Science.gov

Sample records for age glacier advance

  1. Younger Dryas Age advance of Franz Josef Glacier in the Southern Alps of New Zealand

    SciTech Connect

    Denton, G.H. ); Hendy, C.H. )

    1994-06-03

    A corrected radiocarbon age of 11,050 [+-] 14 years before present for an advance of the Franz Josef Glacier to the Waiho Loop terminal moraine on the western flank of New Zealand's Southern Alps shows that glacier advance on a South Pacific island was synchronous with initiation of the Younger Dryas in the North Atlantic region. Hence, cooling at the beginning of the Younger Dryas probably reflects global rather than regional forcing. The source for Younger Dryas climatic cooling may thus lie in the atmosphere rather than in a North Atlantic thermohaline switch. 36 refs., 2 figs., 1 tab.

  2. Influences of the Little Ice Age glacier advance on hillslope morphometry and development in paraglacial valley systems around the Jostedalsbreen ice cap in Western Norway

    NASA Astrophysics Data System (ADS)

    Laute, Katja; Beylich, Achim A.

    2012-09-01

    This paper focuses on the influence of the "Little Ice Age" (LIA) glacier advance on hillslope morphometry and development in selected U-shaped and (para)glacial tributary valleys, which are still occupied in their upper parts by outlet glaciers of the Jostedalsbreen ice cap in Western Norway. Especially the morphometric influences and geomorphic consequences of the LIA glacier advance on the development of the valley-side hillslope systems and associated denudative processes are assessed by comparing hillslope systems located inside and outside of the LIA glacier maximum extent. The process-based approach applied includes orthophoto- and topographical map interpretation as well as hillslope profile surveying in field for morphometric analyses and detailed geomorphological mapping for process analyses. In addition GIS and DEM computing as well as geophysical measurements (georadar) for storage analyses are performed. It is found that hillslopes inside the LIA glacier limit have steepened lower hillslope segments due to a negative sediment net balance of removal and deposition of material by the advancing LIA glacier front. There are significant differences in the present-day slope debris thickness and composition between hillslopes inside or outside the LIA glacier limit. Slope debris from hillslopes inside the glacier maximum extent are clearly less thick and display a different internal structure originating from a combination of debris from gravitational processes and reworked modern glacial deposits. Compared to that slope debris covers on hillslopes outside the LIA glacier limit are in general noticeable thicker and less influenced by glacial deposits. The combined effects of modified slope morphometry and altered composition of material covering lower hillslope segments have generated a higher intensity of post-LIA denudative hillslope processes.

  3. Advances in Modelling of Valley Glaciers

    NASA Astrophysics Data System (ADS)

    Adhikari, Surendra

    For glaciological conditions typical of valley glaciers, the central idea of this research lies in understanding the effects of high-order mechanics and parameterizing these for simpler dynamical and statistical methods in glaciology. As an effective tool for this, I formulate a new brand of dynamical models that describes distinct physical processes of deformational flow. Through numerical simulations of idealized glacier domains, I calculate empirical correction factors to capture the effects of longitudinal stress gradients and lateral drag for simplified dynamical models in the plane-strain regime. To get some insights into real glacier dynamics, I simulate Haig Glacier in the Canadian Rocky Mountains. As geometric effects overshadow dynamical effects in glacier retreat scenarios, it appears that high-order physics are not very important for Haig Glacier, particularly for evaluating its fate. Indeed, high-order and reduced models all predict that Haig Glacier ceases to exist by about AD2080 under ongoing climate warming. This finding regarding the minimal role of high-order physics may not be broadly valid, as it is not true in advance scenarios at Haig Glacier and it may not be representative of other glaciological settings. Through a 'bulk' parameterization of high-order physics, geometric and climatic settings, sliding conditions, and transient effects, I also provide new insights into the volume-area relation, a widely used statistical method for estimating glacier volume. I find a steady-state power-law exponent of 1:46, which declines systematically to 1:38 after 100 years of sustained retreat, in good accord with the observations. I recommend more accurate scaling relations through characterization of individual glacier morphology and degree of climatic disequilibrium. This motivates a revision of global glacier volume estimates, of some urgency in sea level rise assessments.

  4. The slow advance of a calving glacier: Hubbard Glacier, Alaska, U.S.A

    USGS Publications Warehouse

    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.

  5. Little Ice Age glaciers in the Mediterranean mountains

    NASA Astrophysics Data System (ADS)

    Hughes, Philip

    2014-05-01

    Only a few small glaciers survive today in the Mountains of the Mediterranean. Notable examples are found in the Pyrenees, Maritime Alps, Italian Apennines, the Dinaric and Albanian Alps and the mountains of Turkey. Many glaciers disappeared during the 20th Century. Glaciers were much larger and more numerous during the Little Ice Age (Hughes, 2014). Small glaciers even existed as far south as the High Atlas of Morocco and the Sierra Nevada of southern Spain. In more northerly areas, such as the western Balkans, glaciers and permanent snow patches occupied hundreds of cirques on relatively low-lying mountains. In the High Atlas and the Sierra Nevada no glaciers exist today, whilst in the Balkans only a few modern glaciers have been reported. A similar situation is apparent throughout the mountains of the Mediterranean region. New evidence for glacier change since the Little Ice Age will be published soon in Hughes (2014) and this paper reviews the extent, timing and climatic significance of Little Ice Age glaciation in the Mediterranean region. Reference: Hughes, P.D. (2014) Little Ice Age glaciers in the Mediterranean mountains. In: Carozza, J.-M., Devillers, B., Morhange, C. (eds) Little Ice Age in the Mediterranean, Méditerranée, volume 123.

  6. Glacier advance during Marine Isotope Stage 11 in the McMurdo Dry Valleys of Antarctica

    PubMed Central

    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

  7. Glacier advance during Marine Isotope Stage 11 in the McMurdo Dry Valleys of Antarctica

    NASA Astrophysics Data System (ADS)

    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.

  8. Glacier advance during Marine Isotope Stage 11 in the McMurdo Dry Valleys of Antarctica.

    PubMed

    Swanger, Kate M; Lamp, Jennifer L; Winckler, Gisela; Schaefer, Joerg M; Marchant, David R

    2017-01-31

    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 (3)He. 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.

  9. The controversial age of Kilimanjaro's plateau glaciers

    NASA Astrophysics Data System (ADS)

    Uglietti, Chiara; Zapf, Alexander; Szidat, Sönke; Salazar, Gary; Hardy, Doug; Schwikowski, Margit

    2015-04-01

    Interpreting climate signals contained in natural archives requires a precise chronology. Radiocarbon analysis can be a powerful tool for dating high-altitude ice cores, especially for the lowermost segments for which ice flow-induced thinning limits the counting of annual layers. Radiocarbon dating has been applied to ice cores containing sufficient organic material, which is a limiting factor to the wider application of this technique. We present a novel radiocarbon dating approach using carbonaceous aerosols enclosed in the ice to help resolve the debate about the age of the Kilimanjaro's plateau glaciers. Paleoclimate reconstructions based on six ice cores drilled in 2000 assigned a basal age of 11'700 years. A recent study claims recurring cycles of waxing and waning controlled primarily by atmospheric moisture and an absence of the ice bodies was suggested for 1200 AD. The Kilimanjaro ice fields are subject to rapid areal shrinkage and thinning and are expected to disappear within several decades. Resolving the controversy of the time frame for the extinction of the Kilimanjaro ice might have wide implications for the understanding of the natural climate variability in the tropics. A stratigraphic sequence of samples from the exposed vertical ice cliffs at the margins of the Northern Ice Field (NIF) was collected in 2011. A total of 45 horizontal short cores (50 cm length) were extracted from 22 horizons characterized by varying micro-particle concentrations. Additionally, 3 samples were taken from the glacier surface to investigate a potential age offset. All samples were shipped frozen to Paul Scherrer Institute, decontaminated in a cold room by removing the outer layer (0.3 mm) and by rinsing the samples with ultra-pure water. The insoluble carbonaceous particles were filtrated by using freshly preheated quartz fibre filters. Procedural blanks were estimated using artificial ice blocks of frozen ultra-pure water treated as real ice samples and were

  10. Complex patterns of glacier advances during the Lateglacial in the Chagan-Uzun Valley, Russian Altai

    NASA Astrophysics Data System (ADS)

    Gribenski, Natacha; Lukas, Sven; Jansson, Krister N.; Stroeven, Arjen P.; Preusser, Frank; Harbor, Jonathan M.; Blomdin, Robin; Ivanov, Mikhail N.; Heyman, Jakob; Petrakov, Dmitry; Rudoy, Alexei; Clifton, Tom; Lifton, Nathaniel A.; Caffee, Marc W.

    2016-04-01

    Over the last decades, numerous paleoglacial reconstructions have been carried out in Central Asian mountain ranges because glaciers in this region are sensitive to climate change, and thus their associated glacial deposits can be used as proxies for paleoclimate inference. However, non-climatic factors can complicate the relationship between glacier fluctuation and climate change. Careful investigations of the geomorphological and sedimentological context are therefore required to understand the mechanisms behind glacier retreat and expansion. In this study we present the first detailed paleoglacial reconstruction of the Chagan Uzun valley, located in the Russian Altai. This reconstruction is based on detailed geomorphological mapping, sedimentological logging, in situ cosmogenic 10Be and 26Al surface exposure dating of glacially transported boulders, and Optically Stimulated Luminescence (OSL) dating. The Chagan Uzun valley includes extensive lobate moraine belts (>100 km2) deposited in the intramontane Chuja basin, reflecting a series of pronounced former glacial advances. Observation of "hillside-scale" folding and extensive faulting of pre-existing soft sediments within the outer moraine belts, together with the geomorphology, indicate that these moraine belts were formed during glacier-surge like events. In contrast, the inner (up-valley) glacial landforms of the Chagan Uzun valley indicate that they were deposited by retreat of temperate valley glaciers and do not include features indicative of surging. Cosmogenic ages associated with the outermost, innermost and intermediary stages, all indicate deposition times clustered around 19.5 ka, although the 10Be ages of the outermost margin are likely slightly underestimated due to brief episode of glacial lake water coverage. Such close deposition timings are consistent with periods of fast or surge advances, followed by active glacier retreat. OSL dating yields significantly older ages of thick lacustrine

  11. Observations of Dynamic Changes at an Advancing Tidewater Glacier: Hubbard Glacier, Southeast Alaska

    NASA Astrophysics Data System (ADS)

    Elliott, J.; Stearns, L. A.; Pritchard, M. E.; Bartholomaus, T.

    2015-12-01

    Hubbard Glacier, located in southeast Alaska, is the largest non-polar tidewater glacier in the world and one of a small number of glaciers that is steadily advancing. These attributes make it an intriguing target for observations of variations in ice dynamics over time. We use synthetic aperture radar data (ALOS and TerraSAR-X) and high-resolution optical imagery (WorldView and Quickbird) with a pixel tracking technique to map surface velocities from 2008 to the present, lengthening and broadening the time series of ice velocities presented in previous studies. A key result from our analysis is that Hubbard displays peak speeds of up to 12 m/day during the winter months (December - February) and minimum speeds during late summer (August - September). The times of peak and minimum speeds is quite different from those found in previous studies of Hubbard surface velocities derived from Landsat imagery, GPS, and photogrammetric methods. Those studies found peak speeds during late spring (May - June) and minimum speeds in fall (October-November), a pattern observed generally at tidewater glaciers. A second major feature we observe in our time series is the dramatic seasonal variation in surface speeds. The minimum speeds we find along the terminal lobe of the glacier are much lower than those found in previous studies, with values decreasing to near zero. Such a dramatic slow down of a tidewater glacier has not been widely observed. This result, along with the recent pattern of seasonal velocity peaks and minimas, suggests that Hubbard has undergone a change in ice dynamics.

  12. A Younger Dryas re-advance of local glaciers in north Greenland

    NASA Astrophysics Data System (ADS)

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

    2016-09-01

    The Younger Dryas (YD) is a well-constrained cold event from 12,900 to 11,700 years ago but it remains unclear how the cooling and subsequent abrupt warming recorded in ice cores was translated into ice margin fluctuations in Greenland. Here we present 10Be surface exposure ages from three moraines in front of local glaciers on a 50 km stretch along the north coast of Greenland, facing the Arctic Ocean. Ten ages range from 11.6 ± 0.5 to 27.2 ± 0.9 ka with a mean age of 12.5 ± 0.7 ka after exclusion of two outliers. We consider this to be a minimum age for the abandonment of the moraines. The ages of the moraines are furthermore constrained using Optically Stimulated Luminescence (OSL) dating of epishelf sediments, which were deposited prior to the ice advance that formed the moraines, yielding a maximum age of 12.4 ± 0.6 ka, and bracketing the formation and subsequent abandonment of the moraines to within the interval 11.8-13.0 ka ago. This is the first time a synchronous YD glacier advance and subsequent retreat has been recorded for several independent glaciers in Greenland. In most other areas, there is no evidence for re-advance and glaciers were retreating during YD. We explain the different behaviour of the glaciers in northernmost Greenland as a function of their remoteness from the Atlantic Meridional Overturning Circulation (AMOC), which in other areas has been held responsible for modifying the YD drop in temperatures.

  13. Latest Pleistocene advance and collapse of the Matanuska - Knik glacier system, Anchorage Lowland, southern Alaska

    NASA Astrophysics Data System (ADS)

    Kopczynski, Sarah E.; Kelley, Samuel E.; Lowell, Thomas V.; Evenson, Edward B.; Applegate, Patrick J.

    2017-01-01

    At the end of the last ice age, glacier systems worldwide underwent dramatic retreat. Here, we document the advance and retreat of a glacier system with adjacent marine- and land-based components during the latter part of the Termination. We utilize three lines of evidence: lithologic provenance, geomorphic mapping, and radiocarbon ages derived from lake cores to reconstruct glacier extent and timing of advance and retreat within our study area centered at N 61.50°, W 149.50°, just north of Anchorage, Alaska. Two glaciers, sourced in the Talkeetna and Chugach Mountains, flowed down the Matanuska and Knik Valleys forming a coalesced lobe that advanced onto the Anchorage Lowlands and terminated at Elmendorf Moraine. We use the presence of lithologies unique to the Matanuska catchment in glacial drift to delineate the paleoflow lines and to estimate the suture line of the two glacier systems. The eastern side of the lobe, attributed to ice flow from the Knik Valley, was in contact with elevated marine waters within the Knik Arm fjord, and thus retreat was likely dominated by calving. Geomorphic evidence suggests the western side of the lobe, attributed to ice flow from Matanuska Valley, retreated due to stagnation. We constrain retreat of the combined Matanuska and Knik lobe with thirteen new radiocarbon ages, in addition to previously published radiocarbon ages, and with geomorphic evidence suggesting the retreat occurred in two phases. Retreat from the Elmendorf Moraine began between 16.8 and 16.4 ka BP. A second, faster retreat phase occurred later and was completed by 13.7 ka BP. With the 140 km of total retreat occurring over ∼3000 years or less. This pattern of glacial advance and retreats agrees well with the deglacial histories from the southern sectors of the Cordilleran Ice Sheet, as well as many other alpine glacier systems in the western U.S. and northern Alaska. This consistent behavior of glacier systems may indicate that climate oscillated over

  14. Glacier retreat since the Little Ice Age in the eastern Nyainqêntanglha Range, southeastern Tibet

    NASA Astrophysics Data System (ADS)

    Loibl, David; Grießinger, Jussi; Lehmkuhl, Frank

    2014-05-01

    The remote eastern Nyainqêntanglha Range in southeastern Tibet is situated in a transition zone between warm-wet subtropical and cold-dry plateau climate conditions. In this high mountain environment, intense summer monsoon rainfalls support numerous temperate glaciers despite the latitude of ~29° to ~31°N. Due to the outstanding importance of the monsoonal airmasses for the water cycle of the whole region, it is a key area to study climate and subsequent glacier change in High Asia. Here, we present the results of a study in which 1964 glaciers were mapped by remote sensing from a Landsat ETM+ scene and subsequently parameterized by DEM supported measurements. Geomorphological evidence, such as glacier trimlines and latero-frontal moraines, was used to delineate the Little Ice Age (LIA) maximum glacier advance terminus positions. Statistical analysis of glacier length change revealed an average retreat of ~40 % and a trend towards stronger retreat for smaller glaciers. Calculated ELAs show a southeast-northwest gradient ranging from 4,400 to 5,600 m a.s.l. and an average ELA rise of ~98 m since the LIA. Due to the large amount of measurements the ELA distribution reveals topographic effects down to the catchment scale, i.e. orographic rainfall and leeward shielding. This gives numerous hints on the relief-climate-glacier interactions and allows a simplified reconstruction of the flow patterns of the monsoonal air masses. Contrasting to the expectations for subtropical settings, glaciers on south facing slopes have not retreated strongest and ELAs on south facing slopes did not rise furthest. Instead, highly heterogeneous spatial patterns emerge that show a strong imprint of both, topography and monsoonal dynamics. Our results indicate that the monsoonal temperate glaciers' high sensitivity to climate change is driven by two double forcings due to the coincidence of accumulation and ablation phases. First, monsoon intensity directly controls the amount of

  15. A major advance of tropical Andean glaciers during the Antarctic cold reversal.

    PubMed

    Jomelli, V; Favier, V; Vuille, M; Braucher, R; Martin, L; Blard, P-H; Colose, C; Brunstein, D; He, F; Khodri, M; Bourlès, D L; Leanni, L; Rinterknecht, V; Grancher, D; Francou, B; Ceballos, J L; Fonseca, H; Liu, Z; Otto-Bliesner, B L

    2014-09-11

    The Younger Dryas stadial, a cold event spanning 12,800 to 11,500 years ago, during the last deglaciation, is thought to coincide with the last major glacial re-advance in the tropical Andes. This interpretation relies mainly on cosmic-ray exposure dating of glacial deposits. Recent studies, however, have established new production rates for cosmogenic (10)Be and (3)He, which make it necessary to update all chronologies in this region and revise our understanding of cryospheric responses to climate variability. Here we present a new (10)Be moraine chronology in Colombia showing that glaciers in the northern tropical Andes expanded to a larger extent during the Antarctic cold reversal (14,500 to 12,900 years ago) than during the Younger Dryas. On the basis of a homogenized chronology of all (10)Be and (3)He moraine ages across the tropical Andes, we show that this behaviour was common to the northern and southern tropical Andes. Transient simulations with a coupled global climate model suggest that the common glacier behaviour was the result of Atlantic meridional overturning circulation variability superimposed on a deglacial increase in the atmospheric carbon dioxide concentration. During the Antarctic cold reversal, glaciers advanced primarily in response to cold sea surface temperatures over much of the Southern Hemisphere. During the Younger Dryas, however, northern tropical Andes glaciers retreated owing to abrupt regional warming in response to reduced precipitation and land-surface feedbacks triggered by a weakened Atlantic meridional overturning circulation. Conversely, glacier retreat during the Younger Dryas in the southern tropical Andes occurred as a result of progressive warming, probably influenced by an increase in atmospheric carbon dioxide. Considered with evidence from mid-latitude Andean glaciers, our results argue for a common glacier response to cold conditions in the Antarctic cold reversal exceeding that of the Younger Dryas.

  16. A major advance of tropical Andean glaciers during the Antarctic cold reversal

    NASA Astrophysics Data System (ADS)

    Jomelli, V.; Favier, V.; Vuille, M.; Braucher, R.; Martin, L.; Blard, P.-H.; Colose, C.; Brunstein, D.; He, F.; Khodri, M.; Bourlès, D. L.; Leanni, L.; Rinterknecht, V.; Grancher, D.; Francou, B.; Ceballos, J. L.; Fonseca, H.; Liu, Z.; Otto-Bliesner, B. L.

    2014-09-01

    The Younger Dryas stadial, a cold event spanning 12,800 to 11,500 years ago, during the last deglaciation, is thought to coincide with the last major glacial re-advance in the tropical Andes. This interpretation relies mainly on cosmic-ray exposure dating of glacial deposits. Recent studies, however, have established new production rates for cosmogenic 10Be and 3He, which make it necessary to update all chronologies in this region and revise our understanding of cryospheric responses to climate variability. Here we present a new 10Be moraine chronology in Colombia showing that glaciers in the northern tropical Andes expanded to a larger extent during the Antarctic cold reversal (14,500 to 12,900 years ago) than during the Younger Dryas. On the basis of a homogenized chronology of all 10Be and 3He moraine ages across the tropical Andes, we show that this behaviour was common to the northern and southern tropical Andes. Transient simulations with a coupled global climate model suggest that the common glacier behaviour was the result of Atlantic meridional overturning circulation variability superimposed on a deglacial increase in the atmospheric carbon dioxide concentration. During the Antarctic cold reversal, glaciers advanced primarily in response to cold sea surface temperatures over much of the Southern Hemisphere. During the Younger Dryas, however, northern tropical Andes glaciers retreated owing to abrupt regional warming in response to reduced precipitation and land-surface feedbacks triggered by a weakened Atlantic meridional overturning circulation. Conversely, glacier retreat during the Younger Dryas in the southern tropical Andes occurred as a result of progressive warming, probably influenced by an increase in atmospheric carbon dioxide. Considered with evidence from mid-latitude Andean glaciers, our results argue for a common glacier response to cold conditions in the Antarctic cold reversal exceeding that of the Younger Dryas.

  17. Glacier advances in northeastern Turkey before and during the global Last Glacial Maximum

    NASA Astrophysics Data System (ADS)

    Reber, Regina; Akçar, Naki; Yesilyurt, Serdar; Yavuz, Vural; Tikhomirov, Dmitry; Kubik, Peter W.; Schlüchter, Christian

    2014-10-01

    Our study in the Başyayla Valley in northeastern Anatolia showed evidence of four glacier advances that built terminal and lateral moraines. Surface exposure dating of boulders on these moraines showed that the Maximum Ice Extent (MIE) was asynchronous with the global Last Glacial Maximum (LGM; 22.1 ± 4.3 thousand years; ka). The local MIE took place at least 57.0 ± 3.5 ka ago. The extent of the Başyayla Glacier during this advance is not known exactly because the boulders are only preserved on a lateral moraine. The next advance was prior to 41.5 ± 2.5 ka, and it descended down the valley to approximately 2320 m above sea level (m a.s.l.), with a glacier length of 5.3 km. During the early global LGM, the Başyayla Glacier extended for a distance of 4.9 km down to approx. 2430 m a.s.l. The last recorded advance occurred during the global LGM. This extension was 0.7 km smaller than the local MIE and its terminus reached 2490 m a.s.l. only. The exposure ages of boulders in a retreat position at an altitude of approx. 3045 m a.s.l. indicate that the valley has remained ice-free since the Lateglacial period. Therefore, the Lateglacial extent was limited to the cirque system in the uppermost part of the catchment. Furthermore, Holocene glacier oscillations seem to be either absent or restricted to solifluction in the whole catchment and to rock glacier movements in the southern tributary of the Başyayla Valley system.

  18. Imaging evidence for Hubbard Glacier advances and retreats since the last glacial maximum in Yakutat and Disenchantment Bays, Alaska

    NASA Astrophysics Data System (ADS)

    Zurbuchen, Julie M.; Gulick, Sean P. S.; Walton, Maureen A. L.; Goff, John A.

    2015-06-01

    High-resolution 2-D multichannel seismic data, collected during the 2012 UTIG-USGS National Earthquake Hazards Reduction Program survey of Disenchantment and Yakutat Bays in southeast Alaska, provide insight into their glacial history. These data show evidence of two unconformities, appearing in the form of channels, and are interpreted to be advance pathways for Hubbard Glacier. The youngest observable channel, thought to have culminated near the main phase of the Little Ice Age (LIA), is imaged in Disenchantment Bay and ends at a terminal moraine near Blizhni Point. An older channel, thought to be from an advance that culminated in the early phase of the LIA, extends from Disenchantment Bay into the northeastern edge of Yakutat Bay, turning southward at Knight Island and terminating on the southeastern edge of Yakutat Bay. Our interpretation is that Hubbard Glacier has repeatedly advanced around the east side of Yakutat Bay in Knight Island Channel, possibly due to the presence of Malaspina Glacier cutting off access to central Yakutat Bay during times of mutual advance. We observe two distinct erosional surfaces and retreat sequences of Hubbard Glacier in Yakutat Bay, supporting the hypothesis that minor glacial advances in fjords do not erode all prior sediment accumulations. Interpretation of chaotic seismic facies between these two unconformities suggests that Hubbard Glacier exhibits rapid retreats and that Disenchantment Bay is subject to numerous episodes of outburst flooding and morainal bank collapse. These findings also suggest that tidewater glaciers preferentially reoccupy the same channels in bay and marine settings during advances.

  19. Glaciers

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2008-12-01

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

  1. Rapid advance of two mountain glaciers in response to mine-related debris loading

    NASA Astrophysics Data System (ADS)

    Jamieson, Stewart S. R.; Ewertowski, Marek W.; Evans, David J. A.

    2015-07-01

    Rapid glacier advance is known to occur by a range of mechanisms. However, although large-scale debris loading has been proposed as a process for causing rapid terminus advance, it has rarely been observed. We use satellite remote sensing data to observe accelerated glacier terminus advance in response to massive supraglacial loading on two glaciers in Kyrgyzstan. Over a 15 year period, mining activity has led to the dumping of spoil of up to 180 m thick on large parts of these valley glaciers. We find that the termini of these glaciers advance by 1.2 and 3.2 km, respectively, at a rate of up to 350 m yr-1. Our analysis suggests that although enhanced basal sliding could be an important process, massive supraglacial loads have also caused enhanced internal ice deformation that would account for most, or all, of the glacier terminus advance. In addition, narrowing of the glacier valley and mining and dumping of ice alter the mass balance and flow regime of the glaciers. Although the scale of supraglacial loading is massive, this full-scale experiment provides insight into glacier flow acceleration response where small valley glaciers are impacted by very large volumes of landslide debris.

  2. Cosmogenic 36Cl exposure ages reveal a 9.3 ka BP glacier advance and the Late Weichselian-Early Holocene glacial history of the Drangajökull region, northwest Iceland

    NASA Astrophysics Data System (ADS)

    Brynjólfsson, Skafti; Schomacker, Anders; Ingólfsson, Ólafur; Keiding, Jakob K.

    2015-10-01

    We present twenty-four new cosmogenic isotope (36Cl) surface exposure ages from erratic boulders, moraine boulders and glacially eroded bedrock that constrain the late Weichselian to Holocene glacial history of the Drangajökull region, northwest Iceland. The results suggest a topographically controlled ice sheet over the Vestfirðir (Westfjords) peninsula during the last glaciation. Cold based non-erosive sectors of the ice sheet covered most of the mountains while fjords and valleys were occupied with erosive, warm-based ice. Old36Cl exposure ages from highlands and mountain plateaux (L8; 76.5 ka and H1; 41.6 ka) in combination with younger erratic boulders (L7; 26.2 and K1-K4; 15.0-13.8 ka) superimposed on such surfaces suggest the presence of non-erosive ice over uplands and plateaux in the Vestfirðir peninsula during the last glaciation. Glacially scoured terrain and erratic boulders yielding younger exposure ages (L1-L6; 11.3-9.1 ka and R1, R6-R7; 10.6-9.4 ka) in the lowland areas indicate that the valleys and fjords of the Vestfirðir peninsula were occupied by warm-based, dynamic ice during the last glaciation. The deglaciation of mountain Leirufjall by 26.2 ka BP suggests that ice thinning and deglaciation of some mountains and plateaux preceded any significant lateral retreat of the ice sheet. Subsequently this initial ice thinning was followed by break-up of the shelf based ice sheet off Vestfirðir about 15 ka BP. Hence, the new exposure ages suggest a stepwise asynchronous deglaciation on land, following the shelf break-up with some valleys and most of the highlands, ice free by 14-15 ka BP. The outermost moraine at the mouth of Leirufjörður is dated to 9.3 ka BP, and we suggest the moraine to be formed by a glacier re-advance in response to a cooler climate forced by the reduced Atlantic Meridional Overturning Circulation at around 9.3 ka BP. A system of moraines proximal to the 9.3 ka moraine in Leirufjörður as well as a 9.4 ka deglaciation age

  3. Growth of a post-Little Ice Age submarine fan, Glacier Bay, Alaska

    USGS Publications Warehouse

    Carlson, P.R.; Cowan, E.A.; Powell, R.D.; Cai, J.

    1999-01-01

    A small Holocene fan is forming where Queen Inlet, a hanging valley, enters West Arm fjord, Glacier Bay, Alaska. Queen fan formed in the last 80 years following retreat of the Little Ice Age glacier that filled Glacier Bay about 200 yr BP. It was built mainly by a turbidite system originating from Carroll Glacier delta, as the delta formed in the early 1900s at the head of Queen Inlet. The Late Holocene Queen fan is comparable to large Pleistocene fans that formed in the Gulf of Alaska and differs from trough-mouth fans formed by cooler climate glacier systems.

  4. Chronology of Late Pleistocene glacier advances in the Rı´o Mendoza Valley, Argentina

    NASA Astrophysics Data System (ADS)

    Espizua, Lydia E.

    1999-10-01

    The Rı´o Mendoza valley at 33°S latitude has been repeatedly invaded by glaciers during the Late Pleistocene. Relative-age criteria, U-series ages, and thermoluminescense dating, permitted the glacial deposits to be separated into three mappable units, each less extensive than its predecessor, designed from oldest to youngest, Penitentes, Horcones and Almacenes drifts. Previous studies have shown that during the Penitentes advance the glacier system terminated at 2500 m, while during the subsequent Horcones advance, ice terminated at 2750 m and the Almacenes moraine reached 3250 m. A travertine layer overlying Penitentes till yielded 230Th/ 232Th ages of 38,300±5300, 24,200±2000 and 22,800±3100 yr B.P. This study focuses on dating interstadial sediments in the upper Rı´o Mendoza valley in order to constrain the ages of the drifts. A date was obtained from a composite stratigraphic profile based on exposures along the east side of the Rı´o de los Horcones Inferior valley, a tributary of the Rı´o de las Cuevas valley, which includes the Penitentes and Horcones tills separated by nonglacial sediments (silt, fine sand and clay), and are interpreted as representing the Penitentes-Horcones nonglacial interval. The fine quartz grains (4-11 μm) of these sediments were TL dated as 31,000±3100 yr. All these dates, which are minimum ages for the underlying Penitentes till, imply that the Penitentes ice advanced prior to the last glacial maximum and sometime before ca. 40,000 years ago. A minimum date for Horcones till comes from an exposure on the east side of the Rı´o de los Horcones Inferior valley where the Horcones and Almacenes tills are separated by sediments of nonglacial origin. The fine quartz grains (4-11 μm) of these sediments have been dated by TL as 15,000±2100 years ago. Almacenes till is inferred to represent a standstill or a readvance that occurred late during the Horcones glacier advance. These dates imply that the Penitentes advance may

  5. Asynchronous Little Ice Age glacier fluctuations in Iceland and European Alps linked to shifts in subpolar North Atlantic circulation

    NASA Astrophysics Data System (ADS)

    Larsen, Darren J.; Miller, Gifford H.; Geirsdóttir, Áslaug

    2013-10-01

    Records of past glacier fluctuations are an important source of paleoclimate data and provide context for future changes in global ice volume. In the North Atlantic region, glacier chronologies can be used to track the response of terrestrial environments to variations in marine conditions including circulation patterns and sea ice cover. However, the majority of glacier records are discontinuous and temporally restricted, owing in part to the extensive advance of Northern Hemisphere glaciers during the Little Ice Age (LIA), the most recent and severe climate anomaly of the Neoglacial period. Here, we combine an absolutely dated and continuous record of Langjökull ice marginal fluctuations with new reconstructions of sediment flux through the past 1.2 ka using varved sediments from Hvítárvatn, a proglacial lake in Iceland's central highlands. Large spatial and temporal variations in sediment flux related to changing ice cap dimensions are reconstructed from six sediment cores and seismic reflection profiles. Sediment data reveal two discrete phases of ice expansion occurring ca. 1400 to 1550 AD and ca. 1680 to 1890 AD. These advances are separated by a persistent interval of ice retreat, suggesting that a substantial period of warming interrupted LIA cold. The pattern of Icelandic glacier activity contrasts with that of European glaciers but shows strong similarities to reconstructed changes in North Atlantic oceanographic conditions, indicating differing regional responses to coupled ocean-atmosphere-sea ice variations. Our data suggest that subpolar North Atlantic circulation dynamics may have led to coherent asynchronous glacier fluctuations during the mid LIA and highlight the importance of circulation variability in triggering and transmitting multidecadal scale climate changes to nearby terrestrial environments.

  6. Asynchronous Little Ice Age glacier fluctuations in Iceland and European Alps linked to shifts in subpolar North Atlantic circulation

    NASA Astrophysics Data System (ADS)

    Larsen, D. J.; Miller, G. H.; Geirsdottir, A.

    2013-12-01

    Records of past glacier fluctuations are an important source of paleoclimate data and provide context for future changes in global ice volume. In the North Atlantic region, glacier chronologies can be used to track the response of terrestrial environments to variations in marine conditions including circulation patterns and sea ice cover. However, the majority of glacier records are discontinuous and temporally restricted, owing in part to the extensive advance of Northern Hemisphere glaciers during the Little Ice Age (LIA), the most recent and severe climate anomaly of the Neoglacial period. Here, we combine an absolutely dated and continuous record of Langjökull ice marginal fluctuations with new reconstructions of sediment flux through the past 1.2 ka using varved sediments from Hvítárvatn, a proglacial lake in Iceland's central highlands. Large spatial and temporal variations in sediment flux related to changing ice cap dimensions are reconstructed from six sediment cores and seismic reflection profiles. Sediment data reveal two discrete phases of ice expansion occurring ca. 1400 to 1550 AD and ca. 1680 to 1890 AD. These advances are separated by a persistent interval of ice retreat, suggesting that a substantial period of warming interrupted LIA cold. The pattern of Icelandic glacier activity contrasts with that of European glaciers but shows strong similarities to reconstructed changes in North Atlantic oceanographic conditions, indicating differing regional responses to coupled ocean-atmosphere-sea ice variations. Our data suggest that subpolar North Atlantic circulation dynamics may have led to coherent asynchronous glacier fluctuations during the mid LIA and highlight the importance of circulation variability in triggering and transmitting multidecadal scale climate changes to nearby terrestrial environments.

  7. Moraine formation during an advance/retreat cycle at a temperate alpine glacier

    NASA Astrophysics Data System (ADS)

    Brook, M.; Quincey, D.; Winkler, S.

    2012-04-01

    Mountain glaciers are highly sensitive to variations in temperature and precipitation, and so moraine records from such systems are strong indicators of climate change. Due to the prevailing trend of retreat of the majority of mountain glaciers globally over the last few decades, there are limited opportunities to observe moraine formation, especially at temperate alpine glaciers. In the Southern Alps of New Zealand, while glaciers have all experienced a major retreat since the late 19th century, within this loss of ice mass, there has been a distinct variance in individual glacier response. Indeed, while Tasman Glacier, the longest glacier in the Southern Alps has thinned and entered into the current phase of calving retreat in the early 1990s, the steeper, more responsive glaciers to the west of the Main Divide, such as Franz Josef and Fox Glacier have experienced more elaborate advance/retreat phases. We focus on moraine formation at Fox Glacier, a c. 12.5 km long valley glacier terminating at 300 m above sea level. Fox Glacier retreated substantially since the 1930s, before advancing 800 m between the mid-1980s and 1999. A minor retreat then followed until 2005, succeeded by a 300 m re-advance until 2007-8. Continued retreat and down-wasting has since followed. Superimposed on this alternating advance/retreat cycle, have been minor winter re-advances. Sedimentological and morphological information were combined with detailed observations, historical photos and recent time-lapse photography of the terminus. Characteristics of several modes of moraine formation have been observed: (1) the late 20th century advance culminated in a broad <5 m high terminal moraine, formed by an admixture of "bulldozed" proglacial sediments and dumping of supraglacial material; (2) the 21st century short-lived advances were characterized by 1-2 m high (often multi-crested) ridges with a "saw-tooth" plan-form controlled by longitudinal crevasses outcropping at the terminus; (3) time

  8. a Younger Dryas Advance of Cirque Glaciers Near the 60TH Parallel, Westernmost Canada

    NASA Astrophysics Data System (ADS)

    Osborn, G.; Menounos, B.; Goehring, B. M.

    2013-12-01

    Our previous work demonstrates that following the decay of the Cordilleran Ice Sheet which commenced at 16 ka (kilo calendar yrs BP), alpine glaciers in southern and central latitudes of British Columbia advanced during the Younger Dryas Chronozone (YD) [12.9-11.7 ka]. The magnitude of this advance, however, markedly differs throughout this region; this difference likely arises from the complexity of a decaying ice sheet in mountainous terrain instead of climatic factors. In an attempt to constrain the timing of the YD and the timing and style of Cordilleran Ice Sheet decay near its northern limit (northwest British Columbia and southern Yukon), we used satellite imagery and aerial photography to identify probable late Pleistocene moraines in regions which would have been major accumulation centers for the ice sheet. Based on that analysis, we studied cirques which lie in the headwaters of Kusawa and Bennett lakes, northernmost British Columbia and cirques 20 km to the south of Kaskawulsh Glacier, Kluane National Park. Yukon. Moraines believed to predate the Little Ice Age [1.0-0.15 ka] are present in less than 10% of the cirques studied in both regions. The subdued, vegetated moraines lie 150-500 m beyond those ascribed to the Little Ice Age. We sampled multiple boulders for 10Be dating from four of these moraines, in addition to moraines interpreted to be Little Ice Age deposits. Two of these pre-LIA moraines yielded statistically equivalent median ages of 11.21 × 0.91 [n=4] and 11.35 × 0.96 ka [n=2]. We await analyses from the other moraines. These results imply that: 1) high-elevation cirques were deglaciated prior to the YD; 2) cirque glaciers advanced at the same time a retreating northerly lobe of the Cordilleran Ice Sheet constructed moraines of YD age in valleys near Whitehorse, 500 m lower in elevation. The implication would be a complex pattern of late Pleistocene advances in the northern part of the Cordilleran Ice Sheet, similar to the observed

  9. Regional cooling caused recent New Zealand glacier advances in a period of global warming.

    PubMed

    Mackintosh, Andrew N; Anderson, Brian M; Lorrey, Andrew M; Renwick, James A; Frei, Prisco; Dean, Sam M

    2017-02-14

    Glaciers experienced worldwide retreat during the twentieth and early twenty first centuries, and the negative trend in global glacier mass balance since the early 1990s is predominantly a response to anthropogenic climate warming. The exceptional terminus advance of some glaciers during recent global warming is thought to relate to locally specific climate conditions, such as increased precipitation. In New Zealand, at least 58 glaciers advanced between 1983 and 2008, and Franz Josef and Fox glaciers advanced nearly continuously during this time. Here we show that the glacier advance phase resulted predominantly from discrete periods of reduced air temperature, rather than increased precipitation. The lower temperatures were associated with anomalous southerly winds and low sea surface temperature in the Tasman Sea region. These conditions result from variability in the structure of the extratropical atmospheric circulation over the South Pacific. While this sequence of climate variability and its effect on New Zealand glaciers is unusual on a global scale, it remains consistent with a climate system that is being modified by humans.

  10. Regional cooling caused recent New Zealand glacier advances in a period of global warming

    NASA Astrophysics Data System (ADS)

    Mackintosh, Andrew N.; Anderson, Brian M.; Lorrey, Andrew M.; Renwick, James A.; Frei, Prisco; Dean, Sam M.

    2017-02-01

    Glaciers experienced worldwide retreat during the twentieth and early twenty first centuries, and the negative trend in global glacier mass balance since the early 1990s is predominantly a response to anthropogenic climate warming. The exceptional terminus advance of some glaciers during recent global warming is thought to relate to locally specific climate conditions, such as increased precipitation. In New Zealand, at least 58 glaciers advanced between 1983 and 2008, and Franz Josef and Fox glaciers advanced nearly continuously during this time. Here we show that the glacier advance phase resulted predominantly from discrete periods of reduced air temperature, rather than increased precipitation. The lower temperatures were associated with anomalous southerly winds and low sea surface temperature in the Tasman Sea region. These conditions result from variability in the structure of the extratropical atmospheric circulation over the South Pacific. While this sequence of climate variability and its effect on New Zealand glaciers is unusual on a global scale, it remains consistent with a climate system that is being modified by humans.

  11. Regional cooling caused recent New Zealand glacier advances in a period of global warming

    PubMed Central

    Mackintosh, Andrew N.; Anderson, Brian M.; Lorrey, Andrew M.; Renwick, James A.; Frei, Prisco; Dean, Sam M.

    2017-01-01

    Glaciers experienced worldwide retreat during the twentieth and early twenty first centuries, and the negative trend in global glacier mass balance since the early 1990s is predominantly a response to anthropogenic climate warming. The exceptional terminus advance of some glaciers during recent global warming is thought to relate to locally specific climate conditions, such as increased precipitation. In New Zealand, at least 58 glaciers advanced between 1983 and 2008, and Franz Josef and Fox glaciers advanced nearly continuously during this time. Here we show that the glacier advance phase resulted predominantly from discrete periods of reduced air temperature, rather than increased precipitation. The lower temperatures were associated with anomalous southerly winds and low sea surface temperature in the Tasman Sea region. These conditions result from variability in the structure of the extratropical atmospheric circulation over the South Pacific. While this sequence of climate variability and its effect on New Zealand glaciers is unusual on a global scale, it remains consistent with a climate system that is being modified by humans. PMID:28195582

  12. Advancing Glaciers and Positive Mass Anomaly in the Karakoram Himalaya, Pakistan

    NASA Astrophysics Data System (ADS)

    Bishop, M. P.; Bush, A. B.; Collier, E.; Copland, L.; Haritashya, U. K.; John, S. F.; Swenson, S. C.; Wahr, J.

    2008-12-01

    Himalayan glaciers are thought to be extremely sensitive to climate change given their altitude and supraglacial debris characteristics. Limited field and space-based assessment of glaciers in the Karakoram suggests that these glaciers may be responding differently to climate forcing compared to rapidly retreating glaciers in the eastern Himalaya. Relatively little is known about glacier sensitivity to climate forcing in the western Himalaya. Consequently, we conducted an extensive investigation of glacier fluctuations in the Karakoram Himalaya of Pakistan, which is part of the international Global Land Ice Measurements From Space (GLIMS) project. Our specific objective was to estimate average retreat rates and ascertain the regional mass balance. To accomplish this, we utilized a variety of multi-temporal imagery including ASTER (Advanced Spaceborn Thermal Emission and Reflectance Radiometer), Landsat ETM (Enhanced Thematic Mapper), and declassified satellite imagery (KH-9), acquired from approximately 1980 to 2004. Climate reanalysis data sets (NCEP/NCAR and ERA40) and TRMM (Tropical Rainfall Mapping Mission) data were also utilized to examine precipitation patterns. We sampled approximately 250 glaciers in the region. Our result indicate that 65 percent of the glaciers either advanced or showed no change in terminus position. We also discovered a glacier surge anomaly and have identified and mapped 53 new surging glaciers that have not been previously reported. Paleoclimate proxies and climate data indicate that the region has experienced a general increase in precipitation over time. Satellite observations and climate data strongly suggest a regional positive mass balance. Direct confirmation of this has been determined from an analysis of GRACE (Gravity Recovery And Climate Experiment) gravity field data, which depicts a positive mass anomaly that is spatially coincident with advancing and surging glaciers, caused by increasing snowfall. Regional climate

  13. Age and significance of former low-altitude corrie glaciers on Hoy, Orkney Islands

    USGS Publications Warehouse

    Ballantyne, C.K.; Hall, A.M.; Phillips, W.; Binnie, S.; Kubik, P.W.

    2007-01-01

    Geomorphological mapping provides evidence for two former low-level corrie glaciers on Hoy, both defined by end moraines. Five 10Be exposure ages obtained from sandstone boulders on moraine crests fall within the range 12.4??1.5 ka to 10.4??1.7 ka (weighted mean 11.7??0.6 ka), confirming that these glaciers developed during the Loch Lomond (Younger Dryas) Stade (LLS) of 12.9-11.5 cal. ka BP, and demonstrate the feasibility of using this approach to establish the age of LLS glacier limits. The equilibrium line altitude (ELA) of one of the glaciers (99 m) is the lowest recorded for any LLS glacier, and the area-weighted mean ELA for both (141 m) is consistent with a general northward ELA decrease along the west coast of Britain. The size of moraines fronting these small (???0.75 km2) glaciers implies that glacier termini remained at or close to their limits for a prolonged period. The apparent restriction of LLS glaciers to only two sites on Hoy probably reflects topographic favourability, and particularly the extent of snow-contributing areas.

  14. Development of Ideas About Holocene and Latest Pleistocene Glacier Advances in the North American Cordillera

    NASA Astrophysics Data System (ADS)

    Osborn, G.

    2014-12-01

    It all started when Francois Matthes coined the phrase "little ice age" (LIA) in 1939 to explain cirque moraines in the Sierra Nevada. Porter and Denton in the late 60's promoted the concept that the LIA was part of a multi-millennium regrowth of glaciers called "Neoglaciation."A second set of small moraines found in a few cirques short distances downvalley of LIA moraines in the American Rockies began attracting some attention in the 1940s-50s. By the 1960s-70s there was much argument over the age(s) of these moraines. A proliferation of ages appeared in the literature in the 1970s-80s, but Thom Davis and Jerry Osborn in 1987 proposed that most or all these outer cirque moraines are actually Younger Dryas (YD) in age.In Alberta in the 1970s, Brian Luckman began studying LIA deposits and Osborn began mapping outer cirque moraines (Crowfoot moraines). The two joined forces for an overview of Holocene glacial history in the Canadian Rockies in 1979.Eric Leonard and Mel Reasoner began lake-sediment studies in the Canadian Rockies in the 1980s-90s. Reasoner and Osborn concluded using lake sediments that the type Crowfoot moraine is YD in age, and in Colorado and Wyoming, Davis, Reasoner, and Brian Menounos established YD ages of outer cirque moraines. Lateral-moraine stratigraphy, begun in the 1980s by June Ryder and Osborn in British Columbia, corroborated the evidence from lake sediments that minor advances and retreats punctuated a gradual Neoglacial expansion of glaciers that began 7 or 8 ka.The era of cosmogenic dating began in the 1990s, with John Gosse's work in the Wind River Range. Most, but not all, cosmogenic ages on outer cirque moraines, including those yielded by Shaun Marcott's broad survey, are in support of the concept that such moraines are YD or pre-YD in age, although uncertainties resulting from production-rate questions remain. There have been various claims of early Holocene advances greater in magnitude than the LIA, but these have been

  15. Historical Glacier Variations in Southern South America since the Little Ice Age: Examples from Lago Viedma (Southern Patagonia) and Mendoza (Central Andes), Argentina

    NASA Astrophysics Data System (ADS)

    Nussbaumer, S. U.; Masiokas, M.; Pitte, P.; Berthier, E.; Guerrido, C.; Luckman, B. H.; Villalba, R.

    2013-12-01

    The evaluation of historical information can give valuable insight into past glacier dynamics, especially before the onset of modern measurements. Early photographs and maps depict changes for selected glaciers in southern South America. Within this study, written documents and pictorial historical records (drawings, sketches, engravings, photographs, chronicles, topographic maps) are analysed critically, with a particular focus on two regions: Lago Viedma (El Chaltén, southern Patagonia, 49.5°S, 73.0°W) and the Río Mendoza basin (Mendoza, central Andes, 33.1°S, 69.9°W). For the Lago Viedma area, early historical data for the end of the 19th century stem from the expedition of the Chilean-Argentinean border commission. In addition, the expedition by the German Scientific Society, conducted between 1910 and 1916, and the later photographs by Alberto M. de Agostini give an excellent depiction of the glaciers. Glaciar Viedma is a calving glacier which shows distinct retreat from 1896 until the present (though with a stationary or possibly advancing glacier front between 1930/31 and 1951/52), similar to the neighbouring glaciers. On the contrary, nearby Glaciar Perito Moreno shows an exceptional behaviour: the glacier front has been advancing during the first half of the 20th century, staying in an advanced position until the present. At the beginning of the 20th century, Robert Helbling explored the Argentinean-Chilean Andes together with his friend Friedrich Reichert. In the summer of 1909/10, they started a detailed survey of the highly glacierized Juncal-Tupungato mountains (Río Mendoza basin), leading to the first accurate topographic map of the area published in 1914. Its outstanding quality allows a comparison with contemporary satellite imagery. The area received attention in 1934, when the sudden drainage of a glacier-dammed lake in the upper Río del Plomo valley caused fatalities and considerable damage to constructions and the Transandine Railway. A

  16. Complex patterns of glacier advances during the late glacial in the Chagan Uzun Valley, Russian Altai

    NASA Astrophysics Data System (ADS)

    Gribenski, Natacha; Jansson, Krister N.; Lukas, Sven; Stroeven, Arjen P.; Harbor, Jonathan M.; Blomdin, Robin; Ivanov, Mikhail N.; Heyman, Jakob; Petrakov, Dmitry A.; Rudoy, Alexei; Clifton, Tom; Lifton, Nathaniel A.; Caffee, Marc W.

    2016-10-01

    The Southern part of the Russian Altai Mountains is recognized for its evidence of catastrophic glacial lake outbursts. However, little is known about the late Pleistocene paleoglacial history, despite the interest in such reconstructions for constraining paleoclimate. In this study, we present a detailed paleoglaciological reconstruction of the Chagan Uzun Valley, in the Russian Altai Mountains, combining for the first time detailed geomorphological mapping, sedimentological logging, and in situ cosmogenic 10Be and 26Al surface exposure dating of glacially-transported boulders. The Chagan Uzun Valley exhibits the most impressive glacial landforms of this sector of the Altai, with extensive lobate moraine belts deposited in the intramontane Chuja Basin, reflecting a series of pronounced former glacial advances. Observations of "hillside-scale" folding and extensive faulting of pre-existing soft sediments within the outer moraine belts, together with the geomorphology, strongly indicate that these moraine belts were formed during surge-like events. Identification of surge-related features is essential for paleoclimate inference because these features correspond to a glacier system that is not in equilibrium with the contemporary climate, but instead largely influenced by various internal and external factors. Therefore, no strict relationship can be established between climatic variables and the pronounced distal glacial extent observed in the Chagan Uzun Valley/Chuja basin. In contrast, the inner (up-valley) glacial landforms of the Chagan Uzun valley were likely deposited during retreat of temperate valley glaciers, close to equilibrium with climate, and so most probably triggered by a general warming. Cosmogenic ages associated with the outermost, innermost, and intermediate moraines all indicate deposition times clustered around 19 ka. However, the actual deposition time of the outermost moraine may slightly predate the 10Be ages due to shielding caused by

  17. Climates during Late Quaternary glacier advances: glacier-climate modeling in the Yingpu Valley, eastern Tibetan Plateau

    NASA Astrophysics Data System (ADS)

    Xu, Xiangke

    2014-10-01

    The Last Glacial Maximum (LGM) featured a major cooling of Earth's climate, after which the climate evolved in the largest reconfiguration of the past 100 ka. Despite its significance, full understanding of the climate history during and since the LGM is still lacking on the eastern Tibetan Plateau. Recent improvements in understanding glacial extents and chronologies in the Yingpu Valley, eastern Tibetan Plateau present an opportunity to estimate the glacial climatic conditions during and since the LGM. Using a relatively new glacier-climate model, this study reconstructs glacier advances in the Yingpu Valley and quantifies the related climate conditions during the LGM, Lateglacial, and Late Holocene glacial stages. The model results show that the Yingpu Valley contained ice volumes of ˜1.65 km3, 1.03 km3, and 0.29 km3 with equilibrium line altitude (ELA) lowering values of ˜500 m, ˜410 m, and ˜150 m in the three successive glacial stages, respectively. By examining other independent paleoclimatic reconstructions, it is concluded that the temperature decreased by 4.0-5.9 °C, 3.4-3.7 °C, 0.3-0.6 °C with the precipitation amounts being 40-80%, 80-100%, and 100-110% of modern values during the LGM, Lateglacial, and Late Holocene glacial stages, respectively. The climate estimates for the three glacial stages are generally in agreement with other climatic proxy records on the Tibetan Plateau and atmospheric circulation modeling results.

  18. Glacier fluctuations during the past 2000 years

    NASA Astrophysics Data System (ADS)

    Solomina, Olga N.; Bradley, Raymond S.; Jomelli, Vincent; Geirsdottir, Aslaug; Kaufman, Darrell S.; Koch, Johannes; McKay, Nicholas P.; Masiokas, Mariano; Miller, Gifford; Nesje, Atle; Nicolussi, Kurt; Owen, Lewis A.; Putnam, Aaron E.; Wanner, Heinz; Wiles, Gregory; Yang, Bao

    2016-10-01

    A global compilation of glacier advances and retreats for the past two millennia grouped by 17 regions (excluding Antarctica) highlights the nature of glacier fluctuations during the late Holocene. The dataset includes 275 time series of glacier fluctuations based on historical, tree ring, lake sediment, radiocarbon and terrestrial cosmogenic nuclide data. The most detailed and reliable series for individual glaciers and regional compilations are compared with summer temperature and, when available, winter precipitation reconstructions, the most important parameters for glacier mass balance. In many cases major glacier advances correlate with multi-decadal periods of decreased summer temperature. In a few cases, such as in Arctic Alaska and western Canada, some glacier advances occurred during relatively warm wet times. The timing and scale of glacier fluctuations over the past two millennia varies greatly from region to region. However, the number of glacier advances shows a clear pattern for the high, mid and low latitudes and, hence, points to common forcing factors acting at the global scale. Globally, during the first millennium CE glaciers were smaller than between the advances in 13th to early 20th centuries CE. The precise extent of glacier retreat in the first millennium is not well defined; however, the most conservative estimates indicate that during the 1st and 2nd centuries in some regions glaciers were smaller than at the end of 20th/early 21st centuries. Other periods of glacier retreat are identified regionally during the 5th and 8th centuries in the European Alps, in the 3rd-6th and 9th centuries in Norway, during the 10th-13th centuries in southern Alaska, and in the 18th century in Spitsbergen. However, no single period of common global glacier retreat of centennial duration, except for the past century, has yet been identified. In contrast, the view that the Little Ice Age was a period of global glacier expansion beginning in the 13th century

  19. Little Ice Age glaciers in Britain: Glacier–climate modelling in the Cairngorm Mountains

    SciTech Connect

    Stephan Harrison; Ann V. Rowan; Neil F. Glasser; Jasper Knight; Mitchell A. Plummer; Stephanie C. Mills

    2014-02-01

    It is widely believed that the last glaciers in the British Isles disappeared at the end of the Younger Dryas stadial (12.9–11.7 cal. kyr BP). Here, we use a glacier–climate model driven by data from local weather stations to show for the first time that glaciers developed during the Little Ice Age (LIA) in the Cairngorm Mountains. Our model is forced from contemporary conditions by a realistic difference in mean annual air temperature of -1.5 degrees C and an increase in annual precipitation of 10%, and confirmed by sensitivity analyses. These results are supported by the presence of small boulder moraines well within Younger Dryas ice limits, and by a dating programme on a moraine in one cirque. As a result, we argue that the last glaciers in the Cairngorm Mountains (and perhaps elsewhere in upland Britain) existed in the LIA within the last few hundred years, rather than during the Younger Dryas.

  20. Episodic Neoglacial snowline descent and glacier expansion on Svalbard reconstructed from the 14C ages of ice-entombed plants

    NASA Astrophysics Data System (ADS)

    Miller, Gifford H.; Landvik, Jon Y.; Lehman, Scott J.; Southon, John R.

    2017-01-01

    The response of the Northern Hemisphere cryosphere to the monotonic decline in summer insolation and variable radiative forcing during the Holocene has been one of irregular expansion culminating in the Little Ice Age, when most glaciers attained their maximum late Holocene dimensions. Although periods of intervening still-stand or ice-retreat can be reconstructed by direct dating of ice-recessional features, defining times of Neoglacial ice growth has been limited to indirect proxies preserved in distal archives. Here we report 45 precise radiocarbon dates on in situ plants emerging from beneath receding glaciers on Svalbard that directly date the onset of snowline descent and glacier expansion, entombing the plants. Persistent snowline lowering occurred between 4.0 and 3.4 ka, but with little additional persistent lowering until early in the first millennium AD. Populations of individual 14C calendar age results and their aggregate calendar age probabilities define discrete episodes of vegetation kill and snowline lowering 240-340 AD, 410-540 AD and 670-750 AD, each with a lower snowline than the preceding episode, followed by additional snowline lowering between 1000 and 1220 AD, and between 1300 and 1450 AD. Snowline changes after 1450 AD, including the maximum ice extent of the Little Ice Age are not resolved by our collections, although snowlines remained lower than their 1450 AD level until the onset of modern warming. A time-distance diagram derived from a 250-m-long transect of dated ice-killed plants documents ice-margin advances ∼750, ∼1100 and after ∼1500 AD, concordant with distributed vegetation kill ages seen in the aggregate data set, supporting our central thesis that vegetation kill ages provide direct evidence of snowline lowering and cryospheric expansion. The mid- to late-Holocene history of snowline lowering on Svalbard is similar to ELA reconstructions of Norwegian and Svalbard cirque glaciers, and consistent with a cryospheric response

  1. Glacier fluctuations in the Kenai Fjords, Alaska, U.S.A.: An evaluation of controls on Iceberg-calving glaciers

    SciTech Connect

    Wiles, G.C.; Calkin, P.E.; Post, A.

    1995-08-01

    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 synchronously 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.

  2. The Impacts of Advancing Glaciers and Jökulhlaups on the 19th Century Farming Community in the Suðursveit District South of Vatnajökull Glacier, Iceland.

    NASA Astrophysics Data System (ADS)

    Sigurmundsson, F. S.; Gísladóttir, G.; Erlendsson, E.

    2014-12-01

    Few areas in Iceland were as vulnerable to climate changes during the 19th century as the region south of Vatnajökull glacier. The region was repeatedly affected by glacier advance and jökulhlaups (glacier outburst floods) during the Little Ice Age AD 1300-1900 (LIA). The land area between the glacier and the coast was occupied by farming community. The aim of this research is to quantify and map the size of lost vegetated area in the 19th century during the glacial advance in the climax of the LIA and the impact these events had on the community, land-use, ownership, value of estates and livelihood. This research employs historical written sources to investigate changes in the cultural and natural landscape. Historical data and field observations will be collected and stored in a GIS database designed for the research, allowing data to be analyzed and presented on maps. The first recorded impact on the settlement is from 1794 when the Breiðármerkurjökull outlet glacier advanced and devastated pastures and crofts belonging in west of the district. Seventy five years later, in 1868, the largest estate was completely destroyed by a jökulhlaup. In 1829 a farm site in the middle of the district was moved due to repeated jökulhlaup. The outlet glacier Brókarjökull initiated annual jökulhlaups during 1820 -1870, devastating pastures and hayfields and woodlands of a total of 3 prominent estates in the area (by 1200 ha), causing devaluation of 33-66% on these estates. In the eastern part extensive jökulhlaups changed the glacial river channel causing the river to flow over vast area devastating 80 % of the eastern most estate causing its abandonment in 1892. The climate change and accompanied hazards during the 19th century changed the landscape of the Suðursveit district significantly. By the turn of the 20thcentury the vegetated land in the district had been reduced by 35% and areas of sediments increased by 25% and glaciated area increased by 10%. These

  3. A high glacier opens a view of the ice age tropics

    SciTech Connect

    Mlot, C.

    1995-07-07

    This article discusses new information about the ice age tropics as cores from a mountain glacier in the Peruvian Andes are analysed. Chemical markers in the ice of the two cores (160 and 166 meters long), covering 20,000 years, are starting to provide detailed support for understanding the ice age in the tropics. they show that climate in the tropics experience sharp oscillations at the end of the ice ages as it did in more northerly regions. Information about El Ninos and how the tropics respond to global climate changes is forthcoming. Comments on the actual expedition to obtain the ice cores are included.

  4. Radiocarbon Dates Link Marine Incursion and Neoglacial Ice Terminus Advance With Tlingit Ethnohistory and Archeology in Lower Glacier Bay

    NASA Astrophysics Data System (ADS)

    Connor, C. L.; Monteith, D.; Howell, W.; Strevelar, G.; Leirer, M.

    2004-12-01

    Radiocarbon dates from wood, organic sediments, and marine shells were collected from eroded beach terraces and upper beach sediments in the Beardslee Islands and Berg Bay in Glacier Bay National Park, Alaska. These provide a timetable for the the outwash plain construction and final advance of the Late Neoglacial glacier front over this outwash plain into lower Glacier Bay. On Kidney Island in the central Beardslee Islands, marine sediments containing Macoma baltica shells were deposited 4310 +/- 40 years BP. Outwash from advancing up-bay glaciers, buried these sediments and created terrestrial substrates upon which forests existed by 1630 +/- 60 BP and 1300 +/- 50 yrs BP. Final ice advance over this forested outwash plain occurred after 430 +/- 60 BP (1430 to 1510 AD) on Kidney Island. This ice arrived at the southern edge of Lester Island in Bartlett Cove after 370 +/- 50 BP (1440 to 1520 AD); preceding the arrival of George Vancouver in 1794 AD. In nearby Icy Straits, archeological investigations have yielded some of the oldest dates of human occupation in the region at 10,180 +/- 800 uncorrected years BP (Ackerman, 1968). In Glacier Bay's ethno-historically rich areas of Bartlett Cove, the Beardslee Islands and Berg Bay the Huna people have names for places and narratives that describe late Neoglacial landscapes. S'é Shuyee is the "area at the end of the glacial mud", L'awsha Shakee Aan "town on top of the glacial sand dunes". There are accounts of villages overrun by surging glaciers, and a name for the bay Sit' eeti Geeyi that translates as "bay in place of the glacier". These dates provide linkage between the geological, archeological, and ethnohistorical evidence that chronicles the history of the Huna people in this dynamic glacier marine environment.

  5. Advances in ice radar studies of a temperate alpine glacier, South Cascade Glacier, Washington, U.S.A.

    USGS Publications Warehouse

    Fountain, A.G.; Jacobel, R.W.

    1997-01-01

    South Cascade Glacier, Washington, U.S.A., is one of the most extensively studied glaciers in the Western Hemisphere. In addition to mass-balance measurements, which date to 1958, numerous hydrological investigations have been carried out during the last three decades, and repeated ice-thickness determinations have been made using a variety of techniques. In the late 1960s, the basal topography was initially determined by gravitimetric methods. In the mid-1970s some of the first depth measurements using radar on temperate ice were made. The basal topography was remapped soon after from a series of point radar measurements and boreholes drilled to the glacier bottom. During the 1990s, the ice thickness was remapped using digital recording of continuous profiles that obtained over 5000 ice-thickness measurements. Profiles have been corrected for the finite beamwidth of the antenna radiation pattern and reflections in steep terrain, resulting in a significantly improved depiction of the basal surface and internal structures. The map based on our recent radar profiles confirms the large-scale features of the basal topography previously depicted and reveals more structural detail. A bright reflector was detected at the base of the glacier and could be traced in adjacent profiles. Comparison with results from water-level measurements in boreholes drilled to the bed indicates that the reflector is a subglacial conduit.

  6. Cosmogenic 10Be Exposure Age for the Cut Bank Creek terminal moraine, Glacier National Park, MT

    NASA Astrophysics Data System (ADS)

    Quirk, B.; Laabs, B. J.; Leonard, E. M.; Caffee, M. W.

    2012-12-01

    Mountain glaciers are highly sensitive to temperature and precipitation with geologic records that are superb proxies of climate change. In the Rocky Mountains of the western United States, abundant records of Late Pleistocene glaciation provide an opportunity for understanding paleoclimate throughout this region, especially in places where the chronology of glaciation is precisely known. Cosmogenic 10Be exposure dating has been widely applied to glacial deposits in the Rocky Mountains, providing precise numerical ages and improving the understanding of glacial chronologies in this region. Despite these improvements, the chronology of the last Pleistocene glaciation of the northernmost Rocky Mountains is not completely understood. Cosmogenic 10Be exposure dating was applied to the Cut Bank Creek valley in the Lewis Range of the Northern Rocky Mountains, where a discrete mountain glacier deposited a broad terminal moraine during the last Pleistocene glaciation. Exposure ages of eight quartzite and sandstone boulders at the crest of the ice-distal sector of the terminal moraine indicate that abandonment occurred at 15.6 ± 0.8 ka. This age is consistent with age limits of several terminal moraines elsewhere in the Northern Rocky Mountains, suggesting that the last Pleistocene glaciation culminated in this region after the global Last Glacial Maximum.

  7. Postponing parenthood to advanced age

    PubMed Central

    Waldenström, Ulla

    2016-01-01

    The aim of the Postponing Parenthood project was to investigate several aspects of the delaying of childbearing phenomenon in Sweden and Norway, such as medical risks and parental experiences. Data were retrieved from the Swedish and Norwegian Medical Birth Registers and three different cohorts: the Swedish Young Adult Panel Study, the Norwegian Mother and Child Cohort, and the Swedish Women’s Experiences of Childbirth cohort. Postponing childbirth to age 35 years and later increased the risk of rare but serious pregnancy outcomes, such as stillbirth and very preterm birth. Older first-time parents were slightly more anxious during pregnancy, and childbirth overall was experienced as more difficult, compared with younger age groups. First-time mothers’ satisfaction with life decreased from about age 28 years, both when measured during pregnancy and early parenthood. Delaying parenthood to mid-30 or later was more related to lifestyle than socioeconomic factors, suggesting that much could be done in terms of informing young persons about the limitations of fertility and assisted reproductive techniques, and the risks associated with advanced parental age. PMID:27385461

  8. Initial AUV Investigation of the Dynamic Morainal Bank Environment of the Advancing Hubbard Glacier, Alaska

    NASA Astrophysics Data System (ADS)

    Lawson, D. E.; Gulick, S. P. S.; Goff, J. A.

