The movements of Alpine glaciers throughout the last 10,000 years as sensitive proxies of temperature and climate changes
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EPJ Web of Conferences 232, 02002 (2020) https://doi.org/10.1051/epjconf/202023202002
HIAS 2019
The movements of Alpine glaciers throughout the last 10,000 years as sensitive
proxies of temperature and climate changes
Walter Kutschera1,*, Gernot Patzelt2, Joerg M. Schaefer3, Christian Schlüchter4, Peter Steier1, and Eva Maria Wild1
1
VERA Laboratory, Faculty of Physics, University of Vienna, A-1090 Vienna, Austria
2
Gernot Patzelt, Patscher Strasse 20, A-6080 Innsbruck-Igls, Austria
3
Joerg M. Schaefer, Geochemistry, Lamont-Doherty Earth Observatory, Pallisades, NY 10964-8000, USA
4
Christian Schlüchter, Institute of Geological Sciences, University of Bern, CH-3012 Bern, Switzerland
Abstract
A brief review of the movements of Alpine glaciers throughout the Holocene in the Northern Hemisphere (European
Alps) and in the Southern Hemisphere (New Zealand Southern Alps) is presented. It is mainly based on glacier studies
where 14C dating, dendrochronology and surface exposure dating with cosmogenic isotopes is used to establish the
chronology of advances and retreats of glaciers. An attempt is made to draw some general conclusions on the
temperature and climate differences between the Northern and Southern Hemisphere.
1 Introduction radiocarbon dating, surface exposure dating of rocks and
moraines with various cosmogenic radionuclides (10Be,
It is well known that the Holocene, i.e. the geological time 14
C, 26Al, 36Cl), and geomorphological considerations [10-
period following the end of the Last Ice Age, enjoyed 22].
relatively stable temperatures. But glaciers are sensitive The atmospheric CO2 concentration was remarkably
proxies to even small temperature and/or climate changes. constant during the last 10,000 years, changing by only 20
Thus, the globally observed retreat of Alpine glaciers and ppm [1]. Such small CO2 variations are unlikely to trigger
polar ices sheets since about 1850 AD (the end of the so- the observed glacier movements. It is therefore possible
called Little Ice Age and interrupted by three re-advances) that small solar activity variations [23], enhanced by
has been linked to the temperature increase caused by (hitherto largely unknown) feed-back processes on Earth
human activities, particularly due to the continuous caused the observed glacial fluctuations [24]. Whatever
increase of the CO2 concentration in the atmosphere [1]. It the cause of these natural fluctuations, they constitute a
is interesting to note that a change in the surface “background” which is now being modified in a complex
temperature on Earth with increasing CO2 concentration in way by human activities. The challenge is then to evaluate
the atmosphere was already discussed more than 100 years the human signal correctly, and try to make predictions
ago by the Swedish chemist and Nobel Laureate Svante about the climate in the near future [25]. There is an
Arrhenius [2]. Discussions are ongoing now to define a ongoing discussion about the certainties and uncertainties
new geological period called “Anthropocene” [3, 4], of these predictions [e.g. 26]. In spite of great efforts
where man’s influence on the environment is significant around the world to reduce anthropogenic CO2 emissions,
and distinct [5, 6]. Even though the global retreat of it appears doubtful whether this is currently more than a
glaciers since 1850 is considered to be a fingerprint of “pious wish” [27].
man’s influence on the climate, it is now evident that The current work cannot give an answer to these
considerable glacial fluctuations occurred already much important questions. Rather it will present evidence for the
earlier during the Holocene, when human impact was waxing and waning of Alpine glaciers in both the Northern
negligible. and Southern Hemispheres throughout the Holocene. An
In a way, the interest in Alpine glaciers of the past attempt will be made to explain at least some of these
started with the accidental discovery of the famous Iceman fluctuations from first principles. Even though the
Ötzi in 1991, a naturally mummified body which was well complexity of the climate may only allow crude estimates
preserved for 5200 years in the icy environment of a high of those principles, we simply follow the advice of the late
mountain pass (3210 m a.s.l.) in the Ötztal Alps [7-9]. Murray Gell-Man: “Nature is most easily described by a
Since then, several forward and backward movements of sequence of approximations,” [28].
