we applied data from the Greenland GNET network of stations - consisting of 62 stations, while the scintillations data are based on 50 Hz sampled data from a set of sites on the west coast of Greenland (i.e., Thule, Sisimiut, and Kangerlussuaq). The GNSS-derived data is augmented by ground-based geomagnetic measurements, such as the Dst-index and magnetic H-component data obtained from the Greenland magnetic stations. Extreme ionosphere events will be presented and the underlying geophysical process will be identified and discussed. Especially results where large-scale gradients in the regional TEC are compared with the growth of scintillations. We will identify crucial elements and parameters (such as the auroral oval and the auroral electrojet), driving these changes in the Greenland TEC, S4 and σϕ distributions, in order to come up with appropriate algorithms and tools for monitoring and predicting Arctic TEC and scintillation large-scale patterns.

  1. 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

  2. Multi-sensor detection of glacial lake outburst floods in Greenland from space

    NASA Astrophysics Data System (ADS)

    Citterio, M.

    2015-12-01

    GLOFs cause substantial erosion, transport and delivery of sediment along the river system from the glaciated parts of the hydrologic catchment to the sea, and have been found to control the riverine export dynamics of some pollutants like mercury in NE Greenland. GLOFs also pose a risk to human presence and infrastracture. Ice-dammed lakes at the margin of the ice sheet and of local glaciers and ice caps are common features of Greenland's landscape. The occasional or periodic emptying of some of these lakes have been described as early as the 18thcentury. Thinning glaciers in a warming climate are already changing the behaviour of some of these lakes. However, little is known of the frequency and seasonality of glacier lake outburst floods (GLOF) outside of the relatively more densely populated parts of West and South Greenland. This contribution demonstrates automatic multi-sensor detection of ice-dammed lake emptying events from space for three test regions in West, South and Northeast Greenland, using visible imagery from Landsat, ASTER, PROBA-V and MODIS. The current detection algorithm relies on prior knowledge of lakes location and approximate shape from a topographic map at the scale of 1:250.000, and it is meant as a prototype for a future operational product. For the well documented case of the glacier-dammed lake of A.P. Olsen Ice Cap (NE Greenland), where GLOF's observations at Zackenberg Research Station started in 1996, the remote sensing and in situ records are compared, showing good agreement. ICESat altimetry, MODIS and AVHRR thermal imagery, and the ENVISAR ASAR signature of two detected GLOFs that took place late autumn and winter are also discussed to demonstrate the potential for successful retrievals during the polar night. The upcoming Sentinel-3 missions will alleviate what is currently the major drawback of implementing this prototype into an operational service, namely the limited availability of high resolution imagery. This is of special

  3. 13. VIEW TO WEST. DETAIL, WEST PIER, WEST APPROACH SPAN, ...

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

    13. VIEW TO WEST. DETAIL, WEST PIER, WEST APPROACH SPAN, LOCKING GEAR AT WEST END OF SWING SPAN. (photographed from boat) - Gianella Bridge, Spanning Sacramento River at State Highway 32, Hamilton City, Glenn County, CA

  4. A coupled ocean-sea ice-iceberg model over the 20th Century: Iceberg flux at 48°N as a proxy for Greenland iceberg discharge

    NASA Astrophysics Data System (ADS)

    Wilton, David; Bigg, Grant

    2013-04-01

    We have used a coupled ocean-sea ice-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] as a proxy for the variation in the calving rate of Greenland tidewater glaciers. 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, allied analysis using non-linear systems modelling, suggests that this series can be used as a proxy for the interannual Greenland Ice Sheet iceberg discharge. Our models find 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. 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

  5. Elevation and elevation change of Greenland and Antarctica derived from CryoSat-2

    NASA Astrophysics Data System (ADS)

    Helm, V.; Humbert, A.; Miller, H.

    2014-03-01

    The ESA satellite CryoSat-2 has been observing Earth's polar regions since April 2010. It carries a sophisticated radar altimeter and aims for the detection of changes in sea ice thickness as well as surface elevation changes of Earth's land and marine ice sheets. This study focuses on the Greenland and Antarctic ice sheets, considering the contemporary elevation of their surfaces. Based on 2 years of CryoSat-2 data acquisition, elevation change maps and mass balance estimates are presented. Additionally, new digital elevation models (DEMs) and the corresponding error maps are derived. Due to the high orbit of CryoSat-2 (88° N/S) and the narrow across-track spacing, more than 99% of Antarctica's surface area is covered. In contrast, previous radar altimeter measurements of ERS1/2 and ENVISAT were limited to latitudes between 81.5° N and 81.5° S and to surface slopes below 1°. The derived DEMs for Greenland and Antarctica have an accuracy which is similar to previous DEMs obtained by satellite-based laser and radar altimetry (Liu et al., 2001; Bamber et al., 2009, 2013; Fretwell et al., 2013; Howat et al., 2014). Comparisons with ICESat data show that 80% of the CryoSat-2 DEMs have an error of less than 3 m ± 30 m. For both ice sheets the surface elevation change rates between 2011 and 2012 are presented at a resolution of 1 km. Negative elevation changes are concentrated at the west and south-east coast of Greenland and in the Amundsen Sea embayment in West Antarctica (e.g. Pine Island and Thwaites glaciers). They agree well with the dynamic mass loss observed by ICESat between 2003 and 2008 (Pritchard et al., 2009). Thickening occurs along the main trunk of Kamb Ice Stream and in Dronning Maud Land. While the former is a consequence of an ice stream stagnated ∼150 years ago (Rose, 1979; Retzlaff and Bentley, 1993), the latter represents a known large-scale accumulation event (Lenaerts et al., 2013). This anomaly partly compensates for the observed

  6. Developing a Climatology of Atmospheric Rivers Impacting Greenland Using the Twentieth Century Reanalysis

    NASA Astrophysics Data System (ADS)

    Neff, W. D.; Compo, G. P.

    2014-12-01

    A recent paper [Neff et al., 2014]examined the factors underlying the 2012 melt episode that covered the Greenland ice sheet and compared it with the same factors identified for the last episode in 1889, using the Twentieth Century Reanalysis (20CR: [Compo et al., 2011]). A key factor 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 ice sheet. The 20CR proved quite effective in defining the structure and transport paths for both events. Although these events with wide spread melting of the ice sheet surface are extremely rare, a question remains as to the frequency of AR events and the ancillary conditions required for extensive melting of the ice sheet. Although the 20CR was effective in capturing the structure of AR events in 1889, an analysis of the northward transport of moisture off the west coast of Greenland at 850 hPa shows weaker transport prior to 1921 than after. In this study, we use time series of meridional velocity and specific humidity at 850 hPa during boreal summer months as a screening tool for high transport events. We attribute the muted representation of synoptic features to be an artifact of of sparse available stations reporting pressure along the northeast coast of Canada prior to 1921. For this reason we use different thresholds before and after 1921 to identify potential AR events. For each potential event we then examine maps of integrated water vapor between 240oW to 340oW and 20oN to 80oN to identify those with the IWV pattern characteristic of an AR. In our earlier study, we used the only station, Ilulissat, recording daily data on the west coast of Greenland corresponding to the entire1871-2012 period of the 20CR for verification of events in 1889 and 2012. In that analysis, temperatures maximized prior to each event together with light precipitation on the coast. In this study, we have used this

  7. 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

  8. 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.

