C23A-0580
Quantification of Sediment Transport During Glacier Surges and its Impact on Landform Architecture
Multi-temporal DEMs (Digital Elevation Models) of glaciers and ice streams have successfully been used for extraction of changes in ice volume over time. In this study, we analysed DEMs of the Brúarjökull glacier forefield (Iceland) for 1945, prior to the last surge in 1964, and for 2003 in order to assess the effect of the surge on the sediment architecture in the forefield. The pre- and post-surge DEMs allow direct quantification of the sediment volumes that were re-distributed in the forefield by the surging ice mass in 1964. The surge-type glacier Brúarjökull has experienced six surges during the last four centuries; these are the largest surges known to have occurred in Iceland. During the most recent surge in 1963-64, the glacier advanced 8 km over a period of c. 3 months with a maximum ice flow velocity of 5 m/hr, and 700 km3 of ice were moved downglacier. The continued recession of Brúarjökull since the 1963-64 surge reveals a young landscape consisting of widely spaced and elongated bedrock hills interspaced with shallow sedimentary basins. The majority of the forefield is covered with a basal till sheet or glaciofluvial outwash fans. Mapping of the sediment thickness in the glacier forefield shows higher accumulation along ice marginal positions related to wedge formation during extremely rapid ice flow. Fast flow was sustained by overpressurized water causing sediment-bedrock decoupling beneath a thick sediment sequence that was coupled to the glacier. Elevation differences between the terrain surface in 1945 and 2003 confirm this scenario as huge quantities of sediment was eroded, deformed and transported during the last surge event. On the scale of individual landforms, it appears for a drumlin surface that is has been lowered 20 m from 1945-2003. Dead-ice melting can explain roughly 8 m of this lowering. Thus, the drumlin must have experienced 12 m of subglacial erosion during the 1964 surge. The imprint of at least four landform generations is seen on the present terrain surface. The simplest landscape architecture occurs distal to the 1810 ice margin, where the 1890 surge advanced over hitherto undeformed sediments. Proximal to the 1810 ice margin, the landscape have been transgressed by either one or two glaciers (in 1890 and 1964). The most complex landscape architecture is found proximal to the 1964 ice margin, where the impact of four surges is evident. Thus, the landscape at Brúarjökull is a product of multiple generations of superimposed landforms associated with extensive sediment transport through subglacial deformation.
C23A-0581
Alaska Glacier velocities from L-band InSAR: A basis for change detection
Global totals of ice area and volume for mountain glaciers are small compared to the Antarctic and Greenland ice sheets, however, their present contribution to sea level rise (SLR) is on par with the ice sheets. Alaska Glaciers provide the largest contribution of all mountain glaciers to SLR. We present ice surface velocity maps from L-band interferometric synthetic aperture radar (InSAR) using PALSAR/ALOS data. Results of the Seward and Hubbard glaciers indicate the traditional phase-based InSAR technique is limited due to frequent melt episodes and large precipitation events. However, offset-tracking to measure two-dimensional ice surface displacement produces velocity maps over significant portions of the glaciers even in the presence of documented melt and precipitation events. Complex flow patterns in the upper Seward Glacier formed by the confluence of tributary glaciers and nunatak ridges are evident on the offset- tracking velocity map. Speeds of up to 1.8 and 2.2 km/yr are measured on the Seward and Hubbard glaciers respectively between January and March 2007. Comparison with ice speeds from earlier time periods measured from other remote sensing platforms will also be presented. For example, a preliminary comparison to ice velocities estimated with ERS tandem mission from October 1995 data suggest ice speeds have increased.
