Surge dynamics of Aavatsmarkbreen, Svalbard, inferred from the geomorphological record

Sobota, Ireneusz; Weckwerth, Piotr; Nowak, Marcin

doi:10.1111/bor.12160

Cited by 25 publications

(22 citation statements)

References 77 publications

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“…A connection between glacier surging and till has been established through the observation of till in the forefield of surging glaciers (e.g., Christoffersen et al, ; Evans & Rea, ; Sobota et al, ), through borehole and geophysical observations of the subglacial environment (e.g., Blake et al, ; Harrison & Post, ; Porter et al, ; Truffer et al, ), and through the study of basal ice facies (Sharp et al, ). Till displays both pseudoviscous and Coulomb behavior (e.g., Iverson et al, ; Rathbun et al, ), allowing it to deform plastically above the yield strength, with recoverable elastic strain dominating below the yield strength.…”

Section: Discussionmentioning

confidence: 99%

Bedrock Fracture Characteristics as a Possible Control on the Distribution of Surge‐Type Glaciers

2018

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Glacier surging has been studied extensively and is understood as a dynamic instability at the glacier bed. Yet an explanation for the heterogeneous distribution of surge‐type glaciers at the scale of a mountain range remains elusive. Here we investigate bedrock discontinuity properties in the basins of 16 surge‐type and nonsurge‐type glaciers in the St. Elias Mountains of Yukon, Canada. Using scaled photographs of bedrock outcrops at the margins of each glacier, we digitize traces of the bedrock discontinuities and with automated purpose‐built software, quantify discontinuity properties that are a function of length, orientation, and spacing of bedrock fractures. We obtain an unexpected result: outcrops in the basins of surge‐type glaciers are less fractured than those in the basins of nonsurge‐type glaciers. We hypothesize that the degree of bedrock fracture may control the extent and location of a clast‐rich till transition zone at the glacier bed. This zone would provide flow resistance conducive to the development of an ice reservoir and thus to surging behavior. To reconcile our observations with the global distribution of surge‐type glaciers, we speculate that surge‐type glaciers may occur in geological settings characterized by an intermediate range of bedrock fracture.

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Section: Discussionmentioning

confidence: 99%

Bedrock Fracture Characteristics as a Possible Control on the Distribution of Surge‐Type Glaciers

2018

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“…Several unnamed minor tributaries join the upper half of the main trunk above 250 m a.s.l. Recent observations at the margins of Aavatsmarkbreen have revealed that the glacier is resting on a thin layer of glacial deposits (up to 0.5 m; Sobota et al, ).…”

Section: Study Areasmentioning

confidence: 99%

Tidewater Glacier Surges Initiated at the Terminus

et al. 2018

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There have been numerous reports that surges of tidewater glaciers in Svalbard were initiated at the terminus and propagated up-glacier, in contrast with downglacier-propagating surges of land-terminating glaciers. Most of these surges were poorly documented, and the cause of this behavior was unknown. We present detailed data on the recent surges of two tidewater glaciers, Aavatsmarkbreen and Wahlenbergbreen, in Svalbard. High-resolution time series of glacier velocities and evolution of crevasse patterns show that both surges propagated up-glacier in abrupt steps. Prior to the surges, both glaciers underwent retreat and steepening, and in the case of Aavatsmarkbreen, we demonstrate that this was accompanied by a large increase in driving stress in the terminal zone. The surges developed in response to two distinct processes. (1) During the late quiescent phase, internal thermodynamic processes and/or retreat from a pinning point caused acceleration of the glacier front, leading to the development of terminal crevasse fields.(2) Crevasses allowed surface meltwater and rainwater to access the bed, causing flow acceleration and development of new crevasses up-glacier. Upward migration of the surge coincided with stepwise expansion of the crevasse field. Geometric changes near the terminus of these glaciers appear to have led to greater strain heating, water production, and storage at the glacier bed. Water routing via crevasses likely plays an important role in the evolution of surges. The distinction between internally triggered surges and externally triggered speedups may not be straightforward. The behavior of these glaciers can be understood in terms of the enthalpy cycle model.Many aspects of this class of surges remain poorly known. In particular, it is unclear whether surges of Svalbard tidewater glaciers are driven by similar cyclic internal processes to land-terminating glaciers SEVESTRE ET AL.

