Supraglacial Surveys

CGI, Supraglacial Survey Campaign 2012

by Manuela Pelfini e Giovanni Leonelli

Earth Sciences Department
University of Milan, Italy

Overall 2 reports were collected for the year 2012 in the e-mail account, a decrease with respect to 2011, and they are only from Valle d’Aosta.
Reports were from the following glaciers: Pré de Bard and Morion.

More information was collected for the Miage Glacier, the only Italian glacier characterized by an extensive colonization of supraglacial trees composed primarily of larch and spruce, studied for several years by researchers of the Dendrogeomorphology Group of the Department of Earth Sciences of University of Milan.
Starting from an altitude of about 2000 m down to the front (at about 1750 m), the two glacier lobes, that characterize a pincer-shaped tongue, are colonized by trees.
The supraglacial debris, however, is continuously moved downvalley, and along with the supraglacial vegetation moves gradually towards the front until it falls into the slope or they are felled by the ice cliff retreat.
The climatic and glaciological signals recorded in the tree ring growth anomalies has allowed the reconstruction of the past surface movements of the glacier for the last 60 years, mean survival age of the supraglacial trees at the Miage Glacier (Pelfini et al 2007; Leonelli and Pelfini 2012). Recent researches on the distribution of supraglacial trees (Pelfini et al., 2012) have shown that the trees are more densely distributed, especially along the internal margin of the northern lobe, where trees smaller less than 30 cm height are abundant and usually younger than 15 years at the time of detection. Here there are also specimens of over 2 meters height, while at the glacier front there are numerous saplings and older and taller specimens are missing. The southern lobe instead, is home to the oldest larch specimens, with trees showing an average age ranging 50-60 years. The oldest tree found so far is germinated some years before 1943, although it is possible that older generations of trees have lived in the past, since the debris cover is present since the 80s of the XIX century.
The colonization above the glacier is strongly controlled with regard to tree growth and distribution by the substrate characteristics and by its instability (ice and debris). The dendrochronological analysis of the growth anomalies for the period 1987-2006 combined with the distribution and characteristics of the supraglacial trees has allowed the identification of areas of higher stress: namely, at the south lobe, the medium-lower portion of the tongue towards the edges, is the one that presents more areas of major surface instability (Leonelli and Pelfini, 2012) and in the temporal scale the years 1988-1989 showed a markedly higher surface instability.
The most advanced researches on this glacier include the study of stable isotopes in tree rings that allow to understand the type of water (glacier melt or meteoric) absorbed by the trees as demonstrated by the first results obtained from the Miage Glacier ice-contact lake Lago Verde site (Leonelli et al. submitted).

The following researchers and experts, that we wish to thank, have contributed by sending the required information: Alberto Fusinaz, Marco Bettio.

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