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
Burgess, Evan W; Forster, Richard R; Larsen, Christopher F
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. PMID:23857302
Choudhari, Sulbha; Lohia, Ruchi; Grigoriev, Andrey
The temperature in the Arctic region has been increasing in the recent past accompanied by melting of its glaciers. We took a snapshot of the current microbial inhabitation of an Alaskan glacier (which can be considered as one of the simplest possible ecosystems) by using metagenomic sequencing of 16S rRNA recovered from ice/snow samples. Somewhat contrary to our expectations and earlier estimates, a rich and diverse microbial population of more than 2,500 species was revealed including several species of Archaea that has been identified for the first time in the glaciers of the Northern hemisphere. The most prominent bacterial groups found were Proteobacteria, Bacteroidetes, and Firmicutes. Firmicutes were not reported in large numbers in a previously studied Alpine glacier but were dominant in an Antarctic subglacial lake. Representatives of Cyanobacteria, Actinobacteria and Planctomycetes were among the most numerous, likely reflecting the dependence of the ecosystem on the energy obtained through photosynthesis and close links with the microbial community of the soil. Principal component analysis (PCA) of nucleotide word frequency revealed distinct sequence clusters for different taxonomic groups in the Alaskan glacier community and separate clusters for the glacial communities from other regions of the world. Comparative analysis of the community composition and bacterial diversity present in the Byron glacier in Alaska with other environments showed larger overlap with an Arctic soil than with a high Arctic lake, indicating patterns of community exchange and suggesting that these bacteria may play an important role in soil development during glacial retreat. PMID:24712530
van Beusekom, A. E.; O'Neel, S.; March, R. S.; Sass, L. C.
Resolving the relationship between glacier surface-forcing (climate) and glacier geometry changes is accomplished through mass-balance estimates which can be made with remote sensing methods or field-based observations. The small scale of Alaskan glaciers has prevented remote sensing methods until recently, and field data are essential for validating new techniques. Field data provide the only long duration record that can be studied with respect to climate. The United States Geological Survey has maintained a 44-year mass-balance program at Alaska’s Gulkana Glacier and Wolverine Glacier. We have reanalyzed the Alaskan benchmark glaciers mass balance time series so that all data are treated similarly and systematically. Both glaciers are undergoing sustained mass loss with an increasing rate in recent years. However, the magnitude of the calculated loss depends on the number and location of the data collection sites. We explore the sensitivity of the glacier-wide balance estimates to the method of integration used on the necessarily point data. The robustness of the balance is strengthened with use of independent photogrammetric measurements.
Berthier, E.; Schiefer, E.; Clarke, G. K.; Menounos, B.; Rémy, F.; Cazenave, A. A.
Over the last 50 years, retreating glaciers and ice caps (GIC) contributed 0.5 mm/yr to SLR, and one third is believed to originate from ice masses bordering the Gulf of Alaska. However, these estimates of ice wastage in Alaska are based on methods that directly measure mass changes from a limited number of glaciers and extrapolate the results to estimate ice loss for the many thousands of others. Here, using a new glacier inventory with elevation changes derived from sequential digital elevation models (DEMs), we found that, between 1962 and 2006, Alaskan glaciers lost 41.9 ± 8.6 km**3/yr water equivalent (w.e.) and contributed 0.12 ± 0.02 mm/yr to SLR. Our ice loss is 34% lower than previous estimates. Reasons for our lower values include the higher spatial resolution of the glacier inventory used in our study and the complex pattern of ice elevation changes at the scale of individual glaciers and mountain ranges which was not resolved in earlier work. Our ice elevation changes reveal that glacier dynamics (surges, phase of the tidewater cycle, etc...) have a profound effect on the wastage of Alaska glaciers. 3D satellite view of Columbia glacier, Chugach Mountains, Alaska. (Copyright CNES 2007, Distribution Spot Image, processing E. Berthier CNRS)
Preliminary aerial photographic studies indicate that the Alaskan earthquake produced some rockfalls but no significant snow and ice avalanches on glaciers. No rapid, short-lived glacier advances (surges) are conclusively associated with this earthquake. Recent evidence fails to support the earthquake-advance theory of Tarr and Martin.
Molnia, B. F.
, Wrangell-St. Elias National Park and Preserve, Denali National Park and Preserve, the northern and northwestern Prince William Sound area of the Chugach National Forest, and the Mendenhall Glacier area of the Tongass National Forest to document and determine the extent of changing glaciers and landscapes. The use of repeat photography to document temporal change is not new. It originated as a glacier-monitoring technique in the European Alps more than 150 years ago. What is unique in this Alaskan application of repeat photography is the systematic approach being used to obtain photographic documentation of glacier and landscape change for every glacier-hosting fiord in western southcentral Alaska, as well as at many Alaskan valley glacier sites. What is also unique is the development of an annotated website which presents many pairs of these photographs as well as ancillary materials to help convey the basics of Alaskan glaciers and climate change. The website, titled 'Glacier and Landscape Change in Response to Changing Climate', (http://www.usgs.gov/climate_landuse/glaciers/) was awarded the 2010 USGS Shoemaker External Communications Award.
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.
Spencer, Robert G. M.; Vermilyea, Andrew; Fellman, Jason; Raymond, Peter; Stubbins, Aron; Scott, Durelle; Hood, Eran
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.
Van Beusekom, Ashely E.; O'Nell, Shad R.; March, Rod S.; Sass, Louis C.; Cox, Leif H.
At Gulkana and Wolverine Glaciers, designated the Alaskan benchmark glaciers, we re-analyzed and re-computed the mass balance time series from 1966 to 2009 to accomplish our goal of making more robust time series. Each glacier's data record was analyzed with the same methods. For surface processes, we estimated missing information with an improved degree-day model. Degree-day models predict ablation from the sum of daily mean temperatures and an empirical degree-day factor. We modernized the traditional degree-day model and derived new degree-day factors in an effort to match the balance time series more closely. We estimated missing yearly-site data with a new balance gradient method. These efforts showed that an additional step needed to be taken at Wolverine Glacier to adjust for non-representative index sites. As with the previously calculated mass balances, the re-analyzed balances showed a continuing trend of mass loss. We noted that the time series, and thus our estimate of the cumulative mass loss over the period of record, was very sensitive to the data input, and suggest the need to add data-collection sites and modernize our weather stations.
Schmidt, Susanne; Nüsser, Marcus
The widely discussed controversy about Himalayan glacier changes instigated a current boom in studies on a regional scale. In contrast to often simplified assumptions of general and mostly rapid glacier retreat, recent studies show a more complex pattern with stable, advancing and retreating glaciers. Furthermore, changes of debris covered glaciers are discussed controversial. Due to the great vertical span and steep relief, large ice streams in the Himalaya and Karakoram are often primarily fed by avalanches. Their impact on glacier mass balances is often unconsidered in present studies. However, Hewitt (2014) highlighted the crucial role of snow and ice re-distribution by avalanches for Karakoram glaciers. He used a concept of glacier typology based on different nourishment processes introduced at the beginning of the 20th century. By using this concept, Hewitt classified large glaciers in order to identify the effect of avalanches on the mass balance, because many Karakoram glaciers show low down-wasting or even thickening processes described as the "Karakoram anomaly" (Hewitt 2005). Also in the Nanga Parbat region, the western corner of the High Himalaya, the topography is characterized by steep rock walls with vertical distances up to 4700 m. The debris covered glaciers reach down to 2920 m a.s.l. and are regularly fed by small and large avalanches. Our field based investigations show that the glaciers are characterized by small retreating rates since 1857, when Adolph Schlagintweit has mapped them for the first time; others such as the Raikot Glacier are fluctuating since 1934. Furthermore, the extent of down-wasting varies between different glaciers. By using multi-temporal satellite data, topographical maps, sketches and terrestrial photographs changes of glacier lengths were measured. In order to calculate the down-wasting rates, a digital elevation model (DEM) with a spatial resolution of 30x30 m² was derived from the digitized contour lines of the
Grimm, R. E.; Stillman, D. E.; Kowalewski, D. E.
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
Kopczynski, S.E.; Ramage, J.; Lawson, D.; Goetz, S.; Evenson, E.; Denner, J.; Larson, G.
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.
Snow and ice algae are cold tolerant algae growing on the surface of snow and ice, and they play an important role in the carbon cycles for glaciers and snowfields in the world. Seasonal and altitudinal variations in seven major taxa of algae (green algae and cyanobacteria) were investigated on the Gulkana glacier in Alaska at six different elevations from May to September in 2001. The snow algal communities and their biomasses changed over time and elevation. Snow algae were rarely observed on the glacier in May although air temperature had been above 0 ° C since the middle of the month and surface snow had melted. In June, algae appeared in the lower areas of the glacier, where the ablation ice surface was exposed. In August, the distribution of algae was extended to the upper parts of the glacier as the snow line was elevated. In September, the glacier surface was finally covered with new winter snow, which terminated algal growth in the season. Mean algal biomass of the study sites continuously increased and reached 6.3 × 10 μl m-2 in cell volume or 13 mg carbon m-2 in September. The algal community was dominated by Chlamydomonas nivalis on the snow surface, and by Ancylonema nordenskiöldii and Mesotaenium berggrenii on the ice surface throughout the melting season. Other algae were less abundant and appeared in only a limited area of the glacier. Results in this study suggest that algae on both snow and ice surfaces significantly contribute to the net production of organic carbon on the glacier and substantially affect surface albedo of the snow and ice during the melting season.
Womble, J. N.; McNabb, R. W.; Gens, R.; Prakash, A.
Some of the largest aggregations of harbor seals (Phoca vitulina richardii) in Alaska occur in tidewater glacier fjords where seals rest upon icebergs that are calved from tidewater glaciers into the marine environment. The distribution, amount, and size of floating ice in fjords are likely important factors influencing the spatial distribution and abundance of harbor seals; however, fine-scale characteristics of ice habitat that are used by seals have not been quantified using automated methods. We quantified the seasonal changes in ice habitat for harbor seals in Johns Hopkins Inlet, a tidewater glacier fjord in Glacier Bay National Park, Alaska, using aerial photography, object-based image analysis, and spatial models. Aerial photographic surveys (n = 53) were conducted of seals and ice during the whelping (June) and molting (August) seasons from 2007-2014. Surveys were flown along a grid of 12 transects and high-resolution digital photos were taken directly under the plane using a vertically aimed camera. Seal abundance and spatial distribution was consistently higher during June (range: 1,672-4,340) than August (range: 1,075-2,582) and corresponded to the spatial distribution and amount of ice. Preliminary analyses from 2007 suggest that the average percent of icebergs (ice ≥ than 1.6m2) and brash ice (ice < 1.6m2) per scene were greater in June (icebergs: 1.8% ± 1.6%; brash ice: 43.8% ± 38.9%) than August (icebergs: 0.2% ± 0.7%; brash ice; 15.8% ± 26.4%). Iceberg angularity (an index of iceberg shape) was also greater in June (1.7 ± 0.9) than August (0.9 ± 0.9). Potential factors that may influence the spatio-temporal variation in ice habitat for harbor seals in tidewater glacier fjords include frontal ablation rates of glaciers, fjord circulation, and local winds. Harbor seals exhibit high seasonal fidelity to tidewater glacier fjords, thus understanding the relationships between glacier dynamics and harbor seal distribution will be critical for
Song, Yu; Zhu, Tong; Cai, Xuhui; Lin, Weili; Kang, Ling
Persistent glacier winds blowing from noon to midnight in summer are present in the Rongbuk Valley, north of Mount Everest, with a maximum speed of 10 m s-1 and a vertical thickness as high as 1 km. These glacier winds may bring upper level atmosphere ozone to the surface, having a significant impact on the atmospheric environment. Such phenomena may be typical of the Tibetan Plateau, where most high mountains are covered by snow or glacier ice throughout the year. The Advanced Regional Prediction Model was used to simulate the down-valley flows, using realistic topography but neglecting synoptic winds. The modeling results agree well with the observations obtained in June 2002, revealing that the glacier winds are thermal flows primarily driven by the along-valley temperature gradient between the colder air over the glacier surface and the warmer air over surface areas covered by rock debris, which maintains air advection along the Rongbuk Valley. Downslope winds over the glacier slopes, especially from the western valley side, and the West Rongbuk Glacier, were forced by their inertia farther down into the valley and would intensify the glacier winds. The narrowing of the Rongbuk Valley could also speed up the glacier winds. Sensitivity tests showed that the detailed distribution of the Rongbuk Glacier, delineated by data from the Enhanced Thematic Mapper Plus on Landsat 7, plays an important role in glacier winds development. The glacier winds could be much weaker in winter when the area is completely snow covered.
Viani, Cristina; Machguth, Horst; Huggel, Christian; Perotti, Luigi; Giardino, Marco
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
The article tackles the issue of which factors may influence the flow direction and morphological shape of glacier tongues terminating at tributary junctions to the main valley in high mountain landscapes. A very particular morphological form of a glacier tongue shows the Jatunraju Glacier in the Cordillera Blanca (Perú). It terminates in the superior Parón Valley with a prominent crooked form, embedded in a 250 m-high moraine pedestal. Lliboutry (1977) has explained the deviation of the Jatunraju Glacier tongue as a result of a proglacial lake outburst. Alternative hypothetical models on a general scale have been developed for the causes determining the morphological characteristics of glacier tongues. These are based on empirical field evidence from the Parón Valley and from glaciers located in other high mountain areas, in particular in the Himalaya Region, where glacier tongues in confluence settings are abundant. The comparative investigations demonstrate that the pronounced crooked form of the Jatunraju Glacier may not be the result of a single extreme event, but may have been produced as well by gradual processes. In a general context, the study shows that crooked glacier tongues are common landforms in other mountain regions and mainly intrinsic to debris-covered glaciers. The morphological evolution of glacier tongues may involve a polygenetic process pattern over a longer geological time period. Apart from the steepness of the valley gradient of the main valley, the former confluence from the source glacier with the main glacier during times of a more extensive glaciation is regarded as one of the dominating factors controlling the later evolution of glacier tongues in general ("inherited confluence model").
Nagorski, Sonia A; Engstrom, Daniel R; Hudson, John P; Krabbenhoft, David P; Hood, Eran; DeWild, John F; Aiken, George R
Southeastern Alaska is a remote coastal-maritime ecosystem that is experiencing increased deposition of mercury (Hg) as well as rapid glacier loss. Here we present the results of the first reported survey of total and methyl Hg (MeHg) concentrations in regional streams and biota. Overall, streams draining large wetland areas had higher Hg concentrations in water, mayflies, and juvenile salmon than those from glacially-influenced or recently deglaciated watersheds. Filtered MeHg was positively correlated with wetland abundance. Aqueous Hg occurred predominantly in the particulate fraction of glacier streams but in the filtered fraction of wetland-rich streams. Colonization by anadromous salmon in both glacier and wetland-rich streams may be contributing additional marine-derived Hg. The spatial distribution of Hg in the range of streams presented here shows that watersheds are variably, yet fairly predictably, sensitive to atmospheric and marine inputs of Hg. PMID:24035911
Staiger, J. W.; Marchant, D. R.; Schaefer, J. M.; Johnson, J. V.; Oberholzer, P.
Vernier Valley (78o S, 161o E) opens onto a peripheral lobe of upper Ferrar glacier in the Dry Valleys of southern Victoria Land, Antarctica. The areal distribution of Ferrar drifts, along with a relative and numerical chronology afforded by surface-weathering characteristics and 3He - 21Ne exposure-age data, are used to reconstruct the Late Miocene-to-Pleistocene history of upper Ferrar Glacier. Applying a modest erosion rate correction of 10 cm Ma-1, our results show that the glacial record provided by Ferrar (1, 2, 3, and 4) drifts in Vernier Valley extends back into late Miocene time. Cosmogenic ages for clasts on the modern, ice-cored Ferrar 1 moraine suggest that nuclide inheritance is negligible. The development of weathering pits and desert varnish on surface cobbles varies linearly with cosmogenic age. Ice-surface profiles reconstructed from the moraine distribution and exposure-ages of boulders atop the moraines indicate that the ice-surface elevation of upper Ferrar Glacier has lowered roughly 50 m throughout the Quaternary Period and roughly 125 m since late Miocene time. Conversely, during MIS 2, the ice-surface elevation of upper Ferrar Glacier was likely no higher than today and may have been below modern levels. The moraine now forming through ice sublimation and debris accumulation at the modern, cold-based Ferrar Glacier margin is texturally similar to older drifts up-valley. The slow recession of cold-based glacier ice (and without surface melting ablation zones) in lower Vernier Valley implies enduring cold-desert conditions, much like those of today, for at least the last ~6.5 Ma. Results from a 2-D glacier flow-band model also demonstrate that upper Ferrar Glacier lacked basal-melting zones even during the Pliocene optimum. The overall stability of this glacial system has implications for the response of ice in this sector of Antarctica to future polar warming.
Muskett, Reginald R.; Lingle, Craig S.; Tangborn, Wendell V.; Rabus, Bernhard T.
Digital elevation models (DEMs) of Bagley Ice Valley and Malaspina Glacier produced by (i) Intermap Technologies, Inc. (ITI) from airborne interferometric synthetic aperture radar (InSAR) data acquired 4-13 September 2000, (ii) the German Aerospace Center (DRL) from spaceborne InSAR data acquired by the Shuttle Radar Topography Mission (SRTM) 11-22 February 2000, and (iii) the US Geological Survey (USGS) from aerial photographs acquired in 1972/73, were differenced to estimate glacier surface elevation changes from 1972 to 2000. Spatially non-uniform thickening, 10 +/- 7 m on average, is observed on Bagley Ice Valley (accumulation area) while non-uniform thinning, 47 +/- 5 m on average, is observed on the glaciers of the Malaspina complex (mostly ablation area). Even larger thinning is observed on the retreating tidewater Tyndall Glacier. These changes have resulted from increased temperature and precipitation associated with climate warming, and rapid tidewater retreat.
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.
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
Campbell, Seth William
Mountain glaciers and ice caps (GICs) currently contribute ~0% to annual sea level rise. Most are temperate, therefore having the potential for rapid retreat from rising atmospheric temperatures. This climate sensitivity makes GIC stability and their impact on sea level rise a scientific problem with societal implications. To accurately predict impacts from GIC changes, knowledge of glacier components (e.g., basin geometry, mass balance, and dynamics) is needed. The goal of my dissertation research is to determine information about glacier geometry, snow-fire, and englacial stratigraphy using ground-penetrating radar (GPR) to enhance our understanding of valley glacier mass balance, dynamics, and stability. I first examine glacier basin geometry and ice volume of two temperate glaciers (Jarvis Glacier, Alaska and Nisqually Glacier, Washington) and demonstrate that significant errors (≥30-50%) can arise when using empirically-based volume estimates without geophysical constraints. I next determine spatial variability of accumulation across the temperate Juneau Icefield in Alaska usina GPR to interpolate between snowpits. To accomplish this, the dependence of radar velocity on snow density (~.3-0.7 g cm -3) and water content (0-9% by volume) needs to be addressed. Results show that on average, 2.1+/-0.5 m (water equivalent) of winter snow accumulates across the icefield with accumulation patterns depending on elevation, aspect, and proximity to moisture source. The third component of my dissertation combines locally measured accumulation rates, ice flow velocities, and englacial structures imaged with GPR to calculate that a negative mass balance (-0.25 cm a -1) has existed in valley glaciers of the Pensacola Mountains, West Antarctica over the past 1200 years. Finally, 1 use a 3-dimensional finite element non-Newtonian model to characterize the stress fields and current dynamics of a small ice divide. GPR-derived basin geometry is used for model boundary
Lama, L.; Kayastha, R. B.; Maharjan, S. B.; Bajracharya, S. R.; Chand, M. B.; Mool, P. K.
Glaciers are one of the important natural resources of freshwater and sources of water for hydropower, agriculture and drinking whenever the water is scarce. This mapping and change analysis helps to understand the status and decadal changes of glaciers in Hidden Valley, Mustang district, Nepal. The investigation is carried out using Landsat images of the years 1977 (~1980s), 1990, 2000 and 2010. We mapped 10 glaciers of the Hidden Valley covering an area of 19.79 km2 based on the object-based image classification method using an automatic method and manual delineation by a Geographic Information System (GIS), separately. The glacier outlines for 2010, 2000, 1990 and 1980s in both methods are delineated from the multispectral Landsat images of the respective years. The total area losses of the glaciers from the automatic method are 1.713 and 0.625 km2 between 1990-2000 and 2000-2010 and from manual delineation are 2.021, 1.264, 1.041 km2 between ~1980s-1990, 1990-2000 and 2000-2010. The amount of average estimated glacier ice reserves lost is 0.326 km3 (26.26 %) and the total glacier area loss is 4.33 km2 (21.87 %) from the 1980s to 2010 based on manual delineation. The glaciers of Hidden Valley are shrinking and fragmented due to decrease in glacier area and ice reserves.
Sletten, R. S.; Hallet, B.; Hagedorn, B.; Stone, J.
Soil inflation in dry environments is a common occurrence in areas where extensive desert pavements overlie silt-size particles of eolian origin. Another type of surface inflation, which we term hyperinflation, has been documented in the Dry Valleys where fines drop into contraction cracks that annually open and close 0.5 to 1.5 cm. Particles of local or eolian origin that are smaller than the crack opening can fall into the cracks,. We have cored over 30 m into such a hyperinflated surface in lower Beacon Valley. Large clasts several cm to over 10 m are suspended on top of the finer sediments leading to the characteristic rocky surface of Beacon Valley. These processes have been active over at least several million years based on cosmogenic 10 Be and 26 Al profiles with depth. This new hyperinflation has much in common with the progressive addition of ice into the permafrost in Siberia forming the classic edoma or ice-wedge complexes. We propose that these “sand-wedge complexes” form in a similar way but are only sand because liquid water seldom forms in sufficient amounts to fill the contraction cracks in the hyperarid Beacon Valley. Furthermore, our analysis of a 10-m core collected earlier reveal historical waxing and waning of the Taylor Glacier over lower Beacon Valley in the past several million years; one of these incursions of ice may be responsible for the formation of buried glacial ice found in middle Beacon Valley. We are currently processing our 30-m core and believe that this will improve definition of the extent and chronology of Taylor Glacier advances.
Knauf, M.; Williams, M. W.; Caine, N.
An ongoing concern in alpine areas of the western United States is the high concentrations of nitrate in surface waters. A number of research scientists have shown that talus areas are one source of this elevated nitrate (Williams et al., 1997; Campbell et al., 2002). Here we evaluate the potential contribution of nitrate to surface waters from a previously overlooked source: rock glaciers. Water draining from the Green Lake 5 rock glacier in the Colorado Front Range has been sampled for nitrate and ammonium since 1998 as part of the Niwot Ridge LTER program. The mean concentration of nitrate in stream waters in the Green Lakes Valley is 16.12 ueq/L, and for talus streams is 20 ueq/L. In comparison, the stream draining the rock glacier has an average nitrate concentration of 54 ueq/L. Moreover, nitrate values from the stream draining the rock glacier peak in the late summer at over 100 ueq/L. The sources of these high nitrate values from the rock glacier are unknown at this time; we evaluate several hypotheses. Increased nitrate could be a result of dry deposition on the rock glacier that is flushed during snowmelt and rain events. Another hypothesis is that microbial processes within the rock glacier have contribute to higher nitrate concentrations. Here we evaluate the sources and fate of nitrate in waters draining the Green Lake 5 rock glacier in 2003 using a combination of stable (delta O18) and radiogenic (tritium) water isotopes, fractionation of dissolved organic matter, fluorescence index of dissolved organic matter, and mineralization experiments. These site-specific results are then placed in a regional context through a synoptic sampling of streams draining rock glaciers throughout the Rocky Mountain region. Works Cited Williams, M. W., T. Davinroy, and P. D. Brooks. 1997. Organic and inorganic nitrogen pools in talus soils and water, Green Lakes Valley, Colorado Front Range, Hydrologic Processes, 11(13): 1747-1760. Campbell, Donald H., Carol Kendall
Duhnforth, M.; Anderson, R. S.; Colgan, W.
The erosional signature of a glacier is often characterized by a longitudinal valley profile that exhibits a stepped morphology, decreased valley floor slope, and overdeepened basin. Numerical modeling experiments have demonstrated that the evolution of such profiles is highly dependent on ice discharge, and hence subglacial water pressure-dependent sliding speed, as well as the material properties of the underlying bedrock. While there are abundant examples of landscapes that demonstrate the valley profile characteristic of efficient glacial erosion, some highly glaciated mountain ranges such as the Himalayas maintain exceptionally tall peaks. These exceptionally tall peaks may be interpreted as evidence for the absence of efficient glacial erosion. One possible explanation for the absence of efficient glacial erosion is the presence of cold-based glacial conditions. Alternatively, the presence of erosionally resistant bedrock with wide fracture spacing may limit erosion. In temperate glaciers, in which basal ice temperatures are warm, or at the pressure melting point (PMP), sliding and erosion occur whenever and wherever high subglacial water pressures exist. In polythermal glaciers, by contrast, erosion efficiency is strongly modulated by basal ice temperature. Sliding, and hence erosion, is prevented when and where basal ice temperatures are cold, or below the PMP. To date, the influence of spatial and temporal variations in basal ice temperature on the efficiency of glacial erosion over long timescales (>1 Ma) remains largely unexplored. We present numerical model results in which we explore the influence of glacier ice temperature on the longitudinal valley profile that emerges during long-term glacial erosion. We focus on identifying conditions that maintain polythermal glaciers in which the basal ice at high elevations is cold, while the basal ice at lower elevations is at the PMP. These unique conditions limit sliding and erosion to low elevations. In
McGrath, D.; Gusmeroli, A.; Oneel, S.; Sass, L. C.; Arendt, A. A.; Wolken, G. J.; Kienholz, C.; McNeil, C.
Constraining annual snowfall accumulation in mountain glacier environments is essential for determining the annual mass balance of individual glaciers and predicting seasonal meltwater runoff to river and marine ecosystems. However, large spatial and elevation gradients, coupled with sparse point measurements preclude accurate quantification of this variable using traditional methods. Here, we report on an extensive field campaign conducted in March-May 2013 on key benchmark glaciers in Alaska, including Taku Glacier near Juneau, Scott Glacier near Cordova, both Eklutna and Wolverine Glacier near Anchorage and Gulkana Glacier in the interior Alaska Range. Over 50 km of 500 MHz common-offset ground penetrating radar (GPR) surveys were collected on each glacier, with an emphasis on capturing spatial variability in the accumulation zone. Frequent in situ observations were collected for comparison with the GPR, including probe depths, snow pits and shallow firn cores (~8 m). We report on spatial and elevation gradients across this suite of glaciers and across numerous climatic zones and discuss differences between GPR and in situ derived annual accumulation estimates. This comparison is an essential first step in order to effectively evaluate regional atmospheric re-analysis products.
Medwedeff, W. G.; Roe, G.
Glacier mass balance (i.e., accumulation and ablation) is the most direct connection between climate and glaciers. We perform a comprehensive evaluation of the available global network of mass-balance measurements, with a particular interest given to mountain and valley glaciers. Each mass-balance time series is decomposed into a trend and the variability about that trend. Observed variability ranges by an order of magnitude, depending on climate setting (i.e., maritime vs. continental). For the great majority of glaciers, variability is well characterized by normally distributed, random fluctuations that are uncorrelated between seasons, or in subsequent years. The magnitude of variability for both summer and winter is well correlated with mean wintertime balance, which reflects the climatic setting. Collectively, summertime variability exceeds wintertime variability, except for maritime glaciers. Trends in annual mass balance are generally negative, driven primarily by summertime changes. Approximately 25% of annual-mean records show statistically significant negative trends when judged in isolation. In aggregate, the global trend is negative and significant. We further evaluate the magnitude of trends relative to the variability. We find that, on average, trends are approximately -0.2 standard deviations per decade, although there is a broad spread among individual glaciers. Finally, for two long records we also compare mass-balance trends and variability with nearby meteorological stations. We find significant differences among stations meaning caution is warranted in interpreting any point measurement (such as mass balance) as representative of region-wide behavior. By placing observed trends in the context of natural variability, the results are useful for interpreting past glacial history, and for placing constraints on future predictability.
Lingle, Craig S.; Fatland, Dennis R.; Voronina, Vera A.; Ahlnaes, Kristina; Troshina, Elena N.
ERS-1 synthetic aperture radar (SAR) imagery was employed for the measurement of the dynamics of the Bagley icefield during a major surge in 1993-1994, the measurement of ice velocities on the Malaspina piedmont glacier during a quiescent phase between surges, and for mapping the snow lines and the position of the terminus of Nabesna glacier on Mount Wrangell (a 4317 m andesitic shield volcano) in the heavily glacierized Saint Elias and Wrangell Mountains of Alaska. An overview and summary of results is given. The methods used include interferometry, cross-correlation of sequential images, and digitization of boundaries using terrain-corrected SAR imagery.
Barclay, David J.; Yager, Elowyn M.; Graves, Jason; Kloczko, Michael; Calkin, Parker E.
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.
Hambrey, Michael; Alean, Jürg
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.
