Quiescent-phase evolution of a surge-type glacier: Black Rapids Glacier, Alaska, U.S.A.

Heinrichs, Thomas; Mayo, L.R.; Echelmeyer, Κ. A.; Harrison, W. D.

doi:10.3189/s0022143000030574

Cited by 31 publications

(83 citation statements)

References 25 publications

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“…The pattern and timing of these oscillations are consistent at km 20 and km 14, suggesting strong longitudinal stress coupling in the middle reach of the glacier [ Nolan , 2003]. Heinrichs et al [1996] attributed these flow variations to changes in basal motion rather than ice deformation. The decadal‐scale oscillations on the upper half of the glacier have been large – more than 50% in the case of the km 8 and km 14 survey stations [ Truffer et al , 2005].…”

Section: Settingmentioning

confidence: 92%

“…Black Rapids Glacier is a 40 km long, surge‐type valley glacier in the eastern Alaska Range of interior Alaska (Figure 1). The glacier last surged in 1936–1937 [ Hance , 1937] and has been extensively studied since then [ Péwé , 1951; Post , 1960; Harrison et al , 1975; Heinrichs et al , 1996; Truffer et al , 1999; Rabus and Fatland , 2000; Truffer et al , 2001; Nolan , 2003; Amundson et al , 2006; Shugar et al , 2010; Shugar and Clague , 2011].…”

Section: Settingmentioning

confidence: 99%

“…Since it was first surveyed in 1973, the surface velocity of Black Rapids Glacier has oscillated, with a period of approximately 12 years [ Heinrichs et al , 1996]. The pattern and timing of these oscillations are consistent at km 20 and km 14, suggesting strong longitudinal stress coupling in the middle reach of the glacier [ Nolan , 2003].…”

Section: Settingmentioning

confidence: 99%

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The response of Black Rapids Glacier, Alaska, to the Denali earthquake rock avalanches

Shugar¹,

Rabus²,

Clague³

et al. 2012

J. Geophys. Res.

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[1] We describe the impact of three simultaneous earthquake-triggered rock avalanches on the dynamics of Black Rapids Glacier, Alaska, by using spaceborne radar imagery and numerical modeling. We determined the velocities of the glacier before and after landslide deposition in 2002 by using a combination of ERS-1/ERS-2 tandem, RADARSAT-1, and ALOS PALSAR synthetic aperture radar data. Ice velocity above the debris-covered area of the glacier increased up to 14% after the earthquake but then decreased 20% by 2005. Within the area of the debris sheets, mean glacier surface velocity increased 44% within 2 years of the landslides. At the downglacier end of the lowest landslide, where strong differential ablation produced a steep ice cliff, velocities increased by 109% over the same period. By 2007, ice velocity throughout the debris area had become more uniform, consistent with a constant ice flux resulting from drastically reduced ablation at the base of the debris. Without further analysis, we cannot prove that these changes resulted from the landslides, because Black Rapids Glacier displays large seasonal and interannual variations in velocity. However, a full Stokes numerical ice flow model of a simplified glacier geometry produced a reversal of the velocity gradient from compressional to extensional flow after 5 years, which supports our interpretation that the recent changes in the velocity field of the glacier are related to landslide-induced mass balance changes.

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Section: Settingmentioning

confidence: 92%

Section: Settingmentioning

confidence: 99%

See 1 more Smart Citation

The response of Black Rapids Glacier, Alaska, to the Denali earthquake rock avalanches

Shugar¹,

Rabus²,

Clague³

et al. 2012

J. Geophys. Res.

View full text Add to dashboard Cite

show abstract

“…The baseline vectors were added to estimated ITRF positions for well documented control stations to produce the final coordinates. For sites only measured with EDM and theodolite prior to the earthquake we used preearthquake site coordinates from Heinrichs [1994], reported in a local coordinate system, along with preearthquake GPS derived coordinates (ITRF97) from two sites within the network to tie the local system to universal transverse Mercator (UTM). Details are given by Hreinsdóttir [2005].…”

