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Multicentury glacier fluctuations in the
Swiss Alps during the Holocene
Ulrich E. Joerin,
1
*Thomas F. Stocker
2
and
Christian Schlu
¨chter
1
(
1
Institute of Geological Sciences, University of Bern, Baltzerstrasse 1, CH-3012
Bern, Switzerland;
2
Climate and Environmental Physics, Physics Institute,
University of Bern, Sidlerstrasse 5, CH-3012 Bern, Switzerland)
Received 5 September 2005; revised manuscript accepted 2 February 2006
Abstract: Subfossil remains of wood and peat from six Swiss glaciers found in proglacial fluvial sediments
indicate that glaciers were smaller than the 1985 reference level and climatic conditions allowed vegetation
growth in now glaciated basins. An extended data set of Swiss glacier recessions consisting of
143 radiocarbon dates is presented to improve the chronology of glacier fluctuations. A comparison
with other archives and dated glacier advances suggests 12 major recession periods occurring at 9850
9600, 93008650, 85508050, 77007550, 74506550, 61505950, 57005500, 52004400, 43003400,
28002700, 21501850, 14001200 cal. yr BP. It is proposed that major glacier fluctuations occurred on a
multicentennial scale with a changing pattern during the course of the Holocene. After the Younger Dryas,
glaciers receded to a smaller extent and prolonged recessions occurred repeatedly, culminating around 7
cal. kyr BP. After a transition around 6 cal. kyr BP weak fluctuations around the present level dominated.
After 3.6 cal. kyr BP less frequent recessions interrupted the trend to advanced glaciers peaking with the
prominent ‘Little Ice Age’. This trend is in line with a continuous decrease of summer insolation during the
Holocene.
Key words: Multicentury, glacier recession, glacier fluctuations, climate records, climate variability, Alps,
Switzerland, Holocene.
Introduction
A stable level of Holocene climate is revealed by oxygen
isotopes as a proxy of annual temperature in greenland ice
cores (Johnsen et al., 1997) and northern Alpine lake sediments
(von Grafenstein et al., 1999). This is surprising given the
decreasing summer insolation reduction at 658N totalling
about 50 W/m
2
since 10 kyr BP (Berger, 1978). However, a
growing number of studies (Mayewski et al., 2004 and
references therein) have demonstrated that distinct periods of
climate change occurred repeatedly throughout the Holocene.
Considering the Alps, the analysis of lake sediments provided
broad insights into the characteristics of Holocene environ-
mental conditions. Several periods with pronounced warming
were identified during the Holocene by studies based on pollen
(Haas et al., 1998), tree line positions (Tinner and Theurillat,
2003) or chironomid assemblages (Heiri et al., 2003).
The impact of cooler conditions, including the well known
8.2 ka event (Alley et al., 1997), was reported by studies
on biotic proxies (von Grafenstein et al., 1999; Tinner and
Lotter, 2001) and by model simulations (Renssen et al., 2001).
These cold events have been related to known periods of
glacier advances (Denton and Karle´n, 1973), but information
on retreated glaciers during warmer periods remained sparse
(Ro
¨thlisberger, 1986). In fact, the exceptional trend of warming
during the twentieth century in relation to the last 1000
years (Intergovernmental Panel on Climate Change (IPCC),
2001) highlights the importance of assessing natural variability
of climate change including periods of both, cooling and
warming.
After the ‘Little Ice Age’ (
AD
1850) alpine glaciers have
retreated substantially, exposing high walls of lateral moraines.
In some places, these moraines consist of a stack of different
till units indicating several Holocene glacial advances. Previous
work focused on mapping and dating of organic soils in
moraine sequences, interpreting radiocarbon ages as the date
of embedding related to glacier advances (Ro
¨thlisberger, 1986).