Stumm, Dorothea; Fujita, Koji; Gurung, Tika; Joshi, Sharad; Litt, Maxime; Shea, Joseph; Sherpa, Mingma; Sinisalo, Anna; Wagnon, Patrick
In-situ glacier mass balance measurements are still scarce in the Hindu Kush Himalayan (HKH) region and little is known about the seasonal balances. The glaciers in the Nepalese Himalaya have been considered summer accumulation glacier types because of the assumption that the majority of the accumulation occurs in the summer months during the monsoon. The glacier mass balance of Yala Glacier in the Langtang Valley of Nepal has been measured using the glaciological method since autumn 2011. Stakes were measured biannually in pre- and post-monsoon, usually in early May and in November, respectively. The measured mass balance gradient for the summer balance was larger than the winter balance, which is typical for glaciers with distinct ablation and accumulation seasons. On Yala Glacier, the summer balance was negative, and the winter balance was positive in all years with measurements. However, the annual net balance was negative for all four mass balance years from 2011 to 2015. The mass balances were further compared to temperature and precipitation data measured at nearby climate stations during the same time periods. In October 2013 and 2014, the Central Himalayas received large amounts of precipitation brought by the cyclones Phailin and Hudhud. These precipitation events contributed to the summer balance since the measurements were taken after the cyclones passed. In conclusion, on Yala Glacier accumulation processes dominated ablation processes during the winter, and ablation processes dominated during the summer, which could be explained by the low elevation range of Yala Glacier and precipitation from westerlies in the winter. Hence, this should be kept in mind when using the term 'summer accumulation glacier' for Yala Glacier. For future research in the HKH region, seasonal mass balances should be measured, and the processes impacting the mass balance and the role of winter precipitation should be investigated for other glaciers in the HKH region.
Gomez, C. A.; Purdie, H.
As global climate continues warm, mountain environments are changing, and rates of glacial retreat are unprecedented. The hydrologic implications of this rapid ice retreat and changing climate conditions have been the focus of numerous studies, but the consequent effects on the sediment cascade in valleys and tributaries has received considerably less attention. In the present study, we investigated the role of glacial recession on sediment mobilization and deposition in a mountain valley catchment at Fox Glacier, New Zealand. In particular, we analyze the role of glacier recession on the formation of sediment fans in the main valley. Emphasis was put on the role of sediment, impounded by the glacier in side tributaries, becoming rapidly available for remobilization as the glacier retreats. The method is based on field observations, and measurements using high resolution GNSS (Trimble R8 survey grade differential GNSS) and photogrammetric methods using Structure from Motion based on ground-, helicopter- and UAV- photographs. Field observations were conducted in the period 2014 - 2015, and have been complimented with analogic modeling in the laboratory, in order to comprehend the processes driving rapid fan formation. The analogic model reproduced the retreat of the glacier and the response of a tributary, with simulations for both glaciated and de-glaciated conditions. For similar hydrologic and slope parameters, the fans created after glacial retreat have shown an acceleration in their formation of up to 12 times compared to fanes created without glacial influence. Field observations within the period 2013 - 2015 of Straight Creek Fan (Fox Valley, New Zealand) have confirmed laboratory simulations, with the fan growing to a radius superior to 200 m and a valley-long width superior to 450 m. As glaciers continue to retreat, it can be expected that sediment surges will occur in affected valleys, without the requirements of other forcing like earthquake or extreme
Holt, John; Levy, Joseph; Petersen, Eric; Larsen, Chris; Fahnestock, Mark
Debris-covered glaciers and rock glaciers encompass a range of compositions and activity, and can be useful paleoclimate indicators. They also respond differently to ongoing climate change than glaciers without a protective cover. Their flow dynamics are not well understood, and their unique surface morphologies, including lobate fronts and arcuate ridges, likely result from viscous flow influenced by a combination of composition, structure, and climatic factors. However, basic connections between flow kinematics and surface morphology have not yet been established, limiting our ability to understand these features. In order to begin to address this problem we have undertaken airborne and surface studies of multiple debris-covered glaciers in Alaska and the western U.S. Sourdough Rock Glacier in the St. Elias Mountains, Alaska, is completely debris-covered and exhibits numerous transverse compressional ridges. Its trunk also exhibits highly regular bumps and swales with a wavelength of ~175 m and amplitudes up to 12 m. In the middle trunk, lineations (boulder trains and furrows) bend around a point roughly 200m from the eastern edge. We acquired five high-resolution airborne surveys of Sourdough Rock Glacier between late 2013 and late 2015 using lidar and photogrammetry to assess annual and seasonal change at the sub-meter level. Differencing the DTMs provides vertical change while feature tracking in orthophotos provide horizontal velocities that indicate meters of annual motion. The flow field is highly correlated with surface features; in particular, compressional ridges in the lower lobe. Stranded, formerly active lobes are also apparent. Surface geophysical studies were undertaken to constrain internal structure and composition using a combination of ground-penetrating radar (GPR) at 50 and 100 MHz in six transects, and time-domain electromagnetic (TDEM) measurements at 47 locations, primarily in an along-flow transect and two cross-flow transects. We infer
Ward, D.; Anderson, R. S.
The Kichatna Mountains, Alaska Range, Alaska comprise a dramatic landscape carved into a small ~65 Ma granitic pluton about 100 km west of Denali, in which kilometer-tall rock walls and “cathedral” spires tower over a radial array of over a dozen individual valley glaciers. The sheer scale of the relief speaks to the relative rates of valley incision by glaciers and rockwall retreat, but absolute rates are difficult to determine. We use cosmogenic 10Be to measure rockwall backwearing rates (and discuss several very important caveats to this use) on timescales of 103-104 yr, with a straightforward sampling strategy that exploits ablation-dominated medial moraines. In simple cases, a medial moraine and its associated englacial debris serve as a conveyor belt that brings supraglacial rockfall debris from the accumulation zone valley wall to a moraine crest in the ablation zone. Our samples come from the largest medial moraine on each of three glaciers. The northeast-flowing Trident glacier is the largest (15 km long, 1.4 km wide) and most deeply incised, and it has the lowest modern snowline in the range (~1200 m). Its primary medial moraine is sourced from west-facing sidewalls. The north-flowing Shadows glacier is slightly smaller (13 km long, 0.8 km wide) and has a large moraine sourced in dominantly east-facing sidewalls. The south-flowing Caldwell glacier is the smallest of the three (7 km long, 0.7 km wide), has a high modern snowline (~1500 m), and is nearly completely covered in debris. Its primary moraine is sourced from all south-facing aspects. These three glaciers share divides in their headwaters, and so are sourced in identical rock. Sidewall relief is similar (~1 km) in all three catchments. Each sample was amalgamated from 25-35 clasts collected over a 1 km longitudinal transect of each moraine. Replicate samples are internally consistent. The lowest 10Be concentrations (8000 at/g), and thus the highest inferred sidewall erosion rates (1.4 mm
Hynek, Bernhard; Binder, Daniel; Boffi, Geo; Schöner, Wolfgang; Verhoeven, Geert
Terrestrial photogrammetry was the standard method for mapping high mountain terrain in the early days of mountain cartography, until it was replaced by aerial photogrammetry and airborne laser scanning. Modern low-price digital single-lens reflex (DSLR) cameras and highly automatic and cheap digital computer vision software with automatic image matching and multiview-stereo routines suggest the rebirth of terrestrial photogrammetry, especially in remote regions, where airborne surveying methods are expensive due to high flight costs. Terrestrial photogrammetry and modern automated image matching is widely used in geodesy, however, its application in glaciology is still rare, especially for surveying ice bodies at the scale of some km², which is typical for valley glaciers. In August 2013 a terrestrial photogrammetric survey was carried out on Freya Glacier, a 6km² valley glacier next to Zackenberg Research Station in NE-Greenland, where a detailed glacier mass balance monitoring was initiated during the last IPY. Photos with a consumer grade digital camera (Nikon D7100) were taken from the ridges surrounding the glacier. To create a digital elevation model, the photos were processed with the software photoscan. A set of ~100 dGPS surveyed ground control points on the glacier surface was used to georeference and validate the final DEM. Aim of this study was to produce a high resolution and high accuracy DEM of the actual surface topography of the Freya glacier catchment with a novel approach and to explore the potential of modern low-cost terrestrial photogrammetry combined with state-of-the-art automated image matching and multiview-stereo routines for glacier monitoring and to communicate this powerful and cheap method within the environmental research and glacier monitoring community.
Cai, Xuhui; Song, Yu; Zhu, Tong; Lin, Weili; Kang, Ling
High ozone concentrations, combined with low humidity and strong, persistent glacier winds, were found at the surface of Rongbuk Valley, north of Mount Everest, with sharply increased ozone concentrations in their vertical profiles. Glacier winds and their roles in vertical exchange of the atmosphere were investigated numerically to understand the phenomena. A Lagrangian particle dispersion model was used to carry out numerical experiments (forward-in-time simulations) and footprint analysis (backward-in-time simulations). The meteorological data inputs for these experiments were derived from the Advanced Regional Prediction System. Results showed that glacier winds may lead to significant downward transport of 1.5-2 km during the daytime from the northern slopes of Mount Everest. Glacier winds could advance down through the valley, with strong upward motions shown as a rolling up in front of their leading edge. Combining with upslope winds at two sidewalls of the valley or up-valley winds of tributaries, the lifting flows produced strong mixing of the atmosphere to a depth of approximately 3 km. Three-dimensional footprints derived from the particle dispersion model for the observational site, Rongbuk Monastery, clearly show influence from the mountainside of Mount Everest and from the southern part of the valley. The vertical extension of influence was as much as 2-3 km. Good correlation was found between the influence height and the ozone concentration. All the simulation results strongly indicate that the glacier winds and their related vertical exchange processes "pump down" ozone-rich air from upper levels to the surface of the valley.
Gabbud, Chrystelle; Tahir, Adnan Ahmad; Micheletti, Natan; Lane, Stuart
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
Otto, Jan-Christoph; Götz, Joachim; Keuschnig, Markus; Hartmeyer, Ingo; Trombotto, Dario; Schrott, Lothar
ground at at least two different altitudes. However, ice characteristics revealed by resistivity values and radar wave velocities vary significantly between the sites indicating changing ice contents and ice origin that indicate differences in landform evolution. Active layer thickness detected at two sites corresponds to ongoing borehole temperature measurements that help to interpret the geophysical modelling results. The valley of Morenas Coloradas presents a unique location to investigate the transition of debris-covered glacier ice to permafrost conditions in close proximity and contributes to the ongoing debate on rock glacier origin. The study reveals that the chosen combination of ERT and GPR is a best practice complement delivering detailed information on ice characteristics (ERT) and location of frozen ground and active layer depths (GPR). However, more geophysical data is required to fully understand the evolution of the nested landform composition and its future reaction to climate change.
MacClune, Karen Lewis; Fountain, Andrew G.; Kargel, Jeffery S.; MacAyeal, Douglas R.
The surfaces of the Martian north and south polar residual caps are marked by unusual ice features: Dark spiralesque troughs up to 1 km deep, 10 km wide, and 300 km long appear on both ice caps, and circular pits that make up the ``Swiss cheese'' terrain appear on the south polar cap. Both types of features are of interest to researchers as a potential means of understanding ice composition and flow rates. Some glaciers of the McMurdo dry valleys have surface features unknown elsewhere on terrestrial glaciers, including canyons over 6 km long, 100 m wide, and tens of meters deep and basins up to 100 m across. High sublimation, dust accumulation, and very little melting is key to their origin. These processes and ice landforms are suggested as terrestrial analogs for the sublimation behavior of Martian ice caps, where dust accumulation and sublimation are significant but surface melting is absent. We have developed a solar radiation model of canyon formation and have applied it to the Martian polar caps. The modeled processes do well to describe direct and reflected radiation within V grooves, a process that may be significant in the development of the spiral troughs and Swiss cheese terrain. The model fails to reproduce the low observed slopes of the Martian troughs. The grooves are too shallow, with opening angles of ~165° compared with model predictions of ~90°. The reason for the failure may be that we have not included creep closure, which should flatten their slopes.
Zhu, Zhuo-Yi; Wu, Ying; Liu, Su-Mei; Wenger, Fred; Hu, Jun; Zhang, Jing; Zhang, Rui-Feng
In the face of ongoing global warming and glacier retreat, the composition and flux of organic matter in glacier-fjord systems are key variables for updating the carbon cycle and budget, whereas the role of Arctic valley glaciers seems unimportant when compared with the huge Greenland Ice Sheet. Our field observations of the glacier-fed Bayelva River, Svalbard, and the adjacent Kongsfjorden allowed us to determine the compositions of particulate organic matter from glacier to fjord and also to estimate the flux of organic carbon, both for the river and for Svalbard in general. Particulate organic carbon (POC) and dissolved organic carbon (DOC) in the Bayelva River averaged 56 and 73 µM, respectively, in August, 2012. Amino acids (AAs) and phytoplankton carbon accounted for ˜ 10 % of the bulk POC in the Bayelva River, while AAs represented > 90 % of particulate nitrogen (PN) in fjord surface water, suggesting the strong in situ assimilation of organic matter. Bacteria accounted for 13 and 19 % of the POC in the Bayelva River and the Kongsfjorden, respectively, while values for PN were much higher (i.e., 36 % in Kongsfjorden). The total discharge from the Bayelva River in 2012 was 29 × 106 m3. Furthermore, we calculated the annual POC, DOC, and PN fluxes for the river as 20 ± 1.6 tons, 25 ± 5.6 tons, and 4.7 ± 0.75 tons, respectively. Using the POC content and DOC concentration data, we then estimated the annual POC and DOC fluxes for Svalbard glaciers. Although the estimated POC (0.056 ± 0.02 × 106 tons year-1) and DOC (0.02 ± 0.01 × 106 tons year-1) fluxes of Svalbard glaciers are small in amount, its discharge-weighted flux of DOC was over twice higher than other pan-Arctic glacier systems, suggesting its important role as a terrestrial DOC source.
Zhu, Z.-Y.; Wu, Y.; Liu, S.-M.; Wenger, F.; Hu, J.; Zhang, J.; Zhang, R.-F.
In the face of ongoing global warming and glacier retreat, the composition and flux of organic matter in glacier-fjord systems are key variables for updating the carbon cycle and budget, whereas the role of Arctic valley glaciers seems unimportant when compared with the huge Greenland Ice Sheet. Our field observations of the glacier-fed Bayelva River, Svalbard, and the adjacent Kongsfjorden allowed us to determine the compositions of particulate organic matter from glacier to fjord and also to estimate the flux of organic carbon, both for the river and for Svalbard in general. Particulate organic carbon (POC) and dissolved organic carbon (DOC) in the Bayelva River averaged 56 and 73 μM, respectively, in August 2012. Amino acids (AAs) and phytoplankton pigments accounted for ~ 10 % of the particulate organic matter (POM) in the Bayelva River, while AAs represented > 90 % of particulate nitrogen in fjord surface water, suggesting the strong in situ assimilation of organic matter. Bacteria accounts for 13 and 19 % of the POC in the Bayelva River and the Kongsfjorden, respectively, while values for particulate nitrogen (PN) are much higher (i.e., 36 % in Kongsfjorden). The total discharge from the Bayelva River in 2012 was 29 × 106 m3. Furthermore, we calculated the annual POC, DOC, and PN fluxes for the river as 20 ± 1.6, 25 ± 5.6, and 4.7 ± 0.75 t, respectively. Using the POC content and DOC concentration data, we then estimated the annual POC and DOC fluxes for Svalbard glaciers. Although the estimated POC (0.056 ± 0.02 × 106 t yr-1) and DOC (0.02 ± 0.01 × 106 t yr-1) fluxes of Svalbard glaciers are small compared with those of the Greenland Ice Sheet, the area-weighted POC flux of Svalbard glaciers is twice that of the Greenland Ice Sheet, while the flux of DOC can be 4 to 7 times higher. Therefore, we propose that valley glaciers are efficient high-latitude sources of organic carbon.
Laute, Katja; Beylich, Achim A.; Oppikofer, Thierry
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
Miles, Evan; Willis, Ian; Arnold, Neil; Pellicciotti, Francesca
Debris-covered glaciers have received renewed interest in recent years in an attempt to improve understanding of climate-glacier interactions in High Mountain Asia. Understanding of key processes occurring in supraglacial ponds has advanced conceptually to include conduit-collapse formation, subaqueous and waterline melting, calving, and englacial filling and drainage. The behaviour of systems of ponds, however, has received little attention, as most process observations have been made on individual features. Several studies have used satellite data to determine pond distributions at a single point in time or their variability across several years or decades. However, no attempt has been made to document the seasonal and inter-annual variability of ponds, even though individual ponds have been observed to fill and drain periodically. We analyse 172 Landsat TM/ETM+ scenes for the period 1999-2013 to identify thawed supraglacial ponds for the debris-covered tongues of five glaciers in the Langtang Valley of Nepal. We apply an advanced atmospheric correction routine (LandCor/6S) and improve upon previous band-ratio and image morphological techniques to identify ponds, then apply this database of identified ponds to: 1) measure the density of supraglacial ponding for five glaciers with differing characteristics, and evaluate the dependency of pond density to those glaciers' characteristics; 2) evaluate the controls that surface gradient and glacier velocity in particular exert on pond occurrence; 3) document the seasonal cycle of pond thawing and formation followed by freezing and draining; 4) document pond persistence, recurrence, and evolution over the 15-year period; and 5) determine if surface ponding has increased over time for the study glaciers. We find high variability between glaciers (0.08-1.69% of debris-covered area during ablation season), related primarily to glacier size, velocity, and surface gradient. At the glacier scale, pond cover is also correlated
Hoffman, Matthew J.; Fountain, Andrew G.; Liston, Glen E.
Here, the McMurdo Dry Valleys of Antarctica host the coldest and driest ecosystem on Earth, which is acutely sensitive to the availability of water coming from glacial runoff. We modeled the spatial variability in ablation and assessed climate sensitivity of the glacier ablation zones using 16 years of meteorological and surface mass-balance observations collected in Taylor Valley. Sublimation was the primary form of mass loss over much of the ablation zones, except for near the termini where melt, primarily below the surface, dominated. Microclimates in ~10 m scale topographic basins generated melt rates up to ten times higher than overmore » smooth glacier surfaces. In contrast, the vertical terminal cliffs on the glaciers can have higher or lower melt rates than the horizontal surfaces due to differences in incoming solar radiation. The model systematically underpredicted ablation for the final 5 years studied, possibly due to an increase of windblown sediment. Surface mass-balance sensitivity to temperature was ~–0.02 m w.e. K–1, which is among the smallest magnitudes observed globally. We also identified a high sensitivity to ice albedo, with a decrease of 0.02 having similar effects as a 1 K increase in temperature, and a complex sensitivity to wind speed.« less
Powell, R.D. . Geology Dept.); Pyne, A.R. . Antarctic Research Center); Hunter, L.E.; Rynes, N.R.
Marine-ending glaciers may retreat with global warming as sea level rises by ocean thermal expansion. If the sea floor rises by sediment accumulation, then glaciers may not feel the effect of sea level rise. A submersible ROV and other techniques have been used to collect data from temperate and polar glaciers to compare sediment production and mass balance of their grounding-line systems. Temperature Alaskan valley glaciers flow at about 0.2--2 km/a and have high volumes of supraglacial, englacial and subglacial debris. However, most sediment contributed to the base of their tidewater cliffs comes from subglacial streams or squeezing out subglacial sediment and pushing it with other marine sediment into a morainal bank. Blue Glacier, a thin, locally fed polar glacier in Antarctica, flows slowly and has minimal glacial debris. The grounding-line system at the tidewater cliff is a morainal bank that forms solely by pushing of marine sediment. An Antarctic polar outlet glacier, Mackay Glacier, terminating as a floating glacier-tongue, has similar volumes of basal debris to Alaskan temperature glaciers and flows at 250 m/a. However, no subglacial streams issued from Mackay's grounding line and all sedimentation was by rockfall and grainfall rainout from seawater undermelt of the tongue. A grounding-line wedge of glacimarine diamicton is deposited over subglacial (lodgement ) till. Although Antarctic grounding-line accumulation rates are three orders of magnitude smaller than Alaskan rates, both are capable of compensating for predicted rises in sea level by thermal heating from global warming.
Liu, Guoxiang; Zhang, Qi; Zhu, Huan; Hu, Zhengyu
Trentepohlia is a genus of subaerial green algae which is widespread in tropical, subtropical, and also temperate regions with humid climates. For many years, small-scale Trentepohlia coverage had been found on the rocks of some glacier valleys on the northern slopes of Mt. Gongga, China. However, since 2005, in the Yajiageng river valley, most of the rocks are covered with deep red coloured algal carpets, which now form a spectacular sight and a tourist attraction known as ‘Red-Stone-Valley’. Based on morphology and molecular data, we have named this alga as a new variety: Trentepohlia jolithus var. yajiagengensis var. nov., it differs from the type variety in that its end cells of the main filament are often rhizoid, unilateral branches. This new variety only grows on the native rock, both global warming and human activity have provided massive areas of suitable substrata: the rocks surfaces of the Yajiageng river valley floodplain were re-exposed because of heavy debris flows in the summer of 2005; plus human activities such as tourism and road-building have also created a lot of exposed rock! In summer, the glaciers of the northern slopes of Mt. Gongga have brought to the valleys wet and foggy air, ideal for Trentepohlia growth. The cells of the new variety are rich in secondary carotenoids (astaxanthin?), which helps the algal cells resistance to strong ultraviolet radiation at high altitudes (they are only found on rock surfaces at alt. 1900–3900 m); the cells are also rich in oils, which gives them high resistance to cold dry winters. PMID:22815686
Kitchens, S. . Dept. of Geology)
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.
Three Pleistocene stages are recorded by 3D Google-Earth geomorphology, cave sediments, river terraces, megafauna, archaeological sites of the Harz Mountain Range and its forelands of northern Germany (central Europe, peak 1141 a.s.l.). Late Pleistocene glaciation stages are modeled preliminary in valley elevations between 407 and 760 a.s.l., starting all southeast below the Brocken Ice Field (above 750 a.s.l.). The 14-11 km long Oder and Bode Valley glaciers left typical moraines, kames, or dead ice depressions, such as fluvial cave relic sediments. The Bode River glacier passed during the LGM the Rübeland Caves, where it deposited reworked kames/lateral moraines in the Baumann's Cave, which floods mixed a Neanderthal camp, leopard lair and cave bear den area. 60 km downstream, fluvial to aeolian deposits were trapped in the gypsum karst doline Westeregeln (Neanderthal camp/hyena den). Late Aurignacians replaced in the region Neanderthals, but a gap of Late Palaeolithic (Gravettian-Magdalenian - 26,000-16,000 BP) settlement, and latest starting speleothem genesis (around 24,260 ± 568 BP) correlate to the LGM, when an "arctic reindeer fauna" with alpine elements (ibex, chamois) accumulated in bone assemblages of a wolverine, polar fox, mustelid, such as European eagle owl dens, which allow landscape reconstructions.
Hambrey, Michael J.; Murray, Tavi; Glasser, Neil F.; Hubbard, Alun; Hubbard, Bryn; Stuart, Graham; Hansen, Siri; Kohler, Jack
Most polythermal glaciers in Svalbard, other than those of surge type, have receded steadily since the early 20th century. Midre Lovénbreen, a slow-moving, 4-km-long valley glacier terminating on land, is a typical example, and its internal structures reflect changing dynamics over this period. The three-dimensional structural style of this glacier and the sequential development of structures have been determined from surface mapping, ground-penetrating radar, and numerical flow modeling. In order of formation the structures observed today at the glacier surface are (1) primary stratification that has become folded about flow-parallel axes; (2) axial plane longitudinal foliation associated with this folding; (3) several sets of intersecting crevasse traces; (4) arcuate upglacier-dipping fractures developed as part of a thrust complex near the snout; and (5) longitudinal splaying fractures in the snout area. The long-term evolution and dynamic significance of these structures can be ascertained from historical ground and aerial photographs. Modeling indicates that stratification and foliation continue to evolve today as a result of internal deformation, especially in zones of converging flow, where simple shear is most pronounced, but within the tongue are carried passively toward the snout. Crevasse traces appear to be no longer actively forming but are interpreted as relict structures when the ice was more dynamic and mostly wet based. The interpretation of arcuate fractures near the snout as thrusts is supported by the matching orientations of modeled strain ellipses, which illustrate the importance of longitudinal compression.
Gatto, L. W.; Anderson, D. M.
A first-order analog to Martian fretted terrain has been recognized on enhanced, ERTS-1 (Earth Resources Technology Satellite) imagery of Alaskan Arctic thermokarst terrain. The Alaskan analog displays flat-floored valleys and intervalley uplands characteristic of fretted terrain. The thermokarst terrain has formed in a manner similar to one of the processes postulated for the development of the Martian fretted terrain.
Aaron E. Putnam; Joerg M. Schaefe; George H .Denton; DavidJ. A. Barrell; Bjørn G. Andersen; Tobias N.B. Koffman; Ann V. Rowan; Robert C. Finkel; Dylan H. Rood; Roseanne Schwartz; Marcus J. Vandergoes; Mitchell A. Plummer; Simon H. Brocklehurst; Samuel E. Kelley; Kathryn L. Ladig
The termination of the last ice age featured a major reconfiguration of Earth's climate and cryosphere, yet the underlying causes of these massive changes continue to be debated. Documenting the spatial and temporal variations of atmospheric temperature during deglaciation can help discriminate among potential drivers. Here, we present a 10Be surface-exposure chronology and glaciological reconstruction of ice recession following the Last Glacial Maximum (LGM) in the Rakaia valley, Southern Alps of New Zealand. Innermost LGM moraines at Big Ben have an age of 17,840 +/- 240 yrs, whereas ice-marginal moraines or ice-molded bedrock surfaces at distances up-valley from Big Ben of 12.5 km (Lake Coleridge), approximately 25 km (Castle Hill), approximately 28 km (Double Hill), approximately 43 km (Prospect Hill), and approximately 58 km (Reischek knob) have ages of 17,020 +/- 70 yrs, 17,100 +/- 110 yrs, 16,960 +/- 370 yrs, 16,250 +/- 340 yrs, and 15,660 +/- 160 yrs, respectively. These results indicate extensive recession of the Rakaia glacier, which we attribute primarily to the effects of climatic warming. In conjunction with geomorphological maps and a glaciological reconstruction for the Rakaia valley, we use our chronology to infer timing and magnitude of past atmospheric temperature changes. Compared to an overall temperature rise of approximately 4.65?degrees C between the end of the LGM and the start of the Holocene, the glacier recession between approximately 17,840 and approximately 15,660 yrs ago is attributable to a net temperature increase of approximately 4.0?degrees C (from -6.25 to -2.25?degrees C), accounting for approximately 86% of the overall warming. Approximately 3.75?degrees C (approximately 70%) of the warming occurred between approximately 17,840 and approximately 16,250 yrs ago, with a further 0.75?degrees C (approximately 16%) increase between approximately 16,250 and approximately 15,660 yrs ago. A sustained southward shift of the Subtropical
Eugster, Patricia; Scherler, Dirk; Thiede, Rasmus C.; Codilean, Alexandru T.; Strecker, Manfred R.
Despite a large number of dated glacial landforms in the Himalaya, the ice extent during the global Last Glacial Maximum (LGM) from 19 to 23 ka is only known to first order. New cosmogenic 10Be exposure ages from well-preserved glacially polished surfaces, combined with published data, and an improved production rate scaling model allow reconstruction of the LGM ice extent and subsequent deglaciation in the Chandra Valley of NW India. We show that a >1000 m thick valley glacier retreated >150 km within a few thousand years after the onset of LGM deglaciation. By comparing the recession of the Chandra Valley Glacier and other Himalayan glaciers with those of Northern and Southern Hemisphere glaciers, we demonstrate that post-LGM deglaciation was similar and nearly finished prior to the Bølling/Allerød interstadial. Our study supports the view that many Himalayan glaciers advanced during the LGM, likely in response to global variations in temperature.
Prokop, Alexander; Tolle, Florian; Bernard, Eric; Friedt, Jean-Michel; Griselin, Madeleine
For 3 consecutive years, terrestrial laser scanning surveys have been conducted in the glacier basin of Austre Lovénbreen (Svalbard, 79°N). Each year, high density point clouds were acquired on the glacier surface and on the surrounding slopes. Two yearly scanning sessions were required in order to spatialize and quantify snow cover. The first session was done late April at the expected annual snow maximum. The second session was done in August near the end of the melting season. On the glacier itself, laser scans were produced on the glacier snout, in the area close to the equilibrium line, and in the upper reaches of the glacier. Manual snow drilling measurements and glacier mass balance data were subsequently used to validate snow cover results. In the steep slopes surrounding the glacier, scans were acquired on slopes at various altitudes and orientations in order to get a representative view of different snow cover settings. Particular attention was granted to snowdrift and avalanche processes, and their consequences on remaining packed snow stored in perennial snow accumulation at the bottom of slopes. A good knowledge of the dynamics of the snow cover is of particular interest in a glacier undergoing a clear retreat. Snow is protecting the ice from melting for part of the season, and snow is also providing what will constitute future glacier ice in the upper reaches of the basin. Snow on slopes is also of importance as avalanches reaching on the glacier can contribute to the overall mass balance. Snow cover, by keeping the slopes permafrost from thawing early in the season, or by providing liquid water affecting it later in the season, is also playing a key role in the glacier basin morphology and its interactions with the glacier body.
Diolaiuti, G.; D Agata, C.; Pavan, M.; Belo, M.; Smiraglia, C.
