This study investigates the subglacial sedimentary archive at Tschierva Glacier, Eastern Swiss Alps. Subfossil wood remains found at the retreating glacier tongue indicate that their emergence ...results from recent transport from an upvalley basin. A confluence-basin-like structure was found to exist by georadar measurements underneath the present glacier. In combination with high resolution age determinations based on dendrochronology and radiocarbon dating it is implied that a retreated Tschierva Glacier allowed vegetation growth and sediment accumulation in that basin. Three periods of glacier recession were detected, which occurred around 9200
cal
yr
BP, from 7450 to 6650
cal
yr
BP and from 6200 to 5650
cal
yr
BP. These periods are called Holocene optimum events (HOE). Accordingly, an equilibrium line rise >220
m compared to the reference period from 1960 to 1985 was inferred from digital elevation models of former glacier extents. Since glacier mass balance depends on summer (June–July–August) temperature and precipitation, an equilibrium line altitude (ELA) rise of 220
m implies a summer temperature increase of about 1.8
°C assuming unchanged precipitation during the dated HOE. Alternative calculations point to probable temperature increase in a broad interval between +1.0
°C taking into account a precipitation change of −250
mm/a to +2.5
°C with +250
mm/a precipitation change, supporting earlier paleotemperature estimates. It is proposed that higher mean summer insolation caused a stronger seasonality during the mid-Holocene as compared to late Holocene conditions.
Glacially deformed pieces of wood, organic lake sediments and clasts of reworked peat have been collected in front of Alpine glaciers since AD 1990. The palaeoglaciological interpretation of these ...organic materials is related to earlier phases of glacier recession surpassing that of today's shrunken glaciers and to tree growth and peat accumulation in the valleys now occupied by the glaciers. Glacial transport of the material is indicated by wood anatomy, incorporated silt, sand and gravel particles, missing bark and deformed treerings. A total of 65 samples have been radiocarbon dated so far, and clusters of dates provide evidence of eight phases of glacier recession: 9910-9550, 9010-7980, 7250-6500, 6170-5950, 5290-3870, 3640-3360, 2740-2620 and 1530-1170 calibrated years BP. Allowing for the timelag between climatic fluctuations, glacier response and vegetation colonization, these recession phases may lag behind climatic changes by 100-200 years.
Stable isotopes in tree-ring cellulose are important tools for climatic reconstructions even though their interpretation could be challenging due to nonclimate signals, primarily those related to ...tree aging. Previous studies on the presence of tree-age-related trends during juvenile as well as adult growth phases in δD, δ18O, and δ13C time series yielded variable results that are not coherent among different plant species. We analyzed possible trends in the extracted cellulose of tree rings of 85 larch trees and 119 cembran pine trees, i.e., in samples of one deciduous and one evergreen conifer species collected at the tree line in the Alps, covering nearly the whole Holocene. The age trend analyses of all tree-ring variables were conducted on the basis of mean curves established by averaging the cambial-age-aligned tree series. For cambial ages over 100 years, our results prove the absence of any age-related effect in the δD, δ18O, and δ13C time series for both the evergreen and the deciduous conifer species, with the only exception being larch δD. However, for lower cambial ages, we found trends that differ for each isotope and species; i.e., mean δ13C values in larch do not vary with aging and can be used without detrending, whereas those in cembran pine show a juvenile effect, and the data should be detrended. Mean δ18O values present two distinct aging phases for both species, complicating detrending. Similarly, mean δD values in larch change in the first 50 years, whereas cembran pine changes between 50 and 100 years. Values for these two periods of cambial age for δD and δ18O should be used with caution for climatic reconstructions, ideally complemented by additional information regarding mechanisms for these trends.
Surface exposure ages with cosmogenic
10Be and
26Al on glaciogenic landforms at the Uludağ Mountain, NW Turkey (Mt. Uludağ: 40°04′15″N, 29°13′18″E, 2542 m above sea level), indicate that the local ...maximum glaciation occurred no later than 20.3 ± 1.5 ka ago. This is in agreement with other exposure age data sets from Anatolia and is in accordance with the timing of the last maximum glaciation in the European Alps coinciding with the global Last Glacial Maximum (LGM; 21 ± 2 ka). Geomorphologically-constrained subsequent glacier oscillations were dated to the Lateglacial period and show distinct phases of readvanced glaciers around 16.1 ± 1.2 ka, 13.3 ± 1.1 ka, and 11.5 ± 1.0 ka ago. This indicates an oscillating glacier recession in NW Anatolia during Termination 1. Published surface exposure ages related to the Lateglacial Gschnitz and Egesen moraines in the European Alps are in good agreement with the derived glacier chronology at the Uludağ Mountain. This implies the parallel occurrence of major climatic shifts on millennial time-scale in the European Alps and NW Turkey during the Marine Isotope Stage (MIS) 2.
