Surges of glaciers in Iceland

Björnsson, Helgi; Pálsson, Finnur; Sigurðsson, Oddur; Flowers, G. E.

doi:10.3189/172756403781816365

Cited by 190 publications

(254 citation statements)

References 20 publications

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“…Among these, with an ice volume of 3100 km 3 [Björnsson and Pálsson, 2008], Vatnajökull (Figure 1) is the largest ice cap in Europe, although it has been decreasing in volume rapidly since 1890, from the time of the end of the Little Ice Age. This decrease is likely to have accelerated nowadays due to global warming [Björnsson and Pálsson, 2008]. The overall retreat of the icelandic glaciers is causing a mechanical response in the Earth crust [Pagli et al, 2007;Arnadóttir et al, 2009;Pinel et al, 2007].…”

Section: Geodynamic Contextmentioning

confidence: 99%

A two‐magma chamber model as a source of deformation at Grímsvötn Volcano, Iceland

et al. 2014

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Grímsvötn Volcano is the most active volcano in Iceland, and its last three eruptions were in 1998, 2004, and 2011. Here we analyze the displacement around Grímsvötn during these last three eruptive cycles using 10 GPS stations. The observed displacements in this region generally contain a linear component of tectonic and glacio‐isostatic origin, in agreement with the previously estimated values of plate motions and vertical rebound. Larger amplitude deformation observed close to Grímsvötn at the GFUM continuous GPS station clearly reflects a major volcanic contribution superimposed on a tectonic component. We estimate and subtract the tectonic trend at this station using regional observed displacement. The direction and pattern of the residual volcanic displacement (for coeruptive and intereruptive periods) are consistent for all three of these eruptive cycles. The posteruptive inflation is characterized by an exponential trend, followed by a linear trend. In this study, we explain this temporal behavior using a new analytic model that has two connected magma chambers surrounded by an elastic medium and fed by a constant basal magma inflow. During the early posteruptive phase, pressure readjustment occurs between the two reservoirs, with replenishment of the shallow chamber from the deep chamber. Afterward, due to the constant inflow of magma into the deep reservoir, the pressurization of the system produces linear uplift. A large deep reservoir favors magma storage rather than surface emission. Based on displacement measured at GFUM station, we estimate an upper limit for the radius of the deep reservoir of ∼10 km.

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Section: Geodynamic Contextmentioning

confidence: 99%

A two‐magma chamber model as a source of deformation at Grímsvötn Volcano, Iceland

et al. 2014

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“…Howard et al (2012) did not suggest how either individually or in combination all these lakes might have drained simultaneously. According to Björnsson and Pálsson (2008) Howard et al (2012) would have surely been detected in offshore deposits and it would have increased global sea level by~4 mm!…”

Section: Implications Of the Calculation Of A Very Large Peak Dischargementioning

confidence: 99%

Discussion of ‘Field evidence and hydraulic modeling of a large Holocene jökulhlaup at Jökulsá á Fjöllum channel, Iceland’ by Douglas Howard, Sheryl Luzzadder-Beach and Timothy Beach, 2012

Carrivick¹,

Tweed²,

Carling³

et al. 2013

Geomorphology

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This paper discusses Howard et al. (2012) who reconstruct the peak discharge of a glacial outburst flood, or 'jökulhlaup', for part of the Jökulsá á Fjöllum in north-central Iceland. They propose that this flood was the largest on Earth. We consider that the magnitude of the jökulhlaup 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 jökulhlaups, and (iii) consider uncertainty regarding the timing and magnitude of jökulhlaups along the Jökulsá á Fjöllum. We argue herein that whilst a range of landforms and sediments that are attributable to jökulhlaups can be observed along the Jökulsá á Fjöllum, these are not necessarily diagnostic of jökulhlaups. 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.© 2012 Elsevier B.V. All rights reserved. IntroductionHoward et al. (2012) suggested that a glacial outburst flood or 'jökulhlaup' that routed along the Jökulsá á Fjöllum in northern Iceland during the early Holocene was the largest flood to have occurred on Earth. They present field data, most importantly large boulders, that they attribute to deposition by this flood and they use the elevation of these boulders to drive a hydraulic model that they suggest reasonably represents the characteristics of this flood. However, we feel that the field data as presented in their paper is both ambiguous and insufficient. We therefore briefly review the field evidence for, and research into, Jökulsá a Fjöllum jökulhlaups. Given the emphasis placed on the exceptional magnitude of the flood and on the applicability of the work for studies on Mars, we also feel that it is very important to question several assumptions that Howard et al. (2012) relied upon for their calculations. This paper therefore proceeds to discuss these assumptions, namely that: isolated large 'erratic' boulders are the product of jökulhlaup deposition, that the position and location of the boulders are sufficient to parameterise a step-backwater hydraulic model, that a hill named 'Ferjufjall' must have been overtopped, that Manning's n can be treated as a fixed quantity, that modelling a single reach of the Jökulsá á Fjöllum can generate meaningful results, and finally that the volume of water implied by such a large peak discharge could have been sourced from northern Vatnajökull. Discussion of research on Jökulsá á Fjöllum jökulhlaupsAttributing landforms and sediments to jökulhlaups (Table 1), particularly those jökulhlaups that occurred millennia ago, is far from straight forward and has occupied many m...

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“…As exceptionally high discharge of turbid meltwater is common during and immediately after glacier surges (e.g. [6,18,34]), a former SAR of about 30 cm a À1 at the core site seems reasonable. Such high accumulation rates are also in accordance with the low number of IRD in lithological Unit 3, which was linked to high input of fine-grained material from meltwater plumes, masking the contribution of IRD (see section ''Sedimentology'').…”

Section: Sediment Accumulation Ratesmentioning

confidence: 99%

Submarine landform assemblages and sedimentary processes related to glacier surging in Kongsfjorden, Svalbard

Streuff

Forwick

Szczuciński

et al. 2015

Arktos

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Surges of glaciers in Iceland

Cited by 190 publications

References 20 publications

A two‐magma chamber model as a source of deformation at Grímsvötn Volcano, Iceland

A two‐magma chamber model as a source of deformation at Grímsvötn Volcano, Iceland

Discussion of ‘Field evidence and hydraulic modeling of a large Holocene jökulhlaup at Jökulsá á Fjöllum channel, Iceland’ by Douglas Howard, Sheryl Luzzadder-Beach and Timothy Beach, 2012

Submarine landform assemblages and sedimentary processes related to glacier surging in Kongsfjorden, Svalbard

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