Alpine lacustrine varved record reveals summer temperature as main control of glacier fluctuations over the past 2250 years

Abstract

Glacier fluctuations are a key indicator of changing climate. Their reconstruction beyond historical times unravels glacier variability and its forcing factors on long time scales, which can considerably improve our understanding of the climate–glacier relationship. Here, we present a 2250-year-long reconstruction of particle-mass accumulation rates recorded in the lacustrine sediments of Lake Trüebsee (Central Swiss Alps) that are directly related to glacier extent, thus reflecting a continuous record of fluctuations of the upstream-located Titlis Glacier. Mass accumulation rate values show strong centennial to multi-centennial fluctuations and reveal 12 well-pronounced periods of enhanced values corresponding to times of maximum extent of the neighboring Lower Grindelwald Glacier. This result supports previous studies of proglacial lake sediments that documented high mass accumulation rate values during glacier advances. The strong variability in the Lake Trüebsee mass accumulation rate record thus represents a highly sensitive paleoclimatic archive, which mirrors rapid and pronounced feedbacks of Titlis Glacier to climatic changes over the past 2250 years. The comparison of our data with independent paleo-temperature reconstructions from tree rings suggests that variations in mean summer temperature were the primary driving factor of fluctuations of Titlis Glacier. Also, advances of Titlis Glacier occurred during the grand solar minima (Dalton, Maunder, Spörer, Wolf) of the last millennium. This relation of glacier extent with summer temperature reveals strong evidence that the mass balance of this Alpine glacier is primarily controlled by the intensity of glacier melting during summer.

Keywords

Alps glacier fluctuations mass accumulation rate (MAR)proglacial lake sediments summer temperature varves

Introduction

Glaciers are considered as sensitive indicators of changing climate conditions as it has recently been observed by the substantial retreat of Alpine glaciers accompanying climate change (Lemke et al., 2007; Paul et al., 2004). The retreat of Alpine glaciers and its consequences for modern ecosystems and civilization has, therefore, been extensively studied (e.g. Chiarle et al., 2007; Huggel, 2009; Kääb et al., 2005; Meehl et al., 2007). Since Alpine glaciers represent important natural water reservoirs for the hydrological budget of Central Europe (Jansson et al., 2003), a distinct decrease and/or loss of glaciated areas due to the projected increase in mean temperature during all seasons in the Alpine region (CH2011, 2011; Paul et al., 2004) will significantly change the seasonal water availability for the Alpine area as well as for downstream regions. Moreover, glacier loss associated with a projected decrease in mean precipitation amounts during summer (CH2011, 2011; Meehl et al., 2007) will result in drier summer conditions and thus affect civilization and ecosystems in Alpine regions with its adjoining lowlands. The reconstruction of past glacier extension/retreat thus unravels natural glacier fluctuations as well as underlying climatic factors, providing important knowledge for the projection of glacier behavior under climate change.

Systematic measurements of Alpine glacier fluctuations only cover the past ~150 years, while the combination with historical reconstructions extends this record of glacier dynamics to the last ~450 years (e.g. Nussbaumer and Zumbühl, 2012). In order to expand this time scale, chronologies of Alpine glacier fluctuations throughout the Holocene were established using radiocarbon and/or dendrochronologically dated wood fragments, in situ found fossil trees as well as paleosols found in glacier forelands, all indicating stages of glacier retreats (Holzhauser et al., 2005; Hormes et al., 2001; Joerin et al., 2006). Additionally, cosmogenic exposure dating of moraine ridges provides valuable age constraints of prominent glacier stands (e.g. Schimmelpfennig et al., 2012). However, these approaches do not yield continuous records of glacier fluctuations, why the possibility to study multi-decadal to centennial variability during prehistoric times is limited.

Lake sediments are accurate archives of past climate conditions and have been used for various paleoclimatic studies (e.g. Brauer et al., 2008; Corella et al., 2012; Schwörer et al., 2014; Wilhelm et al., 2012; Wirth et al., 2013a). In particular, proglacial lake sediments have been studied to reconstruct glacier activity (Blass et al., 2007; Larsen et al., 2011; Leemann and Niessen, 1994a, 1994b; Nussbaumer et al., 2011; Stewart et al., 2011; Vasskog et al., 2012). These studies documented past glacier fluctuations based on the mass accumulation rate (MAR) of the sediment records. The approach was validated in Lake Silvaplana, whose sediments reveal a close correlation between MAR and instrumentally recorded fluctuations of the nearby glacier (Nussbaumer et al., 2011). An increased MAR in the lacustrine sediment record during glacial extension is explained by enhanced sub-glacial erosion with increased glacial cover in the respective catchment (Blass et al., 2007; Leonard, 1997; Leemann and Niessen, 1994a; Stewart et al., 2011; Trachsel et al., 2010). Therefore, annually laminated sediments of proglacial lakes have the potential to record glacier-length variations in high resolution. In this study, we present a 2250-year-long and continuous MAR record based on the annually laminated sediments of proglacial Lake Trüebsee (Central Swiss Alps), revealing fluctuations of Titlis Glacier and thus Central Alpine climate variability.