C23A-0582
High Resolution Temperature and Precipitation Downscaling for Glacier Modelling
The North American Regional Reanalysis (NARR) provides a high-quality retrospective on climate in the Northwest hemisphere by providing atmospheric variables at 3 hour intervals on a roughly 32 km grid spacing with 29 vertical levels. Despite this fairly high spatial resolution, the NARR data are too widely spaced to directly drive spatially distributed modelling of alpine glaciers, where fine-scale topographic detail generates sharp gradients in temperature and precipitation. Thus, we present techniques for downscaling the two variables of primary interest for glacier mass balance temperature and precipitation. For precipitation, we rely on a linear model of orographic precipitation with modifications for air mass tracking and dynamic calculation of nucleation and fallout timescales. Our temperature downscale calculates free-air and inversion lapse rates and uses these to adjust mid-tropospheric temperature to ground-level on the high- resolution DEM. The regions of focus for our study are southern British Columbia and northern Washington state where observational station density is high. We next perform downscaling over these regions to generate a high resolution 29 year climatology of temperature and precipitation for the years 1979 through 2007. We have validated our downscaling against Environment Canada's observational data, the Global Summary of the Day data set, and snow pillow data for validating precipitation in mountainous terrain. Our downscaling shows good agreement with annual precipitation amounts and mean annual temperatures and captures daily events as well. Downscaled temperature shows best performance in summer likely due to simpler boundary layer structure than winter in which cold air pooling can predominate. The physics based orographic precipitation model significantly improves downscaled precipitation fields in high altitude, mountainous regions. Overall, our downscaling agrees with measured data and can be considered a reliable driver for regional glacier modelling (e.g. Jarosch, A. H. et al., Session C20, AGU FM 2008).
C23A-0583
Mass balance of Potanin glacier, Mongolia Altai
Field observation has conducted at Potanin glacier, Mongolia Altai. There are many glaciers in Altai Mountains which range around border of Mongolia, Russia and China. Although some glaciers in Russian Altay are monitored for several decades, those in Mongolia are not well surveyed. Potanin glacier ranges from 2800 to 4000 m a.s.l. and its length is about 11km. We conducted meteorological observation in ablation area of the glacier. We installed automatic weather station and ablation stakes. Although the accumulation rate data was not obtained in winter, small amount of snowpack was seen at the beginning of ablation season in ablation area. Thus, we assumed mass balance with assuming that accumulation rate is very small in winter. For estimating specific net balance, net balance in each altitude has examined. Our stakes data showed linear trend toward altitude. ELA was roughly estimated as 3600 m.a.s.l.. Accounting for the area allocation, mass balance of Potanin glacier is negative. And it is probable that mass balance of Potanin glacier is in negative trend. This characteristic of mass balance of Potanin glacier is likely to be similar to that of a glacier in Russia Altay.
C23A-0584
Glacier Fluctuations in the Nanga Parbat Region of Western Himalaya
Glaciers in many mountain environments have shown general retreat patterns, most likely due to atmospheric warming. Glaciers in the Western Himalaya are perhaps more complicated than other regions due to their complex topography, extensive supraglacial debris cover, and climate-system coupling involving the westerlies and the monsoon. Consequently, our objectives were to assess glacier fluctuations in the Nanga Parbat Himalaya as a part of the International Global Land Ice Measurements from Space (GLIMS) project. Specifically, we conducted change-detection studies to estimate fluctuation rates. A high-quality topographic map from 1934, Keyhole imagery from the 1970s, SPOT images from 1990 and 2005, and ASTER satellite imagery from 2004 were utilized to identify terminus positions, and triangulation methods were used to account for variations in terminus shape and orientation. Our results indicate that some glaciers are retreating and/or maintaining their frontal position while others have advanced at different time periods. Some of these glaciers have also shown downwasting characteristics in the form of increased frequency and size of supraglacial lakes. Average retreat rates, however, are not nearly as large as those reported in India, the Eastern Himalaya, and the Hindu Kush region. Glacier advances in this region have neither been reported as surge-type glaciers in the past, nor have any shown surge-type patterns; therefore, these advances may be due to positive mass balance. Analysis of climate reanalysis data (ERA40) suggest an increase in precipitation in the region. Nanga Parbat glaciers appear to be oscillating, although a recent retreat pattern can be found. There is an urgent need for regional climate and surface energy-budget modeling to assess these complexities to determine the nature of these oscillations.
