Microbial Energetics Beneath the Taylor Glacier, Antarctica
NASA Astrophysics Data System (ADS)
Mikucki, J. A.; Turchyn, A. V.; Farquhar, J.; Priscu, J. C.; Schrag, D. P.; Pearson, A.
2007-12-01
Subglacial microbiology is controlled by glacier hydrology, bedrock lithology, and the preglacial ecosystem. These factors can all affect metabolic function by influencing electron acceptor and donor availability in the subglacial setting leaving biogeochemical signatures that can be used to determine ecosystem processes. Blood Falls, an iron-rich, episodic subglacial outflow from the Taylor Glacier in the McMurdo Dry Valleys Antarctica provides an example of how microbial community structure and function can provide insight into subglacial hydrology. This subglacial outflow contains cryoconcentrated, Pliocene-age seawater salts that pooled in the upper Taylor Valley and was subsequently covered by the advance of the Taylor Glacier. Biogeochemical measurements, culture-based techniques, and genomic analysis were used to characterize microbes and chemistry associated with the subglacial outflow. The isotopic composition of important geochemical substrates (i.e., δ34Ssulfate, Δ33Ssulfate, δ18Osulfate, δ18Owater, Δ14SDIC) were also measured to provide more detail on subglacial microbial energetics. Typically, subglacial systems, when driven to anoxia by the hydrolysis of organic matter, will follow a continuum of redox chemistries utilizing electron acceptors with decreasing reduction potential (e.g., Fe (III), sulfate, CO2). Our data provide no evidence for sulfate reduction below the Taylor Glacier despite high dissolved organic carbon (450 μM C) and measurable metabolic activity. We contend that, in the case of the Taylor Glacier, the in situ bioenergetic reduction potential has been 'short-circuited' at Fe(III)-reduction and excludes sulfate reduction and methanogenesis. Given the length of time that this marine system has been isolated from phototrophic production (~2 Mya) the ability to degrade and consume increasingly recalcitrant organic carbon is likely an important component to the observed redox chemistry. Our work indicates that glacier hydrology
Observed Melt Season Seismicity of Taylor Glacier, Antarctica
NASA Astrophysics Data System (ADS)
Carmichael, J. D.; Pettit, E. C.; Creager, K. C.
2006-12-01
Sufficient evidence exists to suggest that interaction of crevasses and meltwater accelerates ice cliff disintegration of tidewater glaciers. It is not clear what role meltwater plays in calving characteristics from dry- based polar glaciers. We have obtained seismic data from a six-sensor seismic array deployed in October of 2004 near the terminus cliffs of Taylor Glacier, West Antarctica, to analyze near-cliff seismicity throughout a melt season. Discharge data from the adjacent Lawson stream suggests that dramatic increases in meltwater volume temporally correlate with changes in seismic character near ice cliffs. We calculated source-locations for ice-quake during hours of melting and re-freezing and found most large energy events to be located near the ice cliffs. The associated spectra and waveform characteristics are indicative of literature descriptions of crevassing events.
Calving of Talyor Glacier, Dry Valleys, Antarctica
NASA Astrophysics Data System (ADS)
Carmichael, J. D.; Pettit, E. C.; Creager, K. C.; Hallet, B.
2007-12-01
Calving of tide-water glaciers has received considerable attention, with seismic arrays in Alaska, Greenland, and Antarctica devoted to their observation. In these environments, ice cliffs are directly coupled to oceanic temperatures. The land-based polar glaciers of the McMurdo Dry Valleys in Antarctica represent a simpler environment unaffected directly by water contact where other factors can be isolated. In particular, summer calving events of Taylor Glacier are observed to consist of precursory activity including crack growth, cliff overhang, and active seismicity at least 1 hour before collapse. We propose that collapse occurs only after a stress threshold has been crossed, evident from 'pre-calving' of ice from the cliff base 1-3 days prior to the major event. We provide photographic, seismic, and temperature data to illustrate the thermal and stress landscape for land-based calving of polar glaciers.
Seismic multiplet response triggered by melt at Blood Falls, Taylor Glacier, Antarctica
NASA Astrophysics Data System (ADS)
Carmichael, Joshua D.; Pettit, Erin C.; Hoffman, Matt; Fountain, Andrew; Hallet, Bernard
2012-09-01
Meltwater input often triggers a seismic response from glaciers and ice sheets. It is difficult, however, to measure melt production on glaciers directly, while subglacial water storage is not directly observable. Therefore, we document temporal changes in seismicity from a dry-based polar glacier (Taylor Glacier, Antarctica) during a melt season using a synthesis of seismic observation and melt modeling. We record icequakes using a dense six-receiver network of three-component geophones and compare this with melt input generated from a calibrated surface energy balance model. In the absence of modeled surface melt, we find that seismicity is well-described by a diurnal signal composed of microseismic events in lake and glacial ice. During melt events, the diurnal signal is suppressed and seismicity is instead characterized by large glacial icequakes. We perform network-based correlation and clustering analyses of seismic record sections and determine that 18% of melt-season icequakes are repetitive (multiplets). The epicentral locations for these multiplets suggest that they are triggered by meltwater produced near a brine seep known as Blood Falls. Our observations of the correspondingp-wave first motions are consistent with volumetric source mechanisms. We suggest that surface melt enables a persistent pathway through this cold ice to an englacial fracture system that is responsible for brine release episodes from the Blood Falls seep. The scalar moments for these events suggest that the volumetric increase at the source region can be explained by melt input.
Radiometric 81Kr dating identifies 120,000-year-old ice at Taylor Glacier, Antarctica
Buizert, Christo; Baggenstos, Daniel; Jiang, Wei; Purtschert, Roland; Petrenko, Vasilii V.; Lu, Zheng-Tian; Müller, Peter; Kuhl, Tanner; Lee, James; Severinghaus, Jeffrey P.; Brook, Edward J.
2014-01-01
We present successful 81Kr-Kr radiometric dating of ancient polar ice. Krypton was extracted from the air bubbles in four ∼350-kg polar ice samples from Taylor Glacier in the McMurdo Dry Valleys, Antarctica, and dated using Atom Trap Trace Analysis (ATTA). The 81Kr radiometric ages agree with independent age estimates obtained from stratigraphic dating techniques with a mean absolute age offset of 6 ± 2.5 ka. Our experimental methods and sampling strategy are validated by (i) 85Kr and 39Ar analyses that show the samples to be free of modern air contamination and (ii) air content measurements that show the ice did not experience gas loss. We estimate the error in the 81Kr ages due to past geomagnetic variability to be below 3 ka. We show that ice from the previous interglacial period (Marine Isotope Stage 5e, 130–115 ka before present) can be found in abundance near the surface of Taylor Glacier. Our study paves the way for reliable radiometric dating of ancient ice in blue ice areas and margin sites where large samples are available, greatly enhancing their scientific value as archives of old ice and meteorites. At present, ATTA 81Kr analysis requires a 40–80-kg ice sample; as sample requirements continue to decrease, 81Kr dating of ice cores is a future possibility. PMID:24753606
Radiometric 81Kr dating identifies 120,000-year-old ice at Taylor Glacier, Antarctica.
Buizert, Christo; Baggenstos, Daniel; Jiang, Wei; Purtschert, Roland; Petrenko, Vasilii V; Lu, Zheng-Tian; Müller, Peter; Kuhl, Tanner; Lee, James; Severinghaus, Jeffrey P; Brook, Edward J
2014-05-13
We present successful (81)Kr-Kr radiometric dating of ancient polar ice. Krypton was extracted from the air bubbles in four ∼350-kg polar ice samples from Taylor Glacier in the McMurdo Dry Valleys, Antarctica, and dated using Atom Trap Trace Analysis (ATTA). The (81)Kr radiometric ages agree with independent age estimates obtained from stratigraphic dating techniques with a mean absolute age offset of 6 ± 2.5 ka. Our experimental methods and sampling strategy are validated by (i) (85)Kr and (39)Ar analyses that show the samples to be free of modern air contamination and (ii) air content measurements that show the ice did not experience gas loss. We estimate the error in the (81)Kr ages due to past geomagnetic variability to be below 3 ka. We show that ice from the previous interglacial period (Marine Isotope Stage 5e, 130-115 ka before present) can be found in abundance near the surface of Taylor Glacier. Our study paves the way for reliable radiometric dating of ancient ice in blue ice areas and margin sites where large samples are available, greatly enhancing their scientific value as archives of old ice and meteorites. At present, ATTA (81)Kr analysis requires a 40-80-kg ice sample; as sample requirements continue to decrease, (81)Kr dating of ice cores is a future possibility.
NASA Astrophysics Data System (ADS)
Aarons, Sarah M.; Aciego, Sarah M.; Arendt, Carli A.; Blakowski, Molly A.; Steigmeyer, August; Gabrielli, Paolo; Sierra-Hernández, M. Roxana; Beaudon, Emilie; Delmonte, Barbara; Baccolo, Giovanni; May, Nathaniel W.; Pratt, Kerri A.
2017-04-01
Mineral dust is transported in the atmosphere and deposited in oceans, ice sheets and the terrestrial biosphere. Temporal changes in locations of dust source areas and transport pathways have implications for global climate and biogeochemical cycles. The chemical and physical characterization of the dust record preserved in ice cores is useful for identifying of dust source regions, dust transport, dominant wind direction and storm trajectories. Here, we present a 50,000-year geochemical characterization of mineral dust entrapped in a horizontal ice core from the Taylor Glacier in East Antarctica. Strontium (Sr) and neodymium (Nd) isotopes, grain size distribution, trace and rare earth element (REE) concentrations, and inorganic ion (Cl- and Na+) concentrations were measured in 38 samples, corresponding to a time interval from 46 kyr before present (BP) to present. The Sr and Nd isotope compositions of insoluble dust in the Taylor Glacier ice shows distinct changes between the Last Glacial Period (LGP in this study ranging from ∼46.7-15.3 kyr BP) the early Holocene (in this study ranging from ∼14.5-8.7 kyr BP), and zero-age samples. The 87Sr/86Sr isotopic composition of dust in the Taylor Glacier ice ranged from 0.708 to 0.711 during the LGP, while the variability during the early Holocene is higher ranging from 0.707 to 0.714. The εNd composition ranges from 0.1 to -3.9 during the LGP, and is more variable from 1.9 to -8.2 during the early Holocene. The increased isotopic variability during the early Holocene suggests a shift in dust provenance coinciding with the major climate transition from the LGP to the Holocene. The isotopic composition and multiple physical and chemical constraints support previous work attributing Southern South America (SSA) as the main dust source to East Antarctica during the LGP, and a combination of both local Ross Sea Sector dust sources and SSA after the transition into the Holocene. This study provides the first high time
Koh, Hye Yeon; Lee, Sung Gu; Lee, Jun Hyuck; Doyle, Shawn; Christner, Brent C; Kim, Hak Jun
2012-12-01
The psychrophilic bacterium Paenisporosarcina sp. TG-14 was isolated from sediment-laden stratified basal ice from Taylor Glacier, McMurdo Dry Valleys, Antarctica. Here we report the draft genome sequence of this strain, which may provide useful information on the cold adaptation mechanism in extremely variable environments.
An Active Englacial Hydrological System in a Cold Glacier: Blood Falls, Taylor Glacier, Antarctica
NASA Astrophysics Data System (ADS)
Carr, C. G.; Pettit, E. C.; Carmichael, J.; Badgeley, J.; Tulaczyk, S. M.; Lyons, W. B.; Mikucki, J.
2016-12-01
Blood Falls is a supraglacial hydrological feature formed by episodic release of iron-rich subglacial brine derived from an extensive aquifer beneath the cold, polar, Taylor Glacier. While fluid transport in non-temperate ice typically occurs through meltwater delivery from the glacier surface to the bed (hydrofracturing, supraglacial lake drainage), Blood Falls represents the opposite situation: brine moves from a subglacial source to the glacier surface. Here, we present the first complete conceptual model for brine transport and release, as well as the first direct evidence of a wintertime brine release at Blood Falls obtained through year-round time-lapse photography. Related analyses show that brine pools subglacially underneath the northern terminus of Taylor Glacier, rather than flowing directly into proglacial Lake Bonney because ice-cored moraines and channelized surface topography provide hydraulic barriers. This pooled brine is pressurized by hydraulic head from the upglacier brine source region. Based on seismic data, we propose that episodic supraglacial release is initiated by high strain rates coupled with pressurized subglacial brine that drive intermittent subglacial and englacial fracturing. Ultimately, brine-filled basal crevasses propagate upward to link with surface crevasses, allowing brine to flow from the bed to the surface. The observation of wintertime brine release indicates that surface-generated meltwater is not necessary to trigger crack propagation or to maintain the conduit as previously suggested. The liquid brine persists beneath and within the cold ice (-17°C) despite ambient ice/brine temperature differences of as high as 10°C through both locally depressed brine freezing temperatures through cryoconcentration of salts and increased ice temperatures through release of latent heat during partial freezing of brine. The existence of an englacial hydrological system initiated by basal crevassing extends to polar glaciers a process
Distribution of glacial deposits, soils, and permafrost in Taylor Valley, Antarctica
Bockheim, James G.; Prentice, M.L.; McLeod, M.
2008-01-01
We provide a map of lower and central Taylor Valley, Antarctica, that shows deposits from Taylor Glacier, local alpine glaciers, and grounded ice in the Ross Embayment. From our electronic database, which includes 153 sites from the coast 50 km upvalley to Pearse Valley, we show the distribution of permafrost type and soil subgroups according to Soil Taxonomy. Soils in eastern Taylor Valley are of late Pleistocene age, cryoturbated due to the presence of ground ice or ice-cemented permafrost within 70 cm of the surface, and classified as Glacic and Typic Haploturbels. In central Taylor Valley, soils are dominantly Typic Anhyorthels of mid-Pleistocene age that have dry-frozen permafrost within the upper 70 cm. Salt-enriched soils (Salic Anhyorthels and Petrosalic Anhyorthels) are of limited extent in Taylor Valley and occur primarily on drifts of early Pleistocene and Pliocene age. Soils are less developed in Taylor Valley than in nearby Wright Valley, because of lesser salt input from atmospheric deposition and salt weathering. Ice-cemented permafrost is ubiquitous on Ross Sea, pre-Ross Sea, and Bonney drifts that occur within 28 km of the McMurdo coast. In contrast, dry-frozen permafrost is prevalent on older (???115 ky) surfaces to the west. ?? 2008 Regents of the University of Colorado.
DOE Office of Scientific and Technical Information (OSTI.GOV)
Hoffman, Matthew J.; Fountain, Andrew G.; Liston, Glen E.
Here, the McMurdo Dry Valleys of Antarctica host the coldest and driest ecosystem on Earth, which is acutely sensitive to the availability of water coming from glacial runoff. We modeled the spatial variability in ablation and assessed climate sensitivity of the glacier ablation zones using 16 years of meteorological and surface mass-balance observations collected in Taylor Valley. Sublimation was the primary form of mass loss over much of the ablation zones, except for near the termini where melt, primarily below the surface, dominated. Microclimates in ~10 m scale topographic basins generated melt rates up to ten times higher than overmore » smooth glacier surfaces. In contrast, the vertical terminal cliffs on the glaciers can have higher or lower melt rates than the horizontal surfaces due to differences in incoming solar radiation. The model systematically underpredicted ablation for the final 5 years studied, possibly due to an increase of windblown sediment. Surface mass-balance sensitivity to temperature was ~–0.02 m w.e. K –1, which is among the smallest magnitudes observed globally. We also identified a high sensitivity to ice albedo, with a decrease of 0.02 having similar effects as a 1 K increase in temperature, and a complex sensitivity to wind speed.« less
Hoffman, Matthew J.; Fountain, Andrew G.; Liston, Glen E.
2016-02-24
Here, the McMurdo Dry Valleys of Antarctica host the coldest and driest ecosystem on Earth, which is acutely sensitive to the availability of water coming from glacial runoff. We modeled the spatial variability in ablation and assessed climate sensitivity of the glacier ablation zones using 16 years of meteorological and surface mass-balance observations collected in Taylor Valley. Sublimation was the primary form of mass loss over much of the ablation zones, except for near the termini where melt, primarily below the surface, dominated. Microclimates in ~10 m scale topographic basins generated melt rates up to ten times higher than overmore » smooth glacier surfaces. In contrast, the vertical terminal cliffs on the glaciers can have higher or lower melt rates than the horizontal surfaces due to differences in incoming solar radiation. The model systematically underpredicted ablation for the final 5 years studied, possibly due to an increase of windblown sediment. Surface mass-balance sensitivity to temperature was ~–0.02 m w.e. K –1, which is among the smallest magnitudes observed globally. We also identified a high sensitivity to ice albedo, with a decrease of 0.02 having similar effects as a 1 K increase in temperature, and a complex sensitivity to wind speed.« less
2008-11-17
Byrd Glacier is a major glacier in Antarctica; it drains an extensive area of the polar plateau and flows eastward between the Britannia Range and the Churchill Mountains to discharge into the Ross Ice Shelf. This image is from NASA Terra satellite.
Williams, Richard S.; Ferrigno, Jane G.
1988-01-01
Of all the world?s continents Antarctica is the coldest, the highest, and the least known. It is one and a half times the size of the United States, and on it lies 91 percent (30,109,800 km3) of the estimated volume of all the ice on Earth. Because so little is known about Antarctic glaciers compared with what is known about glaciers in populated countries, satellite imagery represents a great leap forward in the provision of basic data. From the coast of Antarctica to about 81?south latitude, there are 2,514 Landsat nominal scene centers (the fixed geographic position of the intersection of orbital paths and latitudinal rows). If there were cloud-free images for all these geographic centers, only about 520 Landsat images would be needed to provide complete coverage. Because of cloud cover, however, only about 70 percent of the Landsat imaging area, or 55 percent of the continent, is covered by good quality Landsat images. To date, only about 20 percent of Antarctica has been mapped at scales of 1:250,000 or larger, but these maps do include about half of the coastline. The area of Antarctica that could be planimetrically mapped at a scale of 1:250,000 would be tripled if the available Landsat images were used in image map production. This chapter contains brief descriptions and interpretations of features seen in 62 carefully selected Landsat images or image mosaics. Images were chosen on the basis of quality and interest; for this reason they are far from evenly spaced around the continent. Space limitations allow less than 15 percent of the Landsat imaging area of Antarctica to be shown in the illustrations reproduced in this chapter. Unfortunately, a wealth of glaciological and other features of compelling interest is present in the many hundreds of images that could not be included. To help show some important features beyond the limit of Landsat coverage, and as an aid to the interpretation of certain features seen in the images, 38 oblique aerial photographs
Shallow Sub-Permafrost Groundwater Systems In A Buried Fjord: Taylor Valley, Antarctica
NASA Astrophysics Data System (ADS)
Foley, N.; Tulaczyk, S. M.; Auken, E.; Mikucki, J.
2014-12-01
The McMurdo Dry Valleys (MDV), Antarctica, represent a unique geologic setting where permanent lakes, ephemeral streams, and subglacial waters influence surface hydrology in a cold polar desert. Past research suggested that the MDV are underlain by several hundreds of meters of permafrost. Here, we present data collected from an Airborne EM (AEM) resistivity sensor flown over the MDV during the 2011-12 austral summer. A focus of our survey was over the Taylor Glacier where saline, iron-rich subglacial fluid releases at the glacier snout at a feature known as Blood Falls, and over Taylor Valley, where a series of isolated lakes lie between Taylor Glacier and the Ross Sea. Our data show that in Taylor Valley there are extensive areas of low resistivity, interpreted as hypersaline brines, beneath a relatively thin layer of high resistivity material, interpreted as dry- or ice-cemented permafrost. These hypersaline brines remain liquid at temperatures well below 0°C due to their salinity. They appear to be contained within the sedimentary fill deposited in Taylor Valley when it was still a fjord. This brine system continues up valley and has a subglacial extension beneath Taylor Glacier, where it may provide the source that feeds Blood Falls. By categorizing the resistivity measurements according to surficial land cover, we are able to distinguish between ice, permafrost, lake water, and seawater based on characteristic resistivity distributions. Furthermore, this technique shows that areas of surface permafrost become increasingly conductive (brine-filled) with depth, whereas the large lakes exhibit taliks that extend through the entire thickness of the permafrost. The subsurface brines represent a large, unstudied and potentially connected hydrogeologic system, in which subsurface flows may help transfer water and nutrients between lakes in the MDV and into the Ross Sea. Such a system is a potential habitat for extremophile life, similar to that already detected in
Seismic Signatures of Brine Release at Blood Falls, Taylor Glacier, Antarctica
NASA Astrophysics Data System (ADS)
Carr, C. G.; Pettit, E. C.; Carmichael, J.
2017-12-01
Blood Falls is created by the release of subglacially-sourced, iron-rich brine at the surface of Taylor Glacier, McMurdo Dry Valleys, Antarctica. The supraglacial portion of this hydrological feature is episodically active. Englacial liquid brine flow occurs despite ice temperatures of -17°C and we document supraglacial liquid brine release despite ambient air temperatures average -20°C. In this study, we use data from a seismic network, time-lapse cameras, and publicly available weather station data to address the questions: what are the characteristics of seismic events that occur during Blood Falls brine release and how do these compare with seismic events that occur during times of Blood Falls quiescence? How are different processes observable in the time-lapse imagery represented in the seismic record? Time-lapse photography constrains the timing of brine release events during the austral winter of 2014. We use a noise-adaptive digital power detector to identify seismic events and cluster analysis to identify repeating events based on waveform similarity across the network. During the 2014 wintertime brine release, high-energy repeated seismic events occurred proximal to Blood Falls. We investigate the ground motions associated with these clustered events, as well as their spatial distribution. We see evidence of possible tremor during the brine release periods, an indicator of fluid movement. If distinctive seismic signatures are associated with Blood Falls brine release they could be identified based solely on seismic data without any aid from time-lapse cameras. Passive seismologic monitoring has the benefit of continuity during the polar night and other poor visibility conditions, which make time-lapse imagery unusable.
NASA Astrophysics Data System (ADS)
Gooseff, M. N.; Bergstrom, A.
2016-12-01
The Dry Valleys of Antarctica are a polar desert ecosystem consisting of piedmont and alpine glaciers, ice-covered lakes, and vast expanses of bare soil. The ecosystem is highly dependent on glacial melt a water source. Because average summer temperatures are close to freezing, glacier ice and lake ice are very closely linked to the energy balance. A slight increase in incoming radiation or decrease in albedo can have large effects on the timing and volume of available liquid water. However, we have yet to fully characterize the seasonal evolution of albedo in the valleys. In this study, we used a camera, gps, and short wave radiometer to characterize the albedo within and across landscape types in the Taylor Valley. These instruments were attached to a helicopter and flown on a prescribed path along the valley at approximately 300 feet above the ground surface five different times throughout the season from mid-November to mid-January, 2015-2016. We used these data to calculate the albedo of each glacier, lake, and the soil surface of the lake basins in the valley for each flight. As expected, we found that all landscape types had significantly different albedo, with the glaciers consistently the highest throughout the season and the bare soils the lowest (p-value < 0.05). We hypothesized that albedo would decrease throughout the season with snow melt and increasing sediment exposure on the glacier and lake surfaces. However, small snow events (< 3 cm) caused somewhat persistent high albedo on the lakes and glaciers. Furthermore, there was a range in albedo across glaciers and each responded to seasonal snow and melt differently. These findings highlight the importance of understanding the spatial and temporal variability in albedo and the close coupling of climate and landscape response. We can use this new understanding of landscape albedo to better predict how the Dry Valley ecosystems will respond to changing climate at the basin scale.
Icefall, Lambert Glacier, Antarctica
2017-12-08
Image taken 12/2/2000: The Lambert Glacier in Antarctica, is the world's largest glacier. The focal point of this image is an icefall that feeds into the Lambert glacier from the vast ice sheet covering the polar plateau. Ice flows like water, albeit much more slowly. Cracks can be seen in this icefall as it bends and twists on its slow-motion descent 1300 feet (400 meters) to the glacier below. This Icefall can be found on Landsat 7 WRS Path 42 Row 133/134/135, center: -70.92, 69.15. To learn more about the Landsat satellite go to: landsat.gsfc.nasa.gov/
Pine Island Glacier, Antarctica, MISR Multi-angle Composite
2013-11-15
NASA Terra satellite passed over the Pine Island Glacier in Antarctica around Oct. 27, 2013, just days before iceberg B-31 broke completely free. B-31 is finally moving away from the coast, with open water between the iceberg and the glacier.
USDA-ARS?s Scientific Manuscript database
In this paper, we describe the importance of hyporheic dynamics within Andersen Creek and Von Guerard Stream, Taylor Valley, Antarctica, from the 2010-11 melt season using natural tracers. Water collection started at flow onset and continued, with weekly hyporheic zone sampling. The water d18O and d...
Doyle, Shawn M.; Montross, Scott N.; Skidmore, Mark L.; Christner, Brent C.
2013-01-01
Measurement of gases entrapped in clean ice from basal portions of the Taylor Glacier, Antarctica, revealed that CO2 ranged from 229 to 328 ppmv and O2 was near 20% of the gas volume. In contrast, vertically adjacent sections of the sediment laden basal ice contained much higher concentrations of CO2 (60,000 to 325,000 ppmv), whereas O2 represented 4 to 18% of the total gas volume. The deviation in gas composition from atmospheric values occurred concurrently with increased microbial cell concentrations in the basal ice profile, suggesting that in situ microbial processes (i.e., aerobic respiration) may have altered the entrapped gas composition. Molecular characterization of 16S rRNA genes amplified from samples of the basal ice indicated a low diversity of bacteria, and most of the sequences characterized (87%) were affiliated with the phylum, Firmicutes. The most abundant phylotypes in libraries from ice horizons with elevated CO2 and depleted O2 concentrations were related to the genus Paenisporosarcina, and 28 isolates from this genus were obtained by enrichment culturing. Metabolic experiments with Paenisporosarcina sp. TG14 revealed its capacity to conduct macromolecular synthesis when frozen in water derived from melted basal ice samples and incubated at −15 °C. The results support the hypothesis that the basal ice of glaciers and ice sheets are cryospheric habitats harboring bacteria with the physiological capacity to remain metabolically active and biogeochemically cycle elements within the subglacial environment. PMID:24833055
Low-frequency radar sounder over Glaciers in Alaska, Greenland and Antarctica
NASA Astrophysics Data System (ADS)
Mouginot, J.; Rignot, E. J.; Gim, Y.; Kirchner, D. L.; Merritt, S.; Robison, W. T.
2009-12-01
Ice-thickness and basal layer topography measurements are needed to calculate fluxes through fast-flowing outlet glaciers in Greenland, Alaska, Patagonia and Antarctica. However, relatively high attenuation of radio waves by dielectric absorption and volume scattering from englacial water restrains detection of the bed through warm deep ice. Using a low-frequency (1-5 MHz) airborne radar, we have sounded outlet fast glaciers over Greenland (Store, Upernavik, Hellheim, …), East Antarctica (David, Mertz, Dibble, Byrd, …) and Alaska (Bering, Maslapina, Bagley, …). We will show that we detected the bed through temperate ice up to 1000m thick over Bering and Maslapina Glaciers and also point out difficulty in detecting bed of other Alaska glaciers due to off-nadir returns. We will also make direct comparison of this radar and previous airborne measurements in Greenland and Antarctica in order to discuss a potential improvement of bedrock detectability in temperate ice.
NASA Astrophysics Data System (ADS)
Fortner, Sarah K.; Lyons, W. Berry
2018-04-01
Here we present a synthesis of the trace element chemistry in melt on the surface Canada Glacier, Taylor Valley, McMurdo Dry Valleys (MDV), Antarctica ( 78°S). The MDV is largely ice-free. Low accumulation rates, strong winds, and proximity to the valley floor make these glaciers dusty in comparison to their inland counterparts. This study examines both supraglacial melt streams and cryoconite holes. Supraglacial streams on the lower Canada Glacier have median dissolved (<0.4 µm) concentrations of Fe, Mn, As, Cu, and V of 71.5, 75.5, 3.7, 4.6, and 4.3 nM. All dissolved Cd concentrations and the vast majority of Pb values are below our analytical detection (i.e. 0.4 and 0.06 nM). Chemical behavior did not follow similar trends for eastern and western draining waters. Heterogeneity likely reflects distinctions eolian deposition, rock:water ratios, and hydrologic connectivity. Future increases in wind-delivered sediment will likely drive dynamic responses in melt chemistry. For elements above detection limits, dissolved concentrations in glacier surface melt are within an order of magnitude of concentrations observed in proglacial streams (i.e. flowing on the valley floor). This suggests that glacier surfaces are an important source of downstream chemistry. The Fe enrichment of cryoconite water relative to N, P, or Si exceeds enrichment observed in marine phytoplankton. This suggests that the glacier surface is an important source of Fe to downstream ecosystems.
Increased Ocean Access to Totten Glacier, East Antarctica
NASA Astrophysics Data System (ADS)
Blankenship, D. D.; Greenbaum, J. S.; Young, D. A.; Richter, T. G.; Roberts, J. L.; Aitken, A.; Legresy, B.; Warner, R. C.; van Ommen, T. D.; Siegert, M. J.
2015-12-01
The Totten Glacier is the largest ice sheet outlet in East Antarctica, draining 3.5 meters of eustatic sea level potential from the Aurora Subglacial Basin (ASB) into the Sabrina Coast. Recent work has shown that the ASB has drained and filled many times since largescale glaciation began including evidence that it collapsed during the Pliocene. Steady thinning rates observed near Totten Glacier's grounding line since the beginning of the satellite altimetry record are the largest in East Antarctica and the nature of the thinning suggests that it is driven by enhanced basal melting due to ocean processes. Warm Modified Circumpolar Deep Water (MCDW), which has been linked to glacier retreat in West Antarctica, has been observed in summer and winter on the Sabrina Coast continental shelf in the 400-500 m depth range. Using airborne geophysical data acquired over multiple years we delineate seafloor valleys connecting the inner continental shelf to the cavity beneath Totten Glacier that cut through a large sill centered along the ice shelf calving front. The sill shallows to depths of about 300 mbsl and was likely a grounding line pinning point during Holocene retreat, however, the two largest seafloor valleys are deeper than the observed range of thermocline depths. The deeper of the two valleys, a 4 km-wide trough, connects to the ice shelf cavity through an area of the coastline that was previously believed to be grounded but that our analysis demonstrates is floating, revealing a second, deeper entryway to ice shelf cavity. The previous coastline was charted using satellite-based mapping techniques that infer subglacial properties based on surface expression and behavior; the new geophysical analysis techniques we use enable inferences of subglacial characteristics using direct observations of the ice-water interface. The results indicate that Totten Glacier and, by extension, the Aurora Subglacial Basin are vulnerable to MCDW that has been observed on the nearby
Utilizing Lidar Data for Detection of Channel Migration: Taylor Valley, Antarctica
NASA Astrophysics Data System (ADS)
Barlow, M. C.; Telling, J. W.; Glennie, C.; Fountain, A.
2017-12-01
The McMurdo Dry Valleys is the largest ice-free expanse in Antarctica and one of the most studied regions on the continent. The valleys are a hyper-arid, cold-polar desert that receives little precipitation (<50 mm weq yr-1). The valley bottoms are covered in a sandy-gravel, dotted with ice-covered lakes and ponds, and alpine glaciers that descend from the surrounding mountains. Glacial melt feeds the lakes via ephemeral streams that flow 6 - 10 weeks each summer. Field observations indicate that the valley floors, particularly in Taylor Valley, contain numerous abandoned stream channels but, given the modest stream flows, channel migration is rarely observed. Only a few channels have been surveyed in the field due to the slow pace of manual methods. Here we present a method to assess channel migration over a broad region in order to study the pattern of channel migration as a function of climatic and/or geologic gradients in Taylor Valley. Raster images of high-resolution topography were created from two lidar (Light Detection and Ranging) datasets and were used to analyze channel migration in Taylor Valley. The first lidar dataset was collected in 2001 by NASA's Airborne Topographic Mapper (ATM) and the second was collected by the National Center for Airborne Laser Mapping (NCALM) in 2014 with an Optech Titan Sensor. The channels were extracted for each dataset using GeoNet, which is an open source tool used for the automatic extraction of channel networks. Channel migration was found to range from 0 to 50 cm per year depending upon the location. Channel complexity was determined based on the change in the number of channel branches and their length. We present the results for various regions in Taylor Valley with differing degrees of stream complexity. Further research is being done to determine factors that drive channel migration rates in this unique environment.
NASA Astrophysics Data System (ADS)
Greenbaum, Jamin; Schroeder, Dustin; Grima, Cyril; Habbal, Feras; Dow, Christine; Roberts, Jason; Gwyther, David; van Ommen, Tas; Siegert, Martin; Blankenship, Donald
2017-04-01
Totten Glacier drains at least 3.5 meters of eustatic sea level potential from marine-based ice in the Aurora Subglacial Basin (ASB) in East Antarctica, more than the combined total of all glaciers in West Antarctica. Totten Glacier has been the most rapidly thinning glacier in East Antarctica since satellite altimetry time series began and the nature of the thinning suggests that it is driven by enhanced basal melting due to ocean processes. While grounded ice thinning rates have been steady, recent work has shown that Totten's floating ice shelf may not have the same thinning behavior; as a result, it is critical to observe ice shelf and cavity boundary conditions and basal processes to understand this apparent discrepancy. Warm Modified Circumpolar Deep Water (MCDW), which has been linked to glacier retreat in West Antarctica, has been observed in summer and winter on the nearby Sabrina Coast continental shelf and deep depressions in the seafloor provide access for MCDW to reach the ice shelf cavity. Given its northern latitude, numerical ice sheet modeling indicates that Totten Glacier may be prone to retreat caused by hydrofracture in a warming climate, so it is important to understand how intruding MCDW is affecting thinning of Totten Glacier's ice shelf. Here we use post-processed, focused airborne radar observations of the Totten Glacier Ice Shelf to delineate multi-km wide basal channels and flat basal terraces associated with high basal reflectivity and specularity (flatness) anomalies and correspondingly large ice surface depressions that indicate active basal melting. Using a simple temperature-attenuation model, and basal roughness corrections, we present basal melt rates associated with the radar reflection and specularity anomalies and compare them to those derived from numerical ocean circulation modeling and an ice flow divergence calculation. Sub-ice shelf ocean circulation modeling and under-ice robotic observations of Pine Island Glacier Ice
Glacier advance during Marine Isotope Stage 11 in the McMurdo Dry Valleys of Antarctica
Swanger, Kate M.; Lamp, Jennifer L.; Winckler, Gisela; Schaefer, Joerg M.; Marchant, David R.
2017-01-01
We mapped six distinct glacial moraines alongside Stocking Glacier in the McMurdo Dry Valleys, Antarctica. Stocking Glacier is one of several alpine glaciers in the Dry Valleys fringed by multiple cold-based drop moraines. To determine the age of the outermost moraine, we collected 10 boulders of Ferrar Dolerite along the crest of the moraine and analyzed mineral separates of pyroxene for cosmogenic 3He. On the basis of these measurements, the exposure age for the outermost moraine is 391 ± 35 ka. This represents the first documented advance of alpine glacier ice in the Dry Valleys during Marine Isotope Stage (MIS) 11. At this time, Stocking Glacier was ~20–30% larger than today. The cause of ice expansion is uncertain, but most likely it is related to increased atmospheric temperature and precipitation, associated with reduced ice extent in the nearby Ross Embayment. The data suggest complex local environmental response to warm climates in Antarctica and have implications for glacial response to Holocene warming. The study also demonstrates the potential for using alpine glacier chronologies in the Transantarctic Mountains as proxies for retreat of grounded glacier ice in the Ross Embayment. PMID:28139676
Glaciers in Equilibrium - Results from the McMurdo Dry Valleys, Antarctica
NASA Astrophysics Data System (ADS)
Fountain, A. G.; Nylen, T. H.; Doran, P. T.
2004-12-01
Since 1993 the mass balance of two glaciers in the McMurdo Dry Valleys, Antarctica (163° E 77.5° S) has been measured. The magnitude of annual mass gain or loss does not exceed 10 cm water equivalent averaged over each glacier, consistent with the local climate of a polar desert. The overall trend in mass balance shows that the glaciers are in approximate balance with the current climate and no obvious trends exist in either the winter or summer balances. These are similar to a set of mass balance measurements made in another part of the dry valleys during the 1970s (Chinn, 1985). Recent analysis of the climate of the dry valleys shows this region is cooling at a rate of 0.7° C per decade during this period since 1986, which is reflected in the overall lowering of lake levels, decreased primary productivity of the lakes, and declining number of invertebrates (Doran et al., 2002). Although an unusually warm period occurred in the summer of 2001-2002, annual temperatures continue to cool. This region seems to be isolated from the warming elsewhere in Antarctica and the cooling in this part of the Ross Sea region may be due to El Nino forcing (Bertler et al, 2004). The sluggish behavior of the glaciers results from a low mass exchange and an apparent climatic buffering, which supports evidence from the geologic record that these glaciers have not advanced more than a few hundred meters over the past 3 million years (Hall et al., 1993). Many of the glaciers, however, are advancing which probably results from a slow time-scale response from warming conditions in the past millennium.
NASA Astrophysics Data System (ADS)
Auken, E.; Tulaczyk, S. M.; Foley, N.; Dugan, H.; Schamper, C.; Peter, D.; Virginia, R. A.; Sørensen, K.
2015-12-01
Here, we demonstrate how high powered airborne electromagnetic resistivity is efficiently used to map 3D domains of unfrozen water below glaciers and permafrost in the cold regions of the Earth. Exploration in these parts of the world has typically been conducted using radar methods, either ground-based or from an airborne platform. Radar is an excellent method if the penetrated material has a low electrical conductivity, but in materials with higher conductivity, such as sediments with liquid water, the energy is attenuated . Such cases are efficiently explored with electromagnetic methods, which attenuate less quickly in conductive media and can therefore 'see through' conductors and return valuable information about their electrical properties. In 2011, we used a helicopter-borne, time-domain electromagnetic sensor to map resistivity in the subsurface across the McMurdo Dry Valleys (MDV). The MDV are a polar desert in coastal Antarctica where glaciers, permafrost, ice-covered lakes, and ephemeral summer streams coexist. In polar environments, this airborne electromagnetic system excels at finding subsurface liquid water, as water which remains liquid under cold conditions must be sufficiently saline, and therefore electrically conductive. In Taylor Valley, in the MDV, our data show extensive subsurface low resistivity layers beneath higher resistivity layers, which we interpret as cryoconcentrated hypersaline brines lying beneath glaciers and frozen permafrost. These brines appear to be contiguous with surface lakes, subglacial regions, and the Ross Sea, which could indicate a regional hydrogeologic system wherein solutes may be transported between surface reservoirs by ionic diffusion and subsurface flow. The system as of 2011 had a maximum exploration depth of about 300 m. However, newer and more powerful airborne systems can explore to a depth of 500 - 600 m and new ground based instruments will get to 1000 m. This is sufficient to penetrate to the base of
Holocene glacier and deep water dynamics, Adélie Land region, East Antarctica
NASA Astrophysics Data System (ADS)
Denis, Delphine; Crosta, Xavier; Schmidt, Sabine; Carson, Damien S.; Ganeshram, Raja S.; Renssen, Hans; Bout-Roumazeilles, Viviane; Zaragosi, Sebastien; Martin, Bernard; Cremer, Michel; Giraudeau, Jacques
2009-06-01
This study presents a high-resolution multi-proxy investigation of sediment core MD03-2601 and documents major glacier oscillations and deep water activity during the Holocene in the Adélie Land region, East Antarctica. A comparison with surface ocean conditions reveals synchronous changes of glaciers, sea ice and deep water formation at Milankovitch and sub-Milankovitch time scales. We report (1) a deglaciation of the Adélie Land continental shelf from 11 to 8.5 cal ka BP, which occurred in two phases of effective glacier grounding-line retreat at 10.6 and 9 cal ka BP, associated with active deep water formation; (2) a rapid glacier and sea ice readvance centred around 7.7 cal ka BP; and (3) five rapid expansions of the glacier-sea ice systems, during the Mid to Late Holocene, associated to a long-term increase of deep water formation. At Milankovich time scales, we show that the precessionnal component of insolation at high and low latitudes explains the major trend of the glacier-sea ice-ocean system throughout the Holocene, in the Adélie Land region. In addition, the orbitally-forced seasonality seems to control the coastal deep water formation via the sea ice-ocean coupling, which could lead to opposite patterns between north and south high latitudes during the Mid to Late Holocene. At sub-Milankovitch time scales, there are eight events of glacier-sea ice retreat and expansion that occurred during atmospheric cooling events over East Antarctica. Comparisons of our results with other peri-Antarctic records and model simulations from high southern latitudes may suggest that our interpretation on glacier-sea ice-ocean interactions and their Holocene evolutions reflect a more global Antarctic Holocene pattern.
Lyons, W.B.; Nezat, C.A.; Benson, L.V.; Bullen, T.D.; Graham, E.Y.; Kidd, J.; Welch, K.A.
2002-01-01
We have collected and analyzed a series of water samples from three closed-basin lakes (Lakes Bonney, Fryxell, and Hoare) in Taylor Valley, Antarctica, and the streams that flow into them. In all three lakes, the hypolimnetic waters have different 87Sr/86Sr ratios than the surface waters, with the deep water of Lakes Fryxell and Hoare being less radiogenic than the surface waters. The opposite occurs in Lake Bonney. The Lake Fryxell isotopic ratios are lower than modern-day ocean water and most of the whole-rock ratios of the surrounding geologic materials. A conceivable source of Sr to the system could be either the Cenozoic volcanic rocks that make up a small portion of the till deposited in the valley during the Last Glacial Maximum or from marble derived from the local basement rocks. The more radiogenic ratios from Lake Bonney originate from ancient salt deposits that flow into the lake from Taylor Glacier and the weathering of minerals with more radiogenic Sr isotopic ratios within the tills. The Sr isotopic data from the streams and lakes of Taylor Valley strongly support the notion documented by previous investigators that chemical weathering has been, and is currently, a major process in determining the overall aquatic chemistry of these lakes in this polar desert environment.
Basal and thermal control mechanisms of the Ragnhild glaciers, East Antarctica
NASA Astrophysics Data System (ADS)
Pattyn, Frank; de Brabander, Sang; Huyghe, Ann
The Ragnhild glaciers are three enhanced-flow features situated between the Sør Rondane and Yamato Mountains in eastern Dronning Maud Land, Antarctica. We investigate the glaciological mechanisms controlling their existence and behavior, using a three-dimensional numerical thermomechanical ice-sheet model including higher-order stress gradients. This model is further extended with a steady-state model of subglacial water flow, based on the hydraulic potential gradient. Both static and dynamic simulations are capable of reproducing the enhanced ice-flow features. Although basal topography is responsible for the existence of the flow pattern, thermomechanical effects and basal sliding seem to locally soften and lubricate the ice in the main trunks. Lateral drag is a contributing factor in balancing the driving stress, as shear margins can be traced over a distance of hundreds of kilometers along west Ragnhild glacier. Different basal sliding scenarios show that central Ragnhild glacier stagnates as west Ragnhild glacier accelerates and progressively drains the whole catchment area by ice and water piracy.
Velocities along Byrd Glacier, East Antarctica, derived from Automatic Feature Tracking
NASA Astrophysics Data System (ADS)
Stearns, L. A.; Hamilton, G. S.
2003-12-01
Automatic feature tracking techniques are applied to recently acquired ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer) imagery in order to determine the velocity field of Byrd Glacier, East Antarctica. The software IMCORR tracks the displacement of surface features (crevasses, drift mounds) in time sequential images, to produce the velocity field. Due to its high resolution, ASTER imagery is ideally suited for detecting small features changes. The produced result is a dense array of velocity vectors, which allows more thorough characterization of glacier dynamics. Byrd Glacier drains approximately 20.5 km3 of ice into the Ross Ice Shelf every year. Previous studies have determined ice velocities for Byrd Glacier by using photogrammetry, field measurements and manual feature tracking. The most recent velocity data is from 1986 and, as evident in the West Antarctic ice streams, substantial changes in velocity can occur on decadal time scales. The application of ASTER-based velocities fills this time lapse, and increased temporal resolution allows for a more complete analysis of Byrd Glacier. The ASTER-derived ice velocities are used in updating mass balance and force budget calculations to assess the stability of Byrd Glacier. Ice thickness information from BEDMAP, surface slopes from the OSUDEM and a compilation of accumulation rates are used to complete the calculations.
NASA Astrophysics Data System (ADS)
Foley, N.; Tulaczyk, S. M.; Auken, E.; Schamper, C.; Dugan, H. A.; Mikucki, J.; Virginia, R. A.; Doran, P. T.
2015-12-01
We used a helicopter-borne time domain electromagnetic resistivity survey to detect and map hypersaline brines beneath glaciers and permafrost in the McMurdo Dry Valleys (MDV). In the MDV, a substantially ice-free region of coastal Antarctica, liquid water is present at the surface only in summer streams, ice-covered lakes with brackish to hypersaline bottom waters, and at Blood Falls, a hypersaline discharge from Taylor Glacier. Beneath the surface, however, water can remain liquid at temperatures below 0 °C (and therefore at unexpectedly shallow depths) as a hypersaline brine. These brines, which are measured as zones of low resistivity in an otherwise high resistivity environment, are widespread in Taylor Valley, where they may connect lakes, subglacial waters, and the ocean. By using surface landscape characteristics - such as the presence of lakes, glaciers, or bare ground - we are able to compare changes in resistivity with depth. We find that in areas of surface permafrost (most of the MDV) there is a marked shift to low resistivity material around 200 m below the surface. At lakes, the stratified nature of their waters is detectable and sufficiently large lakes create taliks (unfrozen 'holes' in permafrost) that penetrate to the low resistivity zone around 200 m depth, suggesting connectivity through a regional aquifer. Underneath Taylor Glacier, we detect similar brines, which are the probable source for Blood Falls. These subglacial brines extend from the snout of Taylor Glacier (where they appear to connect to the hypersaline waters of West Lake Bonney) to the limit of our detection ability several kilometers up glacier where the ice became too thick for measurements. Our measurements are consistent with limited drilling done in the MDV during the 1970s and radar measurements taken more recently on Taylor Glacier. The transition to low resistivity at ~200 m depth occurs over a temperature range measured in boreholes of about -10 to -5 °C, which is
NASA Astrophysics Data System (ADS)
Petrenko, Vasilii V.; Severinghaus, Jeffrey P.; Schaefer, Hinrich; Smith, Andrew M.; Kuhl, Tanner; Baggenstos, Daniel; Hua, Quan; Brook, Edward J.; Rose, Paul; Kulin, Robb; Bauska, Thomas; Harth, Christina; Buizert, Christo; Orsi, Anais; Emanuele, Guy; Lee, James E.; Brailsford, Gordon; Keeling, Ralph; Weiss, Ray F.
2016-03-01
Carbon-14 (14C) is incorporated into glacial ice by trapping of atmospheric gases as well as direct near-surface in situ cosmogenic production. 14C of trapped methane (14CH4) is a powerful tracer for past CH4 emissions from ;old; carbon sources such as permafrost and marine CH4 clathrates. 14C in trapped carbon dioxide (14CO2) can be used for absolute dating of ice cores. In situ produced cosmogenic 14C in carbon monoxide (14CO) can potentially be used to reconstruct the past cosmic ray flux and past solar activity. Unfortunately, the trapped atmospheric and in situ cosmogenic components of 14C in glacial ice are difficult to disentangle and a thorough understanding of the in situ cosmogenic component is needed in order to extract useful information from ice core 14C. We analyzed very large (≈1000 kg) ice samples in the 2.26-19.53 m depth range from the ablation zone of Taylor Glacier, Antarctica, to study in situ cosmogenic production of 14CH4 and 14CO. All sampled ice is >50 ka in age, allowing for the assumption that most of the measured 14C originates from recent in situ cosmogenic production as ancient ice is brought to the surface via ablation. Our results place the first constraints on cosmogenic 14CH4 production rates and improve on prior estimates of 14CO production rates in ice. We find a constant 14CH4/14CO production ratio (0.0076 ± 0.0003) for samples deeper than 3 m, which allows the use of 14CO for correcting the 14CH4 signals for the in situ cosmogenic component. Our results also provide the first unambiguous confirmation of 14C production by fast muons in a natural setting (ice or rock) and suggest that the 14C production rates in ice commonly used in the literature may be too high.
NASA Astrophysics Data System (ADS)
Machío, Francisco; Rodríguez-Cielos, Ricardo; Navarro, Francisco; Lapazaran, Javier; Otero, Jaime
2017-10-01
We present a 14-year record of in situ glacier surface velocities determined by repeated global navigation satellite system (GNSS) measurements in a dense network of 52 stakes distributed across two glaciers, Johnsons (tidewater) and Hurd (land-terminating), located on Livingston Island, South Shetland Islands, Antarctica. The measurements cover the time period 2000-2013 and were collected at the beginning and end of each austral summer season. A second-degree polynomial approximation is fitted to each stake position, which allows estimating the approximate positions and associated velocities at intermediate times. This dataset is useful as input data for numerical models of glacier dynamics or for the calibration and validation of remotely sensed velocities for a region where very scarce in situ glacier surface velocity measurements have been available so far. The link to the data repository is as follows: http://doi.pangaea.de/10.1594/PANGAEA.846791.
NASA Astrophysics Data System (ADS)
Stump, Edmund; Miller, Julia M. G.; Korsch, Russell J.; Edgerton, David G.
1988-03-01
Late Proterozoic glacial deposits have been found on all continents except Antarctica. Here we describe four units of Late Proterozoic diamictite, with a total thickness of about 10m, from Panorama Point, Nimrod Glacier area, Antarctica, which have characteristics compatible with glaciogenic origin. The diamictite occurs within the Goldie Formation, a sequence of marine turbidites, and is associated with a unit of mafic pillow lavas. The diamictite is commonly structureless and in places laminated. Coarse clasts occur as scattered pebbles and cobbles and as pebbly pods and beds. No striated or faceted clasts were found. A few pebbles may pierce the laminae, but a drop-stone origin is uncertain. Deformation and metamorphism have obscured subtleties of original sedimentary structure. Outsize clasts in laminated sandy siltstone (now schistose) suggest a glaciogenic origin for these diamictites, but deposition by mass-flow processes cannot be ruled out. The discovery in Antarctica of possible Late Proterozoic glaciogenic deposits extends their geographic distribution to all of the major continental masses.
Krusic, A.G.; Prentice, M.L.; Licciardi, J.M.
2009-01-01
Early-mid Pliocene moraines in the McMurdo Dry Valleys, Antarctica, are more extensive than the present alpine glaciers in this region, indicating substantial climatic differences between the early-mid Pliocene and the present. To quantify this difference in the glacier-climate regime, we estimated the equilibrium-line altitude (ELA) change since the early-mid Pliocene by calculating the modern ELA and reconstructing the ELAs of four alpine glaciers in Wright and Taylor Valleys at their early-mid Pliocene maxima. The area-altitude balance ratio method was used on modern and reconstructed early-mid Pliocene hypsometry. In Wright and Victoria Valleys, mass-balance data identify present-day ELAs of 800-1600 m a.s.l. and an average balance ratio of 1.1. The estimated ELAs of the much larger early-mid Pliocene glaciers in Wright and Taylor Valleys range from 600 to 950 ?? 170 m a.s.l., and thus are 250-600 ??170 m lower than modern ELAs in these valleys. The depressed ELAs during the early-mid-Pliocene most likely indicate a wetter and therefore warmer climate in the Dry Valleys during this period than previous studies have recognized.
Motion of David Glacier in East Antarctica Observed by COSMO-SkyMed Differential SAR Interferometry
NASA Astrophysics Data System (ADS)
Han, H.; Lee, H.
2011-12-01
David glacier, located in Victoria Land, East Antarctica (75°20'S, 161°15'E), is an outlet glacier of 13 km width near the grounding line and 50 km long from the source to the grounding line. David glacier flows into Ross Sea forming Drygalski Ice Tongue, 100 km long and 23 km wide. In this study, we extracted a surface displacement map of David by applying differential SAR interferometry (DInSAR) to one-day tandem pairs obtained from COSMO-SkyMed satellites on April 28-29 (descending orbit) and May 5-6 (ascending orbit), 2011, respectively. Terra ASTER global digital elevation model (GDEM) is used to remove the topographic effect from the COSMO-SkyMed interferograms. David glacier showed maximum displacement of 35 cm during April 28-29 and 20 cm during May 5-6 in the direction of radar line of sight. The glacier can be divided into several blocks by the disparities of displacement between the different sliding zone. Surface displacement map contains errors originated from orbit data, atmospheric conditions, DEM error. GDEM is generated from the ASTER optical images acquired from 2000 to 2008. It has the vertical accuracy of about 20 m at 95% confidence with the 30 m of horizontal posting. The accuracy of GDEM reduces when cloud cover is included in the ASTER image. Particularly in the snow and ice area, GDEM is inaccurate due to whiteout effect during stereo matching. The inaccuracy of GDEM could be a reason of the observed glacier motion in the opposite direction of gravity. This problem can be solved by using TanDEM-X DEM. Bistatic acquisition of SAR images from the constellation of TerraSAR-X and TanDEM-X will generate a global DEM with the vertical accuracy better than 2 m and the horizontal posting of 12 m. We plan to perform DInSAR of COSMO-SkyMed one-day tandem pairs again when the high-accuracy TanDEM-X DEM is available in the near future. As a conclusion, we could analyze the displacement of David glacier in East Antarctica. The glacier showed very fast
A Novel Approach to Measuring Glacier Motion Remotely using Aerial LiDAR
NASA Astrophysics Data System (ADS)
Telling, J. W.; Fountain, A. G.; Glennie, C. L.; Obryk, M.
2016-12-01
Glaciers play an important role in the Earth's climate system, affecting climate and ocean circulation at the largest scales, and contributing to runoff and sea level rise at local scales. A key variable is glacier motion and tracking motion is critical to understanding how flow responds to changes in boundary conditions and to testing predictive models of glacier behavior. Although field measurements of glacier motion have been collected since the 19th Century, field operations remain a slow, laborious, sometimes dangerous, task yielding only a few data points per glacier. In recent decades satellite imaging of glacier motion has proved very fruitful, but the spatial resolution of the imagery restricts applications to regional scale analyses. Here we assess the utility of using aerial LiDAR surveys and particle image velocimetry (PIV) as a method for tracking glacier motion over relatively small regions (<50km2). Five glaciers in Taylor Valley, Antarctica, were surveyed twice; the first LiDAR survey was conducted in 2001 and the second was conducted in 2014. The cold-dry climate conditions of Taylor Valley and the relatively slow motion of its polar glaciers (≤ 8m yr-1) preserve the surface roughness and limit the advected distance of the features making the 13-year interval between surveys sufficient for monitoring glacier motion. Initial results yield reasonable flow fields and show great promise. The range of flow speeds, surface roughness, and transient snow patches found on these glaciers provide a robust test of PIV methods. Results will be compared to field measurements of glacier velocity and to results from feature tracking, a common technique based on paired optical images. The merits of using this technique to measure glacier motion will be discussed in the context of these results. Applying PIV to LiDAR point clouds may offer a higher resolution data set of glacier velocity than satellite images or field measurements.
Experimental Analysis of Sublimation Dynamics for Buried Glacier Ice in Beacon Valley, Antarctica
NASA Astrophysics Data System (ADS)
Ehrenfeucht, S.; Dennis, D. P.; Marchant, D. R.
2017-12-01
The age of the oldest known buried ice in Beacon Valley, McMurdo Dry Valleys (MDV) Antarctica is a topic of active debate due to its implications for the stability of the East Antarctic Ice Sheet. Published age estimates range from as young as 300 ka to as old as 8.1 Ma. In the upland MDV, ablation occurs predominantly via sublimation. The relict ice in question (ancient ice from Taylor Glacier) lies buried beneath a thin ( 30-70 cm) layer of sublimation till, which forms as a lag deposit as underlying debris-rich ice sublimes. As the ice sublimates, the debris held within the ice accumulates slowly on the surface, creating a porous boundary between the buried-ice surface and the atmosphere, which in turn influences gas exchange between the ice and the atmosphere. Additionally, englacial debris adds several salt species that are ultimately concentrated on the ice surface. It is well documented the rate of ice sublimation varies as a function of overlying till thickness. However, the rate-limiting dynamics under varying environmental conditions, including the threshold thicknesses at which sublimation is strongly retarded, are not yet defined. To better understand the relationships between sublimation rate, till thickness, and long-term surface evolution, we build on previous studies by Lamp and Marchant (2017) and evaluate the role of till thickness as a control on ice loss in an environmental chamber capable of replicating the extreme cold desert conditions observed in the MDV. Previous work has shown that this relationship exhibits exponential decay behavior, with sublimation rate significantly dampened under less than 10 cm of till. In our experiments we pay particular attention to the effect of the first several cm of till in order to quantify the dynamics that govern the transition from bare ice to debris-covered ice. We also examine this transition for various forms of glacier ice, including ice with various salt species.
Bajerski, Felizitas; Wagner, Dirk
2013-07-01
Antarctic glacier forefields are extreme environments and pioneer sites for ecological succession. Increasing temperatures due to global warming lead to enhanced deglaciation processes in cold-affected habitats, and new terrain is becoming exposed to soil formation and microbial colonization. However, only little is known about the impact of environmental changes on microbial communities and how they develop in connection to shifting habitat characteristics. In this study, using a combination of molecular and geochemical analysis, we determine the structure and development of bacterial communities depending on soil parameters in two different glacier forefields on Larsemann Hills, East Antarctica. Our results demonstrate that deglaciation-dependent habitat formation, resulting in a gradient in soil moisture, pH and conductivity, leads to an orderly bacterial succession for some groups, for example Cyanobacteria, Bacteroidetes and Deltaproteobacteria in a transect representing 'classical' glacier forefields. A variable bacterial distribution and different composed communities were revealed according to soil heterogeneity in a slightly 'matured' glacier forefield transect, where Gemmatimonadetes, Flavobacteria, Gamma- and Deltaproteobacteria occur depending on water availability and soil depth. Actinobacteria are dominant in both sites with dominance connected to certain trace elements in the glacier forefields. © 2013 Federation of European Microbiological Societies. Published by Blackwell Publishing Ltd. All rights reserved.
Carosi, R.; Giacomini, F.; Talarico, F.; Stump, E.
2007-01-01
Field activities in the Britannia Range (Transantarctic Mountains, Antarctica) highlighted new geological features around the so-called Byrd Glacier discontinuity. Recent field surveys revealed the occurrence of significant amounts of medium- to high-grade metamorphic rocks, intruded by abundant coarse-grained porphyritic granitoids. Most of the granitoids are deformed, with foliation parallel to the regional foliation in the metamorphics. Two main episodes of deformation are observed. Tight to isoclinal folds and penetrative axial plane foliation are related to the D1 phase, open folds to the D2. The main foliation (D1) trends nearly E-W in agreement with the trend in the southern portion of the Byrd Glacier. In most outcrops, granitic dykes are folded and stretched by the D2 deformation, which shows similar characteristics with the D2 deformation south of the Byrd Glacier. This suggests the occurrence in the Ross orogen of an orogen-normal structure south and north of the Byrd Glacier.
Seismic reflection constraints on the glacial dynamics of Johnsons Glacier, Antarctica
NASA Astrophysics Data System (ADS)
Benjumea, Beatriz; Teixidó, Teresa
2001-01-01
During two Antarctic summers (1996-1997 and 1997-1998), five seismic refraction and two reflection profiles were acquired on the Johnsons Glacier (Livingston Island, Antarctica) in order to obtain information about the structure of the ice, characteristics of the ice-bed contact and basement topography. An innovative technique has been used for the acquisition of reflection data to optimise the field survey schedule. Different shallow seismic sources were used during each field season: Seismic Impulse Source System (SISSY) for the first field survey and low-energy explosives (pyrotechnic noisemakers) during the second one. A comparison between these two shallow seismic sources has been performed, showing that the use of the explosives is a better seismic source in this ice environment. This is one of the first studies where this type of source has been used. The analysis of seismic data corresponding to one of the reflection profiles (L3) allows us to delineate sectors with different glacier structure (accumulation and ablation zones) without using glaciological data. Moreover, vertical discontinuities were detected by the presence of back-scattered energy and the abrupt change in frequency content of first arrivals shown in shot records. After the raw data analysis, standard processing led us to a clear seismic image of the underlying bed topography, which can be correlated with the ice flow velocity anomalies. The information obtained from seismic data on the internal structure of the glacier, location of fracture zones and the topography of the ice-bed interface constrains the glacial dynamics of Johnsons Glacier.
Ocean mixing beneath Pine Island Glacier ice shelf, West Antarctica
NASA Astrophysics Data System (ADS)
Kimura, Satoshi; Jenkins, Adrian; Dutrieux, Pierre; Forryan, Alexander; Naveira Garabato, Alberto C.; Firing, Yvonne
2016-12-01
Ice shelves around Antarctica are vulnerable to an increase in ocean-driven melting, with the melt rate depending on ocean temperature and the strength of flow inside the ice-shelf cavities. We present measurements of velocity, temperature, salinity, turbulent kinetic energy dissipation rate, and thermal variance dissipation rate beneath Pine Island Glacier ice shelf, West Antarctica. These measurements were obtained by CTD, ADCP, and turbulence sensors mounted on an Autonomous Underwater Vehicle (AUV). The highest turbulent kinetic energy dissipation rate is found near the grounding line. The thermal variance dissipation rate increases closer to the ice-shelf base, with a maximum value found ˜0.5 m away from the ice. The measurements of turbulent kinetic energy dissipation rate near the ice are used to estimate basal melting of the ice shelf. The dissipation-rate-based melt rate estimates is sensitive to the stability correction parameter in the linear approximation of universal function of the Monin-Obukhov similarity theory for stratified boundary layers. We argue that our estimates of basal melting from dissipation rates are within a range of previous estimates of basal melting.
Miles, Bertie W. J.; Stokes, Chris R.; Jamieson, Stewart S. R.
2016-01-01
The dynamics of ocean-terminating outlet glaciers are an important component of ice-sheet mass balance. Using satellite imagery for the past 40 years, we compile an approximately decadal record of outlet-glacier terminus position change around the entire East Antarctic Ice Sheet (EAIS) marine margin. We find that most outlet glaciers retreated during the period 1974–1990, before switching to advance in every drainage basin during the two most recent periods, 1990–2000 and 2000–2012. The only exception to this trend was in Wilkes Land, where the majority of glaciers (74%) retreated between 2000 and 2012. We hypothesize that this anomalous retreat is linked to a reduction in sea ice and associated impacts on ocean stratification, which increases the incursion of warm deep water toward glacier termini. Because Wilkes Land overlies a large marine basin, it raises the possibility of a future sea level contribution from this sector of East Antarctica. PMID:27386519
Miles, Bertie W J; Stokes, Chris R; Jamieson, Stewart S R
2016-05-01
The dynamics of ocean-terminating outlet glaciers are an important component of ice-sheet mass balance. Using satellite imagery for the past 40 years, we compile an approximately decadal record of outlet-glacier terminus position change around the entire East Antarctic Ice Sheet (EAIS) marine margin. We find that most outlet glaciers retreated during the period 1974-1990, before switching to advance in every drainage basin during the two most recent periods, 1990-2000 and 2000-2012. The only exception to this trend was in Wilkes Land, where the majority of glaciers (74%) retreated between 2000 and 2012. We hypothesize that this anomalous retreat is linked to a reduction in sea ice and associated impacts on ocean stratification, which increases the incursion of warm deep water toward glacier termini. Because Wilkes Land overlies a large marine basin, it raises the possibility of a future sea level contribution from this sector of East Antarctica.
90-year-old firn air from Styx glacier, East Antarctica
NASA Astrophysics Data System (ADS)
Jang, Y.; Ahn, J.; Buizert, C.; Lee, H. G.; Hong, S.; Han, Y.; Jun, S. J.; Hur, S. D.
2017-12-01
Firn is the upper part of the glacier that has not yet been completely changed to the ice. In this layer, firn air can move through the open pores and be pumped for sampling. We obtained firn air and ice cores from Styx glacier (73°51'95″ S, 163°41'217″ E, 1623m asl.), East Antarctica during 2014-2015. The Styx glacier is located near coast, and has an accumulation rate of 0.13 Mgm-2y-1 with a mean annual temperature of -31.7 °. We found that the lock-in depth (depth where gas diffusion starts to stop, "LID") is 52.4 m and bubble close-off depth (the depth to the snow-ice transition perfectly, "COD") is 65.1 m. Therefore lock-in zone (between LID and COD, "LIZ") is 52.4 - 65.1 m. Concentrations of greenhouse gases (CO2, CH4, n=13) in the firn air were analyzed at US National Oceanic and Atmospheric Administration (NOAA) and 15N of N2 was measured at the Scripps Institution of Oceanography (SIO). We find that the firn air ages are up to about 90 years, the oldest firn air ages observed among coastal glaciers. In order to better understand physical properties and chemical composition, methane concentration and total air content of the closed bubbles in the LIZ (3 cm resolution, n=124) were analyzed by a wet extraction method at Seoul National University. The CH4 concentration and total air content show large variations in cm-scale depth intervals, and they are anti-correlated with each other. The CH4 concentration changes in a few cm corresponds to up to 40 years in CH4 age. We also applied Centre for Ice and Climate (CIC) 1-dimensional diffusion model and simulated greenhouse gas concentration profiles to quantitatively understand how the air moves in the Styx firn column. We hypothesize that density variations in the firn may increase thickness of LIZ and consequently increase of firn gas ages.
Carbon-Isotopic Dynamics of Streams, Taylor Valley, Antarctica: Biological Effects
NASA Technical Reports Server (NTRS)
Neumann, K.; DesMarais, D. J.
1998-01-01
We have investigated the role of biological processes in the C-isotopic dynamics of the aquatic ecosystems in Taylor Valley, Antarctica. This cold desert ecosystem is characterized by the complete lack of vascular plants, and the presence of algal mats in ephemeral streams and perennially ice covered lakes. Streams having abundant algal mats and mosses have very low sigma CO2 concentrations, as well as the most depleted delta C-13 values (-4%). Previous work has shown that algal mats in these streams have delta C-13 values averaging -7.01%. These values are similar to those observed in the algal mats in shallow areas of the lakes in Taylor Valley, where CO2 is thought to be colimiting to growth. These low Sigma CO2 concentrations, and delta C(13) signatures heavier than the algal mats, suggest that CO2 may be colimiting in the streams, as well. Streams with little algal growth, especially the longer ones in Fryxell Basin, have higher Sigma CO2 concentrations and much more enriched isotopic signatures (as high as +8%). In these streams, the dissolution of isotopically enriched, cryogenic CaCO3 is probably the major source of dissolved carbonate. The delta C(13) geochemistry of Antarctic streams is radically different from the geochemistry of more temperate streams, as it is not affected by terrestrially produced, isotopically depleted Sigma CO2. These results have important implications for the understanding of "biogenic" carbonate that might have been produced from aquatic ecosystems in the past on Mars.
Distribution and abundance of fungi in the soils of Taylor Valley, Antarctica
Connell, L.; Redman, R.; Craig, S.; Rodriguez, R.
2006-01-01
The occurrence and distribution of culturable fungi in Taylor Valley, Antarctica was assessed in terms of soil habitat. Soil transects throughout the valley revealed differential habitat utilization between filamentous and non-filamentous (yeast and yeast-like) fungi. In addition, there were significant differences in species distribution patterns with respect to soil pH, moisture, distance from marine coastline, carbon, chlorophyll a, salinity, elevation and solar inputs. Filamentous fungal abundance is most closely associated with habitats having higher pH, and soil moistures. These close associations were not found with yeast and yeast-like fungi demonstrating that yeast and yeast-like fungi utilize a broader range of habitat. An intensive survey of the Victoria Land is necessary to gain a better understanding of their role in soil functioning and nutrient cycling processes. ?? 2006 Elsevier Ltd. All rights reserved.
Williams, Richard S.; Ferrigno, Jane G.
1998-01-01
Landsat images, together with maps and aerial photographs, have been used to produce glacier inventories, define glacier locations, and study glacier dynamics in the countries of South America, along with the Andes Mountains. In Venezuela, Colombia, Ecuador, and Bolivia, the small glaciers have been undergoing extensive glacier recession since the late 1800's. Glacier-related hazards (outburst floods, mud flows, and debris avalanches) occur in Colombia, in Ecuador, and associated with the more extensive (2,600 km2) glaciers of Peru. The largest area of glacier ice is found in Argentina and Chile, including the northern Patagonian ice field (about 4,200 km2) and the southern Patagonian ice field (about 13,000 km2), the largest glacier in the Southern Hemisphere outside Antarctica.
NASA Astrophysics Data System (ADS)
Yu, Hongju; Rignot, Eric; Morlighem, Mathieu; Seroussi, Helene
2017-05-01
Thwaites Glacier (TG), West Antarctica, has been losing mass and retreating rapidly in the past few decades. Here, we present a study of its calving dynamics combining a two-dimensional flow-band full-Stokes (FS) model of its viscous flow with linear elastic fracture mechanics (LEFM) theory to model crevasse propagation and ice fracturing. We compare the results with those obtained with the higher-order (HO) and the shallow-shelf approximation (SSA) models coupled with LEFM. We find that FS/LEFM produces surface and bottom crevasses that are consistent with the distribution of depth and width of surface and bottom crevasses observed by NASA's Operation IceBridge radar depth sounder and laser altimeter, whereas HO/LEFM and SSA/LEFM do not generate crevasses that are consistent with observations. We attribute the difference to the nonhydrostatic condition of ice near the grounding line, which facilitates crevasse formation and is accounted for by the FS model but not by the HO or SSA models. We find that calving is enhanced when pre-existing surface crevasses are present, when the ice shelf is shortened or when the ice shelf front is undercut. The role of undercutting depends on the timescale of calving events. It is more prominent for glaciers with rapid calving rates than for glaciers with slow calving rates. Glaciers extending into a shorter ice shelf are more vulnerable to calving than glaciers developing a long ice shelf, especially as the ice front retreats close to the grounding line region, which leads to a positive feedback to calving events. We conclude that the FS/LEFM combination yields substantial improvements in capturing the stress field near the grounding line of a glacier for constraining crevasse formation and iceberg calving.
NASA Astrophysics Data System (ADS)
Ruiz Fernández, Jesús; Oliva, Marc; Fernández Menéndez, Susana del Carmen; García Hernández, Cristina; Menéndez Duarte, Rosa Ana; Pellitero Ondicol, Ramón; Pérez Alberti, Augusto; Schimmelpfennig, Irene
2017-04-01
CRONOANTAR brings together researchers from Spain, Portugal, France and United Kingdom with the objective of spatially and temporally reconstruct the deglaciation process at the two largest islands in the South Shetlands Archipelago (Maritime Antarctica), since the Global Last Glacial Maximum. Glacier retreat in polar areas has major implications at a local, regional and even planetary scale. Global average sea level rise is the most obvious and socio-economically relevant, but there are others such as the arrival of new fauna to deglaciated areas, plant colonisation or permafrost formation and degradation. This project will study the ice-free areas in Byers and Hurd peninsulas (Livingston Island) and Fildes and Potter peninsulas (King George Island). Ice-cap glacier retreat chronology will be revealed by the use of cosmogenic isotopes (mainly 36Cl) on glacially originated sedimentary and erosive records. Cosmogenic dating will be complemented by other dating methods (C14 and OSL), which will permit the validation of these methods in regions with cold-based glaciers. Given the geomorphological evidences and the obtained ages, a deglaciation calendar will be proposed and we will use a GIS methodology to reconstruct the glacier extent and the ice thickness. The results emerging from this project will allow to assess whether the high glacier retreat rates observed during the last decades were registered in the past, or if they are conversely the consequence (and evidence) of the Global Change in Antarctica. Acknowledgements This work has been funded by the Spanish Ministry of Economy, Industry and Competitiveness (Reference: CTM2016-77878-P).
CO(2) and N(2)O emissions in a soil chronosequence at a glacier retreat zone in Maritime Antarctica.
Thomazini, A; Mendonça, E S; Teixeira, D B; Almeida, I C C; La Scala, N; Canellas, L P; Spokas, K A; Milori, D M B P; Turbay, C V G; Fernandes, R B A; Schaefer, C E G R
2015-07-15
Studies of C cycle alterations are extremely important to identify changes due to climate change, especially in the polar ecosystem. The objectives of this study were to (i) examine patterns of soil CO2-C and N2O-N emissions, and (ii) evaluate the quantity and quality of soil organic matter across a glacier retreat chronosequence in the Maritime Antarctica. Field measurements were carried out during January and February 2010 (summer season) along a retreating zone of the White Eagle Glacier, at King George Island, Maritime Antarctica. Soil samples (0-10cm) were collected along a 500-m transect at regular intervals to determine changes in soil organic matter. Field CO2-C emission measurements and soil temperature were carried out at regular intervals. In addition, greenhouse gas production potentials were assessed through 100days laboratory incubations. Soils exposed for a longer time tended to have greater concentrations of soluble salts and possess sandier textures. Total organic C (3.59gkg(-1)), total N (2.31gkg(-1)) and labile C (1.83gkg(-1)) tended to be lower near the glacier front compared with sites away from it, which is correlated with decreasing degree of humification of the soil organic matter with exposure time. Soil CO2-C emissions tended to increase with distance from the glacier front. On average, the presence of vegetation increased CO2-C emissions by 440%, or the equivalent of 0.633g of CO2-C m(-2)h(-1). Results suggest that newly exposed landsurfaces undergo soil formation with increasing labile C input from vegetation, accompanied by increasing soil CO2-C emissions. Despite the importance of exposure time on CO2-C production and emissions, there was no similar trend in soil N2O-N production potentials as a function of glacial retreat. For N2O, instead, the maximum production occurred in sites with the first stages of vegetation growth. Copyright © 2015 Elsevier B.V. All rights reserved.
3D full-Stokes modeling of the grounding line dynamics of Thwaites Glacier, West Antarctica
NASA Astrophysics Data System (ADS)
Yu, H.; Rignot, E. J.; Morlighem, M.; Seroussi, H. L.
2016-12-01
Thwaites Glacier (TG) is the broadest and second largest ice stream in the West Antarctica. Satellite observations have revealed rapid grounding line retreat and mass loss of this glacier in the past few decades, which has been attributed to the enhanced basal melting in the Amundsen Sea Embayment. With a retrograde bed configuration, TG is on the verge of collapse according to the marine ice sheet instability theory. Here, we use the UCI/JPL Ice Sheet System Model (ISSM) to simulate the grounding line position of TG to determine its stability, rate of retreat and sensitivity to enhanced basal melting using a three-dimensional full-Stokes numerical model. Simulations with simplified models (Higher Order (HO), and Shelfy-Stream Approximation (SSA)) are also conducted for comparison. We first validate our full Stokes model by conducting MISMIP3D experiments. Then we applied the model to TG using new bed elevation dataset combining IceBridge (OIB) gravity data, OIB ice thickness, ice flow vectors from interferometry and a mass conservation method at 450 m spacing. Basal friction coefficient and ice rheology of floating ice are inferred to match observed surface velocity. We find that the grounding line is capable of retreating at rate of 1km/yr under current forcing and that the glacier's sensitivity to melt is higher in the Stokes model than HO or SSA, which means that projections using SSA or HO might underestimate the future rate of retreat of the glacier. This work has been performed at UC Irvine and Caltech's Jet Propulsion Laboratory under a contract with NASA's Cryospheric Science Program.
NASA Astrophysics Data System (ADS)
Swanger, K. M.; Schaefer, J. M.; Winckler, G.; Lamp, J. L.; Marchant, D. R.
2016-12-01
Based on surface exposure dating of moraines and drifts, East Antarctic outlet glaciers in the McMurdo Dry Valleys (MDV) advanced during the mid-Pliocene and/or early-Pleistocene. However, scatter in exposure ages is common for these deposits (and other glacial drifts throughout Antarctica), making it difficult to tie glacial advances to specific climate intervals. In order to constrain the sources of scatter, we mapped and dated 15 cold-based drifts in Taylor Valley and the Olympus Range in the MDV. A secondary goal was to build a regional climate record, for comparison with fluctuations of the local outlet glaciers. Our alpine drift record is confined to the late-Pleistocene, with glacial advances during interglacial periods. Based on 54 3He exposure dates on alpine drifts, age scatter is common in the MDV on both recent and ancient deposits. Where it occurs, age scatter is likely caused by inheritance of cosmogenic nuclides previous to glacial entrainment and stacking of multiple cold-based drifts. Nuclide inheritance of >1 Myr is possible, but this is relatively rare and confined to regions where englacial debris is sourced from stable, high-elevation plateaus. On the other hand, drifts associated with glaciers bound by steep cirque headwalls and arêtes exhibit significantly less age scatter. Given the cold-based nature of MDV alpine and outlet glaciers, deposition of multiple stacked drift sheets also contributes to age scatter, with the implication that it might be possible to date multiple advances of cold-based ice. These results serve to inform better sampling strategies on cold-based drifts throughout Antarctica.
Surface winds over West Antarctica
NASA Astrophysics Data System (ADS)
Bromwich, David
1993-07-01
Five winter months (April-August 1988) of thermal infrared satellite images were examined to investigate the occurrence of dark (warm) signatures across the Ross Ice Shelf in the Antarctic continent. These features are inferred to be generated by katabatic winds that descend from southern Marie Byrd Land and then blow horizontally across the ice shelf. Significant mass is added to this airstream by katabatic winds blowing from the major glaciers that flow through the Transantarctic Mountains from East Antarctica. These negatively buoyant katabatic winds can reach the northwestern edge of the shelf - a horizontal propagation distance of up to 1,000 km - 14 percent of the time. Where the airstream crosses from the ice shelf to the ice-covered Ross Sea, a prominent coastal polynya is formed. Because the downslope buoyancy force is near zero over the Ross Ice Shelf, the northwestward propagation of the katabatic air mass requires pressure gradient support. The study shows that the extended horizontal propagation of this atmospheric density current occurred in conjunction with the passage of synoptic cyclones over the southern Amundsen Sea. These cyclones can strengthen the pressure gradient in the interior of West Antarctica and make the pressure field favorable for northwestward movement of the katabatic winds from West Antarctica across the ice shelf in a geostrophic direction. The glacier winds from East Antarctica are further accelerated by the synoptic pressure gradient, usually undergo abrupt adjustment beyond the exit to the glacier valley, and merge into the mountain-parallel katabatic air mass.
Airfields on Antarctic Glacier Ice
1989-12-01
glacier ice Vu., vA2 2~ FEB 0C DLSPM ONSAEM- T r it Cover: Blue ice areas near the Scott Glacier. There is a possible landing field at 86035"S, 148025"W...pi. Ii7 t E 9 v 1.. - Site$ At Moliunt HoWe t87*20S. 14W 0W) -nd P-411 lardain t leois lower than that of clear Glacier (85ൎ’S, 16795T~) wur-a...emphasis much more vigorous than isthecasein thehighin- on the area of Mount Howe and D’Angelo Bluff teior of Antarctica. For example, near Mawson
Groundwater seeps in Taylor Valley Antarctica: an example of a subsurface melt event
NASA Astrophysics Data System (ADS)
Lyons, W. Berry; Welch, Kathleen A.; Carey, Anne E.; Doran, Peter T.; Wall, Diana H.; Virginia, Ross A.; Fountain, Andrew G.; Csathó, Bea M.; Tremper, Catherine M.
The 2001/02 austral summer was the warmest summer on record in Taylor Valley, Antarctica, (˜78° S) since continuous records of temperature began in 1985. The highest stream-flows ever recorded in the Onyx River, Wright Valley, were also recorded that year (the record goes back to the 1969/70 austral summer). In early January 2002, a groundwater seep was observed flowing in the southwest portion of Taylor Valley. This flow has been named 'Wormherder Creek' (WHC) and represents an unusual event, probably occurring on a decadal time-scale. The physical characteristics of this feature suggest that it may have flowed at other times in the past. Other groundwater seeps, emanating from the north-facing slope of Taylor Valley, were also observed. Little work has been done previously on these very ephemeral seeps, and the source of water is unknown. These features, resembling recently described features on Mars, represent the melting of subsurface ice. The Martian features have been interpreted as groundwater seeps. In this paper we compare the chemistry of the WHC groundwater seep to that of the surrounding streams that flow every austral summer. The total dissolved solids content of WHC was ˜6 times greater than that of some nearby streams. The Na : Cl and SO4 : Cl ratios of the seep waters are higher than those of the streams, but the Mg : Cl and HCO3 : Cl ratios are lower, indicating different sources of solutes to the seeps compared to the streams. The enrichment of Na and SO4 relative to Cl may suggest significant dissolution of mirabilite within the previously unwetted soil. The proposed occurrence of abundant mirabilite in higher-elevation soils of the dry valley region agrees with geochemical models developed, but not tested, in the late 1970s. The geochemical data demonstrate that these seeps could be important in 'rinsing' the soils by dissolving and redistributing the long-term accumulation of salts, and perhaps improving habitat suitability for soil biota
Rift in Antarctic Glacier: a Unique Chance to Study Ice Shelf Retreat
NASA Technical Reports Server (NTRS)
Howat, Ian M.; Jezek, Ken; Studinger, Michael; Macgregor, Joseph A.; Paden, John; Floricioiu, Dana; Russell, Rob; Linkswiler, Matt; Dominguez, Roseanne T.
2012-01-01
It happened again, but this time it was caught in the act. During the last week of September 2011 a large transverse rift developed across thefloating terminus of West Antarcticas PineIsland Glacier, less than 5 years after its lastlarge calving event, in 2007 (Figure 1). PineIsland Glaciers retreat has accelerated substantiallyin the past 2 decades, and it is nowlosing 50 gigatons of ice per year, or roughly 25 of Antarcticas total annual contributionto sea level rise [Rignot et al., 2008]. The glaciers recent accelerated retreat is likely triggered by ocean warming and increased submarine melting. As such, it is of significant interest to glaciologists and of heightened societal relevance.
NASA Astrophysics Data System (ADS)
Diehl, T. M.; Holt, J. W.; Blankenship, D. D.; Richter, T. G.; Filina, I. Y.