Reconstructing past glacier fluctuations and understanding them to forecast future trend of water availability in the Alps is an aim of general interest. For this reason continuous monitoring on sample glaciers is required to collect mass balance data, area and volume changes, ice thickness variations. The case-study of Dosdè Est Glacier, Piazzi-Campo Group, Italian Alps, representative of Italian small valley glaciers, is a good example of long term documentation of the evolution of this kind of glacier in the Central Alps. Dosdè Est Glacier is a North facing valley glacier, located in Italian Lombardy Alps (46 23 30 N, 10 13 05 E). In 2002 its area was approximately 2 kmq, extending from 2580 to 3294 m a.s.l., with a maximum widht of about 1000 m and a maximum lenght of about 2000 m. Observations to monitor the evolution of the glacier and to reconstruct past areas and volumes involve (in descending order of accuracy) direct mass balance measurements since 1995, topographic surveys (GPS) since 1996, GPR survey in order to evaluate ice thickness in 1999, seismic prospection and geoelectrical survey (VES) in 1997, glacier terminus variations field measurements from 1934 up to now (thanks to CGI operators), reconstruction of the 20th century maximum and of the LIA maximum using the well preserved moraines. Since hydrological year 1995-1996, mass balance of the glacier has been surveyed every year by glaciological field method. The stakes position is calculated by GPS technique and is used also to evaluate glacier surface velocity. The net mass balance during the 7 years of measurements was almost always negative with only one positive value recorded in the year 2001. During the 7 years of measures Dosdè Est Glacier lost about 7 m of ice thickness, it means 14.000.000 mc w.e. The mean yearly value of mass balance on 7 years of measures is -0,85 m w.e. and the mass balance gradient is 0,60 m w.e./100 m of altitude. Since 1925 Dosdè Est Glacier terminus variations
Muskett, R. R.; Sauber, J. M.; Lingle, C. S.; Rabus, B. T.; Tangborn, W. V.; Echelmeyer, K. A.
Three- to 5-year surface elevation changes on Bagley Ice Valley, Guyot and Yahtse Glaciers, in the eastern Chugach and St. Elias Mtns of south-central Alaska, are estimated using ICESat-derived data and digital elevation models (DEMs) derived from interferometric synthetic aperture radar (InSAR) data. The surface elevations of these glaciers are influenced by climatic warming superimposed on surge dynamics (in the case of Bagley Ice Valley) and tidewater glacier dynamics (in the cases of Guyot and Yahtse Glaciers) in this coastal high-precipitation regime. Bagley Ice Valley / Bering Glacier last surged in 1993-95. Guyot and Yahtse Glaciers, as well as the nearby Tyndell Glacier, have experienced massive tidewater retreat during the past century, as well as during recent decades. The ICESat-derived elevation data we employ were acquired in early autumn in both 2003 and 2004. The NASA/NIMA Shuttle Radar Topography Mission (SRTM) DEM that we employ was derived from X-band InSAR data acquired during this 11-22 Feb. 2000 mission and processed by the German Aerospace Center. This DEM was corrected for estimated systematic error, and a mass balance model was employed to account for seasonal snow accumulation. The Star-3i airborne, X-band, InSAR-derived DEM that we employ was acquired 4-13 Sept. 2000 by Intermap Technologies, Inc., and was also processed by them. The ICESat-derived profiles crossing Bagley Ice Valley, differenced with Star-3i DEM elevations, indicate preliminary mean along-profile elevation increases of 5.6 ± 3.4 m at 1315 m altitude, 7.4 ± 2.7 m at 1448 m altitude, 4.7 ± 1.9 m at 1557 m altitude, 1.3 ± 1.4 m at 1774 m altitude, and 2.5 ± 1.5 m at 1781 m altitude. This is qualitatively consistent with the rising surface on Bagley Ice Valley observed by Muskett et al. . The ICESat-derived profiles crossing Yahtse Glacier, differenced with the SRTM DEM elevations, indicate preliminary mean elevation changes (negative implies decrease) of -0.9 ± 3
Torsnes, I.; Rye, N. ); Nesje, A. )
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.
Sauter, Tobias; Galos, Stephan
While the large-scale climate conditions play an important role in shaping the environment in which glaciers exist, the mass and energy balance of each individual glacier are dictated by local conditions. Given the complex mountain topography around alpine glaciers, it is not trivial to find a direct link between the large-scale atmospheric motions and the local-scale weather conditions at an individual glacier. Non-local dynamic effects due to the surrounding complex topography can significantly modify the spatial variability of exchange processes, either by small scale circulations or episodic entrainment of heat and momentum by burst events. Motivated by the fact that distributed glacier models strongly rely on the quality of high resolution forcing data to adequately represent the glacier wide ablation and accumulation processes, the present study investigates (i) whether non-local topographic effects have a significant impact on the spatial distribution of turbulent sensible heat fluxes (local microclimates) over alpine glaciers, and (ii) how much variability is smoothed out when using linearly interpolated fields together with the commonly used bulk approach. To answer these questions, we perform highly resolved and properly designed case experiments by Large-Eddy Simulations with real topography to determine the impact of topographic flow features on the spatial variability of the surface sensible heat flux and compare the fields with those derived with the bulk approach. The analysis shows that there is a significant spatial variability of the mean fluxes with values ranging from -10 Wm‑2 to -120 Wm‑2. Since the sensible heat flux can make up to 40% of the total melting on mid-latitude alpine valley glaciers, the heterogeneity of the fluxes can substantially dictate the local melting rates. When estimating the glacier-wide surface heat fluxes on the basis of point-measurements and the bulk approach, a considerable amount of spatial information is lost
Lukas, S.; Graf, A.; Coray, S.; Schlüchter, C.
Lateral moraines are prominent features of glaciated landscapes in high-mountain environments and key landforms in glacier and palaeoclimatic reconstructions, yet, compared to smaller moraines, they have been little studied and several aspects are not well understood. This presentation will present detailed sedimentological results from the lateral moraines of Findelengletscher in SW Switzerland to gain new insights into the formation of these landforms. The lateral moraines studied here stand up to 140 m above the valley floor, are over 3 km long and strongly asymmetrical in cross-profile, with distal slopes between 29-36° and proximal slopes that are commonly 41-64°, but locally reach angles of up to 80°. Recorded lithofacies comprise loose clast and matrix-supported, stratified diamicts and intercalated sorted sediments in the distal slopes and near the crestline; overconsolidated matrix-supported, massive and weakly stratified diamicts and streaked-out sorted sediment lenses in the core and proximal slopes; and partly intercalated dark-brown layers overlain by loose and consolidated diamicts exposed in near-vertical walls in the proximal flank. These are interpreted as supraglacial debris flow units with intercalated fluvial 'wash' horizons; glaciotectonised and subglacial traction till with boudinaged and streaked-out sediment lenses; and palaeosoils overlain by sediment produced by overtopping of the former moraine surface during a subsequent advance of the glacier. Clast shape analysis and process observations reveal that the dominant mode of transport is subglacial and glaciofluvial, and that the main mode of sediment delivery to the moraines is by debris flows after the material has been transferred from the bed via englacial debris bands and meltout at the surface. This differs from previous studies that found that a supraglacial source was dominant. Sedimentary structures, clast fabric and process observations during the 1979/1980 readvance of
Achatz, Mary, Ed.; Caldera, Debra, Ed.; Saylor, Brian; DeGross, Denny
This paper examines the attitudes of adults and teenagers in 10 predominantly rural Alaskan communities toward their own health and well-being and that of children and families in their community. The communities were located across the state and ranged in size from populations of under 900 to over 50,000. The proportion of Alaska Natives in the…
Zasadni, Jerzy; Kłapyta, Piotr
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
Putnam, Aaron E.; Schaefer, Joerg M.; Denton, George H.; Barrell, David J. A.; Andersen, Bjørn G.; Koffman, Tobias N. B.; Rowan, Ann V.; Finkel, Robert C.; Rood, Dylan H.; Schwartz, Roseanne; Vandergoes, Marcus J.; Plummer, Mitchell A.; Brocklehurst, Simon H.; Kelley, Samuel E.; Ladig, Kathryn L.
The termination of the last ice age featured a major reconfiguration of Earth's climate and cryosphere, yet the underlying causes of these massive changes continue to be debated. Documenting the spatial and temporal variations of atmospheric temperature during deglaciation can help discriminate among potential drivers. Here, we present a 10Be surface-exposure chronology and glaciological reconstruction of ice recession following the Last Glacial Maximum (LGM) in the Rakaia valley, Southern Alps of New Zealand. Innermost LGM moraines at Big Ben have an age of 17,840 ± 240 yrs, whereas ice-marginal moraines or ice-molded bedrock surfaces at distances up-valley from Big Ben of 12.5 km (Lake Coleridge), ∼25 km (Castle Hill), ∼28 km (Double Hill), ∼43 km (Prospect Hill), and ∼58 km (Reischek knob) have ages of 17,020 ± 70 yrs, 17,100 ± 110 yrs, 16,960 ± 370 yrs, 16,250 ± 340 yrs, and 15,660 ± 160 yrs, respectively. These results indicate extensive recession of the Rakaia glacier, which we attribute primarily to the effects of climatic warming. In conjunction with geomorphological maps and a glaciological reconstruction for the Rakaia valley, we use our chronology to infer timing and magnitude of past atmospheric temperature changes. Compared to an overall temperature rise of ∼4.65 °C between the end of the LGM and the start of the Holocene, the glacier recession between ∼17,840 and ∼15,660 yrs ago is attributable to a net temperature increase of ∼4.0 °C (from -6.25 to -2.25 °C), accounting for ∼86% of the overall warming. Approximately 3.75 °C (∼70%) of the warming occurred between ∼17,840 and ∼16,250 yrs ago, with a further 0.75 °C (∼16%) increase between ∼16,250 and ∼15,660 yrs ago. A sustained southward shift of the Subtropical Front (STF) south of Australia between ∼17,800 and ∼16,000 yrs ago coincides with the warming over the Rakaia valley, and suggests a close link between Southern Ocean frontal boundary positions and
Bibby, T.; Putkonen, J.; Morgan, D. J.; Balco, G.
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.
Davies, Bethan; Hambrey, Michael; Glasser, Neil; Smellie, John; Carrivick, Jonathan; Bentley, Michael
Recent rapid warming across the Antarctic Peninsula has resulted in ice-sheet thinning, dramatic ice-shelf collapse, acceleration of ice-flow velocities and widespread glacier recession. Reconstructing past rates, volumes and magnitudes of cryospheric change, particularly with respect to the former configuration of ice sheets and ice shelves, and their response to changing oceanic and climatic regimes, is vital in providing a context for this change, in order to improve predictions of future ice-sheet behaviour, and to provide glacio-isostatic adjustment corrections for gravimetric measurements of contemporary ice loss. This research aimed to investigate valley glacier and ice-shelf interactions during the Last Glacial Maximum (LGM) and Holocene Epoch across George VI Sound and Alexander Island, western Antarctic Peninsula, an area with a well-preserved but poorly dated record. We identify four principal stratigraphic units: (1) a high-elevation drift with Alexander Island erratics only (interpreted as recording older advances of ice from the interior of the island), (2) a lower-elevation drift with exotic Palmer Land erratics (interpreted as ice-shelf moraine, representing incursions of George VI Ice Shelf onto Ablation Point Massif), (3) multiple overlapping sequences of valley glacier moraine and ice-shelf moraine, presumed to be Holocene in age, and (4) more recent processes and units, including frozen epishelf lakes, slope processes and alluvial fans. On-going cosmogenic nuclide dating on these sediments (in progress; 25 10Be exposure ages) has the potential to unlock the complex history and interactions of ice streams, valley glaciers and ice shelves in this area. This work will also provide the first long-term record of sea-level indicators, allowing the first estimates of glacial unloading, rates of uplift and ice-sheet thinning to be calculated. The Holocene record of the ice shelf, preserved in the younger ice-shelf moraines and in the overlapping
Carrara, P.E.; Trimble, D.A.
A Late Pleistocene volcanic ash couplet consisting of a glacier Peak ash layer and an underlying Mount Saint Helens J ash layer has been identified at three sites in the Colville Valley area of northeastern Washington. This ash couplet has been reported as far east as northwestern Montana and therefore appears to have widespread distribution south of the International Boundary. Because areas covered by the Cordilleran Ice Sheet, as well as by local mountain glaciers and icefields, were undergoing extensive deglaciation when these ash layers were deposited, about 11 200 BP, the ash couplet is an important time-stratigraphic marker, and its identification at a site provides information about the extent of deglaciation at that time. The presence of the Glacier Peak and Mount Saint Helens J ash couplet in the Colville Valley, about 50km north (upglacier) from the Late Wisconsin terminal moraine near the town of Springdale, indicates that the active margin of the Colville sublobe of the Cordilleran Ice Sheet had retreated at least that distance by 11 200 BP. -from Authors
Chakraborty, M.; Panigrahy, S.; Kundu, S.
A semi automated technique has been developed to extract the spatial extension of valleys and mountain glaciers. The method is based on morphological properties of glaciated area extracted from Digital Elevation Model (DEM). Identification of glacial boundary based on spectral information from optical remote sensing imageries produces errors due to misclassification of debris-covered ablation area with surrounding rocky terrain and perennially snow-covered slope with debris free glaciated area. Elevation information DEM of Shuttle Radar Topography Mission (SRTM), CartoDEM and ASTER DEM have been used. A part of western Himalayas was selected as the study area that contains large glaciated basins, e.g., Bhagirathi, Baspa, Chandra basin. First order derivatives, slope aspect, and second order derivatives like, profile and plan curvatures are computed from the DEM. The derivatives are used to quantify and characterise the morphological aspects of the glaciated area and used in the decision rule models to generate the glacial boundaries. The ridge lines of the study areas are also generated from the plan curvature and used in the model to delineate the catchments areas of the glaciers. The slope based boundary is checked for consistency with the boundary from profile curvature and combined manually to generate the final glacier boundary. Area and length under the derived boundary of Gangotri glacier of Bhagirathi catchments are 90.25 sq km and 30.5 km. The result has been checked with high resolution optical data. This objective approach is important to delineate glaciated area, measure the length, width and area and generate glacial hypsometry, concentration factor of the glaciers. Accuracy of the result depends up on the quality of the DEM. DEM generated by SAR interferometric technique is found superior over DEM generated from other interpolation techniques.
MacDonell, Shelley; Cullen, Nicolas; Nicholson, Lindsey; Mölg, Thomas; Kinnard, Christophe
On the cold, arid glaciers of the Norte Chico region, Chile, sublimation plays an important role in mass loss from the glacier surface. The ratio of sublimation : melt on these glaciers dictates not only the amount of meltwater delivered to the watershed, but it also drives the development of morphological features on the glacier surface, such as penitentes. As the rate of sublimation is driven by the latent heat flux, understanding the behaviour of the turbulent heat flux across the glacier surface is key to quantifying the spatial and temporal patterns of ablation. We measured the turbulent heat fluxes at a point on the surface of the Guanaco Glacier during 23-31 January, 2008 using an open-path eddy covariance system. The eddy covariance system was installed adjacent to an existing automatic weather station operating at 5325 m on the glacier surface, in a region devoid of penitents and other surface deformities. The results from the eddy covariance measurements were subsequently used to assess the sublimation results calculated using a point energy balance model. Results showed that 0.5-3 mm w.e. of sublimation occurred per day during the study period, which corresponded well with the energy balance results. However to assess the total sublimation rate on this glacier, sublimation rates from penitentes, ablation cusps and debris-covered regions must also be calculated. Thus this paper will also take a first look at another set of eddy covariance measurements made in a penitente field on the Toro 1 Glacier between December 2009-January 2010 to quantify the importance of penitentes for producing ablation on these glaciers as well. The eddy covariance system was installed adjacent to an existing automatic weather station operating at 5200 m on the glacier surface, in a location with a 100 m fetch of penitentes. From these measurements we are able to ascertain the role that penitentes play in modifying turbulent heat fluxes in the main part of the ablation season
Liermann, S.; Beylich, A. A.; Hansen, L.
This PhD project is part of the NFR funded Norwegian Individual Project within the ESF SedyMONT (Timescales of sediment dynamics, climate and topographic change in mountain landscapes) TOPO-EUROPE program. Two neighboring glacier-fed valley-fjord systems (Erdalen & Bødalen) with a different topographic inheritance from Pleistocene glaciations are compared. It is of special interest how the different valley morphometries have influenced Holocene to contemporary sediment fluxes and budgets. To understand the spatial and temporal sediment flux variability during the Holocene the main focus lays on i) quantification and analysis of storage element volumes for estimation of Holocene sedimentation rates and sediment yields, ii) analysis of the spatial and temporal sediment flux variability, iii) analysis of the linkages between sediment transfer and storage, iv) analysis of controlling factors for postglacial, sub-recent and contemporary sediment fluxes and v) construction of Holocene to contemporary sediment budgets for Erdalen and Bødalen. The analysis of sedimentary fluxes and budgets as well as their controls at different timescales (Holocene to contemporary) is a basis for the assessment of complex landscape responses of Holocene to recent changes in temperature, precipitation and runoff. For constructing sediment budgets at a small-catchment scale (50-100 km2) it is necessary to integrate the temporal and spatial variations of supply of material from sediment sources, sediment transport and storage and to identify, how far the different system components are coupled to each other. Both valleys are instrumented with a year-round monitoring system (runoff, suspended and solute transport) for analyzing fluvial sediment fluxes. The results enable to link sediment transport and runoff (events) and the spatial and temporal variability of sediment transport processes. In addition, glacier sediment supply and its spatial variability in Erdalen and Bødalen is monitored
Koh, Hye Yeon; Lee, Sung Gu; Lee, Jun Hyuck; Doyle, Shawn; Christner, Brent C.
The psychrophilic bacterium Paenisporosarcina sp. TG-14 was isolated from sediment-laden stratified basal ice from Taylor Glacier, McMurdo Dry Valleys, Antarctica. Here we report the draft genome sequence of this strain, which may provide useful information on the cold adaptation mechanism in extremely variable environments. PMID:23144403
Lingle, Craig S.; Harrison, William D.
The objective of this project was to investigate the utility of satellite synthetic aperture radar (SAR) imagery for measurement of geophysical parameters on Alaskan glaciers relevant to their mass balance and dynamics, including: (1) the positions of firn lines (late-summer snow lines); (2) surface velocities on fast-flowing (surging) glaciers, and also on slower steady-flow glaciers; and (3) the positions and changes in the positions of glacier termini. Preliminary studies of topography and glacier surface velocity with SAR interferometry have also been carried out. This project was motivated by the relationships of multi-year to decadal changes in glacier geometry to changing climate, and the probable significant contribution of Alaskan glaciers to rising sea level.
Foster, David; Brocklehurst, Simon H.; Gawthorpe, Rob L.
The glacial buzzsaw hypothesis suggests that efficient erosion limits topographic elevations in extensively glaciated orogens. Studies to date have largely focussed on regions where large glaciers (tens of kilometres long) have been active. In light of recent studies emphasising the importance of lateral glacial erosion in lowering peaks and ridgelines, we examine the effectiveness of small glaciers in limiting topography under both relatively slow and rapid rock uplift conditions. Four ranges in the northern Basin and Range, Idaho, Montana, and Wyoming, USA, were chosen for this analysis. Estimates of maximum Pleistocene slip rates along normal faults bounding the Beaverhead-Bitterroot Mountains (~ 0.14 mm y - 1 ), Lemhi Range (~ 0.3 mm y - 1 ) and Lost River Range (~ 0.3 mm y - 1 ) are an order of magnitude lower than those on the Teton Fault (~ 2 mm y - 1 ). We compare the distribution of glacial erosion (estimated from cirque floor elevations and last glacial maximum (LGM) equilibrium line altitude (ELA) reconstructions) and fault slip rate with three metrics of topography in each range: the along-strike maximum elevation swath profile, hypsometry, and slope-elevation profiles. In the slowly uplifting Beaverhead-Bitterroot Mountains, and Lemhi and Lost River Ranges, trends in maximum elevation parallel ELAs, independent of variations in fault slip rate. Maximum elevations are offset ~ 500 m from LGM ELAs in the Lost River Range, Lemhi Range, and northern Beaverhead-Bitterroot Mountains, and by ~ 350 m in the southern Beaverhead-Bitterroot Mountains, where glacial extents were less. The offset between maximum topography and mean Quaternary ELAs, inferred from cirque floor elevations, is ~ 350 m in the Lost River and Lemhi Ranges, and 200-250 m in the Beaverhead-Bitterroot Mountains. Additionally, slope-elevation profiles are flattened and hypsometry profiles show a peak in surface areas close to the ELA in the Lemhi Range and Beaverhead-Bitterroot Mountains
Lukas, Sven; Graf, Andreas; Coray, Sandro; Schlüchter, Christian
Lateral moraines are prominent features of glaciated landscapes in high-mountain environments and key landforms in glacier and palaeoclimatic reconstructions, yet, compared to smaller moraines, they have been little studied and several aspects are not well understood. We here present detailed sedimentological results from the lateral moraines of Findelengletscher in SW Switzerland to gain new insights into the formation of these landforms. The lateral moraines studied here stand up to 140 m above the valley floor, are over 3 km long and strongly asymmetrical in cross-profile, with distal slopes between 29 and 36° and proximal slopes that are commonly 41-64°, but locally reach angles of up to 80°. Recorded lithofacies comprise loose clast and matrix-supported, stratified diamicts and intercalated sorted sediments in the distal slopes and near the crestline; overconsolidated matrix-supported, massive and weakly stratified diamicts and streaked-out sorted sediment lenses in the core and proximal slopes; and partly intercalated dark-brown layers overlain by loose and consolidated diamicts exposed in near-vertical walls in the proximal flank. These are interpreted as supraglacial debris flow units with intercalated fluvial 'wash' horizons; glaciotectonised and subglacial traction till with boudinaged and streaked-out sediment lenses; and palaeosoils overlain by sediment produced by overtopping of the former moraine surface during a subsequent advance of the glacier. Clast shape analysis and process observations reveal that the dominant mode of transport is subglacial and glaciofluvial, and that the main mode of sediment delivery to the moraines is by debris flows after the material has been transferred from the bed via englacial debris bands and meltout at the surface. This differs from previous studies that found that a supraglacial source was dominant. Sedimentary structures, clast fabric and process observations during the 1979/1980 readvance of Findelengletscher
Hochreuther, Philipp; Grießinger, Jussi; Wernicke, Jakob; Zhu, Haifeng; Bräuning, Achim
South- and Southeast Asia is home to more than one third of the world's population, with the monsoon system as the main provider of precipitation. While the glaciers act as a reservoir, the system is characterized by a high year-to-year variability. Presuming a changing climate, this combination means great vulnerability of the whole region. The reconstruction of patterns regarding onset, intensity and duration of the different monsoonal branches poses therefore an important and challenging task since high-quality instrumental climate data is sparse in High Asia. Our paleoclimatic study is based on two approaches: a) the analysis of different dendrochronological parameters to disentangle and to reconstruct monsoonal activities in southeast Tibet, and b) the dating and analysis of recently developed glacial landforms due to climate warming. Our analyses include dating of glacial moraine stands, as well as an inter-site comparison with regards to date and speed of glacial shrinkage since the Little Ice Age (LIA). Subject to our studies were four glaciers of different size and altitude of the accumulation and ablation area. While the resulting landforms and processes are divers, all studied glaciers react very similar in terms of beginning and speed of their retreat. Also, two major phases of retreat and advance at around 1670 AD and 1745 AD can be deduced from tree-ring data in case of all studied glaciers. The findings are confirmed by side-to-side geochemical analyses of glacial and glacio-fluvial sediments. While the tree stands on the lateral LIA moraines remain nearly undisturbed since around 1750, the terminal moraines offer only much younger material (maximum 80 years). This points towards an active moraine deposition until the beginning of the 20th century. These findings indicate a pronounced thickness reduction since the LIA, while length reduction of the tongue and development of dead ice bodies occurred only very recently. Regarding the tree
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.
Conway, J. P.; Helgason, W.; Pomeroy, J. W.; Sicart, J. E.
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.
Tolle, F.; Prokop, A.; Bernard, É.; Friedt, J. M.; Griselin, M.
For 3 consecutive years, terrestrial laser scanning surveys have been conducted in the glacier basin of Austre Lovénbreen (Svalbard, 79°N). Each year, high density point clouds were acquired on the glacier surface and on the surrounding slopes. Two yearly scanning sessions were required in order to spatialize and quantify snow cover. The first session was done late April at the expected annual snow maximum. The second session was done in August near the end of the melting season and before the first potential significant snow falls. On the glacier itself, laser scans were produced on the glacier snout, in the area close to the equilibrium line, and in the upper reaches of the glacier. Manual snow drilling measurements and glacier mass balance data were subsequently used to validate snow cover results. In the steep slopes surrounding the glacier, scans were acquired on slopes at various altitudes and orientations in order to get a representative view of different snow cover settings. Particular attention was granted to snowdrift and avalanche processes, and their consequences on remaining packed snow stored in perennial snow accumulation at the bottom of slopes. A good knowledge of the dynamics of the snow cover is of particular interest in a glacier undergoing a clear retreat. Snow is slowing the melting of the ice for part of the season, and snow is also providing what will constitute future glacier ice in the upper reaches of the basin. Snow on slopes is also of importance as avalanches reaching on the glacier can contribute to the overall mass balance. Snow cover, by keeping the slopes permafrost from thawing early in the season, or by providing liquid water affecting it later in the season, is also playing a key role in the glacier basin morphology and its interactions with the glacier body.
Fountain, Andrew G.; Nylen, Thomas H.; Tranter, Martyn; Bagshaw, Elizabeth
Cryoconite holes in the McMurdo Dry Valleys are ice-lidded, thus isolating the pools of water from the atmosphere and from potential surface melt. Hourly measurements of ice and water temperature and water electrical conductivity (EC) were recorded to broadly characterize the physical and chemical changes on daily to seasonal timescales. Overall, subsurface ice/water temperatures were typically several degrees warmer than air temperatures, underscoring the importance of subsurface solar heating. At no time was surface melt observed and the holes melted from within. Detailed differences in the timing and magnitude of both temperature and EC variations during melt-out and freezeup existed between holes despite short separation distances (<1 m). We attribute these differences to small-scale changes in the optical characteristics of the ice and perhaps different efficiencies in hydrologic connections between holes. The holes melt-deepened quickly in the first half of the summer before slowing to a rate equal to the rate of surface ablation that kept hole depth constant for the remainder of the season. The relatively constant EC of the hole waters during midsummer indicates that these holes were connected to a subsurface water system that flushed the holes with fresher meltwater. The early and late season ECs are dominated by freeze-thaw effects that concentrate/dilute the solutes. We speculate that high solute concentrations imply high nutrient concentrations in early summer that may help alleviate potential stresses caused by the production of new biomass after the winter freeze.
... Icebergs released from the glacier drift slowly with the ocean currents and pose hazards for shipping along the coast. The Multi-angle Imaging ... Glacier location: Greenland Arctic Ocean thumbnail: ...
Laute, Katja; Beylich, Achim A.
Hillslopes within defined drainage basin systems function as key elements for sediment production, storage and transfers from sources to sinks, both for short-term and longer-term periods. Rates of hillslope processes are exceptionally varied and affected by numerous influences of varying intensity, especially in sensitive cold climate environments. This research has been conducted over four years (since 2009) as part of a doctoral thesis, which is integrated in the Norwegian Research Council (NFR) funded SedyMONT-Norway project within the ESF TOPO-EUROPE SedyMONT (Timescales of sediment dynamics, climate and topographic change in mountain landscapes) Programme. Focus of this study is on (i) contemporary geomorphic process rates and sedimentary mass transfers within the drainage basins Erdalen (79.5 km2) and Bødalen (60.1 km2) in western Norway, (ii) the absolute and relative importance of the identified relevant denudational processes and (iii) the importance of sediment delivery from slope systems for the drainage basin sedimentary budgets. Identified relevant contemporary denudational processes in both valley systems include rock and boulder falls, snow avalanches, slush flows, debris flows, creep processes, wash- and chemical denudation and fluvial transport of solutes, suspended sediments and bedload. These processes are analysed by combining geomorphologic mapping, geophysical subsurface investigations, terrestrial laser scanning and spatial data analysis with process monitoring. For monitoring contemporary surface processes a designed program has been applied at selected hillslope test sites including e.g. installed nets for collecting freshly accumulated rockfall debris, 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 walls and talus slopes for analysing rock temperatures and mechanical weathering. Slope wash traps
Rapidly Deglaciating and Uplifting Landscapes in Glacier Bay National Park and Preserve GBNPP Provide Alaskan High School Students with Summer Field Research Experiences in Paleoclimate Disciplines and Exposure to Active Researchers in Synergistic Sciences
Connor, C. L.; Hekkers, M.; Schaller, S.; Parks, R.
During summer 2011, ten Alaska high school students enrolled in a summer college introductory field science course through the Design Discover Research Program (DDR) at University Alaska Southeast, with support from the Juneau Economic Development Council, the University Alaska Fairbanks Alaska Summer Research Academy (ASRA), the National Park Service, and the National Oceanic and Atmospheric Administration (NOAA)-Interdisciplinary Scientific Environmental Technology (ISET) Cooperative Science Center (CSC). They conducted field surveys in Glacier Bay National Park and across the adjacent Gustavus glacier forefield landscape. This was the 4th summer for this program. Following a 2-1/2 day orientation on the UAS campus, students traveled by a newly established (2011) Alaska Marine Highway service from Juneau to Gustavus. They utilized bicycles and hiking to access the Dude Creek Critical Habitat, Good Creek watershed, and the Nagoonberry Trail built by the Nature Conservancy along the emerging shoreline of Icy Strait. This region is currently experiencing uplift rates of 20-28 mm/year as a result of Little Ice Age deglaciation and isostatic rebound, rates much higher than eustatic sea level rise. North of the Gustavus ferry dock, roughly 19 acres of emergent land is now a 9-hole golf course, raised from the sea since the 1950s. DDR-students interacted with wildlife biologists, ornithologists, quaternary geologists, glaciologists, and botanists to integrate their understanding of the response of plants and animals to this dynamic landscape. Radio-collared moose populations, which migrated into this area from Haines since the mind-1960s, are being studied to asses their impacts to local vegetation and the behavior of local predators (bears, wolves, and coyotes). Sitka spruce forest expansion onto Icy Strait uplifting salt marshes, now threaten Sandhill Crane habitat and their flyover stops along the Pacific Flyway. Intertidal areas in Bartlett Cove in GBNPP feature
Irvine-Fynn, Tristram D. L.; Hodson, Andrew J.; Moorman, Brian J.; Vatne, Geir; Hubbard, Alun L.
