The chemistry and element fluxes of the July 2011 Múlakvísl and Kaldakvísl glacial floods, Iceland

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Abstract

This study describes the chemical composition and fluxes of two ~2000m3/s glacial floods which emerged from the Icelandic Mýrdalsjökull and Vatnajökull glaciers into the Múlakvísl and Kaldakvísl rivers in July 2011. Water samples collected during both floods had neutral to alkaline pH and conductivity from 100 to 900μS/cm. The total dissolved inorganic carbon (DIC), present mostly as HCO3-, was ~9mmol/kg during the flood peak in the Múlakvísl but stabilized at around 1mmol/kg; a similar behaviour was observed in the Kaldakvísl. Up to 1.5μmol/kg of H2S was detected. Concentrations of most of the dissolved constituents in the flood waters were comparable to those commonly observed in these rivers. In contrast, the particulate suspended material concentration increased dramatically during the floods and dominated chemical transport during these events. Waters were supersaturated with respect to a number of clays, zeolites, carbonates, and Fe hydroxides. The most soluble elements were Na, Ca, K, Sr, Mn, and Mg, whereas the least soluble were Ti, Al, and REE. This is consistent with the compositions of typical surface waters in basaltic terrains and the compositions of global rivers in general. The toxic metal concentrations were below drinking water limits, suggesting that there was no detrimental effect of flood waters chemistry on the environment. Increased concentration of DOC, formate, and acetate in the flood waters suggests substantial subglacial microbiological activity in the melt water prior to the floods. Reaction path modelling of the flood water chemical evolution suggests that it experienced subglacial water-rock interaction for at least a year in the presence of limited amounts of acid gases (e.g. SO2, HCl and HF). This suggests that the heat source for glacier melting was geothermal rather than volcanic.

Original languageEnglish
Pages (from-to)41-57
Number of pages17
JournalJournal of Volcanology and Geothermal Research
Volume273
DOIs
Publication statusPublished - 1 Mar 2014

Bibliographical note

Funding Information:
The authors would like to thank associated editor Alessandro Aiuppa for his useful comments and in handling the manuscript, Evgenia Ilyinskaya and anonymous reviewer for their constructive comments which helped improve the manuscript. Sigurður P. Ásólfsson, Eric Sturkell and Reynir Ragnarsson are acknowledged for their help in collecting the water samples. Rósa Ólafsdóttir and Þórdís Högnadóttir are gratefully thanked for their assistance in preparing the figures. The Icelandic Meteorological Office is thanked for permission to publish Fig. 2 b. We thank all colleagues and co-workers in particular: Eydis Eiriksdottir, Niels Óskarsson, Domenik Wolff-Boenisch, Kiflom Gebrehiwot, Snorri Gudbrandsson, Nicole Keller and Hanna Kaasalainen. The work was funded by the Icelandic Science Foundation RANNÍS 121071-0061, the European Union through the European Marie Curie network Delta-Min Grant#PITN-GA-2008-215360, Landsvirkjun and the Institute of Earth Sciences, University of Iceland .

Other keywords

  • Dissolved and particulate element transport
  • Reaction path modelling
  • Subglacial floods

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