Study site

Lake Trüebsee, hereafter called Trüebsee, is a proglacial lake situated in the Swiss Alps (46°47′44″N, 8°23′17″E) at 1766 m.a.s.l. The lake is completely ice-covered during winter (Müller et al., 1998) and modern maximum water depth is ~8 m. The latter is the result of artificial damming of the outflow for electric power production in the early 20th century (Merian, 1946), which increased the lake level by ~3 m and thus enlarged the lake-surface area from 0.1 to 0.26 km² (Figure 1). The catchment area (7.07 km²) reaches a maximum elevation of 3238 m.a.s.l. and comprises a glacially covered area of ~0.9 km² (13%) (as of 2006 CE), which has been drastically decreased since the end of the ‘Little Ice Age’ (LIA; Figure 1). Sediment supply to the lake mainly consists of glacially eroded material as the lake is located directly downstream of Titlis Glacier. The geological setting of the lake’s catchment area is rather complex and is primarily composed of Helvetic and Infrahelvetic limestones, marls, and flysch units (Hotz, 1989). The study area is characterized by cool Alpine climate conditions with annual and summer (JJA) mean temperatures of −3.9°C and 2.5°C, respectively, measured at Mt Titlis (3238 m.a.s.l.) between 1993 and 2012 (MeteoSchweiz, 2013).

Figure 1.

(a) Regional setting of Trüebsee and Titlis Glacier (glacier extent after Dufour et al., 1864, and lidar data provided by swisstopo). Map of Switzerland shows location of Trüebsee (TR; orange asterisk), Lower Grindelwald Glacier (LGG), Great Aletsch Glacier (GAG) (blue dots), and Lake Silvaplana (LS) (gray asterisk). (b) Bathymetric map of Trüebsee based on reflection seismic data. Coring location is indicated by red dot.

Methods

Core recovery and sediment analysis

A high-resolution 3.5-kHz reflection seismic survey was conducted on Trüebsee to reveal information about the lake-basin morphology and the basin-wide sediment distribution. Based on the interpretation of these data, a bathymetric map and the seismic stratigraphy were established, and the coring site in the lake’s depositional center was defined (Figure 1b). Two parallel sediment cores were retrieved with an UWITEC percussion-coring device in March 2011, revealing a composite sediment-core length of 6.4 m. The closed sediment cores were analyzed for gamma-ray attenuation bulk density at a resolution of 0.5 cm with a GEOTEK multi-sensor core logger (MSCL). Then, sediment cores were longitudinally cut into halves and the sediment surface was photographed in fresh and slightly dried state (after about 2 days of exposure at room temperature, which considerably increased the clarity of the lamination; Figure 2). The detailed lithological characterization of the sediment succession was realized by visual description of the sediments combined with smear-slide analysis and core pictures of the dried sediment surface (Gilli et al., 2013). Microfacies analysis of thin sections of selected sediment intervals were performed using light microscopy as well as scanning electron microscopy (SEM) in combination with an energy-dispersive x-ray analysis system (EDX) and are presented in Glur (2013).

Figure 2.

(a) Age–depth model based on three independent varve counts (V1–V3) and confirmed by four radiocarbon ages, which are shown with their respective 2σ error ranges. The oldest of these ages (indicated in gray) was rejected because it originates from a mass-movement deposit (i.e. reworked material). Event deposits (mass movements, floods) were excluded from the sediment record for establishing the age–depth model. (b) Core photograph of deformed laminae (gray bar) and overlying homogenite (black bar) induced by the earthquake event in 1601 CE. (c) Core photograph of annual laminations and two interbedded turbidite deposits (blue bars). Arrows indicate winter laminae.

