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Increased capture of magma in the crust promoted by ice-cap retreat in Iceland

Abstract

Climate warming at the end of the last glaciation caused ice caps on Icelandic volcanoes to retreat. Removal of surface ice load is thought to have decreased pressures in the underlying mantle, triggering decompression melting, enhanced magma generation and increased volcanic activity1,2,3. Present-day climate change could have the same effect, although there may be a time lag of hundreds of years between magma generation and eruption4,5. However, in addition to increased magma generation, pressure changes associated with ice retreat should also alter the capacity for storing magma within the crust. Here we use a numerical model to evaluate the effect of the current decrease in ice load on magma storage in the crust at the Kverkfjöll volcanic system, located partially beneath Iceland’s largest ice cap. We compare the model results with radar and global positioning system measurements of surface displacement and changes in crustal stress between 2007 and 2008, during the intrusion of a deep dyke at Upptyppingar. We find that although the main component of stress recorded during dyke intrusion relates to plate extension, another component of stress is consistent with the stress field caused by the retreating ice cap. We conclude that the retreating ice cap led to enhanced capture of magma within the crust. We suggest that ice-cap retreat can promote magma storage, rather than eruption, at least in the short term.

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Figure 1: Contribution to ΔP due to ice loss from all Icelandic ice caps between 1890 and 2003.
Figure 2: Satellite radar and GPS data, and corresponding model results.
Figure 3: Hydrostatic dyke model.

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Acknowledgements

We thank G. Guðmundsson and R. Slunga for their relocated earthquake locations. Envisat data were provided by the European Space Agency. This research was supported by the European Commission, 6th Framework Project ‘VOLUME’, contract 08471. Some figures were prepared using the public-domain GMT software.

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Contributions

A.H. developed the hydrostatic dyke boundary element model, and inverted InSAR and GPS data for the model parameters. He also did the InSAR analysis, calculated the elastic stress changes due to thinning of Vatnajökull, and led the writing of the paper together with F.S. B.Ó. analysed the GPS data, collected by himself, H.G., E.S., P.E., F.S. and others. B.L modelled the viscoelastic stress change due to thinning of ice caps. P.E. mapped the eruptive fissures. All the authors contributed to developing of the ideas presented and the writing of the paper.

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Correspondence to Andrew Hooper.

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Hooper, A., Ófeigsson, B., Sigmundsson, F. et al. Increased capture of magma in the crust promoted by ice-cap retreat in Iceland. Nature Geosci 4, 783–786 (2011). https://doi.org/10.1038/ngeo1269

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