2005-12-01
The West Antarctic Ice Sheet is a marine ice sheet of which 75% is resting on bedrock below sea level. This situation is highly unstable and as the climate warms, the potential for rapid discharge of the ice sheet grows. Examining the areas of the ice sheet that are most likely to react to changing climate is essential. The Amundsen Sea Embayment contains two of the most important outlet glaciers in West Antarctica: Thwaites and Pine Island Glaciers. These two glaciers have among the highest discharge velocities in West Antarctica and they lack large protective ice shelves, making them susceptible to warming ocean waters. The area is currently a target of interest for both GRACE and GLAS, as well as future land- and air-based surveys. To date, we have conducted the only large-scale geophysical survey over the catchment of Thwaites Glacier: an airborne survey completed during the austral summer 2004-2005. Over 43,500 line-kilometers of data were collected with a geophysical platform that included ice-penetrating radar, gravity, magnetics, laser and pressure altimetry, and GPS. Free-air gravity, in conjunction with magnetics and radar-derived subglacial topography, is capable of delineating microplate and rift boundaries as well as basin and volcano locations. A free-air gravity map of these structures helps ascertain the contribution of subglacial geology to the ice sheet's decay in the Thwaites Glacier catchment. The acquisition, reduction, and initial results of the airborne gravity survey will be presented and then compared to GRACE gravity anomalies. Extreme relief in ice surface elevation across the survey area necessitated short, smooth vertical altitude changes at survey block boundaries to maintain adequate flight altitude for the onboard ice-penetrating radar systems. Weather conditions sometimes required additional elevation changes or course corrections, producing significant aircraft motion during data acquisition. The impacts of these aircraft motions
Obliquity-paced climate change recorded in Antarctic debris-covered glaciers
Mackay, Sean L.; Marchant, David R.
2017-01-01
The degree to which debris-covered glaciers record past environmental conditions is debated. Here we describe a novel palaeoclimate archive derived from the surface morphology and internal debris within cold-based debris-covered glaciers in Antarctica. Results show that subtle changes in mass balance impart major changes in the concentration of englacial debris and corresponding surface topography, and that over the past ∼220 ka, at least, the changes are related to obliquity-paced solar radiation, manifest as variations in total summer energy. Our findings emphasize solar radiation as a significant driver of mass balance changes in high-latitude mountain systems, and demonstrate that debris-covered glaciers are among the most sensitive recorders of obliquity-paced climate variability in interior Antarctica, in contrast to most other Antarctic archives that favour eccentricity-paced forcing over the same time period. Furthermore, our results open the possibility that similar-appearing debris-covered glaciers on Mars may likewise hold clues to environmental change. PMID:28186094
Geoengineering Outlet Glaciers and Ice Streams
NASA Astrophysics Data System (ADS)
Wolovick, Michael
2017-04-01
Mass loss from Greenland and Antarctica is highly sensitive to the presence of warm ocean water that drives melting of ice shelves and marine terminated glaciers. This warm water resides offshore at depth and accesses the grounding line through deep but narrow troughs and fjords. Here, we investigate the possibility of blocking warm water transport through these choke points with an artificial sill. Using a simple width-averaged model of ice stream flow coupled to a buoyant-plume model of submarine melt, we find that grounding line retreat and sea level rise can be delayed or reversed for hundreds of years if warm water is prevented from accessing outlet glaciers and ice-shelf cavities. Glaciers with a floating shelf exhibit a strong response to the presence of the artificial sill regardless of our choice of calving law, while tidewater glaciers require a strong linkage between submarine melt and iceberg calving for the artificial sill to have an effect. As a result of this difference and as a result of differing degrees of overdeepening in the basal topography, Antarctica and Greenland present very different societal cost-benefit analyses. Intervention in Greenland would be low-cost and low-reward: the volume of the artificial sill is comparable to existing large public works projects such as the Dubai Islands or the Suez Canal, but the magnitude of averted sea-level rise is small, the success of the intervention depends on the choice of calving law, and the glaciers return to their non-geoengineered trajectories within one to two centuries. Intervention in Antarctica, on the other hand, would be high-cost and high-reward: the volume of the artificial sill is one to two orders of magnitude greater, but the averted sea level rise is much larger, the intervention is successful regardless of the choice of calving law, and the ice streams remain far from their non-geoengineered trajectories throughout the 1000 year duration of our model runs. In both cases, an
NASA Astrophysics Data System (ADS)
Walker, C. C.; Gardner, A. S.
2017-10-01
Here we investigate the largest acceleration in ice flow across all of Antarctica between ∼2008 InSAR and 2014 Landsat velocity mappings. This occurred in glaciers that used to feed into the Wordie Ice Shelf on the west Antarctic Peninsula, which rapidly disintegrated in ∼1989. Between 2008 and 2014, these glaciers experienced at least a threefold increase in surface elevation drawdown relative to the 2002-2008 time period. After ∼20 yrs of relative stability, it is unlikely that the ice shelf collapse played a role in the large response. Instead, we find that the rapid acceleration and surface drawdown is linked to enhanced melting at the ice-ocean boundary, attributable to changes in winds driven by global atmospheric circulation patterns, namely the El Niño-Southern Oscillation (ENSO) and Southern Annular Mode (SAM), linking changes in grounded ice to atmospheric-driven ocean warming.
NASA Astrophysics Data System (ADS)
Bingham, R. G.; Davies, D.; King, E. C.; Vaughan, D. G.; Cornford, S. L.; Brisbourne, A.; Smith, A.; De Rydt, J.; Graham, A. G. C.; Spagnolo, M.
2016-12-01
Deglaciated landscapes and landforms are much used in the quest to reconstruct past ice-sheet behaviour, on the principle that aspects of landform shapes, sizes and relative associations "fossilise" palaeo-ice-sheet processes. Such techniques have been widely used around the margin of the marine West Antarctic Ice Sheet, taking advantage of bathymetric surveying techniques which have exposed a rich suite of landform assemblages across West Antarctica's continental shelf. Though these geomorphological interpretations are solidly grounded in glacial geological theory, there has, until now, been little ability to compare these deglaciated, and potentially postglacially-modified, landforms offshore with landforms currently situated (and potentially still evolving) beneath the contemporary ice sheet. This paper presents a widespread view of glacial landforms presently situated beneath 1-2 km of ice in multi-square-km "windows to the bed" distributed throughout the catchment of Pine Island Glacier, West Antarctica. Imaged over three field seasons between 2007 and 2013 by dedicated radar surveys designed specifically to capture landforms analogous to those surveyed offshore by bathymetric surveying, the results provide significant insights for the interpretation of palaeo-ice-stream landforms, and their use in modelling ice-ocean interactions around the fringes of marine ice sheets. We show that landform sizes, shapes and associations vary significantly around Pine Island Glacier's catchment. The key controls appear to be substrate composition, pre-existing tectonic structure, and longstanding spatial stability of the ice-stream's flow distribution. The findings offer crucial information for modelling ice coupling to the bed, which should feed through to wider efforts to reconstruct the past behaviour of this significant marine ice sheet using its palaeoglacial landforms.
Iceberg from Pine Island Glacier, Antarctica
2014-01-14
The voyage of Iceberg B-31 continued in January, 2014 as the giant iceberg drifted over the frigid waters of Pine Island Bay and widened the gap between the newly-calved iceberg and the “mother” glacier. Between November 9 and 11, 20143 a giant crack in the Pine Island Glacier gave completely away, liberating Iceberg B-31 from the end of the glacial tongue. The new iceberg was estimated to be 35 km by 20 km (21 mi by 12 mi) in size – or roughly the size of Singapore. On January 5, 2014 the Moderate Resolution Imaging Spectroradiometer (MODIS) aboard NASA’s Terra satellite captured this true-color image of B-31 floating in the center of Pine Island Bay on an approach to the Amundsen Sea. Pine Island Glacier can be seen on the upper right coast of the bay, and is marked by parallel lines in the ice. According to measurements reported by the National U.S. Ice Center, on January 10, B-31 was maintaining its size, and was located at 74°24'S and 104°33'W. Credit: NASA/GSFC/Jeff Schmaltz/MODIS Land Rapid Response Team 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
Velocities of antarctic outlet glaciers determined from sequential Landsat images
MacDonald, Thomas R.; Ferrigno, Jane G.; Williams, Richard S.; Lucchitta, Baerbel K.
1989-01-01
Approximately 91.0 percent of the volume of present-day glacier ice on Earth is in Antarctica; Greenland contains about another 8.3 percent of the volume. Thus, together, these two great ice sheets account for an estimated 99.3 percent of the total. Long-term changes in the volume of glacier ice on our planet are the result of global climate change. Because of the relationship of global ice volume to sea level (± 330 cubic kilometers of glacier ice equals ± 1 millimeter sea level), changes in the mass balance of the antarctic ice sheet are of particular importance.Whether the mass balance of the east and west antarctic ice sheets is positive or negative is not known. Estimates of mass input by total annual precipitation for the continent have been made from scattered meteorological observations (Swithinbank 1985). The magnitude of annual ablation of the ice sheet from calving of outlet glaciers and ice shelves is also not well known. Although the velocities of outlet glaciers can be determined from field measurements during the austral summer,the technique is costly, does not cover a complete annual cycle,and has been applied to just a few glaciers. To increase the number of outlet glaciers in Antarctica for which velocities have been determined and to provide additional data for under-standing the dynamics of the antarctic ice sheets and their response to global climate change, sequential Landsat image of several outlet glaciers were measured.
Reconnaissance and deep-drill site selection on Taylor Dome, Antarctica
NASA Technical Reports Server (NTRS)
Grootes, Pieter M.; Waddington, Edwin D.
1993-01-01
Taylor Dome is a small ice dome near the head of Taylor Valley, Southern Victoria Land. The location of the dome, just west of the Transantarctic Mountains, is expected to make the composition of the accumulating snow sensitive to changes in the extent of the Ross Ice Shelf. Thus, it is linked to the discharge of the West Antarctic Ice Sheet but protected against direct influences of glacial-interglacial sea-level rise. The record of past climatic and environmental changes in the ice provides a valuable complement to the radiocarbon-dated proxy record of climate derived from perched deltas, strandlines, and moraines that have been obtained in the nearby Dry Valleys. We carried out a reconnaissance of the Taylor Dome area over the past two field seasons to determine the most favorable location to obtain a deep core to bedrock. A stake network has been established with an 80-km line roughly along the crest of Taylor Dome, and 40-km lines parallel to it and offset by 10 km. These lines have been surveyed 1990/91, and the positions of 9 grid points have been determined with geoceivers. A higher density stake network was placed and surveyed around the most likely drill area in the second year. Ground-based radar soundings in both years provided details on bedrock topography and internal layering of the ice in the drill area. An airborne radar survey in January 1992, completed the radar coverage of the Taylor Dome field area.
Antarctica--the Ultimate Summer Institute.
ERIC Educational Resources Information Center
Van Wey, Nate J.
1995-01-01
Describes personal experiences of a participant in the National Science Foundation program, Teachers Experiencing Antarctica. Uses the study of the temperature history of Taylor Dome to provide teachers with the experience of research and help other teachers recognize that there are opportunities outside the classroom for personal and professional…
Prolific Sources of Icequakes: The Mulock and Skelton Glaciers, Antarctica
NASA Astrophysics Data System (ADS)
Lloyd, A. J.; Wiens, D.; Lough, A. C.; Anandakrishnan, S.; Nyblade, A.; Aster, R. C.; Huerta, A. D.; Winberry, J. P.
2015-12-01
The Mulock and Skelton Glaciers are large outlet glaciers that flow through the Transantarctic Mountains and into the Ross Ice Shelf. A regional seismic deployment in the central Transantarctic Mountains (TAM) in 1999-2000 led to the identification of 63 events in the vicinity of Mulock and Skelton Glaciers [Bannister and Kennett, 2002]. A more recent study utilizing seismic data collected as part of the POLENET/A-NET and AGAP projects during 2009 again identified significant seismicity associated with these glaciers and suggested that many of these events were icequakes based on their shallow depths [Lough, 2014]. These two glaciers represent the most seismically active regions in the TAM aside from the well-studied David Glacier region [Danesi et al, 2007; Zoet et al., 2012]. In addition, many of the icequakes from this region have magnitude ML > 2.5, in contrast to most glacial events that are generally of smaller magnitude. Using the waveforms of previously identified icequakes as templates, nearby POLENET/A-NET, AGAP, and GSN seismic stations were scanned using a cross-correlation method to find similar waveforms. We then used a relative location algorithm to determine high-precision locations and depths. The use of regional velocity models derived from recent seismic studies facilitates accurate absolute locations that we interpret in the context of the local geological and glacial features. The icequakes are concentrated in heavily crevassed regions associated with steep bedrock topography, likely icefalls. Future work will focus on determining whether these events are associated with stick-slip events at the bed of the glacier and/or crevasse formation near the surface. In addition the temporal pattern of seismicity will also be examined to search for repeating icequakes, which have been identified at the base of several other glaciers.
NASA Astrophysics Data System (ADS)
Aoki, S.; Kobayashi, R.; Rintoul, S. R.; Tamura, T.; Kusahara, K.
2017-08-01
Oceanic changes before and after the relocation of iceberg B9B and calving of the Mertz Glacier Tongue (MGT) in February 2010 are examined on the continental shelf off the Adélie Land/George V Land coast, East Antarctica. Summer hydrographic observations, including stable oxygen isotope ratio (δ18O), in 2001/2008 and 2011/2015 and results of a numerical model are used. Along the western flank of the MGT, temperature decreased between 2001 and 2015 for most of the water column in the Adélie Depression. δ18O generally decreased, especially at the MGT draft depths on the northern side. West of the MGT, temperature, salinity, and δ18O decreased in the intermediate layer. East of the MGT, in contrast, temperature increased between 2001 and 2011 at intermediate depths, salinity increased in the intermediate and deep layers, and δ18O slightly decreased in the deep layer but did not change much around 300 dbar. The numerical experiment exhibits a change in ocean circulation, revealing an increase in modified Circumpolar Deep Water (mCDW) inflow in the east and a decrease in the west. The contrasting changes in mCDW intrusion are consistent between the observations and numerical model, and are indicative of the effect of removal of the ice barriers. The contrast is overlain by overall decreases in salinity and δ18O, which suggests an increase in the continental meltwater fraction of 5-20% and might reveal a wide-ranging influence from West Antarctica. The oxygen isotope ratio is, hence, effective in monitoring the increase in continental melt over the Antarctic shelf.
Pine Island Glacier, Antarctica
2001-10-22
This ASTER image was acquired on December 12, 2000, and covers an area of 38 x 48 km. Pine Island Glacier has undergone a steady loss of elevation with retreat of the grounding line in recent decades. Now, space imagery has revealed a wide new crack that some scientists think will soon result in a calving event. Glaciologist Robert Bindschadler of NASA's Goddard Space Flight Center predicts this crack will result in the calving of a major iceberg, probably in less than 18 months. Discovery of the crack was possible due to multi-year image archives and high resolution imagery. This image is located at 74.1 degrees south latitude and 105.1 degrees west longitude. http://photojournal.jpl.nasa.gov/catalog/PIA11095
Net retreat of Antarctic glacier grounding lines
NASA Astrophysics Data System (ADS)
Konrad, Hannes; Shepherd, Andrew; Gilbert, Lin; Hogg, Anna E.; McMillan, Malcolm; Muir, Alan; Slater, Thomas
2018-04-01
Grounding lines are a key indicator of ice-sheet instability, because changes in their position reflect imbalance with the surrounding ocean and affect the flow of inland ice. Although the grounding lines of several Antarctic glaciers have retreated rapidly due to ocean-driven melting, records are too scarce to assess the scale of the imbalance. Here, we combine satellite altimeter observations of ice-elevation change and measurements of ice geometry to track grounding-line movement around the entire continent, tripling the coverage of previous surveys. Between 2010 and 2016, 22%, 3% and 10% of surveyed grounding lines in West Antarctica, East Antarctica and at the Antarctic Peninsula retreated at rates faster than 25 m yr-1 (the typical pace since the Last Glacial Maximum) and the continent has lost 1,463 km2 ± 791 km2 of grounded-ice area. Although by far the fastest rates of retreat occurred in the Amundsen Sea sector, we show that the Pine Island Glacier grounding line has stabilized, probably as a consequence of abated ocean forcing. On average, Antarctica's fast-flowing ice streams retreat by 110 metres per metre of ice thinning.
NASA Astrophysics Data System (ADS)
Smith, B. E.; Gourmelen, N.; Huth, A.; Joughin, I. R.
2016-12-01
In this presentation we show the results of a multi-sensor survey of a system of subglacial lakes beneath Thwaites Glacier, West Antarctica. This is the first substantial active (meaning draining or filling on annual time scales) lake system detected under the fast-flowing glaciers of the Amundsen Coast. Altimetry data show that over the 2013 calendar year, four subglacial lakes drained, essentially simultaneously, with the bulk of the drainage taking place over the course the first three months of the year. The largest of the lakes appears to have drained around 3.7 km3 of water, with the others each draining less than 1 km3. The high-resolution radar surveys conducted in this area by NASA's IceBridge program allow detailed analysis of the subglacial hydrologic potential, which shows that the potential map in this area is characterized by small closed basins that should not, under the common assumption that water flow is directed down the gradient of the hydropotential, allow long-range water transport. The lakes' discharge demonstrates that, at least in some cases, water can flow out of apparently closed hydropotential basins. Combining a basal-flow routing map with a map of basal melt production suggests that the largest drainage event could recur as often as every 22 years, provided that overflow or leakage of mapped hydropotential basins allows melt water transport to refill the lake. An analysis of ice-surface speed records both around the lakes and at the Thwaites grounding line shows small changes in ice speed, but none clearly associated with the drainage event, suggesting that, at least in this area where subglacial melt is abundant, the addition of further water to the subglacial hydrologic system need not have any significant effect on ice flow. It is likely that the main impact of the lake system on the glacier is that as an efficient mechanism to remove meltwater from the system, it drains water that would otherwise flow through less efficient
NASA Spacecraft Images Massive Crack in Antarctica Pine Island Glacier
2011-11-15
This image from NASA Terra spacecraft shows a massive crack across the Pine Island Glacier, a major ice stream that drains the West Antarctic Ice Sheet. Eventually, the crack will extend all the way across the glacier.
Antarctic glacier-tongue velocities from Landsat images: First results
Lucchitta, Baerbel K.; Mullins, K.F.; Allison, A.L.; Ferrigno, Jane G.
1993-01-01
We measured the velocities of six glacier tongues and a few tongues within ice shelves distributed around the Antarctic coastline by determining the displacement of crevasse patterns seen on sequential Landsat images. The velocities range from less than 0.2 km a−1 for East Antarctic ice-shelf tongues to more than 2.5 km a−1 for the Thwaites Glacier Tongue. All glacier tongues show increases in velocity toward their distal margins. In general, the tongues of glaciers draining the West Antarctic ice sheet have moved significantly faster than those in East Antarctica. This observation may be significant in light of the hypothesized possible disintegration of the West Antarctic ice sheet.
Modeling the Thickness of Perennial Ice Covers on Stratified Lakes of the Taylor Valley, Antarctica
NASA Technical Reports Server (NTRS)
Obryk, M. K.; Doran, P. T.; Hicks, J. A.; McKay, C. P.; Priscu, J. C.
2016-01-01
A one-dimensional ice cover model was developed to predict and constrain drivers of long term ice thickness trends in chemically stratified lakes of Taylor Valley, Antarctica. The model is driven by surface radiative heat fluxes and heat fluxes from the underlying water column. The model successfully reproduced 16 years (between 1996 and 2012) of ice thickness changes for west lobe of Lake Bonney (average ice thickness = 3.53 m; RMSE = 0.09 m, n = 118) and Lake Fryxell (average ice thickness = 4.22 m; RMSE = 0.21 m, n = 128). Long-term ice thickness trends require coupling with the thermal structure of the water column. The heat stored within the temperature maximum of lakes exceeding a liquid water column depth of 20 m can either impede or facilitate ice thickness change depending on the predominant climatic trend (temperature cooling or warming). As such, shallow (< 20 m deep water columns) perennially ice-covered lakes without deep temperature maxima are more sensitive indicators of climate change. The long-term ice thickness trends are a result of surface energy flux and heat flux from the deep temperature maximum in the water column, the latter of which results from absorbed solar radiation.
Clow, G.D.; Saltus, R.W.; Waddington, E.D.
1996-01-01
We describe a high-precision (0.1-1.0 mK) borehole-temperature (BT) logging system developed at the United States Geological Survey (USGS) for use in remote polar regions. We discuss calibration, operational and data-processing procedures, and present an analysis of the measurement errors. The system is modular to facilitate calibration procedures and field repairs. By interchanging logging cables and temperature sensors, measurements can be made in either shallow air-filled boreholes or liquid-filled holes up to 7 km deep. Data can be acquired in either incremental or continuous-logging modes. The precision of data collected by the new logging system is high enough to detect and quantify various thermal effects at the milli-Kelvin level. To illustrate this capability, we present sample data from the 3 km deep borehole at GISP2, Greenland, and from a 130m deep air-filled hole at Taylor Dome, Antarctica. The precision of the processed GTSP2 continuous temperature logs is 0.25-0.34 mK, while the accuracy is estimated to be 4.5 mK. The effects of fluid convection and the dissipation of the thermal disturbance caused by drilling the borehole are clearly visible in the data. The precision of the incremental Taylor Dome measurements varies from 0.11 to 0.32mK, depending on the wind strength during the experiments. With this precision, we found that temperature fluctuations and multi-hour trends in the BT measurements correlate well with atmospheric-pressure changes.
Fast Recession of a West Antarctic Glacier
NASA Technical Reports Server (NTRS)
Rignot, E. J.
1998-01-01
Satellite radar interferometry observations of Pine Island Glacier, in West Antarctica, reveal that the hinge-line position of this major ice stream retreated 1.2+/-0.2 km per year between 1992 and 1996, which in turn implies ice thinning at 3.5+/-0.6m ice per year.
NASA Astrophysics Data System (ADS)
Aarons, S. M.; Aciego, S.; McConnell, J.
2017-12-01
Dust emissions and transport are linked to spatial and temporal climate variability, with dust provenance providing clues to past climate and climate impacts. The penultimate interglacial period (MIS 5e) has been suggested as an analog to Holocene climate change. We present the first evaluation of the MIS 5e ice archive developed at Taylor Glacier, East Antarctica and provide a record of dust transported to Taylor Glacier during MIS 5e. Our record shows significant differences between MIS 5e, Holocene, and pre-industrial dust transported to East Antarctica. The MIS 5e dust is sourced from New Zealand and southern South America (SSA), while the Holocene dust is sourced from local Antarctic, SSA, and potentially Australian sources. This profound change in composition suggests a variation in atmospheric transport pathways and/or paleo-environmental conditions between the interglacial periods, and indicates that MIS 5e should be reassessed as an analog for climate change and associated impacts.
Variability of Basal Melt Beneath the Pine Island Glacier Ice Shelf, West Antarctica
NASA Technical Reports Server (NTRS)
Bindschadler, Robert; Vaughan, David G.; Vornberger, Patricia
2011-01-01
Observations from satellite and airborne platforms are combined with model calculations to infer the nature and efficiency of basal melting of the Pine Island Glacier ice shelf, West Antarctica, by ocean waters. Satellite imagery shows surface features that suggest ice-shelf-wide changes to the ocean s influence on the ice shelf as the grounding line retreated. Longitudinal profiles of ice surface and bottom elevations are analyzed to reveal a spatially dependent pattern of basal melt with an annual melt flux of 40.5 Gt/a. One profile captures a persistent set of surface waves that correlates with quasi-annual variations of atmospheric forcing of Amundsen Sea circulation patterns, establishing a direct connection between atmospheric variability and sub-ice-shelf melting. Ice surface troughs are hydrostatically compensated by ice-bottom voids up to 150m deep. Voids form dynamically at the grounding line, triggered by enhanced melting when warmer-than-average water arrives. Subsequent enlargement of the voids is thermally inefficient (4% or less) compared with an overall melting efficiency beneath the ice shelf of 22%. Residual warm water is believed to cause three persistent polynyas at the ice-shelf front seen in Landsat imagery. Landsat thermal imagery confirms the occurrence of warm water at the same locations.
Geomicrobiology of a Supraglacial Stream on the Cotton Glacier, Victoria Land, Antarctica.
NASA Astrophysics Data System (ADS)
Foreman, C. M.; Morris, C. E.; Cory, R. M.
2006-12-01
The Cotton Glacier lies in the Transantarctic Mountains north of Cape Roberts and has a limited catchment area in the Clare and St. Johns ranges, but receives a large amount of sedimentary deposits from surrounding areas. The bedrock geology of the area is dominated by basement granite and Ferrar dolerite sills, with minor amounts of amphibolite and schist sandwiched between granite bodies. A unique fluvial system forms on the Cotton Glacier as a result of its location in the Transantarctic Mountains. The prevailing winds converge and deposit debris on the Cotton Glacier, warming up the surface and increasing meltwater production. During the austral summer of 2004-2005 we sampled a braided stream that flowed from mid glacier into a series of crevasses downstream. While low in dissolved organic carbon (44-47 μM C) and nutrients the supraglacial stream on the Cotton Glacier is capable of sustaining life, with bacterial cell abundances from 2.7 - 8.2 x 104 cells ml-1, and bacterial production ranging from 58.84 - 293.18 ng C d-1. Isolates recovered from the Cotton Glacier produced a rainbow of pigment colors and were similar to those recovered from other icy systems (Cytophaga- Flavobateria-Bacteroides and β-Proteobacteria lineages), suggesting that the occurrence of these related phylotoyes from diverse environs is due to similar survival strategies allowing them to remain active at sub- zero temperatures and survive multiple freeze-thaw events. Two isolates from the Cotton Glacier have been shown to possess ice nucleating activity. These bacteria can catalyze ice formation at -3.5°C and colder temperatures and likely possess Type I ice nuclei proteins. The fluorescence and absorbance spectra of the filtered Cotton Glacier water were analyzed to characterize the dissolved organic matter (DOM). The absorbance spectra of the Cotton Glacier sample exhibited a peak around 270 nm, which disappeared over time in the dark at 4°C. Analysis of excitation-emission matrices
2017-12-08
NASA image acquired September 6, 2010 The Matusevich Glacier flows toward the coast of East Antarctica, pushing through a channel between the Lazarev Mountains and the northwestern tip of the Wilson Hills. Constrained by surrounding rocks, the river of ice holds together. But stresses resulting from the glacier’s movement make deep crevasses, or cracks, in the ice. After passing through the channel, the glacier has room to spread out as it floats on the ocean. The expanded area and the jostling of ocean waves prompts the ice to break apart, which it often does along existing crevasses. On September 6, 2010, the Advanced Land Imager (ALI) on NASA’s Earth Observing-1 (EO-1) satellite captured this natural-color image of the margin of Matusevich Glacier. Shown here just past the rock-lined channel, the glacier is calving large icebergs. Low-angled sunlight illuminates north-facing surfaces and casts long shadows to the south. Fast ice anchored to the shore surrounds both the glacier tongue and the icebergs it has calved. Compared to the glacier and icebergs, the fast ice is thinner with a smoother surface. Out to sea (image left), the sea ice is even thinner and moves with winds and currents. Matusevich Glacier does not drain a significant amount of ice off of the Antarctic continent, so the glacier’s advances and retreats lack global significance. Like other Antarctic glaciers, however, Matusevich helps glaciologists form a larger picture of Antarctica’s glacial health and ice sheet volume. NASA Earth Observatory image created by Jesse Allen and Robert Simmon, using EO-1 ALI data provided courtesy of the NASA EO-1 team. Caption by Michon Scott based on image interpretation by Robert Bindschadler, NASA Goddard Space Flight Center, and Walt Meier, National Snow and Ice Data Center. Instrument: EO-1 - ALI Credit: NASA Earth Observatory NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar
Antarctica: Is It More Than Just Ice?
ERIC Educational Resources Information Center
Johnson, Cheryl; Gutierrez, Melida
2009-01-01
The authors introduced polar science in a fourth-grade classroom by means of 3 hands-on activities that addressed (1) the melting of glaciers and ice, (2) the differences between the North and the South Pole, and (3) the geography and landforms of Antarctica. An assessment 4 months after the original activity showed that students remembered the…
Birth of a Large Iceberg in Pine Island Bay, Antarctica
NASA Technical Reports Server (NTRS)
2001-01-01
A large tabular iceberg (42 kilometers x 17 kilometers) broke off Pine Island Glacier, West Antarctica (75oS latitude, 102oW longitude) sometime between November 4 and 12, 2001. Images of the glacier were acquired by the Multi-angle Imaging SpectroRadiometer (MISR) instrument aboard NASA's Terra spacecraft. This event was preceded by the formation of a large crack across the glacier in mid 2000. Data gathered by other imaging instruments revealed the crack to be propagating through the shelf ice at a rate averaging 15 meters per day, accompanied by a slight rotation of about one percent per year at the seaward margin of the rift.The image set shows three views of Pine Island Glacier acquired by MISR's vertical-viewing (nadir) camera. The first was captured in late 2000, early in the development of the crack. The second and third views were acquired in November 2001, just before and just after the new iceberg broke off. The existence of the crack took the glaciological community by surprise, and the rapid rate at which the crack propagated was also not anticipated. Glaciologists predicted that the rift would reach the other side of the glacier sometime in 2002. However, the iceberg detached much sooner than anticipated, and the last 10-kilometer segment that was still attached to the ice shelf snapped off in a matter of days.The animated sequence consists of 11 snapshots acquired by MISR's nadir camera between September 16, 2000 and November 12, 2001. Due to frequent cloud cover, the time interval between successive frames is not uniform. The flow of the glacier, widening of the rift, and subsequent break-off of the iceberg are evident. A 'jump' in the position of the rift near the middle of the sequence is due to a gap in image acquisition during Antarctic winter, when the glacier was in continuous darkness. Pine Island Glacier is the largest discharger of ice in Antarctica and the continent's fastest moving glacier. This area of the WestPoreda, R.J.; Hunt, A.G.; Berry, Lyons W.; Welch, K.A.
2004-01-01
To better understand the long-term climate history of Antarctica, we studied Lake Bonney in Taylor Valley, Southern Victoria Land (78?? S). Helium isotope ratios and He, Ne, Ar and N2 concentration data, obtained from hydrocasts in the East (ELB) and West (WLB) Lobesof Lake Bonney, provided important constraints on the lake's Holocene evolution. Based on very low concentrations of Ar and N2 in the ELB bottom waters, ELB was free of ice until 200 ?? 50 years ago. After which, low salinity water flowing over the sill from WLB to ELB, covered ELB and formed a perennial ice cover, inhibiting the exchange of gases with the atmosphere. In contrast to the ELB, the WLB retained an ice cover through the Holocene. The brine in the WLB bottom waters has meteoric N2 and Ar gas concentrations indicating that it has not been significantly modified by atmospheric exchange or ice formation. The helium concentrations in the deep water of WLB are the highest measured in non-thermal surface water. By fitting a diffusional loss to the 3He/4He, helium, and Cl profiles, we calculate a time of ???3000 years for the initiation of flow over the sill separating the East and West Lobes. To supply this flux of helium to the lake, a helium-rich sediment beneath the lake must be providing the helium by diffusion. If at any time during the last million years the ice cover left WLB, there would be insufficient helium available to provide the current flux to WLB. The variations in water levels in Lake Bonney can be related to climatic events that have been documented within the Southern Victoria Land region and indicate that the lakes respond significantly to regional and, perhaps, global climate forcing. ?? 2004 Kluwer Academic Publishers.
NASA Astrophysics Data System (ADS)
Aoyama, Yuichi; Kim, Tae-Hee; Doi, Koichiro; Hayakawa, Hideaki; Higashi, Toshihiro; Ohsono, Shingo; Shibuya, Kazuo
2016-06-01
A dual-frequency GPS receiver was deployed on a floating iceberg downstream of the calving front of Shirase Glacier, East Antarctica, on 28 December 2011 for utilizing as floating buoy. The three-dimensional position of the buoy was obtained by GPS every 30 s with a 4-5-cm precision for ca. 25 days. The height uncertainty of the 1-h averaged vertical position was ∼0.5 cm, even considering the uncertainties of un-modeled ocean loading effects. The daily evolution of north-south (NS), east-west (EW), and up-down (UD) motions shows periodic UD variations sometimes attaining an amplitude of 1 m. Observed amplitudes of tidal harmonics of major constituents were 88%-93% (O1) and 85%-88% (M2) of values observed in the global ocean tide models FES2004 and TPXO-8 Atlas. The basal melting rate of the iceberg is estimated to be ∼0.6 m/day, based on a firn densification model and using a quasi-linear sinking rate of the iceberg surface. The 30-s sampling frequency geodetic-mode GPS buoy helps to reveal ice-ocean dynamics around the calving front of Antarctic glaciers.
NASA Astrophysics Data System (ADS)
Chen, C.; Box, J. E.; Hock, R. M.; Cogley, J. G.
2011-12-01
Current estimates of global Mountain Glacier and Ice Caps (MG&IC) mass changes are subject to large uncertainties due to incomplete inventories and uncertainties in land surface classification. This presentation features mitigative efforts through the creation of a MODIS dependent land ice classification system and its application for glacier inventory. Estimates of total area of mountain glaciers [IPCC, 2007] and ice caps (including those in Greenland and Antarctica) vary 15%, that is, 680 - 785 10e3 sq. km. To date only an estimated 40% of glaciers (by area) is inventoried in the World Glacier Inventory (WGI) and made available through the World Glacier Monitoring System (WGMS) and the National Snow and Ice Data Center [NSIDC, 1999]. Cogley [2009] recently compiled a more complete version of WGI, called WGI-XF, containing records for just over 131,000 glaciers, covering approximately half of the estimated global MG&IC area. The glaciers isolated from the conterminous Antarctic and Greenland ice sheets remain incompletely inventoried in WGI-XF but have been estimated to contribute 35% to the MG&IC sea-level equivalent during 1961-2004 [Hock et al., 2009]. Together with Arctic Canada and Alaska these regions alone make up almost 90% of the area that is missing in the global WGI-XF inventory. Global mass balance projections tend to exclude ice masses in Greenland and Antarctica due to the paucity of data with respect to basic inventory base data such as area, number of glaciers or size distributions. We address the need for an accurate Greenland and Antarctic peninsula land surface classification with a novel glacier surface classification and inventory based on NASA Moderate Resolution Imaging Spectroradiometer (MODIS) data gridded at 250 m pixel resolution. The presentation includes a sensitivity analysis for surface mass balance as it depends on the land surface classification. Works Cited +Cogley, J. G. (2009), A more complete version of the World Glacier
Glacier extent in sub-Antarctic Kerguelen archipelago from MIS 3 period: Evidence from 36Cl dating
NASA Astrophysics Data System (ADS)
Jomelli, Vincent; Schimmelpfennig, Irene; Favier, Vincent; Mokadem, Fatima; Landais, Amaelle; Rinterknecht, Vincent; Brunstein, Daniel; Verfaillie, Deborah; Legentil, Claude; Aumaitre, Georges; Bourlès, Didier L.; Keddadouche, Karim
2018-03-01
Documenting sub-Antarctic glacier variations during the local last glacial maximum is of major interest to better understand their sensitivity to atmospheric and oceanic temperature changes in conjunction with Antarctic ice sheet changes. However, data are sparse because evidence of earlier glacier extents is for most sub-Antarctic islands located offshore making their observation complex. Here, we present 22 cosmogenic 36Cl surface exposure ages obtained from five sites at Kerguelen to document the glacial history. The 36Cl ages from roche moutonnee surfaces, erratics and boulders collected on moraines span from 41.9 ± 4.4 ka to 14.3 ± 1.1 ka. Ice began to retreat on the eastern part of the main island before 41.4 ± 4.4 ka. Slow deglaciation occurred from ∼41 to ∼29 ka. There is no evidence of advances between 29 ka and the Antarctic Cold Reversal (ACR) period (∼14.5-12.9 ka) period. During the ACR, however, the Bontemps and possibly Belvedere moraines were formed by the advance of a Cook Ice Cap outlet glacier and a local glacier on the Presque Ile Jeanne d'Arc, respectively. This glacier evolution differs partly from that of glaciers in New Zealand and in Patagonia. These asynchronous glacier changes in the sub-Antarctic region are however in agreement with sea surface temperature changes recorded around Antarctica, which suggest differences in the climate evolution of the Indo-Pacific and Atlantic sectors of Antarctica.
Asia High Mountain Glacier Mass Balance
NASA Astrophysics Data System (ADS)
Shum, C. K.; Su, X.; Shang, K.; Cogley, J. G.; Zhang, G.; Howat, I. M.; Braun, A.; Kuo, C. Y.
2015-12-01
The Asian High Mountain encompassing the Qinghai-Tibetan Plateau has the largest glaciated regions in the world outside of Greenland and Antarctica. The Tibetan Plateau is the source or headwater of many major river systems, which provide water resources to more than a billion people downstream. The impact of climate change on the Tibetan Plateau physical processes, including mountain glacier wastage, permafrost active layer thickening, the timing and the quantity of the perennial snowpack melt affecting upstream catchments, river runoffs, land-use, have significant effects on downstream water resources. Exact quantification of the Asian High Mountain glacier wastage or its mass balance on how much of the melt water contributes to early 21st century global sea-level rise, remain illusive or the published results are arguably controversial. The recent observed significant increase of freshwater storage within the Tibetan Plateaus remains a limitation to exactly quantify mountain glacier wastage. Here, we provide an updated estimate of Asia high mountain glacier mass balance using satellite geodetic observations during the last decade, accounting for the hydrologic and other processes, and validated against available in situ mass balance data.
NASA Astrophysics Data System (ADS)
Smiraglia, C.; Motta, M.; Vassena, G.; Diolaiuti, G.
2003-04-01
In Antartic coastal area, where the ice sheet and the large outlet glaciers do not reach the sea and where some rugged mountain chains are often present, many small glaciers can be found. They are the so called local or alpine type glaciers, which have their terminus ground-based such as the real alpine glaciers and rarely reach the main valley floors. They are practically isolated and independent from the supply flowing down from the plateau and their mass balance is mainly controlled by sublimation and aeolic erosion and accumulation. The glaciers closer to the coast are submitted to the melting as well, and when the terminus is cliff-shaped they are also affected by dry calving. The most known and studied Antarctic local glaciers are placed in the Dry Valleys region (Chinn, 1985), but this kind of glaciers is also diffused all along the Northern Victoria Land coastal region (Chinn and others, 1989). Since the first Italian Antarctic expedition (1985), many studies have been carried out on this type of glaciers, which can be usefull for detailed mass balance evaluations and for obtaining information about the effects of the present climatic dynamics on the Antarctic coastal environment (Baroni and Orombelli, 1987; Baroni and others, 1995; Meneghel, 1999; Vassena and others., 2001). The Strandline Glacier (74 41 S; 164 07 E), in particular is a small alpine glacier (0,79 kmq) on the coast of Terra Nova Bay, Northern Victoria Land; it is a cold glacier where accumulation and ablation basins are mainly controlled by wind processes. Its terminus forms in the central part a grounded ice cliff about 30 m high, about 130 m far from the sea. On that glacier mass balance, surface velocity and calving rate were measured. During the southern summer season 2000-2001 many topographycal profiles of the ice cliff were surveyed by using both classical topographical and glaciological methods (total station and stakes) and GPS technique. It was so possible to detect the short term
NASA Astrophysics Data System (ADS)
Walker, C. C.; Gardner, A. S.; Nilsson, J.
2017-12-01
The East Antarctic has started to show signs of measureable change, albeit slow. Of particular note is the Totten Glacier that drains the Aurora Subglacial Basin (ASB), one of two vast basins in East Antarctica with the potential to significantly alter sea levels. Totten experienced flow acceleration between 2001-2007 linked to warm waters reaching its subglacial cavity (Rintoul et al., 2016). Directly to the west of Totten are the Vincennes Bay (VB) glaciers. They also drain the ASB, and are grounded considerably below sea level. They have not been identified as changing - until now. Recent mapping of Antarctic-wide velocity via Landsat image pairs (Gardner et al., 2017) confirmed earlier findings (Li et al. 2016) that Totten's 2001-2007 velocity increase has since stabilized. At the same time, we have detected evidence of increased flow acceleration in VB, between 2008-2015. Here, we characterize these recent changes in the VB glacier system to determine (1) the mechanisms driving change; (2) if the changes signify long- or short-term response; (3) if the temporal offset in response between Totten ( 2001-2007) and VB glaciers ( 2008-2015) is representative of a scavenging relationship between the Law Dome neighbors. We use several datasets in addition to Landsat-derived velocities. We use space-borne altimetry measurements from the ICESat (2003-2009) and CryoSat-2 (2011-present) missions, and airborne laser altimetry (Operation IceBridge) where available, to show that after separating the dynamic signal from the detected elevation signal, sections of VB glaciers lowered by 0.25 m/yr between satellite epochs. Seemingly small, this means they have approximately doubled their rate of lowering since 2009. We use ice penetrating radar (HICARS) measurements (2009-2012) to determine changes in subsurface ice structure, layering, and bed topography. We identify possible links to changes in ocean conditions using shipboard CTD measurements and those collected via
NASA Astrophysics Data System (ADS)
Watson, C. S.; Burgette, R. J.; Tregoning, P.; Coleman, R.; Roberts, J.; Lieser, J. L.; Fricker, H. A.; Legresy, B.
2010-12-01
The Australian TOT-Cal project seeks to provide a contribution to the calibration and validation of the CryoSat-II mission over two adjacent important regions in East Antarctica. The first focuses on the Totten glacier, arguably one of the most important outlet glaciers in the East Antarctic, known to be undergoing significant surface lowering. The second includes the coastal slope regions behind Casey station and up on the plateau areas near Law Dome where significant spatial variation in annual accumulation is known to occur. The 2010/11 austral summer is the first field season for this project, with fieldwork to be underway at the time of the AGU FM10. In this poster, we present our current field activities and forward plans for the 2011/12 season. Our field campaign includes three components. A total of six in-situ GPS sites will be deployed over the summer period throughout the Law Dome / Totten Glacier region. These sites will facilitate the computation of the integrated water vapour content of the atmosphere, enabling an assessment against the ECMWF product used in the CyroSat-II data stream. The GPS sites also serve to provide reference stations for the AWI Polar-5 aircraft that will fly over the study area equipped with a scanning LiDAR and the ESA ASIRAS instrument. Finally, a series of kinematic GPS transects, corner cube reflector placements and surface density measurements will be undertaken from our field camp on the western flank of Law Dome to provide high resolution ground measurements for cal/val activities. In a separate project, Antarctic sea ice freeboard measurements will also contribute to the calibration and validation efforts by the Australian Antarctic program. In November 2010, the first set of such measurements will be carried out in the East Antarctic sea ice zone between 77 and 90 degrees East. The primary measurement tools for this campaign will include helicopter mounted scanning LiDAR and aerial photography, combined with in
Glacier calving, dynamics, and sea-level rise. Final report
DOE Office of Scientific and Technical Information (OSTI.GOV)
Meier, M.F.; Pfeffer, W.T.; Amadei, B.
1998-08-01
The present-day calving flux from Greenland and Antarctica is poorly known, and this accounts for a significant portion of the uncertainty in the current mass balance of these ice sheets. Similarly, the lack of knowledge about the role of calving in glacier dynamics constitutes a major uncertainty in predicting the response of glaciers and ice sheets to changes in climate and thus sea level. Another fundamental problem has to do with incomplete knowledge of glacier areas and volumes, needed for analyses of sea-level change due to changing climate. The authors proposed to develop an improved ability to predict the futuremore » contributions of glaciers to sea level by combining work from four research areas: remote sensing observations of calving activity and iceberg flux, numerical modeling of glacier dynamics, theoretical analysis of the calving process, and numerical techniques for modeling flow with large deformations and fracture. These four areas have never been combined into a single research effort on this subject; in particular, calving dynamics have never before been included explicitly in a model of glacier dynamics. A crucial issue that they proposed to address was the general question of how calving dynamics and glacier flow dynamics interact.« less
A varied subglacial landscape under Thwaites Glacier, West Antarctica
NASA Astrophysics Data System (ADS)
Christianson, K. A.; Holschuh, N.; Paden, J. D.; Sprick, J.; Peters, L. E.; Anandakrishnan, S.; Alley, R. B.
2017-12-01
Deglaciated landscapes, whether subaerial or submarine, are often host to a rich panoply of subglacial landforms, such as drumlims, crags, megascale glacial lineations, grounding-line wedges, deep meltwater channels, and more. These landforms are formed and shaped by interactions between the ice and underlying substrate, and thus have implications for the flow of the overlying ice. Robust interpretations of the relationship between the ice and its substrate based on subglacial landforms that remain after deglaciation have been inhibited by a dearth of high-resolution observations of currently glaciated subglacial landscapes, where ice flow speed is known and where subglacial conditions can be ascertained using geophysical methods. Past direct observations of landforms under currently fast-flowing ice have been limited to a few ice streams, where relatively homogeneous, thick dilatant till layers may favor formation of specific subglacial features, i.e., megascale glacial lineations and grounding-zone wedges. Here we present two detailed gridded subglacial topographies, obtained from ice-penetrating radar measurements, from Thwaites Glacier, West Antarctica, where ice flows over a highly variable bed (in both topography and model-inferred basal shear stress). One grid is located ˜170 km downstream from the ice divide where ice is moving ˜100 m/yr. Here the ice advects over a broad basin and then flows into a subglacial ridge (of several hundred meters amplitude) oriented orthogonally to flow. A deep canyon ( 400 m) that cuts through this ridge in roughly the ice-flow direction and relatively soft sediments on the downstream side of the basin (immediately upstream of the canyon) suggest that a large subglacial lake may have formed in this location and drained catastrophically, as has been hypothesized as the formation mechanism for the deep canyons observed on the Amundsen Sea continental shelf. Numerous multiscale glacial lineations are also observed in the
Debris-Covered Glaciers in Antarctica: Analogs for Viscous-Flow Features on Mars
NASA Astrophysics Data System (ADS)
Marchant, D. R.; Phillips, W. M.; Schaefer, J.; Fastook, J.; Landis, G.
2007-12-01
The McMurdo Dry Valleys (MDV) are generally classified as a hyper-arid, cold-polar desert. Subtle variations in climate parameters throughout the region result in considerable differences in the distribution, origin, and morphology of buried ice. In the coastal thaw zone, near-surface buried ice experiences seasonal melt and may have formed where pore water from surface snowmelt freezes underground (segregation ice). Characteristic landforms associated with this type of buried ice include thermokarst, shallow planar slides, and solifluction. In contrast, in the coldest and driest regions of the MDV, the stable upland zone, there is insufficient meltwater to produce extensive segregation ice. Rather, widespread buried ice in this zone is typically glacier ice. Temperature data indicate that ice remains frozen in this zone if buried beneath ~15 cm of debris. The Mullins-valley debris-covered glacier, which lies within the stable upland zone, contains ancient glacier ice beneath a thin layer of sublimation till. Four independent dating techniques confirm that the glacier age ranges from ~10 ka near the valley head, to >8 Ma at its diffuse terminus in central Beacon Valley. The dating methods include cosmogenic-nuclide analyses of surface boulders; horizontal ice-flow velocities as determined from synthetic aperture radar interferometry; 40Ar/39Ar analyses of in-situ ash fall in relict polygon troughs at the till surface; and numerical ice-flow models. Age results so derived are in accord with measured variations in ancient community DNA extracted from pristine ice samples along the length of the glacier. Multi- channel seismic and ground-penetrating radar surveys demonstrate that the ice is relatively clean and that it averages from ~45 m to ~150 m thick. Morphologic comparisons of the Mullins Valley debris-covered glacier are used to shed light on the origin and modification of near-surface ice on Mars.
NASA Astrophysics Data System (ADS)
An, L.; Rignot, E.; Rivera, A.; Bunetta, M.
2012-12-01
The North and South Patagonia Ice fields are the largest ice masses outside Antarctica in the Southern Hemisphere. During the period 1995-2000, these glaciers lost ice at a rate equivalent to a sea level rise of 0.105 ± 0.001 mm/yr. In more recent years, the glaciers have been thinning more quickly than can be explained by warmer air temperatures and decreased precipitation. A possible cause is an increase in flow speed due to enhanced ablation of the submerged glacier fronts. To understand the dynamics of these glaciers and how they change with time, it is critical to have a detailed view of their ice thickness, the depth of the glacier bed below sea or lake level, how far inland these glaciers remain below sea or lake level, and whether bumps or hollows in the bed may slow down or accelerate their retreat. A grid of free-air gravity data over the Patagonia Glaciers was collected in May 2012 and October 2012, funded by the Gordon and Betty Moore Foundation (GBMF) to measure ice thickness and sea floor bathymetry. This survey combines the Sander Geophysics Limited (SGL) AIRGrav system, SGL laser altimetry and Chilean CECS/UCI ANDREA-2 radar. To obtain high-resolution and high-precision gravity data, the helicopter operates at 50 knots (25.7 m/s) with a grid spacing of 400m and collects gravity data at sub mGal level (1 Gal =1 Galileo = 1 cm/s2) near glacier fronts. We use data from the May 2012 survey to derive preliminarily high-resolution, high-precision thickness estimates and bathymetry maps of Jorge Montt Glacier and San Rafael Glacier. Boat bathymetry data is used to optimize the inversion of gravity over water and radar-derived thickness over glacier ice. The bathymetry maps will provide a breakthrough in our knowledge of the ice fields and enable a new era of glacier modeling and understanding that is not possible at present because ice thickness is not known.
Glacier Acceleration and Thinning after Ice Shelf Collapse in the Larsen B Embayment, Antarctica
NASA Technical Reports Server (NTRS)
Scambos, T. A.; Bohlander, J. A.; Shuman, C. A.; Skvarca, P.
2004-01-01
Ice velocities derived from five Landsat 7 images acquired between January 2000 and February 2003 show a two- to six-fold increase in centerline speed of four glaciers flowing into the now-collapsed section of the Larsen B Ice Shelf. Satellite laser altimetry from ICEsat indicates the surface of Hektoria Glacier lowered by up to 38 +/- 6 m a six-month period beginning one year after the break-up in March 2002. Smaller elevation losses are observed for Crane and Jorum glaciers over a later 5-month period. Two glaciers south of the collapse area, Flask and Leppard, show little change in speed or elevation. Seasonal variations in speed preceding the large post-collapse velocity increases suggest that both summer melt percolation and changes in the stress field due to shelf removal play a major role in glacier dynamics.
Basal Settings Control Fast Ice Flow in the Recovery/Slessor/Bailey Region, East Antarctica
NASA Astrophysics Data System (ADS)
Diez, Anja; Matsuoka, Kenichi; Ferraccioli, Fausto; Jordan, Tom A.; Corr, Hugh F.; Kohler, Jack; Olesen, Arne V.; Forsberg, René
2018-03-01
The region of Recovery Glacier, Slessor Glacier, and Bailey Ice Stream, East Antarctica, has remained poorly explored, despite representing the largest potential contributor to future global sea level rise on a centennial to millennial time scale. Here we use new airborne radar data to improve knowledge about the bed topography and investigate controls of fast ice flow. Recovery Glacier is underlain by an 800 km long trough. Its fast flow is controlled by subglacial water in its upstream and topography in its downstream region. Fast flow of Slessor Glacier is controlled by the presence of subglacial water on a rough crystalline bed. Past ice flow of adjacent Recovery and Slessor Glaciers was likely connected via the newly discovered Recovery-Slessor Gate. Changes in direction and speed of past fast flow likely occurred for upstream parts of Recovery Glacier and between Slessor Glacier and Bailey Ice Stream. Similar changes could also reoccur here in the future.
Deep groundwater and potential subsurface habitats beneath an Antarctic dry valley
Mikucki, J. A.; Auken, E.; Tulaczyk, S.; Virginia, R. A.; Schamper, C.; Sørensen, K. I.; Doran, P. T.; Dugan, H.; Foley, N.
2015-01-01
The occurrence of groundwater in Antarctica, particularly in the ice-free regions and along the coastal margins is poorly understood. Here we use an airborne transient electromagnetic (AEM) sensor to produce extensive imagery of resistivity beneath Taylor Valley. Regional-scale zones of low subsurface resistivity were detected that are inconsistent with the high resistivity of glacier ice or dry permafrost in this region. We interpret these results as an indication that liquid, with sufficiently high solute content, exists at temperatures well below freezing and considered within the range suitable for microbial life. These inferred brines are widespread within permafrost and extend below glaciers and lakes. One system emanates from below Taylor Glacier into Lake Bonney and a second system connects the ocean with the eastern 18 km of the valley. A connection between these two basins was not detected to the depth limitation of the AEM survey (∼350 m). PMID:25919365
NASA Astrophysics Data System (ADS)
Park, I. W.; Lee, S. H.; Lee, W. S.; Lee, C. K.; Lee, K. K.
2017-12-01
As global mean temperature increases, it affects increase in polar glacier melt and thermal expansion of sea, which contributed to global sea level rise. Unlike large sea level rise contributors in Western Antarctica (e. g. Pine island glacier, Thwaites glacier), glaciers in East Antarctica shows relatively stable and slow ice velocity. However, recent calving events related to increase of supraglacier lake in Nansen ice shelf arouse the questions in regards to future evolution of ice dynamics at Victoria Land, East Antarctica. Here, using Ice Sheet System Model (ISSM), a series of numerical simulations were carried out to investigate ice dynamics evolution (grounding line migration, ice velocity) and sea level rise contribution in response to external forcing conditions (surface mass balance, floating ice melting rate, and ice front retreat). In this study, we used control method to set ice dynamic properties (ice rigidity and friction coefficient) with shallow shelf approximation model and check each external forcing conditions contributing to sea level change. Before 50-year transient simulations were conducted based on changing surface mass balance, floating ice melting rate, and ice front retreat of Drygalski ice tongue and Nansen ice shelf, relaxation was performed for 10 years to reduce non-physical undulation and it was used as initial condition. The simulation results showed that sea level rise contribution were expected to be much less compared to other fast glaciers. Floating ice melting rate was most sensitive parameter to sea level rise, while ice front retreat of Drygalski tongue was negligible. The regional model will be further updated utilizing ice radar topography and measured floating ice melting rate.
NASA Astrophysics Data System (ADS)
Fink, David
2015-04-01
Ice volume changes at the coastal margins of Antarctica during the global LGM are uncertain. The little evidence available suggests that behaviour of the East and West Antarctic Ice Sheets are markedly different and complex. It is hypothesised that during interglacials, thinning of the Ross Ice Shelf, a more open-water environment and increased precipitation, allowed outlet glaciers draining the Transantarctic Mnts and fed by interior Ice Sheets to advance during moist warmer periods, out of phase with colder arid periods. In contrast, glacier dynamics along the vast coastal perimeter of East Antarctica is strongly influenced by Southern Ocean conditions. Cosmogenic 10Be and 26Al chronologies, although restricted to ice-free oasis and mountains flanking drainage glaciers, has become an invaluable, if not unique, tool to quantify spatial and temporal Pleistocene ice sheet variability over the past 2 Ma. Despite an increasing number of well documented areas, extracting reliable ages from glacial deposits in polar regions is problematic. Recycling of previously exposed/ buried debris and continual post-depositional modification leads to age ambiguities for a coeval glacial landform. More importantly, passage of cold-based ice can leave a landform unmodified resulting in young erratics deposited on ancient bedrock. Advances in delivering in-situ radiocarbon to routine application offer some relief. Exposure ages from different localities throughout East Antarctica (Framnes Mnts, Lutzow-Holm Bay, Vestfold Hills) and West Antarctica (Denton Ranges, Hatherton Glacier, Shackleton Range) highlight some of the new findings. This talk presents results which quantify the magnitude and timing of paleo-ice sheet thickness changes, questions the validity of an Antarctic LGM and discusses the complexities encountered in the often excessive spread in exposure ages.
Measurements of Refractory Black Carbon (rBC) Aerosols in the McMurdo Dry Valleys, Antarctica
NASA Astrophysics Data System (ADS)
Khan, A. L.; McMeeking, G. R.; Lyons, W. B.; Schwarz, J. P.; Welch, K. A.; McKnight, D. M.
2015-12-01
Measurements of light absorbing particles in the boundary layer of the high southern latitudes are scarce. During the 2013-2014 austral summer field season refractory black carbon (rBC) aerosols were quantified by a single particle soot photometer (SP2) in the McMurdo Dry Valleys, Antarctica. The dark rBC particles absorb more radiation thereby increasing atmospheric heating, as well as reducing surface albedo and enhancing hydrologic melt when deposited on highly reflective surfaces such as snow and ice. Quantifying both local and long-range atmospheric transport of rBC to this region of a remote continent mostly covered by ice and snow would be useful in understanding meltwater generation as climate changes. Although the Dry Valleys are the largest ice-free region of Antarctica, they contain many alpine glaciers, some of which are fed from the East Antarctic Ice Sheet (EAIS). Continuous rBC measurements were collected at Lake Hoare Camp in the Taylor Valley for two months, along with shorter periods at more remote locations within the Dry Valleys. Conditions at the Lake Hoare Camp were dominated by up-valley winds from McMurdo Sound, however, winds also brought air down-valley from the EAIS polar plateau. Here we investigated periods dominated by both up and down-valley winds to explore differences in rBC concentrations, size distributions, and scattering properties. The average background rBC mass concentration was 1ng/m3, though concentrations as high as 50 ng/m3 were observed at times, likely due to local sources.
Ice thickness measurements over Pine Island and Thwaites Glaciers
NASA Astrophysics Data System (ADS)
Kanagaratnam, P.; Casassa, G.; Thomas, R.; Gogineni, S.
2003-04-01
The Pine Island and Thwaites glaciers (PIG and TG) are the fastest measured glaciers in Antarctica and have been identified as the part of the West Antarctica ice sheet most prone to instability. However, the reasons for the rapid retreat of these glaciers have not been resolved due to insufficient data. In particular, the role of ice shelves in regulating the ice discharge of these glaciers has been a point of contention in the glaciology community. To help resolve this issue the Centro de Estudios Científicos (CECS) and NASA with the support of the Armada de Chile conducted four airborne remote sensing missions over the PIG/TG regions. In addition, two missions were conducted over the Antarctic Peninsula. The University of Kansas operated its Coherent Radar Depth Sounder (CORDS) to measure the thickness of the ice sheet in these regions. CORDS is a pulse-compression radar that has proven its utility in the glaciological surveys over Greenland. The combination of pulse compression and coherent processing has allowed us to obtain high-sensitivity and high-resolution in the along-track direction while keeping the transmitted power low. CORDS transmits a 140-160 MHz chirp signal with 200 Watts of peak power and has a vertical resolution of about 5 meters in ice. We used a four-element dipole array on either side of the wing to transmit and receive the radar signals. We successfully mapped the thickness of the ice sheet over 99% of the PIG/TG flight lines. In this paper we will provide a description of the radar, experiment and signal processing. We will also discuss samples results of the ice thickness, basal conditions and surface roughness.
NASA Astrophysics Data System (ADS)
Jones, R. S.; Whitmore, R.; Mackintosh, A.; Norton, K. P.; Eaves, S.; Stutz, J.
2017-12-01
Investigating Antarctic deglaciation following the LGM provides an opportunity to better understand patterns, mechanisms and drivers of ice sheet retreat. In the Ross Sea sector, geomorphic features preserved on the seafloor indicate that streaming East Antarctic outlet glaciers once extended >100 km offshore of South Victoria Land prior to back-stepping towards their modern configurations. In order to adequately interpret the style and causes of this retreat, the timing and magnitude of corresponding ice thickness change is required. We present new constraints on ice surface lowering from Mawson Glacier, an outlet of the East Antarctic Ice Sheet that flows into the western Ross Sea. Surface-exposure (10Be) ages from samples collected in elevation transects above the modern ice surface reveal that rapid thinning occurred at 5-8 ka, broadly coeval with new ages of grounding-line retreat at 6 ka and rapid thinning recorded at nearby Mackay Glacier at 7 ka. Our data also show that a moraine formed near to the modern ice margin of Mawson Glacier at 0.8 ka, which, together with historical observations, indicates that glaciers in this region readvanced during the last thousand years. We argue that 1) the accelerated thinning of outlet glaciers was driven by local grounding-line retreat through overdeepened basins during the early-mid Holocene, and 2) the glaciers subsequently readvanced, possibly linked to late Holocene sea-ice expansion, before retreating to their current positions. Our work demonstrates that these outlet glaciers were closely coupled to environmental and topography-induced perturbations near their termini throughout the Holocene.
Unusually loud ambient noise in tidewater glacier fjords: a signal of ice melt
Pettit, Erin C.; Lee, Kevin M.; Brann, Joel P.; Nystuen, Jeffrey A.; Wilson, Preston S.; O'Neel, Shad
2015-01-01
In glacierized fjords, the ice-ocean boundary is a physically and biologically dynamic environment that is sensitive to both glacier flow and ocean circulation. Ocean ambient noise offers insight into processes and change at the ice-ocean boundary. Here we characterize fjord ambient noise and show that the average noise levels are louder than nearly all measured natural oceanic environments (significantly louder than sea ice and non-glacierized fjords). Icy Bay, Alaska has an annual average sound pressure level of 120 dB (re 1 μPa) with a broad peak between 1000 and 3000 Hz. Bubble formation in the water column as glacier ice melts is the noise source, with variability driven by fjord circulation patterns. Measurements from two additional fjords, in Alaska and Antarctica, support that this unusually loud ambient noise in Icy Bay is representative of glacierized fjords. These high noise levels likely alter the behavior of marine mammals.
Inferring Ice Thickness from a Glacier Dynamics Model and Multiple Surface Datasets.
NASA Astrophysics Data System (ADS)
Guan, Y.; Haran, M.; Pollard, D.
2017-12-01
The future behavior of the West Antarctic Ice Sheet (WAIS) may have a major impact on future climate. For instance, ice sheet melt may contribute significantly to global sea level rise. Understanding the current state of WAIS is therefore of great interest. WAIS is drained by fast-flowing glaciers which are major contributors to ice loss. Hence, understanding the stability and dynamics of glaciers is critical for predicting the future of the ice sheet. Glacier dynamics are driven by the interplay between the topography, temperature and basal conditions beneath the ice. A glacier dynamics model describes the interactions between these processes. We develop a hierarchical Bayesian model that integrates multiple ice sheet surface data sets with a glacier dynamics model. Our approach allows us to (1) infer important parameters describing the glacier dynamics, (2) learn about ice sheet thickness, and (3) account for errors in the observations and the model. Because we have relatively dense and accurate ice thickness data from the Thwaites Glacier in West Antarctica, we use these data to validate the proposed approach. The long-term goal of this work is to have a general model that may be used to study multiple glaciers in the Antarctic.
Glacier discharge and climate variations
NASA Astrophysics Data System (ADS)
Dominguez, M. Carmen; Rodriguez-Puebla, Concepcion; Encinas, Ascension H.; Visus, Isabel; Eraso, Adolfo
2010-05-01
Different studies account for the warming in the polar regions that consequently would affect Glacier Discharge (GD). Since changes in GD may cause large changes in sensible and latent heat fluxes, we ask about the relationships between GD and climate anomalies, which have not been quantified yet. In this study we apply different statistical methods such as correlation, Singular Spectral Analysis and Wavelet to compare the behaviour of GD data in two Experimental Pilot Catchments (CPE), one (CPE-KG-62°S) in the Antarctica and the other (CPE-KVIA-64°N) in the Arctic regions. Both CPE's are measuring sub- and endo-glacier drainage for recording of glacier melt water run-off. The CPE-KG-62°S is providing hourly GD time series since January 2002 in Collins glacier of the Maxwell Bay in King George Island (62°S, 58°W). The second one, CPE-KVIA-64°N, is providing hourly GD time series since September 2003 in the Kviarjökull glacier of the Vatnajökull ice cap in Iceland (64°N, 16°W). The soundings for these measurements are pressure sensors installed in the river of the selected catchments for the ice cap (CPE-KG-62°S) and in the river of the glacier for (CPE-KVIA-64°N). In each CPE, the calibration function between level and discharge has been adjusted, getting a very high correlation coefficient (0.99 for the first one and 0.95 for the second one), which let us devise a precise discharge law for the glacier. We obtained relationships between GD with atmospheric variables such as radiation, temperature, relative humidity, atmospheric pressure and precipitation. We also found a negative response of GD to El Niño teleconnection index. The results are of great interest due to the GD impact on the climate system and in particular for sea level rise.
Low latitude ice core evidence for dust deposition on high altitude glaciers
NASA Astrophysics Data System (ADS)
Gabrielli, P.; Thompson, L. G.
2017-12-01
Polar ice cores from Antarctica and Greenland have provided a wealth of information on dust emission, transport and deposition over glacial to interglacial timescales. These ice cores mainly entrap dust transported long distances from source areas such as Asia for Greenland and South America for Antarctica. Thus, these dust records provide paleo-information about the environmental conditions at the source and the strength/pathways of atmospheric circulation at continental scales. Ice cores have also been extracted from high altitude glaciers in the mid- and low-latitudes and provide dust records generally extending back several centuries and in a few cases back to the last glacial period. For these glaciers the potential sources of dust emission include areas that are close or adjacent to the drilling site which facilitates the potential for a strong imprinting of local dust in the records. In addition, only a few high altitude glaciers allow the reconstruction of past snow accumulation and hence the expression of the dust records in terms of fluxes. Due to their extreme elevation, a few of these high altitude ice cores offer dust histories with the potential to record environmental conditions at remote sources. Dust records (in terms of dust concentration/size, crustal trace elements and terrigenous cations) from Africa, the European Alps, South America and the Himalayas are examined over the last millennium. The interplay of the seasonal atmospheric circulation (e.g. westerlies, monsoons and vertical convection) is shown to play a major role in determining the intensity and origin of dust fallout to the high altitude glaciers around the world.
Icequake Tremors During Glacier Calving (Invited)
NASA Astrophysics Data System (ADS)
Walter, F.; O'Neel, S.; Bassis, J. N.; Fricker, H. A.; Pfeffer, W. T.
2009-12-01
ice shelf calving in Antarctica. The similarities and differences in seismic signatures of these different calving settings provide valuable insights and will be helpful in the theoretical treatment of glacier calving.
Hydrological Controls on Ecosystem Dynamics in Lake Fryxell, Antarctica.
Herbei, Radu; Rytel, Alexander L; Lyons, W Berry; McKnight, Diane M; Jaros, Christopher; Gooseff, Michael N; Priscu, John C
2016-01-01
The McMurdo Dry Valleys constitute the largest ice free area of Antarctica. The area is a polar desert with an annual precipitation of ∼ 3 cm water equivalent, but contains several lakes fed by glacial melt water streams that flow from four to twelve weeks of the year. Over the past ∼20 years, data have been collected on the lakes located in Taylor Valley, Antarctica as part of the McMurdo Dry Valley Long-Term Ecological Research program (MCM-LTER). This work aims to understand the impact of climate variations on the biological processes in all the ecosystem types within Taylor Valley, including the lakes. These lakes are stratified, closed-basin systems and are perennially covered with ice. Each lake contains a variety of planktonic and benthic algae that require nutrients for photosynthesis and growth. The work presented here focuses on Lake Fryxell, one of the three main lakes of Taylor Valley; it is fed by thirteen melt-water streams. We use a functional regression approach to link the physical, chemical, and biological processes within the stream-lake system to evaluate the input of water and nutrients on the biological processes in the lakes. The technique has been shown previously to provide important insights into these Antarctic lacustrine systems where data acquisition is not temporally coherent. We use data on primary production (PPR) and chlorophyll-A (CHL)from Lake Fryxell as well as discharge observations from two streams flowing into the lake. Our findings show an association between both PPR, CHL and stream input.
NASA Astrophysics Data System (ADS)
Young, D. A.; Blankenship, D. D.; Greenbaum, J. S.; Richter, T.; Aitken, A.; Siegert, M. J.; Roberts, J. L.
2013-12-01
The ice-rock interface underlying the Antarctic Ice Sheet was shaped by interactions between underlying gondwanan geology and the overlying ice sheet. The ice sheet now preserves from sedimentary infill an incredibly rugged terrain which now plays a critical role in shaping subglacial hydrology, and thus shape ice sheet behavior. This terrain can by imaged through aerogeophysical means, in particular through ice penetrating radar, while airborne potential fields measurements provide insight into the geological framework that controlled erosion. Over the post IPY era, the density of airborne coverage is only now reaching the point where small scale structure can be identified and placed in context. Of particular importance is understanding the formation of focused erosional valleys, 30-50 km wide, representing now buried subglacial fjords. After initial data from the GIMBLE project in West Antarctica, and five years of sustained long range ICECAP surveys over East Antarctica , we now have a better view of the diversity of these features. The local erosion of these valleys, often cutting through significant topographic barriers, irregularly samples the underlying geology, provided a complex story in the sediment to the Antarctic margin. These valleys now provide the subglacial conduits for significant ice sheet catchments, in particular for subglacial water, including the inland catchments of DeVicq, Thwaites, and Pine Island Glaciers in West Antarctica, and Denman Glacier, Totten Glacier, Byrd Glacier and Cook Ice Shelf in East Antarctica. We find that these features, now sometimes hundreds of kilometers inland of the modern grounding line, often nucleate on or are aligned with structure inherited from the assembly of the Antarctic continent. While many of these features currently host active outlet glaciers or their tributaries, some do not, implying avenues for ice sheet change. In West Antarctica, we find a new deep connection between the coast and interior basin
Channelized ice melting in the ocean boundary layer beneath Pine Island Glacier, Antarctica.
Stanton, T P; Shaw, W J; Truffer, M; Corr, H F J; Peters, L E; Riverman, K L; Bindschadler, R; Holland, D M; Anandakrishnan, S
2013-09-13
Ice shelves play a key role in the mass balance of the Antarctic ice sheets by buttressing their seaward-flowing outlet glaciers; however, they are exposed to the underlying ocean and may weaken if ocean thermal forcing increases. An expedition to the ice shelf of the remote Pine Island Glacier, a major outlet of the West Antarctic Ice Sheet that has rapidly thinned and accelerated in recent decades, has been completed. Observations from geophysical surveys and long-term oceanographic instruments deployed down bore holes into the ocean cavity reveal a buoyancy-driven boundary layer within a basal channel that melts the channel apex by 0.06 meter per day, with near-zero melt rates along the flanks of the channel. A complex pattern of such channels is visible throughout the Pine Island Glacier shelf.
Coastal-change and glaciological map of the Ross Island area, Antarctica
Ferrigno, Jane G.; Foley, Kevin M.; Swithinbank, Charles; Williams, Richard S.
2010-01-01
Reduction in the area and volume of Earth?s two polar ice sheets is intricately linked to changes in global climate and to the resulting rise in sea level. Measurement of changes in area and mass balance of the Antarctic ice sheet was given a very high priority in recommendations by the Polar Research Board of the National Research Council. On the basis of these recommendations, the U.S. Geological Survey used its archive of satellite images to document changes in the cryospheric coastline of Antarctica and analyze the glaciological features of the coastal regions. The Ross Island area map is bounded by long 141? E. and 175? E. and by lat 76? S. and 81? S. The map covers the part of southern Victoria Land that includes the northwestern Ross Ice Shelf, the McMurdo Ice Shelf, part of the polar plateau and Transantarctic Mountains, the McMurdo Dry Valleys, northernmost Shackleton Coast, Hillary Coast, the southern part of Scott Coast, and Ross Island. Little noticeable change has occurred in the ice fronts on the map, so the focus is on glaciological features. In the western part of the map area, the polar plateau of East Antarctica, once thought to be a featureless region, has subtle wavelike surface forms (megadunes) and flow traces of glaciers that originate far inland and extend to the coast or into the Ross Ice Shelf. There are numerous outlet glaciers. Glaciers drain into the McMurdo Dry Valleys, through the Transantarctic Mountains into the Ross Sea, or into the Ross Ice Shelf. Byrd Glacier is the largest. West of the Transantarctic Mountains are areas of blue ice, readily identifiable on Landsat images, that have been determined to be prime areas for finding meteorites. Three subglacial lakes have been identified in the map area. Because McMurdo Station, the main U.S. scientific research station in Antarctica, is located on Ross Island in the map area, many of these and other features in the area have been studied extensively. The paper version of this map is
A sensitivity study of fast outlet glaciers to short timescale cyclical perturbations
NASA Astrophysics Data System (ADS)
Aykutlug, E.; Dupont, T. K.
2015-01-01
The dynamic response of outlet glaciers on short (annual to decadal) timescales is affected by various external forcings, such as basal or oceanic conditions. Understanding the sensitivity of the dynamic response to such forcings can help assess more accurate ice volume projections. In this work, we investigate the spatiotemporal sensitivity of outlet glaciers to fast cyclical forcings using a one-dimensional depth and width-averaged heuristic model. Our results indicate that even on such short timescales, nonlinearities in ice dynamics may lead to an asymmetric response, despite the forcing functions being symmetric around each reference value. Results also show that such short-timescale effects become more pronounced as glaciers become closer to flotation. While being qualitatively similar for both downsloping and upsloping bed geometries, the results indicate higher sensitivity for upsloping ("West Antarctica-like") beds. The range in asymmetric response for different configurations motivate parameterizing or including short-timescale effects in models while investigating the dynamic behavior of outlet glaciers.
Smith, J. A.; Andersen, T. J.; Shortt, M.; ...
2016-11-23
The West Antarctic Ice Sheet is one of the largest potential sources of rising sea levels. Over the past 40 years, glaciers flowing into the Amundsen Sea sector of the ice sheet have thinned at an accelerating rate, and several numerical models suggest that unstable and irreversible retreat of the grounding line—which marks the boundary between grounded ice and floating ice shelf—is underway. Understanding this recent retreat requires a detailed knowledge of grounding-line history, but the locations of the grounding line before the advent of satellite monitoring in the 1990s are poorly dated. In particular, a history of grounding-line retreatmore » is required to understand the relative roles of contemporaneous ocean-forced change and of ongoing glacier response to an earlier perturbation in driving ice-sheet loss. Here we show that the present thinning and retreat of Pine Island Glacier in West Antarctica is part of a climatically forced trend that was triggered in the 1940s. Our conclusions arise from analysis of sediment cores recovered beneath the floating Pine Island Glacier ice shelf, and constrain the date at which the grounding line retreated from a prominent seafloor ridge. We find that incursion of marine water beyond the crest of this ridge, forming an ocean cavity beneath the ice shelf, occurred in 1945 (±12 years); final ungrounding of the ice shelf from the ridge occurred in 1970 (±4 years). The initial opening of this ocean cavity followed a period of strong warming of West Antarctica, associated with El Niño activity. Furthermore our results suggest that, even when climate forcing weakened, ice-sheet retreat continued.« less
DOE Office of Scientific and Technical Information (OSTI.GOV)
Smith, J. A.; Andersen, T. J.; Shortt, M.
The West Antarctic Ice Sheet is one of the largest potential sources of rising sea levels. Over the past 40 years, glaciers flowing into the Amundsen Sea sector of the ice sheet have thinned at an accelerating rate, and several numerical models suggest that unstable and irreversible retreat of the grounding line—which marks the boundary between grounded ice and floating ice shelf—is underway. Understanding this recent retreat requires a detailed knowledge of grounding-line history, but the locations of the grounding line before the advent of satellite monitoring in the 1990s are poorly dated. In particular, a history of grounding-line retreatmore » is required to understand the relative roles of contemporaneous ocean-forced change and of ongoing glacier response to an earlier perturbation in driving ice-sheet loss. Here we show that the present thinning and retreat of Pine Island Glacier in West Antarctica is part of a climatically forced trend that was triggered in the 1940s. Our conclusions arise from analysis of sediment cores recovered beneath the floating Pine Island Glacier ice shelf, and constrain the date at which the grounding line retreated from a prominent seafloor ridge. We find that incursion of marine water beyond the crest of this ridge, forming an ocean cavity beneath the ice shelf, occurred in 1945 (±12 years); final ungrounding of the ice shelf from the ridge occurred in 1970 (±4 years). The initial opening of this ocean cavity followed a period of strong warming of West Antarctica, associated with El Niño activity. Furthermore our results suggest that, even when climate forcing weakened, ice-sheet retreat continued.« less
Rapid Holocene thinning of an East Antarctic outlet glacier driven by marine ice sheet instability
Jones, R. S.; Mackintosh, A. N.; Norton, K. P.; Golledge, N. R.; Fogwill, C. J.; Kubik, P. W.; Christl, M.; Greenwood, S. L.
2015-01-01
Outlet glaciers grounded on a bed that deepens inland and extends below sea level are potentially vulnerable to ‘marine ice sheet instability'. This instability, which may lead to runaway ice loss, has been simulated in models, but its consequences have not been directly observed in geological records. Here we provide new surface-exposure ages from an outlet of the East Antarctic Ice Sheet that reveal rapid glacier thinning occurred approximately 7,000 years ago, in the absence of large environmental changes. Glacier thinning persisted for more than two and a half centuries, resulting in hundreds of metres of ice loss. Numerical simulations indicate that ice surface drawdown accelerated when the otherwise steadily retreating glacier encountered a bedrock trough. Together, the geological reconstruction and numerical simulations suggest that centennial-scale glacier thinning arose from unstable grounding line retreat. Capturing these instability processes in ice sheet models is important for predicting Antarctica's future contribution to sea level change. PMID:26608558
Coastal-change and glaciological map of the Amery Ice Shelf area, Antarctica: 1961–2004
Foley, Kevin M.; Ferrigno, Jane G.; Swithinbank, Charles; Williams, Richard S.; Orndorff, Audrey L.
2013-01-01
Reduction in the area and volume of Earth’s two polar ice sheets is intricately linked to changes in global climate and to the resulting rise in sea level. Measurement of changes in area and mass balance of the Antarctic ice sheet was given a very high priority in recommendations by the Polar Research Board of the National Research Council. On the basis of these recommendations, the U.S. Geological Survey used its archive of satellite images to document changes in the cryospheric coastline of Antarctica and analyze the glaciological features of the coastal regions. Amery Ice Shelf, lying between 67.5° and 75° East longitude and 68.5° and 73.2° South latitude, is the largest ice shelf in East Antarctica. The latest measurements of the area of the ice shelf range between 62,620 and 71,260 square kilometers. The ice shelf is fed primarily by Lambert, Mellor, and Fisher Glaciers; its thickness ranges from 3,000 meters in the center of the grounding line to less than 300 meters at the ice front. Lambert Glacier is considered to be the largest glacier in the world, and its drainage basin is more than 1 million square kilometers in area. It is possible to see some coastal change on the outlet glaciers along the coast, but most of the noticeable change occurs on the Amery Ice Shelf front.
Glacier topography and elevation changes derived from Pléiades sub-meter stereo images
NASA Astrophysics Data System (ADS)
Berthier, E.; Vincent, C.; Magnússon, E.; Gunnlaugsson, Á. Þ.; Pitte, P.; Le Meur, E.; Masiokas, M.; Ruiz, L.; Pálsson, F.; Belart, J. M. C.; Wagnon, P.
2014-12-01
In response to climate change, most glaciers are losing mass and hence contribute to sea-level rise. Repeated and accurate mapping of their surface topography is required to estimate their mass balance and to extrapolate/calibrate sparse field glaciological measurements. In this study we evaluate the potential of sub-meter stereo imagery from the recently launched Pléiades satellites to derive digital elevation models (DEMs) of glaciers and their elevation changes. Our five evaluation sites, where nearly simultaneous field measurements were collected, are located in Iceland, the European Alps, the central Andes, Nepal and Antarctica. For Iceland, the Pléiades DEM is also compared to a lidar DEM. The vertical biases of the Pléiades DEMs are less than 1 m if ground control points (GCPs) are used, but reach up to 7 m without GCPs. Even without GCPs, vertical biases can be reduced to a few decimetres by horizontal and vertical co-registration of the DEMs to reference altimetric data on ice-free terrain. Around these biases, the vertical precision of the Pléiades DEMs is ±1 m and even ±0.5 m on the flat glacier tongues (1σ confidence level). Similar precision levels are obtained in the accumulation areas of glaciers and in Antarctica. We also demonstrate the high potential of Pléiades DEMs for measuring seasonal, annual and multi-annual elevation changes with an accuracy of 1 m or better if cloud-free images are available. The negative region-wide mass balances of glaciers in the Mont-Blanc area (-1.04 ± 0.23 m a-1 water equivalent, w.e.) are revealed by differencing Satellite pour l'Observation de la Terre 5 (SPOT 5) and Pléiades DEMs acquired in August 2003 and 2012, confirming the accelerated glacial wastage in the European Alps.
Terra Nova Bay Polynya, Antarctica
NASA Technical Reports Server (NTRS)
2007-01-01
In Terra Nova Bay, off the Scott Coast of Victoria Land, Antarctica, a large pocket of open water persists throughout most of the Southern Hemisphere winter, even while most of the rest of the Antarctic coastline is firmly embraced by the frozen Southern Ocean. This pocket of open water--a polynya--results from exceptionally strong winds that blow downslope from the Trans-Antarctic Mountains. These fierce katabatic winds drive the sea ice eastward. Since the dominant ice drift pattern in the area is northward, the Drygalski Ice Tongue prevents the bay from being re-populated with sea ice. This image of the Terra Nova Bay polynya was captured by the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA's Aqua satellite on October 16, 2007. Sea ice sits over the Ross Sea like a cracked and crumbling windshield. Blue-tinged glaciers flow down from the Trans-Antarctic Mountains. Although glaciers can appear blue because of melt water, they can also get that tint when the wind scours and polishes the ice surface. Given the strength of the katabatic winds along this part of the Antarctic coast, it is likely that the blue color of these glaciers is a result of their having been swept clean of snow. The large image has a spatial resolution (level of detail) of 250 meters per pixel.
They're M-e-e-elting!: An Investigation of Glacial Retreat in Antarctica
ERIC Educational Resources Information Center
Bugg, Samuel R., IV; Constible, Juanita; Kaput, Marianne; Lee, Richard E., Jr.
2007-01-01
In this article, the authors describe the mechanics of They're M-e-e-elting!, an activity wherein middle school students can simulate glacial retreat in Antarctica. They're M-e-e-elting! allows students to melt glaciers, change the water level and salinity of the Southern Ocean, and examine alterations to the Antarctic food web--all without…
Magnetotelluric investigation of the Vestfold Hills and Rauer Group, East Antarctica
Peacock, Jared R.; Selway, Katherine
2016-01-01
The Vestfold Hills and Rauer Group in East Antarctica have contrasting Archean to Neoproterozoic geological histories and are believed to be juxtaposed along a suture zone that now lies beneath the Sørsdal Glacier. Exact location and age of this suture zone are unknown, as is its relationship to regional deformation associated with the amalgamation of East Gondwana. To image the suture zone, magnetotelluric (MT) data were collected in Prydz Bay, East Antarctica, mainly along a profile crossing the Sørsdal Glacier and regions inland of the Vestfold Hills and Rauer Group islands. Time-frequency analysis of the MT time series yielded three important observations: (1) Wind speeds in excess of ∼8 m/s reduce coherence between electric and magnetic fields due to charged wind-blown particles of ice and snow. (2) Estimation of the MT transfer function is best between 1000 and 1400 UT when ionospheric Hall currents enhance the magnetic source field. (3) Nonplanar source field effects were minimal but detectable and removed from estimation of the MT transfer function. Inversions of MT data in 2-D and 3-D produce similar resistivity models, where structures in the preferred 3-D resistivity model correlate strongly with regional magnetic data. The electrically conductive Rauer Group is separated from the less conductive Vestfold Hills by a resistive zone under the Sørsdal Glacier, which is interpreted to be caused by oxidation during suturing. Though a suture zone has been imaged, no time constrains on suturing can be made from the MT data.
