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Ice‐borne prehistoric finds in the Swiss Alps reflect Holocene glacier fluctuations
Abstract
During the hot summer of 2003, reduction of an ice field in the Swiss Alps (Schnidejoch) uncovered spectacular archaeological hunting gear, fur, leather and woollen clothing and tools from four distinct windows of time: Neolithic Age (4900 to 4450 cal. yr BP), early Bronze Age (4100–3650 cal. yr BP), Roman Age (1st–3rd century AD), and Medieval times (8–9th century AD and 14–15th century AD). Transalpine routes connecting northern Italy with the northern Alps during these slots is consistent with late Holocene maximum glacier retreat. The age cohorts of the artefacts are separated which is indicative of glacier advances when the route was difficult and not used for transit. The preservation of Neolithic leather indicates permanent ice cover at that site from ca. 4900 cal. yr BP until AD 2003, implying that the ice cover was smaller in 2003 than at any time during the last 5000 years. Current glacier retreat is unprecedented since at least that time. This is highly significant regarding the interpretation of the recent warming and the rapid loss of ice in the Alps. Copyright © 2007 John Wiley & Sons, Ltd.
... In a way, the interest in Alpine glaciers of the past started with the accidental discovery of the famous Iceman Ötzi in 1991, a naturally mummified body which was well preserved for 5200 years in the icy environment of a high mountain pass (3210 m a.s.l.) in the Ötztal Alps [7][8][9]. Since then, several forward and backward movements of 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, radiocarbon dating, surface exposure dating of rocks and moraines with various cosmogenic radionuclides ( 10 Be, 14 C, 26 Al, 36 Cl), and geomorphological considerations [10][11][12][13][14][15][16][17][18][19][20][21][22]. ...
... In a way, the interest in Alpine glaciers of the past started with the accidental discovery of the famous Iceman Ötzi in 1991, a naturally mummified body which was well preserved for 5200 years in the icy environment of a high mountain pass (3210 m a.s.l.) in the Ötztal Alps [7][8][9]. Since then, several forward and backward movements of 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, radiocarbon dating, surface exposure dating of rocks and moraines with various cosmogenic radionuclides ( 10 Be, 14 C, 26 Al, 36 Cl), and geomorphological considerations [10][11][12][13][14][15][16][17][18][19][20][21][22]. ...
... Glacier movements of the past have been studied in many mountain ranges of the European Alps [10,11, 13-15, 17, 19-22]. In 2001, 14 C dating of a variety of organic materials released from glaciers in the Swiss Alps revealed eight Holocene phases of reduced glacier extent: 9910-9550, 9010-7980, 7250-6500, 6170-5950, 5290-3870, 3640-3360, 2740-2620, and 1530-1170 calibrated years BP (BP = before present = 1950 AD) [11]. In the following we discuss a few selected cases of glacier movements in the European Alps. ...
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 ¹⁴ C 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.
... Several studies have shown that the COMNISPA records are representative of the alpine climate [92,95,96]. However, other studies have also shown that the observed O signal from this site follows large-scale atmospheric climate variations. ...
With their rich Late Neolithic to Early Bronze Age archives, the Circumharz region, the Czech Republic/Lower Austria region, and the Northern Alpine Foreland are well-suited for research on potential links between human activities and climate fluctuations of this period with pronounced archaeological changes. In this paper, we reconstruct the rate and density of the available ¹⁴ C data from 5500 to 3500 calBP (3550–1550 BCE). We ask to what extent population patterns varied over time and space, and whether fluctuations in human populations and their activities varied with local/regional climate changes. To answer these questions, we have compiled an extensive list of published radiocarbon dates and created ¹⁴ C sum calibrations for each region. We also compare population dynamics with local and regional palaeoclimate records derived from high-resolution speleothems. At the regional scale, the results suggest a causal relationship between regional climate and population trends. Climate and associated environmental changes were thus at least partly responsible for demographic trends. These results also allow us to question the motivation for the construction of so-called “Early Bronze Age princely tombs” in the Circumharz region during a period of population decline. Among other things, it can be argued that the upper echelons of society may have benefited from trade relations. However, this process was accompanied by ecological stress, a cooling of the winter climate, a decline in the total population and an increase in social inequality.