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“…; Sobota et al . ). These studies have provided new insights into past glacial and climatic changes in western Spitsbergen.…”

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confidence: 97%

“…Several of these have been inferred to be of surge type, implying that they experience cyclical changes in their flow velocities, triggered by internal mechanisms rather than external forcing, such as climate change (Lefauconnier & Hagen 1991;Solheim 1991;Hagen et al 1993;Ottesen & Dowdeswell 2006;Ottesen et al 2008;Blaszczyk et al 2009;Flink et al 2015;Streuff et al 2015). The dynamics and recent glacial history of the tidewater glaciers in the fjords of western Spitsbergen have been relatively well studied using marine geophysical, sedimentological, remote sensing and field-based methods (Vieli et al 2002;Hald et al 2004;Plassen et al 2004;Ottesen & Dowdeswell 2006;Ottesen et al 2008;Kristensen et al 2009;Baeten et al 2010;Mansell et al 2012;Blaszczyk et al 2013;Kempf et al 2013;Burton et al 2015;Flink et al 2015;Streuff et al 2015;Sobota et al 2016). These studies have provided new insights into past glacial and climatic changes in western Spitsbergen.…”

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confidence: 99%

Holocene glacial evolution of Mohnbukta in eastern Spitsbergen

Flink¹,

Hill²,

Noormets³

et al. 2017

Boreas

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Submarine geomorphology is one of the main tools for understanding past fluctuations of tidewater glaciers. In this study we investigate the glacial history of Mohnbukta, on the east coast of Spitsbergen, Svalbard, by combining multibeam‐bathymetric data, marine sediment cores and remote sensing data. Presently, three tidewater glaciers, Heuglinbreen, Königsbergbreen and Hayesbreen calve into Mohnbukta. Hayesbreen surged at the end of the Little Ice Age, between 1901 and 1910. The submarine landform assemblage in Mohnbukta contains two large transverse ridges, interpreted as terminal moraines, with debrisflow lobes on their distal slopes and sets of well‐preserved geometric networks of ridges, interpreted as crevasse‐squeeze ridges inshore of the moraines. The arrangement of crevasse‐squeeze ridges suggests that both landform sets were produced during surge‐type advances. The terminus position of the 1901–1910 Hayesbreen surge correlates with the inner (R.2) terminal moraine ridge suggesting that the R.1 ridge formed prior to 1901. Marine sediment cores display 14C ages between 5700–7700 cal. a BP derived from benthic foraminifera, from a clast‐rich mud unit. This unit represents pre‐surge unconsolidated Holocene sediments pushed in front of the glacier terminus and mixed up during the 1901 surge. An absence of retreat moraines in the deeper part of the inner basin and the observation of tabular icebergs calving off the glacier front during retreat suggest that the front of Hayesbreen was close to flotation, at least in the deeper parts of the basin. As the MOH15‐01 core does not penetrate into a subglacial till and the foraminifera in the samples were well preserved, the R.1 ridge is suggested to have formed prior to the deposition of the foraminifera. Based on these data we propose that a surge‐type advance occurred in Mohnbukta in the early Holocene, prior to 7700 cal. a BP, which in turn indicates that glaciers can switch to and from surge mode.

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Surge dynamics of Aavatsmarkbreen, Svalbard, inferred from the geomorphological record

Cited by 25 publications

References 77 publications

Bedrock Fracture Characteristics as a Possible Control on the Distribution of Surge‐Type Glaciers

Bedrock Fracture Characteristics as a Possible Control on the Distribution of Surge‐Type Glaciers

Tidewater Glacier Surges Initiated at the Terminus

Holocene glacial evolution of Mohnbukta in eastern Spitsbergen

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