  9. Iceberg calving dynamics of Jakobshavn Isbrae, Greenland

    NASA Astrophysics Data System (ADS)

    Amundson, Jason Michael

    Jakobshavn Isbrae, a fast-flowing outlet glacier in West Greenland, began a rapid retreat in the late 1990's. The glacier has since retreated over 15 km, thinned by tens of meters, and doubled its discharge into the ocean. The glacier's retreat and associated dynamic adjustment are driven by poorly-understood processes occurring at the glacier-ocean interface. These processes were investigated by synthesizing a suite of field data collected in 2007--2008, including timelapse imagery, seismic and audio recordings, iceberg and glacier motion surveys, and ocean wave measurements, with simple theoretical considerations. Observations indicate that the glacier's mass loss from calving occurs primarily in summer and is dominated by the semi-weekly calving of full-glacier-thickness icebergs, which can only occur when the terminus is at or near flotation. The calving icebergs produce long-lasting and far-reaching ocean waves and seismic signals, including "glacial earthquakes". Due to changes in the glacier stress field associated with calving, the lower glacier instantaneously accelerates by ˜3% but does not episodically slip, thus contradicting the originally proposed glacial earthquake mechanism. We furthermore showed that the predominance of calving during summer can be attributed to variations in the strength of the proglacial ice melange (dense pack of sea ice and icebergs). Sea ice growth in winter stiffens the melange and prevents calving; each summer the melange weakens and calving resumes. Previously proposed calving models are unable to explain the terminus dynamics of Jakobshavn Isbrae (and many other calving glaciers). Using our field observations as a basis, we developed a general framework for iceberg calving models that can be applied to any calving margin. The framework is based on mass continuity, the assumption that calving rate and terminus velocity are not independent, and the simple idea that terminus thickness following a calving event is larger than

  10. Peopling of the North Circumpolar Region – Insights from Y Chromosome STR and SNP Typing of Greenlanders

    PubMed Central

    Olofsson, Jill Katharina; Pereira, Vania; Børsting, Claus; Morling, Niels

    2015-01-01

    The human population in Greenland is characterized by migration events of Paleo- and Neo-Eskimos, as well as admixture with Europeans. In this study, the Y-chromosomal variation in male Greenlanders was investigated in detail by typing 73 Y-chromosomal single nucleotide polymorphisms (Y-SNPs) and 17 Y-chromosomal short tandem repeats (Y-STRs). Approximately 40% of the analyzed Greenlandic Y chromosomes were of European origin (I-M170, R1a-M513 and R1b-M343). Y chromosomes of European origin were mainly found in individuals from the west and south coasts of Greenland, which is in agreement with the historic records of the geographic placements of European settlements in Greenland. Two Inuit Y-chromosomal lineages, Q-M3 (xM19, M194, L663, SA01 and L766) and Q-NWT01 (xM265) were found in 23% and 31% of the male Greenlanders, respectively. The time to the most recent common ancestor (TMRCA) of the Q-M3 lineage of the Greenlanders was estimated to be between 4,400 and 10,900 years ago (y. a.) using two different methods. This is in agreement with the theory that the North Circumpolar Region was populated via a second expansion of humans in the North American continent. The TMRCA of the Q-NWT01 (xM265) lineage in Greenland was estimated to be between 7,000 and 14,300 y. a. using two different methods, which is older than the previously reported TMRCA of this lineage in other Inuit populations. Our results indicate that Inuit individuals carrying the Q-NWT01 (xM265) lineage may have their origin in the northeastern parts of North America and could be descendants of the Dorset culture. This in turn points to the possibility that the current Inuit population in Greenland is comprised of individuals of both Thule and Dorset descent. PMID:25635810

  11. 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.

  12. 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

  13. 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.

  14. Chutes and Fissures in Greenland

    NASA Image and Video Library

    2015-05-12

    Scientists and crew with NASA’s Operation IceBridge, which makes annual aerial surveys of polar ice, are wrapping up their seventh campaign over the Arctic. In spring 2015, the team began using a different research aircraft—an adapted C-130 Hercules. They also added four new high-priority targets in the rapidly changing region of northeast Greenland. Many of the flights, however, were routine. And that’s exactly the point; making measurements over the same path each year provides continuity between NASA’s Ice, Cloud, and Land Elevation Satellite (ICESat) missions—the first of which ended in 2009 and the second of which is scheduled for launch in 2017. Repeat measurements show how a landscape changes over time. One area that has been surveyed repeatedly is northern Greenland’s Ryder Glacier. This photograph, taken during the IceBridge flight on May 6, 2015, shows a large moulin—dozens of meters across—atop this glacier. Moulins are holes in the ice sheet that drain melt water from the ice sheet’s surface to the bottom or out to the sea. Scientists are working to figure out what happens to melt water once it enters a moulin.

  15. 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.

  16. The Danish Greenland Magnetometer Chain - Status and Outlook

    NASA Astrophysics Data System (ADS)

    Behlke, R.

    2016-12-01

    DTU Space operates the Greenland magnetometer array, including 19 variometer stations whereof 3 are geomagnetic observatories. This array consists of a West Coast Chain with 13 stations including three observatories between 77.47 and 61.16 geographic North. On the East Coast 5 variometer stations are located between 81.6 and 65.6 geographic North. The Greenland Array covers polar cap, cusp and auroral regions. These data allow the monitoring of electromagnetic processes in the polar ionosphere and magnetosphere, and are a significant contribution to global data sets. The vast majority of the sensors now employed are the Danish FGE 3-axis linear-core fluxgate magnetometers designed and built under the supervision of Ole Rasmussen and later Lars William Pedersen. They are optimized for long-term stability (observatory-quality instruments) rather than high sensitivity. The stations use 16 bit A/D converters with 20s or 1s sampling rate, optimized for 1 minute mean data. Hence, the rms-noise is approximately 0.1 nT in the 1 mHz - 1 Hz band, the time accuracy is 1s and the final resolution is 0.25 nT for most data at 20s sampling rate and 0.125 nT for most data at 1s sampling rate. During setup, the sensor axes are oriented along local magnetic north (H), local magnetic east (E) and vertical down (Z). Sensors at some stations are equipped with a suspension which guarantees vertical alignment. The instruments run fully automatically and require (normally) no manual intervention. All stations use the FGE vector magnetometer. Greenland magnetometer data has been aquired in digital form since 1981. From 1981 through 1990 all stations recorded with 1-min sampling rate. In 1986 the acquisition systems was gradually modified in order to record with 20-s sampling rate. Modification was completed by 1991, and since then all stations run at 20-s sampling rate. In 1999 acquisition system was made capable to record at 1-s sampling in addition to the continued 20-s sampoling rate

  17. Sonification of cryoconite landscapes over the Greenland ice sheet

    NASA Astrophysics Data System (ADS)

    Tedesco, M.