Age model

The age model is based on varve counting supported by radiocarbon dating and tied to one marker horizon, which was generated by a historic earthquake in the year 1601 that ranks among the strongest earthquakes in Switzerland during the last millennium (Schwarz-Zanetti et al., 2003; Strasser et al., 2006). This earthquake occurred near the village of Sarnen, Central Switzerland, less than 20 km away from Trüebsee. The epicentral area, including Trüebsee, was affected by intensities of VII on the European Macroseismic Scale, thus exceeding the threshold for the deformation of lake sediments (intensities of VI–VII; Monecke et al., 2004; Strasser et al., 2007). In the Trüebsee sediment record, a prominent 8-cm-thick interval that consists of disturbed and contorted laminations as well as liquefaction structures topped by a ~3-cm-thick homogenite is interpreted to be the result of this earthquake event (Figure 2b). Within this highly deformed sediment interval, 10 winter layers could be identified and were interpreted to represent the in situ deformed layers of the respective annual laminations (Monecke et al., 2006; Rodriguez-Pascua et al., 2000). Thus, the top of the homogenite and the bottom of the deformation structure with absolute ages of 1602 and 1592 were used as tie-points for the varve counting. The finally used varve age model (age model V1 in Figure 2a) reveals a continuous annually resolved chronology spanning the period from 1884 CE to 231 BCE. The varve age model V1 was verified by two independent varve counts (V2 and V3) performed by a second person. Both counts (V2 and V3) are in very good agreement with the used age model V1. Slight differences only occur in strongly deformed parts (deformation from coring operations), expressed in maximum age differences of ±21 and ±34 years, respectively. In addition, four samples of terrestrial plant remains were radiocarbon dated. However, the oldest sample was rejected as it represents reworked material from a turbidite deposit and thus implies a too old age (Table 1). All varve age models (V1–V3) lie within the 2σ error ranges of the three respective radiocarbon ages. For establishing the final age–depth model, event layers such as mass-movement-related and flood-related deposits were removed from the sediment sequence as they were deposited rapidly during only hours to days (Glur et al., 2013; Wirth et al., 2013b).

Table 1.

AMS radiocarbon ages.

Sample ID	Composite depth (cm)	Composite depth without event deposits (cm)	Radiocarbon age (BP)	±1σ	2σ age range of calibrated radiocarbon ages (BP)
ETH-42680	360.6	288	620	40	546–662
ETH-42683	507.6	413.3	1245	35	1075–1270
ETH-42681	629.7	515.3	1760	60	1541–1822
ETH-42908	766.9	635.4	2515	35	2471–2742^a

AMS: accelerator mass spectrometry.

Radiocarbon ages were calibrated with the OxCal software (Version 4.1.7) using the IntCal09 calibration curve (Reimer et al., 2009).

Discarded age: sample material derived from reworked material.

Varve thickness and MAR

Varve-thickness measurements were performed on the core photographs of the dried sediment surface using digital benchmarks (Figure 2c). Since the laminations suffer from coring-induced deformation and bending, varve thickness was consistently measured between the respective vertexes of the deformed dark-colored winter laminae. Varve thickness was transformed into flux by calculating the annual MAR using the following equation (Blass et al., 2007; Niessen et al., 1992)

MAR = s \times δ_{grain} \times (1 - n)

where s = varve thickness, δ_grain = 2.65 g/cm³, and n = fractional porosity.

Since previous studies (Stalder, 2011) revealed a low organic carbon content (~1%) and a consistent mineralogical composition (mostly detrital calcite without dissolution structures as well as few quartz grains and clay minerals) throughout the entire sediment succession, a constant grain-density value (δ_grain) of 2.65 g/cm³ was used for the MAR calculation. The fractional porosity was calculated by comparing the grain density with the measured wet bulk density (δ_{wet bulk}) provided by the core-logger measurements of the respective sediment sections (Anselmetti and Eberli, 1993).

n = \frac{(δ_{grain} - δ_{wet bulk})}{(δ_{grain} - δ_{water})}

Due to rather stable wet bulk density values along the entire sediment sequence and assumed constant grain density, varve thickness and MAR strongly correlate with a Pearson correlation coefficient of p = −0.98 (Supplementary Figure 1, available online).

In order to analyze varying amplitudes of periodicities of the Trüebsee MAR record over time, we calculated the wavelet spectrum using a MATLAB^™ code (Torrence and Compo, 1998).

Results

The topmost ~1 m of the sediment succession contains a mostly chaotic interval of gravel- to silt-grained material, which likely originates from the artificial damming of the lake and further construction activities in close proximity to the lake during the early to mid-20th century. Also, the first ~0.3 m of the subsequent underlying laminated sediment is strongly disturbed due to these activities. The topmost 1.3 m of the sediment core was thus not included into our analysis.

The undisturbed sediment succession (below 1.3 m depth) consists of light-colored, few millimeter- to centimeter-thick laminae alternating with dark-colored laminae of maximal 2 mm thickness. These two laminae types form the macroscopically regular and rhythmic annual lamination (i.e. clastic varves; Guyard et al., 2007; Sturm and Matter, 1978; Figure 2c). The light-colored laminae are interpreted to comprise several ice-/snow-melting events during the warm season, whereas the dark-colored and thinner laminae are formed by the settling of the finest clay-sized particles during late fall to late spring when the lake is ice-covered (Guyard et al., 2007). The laminated sequence is interrupted by several millimeter- to few centimeter-thick deposits of brownish color indicating a higher content of organic material and showing in most cases a fining upward gradation. They were interpreted as event deposits triggered by heavy precipitation events (Gilli et al., 2013; Glur et al., 2013; Wirth et al., 2013b) or by earthquakes (Monecke et al., 2006; Rodriguez-Pascua et al., 2000).

