1 Research Group of High Mountain Physical Geography, Departament of Geography, Universidad Complutense de Madrid, Madrid, 28040 Madrid, Spain. Electronic address: pace@ghis.ucm.es.
2 Research Group of High Mountain Physical Geography, Departament of Geography, Universidad Complutense de Madrid, Madrid, 28040 Madrid, Spain.
3 Institute of Geography, Universidad Nacional Autónoma de México, México DF, Mexico.
4 Faculty of Life and Environmental Science, University of Iceland, Reykjavík, Iceland.
5 Icelandic Institute of Natural History, Akureyri, Iceland.