However, reconstructions based only on moraines are incom-
plete because of discontinuous deposition and are subject to
problems concerning the dating of palaeosoils (Matthews,
1997; Hormes et al., 2004) and their stratigraphic interpreta-
tion (Matthews, 1997). Information is generally sparse on
periods of retreated glaciers because subsequent glacier
advances destroyed smaller moraines. Some studies indicated
*Author for correspondence (e-mail: ujoerin@geo.unibe.ch)
The Holocene 16,5 (2006) pp. 697704
#2006 SAGE Publications 10.1191/0959683606hl964rp
that glaciers were once smaller (Porter and Orombelli, 1985;
Slupetzky, 1993), but the temporal and spatial singularity
of data precluded an accurate control on the timing and extent
of retreated glaciers. Recent findings of wood and peat
fragments associated with meltwater outburst events have
directed attention to the palaeoclimatic significance of sub-
glacial sedimentary basins (Nicolussi and Patzelt, 2000a;
Hormes et al., 2001).
This study examines Holocene glacier recessions in the Swiss
Alps based on radiocarbon-dated material found in proglacial
fluvial sediments of subglacial origin. New data, mainly from
the Bernina Massif, are combined with earlier data resulting in
a chronology of Swiss glacier fluctuations.
Characterization of glaciers and
subfossil wood and peat
Location and characteristics of the investigated glaciers are
presented in Figure 1 and Table 1. Tschierva and Forno
Glaciers belong to the Bernina Massif of the Eastern Swiss
Alps with precipitation originating mainly from the south. The
Unteraar and Steinlimi Glaciers are located in the Central
Swiss Alps (Grimsel) dominated by North-Atlantic weather.
Ried and Mont Mine´ Glaciers experience the inner alpine,
relatively dry climate of the Valais surrounded by high
mountains (Figure 1).
The following criteria for the selection of suitable glaciers
were used in order to obtain a consistent data set: (1) no
modern sources of wood growth on unglaciated slopes in the
catchment, (2) no possible input of wood fragments from
avalanches, (3) no short or steep glaciers, because of their short
response times to climatic fluctuations and other limitations
such as topography or special local wind conditions. All
glaciers of this study satisfy these criteria by being long and
flat with low bed roughness. All glaciers terminate at an
altitude of 1950 to 2300 m a.s.l., which is close to the local
tree line. The volume response time was estimated as the ratio
of maximum ice thickness to ablation at the terminus
(Johannesson et al., 1989). Response times of 21 to 67 years
resulting from the estimates given in Table 1 indicate that the
investigated glaciers reflect significant periods of climatic
change with durations exceeding 50 years. Therefore, we
assume that our samples are evidence of vegetation growth in
basins that are unvegetated at present. Because of rapid
downwasting of glacier tongues for the last 15 years glaciers
are far out of equilibrium. This does not allow a reasonable
relation of terminus position to climatic conditions. Since
glaciers readvanced after 1965, approaching a near equilibrium
state around the early 1980s, the glacier length in 1985 was
chosen as a reference level (approximating present conditions).
Therefore, the usage of the term ‘recession’ refers to the fact
that glacier length was shorter than the 1985 reference level
and the corresponding climatic conditions (Table 1).
A
I
F
D
8°E 10°E
47°N
46°N
48°N
Southern alpine border
Northern alpine border
RG
UA
Ts
Fo
SG
AL
MM
A
Figure 1 Sketch map of the Swiss Alps showing the locations of the investigated glaciers. Fo, Forno Glacier and Ts, Tschierva Glacier
belong to the Bernina Massif; SG, Steinlimi Glacier; UA, Unteraar Glacier (Grimsel); MM, Mont Mine´ Glacier; and RG, Ried Glacier
(Valais). Further locations A, Arolla; AL, Aletsch Glacier
Table 1 Properties of investigated glaciers in the Swiss Alps on the 1985 reference date and according to the Swiss Glacier observation
network data base
Unit Tschierva Forno Ried Mont Mine´ Unteraar Steinlimi
Terminus altitude m a.s.l. 2280 2210 2000 2000 1950 2140
Glacier area
a
km
2
6.2 8.72 8.22 10.97 29.48 2.3
Length of flowline
a
km 4.75 6.15 6.35 8.35 12.95 2.8
H
max
(estimated)
b
m 200 300 250 250 400 150
Ablation at terminus
a
m/yr 8 7 6.5 6 6 7
Response time yr 25 43 38 42 67 21
a
Data from http://glaciology.ethz.ch/swiss-glaciers/ (last accessed 27 April 2006).
b
The maximum ice thickness (H
max
) is estimated based on reconstructions of glaciers and topography after Maisch et al. (1999).