For interpretation and comparison with other paleoclimate records, we applied a 50-year moving average to the 2250-year-long MAR reconstruction of Trüebsee (Figure 3). The MAR data show strong variation between 0.17 and 0.56 g/cm²/yr (minimum at 109 and maximum at 1825 CE) with an average value of ~0.3 g/cm²/yr. Twelve well-pronounced intervals of enhanced MAR occur around 1850–1820, 1700–1675, 1620–1600, 1540–1460, 1300–1260, 1120–1100, 810–730, 630–530, 400–370, 240–170 CE as well as 30 CE–30 BCE and 140–225 BCE (gray bars in Figure 3a). During the past 800 years and from 800 CE to 225 BCE, the MAR record is characterized by distinct centennial to multi-centennial fluctuations. The period between 1200 and 800 CE, which includes the Medieval Climate Anomaly (MCA; 1250–950 CE), shows consistently low MAR values.

Figure 3.

(a) Glacier reconstructions of the Great Aletsch Glacier (black line; Holzhauser et al., 2005) and the Lower Grindelwald Glacier (blue line; Holzhauser et al., 2005); and lacustrine MAR records of Lake Silvaplana (black line; 50-year moving average; Stewart et al., 2011; Trachsel et al., 2010) and Lake Trüebsee (blue line; 50-year moving average; lighter blue line indicates highly deformed core section) over the past 2500 years. Further illustrated is a tree-ring-based Central European summer-temperature reconstruction (orange line; 50-year moving average; Büntgen et al., 2011) and variations in total solar irradiance (green line; Steinhilber et al., 2009). Gray-shaded areas indicate periods of high MAR values recorded in the Trüebsee sediments. (b) Zoom for the past 800 years: MAR record of Trüebsee (blue line; 25-year running average), Alpine summer mean temperature and winter mean precipitation (light blue and violet line; Casty et al., 2005), tree-ring-based Central European summer temperature (orange line; 25-year running average; Büntgen et al., 2011) and variations in total solar irradiance (TSI, green line; Steinhilber et al., 2009). Yellow-shaded areas indicate grand solar minima (on the basis of TSI reconstruction of Steinhilber et al., 2009) correlating with high MAR values and low summer temperatures.

The MAR chronology of Trüebsee was compared with three independent paleoclimatic data sets that reveal Alpine glacier variations back to prehistoric times (Figure 3). These datasets include glacier fluctuations of the Great Aletsch Glacier, the largest Alpine Glacier (surface area of 81.69 km² in 1998 CE; Paul, 2003) and of the Lower Grindelwald Glacier (surface area of 18.7 km² in 1998 CE; Paul, 2003), which are based on written and historical photographs/paintings for the past ~450 years and on radiocarbon and dendrochronologically dated fossil trees for the past 3500 years (Holzhauser et al., 2005). Additionally, MAR values from the annually laminated sediment record of Lake Silvaplana reflect continuous length changes of the nearby Tschierva Glacier (surface area of 6.2 km² in 1973 CE; Nussbaumer et al., 2011) but only covers the time period until 1142 CE and between 420 CE and 1450 BCE (Stewart et al., 2011; Trachsel et al., 2010). However, in contrast to our MAR record from Trüebsee, these datasets are noncontinuous over the past 2000 years.

Overall, the records of the Lower Grindelwald Glacier and of Lake Silvaplana indicate similar patterns of glacier fluctuations as our Trüebsee MAR record (Figure 3a). In particular, each peak of enhanced MAR values in Trüebsee corresponds to major glacial advances of the Lower Grindelwald Glacier back to the 14th century CE. Absolute MAR values of Lake Silvaplana are generally lower (ranging between 0.12 and 0.35 g/cm²/yr) and their variation is less pronounced than in Trüebsee. However, specific peaks of MAR values of these two records match well around 1850–1820, 1620–1600, 240–170 CE and 30 CE–30 BCE. In addition, modest highs in MAR match around 1540–1460 and 400–370 CE. When considering the reconstruction of the Great Aletsch Glacier, a decadal to multi-decadal delay of its advances in respect to the much smaller Titlis Glacier and Lower Grindelwald Glacier is observed around 1620–1600, 1300–1260, 1120–1100, 810–730, 630–530, and 240–170 CE.

The performed wavelet analysis reveals a distinct periodicity of 180–210 years, except for the interval between 1000 and 700 CE. Moreover, significant (95% confidence level) periods of 80–140 and 260–300 years can be found for the past 1000 years, and also several shorter intervals with periods centered at 55 and 13 years occur (Figure 4). The presence of similar cycles of ~100 and 210 years in Lake Silvaplana and of ~70–100 years at the Lower Grindelwald Glacier (Nussbaumer et al., 2011) underscores the above-discussed visual agreement of these records and our MAR reconstruction.

