Cosmogenic nuclide exposure age constraints on the glacial history of the Lake Wellman area, Darwin Mountains, Antarctica

2010 ◽  
Vol 22 (6) ◽  
pp. 603-618 ◽  
Author(s):  
B.C. Storey ◽  
D. Fink ◽  
D. Hood ◽  
K. Joy ◽  
J. Shulmeister ◽  
...  
Keyword(s):  
Ross Ice Shelf ◽  
Ice Volume ◽  
Model Interpretation ◽  
Ice Surface ◽  
Exposure Age ◽  
Glacier Ice ◽  
History Of ◽  
Age Model ◽  
Elevation Model ◽  
Exposure Ages

AbstractWe present direct terrestrial evidence of ice volume change of the Darwin and Hatherton glaciers which channel ice from the Transantarctic Mountains into the Ross Ice Shelf. Combining glacial geomorphology with cosmogenic exposure ages from 25 erratics indicates a pre-LGM ice volume at least 600 m thicker than current Hatherton ice elevation was established at least 2.2 million years ago. In particular, five erratics spread across a drift deposit at intermediate elevations located below a prominent moraine feature mapped previously as demarcating the LGM ice advance limits, give a well-constrained single population with mean 10Be age of 37.0 ± 5.5 ka (1σ). At lower elevations of 50–100 m above the surface of Lake Wellman, a further five samples from within a younger drift deposit range in exposure age from 1 to 19 ka. Our preferred age model interpretation, which is partly dependent on the selection of a minimum or maximum age-elevation model, suggests that LGM ice volume was not as large as previously estimated and constrains LGM ice elevation to be within ± 50 m of the modern Hatherton Glacier ice surface, effectively little different from what is observed today.

scholarly journals Melt regimes, stratigraphy, flow dynamics and glaciochemistry of three glaciers in the Alaska Range

2012 ◽  
Vol 58 (207) ◽  
pp. 99-109 ◽  
Author(s):  
Seth Campbell ◽  
Karl Kreutz ◽  
Erich Osterberg ◽  
Steven Arcone ◽  
Cameron Wake ◽  
...  
Keyword(s):  
Ground Penetrating Radar ◽  
Ice Core ◽  
Chemical Diffusion ◽  
Flow Dynamics ◽  
Alaska Range ◽  
Ice Volume ◽  
Glacier Ice ◽  
Age Model ◽  
Ground Penetrating ◽  
Climate Studies

AbstractWe used ground-penetrating radar (GPR), GPS and glaciochemistry to evaluate melt regimes and ice depths, important variables for mass-balance and ice-volume studies, of Upper Yentna Glacier, Upper Kahiltna Glacier and the Mount Hunter ice divide, Alaska. We show the wet, percolation and dry snow zones located below ~2700ma.s.l., at ~2700 to 3900ma.s.l. and above 3900ma.s.l., respectively. We successfully imaged glacier ice depths upwards of 480 m using 40-100 MHz GPR frequencies. This depth is nearly double previous depth measurements reached using mid-frequency GPR systems on temperate glaciers. Few Holocene-length climate records are available in Alaska, hence we also assess stratigraphy and flow dynamics at each study site as a potential ice-core location. Ice layers in shallow firn cores and attenuated glaciochemical signals or lacking strata in GPR profiles collected on Upper Yentna Glacier suggest that regions below 2800ma.s.l. are inappropriate for paleoclimate studies because of chemical diffusion, through melt. Flow complexities on Kahiltna Glacier preclude ice-core climate studies. Minimal signs of melt or deformation, and depth-age model estimates suggesting ~4815 years of ice on the Mount Hunter ice divide (3912ma.s.l.) make it a suitable Holocene-age ice-core location.