    2015-12-01

    Sonification is the use of non-speech audio to convey information. In sonification, several elements can be altered, modified or manipulated to change the perception of the sound, and in turn, the perception of the information being transmitted. For example, an increase or decrease in pitch, tempo and amplitude can be used to convey the information but this can also happen by varying other less commonly used components. One of the advantages of using sonification lies in the temporal, spatial, amplitude, and frequency resolution that offer complementary and supplementary possibilities with respect to visualization techniques. Two years ago, the outcomes of the PolarSEEDS project (www.polaseeds.org), consisting of sonification of time series of albedo, melting and surface temperature over the Greenland ice sheet, were presented in this very same session. The work that I will discuss in this presentation builds on the PolarSEEDS experience, focusing on the fascinating microcosm of cryoconite. Cryoconite is a unique and extremely fascinating form of glacial cover consisting of aggregated rock dust, inorganic and detrital organic matter, and active microbial colonies. It can be seen as 'living stones', with this ecosystem containing the only form of life that is sustained on the majestic surface of the Greenland ice sheet. Microbes are, indeed, the catalyst for cryoconite formation and growth. The cryoconite constituents radiate metabolic heat promoting glacier hole development, melt water formation, and decreasing glacier surface albedo. Lower albedos cause a positive feedback that further contributes to glacier ablation. Despite their importance, cryoconite systems are poorly studied and little is known about their evolution. In the talk, I will first present and discuss previous sonification projects whose main focus was on the polar regions; then, I will present new sonifications based on data quantifying the distribution and evolution of cryoconite over the west

  18. 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.

  19. Skerrylike mirages and the discovery of greenland.

    PubMed

    Lehn, W H

    2000-07-20

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

  20. Measurements of Glacial Isostatic Adjustment in Greenland

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

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

  1. A multi-element study of ISUA iron-formation, W-Greenland

    NASA Technical Reports Server (NTRS)

    Rast, U.

    1983-01-01

    Meta-sediments from Isua, West Greenland were analyzed by instrumental thermal neutron activation analysis (ITNAA). These sediments are chemical precipitates having some layers of remarkably high Cr content. The latter were compared to Cr poor layers. It turned out that the Cr enriched layers had higher Ir and Ni contents than the samples from the Cr poor layers. Compared to phanerozoic samples the highest Ir contents are not extraordinarily higher than in a modern sediment, and the Cr poor layers, representing more or less phanerozoic shale. From the cratering record of the Moon one can assume a similar cratering of the Earth at about the time when the Isua rocks were formed.

  2. 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.

  3. 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.

  4. Quaternary vertebrates from Greenland: A review

    NASA Astrophysics Data System (ADS)

    Bennike, Ole

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

  5. Pilot study completed: Paving the way for stereoscopic DEMs, orthophotos and vector maps over the ice-free parts of Greenland

    NASA Astrophysics Data System (ADS)

    Levinsen, Joanna F.; Borgstrøm, Rasmus E.

    2017-04-01

    We present the work towards developing new Digital Elevation Models (DEMs), orthophotos, and vector maps over the ice-free parts of Greenland. The products will be based on high-resolution stereoscopic images co-registered to Ground Control Points (GCPs) to reduce horizontal and vertical errors. Here, we provide a status overview of our achievements wrt. DEMs and orthophotos. We have conducted a pilot study in which four areas have been mapped using SPOT-6 and -7 images: The Disko Bay, Narsaq, Tasiilaq, and Zackenberg. The images have been acquired in 2016, with a few additions from 2014, and the areas cover approximately 82.000 km2, i.e. ˜20% of the total ice-free area. The technical requirements for the products have been defined in close collaboration with end-users from governmental institutions, emergency management offices, the tourist industry, etc., to ensure a direct applicability following product completion. This has resulted in 8 m DEMs and 1.5 m orthophotos. Validation against GCPs shows horizontal and vertical offsets of approximately 0.5 ± 2 m, i.e. values that meet our expectations and satisfy end-user needs. The GCPs make out an extensive network of huts, helipads, ports, large boulders, etc., measured using GPS by collaborators during field campaigns. The experiences gained in the product development as well as the broad range of collaborations provides confidence that the set-up for a production of the total ice-free area has been established, which can deliver products with a high accuracy in time and space. That will make them useful for a wide range of purposes. The next step therefore is to secure the given upgrade. More on that to come!

  6. Winter warming as an important co-driver for Betula nana growth in western Greenland during the past century.

    PubMed

    Hollesen, Jørgen; Buchwal, Agata; Rachlewicz, Grzegorz; Hansen, Birger U; Hansen, Marc O; Stecher, Ole; Elberling, Bo

    2015-06-01

    Growing season conditions are widely recognized as the main driver for tundra shrub radial growth, but the effects of winter warming and snow remain an open question. Here, we present a more than 100 years long Betula nana ring-width chronology from Disko Island in western Greenland that demonstrates a highly significant and positive growth response to both summer and winter air temperatures during the past century. The importance of winter temperatures for Betula nana growth is especially pronounced during the periods from 1910-1930 to 1990-2011 that were dominated by significant winter warming. To explain the strong winter importance on growth, we assessed the importance of different environmental factors using site-specific measurements from 1991 to 2011 of soil temperatures, sea ice coverage, precipitation and snow depths. The results show a strong positive growth response to the amount of thawing and growing degree-days as well as to winter and spring soil temperatures. In addition to these direct effects, a strong negative growth response to sea ice extent was identified, indicating a possible link between local sea ice conditions, local climate variations and Betula nana growth rates. Data also reveal a clear shift within the last 20 years from a period with thick snow depths (1991-1996) and a positive effect on Betula nana radial growth, to a period (1997-2011) with generally very shallow snow depths and no significant growth response towards snow. During this period, winter and spring soil temperatures have increased significantly suggesting that the most recent increase in Betula nana radial growth is primarily triggered by warmer winter and spring air temperatures causing earlier snowmelt that allows the soils to drain and warm quicker. The presented results may help to explain the recently observed 'greening of the Arctic' which may further accelerate in future years due to both direct and indirect effects of winter warming. © 2015 John Wiley & Sons

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

    PubMed

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

    2016-08-10

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

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

    PubMed Central

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

    2017-01-01

    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. PMID:28163988

  9. Investigating Greenland Outlet Glacier Annual Motion in Response to Varying Subglacial Hydraulic Structure

    NASA Astrophysics Data System (ADS)

    Nienow, P. W.; Tedstone, A. J.; Gourmelen, N.; Sole, A. J.

    2014-12-01

    The relationship between surface melting and ice motion will affect how the Greenland Ice Sheet responds to climate and the structure of the subglacial drainage system may be crucial in controlling how changing melt-rates impact ice motion. Several lines of evidence indicate that hydraulically efficient subglacial channels extend tens of km inland from land-terminating margins of the Greenland Ice Sheet during the melt-season. However, it remains unclear the extent to which water pressure variations in these drainage axes perturb ice-motion in areas both proximal and distal to the channels where the drainage system is likely hydraulically inefficient. Here, we present ice velocities observed with field based GPS and remotely sensed TerraSAR-X data across a land-terminating region of the south-west Greenland ice sheet during the melt-year 2012-2013, to examine the impact of varying drainage system structure on the spatial pattern of seasonal and annual ice motion. We find that whilst spatial variability in the configuration of the subglacial drainage system controls ice motion at short timescales, this configuration has negligible impact on the spatial pattern of the proportion of annual motion which occurs during summer. Whilst absolute annual velocities vary substantially, the proportional contribution of summer motion to annual motion does not. Subglacial hydrology does not therefore have a significant impact on the overall extent to which summer motion contributes to annual motion. These findings imply that the representation of hydrology in ice sheet models may be simplified.

