19Th Century Glacier Representations and Fluctuations in the Central and Western European Alps: an Interdisciplinary Approach ⁎ ⁎ H.J

Available online at www.sciencedirect.com Global and Planetary Change 60 (2008) 42–57 www.elsevier.com/locate/gloplacha 19th century glacier representations and fluctuations in the central and western European Alps: An interdisciplinary approach ⁎ ⁎ H.J. Zumbühl , D. Steiner , S.U. Nussbaumer Institute of Geography, University of Bern, Hallerstrasse 12, CH-3012 Bern, Switzerland Received in revised form 22 August 2006; accepted 24 August 2006 Available online 22 February 2007 Abstract European Alpine glaciers are sensitive indicators of past climate and are thus valuable sources of climate history. Unfortunately, direct determinations of glacier changes (length variations and mass changes) did not start with increasing accuracy until just before the end of the 19th century. Therefore, historical and physical methods have to be used to reconstruct glacier variability for preceeding time periods. The Lower Grindelwald Glacier, Switzerland, and the Mer de Glace, France, are examples of well-documented Alpine glaciers with a wealth of different historical sources (e.g. drawings, paintings, prints, photographs, maps) that allow reconstruction of glacier length variations for the last 400–500 years. In this paper, we compare the length fluctuations of both glaciers for the 19th century until the present. During the 19th century a majority of Alpine glaciers – including the Lower Grindelwald Glacier and the Mer de Glace – have been affected by impressive glacier advances. The first maximum extent around 1820 has been documented by drawings from the artist Samuel Birmann, and the second maximum extent around 1855 is shown by photographs of the Bisson Brothers. These pictorial sources are among the best documents of the two glaciers for the 19th century. In addition to an analysis of historical sources of the 19th century, we also study the sensitivity of the Lower Grindelwald Glacier to climate parameters (multiproxy reconstructions of seasonal temperature and precipitation) for an advance and a retreat period in the 19th century using a new neural network approach. The advance towards 1820 was presumably driven by low summer temperatures and high autumn precipitation. The 1860–1880 retreat period was mainly forced by high temperatures. Finally, this nonlinear statistical approach is a new contribution to the various investigations of the complex climate–glacier system. © 2007 Elsevier B.V. All rights reserved. Keywords: glacier fluctuations; historical sources; sensitivity analysis; neural network 1. Introduction deduced from natural archives and a wealth of documentary evidence (e.g. Zumbühl and Holzhauser, During the 19th century impressive glacier advances 1988; Maisch et al., 1999). In general, historical records affected the majority of the Alpine glaciers. This can be give a detailed picture of glacial fluctuations and allow studying glacier history further back in time than would be possible from direct measurements alone (e.g. ⁎ Corresponding authors. Tel.: +41 31 631 85 51; fax: +41 31 631 85 11. Holzhauser et al., 2005). For instance, empirical quali- E-mail addresses: [email protected] (H.J. Zumbühl), tative and/or quantitative data on the length, area and [email protected] (D. Steiner). volume of glaciers can be derived from these sources. 0921-8181/$ - see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.gloplacha.2006.08.005 H.J. Zumbühl et al. / Global and Planetary Change 60 (2008) 42–57 43 This study focuses on two well-documented Alpine we present different kinds of historical pictorial sources glaciers, the Lower Grindelwald Glacier, Switzerland, (drawings and photographs) that together document the and the Mer de Glace, France (Fig. 1). For both glaciers 19th century glacier maximum extents around 1820 Fig. 1. Geographical location of study sites: (a) the Grindelwald region with the Lower Grindelwald Glacier, (b) the Mont Blanc region with the Mer de Glace. 44 H.J. Zumbühl et al. / Global and Planetary Change 60 (2008) 42–57 and 1855. Samuel Birmann (1793–1847), an important of the Mont Blanc (France). The topography and some Swiss landscape artist, portrayed the Lower Grindel- landmark locations of these two glaciers are shown in wald Glacier and the Mer de Glace at their first Fig. 1. maximum extent around 1820 in detailed drawings of The Lower Grindelwald Glacier (46°35′ N, 8°05′ E) their glacier snouts. The Bisson Brothers, famous is a valley glacier, 8.85 km long and covering a surface photographers of that time, made pictures of the two of 20.6 km2. Ischmeer in the east and the Bernese glaciers at their second maximum extent around 1855, Fiescher Glacier in the west join to form the tongue of again including detailed views of their glacier