C23A-0585
Study of Retreat and Movement of Himalayan Glaciers Using Spaceborne Repeat Pass SAR Data
In this study retreat and movement of Himalayan glaciers using Spaceborne SAR data have been attempted. Gangotri, Siachen, Bara Shigri and Patsio are major glaciers in the Himalayan region which are showing retreat and their respective tributary glaciers are completely disconnected from main body of glaciers. Glacier retreat study will be done using time series coregistered multi temporal SAR data. Simultaneously InSAR coherence thresholding will be applied for tracking snout of Gangotri glacier. Information about dynamism of glaciated terrain can be retrieved by differential interferograms. In this study, movement of Himalayan glaciers will be deciphered using Spaceborne InSAR technique. ERS-1/2 tandem observations showed high correlation on glacier area and hence movement of Siachen and Gangotri glacier are measured for year 1996. Displacement of Gangotri glacier in the radar look direction has been observed as 8.4 cm per day whereas Siachen glacier exhibits a displacement of 22 cm per day (Venkataraman et al. 2005). ERS-1/2 tandem data over all these glaciers show highest correlation over glacier areas but ENVISAT ASAR data shows coherence loss over glacier area due to decorrelation (Vijay et al. 2008). Coherence loss is usual phenomena in glaciated terrain as repeativity of sensor is high (35 days for ENVISAT). A tandem pair of ERS- 1&2 acquired on April 1 and 2, 1996 in descending pass over Siachen shows high coherence than the ascending pair acquired on May 2 and 3, 1996. It is due to change in climate between two acquisitions at glacier locations. Due to the X-band frequency TerraSAR-X interferometry will be more sensitive to orbit errors than current SAR sensors that operate in C-band or L-band (Eineder et al. 2003). A single frequency GPS receiver plus an additional dual-frequency GPS flown as an experimental payload will deliver an orbit accuracy in the order of centimeters. TerraSAR-X will supplement and enhance the InSAR based observations using other satellite data sets because of its high phase to deformation sensitivity, high spatial resolution (1 meter in High Resolution Spot Light Mode) and short (11 day) repeativity.
C23A-0586
Structural Glaciology and Recent Changes of Helheimgletscher and Fenrisgletscher, East Greenland
Drastic changes have been affecting the Greenland Ice Sheet and its outlet glaciers in recent years. While a general trend to increased melting and accelerated ice discharge is apparent, individual glaciers behave quite differently. We present a structural analysis of Helheimgletscher and Fenrisgletscher based on aerial surveys and remote-sensing data to assess their kinematics and dynamics. Our approach combines principles and techniques from structural geology with continuum mechanics and remote sensing to characterize and classify structural units within glaciers. Time series of structural classification and segmentation of a glacier derived from repeat observations provide a detailed record of its kinematic and dynamic development. Helheimgletscher is the only glacier in the Sermilik area of East Greenland that showed significant and prolonged periods of advance during the twentieth century. Our field observations of 2001 revealed that Helheimgletscher was still advancing then. Neighboring Fenrisgletscher, in contrast, was moving and retreating slowly. Since then, Helheimgletscher has changed into a phase of rapid retreat and acceleration of flow. We analyze the most recent changes based on high-resolution remote-sensing imagery.
C23A-0587
Remotely-Sensed Glacial Velocities: Mt. Shasta Advance vs. Sierra Nevada Retreat
Monitoring changes in alpine glaciers is crucial to understanding the impacts of global climate change because alpine glacier systems respond quickly to changes in the earth“s climate. The glaciers of the Sierra Nevada and southern Cascades are of particular interest because they provide a major water reservoir to the state of California. Oddly, while most glaciers worldwide (including in the Sierra Nevada) are retreating, glaciers in northern California are advancing, and examining differences between these two locations will help resolve this paradox. Whereas previous studies have mapped the spatial extents of glaciers from aerial and satellite imagery, this study utilizes glacial velocities as a monitoring tool to examine the differences of the glaciers in the Sierra Nevada and on Mount Shasta. Using the program COSI-Corr in ENVI, horizontal surface ice flow velocities are calculated at the subpixel level from a time-series of co-registered, orthorectified, and correlated, late-summer satellite imagery. Through a combination of 15-meter Advanced Spaceborne Thermal Emission Radiometer (ASTER) and 5-meter SPOT imagery, orthorectified using a 15-meter resampled Shuttle Radar Topographic Mission (SRTM) digital elevation model (DEM), glacial velocities are derived on major glaciers on Mount Shasta and in the Palisades of the Sierra Nevada for 2000-2008. This study demonstrates the utility of combining various types of remote sensing imagery to create a complete time record, and from this record derive glacial velocities for use in monitoring climate change effectively.