  10. High-resolution in situ measurement of nitrate in runoff from the Greenland Ice Sheet.

    PubMed

    Beaton, Alexander David; Wadham, Jemma L; Hawkings, Jon; Bagshaw, Elizabeth A; Lamarche-Gagnon, Guillaume; Mowlem, Matthew C; Tranter, Martyn

    2017-09-27

    We report the first in situ high-resolution nitrate time series from two proglacial meltwater rivers draining the Greenland Ice Sheet, using a recently developed submersible analyser based on lab-on-chip (LOC) technology. The low sample volume (320 μL) required by the LOC analyser meant that low concentration (few to sub μM), highly turbid subglacial meltwater could be filtered and colourimetrically analysed in situ. These data are linked to an unparalleled, multi-component data set. Nitrate concentrations in rivers draining Leverett Glacier in South-West Greenland and Kiattuut Sermiat in Southern Greenland exhibited a clear diurnal signal and a gradual decline at the commencement of the melt season, displaying trends would not be discernible using traditional daily manual sampling. Nitrate concentrations varied by 4.4 μM (+/- 0.2 μM) over a 10-day period at Kiattuut Sermiat and 3.0 μM (+/- 0.2 μM) over a 14 day period at Leverett Glacier. Marked changes in nitrate concentrations were observed when discharge began to increase. High resolution in situ measurements such as these have the potential to significantly advance the understanding of nutrient cycling in remote systems, where the dynamics of nutrient release are complex but are important for downstream biogeochemical cycles.

  11. Tectonic inversion in the Wandel Sea Basin: A new structural model of Kilen (eastern North Greenland)

    NASA Astrophysics Data System (ADS)

    Svennevig, Kristian; Guarnieri, Pierpaolo; Stemmerik, Lars

    2016-12-01

    The seminunatak Kilen in eastern North Greenland, with its complexly deformed Carboniferous-Cretaceous strata, is a key area to understand the tectonic history of the transform plate boundary between eastern North Greenland and Svalbard. Detailed 3-D geological mapping from oblique photogrammetry along with limited ground fieldwork and interpretation of previously published data forms the basis for a new structural model of Kilen. Previous structural models interpreted rhombic-shaped fault patterns as the evidence for strike-slip tectonics. These structures are here interpreted to be the result of a post-Coniacian NE-SW extension with NW-SE trending normal faults followed by later, N-S compression of presumable Paleocene-Eocene age, folding the faults passively and suggesting the presence of a basal detachment. Furthermore, two thrust sheets have been distinguished on Kilen: a lower Kilen Thrust Sheet and an upper Hondal Elv Thrust Sheet separated by a subhorizontal fault: the Central Detachment. The style of deformation and the structures described are interpreted as the result of Paleocene-Eocene N-S directed compression resulting in basin inversion with strike-slip faults only having minor status. This indicates that the Greenland margin as exposed on Kilen and the conjugate Svalbard margin in the West Spitsbergen fold-and-thrust belt are more similar than previously anticipated.

  12. 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.

  13. Emerging impact of Greenland meltwater on deepwater formation in the North Atlantic Ocean

    NASA Astrophysics Data System (ADS)

    Böning, Claus W.; Behrens, Erik; Biastoch, Arne; Getzlaff, Klaus; Bamber, Jonathan L.

    2016-07-01

    The Greenland ice sheet has experienced increasing mass loss since the 1990s. The enhanced freshwater flux due to both surface melt and outlet glacier discharge is assuming an increasingly important role in the changing freshwater budget of the subarctic Atlantic. The sustained and increasing freshwater fluxes from Greenland to the surface ocean could lead to a suppression of deep winter convection in the Labrador Sea, with potential ramifications for the strength of the Atlantic meridional overturning circulation. Here we assess the impact of the increases in the freshwater fluxes, reconstructed with full spatial resolution, using a global ocean circulation model with a grid spacing fine enough to capture the small-scale, eddying transport processes in the subpolar North Atlantic. Our simulations suggest that the invasion of meltwater from the West Greenland shelf has initiated a gradual freshening trend at the surface of the Labrador Sea. Although the freshening is still smaller than the variability associated with the episodic `great salinity anomalies', the accumulation of meltwater may become large enough to progressively dampen the deep winter convection in the coming years. We conclude that the freshwater anomaly has not yet had a significant impact on the Atlantic meridional overturning circulation.

  14. Reconstructing the dynamics of the Greenland ice sheet during the last deglaciation

    NASA Astrophysics Data System (ADS)

    Keisling, Benjamin; DeConto, Robert

    2016-04-01

    Today, some outlet glaciers of the Greenland ice sheet (GrIS) are rapidly retreating and may mobilize large volumes of interior ice in the coming centuries. The last period that saw such dramatic, sustained retreat of the GrIS was the last deglaciation, when the ice sheet retreated from its Last Glacial Maximum (LGM) extent. Previous studies have used relative sea level observations to constrain changes in ice thickness and retreat timing during the deglaciation (e.g. Fleming and Lambert 2004, Simpson et al. 2009, Lecavalier et al. 2014). Here we build on these studies by isolating the drivers of ice-sheet retreat, and their spatial and temporal dynamics, during this period. Inclusion of ice-cliff failure and hydrofracturing parameterizations in our model has resulted in a better fit to paleodata for the Antarctic ice sheet, but this modeling approach has not been applied to the GrIS. Here we use a three-dimensional hybrid SSA/SIA ice-sheet model (Pollard et al. 2015) at 10km resolution over Greenland to simulate the last deglaciation. Boundary conditions for the last glacial maximum produce an LGM ice sheet with 3.81 meters sea level equivalent (m s.l.e.) of additional ice. The LGM ice sheet advances to the shelf-break in west, south, and east Greenland with an expansive ice shelf extending across Davis Strait. Applying modern atmospheric and oceanic forcing to the LGM ice sheet yields 1.25 and 1.09 m s.l.e. of melt, respectively, and 1.72 m s.l.e. for both. Ocean warming initially results in a higher rate and magnitude of retreat, but increased surface evaporation over open water results in additional accumulation that offsets losses in 10 kyr simulations. Here, we test the sensitivity of the magnitude of deglacial ice-sheet retreat to uncertainty in bedrock elevation and basal slding coefficients, the applied climate forcing, and the mass balance scheme (positive degree-day or energy balance). We also implement a deglacial climate forcing based on recently

  15. A 70-year record of outlet glacier retreat in northern Greenland

    NASA Astrophysics Data System (ADS)

    Hill, Emily; Carr, Rachel; Stokes, Chris; Gudmundsson, Hilmar

    2017-04-01

    Over the past two decades, the Greenland Ice Sheet (GrIS) has undergone accelerated mass loss increasing its contribution to sea level rise. This is partly attributed to increased mass loss from dynamic marine-terminating outlet glaciers. Despite marine-terminating outlet glaciers in northern Greenland draining 40% of the ice sheet by area, they are comparatively less well-studied than other regions of the ice sheet (e.g. central west or south-east). This region could be susceptible to marine-ice sheet instability due to large proportions of the bedrock rested below sea level and is also unique in the presence of large floating ice tongues. Here, we use a range of satellite imagery sources, accompanied by historical maps, to examine multi-decadal front position changes at 21 outlet glaciers in northern Greenland between 1948 and 2016. We accompany these terminus changes, with annual records of ice velocity, climate-ocean forcing data, and glacier-specific factors (e.g. fjord-width and basal topography) to understand the dominant forcing on glacier dynamics in the region. Over the last 70 years, there has been a clear pattern of glacier retreat in northern Greenland. This is particularly notable during the last two decades, where 62% of our study glaciers showed accelerated retreat. This was most notable at Humboldt, Tracy, Hagen Brae, C. H. Ostenfeld and Petermann Glaciers, and in the case of the latter three glaciers, this involved substantial retreat of their floating ice tongues (> 10 km). Alongside retreat, several study glaciers underwent simultaneous velocity increases. However, the collapse of floating ice tongues did not always result in increased velocity. Similar to other regions of the ice sheet, recent glacier retreat in the northern regions of the Greenland Ice Sheet could be linked to climatic-oceanic forcing, but at this stage this remains largely unknown. This response to external forcing is further complicated by the presence of glacier

  16. The influence of sea ice extent variability on the Greenland surface mass and energy balance

    NASA Astrophysics Data System (ADS)

    Tedesco, M.; Quillet, A.; Alexander, P. M.; Rennermalm, A. K.; Stroeve, J. C.; Fettweis, X.; Orantes, E. J.; Tuia, D.; Parkan, M.