    2015-12-01

    Hubbard Glacier has been steadily advancing into tidewater > 200 years; advance over last 40 years has averaged ~34 m/yr, although at spatially variable rates across the terminus (14-80 m/yr) and with a seasonal advance and retreat cycle of ~100 m to 300 m, but as much as 600 m. The advance of the terminus is synchronous with the movement of the morainal bank that underlies it. The mechanics of this motion and the related sedimentological processes responsible for this coordinated advance of the grounding line are based largely on inferences from geophysical surveys of remnant morainal banks. In situ and repeated observations of the submarine margin are required to improve our understanding of how the terminus advances into deep fjords. We conducted initial submarine observations using a Bluefin 9M AUV (Autonomous Underwater Vehicle) and acquired high-resolution swath bathymetry and sidescan backscatter along a ~2 km long section of the ice face of the glacier. Onboard oceanographic measurements and surface CTD casts were obtained during AUV deployment. Decimeter-scale imagery of the seabed reveals numerous erosional and depositional bedforms and gravitational features next to the ice face and down the morainal bank's proximal slope. The moraine surface adjacent to the ice face is coarse, apparently swept clear of finer materials, exhibits gravel stripes and boulder lags. The slope into the fjord displays a sequence of bedforms from barchan-shaped dunes up to 15 m on a side to barchanoid transverse ridges >50 m long to transverse ridges >100 m long. This transition implies increased sand supply to the bed downslope. Channels, erosional gullies and scours cross the upper slope, while localized slump and flow failures occur sporadically across the face. We speculate that high concentration bottom flows originating from turbulent subglacial discharge are likely processes creating the barchan forms and that the flow velocity reduces with distance from the grounding

  9. Repeated large-scale retreat and advance of Totten Glacier indicated by inland bed erosion.

    PubMed

    Aitken, A R A; Roberts, J L; van Ommen, T D; Young, D A; Golledge, N R; Greenbaum, J S; Blankenship, D D; Siegert, M J

    2016-05-19

    Climate variations cause ice sheets to retreat and advance, raising or lowering sea level by metres to decametres. The basic relationship is unambiguous, but the timing, magnitude and sources of sea-level change remain unclear; in particular, the contribution of the East Antarctic Ice Sheet (EAIS) is ill defined, restricting our appreciation of potential future change. Several lines of evidence suggest possible collapse of the Totten Glacier into interior basins during past warm periods, most notably the Pliocene epoch, causing several metres of sea-level rise. However, the structure and long-term evolution of the ice sheet in this region have been understood insufficiently to constrain past ice-sheet extents. Here we show that deep ice-sheet erosion-enough to expose basement rocks-has occurred in two regions: the head of the Totten Glacier, within 150 kilometres of today's grounding line; and deep within the Sabrina Subglacial Basin, 350-550 kilometres from this grounding line. Our results, based on ICECAP aerogeophysical data, demarcate the marginal zones of two distinct quasi-stable EAIS configurations, corresponding to the 'modern-scale' ice sheet (with a marginal zone near the present ice-sheet margin) and the retreated ice sheet (with the marginal zone located far inland). The transitional region of 200-250 kilometres in width is less eroded, suggesting shorter-lived exposure to eroding conditions during repeated retreat-advance events, which are probably driven by ocean-forced instabilities. Representative ice-sheet models indicate that the global sea-level increase resulting from retreat in this sector can be up to 0.9 metres in the modern-scale configuration, and exceeds 2 metres in the retreated configuration.

  10. Repeated large-scale retreat and advance of Totten Glacier indicated by inland bed erosion

    NASA Astrophysics Data System (ADS)

    Aitken, A. R. A.; Roberts, J. L.; Ommen, T. D. Van; Young, D. A.; Golledge, N. R.; Greenbaum, J. S.; Blankenship, D. D.; Siegert, M. J.

    2016-05-01

    Climate variations cause ice sheets to retreat and advance, raising or lowering sea level by metres to decametres. The basic relationship is unambiguous, but the timing, magnitude and sources of sea-level change remain unclear; in particular, the contribution of the East Antarctic Ice Sheet (EAIS) is ill defined, restricting our appreciation of potential future change. Several lines of evidence suggest possible collapse of the Totten Glacier into interior basins during past warm periods, most notably the Pliocene epoch, causing several metres of sea-level rise. However, the structure and long-term evolution of the ice sheet in this region have been understood insufficiently to constrain past ice-sheet extents. Here we show that deep ice-sheet erosion—enough to expose basement rocks—has occurred in two regions: the head of the Totten Glacier, within 150 kilometres of today’s grounding line; and deep within the Sabrina Subglacial Basin, 350-550 kilometres from this grounding line. Our results, based on ICECAP aerogeophysical data, demarcate the marginal zones of two distinct quasi-stable EAIS configurations, corresponding to the ‘modern-scale’ ice sheet (with a marginal zone near the present ice-sheet margin) and the retreated ice sheet (with the marginal zone located far inland). The transitional region of 200-250 kilometres in width is less eroded, suggesting shorter-lived exposure to eroding conditions during repeated retreat-advance events, which are probably driven by ocean-forced instabilities. Representative ice-sheet models indicate that the global sea-level increase resulting from retreat in this sector can be up to 0.9 metres in the modern-scale configuration, and exceeds 2 metres in the retreated configuration.

  11. Imaging Evidence for Hubbard Glacier Advances and Retreats since the Last Glacial Maximum in Disenchantment and Yakutat Bays, Alaska

    NASA Astrophysics Data System (ADS)

    Zurbuchen, J.; Gulick, S. P.; Levoir, M. A.; Goff, J. A.; Haeussler, P. J.

    2013-12-01

    As glaciers advance and retreat, they leave erosional surfaces, retreat sequences, morainal banks, and terminal moraines. These features can be imaged and interpreted in seismic reflection data to gain insight into ice routing, ice-sediment processes, and preserved glacial history. High-resolution 2-D multichannel seismic data gathered on the August 2012 UTIG-USGS National Earthquake Hazards Reduction Program survey of Disenchantment and Yakutat Bays have provided understanding of the advance pathways of the Hubbard Glacier and the glacial history of the bays. These data show evidence of three unconformities appearing in the form of channels and interpreted to be glacial advance and retreat paths. The youngest observable channel in Disenchantment Bay is ~2 km wide, forming morainal banks along the edges of the bay. The depth below modern sea level in two-way travel time (twtt) shallows from 510 ms in the middle of the bay to 400 ms ~4 km north of the entrance to Yakutat Bay. The sediment contained within the youngest channel measured from the seafloor thins southward from a twtt thickness of 260 ms to 115 ms. Beneath the youngest channel lies an older, 2.2 km-wide channel which is observed at ~580 ms below sea level, and is filled with sediments ranging in thickness from 480 ms to 180 ms at the terminus. This older channel extends from Disenchantment Bay into Yakutat Bay, staying to the northeast of Yakutat Bay, then turns southward at Knight Island and shallows to 450 ms twtt before forming a terminal moraine ~10 km north of the mouth of Yakutat Bay. Evidence for the third and oldest unconformity can only be seen within a very small number of short seismic lines in Disenchantment Bay. It is the largest of the channels, at ~3 km wide and 720 ms below modern sea level. The evidence of three nested unconformities suggests that the Hubbard Glacier has had at least three major advances in recent history. Radiocarbon dating of wooden branches in moraine deposits

  12. Detailed Reconstructions of Fluctuations of Seven Glaciers during the "little Ice Age" in the Northern Caucasus, Russian Federation

    NASA Astrophysics Data System (ADS)

    Bushueva, I.

    2012-12-01

    The main task of this work is the development of detailed reconstructions of mountain glaciers' fluctuations with precise spatial references in the Northern Caucasus, their analyses in terms of glacier length, area and volume changes and identification of climate role in these fluctuations. The studied glaciers (Alibek, Ullukam, Terskol, Kashkatash, Bezingi, Mijirgi, Tsey) are situated along the Bolshoy Caucasus Range from the very west (Teberda river basin) to the east (Tseydon river basin). These valley glaciers have different size, aspect and percent of debris-cover. Basing on instrumental data (since the middle of 20th century), remote sensing images (CORONA, Geoeye, Cartosat, IRS, ASTER, etc.), aerial photos of 1950s-1980s, maps (since 1887), old photographs, as well as proxy data (historical descriptions, lichenometry, dendrochronology, 14C, 10Be), we reconstructed 15-20 positions of the glaciers tongues for each glacier and produced maps showing variations of the glaciers with precise spatial reference since their maximum in the mid 17th or first half of 19th century. For example, for Alibek glacier seven former front positions and eleven moraines were photo-identified and dated. We obtained the carbon dating of intermorainal peat-bog (103%), moraine dating based on isotopes of 10Be (1900±12) and determined minimum age of most distant moraine according to dendrochronological analysis of trees (Abies nordmanniana), growing on its surface (more than 200 years). At that time (1895) the glacier was 290 m longer than today, its surface was 0.31 km2 larger (5.94 km2 in 1895, 5.63 km2 in 2008). We calculated glaciers' length and area changes, using different methods (GLIMS; Bhambri et al., 2012) and analyzed advantages and disadvantages of each method in case of their application for Caucasian glaciers. Based on our measurements we evaluated changes of equilibrium line altitude and volume. Volume changes have been reconstructed using the model offered by Lüthi et

  13. Cosmogenic 10Be constraints on Little Ice Age glacial advances in the eastern Tian Shan, China

    NASA Astrophysics Data System (ADS)

    Li, Yanan; Li, Yingkui; Harbor, Jon; Liu, Gengnian; Yi, Chaolu; Caffee, Marc W.

    2016-04-01

    Presumed Little Ice Age (LIA) glacial advances, represented by a set of fresh, sharp-crested, boulder covered and compact moraines a few hundred meters downstream from modern glaciers, have been widely recognized in the Central Asian highlands. However, few studies have constrained the formation ages of these moraines. We report 31 10Be exposure ages from presumed LIA moraines in six glacial valleys in the Urumqi River headwater area and the Haxilegen Pass area of the eastern Tian Shan, China. Our results reveal that the maximum LIA glacial extent occurred mainly around 430 ± 100 yr, a cold and wet period as indicated by proxy data from ice cores, tree rings, and lake sediments in Central Asia. We also dated a later glacial advance to 270 ± 55 yr. However, 10Be exposure ages on several presumed LIA moraines in front of small, thin glaciers are widely scattered and much older than the globally recognized timing of the LIA. Historical topographic maps indicate that most glaciers were more extensive in the early 1960s, and two of our 10Be sample sites were located close to the ice front at that time. Boulders transported by these small and thin glaciers may be reworked from deposits originally formed prior to the LIA glacial advances, producing apparently old and widely scattered exposure ages due to varied nuclide inheritance. Other published ages indicated an earlier LIA advance around 790 ± 300 yr in the easternmost Tian Shan, but in our study area the more extensive advance around 430 ± 100 yr likely reworked or covered deposits from this earlier event.

  14. Changing tidewater glacier extent and response to climate from Little Ice Age to present: observations and modelling of Kangiata Nunaata Sermia, SW Greenland

    NASA Astrophysics Data System (ADS)

    Mair, D.; Lea, J. M.; Nick, F. M.; Rea, B. R.; Nienow, P. W.

    2013-12-01

    Records of Greenlandic tidewater glacier (TWG) change are primarily restricted to the period covered by satellite observation. This study extends the record of terminus change of the tidewater outlet glacier Kangiata Nunaata Sermia (KNS), SW Greenland to its Little Ice Age maximum (LIAmax). This is achieved using a combination of geomorphology, written observations, and historical and satellite imagery. We explore likely marine and atmospheric controls on terminus change by comparison with existing records of local air and ocean temperatures and, for earlier periods, by modelling glacier response to systematic changes in marine and oceanic forcings at the terminus. Results from the glacier reconstruction show that retreat began in the late 18th century, with the terminus retreating at least 12 km from its LIAmax by 1859. KNS then experienced a period of relative stability before advancing to its 20th century maximum by ~1920. Significant retreat occurred from 1921-1965, before periods of advance and retreat up until 1997. Subsequent to this, KNS has retreated by 2 km up to the end of the 2012 melt season. The LIAmax to present retreat of KNS totals 22.6 km. Comparison of terminus fluctuations to local air temperature (1866-present) and sea surface temperature (1870-present) anomalies demonstrate that air temperature exerts a significant modulating control on terminus stability for the duration of the record. A state-of-the-art 1-dimensional flow-band model driven by submarine melt (SM) and crevasse water depth (CWD; Nick et al, 2010) is capable of reconstructing observed terminus fluctuations during earlier periods for realistic values of SM using a range of CWD. This provides confidence that such models are capable of predicting TWG terminus variability over centennial timescales.

  15. Synchoronous inter-hemispheric alpine glacier advances during the Late Glacial?

    NASA Astrophysics Data System (ADS)

    Bakke, Jostein; Paasche, Øyvind

    2016-04-01

    The termination of the last glaciation in both hemispheres was a period of rapid climate swings superimposed on the overall warming trend, resulting from large-scale reorganizations of the atmospheric and oceanic circulation patterns in both hemispheres. Environmental changes during the deglaciation have been inferred from proxy records, as well as by model simulations. Several oscillations took place both in northern and southern hemispheres caused by melt water releases such as during the Younger Dryas in north and the Antarctic Cold Reversal in south. However, a consensus on the hemispheric linkages through ocean and atmosphere are yet to be reached. Here we present a new multi-proxy reconstruction from a sub-annually resolved lake sediment record from Lake Lusvatnet in Arctic Norway compared with a new reconstruction from the same time interval at South Georgia, Southern Ocean, suggesting inter-hemispheric climate linkages during the Bølling/Allerød time period. Our reconstruction of the alpine glacier in the lake Lusvatnet catchment show a synchronous glacier advance with the Birch-hill moraine complex in the Southern Alps, New Zealand during the Intra Allerød Cooling period. We propose these inter hemispheric climate swings to be forced by the northward migration of the southern Subtropical Front during the Antarctic Cold Reversal. Such a northward migration of the Subtropical Front is shown in model simulation and in palaeorecords to reduce the Agulhas leakage impacting the strength of the Atlantic meridional overturning circulation. We simply ask if this can be the carrier of rapid climate swings from one hemisphere to another? Our high-resolution reconstructions provide the basis for an enhanced understanding of the tiny balance between migration of the Subtropical Front in the Southern Ocean and the teleconnection to northern hemisphere.

  16. Age and stability of sublimation till over buried glacier ice, inferred from 21Ne measurements, Ong Valley, Antarctica

    NASA Astrophysics Data System (ADS)

    Bibby, T.; Putkonen, J.; Morgan, D. J.; Balco, G.

    2014-12-01

    Ong Valley, in the Central Transantarctic Mountains, contains three distinct glacial drifts deposited by past advances of the Argosy glacier into the valley. Massive ice occurs below two of the till deposits. Potentially, such buried ice under shallow regolith cover could provide access to past climate and biological records more easily than deep ice coring. We measured cosmic-ray produced 21Ne in these tills as a means of constraining the age and stability of the three drifts, as well as the ice below them. We collected samples in vertical profiles from two hand-dug sections through each drift. The pits from two drifts overlying buried ice extended to the buried ice surface. The hypothesis that these are sublimation tills implies that 21Ne concentrations are a function of i) any inheritance from prior exposure; ii) the age since emplacement of the ice and till; iii) the sublimation rate of the ice; and iv) the surface erosion rate of the till. 21Ne concentrations in the youngest drift are ca. 10 M atoms/g and invariant with depth, indicating that they are predominantly due to inheritance, and provide only a weak maximum age constraint of ca. 0.1 Mya. The two older drifts have surface 21Ne concentrations of 200-250 M atoms/ g and depth concentration profiles consistent with a sublimation till origin. Given that 21Ne concentrations in the deepest samples in each of the two older drifts provide an upper limit on the inherited 21Ne concentration, these imply minimum ages of 1 Mya for the middle drift and 1.6 Mya for the oldest. This implies a 1 Mya minimum age for the ice underlying the middle drift.

  17. Glaciers of Europe

    USGS Publications Warehouse

    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

  18. Recent Activity of Glaciers of Mount Rainier, Washington

    USGS Publications Warehouse

    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

  19. Synchronous inter-hemispheric alpine glacier advances during the Antarctic Cold Reversal

    NASA Astrophysics Data System (ADS)

    Bakke, J.; Bradley, R. S.; Dahl, S.; Balascio, N. L.

    2013-12-01

    The termination of the last glaciation in both hemispheres was a period of rapid climate oscillations superimposed on the overall warming trend, resulting from large-scale reorganizations of the atmospheric and oceanic circulation patterns in both hemispheres. Environmental changes during the deglaciation have been inferred from proxy records, as well as by model simulations. Several oscillations took place in both the northern and southern hemispheres caused by melt water releases such as during the Younger Dryas in the north and the Antarctic Cold Reversal in the south. However, a consensus on the hemispheric linkages through ocean and atmosphere are yet to be reached. Here we present a new multi-proxy reconstruction from a sub-annually resolved lake sediment record from lake Lusvatnet in arctic Norway suggesting inter-hemispheric climate linkages during the Bølling/Allerød time period. Our reconstruction of the Lusvatnet cirque glacier shows a synchronous glacier advance with the Birch-hill moraine complex in the Southern Alps, New Zealand, during the Intra Allerød Cooling. We propose these inter-hemispheric climate oscillations to be forced by the northward migration of the southern Subtropical Front during the Antarctic Cold Reversal. Such a northward migration of the Subtropical Front is shown in model simulation and in palaeorecords to reduce the Agulhas leakage impacting the strength of the Atlantic meridional overturning circulation. The Bølling-Allerød time period was a warm interval in the North Atlantic with a strong Atlantic meridional overturning circulation setting the stage for the later fresh water forcing of the Younger Dryas cold reversal with reduced overturning. Two minor cold reversals, the Older Dryas and the Intra Allerød Cooling, took place during this time span and we suggest a reduction in the Agulhas leakage during peak cooling over Antarctica as the mechanism teleconnecting arctic rapid climate oscillations with rapid climate

  20. Schmidt-hammer exposure-age dating (SHD) of Lateglacial rock glacier systems near the eastern margin of the European Alps

    NASA Astrophysics Data System (ADS)

    Kellerer-Pirklbauer, Andreas

    2016-04-01

    Rock glaciers are widespread permafrost landforms in Austria. Various rock glacier inventories list more than 4500 rock glaciers in the country; some 30-40% of them are intact. Relict (permafrost free) and pseudo-relict rock glaciers (sporadic and isolated permafrost particularly near the root zone) prevail in number. Rock glaciers are commonly formed over a period of several ka. Dating such landforms helps to understand palaeoclimatic conditions. In this study three rock glaciers consisting of gneiss were dated applying the Schmidt-hammer exposure-age dating (SHD) method. The rock glaciers are located at three neighbouring cirques in the Seckauer Tauern Range named Reichart Rock Glacier (RRG, area 1.26 km², length 1800 m, elevation range 1520-1940 m a.s.l.), Schöneben Rock Glacier (SRG, 0.11 km², 750 m, 1715-1905 m a.s.l.), and Dürrtal Rock Glacier (DRG, 0.08 km², 850 m, 1750-1980 m a.s.l.). RRG is one of the largest rock glaciers in Austria. All three landforms are influenced by lenses of permafrost at present (as indicated by ERT). During the LGM the Seckauer Tauern were covered by valley glaciers and deglaciation occurred presumably already early in the Alpine Lateglacial period. An analogue N-type Schmidt-hammer (proceq) was used for measuring the surface strength of stable blocks at the rock glacier surface by recording a rebound value (R-value) of a spring-loaded bolt. The R-value gives a relative measure of the surface hardness and hence time since exposure to weathering. Eight (RRG) or six (SRG, DRG) Schmidt-hammer measurement sites (with 50-100 individual readings) aligned along longitudinal transects (=former central flow line) between a talus slope (with relatively fresh boulders) in the root zone and the frontal ridge were measured. Mean R-value differences of 30.5 at RRG, 25.1 at SRG, and 20.7 at DRG were revealed along the three transects. The differences between the lowest and the highest R-value at the rock glaciers itself were 19.0 at RRG, 15

  1. Forcing and timing of Holocene glacier advances in the hyperhumid southernmost Andes (50-53°S): an evaluation based on continuous glacial clay and paleoclimate records as well as modelling

    NASA Astrophysics Data System (ADS)

    Kilian, R.; Lamy, F.; Arz, H.; Baeza, O.; Breuer, S.; Caniupan, M.; Möller, M.; Schneider, C.

    2012-04-01

    The Southern Patagonian Icefield (PIF) constitutes the largest continental ice-sheet outside the polar regions. Its Holocene glacier fluctuations and their forcing mechanism are still poorly explored, especially on the western hyperhumid side of the Andes. Glacier fluctuations have been previously constrained by 14C and/or cosmogenic ages of moraines on the eastern side of the PIF providing single advance ages but no constraints on advance and retreat dynamic. To the west of the PIF moraines are often subaquatic which complicates their mapping and dating. Furthermore, younger and more extended Neoglacial advances could have obliterated the remnants of earlier less extended advances. We present four sediments cores from the Andean fjord zone between 50 to 53°S which cover the time span of the Holocene and document variations in the glacial clay transport (clay mineralogy and related geochemical composition based on high resolution XRF records) along fjord pathways of glacial clay plumes. Additional subaquatic and terrestrial mapping of moraine extents as well as dating of glacier advances by stalagmites within the Neoglacial moraine belt document that the timing and length of these advances is correlated with an increased glacial clay signature in the sediment cores. Based on our records we distinguish two limited early Holocene advances (A0 at ~10 kyrs and A1 from 8.5 to 7.9 kyrs BP) and four Neoglacial advances from 5.4 to 4.9 kyrs BP (A2), from 4.1 to 3.7 (A3), from 2.34 to 2.1 (A4), from 1.15 to 0.85 (A5), and from 0.65 to 0.05 Kyr BP (A6). Stalagmite dating, well-dated lake sediment records and moraine mapping indicate that A4 was the most extended Holocene advance, again consistent with the most pronounced glacial clay signature in the sediment records. Tree-ring based temperature reconstructions, alkenone-derived open marine and fjord SST records as well as precipitation records from a stalagmite (53°S) and lake sediments are considered as the paleoclimatic

  2. Age, origin and evolution of Antarctic debris-covered glaciers: Implications for landscape evolution and long-term climate change

    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

  3. Glaciers of North America - Glaciers of Alaska

    USGS Publications Warehouse

    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

  4. Latest Pleistocene and Holocene glacier fluctuations on Mount Baker, Washington

    NASA Astrophysics Data System (ADS)

    Osborn, Gerald; Menounos, Brian; Ryane, Chanone; Riedel, Jon; Clague, John J.; Koch, Johannes; Clark, Douglas; Scott, Kevin; Davis, P. Thompson

    2012-08-01

    Glaciers on stratovolcanoes of the Pacific Northwest of North America offer opportunities for dating late Pleistocene and Holocene glacier advances because tephra and fossil wood are common in lateral moraines and in glacier forefields. We capitalize on this opportunity by examining the Holocene glacial record at Mount Baker, an active stratovolcano in northwest Washington. Earlier workers concluded that glaciers on Mount Baker during the early Holocene were more extensive than during the Little Ice Age and hypothesized that the explanation lay in unusual climatic or hypsometric effects peculiar to large volcanoes. We show that the main argument for an early Holocene glacier advance on Mount Baker, namely the absence of ca 10,000-year-old tephra on part of the south flank of the mountain, is incorrect. Moreover, a lake-sediment core indicates that a small cirque moraine previously thought be of early Holocene age is also likely older than the tephra and consequently of late Pleistocene age. Lateral and end moraines and wood mats ca 2 km downvalley of the present snout of Deming Glacier indicate that an advance during the Younger Dryas interval was little more extensive than the climactic Little Ice Age advance. Tephra and wood between tills in the left lateral moraine of Easton Glacier suggest that ice on Mount Baker was restricted in the early Holocene and that Neoglaciation began ca 6 ka. A series of progressively more extensive Neoglacial advances, dated to about 2.2, 1.6, 0.9, and 0.4 ka, are recorded by stacked tills in the right lateral moraine of Deming Glacier. Intervening retreats were long enough to allow establishment of forests on the moraine. Wood mats in moraines of Coleman and Easton glaciers indicate that Little Ice Age expansion began before 0.7 ka and was followed by retreat and a readvance ca 0.5 ka. Tree-ring and lichen data indicate glaciers on the south side of the mountain reached their maximum extents in the mid-1800s. The similarity between

  5. Chronology of a Small Glacier in Eastern British Columbia, Canada.

    PubMed

    Bray, J R

    1964-04-17

    The age of trees growing on the moraines of a small, high-altitude glacier in the Canadian Rockies suggests that the date of the maximum post-Pleistocene ice advance was around A.D. 1714, with another later advance about 1832. These two dates are synchronous with the two major periods of recent ice advance in the area.

  6. Neoglacial fluctuations of terrestrial, tidewater, and calving lacustrine glaciers, Blackstone-Spencer Ice Complex, Kenai Mountains, Alaska

    NASA Astrophysics Data System (ADS)

    Crossen, Kristine June

    1997-12-01

    The glaciers surrounding the Blackstone-Spencer Ice Complex display a variety of termini types: Tebenkov, Spencer, Bartlett, Skookum, Trail, Burns, Shakespeare, Marquette, Lawrence, and Ripon glaciers end in terrestrial margins; Blackstone and Beloit glaciers have tidewater termini; and Portage Glacier has a calving lacustrine margin. In addition, steep temperature and precipitation gradients exist across the ice complex from the maritime environment of Prince William Sound to the colder, drier interior. The Neoglacial history of Tebenkov Glacier, as based on overrun trees near the terminus, shows advances ca. 250- 430 AD (calibrated date), ca. 1215-1275 AD (calibrated date), and ca. 1320-1430 AD (tree ring evidence), all intervals of glacier advance around the Gulf of Alaska. However, two tidewater glaciers in Blackstone Bay retreated from their outermost moraines by 1350 AD, apparently asynchronously with respect to the regional climate signal. The most extensive Kenai Mountain glacier expansions during Neoglaciation occurred in the late Little Ice Age. The outermost moraines are adjacent to mature forest stands and bog peats that yield dates as old as 5,600 BP. Prince William Sound glaciers advanced during two Little Ice Age cold periods, 1380-1680 and 1830-1900 AD. The terrestrial glaciers around the Blackstone-Spencer Ice Complex all built moraines during the 19th century and began retreating between 1875 and 1900 AD. Portage and Burns glaciers began retreating between 1790 and 1810 AD, but their margins remained close to the outermost moraines during the 19th century. Regional glacier fluctuations are broadly synchronous in the Gulf of Alaska region. With the exception of the two tidewater glaciers in Blackstone Bay, all glaciers in the Kenai Mountains, no matter their sizes, altitudes, orientations, or types of margins, retreated at the end of the Little Ice Age. The climate signal, especially temperature, appears to be the strongest control on glacier

  7. [Psychosocial rehabilitation in advanced age].

    PubMed

    Haag, G

    1985-02-01

    The psychosocial rehabilitation of older persons is one of the main problems in health policy. About one quarter of the over 65-year-olds face psychic problems, without, to a large extent, receiving adequate treatment and rehabilitative care. Substantial deficits exist above all in the out-patient and non-residential service sectors. In in-patient care, existing methods for psychosocial intervention (such as psychoanalysis, behavioural, client-centered, family, Gestalt, milieu, or music and dance therapy, psychodrama, reality orientation training, or resensitization techniques) are hardly ever used. This absence of applied geronto-psychology is attributable to the shortcomings of available assessment methods, multiple methodical problems of intervention research, and--above all--to insufficient staff positions for psychosocial professions in the gerontological sector. Provision of further permanent posts for psychosocial workers; development of age-specific assessment methods; interdisciplinary and systematic interventional research; the development of ambulatory, community-based services as well as intensive support for existing self-help efforts are therefore called for.

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

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

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

  9. Major advance of South Georgia glaciers during the Antarctic Cold Reversal following extensive sub-Antarctic glaciation

    NASA Astrophysics Data System (ADS)

    Graham, Alastair G. C.; Kuhn, Gerhard; Meisel, Ove; Hillenbrand, Claus-Dieter; Hodgson, Dominic A.; Ehrmann, Werner; Wacker, Lukas; Wintersteller, Paul; Dos Santos Ferreira, Christian; Römer, Miriam; White, Duanne; Bohrmann, Gerhard

    2017-03-01

    The history of glaciations on Southern Hemisphere sub-polar islands is unclear. Debate surrounds the extent and timing of the last glacial advance and termination on sub-Antarctic South Georgia in particular. Here, using sea-floor geophysical data and marine sediment cores, we resolve the record of glaciation offshore of South Georgia through the transition from the Last Glacial Maximum to Holocene. We show a sea-bed landform imprint of a shelf-wide last glacial advance and progressive deglaciation. Renewed glacier resurgence in the fjords between c. 15,170 and 13,340 yr ago coincided with a period of cooler, wetter climate known as the Antarctic Cold Reversal, revealing a cryospheric response to an Antarctic climate pattern extending into the Atlantic sector of the Southern Ocean. We conclude that the last glaciation of South Georgia was extensive, and the sensitivity of its glaciers to climate variability during the last termination more significant than implied by previous studies.

  10. Major advance of South Georgia glaciers during the Antarctic Cold Reversal following extensive sub-Antarctic glaciation.

    PubMed

    Graham, Alastair G C; Kuhn, Gerhard; Meisel, Ove; Hillenbrand, Claus-Dieter; Hodgson, Dominic A; Ehrmann, Werner; Wacker, Lukas; Wintersteller, Paul; Dos Santos Ferreira, Christian; Römer, Miriam; White, Duanne; Bohrmann, Gerhard

    2017-03-17

    The history of glaciations on Southern Hemisphere sub-polar islands is unclear. Debate surrounds the extent and timing of the last glacial advance and termination on sub-Antarctic South Georgia in particular. Here, using sea-floor geophysical data and marine sediment cores, we resolve the record of glaciation offshore of South Georgia through the transition from the Last Glacial Maximum to Holocene. We show a sea-bed landform imprint of a shelf-wide last glacial advance and progressive deglaciation. Renewed glacier resurgence in the fjords between c. 15,170 and 13,340 yr ago coincided with a period of cooler, wetter climate known as the Antarctic Cold Reversal, revealing a cryospheric response to an Antarctic climate pattern extending into the Atlantic sector of the Southern Ocean. We conclude that the last glaciation of South Georgia was extensive, and the sensitivity of its glaciers to climate variability during the last termination more significant than implied by previous studies.

  11. Major advance of South Georgia glaciers during the Antarctic Cold Reversal following extensive sub-Antarctic glaciation

    PubMed Central

    Graham, Alastair G. C.; Kuhn, Gerhard; Meisel, Ove; Hillenbrand, Claus-Dieter; Hodgson, Dominic A.; Ehrmann, Werner; Wacker, Lukas; Wintersteller, Paul; dos Santos Ferreira, Christian; Römer, Miriam; White, Duanne; Bohrmann, Gerhard

    2017-01-01

    The history of glaciations on Southern Hemisphere sub-polar islands is unclear. Debate surrounds the extent and timing of the last glacial advance and termination on sub-Antarctic South Georgia in particular. Here, using sea-floor geophysical data and marine sediment cores, we resolve the record of glaciation offshore of South Georgia through the transition from the Last Glacial Maximum to Holocene. We show a sea-bed landform imprint of a shelf-wide last glacial advance and progressive deglaciation. Renewed glacier resurgence in the fjords between c. 15,170 and 13,340 yr ago coincided with a period of cooler, wetter climate known as the Antarctic Cold Reversal, revealing a cryospheric response to an Antarctic climate pattern extending into the Atlantic sector of the Southern Ocean. We conclude that the last glaciation of South Georgia was extensive, and the sensitivity of its glaciers to climate variability during the last termination more significant than implied by previous studies. PMID:28303885

  12. Reconstruction of mass balance of Nevado Coropuna glaciers (Southern Peru) for Late Pleistocene, Little Ice Age and the present.

    NASA Astrophysics Data System (ADS)

    Ubeda, J.; Palacios, D.

    2009-04-01

    The Nevado Coropuna volcanic complex (15th 31'S-72 ° 39 ° W) is the quaternary stratovolcano northernmost of the central volcanic zone (CVZ) in the western flank of the Central Andes (Southern Peru). This consists in four adjacent volcanic buildings that are occupied over 5.100-5.700 masl by a system of glaciers covering an area of 47 Km2 in 2007 (Ubeda et al, 2008). The maximum expansion of glaciers during the Pleistocene affected an area of ~449 Km2, dropping to altitudes around 3.600-4800 m (Ubeda et al, 2007). In this work were mapped several hundreds of moraines which constitute a record of climate change since the last glacial maximum (LGM). Current glacier system is formed by dozen of glaciers descending slope down in all directions. Coropuna complex is an excellent laboratory for to investigate the control that climate change, tectonics and volcanism exert on the dynamics of glaciers, a scale of tens of years (by studying current glaciers) and also of tens of thousands of years (by analyzing the geomorphological evidence of its evolution in the past). Ubeda et al. (2008) analyzed the evolution of eighteen glaciers of Nevado Coropuna using indicators as surfaces and Equilibrium Line Altitudes (ELAs) of ice masses in 2007, 1986, 1955, Little the Ice Age (LIA) and Last Glacial Maximum (LGM). The glaciers were grouped into two sets: NE group (seven glaciers) and SE group (eleven glaciers). The work included statistical series of ELAs in each phase, estimates by Area x Altitud Balance Ratio (AABR) method, which was proposed by Osmaston (2005), in addition with estimates of timing (~17Cl36 Ka) and magnitude (~ 782-911 m) of ELA depression during LGM. The work included statistical series of ELAs in each phase, estimates by the method Area x Altitud Balance Ratio (AABR) proposed by Osmaston (2005), and in addition estimates of the timing (~17Cl36 Ka) and magnitude (~ 782-911 m) of ELA depression during LGM. The objective of this work is to estimate the current

  13. Regeneration of Little Ice Age bryophytes emerging from a polar glacier with implications of totipotency in extreme environments

    PubMed Central

    La Farge, Catherine; Williams, Krista H.; England, John H.

    2013-01-01

    Across the Canadian Arctic Archipelago, widespread ice retreat during the 20th century has sharply accelerated since 2004. In Sverdrup Pass, central Ellesmere Island, rapid glacier retreat is exposing intact plant communities whose radiocarbon dates demonstrate entombment during the Little Ice Age (1550–1850 AD). The exhumed bryophyte assemblages have exceptional structural integrity (i.e., setae, stem structures, leaf hair points) and have remarkable species richness (60 of 144 extant taxa in Sverdrup Pass). Although the populations are often discolored (blackened), some have developed green stem apices or lateral branches suggesting in vivo regrowth. To test their biological viability, Little Ice Age populations emerging from the ice margin were collected for in vitro growth experiments. Our results include a unique successful regeneration of subglacial bryophytes following 400 y of ice entombment. This finding demonstrates the totipotent capacity of bryophytes, the ability of a cell to dedifferentiate into a meristematic state (analogous to stem cells) and develop a new plant. In polar ecosystems, regrowth of bryophyte tissue buried by ice for 400 y significantly expands our understanding of their role in recolonization of polar landscapes (past or present). Regeneration of subglacial bryophytes broadens the concept of Ice Age refugia, traditionally confined to survival of land plants to sites above and beyond glacier margins. Our results emphasize the unrecognized resilience of bryophytes, which are commonly overlooked vis-a-vis their contribution to the establishment, colonization, and maintenance of polar terrestrial ecosystems. PMID:23716658

  14. Regeneration of Little Ice Age bryophytes emerging from a polar glacier with implications of totipotency in extreme environments.

    PubMed

    La Farge, Catherine; Williams, Krista H; England, John H

    2013-06-11

    Across the Canadian Arctic Archipelago, widespread ice retreat during the 20th century has sharply accelerated since 2004. In Sverdrup Pass, central Ellesmere Island, rapid glacier retreat is exposing intact plant communities whose radiocarbon dates demonstrate entombment during the Little Ice Age (1550-1850 AD). The exhumed bryophyte assemblages have exceptional structural integrity (i.e., setae, stem structures, leaf hair points) and have remarkable species richness (60 of 144 extant taxa in Sverdrup Pass). Although the populations are often discolored (blackened), some have developed green stem apices or lateral branches suggesting in vivo regrowth. To test their biological viability, Little Ice Age populations emerging from the ice margin were collected for in vitro growth experiments. Our results include a unique successful regeneration of subglacial bryophytes following 400 y of ice entombment. This finding demonstrates the totipotent capacity of bryophytes, the ability of a cell to dedifferentiate into a meristematic state (analogous to stem cells) and develop a new plant. In polar ecosystems, regrowth of bryophyte tissue buried by ice for 400 y significantly expands our understanding of their role in recolonization of polar landscapes (past or present). Regeneration of subglacial bryophytes broadens the concept of Ice Age refugia, traditionally confined to survival of land plants to sites above and beyond glacier margins. Our results emphasize the unrecognized resilience of bryophytes, which are commonly overlooked vis-a-vis their contribution to the establishment, colonization, and maintenance of polar terrestrial ecosystems.

  15. Holocene and latest Pleistocene glacial chronology, Glacier National Park, Montana.

    USGS Publications Warehouse

    Carrara, P.E.

    1987-01-01

    Moraines of two different age groups have been identified; the subdued, vegetated moraines of the older group have been found at 25 sites, mainly in the central part of the Lewis Range. These older moraines are in places overlain by the Mazama ash; they date from 10 000 BP or earlier. Moraines of the younger group, consisting of fresh bouldery rubble, are common throughout Glacier Park. Tree- ring analyses indicate that some of these younger moraines were deposited by advances that culminated during the mid-19th century. At that time there were more than 150 glaciers in Glacier Park. -from Author

  16. Late nineteenth to early twenty-first century behavior of Alaskan glaciers as indicators of changing regional climate

    USGS Publications Warehouse

    Molnia, B.F.

    2007-01-01

    Alaska's climate is changing and one of the most significant indications of this change has been the late 19th to early 21st century behavior of Alaskan glaciers. Weather station temperature data document that air temperatures throughout Alaska have been increasing for many decades. Since the mid-20th century, the average change is an increase of ?????2.0????C. In order to determine the magnitude and pattern of response of glaciers to this regional climate change, a comprehensive analysis was made of the recent behavior of hundreds of glaciers located in the eleven Alaskan mountain ranges and three island areas that currently support glaciers. Data analyzed included maps, historical observations, thousands of ground-and-aerial photographs and satellite images, and vegetation proxy data. Results were synthesized to determine changes in length and area of individual glaciers. Alaskan ground photography dates from 1883, aerial photography dates from 1926, and satellite photography and imagery dates from the early 1960s. Unfortunately, very few Alaskan glaciers have any mass balance observations. In most areas analyzed, every glacier that descends below an elevation of ?????1500??m is currently thinning and/or retreating. Many glaciers have an uninterrupted history of continuous post-Little-Ice-Age retreat that spans more than 250??years. Others are characterized by multiple late 19th to early 21st century fluctuations. Today, retreating and/or thinning glaciers represent more than 98% of the glaciers examined. However, in the Coast Mountains, St. Elias Mountains, Chugach Mountains, and the Aleutian Range more than a dozen glaciers are currently advancing and thickening. Many currently advancing glaciers are or were formerly tidewater glaciers. Some of these glaciers have been expanding for more than two centuries. This presentation documents the post-Little-Ice-Age behavior and variability of the response of many Alaskan glaciers to changing regional climate. ?? 2006.

  17. 4300-Year Old 'Glacier Forests', Southern Coast Mountains, British Columbia and their Global Context

    NASA Astrophysics Data System (ADS)

    Koch, J.

    2014-12-01

    Dendrochronology and radiocarbon dating of in situ and detrital wood have been utilized to date Holocene glacier fluctuations in Garibaldi Provincial Park and at the Pemberton Icefield in the southern Coast Mountains of British Columbia. Fieldwork at over 30 glaciers has been carried out since 2002. The focus of this paper is on wood that has been radiocarbon dated between 4500 and 4000 years ago, which has been found at six glaciers. At four glaciers the wood was washing out from beneath present-day glacier snouts. At Helm Glacier in Garibaldi Park thirteen detrital branches and stumps were recovered, and at West Squamish Glacier at the Pemberton Icefield seven detrital branches, stems, and stumps were sampled. Some of these samples had diameters of up to 40 cm and were up to 250 cm long, and thus are much larger than any living trees near the present treeline. Tree-ring analysis shows that these glaciers advanced into and over mature forests that had grown near present-day glacier margins for at least 135 years (Helm) and 357 years (W Squamish). Evidence for permanent snow and ice patches forming, as well as glaciers advancing beyond present-day extents at this time is found in the central Coast Mountains, Yukon Territory, Arctic Canada, Norway, and the Swiss Alps. Glacier advances of similar age have been reconstructed not only in western Canada, but also in Europe, Asia, South America, New Zealand, and Antarctica indicating the global nature of this event. A peak in ice-rafted debris in the North Atlantic about 4200 years ago may have been the result of reduced solar output, and based on Earth's position in the obliquity cycle glaciers should have started to expand 4000 years ago. These 'glacier forests' thus could provide a probable start date for Neoglaciation.

  18. Cardiovascular KATP channels and advanced aging

    PubMed Central

    Yang, Hua-Qian; Subbotina, Ekaterina; Ramasamy, Ravichandran; Coetzee, William A.

    2016-01-01

    With advanced aging, there is a decline in innate cardiovascular function. This decline is not general in nature. Instead, specific changes occur that impact the basic cardiovascular function, which include alterations in biochemical pathways and ion channel function. This review focuses on a particular ion channel that couple the latter two processes, namely the KATP channel, which opening is promoted by alterations in intracellular energy metabolism. We show that the intrinsic properties of the KATP channel changes with advanced aging and argue that the channel can be further modulated by biochemical changes. The importance is widespread, given the ubiquitous nature of the KATP channel in the cardiovascular system where it can regulate processes as diverse as cardiac function, blood flow and protection mechanisms against superimposed stress, such as cardiac ischemia. We highlight questions that remain to be answered before the KATP channel can be considered as a viable target for therapeutic intervention. PMID:27733235

  19. Glacier change from the early Little Ice Age to 2005 in the Torngat Mountains, northern Labrador, Canada

    NASA Astrophysics Data System (ADS)

    Way, Robert G.; Bell, Trevor; Barrand, Nicholas E.

    2015-10-01

    The glaciers of the Torngat Mountains of northern Labrador are the southernmost of the Canadian Arctic and the easternmost of continental North America. Currently, 195 small mountain glaciers cover an area in excess of 24 km2, confined mostly to small cirques and upland depressions. Using a combination of field and remote sensing methods this study reconstructs and dates the areal extent of Torngat glaciers at their Neoglacial maximums, enabling the first assessment of regional glacier change over the past several centuries. Mapped glacier paleomargins (n = 165) are compared to current (2005) glaciers and ice masses, showing a 52.5% reduction in glacier area, with at least 11 former glaciers altogether disappearing. Glacier change is spatially homogenous and independent of most geographic and topographic factors; however, glacier elevation and glacier size mitigated total change. Previously established lichen growth stations were revisited, and growth rates recalculated based on 30-year-long records, enabling the construction of locally derived low- and high-altitude lichen growth curves. Using growth rates and in situ lichen measurements, the retreat from maximum Neoglacial moraine extents are suggested to have occurred between A.D. 1581 and 1673. These findings indicate a similar magnitude of post-LIA retreat to mountain glaciers elsewhere, yet a much earlier timing ( 200 years) of retreat than other glaciers in the eastern Canadian Arctic. Though no definitive answer explaining this discrepancy is presented, evidence suggests that regional climate dynamics and the importance of solar radiation for Torngat glaciers may play an important role in local glacierization.

  20. Modern and Little Ice Age equilibrium-line altitudes on Outlet Valley glaciers from Jostedalsbreen, western Norway: An evaluation of different approaches to their calculation

    SciTech Connect

    Torsnes, I.; Rye, N. ); Nesje, A. )

    1993-05-01

    The modern and Little Ice Age (LIA) equilibrium-line altitude (ELA) of 20 outlet valley glacier from Jostedalsbreen, western Norway, has been calculated using different approaches. Using an accumulation area ratio (AAR) of 0.6 [+-] 0.05 gave a mean little Ice Age ELA depression of 70 m. A method developed by M. Kuhle, taking the influence by topography into account gave a mean ELA depression of 35-255 m, the median elevation of glaciers 115 m, and the toe-to-headwall altitude ration 140 m. Differences in the ELA estimates can be attributed to the differences in topography and morphology of the glaciers. The AAR method appears to provide the most reliable results. This will aid in determining mean global temperatures during the LIA. 34 refs., 9 figs., 5 tabs.

  1. Paraglacial and postglacial debris flows on a Little Ice Age terminal moraine: Jamapa Glacier, Pico de Orizaba (Mexico)

    NASA Astrophysics Data System (ADS)

    Palacios, David; Parrilla, Gemma; Zamorano, Jose J.

    1999-05-01

    The study area is located on the northern face of Pico de Orizaba (Mexico, 5700 m ASL), on the terminal moraine of Jamapa Glacier, which dates from the Little Ice Age. Large debris flows are recurrent on the proglacial ramp. The comparison of lichen colonies growing on the deposits of the flows reveals that two generations of flows are present: an old one and a very recent one that occurred between 1994 and 1995. Studies were made of the sedimentologic characteristics of the flows and ground temperatures were recorded to a depth of 70 cm on the floor of the channels. Comparison of the lichen-growth on the exposed surfaces of the deposits led to the relative dating of the older debris flow, which is associated with the beginning of the retreat of the glacier and the saturation of the terminal moraine deposits by meltwater. The more recent flow has less transport capacity and is identified with the formation of an impermeable layer of permafrost that covers the bottom of the channel of the old debris flow. The permafrost layer formed when snow accumulations on the bottom of the channel were covered by ash that fell from the slopes.

  2. Peak water from glaciers: advances and challenges in a global perspective (Arne Richter Award for Outstanding Young Scientists Lecture)

    NASA Astrophysics Data System (ADS)

    Huss, Matthias; Hock, Regine

    2014-05-01

    Mountain glaciers show a high sensitivity to changes in climate forcing. In a global perspective, their anticipated retreat will pose far-reaching challenges to the manage- ment of fresh water resources and will raise sea levels significantly within only a few decades. Different model frameworks have been applied to simulate melt water con- tributions of glaciers outside the two ice sheets for the recent IPCC report. However, these models depend on strongly simplified, and often empirical descriptions of the driving processes hampering the reliability of the results. For example, glacier retreat is parameterized with volume-area scaling thus neglecting the glacier's actual geome- try and the surface elevation feedback. Frontal ablation of tidewater and lake-calving glaciers, an important mass loss component for a third of the world's glacier area, is not accounted for. Thus, a transition from the physically-based mass balance-ice flow models developed for single glaciers to the application at the global scale is urgently needed. The chal- lenges are manifold but can be tackled with the new data sets, methods and process- understanding that have emerged during the last years. Here, we present a novel glacier model for calculating the response of surface mass balance and 3D glacier geometry for each individual glacier around the globe. Our approach accounts for feedbacks due to glacier retreat and includes models for mass loss due to frontal ablation and the refreezing of water in the snow/firn. The current surface geometry and thickness distribution for each of the world's roughly 200'000 glaciers is extracted from the Randolph Glacier Inventory v3.2 and terrain models. Our simulations are driven with 14 Global Circulation Models from the CMIP5 project using the RCP4.5, RCP8.5 and RCP2.6 scenarios. Regionally specified cumulative global sea level rise due to glacier mass loss until 2100 is discussed in the light of model uncertainties and the advantages of using a

  3. Debris-Covered Glaciers in the Sierra Nevada, California, and Their Implications for Snowline Reconstructions

    USGS Publications Warehouse

    Clark, D.H.; Clark, M.M.; Gillespie, A.R.

    1994-01-01

    Ice-walled melt ponds on the surfaces of active valley-floor rock glaciers and Matthes (Little Ice Age) moraines in the southern Sierra Nevada indicate that most of these landforms consist of glacier ice under thin (ca. 1 - 10 m) but continuous covers of rock-fall-generated debris. These debris blankets effectively insulate the underlying ice and greatly reduce rates of ablation relative to that of uncovered ice. Such insulation explains the observations that ice-cored rock glaciers in the Sierra, actually debris-covered glaciers, are apparently less sensitive to climatic warming and commonly advance to lower altitudes than do adjacent bare-ice glaciers. Accumulation-area ratios and toe-to-headwall-altitude ratios used to estimate equilibrium-line altitudes (ELAs) of former glaciers may therefore yield incorrect results for cirque glaciers subject to abundant rockfall. Inadvertent lumping of deposits from former debris-covered and bare-ice glaciers partially explains an apparently anomalous regional ELA gradient reported for the pre-Matthes Recess Peak Neoglacial advance. Distinguishing such deposits may be important to studies that rely on paleo-ELA estimates. Moreover, Matthes and Recess Peak ELA gradients along the crest evidently depend strongly on local orographic effects rather than latitudinal climatic trends, indicating that simple linear projections and regional climatic interpretations of ELA gradients of small glaciers may be unreliable.

  4. The latest LGM culmination of the Garda Glacier (Italian Alps) and the onset of glacial termination. Age of glacial collapse and vegetation chronosequence

    NASA Astrophysics Data System (ADS)

    Ravazzi, Cesare; Pini, Roberta; Badino, Federica; De Amicis, Mattia; Londeix, Laurent; Reimer, Paula J.

    2014-12-01

    In the deglacial sequence of the largest end moraine system of the Italian Alps, we focused on the latest culmination of the Last Glacial Maximum, before a sudden downwasting of the piedmontane lobe occupying the modern lake basin. We obtained a robust chronology for this culmination and for the subsequent deglacial history by cross-radiocarbon dating of a proximal fluvioglacial plain and of a deglacial continuous lake sedimentation. We used reworked dinocysts to locate sources of glacial abrasion and to mark the input of glacial meltwater until depletion. The palynological record from postglacial lake sediments provided the first vegetation chronosequence directly reacting to the early Lateglacial withdrawal so far documented in the Alps. Glacier collapse occurred soon after 17.46 ± 0.2 ka cal BP, which is, the Manerba advance culmination. Basin deglaciation of several overdeepened foreland piedmont lakes on southern and northern sides of the Alps appears to be synchronous at millennial scale and near-synchronous with large-scale glacial retreat at global scale. The pioneering succession shows a first afforestation step at a median modeled age of 64 years after deglaciation, while rapid tree growth lagged 7 centuries. Between 16.4 ± 0.16 and 15.5 ± 0.16 ka cal BP, a regressive phase interrupted forest growth marking a Lateglacial phase of continental-dry climate predating GI-1. This event, spanning the most advanced phases of North-Atlantic H1, is consistently radiocarbon-framed at three deglacial lake records so far investigated on the Italian side of the Alps. Relationships with the Gschnitz stadial from the Alpine record of Lateglacial advances are discussed.

  5. Molecular evidence of the survival of subterranean amphipods (Arthropoda) during Ice Age underneath glaciers in Iceland.

    PubMed

    Kornobis, Etienne; Pálsson, Snaebjörn; Kristjánsson, Bjarni K; Svavarsson, Jörundur

    2010-06-01

    A Two endemic groundwater arthropod crustacean species, Crangonyx islandicus and Crymostygius thingvallensis, were recently discovered on the mid-Atlantic volcanic island of Iceland. The extent of morphological differences from closest relatives, endemism, along with the geographic isolation of Iceland and its complete coverage by glaciers 21,000 years ago, suggests that these two species have survived glaciation periods in sub-glacial refugia. Here we provide strong support for this hypothesis by an analysis of mitochondrial genetic variation within Crangonyx islandicus. Our results show that the species is divided into several distinct monophyletic groups that are found along the volcanic zone in Iceland, which have been separated by 0.5 to around 5 million years. The genetic divergence between groups reflects geographic distances between sampling sites, indicating that divergence occurred after the colonization of Iceland. The genetic patterns, as well as the dependency of genetic variation on distances from the tectonic plate boundary and altitude, points to recent expansion from several refugia within Iceland. This presents the first genetic evidence of multicellular organisms as complex as crustacean amphipods which have survived glaciations beneath an ice sheet. This survival may be explained by geothermal heat linked to volcanic activities, which may have maintained favourable habitats in fissures along the tectonic plate boundary in Iceland during glaciations.

  6. 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

  7. The Arctic Mountain Glacier, Austre Okstindbreen in Northern Norway, survived the 'Holocene Thermal Optimum

    NASA Astrophysics Data System (ADS)

    Bakke, Jostein; Paasche, Øyvind; Olaf Dahl, Svein

    2010-05-01

    Arctic glaciers are currently undergoing major changes, but accurate knowledge about how they have varied continuously during the Holocene (<11 700 years) is still scarce. Here we present a new glacier record from Austre Okstindbreen in Nordland, northern Norway. This continuous reconstruction is based on a number of short and long cores collected from several downstream basins, which have been analyzed by a suit of methods including geochemical elements (XRF), rock magnetic properties, dry bulk density (DBD) and Loss-on-ignition (LOI). Lake sediment distribution was surveyed and mapped by the use of ground penetrating radar (GPR), securing optimal coring sites. Independently lichen-dated marginal moraines and historical information from old photographs and maps have ensured that the moraine sequence can be closely linked to the lake sediment chronology. This new glacier reconstruction reveals that Austre Okstindbreen is the first known glacier in Scandinavia to have survived the "Holocene Thermal Optimum". It also brackets the four largest glacier advances to c 7000, 1300, 800 and 250 b2k. In contrast to most glaciers in Scandinavia, the largest glacier advance was not associated with the "Little Ice Age", but rather to an earlier period centred at 1300 b2k. Both the moraine chronology and the lacustrine records document this foremost Neoglacial advance. Compared to other glacier reconstructions from the Northern Hemisphere we identify near-synchronous glacier advances occurring roughly at 4ka, 1.3ka and during the "Little Ice Age". These shared advances across the Northern Hemisphere suggest that these centennial-scale events are a shared feature regardless of the large geographical distances separating them. Some of the events are not synchronous between the different records, which are probably due to lack of precise dating as well as the potential influence of local climatic conditions.

  8. A complete record of Holocene glacier variability at Austre Okstindbreen, northern Norway: an integrated approach

    NASA Astrophysics Data System (ADS)

    Bakke, Jostein; Dahl, Svein Olaf; Paasche, Øyvind; Riis Simonsen, Joachim; Kvisvik, Bjørn; Bakke, Kristina; Nesje, Atle

    2010-05-01

    Arctic glaciers are currently undergoing major changes, but accurate knowledge about how they varied during the entire Holocene is still scarce. Here we present a new complete glacier record from Austre Okstindbreen in Nordland, northern Norway. This reconstruction is based on a number of short and long cores retrieved from several downstream basins, which have been analyzed by a suite of methods including geochemical elements (XRF), rock magnetic properties, dry bulk density (DBD) and Loss-on-ignition (LOI). Lake sediment distribution was surveyed and mapped prior to coring by the use of ground penetrating radar (GPR). Independently lichen-dated marginal moraines and historical information about the glacier frontal positions from old photographs and maps have made it possible to link the moraine sequence to the 210Pb dated lake sediment chronology. This integrated approach reveals that Austre Okstindbreen is the first known glacier in Scandinavia to possibly have survived the "Holocene Thermal Optimum". It also brackets the four largest glacier advances to c 7400-7000, 1400-1200, 900-700 and 300-150 years before AD 2000 (b2k). In contrast to most reconstructed glaciers in Scandinavia, the largest glacier advance was not associated with the "Little Ice Age", but rather to an earlier period centred at 1300 b2k. Both the moraine chronology and the lacustrine records document this Neoglacial advance. Compared to other glacier reconstructions from the Northern Hemisphere, we identify near-synchronous glacier advances occurring roughly at 4000 b2k; 2700 b2k; 1300 b2k and during the "Little Ice Age". These correlative advances across the Northern Hemisphere suggest that these observed centennial-scale events are a shared feature regardless of the large geographical distances separating them. Some minor discrepancies between different geographical areas may be caused by lack of precise dating, but local climatic conditions may play a role as well.

  9. 10Be dating of the end of low-altitude rock glacier activity in the Alps - evidence for cold conditions during the early Preboreal.

    NASA Astrophysics Data System (ADS)

    Kerschner, Hanns; Ivy-Ochs, Susan

    2010-05-01

    Large relict rock glacier complexes are conspicious features in the Alps. Their occurence can roughly be subdivided into a "lower rock glacier belt", which reaches down to about 1900 m a.s.l., an "intermediate rock glacier belt" with rock glacier snouts at around present-day timberline (approx. 2200 m a.s.l) in the central Alps and an "upper rock glacier belt" at similar altitudes as presently active rock glaciers. All these rock glaciers indicate the former presence of discontinuous permafrost at their respective altitudes and are good indicators for the mean annual air temperature during their active period. The end of rock glacier activity at a given altitude marks also the end of the existence of permafrost conditions. Experience from the Alps shows that it may take about a century until the surface of a rock glacier is stabilized, Hence, if it is possible to date the surface of a relict rock glacier with 10Be, we get a close date for the end of permafrost activity at the altitude of the rock glacier. From the difference between the altitude of the relict rock glacier and presently active rock glaciers, the rise of mean annual air temperature can be calculated. Relict rock glaciers at present-day timberline at Julierpass (Swiss Alps) and at Larstigtal (Austrian Alps) gave ages in the order of 10.5 ka BP for surface stabilization. Both rock glaciers, which belong to the "intermediate rock glacier belt", developed from lateral moraines and scree slopes. They started to move into former glacier beds after ice recession from the Younger Dryas "Egesen" advance. Their age indicates that climatic conditions favouring permafrost existence about 300 - 400 m below 20th century permafrost occurence prevailed during most of the Preboreal. Taken together with the Kartell glacier advance (10.8 ka) they show that rapid climatic warming at the Younger Dryas / Holocene boundary was followed by more unstable climatic conditions and and somewhat slower warming until full Holocene

  10. Late Holocene glacial history of the Copper River Delta, coastal south-central Alaska, and controls on valley glacier fluctuations

    NASA Astrophysics Data System (ADS)

    Barclay, David J.; Yager, Elowyn M.; Graves, Jason; Kloczko, Michael; Calkin, Parker E.

    2013-12-01

    Fluctuations of four valley glaciers in coastal south-central Alaska are reconstructed for the past two millennia. Tree-ring crossdates on 216 glacially killed stumps and logs provide the primary age control, and are integrated with glacial stratigraphy, ages of living trees on extant landforms, and historic forefield photographs to constrain former ice margin positions. Sheridan Glacier shows four distinct phases of advance: in the 530s to c.640s in the First Millennium A.D., and the 1240s to 1280s, 1510s to 1700s, and c.1810s to 1860s during the Little Ice Age (LIA). The latter two LIA advances are also recorded on the forefields of nearby Scott, Sherman and Saddlebag glaciers. Comparison of the Sheridan record with other two-millennia long tree-ring constrained valley glacier histories from south-central Alaska and Switzerland shows the same four intervals of advance. These expansions were coeval with decreases in insolation, supporting solar irradiance as the primary pacemaker for centennial-scale fluctuations of mid-latitude valley glaciers prior to the 20th century. Volcanic aerosols, coupled atmospheric-oceanic systems, and local glacier-specific effects may be important to glacier fluctuations as supplemental forcing factors, for causing decadal-scale differences between regions, and as a climatic filter affecting the magnitude of advances.

  11. Holocene glacier fluctuations inferred from lacustrine sediment, Emerald Lake, Kenai Peninsula, Alaska

    NASA Astrophysics Data System (ADS)

    LaBrecque, Taylor S.; Kaufman, Darrell S.

    2016-01-01

    Physical and biological characteristics of lacustrine sediment from Emerald Lake were used to reconstruct the Holocene glacier history of Grewingk Glacier, southern Alaska. Emerald Lake is an ice-marginal threshold lake, receiving glaciofluvial sediment when Grewingk Glacier overtops the topographic divide that separates it from the lake. Sub-bottom acoustical profiles were used to locate core sites to maximize both the length and resolution of the sedimentary sequence recovered in the 4-m-long cores. The age model for the composite sequence is based on 13 14C ages and a 210Pb profile. A sharp transition from the basal inorganic mud to organic-rich mud at 11.4 ± 0.2 ka marks the initial retreat of Grewingk Glacier below the divide of Emerald Lake. The overlaying organic-rich mud is interrupted by stony mud that records a re-advance between 10.7 ± 0.2 and 9.8 ± 0.2 ka. The glacier did not spill meltwater into the lake again until the Little Ice Age, consistent with previously documented Little Ice Ages advances on the Kenai Peninsula. The retreat of Grewingk Glacier at 11.4 ka took place as temperature increased following the Younger Dryas, and the subsequent re-advance corresponds with a climate reversal beginning around 11 ka across southern Alaska.

  12. Male biological clock: a critical analysis of advanced paternal age

    PubMed Central

    Ramasamy, Ranjith; Chiba, Koji; Butler, Peter; Lamb, Dolores J.

    2016-01-01

    Extensive research defines the impact of advanced maternal age on couples’ fecundity and reproductive outcomes, but significantly less research has been focused on understanding the impact of advanced paternal age. Yet it is increasingly common for couples at advanced ages to conceive children. Limited research suggests that the importance of paternal age is significantly less than that of maternal age, but advanced age of the father is implicated in a variety of conditions affecting the offspring. This review examines three aspects of advanced paternal age: the potential problems with conception and pregnancy that couples with advanced paternal age may encounter, the concept of discussing a limit to paternal age in a clinical setting, and the risks of diseases associated with advanced paternal age. As paternal age increases, it presents no absolute barrier to conception, but it does present greater risks and complications. The current body of knowledge does not justify dissuading older men from trying to initiate a pregnancy, but the medical community must do a better job of communicating to couples the current understanding of the risks of conception with advanced paternal age. PMID:25881878

  13. Glacier recession in Iceland and Austria

    SciTech Connect

    Hall, D.K.; Williams, R.S. Jr.; Bayr, K.J. USGS, Reston, VA Keene State College, NH )

    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 tidewater glacier cycle. 21 refs.

  14. Glacier recession in Iceland and Austria

    NASA Technical Reports Server (NTRS)

    Hall, Dorothy K.; Williams, Richard S., Jr.; Bayr, Klaus J.

    1992-01-01

    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 tidewater glacier cycle.

  15. Holocene record of glacier variability from lake sediments reveals tripartite climate history for Svalbard

    NASA Astrophysics Data System (ADS)

    van der Bilt, Willem; Bakke, Jostein; Vasskog, Kristian; D`Andrea, William; Bradley, Raymond; Olafsdottir, Sædis

    2016-04-01

    The Arctic is responding sensitively to ongoing global climate change, warming and moistening faster than any other region on the planet. Holocene proxy paleoclimate time series are increasingly used to put this amplified response in perspective by understanding Arctic climate processes beyond the instrumental period. Glaciers rapidly respond to climate shifts as demonstrated by their current demise around the world. This response has a composite climate signature, marked by shifts in hydroclimate (winter precipitation) as well as (summer) temperature. Attendant changes in glacier size are recorded by variations in glacigenic rock flour that may be deposited in downstream lakes. Here, we present a Holocene reconstruction of glacier activity, based on sediments from Hajeren, a glacier-fed lake on northwest Spitsbergen in the High Arctic Svalbard archipelago. Owing to undisturbed sediments and robust age control, we could resolve variability on a sub-centennial scale. To ensure the accurate detection of glacier activity, we applied a toolbox of physical, magnetic and geochemical proxies in conjunction with multivariate statistics. Our findings indicate a three-stage Holocene climate history for Svalbard, driving by melt water pulses, episodic Atlantic cooling and a decline in orbitally driven summer insolation. Correspondence between inferred advances, including a Holocene glacier maximum around 9.5 ka BP, suggests forcing by the melting LIS during the Early Holocene. Following a late Holocene Thermal Maximum around 7.4 ka BP, glaciers disappeared from the catchment. Glaciers reformed around 4.2 ka BP during the regional onset of the Neoglacial, supporting previous findings. This transition did, however, not mark the onset of persistent glacier activity in the catchment, but a series of centennial-scale cycles of growth and decay, including events around 3.3 and 1.1 ka BP. As orbitally driven insolation declined towards the present, the glaciation threshold

  16. South Georgia glaciers through periods of fast and slow retreat

    NASA Astrophysics Data System (ADS)

    Paasche, O.; Bakke, J.; Schaefer, J. M.