C23A-0588
Estimating the future ice sheet hydropower potential in Paakitsoq, Ilulissat, West Greenland
Meltwater running off the Greenland ice sheet yield significant hydropower potentials in catchments bordering the ice sheet, especially in West and South Greenland. Hydropower has been chosen as the most desired source of energy by the Greenland Home Rule, but recent changes in the Greenland ice sheet has emphasized the risk of sudden changes in catchment supply. In this study, we present a thorough investigation of hydropower feasibility at the Paakitsoq basin, near Ilulissat in West Greenland. The catchment is completely dominated by the Greenland ice sheet which provides large quantities of meltwater during the summer season. However, geometrical changes in the ice sheet, for example due to a retreat or an advance of the ice sheet margin, could change the hydrological catchment within the ice sheet. Such a change would have a devastating economical impact as a hydropower plant is a significant long-term investment for an Arctic community of modest population. Here we present a new bedrock and surface map of the Paakitsoq/Swiss Camp part of the Greenland ice sheet and a prediction of the future discharge up to 2080 AD using regional climate model output, dynamic ice sheet modelling and surface melt modelling. The results are aimed at supporting the political decision-making regarding the future energy supply in Greenland.
C23A-0589
Fuzzy Logic and Glacier Dynamics Assessment: New Paradigms for Operational Hazard Detection Systems
Satellite-based remote sensing is critical for monitoring highly dynamic environments that include rapidly changing alpine glaciers, melt-water production, and a variety of natural hazards. Multi-spectral and multi- temporal satellite data in conjunction with digital elevation models can be utilized to assess supraglacial and proglacial lakes, valley impoundment water volumes, and the potential for flood and debris-flow hazards. Advanced remote sensing and GIS-based methodologies represent the only effective approach for periodic assessment and detection of glacier hazards using spatio-temporal data and analysis. Such approaches, however, do not address all of the requirements needed for the development of hazard/disaster warning systems and the generation of unique information to help establish mitigation strategies. Consequently, our objectives are to introduce the methods of fuzzy logic as an additional level of analysis and interpretation to demonstrate how intelligent, knowledge-driven algorithms can be used to assess glacier dynamics and glacier-induced hazards. Operational monitoring of dynamic environments and natural hazards will require multiple levels of analysis and information production using on-board automation. These systems must autonomously assess the hazard potential related to surface processes and the topography, while being able to identify disaster conditions. Such systems should (1) include analytical capabilities to permit automated and comprehensive identification, characterization, and quantification of terrain features (e.g., via Automated Global Feature Analyzer "AGFA"); (2) permit operational multi-scale hazard potential assessment (e.g., automatic global, regional and local assessment capabilities); and (3) permit data integration that fuses existing data and real-time data acquisition into a spatio-temporal framework that facilitates intelligent assessment and monitoring. The fuzzy logic framework may be an ideal approach that serves to represent the intelligent analysis requirement of an operation system because application domain knowledge can be represented in linguistic and numeric form, and can be easily incorporated into a conceptual and numerical model. Such fuzzy systems recently have been proposed as the basis for intelligent, autonomous, science- driven planetary reconnaissance, including systems specifically designed to assess the potential for habitability on Mars and Titan. Here we demonstrate the utility of remote sensing, GIS and fuzzy systems for operational assessment of glacier dynamics and glacier-induced hazards, with an emphasis on design and implementation examples.
C23A-0590
Glacier Retreat in the Cordillera Quimza Cruz (Tres Cruces), Bolivia from 1975 to present
The glaciers in the Cordillera Quimza Cruz (Tres Cruces) and two smaller Bolivian massifs represent the southernmost tropical glaciers found along the eastern margin of the Andes. Their marginal location makes them of particular interest. The extent of glaciers in the mid 1970s was determined though digitization of the published glacier inventory of Bolivia. In 1975, extent of glaciers in the Tres Cruces region was approximately 55.4 square kilometers. More recent extents were determined from Landsat and ASTER satellite images. Cloud-free Landsat images from 1986, 1992 and 2000 were georegistered and surface reflectances were computed. Normalized Difference Snow Index (NDSI) images were then computed and thresholded to create binary maps of snow- and glacier-covered pixels. From 1975 through 2000, the Tres Cruces Region lost a significant amount of its glacier area. Of the area identified as being glacier covered in 1975 only 27.4 square kilometers (49%) were identified as containing snow and ice in Landsat images from 2000. The glacier retreat time series is being updated as part of an ongoing undergraduate research program. More recent retreat mapped from multiple ASTER images from 2000-2006 indicates that glacier recession is continuing. Changes in glacier hypsometries indicate that much of the areal loss has occurred at lower altitudes. The influence of aspect on glacier retreat is the next area of investigation.