glaciers in the European Alps and in the New Zealand
Southern Alps throughout the last 10,000 years have been
established with the help of dendrochronology,
______________________________
*
email: walter.kutschera@univie.ac.at
© The Authors, published by EDP Sciences. This is an open access article distributed under the terms of the Creative Commons Attribution License 4.0
(http://creativecommons.org/licenses/by/4.0/).
EPJ Web of Conferences 232, 02002 (2020) https://doi.org/10.1051/epjconf/202023202002
HIAS 2019
2 Paleorecord of Temperature and CO2 currently goes back 800,000 years [29, 30], and shows the
well-known Milankovic cycles of the ice ages first
The records of temperature and atmospheric CO2 discovered in the δ18O record of foraminifera in deep-sea
concentration on Earth show considerable variation over sediment cores [31]. Efforts to drill ice cores in Antarctica
the last 500 million years (Fig. 1). In particular, the CO2 back to 1.5 million years are under way [32, 33]. Except
concentration during the time of the dinosaurs (~240 – 65 for the brief interglacial periods, the CO2 concentration
million years ago) was around 1000 ppm, and the mean stays at its lowest value in this period and reaches about
temperature about 6 oC warmer than today. From Fig. 1, 200 ppm at the glacial maximum 20,000 years ago. After
one can see that during the last 10 million years, a gradual warming up to the Holocene some 10,000 years ago, both
lowering of the temperature and of the CO2 concentration relatively stable temperature and CO2 concentrations
occurred. persist. The rapid increase of CO2 during the last 60 years
Around 2.5 million years ago (beginning of the from about 300 ppm to currently 415 ppm is well
Pleistocene), major glaciations in both Antarctica and documented [1].
Greenland set in. The record of ice cores from Antarctica
Temperature of Planet Earth
https://en.wikipedia.org/wiki/File:All_palaeotemps.png
∆T ∆T
(oC) (oC)
+14 +14
+12 +12
+10 +10
+8 +8
+6 +6
+4 2100 +4
+2 2050 +2
0 0
-2 -2
-4 -4
-6 -6
500 400 300 200 100 60 50 40 30 20 10 5 4 3 2 1 800 600 400 200 20 15 10 5 1
Years before present (Myr) Years before present (kyr)
CO2 CO2
(ppm) (ppm)
5,000 5,000
Atmospheric CO2 concentration of Planet Earth
Foster et al., Nature Comm. 8:14845 (2017)
2,000 2,000
1,000 1,000
500 500
200 200
100 100
500 400 300 200 100 60 50 40 30 20 10 5 4 3 2 1 800 600 400 200 20 15 10 5 1
Figure 1. Summary of temperature and CO2 concentrations on Earth for the last 500 million years. The figure is a composite from the
original temperature record [34] and the CO2 record [35]. The CO2 record was adjusted to the same time scale as the temperature record.
Possible temperature increase in 2050 and 2100, respectively, predicted by some climate models are indicated with red dots on the
rightmost temperature axis.
3 Movement of Alpine glaciers during evolved into a new field sometimes called “glacial
the Holocene archaeology”. Besides the archaeological aspect in the
study of glaciers, there is the sensitivity to small climate
The accidental discovery of the Iceman “Ötzi” in 1991 [7- changes which became apparent through multiple periods
9], and the appearance of human artefacts and natural of forward and backward movements of glaciers
materials released from receding Alpine glaciers [22], throughout the Holocene [11].