Modeling and Understanding the Mass Balance of Himalayan Glaciers
NASA Astrophysics Data System (ADS)
Rengaraju, S.; Achutarao, K. M.
2017-12-01
Changes in glaciers are among the most visible manifestations of a changing climate. Retreating glaciers have significant impacts on global sea-level rise and stream flow of rivers. Modeling the response of glaciers to climate change is important for many reasons including predicting changes in global sea level and water resources. The mass balance of a glacier provides a robust way of ascertaining whether there has been a net loss or gain of ice from the glacier. The mass balance reflects all of the meteorological forcing of the glacier - from the accumulation of snow and the combined losses from ablation and sublimation. The glaciers in the Himalayan region are considered sensitive to climate change and their fate under climate change is critical to the billions of humans that rely on rivers originating from these glaciers. Owing to complex terrain and harsh climate, Himalayan glaciers have historically been poorly monitored and this makes it harder to understand and predict their fate.In this study we model the observed mass balance of Himalayan glaciers using the methods of Radic and Hock (2011) and analyze the response to future changes in climate based on the model projections from the Coupled Model Intercomparison Project Phase-5 (CMIP5; Taylor et al., 2012). We make use of available observations of mass balance from various sources for 14 glaciers across the Himalayas. These glaciers are located across distinct climatic conditions - from the Karakoram and Hindu Kush in the West that are fed by winter precipitation caused by westerly disturbances to the Eastern Himalayas where the summer monsoon provides the bulk of the precipitation. For the historical observed period, we use the ECMWF Re-Analysis (ERA-40) for temperature and VASClimO (GPCC) data at 2.5°x2.5° resolution to calibrate the mass balance model. We evaluate the CMIP5 model simulations for their fidelity in capturing the distinct climatic conditions across the Himalayas in order to select
How can we Optimize Global Satellite Observations of Glacier Velocity and Elevation Changes?
NASA Astrophysics Data System (ADS)
Willis, M. J.; Pritchard, M. E.; Zheng, W.
2015-12-01
We have started a global compilation of glacier surface elevation change rates measured by altimeters and differencing of Digital Elevation Models and glacier velocities measured by Synthetic Aperture Radar (SAR) and optical feature tracking as well as from Interferometric SAR (InSAR). Our goal is to compile statistics on recent ice flow velocities and surface elevation change rates near the fronts of all available glaciers using literature and our own data sets of the Russian Arctic, Patagonia, Alaska, Greenland and Antarctica, the Himalayas, and other locations. We quantify the percentage of the glaciers on the planet that can be regarded as fast flowing glaciers, with surface velocities of more than 50 meters per year, while also recording glaciers that have elevation change rates of more than 2 meters per year. We examine whether glaciers have significant interannual variations in velocities, or have accelerated or stagnated where time series of ice motions are available. We use glacier boundaries and identifiers from the Randolph Glacier Inventory. Our survey highlights glaciers that are likely to react quickly to changes in their mass accumulation rates. The study also identifies geographical areas where our knowledge of glacier dynamics remains poor. Our survey helps guide how frequently observations must be made in order to provide quality satellite-derived velocity and ice elevation observations at a variety of glacier thermal regimes, speeds and widths. Our objectives are to determine to what extent the joint NASA and Indian Space Research Organization Synthetic Aperture Radar mission (NISAR) will be able to provide global precision coverage of ice speed changes and to determine how to optimize observations from the global constellation of satellite missions to record important changes to glacier elevations and velocities worldwide.
Sub-ice-shelf sediments record history of twentieth-century retreat of Pine Island Glacier.
Smith, J A; Andersen, T J; Shortt, M; Gaffney, A M; Truffer, M; Stanton, T P; Bindschadler, R; Dutrieux, P; Jenkins, A; Hillenbrand, C-D; Ehrmann, W; Corr, H F J; Farley, N; Crowhurst, S; Vaughan, D G
2017-01-05
The West Antarctic Ice Sheet is one of the largest potential sources of rising sea levels. Over the past 40 years, glaciers flowing into the Amundsen Sea sector of the ice sheet have thinned at an accelerating rate, and several numerical models suggest that unstable and irreversible retreat of the grounding line-which marks the boundary between grounded ice and floating ice shelf-is underway. Understanding this recent retreat requires a detailed knowledge of grounding-line history, but the locations of the grounding line before the advent of satellite monitoring in the 1990s are poorly dated. In particular, a history of grounding-line retreat is required to understand the relative roles of contemporaneous ocean-forced change and of ongoing glacier response to an earlier perturbation in driving ice-sheet loss. Here we show that the present thinning and retreat of Pine Island Glacier in West Antarctica is part of a climatically forced trend that was triggered in the 1940s. Our conclusions arise from analysis of sediment cores recovered beneath the floating Pine Island Glacier ice shelf, and constrain the date at which the grounding line retreated from a prominent seafloor ridge. We find that incursion of marine water beyond the crest of this ridge, forming an ocean cavity beneath the ice shelf, occurred in 1945 (±12 years); final ungrounding of the ice shelf from the ridge occurred in 1970 (±4 years). The initial opening of this ocean cavity followed a period of strong warming of West Antarctica, associated with El Niño activity. Thus our results suggest that, even when climate forcing weakened, ice-sheet retreat continued.
NASA Astrophysics Data System (ADS)
Oliva, Marc; Ruiz-Fernández, Jesús
2017-09-01
Elephant Point is an ice-free area in the SW corner of Livingston Island (Maritime Antarctica). The retreat of Rotch Dome glacier during the Holocene has exposed a land area of 1.16 km2. Up to 17.3% of this surface has become ice-free between 1956 and 2010. A detailed geomorphological mapping of this ice-free environment was conducted in late January 2014. A wide range of active periglacial landforms show that periglacial processes are widespread. From the glacier to the coast four different geomorphological areas are identified: proglacial environment, moraine complex, bedrock plateaus and marine terraces. In situ measurements of the thawed soil depth show evidence of the widespread frozen ground conditions in the area. Field observations of permafrost exposures suggest that these frost conditions may be related to a soil permafrost regime, almost down to sea level. The activity of penguin colonies and elephant seals has created minor geomorphological features in the raised marine terraces. Here, several archaeological sites related to early human colonization of Antarctica were also found in natural shelters.
Timing of recent accelerations of Pine Island Glacier, Antarctica
Joughin, I.; Rignot, E.; Rosanova, C.E.; Lucchitta, B.K.; Bohlander, J.
2003-01-01
We have used Interferometric Synthetic Aperture Radar (InSAR) data and sequential Landsat imagery to identify and temporally constrain two acceleration events on Pine Island Glacier (PIG). These two events are separated by a period of at least seven years (1987 - 1994). The change in discharge between two flux gates indicates that the majority of the increase in discharge associated with the second acceleration originates well inland (>80 km) from the grounding line. An analysis indicates that changes in driving stress consistent with observed thinning rates are sufficient in magnitude to explain much of the acceleration.
Glacier and Ice Shelves Studies Using Satellite SAR Interferometry
NASA Technical Reports Server (NTRS)
Rignot, Eric
1999-01-01
Satellite radar interferometry is a powerful technique to measure the surface velocity and topography of glacier ice. On ice shelves, a quadruple difference technique separates tidal motion from the steady creep flow deformation of ice. The results provide a wealth of information about glacier grounding lines , mass fluxes, stability, elastic properties of ice, and tidal regime. The grounding line, which is where the glacier detaches from its bed and becomes afloat, is detected with a precision of a few tens of meters. Combining this information with satellite radar altimetry makes it possible to measure glacier discharge into the ocean and state of mass balance with greater precision than ever before, and in turn provide a significant revision of past estimates of mass balance of the Greenland and Antarctic Ice Sheets. Analysis of creep rates on floating ice permits an estimation of basal melting at the ice shelf underside. The results reveal that the action of ocean water in sub-ice-shelf cavities has been largely underestimated by oceanographic models and is the dominant mode of mass release to the ocean from an ice shelf. Precise mapping of grounding line positions also permits the detection of grounding line migration, which is a fine indicator of glacier change, independent of our knowledge of snow accumulation and ice melting. This technique has been successfully used to detect the rapid retreat of Pine Island Glacier, the largest ice stream in West Antarctica. Finally, tidal motion of ice shelves measured interferometrically provides a modern, synoptic view of the physical processes which govern the formation of tabular icebergs in the Antarctic.
Status of DORIS stations in Antarctica for precise geodesy
NASA Technical Reports Server (NTRS)
Willis, P.; Amalvict, M.; Shibuya, K.
2005-01-01
In Antarctica, besides the quite numerous GPS stations, four DORIS stations are permanently operating. In addition to the permanent DORIS stations, episodic campaigns took place at DomeC/Conccordia and on Sorsdal and Lambert glaciers. In this paper, we first collect general information concerning the stations and the campaigns (location, start of measurements, etc). We then present the results of observations of the permanent stations keeping in mind that we are primarily interested here in the vertical component, which is the most uncertain component.
Rodriguez, Russell J.; Connell, L.; Redman, R.; Barrett, A.; Iszard, M.; Fonseca, A.
2010-01-01
During a survey of the culturable soil fungal population in samples collected in Taylor Valley, South Victoria Land, Antarctica, 13 basidiomycetous yeast strains with orange-coloured colonies were isolated. Phylogenetic analyses of internal transcribed spacer (ITS) and partial LSU rRNA gene sequences showed that the strains belong to the Dioszegia clade of the Tremellales (Tremellomycetes, Agaricomycotina), but did not correspond to any of the hitherto recognized species. Two novel species, Dioszegia antarctica sp. nov. (type strain ANT-03-116T =CBS 10920T =PYCC 5970T) and Dioszegia cryoxerica sp. nov. (type strain ANT-03-071T =CBS 10919T =PYCC 5967T), are described to accommodate ten and three of these strains, respectively. Analysis of ITS sequences demonstrated intrastrain sequence heterogeneity in D. cryoxerica. The latter species is also notable for producing true hyphae with clamp connections and haustoria. However, no sexual structures were observed. The two novel species can be considered obligate psychrophiles, since they failed to grow above 20 °C and grew best between 10 and 15 °C.
Newly Found Crack Across the Pine Island Glacier
2017-12-08
A close-up image of the crack spreading across the ice shelf of Pine Island Glacier shows the details of the boulder-like blocks of ice that fell into the rift when it split. For most of the 18-mile stretch of the crack that NASA’s DC-8 flew over on Oct. 26, 2011, it stretched about 240 feet wide, as roughly seen here. The deepest points ranged from about 165 to 190 feet, roughly equal to the top of the ice shelf down to sea level. Scientists expect the crack to propagate and the ice shelf to calve an iceberg of more than 300 square miles in the coming months. This image was captured by the Digital Mapping System (DMS) aboard the DC-8. Credit: NASA/DMS NASA's Operation IceBridge returns to a base camp of Punta Arenas, Chile for the third year of flights over Antarctica's changing sea ice, glaciers and ice sheets. NASA's DC-8, outfitted with seven remote-sensing instruments, and a Gulfstream 5 operated by the National Science Foundation and National Center for Atmospheric Research and outfitted with a high-altitude laser-ranging mapper, will fly from Chile over Antarctica in October and November. The mission is designed to record changes to Antarctica's ice sheets and give scientists insight into what is driving those changes. Follow the progress of the mission: Campaign News site: www.nasa.gov/mission_pages/icebridge/index.html IceBridge blog: blogs.nasa.gov/cm/newui/blog/viewpostlist.jsp?blogname=ic... Twitter: @nasa_ice 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
Birth of a Large Iceberg in Pine Island Bay, Antarctica
2001-11-14
A large tabular iceberg (42 kilometers x 17 kilometers) broke off Pine Island Glacier, West Antarctica (75ºS latitude, 102ºW longitude) sometime between November 4 and 12, 2001. Images of the glacier were acquired by the Multi-angle Imaging SpectroRadiometer (MISR) instrument aboard NASA's Terra spacecraft. This event was preceded by the formation of a large crack across the glacier in mid 2000. Data gathered by other imaging instruments revealed the crack to be propagating through the shelf ice at a rate averaging 15 meters per day, accompanied by a slight rotation of about one percent per year at the seaward margin of the rift. The image set shows three views of Pine Island Glacier acquired by MISR's vertical-viewing (nadir) camera. The first was captured in late 2000, early in the development of the crack. The second and third views were acquired in November 2001, just before and just after the new iceberg broke off. The existence of the crack took the glaciological community by surprise, and the rapid rate at which the crack propagated was also not anticipated. Glaciologists predicted that the rift would reach the other side of the glacier sometime in 2002. However, the iceberg detached much sooner than anticipated, and the last 10-kilometer segment that was still attached to the ice shelf snapped off in a matter of days. http://photojournal.jpl.nasa.gov/catalog/PIA03431
Tephra layers in the Siple Dome and Taylor Dome ice cores, Antarctica: Sources and correlations
NASA Astrophysics Data System (ADS)
Dunbar, Nelia W.; Zielinski, Gregory A.; Voisins, Daniel T.
2003-08-01
Volcanic ash, or tephra layers, are found in the Taylor Dome, Siple Dome A, and Siple Dome B ice cores. Significant shard concentrations are found at a number of depths in all three cores. Electron and ion microprobe analyses indicate that the geochemical composition of most layers is basaltic, basanitic, or trachytic, and the geochemical signatures of the layers suggest derivation from the Pleiades volcanic center, Mt. Melbourne volcano, or small mafic centers, probably in the Royal Society Range area. Presence of tephra layers suggests an episode of previously unrecognized Antarctic volcanic activity between 1776 and 1805 A.D., from at least two volcanic centers. A strong geochemical correlation (D = 3.49 and 3.97 with a value of 4 considered identical) is observed between tephra layers at depth of 79.2 m in the Taylor Dome ice core, and layers between 97.2 and 97.7 m depth in the Siple B core. This correlation, and the highly accurate depth-age scale of the Siple B core suggest that the age of this horizon in the Taylor Dome ice core presented by [1998a, 2000] should be revised downward, to the younger age of 675 ± 25 years before 1995. This revised chronology is consistent with vertical strain measurements presented by [2003].
Glacier mass loss. Dynamic thinning of glaciers on the Southern Antarctic Peninsula.
Wouters, B; Martin-Español, A; Helm, V; Flament, T; van Wessem, J M; Ligtenberg, S R M; van den Broeke, M R; Bamber, J L
2015-05-22
Growing evidence has demonstrated the importance of ice shelf buttressing on the inland grounded ice, especially if it is resting on bedrock below sea level. Much of the Southern Antarctic Peninsula satisfies this condition and also possesses a bed slope that deepens inland. Such ice sheet geometry is potentially unstable. We use satellite altimetry and gravity observations to show that a major portion of the region has, since 2009, destabilized. Ice mass loss of the marine-terminating glaciers has rapidly accelerated from close to balance in the 2000s to a sustained rate of -56 ± 8 gigatons per year, constituting a major fraction of Antarctica's contribution to rising sea level. The widespread, simultaneous nature of the acceleration, in the absence of a persistent atmospheric forcing, points to an oceanic driving mechanism. Copyright © 2015, American Association for the Advancement of Science.
NASA Astrophysics Data System (ADS)
Dowling, C. B.; Poreda, R. J.; Snyder, G. T.
2008-12-01
The McMurdo Dry Valleys (MDV), Antarctica, is the largest ice-free region on Antarctica. Lake Vanda, located in central Wright Valley, is the deepest lake among the MDV lakes. It has a relatively fresh water layer above 50 m with a hypersaline calcium-chloride brine below (50-72 m). The Onyx River is the only stream input into Lake Vanda. It flows westward from the coastal Lower Wright Glacier and discharges into Lake Vanda. Suggested by the published literature and this study, there has been and may still be groundwater input into Lake Vanda. Stable isotopes, major ions, and noble gas data from this study coupled with previously published data indicate that the bottom waters of Lake Vanda have had significant contributions from a deep groundwater system. The dissolved gas of the bottom waters of Lake Vanda display solubility concentrations rather than the Ar-enriched dissolved gas seen in the Taylor Valley lakes (such as Lake Bonney). The isotopic data indicate that the bottom calcium-chloride-brine of Lake Vanda has undergone very little evaporation. The calcium-chloride chemistry of the groundwater that discharges into Lake Vanda most likely results from the chemical weathering and dissolution of cryogenic evaporites (antarcticite and gypsum) within the glacial sediments of Wright Valley. The high calcium concentrations of the brine have caused gypsum to precipitate on the lake bottom. Our work also supports previous physical and chemical observations suggesting that the upper portion actively circulates and the hypersaline bottom layer does not. The helium and calcium chloride values are concentrated at the bottom, with a very narrow transition layer between it and the above fresh water. If the freshwater layer did not actively circulate, then diffusion over time would have caused the helium and calcium chloride to slowly permeate upwards through the water column.
2017 Rapid Retreat Of Thwaites Glacier
NASA Astrophysics Data System (ADS)
Milillo, P.; Rignot, E. J.; Mouginot, J.; Scheuchl, B.
2017-12-01
We employ data from the second generation of SAR systems e.g. the Italian COSMO- SkyMed (CSK) constellation and the German TanDEM-X (TDX) formation to monitor grounding line retreat using short repeat-time interferometry and accurate InSAR DEM on Thwaites glacier in the Amundsen Sea Embayment (ASE), West Antarctica. The ASE is a marine-based ice sheet with a retrograde bed containing enough ice to raise global sea level by 120 cm. Several studies have inferred the mechanical properties of portions of ASE using observationally constrained numerical models, but these studies offer only temporal snapshots of basal mechanics owing to a dearth of observational time series. Prior attempts of grounding lines mapping have been limited because few space-borne SAR missions offer the short-term repeat pass capability required to map the differential vertical displacement of floating ice at tidal frequencies with sufficient detail to resolve grounding line boundaries in areas of fast ice deformation. Using 1-day CSK repeat pass data and TDX DEMs, we collected frequent, high-resolution grounding line measurements of Thwaites glaciers spanning 2015-2017. We compare the results with ERS data spanning 1996-2011, and Sentinel-1a 2014-2015 data. Between 2011 and 2017 we observe a maximum retreat of 5-7 km across the main Thwaites glacier tongue and Thwaites Eastern ice shelf (TEIS) corresponding to an increased retreat rate of 0.5 km/yr. Grounding line retreat has been fueled by the enhanced intrusion of warm, salty, subsurface ocean water of circumpolar deep water origin onto the continental shelf, beneath the floating ice shelf, to reach the glacier grounding zone and melt it from below at rates varying from 50 to 150 m/yr. The retreat rate varies depending on the magnitude of ice melt by the ocean, the rate of ice thinning and the shape of the glacier surface and bed topography.
Uneven onset and pace of ice-dynamical imbalance in the Amundsen Sea Embayment, West Antarctica
NASA Astrophysics Data System (ADS)
Konrad, Hannes; Gilbert, Lin; Cornford, Stephen L.; Payne, Antony; Hogg, Anna; Muir, Alan; Shepherd, Andrew
2017-01-01
We combine measurements acquired by five satellite altimeter missions to obtain an uninterrupted record of ice sheet elevation change over the Amundsen Sea Embayment, West Antarctica, since 1992. Using these data, we examine the onset of surface lowering arising through ice-dynamical imbalance, and the pace at which it has propagated inland, by tracking elevation changes along glacier flow lines. Surface lowering has spread slowest (<6 km/yr) along the Pope, Smith, and Kohler (PSK) Glaciers, due to their small extent. Pine Island Glacier (PIG) is characterized by a continuous inland spreading of surface lowering, notably fast at rates of 13 to 15 km/yr along tributaries draining the southeastern lobe, possibly due to basal conditions or tributary geometry. Surface lowering on Thwaites Glacier (THG) has been episodic and has spread inland fastest (10 to 12 km/yr) along its central flow lines. The current episodes of surface lowering started approximately 10 years before the first measurements on PSK, around 1990 on PIG, and around 2000 on THG. Ice-dynamical imbalance across the sector has therefore been uneven during the satellite record.
Pathways of warm water to the Northeast Greenland outlet glaciers
NASA Astrophysics Data System (ADS)
Schaffer, Janin; Timmermann, Ralph; Kanzow, Torsten; Arndt, Jan Erik; Mayer, Christoph; Schauer, Ursula
2015-04-01
The ocean plays an important role in modulating the mass balance of the Greenland Ice Sheet by delivering heat to the marine-terminating outlet glaciers surrounding the Greenland coast. The warming and accumulation of Atlantic Water in the subpolar North Atlantic has been suggested to be a potential driver of the glaciers' retreat over the last decades. The shelf regions thus play a critical role for the transport of Atlantic Water towards the glaciers, but also for the transfer of freshwater towards the deep ocean. A key region for the mass balance of the Greenland Ice Sheet is the Northeast Greenland Ice Stream. This large ice stream drains the second-largest basin of the Greenland Ice Sheet and feeds three outlet glaciers. The largest one is Nioghalvfjerdsfjorden (79°N-Glacier) featuring an 80 km long floating ice tongue. Both the ocean circulation on the continental shelf off Northeast Greenland and the circulation in the cavity below the ice tongue are weakly constrained so far. In order to study the relevant processes of glacier-ocean interaction we combine observations and model work. Here we focus on historic and recent hydrographic observations and on the complex bathymetry in the Northeast Greenland shelf region, which is thought to steer the flux of warm Atlantic water onto the continental shelf and into the sub-ice cavity beneath the 79°N-Glacier. We present a new global topography data set, RTopo-2, which includes the most recent surveys on the Northeast Greenland continental shelf and provides a detailed bathymetry for all around Greenland. In addition, RTopo-2 contains ice and bedrock surface topographies for Greenland and Antarctica. Based on the updated ocean bathymetry and a variety of hydrographic observations we show the water mass distribution on the continental shelf off Northeast Greenland. These maps enable us to discuss possible supply pathways of warm modified Atlantic waters on the continental shelf and thus potential ways of heat
The potential for retreating alpine glaciers to alter alpine ecosystems in the Colorado Front Range
NASA Astrophysics Data System (ADS)
Hall, E.; Baron, J.
2013-12-01
Glaciers are retreating at an unprecedented rate. In mid-latitude alpine ecosystems the presence of glaciers and rock glaciers govern rates and ecology of alpine and sub-alpine ecosystems. Changes in the thermal environment due to the loss of isothermal habitat and inputs from glacier melt chemistry are altering alpine ecosystems in unpredictable ways. In particular, glacier may be a source of nitrogen that is altering alpine ecosystem dynamics. Loch Vale Watershed (LVWS) located within Rocky Mountain National Park. LVWS contains a surface glacier (Andrew's glacier) and a rock glacier (Taylor's glacier) at the headwater of each of the two drainages within the watershed. We collected precipitation from a National Atmospheric Deposition Site and surface water from multiple alpine lakes and streams during a particularly high and low snow year in the Colorado Front Range. We also sampled stream and lake sediments at each site to analyze the associated microbial community. Concentrations of nitrate and ammonium, relative abundance of amoA (the gene responsible for a key step in the microbial nitrification pathway), and the dual isotope signal to nitrate all point to snow melt as a key deliverer of nitrogen to ecosystems along the Colorado Front Range. However, late summer surface water chemistry is isotopically similar to the chemistry of glacial ice. This suggests that retreating glacier may be an additional source of N to alpine ecosystems and have the potential to alter microbial community composition, biogeochemical rate processes, and ecosystem function. These dynamics are most likely not unique to the Colorado Front Range and should be globally distributed as glaciers continue to retreat in high altitude ecosystems around the world.
Glaciation of alpine valleys: The glacier - debris-covered glacier - rock glacier continuum
NASA Astrophysics Data System (ADS)
Anderson, Robert S.; Anderson, Leif S.; Armstrong, William H.; Rossi, Matthew W.; Crump, Sarah E.
2018-06-01
Alpine ice varies from pure ice glaciers to partially debris-covered glaciers to rock glaciers, as defined by the degree of debris cover. In many low- to mid-latitude mountain ranges, the few bare ice glaciers that do exist in the present climate are small and are found where snow is focused by avalanches and where direct exposure to radiation is minimized. Instead, valley heads are more likely to be populated by rock glaciers, which can number in the hundreds. These rock-cloaked glaciers represent some of the most identifiable components of the cryosphere today in low- to mid-latitude settings, and the over-steepened snouts pose an often overlooked hazard to travel in alpine terrain. Geomorphically, rock glaciers serve as conveyor belts atop which rock is pulled away from the base of cliffs. In this work, we show how rock glaciers can be treated as an end-member case that is captured in numerical models of glaciers that include ice dynamics, debris dynamics, and the feedbacks between them. Specifically, we focus on the transition from debris-covered glaciers, where the modern equilibrium line altitude (ELA) intersects the topography, to rock glaciers, where the modern ELA lies above the topography. On debris-covered glaciers (i.e., glaciers with a partial rock mantle), rock delivered to the glacier from its headwall, or from sidewall debris swept into the glacier at tributary junctions, travels englacially to emerge below the ELA. There it accumulates on the surface and damps the rate of melt of underlying ice. This allows the termini of debris-covered glaciers to extend beyond debris-free counterparts, thereby decreasing the ratio of accumulation area to total area of the glacier (AAR). In contrast, rock glaciers (i.e., glaciers with a full rock mantle) occur where and when the environmental ELA rises above the topography. They require avalanches and rockfall from steep headwalls. The occurrence of rock glaciers reflects this dependence on avalanche sources
NASA Astrophysics Data System (ADS)
Doran, P. T.; Myers, K. F.; Foley, N.; Tulaczyk, S. M.; Dugan, H. A.; Auken, E.; Mikucki, J.; Virginia, R. A.
2017-12-01
The McMurdo Dry Valleys (MDVs) in east Antarctica contain a number of perennial ice-covered lakes fed by ephemeral meltwater streams. Lake Fryxell in Taylor Valley, is roughly 5.5 km long and approximately 22 m deep. Paleodeltas and paleoshorelines throughout Fryxell Basin provide evidence of significant lake level change occurring since the Last Glacial Maximum (LGM). During the LGM, grounded ice in the Ross Sea extended into the eastern portion of Taylor Valley, creating a large ice dammed paleolake. Glacial Lake Washburn (GLW) was roughly 300 m higher than modern day Lake Fryxell and its formation and existence has been debated. In this study, we use Geographical Information System and remote sensing techniques paired with regional resistivity data to provide new insight into the paleohydrology of the region. The existence of GLW is supported by new findings of a deep groundwater system beneath Lake Fryxell, which is interpreted as the degrading thaw bulb of GLW. Airborne resistivity data collected by SkyTEM, a time-domain airborne electromagnetic sensor system was used to map groundwater systems in the lake basin. Subsurface characteristics can be inferred from the relationship of resistivity to temperature, salinity, porosity, and degree of saturation. A large low resistivity region indicative of liquid water extends hundreds of meters away from the modern lake extent which is consistent with the presence of a degrading thaw bulb from GLW. As lake level in Fryxell Basin fell to modern levels, the saturated sediment beneath the lake began to freeze as it became exposed to low atmospheric temperatures. We hypothesize that this process is ongoing and will continue until equilibrium is reached between the geothermal gradient and atmospheric temperatures. Though liquid groundwater systems were previously thought to be minimal or nonexistent in the MDVs, regional resistivity data now show that extensive groundwater reservoirs exist beneath these lakes. In addition
Active water exchange and life near the grounding line of an Antarctic outlet glacier
NASA Astrophysics Data System (ADS)
Sugiyama, Shin; Sawagaki, Takanobu; Fukuda, Takehiro; Aoki, Shigeru
2014-08-01
The grounding line (GL) of the Antarctic ice sheet forms the boundary between grounded and floating ice along the coast. Near this line, warm oceanic water contacts the ice shelf, producing the ice sheet's highest basal-melt rate. Despite the importance of this region, water properties and circulations near the GL are largely unexplored because in-situ observations are difficult. Here we present direct evidence of warm ocean-water transport to the innermost part of the subshelf cavity (several hundred meters seaward from the GL) of Langhovde Glacier, an outlet glacier in East Antarctica. Our measurements come from boreholes drilled through the glacier's ∼400-m-thick grounding zone. Beneath the grounding zone, we find a 10-24-m-deep water layer of uniform temperature and salinity (-1.45 °C; 34.25 PSU), values that roughly equal those measured in the ocean in front of the glacier. Moreover, living organisms are found in the thin subglacial water layer. These findings indicate active transport of water and nutrients from the adjacent ocean, meaning that the subshelf environment interacts directly and rapidly with the ocean.
Atmospheric Boundary Layer Dynamics Near Ross Island and Over West Antarctica.
NASA Astrophysics Data System (ADS)
Liu, Zhong
The atmospheric boundary layer dynamics near Ross Island and over West Antarctica has been investigated. The study consists of two parts. The first part involved the use of data from ground-based remote sensing equipment (sodar and RASS), radiosondes, pilot balloons, automatic weather stations, and NOAA AVHRR satellite imagery. The second part involved the use of a high resolution boundary layer model coupled with a three-dimensional primitive equation mesoscale model to simulate the observed atmospheric boundary layer winds and temperatures. Turbulence parameters were simulated with an E-epsilon turbulence model driven by observed winds and temperatures. The observational analysis, for the first time, revealed that the airflow passing through the Ross Island area is supplied mainly by enhanced katabatic drainage from Byrd Glacier and secondarily drainage from Mulock and Skelton glaciers. The observed diurnal variation of the blocking effect near Ross Island is dominated by the changes in the upstream katabatic airflow. The synthesized analysis over West Antarctica found that the Siple Coast katabatic wind confluence zone consists of two superimposed katabatic airflows: a relatively warm and more buoyant katabatic flow from West Antarctica overlies a colder and less buoyant katabatic airflow from East Antarctica. The force balance analysis revealed that, inside the West Antarctic katabatic wind zone, the pressure gradient force associated with the blocked airflow against the Transantarctic Mountains dominates; inside the East Antarctic katabatic wind zone, the downslope buoyancy force due to the cold air overlying the sloping terrain is dominant. The analysis also shows that these forces are in geostrophic balance with the Coriolis force. An E-epsilon turbulence closure model is used to simulate the diurnal variation of sodar backscatter. The results show that the model is capable of qualitatively capturing the main features of the observed sodar backscatter. To
Cleaning the IceMole: collection of englacial samples from Blood Falls, Antarctica
NASA Astrophysics Data System (ADS)
Mikucki, J.; Digel, I.; Chua, M.; Davis, J.; Ghosh, D.; Lyons, W. B.; Welch, K. A.; Purcell, A.; Francke, G.; Feldmann, M.; Espe, C.; Heinen, D.; Dachwald, B.; Kowalski, J.; Tulaczyk, S. M.
2016-12-01
The Minimally Invasive Direct Glacial Access project (MIDGE) used a maneuverable thermoelectric melting probe called the IceMole to collect the first englacial samples of brine from Blood Falls, Antarctica. In order to maintain the scientific integrity of samples collected and minimize impact to this specially protected ecosystem, microbial and chemical contamination of the IceMole needed to be minimized. Guidelines have been established for research in Antarctic subglacial systems by the scientific and regulatory community and have been detailed by the "Code of Conduct for the Exploration and Research of Subglacial Aquatic Environments" put forth by the Scientific Committee on Antarctic Research (SCAR) Action Group, and was submitted to the Antarctic Treaty System. This Code of Conduct (CoC) recognizes the ecological importance and pristine nature of subglacial habitats and recommends a path forward towards clean exploration. Similarly, the US and European space agencies (NASA and ESA) have detailed instrument preparation protocols for the exploration of icy worlds in our solar system for planetary protection. Given the synergistic aims of these two groups we have adopted protocols from both subglacial and space exploration approaches. Here we present our approach to cleaning the IceMole in the field and report on ability to reduce the bioload inherent on the melter. Specifically our protocol reduced the exterior bio-load by an order of magnitude, to levels common in most clean rooms, and 1-3 orders of magnitude below that of Taylor Glacier ice surrounding Blood Falls. Our results indicate that the collection of englacial samples for microbiological analysis is feasible with melting probes.
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.
Diversity patterns of microbial eukaryotes mirror those of bacteria in Antarctic cryoconite holes.
Sommers, Pacifica; Darcy, John L; Gendron, Eli M S; Stanish, Lee F; Bagshaw, Elizabeth A; Porazinska, Dorota L; Schmidt, Steven K
2018-01-01
Ice-lidded cryoconite holes on glaciers in the Taylor Valley, Antarctica, provide a unique system of natural mesocosms for studying community structure and assembly. We used high-throughput DNA sequencing to characterize both microbial eukaryotic communities and bacterial communities within cryoconite holes across three glaciers to study similarities in their spatial patterns. We expected that the alpha (phylogenetic diversity) and beta (pairwise community dissimilarity) diversity patterns of eukaryotes in cryoconite holes would be related to those of bacteria, and that they would be related to the biogeochemical gradient within the Taylor Valley. We found that eukaryotic alpha and beta diversity were strongly related to those of bacteria across scales ranging from 140 m to 41 km apart. Alpha diversity of both was significantly related to position in the valley and surface area of the cryoconite hole, with pH also significantly correlated with the eukaryotic diversity. Beta diversity for both bacteria and eukaryotes was significantly related to position in the valley, with bacterial beta diversity also related to nitrate. These results are consistent with transport of sediments onto glaciers occurring primarily at local scales relative to the size of the valley, thus creating feedbacks in local chemistry and diversity. © FEMS 2017. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.
DOE Office of Scientific and Technical Information (OSTI.GOV)
Powell, R.D.; Pyne, A.R.; Hunter, L.E.
1992-01-01
Marine-ending glaciers may retreat with global warming as sea level rises by ocean thermal expansion. If the sea floor rises by sediment accumulation, then glaciers may not feel the effect of sea level rise. A submersible ROV and other techniques have been used to collect data from temperate and polar glaciers to compare sediment production and mass balance of their grounding-line systems. Temperature Alaskan valley glaciers flow at about 0.2--2 km/a and have high volumes of supraglacial, englacial and subglacial debris. However, most sediment contributed to the base of their tidewater cliffs comes from subglacial streams or squeezing out subglacialmore » sediment and pushing it with other marine sediment into a morainal bank. Blue Glacier, a thin, locally fed polar glacier in Antarctica, flows slowly and has minimal glacial debris. The grounding-line system at the tidewater cliff is a morainal bank that forms solely by pushing of marine sediment. An Antarctic polar outlet glacier, Mackay Glacier, terminating as a floating glacier-tongue, has similar volumes of basal debris to Alaskan temperature glaciers and flows at 250 m/a. However, no subglacial streams issued from Mackay's grounding line and all sedimentation was by rockfall and grainfall rainout from seawater undermelt of the tongue. A grounding-line wedge of glacimarine diamicton is deposited over subglacial (lodgement ) till. Although Antarctic grounding-line accumulation rates are three orders of magnitude smaller than Alaskan rates, both are capable of compensating for predicted rises in sea level by thermal heating from global warming.« less
Mechanisms of basal ice formation in polar glaciers: An evaluation of the apron entrainment model
NASA Astrophysics Data System (ADS)
Fitzsimons, Sean; Webb, Nicola; Mager, Sarah; MacDonell, Shelley; Lorrain, Regi; Samyn, Denis
2008-06-01
Previous studies of polar glaciers have argued that basal ice can form when these glaciers override and entrain ice marginal aprons that accumulate adjacent to steep ice cliffs. To test this idea, we have studied the morphology, structure, composition, and deformation of the apron and basal ice at the terminus of Victoria Upper Glacier in the McMurdo dry valleys, which are located on the western coast of the Ross Sea at 77°S in southern Victoria Land, Antarctica. Our results show that the apron has two structural elements: an inner element that consists of strongly foliated ice that has a steep up-glacier dip, and an outer element that lacks a consistent foliation and has a down-glacier, slope-parallel dip. Although strain measurements show that the entire apron is deforming, the inner element is characterized by high strain rates, whereas relatively low rates of strain characterize the outer part of the apron. Co-isotopic analyses of the ice, together with analysis of solute chemistry and sedimentary characteristics, show that the apron is compositionally different from the basal ice. Our observations show that aprons may become deformed and partially entrained by advancing glaciers. However, such an ice marginal process does not provide a satisfactory explanation for the origin of basal ice observed at the ice margin. Our interpretation of the origin of basal ice is that it is formed by subglacial processes, which are likely to include deformation and entrainment of subglacial permafrost.
Diverse landscapes beneath Pine Island Glacier influence ice flow.
Bingham, Robert G; Vaughan, David G; King, Edward C; Davies, Damon; Cornford, Stephen L; Smith, Andrew M; Arthern, Robert J; Brisbourne, Alex M; De Rydt, Jan; Graham, Alastair G C; Spagnolo, Matteo; Marsh, Oliver J; Shean, David E
2017-11-20
The retreating Pine Island Glacier (PIG), West Antarctica, presently contributes ~5-10% of global sea-level rise. PIG's retreat rate has increased in recent decades with associated thinning migrating upstream into tributaries feeding the main glacier trunk. To project future change requires modelling that includes robust parameterisation of basal traction, the resistance to ice flow at the bed. However, most ice-sheet models estimate basal traction from satellite-derived surface velocity, without a priori knowledge of the key processes from which it is derived, namely friction at the ice-bed interface and form drag, and the resistance to ice flow that arises as ice deforms to negotiate bed topography. Here, we present high-resolution maps, acquired using ice-penetrating radar, of the bed topography across parts of PIG. Contrary to lower-resolution data currently used for ice-sheet models, these data show a contrasting topography across the ice-bed interface. We show that these diverse subglacial landscapes have an impact on ice flow, and present a challenge for modelling ice-sheet evolution and projecting global sea-level rise from ice-sheet loss.
Application of Control Method on a West Antarctic Glacier
NASA Astrophysics Data System (ADS)
Schmeltz, M.; Rignot, E. J.; Macayeal, D. R.
2002-12-01
We use surface velocity inferred with Interferometric synthetic-aperture radar and a control method to estimate unknown basal characteristics of a fast-moving glacier in West Antarctica, Pine Island Glacier. Previous modelling experiments on Pine Island Glacier have shown that using a coupled ice-stream/ice-shelf flow model in a forward approach (trial and error method) we were able to reproduce fairly well the surface velocity. Some discrepancies remained, however, that are partly due to uncertainties in the thickness map and incertainty in our chosen basal stress distribution (because of the non-unicity of the solution). The control method allow us to take the basal stress (or basal friction, since they are related through the velocity), as an unknown parameter. Results given by the control method should provide better reliable inputs for further modelling experiments. We investigate the results' sensitivity to the initial value of the basal stress. The inferred ratio basal drag/driving stress seems to be always low upstream, 60 to 80 km upstream of the grounding line, as if the ice stream was behaving like an ice shelf, and also reveals the presence of a snake shape channel of low ratio basal drag/driving stress, surrounded by a higher ratio, in the main flow of increasing velocity, from 20 to 40 km upstream of the grounding line.
Glaciers of North America - Glaciers of Alaska
Molnia, Bruce F.
2008-01-01
Glaciers cover about 75,000 km2 of Alaska, about 5 percent of the State. The glaciers are situated on 11 mountain ranges, 1 large island, an island chain, and 1 archipelago and range in elevation from more than 6,000 m to below sea level. Alaska's glaciers extend geographically from the far southeast at lat 55 deg 19'N., long 130 deg 05'W., about 100 kilometers east of Ketchikan, to the far southwest at Kiska Island at lat 52 deg 05'N., long 177 deg 35'E., in the Aleutian Islands, and as far north as lat 69 deg 20'N., long 143 deg 45'W., in the Brooks Range. During the 'Little Ice Age', Alaska's glaciers expanded significantly. The total area and volume of glaciers in Alaska continue to decrease, as they have been doing since the 18th century. Of the 153 1:250,000-scale topographic maps that cover the State of Alaska, 63 sheets show glaciers. Although the number of extant glaciers has never been systematically counted and is thus unknown, the total probably is greater than 100,000. Only about 600 glaciers (about 1 percent) have been officially named by the U.S. Board on Geographic Names (BGN). There are about 60 active and former tidewater glaciers in Alaska. Within the glacierized mountain ranges of southeastern Alaska and western Canada, 205 glaciers (75 percent in Alaska) have a history of surging. In the same region, at least 53 present and 7 former large ice-dammed lakes have produced jokulhlaups (glacier-outburst floods). Ice-capped volcanoes on mainland Alaska and in the Aleutian Islands have a potential for jokulhlaups caused by subglacier volcanic and geothermal activity. Because of the size of the area covered by glaciers and the lack of large-scale maps of the glacierized areas, satellite imagery and other satellite remote-sensing data are the only practical means of monitoring regional changes in the area and volume of Alaska's glaciers in response to short- and long-term changes in the maritime and continental climates of the State. A review of the
NASA Astrophysics Data System (ADS)
McKnight, D. M.; Lyons, W. B.; Fountain, A. G.; Gooseff, M. N.; Doran, P. T.; Wall, D. H.; Virginia, R. A.; Priscu, J. C.; Adams, B.; Vesbach-Takacs, C.; Barrett, J. E.; Howkins, A.
2014-12-01
The McMurdo Dry Valleys of Antarctica is comprised of alpine and terminal glaciers, large expanses of patterned ground, and permanently ice-covered lakes in the valley floors, which are linked by glacial meltwater streams that flow during the austral summer. These valleys were first explored by Robert Scott and his party in 1903. In 1968 the New Zealand Antarctic Program began a gauging network on the Onyx River, a 32 km river in Wright Valley which is the longest river in Antarctica. As part of the McMurdo Dry Valleys Long-Term Ecological research project our research group has monitored meteorological conditions, glacial mass balance, lake level and streamflow in the adjacent Taylor Valley. The extent of liquid water throughout the landscape is strongly controlled by summer climate, and the availability of liquid water in turn is a limitation to the microscopic life that is present in the diverse habitats in the valleys. We have studied the responses of soil, lake, stream and cryoconite ecosystems through a sustained cooling period that has been driven by atmospheric changes associated with the ozone hole. In the past decade, this cooling period appears to have ceased and summer conditions have become more variable. Three warm sunny summers have occurred since 2001/02. These conditions have created weeks long "flood events" in the valleys, causing wet areas to emerge in the soils, thermokarsting in some stream channels and increases in lake level. These flood events can be considered as pulse events that drive an increase in ecosystem connectivity, changing rates of biogeochemical processes and the distribution of biota. Collectively the ecosystems of the McMurdo Dry Valleys are highly responsive to dynamic climatic influences associated with the ozone hole and global warming.
NASA Astrophysics Data System (ADS)
Buizert, Christo; Petrenko, Vasilii V.; Kavanaugh, Jeffrey L.; Cuffey, Kurt M.; Lifton, Nathaniel A.; Brook, Edward J.; Severinghaus, Jeffrey P.
2012-06-01
Radiocarbon measurements at ice margin sites and blue ice areas can potentially be used for ice dating, ablation rate estimates and paleoclimatic reconstructions. Part of the measured signal comes from in situ cosmogenic 14C production in ice, and this component must be well understood before useful information can be extracted from 14C data. We combine cosmic ray scaling and production estimates with a two-dimensional ice flow line model to study cosmogenic 14C production at Taylor Glacier, Antarctica. We find (1) that 14C production through thermal neutron capture by nitrogen in air bubbles is negligible; (2) that including ice flow patterns caused by basal topography can lead to a surface 14C activity that differs by up to 25% from the activity calculated using an ablation-only approximation, which is used in all prior work; and (3) that at high ablation margin sites, solar modulation of the cosmic ray flux may change the strength of the dominant spallogenic production by up to 10%. As part of this effort we model two-dimensional ice flow along the central flow line of Taylor Glacier. We present two methods for parameterizing vertical strain rates, and assess which method is more reliable for Taylor Glacier. Finally, we present a sensitivity study from which we conclude that uncertainties in published cosmogenic production rates are the largest source of potential error. The results presented here can inform ongoing and future 14C and ice flow studies at ice margin sites, including important paleoclimatic applications such as the reconstruction of paleoatmospheric 14C content of methane.
Large basal crevasses as a proxy for historic subglacial flooding events on Byrd Glacier
NASA Astrophysics Data System (ADS)
Child, S. F.; Stearns, L. A.; van der Veen, C. J.; Hamilton, G. S.
2016-12-01
Active networks of subglacial lakes have recently been found beneath the Antarctic Ice Sheet. On Byrd Glacier, East Antarctica, a subglacial lake outburst event in 2005/07 led to a short-lived glacier acceleration. Due to the sparse record of historical observations, it is unclear how frequently these outburst events occur, and the role they play in the dynamics of Antarctic outlet glaciers. Crevasses form when the tensile stress is greater than the fracture strength of ice. High extensional strain rates often exist at the grounding line where grounded ice begins to float. We hypothesize that the formation of anomalously large basal crevasses coincides with the higher strain rates observed during flooding events. In this study, we use the location of large basal crevasses ( 330 m tall), located along the floating portion of the Byrd Glacier flowline, to create a timeline of past flooding events. We first model crevasse formation to demonstrate that basal crevasses likely form at the grounding line. To do this, we use linear elastic fracture mechanics (LEFM) to estimate crevasse heights based on strain rates during known flood (300-350 m) and non-flood (100-150 m) time periods at Byrd Glacier's grounding line. Basal crevasse locations and heights are determined directly from radar echograms (2011/12 CReSIS radar data and 1974/75 SPRI NSF TUD radar data) along the Byrd Glacier flowline. We also use the locations of large surface depressions to infer the presence of basal crevasses. When crevasses penetrate a threshold proportion of the ice column, the overlying ice is no longer supported and a surface depression forms. We identify 22 large basal crevasses through these combined methods; the oldest crevasse likely formed 600 years ago. This research provides a framework of Antarctic subglacial flooding frequency and the effects that subglacial water drainage events have on outlet glacier dynamics.
Deglacial temperature history of West Antarctica.
Cuffey, Kurt M; Clow, Gary D; Steig, Eric J; Buizert, Christo; Fudge, T J; Koutnik, Michelle; Waddington, Edwin D; Alley, Richard B; Severinghaus, Jeffrey P
2016-12-13
The most recent glacial to interglacial transition constitutes a remarkable natural experiment for learning how Earth's climate responds to various forcings, including a rise in atmospheric CO 2 This transition has left a direct thermal remnant in the polar ice sheets, where the exceptional purity and continual accumulation of ice permit analyses not possible in other settings. For Antarctica, the deglacial warming has previously been constrained only by the water isotopic composition in ice cores, without an absolute thermometric assessment of the isotopes' sensitivity to temperature. To overcome this limitation, we measured temperatures in a deep borehole and analyzed them together with ice-core data to reconstruct the surface temperature history of West Antarctica. The deglacial warming was [Formula: see text]C, approximately two to three times the global average, in agreement with theoretical expectations for Antarctic amplification of planetary temperature changes. Consistent with evidence from glacier retreat in Southern Hemisphere mountain ranges, the Antarctic warming was mostly completed by 15 kyBP, several millennia earlier than in the Northern Hemisphere. These results constrain the role of variable oceanic heat transport between hemispheres during deglaciation and quantitatively bound the direct influence of global climate forcings on Antarctic temperature. Although climate models perform well on average in this context, some recent syntheses of deglacial climate history have underestimated Antarctic warming and the models with lowest sensitivity can be discounted.
Widespread surface meltwater drainage in Antarctica
NASA Astrophysics Data System (ADS)
Kingslake, J.; Ely, J.; Das, I.; Bell, R. E.
2016-12-01
Surface meltwater is thought to cause ice-shelf disintegration, which accelerates the contribution of ice sheets to sea-level rise. Antarctic surface melting is predicted to increase and trigger further ice-shelf disintegration during this century. These climate-change impacts could be modulated by an active hydrological network analogous to the one in operation in Greenland. Despite some observations of Antarctic surface and sub-surface hydrological systems, large-scale active surface drainage in Antarctica has rarely been studied. We use satellite imagery and aerial photography to reveal widespread active hydrology on the surface of the Antarctic Ice Sheet as far south as 85o and as high as 1800 m a.s.l., often near mountain peaks that protrude through the ice (nunataks) and relatively low-albedo `blue-ice areas'. Despite predominantly sub-zero regional air temperatures, as simulated by a regional climate model, Antarctic active drainage has persisted for decades, transporting water through surface streams and feeding vast melt ponds up to 80 km long. Drainage networks (the largest are over 100 km in length) form on flat ice shelves, steep outlet glaciers and ice-sheet flanks across the West and East Antarctica Ice Sheets. Motivated by the proximity of many drainage systems to low-albedo rock and blue-ice areas, we hypothesize a positive feedback between exposed-rock extent, BIA formation, melting and ice-sheet thinning. This feedback relies on drainage moving water long distances from areas near exposed rock, across the grounding line onto and across ice shelves - a process we observe, but had previously thought to be unlikely in Antarctica. This work highlights previously-overlooked processes, not captured by current regional-scale models, which may accelerate the retreat of the Antarctic Ice Sheet.
NASA Astrophysics Data System (ADS)
Rodríguez Cielos, Ricardo; Aguirre de Mata, Julián; Díez Galilea, Andrés; Álvarez Alonso, Marina; Rodríguez Cielos, Pedro; Navarro Valero, Francisco
2016-08-01
Various geomatic measurement techniques can be efficiently combined for surveying glacier fronts. Aerial photographs and satellite images can be used to determine the position of the glacier terminus. If the glacier front is easily accessible, the classic surveys using theodolite or total station, GNSS (Global Navigation Satellite System) techniques, laser-scanner or close-range photogrammetry are possible. When the accessibility to the glacier front is difficult or impossible, close-range photogrammetry proves to be useful, inexpensive and fast. In this paper, a methodology combining photogrammetric methods and other techniques is applied to determine the calving front position of Johnsons Glacier. Images taken in 2013 with an inexpensive nonmetric digital camera are georeferenced to a global coordinate system by measuring, using GNSS techniques, support points in accessible areas close to the glacier front, from which control points in inaccessible points on the glacier surface near its calving front are determined with theodolite using the direct intersection method. The front position changes of Johnsons Glacier during the period 1957-2013, as well as those of the land-terminating fronts of Argentina, Las Palmas and Sally Rocks lobes of Hurd glacier, are determined from different geomatic techniques such as surface-based GNSS measurements, aerial photogrammetry and satellite optical imagery. This provides a set of frontal positions useful, e.g., for glacier dynamics modeling and mass balance studies.Link to the data repository: https://doi.pangaea.de/10.1594/PANGAEA.845379.
NASA Astrophysics Data System (ADS)
Hauber, E.; Sassenroth, C.; De Vera, J.-P.; Schmitz, N.; Reiss, D.; Hiesinger, H.; Johnsson, A.
2017-09-01
Most studies using Antarctica as a Mars analogue have focused on the McMurdo Dry Valleys, which are among the coldest and driest places on Earth. However, other ice-free areas in continental Antarctica also display landforms that can inform the study of the possible geomorphic impact of water in a polar desert. Here we present a new analogue site in the interior of the Transantarctic Mountains in Northern Victoria Land. Gullies show unambiguous evidence for debris flows, and water tracks act as shallow subsurface pathways of water on top of the permafrost tale. Both processes are driven by meltwater from glacier ice and snow in an environ-ment which never experiences rainfall and in which the air temperatures probably never exceed 0°C.
Williams, Richard S.; Ferrigno, Jane G.
2010-01-01
This chapter is the ninth to be released in U.S. Geological Survey Professional Paper 1386, Satellite Image Atlas of Glaciers of the World, a series of 11 chapters. In each of the geographic area chapters, remotely sensed images, primarily from the Landsat 1, 2, and 3 series of spacecraft, are used to analyze the specific glacierized region of our planet under consideration and to monitor glacier changes. Landsat images, acquired primarily during the middle to late 1970s and early 1980s, were used by an international team of glaciologists and other scientists to study various geographic regions and (or) to discuss related glaciological topics. In each glacierized geographic region, the present areal distribution of glaciers is compared, wherever possible, with historical information about their past extent. The atlas provides an accurate regional inventory of the areal extent of glacier ice on our planet during the 1970s as part of a growing international scientific effort to measure global environmental change on the Earth?s surface. The chapter is divided into seven geographic parts and one topical part: Glaciers of the Former Soviet Union (F-1), Glaciers of China (F-2), Glaciers of Afghanistan (F?3), Glaciers of Pakistan (F-4), Glaciers of India (F-5), Glaciers of Nepal (F?6), Glaciers of Bhutan (F-7), and the Paleoenvironmental Record Preserved in Middle-Latitude, High-Mountain Glaciers (F-8). Each geographic section describes the glacier extent during the 1970s and 1980s, the benchmark time period (1972-1981) of this volume, but has been updated to include more recent information. Glaciers of the Former Soviet Union are located in the Russian Arctic and various mountain ranges of Russia and the Republics of Georgia, Kyrgyzstan, Tajikistan, and Kazakstun. The Glacier Inventory of the USSR and the World Atlas of Ice and Snow Resources recorded a total of 28,881 glaciers covering an area of 78,938 square kilometers (km2). China includes many of the mountain-glacier
Radar Sounding Investigations at the Boundary of Thwaites and Pine Island Glaciers
NASA Astrophysics Data System (ADS)
Schroeder, Dustin; Hilger, Andrew; Paden, John; Corr, Hugh; Blankenship, Donald
2017-04-01
Recent observational and modeling studies have shown that the behavior and stability of both Thwaites Glacier and Pine Island Glacier in the Amundsen Sea Embayment of the West Antarctic Ice Sheet are modulated by a combination of ocean forcing, bed topography, and basal conditions. In terms of future deglaciation scenarios and their ultimate sea level contribution, the configuration, evolution, and ice-dynamical impact of basal conditions in the boundary region between Thwaites Glacier and Pine Island Glacier stand to play a particularly significant role. This region not only separates the two most rapidly changing glaciers in Antarctica, but - as a result - also has the potential to be the site of dynamic and destabilizing interactions between them as either glacier retreats. Despite this potential, little research has focused on characterizing the basal condition context for modeling current and potential interaction across this boundary. One reason for this is the fact that (despite relatively dense airborne radar sounding coverage in the area) the data in this region was collected by three different radar systems and much of the Thwaites / Pine Island boundary lies at the boundary of these data sets. These include the 2004 survey of Thwaites Glacier by the UTIG HiCARS system, the 2004 campaign over Pine Island Glacier by the BAS PASIN system, and the 2011 - 2014 surveys of the Amundsen Sea Embayment by the CReSIS MCoRDS system. This has resulted in distinct sets of observations, collected across a range of frequencies, bandwidths, coherency, and observing geometries. To date, these data have also been processed by different institutions with software, algorithms and approaches that were specifically developed for each radar system. While each produce consistent ice thickness measurements, the character of their bed echoes have yet to be exploited. Here, we present initial results from processing, analyzing, and synthesizing these three distinct data sets to
, The Environmental Law Institute, Washington, D.C. (2014) Featured Publication Curtis, Taylor L., Aaron . Golden, CO: National Renewable Energy Laboratory. NREL/TP-6A20-70098. Levine, Aaron. Taylor L. Curtis . Golden, CO: National Renewable Energy Laboratory: NREL/TP-6A20-70121. Kevin B. Jones, Curtis, Taylor L
The health of glaciers: Recent changes in glacier regime
Meier, M.F.; Dyurgerov, M.B.; McCabe, G.J.
2003-01-01
Glacier wastage has been pervasive during the last century; small glaciers and those in marginal environments are disappearing, large mid-latitude glaciers are shrinking slightly, and arctic glaciers are warming. Net mass balances during the last 40 years are predominately negative and both winter and summer balances (accumulation and ablation) and mass turnover are increasing, especially after 1988. Two principal components of winter balance time-series explain about 50% of the variability in the data. Glacier winter balances in north and central Europe correlate with the Arctic Oscillation, and glaciers in western North America correlate with the Southern Oscillation and Northern Hemisphere air temperature. The degree of synchronization for distant glaciers relates to changes in time of atmospheric circulation patterns as well as differing dynamic responses.
NASA Astrophysics Data System (ADS)
Hambrey, Michael; Alean, Jürg
2004-12-01
Glaciers are among the most beautiful natural wonders on Earth, as well as the least known and understood, for most of us. Michael Hambrey describes how glaciers grow and decay, move and influence human civilization. Currently covering a tenth of the Earth's surface, glacier ice has shaped the landscape over millions of years by scouring away rocks and transporting and depositing debris far from its source. Glacier meltwater drives turbines and irrigates deserts, and yields mineral-rich soils as well as a wealth of valuable sand and gravel. However, glaciers also threaten human property and life. Our future is indirectly connected with the fate of glaciers and their influence on global climate and sea level. Including over 200 stunning photographs, the book takes the reader from the High-Arctic through North America, Europe, Asia, Africa, New Zealand and South America to the Antarctic. Michael Hambrey is Director of the Centre for Glaciology at the University of Wales, Aberystwyth. A past recipient of the Polar Medal, he was also given the Earth Science Editors' Outstanding Publication Award for the first edition of Glaciers (Cambridge, 1995). Hambrey is also the author of Glacial Environments (British Columbia, 1994). JÜrg Alean is Professor of Geography at the Kantonsschule ZÜrcher Unterland in BÜlach, Switzerland.
Williams, Richard S.; Ferrigno, Jane G.
1993-01-01
ALPS: AUSTRIAN: An overview is provided on the occurrence of the glaciers in the Eastern Alps of Austria and on the climatic conditions in this area, Historical documents on the glaciers have been available since the Middle Ages. Special glaciological observations and topographic surveys of individual glaciers were initiated as early as 1846. Recent data in an inventory based on aerial photographs taken in 1969 show 925 glaciers in the Austrian Alps with a total area of 542 square kilometers. Present research topics include studies of mass and energy balance, relations of glaciers and climate, physical glaciology, a complete inventory of the glaciers, and testing of remote sensing methods. The location of the glacier areas is shown on Landsat multispectral scanner images; the improved capabilities of the Landsat thematic mapper are illustrated with an example from the Oztaler Alpen group. ALPS: SWISS: According to a glacier inventory published in 1976, which is based on aerial photography of 1973, there are 1,828 glacier units in the Swiss Alps that cover a total area of 1fl42 square kilometers. The Rhonegletscher, currently the ninth largest in the country, was one of the first to be studied in detail. Its surface has been surveyed repeatedly; velocity profiles were measured, and the fluctuations of its terminus were mapped and recorded from 1874 to 1914. Recent research on the glacier has included climatological, hydrological, and massbalance studies. Glaciological research has been conducted on various other glaciers in Switzerland concerning glacier hydrology, glacier hazards, fluctuations of glacier termini, ice mechanics, ice cores, and mass balance. Good maps are available showing the extent of glaciers from the latter decades of the 19th century. More recently, the entire country has been mapped at scales of 1:25,000, 1:50,000, 1:100,000, 1:200,000, and 1:500,000. The 1:25,000-scale series very accurately represents the glaciers as well as locates
Satellite image atlas of glaciers of the world
Williams, Richard S.; Ferrigno, Jane G.; Williams, Richard S.; Ferrigno, Jane G.
1988-01-01
U.S. Geological Survey Professional Paper 1386, Satellite Image Atlas of Glaciers of the World, contains 11 chapters designated by the letters A through K. Chapter A provides a comprehensive, yet concise, review of the "State of the Earth's Cryosphere at the Beginning of the 21st Century: Glaciers, Global Snow Cover, Floating Ice, and Permafrost and Periglacial Environments," and a "Map/Poster of the Earth's Dynamic Cryosphere," and a set of eight "Supplemental Cryosphere Notes" about the Earth's Dynamic Cryosphere and the Earth System. The next 10 chapters, B through K, are arranged geographically and present glaciological information from Landsat and other sources of historic and modern data on each of the geographic areas. Chapter B covers Antarctica; Chapter C, Greenland; Chapter D, Iceland; Chapter E, Continental Europe (except for the European part of the former Soviet Union), including the Alps, the Pyrenees, Norway, Sweden, Svalbard (Norway), and Jan Mayen (Norway); Chapter F, Asia, including the European part of the former Soviet Union, China, Afghanistan, Pakistan, India, Nepal, and Bhutan; Chapter G, Turkey, Iran, and Africa; Chapter H, Irian Jaya (Indonesia) and New Zealand; Chapter I, South America; Chapter J, North America (excluding Alaska); and Chapter K, Alaska. Chapters A–D each include map plates.
Deglacial temperature history of West Antarctica
Cuffey, Kurt M.; Clow, Gary D.; Steig, Eric J.; Buizert, Christo; Fudge, T.J.; Koutnik, Michelle; Waddington, Edwin D.; Alley, Richard B.; Severinghaus, Jeffrey P.
2016-01-01
The most recent glacial to interglacial transition constitutes a remarkable natural experiment for learning how Earth’s climate responds to various forcings, including a rise in atmospheric CO2. This transition has left a direct thermal remnant in the polar ice sheets, where the exceptional purity and continual accumulation of ice permit analyses not possible in other settings. For Antarctica, the deglacial warming has previously been constrained only by the water isotopic composition in ice cores, without an absolute thermometric assessment of the isotopes’ sensitivity to temperature. To overcome this limitation, we measured temperatures in a deep borehole and analyzed them together with ice-core data to reconstruct the surface temperature history of West Antarctica. The deglacial warming was 11.3±1.8∘">11.3±1.8∘11.3±1.8∘C, approximately two to three times the global average, in agreement with theoretical expectations for Antarctic amplification of planetary temperature changes. Consistent with evidence from glacier retreat in Southern Hemisphere mountain ranges, the Antarctic warming was mostly completed by 15 kyBP, several millennia earlier than in the Northern Hemisphere. These results constrain the role of variable oceanic heat transport between hemispheres during deglaciation and quantitatively bound the direct influence of global climate forcings on Antarctic temperature. Although climate models perform well on average in this context, some recent syntheses of deglacial climate history have underestimated Antarctic warming and the models with lowest sensitivity can be discounted.
Deglacial temperature history of West Antarctica
Clow, Gary D.; Steig, Eric J.; Buizert, Christo; Fudge, T. J.; Koutnik, Michelle; Waddington, Edwin D.; Alley, Richard B.
2016-01-01
The most recent glacial to interglacial transition constitutes a remarkable natural experiment for learning how Earth’s climate responds to various forcings, including a rise in atmospheric CO2. This transition has left a direct thermal remnant in the polar ice sheets, where the exceptional purity and continual accumulation of ice permit analyses not possible in other settings. For Antarctica, the deglacial warming has previously been constrained only by the water isotopic composition in ice cores, without an absolute thermometric assessment of the isotopes’ sensitivity to temperature. To overcome this limitation, we measured temperatures in a deep borehole and analyzed them together with ice-core data to reconstruct the surface temperature history of West Antarctica. The deglacial warming was 11.3±1.8∘C, approximately two to three times the global average, in agreement with theoretical expectations for Antarctic amplification of planetary temperature changes. Consistent with evidence from glacier retreat in Southern Hemisphere mountain ranges, the Antarctic warming was mostly completed by 15 kyBP, several millennia earlier than in the Northern Hemisphere. These results constrain the role of variable oceanic heat transport between hemispheres during deglaciation and quantitatively bound the direct influence of global climate forcings on Antarctic temperature. Although climate models perform well on average in this context, some recent syntheses of deglacial climate history have underestimated Antarctic warming and the models with lowest sensitivity can be discounted. PMID:27911783
The Microseismicity of Glacier Sliding
NASA Astrophysics Data System (ADS)
Walter, Fabian; Röösli, Claudia; Kissling, Edi
2017-04-01
Our understanding of glacier and ice sheet basal motion remains incomplete. The past decades have witnessed a shift away from initially proposed hard bed theories towards soft, till-laden beds, which deform and thus participate in basal motion. The theoretical treatment of deformable beds is subject to debate, yet our capability to predict ice sheet flow and ultimately sea level rise is contingent upon correct parameterization of basal motion (Ritz et al., 2015). Both hard and soft bed theories neglect frictional sliding across distinct basal fault planes and elastic deformation in response to sudden dislocation. Over recent years, this view has been repeatedly challenged as more and more studies report seismogenic faulting associated with basal sliding. For instance, large parts of the Whillans Ice Stream at Antarctica's Siple Coast move nearly exclusively during sudden sliding episodes (Wiens et al., 2008). This "stick-slip motion" is difficult to explain with traditional glacier sliding theories but more analogous to earthquake dislocation on tectonic faults. Although the Whillans Ice Stream motion may be an extreme example, there exists evidence for much smaller microseismic stick-slip events beneath the Greenland Ice Sheet and non-polar glaciers (Podolskiy and Walter, 2016). This raises the question how relevant and widespread the stick-slip phenomenon is and if it is necessary to include it into ice sheet models. Here we discuss recent seismic deployments, which focused on detection of stick-slip events beneath the Greenland Ice Sheet and European Alpine Glaciers. For all deployments, a considerable challenge lies in detection of stick-slip seismograms in the presence of a dominant background seismicity associated with surface crevassing. Nevertheless, automatic search algorithms and waveform characteristics provide important insights into temporal variation of stick-slip activity as well as information about fault plane geometry and co-seismic sliding
NASA Astrophysics Data System (ADS)
Lammers, Richard; Hock, Regine; Prusevich, Alexander; Bliss, Andrew; Radic, Valentina; Glidden, Stanley; Grogan, Danielle; Frolking, Steve
2014-05-01
Glacier and small ice cap melt water contributions to the global hydrologic cycle are an important component of human water supply and for sea level rise. This melt water is used in many arid and semi-arid parts of the world for direct human consumption as well as indirect consumption by irrigation for crops, serving as frozen reservoirs of water that supplement runoff during warm and dry periods of summer when it is needed the most. Additionally, this melt water reaching the oceans represents a direct input to sea level rise and therefore accurate estimates of this contribution have profound economic and geopolitical implications. It has been demonstrated that, on the scale of glacierized river catchments, land surface hydrological models can successfully simulate glacier contribution to streamflow. However, at global scales, the implementation of glacier melt in hydrological models has been rudimentary or non-existent. In this study, a global glacier mass balance model is coupled with the University of New Hampshire Water Balance/Transport Model (WBM) to assess recent and projected future glacier contributions to the hydrological cycle over the global land surface (excluding the ice sheets of Greenland and Antarctica). For instance, results of WBM simulations indicate that seasonal glacier melt water in many arid climate watersheds comprises 40 % or more of their discharge. Implicitly coupled glacier and WBM models compute monthly glacier mass changes and resulting runoff at the glacier terminus for each individual glacier from the globally complete Randolph Glacier Inventory including over 200 000 glaciers. The time series of glacier runoff is aggregated over each hydrological modeling unit and delivered to the hydrological model for routing downstream and mixing with non-glacial contribution of runoff to each drainage basin outlet. WBM tracks and uses glacial and non-glacial components of the in-stream water for filling reservoirs, transfers of water between
2. HORSESHOE CURVE IN GLACIER POINT ROAD NEAR GLACIER POINT. ...
2. HORSESHOE CURVE IN GLACIER POINT ROAD NEAR GLACIER POINT. HALF DOME AT CENTER REAR. LOOKING NNE. GIS N-37 43 44.3 / W-119 34 14.1 - Glacier Point Road, Between Chinquapin Flat & Glacier Point, Yosemite Village, Mariposa County, CA
Spatial and Temporal Dynamics of Carbon Fluxes in Glacial Meltwater Streams, Antarctica
NASA Astrophysics Data System (ADS)
Torrens, C.; Lyons, W. B.; McKnight, D. M.; Welch, K. A.; Gooseff, M. N.
2017-12-01
In the McMurdo Dry Valleys [MDV], Antarctica, glacial meltwater streams are the primary biogeochemical connectors linking glaciers, soils and lakes. These streams control the supply of nutrients and carbon to their terminal lakes, yet little is known about the magnitude, timing or distribution of these fluxes. The McMurdo Long Term Ecological Research project [MCM LTER] has collected over 20 years of sample data on dissolved organic and inorganic carbon in Taylor Valley streamwater; this is the first spatial and temporal analysis of this data. MDV streams are characterized by strong diel pulses in streamflow, specific electrical conductance, and temperature. Unlike temperate stream systems, there is no terrestrial vegetation, lateral overland flow or deep groundwater connection in MDV streams. As a result, the organic carbon is autochthonous, originating from stream microbial mats. Inorganic carbon is primarily bicarbonate; its source is hyporheic zone weathering. The carbonate system is in atmospheric equilibrium, reflecting the wide and shallow stream channels. Preliminary data show that the DOC flux varies with streamflow and is greater on the rising limb of the diel flow pulse. This pattern is more distinct in longer streams. DIC data does not show the same pattern, although the response may be blurred by a lag in hyporheic response to flood pulses and the lack of time-series data for alkalinity. Stream flood pulse dynamics control carbon loading to MDV lakes. As the climate changes, so will the timing and magnitude of diel flood pulses. This is likely to increase carbon loading to the Dry Valley lakes, altering the ecosystem carbon balance. This study increases our understanding of past and current patterns of carbon fluxes from streams to lakes; understanding past patterns will improve predictions of future changes.
HORSESHOE CURVE IN GLACIER POINT ROAD NEAR GLACIER POINT. HALF ...
HORSESHOE CURVE IN GLACIER POINT ROAD NEAR GLACIER POINT. HALF DOME AT CENTER REAR. SAME VIEW AT CA-157-2. LOOKING NNE. GIS: N-37' 43 44.3 / W-119 34 14.1 - Glacier Point Road, Between Chinquapin Flat & Glacier Point, Yosemite Village, Mariposa County, CA
Airborne Surveys Conducted by SOAR for Geologic Studies in Antarctica, 1998-2001
NASA Astrophysics Data System (ADS)
Holt, J. W.
2001-05-01
During the three austral summers that occurred in the period October, 1998 to February, 2001, the Support Office for Aerogeophysical Research (SOAR) of the University of Texas Institute for Geophysics (UTIG) conducted aerogeophysical campaigns for eight separate projects in both East and West Antarctica. Measurements were made of magnetic and gravitational fields, surface elevation and sub-glacial bed elevation. Surveys were accomplished with a modified deHavilland Twin Otter aircraft equipped with a towed magnetometer, gyro-stabilized gravity meter, laser altimeter, ice-penetrating radar, and carrier-phase GPS receivers. Diurnal variations of the geomagnetic field were measured at nearby base stations where static GPS data were collected for differential aircraft positioning. Four of the experiments performed were designed to address fundamental geologic questions when combined with ground-based studies and/or geophysical modeling in studies by multiple investigators at several institutions. In western Marie Byrd Land (MBL), a 330 x 440 km survey (line spacing ranged from 5.3 x 5.3 km to 10.6 x 10.6 km) was flown in order to understand the tectonic and geologic devolpment of the boundary between the Ross Sea Rift and the MBL volcanic province. A series of corridors were flown across the Transantarctic Mountains (TAM) in order to study extreme and variable rift flank uplift. These consist of a 100 x 810 km corridor extending from Ice Stream B across the Watson Escarpment and into central East Antarctica beyond South Pole, a 100 x 1170 km corridor from Ross Island to Dome C, and a single line across the TAM near Robb Glacier (line spacing for corridors was 10 km with 30 km tie-lines). Three parallel lines, 1300 km long and separated by 5 km, were flown from near Taylor Dome to AGO4, complementing a passive seismic array planned in order to investigate the crust and upper mantle structure beneath the East-West Antarctic boundary. Another survey was performed in order
Afghanistan Glacier Diminution
NASA Astrophysics Data System (ADS)
Shroder, J. F.; Bishop, M.; Haritashya, U.; Olsenholler, J.
2008-12-01
Glaciers in Afghanistan represent a late summer - early fall source of melt water for late season crop irrigation in a chronically drought-torn region. Precise river discharge figures associated with glacierized drainage basins are generally unavailable because of the destruction of hydrological gauging stations built in pre-war times although historic discharge data and prior (1960s) mapped glacier regions offer some analytical possibilities. The best satellite data sets for glacier-change detection are declassified Cornona and Keyhole satellite data sets, standard Landsat sources, and new ASTER images assessed in our GLIMS (Global Land Ice Measurements from Space) Regional Center for Southwest Asia (Afghanistan and Pakistan). The new hyperspectral remote sensing survey of Afghanistan completed by the US Geological Survey and the Afghanistan Ministry of Mines offers potential for future detailed assessments. Long-term climate change in southwest Asia has decreased precipitation for millennia so that glaciers, rivers and lakes have all declined from prehistoric and historic highs. As many glaciers declined in ice volume, they increased in debris cover until they were entirely debris-covered or became rock glaciers, and the ice was protected thereby from direct solar radiation, to presumably reduce ablation rates. We have made a preliminary assessment of glacier location and extent for the country, with selected, more-detailed, higher-resolution studies underway. In the Great Pamir of the Wakhan Corridor where the largest glaciers occur, we assessed fluctuations of a randomly selected 30 glaciers from 1976 to 2003. Results indicate that 28 glacier-terminus positions have retreated, and the largest average retreat rate was 36 m/yr. High albedo, non-vegetated glacier forefields formed prior to 1976, and geomorphological evidence shows apparent glacier-surface downwasting after 1976. Climatic conditions and glacier retreat have resulted in disconnection of tributary
Topographic context of glaciers and perennial snowfields, Glacier National Park, Montana
NASA Astrophysics Data System (ADS)
Allen, Thomas R.
1998-01-01
Equilibrium-line altitudes (ELAs) of modem glaciers in the northern Rocky Mountains are known to correspond with regional climate, but strong subregional gradients such as across the Continental Divide in Glacier National Park, Montana, also exert topoclimatic influences on the ELA. This study analyzed the relationships between glacier and snowfield morphology, ELA, and surrounding topography. Glaciers and perennial snowfields were mapped using multitemporal satellite data from the Landsat Thematic Mapper and aerial photography within an integrated Geographic Information System (GIS). Relationships between glacier morphology and ELA were investigated using discriminant analysis. Four morphological categories of perennial snow and ice patches were identified: cirque glacier, niche glacier, ice cap, and snowfield. ELA was derived from overlaid glacier boundaries and Digital Elevation Models (DEMs) within the GIs. DEMs provided topographic variables and models of solar radiation and wind exposure/shelteredness. Regression analysis showed the effects of exposure; on snow accumulation, the strong influence of local topography through upslope zone morphology such as cirque backwalls, and the tendency for glaciers with high ELAs to exhibit compactness in morphology. Results highlight the relatively compact shape and larger area of glaciers adjacent to the Continental Divide. Discriminant analysis correctly predicted the type of glacier morphology in more than half the observations using factored variables of glacier shape, elevation range, and upslope area.
2003-05-01
Malaspina Glacier in southeastern Alaska is considered the classic example of a piedmont glacier. Piedmont glaciers occur where valley glaciers exit a mountain range onto broad lowlands, are no longer laterally confined, and spread to become wide lobes.
How do glacier inventory data aid global glacier assessments and projections?
NASA Astrophysics Data System (ADS)
Hock, R.
2017-12-01
Large-scale glacier modeling relies heavily on datasets that are collected by many individuals across the globe, but managed and maintained in a coordinated fashion by international data centers. The Global Terrestrial Network for Glaciers (GTN-G) provides the framework for coordinating and making available a suite of data sets such as the Randolph Glacier Inventory (RGI), the Glacier Thickness Dataset or the World Glacier Inventory (WGI). These datasets have greatly increased our ability to assess global-scale glacier mass changes. These data have also been vital for projecting the glacier mass changes of all mountain glaciers in the world outside the Greenland and Antarctic ice sheet, a total >200,000 glaciers covering an area of more than 700,000 km2. Using forcing from 8 to 15 GCMs and 4 different emission scenarios, global-scale glacier evolution models project multi-model mean net mass losses of all glaciers between 7 cm and 24 cm sea-level equivalent by the end of the 21st century. Projected mass losses vary greatly depending on the choice of the forcing climate and emission scenario. Insufficiently constrained model parameters likely are an important reason for large differences found among these studies even when forced by the same emission scenario, especially on regional scales.
Listening to Glaciers: Passive hydroacoustics near marine-terminating glaciers
Pettit, E.C.; Nystuen, J.A.; O'Neel, Shad
2012-01-01
The catastrophic breakup of the Larsen B Ice Shelf in the Weddell Sea in 2002 paints a vivid portrait of the effects of glacier-climate interactions. This event, along with other unexpected episodes of rapid mass loss from marine-terminating glaciers (i.e., tidewater glaciers, outlet glaciers, ice streams, ice shelves) sparked intensified study of the boundaries where marine-terminating glaciers interact with the ocean. These dynamic and dangerous boundaries require creative methods of observation and measurement. Toward this effort, we take advantage of the exceptional sound-propagating properties of seawater to record and interpret sounds generated at these glacial ice-ocean boundaries from distances safe for instrument deployment and operation.
NASA Astrophysics Data System (ADS)
Heid, T.; Kääb, A.
2011-12-01
Automatic matching of images from two different times is a method that is often used to derive glacier surface velocity. Nearly global repeat coverage of the Earth's surface by optical satellite sensors now opens the possibility for global-scale mapping and monitoring of glacier flow with a number of applications in, for example, glacier physics, glacier-related climate change and impact assessment, and glacier hazard management. The purpose of this study is to compare and evaluate different existing image matching methods for glacier flow determination over large scales. The study compares six different matching methods: normalized cross-correlation (NCC), the phase correlation algorithm used in the COSI-Corr software, and four other Fourier methods with different normalizations. We compare the methods over five regions of the world with different representative glacier characteristics: Karakoram, the European Alps, Alaska, Pine Island (Antarctica) and southwest Greenland. Landsat images are chosen for matching because they expand back to 1972, they cover large areas, and at the same time their spatial resolution is as good as 15 m for images after 1999 (ETM+ pan). Cross-correlation on orientation images (CCF-O) outperforms the three similar Fourier methods, both in areas with high and low visual contrast. NCC experiences problems in areas with low visual contrast, areas with thin clouds or changing snow conditions between the images. CCF-O has problems on narrow outlet glaciers where small window sizes (about 16 pixels by 16 pixels or smaller) are needed, and it also obtains fewer correct matches than COSI-Corr in areas with low visual contrast. COSI-Corr has problems on narrow outlet glaciers and it obtains fewer correct matches compared to CCF-O when thin clouds cover the surface, or if one of the images contains snow dunes. In total, we consider CCF-O and COSI-Corr to be the two most robust matching methods for global-scale mapping and monitoring of glacier
NASA Astrophysics Data System (ADS)
Fountain, Andrew
The term "tropical glacier" calls to mind balmy nights and palm trees on one hand and cold, blue ice on the other. Certainly author Gabriel Garcia Marqez exploited this contrast in One Hundred Years of Solitude. We know that tropical fish live in warm, Sun-kissed waters and tropical plants provide lush, dense foliage populated by colorful tropical birds. So how do tropical glaciers fit into this scene? Like glaciers everywhere, tropical glaciers form where mass accumulation—usually winter snow—exceeds mass loss, which is generally summer melt. Thus, tropical glaciers exist at high elevations where precipitation can occur as snowfall exceeds melt and sublimation losses, such as the Rwenzori Mountains in east Africa and the Maoke Range of Irian Jaya.
NASA Astrophysics Data System (ADS)
Janke, Jason R.; Ng, Sam; Bellisario, Antonio
2017-11-01
An inventory of firn fields, glaciers, debris-covered glaciers, and rock glaciers was conducted in the Aconcagua River Basin of the semiarid Andes of central Chile. A total of 916 landforms were identified, of which rock glaciers were the most abundant (669) and occupied the most total area. Glaciers and debris-covered glaciers were less numerous, but were about five times larger in comparison. The total area occupied by glaciers and debris-covered glaciers was roughly equivalent to the total area of rock glaciers. Debris-covered glaciers and rock glaciers were subcategorized into six ice-content classes based on interpretation of surface morphology with high-resolution satellite imagery. Over 50% of rock glaciers fell within a transitional stage; 85% of debris-covered glaciers were either fully covered or buried. Most landforms occupied elevations between 3500 and 4500 m. Glaciers and firn occurred at higher elevations compared to rock glaciers and debris-covered glaciers. Rock glaciers had a greater frequency in the northern part of the study area where arid climate conditions exist. Firn and glaciers were oriented south, debris-covered glaciers west, and rock glaciers southwest. An analysis of water contribution of each landform in the upper Andes of the Aconcagua River Basin was conducted using formulas that associate the size of the landforms to estimates of water stored. Minimum and maximum water storage was calculated based on a range of debris to ice content ratios for debris-covered glaciers and rock glaciers. In the Aconcagua River Basin, rock glaciers accounted for 48 to 64% of the water stored within the landforms analyzed; glaciers accounted for 15 to 25%; debris-covered glaciers were estimated at 15 to 19%; firn fields contained only about 5 to 8% of the water stored. Expansion of agriculture, prolonged drought, and removal of ice-rich landforms for mining have put additional pressure on already scarce water resources. To develop long
Suppressing Taylor vortices in a Taylor-Couette flow system with free surface
NASA Astrophysics Data System (ADS)
Bouabdallah, A.; Oualli, H.; Mekadem, M.; Gad-El-Hak, M.
2016-11-01
Taylor-Couette flows have been extensively investigated due to their many industrial applications, such as catalytic reactors, electrochemistry, photochemistry, biochemistry, and polymerization. Mass transfer applications include extraction, tangential filtration, crystallization, and dialysis. A 3D study is carried out to simulate a Taylor-Couette flow with a rotating and pulsating inner cylinder. We utilize FLUENT to simulate the incompressible flow with a free surface. The study reveals that flow structuring is initiated with the development of an Ekman vortex at low Taylor number, Ta = 0 . 01 . For all encountered flow regimes, the Taylor vortices are systematically inhibited by the pulsatile motion of the inner cylinder. A spectral analysis shows that this pulsatile motion causes a rapid decay of the free surface oscillations, from a periodic wavy movement to a chaotic one, then to a fully turbulent motion. This degenerative free surface behavior is interpreted as the underlying mechanism responsible for the inhibition of the Taylor vortices.
NASA Astrophysics Data System (ADS)
Hilger, A. M.; Schroeder, D. M.; Corr, H. F. J.; Blankenship, D. D.; Paden, J. D.
2017-12-01
Recent observational studies and models have shown that ocean forcing, bed topography, and basal conditions are major controls of the behavior of the Amundsen Sea Embayment of the West Antarctic Ice Sheet. This region contains Thwaites Glacier and Pine Island Glacier, the two most rapidly changing glaciers in Antarctica. Because they are adjacent, interactions between these two glaciers could potentially cause further destabilization as either glacier retreats. Accordingly, it is important to understand the basal conditions on the Thwaites-Pine Island boundary in order to accurately model the present and future behavior of these glaciers. Previous airborne geophysical surveys in this area have provided dense radar sounding coverage using multiple radar sounding systems, including the UTIG HiCARS system and the BAS PASIN system used in the 2004 AGASEA survey. Because the boundary region between Thwaites and Pine Island Glacier is at the respective boundaries of the UTIG and BAS surveys, accurate characterization of the basal conditions requires a synthesis of the data produced by the BAS and HiCARS systems. To this end, we present estimates of bed reflectivity spanning both glacier catchments. These estimates were produced using empirically determined attenuation rates. To improve the consistency of these attenuation rates, we fit across a two-dimensional area, rather than a one-dimensional line as in previous work. These estimates also include cross-calibration to account for the radar sounding systems' differing power and center frequency. This will provide the first cross-survey map of basal reflectivity spanning the entire Amundsen Sea Embayment.
