Evolution of Variegated Glacier, Alaska, U.S.A., Prior to its Surge

Raymond, C. F.; Harrison, W. D.

doi:10.3189/s0022143000032184

Cited by 16 publications

(1 citation statement)

References 39 publications

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“…It allows speedup down through the icefall that can propagate and distribute mass down-glacier, but appears to dampen up-glacier propagation of speedup and dynamic thinning, shielding the upper northern tributary from velocity and mass fluctuations associated with the surge (Felikson and others, 2017). Icefalls that kinematically shield upper regions of glaciers from surges have been documented on Medvezhiy Glacier and Variegated Glacier (Raymond, 1987;Raymond and Harrison, 1988). At Medvezhiy Glacier, the surges also initiate from the base of the icefall that feeds its reservoir zone (Raymond, 1987).…”

Section: Speedup Originmentioning

confidence: 99%

Propagating speedups during quiescence escalate to the 2020–2021 surge of Sít’ Kusá, southeast Alaska

Liu,

Enderlin,

Bartholomaus

et al. 2024

J. Glaciol.

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We use satellite image processing techniques to measure surface elevation and velocity changes on a temperate surging glacier, Sít’ Kusá, throughout its entire 2013–2021 surge cycle. We present detailed records of its dynamic changes during quiescence (2013–2019) and its surge progression (2020–2021). Throughout quiescence, we observe order-of-magnitude speedups that propagate down-glacier seasonally from the glacier's upper northern tributary, above a steep icefall, into the reservoir zone for the surging portion of the glacier. The speedups initiate in fall and gradually accelerate through winter until they peak in late spring, ~1 − 2 months after the onset of melt. Propagation distance of the speedups controls the distribution of mass accumulation in the reservoir zone prior to the surge. Furthermore, the intensity and propagation distance of each year's speedup is correlated with the positive degree day sum from the preceding melt season, suggesting that winter melt storage drives the seasonal speedups. We demonstrate that the speedups are kinematically similar to the 2020–2021 surge, differing mainly in that the surge propagates past the dynamic balance line at the lower limit of the reservoir zone, likely triggered by the exceedance of a tipping point in mass accumulation and basal enthalpy in the reservoir zone.

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Section: Speedup Originmentioning

confidence: 99%

Propagating speedups during quiescence escalate to the 2020–2021 surge of Sít’ Kusá, southeast Alaska

Liu,

Enderlin,

Bartholomaus

et al. 2024

J. Glaciol.

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Enthalpy balance theory unifies diverse glacier surge behaviour

2022

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It is commonly asserted that there are two distinct classes of glacier surges: slow, long-duration ‘Svalbard-type’ surges, triggered by a transition from cold- to warm-based conditions (thermal switching), and fast, shorter-duration ‘Alaska-type’ surges triggered by a reorganisation of the basal drainage system (hydraulic switching). This classification, however, reflects neither the diversity of surges in Svalbard and Alaska (and other regions), nor the fundamental dynamic processes underlying all surges. We argue that enthalpy balance theory offers a framework for understanding the spectrum of glacier surging behaviours while emphasising their essential dynamic unity. In this paper, we summarise enthalpy balance theory, illustrate its potential to explain so-called ‘Svalbard-type’ and ‘Alaska-type’ surges using a single set of principles, and show examples of a much wider range of glacier surge behaviour than previously observed. We then identify some future directions for research, including strategies for testing predictions of the theory against field and remote sensing data, and priorities for numerical model development.

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Is there a single surge mechanism? Contrasts in dynamics between glacier surges in Svalbard and other regions

et al. 2003

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[1] During the 1990s, Monacobreen, a 40-km-long tidewater glacier in Svalbard, underwent a major surge. We mapped the surge dynamics using ERS synthetic aperture radar images, differential dual-azimuth interferometry and intensity correlation tracking. A series of 11 three-dimensional (3-D) velocity maps covering the period 1991-1997 show a months-long initiation and years-long termination to the surge, with no indication of a surge front travelling downglacier. During the surge, the front of the glacier advanced $2 km, the velocity and derived strain rate increased by more than an order of magnitude, and maximum ice flow rates measured during 1994 were $5 m d À1 . The spatial pattern of both velocity and strain rate was remarkably consistent and must therefore be controlled by spatially fixed processes operating at the glacier bed. We combine these results with those published in the literature to construct a typical Svalbard glacier surge cycle and compare this to surge dynamics of glaciers from other cluster regions, especially those of Variegated Glacier in Alaska. The strong contrast in dynamics suggests that there exist at least two distinct surge mechanisms.

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Evolution of Variegated Glacier, Alaska, U.S.A., Prior to its Surge

Cited by 16 publications

References 39 publications

Propagating speedups during quiescence escalate to the 2020–2021 surge of Sít’ Kusá, southeast Alaska

Propagating speedups during quiescence escalate to the 2020–2021 surge of Sít’ Kusá, southeast Alaska

Enthalpy balance theory unifies diverse glacier surge behaviour

Is there a single surge mechanism? Contrasts in dynamics between glacier surges in Svalbard and other regions

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