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Articles 1 - 12 of 12
Full-Text Articles in Physical Sciences and Mathematics
Decadal Topographic Change In The Mcmurdo Dry Valleys Of Antarctica: Thermokarst Subsidence, Glacier Thinning, And Transfer Of Water Storage From The Cryosphere To The Hydrosphere, J. S. Levy, Andrew G. Fountain, M. K. Obryk, J. Telling, Craig Glennie, M. Gooseff, David J. Van Horn
Decadal Topographic Change In The Mcmurdo Dry Valleys Of Antarctica: Thermokarst Subsidence, Glacier Thinning, And Transfer Of Water Storage From The Cryosphere To The Hydrosphere, J. S. Levy, Andrew G. Fountain, M. K. Obryk, J. Telling, Craig Glennie, M. Gooseff, David J. Van Horn
Geology Faculty Publications and Presentations
Recent local-scale observations of glaciers, streams, and soil surfaces in the McMurdo Dry Valleys of Antarctica (MDV) have documented evidence for rapid ice loss, glacial thinning, and ground surface subsidence associated with melting of ground ice. To evaluate the extent,magnitude, and location of decadal-scale landscape change in the MDV, we collected airborne lidar elevation data in 2014–2015 and compared these data to a 2001–2002 airborne lidar campaign. This regional assessment of elevation change spans the recent acceleration of warming and melting observed by long-term meteorological and ecosystem response experiments, allowing us to assess the response of MDV surfaces to warming …
Drivers Of Solar Radiation Variability In The Mcmurdo Dry Valleys, Antarctica, Maciej K. Obryk, Andrew G. Fountain, Peter T. Doran
Drivers Of Solar Radiation Variability In The Mcmurdo Dry Valleys, Antarctica, Maciej K. Obryk, Andrew G. Fountain, Peter T. Doran
Geology Faculty Publications and Presentations
Annually averaged solar radiation in the McMurdo Dry Valleys, Antarctica has varied by over 20 W m−2 during the past three decades; however, the drivers of this variability are unknown. Because small differences in radiation are important to water availability and ecosystem functioning in polar deserts, determining the causes are important to predictions of future desert processes. We examine the potential drivers of solar variability and systematically eliminate all but stratospheric sulfur dioxide. We argue that increases in stratospheric sulfur dioxide increase stratospheric aerosol optical depth and decrease solar intensity. Because of the polar location of the McMurdo Dry Valleys …
High-Resolution Elevation Mapping Of The Mcmurdo Dry Valleys, Antarctica, And Surrounding Regions, Andrew G. Fountain, Juan C. Fernandez-Diaz, Maciej K. Obryk, Joseph Levy, Michael N. Gooseff, David J. Van Horn, Paul Morin, Ramesh Shrestha
High-Resolution Elevation Mapping Of The Mcmurdo Dry Valleys, Antarctica, And Surrounding Regions, Andrew G. Fountain, Juan C. Fernandez-Diaz, Maciej K. Obryk, Joseph Levy, Michael N. Gooseff, David J. Van Horn, Paul Morin, Ramesh Shrestha
Geology Faculty Publications and Presentations
We present detailed surface elevation measurements for the McMurdo Dry Valleys, Antarctica derived from aerial lidar surveys flown in the austral summer of 2014–2015 as part of an effort to understand geomorphic changes over the past decade. Lidar return density varied from 2 to > 10 returns m−2with an average of about 5 returns m−2. Vertical and horizontal accuracies are estimated to be 7 and 3 cm, respectively. In addition to our intended targets, other ad hoc regions were also surveyed including the Pegasus flight facility and two regions on Ross Island, McMurdo Station, Scott Base (and surroundings), and the coastal …
Variability In The Mass Flux Of The Ross Sea Ice Streams, Antarctica, Over The Last Millennium, Ginny Catania, Christina L. Hulbe, Howard Conway, Ted A. Scambos, C. F. Raymond
Variability In The Mass Flux Of The Ross Sea Ice Streams, Antarctica, Over The Last Millennium, Ginny Catania, Christina L. Hulbe, Howard Conway, Ted A. Scambos, C. F. Raymond
Geology Faculty Publications and Presentations