C23A-0591
Climatic and Dynamic Influences on Geodetic Mass Malance Estimate of Svalbard
We estimate glacier volume change for 27,000 km2 of the glaciated area of the Svalbard archipelago by comparing 4 years of ICESat elevation data (2003-2007) to older maps and DEMs (1961-1990). We observe significant thinning at glacier fronts (-1 to -3 m a-1), and slight thinning or thickening at higher altitudes (-0.3 to 0.3 m a-1). Exceptions occur within surge-type basins. Marine terminating glaciers experience more extreme thinning than land terminating glaciers, due to calving front retreat. We obtain volume changes over different spatial scales, from drainage basin to regional scale. Thickness change by altitude relationships are integrated over glacier hypsometry to yield a net volume change. Dividing volume change by glacier area and time yields mean geodetic mass balance rates when converted into water equivalents. At the individual glacier scale, dynamical effects such as surges have a major impact on this estimate. For example, two adjacent basins, Hinlopenbreen and Negribreen, have different geodetic mass balances, which can be accounted for by the fact that the former surged in the observation period (extremely negative mass balance) while the latter was in a quiescent phase build up period (almost positive mass balance), respectively. At the regional scale, however, this dynamic influence averages out to permit regional-scale volume change estimation which is more directly tied to climate. We estimate that for the period 1965 to ~2005, Svalbard glaciers (excluding Austfonna) have lost 9.6 ± 1.8 km3 of ice per year, for an average geodetic mass balance of -0.36 ± 0.07 m a-1 w. eq. This amounts to ~0.0278 mm of sea level rise per year, 5% of the total contribution from global glaciers.
C23A-0592
QUANTIFICATION OF GLACIER CHANGES USING ICESAT ELEVATION DATA AND THE SRTM DIGITAL ELEVATION MODEL IN THE WESTERN KARAKORAM HIMALAYA REGION
Although notable rates of glacier retreat have been monitored across the Eastern Himalaya region in recent years, glacier changes due to increases in global air temperature in the Western Karakoram Himalaya are not well documented. The objective of this study is to quantify ice mass changes of major glaciers in the Upper Indus Basin (UIB) of the Western Karakoram Himalaya using ICESat elevation data and Shuttle Radar Topography Mission (SRTM) C-band digital elevation model. ICESat GLA06 elevations data, release 28 over the glaciers in the UIB were examined for the period of 2004-2008. The SRTM 90-meter resolution was used as reference DEM for computing elevation changes since February, 2000. The difference in elevation at each ICESat footprint location was computed by subtracting the SRTM elevation data from the ICESat data. In order to estimate the glacier elevation changes in snow accumulation and ablation zones, the glaciated area was classified as either clean ice or debris-covered ice using Landsat ETM and TM data available for the period of 1990-2001. The elevation differences were then computed for all available ICESat data points in the accumulation and ablation zones at the scale of individual glaciers and sub-watersheds. The preliminary results for the Hunza watershed in the UIB showed that the mean difference for all years combined is +0.64 m/year in the accumulation zone, while +0.01 m/year in the ablation zone. The mean elevation difference from February, 2000 to March, 2008 for two major glaciers (i.e. Hispar and Batura glaciers) in the Hunza watershed showed a mean altitude gain in the ablation and accumulation zones of 0.1 m/year and 0.88 m/year, respectively for the Batura glacier, while a mean altitude loss of 0.91 m/year and mean altitude gain of 1.28 m/year were detected in the ablation and accumulation zones, respectively for the Hispar glacier. Such results show the potential of ICESat data for assessing relief changes on mountain glaciers and could be used in the estimation of glacier mass balance at higher temporal resolutions. Further work will focus on isolating changes in glacier altitude from seasonal snow cover differences through comparisons between ICESat data acquisitions in spring and fall campaigns.