698 The Holocene 16 (2006)
The post ‘Little Ice Age’ retreat of glaciers has led
to extended forefields where unconsolidated glacial and
fluvioglacial sediments are exposed to fluvial processes of
meltwater rivers. Occasional meltwater outbursts from the
glacier terminus remobilize large amounts of sediment, which
produce aggradations. Figure 2a illustrates the geological
setting at the Forno Glacier forefield as an example. Pieces
of subfossil wood and peat were found on aggradations in front
of the glacier tongue, as shown in Figure 2b. The wood
samples, usually fragments of a log, show abrasion and
polished surfaces, are often heavily deformed because of
subglacial transport and are imbricated in the coarse meltwater
deposits. Peat samples are flat discs of parallel layers of sand
and organic material. The peat is heavily compressed, indicat-
ing burial beneath glacial overburden, and their rounded shape
is due to abrasion during meltwater transport (Figure 2).
Original information about the samples was reported by
Hormes et al. (2001). Since then, additional samples were
collected at Unteraar and Steinlimi Glaciers and the investiga-
tion was extended to Forno and Tschierva Glaciers. Because of
different glaciological factors that influence the frequency of
meltwater outbursts, the number of recovered samples varies
between 5 at Ried Glacier and /100 at Tschierva Glacier and
at Unteraar Glacier.
Conventional radiocarbon dating on the outermost 10 to 20
rings of a log fragment was used for age determinations. In case
of observed bark or a terminal ring, such ages are interpreted
as the date of death of a given tree. However, most ages is this
study represent dates older than the tree death, because some
outer rings were eroded during subglacial transport. The
duration of tree growth is given by the number of rings,
but our lifespan estimations are based on counted rings
only and an estimation of the missing part due to abrasion.
The estimated lifespans are rounded to the nearest 50 years.
Fragments of roots are classified as samples with an estimated
50 year lifespan. The dated material of peat samples was taken
from the top layer of bulk sediment. The measured conven-
tional radiocarbon ages were calibrated by applying the
CALIB Rev 5.0 program (Stuiver and Reimer, 1993) in
combination with the IntCal04 calibration data set (Reimer
et al., 2004). The corresponding lowest and highest limits of the
2-sigma standard deviation and the median of the calibrated
ages are reported here.
Results and discussion
Periods of small ice extent
Alpine glacier recessions occurred at least 12 times during the
Holocene (Table 2). This result is based on 143 radiocarbon
ages (Table 3) of which 70 ages were reported previously by
Hormes (2001). Figure 3a shows a histogram counting the
number of samples per century using the median calibrated
age. The bin size is 100 years and centred around multiples of
100 cal. yr (eg, a bin starts at x
/51 and ends at x/150 cal. yr
BP). The dates are clustered into distinct periods, which we call
major glacier recessions, because all (n/143) dates indicate a
smaller glacier extent than the 1985 reference level. In
principle, each sample represents a receded glacier position
for a certain period defined by the lifetime of the plant before
its death. Adding the estimated lifespans to the calibrated
radiocarbon ages links various dated samples to one reces-
sional phase because of overlapping tree growth (Figure 3b).