We synthesize previously published remote-sensing observations, radar data and model output to obtain a ~1000 year ice flow history for the Siple Coast ice-stream system in West Antarctica to investigate the timing and magnitude of changes in mass flux. The synthesized history shows significant short-term variability in ice-stream shear margin and grounding line position due to internal variability of the coupled system. The chronology highlights the interplay between adjacent ice streams, which implies that the behavior of any individual ice stream should not be examined in isolation. Furthermore, individual events cannot be fully interpreted without an understanding of the broad-scale, …
Marine Ice Modification Of Fringing Ice Shelf Flow, Christina L. Hulbe, R. Johnston, Ian R. Joughin, Ted A. Scambos
Marine Ice Modification Of Fringing Ice Shelf Flow, Christina L. Hulbe, R. Johnston, Ian R. Joughin, Ted A. Scambos
Geology Faculty Publications and Presentations
Locally derived ice is often observed to fill through-cutting rifts and uneven fronts in ice shelves. That ice may nucleate as fast ice at the shelf front, by growth at the sea surface within rifts, or by basal accretion. Here, we investigate the role of such ice in the flow of the Brunt Ice Shelf and adjacent Stancomb-Wills ice tongue, along the Caird Coast of Antarctica. Much of the shelf system is severely rifted, with locally derived ice filling the space between rift walls and around ice rafts. A series of numerical experiments that account for thermal properties of the …
West Antarctic Ice Stream Discharge Variability: Mechanism, Controls, And Pattern Of Grounding Line Retreat, Christina L. Hulbe, Mark A. Fahnestock
West Antarctic Ice Stream Discharge Variability: Mechanism, Controls, And Pattern Of Grounding Line Retreat, Christina L. Hulbe, Mark A. Fahnestock
Geology Faculty Publications and Presentations
West Antarctic ice streams show pronounced flow variability in their downstream reaches, with changes stranding formerly fast-flowing ice and redirecting discharge. A simple model, in which the temperature gradient in basal ice provides control of fast sliding in the downstream reach, can explain this behavior. Downstream thinning steepens the temperature gradient near the bed, increasing upward heat flow and the tendency toward basal freezing. The basal temperature gradient is steepest and the tendency toward basal freezing the strongest in ice that has experienced the most rapid downstream thinning, that is, the fastest-flowing ice. The most ?successful? rapid outflows are regions …
The Role Of Lateral And Vertical Shear In Tributary Flow Toward A West Antarctic Ice Stream, Christina L. Hulbe, Weili Wang, Ian R. Joughin, Martin J. Siegert
The Role Of Lateral And Vertical Shear In Tributary Flow Toward A West Antarctic Ice Stream, Christina L. Hulbe, Weili Wang, Ian R. Joughin, Martin J. Siegert
Geology Faculty Publications and Presentations
Narrow lateral shear margins are the most distinctive visual feature of the West Antarctic ice streams. Large shear stresses within these layers support the majority of the gravitational driving stress within a fast-flowing ice stream.The present contribution looks upstream, to the tributaries that feed ice-stream onsets, and considers the effects of both horizontal and vertical shear on their flow. Numerical and direct simulations of vertical and horizontal shear are used.Vertical shear, simulated using an anisotropic flow law, is of particular interest.We conclude that by isolating overlying ice from large-amplitude variations in bed elevation -vertical shear margins - play an important …
Subglacial Thermal Balance Permits Ongoing Grounding Line Retreat Along The Siple Coast Of West Antarctica, Byron R. Parizek, Richard B. Alley, Christina L. Hulbe
Subglacial Thermal Balance Permits Ongoing Grounding Line Retreat Along The Siple Coast Of West Antarctica, Byron R. Parizek, Richard B. Alley, Christina L. Hulbe
Geology Faculty Publications and Presentations