    2012-12-01

    removal of the dependency of or results from near-surface temperature trends. We describe the results of our analysis concerning not only the southwest region but we also focus on the northeast area, where we find also statistically significant correlation between ILWC and open water fraction but later in the summer (e.g. September). We lastly discuss the potential sources of the differences between the results over the west and east regions and suggest a plan for future studies. To our knowledge, this is the first study aiming at combining observations and surface energy balance quantities to improve our understanding of the impact of sea ice loss on surface processes over the Greenland ice sheet.

  17. JPRS Report, West Europe.

    DTIC Science & Technology

    1987-07-15

    and the Greenlanders. When the exterior symbol—the Ministry for Greenland Affairs—is closed down, there will be more direct contact between the...period, and I shared them to the full." [Question] So, on 15 December 1981, after Jaruzelski’s coup in Warsaw, Berlinguer went to TRIBUNA POLITICA

  18. Response of major Greenland outlet glaciers to oceanic and atmospheric forcing: Results from numerical modeling on Petermann, Jakobshavn and Helheim Glacier.

    NASA Astrophysics Data System (ADS)

    Nick, F. M.; Vieli, A.; Pattyn, F.; Van de Wal, R.

    2011-12-01

    Oceanic forcing has been suggested as a major trigger for dynamic changes of Greenland outlet glaciers. Significant melting near their calving front or beneath the floating tongue and reduced support from sea ice or ice melange in front of their calving front can result in retreat of the terminus or the grounding line, and an increase in calving activities. Depending on the geometry and basal topography of the glacier, these oceanic forcing can affect the glacier dynamic differently. Here, we carry out a comparison study between three major outlet glaciers in Greenland and investigate the impact of a warmer ocean on glacier dynamics and ice discharge. We present results from a numerical ice-flow model applied to Petermann Glacier in the north, Jakobshavn Glacier in the west, and Helheim Glacier in the southeast of Greenland.

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

    NASA Astrophysics Data System (ADS)

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

    2016-12-01

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

  20. 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.

  1. Greenland's pronounced glacier retreat not irreversible

    NASA Astrophysics Data System (ADS)

    Schultz, Colin

    2012-02-01

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

  2. 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.

  3. 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.

  4. Characterization of household waste in Greenland.

    PubMed

    Eisted, Rasmus; Christensen, Thomas H

    2011-07-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

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

  6. Oxygen isotope ratios in the shell of Mytilus edulis: archives of glacier meltwater in Greenland?

    NASA Astrophysics Data System (ADS)

    Versteegh, E. A. A.; Blicher, M. E.; Mortensen, J.; Rysgaard, S.; Als, T. D.; Wanamaker, A. D., Jr.

    2012-09-01

    Melting of the Greenland Ice Sheet (GrIS) is accelerating and will contribute significantly to global sea level rise during the 21st century. Instrumental data on GrIS melting only cover the last few decades, and proxy data extending our knowledge into the past are vital for validating models predicting the influence of ongoing climate change. We investigated a potential meltwater proxy in Godthåbsfjord (West Greenland), where glacier meltwater causes seasonal excursions with lower oxygen isotope water (δ18Ow) values and salinity. The blue mussel (Mytilus edulis) potentially records these variations, because it precipitates its shell calcite in oxygen isotopic equilibrium with ambient seawater. As M. edulis shells are known to occur in raised shorelines and kitchen middens from previous Holocene warm periods, this species may be ideal in reconstructing past meltwater dynamics. We investigate its potential as a palaeo-meltwater proxy. First, we confirmed that M. edulis shell calcite oxygen isotope (δ18Oc) values are in equilibrium with ambient water and generally reflect meltwater conditions. Subsequently we investigated if this species recorded the full range of δ18Ow values occurring during the years 2007 to 2010. Results show that δ18Ow values were not recorded at very low salinities (< ~19), because the mussels appear to cease growing. This implies that M. edulis δ18Oc values are suitable in reconstructing past meltwater amounts in most cases, but care has to be taken that shells are collected not too close to a glacier, but rather in the mid region or mouth of the fjord. The focus of future research will expand on the geographical and temporal range of the shell measurements by sampling mussels in other fjords in Greenland along a south-north gradient, and by sampling shells from raised shorelines and kitchen middens from prehistoric settlements in Greenland.

  7. 3D viscosity maps for Greenland and effect on GRACE mass balance estimates

    NASA Astrophysics Data System (ADS)

    van der Wal, Wouter; Xu, Zheng

    2016-04-01

    The GRACE satellite mission measures mass loss of the Greenland ice sheet. To correct for glacial isostatic adjustment numerical models are used. Although generally found to be a small signal, the full range of possible GIA models has not been explored yet. In particular, low viscosities due to a wet mantle and high temperatures due to the nearby Iceland hotspot could have a significant effect on GIA gravity rates. The goal of this study is to present a range of possible viscosity maps, and investigate the effect on GRACE mass balance estimates. Viscosity is derived using flow laws for olivine. Mantle temperature is computed from global seismology models, based on temperature derivatives for different mantle compositions. An indication for grain sizes is obtained by xenolith findings at a few locations. We also investigate the weakening effect of the presence of melt. To calculate gravity rates, we use a finite-element GIA model with the 3D viscosity maps and the ICE-5G loading history. GRACE mass balances for mascons in Greenland are derived with a least-squares inversion, using separate constraints for the inland and coastal areas in Greenland. Biases in the least-squares inversion are corrected using scale factors estimated from a simulation based on a surface mass balance model (Xu et al., submitted to The Cryosphere). Model results show enhanced gravity rates in the west and south of Greenland with 3D viscosity maps, compared to GIA models with 1D viscosity. The effect on regional mass balance is up to 5 Gt/year. Regional low viscosity can make present-day gravity rates sensitivity to ice thickness changes in the last decades. Therefore, an improved ice loading history for these time scales is needed.

  8. Hepatitis D outbreak among children in a hepatitis B hyper-endemic settlement in Greenland.

    PubMed

    Børresen, M L; Olsen, O R; Ladefoged, K; McMahon, B J; Hjuler, T; Panum, I; Simonetti, J; Jones, C; Krarup, H; Koch, A

    2010-03-01

    Hepatitis B virus (HBV) infection is endemic in Greenland with 5-10% of the population being HBsAg-positive (chronic carriers). Surprisingly, despite of the high prevalence of HBV infection, acute and chronic hepatitis B, liver cirrhosis and primary hepatocellular carcinoma appear much less frequently than expected. The reasons for the low frequencies are unknown, but as a consequence implementation of a childhood HBV vaccination programme, though debated for years, has never been instituted. We describe an outbreak of hepatitis D (HDV) infection among children in a hepatitis B hyper-endemic settlement of 133 inhabitants on the west coast of Greenland. In 2006 a total of 27% of the inhabitants were HBsAg-positive (chronic carriers) and 83% were HBcAb-positive (previously exposed). Forty-six percent of the HBsAg-positive persons were below 20 years of age. On follow-up 1 year later a total of 68% of the HBsAg-positive persons were HDV-IgG positive. Five children, who were HBsAg-positive in 2006, had HDV-seroconverted from 2006 to 2007, indicating a HDV-super-infection. Most of the HDV-IgG positive children had markedly elevated liver enzymes. In the multivariate analysis, among the HBV and HDV markers, presence of HDV-IgG was most strongly associated with elevation of liver enzymes. In conclusion, the HBV-HDV super-infection and presumed HDV outbreak in this settlement challenges the notion that HBV infection may not be as harmless in Greenland as previously anticipated. The findings strongly suggest that HBV vaccination should be included in the child-immunization program in Greenland.

