West Glacier Research Articles

Contribution of loading deformation to the GNSS vertical velocity field in the Chinese mainland

SUMMARYTo obtain the deformation of the solid Earth from a global navigation satellite system (GNSS)-observed velocity field, the loading effect of the surface mass variations should be effectively deducted. However, the GNSS-observed velocity field in mainland China is currently limited only to the loading correction calculated using Gravity Recovery and Climate Experiment (GRACE) spherical harmonic coefficients, which is equivalent to the approximately 300-km smoothed result in the spatial domain; thus, the derived tectonic deformation is inaccurate. Therefore, it is important to study and identify a reasonable method for calculating the loading effect of the surface mass change model and to carry out an effective loading correction of the GNSS velocity field. In this study, the performances of two calculation methods, namely the GRACE spherical harmonic coefficient and Green's function, were analyzed and compared. In addition, we constructed a comprehensive model of the global surface mass variations, calculated the vertical load velocity in mainland China using Green's function method and compared the results with those for the GRACE spherical harmonic products. We found that the difference between the results of the GRACE spherical harmonic coefficient and Green's function methods was more than 1 mm/yr in the North China Plain, implying that the GRACE spherical harmonic coefficient method cannot be used for loading correction of the observed GNSS vertical velocity field. In contrast, the loading effect calculated using Green's function method can be more effectively applied for loading correction of the GNSS vertical velocity field in mainland China. The GNSS-observed velocity exhibited a clear uplift in the North China Plain and the west glacier areas; however, the GNSS velocity fields were significantly reduced after the loading correction, indicating that the observed GNSS vertical velocity fields were mainly caused by the surface mass loading due to the negative correlation between the vertical load velocity and the surface mass changes. Moreover, we found that the loading correction accounted for more than 50 per cent of the GNSS vertical velocity field in most of the glaciated regions in eastern and western China, and the maximum value exceeded 300 per cent, indicating that the loading effect was large. Finally, we obtained the GNSS vertical velocity field for mainland China with a loading correction. Additionally, the spectral characteristics of the time-varying gravity field in mainland China were investigated. The results showed that clear annual, semi-annual and 10-year medium- and long-period signals exist.

Snowpack Distribution Using Topographical, Climatological and Winter Season Index Inputs

A majority of the annual precipitation in many mountains falls as snow, and obtaining accurate estimates of the amount of water stored within the snowpack is important for water supply forecasting. Mountain topography can produce complex patterns of snow distribution, accumulation, and ablation, yet the interaction of topography and meteorological patterns tends to generate similar inter-annual snow depth distribution patterns. Here, we question whether snow depth patterns at or near peak accumulation are repeatable for a 10-year time frame and whether years with limited snow depth measurement can still be used to accurately represent snow depth and mean snow depth. We used snow depth measurements from the West Glacier Lake watershed, Wyoming, USA, to investigate the distribution of snow depth. West Glacier Lake is a small (0.61 km2) windswept (mean of 8 m/s) watershed that ranges between 3277 m and 3493 m. Three interpolation methods were compared: (1) a binary regression tree, (2) multiple linear regression, and (3) generalized additive models. Generalized additive models using topographic parameters with measured snow depth presented the best estimates of the snow depth distribution and the basin mean amounts. The snow depth patterns near peak accumulation were found to be consistent inter-annually with an average annual correlation coefficient (r2) of 0.83, and scalable based on a winter season accumulation index (r2 = 0.75) based on the correlation between mean snow depth measurements to Brooklyn Lake snow telemetry (SNOTEL) snow depth data.

Velocity increases at Cook Glacier, East Antarctica, linked to ice shelf loss and a subglacial flood event

Abstract. Cook Glacier drains a large proportion of the Wilkes Subglacial Basin in East Antarctica, a region thought to be vulnerable to marine ice sheet instability and with potential to make a significant contribution to sea level. Despite its importance, there have been very few observations of its longer-term behaviour (e.g. of velocity or changes at its ice front). Here we use a variety of satellite imagery to produce a time series of ice front position change from 1947 to 2017 and ice velocity from 1973 to 2017. Cook Glacier has two distinct outlets (termed East and West), and we observe the near-complete loss of the Cook West Ice Shelf at some time between 1973 and 1989. This was associated with a doubling of the velocity of Cook West Glacier, which may also be linked to previously published reports of inland thinning. The loss of the Cook West Ice Shelf is surprising given that the present-day ocean climate conditions in the region are not typically associated with catastrophic ice shelf loss. However, we speculate that a more intense ocean climate forcing in the mid-20th century may have been important in forcing its collapse. Since the loss of the Cook West Ice Shelf, the presence of landfast sea ice and mélange in the newly formed embayment appears to be important in stabilizing the glacier front and enabling periodic advances. We also show that the last calving event at the larger Cook East Ice Shelf resulted in the retreat of its ice front into a dynamically important portion of the ice shelf and observe a short-lived increase in velocity of Cook East between 2006 and 2007, which we link to the drainage of subglacial Lake Cook. Taken together, these observations suggest that the velocity, and hence discharge, of Cook Glacier is highly sensitive to changes at its terminus, but a more detailed process-based analysis of this potentially vulnerable region requires further oceanic and bathymetric data.

