Climatic drivers of seasonal glacier mass balances: an analysis of 6 decades at Glacier de Sarennes (French Alps) 1IRSTEA, UR ETGR Erosion Torrentielle Neige et Avalanches, BP 76, 2 rue de la papeterie, Saint Martin d'Hères, France
15 Jan 2013
2CNRS/UJF-Grenoble 1, LGGE Laboratoire de Glaciologie et Géophysique de l'Environnement, BP 96, 54 rue Molières, Saint Martin d'Hères, France
Received: 07 May 2012 – Published in The Cryosphere Discuss.: 14 June 2012 Abstract. Refined temporal signals extracted from a winter and summer mass balance
series recorded at Glacier de Sarennes (French Alps) using variance
decomposition are related to local meteorological data and large-scale North
Atlantic Oscillation (NAO) anomalies in terms of interannual variability, trends of the low-frequency
signals, and breaks in the time series. The winter balance has increased by
+23% since 1976 due to more precipitation in early and late winter.
The summer balance has decreased since 1982 due to a 43% increase in
snow and ice melt. A 24-day lengthening of the ablation period – mainly due
to longer ice ablation – is the main component in the overall increase in
ablation. In addition, the last 25 yr have seen increases in ablation rates
of 14 and 10% for snow and ice, respectively. A simple degree-day
analysis can account for both the snow/ice melt rate rise and the lengthening
of the ablation period as a function of higher air temperatures. From the
same analysis, the equilibrium-line altitude of this 45° N latitude
south-facing glacier has a sensitivity to temperature of
+93 m °C−1 around its mean elevation of 3100 m a.s.l. over
6 decades. The sensitivity of summer balance to temperature is
−0.62 m w.e. yr−1 °C−1 for a typical 125-day-long
ablation season. Finally, the correlation of winter and summer mass balance
terms with NAO anomalies is investigated. Singularly, highest values are
obtained between winter NAO anomalies and summer balance. Winter NAO
anomalies and winter balance and precipitation are almost disconnected.
However, these results strongly depend on how the NAO signal is smoothed, so
that the link between Sarennes mass balance seasonal terms and NAO signal
remains tenuous and hard to interpret.
Revised: 11 December 2012 – Accepted: 12 December 2012 – Published: 15 January 2013
Citation: Thibert, E., Eckert, N., and Vincent, C.: Climatic drivers of seasonal glacier mass balances: an analysis of 6 decades at Glacier de Sarennes (French Alps), The Cryosphere, 7, 47-66, doi:10.5194/tc-7-47-2013, 2013.