Glacial effects limiting mountain height

Egholm, David Lundbek; Nielsen, Søren B.; Pedersen, Vivi Kathrine; Lesemann, J E

doi:10.1038/nature08263

Cited by 327 publications

(333 citation statements)

References 39 publications

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“…5B). This latter scenario is particularly relevant as glacial occupation of mountain ranges increases rates of erosion (denudation), generally reducing the elevation of accumulation areas (see Brozović et al, 1997;Whipple et al, 1999;Tomkin, 2003;Mitchell and Montgomery, 2006;Egholm et al, 2009). Thus, where the erosion of upland topography is efficient, and outpaces uplift, glaciers may become smaller over successive glacial cycles (Kaplan et al, 2009).…”

Section: Ice Extent and Evolving Upland Topographymentioning

confidence: 99%

“…This occurs because during an initial phase of glaciation, basin topography is eroded and deepened. This erosion is typically most intense at the ELA where total ice-flux is maximised (Boulton, 1996;Hallet et al, 1996;MacGregor et al, 2000;Anderson et al, 2006), and land surface area therefore becomes concentrated at just this altitude (i.e., a hypsometric maximum develops) (Egholm et al, 2009;Pedersen et al, 2010;Pedersen and Egholm, 2013) (Fig. 6B).…”

Section: Confounding Factorsmentioning

confidence: 99%

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A review of topographic controls on moraine distribution

2014

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Ice-marginal moraines are often used to reconstruct the dimensions of former ice masses, which are then used as proxies for palaeoclimate. This approach relies on the assumption that the distribution of moraines in the modern landscape is an accurate reflection of former ice margin positions during climatically controlled periods of ice margin stability. However, the validity of this assumption is open to question, as a number of additional, nonclimatic factors are known to influence moraine distribution. This review considers the role played by topography in this process, with specific focus on moraine formation, preservation, and ease of identification (topoclimatic controls are not considered). Published literature indicates that the importance of topography in regulating moraine distribution varies spatially, temporally, and as a function of the ice mass type responsible for moraine deposition. In particular, in the case of ice sheets and ice caps ( > 1000 km 2 ), one potentially important topographic control on where in a landscape moraines are deposited is erosional feedback, whereby subglacial erosion causes ice masses to become less extensive over successive glacial cycles. For the marine-terminating outlets of such ice masses, fjord geometry also exerts a strong control on where moraines are deposited, promoting their deposition in proximity to valley narrowings, bends, bifurcations, where basins are shallow, and/or in the vicinity of topographic bumps. Moraines formed at the margins of ice sheets and ice caps are likely to be large and readily identifiable in the modern landscape. In the case of icefields and valley glaciers (10-1000 km 2 ), erosional feedback may well play some role in regulating where moraines are deposited, but other factors, including variations in accumulation area topography and the propensity for moraines to form at topographic pinning points, are also likely to be important. This is particularly relevant where land-terminating glaciers extend into piedmont zones (unconfined plains, adjacent to mountain ranges) where large and readily identifiable moraines can be deposited. In the case of cirque glaciers (< 10 km 2 ), erosional feedback is less important, but factors such as topographic controls on the accumulation of redistributed snow and ice and the availability of surface debris, regulate glacier dimensions and thereby determine where moraines are deposited. In such cases, moraines are likely to be small and particularly susceptible to post-depositional modification, sometimes making them difficult to identify in the modern landscape. Based on this review, we suggest that, despite often being difficult to identify, quantify, and mitigate, topographic controls on moraine distribution should be explicitly considered when reconstructing the dimensions of palaeoglaciers and that moraines should be judiciously chosen before being used as indirect proxies for palaeoclimate (i.e., palaeoclimatic inferences should only be drawn from moraines when topographic controls on mora...