2
EPJ Web of Conferences 232, 02002 (2020) https://doi.org/10.1051/epjconf/202023202002
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3.1 The European Alps 3.1.1 The Pasterze glacier
Glacier movements of the past have been studied in many The rapidly receding glaciers in our time sometimes
mountain ranges of the European Alps [10,11, 13-15, 17, release well-preserved subfossil trees, which can be dated
19-22]. In 2001, 14C dating of a variety of organic with 14C and dendrochronology. Surprisingly, up to
materials released from glaciers in the Swiss Alps revealed 10,000-year old logs were found in the forefield of the
eight Holocene phases of reduced glacier extent: 9910- Pasterze glacier, the largest glacier in the Austrian Alps
9550, 9010-7980, 7250-6500, 6170-5950, 5290-3870, [10], The situation of the finds is depicted in Fig. 2. This
3640-3360, 2740-2620, and 1530-1170 calibrated years indicated that in the Early Holocene these glaciers were
BP (BP = before present = 1950 AD) [11]. In the following even smaller than today, allowing trees to grow in an area
we discuss a few selected cases of glacier movements in still covered by ice today.
the European Alps.
A Großglockner, 3798 m
B Johannisberg, 3463 m
Johannisberg, 3463 m
Pasterze Glacier
(2000 AD)
Pasterze Glacier
(1832 AD)
C PAZ-33
D
PAZ-28
PAZ-23
PAZ-26
PAZ-21
PAZ-27
PAZ-30 PAZ-16
PAZ-31 PAZ-4
PAZ-29 PAZ-22 PAZ-5
PAZ-25 PAZ-2 PAZ-1
8400 10200
8200 10000
8000 9800
7800 7600 9400
9600 7400 9200
7200 9000
7000 8800
6800
cal BC
cal BP
Figure 2 Old wood found in the forefield of the Pasterze Glacier in the Austrian Alps. The dramatic loss of glacier mass can be
assessed from the painted landscape of 1832 (A) and the photo of the twindling glacier in 2000 (B). Panel (D) zooms into the
trapezoidal section of (B) and shows one log found in the forefield of the glacier. Panel (C) shows the age distribution of all wood
specimens collected from the glacier forefield [10] by combining dendro dating (filled sections) with 14C measurements (error bars
indicate 65% calibrated age ranges). The open sections depict missing inner tree-ring sections, and the hatched sections indicate
compressed wood. This composite figure is reproduced from Ref. [22].
3.1.2 Ice cores at Mount Ortles and Monte Rosa interval in the European Alps during the Holocene” [36].
A somewhat different result was reported from an ice core
A recent ice core from the summit of Mt. Ortles in South
at Col Gnifetti (4455 m a.s.l.) in the Monte Rosa mountain
Tyrol (3859 m a.s.l.) revealed that the deepest ice near
range of Switzerland, where the deepest ice sample of this
bedrock is about 7000 years old [36]. “Absence of older
high-altitude glacier indicated an age of about 10,000
ice on the highest glacier of South Tyrol is consistent with
years [37]. The higher altitude as compared to Mt. Ortles
the removal of basal ice from bedrock during the Northern
may have prevented the loss of basal ice during the
Hemisphere Climatic Optimum (6-9 kyrs BP), the warmest
Climatic Optimum mentioned above.
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EPJ Web of Conferences 232, 02002 (2020) https://doi.org/10.1051/epjconf/202023202002