Figure 4.

Time series analysis of annually resolved mass accumulation rates (MARs) recorded in the sediments of Trüebsee over the past 2250 years. The presented wavelet power spectrum was calculated using a modified code from Torrence and Compo (1998). Black lines mark 95% significance levels.

Discussion

The strong similarity of glacier-length reconstructions of the Lower Grindelwald and the Great Aletsch Glacier with our MAR dataset indicates that the Trüebsee record represents a common Central Alpine climate signal. The weaker correlation between our MAR record and the Lake Silvaplana MAR record is most likely caused by the special location of Lake Silvaplana that lies in the enclosed Engadine valley within the Alpine main chain. This area is characterized by a different climatic setting that is considerably influenced by South Alpine weather patterns (Blass et al., 2007). Moreover, the high variability and pronounced multi-decadal to centennial fluctuations of our MAR record indicates rapid feedbacks of the Titlis Glacier to even small and short-term climate variations. In fact, the small size of the Titlis Glacier seems to be an advantage for tracking these rapid variations. In contrast, the Great Aletsch Glacier reveals, as a result of its much larger area, multi-centennial fluctuations, which rather indicate long-term climate fluctuations with a delayed response time of 50–100 years to climatic changes (Haeberli and Holzhauser, 2003; Holzhauser et al., 2005). This time-delayed and attenuated response of the Great Aletsch Glacier could explain the weaker correlation between fluctuations of the Great Aletsch Glacier and the Trüebsee MAR record. Consequently, the two well-pronounced but short-term glacier advances of the much smaller Titlis Glacier around 1700–1675 CE and 1620–1600 CE seem thus to be ‘merged’ into only one glacier advance of the Great Aletsch Glacier between 1700 and 1600 CE.

Summer mean temperature has been proposed to be the dominant control on the mass balance of Alpine glaciers (Huss et al., 2010; Steiner et al., 2008). In order to study the impact of changing summer temperatures on glacier fluctuations over the past 2250 years, we compared our MAR record with a tree-ring-based summer temperature reconstruction for Central Europe (Büntgen et al., 2011; Figure 3a). Throughout the entire record, all peaks of high MAR values, and thus of advances of Titlis Glacier, correspond to low mean summer temperatures. In addition to this visual agreement, we also find a strong numerical inverse relationship expressed by a Pearson correlation of p = −0.47 (both data series are smoothed with a 50-year moving average). For the past 500 years, an additional independent Alpine summer mean temperature record based on instrumental and historical evidence (Casty et al., 2005) confirms this strong negative correlation (Figure 3b). On the contrary, when studying the influence of changing winter precipitation and its potential to decrease or enhance snow accumulation at the Titlis Glacier, we find no relationship between our MAR record and the reconstructed mean winter precipitation over the past 500 years (Casty et al., 2005; Figure 3b). These findings indicate that major advances of the Titlis Glacier occurred during periods of decreased summer mean temperatures, whereas winter precipitation seems to have an insignificant influence on glacier fluctuations.

In addition, solar influence on glacier fluctuations is widely discussed in the scientific literature, and coinciding periods of low solar activity and glacier advances have been found (e.g. Joerin et al., 2006; Nussbaumer et al., 2011; Wanner et al., 2008). Variations in solar activity potentially cause changes in air temperatures (Wanner et al., 2008); however, solar influence on climate and in particular on air temperature is complex and not yet thoroughly understood (Steinhilber et al., 2012; Wanner et al., 2008). Still, several studies suggest that cooler winters occur when solar activity is low (Ineson et al., 2011; Lockwood, 2012). Assuming that periods of low winter temperatures are also characterized by lower summer temperatures, this would indicate solar influence on our MAR record and thus on Alpine glacier fluctuations. In fact, solar influence on the MAR record of Trüebsee is supported by a strong spectral presence of the solar ~210-year de Vries cycle, a less pronounced occurrence of the ~88-year Gleissberg cycle and of the ~11-year solar Schwabe cycle (Peristykh and Damon, 2003; Steinhilber et al., 2009; Wanner et al., 2008; Figure 4). Over the past 800 years, the relation with solar activity is also evident in glacial advances of the Titlis Glacier during the Dalton (~1820 CE), Maunder (~1680 CE), Spörer (~1470 CE), and Wolf (~1300 CE) grand solar minima, which were all accompanied by low summer mean temperatures (Büntgen et al., 2011; Casty et al., 2005; Steinhilber et al., 2009; Usoskin et al., 2007; Figure 3b). However, the number of advances of the Titlis Glacier indicated by our MAR record correlating to low summer temperature exceeds the number of solar lows present in the reconstruction of Steinhilber et al. (2009). Therefore, we consider varying summer temperatures as the main forcing factor controlling fluctuations of this Alpine glacier over the past 2250 years.