    2013-12-01

    Along the Antarctic Peninsula and across the sub-Antarctic islands most glaciers, regardless of size and configuration, are in a state of demise and have been so for several decades. An emerging question is: how unique is this modern retreat when compared to glacier activity in this region during the last 10 000 years, if at all and to what extent? And also, how is this pattern different from the Northern Hemisphere where glaciers generally were small or even absent during the Holocene Optimum (9000-6000 years ago) and expanding after the onset of the Neoglacial (4000 years ago), with a typical late maximum around the Little Ice age (1400-1800 AD)? Here we address these questions in an effort to further our understanding of natural environmental variability in the Southern Hemisphere on time scales, and with a resolution, high enough to capture glacier trends on multi-decadal to centennial time scales. This is accomplished by acquiring and analyzing new terrestrial glacier records from the remote island South Georgia (54-55°S, 36-38°W) covering at least the last 13 000 years. Results from downstream lake sediment archives together with cosmogenic nuclide dating of a complete moraine sequence add new insight to the glacier history of South Georgia. The Hodges cirque glacier, which was mapped and investigated intermittently by the British Antarctic Survey between 1955-1982, was according to our observations present during the entire Holocene, but smaller advances were superimposed on a long-term pattern of retreat. The Hodges, as one of the first glaciers on South Georgia, had completely melted away by 2008, which indicate a retreat of circa 900 meter since early Holocene.

  17. Latest Pleistocene and Holocene glacier fluctuations in southernmost Tierra del Fuego, Argentina

    NASA Astrophysics Data System (ADS)

    Menounos, Brian; Clague, John J.; Osborn, Gerald; Davis, P. Thompson; Ponce, Federico; Goehring, Brent; Maurer, Malyssa; Rabassa, Jorge; Coronato, Andrea; Marr, Rob

    2013-10-01

    Some researchers propose that summer insolation controls long-term changes in glacier extent during the Holocene. If this hypothesis is correct, the record of glacier fluctuations at high latitudes in the Southern Hemisphere should differ from that in the Northern Hemisphere. Although the chronology of Holocene glacier fluctuations in the Northern Hemisphere is well established, much uncertainty remains in the ages of Holocene glacier fluctuations in the Southern Hemisphere, especially South America. Here we report on latest Pleistocene and Holocene glacier fluctuations at the southern end of the Andes north and west of Ushuaia, Argentina. Surface exposure ages (10Be) from glaciated bedrock beyond cirque moraines indicate that alpine areas were free of ice by ca 16.9 ka. One, and in some cases two, closely spaced moraines extend up to 2 km beyond Little Ice Age moraines within many of the cirques in the region. The mean age of five 10Be ages from two pre-Little Ice Age moraines is 14.27-12.67 ka, whereas a minimum limiting radiocarbon age for a smaller, recessional moraine in one cirque is 12.38-12.01 ka. Our ages imply that, following glacier retreat beginning about 18.52-17.17 ka, cirque glaciers first advanced during the Antarctic Cold Reversal (14.5-12.9 ka) and may have later advanced or stabilized in the Younger Dryas Chronozone (12.9-11.7 ka). Based on the distribution of thick, geochemically distinct, and well-dated Hudson tephra, no Holocene moraines appear to be older than 7.96-7.34 ka. At some sites, there is evidence for one or more advances of glaciers sometime between 7.96-7.34 ka and 5.29-5.05 ka to limits only tens of meters beyond Little Ice Age maximum positions. Taken together, the data: 1) do not support the summer insolation hypothesis to explain Holocene glacier fluctuations in southernmost Patagonia; 2) confirm paleobotanical evidence for a warm, dry early Holocene; and 3) suggest that some glaciers in the region reached extents comparable to

  18. Glaciers of Greenland

    USGS Publications Warehouse

    Williams, Richard S.; Ferrigno, Jane G.

    1995-01-01

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

  19. Research Advances in Aging 1984-1986.

    ERIC Educational Resources Information Center

    National Inst. on Aging (DHHS/NIH), Bethesda, MD.

    The National Institute on Aging (NIA) has, for the past several years, focused attention on a wide range of clinical problems associated with aging, including falls and gait disorders, bone fractures, urinary incontinence, and hypertension. Understanding the causes of and exploring possible treatments for Alzheimer's disease has been another of…

  20. Palynology as an age-control tool for ice cores. First results of PAMOGIS - Pollen Analyses of the Mt. Ortles Glacier Ice Samples

    NASA Astrophysics Data System (ADS)

    Festi, Daniela; Kofler, Werner; Gabrielli, Paolo; Oeggl, Klaus

    2014-05-01

    Glacier ice cores from the mid latitude are capable of retaining essential information on past climate, environmental and human activities on a seasonal/annual time resolution. However, for a correct interpretation of the ice record a good chronological control is essential. Absolute time markers such as 3H peaks and Sahara dust horizons, together with radiometric methods such as 210Pb, radiocarbon from carbonaceous aerosol particles and AMS-dating are commonly used to obtain the age depth model of ice cores. In this frame we present the first pollen-based chronology from the Eastern Alps. Results of pollen analyses performed on a 10 m firn core taken on the top of Alto dell'Ortles Glacier (3905 m a.s.l.) will be discussed. Palynological data are compared and complemented with stable isotopes, major ions and trace elements analyses. Based on the single species flowering periods, our results show that the pollen spectrum presents seasonal and inter-annual variability that enables to distinguish snow accumulated in the three different flowering seasons and winter snow. According to these four components a seasonal and annual chronology was established, proving that the 10 m firn core encompasses four years of snow accumulation and presents a clear seasonal palynological signal. These first results reveal the potential of pollen content of glacier snow and ice as a chronological tool that can contribute to the construction of a robust chronological model with a seasonal to annual resolution. This study is the first step and the base for future research on deeper ice cores on the Alto dell'Ortles Glacier (Ortles project: www.ortles.org).

  1. Advanced paternal age and reproductive outcome

    PubMed Central

    Wiener-Megnazi, Zofnat; Auslender, Ron; Dirnfeld, Martha

    2012-01-01

    Women have been increasingly delaying the start of motherhood in recent decades. The same trend is seen also for men. The influence of maternal age on fertility, chromosomal anomalies, pregnancy complications, and impaired perinatal and post-natal outcome of offspring, has been thoroughly investigated, and these aspects are clinically applied during fertility and pregestational counseling. Male aging and reproductive outcome has gained relatively less attention. The purpose of this review is to evaluate updated and relevant literature on the effect of paternal age on reproductive outcome. PMID:22157982

  2. From valley to marginal glaciation in alpine-type relief: Lateglacial glacier advances in the Pięć Stawów Polskich/Roztoka Valley, High Tatra Mountains, Poland

    NASA Astrophysics Data System (ADS)

    Zasadni, Jerzy; Kłapyta, Piotr

    2016-01-01

    The Pięć Stawów Polskich-Roztoka Valley in the High Tatras (Western Carpathians) features typical alpine-type relief with a deeply incised glacial trough and large, compound trough head cirque. The prominent hypsographic maximum in the valley (1680-2000 m) along with a broad cirque bottom had provided a vast space for recording glacial and periglacial landforms, specifically the most recent Lateglacial advances. The valley has been intensively studied before in the context of glacial chronology. In this paper, we re-establish the post-Last Glacial Maximum (LGM) glacial chronology of the valley via detailed geomorphologic mapping, equilibrium line altitude (ELA) reconstruction, and Schmidt hammer (SH) dating, along with a critical review of previously published cosmogenic exposure age data (36Cl) and lacustrine sediment chronology. Our results indicate that the first four of the five distinguished Lateglacial stages (Roztoka I-III, Pusta I) occurred before the Bølling/Allerød (B/A) interstadial; thus, virtually the entire valley became deglaciated in course of the Oldest Dryas cold phase. A distinct reorganization of deglacial patterns from valley-type to marginal-type occurred before B/A warming when the ELA increased above the valley hypsographic maximum concentrated at the cirque bottom elevation. It shows that noticeable deglaciation step can be caused due to topographic reason with a minimal climate forcing. This points also to an important role of glaciated valley hypsography in regulating the distribution of moraines which is rarely taken into account in paleoglaciological reconstructions. We infer that glaciers vanished in the Tatra Mountains during the B/A interstadial. Later, a renewed advance during the Younger Dryas (Pusta II) formed a nearly continuous, festoon shaped pattern of moraines and rock glaciers in close distance to cirque backwalls. Furthermore, we discus some paleoenvironmental significance of the geomorphological record in the valley

  3. Investigating Long-term Behavior of Outlet Glaciers in Greenland

    NASA Technical Reports Server (NTRS)

    Csatho, Beata; vanderVeen, Kees; Schenk, Toni

    2005-01-01

    Repeat surveys by airborne laser altimetry in the 1990s have revealed significant thinning of outlet glaciers draining the interior of the Greenland Ice Sheet, with thinning rates up to several meters per year. To fully appreciate the significance of these recent glacier changes, the magnitude of retreat and surface lowering must be placed within the broader context of the retreat since the Last Glacial Maximum and, more significantly, of the retreat following the temporary glacier advance during the Little Ice Age (LIA). The LIA maximum stand is marked by trimlines, sharp boundaries between recently deglacifated unvegetated rocks, and vegetated surfaces at higher elevations. The objective of this project was to demonstrate the use of remote sensing data to map these trimlines and other glacial geomorphologic features.

  4. Reconstruction of glacier variability from lake sediments reveals dynamic Holocene climate in Svalbard

    NASA Astrophysics Data System (ADS)

    van der Bilt, Willem G. M.; Bakke, Jostein; Vasskog, Kristian; D'Andrea, William J.; Bradley, Raymond S.; Ólafsdóttir, Sædis

    2015-10-01

    climate-sensitivity of the small glaciers studied, which rapidly responded to climate shifts. The start of prolonged Neoglacial glacier activity commenced during the Little Ice Age (LIA) around 700 cal BP, in agreement with reported advances from other glaciers on Svalbard. In conclusion, this study proposes a three-stage Holocene climate history of Svalbard, successively driven by LIS meltwater pulses, episodic Atlantic cooling and declining summer insolation.

  5. An Initial AUV Investigation of the Morainal Bank and Ice-Proximal Submarine Processes of the Advancing Hubbard Glacier, Southeast Alaska

    NASA Astrophysics Data System (ADS)

    Lawson, D. E.; Gulick, S. P. S.; Goff, J. A.; O'Halloran, W.

    2014-12-01

    The movement of an advancing tidewater glacier occurs in concert with the morainal bank that underlies its terminus. The mechanics of motion and sedimentological processes responsible for this advance of the morainal bank with the calving terminus are not well-defined and based largely on inferences from geophysical analyses of remnant morainal banks on fjord floors. There is a general absence of in situ or direct observation of the submarine margin because it is nearly impossible to access the immediate area of the ice face by boat safely. In order to obtain such data, in June 2014 we tested the ability of a Bluefin 9M AUV (autonomous underwater vehicle) to acquire high resolution swath bathymetry and sidescan backscatter across a ~2 km long section of the ice face of Hubbard Glacier (see also Goff et al., this meeting). Additionally onboard oceanographic measurements were taken that can be compared with surface cast CTD profiles obtained during AUV deployment, including locations with subglacial discharges. The AUV test provides details on the geometry of the morainal bank and nature of the fjord wall surfaces. The decimeter-scale imagery of the seabed reveals numerous erosional and depositional bedforms and gravitational features on the morainal bank's proximal slope. Closer to the ice face, the morainal bank surface appears much coarser, with textural patterns of unknown origin, and gravel lags including boulder fields. Comparing the water depth from the AUV survey with that of NOAA bathymetric data from 2004/2006 shows the morainal bank continued to advance in pace with ice advance into fjord waters over 200m deep, water depths shoaling up to 100m near the present ice margin. The glimpse of the morainal bank afforded by the AUV test clearly demonstrated the value of this technology to ice marginal submarine investigations.

  6. Comparison of the responses of two temperate Alpine valley glaciers to climate change at the decadal scale

    NASA Astrophysics Data System (ADS)

    Gabbud, Chrystelle; Tahir, Adnan Ahmad; Micheletti, Natan; Lane, Stuart

    2015-04-01

    Glacier advance and recession are considered as key indicators of climate change by the Intergovernmental Panel on Climate Change. Understanding the relationship between climatic variations and glacial responses is crucial. Here, we use archival photogrammetric methods to generate high resolution and precise Digital Elevation Models (DEMs) of two Alpine valley glaciers that have shown a contrasting response to recent climatic variability. Digital photogrammetry is well-established for glacier monitoring, mass balance determination and computation of the volumes of ice mass change. Reconstructions of the recent history of glaciers have been performed through and since the Little Ice Age and also more recently in relation to recent global warming. This study uses aerial imagery available from the early 1960s. Archival digital photogrammetry is applied to reconstruct the decadal scale glacial history of the Haut Glacier d'Arolla and the Glacier de Tsijiore Nouve in south western Switzerland. The data generated are used to explore the linkages between glacier changes and climate forcing. While both of the glaciers were subject to exactly the same climatic settings (they are only a few km apart), the responses to climatic variability have been markedly different. The data show continual recession of the Haut Glacier d'Arolla since 1967, associated with long-term climatic amelioration but only a weak response to shorter-term climatic deterioration. Glacier surface velocity estimates obtained using surface particle tracking showed that, unlike for most Swiss glaciers during the late 1970s and early 1980s, ice mass flux from the accumulation zone was too low to compensate for the effects of glacier thinning. Associated with glacier response time, that means that whilst there may have been a reduction in the ablation rate during the colder period, the flux did still not exceed the ablation rate, and hence snout advance was prevented. By contrast, the Tsijiore Nouve Glacier

  7. The Little Ice Age climate of New Zealand reconstructed from Southern Alps cirque glaciers: a synoptic type approach

    NASA Astrophysics Data System (ADS)

    Lorrey, Andrew; Fauchereau, Nicolas; Stanton, Craig; Chappell, Petra; Phipps, Steven; Mackintosh, Andrew; Renwick, James; Goodwin, Ian; Fowler, Anthony

    2014-06-01

    Little Ice Age (LIA) austral summer temperature anomalies were derived from palaeoequilibrium line altitudes at 22 cirque glacier sites across the Southern Alps of New Zealand. Modern analog seasons with temperature anomalies akin to the LIA reconstructions were selected, and then applied in a sampling of high-resolution gridded New Zealand climate data and global reanalysis data to generate LIA climate composites at local, regional and hemispheric scales. The composite anomaly patterns assist in improving our understanding of atmospheric circulation contributions to the LIA climate state, allow an interrogation of synoptic type frequency changes for the LIA relative to present, and provide a hemispheric context of the past conditions in New Zealand. An LIA summer temperature anomaly of -0.56 °C (±0.29 °C) for the Southern Alps based on palaeo-equilibrium lines compares well with local tree-ring reconstructions of austral summer temperature. Reconstructed geopotential height at 1,000 hPa (z1000) suggests enhanced southwesterly flow across New Zealand occurred during the LIA to generate the terrestrial temperature anomalies. The mean atmospheric circulation pattern for summer resulted from a crucial reduction of the `HSE'-blocking synoptic type (highs over and to the west of NZ; largely settled conditions) and increases in both the `T'- and `SW'-trough synoptic types (lows passing over NZ; enhanced southerly and southwesterly flow) relative to normal. Associated land-based temperature and precipitation anomalies suggest both colder- and wetter-than-normal conditions were a pervasive component of the base climate state across New Zealand during the LIA, as were colder-than-normal Tasman Sea surface temperatures. Proxy temperature and circulation evidence were used to corroborate the spatially heterogeneous Southern Hemisphere composite z1000 and sea surface temperature patterns generated in this study. A comparison of the composites to climate mode archetypes

  8. [Drivers of advanced age in traffic accidents].

    PubMed

    Bilban, Marjan

    2002-12-01

    The elderly are vulnerable and potentially unpredictable active participants in traffic who deserve special attention. Longer life expectancy entails a greater number of senior drivers, that is, persons with various health problems and difficulties accompanying old age. At the turn of the millennium, the share of population aged 65 or more in Slovenia was around 13%, and in 25 years it will be near as much as 19%. The share of drivers from this age group was 28% a year ago, and it is expected to reach about 54%. Numerous studies have shown that there are many differences in driving attitude between the young and the elderly. The young are by large active victims, and their main offense and cause of accident is speeding, while the elderly are more passive and their main offense is ignoring and enforcing the right of way. This paper focuses on the differences in the occurrence and type of injuries between the young and the elderly drivers, based on an analysis of all road accidents in Slovenia in the period between 1998-2000. Older people (over 65) caused only 4.7% of all road accidents (16.7% of all accidents involving pedestrians, 11.5% of all involving cyclists, 2.7% involving motorcyclists and 5% of all accidents involving car drivers). Of all accidents, 89.3% were without injuries, and the fatal outcome was registered in 0.4% accidents. Among the elderly (65-74 years of age), however, this share was 1%, and rising to 2.7% with the age 75 and above. By calculating the weight index, which discriminates between minor and severe injuries, and the fatal outcome, it was established that age groups 65-74 and > or = 75 cause three and five times greater damage, respectively than age groups from 18 to 54 years. With years, psychophysical changes lead to a drop in driving ability, which in turn increases the risk of road accidents. It is true that elderly people cause less traffic accidents (and also drive less) than the young, but when they are involved in an accident

  9. Recent evolution and mass balance of Cordón Martial glaciers, Cordillera Fueguina Oriental

    NASA Astrophysics Data System (ADS)

    Strelin, Jorge; Iturraspe, Rodolfo

    2007-10-01

    Past and present glacier changes have been studied at Cordón Martial, Cordillera Fueguina Oriental, Tierra del Fuego, providing novel data for the Holocene deglaciation history of southern South America and extrapolating as well its future behavior based on predicted climatic changes. Regional geomorphologic and stratigraphic correlations indicate that the last glacier advance deposited the ice-proximal ("internal") moraines of Cordón Martial, around 330 14C yr BP, during the Late Little Ice Age (LLIA). Since then glaciers have receded slowly, until 60 years ago, when major glacier retreat started. There is a good correspondence for the past 100 years between the surface area variation of four small cirque glaciers at Cordón Martial and the annual temperature and precipitation data of Ushuaia. Between 1984 and 1998, Martial Este Glacier lost 0.64 ± 0.02 × 10 6 m 3 of ice mass (0.59 ± 0.02 × 10 6 m 3 w.e.), corresponding to an average ice thinning of 7.0 ± 0.2 m (6.4 ± 0.2 m w.e), according to repeated topographic mapping. More detailed climatic data have been obtained since 1998 at the Martial Este Glacier, including air temperature, humidity and solar radiation. These records, together with the monthly mass balance measured since March 2000, document the annual response of the Martial Este Glacier to the climate variation. Mass balances during hydrological years were positive in 2000, negative in 2001 and near equilibrium in 2002. Finally, using these data and the regional temperature trend projections, modeled for different future scenarios by the Atmosphere-Ocean Model (GISS-NASA/GSFC), potential climatic-change effects on this mountain glacier were extrapolated. The analysis shows that only the Martial Este Glacier may survive this century.

  10. Glacier outburst floods from Ghulkin Glacier, upper Hunza Valley, Pakistan

    NASA Astrophysics Data System (ADS)

    Richardson, S. D.; Quincey, D. J.

    2009-04-01

    Outburst floods from Ghulkin Glacier in 2008 caused localised damage to properties, land and infrastructure of Ghulkin village and to the Karakoram Highway in the upper Hunza Valley of northern Pakistan. The unexpected nature of the floods highlights a poor understanding of glacial flood potential related to advancing glaciers in the Karakoram. Here we describe the Ghulkin floods and examine the broader glaciological controls on flood generation. Ghulkin Glacier is an active mountain glacier, its steep (up to 12˚ ), debris-covered snout bound by a continuous latero-terminal moraine. Three separate outburst floods during May and June 2008 exited the right lateral moraine close to the glacier terminus, resulting in two separate flood paths; one flowing down the existing outwash fan that resulted in no damage and the other flowing directly through properties and land of Ghulkin village. In 2008, the snout of Ghulkin Glacier was overriding its terminal moraine, and local villagers report an associated increase in debris flows and rock fall since 2005. High surface velocities (of the order of 50 m a-1) near the terminus are associated with the current period of advance, and an increase in the number and size of transient supraglacial lakes during the melt season has been observed. Assessment of the processes and characteristics of the summer 2008 floods provides a conceptual model for local glacier hazards associated with advancing mountain glaciers in the Karakoram. Crevasses and seracs associated with the high flow velocities have steep, debris-free ice cliffs that melt rapidly during the summer ablation season and provide a route for the meltwater to enter the englacial drainage system. Meltwater is stored temporarily in supraglacial, and probably englacial, settings; whilst drainage is facilitated by the formation of new, or re-organisation of existing, conduits under the active ice conditions. The steep glacier surface gradient and active ice results in

  11. Jakobshavn Glacier

    Atmospheric Science Data Center

    2013-04-17

    ... are visible in the bright white ice. A scattering of small icebergs in Disco Bay adds a touch of glittery sparkle to the scene. The ... for a large portion of the western side of the ice sheet. Icebergs released from the glacier drift slowly with the ocean currents and ...

  12. Glacier microseismicity

    USGS Publications Warehouse

    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.

  13. Predictors of Driving Outcomes in Advancing Age

    PubMed Central

    Emerson, Jamie L.; Johnson, Amy M.; Dawson, Jeffrey D.; Uc, Ergun Y.; Anderson, Steven W.

    2012-01-01

    This study aimed to develop predictive models for real-life driving outcomes in older drivers. Demographics, driving history, on-road driving errors, and performance on visual, motor, and neuropsychological test scores at baseline were assessed in 100 older drivers (ages 65–89 years [72.7]). These variables were used to predict time to driving cessation, first moving violation, or crash. Using Cox proportional hazards regression models, significant individual predictors for driving cessation were greater age and poorer scores on Near Visual Acuity, Contrast Sensitivity, Useful Field of View, Judgment of Line Orientation, Trail Making Test-Part A, Benton Visual Retention Test, Grooved Pegboard, and a composite index of overall cognitive ability. Greater weekly mileage, higher education, and “serious” on-road errors predicted moving violations. Poorer scores from Trail Making Test-Part B or Trail Making Test (B-A) and serious on-road errors predicted crashes. Multivariate models using “off-road” predictors revealed (1) age and Contrast Sensitivity as best predictors for driving cessation; (2) education, weekly mileage, and Auditory Verbal Learning Task-Recall for moving violations; and (3) education, number of crashes over the past year, Auditory Verbal Learning Task-Recall, and Trail Making Test (B-A) for crashes. Diminished visual, motor, and cognitive abilities in older drivers can be easily and noninvasively monitored with standardized off-road tests, and performances on these measures predict involvement in motor vehicle crashes and driving cessation, even in the absence of a neurological disorder. PMID:22182364

  14. Svalbard surging glacier landsystems

    NASA Astrophysics Data System (ADS)

    Lovell, Harold; Benn, Douglas; Lukas, Sven; Flink, Anne

    2014-05-01

    The percentage of Svalbard glaciers thought to be of surge-type is somewhere between 13-90% according to different sources variously based on statistical analysis and observations of diagnostic glaciological and geomorphological features, e.g. looped moraines. Developing a better understanding of which of these figures, if either, is most realistic is important in the context of glacier dynamics and related contributions of small glaciers and ice caps to sea level change in the immediate future. We present detailed geomorphological assessments of the margins of several known surge-type glaciers in Svalbard in order to update and improve the existing framework by which they are identified, and to provide a foundation for future reassessments of the surge-type glacier population based on distinct landform-sediment assemblages. Three landsystems are proposed: (1) Surges of small valley glaciers produce a prominent ice-cored latero-frontal moraine at their surge maximum and are characterised by an inner zone of ice stagnation terrain (hummocky topography, kettle lakes, debris flows) with no or only very few poorly-defined bedforms (crevasse squeeze ridges, eskers and flutes) and no recessional moraines. Many of these glaciers may have surged in the past but show no signs that they have the capability to do so again in the future. (2) Larger land-terminating glaciers, often with several tributaries, typically produce a push moraine complex which contains evidence for multiple advances, as identified from ridge-meltwater channel relationships. The inner zone often contains a large lagoon, partly dammed by the push moraine complex, and widespread ice stagnation terrain. Crevasse squeeze ridges, eskers and flutes are well-defined but small and limited in number and distribution. (3) Surges of large tidewater glaciers produce distinctive, often multi-generational, landform assemblages both in submarine and lateral terrestrial positions. The well-preserved submarine record

  15. Primiparity at very advanced maternal age (≥ 45 years).

    PubMed

    Glasser, Saralee; Segev-Zahav, Aliza; Fortinsky, Paige; Gedal-Beer, Debby; Schiff, Eyal; Lerner-Geva, Liat

    2011-06-30

    This study describes maternal and birth outcomes of primiparae aged ≥ 45. High rates of pregnancy complications and poor birth outcomes were found, stressing that the personal risks and ramifications to the health system should be taken into account in establishing obstetric health policy regarding primiparity at advanced maternal age.

  16. OMEGA - an operational glacier monitoring system

    NASA Astrophysics Data System (ADS)

    Pellikka, P. K. E.

    2003-04-01

    Glacier changes reflect local climate changes and are one of the most important direct indicators of global climate change. In general, the glaciers are retreating in Europe, but some glaciers are advancing. However, even in small areas glacier responses can be different. The application of glaciers as indicators requires sufficient amount of glaciers, which is possible only with remote sensing methods. Remote sensing data have been used for glacier monitoring from the late 19th century, first as terrestrial photographs, but later as aerial photographs. A new era began in the 1970’s as optical satellite data became available. Since late 1990’s the glacier monitoring could be performed with numerous satellite and airborne sensors ranging from satellite radar data to airborne laser scanner data. All together, the development of new remote sensing technologies and methods provides many possibilities for studies of glacier features and parameters. The glacier parameters of interest in operational monitoring are the changes of glacier area and volume, and the variation of glacier zones, such as snow, firn and ice. These parameters enable the estimation of relative volume change, AAR and equilibrium line, for example. Operational monitoring involves that the remote sensing data to be used is available continuously, the image processing methods are accurate and the processing chain is developed so that the derivation of the aimed parameters works fluently. The OMEGA project aims at the development of an operational glacier monitoring system applying all the potential remote sensing data. The objectives are to develop workflows and semi-automatic image processing methodologies for different data types in order to retrieve glacier parameters, to construct databases of the study glaciers and to develop the prototype of an operational monitoring system. The test glaciers are Hintereisferner in Austria and Engabreen in Norway. The deliverable of the project is the OMEGA

  17. 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.

  18. Rapid Late Holocene glacier fluctuations reconstructed from South Georgia lake sediments using novel analytical and numerical techniques

    NASA Astrophysics Data System (ADS)

    van der Bilt, Willem; Bakke, Jostein; Werner, Johannes; Paasche, Øyvind; Rosqvist, Gunhild

    2016-04-01

    The collapse of ice shelves, rapidly retreating glaciers and a dramatic recent temperature increase show that Southern Ocean climate is rapidly shifting. Also, instrumental and modelling data demonstrate transient interactions between oceanic and atmospheric forcings as well as climatic teleconnections with lower-latitude regions. Yet beyond the instrumental period, a lack of proxy climate timeseries impedes our understanding of Southern Ocean climate. Also, available records often lack the resolution and chronological control required to resolve rapid climate shifts like those observed at present. Alpine glaciers are found on most Southern Ocean islands and quickly respond to shifts in climate through changes in mass balance. Attendant changes in glacier size drive variations in the production of rock flour, the suspended product of glacial erosion. This climate response may be captured by downstream distal glacier-fed lakes, continuously recording glacier history. Sediment records from such lakes are considered prime sources for paleoclimate reconstructions. Here, we present the first reconstruction of Late Holocene glacier variability from the island of South Georgia. Using a toolbox of advanced physical, geochemical (XRF) and magnetic proxies, in combination with state-of-the-art numerical techniques, we fingerprinted a glacier signal from glacier-fed lake sediments. This lacustrine sediment signal was subsequently calibrated against mapped glacier extent with the help of geomorphological moraine evidence and remote sensing techniques. The outlined approach enabled us to robustly resolve variations of a complex glacier at sub-centennial timescales, while constraining the sedimentological imprint of other geomorphic catchment processes. From a paleoclimate perspective, our reconstruction reveals a dynamic Late Holocene climate, modulated by long-term shifts in regional circulation patterns. We also find evidence for rapid medieval glacier retreat as well as a

  19. Alpine Glaciers

    NASA Technical Reports Server (NTRS)

    2003-01-01

    [figure removed for brevity, see original site]

    Released 27 August 2003

    This image shows part of the western flank of Arsia Mons, the southernmost of the three great Tharsis Montes. The surface shows parallel ridges more reminiscent of a Zen garden than any typical geological feature. These ridges are not typical of lava flow fronts, so a different explanation has been proposed by Mars scientists. These ridges may instead be ancient signs of previously existing glaciers that formed high on the volcano's flank. As glaciers retreat with the seasons and shifting climate, they leave behind a mound of debris along their receding edge. Successive retreats can produce a series of parallel ridges similar to those seen here.

    Image information: VIS instrument. Latitude -6.9, Longitude 230.5 East (129.5 West). 19 meter/pixel resolution.

  20. GLACIER SLIDING,

    DTIC Science & Technology

    The theory of the sliding of glaciers presented in earlier papers has been generalized (1) by taking into account the resistance to sliding offered...bed at the downstream side of an obstacle. The sliding velocities and controlling obstacle sizes which are found from the generalized theory are...magnitude smaller in thickness than the height of the controlling obstacles can cause an appreciable increase in the sliding velocity. The generalized

  1. Using Metaphorical Models for Describing Glaciers

    NASA Astrophysics Data System (ADS)

    Felzmann, Dirk

    2014-11-01

    To date, there has only been little conceptual change research regarding conceptions about glaciers. This study used the theoretical background of embodied cognition to reconstruct different metaphorical concepts with respect to the structure of a glacier. Applying the Model of Educational Reconstruction, the conceptions of students and scientists regarding glaciers were analysed. Students' conceptions were the result of teaching experiments whereby students received instruction about glaciers and ice ages and were then interviewed about their understandings. Scientists' conceptions were based on analyses of textbooks. Accordingly, four conceptual metaphors regarding the concept of a glacier were reconstructed: a glacier is a body of ice; a glacier is a container; a glacier is a reflexive body and a glacier is a flow. Students and scientists differ with respect to in which context they apply each conceptual metaphor. It was observed, however, that students vacillate among the various conceptual metaphors as they solve tasks. While the subject context of the task activates a specific conceptual metaphor, within the discussion about the solution, the students were able to adapt their conception by changing the conceptual metaphor. Educational strategies for teaching students about glaciers require specific language to activate the appropriate conceptual metaphors and explicit reflection regarding the various conceptual metaphors.

  2. Transient Meltwater in Mullins Valley Glacier, McMurdo Dry Valleys, Antarctica

    NASA Astrophysics Data System (ADS)

    Grimm, R. E.; Stillman, D. E.; Kowalewski, D. E.

    2014-12-01

    Mullins Glacier is a cold-based debris-covered glacier feeding into Beacon Valley, at high altitude in the McMurdo Dry Valleys of Antarctica. Ice is exposed at the headwall in Mullins Valley but the majority of the glacier is buried beneath a sublimation till (lag deposit composed of englacial and supraglacial debris). This till is initially ~10 cm thick but gradually thickens to ~60 cm at the glacier terminus (~8 km distant). Mullins Glacier has been postulated to be one of the world's oldest alpine glaciers: tephrachronology places a minimum age of the overlying sublimation till near the terminus at 7.9 Ma. Our measurements of the complex resistivity (aka spectral induced polarization or dielectric spectroscopy) of massive Mullins Glacier ice reveal two distinct origins. The electrical properties of clean ice or ice with rock fragments are typical of meteoric polar ice (Stillman et al., JGR, 2013). However, "dirty" ice is electrically distinct, indicating soluble impurity content near lattice saturation. This behavior, which we also observed for Lake Vostok accretion ice, is consistent with freezing from saline, draining water. Therefore one hypothesis it that the dirty ice formed by infiltration in former clement environments. However, very efficient segregation is subsequently required, and not all dirty ice is at the top of the ice column. Dirty ice likely samples debris bands, which are more commonly observed in cores where Mullins Glacier has advanced onto the main (Beacon) valley floor and is nearly stagnant. If debris bands are correlated to lattice impurity saturation via the dirty ice, then they may have been transiently at or near melting. This may be a primary feature of the environment during debris accumulation or simply due to the high thermal inertia of debris. Alternatively, debris bands and associated salts may be carried below the annual thermal wave where they experience near-constant, supereutectic temperatures. Elevated temperatures may be

  3. Precipitation as the main driver of Neoglacial fluctuations of Gualas glacier, Northern Patagonian Icefield

    NASA Astrophysics Data System (ADS)

    Bertrand, S.; Hughen, K. A.; Lamy, F.; Stuut, J.-B. W.; Torrejón, F.; Lange, C. B.

    2011-09-01

    Glaciers are frequently used as indicators of climate change. However, the link between past glacier fluctuations and climate variability is still highly debated. Here, we investigate the mid- to late-Holocene fluctuations of Gualas Glacier, one of the northernmost outlet glaciers of the Northern Patagonian Icefield, using a multi-proxy sedimentological and geochemical analysis of a 15 m long fjord sediment core from Golfo Elefantes, Chile, and historical documents from early Spanish explorers. Our results show that the core can be sub-divided in three main lithological units that were deposited under very different hydrodynamic conditions. Between 5400 and 4180 cal yr BP and after 750 cal yr BP, sedimentation in Golfo Elefantes was characterized by the rapid deposition of fine silt, most likely transported by fluvio-glacial processes. By contrast, the sediment deposited between 4130 and 850 cal yr BP is composed of poorly sorted sand that is free of shells. This interval is particularly marked by high magnetic susceptibility values and Zr concentrations, and likely reflects a major advance of Gualas glacier towards Golfo Elefantes during the Neoglaciation. Several thin silt layers observed in the upper part of the core are interpreted as secondary fluctuations of Gualas glacier during the Little Ice Age, in agreement with historical and dendrochronological data. Our interpretation of the Golfo Elefantes glaciomarine sediment record in terms of fluctuations of Gualas glacier is in excellent agreement with the glacier chronology proposed for the Southern Patagonian Icefield, which is based on terrestrial (moraine) deposits. By comparing our results with independent proxy records of precipitation and sea surface temperature, we demonstrate that the fluctuations of Gualas glacier during the last 5400 yr were mainly driven by changes in precipitation in the Andes.

  4. Precipitation as the main driver of Neoglacial fluctuations of Gualas glacier, Northern Patagonian Icefield

    NASA Astrophysics Data System (ADS)

    Bertrand, S.; Hughen, K. A.; Lamy, F.; Stuut, J.-B. W.; Torrejón, F.; Lange, C. B.

    2012-03-01

    Glaciers are frequently used as indicators of climate change. However, the link between past glacier fluctuations and climate variability is still highly debated. Here, we investigate the mid- to late-Holocene fluctuations of Gualas Glacier, one of the northernmost outlet glaciers of the Northern Patagonian Icefield, using a multi-proxy sedimentological and geochemical analysis of a 15 m long fjord sediment core from Golfo Elefantes, Chile, and historical documents from early Spanish explorers. Our results show that the core can be sub-divided into three main lithological units that were deposited under very different hydrodynamic conditions. Between 5400 and 4180 cal yr BP and after 750 cal yr BP, sedimentation in Golfo Elefantes was characterized by the rapid deposition of fine silt, most likely transported by fluvio-glacial processes. By contrast, the sediment deposited between 4130 and 850 cal yr BP is composed of poorly sorted sand that is free of shells. This interval is particularly marked by high magnetic susceptibility values and Zr concentrations, and likely reflects a major advance of Gualas glacier towards Golfo Elefantes during the Neoglaciation. Several thin silt layers observed in the upper part of the core are interpreted as secondary fluctuations of Gualas glacier during the Little Ice Age, in agreement with historical and dendrochronological data. Our interpretation of the Golfo Elefantes glaciomarine sediment record in terms of fluctuations of Gualas glacier is in excellent agreement with the glacier chronology proposed for the Southern Patagonian Icefield, which is based on terrestrial (moraine) deposits. By comparing our results with independent proxy records of precipitation and sea surface temperature, we suggest that the fluctuations of Gualas glacier during the last 5400 yr were mainly driven by changes in precipitation in the North Patagonian Andes.

  5. Cosmogenic 10Be and 26Al exposure ages of glaciations in the Frankland Range, southwest Tasmania reveal a limited MIS-2 ice advance

    NASA Astrophysics Data System (ADS)

    Kiernan, Kevin; Fink, David; McConnell, Anne

    2017-02-01

    New mapping of the glacial geomorphology coupled with 10Be and 26Al exposure age dating of moraines on the flanks of the Frankland Range in south west Tasmania indicate that glacier extent during MIS-2 was far smaller than during earlier glaciations with the ice cover being confined to only the uppermost cirques of the range. Moraines further down the range flanks, ∼50-150 m lower in altitude than the MIS-2 dated advance, indicate that glaciers were only slightly larger during earlier glaciations and, depending on the interpretation of their exposure ages, may range from MIS 7 to MIS 12. These older moraines are nested inside the maximum ice limits of an even more ancient and extensive glaciation, defined by degraded valley floor moraines and coalescing glacio-fluvial fans that remain undated but appear no younger than MIS 12. Patterns of glacial erosion and moraine deposition on the Frankland Range suggest that the more recent glaciations were increasingly influenced by the erosional morphology initiated by earlier glaciers. Microclimatic differences resulting from this earlier glacial topography were particularly influential determinants of glaciation during MIS 2. These results are consistent with emerging evidence from studies of other ranges in southwest Tasmania.

  6. 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

  7. Recent fluctuations of the Argentinian glaciers

    NASA Astrophysics Data System (ADS)

    Leiva, Juan Carlos

    1999-10-01

    Some of the results obtained in the glaciological research carried out since 1979 at the Argentinian Andes are shown in this paper. The research covers a wide latitudinal gap extending from the Agua Negra glacier in the province of San Juan to the Frı´as glacier situated at Mount Tronador. Agua Negra and Piloto glaciers show a very similar behavior of almost continuous retreat since 1965 while at the Plomo region a small advance period, starting in 1982, is observed in five of the 10 glaciers studied. Finally, the Frı´as glacier fluctuations record shows a very strong recession since 1850 only interrupted by the 1976 advance that continued in 1977.

  8. Management and counseling of the male with advanced paternal age.

    PubMed

    Jennings, Michael O; Owen, Ryan C; Keefe, David; Kim, Edward D

    2017-02-01

    Increasing percentages of children are being born to older fathers. This has resulted in concerns about the potential adverse effects of advanced paternal age. To help clinicians counsel couples, a systemic review was performed to attempt to address questions that these couples may ask: Should routine sperm testing be performed in older males? Should preimplantation genetic diagnosis (PGD) be performed? How do providers counsel patients about risk? Should young males freeze sperm if they plan to delay paternity? Using the terms "advanced paternal age", "semen testing", "preimplantation genetic diagnosis/screening", and "cryopreservation", a comprehensive search was performed in PubMed and the Cochrane Library, and numerous international societal guidelines were reviewed. In total, 42 articles or guidelines were reviewed. There were no limits placed on the timing of the articles. Thirty articles were found to be relevant and beneficial to answering the above questions. Each question was answered separately by the supporting literature. While primary research exists to support the role of semen testing, PGD/preimplantation genetic screening, and sperm banking in males who may be affected by advancing age, comprehensive studies on the possible clinical benefit of these interventions have yet to be performed. As a result, societal guidelines have yet to incorporate distinct best-practice guidelines on advanced paternal age.

  9. Modeling debris-covered glaciers: response to steady debris deposition

    NASA Astrophysics Data System (ADS)

    Anderson, Leif S.; Anderson, Robert S.

    2016-05-01

    Debris-covered glaciers are common in rapidly eroding alpine landscapes. When thicker than a few centimeters, surface debris suppresses melt rates. If continuous debris cover is present, ablation rates can be significantly reduced leading to increases in glacier length. In order to quantify feedbacks in the debris-glacier-climate system, we developed a 2-D long-valley numerical glacier model that includes englacial and supraglacial debris advection. We ran 120 simulations on a linear bed profile in which a hypothetical steady state debris-free glacier responds to a step increase of surface debris deposition. Simulated glaciers advance to steady states in which ice accumulation equals ice ablation, and debris input equals debris loss from the glacier terminus. Our model and parameter selections can produce 2-fold increases in glacier length. Debris flux onto the glacier and the relationship between debris thickness and melt rate strongly control glacier length. Debris deposited near the equilibrium-line altitude, where ice discharge is high, results in the greatest glacier extension when other debris-related variables are held constant. Debris deposited near the equilibrium-line altitude re-emerges high in the ablation zone and therefore impacts melt rate over a greater fraction of the glacier surface. Continuous debris cover reduces ice discharge gradients, ice thickness gradients, and velocity gradients relative to initial debris-free glaciers. Debris-forced glacier extension decreases the ratio of accumulation zone to total glacier area (AAR). Our simulations reproduce the "general trends" between debris cover, AARs, and glacier surface velocity patterns from modern debris-covered glaciers. We provide a quantitative, theoretical foundation to interpret the effect of debris cover on the moraine record, and to assess the effects of climate change on debris-covered glaciers.

  10. Reproduction at an advanced maternal age and maternal health.

    PubMed

    Sauer, Mark V

    2015-05-01

    Advanced age is a risk factor for female infertility, pregnancy loss, fetal anomalies, stillbirth, and obstetric complications. These concerns are based on centuries-old observations, yet women are delaying childbearing to pursue educational and career goals in greater numbers than ever before. As a result, reproductive medicine specialists are treating more patients with age-related infertility and recurrent pregnancy loss, while obstetricians are faced with managing pregnancies often complicated by both age and comorbidities. The media portrayal of a youthful but older woman, able to schedule her reproductive needs and balance family and job, has fueled the myth that "you can have it all," rarely characterizing the perils inherent to advanced-age reproduction. Reproductive medicine specialists and obstetrician/gynecologists should promote more realistic views of the evidence-based realities of advanced maternal age pregnancy, including its high-risk nature and often compromised outcomes. Doctors should also actively educate both patients and the public that there is a real danger of childlessness if individuals choose to delay reproduction.

  11. Seasonal variability of organic matter composition in an Alaskan glacier outflow: insights into glacier carbon sources

    NASA Astrophysics Data System (ADS)

    Spencer, Robert G. M.; Vermilyea, Andrew; Fellman, Jason; Raymond, Peter; Stubbins, Aron; Scott, Durelle; Hood, Eran

    2014-05-01

    Glacier ecosystems are a significant source of bioavailable, yet ancient dissolved organic carbon (DOC). Characterizing DOC in Mendenhall Glacier outflow (southeast Alaska) we document a seasonal persistence to the radiocarbon-depleted signature of DOC, highlighting ancient DOC as a ubiquitous feature of glacier outflow. We observed no systematic depletion in Δ 14C-DOC with increasing discharge during the melt season that would suggest mobilization of an aged subglacial carbon store. However, DOC concentration, δ 13C-DOC, Δ 14C-DOC and fluorescence signatures appear to have been influenced by runoff from vegetated hillslopes above the glacier during onset and senescence of melt. In the peak glacier melt period, the Δ 14C-DOC of stream samples at the outflow (-181.7 to -355.3‰) was comparable to the Δ 14C-DOC for snow samples from the accumulation zone (-207.2 to -390.9‰), suggesting that ancient DOC from the glacier surface is exported in glacier runoff. The pre-aged DOC in glacier snow and runoff is consistent with contributions from fossil fuel combustion sources similar to those documented previously in ice cores and thus provides evidence for anthropogenic perturbation of the carbon cycle. Overall, our results emphasize the need to further characterize DOC inputs to glacier ecosystems, particularly in light of predicted changes in glacier mass and runoff in the coming century.

  12. Reconstruction of late Holocene glacier retreat and relevant climatic and topographic patterns in southeastern Tibet by glacier mapping and equilibrium line altitude calculation

    NASA Astrophysics Data System (ADS)

    Loibl, David; Lehmkuhl, Frank

    2014-05-01

    Temperate glaciers in the eastern Nyainqêntanglha range, southeastern Tibet, are highly sensitive to climate change and are therefore of particular high interest for research on late Holocene changes of the monsoonal climate in High Asia. However, due to the remoteness of the area, the scarcity of empirical data, and the challenges to remote sensing work posed by cloud and snow cover, knowledge about the glacier dynamics and changes is still very limited. We applied a remote sensing approach that allowed a comprehensive regional glacier survey despite the few available data. Geomorphologic characteristics, distribution and late Holocene changes of 1964 glaciers were mapped from one of the few appropriate late summer satellite images: a Landsat ETM+ scene from September 23, 1999. The glacier dataset was subsequently parameterized by DEM supported measurements. Complex climate-relief-glacier interactions were studied in detail for three large glaciers in neighboring valleys. Despite their spatial proximity, these display strong heterogeneity in terms of catchment morphology, debris cover, and glacier characteristics. The results of this case study then provided the conceptual basis to use geomorphological evidence, i.e. trimlines and latero-frontal moraines, to obtain quantitative data on the changes since the Little Ice Age (LIA) maximum glacier advance. Statistical analysis of glacier length change revealed an average retreat of ~ 40 % and a trend towards stronger retreat for smaller glaciers. An evaluation of different methods to calculate equilibrium line altitudes (ELAs) indicates that an optimized toe-to-ridge altitude method (TRAM) outperforms other methods in settings with complex topography and a lack of mass-balance measurements. However, a large number of glacier measurements is crucial for high quality TRAM results and special attention has to be paid to different morphological glacier characteristics: debris-cover, reconstitution, valley floor

  13. Principles of Glacier Mechanics

    NASA Astrophysics Data System (ADS)

    Waddington, Edwin D.

    Glaciers are awesome in size and move at a majestic pace, and they frequently occupy spectacular mountainous terrain. Naturally, many Earth scientists are attracted to glaciers. Some of us are even fortunate enough to make a career of studying glacier flow. Many others work on the large, flat polar ice sheets where there is no scenery. As a leader of one of the foremost research projects now studying the flow of mountain glaciers (Storglaciaren, Norway), Roger Hooke is well qualified to describe the principles of glacier mechanics. Principles of Glacier Mechanics is written for upper-level undergraduate students and graduate students with an interest in glaciers and the landforms that glaciers produce. While most of the examples in the text are drawn from valley glacier studies, much of the material is also relevant to “glacier flatland” on the polar ice sheets.

  14. 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

  15. Mais comment s'écoule donc un glacier ? Aperçu historique

    NASA Astrophysics Data System (ADS)

    Rémy, Frédérique; Testut, Laurent

    2006-05-01

    Ice and snow have often helped physicists understand the world. On the contrary it has taken them a very long time to understand the flow of the glaciers. Naturalists only began to take an interest in glaciers at the beginning of the 19th century during the last phase of glacier advances. When the glacier flow from the upslope direction became obvious, it was then necessary to understand how it flowed. It was only in 1840, the year of the Antarctica ice sheet discovery by Dumont d'Urville, that two books laid the basis for the future field of glaciology: one by Agassiz on the ice age and glaciers, the other one by canon Rendu on glacier theory. During the 19th century, ice flow theories, adopted by most of the leading scientists, were based on melting/refreezing processes. Even though the word 'fluid' was first used in 1773 to describe ice, more the 130 years would have to go by before the laws of fluid mechanics were applied to ice. Even now, the parameter of Glen's law, which is used by glaciologists to model ice deformation, can take a very wide range of values, so that no unique ice flow law has yet been defined. To cite this article: F. Rémy, L. Testut, C. R. Geoscience 338 (2006).

  16. Franz Josef and Fox Glaciers, New Zealand: Historic length records

    NASA Astrophysics Data System (ADS)

    Purdie, Heather; Anderson, Brian; Chinn, Trevor; Owens, Ian; Mackintosh, Andrew; Lawson, Wendy

    2014-10-01

    Compilation of modern and historical length change records for Franz Josef and Fox Glaciers demonstrates that these glaciers have lost ~ 3 km in length and at least 3-4 km2 in area since the 1800s, with the greatest overall loss occurring between 1934 and 1983. Within this dramatic and ongoing retreat, both glaciers have experienced periods of re-advance. The record from Franz Josef Glacier is the most detailed, and shows major advances from 1946 to 1951 (340 m), 1965-1967 (400 m), 1983-1999 (1420 m) and 2004-2008 (280 m). At Fox Glacier the record is similar, with advances recorded during 1964-1968 (60 m), 1985-1999 (710 m) and 2004-2008 (290 m). Apart from the latest advance event, the magnitude of advance has been greater at Franz Josef Glacier, suggesting a higher length sensitivity. Analysis of the relationship between glacier length and a reconstructed annual equilibrium line altitude (ELA) record shows that the glaciers react very quickly to ELA variations - with the greatest correlation at 3-4 years' lag. The present (2014) retreat is the fastest retreat in the records of both glaciers. While decadal length fluctuations have been linked to hemispheric ocean-atmosphere variability, the overall reduction in length is a clear sign of twentieth century warming. However, documenting glacier length changes can be challenging; especially when increased surface debris-cover makes identification of the 'true' terminus a convoluted process.

  17. South Cascade Glacier bibliography

    SciTech Connect

    Fountain, A.G.; Fulk, M.A.

    1984-01-01

    South Cascade Glacier, in Washington State, resides in a well-defined basin with mainly unglacierized divides making it ideal for most glaciological and hydrological studies. This bibliography is divided into three cateogories: (1) studies done about South Cascade Glacier specifically; (2) studies that use data from South Cascade Glacier but do not focus on or give insight to the glacier itself; and (3) instrumentation studies and non-glacier projects including snow studies done in the basin. (ACR)

  18. 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.

  19. Debris-covered Himalayan glaciers under a changing climate: observations and modelling of Khumbu Glacier, Nepal

    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

  20. Advanced glycation end products (AGEs) promote melanogenesis through receptor for AGEs

    PubMed Central

    Lee, Eun Jung; Kim, Ji Young; Oh, Sang Ho

    2016-01-01

    Accumulation of advanced glycation end products (AGEs) is linked with development or aggravation of many degenerative processes or disorders, including aging and atherosclerosis. AGEs production in skin cells is known to promote stiffness and loss of elasticity through their buildup in connective tissue. However, the impact of AGEs has yet to be fully explored in melanocytes. In this study, we confirmed the existence of receptor for AGE (RAGE) in melanocytes in western blot and immunofluorescence along with increased melanin production in ex vivo skin organ culture and in vitro melanocyte culture following AGEs treatment. Cyclic AMP response element-binding protein (CREB) and extracellular signal-regulated kinases (ERK) 1/2 are considered as key regulatory proteins in AGEs-induced melanogenesis. In addition, blockage experiment using anti-RAGE blocking antibody has indicated that RAGE plays a pivotal role in AGE-mediated melanogenesis. Therefore, it is apparent that AGEs, known markers of aging, promote melanogenesis via RAGE. In addition, AGEs could be implicated in pigmentation associated with photoaging according to the results of increased secretion of AGEs from keratinocytes following UV irradiation. AGE-mediated melanogenesis may thus hold promise as a novel mean of altering skin pigmentation. PMID:27293210

  1. Malaspina Glacier, Alaska

    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 and

  2. Glaciers of South America

    USGS Publications Warehouse

    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.

  3. Patagonia Glacier, Chile

    NASA Technical Reports Server (NTRS)

    2000-01-01

    This ASTER images 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.

    Advanced Spaceborne Thermal Emission and Reflection Radiometer (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 International 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; Moshe Pniel of JPL is the project manager. ASTER is the only high resolution imaging sensor on Terra. The primary goal of the ASTER mission is to obtain high-resolution image data in 14 channels over the entire land surface, as well as black and white stereo images. With revisit time of between 4 and 16 days, ASTER will provide the capability for repeat coverage of changing areas on Earth's surface.

    The broad spectral coverage and high spectral resolution of ASTER will provide scientists in numerous disciplines with critical information for surface mapping, and monitoring dynamic conditions and temporal change. Example applications are: monitoring glacial advances and retreats, monitoring potentially active volcanoes, identifying crop stress, determining cloud

  4. Oxidative stress in aging: advances in proteomic approaches.

    PubMed

    Ortuño-Sahagún, Daniel; Pallàs, Mercè; Rojas-Mayorquín, Argelia E

    2014-01-01

    Aging is a gradual, complex process in which cells, tissues, organs, and the whole organism itself deteriorate in a progressive and irreversible manner that, in the majority of cases, implies pathological conditions that affect the individual's Quality of Life (QOL). Although extensive research efforts in recent years have been made, the anticipation of aging and prophylactic or treatment strategies continue to experience major limitations. In this review, the focus is essentially on the compilation of the advances generated by cellular expression profile analysis through proteomics studies (two-dimensional [2D] electrophoresis and mass spectrometry [MS]), which are currently used as an integral approach to study the aging process. Additionally, the relevance of the oxidative stress factors is discussed. Emphasis is placed on postmitotic tissues, such as neuronal, muscular, and red blood cells, which appear to be those most frequently studied with respect to aging. Additionally, models for the study of aging are discussed in a number of organisms, such as Caenorhabditis elegans, senescence-accelerated probe-8 mice (SAMP8), naked mole-rat (Heterocephalus glaber), and the beagle canine. Proteomic studies in specific tissues and organisms have revealed the extensive involvement of reactive oxygen species (ROS) and oxidative stress in aging.

  5. Oxidative Stress in Aging: Advances in Proteomic Approaches

    PubMed Central

    Ortuño-Sahagún, Daniel; Pallàs, Mercè; Rojas-Mayorquín, Argelia E.

    2014-01-01

    Aging is a gradual, complex process in which cells, tissues, organs, and the whole organism itself deteriorate in a progressive and irreversible manner that, in the majority of cases, implies pathological conditions that affect the individual's Quality of Life (QOL). Although extensive research efforts in recent years have been made, the anticipation of aging and prophylactic or treatment strategies continue to experience major limitations. In this review, the focus is essentially on the compilation of the advances generated by cellular expression profile analysis through proteomics studies (two-dimensional [2D] electrophoresis and mass spectrometry [MS]), which are currently used as an integral approach to study the aging process. Additionally, the relevance of the oxidative stress factors is discussed. Emphasis is placed on postmitotic tissues, such as neuronal, muscular, and red blood cells, which appear to be those most frequently studied with respect to aging. Additionally, models for the study of aging are discussed in a number of organisms, such as Caenorhabditis elegans, senescence-accelerated probe-8 mice (SAMP8), naked mole-rat (Heterocephalus glaber), and the beagle canine. Proteomic studies in specific tissues and organisms have revealed the extensive involvement of reactive oxygen species (ROS) and oxidative stress in aging. PMID:24688629

  6. Age-Related Effects of Advanced Glycation End Products (Ages) in Bone Matrix on Osteoclastic Resorption.

    PubMed

    Yang, Xiao; Gandhi, Chintan; Rahman, Md Mizanur; Appleford, Mark; Sun, Lian-Wen; Wang, Xiaodu

    2015-12-01

    Advanced glycation end products (AGEs) accumulate in bone extracellular matrix as people age. Previous studies have shown controversial results regarding the role of in situ AGEs accumulation in osteoclastic resorption. To address this issue, this study cultured human osteoclast cells directly on human cadaveric bone slices from different age groups (young and elderly) to warrant its relevance to in vivo conditions. The cell culture was terminated on the 3rd, 7th, and 10th day, respectively, to assess temporal changes in the number of differentiated osteoclasts, the number and size of osteoclastic resorption pits, the amount of bone resorbed, as well as the amount of matrix AGEs released in the medium by resorption. In addition, the in situ concentration of matrix AGEs at each resorption pit was also estimated based on its AGEs autofluorescent intensity. The results indicated that (1) osteoclastic resorption activities were significantly correlated with the donor age, showing larger but shallower resorption pits on the elderly bone substrates than on the younger ones; (2) osteoclast resorption activities were not significantly dependent on the in situ AGEs concentration in bone matrix, and (3) a correlation was observed between osteoclast activities and the concentration of AGEs released by the resorption. These results suggest that osteoclasts tend to migrate away from initial anchoring sites on elderly bone substrate during resorption compared to younger bone substrates. However, such behavior is not directly related to the in situ concentration of AGEs in bone matrix at the resorption sites.

  7. Glaciers along proposed routes extending the Copper River Highway, Alaska

    USGS Publications Warehouse

    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.

  8. Global Monitoring of Mountain Glaciers Using High-Resolution Spotlight Imaging from the International Space Station

    NASA Astrophysics Data System (ADS)

    Donnellan, A.; Green, J. J.; Bills, B. G.; Goguen, J.; Ansar, A.; Knight, R. L.; Hallet, B.; Scambos, T. A.; Thompson, L. G.; Morin, P. J.

    2013-12-01

    Mountain glaciers around the world are retreating rapidly, contributing about 20% to present-day sea level rise. Numerous studies have shown that mountain glaciers are sensitive to global environmental change. Temperate-latitude glaciers and snowpack provide water for over 1 billion people. Glaciers are a resource for irrigation and hydroelectric power, but also pose flood and avalanche hazards. Accurate mass balance assessments have been made for only 280 glaciers, yet there are over 130,000 in the World Glacier Inventory. The rate of glacier retreat or advance can be highly variable, is poorly sampled, and inadequately understood. Liquid water from ice front lakes, rain, melt, or sea water and debris from rocks, dust, or pollution interact with glacier ice often leading to an amplification of warming and further melting. Many mountain glaciers undergo rapid and episodic events that greatly change their mass balance or extent but are sparsely documented. Events include calving, outburst floods, opening of crevasses, or iceberg motion. Spaceborne high-resolution spotlight optical imaging provides a means of clarifying the relationship between the health of mountain glaciers and global environmental change. Digital elevation models (DEMs) can be constructed from a series of images from a range of perspectives collected by staring at a target during a satellite overpass. It is possible to collect imagery for 1800 targets per month in the ×56° latitude range, construct high-resolution DEMs, and monitor changes in high detail over time with a high-resolution optical telescope mounted on the International Space Station (ISS). Snow and ice type, age, and maturity can be inferred from different color bands as well as distribution of liquid water. Texture, roughness, albedo, and debris distribution can be estimated by measuring bidirectional reflectance distribution functions (BRDF) and reflectance intensity as a function of viewing angle. The non-sun-synchronous orbit

  9. Advanced glycation end-products (AGEs): involvement in aging and in neurodegenerative diseases.

    PubMed

    Grillo, M A; Colombatto, S

    2008-06-01

    Advanced glycation end-products (AGEs) are formed from the so-called Amadori products by rearrangement followed by other reactions giving rise to compounds bound irreversibly. The structure of some of them is shown and the mechanism of formation is described. Several AGE binding molecules (Receptors for AGE, RAGE) are known and it is thought that many of the effects caused by AGEs are mediated by RAGE. Some of these were shown to be toxic, and called TAGE. The mechanism of detoxification of glyoxal and methylglyoxal by the glyoxalase system is described and also the possibility to eliminate glycated proteins by deglycation enzymes. Compounds able to inhibit AGEs formation are also taken into consideration.

  10. Neoglaciation, glacier-dammed lakes, and vegetation change in northwestern British Columbia, Canada

    SciTech Connect

    Clague, J.J. |; Mathewes, R.W.

    1996-02-01

    An integrated geomorphic, stratigraphic, paleoecological, and geochronological study of a system of linked valley glaciers and ice-dammed lakes has provided insights into the Neoglacial history and climate of the northern Coast Mountains of British Columbia. Cores collected from a small lake in the glacier foreland of Berendon Glacier and pits dug in a nearby fen record Little Ice Age and earlier Neoglacial advances. AMS and conventional radiocarbon dating of fossil plant material from these sites, supplemented by dendrochronological data, indicate that the Little Ice Age began more than 500 yr ago and peaked in the early 17th century. A middle Neoglacial advance of comparable extent occurred about 2200 to 2800 yr ago. The chronology of Neoglacial advances is generally similar to that at other sites in western Canada, although the Little Ice Age may have peaked as much as 100 yr earlier in our study area than elsewhere. The Little Ice Age advances are also broadly synchronous with those in other parts of the world, suggesting that they were caused by global changes in climate.

  11. 10Be surface exposure dating of rock glaciers in Larstigtal, Tyrol, Austria

    NASA Astrophysics Data System (ADS)

    Ivy-Ochs, S.; Kerschner, H.; Maisch, M.; Christl, M.; Kubik, P. W.; Schluchter, C.

    2009-04-01

    In the context of Lateglacial and Holocene climate change research, rock glaciers (creeping mountain permafrost) also play an important role. They are phenomena of discontinuous alpine permafrost and as such good indicators for the mean annual air temperature for the period they are active. We have 10Be surface exposure dated boulders from two relict rock glaciers in Larstigtal, Austria. This is the type area for a postulated mid-Holocene cold period called the Larstig oscillation. The period of activity was suggested to be of similar age as the mid-Holocene Frosnitz advance of glaciers in the Venediger Mountains farther to the east (Patzelt and Bortenschlager, 1973). For rock glaciers of this size to be active at 2200 m a.s.l. in Larstig valley would have required a significant drop in temperatures, thus a marked mid-Holocene cold pulse, for at least several centuries at around 7.0 ka. In contrast, our exposure dates show that the rock glaciers stabilized during the early Preboreal (Ivy-Ochs et al., submitted). We see no distinct pattern with respect to exposure age and boulder location on the rock glaciers. This implies that for our site the blocks did not acquire inherited 10Be during exposure in the free rock face, in the talus at the base of the slope, or during transport on the rock glaciers. Our data point to final stabilization of the Larstigtal rock glaciers in the earliest Holocene and not in the middle Holocene. Combined with data from other archives (Nicolussi et al., 2005), there appears to have been no time window in the middle Holocene long enough for rock glaciers of the size and at the elevation of the Larstig site to have formed. Ivy-Ochs, S., Kerschner, H., Maisch, M., Christl, M., Kubik, P.W., Schlüchter, C., Latest Pleistocene and Holocene glacier variations in the European Alps. Quaternary Science Reviews (submitted). Nicolussi, K., Kaufmann, M., Patzelt, G., van der Plicht, J., Thurner, A., 2005. Holocene tree-line variability in the Kauner

  12. Soil carbon accretion along an age chronosequence formed by the retreat of the Skaftafellsjökull glacier, SE-Iceland

    NASA Astrophysics Data System (ADS)

    Vilmundardóttir, O. K.; Gísladóttir, G.; Lal, R.

    2015-01-01

    Climate warming has led to glacial retreat worldwide, where surfaces exposed to the atmosphere are subjected to weathering, vegetation colonization and new soil formation. On young soils developing along the recessional path left by the Skaftafellsjökull glacier, SE-Iceland, we investigated the accretion of soil organic carbon (SOC) and nitrogen (N), representing an age chronosequence of 120 years. In total, 54 sampling sites were distributed along three moraines deposited in 1890, 1945, and 2003. For comparison, soil samples were collected from nearby birch woodlands (Betula pubescens Ehrh.), representing soils in a mature ecosystem likely to establish on the moraines in the future. Results show that the average SOC and N concentrations increase with time and at faster rates over the latter part of the chronosequence period investigated (1945-1890). After 120 yrs, the soil contains 1.1 kg C m- 2 in the surface layer (0-10 cm), which is still about one third of the 3.2 kg C m- 2 in soil under the birch woodlands. The N stock estimated at 0.06 kg N m- 2 after 120 yrs is almost one fourth of that under the woodlands. The data suggest that landscape affects vegetation establishment and in turn, both landscape and vegetation affect soil development. Thus, concentrations of SOC, N and noncrystalline oxalate extractable Al and Fe are higher within depressions in the proglacial landscape. The comparison of SOC stock in the moraine soils with that under the birch forest shows that the young proglacial soils still have a large potential to accrete SOC within the developing pedosphere. With the observed accrual rate of 9.1 g C m- 2 yr- 1 in the top at 10 cm, it may take the moraine soils an additional period of 220 yrs to accrue SOC stocks comparable with those under the birch forest. Given the fact that all Icelandic glaciers are receding, assessing SOC accretion in new soil formation may be important to off-setting the greenhouse gas emissions.

  13. An advanced glycation endproduct (AGE)-rich diet promotes accumulation of AGEs in Achilles tendon.

    PubMed

    Skovgaard, Dorthe; Svensson, Rene B; Scheijen, Jean; Eliasson, Pernilla; Mogensen, Pernille; Hag, Anne Mette F; Kjær, Michael; Schalkwijk, Casper G; Schjerling, Peter; Magnusson, Stig P; Couppé, Christian

    2017-03-01

    Advanced Glycation Endproducts (AGEs) accumulate in long-lived tissue proteins like collagen in bone and tendon causing modification of the biomechanical properties. This has been hypothesized to raise the risk of orthopedic injury such as bone fractures and tendon ruptures. We evaluated the relationship between AGE content in the diet and accumulation of AGEs in weight-bearing animal Achilles tendon. Two groups of mice (C57BL/6Ntac) were fed with either high-fat diet low in AGEs high-fat diet (HFD) (n = 14) or normal diet high in AGEs (ND) (n = 11). AGE content in ND was six to 50-fold higher than HFD The mice were sacrificed at week 40 and Achilles and tail tendons were carefully excised to compare weight and nonweight-bearing tendons. The amount of the AGEs carboxymethyllysine (CML), methylglyoxal-derived hydroimidazolone (MG-H1) and carboxyethyllysine (CEL) in Achilles and tail tendon was measured using ultraperformance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) and pentosidine with high-pressure liquid chromatography (HPLC) with fluorescent detection. AGEs in Achilles tendon were higher than in tail tendon for CML (P < 0.0001), CEL (P < 0.0001), MG-H1 and pentosidine (for both ND and HFD) (P < 0.0001). The AGE-rich diet (ND) resulted in an increase in CML (P < 0.0001), MG-H1 (P < 0.001) and pentosidine (P < 0.0001) but not CEL, in Achilles and tail tendon. This is the first study to provide evidence for AGE accumulation in injury-prone, weight-bearing Achilles tendon associated with intake of an AGE-rich diet. This indicates that food-derived AGEs may alter tendon properties and the development of tendon injuries.