Figure 3b displays the backward overlaps resulting from the
lifespan estimations. The combination of Figure 3a and 3b
defines the periods of glacier recessions, shown as shaded bars
in Figure 3. An overview of the durations of the periods is
listed in Table 2, where all numbers are rounded to the next
Figure 2 (a) The geological setting at the Forno Glacier forefield (oblique view, 17 July 2004). The glacier descends from left to right with a
debris-covered tongue from which meltwaters emerge and subsequently flood the outwash plain. Large areas beside the main channel (shown
at medium water level) are composed of high flood sediments originating from outburst events. (b) A closer view towards the Forno Glacier
tongue with peat samples marked (white circles) imbricated in higher elevated flood deposits (photo by S. Strasky, 18 July 2004)
Table 2 Major periods of glacier recessions in the Swiss Alps
based on 143 dated wood and peat fragments. Dates are given in
calibrated years before present (
AD
1950) and rounded to the next
50 years
Period Begin End Duration No. of samples
1 1400 1200 200 3
2 2150 1850 300 4
3 2800 2700 100 1
4 4300 3400 900 23
5 5200 4400 800 14
6 5700 5500 200 9
7 6150 5950 200 3
8 7450 6550 900 55
9 7700 7550 150 3
10 8550 8050 500 11
11 9300 8650 650 14
12 9850 9600 250 3
Total 5150 143
Ulrich E. Joerin et al.: Multicentury glacier fluctuations in the Swiss Alps 699
Table 3 New radiocarbon dates and calibration results of this study, which are used together with earlier results (Hormes et al., 2001, not
included in this table) to define the glacier recessions in the Swiss Alps
Sample
a
Labcode
b14
Cage
c
1 std
d
d
13
C 2-std, cal. yr BP Median Material Lifespan
e
Fo-101 B-8518 8252 31 /24.3 91209400 9230 wood no
Fo-102 B-8519 8016 31 /24.0 87709010 8890 wood no
Fo-03 B-7785 6836 51 /25.9 7590 7790 7670 wood no
Fo-10 B-7766 6807 49 /26.0 7570 7730 7640 wood no
Fo-16 B-7611 6652 40 /25.4 7440 7590 7530 wood no
Fo-11A B-7786 6150 38 /26.3 69507160 7060 peat no
Fo-09A B-7613 6137 39 /29.4 69107160 7040 peat no
Fo-04 B-7612 6032 39 /28.7 6760 6980 6880 wood no
Fo-12-1 B-76161 5826 39 /21.9 6500 6740 6640 peat no
Fo-12 B-7616 5774 37 /22.4 6490 6670 6580 peat no
Fo-105 B-8521 5184 26 /26.2 59105990 5940 peat no
Fo-17 B-7615 4809 36 /28.6 5470 5610 5520 peat no
Fo-14 B-7614 4785 35 /27.1 5330 5600 5520 peat no
Fo-15 B-7767 4785 76 /26.8 5320 5650 5510 wood no
Fo-19 B-7765 4783 28 /23.1 5470 5590 5520 wood no
Fo-21 B-7787 4759 37 /26.2 5330 5590 5520 peat no
Fo-106 B-8522 3835 24 /26.3 41504410 4230 wood no
Fo-104 B-8520 3398 23 /25.6 35803700 3650 wood no
Ts-25 B-7627 8221 34 /24.0 9030 9300 9190 wood 34
Ts-54 B-7783 6471 30 /24.4 7320 7430 7380 wood no
Ts-57 B-7762 6302 30 /24.0 7170 7290 7220 wood no
Ts-08 B-7758 6253 29 /23.2 7030 7260 7210 wood no
Ts-10a B-7623 6237 29 /25.7 70207250 7180 wood no
Ts-13a B-7773 6233 28 /24.0 70207250 7170 wood no
Ts-47 B-7761 6205 29 /24.3 7000 7240 7090 wood no
Ts-39a B-7764 6182 39 /22.8 69507230 7080 wood no
Ts-16 B-7618 6098 29 /25.4 6880 7160 6970 wood no
Ts-40 B-7780 6085 28 /25.0 6810 7150 6950 wood no
Ts-143 B-8554 6052 37 /23.4 67907000 6910 wood 177
Ts-26 B-7775 6047 30 /24.4 6800 6970 6900 wood no
Ts-04 B-7757 6044 30 /25.6 6800 6970 6900 wood no