C23A-0593
Geometry changes on the Kronebreen-Holtedahlfonna glacier system, NW Svalbard
Kronebreen is one of Svalbard's fastest glaciers, moving at ~2 m d-1 at its tidewater calving front. The glacier drains an area of ~400 km2, including the Holtedahlfonna ice field and several smaller glaciers. We compile a variety of surface elevation data to calculate geometrical changes that have occurred since the first photogrammetric quality photographs were obtained in the 1960s. Two new DEMs were constructed photogrammetrically from vertical 1:50,000 aerial photographs taken in 1966 and 1990, with common tie points used between the two DEMs to reduce differencing errors. We also use airborne lidar data obtained in 2007, ICEsat data collected in the period 2003-2007, and differential GPS data collected in ground campaigns between 2003 and 2007. There is not full spatial coverage in all of the data; the DEMs have large gaps in the upper accumulation area from poor quality stereo matching, the GPS data do not extend to the lower part of the glacier due to extensive crevassing, the lidar profile is restricted to the centerline, and the ICEsat profiles are relatively widely spaced and do not sample evenly the lower part of Holtedahlfonna. Nevertheless, there are enough data to calculate meaningful elevation changes for two periods, the first from 1966 to 1990, and a recent period, from 1990 to the mid-2000s (data from 2003-2007). In the first period, the glacier surface changes in a pattern widely observed around Svalbard: large elevation decreases at the front and lower glacier, ranging from -3 to -1 m a-1, and a smaller decrease in the upper part of the glacier, ~-0.5 to 0 m a-1. In contrast, the second period shows a surprisingly uniform elevation decrease of ~-0.5 m a-1, from the front to the top of the glacier. In addition, during the same period the calving front of Kronebreen has been stable, in contrast to the earlier period, during which time the front retreated 3.5 km. These recent geometry changes observed on Kronebreen contrast with those on neighboring glaciers, whether tidewater or land-terminating; all are experiencing continued retreat and significant thinning.
C23A-0594
Reconstructing the history of major Greenland glaciers since the Little Ice Age
The Greenland Ice Sheet may have been responsible for rapid sea level rise during the last interglacial period and recent studies indicate that it is likely to make a faster contribution to sea-level rise than previously believed. Rapid thinning and velocity increase has been observed on most major outlet glaciers with terminus retreat that might lead to increased discharge from the interior and consequent further thinning and retreat. Potentially, such behavior could have serious implications for global sea level. However, the current thinning may simply be a manifestation of longer-term behavior of the ice sheet as it responds to the general warming following the Little Ice Age (LIA). Although Greenland outlet glaciers have been comprehensively monitored since the 1980s, studies of long-term changes mostly rely on records of the calving front position. Such records can be misleading because the glacier terminus, particularly if it is afloat, can either advance or retreat as ice further upstream thins and accelerates. To assess whether recent trends deviate from longer-term behavior, we examined three rapidly thinning and retreating outlet glaciers, Jakobshavn Isbrae in west, Kangerdlussuaq Glacier in east and Petermann Glacier in northwest Greenland. Glacier surface and trimline elevations, as well as terminus positions were measured using historical photographs and declassified satellite imagery acquired between the 1940s and 1985. These results were combined with data from historical records, ground surveys, airborne laser altimetry, satellite observations and field mapping of lateral moraines and trimlines, to reconstruct the history of changes since the (LIA) up to the present. We identified several episodes of rapid thinning and ice shelf break-up, including thinning episodes that occurred when the calving front was stationary. Coastal weather station data are used to assess the influence of air temperatures and intensity of surface melting, and to isolate glacier changes likely associated with changes in glacier dynamics. We also examined the potential influence of geologic control, including the effect of increased heat flux and high rates of subglacial melt suggested by geophysical data.