Conclusion

The annually resolved and thus highly sensitive paleoclimatic record of the lacustrine sediments of Trüebsee reflect fluctuations of the nearby Titlis Glacier in the Central Alps by varying MAR values over the past 2250 years. Unlike other glacier reconstructions, the MAR record reveals glacial fluctuations in a continuous fashion. We identified 12 well-pronounced periods of glacier advances, all coinciding with low summer temperatures and partly with solar minima. Therefore, we conclude that summer mean temperature is the primary mass-balance control of Alpine glaciers due to enhanced or decreased glacier melting. In terms of global climate change, our findings corroborate that the projected increase in summer temperatures (CH2011, 2011; Meehl et al., 2007) is the most effective process to cause significant loss of glaciated areas in the Alpine region. As we found no evidence of glacier advances caused by increased amounts of winter precipitation, the projected increase of this type of precipitation in the Alpine region (CH2011, 2011; Meehl et al., 2007) will most likely not be able to compensate the glacier-mass loss from increased summer-time melting under climate warming.

Footnotes

Acknowledgements

We thank Michael Hilbe, Christoph Schär, and Mario M. Morellon for support during the seismic survey and coring campaign at Lake Trüebsee; the mountain railway operators of the Titlis region (Engelberg-Titlis Tourismus AG) for sponsored transports of material and persons to the lake; EWN (electric power company of Nidwalden, Switzerland) for giving us the opportunity to retrieve sediment cores from Lake Trüebsee; Ulf Büntgen, Jürg Beer, Martin Grosjean, Michael Hilbe, and Monique Stewart for fruitful discussions of the results and/or manuscript; and Irene Brunner for sediment-sample analysis.

Funding

This study was funded by the Swiss National Science Foundation (SNF) (Grant 200020-137930 and 200021-121909).

References

Anselmetti

Eberli

(1993) Controls on sonic velocity in carbonates. Pure and Applied Geophysics 141: 287–323.

Blass

Grosjean

Troxler

. (2007) How stable are twentieth-century calibration models? A high-resolution summer temperature reconstruction for the eastern Swiss Alps back to AD 1580 derived from proglacial varved sediments. The Holocene 17: 51–63.

Brauer

Haug

Dulski

. (2008) An abrupt wind shift in western Europe at the onset of the Younger Dryas cold period. Nature Geoscience 1: 520–523.

Büntgen

Tegel

Nicolussi

. (2011) 2500 years of European climate variability and human susceptibility. Science 331: 578–582.

Casty

Wanner

Luterbacher

. (2005) Temperature and precipitation variability in the European Alps since 1500. International Journal of Climatology 25: 1855–1880.

CH2011 (2011) Swiss Climate Change Scenarios CH2011. Zürich: C2SM, MeteoSwiss, ETH, NCCR Climate, and OcCC, 88 pp.

Chiarle

Iannotti

Mortara

. (2007) Recent debris flow occurrences associated with glaciers in the Alps. Global and Planetary Change 56: 123–136.

Corella

Brauer

Mangili

. (2012) The 1.5-ka varved record of Lake Montcortès (southern Pyrenees, NE Spain). Quaternary Research 78: 323–332.

Dufour

Müllhaupt

Koegel

(1864) Interlachen, Sarnen, Stanz (Kartenmaterial). Topographische Karte der Schweiz. Geneva: Schweiz Eidgenössisches Topographisches Bureau.

10.

Gilli

Anselmetti

Glur

. (2013) Lake sediments as archives of recurrence rates and intensities of past flood events. In: Schneuwly-Bollschweiler

Stoffel

Rudolf-Miklau

(eds) Dating Torrential Processes on Fans and Cones – Methods and Their Application for Hazard and Risk Assessment (Advances in Global Change Research). Dordrecht: Springer, pp. 225–242.

11.

Glur

(2013) Holocene flood variability and glacier fluctuations in the Central Alps revealed by lacustrine sediments. PhD Thesis, No. 21027, ETH Zürich. Available at: https://dx-doi-org.web.bisu.edu.cn/10.3929/ethz-a-009906720.

12.

Glur

Wirth

Büntgen

. (2013) Frequent floods in the European Alps coincide with cooler periods of the past 2500 years. Scientific Reports 3: Article 2770. DOI:10.1038/srep02770.

13.

Guyard

Chapron

St-Onge

. (2007) High-altitude varve records of abrupt environmental changes and mining activity over the last 4000 years in the Western French Alps (Lake Bramant, Grandes Rousses Massif). Quaternary Science Reviews 26: 2644–2660.

14.

Haeberli

Holzhauser

(2003) Alpine glacier mass changes during the past millennia. Pages News 11: 13–15.

15.

Holzhauser

Magny

Zmbühl

(2005) Glacier and lake-level variations in west-central Europe over the last 3500 years. The Holocene 15: 789–801.