Section: Gps Data and Analysismentioning

confidence: 99%

“…The sites are distributed along about 9 km of the Denali Fault (about 44.5 to 53.5 km distance along the fault from the epicenter) and are all within 7 km of the fault. Three of these sites had only been measured with EDM and theodolite prior to the earthquake [ Heinrichs , 1994; Hreinsdóttir , 2005]. The sites were displaced parallel to the fault in a right‐lateral sense, with displacements of up to 2.3 ± 0.2 m at a site on the south side of the fault.…”

Section: Coseismic Deformation Of the Denali Fault Earthquakementioning

confidence: 99%

Coseismic deformation of the 2002 Denali Fault earthquake: Insights from GPS measurements

et al. 2006

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[1] We estimate coseismic displacements from the 2002 M w 7.9 Denali Fault earthquake at 232 GPS sites in Alaska and Canada. Displacements along a N-S profile crossing the fault indicate right-lateral slip on a near-vertical fault with a significant component of vertical motion, north-side up. We invert both GPS displacements and geologic surface offsets for slip on a three-dimensional (3-D) fault model in an elastic half-space. We restrict the motion to right-lateral slip and north-side-up dip slip. Allowing for oblique slip along the Denali and Totschunda faults improves the model fit to the GPS data by about 30%. We see mostly right-lateral strike-slip motion on the Denali and Totschunda faults, but in a few areas we see a significant component of dip slip. The slip model shows increasing slip from west to east along the Denali Fault, with four localized higherslip patches, three near the Trans-Alaska pipeline crossing and a large slip patch corresponding to a M w 7.5 subevent about 40 km west of the Denali-Totschunda junction. Slip of 1-3 m was estimated along the Totschunda Fault with the majority of slip being at shallower than 9 km depth. We have limited resolution on the Susitna Glacier Fault, but the estimated slip along the fault is consistent with a M w 7.2 thrust subevent. Total estimated moment in the Denali Fault earthquake is equivalent to M w 7.89. The estimated slip distribution along the surface is in very good agreement with geological surface offsets, but we find that surface offsets measured on glaciers are biased toward lower values.

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Automated detection of unstable glacier flow and a spectrum of speedup behavior in the Alaska Range

Herreid

Truffer

2016

JGR Earth Surface

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Surge‐type glaciers are loosely defined as glaciers that experience periodic alterations between slow and fast flow regimes. Glaciers from a variety of mountain ranges around the world have been classified as surge type, yet consensus of what defines a glacier as surge type has not always been met. A common source of dispute is the lack of a succinct and globally applicable delimiter between a surging and nonsurging glacier. The attempt is often a Boolean classification; however, glacier speedup events can vary significantly with respect to event magnitude, duration, and the fraction of the glacier that participates in the speedup. For this study, we first updated the inventory of glaciers that show flow instabilities in the Alaska Range and then quantified the spectrum of speedup behavior. We developed a new method that automatically detects glaciers with flow instabilities. Our automated results show a 91% success rate when compared to direct observations of speedup events and glaciers that are suspected to display unstable flow based on surface features. Through a combination of observations from the Landsat archive and previously published data, our inventory now contains 36 glaciers that encompass at least one branch exhibiting unstable flow and we document 53 speedup events that occurred between 1936 and 2014. We then present a universal method for comparing glacier speedup events based on a normalized event magnitude metric. This method provides a consistent way to include and quantify the full spectrum of speedup events and allows for comparisons with glaciers that exhibit clear surge characteristics yet have no observed surge event to date. Our results show a continuous spectrum of speedup magnitudes, from steady flow to clearly surge type, which suggests that qualitative classifications, such as “surge‐type” or “pulse‐type” behavior, might be too simplistic and should be accompanied by a standardized magnitude metric.

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Quiescent-phase evolution of a surge-type glacier: Black Rapids Glacier, Alaska, U.S.A.

Cited by 31 publications

References 25 publications

The response of Black Rapids Glacier, Alaska, to the Denali earthquake rock avalanches

The response of Black Rapids Glacier, Alaska, to the Denali earthquake rock avalanches

Coseismic deformation of the 2002 Denali Fault earthquake: Insights from GPS measurements

Automated detection of unstable glacier flow and a spectrum of speedup behavior in the Alaska Range

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