Improved Estimates Of Glacier Change Rates At Nevado Coropuna Ice Cap, Peru, 2018 Dickinson College
Improved Estimates Of Glacier Change Rates At Nevado Coropuna Ice Cap, Peru, William Hardy Kochtitzky, Benjamin R. Edwards, Ellyn M. Enderlin, Jersy Marino, Nelida Marinque
Faculty and Staff Publications By Year
Accurate quantification of rates of glacier mass loss is critical for managing water resources and for assessing hazards at ice-clad volcanoes, especially in arid regions like southern Peru. In these regions, glacier and snow melt are crucial dry season water resources. In order to verify previously reported rates of ice area decline at Nevado Coropuna in Peru, which are anomalously rapid for tropical glaciers, we measured changes in ice cap area using 259 Landsat images acquired from 1980 to 2014. We find that Coropuna Ice Cap is presently the most extensive ice mass in the tropics, with an area of ...
The Impact Of Reduced Arctic Sea Ice Extent On Cryospheric Snowfall, 2017 University of Nebraska-Lincoln
The Impact Of Reduced Arctic Sea Ice Extent On Cryospheric Snowfall, Alexander Carne
Dissertations & Theses in Earth and Atmospheric Sciences
Satellite observations show that sea ice extent in the Arctic has been declining from 1979 through present day, reaching record minimum extents in 2007 and 2012. Reduced sea ice extent allows for greater expanses of open water to interact with the Arctic atmosphere, potentially leading to changes in the Arctic climate. The greatest declines in Arctic sea ice extent have occurred in summer and autumn. During these seasons, it is likely that the decrease in Arctic sea ice extent led to an increase in atmospheric sensible and latent heat fluxes, possibly leading to increases in Arctic temperature and moisture. Increases ...
Revealing Our Melting Past: Rescuing Historical Snow And Ice Data, 2017 University of Denver
Revealing Our Melting Past: Rescuing Historical Snow And Ice Data, Jack Maness, Ruth Duerr, Michael Dulock, Florence Fetterer, Gloria Hicks, Athea Merredyth, William Sampson, Allaina Wallace
University Libraries Faculty & Staff Contributions
Analog archival data can supplement modern digital research, but only if those data are preserved, described, and migrated to appropriate formats. The National Snow and Ice Data Center (NSIDC) at the University of Colorado Boulder (CU) is responsible for managing, archiving, and disseminating cryospheric and polar data. The clear majority of these data are digital, but the NSIDC also houses a collection of historical archival materials that include measurements related to the earth's glaciated regions prior to the development of modern instrumentation. Their formats, however, are not conducive to contemporary analysis, rendering them ostensibly “lost” to research. This paper ...
Monitoring Tropical Debris-Covered Glacier Dynamics From High-Resolution Unmanned Aerial Vehicle Photogrammetry, Cordillera Blanca, Peru, Oliver Wigmore, Bryan G. Mark
University Libraries Open Access Fund Supported Publications
The glaciers of the Cordillera Blanca, Peru, are rapidly retreating and thinning as a result of climate change, altering the timing, quantity and quality of water available to downstream users. Furthermore, increases in the number and size of proglacial lakes associated with these melting glaciers is increasing potential exposure to glacier lake outburst floods (GLOFs). Understanding how these glaciers are changing and their connection to proglacial lake systems is thus of critical importance. Most satellite data are too coarse for studying small mountain glaciers and are often affected by cloud cover, while traditional airborne photogrammetry and lidar are costly. Recent ...
Raritan Formation (Upper Cretaceous), Long Island, New York: Sedimentological And Geochemical Assessment, Nazrul I. Khandaker, Arif Sikder, Stanley Schleifer, Xin-Chen Liu, Carlos E. Castano Londano, Joseph B. Mcgee Turner
Publications and Research
The lithology of the Upper Cretaceous Raritan Formation (RF) consists of two members: an upper clay member (Raritan clay) and a lower unit, the Lloyd Sand Member. RF is unconformably overlain by upper Pleistocene glacial deposits. The RF consists of stratified white, light- to dark-gray, and red beds and lenses of clay, silt, and sand; lignite and pyrite are common. Variegated, thin to thickly-bedded Lloyd sandstone (LS) is considered to be one of the extensive regional aquifers in Long Island and interpreted to be nearshore, fluvio-deltaic deposit. Proximity to fluvial axes and active deltaic lobes plays an important role in ...