16.

Hormes

Müller

Schlüchter

(2001) The Alps with little ice: Evidence for eight Holocene phases of reduced glacier extent in the Central Swiss Alps. The Holocene 11: 255–265.

17.

Hotz

(1989) Zur Geologie zwischen Jochpass und Titlis. Diplomarbeit (Master’s Thesis), ETH Zurich.

18.

Huggel

(2009) Recent extreme slope failures in glacial environments: Effects of thermal perturbation. Quaternary Science Reviews 28: 1119–1130.

19.

Huss

Hock

Bauder

. (2010) 100-year mass changes in the Swiss Alps linked to the Atlantic Multidecadal Oscillation. Geophysical Research Letters 37: L10501.

20.

Ineson

Scaife

Knight

. (2011) Solar forcing of winter climate variability in the Northern Hemisphere. Nature Geoscience 4: 753–757.

21.

Jansson

Hock

Schneider

(2003) The concept of glacier storage: A review. Journal of Hydrology 282: 116–129.

22.

Joerin

Stocker

Schlüchter

(2006) Multicentury glacier fluctuations in the Swiss Alps during the Holocene. The Holocene 16: 697–704.

23.

Kääb

Reynolds

Haeberli

(2005) Glacier and permafrost hazards in high mountains. In: Huber

Bugmann

HKM

Reasoner

(eds) Global Change and Mountain Regions (Advances in Global Change Research). Dordrecht: Springer, pp. 225–234.

24.

Larsen

Miller

Geirsdóttir

. (2011) A 3000-year varved record of glacier activity and climate change from the proglacial lake Hvítárvatn, Iceland. Quaternary Science Reviews 30: 2715–2731.

25.

Leemann

Niessen

(1994a) Holocene glacial activity and climatic variations in the Swiss Alps: Reconstructing a continuous record from proglacial lake sediments. The Holocene 4: 259–268.

26.

Leemann

Niessen

(1994b) Varve formation and the climatic record in an Alpine proglacial lake: Calibrating annually-laminated sediments against hydrological and meteorological data. The Holocene 4: 1–8.

27.

Lemke

Ren

Alley

. (2007) Observations: Changes in snow, ice and frozen ground. In: Solomon

Qin

Manning

. (eds) Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge and New York: Cambridge University Press, pp. 337–384.

28.

Leonard

(1997) The relationship between glacial activity and sediment production: Evidence from a 4450-year varve record of neoglacial sedimentation in Hector Lake, Alberta, Canada. Journal of Paleolimnology 17: 319–330.

29.

Lockwood

(2012) Solar influence on global and regional climates. Surveys in Geophysics 33: 503–534. DOI:10.1007/s10712-012-9181-3.

30.

Meehl

Stocker

Collins

. (2007) Global climate projections. In: Solomon

Qin

Manning

31.

Merian

(1946) Eine neue geomorphologische Untersuchungs und Darstellungsmethode am Beispiel des oberen Engelberger Tales. PhD Thesis, Universität Zürich.

32.

MeteoSchweiz (2013) Climap-net database. Available at: http://www.meteoschweiz.admin.ch/web/en/services/data_portal/climap-net.html (accessed 16 April 2014).

33.

Monecke

Anselmetti

Becker

. (2004) The record of historic earthquakes in lake sediments of Central Switzerland. Tectonophysics 394: 21–40.

34.

Monecke

Anselmetti

Becker

. (2006) Earthquake induced deformation structures in lake deposits: A Late Pleistocene to Holocene paleoseismic record for Central Switzerland. Eclogae Geologicae Helvetiae 99: 343–362.

35.

Müller

Lotter

Sturm

. (1998) Influence of catchment quality and altitude on the water and sediment composition of 68 small lakes in Central Europe. Aquatic Sciences 60: 316–337.

36.

Niessen

Wick

Bonani

. (1992) Aquatic system response to climate and human changes: Productivity, bottom water oxygen status, and sapropel formation in Lake Lugano over the last 10 000 years. Aquatic Sciences 54: 257–276.

37.

Nussbaumer

Zumbühl

(2012) The Little Ice Age history of the Glacier des Bossons (Mont Blanc area, France): A new high-resolution glacier length curve based on historical documents. Climatic Change 111: 301–334.

38.

Nussbaumer

Steinhilber

Trachsel

. (2011) Alpine climate during the Holocene: A comparison between record of glaciers, lake sediments and solar activity. Journal of Quaternary Science 26: 703–713.

39.

Paul

(2003) The new Swiss glacier inventory 2000 – Application of remote sensing and GIS. PhD Thesis, Universität Zürich.

40.

Paul

Kääb

Maisch

. (2004) Rapid disintegration of Alpine glaciers observed with satellite data. Geophysical Research Letters 31: L21402.