Ultra-low rare earth element content in accreted ice from sub-glacial Lake Vostok, Antarctica
NASA Astrophysics Data System (ADS)
Gabrielli, Paolo; Planchon, Frederic; Barbante, Carlo; Boutron, Claude F.; Petit, Jean Robert; Bulat, Sergey; Hong, Sungmin; Cozzi, Giulio; Cescon, Paolo
2009-10-01
This paper reports the first rare earth element (REE) concentrations in accreted ice refrozen from sub-glacial Lake Vostok (East Antarctica). REE were determined in various sections of the Vostok ice core in order to geochemically characterize its impurities. Samples were obtained from accreted ice and, for comparison, from the upper glacier ice of atmospheric origin (undisturbed, disturbed and glacial flour ice). REE concentrations ranged between 0.8-56 pg g -1 for Ce and 0.0035-0.24 pg g -1 for Lu in glacier ice, and between <0.1-24 pg g -1 for Ce and <0.0004-0.02 pg g -1 for Lu in accreted ice. Interestingly, the REE concentrations in the upper accreted ice (AC 1; characterized by visible aggregates containing a mixture of very fine terrigenous particles) and in the deeper accreted ice (AC 2; characterized by transparent ice) are lower than those in fresh water and seawater, respectively. We suggest that such ultra-low concentrations are unlikely to be representative of the real REE content in Lake Vostok, but instead may reflect phase exclusion processes occurring at the ice/water interface during refreezing. In particular, the uneven spatial distribution (on the order of a few cm) and the large range of REE concentrations observed in AC 1 are consistent with the occurrence/absence of the aggregates in adjacent ice, and point to the presence of solid-phase concentration/exclusion processes occurring within separate pockets of frazil ice during AC 1 formation. Interestingly, if the LREE enrichment found in AC 1 was not produced by chemical fractionation occurring in Lake Vostok water, this may reflect a contribution of bedrock material, possibly in combination with aeolian dust released into the lake by melting of the glacier ice. Collectively, this valuable information provides new insight into the accreted ice formation processes, the bedrock geology of East Antarctica as well as the water chemistry and circulation of Lake Vostok.
Ultra-low rare earth element content in accreted ice from sub-glacial Lake Vostok, Antarctica
NASA Astrophysics Data System (ADS)
Barbante, C.; Gabrielli, P.; Turetta, C.; Planchon, F.; Boutron, C.; Petit, J. R.; Bulat, S.; Hong, S.; Cozzi, G.; Cescon, P.
2009-12-01
We report the first rare earth element (REE) concentrations in accreted ice refrozen from sub-glacial Lake Vostok (East Antarctica). REE were determined in various sections of the Vostok ice core in order to geochemically characterize its impurities. Samples were obtained from accreted ice and, for comparison, from the upper glacier ice of atmospheric origin (undisturbed, disturbed and glacial flour ice). REE concentrations ranged between 0.8-56 pg g-1 for Ce and 0.0035- 0.24 pg g-1 for Lu in glacier ice, and between <0.1-24 pg g-1 for Ce and <0.0004-0.02 pg g-1 for Lu in accreted ice. Interestingly, the REE concentrations in the upper accreted ice (AC1;characterized by visible aggregates containing a mixture of very fine terrigenous particles) and in the deeper accreted ice (AC2; characterized by transparent ice) are lower than those in fresh water and seawater, respectively. We suggest that such ultra-low concentrations are unlikely to be representative of the real REE content in Lake Vostok, but instead may reflect phase exclusion processes occurring at the ice/water interface during refreezing. In particular, the uneven spatial distribution (on the order of a few cm) and the large range of REE concentrations observed in AC1 are consistent with the occurrence/absence of the aggregates in adjacent ice, and point to the presence of solid-phase concentration/exclusion processes occurring within separate pockets of frazil ice during AC1 formation. Interestingly, if the LREE enrichment found in AC1 was not produced by chemical fractionation occurring in Lake Vostok water, this may reflect a contribution of bedrock material, possibly in combination with aeolian dust released into the lake by melting of the glacier ice. Collectively, this valuable information provides new insight into the accreted ice formation processes, the bedrock geology of East Antarctica as well as the water chemistry and circulation of Lake Vostok.
Evolution of glacier-dammed lakes through space and time; Brady Glacier, Alaska, USA
NASA Astrophysics Data System (ADS)
Capps, Denny M.; Clague, John J.
2014-04-01
Glacier-dammed lakes and their associated jökulhlaups cause severe flooding in downstream areas and substantially influence glacier dynamics. Brady Glacier in southeast Alaska is well suited for a study of these phenomena because it presently dams 10 large (> 1 km2) lakes. Our objectives are to demonstrate how Brady Glacier and its lakes have co-evolved in the past and to apply this knowledge to predict how the glacier and its lakes will likely evolve in the future. To accomplish these objectives, we georeferenced a variety of maps, airphotos, and optical satellite imagery to characterize the evolution of the glacier and lakes. We also collected bathymetry data and created bathymetric maps of select lakes. Despite small advances and retreats, the main terminus of Brady Glacier has changed little since 1880. However, it downwasted at rates of 2-3 m/y between 1948 and 2000, more than the regional average. The most dramatic retreat (2 km) and downwasting (120 m) have occurred adjacent to glacier-dammed lakes and are primarily the result of calving. Brady Glacier is a former tidewater glacier. With continued downwasting, Brady Glacier may return to a tidewater regime and enter into a phase of catastrophic retreat. The situation at Brady Glacier is not unique, and the lessons learned here can be applied elsewhere to identify future glacier-dammed lakes, jökulhlaups, and glacier instability.
Bacterial community initial development in proglacial soils of Larsemann hill, East Antarctica
NASA Astrophysics Data System (ADS)
Ma, H.; Yan, W.; Shi, G.; Sun, B.; Zhang, Y.; Xiao, X.
2016-12-01
Glacial forefields are considered ideal places to explore how microbial communities will response to climate-driven environmental changes. Our knowledge of how the bacterial community activities and structure was influenced by changing environment due to glacier retreat is still very limited, especially at the initial stage of glacier retreat. The short gradient soil samples including the ice free and ice covered sites were sampled in the forehead of East Antarctica ice sheet, in Larsemann Hills. By employing the Miseq sequencing methods, 1.8 x104 high-quality sequences were gotten for each sample and the bacterial diversity including abundant bacteria and rare bacteria were studied and compared between the gradient samples. Even though in such an extreme stress condition, the bacterial diversity was high. The coefficient of variance between the five sites of abundant group was 0.886 which was higher than that of the top 20 rare group (0.159) significantly (unpaired t test, p-value<0.0001) suggesting that the abundant bacterial communities were more sensitive to the ice sheet change in the initial stage than rare bacteria did. And the abundant bacteria contributed the community structure more than the rare bacteria did. The rare group acted more like seed bank to keep the community functionality in the forehead of sheet. And the ice thickness was the major factor to affect the abundant bacterial community. Given the fact that Antarctica environment was more sensitive to the global warming, the study about abundant and rare bacteria response to condition change will be helpful to precisely predict community response to climate change in polar region. This finding will improve the understanding about the relationship between community structure and environment condition in extreme stress condition.
Climate change and glacier retreat drive shifts in an Antarctic benthic ecosystem.
Sahade, Ricardo; Lagger, Cristian; Torre, Luciana; Momo, Fernando; Monien, Patrick; Schloss, Irene; Barnes, David K A; Servetto, Natalia; Tarantelli, Soledad; Tatián, Marcos; Zamboni, Nadia; Abele, Doris
2015-11-01
The Antarctic Peninsula (AP) is one of the three places on Earth that registered the most intense warming in the last 50 years, almost five times the global mean. This warming has strongly affected the cryosphere, causing the largest ice-shelf collapses ever observed and the retreat of 87% of glaciers. Ecosystem responses, although increasingly predicted, have been mainly reported for pelagic systems. However, and despite most Antarctic species being benthic, responses in the Antarctic benthos have been detected in only a few species, and major effects at assemblage level are unknown. This is probably due to the scarcity of baselines against which to assess change. We performed repeat surveys of coastal benthos in 1994, 1998, and 2010, analyzing community structure and environmental variables at King George Island, Antarctica. We report a marked shift in an Antarctic benthic community that can be linked to ongoing climate change. However, rather than temperature as the primary factor, we highlight the resulting increased sediment runoff, triggered by glacier retreat, as the potential causal factor. The sudden shift from a "filter feeders-ascidian domination" to a "mixed assemblage" suggests that thresholds (for example, of tolerable sedimentation) and alternative equilibrium states, depending on the reversibility of the changes, could be possible traits of this ecosystem. Sedimentation processes will be increasing under the current scenario of glacier retreat, and attention needs to be paid to its effects along the AP.
2017-12-08
The ice of a piedmont glacier spills from a steep valley onto a relatively flat plain, where it spreads out unconstrained like pancake batter. Elephant Foot Glacier in northeastern Greenland is an excellent example; it is particularly noted for its symmetry. But the largest piedmont glacier in North America (and possibly the world) is Malaspina in southeastern Alaska. On September 24, 2014, the Operational Land Imager (OLI) on Landsat 8 acquired this image of Malaspina Glacier. The main source of ice comes from Seward Glacier, located at the top-center of this image. The Agassiz and Libbey glaciers are visible on the left side, and the Hayden and Marvine glaciers are on the right. The brown lines on the ice are moraines—areas where soil, rock, and other debris have been scraped up by the glacier and deposited at its sides. Where two glaciers flow together, the moraines merge to form a medial moraine. Glaciers that flow at a steady speed tend to have moraines that are relatively straight. But what causes the dizzying pattern of curves, zigzags, and loops of Malaspina’s moraines? Glaciers in this area of Alaska periodically “surge,”meaning they lurch forward quickly for one to several years. As a result of this irregular flow, the moraines at the edges and between glaciers can become folded, compressed, and sheared to form the characteristic loops seen on Malaspina. For instance, a surge in 1986 displaced moraines on the east side of Malaspina by as much as 5 kilometers (3 miles). NASA Earth Observatory image by Jesse Allen, using Landsat data from the U.S. Geological Survey. Caption by Kathryn Hansen. Credit: NASA Earth Observatory 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
Space Radar Image of San Rafael Glacier, Chile
1999-04-15
A NASA radar instrument has been successfully used to measure some of the fastest moving and most inaccessible glaciers in the world -- in Chile's huge, remote Patagonia ice fields -- demonstrating a technique that could produce more accurate predictions of glacial response to climate change and corresponding sea level changes. This image, produced with interferometric measurements made by the Spaceborne Imaging Radar-C and X-band Synthetic Aperture Radar (SIR-C/X-SAR) flown on the Space Shuttle last fall, has provided the first detailed measurements of the mass and motion of the San Rafael Glacier. Very few measurements have been made of the Patagonian ice fields, which are the world's largest mid-latitude ice masses and account for more than 60 percent of the Southern Hemisphere's glacial area outside of Antarctica. These features make the area essential for climatologists attempting to understand the response of glaciers on a global scale to changes in climate, but the region's inaccessibility and inhospitable climate have made it nearly impossible for scientists to study its glacial topography, meteorology and changes over time. Currently, topographic data exist for only a few glaciers while no data exist for the vast interior of the ice fields. Velocity has been measured on only five of the more than 100 glaciers, and the data consist of only a few single-point measurements. The interferometry performed by the SIR-C/X-SAR was used to generate both a digital elevation model of the glaciers and a map of their ice motion on a pixel-per-pixel basis at very high resolution for the first time. The data were acquired from nearly the same position in space on October 9, 10 and 11, 1994, at L-band frequency (24-cm wavelength), vertically transmitted and received polarization, as the Space Shuttle Endeavor flew over several Patagonian outlet glaciers of the San Rafael Laguna. The area shown in these two images is 50 kilometers by 30 kilometers (30 miles by 18 miles) in
Shallow groundwater systems in a polar desert, McMurdo Dry Valleys, Antarctica
NASA Astrophysics Data System (ADS)
Gooseff, Michael N.; Barrett, John E.; Levy, Joseph S.
2013-02-01
The McMurdo Dry Valleys (MDVs), Antarctica, exist in a hyperarid polar desert, underlain by deep permafrost. With an annual mean air temperature of -18 °C, the MDVs receive <10 cm snow-water equivalent each year, collecting in leeward patches across the landscape. The landscape is dominated by expansive ice-free areas of exposed soils, mountain glaciers, permanently ice-covered lakes, and stream channels. An active layer of seasonally thawed soil and sediment extends to less than 1 m from the surface. Despite the cold and low precipitation, liquid water is generated on glaciers and in snow patches during the austral summer, infiltrating the active layer. Across the MDVs, groundwater is generally confined to shallow depths and often in unsaturated conditions. The current understanding and the biogeochemical/ecological significance of four types of shallow groundwater features in the MDVs are reviewed: local soil-moisture patches that result from snow-patch melt, water tracks, wetted margins of streams and lakes, and hyporheic zones of streams. In general, each of these features enhances the movement of solutes across the landscape and generates soil conditions suitable for microbial and invertebrate communities.
Glaciers. Attribution of global glacier mass loss to anthropogenic and natural causes.
Marzeion, Ben; Cogley, J Graham; Richter, Kristin; Parkes, David
2014-08-22
The ongoing global glacier retreat is affecting human societies by causing sea-level rise, changing seasonal water availability, and increasing geohazards. Melting glaciers are an icon of anthropogenic climate change. However, glacier response times are typically decades or longer, which implies that the present-day glacier retreat is a mixed response to past and current natural climate variability and current anthropogenic forcing. Here we show that only 25 ± 35% of the global glacier mass loss during the period from 1851 to 2010 is attributable to anthropogenic causes. Nevertheless, the anthropogenic signal is detectable with high confidence in glacier mass balance observations during 1991 to 2010, and the anthropogenic fraction of global glacier mass loss during that period has increased to 69 ± 24%. Copyright © 2014, American Association for the Advancement of Science.
GlacierRocks - Glacier-Headwall Interaction and its Influence on Rockfall Activity
NASA Astrophysics Data System (ADS)
Hartmeyer, Ingo; Keuschnig, Markus; Krautblatter, Michael; Helfricht, Kay; Leith, Kerry; Otto, Jan-Christoph
2017-04-01
Climate models predict continued climate warming and a decrease of Austrian glaciers to less than 20% of their present area by the end of this century. Rockfall from freshly exposed headwalls has been documented as an increasing risk factor with considerable significance for man and high-alpine infrastructure. Recent findings of a five-year terrestrial laserscanning campaign (2011-2016) monitoring glacial headwalls at the Kitzsteinhorn (3.203 m a.s.l.), Hohe Tauern Range, Austria, show the dramatic impact of glacier thinning on adjacent headwalls: 80 % of the detected rockfall volumes were triggered from areas located less than 20 m above the current glacier surface. Despite these implications, little is known about the thermal, mechanical and hydrological processes that operate at the glacier-headwall interface (randkluft). Systemic in-situ monitoring of stability-relevant parameters are lacking, leaving fundamental gaps in the understanding of rockfall preconditioning in glacial headwalls and the geomorphological evolution of glaciated catchments. In this contribution we introduce the recently approved research project 'GlacierRocks', which starts in 2017 and will run for at least three years. 'GlacierRocks' will establish the worldwide first research site for long-term monitoring of stability-relevant processes inside a randkluft system. Based on the acquired monitoring data 'GlacierRocks' is pursuing three overall aims at (1) gaining a better understanding of rockfall preconditioning in randklufts and related geomorphological shaping of headwalls, (2) analyzing poorly understood glacial thinning dynamics near headwalls, and (3) estimating present and future rockfall hazard potential in headwalls on a regional scale. The three system components (headwall, glacier, randkluft) will be investigated by combining geomorphological, glaciological and meteorological methods. 'GlacierRocks' will continuously monitor rock temperature, rock moisture, frost cracking
NASA Astrophysics Data System (ADS)
Roberts, S. J.; Johnson, J.; Ireland, L.; Rood, D. H.; Schaefer, J. M.; Whitehouse, P. L.; Pollard, D.
2016-12-01
Reliable model predictions of the future evolution of the West Antarctic Ice Sheet in the Amundsen Sea Embayment of Antarctica are currently hindered by a lack of data on the regional thinning history, particularly to the west of Thwaites Glacier. Our project will fill this critical gap by acquiring glacial-geological data, in particular, a high density of cosmogenic exposure ages that record ice sheet changes in the western Amundsen Sea Embayment over the past 20,000 years. In 2015/6, during the first of two field seasons in the region, we collected glacial-geomorphological evidence and cosmogenic surface exposure dating samples to constrain past ice cover of nunataks around Mt Murphy, which are adjacent to the Pope Glacier. The presence of abundant rounded granite and gneiss cobbles perched on bedrock ridges and terraces up to 885 m asl, as well as extensive striated bedrock above this height, indicate that ice was much thicker in the past. We also present preliminary results from a novel study on Turtle Rock, a key site for understanding past fluctuations of Pope Glacier. We used an unmanned aerial vehicle (UAV) to map the geomorphology of selected areas in greater detail than is currently possible from high-resolution satellite imagery, and ground-truthed the data by measuring the size, orientation and lithological composition of erratic cobbles and boulders. Combined with surface exposure dating, we will use these datasets to determine whether there were multiple phases of ice overriding, and the timing of thinning of Pope Glacier since the Last Glacial Maximum.
The differing biogeochemical and microbial signatures of glaciers and rock glaciers
Fegel, Timothy S.; Baron, Jill S.; Fountain, Andrew G.; Johnson, Gunnar F.; Hall, Edward K.
2016-01-01
Glaciers and rock glaciers supply water and bioavailable nutrients to headwater mountain lakes and streams across all regions of the American West. Here we present a comparative study of the metal, nutrient, and microbial characteristics of glacial and rock glacial influence on headwater ecosystems in three mountain ranges of the contiguous U.S.: The Cascade Mountains, Rocky Mountains, and Sierra Nevada. Several meltwater characteristics (water temperature, conductivity, pH, heavy metals, nutrients, complexity of dissolved organic matter (DOM), and bacterial richness and diversity) differed significantly between glacier and rock glacier meltwaters, while other characteristics (Ca2+, Fe3+, SiO2 concentrations, reactive nitrogen, and microbial processing of DOM) showed distinct trends between mountain ranges regardless of meltwater source. Some characteristics were affected both by glacier type and mountain range (e.g. temperature, ammonium (NH4+) and nitrate (NO3- ) concentrations, bacterial diversity). Due to the ubiquity of rock glaciers and the accelerating loss of the low latitude glaciers our results point to the important and changing influence that these frozen features place on headwater ecosystems.
Modeled climate-induced glacier change in Glacier National Park, 1850-2100
Hall, M.H.P.; Fagre, D.B.
2003-01-01
The glaciers in the Blackfoot-Jackson Glacier Basin of Glacier National Park, Montana, decreased in area from 21.6 square kilometers (km2) in 1850 to 7.4 km2 in 1979. Over this same period global temperatures increased by 0.45??C (?? 0. 15??C). We analyzed the climatic causes and ecological consequences of glacier retreat by creating spatially explicit models of the creation and ablation of glaciers and of the response of vegetation to climate change. We determined the melt rate and spatial distribution of glaciers under two possible future climate scenarios, one based on carbon dioxide-induced global warming and the other on a linear temperature extrapolation. Under the former scenario, all glaciers in the basin will disappear by the year 2030, despite predicted increases in precipitation; under the latter, melting is slower. Using a second model, we analyzed vegetation responses to variations in soil moisture and increasing temperature in a complex alpine landscape and predicted where plant communities are likely to be located as conditions change.
Deglacial temperature history of West Antarctica
NASA Astrophysics Data System (ADS)
Cuffey, Kurt M.; Clow, Gary D.; Steig, Eric J.; Buizert, Christo; Fudge, T. J.; Koutnik, Michelle; Waddington, Edwin D.; Alley, Richard B.; Severinghaus, Jeffrey P.
2016-12-01
The most recent glacial to interglacial transition constitutes a remarkable natural experiment for learning how Earth’s climate responds to various forcings, including a rise in atmospheric CO2. This transition has left a direct thermal remnant in the polar ice sheets, where the exceptional purity and continual accumulation of ice permit analyses not possible in other settings. For Antarctica, the deglacial warming has previously been constrained only by the water isotopic composition in ice cores, without an absolute thermometric assessment of the isotopes’ sensitivity to temperature. To overcome this limitation, we measured temperatures in a deep borehole and analyzed them together with ice-core data to reconstruct the surface temperature history of West Antarctica. The deglacial warming was
Perennially ice-covered Lake Hoare, Antarctica: physical environment, biology and sedimentation
NASA Technical Reports Server (NTRS)
Wharton, R. A. Jr; Simmons, G. M. Jr; McKay, C. P.; Wharton RA, J. r. (Principal Investigator)
1989-01-01
Lake Hoare (77 degrees 38' S, 162 degrees 53' E) is a perennially ice-covered lake at the eastern end of Taylor Valley in southern Victoria Land, Antarctica. The environment of this lake is controlled by the relatively thick ice cover (3-5 m) which eliminates wind generated currents, restricts gas exchange and sediment deposition, and reduces light penetration. The ice cover is in turn largely controlled by the extreme seasonality of Antarctica and local climate. Lake Hoare and other dry valley lakes may be sensitive indicators of short term (< 100 yr) climatic and/or anthropogenic changes in the dry valleys since the onset of intensive exploration over 30 years ago. The time constants for turnover of the water column and lake ice are 50 and 10 years, respectively. The turnover time for atmospheric gases in the lake is 30-60 years. Therefore, the lake environment responds to changes on a 10-100 year timescale. Because the ice cover has a controlling influence on the lake (e.g. light penetration, gas content of water, and sediment deposition), it is probable that small changes in ice ablation, sediment loading on the ice cover, or glacial meltwater (or groundwater) inflow will affect ice cover dynamics and will have a major impact on the lake environment and biota.
ERIC Educational Resources Information Center
Lonergan, David
2011-01-01
Frederick Winslow Taylor (1856-1915) was an efficiency expert whose concerns were less about avoiding worker fatigue and more about increasing profit margins by any means necessary. Taylor was devoted to finding the One Best Way to carry out a task and then training workers to do that task unvaryingly; attempts by employees to improve their own…
Glacier monitoring and glacier-climate interactions in the tropical Andes: A review
NASA Astrophysics Data System (ADS)
Veettil, Bijeesh Kozhikkodan; Wang, Shanshan; Florêncio de Souza, Sergio; Bremer, Ulisses Franz; Simões, Jefferson Cardia
2017-08-01
In this review, we summarized the evolution of glacier monitoring in the tropical Andes during the last few decades, particularly after the development of remote sensing and photogrammetry. Advantages and limitations of glacier mapping, applied so far, in Venezuela, Colombia, Ecuador, Peru and Bolivia are discussed in detail. Glacier parameters such as the equilibrium line altitude, snowline and mass balance were given special attention in understanding the complex cryosphere-climate interactions, particularly using remote sensing techniques. Glaciers in the inner and the outer tropics were considered separately based on the precipitation and temperature conditions within a new framework. The applicability of various methods to use glacier records to understand and reconstruct the tropical Andean climate between the Last Glacial Maximum (11,700 years ago) and the present is also explored in this paper. Results from various studies published recently were analyzed and we tried to understand the differences in the magnitudes of glacier responses towards the climatic perturbations in the inner tropics and the outer tropics. Inner tropical glaciers, particularly those in Venezuela and Colombia near the January Intertropical Convergence Zone (ITCZ), are more vulnerable to increase in temperature. Surface energy balance experiments show that outer tropical glaciers respond to precipitation variability very rapidly in comparison with the temperature variability, particularly when moving towards the subtropics. We also analyzed the gradients in glacier response to climate change from the Pacific coast towards the Amazon Basin as well as with the elevation. Based on the current trends synthesised from recent studies, it is hypothesized that the glaciers in the inner tropics and the southern wet outer tropics will disappear first as a response to global warming whereas glaciers in the northern wet outer tropics and dry outer tropics show resistance to warming trends due to
NASA Astrophysics Data System (ADS)
Racoviteanu, A.
2014-12-01
High rates of glacier retreat for the last decades are often reported, and believed to be induced by 20th century climate changes. However, regional glacier fluctuations are complex, and depend on a combination of climate and local topography. Furthermore, in ares such as the Hindu-Kush Himalaya, there are concerns about warming, decreasing monsoon precipitation and their impact on local glacier regimes. Currently, the challenge is in understanding the magnitude of feedbacks between large-scale climate forcing and small-scale glacier behavior. Spatio-temporal patterns of glacier distribution are still llimited in some areas of the high Hindu-Kush Himalaya, but multi-temporal satellite imagery has helped fill spatial and temporal gaps in regional glacier parameters in the last decade. Here I present a synopsis of the behavior of glaciers across the Himalaya, following a west to east gradient. In particular, I focus on spatial patterns of glacier parameters in the eastern Himalaya, which I investigate at multi-spatial scales using remote sensing data from declassified Corona, ASTER, Landsat ETM+, Quickbird and Worldview2 sensors. I also present the use of high-resolution imagery, including texture and thermal analysis for mapping glacier features at small scale, which are particularly useful in understanding surface trends of debris-covered glaciers, which are prevalent in the Himalaya. I compare and contrast spatial patterns of glacier area and élévation changes in the monsoon-influenced eastern Himalaya (the Everest region in the Nepal Himalaya and Sikkim in the Indian Himalaya) with other observations from the dry western Indian Himalaya (Ladakh and Lahul-Spiti), both field measurements and remote sensing-based. In the eastern Himalaya, results point to glacier area change of -0.24 % ± 0.08% per year from the 1960's to the 2006's, with a higher rate of retreat in the last decade (-0.43% /yr). Debris-covered glacier tongues show thinning trends of -30.8 m± 39 m
NASA Astrophysics Data System (ADS)
Trantow, T.; Herzfeld, U. C.
2015-12-01
The Bering-Bagley Glacier System (BBGS), Alaska, one of the largest ice systems outside of Greenland and Antarctica, has recently surged (2011-2013), providing a rare opportunity to study the surge phenomenon in a large and complex system. Understanding fast-flowing glaciers and accelerations in ice flow, of which surging is one type, is critical to understanding changes in the cryosphere and ultimately changes in sea level. It is important to distinguish between types of accelerations and their consequences, especially between reversible or quasi-cyclic and irreversible forms of glacial acceleration, but current icesheet models treat all accelerating ice identically. Additionally, the surge provides an exceptional opportunity to study the influence of surface roughness and water content on return signals of altimeter systems. In this presentation, we analyze radar and laser altimeter data from CryoSat-2, NASA's Operation IceBridge (OIB), the ICESat Geoscience Laser Altimeter System (GLAS), ICESat-2's predecessor the Multiple Altimeter Beam Experimental Lidar (MABEL), and airborne laser altimeter and imagery campaigns by our research group. These measurements are used to study elevation, elevation change and crevassing throughout the glacier system. Analysis of the imagery from our airborne campaigns provides comprehensive characterizations of the BBGS surface over the course of the surge. Results from the data analysis are compared to numerical modeling experiments.
Modeling the Rock Glacier Cycle
NASA Astrophysics Data System (ADS)
Anderson, R. S.; Anderson, L. S.
2016-12-01
Rock glaciers are common in many mountain ranges in which the ELA lies above the peaks. They represent some of the most identifiable components of today's cryosphere in these settings. Their oversteepened snouts pose often-overlooked hazards to travel in alpine terrain. Rock glaciers are supported by avalanches and by rockfall from steep headwalls. The winter's avalanche cone must be sufficiently thick not to melt entirely in the summer. The spatial distribution of rock glaciers reflects this dependence on avalanche sources; they are most common on lee sides of ridges where wind-blown snow augments the avalanche source. In the absence of rockfall, this would support a short, cirque glacier. Depending on the relationship between rockfall and avalanche patterns, "talus-derived" and "glacier-derived" rock glaciers are possible. Talus-derived: If the spatial distribution of rock delivery is similar to the avalanche pattern, the rock-ice mixture will travel an englacial path that is downward through the short accumulation zone before turning upward in the ablation zone. Advected debris is then delivered to the base of a growing surface debris layer that reduces the ice melt rate. The physics is identical to the debris-covered glacier case. Glacier-derived: If on the other hand rockfall from the headwall rolls beyond the avalanche cone, it is added directly to the ablation zone of the glacier. The avalanche accumulation zone then supports a pure ice core to the rock glacier. We have developed numerical models designed to capture the full range of glacier to debris-covered glacier to rock glacier behavior. The hundreds of meter lengths, tens of meters thicknesses, and meter per year speeds of rock glaciers are well described by the models. The model can capture both "talus-derived" and "glacier-derived" rock glaciers. We explore the dependence of glacier behavior on climate histories. As climate warms, a pure ice debris-covered glacier can transform to a much shorter rock
Generation of a high-accuracy regional DEM based on ALOS/PRISM imagery of East Antarctica
NASA Astrophysics Data System (ADS)
Shiramizu, Kaoru; Doi, Koichiro; Aoyama, Yuichi
2017-12-01
A digital elevation model (DEM) is used to estimate ice-flow velocities for an ice sheet and glaciers via Differential Interferometric Synthetic Aperture Radar (DInSAR) processing. The accuracy of DInSAR-derived displacement estimates depends upon the accuracy of the DEM. Therefore, we used stereo optical images, obtained with a panchromatic remote-sensing instrument for stereo mapping (PRISM) sensor mounted onboard the Advanced Land Observing Satellite (ALOS), to produce a new DEM ("PRISM-DEM") of part of the coastal region of Lützow-Holm Bay in Dronning Maud Land, East Antarctica. We verified the accuracy of the PRISM-DEM by comparing ellipsoidal heights with those of existing DEMs and values obtained by satellite laser altimetry (ICESat/GLAS) and Global Navigation Satellite System surveying. The accuracy of the PRISM-DEM is estimated to be 2.80 m over ice sheet, 4.86 m over individual glaciers, and 6.63 m over rock outcrops. By comparison, the estimated accuracy of the ASTER-GDEM, widely used in polar regions, is 33.45 m over ice sheet, 14.61 m over glaciers, and 19.95 m over rock outcrops. For displacement measurements made along the radar line-of-sight by DInSAR, in conjunction with ALOS/PALSAR data, the accuracy of the PRISM-DEM and ASTER-GDEM correspond to estimation errors of <6.3 mm and <31.8 mm, respectively.
2017-12-08
NASA image acquired August 27, 2009 Like rivers of liquid water, glaciers flow downhill, with tributaries joining to form larger rivers. But where water rushes, ice crawls. As a result, glaciers gather dust and dirt, and bear long-lasting evidence of past movements. Alaska’s Susitna Glacier revealed some of its long, grinding journey when the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) on NASA’s Terra satellite passed overhead on August 27, 2009. This satellite image combines infrared, red, and green wavelengths to form a false-color image. Vegetation is red and the glacier’s surface is marbled with dirt-free blue ice and dirt-coated brown ice. Infusions of relatively clean ice push in from tributaries in the north. The glacier surface appears especially complex near the center of the image, where a tributary has pushed the ice in the main glacier slightly southward. A photograph taken by researchers from the U.S. Geological Survey (archived by the National Snow and Ice Data Center) shows an equally complicated Susitna Glacier in 1970, with dirt-free and dirt-encrusted surfaces forming stripes, curves, and U-turns. Susitna flows over a seismically active area. In fact, a 7.9-magnitude quake struck the region in November 2002, along a previously unknown fault. Geologists surmised that earthquakes had created the steep cliffs and slopes in the glacier surface, but in fact most of the jumble is the result of surges in tributary glaciers. Glacier surges—typically short-lived events where a glacier moves many times its normal rate—can occur when melt water accumulates at the base and lubricates the flow. This water may be supplied by meltwater lakes that accumulate on top of the glacier; some are visible in the lower left corner of this image. The underlying bedrock can also contribute to glacier surges, with soft, easily deformed rock leading to more frequent surges. NASA Earth Observatory image created by Jesse Allen and Robert
Recent Observations and Structural Analysis of Surge-Type Glaciers in the Glacier Bay Area
NASA Astrophysics Data System (ADS)
Mayer, H.; Herzfeld, U. C.
2003-12-01
The Chugach-St.-Elias Mountains in North America hold the largest non-polar connected glaciated area of the world. Most of its larger glaciers are surge-type glaciers. In the summer of 2003, we collected aerial photographic and GPS data over numerous glaciers in the eastern St. Elias Mountains, including the Glacier Bay area. Observed glaciers include Davidson, Casement, McBride, Riggs, Cushing, Carroll, Rendu, Tsirku, Grand Pacific, Melbern, Ferris, Margerie, Johns Hopkins, Lamplugh, Reid, Burroughs, Morse, Muir and Willard Glaciers, of which Carroll, Rendu, Ferris, Grand Pacific, Johns Hopkins and Margerie Glaciers are surge-type glaciers. Our approach utilizes a quantitative analysis of surface patterns, following the principles of structural geology for the analysis of brittle-deformation patterns (manifested in crevasses) and ductile deformation patterns (visible in folded moraines). First results will be presented.
NASA Technical Reports Server (NTRS)
Koeberl, Christian
1989-01-01
The analysis of samples of volcanic ash dust layers from the Lewis Cliff/Beardmore Glacier in Antarctica shows that some of the samples contain Ir concentrations up to 7.5 ppb. It is shown that the Ir is positively correlated with Se, As, Sb, and other volcanogenic elements. The results show that Ir may be present in some volcanic ash deposits, suggesting that the Ir in the K/T boundary clays is not necessarily of cosmic origin, but may have originated from mantle reservoirs tapped during extensive volcanic eruptions possibly triggered by impact events.
The slow advance of a calving glacier: Hubbard Glacier, Alaska, U.S.A
Trabant, D.C.; Krimmel, R.M.; Echelmeyer, K.A.; Zirnheld, S.L.; Elsberg, D.H.
2003-01-01
Hubbard Glacier is the largest tidewater glacier in North America. In contrast to most glaciers in Alaska and northwestern Canada, Hubbard Glacier thickened and advanced during the 20th century. This atypical behavior is an important example of how insensitive to climate a glacier can become during parts of the calving glacier cycle. As this glacier continues to advance, it will close the seaward entrance to 50 km long Russell Fjord and create a glacier-dammed, brackish-water lake. This paper describes measured changes in ice thickness, ice speed, terminus advance and fjord bathymetry of Hubbard Glacier, as determined from airborne laser altimetry, aerial photogrammetry, satellite imagery and bathymetric measurements. The data show that the lower regions of the glacier have thickened by as much as 83 m in the last 41 years, while the entire glacier increased in volume by 14.1 km3. Ice speeds are generally decreasing near the calving face from a high of 16.5 m d-1 in 1948 to 11.5 m d-1 in 2001. The calving terminus advanced at an average rate of about 16 m a-1 between 1895 and 1948 and accelerated to 32 m a-1 since 1948. However, since 1986, the advance of the part of the terminus in Disenchantment Bay has slowed to 28 m a-1. Bathymetric data from the lee slope of the submarine terminal moraine show that between 1978 and 1999 the moraine advanced at an average rate of 32 m a-1, which is the same as that of the calving face.
Aerosol size distribution at Nansen Ice Sheet Antarctica
NASA Astrophysics Data System (ADS)
Belosi, F.; Contini, D.; Donateo, A.; Santachiara, G.; Prodi, F.
2012-04-01
During austral summer 2006, in the framework of the XXII Italian Antarctic expedition of PNRA (Italian National Program for Research in Antarctica), aerosol particle number size distribution measurements were performed in the 10-500 range nm over the Nansen Ice Sheet glacier (NIS, 74°30' S, 163°27' E; 85 m a.s.l), a permanently iced branch of the Ross Sea. Observed total particle number concentrations varied between 169 and 1385 cm- 3. A monomodal number size distribution, peaking at about 70 nm with no variation during the day, was observed for continental air mass, high wind speed and low relative humidity. Trimodal number size distributions were also observed, in agreement with measurements performed at Aboa station, which is located on the opposite side of the Antarctic continent to the NIS. In this case new particle formation, with subsequent particle growth up to about 30 nm, was observed even if not associated with maritime air masses.
UV irradiance and albedo at Union Glacier Camp (Antarctica): a case study.
Cordero, Raul R; Damiani, Alessandro; Ferrer, Jorge; Jorquera, Jose; Tobar, Mario; Labbe, Fernando; Carrasco, Jorge; Laroze, David
2014-01-01
We report on the first spectral measurements of ultraviolet (UV) irradiance and the albedo at a Camp located in the southern Ellsworth Mountains on the broad expanse of Union Glacier (700 m altitude, 79° 46' S; 82° 52'W); about 1,000 km from the South Pole. The measurements were carried out by using a double monochromator-based spectroradiometer during a campaign (in December 2012) meant to weight up the effect of the local albedo on the UV irradiance. We found that the albedo measured at noon was about 0.95 in the UV and the visible part of the spectrum. This high surface reflectivity led to enhancements in the UV index under cloudless conditions of about 50% in comparison with snow free surfaces. Spectral measurements carried out elsewhere as well as estimates retrieved from the Ozone Monitoring Instrument (OMI) were used for further comparisons.
UV Irradiance and Albedo at Union Glacier Camp (Antarctica): A Case Study
Cordero, Raul R.; Damiani, Alessandro; Ferrer, Jorge; Jorquera, Jose; Tobar, Mario; Labbe, Fernando; Carrasco, Jorge; Laroze, David
2014-01-01
We report on the first spectral measurements of ultraviolet (UV) irradiance and the albedo at a Camp located in the southern Ellsworth Mountains on the broad expanse of Union Glacier (700 m altitude, 79° 46′ S; 82° 52′W); about 1,000 km from the South Pole. The measurements were carried out by using a double monochromator-based spectroradiometer during a campaign (in December 2012) meant to weight up the effect of the local albedo on the UV irradiance. We found that the albedo measured at noon was about 0.95 in the UV and the visible part of the spectrum. This high surface reflectivity led to enhancements in the UV index under cloudless conditions of about 50% in comparison with snow free surfaces. Spectral measurements carried out elsewhere as well as estimates retrieved from the Ozone Monitoring Instrument (OMI) were used for further comparisons. PMID:24598906
NASA Astrophysics Data System (ADS)
Jawak, S. D.; Luis, A. J.
2017-12-01
Estimating mass loss of the Antarctic ice sheet caused by iceberg calving is a challenging job. Antarctica is surrounded by a variety of large, medium and small sized ice shelves, glacier tongues and coastal areas without offshore floating ice masses. It is possible to monitor surface structures on the continental ice and the ice shelves as well as calved icebergs using NASA-ISRO synthetic aperture radar (NISAR) satellite images in future. The NISAR, which is planned to be launched in 2020, can be used as an all-weather and all-season system to classify the coastline of Antarctica to map patterns of surface structures close to the calving front. Additionally, classifying patterns and density of surface structures distributed over the ice shelves and ice tongues can be a challenging research where NISAR can be of a great advantage. So this work explores use of NISAR to map surface structures visible on ice shelves which can provide advisories to field teams. The ice shelf fronts has been categorized into various classes based on surface structures relative to the calving front within a 30 km-wide seaward strip. The resulting map of the classified calving fronts around Antarctica and their description would provide a detailed representation of crevasse formation and dominant iceberg in the southern ocean which pose a threat to navigation of Antarctic bound ships.
Changes in ice dynamics and mass balance of the Antarctic ice sheet.
Rignot, Eric
2006-07-15
The concept that the Antarctic ice sheet changes with eternal slowness has been challenged by recent observations from satellites. Pronounced regional warming in the Antarctic Peninsula triggered ice shelf collapse, which led to a 10-fold increase in glacier flow and rapid ice sheet retreat. This chain of events illustrated the vulnerability of ice shelves to climate warming and their buffering role on the mass balance of Antarctica. In West Antarctica, the Pine Island Bay sector is draining far more ice into the ocean than is stored upstream from snow accumulation. This sector could raise sea level by 1m and trigger widespread retreat of ice in West Antarctica. Pine Island Glacier accelerated 38% since 1975, and most of the speed up took place over the last decade. Its neighbour Thwaites Glacier is widening up and may double its width when its weakened eastern ice shelf breaks up. Widespread acceleration in this sector may be caused by glacier ungrounding from ice shelf melting by an ocean that has recently warmed by 0.3 degrees C. In contrast, glaciers buffered from oceanic change by large ice shelves have only small contributions to sea level. In East Antarctica, many glaciers are close to a state of mass balance, but sectors grounded well below sea level, such as Cook Ice Shelf, Ninnis/Mertz, Frost and Totten glaciers, are thinning and losing mass. Hence, East Antarctica is not immune to changes.
The Larsen Ice Shelf in Antarctica viewed from NASA's DC-8 aircraft during the AirSAR 2004 campaign
2004-03-16
The Larsen Ice Shelf in Antarctica viewed from NASA's DC-8 aircraft during the AirSAR 2004 campaign. AirSAR 2004 is a three-week expedition in Central and South America by an international team of scientists that is using an all-weather imaging tool, called the Airborne Synthetic Aperture Radar (AirSAR), located onboard NASA's DC-8 airborne laboratory. Scientists from many parts of the world are combining ground research with NASA's AirSAR technology to improve and expand on the quality of research they are able to conduct. These photos are from the DC-8 aircraft while flying an AirSAR mission over Antarctica. The Antarctic Peninsula is more similar to Alaska and Patagonia than to the rest of the Antarctic continent. It is drained by fast glaciers, receives abundant precipitation, and melts significantly in the summer months. In recent decades, the Peninsula has experienced significant atmospheric warming (about 2 degrees C since 1950), which has triggered a vast and spectacular retreat of its floating ice shelves, glacier reduction, a decrease in permanent snow cover and a lengthening of the melt season. As a result, the contribution to sea level from this region could be rapid and substantial. With an area of 120,000 km, or ten times the Patagonia ice fields, the Peninsula could contribute as much as 0.4mm/yr sea level rise, which would be the largest single contribution to sea level from anywhere in the world. This region is being studied by NASA using a DC-8 equipped with the Airborne Synthetic Aperture Radar developed by scientists from NASA’s Jet Propulsion Laboratory. AirSAR will provide a baseline model and unprecedented mapping of the region. This data will make it possible to determine whether the warming trend is slowing, continuing or accelerating. AirSAR will also provide reliable information on ice shelf thickness to measure the contribution of the glaciers to sea level.
The Larsen Ice Shelf in Antarctica viewed from NASA's DC-8 aircraft during the AirSAR 2004 campaign
2004-03-13
The Larsen Ice Shelf in Antarctica viewed from NASA's DC-8 aircraft during the AirSAR 2004 campaign. AirSAR 2004 is a three-week expedition in Central and South America by an international team of scientists that is using an all-weather imaging tool, called the Airborne Synthetic Aperture Radar (AirSAR), located onboard NASA's DC-8 airborne laboratory. Scientists from many parts of the world are combining ground research with NASA's AirSAR technology to improve and expand on the quality of research they are able to conduct. These photos are from the DC-8 aircraft while flying an AirSAR mission over Antarctica. The Antarctic Peninsula is more similar to Alaska and Patagonia than to the rest of the Antarctic continent. It is drained by fast glaciers, receives abundant precipitation, and melts significantly in the summer months. In recent decades, the Peninsula has experienced significant atmospheric warming (about 2 degrees C since 1950), which has triggered a vast and spectacular retreat of its floating ice shelves, glacier reduction, a decrease in permanent snow cover and a lengthening of the melt season. As a result, the contribution to sea level from this region could be rapid and substantial. With an area of 120,000 km, or ten times the Patagonia ice fields, the Peninsula could contribute as much as 0.4mm/yr sea level rise, which would be the largest single contribution to sea level from anywhere in the world. This region is being studied by NASA using a DC-8 equipped with the Airborne Synthetic Aperture Radar developed by scientists from NASA’s Jet Propulsion Laboratory. AirSAR will provide a baseline model and unprecedented mapping of the region. This data will make it possible to determine whether the warming trend is slowing, continuing or accelerating. AirSAR will also provide reliable information on ice shelf thickness to measure the contribution of the glaciers to sea level.
The Larsen Ice Shelf in Antarctica viewed from NASA's DC-8 aircraft during the AirSAR 2004 campaign
2004-03-16
The Larsen Ice Shelf in Antarctica viewed from NASA's DC-8 aircraft during the AirSAR 2004 campaign. AirSAR 2004 is a three-week expedition in Central and South America by an international team of scientists that is using an all-weather imaging tool, called the Airborne Synthetic Aperture Radar (AirSAR), located onboard NASA's DC-8 airborne laboratory. Scientists from many parts of the world are combining ground research with NASA's AirSAR technology to improve and expand on the quality of research they are able to conduct. These photos are from the DC-8 aircraft while flying an AirSAR mission over Antarctica. The Antarctic Peninsula is more similar to Alaska and Patagonia than to the rest of the Antarctic continent. It is drained by fast glaciers, receives abundant precipitation, and melts significantly in the summer months. In recent decades, the Peninsula has experienced significant atmospheric warming (about 2 degrees C since 1950), which has triggered a vast and spectacular retreat of its floating ice shelves, glacier reduction, a decrease in permanent snow cover and a lengthening of the melt season. As a result, the contribution to sea level from this region could be rapid and substantial. With an area of 120,000 km, or ten times the Patagonia ice fields, the Peninsula could contribute as much as 0.4mm/yr sea level rise, which would be the largest single contribution to sea level from anywhere in the world. This region is being studied by NASA using a DC-8 equipped with an Airborne Synthetic Aperture Radar (AirSAR) developed by scientists from NASA’s Jet Propulsion Laboratory. AirSAR will provide a baseline model and unprecedented mapping of the region. This data will make it possible to determine whether the warming trend is slowing, continuing or accelerating. AirSAR will also provide reliable information on ice shelf thickness to measure the contribution of the glaciers to sea level.
Grinnell and Sperry Glaciers, Glacier National Park, Montana: A record of vanishing ice
Johnson, Arthur
1980-01-01
Grinnell and Sperry Glaciers, in Glacier National Park, Mont., have both shrunk considerably since their discovery in 1887 and 1895, respectively. This shrinkage, a reflection of climatic conditions, is evident when photographs taken at the time of discovery are compared with later photographs. Annual precipitation and terminus-recession measurements, together with detailed systematic topographic mapping since 1900, clearly record the changes in the character and size of these glaciers. Grinnell Glacier decreased in area from 530 acres in 1900 to 315 acres in 1960 and to 298 acres in 1966. Between 1937 and 1969 the terminus receded nearly 1,200 feet. Periodic profile measurements indicate that in 1969 the surface over the main part of the glacier was 25-30 feet lower than in 1950. Observations from 1947 to 1969 indicate annual northeastward movement ranging from 32 to 52 feet and generally averaging 35-45 feet. The annual runoff at the glacier is estimated to be 150 inches, of which approximately 6 inches represents reduction in glacier volume. The average annual runoff at a gaging station on Grinnell Creek 1.5 miles downvalley from the glacier for the 20-year period, 1949-69, was 100 inches. The average annual precipitation over the glacier was probably 120-150 inches. Sperry Glacier occupied 800 acres in 1901; by 1960 it covered only 287 acres, much of its upper part having disappeared from the enclosing cirque. From 1938 to 1969 certain segments of the terminus receded more than 1,000 feet. Profile measurements dating from 1949 indicate a lowering of the glacier surface below an altitude of 7,500 feet, but a fairly constant or slightly increased elevation of the surface above an altitude of 7,500 feet. Along one segment of the 1969 terminus the ice had been more than 100 feet thick in 1950. According to observations during 1949-69, average annual downslope movement was less than 15 feet per year in the central part of the glacier and slightly more rapid toward
ERIC Educational Resources Information Center
Gozzard, David
2017-01-01
Australian company Antarctica Flights runs summer sightseeing trips out of Australian capital cities to tour the Antarctic coast. The Laby Foundation of the University of Melbourne, through its "Classroom Antarctica" program, sponsored Kent Street High School science teacher, Ms Suzy Urbaniak and 18 of her students to take the trip, to…
Glacier retreat in New Zealand during the Younger Dryas stadial.
Kaplan, Michael R; Schaefer, Joerg M; Denton, George H; Barrell, David J A; Chinn, Trevor J H; Putnam, Aaron E; Andersen, Bjørn G; Finkel, Robert C; Schwartz, Roseanne; Doughty, Alice M
2010-09-09
Millennial-scale cold reversals in the high latitudes of both hemispheres interrupted the last transition from full glacial to interglacial climate conditions. The presence of the Younger Dryas stadial (approximately 12.9 to approximately 11.7 kyr ago) is established throughout much of the Northern Hemisphere, but the global timing, nature and extent of the event are not well established. Evidence in mid to low latitudes of the Southern Hemisphere, in particular, has remained perplexing. The debate has in part focused on the behaviour of mountain glaciers in New Zealand, where previous research has found equivocal evidence for the precise timing of increased or reduced ice extent. The interhemispheric behaviour of the climate system during the Younger Dryas thus remains an open question, fundamentally limiting our ability to formulate realistic models of global climate dynamics for this time period. Here we show that New Zealand's glaciers retreated after approximately 13 kyr bp, at the onset of the Younger Dryas, and in general over the subsequent approximately 1.5-kyr period. Our evidence is based on detailed landform mapping, a high-precision (10)Be chronology and reconstruction of former ice extents and snow lines from well-preserved cirque moraines. Our late-glacial glacier chronology matches climatic trends in Antarctica, Southern Ocean behaviour and variations in atmospheric CO(2). The evidence points to a distinct warming of the southern mid-latitude atmosphere during the Younger Dryas and a close coupling between New Zealand's cryosphere and southern high-latitude climate. These findings support the hypothesis that extensive winter sea ice and curtailed meridional ocean overturning in the North Atlantic led to a strong interhemispheric thermal gradient during late-glacial times, in turn leading to increased upwelling and CO(2) release from the Southern Ocean, thereby triggering Southern Hemisphere warming during the northern Younger Dryas.
NASA Astrophysics Data System (ADS)
Gooseff, M. N.; Priscu, J. C.; Doran, P. T.; Chiuchiolo, A.; Obryk, M.
2014-12-01
Lakes integrate landscape processes and climate conditions. Most of the permanently ice-covered lakes in the McMurdo Dry Valleys, Antarctica are closed basin, receiving glacial melt water from streams for 10-12 weeks per year. Lake levels rise during the austral summer are balanced by sublimation of ice covers (year-round) and evaporation of open water moats (summer only). Vertical profiles of water temperature have been measured in three lakes in Taylor Valley since 1988. Up to 2002, lake levels were dropping, ice covers were thickening, and total heat contents were decreasing. These lakes have been gaining heat since the mid-2000s, at rates as high as 19.5x1014 cal/decade). Since 2002, lake levels have risen substantially (as much as 2.5 m), and ice covers have thinned (1.5 m on average). Analyses of lake ice thickness, meteorological conditions, and stream water heat loads indicate that the main source of heat to these lakes is from latent heat released when ice-covers form during the winter. An aditional source of heat to the lakes is water inflows from streams and direct glacieal melt. Mean lake temperatures in the past few years have stabilized or cooled, despite increases in lake level and total heat content, suggesting increased direct inflow of meltwater from glaciers. These results indicate that McMurdo Dry Valley lakes are sensitive indicators of climate processes in this polar desert landscape and demonstrate the importance of long-term data sets when addressing the effects of climate on ecosystem processes.
NASA Astrophysics Data System (ADS)
Ren, Diandong; Karoly, David J.
2008-03-01
Observations from seven Central Asian glaciers (35-55°N; 70-95°E) are used, together with regional temperature data, to infer uncertain parameters for a simple linear model of the glacier length variations. The glacier model is based on first order glacier dynamics and requires the knowledge of reference states of forcing and glacier perturbation magnitude. An adjoint-based variational method is used to optimally determine the glacier reference states in 1900 and the uncertain glacier model parameters. The simple glacier model is then used to estimate the glacier length variations until 2060 using regional temperature projections from an ensemble of climate model simulations for a future climate change scenario (SRES A2). For the period 2000-2060, all glaciers are projected to experience substantial further shrinkage, especially those with gentle slopes (e.g., Glacier Chogo Lungma retreats ˜4 km). Although nearly one-third of the year 2000 length will be reduced for some small glaciers, the existence of the glaciers studied here is not threatened by year 2060. The differences between the individual glacier responses are large. No straightforward relationship is found between glacier size and the projected fractional change of its length.
Hydroacoustic habitat mapping in Potter Cove (King George Island, Antarctica)
NASA Astrophysics Data System (ADS)
Hass, H. Christian; Wölfl, Anne-Cathrin; Kuhn, Gerhard; Jerosch, Kerstin; Scharf, Frauke; Abele, Doris
2016-04-01
Climate change increasingly affects the coastal areas off Antarctica. Strongest environmental response occurs in the transition zones that mediate between the polar and subpolar latitudes. Potter Cove, a minor fjord at the northern tip of the Antarctic Peninsula is significantly affected by rising temperatures and retreating ice sheets. Large amounts of turbid meltwaters affect both, the seafloor and the water column and cause stress for many biota. There is an increasing demand to monitor the ongoing change and to work out means for comparison with similar coastal ecosystems under pressure. Marine habitat maps provide information on the seafloor characteristics that allow to describe and evaluate the status of the recent coastal ecosystem and to predict its future development. We used a RoxAnn acoustic ground discrimination system, a sidescan sonar, grab samples (grain size and TOC) and underwater video footage to gain habitat information. Supervised and unsupervised classification routines (including fuzzy k-means clustering and LDA) were employed to calculate models ranging from two classes (soft bottom habitat, stone habitat) to 7 classes (including classes of rocks with and without macroalgae as well as classes of gravels, sands and silts). Including organic carbon in the database allowed to identify a carbon-depleted class proximal to the glacier front. Potter Cove reveals features that are related to the climate-controlled environmental change: very rough seafloor topography in a small basin close to the fjord head which was cleared by the retreating tidewater glacier through the past two decades. The increasing distance to the glacier down-fjord causes existing habitats to smooth and mature and new habitats to form. This process will change the terrestrial and marine face of Potter Cove until the ongoing climatic change stops or even reverses. It becomes apparent that the final interpretation of the results benefits significantly from the different
Doran, P T; Wharton, R A; Lyons, W B; Des Marais, D J; Andersen, D T
2000-01-01
A process-oriented study was carried out in White Smoke lake, Bunger Hills, East Antarctica, a perennially ice-covered (1.8 to 2.8 m thick) epishelf (tidally-forced) lake. The lake water has a low conductivity and is relatively well mixed. Sediments are transferred from the adjacent glacier to the lake when glacier ice surrounding the sediment is sublimated at the surface and replaced by accumulating ice from below. The lake bottom at the west end of the lake is mostly rocky with a scant sediment cover. The east end contains a thick sediment profile. Grain size and delta 13C increase with sediment depth, indicating a more proximal glacier in the past. Sedimentary 210Pb and 137Cs signals are exceptionally strong, probably a result of the focusing effect of the large glacial catchment area. The post-bomb and pre-bomb radiocarbon reservoirs are c. 725 14C yr and c. 1950 14C yr, respectively. Radiocarbon dating indicates that the east end of the lake is >3 ka BP, while photographic evidence and the absence of sediment cover indicate that the west end has formed only over the last century. Our results indicate that the southern ice edge of Bunger Hills has been relatively stable with only minor fluctuations (on the scale of hundreds of metres) over the last 3000 years.
NASA Astrophysics Data System (ADS)
Rowan, Ann; Quincey, Duncan; Egholm, David; Gibson, Morgan; Irvine-Fynn, Tristram; Porter, Philip; Glasser, Neil
2016-04-01
Many mountain glaciers are characterised in their lower reaches by thick layers of rock debris that insulate the glacier surface from solar radiation and atmospheric warming. Supraglacial debris modifies the response of these glaciers to climate change compared to glaciers with clean-ice surfaces. However, existing modelling approaches to predicting variations in the extent and mass balance of debris-covered glaciers have relied on numerical models that represent the processes governing glaciers with clean-ice surfaces, and yield conflicting results. Moreover, few data exist describing the mass balance of debris-covered glaciers and many observations are only made over short periods of time, but these data are needed to constrain and validate numerical modelling experiments. To investigate the impact of supraglacial debris on the response of a glacier to climate change, we developed a numerical model that couples the flow of ice and debris to include important feedbacks between mass balance, ice flow and debris accumulation. We applied this model to a large debris-covered Himalayan glacier - Khumbu Glacier in the Everest region of Nepal. Our results demonstrate that supraglacial debris prolongs the response of the glacier to warming air temperatures and causes lowering of the glacier surface in situ, concealing the magnitude of mass loss when compared with estimates based on glacierised area. Since the Little Ice Age, the volume of Khumbu Glacier has reduced by 34%, while glacier area has reduced by only 6%. We predict a further decrease in glacier volume of 8-10% by AD2100 accompanied by dynamic and physical detachment of the debris-covered tongue from the active glacier within the next 150 years. For five months during the 2014 summer monsoon, we measured temperature profiles through supraglacial debris and proglacial discharge on Khumbu Glacier. We found that temperatures at the ice surface beneath 0.4-0.7 m of debris were sufficient to promote considerable
Accelerated ice shelf rifting and retreat at Pine Island Glacier, West Antarctica
NASA Astrophysics Data System (ADS)
Jeong, Seongsu; Howat, Ian M.; Bassis, Jeremy N.
2016-11-01
Pine Island Glacier has undergone several major iceberg calving events over the past decades. These typically occurred when a rift at the heavily fractured shear margin propagated across the width of the ice shelf. This type of calving is common on polar ice shelves, with no clear connection to ocean-ice dynamic forcing. In contrast, we report on the recent development of multiple rifts initiating from basal crevasses in the center of the ice shelf, resulted in calving further upglacier than previously observed. Coincident with rift formation was the sudden disintegration of the ice mélange that filled the northern shear margin, resulting in ice sheet detachment from this margin. Examination of ice velocity suggests that this internal rifting resulted from the combination of a change in ice shelf stress regime caused by disintegration of the mélange and intensified melting within basal crevasses, both of which may be linked to ocean forcing.
Do Glaciers on Cascade Volcanoes Behave Differently Than Other Glaciers in the Region?
NASA Astrophysics Data System (ADS)
Riedel, J. L.; Ryane, C.; Osborn, J.; Davis, T.; Menounos, B.; Clague, J. J.; Koch, J.; Scott, K. M.; Reasoner, M.
2006-12-01
It has been suggested that glaciers on two stratovolcanoes in the Cascade Range of Washington state, Mt. Baker and Glacier Peak, achieved their maximum extent of the past 10,000 years during the early Holocene. These findings differ from most evidence in western North America, which indicates that Little Ice Age moraines represent the most extensive glacier advances of the Holocene. Significant early Holocene advances are difficult to reconcile with the documented warm, dry conditions at this time in western North America. Our data indicate that glaciers on these volcanoes responded similarly to Holocene climatic events as glaciers in other areas in Washington and British Columbia. Heavy winter accumulation and favorable hypsometry have been proposed as the explanations for the unusual behavior of glaciers on volcanoes compared to similar-sized glaciers elsewhere in the Cascade Range. However, glacier mass balance on the volcanoes is controlled by not only these factors, but also by glacier geometry, snow erosion and ablation. Accumulation zones of glaciers on isolated Cascade stratovolcanoes are high, but are narrow at the top. For example, the accumulation zone of Deming Glacier on the southwest side of Mt. Baker extends above 3000 m asl, but due to its wedge shape lies largely below 2500 m asl. Furthermore, glaciers on Mt. Baker and other symmetrical volcanoes have high ablation rates because they are not shaded, and south-southwest aspects are subject to erosion of snow by prevailing southwesterly winds. Modern glacier observations in the North Cascades quantify the important influence of aspect and snow erosion on glacier mass balance. For example, average equilibrium line altitude (ELA) of Easton Glacier on the south flank of Mt. Baker is 2160 m, whereas the ELA of a north-facing cirque glacier 25km to the east is 2040m. Our research at Mt. Baker contradicts the claim of extensive early Holocene advances on the south flank of the volcano. Tephra set SC, which
NASA Astrophysics Data System (ADS)
Muto, A.; Peters, L. E.; Anandakrishnan, S.; Alley, R. B.; Riverman, K. L.
2013-12-01
Recent estimates indicate that ice shelves along the Amundsen Sea coast in West Antarctica are losing substantial mass through sub-ice-shelf melting and contributing to the accelerating mass loss of the grounded ice buttressed by them. For Pine Island Glacier (PIG), relatively warm Circumpolar Deep Water has been identified as the key driver of the sub-ice-shelf melting although poor constraints on PIG sub-ice shelf have restricted thorough understanding of these ice-ocean interactions. Aerogravity data from NASA's Operation IceBridge (OIB) have been useful in identifying large-scale (on the order of ten kilometers) features but the results have relatively large uncertainties due to the inherent non-uniqueness of the gravity inversion. Seismic methods offer the most direct means of providing water thickness and upper crustal geological constraints, but availability of such data sets over the PIG ice shelf has been limited due to logistical constraints. Here we present a comparative analysis of the bathymetry and upper crustal structure beneath the ice shelf of PIG through joint inversion of OIB aerogravity data and in situ active-source seismic measurements collected in the 2012-13 austral summer. Preliminary results indicate improved resolution of the ocean cavity, particularly in the interior and sides of the PIG ice shelf, and sedimentary drape across the region. Seismically derived variations in ice and ocean water densities are also applied to the gravity inversion to produce a more robust model of PIG sub-ice shelf structure, as opposed to commonly used single ice and water densities across the entire study region. Misfits between the seismically-constrained gravity inversion and that estimated previously from aerogravity alone provide insights on the sensitivity of gravity measurements to model perturbations and highlight the limitations of employing gravity data to model ice shelf environments when no other sub-ice constraints are available.
Where glaciers meet water: Subaqueous melt and its relevance to glaciers in various settings
NASA Astrophysics Data System (ADS)
Truffer, Martin; Motyka, Roman J.
2016-03-01
Glacier change is ubiquitous, but the fastest and largest magnitude changes occur in glaciers that terminate in water. This includes the most rapidly retreating glaciers, and also several advancing ones, often in similar regional climate settings. Furthermore, water-terminating glaciers show a large range in morphology, particularly when ice flow into ocean water is compared to that into freshwater lakes. All water-terminating glaciers share the ability to lose significant volume of ice at the front, either through mechanical calving or direct melt from the water in contact. Here we present a review of the subaqueous melt process. We discuss the relevant physics and show how different physical settings can lead to different glacial responses. We find that subaqueous melt can be an important trigger for glacier change. It can explain many of the morphological differences, such as the existence or absence of floating tongues. Subaqueous melting is influenced by glacial runoff, which is largely a function of atmospheric conditions. This shows a tight connection between atmosphere, oceans and lakes, and glaciers. Subaqueous melt rates, even if shown to be large, should always be discussed in the context of ice supply to the glacier front to assess its overall relevance. We find that melt is often relevant to explain seasonal evolution, can be instrumental in shifting a glacier into a different dynamical regime, and often forms a large part of a glacier's mass loss. On the other hand, in some cases, melt is a small component of mass loss and does not significantly affect glacier response.
Response of small glaciers to climate change: runoff from glaciers of the Wind River range, Wyoming
NASA Astrophysics Data System (ADS)
Bliss, A. K.; Stamper, B.
2017-12-01
Runoff from glaciers affects downstream ecosystems by influencing the quantity, seasonality, and chemistry of the water. We describe the present state of glaciers in the Wind River range, Wyoming and consider how these glaciers will change in the future. Wind River glaciers have been losing mass in recent decades, as seen with geodetic techniques and by examining glacier morphology. Interestingly, the 2016/7 winter featured one of the largest snowfalls on record. Our primary focus is the Dinwoody Glacier ( 3 km^2, 3300-4000 m above sea level). We present data collected in mid-August 2017 including glacier ablation rates, snow line elevations, and streamflow. We compare measured glacier mass loss to streamflow at the glacier terminus and at a USGS stream gauge farther downstream. Using a hydrological model, we explore the fate of glacial runoff as it moves into downstream ecosystems and through ranchlands important to local people. The techniques used here can be applied to similar small-glacier systems in other parts of the world.
Ocean forcing drives glacier retreat sometimes
NASA Astrophysics Data System (ADS)
Bassis, J. N.; Ultee, E.; Ma, Y.
2015-12-01
Observations show that marine-terminating glaciers respond to climate forcing nonlinearly, with periods of slow or negligible glacier advance punctuated by abrupt, rapid retreat. Once glacier retreat has initiated, glaciers can quickly stabilize with a new terminus position. Alternatively, retreat can be sustained for decades (or longer), as is the case for Columbia Glacier, Alaska where retreat initiated ~1984 and continues to this day. Surprisingly, patterns of glacier retreat show ambiguous or even contradictory correlations with atmospheric temperature and glacier surface mass balance. Despite these puzzles, observations increasingly show that intrusion of warm subsurface ocean water into fjords can lead to glacier erosion rates that can account for a substantial portion of the total mass lost from glaciers. Here we use a simplified flowline model to show that even relatively modest submarine melt rates (~100 m/a) near the terminus of grounded glaciers can trigger large increases in iceberg calving leading to rapid glacier retreat. However, the strength of the coupling between submarine melt and calving is a strong function of the geometry of the glacier (bed topography, ice thickness and glacier width). This can lead to irreversible retreat when the terminus is thick and grounded deeply beneath sea level or result in little change when the glacier is relatively thin, grounded in shallow water or pinned in a narrow fjord. Because of the strong dependence on glacier geometry, small perturbations in submarine melting can trigger glaciers in their most advanced—and geometrically precarious—state to undergo sudden retreat followed by much slower re-advance. Although many details remain speculative, our model hints that some glaciers are more sensitive than others to ocean forcing and that some of the nonlinearities of glacier response to climate change may be attributable to variations in difficult-to-detect subsurface water temperatures that need to be better
Detection and Analysis of Complex Patterns of Ice Dynamics in Antarctica from ICESat Laser Altimetry
NASA Astrophysics Data System (ADS)
Babonis, Gregory Scott
There remains much uncertainty in estimating the amount of Antarctic ice mass change, its dynamic component, and its spatial and temporal patterns. This work remedies the limitations of previous studies by generating the first detailed reconstruction of total and dynamic ice thickness and mass changes across Antarctica, from ICESat satellite altimetry observations in 2003-2009 using the Surface Elevation Reconstruction and Change Detection (SERAC) method. Ice sheet thickness changes are calculated with quantified error estimates for each time when ICESat flew over a ground-track crossover region, at approximately 110,000 locations across the Antarctic Ice Sheet. The time series are partitioned into changes due to surficial processes and ice dynamics. The new results markedly improve the spatial and temporal resolution of surface elevation, volume, and mass change rates for the AIS, and can be sampled at annual temporal resolutions. The results indicate a complex spatiotemporal pattern of dynamic mass loss in Antarctica, especially along individual outlet glaciers, and allow for the quantification of the annual contribution of Antarctic ice loss to sea level rise. Over 5000 individual locations exhibit either strong dynamic ice thickness change patterns, accounting for approximately 500 unique spatial clusters that identify regions likely influenced by subglacial hydrology. The spatial distribution and temporal behavior of these regions reveal the complexity and short-time scale variability in the subglacial hydrological system. From the 500 unique spatial clusters, over 370 represent newly identified, and not previously published, potential subglacial water bodies indicating an active subglacial hydrological system over a much larger region than previously observed. These numerous new observations of dynamic changes provide more than simply a larger set of data. Examination of both regional and local scale dynamic change patterns across Antarctica shows newly
NASA Astrophysics Data System (ADS)
Velicogna, I.; Sutterley, T. C.; A, G.; van den Broeke, M. R.; Ivins, E. R.
2016-12-01
We use Gravity Recovery and Climate Experiment (GRACE) monthly gravity fields to determine the regional acceleration in ice mass loss in Antarctica for 2002-2016. We find that the total mass loss is controlled by only a few regions. In Antarctica, the Amundsen Sea (AS) sector and the Antarctic Peninsula account for 65% and 18%, respectively, of the total loss (186 ± 10 Gt/yr) mainly from ice dynamics. The AS sector contributes most of the acceleration in loss (9 ± 1 Gt/yr2 ), and Queen Maud Land, East Antarctica, is the only sector with a significant mass gain due to a local increase in SMB (57 ± 5 Gt/yr). We compare GRACE regional mass balance estimates with independent estimates from ICESat-1 and Operation IceBridge laser altimetry, CryoSat-2 radar altimetry, and surface mass balance outputs from RACMO2.3. In the Amundsen Sea Embayment of West Antarctica, an area experiencing rapid retreat and mass loss to the sea, we find good agreement between GRACE and altimetry estimates. Comparison of GRACE with these independent techniques in East Antarctic shows that GIA estimates from the new regional ice deglaciation models underestimate the GIA correction in the EAIS interior, which implies larger losses of the Antarctica ice sheet by about 70 Gt/yr. Sectors where we are observing the largest losses are closest to warm circumpolar water, and with polar constriction of the westerlies enhanced by climate warming, we expect these sectors to contribute more and more to sea level as the ice shelves that protect these glaciers will melt faster in contact with more heat from the surrounding oc
Taylor Elected to Royal Society of London
SLAC, 28 May 1997 Taylor Elected to Royal Society of London Richard Taylor, physics professor at statements must be verified by facts. Taylor will travel to London in the near future for his induction, part Isaac Newton and Michael Faraday. Taylor, a Canadian citizen, received his Ph.D. at Stanford in 1962 and
Glacier-derived August runoff in northwest Montana
Clark, Adam; Harper, Joel T.; Fagre, Daniel B.
2015-01-01
The second largest concentration of glaciers in the U.S. Rocky Mountains is located in Glacier National Park (GNP), Montana. The total glacier-covered area in this region decreased by ∼35% over the past 50 years, which has raised substantial concern about the loss of the water derived from glaciers during the summer. We used an innovative weather station design to collect in situ measurements on five remote glaciers, which are used to parameterize a regional glacier melt model. This model offered a first-order estimate of the summer meltwater production by glaciers. We find, during the normally dry month of August, glaciers in the region produce approximately 25 × 106 m3 of potential runoff. We then estimated the glacier runoff component in five gaged streams sourced from GNP basins containing glaciers. Glacier-melt contributions range from 5% in a basin only 0.12% glacierized to >90% in a basin 28.5% glacierized. Glacier loss would likely lead to lower discharges and warmer temperatures in streams draining basins >20% glacier-covered. Lower flows could even be expected in streams draining basins as little as 1.4% glacierized if glaciers were to disappear.
Recent thinning of Bowdoin Glacier, a marine terminating outlet glacier in northwestern Greenland
NASA Astrophysics Data System (ADS)
Tsutaki, S.; Sugiyama, S.; Sakakibara, D.; Sawagaki, T.; Maruyama, M.
2014-12-01
Ice discharge from calving glaciers has increased in the Greenland ice sheet (GrIS), and this increase plays important roles in the volume change of GrIS and its contribution to sea level rise. Thinning of GrIS calving glaciers has been studied by the differentiation of digital elevation models (DEMs) derived by satellite remote-sensing (RS). Such studies rely on the accuracy of DEMs, but calibration of RS data with ground based data is difficult. This is because field data on GrIS calving glaciers are few. In this study, we combined field and RS data to measure surface elevation change of Bowdoin Glacier, a marine terminating outlet glacier in northwestern Greenland (77°41'18″N, 68°29'47″W). The fast flowing part of the glacier is approximately 3 km wide and 10 km long. Ice surface elevation within 6 km from the glacier terminus was surveyed in the field in July 2013 and 2014, by using the global positioning system. We also measured the surface elevation over the glacier on August 20, 2007 and September 4, 2010, by analyzing Advanced Land Observing Satellite (ALOS), Panchromatic remote-sensing Instrument for Stereo Mapping (PRISM) images. We calibrated the satellite derived elevation data with our field measurements, and generated DEM for each year with a 25 m grid mesh. The field data and DEMs were compared to calculate recent glacier elevation change. Mean surface elevation change along the field survey profiles were -16.3±0.2 m (-5.3±0.1 m yr-1) in 2007-2010 and -10.8±0.2 m (-3.8±0.1 m yr-1) in 2010-2013. These rates are much greater than those observed on non-calving ice caps in the region, and similar to those reported for other calving glaciers in northwestern Greenland. Loss of ice was greater near the glacier terminus, suggesting the importance of ice dynamics and/or interaction with the ocean.
Warm water and life beneath the grounding zone of an Antarctic outlet glacier
NASA Astrophysics Data System (ADS)
Sugiyama, Shin; Sawagaki, Takanobu; Fukuda, Takehiro
2013-04-01
Ice-ocean interaction plays a key role in rapidly changing Antarctic ice sheet margins. Recent studies demonstrated that warming ocean is eroding floating part of the ice sheet, resulting in thinning, retreat and acceleration of ice shelves and outlet glaciers. Field data are necessary to understand such processes, but direct observations at the interface of ice and the ocean are lacking, particularly beneath the grounding zone. To better understand the interaction of Antarctic ice sheet and the ocean, we performed subglacial measurements through boreholes drilled in the grounding zone of Langhovde Glacier, an outlet glacier in East Antarctica. Langhovde Glacier is located at 69°12'S, 39°48'E, approximately 20 km south of a Japanese research station Syowa. The glacier discharges ice into Lützow-holm Bay through a 3-km-wide floating terminus at a rate of 130 m a-1. Fast flowing feature is confined by bedrock to the west and slow moving ice to the east, and it extends about 10 km upglacier from the calving front. In 2011/12 austral summer season, we operated a hot water drilling system to drill through the glacier at 2.5 and 3 km from the terminus. Inspections of the boreholes revealed the ice was underlain by a shallow saline water layer. Ice and water column thicknesses were found to be 398 and 24 m at the first site, and 431 and 10 m at the second site. Judging from ice surface and bed elevations, the drilling sites were situated at within a several hundred meters from the grounding line. Sensors were lowered into the boreholes to measure temperature, salinity and current within the subglacial water layer. Salinity and temperature from the two sites were fairly uniform (34.25±0.05 PSU and -1.45±0.05°C), indicating vertical and horizontal mixing in the layer. The measured temperature was >0.7°C warmer than the in-situ freezing point, and very similar to the values measured in the open ocean near the glacier front. Subglacial current was up to 3 cm/s, which
Cosmogenic evidence for limited local LGM glacial expansion, Denton Hills, Antarctica
NASA Astrophysics Data System (ADS)
Joy, Kurt; Fink, David; Storey, Bryan; De Pascale, Gregory P.; Quigley, Mark; Fujioka, Toshiyuki
2017-12-01
The geomorphology of the Denton Hills provides insight into the timing and magnitude of glacial retreats in a region of Antarctica isolated from the influence of the East Antarctic ice sheet. We present 26 Beryllium-10 surface exposure ages from a variety of glacial and lacustrine features in the Garwood and Miers valleys to document the glacial history of the area from 10 to 286 ka. Our data show that the cold-based Miers, Joyce and Garwood glaciers retreated little since their maximum positions at 37.2 ± 6.9 (1σ n = 4), 35.1 ± 1.5 (1σ, n = 3) and 35.6 ± 10.1 (1σ, n = 6) ka respectively. The similar timing of advance of all three glaciers and the lack of a significant glacial expansion during the global LGM suggests a local LGM for the Denton Hills between ca. 26 and 51 ka, with a mean age of 36.0 ± 7.5 (1σ, n = 13) ka. A second cohort of exposure ages provides constraints to the behaviour of Glacial Lake Trowbridge that formerly occupied Miers Valley in the late Pleistocene. These data show active modification of the landscape from ∼20 ka until the withdrawal of ice from the valley mouths, and deposition of Ross Sea Drift, at 10-14 ka.
Assessing glacier melt contribution to streamflow at Universidad Glacier, central Andes of Chile
NASA Astrophysics Data System (ADS)
Bravo, Claudio; Loriaux, Thomas; Rivera, Andrés; Brock, Ben W.
2017-07-01
Glacier melt is an important source of water for high Andean rivers in central Chile, especially in dry years, when it can be an important contributor to flows during late summer and autumn. However, few studies have quantified glacier melt contribution to streamflow in this region. To address this shortcoming, we present an analysis of meteorological conditions and ablation for Universidad Glacier, one of the largest valley glaciers in the central Andes of Chile at the head of the Tinguiririca River, for the 2009-2010 ablation season. We used meteorological measurements from two automatic weather stations installed on the glacier to drive a distributed temperature-index and runoff routing model. The temperature-index model was calibrated at the lower weather station site and showed good agreement with melt estimates from an ablation stake and sonic ranger, and with a physically based energy balance model. Total modelled glacier melt is compared with river flow measurements at three sites located between 0.5 and 50 km downstream. Universidad Glacier shows extremely high melt rates over the ablation season which may exceed 10 m water equivalent in the lower ablation area, representing between 10 and 13 % of the mean monthly streamflow at the outlet of the Tinguiririca River Basin between December 2009 and March 2010. This contribution rises to a monthly maximum of almost 20 % in March 2010, demonstrating the importance of glacier runoff to streamflow, particularly in dry years such as 2009-2010. The temperature-index approach benefits from the availability of on-glacier meteorological data, enabling the calculation of the local hourly variable lapse rate, and is suited to high melt regimes, but would not be easily applicable to glaciers further north in Chile where sublimation is more significant.
Mesoscale cyclogenesis dynamics over the southwestern Ross Sea, Antarctica
NASA Astrophysics Data System (ADS)
Carrasco, Jorge F.; Bromwich, David H.
1993-07-01
Previous work has shown that frequent mesoscale cyclogenesis adjacent to Franklin Island is linked to the strong and persistent katabatic winds from East Antarctica which funnel into Terra Nova Bay and then blow out over the southwestern Ross Sea. Four mesoscale cyclones that formed near Terra Nova Bay between February 16 and 20, 1988 are examined to more clearly define the governing mechanisms. These events are investigated using all available observations, including automatic weather station data, high-resolution satellite images, satellite soundings, and hemispheric synoptic analyses. The first two cyclones formed on low-level baroclinic zones established by the synoptic scale advection of warm moist air toward the cold continental air blowing gently from East Antarctica. In the second case, baroclinic instability of this small-scale cold front was apparently triggered by the enhanced upward vertical motion associated with the approach of a midtropospheric trough. The third mesocyclone formed shortly after on a baroclinic zone over the polar plateau; the second vortex completely disrupted the usual katabatic drainage over the plateau and forced warm moist air over the coastal slopes. All three cyclones moved to the north in the prevailing cyclonic flow, but the plateau vortex lasted for only 6 hours. The fourth mesoscale low formed in conjunction with an abrupt and intense surge of katabatic air from Terra Nova Bay which resharpened the coastal baroclinic zone. At the same time a transiting midtropospheric trough probably associated with lower tropospheric upward vertical motion apparently accelerated the katabatic winds and triggered the vortex formation. A similar katabatic wind-forced mesocyclone formed near Byrd Glacier. The two vortices moved to the east-southeast and northeast, respectively, apparently being steered by the generating katabatic airstreams, and merged just to the north of the Ross Ice Shelf. The combined vortex reintensified as another
Malaspina Glacier: a modern analog to the Laurentide Glacier in New England
DOE Office of Scientific and Technical Information (OSTI.GOV)
Gustavson, T.C.; Boothroyd, J.C.
1985-01-01
The land-based temperate Malaspina Glacier is a partial analog to the late Wisconsinan Laurentide Ice Sheet that occupied New England and adjacent areas. The Malaspina occupies a bedrock basin similar to basins occupied by the margin of the Laurentide Ice Sheet. Ice lobes of the Malaspina are similar in size to end moraine lobes in southern New England and Long Island,New York. Estimated ice temperature, ablation rates, surface slopes and meltwater discharge per unit of surface area for the Laurentide Ice Sheet are similar to those for the Malaspina Glacier. In a simple hydrologic-fluvial model for the Malaspina Glacier meltwatermore » moves towards the glacier bed and down-glacier along intercrystalline pathways, crevasses and moulins, and a series of tunnels. Regolith and bedrock at the glacier floor, which are eroded and transported by subglacial and englacial streams, are the sources of essentially all fluvio-lacustrine sediment on the Malaspina Foreland. Supraglacial eskers containing coarse gravels occur as much as 100 m above the glacier bed and are evidence that bedload can be lifted hydraulically. Subordinant amounts of sediment are contributed to outwash by small surface streams draining the ice margin. By analogy a similar hydrologic-fluvial system existed along the southeastern margin of the Laurentide Ice Sheet. Subglacial regolith and bedrock eroded from beneath the Laurentide Ice Sheet by meltwater was also the source of most glaciofluvial and glaciolacustrine deposits in southern New England, not sediment carried to the surface of the ice sheet along shear planes and washed off the glacier by meltwater.« less
Taylor instability in rhyolite lava flows
NASA Technical Reports Server (NTRS)
Baum, B. A.; Krantz, W. B.; Fink, J. H.; Dickinson, R. E.
1989-01-01
A refined Taylor instability model is developed to describe the surface morphology of rhyolite lava flows. The effect of the downslope flow of the lava on the structures resulting from the Taylor instability mechanism is considered. Squire's (1933) transformation is developed for this flow in order to extend the results to three-dimensional modes. This permits assessing why ridges thought to arise from the Taylor instability mechanism are preferentially oriented transverse to the direction of lava flow. Measured diapir and ridge spacings for the Little and Big Glass Mountain rhyolite flows in northern California are used in conjunction with the model in order to explore the implications of the Taylor instability for flow emplacement. The model suggests additional lava flow features that can be measured in order to test whether the Taylor instability mechanism has influenced the flows surface morphology.