The manner by which meltwater drains through a glacier is critical to ice dynamics, runoff characteristics, and water quality. However, much of the contemporary knowledge relating to glacier hydrology has been based upon, and conditioned by, understanding gleaned from temperate valley glaciers. Globally, a significant proportion of glaciers and ice sheets exhibit nontemperate thermal regimes. The recent, growing concern over the future response of polar glaciers and ice sheets to forecasts of a warming climate and lengthening summer melt season necessitates recognition of the hydrological processes in these nontemperate ice masses. It is therefore timely to present an accessible review of the scientific progress in glacial hydrology where nontemperate conditions are dominant. This review provides an appraisal of the glaciological literature from nontemperate glaciers, examining supraglacial, englacial, and subglacial environments in sequence and their role in hydrological processes within glacierized catchments. In particular, the variability and complexity in glacier thermal regimes are discussed, illustrating how a unified model of drainage architecture is likely to remain elusive due to structural controls on the presence of water. Cold ice near glacier surfaces may reduce meltwater flux into the glacier interior, but observations suggest that the transient thermal layer of near surface ice holds a hydrological role as a depth-limited aquifer. Englacial flowpaths may arise from the deep incision of supraglacial streams or the propagation of hydrofractures, forms which are readily able to handle varied meltwater discharge or act as locations for water storage, and result in spatially discrete delivery of water to the subglacial environment. The influence of such drainage routes on seasonal meltwater release is explored, with reference to summer season upwellings and winter icing formation. Moreover, clear analogies emerge between nontemperate valley glacier and
Klein, E. S.; Nolan, M.; McConnell, J.; Sigl, M.; Cherry, J.; Young, J.; Welker, J. M.
We explored modern precipitation and ice core isotope ratios to better understand both modern and paleo climate in the Arctic. Paleoclimate reconstructions require an understanding of how modern synoptic climate influences proxies used in those reconstructions, such as water isotopes. Therefore we measured periodic precipitation samples at Toolik Lake Field Station (Toolik) in the northern foothills of the Brooks Range in the Alaskan Arctic to determine δ18O and δ2H. We applied this multi-decadal local precipitation δ18O/temperature regression to ∼65 years of McCall Glacier (also in the Brooks Range) ice core isotope measurements and found an increase in reconstructed temperatures over the late-20th and early-21st centuries. We also show that the McCall Glacier δ18O isotope record is negatively correlated with the winter bidecadal North Pacific Index (NPI) climate oscillation. McCall Glacier deuterium excess (d-excess, δ2H - 8*δ18O) values display a bidecadal periodicity coherent with the NPI and suggest shifts from more southwestern Bering Sea moisture sources with less sea ice (lower d-excess values) to more northern Arctic Ocean moisture sources with more sea ice (higher d-excess values). Northern ice covered Arctic Ocean McCall Glacier moisture sources are associated with weak Aleutian Low (AL) circulation patterns and the southern moisture sources with strong AL patterns. Ice core d-excess values significantly decrease over the record, coincident with warmer temperatures and a significant reduction in Alaska sea ice concentration, which suggests that ice free northern ocean waters are increasingly serving as terrestrial precipitation moisture sources; a concept recently proposed by modeling studies and also present in Greenland ice core d-excess values during previous transitions to warm periods. This study also shows the efficacy and importance of using ice cores from Arctic valley glaciers in paleoclimate reconstructions.
Dordan, Mary Lou; Nicholson, Deborah
This resource guide tells the story of Alaskan women and minority aviators and those in aviation-related businesses, from the early 20th century to the present. Developed for secondary students but also suitable for younger students, the guide combines six accounts of Alaskan women and minority aviators with classroom activities centered around…
Blöthe, Jan Henrik; Höser, Thorsten; Rosenwinkel, Swenja; Korup, Oliver
Rock glaciers are common periglacial features in highest elevations of semiarid to arid mountain ranges. Rock glaciers predominate in realms where precipitation values fall below thresholds that allow for ice glacier formation, then even outranging ice glaciers in size and number. The influence of ice glaciers on high-mountain's sediment dynamics is manifold: ice-glacier-driven erosion produces large amounts of clastic material; ice glaciers act as a conveyor belt for sediments, delivering material from their source regions to their terminus; ice glaciers entering trunk valleys form efficient dams that interrupt sediment delivery. While these mechanisms have been addressed in numerous earlier studies, the role of rock glaciers for the sediment dynamics of arid mountain belts remains elusive. We address this shortcoming by analysing a rock glacier inventory that we compiled for the Himalaya-Karakoram ranges and the Tien Shan ranges in Central Asia. Our inventory comprises more than 1000 specimen, a large number of which form dams of large trunk rivers and minor tributaries, disconnecting the sediment fluxes from upstream. In certain regions that are nearly devoid of ice-glaciers, like the Gamugah surface of NW Pakistan, rock glaciers of >10^4-m length occupy valley bottoms entirely, constituting the only mode of transport for sediments produced in headwaters. In conclusion, we call for a better understanding of the role that rock glaciers take in the sediment dynamics of arid mountain belts.
Oneel, S.; Hood, E. W.; Arendt, A. A.; Sass, L. C.; March, R. S.
We examine long-term streamflow and mass balance data from two Alaskan glaciers located in climatically distinct basins: Gulkana Glacier, a continental glacier located in the Alaska Range, and Wolverine Glacier, a maritime glacier located in the Kenai Mountains. Both glaciers lost mass, primarily as a result of summer warming, and both basins exhibit increasing streamflow over the 1966-2011 study interval. We estimated total glacier runoff via summer mass balance, and separated the fraction related to annual mass imbalances. In both climates, the fraction of streamflow related to annual mass balance averages less than 20%, substantially smaller than the fraction related to total summer mass loss (>50%), which occurs even in years of glacier growth. The streamflow fraction related to changes in annual mass balance has increased only in the continental environment. In the maritime climate, where deep winter snowpacks and frequent rain events drive consistently high runoff, the magnitude of this streamflow fraction is small and highly variable, precluding detection of any existing trend. Changes in streamflow related to annual balance are often masked by interannual variability of maritime glacier mass balance, such that predicted scenarios of continued glacier recession are more likely to impact the quality and timing of runoff than the total basin water yield.
Zarling, J.P.; Swanson, R.B.; Logan, R.R.; Das, D.K.; Lewis, C.E.; Workman, W.G.; Tumeo, M.A.; Hok, C.I.; Birklid, C.A.; Bennett, F.L.
The ninety-ninth US Congress commissioned a six-state food irradiation research and development program to evaluate the commercial potential of this technology. Hawaii, Washington, Iowa, Oklahoma and Florida as well as Alaska have participated in the national program; various food products including fishery products, red meats, tropical and citrus fruits and vegetables have been studied. The purpose of the Alaskan study was to review and evaluate those factors related to the technical and economic feasibility of an irradiator in Alaska. This options analysis study will serve as a basis for determining the state's further involvement in the development of food irradiation technology. 40 refs., 50 figs., 53 tabs.
Lovell, Harold; Benn, Douglas; Lukas, Sven; Flink, Anne
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
Le Moine, Nicolas; Gsell, Pierre-Stéphane
In this paper we propose a new, graph-based approach to glacier segmentation and flowline extraction. The method, which requires a set of glacier contours and a Digital Elevation Model (DEM), consists in finding an optimum branching that connects a set of vertices belonging to the topological skeleton of each glacier. First, the challenges associated with glacier flowline extraction are presented. Then, the three main steps of the method are described: the skeleton extraction and pruning algorithm, the definition and computation of a travel cost between all pairs of skeleton vertices, and the identification of the directed minimum spanning tree in the resulting directed graph. The method, which is mainly designed for valley glaciers, is applied to glaciers in Switzerland.
Paul, Frank; Mölg, Nico
Mapping glacier extent from optical satellite data has become a most efficient tool to create or update glacier inventories and determine glacier changes over time. A most valuable archive in this regard is the nearly 30-year time series of Landsat Thematic Mapper (TM) data that is freely available (already orthorectified) for most regions in the world from the USGS. One region with a most dramatic glacier shrinkage and a missing systematic assessment of changes, is the Palena province in Chile, located south of Puerto Montt in northern Patagonia. A major bottleneck for accurate determination of glacier changes in this region is related to the huge amounts of snow falling in this very maritime region, hiding the perimeter of glaciers throughout the year. Consequently, we found only three years with Landsat scenes that can be used to map glacier extent through time. We here present the results of a glacier change analysis from six Landsat scenes (path-rows 232-89/90) acquired in 1985, 2000 and 2011 covering the Palena district in Chile and neighbouring regions. Clean glacier ice was mapped automatically with a standard technique (TM3/TM band ratio) and manual editing was applied to remove wrongly classified lakes and to add debris-covered glacier parts. The digital elevation model (DEM) from ASTER (GDEM2) was used to derive drainage divides, determine glacier specific topographic parameters, and analyse the area changes in regard to topography. The scene from the year 2000 has the best snow conditions and was used to eliminate seasonal snow in the other two scenes by digital combination of the binary glacier masks and neighbourhood analysis. The derived mean relative area loss over the entire study area is 25%, showing a large spatial variability and a strong dependence on elevation. While small mountain glaciers at high elevations and steep slopes show only little change over the 26-year period, ice at low elevations from large valley glaciers shows a dramatic
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
Monnier, S.; Kinnard, C.
In the dry Andes of Chile, rock glaciers are the most widespread and remarkable superficial landforms, and may constitute important solid water reservoirs. The existence of huge (up to 2-3 kilometres of length) rock glaciers located in deep cirques questions possible derivation from former 'true' glaciers. The issue is of importance (i) for understanding the mechanisms of the landscape evolution from glacial realm to periglacial realm, and (ii) because it may determine the ice content of the concerned rock glaciers. In the Colorado Río valley, in the upper part of the Elqui catchment (~30.15 deg. S and 70.80 deg. W), we investigated the internal structure of the Llanos la Liebre rock glacier using ground-penetrating radar (GPR). With 50 MHz antennas and a constant offset of 2 m between antennas, we performed various GPR profiles, especially a ~2.2 km-long one almost covering the entire length of the rock glacier. The processing and the subsequent interpretation of the GPR data were mainly based on the modelling of the radar wave velocity. Hence, the final representation of the internal structure of the rock glacier integrates the reconstructed stratigraphy, the 2-D velocity model, and first attempts for estimating the ice/water contents. The most striking results are: the neat identification of the base of the superficial blocky layer and of the rock glacier floor; the occurrence of stratigraphic patterns reminiscent of 'true' glaciers; the supremacy of high radar wave velocities in the upper part of the rock glacier. On the latter bases and taking into account the whole geomorphology of the site, the derivation of the Llanos la Liebre rock glacier from a former, buried glacier is debated.
Anderson, Leif S.; Anderson, Robert S.
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.
Pettit, E. C.; Scambos, T. A.; Haran, T. M.; Wellner, J. S.; Domack, E. W.; Vernet, M.
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
Sauber, Jeanne; Molnia, Bruce F.; Mitchell, Darius
In late February and March, 2003, the Ice, Cloud, and land Elevation Satellite (ICESat) measured ice and land elevations along profiles across southern Alaska. During this initial data acquisition stage ICESat observations were made on 8-day repeat tracks to enable calibration and validation of the ICESat data products. Each profile consists of a series of single point values derived from centroid elevations of an $\\approx$70 m diameter laser footprint. The points are s4pakated by $\\approx$172 m along track. Data siets of 8-day observations (an ascending and descending ground track) crossed the Bering and Malaspina Glacier. Following its 1993--1995 surge; the Bering Glacier has undergone major terminus retreat as well as ike thinning in the abtation zone. During the later part of the 20th century, parts of the Malaspina thinned by about 1 m/yr. The multiple observation profiles across the Bering and Malaspina piedmont lobes obtained in February/March are being geolocated on Landsat images and the elevation profiles will be used for a number o scientific objectives. Based on our simulations of ICESat performance over the varied ice surface of the Jakobshavn Glacier of GReenland, 2003, we expect to measure annual, and possibly seasonal, ice elevation changes on the large Alaskan glaciers. Using elevation data obtained from a second laser, we plan to estimate ice elevation changes on the Bering Glacier between March and October 2003.
Birajdar, F.; Venkataraman, G.; Bahuguna, I.; Samant, H.
Himalayan glaciers show large uncertainty regarding their present and future state due to their sensitive reaction towards change in climatic condition. Himalayan glaciers are unique as they are located in tropical, high altitude regions, predominantly valley type and many are covered with debris. The great northern plains of India sustain on the perennial melt of glaciers meeting the water requirements of agriculture, industries, domestic sector even in the months of summer when large tracts of the country go dry. Therefore, it is important to monitor and assess the state of snow and glaciers and to know the sustainability of glaciers in view of changing global scenarios of climate and water security of the nation. Any information pertaining to Himalayan glaciers is normally difficult to be obtained by conventional means due to its harsh weather and rugged terrains. Due to the ecological diversity and geographical vividness, major part of the Indian Himalaya is largely un-investigated. Considering the fact that Himalayan glaciers are situated in a harsh environment, conventional techniques of their study is challenging and difficult both in terms of logistics and finances whereas the satellite remote sensing offers a potential mode for monitoring glaciers in long term. In order to gain an updated overview of the present state of the glacier cover and its changes since the previous inventories, an attempt has been made to generate a new remotesensing- derived glacier inventory on 1:50,000 scale for Bhaga basin (N32°28'19.7'' - N33°0'9.9'' ; E76°56'16.3'' - E77°25'23.7'' ) Western Himalaya covering an area of 1695.63 km2. having 231 glaciers and occupying glacierized area of 385.17 ±3.71 km2. ranging from 0.03 km2. to 29.28 km2. Glacier inventory has been carried out using high resolution IRS P6 LISS III data of 2011, ASTER DEM and other ancillary data. Specific measurements of mapped glacier features are the inputs for generating the glacier inventory data
Nagatsuka, N.; Takeuchi, N.; Nakano, T.
higher Sr and lower Nd ratios in the north and also showed little variation within a glacier. On the other hand, those on Alaskan glacier showed lower Sr and large spatial variation in Nd on a glacier. Cryoconite on Greenlandic glaciers showed further high Sr and low Nd than the other glaciers. This suggests that origins of silicate minerals in cryoconite are substantially different among the glaciers. Compared with the isotopic ratios of silicate minerals in moraine, desert, and loess reported over the regions, those in cryoconite on Asian, Alaskan, and Greenlandic glaciers were close to those in respective regions. This result indicates that silicate minerals in cryoconite were derived from surrounding the glaciers. The Sr isotopic ratios of organic matter in cryoconite also varied among the glaciers. They may reflect the minerals used by glacial microbes as nutrients.
2003-01-01[figure removed for brevity, see original site] Released 27 August 2003This 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.
Motyka, R. J.; Truffer, M.
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
Fukui, Kotaro; Sone, Toshio; Strelin, Jorge A.; Torielli, Cesar A.; Mori, Junko; Fujii, Yoshiyuki
We describe field measurements (ground-penetrating radar (GPR), geodetic survey and ice-core drilling) to provide new information on the movement mechanism and internal structure of a polar rock glacier on James Ross Island, Antarctic Peninsula. We collected GPR data along longitudinal and transverse profiles. The longitudinal GPR profiles identify inter-bedded debris-rich layers that dip up-glacier, similar to the thrust structures in the compression zone of a valley glacier. The transverse GPR profiles indicate a syncline structure inclined towards the central part of the rock glacier, resembling the transverse foliation of a valley glacier. The stratigraphy of two boreholes shows that the rock glacier consists primarily of bubbly ice with thin debris-rich layers, an internal structure similar to the `nested spoons' structure common in the interior of valley glaciers. These results indicate that the glacier motion is controlled by shear movement, common in valley glaciers. The geodetic survey confirms that flow velocities decrease towards the lower part of the rock glacier. Such heterogeneous movement causes longitudinal compression and forms thrusts which then create the debris-rich layer by uplifting basal ice and debris. Pushing of the upstream ice against the downstream ice bends the surface layers, forming transverse ridges on the rock glacier surface.
Hall, D. K.; Ormsby, J. P.
Three Seasat synthetic aperture radar (SAR) and three Landsat multispectral scanner subsystem (MSS) scenes of three areas of Alaska were analyzed for hydrological information. The areas were: the Dease Inlet in northern Alaska and its oriented or thaw lakes, the Ruth and Tokositna valley glaciers in south central Alaska, and the Malaspina piedmont glacier on Alaska's southern coast. Results for the first area showed that the location and identification of some older remnant lake basins were more easily determined in the registered data using an MSS/SAR overlay than in either SAR or MSS data alone. Separately, both SAR and MSS data were useful for determination of surging glaciers based on their distinctive medial moraines, and Landsat data were useful for locating the glacier firn zone. For the Malaspina Glacier scenes, the SAR data were useful for locating heavily crevassed ice beneath glacial debris, and Landsat provided data concerning the extent of the debris overlying the glacier.
Liermann, Susan; Beylich, Achim A.; Rubensdotter, Lena; Hansen, Louise
A sediment budget study contains analysis and quantification of the processes of sediment production, storage and transfer. For constructing a sediment budget at a small-catchment scale (50-100 km2) it is necessary to integrate the temporal and spatial variations of supply of material from sediment sources, sediment transport and storage and to identify how far the different system components are coupled to each other. The analysis of sedimentary fluxes and budgets as well as their controls at different timescales (Holocene to contemporary) is a basis for the assessment of complex landscape responses to Holocene to recent changes in temperature, precipitation and runoff. This PhD project is part of the NFR funded Norwegian Individual Project within the ESF SedyMONT (Timescales of sediment dynamics, climate and topographic change in mountain landscapes) TOPO-EUROPE Programme. Two neighbouring glacier-fed valley-fjord systems (Erdalen & Bødalen) with a different topographic inheritance from Pleistocene glaciations are compared. It is of special interest how the different valley morphometries have influenced Holocene to contemporary sediment fluxes and budgets. Different approaches for sediment budget studies are used to interpret and understand the spatial and temporal sediment flux variability during the Holocene with the main focus on i) the quantification and analysis of storage element volumes for estimation of Holocene sedimentation rates and sediment yields, ii) the analysis of the spatial and temporal sediment flux variability, iii) the analysis of the linkages between sediment transfer and storage, iv) the analysis of controlling factors for postglacial, subrecent and contemporary sediment fluxes and v) the construction of Holocene to contemporary sediment budgets for Erdalen and Bødalen. Both valleys are instrumented with a year-round monitoring system (runoff, suspended and solute transport) for analysing fluvial sediment fluxes. The results enable to
Mölg, Nico; Vieli, Andreas; Bolch, Tobias; Bauder, Andreas; Bhattacharya, Atanu
Global climate change has led to increasing glacier retreat in most parts of the world. However, many heavily debris-covered glaciers have shown much smaller recession rates than their clean-ice neighbours. This can be attributed to the insulation effect of the supraglacial debris. Remote-sensing based investigations revealed that recent mass balances of debris-covered glaciers are equally negative. This fact is partly due to enhanced melting at supra-glacial lakes and ice cliffs but can also be caused by reduced mass flux. In this context, insufficient process understanding constitutes a major challenge for large scale glacier change assessment and modelling. In this project, we aim at better understanding the evolution of glaciers in connection with changes in supra-glacial debris coverage. It is performed on Zmutt Glacier in Matter valley in Switzerland and on Gangotri Glacier in Garwhal Himalaya in India. Changes in glacier length, area, debris coverage, and surface elevation were compiled based on topographic maps, oblique photos, aerial and satellite orthoimages, digital terrain models (DTMs), and glacier monitoring data for a 50 (Gangotri) and 120 (Zmutt) year period, respectively. The subsequent analysis revealed that Zmutt Glacier has been in a slow but almost continuous retreating state since the end of the 19th century and showed a clear reduction in glacier area and volume. Similarly, Gangotri Glacier has retreated and, to a smaller degree, lost volume. However, the change in glacier length and area is clearly smaller than for other nearby, less debris-covered or debris-free glaciers. This fact is attributed to the larger debris-covered area that has steadily increased. Further in the project, this data will serve as an important input and validation for the envisaged 3D flow modelling and, hence, will contribute to the understanding of the development of glaciers and debris-covered ice in a period of fast climatic changes.
Fountain, A.G.; Fulk, M.A.
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)
2003-01-01Malaspina Glacier in southeastern Alaska is considered the classic example of a piedmont glacier. Piedmont glaciers occur where valley glaciers exit a mountain range onto broad lowlands, are no longer laterally confined, and spread to become wide lobes. Malaspina Glacier is actually a compound glacier, formed by the merger of several valley glaciers, the most prominent of which seen here are Agassiz Glacier (left) and Seward Glacier (right). In total, Malaspina Glacier is up to 65 kilometers (40 miles) wide and extends up to 45 kilometers (28 miles) from the mountain front nearly to the sea. This perspective view was created from a Landsat satellite image and an elevation model generated by the Shuttle Radar Topography Mission (SRTM). Landsat views both visible and infrared light, which have been combined here into a color composite that generally shows glacial ice in light blue, snow in white, vegetation in green, bare rock in grays and tans, and the ocean (foreground) in dark blue. The back (northern) edge of the data set forms a false horizon that meets a false sky. Glaciers erode rocks, carry them down slope, and deposit them at the edge of the melting ice, typically in elongated piles called moraines. The moraine patterns at Malaspina Glacier are quite spectacular in that they have huge contortions that result from the glacier crinkling as it gets pushed from behind by the faster-moving valley glaciers. Glaciers are sensitive indicators of climatic change. They can grow and thicken with increasing snowfall and/or decreased melting. Conversely, they can retreat and thin if snowfall decreases and/or atmospheric temperatures rise and cause increased melting. Landsat imaging has been an excellent tool for mapping the changing geographic extent of glaciers since 1972. The elevation measurements taken by SRTM in February 2000 now provide a near-global baseline against which future non-polar region glacial thinning or thickening can be assessed.
Kargel, J. S.; Wessels, R.; Kieffer, H. H.
Glaciers are ablating rapidly the world over. Nowhere are the rates of retreat and downwasting greater than in the Hindu Kush-Himalaya (HKH) region. It is estimated that over the next century, 40,000 square kilometers of present glacier area in the HKH region will become ice free. Most of this area is in major valleys and the lowest glaciated mountain passes. The existence and characteristics of glaciers have security impacts, and rapidly changing HKH glaciers have broad strategic implications: (1) Glaciers supply much of the fresh water and hydroelectric power in South and Central Asia, and so glaciers are valuable resources. (2) Shared economic interests in water, hydroelectricity, flood hazards, and habitat preservation are a force for common cause and reasoned international relations. (3) Glaciers and their high mountains generally pose a natural barrier tending to isolate people. Historically, they have hindered trade and intercultural exchanges and have protected against aggression. This has further promoted an independent spirit of the region's many ethnic groups. (4) Although glaciers are generally incompatible with human development and habitation, many of the HKH region's glaciers and their mountains have become sanctuaries and transit routes for militants. Siachen Glacier in Kashmir has for 17 years been "the world's highest battlefield," with tens of thousands of troops deployed on both sides of the India/Pakistan line of control. In 1999, that conflict threatened to trigger all-out warfare, and perhaps nuclear warfare. Other recent terrorist and military action has taken place on glaciers in Kyrgyzstan and Tajikistan. As terrorists are forced from easily controlled territories, many may tend to migrate toward the highest ground, where definitive encounters may take place in severe alpine glacial environments. This should be a major concern in Nepali security planning, where an Army offensive is attempting to reign in an increasingly robust and brutal
Mandal, Arindan; Ramanathan, Alagappan; Farooq Azam, Mohd; Wagnon, Patrick; Vincent, Christian; Linda, Anurag; Sharma, Parmanand; Angchuk, Thupstan; Bahadur Singh, Virendra; Pottakkal, Jose George; Kumar, Naveen; Soheb, Mohd
Several studies on Himalayan glaciers have been recently initiated as they are of particular interest in terms of future water supply, regional climate change and sea-level rise. In 2002, a long-term monitoring program was initiated on Chhota Shigri Glacier (15.7 square km, 9 km long, 6263-4050 m a.s.l.) located in Lahaul and Spiti Valley, Himachal Pradesh, India. This glacier lies in the monsoon-arid transition zone (western Himalaya) and is a representative glacier in Lahaul and Spiti Valley. While annual mass balances have been measured continuously since 2002 using the glaciological method, seasonal scale observations began in 2009. The annual and seasonal mass balances were then analyzed along with meteorological conditions in order to understand the role of winter and summer balances on annual glacier-wide mass balance of Chhota Shigri glacier. During the period 2002-2013, the glacier experienced a negative glacier-wide mass balance of -0.59±0.40 m w.e. a-1 with a cumulative glaciological mass balance of -6.45 m w.e. Annual glacier-wide mass balances were negative except for four years (2004/05, 2008/09, 2009/10 and 2010/11) where it was generally close to balanced conditions. Equilibrium line altitude (ELA) for steady state condition is calculated as 4950 m a.s.l. corresponding to an accumulation area ratio (AAR) of 62% using annual glacier-wide mass balance, ELA and AAR data between 2002 and 2013. The winter glacier-wide mass balance between 2009 and 2013 ranges from a maximum value of 1.38 m w.e. in 2009/10 to a minimum value of 0.89 in 2012/13 year whereas the summer glacier-wide mass balance varies from the highest value of -0.95 m w.e. in 2010/11 to the lowest value of -1.72 m w.e. in 2011/12 year. The mean vertical mass balance gradient between 2002 and 2013 was 0.66 m w.e. (100 m)-1 quite similar to Alps, Nepalese Himalayas etc. Over debris covered area, the gradients are highly variable with a negative mean value of -2.15 m w.e. (100 m)-1 over 2002
Furfaro, R.; Kargel, J. S.; Fink, W.; Bishop, M. P.
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
Williams, Richard S., Jr.; Ferrigno, Jane G.
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
Vogt, R.; Mlynowski, T. J.; Menounos, B.
Glaciers are effective agents of erosion for many mountainous regions, but primary rates of erosion are difficult to quantify due to unknown conditions at the glacier bed. We develop a numerical model of subglacial erosion and passively couple it to a vertically integrated ice flow model (UBC regional glaciation model). The model accounts for seasonal changes in water pressure at the glacier bed which affect rates of abrasion and quarrying. We apply our erosion model to Peyto Glacier, and compare estimates of glacier erosion to the mass of fine sediment contained in a lake immediately down valley from the glacier. A series of experiments with our model and ones based on subglacial sliding rates are run to explore model sensitivity to bedrock hardness, seasonal hydrology, changes in mass balance, and longer-term dimensional changes of the glacier. Our experiments show that, as expected, erosion rates are most sensitive to bedrock hardness and changes in glacier mass balance. Silt and clay contained in Peyto Lake primarily originate from the glacier, and represent sediments derived from abrasion and comminution of material produced by quarrying. Average specific sediment yield during the period AD1917-1970 from the lake is 467×190 Mg km-2yr-1 and reaches a maximum of 928 Mg km-2yr-1 in AD1941. Converting to a specific sediment yield, modelled average abrasion and quarrying rates during the comparative period are 142×44 Mg km-2yr-1 and 1167×213 Mg km-2yr-1 respectively. Modelled quarrying accounts for approximately 85-95% of the erosion occurring beneath the glacier. The basal sliding model estimates combined abrasion and quarrying. During the comparative period, estimated yields average 427×136 Mg km-2yr-1, lower than the combined abrasion and quarrying models. Both models predict maximum sediment yield when Peyto Glacier reached its maximum extent. The simplistic erosion model shows higher sensitivity to climate, as seen by accentuated sediment yield peaks
Carlson, P.R.; Cowan, E.A.; Powell, R.D.; Cai, J.
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.
Meier, Mark; Post, Austin
Most Americans have never seen a glacier, and most would say that glaciers are rare features found only in inaccessible, isolated wilderness mountains. Are they really so rare? Or are they really potentially important sources of water supply?
Jamieson, Stewart S. R.; Ewertowski, Marek W.; Evans, David J. A.
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.
Sagredo, E. A.; Rupper, S.; Lowell, T. V.