41.

Peristykh

Damon

(2003) Persistence of the Gleissberg 88-year solar cycle over the last ~12,000 years: Evidence from cosmogenic isotopes. Journal of Geophysical Research 108: 1–15. DOI:10.1029/2002JA009390.

42.

Reimer

Baillie

MGL

Bard

. (2009) Intcal09 and Marine09 radiocarbon age calibration curves, 0–50,000 years cal BP. Radiocarbon 51: 1111–1150.

43.

Rodriguez-Pascua

Calvo

De Vicente

. (2000) Soft-sediment deformation structures interpreted as seismites in lacustrine sediments of the Prebetic Zone, SE Spain, and their potential use as indicators of earthquake magnitudes during the late Miocene. Sedimentary Geology 135: 117–135.

44.

Schimmelpfennig

Schaefer

Akçar

. (2012) Holocene glacier culminations in the Western Alps and their hemispheric relevance. Geology 40: 891–894.

45.

Schwarz-Zanetti

Deichmann

Fäh

. (2003) The earthquake in Unterwalden on September 18, 1601: A historico-critical macroseismic evaluation. Eclogae Geologicae Helvetiae 96: 441–450.

46.

Schwörer

Kaltenrieder

Glur

. (2014) Holocene climate, fire and vegetation dynamics at the treeline in the Northwestern Swiss Alps. Vegetation History and Archaeobotany 23: 479–496. DOI:10.1007/s00334-013-0411-5.

47.

Stalder

(2011) Die Sedimente des Trüebsees – Rekonstruktion holozäner Klima- und Umweltveränderungen. Bachelor’s Thesis, ETH Zurich.

48.

Steiner

Pauling

Nussbaumer

. (2008) Sensitivity of European glaciers to precipitation and temperature – Two case studies. Climatic Change 90: 413–441.

49.

Steinhilber

Beer

Fröhlich

(2009) Total solar irradiance during the Holocene. Geophysical Research Letters 36: L19704.

50.

Steinhilber

Abreu

Beer

. (2012) 9400 years of cosmic radiation and solar activity from ice cores and tree rings. Proceedings of the National Academy of Sciences of the United States of America 109: 5967–5971.

51.

Stewart

Grosjean

Kuglitsch

. (2011) Reconstructions of late Holocene paleofloods and glacier length changes in the Upper Engadine, Switzerland (c. 1450 BC–AD 420). Palaeogeography, Palaeoclimatology, Palaeoecology 311: 215–223.

52.

Strasser

Anselmetti

Fäh

. (2006) Magnitudes and source areas of large prehistoric northern Alpine earthquakes revealed by slope failures in lakes. Geology 34: 1005–1008.

53.

Strasser

Stegmann

Bussmann

. (2007) Quantifying subaqueaous slope stability during seismic shaking: Lake Lucerne as model for ocean margins. Marine Geology 240: 77–97.

54.

Sturm

Matter

(1978) Turbidites and varves in Lake Brienz (Switzerland): Deposition of clastic detritus by density currents. In: Matter

Tucker

(eds) Modern and Ancient Lake Sediments (Special Publications no. 2 of International Association of Sedimentologist). Oxford: Blackwell Scientific Publications, pp. 147–168.

55.

Torrence

Compo

(1998) A practical guide to wavelet analysis. Bulletin of the American Meteorological Society 79: 61–78.

56.

Trachsel

Grosjean

Larocque-Tobler

. (2010) Quantitative summer temperature reconstruction derived from combined biogenic Si and chironomid record from varved sediments of Lake Silvaplana (south-eastern Swiss Alps) back to AD 1177. Quaternary Science Reviews 29: 2719–2730.

57.

Usoskin

Solanki

Kovaltsov

(2007) Grand minima and maxima of solar activity: New observational constraints. Astronomy and Astrophysics 471: 301–309.

58.

Vasskog

Paasche

Nesje

. (2012) A new approach for reconstructing glacier variability based on lake sediments recording input from more than one glacier. Quaternary Research 77: 192–204.

59.

Wanner

Beer

Bütikofer

. (2008) Mid- to Late Holocene climate change: An overview. Quaternary Science Reviews 27: 1791–1828.

60.

Wilhelm

Arnaud

Sabatier

. (2012) 1400yr of extreme precipitation patterns over the Mediterranean French Alps and possible forcing mechanisms. Quaternary Research 78: 1–12.

61.

Wirth

Gilli

Simonneau

. (2013a) A 2000 year long seasonal record of floods in the southern European Alps. Geophysical Research Letters 40: 1–5. DOI:10.1002/grl.50741.

62.

Wirth

Glur

Gilli

. (2013b) Holocene flood frequency across the Central Alps – Solar forcing and evidence for variations in North Atlantic atmospheric circulation. Quaternary Science Reviews 80: 112–128.