Ts-05 B-7622 6015 29 /24.4 6760 6940 6860 wood no
Ts-41 B-7760 6010 28 /23.4 6760 6940 6850 wood no
Ts-53 B-7782 6004 30 /23.0 6750 6940 6840 wood no
Ts-39b B-7779 5998 30 /23.6 67506930 6840 wood no
Ts-29 B-7628 5990 30 /25.1 6740 6910 6830 wood 109
Ts-06 B-7624 5975 40 /26.4 6680 6930 6810 wood no
Ts-15-1 B-76171 5972 39 /23.9 66806910 6810 wood no
Ts-32 B-7777 5968 28 /25.0 6730 6890 6800 wood no
Ts-12 B-7621 5964 28 /24.5 6730 6890 6790 wood no
Ts-06 B-7619 5962 28 /25.4 6720 6890 6790 wood no
Ts-09 B-7620 5959 28 /26.2 6700 6880 6790 wood no
Ts-37 B-7778 5947 30 /24.1 6680 6880 6770 wood no
Ts-55 B-7784 5946 29 /23.1 6680 6860 6770 wood no
Ts-13b B-7625 5936 30 /25.8 66706850 6760 wood no
Ts-28 B-7776 5914 28 /24.4 6670 6790 6730 wood no
Ts-15 B-7617 5909 28 /26.2 6670 6790 6730 wood no
Ts-24 B-7774 5899 30 /24.0 6660 6790 6720 wood no
Ts-112 B-8302 5896 28 /22.1 66606780 6710 wood no
Ts-63 B-7630 5890 38 /26.8 6640 6800 6710 wood no
Ts-10b B-7759 5873 38 /24.3 65706790 6700 wood no
Ts-22 B-7626 5869 28 /25.2 6640 6770 6690 wood no
Ts-42 B-7781 5822 30 /24.3 6540 6730 6640 wood no
Ts-36 B-7629 5756 28 /26.5 6480 6640 6560 wood no
Ts-58 B-7763 5261 27 /24.9 5930 6180 6020 wood no
Ts-111 B-8301 4912 26 /22.2 55905710 5630 wood no
UA-2001A B-8001 8712 34 /25.0 95509880 9650 wood no
UA-160 B-8132 6418 30 /24.3 72807420 7360 wood no
UA-233 B-8133 6246 31 /25.7 70307260 7200 wood 174
UA-201 B-8135 6015 28 /25.8 67606940 6860 wood 147
UA-2001B UZ-1899 5880 75 /25.6 65006880 6700 wood no
UA-126 B-8130 4938 26 /24.5 56005720 5660 wood no
UA-226 B-8131 4910 26 /25.3 55905710 5630 wood no
UA-209 B-8134 4089 25 /24.0 44504810 4590 wood 114
UA-252b B-8180 3741 33 /25.0 39804230 4100 wood no
UA-252a B-8179 3694 33 /26.1 39304150 4040 peat no
UA-254 B-8141 3672 25 /24.7 39104090 4010 peat no
UA-2000A UZ-1897 3655 65 /27.6 37804220 3980 peat no
700 The Holocene 16 (2006)
50 years accounting for uncertainties of the dating and cali-
bration procedure as well as the lifespan estimates. The total
duration of dated recessions counts more than 51 centuries,
amounting to about half of the Holocene epoch, which is
approximately double previous estimates (Ro
¨thlisberger, 1986).
The decreasing number of samples that are found since
about 7 cal. kyr BP (Figure 3a) suggests that glacier recessions
have decreased in frequency since then, culminating in the
maximum glacier extent of the ‘Little Ice Age’. It appears that
the record shows both the fluctuations of glacier extent
Table 3 (continued )
Sample
a
Labcode
b14
Cage
c
1 std
d
d
13
C 2-std, cal. yr BP Median Material Lifespan
e
UA-2000B UZ-1898 3500 60 /25.2 36303960 3770 peat no
UA-255 B-8140 3406 25 /25.1 35803720 3660 peat no
SG-Rb14a B-8136 2103 30 /22.8 20002150 2080 peat no
SG-Rb14b B-8137 1968 30 /23.8 18401990 1920 peat no
SG-01 B-8006 4108 25 /26.0 4530 4810 4620 peat no
a
Abbreviations for the glaciers are as given Figure 1.
b
Labcode: radiocarbon measurements by Physics Institute, University of Bern (B) and by University of Zu
¨rich/ETHZ (UZ).
c14
C age is conventional radiocarbon age.
d
1 std is 1-sstandard deviation; calibrated ages are given at the 2-slevel applying the Intcal04 calibration data set (Reimer et al., 2004).
e
Lifespan denotes the values rounded to the nearest 50 yr used for Figure 3b.
