A1 Refereed original research article in a scientific journal
Discussion of 'Field evidence and hydraulic modeling of a large Holocene jokulhlaup at Jokulsa a Fjollum channel, Iceland' by Douglas Howard, Sheryl Luzzadder-Beach and Timothy Beach, 2012
Authors: Carrivick JL, Tweed FS, Carling P, Alho P, Marren PM, Staines K, Russell AJ, Rushmer EL, Duller R
Publisher: ELSEVIER SCIENCE BV
Publication year: 2013
Journal: Geomorphology
Journal name in source: GEOMORPHOLOGY
Journal acronym: GEOMORPHOLOGY
Volume: 201
First page : 512
Last page: 519
Number of pages: 8
ISSN: 0169-555X
DOI: https://doi.org/10.1016/j.geomorph.2012.10.024
Abstract
This paper discusses Howard et al. (2012) who reconstruct the peak discharge of a glacial outburst flood, or jokulhlaup', for part of the jokulsa a Fjollum in north-central Iceland. They propose that this flood was the largest on Earth. We consider that the magnitude of the jokulhlaup proposed by Howard et al. (2012) warrants much more robust field evidence and demands more carefully parameterised hydraulic modelling. For these reasons we firstly (i) present their study in the context of previous research (ii) highlight issues with attributing landforms and sediments to jokulhlaups, and (iii) consider uncertainty regarding the timing and magnitude of jokulhlaups along the jokulsa a Fjollum. We argue herein that whilst a range of landforms and sediments that are attributable to jokulhlaups can be observed along the jokulsa a Fjollum, these are not necessarily diagnostic of jokulhlaups. Secondly, we critically discuss (iv) the major underlying assumptions of their study, and (v) their calculations and subsequent interpretations. These assessments lead us to consider that the proposal by Howard et al. (2012) of the largest flood on Earth is highly unrealistic, especially when due consideration is given to a possible source area and a trigger mechanism. (C) 2012 Elsevier B.V. All rights reserved.
This paper discusses Howard et al. (2012) who reconstruct the peak discharge of a glacial outburst flood, or jokulhlaup', for part of the jokulsa a Fjollum in north-central Iceland. They propose that this flood was the largest on Earth. We consider that the magnitude of the jokulhlaup proposed by Howard et al. (2012) warrants much more robust field evidence and demands more carefully parameterised hydraulic modelling. For these reasons we firstly (i) present their study in the context of previous research (ii) highlight issues with attributing landforms and sediments to jokulhlaups, and (iii) consider uncertainty regarding the timing and magnitude of jokulhlaups along the jokulsa a Fjollum. We argue herein that whilst a range of landforms and sediments that are attributable to jokulhlaups can be observed along the jokulsa a Fjollum, these are not necessarily diagnostic of jokulhlaups. Secondly, we critically discuss (iv) the major underlying assumptions of their study, and (v) their calculations and subsequent interpretations. These assessments lead us to consider that the proposal by Howard et al. (2012) of the largest flood on Earth is highly unrealistic, especially when due consideration is given to a possible source area and a trigger mechanism. (C) 2012 Elsevier B.V. All rights reserved.
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