C23A-0595
Global and regional climate modeling with implications for current and future glacier mass balance in the Western Himalaya and the Western Cordillera
Results from regional climate modeling for the Himalayan region are presented with an emphasis on the large scale circulation patterns (such as the monsoon and ENSO) that can impact snow accumulation and glacier mass balance in the western Himalaya between 2000 and 2007. Diagnostic analyses indicate this region to be uniquely sensitive to the respective strengths of the westerlies and the summer monsoon, which is in turn affected by ENSO. Competition between the relatively warm monsoon winds versus the relatively cold westerlies in this region of confluence determine both the summer temperature and summer snow accumulation. Results from a global model configured with a conservative greenhouse gas emission scenario are also presented for 2010-2100. Results from nested regional modeling over North America's Western Cordillera are presented. Initial increases in snow accumulation over high topography during the first 25 years are subsequently dominated by the warming by 2075 with dramatic decreases in accumulation by 2100. Implications for glacier ELAs in the region are discussed.
C23A-0596
Patterns of Glacier Change in the American West
We examine a century of glacier area change in the American West, exclusive of Alaska, using historic
photography, historic maps, and recent aerial photos. Of the approximately 3200 glaciers and permanent
snow masses, we track about 400 glaciers across a region that spans from Washington to California and
Colorado to Montana. All glaciers have retreated since 1900 with the greatest change in Montana (Lewis
Range) and the Sierra Nevada of California, and the least change in Washington including the North
Cascades and the Olympic Peninsula. The pattern since 1970s is more complex, with the majority of
glaciers having retreated since the 1970s, some vastly more than others. The glaciers that exhibit relatively
little retreat are largely restricted to the high stratovolcanoes >3500m in elevation. In these cases we infer
elevated snow accumulation at higher elevations compensates for increased ablation (melt) at lower
elevations. In addition, many of the most stable glaciers are debris covered in their lower elevations, due to
rock fall from the relatively weak volcanic edifice. Small glaciers, <1 km2, show great variability in
their behavior, with a few glaciers at equilibrium or slightly advancing, to the majority retreating, with some
losing 67% of their area. These differences are more difficult to explain. We infer that local
climatic/topographic influences play a dominant role in the magnitude of change while regional climate
patterns control the sign of the change. Temporal patterns of glacier change are very similar across broad
regions while the magnitude of that change is particular to individual glaciers.
http://www.glaciers.us/
C23A-0597
The contribution of glacier melt to stream flow in the Wind River Range, WY
The Wind River Range (Wyoming) boasts the largest concentration of glaciers in the American Rockies, and together with adjacent mountain ranges is the source of several major river systems in the western US. Declines in the volume of these glaciers associated with recent climate warming are well documented. Such declines of alpine glaciers will reduce the amount of water available for agricultural and domestic use, especially in late summer and fall. The contribution of glacial melt to stream flow remains largely unquantified in many parts of the U.S., particularly in Wyoming. In this study, we estimated the fractional contribution of glacier melt water from Dinwoody Glacier to flow in Dinwoody Creek in the Wind River Range on diurnal, seasonal, and interannual time scales. The stable isotope composition of water from the Dinwoody Creek watershed was determined on spatially and temporally intensive scales in 2007 and 2008. Spatially intensive sampling took place in the summers of both years; water samples were collected from (1) above and below major confluences along Dinwoody Creek, from (2) Dinwoody Glacier, (3) rain water, and (4) snow. Stream samples were collected over the entire melt season using an automated stream sampler placed beside an unimpaired USGS gauging station low in the watershed. Glacial melt contributed significantly to stream flow during periods of peak daily discharge (afternoon) and during late summer peak flow (late-August). In 2008, snow persisted late into the summer, so snowmelt was the main source of streamflow in mid-summer (July). Disappearance of glaciers in this watershed will affect both ecosystem and human water supplies during the late summer period, particularly in years when snowfields do not persist late into the summer.