Late Pleistocene Cosmogenic 36Cl Glacial Chronology of the Southwestern Ahklun Mountains, Alaska

2001 ◽  
Vol 56 (2) ◽  
pp. 148-154 ◽  
Author(s):  
Jason P. Briner ◽  
Terry W. Swanson ◽  
Marc Caffee
Keyword(s):  
Late Pleistocene ◽  
Outlet Glacier ◽  
Ice Volume ◽  
Ice Cap ◽  
Global Ice Volume ◽  
Exposure Age ◽  
Alpine Glaciers ◽  
Glacial Chronology ◽  
Glacier Advance ◽  
Exposure Ages

AbstractThirty-two cosmogenic 36Cl surface exposure ages constrain the timing of two late Pleistocene glacial advances in the western Ahklun Mountains, southwestern Alaska. Boulders were sampled from one early Wisconsin (sensu lato) and six late Wisconsin moraines deposited by ice-cap outlet glaciers and local alpine glaciers. Four moraine boulders deposited during an extensive early Wisconsin ice-cap outlet glacier advance have a mean surface exposure age of 60,300±3200 yr. A moraine deposited by an ice-cap outlet glacier during the restricted late Wisconsin advance has a mean surface exposure age of 19,600±1400 yr. Five moraines deposited by late Wisconsin alpine glaciers have mean ages that range between 30,000 and 17,000 yr. The 36Cl ages are consistent with limiting 14C and thermoluminescence ages from related deposits and indicate that Ahklun Mountains glaciers reached their most extensive position of the last glaciation early during the late Pleistocene, in contrast to the deep-sea isotopic record of global ice volume.1

scholarly journals Rapid thinning of the Welsh Ice Cap at 20–19 ka Based on 10Be Ages

2016 ◽  
Vol 85 (1) ◽  
pp. 107-117 ◽  
Author(s):  
Philip D. Hughes ◽  
Neil F. Glasser ◽  
David Fink
Keyword(s):  
Arithmetic Mean ◽  
Last Deglaciation ◽  
Mountain Areas ◽  
Ice Cap ◽  
Ice Surface ◽  
Exposure Age ◽  
Vertical Range ◽  
North Wales ◽  
Complete Dataset ◽  
Exposure Ages

New 10Be ages from the summits of three mountain areas of North Wales reveal a very similar exposure timing as the Welsh Ice Cap thinned after the global Last Glacial Maximum. Eight bedrock and one boulder sample gave a combined arithmetic mean exposure age of 19.08 ± 0.80 ka (4.2%, 1σ). Similar exposure ages over a 320 m vertical range (824 to 581 m altitude) show that ice cap thinning was very rapid and spatially uniform. Using the same production rate and scaling scheme, we recalculated six published 10Be exposure ages from the nearby Arans, which also covered a similar elevation range from 608 to 901 m and obtained an arithmetic mean of 19.41 ± 1.45 ka (7.5%, 1σ). The average exposure age of all 15 accepted deglaciation ages is 19.21 ± 1.07 (5.6%, 1σ). The complete dataset from North Wales provides very strong evidence indicating that these summits became exposed as nunataks at 20–19 ka. This result provides important insight to the magnitude of ice surface lowering and behavior of the Welsh Ice Cap during the last deglaciation that can be compared to other ice masses that made up the British-Irish Ice Sheet.

Late Quaternary Ice-Surface Fluctuations of Hatherton Glacier, Transantarctic Mountains

1989 ◽  
Vol 31 (2) ◽  
pp. 229-254 ◽  
Author(s):  
James G. Bockheim ◽  
Scott C. Wilson ◽  
George H. Denton ◽  
Björn G. Andersen ◽  
Minze Stuiver
Keyword(s):  
Late Quaternary ◽  
Marine Isotope Stage ◽  
Ice Shelf ◽  
Ross Ice Shelf ◽  
Ice Surface ◽  
Surface Fluctuations ◽  
Age Model ◽  
Transantarctic Mountains ◽  
Longitudinal Profiles ◽  
Drift Limit