Giovanni Badino (1953-2017), 2017 International Union of speleology
Giovanni Badino (1953-2017), Arrigo Cigna, Paolo Forti
International Journal of Speleology
Short obituary of Giovanni Badino.
Oxygen Isotope Ratios In The Shell Of Mytilus Edulis: Archives Of Glacier Meltwater In Greenland?, 2017 University of Reading
Oxygen Isotope Ratios In The Shell Of Mytilus Edulis: Archives Of Glacier Meltwater In Greenland?, E. A. A. Verteegh, M. E. Blicher, J. Mortensen, S. Rysgaard, T. D. Als, Alan D. Wanamaker
Melting of the Greenland Ice Sheet (GrIS) is accelerating and will contribute significantly to global sea level rise during the 21st century. Instrumental data on GrIS melting only cover the last few decades, and proxy data extending our knowledge into the past are vital for validating models predicting the influence of ongoing climate change. We investigated a potential meltwater proxy in Godthåbsfjord (West Greenland), where glacier meltwater causes seasonal excursions with lower oxygen isotope water (δ18Ow) values and salinity. The blue mussel (Mytilus edulis) potentially records these variations, because it precipitates its shell calcite in oxygen isotopic equilibrium with ambient ...
Odu Scientists Address Antarctic Ice Melt Affecting Sea Levels, 2017 Old Dominion University
Odu Scientists Address Antarctic Ice Melt Affecting Sea Levels, Miasia Osbey
No abstract provided.
The Geography Of Glaciers And Perennial Snowfields In The American West, 2017 Portland State University
The Geography Of Glaciers And Perennial Snowfields In The American West, Andrew G. Fountain, Bryce Glenn, Hassan J. Basagic
Geology Faculty Publications and Presentations
A comprehensive mid-20th century inventory of glaciers and perennial snowfields (G&PS) was compiled for the American West, west of the 100° meridian. The inventory was derived from U.S. Geological Survey 1:24,000 topographic maps based on aerial photographs acquired during 35 years, 1955–1990, of which the first 20 years or more was a cool period with little glacier change. The mapped features were filtered for those greater than 0.01 km2. Results show that 5036 G&PS (672 km2, 14 km3) populate eight states, of which about 1276 (554 km2, 12 km3) are glaciers. Uncertainty is ...
Analyzing Glacier Surface Motion Using Lidar Data, 2017 University of Houston
Analyzing Glacier Surface Motion Using Lidar Data, Jennifer W. Tellig, Craig Glennie, Andrew G. Fountain, David C. Finnegan
Andrew G. Fountain
Understanding glacier motion is key to understanding how glaciers are growing, shrinking, and responding to changing environmental conditions. In situ observations are often difficult to collect and offer an analysis of glacier surface motion only at a few discrete points. Using light detection and ranging (LiDAR) data collected from surveys over six glaciers in Greenland and Antarctica, particle image velocimetry (PIV) was applied to temporally-spaced point clouds to detect and measure surface motion. The type and distribution of surface features, surface roughness, and spatial and temporal resolution of the data were all found to be important factors, which limited the ...
Investigation Of Wing Crack Formation With A Combined Phase-Field And Experimental Approach, 2017 University of Texas at Austin
Investigation Of Wing Crack Formation With A Combined Phase-Field And Experimental Approach, Sanghyun Lee, Jacqueline E. Reber, Nicholas W. Hayman, Mary F. Wheeler
Fractures that propagate off of weak slip planes are known as wing cracks and often play important roles in both tectonic deformation and fluid flow across reservoir seals. Previous numerical models have produced the basic kinematics of wing crack openings but generally have not been able to capture fracture geometries seen in nature. Here we present both a phase-field modeling approach and a physical experiment using gelatin for a wing crack formation. By treating the fracture surfaces as diffusive zones instead of as discontinuities, the phase-field model does not require consideration of unpredictable rock properties or stress inhomogeneities around crack ...
