Macro- and micro-sedimentology of a modern melt-out till - Matanuska Glacier, Alaska, USA

Boreas ◽  
2015 ◽  
Vol 45 (2) ◽  
pp. 235-251 ◽  
Author(s):  
Grahame J. Larson ◽  
John Menzies ◽  
Daniel E. Lawson ◽  
Edward B. Evenson ◽  
Nathan R. Hopkins
Keyword(s):  
Matanuska Glacier

An intelligent algorithm for autonomous scientific sampling with the VALKYRIE cryobot

2017 ◽  
Vol 17 (3) ◽  
pp. 247-257 ◽  
Author(s):  
Evan B. Clark ◽  
Nathan E. Bramall ◽  
Brent Christner ◽  
Chris Flesher ◽  
John Harman ◽  
...  
Keyword(s):  
Human Performance ◽  
Autonomous Underwater Vehicles ◽  
Field Performance ◽  
Planetary Science ◽  
Operating Environment ◽  
Intelligent Algorithm ◽  
Future State ◽  
Science Operations ◽  
Wide Range ◽  
Matanuska Glacier

AbstractThe development of algorithms for agile science and autonomous exploration has been pursued in contexts ranging from spacecraft to planetary rovers to unmanned aerial vehicles to autonomous underwater vehicles. In situations where time, mission resources and communications are limited and the future state of the operating environment is unknown, the capability of a vehicle to dynamically respond to changing circumstances without human guidance can substantially improve science return. Such capabilities are difficult to achieve in practice, however, because they require intelligent reasoning to utilize limited resources in an inherently uncertain environment. Here we discuss the development, characterization and field performance of two algorithms for autonomously collecting water samples on VALKYRIE (Very deep Autonomous Laser-powered Kilowatt-class Yo-yoing Robotic Ice Explorer), a glacier-penetrating cryobot deployed to the Matanuska Glacier, Alaska (Mission Control location: 61°42′09.3″N 147°37′23.2″W). We show performance on par with human performance across a wide range of mission morphologies using simulated mission data, and demonstrate the effectiveness of the algorithms at autonomously collecting samples with high relative cell concentration during field operation. The development of such algorithms will help enable autonomous science operations in environments where constant real-time human supervision is impractical, such as penetration of ice sheets on Earth and high-priority planetary science targets like Europa.

scholarly journals Preliminary results of tritium analyses in basal ice, Matanuska Glacier, Alaska, U.S.A.: evidence for subglacial ice accretion

1996 ◽  
Vol 22 ◽  
pp. 126-133 ◽  
Author(s):  
Jeffrey C. Strasser ◽  
Daniel E. Lawson ◽  
Grahame J. Larson ◽  
Edward B. Evenson ◽  
Richard B. Alley
Keyword(s):  
Drainage System ◽  
Supercooled Water ◽  
Ice Formation ◽  
Flowing Water ◽  
Ice Accretion ◽  
Preliminary Results ◽  
Basal Ice ◽  
Basal Zone ◽  
Matanuska Glacier ◽  
Initial Results

The stratified-facies ice of the basal zone of Matanuska Glacier, Alaska. U.S.A., contains significant concentrations of anthropogenic tritium, whereas unaltered englacial-zone ice is devoid of tritium. Supercooled water flowing through subglacial conduits during the melt season likewise contains tritium, as does frazil and other platy ice that nucleates and grows within this subglacially flowing water. These initial results demonstrate net accretion of more than 1.4 m of stratified basal-zone ice since initiation of above-ground, thermonuclear bomb testing in 1952. Furthermore, these results support a theory of basal ice formation by ice accretion and debris entrainment from supercooled water within a distributed subglacial drainage system.

scholarly journals Distinguishing characteristics of Diamictons at the Margin of the Matanuska Glacier, Alaska

1981 ◽  
Vol 2 ◽  
pp. 78-84 ◽  
Author(s):  
Daniel E. Lawson
Keyword(s):  
Grain Size ◽  
Size Distribution ◽  
Internal Structure ◽  
Grain Size Distribution ◽  
Source Material ◽  
Basal Ice ◽  
Gravel Size ◽  
Sediment Flow ◽  
Matanuska Glacier ◽  
Stratigraphic Sequences

The origins of diamictons deposited at the Matanuska Glacier are identified in stratigraphic sequences mainly by the presence or absence of a pebble fabric, internal structure, and variation in gravel-size clast distribution. These properties correlate with major differences in depositional mechanisms and source material. Melt-out till mostly inherits fabric, internal structure, and grain-size distribution from its debris-laden basal ice source. Sediment flow deposits and ice-slope colluvium (deposited by ablational slope processes) have properties developed by resedimentation mechanisms. Melt-out till ranges from structureless to stratified with interspersed lenses and discontinuous laminae, and generally possesses a well-defined pebble fabric. Sediment flow deposits show various combinations of six sedimentologic units with distinct sedimentary features and clast dispersion. Pebble fabric is absent or poorly defined, depending upon the unit's origin. Ice-slope colluvium is usually featureless, except for randomly-dispersed laminated lenses and irregularly-shaped gravelly zones in an otherwise disarrayed assemblage of particles, and is without a pebble fabric.