  14. Glacier variations in the Northern Caucasus compared to climatic reconstructions over the past millennium

    NASA Astrophysics Data System (ADS)

    Solomina, Olga; Bushueva, Irina; Dolgova, Ekaterina; Jomelli, Vincent; Alexandrin, Mikhail; Mikhalenko, Vladimir; Matskovsky, Vladimir

    2016-05-01

    resolution of the data available and ambiguous interpretation of the evidence. The first LIA maximum glacier extent in the past millennium is poorly constrained. According to our data, it occurred prior to the year 1598 CE (tree-ring-based minimum age). Two other major phases of advances occurred in the second half of the 17th century CE and the first half of 19th century CE. General glacier retreat in the Northern Caucasus started in the late 1840s CE, with four to five minor readvances in the 1860s-1880s CE and three readvances or steady states in the 20th century CE (1910s, 1920s and 1970s-1980s). Since the last LIA maximum in the middle of the 19th century CE, most glaciers have decreased in length by more than 1000 m, and the rise in the elevation of the glacier fronts has exceeded 200 m. The glacier advances correspond to summer temperature minima and are generally coherent with the reconstructed mass balance of the Garabashi Glacier. A comparison of a tree-ring-based summer temperature reconstruction in the Northern Caucasus with detailed reconstructions of summer temperature and glacier fluctuations in the Alps shows a pronounced agreement between the records and supports the similarity between the patterns of climatic and glacier variations in the two regions.

  15. A complex relationship between calving glaciers and climate

    USGS Publications Warehouse

    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.

  16. A complex relationship between calving glaciers and climate

    NASA Astrophysics Data System (ADS)

    Post, Austin; O'Neel, Shad; Motyka, Roman J.; Streveler, Gregory

    2011-09-01

    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 seafloor—also 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.

  17. Definition of advanced age in HIV infection: looking for an age cut-off.

    PubMed

    Blanco, José R; Jarrín, Inmaculada; Vallejo, Manuel; Berenguer, Juan; Solera, Carmen; Rubio, Rafael; Pulido, Federico; Asensi, Victor; del Amo, Julia; Moreno, Santiago

    2012-09-01

    The age of 50 has been considered as a cut-off to discriminate older subjects within HIV-infected people according to the Centers for Disease Control and Prevention (CDC). However, the International AIDS Society (IAS) mentions 60 years of age and the Department of Health and Human Services (DHHS) makes no consideration. We aimed to establish an age cut-off that could differentiate response to highly active antiretroviral therapy (HAART) and, therefore, help to define advanced age in HIV-infected patients. CoRIS is an open, prospective, multicenter cohort of HIV adults naive to HAART at entry (January 2004 to October 2009). Survival, immunological response (IR) (CD4 increase of more than 100 cell/ml), and virological response (VR) (HIV RNA less than 50 copies/ml) were compared among 5-year age intervals at start of HAART using Cox proportional hazards models, stratified by hospital and adjusted for potential confounders. Among 5514 patients, 2726 began HAART. During follow-up, 2164 (79.4%) patients experienced an IR, 1686 (61.8%) a VR, and 54 (1.9%) died. Compared with patients aged <25 years at start of HAART, those aged 50-54, 55-59, 60-64, 65-59, and 70 or older were 32% (aHR: 0.68, 95% CI: 0.52-0.87), 29% (aHR: 0.71, 95% CI: 0.53-0.96), 34% (aHR: 0.66, 95% CI: 0.46-0.95), 39% (aHR: 0.61, 95% CI: 0.37-1.00), and 43% (aHR: 0.57, 95% CI: 0.31-1.04) less likely to experience an IR. The VR was similar across all age groups. Finally, patients aged 50-59 showed a 3-fold increase (aHR: 3.58; 95% CI: 1.07-11.99) in their risk of death compared to those aged <30 years. In HIV infection, patients aged ≥50 years have a poorer immunological response to HAART and a poorer survival. This age could be used to define medically advanced age in HIV-infected people.

  18. Definition of Advanced Age in HIV Infection: Looking for an Age Cut-Off

    PubMed Central

    Jarrín, Inmaculada; Vallejo, Manuel; Berenguer, Juan; Solera, Carmen; Rubio, Rafael; Pulido, Federico; Asensi, Victor; del Amo, Julia; Moreno, Santiago

    2012-01-01

    Abstract The age of 50 has been considered as a cut-off to discriminate older subjects within HIV-infected people according to the Centers for Disease Control and Prevention (CDC). However, the International AIDS Society (IAS) mentions 60 years of age and the Department of Health and Human Services (DHHS) makes no consideration. We aimed to establish an age cut-off that could differentiate response to highly active antiretroviral therapy (HAART) and, therefore, help to define advanced age in HIV-infected patients. CoRIS is an open, prospective, multicenter cohort of HIV adults naive to HAART at entry (January 2004 to October 2009). Survival, immunological response (IR) (CD4 increase of more than 100 cell/ml), and virological response (VR) (HIV RNA less than 50 copies/ml) were compared among 5-year age intervals at start of HAART using Cox proportional hazards models, stratified by hospital and adjusted for potential confounders. Among 5514 patients, 2726 began HAART. During follow-up, 2164 (79.4%) patients experienced an IR, 1686 (61.8%) a VR, and 54 (1.9%) died. Compared with patients aged <25 years at start of HAART, those aged 50–54, 55–59, 60–64, 65–59, and 70 or older were 32% (aHR: 0.68, 95% CI: 0.52–0.87), 29% (aHR: 0.71, 95% CI: 0.53–0.96), 34% (aHR: 0.66, 95% CI: 0.46–0.95), 39% (aHR: 0.61, 95% CI: 0.37–1.00), and 43% (aHR: 0.57, 95% CI: 0.31–1.04) less likely to experience an IR. The VR was similar across all age groups. Finally, patients aged 50–59 showed a 3-fold increase (aHR: 3.58; 95% CI: 1.07–11.99) in their risk of death compared to those aged <30 years. In HIV infection, patients aged ≥50 years have a poorer immunological response to HAART and a poorer survival. This age could be used to define medically advanced age in HIV-infected people. PMID:22607516

  19. Glacier Ecosystems of Himalaya

    NASA Astrophysics Data System (ADS)

    Kohshima, S.; Yoshimura, Y.; Takeuchi, N.; Segawa, T.; Uetake, J.

    2012-12-01

    Biological activity on glaciers has been believed to be extremely limited. However, we found various biotic communities specialized to the glacier environment in various part of the world, such as Himalaya, Patagonia and Alaska. Some of these glacier hosted biotic communities including various cold-tolerant insects, annelids and copepods that were living in the glacier by feeding on algae and bacteria growing in the snow and ice. Thus, the glaciers are simple and relatively closed ecosystems sustained by the primary production in the snow and ice. In this presentation, we will briefly introduce glacier ecosystems in Himalaya; ecology and behavior of glacier animals, altitudinal zonation of snow algal communities, and the structure of their habitats in the glacier. Since the microorganisms growing on the glacier surface are stored in the glacial strata every year, ice-core samples contain many layers with these microorganisms. We showed that the snow algae in the ice-core are useful for ice core dating and could be new environmental signals for the studies on past environment using ice cores. These microorganisms in the ice core will be important especially in the studies of ice core from the glaciers of warmer regions, in which chemical and isotopic contents are often heavily disturbed by melt water percolation. Blooms of algae and bacteria on the glacier can reduce the surface albedo and significantly affect the glacier melting. For example, the surface albedo of some Himalayan glaciers was significantly reduced by a large amount of dark-colored biogenic material (cryoconite) derived from snow algae and bacteria. It increased the melting rates of the surfaces by as much as three-fold. Thus, it was suggested that the microbial activity on the glacier could affect the mass balance and fluctuation of the glaciers.

  20. 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

  1. The complex behavior of the Cordilleran Ice Sheet and mountain glaciers to abrupt climate change during the latest Pleistocene

    NASA Astrophysics Data System (ADS)

    Menounos, Brian; Goehring, Brent; Osborn, Gerald; Clarke, Garry K. C.; Ward, Brent; Margold, Martin; Bond, Jeff; Clague, John J.; Lakeman, Tom; Schaefer, Joerg; Koch, Joe; Gosse, John; Stroeven, Arjen P.; Seguinot, Julien; Heyman, Jakob; Fulton, Robert

    2014-05-01

    Surficial mapping and more than 70 radiometric ages 10Be, 14C] constrain the evolution of the Cordilleran Ice Sheet (CIS) and associated mountain glaciers in western Canada during the latest Pleistocene. Our data suggest that: i) there is widespread evidence for the Younger Dryas (YD) throughout the mountains of western Canada; ii) late Pleistocene climate reconstructions based solely on alpine moraines may be misleading in regions with decaying ice sheets; iii) extensive interfluves in some mountain regions were ice-free between 16 ka and 13 ka (kilo calibrated yrs BP). Initial decay of the CIS from its maximum extent around 16 ka was likely due to a combination of climatic (surface melting) and dynamical factors. Climate amelioration during the Bølling-Allerød Warm Period [14.7-12.9 ka], likely the cause for the major phase of CIS decay, resulted in ice sheet equilibrium line altitudes (ELAs) ranging from 2500 m asl in southern BC to around 2000 m asl along the BC-Yukon border. Hence, before the onset of the Younger Dryas (YD) Cold Period [12.9-11.7 ka], the ice sheet shrank and became a labyrinth of individual and coalescing valley glaciers fed by major accumulation zones centered on the Coast Mountains and other high ranges of NW Canada. The response of remnant ice and cirque glaciers to the YD climate deterioration was highly variable. In some cases, small glaciers (0.5-2 km2) built YD moraines that were only hundreds of meters beyond those constructed during the Little Ice Age (LIA) [0.30-0.15 ka]. Our dating also reveals that much larger glaciers persisted in nearby valleys that lie hundreds of meters below the cirques. Hence, we infer that many cirques were completely deglaciated prior the YD, in contrast to low-lying valleys where ice sheet remnants persisted. Glaciers also advanced in north-central British Columbia during the YD, but here glaciers constructed large terminal and lateral moraines. In the Cassiar and northern Coast mountains, for example

  2. Glacier Contributions to Sea Level Rise

    NASA Astrophysics Data System (ADS)

    Gardner, A. S.; Cogley, J. G.; Moholdt, G.; Wouters, B.; Wiese, D. N.

    2015-12-01

    Global mean sea level is rising in response to two primary factors: warming oceans and diminishing glaciers and ice sheets. If melted completely, glaciers would raise sea levels by half a meter, much less than that the 80 meters or so that would result from total melt of the massive Greenland and Antarctic ice sheets. That is why glacier contributions to sea level rise have been less studied, allowing estimates of to vary widely. Glacier contributions to sea level change are challenging to quantify as they are broadly distributed, located in remote and poorly accessible high latitude and high altitude regions, and ground observations are sparse. Advances in satellite altimetry (ICESat) and gravimetry (GRACE) have helped, but they also have their own challenges and limitations. Here we present an updated (2003-2014) synthesis of multiple techniques adapted for varying regions to show that rates of glacier loss change little between the 2003-2009 and 2003-2014 periods, accounting for roughly one third of global mean sea level rise. Over the next century and beyond glaciers are expected to continue to contribute substantial volumes of water to the world's oceans, motivating continued study of how glaciers respond to climate change that will improve projections of future sea levels.

  3. 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.

  4. Fuzzy Cognitive Maps for Glacier Hazards Assessment: Application to Predicting the Potential for Glacier Lake Outbursts

    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

  5. Advanced maternal age and risk perception: A qualitative study

    PubMed Central

    2012-01-01

    Background Advanced maternal age (AMA) is associated with several adverse pregnancy outcomes, hence these pregnancies are considered to be “high risk.” A review of the empirical literature suggests that it is not clear how women of AMA evaluate their pregnancy risk. This study aimed to address this gap by exploring the risk perception of pregnant women of AMA. Methods A qualitative descriptive study was undertaken to obtain a rich and detailed source of explanatory data regarding perceived pregnancy risk of 15 women of AMA. The sample was recruited from a variety of settings in Winnipeg, Canada. In-depth interviews were conducted with nulliparous women aged 35 years or older, in their third trimester, and with singleton pregnancies. Interviews were recorded and transcribed verbatim, and content analysis was used to identify themes and categories. Results Four main themes emerged: definition of pregnancy risk, factors influencing risk perception, risk alleviation strategies, and risk communication with health professionals. Conclusions Several factors may influence women's perception of pregnancy risk including medical risk, psychological elements, characteristics of the risk, stage of pregnancy, and health care provider’s opinion. Understanding these influential factors may help health professionals who care for pregnant women of AMA to gain insight into their perspectives on pregnancy risk and improve the effectiveness of risk communication strategies with this group. PMID:22988825

  6. How can we utilize livers from advanced aged donors for liver transplantation for hepatitis C?

    PubMed

    Uemura, Tadahiro; Nikkel, Lucas E; Hollenbeak, Christopher S; Ramprasad, Varun; Schaefer, Eric; Kadry, Zakiyah

    2012-06-01

    Advanced age donors have inferior outcomes of liver transplantation for Hepatitis C (HCV). Aged donors grafts may be transplanted into young or low model for end stage liver disease (MELD) patients in order to offset the effect of donor age. However, it is not well understood how to utilize liver grafts from advanced aged donors for HCV patients. Using the UNOS database, we retrospectively studied 7508 HCV patients who underwent primary liver transplantation. Risk factors for graft failure and graft survival using advanced aged grafts (donor age ≥ 60 years) were analyzed by Cox hazards models, donor risk index (DRI) and organ patient index (OPI). Recipient's age did not affect on graft survival regardless of donor age. Advanced aged grafts had significant inferior survival compared to younger aged grafts regardless of MELD score (P < 0.0001). Risk factors of HCV patients receiving advanced aged grafts included donation after cardiac death (DCD, HR: 1.69) and recent hospitalization (HR: 1.43). Advanced aged grafts showed significant difference in graft survival of HCV patients with stratification of DRI and OPI. In conclusion, there was no offsetting effect by use of advanced aged grafts into younger or low MELD patients. Advanced aged grafts, especially DCD, should be judiciously used for HCV patients with low MELD score.

  7. Middle to late Holocene fluctuations of the Vindue glacier, an outlet glacier of the Greenland Ice Sheet, central East Greenland.

    NASA Astrophysics Data System (ADS)

    Levy, L.; Hammer, S. K.; Kelly, M. A.; Lowell, T. V.; Hall, B. L.; Howley, J. A.; Wilcox, P.; Medford, A.

    2014-12-01

    The margins of the Greenland Ice Sheet are currently responding to present-day climate changes. Determining how the ice sheet margins have responded to past climate changes provides a means to understand how they may respond in the future. Here we present a multi-proxy record used to reconstruct the Holocene fluctuations of the Vindue glacier, an ice sheet outlet glacier in eastern Greenland. Lake sediment cores from Qiviut lake (informal name), located ~0.75 km from the present-day Vindue glacier margin contain a sharp transition from medium sand/coarse silt to laminated gyttja just prior to 6,340±130 cal yr BP. We interpret this transition to indicate a time when the Vindue glacier retreated sufficiently to cease glacial sedimentation into the lake basin. Above this contact the core contains laminated gyttja with prominent, ~0.5 cm thick, silt layers. 10Be ages of boulders on bedrock located between Qiviut lake and the present-day ice margin date to 6.81 ± 0.67 ka (n = 3), indicating the time of deglaciation. These ages also agree well with the radiocarbon age of the silt-gyttja transition in Qiviut lake cores. 10Be ages on boulders on bedrock located more proximal to the ice margin (~0.5 km) yield ages of 2.67 ± 0.18 ka (n = 2). These ages indicate either the continued recession of the ice margin during the late Holocene or an advance at this time. Boulders on the historical moraines show that ice retreated from the moraine by AD 1620 ± 20 yrs (n = 2). These results are in contrast with some areas of the western margin of the ice sheet where 10Be ages indicate that the ice sheet was behind its Historical limit from the middle Holocene (~6-7 ka) to Historical time. This may indicate that the eastern margin may have responded to late Holocene cooling more sensitively or that the advance associated with the Historical moraines overran any evidence of late Holocene fluctuations along the western margin of the ice sheet.

  8. Glaciers of Asia

    USGS Publications Warehouse

    Williams, Richard S., Jr.; 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

  9. 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

  10. In Brief: Melting glaciers

    NASA Astrophysics Data System (ADS)

    Showstack, Randy; Tretkoff, Ernie

    2010-12-01

    Glaciers in Patagonia and Alaska have been losing their mass, and for longer than glaciers elsewhere in the world, according to a 7 December report compiled by the United Nations Environment Programme (UNEP). “Climate change is causing significant mass loss of glaciers in high mountains worldwide,” notes the report, which calls for accelerated research, monitoring, and modeling of glaciers and snow and their role in water supplies. The report “also highlights the vulnerability and exposure of people dependent upon [glacier-fed] rivers to floods, droughts and eventually shortages as a result of changes in the melting and freezing cycles linked with climate change and other pollution impacts,” according to UNEP executive director Achim Steiner. For more information, visit http://www.grida.no/publications/high­mountain-glaciers/.

  11. The thermophysics of glaciers

    SciTech Connect

    Zotikov, I.A.

    1986-01-01

    This volume presents the results of experimental and theoretical work on the thermodynamics of ice sheets and glaciers. The author has carried out extensive field work in both the Soviet Union and Antarctica over the last 25 years and has contributed to the understanding of the thermophysics of glaciers. The topics covered in this volume embrace heat flow measurement and temperature distributions in glaciers, the thermal drilling of glaciers, the melting and freezing of ice sheets, and other thermophysical problems. Also included are topics of relevance to glacial engineering.

  12. Contribution of dietary advanced glycation end products (AGE) to circulating AGE: role of dietary fat.

    PubMed

    Davis, Kathleen E; Prasad, Chandan; Vijayagopal, Parakat; Juma, Shanil; Adams-Huet, Beverley; Imrhan, Victorine

    2015-12-14

    The purpose of this pilot study was to determine whether macronutrient content (low-fat v. high-fat diet) influences an indicator of advanced glycation end products (AGE), N(ε) carboxymethyl-lysine (CML), in the context of a 1-d, high-AGE diet. The effect of the diets on inflammatory markers was also assessed. A total of nineteen overweight and obese adults (nine men and ten women) without known disease were recruited to participate in a crossover challenge of a high-fat, high-AGE (HFHA) and low-fat, high-AGE (LFHA) diet. In each phase patients had fasting blood drawn, followed by consumption of a high-fat or low-fat breakfast test meal, then three postprandial blood draws at 1, 2 and 3 h after consuming the test meal. After consuming high-AGE meals for the remainder of the day, participants returned the next day for a follow-up analysis. A different pattern in the 3-h post-meal CML and soluble receptor for AGE response to the two diets was observed (P=0·01 and 0·05, respectively). No change in serum CML was observed following consumption of a LFHA breakfast (535 (25th-75th percentile 451-790) to 495 (25th-75th percentile 391-682) ng/ml; P=0·36), whereas a rise in CML occurred after the HFHA breakfast (463 (25th-75th percentile 428-664) to 578 (25th-75th percentile 474-865) ng/ml; P=0·05). High sensitivity C-reactive protein and high molecular weight adiponectin were not affected by either diet. These findings suggest that dietary CML may not be as important in influencing serum CML as other dietary factors. In addition, acute exposure to dietary CML may not influence inflammation in adults without diabetes or kidney disease. This is contrary to previous findings.

  13. Evaluating the performance of a glacier erosion model applied to Peyto Glacier, Alberta, Canada

    NASA Astrophysics Data System (ADS)

    Vogt, R.; Mlynowski, T. J.; Menounos, B.

    2013-12-01

    during the Little Ice Age. In all of our experiments to date, modelled sediment yield closely follow maximum ice cover. In contrast, sediment yields obtained from the lake indicate that maximum sediment delivery to the lake lagged maximum ice cover and occurred during a period of rapid glacier retreat. We interpret this lag to indicate removal of stored sediments beneath the glacier and subaerial erosion from recently exposed sediments in the glacier forefield rather than an increase in primary erosion of bedrock.

  14. Variability in glacier hazards across the Himalayan range

    NASA Astrophysics Data System (ADS)

    Quincey, D. J.

    2011-12-01

    The dynamic response of Himalayan glaciers to recent (decadal) climatic changes varies across the range, reflecting local precipitation and temperature patterns. Glaciers in the eastern (Nepal) Himalaya are widely in recession, with mass loss dominated by surface lowering rather than terminus retreat. The formation of large glacial lakes, either behind morainic sediments or remnant glacier ice, is an ongoing concern. Topographic and surface velocity data suggest that the largest glacial lakes are situated on stagnant glacier ice, at relatively low-elevation and on glaciers with a large elevation range, reflecting the greater climatic sensitivity of low-elevation termini. In the western (Karakoram) Himalaya, an increasing number of glaciers have been reported to be advancing and thickening. Here, breaching from ice-dammed lakes, formed as glacier tongues advance across trunk valleys, is potentially the most destructive hazard. Surface velocity data reveal ice movement of 'block flow' type that is likely to influence dam formation and breaching, and also reveal local changes in ablation that regulate ice dynamics once a lake has formed. Multi-temporal satellite data show that many of the glaciers historically responsible for ice-dammed lake formation are advancing, and two that are of particular concern, are highlighted.

  15. Reconstructing the behaviour of a major SW Greenland tidewater glacier over the last millennium.

    NASA Astrophysics Data System (ADS)

    Pearce, Danni; Mair, Doug W. F.; Rea, Brice R.; Schofield, J. Ed; Lea, James M.; Kamenos, Nick; Schoenrock, Kate; Stachnik, Lukasz

    2016-04-01

    Greenlandic tidewater glaciers have experienced widespread retreat over the last century. However, information on their dynamics prior to this are poorly constrained due to a lack of observations and paucity, in many cases of mapped or mappable deglacial evidence. Especially lacking is evidence for tidewater glacier advance during the Little Ice Age (LIA). This severely restricts our understanding of the long-term (centennial-millennial timescale) relationships between climate and calving at marine terminating margins in Greenland and elsewhere. Kangiata Nunaata Sermia (KNS) is the most dynamic tidewater glacier in southwest Greenland having retreated >22 km since its LIA-maximum (c. 1761). This project takes advantage of the site's unique combination of terrestrial evidence of glacier change (glacial geomorphology, sedimentology, and Norse archaeology) and novel marine evidence (coralline algae) to reconstruct both its advance and retreat over the last millennium. We present glacial geomorphological mapping, which followed a morphstratigraphic approach, using a combination of aerial photos, a DEM and field mapping. Radiocarbon dating from peat sequences were used to determine the timing and rates of advance of KNS to the LIAmax. This has provided evidence for pre-LIA moraines, deglacial and neoglacial, and rapid changes in meltwater routing that may have contributed to the abandonment of nearby Norse settlements. Isotopic analysis of annually banded coralline algae (Lithothamnion glaciale), collected during summer 2015, will provide proxy evidence for changes in fjord water conditions. This data will contribute towards a millennial timescale record of tidewater glacier dynamics that will help to validate models linking calving to climate.

  16. Aletsch Glacier, Switzerland

    NASA Technical Reports Server (NTRS)

    2002-01-01

    Aletsch Glacier, the largest glacier of Europe, covers more than 120 square kilometers (more than 45 square miles)in southern Switzerland. At its eastern extremity lies a glacierlake, Mdrjelensee (2,350 meters/7,711 feet above sea level). To the west rises Aletschhorn (4,195 meters/13,763 feet), which was first climbed in 1859. The Rhone River flows along the southern flank of the mountains.

    This image was acquired on July 23, 2001 by the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) on NASA's Terra satellite. 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 6 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.

    The broad spectral coverage and high spectral resolution of ASTER will provide scientists in numerous disciplines with critical information for surface mapping, and monitoring dynamic conditions and temporal change. Example applications are: monitoring glacial advances and retreats; monitoring potentially active volcanoes; identifying crop stress; determining cloud morphology and physical properties; wetlands evaluation; thermal pollution monitoring; coral reef degradation; surface temperature mapping of soils and geology; and measuring surface heat balance.

    Dr. Anne Kahle at NASA's Jet Propulsion Laboratory, Pasadena, California, is the U.S. Science team leader; Bjorn Eng of JPL is the project manager. The Terra mission is part of NASA's Earth Science Enterprise, a long-term research and technology program designed to examine Earth's land, oceans, atmosphere, ice and life as

  17. HORSESHOE CURVE IN GLACIER POINT ROAD NEAR GLACIER POINT. HALF ...

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

    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

  18. 2. HORSESHOE CURVE IN GLACIER POINT ROAD NEAR GLACIER POINT. ...

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

    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

  19. Glacier-terminus fluctuations in the Wrangell and Chugach mountains resulting from non-climate controls

    SciTech Connect

    Sturm, M.; Hall, D.K.; Benson, C.S.; Field, W.O.

    1992-03-01

    Non-climatically controlled fluctuations of glacier termini were studied in two regions in Alaska. In the Wrangell Mountains, eight glaciers on Mt. Wrangell, an active volcano, have been monitored over the past 30 years using terrestrial surveys, aerial photogrammetry and digitally registered satellite images. Results, which are consistent between different methods of measurement, indicate that the termini of most glaciers were stationary or had retreated slightly. However, the termini of the 30-km-long Ahtna Glacier and the smaller Center and South MacKeith glaciers began to advance in the early 1960s and have advanced steadily at rates between 5 and 18 m yr-1 since then. These three glaciers flow from the summit caldera of ML Wrangell near the active North Crater, where increased volcanic heating since 1964 has melted over 7 x 107 M3 of ice. The authors suspect that volcanic meltwater has changed the basal conditions for the glaciers, resulting in their advance. In College Fjord, Prince William Sound, the terminus fluctuations of two tidewater glaciers have been monitored since 1931 by terrestrial surveying, photogrammetry, and most recently, from satellite imagery. Harvard Glacier, a 40-kmlong tidewater glacier, has been advancing steadily at nearly 20 m yr-1 since 1931, while the adjacent Yale Glacier has retreated at approximately 50 m yr-1 during the same period, though for short periods, both rates have been much higher.

  20. The Response of Rock Glaciers and Protalus Lobes to Ice and Debris Supply in a Warming World

    NASA Astrophysics Data System (ADS)

    Whalley, B.; Azizi, F.

    2012-12-01

    landforms as the (glacier) ice core melts. This situation can be shown from climatic amelioration since the Little Ice Age. It is also shown that protalus lobe features are rarely found as extant (showing creep) or even fossil (non-moving) forms in locations where there are glaciers or rock glaciers, even on talus in permafrost areas. For the most part, they are independent forms. Permafrost may be a sufficient, but not necessary, component of protalus lobe formation; snow precipitation rather than temperature being the main formative control. Currently active (flowing) protalus lobes occur mainly where there has been, high snow accumulation and burial and protection of snowbanks by copious debris supplies. Finite Element Modeling shows that burial of a substantial snowbank is a feasible model for protalus lobe formation and flow but that interstitial ice-rock admixtures are unlikely to flow at observed velocities. Debris supply as well as ice presence needs to be accounted for in the dynamics of these systems. Global warming will affect rock glaciers and protalus lobes in different ways and it is now possible to remotely monitor these changes. We predict: Protalus lobes: decreasing velocity, no ice exposures seen, active snouts become inactive. Rock glaciers (ice with thick debris cover): slowing as surface lowers, snout still advancing and ice exposures increasingly seen.

  1. Warm Oceans, Fast Glaciers: the connections

    NASA Astrophysics Data System (ADS)

    Truffer, M.; Fahnestock, M. A.; Amundson, J. M.

    2009-12-01

    Over the last decade many outlet glaciers from the Greenland Ice Sheet have accelerated and thinned, and in a number of cases their termini have retreated. There is much in common from glacier to glacier that emerges as these changes are studied, yet the actual physical mechanisms remain unclear. One can show that the spatial patterns and timing of outlet glacier changes around Greenland coincide with changes in sea surface temperature and length of the sea-ice-free season in the surrounding ocean, and that large glacier changes appear to initiate within one to a few years of shifts in these conditions. While ocean warming has a direct impact on rates of melting at the glacier ice/ocean interface, its impact on ice flow is less direct. The spatial and temporal coincidence between changing ocean conditions and speedup is compelling, but the causal link between warmer ocean water and rapid responses from outlet glaciers around Greenland is more complex. Observations of rapid calving retreats, the appearance of calving-related long-period seismicity at some large glaciers undergoing change, and the loss of floating ice tongues all suggest that the direct impact of ocean-driven change is on the stability of the lowest reach of these tidewater outlets. In glaciers with a floating tongue, enhanced basal melt may be destabilizing by thinning the tongue to below its structural integrity; at grounded termini this effect is lacking. However, rapid melt at the near-vertical face can play a significant role for slowly flowing systems. For large grounded glaciers with terminus flow rates of meters per day, the impact of increased melt in summer would seem less important. At such glaciers the link between ocean temperatures, sea ice cover and terminus stability manifests itself by the cessation of calving in fall and winter, which leads to terminus advance and the formation of a floating tongue. The loss of sea ice cover in early spring leads to a disintegration of the seasonal

  2. Monitoring and Modelling Glacier Melt and Runoff on Juncal Norte Glacier, Aconcagua River Basin, Central Chile

    NASA Astrophysics Data System (ADS)

    Pellicciotti, F.; Helbing, J. F.; Araos, J.; Favier, V.; Rivera, A.; Corripio, J.; Sicart, J. M.

    2006-12-01

    Results from a recent glacio-meteorological experiment on the Juncal Norte glacier, in central Chile, are presented. Melt water is a crucial resource in the Central Andes, as it provides drinking water, water for agriculture and for industrial uses. There is also increasing competition for water use and allocation, as water demands from mining and industry are rising. Assessing water availability in this region and its relation with climatic variations is therefore crucial. The Dry Central Andes are characterised by a climatic setting different from that of the Alps and the subtropical Andes of Bolivia and Peru. Summers are very dry and stable, with precipitation close to zero and low relative humidity. Solar radiation is very intense, and plays a key role in the energy balance of snow covers and glaciers. The main aim of this study is to investigate the glacier-climate interaction in this area, with particular attention devoted to advanced modelling techniques for the spatial redistribution of meteorological variables, in order to gain an accurate picture of the ablation processes typical of these latitudes. During the ablation season 2005/2006, an extensive field campaign was conducted on the Juncal Norte glacier, aimed at monitoring the melt and runoff generation processes on this remote glacier in the dry Andes. Melt rates, runoff at the snout, meteorological variables over and near the glacier, GPS data and glacier topography were recorded over the entire ablation season. Using this extensive and accurate data set, the spatial and temporal variability of the meteorological variables that drive the melt process on the glacier is investigated, together with the process of runoff generation. An energy balance model is used to simulate melt across the glacier, and special attention is devoted to the modelling of the solar radiation energy flux. The components of the energy balance are compared with those of Alpine basins. The validity of parameterisations of the

  3. Holocene cirque glacier activity in Rondane, southern Norway

    NASA Astrophysics Data System (ADS)

    Kvisvik, Bjørn Christian; Paasche, Øyvind; Dahl, Svein Olaf

    2015-10-01

    Skriufonnen is a small cirque glacier (0.03 km2) in the continental mountains of Rondane in southern Norway. At present, it is the only glacier in Rondane, and very little is known about Holocene glacier fluctuations in this region. Direct observations of the glacier began in 2002, since which time Skriufonnen has been in a state of strong decline. In order to provide a temporal context, past glacier fluctuations were reconstructed based on a series of short HTH gravity cores (n = 8) and long piston cores (n = 6) retrieved from three downstream lakes of Skriufonnen. The cores were analysed for selected magnetic properties (χbulk, ARM, SIRM, 77 K/293 K), organic content (LOI), and geochemical trace elements. Soil catchment samples (n = 6) were collected along a transect running from the three lakes up to the present glacier terminus. Bulk susceptibility (χbulk) measurements show that the finest fractions systematically return the highest values and that ferromagnetic minerals are depleted with distance to the glacier front. This means that periods dominated by paramagnetic minerals indicate very little or no glacier activity, whereas intervals with more ferromagnetic minerals suggest increased glacier activity. The quantitative core analyses indicate that Skriufonnen existed prior to 10,200 b2k (years before A.D. 2000) and disappeared ~ 10,000 b2k. No glacier activity is recorded from c. 10,000 b2k until the glacier reoccurred at the onset of the local Neoglacial period, c. 4000 b2k. The glacier attained its maximum extent between 3200 and 2400 b2k and during the end of the 'Little Ice Age' (LIA) c. A.D. 1800. Neoglacial fluctuations of Skriufonnen are in line with shifts in local summer temperatures and show a delayed Neoglacial inception compared to western Norway.

  4. Taku Glacier: Proglacial Deformation and Subglacial Erosion

    NASA Astrophysics Data System (ADS)

    Kuriger, E. M.; Motyka, R. J.; Truffer, M.; Bucki, A. K.

    2003-12-01

    Taku Glacier has advanced about 7~km since 1890 and is continuing its advance today. Located in southeastern Alaska, this glacier flows from the Juneau Ice Field down to sea level. In the last several decades the glacier has bulldozed a berm of marine and fluvial sediments from the fjord bottom; this berm now separates the terminus from tidewater. The force of the advancing glacier is causing large-scale deformation within these sediments. In 2001, a series of thrust scarps began to form in front of a 200~m section of the terminus. These scarps were active for several months and produced a series of bulges that grew to be several meters in height above the surrounding sediments. Ground penetrating radar (GPR) was used to image the internal structure of these bulges. A trench dug into one of the proglacial ridges revealed that a >2~m clay/sand layer might have played an important role as a thrust zone during deformation. This layer could also be identified in the GPR returns. Beside these scarp-formed bulges there are numerous indicators of the continued advance. Push moraines along the terminus range in height from 1~m to a towering 10~m. In some areas the advancing ice has dug into the sediments and has lifted the vegetation from below. We also observed up to 1~m thick debris freeze-on layers that, when exposed at the terminus, melt and contribute to the development of some moraines. In addition to these observations we performed a series of radio echo-soundings over a grid that extends about 5~km upglacier. These data are compared with depth measurements made in 1989. Since then the glacier has advanced about 180~m. Within 1~km of the present terminus the glacier has deepened its bed by about 15~m, which indicates an erosion rate of about 1~my-1 in this area. This rate agrees with the one observed over the past 100~years. Entrenchment plays an important role in the glacier's dynamics and needs to be taken into account when measuring volume changes.

  5. Rock glaciers on the run - understanding rock glacier landform evolution and recent changes from numerical flow modeling

    NASA Astrophysics Data System (ADS)

    Müller, Johann; Vieli, Andreas; Gärtner-Roer, Isabelle

    2016-11-01

    Rock glaciers are landforms that form as a result of creeping mountain permafrost which have received considerable attention concerning their dynamical and thermal changes. Observed changes in rock glacier motion on seasonal to decadal timescales have been linked to ground temperature variations and related changes in landform geometries interpreted as signs of degradation due to climate warming. Despite the extensive kinematic and thermal monitoring of these creeping permafrost landforms, our understanding of the controlling factors remains limited and lacks robust quantitative models of rock glacier evolution in relation to their environmental setting. Here, we use a holistic approach to analyze the current and long-term dynamical development of two rock glaciers in the Swiss Alps. Site-specific sedimentation and ice generation rates are linked with an adapted numerical flow model for rock glaciers that couples the process chain from material deposition to rock glacier flow in order to reproduce observed rock glacier geometries and their general dynamics. Modeling experiments exploring the impact of variations in rock glacier temperature and sediment-ice supply show that these forcing processes are not sufficient to explain the currently observed short-term geometrical changes derived from multitemporal digital terrain models at the two different rock glaciers. The modeling also shows that rock glacier thickness is dominantly controlled by slope and rheology while the advance rates are mostly constrained by rates of sediment-ice supply. Furthermore, timescales of dynamical adjustment are found to be strongly linked to creep velocity. Overall, we provide a useful modeling framework for a better understanding of the dynamical response and morphological changes of rock glaciers to changes in external forcing.

  6. Glacier response to North Atlantic climate variability during the Holocene

    NASA Astrophysics Data System (ADS)

    Balascio, N. L.; D'Andrea, W. J.; Bradley, R. S.

    2015-12-01

    Small glaciers and ice caps respond rapidly to climate variations, and records of their past extent provide information on the natural envelope of past climate variability. Millennial-scale trends in Holocene glacier size are well documented and correspond with changes in Northern Hemisphere summer insolation. However, there is only sparse and fragmentary evidence for higher-frequency variations in glacier size because in many Northern Hemisphere regions glacier advances of the past few hundred years were the most extensive and destroyed the geomorphic evidence of ice growth and retreat during the past several thousand years. Thus, most glacier records have been of limited use for investigating centennial-scale climate forcing and feedback mechanisms. Here we report a continuous record of glacier activity for the last 9.5 ka from southeast Greenland derived from high-resolution measurements on a proglacial lake sediment sequence. Physical and geochemical parameters show that the glaciers responded to previously documented Northern Hemisphere climatic excursions, including the "8.2 ka" cooling event, the Holocene Thermal Maximum, Neoglacial cooling, and 20th century warming. In addition, the sediments indicate centennial-scale oscillations in glacier size during the late Holocene. Beginning at 4.1 ka, a series of abrupt glacier advances occurred, each lasting ~100 years and followed by a period of retreat, that were superimposed on a gradual trend toward larger glacier size. Thus, while declining summer insolation caused long-term cooling and glacier expansion during the late Holocene, climate system dynamics resulted in repeated episodes of glacier expansion and retreat on multi-decadal to centennial timescales. These episodes coincided with ice rafting events in the North Atlantic Ocean and periods of regional ice cap expansion, which confirms their regional significance and indicates that considerable glacier activity on these timescales is a normal feature of

  7. Calendar-dated glacier variations in the western European Alps during the Neoglacial: the Mer de Glace record, Mont Blanc massif

    NASA Astrophysics Data System (ADS)

    Le Roy, Melaine; Nicolussi, Kurt; Deline, Philip; Astrade, Laurent; Edouard, Jean-Louis; Miramont, Cécile; Arnaud, Fabien

    2015-01-01

    Holocene glacier records from the western European Alps are still sparse, although a number of sites are well suited to constraining pre- and early- Little Ice Age (LIA) glacier advances. The present study provides the first dendrochronologically-based and calendar-dated Neoglacial glacier chronology for the Mont Blanc massif, French Alps. It is based on the analysis of over 240 glacially buried Pinus cembra subfossil logs and wood remains found either embedded-in-till or as detrital material in the Mer de Glace right lateral moraine. Only a few of the samples were found to be 'formally in situ' but we show that some logs were 'virtually in situ' (not rooted but showing little or no evidence of reworking) and could be used to accurately reconstruct past glacier margin behavior in space and time. Uncertainties regarding the other samples may relate to original growth location and/or to outer wood decay. The resulting dates (followed by a '+') were therefore considered maximum-limiting ages for glacier advances. The main burial events - interpreted as glacier advances - occurred between ca 1655+ and 1544+ BC, between ca 1230+ and 1105+ BC, between ca 1013+ and 962+/937+ BC, at ca 802-777 BC, after 608+ BC, between 312 and 337 AD, between ca 485+ AD and 606+ AD, between 1120 and 1178 AD, between ca 1248 and 1278+/1296 AD, and after 1352+ AD. These advances predate the late LIA maxima known from historical sources. The magnitude of the advances gradually increased to culminate in three near-Neoglacial maxima during the 7th, 12th and 13th centuries AD, followed by a first LIA/Neoglacial maximum in the second half of the 14th century AD. The pattern of Neoglacial events described here is coherent with Central and Eastern Alpine glacier chronologies. This indicates marked synchronicity of late Holocene glacier variability and forcing at a regional scale, although occasional differences could be detected between 'Western' and 'Eastern' records. The Mer de Glace record also

  8. Climate change and glacier retreat from 1955 to 2006 on Cilo Mountains, Southeast Anatolia, Turkey

    NASA Astrophysics Data System (ADS)

    Yeşilyurt, Serdar; Uǧur, Doǧan; Kılar, Hatice

    2013-04-01

    Alpine glaciers are amongst key indicators of global-scale climate changes because of their natural dynamics and quick response to global warming. Although there is vast number of studies on recent glaciers of the world, less attention has been paid to the glaciers of Turkey and the Middle East. In the present study, present glaciers of Cilo Mountains (4135 m) located in Southeast Anatolia, one of the most important recent glacier areas of Turkey, is dealt with within the context of the impacts of climatic changes on glaciers. Based on aerial photographs taken in 1955, 1968 and 1988 together with Quickbird satellite images taken in 2006, four main stages were examined using remote sensing and GIS technologies. The paleo-glacier cover of the Last Glacial age (most likely the Last Glacial Maximum) on the Cilo Range was about 100 km² in area as compared to the actual glaciers found in the three valley system around Uludoruk summit with an area of only 5.6 km². Actual glacier have retreated between 100 and 360 m in the period from 1955 to 2006. According to elevation, thickness-mass characteristics of the glaciers and geomorphic conditions of their cirques, retreat rates were found to be between 2 and 7 m/yr. The ages of young terminal moraines were also calculated on the basis of annual decline rates of these glaciers. Consequently, the oldest moraines should have probably been deposited between 1850 and 1870 matching end of the Little Ice Age. This age is compatible with the glacier retreat of the European Alps. We determined a warming trend both in summer temperatures and annual averages based on data from three meteorological stations located in the vicinity of this mountain area. Keywords: Cilo Mountains, actual glacier, glacier retreat, climate change, Little Ace Age, Turkey

  9. Planetary science: are there active glaciers on Mars?

    PubMed

    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.

  10. Holocene glacier variability and Neoglacial hydroclimate at Ålfotbreen, western Norway

    NASA Astrophysics Data System (ADS)

    Gjerde, Marthe; Bakke, Jostein; Vasskog, Kristian; Nesje, Atle; Hormes, Anne

    2016-02-01

    subsequently absent or very small until a short-lived glacier event is seen in the lake sediments ∼8200 cal yr BP. The ice cap was most likely completely melted until a new glacier event occurred around ∼5300 cal yr BP, coeval with the onset of the Neoglacial at several other glaciers in southwestern Norway. Ålfotbreen was thereafter absent (or very small) until the onset of the Neoglacial period ∼1400 cal yr BP. The 'Little Ice Age' (LIA) ∼650-50 cal yr BP was the largest glacier advance of Ålfotbreen since deglaciation, with a maximum extent at ∼400-200 cal yr BP, when the ELA was lowered approximately 200 m relative to today. The late onset of the Neoglacial at Ålfotbreen is suggested to be a result of its low altitude relative to the regional ELA. A synthesis of Neoglacial ELA fluctuations along the coast of Norway indicates a time-transgressive trend in the maximum extent of the LIA, which apparently seems to have occurred progressively later as we move northwards. We suggest that this trend is likely due to regional winter precipitation differences along the coast of Norway.

  11. The Glaciers of HARMONIE

    NASA Astrophysics Data System (ADS)

    Mottram, Ruth; Gleeson, Emily; Pagh Nielsen, Kristian

    2016-04-01

    Developed by the large ALADIN-HIRLAM consortium, the numerical weather prediction (NWP) model system HARMONIE is run by a large number of national weather services and research institutions in Europe, the Middle East and North Africa for weather forecasting. It is now being adopted for climate research purposes as a limited area model in a form known as HCLIM. It is currently run for a number of domains, mostly in Europe but also including Greenland, at a very high resolution (~2.5 km). HARMONIE is a convection permitting non-hydrostatic model that includes the multi-purpose SURFEX surface model. By improving the characterization of glacier surfaces within SURFEX we show that weather forecast errors over both the Greenland ice sheet and over Icelandic glaciers can be significantly reduced. The improvements also facilitate increasingly accurate ice melt and runoff computations, which are important both for ice surface mass balance estimations and hydropower forecasting. These improvements will also benefit the operational HARMONIE domains that cover the Svalbard archipelago, the Alps and the Scandinavian mountain glaciers. Future uses of HCLIM for these regions, where accurately characterizing glacial terrain will be crucial for climate and glaciological applications, are also expected to benefit from this improvement. Here, we report the first results with a new glacier surface scheme in the HARMONIE model, validated with observations from the PROMICE network of automatic weather stations in Greenland. The scheme upgrades the existing surface energy balance over glaciers by including a new albedo parameterization for bare glacier ice and appropriate coefficients for calculating the turbulent fluxes. In addition the snow scheme from the SURFEX land surface module has been upgraded to allow the retention and refreezing of meltwater in the snowpack. These changes allow us to estimate surface mass balance over glaciers at a range of model resolutions that can take full

  12. Miscarriage at advanced maternal age and the search for meaning.

    PubMed

    Carolan, Marsha; Wright, Rebecca J

    2017-03-01

    Although it has been documented that miscarriage is a common pregnancy outcome and more likely to happen among women aged 35 years and older, there is very little research on the quality of such a lived experience. This study features phenomenological interviews of 10 women aged 35 years and older. Theoretical frameworks of ambiguous loss and feminism guide the design and analysis. The salient themes suggest that women experience miscarriage from a physical, emotional, temporal, and social context that includes intense loss and grief, having a sense of otherness, a continuous search for meaning, and feelings of regret and self-blame.

  13. Transportation and Aging: A Research Agenda for Advancing Safe Mobility

    ERIC Educational Resources Information Center

    Dickerson, Anne E.; Molnar, Lisa J.; Eby, David W.; Adler, Geri; Bedard, Michel; Berg-Weger, Marla; Classen, Sherrilene; Foley, Daniel; Horowitz, Amy; Kerschner, Helen; Page, Oliver; Silverstein, Nina M.; Staplin, Loren; Trujillo, Leonard

    2007-01-01

    Purpose: We review what we currently know about older driver safety and mobility, and we highlight important research needs in a number of key areas that hold promise for achieving the safety and mobility goals for the aging baby boomers and future generations of older drivers. Design and Methods: Through the use of a framework for transportation…

  14. Recommendations for managing cutaneous disorders associated with advancing age

    PubMed Central

    Humbert, Philippe; Dréno, Brigitte; Krutmann, Jean; Luger, Thomas Anton; Triller, Raoul; Meaume, Sylvie; Seité, Sophie

    2016-01-01

    The increasingly aged population worldwide means more people are living with chronic diseases, reduced autonomy, and taking various medications. Health professionals should take these into consideration when managing dermatological problems in elderly patients. Accordingly, current research is investigating the dermatological problems associated with the loss of cutaneous function with age. As cell renewal slows, the physical and chemical barrier function declines, cutaneous permeability increases, and the skin becomes increasingly vulnerable to external factors. In geriatric dermatology, the consequences of cutaneous aging lead to xerosis, skin folding, moisture-associated skin damage, and impaired wound healing. These problems pose significant challenges for both the elderly and their carers. Most often, nurses manage skin care in the elderly. However, until recently, little attention has been paid to developing appropriate, evidence-based, skincare protocols. The objective of this paper is to highlight common clinical problems with aging skin and provide some appropriate advice on cosmetic protocols for managing them. A review of the literature from 2004 to 2014 using PubMed was performed by a working group of six European dermatologists with clinical and research experience in dermatology. Basic topical therapy can restore and protect skin barrier function, which relieves problems associated with xerosis, prevents aggravating moisture-associated skin damage, and enhances quality of life. In conclusion, the authors provide physicians with practical recommendations to assist them in implementing basic skin care for the elderly in an integrated care approach. PMID:26929610

  15. Recent climate trends, Glacier Bay, Alaska

    NASA Astrophysics Data System (ADS)

    Kopczynski, S. E.; Bigl, S. R.; Lawson, D. E.; Finnegan, D. C.

    2003-12-01

    Glaciers and ice caps respond to changes in regional climate at decadal scales and can thus serve as indicators of regional climate change. Many of the tidewater and terrestrial glaciers in Glacier Bay, Alaska have been in a state of rapid retreat since the late 1700s, with highly disparate rates of recession occurring in the western versus eastern arms, yet the combination of environmental and glaciological factors that must exist to catalyze these rapid changes is not clearly understood. The Cold Regions Research and Engineering Laboratory (CRREL) initiated the first systematic analyses of weather and precipitation patterns across Glacier Bay National Park in 2000 by establishing 26 meteorological stations with the long-term objective of better understanding regional and global factors, that control terrestrial and marine physical systems. Initial temperature and precipitation trends show rapid seasonal and annual shifts. This is consistent with apparent paleo-trends in climate and glacier advance and recession over the last 9K years, as well as the historical record that indicate the area is climatically sensitive. Comparisons of summer and winter precipitation totals show a precipitation gradient increasing northward from the lower bay to the head of Muir Inlet (east arm), and decreasing northwestward in the West Arm. Monthly averages of air temperatures span about 3.5 C between the warmest and coldest sites near sea level. Winter temperatures averaged more than 1 C colder in the West Arm than the East. We also found large gradients of increasing rainfall from north to south in the east arm, from north to south in the Western arm. Average temperatures in October decreased westward in the northern half of the Park and were milder at sites within the larger southern Bay. Continuing a long-term climate-monitoring program in Glacier Bay will assist with quantifying climate trends in the context of glacial movement, helping to determine the overall sensitivity of

  16. Detecting glacier-bed overdeepenings for glaciers in the Western Italian Alps using the GlabTop2 model: the test site of the Rutor Glacier, Aosta Valley

    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

  17. Middle-Aged Independent-Living African Americans' Selections for Advance Directives: A Case Study

    ERIC Educational Resources Information Center

    McDaniel, Brenda J.

    2013-01-01

    The purpose of this collective embedded qualitative case study was to examine the perspectives of three middle-aged independent-living African Americans who had participated in the process of advance care planning (ACP) and completed at least two advance directives (ADs), a Durable Power of Attorney for Health Care (DPAHC) and a Living Will (LW).…

  18. Examining a Half Century of Northwestern North American Glacier Behavior

    NASA Astrophysics Data System (ADS)

    Molnia, B. F.; Fahey, M. J.; Friesen, B.; Josberger, E. G.

    2015-12-01

    In 1957, as part of the United States' contribution to the International Geophysical Year (IGY), the American Geographical Society (AGS) initiated a multi-institutional mapping project to produce 1:10,000-scale topographic maps of nine northwestern North American glaciers. The project's goal was to prepare precise maps at large scales of selected small glaciers to form a permanent record of the condition of these glaciers so that at a future date they could be resurveyed and compared. Continued surveys would give the history of wastage and accumulation, and more accurate interpretation of the response of these glaciers to meteorological and other factors. The resulting maps and a descriptive summary brochure were published in 1960 by the American Geographical Society. The USGS Global Fiducials Program (GFP) began to systematically image the same nine glaciers approximately half-century after its IGY mapping. The results of the GFP analyses would permit the types of comparisons that were envisioned by the IGY project. Imagery of each of these nine glaciers has been collected from multiple sources, including Next View licensed commercial imagery, vertical and oblique aerial photography, Landsat, and US National Imagery Systems. Exploitation of the imagery has resulted in the production of new 21st century maps that can be compared and contrasted with the vintage AGS map set. Comparison will permit the calculation of a number of parameters which will provide a direct insight into the changes that northwestern North American glaciers have been experiencing during the past half century. Specifically, these comparisons will permit the calculation of changes in glacier length, area, thickness, and volume; computation of rates of glacier advance and/or retreat, rates of glacier thickening and/or thinning, and rates of volume change; production of digital elevation models (DEMs); and generation of velocity fields from crevasse migration. The subsequent re-mapping and

  19. Advances in Protective Coatings and Their Application to Ageing Aircraft

    DTIC Science & Technology

    2000-04-01

    Materials for the Structure f Aging Aircraft [les Nouveaux Materiaux metalliques pour les structures des aeronefs d’ancienne generation] To order the...corrosion through design, the selection of military and civil aircraft during the last thirty years. Research materials that are resistant to corrosion and...fluid resistance and greater flexibility. New methods of paint stripping and novel processes for the 2.1 Design repair of pre-treatments and metal

  20. Psychometrics in aging and dementia: advances in geropsychological assessments.

    PubMed

    Oswald, W D; Fleischmann, U M

    1985-12-01

    Description, explanation and prediction of changes occurring in old age, which are based on intervention, are outlined as a basic goal in gerontological research. Appropriate psychological assessment techniques are necessary to reach this goal. The Nuremberg Gerontopsychological Inventory (NAI) is introduced as a set of psychological measurements which enable reliable, valid and sensitive evaluation of intervention-induced changes in old age. Four independent assessment levels, i.e. standardized performance tests, observer-ratings, self-ratings and a personality rating are the core components of this inventory. All assessment techniques are adapted for elderly subjects. Standard scores are available for the age range 55-90 years. Interrelations between the applied independent assessment levels are reported and taken to link different aspects of intervention-induced changes. Measuring psychological performance thus gains practical significance, e.g. in terms of activities-of-daily-living. From 14 independent studies the drug sensitivity of the applied measurements is shown. Finally, some recommendations for future psychometrical research are given.

  1. Electrophysiological Advances on Multiple Object Processing in Aging

    PubMed Central

    Mazza, Veronica; Brignani, Debora

    2016-01-01

    EEG research conducted in the past 5 years on multiple object processing has begun to define how the aging brain tracks the numerosity of the objects presented in the visual field for different goals. We review the recent EEG findings in healthy older individuals (age range: 65–75 years approximately) on perceptual, attentional and memory mechanisms-reflected in the N1, N2pc and contralateral delayed activity (CDA) components of the EEG, respectively-during the execution of a variety of cognitive tasks requiring simultaneous processing of multiple elements. The findings point to multiple loci of neural changes in multi-object analysis, and suggest the involvement of early perceptual mechanisms, attentive individuation and working memory (WM) operations in the neural and cognitive modification due to aging. However, the findings do not simply reflect early impairments with a cascade effect over subsequent stages of stimulus processing, but in fact highlight interesting dissociations between the effects occurring at the various stages of stimulus processing. Finally, the results on older adults indicate the occurrence of neural overactivation in association to good levels of performance in easy perceptual contexts, thus providing some hints on the existence of compensatory phenomena that are associated with the functioning of early perceptual mechanisms. PMID:26973520

  2. Categories of manual asymmetry and their variation with advancing age.

    PubMed

    Teixeira, Luis A

    2008-06-01

    Manual asymmetries were analyzed in 18- to 63-year-old right-handers in different motor tasks. This analysis aimed at describing the asymmetry profile for each task and assessing their stability across ages. For this purpose, performance of the right and left hands were analyzed in the following aspects: simple reaction time, rate of sequential finger movements, maximum grip force, accuracy in anticipatory timing, rate of repetitive tapping, and rate of drawing movements. In addition, stability of manual preference across ages was assessed through the Edinburgh inventory (Oldfield, 1971). The results indicated different profiles of manual asymmetry, with identification of three categories across tasks: symmetric performance (asymmetry indices close to zero), inconsistent asymmetry (asymmetry indices variable in magnitude and direction), and consistent asymmetry (asymmetry indices favoring a single hand). The different profiles observed in the young adults were stable across ages with two exceptions: decreased lateral asymmetry for maximum grip force and increased asymmetry for sequential drawing in older individuals. These results indicate that manual asymmetries are task specific. Such task specificity is interpreted to be the result of different sensorimotor requirements imposed by each motor task in association with motor experiences accumulated over the lifetime. Analysis of manual preference showed that strength of preference for the right hand was greater in older individuals.

  3. Advanced glycation end-products (AGEs) and heart failure: pathophysiology and clinical implications.

    PubMed

    Hartog, Jasper W L; Voors, Adriaan A; Bakker, Stephan J L; Smit, Andries J; van Veldhuisen, Dirk J

    2007-12-01

    Advanced glycation end-products (AGEs) are molecules formed during a non-enzymatic reaction between proteins and sugar residues, called the Maillard reaction. AGEs accumulate in the human body with age, and accumulation is accelerated in the presence of diabetes mellitus. In patients with diabetes, AGE accumulation is associated with the development of cardiac dysfunction. Enhanced AGE accumulation is not restricted to patients with diabetes, but can also occur in renal failure, enhanced states of oxidative stress, and by an increased intake of AGEs. Several lines of evidence suggest that AGEs are related to the development and progression of heart failure in non-diabetic patients as well. Preliminary small intervention studies with AGE cross-link breakers in heart failure patients have shown promising results. In this review, the role of AGEs in the development of heart failure and the role of AGE intervention as a possible treatment for heart failure are discussed.

  4. The response of debris-covered glaciers to climate change: A numerical modeling approach

    NASA Astrophysics Data System (ADS)

    Anderson, Leif S.; Anderson, Robert S.

    2016-04-01

    Debris-covered glaciers are common in rapidly-eroding alpine landscapes. When thicker than a few centimeters, surface debris suppresses melt rates. Continuous debris cover can therefore reduce the mass balance gradient in the ablation zone, leading to increases in glacier length. In order to quantify feedbacks in the debris-glacier-climate system, we developed a 2D long-valley numerical glacier model that includes deposition of debris on the glacier surface, and both englacial and supraglacial debris advection. We ran 120 simulations in which a steady state debris-free glacier responds to a step increase of surface debris deposition. Simulated glaciers advance to new steady states in which ice accumulation equals ice ablation, and debris input equals debris loss from the glacier. The debris flux onto the glacier surface, and the details of the relationship between debris thickness and melt rate strongly control glacier length. Debris deposited near the equilibrium-line altitude, where ice discharge is high, results in the greatest glacier extension when other debris-related variables are held constant. Continuous debris cover reduces ice discharge gradients, ice thickness gradients, and velocity gradients relative to debris-free glaciers forced by the same climate. Debris-forced glacier extension decreases the ratio of accumulation zone to total glacier area (AAR). The model reproduces first-order relationships between debris cover, AARs, and glacier surface velocities reported from glaciers in High Asia. We also explore the response of debris-covered glaciers to increases in the equilibrium-line altitude (climate warming). We highlight the conditions required to generate a low surface velocity 'dead' ice terminal reach during a warming climate, and the associated increase of fractional glacier surface debris. We also compare our debris-covered glacier climate response results with data from glaciers in High Asia. Our model provides a quantitative, theoretical

  5. 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.

  6. Advancing the Aging and Technology Agenda in Gerontology

    PubMed Central

    Schulz, Richard; Wahl, Hans-Werner; Matthews, Judith T.; De Vito Dabbs, Annette; Beach, Scott R.; Czaja, Sara J.

    2015-01-01

    Interest in technology for older adults is driven by multiple converging trends: the rapid pace of technological development; the unprecedented growth of the aging population in the United States and worldwide; the increase in the number and survival of persons with disability; the growing and unsustainable costs of caring for the elderly people; and the increasing interest on the part of business, industry, and government agencies in addressing health care needs with technology. These trends have contributed to the strong conviction that technology can play an important role in enhancing quality of life and independence of older individuals with high levels of efficiency, potentially reducing individual and societal costs of caring for the elderly people. The purpose of this “Forum” position article is to integrate what we know about older adults and technology systems in order to provide direction to this vital enterprise. We define what we mean by technology for an aging population, provide a brief history of its development, introduce a taxonomy for characterizing current technology applications to older adults, summarize research in this area, describe existing development and evaluation processes, identify factors important for the acceptance of technology among older individuals, and recommend future directions for research in this area. PMID:25165042

  7. Advancing the Aging and Technology Agenda in Gerontology.

    PubMed

    Schulz, Richard; Wahl, Hans-Werner; Matthews, Judith T; De Vito Dabbs, Annette; Beach, Scott R; Czaja, Sara J

    2015-10-01

    Interest in technology for older adults is driven by multiple converging trends: the rapid pace of technological development; the unprecedented growth of the aging population in the United States and worldwide; the increase in the number and survival of persons with disability; the growing and unsustainable costs of caring for the elderly people; and the increasing interest on the part of business, industry, and government agencies in addressing health care needs with technology. These trends have contributed to the strong conviction that technology can play an important role in enhancing quality of life and independence of older individuals with high levels of efficiency, potentially reducing individual and societal costs of caring for the elderly people. The purpose of this "Forum" position article is to integrate what we know about older adults and technology systems in order to provide direction to this vital enterprise. We define what we mean by technology for an aging population, provide a brief history of its development, introduce a taxonomy for characterizing current technology applications to older adults, summarize research in this area, describe existing development and evaluation processes, identify factors important for the acceptance of technology among older individuals, and recommend future directions for research in this area.

  8. Passive microwave (SSM/I) satellite predictions of valley glacier hydrology, Matanuska Glacier, Alaska

    USGS Publications Warehouse

    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.

  9. Linear and Curvilinear Trajectories of Cortical Loss with Advancing Age and Disease Duration in Parkinson's Disease.

    PubMed

    Claassen, Daniel O; Dobolyi, David G; Isaacs, David A; Roman, Olivia C; Herb, Joshua; Wylie, Scott A; Neimat, Joseph S; Donahue, Manus J; Hedera, Peter; Zald, David H; Landman, Bennett A; Bowman, Aaron B; Dawant, Benoit M; Rane, Swati

    2016-05-01

    Advancing age and disease duration both contribute to cortical thinning in Parkinson's disease (PD), but the pathological interactions between them are poorly described. This study aims to distinguish patterns of cortical decline determined by advancing age and disease duration in PD. A convenience cohort of 177 consecutive PD patients, identified at the Vanderbilt University Movement Disorders Clinic as part of a clinical evaluation for Deep Brain Stimulation (age: M= 62.0, SD 9.3), completed a standardized clinical assessment, along with structural brain Magnetic Resonance Imaging scan. Age and gender matched controls (n=53) were obtained from the Alzheimer Disease Neuroimaging Initiative and Progressive Parkinson's Marker Initiative (age: M= 63.4, SD 12.2). Estimated changes in cortical thickness were modeled with advancing age, disease duration, and their interaction. The best-fitting model, linear or curvilinear (2(nd), or 3(rd) order natural spline), was defined using the minimum Akaike Information Criterion, and illustrated on a 3-dimensional brain. Three curvilinear patterns of cortical thinning were identified: early decline, late decline, and early-stable-late. In contrast to healthy controls, the best-fit model for age related changes in PD is curvilinear (early decline), particularly in frontal and precuneus regions. With advancing disease duration, a curvilinear model depicts accelerating decline in the occipital cortex. A significant interaction between advancing age and disease duration is evident in frontal, motor, and posterior parietal areas. Study results support the hypothesis that advancing age and disease duration differentially affect regional cortical thickness and display regional dependent linear and curvilinear patterns of thinning.

  10. [Cognitive capacity in advanced age: initial results of the Berlin Aging Study].

    PubMed

    Lindenberger, U; Baltes, P B

    1995-01-01

    This study reports data on intellectual functioning in old and very old age from the Berlin Aging Study (N = 516; age range = 70-103 years; mean age = 85 years). A psychometric battery of 14 tests was used to assess five cognitive abilities: reasoning, memory, and perceptual speed from the broad fluid-mechanical as well as knowledge and fluency from the broad crystallized-pragmatic domains. Cognitive abilities had a negative linear relationship with age, with more pronounced age-based reductions in fluid-mechanical than crystallized-pragmatic abilities. At the same time, ability intercorrelations formed a highly positive manifold, and did not follow the fluid-crystallized distinction. Interindividual variability was of about equal magnitude across the entire age range studied. There was, however, no evidence for substantial sex differences. As to origins of individual differences, indicators of sensory and sensorimotor functioning were more powerful predictors of intellectual functioning than cultural-biographical variables, and the two sets of predictors were, consistent with theoretical expectations, differentially related to measures of fluid-mechanical (perceptual speed) and crystallized pragmatic (knowledge) functioning. Results, in general indicative of sizeable and general losses with age, are consistent with the view that aging-induced biological influences are a prominent source of individual differences in intellectual functioning in old and very old age. Longitudinal follow-ups are underway to examine the role of cohort effects, selective mortality, and interindividual differences in change trajectories.

  11. Climate regime of Asian glaciers revealed by GAMDAM glacier inventory

    NASA Astrophysics Data System (ADS)

    Sakai, A.; Nuimura, T.; Fujita, K.; Takenaka, S.; Nagai, H.; Lamsal, D.

    2015-05-01

    Among meteorological elements, precipitation has a large spatial variability and less observation, particularly in high-mountain Asia, although precipitation in mountains is an important parameter for hydrological circulation. We estimated precipitation contributing to glacier mass at the median elevation of glaciers, which is presumed to be at equilibrium-line altitude (ELA) such that mass balance is zero at that elevation, by tuning adjustment parameters of precipitation. We also made comparisons between the median elevation of glaciers, including the effect of drifting snow and avalanche, and eliminated those local effects. Then, we could obtain the median elevation of glaciers depending only on climate to estimate glacier surface precipitation. The calculated precipitation contributing to glacier mass can elucidate that glaciers in arid high-mountain Asia receive less precipitation, while much precipitation makes a greater contribution to glacier mass in the Hindu Kush, the Himalayas, and the Hengduan Shan due to not only direct precipitation amount but also avalanche nourishment. We classified glaciers in high-mountain Asia into summer-accumulation type and winter-accumulation type using the summer-accumulation ratio and confirmed that summer-accumulation-type glaciers have a higher sensitivity than winter-accumulation-type glaciers.

  12. The health of glaciers: Recent changes in glacier regime

    USGS Publications Warehouse

    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.