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26
3.1.3 The Rhone glacier Al (0.72 Myr) was also measured in the samples.
Concordant exposure ages for 10Be and 26Al allowed one
Exposure dating of rock surfaces on Earth by measuring to make the assumption that the Rhone Glacier removed
in-situ produced cosmogenic radioisotopes [38, 39] with several meters of rock during the last Ice Age, leaving the
Accelerator Mass Spectrometry (AMS) has made it sampled bedrock surfaces (Fig. 3) most likely free of
possible to date glacially polished rock surfaces and glacial cosmogenic nuclides at the beginning of the Holocene
moraines. Application of this method allowed one to period. Consequently, the measured cosmogenic nuclide
reconstruct the dynamic history of many glaciers in the concentration in the sampled material integrates the
European Alps, and in other glacial regions around the periods when these rocks were ice-free during the
world. In particular, if the concentration of two Holocene. Since some erosion of the rocks happened also
radioisotopes with very different half-lives are measured, during the Holocene, the 10Be exposure ages shown in
the ratio of these radioisotopes allows one to reconstruct Fig. 3, decrease toward the lowest, central part of the
the chronology of glaciers including erosion of the glacial trough, where ice velocity was greatest and thus
underlying bedrock. Such measurements were performed erosion rate is expected to be fasted. The longest exposure
with 14C (t1/2 = 5.7 kyr) and 10Be (1.39 Myr) in quartz times (4.5 to 5.3 kyr) were found at the left-lateral margin
grains of recently exposed rock surfaces of the Rhone zone of the glacier indicating the longest integral time
Glacier [17], which was one of the dominant glaciers of when the glacier was smaller than today.
the European Alps during the Last Ice Age. In addition,
Figure 3. Sampling location on exposed rocks (darker grey-shaded area) in front of the Rhone Glacier terminus
(lighter grey-shaded area). Contour lines are labelled in meters a.s.l. The minimum 10Be exposure ages are shown.
The figure is adopted from the work of Goehring et al. [17].
Figure 4. Schematic presentation of the time periods where European glaciers were smaller (red) and larger (blue)
than today. The figure is adapted from the work of Goehring et al. [17]. “Nearby proxy records indicate that at least
most of the time during which the Rhone glacier was smaller than today was during the early to mid-Holocene” [17].
In E the hypothetical Holocene advance and retreat scenario of the Rhone Glacier is displayed, indicating the glacier
was smaller than today during the first part of the Holocene.
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There is also evidence that the ice of the Jostedalsbreen, 3.1.4 The Mer de Glace glacier
the largest mountain glacier in Norway, is not a left-over
A detailed radiocarbon and dendrochronological study was
from the Last Ice Age, but only formed during the second
performed by Le Roy et al. [41] at the Mer de Glace glacier
half of the Holocene [40]. Although it is unlikely that the
in the Mont Blanc massif (Fig. 5A), the largest glacier of
European Alps were completely ice-free in the early
the French Alps. Subfossilized wood exposed at the right
Holocene, the evidence for generally lower glaciation as
lateral moraine near the terminus of the glacier was
compared to the second half of the Holocene is mounting,
investigated (Fig. 5B). It revealed 10 glacial advances
as indicated from the ice core result from Ortles mentioned
during the last ~3000 years. These glacial fluctuations are
above [36].
similar to those observed in the Swiss Alps, although not
synchronous in all aspects.
(A) (B)
Figure 5 The lower section of the Mer de Glace glacier in the Mont Blanc mountain range, with the Grandes Jorasse (4208 m a.s.l.) in
the background (A). The right figure (B) from the work of [41] shows the sampling sites at the right lateral moraine near the glacier
terminus. Two positions of the terminus in 1995 and 2013, respectively, are marked with black dashed curves. For a detailed description
of the sampling sites and the material recovered see Ref. [41].
3.1.5 Timberline
An important proxy for temperature changes in the Alps
during the past is the timberline (sometimes also called tree
line). The timberline is the edge of the habitat at which
trees can grow (Fig. 6). Since precipitation in the Alps is
abundant, the movement of the timberline is primarily
affected by the change in summer temperature during the
main growing season.
From studies of subfossil trees preserved at different
altitudes, periods of higher and lower temperatures,
respectively, can be reconstructed by 14C measurements
and dendrochronology. From studies like this (e.g. [12]), it
has been estimated that the timberline moves Figure 6. Typical timberline in an Alpine landscape. The
approximately 100 m up or down for a summer transition from the forested region to grass land can be clearly
temperature change of ±0.6 oC. seen in this picture, which is reproduced from a free download
(https://unsplash.com/s/photos/timberline).