The sensitivity of snowpack sublimation estimates to instrument and measurement uncertainty perturbed in a Monte Carlo framework

The bulk aerodynamic flux equation is often used to estimate snowpack sublimation since it requires meteorological measurements at only one height above the snow surface. However, to date the uncertainty of these estimates and the individual input variables and input parameters uncertainty have not been quantified. We modeled sublimation for three (average snowpack in 2005, deep snowpack in 2011, and shallow snowpack in 2012) different water years (October 1 to September 30) at West Glacier Lake watershed within the Glacier Lakes Ecosystem Experiments Site in Wyoming.We performed a Monte Carlo analysis to evaluate the sensitivity of modeled sublimation to uncertainties of the input variables and parameters from the bulk aerodynamic flux equation. Input variable time series were uniformly adjusted by a normally distributed random variable with a standard deviation given as follows: 1) the manufacturer’s stated instrument accuracy of 0.3°C for temperature (T), 0.3 m/s for wind speed (Uz), 2% for relative humidity (RH), and 1 mb for pressure (P); 2) 0.0093 m for the aerodynamic roughness length (z0) based on z0 profiles calculations from multiple heights; and 3) 0.08 m for measurement height (z). Often z is held constant; here we used a constant z compared to the ground surface, and subsequently altered z to account for the change in snow depth (ds). The most important source of uncertainty was z0, then RH. Accounting for measurement height as it changed due to snowpack accumulation/ablation was also relevant for deeper snow. Snow surface sublimation uncertainties, from this study, are in the range of 1% to 29% for individual input parameter perturbations. The mean cumulative uncertainty was 41% for the three water years with 55%, 37%, and 32% occurring for the wet, average, and low water years. The top three variables (z varying with ds, z0, and RH) accounted for 74% to 84% of the cumulative sublimation uncertainty.

Submarine landform assemblages and sedimentary processes in front of Spitsbergen tidewater glaciers

New swath-bathymetric data from the inner parts of the three Svalbard fjords Ymerbukta, Trygghamna, and Magdalenefjorden reveal the landform assemblages deposited in front of tidewater glaciers in west and northwest Spitsbergen. Overridden moraines in Ymerbukta, a tributary of Isfjorden in central west Spitsbergen, record several re-advances of the Esmarkbreen glacier at the head of the fjord after deglaciation, and glacial lineations formed in seafloor sediments are indicative of fast ice advance during one of these events. A terminal moraine and associated debris lobe mark the maximum ice extent during the Holocene, which, implied by the presence of crevasse-squeeze ridges, is likely related to a surge of Esmarkbreen. Several De Geer moraines provide evidence for subsequent slow and step-wise retreat. In the adjacent Trygghamna and in Magdalenefjorden in northwest Spitsbergen the landforms are similar but the absence of overridden moraines and glacial lineations shows that the glaciers probably only re-advanced once during the Holocene and that ice flow was relatively slow. Terminal moraines and associated debris lobes mark the maximum extent of these advances and formed during the Little Ice Age (LIA). In Magdalenefjorden the relatively small size of the debris lobe suggests that the ice margin was at its maximum position for only a short period of time, or that sediment availability was restricted during the LIA advance. Similar to Esmarkbreen the retreat phase of the glaciers in Trygghamna and Magdalenefjorden was also characterised by periods of still-stand or small re-advances, although the comparatively small number of De Geer moraines in all three fjords shows that these landforms probably formed much less frequently than previously thought. Sub-bottom profiler data, four sediment cores and six radiocarbon dates from Magdalenefjorden further provide information about the Holocene sedimentary environments in a northwest Spitsbergen fjord. The main source of sediment is glacial meltwater entering the fjord from the surrounding coastline, which has led to the accumulation of thick sequences of fine-grained mud. Stratified and laminated muds record glacier-proximal conditions, probably related to a LIA re-advance of Waggonwaybreen around 300calaBP, where the interplay of a range of glacimarine processes led to the formation of partially rhythmic couplets of one coarser and one finer layer, accumulated at a rate of around 3cma−1. Multiple sandy layers intercalated with the glacimarine mud provide evidence for the occurrence of gravitational mass-flow events like turbidity currents. In ice-distal settings, massive to weakly stratified, occasionally bioturbated mud accumulated at a lower rate of 0.04–0.49cma−1. Occasional clasts and diamictic layers show that the depositional environment in Magdalenefjorden is also influenced by sedimentation from icebergs and sea ice, but the ubiquitous glacimarine mud underscores the predominance of meltwater-related sedimentation in the fjord.