  13. Timescale dependence of erosion rates, a case of study: Marinelli Glacier, Cordillera Darwin, southern Patagonia

    NASA Astrophysics Data System (ADS)

    Fernandez-Vasquez, R. A.; Anderson, J. B.; Wellner, J. S.

    2009-12-01

    Glaciers play a key role in understanding the coupling between tectonics and climate through a number of processes and temporal/spatial scales, ranging from short-term glacial advances and retreats and millennial-scale glacial cycles, to million year-scale orogenies and global climate changes. In particular, glacier erosion is a first order control on mountain range exhumation and isostatic processes through the evacuation and removal of crustal material from orogens and its subsequent transport to continental margins. Erosion rates and associated sediment yield have been estimated for a number of glaciated basins. With few exceptions, all of these estimations are based on modern observations (last few decades) of sediment fluxes, and may not represent long-term (centennial, millennial or million-year time scales) fluxes. Indeed, recent works indicate that contemporary high sediment yields and erosion rates might be the result of high ice fluxes associated with the retreat of modern glaciers from their last Neoglacial positions (Little Ice Age) and that long-term erosion rates could be derived by extrapolating the relationship between short-term erosion v/s retreat rates to the steady state condition of no retreat. However, there is an almost absolute lack of empirical studies that support this statement. We use time-constrained sediment volumes delivered by calving glaciers into Marinelli Fjord (55S), an outlet glacier of the Cordillera Darwin Ice Cap, Southern Patagonian Andes in Tierra del Fuego Island, to estimate sediment yields and erosion rates at different timescales. Sediment volumes are derived using a dense grid of high- and low-frequency single channel seismic data and swath bathymetry data along with piston and Kasten cores. Our results show dramatic differences in erosion rates over different timescales. The recent decadal erosion rate (= 29.31± 10.84 mm/yr; estimated for the last 45 years) is 5 times greater than the centennial value (= 5

  14. Isotopic composition of ice cores and meltwater from upper fremont glacier and Galena Creek rock glacier, Wyoming

    USGS Publications Warehouse

    DeWayne, Cecil L.; Green, J.R.; Vogt, S.; Michel, R.; Cottrell, G.

    1998-01-01

    early 1960s during peak weapons testing fallout for this isotope was 360 TU. One meltwater sample from the rock glacier was analyzed for 35S with a measured concentration of 5.4??1.0 millibecquerel per liter (mBeq/l). Modern precipitation in the Rocky Mountains contains 35S from 10 to 40 mBeq/L. The ??18O results in meltwater from the Galena Creek rock glacier (-17.40??0.1 to -17.98??0.1 per mil) are similar to results for modern precipitation in the Rocky Mountains. Comparison of these isotopic concentrations from the two glaciers suggest that the meltwater at the Galena Creek site is composed mostly of melted snow and rain that percolates through the rock debris that covers the glacier. Additionally, this water from the rock debris is much younger (less than two years) than the reported age of about 2000 years for the subsurface ice at the mid-glacier coring site. Thus the meltwater from the Galena Creek rock glacier is composed primarily of melted surface snow and rain water rather than melted glacier ice, supporting previous estimates of slow ablation rates beneath the surface debris of the rock glacier.

  15. Advanced glycation end products (AGEs) and its receptors in the pathogenesis of hyperthyroidism.

    PubMed

    Caspar-Bell, Gudrun; Dhar, Indu; Prasad, Kailash

    2016-03-01

    Oxidative stress has been implicated in the pathogenesis of hyperthyroidism and its complications. Interaction of advanced glycation end products (AGEs) with receptor RAGE (receptor for AGEs) generates reactive oxygen species. Soluble receptor for AGEs (sRAGE) competes with RAGE for binding with AGEs and attenuates the generation of ROS. Low levels sRAGE and high levels AGEs would generate more ROS leading to hyperthyroidism and its complications. The objectives are to determine if levels of serum sRAGE are low and the levels of AGEs and AGEs/sRAGE are high in patients with hyperthyroidism. The study subjects comprised of 33 patients with hyperthyroidism and 20 controls. Levels of serum sRAGE were lower, while that of AGEs and AGEs/sRAGE were higher in patients compared to controls, being significant only for sRAGE and AGEs/sRAGE. When the levels of sRAGE, AGEs, and AGEs/sRAGE were assessed for hyperthyroidism associated with different diseases, the levels of sRAGE were lower in Hashimoto disease, and levels of AGEs were higher in patients with Graves' disease compared to control. The levels of AGEs/sRAGE were elevated in an all except patients with Hashimoto disease. The levels of AGEs, sRAGE, or AGEs/RAGE were not correlated with age, weight, and blood pressures except systolic pressure which was inversely correlated with sRAGE. The levels of sRAGE were negatively correlated with AGEs and AGEs/sRAGE. The levels of AGEs/sRAGE were positively correlated with AGEs. In conclusion, low levels of sRAGE, and high levels of AGEs and AGEs/sRAGE are risk biomarkers in the pathogenesis hyperthyroidism and its complications.

  16. Role of advanced glycation end products (AGEs) and receptor for AGEs (RAGE) in vascular damage in diabetes.

    PubMed

    Yamagishi, Sho-ichi

    2011-04-01

    A non-enzymatic reaction between ketones or aldehydes and the amino groups of proteins, lipids and nucleic acids contributes to the aging of macromolecules and to the development and progression of various age-related disorders such as vascular complications of diabetes, Alzheimer's disease, cancer growth and metastasis, insulin resistance and degenerative bone disease. Under hyperglycemic and/or oxidative stress conditions, this process begins with the conversion of reversible Schiff base adducts, and then to more stable, covalently-bound Amadori rearrangement products. Over a course of days to weeks, these early glycation products undergo further reactions and rearrangements to become irreversibly crossed-linked, fluorescent protein derivatives termed advanced glycation end products (AGEs). There is a growing body of evidence that AGE and their receptor RAGE (receptor for AGEs) interaction elicits oxidative stress, inflammatory reactions and thrombosis, thereby being involved in vascular aging and damage. These observations suggest that the AGE-RAGE system is a novel therapeutic target for preventing diabetic vascular complications. In this paper, we review the pathophysiological role of the AGE-RAGE-oxidative stress system and its therapeutic intervention in vascular damage in diabetes. We also discuss here the potential utility of the restriction of food-derived AGEs in diabetic vascular complications.

  17. Reconstruction of glacier fluctuations in the Western Alps since the LGM using OSL surface exposure dating

    NASA Astrophysics Data System (ADS)

    Lehmann, Benjamin; King, Georgina; Valla, Pierre; Herman, Frederic

    2016-04-01

    Providing tight spatial/temporal constraints on late-Pleistocene glacier fluctuations remains an important challenge for understanding glacier response to climate change. In most mountainous settings, paleo-glacier reconstructions are limited because they lack precise temporal constraint, which would enable their use as a paleoclimate proxy. OSL-surface exposure dating has been recently proposed [Sohbati et al., 2011] and offers the potential to improve paleo-glacier reconstruction. Because the OSL signal is sensitive to light, OSL-signal bleaching within a rock sample depends on its exposure time and environmental conditions, and can therefore be used to date the exposure time of glacially-polished bedrock or erratic boulders. However, successful application of this technique first requires calibration and validation. Here, we focus on the Mer de Glace glacier (Mont Blanc massif, France) where the post-LGM glacier dynamics remain poorly constrained with numerous short glacier re-advances occuring during the mid-Pleistocene and Holocene [LeRoy et al., 2015]. First, the different parameters involved in OSL surface exposure dating were calibrated. Vertical transect of polished bedrock surfaces with known exposure ages (from 10 to 165 years) from the Montenvers train station (1913 m a.sl.) to the present-day position of the Mer de Glace (1600 m a.s.l.) was sampled. Secondly, we sampled the Trelaporte transect where exposed bedrock surfaces are of uniform lithology. Here, we will apply similar approach on a much longer timescale, from the Last Glacial Maximum (LGM, ~24 ka, Coutterand et al., 2006) to the present day. OSL data from rock slices show increasing exposure age with elevation which is consitent with glacier thinning since the Little Ice Age. Moreover, our results confirmed the possibility to first calibrate the model parameters on known-age surface and use it to constrain the exposure time for nearby bedrock surfaces. In summary, OSL-surface exposure dating

  18. Area and Elevation Changes of a Debris-Covered Glacier and a Clean-Ice Glacier Between 1952-2013 Using Aerial Images and Structure-from-Motion

    NASA Astrophysics Data System (ADS)

    Lardeux, P.; Glasser, N. F.; Holt, T.; Irvine-Fynn, T. D.; Hubbard, B. P.

    2015-12-01

    Since 1952, the clean-ice Glacier Blanc has retreated twice as fast as the adjacent debris-covered Glacier Noir. Located in the French Alps and separated by only 1 km, both glaciers experience the same climatic conditions, making them ideal to evaluate the impact of debris cover on glacier evolution. We used aerial photographs from 16 acquisitions from 1952 to 2013 to reconstruct and analyze glacier elevation changes using Structure-from-Motion (SfM) techniques. Here, we present the process of developing sub-metric resolution digital elevation models (DEMs) from these aerial photographs. By combining 16 DEMs, we produced a dataset of elevation changes of Glacier Noir and Glacier Blanc, including time-series analysis of lateral and longitudinal profiles, glacier hypsometry and mass balance variation. Our preliminary results indicate that Glacier Noir and Glacier Blanc have both thinned to a similar magnitude, ≤ 20 m, despite a 1 km retreat for Glacier Blanc and only 500 m for Glacier Noir. However, these elevation change reconstructions are hampered by large uncertainties, principally due to the lack of independent camera calibration on the historical imagery. Initial attempts using posteriori correction grids have proven to significantly increase the accuracy of these data. We will present some of the uncertainties and solutions linked to the use of SfM on such a large scale and on such an old dataset. This study demonstrates how SfM can be used to investigate long-term trends in environmental change, allowing glacier monitoring to be up-scaled. It also highlights the need for on-going validation of methods to increase the accuracy and precision of SfM in glaciology. This work is not only advancing our understanding of the role of the debris layer, but will also aid glacial geology more generally with, for example, detailed geomorphological analysis of proglacial terrain and Quaternary sciences with quick and accurate reconstruction of a glacial paleo-environment.

  19. Glacier generated floods

    USGS Publications Warehouse

    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.

  20. Alaska Glaciers and Rivers

    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.

  1. Geomorphic influences of the Little Ice Age glacial advance on selected hillslope systems in Nordfjord, Western Norway (Erdalen and Bødalen valleys)

    NASA Astrophysics Data System (ADS)

    Laute, Katja; Beylich, Achim A.

    2010-05-01

    Hillslopes in glacially formed landscapes are typically characterized by talus cones developed beneath free rock faces. Studying hillslopes as sedimentary source, storage and transfer zones as well as surface processes acting on hillslopes since the end of the deglaciation is of importance in order to gain a better understanding of the complex sedimentary source-to-sink fluxes in cold climate environments. Hillslopes function as a key component within the geomorphic process response system. Large areas of the Norwegian fjord landscapes are covered by hillslopes and are characterized by the influences of the glacial inheritance. This PhD project is part of the NFR funded SedyMONT-Norway project within the ESF TOPO-EUROPE SedyMONT (Timescales of sediment dynamics, climate and topographic change in mountain landscapes) programme. The focus of this study is on geomorphic influences of the Little Ice Age glacial advance on postglacial hillslope systems in four distinct headwater areas of the Erdalen and Bødalen valleys in the Nordfjord valley-fjord system (inner Nordfjord, Western Norway). Both valleys can be described as steep, U-shaped and glacier-fed, subarctic tributary valleys. Approximately 14% of the 49 km2 large headwater areas of Erdalen are occupied by hillslope deposits and 41% by rock surfaces; in Bødalen hillslope deposits occupy 12% and rock surfaces occupy 38% of the 42 km2 large headwater areas. The main aims of this study are (i) to analyze and compare the morphometric characteristics as well as the composition of hillslope systems inside and outside of the Little Ice Age glacial limit, (ii) to detect possible changes within the mass balances of these hillslope systems, (iii) to identify the type and intensity of currently acting hillslope processes as well as (iv) to determine possible sediment sources and delivery pathways within the headwater areas of the catchments. The process-based approach includes orthophoto- and topographical map

  2. Younger Dryas glaciers in the High Atlas, Morocco

    NASA Astrophysics Data System (ADS)

    Hughes, Philip; Fink, David

    2016-04-01

    Twelve cirque glaciers formed during the Younger Dryas on the mountains of Aksoual (3912 m a.s.l.) and Adrar el Hajj (3129 m a.s.l.) in the Marrakesh High Atlas. Moraines in two separate cirques on these mountains have been dated using 10Be and 36Cl exposure dating. In both cirques the age scatter is relatively small (13.8-10.1 ka) and all ages overlap within error with the Younger Dryas (12.9-11.7 ka). The glaciers were small and covered <2 km2 and formed on north-facing slopes. However, the altitudinal range of the glaciers was very large, with equilibrium line altitudes (ELAs) ranging from 2470 and 3560 m. This large range is attributed to local topoclimatic factors with the lowest glacier (confirmed as Younger Dryas in age by 3 exposure ages) occupying a very steep cirque floor where a combination of steep glacier gradient and a large potential avalanche catchment enabled its low-lying position. This indicates that caution should be taken when using single glacier sites for reconstructing regional palaeoclimate, especially those formed in steep catchments that have strong topoclimatic controls. The average ELA of the twelve Younger Dryas glaciers was c. 3109 m a.s.l. (St Dev = 325 m) and this represents an ELA depression of > 1000 m from the modern theoretical regional ELA. Under precipitation values similar to today this would require a mean annual temperature depression of 9°C. Moreover, the glacier-climate modelling indicates that it is very unlikely that climate was drier than today during the Younger Dryas in the Marrakesh High Atlas.

  3. Fast-flowing outlet glaciers on Svalbard ice caps

    SciTech Connect

    Dowdeswell, J.A. ); Collin, R.L. )

    1990-08-01

    Four well-defined outlet glaciers are present on the 2510 km{sup 2} cap of Vestfonna in Nordaustlandet, Svalbard. Airborne radio echo sounding and aerial-photograph and satellite-image analysis methods are used to analyze the morphology and dynamics of the ice cap and its component outlet glaciers. The heavily crevassed outlets form linear depressions in the ice-cap surface and flow an order of magnitude faster than the ridges of uncrevassed ice between them. Ice flow on the ridges is accounted for by internal deformation alone, whereas rates of outlet glacier flow require basal motion. One outlet has recently switched into and out of a faster mode of flow. Rapid terminal advance, a change from longitudinal compression to tension, and thinning in the upper basin indicate surge behavior. Observed outlet glacier discharge is significantly greater than current inputs of mass of the ice cap, indicating that present rates of flow cannot be sustained under the contemporary climate.

  4. Climatic Slow-down of the Pamir-Karakoram-Himalaya Glaciers Over the Last 25 Years

    NASA Astrophysics Data System (ADS)

    Dehecq, A.; Gourmelen, N.; Trouvé, E.

    2015-12-01

    Climate warming over the 20th century has caused drastic changes in mountain glaciers globally, and of the Himalayan glaciers in particular. The stakes are high; glaciers and ice caps are the largest contributor to the increase in the mass of the world's oceans, and the Himalayas play a key role in the hydrology of the region, impacting on the economy, food safety and flood risk. Partial monitoring of the Himalayan glaciers has revealed a contrasted picture; while many of the Himalayan glaciers are retreating, in some cases locally stable or advancing glaciers in this region have also been observed. Several studies based on field measurements or remote sensing have shown a dominant slow-down of mountain glaciers globally in response to these changes. But they are restricted to a few glaciers or small regions and none has analysed the dynamic response of glaciers to climate changes at regional scales. Here we present a region-wide analysis of annual glacier flow velocity covering the Pamir-Karakoram-Himalaya region obtained from the analysis of the entire archive of Landsat data. Over 90% of the ice-covered regions, as defined by the Randolph Glacier Inventory, are measured, with precision on the retrieved velocity of the order of 4 m/yr. The change in velocities over the last 25 years will be analysed with reference to regional glacier mass balance and topographic caracteristics. We show that the first order temporal evolution of glacier flow mirrors the pattern of glacier mass balance. We observe a general decrease of ice velocity in regions of known ice mass loss, and a more complex patterns consisting of mixed acceleration and decrease of ice velocity in regions that are known to be affected by stable mass balance and surge-like behavior.

  5. Climatic Slow-down of the Pamir-Karakoram-Himalaya Glaciers Over the Last 25 Years

    NASA Astrophysics Data System (ADS)

    Dumont, M.; Brun, E.; Picard, G.; Michou, M.; Libois, Q.; Petit, J. R.; Morin, S.; Josse, B.

    2014-12-01

    Climate warming over the 20th century has caused drastic changes in mountain glaciers globally, and of the Himalayan glaciers in particular. The stakes are high; glaciers and ice caps are the largest contributor to the increase in the mass of the world's oceans, and the Himalayas play a key role in the hydrology of the region, impacting on the economy, food safety and flood risk. Partial monitoring of the Himalayan glaciers has revealed a contrasted picture; while many of the Himalayan glaciers are retreating, in some cases locally stable or advancing glaciers in this region have also been observed. Several studies based on field measurements or remote sensing have shown a dominant slow-down of mountain glaciers globally in response to these changes. But they are restricted to a few glaciers or small regions and none has analysed the dynamic response of glaciers to climate changes at regional scales. Here we present a region-wide analysis of annual glacier flow velocity covering the Pamir-Karakoram-Himalaya region obtained from the analysis of the entire archive of Landsat data. Over 90% of the ice-covered regions, as defined by the Randolph Glacier Inventory, are measured, with precision on the retrieved velocity of the order of 4 m/yr. The change in velocities over the last 25 years will be analysed with reference to regional glacier mass balance and topographic caracteristics. We show that the first order temporal evolution of glacier flow mirrors the pattern of glacier mass balance. We observe a general decrease of ice velocity in regions of known ice mass loss, and a more complex patterns consisting of mixed acceleration and decrease of ice velocity in regions that are known to be affected by stable mass balance and surge-like behavior.

  6. The Rocks and Fossils of Glacier National Park: The Story of Their Origin and History

    USGS Publications Warehouse

    Ross, Clyde P.; Rezak, Richard

    1959-01-01

    The story of Glacier National Park begins about 500 million years ago, at a time when there were no mountains in the region - only a vast, exceedingly shallow sea, bordered by desolate plains. The sand, clay, and mud, in part very limy, that were laid down in this sea eventually hardened into the rocks that are now known as the Belt series. These are the principal rocks in the park. Scattered through these rocks are crinkled, limy masses of many forms, the remains of deposits made by colonies of algae. After the Belt series was laid down, successive seas slowly advanced and retreated through long ages across what is now Glacier National Park, burying the Belt rocks under younger ones. After another very long time, a gentle uplift, the forerunner of later events, brought this part of the continent above the reach of sea water for the last time. Much later, some 50 million years ago, the disturbance became far more intense. To climax this upheaval, a mass of rock thousands of feet thick and hundreds of miles long was shoved eastward for 35 miles or more. This tremendous dislocation, well exposed along the eastern boundary of the park, is known as the Lewis overthrust. When the rocks of the region emerged from the sea they began to be attacked by erosion. As successive periods of crustal movement and erosion continued, the younger rocks were slowly stripped off the Belt series and sculpture of the latter by weather and water shaped the early Rocky Mountains. The final episode in the park's geologic past was the ice age, beginning about a million years ago. Repeated advances and retreats of the great glaciers in the high valleys accentuated the mountain terrain and developed the scenic grandeur that is now Glacier National Park. One may say that the park is still in the ice age, for some glaciers still exist. The present report, companion to two more technical reports on the region, informally presents the story of the park's development through past eras for readers

  7. Surging glaciers and glacial floods in the Upper Indus Basin, Pakistan

    NASA Astrophysics Data System (ADS)

    Reynolds, J. M.

    2003-04-01

    A review of glacial hazards in the Upper Indus Basin, Pakistan, has identified 52 catastrophic floods that have occurred between 1826 and 2000 arising from ice dam failures and glacier lake outburst floods (GLOFs). Surging glaciers have formed large ice dams, where the rapid glacier advances have blocked the adjacent river, and have failed subsequently releasing up to 3 km^3 of water in less than 48 hrs with peak discharges in excess of 40,000 m^3/s. Such catastrophic floods have had run-out distances in excess of 1,200 km and have caused major damage downstream and resulted in many hundreds of fatalities. Since 1980, 75% of recorded glacier-derived floods have originated from GLOFs with only few ice dam failures associated with surging glaciers. Glacier surges have occurred in clusters with individual glaciers going through phases of active surging and then quiescent periods in from 30 to over 100 years. Previous reviews of surging glaciers in the Upper Indus Basin have identified 20 glaciers that have demonstrated surge-type behaviour with the bulk of glacier surges apparently occurring prior to 1933. However, recent satellite imagery (Landsat-5 from 1998/99) has shown that there are a further 16 glaciers that have surged within this region, with several surging simultaneously and in recent years. At least one glacier has been identified on satellite imagery as going through a surge from 1998 to June 2001 when the resultant ice dam failed producing a locally devastating flood. The study has also demonstrated that there is no obvious link between what triggers an individual glacier to surge and climate change. Furthermore, within this seismically very active area, there is no evidence that earthquakes have triggered either surges, collapses of ice dams, or failures of other glacial lake dams, over the period 1927--2001 for which records are available. Surge behaviour within composite glaciers results in highly complex structural effects especially where tributary

  8. Mortality Measurement at Advanced Ages: A Study of the Social Security Administration Death Master File.

    PubMed

    Gavrilov, Leonid A; Gavrilova, Natalia S

    2011-01-01

    Accurate estimates of mortality at advanced ages are essential to improving forecasts of mortality and the population size of the oldest old age group. However, estimation of hazard rates at extremely old ages poses serious challenges to researchers: (1) The observed mortality deceleration may be at least partially an artifact of mixing different birth cohorts with different mortality (heterogeneity effect); (2) standard assumptions of hazard rate estimates may be invalid when risk of death is extremely high at old ages and (3) ages of very old people may be exaggerated. One way of obtaining estimates of mortality at extreme ages is to pool together international records of persons surviving to extreme ages with subsequent efforts of strict age validation. This approach helps researchers to resolve the third of the above-mentioned problems but does not resolve the first two problems because of inevitable data heterogeneity when data for people belonging to different birth cohorts and countries are pooled together. In this paper we propose an alternative approach, which gives an opportunity to resolve the first two problems by compiling data for more homogeneous single-year birth cohorts with hazard rates measured at narrow (monthly) age intervals. Possible ways of resolving the third problem of hazard rate estimation are elaborated. This approach is based on data from the Social Security Administration Death Master File (DMF). Some birth cohorts covered by DMF could be studied by the method of extinct generations. Availability of month of birth and month of death information provides a unique opportunity to obtain hazard rate estimates for every month of age. Study of several single-year extinct birth cohorts shows that mortality trajectory at advanced ages follows the Gompertz law up to the ages 102-105 years without a noticeable deceleration. Earlier reports of mortality deceleration (deviation of mortality from the Gompertz law) at ages below 100 appear to be

  9. Mortality Measurement at Advanced Ages: A Study of the Social Security Administration Death Master File

    PubMed Central

    Gavrilov, Leonid A.; Gavrilova, Natalia S.

    2011-01-01

    Accurate estimates of mortality at advanced ages are essential to improving forecasts of mortality and the population size of the oldest old age group. However, estimation of hazard rates at extremely old ages poses serious challenges to researchers: (1) The observed mortality deceleration may be at least partially an artifact of mixing different birth cohorts with different mortality (heterogeneity effect); (2) standard assumptions of hazard rate estimates may be invalid when risk of death is extremely high at old ages and (3) ages of very old people may be exaggerated. One way of obtaining estimates of mortality at extreme ages is to pool together international records of persons surviving to extreme ages with subsequent efforts of strict age validation. This approach helps researchers to resolve the third of the above-mentioned problems but does not resolve the first two problems because of inevitable data heterogeneity when data for people belonging to different birth cohorts and countries are pooled together. In this paper we propose an alternative approach, which gives an opportunity to resolve the first two problems by compiling data for more homogeneous single-year birth cohorts with hazard rates measured at narrow (monthly) age intervals. Possible ways of resolving the third problem of hazard rate estimation are elaborated. This approach is based on data from the Social Security Administration Death Master File (DMF). Some birth cohorts covered by DMF could be studied by the method of extinct generations. Availability of month of birth and month of death information provides a unique opportunity to obtain hazard rate estimates for every month of age. Study of several single-year extinct birth cohorts shows that mortality trajectory at advanced ages follows the Gompertz law up to the ages 102–105 years without a noticeable deceleration. Earlier reports of mortality deceleration (deviation of mortality from the Gompertz law) at ages below 100 appear to be

  10. Geographic Names of Iceland's Glaciers: Historic and Modern

    USGS Publications Warehouse

    Sigurdsson, 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

  11. Advanced glycation end-products: Mechanics of aged collagen from molecule to tissue.

    PubMed

    Gautieri, Alfonso; Passini, Fabian S; Silván, Unai; Guizar-Sicairos, Manuel; Carimati, Giulia; Volpi, Piero; Moretti, Matteo; Schoenhuber, Herbert; Redaelli, Alberto; Berli, Martin; Snedeker, Jess G

    2017-05-01

    Concurrent with a progressive loss of regenerative capacity, connective tissue aging is characterized by a progressive accumulation of Advanced Glycation End-products (AGEs). Besides being part of the typical aging process, type II diabetics are particularly affected by AGE accumulation due to abnormally high levels of systemic glucose that increases the glycation rate of long-lived proteins such as collagen. Although AGEs are associated with a wide range of clinical disorders, the mechanisms by which AGEs contribute to connective tissue disease in aging and diabetes are still poorly understood. The present study harnesses advanced multiscale imaging techniques to characterize a widely employed in vitro model of ribose induced collagen aging and further benchmarks these data against experiments on native human tissues from donors of different age. These efforts yield unprecedented insight into the mechanical changes in collagen tissues across hierarchical scales from molecular, to fiber, to tissue-levels. We observed a linear increase in molecular spacing (from 1.45nm to 1.5nm) and a decrease in the D-period length (from 67.5nm to 67.1nm) in aged tissues, both using the ribose model of in vitro glycation and in native human probes. Multiscale mechanical analysis of in vitro glycated tendons strongly suggests that AGEs reduce tissue viscoelasticity by severely limiting fiber-fiber and fibril-fibril sliding. This study lays an important foundation for interpreting the functional and biological effects of AGEs in collagen connective tissues, by exploiting experimental models of AGEs crosslinking and benchmarking them for the first time against endogenous AGEs in native tissue.

  12. Pine Island Glacier, Antarctica

    NASA Technical Reports Server (NTRS)

    2001-01-01

    This pair of MISR images of the Pine Island Glacier in western Antarctica was acquired on December 12, 2000 during Terra orbit 5246. At left is a conventional, true-color image from the downward-looking (nadir) camera. The false-color image at right is a composite of red band data taken by the MISR forward 60-degree, nadir, and aftward 60-degree cameras, displayed in red, green, and blue colors, respectively. Color variations in the left (true-color) image highlight spectral differences. In the multi-angle composite, on the other hand, color variations act as a proxy for differences in the angular reflectance properties of the scene. In this representation, clouds show up as light purple. Blue to orange gradations on the surface indicate a transition in ice texture from smooth to rough. For example, the bright orange 'carrot-like' features are rough crevasses on the glacier's tongue. In the conventional nadir view, the blue ice labeled 'rough crevasses' and 'smooth blue ice' exhibit similar coloration, but the multi-angle composite reveals their different textures, with the smoother ice appearing dark purple instead of orange. This could be an indicator of different mechanisms by which this ice is exposed. The multi-angle view also reveals subtle roughness variations on the frozen sea ice between the glacier and the open water in Pine Island Bay.

    To the left of the 'icebergs' label are chunks of floating ice. Additionally, smaller icebergs embedded in the frozen sea ice are visible below and to the right of the label. These small icebergs are associated with dark streaks. Analysis of the illumination geometry suggests that these streaks are surface features, not shadows. Wind-driven motion and thinning of the sea ice in the vicinity of the icebergs is one possible explanation.

    Recently, Robert Bindschadler, a glaciologist at the NASA Goddard Space Flight Center discovered in Landsat 7 imagery a newly-formed crack traversing the Pine Island Glacier. This crack

  13. Advancing age increases sperm chromatin damage and impairs fertility in peroxiredoxin 6 null mice

    PubMed Central

    Ozkosem, Burak; Feinstein, Sheldon I.; Fisher, Aron B.; O’Flaherty, Cristian

    2015-01-01

    Due to socioeconomic factors, more couples are choosing to delay conception than ever. Increasing average maternal and paternal age in developed countries over the past 40 years has raised the question of how aging affects reproductive success of males and females. Since oxidative stress in the male reproductive tract increases with age, we investigated the impact of advanced paternal age on the integrity of sperm nucleus and reproductive success of males by using a Prdx6−/− mouse model. We compared sperm motility, cytoplasmic droplet retention sperm chromatin quality and reproductive outcomes of young (2-month-old), adult (8-month-old), and old (20-month-old) Prdx6−/− males with their age-matched wild type (WT) controls. Absence of PRDX6 caused age-dependent impairment of sperm motility and sperm maturation and increased sperm DNA fragmentation and oxidation as well as decreased sperm DNA compaction and protamination. Litter size, total number of litters and total number of pups per male were significantly lower in Prdx6−/− males compared to WT controls. These abnormal reproductive outcomes were severely affected by age in Prdx6−/− males. In conclusion, the advanced paternal age affects sperm chromatin integrity and fertility more severely in the absence of PRDX6, suggesting a protective role of PRDX6 in age-associated decline in the sperm quality and fertility in mice. PMID:25796034

  14. Advancing Age, Advantaged Youth: Parental Age and the Transmission of Resources to Children

    ERIC Educational Resources Information Center

    Powell, Brian; Steelman, Lala Carr; Carini, Robert M.

    2006-01-01

    Using data from the National Education Longitudinal Study of 1988, we identify parental age as influential in the parental provision of economic resources, social capital and cultural capital to adolescents, as well as in parental educational expectations for their children. At the bivariate level, the relationship is curvilinear, suggesting that…

  15. Retreating glacier fronts on the Antarctic Peninsula over the past half-century

    USGS Publications Warehouse

    Cook, A.J.; Fox, A.J.; Vaughan, D.G.; Ferrigno, J.G.

    2005-01-01

    The continued retreat of ice shelves on the Antarctic Peninsula has been widely attributed to recent atmospheric warming, but there is little published work describing changes in glacier margin positions. We present trends in 244 marine glacier fronts on the peninsula and associated islands over the past 61 years. Of these glaciers, 87% have retreated and a clear boundary between mean advance and retreat has migrated progressively southward. The pattern is broadly compatible with retreat driven by atmospheric warming, but the rapidity of the migration suggests that this may not be the sole driver of glacier retreat in this region.

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

    NASA Astrophysics Data System (ADS)

    Motyka, R. J.; Truffer, M.

    2011-12-01

    Meltwater from Alaska's coastal glaciers and icefields accounts for nearly half of the total freshwater discharged into the Gulf of Alaska (GOA), with 10% coming from glacier volume loss associated with rapid thinning and retreat of glaciers (Neal et al, 2010). This glacier freshwater discharge contributes to maintaining the Alaska Coastal Current (ACC), which eventually reaches the Arctic Ocean (Royer and Grosch, 2006), thereby linking changes of glaciers along the coast of Alaska to the whole Arctic system. Water column temperatures on the shelf of northern GOA, monitored at buoy GAK1 near Seward, have increased by about 1 deg C since 1970 throughout the 250 m depth and vertical density stratification has also increased. Roughly half of the glacier contribution to ACC is derived from the ~ 50 tidewater glaciers (TWG) that drain from Alaska's coastal mountains into the Gulf of Alaska (GOA). Fjord systems link these TWGs to the GOA, with fjord circulation patterns driven in part by buoyancy-driven convection of subglacial freshwater discharge at the head of the fjord. Neoglacial shallow sills (< 50 m deep) modulate the influx of warm ocean waters (up to 10 deg C) into these fjords. Convection of these warm waters melts icebergs and submerged faces of TWGs. The study of interactions between glaciers, fjords, and the ocean in coastal Alaska has had a long but very sporadic history. We examine this record starting with the "TWG cycle" hypothesis. We next examine recent hydrographic data from several different TWG fjords, representative of advancing and retreating TWGs (Columbia, Yahtse, Hubbard, and LeConte Glaciers), evaluate similarities and differences, and estimate the relative contributions of submarine glacier melting and subglacial discharge to fjord circulation. Circulation of warm ocean waters in fjords has also been hypothesized to play an important role in destabilizing and modulating glacier discharge from outlet glaciers in Greenland. We therefore compare

  17. Seasonal and short term fluctuations of iceberg flux from Hans Glacier Spitsbergen

    NASA Astrophysics Data System (ADS)

    Jania, Jacek; Blaszczyk, Malgorzata; Cieply, Michal; Grabiec, Mariusz; Budzik, Tomasz; Ignatiuk, Dariusz; Uszczyk, Aleksander; Tymrowska, Patrycja; Majchrowska, Elzbieta; Prominska, Agnieszka; Walczowski, Waldemar; Pastusiak, Tadeusz; Petlicki, Michal; Puczko, Dariusz

    2016-04-01

    Glacier iceberg flux due to calving might be an important source of freshwater deliver to Arctic fjords. Mass loss due to calving gives also significant contribution of glacier mass budget. Seasonal changes of dynamics of tidewater glaciers is generally known. After advance of glacier front during winter, summer recession occurs thanks to higher calving in the warmer period of the year. Nevertheless, annual course of iceberg flux intensity is not calculated frequently. Observations and survey of glacier dynamics were conducted on Hans Glacier a polythermal glacier ending down into Hornsund Fiord in Southern Spitsbergen. They provide information for discernment of seasonal calving intensity and iceberg supply to the fiord as a source of freshwater seasonally and in shorter periods of time. Source data on glacier front geometry, bathymetry of the fore bay, seasonal fluctuation of ice-cliff position and glacier velocity were obtained by different field survey and remote sensing methods. Time lapse photos, repeated terrestrial laser scanning and measurements of sea water temperature, salinity and dynamics as well, together with record from meteorological stations were used to determine factors of calving intensity. Calving flux from the glacier to Hornsund Fjord was calculated for short-period events and selected summer seasons between 2007 and 2015. Interannual differences in calving flux were also estimated. Ratios of meltwater to iceberg freshwater supply to the fiord was preliminarily estimated as well.

  18. The Lateglacial to Holocene transition as recorded by glacier fluctuations

    NASA Astrophysics Data System (ADS)

    Schindelwig, I.; Akçar, N.; Kubik, P. W.; Schlüchter, C.

    2009-04-01

    Examination of glacier associated records may contribute to a better understanding of the ice-continent-ocean-atmosphere interactions, since glacial deposits related to short-term temperature fluctuations, driven by climate change, might be preserved. Surface exposure dating (SED) of such glacial deposits can improve the chronology of climate records. The western Swiss Alps repeatedly hosted mountain glaciers during the Pleistocene, and even during the Last Glacial-Interglacial transition, with abundant stadial and interstadial transitions during the Lateglacial (e.g. Björck et al. 1998). In this study, the adjacent valleys of Belalp and Great Aletsch (catchment area is generally south facing) in the western Swiss Alps are investigated. The slow responding Great Aletsch valley glacier shows only one confirmed moraine ridge related to the Lateglacial (Egesen stadial) (Kelly et al. 2004). However, the rather fast responding Unnerbäch cirque (recent) glacier at the Belalp (a similarly exposed - and tributary - valley to the Great Aletsch valley), features 6 individual lateral-terminal moraine ridges related to Lateglacial and early Holocene times. In the Belalp valley, 22 erratic boulders from four out of six well-preserved moraines were sampled in order to establish a detailed chronological framework. From the Great Aletsch valley four samples (boulder and ice moulded bedrock) of the lateral moraine were collected for SED. Our 10Be exposure dates suggest a stabilization of the Great Aletsch moraine related to the Egesen advance in the beginning of the Younger Dryas, assuming that the ages of the oldest erratic boulders on a single moraine ridge are representative for the time of moraine stabilization (Putkonen & Swanson, 2003). According to our investigations on the right-lateral moraine and the dataset (recalculated from Kelly et al. 2004) for the left-lateral moraine, the Egesen stadial is the first preserved re-advance after the last deglaciation. In contrast

  19. Advancing Age and 30-Day Adverse Outcomes Following Non-Emergent General Surgical Operations

    PubMed Central

    Gajdos, Csaba; Kile, Deidre; Hawn, Mary T.; Finlayson, Emily; Henderson, William G.; Robinson, Thomas N.

    2014-01-01

    Background While some single center studies have demonstrated that major surgical operations are safe to perform in older adults, most multicenter database studies find advancing age to independently predict adverse postoperative outcomes. We hypothesized that thirty-day postoperative mortality, complications, failure to rescue rates and postoperative length of stay will increase with advancing age. Design Retrospective cohort study. Setting Hospitals participating in the American College of Surgeons National Surgical Quality Improvement Program (ACS-NSQIP) Participants Patients undergoing non-emergent major general surgical operations between 2005 and 2008 were studied. Measures Postoperative outcomes of interest were complications occurring within 30 days of the index operation, return to OR within 30 days, failure to rescue after a postoperative complication, post-surgical length of stay and 30 day mortality. Results A total of 165,600 patients were studied. The rates of postoperative mortality, overall morbidity, and each type of postoperative complication increased as age increased. The rates of failure to rescue after each type of postoperative complication also increased with age. Mortality rates in patients ≥80 following renal insufficiency (43.3%), stroke (36.5%), myocardial infarction (35.6%), and pulmonary complications (25-39%) were particularly high. Median postoperative length of stay increased with age following surgical site infection, UTI, pneumonia, return to OR, and overall morbidity, but not after venous thromboembolism, stroke, myocardial infarction, renal insufficiency, failure to wean from the ventilator or reintubations. Conclusion Thirty-day mortality, complications and failure to rescue rates increase with advancing age following non-emergent general surgical operations. Patients over 80 years of age have especially high mortality following renal, cardiovascular, and pulmonary complications. As patient age advances, surgeons need to be

  20. Optical Remote Sensing of Glacier Characteristics: A Review with Focus on the Himalaya

    PubMed Central

    Racoviteanu, Adina E.; Williams, Mark W.; Barry, Roger G.

    2008-01-01

    The increased availability of remote sensing platforms with appropriate spatial and temporal resolution, global coverage and low financial costs allows for fast, semi-automated, and cost-effective estimates of changes in glacier parameters over large areas. Remote sensing approaches allow for regular monitoring of the properties of alpine glaciers such as ice extent, terminus position, volume and surface elevation, from which glacier mass balance can be inferred. Such methods are particularly useful in remote areas with limited field-based glaciological measurements. This paper reviews advances in the use of visible and infrared remote sensing combined with field methods for estimating glacier parameters, with emphasis on volume/area changes and glacier mass balance. The focus is on the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) sensor and its applicability for monitoring Himalayan glaciers. The methods reviewed are: volumetric changes inferred from digital elevation models (DEMs), glacier delineation algorithms from multi-spectral analysis, changes in glacier area at decadal time scales, and AAR/ELA methods used to calculate yearly mass balances. The current limitations and on-going challenges in using remote sensing for mapping characteristics of mountain glaciers also discussed, specifically in the context of the Himalaya. PMID:27879883

  1. Mindful Sustainable Aging: Advancing a Comprehensive Approach to the Challenges and Opportunities of Old Age

    PubMed Central

    Nilsson, Håkan; Bülow, Pia H.; Kazemi, Ali

    2015-01-01

    The primary aim of this article is to present a new concept called mindful sustainable aging (MSA), which is informed by mindfulness practices that support the physical, the mental, and especially, the social and the existential dimensions of old life. The concept of MSA is discussed and compared with four influential psychosocial theories in the field of gerontology, i.e., activity theory, disengagement theory, successful aging theory and gerotranscendence theory. The article ends with reviewing research on how mindfulness practice can help to manage, diminish and/or improve a number of serious physical conditions that are common among older people. The potential of mindfulness when it comes to facilitating for older adults in their quest for spiritual and existential meaning is discussed extensively throughout the article. PMID:27247673

  2. Mindful Sustainable Aging: Advancing a Comprehensive Approach to the Challenges and Opportunities of Old Age.

    PubMed

    Nilsson, Håkan; Bülow, Pia H; Kazemi, Ali

    2015-08-01

    The primary aim of this article is to present a new concept called mindful sustainable aging (MSA), which is informed by mindfulness practices that support the physical, the mental, and especially, the social and the existential dimensions of old life. The concept of MSA is discussed and compared with four influential psychosocial theories in the field of gerontology, i.e., activity theory, disengagement theory, successful aging theory and gerotranscendence theory. The article ends with reviewing research on how mindfulness practice can help to manage, diminish and/or improve a number of serious physical conditions that are common among older people. The potential of mindfulness when it comes to facilitating for older adults in their quest for spiritual and existential meaning is discussed extensively throughout the article.

  3. Comparison of multiple glacier inventories with a new inventory derived from high-resolution ALOS imagery in the Bhutan Himalaya

    NASA Astrophysics Data System (ADS)

    Nagai, H.; Fujita, K.; Sakai, A.; Nuimura, T.; Tadono, T.

    2016-01-01

    Digital glacier inventories are invaluable data sets for revealing the characteristics of glacier distribution and for upscaling measurements from selected locations to entire mountain ranges. Here, we present a new inventory of Advanced Land Observing Satellite (ALOS) imagery and compare it with existing inventories for the Bhutan Himalaya. The new inventory contains 1583 glaciers (1487 ± 235 km2), thereof 219 debris-covered glaciers (951 ± 193 km2) and 1364 debris-free glaciers (536 ± 42 km2). Moreover, we propose an index for quantifying consistency between two glacier outlines. Comparison of the overlap ratio demonstrates that the ALOS-derived glacier inventory contains delineation uncertainties of 10-20 % which depend on glacier size, that the shapes and geographical locations of glacier outlines derived from the fourth version of the Randolph Glacier Inventory have been improved in the fifth version, and that the latter is consistent with other inventories. In terms of whole glacier distribution, each data set is dominated by glaciers of 1.0-5.0 km2 area (31-34 % of the total area), situated at approximately 5400 m elevation (nearly 10 % in 100 m bin) with either north or south aspects (22 and 15 %). However, individual glacier outlines and their area exhibit clear differences among inventories. Furthermore, consistent separation of glaciers with inconspicuous termini remains difficult, which, in some cases, results in different values for glacier number. High-resolution imagery from Google Earth can be used to improve the interpretation of glacier outlines, particularly for debris-covered areas and steep adjacent slopes.

  4. Advanced glycoxidation and lipoxidation end products (AGEs and ALEs): an overview of their mechanisms of formation.

    PubMed

    Vistoli, G; De Maddis, D; Cipak, A; Zarkovic, N; Carini, M; Aldini, G

    2013-08-01

    Advanced lipoxidation end products (ALEs) and advanced glycation end products (AGEs) have a pathogenetic role in the development and progression of different oxidative-based diseases including diabetes, atherosclerosis, and neurological disorders. AGEs and ALEs represent a quite complex class of compounds that are formed by different mechanisms, by heterogeneous precursors and that can be formed either exogenously or endogenously. There is a wide interest in AGEs and ALEs involving different aspects of research which are essentially focused on set-up and application of analytical strategies (1) to identify, characterize, and quantify AGEs and ALEs in different pathophysiological conditions; (2) to elucidate the molecular basis of their biological effects; and (3) to discover compounds able to inhibit AGEs/ALEs damaging effects not only as biological tools aimed at validating AGEs/ALEs as drug target, but also as promising drugs. All the above-mentioned research stages require a clear picture of the chemical formation of AGEs/ALEs but this is not simple, due to the complex and heterogeneous pathways, involving different precursors and mechanisms. In view of this intricate scenario, the aim of the present review is to group the main AGEs and ALEs and to describe, for each of them, the precursors and mechanisms of formation.

  5. Glaciers of Antarctica

    USGS Publications Warehouse

    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

  6. Glacier volume and area change by 2050 in high mountain Asia

    NASA Astrophysics Data System (ADS)

    Zhao, Liyun; Ding, Ran; Moore, John C.

    2014-11-01

    We estimate individual area and volume change by 2050 of all 67,028 glaciers, with a total area of 122,969 km2, delineated in the Randolph Glacier Inventory 2.0 of high mountain Asia (HMA). We used the 25 km resolution regional climate model RegCM 3.0 temperature and precipitation change projections forced by the IPCC A1B scenario. Glacier simulations were based on a novel surface mass balance-altitude parameterization fitted to observational data, and various volume-area scaling approaches using Shuttle Radar Topography Mission surface topography of each individual glacier. We generate mass balance-altitude relations for all the glaciers by region using nearest available glacier measurements. Equilibrium line altitude (ELA) sensitivities to temperature and precipitation change vary by region based on the relative importance of sublimation and melting processes. We also made simulations with mass balance tuned to match satellite observations of glacier thickness changes in HMA from 2003 to 2009. Net mass loss is half as much using the tuned model than using just glaciological calibration data, suggesting the representativity of benchmark glaciers is a larger source of uncertainty in future HMA contributions to sea level rise than errors in glacier inventories or volume-area scaling. Both models predict that about 35% of the glaciers in Karakoram and the northwestern Himalaya are advancing, which is consistent with the observed slight mass gain of glaciers in these regions in recent years. However, we find that 76% of all the glaciers will retreat, most of which are of the maritime type. We project total glacier area loss in high mountain Asia in 2050 to be 22% (in the tuned model) or 35% (un-tuned) of their extent in 2000, and they will contribute 5 mm (tuned model) to global sea level rise.

  7. Austrian glaciers in historical documents of the last 400 years: implications for historical hydrology

    NASA Astrophysics Data System (ADS)

    Fischer, Andrea; Seiser, Bernd

    2014-05-01

    First documentations of Austrian glaciers date from as early as 1601. Early documentations were triggered by glacier advances that created glacier-dammed lakes that caused floods whenever the dam collapsed . Since then, Austrian glaciers have been documented in drawings, descriptions and later on in maps and photography. These data are stored in historical archives but today only partly exploited for historical glaciology. They are of special interest for historical hydrology in glacier-covered basins, as the extent of the snow, firn and ice cover and its elevation affect the hydrological response of the basin to precipitation events in several ways: - Firn cover: the more area is covered by firn, the higher is the capacity for retention or even refreezing of liquid precipitation and melt water. - Ice cover: the area covered by glaciers can be affected by melt and contributes to a peak discharge on summer afternoons. - Surface elevation and temperatures: in case of precipitation events, the lower surface temperatures and higher surface elevation of the glaciers compared to ice-free ground have some impact on the capacity to store precipitation. - Glacier floods: for the LIA maximum around 1850, a number of advancing glaciers dammed lakes which emptied during floods. These parameters show different variability with time: glacier area varies only by about 60% to 70% between the LIA maximum and today. The variability of the maximum meltwater peak changes much more than the area. Even during the LIA maximum, several years were extremely warm, so that more than twice the size of today's glacier area was subject to glacier melt. The minimum elevations of large glaciers were several hundred meters lower than today, so that in terms of today's summer mean temperatures, the melt water production from ice ablation would have been much higher than today. A comparison of historical glacier images and description with today's makes it clear that the extent of the snow cover and

  8. Glacier changes on South Georgia since the late-19th century documented in historical photographs

    NASA Astrophysics Data System (ADS)

    Gordon, John; Haynes, Valerie

    2014-05-01

    South Georgia is one of the few landmasses in the Southern Ocean. It provides a crucial geographical datapoint for glacier responses to climate change over different timescales. As part of an ongoing glacier inventory of the island, we are compiling a database of historical glacier photographs. Since the late 19th century, the island has been visited by numerous scientific and survey expeditions, as well as being the land-base for a major whaling industry. Historical photographs of the island are available from the late-19th century, beginning with the 1882-83 German International Polar Year Expedition. Many more exist from the 20th century, notably from the South Georgia Surveys in the 1950s. An assessment of the value of the photographs indicates that spatial coverage is variable, many lack reference features to pinpoint glacier positions and, in the case of smaller glaciers, the presence of snowcover makes it difficult to define the ice edge. Nevertheless, the photographs provide useful corroboration of more advanced glacier positions during the late-19th century and recession of smaller mountain and valley glaciers during the mid-20th century, while larger tidewater and sea-calving glaciers generally remained in relatively advanced positions until the 1980s. Since then, nearly all the glaciers have retreated; some of these retreats have been dramatic and a number of small mountain glaciers have fragmented or disappeared. The response of the glaciers can be related to synoptic-scale warming, particularly since the 1950s, moderated by individual glacier geometry and topography.

  9. THE INFLUENCE OF ADVANCED AGE ON THE HEPATIC AND RENAL TOXICITY OF CHLOROFORM

    EPA Science Inventory

    THE INFLUENCE OF ADVANCED AGE ON THE HEPATIC AND RENAL TOXICITY OF CHLOROFORM (CHC13). A McDonald, Y M Sey and J E Simmons. NHEERL, ORD, U.S. EPA, RTP, NC.
    Disinfection, by chlorination or by ozonation followed by treatment with either chlorine or chloramine, of water containi...

  10. Monitoring of two rapidly changing glacier tongues in the Swiss Alps by new drone data and historical documents

    NASA Astrophysics Data System (ADS)

    Nussbaumer, Samuel U.; Jörg, Philip C.; Gärtner-Roer, Isabelle; Rastner, Philipp; Ruff, Alexander; Steiner, Daniel; Vieli, Andreas; Zumbühl, Heinz J.

    2015-04-01

    glacier change into a long-term context, we compare the recent findings with available observation data (in situ measurements) and historical documents of a high quality, such as the original plane-table sheets (prepared for the Swiss Dufour map) surveyed by W. Jacky for the area of Unterer Grindelwaldgletscher in 1860/61, and by A. Bétemps for Findelengletscher in 1859. To complement our findings we show pictorial documents, such as early photographs, captured in the mid-19th century and part of a newly discovered collection of photographs for Unterer Grindelwaldgletscher, which depict both glaciers' splendor during the last Little Ice Age advance. Vertical ice loss since the Little Ice Age amounts to about 350 m for the tongue of Unterer Grindelwaldgletscher, and 150 m for Findelengletscher.

  11. Marine Geophysical Surveying Along the Hubbard Glacier Terminus, Southeast Alaska

    NASA Astrophysics Data System (ADS)

    Goff, J. A.; Davis, M.; Gulick, S. P.; Lawson, D. E.; Willems, B. A.

    2010-12-01

    Tidewater glaciers are a challenging environment for marine investigations, owing to the dangers associated with calving and restrictions on operations due to dense floating ice. We report here on recent efforts to conduct marine geophysical surveys proximal to the ice face of Hubbard Glacier, in Disenchantment Bay, Alaska. Hubbard is an advancing tidewater glacier that has twice recently (1986 and 2002) impinged on Gilbert Point, which separates Russell Fiord from Disenchantment Bay, thereby temporarily creating a glacially-dammed Russell Lake. Continued advance will likely form a more permanent dam, rerouting brackish outflow waters into the Situk River, near Yakutat, Alaska. Our primary interest is in studying the development and motion of the morainal bank which, for an advancing tidewater glacier, stabilizes it against rapid retreat. For survey work, we operated with a small, fast, aluminum-hulled vessel and a captain experienced in operating in ice-bound conditions, providing a high margin of safety and maneuverability. Differencing of multibeam bathymetric data acquired in different years can identify and quantify areas of deposition and erosion on the morainal bank front and in Disenchantment Bay proper, where accumulation rates are typically > 1 m/yr within 1 km of the glacier terminus. The advance or retreat rate of the morainal bank can be determined by changes in the bed elevation through time; we document advance rates that average > 30 m/yr in Disenchantment Bay, but which vary substantially over different time periods and at different positions along the ice face. Georeferencing of available satellite imagery allows us to directly compare the position of the glacial terminus with the position of the morainal bank. From 1978 to 1999, and then to 2006, the advances in terminus and morainal bank positions were closely synchronized along the length of the glacier face. In the shallower Russell Fiord side of the terminus, a sediment ridge was mapped both

  12. Advanced Colorectal Adenomas in Patients Under 45 Years of Age Are Mostly Sporadic

    PubMed Central

    Nalbantoglu, ILKe; Watson, Rao; Goodwin, Jonathan; Safar, Elyas; Chokshi, Reena V.; Azar, Riad R.; Davidson, Nicholas O.

    2014-01-01

    Background The presence of advanced adenomas in younger individuals is a criterion for Lynch syndrome (LS). However, the utility of screening advanced adenomas for loss of mismatch repair (MMR) protein expression to identify suspected LS remains unclear. Aims Determine the prevalence of MMR defects to understand whether these patients harbor a defined genetic risk for CRC. Methods The study cohort included adult patients ≤45 years of age with advanced adenomas (villous histology, ≥1 cm in diameter, ≥3 polyps of any size) endoscopically removed between 2001 and 2011. Clinical records were reviewed along with detailed pathological review and immunohistochemical MMR analysis. Results A total of 76 (40.1 % male, age 40.6 ± 5.4 years) patients met inclusion and exclusion criteria. Indications for colonoscopy were gastrointestinal (GI) bleeding 39 (51.3 %), CRC in a first-degree relative 17 (22.4 %) and somatic GI symptoms 20 (26.3 %). Index colonoscopy revealed a median of 1 adenoma (range 1–4), mean diameter of 12.9 ±7.1 mm, 40 (52.6 %) with villous histology. The mean follow-up duration was 3.3 ± 2 years. Recurrent adenomas developed in 24 (31.6 %), of which 8 (10.5 %) were advanced adenomas; none of these patients developed CRC. One of 66 (1.5 %) adenomas available for immunohistochemical (IHC) testing revealed loss of MLH1 and PMS2. Conclusions IHC screening of advanced adenomas from patients younger than 45 years of age identified potential LS in one of 64 patients. The low yield of IHC screening in this population suggests that universal IHC screening of advanced adenomas from patients younger than 45 years of age for MMR defects is not an efficient strategy for identifying LS subjects. PMID:24925148

  13. Aging induces cardiac diastolic dysfunction, oxidative stress, accumulation of advanced glycation endproducts and protein modification.

    PubMed

    Li, Shi-Yan; Du, Min; Dolence, E Kurt; Fang, Cindy X; Mayer, Gabriele E; Ceylan-Isik, Asli F; LaCour, Karissa H; Yang, Xiaoping; Wilbert, Christopher J; Sreejayan, Nair; Ren, Jun

    2005-04-01

    Evidence suggests that aging, per se, is a major risk factor for cardiac dysfunction. Oxidative modification of cardiac proteins by non-enzymatic glycation, i.e. advanced glycation endproducts (AGEs), has been implicated as a causal factor in the aging process. This study was designed to examine the role of aging on cardiomyocyte contractile function, cardiac protein oxidation and oxidative modification. Mechanical properties were evaluated in ventricular myocytes from young (2-month) and aged (24-26-month) mice using a MyoCam system. The mechanical indices evaluated were peak shortening (PS), time-to-PS (TPS), time-to-90% relengthening (TR90) and maximal velocity of shortening/relengthening (+/- dL/dt). Oxidative stress and protein damage were evaluated by glutathione and glutathione disulfide (GSH/GSSG) ratio and protein carbonyl content, respectively. Activation of NAD(P)H oxidase was determined by immunoblotting. Aged myocytes displayed a larger cell cross-sectional area, prolonged TR90, and normal PS, +/- dL/dt and TPS compared with young myocytes. Aged myocytes were less tolerant of high stimulus frequency (from 0.1 to 5 Hz) compared with young myocytes. Oxidative stress and protein oxidative damage were both elevated in the aging group associated with significantly enhanced p47phox but not gp91phox expression. In addition, level of cardiac AGEs was approximately 2.5-fold higher in aged hearts than young ones determined by AGEs-ELISA. A group of proteins with a molecular range between 50 and 75 kDa with pI of 4-7 was distinctively modified in aged heart using one- or two-dimension SDS gel electrophoresis analysis. These data demonstrate cardiac diastolic dysfunction and reduced stress tolerance in aged cardiac myocytes, which may be associated with enhanced cardiac oxidative damage, level of AGEs and protein modification by AGEs.

  14. Prokaryotic diversity in sediments beneath two polar glaciers with contrasting organic carbon substrates.

    PubMed

    Stibal, Marek; Hasan, Fariha; Wadham, Jemma L; Sharp, Martin J; Anesio, Alexandre M

    2012-03-01

    Microbial ecosystems beneath glaciers and ice sheets are thought to play an active role in regional and global carbon cycling. Subglacial sediments are assumed to be largely anoxic, and thus various pathways of organic carbon metabolism may occur here. We examine the abundance and diversity of prokaryotes in sediment beneath two glaciers (Lower Wright Glacier in Antarctica and Russell Glacier in Greenland) with different glaciation histories and thus with different organic carbon substrates. The total microbial abundance in the Lower Wright Glacier sediment, originating from young lacustrine sediment, was an order of magnitude higher (~8 × 10(6) cells per gram of wet sediment) than in Russell Glacier sediment (~9 × 10(5) cells g(-1)) that is of Holocene-aged soil origin. 4% of the microbes from the Russell Glacier sediment and 0.04-0.35% from Lower Wright Glacier were culturable at 10°C. The Lower Wright Glacier subglacial community was dominated by Proteobacteria, followed by Firmicutes. The Russell Glacier library was much less diverse and also dominated by Proteobacteria. Low numbers and diversity of both Euryarchaeota and Crenarchaeota were found in both sediments. The identified clones were related to bacteria with both aerobic and anaerobic metabolisms, indicating the presence of both oxic and anoxic conditions in the sediments.

  15. Mass balance investigation of alpine glaciers through LANDSAT TM data

    NASA Technical Reports Server (NTRS)

    Bayr, Klaus J.

    1989-01-01

    An analysis of LANDSAT Thematic Mapper (TM) data of the Pasterze Glacier and the Kleines Fleisskees in the Austrian Alps was undertaken and compared with meteorological data of nearby weather stations. Alpine or valley glaciers can be used to study regional and worldwide climate changes. Alpine glaciers respond relatively fast to a warming or cooling trend in temperature through an advance or a retreat of the terminus. In addition, the mass balance of the glacier is being affected. Last year two TM scenes of the Pasterze Glacier of Aug. 1984 and Aug. 1986 were used to study the difference in reflectance. This year, in addition to the scenes from last year, one MSS scene of Aug. 1976 and a TM scene from 1988 were examined for both the Pasterze Glacier and the Kleines Fleisskees. During the overpass of the LANDSAT on 6 Aug. 1988 ground truthing on the Pasterze Glacier was undertaken. The results indicate that there was considerable more reflectance in 1976 and 1984 than in 1986 and 1988. The climatological data of the weather stations Sonnblick and Rudolfshuette were examined and compared with the results found through the LANDSAT data. There were relations between the meteorological and LANDSAT data: the average temperature over the last 100 years showed an increase of .4 C, the snowfall was declining during the same time period but the overall precipitation did not reveal any significant change over the same period. With the use of an interactive image analysis computer, the LANDSAT scenes were studied. The terminus of the Pasterze Glacier retreated 348 m and the terminus of the Kleines Fleisskees 121 m since 1965. This approach using LANDSAT MSS and TM digital data in conjunction with meteorological data can be effectively used to monitor regional and worldwide climate changes.

  16. Implications of Advancing Paternal Age: Does It Affect Offspring School Performance?

    PubMed Central

    Svensson, Anna C.; Abel, Kathryn; Dalman, Christina; Magnusson, Cecilia

    2011-01-01

    Average paternal age is increasing in many high income countries, but the implications of this demographic shift for child health and welfare are poorly understood. There is equivocal evidence that children of older fathers are at increased risk of neurodevelopmental disorders and reduced IQ. We therefore report here on the relationship between paternal age and a composite indicator of scholastic achievement during adolescence, i.e. compulsory school leaving grades, among recent birth cohorts in Stockholm County where delayed paternity is notably common. We performed a record-linkage study comprising all individuals in Stockholm County who finished 9 years of compulsory school from 2000 through 2007 (n = 155,875). Data on school leaving grades and parental characteristics were retrieved from administrative and health service registers and analyzed using multiple linear regression. Advancing paternal age at birth was not associated with a decrease in school leaving grades in adolescent offspring. After adjustment for year of graduation, maternal age and parental education, country of birth and parental mental health service use, offspring of fathers aged 50 years or older had on average 0.3 (95% CI −3.8, 4.4) points higher grades than those of fathers aged 30–34 years. In conclusion, advancing paternal age is not associated with poorer school performance in adolescence. Adverse effects of delayed paternity on offspring cognitive function, if any, may be counterbalanced by other potential advantages for children born to older fathers. PMID:21957460

  17. Revealing glacier flow and surge dynamics from animated satellite image sequences: examples from the Karakoram

    NASA Astrophysics Data System (ADS)

    Paul, F.

    2015-04-01

    Although animated images are very popular on the Internet, they have so far found only limited use for glaciological applications. With long time-series of satellite images becoming increasingly available and glaciers being well recognized for their rapid changes and variable flow dynamics, animated sequences of multiple satellite images reveal glacier dynamics in a time-lapse mode, making the otherwise slow changes of glacier movement visible and understandable for a wide public. For this study animated image sequences were created from freely available image quick-looks of orthorectified Landsat scenes for four regions in the central Karakoram mountain range. The animations play automatically in a web-browser and might help to demonstrate glacier flow dynamics for educational purposes. The animations revealed highly complex patterns of glacier flow and surge dynamics over a 15-year time period (1998-2013). In contrast to other regions, surging glaciers in the Karakoram are often small (around 10 km2), steep, debris free, and advance for several years at comparably low annual rates (a few hundred m a-1). The advance periods of individual glaciers are generally out of phase, indicating a limited climatic control on their dynamics. On the other hand, nearly all other glaciers in the region are either stable or slightly advancing, indicating balanced or even positive mass budgets over the past few years to decades.

  18. Short-term variations in the dynamics of Bowdoin Glacier in northwestern Greenland

    NASA Astrophysics Data System (ADS)

    Minowa, Masahiro; Sugiyama, Shin; Sawagaki, Takanobu; Tsutaki, Shun; Sakakibara, Daiki

    2016-04-01

    Tidewater glaciers in Greenland ice sheet are rapidly retreating by under the influence of changes in ice dynamics. For example, Bowdoin Glacier began rapid retreat in 2008, which was accompanied by significant acceleration near the glacier front. Submarine melting and ice-mélange weakening are suspected as triggering mechanisms of the rapid retreat of tidewater glaciers in the Greenland ice sheet, but details of processes at the ice-ocean interface are poorly understood. To better understand these processes, we measured ice-front position of Bowdoin Glacier in northwestern Greenland and glacier/ice-mélange movement in front of the glacier. The glacier/ice-mélange measurement was performed by processing 3-hourly photographs taken by a time-lapse camera operated over two years since July 2013. We also operated a dual-frequency GPS at 3 km from the calving front to measure ice speed from May to July in 2014 and 2015. The image analysis revealed clear seasonal variations in the ice-front position with an amplitude of ~200 m. Seasonal changes were also observed in ice speed along the center of the glacier (amplitude ~50%). During summer, the ice-front position was relatively stable, but retreated occasionally by large calving events. These events occurred near upwelling of subglacial discharge, where a large submarine melt rate is expected. The glacier began to advance in September approximately when daily mean air temperature dropped below 0°C. The glacier advanced the most in winter when the fjord was covered by ice-mélange. After winter, extended portion of the glacier rapidly disintegrated by a few calving events. Such event coincided with onset of ice-mélange movement in front of the glacier. This movement occurs when air temperature above 0°C and high wind speed were observed, suggesting the calving event was due to decrease in the mechanical support from the ice-mélange. These results indicate both ice-mélange and submarine melting play roles in

  19. Advanced BrainAGE in older adults with type 2 diabetes mellitus

    PubMed Central

    Franke, Katja; Gaser, Christian; Manor, Brad; Novak, Vera

    2013-01-01

    Aging alters brain structure and function and diabetes mellitus (DM) may accelerate this process. This study investigated the effects of type 2 DM on individual brain aging as well as the relationships between individual brain aging, risk factors, and functional measures. To differentiate a pattern of brain atrophy that deviates from normal brain aging, we used the novel BrainAGE approach, which determines the complex multidimensional aging pattern within the whole brain by applying established kernel regression methods to anatomical brain magnetic resonance images (MRI). The “Brain Age Gap Estimation” (BrainAGE) score was then calculated as the difference between chronological age and estimated brain age. 185 subjects (98 with type 2 DM) completed an MRI at 3Tesla, laboratory and clinical assessments. Twenty-five subjects (12 with type 2 DM) also completed a follow-up visit after 3.8 ± 1.5 years. The estimated brain age of DM subjects was 4.6 ± 7.2 years greater than their chronological age (p = 0.0001), whereas within the control group, estimated brain age was similar to chronological age. As compared to baseline, the average BrainAGE scores of DM subjects increased by 0.2 years per follow-up year (p = 0.034), whereas the BrainAGE scores of controls did not change between baseline and follow-up. At baseline, across all subjects, higher BrainAGE scores were associated with greater smoking and alcohol consumption, higher tumor necrosis factor alpha (TNFα) levels, lower verbal fluency scores and more severe deprepession. Within the DM group, higher BrainAGE scores were associated with longer diabetes duration (r = 0.31, p = 0.019) and increased fasting blood glucose levels (r = 0.34, p = 0.025). In conclusion, type 2 DM is independently associated with structural changes in the brain that reflect advanced aging. The BrainAGE approach may thus serve as a clinically relevant biomarker for the detection of abnormal patterns of brain aging associated with type 2

  20. Modelling the feedbacks between mass balance, ice flow and debris transport to predict the response to climate change of debris-covered glaciers in the Himalaya

    NASA Astrophysics Data System (ADS)

    Rowan, Ann V.; Egholm, David L.; Quincey, Duncan J.; Glasser, Neil F.