... At the Ji'erzankale Necropolis (2,500 cal BP) on the Pamir Plateau, Xinjiang, all shafts were made of Lonicera sp., taking advantage of its high rigidity (Shen et al., 2015). Other examples of manufacturing arrow shafts from shrubby woods have been widely reported, such as Viburnum sp. in prehistoric Europe, Berberis sp. in Argentina, and Abelia sp. in China (Fermé, 2021;Grosjean et al., 2007;Yi & Zhang, 2003). Some branches or saplings naturally grow rather straight or can be straightened by heating and bending (Reisinger, 2010), thus making arrow manufacture from shrubs possible. ...
In the present study, we analyzed 7 wooden bows and 13 arrows excavated from the cemeteries of Subeixi Culture (13th century BC‐AD 2nd century) in the Turpan Basin, northwest China. A total of six taxa, viz. Morus sp., Salix sp., Picea sp., Lonicera sp., Betula sp., and Tamarix sp. were identified. Some of these taxa have been generally accepted to be suitable for bow‐and‐arrow production. All these taxa were local in origin but distributed in different ecotonal zones, including oases, saline‐alkali lands, and mountain areas. Previous archaeological studies have confirmed that the Subeixi populations lived an agro‐pastoral life. By analyzing the possible provenance of these wood samples, it can be hypothesized that these ancient agro‐pastoralists moved between the Turpan Basin and the Tianshan Mountains on a seasonal basis.
... As they are characterized by favorable conditions of altitude and climate, the Swiss Alps have proved a great potential for conservation of such archaeological remains (Curdy and Nicod 2019). Notable locations encompass Graubünden (Kaufmann 1996), Bern (Hafner 2012), and Valais/Wallis (Andenmatten & Aberson 2019; Eschmann Richon et al., 2016) cantons, where numerous discoveries of organic objects or human bones revealed a regular presence on alpine ridges from the Neolithic period to modern times (Grosjean et al., 2007;Rogers et al. 2014). ...
The Alps have historically been crossed by populations moving between northern and southern Europe for various purposes. Testimonies of such human presence were long preserved from decomposition being covered and protected by perennial ice and snow. However, with ongoing climate change, large portion of these permanent snowed and frozen areas are being freed up exposing artifacts to rapid deterioration. Consequently, archaeologists are requiring new methods to monitor the cryosphere enabling them to efficiently identify potential areas of conservation and protection of archaeological remains. Herein, we used a 34-year satellite-derived time-series of snow cover estimates to identify potential zones for conservation of archaeological remains in the Valais alpine region (Switzerland). Findings suggest that over the considered analysis period (1984–2018), snow cover has declined of about 15% during the summer maximum melting season releasing a surface of approximately 45km² in the study area. Moreover, crossing snow probabilities with Topographic Position Index (TPI) and slope data allowed to compute an Archeological Potential (AP) map to derive zones with high potential of current or imminent release of archaeological remains. Combining this map with density of wood artefacts found on the field in a test area showed that 92.5% are inside identified receding snow/ice areas. Results of this analysis demonstrate that the proposed methodology can be a valid approach to monitor snow/ice minimum extension and identify perennial snowed and iced fields with archaeological potential. It provides the basis for defining new archaeological protection areas, preventing the loss of threatened ancient organic remains and enhances future field research campaigns in mountainous regions.
‘Resilience’, in addition to ‘collapse’, has become increasingly important as a concept for the study of social challenges in archaeology since the turn of the millennium. In this paper, we critically examine both terms and their conceptualisations in archaeology and argue for a data-driven bottom-up approach that harnesses ‘resilience’ beyond system-theoretical approaches such as Resilience Theory and Adaptive Cycle Models. Using high temporal resolution data from the UNESCO World Heritage pile dwellings in the northern Alpine Foreland, this contribution examines how Neolithic communities coped with climatic challenges between 3500 and 3250 BCE. Rising lake-levels destroyed former settlement areas on the lakeshores and led to temporal interruptions of settlement activities. To question their causal relation to climatic fluctuations, we use archaeological information on settlement features as well as various global and regional paleoclimatic proxy data by applying qualitative and quantitative methods utilizing concluding statistics. It can be inferred that especially the longer-term lake-level rises of higher magnitudes hit the agricultural communities hard but did not lead to any form of social collapse. On the contrary, the immediate repopulation of the lakeshores after the lake floods suggests that spatial mobility and the temporary relocation of settlements to the hinterland were a successful social coping practice in dealing with these challenges. Since the frequent relocation of settlements was already immanent to these communities’ social practices, their capacity for residence-based spatial mobility served them as resilience capacity.