3.1.6 Temperature change during the Holocene Holocene Thermal Maximum (HTM), and continuously
decreased in the second half of the Holocene approaching
In Figure 7, information on glacier and tree-line its lowest values during the Little Ice Age (LIA) between
movements are summarized and converted into 1300 and 1850 AD. This period also resulted in the largest
approximate temperature variations during the entire glacier advance during the Holocene. The Holocene
Holocene [22]. Glacial retreats are usually accompanied temperature trend is also supported by other temperature-
with higher timberlines indicating higher temperatures. sensitive proxies, e.g. by the study of chronomids in a
Overall, the mean temperature went through a maximum high-altitude lake (2796 m a.s.l.) in the Austrian Alps [42].
during the first half of the Holocene, sometimes called the
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EPJ Web of Conferences 232, 02002 (2020) https://doi.org/10.1051/epjconf/202023202002
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+0.5
∆T (oC) Summer temperature, (May to September)
0
-0.5
-1.0
Iceman
Tree line, higher than today (movement: 100m/0.6oC)
Glacier periods of retreat, Western Alps
Hormes 2001
Joerin 2006
Glacier extent, Eastern Alps
Smaller than today
Advance as in
modern times
BA
Mesolithic Neolithic BA H L RT MA MT
10 9 8 7 6 5 4 3 2 1 BC / AD 1 2
Calibrated date (kiloyears)
Figure 7. Schematic presentation of glacier and tree-line movements in the European Alps during the Holocene [22]. The periods of
smaller glaciers and higher tree lines are indicated with the box symbols. Glacial advances are indicated with filled triangles and curves.
The largest advances took place during the Little Ice Age (~AD 1300 to 1850). The top curve depicts the relative summer temperature
variations deduced mainly from tree-line movements. The mean temperature between AD 1900 and 2000 is used as reference
(ΔT = 0 oC). The red vertical line marks the time where the Iceman Ötzi died [43].
3.2 The New Zealand Southern Alps 3.2.1 The Mueller glacier
Most of the information on Alpine glacier movements The chronology of glacier advances through the past 7000
through the Holocene comes from the Northern years were reconstructed from measurements of
Hemisphere. However, the New Zealand Southern Alps cosmogenic in-situ produced 10Be in moraines of the
allow one to get information on glacier movements in the Mueller glacier, which is located at Mt. Sefton in the Mt.
Southern Hemisphere at comparable latitudes. While Mont Cook mountain range [16]. Figure 8 is reproduced from
Blanc, the highest mountain of the European Alps (4810 m this work and shows the area where the extensive 10Be
a.s.l.) is located at 45.8o N, Aroaki/Mount Cook, the measurements were performed. The deduced exposure
highest mountain of the NZ Southern Alps (3927 m a.s.l.) ages are listed which allow one to draw some conclusions
is located at 43.5o S. Because of the closeness of the Pacific for the glacier advances with respect to the ones in the
Ocean to the East and the Tasman Sea to the West of the European Alps. Interestingly, glacier advances seem not to
NZ Southern Island, the glaciation of the NZ Southern be synchronous between the two hemispheres. Simply
Alps is more intense as compared to the European Alps, speaking, during some time periods glaciers advanced in
even though the latter reach up to considerably higher the Southern Hemisphere (SH) whilst they simultaneously
altitudes. Particularly the western slopes of the NZ retreated in the Northern Hemisphere (NH), and vice
Southern Alps, which are under the influence of the versa.
Tasman Sea and westerlies, are the home of large glaciers As discussed by Schaefer et al. [16], it is possible
(e.g. Fox and Franz Josef glacier), which still reach down that regional effects influenced the pattern of glacier
to about 300 m above sea level. Due to regional cooling, movements in this region. There is, however, some
these two glaciers even advanced during a period of global indication that the oldest ages are found for the most
warming [44]. advanced stages of the glacier. This is more clearly seen in
Here, we describe two rather detailed studies of the chronology of moraines for the Cameron glacier
glacier movements on the eastern side the NZ Southern discussed in the next section (3.2.2).
Alps.