20 4 6 8 10 12
cal kyr BP
number of samples
per century
lifespan [yr]
0
100
200
Subatlantic Subboreal Atlantic Boreal Preboreal
a
b
c
d
n=143
n=33
estimated lifespan overlaps
Histogram of dates
indicating glacier
recessions
Younger Dryas
reference positions:
Pasterze: 2000
Gepatsch: 1950
Pasterze glacier recessions
Aletsch glacier length curve
ePasterze and Gepatsch glacier: interpreted advances
glacier
advanced retreated
0
5
10
?
?
L = 1860
L = 2002
L = 1850
L < 2000
Bernina
Valais
Grimsel
Figure 3 Overview of dated glacier recessions compared with glacier advances in the European Alps. (a) Histogram of dated glacier
recessions from the Swiss Alps (this study). (b) Estimated lifespans of the dated samples illustrating the overlaps of individual tree growth.
The combination of (a) and (b) determines the 12 periods of recessions (grey shaded). (c) Schematic plot of recession periods of Pasterze
Glacier, Austria (Nicolussi and Patzelt, 2000b). Boxes above the dashed line represent evidence for smaller glacier length (LB/2000) and
boxes in the lower part indicate advanced positions with the maximum during the ‘Little Ice Age’ (L/1850). (d) Aletsch Glacier length
curve after Holzhauser et al. (2005) indicating a small glacier length above the upper line (comparable with
AD
2002) and a position
comparable with the ‘Little Ice Age’ extent (lower line, L/1860). (e) Arrows represent interpreted advances when Pasterze Glacier
or Gepatsch Glacier advanced from a smaller extent over the reference position, which is the glacier terminus position at Pasterze Glacier in
AD
2000 and at Gepatsch Glacier in
AD
1950, respectively (Nicolussi and Patzelt, 2000b)
Ulrich E. Joerin et al.: Multicentury glacier fluctuations in the Swiss Alps 701
associated with natural climate variability on a multicentury
timescale and a superimposed long-term, multimillennial trend
of increasing Alpine glaciation during the Holocene. Such a
trend is in line with the precessional signal found in summer
insolation at 658N (Berger, 1978), which has been decreasing
since about 10 kyr BP. The associated cumulative change of
summer insolation amounts to approximately 50 W/m
2
.A
synthesis of reconstructions of sea surface temperatures from
marine sediments cores from the North Atlantic revealed a
consistent large-scale pattern of decreasing temperatures dur-
ing the Holocene (Marchal et al., 2002). The multimillennial
decrease of recession frequency could thus be due to a
continuous decrease in summer insolation in the Northern
Hemisphere and the associated reduction in summer melting.
Glaciological interpretation of dated samples
The resolution of the histogram is limited to a class width of
100 years because of uncertainties of dating and calibration
and in order to retain a sizeable sample number per bin. The
investigated glaciers reflect changes in climate on a scale longer
than their response time (Table 1). Each sample indicates a
minimum of 50 years of ice-free conditions based on the
estimated lifespan (/30 yr) and the recolonization time
defined as the delay until the first trees start to grow on a
newly exposed (ice-free) forefield. Although the recolonization
strongly depends on local conditions, a period of 20 yr as a first
order approximation agrees with reconstructions (Luckman,
1993) and observations (Nicolussi et al., 2005). Trees start to
grow within the extent of the 1985 position (Swiss glacier
length observation network). These considerations suggest that
our indicator is suitable to reconstruct centennial-scale but not
decadal-scale fluctuations of glacier extent.