  9. Oxygen isotope ratios in the shell of Mytilus edulis: archives of glacier meltwater in Greenland?

    NASA Astrophysics Data System (ADS)

    Versteegh, E. A. A.; Blicher, M. E.; Mortensen, J.; Rysgaard, S.; Als, T. D.; Wanamaker, A. D., Jr.

    2012-12-01

    Melting of the Greenland Ice Sheet (GrIS) is accelerating and will contribute significantly to global sea level rise during the 21st century. Instrumental data on GrIS melting only cover the last few decades, and proxy data extending our knowledge into the past are vital for validating models predicting the influence of ongoing climate change. We investigated a potential meltwater proxy in Godthåbsfjord (West Greenland), where glacier meltwater causes seasonal excursions with lower oxygen isotope water (δ18Ow) values and salinity. The blue mussel (Mytilus edulis) potentially records these variations, because it precipitates its shell calcite in oxygen isotopic equilibrium with ambient seawater. As M. edulis shells are known to occur in raised shorelines and archaeological shell middens from previous Holocene warm periods, this species may be ideal in reconstructing past meltwater dynamics. We investigate its potential as a palaeo-meltwater proxy. First, we confirmed that M. edulis shell calcite oxygen isotope (δ18Oc) values are in equilibrium with ambient water and generally reflect meltwater conditions. Subsequently we investigated if this species recorded the full range of δ18Ow values occurring during the years 2007 to 2010. Results show that δ18Ow values were not recorded at very low salinities (< ~ 19), because the mussels appear to cease growing. This implies that Mytilus edulis δ18Oc values are suitable in reconstructing past meltwater amounts in most cases, but care has to be taken that shells are collected not too close to a glacier, but rather in the mid-region or mouth of the fjord. The focus of future research will expand on the geographical and temporal range of the shell measurements by sampling mussels in other fjords in Greenland along a south-north gradient, and by sampling shells from raised shorelines and archaeological shell middens from prehistoric settlements in Greenland.

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

    DOE PAGES

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

    2015-06-11

    Atmospheric warming over the Greenland Ice Sheet during the last 2 decades has increased the amount of surface meltwater production, resulting in the migration of melt and percolation regimes to higher altitudes and an increase in the amount of ice content from refrozen meltwater found in the firn above the superimposed ice zone. Here we present field and airborne radar observations of buried ice layers within the near-surface (0–20 m) firn in western Greenland, obtained from campaigns between 1998 and 2014. We find a sharp increase in firn-ice content in the form of thick widespread layers in the percolation zone,more » which decreases the capacity of the firn to store meltwater. The estimated total annual ice content retained in the near-surface firn in areas with positive surface mass balance west of the ice divide in Greenland reached a maximum of 74 ± 25 Gt in 2012, when 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. Furthermore, 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

  11. 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, when 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. Furthermore, 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.

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

    NASA Astrophysics Data System (ADS)

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

    2015-06-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-01-01

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

  14. Continuous, Pulsed Export of Methane-Supersaturated Meltwaters from the Bed of the Greenland Ice Sheet

    NASA Astrophysics Data System (ADS)

    Lamarche-Gagnon, G.; Wadham, J.; Beaton, A.; Fietzek, P.; Stanley, K. M.; Tedstone, A.; Sherwood Lollar, B.; Lacrampe Couloume, G.; Telling, J.; Liz, B.; Hawkings, J.; Kohler, T. J.; Zarsky, J. D.; Stibal, M.; Mowlem, M. C.

    2016-12-01

    Both past and present ice sheets have been proposed to cap large quantities of methane (CH4), on orders of magnitude significant enough to impact global greenhouse gas concentrations during periods of rapid ice retreat. However, to date most evidence for sub-ice sheet methane has been indirect, derived from calculations of the methanogenic potential of basal-ice microbial communities and biogeochemical models; field-based empirical measurements are lacking from large ice sheet catchments. Here, we present the first continuous, in situ record of dissolved methane export from a large catchment of the Greenland Ice Sheet (GrIS) in South West Greenland from May-July 2015. Our results indicate that glacial runoff was continuously supersaturated with methane over the observation period (dissolved CH4 concentrations of 30-700 nM), with total methane flux rising as subglacial discharge increased. Periodic subglacial drainage events, characterised by rapid changes (i.e. pulses) in meltwater hydrochemistry, also coincided with a rise in methane concentrations. We argue that these are likely indicative of the flushing of subglacial reservoirs of CH4 beneath the ice sheet. Total methane export was relatively modest when compared to global methane budgets, but too high to be explained by previously determined methanogenic rates from Greenland basal ice. Discrepancies between estimated Greenland methane reserves and observed fluxes stress the need to further investigate GrIS methane fluxes and sources, and suggest a more biogeochemically active subglacial environment than previously considered. Results indicate that future warming, and a coincident increase in ice melt rates, would likely make the GrIS, and by extension the Antarctic Ice Sheet, more significant sources of atmospheric methane, consequently acting as a positive feedback to a warming climate.

  15. Greenland Ice Sheet retreat during the Eemian

    NASA Astrophysics Data System (ADS)

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

    2012-04-01

    We present a new estimate of the evolution of the Greenland Ice Sheet through the Eemian (130 till 115 ky BP). This estimate is determined using the 3D 'shallow' ice sheet model ANICE and the regional climate model RACMO2/GR. The two models are time-slice coupled with an interval of 1500 years. 3D interpolated surface mass balance fields from RACMO2/GR force ANICE. Eemian and post-Eemian climate from the GCM ECHO-G drives RACMO2/GR on its lateral boundaries. These boundaries are gradually adjusted from maximum Eemian conditions to post-Eemian inception conditions, following the orbital parameters and Greenhouse gas concentrations derived from ice cores. The simulation shows a steady mass loss till the insolation conditions decline and the summer climate cools, with a typical rate of mass loss equivalent to 5 cm sea level rise per century for most of the time. Once summer start to cool the Greenland ice sheet recovers fast. The maximum ice loss is about 2 m eustatic sea level compared to present day volume and originates predominantly from southwest Greenland. Our results align with paleo-observations of Eemian ice sheet existence in South Greenland. Strong summer radiation also induces ice retreat in northern Greenland. Moreover, it agrees with preceding studies that the Greenland ice sheet had only a limited contribution to the Eemian sea level high stand. A finding of this novel approach is the impact of topographic pinpoints on the ice sheet evolution. Subglacial topography, like at 52° W 72° N (near Uummannaq), cause promontories in the ice sheet that enhances snowfall. Locations with high snowfall react less on warming than dry locations, because more melt is needed before all snow is removed, and the more efficient ice melt starts. The reduced ice depth also buttresses inland ice, limiting the ice sheet response to enhanced ablation. As a result, this topographical feature becomes the northern limit of significant ice sheet retreat, and shields the north

  16. 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

  17. From volcanic plains to glaciated peaks: Burial, uplift and exhumation history of southern East Greenland after opening of the NE Atlantic

    NASA Astrophysics Data System (ADS)

    Japsen, Peter; Green, Paul F.; Bonow, Johan M.; Nielsen, Troels F. D.; Chalmers, James A.