NASA Astrophysics Data System (ADS)
Navas, Ana; Oliva, Marc; Ruiz-Fernández, Jesús; Quijano, Laura; Gaspar, Leticia; Lizaga, Iván
2017-04-01
In Maritime Antarctica important environmental changes are affecting ice-free environments of the South Shetland Islands and the northern Antarctica Peninsula. In the Elephant Point Peninsula (Livingstone Island) a rapid glacier retreat during the last decades has exposed already around 20% of its 1.16 km2 surface. Despite soil development is taken place in these new created lands little is known on the characteristics and properties of soils on different parent materials and landforms. One of the main soil properties is the organic carbon but the SOC pool dynamics in Antarctica environments is still poorly understood. This work aims to gain knowledge on the lateral and vertical variations of soil organic carbon (SOC) and organic carbon fractions in surface profiles that have been exposed succeeding the phases of glacier retreat. To this purpose a sampling scheme following the direction of the glacier retreat was established along a moraine extending from the western to the eastern coastlines and a sequence of Holocene marine terraces in Elephant Point. To assess the lateral and vertical variations of SOC and SOC fractions a total of 10 sites were sampled until a depth of 12 cm then sectioned at 3 cm depth intervals. According to its chemical stability and turnover times, SOC can be divided into the active carbon fraction (ACF) composed of labile aliphatic and carboxyl groups with turnover rates of days to few years and a more stable refractory aromatic carbon fraction (SCF) with turnover rates from few years to centuries, highly resistant to microbial and chemical decomposition. The SOC content (%) was measured at 550 °C by the dry combustion method using a LECO, RC-612 multiphase carbon analyser. For the characterization of the active and stable carbon fractions the temperature of the furnace was stepped at 350 °C and 550 °C, respectively. Estimates of SOC and SOC fractions inventories (kg m-2) were done to assess their stocks on the different landforms. SOC
2018-03-26
In October 2016, the Khurdopin Glacier in Pakistan began a rapid surge after 20 years of little movement. By March, 2017, a large lake had formed in the Shimshal River, where the glacier had formed a dam. Fortunately, the river carved an outlet through the glacier before the lake could empty catastrophically. In this pair of ASTER images, acquired August 20, 2015 and May 21, 2017, the advance of the Khurdopin Glacier (dark gray and white "river" in lower right quarter of image) is obvious by comparing the before and after images. The images cover an area of 25 by 27.8 km, and are located at 36.3 degrees north, 75.5 degrees east. https://photojournal.jpl.nasa.gov/catalog/PIA22304
West, Michael E.; Larsen, Christopher F.; Truffer, Martin; O'Neel, Shad; LeBlanc, Laura
2010-01-01
We present a framework for interpreting small glacier seismic events based on data collected near the center of Bering Glacier, Alaska, in spring 2007. We find extremely high microseismicity rates (as many as tens of events per minute) occurring largely within a few kilometers of the receivers. A high-frequency class of seismicity is distinguished by dominant frequencies of 20–35 Hz and impulsive arrivals. A low-frequency class has dominant frequencies of 6–15 Hz, emergent onsets, and longer, more monotonic codas. A bimodal distribution of 160,000 seismic events over two months demonstrates that the classes represent two distinct populations. This is further supported by the presence of hybrid waveforms that contain elements of both event types. The high-low-hybrid paradigm is well established in volcano seismology and is demonstrated by a comparison to earthquakes from Augustine Volcano. We build on these parallels to suggest that fluid-induced resonance is likely responsible for the low-frequency glacier events and that the hybrid glacier events may be caused by the rush of water into newly opening pathways.
NASA Astrophysics Data System (ADS)
Falatkova, Kristyna; Schöner, Wolfgang; Häusler, Hermann; Reisenhofer, Stefan; Neureiter, Anton; Sobr, Miroslav; Jansky, Bohumir
2017-04-01
Mountain glacier retreat has a well-known impact on life of local population - besides anxiety over water supply for agriculture, industry, or households, it has proved to have a direct influence on glacier hazard occurrence. The paper focuses on lake outburst hazard specifically, and aims to describe the previous and future development of Adygine glacier complex and identify its relationship to the hazard. The observed glacier is situated in the Northern Tien Shan, with an area of 4 km2 in northern exposition at an elevation range of 3,500-4,200 m a.s.l. The study glacier ranks in the group of small-sized glaciers, therefore we expect it to respond faster to changes of the climate compared to larger ones. Below the glacier there is a three-level cascade of proglacial lakes at different stages of development. The site has been observed sporadically since 1960s, however, closer study has been carried out since 2007. Past development of the glacier-lake complex is analyzed by combination of satellite imagery interpretations and on-site measurements (geodetic and bathymetric survey). A glacier mass balance model is used to simulate future development of the glacier resulting from climate scenarios. We used the simulated future glacier extent and the glacier base topography provided by GPR survey to assess potential for future lake formation. This enables us to assess the outburst hazard for the three selected lakes with an outlook for possible/probable hazard changes linked to further complex succession/progression (originating from climate change scenarios). Considering the proximity of the capital Bishkek, spreading settlements, and increased demand for tourism-related infrastructure within the main valley, it is of high importance to identify the present and possible future hazards that have a potential to affect this region.
2001-07-21
This ASTER image was acquired on May 2, 2000 over the North Patagonia Ice Sheet, Chile near latitude 47 degrees south, longitude 73 degrees west. The image covers 36 x 30 km. The false color composite displays vegetation in red. The image dramatically shows a single large glacier, covered with crevasses. A semi-circular terminal moraine indicates that the glacier was once more extensive than at present. ASTER data are being acquired over hundreds of glaciers worldwide to measure their changes over time. Since glaciers are sensitive indicators of warming or cooling, this program can provide global data set critical to understand climate change. This image is located at 46.5 degrees south latitude and 73.9 degrees west longitude. http://photojournal.jpl.nasa.gov/catalog/PIA02670
NASA Astrophysics Data System (ADS)
Machguth, H.; Huss, M.
2014-05-01
Glacier length is an important measure of glacier geometry but global glacier inventories are mostly lacking length data. Only recently semi-automated approaches to measure glacier length have been developed and applied regionally. Here we present a first global assessment of glacier length using a fully automated method based on glacier surface slope, distance to the glacier margins and a set of trade-off functions. The method is developed for East Greenland, evaluated for the same area as well as for Alaska, and eventually applied to all ∼200 000 glaciers around the globe. The evaluation highlights accurately calculated glacier length where DEM quality is good (East Greenland) and limited precision on low quality DEMs (parts of Alaska). Measured length of very small glaciers is subject to a certain level of ambiguity. The global calculation shows that only about 1.5% of all glaciers are longer than 10 km with Bering Glacier (Alaska/Canada) being the longest glacier in the world at a length of 196 km. Based on model output we derive global and regional area-length scaling laws. Differences among regional scaling parameters appear to be related to characteristics of topography and glacier mass balance. The present study adds glacier length as a central parameter to global glacier inventories. Global and regional scaling laws might proof beneficial in conceptual glacier models.
NASA Astrophysics Data System (ADS)
Mackay, Sean Leland
Antarctic debris-covered glaciers are potential archives of long-term climate change. However, the geomorphic response of these systems to climate forcing is not well understood. To address this concern, I conducted a series of field-based and numerical modeling studies in the McMurdo Dry Valleys of Antarctica (MDV), with a focus on Mullins and Friedman glaciers. I used data and results from geophysical surveys, ice-core collection and analysis, geomorphic mapping, micro-meteorological stations, and numerical-process models to (1) determine the precise origin and distribution of englacial and supraglacial debris within these buried-ice systems, (2) quantify the fundamental processes and feedbacks that govern interactions among englacial and supraglacial debris, (3) establish a process-based model to quantify the inventory of cosmogenic nuclides within englacial and supraglacial debris, and (4) isolate the governing relationships between the evolution of englacial /supraglacial debris and regional climate forcing. Results from 93 field excavations, 21 ice cores, and 24 km of ground-penetrating radar data show that Mullins and Friedman glaciers contain vast areas of clean glacier ice interspersed with inclined layers of concentrated debris. The similarity in the pattern of englacial debris bands across both glaciers, along with model results that call for negligible basal entrainment, is best explained by episodic environmental change at valley headwalls. To constrain better the timing of debris-band formation, I developed a modeling framework that tracks the accumulation of cosmogenic 3He in englacial and supraglacial debris. Results imply that ice within Mullins Glacier increases in age non-linearly from 12 ka to ˜220 ka in areas of active flow (up to >> 1.6 Ma in areas of slow-moving-to-stagnant ice) and that englacial debris bands originate with a periodicity of ˜41 ka. Modeling studies suggest that debris bands originate in synchronicity with changes in
2017-12-08
Calving front of the Perito Moreno Glacier (Argentina). Contrary to the majority of the glaciers from the southern Patagonian ice field, the Perito Moreno Glacier is currently stable. It is also one of the most visited glaciers in the world. To learn about the contributions of glaciers to sea level rise, visit: www.nasa.gov/topics/earth/features/glacier-sea-rise.html Credit: Etienne Berthier, Université de Toulouse 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
NASA Astrophysics Data System (ADS)
Hams, J. E.; Marchant, D. R.
2009-12-01
PolarTREC is an educational research experience in which K-14 teachers participate in polar research with scientists as a pathway to improving science education. The program is funded by the National Science Foundation and managed by the Arctic Research Consortium of the United States. Teachers share their experiences with scientists, educators, communities, and students around the world during the expeditions through online journals, and translate the experience to the classroom by developing curricula based on the research expedition. A 2008 PolarTREC teacher research experience involved drilling through buried ice beneath glaciers in one of the Dry Valleys located in the cold-polar desert region of Antarctica. PolarTREC teacher Jacquelyn Hams accompanied Boston University researchers Dr. David Marchant and Sean Mackay to Beacon Valley, Antarctica. Beacon Valley is significant because the ice beneath it is estimated to be over several million years in age, making it the oldest ice known on this planet and it is one of the most Mars-like climatic environments and landscapes on Earth. In order to translate this unique environment to the classroom, lesson plans were created for students to study the topography, glacial landforms, and wind patterns of Beacon Valley. Students also examine the same imagery that scientists use to study the processes that operate in the extreme environments of Antarctica and Mars. The topographic maps and aerial images of Beacon Valley were obtained from the NASA LIMA (Landsat Image Mosaic of Antarctica) website and Mars imagery was obtained from the University of Arizona HiRISE (Hi Resolution Imaging Science Experiment) website. Wind data was downloaded from an anemometer in Beacon Valley and provided courtesy of Sean Mackay of Boston University. The lesson plans are available through the PolarTREC website or by contacting Jacquelyn Hams at hamsje@lavc.edu.
2010-09-13
Folds in the lower reaches of valley glaciers can be caused by powerful surges of tributary ice streams. This phenomenon is spectacularly displayed by the Sustina Glacier in the Alaska Range as seen by NASA Terra spacecraft.
NASA Astrophysics Data System (ADS)
Marzeion, B.; Maussion, F.
2017-12-01
Mountain glaciers are one of the few remaining sub-systems of the global climate system for which no globally applicable, open source, community-driven model exists. Notable examples from the ice sheet community include the Parallel Ice Sheet Model or Elmer/Ice. While the atmospheric modeling community has a long tradition of sharing models (e.g. the Weather Research and Forecasting model) or comparing them (e.g. the Coupled Model Intercomparison Project or CMIP), recent initiatives originating from the glaciological community show a new willingness to better coordinate global research efforts following the CMIP example (e.g. the Glacier Model Intercomparison Project or the Glacier Ice Thickness Estimation Working Group). In the recent past, great advances have been made in the global availability of data and methods relevant for glacier modeling, spanning glacier outlines, automatized glacier centerline identification, bed rock inversion methods, and global topographic data sets. Taken together, these advances now allow the ice dynamics of glaciers to be modeled on a global scale, provided that adequate modeling platforms are available. Here, we present the Open Global Glacier Model (OGGM), developed to provide a global scale, modular, and open source numerical model framework for consistently simulating past and future global scale glacier change. Global not only in the sense of leading to meaningful results for all glaciers combined, but also for any small ensemble of glaciers, e.g. at the headwater catchment scale. Modular to allow combinations of different approaches to the representation of ice flow and surface mass balance, enabling a new kind of model intercomparison. Open source so that the code can be read and used by anyone and so that new modules can be added and discussed by the community, following the principles of open governance. Consistent in order to provide uncertainty measures at all realizable scales.
Surge of a Complex Glacier System - The Current Surge of the Bering-Bagley Glacier System, Alaska
NASA Astrophysics Data System (ADS)
Herzfeld, U. C.; McDonald, B.; Trantow, T.; Hale, G.; Stachura, M.; Weltman, A.; Sears, T.
2013-12-01
Understanding fast glacier flow and glacial accelerations is important for understanding changes in the cryosphere and ultimately in sea level. Surge-type glaciers are one of four types of fast-flowing glaciers --- the other three being continuously fast-flowing glaciers, fjord glaciers and ice streams --- and the one that has seen the least amount of research. The Bering-Bagley Glacier System, Alaska, the largest glacier system in North America, surged in 2011 and 2012. Velocities decreased towards the end of 2011, while the surge kinematics continued to expand. A new surge phase started in summer and fall 2012. In this paper, we report results from airborne observations collected in September 2011, June/July and September/October 2012 and in 2013. Airborne observations include simultaneously collected laser altimeter data, videographic data, GPS data and photographic data and are complemented by satellite data analysis. Methods range from classic interpretation of imagery to analysis and classification of laser altimeter data and connectionist (neural-net) geostatistical classification of concurrent airborne imagery. Results focus on the characteristics of surge progression in a large and complex glacier system (as opposed to a small glacier with relatively simple geometry). We evaluate changes in surface elevations including mass transfer and sudden drawdowns, crevasse types, accelerations and changes in the supra-glacial and englacial hydrologic system. Supraglacial water in Bering Glacier during Surge, July 2012 Airborne laser altimeter profile across major rift in central Bering Glacier, Sept 2011
2002-02-26
This image from the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) instrument on NASA's Terra satellite covers an area of 55 by 40 kilometers (34 by 25 miles) over the southwest part of the Malaspina Glacier and Icy Bay in Alaska. The composite of infrared and visible bands results in the snow and ice appearing light blue, dense vegetation is yellow-orange and green, and less vegetated, gravelly areas are in orange. According to Dr. Dennis Trabant (U.S. Geological Survey, Fairbanks, Alaska), the Malaspina Glacier is thinning. Its terminal moraine protects it from contact with the open ocean; without the moraine, or if sea level rises sufficiently to reconnect the glacier with the ocean, the glacier would start calving and retreat significantly. ASTER data are being used to help monitor the size and movement of some 15,000 tidal and piedmont glaciers in Alaska. Evidence derived from ASTER and many other satellite and ground-based measurements suggests that only a few dozen Alaskan glaciers are advancing. The overwhelming majority of them are retreating. This ASTER image was acquired on June 8, 2001. With its 14 spectral bands from the visible to the thermal infrared wavelength region, and its high spatial resolution of 15 to 90 meters (about 50 to 300 feet), ASTER will image Earth for the next six years to map and monitor the changing surface of our planet. http://photojournal.jpl.nasa.gov/catalog/PIA03475
Water flow through temperate glaciers
Fountain, A.G.; Walder, J.S.
1998-01-01
Understanding water movement through a glacier is fundamental to several critical issues in glaciology, including glacier dynamics, glacier-induced floods, and the prediction of runoff from glacierized drainage basins. to this end we have synthesized a conceptual model os water movement through a temperate glacier from the surface to the outlet stream. Processes that regulate the rate and distribution of water input at the glacier surface and that regulate water movement from the surface to the bed play important but commonly neglected roles in glacier hydrology. Where a glacier is covered by a layer of porous, permeable firn (the accumulation zone), the flux of water to the glacier interior varies slowly because the firn temporarily stores water and thereby smooths out variations in the supply rate. In the firn-free ablation zone, in contrast, the flux of water into the glacier depends directly on the rate of surface melt or rainfall and therefore varies greatly in time. Water moves from the surface to the bed through an upward branching arborescent network consisting of both steeply inclined conduits, formed by the enlargement of intergranular veins, and gently inclined conduits, sprqwned by water flow along the bottoms of near-surface fractures (crevasses). Englacial drainage conduits deliver water to the glacier bed at a linited number of points, probably a long distance downglacier of where water enters the glacier. Englacial conduits supplied from the accumulation zone are quasi steady state features that convey the slowly varying water flux delivered via the firn. their size adjusts so that they are usually full of water and flow is pressurized. In contrast, water flow in englacial conduits supplied from the ablation area is pressurized only near times of peak daily flow or during rainstorms; flow is otherwise in an open-channel configuration. The subglacial drainage system typically consists of several elements that are distinct both morpphologically and
Rayleigh-Taylor mixing in supernova experiments
DOE Office of Scientific and Technical Information (OSTI.GOV)
Swisher, N. C.; Abarzhi, S. I., E-mail: snezhana.abarzhi@gmail.com; Kuranz, C. C.
We report a scrupulous analysis of data in supernova experiments that are conducted at high power laser facilities in order to study core-collapse supernova SN1987A. Parameters of the experimental system are properly scaled to investigate the interaction of a blast-wave with helium-hydrogen interface, and the induced Rayleigh-Taylor instability and Rayleigh-Taylor mixing of the denser and lighter fluids with time-dependent acceleration. We analyze all available experimental images of the Rayleigh-Taylor flow in supernova experiments and measure delicate features of the interfacial dynamics. A new scaling is identified for calibration of experimental data to enable their accurate analysis and comparisons. By properlymore » accounting for the imprint of the experimental conditions, the data set size and statistics are substantially increased. New theoretical solutions are reported to describe asymptotic dynamics of Rayleigh-Taylor flow with time-dependent acceleration by applying theoretical analysis that considers symmetries and momentum transport. Good qualitative and quantitative agreement is achieved of the experimental data with the theory and simulations. Our study indicates that in supernova experiments Rayleigh-Taylor flow is in the mixing regime, the interface amplitude contributes substantially to the characteristic length scale for energy dissipation; Rayleigh-Taylor mixing keeps order.« less
ERIC Educational Resources Information Center
Constible, Juanita; Williams, Lauren; Faure, Jaime; Lee, Richard E., Jr.
2012-01-01
When one thinks of the amazing creatures of Antarctica, an insect probably does not come to mind. But this unlikely animal, and a scientific expedition to Antarctica, was the foundation for a learning event that created a community of learners spanning kindergarten through sixth grade and extended beyond the classroom. Miami University's Antarctic…
NASA Astrophysics Data System (ADS)
Hall, E.; Fegel, T. S., II; Baron, J.; Boot, C. M.
2015-12-01
While alpine glaciers in montane regions represent the largest flux of dissolved organic matter (DOM) from global ice melt no research has examined the bioavailability of DOM melted out of glacial ice in the western continental United States. Furthermore, rock glaciers are an order of magnitude more abundant than ice glaciers in U.S., yet are not included in budgets for perennial ice carbon stores. Our research aims to understand differences in the bioavailability of carbon from ice glaciers and rock glaciers along the Central Rocky Mountains of Colorado. Identical microbial communities were fed standardized amounts of DOM from four different ice glacier-rock glaciers pairs. Using laboratory incubations, paired with mass spectrometry based metabolomics and 16S gene sequencing; we were able to examine functional definitions of DOM lability in glacial ice. We hypothesized that even though DOM quantities are similar in the outputs of both glacial types in our study area, ice glacial DOM would be more bioavailable than DOM from rock glaciers due to higher proportions of byproducts from microbial metabolism than rock glacier DOM, which has higher amounts of "recalcitrant" plant material. Our results show that DOM from ice glaciers is more labile than DOM from geologically and geographically similar paired rock glaciers. Ice glacier DOM represents an important pool of labile carbon to headwater ecosystems of the Rocky Mountains. Metabolomic analysis shows numerous compounds from varying metabolite pathways, including byproducts of nitrification before and after incubation, meaning that, similar to large maritime glaciers in Alaska and Europe, subglacial environments in the mountain ranges of the United States are hotspots for biological activity and processing of organic carbon.
Columbia Glacier in 1984: disintegration underway
DOE Office of Scientific and Technical Information (OSTI.GOV)
Meier, M.F.; Rasmussen, L.A.; Miller, D.S.
1985-01-01
Columbia Glacier is a large, iceberg-calving glacier near Valdez, Alaska. The terminus of this glacier was relatively stable from the time of the first scientific studies in 1899 until 1978. During this period the glacier terminated partly on Heather Island and partly on a submerged moraine shoal. In December, 1978, the glacier terminus retreated from Heather Island, and retreat has accelerated each year since then, except during a period of anomalously low calving in 1980. Although the glacier has not terminated on Heather Island since 1978, a portion of the terminus remained on the crest of the moraine shoal untilmore » the fall of 1983. By December 8, 1983, that feature had receded more than 300 m from the crest of the shoal, and by December 14, 1984, had disappeared completely, leaving most of the terminus more than 2000 meters behind the crest of the shoal. Recession of the glacier from the shoal has placed the terminus in deeper water, although the glacier does not float. The active calving face of the glacier now terminates in seawater that is about 300 meters deep at the glacier centerline. Rapid calving appears to be associated with buoyancy effects due to deep water at the terminus and subglacial runoff. 12 refs., 10 figs.« less
Antarctica Day: An International Celebration
NASA Astrophysics Data System (ADS)
Pope, A.; Hambrook Berkman, J.; Berkman, P. A.
2013-12-01
For more than half a century, the 1959 Antarctic Treaty continues to shine as a rare beacon of international cooperation. To celebrate this milestone of peace in our civilization with hope and inspiration for future generations, Antarctica Day is celebrated each year on December 1st , the anniversary of the Antarctic Treaty signing. As an annual event - initiated by the Foundation for the Good Governance of International Spaces (www.internationalspaces.org/) in collaboration with the Association of Polar Early Carer Scientists (www.apecs.is) - Antarctica Day encourages participation from around the world. The Antarctic Treaty set aside 10% of the earth, 'forever to be used exclusively for peaceful purposes in the interest of mankind.' It was the first nuclear arms agreement and the first institution to govern all human activities in an international region beyond sovereign jurisdictions. In this spirit, Antarctica Day aims to: - Demonstrate how diverse nations can work together peacefully, using science as a global language of cooperation for decision making beyond national boundaries, - Provide strategies for students learning about Antarctica through art, science and history at all school levels, - Increase collaboration and communication between classrooms, communities, researchers and government officials around the world, and - Provide a focus for polar educators to build on each year. Through close collaboration with a number of partners. Antarctica Day activities have included: a Polar Film Festival convened by The Explorers Club; live sessions connecting classrooms with scientists in Antarctica thanks to PolarTREC and ARCUS; an international activity that involved children from 13 countries who created over 600 flags which exemplify Antarctica Day (these were actually flown in Antarctica with signed certificates then returned to the classes); a map where Antarctica Day participants all over the world could share what they were doing; an Antarctic bird count
NASA Astrophysics Data System (ADS)
Mandal, Arindan; Ramanathan, Alagappan; Farooq Azam, Mohd; Wagnon, Patrick; Vincent, Christian; Linda, Anurag; Sharma, Parmanand; Angchuk, Thupstan; Bahadur Singh, Virendra; Pottakkal, Jose George; Kumar, Naveen; Soheb, Mohd
2015-04-01
Several studies on Himalayan glaciers have been recently initiated as they are of particular interest in terms of future water supply, regional climate change and sea-level rise. In 2002, a long-term monitoring program was initiated on Chhota Shigri Glacier (15.7 square km, 9 km long, 6263-4050 m a.s.l.) located in Lahaul and Spiti Valley, Himachal Pradesh, India. This glacier lies in the monsoon-arid transition zone (western Himalaya) and is a representative glacier in Lahaul and Spiti Valley. While annual mass balances have been measured continuously since 2002 using the glaciological method, seasonal scale observations began in 2009. The annual and seasonal mass balances were then analyzed along with meteorological conditions in order to understand the role of winter and summer balances on annual glacier-wide mass balance of Chhota Shigri glacier. During the period 2002-2013, the glacier experienced a negative glacier-wide mass balance of -0.59±0.40 m w.e. a-1 with a cumulative glaciological mass balance of -6.45 m w.e. Annual glacier-wide mass balances were negative except for four years (2004/05, 2008/09, 2009/10 and 2010/11) where it was generally close to balanced conditions. Equilibrium line altitude (ELA) for steady state condition is calculated as 4950 m a.s.l. corresponding to an accumulation area ratio (AAR) of 62% using annual glacier-wide mass balance, ELA and AAR data between 2002 and 2013. The winter glacier-wide mass balance between 2009 and 2013 ranges from a maximum value of 1.38 m w.e. in 2009/10 to a minimum value of 0.89 in 2012/13 year whereas the summer glacier-wide mass balance varies from the highest value of -0.95 m w.e. in 2010/11 to the lowest value of -1.72 m w.e. in 2011/12 year. The mean vertical mass balance gradient between 2002 and 2013 was 0.66 m w.e. (100 m)-1 quite similar to Alps, Nepalese Himalayas etc. Over debris covered area, the gradients are highly variable with a negative mean value of -2.15 m w.e. (100 m)-1 over 2002
Marine ice sheet collapse potentially under way for the Thwaites Glacier Basin, West Antarctica.
Joughin, Ian; Smith, Benjamin E; Medley, Brooke
2014-05-16
Resting atop a deep marine basin, the West Antarctic Ice Sheet has long been considered prone to instability. Using a numerical model, we investigated the sensitivity of Thwaites Glacier to ocean melt and whether its unstable retreat is already under way. Our model reproduces observed losses when forced with ocean melt comparable to estimates. Simulated losses are moderate (<0.25 mm per year at sea level) over the 21st century but generally increase thereafter. Except possibly for the lowest-melt scenario, the simulations indicate that early-stage collapse has begun. Less certain is the time scale, with the onset of rapid (>1 mm per year of sea-level rise) collapse in the different simulations within the range of 200 to 900 years. Copyright © 2014, American Association for the Advancement of Science.
GLIMS Glacier Database: Status and Challenges
NASA Astrophysics Data System (ADS)
Raup, B. H.; Racoviteanu, A.; Khalsa, S. S.; Armstrong, R.
2008-12-01
GLIMS (Global Land Ice Measurements from Space) is an international initiative to map the world's glaciers and to build a GIS database that is usable via the World Wide Web. The GLIMS programme includes 70 institutions, and 25 Regional Centers (RCs), who analyze satellite imagery to map glaciers in their regions of expertise. The analysis results are collected at the National Snow and Ice Data Center (NSIDC) and ingested into the GLIMS Glacier Database. The database contains approximately 80 000 glacier outlines, half the estimated total on Earth. In addition, the database contains metadata on approximately 200 000 ASTER images acquired over glacierized terrain. Glacier data and the ASTER metadata can be viewed and searched via interactive maps at http://glims.org/. As glacier mapping with GLIMS has progressed, various hurdles have arisen that have required solutions. For example, the GLIMS community has formulated definitions for how to delineate glaciers with different complicated morphologies and how to deal with debris cover. Experiments have been carried out to assess the consistency of the database, and protocols have been defined for the RCs to follow in their mapping. Hurdles still remain. In June 2008, a workshop was convened in Boulder, Colorado to address issues such as mapping debris-covered glaciers, mapping ice divides, and performing change analysis using two different glacier inventories. This contribution summarizes the status of the GLIMS Glacier Database and steps taken to ensure high data quality.
DOE Office of Scientific and Technical Information (OSTI.GOV)
Wiles, G.C.; Calkin, P.E.; Post, A.
The histories of four iceberg-calving outlet-glacier systems in the Kenai Fjords National Park underscore the importance of fiord depth, sediment supply, and fiord geometry on glacier stability. These parameters, in turn, limit the reliability of calving glacier chronologies as records of climatic change. Tree-ring analysis together with radiocarbon dating show that the Northwestern and McCarty glaciers, with large drainage basins, were advancing in concert with nearby land-terminating glaciers about A.D. 600. After an interval of retreat and possible nonclimatically induced extension during the Medieval Warm Period, these ice margins advanced again through the Little Ice Age and then retreated synchronouslymore » with the surrounding land-terminating glaciers about A.D. 1900. In contrast, Holgate and Aialik glaciers, with deeper fiords and smaller basins, retreated about 300 yr earlier. Reconstructions of Little Ice Age glaciers suggest that equilibrium-line altitudes of Northwestern and McCarty glaciers were, respectively, 270 and 500 m lower than now. Furthermore, the reconstructions show that these two glaciers were climatically sensitive when at their terminal moranies. However, with ice margins at their present recessional positions and accumulation area ratios between 0.8 and 0.9, only McCarty Glacier shows evidence of advance. Aialik and Holgate glaciers were climatically insensitive during the Little Ice Age maxima and remain insensitive to climate. 40 refs., 7 figs., 2 tabs.« less
Sediment transport drives tidewater glacier periodicity.
Brinkerhoff, Douglas; Truffer, Martin; Aschwanden, Andy
2017-07-21
Most of Earth's glaciers are retreating, but some tidewater glaciers are advancing despite increasing temperatures and contrary to their neighbors. This can be explained by the coupling of ice and sediment dynamics: a shoal forms at the glacier terminus, reducing ice discharge and causing advance towards an unstable configuration followed by abrupt retreat, in a process known as the tidewater glacier cycle. Here we use a numerical model calibrated with observations to show that interactions between ice flow, glacial erosion, and sediment transport drive these cycles, which occur independent of climate variations. Water availability controls cycle period and amplitude, and enhanced melt from future warming could trigger advance even in glaciers that are steady or retreating, complicating interpretations of glacier response to climate change. The resulting shifts in sediment and meltwater delivery from changes in glacier configuration may impact interpretations of marine sediments, fjord geochemistry, and marine ecosystems.The reason some of the Earth's tidewater glaciers are advancing despite increasing temperatures is not entirely clear. Here, using a numerical model that simulates both ice and sediment dynamics, the authors show that internal dynamics drive glacier variability independent of climate.
Attribution of glacier fluctuations to climate change
NASA Astrophysics Data System (ADS)
Oerlemans, J.
2012-04-01
Glacier retreat is a worlwide phenomenon, which started around the middle of the 19th century. During the period 1800-1850 the number of retreating and advancing glaciers was roughly equal (based on 42 records from different continents). During the period 1850-1900 about 92% of all mountain glaciers became shorter (based on 65 records). After this, the percentage of shrinking glaciers has been around 90% until the present time. The glacier signal is rather coherent over the globe, especially when surging and calving glaciers are not considered (for such glaciers the response to climate change is often masked by length changes related to internal dynamics). From theoretical studies as well as extensive meteorological work on glaciers, the processes that control the response of glaciers to climate change are now basically understood. It is useful to make a difference between geometric factors (e.g. slope, altitudinal range, hypsometry) and climatic setting (e.g. seasonal cycle, precipitation). The most sensitive glaciers appear to be flat glaciers in a maritime climate. Characterizing the dynamic properties of a glacier requires at least two quantities: the climate sensitivity, expressing how the equilibrium glacier state depends on the climatic conditions, and the response time, indicating how fast a glacier approaches a new equilibrium state after a stepwise change in the climatic forcing. These quantities can be estimated from relatively simple theory, showing that differences among glaciers are substantial. For larger glaciers, climate sensitivities (in terms of glacier length) vary from 1 to 8 km per 100 m change in the equilibrium-line altitude. Response times are mainly in the range of 20 to 200 years, with most values between 30 and 80 years. Changes in the equilibrium-line altitude or net mass balance of a glacier are mainly driven by fluctuations in air temperature, precipitation, and global radiation. Energy-balance modelling for many glaciers shows that
Living and Working in Antarctica.
ERIC Educational Resources Information Center
Kemp, Noel
This source book, designed for 11- to 14-year-old students, seeks to describe what life is like in Antarctica. In spite of extreme weather conditions, people go to Antarctica to work every summer. Some of them stay there during the winter as well. This book seeks to supply answers to such questions as: How do people get to Antarctica? Why do they…
Recent Advances in the GLIMS Glacier Database
NASA Astrophysics Data System (ADS)
Raup, Bruce; Cogley, Graham; Zemp, Michael; Glaus, Ladina
2017-04-01
Glaciers are shrinking almost without exception. Glacier losses have impacts on local water availability and hazards, and contribute to sea level rise. To understand these impacts and the processes behind them, it is crucial to monitor glaciers through time by mapping their areal extent, changes in volume, elevation distribution, snow lines, ice flow velocities, and changes to associated water bodies. The glacier database of the Global Land Ice Measurements from Space (GLIMS) initiative is the only multi-temporal glacier database capable of tracking all these glacier measurements and providing them to the scientific community and broader public. Here we present recent results in 1) expansion of the geographic and temporal coverage of the GLIMS Glacier Database by drawing on the Randolph Glacier Inventory (RGI) and other new data sets; 2) improved tools for visualizing and downloading GLIMS data in a choice of formats and data models; and 3) a new data model for handling multiple glacier records through time while avoiding double-counting of glacier number or area. The result of this work is a more complete glacier data repository that shows not only the current state of glaciers on Earth, but how they have changed in recent decades. The database is useful for tracking changes in water resources, hazards, and mass budgets of the world's glaciers.
NASA Astrophysics Data System (ADS)
Brisbourne, A.; Bougamont, M. H.; Christoffersen, P.; Cornford, S. L.; Nias, I.; Vaughan, D.; Smith, A.
2017-12-01
Antarctica's main contribution to sea-level rise originates from the Amundsen Coast, when warm ocean water intrudes onto the continental shelf. As a result, strong melting beneath the ice shelves induces thinning near the grounding line of glaciers, which is ensued by large ice flow speed up diffusing rapidly inland. In particular, ice loss from Pine Island Glacier (PIG) accounts for 20% of the total ice loss in West Antarctica, amounting to 0.12 mm yr-1 of global sea-level rise. Forecasting the future flow of Amundsen Coast glaciers is however hindered by large uncertainties regarding how the thinning initiated at the grounding line is transmitted upstream, and how the grounded flow will ultimately respond. This work aims at elucidating the role of subglacial processes beneath PIG tributaries in modulating the ice flow response to frontal perturbations. We used the Community Ice Sheet Model (CISM 2.0) to perform numerical inversions of PIG surface velocity as observed in 1996 and 2014. Over that time period, ice flow acceleration has been widespread over PIG's basin, and the inversions provide insights into the related evolution of the basal thermal and stress conditions. We assume the latter to be directly related to changes in the properties of a soft sediment (till) layer known to exist beneath PIG. We find that the overall bed strength has weakened by 18% in the region of enhanced flow, and that the annual melt production for PIG catchment increased by 25% between 1996 and 2014. Specifically, regions of high melt production are located in the southern tributaries, where the overall stronger bed allows for more frictional melting. However, we find no significant and widespread change in the basal strength of that region, and we infer that the water produced is transported away in a concentrated hydrological system, without much interaction with the till layer. In contrast, we find that relatively less basal melting occurs elsewhere in the catchment, where the
NASA Astrophysics Data System (ADS)
Fugazza, Davide; Scaioni, Marco; Corti, Manuel; D'Agata, Carlo; Azzoni, Roberto Sergio; Cernuschi, Massimo; Smiraglia, Claudio; Diolaiuti, Guglielmina Adele
2018-04-01
Tourists and hikers visiting glaciers all year round face hazards such as sudden terminus collapses, typical of such a dynamically evolving environment. In this study, we analyzed the potential of different survey techniques to analyze hazards of the Forni Glacier, an important geosite located in Stelvio Park (Italian Alps). We carried out surveys in the 2016 ablation season and compared point clouds generated from an unmanned aerial vehicle (UAV) survey, close-range photogrammetry and terrestrial laser scanning (TLS). To investigate the evolution of glacier hazards and evaluate the glacier thinning rate, we also used UAV data collected in 2014 and a digital elevation model (DEM) created from an aerial photogrammetric survey of 2007. We found that the integration between terrestrial and UAV photogrammetry is ideal for mapping hazards related to the glacier collapse, while TLS is affected by occlusions and is logistically complex in glacial terrain. Photogrammetric techniques can therefore replace TLS for glacier studies and UAV-based DEMs hold potential for becoming a standard tool in the investigation of glacier thickness changes. Based on our data sets, an increase in the size of collapses was found over the study period, and the glacier thinning rates went from 4.55 ± 0.24 m a-1 between 2007 and 2014 to 5.20 ± 1.11 m a-1 between 2014 and 2016.
2011-04-11
On April 11, 2011, IceBridge finally got the clear weather necessary to fly over glaciers in southeast Greenland. But with clear skies came winds of up to 70 knots, which made for a bumpy ride over the calving front of glaciers like Gyldenlove. Operation IceBridge, now in its third year, makes annual campaigns in the Arctic and Antarctic where science flights monitor glaciers, ice sheets and sea ice. Credit: NASA/GSFC/Michael Studinger To learn more about Ice Bridge go to: www.nasa.gov/mission_pages/icebridge/news/spr11/index.html 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 Join us on Facebook
NASA Astrophysics Data System (ADS)
Fukuda, Y.; Nogi, Y.; Matsuzaki, K.
2012-12-01
Syowa is the Japanese Antarctic wintering station in Lützow-Holm Bay, East Antarctica. The area around the station is considered to be a key for investigating the formation of Gondwana, because reconstruction models suggest a junction of the continents locates in the area. It is also important from a glaciological point of view, because there locates the Shirase Glacier, one of the major glaciers in Antarctica, near the station. Therefore the Japanese Antarctic Research Expedition (JARE) has been conducting in-situ gravity measurements in the area for a long period. The data sets accumulated are land gravity data since 1967, surface ship data since 1985, and airborne gravity data in 2006. However these in-situ gravity data usually suffered from the effects of instrumental drifts and lack of reference points, their accuracies are decreasing toward the longer wavelength more than several tens km. In particular in Antarctica where very few gravity reference points are available, the long wavelength accuracy and/or consistency among the data sets are quite limited. GOCE (Gravity field and steady-state Ocean Circulation Explorer) satellite launched in March 2009 by ESA (European Space Agency) aims at improving static gravity fields, in particular at short wavelengths. In addition to its low-altitude orbit (250km), the sensitive gravity gradiometer installed is expected to reveal 1 mgal gravity anomalies at the spatial resolution of 100km (half wavelength). Actually recently released GOCE EGMs (Earth Gravity Models) have improved the accuracy of the static gravity filed tremendously. These EGMs are expected to serve as the long wavelength references for the in-situ gravity data. Thus, firstly, we aims at determining an improved gravity fields around Syowa by combining the JARE gravity data and the recent EGMs. And then, using the gravity anomalies, we determine the subsurface density structures. We also evaluated the impacts of the EGMs for estimating the density
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).
NASA Astrophysics Data System (ADS)
Furfaro, R.; Kargel, J. S.; Fink, W.; Bishop, M. P.
2010-12-01
Glaciers and ice sheets are among the largest unstable parts of the solid Earth. Generally, glaciers are devoid of resources (other than water), are dangerous, are unstable and no infrastructure is normally built directly on their surfaces. Areas down valley from large alpine glaciers are also commonly unstable due to landslide potential of moraines, debris flows, snow avalanches, outburst floods from glacier lakes, and other dynamical alpine processes; yet there exists much development and human occupation of some disaster-prone areas. Satellite remote sensing can be extremely effective in providing cost-effective and time- critical information. Space-based imagery can be used to monitor glacier outlines and their lakes, including processes such as iceberg calving and debris accumulation, as well as changing thicknesses and flow speeds. Such images can also be used to make preliminary identifications of specific hazardous spots and allows preliminary assessment of possible modes of future disaster occurrence. Autonomous assessment of glacier conditions and their potential for hazards would present a major advance and permit systematized analysis of more data than humans can assess. This technical leap will require the design and implementation of Artificial Intelligence (AI) algorithms specifically designed to mimic glacier experts’ reasoning. Here, we introduce the theory of Fuzzy Cognitive Maps (FCM) as an AI tool for predicting and assessing natural hazards in alpine glacier environments. FCM techniques are employed to represent expert knowledge of glaciers physical processes. A cognitive model embedded in a fuzzy logic framework is constructed via the synergistic interaction between glaciologists and AI experts. To verify the effectiveness of the proposed AI methodology as applied to predicting hazards in glacier environments, we designed and implemented a FCM that addresses the challenging problem of autonomously assessing the Glacier Lake Outburst Flow
NASA Astrophysics Data System (ADS)
Mohamadi, B.; Balz, T.
2018-04-01
Glaciers are retreating in many parts of the world as a result of global warming. Many researchers consider Qinghai-Tibetan Plateau as a reference for climate change by measuring glaciers retreat on the plateau. This retreat resulted in some topographic changes in retreated areas, and in some cases can lead to geohazards as landslides, and rock avalanches, which is known in glacier retreated areas as paraglacial slope failure (PSF). In this study, Geladandong biggest and main glacier mass was selected to estimate surface deformation on its glacier retreated areas and define potential future PSF based on PS-InSAR technique. 56 ascending and 49 descending images were used to fulfill this aim. Geladandong glacier retreated areas were defined based on the maximum extent of the glacier in the little ice age. Results revealed a general uplift in the glacier retreated areas with velocity less than 5mm/year. Obvious surface motion was revealed in seven parts surround glacier retreated areas with high relative velocity reached ±60mm/year in some parts. Four parts were considered as PSF potential motion, and two of them showed potential damage for the main road in the study area in case of rock avalanche into recent glacier lakes that could result in glacier lake outburst flooding heading directly to the road. Finally, further analysis and field investigations are needed to define the main reasons for different types of deformation and estimate future risks of these types of surface motion in the Qinghai-Tibetan Plateau.
Code of Federal Regulations, 2011 CFR
2011-07-01
... 33 Navigation and Navigable Waters 3 2011-07-01 2011-07-01 false Taylor Creek, navigation lock (S-193) across the entrance to Taylor Creek at Lake Okeechobee, Okeechobee, Fla.; use, administration..., DEPARTMENT OF THE ARMY, DEPARTMENT OF DEFENSE NAVIGATION REGULATIONS § 207.170d Taylor Creek, navigation lock...
Code of Federal Regulations, 2010 CFR
2010-07-01
... 33 Navigation and Navigable Waters 3 2010-07-01 2010-07-01 false Taylor Creek, navigation lock (S-193) across the entrance to Taylor Creek at Lake Okeechobee, Okeechobee, Fla.; use, administration..., DEPARTMENT OF THE ARMY, DEPARTMENT OF DEFENSE NAVIGATION REGULATIONS § 207.170d Taylor Creek, navigation lock...
DeWayne, Cecil L.; Green, J.R.; Vogt, S.; Michel, R.; Cottrell, G.
1998-01-01
Meltwater runoff from glaciers can result from various sources, including recent precipitation and melted glacial ice. Determining the origin of the meltwater from glaciers through isotopic analysis can provide information about such things as the character and distribution of ablation on glaciers. A 9.4 m ice core and meltwater were collected in 1995 and 1996 at the glacigenic Galena Creek rock glacier in Wyoming's Absaroka Mountains. Measurements of chlorine-36 (36Cl), tritium (3H), sulphur-35 (35S), and delta oxygen-18 (??18O) were compared to similar measurements from an ice core taken from the Upper Fremont Glacier in the Wind River Range of Wyoming collected in 1991-95. Meltwater samples from three sites on the rock glacier yielded 36Cl concentrations that ranged from 2.1 ?? 1.0 X 106 to 5.8??0.3 X 106 atoms/l. The ice-core 36Cl concentrations from Galena Creek ranged from 3.4??0.3 X 105 to 1.0??0.1 X 106 atoms/l. Analysis of an ice core from the Upper Fremont Glacier yielded 36Cl concentrations of 1.2??0.2 X 106 and 5.2??0.2 X 106 atoms/l for pre- 1940 ice and between 2 X 106 and 3 X 106 atoms/l for post-1980 ice. Purdue's PRIME Lab analyzed the ice from the Upper Fremont Glacier. The highest concentration of 36Cl in the ice was 77 ?? 2 X 106 atoms/l and was deposited during the peak of atmospheric nuclear weapons testing in the late 1950s. This is an order of magnitude greater than the largest measured concentration from both the Upper Fremont Glacier ice core that was not affected by weapons testing fallout and the ice core collected from the Galena Creek rock glacier. Tritium concentrations from the rock glacier ranged from 9.2??0.6 to 13.2??0.8 tritium units (TU) in the meltwater to -1.3??1.3 TU in the ice core. Concentrations of 3H in the Upper Fremont Glacier ice core ranged from 0 TU in the ice older than 50 years to 6-12 TU in the ice deposited in the last 10 years. The maximum 3H concentration in ice from the Upper Fremont Glacier deposited in the
NASA Astrophysics Data System (ADS)
Kaluzienski, L. M.; Koons, P. O.; Enderlin, E. M.; Courville, Z.; Campbell, S. W.; Arcone, S.; Jordan, M.; Ray, L.
2017-12-01
Antarctica's ice shelves modulate the flow of inland ice towards the ocean. Understanding the controls on ice-shelf stability are critical to predicting the future evolution of the Antarctic Ice Sheet. For the Ross Ice Shelf (RIS), an important region of lateral resistance is the McMurdo Shear Zone (MSZ), a 5-10 km wide strip of heavily crevassed ice. On a yearly basis the United States Antarctic Program (USAP) mitigates crevasse hazards along the South Pole Traverse (SPoT) route that crosses this region. However, as ice advects northward past the lateral buttress of White Island into a region of greater flow divergence, intensified crevassing has been observed which will continue to place a substantial burden on safety mitigation efforts. The route has advected down-glacier towards this complex region since 2002 so the USAP currently has plans to relocate the shear zone crossing upstream in the near future. Our work aims to assess the feasibility of moving the route to several potential locations based on results from an integrated project incorporating detailed field-based observations of crevasse distributions and orientation from ground-penetrating radar (GPR), GPS and remote sensing observations of the flow and stress field within the MSZ, and finite element numerical modeling of local and regional kinematics within the region. In addition, we assess plausible dynamic forcings both upstream and downstream of the MSZ that could influence shear zone stability. These include changes in mass flux across the grounding lines of tributary glaciers such as the observed increase in ice discharge from of Byrd Glacier (Stearns et al., 2008) as well as changes at the MIS front due to recent intensified rift propagation (Banwel et al., 2017). Results from this work will increase our understanding of ice shelf shear margin dynamics and provide a firm basis for predicting the long-term behavior of the MSZ and viability of the SPoT. Stearns, Leigh A., Benjamin E. Smith, and
A Worldwide Glacier Information System to go
NASA Astrophysics Data System (ADS)
Mölg, N.; Steinmann, M.; Zemp, M.
2016-12-01
In the forefront of the Paris Climate Conference COP21 in December 2015, the WGMS and UNESCO jointly launched a glacier application for mobile devices. This new information system aims at bringing scientifically sound facts and figures on worldwide glacier changes to decision makers at governmental and intergovernmental levels as well as reaching out to the interested public. The wgms Glacier App provides a map interface based on satellite images that display all the observed glaciers in the user's proximity. Basic information is provided for each glacier, including photographs and general information on size and elevation. Graphs with observation data illustrate the glacier's development, along with information on latest principal investigators and their sponsoring agencies as well as detailed explanations of the measurement types. A text search allows the user to filter the glacier by name, country, region, measurement type and the current "health" status, i.e. if the glacier has gained or lost ice over the past decade. A compass shows the closest observed glaciers in all directions from the user's current position. Finally, the card game allows the user to compete against the computer on the best monitored glaciers in the world. Our poster provides a visual entrance point to the wgms Glacier App and, hence, provides access to fluctuation series of more than 3'700 glaciers around the world.
Space Radar Image of San Rafael Glacier, Chile
NASA Technical Reports Server (NTRS)
1994-01-01
A NASA radar instrument has been successfully used to measure some of the fastest moving and most inaccessible glaciers in the world -- in Chile's huge, remote Patagonia ice fields -- demonstrating a technique that could produce more accurate predictions of glacial response to climate change and corresponding sea level changes. This image, produced with interferometric measurements made by the Spaceborne Imaging Radar-C and X-band Synthetic Aperture Radar (SIR-C/X-SAR) flown on the Space Shuttle last fall, has provided the first detailed measurements of the mass and motion of the San Rafael Glacier. Very few measurements have been made of the Patagonian ice fields, which are the world's largest mid-latitude ice masses and account for more than 60 percent of the Southern Hemisphere's glacial area outside of Antarctica. These features make the area essential for climatologists attempting to understand the response of glaciers on a global scale to changes in climate, but the region's inaccessibility and inhospitable climate have made it nearly impossible for scientists to study its glacial topography, meteorology and changes over time. Currently, topographic data exist for only a few glaciers while no data exist for the vast interior of the ice fields. Velocity has been measured on only five of the more than 100 glaciers, and the data consist of only a few single-point measurements. The interferometry performed by the SIR-C/X-SAR was used to generate both a digital elevation model of the glaciers and a map of their ice motion on a pixel-per-pixel basis at very high resolution for the first time. The data were acquired from nearly the same position in space on October 9, 10 and 11, 1994, at L-band frequency (24-cm wavelength), vertically transmitted and received polarization, as the Space Shuttle Endeavor flew over several Patagonian outlet glaciers of the San Rafael Laguna. The area shown in these two images is 50 kilometers by 30 kilometers (30 miles by 18 miles) in
Reduced melt on debris-covered glaciers: investigations from Changri Nup Glacier, Nepal
NASA Astrophysics Data System (ADS)
Wagnon, Patrick; Vincent, Christian; Shea, Joseph M.; Immerzeel, Walter W.; Kraaijenbrink, Philip; Shrestha, Dibas; Soruco, Alvaro; Arnaud, Yves; Brun, Fanny; Berthier, Etienne; Futi Sherpa, Sonam
2017-04-01
Approximately 25% of the glacierized area in the Everest region is covered by debris, yet the surface mass balance of debris-covered portions of these glaciers has not been measured directly. In this study, ground-based measurements of surface elevation and ice depth are combined with terrestrial photogrammetry, unmanned aerial vehicle (UAV) and satellite elevation models to derive the surface mass balance of the debris-covered tongue of Changri Nup Glacier, located in the Everest region. Over the debris-covered tongue, the mean elevation change between 2011 and 2015 is -0.93 m year-1 or -0.84 m water equivalent per year (w.e. a-1). The mean emergence velocity over this region, estimated from the total ice flux through a cross section immediately above the debris-covered zone, is +0.37mw.e. a-1. The debris-covered portion of the glacier thus has an area averaged mass balance of -1.21+/-0.2mw.e. a-1 between 5240 and 5525 m above sea level (m a.s.l.). Surface mass balances observed on nearby debris-free glaciers suggest that the ablation is strongly reduced (by ca. 1.8mw.e. a-1) by the debris cover. The insulating effect of the debris cover has a larger effect on total mass loss than the enhanced ice ablation due to supraglacial ponds and exposed ice cliffs. This finding contradicts earlier geodetic studies and should be considered for modelling the future evolution of debris-covered glaciers.
Flow instabilities of Alaskan glaciers
NASA Astrophysics Data System (ADS)
Turrin, James Bradley
Over 300 of the largest glaciers in southern Alaska have been identified as either surge-type or pulse-type, making glaciers with flow instabilities the norm among large glaciers in that region. Consequently, the bulk of mass loss due to climate change will come from these unstable glaciers in the future, yet their response to future climate warming is unknown because their dynamics are still poorly understood. To help broaden our understanding of unstable glacier flow, the decadal-scale ice dynamics of 1 surging and 9 pulsing glaciers are investigated. Bering Glacier had a kinematic wave moving down its ablation zone at 4.4 +/- 2.0 km/yr from 2002 to 2009, which then accelerated to 13.9 +/- 2.0 km/yr as it traversed the piedmont lobe. The wave first appeared in 2001 near the confluence with Bagley Ice Valley and it took 10 years to travel ~64 km. A surge was triggered in 2008 after the wave activated an ice reservoir in the midablation zone, and it climaxed in 2011 while the terminus advanced several km into Vitus Lake. Ruth Glacier pulsed five times between 1973 and 2012, with peak velocities in 1981, 1989, 1997, 2003, and 2010; approximately every 7 years. A typical pulse increased ice velocity 300%, from roughly 40 m/yr to 160 m/yr in the midablation zone, and involved acceleration and deceleration of the ice en masse; no kinematic wave was evident. The pulses are theorized to be due to deformation of a subglacial till causing enhanced basal motion. Eight additional pulsing glaciers are identified based on the spatiotemporal pattern of their velocity fields. These glaciers pulsed where they were either constricted laterally or joined by a tributary, and their surface slopes are 1-2°. These traits are consistent with an overdeepening. This observation leads to a theory of ice motion in overdeepenings that explains the cyclical behavior of pulsing glaciers. It is based on the concept of glaciohydraulic supercooling, and includes sediment transport and erosion
Antarctic Peninsula Tidewater Glacier Dynamics
NASA Astrophysics Data System (ADS)
Pettit, E. C.; Scambos, T. A.; Haran, T. M.; Wellner, J. S.; Domack, E. W.; Vernet, M.
2015-12-01
The northern Antarctic Peninsula (nAP, north of 66°S) is a north-south trending mountain range extending transverse across the prevailing westerly winds of the Southern Ocean resulting in an extreme west-to-east precipitation gradient. Snowfall on the west side of the AP is one to two orders of magnitude higher than the east side. This gradient drives short, steep, fast-flowing glaciers into narrow fjords on the west side, while longer lower-sloping glaciers flow down the east side into broader fjord valleys. This pattern in ice dynamics affects ice-ocean interaction on timescales of decades to centuries, and shapes the subglacial topography and submarine bathymetry on timescales of glacial cycles. In our study, we calculate ice flux for the western and eastern nAP using a drainage model that incorporates the modern ice surface topography, the RACMO-2 precipitation estimate, and recent estimates of ice thinning. Our results, coupled with observed rates of ice velocity from InSAR (I. Joughin, personal communication) and Landsat 8 -derived flow rates (this study), provide an estimate of ice thickness and fjord depth in grounded-ice areas for the largest outlet glaciers. East-side glaciers either still terminate in or have recently terminated in ice shelves. Sedimentary evidence from the inner fjords of the western glaciers indicates they had ice shelves during LIA time, and may still have transient floating ice tongues (tabular berg calvings are observed). Although direct oceanographic evidence is limited, the high accumulation rate and rapid ice flux implies cold basal ice for the western nAP glaciers and therefore weak subglacial discharge relative to eastern nAP glaciers and or other tidewater fjord systems such as in Alaska. Finally, despite lower accumulation rates on the east side, the large elongate drainage basins result in a greater ice flux funneled through fewer deeper glaciers. Due to the relation between ice flux and erosion, these east-side glaciers
Informal STEM Education in Antarctica
NASA Astrophysics Data System (ADS)
Chell, K.
2010-12-01
Tourism in Antarctica has increased dramatically with tens of thousands of tourists visiting the White Continent each year. Tourism cruises to Antarctica offer a unique educational experience for lay people through informal science-technology-engineering-mathematics (STEM) education. Passengers attend numerous scientific lectures that cover topics such as the geology of Antarctica, plate tectonics, glaciology, and climate change. Furthermore, tourists experience the geology and glaciology first hand during shore excursions. Currently, the grand challenges facing our global society are closely connected to the Earth sciences. Issues such as energy, climate change, water security, and natural hazards, are consistently on the legislative docket of policymakers around the world. However, the majority of the world’s population is uninformed about the role Earth sciences play in their everyday lives. Tourism in Antarctica provides opportunities for informal STEM learning and, as a result, tourists leave with a better understanding and greater appreciation for both Antarctica and Earth sciences.
Herringbone streaks in Taylor-Couette turbulence.
Dong, S
2008-03-01
We study near-wall streaks that form herringbonelike patterns in Taylor-Couette turbulence and in counter-rotating Taylor-Couette turbulence through three-dimensional direct numerical simulations. The orientation, axial distribution, onset, and tilting angle of these streaks are characterized.
Surface melt dominates Alaska glacier mass balance
Larsen Chris F,; Burgess, E; Arendt, A.A.; O'Neel, Shad; Johnson, A.J.; Kienholz, C.
2015-01-01
Mountain glaciers comprise a small and widely distributed fraction of the world's terrestrial ice, yet their rapid losses presently drive a large percentage of the cryosphere's contribution to sea level rise. Regional mass balance assessments are challenging over large glacier populations due to remote and rugged geography, variable response of individual glaciers to climate change, and episodic calving losses from tidewater glaciers. In Alaska, we use airborne altimetry from 116 glaciers to estimate a regional mass balance of −75 ± 11 Gt yr−1 (1994–2013). Our glacier sample is spatially well distributed, yet pervasive variability in mass balances obscures geospatial and climatic relationships. However, for the first time, these data allow the partitioning of regional mass balance by glacier type. We find that tidewater glaciers are losing mass at substantially slower rates than other glaciers in Alaska and collectively contribute to only 6% of the regional mass loss.
NASA Astrophysics Data System (ADS)
Vogler, K.; McNeil, C.; Bond, M.; Getraer, B.; Huxley-Reicher, B.; McNamara, G.; Reinhardt-Ertman, T.; Silverwood, J.; Kienholz, C.; Beedle, M. J.
2017-12-01
Glacier-wide annual mass balances (Ba) have been calculated for Taku (726 km2) and Lemon Creek glaciers (10.2 km2) since 1946 and 1953 respectively. These are the longest mass balance records in North America, and the only Ba time-series available for Southeast Alaska, making them particularly valuable for the global glacier mass balance monitoring network. We compared Ba time-series from Taku and Lemon Creek glaciers to Gravity Recovery and Climate Experiment (GRACE) mascon solutions (1352 and 1353) during the 2004-2015 period to assess how well these gravimetric solutions reflect individual glaciological records. Lemon Creek Glacier is a challenging candidate for this comparison because it is small compared to the 12,100 km2 GRACE mascon solutions. Taku Glacier is equally challenging because its mass balance is stable compared to the negative balances dominating its neighboring glaciers. Challenges notwithstanding, a high correlation between the glaciological and gravimetrically-derived Ba for Taku and Lemon Creek glaciers encourage future use of GRACE to measure glacier mass balance. Additionally, we employed high frequency ground penetrating radar (GPR) to measure the variability of accumulation around glaciological sites to assess uncertainty in our glaciological measurements, and the resulting impact to Ba. Finally, we synthesize this comparison of glaciological and gravimetric mass balance solutions with a discussion of potential sources of error in both methods and their combined utility for measuring regional glacier change during the 21st century.
2017-12-08
Calving front of the Upsala Glacier (Argentina). This glacier has been thinning and retreating at a rapid rate during the last decades – from 2006 to 2010, it receded 43.7 yards (40 meters) per year. During summer 2012, large calving events prevented boat access to the glacier. To learn about the contributions of glaciers to sea level rise, visit: www.nasa.gov/topics/earth/features/glacier-sea-rise.html Credit: Etienne Berthier, Université de Toulouse 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
2016-07-15
This image has low-sun lighting that accentuates the many transverse ridges on this slope, extending from Euripus Mons (mountains). These flow-like structures were previously called "lobate debris aprons," but the Shallow Radar (SHARAD) instrument on MRO has shown that they are actually debris-covered flows of ice, or glaciers. There is no evidence for present-day flow of these glaciers, so they appear to be remnants of past climates. http://photojournal.jpl.nasa.gov/catalog/PIA20745
Interactions between surface waters in King George Island, Antarctica - a stable isotope perspective
NASA Astrophysics Data System (ADS)
Perşoiu, Aurel; Bădăluşă, Carmen
2017-04-01
In this paper we present a first study of the isotopic composition of surface waters in the southern peninsulas (Barton, Fildes, Weaver and Potter) of King George Island, Antarctica. We have collected > 200 samples of snow and snowmelt, water (lake, river and spring), ice (glacier ice and permafrost) from the four peninsulas in February 2016 and analyzed them for their oxygen and hydrogen stable isotopic composition. Samples from lake water (50+) indicate a clear west-east depletion trend, suggesting a rain-out process as air masses are moving westward (and are progressively depleted in heavy isotopes) from their origin in the Drake Passage. In both Fildes and Barton Peninsulas, permafrost samples have the heaviest isotopic composition, most probably due to preferential incorporation of heavy isotopes in the ice during freezing (and no fractionation during melting). As permafrost melts, the resulting water mixes with isotopically lighter infiltrated snowmelt, and thus the groundwater has a lower isotopic composition. Further, lake and river (the later fed by lakes) water has the lightest isotopic composition, being derived mostly from the melting of light snow and glacier ice. It seems feasible to separate isotopically water in lakes/rivers (largely fed by melting multi-year glaciers and snow) and water from melting of snow/ground ice This preliminary study suggests that it is possible to separate various water sources in the southern peninsulas of King George Island, and this separation could be used to study permafrost degradation, as well as feeding and migration patterns in the bird fauna, with implications for protection purposes. Acknowledgments. The National Institute of Research and Development for Biological Sciences (Bucharest, Romania) and the Korean polar institute financially supported fieldwork in King George Island. We thank the personal at King Sejong (South Korea), Belingshaussen (Russia) and Carlini (Argentina) stations in King George Island for
Hamilton, W.
1967-01-01
Antarctica consists of large and wholly continental east Antarctica and smaller west Antarctica which would form large and small islands, even after isostatic rebound, if its ice cap were melted. Most of east Antarctica is a Precambrian Shield, in much of which charnockites are characteristic. The high Transantarctic Mountains, along the Ross and Weddell Seas, largely follow a geosyncline of Upper Precambrian sedimentary rocks that were deformed, metamorphosed and intruded by granitic rocks during Late Cambrian or Early Ordovician time. The rocks of the orogen were peneplained, then covered by thin and mostly continental Devonian-Jurassic sediments, which were intruded by Jurassic diabase sheets and overlain by plateau-forming tholeiites. Late Cenozoic doming and block-faulting have raised the present high mountains. Northeastern Victoria Land, the end of the Transantarctic Mountains south of New Zealand, preserves part of a Middle Paleozoic orogen. Clastic strata laid unconformably upon the Lower Paleozoic plutonic complex were metamorphosed at low grade, highly deformed and intruded by Late Devonian or Early Carboniferous granodiorites. The overlying Triassic continental sedimentary rocks have been broadly folded and normal-faulted. Interior west Antarctica is composed of miogeosynclinal clastic and subordinate carbonate rocks which span the Paleozoic Era and which were deformed, metamorphosed at generally low grade, and intruded by granitic rocks during Early Mesozoic time and possibly during other times also. Patterns of orogenic belts, if systematic, cannot yet be defined; but fragmentation and rotation of crustal blocks by oroclinal folding and strike-slip faulting can be suggested. The Ellsworth Mountains, for example, consist of Cambrian-Permian metasedimentary rocks that strike northward toward the noncorrelative and latitudinally striking Mesozoic terrane of the Antarctic Peninsula in one direction and southward toward that of the Lower Paleozoic: terrane
Testing geographical and climatic controls on glacier retreat
NASA Astrophysics Data System (ADS)
Freudiger, Daphné; Stahl, Kerstin; Weiler, Markus
2015-04-01
Glacier melt provides an important part of the summer discharge in many mountainous basins. The understanding of the processes behind the glacier mass losses and glacier retreats observed during the last century is therefore relevant for a sustainable management of the water resources and reliable models for the prediction of future changes. The changes in glacier area of 49 sub-basins of the Rhine River in the Alps were analyzed for the time period 1900-2010 by comparing the glacier areas of Siegfried maps for the years 1900 and 1940 with satellite derived glacier areas for the years 1973, 2003 and 2010. The aim was to empirically investigate the controls of glacier retreat and its regional differences. All glaciers in the glacierized basins retreated over the last 110 years with some variations in the sub-periods. However, the relative changes in glacier area compared to 1900 differed for every sub-basin and some glaciers decreased much faster than others. These observed differences were related to a variety of different potential controls derived from different sources, including mean annual solar radiation on the glacier surface, average slope, mean glacier elevation, initial glacier area, average precipitation (summer and winter), and the precipitation catchment area of the glacier. We fitted a generalized linear model (GLM) and selected predictors that were significant to assess the individual effects of the potential controls. The fitted model explains more than 60% of the observed variance of the relative change in glacier area with the initial area alone only explaining a small proportion. Some interesting patterns emerge with higher average elevation resulting in higher area changes, but steeper slopes or solar radiation resulting in lower relative glacier area changes. Further controls that will be tested include snow transport by wind or avalanches as they play an important role for the glacier mass balance and potentially reduce the changes in glacier
Recent Developments of the GLIMS Glacier Database
NASA Astrophysics Data System (ADS)
Raup, B. H.; Berthier, E.; Bolch, T.; Kargel, J. S.; Paul, F.; Racoviteanu, A.
2017-12-01
Earth's glaciers are shrinking almost without exception, leading to changes in water resources, timing of runoff, sea level, and hazard potential. Repeat mapping of glacier outlines, lakes, and glacier topography, along with glacial processes, is critically needed to understand how glaciers will react to a changing climate, and how those changes will impact humans. To understand the impacts and processes behind the observed changes, it is crucial to monitor glaciers through time by mapping their areal extent, snow lines, ice flow velocities, associated water bodies, and thickness changes. The glacier database of the Global Land Ice Measurements from Space (GLIMS) initiative is the only multi-temporal glacier database capable of tracking all these glacier measurements and providing them to the scientific community and broader public.Recent developments in GLIMS include improvements in the database and web applications and new activities in the international GLIMS community. The coverage of the GLIMS database has recently grown geographically and temporally by drawing on the Randolph Glacier Inventory (RGI) and other new data sets. The GLIMS database is globally complete, and approximately one third of glaciers have outlines from more than one time. New tools for visualizing and downloading GLIMS data in a choice of formats and data models have been developed, and a new data model for handling multiple glacier records through time while avoiding double-counting of glacier number or area is nearing completion. A GLIMS workshop was held in Boulder, Colorado this year to facilitate two-way communication with the greater community on future needs.The result of this work is a more complete and accurate glacier data repository that shows both the current state of glaciers on Earth and how they have changed in recent decades. Needs for future scientific and technical developments were identified and prioritized at the GLIMS Workshop, and are reported here.
NASA Astrophysics Data System (ADS)
Kargel, J. S.; Shugar, D. H.; Leonard, G. J.; Haritashya, U. K.; Harrison, S.; Shrestha, A. B.; Mool, P. K.; Karki, A.; Regmi, D.
2016-12-01
Glacier response dynamics—involving a host of processes—produce a sequence of short- to long-term delayed responses to any step-wise, oscillating, or continuous trending climatic perturbation. We present analysis of Imja Lake, Nepal and examine its thinning and retreat and a sequence of the detachment of tributaries; the inception and growth of Imja Lake and concomitant glacier retreat, thinning, and stagnation, and relationships to lake dynamics; the response dynamics of the ice-cored moraine; the development of the local ecosystem; prediction of short-term dynamical responses to lake lowering (glacier lake outburst flood—GLOF—mitigation); and prospects for coming decades. The evolution of this glacier system provides a case study by which the global record of GLOFs can be assessed in terms of climate change attribution. We define three response times: glacier dynamical response time (for glacier retreat, thinning, and slowing of ice flow), limnological response time (lake growth), and GLOF trigger time (for a variety of hazardous trigger events). Lake lowering (to be completed in August 2016; see AGU abstract by D. Regmi et al.) will reduce hazards, but we expect that the elongation of the lake and retreat of the glacier will continue for decades after a pause in 2016-2017. The narrowing of the moraine dam due to thaw degradation of the ice-cored end moraine means that the hazard due to Imja Lake will soon again increase. We examine both long-term response dynamics, and two aspects of Himalayan glaciers that have very rapid responses: the area of Imja Lake fluctuates seasonally and even with subseasonal weather variations in response to changes in lake temperature and glacier meltback; and as known from other studies, glacier flow speed can vary between years and even on shorter timescales. The long-term development and stabilization of glacial moraines and small lacustrine plains in drained lake basins impacts the development of local ecosystems
Walder, J.S.; Fountain, A.G.; ,
1997-01-01
Destructive floods result from drainage of glacier-dammed lakes and sudden release of water stored within glaciers. There is a good basis - both empirical and theoretical - for predicting the magnitude of floods from ice-dammed lakes, although some aspects of flood initiation need to be better understood. In contrast, an understanding of floods resulting from release of internally stored water remains elusive, owing to lack of knowledge of how and where water is stored and to inadequate understanding of the complex physics of the temporally and spatially variable subglacial drainage system.Destructive floods result from drainage of glacier-dammed lakes and sudden release of water stored within glaciers. There is a good basis - both empirical and theoretical - for predicting the magnitude of floods from ice-dammed lakes, although some aspects of flood initiation need to be better understood. In contrast, an understanding of floods resulting from release of internally stored water remains elusive, owing to lack of knowledge of how and where water is stored and to inadequate understanding of the complex physics of the temporally and spatially variable subglacial drainage system.
Internationally coordinated glacier monitoring: strategy and datasets
NASA Astrophysics Data System (ADS)
Hoelzle, Martin; Armstrong, Richard; Fetterer, Florence; Gärtner-Roer, Isabelle; Haeberli, Wilfried; Kääb, Andreas; Kargel, Jeff; Nussbaumer, Samuel; Paul, Frank; Raup, Bruce; Zemp, Michael
2014-05-01
Internationally coordinated monitoring of long-term glacier changes provide key indicator data about global climate change and began in the year 1894 as an internationally coordinated effort to establish standardized observations. Today, world-wide monitoring of glaciers and ice caps is embedded within the Global Climate Observing System (GCOS) in support of the United Nations Framework Convention on Climate Change (UNFCCC) as an important Essential Climate Variable (ECV). The Global Terrestrial Network for Glaciers (GTN-G) was established in 1999 with the task of coordinating measurements and to ensure the continuous development and adaptation of the international strategies to the long-term needs of users in science and policy. The basic monitoring principles must be relevant, feasible, comprehensive and understandable to a wider scientific community as well as to policy makers and the general public. Data access has to be free and unrestricted, the quality of the standardized and calibrated data must be high and a combination of detailed process studies at selected field sites with global coverage by satellite remote sensing is envisaged. Recently a GTN-G Steering Committee was established to guide and advise the operational bodies responsible for the international glacier monitoring, which are the World Glacier Monitoring Service (WGMS), the US National Snow and Ice Data Center (NSIDC), and the Global Land Ice Measurements from Space (GLIMS) initiative. Several online databases containing a wealth of diverse data types having different levels of detail and global coverage provide fast access to continuously updated information on glacier fluctuation and inventory data. For world-wide inventories, data are now available through (a) the World Glacier Inventory containing tabular information of about 130,000 glaciers covering an area of around 240,000 km2, (b) the GLIMS-database containing digital outlines of around 118,000 glaciers with different time stamps and
Lithospheric Structure and Seismotectonics of Central East Antarctica
NASA Astrophysics Data System (ADS)
Reading, A. M.
2006-12-01
The lithosphere of central East Antarctica, the sector of the continent between 30°E - 120°E, is investigated using seismic methods including receiver function and shear-wave splitting analysis. Data from the broadband stations of the temporary SSCUA deployment (in the continental interior) are used together with records from the permanent GSN stations (on the coast) to carry out the first studies of crustal depth and structure, and patterns of seismic anisotropy across this region. The depth of the Moho is found to be 42 km (+/- 2 km) beneath Mawson station with similar structures extending southward across the Rayner province as far south as Beaver Lake. The Fisher Terrane is characterised by a crustal shear wavespeed profile showing few discontinuties with the Moho at a similar depth to the Rayner. South of Fisher, the crust becomes much shallower, with the Moho at 32 km depth. This shallow crust extends across the Lambert glacier to the Prydz coast and the Lambert Terrane. The characteristic crustal wavespeed profiles provide baseline structure for mapping the extent of the terrance beneath the Antarctic Ice Sheet in future deployments. Observations of seismic anisotropy are less well- defined but, at a reconnaissance level, show fast directions parallel to the present day coastline. This may be controlled by rift-related influences on the lithosphere associated with the breakup of East Gondwana. The seismicity is confirmed to be extremely low. The only seismogenic forces on the Antarctic plate in this region are acting at the boundary between the continental and oceanic lithosphere west of 50°E and east of 100°E and represent a superposition of tectonic and glaciogenic controls. The Lambert Glacier region shows little or no seismotectonic activity in the continental interior or on the oceanic margin.
NASA Astrophysics Data System (ADS)
Malone, A.
2017-12-01
Quantifying mass balance sensitivity to climate change is essential for forecasting glacier evolution and deciphering climate signals embedded in archives of past glacier changes. Ideally, these quantifications result from decades of field measurement, remote sensing, and a hierarchy modeling approach, but in data-sparse regions, such as the Himalayas and tropical Andes, regional-scale modeling rooted in first principles provides a first-order picture. Previous regional-scaling modeling studies have applied a surface energy and mass balance approach in order to quantify equilibrium line altitude sensitivity to climate change. In this study, an expanded regional-scale surface energy and mass balance model is implemented to quantify glacier-wide mass balance sensitivity to climate change for tropical Andean glaciers. Data from the Randolph Glacier Inventory are incorporated, and additional physical processes are included, such as a dynamic albedo and cloud-dependent atmospheric emissivity. The model output agrees well with the limited mass balance records for tropical Andean glaciers. The dominant climate variables driving interannual mass balance variability differ depending on the climate setting. For wet tropical glaciers (annual precipitation >0.75 m y-1), temperature is the dominant climate variable. Different hypotheses for the processes linking wet tropical glacier mass balance variability to temperature are evaluated. The results support the hypothesis that glacier-wide mass balance on wet tropical glaciers is largely dominated by processes at the lowest elevation where temperature plays a leading role in energy exchanges. This research also highlights the transient nature of wet tropical glaciers - the vast majority of tropical glaciers and a vital regional water resource - in an anthropogenic warming world.
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.
The recent glacier changes in Mongolian Altai Mountains
NASA Astrophysics Data System (ADS)
Yabuki, H.; Ohata, T.
2009-12-01
In the 4th IPCC report (AR-4) is reported that global warming in recent years is a clear thing. Shrinkage of the mountain glacier and two poles is reporting as an observation fact as the actual condition of the cryosphere by warming. There are mass balance reports of the glacier of 80 of world by WGMS (World Glacier Monitoring Service) as a report of the actual condition of glacier mass balance change, and the actual condition of the glacier mass change in world is clarified. In the report of WGMS, after 1980’s the glacier mass balance, in the Europe Alps and the Alaska region are decreases, and in Scandinavia region are increases. On the other hand, the glacier mass balance in the Russia Altai Mountains located in Central Asia has the little change after 1980’s. These are research using the long-term observational data of Russian region of western part of Altai Mountains. The Altai Mountains including Russia, China, and Mongolia Kazakhstan, and there are description to a World Glacier Inventory (WGI) about the glaciers of Russia, China and Kazakhstan area, but the glaciers of a Mongolian area, there are no description to the WGI. There is almost no information on the glacier of a Mongolian Altai region, and there are many unknown points about glacier change of the whole Altai Mountain region. In this research, while research clarified the present condition of glacier distribution of the Mongolia Altai region, the actual condition of a glacier change in recent years was clarified by comparison with the past topographical map. In this research, the glacier area was distinguished based on the satellite image of the Mongolian glacier regions. The used satellite image were 17 Landsat 7 ETM+ in 1999 to 2002. The glacier distinguishes using NDSI (Normalized Difference Snow Index) indexusing Band5 and Band2. The topographical map of the Mongolian area was got based on the distribution information on this satellite glacier area. The topographical map is 1/100,000 which
NASA Astrophysics Data System (ADS)
Raup, B. H.; Khalsa, S. S.; Armstrong, R.
2007-12-01
The Global Land Ice Measurements from Space (GLIMS) project has built a geospatial and temporal database of glacier data, composed of glacier outlines and various scalar attributes. These data are being derived primarily from satellite imagery, such as from ASTER and Landsat. Each "snapshot" of a glacier is from a specific time, and the database is designed to store multiple snapshots representative of different times. We have implemented two web-based interfaces to the database; one enables exploration of the data via interactive maps (web map server), while the other allows searches based on text-field constraints. The web map server is an Open Geospatial Consortium (OGC) compliant Web Map Server (WMS) and Web Feature Server (WFS). This means that other web sites can display glacier layers from our site over the Internet, or retrieve glacier features in vector format. All components of the system are implemented using Open Source software: Linux, PostgreSQL, PostGIS (geospatial extensions to the database), MapServer (WMS and WFS), and several supporting components such as Proj.4 (a geographic projection library) and PHP. These tools are robust and provide a flexible and powerful framework for web mapping applications. As a service to the GLIMS community, the database contains metadata on all ASTER imagery acquired over glacierized terrain. Reduced-resolution of the images (browse imagery) can be viewed either as a layer in the MapServer application, or overlaid on the virtual globe within Google Earth. The interactive map application allows the user to constrain by time what data appear on the map. For example, ASTER or glacier outlines from 2002 only, or from Autumn in any year, can be displayed. The system allows users to download their selected glacier data in a choice of formats. The results of a query based on spatial selection (using a mouse) or text-field constraints can be downloaded in any of these formats: ESRI shapefiles, KML (Google Earth), Map
Atmospheric Science Data Center
2013-04-16
article title: Twilight in Antarctica View larger JPEG ... SpectroRadiometer (MISR) instrument on board Terra. The Ross Ice Shelf and Transantarctic Mountains are illuminated by low Sun. MISR was ...
NASA Astrophysics Data System (ADS)
Hoover, Richard B.; Pikuta, Elena V.; Marsic, Damien; Ng, Joseph D.
2002-02-01
Microorganisms preserved within the permafrost, glaciers, and polar ice sheets of planet Earth provide analogs for microbial life forms that may be encountered in ice or permafrost of Mars, Europa, Callisto, Ganymede, asteroids, comets or other frozen worlds in the Cosmos. The psychrophilic and psychrotolerant microbes of the terrestrial cryosphere help establish the thermal and temporal limitations of life on Earth and provide clues to where and how we should search for evidence of life elsewhere in the Universe. For this reason, the cold-loving microorganisms are directly relevant to Astrobiology. Cryopreserved microorganisms can remain viable (in deep anabiosis) in permafrost and ice for millions of years. Permafrost, ice wedges, pingos, glaciers, and polar ice sheets may contain intact ancient DNA, lipids, enzymes, proteins, genes, and even frozen and yet viable ancient microbiota. Some microorganisms carry out metabolic processes in water films and brine, acidic, or alkaline channels in permafrost or ice at temperatures far below 0 degree(s)C. Complex microbial communities live in snow, ice-bubbles, cryoconite holes on glaciers and ancient microbial ecosystems are cryopreserved within the permafrost, glaciers, and polar caps. In the Astrobiology group of the NASA Marshall Space Flight Center and the University of Alabama at Huntsville, we have employed advanced techniques for the isolation, culture, and phylogenetic analysis of many types of microbial extremophiles. We have also used the Environmental Scanning Electron Microscope to study the morphology, ultra-microstructure and chemical composition of microorganisms in ancient permafrost and ice. We discuss several interesting and novel anaerobic microorganisms that we have isolated and cultured from the Pleistocene ice of the Fox Tunnel of Alaska, guano of the Magellanic Penguin, deep-sea sediments from the vicinity of the Rainbow Hydrothermal Vent and enrichment cultures from ice of the Patriot Hills of
NASA Technical Reports Server (NTRS)
Hoover, Richard B.; Pikuta, Elena V.; Marsic, Damien; Ng, Joseph
2002-01-01
Microorganisms preserved within the permafrost, glaciers, and polar ice sheets of planet Earth provide analogs for microbial life forms that may be encountered in ice or permafrost of Mars, Europa, Callisto, Ganymede, asteroids, comets or other frozen worlds in the Cosmos. The psychrophilic and psychrotolerant microbes of the terrestrial cryosphere help establish the thermal and temporal limitations of life on Earth and provide clues to where and how we should search for evidence of life elsewhere in the Universe. For this reason, the cold-loving microorganisms are directly relevant to Astrobiology. Cryopreserved microorganisms can remain viable (in deep anabiosis) in permafrost and ice for millions of years. Permafrost, ice wedges, pingos, glaciers, and polar ice sheets may contain intact ancient DNA, lipids, enzymes, proteins, genes, and even frozen and yet viable ancient microbiota. Some microorganisms carry out metabolic processes in water films and brine, acidic, or alkaline channels in permafrost or ice at temperatures far below 0 C. Complex microbial communities live in snow, ice-bubbles, cryoconite holes on glaciers and ancient microbial ecosystems are cryopreserved within the permafrost, glaciers, and polar caps. In the Astrobiology group of the NASA Marshall Space Flight Center and the University of Alabama at Huntsville, we have employed advanced techniques for the isolation, culture, and phylogenetic analysis of many types of microbial extremophiles. We have also used the Environmental Scanning Electron Microscope to study the morphology, ultra-microstructure and chemical composition of microorganisms in ancient permafrost and ice. We discuss several interesting and novel anaerobic microorganisms that we have isolated and cultured from the Pleistocene ice of the Fox Tunnel of Alaska, guano of the Magellanic Penguin, deep-sea sediments from the vicinity of the Rainbow Hydrothermal Vent and enrichment cultures from ice of the Patriot Hills of Antarctica
NASA Technical Reports Server (NTRS)
Hoover, Richard B.; Pikuta, Elena V.; Marsic, Damien; Ng, Joseph; Six, N. Frank (Technical Monitor)
2001-01-01
Microorganisms preserved within the permafrost, glaciers, and polar ice sheets of planet Earth provide analogs for microbial life forms that may be encountered in ice or permafrost of Mars, Europa, Callisto, Ganymede, asteroids, comets or other frozen worlds in the Cosmos. The psychrophilic and psychrotolerant microbes of the terrestrial cryosphere help establish the thermal and temporal limitations of life on Earth and provide clues to where and how we should search for evidence of life elsewhere in the Universe. For this reason, the cold-loving microorganisms are directly relevant to Astrobiology. Cryo-preserved microorganisms can remain viable (in deep anabiosis) in permafrost and ice for millions of years. Permafrost, ice wedges, pingos, glaciers, and polar ice sheets may contain intact ancient DNA, lipids, enzymes, proteins, genes, and even frozen and yet viable ancient microbiota. Some microorganisms carry out metabolic processes in water films and brine, acidic, or alkaline channels in permafrost or ice at temperatures far below 0 T. Complex microbial communities live in snow, ice-bubbles, cryoconite holes on glaciers and ancient microbial ecosystems are cryopreserved within the permafrost, glaciers, and polar caps. In the Astrobiology group of the NASA Marshall Space Flight Center and the University of Alabama at Huntsville, we have employed advanced techniques for the isolation, culture, and phylogenetic analysis of many types of microbial extremophiles. We have also used the Environmental Scanning Electron Microscope to study the morphology, ultra-microstructure and chemical composition of microorganisms in ancient permafrost and ice. We discuss several interesting and novel anaerobic microorganisms that we have isolated and cultured from the Pleistocene ice of the Fox Tunnel of Alaska, guano of the Magellanic Penguin, deep sea sediments from the vicinity of the Rainbow Hydrothermal Vent and enrichment cultures from ice of the Patriot Hills of Antarctica
NASA Astrophysics Data System (ADS)
Viani, Cristina; Machguth, Horst; Huggel, Christian; Perotti, Luigi; Giardino, Marco
2016-04-01
It is expected that the rapid retreat of glaciers, observed in the European Alps and other mountain regions of the world, will continue in the future. One of the most evident and relevant consequences of this phenomenon is the formation of new glacier lakes in recently deglaciated areas. During glacier retreat overdeepened parts of the glacier bed become exposed and, in some cases, filled with water. It is important to understand where these new lakes can appear because of the associated potential risks (i.e. lake outburst and consequent flood) and opportunities (tourism, hydroelectricity, water reservoir, etc.) especially in densely populated areas such as the European Alps. GlabTop2 (Glacier Bed Topography model version 2) allows to model glacier bed topography over large glaciated areas combining digital terrain information and slope-related estimates of glacier thickness. The model requires a minimum set of input data: glaciers outlines and a surface digital elevation model (DEM). In this work we tested the model on the Rutor Glacier (8,1 km2) located in the Aosta Valley. The glacier has a well-known history of a series of glacier lake outburst floods between 1430 AD and 1864 AD due to front fluctuations. After the last advance occurred during the 70s of the previous century, glacier shrinkage has been continuous and new lakes have formed in newly exposed overdeepenings. We applied GlabTop2 to DEMs derived from historical data (topographic maps and aerial photos pair) representing conditions before the proglacial lake formation. The results obtained have been compared with the present situation and existing lakes. Successively we used the model also on present-day DEMs, which are of higher resolution than the historical derived ones, and compared the modeled bed topography with an existing bedrock map obtained by in-situ geophysical investigations (GPR surveys). Preliminary results, obtained with the 1991 surface model, confirm the robustness of GlabTop2 in
Monitoring Jakobshavn Glacier using Sequential Landsat Images
NASA Astrophysics Data System (ADS)
Jian, Z.; Zhuoqi, C.; Cheng, X.