Detailed knowledge of Holocene climate and glaciers dynamics is essential for sustainable development in warming mountain regions. Yet information about Holocene glacier coverage in the Alps before the Little Ice Age stems mostly from studying advances of glacier tongues at lower elevations. Here we present a new approach to reconstructing past glacier low stands and ice-free conditions by assessing and dating the oldest ice preserved at high elevations. A previously unexplored ice dome at Weißseespitze summit (3500 m), near where the “Tyrolean Iceman” was found, offers almost ideal conditions for preserving the original ice formed at the site. The glaciological settings and state-of-the-art micro-radiocarbon age constraints indicate that the summit has been glaciated for about 5900 years. In combination with known maximum ages of other high Alpine glaciers, we present evidence for an elevation gradient of neoglaciation onset. It reveals that in the Alps only the highest elevation sites remained ice-covered throughout the Holocene. Just before the life of the Iceman, high Alpine summits were emerging from nearly ice-free conditions, during the start of a Mid-Holocene neoglaciation. We demonstrate that, under specific circumstances, the old ice at the base of high Alpine glaciers is a sensitive archive of glacier change. However, under current melt rates the archive at Weißseespitze and at similar locations will be lost within the next two decades.
Carbon consists of the two stable isotopes (¹²C and ¹³C) often accompanied with minute traces of the long-lived radioisotope ¹⁴C (half-life = 5700 years). This allows one to use isotope-sensitive methods to trace carbon throughout the environment at large on Earth. In particular, ¹⁴C can be used for dating during the past 50,000 years. It has thus revolutionized archaeology, but also many fields of geophysics. Although ¹⁴C is a cosmogenic radionuclide produced primarily by cosmic-ray interaction in the atmosphere, the dramatic increase of ¹⁴C by the atmospheric nuclear weapons testing period generated a characteristic spike (¹⁴C bomb peak) in the early 1960s, which can be used for a variety of unique applications. After describing the basic properties of ¹⁴C, the current review focusses on applications of both cosmogenic and anthropogenic ¹⁴C, emphasizing the versatility of this extraordinary radionuclide.
Europe's temperature increases considerably faster than the northern hemisphere average. Detailed month-by-month analyses show temperature and humidity changes for individual months that are similar for all Europe, indicating large-scale weather patterns uniformly influencing temperature. However, superimposed to these changes a strong west-east gradient is observed for all months. The gradual temperature and humidity increases from west to east are not related to circulation but must be due to non-uniform water vapour feedback. Surface radiation measurements in central Europe manifest anthropogenic greenhouse forcing and strong water vapor feedback, enhancing the forcing and temperature rise by about a factor of three. Solar radiation decreases and changing cloud amounts show small net radiative effects. However, high correlation of increasing cloud-free longwave downward radiation with temperature (r = 0.99) and absolute humidity (r = 0.89), and high correlation between ERA-40 integrated water vapor and CRU surface temperature changes (r = 0.84), demonstrates greenhouse forcing with strong water vapor feedback.
We present a radiocarbon data set of 71 samples of wood and peat material that melted out or sheared out from underneath eight presentday mid-latitude glaciers in the Central Swiss Alps. Results indicated that in the past several glaciers have been repeatedly less extensive than they were in the 1990s. The periods when glaciers had a smaller volume and shorter length persisted between 320 and 2500 years. This data set provides greater insight into glacier variability than previously possible, especially for the early and middle Holocene. The radiocarbon-dated periods defined with less extensive glaciers coincide with periods of reduced radio-production, pointing to a connection between solar activity and glacier melting processes. Measured long-term series of glacier length variations show significant correlation with the total solar irradiance. Incoming solar irradiance and changing albedo can account for a direct forcing of the glacier mass balances. Long-term investigations of atmospheric processes that are in interaction with changing solar activity are needed in order to understand the feedback mechanisms with glacier mass balances.