    2014-05-01

    In southern East Greenland (68-70°N), voluminous flood basalts erupted onto a largely horizontal lava plain near sea level at the Paleocene-Eocene transition when sea-floor spreading started in the NE Atlantic. Based on synthesis of geological observations, stratigraphic landform analysis and apatite fission-track analysis data in 90 rock samples, we show how three regional phases of uplift and exhumation subsequently shaped the present-day margin and controlled the discontinuous history of the Greenland ice sheet. A late Eocene phase of uplift led to formation of a regional erosion surface near sea level (the Upper Planation Surface, UPS). Uplift of the UPS in the late Miocene led to formation of the Lower Planation Surface (LPS) by incision below the uplifted UPS, and a Pliocene phase led to incision of valleys and fjords below the uplifted LPS, leaving mountain peaks reaching 3.7 km above sea level. Local uplift affected the Kangerlussuaq area (~ 68°N) during early Eocene emplacement of the Kangerlussuaq Intrusion and during late Oligocene block movements, that may be related to the detachment of the Jan Mayen microcontinent from Greenland, while middle Miocene thermal activity, coeval with lava eruptions, heated rocks along a prominent fault within the early Cretaceous to Paleocene Kangerlussuaq Basin. The three regional uplift phases are synchronous with phases in West Greenland, overlap in time with similar events in North America and Europe and also correlate with changes in plate motion. The much higher elevation of East Greenland compared to West Greenland suggests support in the east from the Iceland plume. These observations indicate a connection between mantle convection, changes in plate motion and vertical movements along passive continental margins.

  18. 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.

  19. Correction of Correlation Errors in Greenland Ice Mass Variations from GRACE using Empirical Orthogonal Function

    NASA Astrophysics Data System (ADS)

    Eom, J.; Seo, K. W.

    2015-12-01

    Since its launch in March 2002, the Gravity Recovery And Climate Experiment (GRACE) has provided monthly geopotential fields represented by Stokes coefficients of spherical harmonics (SH). Nominally, GRACE gravity solutions exclude effects from tides, ocean dynamics and barometric pressure by incorporating geophysical models for them. However, those models are imperfect, and thus GRACE solutions include the residual gravity effects. Particularly, unmodeled gravity variations of sub-monthly or shorter time scale cause aliasing error, which produces peculiar longitudinal stripes. Those north-south patterns are removed by spatial filtering, but caution is necessary for the aliasing correction because signals with longitudinal patterns are possibly removed during the procedure. This would be particularly problematic for studies associated with Greenland ice mass balance since large ice mass variations are expected in the West and South-West coast of Greenland that are elongated along the longitudinal direction. In this study, we develop a novel method to remove the correlation error using extended Empirical Orthogonal Function (extended EOF). The extended EOF is useful to separate spatially and temporally coherent signal from high frequency variations. Since temporal variability of the correlation error is high, the error is possibly removed via the extended EOF. Ice mass variations reduced by the extended EOF show more detail patterns of ice mass loss/gain than those from the conventional spatial filtering. Large amount of ice loss has occurred along the West, South-West and East coastal area during summer. The extended EOF is potentially useful to enhance signal to noise ratio and increase spatial resolution of GRACE data.

  20. Horizons West.

    ERIC Educational Resources Information Center

    Kitses, Jim

    The western is the most popular and enduring of Hollywood forms. It is one embodiment of a traditional theme in American culture: the West as both Garden of natural dignity and innocence and also as treacherous Desert resisting the gradual sweep of agrarian progress and community values. Westerns have in common: a) history, America's past; b)…

  1. Horizons West.

    ERIC Educational Resources Information Center

    Kitses, Jim

    The western is the most popular and enduring of Hollywood forms. It is one embodiment of a traditional theme in American culture: the West as both Garden of natural dignity and innocence and also as treacherous Desert resisting the gradual sweep of agrarian progress and community values. Westerns have in common: a) history, America's past; b)…

  2. Towards Greenland Glaciation: cumulative or abrupt transition?

    NASA Astrophysics Data System (ADS)

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

    2017-04-01

    During the mid-Pliocene warming period (3-3.3 Ma BP), the global annual mean temperatures inferred by data and model studies were 2-3° warmer than pre-industrial values. Accordingly, Greenland ice sheet volume is supposed to reach at the most, only half of that of present-day [Haywood et al. 2010]. Around 2.7-2.6 Ma BP, just ˜ 500 kyr after the warming peak of mid-Pliocene, the Greenland ice sheet has reached its full size [Lunt et al. 2008]. A crucial question concerns the evolution of the Greenland ice sheet from half to full size during the 3 - 2.5 Ma period. Data show 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 with low summer insolation to preserve the ice sheet during insolation maxima. This suggests rather a cumulative process than an abrupt event. In order to diagnose the evolution of the ice sheet build-up, 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 us to investigate the waxing and waning of the ice sheet during several orbital cycles. We use a tri-dimensional interpolation method designed by Ladant et al. (2014), which allows the evolution of CO2 concentration and of orbital parameters, and the evolution of the Greenland ice sheet size to be taken into account. By interpolating climatic snapshot simulations ran with various possible combinations of CO2, orbits and ice sheet sizes, we can build a continuous climatic forcing that is then used to provide 500 kyrs-long ice sheet simulations. With such a tool, we may offer a physically based answer to different CO2 reconstructions scenarios and analyse which one is the most consistent with Greenland ice sheet buildup.

  3. Ice Thicknesses and Driving Stresses of Greenland Ice Sheet

    NASA Technical Reports Server (NTRS)

    Zwally, H. J.; Saba, J.; Giovinetto, M.

    1999-01-01

    Surface elevations from satellite radar altimetry (Geosat, Seasat, and ERS-1) and bedrock topography from airborne radar sounding (Simon Ekholm's Danish compilation) are combined to derive maps of the driving stresses in the Greenland ice sheet. The stress vector, tau = rho g h sin(alpha), is calculated using surface slope vectors, alpha, from surface elevations and ice thicknesses, h, from the difference between surface and basal elevations. Since the 5-km scale of the surface slope is only about 2 times the ice thickness, the stress maps show spatial variations indicative of longitudinal stress gradients associated with topographic undulations. Values of alpha generally vary from near zero at the ice divides to maxima values around 120 kpa, returning to near zero in a narrow band at the edges. The distribution of alpha's peaks at 60 kpa with an approximate sigma of +/- 20 kpa. Areas of very low alpha near the origin of the northeast ice stream may indicate small sub-glacial lakes. The profile of alpha, down the ice stream from near the ice divide, increases to a maximum of about 120 kpa near the margin, which is characteristic of East Antarctic outlet glaciers and in contrast to West Antarctic ice streams where alpha has maximum values 400 to 500 km inland from the grounding lines. Overall distributions of alpha values are compared with those for the Antarctic ice sheet and the Mars Northern ice cap.