2016-12-01
Jakobshavn Glacier is the fastest (19 m per day) and one of the most active glaciers around the world. Discharging more than 35km3 of ice every year, its mass loss surpasses anyone else outside the Antarctic. From Landsat 8 OLI Images on August 14, 2015, we find a huge iceberg about 5 km2 calved from resulting in the front shrinking for 1060.8m. NSIDC ice velocity data and weather station data on Jakobshavn glacier are used to analyze the cause of calving. On one hand, upstream glacier push forward the Jakobshavn glacier westward continually, many cracks were formed over the glacier surface. Surface melting water flow into the interior of glaciers to accelerate calving. On the other hand with the gradually rising temperature, the bottom of glaciers accelerate ablation. When glaciers move into the ocean and the thin bottom can not provide strong enough support, calving occurs. Before this incident, we trace sequential Landsat data during 1986 to 2015. In 2010, it had another large-scale calving. We draw from our data that Jakobshavn retreated intensely in the past 30 years although in the last 10 years it appears more stable. The speed of glacier shrinking during 1996 to 2006 is three times as fast as past 10 years.
Glaciers in Patagonia: Controversy and prospects
NASA Astrophysics Data System (ADS)
Kargel, J. S.; Alho, P.; Buytaert, W.; Célleri, R.; Cogley, J. G.; Dussaillant, A.; Guido, Z.; Haeberli, W.; Harrison, S.; Leonard, G.; Maxwell, A.; Meier, C.; Poveda, G.; Reid, B.; Reynolds, J.; Rodríguez, C. A. Portocarrero; Romero, H.; Schneider, J.
2012-05-01
Lately, glaciers have been subjects of unceasing controversy. Current debate about planned hydroelectric facilities—a US7- to 10-billion megaproject—in a pristine glacierized area of Patagonia, Chile [Romero Toledo et al., 2009; Vince, 2010], has raised anew the matter of how glaciologists and global change experts can contribute their knowledge to civic debates on important issues. There has been greater respect for science in this controversy than in some previous debates over projects that pertain to glaciers, although valid economic motivations again could trump science and drive a solution to the energy supply problem before the associated safety and environmental problems are understood. The connection between glaciers and climate change—both anthropogenic and natural—is fundamental to glaciology and to glaciers' practical importance for water and hydropower resources, agriculture, tourism, mining, natural hazards, ecosystem conservation, and sea level [Buytaert et al., 2010; Glasser et al., 2011]. The conflict between conservation and development can be sharper in glacierized regions than almost anywhere else. Glaciers occur in spectacular natural landscapes, but they also supply prodigious exploitable meltwater.
Pulsating star research from Antarctica
NASA Astrophysics Data System (ADS)
Chadid, Merieme
2017-09-01
This invited talk discusses the pulsating star research from the heart of Antarctica and the scientific polar challenges in the extreme environment of Antarctica, and how the new polar technology could cope with unresolved stellar pulsation enigmas and evolutionary properties challenges towards an understanding of the mysteries of the Universe. PAIX, the first robotic photometer Antarctica program, has been successfully launched during the polar night 2007. This ongoing program gives a new insight to cope with unresolved stellar enigmas and stellar oscillation challenges with a great opportunity to benefit from an access to the best astronomical site on Earth, Dome C. PAIX achieves astrophysical measurement time-series of stellar fields, challenging photometry from space. A continuous and an uninterrupted series of multi-color photometric observations has been collected each polar night - 150 days - without regular interruption, Earth's rotation effect. PAIX shows the first light curve from Antarctica and first step for the astronomy in Antarctica giving new insights in remote polar observing runs and robotic instruments towards a new technology.
Sounding rockets in Antarctica
NASA Technical Reports Server (NTRS)
Alford, G. C.; Cooper, G. W.; Peterson, N. E.
1982-01-01
Sounding rockets are versatile tools for scientists studying the atmospheric region which is located above balloon altitudes but below orbital satellite altitudes. Three NASA Nike-Tomahawk sounding rockets were launched from Siple Station in Antarctica in an upper atmosphere physics experiment in the austral summer of 1980-81. The 110 kg payloads were carried to 200 km apogee altitudes in a coordinated project with Arcas rocket payloads and instrumented balloons. This Siple Station Expedition demonstrated the feasibility of launching large, near 1,000 kg, rocket systems from research stations in Antarctica. The remoteness of research stations in Antarctica and the severe environment are major considerations in planning rocket launching expeditions.
Glacier recession in Iceland and Austria
DOE Office of Scientific and Technical Information (OSTI.GOV)
Hall, D.K.; Williams, R.S. Jr.; Bayr, K.J.
1992-03-01
It has been possible to measure glacier recession on the basis of Landsat data, in conjunction with comparisons of the magnitude of recession of a glacier margin with in situ measurements at fixed points along the same margin. Attention is presently given to the cases of Vatnajokull ice cap, in Iceland, and the Pasterze Glacier, in Austria, on the basis of satellite data from 1973-1987 and 1984-1990, respectively. Indications of a trend toward negative mass balance are noted. Nevertheless, while most of the world's small glaciers have been receding, some are advancing either due to local climate or the tidewatermore » glacier cycle. 21 refs.« less
Direct evidence of warm water access to the Totten Glacier sub-ice shelf cavity
NASA Astrophysics Data System (ADS)
Orsi, A. H.; Rintoul, S. R.; Silvano, A.; van Wijk, E.; Pena-Molino, B.; Rosenberg, M. A.
2015-12-01
The Totten Glacier holds enough ice to raise global sea level by 3.5 m, is thinning according to (some) satellite data, and is grounded well below sea level on a retrograde bed and hence is potentially unstable. Basal melt driven by ocean heat flux has been linked to ice shelf thinning elsewhere in Antarctica, but no oceanographic measurements had been made near the Totten. In January 2015 the RSV Aurora Australis was the first ship to reach the Totten calving front. Observations from ship-board CTD, moorings and profiling floats provide direct confirmation that warm water reaches the ice shelf cavity. Warm water is present near the sea floor at every station deeper than 300 m depth, with maximum temperatures at mid-shelf >0.5°C. Mooring data confirm that the warm water is present year-round. A deep (>1100 m) channel at the calving front allows warm water (-0.4°C, >2°C above the local freezing point) to access the ice shelf cavity. The contrast between the oceanographic conditions near the Totten and near the Mertz Glacier is stark, although they are separated by only 30 degrees of longitude. East Antarctic ice shelves have often been assumed to behave in a similar manner and to be invulnerable to ocean change; these measurements suggest these assumptions need to be reconsidered.
NASA Technical Reports Server (NTRS)
Ming, D. W.; Morris, R. V.; Rampe, E. B.; Golden, D. C.; Quinn, J. E.
2015-01-01
The Chemistry and Mineralogy (CheMin) instrument onboard the Mars Curiosity rover has detected abundant amounts (approx. 25-30 weight percentage) of X-ray amorphous materials in a windblown deposit (Rocknest) and in a sedimentary mudstone (Cumberland and John Klein) in Gale crater, Mars. On Earth, X-ray amorphous components are common in soils and sediments, but usually not as abundant as detected in Gale crater. One hypothesis for the abundant X-ray amorphous materials on Mars is limited interaction of liquid water with surface materials, kinetically inhibiting maturation to more crystalline phases. The objective of this study was to characterize the chemistry and mineralogy of soils formed in the Antarctica Dry Valleys, one of the driest locations on Earth. Two soils were characterized from different elevations, including a low elevation, coastal, subxerous soil in Taylor Valley and a high elevation, ultraxerous soil in University Valley. A variety of techniques were used to characterize materials from each soil horizon, including Rietveld analysis of X-ray diffraction data. For Taylor Valley soil, the X-ray amorphous component ranged from about 4 weight percentage in the upper horizon to as high as 15 weight percentage in the lowest horizon just above the permafrost layer. Transmission electron microscopy indicated that the presence of short-range ordered (SRO) smectite was the most likely candidate for the X-ray amorphous materials in the Taylor Valley soils. The SRO smectite is likely an aqueous alteration product of mica inherited from granitic materials during glaciation of Taylor Valley. The drier University Valley soils had lower X-ray amorphous contents of about 5 weight percentage in the lowest horizon. The X-ray amorphous materials in University Valley are attributed to nanoparticles of TiO2 and possibly amorphous SiO2. The high abundance of X-ray amorphous materials in Taylor Valley is surprising for one of the driest places on Earth. These materials
Assessing streamflow sensitivity to variations in glacier mass balance
O'Neel, Shad; Hood, Eran; Arendt, Anthony; Sass, Louis
2014-01-01
The purpose of this paper is to evaluate relationships among seasonal and annual glacier mass balances, glacier runoff and streamflow in two glacierized basins in different climate settings. We use long-term glacier mass balance and streamflow datasets from the United States Geological Survey (USGS) Alaska Benchmark Glacier Program to compare and contrast glacier-streamflow interactions in a maritime climate (Wolverine Glacier) with those in a continental climate (Gulkana Glacier). Our overall goal is to improve our understanding of how glacier mass balance processes impact streamflow, ultimately improving our conceptual understanding of the future evolution of glacier runoff in continental and maritime climates.
Contemporary glacier retreat triggers a rapid landslide response, Great Aletsch Glacier, Switzerland
NASA Astrophysics Data System (ADS)
Kos, Andrew; Amann, Florian; Strozzi, Tazio; Delaloye, Reynald; Ruette, Jonas; Springman, Sarah
2016-12-01
The destabilization and catastrophic failure of landslides triggered by retreating glaciers is an expected outcome of global climate change and poses a significant threat to inhabitants of glaciated mountain valleys around the globe. Of particular importance are the formation of landslide-dammed lakes, outburst floods, and related sediment entrainment. Based on field observations and remote sensing of a deep-seated landslide, located at the present-day terminus of the Great Aletsch Glacier, we show that the spatiotemporal response of the landslide to glacier retreat is rapid, occurring within a decade. Our observations uniquely capture the critical period of increase in slope deformations, onset of failure, and show that measured displacements at the crown and toe regions of the landslide demonstrate a feedback mechanism between glacier ice reduction and response of the entire landslide body. These observations shed new light on the geomorphological processes of landslide response in paraglacial environments, which were previously understood to occur over significantly longer time periods.
2017-12-08
This ice cave in Belcher Glacier (Devon Island, Canada) was formed by melt water flowing within the glacier ice. To learn about the contributions of glaciers to sea level rise, visit: www.nasa.gov/topics/earth/features/glacier-sea-rise.html Credit: Angus Duncan, University of Saskatchewan 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
Large subglacial lakes in East Antarctica at the onset of fast-flowing ice streams.
Bell, Robin E; Studinger, Michael; Shuman, Christopher A; Fahnestock, Mark A; Joughin, Ian
2007-02-22
Water plays a crucial role in ice-sheet stability and the onset of ice streams. Subglacial lake water moves between lakes and rapidly drains, causing catastrophic floods. The exact mechanisms by which subglacial lakes influence ice-sheet dynamics are unknown, however, and large subglacial lakes have not been closely associated with rapidly flowing ice streams. Here we use satellite imagery and ice-surface elevations to identify a region of subglacial lakes, similar in total area to Lake Vostok, at the onset region of the Recovery Glacier ice stream in East Antarctica and predicted by ice-sheet models. We define four lakes through extensive, flat, featureless regions of ice surface bounded by upstream troughs and downstream ridges. Using ice velocities determined using interferometric synthetic aperture radar (InSAR), we find the onset of rapid flow (moving at 20 to 30 m yr(-1)) of the tributaries to the Recovery Glacier ice stream in a 280-km-wide segment at the downslope margins of these four subglacial lakes. We conclude that the subglacial lakes initiate and maintain rapid ice flow through either active modification of the basal thermal regime of the ice sheet by lake accretion or through scouring bedrock channels in periodic drainage events. We suggest that the role of subglacial lakes needs to be considered in ice-sheet mass balance assessments.
33 CFR 117.987 - Taylor Bayou.
Code of Federal Regulations, 2010 CFR
2010-07-01
... 33 Navigation and Navigable Waters 1 2010-07-01 2010-07-01 false Taylor Bayou. 117.987 Section 117.987 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND SECURITY BRIDGES DRAWBRIDGE OPERATION REGULATIONS Specific Requirements Texas § 117.987 Taylor Bayou. The draws of the Union Pacific...
33 CFR 117.987 - Taylor Bayou.
Code of Federal Regulations, 2011 CFR
2011-07-01
... 33 Navigation and Navigable Waters 1 2011-07-01 2011-07-01 false Taylor Bayou. 117.987 Section 117.987 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND SECURITY BRIDGES DRAWBRIDGE OPERATION REGULATIONS Specific Requirements Texas § 117.987 Taylor Bayou. The draws of the Union Pacific...
Radio-echo sounding of Caucasus glaciers
NASA Astrophysics Data System (ADS)
Lavrentiev, Ivan; Kutuzov, Stanislav; Vasilenko, Evgeny; Macheret, Yuri
2013-04-01
Accurate glacier volume and ice-thickness estimations are highly important for many glaciological applications. Recent glacier reduction is affecting local river discharge and contributes to the global sea level rise. However, direct measurements of ice thickness are very sparse due to its high cost and laboriousness. One of the glacierized mountain regions with a lack of direct ice-thickness measurements is Caucasus. So far data for several seismic and GPR profiles have been reported for only 3 glaciers from more than 1.7 thousands located in Caucasus. In 2010-2012 a number of ground base and airborne radio-echo sounding surveys have been accomplished in Caucasus Mountains using 20 MHz monopulse radar VIRL-6. Special aerial version of this ground penetrating radar was designed for helicopter-born measurements. The radar has a relatively long (10 m) receiving and transmitting antennas, which together with receiving, recording and transmitting devices can be mounted on a special girder, being suspended from a helicopter. VIRL-6 radar is light weight and can be quickly transformed into ground version. Equipment has been used on 16 glaciers including biggest glacier in Caucasus - Bezengi (36 km2) most of which have a highly crevassed surfaces and heterogeneous internal structure. Independent data were obtained also for two glaciers using ground version of the same VIRL-6 radar. In total more than 120 km of radar profiles were obtained. Results showed good agreement between ground and aerial measurements. Ice-thickness values exceeded 420 m for some of the Central Caucasus glaciers. Successful use of VIRL-6 radar in Caucasus opens up the possibility of using such equipment on different types of glaciers in polar and mountain regions, including temperate, polythermal and surging glaciers.
33 CFR 117.335 - Taylor Creek.
Code of Federal Regulations, 2010 CFR
2010-07-01
... 33 Navigation and Navigable Waters 1 2010-07-01 2010-07-01 false Taylor Creek. 117.335 Section 117.335 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND SECURITY BRIDGES DRAWBRIDGE OPERATION REGULATIONS Specific Requirements Florida § 117.335 Taylor Creek. The draw of US441 bridge, mile 0...
33 CFR 117.335 - Taylor Creek.
Code of Federal Regulations, 2011 CFR
2011-07-01
... 33 Navigation and Navigable Waters 1 2011-07-01 2011-07-01 false Taylor Creek. 117.335 Section 117.335 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND SECURITY BRIDGES DRAWBRIDGE OPERATION REGULATIONS Specific Requirements Florida § 117.335 Taylor Creek. The draw of US441 bridge, mile 0...
Soils and landforms from Fildes Peninsula and Ardley Island, Maritime Antarctica
NASA Astrophysics Data System (ADS)
Michel, Roberto F. M.; Schaefer, Carlos E. G. R.; López-Martínez, Jerónimo; Simas, Felipe N. B.; Haus, Nick W.; Serrano, Enrique; Bockheim, James G.
2014-11-01
Fildes Peninsula (F.P.) and Ardley Island (A.I.) are among the first ice-free areas in Maritime Antarctica. Since the last glacial retreat in this part of Antarctica (8000 to 5000 years BP), the landscape in these areas evolved under paraglacial to periglacial conditions, with pedogenesis marked by cryogenic processes. We carried out a detailed soil and geomorphology survey, with full morphological and analytical description for both areas; forty-eight soil profiles representing different landforms were sampled, analyzed and classified according to the U.S. Soil Taxonomy and the World Reference Base for Soil Resources (WRB). Soils are mostly turbic, moderately developed, with podzolization and strong phosphatization (chemical weathering of rock minerals and formation of amorphous Al and Fe minerals) in former ornithogenic sites while in areas with poor vegetation show typical features of cryogenic weathering. Nivation, solifluction, cryoturbation, frost weathering, ablation and surface erosion are widespread. The most represented landform system by surface in Fildes Peninsula is the periglacial one, and 15 different periglacial landforms types have been identified and mapped. These features occupy about 30% of the land surface, in which patterned ground and stone fields are the most common landforms. Other significant landforms as protalus lobes, rock glaciers or debris lobes indicate the extensive presence of permafrost. Soil variability was high, in terms of morphological, physical and chemical properties, due to varying lithic contributions and mixing of different rocks, as well as to different degrees of faunal influence. Three soil taxonomy orders were identified, whereas thirty four individual pedons were differentiated. Fildes Peninsula experiences a south-north gradient from periglacial to paraglacial conditions, and apparently younger soils and landforms are located close to the Collins Glacier. Arenosols/Entisols and Cryosols/Gelisols (frequently
2017-12-08
NASA image captured August 31, 2000 The tongue of the Malaspina Glacier, the largest glacier in Alaska, fills most of this image. The Malaspina lies west of Yakutat Bay and covers 1,500 sq. MI (3,880 sq. km). Credit: NASA/Landsat 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 Join us on Facebook
Quantifying global warming from the retreat of glaciers.
Oerlemans, J
1994-04-08
Records of glacier fluctuations compiled by the World Glacier Monitoring Service can be used to derive an independent estimate of global warming during the last 100 years. Records of different glaciers are made comparable by a two-step scaling procedure: one allowing for differences in glacier geometry, the other for differences in climate sensitivity. The retreat of glaciers during the last 100 years appears to be coherent over the globe. On the basis of modeling of the climate sensitivity of glaciers, the observed glacier retreat can be explained by a linear warming trend of 0.66 kelvin per century.
Kamb, B
1964-10-16
From physical measurements on glaciers and experimental studies of ice properties a framework of concept and theory is being built which bids fair to place glaciers among the more quantitatively understandable phenomena in the earth sciences. Measurements of flow velocity, deformation and stress, ice thickness and channel configuration, temperature, internal structure of theice, mass and energy balance, and response to meteorological variables all contribute to this understanding, as do still other measurements hardly discussed here, such as electrical properties, radioactive age measurements, and detailed studies of chemical and isotopic composition. The obvious goals of this work-the interpretation of past and present glacier fluctuations in terms of changes in world climate, and the prediction of glacier behavior-remain elusive, even though a good conceptual groundwork has been laid for dealing with the more tractable aspects of these problems. Intriguing recent discoveries have been made about such matters as the way in which glaciers react dynamically to changing conditions, the inter-relations between thermal regime and ice motion, the structural mechanisms of glacier flow, and the changes produced in ice by flow. One can recognize in these developments the possibility that concepts derived from the study of glacier flow may be applicable to phenomena of solid deformation deep in the earth. In this way glacier geophysics may have a useful impact beyond the study of glaciers themselves.
Diversity of soil yeasts isolated from South Victoria Land, Antarctica
Connell, L.; Redman, R.; Craig, S.; Scorzetti, G.; Iszard, M.; Rodriguez, R.
2008-01-01
Unicellular fungi, commonly referred to as yeasts, were found to be components of the culturable soil fungal population in Taylor Valley, Mt. Discovery, Wright Valley, and two mountain peaks of South Victoria Land, Antarctica. Samples were taken from sites spanning a diversity of soil habitats that were not directly associated with vertebrate activity. A large proportion of yeasts isolated in this study were basidiomycetous species (89%), of which 43% may represent undescribed species, demonstrating that culturable yeasts remain incompletely described in these polar desert soils. Cryptococcus species represented the most often isolated genus (33%) followed by Leucosporidium (22%). Principle component analysis and multiple linear regression using stepwise selection was used to model the relation between abiotic variables (principle component 1 and principle component 2 scores) and yeast biodiversity (the number of species present at a given site). These analyses identified soil pH and electrical conductivity as significant predictors of yeast biodiversity. Species-specific PCR primers were designed to rapidly discriminate among the Dioszegia and Leucosporidium species collected in this study. ?? 2008 Springer Science+Business Media, LLC.
NASA Astrophysics Data System (ADS)
Van Tiel, Marit; Van Loon, Anne; Wanders, Niko; Vis, Marc; Teuling, Ryan; Stahl, Kerstin
2017-04-01
In glacierized catchments, snowpack and glaciers function as an important storage of water and hydrographs of highly glacierized catchments in mid- and high latitudes thus show a clear seasonality with low flows in winter and high flows in summer. Due to the ongoing climate change we expect this type of storage capacity to decrease with resultant consequences for the discharge regime. In this study we focus on streamflow droughts, here defined as below average water availability specifically in the high flow season, and which methods are most suitable to characterize future streamflow droughts as regimes change. Two glacierized catchments, Nigardsbreen (Norway) and Wolverine (Alaska), are used as case study and streamflow droughts are compared between two periods, 1975-2004 and 2071-2100. Streamflow is simulated with the HBV light model, calibrated on observed discharge and seasonal glacier mass balances, for two climate change scenarios (RCP 4.5 & RCP 8.5). In studies on future streamflow drought often the same variable threshold of the past has been applied to the future, but in regions where a regime shift is expected this method gives severe "droughts" in the historic high-flow period. We applied the new alternative transient variable threshold, a threshold that adapts to the changing hydrological regime and is thus better able to cope with this issue, but has never been thoroughly tested in glacierized catchments. As the glacier area representation in the hydrological modelling can also influence the modelled discharge and the derived streamflow droughts, we evaluated in this study both the difference between the historical variable threshold (HVT) and transient variable threshold (TVT) and two different glacier area conceptualisations (constant area (C) and dynamical area (D)), resulting in four scenarios: HVT-C, HVT-D, TVT-C and TVT-D. Results show a drastic decrease in the number of droughts in the HVT-C scenario due to increased glacier melt. The deficit
NASA Astrophysics Data System (ADS)
Donat-Magnin, Marion; Jourdain, Nicolas C.; Spence, Paul; Le Sommer, Julien; Gallée, Hubert; Durand, Gaël.
2017-12-01
It has been suggested that the coastal Southern Ocean subsurface may warm over the 21st century in response to strengthening and poleward shifting winds, with potential adverse effects on West Antarctic glaciers. However, using a 1/12° ocean regional model that includes ice-shelf cavities, we find a more complex response to changing winds in the Amundsen Sea. Simulated offshore subsurface waters get colder under strengthened and poleward shifted winds representative of the SAM projected trend. The buoyancy-driven circulation induced by ice-shelf melt transports this cold offshore anomaly onto the continental shelf, leading to cooling and decreased melt below 450 m. In the vicinity of ice-shelf fronts, Ekman pumping contributes to raise the isotherms in response to changing winds. This effect overwhelms the horizontal transport of colder offshore waters at intermediate depths (between 200 and 450 m), and therefore increases melt rates in the upper part of the ice-shelf cavities, which reinforces the buoyancy-driven circulation and further contributes to raise the isotherms. Then, prescribing an extreme grounding line retreat projected for 2100, the total melt rates simulated underneath Thwaites and Pine Island are multiplied by 2.5. Such increase is explained by a larger ocean/ice interface exposed to CDW, which is then amplified by a stronger melt-induced circulation along the ice draft. Our main conclusions are that (1) outputs from ocean models that do not represent ice shelf cavities (e.g., CMIP5 models) should not be directly used to predict the thermal forcing of future ice shelf cavities; (2) coupled ocean/ice sheet models with a velocity-dependent melt formulation are needed for future projections of glaciers experiencing a significant grounding line retreat.
Modeling water mass formation in the Mertz Glacier Polynya and Adélie Depression, East Antarctica
NASA Astrophysics Data System (ADS)
Marsland, S. J.; Bindoff, N. L.; Williams, G. D.; Budd, W. F.
2004-11-01
High rates of sea ice growth and brine rejection in the Mertz Glacier Polynya drive the production of dense continental shelf waters in the Adélie Depression. We consider the rate of outflow of waters having sufficient density to sink into the neighboring abyssal ocean and form Adélie Land Bottom Water (ALBW). Along with Weddell and Ross Sea Bottom Waters, the ALBW is an important source of Antarctic Bottom Water. The relevant processes are modeled using a variant of the Max Planck Institute Ocean Model (MPIOM) under daily NCEP-NCAR reanalysis forcing for the period 1991-2000. The orthogonal curvilinear horizontal grid allows for the construction of a global domain with high resolution in our region of interest. The modeled Mertz Glacier Polynya is realistic in location and extent, exhibiting low ice thickness (<0.4 m) and low ice fraction (<50%). The net surface ocean to atmosphere heat flux exceeds 200 W m2 and is dominated by sensible heat exchange. In wintertime (May through September inclusive), 7.5 m of sea ice forms over the Adélie Depression at a rate of 4.9 cm d-1: this results in annual average volumetric production of 99 km3 of sea ice. The associated brine release drives dense shelf water formation. The off-shelf flow of dense water exhibits strong interannual variability in response to variability in both atmospheric forcing and ocean preconditioning. Averaged over the period 1991-2000 the off shelf flow of dense water is 0.15 Sv: for a period of strong outflow (1993-1997), this increases to 0.24 Sv. Most of the outflow occurs during July through October, at a rate of 0.40 (0.63) Sv over the period 1991-2000 (1993-1997). The peak mean monthly outflow can exceed 1 Sv.
Landsat Image Mosaic of Antarctica (LIMA)
,
2007-01-01
For most of us, Antarctica was at best a distant acquaintance. Now, with the Landsat Image Mosaic of Antarctica (LIMA), we are on intimate terms. In stunning, up-close and personal detail, LIMA brings Antarctica to life. Explore this virtually cloudless, seamless, most geometrically accurate, and highest resolution satellite mosaic of Antarctica. A team of scientists from the U.S. Geological Survey, the British Antarctic Survey, and the National Aeronautics and Space Administration, with funding from the National Science Foundation, created LIMA in support of the International Polar Year (IPY; 2007?08). As the first major scientific outcome of the IPY, LIMA truly fulfills the IPY goals. LIMA is an international effort, supports current scientific polar research, encourages new projects, and helps the general public visualize Antarctica and changes happening in this southernmost environment. Researchers and the general public can download LIMA and all component Landsat scenes at no charge.
Ocean impact on Nioghalvfjerdsfjorden Glacier, Northeast Greenland
NASA Astrophysics Data System (ADS)
Schaffer, Janin; Kanzow, Torsten; von Appen, Wilken-Jon; Mayer, Christoph
2017-04-01
The ocean plays an important role in modulating the mass balance of the Greenland Ice Sheet by delivering heat to the marine-terminating outlet glaciers around Greenland. The largest of three outlet glaciers draining the Northeast Greenland Ice Stream is Nioghalvfjerdsfjorden Glacier (also referred to as 79 North Glacier). Historic observations showed that warm waters of Atlantic origin are present in the subglacial cavity below the 80 km long floating ice tongue of the Nioghalvfjerdsfjorden Glacier and cause strong basal melt at the grounding line, but to date it has been unknown how those warm water enter the cavity. In order to understand how Atlantic origin waters carry heat into the subglacial cavity beneath Nioghalvfjerdsfjorden Glacier, we performed bathymetric, hydrographic, and velocity observations in the vicinity of the main glacier calving front aboard RV Polarstern in summer 2016. The bathymetric multibeam data shows a 500 m deep and 2 km narrow passage downstream of a 310 m deep sill. This turned out to be the only location deep enough for an exchange of Atlantic waters between the glacier cavity and the continental shelf. Hydrographic and velocity measurements revealed a density driven plume in the vicinity of the glacier calving front causing a rapid flow of waters of Atlantic origin warmer 1°C into the subglacial cavity through the 500 m deep passage. In addition, glacially modified waters flow out of the glacier cavity below the 80 m deep ice base. In the vicinity of the glacier, the glacially modified waters form a distinct mixed layer situated above the Atlantic waters and below the ambient Polar water. At greater distances from the glacier this layer is eroded by lateral mixing with ambient water. Based on our observations we will present an estimate of the ocean heat transport into the subglacial cavity. In comparison with historic observations we find an increase in Atlantic water temperatures throughout the last 20 years. The resulting
Internationally coordinated glacier monitoring - a timeline since 1894
NASA Astrophysics Data System (ADS)
Nussbaumer, Samuel U.; Armstrong, Richard; Fetterer, Florence; Gärtner-Roer, Isabelle; Hoelzle, Martin; Machguth, Horst; Mölg, Nico; Paul, Frank; Raup, Bruce H.; Zemp, Michael
2016-04-01
Changes in glaciers and ice caps provide some of the clearest evidence of climate change, with impacts on sea-level variations, regional hydrological cycles, and natural hazard situations. Therefore, glaciers have been recognized as an Essential Climate Variable (ECV). Internationally coordinated collection and distribution of standardized information about the state and change of glaciers and ice caps was initiated in 1894 and is today organized within the Global Terrestrial Network for Glaciers (GTN-G). GTN-G ensures the continuous development and adaptation of the international strategies to the long-term needs of users in science and policy. A GTN-G Steering Committee coordinates, supports and advices the operational bodies responsible for the international glacier monitoring, which are the World Glacier Monitoring Service (WGMS), the US National Snow and Ice Data Center (NSIDC), and the Global Land Ice Measurements from Space (GLIMS) initiative. In this presentation, we trace the development of the internationally coordinated glacier monitoring since its beginning in the 19th century. Today, several online databases containing a wealth of diverse data types with different levels of detail and global coverage provide fast access to continuously updated information on glacier fluctuation and inventory data. All glacier datasets are made freely available through the respective operational bodies within GTN-G, and can be accessed through the GTN-G Global Glacier Browser (http://www.gtn-g.org/data_browser.html). Glacier inventory data (e.g., digital outlines) are available for about 180,000 glaciers (GLIMS database, RGI - Randolph Glacier Inventory, WGI - World Glacier Inventory). Glacier front variations with about 45,000 entries since the 17th century and about 6,200 glaciological and geodetic mass (volume) change observations dating back to the 19th century are available in the Fluctuations of Glaciers (FoG) database. These datasets reveal clear evidence that
The contribution of glacier melt to streamflow
DOE Office of Scientific and Technical Information (OSTI.GOV)
Schaner, Neil; Voisin, Nathalie; Nijssen, Bart
2012-09-13
Ongoing and projected future changes in glacier extent and water storage globally have lead to concerns about the implications for water supplies. However, the current magnitude of glacier contributions to river runoff is not well known, nor is the population at risk to future glacier changes. We estimate an upper bound on glacier melt contribution to seasonal streamflow by computing the energy balance of glaciers globally. Melt water quantities are computed as a fraction of total streamflow simulated using a hydrology model and the melt fraction is tracked down the stream network. In general, our estimates of the glacier meltmore » contribution to streamflow are lower than previously published values. Nonetheless, we find that globally an estimated 225 (36) million people live in river basins where maximum seasonal glacier melt contributes at least 10% (25%) of streamflow, mostly in the High Asia region.« less
Glacier Sensitivity Across the Andes
NASA Astrophysics Data System (ADS)
Sagredo, E. A.; Lowell, T. V.; Rupper, S.
2010-12-01
Most of the research on causes driving former glacial fluctuations, and the climatic signals involved, has focused on the comparisons of sequences of glacial events in separate regions of the world and their temporal-phasing relationship with terrestrial or extraterrestrial climate-forcing mechanisms. Nevertheless the climatic signals related with these glacial advances are still under debate. This impossibility to resolve these questions satisfactorily have been generally attributed to the insufficiently precise chronologies and unevenly distributed records. However, behind these ideas lies the implicit assumption that glaciers situated in different climate regimes respond uniformly to similar climatic perturbations. This ongoing research is aimed to explore the climate-glacier relationship at regional scale, through the analysis of the spatial variability of glacier sensitivity to climatic change. By applying a Surface Energy Mass Balance model (SEMB) developed by Rupper and Roe (2008) to glaciers located in different climatic regimes, we analyzed the spatial variability of mass balance changes under different baseline conditions and under different scenarios of climatic change. For the sake of this research, the analysis is being focused on the Andes, which in its 9,000 km along the western margin of South America offers an unparalleled climatic diversity. Preliminary results suggest that above some threshold of climate change (a hypothetical uniform perturbation), all the glaciers across the Andes would respond in the “same direction” (advancing or retreating). Below that threshold, glaciers located in some climatic regimes may be insensitive to the specific perturbation. On the other hand, glaciers located in different climatic regimes may exhibit a “different magnitude” of change under a uniform climatic perturbation. Thus, glaciers located in the dry Andes of Perú, Chile and Argentina are more sensitive to precipitation changes than variations in
Glacier-specific elevation changes in western Alaska
NASA Astrophysics Data System (ADS)
Paul, Frank; Le Bris, Raymond
2013-04-01
Deriving glacier-specific elevation changes from DEM differencing and digital glacier outlines is rather straight-forward if the required datasets are available. Calculating such changes over large regions and including glaciers selected for mass balance measurements in the field, provides a possibility to determine the representativeness of the changes observed at these glaciers for the entire region. The related comparison of DEM-derived values for these glaciers with the overall mean avoids the rather error-prone conversion of volume to mass changes (e.g. due to unknown densities) and gives unit-less correction factors for upscaling the field measurements to a larger region. However, several issues have to be carefully considered, such as proper co-registration of the two DEMs, date and accuracy of the datasets compared, as well as source data used for DEM creation and potential artefacts (e.g. voids). In this contribution we present an assessment of the representativeness of the two mass balance glaciers Gulkana and Wolverine for the overall changes of nearly 3200 glaciers in western Alaska over a ca. 50-year time period. We use an elevation change dataset from a study by Berthier et al. (2010) that was derived from the USGS DEM of the 1960s (NED) and a more recent DEM derived from SPOT5 data for the SPIRIT project. Additionally, the ASTER GDEM was used as a more recent DEM. Historic glacier outlines were taken from the USGS digital line graph (DLG) dataset, corrected with the digital raster graph (DRG) maps from USGS. Mean glacier specific elevation changes were derived based on drainage divides from a recently created inventory. Land-terminating, lake-calving and tidewater glaciers were marked in the attribute table to determine their changes separately. We also investigated the impact of handling potential DEM artifacts in three different ways and compared elevation changes with altitude. The mean elevation changes of Gulkana and Wolverine glaciers (about -0
Kim, Jun-Tae; Choi, Yun-Jeong; Barghi, Mandana; Yoon, Young-Jun; Kim, Jeong-Hoon; Kim, Ji Hee; Chang, Yoon-Seok
2018-04-01
The spatial distribution of old and new halogenated flame retardants (HFRs), including polybrominated diphenyl ethers (PBDEs), hexabromocyclododecanes (HBCDs), and Dechlorane Plus (DPs) and related compounds (Dechloranes), were investigated in the South Shetland Islands of Antarctica, employing mosses (Andreaea depressinervis and Sanionia uncinata) and lichens (Himantormia lugubris and Usnea antarctica) as bioindicators. The levels of PBDEs, HBCDs, and Dechloranes ranged from 3.2 to 71.5, 0.63-960, and 2.04-2400 pg/g dw (dry weight) in the mosses, and from 1.5 to 188, 0.1-21.1, and 1.0-83.8 pg/g dw in the lichens, respectively. HFRs were detected in all of the collected samples, even in those from the remote regions. The dominance of high brominated-BDE, anti-DP fraction, and HBCD diastereomeric ratio in the samples from remote regions suggested the long-range atmospheric transport (LRAT) of the HFRs. The relatively high HBCDs and Dechloranes contamination and their similar chemical profile with commercial products in the vicinity of Antarctic research stations indicated that human activities might act as local sources, while PBDEs appeared to be more influenced by LRAT and bioaccumulation rather than local emission. Lastly, the relatively high HFR levels and dominance of more brominated BDEs at the Narębski Point and in the wet lowlands suggested that penguin colonies and melting glacier water could be secondary HFR sources in Antarctica. The HFR levels differed by sample species, suggesting that further research on the factors associated with the HFR accumulation in the different species is necessary. This study firstly reports the alternative HFR levels in a wide area of the Antarctica, which could improve our understanding of the source, transport, and fate of the HFRs. Copyright © 2017 Elsevier Ltd. All rights reserved.
Thickness of unconsolidated deposits in the towns of Solon and Taylor, Cortland County, New York
Miller, Todd S.
1999-01-01
IntroductionSiting of waste-disposal facilities in Cortland County poses a potential threat to local ground-water resources. An especially sensitive waste-disposal siting issue arose in 1988, when the New York State Low-Level Radioactive Waste Siting Commission (NYSLLWSC) identified 15 sites in six towns (Towns of Solon, Taylor, Freetown, Cincinnatus, Marathon, and Willet) in the eastern part of the county for possible disposal of low-level radioactive waste (New York State Low-Level Radioactive Waste Siting Commission, 1988). Eventually, two sites in the Town of Taylor became finalist sites; one was selected from the list of 15 potential sites, and the other was offered by a private landowner. Little information was available on geohydrologic conditions in eastern Cortland County, such as the extent of aquifers and the thickness of unconsolidated deposits of low permeability (such as clay and till), even though these two criteria were among those used by NYSLLWSC for selection of potential disposal sites. The source of information on thickness of drift over bedrock was the surficial geologic map of New York (Muller and Cadwell, 1986). The siting effort was terminated before a final selection was made, but the issue had made county managers aware that detailed information on the extent and thickness of unconsolidated deposits (particularly till, which typically has low permeability and can limit the migration of contaminants) is needed before sound decisions on waste-disposal siting can be made.Glaciers deposited till nearly everywhere over bedrock in the uplands of central New York, but the thickness of the till varies greatly from place to place. An analysis by Coates (1966) of 400 drillers' logs of wells in a 2,000-mi2 area in the uplands of south-central New York (south of the Cortland County) indicated that (1) till is thin or absent on hilltops and is thickest on the lower parts of hills, (2) overall till thickness averages 60 ft, and (3) till thickness on
String-theoretic deformation of the Parke-Taylor factor
NASA Astrophysics Data System (ADS)
Mizera, Sebastian; Zhang, Guojun
2017-09-01
Scattering amplitudes in a range of quantum field theories can be computed using the Cachazo-He-Yuan (CHY) formalism. In theories with color ordering, the key ingredient is the so-called Parke-Taylor factor. In this paper we give a fully SL (2 ,C )-covariant definition and study the properties of a new integrand called the "string Parke-Taylor" factor. It has an α' expansion whose leading coefficient is the field-theoretic Parke-Taylor factor. Its main application is that it leads to a CHY formulation of open string tree-level amplitudes. In fact, the definition of the string Parke-Taylor factor was motivated by trying to extend the compact formula for the first α' correction found by He and Zhang, while the main ingredient in its definition is a determinant of a matrix introduced in the context of string theory by Stieberger and Taylor.
2017-03-09
New Zealand contains over 3,000 glaciers, most of which are in the Southern Alps on the South Island. Since 1890, the glaciers have been retreating, with short periods of small advances, as shown in this image from NASA Terra spacecraft. The image cover an area of 39 by 46 km, and are located at 43.7 degrees south, 170 degrees east. http://photojournal.jpl.nasa.gov/catalog/PIA21509
Microbial biodiversity in glacier-fed streams
Wilhelm, Linda; Singer, Gabriel A; Fasching, Christina; Battin, Tom J; Besemer, Katharina
2013-01-01
While glaciers become increasingly recognised as a habitat for diverse and active microbial communities, effects of their climate change-induced retreat on the microbial ecology of glacier-fed streams remain elusive. Understanding the effect of climate change on microorganisms in these ecosystems is crucial given that microbial biofilms control numerous stream ecosystem processes with potential implications for downstream biodiversity and biogeochemistry. Here, using a space-for-time substitution approach across 26 Alpine glaciers, we show how microbial community composition and diversity, based on 454-pyrosequencing of the 16S rRNA gene, in biofilms of glacier-fed streams may change as glaciers recede. Variations in streamwater geochemistry correlated with biofilm community composition, even at the phylum level. The most dominant phyla detected in glacial habitats were Proteobacteria, Bacteroidetes, Actinobacteria and Cyanobacteria/chloroplasts. Microorganisms from ice had the lowest α diversity and contributed marginally to biofilm and streamwater community composition. Rather, streamwater apparently collected microorganisms from various glacial and non-glacial sources forming the upstream metacommunity, thereby achieving the highest α diversity. Biofilms in the glacier-fed streams had intermediate α diversity and species sorting by local environmental conditions likely shaped their community composition. α diversity of streamwater and biofilm communities decreased with elevation, possibly reflecting less diverse sources of microorganisms upstream in the catchment. In contrast, β diversity of biofilms decreased with increasing streamwater temperature, suggesting that glacier retreat may contribute to the homogenisation of microbial communities among glacier-fed streams. PMID:23486246
NASA Astrophysics Data System (ADS)
Fernandez-Vasquez, R. A.; Anderson, J. B.; Wellner, J. S.; Minzoni, R. L.
2012-12-01
We present the results of the study of tidewater glacier depositional basins, across a broad latitudinal transect from central Patagonia (46°S) to the Antarctic Peninsula (65°S). Based on sediment cores and seismic records, we estimate accumulation rates at several timescales as well as sediment-volume derived erosion rates (Er) for millennial time scales. In the Antarctic Peninsula, accumulation rates are ~100 mm/yr for centennial and millennial timescales. In Patagonia, proximal basins are in general well isolated and have short timescale (decadal-centennial) sedimentary records and high accumulation rates, whereas medial (more distal) basins have millennial scale sedimentary records and low accumulation rates. We hypothesize that the "Saddler effect" in the accumulation rates of the Patagonian study areas exists because Neoglacial advance and recent post-Little Ice Age retreat has left well isolated proximal basins that effectively trap sediments. This, along with high sediment yields, produces high decadal accumulation rates. There is no such organization of basins in the Antarctic Peninsula fjords and bays and no such clear manifestation of Neoglacial advances or morphologies. Erosion rates span two orders of magnitude from 0.03 mm/yr for Lapeyrère Bay at Anvers Island, Antarctica (~64.5°S), to 1.09 mm/yr for San Rafael Glacier in northern Patagonia (~46.5°S). Rates for Antarctic Peninsula glaciers are in general lower than those of temperate Patagonian glaciers. A good correlation of erosion rates and modern sea level annual temperature was found. A latitudinal decrease in millennial erosion rates is interpreted as a result of decreasing annual temperature although decreasing annual precipitation may also be a factor. However, local variability within each region might be influenced by differences in bedrock geology (e.g. Herbert Sound versus Lapeyrère and Andvord bays ) and drainage basin morphology (hypsometry, number of glaciers and length of overall
Glaciers in 21st Century Himalayan Geopolitics
NASA Astrophysics Data System (ADS)
Kargel, J. S.; Wessels, R.; Kieffer, H. H.
2002-05-01
Glaciers are ablating rapidly the world over. Nowhere are the rates of retreat and downwasting greater than in the Hindu Kush-Himalaya (HKH) region. It is estimated that over the next century, 40,000 square kilometers of present glacier area in the HKH region will become ice free. Most of this area is in major valleys and the lowest glaciated mountain passes. The existence and characteristics of glaciers have security impacts, and rapidly changing HKH glaciers have broad strategic implications: (1) Glaciers supply much of the fresh water and hydroelectric power in South and Central Asia, and so glaciers are valuable resources. (2) Shared economic interests in water, hydroelectricity, flood hazards, and habitat preservation are a force for common cause and reasoned international relations. (3) Glaciers and their high mountains generally pose a natural barrier tending to isolate people. Historically, they have hindered trade and intercultural exchanges and have protected against aggression. This has further promoted an independent spirit of the region's many ethnic groups. (4) Although glaciers are generally incompatible with human development and habitation, many of the HKH region's glaciers and their mountains have become sanctuaries and transit routes for militants. Siachen Glacier in Kashmir has for 17 years been "the world's highest battlefield," with tens of thousands of troops deployed on both sides of the India/Pakistan line of control. In 1999, that conflict threatened to trigger all-out warfare, and perhaps nuclear warfare. Other recent terrorist and military action has taken place on glaciers in Kyrgyzstan and Tajikistan. As terrorists are forced from easily controlled territories, many may tend to migrate toward the highest ground, where definitive encounters may take place in severe alpine glacial environments. This should be a major concern in Nepali security planning, where an Army offensive is attempting to reign in an increasingly robust and brutal
A fjord-glacier coupled system model
NASA Astrophysics Data System (ADS)
de Andrés, Eva; Otero, Jaime; Navarro, Francisco; Prominska, Agnieszka; Lapazaran, Javier; Walczowski, Waldemar
2017-04-01
With the aim of studying the processes occurring at the front of marine-terminating glaciers, we couple a fjord circulation model with a flowline glacier dynamics model, with subglacial discharge and calving, which allows the calculation of submarine melt and its influence on calving processes. For ocean modelling, we use a general circulation model, MITgcm, to simulate water circulation driven by both fjord conditions and subglacial discharge, and for calculating submarine melt rates at the glacier front. To constrain freshwater input to the fjord, we use estimations from European Arctic Reanalysis (EAR). To determine the optimal values for each run period, we perform a sensitivity analysis of the model to subglacial discharge variability, aimed to get the best fit of model results to observed temperature and salinity profiles in the fjord for each of these periods. Then, we establish initial and boundary fjord conditions, which we vary weekly-fortnightly, and calculate the submarine melt rate as a function of depth at the calving front. These data are entered into the glacier-flow model, Elmer/Ice, which has been added a crevasse-depth calving model, to estimate the glacier terminus position at a weekly time resolution. We focus our study on the Hansbreen Glacier-Hansbukta Fjord system, in Southern Spitsbergen, Svalbard, where a large set of data are available for both glacier and fjord. The bathymetry of the entire system has been determined from ground penetrating radar and sonar data. In the fjord we have got temperature and salinity data from CTDs (May to September, 2010-2014) and from a mooring (September to May, 2011-2012). For Hansbreen, we use glacier surface topography data from the SPIRIT DEM, surface mass balance from EAR, centre line glacier velocities from stake measurements (May 2005-April 2011), weekly terminus positions from time-lapse photos (Sept. 2009-Sept. 2011), and sea-ice concentrations from time-lapse photos and Nimbus-7 SMMR and DMSP SSM
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.
2017-12-08
The Aletsch Glacier in Switzerland is the largest valley glacier in the Alps. Its volume loss since the middle of the 19th century is well-visible from the trimlines to the right of the image. To learn about the contributions of glaciers to sea level rise, visit: www.nasa.gov/topics/earth/features/glacier-sea-rise.html Credit: Frank Paul, University of Zurich 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
Tracer-based identification of rock glacier thawing in a glacierized Alpine catchment
NASA Astrophysics Data System (ADS)
Engel, Michael; Penna, Daniele; Tirler, Werner; Comiti, Francesco
2017-04-01
Current warming in high mountains leads to increased melting of snow, glacier ice and permafrost. In particular rock glaciers, as a creeping form of mountain permafrost, may release contaminants such as heavy metals into the stream during intense melting periods in summer. This may have strong impacts on both water quantity and quality of fresh water resources but might also harm the aquatic fauna in mountain regions. In this context, the present study used stable isotopes of water and electrical conductivity (EC) combined with trace, major and minor elements to identify the influence of permafrost thawing on the water quality in the glacierized Solda catchment (130 km2) in South Tyrol (Italy). We carried out a monthly sampling of two springs fed by an active rock glacier at about 2600 m a.s.l. from July to October 2015. Furthermore, we took monthly water samples from different stream sections of the Solda River (1110 to m a.s.l.) from March to November 2015. Meteorological data were measured by an Automatic Weather Station at 2825 m a.s.l. of the Hydrographic Office (Autonomous Province of Bozen-Bolzano). First results show that water from the rock glacier springs and stream water fell along the global meteoric water line. Spring water was slightly more variable in isotopic ratio (δ2H: -91 to - 105 ) and less variable in dissolved solutes (EC: 380 to 611 μS/cm) than stream water (δ2H: -96 to - 107 ‰ and EC: 212 to 927 μS/cm). Both spring water and stream water showed a pronounced drop in EC during July and August, very likely induced by increased melt water dilution. In both water types, element concentrations of Ca and Mg were highest (up to 160 and 20 mg/l, respectively). In September, spring water showed higher concentrations in Cu, As, and Pb than stream water, indicating that these elements partly exceeded the concentration limit for drinking water. These observations highlight the important control, which rock glacier thawing may have on water quality
NASA Astrophysics Data System (ADS)
Strigaro, Daniele; Moretti, Massimiliano; Mattavelli, Matteo; Frigerio, Ivan; Amicis, Mattia De; Maggi, Valter
2016-09-01
The aim of this work is to integrate the Minimal Glacier Model in a Geographic Information System Python module in order to obtain spatial simulations of glacier retreat and to assess the future scenarios with a spatial representation. The Minimal Glacier Models are a simple yet effective way of estimating glacier response to climate fluctuations. This module can be useful for the scientific and glaciological community in order to evaluate glacier behavior, driven by climate forcing. The module, called r.glacio.model, is developed in a GRASS GIS (GRASS Development Team, 2016) environment using Python programming language combined with different libraries as GDAL, OGR, CSV, math, etc. The module is applied and validated on the Rutor glacier, a glacier in the south-western region of the Italian Alps. This glacier is very large in size and features rather regular and lively dynamics. The simulation is calibrated by reconstructing the 3-dimensional dynamics flow line and analyzing the difference between the simulated flow line length variations and the observed glacier fronts coming from ortophotos and DEMs. These simulations are driven by the past mass balance record. Afterwards, the future assessment is estimated by using climatic drivers provided by a set of General Circulation Models participating in the Climate Model Inter-comparison Project 5 effort. The approach devised in r.glacio.model can be applied to most alpine glaciers to obtain a first-order spatial representation of glacier behavior under climate change.
NASA Astrophysics Data System (ADS)
Bolch, Tobias; Kutuzov, Stanislav; Rohrbach, Nico; Fischer, Andrea; Osmonov, Azamat
2015-04-01
Meltwater originating from the Tien Shan is of high importance for the runoff to the arid and semi-arid region of Central Asia. Previous studies estimate a glaciers' contribution of about 40% for the Aksu-Tarim Catchment, a transboundary watershed between Kyrgyzstan and China. Large parts of the Ak-Shiirak Range drain into this watershed. Glaciers in Central and Inner Tien Shan are typically polythermal or even cold and surrounded by permafrost. Several glaciers terminate into large moraine complexes which show geomorphological indicators of ice content such as thermo-karst like depressions, and further downvalley signs of creep such as ridges and furrows and a fresh, steep rock front which are typical indicators for permafrost creep ("rock glacier"). Hence, glaciers and permafrost co-exist in this region and their interactions are important to consider, e.g. for the understanding of glacial and periglacial processes. It can also be assumed that the ice stored in these relatively large dead-ice/moraine-complexes is a significant amount of the total ice storage. However, no detailed investigations exist so far. In an initial study, we investigated the structure and ice content of two typical glacier-moraine complexes in the Ak-Shiirak-Range using different ground penetrating radar (GPR) devices. In addition, the geomorphology was mapped using high resolution satellite imagery. The structure of the moraine-rock glacier complex is in general heterogeneous. Several dead ice bodies with different thicknesses and moraine-derived rock glaciers with different stages of activities could be identified. Few parts of these "rock glaciers" contain also massive ice but the largest parts are likely characterised by rock-ice layers of different thickness and ice contents. In one glacier forefield, the thickness of the rock-ice mixture is partly more than 300 m. This is only slightly lower than the maximum thickness of the glacier ice. Our measurements revealed that up to 20% of
Debris thickness patterns on debris-covered glaciers
NASA Astrophysics Data System (ADS)
Anderson, Leif S.; Anderson, Robert S.
2018-06-01
Many debris-covered glaciers have broadly similar debris thickness patterns: surface debris thickens and tends to transition from convex- to concave-up-down glacier. We explain this pattern using theory (analytical and numerical models) paired with empirical observations. Down glacier debris thickening results from the conveyor-belt-like nature of the glacier surface in the ablation zone (debris can typically only be added but not removed) and from the inevitable decline in ice surface velocity toward the terminus. Down-glacier thickening of debris leads to the reduction of sub-debris melt and debris emergence toward the terminus. Convex-up debris thickness patterns occur near the up-glacier end of debris covers where debris emergence dominates (ablation controlled). Concave-up debris thickness patterns occur toward glacier termini where declining surface velocities dominate (velocity controlled). A convex-concave debris thickness profile inevitably results from the transition between ablation-control and velocity-control down-glacier. Debris thickness patterns deviating from this longitudinal shape are most likely caused by changes in hillslope debris supply through time. By establishing this expected debris thickness pattern, the effects of climate change on debris cover can be better identified.
SAR investigations of glaciers in northwestern North America
NASA Technical Reports Server (NTRS)
Lingle, Craig S.; Harrison, William D.
1995-01-01
The objective of this project was to investigate the utility of satellite synthetic aperture radar (SAR) imagery for measurement of geophysical parameters on Alaskan glaciers relevant to their mass balance and dynamics, including: (1) the positions of firn lines (late-summer snow lines); (2) surface velocities on fast-flowing (surging) glaciers, and also on slower steady-flow glaciers; and (3) the positions and changes in the positions of glacier termini. Preliminary studies of topography and glacier surface velocity with SAR interferometry have also been carried out. This project was motivated by the relationships of multi-year to decadal changes in glacier geometry to changing climate, and the probable significant contribution of Alaskan glaciers to rising sea level.
Remote Sensing Observations of Advancing and Surging Tidewater Glaciers
NASA Astrophysics Data System (ADS)
McNabb, R. W.; Kääb, A.; Nuth, C.; Girod, L.; Truffer, M.; Fahnestock, M. A.
2017-12-01
Progress has been made in understanding the glaciological frontiers of tidewater glacier dynamics and surge dynamics, though many aspects of these topics are not well-understood. Advances in the processing of digital elevation models (DEMs) from ASTER imagery, as well as the increased availability and temporal density of satellite images such as Landsat and the Sentinel missions, provide an unprecedented wealth of satellite data over glaciers, providing new opportunities to learn about these topics. As one of the largest glaciated regions in the world outside of the Greenland and Antarctic ice sheets, glaciers in Alaska and adjacent regions in Canada have been highlighted for their elevated contributions to global sea level rise, through both high levels of melt and frontal ablation/calving from a large number of tidewater glaciers. The region is also home to a number of surging glaciers. We focus on several tidewater glaciers in the region, including Turner, Tsaa, Harvard, and Meares Glaciers. Turner Glacier is a surge-type tidewater glacier with a surge period of approximately eight years, while Tsaa Glacier is a tidwewater glacier that has shown rapid swings in terminus position on the order of a year. Harvard and Meares Glaciers have been steadily advancing since at least the mid-20th century, in contrast with neighboring glaciers that are retreating. Using a combination of ASTER, Landsat, and Sentinel data, we present and examine high-resolution time series of elevation, velocity, and terminus position for these glaciers, as well as updated estimates of volume change and frontal ablation rates, including on sub-annual time scales. Preliminary investigations of elevation change on Turner Glacier show that changes are most pronounced in the lower reaches of the glacier, below a prominent icefall approximately 15km from the head of the glacier. On Harvard and Meares Glaciers, elevation changes in the upper reaches of both glaciers have been generally small or
A complex relationship between calving glaciers and climate
Post, A.; O'Neel, S.; Motyka, R.J.; Streveler, G.
2011-01-01
Many terrestrial glaciers are sensitive indicators of past and present climate change as atmospheric temperature and snowfall modulate glacier volume. However, climate interpretations based on glacier behavior require careful selection of representative glaciers, as was recently pointed out for surging and debris-covered glaciers, whose behavior often defies regional glacier response to climate [Yde and Paasche, 2010]. Tidewater calving glaciers (TWGs)mountain glaciers whose termini reach the sea and are generally grounded on the seaflooralso fall into the category of non-representative glaciers because the regional-scale asynchronous behavior of these glaciers clouds their complex relationship with climate. TWGs span the globe; they can be found both fringing ice sheets and in high-latitude regions of each hemisphere. TWGs are known to exhibit cyclic behavior, characterized by slow advance and rapid, unstable retreat, largely independent of short-term climate forcing. This so-called TWG cycle, first described by Post [1975], provides a solid foundation upon which modern investigations of TWG stability are built. Scientific understanding has developed rapidly as a result of the initial recognition of their asynchronous cyclicity, rendering greater insight into the hierarchy of processes controlling regional behavior. This has improved the descriptions of the strong dynamic feedbacks present during retreat, the role of the ocean in TWG dynamics, and the similarities and differences between TWG and ice sheet outlet glaciers that can often support floating tongues.
NASA Astrophysics Data System (ADS)
Davidson, Robert Howard
Global Land Survey (GLS) data encompassing Landsat Multispectral Scanner (MSS), Landsat 5's Thematic Mapper (TM), and Landsat 7's Enhanced Thematic Mapper Plus (ETM+) were used to determine the terminus locations of Baird, Patterson, LeConte, and Shakes Glaciers in Alaska in the time period 1975-2010. The sequences of the terminuses locations were investigated to determine the movement rates of these glaciers with respect to specific physical and environmental conditions. GLS data from 1975, 1990, 2000, 2005, and 2010 in false-color composite images enhancing ice-snow differentiation and Iterative Self-Organizing (ISO) Data Cluster Unsupervised Classifications were used to 1) quantify the movement rates of Baird, Patterson, LeConte, and Shakes Glaciers; 2) analyze the movement rates for glaciers with similar terminal terrain conditions and; 3) analyze the movement rates for glaciers with dissimilar terminal terrain conditions. From the established sequence of terminus locations, movement distances were quantified between the glacier locations. Movement distances were then compared to see if any correlation existed between glaciers with similar or dissimilar terminal terrain conditions. The Global Land Ice Measurement from Space (GLIMS) data was used as a starting point from which glacier movement was measured for Baird, Patterson, and LeConte Glaciers only as the Shakes Glacier is currently not included in the GLIMS database. The National Oceanographic and Atmospheric Administration (NOAA) temperature data collected at the Petersburg, Alaska, meteorological station (from January 1, 1973 to December 31, 2009) were used to help in the understanding of the climatic condition in this area and potential impact on glaciers terminus. Results show that glaciers with similar terminal terrain conditions (Patterson and Shakes Glaciers) and glaciers with dissimilar terminal terrain conditions (Baird, Patterson, and LeConte Glaciers) did not exhibit similar movement rates
Dynamics of glacier calving at the ungrounded margin of Helheim Glacier, southeast Greenland
Selmes, Nick; James, Timothy D.; Edwards, Stuart; Martin, Ian; O'Farrell, Timothy; Aspey, Robin; Rutt, Ian; Nettles, Meredith; Baugé, Tim
2015-01-01
Abstract During summer 2013 we installed a network of 19 GPS nodes at the ungrounded margin of Helheim Glacier in southeast Greenland together with three cameras to study iceberg calving mechanisms. The network collected data at rates up to every 7 s and was designed to be robust to loss of nodes as the glacier calved. Data collection covered 55 days, and many nodes survived in locations right at the glacier front to the time of iceberg calving. The observations included a number of significant calving events, and as a consequence the glacier retreated ~1.5 km. The data provide real‐time, high‐frequency observations in unprecedented proximity to the calving front. The glacier calved by a process of buoyancy‐force‐induced crevassing in which the ice downglacier of flexion zones rotates upward because it is out of buoyant equilibrium. Calving then occurs back to the flexion zone. This calving process provides a compelling and complete explanation for the data. Tracking of oblique camera images allows identification and characterisation of the flexion zones and their propagation downglacier. Interpretation of the GPS data and camera data in combination allows us to place constraints on the height of the basal cavity that forms beneath the rotating ice downglacier of the flexion zone before calving. The flexion zones are probably formed by the exploitation of basal crevasses, and theoretical considerations suggest that their propagation is strongly enhanced when the glacier base is deeper than buoyant equilibrium. Thus, this calving mechanism is likely to dominate whenever such geometry occurs and is of increasing importance in Greenland. PMID:27570721
Taylorism and the Logic of Learning Outcomes
ERIC Educational Resources Information Center
Stoller, Aaron
2015-01-01
This essay examines the shared philosophical foundations of Fredrick W. Taylor's scientific management principles and the contemporary learning outcomes movement (LOM). It analyses the shared philosophical ground between the focal point of Taylor's system--"the task"--and the conceptualization and deployment of "learning…
NASA Astrophysics Data System (ADS)
Brook, Martin; Hagg, Wilfried; Winkler, Stefan
2017-08-01
Medial moraines form important pathways for sediment transportation in valley glaciers. Despite the existence of well-defined medial moraines on several glaciers in the New Zealand Southern Alps, medial moraines there have hitherto escaped attention. The evolving morphology and debris content of medial moraines on Franz Josef Glacier and Fox Glacier on the western flank of the Southern Alps is the focus of this study. These temperate maritime glaciers exhibit accumulation zones of multiple basins that feed narrow tongues flowing down steep valleys and terminate 400 m above sea level. The medial moraines at both glaciers become very prominent in the lower ablation zones, where the medial moraines widen, and develop steeper flanks coeval with an increase in relative relief. Medial moraine growth appears somewhat self-limiting in that relief and slope angle increase eventually lead to transport of debris away from the medial moraine by mass-movement-related processes. Despite similarities in overall morphologies, a key contrast in medial moraine formation exists between the two glaciers. At Fox Glacier, the medial moraine consists of angular rockfall-derived debris, folded to varying degrees along flow-parallel axes throughout the tongue. The debris originates above the ELA, coalesces at flow-unit boundaries, and takes a medium/high level transport pathway before subsequently emerging at point-sources aligned with gently dipping fold hinges near the snout. In contrast at Franz Josef Glacier, the medial moraine emerges farther down-glacier immediately below a prominent rock knob. Clasts show a mix of angular to rounded shapes representing high level transport and subglacially transported materials, the latter facies possibly also elevated by supraglacial routing of subglacial meltwater. Our observations confirm that a variety of different debris sources, transport pathways, and structural glaciological processes can interact to form medial moraines within New Zealand
Repeating ice-earthquakes beneath David Glacier from the 2012-2015 TAMNNET array
NASA Astrophysics Data System (ADS)
Walter, J. I.; Peng, Z.; Hansen, S. E.
2017-12-01
The continent of Antarctica has approximately the same surface area as the continental United States, though we know significantly less about its underlying geology and seismic activity. In recent years, improvements in seismic instrumentation, battery technology, and field deployment practices have allowed for continuous broadband stations throughout the dark Antarctic winter. We utilize broadband seismic data from a recent experiment (TAMNNET), which was originally proposed as a structural seismology experiment, for seismic event detection. Our target is to address fundamental questions about regional-scale crustal and environmental seismicity in the study region that comprises the Transantarctic Mountain area of Victoria and Oates Land. We identify most seismicity emanating from David Glacier, upstream of the Drygalski Ice Tongue, which has been documented by several other studies. In order to improve the catalog completeness for the David Glacier area, we utilize a matched-filter technique to identify potential missing earthquakes that may not have been originally detected. This technique utilizes existing cataloged waveforms as templates to scan through continuous data and to identify repeating or nearby earthquakes. With a more robust catalog, we evaluate relative changes in icequake positions, recurrence intervals, and other first-order information. In addition, we attempt to further refine locations of other regional seismicity using a variety of methods including body and surface wave polarization, beamforming, surface wave dispersion, and other seismological methods. This project highlights the usefulness of archiving raw datasets (i.e., passive seismic continuous data), so that researchers may apply new algorithms or techniques to test hypotheses not originally or specifically targeted by the original experimental design.
The Life and Legacy of G. I. Taylor
NASA Astrophysics Data System (ADS)
Batchelor, G. K.
1996-07-01
G.I. Taylor, one of the most distinguished physical scientists of this century, used his deep insight and originality to increase our understanding of phenomena such as the turbulent flow of fluids. His interest in the science of fluid flow was not confined to theory; he was one of the early pioneers of aeronautics, and designed a new type of anchor that was inspired by his passion for sailing. Taylor spent most of his working life in the Cavendish Laboratory in Cambridge, where he investigated the mechanics of fluid and solid materials; his discoveries and ideas have had application throughout mechanical, civil, and chemical engineering, meteorology, oceanography and materials science. He was also a noted research leader, and his group in Cambridge became one of the most productive centers for the study of fluid mechanics. How was Taylor able to be innovative in so many different ways? This interesting and unusual biography helps answer that question. Professor Batchelor, himself a student and close collaborator of Taylor, is ideally placed to describe Taylor's life, achievements and background. He does so without introducing any mathematical details, making this book enjoyable reading for a wide range of people--and especially those whose own interests have brought them into contact with the legacy of Taylor.
A new satellite-derived glacier inventory for Western Alaska
NASA Astrophysics Data System (ADS)
Le Bris, Raymond; Frey, Holger; Paul, Frank; Bolch, Tobias
2010-05-01
Glaciers and ice caps are essential components of studies related to climate change impact assessment. Glacier inventories provide the required baseline data to perform the related analysis in a consistent and spatially representative manner. In particular, the calculation of the current and future contribution to global sea-level rise from heavily glacierized regions is a major demand. One of the regions, where strong mass losses and geometric changes of glaciers have been observed recently is Alaska. Unfortunately, the digitally available data base of glacier extent is quite rough and based on rather old maps from the 1960s. Accordingly, the related calculations and extrapolations are imprecise and an updated glacier inventory is urgently required. Here we present first results of a new glacier inventory for Western Alaska that is prepared in the framework of the ESA project GlobGlacier and is based on freely available orthorectified Landsat TM and ETM+ scenes from USGS. The analysed region covers the Tordrillo, Chigmit and Chugach Mts. as well as the Kenai Peninsula. In total, 8 scenes acquired between 2002 and 2009 were used covering c. 20.420 km2 of glaciers. All glacier types are present in this region, incl. outlet glaciers from icefields, glacier clad volcanoes, and calving glaciers. While well established automated glacier mapping techniques (band rationing) are applied to map clean and slightly dirty glacier ice, many glaciers are covered by debris or volcanic ash and outlines need manual corrections during post-processing. Prior to the calculation of drainage divides from DEM-based watershed analysis, we performed a cross-comparative analysis of DEMs from USGS, ASTER (GDEM) and SRTM 1 for Kenai Peninsula. This resulted in the decision to use the USGS DEM for calculating the drainage divides and most of the topographic inventory parameters, and the more recent GDEM to derive minimum elevation for each glacier. A first statistical analysis of the results
NASA Astrophysics Data System (ADS)
Wu, Kunpeng; Liu, Shiyin; Jiang, Zongli; Xu, Junli; Wei, Junfeng; Guo, Wanqin
2018-01-01
Due to the influence of the Indian monsoon, the Kangri Karpo Mountains in the south-east of the Tibetan Plateau is in the most humid and one of the most important and concentrated regions containing maritime (temperate) glaciers. Glacier mass loss in the Kangri Karpo is an important contributor to global mean sea level rise, and changes run-off distribution, increasing the risk of glacial-lake outburst floods (GLOFs). Because of its inaccessibility and high labour costs, information about the Kangri Karpo glaciers is still limited. Using geodetic methods based on digital elevation models (DEMs) derived from 1980 topographic maps from the Shuttle Radar Topography Mission (SRTM) (2000) and from TerraSAR-X/TanDEM-X (2014), this study has determined glacier elevation changes. Glacier area and length changes between 1980 and 2015 were derived from topographical maps and Landsat TM/ETM+/OLI images. Results show that the Kangri Karpo contained 1166 glaciers with an area of 2048.50 ± 48.65 km2 in 2015. Ice cover diminished by 679.51 ± 59.49 km2 (24.9 ± 2.2 %) or 0.71 ± 0.06 % a-1 from 1980 to 2015, although nine glaciers advanced. A glacierized area of 788.28 km2, derived from DEM differencing, experienced a mean mass loss of 0.46 ± 0.08 m w.e. a-1 from 1980 to 2014. Shrinkage and mass loss accelerated significantly from 2000 to 2015 compared to 1980-2000, consistent with a warming climate.
Geenland Glacier Albedo Variability
NASA Astrophysics Data System (ADS)
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.
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.
Five 'Supercool' Icelandic Glaciers
NASA Astrophysics Data System (ADS)
Knudsen, O.; Roberts, M. J.; Roberts, M. J.; Tweed, F. S.; Russell, A. J.; Lawson, D. E.; Larson, G. J.; Evenson, E. B.; Bjornsson, H.
2001-12-01
Sediment entrainment by glaciohydraulic supercooling has recently been demonstrated as an effective process at Matanuska glacier, Alaska. Although subfreezing meltwater temperatures have been recorded at several Alaskan glaciers, the link between supercooling and sediment accretion remains confined to Matanuska. This study presents evidence of glaciohydraulic supercooling and associated basal ice formation from five Icelandic glaciers: Skeidarárjökull, Skaftafellsjökull, Kvíárjökull, Flaájökull, and Hoffellsjökull. These observations provide the best example to-date of glaciohydraulic supercooling and related sediment accretion outside Alaska. Fieldwork undertaken in March, July and August 2001 confirmed that giant terraces of frazil ice, diagnostic of the presence of supercooled water, are forming around subglacial artesian vents. Frazil flocs retrieved from these vents contained localised sandy nodules at ice crystal boundaries. During periods of high discharge, sediment-laden frazil flocs adhere to the inner walls of vents, and continue to trap suspended sediment. Bands of debris-rich frazil ice, representing former vents, are texturally similar to basal ice exposures at the glacier margins, implying a process-form relationship between glaciohydraulic freeze-on and basal ice formation. It is hypothesised that glaciohydraulic supercooling is generating thick sequences of basal ice. Observations also confirm that in situ melting of basal ice creates thick sedimentary sequences, as sediment structures present in the basal ice can be clearly traced into ice-marginal ridges. Glaciohydraulic supercooling is an effective sediment entrainment mechanism at Icelandic glaciers. Supercooling has the capacity to generate thick sequences of basal ice and the sediments present in basal ice can be preserved. These findings are incompatible with established theories of intraglacial sediment entrainment and basal ice formation; instead, they concur with, and extend, the
NASA Astrophysics Data System (ADS)
Wittmeier, Hella E.; Bakke, Jostein; Vasskog, Kristian; Trachsel, Mathias
2015-04-01
Late Glacial and Holocene glacier fluctuations are important indicators of climate variability in the northern polar region and contain knowledge vital to understanding and predicting present and future climate changes. However, there still is a lack of robustly dated terrestrial climate records from Arctic Norway. Here, we present a high-resolution relative glacier activity record covering the past ∼10,000 cal. a BP from the northern outlet of the Langfjordjøkelen ice cap in Arctic Norway. This record is reconstructed from detailed geomorphic mapping, multi-proxy sedimentary fingerprinting and analyses of distal glacier-fed lake sediments. We used Principal Component Analysis to characterize sediments of glacial origin and trace them in a chain of downstream lakes. Of the variability in the sediment record of the uppermost Lake Jøkelvatnet, 73% can be explained by the first Principal Component axis and tied directly to upstream glacier erosion, whereas the glacial signal becomes weaker in the more distal Lakes Store Rundvatnet and Storvatnet. Magnetic susceptibility and titanium count rates were found to be the most suitable indicators of Holocene glacier activity in the distal glacier-fed lakes. The complete deglaciation of the valley of Sør-Tverrfjorddalen occurred ∼10,000 cal. a BP, followed by a reduced or absent glacier during the Holocene Thermal Optimum. The Langfjordjøkelen ice cap reformed with the onset of the Neoglacial ∼4100 cal. a BP, and the gradually increasing glacier activity culminated at the end of the Little Ice Age in the early 20th century. Over the past 2000 cal. a BP, the record reflects frequent high-amplitude glacier fluctuations. Periods of reduced glacier activity were centered around 1880, 1600, 1250 and 950 cal. a BP, while intervals of increased glacier activity occurred around 1680, 1090, 440 and 25 cal. a BP. The large-scale Holocene glacier activity of the Langfjordjøkelen ice cap is consistent with regional temperature
Bendia, Amanda G; Signori, Camila N; Franco, Diego C; Duarte, Rubens T D; Bohannan, Brendan J M; Pellizari, Vivian H
2018-01-01
Active volcanoes in Antarctica contrast with their predominantly cold surroundings, resulting in environmental conditions capable of selecting for versatile and extremely diverse microbial communities. This is especially true on Deception Island, where geothermal, marine, and polar environments combine to create an extraordinary range of environmental conditions. Our main goal in this study was to understand how microbial community structure is shaped by gradients of temperature, salinity, and geochemistry in polar marine volcanoes. Thereby, we collected surface sediment samples associated with fumaroles and glaciers at two sites on Deception, with temperatures ranging from 0 to 98°C. Sequencing of the 16S rRNA gene was performed to assess the composition and diversity of Bacteria and Archaea. Our results revealed that Deception harbors a combination of taxonomic groups commonly found both in cold and geothermal environments of continental Antarctica, and also groups normally identified at deep and shallow-sea hydrothermal vents, such as hyperthermophilic archaea. We observed a clear separation in microbial community structure across environmental gradients, suggesting that microbial community structure is strongly niche driven on Deception. Bacterial community structure was significantly associated with temperature, pH, salinity, and chemical composition; in contrast, archaeal community structure was strongly associated only with temperature. Our work suggests that Deception represents a peculiar "open-air" laboratory to elucidate central questions regarding molecular adaptability, microbial evolution, and biogeography of extremophiles in polar regions.
ERIC Educational Resources Information Center
Campbell, Brian; Bindschadler, Robert
2009-01-01
By studying Antarctica via satellite and through ground-truthing research, we can learn where the ice is melting and why. The Landsat Image Mosaic of Antarctica (LIMA), a new and cutting-edge way for scientists, researchers, educators, students, and the public to look at Antarctica, supports this research and allows for unprecedented views of our…
NASA Astrophysics Data System (ADS)
Juen, I.; Mölg, T.; Wagnon, P.; Cullen, N. J.; Kaser, G.
2006-12-01
The Cordillera Blanca in Perú is situated in the Outer Tropics spanning from 8 to 10 ° South. Solar incidence and air temperature show only minor seasonal variations whereas precipitation occurs mainly from October to April. An energy balance station was installed on the tongue of glacier Artesonraju (4850 m a.s.l.) in March 2004. In this study each component of the energy balance on the glacier surface is analysed separately over a full year, covering one dry and one wet season. During the dry season glacier melt at the glacier tongue is app. 0.5 m we per month. In the wet season glacier melt is twice as much with 1 m we per month. This is due to higher energy fluxes and decreased sublimation during the wet season. With an energy balance model that has already been proved under tropical climate conditions (Mölg and Hardy, 2004) each energy flux is changed individually to evaluate the change in the amount of glacier melt. First results indicate that a change in humidity related variables affects glacier melt very differently in the dry and wet season, whereas a change in air temperature changes glacier melt more constantly throughout the year.
An Analysis of Mass Balance of Chilean Glaciers
NASA Astrophysics Data System (ADS)
Ambinakudige, S.; Tetteh, L.
2013-12-01
Glaciers in Chile range from very small glacierets found on the isolated volcanoes of northern Chile to the 13,000 sq.km Southern Patagonian Ice Field. Regular monitoring of these glaciers is very important as they are considered as sensitive indicators of climate change. Millions of people's lives are dependent on these glaciers for fresh water and irrigation purpose. In this study, mass balances of several Chilean glaciers were estimated using Aster satellite images between 2007 and 2012. Highly accurate DEMs were created with supplementary information from IceSat data. The result indicated a negative mass balance for many glaciers indicating the need for further monitoring of glaciers in the Andes.
Arctic polynya and glacier interactions
NASA Astrophysics Data System (ADS)
Edwards, Laura
2013-04-01
Major uncertainties surround future estimates of sea level rise attributable to mass loss from the polar ice sheets and ice caps. Understanding changes across the Arctic is vital as major potential contributors to sea level, the Greenland Ice Sheet and the ice caps and glaciers of the Canadian Arctic archipelago, have experienced dramatic changes in recent times. Most ice mass loss is currently focused at a relatively small number of glacier catchments where ice acceleration, thinning and calving occurs at ocean margins. Research suggests that these tidewater glaciers accelerate and iceberg calving rates increase when warming ocean currents increase melt on the underside of floating glacier ice and when adjacent sea ice is removed causing a reduction in 'buttressing' back stress. Thus localised changes in ocean temperatures and in sea ice (extent and thickness) adjacent to major glacial catchments can impact hugely on the dynamics of, and hence mass lost from, terrestrial ice sheets and ice caps. Polynyas are areas of open water within sea ice which remain unfrozen for much of the year. They vary significantly in size (~3 km2 to > ~50,000 km2 in the Arctic), recurrence rates and duration. Despite their relatively small size, polynyas play a vital role in the heat balance of the polar oceans and strongly impact regional oceanography. Where polynyas develop adjacent to tidewater glaciers their influence on ocean circulation and water temperatures may play a major part in controlling subsurface ice melt rates by impacting on the water masses reaching the calving front. Areas of open water also play a significant role in controlling the potential of the atmosphere to carry moisture, as well as allowing heat exchange between the atmosphere and ocean, and so can influence accumulation on (and hence thickness of) glaciers and ice caps. Polynya presence and size also has implications for sea ice extent and therefore potentially the buttressing effect on neighbouring
Josberger, Edward G.; Bidlake, William R.
2010-01-01
The long-term USGS measurement and reporting of mass balance at South Cascade Glacier was assisted in balance years 2006 and 2007 by a new mass balance model. The model incorporates a temperature-index melt computation and accumulation is modeled from glacier air temperature and gaged precipitation at a remote site. Mass balance modeling was used with glaciological measurements to estimate dates and magnitudes of critical mass balance phenomena. In support of the modeling, a detailed analysis was made of the "glacier cooling effect" that reduces summer air temperature near the ice surface as compared to that predicted on the basis of a spatially uniform temperature lapse rate. The analysis was based on several years of data from measurements of near-surface air temperature on the glacier. The 2006 and 2007 winter balances of South Cascade Glacier, computed with this new, model-augmented methodology, were 2.61 and 3.41 mWE, respectively. The 2006 and 2007 summer balances were -4.20 and -3.63 mWE, respectively, and the 2006 and 2007 net balances were -1.59 and -0.22 mWE. PDF version of a presentation on the mass balance of South Cascade Glacier in Washington state. Presented at the American Geophysical Union Fall Meeting 2010.
A new glacier inventory for the Karakoram-Pamir region
NASA Astrophysics Data System (ADS)
Rastner, P.; Paul, F.; Bolch, T.; Moelg, N.
2015-12-01
High-quality glacier inventories are required as a reference dataset to determine glacier changes and model their reaction to climate change, among others. In particular in High Mountain Asia such an inventory was missing for several heavily glacierized regions with reportedly strongly changing glaciers. As a contribution to GLIMS and the Randolph Glacier Inventory (RGI) we have mapped all glaciers in the Karakoram and Pamir region within the framework of ESAs Glaciers_cci project. Glacier mapping was performed using the band ratio method (TM3/TM5) and manual editing of Landsat TM/ETM+ imagery acquired around the year 2000. The mapping was challenged by frequent seasonal snow at high elevations, debris-covered glacier tongues, and several surging glaciers. We addressed the snow issue by utilizing multi-temporal imagery and improved manual mapping of debris-covered glacier tongues with ALOS PALSAR coherence images. Slow disintegration of glacier tongues after a surge (leaving still-connected dead ice) results in a difficult identification of the terminus and assignment of entities. Drainage divides were derived from the ASTER GDEM II and manually corrected to calculate topographic parameters. All glaciers larger 0.02 km2 cover an area of about 21,700 km2 in the Karakoram and about 11,800 km² in the Pamir region. Most glaciers are in the 0.1-0.5 km2 size class for Pamir, whereas for the Karakoram they are in the class <0.1 km2. Glaciers between 1 and 5 km2 contribute more than 30% to the total area in Pamir, whereas for the Karakoram region it is only 17%. The mean glacier elevation in the Karakoram (Pamir) region is 5426 (4874) m. A comparison with other recently published inventories reveals differences in the interpretation of glacier extents (mainly in the accumulation region) that would lead to large area changes if unconsidered for change assessment across different inventories.
Recent Activity of Glaciers of Mount Rainier, Washington
Sigafoos, Robert S.; Hendricks, E.L.
1972-01-01
Knowing the ages of trees growing on recent moraines at Mount Rainier, Wash., permits the moraines to be dated. Moraines which are ridges of boulders, gravel, sand, and dust deposited at the margins of a glacier, mark former limits of a receding glacier. Knowing past glacial activity aids our understanding of past climatic variations. The report documents the ages of moraines deposited by eight glaciers. Aerial photographs and planimetric maps show areas where detailed field studies were made below seven glaciers. Moraines, past ice positions, and sample areas are plotted on the photographs and maps, along with trails, roads, streams, and landforms, to permit critical areas to be identified in the future. Ground photographs are included so that sample sites and easily accessible moraines can be found along trails. Tables present data about trees sampled in areas near the glaciers of Mount Rainier, Wash. The data in the tables show there are modern moraines of different age around the mountain; some valleys contain only one modern moraiine; others contain as many as nine. The evidence indicates a sequence of modern glacial advances terminating at about the following A.D. dates: 1525, 1550, 1625-60, 1715, 1730-65, 1820-60, 1875, and 1910. Nisqually River valley near Nisqually Glacier contains one moraine formed before A.D. 1842; Tahoma Creek valley near South Tahoma Glacier contains three moraines formed before A.D. 1528; 1843, and 1864; South Puyallup River valley near Tahoma Glacier, six moraines A.D. 1544, 1761, 1841, 1851, 1863, 1898; Puyallup Glacier, one moraine, A.D. 1846; Carbon Glacier, four moraines, 1519, 1763, 1847, 1876; Winthrop Glacier, four moraines, 1655, 1716, 1760, amid 1822; Emmons Glacier, nine moraines, 1596, 1613, 1661, 1738, 1825, 1850, 1865, 1870, 1901; and Ohanapecosh Glacier, three moraines, 1741, 1846, and 1878. Abandoned melt-water and flood channels were identified within moraine complexes below three glaciers, and their time of
Satellite Observations of Glacier Surface Velocities in Southeast Alaska
NASA Astrophysics Data System (ADS)
Elliott, J.; Melkonian, A. K.; Pritchard, M. E.
