Icy thermometers: quantifying the impact of volcanic heat on glacier elevation

Howcutt, Stephen, Spagnolo, Matteo, Rea, Brice, Jaszewski, Jan, Barr, Iestyn ORCID: https://orcid.org/0000-0002-9066-8738, Coppola, Diego, De Siena, Luca, Girona, Társilo, Gomez-Patron, Andie, Mullan, Donal and Pritchard, Matthew (2023) Icy thermometers: quantifying the impact of volcanic heat on glacier elevation. Geology. ISSN 0091-7613

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Abstract

We present a continent-wide study of 600 glaciers located on and near 37 ice-clad volcanoes in South America, that demonstrates glacier sensitivity to volcanic heat. We distinguish between ‘volcanic-glaciers’ (≤1 km from volcanic centres; n=74), and ‘proximal glaciers’ (1-15 km; n=526) and calculate their equilibrium line altitudes (ELA). For each ice-clad volcano we compare the ELAs of its volcanic-glaciers to those of its proximal glaciers which shows that the ELAs of the former are higher than the ELAs of the latter. ΔELAmean, defined as the offset between the mean ELA of the volcanic-glaciers and that of the proximal glaciers, is calculated for each ice-clad volcano. ΔELAmean is positive for 92% of the 37 volcanoes, and a quantitative relationship between ΔELAmean and volcanic thermal anomaly is established. Results highlight the impact of volcanic heat on glacier elevation; emphasise the need to exclude glaciers on, or near, volcanoes from glacier-climate investigations; and demonstrate the first-order potential for glaciers as ‘volcanic thermometers’. Volcanic-glacier monitoring could contribute to our understanding of magmatic and thermal activity, with changes in glacier geometries potentially reflecting long-term fluctuations in volcanic heat and unrest.