Long-term Change in Ablation Area of Tropical Glaciers by Landsat Data

Glacier meltwater is one of the main water resources in the capital of Bolivia. To understand current situation of glacier decline is crucial for better water resources management. This study investigated temporal and spatial glacial area during the past three decades between 1984 and 2014. Object glaciers were Tuni, Condoriri, and Huayna Potosi West Glacier with Landsat images. Glacier-covered area by Tuni, Condoriri, and Huayna Potosi West Glacier diminished by 70%, 52%, and 50%, individually from 1984 to 2014. Second, we estimated a front altitude and an equilibrium line altitude for each glacier. Front altitudes for three glaciers rise rapidly after 2000. Finally, we evaluated long-term change in ablation area for selected glaciers. Results showed that accumulation area ratio (AAR) increased with decrease in ablation area and this led to decrease in water resources.

氷河融解・質量収支モデルを用いた熱帯Huayna Potosi West氷河の将来展望

本研究ではボリビア多民族国のラパス首都圏の主要な水源となっているHuayna Potosi West氷河を対象として複数の気温上昇シナリオに対する今後30年間の氷河変動と融解量をシミュレーションした．氷河を標高50m毎に分割して質量収支の計算を行った．初期条件となる氷河の断面形状と氷厚は地形データから推定した．モデル計算の結果，現状の気候が続くと仮定する場合，8年後にほぼ平衡状態に達し，30年後の氷河面積は4%，総融解量は52%減少する．また，気候変動に伴い0.024~0.044℃/年の気温上昇が続くと仮定する場合も氷河は消失せず，30年後の氷河面積は21~44%の減少，総融解量は12%の増加から39%の減少と推定された．現在気候の平衡線高度付近における氷河面積が大きいため，平衡線高度の増加に伴い気温上昇に対する30年間の融解量の不確実性が大きいことも示された．

Symposium 9: Rocky Mountain Futures: Preserving, Utilizing, and Sustaining Rocky Mountain Ecosystems

Symposium 9: Rocky Mountain Futures: Preserving, Utilizing, and Sustaining Rocky Mountain Ecosystems

Brief communication "Historical glacier length changes in West Greenland"

Abstract. Past glacier fluctuations provide insight into glacier dynamics, climate change, and the contribution of glaciers to sea-level rise. Here, the length fluctuations since the 19th century of 18 local glaciers in West and South Greenland are presented, extending and updating the study by Weidick (1968). The studied glaciers all showed an overall retreat with an average of 1.2 ± 0.2 km over the 20th century, indicating a general rise of the equilibrium line along the west coast of Greenland during the last century. Furthermore, the average rate of retreat was largest in the first half of the 20th century.

Tracing dissolved O 2 and dissolved inorganic carbon stable isotope dynamics in the Nyack aquifer: Middle Fork Flathead River, Montana, USA

The geochemistry and microbiology of shallow groundwater aquifers is greatly influenced by the concentration of dissolved oxygen gas (DO); however, the mechanisms that consume DO in groundwater (e.g., biotic or abiotic) are often ambiguous. The use of stable isotopes of molecular O 2 (δ 18O-DO), in conjunction with stable isotopes of dissolved inorganic carbon (δ 13C-DIC), has potential to discriminate between the various mechanisms causing DO depletion in subsurface waters. Here we report the results of spatial and seasonal changes in δ 18O-DO and δ 13C-DIC at the Nyack floodplain aquifer along the Middle Fork of the Flathead River near West Glacier, Montana, USA. Over a short, well constrained flow path (∼100 m) near a main recharge zone of the floodplain, the δ 18O-DO consistently increased as DO concentrations decreased with distance from the recharge source. Concurrently, DIC concentrations increased and δ 13C-DIC values decreased. These observations are explained by community respiration coupled with dissolution of calcite from cobbles in the aquifer matrix. When these results are compared to data from wells distributed over the entire floodplain (several km) a much less predictable relationship was observed between DO concentration and δ 18O-DO. Many wells with low DO concentrations (e.g., <125 μmol L −1 or 4 mg L −1) had anomalously low δ 18O-DO values (e.g., <20‰). Mass balance calculations show that approximately equal amounts of O 2 may be contributed to the aquifer by diffusion from the vadose zone and by advection from the river recharge. Calculations presented here suggest that diffusion across a narrow air–water interface can contribute isotopically light δ 18O-DO to the saturated zone. Possible contributions of light δ 18O-DO from other processes, such as isotopic exchange and radial oxygen loss from plant roots in or near the water table, are compared and evaluated.