2012-12-01
Glaciers in southeast Alaska are undergoing rapid changes and are significant contributors to sea level rise. A key to understanding the ice dynamics is knowledge of the surface velocities, which can be used with ice thickness measurements to derive mass flux rates. For many glaciers in Alaska, surface velocity estimates either do not exist or are based on data that are at least a decade old. Here we present updated maps of glacier surface velocities in southeast Alaska produced through a pixel tracking technique using synthetic aperture radar data and high-resolution optical imagery. For glaciers with previous velocity estimates, we will compare the results and discuss possible implications for ice dynamics. We focus on Glacier Bay and the Stikine Icefield, which contain a number of fast-flowing tidewater glaciers including LeConte, Johns Hopkins, and La Perouse. For the Johns Hopkins, we will also examine the influence a massive landslide in June 2012 had on flow dynamics. Our velocity maps show that within Glacier Bay, the highest surface velocities occur on the tidewater glaciers. La Perouse, the only Glacier Bay glacier to calve directly into the Pacific Ocean, has maximum velocities of 3.5 - 4 m/day. Johns Hopkins Glacier shows 4 m/day velocities at both its terminus and in its upper reaches, with lower velocities of ~1-3 m/day in between those two regions. Further north, the Margerie Glacier has a maximum velocity of ~ 4.5 m/day in its upper reaches and a velocity of ~ 2 m/day at its terminus. Along the Grand Pacific terminus, the western terminus fed by the Ferris Glacier displays velocities of about 1 m/day while the eastern terminus has lower velocities of < 0.5 m/day. The lake terminating glaciers along the Pacific coast have overall lower surface velocities, but they display complex flow patterns. The Alsek Glacier displays maximum velocities of 2.5 m/day above where it divides into two branches. Velocities at the terminus of the northern branch reach 1
NASA Astrophysics Data System (ADS)
Miller, K.; Marshall, S.
2017-12-01
With rising temperatures, Alberta's glaciers are under stresses which change and alter the timing, amount, and composition of meltwater contributions to rivers that flow from the Rocky Mountains. Meltwater can be stored within a glacier or it can drain through the groundwater system, reducing and delaying meltwater delivery to glacier-fed streams. This study tests whether the glacier meltwater is chemically distinct from rain or snow melt, and thus whether meltwater contributions to higher-order streams that flow from the mountains can be determined through stream chemistry. Rivers like the Bow, North Saskatchewan, and Athabasca are vital waterways for much of Alberta's population. Assessing the extent of glacier meltwater is vital to future water resource planning. Glacier snow/ice and meltwater stream samples were collected during the 2017 summer melt season (May- September) and analyzed for isotope and ion chemistry. The results are being used to model water chemistry evolution in the melt stream through the summer season. A chemical mixing model will be constructed to determine the fractional contributions to the Haig meltwater stream from precipitation, surface melt, and subglacial meltwaters. Distinct chemical water signatures have not been used to partition water sources and understand glacier contributions to rivers in the Rockies. The goal of this work is to use chemical signatures of glacial meltwater to help assess the extent of glacier meltwater in Alberta rivers and how this varies through the summer season.
2017-12-08
Small valley glacier exiting the Devon Island Ice Cap in Canada. To learn about the contributions of glaciers to sea level rise, visit: www.nasa.gov/topics/earth/features/glacier-sea-rise.html Credit: Alex Gardner, Clark University 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
Geographic Names of Iceland's Glaciers: Historic and Modern
Sigurðsson, Oddur; Williams, Richard S.
2008-01-01
Climatic changes and resulting glacier fluctuations alter landscapes. In the past, such changes were noted by local residents who often documented them in historic annals; eventually, glacier variations were recorded on maps and scientific reports. In Iceland, 10 glacier place-names are to be found in Icelandic sagas, and one of Iceland's ice caps, Snaefellsjokull, appeared on maps of Iceland published in the 16th century. In the late 17th century, the first description of eight of Iceland's glaciers was written. Therefore, Iceland distinguishes itself in having a more than 300-year history of observations by Icelanders on its glaciers. A long-term collaboration between Oddur Sigurdsson and Richard S. Williams, Jr., led to the authorship of three books on the glaciers of Iceland. Much effort has been devoted to documenting historical glacier research and related nomenclature and to physical descriptions of Icelandic glaciers by Icelanders and other scientists from as far back as the Saga Age to recent (2008) times. The first book, Icelandic Ice Mountains, was published by the Icelandic Literary Society in 2004 in cooperation with the Icelandic Glaciological Society and the International Glaciological Society. Icelandic Ice Mountains was a glacier treatise written by Sveinn Palsson in 1795 and is the first English translation of this important scientific document. Icelandic Ice Mountains includes a Preface, including a summary of the history and facsimiles of page(s) from the original manuscript, a handwritten copy, and an 1815 manuscript (without maps and drawings) by Sveinn Palsson on the same subject which he wrote for Rev. Ebenezer Henderson; an Editor's Introduction; 82 figures, including facsimiles of Sveinn Palsson's original maps and perspective drawings, maps, and photographs to illustrate the text; a comprehensive Index of Geographic Place-Names and Other Names in the treatise; References, and 415 Endnotes. Professional Paper 1746 (this book) is the second
76 FR 3570 - Proposed Amendment of Class E Airspace; Taylor, AZ
Federal Register 2010, 2011, 2012, 2013, 2014
2011-01-20
...-1189; Airspace Docket No. 10-AWP-19] Proposed Amendment of Class E Airspace; Taylor, AZ AGENCY: Federal... proposes to modify Class E airspace at Taylor Airport, Taylor, AZ. Controlled airspace is necessary to accommodate aircraft using the CAMBO One Departure Area Navigation (RNAV) out of Taylor Airport. The FAA is...
Get Close to Glaciers with Satellite Imagery.
ERIC Educational Resources Information Center
Hall, Dorothy K.
1986-01-01
Discusses the use of remote sensing from satellites to monitor glaciers. Discusses efforts to use remote sensing satellites of the Landsat series for examining the global distribution, mass, balance, movements, and dynamics of the world's glaciers. Includes several Landsat images of various glaciers. (TW)
The Neogene Environment of the Beardmore Glacier, Transantarctic Mountains
NASA Astrophysics Data System (ADS)
Ashworth, A. C.; Cantrill, D. J.; Francis, J. E.; Roof, S. R.
2004-12-01
Discontinuous sequences of Neogene marine and non-marine glacigenic sequences, including the Meyer Desert Formation (MDF), occur throughout the Transantarctic Mountains. The upper 85m of the MDF, consisting of interbedded diamictites, conglomerates, sandstones and siltstones, outcrops in the Oliver Bluffs on the Beardmore Glacier at 85° 07'S, 166° 35'E. The location is about 170 km south of the confluence of the Beardmore Glacier with the Ross Ice Shelf and about 500 km north of the South Pole The glacial, fluvioglacial and glaciolacustrine facies of the MDF represent a dynamic glacial margin which advanced and retreated on at least four occasions. On at least one occasion, the retreat was sufficiently long for plants and animals to colonize the head of a major fjord which existed in the place of the existing Beardmore Glacier. From the fossils we have identified at least 18 species of plants, 3 species of insects, 2 species of freshwater mollusks, and a species of fish. The plant fossils consist of pollen, seeds, fruits, flowers, leaves, wood, and in situ plants. The plants include a cryptogamic flora of mosses and liverworts, conifers, and angiosperms in the families Gramineae, Cyperaceae, Nothofagaceae, Ranunculaceae, Hippuridaceae, ?Caryophyllaceae, and ?Chenopodiaceae or ?Myrtaceae. The plants grew in a weakly developed soil developed on a complex periglacial environment that included moraines, glacial outwash streams, well-drained gravel ridges, and poorly drained depressions in which peat and marl were being deposited. The fossil assemblage represents a mosaic tundra environment of well- and poorly-drained micro-sites, in which nutrient availability would have been patchily distributed. Antarctica has been essentially in a polar position since the Early Cretaceous and at 85° S receives no sunlight from the middle of March until the end of September. Today, the annual radiation received is about 42% that of Tierra del Fuego at 55° S. During the Neogene
Hypsometric control on glacier mass balance sensitivity in Alaska
NASA Astrophysics Data System (ADS)
McGrath, D.; Sass, L.; Arendt, A. A.; O'Neel, S.; Kienholz, C.; Larsen, C.; Burgess, E. W.
2015-12-01
Mass loss from glaciers in Alaska is dominated by strongly negative surface balances, particularly on small, continental glaciers but can be highly variable from glacier to glacier. Glacier hypsometry can exert significant control on mass balance sensitivity, particularly if the equilibrium line altitude (ELA) is in a broad area of low surface slope. In this study, we explore the spatial variability in glacier response to future climate forcings on the basis of hypsometry. We first derive mass balance sensitivities (30-70 m ELA / 1° C and 40-90 m ELA / 50% decrease in snow accumulation) from the ~50-year USGS Benchmark glaciers mass balance record. We subsequently assess mean climate fields in 2090-2100 derived from the IPCC AR5/CMIP5 RCP 6.0 5-model mean. Over glaciers in Alaska, we find 2-4° C warming and 10-20% increase in precipitation relative to 2006-2015, but a corresponding 0-50% decrease in snow accumulation due to rising temperatures. We assess changes in accumulation area ratios (AAR) to a rising ELA using binned individual glacier hypsometries. For an ELA increase of 150 m, the mean statewide AAR drops by 0.45, representing a 70% reduction in accumulation area on an individual glacier basis. Small, interior glaciers are the primary drivers of this reduction and for nearly 25% of all glaciers, the new ELA exceeds the glacier's maximum elevation, portending eventual loss. The loss of small glaciers, particularly in the drier interior of Alaska will significantly modify streamflow properties (flashy hydrographs, earlier and reduced peak flows, increased interannual variability, warmer temperatures) with poorly understood downstream ecosystem and oceanographic impacts.
The Greater Caucasus Glacier Inventory (Russia, Georgia and Azerbaijan)
NASA Astrophysics Data System (ADS)
Tielidze, Levan G.; Wheate, Roger D.
2018-01-01
There have been numerous studies of glaciers in the Greater Caucasus, but none that have generated a modern glacier database across the whole mountain range. Here, we present an updated and expanded glacier inventory at three time periods (1960, 1986, 2014) covering the entire Greater Caucasus. Large-scale topographic maps and satellite imagery (Corona, Landsat 5, Landsat 8 and ASTER) were used to conduct a remote-sensing survey of glacier change, and the 30 m resolution Advanced Spaceborne Thermal Emission and Reflection Radiometer Global Digital Elevation Model (ASTER GDEM; 17 November 2011) was used to determine the aspect, slope and height distribution of glaciers. Glacier margins were mapped manually and reveal that in 1960 the mountains contained 2349 glaciers with a total glacier surface area of 1674.9 ± 70.4 km2. By 1986, glacier surface area had decreased to 1482.1 ± 64.4 km2 (2209 glaciers), and by 2014 to 1193.2 ± 54.0 km2 (2020 glaciers). This represents a 28.8 ± 4.4 % (481 ± 21.2 km2) or 0.53 % yr-1 reduction in total glacier surface area between 1960 and 2014 and an increase in the rate of area loss since 1986 (0.69 % yr-1) compared to 1960-1986 (0.44 % yr-1). Glacier mean size decreased from 0.70 km2 in 1960 to 0.66 km2 in 1986 and to 0.57 km2 in 2014. This new glacier inventory has been submitted to the Global Land Ice Measurements from Space (GLIMS) database and can be used as a basis data set for future studies.
NASA Astrophysics Data System (ADS)
Larocca, L. J.; Axford, Y.; Lasher, G. E.; Lee, C. W.
2017-12-01
Due to anthropogenic climate change, the Arctic region is currently undergoing major transformation, and is expected to continue warming much faster than the global average. To put recent and future changes into context, a longer-term understanding of this region's past response to natural climate variability is needed. Given their sensitivity to modest climate change, small alpine glaciers and ice caps on Greenland's coastal margin (beyond the Greenland Ice Sheet) represent ideal features to record climate variability through the Holocene. Here we investigate the Holocene history of a small ( 160 square km) ice cap and adjacent alpine glaciers, located in southwest Greenland approximately 50 km south of Nuuk. We employ measurements on sediment cores from a glacier-fed lake in combination with geospatial analysis of satellite images spanning the past several decades. Sedimentary indicators of sediment source and thus glacial activity, including organic matter abundance, inferred chlorophyll-a content, sediment major element abundances, grain size, and magnetic susceptibility are presented from cores collected from a distal glacier-fed lake (informally referred to here as Per's Lake) in the summer of 2015. These parameters reflect changes in the amount and character of inorganic detrital input into the lake, which may be linked to the size of the upstream glaciers and ice cap and allow us to reconstruct their status through the Holocene. Additionally, we present a complementary record of recent changes in Equilibrium Line Altitude (ELA) for the upstream alpine glaciers. Modern ELAs are inferred using the accumulation area ratio (AAR) method in ArcGIS via Landsat and Worldview-2 satellite imagery, along with elevation data obtained from digital elevation models (DEMs). Paleo-ELAs are inferred from the positions of moraines and trim lines marking the glaciers' most recent expanded state, which we attribute to the Little Ice Age (LIA). This approach will allow us to
NASA Astrophysics Data System (ADS)
Davies, D.; Bingham, R. G.; Graham, A. G. C.; Spagnolo, M.; Dutrieux, P.; Vaughan, D. G.; Jenkins, A.; Nitsche, F. O.
2017-09-01
Pine Island Glacier Ice Shelf (PIGIS) has been thinning rapidly over recent decades, resulting in a progressive drawdown of the inland ice and an upstream migration of the grounding line. The resultant ice loss from Pine Island Glacier (PIG) and its neighboring ice streams presently contributes an estimated ˜10% to global sea level rise, motivating efforts to constrain better the rate of future ice retreat. One route toward gaining a better understanding of the processes required to underpin physically based projections is provided by examining assemblages of landforms and sediment exposed over recent decades by the ongoing ungrounding of PIG. Here we present high-resolution bathymetry and sub-bottom-profiler data acquired by autonomous underwater vehicle (AUV) surveys beneath PIGIS in 2009 and 2014, respectively. We identify landforms and sediments associated with grounded ice flow, proglacial and subglacial sediment transport, overprinting of lightly grounded ice-shelf keels, and stepwise grounding line retreat. The location of a submarine ridge (Jenkins Ridge) coincides with a transition from exposed crystalline bedrock to abundant sediment cover potentially linked to a thick sedimentary basin extending upstream of the modern grounding line. The capability of acquiring high-resolution data from AUV platforms enables observations of landforms and understanding of processes on a scale that is not possible in standard offshore geophysical surveys.
Murakami, Takumi; Segawa, Takahiro; Dial, Roman; Takeuchi, Nozomu; Kohshima, Shiro; Hongoh, Yuichi
2017-01-01
The community structure of bacteria associated with the glacier ice worm Mesenchytraeus solifugus was analyzed by amplicon sequencing of 16S rRNA genes and their transcripts. Ice worms were collected from two distinct glaciers in Alaska, Harding Icefield and Byron Glacier, and glacier surfaces were also sampled for comparison. Marked differences were observed in bacterial community structures between the ice worm and glacier surface samples. Several bacterial phylotypes were detected almost exclusively in the ice worms, and these bacteria were phylogenetically affiliated with either animal-associated lineages or, interestingly, clades mostly consisting of glacier-indigenous species. The former included bacteria that belong to Mollicutes, Chlamydiae, Rickettsiales, and Lachnospiraceae, while the latter included Arcicella and Herminiimonas phylotypes. Among these bacteria enriched in ice worm samples, Mollicutes, Arcicella, and Herminiimonas phylotypes were abundantly and consistently detected in the ice worm samples; these phylotypes constituted the core microbiota associated with the ice worm. A fluorescence in situ hybridization analysis showed that Arcicella cells specifically colonized the epidermis of the ice worms. Other bacterial phylotypes detected in the ice worm samples were also abundantly recovered from the respective habitat glaciers; these bacteria may be food for ice worms to digest or temporary residents. Nevertheless, some were overrepresented in the ice worm RNA samples; they may also function as facultative gut bacteria. Our results indicate that the community structure of bacteria associated with ice worms is distinct from that in the associated glacier and includes worm-specific and facultative, glacier-indigenous lineages. PMID:28302989
Murakami, Takumi; Segawa, Takahiro; Dial, Roman; Takeuchi, Nozomu; Kohshima, Shiro; Hongoh, Yuichi
2017-03-31
The community structure of bacteria associated with the glacier ice worm Mesenchytraeus solifugus was analyzed by amplicon sequencing of 16S rRNA genes and their transcripts. Ice worms were collected from two distinct glaciers in Alaska, Harding Icefield and Byron Glacier, and glacier surfaces were also sampled for comparison. Marked differences were observed in bacterial community structures between the ice worm and glacier surface samples. Several bacterial phylotypes were detected almost exclusively in the ice worms, and these bacteria were phylogenetically affiliated with either animal-associated lineages or, interestingly, clades mostly consisting of glacier-indigenous species. The former included bacteria that belong to Mollicutes, Chlamydiae, Rickettsiales, and Lachnospiraceae, while the latter included Arcicella and Herminiimonas phylotypes. Among these bacteria enriched in ice worm samples, Mollicutes, Arcicella, and Herminiimonas phylotypes were abundantly and consistently detected in the ice worm samples; these phylotypes constituted the core microbiota associated with the ice worm. A fluorescence in situ hybridization analysis showed that Arcicella cells specifically colonized the epidermis of the ice worms. Other bacterial phylotypes detected in the ice worm samples were also abundantly recovered from the respective habitat glaciers; these bacteria may be food for ice worms to digest or temporary residents. Nevertheless, some were overrepresented in the ice worm RNA samples; they may also function as facultative gut bacteria. Our results indicate that the community structure of bacteria associated with ice worms is distinct from that in the associated glacier and includes worm-specific and facultative, glacier-indigenous lineages.
NASA Astrophysics Data System (ADS)
Womble, J. N.; McNabb, R. W.; Gens, R.; Prakash, A.
2015-12-01
Some of the largest aggregations of harbor seals (Phoca vitulina richardii) in Alaska occur in tidewater glacier fjords where seals rest upon icebergs that are calved from tidewater glaciers into the marine environment. The distribution, amount, and size of floating ice in fjords are likely important factors influencing the spatial distribution and abundance of harbor seals; however, fine-scale characteristics of ice habitat that are used by seals have not been quantified using automated methods. We quantified the seasonal changes in ice habitat for harbor seals in Johns Hopkins Inlet, a tidewater glacier fjord in Glacier Bay National Park, Alaska, using aerial photography, object-based image analysis, and spatial models. Aerial photographic surveys (n = 53) were conducted of seals and ice during the whelping (June) and molting (August) seasons from 2007-2014. Surveys were flown along a grid of 12 transects and high-resolution digital photos were taken directly under the plane using a vertically aimed camera. Seal abundance and spatial distribution was consistently higher during June (range: 1,672-4,340) than August (range: 1,075-2,582) and corresponded to the spatial distribution and amount of ice. Preliminary analyses from 2007 suggest that the average percent of icebergs (ice ≥ than 1.6m2) and brash ice (ice < 1.6m2) per scene were greater in June (icebergs: 1.8% ± 1.6%; brash ice: 43.8% ± 38.9%) than August (icebergs: 0.2% ± 0.7%; brash ice; 15.8% ± 26.4%). Iceberg angularity (an index of iceberg shape) was also greater in June (1.7 ± 0.9) than August (0.9 ± 0.9). Potential factors that may influence the spatio-temporal variation in ice habitat for harbor seals in tidewater glacier fjords include frontal ablation rates of glaciers, fjord circulation, and local winds. Harbor seals exhibit high seasonal fidelity to tidewater glacier fjords, thus understanding the relationships between glacier dynamics and harbor seal distribution will be critical for
Malaspina Glacier, Alaska, Perspective with Landsat Overlay
NASA Technical Reports Server (NTRS)
2003-01-01
Malaspina Glacier in southeastern Alaska is considered the classic example of a piedmont glacier. Piedmont glaciers occur where valley glaciers exit a mountain range onto broad lowlands, are no longer laterally confined, and spread to become wide lobes. Malaspina Glacier is actually a compound glacier, formed by the merger of several valley glaciers, the most prominent of which seen here are Agassiz Glacier (left) and Seward Glacier (right). In total, Malaspina Glacier is up to 65 kilometers (40 miles) wide and extends up to 45 kilometers (28 miles) from the mountain front nearly to the sea. This perspective view was created from a Landsat satellite image and an elevation model generated by the Shuttle Radar Topography Mission (SRTM). Landsat views both visible and infrared light, which have been combined here into a color composite that generally shows glacial ice in light blue, snow in white, vegetation in green, bare rock in grays and tans, and the ocean (foreground) in dark blue. The back (northern) edge of the data set forms a false horizon that meets a false sky. Glaciers erode rocks, carry them down slope, and deposit them at the edge of the melting ice, typically in elongated piles called moraines. The moraine patterns at Malaspina Glacier are quite spectacular in that they have huge contortions that result from the glacier crinkling as it gets pushed from behind by the faster-moving valley glaciers. Glaciers are sensitive indicators of climatic change. They can grow and thicken with increasing snowfall and/or decreased melting. Conversely, they can retreat and thin if snowfall decreases and/or atmospheric temperatures rise and cause increased melting. Landsat imaging has been an excellent tool for mapping the changing geographic extent of glaciers since 1972. The elevation measurements taken by SRTM in February 2000 now provide a near-global baseline against which future non-polar region glacial thinning or thickening can be assessed.
The New Taylorism: Hacking at the Philosophy of the University's End
ERIC Educational Resources Information Center
Goodman, Robin Truth
2012-01-01
This article looks at the critical writings of Mark C. Taylor. It suggests that Mark C. Taylor is rewriting a global imaginary devoid of the kind of citizenship that Henry Giroux claims as the basis for public education. Instead, Taylor wants to see the university take shape as profit-generating. According to Taylor, in lieu of learning to take…
NASA Astrophysics Data System (ADS)
Monnier, Sébastien; Kinnard, Christophe
2017-08-01
Three glacier-rock glacier transitional landforms in the central Andes of Chile are investigated over the last decades in order to highlight and question the significance of their landscape and flow dynamics. Historical (1955-2000) aerial photos and contemporary (> 2000) Geoeye satellite images were used together with common processing operations, including imagery orthorectification, digital elevation model generation, and image feature tracking. At each site, the rock glacier morphology area, thermokarst area, elevation changes, and horizontal surface displacements were mapped. The evolution of the landforms over the study period is remarkable, with rapid landscape changes, particularly an expansion of rock glacier morphology areas. Elevation changes were heterogeneous, especially in debris-covered glacier areas with large heaving or lowering up to more than ±1 m yr-1. The use of image feature tracking highlighted spatially coherent flow vector patterns over rock glacier areas and, at two of the three sites, their expansion over the studied period; debris-covered glacier areas are characterized by a lack of movement detection and/or chaotic displacement patterns reflecting thermokarst degradation; mean landform displacement speeds ranged between 0.50 and 1.10 m yr-1 and exhibited a decreasing trend over the studied period. One important highlight of this study is that, especially in persisting cold conditions, rock glaciers can develop upward at the expense of debris-covered glaciers. Two of the studied landforms initially (prior to the study period) developed from an alternation between glacial advances and rock glacier development phases. The other landform is a small debris-covered glacier having evolved into a rock glacier over the last half-century. Based on these results it is proposed that morphological and dynamical interactions between glaciers and permafrost and their resulting hybrid landscapes may enhance the resilience of the mountain cryosphere
NASA Technical Reports Server (NTRS)
2007-01-01
The Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA's Terra satellite captured this image on October 7, 2007, showing the Alaska Mountains of south-central Alaska already coated with snow. Purple shadows hang in the lee of the peaks, giving the snow-clad land a crumpled appearance. White gives way to brown on the right side of the image where the mountains yield to the lower-elevation Susitna River Valley. The river itself cuts a silver, winding path through deep green forests and brown wetlands and tundra. Extending from the river valley, are smaller rivers that originated in the Alaska Mountains. The source of these rivers is evident in the image. Smooth white tongues of ice extend into the river valleys, the remnants of the glaciers that carved the valleys into the land. Most of the water flowing into the Gulf of Alaska from the Susitna River comes from these mountain glaciers. Glacier melt also feeds glacier lakes, only one of which is large enough to be visible in this image. Immediately left of the Kahiltna River, the aquamarine waters of Chelatna Lake stand out starkly against the brown and white landscape.
Kopczynski, S.E.; Ramage, J.; Lawson, D.; Goetz, S.; Evenson, E.; Denner, J.; Larson, G.
2008-01-01
We advance an approach to use satellite passive microwave observations to track valley glacier snowmelt and predict timing of spring snowmelt-induced floods at the terminus. Using 37 V GHz brightness temperatures (Tb) from the Special Sensor Microwave hnager (SSM/I), we monitor snowmelt onset when both Tb and the difference between the ascending and descending overpasses exceed fixed thresholds established for Matanuska Glacier. Melt is confirmed by ground-measured air temperature and snow-wetness, while glacier hydrologic responses are monitored by a stream gauge, suspended-sediment sensors and terminus ice velocity measurements. Accumulation area snowmelt timing is correlated (R2 = 0.61) to timing of the annual snowmelt flood peak and can be predicted within ??5 days. Copyright 2008 by the American Geophysical Union.
Comparative Analysis of Glaciers in the Chugach-St.-Elias Mountains
NASA Astrophysics Data System (ADS)
Herzfeld, U. C.; Mayer, H.
2003-12-01
The phenomenon of glacier surges has to date been studied for only relatively few examples. 136 of the 204 surge-type glaciers in North America listed by Post (1969) are located in the St. Elias Mountains. In August 2003 we increased our data inventory of observations on surge glaciers by collecting material for 19 glaciers in the Glacier Bay area and neighboring regions in the eastern St. Elias Mountains, including 6 surge-type glaciers (Carroll, Rendu, Ferris, Grand Pacific, Margerie, and Johns Hopkins Glaciers). Analyses utilize digital video and photographic data, satellite data and GPS data. Geostatistical classification parameters and algebraic parameters characteristic of surge motions are derived for selected glaciers. During the 1993-1995 surge of Bering Glacier the entire surface of Alaska's longest glacier was crevassed and could be segmented into several dynamic provinces, where patterns changed as the surge progressed and the affected areas expanded downglacier and upglacier, finally affecting the Bagley Ice Field. The middle moraine of Grand Pacific and Ferris Glaciers is pushed over to the Grand Pacific side, caused by a recent surge of the heavily crevassed Ferris Glacier. The front of Johns Hopkins Glacier advances, as its lower reaches are affected by a surge. The surge history of Bering Glacier goes back to the Holocene, whereas Carroll and Rendu Glaciers have surged only 3-4 times. These observations pose questions on the possible relationship between surge dynamics and climatic changes.
NASA Astrophysics Data System (ADS)
Davies, B. J.; Carrivick, J. L.; Glasser, N. F.; Hambrey, M. J.; Smellie, J. L.
2011-12-01
The Northern Antarctic Peninsula has recently exhibited ice-shelf disintegration, glacier recession and acceleration. However, the dynamic response of land-terminating, ice-shelf tributary and tidewater glaciers has not yet been quantified or assessed for variability, and there are sparse published data for glacier classification, morphology, area, length or altitude. This paper firstly uses ASTER images from 2009 and a SPIRIT DEM from 2006 to classify the area, length, altitude, slope, aspect, geomorphology, type and hypsometry of 194 glaciers on Trinity Peninsula, Vega Island and James Ross Island. Secondly, this paper uses LANDSAT-4 and ASTER images from 1988 and 2001 and data from the Antarctic Digital Database (ADD) from 1997 to document glacier change 1988-2009. From 1988-2001, 90 % of glaciers receded, and from 2001-2009, 79 % receded. Glaciers on the western side of Trinity Peninsula retreated relatively little. On the eastern side of Trinity Peninsula, the rate of recession of ice-shelf tributary glaciers has slowed from 12.9 km2 a-1 (1988-2001) to 2.4 km2 a-1 (2001-2009). Tidewater glaciers on the drier, cooler Eastern Trinity Peninsula experienced fastest recession from 1988-2001, with limited frontal retreat after 2001. Land-terminating glaciers on James Ross Island also retreated fastest in the period 1988-2001. Large tidewater glaciers on James Ross Island are now declining in areal extent at rates of up to 0.04 km2 a-1. This east-west difference is largely a result of orographic temperature and precipitation gradients across the Antarctic Peninsula. Strong variability in tidewater glacier recession rates may result from the influence of glacier length, altitude, slope and hypsometry on glacier mass balance. High snowfall means that the glaciers on the Western Peninsula are not currently rapidly receding. Recession rates on the eastern side of Trinity Peninsula are slowing as the floating ice tongues retreat into the fjords and the glaciers reach a
NASA Astrophysics Data System (ADS)
Molnia, B. F.; Karpilo, R. D.; Pranger, H. S.
2004-12-01
Historical photographs, many dating from the late-19th century are being used to document landscape and glacier change in the Glacier Bay area. More than 350 pre-1980 photographs that show the Glacier Bay landscape and glacier termini positions have been acquired by the authors. Beginning in 2003, approximately 150 of the sites from which historical photographs had been made were revisited. At each site, elevation and latitude and longitude were recorded using WAAS-enabled GPS. Compass bearings to photographic targets were also determined. Finally, using the historical photographs as a composition guide, new photographs were exposed using digital imaging and film cameras. In the laboratory, 21st century images and photographs were compared with corresponding historical photographs to determine, and to better understand rates, timing, and mechanics of Glacier Bay landscape evolution, as well as to clarify the response of specific glaciers to changing climate and environment. The comparisons clearly document rapid vegetative succession throughout the bay; continued retreat of larger glaciers in the East Arm of the bay; a complex pattern of readvance and retreat of the larger glaciers in the West Arm of the bay, coupled with short-term fluctuations of its smaller glaciers; transitions from tidewater termini to stagnant, debris-covered termini; fiord sedimentation and erosion; development of outwash and talus features; and many other dramatic changes. As might be expected, 100-year-plus photo comparisons show significant changes throughout the Glacier Bay landscape, especially at the southern ends of East and West Arms. Surprisingly, recent changes, occurring since the late-1970s were equally dramatic, especially documenting the rapid thinning and retreat of glaciers in upper Muir Inlet.
20. TURNTABLE WITH CABLE CAR BAY & TAYLOR: View ...
20. TURNTABLE WITH CABLE CAR - BAY & TAYLOR: View to northwest of the Bay and Taylor turntable. The gripman and conductor are turning the car around. - San Francisco Cable Railway, Washington & Mason Streets, San Francisco, San Francisco County, CA
Pavlova, Pavlina Aneva; Jenk, Theo Manuel; Schmid, Peter; Bogdal, Christian; Steinlin, Christine; Schwikowski, Margit
2015-12-15
In Alpine regions, glaciers act as environmental archives and can accumulate significant amounts of atmospherically derived pollutants. Due to the current climate-warming-induced accelerated melting, these pollutants are being released at correspondingly higher rates. To examine the effect of melting on the redistribution of legacy pollutants in Alpine glaciers, we analyzed polychlorinated biphenyls in an ice core from the temperate Silvretta glacier, located in eastern Switzerland. This glacier is affected by surface melting in summer. As a result, liquid water percolates down and particles are enriched in the current annual surface layer. Dating the ice core was a challenge because meltwater percolation also affects the traditionally used parameters. Instead, we counted annual layers of particulate black carbon in the ice core, adding the years with negative glacier mass balance, that is, years with melting and subsequent loss of the entire annual snow accumulation. The analyzed samples cover the time period 1930-2011. The concentration of indicator PCBs (iPCBs) in the Silvretta ice core follows the emission history, peaking in the 1970s (2.5 ng/L). High PCB values in the 1990s and 1930s are attributed to meltwater-induced relocation within the glacier. The total iPCB load at the Silvretta ice core site is 5 ng/cm(2). A significant amount of the total PCB burden in the Silvretta glacier has been released to the environment.
Sun, Shiwei; Kang, Shichang; Huang, Jie; Li, Chengding; Guo, Junming; Zhang, Qianggong; Sun, Xuejun; Tripathee, Lekhendra
2016-06-01
The Tibetan Plateau is home to the largest aggregate of glaciers outside the Polar Regions and is a source of fresh water to 1.4 billion people. Yet little is known about the transportation and cycling of Hg in high-elevation glacier basins on Tibetan Plateau. In this study, surface snow, glacier melting stream water and lake water samples were collected from the Qiangyong Glacier Basin. The spatiotemporal distribution and transportation of Hg from glacier to lake were investigated. Significant diurnal variations of dissolved Hg (DHg) concentrations were observed in the river water, with low concentrations in the morning (8:00am-14:00pm) and high concentrations in the afternoon (16:00pm-20:00pm). The DHg concentrations were exponentially correlated with runoff, which indicated that runoff was the dominant factor affecting DHg concentrations in the river water. Moreover, significant decreases of Hg were observed during transportation from glacier to lake. DHg adsorption onto particulates followed by the sedimentation of particulate-bound Hg (PHg) could be possible as an important Hg removal mechanism during the transportation process. Significant decreases in Hg concentrations were observed downstream of Xiao Qiangyong Lake, which indicated that the high-elevation lake system could significantly affect the distribution and transportation of Hg in the Qiangyong Glacier Basin. Copyright © 2016. Published by Elsevier B.V.
Remote Characterization of Ice Shelf Surface and Basal Processes: Examples from East Antarctica
NASA Astrophysics Data System (ADS)
Greenbaum, J. S.; Blankenship, D. D.; Grima, C.; Schroeder, D. M.; Soderlund, K. M.; Young, D. A.; Kempf, S. D.; Siegert, M. J.; Roberts, J. L.; Warner, R. C.; van Ommen, T. D.
2017-12-01
The ability to remotely characterize surface and basal processes of ice shelves has important implications for conducting systematic, repeatable, and safe evaluations of their stability in the context of atmospheric and oceanic forcing. Additionally, techniques developed for terrestrial ice shelves can be adapted to orbital radar sounding datasets planned for forthcoming investigations of icy moons. This has been made possible through recent advances in radar signal processing that enable these data to be used to test hypotheses derived from conceptual and numerical models of ice shelf- and ice shell-ocean interactions. Here, we present several examples of radar sounding-derived characterizations of surface and basal processes underway on ice shelves in East Antarctica. These include percolation of near-surface meltwater in warm austral summers, brine infiltration along ice shelf calving fronts, basal melt rate and distribution, and basal freeze distribution. On Europa, near-surface brines and their migration may impact local geological variability, while basal processes likely control the distribution of melt and freeze. Terrestrially, we emphasize radar-sounding records of the Totten Glacier Ice Shelf which hosts each of these processes as well as the highest known density of basal melt channels of any terrestrial ice shelf. Further, with a maximum floating ice thickness of over 2.5 km, the pressure at Totten's basal interface may be similar to that at Europa's ice-ocean interface; therefore, evaluating surface and basal processes of Totten Glacier and other ice shelves could serve as analogs for understanding melting processes of Europa's ice shell.
Effect of fjord geometry on tidewater glacier stability
NASA Astrophysics Data System (ADS)
Åkesson, Henning; Nisancioglu, Kerim H.; Nick, Faezeh M.
2016-04-01
Many marine-terminating glaciers have thinned, accelerated and retreated during the last two decades, broadly consistent with warmer atmospheric and oceanic conditions. However, these patterns involve considerable spatial and temporal variability, with diverse glacier behavior within the same regions. Similarly, reconstructions of marine-terminating glaciers indicate highly asynchronous retreat histories. While it is well known that retrograde slopes can cause marine ice sheet instabilities, the effect of lateral drag and fjord width has received less attention. Here, we test the hypothesis that marine outlet glacier stability is largely controlled by fjord width, and to a less extent by regional climate forcing. We employ a dynamic flowline model on idealized glacier geometries (representative of different outlet glaciers) to investigate geometric controls on decadal and longer times scales. The model accounts for driving and resistive stresses of glacier flow as well as along-flow stress transfer. It has a physical treatment of iceberg calving and a time-adaptive grid allowing for continuous tracking of grounding-line migration. We apply changes in atmospheric and oceanic forcing and show how wide and narrow fjord sections foster glacier (in)stabilities. We also evaluate the effect of including a surface mass balance - elevation feedback in such a setting. Finally, the relevance of these results to past and future marine-terminating glacier stability is discussed.
Solar Eclipses Observed from Antarctica
NASA Astrophysics Data System (ADS)
Pasachoff, Jay M.
2013-01-01
Aspects of the solar corona are still best observed during totality of solar eclipses, and other high-resolution observations of coronal active regions can be observed with radio telescopes by differentiation of occultation observations, as we did with the Jansky Very Large Array for the annular solar eclipse of 2012 May 20 in the US. Totality crossing Antarctica included the eclipse of 2003 November 23, and will next occur on 2021 December 4; annularity crossing Antarctica included the eclipse of 2008 February 7, and will next occur on 2014 April 29. Partial phases as high as 87% coverage were visible and were imaged in Antarctica on 2011 November 25, and in addition to partial phases of the total and annular eclipses listed above, partial phases were visible in Antarctica on 2001 July 2011, 2002 December 4, 2004 April 19, 2006 September 22, 2007 September 11, and 2009 January 26, and will be visible on 2015 September 13, 2016 September 1, 2017 February 26, 2018 February 15, and 2020 December 14. On behalf of the Working Group on Solar Eclipses of the IAU, the poster showed the solar eclipses visible from Antarctica and this article shows a subset (see www.eclipses.info for the full set). A variety of investigations of the Sun and of the response of the terrestrial atmosphere and ionosphere to the abrupt solar cutoff can be carried out at the future eclipses, making the Antarctic observations scientifically useful.
A revised Canadian perspective: progress in glacier hydrology
NASA Astrophysics Data System (ADS)
Munro, D. Scott
2005-01-01
Current research into glacier hydrology is occurring at a time when glaciers around the world, particularly those whose hydrological regimes affect populated areas, are shrinking as they go through a state of perpetual negative annual mass balance. Small glaciers alone are likely to contribute 0·5 to 1 mm year-1 to global sea-level rise, with associated reductions in local freshwater resources, impacts upon freshwater ecosystems and increased risk of hazard due to outburst floods. Changes to the accumulation regimes of glaciers and ice sheets may be partly responsible, so the measurement and distribution of snowfall in glacierized basins, a topic long represented in non-glacierized basin research, is now beginning to receive more attention than it did before, aided by the advent of reliable automatic weather stations that provide data throughout the year. Satellite data continue to be an important information source for summer meltwater estimation, as distributed models, and their need for albedo maps, continue to develop. This further entails the need for simplifications to energy balance components, sacrificing point detail so that spatial calculation may proceed more quickly. The understanding of surface meltwater routing through the glacier to produce stream outflow continues to be a stimulating area of research, as demonstrated by activity at the Trapridge Glacier, Canada, and Canadian involvement in the Haut Glacier d'Arolla, Switzerland. As Canadian glacier monitoring continues to evolve, effort must be directed toward developing situations where mass balance, meltwater generation and flow routing studies can be done together at selected sites. Copyright
Taylor dispersion of colloidal particles in narrow channels
NASA Astrophysics Data System (ADS)
Sané, Jimaan; Padding, Johan T.; Louis, Ard A.
2015-09-01
We use a mesoscopic particle-based simulation technique to study the classic convection-diffusion problem of Taylor dispersion for colloidal discs in confined flow. When the disc diameter becomes non-negligible compared to the diameter of the pipe, there are important corrections to the original Taylor picture. For example, the colloids can flow more rapidly than the underlying fluid, and their Taylor dispersion coefficient is decreased. For narrow pipes, there are also further hydrodynamic wall effects. The long-time tails in the velocity autocorrelation functions are altered by the Poiseuille flow.
NASA Astrophysics Data System (ADS)
Iribarren Anacona, Pablo; Bodin, Xavier
2010-05-01
Mountain areas are occasionaly affected by complex mass movements of high magnitude and large extent, which generally involve water, snow, rock and ice in variable proportions. Those events can take the form of rock avalanche, landslide, debris flow, glacier collapse or a combination of these phenomenons. In the Central Andes of Chile, they affect hardly accessible regions with low population, explaining the scarcity of previous studies. Nevertheless, during the last 30 years, some documented examples of such events in this region have shown that the volume of material involved is in the order of several millions of m³, the areas affected can reach several tenth of km² and the velocity of the movement can exceed several tenths of m/s. In this context, this study intends i) to inventory and to describe the main characteristics of events previously documented in the Central Andes of Chile, and ii) analyse in detail two recent events (2005-2007) never described before which have affected in one case a glacier and in another case a rock glacier. With the objectives of determining the possible chain of triggering factors and interpreting the event's significance in terms of geomorphic, cryogenic and climatic dynamics, we used air photographs, satellite imagery (Landsat TM & ETM+; Quick Bird when available in Google Earth 5.0), data from the closest meteorological stations, glacier mass balance data and seismic records to investigate the collapse of a rock glacier occurred in 2006 on the west-facing flank of the Cerro Las Tórtolas (6160 m asl; 29°58' S. - 69°55' W.), in the arid North of Chile, and the collapse of a glacier that occurred during austral summer 2006-2007 on the South side of the Tinguiririca Volcano (4075 m asl; 34°48' S. - 70°21' W.). The rock glacier collapse of the Cerro Las Tórtolas West flank occurred during the spring of 2006, but signs of destabilization were already observable since the end of 2005. The deposit of the collapsed mass of the
Uncovering glacier dynamics beneath a debris mantle
NASA Astrophysics Data System (ADS)
Lefeuvre, P.-M.; Ng, F. S. L.
2012-04-01
Debris-covered glaciers (DCGs) have an extensive sediment mantle whose low albedo influences their surface energy balance to cause a buffering effect that could enhance or reduce ablation rates depending on the sediment thickness. The last effect suggests that some DCGs may be less sensitive to climate change and survive for longer than debris-free (or 'clean') glaciers under sustained climatic warming. However, the origin of DCGs is debated and the precise impact of the debris mantle on their flow dynamics and surface geometry has not been quantified. Here we investigate these issues with a numerical model that encapsulates ice-flow physics and surface debris evolution and transport along a glacier flow-line, as well as couples these with glacier mass balance. We model the impact of surface debris on ablation rates by a mathematical function based on published empirical data (including Ostrem's curve). A key interest is potential positive feedback of ablation on debris thickening and lowering of surface albedo. Model simulations show that when DCGs evolve to attain steady-state profiles, they reach lower elevations than clean glaciers do for the same initial and climatic conditions. Their mass-balance profile at steady state displays an inversion near the snout (where the debris cover is thickest) that is not observed in the clean-glacier simulations. In these cases, where the mantle causes complete buffering to inhibit ablation, the DCG does not reach a steady-state profile, and the sediment thickness evolves to a steady value that depends sensitively on the glacier surface velocities. Variation in the assumed englacial debris concentration in our simulations also determines glacier behaviour. With low englacial debris concentration, the DCG retreats initially while its mass-balance gradient steepens, but the glacier re-advances if it subsequently builds up a thick enough debris cover to cause complete buffering. We identify possible ways and challenges of
ICESat laser altimetry over small mountain glaciers
NASA Astrophysics Data System (ADS)
Treichler, Désirée; Kääb, Andreas
2016-09-01
Using sparsely glaciated southern Norway as a case study, we assess the potential and limitations of ICESat laser altimetry for analysing regional glacier elevation change in rough mountain terrain. Differences between ICESat GLAS elevations and reference elevation data are plotted over time to derive a glacier surface elevation trend for the ICESat acquisition period 2003-2008. We find spatially varying biases between ICESat and three tested digital elevation models (DEMs): the Norwegian national DEM, SRTM DEM, and a high-resolution lidar DEM. For regional glacier elevation change, the spatial inconsistency of reference DEMs - a result of spatio-temporal merging - has the potential to significantly affect or dilute trends. Elevation uncertainties of all three tested DEMs exceed ICESat elevation uncertainty by an order of magnitude, and are thus limiting the accuracy of the method, rather than ICESat uncertainty. ICESat matches glacier size distribution of the study area well and measures small ice patches not commonly monitored in situ. The sample is large enough for spatial and thematic subsetting. Vertical offsets to ICESat elevations vary for different glaciers in southern Norway due to spatially inconsistent reference DEM age. We introduce a per-glacier correction that removes these spatially varying offsets, and considerably increases trend significance. Only after application of this correction do individual campaigns fit observed in situ glacier mass balance. Our correction also has the potential to improve glacier trend significance for other causes of spatially varying vertical offsets, for instance due to radar penetration into ice and snow for the SRTM DEM or as a consequence of mosaicking and merging that is common for national or global DEMs. After correction of reference elevation bias, we find that ICESat provides a robust and realistic estimate of a moderately negative glacier mass balance of around -0.36 ± 0.07 m ice per year. This regional
Melting beneath Greenland outlet glaciers and ice streams
NASA Astrophysics Data System (ADS)
Alexander, David; Perrette, Mahé; Beckmann, Johanna
2015-04-01
Basal melting of fast-flowing Greenland outlet glaciers and ice streams due to frictional heating at the ice-bed interface contributes significantly to total glacier mass balance and subglacial meltwater flux, yet modelling this basal melt process in Greenland has received minimal research attention. A one-dimensional dynamic ice-flow model is calibrated to the present day longitudinal profiles of 10 major Greenland outlet glaciers and ice streams (including the Jakobshavn Isbrae, Petermann Glacier and Helheim Glacier) and is validated against published ice flow and surface elevation measurements. Along each longitudinal profile, basal melt is calculated as a function of ice flow velocity and basal shear stress. The basal shear stress is dependent on the effective pressure (difference between ice overburden pressure and water pressure), basal roughness and a sliding parametrization. Model output indicates that where outlet glaciers and ice streams terminate into the ocean with either a small floating ice tongue or no floating tongue whatsoever, the proportion of basal melt to total melt (surface, basal and submarine melt) is 5-10% (e.g. Jakobshavn Isbrae; Daugaard-Jensen Glacier). This proportion is, however, negligible where larger ice tongues lose mass mostly by submarine melt (~1%; e.g. Nioghalvfjerdsfjorden Glacier). Modelled basal melt is highest immediately upvalley of the grounding line, with contributions typically up to 20-40% of the total melt for slippery beds and up to 30-70% for resistant beds. Additionally, modelled grounding line and calving front migration inland for all outlet glaciers and ice streams of hundreds of metres to several kilometres occurs. Including basal melt due to frictional heating in outlet glacier and ice stream models is important for more accurately modelling mass balance and subglacial meltwater flux, and therefore, more accurately modelling outlet glacier and ice stream dynamics and responses to future climate change.
76 FR 18378 - Amendment of Class E Airspace; Taylor, AZ
Federal Register 2010, 2011, 2012, 2013, 2014
2011-04-04
...-1189; Airspace Docket No. 10-AWP-19] Amendment of Class E Airspace; Taylor, AZ AGENCY: Federal Aviation Administration (FAA), DOT. ACTION: Final rule. SUMMARY: This action will amend Class E airspace at Taylor Airport, Taylor, AZ, to accommodate aircraft using the CAMBO One Departure, and the Area Navigation (RNAV...
2017-02-04
Cyclones swirl around the south pole, and white oval storms can be seen near the limb -- the apparent edge of the planet -- in this image of Jupiter's south polar region taken by the JunoCam imager aboard NASA's Juno spacecraft. The image was acquired on February 2, 2017, at 5:52 a.m. PST (8:52 a.m. EST) from an altitude of 47,600 miles (76,600 kilometers) above Jupiter's swirling cloud deck. Prior to the Feb. 2 flyby, the public was invited to vote for their favorite points of interest in the Jovian atmosphere for JunoCam to image. The point of interest captured here was titled "Jovian Antarctica" by a member of the public, in reference to Earth's Antarctica. http://photojournal.jpl.nasa.gov/catalog/PIA21380
Glacier Dynamics and Outburst Flood Potential from the Imja and Thulagi Glacier-Lake Systems (Nepal)
NASA Astrophysics Data System (ADS)
Kargel, Jeffrey; Leonard, Gregory; Regmi, Dhananjay; Haritashya, Umesh; Chand, Mohan; Pradhan, Suresh; Sapkota, Nawaraj; Byers, Alton; Joshi, Sharad; McKinney, Daene; Mool, Pradeep; Somos-Valenzuela, Marcelo; Huggel, Christian
2015-04-01
Thulagi and Imja lakes are, according to ICIMOD, among Nepal's most dangerous glacier lakes, i.e., most likely to cause death and destruction in case of a glacier lake outburst flood (GLOF). Imja Lake and the associated Imja and Lhoste-Shar glaciers have been intensively studied; Thulagi Glacier and its lake are much less studied. Collectively, we have undertaken a series of increasingly thorough bathymetric and land surveys and satellite remote sensing analyses of Imja Lake and its glacier setting. We are analyzing several expeditions' data to build a detailed assessment of the glacier and lake to better establish the dynamical evolution of the system and its future GLOF potential. Our most recent, most complete bathymetric survey of Imja Lake has revealed a much greater volume (75,200,000 cubic meters) and maximum depth (149.8 m) than found before. Our analysis suggests that not all possible Imja GLOF scenarios would result in devastation. Some moraine melt-through or down-cutting mechanisms -- perhaps induced by extreme monsoon precipitation or an earthquake -- could generate outbursts lasting from 10,000-100,000 seconds ("slow GLOFs"), thus limiting peak flows and downstream damage. The potential damage from a slow GLOF from Imja Lake -- even if there is a large total volume -- is lessened by the relatively low peak discharge and because the major villages downstream from Imja Lake are situated just outside of and above a deep, broad outwash and debris-flow channel system. Imja and other glaciers in the area have built a large fan, now deeply trenched, which is able to accommodate the peak discharges of potential slow GLOFs, such that Dingboche and other villages would be spared. However, local geomorphology also bears evidence of "fast GLOFs," such as may be issued by a tsunami, which could be initiated by a large mass movement into Imja Lake and which might override and damage the end moraine in <100 seconds. Dingboche and other villages are vulnerable to
Updating the New Zealand Glacier Inventory
NASA Astrophysics Data System (ADS)
Baumann, S. C.; Anderson, B.; Mackintosh, A.; Lorrey, A.; Chinn, T.; Collier, C.; Rack, W.; Purdie, H.
2017-12-01
The last complete glacier inventory of New Zealand dates from the year 1978 (North Island 1988) and was manually constructed from oblique aerial photographs and geodetic maps (Chinn 2001). The inventory has been partly updated by Gjermundsen et al. (2011) for the year 2002 (40% of total area) and by Sirguey & More (2010) for the year 2009 (32% of total area), both using ASTER satellite imagery. We used Landsat 8 OLI/TIRS satellite data from February/March 2016 to map the total glaciated area. Clean and debris-covered ice were mapped semi-automatically. The band ratio approach was used for clean ice (ratio: red/SWIR). We mapped debris-covered ice using a supervised classification (maximum likelihood). Manual post processing was necessary due to misclassifications (e.g. lakes, clouds) or mapping in shadowed areas. It was also necessary to manually combine the clean and debris-covered parts into single glaciers. Additional input data for the post processing were Sentinel 2 images from the same time period, orthophotos from Land Information New Zealand (resolution: 0.75 m, date: Nov 2014), and the 1978/88 outlines from the GLIMS database (http://www.glims.org/). As the Sentinel 2 data were more heavily cloud covered compared to the Landsat 8 images, they were only used for post processing and not for the classification itself. Initial results show that New Zealand glaciers covered an area of about 1050 km² in 2016, a reduction of 16% since 1978. Approximately 17% of glacier area was covered in surface debris. The glaciers in the central Southern Alps around Mt Cook reduced in area by 24%. Glaciers in the North Island of New Zealand reduced by 71% since 1988, and only 2 km² of ice cover remained in 2016. Chinn, TJH (2001). "Distribution of the glacial water resources of New Zealand." Journal of Hydrology (NZ) 40(2): 139-187 Gjermundsen, EF, Mathieu, R, Kääb, A, Chinn, TJH, Fitzharris, B & Hagen, JO (2011). "Assessment of multispectral glacier mapping methods and
Oceanic Forcing of Ice-Sheet Retreat: West Antarctica and More
NASA Astrophysics Data System (ADS)
Alley, Richard B.; Anandakrishnan, Sridhar; Christianson, Knut; Horgan, Huw J.; Muto, Atsu; Parizek, Byron R.; Pollard, David; Walker, Ryan T.
2015-05-01
Ocean-ice interactions have exerted primary control on the Antarctic Ice Sheet and parts of the Greenland Ice Sheet, and will continue to do so in the near future, especially through melting of ice shelves and calving cliffs. Retreat in response to increasing marine melting typically exhibits threshold behavior, with little change for forcing below the threshold but a rapid, possibly delayed shift to a reduced state once the threshold is exceeded. For Thwaites Glacier, West Antarctica, the threshold may already have been exceeded, although rapid change may be delayed by centuries, and the reduced state will likely involve loss of most of the West Antarctic Ice Sheet, causing >3 m of sea-level rise. Because of shortcomings in physical understanding and available data, uncertainty persists about this threshold and the subsequent rate of change. Although sea-level histories and physical understanding allow the possibility that ice-sheet response could be quite fast, no strong constraints are yet available on the worst-case scenario. Recent work also suggests that the Greenland and East Antarctic Ice Sheets share some of the same vulnerabilities to shrinkage from marine influence.
Surge-type glaciers in the Tien Shan (Central Asia)
NASA Astrophysics Data System (ADS)
Mukherjee, Kriti; Bolch, Tobias
2016-04-01
Surge-type glaciers in High Mountain Asia are mostly observed in Karakoram and Pamir. However, few surge-type glaciers also exist in the Tien Shan, but have not comprehensively studied in detail in the recent literature. We identified surge-type glaciers in the Tien Shan either from available literature or by manual interpretation using available satellite images (such as Corona, Hexagon, Landsat, SPOT, IRS) for the period 1960 to 2014. We identified 39 possible surge-type glaciers, showing typical characteristics like looped moraines. Twenty-two of them rapidly advanced during different periods or a surge was clearly described in the literature. For the remaining possible surge-type glaciers either the advance, in terms of time and length, were not mentioned in detail in the literature, or the glaciers have remained either stable or retreated during the entire period of our study. Most of the surge-type glaciers cluster in the Inner Tien Shan (especially in the Ak-Shiirak rage) and the Central Tien Shan, are in size and are facing North, West or North West. Pronounced surge events were observed for North Inylchek and Samoilowitsch glaciers, both of which are located in the Central Tien Shan. Samoilowitsch Glacier retreated by more than 3 km between 1960 (length ~8.9 km) and 1992 (~5.8 km), advanced by almost 3 km until 2006 and slightly retreated thereafter. The most pronounced advance occurred between 2000 and 2002. DEM differencing (based on SRTM3 data and stereo Hexagon and Cartosat-1 data) revealed a significant thickening in the middle reaches (reservoir area) of the glacier between 1973 and 2000 while the surface significantly lowered in the middle and upper parts of the glacier between 2000 and 2006. Hence, the ice mass was transferred to the lower reaches (receiving area) and caused the advance with a maximum thickening of more than 80 m. The ~30 km long North Inylchek Glacier retreated since 1943 and showed a very rapid advance of ~3.5 km especially in
Fate of Glaciers in the Tibetan Plateau by 2100
NASA Astrophysics Data System (ADS)
Duan, K.
2017-12-01
As the third polar on the Earth, the Tibetan plateau holds more than 40,000 glaciers which have experienced a rapid retreat in recent decades. The variability of equilibrium line altitude (ELA) indicates expansion and wastage of glacier directly. Here we simulated the ELA variability in the Tibetan Plateau based on a full surface energy and mass balance model. The simulation results are agreement with the observations. The ELAs have risen at a rate of 2-8m/a since 1970 throughout the Plateau, especially in the eastern Plateau where the ELAs have risen to or over the top altitude of glacier, indicating the glaciers are accelerating to melting over there. Two glaciers, XD glacier in the center of the Plateau and Qiyi glacier in the Qilian Mountain, are chosen to simulate its future ELA variability in the scenarios of RCP2.6, RCP4.5 and RCP 8.5 given by IPCC. The results show the ELAs will arrive to its maximum in around 2040 in RCP2.6, while the ELAs will be over the top altitude of glaciers in 2035-2045 in RCP4.5 and RCP8.5, suggesting the glaciers in the eastern Plateau will be melting until the disappear of the glaciers by the end of 2100.
Malaspina Glacier, Alaska, Anaglyph with Landsat Overlay
NASA Technical Reports Server (NTRS)
2003-01-01
This anaglyph view of Malaspina Glacier in southeastern Alaska was created from a Landsat satellite image and an elevation model generated by the Shuttle Radar Topography Mission (SRTM). Malaspina Glacier is considered the classic example of a piedmont glacier. Piedmont glaciers occur where valley glaciers exit a mountain range onto broad lowlands, are no longer laterally confined, and spread to become wide lobes. Malaspina Glacier is actually a compound glacier, formed by the merger of several valley glaciers, the most prominent of which seen here are Agassiz Glacier (left) and Seward Glacier (right). In total, Malaspina Glacier is up to 65 kilometers (40 miles) wide and extends up to 45 kilometers (28 miles) from the mountain front nearly to the sea. Glaciers erode rocks, carry them down slope, and deposit them at the edge of the melting ice, typically in elongated piles called moraines. The moraine patterns at Malaspina Glacier are quite spectacular in that they have huge contortions that result from the glacier crinkling as it gets pushed from behind by the faster-moving valley glaciers. Numerous other features of the glaciers and the adjacent terrain are clearly seen when viewing this image at full resolution. The series of tonal arcs on Agassiz Glacier's extension onto the piedmont are called 'ogives.' These arcs are believed to be seasonal features created by deformation of the glacier as it passes over bedrock irregularities at differing speeds through the year. Assuming one light-and-dark ogive pair per year, the rate of motion of the glacial ice can be estimated (in this case, about 200 meters per year where the ogives are most prominent). Just to the west, moraine deposits abut the eroded bedrock terrain, forming a natural dam that has created a lake. Near the northwest corner of the scene, a recent landslide has deposited rock debris atop a small glacier. Sinkholes are common in many areas of the moraine deposits. The sinkholes form whenChanges in the Surface Area of Glaciers in Northern Eurasia
NASA Astrophysics Data System (ADS)
Khromova, T.; Nosenko, G.
2012-12-01
Glaciers are widely recognized as key indicators of climate change. Recent evidence suggests an acceleration of glacier mass loss in several key mountain regions. Glacier recession implies the landscape changes in the glacial zone, origin of new lakes and activation of natural disaster processes, catastrophic mudflows, ice avalanches, outburst floods, and etc. The presence of glaciers in itself threats to human life, economic activity and growing infrastructure. Economical and recreational human activity in mountain regions requires relevant information on snow and ice objects. Absence or inadequacy of such information results in financial and human losses. A more comprehensive evaluation of glacier changes is imperative to assess ice contributions to global sea level rise and the future of water resources from glacial basins. One of the urgent steps is a full inventory of all ice bodies, their volume and changes The first estimation of glaciers state and glaciers distribution in the big part of Northern Eurasia has been done in the USSR Glacier Inventory published in 1966 -1980 as a part of IHD activity. The Inventory is based on topographic maps and air photos and reflects the status of the glaciers in 1957-1970y. There is information about 23796 glaciers with area of 78222.3 km2 in the Inventory. It covers 23 glacier systems on Northern Eurasia. In the 80th the USSR Glacier Inventory has been transformed in the digital form as a part of the World Glacier Inventory. Recent satellite data provide a unique opportunity to look again at these glaciers and to evaluate changes in glacier extent for the second part of XX century. In the paper we report about 15 000 glaciers outlines for Caucasus, Pamir, Tien-Shan, Altai, Syntar-Khayata, Cherskogo Range, Kamchatka and Russian Arctic which have been derived from ASTER and Landsat imagery and could be used for glacier changes evaluation. The results show that glaciers are retreating in all these regions. There is, however
Hydro-chemical Characterization of Glacier Melt Water of Ponkar Glacier, Manang, Nepal.
NASA Astrophysics Data System (ADS)
Shrestha, R.; Sandeep, S.
2017-12-01
The study was carried out in Ponkar Glacier, representing Himalayan glacier of Nepal. The study aims in determining the physical-chemical properties of the glacier melt water. The sampling sites included moraine dammed, Ponkar Lake at 4100 m a.s.l to the downstream glaciated stream at 3580 m a.s.l. The water samples were collected from the seven different sites. Temperature was recorded by digital multi-thermometer on site. The samples were brought to the laboratory and the parameters were analyzed according to the APHA, AWWA and WEF standards. The glacier meltwater was slightly basic with pH 7.44 (±0.307). The meltwater was found to be in the range 30-60 which implies the water is moderately soft resulting value of concentration 36.429±8.664 mg CaCO3 L-1 and the electrical conductivity was found to be 47.14 (±11.18) µS/cm. The concentration of anion was in the order of HCO3 - > Cl- > SO42- > NO3- > TP-PO43- with the concentration 194.286±40.677, 55.707±30.265, 11.533±1.132 mgL-1, 1.00±0.7 mgL-1 and 0.514±0.32 mgL-1 respectively. Calcium carbonate weathering was found out to be the major source of dissolved ions in the region. The heavy metals were found in the order Al>Fe>Mn>Zn with concentration 1.34±0.648, 1.103±0.917, 0.08±0.028 and 0.023±0.004 mgL-1 respectively. The concentration of iron, manganese and zinc in some sites were below the detection limit. These results represent baseline data for the physical-chemical properties of the glacier meltwater
NASA Astrophysics Data System (ADS)
Kehrl, L. M.; Joughin, I. R.; Shean, D. E.
2016-12-01
Marine-terminating glaciers can be very sensitive to changes in ice-front position, depending on their geometry. If a nearly grounded glacier retreats into deeper water, the glacier typically must speed up to produce the additional longitudinal and lateral stress gradients necessary to restore force balance. This speedup often causes thinning, which can increase the glacier's susceptibility to further retreat. In this study, we combine satellite observations and numerical modeling (Elmer/Ice) to investigate how seasonal changes in ice-front position affect glacier speed and surface elevation at Helheim Glacier, SE Greenland, from 2010-2016. Helheim's calving front position fluctuated about a mean position from 2010-2016. During 2010/11, 2013/14, and 2015/16, Helheim seasonally retreated and advanced along a reverse bed slope by > 3 km. During these years, the glacier retreated from winter/spring to late summer and then readvanced until winter/spring. During the retreat, Helheim sped up by 20-30% and thinned by 20 m near its calving front. This thinning caused the calving front to unground, and a floating ice tongue was then able to readvance over the following winter with limited iceberg calving. The advance, which continued until the glacier reached the top of the bathymetric high, caused the glacier to slow and thicken. During years when Helheim likely did not form a floating ice tongue, iceberg calving continued throughout the winter. Consequently, the formation of this floating ice tongue may have helped stabilize Helheim after periods of rapid retreat and dynamic thinning. Helheim's rapid retreat from 2001-2005 also ended when a floating ice tongue formed and readvanced over the 2005/06 winter. These seasonal retreat/advance cycles may therefore be important for understanding Helheim's long-term behavior.
NASA Astrophysics Data System (ADS)
Friedl, Peter; Seehaus, Thorsten; Wendt, Anja; Braun, Matthias
2017-04-01
The Antarctic Peninsula is one of the world`s most affected regions by Climate Change. Dense and long time series of remote sensing data enable detailed studies of the rapid glaciological changes in this area. We present results of a study on Fleming Glacier, which was the major tributary glacier of former Wordie Ice Shelf, located at the south-western side of the Antarctic Peninsula. Since the ice shelf disintegrated in a series of events starting in the 1970s, only disconnected tidewater glaciers have remained today. As a reaction to the loss of the buttressing force of the ice shelf, Fleming Glacier accelerated and dynamically thinned. However, all previous studies conducted at Wordie Bay covered only relatively short investigation periods and ended in 2008 the latest. Hence it was not well known how long the process of adaption to the changing boundary conditions exactly lasts and how it is characterized in detail. We provide long time series (1994 - 2016) of glaciological parameters (i.e. ice extent, velocity, grounding line position, ice elevation) for Fleming Glacier obtained from multi-mission remote sensing data. For this purpose large datasets of previously active (e.g. ERS, Envisat, ALOS PALSAR, Radarsat-1) as well as currently recording SAR sensors (e.g. Sentinel-1, TerraSAR-X, TanDEM-X) were processed and combined with data from other sources (e.g. optical images, laser altimeter and ice thickness data). The high temporal resolution of our dataset enables us to present a detailed history of 22 years of glacial dynamics at Fleming Glacier after the disintegration of Wordie Ice Shelf. We found strong evidence for a rapid grounding line retreat of up to 13 km between 2008 and 2011, which led to a further amplification of dynamic ice thinning. Today Fleming Glacier seems to be far away from approaching a new equilibrium. Our data show that the current glacier dynamics of Fleming Glacier are not primarily controlled by the loss of the ice shelf anymore, but
2017-12-08
Aerial view of the Sverdrup Glacier, a river of ice that flows from the interior of the Devon Island Ice Cap (Canada) into the ocean. To learn about the contributions of glaciers to sea level rise, visit: www.nasa.gov/topics/earth/features/glacier-sea-rise.html Credit: Alex Gardner, Clark University 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
2017-12-08
Melt water ponded at surface in the accumulation zone of Columbia Glacier, Alaska, in July 2008. To learn about the contributions of glaciers to sea level rise, visit: www.nasa.gov/topics/earth/features/glacier-sea-rise.html Credit: W. Tad Pfeffer, University of Colorado at Boulder 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
2017-12-08
Peripheral glaciers and ice caps (isolated from the main ice sheet, which is seen in the upper right section of the image) in eastern Greenland. To learn about the contributions of glaciers to sea level rise, visit: www.nasa.gov/topics/earth/features/glacier-sea-rise.html Credit: Frank Paul, University of Zurich 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
A cryptic Gondwana-forming orogen located in Antarctica.
Daczko, Nathan R; Halpin, Jacqueline A; Fitzsimons, Ian C W; Whittaker, Joanne M
2018-05-30
The most poorly exposed and least understood Gondwana-forming orogen lies largely hidden beneath ice in East Antarctica. Called the Kuunga orogen, its interpolation between scattered outcrops is speculative with differing and often contradictory trends proposed, and no consensus on the location of any sutures. While some discount a suture altogether, paleomagnetic data from Indo-Antarctica and Australo-Antarctica do require 3000-5000 km relative displacement during Ediacaran-Cambrian Gondwana amalgamation, suggesting that the Kuunga orogen sutured provinces of broadly Indian versus Australian affinity. Here we use compiled data from detrital zircons offshore of East Antarctica that fingerprint two coastal subglacial basement provinces between 60 and 130°E, one of Indian affinity with dominant ca. 980-900 Ma ages (Indo-Antarctica) and one of Australian affinity with dominant ca. 1190-1140 and ca. 1560 Ma ages (Australo-Antarctica). We combine this offshore compilation with existing and new onshore U-Pb geochronology and previous geophysical interpretations to delimit the Indo-Australo-Antarctic boundary at a prominent geophysical lineament which intersects the coast east of Mirny at ~94°E.
NASA Astrophysics Data System (ADS)
Jomelli, Vincent; Mokadem, Fatima; Schimmelpfennig, Irene; Chapron, Emmanuel; Rinterknecht, Vincent; Favier, Vincent; Verfaillie, Deborah; Brunstein, Daniel; Legentil, Claude; Michel, Elisabeth; Swingedouw, Didier; Jaouen, Alain; Aumaitre, Georges; Bourlès, Didier L.; Keddadouche, Karim
2017-04-01
Similar to many other regions in the world, glaciers in the southern sub-polar regions are currently retreating. In the Kerguelen Islands (49°S, 69°E), the mass balance of the Cook Ice Cap (CIC), the largest ice cap in this region, experienced dramatic shrinking between 1960 and 2013 with retreat rates among the highest in the world. This observation needs to be evaluated in a long-term context. However, data on the past glacier extents are sparse in the sub-Antarctic regions. To investigate the deglaciation pattern since the Last Glacial Maximum (LGM) period, we present the first 13 cosmogenic 36Cl surface exposure ages from four sites in the Kerguelen Islands. The 36Cl ages from erratic and moraine boulders span from 24.4 ± 2.7 ka to 0.3 ± 0.1 ka. We combined these ages with existing glacio-marine radiocarbon ages and bathymetric data to document the temporal and spatial changes of the island's glacial history. Ice began to retreat on the main island before 24.4 ± 2.7 ka until around the time of the Antarctic Cold Reversal (ACR) period (∼14.5-12.9 ka), during which the Bontemps moraine was formed by the advance of a CIC outlet glacier. Deglaciation continued during the Holocene probably until 3 ka with evidence of minor advances during the last millennium. This chronology is in pace with major changes in δ18O in a recent West Antarctica ice core record, showing that Kerguelen Islands glaciers are particularly sensitive and relevant to document climate change in the southern polar regions.
Climate sensitivity of Tibetan Plateau glaciers - past and future implications
NASA Astrophysics Data System (ADS)
Heyman, Jakob; Hubbard, Alun; Stroeven, Arjen P.; Harbor, Jonathan M.
2013-04-01
The Tibetan Plateau is one of the most extensively glaciated, non-Polar regions of the world, and its mountain glaciers are the primary source of melt water for several of the largest Asian rivers. During glacial cycles, Tibetan Plateau glaciers advanced and retreated multiple times, but remained restricted to the highest mountain areas as valley glaciers and ice caps. Because glacier extent is dominantly controlled by climate, the past extent of Tibetan glaciers provide information on regional climate. Here we present a study analyzing the past maximum extents of glaciers on the Tibetan Plateau with the output of a 3D glacier model, in an effort to quantify Tibetan Plateau climate. We have mapped present-day glaciers and glacial landforms deposited by formerly more extensive glaciers in eight mountain regions across the Tibetan Plateau, allowing us to define present-day and past maximum glacier outlines. Using a high-resolution (250 m) higher-order glacier model calibrated against present-day glacier extents, we have quantified the climate perturbations required to expand present-day glaciers to their past maximum extents. We find that a modest cooling of at most 6°C for a few thousand years is enough to attain past maximum extents, even with 25-75% precipitation reduction. This evidence for limited cooling indicates that the temperature of the Tibetan Plateau remained relatively stable over Quaternary glacial cycles. Given the significant sensitivity to temperature change, the expectation is perhaps that a future warmer climate might result in intense glacier reduction. We have tested this hypothesis and modeled the future glacier development for the three mountain regions with the largest present-day glacier cover using a projected warming of 2.8 to 6.2°C within 100 years (envelope limits from IPCC). These scenarios result in dramatic glacier reductions, including 24-100% ice volume loss after 100 years and 77-100% ice volume loss after 300 years.
G.I. Taylor and the Trinity Test
ERIC Educational Resources Information Center
Deakin, Michael A. B.
2011-01-01
The story is often told of the calculation by G.I. Taylor of the yield of the first ever atomic bomb exploded in New Mexico in 1945. It has indeed become a staple of the classroom whenever dimensional analysis is taught. However, while it is true that Taylor succeeded in calculating this figure at a time when it was still classified, most versions…
SPaMOB eat atmospheric methane in Antarctica
NASA Astrophysics Data System (ADS)
Lau, C. Y. M.; Edwards, C. R.; Onstott, T. C.
2016-12-01
The diverse and endemic soil microorganisms that have adapted to the hostile environments in Antarctica are facing challenges due to climate change. The seasonally thawed active layer would exhibit greater daily and/or seasonal temperature variations and different soil moisture regimes, which would cause compositional shifts in these microbial communities. Our preliminary data reveal that Antarctic cryosols from the Taylor Dry Valley are capable of oxidizing methane at atmospheric concentration ( 2 ppmv) at significantly higher rates than the acidic mineral cryosols from the Canadian High Arctic (N 79°) [The ISME J (2015) 9: 1880-1891]. Understanding of this understudied behavior for these active layer cryosols is important for determining the potential methane feedback responses in the Antarctic region. We therefore investigate the biodiversity and genome-wide adaptation of the responsible Southern Polar atmospheric methane-oxidizing bacteria (SPaMOB) in these cryosols. Methane consumption at atmospheric concentration at 4 and 10°C was monitored over a period of four weeks. Two cryosol samples that oxidized methane at both temperatures were selected for molecular analyses. PCR-cloning and sequencing of pmoA (particulate methane monooxygenase beta subunit), the marker gene of methane oxidation, revealed that the SPaMOB in alkaline Antarctic cryosols are closely related to Upland Soil Cluster γ (USCγ), whereas the high Canadian Arctic cryosols contain predominantly USCa-like phylotypes. Four metagenomic libraries were prepared from total DNA and sequenced (2x100bp, Illumina). Quality-filtered reads (avg. 20 M reads per library) were de novo assembled and annotated. A 42.8 kb-long contig containing the pmoCBAcluster was successfully assembled. The pmoA gene is closely related to our USCγ clone sequences. In addition to pmo genes, the presence of genes for conversion of methanol to formaldehyde, production of formate and eventually CO2 indicates SPaMOB's ability
Combined Gravimetric-Seismic Crustal Model for Antarctica
NASA Astrophysics Data System (ADS)
Baranov, Alexey; Tenzer, Robert; Bagherbandi, Mohammad
2018-01-01
The latest seismic data and improved information about the subglacial bedrock relief are used in this study to estimate the sediment and crustal thickness under the Antarctic continent. Since large parts of Antarctica are not yet covered by seismic surveys, the gravity and crustal structure models are used to interpolate the Moho information where seismic data are missing. The gravity information is also extended offshore to detect the Moho under continental margins and neighboring oceanic crust. The processing strategy involves the solution to the Vening Meinesz-Moritz's inverse problem of isostasy constrained on seismic data. A comparison of our new results with existing studies indicates a substantial improvement in the sediment and crustal models. The seismic data analysis shows significant sediment accumulations in Antarctica, with broad sedimentary basins. According to our result, the maximum sediment thickness in Antarctica is about 15 km under Filchner-Ronne Ice Shelf. The Moho relief closely resembles major geological and tectonic features. A rather thick continental crust of East Antarctic Craton is separated from a complex geological/tectonic structure of West Antarctica by the Transantarctic Mountains. The average Moho depth of 34.1 km under the Antarctic continent slightly differs from previous estimates. A maximum Moho deepening of 58.2 km under the Gamburtsev Subglacial Mountains in East Antarctica confirmed the presence of deep and compact orogenic roots. Another large Moho depth in East Antarctica is detected under Dronning Maud Land with two orogenic roots under Wohlthat Massif (48-50 km) and the Kottas Mountains (48-50 km) that are separated by a relatively thin crust along Jutulstraumen Rift. The Moho depth under central parts of the Transantarctic Mountains reaches 46 km. The maximum Moho deepening (34-38 km) in West Antarctica is under the Antarctic Peninsula. The Moho depth minima in East Antarctica are found under the Lambert Trench (24
Dynamic interactions between glacier and glacial lake in the Bhutan Himalaya
NASA Astrophysics Data System (ADS)
Tsutaki, S.; Fujita, K.; Yamaguchi, S.; Sakai, A.; Nuimura, T.; Komori, J.; Takenaka, S.; Tshering, P.
2012-04-01
A number of supraglacial lakes formed on the termini of debris-covered glaciers in the Bhutan Himalaya as a result of glacier retreat due to climate change. The terminal part of the lake-terminating glaciers flow faster than that of the land-terminating glaciers because the basal ice motion is enhanced by high subglacial water pressure generated by lake water. Increased ice flux caused by the accelerated glacier flow could be dissipated through the calving process which reduced the glacier thickness. It is important to understand the interaction between lake formation and glacier dynamics. Although glacier flow velocity has been measured by remote-sensing analysis in several regions of the Himalayas, glacier thinning rates have not been observed by neither in-situ nor remote-sensing approaches. The lack of field data raises limitation to interpretations for glacier dynamics. We investigate the influence of the presence/absence of glacial lakes on glacier dynamics and changes in surface elevation. We study two debris-covered glaciers in the Lunana region, the Bhutan Himalaya. Thorthormi Glacier is a land-terminating glacier with some supraglacial lakes while Lugge Glacier is a lake-terminating glaciers. We surveyed the surface elevation of debris-covered areas of the two glaciers in 2004 and 2011 by a differential GPS. Change in surface elevation of the lake-terminating Lugge Glacier (-5.4--2.4 m yr-1) was much more negative than that of the land-terminating Thorthormi Glacier (-3.3-0.6 m yr-1). Surface flow speed of the Thorthormi Glacier measured during 2002-2004 was faster in the upper reaches (~90 m yr-1) and reduced toward the downstream (40 m yr-1). In contrast, the surface flow speed at the Lugge Glacier measured in the same periods was 40-55 m yr-1 and the greatest at the lower most part. Observed spatial distribution of surface flow velocity at both glaciers were evaluated by a two-dimensional numerical flow model. Calculated emergence velocities are 1
Bidlake, William R.; Josberger, Edward G.; Savoca, Mark E.
2010-01-01
Winter snow accumulation and summer snow and ice ablation were measured at South Cascade Glacier, Washington, to estimate glacier mass balance quantities for balance years 2006 and 2007. Mass balances were computed with assistance from a new model that was based on the works of other glacier researchers. The model, which was developed for mass balance practitioners, coupled selected meteorological and glaciological data to systematically estimate daily mass balance at selected glacier sites. The North Cascade Range in the vicinity of South Cascade Glacier accumulated approximately average to above average winter snow packs during 2006 and 2007. Correspondingly, the balance years 2006 and 2007 maximum winter snow mass balances of South Cascade Glacier, 2.61 and 3.41 meters water equivalent, respectively, were approximately equal to or more positive (larger) than the average of such balances since 1959. The 2006 glacier summer balance, -4.20 meters water equivalent, was among the four most negative since 1959. The 2007 glacier summer balance, -3.63 meters water equivalent, was among the 14 most negative since 1959. The glacier continued to lose mass during 2006 and 2007, as it commonly has since 1953, but the loss was much smaller during 2007 than during 2006. The 2006 glacier net balance, -1.59 meters water equivalent, was 1.02 meters water equivalent more negative (smaller) than the average during 1953-2005. The 2007 glacier net balance, -0.22 meters water equivalent, was 0.37 meters water equivalent less negative (larger) than the average during 1953-2006. The 2006 accumulation area ratio was less than 0.10, owing to isolated patches of accumulated snow that endured the 2006 summer season. The 2006 equilibrium line altitude was higher than the glacier. The 2007 accumulation area ratio and equilibrium line altitude were 0.60 and 1,880 meters, respectively. Accompanying the glacier mass losses were retreat of the terminus and reduction of total glacier area. The
NASA Astrophysics Data System (ADS)
Chuter, S. J.; Martín-Español, A.; Wouters, B.; Bamber, J. L.
2017-07-01
We present a reassessment of input-output method ice mass budget estimates for the Abbot and Getz regions of West Antarctica using CryoSat-2-derived ice thickness estimates. The mass budget is 8 ± 6 Gt yr-1 and 5 ± 17 Gt yr-1 for the Abbot and Getz sectors, respectively, for the period 2006-2008. Over the Abbot region, our results resolve a previous discrepancy with elevation rates from altimetry, due to a previous 30% overestimation of ice thickness. For the Getz sector, our results are at the more positive bound of estimates from other techniques. Grounding line velocity increases up to 20% between 2007 and 2014 alongside mean elevation rates of -0.67 ± 0.13 m yr-1 between 2010 and 2013 indicate the onset of a dynamic thinning signal. Mean snowfall trends of -0.33 m yr-1 water equivalent since 2006 indicate recent mass trends are driven by both ice dynamics and surface processes.
NASA Astrophysics Data System (ADS)
Li, Zhongqin; Ren, Jiawen; Li, Huilin; Wang, Puyu; Wang, Feiteng
2016-04-01
Similar to most mountain glaciers in the world, Urumqi Glacier No. 1 (UG1), the best observed glacier in China with continued glaciological and climatological monitoring records of longer than 50 years has experienced an accelerated recession during the past several decades. The purpose of this study is to investigate the acceleration of recession. By taking UG1 as an example, we analyze the generic mechanisms of acceleration of shrinkage of continental mountain glaciers. The results indicate that the acceleration of mass loss of UG1 commenced first in 1985 and second in 1996 and that the latter was more vigorous. The air temperature rises during melting season, the ice temperature augment of the glacier and the albedo reduction on the glacier surface are considered responsible for the accelerated recession. In addition, the simulations of the accelerated shrinkage of UG1 are introduced.
Geoethical approach to mineral activities in Antarctica
NASA Astrophysics Data System (ADS)
Talalay, Pavel
2013-04-01
Antarctica is the outermost from civilization space continent. From 14.0 million km2 of surface area about 98% of Antarctica is covered by ice that averages at least 1.6 km in thickness. Geologically, the continent is the least explored in the world, and it is almost absolutely unknown what mineral resources Antarctica has as they are buried in rock that is covered by a thick ice sheet. It is thought to have large and valuable mineral deposits under the ice. This is because of what has been found in samples taken from the small areas of rock that are exposed, and also from what has been found in South Africa and South America. Up until 180 million years ago, Antarctica was a part of the Gondwanaland super continent, attached to South America, the Southern part of Africa, India and Australia, these continents then drifted apart until they reached their current positions. This leads to a possibility that Antarctica may also share some of the mineral wealth of these continents. Right now on the ice-free areas of Antarctica iron ore, chromium, copper, gold, nickel, platinum, coal and hydrocarbons have been found. The Protocol on Environmental Protection to the Antarctic Treaty, also known as the Madrid Protocol, was signed in 1991 by the signatories to the Antarctic Treaty and became law in January 1998. The Protocol provides for comprehensive protection of the Antarctic environment and associated ecosystems and includes a ban on all commercial mining for at least fifty years (this is up for review in 2041). Current climate change and melting ice in Polar Regions is opening up new opportunities to exploit mineral and oil resources. Even Antarctica's weather, ice and distance from any industrialized areas mean that mineral extraction would be extremely expensive and also extremely dangerous, the depletion of mineral recourses on the Earth can reverse banning of mining in Antarctica in future. There is no question that any resource exploitation in Antarctica will cause
NASA Astrophysics Data System (ADS)
Sinclair, K. E.; Bertler, N. A. N.; Trompetter, W. J.