Changes in the discharge of West Antarctic ice streams are of potential concern with respect to global sea level. The six relatively thin, fast-flowing Ross ice streams are of interest as low-slope end-members among Antarctic ice streams. Extensive research has demonstrated that these "rivers of ice" have a history of relatively high-frequency (óO(100) years), asynchronous discharge variations with evolving lateral boundaries. Amidst this variability, a ~1300 km grounding-line retreat has occurred since the Last GlacialMaximum. Numerical studies of Ice Stream D (Parizek and others, 2002) indicate that a proposed thermal-regulation mechanism(Clarke and Marshall, 1998; Hulbe and MacAyeal,1999; Tulaczyk and others, …
Force Balance Along An Inland Tributary And Onset To Ice Stream D, West Antarctica, Stephen F. Price, R. A. Bindschadler, Christina L. Hulbe, Donald D. Blankenship
Force Balance Along An Inland Tributary And Onset To Ice Stream D, West Antarctica, Stephen F. Price, R. A. Bindschadler, Christina L. Hulbe, Donald D. Blankenship
Geology Faculty Publications and Presentations
The transition from inland- to streaming-style ice flow near to and upstream from the onset to Ice Stream D, West Antarctica, is investigated using the force- balance technique. Basal drag provides the majority of the flow resistance over the study area but is substantially modified by non-local stress gradients. Lateral drag increases with distance downstream, balancing ~50-100% of the driving stress at the onset. Longitudinal stress gradients (LSG) are also found to be significant, an observation that distinguishes ice flow in this region from the inland- and streaming-flow regimes that bound it, in which LSG are usually negligible. LSG decrease …
Researchers Pool Knowledge About Antarctic Dry Valleys, Andrew G. Fountain, Sarah Spaulding
Researchers Pool Knowledge About Antarctic Dry Valleys, Andrew G. Fountain, Sarah Spaulding
Geology Faculty Publications and Presentations
Most of us think of ice when we think of the Antarctic, and rightly so, considering that only 5% of it is ice-free. Dry valleys--the ice-free areas--have sandy, rocky valley floors, ice-covered lakes, and streams that flow only two months of the year. The McMurdo Dry Valleys (78øS 163øE) are the largest of these regions.
Weak Bands Within Ice Stream B, West Antarctica, Christina L. Hulbe, I. M. Whillans
Weak Bands Within Ice Stream B, West Antarctica, Christina L. Hulbe, I. M. Whillans
Geology Faculty Publications and Presentations
Kilometer-scale variations in ice velocity and surface topography are used to investigate the style of glacier deformation in the main body of Ice Stream B, West Antarctica. The pattern is very different from that reported for other glaciers. For the 250 km2 area studied on Ice Stream B, most of the observed deformation occurs within two narrow bands, in which there is large across-flow compression and slow lateral shearing. The bands underlie valleys in the ice-surface topography. Measured upward displacement of ice adjacent to the rapidly compressing bands appears to be linked to the creation of the ice stream's topography. …
An Ice-Shelf Model Test Based On The Ross Ice Shelf, D. R. Macayeal, V. Rommelaere, P. Huybrechts, Christina L. Hulbe, J. Determann, C. Ritz
An Ice-Shelf Model Test Based On The Ross Ice Shelf, D. R. Macayeal, V. Rommelaere, P. Huybrechts, Christina L. Hulbe, J. Determann, C. Ritz
Geology Faculty Publications and Presentations
A standard numerical experiment featuring the Ross Ice Shelf, Antarctica, is presented as a test package for the development and intercomparison of ice-shelf models. The emphasis of this package is solution of stress-equilibrium equations for an ice-shelf velocity consistent with present observations. As a demonstration, we compare five independently developed ice-shelf models based on finite-difference and finite-element methods. Our results suggest that there is little difference between finite-element and finite-difference methods in capturing the basic, large-scale flow features of the ice shelf. We additionally show that the fit between model and observed velocity depends strongly on the ice-shelf temperature field …