AbstractFormer longitudinal profiles of Hatherton Glacier, an outlet through the Transantarctic Mountains, constrain nearby polar plateau elevations and ice-shelf grounding in the southwestern Ross Embayment. Four gravel drift sheets of late Quaternary age beside Hatherton Glacier are, from youngest to oldest, Hatherton, Britannia I, Britannia II, and Danum. The Hatherton drift limit is uniformly 20 to 70 m above the present ice surface. The Britannia II drift limit is within 100 m of the present surface of uppermost Hatherton Glacier but is 450 m above middle Hatherton Glacier. Extrapolation of this profile downglacier indicates a surface elevation 1100 m above the present Ross Ice Shelf. The Britannia I drift limit is parallel to, but 50–100 m below, Britannia II drift. The Danum drift limit is parallel to, but 50–100 m above, the Britannia II profile. From correlation with drifts near McMurdo Sound and from local 14C dates, we assign an early Holocene age to Hatherton drift, a late Wisconsin age to Britannia drifts, and an age of marine isotope Stage 6 to Danum drift. By our age model, the upper reaches of Hatherton Glacier (and presumably the adjacent polar plateau) have not exceeded their current elevations by more than 100–150 m during the last two complete global glacial-interglacial cycles, whereas the middle and lower reaches of Hatherton Glacier have thickened considerably during the last two global glaciations (late Wisconsin and marine isotope Stage 6). The effect of ice-shelf grounding probably was the major control of these changes of Hatherton Glacier. Holocene ice-surface lowering probably represents the last pulse of grounding-line recession in the southwestern Ross Embayment.

scholarly journals Brief communication: Glacier thickness reconstruction on Mt. Kilimanjaro

2020 ◽  
Author(s):  
Catrin Stadelmann ◽  
Johannes Jakob Fürst ◽  
Thomas Mölg ◽  
Matthias Braun
Keyword(s):  
Ground Truth ◽  
Climatic Changes ◽  
Ice Thickness ◽  
Glacier Area ◽  
Ice Volume ◽  
Satellite Information ◽  
Multi Temporal ◽  
Glacier Ice ◽  
History Of ◽  
Thickness Measurements

Abstract. Glaciers on Kilimanjaro are unique indicators for climatic changes in the tropical mid-troposphere of Africa. The history of severe glacier area loss raises concerns about an imminent future disappearance. Yet, the remaining ice volume is not well known. We reconstruct thickness maps for 2000 and 2011 for the Northern Icefield (NIF) and Kersten Glacier (KG) that are informed by ground-truth thickness measurements and multi-temporal satellite information. For 2011, we find mean thickness values of 26.6 and 9.3 m, respectively. The existing consensus estimate for global glacier ice thickness shows unrealistically thick values for KG in areas that are meanwhile ice-free.

scholarly journals A Whole-Field Interferometric Scheme for Measuring strain and Flow Rates of Glacier and Other Natural Surfaces

1983 ◽  
Vol 29 (103) ◽  
pp. 492-497
Author(s):  
Gary Cloud ◽  
Edgar Conley
Keyword(s):  
Displacement Vector ◽  
Surface Displacement ◽  
Time Lapse ◽  
Speckle Interferometry ◽  
Narrow Beam ◽  
Coherent Light ◽  
Ice Surface ◽  
Glacier Ice ◽  
Fringe Patterns ◽  
Small Overlap

AbstractThe flow of glacier ice is mapped using high-resolution photography and non-coherent-light speckle interferometry. Young’s fringe patterns result when a double-exposed photoplate image of the straining surface is illuminated by a narrow beam of coherent light. Geometry gives a relationship between the ice surface displacement vector and the interference fringe patterns. This displacement vector is corrected for rigid-body (camera) movement and projected onto the ice surface using topological maps. The strain during the time-lapse interval is thus known. Comparison with data acquired by surveying techniques at Nisqually Glacier, Washington, U.S.A., is limited because of small overlap of the surface studied. In the areas for which results can be compared, our experiments yield a flow of 0.6 m/d where conventional methods yield about 0.4 m/d.

Ross Ice Shelf temperatures support a history of ice-shelf thickening

Nature ◽  
1979 ◽  
Vol 282 (5740) ◽  
pp. 703-705 ◽  
Author(s):  
Douglas R. MacAyeal ◽  
Robert H. Thomas
Keyword(s):  
Ice Shelf ◽  
Ross Ice Shelf ◽  
History Of

scholarly journals Airborne fine-resolution UHF radar: an approach to the study of englacial reflections, firn compaction and ice attenuation rates