snouts. the Lower Grindelwald Glacier (Fig. 1a). The main Therefore, the historical sources of the two glaciers contribution of ice presently originates from the Bernese allow comparison of these extraordinary high-quality Fiescher Glacier (Holzhauser and Zumbühl, 1996; glacier representations at their maximum extent. It Schmeits and Oerlemans, 1997). The approximated must be noted that the change of glacier representation equilibrium line altitude (ELA), derived from digital techniques from drawings to photographs demonstrates elevation models (DEMs), is at 2640 m a.s.l. The glacier also the changing view on glaciers from the magic today terminates at 1297 m a.s.l. in a narrow gorge so to the scientific (Haeberli and Zumbühl, 2003; Steiner that reliable observations are difficult to obtain (data et al., in press). from 2004: Steiner et al., in press). Furthermore, the 19th century provides also an The Mer de Glace (45°54′ N, 8°57′ E) sensu lato is a opportunity to analyze the climatic conditions of the compound valley glacier, 12.0 km long and covering a last widespread glacier advance and the following surface of 31.9 km2 (without including Glacier de retreat. This is done by connecting new gridded Talèfre). The glacier is fed by several tributaries with the reconstructions of temperature and precipitation (Luter- Glacier du Géant being the most important one (Fig. 1b). bacher et al., 2004; Pauling et al., 2006) with the data Since the 1931–1969 retreat, the Glacier du Talèfre is of length fluctuations of the Lower Grindelwald separated from the main ice stream. The Mer de Glace Glacier. Because the climate–glacier relation is, in sensu stricto refers to the lowest approximately 5 km part, nonlinear (Steiner et al., 2005), we suggest a new of the ice stream, forming the glacier tongue beneath statistical nonlinear approach based on a neural Montenvers. The ELA is situated at around 2775 m a.s.l., network to investigate the climate–glacier system, i.e. and the glacier today terminates at 1467 m a.s.l. (data to study the meteorological conditions which led to a from 2001: Nussbaumer et al., in press). glacier advance or retreat. In a sensitivity analysis that The Bernese Alps is a group of mountain ranges in explores the significance of climatic inputs to the the central part of the Alps drained by the river Aare and glacier system we evaluate the relevant climatic its tributary Saane in the north, and the Rhône in the variables that caused the advance towards 1820 and south and the Reuss in the east. The northern part of the the rapid retreat of the Lower Grindelwald Glacier after Bernese Alps, including the Lower Grindelwald Glacier, 1860. is exposed to the westerlies and receives maximum In this paper, we compare the length fluctuations of precipitation during summer, with low variability. The the Lower Grindelwald Glacier and the Mer de Glace mean annual temperature at Grindelwald (1040 m a.s.l.), since 1800. Since this approach is descriptive, we also located approximately 3 km from the glacier front of the present a neural network model to explore potential Lower Grindelwald Glacier, was 6.7 °C during the climate forcings to explain glacier length fluc- 1966–1989 period. The mean temperature during the tuations with the Lower Grindelwald Glacier. There- accumulation season (October–April) and ablation fore, the analysis of historical sources provides a season (May–September) during the 1966–1989 period framework for which we can test the relative im- was 2.3 °C and 12.9 °C, respectively. portance of climate variables forcing glacier advance The mean annual precipitation during the 1961–1990 and retreat. period was 1428 mm with precipitation during the accumulation season (October–April) and ablation 2. Data and methods season (May–September) of 720 mm and 708 mm, respectively (data from the online database of Meteo- 2.1. Study area Swiss). Because of high precipitation (locally exceeding 4000 mm per year), the Bernese Alps have a relative low Our study focuses on the Lower Grindelwald glacier equilibrium line altitude and is the heaviest Glacier, located in the northern Bernese Alps (Switzer- glacierized region in the Alps. Both the glacier with the land), and the Mer de Glace, located on the north face lowest front (Lower Grindelwald Glacier) and the H.J. Zumbühl et al. / Global and Planetary Change 60 (2008) 42–57 45 largest glacier of the Alps (Great Aletsch Glacier) are et al., 2005). The density of historical material prior to located within this region (Kirchhofer and Sevruk, 1800 highly depends on the elevation of the tongue and 1992; Imhof, 1998). the relationship between settlements and cultivated land Due to the extraordinary low position of the terminus and the glacier advances. and its easy accessibility, the Lower Grindelwald

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