  4. The Greenland Sea Odden: Intra- and inter-annual variability

    USGS Publications Warehouse

    Russell, C.A.; Fischer, K.W.; Shuchman, R.A.; Josberger, E.G.

    1997-01-01

    The "Odden" is a large sea ice feature that forms in the East Greenland Sea which generally forms at the beginning of the winter season and can cover 300,000 km2. Throughout the winter, the outer edge of the Odden may advance and retreat by several hundred kilometers on time scales of a few days to weeks. Satellite passive microwave observations from 1978 through 1995 provide a continuous record of the spatial and temporal variations of this extremely dynamic phenomenon. The 17 year record shows both strong inter- and intra-annual variations in Odden extent and temporal behavior. An analysis of the satellite passive microwave derived ice area and extent time series along with meteorological data from the Arctic Drifting Buoy Network determined the meteorological forcing required for Odden growth, maintenance and decay. The key meteorological parameters which cause the rapid ice formation and decay associated with the Odden are, in order of importance, air temperature, wind speed, and wind direction. Atmospheric pressure was found not to play a significant role in the Odden events. Air temperature and wind direction are the dominant variables with temperatures below -9.5??C and winds from the west required to trigger significant Odden ice formation events. ??2004 Copyright SPIE - The International Society for Optical Engineering.

  5. Greenland outlet glacier dynamics from Extreme Ice Survey (EIS) photogrammetry

    NASA Astrophysics Data System (ADS)

    Hawbecker, P.; Box, J. E.; Balog, J. D.; Ahn, Y.; Benson, R. J.

    2010-12-01

    Time Lapse cameras fill gaps in our observational capabilities: 1. By providing much higher temporal resolution than offered by conventional airborne or satellite remote sensing. 2. While GPS or auto-theodolite observations can provide higher time resolution data than from photogrammetry, survival of these instruments on the hazardous glacier surface is limited, plus, the maintenance of such systems can be more expensive than the maintenance of a terrestrial photogrammetry installation. 3. Imagery provide a high spatial density of observations across the glacier surface, higher than is realistically available from GPS or other in-situ observations. 4. time lapse cameras provide observational capabilities in Eulerian and Lagrangian frames while GPS or theodolite targets, going along for a ride on the glacier, provide only Lagrangian data. Photogrammetry techniques are applied to a year-plus of images from multiple west Greenland glaciers to determine the glacier front horizontal velocity variations at hourly to seasonal time scales. The presentation includes comparisons between glacier front velocities and: 1. surface melt rates inferred from surface air temperature and solar radiation observations; 2. major calving events identified from camera images; 3. surface and near-surface ocean temperature; 4. land-fast sea ice breakup; 5. tidal variations; 6. supra-glacial melt lake drainage events observed in daily optical satellite imagery; and 7.) GPS data. Extreme Ice Survey (EIS) time lapse camera overlooking the Petermann glacier, installed to image glacier dynamics and to capture the predicted ice "island" detachment.

  6. Organochlorine residues in harbour porpoises from Southwest Greenland.

    PubMed

    Borrell, Asunción; Aguilar, Alex; Cantos, Gemma; Lockyer, Christina; Heide-Jørgensen, Mads Peter; Jensen, Jette

    2004-01-01

    During the 1995 hunting season, 75 harbour porpoises (Phocoena phocoena) were sampled in three locations in West Greenland: Maniitsoq, Nuuk, and Paamiut. Sex, age, morphometrics, reproductive condition, and organochlorine compound (OC) levels in blubber were determined for each individual. OC levels were extremely low and, therefore considered unlikely to affect the population adversely: mean blubber concentrations, expressed on lipid weight basis were 1.98 (S.D.=1.1) mg/kg for PCBs, 2.76 (S.D.=1.66) mg/kg for tDDT and 0.21 (S.D.=0.11) mg/kg for HCB. No statistical differences were observed among individuals caught in the various locations. OC concentrations showed statistically significant positive associations with age in males but negative in females; consequently, mature females presented lower pollutant loads than their male counterparts. Juveniles did not show differences between sexes. A higher proportion of less chlorinated and more metabolizable polychlorinated biphenyls (PCBs) compared to tPCBs was found in calves (age< or =1) than in mature females, indicating that the feeding habits of these two groups differ and that a greater transfer of less chlorinated compounds is passed from females to their pups through lactation and parturition. Harbour porpoises significantly contribute to the dietary intake of OCs by local Inuit populations. This contribution could be reduced if mature males were selectively avoided; however, current hunting procedures make this selection impracticable.

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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

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

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

    SciTech Connect

    Lüthi, M. P.; Ryser, C.; Andrews, L. C.; Catania, G. A.; Funk, M.; Hawley, R. L.; Hoffman, M. J.; Neumann, T. A.

    2015-01-01

    Ice temperature profiles from the Greenland Ice Sheet contain information on the deformation history, past climates and recent warming. We present full-depth temperature profiles from two drill sites on a flow line passing through Swiss Camp, West Greenland. Numerical modeling reveals that ice temperatures are considerably higher than would be expected from heat diffusion and dissipation alone. The possible causes for this extra heat are evaluated using a Lagrangian heat flow model. The model results reveal that the observations can be explained with a combination of different processes: enhanced dissipation (strain heating) in ice-age ice, temperate paleo-firn, and cryo-hydrologic warming in deep crevasses.

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

    DOE PAGES

    Lüthi, M. P.; Ryser, C.; Andrews, L. C.; ...

    2015-01-01

    Ice temperature profiles from the Greenland Ice Sheet contain information on the deformation history, past climates and recent warming. We present full-depth temperature profiles from two drill sites on a flow line passing through Swiss Camp, West Greenland. Numerical modeling reveals that ice temperatures are considerably higher than would be expected from heat diffusion and dissipation alone. The possible causes for this extra heat are evaluated using a Lagrangian heat flow model. The model results reveal that the observations can be explained with a combination of different processes: enhanced dissipation (strain heating) in ice-age ice, temperate paleo-firn, and cryo-hydrologic warmingmore » in deep crevasses.« less

  10. Hyperspectral, photogrammetric and morphological characterization of surface impurities over the Greenland ice sheet from remote sensing observations

    NASA Astrophysics Data System (ADS)

    Tedesco, M.; Alexander, P. M.; Briggs, K.; Linares, M.; Mote, T. L.

    2016-12-01

    The spatial and temporal evolution of surface impurities over the Greenland ice sheet plays a crucial role in modulating the meltwater production in view of the associated feedback on albedo. Recent studies have pointed to a `darkening' of the west portion of the ice sheet with this reduction in albedo likely associated with the increasing presence of surface impurities (e.g., soot, dust) and biological activity (e.g., cryoconite holes, algae, bacteria). Regional climate models currently do not account for the presence, evolution and impact on albedo of such impurities, mostly because the underlying processes driving the spectral and morphological evolution of impurities are poorly known. One for the reasons for this is the lack of hyperspectral and high-spatial resolution data over specific regions of the Greenland ice sheet. To put things in perspective: there is more hyperspectral data at high spatial resolution for the planet Mars than for the Greenland ice sheet. In this presentation, we report the results of an analysis using the few available hyperspectral data collected over Greenland by the HYPERION and AVIRIS sensors, in conjunction with visible (RGB) helicopter-based high resolution images and LANDSAT/WorldView data for characterizing the spectral and morphological evolution of surface impurities and cryoconite holes over western Greenland. The hyperspectral data is used to characterize the abundance of different `endmembers' and