Palaeobotanical analysis and radiocarbon dating of lake sediments from Bachalpsee (2265m a.s.l.), a small lake above the present-day timber-line in the northern Swiss Alps reveals that the region was already deglaciated during the Younger Dryas. The sediment record is dominated by long-distance transported pollen that originates from lowland vegetation but the plant macrofossils give evidence of the local vegetation development. Comparison with palaeobotanical results from three sites along an altitudinal transect permits the reconstruction of the regional timber-line history. Throughout the entire Holocene the catchment of Bachalpsee consisted of a mosaic of open meadows and dwarf shrubs (Salix, Vaccinium, Rhododendron). Chironomid and cladoceran assemblages suggest that the early to mid-Holocene was the warmest interval at Bachalpsee. Comparison of the palaeobotanical results with those from the mire “Feld” (2130m a.s.l.) in the vicinity of Bachalpsee showed that during the mid-Holocene the timber-line was formed by Pinus cembra and Picea abies with some scattered Abies alba trees and was situated close to Bachalpsee but never reached its catchment. The maximum timber-line in the Northern Alps was reached between 6000 and 3000 cal b.p. which is several millennia later than in the Central Alps. The species composition of the tree-line (Abies alba, Pinus cembra and the absence of Larix decidua) points to less continental and moister climatic conditions compared with the central Alps during the early to mid-Holocene. From 3000 cal b.p. onwards the timber-line was lowered by human deforestation with the most intense pulses of human impact occurring since the Middle Ages. The catchment of Bachalpsee has been used as alpine pasture since the Bronze Age.
In densely populated high mountain regions such as the European Alps, glaciers are an inherent component of the Alpine culture, landscape and environment. They represent a unique resource of fresh water for agriculture and industry, an important economic component of tourism and hydro-power production, and a potential source of serious natural hazards. Due to their proximity to the melting point, glaciers are considered among the best natural indicators of global climate change. Mountain glaciers have become the leading icon in the current debate on climate change and on the uniqueness of present-day changes as compared to the variations which occurred during the Holocene period. Although numerous studies have investigated the relationship between glaciers and climate change, glacier-climate studies that focus on an entire mountain range and integrate in-situ measurements, remote sensing data and modelling approaches, as proposed by modern monitoring strategies, have for the most part been lacking.
It is to fill this gap in our understanding that this study undertakes to investigate glacier fluctuations in the European Alps after 1850. Glacier inventories, in-situ measurements and a numerical model (based on an empirical relationship between precipitation and temperature at the glacier steady-state equilibrium line altitude) are used in combination with a digital elevation model and GIS techniques to analyse the glacier fluctuations between 1850 and the end of the 21st century of the entire Alpine mountain range.
Overall area loss after 1850 is calculated using different methods as being about 35% until the 1970s, when the approximately 5,150 Alpine glaciers covered a total area of 2,909 km2. This loss reached almost 50% by 2000. Rapidly shrinking glacier areas, spectacular tongue retreats and increasing mass losses are clear signs of the atmospheric warming observed in the Alps during the last 150 years and its acceleration over the past two decades, culminating in an ice loss of another 5–10% of the remaining ice volume during the extraordinary warm year of 2003. From the model experiment it is found that for Alpine glaciers, a change of ±1 °C in 6- month summer temperatures would be compensated by an annual precipitation increase/decrease of about 25%. A summer temperature rise of 3 °C would reduce the glacier cover of the reference period (1971–1990) by some 80%, or up to 10% of the glacier extent of 1850. In the event of a 5 °C summer temperature increase, the Alps would become almost completely ice-free. Annual precipitation changes of ±20% would modify such estimated percentages of remaining ice by a factor of less than two.
The presented study demonstrates how modern monitoring strategies can be applied for the investigation of glaciers of an entire mountain range, and that the probability of glaciers in the European Alps disappearing within the coming decades is far from slight.
The thesis consists of a collection of five papers; the studies reported on were carried out within the framework of the EU-funded ALP-IMP project and of the World Glacier Monitoring Service.
Pollen and plant-macrofossil data are presented for two lakes near the timberline in the Italian (Lago Basso, 2250 m) and Swiss Central Alps (Gouille Rion, 2343 m). The reforestation at both sites started at 9700-9500 BP with Pinus cembra, Larix decidua, and Betula. The timberline reached its highest elevation between 8700 and 5000 BP and retreated after 5000 BP, due to a mid-Holocene climatic change and increasing human impact since about 3500 BP (Bronze Age). The expansion of Picea abies at Lago Basso between ca. 7500 and 6200 BP was probably favored by cold phases accompanied by increased oceanicity, whereas in the area of Gouille Rion, where spruce expanded rather late (between 4500 and 3500 BP), human influence equality might have been important. The mass expansion of Alnus viridis between ca. 5000 and 3500 BP probably can be related to both climatic change and human activity at timberline. During the early and middle Holocene a series of timberline fluctuations is recorded as declines in pollen and macrofossil concentrations of the major tree species, and as increases in nonarboreal pollen in the pollen percentage diagram of Gouille Rion. Most of the periods of low timberline can be correlated by radiocarbon dating the climatic changes in the Alps as indicated by glacier advances in combination with palynological records, solifluction, and dendroclimatical data. Lago Basso and Gouille Rion are the only sites in the Alps showing complete palaeobotanical records of cold phases between 10,000 and 2000 BP with very good time control. The altitudinal range of the Holocene treeline fluctuations caused by climate most likely was not more than 100 to 150 m. A possible correlation of a cold period at ca. 7500-6500 BP (Misox oscillation) in the Alps is made with paleoecological data from North American and Scandinavia and a climate signal in the GRIP ice core from central Greenland 8200 yr ago (ca. 7400 yr uncal. BP).
