Origin of stratified basal ice in outlet glaciers of Vatnajökull and Öræfajökull, Iceland
G. J. Larson, D. E. Lawson, E. B. Evenson, Ó. Knudsen, R. B. Alley, and M. S. Phanikumar
Boreas (1 July 2010)
DOI: 10.1111/j.1502-3885.2009.00134.x
Larson, G.J., Lawson, D.E., Evenson, E.B., Knudsen, Ó., Alley, R.B. & Phanikumar, M.S. 2010: Origin of stratified basal ice in outlet glaciers of Vatnajökull and Öræfajökull, Iceland. Boreas, Vol. 39, pp. 457–470. 10.1111/j.1502-3885.2009.00134.x. ISSN 0300-9483. During the period 2000–2005, we collected samples of englacial ice, vent water, frazil/anchor ice and stratified basal ice from warm-based outlet glaciers of Vatnajökull and Öræfajökull, Iceland, and analysed them for 3H, 18O and D. Results of 3H analyses show that the stratified basal ice contains 3H from atmospheric thermonuclear testing and is younger than the englacial ice. Results of the 18O and D analyses show that frazil/anchor and stratified basal ice are both enriched by an average of 2.4‰ in 18O and 11‰ in D relative to vent water. These values are consistent with fractionation during partial freezing of supercooled subglacial water in an open system, one in which the remaining water is continuously removed and replenished by water of similar composition. The isotopic data and field observations do not support either a regelation or a thermal ad-freeze-on origin for the stratified basal ice.