Alpine climate during the Holocene: a comparison between records of glaciers, lake sediments and solar activity

Abstract

The European Alps are very sensitive and vulnerable to climate change. Recent improvements in Alpine glacier length records and climate reconstructions from annually laminated sediments of Alpine Lake Silvaplana give the opportunity to investigate the relationship between these two data sets of Alpine climate. Two different time frames are considered: the last 500–1000 years as well as the last 7400 years. First, we found good agreement between the two different climate archives during the past millennium: mass accumulation rates and biogenic silica concentration are largely in phase with the glacier length changes of Mer de Glace and Unterer Grindelwaldgletscher, and with the records of glacier length of Grosser Aletschgletscher and Gornergletscher. Secondly, the records are compared with temporally highly resolved data of solar activity. The Sun has had a major impact on the Alpine climate variations in the long term, i.e. several centuries to millennia. Solar activity varies with the Hallstatt periodicity of about 2000 years. Hallstatt minima are identified around 500, 2500 and 5000 a. Around these times grand solar minima (such as the Maunder Minimum) occurred in clusters coinciding with colder Alpine climate expressed by glacier advances. During the Hallstatt maxima around 0, 2000 and 4500 a, the Alpine glaciers generally retreated, indicating a warmer climate. This is supported by archaeological findings at Schnidejoch, a transalpine pass in Switzerland that was only accessible when glaciers had retreated. On shorter timescales, however, the influence of the Sun cannot be as easily detected in Alpine climate change, indicating that in addition to solar forcing, volcanic influence and internal climate variations have played an important role. Copyright © 2011 John Wiley & Sons, Ltd.

Little Ice Age climate reconstruction from ensemble reanalysis of Alpine glacier fluctuations

“…Likely processes leading to this rapid glacier growth are increased accumulation due to 25 % higher winter precipitation than present (Vincent et al, 2005), or reduced melt due to lower incoming shortwave radiation (Miller et al, 2012). More qualitatively, Nussbaumer et al (2011) conclude that "a combination of low solar forcing, frequent and strong volcanic eruptions, and dynamic effects due to internal variability of the climate system led to the prominent glacier advances during the LIA". The rapid recession of the glaciers after 1865 has been explained by glacier surface darkening, and thus albedo reduction, by increasing release of industrial black carbon (Painter et al, 2013).…”

“…Several recent studies state that GLCs are closely related to total solar irradiance (TSI), although the similarity is limited to several time spans (e.g., Beer et al, 2009;Nussbaumer et al, 2011). Since GLCs are mostly a delayed reaction to climate forcing, a more direct relationship should exist between ELA variations and shortwave radiation.…”

“…1550-1850 C.E. ), and the last maximum extent around 1850-1865 cannot be explained using homogenized instrumental temperature data (e.g., Nesje and Dahl, 2003;Vincent et al, 2005;Nussbaumer et al, 2011). Likely processes leading to this rapid glacier growth are increased accumulation due to 25 % higher winter precipitation than present (Vincent et al, 2005), or reduced melt due to lower incoming shortwave radiation (Miller et al, 2012).…”

“…GLCs have been used in a qualitative manner to confirm climate reconstructions from other proxies (Guiot et al, 2010) or compare them with solar forcing reconstructions (e.g., Beer et al, 2009;Nussbaumer et al, 2011). However, such comparisons suffer from the delayed response of glacier length to climatic or radiative forcing, and are only valid on long timescales.…”

Archaeological Discoveries on Schnidejoch and at Other Ice Sites in the European Alps

“…Crossing the pass safely was probably possible only at times when the climate was warmer and the glaciers had greatly retreated. One can postulate a direct link between retreating glaciers and the use of the Schnidejoch pass (Grosjean et al, 2007;Nussbaumer et al, 2011). In general, one may assume that in prehistoric and early historic times, alpine passes that were considered safer and easier to cross were generally preferred.…”