Soft-Bed Experiments Beneath Engabreen, Norway: Regelation Infiltration, Basal Slip And Bed Deformation, 2017 Iowa State University
Soft-Bed Experiments Beneath Engabreen, Norway: Regelation Infiltration, Basal Slip And Bed Deformation, Neal R. Iverson, Thomas S. Hooyer, Urs H. Fischer, Denis Cohen, Peter L. Moore, M. Jackson, G. Lappegard, J. Kohler
To avoid some of the limitations of studying soft-bed processes through boreholes, a prism of simulated till (1.8 m × 1.6 m × 0.45 m) with extensive instrumentation was constructed in a trough blasted in the rock bed of Engabreen, a temperate glacier in Norway. Tunnels there provide access to the bed beneath 213 m of ice. Pore-water pressure was regulated in the prism by pumping water to it. During experiments lasting 7–12 days, the glacier regelated downward into the prism to depths of 50– 80 mm, accreting ice-infiltrated till at rates predicted by theory. During periods of ...
Testing A Glacial Erosion Rule Using Hang Heights Of Hanging Valleys, Jasper National Park, Alberta, Canada, 2017 University of Alaska, Fairbanks
Testing A Glacial Erosion Rule Using Hang Heights Of Hanging Valleys, Jasper National Park, Alberta, Canada, J. M. Amundson, Neal R. Iverson
In most models of glacial erosion, glacier sliding velocity is hypothesized to control rates of bedrock erosion. If this hypothesis is correct, then the elevation difference between hanging and trunk valley floors, the hang height, should be dictated by the relative sliding velocities of the glaciers that occupied these valleys. By considering sliding velocity to be proportional to balance velocity and using mass continuity, hang height is expressed in terms of glacier catchment areas, slopes, and widths, which can be estimated for past glaciers from the morphology of glacial valleys. These parameters were estimated for 46 hanging valleys and their ...
Subglacial Clast/Bed Contact Forces, 2017 Iowa State University
Subglacial Clast/Bed Contact Forces, John Byers, Denis Cohen, Neal R. Iverson
A laboratory device was built to measure the forces that ice exerts on a 0.05 m diameter rigid plastic sphere in two different configurations: in contact with a flat bed or isolated from the bed. Measurements indicated that bed-normal contact forces were 1.8 times larger than drag forces due to creeping flow past a slippery sphere isolated from the bed. Measurements of forces as a function of the bed-normal ice velocity, estimations of the ice viscosity parameter and observations of markers in the ice indicate ice is Newtonian with a viscosity of ∼1.3 × 1011 Pa s. Newtonian ...
Role Of Transient Water Pressure In Quarrying: A Subglacial Experiment Using Acoustic Emissions, 2017 Iowa State University
Role Of Transient Water Pressure In Quarrying: A Subglacial Experiment Using Acoustic Emissions, Denis Cohen, Thomas S. Hooyer, Neal R. Iverson, Jason Thomason, M. Jackson
Probably the most important mechanism of glacial erosion is quarrying: the growth and coalescence of cracks in subglacial bedrock and dislodgement of resultant rock fragments. Although evidence indicates that erosion rates depend on sliding speed, rates of crack growth in bedrock may be enhanced by changing stresses on the bed caused by fluctuating basal water pressure in zones of ice-bed separation. To study quarrying in real time, a granite step, 12 cm high with a crack in its stoss surface, was installed at the bed of Engabreen, Norway. Acoustic emission sensors monitored crack growth events in the step as ice ...