scholarly journals An investigation of the deforming layer/debris-rich basal-ice continuum, illustrated from three Alaskan glaciers

1995 ◽  
Vol 41 (139) ◽  
pp. 619-633 ◽  
Author(s):  
Jane K. Hart
Keyword(s):  
Simple Shear ◽  
Vertical Deformation ◽  
Longitudinal Deformation ◽  
Geological Record ◽  
Basal Ice ◽  
Fabric Strength ◽  
Matanuska Glacier ◽  
Deformation Patterns ◽  
Subglacial Environments

AbstractThree small Alaskan glaciers with different bed conditions were studied: Exit Glacier had a thin deforming layer and produced subglacial and proglacial glaciotectonic land forms; Childs Glacier also had a thin deforming layer but the upper part was frozen to the ice; Matanuska Glacier had no deforming layer but had subglacial debris-rich ice. Since it has been shown that sediment at the base can account for the majority of ice movement, it is suggested that there is a deforming bed/debris-rich continuum whereby similar processes occur throughout the different subglacial environments. These include: similar longitudinal deformation patterns (compression at the margin, extension and simple shear up-glacier); similar vertical deformation patterns, increase in deformation (and fabric strength) upwards through the sequence (leading to the attenuation of stratified ice into dispersed ice); and similar and interrelated incorporation processes. The major differences were that the processes occurred at a much faster rate within the deforming layer and that probably only the deforming layer will be recorded in the geological record.

scholarly journals Preliminary results of tritium analyses in basal ice, Matanuska Glacier, Alaska, U.S.A.: evidence for subglacial ice accretion

1996 ◽  
Vol 22 ◽  
pp. 126-133 ◽  
Author(s):  
Jeffrey C. Strasser ◽  
Daniel E. Lawson ◽  
Grahame J. Larson ◽  
Edward B. Evenson ◽  
Richard B. Alley
Keyword(s):  
Drainage System ◽  
Supercooled Water ◽  
Ice Formation ◽  
Flowing Water ◽  
Ice Accretion ◽  
Preliminary Results ◽  
Basal Ice ◽  
Basal Zone ◽  
Matanuska Glacier ◽  
Initial Results

The stratified-facies ice of the basal zone of Matanuska Glacier, Alaska. U.S.A., contains significant concentrations of anthropogenic tritium, whereas unaltered englacial-zone ice is devoid of tritium. Supercooled water flowing through subglacial conduits during the melt season likewise contains tritium, as does frazil and other platy ice that nucleates and grows within this subglacially flowing water. These initial results demonstrate net accretion of more than 1.4 m of stratified basal-zone ice since initiation of above-ground, thermonuclear bomb testing in 1952. Furthermore, these results support a theory of basal ice formation by ice accretion and debris entrainment from supercooled water within a distributed subglacial drainage system.

Isotopic composition of vent discharge from the Matanuska Glacier, Alaska: Implications for the origin of basal ice

1999 ◽  
Author(s):  
Daniel D. Titus ◽  
Grahame J. Larson ◽  
Jeffrey C. Strasser ◽  
Daniel E. Lawson ◽  
Edward B. Evenson ◽  
...  
Keyword(s):  
Isotopic Composition ◽  
Basal Ice ◽  
Matanuska Glacier

scholarly journals Structural control of englacial conduits in the temperate Matanuska Glacier, Alaska, USA

2009 ◽  
Vol 55 (192) ◽  
pp. 681-690 ◽  
Author(s):  
Jason Gulley
Keyword(s):  
Structural Control ◽  
Three Dimensional ◽  
Structural Features ◽  
Principal Stresses ◽  
Overburden Pressure ◽  
Matanuska Glacier

AbstractFourteen englacial conduits were mapped within 2 km of the terminus of the temperate Matanuska Glacier, Alaska, USA, to ice depths of 65 m using speleological techniques. Detailed three-dimensional maps of the conduits were made over 3 years to characterize conduit relationships with glacier structural features and to track conduit evolution through time. All conduits consisted of single unbranching passages that followed fractures in the ice. All conduits were either too constricted to continue or became water-filled at their deepest explored point and were not able to be followed to the glacier bed. Conduit morphology varied systematically with the orientation of the glacier principal stresses, allowing them to be categorized into two broad classes. The first class of conduits were formed by hydrostatic crevasse penetration where a large supraglacial stream intersected longitudinal crevasses. These conduits plunged toward the glacier bed at angles of 30–40°. The second class of conduits formed where smaller streams sank into the glacier on shear crevasses. Many of these conduits changed direction dramatically where they intersected transverse crevasses at depth. These results suggest that the conduits observed in this study formed along fractures and, over their surveyed length, were not affected by gradients in ice overburden pressure.