The period from 7450 to 6550 cal. yr BP stands out because
of the large number of recovered wood samples and its long
duration. Its abrupt end is best documented at the Tschierva
Glacier with a series of well-preserved pieces of logs suggesting
that trees were overridden by an advancing glacier and rapidly
embedded into till. This process of rapid embedding was
verified by dendrochronological studies (Ryder and Thomson,
1986). Dating of inner parts of long-lived trees or different peat
layers could lead to a dating spread of no more than 300 years
for a recession period. However, the embedding of wood
fragments for periods longer than 500 yr documented in the
recessions from 7450 to 6550 and 5200 to 4400 cal. yr BP
suggests an additional mechanism. We interpret the morphol-
ogy of the tree fragments as indicating that roots or trunks
were embedded on an outwash plain during events of rapid
sediment aggradation. Subsequently, preservation of organic
remains prevailed in small-scale basins with a high ground-
water table. Finally, the emergence of a subfossil sample in
the glacier forefield depends on the varying conditions of
subglacial erosion. The gaps between the clusters of dates
(Figure 3a) are interpreted as periods with possible glacier
advances. An alternative interpretation attributes the gaps to a
reduced remobilization of buried fragments.
Chronology of glacier fluctuations within the Alps
The results from studies by Nicolussi and Patzelt (2000a,b)
at Pasterze Glacier (Austrian Alps) using a similar approach
are displayed in Figure 3c. The boxes above the reference line
represent evidence for smaller glaciers. Most periods coincide
with our recessions except for the Preboreal (c. 11 600
10 200 cal. yr BP), for which no dated material has yet been
discovered in the Swiss Alps. Conversely, a few dates for the
Pasterze Glacier fall into the extended recession from 7450 to
6550 cal. yr BP. Both discrepancies are interpreted to depend
on different preservation and subglacial erosion, or on the
different number and selection criteria of dated samples.
Nevertheless, the data suggest a general agreement between
the Austrian and the Swiss Alps.
The only known Holocene moraines situated below the LIA
reference level (Patzelt and Bortenschlager, 1973) belong to
smaller glaciers with faster adjustment to climatic deteriora-
tions compared with the glaciers of this study. Three periods of
early Holocene moraine deposition were determined by strati-
graphic correlations to peat bogs using minimum and max-
imum ages as limits but no direct dating of till units. The oldest
advance occurred before 10.2 cal. kyr BP, predating our record
of recessions. A younger cold phase was confined to Boreal age
coinciding with a moraine at Arolla (age after Ro
¨thlisberger
(1986) recalibrated to 95009
/200 cal. yr BP). With regard to
our results it is suggested that glacier advance(s) were limited
to the period from 9.6 to 9.3 cal. kyr BP. The subsequent
period from 8.8 to 5.8 cal. kyr BP indicates several deteriora-
tions based on pollen profiles (Patzelt and Bortenschlager,
1973) and results at Pasterze and Gepatsch Glaciers (Nicolussi
and Patzelt, 2000b). Such a deterioration is consistent with
cooling sea surface temperatures found in the North Atlantic
during this period (Marchal et al., 2002). In general, our data
show that conditions for prolonged recessions prevailed. Short
gaps around 8500, 80007800, 7500 and 6500 6200 indicate
possible periods of glacier advances, which are in agreement
with the interpreted advances in the Austrian Alps (Nicolussi
and Patzelt, 2000b). The arrows in Figure 3e indicate that
glaciers were smaller than the reference position at the
beginning, but advanced over the reference position for the
dated periods. The reference position is defined as the glacier
extent at Pasterze Glacier in
AD
2000 and at Gepatsch Glacier
in
AD
1950, respectively. With regard to the different response
times of the glaciers it is proposed that the dated advances
occurred as short pulses interrupting long (/several centuries)
recessions during the first part of the Holocene.
One prominent event with reduced d
18
O in the Greenland ice
cores is centered around 8.2 kyr BP lasting for about 300 years
(Alley et al., 1997). Two of our samples fall into this period:
UA-129 (80508320 cal. yr BP) and UA-182 (79708160 cal.
yr BP). One possible explanation is that both trees were
overridden by an advancing glacier, assuming a time lag of a
few decades. This would be the first, albeit circumstantial,
indication that the Alpine glaciers responded to the 8.2 ka cold
event. An alternative interpretation assumes that glaciers were
very small before the 8.2 ka event, and a minor advance did not
exceed the present level.