Valley glaciers are sensitive indicators of climate change. Records of former glacial fluctuations have been extensively used to reconstruct paleoclimatic conditions at different temporal and spatial scales. These reconstructions typically do not account for variations in regional climate conditions. Based on modeling results, it has been suggested these regional climate conditions could play an important role modulating the magnitude of glacier response for large scale climate perturbations. The climatically diverse Andes mountain range represents an ideal setting to test hypothesis of glacier sensitivity variability. Here, we quantify glacier sensitivity to climate change in different climatic regimes across the Andean. By applying a regional Surface Energy Mass Balance model (SEMB), we analyze the change in the Equilibrium Line Altitude (ELA) for a sample of 234 glaciers, under different climatic perturbations. Our results suggest that ELAs of Andean glaciers respond linearly to changes in temperature, with rates that oscillate between 153 and 186 m/°C. For example, with a perturbation of -6°C (~Global LGM), our model predicts a drop in the ELA of 916 m for the least sensitive glaciers and 1117 m for the more sensitive ones. This glacier sensitivity variability exhibits a very distinctive spatial distribution. The most sensitive glaciers are located in Central Chile (south of 31°C), and the Western Cordillera of Peru (north of 13°S). In contrast, lower sensitivity glaciers are situated in the inner Tropics, Eastern Cordillera of Peru and Bolivia (south of 13°S), and part of southern Patagonia and Tierra del Fuego. When analyzing the response of glaciers to changes in accumulation, our results suggest that under a scenario of increasing precipitation, glacier behavior is nonlinear. A statistical cluster analysis of glacier sensitivity divides our 234 glaciers into three distinct groups. The most sensitive glaciers correspond to those situated in western
Huss, Matthias; Fischer, Mauro
Very small glaciers (<0.5km2) currently account for up to 80% of the total number of glaciers in mountain ranges around the globe. Although their total area and volume is small compared to larger glaciers, they are a relevant component of the cryosphere contributing to landscape formation, local hydrology and sea-level rise. Very small glaciers have generally shorter response times than valley glaciers and their mass balance is strongly dependent on snow redistribution processes. Worldwide glacier monitoring has focused on medium-sized to large glaciers leaving us with a relatively limited understanding of the behavior of very small glaciers. With warming climate there is an increasing concern that very small glaciers might be the first to disappear. Already in the next decades this might result in the complete deglaciation of mountain ranges with glacier equilibrium lines close to the highest peaks. Here, we present a comprehensive modeling framework to assess past and future changes of very small glaciers at the mountain-range scale. Among other processes our model accounts for snow redistribution, changes in glacier geometry and the time-varying effect of supraglacial debris. It computes the mass balance distribution, the englacial temperature regime and proglacial runoff. The past evolution of 1'133 glaciers in the Swiss Alps is individually constrained based on geodetic ice volume changes, and the model is validated against an extensive data base of in-situ measurements on very small glaciers. Our results indicate that 52% of all very small glaciers in Switzerland will completely disappear within the next 25 years. However, a few avalanche-fed glaciers at low elevation might be able to survive even substantial atmospheric warming. We find highly variable sensitivities of very small glaciers to air temperature change, gently-sloping, low-elevation, and debris-covered glaciers being most sensitive.
Grzesiak, Jakub; Górniak, Dorota; Świątecki, Aleksander; Aleksandrzak-Piekarczyk, Tamara; Szatraj, Katarzyna; Zdanowski, Marek K
Surface ice and cryoconite holes of two types of polythermal Svalbard Glaciers (Hans Glacier--grounded tidewater glacier and Werenskiold Glacier-land-based valley glacier) were investigated in terms of chemical composition, microbial abundance and diversity. Gathered data served to describe supraglacial habitats and to compare microbe-environment interactions on those different type glaciers. Hans Glacier samples displayed elevated nutrient levels (DOC, nitrogen and seston) compared to Werenskiold Glacier. Adjacent tundra formations, bird nesting sites and marine aerosol were candidates for allochtonic enrichment sources. Microbial numbers were comparable on both glaciers, with surface ice containing cells in the range of 10(4) mL(-1) and cryoconite sediment 10(8) g(-1) dry weight. Denaturating gradient gel electrophoresis band-based clustering revealed differences between glaciers in terms of dominant bacterial taxa structure. Microbial community on Werenskiold Glacier benefited from the snow-released substances. On Hans Glacier, this effect was not as pronounced, affecting mainly the photoautotrophs. Over-fertilization of Hans Glacier surface was proposed as the major factor, desensitizing the microbial community to the snow melt event. Nitrogen emerged as a limiting factor in surface ice habitats, especially to Eukaryotic algae. PMID:26104673
Kohshima, S.; Yoshimura, Y.; Takeuchi, N.; Segawa, T.; Uetake, J.
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.
The Hatunraju Glacier (9°00'S/70°40'W) is located in the Parón valley in the northern part of the Cordillera Blanca. The almost 4 km long and steeply inclined glacier flows down from the Huandoy-N-Side (6395 m) into the Parón valley to an elevation of 4250 m a.s.l.. The extremely narrow glacier is in its entire ablation area heavily debris-covered. It is one of the few glaciers, which dam with its debris-mantled glacier tongue a main river in this mountain range. In this case the Hatunraju glacier produces the largest glacier-dammed lake in the Cordillera Blanca, the Laguna Parón. In some other aspects, this glacier proves to be distinct from the majority of the glaciers in the Cordillera Blanca: It is flowing on an almost up to 250 m high moraine pedestal ("moraine-dammed raised bed glacier") and the glacier makes a bend of almost 90° when entering into the main valley. The present paper focuses in particular on the last point: the formation of the so called "crooked moraine". It has been explained by Lliboutry (1977) as a result of a glacier lake outburst and the subsequent destruction of the latero-frontal moraine. The later process supposed to be the trigger of the abrupt change in the flow direction of the lower part of the glacier. Recent investigations suggest an alternative genesis of the crooked moraine considering the distinct phases of the glaciation history of the Parón valley. The here proposed formation pattern is also paradigmatic for other crooked debris-covered glaciers, especially in High Asia. Comparative examples will be provided from the Karakoram and Himalayas. The research work on the Hatunraju Glacier is part of a project on the glacial geomorphology in the Tropical Andes financed by the Alexander von Humboldt-Foundation.
Anderson, L. S.; Anderson, R. S.
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, mass balance gradients can be 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 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 steady states in which ice accumulation equals ice ablation, and debris input equals debris loss from the glacier. Our model and parameter selections produce two-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. 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). The model reproduces first-order relationships between debris cover, AARs, and glacier surface velocities from glaciers in High Asia. 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.
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)
Fischer, Mauro; Huss, Matthias; Hoelzle, Martin
Present knowledge about Alpine glaciers is not representative in terms of glacier size distribution. More than 80% of all Swiss glaciers are smaller than 0.5 km2 and hence belong to the class of very small glaciers. In the context of fast glacier wastage in the European Alps, the near-future development of the size class distribution will most probably be in favour of very small glaciers which will comparably increase in number. However, there has been little research carried out about very small glaciers so far. It is not clear whether findings and theoretical concepts elaborated for medium and large valley glaciers (> 3 km2) can be directly transferred to very small glaciers, whose accumulation patterns are, for instance, characteristically exceptional because winter precipitation is multiplied by wind drift and avalanching. The extent of glaciers in the European Alps has recently been mapped and inventoried spatio-temporally consistently. Nevertheless, such glacier outlines derived by satellite remote-sensing techniques are not accurate enough for the special case of investigating changes in very small glaciers. Therefore, glacier outlines are digitized manually using high-resolution (25 cm) orthophotographs covering the entire Swiss Alps acquired twice for every scene (both in the early and late noughties). In contrast to the known shortcomings of satellite remote-sensing based approaches, the margins of very small glaciers are (with few exceptions) clearly distinguishable on these orthophotos, even in shaded, snow- or debris-covered areas. For the eastern Swiss Alps (east of the rivers Reuss and Ticino), about one third of all glaciers has vanished since 1973. The total area presently still glacierized amounts to 140 km2, whereof very small glaciers cover only 25% but account for almost 90% of the total number of glaciers. Retreat rates are highest for very small glaciers but seem to be stabilizing or even decreasing since the early noughties, implying that
Bajracharya, S. R.; Bajracharya, O. R.; Baidya, S.; Maharjan, S. B.; Shrestha, F.
Increase in glacier number and decrease in glacier area are perceived significantly in recent decades in Nepal. The observed glacier changes are one of the key indicators of climate change. In order to understand the impact of climate change on glaciers a repeat decadal glacier inventory since 1980s based on landsat images were carried out in the Langtang and Imja valleys. The recent glacier outlines were delineated semi-automatically from the images using object based image classification (obic) in Definien Developer. The glacier outlines of other decades were obtained by manual editing on the glacier polygons of semi-automatically derived glaciers polygons by overlaying separately on the images of respective years. The result shows that the glacier area has been decreased by 26% in Langtang valley in the period 1976-2009 and 28% in Imja valley in the period 1979-2010. The lowest elevation of glaciers has been shifted upward by 50m and 115m in Imja and Langtang valley respectively. The annual mean temperature from 1988 to 2008 were found to be 4.2oC and 0.3oC in Langtang valley and Imja valley respectively. The rate of temperature rise in this period was 0.116oC yr-1 and 0.09 oC yr-1 in Langtang valley and Imja valley respectively. The rise of mean decadal and annual mean temperature in Langtang and Imja valleys are one of the key factors of shrinking and retreating of glaciers.
Williams, Richard S., Jr.; Ferrigno, Jane G.
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
Jeelani, G.; Hasnain, S. I.
Kolahoi Glacier (340 07-340 12 N: 75016- 750 23 E), Liddar Valley, Kashmir Himalaya is one of the largest glacier in the Kashmir valley. The glacier is nourished by westerly system during winter and ablation takes place during summer period with no impact of SW monsoon system. Liddar Valley covers an area of 1282.55 km2 and sustain about 48 glaciers with total ice covered area of about 39 km2. The melt water feeds the west and east Liddar rivers and downstream in the valley they joined and forms River Jhelum which is the main source of water and livelihood to entire Kashmir valley. The major concern is that melting glaciers in the Kashmir valley will have ‘cascading effects’ across ecosystems, creating chain reactions on the food and water security of marginalised communities. An analysis of the available records is presented in this study. It appears that considerable recession of the snout has taken place since 1857. The glacier has receded about 1.6 km from 1857-1909 (52 years ?), 0.82 km from 1912-1961 (50 years), and 1.0 km from 1962-2008 (47 years). The area of the glacier is decreased by about 15% (0.04 Km2/year) from 1962 to 2008. The data indicate that there is significant increase in the rate of glacier recession for last few decades. It appears that global and regional warming, below normal precipitation occurred during the period of snow accumulation are perhaps the main reasons for accelerating the rate of melting during recent times. The stream (West Liddar) fed by the Kolahoi glacier also shows an increase in the discharge for last few decades as compared to the other streams fed dominantly by snow melt.
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.
2003-01-01This anaglyph view of Malaspina Glacier in southeastern Alaska was created from a Landsat satellite image and an elevation model generated by the Shuttle Radar Topography Mission (SRTM). Malaspina Glacier is considered the classic example of a piedmont glacier. Piedmont glaciers occur where valley glaciers exit a mountain range onto broad lowlands, are no longer laterally confined, and spread to become wide lobes. Malaspina Glacier is actually a compound glacier, formed by the merger of several valley glaciers, the most prominent of which seen here are Agassiz Glacier (left) and Seward Glacier (right). In total, Malaspina Glacier is up to 65 kilometers (40 miles) wide and extends up to 45 kilometers (28 miles) from the mountain front nearly to the sea. Glaciers erode rocks, carry them down slope, and deposit them at the edge of the melting ice, typically in elongated piles called moraines. The moraine patterns at Malaspina Glacier are quite spectacular in that they have huge contortions that result from the glacier crinkling as it gets pushed from behind by the faster-moving valley glaciers. Numerous other features of the glaciers and the adjacent terrain are clearly seen when viewing this image at full resolution. The series of tonal arcs on Agassiz Glacier's extension onto the piedmont are called 'ogives.' These arcs are believed to be seasonal features created by deformation of the glacier as it passes over bedrock irregularities at differing speeds through the year. Assuming one light-and-dark ogive pair per year, the rate of motion of the glacial ice can be estimated (in this case, about 200 meters per year where the ogives are most prominent). Just to the west, moraine deposits abut the eroded bedrock terrain, forming a natural dam that has created a lake. Near the northwest corner of the scene, a recent landslide has deposited rock debris atop a small glacier. Sinkholes are common in many areas of the moraine deposits. The sinkholes form when
Giesen, Rianne H.; Immerzeel, Walter W.; Wanders, Niko
The spatial distribution of precipitation in mountainous terrain is generally not well known due to underrepresentation of gauge observations at higher elevations. Precipitation tends to increase with elevation, but since observations are mainly performed in the valleys, the vertical precipitation gradient cannot be deduced from these measurements. Furthermore, the spatial resolution of gridded meteorological data is often too coarse to resolve individual mountain chains. Still, a reliable estimate of high-elevation precipitation is required for many hydrological applications. We present a method to determine the vertical precipitation gradient in mountainous terrain, making use of glacier mass balance observations. These measurements have the advantage that they provide a basin-wide precipitation estimate at high elevations. The precipitation gradient is adjusted until the solid precipitation over the glacier area combined with the calculated melt gives the measured annual glacier mass balance. Results for the glacierized regions in Central Europe and Scandinavia reveal spatially coherent patterns, with predominantly positive precipitation gradients ranging from -4 to +28 % (100 m)‑1. In some regions, precipitation amounts at high elevations are up to four times as large as in the valleys. A comparison of the modelled winter precipitation with observed snow accumulation on glaciers shows a good agreement. Precipitation measured at the few high-altitude meteorological stations is generally lower than our estimate, which may result from precipitation undercatch. Our findings will improve the precipitation forcing for glacier modelling and hydrological studies in mountainous terrain.
Iturrizaga, Lasafam; Charrier, Reynaldo
Throughout the Andes Mountain range of South America a general trend of glacier shrinkage has taken place in the last century. Only a few glaciers have shown a rather non-continuous trend of glacier retreat and temporally advanced or even surged during the mid-19th to 20th century. One of the earliest assumed glacier surges has occurred in the upper Cachapoal catchment area at the homonymous glacier. In climatic respect the Cachapoal glacier is located in the transition zone from the most southern part of the Dry Central Andes of Chile to the more humid zone of the Wet Andes. The region is affected mainly by winter precipitation deriving from the Westerlies. The debris-covered, 12 km-long Cachapoal glacier represents one of the largest valley glaciers in the Central Andes. It is an avalanche-fed glacier with an almost 1500 m-high head wall in its upper catchment area flowing down from Picos del Barroso (5180 m) and terminates at an elevation of 2630 m a.s.l. with a bifurcated glacier tongue. A large moraine complex, almost 2 km in length and 500 m in width, separates the two glacier lobes. During times of advanced glacier tongue positions the Ríos Molina and Cachapoal may be have blocked independently at two distinct localities which are situated about 2300 m apart from each other. A blockage with temporal lake formation has occurred at least in the years 1848, 1955 and 1981 (cf. Plagemann 1887, Peña 1981), from which the rupture of the earliest glacier barrier has been the most devastating. This event is locally reminded as "la gran avenida en seco" in the historical record. Geomorphological evidence of the past historical and modern glacier expansions is given in the proglacial area by a fresh dead-ice hummocky topography and glacial trimlines at the valley flanks. More down valley broad outwash plains and boulder clusters indicate past high energy floods produced by glacier lake outbursts. Regarding the small size of the catchment area of the Río Molina
Capps, D.; Wiles, G.; Clague, J.
Glacier-dammed lakes typically form during glacier advance or retreat that is in phase with climate change. Most glacier-dammed lakes that have formed in the past century are located in closed basins created by glacier retreat and downwasting. However, tidewater glaciers can be relatively insensitive to climate and can advance when adjacent land-based glaciers are in retreat. The regimen of tidewater glaciers is strongly controlled by the nature of the terminus. When a morainal shoal or fjord constriction limits mass loss due to calving, the glacier may remain stable or advance even in a warming climate. However, a small perturbation in climate can cause the terminus to retreat off a shoal or beyond a constriction into deeper, open water. Once this happens, more mass is lost through calving than is replenished and the glacier may catastrophically retreat. Because many tidewater glaciers are large, this cycle can be several hundred years in length, thereby lagging climatic perturbations that affect other glaciers. Many tidewater glaciers have dammed lakes as they advanced over the past century. Brady Glacier, at the head of Taylor Bay in southeast Alaska, advanced through most of the 20th century. When George Vancouver's party mapped Taylor Bay in 1794, the glacier terminus was a steep calving front. In 1880 John Muir visited the glacier and commented that it was advancing onto an outwash plain that it had built. It continued to advance until the 1960s and has remained at almost the same position since then, despite thinning many tens of meters. As Brady Glacier advanced, it buried trees along the walls of the fjord and impounded large lakes in tributary valleys. At least two of these lakes formed on opposite sides of the glacier in areas occupied by mature forest. We collected incremental cores and discs of trees killed by overriding ice and rising lake waters in order to establish a dendrochronological history of the last glacier advance and the filling of the
Braithwaite, R. J.
Translated into modern terminology, Kurowski suggested in 1891 that the equilibrium line altitude (ELA) of a glacier is equal to the mean altitude of the glacier when the whole glacier is in balance between accumulation and ablation. Kurowski's method has been widely misunderstood, partly due to inappropriate use of statistical terminology by later workers, and has been little tested except by Braithwaite and Müller in a 1980 paper (for 32 glaciers). I now compare Kurowski's mean altitude with balanced-budget ELA calculated for 103 modern glaciers with measured surface mass balance data. Kurowski's mean altitude is significantly higher (at 95% level) than balanced-budget ELA for 19 outlet and 42 valley glaciers, but not significantly higher for 34 mountain glaciers. The error in Kurowski mean altitude as a predictor of balanced-budget ELA might be due to generally lower balance gradients in accumulation area compared with ablation areas for many glaciers, as suggested by several workers, but some glaciers have higher gradients, presumably due to precipitation increase with altitude. The relatively close agreement between balanced-budget ELA and mean altitude for mountain glaciers (mean error -8 m with standard deviation 59 m) may reflect smaller altitude ranges for these glaciers such that there is less room for effects of different balance gradients to manifest themselves.
Braithwaite, R. J.
Translated into modern terminology, Kurowski suggested in 1891 that the equilibrium line altitude (ELA) of a glacier is equal to the mean altitude of the glacier when the whole glacier is in balance between accumulation and ablation. Kurowski's method has been widely misunderstood, partly due to inappropriate use of statistical terminology by later workers, and has only been tested by Braithwaite and Müller in a 1980 paper (for 32 glaciers). I now compare Kurowski's mean altitude with balanced-budget ELA calculated for 103 present-day glaciers with measured surface mass-balance data. Kurowski's mean altitude is significantly higher (at 95 % level) than balanced-budget ELA for 19 outlet and 42 valley glaciers, but not significantly higher for 34 mountain glaciers. The error in Kurowski mean altitude as a predictor of balanced-budget ELA might be due to generally lower balance gradients in accumulation areas compared with ablation areas for many glaciers, as suggested by several workers, but some glaciers have higher gradients, presumably due to precipitation increase with altitude. The relatively close agreement between balanced-budget ELA and mean altitude for mountain glaciers (mean error - 8 m with standard deviation 59 m) may reflect smaller altitude ranges for these glaciers such that there is less room for effects of different balance gradients to manifest themselves.
Bajracharya, S. R.; Maharjan, S. B.; Shrestha, F.
remote-sensing based consistent semi-automated glacier mapping methodology with minimum manual intervention has been developed at ICIMOD. Using this methodology the glaciers of Hindu Kush Himalayan region were mapped in 2011 and continuously used for glacier mapping and monitoring in the region. These data were freely available to download from ICIMOD portal and GLIMS database. These comprehensive glacier information are the only data which is being used for research and development projects for countries like Bhutan, Nepal and Pakistan. Recently decadal glacier change from 1980 to 2010 of Nepal and Bhutan were published to understand the glacier change in the Himalaya. The decadal change assessment will be continued in other basins of HKH region to understand the glacier change. Due to rugged terrain, remote access, and logistic hindrance field verification is a challenging task and can be limited only in selected glaciers. Geodetic mass balance study in the selected glaciers like in Yala of Langtang basin and Rikha Samba of Hidden valley are on progress complement to field validation. High resolution images, lack of hydro-meteorological stations near to the glacier and limited competent manpower are another hindrance in the study of glacier change of the HKH region.
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
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
Middaugh, John P.
Analyzes death certificate data to discover the number of deaths of Alaskan natives caused by cardiovascular disease. Rates from cardiovascular diseases and atherosclerosis from 1980-86 among Alaskan natives were lower than rates among other Alaskans, while death rates from other causes were higher. Discusses the possible impact of diet. (JS)
Anderson, Leif S.; Anderson, Robert S.
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
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.
Meier, M. F. (Principal Investigator)
The author has identified the following significant results. A new procedure to determine snowcovered areas has been devised. Aside from problems in heavily forested areas this method shows promise in predicting snowmelt runoff from mountain areas and will also assist in energy balance modeling of large snowfields. Snowcover results compare favorably with measurements made by high altitude aircraft photography. Changes in snowcover in areas as small as 3 x 5 km can be determined from ERTS-1 images by both optical and electronic methods. Snowcover changes determined by these two methods in the experimental South Cascade Glacier Basin were verified by field mapping. Image enahancement techniques on ERTS-1 images of large Alaskan glaciers (the Hubbard, Yentna, and Kahiltna) have given new insights into the large-scale structures and flow dynamics of these potentially hazardous glaciers. The Hubbard Glacier, in particular, is one which poses a threat to man and should be monitored for future changes.
Yeşilyurt, Serdar; Uǧur, Doǧan; Kılar, Hatice
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
Mark, B. G.; McKenzie, J. M.; Baraer, M.; Lagos, P.; Lautz, L.; Carey, M.; Bury, J.; Crumley, R.; Wigmore, O.; Somers, L. D.
Accelerating glacier recession in the tropical Andes is transforming downstream hydrology, while increasing demands for water by end-users (even beyond the watershed limits) is complicating the assessment of vulnerability. Future scenarios of hydro-climatic vulnerability require a better understanding of coupled hydrologic and human systems, involving both multiscale process studies and more robust models of glacier-climate interactions. We synthesize research in two proglacial valleys of glacierized mountain ranges in different regions of Peru that are both in proximity to growing water usage from urban sectors, agriculture, hydroelectric generation, and mining. In both the Santa River watershed draining the Cordillera Blanca and the Shullcas River watershed below Hyuatapallana Mountain in Junin, glaciers have receded over 25% since the 1980s. Historical runoff and glacier data, combined with glacier-climate modeling, show a long-term decrease in discharge resulting from a net loss of stored water. We find evidence that this altered hydrology is transforming proglacial wetland ecology and water quality, even while water resource use has intensified. Beyond glaciers, our results show that over 60% of the dry season base flow in each watershed is groundwater sourced from heterogeneous aquifers. Municipal water supply in Huancayo already relies on 18 groundwater wells. Perceptions of water availability and actual water use practices remain relatively divorced from the actual water resources provided from each mountain range. Critical changes in glacier volume and water supply are not perceived or acknowledged consistently amongst different water users, nor reflected in water management decisions. In order to identify, understand, model, and adapt to climate-glacier-water changes, it is vital to integrate the analysis of water availability and groundwater processes (the domain of hydrologists) with that of water use (the focus for social scientists). Attention must be
Mikucki, J. A.; Turchyn, A. V.; Farquhar, J.; Priscu, J. C.; Schrag, D. P.; Pearson, A.
Subglacial microbiology is controlled by glacier hydrology, bedrock lithology, and the preglacial ecosystem. These factors can all affect metabolic function by influencing electron acceptor and donor availability in the subglacial setting leaving biogeochemical signatures that can be used to determine ecosystem processes. Blood Falls, an iron-rich, episodic subglacial outflow from the Taylor Glacier in the McMurdo Dry Valleys Antarctica provides an example of how microbial community structure and function can provide insight into subglacial hydrology. This subglacial outflow contains cryoconcentrated, Pliocene-age seawater salts that pooled in the upper Taylor Valley and was subsequently covered by the advance of the Taylor Glacier. Biogeochemical measurements, culture-based techniques, and genomic analysis were used to characterize microbes and chemistry associated with the subglacial outflow. The isotopic composition of important geochemical substrates (i.e., δ34Ssulfate, Δ33Ssulfate, δ18Osulfate, δ18Owater, Δ14SDIC) were also measured to provide more detail on subglacial microbial energetics. Typically, subglacial systems, when driven to anoxia by the hydrolysis of organic matter, will follow a continuum of redox chemistries utilizing electron acceptors with decreasing reduction potential (e.g., Fe (III), sulfate, CO2). Our data provide no evidence for sulfate reduction below the Taylor Glacier despite high dissolved organic carbon (450 μM C) and measurable metabolic activity. We contend that, in the case of the Taylor Glacier, the in situ bioenergetic reduction potential has been 'short-circuited' at Fe(III)-reduction and excludes sulfate reduction and methanogenesis. Given the length of time that this marine system has been isolated from phototrophic production (~2 Mya) the ability to degrade and consume increasingly recalcitrant organic carbon is likely an important component to the observed redox chemistry. Our work indicates that glacier hydrology
McGrath, D.; Oneel, S.; Sass, L. C., III; Gusmeroli, A.; Arendt, A. A.; Wolken, G. J.; Kienholz, C.; McNeil, C.
Mass loss from Alaskan glaciers (-50 ± 17 Gt/a, 2003-2009) constitutes one of the largest contributions to global sea level rise outside of the Greenland and Antarctic ice sheets. The largest process-related uncertainties in this calculation arise from the difficulty in accurately measuring accumulation on glaciers and from the large variability of accumulation over a range of spatio-temporal scales. Further, the physical processes governing snow distribution in complex terrain elude model parameterization. Using ground-penetrating radar, constrained with probe and pit observations, we quantify the magnitude and variability of snow accumulation at six prominent glaciers throughout Alaska at the end of 2013 winter. We find that total SWE magnitude and variability are strongly controlled by the large-scale climate system (i.e. distance from the coastal moisture source along prevailing storm track). On average, total SWE decreases by 0.33 m per 100 km from the coast, while the SWE elevation gradient decreases by 0.06 m / 100 m per 100 km from the coast. SWE variability over small spatial scales (<200 m) is similar at most sites, although two glaciers exhibit notably low and high variability, likely related to their respective climatic provenance. On individual glaciers, strong elevation gradients, increasing from 0.07 m SWE / 100 m at the interior Gulkana Glacier to 0.30 m SWE / 100 m at the coastal Scott Glacier, exert the primary control on accumulation. Results from multi-variable linear regression models (based on topographic variables) find wind exposure/shelter is the most frequent secondary control on accumulation variability. Finally, we find strong agreement (<10% difference) between the radar derived and stake derived total SWE estimates at two glaciers in the USGS Benchmark Glacier Program.
Fountain, Andrew G.; Krimmel, Robert M.; Trabant, Dennis C.
Glaciers are important features in the hydrologic cycle and affect the volume, variability, and water quality of runoff. Assessing and predicting the effect of glaciers on water resources require a monitoring program to provide basic data for this understanding. The monitoring program of the U.S. Geological Survey employs a nested approach whereby an intensively studied glacier is surrounded by less intensively studied glaciers and those monitored solely by remote sensing. Ideally, each glacierized region of the United States would have such a network of glaciers. The intensively studied glacier provides a detailed understanding of the physical processes and their temporal changes that control the mass exchange of the glaciers in that region. The less intensively studied glaciers are used to assess the variability of such processes within the region.
The Expedition 3 crew of the International Space Station caught a rare glimpse of the massive ice fields and glaciers of Patagonia early in the afternoon on September 25, 2001. This part of the South American coast sees frequent storms and is often obscured from view by cloud cover. Bruggen Glacier in southern Chile is the largest western outflow from the Southern Patagonian Ice Field and, unlike most glaciers worldwide, advanced significantly since 1945. From 1945 to 1976, Bruggen surged 5 km across the Eyre Fjord, reaching the western shore by 1962 and cutting off Lake Greve from the sea. The glacier continued advancing both northward and southward in the fjord to near its present position before stabilizing. The growth covers a distance of more than 10 km north to south, adding nearly 60 square km of ice. Additional information on this and other Patagonian glaciers may be found at the following link: USGS - Historic Fluctuations of Outlet Glaciers from the Patagonian Ice Fields. Image ISS003-E-6061 was provided by the Earth Sciences and Image Analysis Laboratory at Johnson Space Center. Additional images taken by astronauts and cosmonauts can be viewed at the NASA-JSC Gateway to Astronaut Photography of Earth.
Association of Alaska School Boards, Juneau.
The purpose of this book is to serve as a tool for individuals helping to make Alaskan communities places where youth can grow up to be strong, capable, and caring. The book is built around the Search Institute's Youth Developmental Assets Framework, which is comprised of the key building blocks in youth development. The book notes 40 assets that…
Magoon, L.B.; Lillis, P.G.; Bird, K.J.; Lampe, C.; Peters, K.E.
Six North Slope petroleum systems are identified, described, and mapped using oil-to-oil and oil-to-source rock correlations, pods of active source rock, and overburden rock packages. To map these systems, we assumed that: a) petroleum source rocks contain 3.2 wt. % organic carbon (TOC); b) immature oil-prone source rocks have hydrogen indices (HI) >300 (mg HC/gm TOC); c) the top and bottom of the petroleum (oil plus gas) window occur at vitrinite reflectance values of 0.6 and 1.0% Ro, respectively; and d) most hydrocarbons are expelled within the petroleum window. The six petroleum systems we have identified and mapped are: a) a southern system involving the Kuna-Lisburne source rock unit that was active during the Late Jurassic and Early Cretaceous; b) two western systems involving source rock in the Kingak-Blankenship, and GRZ-lower Torok source rock units that were active during the Albian; and c) three eastern systems involving the Shublik-Otuk, Hue Shale and Canning source rock units that were active during the Cenozoic. The GRZ-lower Torok in the west is correlative with the Hue Shale to the east. Four overburden rock packages controlled the time of expulsion and gross geometry of migration paths: a) a southern package of Early Cretaceous and older rocks structurally-thickened by early Brooks Range thrusting; b) a western package of Early Cretaceous rocks that filled the western part of the foreland basin; c) an eastern package of Late Cretaceous and Paleogene rocks that filled the eastern part of the foreland basin; and d) an offshore deltaic package of Neogene rocks deposited by the Colville, Canning, and Mackenzie rivers. This petroleum system poster is part of a series of Northern Alaska posters on modeling. The poster in this session by Saltus and Bird present gridded maps for the greater Northern Alaskan onshore and offshore that are used in the 3D modeling poster by Lampe and others. Posters on source rock units are by Keller and Bird as well as
Rupper, S.; Todd, C. E.