6
EPJ Web of Conferences 232, 02002 (2020) https://doi.org/10.1051/epjconf/202023202002
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Mt. Sefton
(3151 m a.s.l.)
Figure 8. This figure is reproduced from Ref. [16] and shows the results of the 10Be ages (given in years with 2σ uncertainties)
with the assignment to the Holocene moraines of the Mueller glacier. The ages marked in purple colour are from moraines which
were deposited during mid- to late-19th century.
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3.2.2 The Cameron glacier interesting conclusion. While in the NH the temperature in
the first half of the Holcene is higher than in the second
Another detailed study of 10Be ages of moraines was half, the opposite seems to be the case in the SH. It is
performed by Putnam et al. [18] at the Cameron glacier in interesting that this trend is supported by the insolation
the Arrowsmith Range, which is a smaller mountain range curves (red curves of panels c and h) calculated from the
parallel to the Southern Alps about 85 km northeast of Milankovic theory of the Earth’s orbital parameter
Arioka/Mt. Cook. The altitude of the Arrowsmith Range is variations [45]. Although the insolation changes only by 4
~1000 m below the highest ones of the Southern Alps, but to 6 % over the Holocene, the general temperature trend is
glaciers are still abundant. Figure 9A show the main results reproduced. A recent study to take possible effects of
from the work of Putnam et al. [18], where the moraines interannual climate variability on the observed glacier
of the Cameron glacier were dated. fluctuations into account, confirms the robustness of the
The detailed comparison of temperature proxies of glacier fluctuations against this short-term climate
the NH and SH displayed in Fig. 9B [18] leads to an fluctuations [46].
(A) Couloir Peak (B)
(2624 m a.s.l.)
1930 AD
520 ± 410
650 ± 30
6,890 ± 410 9,200 ± 100
8,100 ± 200
9,840 ± 470
10,690 ± 410
Figure 9. In Fig 9A the mean 10Be ages in years (uncertainties 1σ) resulting from the work of Putnam et al. [18] are displayed at the
Holocene moraines from the Cameron glacier. The oldest age signals the largest glacier advance at the Early Holocene. Fig. 9B shows
an interesting comparison of various temperatures proxies for the NH (panels a-e) and the SH (panels f-h). For a detailed description of
Fig. 9B, see Ref. [18].
4. Conclusions [18]. The partly asynchronous movements of glaciers in
the two hemisphere is probably influenced by regional
The comparison of glacier movements throughout the effects [16].
Holocene from Alpine mountain ranges in the NH and SH This is not surprising considering that the European Alps
revealed some interesting differences. The opposite are largely imbedded into a continental climate, whereas
temperature development from the Early to the Late the NZ Southern Alps are subject to a maritime
Holocene in the two hemispheres is established by a environment.
number of proxies and supported by the Milankovic theory
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The increasing number of reports about glacier to draw more definite conclusions about the influence of
dynamics in the past from other glaciated regions of the the sun on the glacier movement during the Holocene.
Northern and Southern Hemispheres, e.g. from North and One thing can be said with some certainty: The
South America, will help to develop a more concise picture complex moving patterns of glaciers in both hemispheres
about climatic variations around the globe during the of the past have now given way to an accelerated retreat of
Holocene. Concerning natural causes of the observed all glaciers around the globe, most likely due to the
variations, it is unlikely that they were triggered by anthropogenic impact on our climate.
atmospheric CO2 because it was remarkably constant
throughout the Holocene (Fig. 1 and Ref. [1]). The
possible influence of solar activity variations has been Acknowledgement
discussed [47-49], but since the total solar irradiance
varies by only ~0.1 % during the Holocene [23], other We have benefitted from many discussions with
effects such as volcanic eruptions may have some colleagues around the world on the issue of glacier
influence too. In general, it seems that some amplifying movements. The wisdom of the late Wally Broecker on
terrestrial effect are needed to explain the magnitude of the climate issues is greatly appreciated as an important input
observed glacier movements. It has to be seen whether the into the current work.
recent detailed analysis of solar activity [50] will allow one
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