Subsequent to advances around 5800 and 5400 cal. yr BP,
our data suggest persistent recessions until 3300 cal. yr BP
with the exception of minor fluctuations possibly at 4300 or
3600 cal. yr BP. It is interpreted that glaciers fluctuated around
a level comparable with the 1985 reference position. After
3300 cal. yr BP, the Great Aletsch Glacier record indicates
advances (Figure 3d) peaking around 90, 290, 580, 800, 1250,
2500 cal. yr BP (Holzhauser et al., 2005). Two additional
advances (marked by ‘?’ in Figure 3d) possibly occurred
around 1050 cal. yr BP and 3200 cal. yr BP following earlier
interpretations of dated sections at Aletsch Glacier (Wanner
et al., 2000; Holzhauser, 1997). Several studies documented
conditions favouring glacier advances around 3.2 kyr BP
(Denton and Karle´n, 1973; Schneebeli and Ro
¨thlisberger,
1976; Nicolussi and Patzelt, 2000b). No evidence of advances
was found at Great Aletsch Glacier prior to 3.3 cal. kyr BP.
These results are in agreement with our data indicating
recessions around 2750, 21501850 and 1400 1200 cal. yr
BP, which are relatively short in comparison with the recessions
702 The Holocene 16 (2006)
before 3.2 cal. kyr BP. Constraints on the successions of glacier
fluctuations come from a partial overlap of the Aletsch Glacier
advance around 1250 cal. yr BP and the dated recession from
1400 to 1200 cal. yr BP. Given the uncertainty of the radio-
carbon dates, the two records could be interpreted consistently
as an indication of rapid climate change around 1250 cal. yr BP
supporting the conclusions of Mayewski et al. (2004). The
combination of these records, and the coincidence with the
evidence of advancing glaciers and moraine formations from
the Valais (Schneebeli and Ro
¨thlisberger, 1976), is interpreted
as a trend to more frequent and longer lasting advances
disrupted by reduced recessions.
Conclusions
The radiocarbon ages of tree fragments and peat discs found
on proglacial forefields indicate 12 phases of glacier recessions
during the Holocene. Locations and type of occurrence of the
dated samples show that trees and mires grew where glaciers
exist at present and, therefore, glaciers were smaller at that
time. The extended data set of recessions limits periods of
glacier advances in a complementary way and improves on the
chronology of natural climate fluctuations in the Alpine
region. As a result, it is suggested that major glacier fluctua-
tions occurred on a multicentennial scale and that their pattern
changed from long recessions (/500 yr) interrupted by short
advances (B/200 yr) during the early Holocene to the opposite
pattern with relatively short recessions and prolonged advances
during the late Holocene (after 3.3 cal. kyr BP). It is important
to recognize that this natural variability of glacier extent, which
occurs on a centennial timescale, is superimposed on a much
longer term, multimillennial-scale trend towards increased
glacier extent culminating in the ‘Little Ice Age’. This is
indicated in our data as a progressively reduced occurrence of
wood and peat remnants through the course of the Holocene,
which is consistent with a long-term reduction of sea surface
temperatures in the North Atlantic. The multimillennial trend
that is indicated in our data, therefore, is likely forced by
changes in summer insolation and hence of astronomical
origin. Studies attempting to identify the amplitudes of glacier
fluctuations will help to improve the understanding of the
pattern and forcings of climate change during the Holocene.
Acknowledgements
We acknowledge the long-term support of the Bern Radio-
carbon Lab by the Swiss National Science Foundation, and
the careful sample processing and dating by R. Fischer and
M. Mo
¨ll. We thank Drs G. Bonani, I. Hajdas and W.A. Keller
for support with Radiocarbon dating of selected samples, and
K. Nicolussi for discussion and help with the tree ring analysis.
We wish to thank the reviewers for helpful comments improv-
ing this paper.
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704 The Holocene 16 (2006)