2015 ◽  
Vol 61 (225) ◽  
pp. 89-100 ◽  
Author(s):  
Cameron Lewis ◽  
Sivaprasad Gogineni ◽  
Fernando Rodriguez-Morales ◽  
Ben Panzer ◽  
Theresa Stumpf ◽  
...  
Keyword(s):  
Dynamic Range ◽  
High Sensitivity ◽  
Ultra Wideband ◽  
West Antarctica ◽  
Ice Shelves ◽  
Ross Ice Shelf ◽  
Transmission Coefficients ◽  
Ice Surface ◽  
Wide Range ◽  
Fine Resolution

AbstractWe have built and operated an ultra-wideband UHF pulsed-chirp radar for measuring firn stratigraphy from airborne platforms over the ice sheets of Greenland and West Antarctica. Our analysis found a wide range of capabilities, including imaging of post firn–ice transition horizons and sounding of shallow glaciers and ice shelves. Imaging of horizons to depths exceeding 600 m was possible in the colder interior regions of the ice sheet, where scattering from the ice surface and inclusions was minimal. The radar’s high sensitivity and large dynamic range point to loss tangent variations as the dominant mechanism for these englacial reflective horizons. The radar is capable of mapping interfaces with reflection coefficients as low as −80 dB near the firn–ice transition and as low as −64 dB at depths of 600 m. We found that firn horizon reflectivity strongly mirrored density variance, a result of the near-unity interfacial transmission coefficients. Zones with differing compaction mechanisms were also apparent in the data. We were able to sound many ice shelves and areas of shallow ice. We estimated ice attenuation rates for a few locations, and our attenuation estimates for the Ross Ice Shelf, West Antarctica, appear to agree well with earlier reported results.

scholarly journals Research on the Tunnel Excavated In Urumqi Glacier No. 1, Tianshan Glaciological Station, China

1987 ◽  
Vol 33 (113) ◽  
pp. 99-104 ◽  
Author(s):  
Huang Maohuan ◽  
Wang Zhongxiang
Keyword(s):  
Melting Point ◽  
Shear Strain ◽  
Maximum Shear Strain ◽  
Ice Surface ◽  
Basal Sliding ◽  
Glacier Ice ◽  
Glacier Motion

AbstractA tunnel was excavated in Urumqi Glacier No. 1, at the Tianshan Glaciological Station. Ice temperature, ice displacement, deformation, and basal sliding, etc. were observed at regular intervals. It is shown that the temperature near the glacier bed is close to the melting point and that the largest proportion of the overall glacier motion is within the lowermost ice layers. The glacier ice is in a state of compression. The maximum shear strain increases towards the entrance of the tunnel, corresponding to the change in slope of the ice surface, and also towards the bedrock.

scholarly journals Morphology and late Cenozoic (<5 Ma) glacial history of the area between David and Mawson Glaciers, Victoria Land, Antarctica

1994 ◽  
Vol 20 ◽  
pp. 55-60
Author(s):  
Anja L.L.M. Verbers ◽  
Volkmar Damm
Keyword(s):  
Ice Sheet ◽  
Field Work ◽  
Topographic Map ◽  
Glacial History ◽  
Ice Surface ◽  
Victoria Land ◽  
Radio Echo Sounding ◽  
History Of ◽  
The Last Glacial Maximum ◽  
The Last Glacial

Glacio-geological field work and radar ice-thickness sounding were carried out in the area between David and Mawson Glaciers. A subglacial topographic map has been compiled from radio-echo-sounding data. The northern part of this map shows that the trench of David Glacier reaches a depth of more than 1000 m below sea level. The area south of David Glacier comprises a landscape of nunatak clusters dissected by glaciated valleys with ice thicknesses as much as 800 m. Subglacial cirques occur at the outer margins of the nunatak clusters. A model for the regional glacial history is proposed. It starts with a major deglaciation in the Pliocene, which results in marine transgression in basins west of the Transantarctic Mountains. During the late Pliocene, the ice advanced towards the northeast, depositing a thin layer of (Sirius Group) till containing reworked mid-Pliocene marine diatoms. Due to accelerated mountain uplift, the ice cut iIlto the pre-Pliocene peneplain, eroding broad valleys. A period of ice-sheet retreat followed to expose a landscape of large nunataks separated by wide valleys. During this period, local cirque glaciation occurred. When the ice sheet advanced again, another phase of uplift forced the glaciers to cut deeper into the valleys. Probably since the Last Glacial Maximum the ice surface has lowered by about 100 m.

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