Pôle Alpin Risques Naturels (PARN) Alpes–Climat–Risques Avec le soutien de la Région Rhône-Alpes (2007-2014)
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Réf. Oerlemans & al 2009 - A

Référence bibliographique
OERLEMANS J., GIESEN R.H., VAN DEN BROEKE M.R., Retreating alpine glaciers : increased melt races due to accumulation of dust (Vadret da Morteratsch, Switzerland). Journal of Glaciology, Vol. 55, No. 192, 2009 pp.729-736

Abstract : The automatic weather station (AWS) on the snout of the Vadret da Morteratsch, Switzerland, has delivered a unique 12 year meteorological dataset from the ablation zone of a temperate glacier. This dataset can be used to study multi-annual trends in the character of the surface energy budget. Since 2003 there has been a substantial darkening of the glacier tongue due to the accumulation of mineral and biogenic dust. The typical surface albedo in summer has dropped from 0.32 to 0.15. We have analysed the implications of the lowered albedo for the energy balance and the annual ablation. For the 4 year period 2003–06, the decreased albedo caused an additional removal of about 3.5m of ice. Calculations with an energy-balance model show that the same increase in ablation is obtained by keeping the ice albedo fixed to 0.32 and increasing the air temperature by 1.7 K. Our analysis confirms that for retreating glaciers the deposition of dust from exposed side moraines on the glacier surface constitutes an important feedback mechanism. The mineral dust stimulates the growth of algae, lowers the surface albedo, enhances the melt rates, and thereby facilitates the further retreat of the glacier snout.

Mots-clés
 

Organismes / Contact

Auteurs/Authors :

  • OERLEMANS J., Institute for Marine and Atmospheric Research, Utrecht University
  • GIESEN R.H., Institute for Marine and Atmospheric Research, Utrecht University
  • VAN DEN BROEKE M.R., Institute for Marine and Atmospheric Research, Utrecht University

(1) - Paramètre(s) atmosphérique(s) modifié(s)
(2) - Elément(s) du milieu impacté(s)
(3) - Type(s) d'aléa impacté(s)
(3) - Sous-type(s) d'aléa
  melt rates    

Pays / Zone
Massif / Secteur
Site(s) d'étude
Exposition
Altitude
Période(s) d'observation
suisse Alpes Vadret da Morteratsch      

(1) - Modifications des paramètres atmosphériques
Reconstitutions
 
Observations

 

Modélisations
 
Hypothèses
 

Informations complémentaires (données utilisées, méthode, scénarios, etc.)



(2) - Effets du changement climatique sur le milieu naturel
Reconstitutions
 
Observations
 The long series of meteorological measurements on the snout of the Vadret da Morteratsch makes it possible to study trends in the energy and mass budget of a glacier surface on multiannual timescales. Here we have analysed the effect of accumulation of dust on the melt process. Lowering of the albedo by dust turns out to be a very effective process to enhance the summer melt rate. The equivalent temperature rise of 1.7 K needed to generate the same increase in melt rate demonstrates the significance of the accumulation of dust.

 

Les longues séries de mesures météorologiques effectuées sur la langue terminale du Vadret da Morteratsch rend possible l’étude de l’évolution de des budgets de masses et des budgets énergétiques à une échelle pluri-annuelle. Nous avons ici analysé les effets de l’accumulation de matériaux (Dust) sur les processus de fonte. La diminution de l’albédo suite à l’accumulation de matériaux s’avère être un catalyseur très efficace de l’accélération des processus de fonte. L’augmentation de température de 1.7K nécessaire pour la génération d’une augmentation des taux de fonte similaire à celle engendrée par la diminution de l’albédo montre bien les effets très importants de l’accumulation de matériaux.
Modélisations
 
Hypothèses
 

Sensibilité du milieu à des paramètres climatiques
Informations complémentaires (données utilisées, méthode, scénarios, etc.)
 

 


(3) - Effets du changement climatique sur l'aléa
Reconstitutions
 
Observations
 
Modélisations
 
Hypothèses
 

Paramètre de l'aléa
Sensibilité du paramètres de l'aléa à des paramètres climatiques
Informations complémentaires (données utilisées, méthode, scénarios, etc.)
 
 
 

(4) - Remarques générales
 

(5) - Syntèses et préconisations
 

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