The adiabatic temperature lapse rate imparts a well-studied positive feedback on glacier changes in response to a given change in climate. For example, if temperature increases, the surface of the glacier thins into the warmer temperatures of the lower surface elevation, dependent upon the local lapse rate, which amplifies the glacier response to the original temperature. However, a less well-quantified negative feedback can also be at play. As the length and thickness of a valley glacier changes, the percentage of the glacier surface that is shaded changes as well, decreasing the incident shortwave radiation at the surface. Assuming turbulent heat fluxes are small, the balance between changing downward longwave radiation (adiabatic lapse rate effect) and shortwave radiation (shading effect) in response to a climatic change will determine the equilibrium glacier profile for the new climate state. Here we use an energy balance model to determine the sensitivity of glacial retreat reconstructions to both the temperature lapse rate and the shading by valley topography. We quantify the effect of shading and lapse rates on idealized glaciers and topography, and assess under what conditions one or the other feedback mechanism is expected to dominate the change in energy balance. We then examine the effect of temperature lapse rates and increased shading on a paleoglacier at Monroe Peak, in the Sevier Plateau, Utah. Although the peak is currently ice-free, lateral moraines on Monroe Peak show that a glacier once extended approximately 4000 m from a 4700 m high headwall on the western side of the peak. Preliminary results suggest that as the glacier retreated from its maximum position, increased shading had a significant positive effect on glacial mass balance which partially compensated for the lapse rate feedback. These preliminary results suggest that reconstructions of smaller glaciers surrounded by steep topography must account for changes in shading of the glacier
Riedel, Jon L.; Clague, John J.; Ward, Brent C.
Twenty-two new radiocarbon ages from Skagit valley provide a detailed chronology of alpine glaciation during the Evans Creek stade of the Fraser Glaciation (early marine oxygen isotope stage (MIS) 2) in the Cascade Range, Washington State. Sediments at sites near Concrete, Washington, record two advances of the Baker valley glacier between ca. 30.3 and 19.5 cal ka BP, with an intervening period of glacier recession about 24.9 cal ka BP. The Baker valley glacier dammed lower Skagit valley, creating glacial Lake Concrete, which discharged around the ice dam along Finney Creek, or south into the Sauk valley. Sediments along the shores of Ross Lake in upper Skagit valley accumulated in glacial Lake Skymo after ca. 28.7 cal ka BP behind a glacier flowing out of Big Beaver valley. Horizontally laminated silt and bedded sand and gravel up to 20 m thick record as much as 8000 yr of deposition in these glacially dammed lakes. The data indicate that alpine glaciers in Skagit valley were far less extensive than previously thought. Alpine glaciers remained in advanced positions for much of the Evans Creek stade, which may have ended as early as 20.8 cal ka BP.
Mottram, Ruth; Gleeson, Emily; Pagh Nielsen, Kristian
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
Kolahoi glacier, western Himalaya is located in Jammu and Kashmir, India between N 340 07'-340 12' and E 750 19'-750 23'. The glacier makes the head of Liddar valley and provides origin to west Liddar river, draining into river Jhelum. Kolahoi is characterized by the frontal activities of westerly winds from Dec to March-April and by dry subtropical climate during summer season. The glacier represents a twin glacier system with one branch from two sides of Kolahoi peak-east and west, merging together to form a common ablation zone and a north facing snout. The first recorded visit to Kolahoi Glacier was made by E. F. Neve in 1909. The earliest attempt to establish the quaternary glacial history of Liddar valley can be attributed to Grinlinton (1928) followed by Terra & Patterson (1939). As a result of their work, the quaternary glaciation of Liddar valley has been divided into a main series of four glacial and three interglacial epochs, of which the first two glaciations were more intensive than the later two. A significant result of this history has been that as compared with the interglacial periods the glacial periods were much shorter, in SW Kashmir. Presence of various glacial features of fourth stage, observed in the valley were correlated with the literature, coordinates taken through GPS and built on a GIS platform with overlyering of satellite image time series of recent decades. Decadal history of Kolahoi glacier deglaciation was reconstructed based on the satellite image time series, indirect volume-area scaling methods and field experiments, indicating variable retreat rate contributing to a total recession of 485m in the snout of glacier and an area loss of 15% in previous four decades, since 1965. Annual measurement of mass balance for Kolahoi glacier were conducted through glaciologic method since the first drilling of ablation stakes in 2008, which indicate a range from -2.0 m.w.e. to -3.5 m.w.e. per annum for the glacier. However, field observance
Bayr, Klaus J.
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.
Raup, B. H.; Khalsa, S. S.; Armstrong, R.
The Global Land Ice Measurements from Space (GLIMS) project has built a geospatial and temporal database of glacier data, composed of glacier outlines and various scalar attributes. These data are being derived primarily from satellite imagery, such as from ASTER and Landsat. Each "snapshot" of a glacier is from a specific time, and the database is designed to store multiple snapshots representative of different times. We have implemented two web-based interfaces to the database; one enables exploration of the data via interactive maps (web map server), while the other allows searches based on text-field constraints. The web map server is an Open Geospatial Consortium (OGC) compliant Web Map Server (WMS) and Web Feature Server (WFS). This means that other web sites can display glacier layers from our site over the Internet, or retrieve glacier features in vector format. All components of the system are implemented using Open Source software: Linux, PostgreSQL, PostGIS (geospatial extensions to the database), MapServer (WMS and WFS), and several supporting components such as Proj.4 (a geographic projection library) and PHP. These tools are robust and provide a flexible and powerful framework for web mapping applications. As a service to the GLIMS community, the database contains metadata on all ASTER imagery acquired over glacierized terrain. Reduced-resolution of the images (browse imagery) can be viewed either as a layer in the MapServer application, or overlaid on the virtual globe within Google Earth. The interactive map application allows the user to constrain by time what data appear on the map. For example, ASTER or glacier outlines from 2002 only, or from Autumn in any year, can be displayed. The system allows users to download their selected glacier data in a choice of formats. The results of a query based on spatial selection (using a mouse) or text-field constraints can be downloaded in any of these formats: ESRI shapefiles, KML (Google Earth), Map
Gedney, R. T.; Jirberg, R. J.; Schertler, R. J.; Mueller, R. A.; Chase, T. L.; Kramarchuk, I.; Nagy, L. A.; Hanlon, R. A.; Mark, H.
A near real-time ice information system designed to aid arctic coast shipping along the Alaskan North Slope is described. The system utilizes a X-band Side Looking Airborne Radar (SLAR) mounted aboard a U.S. Coast Guard HC-130B aircraft. Radar mapping procedures showing the type, areal distribution and concentration of ice cover were developed. In order to guide vessel operational movements, near real-time SLAR image data were transmitted directly from the SLAR aircraft to Barrow, Alaska and the U.S. Coast Guard icebreaker Glacier. In addition, SLAR image data were transmitted in real time to Cleveland, Ohio via the NOAA-GOES Satellite. Radar images developed in Cleveland were subsequently facsimile transmitted to the U.S. Navy's Fleet Weather Facility in Suitland, Maryland for use in ice forecasting and also as a demonstration back to Barrow via the Communications Technology Satellite.
Mackay, Sean L.; Marchant, David R.
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.
Clark, D.H.; Clark, M.M.; Gillespie, A.R.
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.
Kutuzov, S.; Lavrentiev, I. I.; Petrakov, D. A.; Macheret, Yu. Ya.
Field studies have been carried out at Marukh glacier located in western part of the Northern Caucasus in summer 2011. Studies included ground-based radio-echo sounding measurements at a frequency of 20 MHz and glacier surface elevation survey using a dual frequency differential GPS receiver. Marukh Glacier is most western valley type glacier in the Russian Greater Caucasus. It is located 60 km from the Black Sea and was selected as most maritime glacier in the Soviet Union for direct measurements of ice, water and energy balances during IHD (International Hydrologycal Decade) in 1966-67-1981-82 when mass balance measurements were accompanied by meteorological observations and several topographic map were completed in scale of 1:10000. Detailed volume and surface area changes of the glacier for the period 1945-2011 were obtained using aerial photo, satellite images and topographic maps analysis. Annual glacier accumulation, ablation and mass balance have been estimated for the period of 1967 to 2011 using direct measurements (1967-1982) and mass balance reconstruction based on meteorological data. It is founded that Marukh glacier is retreating and has reduced its surface area by 17% over the past 66 years. Glacier volume is 0,276 km3 in 2011 and has decreased by 0,06 km3 since 1967.
Quincey, D. J.; Braun, M.; Glasser, N. F.; Bishop, M. P.; Hewitt, K.; Luckman, A.
We examine the surges of five glaciers in the Pakistan Karakoram using satellite remote sensing to investigate the dynamic nature of surges in this region and how they may be affected by climate. Surface velocity maps derived by feature-tracking quantify the surge development spatially in relation to the terminus position, and temporally with reference to seasonal weather. We find that the season of surge initiation varies, that each surge develops gradually over several years, and that maximum velocities are recorded within the lowermost 10 km of the glacier. Measured peak surge velocities are between one and two orders of magnitude greater than during quiescence. We also note that two of the glaciers are of a type not previously reported to surge. The evidence points towards recent Karakoram surges being controlled by thermal rather than hydrological conditions, coinciding with high-altitude warming from long-term precipitation and accumulation patterns.
Falatkova, Kristyna; Sobr, Miroslav; Engel, Zbynek; Jansky, Bohumir
Recent development of glacier complex Adygine and resulting risks Falátková, K., Šobr, M., Engel, Z., Janský, B. Charles University in Prague, Faculty of Science, Prague, Czech republic Glacier complex Adygine (3,400-4,200 m asl) is situated on the northern flank of the Kyrgyz Range, Tien Shan, Kyrgyzstan. The valley downstream is part of National Park Ala Archa, which is popular with tourists, and is heading towards the country's capital - Bishkek. At the study site there is a glacier which is observed since 1960's. The glacier has been monitored by satellite imagery and in last 10 years by on-site geodetic measurement as well. Due to glacier shrinkage several glacial lakes of different genetic types (moraine-dammed, moraine- and rock-dammed, termokarst) have appeared at the site. Nowadays, the lakes are situated on three levels in front of the glacier's terminus and form a cascade, they are also hydrologically connected. The lakes were subjected to detailed bathymetric measurement and some parts of the dams were surveyed by geophysical methods. Especially the newest lakes in proximity of the terminus has been undergoing dynamic changes and may pose a threat in the near future. The risks arising together with changing climatic conditions and retreat of the glacier are associated with mainly three of the lakes. The largest one with area of 3.2 ha is dammed by a rock step overlaid by a moraine. Geophysical research of the dam revealed buried ice and seepage channels in its western part. It is the capacity of these subsurface channels, which are draining the lake throughout the year that represents a weak point in terms of dam stability. The second lake, a termokarst one, is a similar case but drained solely by subsurface channels. Very steep slopes of the lake basin are covered with loose material which could slide down and block the drainage channels. The lake would then fill all the basin (approx. 50,000 m3) very quickly as it is supplied with water from the
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.
Treichler, D.; Kaeaeb, A.
While the use of ICESat GLAS data is well established for monitoring elevation changes on ice sheets, this data holds valuable information also for more complex terrain and small glaciers, as recently demonstrated for example for high mountain Asia. This study aims at exploring the potential and limitations of ICESat over glaciated, mountainous terrain on the example of Southern Norway. The glaciers in Southern Norway are spread over an area of roughly 100'000 km2 in size. Despite high cloud coverage due to coastal proximity, we found that on average 85% of the laser returns per operational campaign contain valid elevation information from the Earth's surface, as compared with reference elevations from DEMs of 20m spatial resolution.While only 1.5% of the study area is glacierised, the laser footprints on ice represent Southern Norway's glaciers well in elevation, aspect, slope, glacier size, and spatial distribution, even for individual campaigns. With decreasing number of data points towards the end of ICESat's operational period, relative oversampling of larger ice bodies and spatial clumping occurs. Employing GLAS data for smaller or less glacierised areas might thus lead to a spatial bias due to overrepresentation of a particular glacier, and contrasting mass change estimates compared to traditional mass balance programs that are rather biased towards smaller valley glaciers with different glacier behaviour. Using only data captured at the end of the hydrological year as a proxy for yearly net mass balance, we find a slightly negative glacier surface elevation trend of -0.28 +/- 0.1 m ice per year for the ICESat period 2003 to 2008. This is in accordance with the heterogeneous but overall negative net balance in the range of -0.82 to +0.36 m w.eq. per year obtained by traditional in-situ measurements for ten glaciers in Southern Norway. When including the ICESat winter campaigns, yearly variations in snow height of 50 to 100 cm in the lowlands are accurately
Sakai, A.; Nuimura, T.; Fujita, K.; Takenaka, S.; Nagai, H.; Lamsal, D.
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.
Sakai, A.; Nuimura, T.; Fujita, K.; Takenaka, S.; Nagai, H.; Lamsal, D.
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 median elevation of glaciers, which is presumed to be at equilibrium-line altitude (ELA) so that mass balance is zero at that elevation, by tuning adjustment parameters of precipitation. We also made comparisons between median elevation of glaciers, including the effect of drifting snow and avalanche, and eliminated those local effects. Then, we could obtain 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 the arid High Mountain Asia have very less precipitation, while much precipitation contribute 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.
Blankenship, D. D.; Greenbaum, J. S.; Young, D. A.; Richter, T. G.; Roberts, J. L.; Aitken, A.; Legresy, B.; Warner, R. C.; van Ommen, T. D.; Siegert, M. J.
The Totten Glacier is the largest ice sheet outlet in East Antarctica, draining 3.5 meters of eustatic sea level potential from the Aurora Subglacial Basin (ASB) into the Sabrina Coast. Recent work has shown that the ASB has drained and filled many times since largescale glaciation began including evidence that it collapsed during the Pliocene. Steady thinning rates observed near Totten Glacier's grounding line since the beginning of the satellite altimetry record are the largest in East Antarctica and the nature of the thinning suggests that it is driven by enhanced basal melting due to ocean processes. Warm Modified Circumpolar Deep Water (MCDW), which has been linked to glacier retreat in West Antarctica, has been observed in summer and winter on the Sabrina Coast continental shelf in the 400-500 m depth range. Using airborne geophysical data acquired over multiple years we delineate seafloor valleys connecting the inner continental shelf to the cavity beneath Totten Glacier that cut through a large sill centered along the ice shelf calving front. The sill shallows to depths of about 300 mbsl and was likely a grounding line pinning point during Holocene retreat, however, the two largest seafloor valleys are deeper than the observed range of thermocline depths. The deeper of the two valleys, a 4 km-wide trough, connects to the ice shelf cavity through an area of the coastline that was previously believed to be grounded but that our analysis demonstrates is floating, revealing a second, deeper entryway to ice shelf cavity. The previous coastline was charted using satellite-based mapping techniques that infer subglacial properties based on surface expression and behavior; the new geophysical analysis techniques we use enable inferences of subglacial characteristics using direct observations of the ice-water interface. The results indicate that Totten Glacier and, by extension, the Aurora Subglacial Basin are vulnerable to MCDW that has been observed on the nearby
Palacios, David; Gómez-Ortiz, Antonio; Andrés, Nuria; Vázquez-Selem, Lorenzo; Salvador-Franch, Ferran; Oliva, Marc
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.
Gordon, John; Haynes, Valerie
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.
Weeks, W. F.; Weller, G.
Oil and gas deposits in the Alaskan Arctic are estimated to contain up to 40 percent of the remaining undiscovered crude oil and oil-equivalent natural gas within U.S. jurisdiction. Most (65 to 70 percent) of these estimated reserves are believed to occuur offshore beneath the shallow, ice-covered seas of the Alaskan continental shelf. Offshore recovery operations for such areas are far from routine, with the primary problems associated with the presence of ice. Some problems that must be resolved if efficient, cost-effective, environmentally safe, year-round offshore production is to be achieved include the accurate estimation of ice forces on offshore structures, the proper placement of pipelines beneath ice-produced gouges in the sea floor, and the cleanup of oil spills in pack ice areas.
Abe, Takahiro; Furuya, Masato; Sakakibara, Daiki
Surge-type glaciers repeat their short active phase and their much longer quiescent phase usually every several decades or longer, but detailed observations of the evolution cycles have been limited to only a few glaciers. Here we report three surging episodes in 1989, 2001, and 2013 at Donjek Glacier in the Yukon, Canada, indicating remarkably regular and short repeat cycles of 12 years. The surging area is limited within the ˜ 20 km section from the terminus, originating in an area where the flow width significantly narrows downstream, suggesting a strong control of the valley constriction on the surge dynamics.
Furuya, M.; Abe, T.
Seasonal glacier velocity changes are attributed to subglacial slip associated with water pressure changes that occur because of the seasonal variability of meltwater input. Abe and Furuya (2014) reported winter speed-up signals and their downglacier propagation at a number of glaciers near the border of Alaska and Yukon, based on ALOS/PALSAR radar image analyses. Here we perform the similar analyses at the Chugach mountain range of South Central Alaska, and report the spatial-temporal evolution of the Matanuska Glacier. Matanuska Glacier is the largest accessible glacier in Alaska with its nearly 40 km length and 5 km width near the terminus. Comparing the winter velocity images in 2007, 2008 and 2010, those in 2010 were about 1.5-2 times faster than those during the previous two years. In addition, comparing the fall and winter velocities, winter velocities were apparently faster at every 2007-2008, 2009-2010, and 2010-2011 season. These data indicate winter speed-up or mini-surge signals even at a temperate and non-surgetype Matanuska Glacier. We also examine the spatial-temporal elevation changes, using data from the LiDAR altimeter in the Icebridge mission, and found significant elevation increase near the terminus. Winter speed-up may not be uncommon at Alaskan/Yukon glaciers. Lingle and Fatland (2003) detected faster speed in winter than in fall at non-surging Seward Glacier in the St. Elias Mountains; this is the only published and unambiguous report of winter speed-up, to our knowledge. Combined with earlier glacier hydrological studies, Lingle and Fatland proposed englacial water storage and gravity-driven water flow toward the bed in winter regardless of whether a given glacier is surge-type or not, and considered that the capacity of englacial water storage would control if a given glacier was surge-type or not. We consider that our measurements are complementary to Lingle and Fatland's observations and lend further support for their hypothesis. Basal
Chisolm, Rachel; Rabatel, Antoine; McKinney, Daene; Condom, Thomas; Cochacin, Alejo; Davila Roller, Luzmilla
Tropical glaciers are an essential component of the water resource systems in the mountainous regions where they are located, and a warming climate has resulted in the accelerated retreat of Andean glaciers in recent decades. The shrinkage of Andean glaciers influences the flood risk for communities living downstream as new glacial lakes have begun to form at the termini of some glaciers. As these lakes continue to grow in area and volume, they pose an increasing risk of glacial lake outburst floods (GLOFs). Ice thickness measurements have been a key missing link in studying the tropical glaciers in Peru and how climate change is likely to impact glacial melt and the growth of glacial lakes. Ground penetrating radar (GPR) has rarely been applied to glaciers in Peru to measure ice thickness, and these measurements can tell us a lot about how a warming climate will affect glaciers in terms of thickness changes. In the upper Paron Valley (Cordillera Blanca, Peru), an emerging lake has begun to form at the terminus of the Artesonraju Glacier, and this lake has key features, including overhanging ice and loose rock likely to create slides, that could trigger a catastrophic GLOF if the lake continues to grow. Because the glacier mass balance and lake mass balance are closely linked, ice thickness measurements and measurements of the bed slope of the Artesonraju Glacier and underlying bedrock can give us an idea of how the lake is likely to evolve in the coming decades. This study presents GPR data taken in July 2013 at the Artesonraju Glacier as part of a collaboration between the Unidad de Glaciologia y Recursos Hidricos (UGRH) of Peru, the Institut de Recherche pour le Développement (IRD) of France and the University of Texas at Austin (UT) of the United States of America. Two different GPR units belonging to UGRH and UT were used for subsurface imaging to create ice thickness profiles and to characterize the total volume of ice in the glacier. A common midpoint
Walder, J.S.; Fountain, A.G.
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.
... 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 ...
Matthes, Francois E.
Projection of the longitudinal profiles of these hanging valleys forward to the axis of the Merced Canyon shows that they are closely accordant in height. Their profiles indicate a series of points on a former profile of the Merced with respect to which the side streams had graded their courses prior to the last uplift. This old profile can be extended upward into the glaciated part of the Merced Canyon above El Portal and even into the profoundly glaciated Yosemite Valley, accordant points being furnished by a number of hanging side valleys (due allowance being made for glacial erosion suffered by those valleys). However, not all the hanging valleys of the Yosemite region are accordant with this set. Several of them, including the upland valley of Yosemite Creek, constitute a separate set indicating another old profile of the Merced at a level 600 to 1,000 feet higher than the first. Others, including the hanging gulch of lower Bridalveil Creek, point to an old profile of the Merced about 1,200 feet lower than the first. There are thus three distinct sets of hanging valleys produced in three cycles of stream erosion. The valleys of the upper set, like those of the middle set, were left hanging as a result of rapid trenching by the Merced induced by an uplift of the range, there having been two such uplifts. Only the valleys of the lower set hang because of glacial deepening and widening of the Yosemite Valley, the cycle in which they were cut having been interrupted by the advent of the Pleistocene glaciers. They consequently indicate the preglacial depth of the Yosemite Valley. That depth, measured from the brow of El Capitan, was about 2,400 feet; measured from the rim at Glacier Point it was about 2,000 feet.
Goldin, Beatrice; Rudaz, Benjamin; Bardou, Eric
the rough surface of the SLBL results. The impact of sediment dynamic changes on the study catchment due to glacier retreat has been assessed by comparing predictions deriving from model application on different scenarios. Simulations allowed the analysis of sediment connectivity evolution over decade scales suggesting an increase of potential sediment transfer and connections in areas close to the main channel network. References: Cavalli, M., Trevisani, S., Comiti, F., Marchi, L., 2013. Geomorphometric assessment of spatial sediment connectivity in small Alpine catchments. Geomorphology 188, 31-41. Jaboyedoff M., Bardou E., Derron M.-H. 2004. Sloping local base level: a tool to estimate potential erodible volume and infilling alluvial sediment of glacial valleys. Swiss Geo-Scientists meeting, November 2004, Lausanne.
Hopkins, Thomas Robert
The study compiles and records the history of the administration of education for Alaskan natives since the United States purchased the territory from Russia in 1876. Chapter 1, An Overview of the Development of the Alaskan Native, covers the development of missionary and government schools, the growth and development of Native education from 1906…
James, William H. M.; Carrivick, Jonathan L.
Ice thickness distribution and volume are both key parameters for glaciological and hydrological applications. This study presents VOLTA (Volume and Topography Automation), which is a Python script tool for ArcGISTM that requires just a digital elevation model (DEM) and glacier outline(s) to model distributed ice thickness, volume and bed topography. Ice thickness is initially estimated at points along an automatically generated centreline network based on the perfect-plasticity rheology assumption, taking into account a valley side drag component of the force balance equation. Distributed ice thickness is subsequently interpolated using a glaciologically correct algorithm. For five glaciers with independent field-measured bed topography, VOLTA modelled volumes were between 26.5% (underestimate) and 16.6% (overestimate) of that derived from field observations. Greatest differences were where an asymmetric valley cross section shape was present or where significant valley infill had occurred. Compared with other methods of modelling ice thickness and volume, key advantages of VOLTA are: a fully automated approach and a user friendly graphical user interface (GUI), GIS consistent geometry, fully automated centreline generation, inclusion of a side drag component in the force balance equation, estimation of glacier basal shear stress for each individual glacier, fully distributed ice thickness output and the ability to process multiple glaciers rapidly. VOLTA is capable of regional scale ice volume assessment, which is a key parameter for exploring glacier response to climate change. VOLTA also permits subtraction of modelled ice thickness from the input surface elevation to produce an ice-free DEM, which is a key input for reconstruction of former glaciers. VOLTA could assist with prediction of future glacier geometry changes and hence in projection of future meltwater fluxes.
Swanger, K.; Marchant, D. R.; Schaefer, J. M.; Winckler, G.; Head, J. W.
We document Plio-Pleistocene changes in the level of Taylor Glacier, an outlet glacier in southern Victoria Land that drains Taylor Dome on the periphery of the East Antarctic Ice Sheet (EAIS). Chronologic control comes from 3He cosmogenic-nuclide analyses of 27 boulders sampled from drifts and moraines in Kennar Valley, a small hanging valley that opens onto a peripheral lobe of Taylor Glacier in the Quartermain Mountains. Assuming a constant boulder-erosion rate of 10 cm Myr-1, our preferred age model spans the last 3.1 Myr and calls for stepped ice recession from a local highstand ~200 m above the present Taylor Glacier at the mouth of Kennar Valley. The texture and sedimentology of all mapped moraines and drifts indicate deposition from cold-based ice, analogous with the situation for the modern Taylor Glacier. Correlation of our moraine record with published reports for fluctuations of Taylor Glacier elsewhere in the Quartermain Mountains, and with a dated moraine record for Ferrar Glacier (a second outlet for Taylor Dome) in the nearby Wilkness Mountains, reveals consistent ice-surface changes, highlighting minor, but widespread ice recession in southern Victoria Land since the mid to late Pliocene. The combined records show an atypical relationship with average global temperatures, with higher-than-present ice levels occurring during globally warm periods, including the Pliocene climatic optimum (˜3.1 Ma), Marine Oxygen Isotope Stage (MIS) 31 (~1.1 Ma), and the penultimate interglacial, MIS 5.5 (~120 ka). The combined records also suggest that the rate of ice-surface lowering for both outlet glaciers accelerated after the Mid-Pleistocene transition at ~0.9 Myr.
Ming, Jing; Xiao, Cunde; Du, Zhencai; Yang, Xingguo
Since 2000, 18 High Asia glaciers have been surveyed for black carbon (BC) deposition 22 times, and numerous snow samples and ice cores have been collected by researchers. However, most of the results were interpreted individually in papers. Here, we assemble the data and discuss the distribution of BC deposition and its impacts on the melting of the glaciers through radiative forcing. We find that BC distribution on the surfaces of High Asia glaciers primarily depends upon their elevations (i.e., higher sites have lower concentrations) and then upon regional BC emissions and surface melting conditions. BC concentrations in High Asia glaciers are similar to the Arctic and western American mountains but are significantly less than heavy industrialized areas such as northern China. Although Himalayan glaciers, which are important due to their water resources, are directly facing the strong emissions from South Asia, their mean BC is the lowest due to high elevations. A new finding indicated by ice core records suggested that great valleys in the eastern Himalayan section are effective pathways for BC entering the Tibetan Plateau and make increasing BC trends in the local glaciers. On average, BC deposition causes a mean forcing of ˜6 W m-2 (roughly estimated 5% of the total forcing) in High Asia glaciers and therefore may not be a major factor impacting the melting of most glaciers.
Stokes, Chris R.; Shahgedanova, Maria; Evans, Ian S.; Popovnin, Victor V.
The recession of mountain glaciers around the world has been linked to anthropogenic climate change and small glaciers (e.g. < 2 km2) are thought to be particularly vulnerable, with reports of their disappearance from several regions. However, the response of small glaciers to climate change can be modulated by non-climatic factors such as topography and debris cover and there remain a number of regions where their recent change has evaded scrutiny. This paper presents results of the first multi-year remote sensing survey of glaciers in the Kodar Mountains, the only glaciers in SE Siberia, which we compare to previous glacier inventories from this continental setting that reported total glacier areas of 18.8 km2 in ca. 1963 (12.6 km2 of exposed ice) and 15.5 km2 in 1974 (12 km2 of exposed ice). Mapping their debris-covered termini is difficult but delineation of debris-free ice on Landsat imagery reveals 34 glaciers with a total area of 11.72 ± 0.72 km2 in 1995, followed by a reduction to 9.53 ± 0.29 km2 in 2001 and 7.01 ± 0.23 km2 in 2010. This represents a ~ 44% decrease in exposed glacier ice between ca. 1963 and 2010, but with 40% lost since 1995 and with individual glaciers losing as much as 93% of their exposed ice. Thus, although continental glaciers are generally thought to be less sensitive than their maritime counterparts, a recent acceleration in shrinkage of exposed ice has taken place and we note its coincidence with a strong summer warming trend in the region initiated at the start of the 1980s. Whilst smaller and shorter glaciers have, proportionally, tended to shrink more rapidly, we find no statistically significant relationship between shrinkage and elevation characteristics, aspect or solar radiation. This is probably due to the small sample size, limited elevation range, and topographic setting of the glaciers in deep valleys-heads. Furthermore, many of the glaciers possess debris-covered termini and it is likely that the ablation of buried
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
Kohshima, S.; Yoshimura, Y.; Takeuchi, N.; Segawa, T.; Uetake, J.
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. Since these microorganisms growing on the glacier surface are stored in the glacial strata every year, ice-core samples contain many layers with these microorganisms. Recently, it was shown 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.
Hambrey, Michael J.; Quincey, Duncan J.; Glasser, Neil F.; Reynolds, John M.; Richardson, Shaun J.; Clemmens, Samuel
This paper presents the sediment, landform and dynamic context of four avalanche-fed valley glaciers (Khumbu, Imja, Lhotse and Chukhung) in the Mount Everest (Sagarmatha) region of Nepal. All four glaciers have a mantle of debris dominated by sandy boulder-gravel that suppresses melting to an increasing degree towards the snout, leading to a progressive reduction in the overall slope of their longitudinal profile. Prominent lateral-terminal moraine complexes, also comprising sandy bouldergravel, enclose the glaciers. These terminal moraines originally grew by accretion of multiple sedimentary facies of basal glacial and supraglacial origin, probably by folding and thrusting when the glaciers were more dynamic during the Little Ice Age. The four glaciers are in various stages of recession, and demonstrate a range of scenarios from down-wasting of the glacier tongue, through morainedammed lake development, to post-moraine-dam breaching. Khumbu Glacier is at the earliest stage of supraglacial pond formation and shows no sign yet of developing a major lake, although one is likely to develop behind its >250 m high composite terminal moraine. Imja Glacier terminates in a substantial body of water behind a partially ice-cored moraine dam (as determined from geophysical surveys), but morphologically appears unlikely to be an immediate threat. Chukhung Glacier already has a breached moraine and a connected debris fan, and therefore no longer poses a threat. Lhotse Glacier has an inclined, free-draining tongue that precludes hazardous lake development. From the data assembled, a conceptual model, applicable to other Himalayan glaciers, is proposed to explain the development of large, lateral-terminal moraine complexes and associated potentially hazardous moraine dams. - 2008 Elsevier Ltd. All rights reserved .