    2015-11-01

    Many Himalayan glaciers are characterised in their lower reaches by a rock debris layer. This debris insulates the glacier surface from atmospheric warming and complicates the response to climate change compared to glaciers with clean-ice surfaces. Debris-covered glaciers can persist well below the altitude that would be sustainable for clean-ice glaciers, resulting in much longer timescales of mass loss and meltwater production. The properties and evolution of supraglacial debris present a considerable challenge to understanding future glacier change. Existing approaches to predicting variations in glacier volume and meltwater production rely on numerical models that represent the processes governing glaciers with clean-ice surfaces, and yield conflicting results. We developed a numerical model that couples the flow of ice and debris and includes important feedbacks between debris accumulation and glacier mass balance. To investigate the impact of debris transport on the response of a glacier to recent and future climate change, we applied this model to a large debris-covered Himalayan glacier-Khumbu Glacier in Nepal. Our results demonstrate that supraglacial debris prolongs the response of the glacier to warming 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, Khumbu Glacier has lost 34% of its volume while its area has reduced by only 6%. We predict a 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 yr. This detachment will accelerate rates of glacier decay, and similar changes are likely for other debris-covered glaciers in the Himalaya.

  1. Listening to Glaciers: Passive hydroacoustics near marine-terminating glaciers

    USGS Publications Warehouse

    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.

  2. Advanced glycation End-products (AGEs): an emerging concern for processed food industries.

    PubMed

    Sharma, Chetan; Kaur, Amarjeet; Thind, S S; Singh, Baljit; Raina, Shiveta

    2015-12-01

    The global food industry is expected to increase more than US $ 7 trillion by 2014. This rise in processed food sector shows that more and more people are diverging towards modern processed foods. As modern diets are largely heat processed, they are more prone to contain high levels of advanced glycation end products (AGEs). AGEs are a group of complex and heterogeneous compounds which are known as brown and fluorescent cross-linking substances such as pentosidine, non-fluorescent cross-linking products such as methylglyoxal-lysine dimers (MOLD), or non-fluorescent, non-cross linking adducts such as carboxymethyllysine (CML) and pyrraline (a pyrrole aldehyde). The chemistry of the AGEs formation, absorption and bioavailability and their patho-biochemistry particularly in relation to different complications like diabetes and ageing discussed. The concept of AGEs receptor - RAGE is mentioned. AGEs contribute to a variety of microvascular and macrovascular complications through the formation of cross-links between molecules in the basement membrane of the extracellular matrix and by engaging the receptor for advanced glycation end products (RAGE). Different methods of detection and quantification along with types of agents used for the treatment of AGEs are reviewed. Generally, ELISA or LC-MS methods are used for analysis of foods and body fluids, however lack of universally established method highlighted. The inhibitory effect of bioactive components on AGEs by trapping variety of chemical moieties discussed. The emerging evidence about the adverse effects of AGEs makes it necessary to investigate the different therapies to inhibit AGEs.

  3. Glacier melt on the Third Pole

    NASA Astrophysics Data System (ADS)

    Yao, T.

    2015-12-01

    With an average elevation above 4,000 metres, the Third Pole (TP) is a unique region with many high mountains centered on the Tibetan Plateau stretching over 5 million square kilometers. Major environmental changes are taking place on the TP characterized by complex interactions of atmospheric, cryospheric, hydrological, geological and environmental processes. These processes are critical for the well-being of the three billion people inhabiting the plateau and the surrounding regions. Glacier melt is one of the most significant environmental changes observed on the TP. Over the past decade, most of the glaciers on the TP have undergone considerable melt. The Third Pole Environment (TPE) has focused on the causes of the glacier melt by conducting large-scale ground in-situ observation and monitoring, analyzing satellite images and remote sensing data, and applying numerical modeling to environmental research on the TP. The studies of long-term record of water stable isotopes in precipitation and ice core throughout the TP have revealed different features with regions, thus proposing significant influence of atmospheric circulations on spatial precipitation pattern over the TP. Validation of the result by isotope-equipped general circulation models confirms the spatial distribution of different atmospheric circulation dominances on the TP, with northern part dominated by the westerlies, southern part by the summer monsoon, and central part featuring the influences of both circulation systems. Such unique circulation patterns also bear directly on the status of glaciers and lakes over the TP and its surroundings. The studies therefore found the largest glacier melt in the monsoon-dominated southern part, moderate melt in the central part of transition, and the least melt, or even slight advance in the westerlies-dominated northern TP. It is clear that some mountains on the TP are undergoing rapid melt and the consequence of without ice and snow will be very soon. The

  4. Accelerating retreat and high-elevation thinning of glaciers in central Spitsbergen

    NASA Astrophysics Data System (ADS)

    Małecki, Jakub

    2016-06-01

    Svalbard is a heavily glacier-covered archipelago in the Arctic. Dickson Land (DL), in the central part of the largest island, Spitsbergen, is relatively arid and, as a result, glaciers there are relatively small and restricted mostly to valleys and cirques. This study presents a comprehensive analysis of glacier changes in DL based on inventories compiled from topographic maps and digital elevation models for the Little Ice Age (LIA) maximum, the 1960s, 1990, and 2009/2011. Total glacier area has decreased by ˜ 38 % since the LIA maximum, and front retreat increased over the study period. Recently, most of the local glaciers have been consistently thinning in all elevation bands, in contrast to larger Svalbard ice masses which remain closer to balance. The mean 1990-2009/2011 geodetic mass balance of glaciers in DL is among the most negative from the Svalbard regional means known from the literature.

  5. A study of discrete glacier motion

    NASA Astrophysics Data System (ADS)

    Zoet, Lucas K.

    Knowledge of process which control glacial dynamics are imperative in quantifying the response of a glacier or ice sheet to external forcing. This dissertation focuses mainly upon the characterization of sliding ice over a bed in an unstable fashion. I investigate unstable sliding through instances where it is observed in passive seismology as well as a focused laboratory study. The laboratory study attempts to isolate specific aspects of the sliding interface, which could lead to unstable sliding. Implications of unstable sliding with regards to erosion are also dealt with. Initially the TAMSEIS array is used to observe a unique set of seismicity originating at the base of David Glacier Antarctica in which ˜ 20,000 events were located over a ˜300 day period as the ice slid over an asperity. Tidal effects at the terminus modulated the interevent spacing and magnitude of events allowing for a basic analysis of healing process between a glacier and its bed. The 300 day period of repeat seismicity is hypothesized to arise from advection of debris rich ice over the asperity. Next the erosion implications of stick slip sliding are investigated. Sudden advancement associated with seismic energy generation is hypothesized to rapidly expand water filled cavities, which form in lee of bedrock highs. The rapid expansion creates a drop in water pressure within the cavity resulting in a pressure gradient leading to rapid fracture of bedrock. During the interseismic period of a stick slipping glacier the static coefficient of friction transfers a larger shear stress to the bed than the dynamic coefficient of friction from stably sliding glacier would. Next laboratory experimentation is conducted using a biaxial shearing apparatus in order to test the hypothesis that debris rich ice can affect the stability regime of a sliding glacier. This is preformed on a suite of ice-debris samples with range entrained debris percentages and temperatures. Both synthetic ice constructed in

  6. Spatial variability of glacier decline in the Indian and Nepalese Himalaya since the 1960s

    NASA Astrophysics Data System (ADS)

    Wilson, R.; Rivera, A.; Collins, D. N.; Entwistle, N. S.

    2013-12-01

    Since reaching their Little Ice Age Maximums, Himalayan glaciers have generally undergone a period of retreat, evident from large moraines left at former ice limits. Currently, however, detailed assessments of Himalayan glacier fluctuations over the past century are limited and fail to compare spatially or temporally to records available in Central Europe, North America and Scandinavia. Consequently, the variability and magnitude of glacial change across the Himalayas, a region that is typified by complex climatic settings, is still yet to be fully understood. Against a back drop of poor data availability, 1960s Corona stereo-imagery and historic GLIMS glacier outlines now offer an opportunity to assess glacier extent in regions of the Himalayas pre-1980. Comparing glacier measurements derived from Corona and GLIMS datasets with those made from more contemporary ASTER data, changes in glacier area and length, between the 1960/70s and 2000s, were quantified for selected glaciers located in Uttaranchal, India (Bhagirathi and Pindar/Kali basins) and Central Nepal (Seti and Trisula basins). Most notably, results indicate that glaciers selected in the Bhagirathi and Pindar/Kali basins reduced in area by 7.97% and 7.54%, respectively. Contrastingly, glaciers located in the Seti and Trisula basins experienced a significantly higher rate of decline, reducing in area by 29.78% and 50.55%, respectively. After reviewing other Himalayan glacier change records, it is suggested that the comparatively limited decline of Uttaranchal glaciers may be attributed to the existence of a climatic transitional zone in this region where glaciers benefit from large amounts of both summer and winter snowfall enabling them to greater withstand recent climate changes. The spatial variability of glacier decline shown here has important implications when considering the future impacts of continued retreat on regional water resources across the Himalaya.

  7. Climate, Ice, and Mud: investigating the relationship between glacier activity and sediment flux using varved lake sediments, Iceland

    NASA Astrophysics Data System (ADS)

    Larsen, D. J.; Miller, G. H.; Geirsdottir, A.; Flowers, G. E.; Bjornsson, H.

    2012-12-01

    The worldwide retreat of many glaciers during the 21st century is expected to have profound impacts on local and regional hydrologic cycles. Associated with the forecasted reductions in global ice volume are changes in meltwater runoff and sediment transport in glacially fed drainage systems. Alpine glaciers and small ice caps are particularly sensitive to climate change because their dimensions can respond quickly to changes in glacier mass balance. Records of past glacier fluctuations are important sources of paleoclimate data and also provide a context for current and future changes to glacier hydrologic systems. Annually laminated (varved) sediments from proglacial lake Hvítárvatn, central Iceland, offer a continuous archive of Langjökull ice cap (~925 km2) activity through the late Holocene. A multi-proxy record from this site indicates that Langjökull's size was more variable during the past millennium than during any other multi-centennial interval of the Holocene. Ice growth culminated in the Little Ice Age (LIA), when Langjökull advanced into Hvítárvatn and reached its maximum aerial extent of the past 10 ka. At present, roughly one-third of the ice cap's discharge flows into the lake catchment, constituting ~70% of the total inflow, and lake sedimentation rates are governed by the production and delivery of glacially eroded clastic material transported to the lake by four primary meltwater streams. Glacier fluctuations of the past 1 ka are reconstructed from physical proxies contained in sediment cores retrieved from six locations throughout the main basin. Total sediment yield and distribution during this period are calculated from sediment accumulation rates and from > 100 km of seismic reflection profiles. A tephra-constrained varve chronology provides high chronologic control, with a maximum age uncertainty of ± 10 years. Low and constant sedimentation rates characterize the 11th and 12th centuries, reflecting minimal glacier activity during

  8. North Pacific atmosphere-ocean variability over the past millennium inferred from coastal glaciers and tree rings

    SciTech Connect

    Wiles, G.

    1997-11-01

    Ocean-atmosphere system fluctuations from annual to centennial time scales in the North Pacific are recorded in histories of coastal glacier advances and in temperature records inferred from coastal tree-ring series. Calendar dates obtained by dating glacially overrun forests with tree rings, show two major intervals of ice expansion over the last millennium. The first occurred between AD 1250 and 1300 and the second between AD 1650 and 1750. This glacial record indicates the onset of the Little Ice Age by AD 1250 and the most widespread advance of the past millennium from the mid 17th to the mid 18th century. Moreover, temperature variations inferred from tree-ring records since AD 1600 show multiple decade-long changes in the climate system, suggesting that lower frequency variation can be derived from these records. Decade-long cool intervals are most frequent between AD 1650 and 1750, a time of general glacier expansion. The warmest decades occur in the 20th century, a time of glacier retreat. 16 refs., 4 figs.

  9. Quaternary history of Red Mountain Creek Valley and its relation to the Rio Grande glacier system near Creede, CO

    SciTech Connect

    Kitchens, S. . Dept. of Geology)

    1993-03-01

    Interactions between the Rio Grande glacier system and the Red Mountain Creek glacier are more complex than previously believed. Although both glaciers were fed by the same ice cap along the continental divide, the timing and number of advances are different. Analysis of air photos and field relationships reveal a series of end moraines at the mouth of Red Mountain Creek. The presence of these moraines disproves the hypothesis of Atwood and Mather (1932) that the two were confluent during the last phase of glaciation. The degree of weathering rind development on mafic cobbles was used together with the degree of clay mineral development in the soils to determine relative ages and the number of advances in each system. The less than 2[mu]m material for X-ray diffraction analysis was separated from soil samples collected from pits excavated on the tops of end moraines. Both smectite and kaolinite were found within the soil profile thus indicating weathering of minerals in tills derived from the local biotite-sanadine-hornblende tuffs. The amount of post glacial weathering was estimated based on the relative intensity of the 17[angstrom] smectite peak after ethylene glycol solvation. Both the X-ray and weathering rind analysis show two separate glacial events in Red Mountain Creek valley. However, in the Rio Grande system the weathering rind data suggests two glacial events while the clay mineralogy suggests only one.

  10. Advanced glycation end products (AGEs) and their receptor (RAGE) induce apoptosis of periodontal ligament fibroblasts.

    PubMed

    Li, D X; Deng, T Z; Lv, J; Ke, J

    2014-12-01

    Diabetics have an increased prevalence of periodontitis, and diabetes is one of the causative factors of severe periodontitis. Apoptosis is thought to be involved in this pathogenic relationship. The aim of this study was to investigate apoptosis in human periodontal ligament (PDL) fibroblasts induced by advanced glycation end products (AGEs) and their receptor (RAGE). We examined the roles of apoptosis, AGEs, and RAGE during periodontitis in diabetes mellitus using cultured PDL fibroblasts that were treated by AGE-modified bovine serum albumin (AGE-BSA), bovine serum albumin (BSA) alone, or given no treatment (control). Microscopy and real-time quantitative PCR indicated that PDL fibroblasts treated with AGE-BSA were deformed and expressed higher levels of RAGE and caspase 3. Cell viability assays and flow cytometry indicated that AGE-BSA reduced cell viability (69.80 ± 5.50%, P<0.01) and increased apoptosis (11.31 ± 1.73%, P<0.05). Hoechst 33258 staining and terminal-deoxynucleotidyl transferase-mediated nick-end labeling revealed that AGE-BSA significantly increased apoptosis of PDL fibroblasts. The results showed that the changes in PDL fibroblasts induced by AGE-BSA may explain how AGE-RAGE participates in and exacerbates periodontium destruction.

  11. Metformin reverts deleterious effects of advanced glycation end-products (AGEs) on osteoblastic cells.

    PubMed

    Schurman, L; McCarthy, A D; Sedlinsky, C; Gangoiti, M V; Arnol, V; Bruzzone, L; Cortizo, A M

    2008-06-01

    Advanced glycation endproducts (AGEs) are implicated in the complications of diabetes and ageing, affecting several tissues, including bone. Metformin, an insulin-sensitizer drug, reduces the risk of life-threatening macrovascular complications. We have evaluated the hypothesis that metformin can abrogate AGE-induced deleterious effects in osteoblastic cells in culture. In two osteoblast-like cell lines (UMR106 and MC3T3E1), AGE-modified albumin induced cell death, caspase-3 activity, altered intracellular oxidative stress and inhibited alkaline phosphatase activity. Metformin-treatment of osteoblastic cells prevented these AGE-induced alterations. We also assessed the expression of AGE receptors as a possible mechanism by which metformin could modulate the action of AGEs. AGEs-treatment of osteoblast-like cells enhanced RAGE protein expression, and this up-regulation was prevented in the presence of metformin. Although the precise mechanisms involved in metformin signaling are still elusive, our data implicate the AGE-RAGE interaction in the modulation of growth and differentiation of osteoblastic cells.

  12. Stimulatory effects of advanced glycation endproducts (AGEs) on fibronectin matrix assembly.

    PubMed

    Pastino, Alexandra K; Greco, Todd M; Mathias, Rommel A; Cristea, Ileana M; Schwarzbauer, Jean E

    2017-05-01

    Advanced glycation endproducts (AGEs) are a heterogeneous group of compounds that form via non-enzymatic glycation of proteins throughout our lifespan and at a higher rate in certain chronic diseases such as diabetes. AGEs contribute to the progression of fibrosis, in part by stimulating cellular pathways that affect gene expression. Long-lived ECM proteins are targets for non-enzymatic glycation but the question of whether the AGE-modified ECM leads to excess ECM accumulation and fibrosis remains unanswered. In this study, cellular changes due to AGE accretion in the ECM were investigated. Non-enzymatic glycation of proteins in a decellularized fibroblast ECM was achieved by incubating the ECM in a solution of methylglyoxal (MGO). Mass spectrometry of fibronectin (FN) isolated from the glycated matrix identified twenty-eight previously unidentified MGO-derived AGE modification sites including functional sites such as the RGD integrin-binding sequence. Mesangial cells grown on the glycated, decellularized matrix assembled increased amounts of FN matrix. Soluble AGE-modified bovine serum albumin (BSA) also stimulated FN matrix assembly and this effect was reduced by function-blocking antibodies against the receptor for AGE (RAGE). These results indicate that cells respond to AGEs by increasing matrix assembly and that RAGE is involved in this response. This raises the possibility that the accumulation of ECM during the progression of fibrosis may be enhanced by cell interactions with AGEs on a glycated ECM.

  13. Advanced glycation end products (AGEs) are cross-sectionally associated with insulin secretion in healthy subjects.

    PubMed

    Forbes, Josephine M; Sourris, Karly C; de Courten, Maximilian P J; Dougherty, Sonia L; Chand, Vibhasha; Lyons, Jasmine G; Bertovic, David; Coughlan, Melinda T; Schlaich, Markus P; Soldatos, Georgia; Cooper, Mark E; Straznicky, Nora E; Kingwell, Bronwyn A; de Courten, Barbora

    2014-02-01

    It has been postulated that chronic exposure to high levels of advanced glycation end products (AGEs), in particular from dietary sources, can impair insulin secretion. In the present study, we investigated the cross-sectional relationship between AGEs and acute insulin secretion during an intravenous glucose tolerance test (IVGTT) and following a 75 g oral glucose tolerance test (OGTT) in healthy humans. We report the cross-sectional association between circulating AGE concentrations and insulin secretory function in healthy humans (17 F: 27 M, aged 30 ± 10 years) with a wide range of BMI (24.6-31.0 kg/m(2)). Higher circulating concentrations of AGEs were related to increased first phase insulin secretion during IVGTT (r = 0.43; p < 0.05) and lower 2-h glucose concentrations during OGTT (r = -0.31; p < 0.05). In addition, fasting (r = -0.36; p < 0.05) and 2-h glucose concentrations were negatively related to circulating levels of soluble receptor for AGE (RAGE) isoforms (r = -0.39; p < 0.01). In conclusion, in healthy humans, we show a cross-sectional association between advanced glycation end products and acute insulin secretion during glucose tolerance testing.

  14. Relationship of decrease in fecundity with advancing age to structural changes in mouse endometrium

    PubMed Central

    SHIMIZU, KIYOSHI; YAMADA, JINZO

    2000-01-01

    The aim of this study was to determine whether a relationship exists between decrease in fecundity and structural changes in the antimesometrial endometrium of the mouse. Fecundity was calculated as the number of animals showing a placental sign/number of copulated animals ×100 (%). Structural changes in the endometrium were examined by electron microscopy. A negative correlation between age and fecundity was found. Fecundity was 50% at 7 mo of age. At this age, amorphous material appeared in the region between the basement membrane deep to the luminal epithelium and the subepithelial cells. This material was sometimes attached to the basement membrane. It increased in amount with advancing age, as fecundity decreased. The structure of the uterine luminal epithelial cells did not alter with age. The results indicated that decrease in fecundity with advancing age is correlated with the appearance of amorphous material beneath the basal lamina of the endometrial epithelium. It is suggested that this could impair communication between the luminal epithelium and the endometrial stroma, which plays an important role in implantation. PMID:10697293

  15. Chernobyl fallout on Alpine glaciers

    SciTech Connect

    Ambach, W.; Rehwald, W.; Blumthaler, M.; Eisner, H.; Brunner, P.

    1989-01-01

    Measurements of the gross beta activity of snow samples from four Alpine glaciers contaminated by radioactive fallout from the Chernobyl nuclear accident and a gamma-spectrum analysis of selected samples are reported. The results are discussed with respect to possible risks to the population from using meltwater from these glaciers as drinking water.

  16. Reduced neutrophil chemotaxis and infiltration contributes to delayed resolution of cutaneous wound infection with advanced age.

    PubMed

    Brubaker, Aleah L; Rendon, Juan L; Ramirez, Luis; Choudhry, Mashkoor A; Kovacs, Elizabeth J

    2013-02-15

    Advanced age is associated with alterations in innate and adaptive immune responses, which contribute to an increased risk of infection in elderly patients. Coupled with this immune dysfunction, elderly patients demonstrate impaired wound healing with elevated rates of wound dehiscence and chronic wounds. To evaluate how advanced age alters the host immune response to cutaneous wound infection, we developed a murine model of cutaneous Staphylococcus aureus wound infection in young (3-4 mo) and aged (18-20 mo) BALB/c mice. Aged mice exhibit increased bacterial colonization and delayed wound closure over time compared with young mice. These differences were not attributed to alterations in wound neutrophil or macrophage TLR2 or FcγRIII expression, or age-related changes in phagocytic potential and bactericidal activity. To evaluate the role of chemotaxis in our model, we first examined in vivo chemotaxis in the absence of wound injury to KC, a neutrophil chemokine. In response to a s.c. injection of KC, aged mice recruited fewer neutrophils at increasing doses of KC compared with young mice. This paralleled our model of wound infection, where diminished neutrophil and macrophage recruitment was observed in aged mice relative to young mice despite equivalent levels of KC, MIP-2, and MCP-1 chemokine levels at the wound site. This reduced leukocyte accumulation was also associated with lower levels of ICAM-1 in wounds from aged mice at early time points. These age-mediated defects in early neutrophil recruitment may alter the dynamics of the inflammatory phase of wound healing, impacting macrophage recruitment, bacterial clearance, and wound closure.

  17. Eukaryotic microorganisms in cold environments: examples from Pyrenean glaciers.

    PubMed

    García-Descalzo, Laura; García-López, Eva; Postigo, Marina; Baquero, Fernando; Alcazar, Alberto; Cid, Cristina

    2013-01-01

    Little is known about the viability of eukaryotic microorganisms preserved in icy regions. Here we report on the diversity of microbial eukaryotes in ice samples derived from four Pyrenean glaciers. The species composition of eukaryotic communities in these glaciers is unknown mostly because of the presence of a multi-year ice cap, and it is not clear whether they harbor the same populations. The recent deglaciation of these areas is allowing an easy access to glacial layers that correspond to the "Little Ice Age" although some isolated deposits are attributed to previous glacial cycles. In this study, we use molecular 18S rRNA-based approaches to characterize some of the microbial eukaryotic populations associated with Pyrenean glaciers. Firstly, we performed a chemical and microscopical characterization of ice samples. Secondly, molecular analyses revealed interesting protist genetic diversity in glaciers. In order to understand the microbial composition of the ice samples the eukaryotic communities resident in the glacial samples were examined by amplifying community DNA and constructing clone libraries with 18S rRNA primers. After removal of potential chimeric sequences and dereplication of identical sequences, phylogenetic analysis demonstrated that several different protists could be identified. Protist diversity was more phylum rich in Aneto and Monte Perdido glaciers. The dominant taxonomic groups across all samples (>1% of all sequences) were Viridiplantae and Rhizaria. Significant variations in relative abundances of protist phyla between higher and lower glaciers were observed. At the genus level, significant differences were also recorded for the dominant genera Chloromonas, Raphidonema, Heteromita, Koliella, and Bodomorpha. In addition, protist community structure showed significant differences between glaciers. The relative abundances of protist groups at different taxonomic levels correlated with the altitude and area of glaciers and with pH of ice

  18. Assessing volume change of tropical Peruvian glaciers from multi-temporal digital elevation models (DEMs)

    NASA Astrophysics Data System (ADS)

    Huh, K.; Mark, B. G.

    2012-12-01

    Although far smaller than large polar ice caps, mountain glaciers are significant contributors to sea level rise and tropical glaciers in particular are sources of critical water resources to regional societies. The glaciers in Cordillera Blanca, the Andes of Peru, hold important environmental and economic concerns of regional water supplies to communities in the arid western part of the country under continued global climate change. Yet steep relief and remote locations present challenges for measuring mass changes in tropical glaciers. Remotely sensed images provide feasible opportunities to measure glacier surface area changes. We use a combination of satellite and airborne remote sensing, digital photogrammetry and geospatial techniques to assess the surface area, volume and topographic changes of key glaciers in the Cordillera Blanca, Peru between 1962 and 2008. The intercomparison of digital elevation models (DEMs) from airborne Light Detection and Range (LiDAR) data of 2008, multispectral Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) of 2001-2008 and stereo-paired airborne photographs of 1962 for deriving elevation differences over time reveal the data quality to measure the volume loss in the area. The DEMs over non-glacier areas in the study sites were selected and differentially corrected Global Positioning System (dGPS) data points were used for comparison as well. The motivation of this study is to refine a surface area to volume scaling for tropical glaciers to enable extrapolation of more detailed inventory of glacier volume and water resources.

  19. Interpreting Terminus Fluctuations at Helheim Glacier, Southeast Greenland, through Modeling and Observations

    NASA Astrophysics Data System (ADS)

    Kehrl, L. M.; Joughin, I. R.; Shapero, D.

    2014-12-01

    Marine-terminating outlet glaciers are highly sensitive to changes at the ice-ocean boundary. Changes at the ice-ocean boundary (calving events, submarine melting) can alter the terminus position and thereby the stress balance. If the terminus retreats into deeper water, more of the driving stress must then be balanced by longitudinal stress gradients, which cause the glacier to speed up. This study combines satellite observations and modeling (Elmer/Ice) to investigate the relationship between glacier dynamics and terminus position at Helheim Glacier, southeast Greenland, from 2000-2014. Helheim Glacier retreated about 7 km from 2001-2005 as warm ocean water entered the nearby fjord. From 2005-2006, the glacier re-advanced by 3 km as a floating or near-floating ice tongue formed over the basal overdeepening in front of the glacier terminus. Since then, Helheim's terminus position has remained relatively stable, with terminus fluctuations of < 2 km. Our model experiments consider both large terminus fluctuations (> 2 km) associated with rapid retreat and small terminus fluctuations (< 500 m) associated with individual calving events. We run the model simulations with both a flowline and three-dimensional model to better constrain our uncertainties. Our results show that Helheim Glacier responds rapidly to changes in terminus position of more than a few hundred meters. Small terminus fluctuations can cause velocity variations that extend up to 30 km inland, which roughly corresponds with the spatial extent of the weak bed (20-40 kPa) underneath Helheim Glacier.

  20. Advance of East Antarctic outlet glaciers during the Hypsithermal: Implications for the volume state of the Antarctic ice sheet under global warming

    SciTech Connect

    Domack, E.W. ); Jull, A.J.T. ); Nakao, Seizo )

    1991-11-01

    The authors present the first circum-East Antarctic chronology for the Holocene, based on 17 radiocarbon dates generated by the accelerator method. Marine sediments form around East Antarctica contain a consistent, high-resolution record of terrigenous (ice-proximal) and biogenic (open-marine) sedimentation during Holocene time. This record demonstrates that biogenic sedimentation beneath the open-marine environment on the continental shelf has been restricted to approximately the past 4 ka, whereas a period of terrigenous sedimentation related to grounding line advance of ice tongues and ice shelves took place between 7 and 4 ka. An earlier period of open-marine (biogenic sedimentation) conditions following the late Pleistocene glacial maximum is recognized from the Prydz Bay (Ocean Drilling Program) record between 10.7 and 7.3 ka. Clearly, the response of outlet systems along the periphery of the East Antarctic ice sheet during the mid-Holocene was expansion. This may have been a direct consequence of climate warming during an Antarctic Hypsithermal. Temperature-accumulation relations for the Antarctic indicate that warming will cause a significant increase in accumulation rather than in ablation. Models that predict a positive mass balance (growth) of the Antarctic ice sheet under global warming are supported by the mid-Holocene data presented herein.

  1. Acetoacetate promotes the formation of fluorescent advanced glycation end products (AGEs).

    PubMed

    Bohlooli, Mousa; Ghaffari-Moghaddam, Mansour; Khajeh, Mostafa; Aghashiri, Zohre; Sheibani, Nader; Moosavi-Movahedi, Ali Akbar

    2016-12-01

    Acetoacetate (AA) is an important ketone body, which produces reactive oxygen species (ROS). Advanced glycation end products (AGEs) are defined as final products of glycation process whose production is influenced by the levels of ROS. The accumulation of AGEs in the body contributes to pathogenesis of many diseases including complications of diabetes, and Alzheimer's and Parkinson's disease. Here, we evaluated the impact of AA on production of AGEs upon incubation of human serum albumin (HSA) with glucose. The effect of AA on the AGEs formation of HSA was studied under physiological conditions after incubation with glucose for 35 days. The physical techniques including circular dichroism (CD) and fluorescence spectroscopy were used to assess the impact of AA on formation and structural changes of glycated HSA (GHSA). Our results indicated that the secondary and tertiary structural changes of GHSA were increased in the presence of AA. The fluorescence intensity measurements of AGEs also showed an increase in AGEs formation. Acetoacetate has an activator effect in formation of AGEs through ROS production. The presence of AA may result in enhanced glycation in the presence of glucose and severity of complications associated with accumulation of AGEs.

  2. The receptor for advanced glycation end products (RAGE) specifically recognizes methylglyoxal-derived AGEs.

    PubMed

    Xue, Jing; Ray, Rashmi; Singer, David; Böhme, David; Burz, David S; Rai, Vivek; Hoffmann, Ralf; Shekhtman, Alexander

    2014-05-27

    Diabetes-induced hyperglycemia increases the extracellular concentration of methylglyoxal. Methylglyoxal-derived hydroimidazolones (MG-H) form advanced glycation end products (AGEs) that accumulate in the serum of diabetic patients. The binding of hydroimidozolones to the receptor for AGEs (RAGE) results in long-term complications of diabetes typified by vascular and neuronal injury. Here we show that binding of methylglyoxal-modified albumin to RAGE results in signal transduction. Chemically synthesized peptides containing hydroimidozolones bind specifically to the V domain of RAGE with nanomolar affinity. The solution structure of an MG-H1-V domain complex revealed that the hydroimidazolone moiety forms multiple contacts with a positively charged surface on the V domain. The high affinity and specificity of hydroimidozolones binding to the V domain of RAGE suggest that they are the primary AGE structures that give rise to AGEs-RAGE pathologies.

  3. Linolenic acid prevents early and advanced glycation end-products (AGEs) modification of albumin.

    PubMed

    Prasanna, Govindarajan; Saraswathi, N T

    2017-02-01

    In this study, we report the protective effects of linolenic acid towards the formation of early (HbA1c) and advanced glycation end-products (AGEs) based on fluorescence, circular dichroism, confocal microscopy and molecular interaction studies. Linolenic acid was found to be a potent inhibitor of AGEs formed by both glucose and fructose. The HbA1c (early glycation product) level was found to be reduced to 7.4% when compared to glycated control (8.4%). Similarly, linolenic acid also inhibited the methylglyoxal mediated AGEs formation. Circular dichroism spectroscopy studies suggested that the protective effect of linolenic acid for the helical structure of albumin. The molecular interaction studies showed that linolenic acid interacts with arginine residues of albumin with high affinity. Results suggested linolenic acid to be a potent antiglycation compound and also it could be a better lead compound for AGE inhibition.

  4. Dating buried glacier ice using cosmogenic 3He in surface clasts: Theory and application to Mullins Glacier, Antarctica

    NASA Astrophysics Data System (ADS)

    Mackay, Sean L.; Marchant, David R.

    2016-05-01

    We develop a modeling framework to describe the accumulation of terrestrial cosmogenic 3He in Antarctic debris-covered glaciers. The framework helps quantify the expected range in cosmogenic-nuclide inventories for measured clasts at the surface of supraglacial debris. We first delineate the physical factors that impact clast movement within, and on top of, debris-covered glaciers, including the effects of (1) ice ablation, (2) erosion at the debris surface, and (3) stochastic geomorphic processes that impact clast movement within and on top of supraglacial debris; we then explicitly calculate the impact of each process in altering the total inventory of cosmogenic nuclides in surface clasts. Assuming basic elements of ice-dynamics and debris entrainment are known, the model results provide an estimate for the total accumulation of cosmogenic nuclides, as well as the expected range in nuclide inventories, for any clast at the surface of debris-covered glaciers. Because the values are quantified, the approach can be applied to help evaluate the robustness of existing and future cosmogenic datasets applied to these systems. As a test, we applied our model framework towards Mullins Glacier, a cold-based debris-covered alpine glacier in the Dry Valleys of Antarctica. Our simulated values for cosmogenic-nuclide inventories compare well with those previously measured from fifteen surface cobbles along Mullins Glacier (3He), both in terms of expected ranges and absolute values, and suggest that our model framework adequately incorporates most of the complicating factors that impact cosmogenic datasets for cold-based, debris-covered glaciers. Relating these cosmogenic-nuclide inventories to ice ages, the results show that ice within Mullins Glacier increases non-linearly, ranging from 12 ka to ∼220 ka in areas of active flow, to ≫1.6 Ma in areas of slow-moving-to-stagnant ice.

  5. Preliminary bathymetry of McCarty Fiord and Neoglacial changes of McCarty Glacier, Alaska

    USGS Publications Warehouse

    Post, Austin

    1980-01-01

    Preliminary bathymetry (at 1:20,000 scale) and other scientific studies of McCarty Fiord, Alaska, Conducted by the Research Vessel Growler in 1978, showed this 15 mile-long waterway to be a narrow, deeply scoured basin enclosed by a terminal-moraine shoal. This valley was formerly filled by McCarty Glacier, which began a drastic retreat shortly after 1909; the glacier reached shallow water at the head of the fiord around 1960. The relative rate of retreat in deep water and on land is disclosed by the slower melting of stagnent ice left in a side valley. Soundings and profiles show the main channel to extend to a depth as great as 957 feet and to have the typical ' U ' shape of a glacier-eroded valley; since the glacier 's retreat, sediments have formed a nearly level deposit in the deepest part of the fiord. Old forest debris dated by carbon-14 indicates that a neoglacial advance of the glacier began before 3,395 years B.P. (before present); by 1,500 B.P. the glacier filled most of the fiord, and before the glacier culminated its advance around 1860 , two glacier-dammed lakes were formed in side valleys. (USGS)

  6. The Photographic History of Greenland's Glaciers - and how the historical data plays an important role in today's glacier research

    NASA Astrophysics Data System (ADS)

    Bjork, A. A.; Kjeldsen, K. K.; Korsgaard, N. J.; Aagaard, S.; Andresen, C. S.; Bamber, J. L.; van den Broeke, M.; Colgan, W. T.; Funder, S.; Khan, S. A.; Larsen, N. K.; Machguth, H.; Nuth, C.; Schomacker, A.; Kjaer, K. H.

    2015-12-01

    As the Greenland Ice Sheet and Greenland's glaciers are continuing to loss mass at high rates, knowledge of their past response to climatic changes is ever important. By harvesting the archives for images, both terrestrial and airborne, we are able to expand the record of glacier observation by several decades, thus supplying crucial knowledge on glacier behavior to important climatic transitions such as the end of the Little Ice Age and the early 20th Century warming. Here we show how a large collection of historical aerial images portray the glacial response to the Little Ice Age deglaciation in Greenland and document frontal change throughout the 20th Century. A detailed story of the LIA-deglaciation is told by supplementing with terrestrial photos that capture the onset of retreat and high resolution aerial images that portray geomorphological evidence of the Little Ice Age maximum extent. This work is the result of several generations of Greenland researches and their efforts to portray and document the state of the glaciers, and highlights that while interpretations and conclusions may be challenged and changed through time, the raw observations remain extremely valuable. Finally, we also show how archival data besides photos may play an important role in future glacier research in Greenland.

  7. Angiogenic inhibitors for older patients with advanced colorectal cancer: Does the age hold the stage?

    PubMed Central

    Aprile, Giuseppe; Fontanella, Caterina; Lutrino, Eufemia Stefania; Ferrari, Laura; Casagrande, Mariaelena; Cardellino, Giovanni Gerardo; Rosati, Gerardo; Fasola, Gianpiero

    2013-01-01

    Although major progress has been achieved in the treatment of advanced colorectal cancer (CRC) with the employment of antiangiogenic agents, several questions remain on the use of these drugs in older patients. Since cardiovascular, renal and other comorbidities are common in the elderly, an accurate assessment of the patients’ conditions should be performed before a treatment decision is made. Since most CRC patients enrolled in clinical trials testing antiangiogenic drugs were aged < 65 years, the efficacy and tolerability of these agents in elderly patients has not been adequately explored. Data suggest that patients with advanced CRC derive similar benefit from bevacizumab treatment regardless of age, but the advantage of other antiangiogenic drugs in the same class of patients appears more blurred. Literature data suggest that specific antiangiogenic-related toxicities such as hypertension or arterial thromboembolic events may be higher in the elderly than in the younger patients. In addition, it should be emphasized that the patients included in the clinical studies discussed herein were selected and therefore may not be representative of the usual elderly population. Advanced age alone should not discourage the use of bevacizumab. However, a careful patients’ selection and watchful monitoring of toxicities are required to optimize the use of antiangiogenics in this population. PMID:23847406

  8. What happens after and during deglaciation? Some insight from observations at the largest glacier in Austria

    NASA Astrophysics Data System (ADS)

    Kellerer-Pirklbauer, Andreas; Avian, Michael; Lieb, Gerhard K.; Kaufmann, Viktor

    2014-05-01

    Pasterze Glacier is the largest glacier in Austria and the Eastern Alps. The glacier is located at the foot of Mt. Großglockner (3798 m a.s.l.), the highest peak in Austria, and is accessible rather easily by a high alpine road ending above the main glacier tongue. At present, the glacier covers an area of about 17 km2, has a length of 8.3 km, a maximum ice thickness of about 190 m and is characterized by two unequally sized glacier tongues. The main glacier tongue is c.4 km long and heavily covered by debris. Since the end of the Little Ice Age (LIA) at around AD 1850 this glacier receded by 2.1 km. During the last c.160 years the main glacier tongue lowered by some 250 m on average. The glacier surface flow velocity decreased substantially, i.e. for example by 32% between the time periods 2003-2006 and 2006-2009. Glacier recession revealed large areas of previously ice-buried bedrock as well as minerogenic and biogenic sediments. In this contribution we present a compendium of research results based on several projects related to pure proglacial but also paraglacial processes and landforms in the vicinity of the present glacier. We will discuss (a) rock slope adjustment processes and its causes influencing for instance the supraglacial debris cover of the main glacier tongue substantially, (b) landform dynamics in the outwash plain and adjacent slopes close to the present glacier terminus, (c) the role of dead-ice for the proglacial landsystem, (d) formation and rapid enlargement of rock outcrops within the ice-fall, and (e) related natural hazard aspects. A further aspect discussed here - which is rather particular for Pasterze Glacier - is the (e) biogenic material (peat lumps and wood fragments) which has been found in recently deglaciated terrain. This material provides valuable insight into past ecological, glaciological and climatological conditions. Further rapid back- and downwasting of this glacier is very likely due to lack of ice replenishment. The

  9. Safety and efficacy of vismodegib in patients aged ≥65 years with advanced basal cell carcinoma.

    PubMed

    Chang, Anne Lynn S; Lewis, Karl D; Arron, Sarah T; Migden, Michael R; Solomon, James A; Yoo, Simon; Day, Bann-Mo; McKenna, Edward F; Sekulic, Aleksandar

    2016-11-15

    Because many patients with unresectable basal cell carcinoma (BCC) are aged ≥65 years, this study explores the efficacy and safety of vismodegib in these patients with locally advanced (la) or metastatic (m) basal cell carcinoma (BCC) in the ERIVANCE BCC trial and the expanded access study (EAS).We compared patients aged ≥65 years to patients aged <65 years taking vismodegib 150 mg/day, using descriptive statistics for response and safety. Patients aged ≥65 years (laBCC/mBCC) were enrolled in ERIVANCE BCC (33/14) and EAS (27/26). Investigator-assessed best overall response rate in patients ≥65 and <65 years was 46.7%/35.7% and 72.7%/52.6% (laBCC/mBCC), respectively, in ERIVANCE BCC and 45.8%/33.3% and 46.9%/28.6%, respectively, in EAS. These differences were not clinically meaningful. Safety was similar in both groups, although those aged ≥65 years had a higher percentage of grade 3-5 adverse events than those aged <65 years. Vismodegib demonstrated similar clinical activity and adverse events regardless of age.

  10. Safety and efficacy of vismodegib in patients aged ≥65 years with advanced basal cell carcinoma

    PubMed Central

    Chang, Anne Lynn S.; Lewis, Karl D.; Arron, Sarah T.; Migden, Michael R.; Solomon, James A.; Yoo, Simon; Day, Bann-Mo; McKenna, Edward F.; Sekulic, Aleksandar

    2016-01-01

    Because many patients with unresectable basal cell carcinoma (BCC) are aged ≥65 years, this study explores the efficacy and safety of vismodegib in these patients with locally advanced (la) or metastatic (m) basal cell carcinoma (BCC) in the ERIVANCE BCC trial and the expanded access study (EAS).We compared patients aged ≥65 years to patients aged <65 years taking vismodegib 150 mg/day, using descriptive statistics for response and safety. Patients aged ≥65 years (laBCC/mBCC) were enrolled in ERIVANCE BCC (33/14) and EAS (27/26). Investigator-assessed best overall response rate in patients ≥65 and <65 years was 46.7%/35.7% and 72.7%/52.6% (laBCC/mBCC), respectively, in ERIVANCE BCC and 45.8%/33.3% and 46.9%/28.6%, respectively, in EAS. These differences were not clinically meaningful. Safety was similar in both groups, although those aged ≥65 years had a higher percentage of grade 3-5 adverse events than those aged <65 years. Vismodegib demonstrated similar clinical activity and adverse events regardless of age. PMID:27764798

  11. Water flow through temperate glaciers

    USGS Publications Warehouse

    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

  12. Sub-Antarctic glacier extensions in the Kerguelen region (49°S, Indian Ocean) over the past 24,000 years constrained by 36Cl moraine dating

    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.

  13. Detection of advanced glycation end products (AGEs) on human skin by in vivo confocal Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Martin, A. A.; Pereira, L.; Ali, S. M.; Pizzol, C. D.; Tellez, C. A.; Favero, P. P.; Santos, L.; da Silva, V. V.; Praes, C. E. O.

    2016-03-01

    The aging process involves the reduction in the production of the major components of skin tissue. During intrinsic aging and photoaging processes, in dermis of human skin, fibroblasts become senescent and have decreased activity, which produce low levels of collagen. Moreover, there is accumulation of advanced glycation end products (AGEs). AGEs have incidence in the progression of age-related diseases, principally in diabetes mellitus and in Alzheimer's diseases. AGEs causes intracellular damage and/or apoptosis leading to an increase of the free radicals, generating a crosslink with skin proteins and oxidative stress. The aim of this study is to detect AGEs markers on human skin by in vivo Confocal Raman spectroscopy. Spectra were obtained by using a Rivers Diagnostic System, 785 nm laser excitation and a CCD detector from the skin surface down to 120 μm depth. We analyzed the confocal Raman spectra of the skin dermis of 30 women volunteers divided into 3 groups: 10 volunteers with diabetes mellitus type II, 65-80 years old (DEW); 10 young healthy women, 20-33 years old (HYW); and 10 elderly healthy women, 65-80 years old (HEW). Pentosidine and glucosepane were the principally identified AGEs in the hydroxyproline and proline Raman spectral region (1000-800 cm-1), in the 1.260-1.320 cm-1 region assignable to alpha-helical amide III modes, and in the Amide I region. Pentosidine and glucosepane calculated vibrational spectra were performed through Density Functional Theory using the B3LYP functional with 3-21G basis set. Difference between the Raman spectra of diabetic elderly women and healthy young women, and between healthy elderly women and healthy young women were also obtained with the purpose of identifying AGEs Raman bands markers. AGEs peaks and collagen changes have been identified and used to quantify the glycation process in human skin.

  14. Advancing paternal age and offspring violent offending: A sibling-comparison study

    PubMed Central

    Kuja-Halkola, Ralf; Pawitan, Yudi; D’Onofrio, Brian M; Långström, Niklas; Lichtenstein, Paul

    2013-01-01

    Children born to older fathers are at higher risk to develop severe psychopathology (e.g., schizophrenia and bipolar disorder), possibly due to increased de novo mutations during spermatogenesis with older paternal age. Since severe psychopathology is correlated with antisocial behavior, we examined possible associations between advancing paternal age and offspring violent offending. Interlinked Swedish national registers provided information on fathers’ age at childbirth and violent criminal convictions in all offspring born 1958–1979 (n=2,359,921). We used ever committing a violent crime and number of violent crimes as indices of violent offending. The data included information on multiple levels; we compared differentially exposed siblings in within-family analyses to rigorously test causal influences. In the entire population, advancing paternal age predicted offspring violent crime according to both indices. Congruent with a causal effect, this association remained for rates of violent crime in within-family analyses. However, in within-analyses, we found no association with ever committing a violent crime, suggesting that factors shared by siblings (genes and environment) confounded this association. Life-course-persistent criminality has been proposed to have a partly biological etiology; our results agree with a stronger biological effect (i.e., de novo mutations) on persistent violent offending. PMID:22781852

  15. Self and identity in advanced old age: validation of theory through longitudinal case analysis.

    PubMed

    Coleman, P G; Ivani-Chalian, C; Robinson, M

    1999-10-01

    Case studies drawn from a 20-year longitudinal study of aging were examined for the support they provide to two theoretical viewpoints on the self in later life: one focusing on management of self-esteem, the other on development of identity as story. The five cases selected for scrutiny represented diverse trajectories of self-esteem. They furnished ample illustrations of certain key aspects of both theories, including assimilative processes of coping, depression related to absence of accommodation, maintenance of life story themes, and life review processes. They did not, however, give strong support to the dichotomy, drawn within both theoretical models, between younger and older old age. Examples of accommodation, disengagement, and self-transcendence, hypothesized to typify advanced old age, were relatively few in number and emerged only toward the very end of life. It is argued that examination of prototypical cases provides a useful approach to validating and developing theory. A conclusion drawn from this study is that more analysis should be carried out on the lives of persons who exemplify the theoretically ideal characteristics of advanced old age.

  16. Advancing paternal age and offspring violent offending: a sibling-comparison study.

    PubMed

    Kuja-Halkola, Ralf; Pawitan, Yudi; D'Onofrio, Brian M; Långström, Niklas; Lichtenstein, Paul

    2012-08-01

    Children born to older fathers are at higher risk to develop severe psychopathology (e.g., schizophrenia and bipolar disorder), possibly because of increased de novo mutations during spermatogenesis with older paternal age. Because severe psychopathology is correlated with antisocial behavior, we examined possible associations between advancing paternal age and offspring violent offending. Interlinked Swedish national registers provided information on fathers' age at childbirth and violent criminal convictions in all offspring born from 1958 to 1979 (N = 2,359,921). We used ever committing a violent crime and number of violent crimes as indices of violent offending. The data included information on multiple levels; we compared differentially exposed siblings in within-family analyses to rigorously test causal influences. In the entire population, advancing paternal age predicted offspring violent crime according to both indices. Congruent with a causal effect, this association remained for rates of violent crime in within-family analyses. However, in within-family analyses, we found no association with ever committing a violent crime, suggesting that factors shared by siblings (genes and environment) confounded this association. Life-course persistent criminality has been proposed to have a partly biological etiology; our results agree with a stronger biological effect (i.e., de novo mutations) on persistent violent offending.

  17. A structured approach to evaluating aging of the advanced test reactor

    SciTech Connect

    Dwight, J.E.

    1990-01-01

    An aging evaluation program has been developed for the United States Department of Energy's Advanced Test Reactor to support the current goal of operation through the year 2014 and beyond. The Aging Evaluation and Life Extension Program (AELEX) employs a three-phased approach. In Phases 1 and 2, now complete, components were identified, categorized and prioritized. Critical components were selected and aging mechanisms for the critical components identified. An initial evaluation of the critical components was performed and extended life operation for the plant appears to be both technically and economically feasible. Detailed evaluations of the critical components are now in progress in the early stages of Phase 3. Some results are available. Evaluations of many non-critical components and refinements to the program based on probabilistic risk assessment results will follow in later stages of Phase 3. 6 refs., 2 figs., 5 tabs.

  18. Advanced paternal age effects in neurodevelopmental disorders—review of potential underlying mechanisms

    PubMed Central

    Janecka, M; Mill, J; Basson, M A; Goriely, A; Spiers, H; Reichenberg, A; Schalkwyk, L; Fernandes, C

    2017-01-01

    Multiple epidemiological studies suggest a relationship between advanced paternal age (APA) at conception and adverse neurodevelopmental outcomes in offspring, particularly with regard to increased risk for autism and schizophrenia. Conclusive evidence about how age-related changes in paternal gametes, or age-independent behavioral traits affect neural development is still lacking. Recent evidence suggests that the origins of APA effects are likely to be multidimensional, involving both inherited predisposition and de novo events. Here we provide a review of the epidemiological and molecular findings to date. Focusing on the latter, we present the evidence for genetic and epigenetic mechanisms underpinning the association between late fatherhood and disorder in offspring. We also discuss the limitations of the APA literature. We propose that different hypotheses relating to the origins of the APA effects are not mutually exclusive. Instead, multiple mechanisms likely contribute, reflecting the etiological complexity of neurodevelopmental disorders. PMID:28140401

  19. Translating Advances from the Basic Biology of Aging into Clinical Application

    PubMed Central

    Kirkland, James L.

    2013-01-01

    Recently, lifespan and healthspan have been extended in experimental animals using interventions that are potentially translatable into humans. A great deal of thought and work are needed beyond the usual steps in drug development to advance these findings into clinical application. Realistic pre-clinical and clinical trials paradigms need to be devised. Focusing on subjects with symptoms of age-related diseases or frailty or who are at imminent risk of developing these problems, measuring effects on short-term, clinically relevant outcomes, as opposed to long-term outcomes such as healthspan or lifespan, and developing biomarkers and outcome measures acceptable to regulatory agencies will be important. Research funding is a major roadblock, as is lack of investigators with combined expertise in the basic biology of aging, clinical geriatrics, and conducting investigational new drug clinical trials. Options are reviewed for developing a path from the bench to the bedside for interventions that target fundamental aging processes. PMID:23237984

  20. Dendrochronology and late Holocene history of Bering piedmont glacier, Alaska

    USGS Publications Warehouse

    Wiles, G.C.; Post, A.; Muller, E.H.; Molnia, B.F.

    1999-01-01

    Fluctuations of the piedmont lobe of Bering Glacier and its sublobe Steller Glacier over the past two millennia are reconstructed using 34 radiocarbon dates and tree-ring data from 16 sites across the glaciers' forelands. The general sequence of glacial activity is consistent with well-dated fluctuations of tidewater and land-terminating glaciers elsewhere along the Gulf of Alaska. Extensive forested areas along 25 km of the Bering ice margin were inundated by glacio-lacustrine and glacio-fluvial sediments during a probable ice advance shortly before 500 cal yr A.D. Regrowth of forests followed the retreating ice as early as the 7th century A.D., with frequent interruptions of tree growth due to outwash aggradation. Forests overrun by ice and buried in outwash indicate readvance about 1080 cal yr A.D. Retreat followed, with ice-free conditions maintained along the distal portions of the forefield until the early 17th century after which the ice advanced to within a few kilometers of its outer Neoglacial moraine. Ice reached this position after the mid-17th century and prior to 200 yr ago. Since the early 20th century, glacial retreat has been punctuated by periodic surges. The record from forests overrun by the nonsurging Steller Lobe shows that this western ice margin was advancing by 1250 A.D., reaching near its outer moraine after 1420 cal yr A.D. Since the late 19th century, the lobe has dominantly retreated.

  1. Effects of advanced aging on the neural correlates of successful recognition memory

    PubMed Central

    Wang, Tracy H.; Kruggel, Frithjof; Rugg, Michael D.

    2009-01-01

    Functional neuroimaging studies have reported that the neural correlates of retrieval success (old>new effects) are larger and more widespread in older than in young adults. In the present study we investigated whether this pattern of age-related ‘over-recruitment’ continues into advanced age. Using functional magnetic resonance imaging (fMRI), retrieval-related activity from two groups (N = 18 per group) of older adults aged 84–96 yrs (‘old-old’) and 64–77 yrs (‘young-old’) was contrasted. Subjects studied a series of pictures, half of which were presented once, and half twice. At test, subjects indicated whether each presented picture was old or new. Recognition performance of the old-old subjects for twice-studied items was equivalent to that of the young-old subjects for once-studied items. Old>new effects common to the two groups were identified in several cortical regions, including medial and lateral parietal and prefrontal cortex. There were no regions where these effects were of greater magnitude in the old-old group, and thus no evidence of over-recruitment in this group relative to the young-old individuals. In one region of medial parietal cortex, effects were greater (and only significant) in the young-old group. The failure to find evidence of over-recruitment in the old-old subjects relative to the young-old group, despite their markedly poorer cognitive performance, suggests that age-related over-recruitment effects plateau in advanced age. The findings for the medial parietal cortex underscore the sensitivity of this cortical region to increasing age. PMID:19428399

  2. Maternal caloric restriction partially rescues the deleterious effects of advanced maternal age on offspring

    PubMed Central

    Gribble, Kristin E; Jarvis, George; Bock, Martha; Mark Welch, David B

    2014-01-01

    While many studies have focused on the detrimental effects of advanced maternal age and harmful prenatal environments on progeny, little is known about the role of beneficial non-Mendelian maternal inheritance on aging. Here, we report the effects of maternal age and maternal caloric restriction (CR) on the life span and health span of offspring for a clonal culture of the monogonont rotifer Brachionus manjavacas. Mothers on regimens of chronic CR (CCR) or intermittent fasting (IF) had increased life span compared with mothers fed ad libitum (AL). With increasing maternal age, life span and fecundity of female offspring of AL-fed mothers decreased significantly and life span of male offspring was unchanged, whereas body size of both male and female offspring increased. Maternal CR partially rescued these effects, increasing the mean life span of AL-fed female offspring but not male offspring and increasing the fecundity of AL-fed female offspring compared with offspring of mothers of the same age. Both maternal CR regimens decreased male offspring body size, but only maternal IF decreased body size of female offspring, whereas maternal CCR caused a slight increase. Understanding the genetic and biochemical basis of these different maternal effects on aging may guide effective interventions to improve health span and life span. PMID:24661622

  3. Advanced Glycation End Products (AGE) and Diabetes: Cause, Effect, or Both?

    PubMed Central

    Vlassara, Helen; Uribarri, Jaime

    2014-01-01

    Despite new and effective drug therapies, insulin resistance (IR), type 2 diabetes mellitus (T2D) and its complications remain major medical challenges. It is accepted that IR, often associated with over-nutrition and obesity, results from chronically elevated oxidant stress (OS) and chronic inflammation. Less acknowledged is that a major cause for this inflammation is excessive consumption of advanced glycation end products (AGEs) with the standard western diet. AGEs, which were largely thought as oxidative derivatives resulting from diabetic hyperglycemia, are increasingly seen as a potential risk for islet β-cell injury, peripheral IR and diabetes. Here we discuss the relationships between exogenous AGEs, chronic inflammation, IR, and T2D. We propose that under chronic exogenous oxidant AGE pressure the depletion of innate defense mechanisms is an important factor, which raises susceptibility to inflammation, IR, T2D and its complications. Finally we review evidence on dietary AGE restriction as a non-pharmacologic intervention, which effectively lowers AGEs, restores innate defenses and improves IR, thus, offering new perspectives on diabetes etiology and therapy. PMID:24292971

  4. Rapid, climate-driven changes in outlet glaciers on the Pacific coast of East Antarctica.

    PubMed

    Miles, B W J; Stokes, C R; Vieli, A; Cox, N J

    2013-08-29

    Observations of ocean-terminating outlet glaciers in Greenland and West Antarctica indicate that their contribution to sea level is accelerating as a result of increased velocity, thinning and retreat. Thinning has also been reported along the margin of the much larger East Antarctic ice sheet, but whether glaciers are advancing or retreating there is largely unknown, and there has been no attempt to place such changes in the context of localized mass loss or climatic or oceanic forcing. Here we present multidecadal trends in the terminus position of 175 ocean-terminating outlet glaciers along 5,400 kilometres of the margin of the East Antarctic ice sheet, and reveal widespread and synchronous changes. Despite large fluctuations between glaciers--linked to their size--three epochal patterns emerged: 63 per cent of glaciers retreated from 1974 to 1990, 72 per cent advanced from 1990 to 2000, and 58 per cent advanced from 2000 to 2010. These trends were most pronounced along the warmer western South Pacific coast, whereas glaciers along the cooler Ross Sea coast experienced no significant changes. We find that glacier change along the Pacific coast is consistent with a rapid and coherent response to air temperature and sea-ice trends, linked through the dominant mode of atmospheric variability (the Southern Annular Mode). We conclude that parts of the world's largest ice sheet may be more vulnerable to external forcing than recognized previously.

  5. Glacier Primitive Area, Wyoming

    SciTech Connect

    Granger, H.C.; Patten, L.L.

    1984-01-01

    A mineral survey of the Glacier Primitive Area and an adjoining area to the northwest was made in 1968 and 1969. The study area was mapped geologically, an aeromagnetic survey was made, a geochemical study was done, and known mineralized occurrences and claims were examined. Two localities were found to contain small concentrations of uranium and several samples displayed minor anomalies in base and precious metals. A probable resource potential for lead, molybdenum, arsenic, barium, fluorite, and uranium exists in the area near the Ross Lakes shear zone and a small area of probable uranium resource potential exists around the Dubois claims. The study area, in general, is believed to have little promise for the occurrence of additional mineral or energy resources.

  6. GLACIER PRIMITIVE AREA, WYOMING.

    USGS Publications Warehouse

    Granger, Harry C.; Patten, Lowell L.

    1984-01-01

    A mineral survey of the Glacier Primitive Area, Wyoming and an adjoining area to the northeast was made. The study area was mapped geologically, an aeromagnetic survey was made, a geochemical study was done, and known mineralized occurrences and claims were examined. Two localities were found to contain small concentrations of uranium and several samples displayed minor anomalies in base and precious metals. A probable resource potential for lead, molybdenum, arsenic, barium, fluorite, and uranium exists in the area near the Ross Lakes shear zone and a small area of probable uranium resource potential exists around the Dubois claims. The study area, in general, is believed to have little promise for the occurrence of additional mineral or energy resources.

  7. Beardmore Glacier proposals wanted

    NASA Astrophysics Data System (ADS)

    Proposals for research projects to be conducted in the upper Beardmore Glacier area of Antarctica during the 1985-1986 field season are being accepted by t h e National Science Foundation (NSF) through August 15. Later proposal submissions should be discussed with the appropriate program managers (see below).A temporary camp with helicopter support will be established in the region. Occupation by scientific parties will likely be between mid-November 1985 and mid-January 1986. Transportation in the field will be by UH1-N twin-engine Huey helicopters (with a range of approximately 185 km) and by motor toboggans. Satellite tent camps will be established within the range of the helicopters. The exact position of the main camp will be determined in November. Likely candidates, however, are Buckley Island Quadrangle, in the area of the Walcott Névé or the Bowden Névé, near Coalsack Bluff or Mount Sirius.

  8. New Cosmogenic Beryllium-10 Exposure-Age Limits on Terminal Moraines of the Last Glaciation in the Bear River Drainage, Uinta Mountains, Utah

    NASA Astrophysics Data System (ADS)

    Laabs, B. J.; Munroe, J. S.; Rosenbaum, J. G.; Refsnider, K. A.

    2006-12-01

    The Uinta Mountains were occupied by numerous glaciers during marine oxygen-isotope stage 2 (MIS 2). Reconstructions for the last glaciation reveal that central and eastern valleys in the Uintas contained discrete valley glaciers, many of which advanced beyond the mountain front. Cosmogenic exposure-age limits on two moraines in the south-central part of the range indicate that glaciers retreated from their maximum extents at 16.8 ± 0.7 ka (Munroe et al., 2006), up to 2000 years later than glaciers elsewhere in the Middle and Southern Rockies. These ages suggest that deglaciation of the Uintas was approximately synchronous with the hydrologic fall of Lake Bonneville (at ~16 cal. ka), which implies that glaciers and the lake responded to the same regional climatic forcing. Glacial reconstructions further indicate that glaciers in the western Uintas, nearest to the lake, had equilibrium-line altitudes as much as 600 m lower than glaciers farther east. This evidence suggests that Lake Bonneville may have amplified moisture in the western Uinta Mountains by providing lake-effect precipitation to valleys located immediately downwind. To further investigate this hypothesis, we acquired cosmogenic 10Be surface-exposure ages from a terminal moraine in the Bear River drainage in the northwestern Uinta Mountains. This valley was occupied by outlet glaciers of the Provo Ice Field (of Refsnider, 2006), which covered an area of about 685 km2 and drained via several valleys in the Uintas. Cosmogenic-exposure ages of moraine boulders range from 24.5 ± 2.5 ka to 19.0 ± 3.5 ka (± 2σ) with an error-weighted mean of 21.5 ± 1.4 ka (n = 7), which we interpret to represent a minimum age of deglaciation in the Bear River drainage. Radiocarbon ages of glacial flour in sediment from Bear Lake, a large lake downstream of the glaciated area, are generally consistent with cosmogenic-exposure ages and indicate that deglaciation began at about 24 cal. ka (Rosenbaum et al., 2005). When

  9. Oral squamous cell carcinoma among Yemenis: Onset in young age and presentation at advanced stage

    PubMed Central

    Al-Mohaya, Maha; Abdulhuq, Mahmoud; Al-Mandili, Ahmad; Al-Anazi, Yousef

    2012-01-01

    Objectives: Oral cancer represents a health burden worldwide. Up to 90% of oral cancer cases are squamous cell carcinomas (SCC). The data on oral SCC in Yemen are lacking. The objective of this study therefore was to describe and analyze the demographic, clinical and histological characteristics of Yemeni patients with oral SCC. Study Design: In this cross-sectional study, two sets of retrospective data for Yemeni cancer patients were obtained officially by two different registries. Patients with oral SCC were included. Their ages were dichotomized using 40 and 45 years alternately as individual cut-points for young and old patients. The patients` demographic, clinical and histological characteristics were statistically analyzed. Results: There were 457 Yemenis with oral SCC; 253 patients (55.4%) were men. The overall mean age was 58.15±14.11 years. The tongue was the most affected oral sub-site accounting for 53% of the reported cases. The well and moderately differentiated oral SCC accounted for 55.5% and 25.6% of the total cases respectively. Noteworthy, 62 patients (14%) were affected by the age of ?40; this increased to 105 patients (23%) aged ?45 years. Additionally, a high proportion of oral SCC patients (62%, 283) were diagnosed at advanced tumor stages (regional extension or metastasized). The distributions of histological grades and tumor stages in young and old patients were significantly different (P=0.006 and 0.026 respectively). Conclusion: The relative frequency of oral SCC among Yemeni young people is high. Unfortunately, most of oral SCC patients in Yemen were diagnosed at advanced stage. Key words:Oral squamous cell carcinoma, Yemen, young patients, advanced stage. PMID:24558559

  10. Timing of glacier fluctuations and trigger mechanisms in eastern Qinghai-Tibetan Plateau during the late Quaternary

    NASA Astrophysics Data System (ADS)

    Ou, XianJiao; Lai, ZhongPing; Zhou, ShangZhe; Zeng, LanHua

    2014-05-01

    It is highly debated whether glacial advances on the Qinghai-Tibetan Plateau (QTP) occurred as a response to temperature cooling, or whether they were forced by an increase in moisture brought by the intensive Indian summer monsoon. We here report a case study investigating this issue. Multiple moraine series in the Yingpu Valley, Queer Shan ranges of the Hengduan Mountains, and eastern QTP, provide an excellent archive for examining the timing and trigger mechanism of glacier fluctuations. Twenty-seven optically stimulated luminescence (OSL) samples of glacial sediments were collected from this valley. The quartz OSL ages show that the moraine series of Y-1, I, M and O were formed during the Late Holocene, Late Glacial, the global Last Glacial Maximum (LGM) and Marine Oxygen Isotope Stage (MIS) 3 (likely mid-MIS-3). The youngest Y-2 moraines probably formed during the Little Ice Age (LIA). The oldest H moraines formed before MIS-3. We found that glacial advances during the late Quaternary at the Yingpu Valley responded to cold stages or cold events rather than episodes of enhanced summer monsoon and moisture. As a result, glaciers in the monsoonal Hengduan Mountains were mainly triggered by changes in temperature. Millennial time scale temperature oscillations might have caused the multiple glacial advances.

