Reconstruction of Late Holocene fluctuations of La Mare Glacier (Eastern Italian Alps): a combined approach.

High-resolution glacier length curves provide valuable insights on glacier fluctuations as response of past climate. Since the end of the XIX and the beginning of the XX century, the Italian Glaciological Committee (CGI) coordinates the systematic monitoring of frontal variations of the Italian glaciers, which however can locally display interruptions or inhomogeneities, supplying anyway one of the longest series of observations of frontal variations in the world. Here we present a combined approach, which uses different sources of data and modern technologies of terrain analysis, for reconstructing the Late Holocene fluctuations of La Mare Glacier, a 4 km2 wide valley glacier located in the Ortles-Cevedale massif (Eastern European Alps). This glacier built one of the most impressive and well-studied Holocene morainic complex of the Italian Alps, and displayed significant fluctuations during the 19th and 20th Centuries, experiencing a frontal withdrawn of about 2.4 km since the maximum Holocene position reached during the Little Ice Age. Frontal variations occurred before the direct monitoring were reconstructed by detailed geomorphologic surveys of the proglacial area, integrated with high-resolution Digital Elevation Models analyses. The chronologic constrain of moraines was assessed by the reconstruction of soils chronosequence on different moraine ridges, comparing historical documents (e.g. maps, paintings, photographs), by lichenometry, radiocarbon dates and surface exposure dating of glacial deposits and relict landforms. The retreat curve deriving from systematic field observations was checked with multitemporal photographs and maps, which enabled the identification of landmarks used by the observers and the reconstruction of fluctuations in periods lacking measurements.