Hambrey, Michael J.; Quincey, Duncan J.; Glasser, Neil F.; Reynolds, John M.; Richardson, Shaun J.; Clemmens, Samuel
This paper presents the sediment, landform and dynamic context of four avalanche-fed valley glaciers (Khumbu, Imja, Lhotse and Chukhung) in the Mount Everest (Sagarmatha) region of Nepal. All four glaciers have a mantle of debris dominated by sandy boulder-gravel that suppresses melting to an increasing degree towards the snout, leading to a progressive reduction in the overall slope of their longitudinal profile. Prominent lateral-terminal moraine complexes, also comprising sandy boulder-gravel, enclose the glaciers. These terminal moraines originally grew by accretion of multiple sedimentary facies of basal glacial and supraglacial origin, probably by folding and thrusting when the glaciers were more dynamic during the Little Ice Age. The four glaciers are in various stages of recession, and demonstrate a range of scenarios from down-wasting of the glacier tongue, through moraine-dammed lake development, to post-moraine-dam breaching. Khumbu Glacier is at the earliest stage of supraglacial pond formation and shows no sign yet of developing a major lake, although one is likely to develop behind its >250 m high composite terminal moraine. Imja Glacier terminates in a substantial body of water behind a partially ice-cored moraine dam (as determined from geophysical surveys), but morphologically appears unlikely to be an immediate threat. Chukhung Glacier already has a breached moraine and a connected debris fan, and therefore no longer poses a threat. Lhotse Glacier has an inclined, free-draining tongue that precludes hazardous lake development. From the data assembled, a conceptual model, applicable to other Himalayan glaciers, is proposed to explain the development of large, lateral-terminal moraine complexes and associated potentially hazardous moraine dams.
Mayer, C.; Lambrecht, A.; Belò, M.; Smiraglia, C.; Diolaiuti, G.
Baltoro glacier in the Karakoram, Pakistan, is one of the world's largest valley glaciers. It drains an area of about 1500 km2 and is >60 km long. In 2004 an Italian/German expedition carried out a glaciological field program on the ablation zone of the glacier, focusing on the ablation conditions and the dynamic state of the glacier. As Baltoro glacier is a debris-covered glacier, ice ablation also depends on the debris properties. Stake measurements of ice ablation and debris cover in combination with meteorological data from automatic weather stations close by have been used to determine the local melt conditions. Results from these calculations have been combined with an analysis of different classes of surface cover and information about precipitation, using remote-sensing techniques, in order to calculate mass fluxes for the upper part of Baltoro glacier. The dynamic state of the glacier has been investigated by GPS-based surface velocity measurements along the stake network. A comparison of these short-term measurements during the melt season with surface velocities computed from feature tracking of satellite images shows a high seasonal variability of the ice motion. We have shown that this variability is up to 100% of the annual mean velocity. On the basis of these investigations, the mass fluxes at the Concordia cross-section have been quantified. This approach can now be used together with the ablation calculations to reconstruct the variability of glacier extent and volume in the past using available climate data from the central Karakoram. From the comparison of historical measurements and photographs it is shown that the snout of Baltoro glacier is oscillating back and forth a couple of hundred metres. Otherwise it seems not to react with the same magnitude as other glaciers to the climatic change. Elevation changes at Concordia are a few tens of metres at the most.
Valley Fever is a disease caused by a fungus (or mold) called Coccidioides. The fungi live in the soil ... from person to person. Anyone can get Valley Fever. But it's most common among older adults, especially ...
Wittmeier, Hella E.; Bakke, Jostein; Vasskog, Kristian; Trachsel, Mathias
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
Benson, C. S.; Follett, A. B.
Most Alaskan volcanoes are glacier covered and provide excellent opportunities to study interactions between glaciers and volcanoes. The present paper is concerned with such a study, taking into account the Mt. Wrangell (4317 m) which is the northernmost active volcano (solfatara activity) on the Pacific Rim (62 deg N; 144 deg W). While the first photographs on the summit of Mt. Wrangell were published more than 75 years ago, research there began in 1953 and 1954. Satellite images reveal activity at the summit of Mt. Wrangell. However, the resolution is not sufficient for conducting important measurements regarding ice volume losses. For this reason, vertical aerial photographs of the summit were obtained, and a field trip to the summit was conducted. Aspects of photogrammetry are discussed, taking into account questions of ground control, aerial photography, topographic mapping, digital cross sections, and orthophotos.
The transHimalayan upper Indus Basin contains thousands of rock glaciers. An exceptional diversity of forms and sizes exist, hitherto largely unresearched. They are in a well-defined elevation band across the mountains, usually less than 1400 m vertically, although total relief exceeds 7000 m. The zone varies from north to south, west to east, and with slope orientation. Interfluve elevations are primary constraints. Rock glaciers are absent below the lowest and the highest interfluves. They are uncommon in the highest Mustagh Karakoram, Nanga Parbat, and Hindu Kush where glacier ice blankets the elevations where they could develop. The heaviest concentrations occur in sub-ranges of intermediate elevation. A full spectrum of generative conditions is found; related to periglacial, talus, glacial, avalanche, wind-blown snow, and rock avalanche processes. Forms vary between north and south slopes; arid, rainshadowed and more snowy, humid valleys. Rock glacier complexes, where two or more join to create extensive lobes, may have tributaries with different source conditions. The larger examples are several kilometres in length,usually glacier-derived, evidently affected by Holocene glacial history, trans-glacial processes, and paraglacial instabilities. In lesser ranges, many smaller rock glaciers are associated with glacier-free cirques, glacially sculpted valley walls, and floors with abundant glacial deposits. In general, they are transitional in genesis, process, and spatially relative to glacierization, to the vertical cascade of moisture and debris, and climate change in the vertical. Their landscape roles include extensive fragmentation of drainage systems. Countless inactive rock glaciers occur, typically continuing below active ones.
Molnia, B.F.; Jones, J.E. )
Two types of radar investigations were conducted at Malaspina glacier, the largest piedmont glacier lobe in North America. Digital x-band side-looking airborne radar (SLAR) data were collected to image surface features; ice-surface, ice-penetrating radar was employed to measure ice thickness and to identify the configuration of subglacial bed rock SLAR revealed a complex pattern of surface backscatter responses related to three types of channellike features on the glacier surface, which mimic the configuration of its underlying bed rock. The features resemble (1) glacially eroded valleys with cirque-like indentations, (2) dendritic stream valleys, and (3) a greater than 40-km-long, arcuate, east-west lineament that corresponds to the Fairweather fault. Field examinations of the three types of features were made to determine relief, slope, and other conditions. The channel-like features had elevations as much as 40 m lower than adjacent high areas and were characterized by fewer crevasses, minimal surface relief, a sediment veneer, and standing and running water. Hundred-m-spaced ice-penetrating radar soundings showed that the ice thickness over these low areas is much greater than over adjacent highs. About 50 ice-thickness measurements were made elsewhere on the glacier. The maximum ice thickness measured exceeded 850 m, whereas the minimum thickness was less than 150 m. Comparison of ice-thickness measurements and ice-surface elevations at each site suggests that the Malaspina Glacier occupies a deep basin or series of basins extending well below sea level.
Fisher, J. B.; Sikka, M.; Oechel, W. C.; Huntzinger, D. N.; Melton, J. R.; Koven, C. D.; Ahlström, A.; Arain, M. A.; Baker, I.; Chen, J. M.; Ciais, P.; Davidson, C.; Dietze, M.; El-Masri, B.; Hayes, D.; Huntingford, C.; Jain, A. K.; Levy, P. E.; Lomas, M. R.; Poulter, B.; Price, D.; Sahoo, A. K.; Schaefer, K.; Tian, H.; Tomelleri, E.; Verbeeck, H.; Viovy, N.; Wania, R.; Zeng, N.; Miller, C. E.
Climate change is leading to a disproportionately large warming in the high northern latitudes, but the magnitude and sign of the future carbon balance of the Arctic are highly uncertain. Using 40 terrestrial biosphere models for the Alaskan Arctic from four recent model intercomparison projects - NACP (North American Carbon Program) site and regional syntheses, TRENDY (Trends in net land atmosphere carbon exchanges), and WETCHIMP (Wetland and Wetland CH4 Inter-comparison of Models Project) - we provide a baseline of terrestrial carbon cycle uncertainty, defined as the multi-model standard deviation (σ) for each quantity that follows. Mean annual absolute uncertainty was largest for soil carbon (14.0 ± 9.2 kg C m-2), then gross primary production (GPP) (0.22 ± 0.50 kg C m-2 yr-1), ecosystem respiration (Re) (0.23 ± 0.38 kg C m-2 yr-1), net primary production (NPP) (0.14 ± 0.33 kg C m-2 yr-1), autotrophic respiration (Ra) (0.09 ± 0.20 kg C m-2 yr-1), heterotrophic respiration (Rh) (0.14 ± 0.20 kg C m-2 yr-1), net ecosystem exchange (NEE) (-0.01 ± 0.19 kg C m-2 yr-1), and CH4 flux (2.52 ± 4.02 g CH4 m-2 yr-1). There were no consistent spatial patterns in the larger Alaskan Arctic and boreal regional carbon stocks and fluxes, with some models showing NEE for Alaska as a strong carbon sink, others as a strong carbon source, while still others as carbon neutral. Finally, AmeriFlux data are used at two sites in the Alaskan Arctic to evaluate the regional patterns; observed seasonal NEE was captured within multi-model uncertainty. This assessment of carbon cycle uncertainties may be used as a baseline for the improvement of experimental and modeling activities, as well as a reference for future trajectories in carbon cycling with climate change in the Alaskan Arctic and larger boreal region.
Yoshikawa, K.; Sparrow, E. B.; Kopplin, M.
The Permafrost/Active Layer Monitoring Program is an ongoing project, which builds on work begun in 2005 to establish long-term permafrost and active layer monitoring sites adjacent to schools in Alaskan communities and in the circumpolar permafrost region. Currently, there are about 200 schools in Alaska involved in the project including also Denali National Park and Preserve. The project has both scientific and outreach components. The monitoring sites collect temperature data on permafrost, and the length and depth of the active layer (the layer above the permafrost that thaws during summer and freezes again during winter). To ensure scientific integrity, the scientist installed all of the monitoring instruments and selected the sites representative of the surrounding biome and thermal conditions. This is a unique collaboration opportunity in that 1) uses scientifically accurate instruments, 2) is scientist led and supervised including instrumentation set-up and data quality check, 3)has teacher/student organized observation network, 4) increased spatial scale of monitoring sites that covers all of the Alaskan communities. Most of the monitoring sites are located in remote communities, where the majority of residents depend on a subsistence lifestyle. Changes in climate, length of seasons, and permafrost conditions directly impact natural resources and subsistence activities. Changes in permafrost conditions also affect local ecosystems and hydrological regimes, and can influence the severity of natural disasters. In addition to extending our knowledge of the arctic environment, the program involves school-age students. Several students have been using the data for their projects and have been inspired to continue their studies. The data gathered from these stations are shared with other schools and made available to the public through our web site (http://www.uaf.edu/permafrost). Also communities have increasingly become interested in this project not only as
Sagredo, E. A.; Araya, P. S.; Schaefer, J. M.; Kaplan, M. R.; Kelly, M. A.; Lowell, T. V.; Aravena, J. C.
Deciphering the timing and the inter-hemispheric phasing of former glacial fluctuations is critical for understanding the mechanisms and climate signals underlying these glacial events. Here, we present a detailed chronology of glacial fluctuations for Río Tranquilo glacier (47°S), since the LGM, including up to the present. Río Tranquilo is a small glacial valley located on the northern flank of Monte San Lorenzo, an isolated granitic massif, ~70 km to the east of the southern limit of the Northern Patagonian Icefield. Although Mt. San Lorenzo is located on the leeward side of the Andes, it is one of the most glacierized mountains in the region, with an ice surface area of ~140 km2. Geomorphic evidence suggests that during past episodes of climate change several small glaciers that today occupy the headwalls of Río Tranquilo valley expanded and coalesced, depositing a series of moraines complexes along the flanks and bottom of the valley. We used two independent dating techniques to constrain the age of the glacial history of the area. 10Be surface exposure ages from boulders located atop moraine ridges reveal that Río Tranquilo valley underwent glacial expansion/stabilization during at least the LGM (late LGM?), Late glacial (ACR and Younger Dryas) and Mid-Holocene. Within the Mid-Holocene limits, tree-ring based chronology indicates that Río Tranquilo glacier expanded during the Late Holocene as well. Our results are the first detailed chronology of glacial fluctuations from a single valley glacier, spanning the entire period from the (end of the) LGM up to the present, in southern South America. By identifying different glacial episodes within a single alpine valley, this study provides baseline data for studying the relative magnitude of the climate events responsible for these glacial events.
Rosenwinkel, Swenja; Landgraf, Angela; Korup, Oliver; Sorg, Annina
Rock glaciers have been traditionally used as landform proxies of the distribution of sporadic alpine permafrost. In the northern Tien Shan mountains of Kyrgyzstan, most distinct lobes of >200 rock glaciers that we mapped from satellite imagery occur at two major elevation levels. However, a number of particularly low-lying lobes seem difficult to reconcile with palaeoclimatic fluctuations and commensurate changes of permafrost patterns: The minimum elevation of the majority of rock-glacier snouts lies between ~2500 up to ~3700 m a.s.l., but some 10% of rock-glaciers extend down to well below 3000 m a.s.l. We hypothesize that some of the rock glaciers in this area may have formed following strong earthquakes that could have triggered massive supraglacial rock-slope failures, which would have subsequently created sediment-rich rock glaciers from clear-ice glaciers. Our hypothesis is based on the observation that the tectonically active northern Tien Shan of Kyrgyzstan and Kazakhstan was affected by a series of major earthquakes in the late 19th and earliest 20th centuries, e.g. in 1885 (Ms 6.9), 1887 (Ms 7.3), 1889 (Ms 8.3), and 1911 (Ms 8.1). All of these earthquakes had triggered numerous landslides in the northern Tien Shan. It is also likely that similarly strong earthquakes had happened before, but their recurrence intervals are long and more palaeoseismological work is in progress. We test whether lichenometry of rock-glacier surfaces together with morphometric analysis are suitable methods to testing our hypothesis. We focus on assessing the possibility of earthquake-triggered rock-glacier advances, and use lichenometry to resolve age patterns of different rock-glacier lobes. We use a dataset of several thousand lichen diameter measurements encompassing seven different species calibrated by gravestones and dated mass-movement deposits. Data on four single and two merging rock glaciers in four selected valleys in Kyrgyzstan and Kazakhstan support the notion
Collins, D. N.
Marked patterns of seasonal and diurnal variations of discharge and temperature characterise meltwater rivers draining from large Alpine glaciers. Meltwater temperature warms with distance downstream, influenced both by energy availability and the volume of meltwater flowing. The amount of meltwater produced depends also on energy availability but also on the area of ice substrate over which melt occurs. As climate warms, meltwater production by ablation in summer will first increase with increasing energy for melting, before decreasing as the area of ice available for melt decreases, off-setting continuing increase in energy availability. Future meltwater temperature changes will depend on the inter-relationship between increasing energy availability and enhancing volume of meltwater produced. Relationships between rates of ice melt, reduction in ice area, and meltwater production will influence melt water temperature changes as climate warms. Meltwater temperature is inversely related to discharge whilst positively related to heat availability. Records of water temperature and discharge of meltwaters in rivers draining from three valley glaciers in Kanton Wallis, Switzerland have been examined. Hourly data for the Massa, Grosser Aletschgletscher, for the period 2003-2014, the Gornera, Gornergletscher , 2007-2014, and Findelenbach, Findelengletscher, 2007-2014 obtained at distances of a few kilometres from the glacier portals have been analysed, for summer months, during which more than 90% of discharge occurs. Distinctive seasonal temperature regimes have highest annual water temperatures during low flows in May., but then as discharge increased with first increasing radiation, increasing ice area as the transient snow line moved up glacier, and higher air temperatures, water temperatures decreased. On a diurnal basis, meltwater temperatures increased with rising radiation ahead of rising discharge (discharge being delayed by flow through time within the glacier
Kreeger, Terry J; Kellie, Kalin A
Free-ranging Alaskan moose calves (Alces alces gigas) were immobilized with 0.12 mg/kg sufentanil (S; n=16), 0.12 mg/kg sufentanil plus 0.27 mg/kg xylazine (SX; n=11), or 0.007 mg/kg carfentanil plus 0.36 mg/kg xylazine (CX; n=13). Immobilants were antagonized with 1.2 mg/kg naltrexone (S) or 1.2 mg/kg naltrexone plus 2.4 mg/kg tolazoline (SX, CX). There were no differences in induction (P ≥ 0.29) or processing (P ≥ 0.44) times between groups. Moose given either S or SX had significantly shorter recovery times than moose given CX (P=0.001) and recovery times from S were shorter than from SX (P=0.02). Oxygen saturation values for all groups averaged 85 ± 8%, but were significantly higher (P=0.048) for CX (89 ± 7%) than for S (82 ± 8%). Based on these data, sufentanil at 0.1 mg/kg or sufentanil at 0.1 mg/kg plus xylazine at 0.25 mg/kg could provide effective remote immobilization for Alaskan moose calves and could be substituted for carfentanil or thiafentanil should the need arise. PMID:23060515
Pettit, E.C.; Nystuen, J.A.; O'Neel, Shad
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.
Swanger, Kate M.; Marchant, David R.; Schaefer, Joerg M.; Winckler, Gisela; Head, James W.
We document Plio-Pleistocene changes in the level of Taylor Glacier, an outlet glacier in southern Victoria Land that drains Taylor Dome on the periphery of the East Antarctic Ice Sheet (EAIS). Chronologic control comes from 3He cosmogenic-nuclide analyses of 27 boulders sampled from drifts and moraines in Kennar Valley, a small hanging valley that opens onto a peripheral lobe of Taylor Glacier in the Quartermain Mountains. Assuming a constant boulder-erosion rate of 10 cm Myr -1, our preferred age model spans the last 3.1 Myr and calls for stepped ice recession from a local highstand ~ 200 m above the present base of Taylor Glacier at the mouth of Kennar Valley. The texture and sedimentology of all mapped moraines and drifts indicate deposition from cold-based ice, analogous with the modern Taylor Glacier at the mouth of Kennar Valley. The Kennar Valley glacial record shows an uncharacteristic relationship with average global temperatures, exhibiting higher-than-present ice levels during globally warm periods, including the Pliocene climatic optimum (~ 3.1 Ma) and Marine Oxygen Isotope Stage (MIS) 31 (~ 1.07 Ma). The Kennar Valley record also suggests that the rate of ice-surface lowering accelerated after the mid-Pleistocene transition at ~ 0.9 Ma. Correlation of our moraine record with published reports for fluctuations of Taylor Glacier elsewhere in the Quartermain Mountains, and with a dated moraine record from Ferrar Glacier (a second outlet for Taylor Dome), reveals similar ice-surface changes, highlighting minor, but widespread ice recession in southern Victoria Land since the mid- to late-Pliocene. Our record for minimal variability in the East Antarctic Ice Sheet contrasts with recent data from nearby marine cores that call for dynamic fluctuations in the volume of grounded ice in the Ross Embayment, and significant reduction of the West Antarctic Ice Sheet (WAIS) during warmer-than-present intervals. Taken together, these records from the Ross Embayment
Giordan, Daniele; Dell'Anese, Federico; Allasia, Paolo; Vagliasindi, Marco; Motta, Elena
In September 2013, an experimental low cost monitoring station has been installed on the top of Mt. de La Saxe (Val Ferret, Aosta Valley, NW of Italy) to monitor the Planpincieux Glacier, located on the Italian side of Mont Blanc Massif. This system is based on two commercial APS-C DSLR cameras equipped with a 297 mm and 120 mm optical zoom respectively. Every hour cameras automatically acquire pictures of the lower part of the glacier, which showed to be the most active. The available dataset is analyzed using both change-detection and pixel-offset techniques, to detect the main surface changes over time, as well as to retrieve quantitative measurements of the glacier displacements. The system is able to work throughout the year. The available dataset has been used to analyze the daily evolution of the lower part of the glacier over the May-November period (when the glacier is free from snow) both in 2014 and 2015. The pixel-offset approach allows to measure the displacement of different parts of the glacier and to describe its seasonal evolution. Furthermore, change detection algorithm allows highlighting sudden changes of the scene, usually due to icefalls. The available dataset shows that the displacement rate of the glacier increases during the warm season, that in 2014 it was higher than in 2015, and that it was distributed in a different way. Actually, in 2015, the maximum rate was reached in August, whereas in 2014 the measured summer velocity was lower but it lasted over the months of July, August and September. The results have been validated using different ground based SARs, both in 2014 and 2015. Here we present the results of a three years monitoring, demonstrating the efficiency of pixel-offset and change-detection techniques for contactless monitoring of unreachable glacier surfaces. Furthermore, we present cross-analysis, considering displacements vs. weather measurements, in order to understand glaciers dynamics.
Child, S.; Stearns, L. A.; Purdon, K.; Li, J.; Rodriguez-Morales, F.; Crowe, R.; Gomez-Garcia, D.
Bed topography controls the pattern and magnitude of ice velocity, far into the catchment basin of many Antarctic outlet glaciers. Predictive models of glacier dynamics and ice sheet mass balance rely on well-prescribed bed topography, but in many regions bed topography is largely unknown. This particular study investigates the relationship between bed and surface topography and ice velocity in the catchment basin and trunk of Byrd Glacier. Byrd Glacier drains ~19 % of the area of the East Antarctic Ice Sheet (1,070,400 km2), and has the potential to play a significant role in the ice sheet's total mass balance. In 2011/2012, the Center for Remote Sensing of Ice Sheets (CReSIS) collected airborne radar data over Byrd Glacier. These new measurements of bed topography, along with updated surface digital elevation models (DEMs) and basin-wide ice velocity maps, are used to investigate the flow dynamics of Byrd Glacier with improved accuracy. Surface DEMs are derived from new high-resolution WorldView imagery; ice velocity is derived from repeat visible imagery, coupled with InSAR results (Rignot et al., 2011). Results exhibit relatively smooth depressions surrounding the inferred subglacial lakes, ~200 km upflow of the grounding line on Byrd Glacier (Stearns et al., 2008). Downflow of the subglacial lakes is a complex pattern of hills and valleys as ice enters the glacier trunk. At the mouth of the trunk is a large overdeepening (~2500 m) that coincides with faster ice flow. We use along- and across-flow radar profiles to perform detailed comparisons of ice velocity, bed topography and surface topography throughout the Byrd Glacier region. Gridded products are used to complete an updated force balance assessment. These results provide us with a better understanding of Byrd Glacier's flow dynamics and sensitivity to external perturbations.
Strelin, Jorge A.; Kaplan, Michael R.; Vandergoes, Marcus J.; Denton, George H.; Schaefer, Joerg M.
We present new geomorphic, stratigraphic, and chronologic data for Holocene glacier fluctuations in the Lago Argentino basin on the eastern side of the southern Patagonian Andes. Chronologic control is based on 14C and surface-exposure 10Be dating. After the Lateglacial maximum at 13,000 cal yrs BP, the large ice lobes that filled the eastern reaches of Lago Argentino retreated and separated into individual outlet glaciers; this recession was interrupted only by a stillstand or minor readvance at 12,200 cal yrs BP. The eight largest of these individual outlet glaciers are, from north to south: Upsala, Agassiz, Onelli, Spegazzini, Mayo, Ameghino, Perito Moreno, and Grande (formerly Frías). Holocene recession of Upsala Glacier exposed Brazo Cristina more than 10,115 ± 100 cal yrs BP, and reached inboard of the Holocene moraines in Agassiz Este Valley by 9205 ± 85 cal yrs BP; ice remained in an inboard position until 7730 ± 50 cal yrs BP. Several subsequent glacier readvances are well documented for the Upsala and Frías glaciers. The Upsala Glacier readvanced at least seven times, the first being a relatively minor expansion - documented only in stratigraphic sections - between 7730 ± 50 and 7210 ± 45 cal yrs BP. The most extensive Holocene advances of Upsala Glacier resulted in the deposition of the Pearson 1 moraines and related landforms, which are divided into three systems. The Pearson 1a advance occurred about 6000-5000 cal yrs BP and was followed by the slightly less-extensive Pearson 1b and 1c advances dated to 2500-2000 and 1500-1100 cal yrs BP, respectively. Subsequent advances of Upsala Glacier resulted in deposition of the Pearson 2 moraines and corresponding landforms, also separated into three systems, Pearson 2a, 2b, and 2c, constructed respectively at ˜700, >400, and <300 cal yrs BP to the early 20th century. Similar advances are also recorded by moraine systems in front of Grande Glacier and herein separated into the Frías 1 and Frías 2a, 2b
Ambach, W.; Rehwald, W.; Blumthaler, M.; Eisner, H.; Brunner, P.
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.
Surazakov, A. B.; Narojniy, Y. K.; Nikitin, S. A.; Aizen, V. B.
To systemize and analyze the information for the period from 1835 to present on altitudinal distributions of glaciers, exposition, their numbers and surface areas in basins, volumes, genetic classification, location of lower and upper level of glaciers, average firn line position and main morphometric characteristics, DataBase on glacier dynamics in the Altai Mountains (AGDB) has been developed in ArcGIS Format [Tomsk State University, Russia]. Data from Glacier Catalogue , topographic maps with the scale of 1:25000 and 1:50000 and air photos, which fixed glaciers' state on 1952, were digitized. Instrumental observational data on glacier tongue retreat from twenty glaciers since 1835, and radio-echo sounding measurements of 120 glacier volumes were also digitized in the AGDB. Modern state of Altai glaciers and their changes since 1952 were assessed from Resurs space images and partially from instrumental observations. Based on estimation from Resurs for the period from 1952 to 1998, the value of Altai glacier retreating was about 56.9 km2, i.e. 7.1 % of total area, varied from 4 % for valley glaciers to 16 % for glaciers of flat mountain tops. Retreat of 2-8 m per year was accompanied by their 10% mass loss. The slightest degradation occurred in inner (central) part of the glacier system, in the heads of river basins with large-scale glaciation, e.g., in the Katunski, Nothern-Chuiski and Southern-Chuiski ranges, amounting to 6.3%. These are the highest regions, reaching up to 4506 m., and 80% of Altai's glaciers are located there. In the river basins with relatively small-glacierized areas, at the peripheral regions, e.g., Kurai, Chihacheva ranges, the degradation reached its maximum values up to 22%.
Loibl, David; Lehmkuhl, Frank
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
Hoffman, A.; Hock, R.; Aubry-Wake, C.; Bliss, A.; Gusmeroli, A.; Liljedahl, A.; Gillispie, L.; Wolken, G. J.
The State of Alaska is reviving analyses of the Susitna River's hydroelectric potential by supporting a multitude of field and modeling studies for the proposed Susitna-Watana Hydroelectric project. Critical to any effective hydroelectric development is a firm understanding of the basin-wide controls on river runoff and how seasonal reservoir recharge may change over the course of the structure's life-span. Effectively projecting future changes in watershed-scale stream flow for the Susitna river demands understanding and quantifying glacier melt in the Alaskan range. Our research is restricted to a sub-catchment of the upper Susitna basin that feeds the Susitna River covering 2,230 km2, of which 25% is glacierized. The goals of our study are to investigate the spatial and seasonal variations of the energy balance and its components across the glaciers and to model resulting streamflow from the catchment for the summer of 2013 using two models of different complexity. We apply DEBAM, a distributive energy balance model and DETIM, an enhanced temperature-index model, both coupled to a linear-reservoir runoff model, to simulate hourly surface energy fluxes, melt rates and glacier runoff using meteorological observations from an automated weather station located in the ablation zone of the West Fork glacier. Model results are compared to measurements of streamflow and mass balance at 20 ablation stakes across the glacierized area. The largest source of energy contributing to 85% of melt is net radiation followed by the sensible and latent heat fluxes. Both models capture well the seasonal and diurnal variations in streamflow and show good agreement with the mass balance point observations. The discrepancies between modeled and measured discharge can be attributed to the high uncertainty in precipitation and initial snow cover across the unglaciated part of the basin which accounts for over 75% of the modeled area.
Bhardwaj, Anshuman; Joshi, PK; Snehmani; Sam, Lydia; Singh, Mritunjay Kumar; Singh, Shaktiman; Kumar, Rajesh
The present work evaluates the applicability of operational land imager (OLI) and thermal infrared sensor (TIRS) on-board Landsat 8 satellite. We demonstrate an algorithm for automated mapping of glacier facies and supraglacial debris using data collected in blue, near infrared (NIR), short wave infrared (SWIR) and thermal infrared (TIR) bands. The reflectance properties in visible and NIR regions of OLI for various glacier facies are in contrast with those in SWIR region. Based on the premise that different surface types (snow, ice and debris) of a glacier should show distinct thermal regimes, the 'at-satellite brightness temperature' obtained using TIRS was used as a base layer for developing the algorithm. This base layer was enhanced and modified using contrasting reflectance properties of OLI bands. In addition to facies and debris cover characterization, another interesting outcome of this algorithm was extraction of crevasses on the glacier surface which were distinctly visible in output and classified images. The validity of this algorithm was checked using field data along a transect of the glacier acquired during the satellite pass over the study area. With slight scene-dependent threshold adjustments, this work can be replicated for mapping glacier facies and supraglacial debris in any alpine valley glacier.
