Historical glacier variations in the western and central Alps

Transcription

1 12th Alpine Glaciological Meeting (AGM), Chamonix Historical glacier variations in the western and central Alps pictorial documents meet neural networks Dr. Daniel Steiner Prof. Dr. Heinz J. Zumbühl Samuel U. Nussbaumer Institute of Geography, University of Bern, Switzerland Outline > Introduction: the Mer de Glace (Mont Blanc area, France) > Methods for investigations of glacier change Pictorial documents in Glaciology Historical documents for reconstructing length fluctuations of the Mer de Glace (the example of J.-A. Linck, S. Birmann and E. Viollet-le-Duc) > Neural network models for simulating glacier length changes > Conclusions and outlook 2 1

2 Mer de Glace (Mont Blanc area, France) (Nussbaumer 2006) 3 Introduction Mer de Glace (data 2001: Nussbaumer, 2006) Area Length Exposition Branches 19th century maximum extent (height in the valley bottom) 31.9 km km N-NW Glacier du Géant Glacier de Leschaux 1821 (1090 m asl.) 4 2

3 Pictorial documents in Glaciology («historical method») > Pictorial documents: drawings, paintings, prints and photographs > Three conditions to be fulfilled in order to obtain reliable results concerning former glacier extents (after Zumbühl 1980): - dating of the pictorial document - correct representation of the glacier and surroundings - position of the artist in the field should be known > Mer de Glace: Jean-Antoine Linck ( ), Samuel Birmann ( ), Eugène Viollet-le-Duc ( ) 5 Jean-Antoine Linck ( ) 1843) , SN «Vue prise de la voûte nommée le Chapeau», 1799, oil on canvas Musée d art et d histoire, Chambéry 6 3

4 Jean-Antoine Linck ( ) 1843) «Vue du Glacier des Bois en retraite», end 18th century, watercolour Musée d'ethnographie, Genève 7 Jean-Antoine Linck ( ) 1843) «Vue de la source du Glacier des Bois», 1804, watercolour Private collection 8 4

5 Jean-Antoine Linck ( ) 1843) «La chaîne du Mont- Blanc vue de la Flégère», around 1820, watercolour Musée d art et d histoire, Genève 9 Samuel Birmann ( ) 1847) «Au village des Prats», August 1823, pencil and watercolour Kunstmuseum Basel (Kupferstichkabinett) 10 5

6 Samuel Birmann ( ) 1847) Mer de Glace in 1823 (Kunstmuseum Basel, Kupferstichkabinett) 11 New technique: photography Samuel Birmann: à la Flégère 1823 Mer de Glace 1857/

7 Eugène Viollet-le le-duc ( ) 1879) Studies in the Mont Blanc massif (Fonds Viollet-le-Duc; Musée Lambinet, Versailles) 13 The history of the Mer de Glace , SN 14 7

8 , LGGE Grenoble 15 Neural networks in glaciological contexts > A short introduction into neural networks Inputs Processing unit Output 16 8

9 Neural networks in glaciological contexts > The technical realization x 1 w 1 x 2 w 2 V y x n Inputs w n Weights Processing function (e.g. sigmoid) Output (Steiner et al. 2005) 17 A neural network approach Inputs: Temp_DJF 0,1,2,,30 Temp_MAM 0,1,2,,30 Temp_JJA 0,1,2,,30 Temp_SON 0,1,2,,30 Prec_DJF 0,1,2,,30 Output: Length fluctuations of the Mer de Glace Prec_MAM 0,1,2,,30 Prec_JJA 0,1,2,,30 Prec_SON 0,1,2,,30 (Casty et al. 2005, Frei 2004, Steiner 2005) 18 9

10 Seasonal Sensitivity Characteristic (SSC) (Prof. J. Oerlemans, unpublished data) 19 Neural networks as validation tool 20 10

11 Neural network simulations (forcing scenario) 21 Neural network simulations (no change scenario) 22 11

12 Glacier sensitivity to climate ( ) 1715) 23 Conclusions (Zumbühl 1980, Zumbühl et al. 1983, Nussbaumer et al. 2007) 24 12

13 Conclusions > Pictorial sources: - rich for the Mont Blanc area - reconstruction of glacier length changes / perception view > Neural networks: - new nonlinear approach complements the historical method - powerful tool (combination with high-resolution climate data) > Revised glacier length curve for the Mer de Glace, back to 1570 LIA maximum: 1643/44 (vs. 1600/41 Lower Grindelwald Glacier) 19 th century maximum: 1821 (vs. 1855/56 Lower Grindelwald Glacier) Heavy retreat since ca up to present: Mer de Glace: 2.2 km (15%) ~ 7 km 2 (14%) 25 Thank you! > S. U. Nussbaumer, C. Casty, P. Deline, R. Eggimann, H. Holzhauser, J. Luterbacher, D. Mihajlovic, C. Vincent, H. Wanner, W. Wetter 26 13