C23A-0598
Metal Concentrations and Hydrochemical Dynamics in a Tropical-Glacier Watershed
The rapid retreat of tropical glaciers and their related changes in hydrology has many implications for water resources, including domestic, agricultural, and industrial consumption water quality. The Cordillera Blanca is especially susceptible to water quality degradation given its abundant natural mineral resources and ongoing mining operations. Here we explore dissolved (<0.4 µm) Al, Fe, Mn, and Zn concentrations and behavior in the glacial-fed headwater region of the Rio Quilcay (9° S, 78° W) a stream that flows into the Rio Santa, Peru. Twenty-four samples were collected in July 2008 from the headwaters of the Rio Quilcay over a distance of 9 km between 4800 m and 3800 m above sea level. Samples were upstream of any mining activity and included the main channel, glacial headwater melt, joining tributaries, and shallow groundwater. Rio Quilcay headwater metal concentrations had broad ranges: (Al= 1.8 to 180 μM, Fe= 1.8 to 3,100 μM, Mn= 5.5 to 180 μM, Zn= 1.3 to 17 μM). Measured pH values had a significant negative correlation with elevation and dissolved Al, Mn, and Zn. However, dissolved Zn also had a significant positive correlation with Al, Fe, and Mn, suggesting possible adsorption of Zn to metal oxide surfaces. The greatest dissolved metal concentrations occurred immediately downstream of a reductive, high-sulfate, water-saturated region in association with the lowest pH values (~3.3). Visible metal precipitation was observed immediately downstream of this reductive environment and at subsequent downstream sites where less acidic tributaries joined the main channel. Dissolved metal concentrations observed in the Rio Quilcay exceed world river averages and are dramatically higher than other headwater streams. For example, both Fe and Mn concentrations were up to three orders of magnitude higher than those observed in tributaries of the Fraser River, British Columbia, Canada (Cameron et al., 1995). The prevalence of water-saturated, shallow groundwater regions in the foreland of tropical glaciers may be important regulators of their metal dynamics and create hydrogeochemical conditions distinct from other glacial systems. Cameron, E. M., Hall, G. E. M., Veizer, J., and Krouse, H. R., 1995. Isotopic and elemental hydrogeochemistry of a major river system: Fraser River, British Columbia, Canada. Chemical Geology 122, 149-169.
C23A-0599
Impact of Upwind Land Cover Change on Mount Kilimanjaro
Studies show local climate in mountain regions are impacted by deforestation at upwind locations. Low land deforestation alters surface energy budget, especially during dry season, altering orographic cloud formation and also surface meteorology at montane locations. While the prior investigations have focused on the effect of low land deforestation on Tropical Montane Cloud Forests, low land deforestation also has the potential to impact alpine glaciers. Retreat of alpine glaciers around the globe has be attributed to global climate change, but at sites such as Kilimanjaro impact of low land deforestation also need to considered. The focus of this study is to address this issue through the use of Regional Atmospheric Modeling System (RAMS) utilizing satellite data to specify realistic land use change scenarios. The atmospheric fields from the RAMS modeling system will be linked to glacier mass energy balance and ice flow model to study the impact of low land deforestation on glacier retreat. The presentation will include details of model development and initial results from the use of the modeling system.
C23A-0600
Adapting to Uncertain Futures: Glacier Recession and Livelihood Vulnerability in the Peruvian Andes
With a large portion of the world's population dependent on hydrologic resources linked to tropical glaciers, the decline of these natural "water towers" has important repercussions for the social and ecological systems that depend on these vital reservoirs of freshwater. In Peru's Cordillera Blanca (the highest and most extensively glaciated range in the tropics) glacial melt water makes up a critical percentage of the discharge of a wide array of water courses, ranging from first-order, highland streams to the Rio Santa, one of the largest and most economically important rivers on Peru's Pacific slope. Climate change-induced warming is occurring rapidly in this region and glaciers have lost a significant percentage of their mass in the past 50 years. While there have been indications that significant and temporary increases in glacial meltwater discharge flows will take place, predictions for the coming decades suggest that these flows will decrease and be more variable across seasons in even the most glaciated catchments of the range. Current population levels and patterns of water use in the Central Andes suggest that many human communities are highly vulnerable to decreasing or variable quantities of water and other changes associated with climate change. Here will be presented the first results from two years of field work assessing human vulnerability to increasing hydrological variability due to glacier-recession and evaluating how changing access to water resources is contributing to livelihood adaptation and potential conflicts over resources in the Cordillera Blanca region of Peru. The findings are drawn from stratified case-study research in two communities and are comprised of an extensive set of key interviews with national, regional and local key informants and semi-structured household surveys that were sampled utilizing stratified systematic unaligned techniques. The results provide insights into key elements of household vulnerability, how households perceive climate-change related glacier recession in the region and the ways in which household livelihoods are already being significantly impacted by these changes. The findings demonstrate that there is significant and very compelling evidence that human vulnerability has been increasing rapidly in the region and serve as an important foundation for the identification of key vectors of social and economic change for future research.