Glacier-Bed Geomorphic Processes And Hydrologic Conditions Relevant To Nuclear Waste Disposal, 2017 Iowa State University
Glacier-Bed Geomorphic Processes And Hydrologic Conditions Relevant To Nuclear Waste Disposal, Neal R. Iverson, Mark Person
Characterizing glaciotectonic deformation, glacial erosion and sedimentation, and basal hydrologic conditions of ice sheets is vital for selecting sites for nuclear waste repositories at high latitudes. Glaciotectonic deformation is enhanced by excess pore pressures that commonly persist near ice sheet margins. Depths of such deformation can extend locally to a few tens of meters, with depths up to approximately 300 m in exceptional cases. Rates of glacial erosion are highly variable (0.05–15 mm a−1), but ratesa−1 are expected in tectonically quiescent regions. Total erosion probably not exceeding several tens of meters is expected during a glacial ...
Rate-Weakening Drag During Glacier Sliding, 2017 University of Wisconsin-Madison
Rate-Weakening Drag During Glacier Sliding, Lucas K. Zoet, Neal R. Iverson
Accurately specifying the relationship between basal drag on a hard, rough glacier bed and sliding speed is a long-standing and central challenge in glaciology. Drag on a rigid bed consisting of steps with linear treads inclined upglacier—a good idealization for the bedrock morphology of some hard-bedded glaciers—has been considered in sliding theories but never studied empirically. Balancing forces parallel to step treads indicates that drag should be independent of sliding speed and cavity size and set by the limit-equilibrium condition sometimes called Iken's bound. In this study we used a large ring-shear device to slide ice at ...
Sliding Of Ice Past An Obstacle At Engabreen, Norway, 2017 University of Minnesota-Twin Cities
Sliding Of Ice Past An Obstacle At Engabreen, Norway, Denis Cohen, Roger Leb. Hooke, Neal R. Iverson, Jack Kohler
At Engabreen, Norway, an instrumented panel containing a decimetric obstacle was mounted flush with the bed surface beneath 210 m of ice. Simultaneous measurements of normaland shear stresses, ice velocity and temperature were obtained as dirty basal ice flowed past the obstacle. Our measurements were broadly consistent with ice thickness, flow conditions and bedrock topography near the site of the experiment. Ice speed 0.45 m above the bed was about 130 mm d–1, much less than the surface velocity of 800 mm d–1. Average normalstress on the panelwas 1.0–1.6 MPa, smaller than the expected ...
Preexisting Fractures And The Formation Of An Iconic American Landscape: Tuolumne Meadows, Yosemite National Park, Usa, 2017 University of Wisconsin-Twin Cities
Preexisting Fractures And The Formation Of An Iconic American Landscape: Tuolumne Meadows, Yosemite National Park, Usa, Richard A. Becker, Basil Tikoff, Paul R. Riley, Neal R. Iverson
Tuolumne Meadows, in Yosemite National Park (USA), is a large sub-alpine meadow in the Sierra Nevada Mountains. Immediately adjacent to Tuolumne Meadows—and underlain by the same bedrock lithology (Cathedral Peak Granodiorite)—are vertical rock faces that provide exceptional opportunities to climbers. While the presence of a broad meadow suggests bedrock erodibility, the vertical rock walls indicate bedrock durability. We propose that the Tuolumne Meadows’s landscape is the result of variable glacial erosion due to the presence or absence of pre-existing bedrock fractures. The meadows and valleys formed because of concentrated tabular fracture clusters—a distinctive and locally pervasive ...
Glacial Landscape Evolution By Subglacial Quarrying: A Multiscale Computational Approach, 2017 Aarhus University
Glacial Landscape Evolution By Subglacial Quarrying: A Multiscale Computational Approach, Sofie V. Ugelvig, David L. Egholm, Neal R. Iverson
Quarrying of bedrock is a primary agent of subglacial erosion. Although the mechanical theory behind the process has been studied for decades, it has proven difficult to formulate the governing principles so that large-scale landscape evolution models can be used to integrate erosion over time. The existing mechanical theory thus stands largely untested in its ability to explain postglacial topography. In this study we relate the physics of quarrying to long-term landscape evolution with a multiscale approach that connects meter-scale cavities to kilometer-scale glacial landscapes. By averaging the quarrying rate across many small-scale bedrock steps, we quantify how regional trends ...