scholarly journals Glaciohydraulic supercooling: a freeze-on mechanism to create stratified, debris-rich basal ice: I. Field evidence

1998 ◽  
Vol 44 (148) ◽  
pp. 547-562 ◽  
Author(s):  
Daniel E. Lawson ◽  
Jeffrey C. Strasser ◽  
Edward B. Evenson ◽  
Richard B. Alley ◽  
Grahame J. Larson ◽  
...  
Keyword(s):  
Great Lakes ◽  
Growth Rates ◽  
Drainage System ◽  
Laurentian Great Lakes ◽  
Sediment Fluxes ◽  
Frazil Ice ◽  
Heinrich Events ◽  
Basal Ice ◽  
Field Evidence ◽  
Matanuska Glacier

AbstractDebris-laden ice accretes to the base of Matanuska Glacier, Alaska, U.S.A., from water that supercools while flowing in a distributed drainage system tip the adverse slope of an overdeepening. Frazil ice grows in the water column and forms aggregates, while other ice grows on the glacier sole or on substrate materials. Sediment is trapped by this growing ice, forming stratified debris-laden basal ice. Growth rates of >0.l ma−1of debris-rich basal ice are possible. The large sediment fluxes that this mechanism allows may have implications for interpretation of the widespread deposits from ice that flowed through other overdeepenings, including Heinrich events and the till sheets south of the Laurentian Great Lakes.

scholarly journals Magnetic anisotropy and debris-dependent rheological heterogeneity within stratified basal ice

2019 ◽  
Vol 65 (253) ◽  
pp. 770-779 ◽  
Author(s):  
Nathan R. Hopkins ◽  
Edward B. Evenson ◽  
Dario Bilardello ◽  
Richard B. Alley ◽  
Claudio Berti ◽  
...  
Keyword(s):  
Magnetic Susceptibility ◽  
Simple Shear ◽  
Crystal Size ◽  
Spatial Scales ◽  
Ice Sheets ◽  
Unfrozen Water ◽  
Ice Flow ◽  
Basal Ice ◽  
Matanuska Glacier ◽  
Rheological Heterogeneity

AbstractBasal ice of glaciers and ice sheets frequently contains a well-developed stratification of distinct, semi-continuous, alternating layers of debris-poor and debris-rich ice. Here, the nature and distribution of shear within stratified basal ice are assessed through the anisotropy of magnetic susceptibility (AMS) of samples collected from Matanuska Glacier, Alaska. Generally, the AMS reveals consistent moderate-to-strong fabrics reflecting simple shear in the direction of ice flow; however, AMS is also dependent upon debris content and morphology. While sample anisotropy is statistically similar throughout the sampled section, debris-rich basal ice composed of semi-continuous mm-scale layers (the stratified facies) possesses well-defined triaxial to oblate fabrics reflecting shear in the direction of ice flow, whereas debris-poor ice containing mm-scale star-shaped silt aggregates (the suspended facies) possesses nearly isotropic fabrics. Thus, deformation within the stratified basal ice appears concentrated in debris-rich layers, likely the result of decreased crystal size and greater availability of unfrozen water associated with high debris content. These results suggest that variations in debris-content over small spatial scales influence ice rheology and deformation in the basal zone.

scholarly journals Preliminary study of laminated, silt-rich debris bands: Matanuska Glacier, Alaska, U.S.A.

1999 ◽  
Vol 28 ◽  
pp. 261-266 ◽  
Author(s):  
Staci L. Ensminger ◽  
Edward B. Evenson ◽  
Grahame J. Larson ◽  
Daniel E. Lawson ◽  
Richard B. Alley ◽  
...  
Keyword(s):  
Open Fracture ◽  
Ice Growth ◽  
Hydrothermal Quartz ◽  
Sediment Content ◽  
Different Types ◽  
Preliminary Study ◽  
Matanuska Glacier

AbstractSeveral different types of laterally extensive debris bands occur along the western terminus region of the Matanuska Glacier, Alaska, U.S.A. An ice-bed process, which to our knowledge has not previously been recognized and described, forms the most common and most prominent type of debris band at Matanuska Glacier’s terminus. The debris bands are composed of one or several millimeter-thick laminations of silt-rich ice having much higher sediment content than that of the surrounding ice. Samples of these bands and their surrounding englacial ice have been analyzed for anthropogenic tritium (3H), oxygen-18 (δ18O), and deuterium (δD).We interpreted the laminated, silt-rich debris bands as basal fractures, along which silt-laden, glaciohydraulically supercooled and pressurized waters flowed, healing the fractures by ice growth. This process is analogous to the inward growth of hydrothermal quartz from the sides of an open fracture.

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