Chemical mass balance and rates of mineral weathering in a high-elevation catchment, west glacier lake, wyoming

Chemical mass balance and rates of mineral weathering in a high-elevation catchment, west glacier lake, wyoming

Herpetofauna of Glacier National Park

The current distribution of amphibians and reptiles in Glacier National Park, Montana was documented from museum records and field surveys conducted in 1990 to 1992. Eight species were recorded at 141 sites at elevations from 1000 m to 2300 m. Rana luteiventris was the most common amphibian, occurring parkwide to elevations of 1800 m. Ambystoma macrodacEylum occurred in woodlands and wet meadows west of the Continental Divide at elevations between 1050 and 1500 m. This salamander was uncommon on the east side of the park with most sightings recorded in the lower Waterton Valley; none were found in the upper Missouri River drainage. Buto boreas was widely distributed to elevations up to 2250 m, but was not abundant at most locations. Ascaphus truei was found in small, cold, high gradient streams throughout the Middle Fork drainage, but occurred intermittently in the North Fork and upper Missouri ltiver drainages. A single population of A. truei was located in the South Saskatchewan River drainage. The range of Hyla regilla was restricted. Most sightings were made near the community of West Glacier, Montana, or at breeding ponds along the Middle Fork, Flathead River, a few km upstream. Chrysemys picta occurred mostly in the lower Lake McDonald valley at elevations between 1000 and 1120 m. A few turtles were seen in the North Fork drainage south of Polebridge, Montana. Thamnophis elegans was more abundant than the similarly distributed T. sirtalis. The widespread introduction of sport fish in park waters may have reduced amphibian populations in some drainages, notably in some of the high elevation valleys east of the Continental Divide. This content downloaded from 207.46.13.52 on Sat, 22 Oct 2016 04:48:40 UTC All use subject to http://about.jstor.org/terms 18 NORTHWESTERN NATURALIST 78(1) an, and terrestrial habitats. Intensive area searches were employed instead of more rigorous sampling methods (i.e., time-constrained searches, trapping, etc.) to ensure maximum coverage within the budget constraints and time available for the survey. Searches were conducted along major stream courses and their principal tributaries from the valley terminus to tree line. Some sites were revisited during successive years, however, most were searched only once. Sighting data were sorted by drainage within the 4 watersheds in the park (Appendix). Site locations were resolved to the nearest 50 m by UTM coordinates determined from standard 7.5', 1:24,000 USGS quad maps. UTM and elevation data were processed via a Unix-based Sun SPARC IPX Geographic Information System (GIS) running GRASS, Version 4.1. Survey data were used to generate range maps for each species. Adjustments were made during GIS processing of location data to minimize errors in the generation of species range maps arising from habitat variability across similar elevations, and to accommodate special circumstances such as disjunct or geographically restricted species distributions. To deal with variable weather influences, exposures, and radically different microhabitats at the same elevation within a watershed, range maps generated by the GIS excluded the highest 5% of recorded elevations for most species. This adjustment was not made for painted turtles, Chrysemys picta, or Pacific treefrogs, Hyla regilla, because both species occupy restricted geographic and altitudinal ranges in the park. The range map for tailed frogs, Ascaphus truei, includes only streams with documented sightings, because this species occupies a highly disjunct range in Glacier National Park. Frogs and toads were collected with a telescoping capture net fitted with a 25 cm diameter bag of 5 mm mesh size. A small handheld dip net was used for capturing tadpoles and salamander larvae. Captured specimens were identified in the field (Stebbins 1985) and in some cases measured and released. Garter snakes were hand-captured for positive identification and released. Field data included location, weather, water temperatures, habitat types, proximity of fish, and developmental stage of specimens. Field work was limited to daylight hours from late May through September 1990 to 1992. Night searches were not made due to the presence of dangerous predators in the study area; occasional night observations were made opportunistically in the vicinity of back country cabins and field camps. Field investigations were supplemented by examination of specimens and collection records from the Glacier Park Museum. Thirteen other museums issued collection permits for herpetofaunal studies in Glacier National Park also provided data. Because the present survey was undertaken to assess current conditions, museum data were not incorporated into the GIS range maps. However, past sighting and collection records are discussed in the accompanying species accounts.

