**3.1 Terminus fluctuations**

In this study, the terminus fluctuations of Lys Glacier were retrieved from different sources; early data concerning the nineteenth century are the same used in Strada [25] and references therein, i.e. early cartographic sources (map of the states of Sardinia from 1818 and cadastral maps), photographs and descriptions, particularly those in Monterin [30]; from the early twentieth century, length changes were obtained by extracting the field measurements available from the journals published by the Italian Glaciological Committee (CGI) [31, 32]. Surveys of the glacier terminus positions consist of tape measurements from fixed

**171**

**Table 1.**

*dd/mm/yyyy.*

*Variations of Lys Glacier (Monte Rosa Massif, Italy) from the Little Ice Age to the Present…*

reference points in the glacier forefield, made at or near the end of the balance year, i.e. in the autumn season, with an estimated accuracy about 0.5 m, which can become worse in case of bad environmental conditions, poorly documented switches to new reference points, measurements taken over very long distances or at points on the snout outside the main flow line, or residual snow patches [12]. While the actual uncertainty from these issues is difficult to quantify, glacier terminus fluctuations remain an important asset to assess global climate and

We followed recommendations by Citterio et al. [12] to perform qualitychecking of the measurements extracted from CGI journals, to minimize the issues related to changing reference points or surveyors over the years. When multiple measurements were available from the same survey, an averaged variation was calculated. In case of missing years in the record, periods up to 5 years where the reference point had remained the same were filled by uniformly distributing the

In case of a gap associated with an undocumented change in a reference point, the gap was not filled, and the first measurement following the gap was considered as the starting point for comparison with the measurement resulting for the following year, as in Citterio et al. [12]. The data record for Lys Glacier from CGI journals is rather uninterrupted and permits analyzing the glacier history in detail over the

Maps, aerial orthophotos and satellite images were analyzed to calculate the area and volume changes of Lys Glacier and changes in the area of the proglacial lakes. The available cartographic sources include large-scale maps from the Val d'Aosta region, produced in 1975 and 1991 at a nominal scale of 1:10000 (**Table 1**). The maps were available in digital form as rasters, projected in the UTM32N coordinate

Aerial orthophoto 07/09/1988 0.5 Glacier outlines, debris cover mapping Regional technical map 1991 10 Glacier outlines, DEM production,

Aerial orthophoto 15/06/1994 0.5 Glacier outlines, debris cover mapping Aerial orthophoto 31/08/1998 0.5 Glacier and lake outlines, debris cover

Aerial orthophoto 16/07/2012 0.5 Glacier and lake outlines, debris cover

Pleiades PHR1B 01/09/2014 2 Glacier outlines, DEM production,

*List of datasets used in this study and their usage; the acquisition date (whenever available) is reported as* 

Aerial orthophoto 12/09/2003 0.5 Glacier and lake outlines Aerial orthophoto 04/09/2006 0.5 Glacier and lake outlines, debris cover

volume change

mapping

mapping

mapping

volume change, debris cover mapping

**Remote sensing data Date Resolution (m) Usage** Regional technical map 1975 10 Glacier outlines

*DOI: http://dx.doi.org/10.5772/intechopen.91202*

total terminus variation over the missing years.

environmental change [19].

last century.

**3.2 Cartographic analysis**

*3.2.1 Data sources and preprocessing*

*Variations of Lys Glacier (Monte Rosa Massif, Italy) from the Little Ice Age to the Present… DOI: http://dx.doi.org/10.5772/intechopen.91202*

reference points in the glacier forefield, made at or near the end of the balance year, i.e. in the autumn season, with an estimated accuracy about 0.5 m, which can become worse in case of bad environmental conditions, poorly documented switches to new reference points, measurements taken over very long distances or at points on the snout outside the main flow line, or residual snow patches [12]. While the actual uncertainty from these issues is difficult to quantify, glacier terminus fluctuations remain an important asset to assess global climate and environmental change [19].

We followed recommendations by Citterio et al. [12] to perform qualitychecking of the measurements extracted from CGI journals, to minimize the issues related to changing reference points or surveyors over the years. When multiple measurements were available from the same survey, an averaged variation was calculated. In case of missing years in the record, periods up to 5 years where the reference point had remained the same were filled by uniformly distributing the total terminus variation over the missing years.

In case of a gap associated with an undocumented change in a reference point, the gap was not filled, and the first measurement following the gap was considered as the starting point for comparison with the measurement resulting for the following year, as in Citterio et al. [12]. The data record for Lys Glacier from CGI journals is rather uninterrupted and permits analyzing the glacier history in detail over the last century.

## **3.2 Cartographic analysis**

*Glaciers and the Polar Environment*

**170**

**Figure 2.**

**3. Materials and methods**

**3.1 Terminus fluctuations**

In this study, the terminus fluctuations of Lys Glacier were retrieved from different sources; early data concerning the nineteenth century are the same used in Strada [25] and references therein, i.e. early cartographic sources (map of the states of Sardinia from 1818 and cadastral maps), photographs and descriptions, particularly those in Monterin [30]; from the early twentieth century, length changes were obtained by extracting the field measurements available from the journals published by the Italian Glaciological Committee (CGI) [31, 32]. Surveys of the glacier terminus positions consist of tape measurements from fixed

*Comparison of historical photographs of Lys glacier. (a) 1989. The glacier exhibits medial moraines on the distal part of its tongue, which is well developed. (b) 2019. The glacier has retreated above a rock wall in the western sector, leaving a dead ice tongue underneath, with a proglacial lake developing in the depression left by the disappearing tongue. The moraine ridges from the 1980s advance phase are also evident. (photo credits: (a) Willy Monterin-© Archivio Monterin. (b) Fabiano Ventura-© F. Ventura-sulletraccedeighiacciai.com).*