Schwalbe, Ellen; Koschitzki, Robert
In recent years, many glaciers all over the world have been distinctly retreating and thinning. One of the consequences of this is the increase of so called glacier lake outburst flood events (GLOFs): Lakes that have been dammed by a glacier spontaneously start to drain through a subglacial channel underneath the glacier due to their outweighing hydrostatic pressure. In a short period of time, the lake water drains under the glacier and causes floods in downstream valleys. In many cases the latter become hazardous for people and their property. Due to glacier movement, the tunnel will soon collapse, and the glacier lake refills, thus starting a new GLOF cycle. The mechanisms ruling GLOF events are yet still not fully understood by glaciologists. Thus, there is a demand for data and measurement values that can help to understand and model the phenomena. In view of the above, we will show how photogrammetric image sequence analysis can be used to collect data which allows for drawing conclusions about the location and development of a subglacial channel. The work is a follow-up on earlier work on a photogrammetric GLOF early warning system (Mulsow et. al., 2013). For the purpose of detecting the subglacial tunnel, a camera has been installed in a pilot study to observe the area of the Colonia glacier (Northern Patagonian ice field) where it dams the lake Lago Cachet II. To verify the hypothesis, that the course of the subglacial tunnel is indicated by irregular surface motion patterns during its collapse, the camera acquired image sequences of the glacier surface during several GLOF events. Applying LSM-based tracking techniques to these image sequences, surface feature motion trajectories could be obtained for a dense raster of glacier points. Since only a single camera has been used for image sequence acquisition, depth information is required to scale the trajectories. Thus, for scaling and georeferencing of the measurements a GPS-supported photogrammetric network
Fisher, J. B.; Sikka, M.; Oechel, W. C.; Huntzinger, D. N.; Melton, J. R.; Koven, C. D.; Ahlström, A.; Arain, A. M.; Baker, I.; Chen, J. M.; Ciais, P.; Davidson, C.; Dietze, M.; El-Masri, B.; Hayes, D.; Huntingford, C.; Jain, A.; Levy, P. E.; Lomas, M. R.; Poulter, B.; Price, D.; Sahoo, A. K.; Schaefer, K.; Tian, H.; Tomelleri, E.; Verbeeck, H.; Viovy, N.; Wania, R.; Zeng, N.; Miller, C. E.
Climate change is leading to a disproportionately large warming in the high northern latitudes, but the magnitude and sign of the future carbon balance of the Arctic are highly uncertain. Using 40 terrestrial biosphere models for Alaska, we provide a baseline of terrestrial carbon cycle structural and parametric uncertainty, defined as the multi-model standard deviation (σ) against the mean (x\\bar) for each quantity. Mean annual uncertainty (σ/x\\bar) was largest for net ecosystem exchange (NEE) (-0.01± 0.19 kg C m-2 yr-1), then net primary production (NPP) (0.14 ± 0.33 kg C m-2 yr-1), autotrophic respiration (Ra) (0.09 ± 0.20 kg C m-2 yr-1), gross primary production (GPP) (0.22 ± 0.50 kg C m-2 yr-1), ecosystem respiration (Re) (0.23 ± 0.38 kg C m-2 yr-1), CH4 flux (2.52 ± 4.02 g CH4 m-2 yr-1), heterotrophic respiration (Rh) (0.14 ± 0.20 kg C m-2 yr-1), and soil carbon (14.0± 9.2 kg C m-2). The spatial patterns in regional carbon stocks and fluxes varied widely with some models showing NEE for Alaska as a strong carbon sink, others as a strong carbon source, while still others as carbon neutral. Additionally, a feedback (i.e., sensitivity) analysis was conducted of 20th century NEE to CO2 fertilization (β) and climate (γ), which showed that uncertainty in γ was 2x larger than that of β, with neither indicating that the Alaskan Arctic is shifting towards a certain net carbon sink or source. Finally, AmeriFlux data are used at two sites in the Alaskan Arctic to evaluate the regional patterns; observed seasonal NEE was captured within multi-model uncertainty. This assessment of carbon cycle uncertainties may be used as a baseline for the improvement of experimental and modeling activities, as well as a reference for future trajectories in carbon cycling with climate change in the Alaskan Arctic.
Hubbard, A., II; Brough, S.; Hubbard, B. P.
Mars' mid-latitudes host a substantial volume of ice, equivalent to a ~1 - 2.5 m-thick global layer or the sum of Earth's glaciers and ice caps outside of Antarctica and Greenland. These deposits are the remnants of what is believed to have been a once far larger 'ice age', culminating in a last martian glacial maximum. Despite the identification of >1,300 glacier-like forms (GLFs) - the first order component of Mars' glacial landsystem - in Mars' mid-latitudes, little is known about their composition, dynamics or former extent. Here, we reconstruct the former 3D extent of a well-studied GLF located in eastern Hellas Planitia. We combine high-resolution geomorphic and topographic data, obtained from the High-Resolution Imaging Science Experiment (HiRISE) camera, to reconstruct the GLF's former limits. We then apply a perfect plasticity rheological model, to generate multiple flow-parallel ice-surface transects. These are combined with the GLF's boundary to guide interpolation using ArcGIS' 'Topo to Raster' function to produce a continuous 3D surface for the reconstructed former GLF. Our results indicate that, since its reconstructed 'recent maximum' extent, the GLF's volume has reduced by 0.31 km3 and its area by 6.85 km2, or 70%. On-going research is addressing the degree to which this change is typical of Mars' full GLF population.
Mood, Bryan J.; Smith, Dan J.
The Coast Mountains flank the Pacific Ocean in western British Columbia, Canada. Subdivided into the southern Pacific Ranges, central Kitimat Ranges and northern Boundary Ranges, the majority of large glaciers and icefields are located in the Boundary and Pacific ranges. Prior descriptions of the Holocene glacial history of this region indicate the Holocene was characterized by repeated episodes of ice expansion and retreat. Recent site-specific investigations augment our understanding of the regional character and duration of these events. In this paper, previously reported and new radiocarbon evidence is integrated to provide an updated regional assessment. The earliest evidence of glacier expansion in the Coast Mountains comes from the Boundary Ranges at 8.9 and 7.8 ka and in the Pacific Ranges at 8.5-8.2 ka, with the latter advance corresponding to an interval of rapid, global climate deterioration. Although generally warm and dry climates from 7.3 to 5.3 ka likely limited the size of glaciers in the region, there is radiocarbon evidence for advances over the interval from 7.3 to 6.0 and at 5.4-5.3 ka in the Pacific Ranges. Following these advances, glaciers in the Pacific Ranges expanded down valley at 4.8-4.6, 4.4-4.0, 3.5-2.6, 1.4-1.2, and 0.8-0.4 ka, while glaciers in Boundary Ranges were advancing at 4.1-4.0, 3.7-3.4, 3.1-2.8, 2.3, 1.7-1.1, and 0.8-0.4 ka. After 0.4 ka, it appears that most glaciers in the Coast Mountains continued to expand to attain their maximum Holocene extents by the early 18th to late 19th centuries. This enhanced record of Holocene glacier activity highlights the temporal synchrony in the Coast Mountains. Individual expansion events in the mid-to late Holocene broadly correspond to intervals of regional glacier activity reported in the Canadian Rocky Mountains, in Alaska, and on high-elevation volcanic peaks in Washington State.
Sauber, J.; Molnia, B. F.; Lutchke, S.; Rowlands, D.; Harding, D.; Carabajal, C.; Hurtado, J. M.; Spade, G.
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
Kamath, V.A.; Sharma, G.D.; Patil, S.L.
The research undertaken in this project pertains to study of various techniques for production of natural gas from Alaskan gas hydrates such as, depressurization, injection of hot water, steam, brine, methanol and ethylene glycol solutions through experimental investigation of decomposition characteristics of hydrate cores. An experimental study has been conducted to measure the effective gas permeability changes as hydrates form in the sandpack and the results have been used to determine the reduction in the effective gas permeability of the sandpack as a function of hydrate saturation. A user friendly, interactive, menu-driven, numerical difference simulator has been developed to model the dissociation of natural gas hydrates in porous media with variable thermal properties. A numerical, finite element simulator has been developed to model the dissociation of hydrates during hot water injection process.
Suarez, Wilson; Cerna, Marcos; Ordoñez, Julio; Frey, Holger; Giráldez, Claudia; Huggel, Christian
The Urubamba and Vilcabamba mountain ranges are two geological structures belonging to the Andes in the southern part of Peru, which is located in the tropical region. These mountain ranges are especially located within the transition area between the Amazon region (altitudes close to 1'000 m a.s.l.) and the Andes. These mountains, with a maximum height of 6'280 m a.s.l. (Salkantay Snow Peak in the Vilcabamba range), are characterized by glaciers mainly higher than 5000 m a.s.l. Here we present a study on the evolution of the ice cover based on "Landsat 5" images from 1991 and 2011 is presented in this paper. These data are freely available from the USGS in a georeferenced format and cover a time span of more than 25 years. The glacier mapping is based on the Normalized Difference Snow Index (NDSI). In 1991 the Vilcabamba mountain range had 221 km2 of glacier cover, being reduced to 116.4 km2 in 2011, which represents a loss of 48%. In the Urubamba mountain range, the total glacier area was 64.9 km2 in 1991 and 29.4 km2 in 2011, representing a loss of 54.7%. It means that the glacier area was halved during the past two decades although precipitation patterns show an increase in recent years (the wet season lasts from September to April with precipitation peaks in February and March). Glacier changes in these two tropical mountain ranges also impact from an economic point of view due to small local farming common in this region (use of water from the melting glacier). Furthermore, potential glacier related hazards can pose a threat to people and infrastructure in the valleys below these glaciers, where the access routes to Machu Picchu Inca City, Peru's main tourist destination, are located too.
Brun, F.; Valla, P.; King, G. E.; Herman, F.
Quantifying glacier dynamics over the late-Pleistocene remains an important challenge for understanding glacial response to climate change. Historical glacier reconstructions are spatially limited (e.g. the European Alps) and cover only the last ~100 yrs, restricting their use as paleoclimatic proxies. Bedrock dating methods such as Terrestrial Cosmogenic Nuclides (TCN) dating or lichenometry allows glacier fluctuations to be reconstructed over longer timescales. However, these methods have limited temporal resolution, and therefore do not enable accurate dating of recent glacier fluctuations (e.g. short glacier re-advances). Here, we use a novel in situ dating method based on Optically Stimulated Luminescence (OSL) to fill this temporal/spatial gap. OSL dating is based on the time-accumulation of trapped electrons in the lattice defects of minerals. OSL-exposure dating is based on the bleaching (i.e. resetting) of the minerals' luminescence signal when they are exposed to light (Sohbati et al., 2012 JGR-Solid Earth), which depends on exposure time, effective photon flux and light attenuation by minerals. We analyzed 10 samples in the Val d'Hérens (Swiss Alps) where post-LGM glacier dynamics remain poorly constrained and short glacier re-advances are thought to occur during the Holocene. Bedrock samples were drilled and small cores were sliced into 1-mm thick discs from which natural luminescence profiles were measured. We calibrated the luminescence model parameters using historically-exposed bedrock samples (~100 yr) near the Mont-Miné glacier, and used this on-site calibration to date surface exposure of glacial bedrock at various elevations along the valley; initial relative dating results are promising. Although OSL-exposure dating appears an efficient tool for historical glacier reconstructions, OSL bleaching over longer timescales (i.e. late-Pleistocene to Holocene) requires more investigation before use as a chronometer.
Rowan, A. V.; Egholm, D. L.; Glasser, N. F.; Quincey, D. J.
variables: (1) simple elevation-dependent rates for accumulation and ablation with empirical values for melt along a flow line beneath supraglacial debris; (2) climate-elevation relationships derived from local automatic weather stations in the Khumbu valley; and (3) 3-D surface energy balance calculations using regional meteorological data. Once we have described glacier-climate sensitivities in the Khumbu Himal, we will use these results to predict the likely magnitude and timescales of glacier mass loss under IPCC future climate change scenarios, and quantify the uncertainties associated with these predictions. Future work will consider: how glacier hydrology modifies variations in ice dynamics; how the spatial distribution of supraglacial debris modifies glacier balance sensitivity; how rock debris is transported within and on these glaciers; and how rates of rock debris delivery from hillslopes affects glacier balance and dynamics. Fieldwork in Nepal is planned for 2014 to collect data from debris-covered Khumbu Glacier with which to validate our numerical model.
Molnia, B. F.
Bear Glacier, with an area of ~225 km2, is a 25-km long valley glacier located in the southern Kenai Mountains. When first mapped in 1909, it had a piedmont lobe with an area of >30 km2. By the mid- 1980s, the terminus had retreated from 1-3 km, thinned by >150 m, and was actively calving small icebergs into an ice-marginal lake. Through the end of the 20th century, the piedmont lobe continued to thin and narrow. Active calving decreased and then ceased as the thickness of the thinning glacier approached Tnb, the thickness of neutral buoyancy (the floatation thickness). As thinning continued, much of the terminus began to float. Passive calving, characterized by the release of large tabular icebergs from Bear's low gradient, low elevation terminus, became the dominant retreat process. Between 2000 and 2007, part of the terminus retreated about 3.6 km. Now, 0.5 km-long icebergs frequently separate from Bear's western terminus. An August 2006 bathymetric survey identified many locations with depths >75 m in Bear Glacier's ice-marginal lake. Calving theory can be used to explain much of Bear's observed behavior. Current calving theory suggests that active calving is initiated when a glacier terminus thins to a critical thickness, (i.e. Tnb plus an additional but limited thickness of ice such as 50 m [Tnb+ 50 m]). The thinning of Bear Glacier during much of the 20th century resulted in it approaching this thickness. In a freshwater lake with a depth of ~75 m, active calving would be initiated when Tnb + 50 m was about 120 m, continuing as the glacier thinned to <100 m. With further thinning, Bear Glacier would transition to a regime dominated by passive calving (disarticulation). This condition was initiated sometime after the mid-1990s, when Bear Glacier became significantly thinner than Tnb. Glacier ice floats because its density is at least 8% less than that of freshwater or saltwater. As Bear Glacier thinned to Tnb (approximately 85 m), active calving decreased and
Brook, M.; Quincey, D.; Winkler, S.
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
Salvador-Franch, Ferran; Pérez-Sánchez, Jordi; Salvà-Catarineu, Montserrat; Gómez-Ortiz, Antonio
In this communication we present a detailed analysis of the spatial distribution and morphometric characteristics of all the rock glaciers identified in the massifs located in the easternmost fringe of the Eastern Pyrenees. From west to east, this area encompasses the massifs of Puigmal (2910 m)-Bastiments (2881 m)-Costabona (2465 m) and Canigó (2784 m). The presence of rock glaciers in these mountains shows evidence of the cold-climate geomorphological processes that occurred during the Late Pleistocene in the Pyrenees. Moreover, they constitute a paleoclimate indicator of the conditions that occurred during their development. Up to 122 rock glaciers have been identified, either formed by individualized or by complex landforms formed by coalescence units. For each of these units several variables have been determined: a) location: topographic and geomorphological setting, valley and flow aspect, maximum and minimum elevation, slope, maximum and mean slope; b) lithology and morphology: underlying/prevailing lithology, general morphology, surface morphological features, grain size characterization, vegetation cover, degree of preservation, maximum elevation of the surrounding area; and c) morphometry: maximum length of the landform in the flow direction, width, perimeter and total surface. The Puigmal-Bastiments-Costabona massifs, most extensive and higher, concentrate 89% of the landforms, while the Canigó massif encompasses the remaining 11%. Most of them are located on the north slopes (69%), with a significant percentage south exposed (31%). In total, they extend over an area of 985 Ha. The distribution of rock glaciers in the study area presents significant irregularities, with a remarkable asymmetry between slopes in some sections. Consequently, we have also analyzed the dual presence/absence of rock glaciers based on the identification and morphometry of all headwaters that due to their altitude and/or morphotopography could be susceptible to house them
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.
Harper, J. T.; Pfeffer, W. T.; Humphrey, N. F.; Lazar, B.
We present a suite of observations that elucidate the subglacial and englacial conditions leading to an eight fold speed-up of a valley glacier. Data were collected on the 7.5 km long temperate Bench Glacier, Chugach Mountains, Alaska. We documented the speed-up event, which lasted for approximately one week of June, with data that include: 1) subglacial water pressure measured in a grid of 16 closely spaced boreholes to the bed; 2) water pressure measured in an additional 31 boreholes at 14 locations spanning the length of the glacier; 3) discharge of the terminus outlet stream; 4) GPS measurements of surface velocity and elevation at 4 locations spaced along the glacier; 5) optical surveys of the velocity and uplift of a network of 24 stakes; 5) vertical strain along two boreholes; 6) borehole slug and pump tests; and, 7) direct observation of englacial and subglacial water flow via borehole video camera. The speed-up event consisted of a two stage velocity increase to a maximum level eight times the background deformational velocity. The speed-up was associated a slight drop in subglacial water pressure (not a pressure rise). Numerous anomalous events occurred in conjunction with the accelerated sliding, for example: pressure variations that were unusually uniform over space, surface uplift due to bed separation, and an episode of massive up-welling and refreezing of englacial waters. Our interpretation of the speed-up cycle is that it began with an initial enhanced sliding event that propagated up-glacier as an insatiability within a thin but widespread layer of subglacial water. After a small displacement, stability was regained and sliding temporarily terminated. This initial event, however, initiated connections between the bed and a large volume of englacial water contained within void spaces, which caused widespread basal flooding, bed separation, and resumed sliding. Sliding accelerated until well developed drainage pathways were established, leading to
Kowalewski, D. E.; Marchant, D. R.
Growing interest in our planet's climate history has placed a premium on acquiring detailed records of past climate change. Of considerable interest are archives of ancient atmosphere trapped within the debris-covered alpine glaciers of the western Dry Valleys region of Antarctica. The Mullins Valley debris-covered glacier (~8 km in length) is sourced from local snowfall at the steep headwall of the valley. The first 1.2 km of this glacier is generally free of overlying debris except for isolated cobbles and boulders. Thereafter, the ice surface is covered with a thin, continuous sheet of dolerite-rich rubble. Factors that influence the origin and modification of this ice include atmospheric temperature and relative humidity, precipitation, incoming solar radiance, surface albedo, till texture, winds, surface roughness, salts, and secondary ice lenses. We applied a diffusion model to track vapor flux within a sublimation till overlying the Mullins Valley debris-covered glacier, purportedly the world's oldest debris-covered alpine glacier. As input, we used meteorological data from HOBO data loggers that captured climate change and till temperatures. Results show that vapor flows into and out of the sublimation till at rates dependent on the non-linear variation of soil temperature with depth. Sublimation rates along the Mullins Glacier varied as a function of till thickness, local climate (using a calculated regional lapse rate of 0.88°C per 100 m), and till texture. Ice loss during the study interval (November 27, 2006 to December 24, 2006) ranged from as high as 2.12 mm for exposed glacier ice in the upper ablation zone, to as low as 0.01 mm for buried ice beneath till >50 cm in thickness. Averaged over the entire ablation zone (6.7 km2), this yields a net ice-surface lowering of 0.32 mm during the study interval. Numerical modeling suggests that a modest ice accumulation rate at the headwall of ~1 cm a-1 appears sufficient to maintain current ice volumes
Peteet, D. M.; Nichols, J. E.; Moy, C. M.; McGeachy, A.
Corser Bog (60.5296364oN, 145.453858oW), 21 km east of Cordova, AK is a sphagnum-dominated peatland 42 m asl. adjacent to Sheridan Glacier and the Copper River Delta. Deglaciation at 11.5 ka began with shallow pond deposition, reflecting regional warmth with the pioneers Alnus crispa subsp. sinuata, Salix, and ferns colonizing the fresh, mineral soils on the landscape. Continued early Holocene warming/melting of glaciers led to the foundation species Alnus dominance and peatland formation, surrounded by shrubs such as Rubus spectabilis, Sambucus racemosa, and wetland species such as Myrica gale and Potentilla palustris. As Sphagnum peat accumulated, the highest rates of carbon accumulation for a few centuries are represented at 50 g/m2/a, similar to short-term very high rates in the early Holocene throughout the circumboreal region but varying within the early Holocene due to development of local wet, bryophytic environments. A shift to sedge peat regionally along the South-Central Alaskan coast 7.6 - 3.7 ka is paralleled by a more evaporative, drier climate with Rhododendron groenlandicum presence, lower carbon accumulation (13 g/m2/a), and minimal macrofossil preservation, which is paralleled regionally in coastal muskegs both to the northwest and southeast and by a hiatus in a nearby lake record. A cooler, moister climate is evident in Corser Bog with the shift to Sphagnum peat at 3.7 ka, regional shifts from sedge to Sphagnum peat throughout the entire coastline from Yakutat to Girdwood, AK and the demonstration of glacial advances in the region. Alnus pollen markedly increases to 60% in the uppermost sample, indicative of a major signal for glacial recession in this region.
Palacios, David; de Andrés, Nuria; López-Moreno, Juan I.; García-Ruiz, José M.
Deglaciation processes in the upper Gállego Valley, central-southern Pyrenees, were studied using geomorphological mapping and 36Cl cosmogenic dating of moraine and rock glacier boulders, as well as polished bedrock. Although the precise position of the Gállego Glacier during the global last glacial maximum is not known, there is evidence that ice tongues retreated to the headwaters, which caused subdivision of the main glacier into a number of individual glaciers prior to 17 ka. A range of ages (16 to 11 ka) was found among three tributary valleys within the general trend of deglaciation. The retreat rate to cirque was estimated to be relatively rapid (approximately 5 km per ka). The mapped glacial sedimentology and geomorphology appears to support the occurrence of multiple minor advances and retreats, or periods of stasis during the late deglaciation. Geomorphological and geological differences among the tributary valleys, and error estimates associated with the results obtained, prevented unambiguous correlations of the advances with the late Pleistocene cold periods. During the latter advances, small glaciers and rock glaciers developed close to the cirque headwalls, and co-occurred under the same climatic conditions. No evidence for Holocene re-advance was found for any of the three tributary valleys.
Tanarro, Luis Miguel; Palacios, David; Andres, Nuria; María Fernández, Jose
The glacial and periglacial environment - linked to the extensive presence of permafrost- which predominates in the Tröllaskagi Peninsula (NE Iceland), has been conducive to the development of numerous glaciers, covered glaciers and rock glaciers located at most of its valley headwalls. This is the case in the Vidinesdalur valley, north of Hólar, where there is a debris-covered glacier (65°42'N-65°44'N and 18°56'W-19°00'W) at the bottom of the Hóladalur valley, one of its tributary valleys, and an extensive rock glacier at the bottom of the Fremri-Grjótárdalur, another tributary valley to the west. These two valleys have been monitored using digital photogrammetry to evaluate their activity in relation to displacement and velocity rates. As a detailed aerial photo from 1946 and also two orthophotos dated 2000 and 2013 were available, our aim was to study the advance rate of the two glaciers from the changes observed in their morphology at these three dates. The methodological approach adopted consisted of a combination of a geomorphological field survey 2012-2014 and photogrammetric analysis of the available material from these three years. The 1946 photograms were scanned in high resolution and georeferenced in the GIS ArcMap 10.1 (ESRI ArcGIS), using the Georeferencing module, with the 2000-2013 orthophotos as support. Between 49 and 63 control points were used for each photo, located along the outer edges of the glaciers. The transformation, applying a third degree polynomial function, obtained an RMS error of 16.10480 m and 9.42038 m respectively. The geomorphological traits were then digitized and observation of the images was carried out in a CAD environment (Bentley MicroStation V8i), which also allowed us to overlay a grid and work simultaneously with various views, facilitating the detection of possible changes in the surface of the rock glacier. During the 2014 fieldwork the limits and main geomorphological units of the two glaciers were
Larsen Chris F; Burgess, E; Arendt, A.A.; O'Neel, Shad; Johnson, A.J.; Kienholz, C.
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.
Fischer, Mauro; Huss, Matthias; Hoelzle, Martin
.s.l. The resulting geodetic mass balance data reveals that the area-weighted mean of 1420 still existing glaciers amounts to -0.73 m w.e. a-1 for our reference period 1986/87-2009/10. For some main hydrological catchments the mean mass balances range from -0.60 m w.e. a-1 for more maritime areas on the north-facing slopes of the Alps to -1.17 m w.e. a-1 for more continental and inner-Alpine valleys in the southeast of Switzerland. Our comprehensive dataset shows that there is no significant correlation between average glacier surface area and geodetic mass balance. However, the surface slope of the glacier tongue (lowermost 10%), median glacier elevation and mean aspect can - to some extent - explain the observed mass changes. The overall volume loss calculated over the analyzed period is -22.1 km3.
Bassis, J. N.; Ultee, E.; Ma, Y.
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
Staiger, J. W.; Marchant, D. R.; Schaefer, J. M.; Oberholzer, P.; Johnson, J. V.; Lewis, A. R.; Swanger, K. M.
The areal distribution and elevation of glacial drifts in Vernier Valley, southern Victoria Land, are used to reconstruct the Plio-Pleistocene history of upper Ferrar Glacier. 21Ne cosmogenic-nuclide analyses of surface cobbles on four moraines, Ferrar 1, 2, 3, and 4, provide age control. A minimum-age estimate for Ferrar Drifts calculated by assuming zero surface erosion indicates that the oldest moraine, Ferrar 4, was deposited at least ˜ 3400 ka. Our preferred age model, which applies a very conservative erosion rate of 5 cm Ma - 1 in age calculations, suggests that Ferrar 4 is ˜ 4000 ka; Ferrar 3 is ˜ 1200 ka; and Ferrar 2 is ˜ 700 ka. Based on glacial geologic data, Ferrar 1 is modern; cosmogenic ages for cobbles on this moraine suggest a value for nuclide inheritance of ˜ 50 ka. The Ferrar drifts are most easily interpreted in terms of a progressive reduction in the ice-surface elevation of upper Ferrar Glacier during Plio-Pleistocene time. Relative to today, the surface of upper Ferrar Glacier was ˜ 100 to 125 m higher during the Pliocene Climatic Optimum and ˜ 50 m higher during early to mid Quaternary time. Conversely, during MIS 2, the ice-surface elevation of upper Ferrar Glacier was likely no larger than today and may have stood below modern levels. The texture and sedimentology of all Ferrar drifts indicate that during ice recession from Vernier Valley the upper Ferrar Glacier lacked surface-melting ablation zones, even during the Pliocene Climatic Optimum. Results from a simple 2-D glaciological flow-band model demonstrate that upper Ferrar Glacier also lacked basal-melting zones during ice recession. We show that the development of weathering pits and desert varnish on cobbles exposed at the surface of Ferrar drifts varies in accord with cosmogenic age. The mean width and depth of the largest surface pits on boulders from Ferrar drifts increases by ˜ 10 mm Ma - 1 and ˜ 6.7 mm Ma - 1 , respectively; the maximum thickness of desert varnish on
Sagredo, E. A.; Lowell, T. V.; Rupper, S.
Most of the research on causes driving former glacial fluctuations, and the climatic signals involved, has focused on the comparisons of sequences of glacial events in separate regions of the world and their temporal-phasing relationship with terrestrial or extraterrestrial climate-forcing mechanisms. Nevertheless the climatic signals related with these glacial advances are still under debate. This impossibility to resolve these questions satisfactorily have been generally attributed to the insufficiently precise chronologies and unevenly distributed records. However, behind these ideas lies the implicit assumption that glaciers situated in different climate regimes respond uniformly to similar climatic perturbations. This ongoing research is aimed to explore the climate-glacier relationship at regional scale, through the analysis of the spatial variability of glacier sensitivity to climatic change. By applying a Surface Energy Mass Balance model (SEMB) developed by Rupper and Roe (2008) to glaciers located in different climatic regimes, we analyzed the spatial variability of mass balance changes under different baseline conditions and under different scenarios of climatic change. For the sake of this research, the analysis is being focused on the Andes, which in its 9,000 km along the western margin of South America offers an unparalleled climatic diversity. Preliminary results suggest that above some threshold of climate change (a hypothetical uniform perturbation), all the glaciers across the Andes would respond in the “same direction” (advancing or retreating). Below that threshold, glaciers located in some climatic regimes may be insensitive to the specific perturbation. On the other hand, glaciers located in different climatic regimes may exhibit a “different magnitude” of change under a uniform climatic perturbation. Thus, glaciers located in the dry Andes of Perú, Chile and Argentina are more sensitive to precipitation changes than variations in
vanderVeen, Cornelis; Abdalati, Waleed (Technical Monitor)
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
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
... remote Alaskan crab meat processing subcategory. 408.50 Section 408.50 Protection of Environment... PROCESSING POINT SOURCE CATEGORY Remote Alaskan Crab Meat Processing Subcategory § 408.50 Applicability; description of the remote Alaskan crab meat processing subcategory. The provisions of this subpart...
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Bury, John; Bury, Susan
The third book in a series of natural science handbooks for Alaskan students focuses on Alaskan plantlife. The first chapter, on trees, gives general information about trees and explains how to identify and locate trees in the three main Alaskan tree families: pine, willow, and birch. The second chapter, on plants, describes 14 kinds of edible…
Congress of the U.S. Washington, DC. American Indian Policy Review Commission.
Impact of the Alaskan Native Claims Settlement Act (ANCSA) on Alaskan Natives, particularly at village levels, is the focus of a joint task force report on Alaskan Native issues. Prepared for the American Indian Policy Review Commission, the report is the work of representatives from task forces on tribal government, federal, state, and tribal…
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