  11. Impact of glacio-morphological parameters in the glacier change: A case study of parts of Western Himalaya, India.

    NASA Astrophysics Data System (ADS)

    Brahmbhatt, R.; Bahuguna, I. M.; Rathore, B. P.; Kulkarni, A. V.; Shah, R.

    2014-12-01

    The Himalayas possess one of the largest resources of snow and ice, which act as a huge freshwater reservoir. Monitoring the glaciers is important to assess the overall reservoir health. In last few decades the most of the mountainous glaciers have undergone negative mass balance and terminal recessions, unlike the advancing glaciers. In this investigation, glaciers of Western Himalaya have been monitored since 1962 and variability in retreat was identified within the region. Thus, further analysis about significant parameters was taken into account to understand the relationship between glacio-morphological factors and change in glacial area. Initially change in areal extent of glaciers was derived for two time frames (1962-2001/02 and 2001/02-2010/11). The study comprised of 324 glaciers for the monitoring period of 1962-2001/02. A loss in glacial area was observed as 11% for this period. Many of these glaciers (238) were further monitored between 2001/02 and 2010/11. These glaciers showed a loss of 1.1%. The annual deglaciation has been found higher during the period of 1962-2001/02, which means rate of melting is less in this region in latest decade. Another observation in deglaciation was found spatial and temporal variability in glaciers which was addressed using glacio-morphic parameters. Areal extent of glaciers was observed to be having significant role on rate of glacial shrinkage. The another important parameter is equilibrium line altitude, i.e. the glaciers located below ELA have experienced 4.6% of deglaciation for the time frame 2001/02 - 2010/11 where as it was found to be 1.1% for the glaciers occurring above ELA. Moreover, glaciers located at lower altitude and having gentle slope show more area retreat. The results of area retreat in debris covered and debris free glaciers supports that the glaciers covered by debris retard ice melting at some extent. 158 glaciers were observed having no debris cover which shows 14% of loss in surface area. In

  12. Morphology, sedimentology and stratigraphic implication of debris-covered glacier deposits from the LGM and Lateglacial (Eastern Alps, Austria)

    NASA Astrophysics Data System (ADS)

    Reitner, Jürgen M.; Seidl, Sabrina; Wagreich, Michael

    2013-04-01

    Understanding the genesis of Quaternary sediments is crucial for establishing a climato-stratigraphy and, further on, to infer paleoclimatic conditions, if possible. Especially diamictons in the high-mountain environment may be formed by variety of processes, i.e. glacial, periglacial and gravitational. On the other hand, the interpretation of morphological features might be ambiguous as for example ridges may document latero-frontal dump moraines, flow of a rock avalanche event or constituents of a rock-glacier. In addition, equilibrium line altitudes (ELAs) of paleo-glaciers are mostly based on calculations using the reconstructed glacier size and applying a more or less fixed accumulation area ration (e.g. AAR - method). However, such ELAs are of no use for stratigraphic correlations and climatic considerations, if the former glacial system was strongly influenced by supraglacial debris deriving from steep back walls of cirques. We present two examples of reconstructed debris-covered or more specifically debris-mantled paleo-glaciers, their geological and morphological setting as well as their documented sedimentology and morphology. The first example is from the easternmost part of the European Alps (Northern Calcareous Alps / Schneeberg mountains / Puchberg) where an up to 60 m high moraine systems of LGM age shows some striking morphological similarities with relict rock glacier. However, based especially on lithofacies analyses as well as on the lithology of the matrix a glacial genesis could be proven. Lateglacial glacier deposits from the interior of the Alps (Lienz Dolomites / area of Karlsbader Hütte) display a quite similar glacial system. The geometry of the deposits in relation to proglacial sturzstrom sediments, showing typical indications of dynamic fragmentation, and the amount of angular, passively transported clasts in the till point to a rock avalanche event which had hit the glacier surface during a glacier advance. As the glacial system shows

  13. Ice thickness estimations based on multi-temporal glacier inventories - potential and challenges

    NASA Astrophysics Data System (ADS)

    Helfricht, Kay; Huss, Matthias; Otto, Jan-Christoph

    2016-04-01

    only partly be reproduced by the model. This may be explained by differences in the dynamical state of the glacier among the considered periods with almost balanced mass balance conditions (GI1 - GI2) and strong disequilibrium (GI2 - GI3). Huss, M., and D. Farinotti (2012), Distributed ice thickness and volume of all glaciers around the globe, J. Geophys. Res., 117, F04010, doi:10.1029/2012JF002523. Fischer, A., Seiser, B., Stocker Waldhuber, M., Mitterer, C., and Abermann, J. (2015), Tracing glacier changes in Austria from the Little Ice Age to the present using a lidar-based high-resolution glacier inventory in Austria, The Cryosphere, 9, 753-766, doi:10.5194/tc-9-753-2015.

  14. Anthropogenic aerosols as a source of ancient dissolved organic matter in glaciers

    USGS Publications Warehouse

    Stubbins, Aron; Hood, Eran; Raymond, Peter A.; Aiken, George R.; Sleighter, Rachel L.; Hernes, Peter J.; Butman, David; Hatcher, Patrick G.; Striegl, Rob; Schuster, Paul F.; Abdulla, Hussain A.N.; Vermilyea, Andrew W.; Scott, Durelle T.; Spencer, Robert G.M.

    2012-01-01

    Glacier-derived dissolved organic matter represents a quantitatively significant source of ancient, yet highly bioavailable carbon to downstream ecosystems. This finding runs counter to logical perceptions of age–reactivity relationships, in which the least reactive material withstands degradation the longest and is therefore the oldest. The remnants of ancient peatlands and forests overrun by glaciers have been invoked as the source of this organic matter. Here, we examine the radiocarbon age and chemical composition of dissolved organic matter in snow, glacier surface water, ice and glacier outflow samples from Alaska to determine the origin of the organic matter. Low levels of compounds derived from vascular plants indicate that the organic matter does not originate from forests or peatlands. Instead, we show that the organic matter on the surface of the glaciers is radiocarbon depleted, consistent with an anthropogenic aerosol source. Fluorescence spectrophotometry measurements reveal the presence of protein-like compounds of microbial or aerosol origin. In addition, ultrahigh-resolution mass spectrometry measurements document the presence of combustion products found in anthropogenic aerosols. Based on the presence of these compounds, we suggest that aerosols derived from fossil fuel burning are a source of pre-aged organic matter to glacier surfaces. Furthermore, we show that the molecular signature of the organic matter is conserved in snow, glacier water and outflow, suggesting that the anthropogenic carbon is exported relatively unchanged in glacier outflows.

  15. Rock glacier development in the Northern Calcareous Alps at the Pleistocene-Holocene boundary

    NASA Astrophysics Data System (ADS)

    Moran, Andrew P.; Ivy Ochs, Susan; Vockenhuber, Christof; Kerschner, Hanns

    2016-11-01

    Relict rock glaciers provide information on past discontinuous permafrost and former mean annual air temperatures. A lack of records showing former permafrost distribution along the northern Alpine fringe prompted the investigation and numerical dating of a belt of relict rock glaciers in the Karwendel Mountains of the Northern Calcareous Austrian Alps. In two neighbouring cirques that were still glaciated during the early Younger Dryas, eleven 36Cl exposure ages from boulder surfaces were obtained. The ages imply the onset of rock glacier activity around 12.3 ka with subsequent stabilization and permafrost melt out no later than 10.1 ka. Hence, rock glacier formation coincided with glacier retreat in the cirques around the mid-Younger Dryas and continued into the early Holocene. As permafrost induced features, the rock glacier termini indicate the local past lower limit of discontinuous permafrost in open cirque floors at 2000 m asl, which is around 400 m lower than during the mid-twentieth century at comparable locations in the Karwendel Mountains. Thus, a mean annual air temperature reduction of - 2.6 to - 3.8 °C relative to the mid-twentieth century is inferred. Based on a minimum glacier equilibrium line altitude in the cirques, a summer temperature reduction of less than - 2.6 to - 1.8 °C is shown, suggesting an increased seasonality at the time of rock glacier activity.

  16. Advanced paternal age and childhood cancer in offspring: A nationwide register-based cohort study.

    PubMed

    Urhoj, Stine Kjaer; Raaschou-Nielsen, Ole; Hansen, Anne Vinkel; Mortensen, Laust Hvas; Andersen, Per Kragh; Nybo Andersen, Anne-Marie

    2017-03-03

    Cancer initiation is presumed to occur in utero for many childhood cancers and it has been hypothesized that advanced paternal age may have an impact due to the increasing number of mutations in the sperm DNA with increasing paternal age. We examined the association between paternal age and specific types of childhood cancer in offspring in a large nationwide cohort of 1,904,363 children born in Denmark from 1978 through 2010. The children were identified in the Danish Medical Birth Registry and were linked to information from other national registers, including the Danish Cancer Registry. In total, 3,492 children were diagnosed with cancer before the age of 15 years. The adjusted hazard ratio of childhood cancer according to paternal age was estimated using Cox proportional hazards regressions. We found a 13% (95% confidence interval: 4-23%) higher hazard rate for every 5 years advantage in paternal age for acute lymphoblastic leukemia, while no clear association was found for acute myeloid leukemia (hazard ratio pr. 5 years = 1.02, 95% confidence interval: 0.80-1.30). The estimates for neoplasms in the central nervous system suggested a lower hazard rate with higher paternal age (hazard ratio pr. 5 years = 0.92, 95% confidence interval: 0.84-1.01). No clear associations were found for the remaining childhood cancer types. The findings suggest that paternal age is moderately associated with a higher rate of childhood acute lymphoblastic leukemia, but not acute myeloid leukemia, in offspring, while no firm conclusions could be made for other specific cancer types.

  17. Age Disparity in Palliative Radiation Therapy Among Patients With Advanced Cancer

    SciTech Connect

    Wong, Jonathan; Xu, Beibei; Yeung, Heidi N.; Roeland, Eric J.; Martinez, Maria Elena; Le, Quynh-Thu; Mell, Loren K.; Murphy, James D.

    2014-09-01

    Purpose/Objective: Palliative radiation therapy represents an important treatment option among patients with advanced cancer, although research shows decreased use among older patients. This study evaluated age-related patterns of palliative radiation use among an elderly Medicare population. Methods and Materials: We identified 63,221 patients with metastatic lung, breast, prostate, or colorectal cancer diagnosed between 2000 and 2007 from the Surveillance, Epidemiology, and End Results (SEER)-Medicare linked database. Receipt of palliative radiation therapy was extracted from Medicare claims. Multivariate Poisson regression analysis determined residual age-related disparity in the receipt of palliative radiation therapy after controlling for confounding covariates including age-related differences in patient and demographic covariates, length of life, and patient preferences for aggressive cancer therapy. Results: The use of radiation decreased steadily with increasing patient age. Forty-two percent of patients aged 66 to 69 received palliative radiation therapy. Rates of palliative radiation decreased to 38%, 32%, 24%, and 14% among patients aged 70 to 74, 75 to 79, 80 to 84, and over 85, respectively. Multivariate analysis found that confounding covariates attenuated these findings, although the decreased relative rate of palliative radiation therapy among the elderly remained clinically and statistically significant. On multivariate analysis, compared to patients 66 to 69 years old, those aged 70 to 74, 75 to 79, 80 to 84, and over 85 had a 7%, 15%, 25%, and 44% decreased rate of receiving palliative radiation, respectively (all P<.0001). Conclusions: Age disparity with palliative radiation therapy exists among older cancer patients. Further research should strive to identify barriers to palliative radiation among the elderly, and extra effort should be made to give older patients the opportunity to receive this quality of life-enhancing treatment at the end

  18. 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

  19. Outlet glaciers of southeast Greenland: rapid, synchronised regional retreat at the start of the Holocene?

    NASA Astrophysics Data System (ADS)

    Dyke, L. M.; Hughes, A. L.; Murray, T.; Ródes

    2012-12-01

    We report new in-situ cosmogenic isotope (10Be) exposure dates from two major fjord systems in southeast (SE) Greenland. Low elevation erratic pairs from Kangerdlugssuaq Fjord reveal the onset of coastal deglaciation at ~11 ky BP. Overlapping exposure ages from a fjord axis transect show this was followed by a period of rapid deglaciation to a position at least 50 km from the mouth. The rapid deglaciation of Kangerdlugssuaq Fjord taken together with similar dates from Sermilik Fjord situated ~350 km southwards (Hughes et al., 2012), shows synchronous coastal deglaciation. This regional synchronicity implies a common regional driving mechanism. Ice sheet retreat from the continental shelf was underway by 15 ky BP, probably in response to long term climate amelioration following the Last Glacial Maximum (LGM). We suggest that the 'fjord phase' of deglaciation occurred rapidly due to significant climatic amelioration and changing oceanic conditions at the end of the Younger Dryas stadial. To test the synchronicity of regional deglaciation further, we will report exposure ages and retreat rates from Bernstorffs Isfjord, 650 km south of Kangerdlugssuaq and 300 km south of Sermilik Fjord. Bathymetric data and geomorphological evidence from Bernstorffs Isfjord hint at a still-stand or re-advance during the Holocene: exposure dates will be used to test this hypothesis. Widespread changes have been reported in the marine terminating glaciers of the southeast sector of the Greenland Ice Sheet (GrIS) during the early 2000s. Our results show retreat rates that are either significantly faster or persist for much longer than those observed recently, and demonstrate the great sensitivity of these marine-terminating glaciers to climatic change. References: Hughes, A.L.C., Rainsley, E., Murray T., Fogwill, C.J., Schnabel, C. and Xu, S. (2012) Rapid response of Helheim Glacier, southeast Greenland, to early Holocene climate warming. Geology, 40, 427-430.

  20. Revealing glacier flow and surge dynamics from animated satellite image sequences: examples from the Karakoram

    NASA Astrophysics Data System (ADS)

    Paul, F.

    2015-11-01

    Although animated images are very popular on the internet, they have so far found only limited use for glaciological applications. With long time series of satellite images becoming increasingly available and glaciers being well recognized for their rapid changes and variable flow dynamics, animated sequences of multiple satellite images reveal glacier dynamics in a time-lapse mode, making the otherwise slow changes of glacier movement visible and understandable to the wider public. For this study, animated image sequences were created for four regions in the central Karakoram mountain range over a 25-year time period (1990-2015) from freely available image quick-looks of orthorectified Landsat scenes. The animations play automatically in a web browser and reveal highly complex patterns of glacier flow and surge dynamics that are difficult to obtain by other methods. In contrast to other regions, surging glaciers in the Karakoram are often small (10 km2 or less), steep, debris-free, and advance for several years to decades at relatively low annual rates (about 100 m a-1). These characteristics overlap with those of non-surge-type glaciers, making a clear identification difficult. However, as in other regions, the surging glaciers in the central Karakoram also show sudden increases of flow velocity and mass waves travelling down glacier. The surges of individual glaciers are generally out of phase, indicating a limited climatic control on their dynamics. On the other hand, nearly all other glaciers in the region are either stable or slightly advancing, indicating balanced or even positive mass budgets over the past few decades.

  1. InSAR Observations and Finite Element Modeling of Crustal Deformation Around a Surging Glacier, Iceland

    NASA Astrophysics Data System (ADS)

    Spaans, K.; Auriac, A.; Sigmundsson, F.; Hooper, A. J.; Bjornsson, H.; Pálsson, F.; Pinel, V.; Feigl, K. L.

    2014-12-01

    Icelandic ice caps, covering ~11% of the country, are known to be surging glaciers. Such process implies an important local crustal subsidence due to the large ice mass being transported to the ice edge during the surge in a few months only. In 1993-1995, a glacial surge occurred at four neighboring outlet glaciers in the southwestern part of Vatnajökull ice cap, the largest ice cap in Iceland. We estimated that ~16±1 km3 of ice have been moved during this event while the fronts of some of the outlet glaciers advanced by ~1 km.Surface deformation associated with this surge has been surveyed using Interferometric Synthetic Aperture Radar (InSAR) acquisitions from 1992-2002, providing high resolution ground observations of the study area. The data show about 75 mm subsidence at the ice edge of the outlet glaciers following the transport of the large volume of ice during the surge (Fig. 1). The long time span covered by the InSAR images enabled us to remove ~12 mm/yr of uplift occurring in this area due to glacial isostatic adjustment from the retreat of Vatnajökull ice cap since the end of the Little Ice Age in Iceland. We then used finite element modeling to investigate the elastic Earth response to the surge, as well as confirm that no significant viscoelastic deformation occurred as a consequence of the surge. A statistical approach based on Bayes' rule was used to compare the models to the observations and obtain an estimate of the Young's modulus (E) and Poisson's ratio (v) in Iceland. The best-fitting models are those using a one-kilometer thick top layer with v=0.17 and E between 12.9-15.3 GPa underlain by a layer with v=0.25 and E from 67.3 to 81.9 GPa. Results demonstrate that InSAR data and finite element models can be used successfully to reproduce crustal deformation induced by ice mass variations at Icelandic ice caps.Fig. 1: Interferograms spanning 1993 July 31 to 1995 June 19, showing the surge at Tungnaárjökull (Tu.), Skaftárjökull (Sk.) and S

  2. Automating the implementation of an equilibrium profile model for glacier reconstruction in a GIS environment

    NASA Astrophysics Data System (ADS)

    Frew, Craig R.; Pellitero, Ramón; Rea, Brice R.; Spagnolo, Matteo; Bakke, Jostein; Hughes, Philip D.; Ivy-Ochs, Susan; Lukas, Sven; Renssen, Hans; Ribolini, Adriano

    2014-05-01

    Reconstruction of glacier equilibrium line altitudes (ELAs) associated with advance stages of former ice masses is widely used as a tool for palaeoclimatic reconstruction. This requires an accurate reconstruction of palaeo-glacier surface hypsometry, based on mapping of available ice-marginal landform evidence. Classically, the approach used to define ice-surface elevations, using such evidence, follows the 'cartographic method', whereby contours are estimated based on an 'understanding' of the typical surface form of contemporary ice masses. This method introduces inherent uncertainties in the palaeoclimatic interpretation of reconstructed ELAs, especially where the upper limits of glaciation are less well constrained and/or the age of such features in relation to terminal moraine sequences is unknown. An alternative approach is to use equilibrium profile models to define ice surface elevations. Such models are tuned, generally using basal shear stress, in order to generate an ice surface that reaches 'target elevations' defined by geomorphology. In areas where there are no geomorphological constraints for the former ice surface, the reconstruction is undertaken using glaciologiaclly representative values for basal shear stress. Numerical reconstructions have been shown to produce glaciologically "realistic" ice surface geometries, allowing for more objective and robust comparative studies at local to regional scales. User-friendly tools for the calculation of equilibrium profiles are presently available in the literature. Despite this, their use is not yet widespread, perhaps owing to the difficult and time consuming nature of acquiring the necessary inputs from contour maps or digital elevation models. Here we describe a tool for automatically reconstructing palaeo-glacier surface geometry using an equilibrium profile equation implemented in ArcGIS. The only necessary inputs for this tool are 1) a suitable digital elevation model and 2) mapped outlines of the

  3. Surface melt dominates Alaska glacier mass balance

    USGS Publications Warehouse

    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.

  4. Surface melt dominates Alaska glacier mass balance

    NASA Astrophysics Data System (ADS)

    Larsen, C. F.; Burgess, E.; Arendt, A. A.; O'Neel, S.; Johnson, A. J.; Kienholz, C.

    2015-07-01

    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.

  5. Successful aging: Advancing the science of physical independence in older adults.

    PubMed

    Anton, Stephen D; Woods, Adam J; Ashizawa, Tetso; Barb, Diana; Buford, Thomas W; Carter, Christy S; Clark, David J; Cohen, Ronald A; Corbett, Duane B; Cruz-Almeida, Yenisel; Dotson, Vonetta; Ebner, Natalie; Efron, Philip A; Fillingim, Roger B; Foster, Thomas C; Gundermann, David M; Joseph, Anna-Maria; Karabetian, Christy; Leeuwenburgh, Christiaan; Manini, Todd M; Marsiske, Michael; Mankowski, Robert T; Mutchie, Heather L; Perri, Michael G; Ranka, Sanjay; Rashidi, Parisa; Sandesara, Bhanuprasad; Scarpace, Philip J; Sibille, Kimberly T; Solberg, Laurence M; Someya, Shinichi; Uphold, Connie; Wohlgemuth, Stephanie; Wu, Samuel Shangwu; Pahor, Marco

    2015-11-01

    The concept of 'successful aging' has long intrigued the scientific community. Despite this long-standing interest, a consensus definition has proven to be a difficult task, due to the inherent challenge involved in defining such a complex, multi-dimensional phenomenon. The lack of a clear set of defining characteristics for the construct of successful aging has made comparison of findings across studies difficult and has limited advances in aging research. A consensus on markers of successful aging is furthest developed is the domain of physical functioning. For example, walking speed appears to be an excellent surrogate marker of overall health and predicts the maintenance of physical independence, a cornerstone of successful aging. The purpose of the present article is to provide an overview and discussion of specific health conditions, behavioral factors, and biological mechanisms that mark declining mobility and physical function and promising interventions to counter these effects. With life expectancy continuing to increase in the United States and developed countries throughout the world, there is an increasing public health focus on the maintenance of physical independence among all older adults.

  6. Ameliorating Effect of Akebia quinata Fruit Extracts on Skin Aging Induced by Advanced Glycation End Products.

    PubMed

    Shin, Seoungwoo; Son, Dahee; Kim, Minkyung; Lee, Seungjun; Roh, Kyung-Baeg; Ryu, Dehun; Lee, Jongsung; Jung, Eunsun; Park, Deokhoon

    2015-11-12

    The accumulation of free radicals and advanced glycation end products (AGEs) in the skin plays a very important role in skin aging. Both are known to interact with each other. Therefore, natural compounds or extracts that possess both antioxidant and antiglycation activities might have great antiageing potential. Akebia quinata fruit extract (AQFE) has been used to treat urinary tract inflammatory disease in traditional Korean and Chinese medicines. In the present study, AQFE was demonstrated to possess antioxidant and antiglycation activity. AQFE protects human dermal fibroblasts (HDFs) from oxidative stress and inhibits cellular senescence induced by oxidative stress. We also found that AQFE inhibits glycation reaction between BSA and glucose. The antiglycation activity of AQFE was dose-dependent. In addition, the antiglycation activity of AQFE was confirmed in a human skin explant model. AQFE reduced CML expression and stimulated fibrillin-1 expression in comparison to the methyglyoxal treatment. In addition, the possibility of the extract as an anti-skin aging agent has also been clinically validated. Our analysis of the crow's feet wrinkle showed that there was a decrease in the depth of deep furrows in RI treated with AQFE cream over an eight-week period. The overall results suggest that AQFE may work as an anti-skin aging agent by preventing oxidative stress and other complications associated with AGEs formation.

  7. Extracellular superoxide dismutase deficiency impairs wound healing in advanced age by reducing neovascularization and fibroblast function

    PubMed Central

    Fujiwara, Toshihiro; Duscher, Dominik; Rustad, Kristine C.; Kosaraju, Revanth; Rodrigues, Melanie; Whittam, Alexander J.; Januszyk, Michael; Maan, Zeshaan N.; Gurtner, Geoffrey C.

    2016-01-01

    Advanced age is characterized by impairments in wound healing, and evidence is accumulating that this may be due in part to a concomitant increase in oxidative stress. Extended exposure to reactive oxygen species (ROS) is thought to lead to cellular dysfunction and organismal death via the destructive oxidation of intra-cellular proteins, lipids and nucleic acids. Extracellular superoxide dismutase (ecSOD/SOD3) is a prime antioxidant enzyme in the extracellular space that eliminates ROS. Here, we demonstrate that reduced SOD3 levels contribute to healing impairments in aged mice. These impairments include delayed wound closure, reduced neovascularization, impaired fibroblast proliferation and increased neutrophil recruitment. We further establish that SOD3 KO and aged fibroblasts both display reduced production of TGF-β1, leading to decreased differentiation of fibroblasts into myofibroblasts. Taken together, these results suggest that wound healing impairments in ageing are associated with increased levels of ROS, decreased SOD3 expression and impaired extracellular oxidative stress regulation. Our results identify SOD3 as a possible target to correct age-related cellular dysfunction in wound healing. PMID:26663425

  8. Remote Sensing of Cryosphere: Estimation of Mass Balance Change in Himalayan Glaciers

    NASA Astrophysics Data System (ADS)

    Ambinakudige, Shrinidhi; Joshi, Kabindra

    2012-07-01

    Glacial changes are an important indicator of climate change. Our understanding mass balance change in Himalayan glaciers is limited. This study estimates mass balance of some major glaciers in the Sagarmatha National Park (SNP) in Nepal using remote sensing applications. Remote sensing technique to measure mass balance of glaciers is an important methodological advance in the highly rugged Himalayan terrain. This study uses ASTER VNIR, 3N (nadir view) and 3B (backward view) bands to generate Digital Elevation Models (DEMs) for the SNP area for the years 2002, 2003, 2004 and 2005. Glacier boundaries were delineated using combination of boundaries available in the Global land ice measurement (GLIMS) database and various band ratios derived from ASTER images. Elevation differences, glacial area, and ice densities were used to estimate the change in mass balance. The results indicated that the rate of glacier mass balance change was not uniform across glaciers. While there was a decrease in mass balance of some glaciers, some showed increase. This paper discusses how each glacier in the SNP area varied in its annual mass balance measurement during the study period.

  9. Constraining millennial scale dynamics of a Greenland tidewater glacier for the verification of a calving criterion based numerical model

    NASA Astrophysics Data System (ADS)

    Lea, J.; Mair, D.; Rea, B.; Nick, F.; Schofield, E.

    2012-04-01

    The ability to successfully model the behaviour of Greenland tidewater glaciers is pivotal to understanding the controls on their dynamics and potential impact on global sea level. However, to have confidence in the results of numerical models in this setting, the evidence required for robust verification must extend well beyond the existing instrumental record. Perhaps uniquely for a major Greenland outlet glacier, both the advance and retreat dynamics of Kangiata Nunata Sermia (KNS), Nuuk Fjord, SW Greenland over the last ~1000 years can be reasonably constrained through a combination of geomorphological, sedimentological and archaeological evidence. It is therefore an ideal location to test the ability of the latest generation of calving criterion based tidewater models to explain millennial scale dynamics. This poster presents geomorphological evidence recording the post-Little Ice Age maximum dynamics of KNS, derived from high-resolution satellite imagery. This includes evidence of annual retreat moraine complexes suggesting controlled rather than catastrophic retreat between pinning points, in addition to a series of ice dammed lake shorelines, allowing detailed interpretation of the dynamics of the glacier as it thinned and retreated. Pending ground truthing, this evidence will contribute towards the calibration of results obtained from a calving criterion numerical model (Nick et al, 2010), driven by an air temperature reconstruction for the KNS region determined from ice core data.

  10. Reconstructing Holocene glacier activity at Langfjordjøkelen, Arctic Norway, using multi-proxy fingerprinting of distal glacier-fed lake sediments

    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

  11. Glacier dynamics of the Pamir-Karakoram-Himalaya region over the last 40 years

    NASA Astrophysics Data System (ADS)

    Gourmelen, N.; Dehecq, A.; Trouvé, E.

    2014-12-01

    Climate warming over the 20th century has caused drastic changes in mountain glaciers globally, and of the Himalayan glaciers in particular. The stakes are high; glaciers and ice caps are the largest contributor to the increase in the mass of the world's oceans, and the Himalayas play a key role in the hydrology of the region, impacting on the economy, food safety and flood risk. Partial monitoring of the Himalayan glaciers has revealed a mixed picture; while many of the Himalayan glaciers are retreating, in some cases locally stable or advancing glaciers in this region have also been observed. But recent controversies have highlighted the need to understand the glaciers dynamic and its relationship with climate change in the region. Earth Observation provides a mean for global and long-term monitoring of mountain glaciers' dynamics. In the frame of the Dragon program, a partnership between the European Space Agency (ESA) and the Chinese Center for Earth Observation (NRSCC), we begun a monitoring program aimed at quantifying multidecadal changes in glaciers' flow at the scale of the entire Himalayas and Karakoram from a 40 years' archive of Earth Observation. Ultimately, the provision of a global and time-sensitive glaciers velocity product will help to understand the evolution of the Himalayan glaciers in lights of glaciological (e.g. presence of debris-cover, surges, proglacial lakes) and climatic conditions. Here we present a region-wide analysis of annual and seasonnal glacier flow velocity covering the Pamir-Karakoram-Himalaya region obtained from the analysis of the entire archive of Landsat data. Over 90% of the ice-covered regions, as defined by the Randolph Glacier Inventory, are measured, with precision on the retrieved velocity of the order of 2 m/yr. We show that the first order temporal evolution of glacier flow mirrors the pattern of glacier mass balance. We observe a general decrease of ice velocity in regions of known ice mass loss, and a more

  12. Southern Alaska Glaciers: Spatial and Temporal Variations in Ice Volume

    NASA Astrophysics Data System (ADS)

    Sauber, J.; Molnia, B. F.; Luthcke, S.; Rowlands, D.; Harding, D.; Carabajal, C.; Hurtado, J. M.; Spada, G.

    2004-12-01

    Although temperate mountain glaciers comprise less than 1% of the glacier-covered area on Earth, they are important because they appear to be melting rapidly under present climatic conditions and, therefore, make significant contributions to rising sea level. In this study, we use ICESat observations made in the last 1.5 years of southern Alaska glaciers to estimate ice elevation profiles, ice surface slopes and roughness, and bi-annual and/or annual ice elevation changes. We report initial results from the near coastal region between Yakutat Bay and Cape Suckling that includes the Malaspina and Bering Glaciers. We show and interpret ice elevations changes across the lower reaches of the Bagley Ice Valley for the period between October 2003 and May 2004. In addition, we use off-nadir pointing observations to reference tracks over the Bering and Malaspina Glaciers in order to estimate annual ice elevation change. Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) and Shuttle Radar Topography Mission (SRTM) derived DEMs are used to estimate across track regional slopes between ICESat data acquisitions. Although the distribution and quantity of ICESat elevation profiles with multiple, exact repeat data is currently limited in Alaska, individual ICESat data tracks, provide an accurate reference surface for comparison to other elevation data (e.g. ASTER and SRTM X- and C-band derived DEMs). Specifically we report the elevation change over the Malaspina Glacier's piedmont lobe between a DEM derived from SRTM C-band data acquired in Feb. 2000 and ICESat Laser #2b data from Feb.-March 2004. We also report use of ICESat elevation data to enhance ASTER derived absolute DEMs. Mountain glaciers generally have rougher surfaces and steeper regional slopes than the ice sheets for which the ICESat design was optimized. Therefore, rather than averaging ICESat observations over large regions or relying on crossovers, we are working with well-located ICESat

  13. Advanced glycation end products, oxidative stress and metalloproteinases are altered in the cerebral microvasculature during aging.

    PubMed

    Safciuc, Florentina; Constantin, Alina; Manea, Adrian; Nicolae, Manuela; Popov, Doina; Raicu, Monica; Alexandru, Dorin; Constantinescu, Elena

    2007-11-01

    Biological aging is associated with an increased incidence of cerebrovascular disease. Recent findings indicate that oxidative stress promoting age-related changes of cerebral circulation are involved in neurodegenerative disorders such as Alzheimer's disease (AD) and Parkinson's disease. The aim of this study was to evaluate the contribution of cerebral microvessels to the oxidative stress during brain aging, by: (i) assessment of precursors for advanced glycation end products (AGE) formation, (ii) activities of antioxidant enzymes, namely superoxide dismutase (SOD), glutathione peroxidase (GPx) and glutathione disulfide reductase (GR), and (iii) the activities of metalloproteinases (MMPs), MMP-2 and MMP-9, involved in synaptogenesis and memory consolidation. The experiments were performed on two groups of male Wistar rats: 15 young (3-6 months old) and 15 aged (18-24 months old) animals. The cerebral microvessels were isolated by mechanical homogenization, the concentration of protein carbonyls and the activity of antioxidant enzymes were evaluated by spectrophotometry, and gelatin SDS-PAGE zymography was employed to evaluate MMP-2 and MMP-9 activities. The results showed that, by comparison with young rats, aged brain microvessels contain: (i) approximately 106 % increase of protein carbonyls production; (ii) approximately 68% higher GPx activity, unmodified activities of SOD and GR; (iii) approximately 30% diminishment in MMP-2 activity, and the specific occurrence of MMP-9 enzyme. The data suggest that the age-related changes of microvessels could increase the propensity for cerebral diseases and might represent, at least in part, a prerequisite for the deterioration of mental and physical status in the elderly.

  14. Reconstruction of Equilibrium Line Altitudes of Nevado Coropuna Glaciers (Southern Peru) from the Late Pleistocene to the present

    NASA Astrophysics Data System (ADS)

    Úbeda, J.; Palacios, D.; Vázquez, L.

    2009-04-01

    The Nevado Coropuna (15°31'S-72°39'W) is a volcanic complex located 200 km NE of the city of Arequipa, in the Southern Peruvian Andes. The summit area in the complex is covered with a glacier system formed by dozens of branches descending in all directions totaling many km2 in surface area. The study of the volcanic complex and its glaciers is of great interest because it is the main water reserve for tens of thousands of people, because of the risk scenario created by the presence of ice masses on a volcano with relatively recent activity, and because it constitutes an excellent geoindicator of the effects of climate change on ice masses in the western mountain chain of the Central Andes. This research aims to analyze glacier evolution using as geoindicators variations in glacier surface and equilibrium line altitudes (ELAs), defining deglaciation rates based on those variations and preparing forecasts with them on when the ice masses might disappear if the same rates were to occur in the future. In addition, a first estimation is attempted of the chronologies of the last phase of volcanic activity and the last phase of maximum glacier advance that can be attributed to the Late Glacial or Last Glacial Maximum periods. To achieve these aims, digital topography with 50m contour interval, two orthophotos of the central section of the Coropuna complex (15-6-1955 and 21-10-1986), an ASTER satellite image (12-11-2007) and geomorphological mapping of the volcanic complex created in a previous phase of the research (Ubeda, 2007) were integrated into a Geographical Information System (GIS). The GIS was used to determine the global extent of the glacier system, and in more detail, that of two groups (NE and SE) in 1955, 1986 and 2007. Using the geomorphological cartography as a basis, the extent of the glaciers during their last advance in the Little Ice Age (LIA) and their last maximum advance were calculated. Next, surface areas for all phases were calculated using

  15. Effects of age, system experience, and navigation technique on driving with an advanced traveler information system.

    PubMed

    Dingus, T A; Hulse, M C; Mollenhauer, M A; Fleischman, R N; McGehee, D V; Manakkal, N

    1997-06-01

    This paper explores the effects of age, system experience, and navigation technique on driving, navigation performance, and safety for drivers who used TravTek, an Advanced Traveler Information System. The first two studies investigated various route guidance configurations on the road in a specially equipped instrumented vehicle with an experimenter present. The third was a naturalistic quasi-experimental field study that collected data unobtrusively from more than 1200 TravTek rental car drivers with no in-vehicle experimenter. The results suggest that with increased experience, drivers become familiar with the system and develop strategies for substantially more efficient and safer use. The results also showed that drivers over age 65 had difficulty driving and navigating concurrently. They compensated by driving slowly and more cautiously. Despite this increased caution, older drivers made more safety-related errors than did younger drivers. The results also showed that older drivers benefited substantially from a well-designed ATIS driver interface.

  16. Community patterns of the small riverine benthos within and between two contrasting glacier catchments.

    PubMed

    Eisendle-Flöckner, Ursula; Jersabek, Christian D; Kirchmair, Martin; Hashold, Kerstin; Traunspurger, Walter

    2013-09-01

    Ongoing glacial retreat is expected to lead to numerous changes in glacier-fed rivers. This study documents the development of community composition of the hitherto widely neglected micro- and meiobenthos (MMB: bacteria, fungi, algae, protists, and meiofauna) in glacier rivers in response to the distinct habitat conditions driven by different stages of (de)glacierization. Our model is based on the glacier catchments of the Möll River (MC) and Kleinelendbach stream (KC), in the Austrian Alps, with 60% and 25% glacierization and glacier retreats of 403 and 26 m, respectively, since 1998. Analyses of overall catchment diversity and resemblance patterns showed that neither intense glacierization nor rapid deglacierization were predominant MMB determinants. This was ascribed to the specific environmental conditions at the MC, where the rapidly retreating Pasterze glacier has formed a harsh unstable proglacial, but also a benign floodplain area, with the former suppressing and the latter supporting the structural development of the MMB. Comparisons of similarly aged riverine habitats of the MC proglacial and the KC main channel further evidenced developmental suppression of the MMB (64 taxa) by the rapidly retreating MC glacier, unlike the moderate glacial retreat in the KC (130 taxa). Habitat conditions interacting with melt periods explained the differences in MMB resemblance patterns, which themselves differentially reflected the spatiotemporal habitat settings imposed by the different glacier activities. The varying glacial influences were represented by a glaciality index (GIm) based on water temperature, electrical conductivity, and stream bed stability. The taxonomic richness of nematodes, rotifers, algae, and diatoms was distinctly related to this index, as were most MMB abundances. However, the strongest relationships to the GIm were those of nematode abundances and maturity. Our observations highlight the intense response of the MMB to ongoing glacier retreat

  17. Modelling Greenland Outlet Glaciers

    NASA Technical Reports Server (NTRS)

    vanderVeen, Cornelis; Abdalati, Waleed (Technical Monitor)

    2001-01-01

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

  18. Maximum extent of Late Pleistocene glaciers and last deglaciation of La Cerdanya mountains, Southeastern Pyrenees

    NASA Astrophysics Data System (ADS)

    Palacios, David; Gómez-Ortiz, Antonio; Andrés, Nuria; Vázquez-Selem, Lorenzo; Salvador-Franch, Ferran; Oliva, Marc

    2015-02-01

    This paper examines glacial evolution in the La Pera and Malniu cirques, and Arànser, La Llosa and Duran valleys, in the Cerdanya massifs on the south-facing slopes of the eastern Pyrenees. A geomorphologic analysis and dating of moraine boulders, glacially polished bedrock and rock glacier blocks were carried out by means of cosmogenic 36Cl surface exposure dating. The maximum ice advance was contemporary with the Last Glacial Maximum at 23 ka ago, and it was of greater or only slightly lesser magnitude than for previous Quaternary advances. The termini of glaciers remained close to maximum positions, with minor advances and retreats until 18-17 ka when the glacial tongues disappeared from the valleys. Depending on the previous topography, these glaciers left behind a single polygenic moraine, in the case of confined valleys, or multiple moraines next to each other in the case of flat, more open areas. A final glacial advance is detected during the Oldest Dryas close to the cirque headwalls, and the glaciers finally disappeared during the Bølling interstadial. The glaciers were then replaced by rock glaciers, whose front immediately became inactive, although their activity continued near their source area until the early Holocene.

  19. Rapid Holocene thinning of an East Antarctic outlet glacier driven by marine ice sheet instability

    PubMed Central

    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

  20. Rapid Holocene thinning of an East Antarctic outlet glacier driven by marine ice sheet instability.

    PubMed

    Jones, R S; Mackintosh, A N; Norton, K P; Golledge, N R; Fogwill, C J; Kubik, P W; Christl, M; Greenwood, S L

    2015-11-26

    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.

  1. Decreased resting-state connections within the visuospatial attention-related network in advanced aging.

    PubMed

    Li, Yujie; Li, Chunlin; Wu, Qiong; Xu, Zhihan; Kurata, Tomoko; Ohno, Seiichiro; Kanazawa, Susumu; Abe, Koji; Wu, Jinglong

    2015-06-15

    Advanced aging is accompanied by a decline in visuospatial attention. Previous neuroimaging and electrophysiological studies have demonstrated dysfunction in specific brain areas related to visuospatial attention. However, it is still unclear how the functional connectivity between brain regions causes the decline of visuospatial attention. Here, we combined task and rest functional magnetic resonance imaging (fMRI) to investigate the age-dependent alterations of resting-state functional connectivity within the task-related network. Twenty-three young subjects and nineteen elderly subjects participated in this study, and a modified Posner paradigm was used to define the region of interest (ROI). Our results showed that a marked reduction in the number of connections occurred with age, but this effect was not uniform throughout the brain: while there was a significant loss of communication in the anterior portion of the brain and between the anterior and posterior cerebral cortices, communication in the posterior portion of the brain was preserved. Moreover, the older adults exhibited weakened resting-state functional connectivity between the supplementary motor area and left anterior insular cortex. These findings suggest that, the disrupted functional connectivity of the brain network for visuospatial attention that occurs during normal aging may underlie the decline in cognitive performance.

  2. Successful Aging: Advancing the Science of Physical Independence in Older Adults

    PubMed Central

    Anton, Stephen D.; Woods, Adam J.; Ashizawa, Tetso; Barb, Diana; Buford, Thomas W.; Carter, Christy S.; Clark, David J.; Cohen, Ronald A.; Corbett, Duane B.; Cruz-Almeida, Yenisel; Dotson, Vonetta; Ebner, Natalie; Efron, Philip A.; Fillingim, Roger B.; Foster, Thomas C.; Gundermann, David M.; Joseph, Anna-Maria; Karabetian, Christy; Leeuwenburgh, Christiaan; Manini, Todd M.; Marsiske, Michael; Mankowski, Robert T.; Mutchie, Heather L.; Perri, Michael G.; Ranka, Sanjay; Rashidi, Parisa; Sandesara, Bhanuprasad; Scarpace, Philip J.; Sibille, Kimberly T.; Solberg, Laurence M.; Someya, Shinichi; Uphold, Connie; Wohlgemuth, Stephanie; Wu, Samuel Shangwu; Pahor, Marco

    2015-01-01

    The concept of ‘Successful Aging’ has long intrigued the scientific community. Despite this long-standing interest, a consensus definition has proven to be a difficult task, due to the inherent challenge involved in defining such a complex, multi-dimensional phenomenon. The lack of a clear set of defining characteristics for the construct of successful aging has made comparison of findings across studies difficult and has limited advances in aging research. The domain in which consensus on markers of successful aging is furthest developed is the domain of physical functioning. For example, walking speed appears to be an excellent surrogate marker of overall health and predicts the maintenance of physical independence, a cornerstone of successful aging. The purpose of the present article is to provide an overview and discussion of specific health conditions, behavioral factors, and biological mechanisms that mark declining mobility and physical function and promising interventions to counter these effects. With life expectancy continuing to increase in the United States and developed countries throughout the world, there is an increasing public health focus on the maintenance of physical independence among all older adults. PMID:26462882

  3. DNA methylation errors in cloned mice disappear with advancement of aging.

    PubMed

    Senda, Sho; Wakayama, Teruhiko; Arai, Yoshikazu; Yamazaki, Yukiko; Ohgane, Jun; Tanaka, Satoshi; Hattori, Naka; Yanagimachi, Ryuzo; Shiota, Kunio

    2007-01-01

    Cloned animals have various health problems. Aberrant DNA methylation is a possible cause of the problems. Restriction landmark genomic scanning (RLGS) that enabled us to analyze more than 1,000 CpG islands simultaneously demonstrated that all cloned newborns had aberrant DNA methylation. To study whether this aberration persists throughout the life of cloned individuals, we examined genome-wide DNA methylation status of newborn (19.5 dpc, n=2), adult (8-11 months old, n=3), and aged (23-27 months old, n=4) cloned mice using kidney cells as representatives. In the adult and aged groups, cloning was repeated using cumulus cells of the adult founder clone of each group as nucleus donor. Two newborn clones had three with aberrantly methylated loci, which is consistent with previous reports that all cloned newborns had DNA methylation aberrations. Interestingly, we could detect only one aberrantly methylated locus in two of the three adult clones in mid-age and none of four senescent clones, indicating that errors in DNA methylation disappear with advancement of animals' aging.

  4. Failure to Modulate Attentional Control in Advanced Aging Linked to White Matter Pathology

    PubMed Central

    Van Dijk, Koene R. A.; Shire, Emily H.; Sperling, Reisa A.; Johnson, Keith A.; Buckner, Randy L.

    2012-01-01

    Advanced aging is associated with reduced attentional control and less flexible information processing. Here, the origins of these cognitive effects were explored using a functional magnetic resonance imaging task that systematically varied demands to shift attention and inhibit irrelevant information across task blocks. Prefrontal and parietal regions previously implicated in attentional control were recruited by the task and most so for the most demanding task configurations. A subset of older individuals did not modulate activity in frontal and parietal regions in response to changing task requirements. Older adults who did not dynamically modulate activity underperformed their peers and scored more poorly on neuropsychological measures of executive function and speed of processing. Examining 2 markers of preclinical pathology in older adults revealed that white matter hyperintensities (WMHs), but not high amyloid burden, were associated with failure to modulate activity in response to changing task demands. In contrast, high amyloid burden was associated with alterations in default network activity. These results suggest failure to modulate frontal and parietal activity reflects a disruptive process in advanced aging associated with specific neuropathologic processes. PMID:21765181

  5. From Glaciers to Icebergs

    NASA Astrophysics Data System (ADS)

    Zhang, Wendy

    I will describe works from a collaboration between physics and glaciology that grew out of interactions at the Computations in Science seminar Leo Kadanoff organized at the University of Chicago. The first project considers the interaction between ocean waves and Antarctic ice shelves, large floating portions of ice formed by glacial outflows. Back-of-envelop calculation and seismic sensor data suggest that crevasses may be distributed within an ice shelf to shield it from wave energy. We also examine numerical scenarios in which changes in environmental forcing causes the ice shelf to fail catastrophically. The second project investigates the aftermath of iceberg calving off glacier terminus in Greenland using data recorded via time-lapse camera and terrestrial radar. Our observations indicate that the mélange of icebergs within the fjord experiences widespread jamming during a calving event and therefore is always close to being in a jammed state during periods of terminus quiescence. Joint work with Jason Amundson, Ivo R. Peters, Julian Freed Brown, Nicholas Guttenberg, Justin C Burton, L. Mac Cathles, Ryan Cassotto, Mark Fahnestock, Kristopher Darnell, Martin Truffer, Dorian S. Abbot and Douglas MacAyeal. Kadanoff Session DCMP.

  6. The Neoglacial landscape and human history of Glacier Bay, Glacier Bay National Park and Preserve, southeast Alaska, USA

    USGS Publications Warehouse

    Connor, C.; Streveler, G.; Post, A.; Monteith, D.; Howell, W.

    2009-01-01

    The Neoglacial landscape of the Huna Tlingit homeland in Glacier Bay is recreated through new interpretations of the lower Bay's fjordal geomorphology, late Quaternary geology and its ethnographic landscape. Geological interpretation is enhanced by 38 radiocarbon dates compiled from published and unpublished sources, as well as 15 newly dated samples. Neoglacial changes in ice positions, outwash and lake extents are reconstructed for c. 5500?????"200 cal. yr ago, and portrayed as a set of three landscapes at 1600?????"1000, 500?????"300 and 300?????"200 cal. yr ago. This history reveals episodic ice advance towards the Bay mouth, transforming it from a fjordal seascape into a terrestrial environment dominated by glacier outwash sediments and ice-marginal lake features. This extensive outwash plain was building in lower Glacier Bay by at least 1600 cal. yr ago, and had filled the lower bay by 500 cal. yr ago. The geologic landscape evokes the human-described landscape found in the ethnographic literature. Neoglacial climate and landscape dynamism created difficult but endurable environmental conditions for the Huna Tlingit people living there. Choosing to cope with environmental hardship was perhaps preferable to the more severely deteriorating conditions outside of the Bay as well as conflicts with competing groups. The central portion of the outwash plain persisted until it was overridden by ice moving into Icy Strait between AD 1724?????"1794. This final ice advance was very abrupt after a prolonged still-stand, evicting the Huna Tlingit from their Glacier Bay homeland. ?? 2009 SAGE Publications.

  7. Strong ELA increase causes fast mass loss of glaciers in central Spitsbergen

    NASA Astrophysics Data System (ADS)

    Małecki, J.

    2015-11-01

    Svalbard is a heavily glacier covered archipelago in the Arctic. Its central regions, including Dickson Land (DL), are occupied by small alpine glaciers, which post-Little Ice Age (LIA) changes remain only sporadically investigated. This study presents a comprehensive analysis of glacier changes in DL based on inventories compiled from topographic maps and digital elevation models (DEMs) for LIA, 1960's, 1990 and 2009/11. The 37.9 ± 12.1 % glacier area decrease in DL (i.e. from 334.1 ± 38.4 km2 during LIA to 207.4 ± 4.6 km2 in 2009/11) has been primarily caused by accelerating termini retreat. The mean 1990-2009/11 geodetic mass balance of glaciers was -0.70 ± 0.06 m a-1 (-0.63 ± 0.05 m w.e. a-1), being one of the most negative from Svalbard regional means known from the literature. If the same figure was to be applied for other similar regions of central Spitsbergen, that would result in a considerable contribution to total Svalbard mass balance despite negligible proportion to total glacier area. Glacier changes in Dickson Land were linked to dramatic equilibrium line altitude (ELA) shift, which in the period 1990-2009/11 has been located ca. 500 m higher than required for steady-state. The mass balance of central Spitsbergen glaciers seems to be therefore more sensitive to climate change than previously thought.

  8. Biogeochemically diverse organic matter in Alpine glaciers and its downstream fate

    NASA Astrophysics Data System (ADS)

    Singer, Gabriel A.; Fasching, Christina; Wilhelm, Linda; Niggemann, Jutta; Steier, Peter; Dittmar, Thorsten; Battin, Tom J.

    2012-10-01

    Besides their role in the hydrological cycle, glaciers could play an important role in the carbon cycle. They store and transform organic carbon, which on release could support downstream microbial life. Yet the origin and composition of glacial organic carbon, and its implications for the carbon cycle, remain unclear. Here, we examine the molecular composition, radiocarbon age and bioavailability of dissolved organic matter (DOM) in 26 glaciers in the European Alps, using ultrahigh-resolution mass spectrometry, fluorescence spectroscopy and incubation experiments. We also measure carbon dioxide partial pressures in glacier-fed streams. We show that the glacier organic matter is highly diverse, and that a significant fraction of this material is bioavailable. Phenolic compounds derived from vascular plants or soil dominate, together with peptides and lipids, potentially derived from in situ microbial communities. Combustion products, in contrast, seem to contribute only marginally to the DOM sampled. We further show that organic matter bioavailability is positively correlated with in-stream carbon dioxide concentrations. We suggest that glacier-derived DOM contributes to downstream carbon cycling in glacier-fed streams. Our findings highlight the relevance of mountain glaciers for carbon cycling--a role that may change as glaciers recede.

  9. Columbia Glacier, Alaska, 1986-2011

    NASA Video Gallery

    The Columbia Glacier in Alaska is one of many vanishing around the world. Glacier retreat is one of the most direct and understandable effects of climate change. The consequences of the decline in ...

  10. Erosion by an Alpine glacier

    NASA Astrophysics Data System (ADS)

    Herman, Frédéric; Beyssac, Olivier; Lane, Stuart; Brughelli, Mattia; Leprince, Sebastien; Brun, Fanny

    2015-04-01

    Most mountain ranges on Earth owe their morphology to the action of glaciers and icecaps over the last few million years. Our current understanding of how glaciers have modified mountainous landforms has mainly been driven through landscape evolution models. These have included an array of erosion laws and mainly progressed through the implementation of various levels of sophistication regarding ice dynamics, subglacial hydrology or thermodynamics of water flow. However, the complex nature of the erosion processes involved and the difficulty of directly examining the ice-bedrock interface of contemporary glaciers has precluded the establishment of a prevailing erosion theory. Here we quantify the spatial variations in ice sliding velocity and erosion rate of a fast-flowing Alpine glacier in New Zealand during a 5-month period. By combining high resolution 3D measurements of surface velocity from optical satellite imagery with the quantification of both the production and provenance of sediments by the glacier, we show that erosion rates are proportional to sliding velocity raised to a power of about two. This result is consistent with abrasion theory. Given that the ice sliding velocity is a nonlinear function of ice thickness and ice surface slope, the response of glacial erosion to precipitation changes is highly nonlinear. Finally, our ability to constrain the glacial abrasion law present opportunities to further examine the interaction between glaciation and mountain evolution.

  11. Radiocarbon dating of glacier ice: overview, optimisation, validation and potential

    NASA Astrophysics Data System (ADS)

    Uglietti, Chiara; Zapf, Alexander; Jenk, Theo Manuel; Sigl, Michael; Szidat, Sönke; Salazar, Gary; Schwikowski, Margit

    2016-12-01

    High-altitude glaciers and ice caps from midlatitudes and tropical regions contain valuable signals of past climatic and environmental conditions as well as human activities, but for a meaningful interpretation this information needs to be placed in a precise chronological context. For dating the upper part of ice cores from such sites, several relatively precise methods exist, but they fail in the older and deeper parts, where plastic deformation of the ice results in strong annual layer thinning and a non-linear age-depth relationship. If sufficient organic matter such as plant, wood or insect fragments were found, radiocarbon (14C) analysis would have thus been the only option for a direct and absolute dating of deeper ice core sections. However such fragments are rarely found and, even then, they would not be very likely to occur at the desired depth and resolution. About 10 years ago, a new, complementary dating tool was therefore introduced by our group. It is based on extracting the µg-amounts of the water-insoluble organic carbon (WIOC) fraction of carbonaceous aerosols embedded in the ice matrix for subsequent 14C dating. Since then this new approach has been improved considerably by reducing the measurement time and improving the overall precision. Samples with ˜ 10 µg WIOC mass can now be dated with reasonable uncertainty of around 10-20 % (variable depending on sample age). This requires about 300 to 800 g of ice for WIOC concentrations typically found in midlatitude and low-latitude glacier ice. Dating polar ice with satisfactory age precision is still not possible since WIOC concentrations are around 1 order of magnitude lower. The accuracy of the WIOC 14C method was validated by applying it to independently dated ice. With this method, the deepest parts of the ice cores from Colle Gnifetti and the Mt Ortles glacier in the European Alps, Illimani glacier in the Bolivian Andes, Tsambagarav ice cap in the Mongolian Altai, and Belukha glacier

  12. Evaluating the timing of former glacier expansions in the Tian Shan: A key step towards robust spatial correlations

    NASA Astrophysics Data System (ADS)

    Blomdin, R.; Stroeven, A. P.; Harbor, J. M.; Lifton, N. A.; Heyman, J.; Gribenski, N.; Petrakov, D. A.; Caffee, M. W.; Ivanov, M. N.; Hättestrand, C.; Rogozhina, I.; Usubaliev, R.

    2016-12-01

    The timing of past glaciation across the Tian Shan provides a proxy for past climate change in this critical area. Correlating glacial stages across the region is difficult but cosmogenic exposure ages have considerable potential. A drawback is the large observed scatter in 10Be surface exposure data. To quantify the robustness of the dating, we compile, recalculate, and perform statistical analyses on sets of 10Be surface exposure ages from 25 moraines, consisting of 114 new and previously published ages. We assess boulder age scatter by dividing boulder groups into quality classes and rejecting boulder groups of poor quality. This allows us to distinguish and correlate robustly dated glacier limits, resulting in a more conservative chronology than advanced in previous publications. Our analysis shows that only one regional glacial stage can be reliably correlated across the Tian Shan, with glacier expansions occurring between 15 and 28 ka during marine oxygen isotope stage (MIS) 2. However, there are examples of older more extensive indicators of glacial stages between MIS 3 and MIS 6. Paleoglacier extent during MIS 2 was mainly restricted to valley glaciation. Local deviations occur: in the central Kyrgyz Tian Shan paleoglaciers were more extensive and we propose that the topographic context explains this pattern. Correlation between glacial stages prior to late MIS 2 is less reliable, because of the low number of samples and/or the poor resolution of the dating. With the current resolution and spatial coverage of robustly-dated glacier limits we advise that paleoclimatic implications for the Tian Shan glacial chronology beyond MIS 2 are speculative and that continued work toward robust glacial chronologies is needed to resolve questions regarding drivers of past glaciation in the Tian Shan and Central Asia.

  13. Current state of glaciers in the tropical Andes: a multi-century perspective on glacier evolution and climate change

    NASA Astrophysics Data System (ADS)

    Rabatel, A.; Francou, B.; Soruco, A.; Gomez, J.; Cáceres, B.; Ceballos, J. L.; Basantes, R.; Vuille, M.; Sicart, J.-E.; Huggel, C.; Scheel, M.; Lejeune, Y.; Arnaud, Y.; Collet, M.; Condom, T.; Consoli, G.; Favier, V.; Jomelli, V.; Galarraga, R.; Ginot, P.; Maisincho, L.; Mendoza, J.; Ménégoz, M.; Ramirez, E.; Ribstein, P.; Suarez, W.; Villacis, M.; Wagnon, P.

    2013-01-01

    The aim of this paper is to provide the community with a comprehensive overview of the studies of glaciers in the tropical Andes conducted in recent decades leading to the current status of the glaciers in the context of climate change. In terms of changes in surface area and length, we show that the glacier retreat in the tropical Andes over the last three decades is unprecedented since the maximum extension of the Little Ice Age (LIA, mid-17th-early 18th century). In terms of changes in mass balance, although there have been some sporadic gains on several glaciers, we show that the trend has been quite negative over the past 50 yr, with a mean mass balance deficit for glaciers in the tropical Andes that is slightly more negative than the one computed on a global scale. A break point in the trend appeared in the late 1970s with mean annual mass balance per year decreasing from -0.2 m w.e. in the period 1964-1975 to -0.76 m w.e. in the period 1976-2010. In addition, even if glaciers are currently retreating everywhere in the tropical Andes, it should be noted that this is much more pronounced on small glaciers at low altitudes that do not have a permanent accumulation zone, and which could disappear in the coming years/decades. Monthly mass balance measurements performed in Bolivia, Ecuador and Colombia show that variability of the surface temperature of the Pacific Ocean is the main factor governing variability of the mass balance at the decadal timescale. Precipitation did not display a significant trend in the tropical Andes in the 20th century, and consequently cannot explain the glacier recession. On the other hand, temperature increased at a significant rate of 0.10 °C decade-1 in the last 70 yr. The higher frequency of El Niño events and changes in its spatial and temporal occurrence since the late 1970s together with a warming troposphere over the tropical Andes may thus explain much of the recent dramatic shrinkage of glaciers in this part of the world.

  14. Surface-exposure ages of Front Range moraines that may have formed during the Younger Dryas, 8.2 cal ka, and Little Ice Age events

    USGS Publications Warehouse

    Benson, L.; Madole, R.; Kubik, P.; McDonald, R.

    2007-01-01

    Surface-exposure (10Be) ages have been obtained on boulders from three post-Pinedale end-moraine complexes in the Front Range, Colorado. Boulder rounding appears related to the cirque-to-moraine transport distance at each site with subrounded boulders being typical of the 2-km-long Chicago Lakes Glacier, subangular boulders being typical of the 1-km-long Butler Gulch Glacier, and angular boulders being typical of the few-hundred-m-long Isabelle Glacier. Surface-exposure ages of angular boulders from the Isabelle Glacier moraine, which formed during the Little Ice Age (LIA) according to previous lichenometric dating, indicate cosmogenic inheritance values ranging from 0 to ???3.0 10Be ka.11Surface-exposure ages in this paper are labeled 10Be; radiocarbon ages are labeled 14C ka, calendar and calibrated radiocarbon ages are labeled cal ka, and layer-based ice-core ages are labeled ka. 14C ages, calibrated 14C ages, and ice core ages are given relative to AD 1950, whereas 10Be ages are given relative to the sampling date. Radiocarbon ages were calibrated using CALIB 5.01 and the INTCAL04 data base Stuiver et al. (2005). Ages estimated using CALIB 5.01 are shown in terms of their 1-sigma range. Subangular boulders from the Butler Gulch end moraine yielded surface-exposure ages ranging from 5 to 10.2 10Be ka. We suggest that this moraine was deposited during the 8.2 cal ka event, which has been associated with outburst floods from Lake Agassiz and Lake Ojibway, and that the large age range associated with the Butler Gulch end moraine is caused by cosmogenic shielding of and(or) spalling from boulders that have ages in the younger part of the range and by cosmogenic inheritance in boulders that have ages in the older part of the range. The surface-exposure ages of eight of nine subrounded boulders from the Chicago Lakes area fall within the 13.0-11.7 10Be ka age range, and appear to have been deposited during the Younger Dryas interval. The general lack of inheritance in

  15. A risk score for the prediction of advanced age-related macular degeneration: Development and validation in 2 prospective cohorts

    Technology Transfer Automated Retrieval System (TEKTRAN)

    We aimed to develop an eye specific model which used readily available information to predict risk for advanced age-related macular degeneration (AMD). We used the Age-Related Eye Disease Study (AREDS) as our training dataset, which consisted of the 4,507 participants (contributing 1,185 affected v...

  16. DNA aptamer raised against advanced glycation end products (AGEs) improves glycemic control and decreases adipocyte size in fructose-fed rats by suppressing AGE-RAGE axis.

    PubMed

    Ojima, A; Matsui, T; Nakamura, N; Higashimoto, Y; Ueda, S; Fukami, K; Okuda, S; Yamagishi, S

    2015-04-01

    Advanced glycation end products (AGEs) decrease adiponectin expression and suppress insulin signaling in cultured adipocytes through the interaction with a receptor for AGEs (RAGE) via oxidative stress generation. We have recently found that high-affinity DNA aptamer directed against AGE (AGE-aptamer) prevents the progression of experimental diabetic nephropathy by blocking the harmful actions of AGEs in the kidney. This study examined the effects of AGE-aptamer on adipocyte remodeling, AGE-RAGE-oxidative stress axis, and adiponectin expression in fructose-fed rats. Although AGE-aptamer treatment by an osmotic mini pump for 8 weeks did not affect serum insulin levels, it significantly decreased average fasting blood glucose and had a tendency to inhibit body weight gain in fructose-fed rats. Furthermore, AGE-aptamer significantly suppressed the increase in adipocyte size and prevented the elevation in AGEs, RAGE, and an oxidative stress marker, 8-hydroxydeoxyguanosine (8-OHdG), levels in adipose tissues of fructose-fed rats at 14-week-old, while it restored the decrease in adiponectin mRNA levels. Our present study suggests that AGE-aptamer could improve glycemic control and prevent adipocyte remodeling in fructose-fed rats partly by suppressing the AGE-RAGE-mediated oxidative stress generation. AGE-aptamer might be a novel therapeutic strategy for fructose-induced metabolic derangements.

  17. Recent Demographic Developments in France: Relatively Low Mortality at Advanced Ages

    PubMed Central

    Prioux, France; Barbieri, Magali

    2013-01-01

    France had 65.3 million inhabitants as of 1 January 2012, including 1.9 million in the overseas départements. The population is slightly younger than that of the European Union as a whole. Population growth continues at the same rate, mainly through natural increase. There are now more African than European immigrants living in France. Fertility was practically stable in 2011 (2.01 children per woman), but the lifetime fertility of the 1971–1972 cohorts reached a historic low in metropolitan France (1.99 children per woman), nevertheless remaining among the highest in Europe. Abortion levels remained stable and rates among young people are no longer increasing. The marriage rate is falling and the divorce rate has stabilized (46.2 divorces per 100 marriages in 2011). The risk of divorce decreases with age, but has greatly increased among the under-70s over the last decade. Life expectancy at birth (78.4 years for men, 85.0 for women) has continued to increase at the same rate, mainly thanks to progress at advanced ages. Among European countries, France has the lowest mortality in the over-65 age group, but it ranks less well for premature mortality. PMID:24285939

  18. Immunoparesis and monoclonal gammopathy of undetermined significance are disassociated in advanced age.

    PubMed

    Cherry, Benjamin M; Costello, Rene; Zingone, Adriana; Burris, Jason; Korde, Neha; Manasanch, Elisabet; Kwok, Mary; Annunziata, Christina; Roschewski, Mark J; Engels, Eric A; Landgren, Ola

    2013-02-01

    Immunoparesis and a skewed serum free light chain (FLC) ratio are indicators of immune dysfunction predictive of progression from monoclonal gammopathy of undetermined significance (MGUS) to multiple myeloma (MM). Previous studies have reported increased prevalence of MGUS by age, but no study has examined the relationship between immunoparesis and abnormal FLC ratios in the elderly. We screened 453 older adults (median age, 80 years; range, 65-96) to characterize the patterns of immunoparesis and abnormal FLC ratio in relation to MGUS. We defined MGUS in 4.4% of the subjects; the prevalence was 12.5% among individuals of >90 years. In MGUS (vs. non-MGUS) cases, immunoparesis and abnormal FLC ratios were detected in 70.0% (vs. 49.0%; P = 0.07) and 50.0% (vs. 12.9%; P = 0.0001), respectively. Based on small numbers, MGUS patients with abnormal FLC ratio were borderline (P = 0.07) more likely to have immunoparesis. Overall, the prevalence of immunoparesis varied in a nonlinear fashion, with lowest frequencies in the youngest and oldest groups. Our observed disassociation between MGUS prevalence and impaired immunoglobulin production suggests that separate mechanisms are involved in the development of MGUS and immunoparesis in advanced age. These findings emphasize the need for molecularly defined methods to characterize myeloma precursor states and better predict progression to MM.