2010-11-01
Dominant storm tracks to two ice core sites on the western margin of the Ross Sea, Antarctica (Skinner Saddle (SKS) and Evans Piedmont Glacier), are investigated to establish key synoptic controls on snow accumulation. This is critical in terms of understanding the seasonality, source regions, and transport pathways of precipitation delivered to these sites. In situ snow depth and meteorological observations are used to identify major accumulation events in 2007-2008, which differ considerably between sites in terms of their magnitude and seasonal distribution. While snowfall at Evans Piedmont Glacier occurs almost exclusively during summer and spring, Skinner Saddle receives precipitation year round with a lull during the months of April and May. Cluster analysis of daily back trajectories reveals that the highest-accumulation days at both sites result from fast-moving air masses, associated with synoptic-scale low-pressure systems. There is evidence that short-duration pulses of snowfall at SKS also originate from mesocyclone development over the Ross Ice Shelf and local moisture sources. Changes in the frequency and seasonal distribution of these mechanisms of precipitation delivery will have a marked impact on annual accumulation over time and will therefore need careful consideration during the interpretation of stable isotope and geochemical records from these ice cores.
NASA Astrophysics Data System (ADS)
Kassab, C.; Lindback, K.; Pettersson, R.; Licht, K.; Graly, J. A.; Kaplan, M. R.
2016-12-01
Blue ice moraines cover a small percentage of Antarctica, but can contain a significant record of ice sheet dynamics and climate over multiple glacial cycles. Previous work has focused on the temporal and provenance record contained within these moraines and less on mechanisms by which such deposits form and their temporal evolution. In order to create a conceptual model of their formation, >25 km of ground penetrating radar transects at 25 and 100 MHz frequencies were collected at the Mt Achernar moraine adjacent to Law Glacier. Here, ice ablation causes debris bands to emerge and deliver sediment to the surface. Most transects were collected perpendicular to the ice-moraine margin, and extend from the actively flowing Law Glacier ice to a distance of 2 km into the moraine. The 25 and 100 MHz transects penetrate to a depth of 200 m and 60 m respectively and reveal a relatively complex internal stratigraphy. Closest to the ice-moraine margin, stratigraphy is not well resolved due to a high amount of clutter. Steeply dipping parallel reflections first emerge 400m away from the ice margin and dip toward Law Glacier. These reflections continue inwards to 1450m, where the reflections become more closely spaced. Hummocky topography and parallel ridge/trough topography dominate the geomorphic expression. The hummocky topography corresponds to the region where reflections are not well resolved. The ridges are interpreted to be debris bands that are emerging at the surface, similar to those along the margin of the Law Glacier where debris is newly emerging. The reflections in the GPR transects indicate that debris is transported from depth to the surface of the ice where it accumulates forming the Mt Achernar moraine. It appears that the various reflection patterns correspond to unique surface geomorphic expressions. The reflections also indicate that at least the first 2 km of debris rich buried ice in the moraine can be linked to the actively flowing Law Glacier
Cathedral house & crocker fence, Taylor Street east and north ...
Cathedral house & crocker fence, Taylor Street east and north elevations, perspective view from the northeast - Grace Cathedral, George William Gibbs Memorial Hall, 1051 Taylor Street, San Francisco, San Francisco County, CA
Hasty retreat of glaciers in the Palena province of Chile
NASA Astrophysics Data System (ADS)
Paul, F.; Mölg, N.; Bolch, T.
2013-12-01
Mapping glacier extent from optical satellite data has become a most efficient tool to create or update glacier inventories and determine glacier changes over time. A most valuable archive in this regard is the nearly 30-year time series of Landsat Thematic Mapper (TM) data that is freely available (already orthorectified) for most regions in the world from the USGS. One region with a most dramatic glacier shrinkage and a missing systematic assessment of changes, is the Palena province in Chile, south of Puerto Montt. A major bottleneck for accurate determination of glacier changes in this region is related to the huge amounts of snow falling in this very maritime region, hiding the perimeter of glaciers throughout the year. Consequently, we found only three years with Landsat scenes that can be used to map glacier extent through time. We here present the results of a glacier change analysis from six Landsat scenes (path-rows 232-89/90) acquired in 1985, 2000 and 2011 covering the Palena district in Chile. Clean glacier ice was mapped automatically with a standard technique (TM3/TM band ratio) and manual editing was applied to remove wrongly classified lakes and to add debris-covered glacier parts. The digital elevation model (DEM) from SRTM was used to derive drainage divides, determine glacier specific topographic parameters, and analyse the area changes in regard to topography. The scene from 2000 has the best snow conditions and was used to eliminate seasonal snow in the other two scenes by digital combination of the binary glacier masks. The observed changes show a huge spatial variability with a strong dependence on elevation and glacier hypsometry. While small mountain glaciers at high elevations and steep slopes show virtually no change over the 26-year period, ice at low elevations from large valley glaciers shows a dramatic decline (area and thickness loss). Some glaciers retreated more than 3 km over this time period or even disappeared completely
NASA Astrophysics Data System (ADS)
He, Z.; Velicogna, I.; Hsu, C. W.; Rignot, E. J.; Mouginot, J.; Scheuchl, B.; Fettweis, X.; van den Broeke, M. R.
2017-12-01
Changes in ice sheets, glaciers and ice caps (GIC) and land water mass cause regional sea level variations that differ significantly from a uniform re-distribution of mass over the ocean, with a decrease in sea level compared to the global mean sea level contribution (GMSL) near the sources of mass added to the ocean and an increase up to 30% larger than the GMSL in the far field. The corresponding sea level fingerprints (SLF) are difficult to separate from ocean dynamics on short time and spatial scales but as ice melt continues, the SLF signal will become increasingly dominant in the pattern of regional sea level rise. It has been anticipated that it will be another few decades before the land ice SLF could be identified in the pattern of regional sea level rise. Here, we combine 40 years of observations of ice sheet mass balance for Antarctica (1975-present) and Greenland (1978-present), along with surface mass balance reconstructions of glacier and ice caps mass balance (GIC) from 1970s to present to determine the contribution to the SLF from melting land ice (MAR and RACMO). We compare the results with observations from GRACE for the time period 2002 to present for evaluation of our approach. Land hydrology is constrained by GRACE data for the period 2002-present and by the GLDAS-NOAH land hydrology model for the longer time period. Over the long time period, we find that the contribution from land ice dominates. We quantify the contribution to the total SLF from Greenland and Antarctica in various parts of the world over the past 40 years. More important, we compare the cumulative signal from SLF with tide gauge records around the world, corrected for earth dynamics, to determine whether the land ice SLF can be detected in that record. Early results will be reported at the meeting. This work was performed at UC Irvine and at Caltech's Jet Propulsion Laboratory under a contract with NASA's Cryospheric Science Program.
Putzke, Jair; Pereira, Antonio B
2016-01-01
This study presents the description of Phaeosphaeria deschampsii, which was found in plant communities from Half Moon Island, South Shetland Archipelago, Antarctica, in February 2014. Many patches of Deschampsia antarctica (Poaceae), the only indigenous Poaceae specie in Antarctic, were found dead, parasitized by a fungi pathogen. Based on the shape of its perithecia, with oblique neck, erumpent in the grass tissues, ascospore form and septation, the specie was identified as new to science.
Mass loss on Himalayan glacier endangers water resources
NASA Astrophysics Data System (ADS)
Kehrwald, Natalie M.; Thompson, Lonnie G.; Tandong, Yao; Mosley-Thompson, Ellen; Schotterer, Ulrich; Alfimov, Vasily; Beer, Jürg; Eikenberg, Jost; Davis, Mary E.
2008-11-01
Ice cores drilled from glaciers around the world generally contain horizons with elevated levels of beta radioactivity including 36Cl and 3H associated with atmospheric thermonuclear bomb testing in the 1950s and 1960s. Ice cores collected in 2006 from Naimona'nyi Glacier in the Himalaya (Tibet) lack these distinctive marker horizons suggesting no net accumulation of mass (ice) since at least 1950. Naimona'nyi is the highest glacier (6050 masl) documented to be losing mass annually suggesting the possibility of similar mass loss on other high-elevation glaciers in low and mid-latitudes under a warmer Earth scenario. If climatic conditions dominating the mass balance of Naimona'nyi extend to other glaciers in the region, the implications for water resources could be serious as these glaciers feed the headwaters of the Indus, Ganges, and Brahmaputra Rivers that sustain one of the world's most populous regions.
Observed Changes in the Himalayan Glaciers: Multiple Driving Factors
NASA Astrophysics Data System (ADS)
Romshoo, Shakil; Rashid, Irfan; Abdullah, Tariq; Fayaz, Midhat
2017-04-01
There is lack of credible knowledge about Himalayan cryosphere as is evident from the contradictory reports about the status of the glaciers in the region. Glacier behavior in Himalaya has to be understood and interpreted in light of the multiple driving factors; topography, climate and anthropocene. The observed changes in Himalayan glaciers, determined by studying a few hundred glaciers in the Himalaya, indicated that the glacier response varies across different ranges. Satellite images (1990-2015), DEM, altimetry data supported by selective field campaigns, were used to map the changes in glacier boundaries, snout, ELA, AAR, volume, thickness, debris cover and several other glacier parameters. The glaciers across the six ranges of Pir Panjal (PR), Greater Himalaya (GH), Shamasbari (SR), Zanaskar (ZR), Leh (LR) and Karakorum (KR) showed quite varied changes. It was observed that the glaciers in the KR show the least glacial area recession (1.59%) primarily due to the extreme cold winters with -18oC average temperature. Other glacial parameters like snout, ELA, AAR and glacier volume also showed very little changes in the KR during the period. The glaciers in the LR, with an average winter temperature of -6o C, have shrunk, on an average, by 4.19 % during the period, followed by the glaciers in the ZR showing a loss of 5.46%. The highest glacier retreat of 7.72% and 6.94% was observed in the GH and SR with the average winter temperature of -1.3oc and -6.2oc respectively. In the PR, almost all the glaciers have vanished during the last 6-7 decades due to the increasing winter temperatures. The glaciers in the Kashmir showed an overall recession of 26.40% in area which is one of the highest reported for the Himalayan glaciers. The glaciers in the valley showed the maximum reduction in thickness (2.56m) using the IceSat data from 2000-08 while as the Karakoram glaciers showed the least reduction in thickness (0.53m). It was found that the maximum recession of glacial
Partitioning the Water Budget in a Glacierized Basin
NASA Astrophysics Data System (ADS)
O'Neel, S.; Sass, L.; McGrath, D.; McNeil, C.; Myers, K. F.; Bergstrom, A.; Koch, J. C.; Ostman, J. S.; Arendt, A. A.; LeWinter, A.; Larsen, C. F.; Marshall, H. P.
2017-12-01
Glaciers couple to the ecosystems in which they reside through their mass balance and subsequent runoff. The unique timing and composition of glacier runoff notably impacts ecological and socio-economically important processes, including thermal modulation of streams, nearshore primary production, and groundwater exchange. Predicting how these linkages will evolve as glaciers continue to retreat requires a better understanding of basin- to region-scale water budgets. Here we develop a partitioned water balance for Alaska's Wolverine Glacier basin for 2016. Our presentation will highlight mass-balance forcing and sensitivity, as well as analyses of hydrometric and geochemical partitioning. These observations provide constraints for hypsometry-based regional projections of glacier change, which form the basis of future biogeochemical scenarios. Local climate records show relatively minor warming and drying over the 1967 -2016 interval, yet the impact on the glacier was substantial; the average annual balance rate over the study interval is -0.5 m/yr. We performed a sensitivity experiment that suggests that elevation-independent processes drive first-order variability in glacier-wide mass balance solutions Analysis of runoff and precipitation data suggest that previously ignored components of the hydrologic cycle (groundwater, evapotranspiration, off-glacier snowpack storage, and snow redistribution) may substantially contribute to the basin wide water budget. Initial geochemical assessments (carbon, water isotopes, major ions) highlight unique source signatures (glacier-derived, snow-melt, groundwater), which will be further explored using a mixing model approach. Applying a range of climate forcings over centennial time-scales suggests the regional equilibrium line altitude is likely to increase by more than 100 m, which will result in extensive glacier area losses. Such changes will likely modify the runoff from this basin by increasing inter-annual streamflow
Glacier Dynamics Within a Small Alpine Cirque
NASA Astrophysics Data System (ADS)
Sanders, J. W.; Cuffey, K. M.; MacGregor, K. R.; Kavanaugh, J. L.; Dow, C. F.
2008-12-01
Cirques, with their steep walls and overdeepened basins, have captivated the imagination of scientists since the mid-1800s. Glaciers in cirques, by generating these spectacular amphitheater-shaped landforms, contribute significantly to erosion in the core of mountain ranges and are one of the principal agents responsible for the relief structure at high elevations. Yet comprehensive studies of the dynamics of cirque glaciers, and their link to erosional processes, have never been undertaken. To this end, we acquired an extensive new set of measurements at the West Washmawapta Glacier, which sits in a cirque on the east side of Helmet Mountain in the Vermillion Range of the Canadian Rockies. Ice thickness surveys with ground penetrating radar revealed that the glacier occupies a classic bowl-shaped depression complete with a nearly continuous riegel. Using GPS-derived surface velocities of a glacier-wide grid network and the tilt of one borehole, we calculated the complete force balance of the glacier. This analysis also produced a map of basal sliding velocity and a value for the viscosity of temperate ice. We will discuss the implications of these findings for the problem of how cirques are formed by glacial erosion.
Bendia, Amanda G.; Signori, Camila N.; Franco, Diego C.; Duarte, Rubens T. D.; Bohannan, Brendan J. M.; Pellizari, Vivian H.
2018-01-01
Active volcanoes in Antarctica contrast with their predominantly cold surroundings, resulting in environmental conditions capable of selecting for versatile and extremely diverse microbial communities. This is especially true on Deception Island, where geothermal, marine, and polar environments combine to create an extraordinary range of environmental conditions. Our main goal in this study was to understand how microbial community structure is shaped by gradients of temperature, salinity, and geochemistry in polar marine volcanoes. Thereby, we collected surface sediment samples associated with fumaroles and glaciers at two sites on Deception, with temperatures ranging from 0 to 98°C. Sequencing of the 16S rRNA gene was performed to assess the composition and diversity of Bacteria and Archaea. Our results revealed that Deception harbors a combination of taxonomic groups commonly found both in cold and geothermal environments of continental Antarctica, and also groups normally identified at deep and shallow-sea hydrothermal vents, such as hyperthermophilic archaea. We observed a clear separation in microbial community structure across environmental gradients, suggesting that microbial community structure is strongly niche driven on Deception. Bacterial community structure was significantly associated with temperature, pH, salinity, and chemical composition; in contrast, archaeal community structure was strongly associated only with temperature. Our work suggests that Deception represents a peculiar “open-air” laboratory to elucidate central questions regarding molecular adaptability, microbial evolution, and biogeography of extremophiles in polar regions. PMID:29867810
NASA Astrophysics Data System (ADS)
Dziadek, R.; Gohl, K.; Diehl, A.; Kaul, N.
2017-07-01
Focused research on the Pine Island and Thwaites glaciers, which drain the West Antarctic Ice Shelf (WAIS) into the Amundsen Sea Embayment (ASE), revealed strong signs of instability in recent decades that result from variety of reasons, such as inflow of warmer ocean currents and reverse bedrock topography, and has been established as the Marine Ice Sheet Instability hypothesis. Geothermal heat flux (GHF) is a poorly constrained parameter in Antarctica and suspected to affect basal conditions of ice sheets, i.e., basal melting and subglacial hydrology. Thermomechanical models demonstrate the influential boundary condition of geothermal heat flux for (paleo) ice sheet stability. Due to a complex tectonic and magmatic history of West Antarctica, the region is suspected to exhibit strong heterogeneous geothermal heat flux variations. We present an approach to investigate ranges of realistic heat fluxes in the ASE by different methods, discuss direct observations, and 3-D numerical models that incorporate boundary conditions derived from various geophysical studies, including our new Depth to the Bottom of the Magnetic Source (DBMS) estimates. Our in situ temperature measurements at 26 sites in the ASE more than triples the number of direct GHF observations in West Antarctica. We demonstrate by our numerical 3-D models that GHF spatially varies from 68 up to 110 mW m-2.
Hazardous Glaciers In Switzerland: A Statistical Analysis of Inventory Data
NASA Astrophysics Data System (ADS)
Raymond, M.; Funk, M.; Wegmann, M.
Because of the recent increase in both occupation and economical activities in high mountain areas, a systematic overview of potential hazard zones of glaciers is needed to avoid the constuction of settlements and infrastructures in endangered areas in fu- ture. Historical informations about glacier disasters show that catastrophic events can happen repeatedly for the same causes and with the same dramatic consequences. Past catastrophic events are not only useful to identify potentially dangerous glaciers, but represent an indication of the kind of glacier hazards to expect for any given glacier. An inventory containing all known events having caused damages in the past has been compiled for Switzerland. Three different types of glacier hazards are distinguished , e.g. ice avalanches, glacier floods and glacier length changes.Hazardous glaciers have been identified in the alpine cantons of Bern, Grison, Uri, Vaud and Valais so far. The inventory data were analysed in terms of periodicity of different types of events as well as of damage occured.
NASA Astrophysics Data System (ADS)
Di Tullio, M.; Nocchi, F.; Camplani, A.; Emanuelli, N.; Nascetti, A.; Crespi, M.
2018-04-01
The glaciers are a natural global resource and one of the principal climate change indicator at global and local scale, being influenced by temperature and snow precipitation changes. Among the parameters used for glacier monitoring, the surface velocity is a key element, since it is connected to glaciers changes (mass balance, hydro balance, glaciers stability, landscape erosion). The leading idea of this work is to continuously retrieve glaciers surface velocity using free ESA Sentinel-1 SAR imagery and exploiting the potentialities of the Google Earth Engine (GEE) platform. GEE has been recently released by Google as a platform for petabyte-scale scientific analysis and visualization of geospatial datasets. The algorithm of SAR off-set tracking developed at the Geodesy and Geomatics Division of the University of Rome La Sapienza has been integrated in a cloud based platform that automatically processes large stacks of Sentinel-1 data to retrieve glacier surface velocity field time series. We processed about 600 Sentinel-1 image pairs to obtain a continuous time series of velocity field measurements over 3 years from January 2015 to January 2018 for two wide glaciers located in the Northern Patagonian Ice Field (NPIF), the San Rafael and the San Quintin glaciers. Several results related to these relevant glaciers also validated with respect already available and renown software (i.e. ESA SNAP, CIAS) and with respect optical sensor measurements (i.e. LANDSAT8), highlight the potential of the Big Data analysis to automatically monitor glacier surface velocity fields at global scale, exploiting the synergy between GEE and Sentinel-1 imagery.
Global-scale hydrological response to future glacier mass loss
NASA Astrophysics Data System (ADS)
Huss, Matthias; Hock, Regine
2018-01-01
Worldwide glacier retreat and associated future runoff changes raise major concerns over the sustainability of global water resources1-4, but global-scale assessments of glacier decline and the resulting hydrological consequences are scarce5,6. Here we compute global glacier runoff changes for 56 large-scale glacierized drainage basins to 2100 and analyse the glacial impact on streamflow. In roughly half of the investigated basins, the modelled annual glacier runoff continues to rise until a maximum (`peak water') is reached, beyond which runoff steadily declines. In the remaining basins, this tipping point has already been passed. Peak water occurs later in basins with larger glaciers and higher ice-cover fractions. Typically, future glacier runoff increases in early summer but decreases in late summer. Although most of the 56 basins have less than 2% ice coverage, by 2100 one-third of them might experience runoff decreases greater than 10% due to glacier mass loss in at least one month of the melt season, with the largest reductions in central Asia and the Andes. We conclude that, even in large-scale basins with minimal ice-cover fraction, the downstream hydrological effects of continued glacier wastage can be substantial, but the magnitudes vary greatly among basins and throughout the melt season.
Glacier Elevation Change in Western Nyainqentanglha Range, Tibetan Plateau
NASA Astrophysics Data System (ADS)
Zhang, Q.; Kang, S.; Zhang, G.
2016-12-01
Glacier retreat is a focus in the world with the global warming, local water resources and sea level rise was influenced greatly. Glacier area in western Nyainqentanglha range have a change of -6.8 to -18.2 percent from 1970 to 2010, the area in the northern slope decreased by larger rate. Changes in glacier area can not be used to estimate glacier mass variation. In this study, we use Landsat OLI images to extract glacier outlines, then glacier elevation change was calculated by Differential interferometry of TerraSAR-X/TanDEM-X and SRTM-C DEM. The decreasing rate of glacier elevation in the western Nyainqentanglha range was -0.28 ±0.11 m yr-1 during 2000 to 2014, the northern slope of -0.44 ±0.11 m yr-1 show a faster annual thinning rate than the southern slope of -0.22 ±0.11 m yr-1, which is conform to the area change trend. Detailed study of the typical glaciers elevation change suggests that , zhadang glacier represent the annual thinning rate of -0.61±0.11 m yr-1, 41 points elevation was measured by RTK-GPS in the field expedition in 2013, this values was used to validate the DInSAR results. The correlation coefficient between them was 0.77. Gurenhekou glacier in the south slope shows glacier elevation change of -0.25 m w.e. yr-1, the value is similar to -0.31 m w.e. yr-1 investigated by stakes and snow pits. Glacier have an elevation change of -0.70 m yr-1 head-ward 500 m from the terminus position along centre line, it approximate to -0.85 m yr-1 measured by RTK-GPS. Otherwise the height difference of zero lies at 5764 m which is close to the average ELA of 5777 m measured by stakes and snow pits. Glacier and climate change interacted with each other. Temperature in western Nyainqentanglha range showed prominent increasing trend from 1964 to 2014, precipitation have increased slowly meanwhile and can not make up the mass loss affected by warming temperature, Glaciers elevation have lowered in recent decades.
Exploration of Uncertainty in Glacier Modelling
NASA Technical Reports Server (NTRS)
Thompson, David E.
1999-01-01
There are procedures and methods for verification of coding algebra and for validations of models and calculations that are in use in the aerospace computational fluid dynamics (CFD) community. These methods would be efficacious if used by the glacier dynamics modelling community. This paper is a presentation of some of those methods, and how they might be applied to uncertainty management supporting code verification and model validation for glacier dynamics. The similarities and differences between their use in CFD analysis and the proposed application of these methods to glacier modelling are discussed. After establishing sources of uncertainty and methods for code verification, the paper looks at a representative sampling of verification and validation efforts that are underway in the glacier modelling community, and establishes a context for these within overall solution quality assessment. Finally, an information architecture and interactive interface is introduced and advocated. This Integrated Cryospheric Exploration (ICE) Environment is proposed for exploring and managing sources of uncertainty in glacier modelling codes and methods, and for supporting scientific numerical exploration and verification. The details and functionality of this Environment are described based on modifications of a system already developed for CFD modelling and analysis.
15. TURNTABLE RECONSTRUCTION BAY & TAYLOR: Photocopy of January ...
15. TURNTABLE RECONSTRUCTION - BAY & TAYLOR: Photocopy of January 1941 photograph taken during reconstruction of the Bay and Taylor turntable. View to the south. The 'spider' that carries the actual turntable is in place in the pit. - San Francisco Cable Railway, Washington & Mason Streets, San Francisco, San Francisco County, CA
NASA Astrophysics Data System (ADS)
Protin, Marie; Schimmelpfennig, Irene; Mugnier, Jean-Louis; Ravanel, Ludovic; Deline, Philip; Le Roy, Melaine; Moreau, Luc; Aster Team
2017-04-01
While reconstruction of glacier fluctuations during the Holocene provides important information about the glacier response to natural climate change, it is still a challenge to accurately constrain chronologies of past glacier advances and retreats. Moraine deposits and roches moutonnées represent valuable geomorphic markers of advanced glacier extensions, while the currently ongoing glacier melt uncovers proglacial bedrock that can be used as a new archive to investigate the durations when a glacier was in retreated position during the Holocene. Our study focuses on the Mont-Blanc massif (MBM), located in the Western Alps and hosting some of the largest glaciers of Europe. Chronologies of Holocene glacier fluctuations in this area are still sparse, even if recent studies considerably improved the temporal reconstruction of Holocene advances of some glaciers in the MBM and locations near-by (e.g. Le Roy et al., 2015). Here we present preliminary 10Be exposure ages obtained from moraine boulders, roches moutonnées and pro- and subglacial bedrock in the area of the Argentière Glacier, located on the north-western flank of the MBM. The ages of moraine boulders and roche moutonnée surfaces outboard of the investigated moraines suggest that the Early Holocene deglaciation of this area started around 11 ka ago. Also, 10Be measurements of recently deglaciated bedrock surfaces indicate that the glacier was at a position at least as retracted as today for a minimum duration of 7 ka throughout the Holocene. The 10Be measurement of one sample from a surface that is currently still covered by 60 m of ice suggests that the glacier was shorter than today for at least a duration of 3 ka. These first results will soon be completed with in situ 14C measurements, which will allow us to quantify and take into account subglacial erosion rates and thus to more accurately determine the cumulative duration of pro- and subglacial bedrock exposure during the Holocene.
Quantifying seasonal velocity at Khumbu Glacier, Nepal
NASA Astrophysics Data System (ADS)
Miles, E.; Quincey, D. J.; Miles, K.; Hubbard, B. P.; Rowan, A. V.
2017-12-01
While the low-gradient debris-covered tongues of many Himalayan glaciers exhibit low surface velocities, quantifying ice flow and its variation through time remains a key challenge for studies aimed at determining the long-term evolution of these glaciers. Recent work has suggested that glaciers in the Everest region of Nepal may show seasonal variability in surface velocity, with ice flow peaking during the summer as monsoon precipitation provides hydrological inputs and thus drives changes in subglacial drainage efficiency. However, satellite and aerial observations of glacier velocity during the monsoon are greatly limited due to cloud cover. Those that do exist do not span the period over which the most dynamic changes occur, and consequently short-term (i.e. daily) changes in flow, as well as the evolution of ice dynamics through the monsoon period, remain poorly understood. In this study, we combine field and remote (satellite image) observations to create a multi-temporal, 3D synthesis of ice deformation rates at Khumbu Glacier, Nepal, focused on the 2017 monsoon period. We first determine net annual and seasonal surface displacements for the whole glacier based on Landsat-8 (OLI) panchromatic data (15m) processed with ImGRAFT. We integrate inclinometer observations from three boreholes drilled by the EverDrill project to determine cumulative deformation at depth, providing a 3D perspective and enabling us to assess the role of basal sliding at each site. We additionally analyze high-frequency on-glacier L1 GNSS data from three sites to characterize variability within surface deformation at sub-seasonal timescales. Finally, each dataset is validated against repeat-dGPS observations at gridded points in the vicinity of the boreholes and GNSS dataloggers. These datasets complement one another to infer thermal regime across the debris-covered ablation area of the glacier, and emphasize the seasonal and spatial variability of ice deformation for glaciers in High
2014-05-16
ISS040-E-000298 (16 May 2014) --- NASA astronaut Steve Swanson, Expedition 40 commander, works with the General Laboratory Active Cryogenic ISS Experiment Refrigerator (GLACIER) in the Destiny laboratory of the International Space Station.
2014-05-16
ISS040-E-000297 (16 May 2014) --- NASA astronaut Steve Swanson, Expedition 40 commander, works with the General Laboratory Active Cryogenic ISS Experiment Refrigerator (GLACIER) in the Destiny laboratory of the International Space Station.
2014-05-16
ISS040-E-000296 (16 May 2014) --- NASA astronaut Steve Swanson, Expedition 40 commander, works with the General Laboratory Active Cryogenic ISS Experiment Refrigerator (GLACIER) in the Destiny laboratory of the International Space Station.
NASA Astrophysics Data System (ADS)
Blankenship, D. D.; Young, D. A.; Siegert, M. J.; van Ommen, T. D.; Roberts, J. L.; Wright, A.; Warner, R. C.; Holt, J. W.; Young, N. W.; Le Meur, E.; Legresy, B.; Cavitte, M.; Icecap Team
2010-12-01
Ice within marine basins of East Antarctica, and their outlets, represent the ultimate limit on sea level change. The region of East Antarctica between the Ross Sea and Wilkes Land hosts a number of major basin, but has been poorly understood. Long range aerogeophysics from US, Australian and French stations, with significant British and IceBridge support, has, under the banner of the ICECAP project, greatly improved our knowledge of ice thickness, surface elevation, and crustal structure of the Wilkes and Aurora Subglacial Basins, as well as the Totten Glacier, Cook Ice Shelf, and Byrd Glacier. We will discuss the evolution of the Wilkes and Aurora Subglacial Basins, new constraints on the geometry of the major outlet glaciers, as well as our results from surface elevation change measurements over dynamic regions of the ice sheet. We will discuss the implications of our data for the presence of mid Pleistocene ice in central East Antarctica. Future directions for ICECAP will be discussed.
Satellite image atlas of glaciers of the world
,
1994-01-01
The world's glaciers react to and interact with changes in global and regional climates. Most mountain glaciers worldwide have been retreating since the latter part of the 19th century; global sea level has risen about 10 centimeters during the past century. Glaciers vary in size as a result of several factors, of which climate variation is probably the most important. The reasons we are interested in glacier variation include its connection to climate change and to global sea level.
NASA Astrophysics Data System (ADS)
Sterzai, P.; Mancini, F.; Corazzato, C.; D Agata, C.; Diolaiuti, G.
2003-04-01
Aiming at reconstructing superficial velocity and volumetric variations of alpine glaciers, SAR interferometry (InSAR) technique is, for the first time in Italy, applied jointly with the glaciological classic field methods. This methodology with its quantitative results provides, together with other space geodesy techniques like GPS, some fundamental elements for the estimation of the climate forcing and the evaluation of the future glacier trend. InSAR is usually applied to antarctic glaciers and to other wide extralpine glaciers, detectable by the SAR orbits; in the Italian Alps, the limited surface area of the glaciers and the deformation of radar images due to strong relief effect, reduce the applicability of this tecnique. The chosen glacier is suitable for this kind of study both for its large size and for the many field data collected and available for the interferometric results validation. Forni Glacier is the largest valley glacier in the Italian Alps and represents a good example of long term monitoring of a valley glacier in the Central Alps. It is a north facing valley glacier formed by 3 ice streams, located in Italian Lombardy Alps (46 23 50 N, 10 35 00 E). In 2002 its area was approximately 13 km2, extending from 2500 to 3684 m a.s.l., with a maximum width of approximately 7500 m and a maximum length of about 5000 m. Available data include mass-balance measurements on the glacier tongue (from the hydrological year 1992-1993 up to now), frontal variations data from 1925 up to now, topographical profiling by means of GPS techniques and profiles of the glacier bed by geoelectrical surveys (VES) (Guglielmin et alii, 1995) and by seismic surveys (Merlanti et alii, 2001). In order to apply radar interferometry on this glacier eight ERS SAR RAW images have been purchased, in addition to the Digital Elevation Model from IGM (Geographic Military Institute), and repeat pass interferometry used. Combining the different passes, differential interferograms are
Linear stability of compressible Taylor-Couette flow
NASA Technical Reports Server (NTRS)
Kao, Kai-Hsiung; Chow, Chuen-Yen
1992-01-01
A temporal stability analysis of compressible Taylor-Couette flow is presented. The viscous flow studied in this paper is contained between two concentric cylinders of infinite length, which are rotating with different angular velocities and are kept at different surface temperatures. The effects of differential rotation and temperature difference on the stability of Taylor-Couette flow are contrasted for a range of Mach numbers ranging from incompressible to Mach 3.0. The relative motion of the cylinders dramatically affects the characteristics of the Couette flow at the onset of instability. The flow is stabilized or destabilized depending upon the temperature ratio and speeds of the two cylinders. Independent of Mach number and temperature ratio, increasing Reynolds number generally promotes a destabilizing effect, indicating the inviscid nature of the Taylor-Couette flow.
NASA Astrophysics Data System (ADS)
O'Neel, S.; Pfeffer, W. T.; Howat, I. M.; Conway, H.; Columbia Glacier Consortium
2010-12-01
Since fulfilling Austin Post’s prediction of impending retreat in the late 1970s, Columbia Glacier has repeatedly surprised both casual and careful observers with its ability for rapid change. Over the last three decades, Columbia Glacier has lost approximately 18 km of its original 66 km length, while thinning by approximately 50% at the present terminus. The total ice volume lost to the Gulf of Alaska Estimates upwards of 120 km3 constrain the total ice volume lost to the Gulf of Alaska. Recently, the terminus supported a ~1.5 km long floating tongue for over than a year, contradicting the common assumption that the mechanical properties of temperate ice prohibit flotation over sustained time intervals. The rich history of study offers an opportunity to better understand tidewater glacier retreat, and a valuable analog to the dynamic instability underway at several ice sheet outlet glaciers. Current research aims to improve processing resolution of existing aerial photographic data, while complimenting the 30-year photogrammetric record with a suite of field observations. Recent instrumentation includes: oblique time lapse and still imagery, semi-permanent GPS, airborne radar, mass balance, passive seismology and LiDAR. This presentation will focus on innovative methods developed in recent field seasons, sharing insight each has provided into the retreat process . 1The Columbia Glacier Consortium consists of: Fabian Walter (SIO), Kenichi Matsuoka (NPI), Ben Smith (UW), Ethan Welty (CU-Boulder), Chris Larsen (UAF), Dave Finnegan (CRREL), Dan McNamara (USGS), Yushin Ahn (OSU), Julie Markus (OSU), Adam LeWinter (EIS).
Glacier shrinkage driving global changes in downstream systems.
Milner, Alexander M; Khamis, Kieran; Battin, Tom J; Brittain, John E; Barrand, Nicholas E; Füreder, Leopold; Cauvy-Fraunié, Sophie; Gíslason, Gísli Már; Jacobsen, Dean; Hannah, David M; Hodson, Andrew J; Hood, Eran; Lencioni, Valeria; Ólafsson, Jón S; Robinson, Christopher T; Tranter, Martyn; Brown, Lee E
2017-09-12
Glaciers cover ∼10% of the Earth's land surface, but they are shrinking rapidly across most parts of the world, leading to cascading impacts on downstream systems. Glaciers impart unique footprints on river flow at times when other water sources are low. Changes in river hydrology and morphology caused by climate-induced glacier loss are projected to be the greatest of any hydrological system, with major implications for riverine and near-shore marine environments. Here, we synthesize current evidence of how glacier shrinkage will alter hydrological regimes, sediment transport, and biogeochemical and contaminant fluxes from rivers to oceans. This will profoundly influence the natural environment, including many facets of biodiversity, and the ecosystem services that glacier-fed rivers provide to humans, particularly provision of water for agriculture, hydropower, and consumption. We conclude that human society must plan adaptation and mitigation measures for the full breadth of impacts in all affected regions caused by glacier shrinkage.
Glacier shrinkage driving global changes in downstream systems
Khamis, Kieran; Battin, Tom J.; Brittain, John E.; Barrand, Nicholas E.; Füreder, Leopold; Cauvy-Fraunié, Sophie; Gíslason, Gísli Már; Jacobsen, Dean; Hannah, David M.; Hodson, Andrew J.; Hood, Eran; Lencioni, Valeria; Ólafsson, Jón S.; Robinson, Christopher T.; Tranter, Martyn; Brown, Lee E.
2017-01-01
Glaciers cover ∼10% of the Earth’s land surface, but they are shrinking rapidly across most parts of the world, leading to cascading impacts on downstream systems. Glaciers impart unique footprints on river flow at times when other water sources are low. Changes in river hydrology and morphology caused by climate-induced glacier loss are projected to be the greatest of any hydrological system, with major implications for riverine and near-shore marine environments. Here, we synthesize current evidence of how glacier shrinkage will alter hydrological regimes, sediment transport, and biogeochemical and contaminant fluxes from rivers to oceans. This will profoundly influence the natural environment, including many facets of biodiversity, and the ecosystem services that glacier-fed rivers provide to humans, particularly provision of water for agriculture, hydropower, and consumption. We conclude that human society must plan adaptation and mitigation measures for the full breadth of impacts in all affected regions caused by glacier shrinkage. PMID:28874558
Glaciers along proposed routes extending the Copper River Highway, Alaska
Glass, R.L.
1996-01-01
Three inland highway routes are being considered by the Alaska Department of Transportation and Public Facilities to connect the community of Cordova in southcentral Alaska to a statewide road system. The routes use part of a Copper River and Northwest Railway alignment along the Copper River through mountainous terrain having numerous glaciers. An advance of any of several glaciers could block and destroy the roadway, whereas retreating glaciers expose large quantities of unconsolidated, unvegetated, and commonly ice-rich sediments. The purpose of this study was to map historical locations of glacier termini near these routes and to describe hazards associated with glaciers and seasonal snow. Historical and recent locations of glacier termini along the proposed Copper River Highway routes were determined by reviewing reports and maps and by interpreting aerial photographs. The termini of Childs, Grinnell, Tasnuna, and Woodworth Glaciers were 1 mile or less from a proposed route in the most recently available aerial photography (1978-91); the termini of Allen, Heney, and Schwan Glaciers were 1.5 miles or less from a proposed route. In general, since 1911, most glaciers have slowly retreated, but many glaciers have had occasional advances. Deserted Glacier and one of its tributary glaciers have surge-type medial moraines, indicating potential rapid advances. The terminus of Deserted Glacier was about 2.1 miles from a proposed route in 1978, but showed no evidence of surging. Snow and rock avalanches and snowdrifts are common along the proposed routes and will periodically obstruct the roadway. Floods from ice-dammed lakes also pose a threat. For example, Van Cleve Lake, adjacent to Miles Glacier, is as large as 4.4 square miles and empties about every 6 years. Floods from drainages of Van Cleve Lake have caused the Copper River to rise on the order of 20 feet at Million Dollar Bridge.
LePain, David L.; Stanley, Richard G.
2015-01-01
The Alaska Division of Geological & Geophysical Surveys (DGGS) and U.S. Geological Survey (USGS) are implementing ongoing programs to characterize the petroleum potential of Cook Inlet basin. Since 2009 this program has included work on the Mesozoic stratigraphy of lower Cook Inlet, including the Middle Jurassic Tuxedni Group between Tuxedni and Iniskin bays (LePain and others, 2013; Stanley and others, 2013; fig. 5-1). The basal unit in the group, the Red Glacier Formation (fig. 5-2), is thought to be the principal source rock for oil produced in upper Cook Inlet, and available geochemical data support this contention (Magoon and Anders, 1992; Magoon, 1994). Despite its economic significance very little has been published on the formation since Detterman and Hartsock’s (1966) seminal contribution on the geology of the Iniskin–Tuxedni area nearly 50 years ago. Consequently its stratigraphy, contact relations with bounding formations, and source rock characteristics are poorly known. During the 2014 field season, a nearly continuous stratigraphic section through the Red Glacier Formation in its type area at Red Glacier was located and measured to characterize sedimentary facies and to collect a suite of samples for analyses of biostratigraphy, Rock-Eval pyrolysis, vitrinite reflectance, and sandstone composition (fig. 5-3).The poorly known nature of the Red Glacier Formation is likely due to its remote location, steep terrain, and the fact that the type section is split into two segments that are more than 3 km apart. The lower 375 m segment of the formation is on the ridge between Red Glacier and Lateral Glacier and the upper 1,009 m segment is on the ridge between Red Glacier and Boulder Creek (fig. 5-3). Structural complications in the area add to the difficulty in understanding how these two segments fit together.
New Aerogeophysical exploration of the Gamburtsev Province (East Antarctica)
NASA Astrophysics Data System (ADS)
Ferraccioli, F.; Bell, R. E.; Studinger, M.; Damaske, D.; Jordan, T. A.; Corr, H.; Braaten, D. A.; Gogineni, P. S.; Fahnestock, M. A.; Finn, C.; Rose, K.
2009-12-01
The enigmatic Gamburstev Subglacial Mountains (GSM) in the interior of East Antarctica, have remained the least understood mountain range on earth, since their discovery some 50 years ago. An improved knowledge of the GSM region is however essential to underpin reconstructions of the Antarctic cryosphere and climate evolution. The GSM are a key nucleation site for the inception of the East Antarctic Ice Sheet approximately 34 Ma ago, and the adjacent Lambert Glacier played a pivotal role for ice sheet dynamics throughout the Neogene (23-0 Ma). The GSM province may also provide tectonic controls for major subglacial lakes flanking the range. In addition, the ice encasing the GSM province has been inferred to contain the oldest detailed climate record of the planet, a prime target for future deep ice core drilling. With the overarching aim of accomplishing the first systematic study of the cryosphere and lithosphere of the GSM province we launched a new geophysical exploration effort- AGAP (Antarctica’s Gamburtsev Province)-, a flagship programme of the International Polar Year. The aerogeophysical and seismology components of AGAP were accomplished by pooling resources from 7 nations. We deployed 2 Twin Otters, equipped with state-of-the art geophysical instrumentation and operating from two remote field camps on either side of Dome A. Over 120,000 line-km of new airborne radar, laser, aerogravity and aeromagnetic data survey were collected during the 2008/09 field campaign. Our grids of ice surface, ice thickness, subglacial topography, and gravity and magnetic anomalies provide a new geophysical foundation to analyse the GSM province, from the surface of the East Antarctic Ice Sheet down to mantle depths beneath the Precambrian shield. The anomalously high-elevation, alpine-type landscape of the GSM is now mapped with unprecedented detail. Two distinct branches of a subglacial rift system are imaged along the north-western and north-eastern margins of the
SEISMIC ANISOTROPY ANALYSIS IN THE VICTORIA LAND REGION (ANTARCTICA)
NASA Astrophysics Data System (ADS)
Salimbeni, S.; Pondrelli, S.; Danesi, S.; Morelli, A.
2009-12-01
We present here shear wave splitting results obtained from analysis of core refracted teleseismic phases in the Victoria Land region (Antarctica). We used data belonging to permanent and temporary stations in the area. The temporary stations are located around the David Glaciers and installation is part of two expeditions inside the Italian National Antarctic program (PNRA, Programma Nazionale di Ricerche in Antartide). The network was composed by 8 seismic stations, located on rocky outcrops around the glacier, and has been active from November 2003 to February 2004, and from November 2005 to February 2006. One of this (STAR) became permanent on 2004 and data until 2007 are analyzed. We use eigenvalue technique of Silver and Chan (1991) to linearize the rotated and shifted shear wave particle motions and determine the best splitting parameters. Scattered distribution of single shear-wave measurements is obtained. Null measurements follow the same distribution. Average measurements show clearly that the main anisotropy direction is NE-SW, accordingly with previous measurements obtained around this zone. Only two stations, OHG and STAR, have a different orientation and a N-S and NNW-SSE main directions are obtained respectively. The distribution of single shear-wave splitting measurements evidenced periodicity respect the back-azimuth of the events analyzed, therefore a possible two layers anisotropic structures could be supposed. To test this hypothesis we used the Menke and Levin (2003) code that allow to model waveforms using a cross convolution technique in one and two layer's cases. Significant improvements of the misfit in the double layer case allow choosing this more complex model. The one layer structure is the best for permanent stations TNV and VNDA with directions and delay time accordingly with average measurements. The double layer models fit better the data on stations STAR, located near the coast, and OHG located inland, and show in both cases the
NASA Technical Reports Server (NTRS)
Luthcke, Scott B.; Sabaka, T. J.; Loomis, B. D.; Arendt, A. A.; McCarthy, J. J.; Camp, J.
2013-01-01
We have determined the ice mass evolution of the Antarctica and Greenland ice sheets (AIS and GIS) and Gulf of Alaska (GOA) glaciers from a new GRACE global solution of equal-area surface mass concentration parcels (mascons) in equivalent height of water. The mascons were estimated directly from the reduction of the inter-satellite K-band range-rate (KBRR) observations, taking into account the full noise covariance, and formally iterating the solution. The new solution increases signal recovery while reducing the GRACE KBRR observation residuals. The mascons were estimated with 10 day and 1 arc degree equal-area sampling, applying anisotropic constraints. An ensemble empirical mode decomposition adaptive filter was applied to the mascon time series to compute annual mass balances. The details and causes of the spatial and temporal variability of the land-ice regions studied are discussed. The estimated mass trend over the total GIS, AIS and GOA glaciers for the time period 1 December 2003 to 1 December 2010 is -380 plus or minus 31 Gt a(exp -1), equivalent to -1.05 plus or minus 0.09 mma(exp -1) sea-level rise. Over the same time period we estimate the mass acceleration to be -41 plus or minus 27 Gt a(exp -2), equivalent to a 0.11 plus or minus 0.08 mm a(exp -2) rate of change in sea level. The trends and accelerations are dependent on significant seasonal and annual balance anomalies.
NASA Technical Reports Server (NTRS)
Luthcke, Scott B.; Sabaka, T. J.; Loomis, B. D.; Arendt, A. A.; McCarthy, J. J.; Camp, J.
2013-01-01
We have determined the ice mass evolution of the Antarctica and Greenland ice sheets (AIS and GIS) and Gulf of Alaska (GOA) glaciers from a new GRACE global solution of equal-area surface mass concentration parcels (mascons) in equivalent height of water. The mascons were estimated directly from the reduction of the inter-satellite K-band range-rate (KBRR) observations, taking into account the full noise covariance, and formally iterating the solution. The new solution increases signal recovery while reducing the GRACE KBRR observation residuals. The mascons were estimated with 10 day and 1 arc degree equal-area sampling, applying anisotropic constraints. An ensemble empirical mode decomposition adaptive filter was applied to the mascon time series to compute annual mass balances. The details and causes of the spatial and temporal variability of the land-ice regions studied are discussed. The estimated mass trend over the total GIS, AIS and GOA glaciers for the time period 1 December 2003 to 1 December 2010 is -380 plus or minus 31 Gt a(exp -1), equivalent to -1.05 plus or minus 0.09 mma(exp -1) sea-level rise. Over the same time period we estimate the mass acceleration to be -41 plus or minus 27 Gt a(exp -2), equivalent to a 0.11 plus or minus 0.08 mm a(exp -2) rate of change in sea level. The trends and accelerations are dependent on significant seasonal and annual balance anomalies.
Extending Glacier Monitoring into the Little Ice Age and Beyond
NASA Astrophysics Data System (ADS)
Nussbaumer, S. U.; Gärtner-Roer, I.; Zemp, M.; Zumbühl, H. J.; Masiokas, M. H.; Espizua, L. E.; Pitte, P.
2011-12-01
Glaciers are among the best natural proxies of climatic changes and, as such, a key variable within the international climate observing system. The worldwide monitoring of glacier distribution and fluctuations has been internationally coordinated for more than a century. Direct measurements of seasonal and annual glacier mass balance are available for the past six decades. Regular observations of glacier front variations have been carried out since the late 19th century. Information on glacier fluctuations before the onset of regular in situ measurements have to be reconstructed from moraines, historical evidence, and a wide range of dating methods. The majority of corresponding data is not available to the scientific community which challenges the reproducibility and direct comparison of the results. Here, we present a first approach towards the standardization of reconstructed Holocene glacier front variations as well as the integration of the corresponding data series into the database of the World Glacier Monitoring Service (www.wgms.ch), within the framework of the Global Terrestrial Network for Glaciers (www.gtn-g.org). The concept for the integration of these reconstructed front variations into the relational glacier database of the WGMS was jointly elaborated and tested by experts of both fields (natural and historical sciences), based on reconstruction series of 15 glaciers in Europe (western/central Alps and southern Norway) and 9 in southern South America. The reconstructed front variation series extend the direct measurements of the 20th century by two centuries in Norway and by four in the Alps and in South America. The storage of the records within the international glacier databases guarantees the long-term availability of the data series and increases the visibility of the scientific research which - in historical glaciology - is often the work of a lifetime. The standardized collection of reconstructed glacier front variations from southern Norway
Planetary science: are there active glaciers on Mars?
Gillespie, Alan R; Montgomery, David R; Mushkin, Amit
2005-12-08
Head et al. interpret spectacular images from the Mars Express high-resolution stereo camera as evidence of geologically recent rock glaciers in Tharsis and of a piedmont ('hourglass') glacier at the base of a 3-km-high massif east of Hellas. They attribute growth of the low-latitude glaciers to snowfall during periods of increased spin-axis obliquity. The age of the hourglass glacier, considered to be inactive and slowly shrinking beneath a debris cover in the absence of modern snowfall, is estimated to be more than 40 Myr. Although we agree that the maximum glacier extent was climatically controlled, we find evidence in the images to support local augmentation of accumulation from snowfall through a mechanism that does not require climate change on Mars.
Fisheries Aspects of Seamounts and Taylor Columns
1986-09-01
the armorhead population. Due to a probable combination of overfishing and poor recruitment, the large fishery of the early 1970’s began a rapid...ACCESSION NO T I TLE (include Security Classification) FISHERIES ASPECTS OF SEAMOUNTS AND TAYLOR COLUMNS 2 PERSONAL AUTHOR(S) Brainard, Russell E. 13a...retention Seamount oceanography Taylor column Fisheries Nutrient enrichment 3ASTRACT (Continue on reverse of necessary and identify by block number
Marra, Kristen R.; Elwood Madden, Megan E; Soreghan, Gerilyn S.; Hall, Brenda L
2014-01-01
BET surface area values are critical for quantifying the amount of potentially reactive sediments available for chemical weathering and ultimately, prediction of silicate weathering fluxes. BET surface area values of fine-grained (<62.5 μm) sediment from the hyporheic zone of polar glacial streams in the McMurdo Dry Valleys, Antarctica (Wright and Taylor Valleys) exhibit a wide range (2.5–70.6 m2/g) of surface area values. Samples from one (Delta Stream, Taylor Valley) of the four sampled stream transects exhibit high values (up to 70.6 m2/g), which greatly exceed surface area values from three temperate proglacial streams (0.3–12.1 m2/g). Only Clark stream in Wright Valley exhibits a robust trend with distance, wherein surface area systematically decreases (and particle size increases) in the mud fraction downstream, interpreted to reflect rapid dissolution processes in the weathering environment. The remaining transects exhibit a range in variability in surface area distributions along the length of the channel, likely related to variations in eolian input to exposed channel beds, adjacent snow drifts, and to glacier surfaces, where dust is trapped and subsequently liberated during summer melting. Additionally, variations in stream discharge rate, which mobilizes sediment in pulses and influences water:rock ratios, the origin and nature of the underlying drift material, and the contribution of organic acids may play significant roles in the production and mobilization of high-surface area sediment. This study highlights the presence of sediments with high surface area in cold-based glacier systems, which influences models of chemical denudation rates and the impact of glacial systems on the global carbon cycle.
Microbial activity in debris-rich basal ice; adaption to sub-zero, saline conditions
NASA Astrophysics Data System (ADS)
Montross, S. N.; Skidmore, M. L.; Christner, B. C.; Griggs, R.; Tison, J.; Sowers, T. A.
2011-12-01
Polycrystalline ice in glaciers and ice sheets has a high preservation potential for biological material and chemical compounds that can be used to document the presence of active microbial metabolism at sub-zero temperatures. The concentration and isotopic composition of gases, in conjunction with other aqueous chemical species in debris-rich basal glacier ice from Taylor Glacier, Antarctica were used as direct evidence that cells entrained in the ice remain metabolically active at temperatures as low as -17°C, likely in thin films of liquid water along ice crystal and mineral grain boundaries. δ18O2 and δ13CO2 values measured in the ice are consistent with the hypothesis that abrupt changes measured in O2 and CO2 concentrations between debris-rich and debris-poor ice are due to in situ microbial mineralization of organic carbon. Low temperature culture-based experiments conducted using organisms isolated from the ice indicate the ability to respire organic carbon to CO2 under oxic conditions and under anoxic conditions couple carbon mineralization to dissimilatory iron reduction using Fe3+ as an electron acceptor. Microorganisms that are active in the debris-rich basal ice layers in terrestrial polar ice masses need to be adapted to surviving subzero temperatures and saline conditions on extended timescales. Thus these terrestrial glacial systems and the isotopic and geochemical biomarkers therein provide good analogues for guiding exploration and analysis of debris-rich ices in extraterrestrial settings, for example, on Mars.
Bright and durable field emission source derived from refractory taylor cones
DOE Office of Scientific and Technical Information (OSTI.GOV)
Hirsch, Gregory
A method of producing field emitters having improved brightness and durability relying on the creation of a liquid Taylor cone from electrically conductive materials having high melting points. The method calls for melting the end of a wire substrate with a focused laser beam, while imposing a high positive potential on the material. The resulting molten Taylor cone is subsequently rapidly quenched by cessation of the laser power. Rapid quenching is facilitated in large part by radiative cooling, resulting in structures having characteristics closely matching that of the original liquid Taylor cone. Frozen Taylor cones thus obtained yield desirable tipmore » end forms for field emission sources in electron beam applications. Regeneration of the frozen Taylor cones in-situ is readily accomplished by repeating the initial formation procedures. The high temperature liquid Taylor cones can also be employed as bright ion sources with chemical elements previously considered impractical to implement.« less
Glacierized headwater streams as aquifer recharge corridors, subarctic Alaska
Lilledahl, Anna K.; Gadeke, Anne; O'Neel, Shad; Gatesman, T. A.; Douglas, T. A.
2017-01-01
Arctic river discharge has increased in recent decades although sources and mechanisms remain debated. Abundant literature documents permafrost thaw and mountain glacier shrinkage over the past decades. Here we link glacier runoff to aquifer recharge via a losing headwater stream in subarctic Interior Alaska. Field measurements in Jarvis Creek (634 km2), a subbasin of the Tanana and Yukon Rivers, show glacier meltwater runoff as a large component (15–28%) of total annual streamflow despite low glacier cover (3%). About half of annual headwater streamflow is lost to the aquifer (38 to 56%). The estimated long-term change in glacier-derived aquifer recharge exceeds the observed increase in Tanana River base flow. Our findings suggest a linkage between glacier wastage, aquifer recharge along the headwater stream corridor, and lowland winter discharge. Accordingly, glacierized headwater streambeds may serve as major aquifer recharge zones in semiarid climates and therefore contributing to year-round base flow of lowland rivers.
NASA Astrophysics Data System (ADS)
Jackson, Margaret S.; Hall, Brenda L.; Denton, George H.
2018-01-01
The stability of the Antarctic Ice Sheet under future warming remains an open question with broad implications for sea-level prediction and adaptation. In particular, knowledge of whether the ice sheet has the capacity for rapid drawdown or collapse, or whether it can remain stable during periods of warming, is essential for predicting its future behavior. Here we use 55 radiocarbon dates, coupled with geomorphologic mapping, to reconstruct the timing of changes in ice extent and elevation during the last ice-age termination in Salmon Valley, adjacent to McMurdo Sound in the western Ross Sea Embayment. Results indicate that a grounded ice sheet in the Ross Sea Embayment achieved its maximum elevation and extent along the headlands of Salmon Valley at ∼18,000 yr BP, during a period of increasing temperatures and accumulation over the Antarctic continent. This ice remained at or near its maximum on the headlands near the valley mouth until after ∼14,000 yr BP. Removal of grounded Ross Sea ice from Salmon Valley was complete shortly after ∼7900 yr BP, indicating that the grounding line had retreated through southern McMurdo Sound by that time. We suggest the primary driver of Ross Sea ice removal from McMurdo Sound was marine-based, either through basal melting or calving due to sea-level rise. When combined with regional data, the Salmon Valley record suggests that this sector of the Antarctic Ice Sheet did not contribute in a significant way to deglacial meltwater pulses, such as meltwater pulse 1a. In contrast to the Ross Sea ice, our work also shows that local, independent alpine glaciers in Salmon Valley have advanced through the Holocene. Land-terminating glaciers such as these elsewhere in the region show a similar pattern, and may reflect the continued influence of increased accumulation following the termination of the last ice age.
NASA Astrophysics Data System (ADS)
Ciraci, E.; Velicogna, I.; Fettweis, X.; van den Broeke, M. R.
2016-12-01
The Arctic hosts more than the 75% of the ice covered regions outside from Greenland and Antarctica. Available observations show that increased atmospheric temperatures during the last century have contributed to a substantial glaciers retreat in all these regions. We use satellite gravimetry by the NASA's Gravity Recovery and Climate Experiment (GRACE), and apply a least square fit mascon approach to calculate time series of ice mass change for the period 2002-2016. Our estimates show that arctic glaciers have constantly contributed to the sea level rise during the entire observation period with a mass change of -170+/-20 Gt/yr equivalent to the 80% of the total ice mass change from the world Glacier and Ice Caps (GIC) excluding the Ice sheet peripheral GIC, which we calculated to be -215+/-32 GT/yr, with an acceleration of 9+/-4 Gt/yr2. The Canadian Archipelago is the main contributor to the total mass depletion with an ice mass trend of -73+/-9 Gt/yr and a significant acceleration of -7+/-3 Gt/yr2. The increasing mass loss is mainly determined by melting glaciers located in the northern part of the archipelago.In order to investigate the physical processes driving the observed ice mass loss we employ satellite altimetry and surface mass balance (SMB) estimates from Regional climate model outputs available for the same time period covered by the gravimetry data. We use elevation data from the NASA ICESat (2003-2009) and ESA CryoSat-2 (2010-2016) missions to estimate ice elevation changes. We compare GRACE ice mass estimates with time series of surface mass balance from the Regional Climate Model (RACMO-2) and the Modèle Atmosphérique Régional (MAR) and determine the portion of the total mass change explained by the SMB signal. We find that in Iceland and in the and the Canadian Archipelago the SMB signal explains most of the observed mass changes, suggesting that ice discharge may play a secondary role here. In other region, e.g. in Svalbar, the SMB signal
Sensitivity and Response of Bhutanese Glaciers to Atmospheric Warming
NASA Technical Reports Server (NTRS)
Rupper, Summer; Schaefer, Joerg M.; Burgener, Landon K.; Koenig, Lora S.; Tsering, Karma; Cook, Edward
2013-01-01
Glacierized change in the Himalayas affects river-discharge, hydro-energy and agricultural production, and Glacial Lake Outburst Flood potential, but its quantification and extent of impacts remains highly uncertain. Here we present conservative, comprehensive and quantitative predictions for glacier area and meltwater flux changes in Bhutan, monsoonal Himalayas. In particular, we quantify the uncertainties associated with the glacier area and meltwater flux changes due to uncertainty in climate data, a critical problem for much of High Asia. Based on a suite of gridded climate data and a robust glacier melt model, our results show that glacier area and meltwater change projections can vary by an order of magnitude for different climate datasets. However, the most conservative results indicate that, even if climate were to remain at the present-day mean values, almost 10% of Bhutan s glacierized area would vanish and the meltwater flux would drop by as much as 30%. Under the conservative scenario of an additional 1 C regional warming, glacier retreat is going to continue until about 25% of Bhutan s glacierized area will have disappeared and the annual meltwater flux, after an initial spike, would drop by as much as 65%. Citation
NASA Astrophysics Data System (ADS)
Iturrizaga, Lasafam; Charrier, Reynaldo
2013-04-01
Throughout the Andes Mountain range of South America a general trend of glacier shrinkage has taken place in the last century. Only a few glaciers have shown a rather non-continuous trend of glacier retreat and temporally advanced or even surged during the mid-19th to 20th century. One of the earliest assumed glacier surges has occurred in the upper Cachapoal catchment area at the homonymous glacier. In climatic respect the Cachapoal glacier is located in the transition zone from the most southern part of the Dry Central Andes of Chile to the more humid zone of the Wet Andes. The region is affected mainly by winter precipitation deriving from the Westerlies. The debris-covered, 12 km-long Cachapoal glacier represents one of the largest valley glaciers in the Central Andes. It is an avalanche-fed glacier with an almost 1500 m-high head wall in its upper catchment area flowing down from Picos del Barroso (5180 m) and terminates at an elevation of 2630 m a.s.l. with a bifurcated glacier tongue. A large moraine complex, almost 2 km in length and 500 m in width, separates the two glacier lobes. During times of advanced glacier tongue positions the Ríos Molina and Cachapoal may be have blocked independently at two distinct localities which are situated about 2300 m apart from each other. A blockage with temporal lake formation has occurred at least in the years 1848, 1955 and 1981 (cf. Plagemann 1887, Peña 1981), from which the rupture of the earliest glacier barrier has been the most devastating. This event is locally reminded as "la gran avenida en seco" in the historical record. Geomorphological evidence of the past historical and modern glacier expansions is given in the proglacial area by a fresh dead-ice hummocky topography and glacial trimlines at the valley flanks. More down valley broad outwash plains and boulder clusters indicate past high energy floods produced by glacier lake outbursts. Regarding the small size of the catchment area of the Río Molina
NASA Astrophysics Data System (ADS)
Mikucki, J.; Tulaczyk, S. M.; Purcell, A. M.; Dachwald, B.; Lyons, W. B.; Welch, K. A.; Auken, E.; Dugan, H. A.; Walter, J. I.; Pettit, E. C.; Doran, P. T.; Virginia, R. A.; Schamper, C.; Foley, N.; Feldmann, M.; Espe, C.; Ghosh, D.; Francke, G.
2015-12-01
Subglacial waters tend to accumulate solutes from extensive rock-water interactions, which, when released to the surface, can provide nutrients to surface ecosystems providing a 'hot spot' for microbial communities. Blood Falls, an iron-rich, saline feature at the terminus of Taylor Glacier in the McMurdo Dry Valleys, Antarctica is a well-studied subglacial discharge. Here we present an overview of geophysical surveys, thermomechanical drilling exploration and geomicrobiological analyses of the Blood Falls system. A helicopter-borne transient electromagnetic system (SkyTEM) flown over the Taylor Glacier revealed a surprisingly extensive subglacial aquifer and indicates that Blood Falls may be the only surface manifestation of this extensive briny groundwater. Ground-based temperature sensing and GPR data combined with the helicopter-borne TEM data enabled targeted drilling into the englacial conduit that delivers brine to the surface. During the 2014-15 austral summer field season, we used a novel ice-melting drill (the IceMole) to collect englacial brine for geomicrobiological analyses. Results from previously collected outflow and more recent samples indicate that the brine harbors a metabolically active microbial community that persists, despite cold, dark isolation. Isotope geochemistry and molecular analysis of functional genes from BF suggested that a catalytic or 'cryptic' sulfur cycle was linked to iron reduction. Recent metagenomic analysis confirms the presence of numerous genes involved in oxidative and reductive sulfur transformations. Metagenomic and metabolic activity data also indicate that subglacial dark CO2 fixation occurs via various pathways. Genes encoding key steps in CO2 fixation pathways including the Calvin Benson Basham and Wood Ljungdahl pathway were present and brine samples showed measureable uptake of 14C-labeled bicarbonate. These results support the notion that, like the deep subsurface, subglacial environments are chemosynthetic
Mountain glaciers caught on camera
NASA Astrophysics Data System (ADS)
Balcerak, Ernie
2011-12-01
Many glaciers around the world are melting, and new research is showing some of the dramatic details. Ulyana Horodyskyj, a graduate student at the Cooperative Institute for Research in Environmental Sciences (CIRES), University of Colorado at Boulder, set up cameras to take time-lapse photographs of three lakes on a glacier in Nepal. This allowed her and her colleagues to see the supraglacial lake drain in real time for the first time, making it possible to estimate how much water was involved and how long it took for the lake to drain and refill. Horodyskyj said in a press conference at the AGU Fall Meeting that such observations of supraglacial lakes are valuable because in a warming climate, melting glaciers can lead to formation of supraglacial lakes.
Small Glacier Area Studies: A New Approach for Turkey
NASA Technical Reports Server (NTRS)
Yavasli, Dogukan D.; Tucker, Compton J.
2012-01-01
Many regions of Earth have glaciers that have been neglected for study because they are small. We report on a new approach to overcome the problem of studying small glaciers, using Turkey as an example. Prior to our study, no reliable estimates of Turkish glaciers existed because of a lack of systematic mapping, difficulty in using Landsat data collected before 1982, snowpack vs. glacier ice differentiation using existing satellite data and aerial photography, the previous high cost of Landsat images, and a lack of high-resolution imagery of small Turkish glaciers. Since 2008, a large number of < 1 m satellite images have become available at no cost to the research community. In addition, Landsat data are now free of charge from the U.S. Geological Survey, enabling the use of multiple images. We used 174 Landsat and eight high-resolution satellite images to document the areal extent of Turkish glaciers from the 1970s to 2007-2011. Multiple Landsat images, primarily Thematic Mapper (TM) data from 1984 to 2011, enabled us to minimize differentiation problems between snow and glacier ice, a potential source of error. In addition, we used Ikonos, Quickbird, and World View-1 & -2 very high-resolution imagery to evaluate our TM accuracies and determine the area of nine smaller glaciers in Turkey. We also used five Landsat-3 Return Beam Videcon (RBV) 30 m pixel resolution images, all from 1980, for six glaciers. The total area of Turkish glaciers decreased from 23 km2 in the 1970s to 10.1 km2 in 2007-2011. By 2007-2011, six Turkish glaciers disappeared, four were < 0.3 km2, and only three were 1.0 km2 or larger. No trends in precipitation from 1970 to 2006 and cloud cover from 1980 to 2010 were found, while surface temperatures increased, with summer minimum temperatures showing the greatest increase. We conclude that increased surface temperatures during the summer were responsible for the 56% recession of Turkish glaciers from the 1970s to 2006-2011.
NASA Astrophysics Data System (ADS)
Bohleber, Pascal; Hoffmann, Helene; Kerch, Johanna; Sold, Leo; Fischer, Andrea
2018-01-01
Cold glaciers at the highest locations of the European Alps have been investigated by drilling ice cores to retrieve their stratigraphic climate records. Findings like the Oetztal ice man have demonstrated that small ice bodies at summit locations of comparatively lower altitudes may also contain old ice if locally frozen to the underlying bedrock. In this case, constraining the maximum age of their lowermost ice part may help to identify past periods with minimum ice extent in the Alps. However, with recent warming and consequent glacier mass loss, these sites may not preserve their unique climate information for much longer. Here we utilized an existing ice cave at Chli Titlis (3030 m), central Switzerland, to perform a case study for investigating the maximum age of cold-based summit glaciers in the Alps. The cave offers direct access to the glacier stratigraphy without the logistical effort required in ice core drilling. In addition, a pioneering exploration had already demonstrated stagnant cold ice conditions at Chli Titlis, albeit more than 25 years ago. Our englacial temperature measurements and the analysis of the isotopic and physical properties of ice blocks sampled at three locations within the ice cave show that cold ice still exists fairly unchanged today. State-of-the-art micro-radiocarbon analysis constrains the maximum age of the ice at Chli Titlis to about 5000 years before present. By this means, the approach presented here will contribute to a future systematic investigation of cold-based summit glaciers, also in the Eastern Alps.
Glacier Changes in the Russian High Arctic.
NASA Astrophysics Data System (ADS)
Pritchard, M. E.; Willis, M. J.; Melkonian, A. K.; Golos, E. M.; Stewart, A.; Ornelas, G.; Ramage, J. M.
2014-12-01
We provide new surveys of ice speeds and surface elevation changes for ~40,000 km2 of glaciers and ice caps at the Novaya Zemlya (NovZ) and Severnaya Zemlya (SevZ) Archipelagoes in the Russian High Arctic. The contribution to sea level rise from this ice is expected to increase as the region continues to warm at above average rates. We derive ice speeds using pixel-tracking on radar and optical imagery, with additional information from InSAR. Ice speeds have generally increased at outlet glaciers compared to those measured using interferometry from the mid-1990s'. The most pronounced acceleration is at Inostrantseva Glacier, one of the northernmost glaciers draining into the Barents Sea on NovZ. Thinning rates over the last few decades are derived by regressing stacked elevations from multiple Digital Elevations Models (DEMs) sourced from ASTER and Worldview stereo-imagery and cartographically derived DEMs. DEMs are calibrated and co-registered using ICESat returns over bedrock. On NovZ thinning of between 60 and 100 meters since the 1950s' is common. Similar rates between the late 1980s' and the present are seen at SevZ. We examine in detail the response of the outlet glaciers of the Karpinsky and Russanov Ice Caps on SevZ to the rapid collapse of the Matusevich Ice Shelf in the late summer of 2012. We do not see a dynamic thinning response at the largest feeder glaciers. This may be due to the slow response of the cold polar glaciers to changing boundary conditions, or the glaciers may be grounded well above sea level. Speed increases in the interior are difficult to assess with optical imagery as there are few trackable features. We therefore use pixel tracking on Terra SARX acquisitions before and after the collapse of the ice shelf to compute rates of flow inland, at slow moving ice. Interior ice flow has not accelerated in response to the collapse of the ice shelf but interior rates at the Karpinsky Ice Cap have increased by about 50% on the largest outlet
Centrifugally Driven Rayleigh-Taylor Instability
NASA Astrophysics Data System (ADS)
Scase, Matthew; Hill, Richard
2017-11-01
The instability that develops at the interface between two fluids of differing density due to the rapid rotation of the system may be considered as a limit of high-rotation rate Rayleigh-Taylor instability. Previously the authors have considered the effect of rotation on a gravitationally dominated Rayleigh-Taylor instability and have shown that some growth modes of instability may be suppressed completely by the stabilizing effect of rotation (Phys. Rev. Fluids 2:024801, Sci. Rep. 5:11706). Here we consider the case of very high rotation rates and a negligible gravitational field. The initial condition is of a dense inner cylinder of fluid surrounded by a lighter layer of fluid. As the system is rotated about the generating axis of the cylinder, the dense inner fluid moves away from the axis and the familiar bubbles and spikes of Rayleigh-Taylor instability develop at the interface. The system may be thought of as a ``fluid-fluid centrifuge''. By developing a model based on an Orr-Sommerfeld equation, we consider the effects of viscosity, surface tension and interface diffusion on the growth rate and modes of instability. We show that under particular circumstances some modes may be stabilized. School of Mathematical Sciences.
Antarctica: Scientific Journeys from McMurdo to the Pole.
ERIC Educational Resources Information Center
Brand, Judith, Ed.
2002-01-01
This issue of Exploratorium Magazine focuses on Antarctica. Antarctica has one of the most extreme climates in the world with an untouched environment inviting researchers with great opportunities for study. This issue describes the journey of four Exploratorium staff members to frozen Antarctica. Chapters include: (1) "Life at the Bottom of…
Malaspina Glacier, Alaska as seen from STS-66 Atlantis
1994-11-14
STS066-117-014 (3-14 Nov. 1994) --- Malaspina Glacier can be seen in this north-northeastern photograph taken in November, 1994. The glacier, located in the south shore of Alaska is a classic example of a piedmont glacier lying along the foot of a mountain range. The principal source of ice for the glacier is provided by the Seward Ice Field to the north (top portion of the view) which flows through three narrow outlets onto the coastal plain. The glacier moves in surges that rush earlier-formed moraines outward into the expanding concentric patterns along the flanks of the ice mass.
What Influences Climate and Glacier Change in the Southwestern China?
NASA Technical Reports Server (NTRS)
Yasunari, Teppei J.
2012-01-01
The subject of climate change in the areas of the Tibetan Plateau (TP) and the Himalayas has taken on increasing importance because of available water resources from their mountain glaciers. Many of these glaciers over the region have been retreating, while some are advancing and stable. Other studies report that some glaciers in the Himalayas show acceleration on their shrinkage. However, the causes of the glacier meltings are still difficult to grasp because of the complexity of climatic change and its influence on glacier issues. However, it is vital that we pursue further study to enable the future prediction on glacier changes.
Bilovitz, Peter O.; Nascimbene, Juri; Mayrhofer, Helmut
2016-01-01
Summary Three sampling sites were established at increasing distance from the Morteratsch glacier to investigate lichen communities on soil in the glacier forefield. The survey yielded 13 lichen species and one lichenicolous fungus. Peltigera extenuata (Nyl. ex Vain.) Lojka (Peltigerales) is new to the canton of Graubünden. PMID:26877564
Animating Nested Taylor Polynomials to Approximate a Function
ERIC Educational Resources Information Center
Mazzone, Eric F.; Piper, Bruce R.
2010-01-01
The way that Taylor polynomials approximate functions can be demonstrated by moving the center point while keeping the degree fixed. These animations are particularly nice when the Taylor polynomials do not intersect and form a nested family. We prove a result that shows when this nesting occurs. The animations can be shown in class or…
Seismic Events and Tidal Forces near the Grounding Line of Beardmore Glacier, Antarctica
NASA Astrophysics Data System (ADS)
Cooley, J.; Winberry, J. P.; Conway, H.; Koutnik, M. R.
2016-12-01
Ice shelves are floating extensions of large ice sheets. Weakening or break-up of these ice shelves allow ice upstream to move off the continent at increased rates, contributing to sea level rise. One prominent mechanism by which shelves are weakened is through crevasse formation. Icequakes are small magnitude seismic events that occur within a volume of ice which reveal areas where crevasses on an ice shelf might form, providing insight into ice shelf stability. The processes that drive these crevassing events are not well-understood, but past research on icequakes near the grounding line has found a correlation with tide. During high tide, there is a large mass of water pushing against the ice shelf, compressing it. As the tide falls, so does this pressure, allowing the ice shelf to stretch. This creates an enormous amount of stress, released as crevasses, near the grounding line. Preliminary examination of data taken over a three week period in the austral summer of 2013/14 at Beardmore Glacier also reveals a tidal correlation, but with rising tide playing a bigger role than previously thought. I aim to find a pattern in the physical locations of events which separates those that occur during rising tide from those that occur during falling tide, to take steps in understanding what constraint rising tide could have on the creation of crevasses. Research methods involve programming scripts to automate counting of events, locating the epicenters with beamforming, calculating the local magnitudes of the events, and utilizing processed GPS data to correlate the events to ocean tide.
Hydro-sliding and the Springtime Dynamical Evolution of Kennicott Glacier, Alaska
NASA Astrophysics Data System (ADS)
Armstrong, W. H., Jr.; Anderson, R. S.
2017-12-01
Glacier basal motion is a poorly understood aspect of glacier mechanics that is responsible for the majority of ice flux on fast-flowing glaciers, enables rapid changes in glacier motion, and provides the means by which glaciers shape alpine landscapes. We collect hydrometerologic data and GPS-derived ice surface motion to probe the link between subglacial water pressure and the evolution of glacier velocity on Kennicott Glacier, Alaska. We find a chaotic timeseries of >50 m fill-and-drain sequences on the well-connected ice-marginal Donoho Falls Lake. Glacier velocity in the down-glacier reach responds sensitively to lake stage, with high amplitude diurnal velocity fluctuations during high or rising stage. The timing of velocity peaks precedes peak stage by 2-3 hours, and synchronously shifts earlier in the day throughout our observation period. We find the up-glacier station appears to first speed up in response to longitudinal coupling with accelerating down-glacier ice before responding to local variations in basal traction. We find the transition to responding to local basal conditions results in the glacier behaving more uniformly, with similar magnitude diurnal velocity fluctuations, synchronous timing of velocity extrema across the 10 km study reach, and steadier longitudinal strain rates.
NASA Technical Reports Server (NTRS)
2001-01-01
This image from the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) instrument on NASA's Terra satellite covers an area of 55 by 40 kilometers (34 by 25 miles) over the southwest part of the Malaspina Glacier and Icy Bay in Alaska. The composite of infrared and visible bands results in the snow and ice appearing light blue, dense vegetation is yellow-orange and green, and less vegetated, gravelly areas are in orange. According to Dr. Dennis Trabant (U.S. Geological Survey, Fairbanks, Alaska), the Malaspina Glacier is thinning. Its terminal moraine protects it from contact with the open ocean; without the moraine, or if sea level rises sufficiently to reconnect the glacier with the ocean, the glacier would start calving and retreat significantly. ASTER data are being used to help monitor the size and movement of some 15,000 tidal and piedmont glaciers in Alaska. Evidence derived from ASTER and many other satellite and ground-based measurements suggests that only a few dozen Alaskan glaciers are advancing. The overwhelming majority of them are retreating.
This ASTER image was acquired on June 8, 2001. With its 14 spectral bands from the visible to the thermal infrared wavelength region, and its high spatial resolution of 15 to 90 meters (about 50 to 300 feet), ASTER will image Earth for the next six years to map and monitor the changing surface of our planet.ASTER is one of five Earth-observing instruments launched December 18,1999, on NASA's Terra satellite. The instrument was built by Japan's Ministry of Economy, Trade and Industry. A joint U.S./Japan science team is responsible for validation and calibration of the instrument and the data products. Dr. Anne Kahle at NASA's Jet Propulsion Laboratory, Pasadena, Calif., is the U.S. science team leader; Bjorn Eng of JPL is the project manager. ASTER is the only high-resolution imaging sensor on Terra. The Terra mission is part of NASA's Earth Science Enterprise, along-term research andMountain Glaciers and Ice Caps
Ananichheva, Maria; Arendt, Anthony; Hagen, Jon-Ove; Hock, Regine; Josberger, Edward G.; Moore, R. Dan; Pfeffer, William Tad; Wolken, Gabriel J.
2011-01-01
Projections of future rates of mass loss from mountain glaciers and ice caps in the Arctic focus primarily on projections of changes in the surface mass balance. Current models are not yet capable of making realistic forecasts of changes in losses by calving. Surface mass balance models are forced with downscaled output from climate models driven by forcing scenarios that make assumptions about the future rate of growth of atmospheric greenhouse gas concentrations. Thus, mass loss projections vary considerably, depending on the forcing scenario used and the climate model from which climate projections are derived. A new study in which a surface mass balance model is driven by output from ten general circulation models (GCMs) forced by the IPCC (Intergovernmental Panel on Climate Change) A1B emissions scenario yields estimates of total mass loss of between 51 and 136 mm sea-level equivalent (SLE) (or 13% to 36% of current glacier volume) by 2100. This implies that there will still be substantial glacier mass in the Arctic in 2100 and that Arctic mountain glaciers and ice caps will continue to influence global sea-level change well into the 22nd century.
NASA Astrophysics Data System (ADS)
Nussbaumer, Samuel U.; Zumbühl, Heinz J.
2010-05-01
Historical and proxy-records have documented a partly asynchronous evolution in temperature, precipitation and glacial variations between European regions during the Little Ice Age (LIA), and the causes of these temporal anomalies are yet being poorly understood. To address this question, highly resolved glacier reconstructions going far back in time based on historical documents (for the last 500 years) or on dendrochronological and radiocarbon dating (for the Holocene) are very important as they give valuable insights in past climate. However, such reconstructions exist only for few glaciers worldwide, depending on the public perception and the accessibility of the corresponding glacier and its surrounding area. One of these regions of interest is the well-documented Mont Blanc area. Here, we present a new high-resolution reconstruction of length changes for the "Glacier des Bossons", situated in the French part of the Mont Blanc area. This reconstruction is based on historical material newly discovered, that has not been evaluated so far for glacier reconstructions. More than 200, often unpublished, artworks (paintings, drawings, prints), photographs, maps and written accounts have been critically analysed and give an univocal picture of the glacier's history. Especially noteworthy are the drawings by Jean-Antoine Linck, Samuel Birmann and Eugène Viollet-le-Duc which depict meticulously the glacier's extent during the vast advance and subsequent retreat during the 19th century. The new reconstruction dates back to AD 1580. Maxima of the "Glacier des Bossons" are proved around 1610/1643, 1685, 1712, 1780, 1818, 1854, 1892, 1921, 1941, and 1983. The LIA maximum extent was reached in 1818. Until the present, the glacier has lost about 1.5 kilometres in length, and it is nowadays shorter than at any time during the reconstruction period. The length curve of the "Glacier des Bossons" is finally analysed regarding climate data and also compared with the nearby "Mer
40 Years of Glacier Change across the Himalayas
NASA Astrophysics Data System (ADS)
Maurer, J. M.; Schaefer, J. M.; Rupper, S.
2017-12-01
Himalayan glaciers are central to societies, ecologies, and landscapes in South Asia. Retreating glaciers have been observed in the Himalayas from in-situ and satellite remote sensing measurements, yet different approaches provide a wide range of mass budget estimates. As glaciers respond dynamically to climate over decades and centuries, more observations of past glacier states are needed to gain perspective on existing shorter-timespan ice loss estimates, minimize effects of interannual variability, and to robustly evaluate glacier dynamics. Here we use a new suite of DEMs (digital elevation models) to estimate geodetic mass balance for over 1000 Himalayan glaciers spanning a 2000 km transect, during the years 1975-2000 and 2001-2016. Recent advances in DEM extraction from declassified Hexagon filmstrips, along with new public access to the global ASTER database have allowed for this large-scale analysis of regional ice loss. An average trendline (using a 30-glacier moving-window) reveals a spatially coherent ice loss signal across the entire transect during both periods, consistent with atmospheric warming as the primary Himalaya-wide driver of change. Our estimate of mean annual ice losses during the more recent period is approximately twice as negative (-0.39 ± 0.1 m.w.e. a-1) compared to the 1975-2000 baseline (-0.18 ± 0.1 m.w.e. a-1). This two-fold acceleration of ice loss during the 21st century agrees with the global average, parallel with recent observations of increasing rates of sea level rise. These surface-integrated geodetic mass balances are negligibly influenced by ice flow dynamics, thus are indicative of climate-driven glacier responses. Further analyses utilizing satellite-derived ice surface velocities will afford deconvolution of the surface mass balance and ice fluxes, providing additional insights into the dynamic responses of the glaciers.
NASA Astrophysics Data System (ADS)
Huggel, C.; Kaeaeb, A.; Haeberli, W.; Mortara, G.; Chiarle, M.; Epifani, F.
2002-12-01
Starting in summer 2000, Belvedere Glacier, near Macugnaga, Italian Alps, developed an extraordinary change in flow, geometry and surface appearance. A surge-type flow acceleration started in the lower parts of the Monte-Rosa east face, leading to strong crevassing and deformation of Belvedere Glacier, accompanied by bulging of its orographic right margin. In September 2001, a small supraglacial lake developed on the glacier. High water pressure and accelerated movement lasted into winter 2001/2002. The ice, in places, started to override moraines from the Little Ice Age. In late spring and early summer 2002, the supraglacial lake grew at extraordinary rates reaching a maximum area of more than 150'000 m2 by end of June. The evolution of such a large supraglacial lake, a rather unique feature in the Alps, was probably enabled by changes in the subglacial drainage system in the course of the surge-like developments with high water pressure in the glacier. At the end of June, an enhanced growth of the lake level with a rise of about 1 m per day was observed such that the supraglacial lake became a urgent hazard problem for the community of Macugnaga. Emergency measures had to be taken by the Italian Civil Protection. The authors thereby acted as the official expert advisers. Temporal evacuations were ordered and a permanent monitoring and alarm system was installed. Pumps with a maximum output of 1 m3/s were brought to the lake. Bathymetric studies yielded a maximum lake depth of 55 m and a volume of 3.3 millions of cubic meters of water. Aerial photography of 1995, 1999, September 2001 and October 2001 was used to calculate ice flow velocities and changes in surface altitude. Compared to the period of 1995 to 1999, the flow accelerated by about five times in 2001 (max. speeds up to 200 m/yr). Surface uplift measured was about 10-15 m/yr. The results of the photogrammetric studies were used to evaluate different possible lake-outburst scenarios, in particular