Pollen and macrofossils were analyzed at two sites above today's treeline (or tree limit) in the Swiss Central Alps (GouilleLoere´, 2503 m a.s.l., and Lengi Egga, 2557 m a.s.l.) to test two contrasting hypotheses about the natural formation of timberline (the upper limit of closed forest) in the Alps. Our results revealed that Pinus cembra-Larix decidua forests near timberline were rather closed between 9000 and 2500 B.C. (9600-4000 14C yr BP), when timberline fluctuations occurred within a belt 100-150 m above today's tree limit. The tree- line ecocline above timberline was characterized by the mixed occurrence of tree, shrub, dwarf-shrub, and herbaceous species, but it did not encompass more than 100-150 altitudinal meters. The uppermost limit reached by timberline and treeline during the Holocene was ca. 2420 and 2530 m, respectively, i.e., about 120 to 180 m higher than today. Between 3500 and 2500 B.C. (4700-4000 14C yr BP) timberline progressively sank by about 300 m, while treeline was lowered only ca. 100 m. This change led to an enlargement of the treeline- ecocline belt (by ca. 300 m) after 2500 B.C. (4000 14C yr BP). Above the treeline ecocline, natural meadows dominated by dwarf shrubs (e.g., Salix herbacea) and herbaceous species (e.g., Helianthemum, Taraxacum, Potentilla, Leontodon t., Cerastium alpinum t., Cirsium spinosissimum, Silene exscapa t., and Saxifraga stellaris) have been present since at least 11,000 cal yr ago. In these meadows tree and tall shrub species (.0.5 m) never played a major role. These results support the conventional hypothesis of a narrow ecocline with rather sharp upper timberline and treeline boundaries and imply that today's treeless alpine communities in the Alps are close to a natural stage. Pollen (percentages and influx), stomata, and charcoal data may be useful for determining whether or not a site was treeless. Nevertheless, a reliable and detailed record of past local vegetation near and above timberline is best achieved through the inclusion of macrofossil analysis.
1] Here we use the d 18 O time-series of three stalagmites from the high alpine Spannagel cave (Austria) which grew in small distance from each other to construct a precisely dated, continuous d 18 O curve for the last 9 kyr (COMNISPA). This speleothem record is not influenced by effects of kinetic isotope fractionation due to the low temperatures in the cave. Thus, the variations in d 18 O can be interpreted in terms of past climate change. COMNISPA exhibits several oscillations within the Holocene, and their timing and duration is in agreement with that documented by other alpine archives. Citation: Vollweiler, N., D. Scholz, C. Mühlinghaus, A. Mangini, and C. Spötl (2006), A precisely dated climate record for the last 9 kyr from three high alpine stalagmites, Spannagel Cave, Austria, Geophys. Res. Lett., 33, L20703, doi:10.1029/2006GL027662.
The taxonomic composition of chironomid, cladoceran and diatom assemblages in small lakes in the Alpine region shows a strong relationship with summer temperature. Since fossils of all three organism groups preserve well and remain identifiable in lake sediments, summer temperature transfer-functions can be developed based on the modern distribution of these organisms and applied to fossil records to reconstruct past summer temperature variability. We provide a summary of the chironomid-, cladoceran- and diatom-based transfer functions available from the Swiss Alps and discuss the potential problem of co-variation between summer temperature and lake nutrient conditions for transfer-function development. Whereas the diatom-based summer temperature transfer function remains to be evaluated in down-core reconstructions, the cladoceran- and chironomid-based transfer functions have been used successfully to produce summer temperature records on Lateglacial and Holocene time scales that are in good agreement with other temperature reconstructions in the Alps. Major problems that can be encountered when using fossil assemblages of aquatic organisms for temperature reconstruction in the Alpine region are biases in the inferred temperatures associated with human impact on lakes and parameters other than temperature affecting the fossil assemblages. A multi-proxy approach to palaeoenvironmental reconstruction is recommended to keep a close control on past catchment and within-lake processes during the time interval of interest.