  19. Curcumin eliminates the effect of advanced glycation end-products (AGEs) on the divergent regulation of gene expression of receptors of AGEs by interrupting leptin signaling.

    PubMed

    Tang, Youcai; Chen, Anping

    2014-05-01

    Non-alcoholic steatohepatitis (NASH) is a major risk factor for hepatic fibrogenesis. NASH is often found in diabetic patients with hyperglycemia. Hyperglycemia induces non-enzymatic glycation of proteins, yielding advanced glycation end-products (AGEs). Effects of AGEs are mainly mediated by two categories of cytoplasmic membrane receptors. Receptor for AGEs (RAGE) is associated with increased oxidative stress and inflammation, whereas AGE receptor-1 (AGE-R1) is involved in detoxification and clearance of AGEs. Activation of hepatic stellate cells (HSC) is crucial to the development of hepatic fibrosis. We recently reported that AGEs stimulated HSC activation likely by inhibiting gene expression of AGE-R1 and inducing gene expression of RAGE in HSC, which were eliminated by the antioxidant curcumin. This study is to test our hypothesis that curcumin eliminates the effects of AGEs on the divergent regulation of the two receptors of AGEs in HSC by interrupting the AGE-caused activation of leptin signaling, leading to the inhibition of HSC activation. We observed herein that AGEs activated leptin signaling by inducing gene expression of leptin and its receptor in HSC. Like AGEs, leptin differentially regulated gene expression of RAGE and AGE-R1. Curcumin eliminated the effects of AGEs in HSC by interrupting leptin signaling and activating transcription factor NF-E2 p45-related factor 2 (Nrf2), leading to the elevation of cellular glutathione and the attenuation of oxidative stress. In conclusions, curcumin eliminated the effects of AGEs on the divergent regulation of gene expression of RAGE and AGE-R1 in HSC by interrupting the AGE-caused activation of leptin signaling, leading to the inhibition of HSC activation.

  20. Curcumin eliminates the effect of advanced glycation end-products (AGEs) on the divergent regulation of gene expression of receptors of AGEs by interrupting leptin signaling

    PubMed Central

    Tang, Youcai; Chen, Anping

    2014-01-01

    Nonalcoholic steatohepatitis (NASH) is a major risk factor for hepatic fibrogenesis. NASH is often found in diabetic patients with hyperglycemia. Hyperglycemia induces non-enzymatic glycation of proteins, yielding advanced glycation end-products (AGEs). Effects of AGEs are mainly mediated by two categories of cytoplasmic membrane receptors. Receptor for AGEs (RAGE) is associated with increased oxidative stress and inflammation, whereas AGE receptor-1 (AGE-R1) is involved in detoxification and clearance of AGEs. Activation of hepatic stellate cells (HSC) is crucial to the development of hepatic fibrosis. We recently reported that AGEs stimulated HSC activation likely by inhibiting gene expression of AGE-R1 and inducing gene expression of RAGE in HSC, which were eliminated by the antioxidant curcumin. This study is to test our hypothesis that curcumin eliminates the effects of AGEs on the divergent regulation of the two receptors of AGEs in HSC by interrupting the AGEs-caused activation of leptin signaling, leading to the inhibition of HSC activation. We observed herein that AGEs activated leptin signaling by inducing gene expression of leptin and its receptor in HSC. Like AGEs, leptin differentially regulated gene expression of RAGE and AGE-R1. Curcumin eliminated the effects of AGEs in HSC by interrupting leptin signaling and activating transcription factor Nrf2, leading to the elevation of cellular glutathione and the attenuation of oxidative stress. In conclusions, curcumin eliminated the effects of AGEs on the divergent regulation of gene expression of RAGE and AGE-R1 in HSC by interrupting the AGEs-caused activation of leptin signaling, leading to the inhibition of HSC activation. PMID:24614199

  1. 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)

  2. Flow velocities of Alaskan glaciers.

    PubMed

    Burgess, Evan W; Forster, Richard R; Larsen, Christopher F

    2013-01-01

    Our poor understanding of tidewater glacier dynamics remains the primary source of uncertainty in sea level rise projections. On the ice sheets, mass lost from tidewater calving exceeds the amount lost from surface melting. In Alaska, the magnitude of calving mass loss remains unconstrained, yet immense calving losses have been observed. With 20% of the global new-water sea level rise coming from Alaska, partitioning of mass loss sources in Alaska is needed to improve sea level rise projections. Here we present the first regionally comprehensive map of glacier flow velocities in Central Alaska. These data reveal that the majority of the regional downstream flux is constrained to only a few coastal glaciers. We find regional calving losses are 17.1 Gt a(-1), which is equivalent to 36% of the total annual mass change throughout Central Alaska.

  3. Erosion by an Alpine glacier.

    PubMed

    Herman, Frédéric; Beyssac, Olivier; Brughelli, Mattia; Lane, Stuart N; Leprince, Sébastien; Adatte, Thierry; Lin, Jiao Y Y; Avouac, Jean-Philippe; Cox, Simon C

    2015-10-09

    Assessing the impact of glaciation on Earth's surface requires understanding glacial erosion processes. Developing erosion theories is challenging because of the complex nature of the erosion processes and the difficulty of examining the ice/bedrock interface of contemporary glaciers. We demonstrate that the glacial erosion rate is proportional to the ice-sliding velocity squared, by quantifying spatial variations in ice-sliding velocity and the erosion rate of a fast-flowing Alpine glacier. The nonlinear behavior implies a high erosion sensitivity to small variations in topographic slope and precipitation. A nonlinear rate law suggests that abrasion may dominate over other erosion processes in fast-flowing glaciers. It may also explain the wide range of observed glacial erosion rates and, in part, the impact of glaciation on mountainous landscapes during the past few million years.

  4. Erosion by an Alpine glacier

    NASA Astrophysics Data System (ADS)

    Herman, Frédéric; Beyssac, Olivier; Brughelli, Mattia; Lane, Stuart N.; Leprince, Sébastien; Adatte, Thierry; Lin, Jiao Y. Y.; Avouac, Jean-Philippe; Cox, Simon C.

    2015-10-01

    Assessing the impact of glaciation on Earth’s surface requires understanding glacial erosion processes. Developing erosion theories is challenging because of the complex nature of the erosion processes and the difficulty of examining the ice/bedrock interface of contemporary glaciers. We demonstrate that the glacial erosion rate is proportional to the ice-sliding velocity squared, by quantifying spatial variations in ice-sliding velocity and the erosion rate of a fast-flowing Alpine glacier. The nonlinear behavior implies a high erosion sensitivity to small variations in topographic slope and precipitation. A nonlinear rate law suggests that abrasion may dominate over other erosion processes in fast-flowing glaciers. It may also explain the wide range of observed glacial erosion rates and, in part, the impact of glaciation on mountainous landscapes during the past few million years.

  5. Southern Alaska Glaciers: Spatial and Temporal Variations in Ice Volume

    NASA Technical Reports Server (NTRS)

    Sauber, J.; Molnia, B. F.; Lutchke, S.; Rowlands, D.; Harding, D.; Carabajal, C.; Hurtado, J. M.; Spade, G.

    2004-01-01

    Although temperate mountain glaciers comprise less than 1% of the glacier-covered area on Earth, they are important because they appear to be melting rapidly under present climatic conditions and, therefore, make significant contributions to rising sea level. In this study, we use ICESat observations made in the last 1.5 years of southern Alaska glaciers to estimate ice elevation profiles, ice surface slopes and roughness, and bi-annual and/or annual ice elevation changes. We report initial results from the near coastal region between Yakutat Bay and Cape Suckling that includes the Malaspina and Bering Glaciers. We show and interpret ice elevations changes across the lower reaches of the Bagley Ice Valley for the period between October 2003 and May 2004. In addition, we use off-nadir pointing observations to reference tracks over the Bering and Malaspina Glaciers in order to estimate annual ice elevation change. Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) and Shuttle Radar Topography Mission (SRTM) derived DEMs are used to estimate across track regional slopes between ICESat data acquisitions. Although the distribution and quantity of ICESat elevation profiles with multiple, exact repeat data is currently limited in Alaska, individual ICESat data tracks, provide an accurate reference surface for comparison to other elevation data (e.g. ASTER and SRTM X- and C-band derived DEMs). Specifically we report the elevation change over the Malaspina Glacier's piedmont lobe between a DEM derived from SRTM C-band data acquired in Feb. 2000 and ICESat Laser #2b data from Feb.-March 2004. We also report use of ICESat elevation data to enhance ASTER derived absolute DEMs. Mountain glaciers generally have rougher surfaces and steeper regional slopes than the ice sheets for which the ICESat design was optimized. Therefore, rather than averaging ICESat observations over large regions or relying on crossovers, we are working with well-located ICESat

  6. Assessing streamflow sensitivity to variations in glacier mass balance

    USGS Publications Warehouse

    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.

  7. Late Pleistocene oscillations of the Drau Glacier (southern Austria)

    NASA Astrophysics Data System (ADS)

    Karnitschar, Christina; Reitner, Jürgen; Draganits, Erich

    2016-04-01

    The Drau Glacier was the largest Pleistocene glacier in the southeastern part of the Alps and significantly shaped the landscape in this region. The study area is located at the termination of the Drau Glacier in the southern part of Austria (Carinthia). The investigation aims to decipher glacial dynamics during the Late Pleistocene glacial advance, stabilisation and final recession of this glacier based on geological/geomorphological mapping, interpretation of airborne laser scan (ALS) topographic data and lithostratigraphic investigations of glacial and periglacial sediments. Special emphasis is laid on the reconstruction of the maximum extent of the glaciation (LGM). Based on previous mapping by Bobek (1959) and Ucik (1996-1998) more details have been gained for the paleogeographic reconstruction based on glacial and non-glacial erosion and accumulation features. These include traces of pre-Upper Pleistocene glaciation, drumlins, terminal moraines and kettle holes. Paleogeographic reconstruction was done with correlation of different outcrops based on lithostratigraphy and ALS topography. Sequences of gravel related to glacial advance covered by till, followed by periglacial sediments allowed detailed reconstruction of the glacial sequence in this area and the complex succession of various extents of the Drau Glacier. References Bobek, Hans. 1959: Der Eisrückgang im östlichen Klagenfurter Becken. In: Mitteilungen der österreichischen geographischen Gesellschaft, Wien. Ucik, Friedrich Hans. 1996: Bericht über geologische Aufnahmen im Quartär auf Blatt 204 Völkermarkt, Jb. Geol. B.-A., 141, S. 340, Wien. Ucik, Friedrich Hans. 1997: Bericht über geologische Aufnahmen im Quartär auf Blatt 204 Völkermarkt, Jb. Geol. B.-A., 141, S. 325-326, Wien. Ucik, Friedrich Hans. 1998: Bericht über geologische Aufnahmen im Quartär auf Blatt 204 Völkermarkt, Jb. Geol. B.-A., 142, S. 333-334, Wien.

  8. Effects of ongoing glacier retreat on steep valley-side drift slopes in the upper Bødalen valley, western Norway

    NASA Astrophysics Data System (ADS)

    Laute, Katja; Beylich, Achim A.; Oppikofer, Thierry

    2013-04-01

    The general pattern and dominant trend of today's mountain glaciers worldwide is a retreat of glacier fronts, indicating a significant volume decrease. Negative glacier net balances have been recorded for all Scandinavian glaciers after 1999. The ongoing glacier retreat enlarges freshly exposed proglacial areas which are characterized by e.g. comparably higher intensities of denudational slope processes and higher sediment availability. This study focuses on influences of rapid glacier regression on contemporary surface processes acting on steep valley-side drift slopes in a characteristic steep, parabolic-shaped and glacier-fed valley (Bødalen,) located on the western side of the Jostedalsbreen ice cap in western Norway. The Bødalsbreen is one of the glaciers with the highest retreat rate in entire Norway. Since the Little Ice Age (LIA) glacier maximum advance (1750) the glacier retreated ca. 1.500 m, including 65 m of retreat within the period of 2001 to 2010. Due to this retreat large areas of unstable hillslopes covered by glacial deposits from the LIA lateral moraines have been exposed. A combination of high resolution terrestrial laser scanning (TLS) and a designed monitoring program has been applied to a selected hillslope site on the eastern flank of the Bødalsbreen. Three sequential terrestrial laser scans have been acquired in the summers of 2010, 2011 and 2012. The analysis of the three series of the high resolution point clouds enables (i) the detection of unstable slope areas, (ii) areas characterized primarily by erosion or deposition processes and (iii) to quantify volumes of mass transfers at the scanned site. The results from the TLS measurements are combined with the results from the monitoring program (installations in operation since 2009) which includes remote cameras for monitoring rapid mass movement events (avalanches, slush- and debris flows), stone tracer lines for measuring surface movements as well as temperature loggers both in rock

  9. The Holocene Sedimentary Record of Climate Change from Gualas Glacier, Golfo Elefantes, Northern Patagonia (46.5°S)

    NASA Astrophysics Data System (ADS)

    Fernandez-Vasquez, R. A.; Anderson, J. B.; Bertrand, S.; Wellner, J. S.

    2010-12-01

    Gualas Glacier is an outlet glacier of the Northern Patagonian Icefield (NPI), one of the largest temperate ice bodies on Earth. NPI is nourished by moisture from the Pacific Ocean, which is transported by the southern hemisphere Westerlies and results in year-round precipitation. This system also creates a strong West to East gradient due to the rain shadow effect of the Andes (Warren, 1993). Most glaciers of the NPI, including Gualas Glacier, are currently receding from their historical maximum position, which was reached during the northern hemisphere Little Ice Age (LIA) (Harrison and Winchester, 2000). However, virtually nothing is known about the Holocene behavior of NPI outlet glaciers prior to the LIA, although it is generally assumed that they followed the pattern of Neoglacial advances described for the Southern Patagonian Icefield (SPI) by Mercer (1965, 1968, 1976). The lack of data in this sensitive area of the Patagonian Andes, the only continental cordillera in the Southern Hemisphere that intersects the entire Westerly Wind Belt, limits our understanding of climate processes that relate mid-latitude circulation patterns with low and high latitudes as well as the inter-hemispheric coupling of climate changes. We present the results of a marine geological survey at Golfo Elefantes, the depositional basin of Gualas Glacier. The dataset includes swath bathymetry, single channel seismic data and sediment cores analyses. The studied sedimentary record spans, with some hiatuses, at least the last 10.5 Ka. No evidences of ice proximal or till deposits were found in the area, and seismic records show no evidence of basin-wide erosional hiatuses. This implies that the arcuate terminal moraines that occur along the edges of Golfo Elefantes, which have been suggested to represent Neoglacial advances of Gualas Glacier, were instead formed during the waning stages of the local LGM (Late Pleistocene) after ~12.6 ka according to paleogeographical reconstructions

  10. Modern Glacial Outwash Sand Thermochronology Along the Denali Fault: Constraints on Strike-slip Fault and Glacier Erosion Dynamics

    NASA Astrophysics Data System (ADS)

    Benowitz, J.; Layer, P. W.

    2011-12-01

    It is now generally accepted that increased climate instability and extent of glaciation associated with late Cenozoic global cooling has led to increased erosion rates in most of the world's orogenic belts. However, the connection between surface processes and mountain building continues to be contentious because while some argue that tectonically driven rock uplift in continental collision zones is the most significant influence on erosion rates others suggest that the deep exhumation found in mountain ranges can mostly be explained by focused erosion driven by climatic processes. The relationship between the introduction of glaciers and erosion rates is also complicated by glacier process behavior in itself. It has been demonstrated that glacial advance-retreat cycles and high basal sliding rates are critical factors affecting if the introduction of glaciers will increase or decrease long-term exhumation rates. Natural experiments using detailed glacial outwash sand thermochronology, by providing an integrated time-space record of material flux, have been shown to be useful on constraining a regions sub-glacial erosion and exhumation history. The Denali Fault system, a continental-scale strike-slip fault and the associated Alaska Range with a known orogenesis development history, a documented increase in exhumation rates correlated to the start of the Northern-Hemisphere glaciation and a known surge-type glacier/fault relationship make the region a prime location to investigate the interaction of active faulting and glacial processes on erosion patterns. We can distinguish between three different scenarios from the full detrital and bedrock age data set: a) Outwash data slightly younger than bedrock data set-This would imply the same trend as bedrock samples, where as bed rock thermochronometric ages get younger as you approach the Denali Fault in agreement with dip-slip on a subglacial Denali Fault master strand as a significant contributor to topographic

  11. Cable aging and condition monitoring of radiation resistant nano-dielectrics in advanced reactor applications

    SciTech Connect

    Duckworth, Robert C; Aytug, Tolga; Paranthaman, Mariappan Parans; Kidder, Michelle; Polyzos, Georgios; Leonard, Keith J

    2015-01-01

    Cross-linked polyethylene (XLPE) nanocomposites have been developed in an effort to improve cable insulation lifetime to serve in both instrument cables and auxiliary power systems in advanced reactor applications as well as to provide an alternative for new or retro-fit cable insulation installations. Nano-dielectrics composed of different weight percentages of MgO & SiO2 have been subjected to radiation at accumulated doses approaching 20 MRad and thermal aging temperatures exceeding 100 C. Depending on the composition, the performance of the nanodielectric insulation was influenced, both positively and negatively, when quantified with respect to its electrical and mechanical properties. For virgin unradiated or thermally aged samples, XLPE nanocomposites with 1wt.% SiO2 showed improvement in breakdown strength and reduction in its dissipation factor when compared to pure undoped XLPE, while XLPE 3wt.% SiO2 resulted in lower breakdown strength. When aged in air at 120 C, retention of electrical breakdown strength and dissipation factor was observed for XLPE 3wt.% MgO nanocomposites. Irrespective of the nanoparticle species, XLPE nanocomposites that were gamma irradiated up to the accumulated dose of 18 MRad showed a significant drop in breakdown strength especially for particle concentrations greater than 3 wt.%. Additional attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy measurements suggest changes in the structure of the XLPE SiO2 nanocomposites associated with the interaction of silicon and oxygen. Discussion on the relevance of property changes with respect to cable aging and condition monitoring is presented.

  12. Clinical profile of patients with advanced age and inflammatoric dilated cardiomyopathy on endomyocardial biopsy

    PubMed Central

    Ohlow, Marc-Alexander; Chen, Ting-Hui; Schmidt, Andreas; Saenger, Joerg; Lauer, Bernward

    2015-01-01

    Background Endomyocardial biopsy (EMB) is an important tool when patients with inflammatoric cardiomyopathy (DCMi) are evaluated. We aimed to assess the clinical profile of elderly patients with DCMi on EMB. Methods Retrospective study of all consecutive patients hospitalized from January 2007 to December 2011 with clinical suspicion of DCMi undergoing EMB. Patients with evidence of DCMi on EMB (Group 1 ≥ 70 years, n = 85; Group 3 < 70 years; n = 418) were compared to patients of the same age group without evidence of DCMi on EMB (Group 2 ≥ 70 years, n = 45; Group 4 < 70 years; n = 147). Results Among 24,275 patients treated at our institution during the study period, 695 had clinical suspicion of DCMi and underwent EMB; 503 (2.1%) patients had DCMi on EMB. There were more male patients in Group 1, mean age was 74 ± 2.8 years, mean ejection fraction was 38% ± 14%. On presentation, signs of hemodynamic compromise (NYHA functional class III/IV, low cardiac output/index, and low cardiac power index) were more frequent in Group 1. EMB revealed viral genome in 78% of the patients, parvovirus B19 (PVB) was frequently encountered in both age groups (Group 1: 69.4% vs. Group 2: 59.6%); detection of more than one viral genome was more frequent in Group 1 (21.2% vs. 11.2%; P = 0.02) whereas the extent of immune response was significantly lower in individuals with advanced age. Conclusions In patients ≥ 70 years with DCMi on EMB signs of hemodynamic compromise, detection of multiple viral genomes together with an overall lower extent of immune response were more frequently observed. PMID:26788036

  13. Post-LIA glacier changes along a latitudinal transect in the Central Italian Alps

    NASA Astrophysics Data System (ADS)

    Scotti, R.; Brardinoni, F.; Crosta, G. B.

    2014-07-01

    The variability of glacier response to atmospheric temperature rise in different topo-climatic settings is still matter of debate. To address this question in the Central Italian Alps we compile a post-LIA (Little Ice Age) multitemporal glacier inventory (1860-1954-1990-2003-2007) along a latitudinal transect that originates north of the continental divide in the Livigno mountains, and extends south through the Disgrazia and Orobie ranges, encompassing continental-to-maritime climatic settings. In these sub-regions we examine area change of 111 glaciers. Overall, total glacierized area has declined from 34.1 to 10.1 km2, with a substantial increase in the number of small glaciers due to fragmentation. Average annual decrease (AAD) in glacier area has risen of about an order of magnitude from 1860-1990 (Livigno: 0.45; Orobie: 0.42; and Disgrazia: 0.39 % a-1) to 1990-2007 (Livigno: 3.08; Orobie: 2.44; and Disgrazia: 2.27 % a-1). This ranking changes when considering glaciers <0.5 km2 only (i.e., we remove the confounding caused by large glaciers in Disgrazia), so that post-1990 AAD follows the latitudinal gradient and Orobie glaciers stand out (Livigno: 4.07; Disgrazia: 3.57; and Orobie: 2.47 % a-1). More recent (2007-2013) field-based mass balances in three selected small glaciers confirm post-1990 trends showing consistent highest retreat in continental Livigno and minimal area loss in maritime Orobie, with Disgrazia displaying a transitional behaviour. We argue that the recent resilience of glaciers in Orobie is a consequence of their decoupling from synoptic atmospheric temperature trends. A decoupling that arises from the combination of local topographic configuration (i.e., deep, north-facing cirques) and high winter precipitation, which ensures high snow-avalanche supply, as well as high summer shading and sheltering. Our hypothesis is further supported by the lack of correlations between glacier change and glacier attributes in Orobie, as well by the higher

  14. Post-LIA glacier changes along a latitudinal transect in the Central Italian Alps

    NASA Astrophysics Data System (ADS)

    Scotti, R.; Brardinoni, F.; Crosta, G. B.

    2014-12-01

    The variability of glacier response to atmospheric temperature rise in different topo-climatic settings is still a matter of debate. To address this question in the Central Italian Alps, we compile a post-LIA (Little Ice Age) multitemporal glacier inventory (1860-1954-1990-2003-2007) along a latitudinal transect that originates north of the continental divide in the Livigno Mountains and extends south through the Disgrazia and Orobie ranges, encompassing continental-to-maritime climatic settings. In these sub-regions, we examine the area change of 111 glaciers. Overall, the total glacierized area has declined from 34.1 to 10.1 km2, with a substantial increase in the number of small glaciers due to fragmentation. The average annual decrease (AAD) in glacier area has risen by about 1 order of magnitude from 1860-1990 (Livigno: 0.45; Orobie: 0.42; and Disgrazia: 0.39 % a-1) to 1990-2007 (Livigno: 3.08; Orobie: 2.44; and Disgrazia: 2.27 % a-1). This ranking changes when considering glaciers smaller than 0.5 km2 only (i.e., we remove the confounding caused by large glaciers in Disgrazia), so that post-1990 AAD follows the latitudinal gradient and Orobie glaciers stand out (Livigno: 4.07; Disgrazia: 3.57; and Orobie: 2.47 % a-1). More recent (2007-2013) field-based mass balances in three selected small glaciers confirm post-1990 trends showing the consistently highest retreat in continental Livigno and minimal area loss in maritime Orobie, with Disgrazia displaying transitional behavior. We argue that the recent resilience of glaciers in Orobie is a consequence of their decoupling from synoptic atmospheric temperature trends, a decoupling that arises from the combination of local topographic configuration (i.e., deep, north-facing cirques) and high winter precipitation, which ensures high snow-avalanche supply, as well as high summer shading and sheltering. Our hypothesis is further supported by the lack of correlations between glacier change and glacier attributes in

  15. Tumor Necrosis Factor Gene Polymorphisms in Advanced Non-exudative Age-related Macular Degeneration

    PubMed Central

    Bonyadi, Mohammad Hossein Jabbarpoor; Bonyadi, Morteza; Ahmadieh, Hamid; Fotuhi, Nikoo; Shoeibi, Nasser; Saadat, Saeed; Yagubi, Zakieh

    2015-01-01

    Purpose: To investigate tumor necrosis factor (TNF)-α gene polymorphisms in advanced dry-type age-related macular degeneration (AMD) in a population from Northeastern Iran. Methods: In this case-control study, 50 patients with geographic macular atrophy and 73 gender-matched controls were enrolled. Genomic deoxyribonucleic acid (DNA) was extracted from the peripheral blood. Polymerase chain reaction was performed to analyze 2 candidate single nucleotide polymorphisms in the TNF-α gene, namely −1031 thymine (T)/cytosine (C) and −308 guanine (G)/adenine (A). Results: The distribution of the - 1031 T/C genotype was TT, 62%; TC, 36%; CC, 2% in the patients and TT, 60%; TC, 36%; CC, 4% in the controls (P = 0.94). Genotype analysis of TNF-α −308 also revealed no significant difference in distribution between patients (G, 78%; GA, 22%; AA, 0%) and controls (GG, 74%; GA, 23%; AA, 3%) (P = 0.51). None of the haplotypes nor alleles of studied TNF-α polymorphisms were significantly associated with advanced dry-type AMD. Conclusion: The findings of this study show that polymorphisms in the TNF-α gene, do not play an important role in dry-type AMD in the studied population. PMID:26425318

  16. Mesoscale Icefield Breezes over Athbasca Glacier.

    NASA Astrophysics Data System (ADS)

    Conway, J. P.; Helgason, W.; Pomeroy, J. W.; Sicart, J. E.

    2015-12-01

    Atmospheric boundary layer (ABL) dynamics over glaciers are of great interest as they can modify the response of glacier mass balance to large scale climate forcing. A key feature of the glacier ABL is formation of katabatic winds driven by turbulent sensible heat exchange with a cooler underlying ice surface. These winds can markedly alter the spatio-temporal distribution of air temperature over glacier surfaces from the environmental lapse rate, which in turn affects the distribution of melt. An intensive field campaign was conducted over 13 days in June 2015 at Athabasca Glacier, an outlet of Columbia Icefield in the Rocky Mountains of Canada. Multiple automatic weather stations, eddy covariance systems, distributed temperature sensors, SODAR and kite profiling systems were used to characterise how the glacier ABL evolved spatially and temporally, how the differences in glacier ABL properties were related to valley and regional circulation and what effect these differences had on surface lapse rates. In general strong daytime down-glacier winds were observed over the glacier. These winds extended well beyond the glacier into the proglacial area and through the depth of lower ice-free valley. On most days wind speed was consistent or increasing through to the top of the above-glacier profiles (100 to 200 m), indicating a quite well mixed surface boundary layer. A wind speed maximum in the lowest few metres above the glacier surface, characteristic of a katabatic wind, was only observed on one day. The dominant circulation within the valley appears to be what could be termed an 'icefield breeze'; strong down-glacier winds driven by mesoscale pressure gradients that are set up by differential suface heating over the non-glaciated valleys and much the larger Columbia Icefield upstream of the glacier. The effect of the different circulations on lapse rates will be explored with a view to developing variable lapse rates for modelling glacier mass balance.

  17. Age of the crowfoot advance in the Canadian Rocky Mountains. A glacial event coeval with the Younger Dryas oscillation

    SciTech Connect

    Reasoner, M.A.; Rutter, N.W. ); Osborn, G. )

    1994-05-01

    A suite of sediment core samples was recovered from two lakes, Crowfoot and Bow lakes, that are adjacent to the Crowfoot moraine type locality, to identify and radiocarbon date sediments related to the Crowfoot advance. The Crowfoot moraine system, widely recognized throughout northwestern North America, represents a glacial advance that is post-Wisconsin and pre-Mazama tephra in age. An interval of inorganic sediments bracketed by accelerator mass spectrometry radiocarbon ages of ca. 11,330 and 10,100 [sup 14]C yr B.P. is associated with the Crowfoot moraine. The Crowfoot advance is therefore approximately synchronous with the European Younger Dryas cold event (ca. 11,000-10,000 [sup 14]C yr B.P.). Furthermore, the termination of the Crowfoot advance also appears to have been abrupt. These findings illustrate that the climatic change responsible for the European Younger Dryas event extended beyond the northern Atlantic basin and western Europe. Equilibrium-line altitude (ELA) depressions associated with the Crowfoot advance are similar to those determined for the Little Ice Age advance, whereas Younger Dryas ELA depressions in Europe significantly exceed Little Ice Age ELA depressions. 26 refs., 3 figs., 1 tab.

  18. 125 years of glacier survey of the Austrian Alpine Club: results and future challenges

    NASA Astrophysics Data System (ADS)

    Fischer, Andrea

    2016-04-01

    One of the aims of the German and Austrian Alpine Club was the scientific investigation of the Alps. In 1891, several years after Swiss initiatives, Richter put out a call to contribute to regular glacier length surveys in the Eastern Alps. Since then more than 100 glaciers have been surveyed on a first biannual and later annual basis. The database includes measured data showing a general glacier retreat since 1891, with two periods of glacier advances in the 1920s and 1980s. Less well known are the sketches and reports which illustrate, for instance, changes in surface texture. The interpretation of length change data requires a larger sample of data for a reasonable interpretation on a regional scale. Nearly every time series in the long history of investigation includes gaps, e.g. in cases of problematic snout positions on steep rock walls or in lakes, or of debris-covered tongues. Current climate change adds the problem of glaciers splitting up into several smaller glaciers which behave differently. Several basic questions need to be addressed to arrive at a most accurate prolongated time series: How should measurements on disintegrating or debris-covered (and thus more or less stagnating) glaciers be documented, and how can we homogenize length change time series? Despite of uncertainties, length change data are amongst the longest available records, bridging the gap to moraine datings of the early holocene.

  19. A Priori Attitudes Predict Amniocentesis Uptake in Women of Advanced Maternal Age: A Pilot Study.

    PubMed

    Grinshpun-Cohen, Julia; Miron-Shatz, Talya; Rhee-Morris, Laila; Briscoe, Barbara; Pras, Elon; Towner, Dena

    2015-01-01

    Amniocentesis is an invasive procedure performed during pregnancy to determine, among other things, whether the fetus has Down syndrome. It is often preceded by screening, which gives a probabilistic risk assessment. Thus, ample information is conveyed to women with the goal to inform their decisions. This study examined the factors that predict amniocentesis uptake among pregnant women of advanced maternal age (older than 35 years old at the time of childbirth). Participants filled out a questionnaire regarding risk estimates, demographics, and attitudes on screening and pregnancy termination before their first genetic counseling appointment and were followed up to 24 weeks of gestation. Findings show that women's decisions are not always informed by screening results or having a medical indication. Psychological factors measured at the beginning of pregnancy: amniocentesis risk tolerance, pregnancy termination tolerance, and age risk perception affected amniocentesis uptake. Although most women thought that screening for Down syndrome risk would inform their decision, they later stated other reasons for screening, such as preparing for the possibility of a child with special needs. Findings suggest that women's decisions regarding amniocentesis are driven not only by medical factors, but also by a priori attitudes. The authors believe that these should be addressed in the dialogue on women's informed use of prenatal tests.

  20. [Cervico-omo-brachial pain and disability in a person of advanced age].

    PubMed

    Usui, M

    1997-07-01

    A person of advanced age usually has degenerative changes of bone, joint and ligament, which can be causes of cervico-omo-brachial pain and disability. He or she may also suffer from metastatic bone tumor of cervical spine or upper extremity. This article described pathology, signs and symptoms and recent treatment of these diseases. Cervical myelopathy and radiculopathy, which are most common causes of cervico-omo-brachial symptoms, are sometimes accompanied by peripheral entrapment neuropathy such as cubital tunnel syndrome or carpal tunnel syndrome (double crush syndrome). In this complicated situation, decompression of neural tissue in both cervical spine and carpal tunnel are necessary. In treatment for carpal tunnel syndrome, release of transverse carpal ligament under an arthroscope has proven to be useful and has been becoming popular. This minimally invasive surgery is also useful in shoulder surgery such as subacromial decompression in aged patients with rotator cuff tear and removal of calcium deposit in the shoulder joint. Osteoarthritis of the elbow also cause pain or disability of the elbow and the hand. Some metastatic bone tumors are treated by tumor resection and reconstruction with instruments, prosthesis or composite grafts, which are attempted not to cure the disease but to maintain or improve the quality of life of the patient.

  1. Historical and future hydrologic response to glacier recession in the Cordillera Real, Bolivia

    NASA Astrophysics Data System (ADS)

    Frans, C. D.; Istanbulluoglu, E.; Naz, B.; Lettenmaier, D. P.; Condom, T.; Clarke, G. K.; Burns, P. J.; Nolin, A. W.

    2013-12-01

    In many partially glaciated watersheds climate-forced glacier recession has altered and will continue to alter seasonal water availability, leading to profound implications for water supply systems. The tropical glaciers of the Cordillera Real, Bolivia, whose melt water significantly contributes to water supply and energy production for the densely populated La Paz area, have retreated at unprecedented rates since the 1970's. This glacier recession will continue with ongoing increasing temperatures projected for the subtropical Andes. We use a recently developed glacio-hydrological model to evaluate the contribution of glacier melt to watershed discharge, and track this contribution in time with changing glacier area. A glacier model, solving time-evolving and spatially-distributed balance equations for glacier mass and momentum, is integrated within the Distributed Hydrology Soil Vegetation Model (DHSVM). The glacio-hydrologic behavior of Cordillera Real watersheds is simulated during the historical period of 1987-2010. This model application is validated through comparisons with satellite derived glacier extent estimates and in-situ mass balance, surface energy flux, and stream discharge measurements. The retrospective analysis indicates that glacier melt contributed, on average, 31% (63%) of total annual (dry season-JJA) watershed discharge. Further, the modeling approach is used to predict the transitioning contribution of glacier melt and watershed hydrology through the 21st century. Multiple realizations of the 21st century meteorological data, used to force the glacier-hydrological model, are produced using a stochastic statistical downscaling technique. In this technique a weather generator (Advanced Weather Generator, AWE-GEN) is employed with statistical parameters of the future climate obtained from predictions of 11 CMIP5 general circulation models (GCMs). Future simulations indicate a 17% (23%) decrease in annual (JJA) runoff by the end of the 21st

  2. Do we need long term terrestrial glacier mass balance monitoring for the future?

    NASA Astrophysics Data System (ADS)

    Slupetzky, H.

    2003-04-01

    the next 60 to 80 years due to the global warming. So, a very new aspect arises: If the area now covered by the glacier is deglaciated and the base topography is known accurately, then it will be very interesting to observe a potential reglaciation in the future. Future glaciologists will much appreciate to use all the previously gathered results and it will be exciting to compare the polarity of the dual processes of mass gain, reconstution and advance of a glacier and the mass loss, shrinking and receding of the glacier.

  3. Serum 25-hydroxyvitamin D and Physical Function in Adults of Advanced Age: The CHS All Stars

    PubMed Central

    Houston, Denise K.; Tooze, Janet A.; Davis, Cralen C.; Chaves, Paulo H. M.; Hirsch, Calvin H.; Robbins, John A.; Arnold, Alice M.; Newman, Anne B.; Kritchevsky, Stephen B.

    2011-01-01

    Objectives To examine the association between 25-hydroxyvitamin D (25[OH]D) and physical function in adults of advanced age. Design Cross-sectional and longitudinal analysis of physical function over 3 years of follow-up in the Cardiovascular Health Study All Stars. Setting Forsyth County, NC; Sacramento County, CA; Washington County, MD; and Allegheny County, PA. Participants Community-dwelling adults aged 77–100 years (n=988). Measurements Serum 25(OH)D, short physical performance battery (SPPB) and grip and knee extensor strength assessed at baseline. Mobility disability (difficulty walking half a mile or up 10 steps) and activities of daily living (ADL) disability were assessed at baseline and every 6 months over 3 years of follow-up. Results 30.8% of participants had deficient 25(OH)D (<20 ng/mL). SPPB scores were lower among those with deficient 25(OH)D compared to those with sufficient 25(OH)D (≥30 ng/mL) after adjusting for sociodemographic characteristics, season, health behaviors and chronic conditions (mean±SE: 6.53±0.24 vs. 7.15±0.25, p <0.01). Grip strength adjusted for body size was also lower among those with deficient versus sufficient 25(OH)D (mean±SE: 24.7±0.6 vs. 26.0±0.6 kg, p <0.05). Participants with deficient 25(OH)D were more likely to have prevalent mobility and ADL disability at baseline (OR (95% CI): 1.44 (0.96–2.14) and 1.51 (1.01–2.25), respectively) compared to those with sufficient 25(OH)D. Furthermore, participants with deficient 25(OH)D were at increased risk of incident mobility disability over 3 years of follow-up (HR (95% CI): 1.56 (1.06–2.30)). Conclusion Vitamin D deficiency was common and was associated with poorer physical performance, lower muscle strength, and prevalent mobility and ADL disability among community-dwelling adults of advanced age. Moreover, vitamin D deficiency predicted incident mobility disability. PMID:22091492

  4. Spatially heterogeneous wastage of Himalayan glaciers.

    PubMed

    Fujita, Koji; Nuimura, Takayuki

    2011-08-23

    We describe volumetric changes in three benchmark glaciers in the Nepal Himalayas on which observations have been made since the 1970s. Compared with the global mean of glacier mass balance, the Himalayan glaciers showed rapid wastage in the 1970s-1990s, but similar wastage in the last decade. In the last decade, a glacier in an arid climate showed negative but suppressed mass balance compared with the period 1970s-1990s, whereas two glaciers in a humid climate showed accelerated wastage. A mass balance model with downscaled gridded datasets depicts the fate of the observed glaciers. We also show a spatially heterogeneous distribution of glacier wastage in the Asian highlands, even under the present-day climate warming.

  5. The contribution of glacier melt to streamflow

    SciTech Connect

    Schaner, Neil; Voisin, Nathalie; Nijssen, Bart; Lettenmaier, D. P.

    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 melt 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.

  6. A comparison of the lichenometric and Schmidt hammer dating techniques based on data from the proglacial areas of some Icelandic glaciers

    NASA Astrophysics Data System (ADS)

    Evans, D. J. A.; Archer, S.; Wilson, D. J. H.

    Measurements of Rhizocarpon section and Schmidt hammer R-values are reported from the proglacial geomorphic features on the forelands of the Icelandic glaciers of Kvı´árjökull, Hólárjökull and Heinabergsjökull (Öræfi and south Vatnajökull), Sandfellsjökull and Öldufellsjökull (east Mýrdalsjökull), and Brúárjökull, Eyjabakkajökull and west Snæfell (north Vatnajökull). These data are used in reconstructions of patterns of glacier recession since the Little Ice Age maximum, and the geomorphic signals of climatic versus non-climatic events are discussed. Age control was obtained from various dated substrates by utilizing historical accounts, aerial photographs and grave stones. Three lichen growth rates are calculated: (a) 0.51 mm a -1 (corrected to 0.50 mm a -1) with a colonization lag time of <16 yr for the arid forelands of north Vatnajökull; (b) 0.56 mm a -1 with a colonization lag time of 5 yr for the Icelandic southeast coast; and (c) 0.80 mm a -1 with a colonization lag time of 6.5 yr for the south Vatnajökull and east Mýrdalsjökull forelands. These compare favourably with a previously published growth rate of 0.44 mm a -1 for the arid north of Iceland. This regional coverage of data allows a comparison between annual precipitation totals and lichen growth rates and the construction of a growth rate prediction curve for Iceland. The success of the Schmidt hammer in differentiating moraines based upon age varied according to the geomorphological setting. Reasonable R-value/lichen size correlations were obtained on the east Mýrdalsjökull and Heinabergsjökull forelands where unrestricted glacier advance into lowlands allows for a higher degree of debris surface freshening by direct glacial processes. Weak correlations were obtained at Kvı´árjökull, where the glacier was restricted by a precursor latero-frontal moraine loop and therefore the debris comprising the Little Ice Age recessional moraines was diluted with material of

  7. Mountain Glaciers and Ice Caps

    USGS Publications Warehouse

    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.

  8. Advanced life events (ALEs) that impede aging-in-place among seniors.

    PubMed

    Lindquist, Lee A; Ramirez-Zohfeld, Vanessa; Sunkara, Priya; Forcucci, Chris; Campbell, Dianne; Mitzen, Phyllis; Cameron, Kenzie A

    2016-01-01

    Despite the wishes of many seniors to age-in-place in their own homes, critical events occur that impede their ability to do so. A gap exists as to what these advanced life events (ALEs) entail and the planning that older adults perceive is necessary. The purpose of this study was to identify seniors' perceptions and planning toward ALEs that may impact their ability to remain in their own home. We conducted focus groups with 68 seniors, age ≥65 years (mean age 73.8 years), living in the community (rural, urban, and suburban), using open-ended questions about perceptions of future heath events, needs, and planning. Three investigators coded transcriptions using constant comparative analysis to identify emerging themes, with disagreements resolved via consensus. Subjects identified five ALEs that impacted their ability to remain at home: (1) Hospitalizations, (2) Falls, (3) Dementia, (4) Spousal Loss, and (5) Home Upkeep Issues. While recognizing that ALEs frequently occur, many subjects reported a lack of planning for ALEs and perceived that these ALEs would not happen to them. Themes for the rationale behind the lack of planning emerged as: uncertainty in future, being too healthy/too sick, offspring influences, denial/procrastination, pride, feeling overwhelmed, and financial concerns. Subjects expressed reliance on offspring for navigating future ALEs, although many had not communicated their needs with their offspring. Overcoming the reasons for not planning for ALEs is crucial, as being prepared for future home needs provides seniors a voice in their care while engaging key supporters (e.g., offspring).

  9. Inhibition of Advanced Glycation End Products (AGEs) Accumulation by Pyridoxamine Modulates Glomerular and Mesangial Cell Estrogen Receptor α Expression in Aged Female Mice.

    PubMed

    Pereira-Simon, Simone; Rubio, Gustavo A; Xia, Xiaomei; Cai, Weijing; Choi, Rhea; Striker, Gary E; Elliot, Sharon J

    2016-01-01

    Age-related increases in oxidant stress (OS) play a role in regulation of estrogen receptor (ER) expression in the kidneys. In this study, we establish that in vivo 17β-estradiol (E2) replacement can no longer upregulate glomerular ER expression by 21 months of age in female mice (anestrous). We hypothesized that advanced glycation end product (AGE) accumulation, an important source of oxidant stress, contributes to these glomerular ER expression alterations. We treated 19-month old ovariectomized female mice with pyridoxamine (Pyr), a potent AGE inhibitor, in the presence or absence of E2 replacement. Glomerular ERα mRNA expression was upregulated in mice treated with both Pyr and E2 replacement and TGFβ mRNA expression decreased compared to controls. Histological sections of kidneys demonstrated decreased type IV collagen deposition in mice receiving Pyr and E2 compared to placebo control mice. In addition, anti-AGE defenses Sirtuin1 (SIRT1) and advanced glycation receptor 1 (AGER1) were also upregulated in glomeruli following treatment with Pyr and E2. Mesangial cells isolated from all groups of mice demonstrated similar ERα, SIRT1, and AGER1 expression changes to those of whole glomeruli. To demonstrate that AGE accumulation contributes to the observed age-related changes in the glomeruli of aged female mice, we treated mesangial cells from young female mice with AGE-BSA and found similar downregulation of ERα, SIRT1, and AGER1 expression. These results suggest that inhibition of intracellular AGE accumulation with pyridoxamine may protect glomeruli against age-related oxidant stress by preventing an increase of TGFβ production and by regulation of the estrogen receptor.

  10. Irregular tropical glacier retreat over the Holocene epoch driven by progressive warming.

    PubMed

    Jomelli, Vincent; Khodri, Myriam; Favier, Vincent; Brunstein, Daniel; Ledru, Marie-Pierre; Wagnon, Patrick; Blard, Pierre-Henri; Sicart, Jean-Emmanuel; Braucher, Régis; Grancher, Delphine; Bourlès, Didier Louis; Braconnot, Pascale; Vuille, Mathias

    2011-06-08

    The causes and timing of tropical glacier fluctuations during the Holocene epoch (10,000 years ago to present) are poorly understood. Yet constraining their sensitivity to changes in climate is important, as these glaciers are both sensitive indicators of climate change and serve as water reservoirs for highland regions. Studies have so far documented extra-tropical glacier fluctuations, but in the tropics, glacier-climate relationships are insufficiently understood. Here we present a (10)Be chronology for the past 11,000 years (11 kyr), using 57 moraines from the Bolivian Telata glacier (in the Cordillera Real mountain range). This chronology indicates that Telata glacier retreated irregularly. A rapid and strong melting from the maximum extent occurred from 10.8 ± 0.9 to 8.5 ± 0.4 kyr ago, followed by a slower retreat until the Little Ice Age, about 200 years ago. A dramatic increase in the rate of retreat occurred over the twentieth century. A glacier-climate model indicates that, relative to modern climate, annual mean temperature for the Telata glacier region was -3.3 ± 0.8 °C cooler at 11 kyr ago and remained -2.1 ± 0.8 °C cooler until the end of the Little Ice Age. We suggest that long-term warming of the eastern tropical Pacific and increased atmospheric temperature in response to enhanced austral summer insolation were the main drivers for the long-term Holocene retreat of glaciers in the southern tropics.

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

    NASA Astrophysics Data System (ADS)

    Yasunari, Teppei J.

    2011-12-01

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

  12. Heterogeneity in Karakoram glacier surges

    NASA Astrophysics Data System (ADS)

    Quincey, Duncan J.; Glasser, Neil F.; Cook, Simon J.; Luckman, Adrian

    2015-07-01

    Many Karakoram glaciers periodically undergo surges during which large volumes of ice and debris are rapidly transported downglacier, usually at a rate of 1-2 orders of magnitude greater than during quiescence. Here we identify eight recent surges in the region and map their surface velocities using cross-correlation feature tracking on optical satellite imagery. In total, we present 44 surface velocity data sets, which show that Karakoram surges are generally short-lived, lasting between 3 and 5 years in most cases, and have rapid buildup and relaxation phases, often lasting less than a year. Peak velocities of up to 2 km a-1 are reached during summer months, and the surges tend to diminish during winter months. Otherwise, they do not follow a clearly identifiable pattern. In two of the surges, the peak velocity travels down-ice through time as a wave, which we interpret as a surge front. Three other surges are characterized by high velocities that occur simultaneously across the entire glacier surface, and acceleration and deceleration are close to monotonic. There is also no consistent seasonal control on surge initiation or termination. We suggest that the differing styles of surge can be partly accounted for by individual glacier configurations and that while some characteristics of Karakoram surges are akin to thermally controlled surges elsewhere (e.g., Svalbard), the dominant surge mechanism remains unclear. We thus propose that these surges represent a spectrum of flow instabilities and the processes controlling their evolution may vary on a glacier by glacier basis.

  13. Glacier terminus fluctuations on Mt. Baker, Washington, USA, 1940-1990, and climatic variations

    SciTech Connect

    Harper, J.T. )

    1993-11-01

    The terminus positions of six glaciers located on Mount Baker, Washington, were mapped by photogrammetric techniques at 2- to 7-yr intervals for the period 1940-1990. Although the timing varied slightly, each of the glaciers experienced a similar fluctuation sequence consisting of three phases: (1) rapid retreat, beginning prior to 1940 and lasting through the late 1940s to early 1950s; (2) approximately 30 yr of advance, ending in the late 1970s to early 1980s; (3) retreat though 1990. Terminus positions changed by up to 750 m during phases, with the advance phase increasing the lengths of glaciers by 13 to 24%. These fluctuations are well explained by variations in a smoothed time-series of accumulation-season precipitation and ablation-season mean temperature. The study glaciers appear to respond to interannual scale changes in climate within 20 yr or less. The glaciers on Mount Baker have a maritime location and a large percentage of area at high elevation, which may make their termini undergo greater fluctuations in response to climatic changes, especially precipitation variations, than most other glaciers in the North Cascades region. 40 refs., 6 figs., 2 tabs.

  14. Age-specific mortality among advanced-age Chinese citizens and its difference between the two genders.

    PubMed

    Gan, J; Zheng, Z; Li, G

    1998-01-01

    This study describes the patterns of age-specific mortality among the elderly in China. Data were obtained from the 1990 census. The age groups ending in zero were validated with the Weber Index and found to be of good quality among those aged under 97 years. Differences were found between censuses and genders. The data for the aged were adjusted with 2-year moving averages in order to smooth the data. The end age of interval mortality is used. Tables provide single years of age between 60 years and 104 years by sex for the actual number and the adjusted number of each census year: 1953, 1964, 1982, and 1990. The pattern of change in age specific mortality rates (ASMRs) was similar in all census years. Mortality rates were highest among infants aged under 1 year, declined with increased age, and were lowest among 10 year olds. Mortality rose gradually after 10 years and sharply after 40-50 years. ASMRs were "U" shaped. Age-specific interval mortality rates among the elderly show that mortality increased drastically as it approached 90 years of age and then grew more slowly or declined. The Gompers rule about exponential increases among the extremely old (over 90 years) does not apply. Male mortality was higher than female mortality until the very old ages, which showed lower male mortality. The ratio declined with rising age until the two genders were equal. Mortality rose to a point and then declined to a lesser extent. The peak was 93 years in 1953, with a sex ratio (SR) of 32.48; 90 years in 1964, with an SR of 35.22; 93 years in 1982, with an SR of 35.96; and 95 years in 1990, with an SR of 32.94.

  15. Aldose reductase (AKR1B3) regulates the accumulation of advanced glycosylation end products (AGEs) and the expression of AGE receptor (RAGE).

    PubMed

    Baba, Shahid P; Hellmann, Jason; Srivastava, Sanjay; Bhatnagar, Aruni

    2011-05-30

    Diabetes results in enhanced chemical modification of proteins by advanced lipoxidation end products (ALEs) and advanced glycation end products (AGEs) precursors. These modifications have been linked to the development of several secondary diabetic complications. Our previous studies showed that aldose reductase (AR; AKR1B3) catalyzes the reduction of ALEs and AGEs precursors; however, the in vivo significance of this metabolic pathway during diabetes and obesity has not been fully assessed. Therefore we examined the role of AR in regulating ALEs and AGEs formation in murine models of diet-induced obesity and streptozotocin-induced diabetes. In comparison with wild-type (WT) and AR-null mice fed normal chow, mice fed a high-fat (HF) diet (42% kcal fat) showed increased accumulation of AGEs and protein-acrolein adducts in the plasma. AGEs and acrolein adducts were also increased in the epididymal fat of WT and AR-null mice fed a HF diet. Deletion of AR increased the accumulation of 4-hydroxy-trans-2-nonenal (HNE) protein adduct in the plasma and increased the expression of the AGE receptor (RAGE) in HF fed mice. No change in AGEs formation was observed in the kidneys of HF-fed mice. In comparison, renal tissue from AR-null mice treated with streptozotocin showed greater AGE accumulation than streptozotocin-treated WT mice. These data indicated that AR regulated the accumulation of lipid peroxidation derived aldehydes and AGEs under conditions of severe, but not mild, hyperglycemia and that deletion of AR increased RAGE-induction via mechanisms that were independent of AGEs accumulation.

  16. Primary succession changes diversity, abundance and function of soil microorganisms across glacier forelands

    NASA Astrophysics Data System (ADS)

    Kandeler, Ellen; Philippot, Laurent; Tscherko, Dagmar

    2010-05-01

    Primary successional ecosystems, such as glacier forelands, present an ideal opportunity to study the biological colonization of substrates. In a glacier foreland, time is substituted by space by using the distance from the retreating glacier as a proxy for soil age. Since the ice covers of many glaciers have receded over the past century, glacier forelands have released substrates for soil development. Autotrophic colonizers are expected to be important in the initial stages of the primary community assembly. Microbial growth, however, might also come from allochthonous dead organic matter and living invertebrates in these newly formed environments. Recently, a previously unrecognized heterotrophic phase which should allow the initial establishment of functional communities was proposed. Current studies in microbial ecology account for both autotrophic and heterotrophic colonization along primary successional gradients, such as glacier forelands, land lifts, floodplains, landslides and volcanoes. The presentation will give a summary of studies focusing on abundance, diversity and function of soil microorganisms along selected successional stages within the forelands of two glaciers in the Austrian Alps.

  17. A Century of Retreat at Portage Glacier, South-Central Alaska

    USGS Publications Warehouse

    Kennedy, Ben W.; Trabant, Dennis C.; Mayo, Lawrence R.

    2006-01-01

    Introduction: The Portage Glacier, in south-central Alaska, is viewed by thousands of visitors annually who come to the U.S. Forest Service Begich, Boggs Visitor Center located on the road system between Anchorage and Whittier, Alaska. During the past century, the terminus of the glacier has retreated nearly 5 kilometers to its present location (fig. 1). Like other glaciers that terminate in water, such as Columbia Glacier near Valdez or Mendenhall Glacier near Juneau, Portage Glacier has experienced accelerated retreats in recent decades that likely were initially triggered by climate change begun at the end of the Little Ice Age in the mid-1800s and subsequently controlled in recent history primarily by calving of the glacier terminus. Photographic records of the terminus covering 1914 until present day track the patterns of retreat. These data, coupled with USGS climate information collected from the southern end of the ice field, provide insight to the patterns of retreat that might be observed in the future.

  18. Differences in community composition of bacteria in four glaciers in western China

    NASA Astrophysics Data System (ADS)

    An, L. Z.; Chen, Y.; Xiang, S.-R.; Shang, T.-C.; Tian, L.-D.

    2010-06-01

    Microbial community patterns vary in glaciers worldwide, presenting unique responses to global climatic and environmental changes. Four bacterial clone libraries were established by 16S rRNA gene amplification from four ice layers along the 42-m-long ice core MuztB drilled from the Muztag Ata Glacier. A total of 151 bacterial sequences obtained from the ice core MuztB were phylogenetically compared with the 71 previously reported sequences from three ice cores extracted from ice caps Malan, Dunde, and Puruogangri. Six phylogenetic clusters Flavisolibacter, Flexibacter (Bacteroidetes), Acinetobacter, Enterobacter (Gammaproteobacteria), Planococcus/Anoxybacillus (Firmicutes), and Propionibacter/Luteococcus (Actinobacteria) frequently occurred along the Muztag Ata Glacier profile, and their proportion varied by seasons. Sequence analysis showed that most of the sequences from the ice core clustered with those from cold environments, and the sequence clusters from the same glacier more closely grouped together than those from the geographically isolated glaciers. Moreover, bacterial communities from the same location or similarly aged ice formed a cluster, and were clearly separate from those from other geographically isolated glaciers. In summary, the findings provide preliminary evidence of zonal distribution of microbial community, and suggest biogeography of microorganisms in glacier ice.

  19. Snow micro-structure at Kongsvegen glacier, Svalbard

    NASA Astrophysics Data System (ADS)

    Bilgeri, F.; Karner, F.; Steinkogler, W.; Fromm, R.; Obleitner, F.; Kohler, J.

    2012-04-01

    Measurements of physical snow properties have been performed at several sites at Kongsvegen glacier, which is a key Arctic glacier in western Spitzbergen (79N, 13E). The data were collected at six locations along the flow line of the glacier at different elevations (161 to 741m asl.) and describe snow that was deposited during winter 2010/11. We basically consider the vertical profiles of snow temperature, density, hardness, grain size and crystal shapes derived from standard stratigraphic methods (snow pits)and measurements using advanced instruments like Snow Micropen® and NIR imagery. Some parameters were measured repeatedly and with different instruments which proves a high quality as well as long-term and spatial representativeness of the data. The general snow conditions at the end of winter are characterized by a linear increase of snow depth and water equivalent with elevation. Snow hardness also increases with elevation while density remains remarkably constant. At most sites the snow temperature, density, hardness and grain size increase from the surface towards the snow-ice interface. The surface and the bottom layers stand out by specific changes in snow signature (crystal types) and delineate the bulk of the snow pack which itself features a rather complex layering. Comparison of the high-resolution profiles measured at different elevations at the glacier suggests some principal correlations of the signatures of hardness, grain size and crystal type. Thus, some major features (e.g. particularly hard layers) can be traced along the glacier, but the high-resolution layering can not straightforwardly be related from one site to the other. This basically reflects a locally different history of the snow pack in terms of precipitation events and post-depositional snow metamorphism. The issue is investigated more quantitatively by enhanced statistical processing of the observed signatures and simulation of the history of individual layers. These studies are

  20. Glacial to paraglacial history and forest recovery in the Oglio glacier system (Italian Alps) between 26 and 15 ka cal BP

    NASA Astrophysics Data System (ADS)

    Ravazzi, Cesare; Badino, Federica; Marsetti, Diego; Patera, Glauco; Reimer, Paula J.

    2012-12-01

    The integrated stratigraphic, radiocarbon and palynological record from an end-moraine system of the Oglio valley glacier (Italian Alps), propagating a lobe upstream in a lateral reach, provided evidence for a complete cycle of glacial advance, culmination and withdrawal during the Last Glacial Maximum and early Lateglacial. The glacier culminated in the end moraine shortly after 25.8 ± 0.8 ka cal BP, and cleared the valley floor 18.3-17.2 ± 0.3 ka cal BP. A primary paraglacial phase is then recorded by fast progradation of the valley floor. As early as 16.7 ± 0.3 ka cal BP, early stabilization of alluvial fans and lake filling promoted expansion of cembran pine. This is an unprecedented evidence of direct tree response to depletion of paraglacial activity during the early Lateglacial, and also documents the cembran pine survival in the mountain belt of the Italian Alps during the last glaciation. Between 16.1 and 14.6 ± 0.5 ka cal BP, debris cones emplacement points to a moisture increase favouring tree Betula and Pinus sylvestris-mugo. A climate perturbation renewed paraglacial activity. According to cosmogenic ages on glacial deposits and AMS radiocarbon ages from lake records in South-Eastern Alps such phase compares favourably with the Gschnitz stadial and with the oscillations recorded at lakes Ragogna, Längsee and Jeserzersee, most probably forced by the latest freshening phases of the Heinrich Event 1. A further sharp pine rise marks the subsequent onset of Bølling interstadial. The chronology of the Oglio glacier compares closely with major piedmont glaciers on the Central and Eastern Alpine forelands. On the other hand, the results of the present study imply a chronostratigraphic re-assessment of the recent geological mapping of the Central Italian Alps.

  1. Cost-Utility Analyses of Cataract Surgery in Advanced Age-Related Macular Degeneration

    PubMed Central

    Ma, Yingyan; Huang, Jiannan; Zhu, Bijun; Sun, Qian; Miao, Yuyu; Zou, Haidong

    2016-01-01

    ABSTRACT Purpose To explore the cost-utility of cataract surgery in patients with advanced age-related macular degeneration (AMD). Methods Patients who were diagnosed as having and treated for age-related cataract and with a history of advanced AMD at the Department of Ophthalmology, Shanghai General Hospital, Shanghai Jiao Tong University, were included in the study. All of the participants underwent successful phacoemulsification with foldable posterior chamber intraocular lens implantation under retrobulbar anesthesia. Best-corrected visual acuity (BCVA) and utility value elicited by time trade-off method from patients at 3-month postoperative time were compared with those before surgery. Quality-adjusted life years (QALYs) gained in a lifetime were calculated at a 3% annual discounted rate. Costs per QALY gained were calculated using the bootstrap method, and probabilities of being cost-effective were presented using a cost-effectiveness acceptability curve. Sensitivity analyses were performed to test the robustness of the results. Results Mean logarithm of the minimum angle of resolution BCVA in the operated eye increased from 1.37 ± 0.5 (Snellen, 20/469) to 0.98 ± 0.25 (Snellen, 20/191) (p < 0.001); BCVA in the weighted average from both eyes (=75% better eye + 25% worse eye) was changed from 1.13 ± 0.22 (Snellen, 20/270) to 0.96 ± 0.17 (Snellen, 20/182) (p < 0.001). Utility values from both patients and doctors increased significantly after surgery (p < 0.001 and p = 0.007). Patients gained 1.17 QALYs by cataract surgery in their lifetime. The cost per QALY was 8835 Chinese yuan (CNY) (1400 U.S. dollars [USD]). It is cost-effective at the threshold of 115,062 CNY (18,235 USD) per QALY in China recommended by the World Health Organization. The cost per QALY varied from 7045 CNY (1116 USD) to 94,178 CNY (14,925 USD) in sensitivity analyses. Conclusions Visual acuity and quality of life assessed by utility value improved significantly after surgery

  2. Female reproductive dysfunction during ageing: role of methylglyoxal in the formation of advanced glycation endproducts in ovaries of reproductively-aged mice.

    PubMed

    Tatone, C; Carbone, M C; Campanella, G; Festuccia, C; Artini, P G; Talesa, V; Focarelli, R; Amicarelli, F

    2010-01-01

    Reproductive dysfunction with ageing has been so far extensively characterized in terms of depletion of ovarian follicles and reduced ability to produce gametes competent for fertilization. Nevertheless, molecular mechanisms underlying this process are still poorly understood. In the present study we addressed the hypothesis that methylglyoxal (MG), a major precursor of Advanced Glycation Endproducts (AGE), may contribute to molecular damage occurring during ovarian ageing. Our results showed that the biochemical activity of glyoxalase 1, the main component of the MG scavenging system, is significantly decreased in ovaries from reproductively-aged mice in comparison with the young group. This effect was associated with decreased expression at protein and RNA level of this enzyme and increased intraovarian level of MG. MG-arginine adducts argpyrimidine as detected with a specific antibody was found to accumulate with ageing in specific ovarian compartments. Separation of ovarian proteins by 2D gels and Western blotting revealed an approximate 30-fold increase in the extent of protein glycation in aged ovaries along with the appearance of eight argpyrimidine modified proteins exclusive for the aged group. In conclusion, the present results show that impaired MG detoxification causing relevant damage to the ovarian proteome might be one of the mechanisms underlying reproductive ageing and/or ageing-like ovarian diseases.

  3. Pan–ice-sheet glacier terminus change in East Antarctica reveals sensitivity of Wilkes Land to sea-ice changes

    PubMed Central

    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

  4. Pan-ice-sheet glacier terminus change in East Antarctica reveals sensitivity of Wilkes Land to sea-ice changes.

    PubMed

    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.

  5. Glacier area changes in Northern Eurasia

    NASA Astrophysics Data System (ADS)

    Khromova, Tatiana; Nosenko, Gennady; Kutuzov, Stanislav; Muraviev, Anton; Chernova, Ludmila

    2014-01-01

    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 landscape changes in the glacial zone, the origin of new lakes and activation of natural disaster processes, catastrophic mudflows, ice avalanches, outburst floods, etc. The 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 and their changes. The first estimation of glacier state and glacier distribution on the territory of the former Soviet Union has been done in the USSR Glacier Inventory (UGI) published in 1965-1982. The UGI is based on topographic maps and air photos and reflects the status of the glaciers in the 1940s-1970s. There is information about 28 884 glaciers with an area of 7830.75 km2 in the inventory. It covers 25 glacier systems in Northern Eurasia. In the 1980s the UGI has been transformed into digital form as a part of the World Glacier Inventory (WGI). 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 the 20th century. About 15 000 glacier outlines for the Caucasus, Polar Urals, Pamir Alay, Tien Shan, Altai, Kamchatka and Russian Arctic have been derived from ASTER and Landsat imagery and can be used for glacier change evaluation. Results of the analysis indicate the steady trend in glacier shrinkage in all mountain regions for the second part of the 20th century. Glacier area loss for the studied regions varies from 13% (Tien Shan) to 22.3% (Polar Urals). The common driver, most likely, is an increase in summer air temperature. There is also a very large variability in the degree of individual

  6. Generation of the relationship between glacier area and volume for a tropical glacier in Bolivian Andes

    NASA Astrophysics Data System (ADS)

    Liu, T.; Kinouchi, T.; Hasegawa, A.; Tsuda, M.; Iwami, Y.; Asaoka, Y.; Mendoza, J.

    2015-12-01

    In Andes, retreat of tropical glaciers is rapid, thus water resources currently available from glacierized catchments would be changed in its volume and temporal variations due to climate change and glacier shrinkage. The relationship between glacier area and volume is difficult to define however which is important to monitor glaciers especially those are remote or inaccessible. Water resources in La Paz and El Alto in Bolivia, strongly depend on the runoff from glacierized headwater catchments in the Cordillera Real, Andes, which is therefore selected as our study region.To predict annual glacier mass balances, PWRI-Distributed Hydrological Model (PWRI-DHM) was applied to simulate runoff from the partially glacierized catchments in high mountains (i.e. Condoriri-Huayna West headwater catchment located in the Cordillera Real, Bolivian Andes). PWRI-DHM is based on tank model concept in a distributed and 4-tank configuration including surface, unsaturated, aquifer, and river course tanks. The model was calibrated and validated with observed meteorological and hydrological data from 2011 to 2014 by considering different phases of precipitation, various runoff components from glacierized and non-glacierized areas, and the retarding effect by glacial lakes and wetlands. The model is then applied with MRI-AGCM outputs from 1987 to 2003 considering the shrinkage of glacier outlines since 1980s derived from Landsat data. Annual glacier mass balance in each 100m-grid was reproduced, with which the glacier area-volume relationship was generated with reasonable initial volume setting. Out study established a method to define the relationship between glacier area and volume by remote sensing information and glacier mass balances simulated by distributed hydrological model. Our results demonstrated that the changing trend of local glacier had a consistency the previous observed glacier area-volume relationship in the Cordillera Real.

  7. Columbia Glacier in 1984: disintegration underway

    SciTech Connect

    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 until 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 fac