Chemical fluxes and sensitivity to acidification of two high-elevation catchments in southern Wyoming

Hydrological and chemical fluxes were examined for East and West Glacier Lakes and their adjacent high-elevation (3200—3700 m) catchments in the Snowy Range of southern Wyoming. Both lakes are approximately 3 ha, but the East Glacier catchment (29 ha) is about half the size of West Glacier. Bedrock is primarily quartzite that has been heavily fractured and crossed with mafic intrusions. Precipitation pH averages about 5.4–5.5, and weighted mean acid neutralizing capacities (ANC) of the discharge are about 50 μequiv.1 −1 for East Glacier lake and 39 μequiv.1 −1 for West Glacier, while the respective annual base cation removals are about 36 mequiv. m −2 and 73 mequiv. m −2. Two West Glacier tributary streams average less than 10 μequiv. 1 −1 ANC, but solute concentrations during the early snow melt are more than five times those found in midsummer. It is inferred that these early high concentrations primarily are due to early elution of solutes from the snowpack rather than the displacement of high-concentration groundwater, but the cations may be substantially affected by exchange reactions. Preliminary evaluation suggests that the mean ANC of both lakes would fall below zero if precipitation pH were to fall to 4.2–4.3. Episodic acidity during snowmelt and acidification of tributary streams would likely occur at a somewhat higher precipitation pH.

Sulfur isotope dynamics in a high-elevation catchment, West Glacier lake, Wyoming

Stable isotopes of S are used in conjunction with dissolved SO 4 2- concentrations to evaluate the utility of δ 34S ratios in tracing contributions of bedrock-derived S to SO 4 2- in runoff. Water samples were collected over the annual hydrograph from two tributaries in the West Glacier Lake, Wyoming, catchment. Concentrations of SO 4 2- ranged from 12.6 to 43.0 μeq L-1; δ 34S ratios ranged from -1.8‰ to +4.9‰. The δ 34S value of atmospherically derived SO 4 2- is about +5.6‰; four samples of pyrite from the bedrock had δ 34S ratios that ranged from +0.7 to +4.1‰. Concentrations of SO4 2- were inversely related to δ 34S and discharge. The data for the tributary with the higher SO 4 2- concentrations were reasonably consistent with mixing between atmospheric S and S from a bedrock source with a δ 34S ratio of about -4.5‰. The difference from the measured bedrock values presumably indicates that S isotopes in the bedrock pyrite are heterogeneously distributed. The data from the tributary with lower SO 4 2- concentrations did not follow a two-component mixing line. Deviation from a two-component mixing line is most likely caused by preferential elution of SO 4 2- from the snowpack during the early stages of snowmelt, although microbially mediated fractionation of S isotopes in the soil zone also may cause the deviation from the mixing line. Sulfur isotopes are useful in identifying whether or not there is a substantial contribution of bedrock S to runoff, but quantifying that contribution is problematic.

Sulfate sources in the Glacier Lakes catchment, Snowy Range, Wyoming, U.S.A.

West Glacier Lake is a small high-elevation (3270 m) dilute (mean SO 4 8.65 μ; alkalinity 37.8 μm) lake underlain by quartzite cut by amphibolite dikes. Estimating the SO 4 budget of the West Glacier Lake catchment requires identification of all sources of S; pyrite in the amphibolite dikes is an intra-basin source. Stable S isotope (δ 34 S) values range from −2.1 to +2.8%o in surface waters, average +1.95%o in bedrock pyrite, and average +5.38%o in snowpack. The isotopic composition of the surface waters is inconsistent with simple mixing of bedrock and atmospheric sources. Seasonal redox transformations by soil microbes during wetting-drying cycles appear to have a major influence on isotopic compositions. Stable S isotopes can be used to quantify the contributions of different SO 4 sources at any instant in time, but biological transformations may make it impossible to calculate the contribution of sulfur from the bedrock on an annual basis.

Least Weasel in Glacier National Park

Journal Article Least Weasel in Glacier National Park Get access R. R. Lechleitner R. R. Lechleitner Ranger Naturalist, West Glacier, Montana Search for other works by this author on: Oxford Academic Google Scholar Journal of Mammalogy, Volume 35, Issue 4, November 1954, Page 594, https://doi.org/10.1093/jmammal/35.4.594a Published: 01 November 1954 Article history Received: 22 September 1953 Published: 01 November 1954