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Section: Ice Extent and Evolving Upland Topographymentioning

confidence: 99%

Section: Confounding Factorsmentioning

confidence: 99%

A review of topographic controls on moraine distribution

2014

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“…The buzzsaw hypothesis states that glacial erosion acts to limit mountain topography, and therefore results in a correlation between peak altitudes and palaeo-ELAs (Brozović et al, 1997;Montgomery et al, 2001;Brocklehurst and Whipple, 2002;Mitchell and Montgomery, 2006;Foster et al, 2008;Egholm et al, 2009;Pedersen et al, 2010). In the Sredinny Mountains, we see a correspondence between peak altitudes and palaeo-ELAs as, when considered for each of the 80 drainage basins, Alt (peak) is positively correlated with both cirq (alt) and gLGM ELA, although the correlation is not exceptionally strong (R = 0.41, and R = 0.27, respectively, see Table 3).…”

Section: Do the Sredinny Mountains Preserve A Record Of The Glacial Bmentioning

confidence: 99%

“…3B) (see Foster et al, 2008). Each hypsometric frequency distribution comprised 40 altitudinal bins (following the method employed by Egholm et al, 2009), and hypsometric maxima (Hmax) were recorded where an altitude bin had greater area than its four closest neighbours (see Fig. 3B).…”

Section: Topographic Attributesmentioning

confidence: 99%

“…Subsequent investigations demonstrated the prevalence of this signature in the mountains of North America (Spotila et al, 2004;Mitchell and Montgomery, 2006;Foster et al, 2008Foster et al, , 2010Ward et al, 2012), South America (Thomson et al, 2010), New Zealand (Brocklehurst and Whipple, 2007), Switzerland (Anders et al, 2010), and at a global scale (Egholm et al, 2009;Pedersen et al, 2010). Deviations from the 'classic' buzzsaw signature have been linked to tectonics and bedrock strength (see Foster et al, 2008Foster et al, , 2010Thomson et al, 2010;Ward et al, 2012) and used to infer the former presence of minimally erosive glaciers (Thomson et al, 2010).…”

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confidence: 99%

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Testing the efficacy of the glacial buzzsaw: insights from the Sredinny Mountains, Kamchatka

Barr

Spagnolo

2014

Geomorphology

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Subglacial extensional fracture development and implications for Alpine Valley evolution

Leith

Moore

Amann³

et al. 2014

JGR Earth Surface

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[1] Bedrock stresses induced through exhumation and tectonic processes play a key role in the topographic evolution of alpine valleys. Using a finite difference model combining the effects of tectonics, erosion, and long-term bedrock strength, we assess the development of near-surface in situ stresses and predict bedrock behavior in response to glacial erosion in an Alpine Valley (the Matter Valley, southern Switzerland). Initial stresses are derived from the regional tectonic history, which is characterized by ongoing transtensional or extensional strain throughout exhumation of the brittle crust. We find that bedrock stresses beneath glacial ice in an initial V-shaped topography are sufficient to induce localized extensional fracturing in a zone extending laterally 600 m from the valley axis. The limit of this zone is reflected in the landscape today by a valley "shoulder," separating linear upper mountain slopes from the deep U-shaped inner valley. We propose that this extensional fracture development enhanced glacial quarrying between the valley shoulder and axis and identify a positive feedback where enhanced quarrying promoted valley incision, which in turn increased in situ stress concentrations near the valley floor, assisting erosion and further driving rapid U-shaped valley development. During interglacial periods, these stresses were relieved through brittle strain or topographic modification, and without significant erosion to reach more highly stressed bedrock, subsequent glaciation caused a reduction in differential stress and suppressed extensional fracturing. A combination of stress relief during interglacial periods, and increased ice accumulation rates in highly incised valleys, will reduce the likelihood of repeat enhanced erosion events.

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Glacial effects limiting mountain height

Cited by 327 publications

References 39 publications

A review of topographic controls on moraine distribution

A review of topographic controls on moraine distribution

Testing the efficacy of the glacial buzzsaw: insights from the Sredinny Mountains, Kamchatka

Subglacial extensional fracture development and implications for Alpine Valley evolution

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