Cellulose content (CC (%)) in tree
rings is usually utilised as a tool to control the quality of the α-cellulose extraction from tree rings in the preparation of stable-isotope
analysis in wooden ...tissues. Reported amounts of CC (%) are often limited
to mean values per tree. For the first time, CC (%) series from two
high-Alpine species, Larix decidua Mill. (European Larch, LADE) and
Pinus cembra L. (Swiss stone pine, PICE) are investigated in modern
wood samples and Holocene wood remains from the Early and mid-Holocene.
Modern CC (%) series reveal a species-specific low-frequency trend
independent of their sampling site over the past 150 years.
Climate–cellulose relationships illustrate the ability of CC (%) to
record temperature in both species but for slightly different periods within
the growing season. The Holocene CC (%) series illustrate diverging low-frequency trends in
both species, independent of sampling site characteristics (latitude,
longitude and elevation). Moreover, potential age trends are not apparent in
the two coniferous species. The arithmetic mean of CC (%) series in the
Early and mid-Holocene indicate low CC (%) succeeding cold events. In
conclusion, CC (%) in tree rings show high potential to be established as
novel supplementary proxy in dendroclimatology.
During the Last Glacial Maximum (LGM), the glaciation in the European Alps reached maximum ice extent. We already simulated the steady states of the Alpine ice coverage for several climate drivers in ...Becker et al. (2016) and heighten in this article such studies for the Swiss Valais region. To this end, we employ the Parallel Ice Sheet Model (PISM), which combines the shallow ice approximation (SIA) with basal sliding elements of the shallow shelf approximation (SSA), and subject this model to various external driving mechanisms. We further test the sensitivity of this kind of the ice coverage in the Valais region to a temporally constant climate and to monotonic ice sheet build-up from inception to steady state as well as to the Dye 3 temperature driving during the past 120 000 years. We also test differences in the precipitation patterns exerted to the northern and southern catchment areas of the Rhone and Toce rivers to possible transfluence changes in ice from the northern to the southern catchment areas and vice versa. Moreover, we study the effect of the ice deformability and estimate the removal up to 1000 m of sediment in the Rhone Valley and study the removal of rock hindering the flow through the valley cross section at the knee of Martigny. All these studies took place because of a discrepancy in the ice height prediction of the modelled ice sheet with its geomorphologically reconstructed counterpart with proxy data obtained by Bini et al. (2009) as well as a difference in ice height between the two of up to 800 m. Unfortunately, all the scenarios in the model do not sufficiently reduce this discrepancy in the height prediction and the geomorphological reconstruction. The model results have discovered an ice dynamical discrepancy with the land map in Bini et al. (2009).
A glaciogenic sediment sequence deposited by a local glacier in the Rhine catchment area near Sargans (Eastern Swiss Alps) was investigated in order to examine the shear behaviour of two different ...tills. In addition to ring–shear experiments, examination of clast lithology, clay mineralogy and physical properties of all samples were determined. SEM–analyses of artificially produced deformation patterns in the till samples show only a very thin shear zones of 2–3
μm thickness, despite long shear distances of up to 145
mm. A clear relationship between local bedrock and the formation of a thin basal layer of heavily deformed till can be demonstrated. This locally derived till layer exhibits distinctly different shearing properties compared to the massive overlying till unit that is composed of more distantly transported lithic material from the upper catchment area of the glacier. The difference in the angle of internal friction between the two tills is >10° at residual shear strength, although the clay mineralogy of both tills is similar. It can further be demonstrated that after the deposition of a 10–15
cm thin till layer directly on bedrock, the flow dynamics of the glacier tongue may have changed due to differences in glacier bed debris lithology. Differences in the shear behaviour of the sediments, allied to microscopic analyses, point to an important environmental change from a deformation till to an overlying “non–deformed till”.
Soluble salts are indigenous to the marine sediments of the Esna Formation and Thebes Formation in central Egypt. Natural weathering processes and human impact cause salt efflorescence in tombs and ...on walls of ancient Egyptian monuments in the Theban Necropolis, resulting in the disintegration of wall paintings and carved hieroglyphs. Determination and quantification of soluble salts and measurements of the porosity were done on tomb marls in order to understand the origin and damage potential of the salts in the royal tombs of the Valley of the Kings. The study shows that sodium chloride (NaCl) is the predominant salt species. Sulphates, anhydrite (CaSO4) and gypsum (CaSO4.2 H2O) also occur in the limestone deposits of the Thebes Formation and the underlying shale deposits of the Esna Formation. Member I of the Thebes Formation, into which most of the ancient tombs were hewn, shows the highest amount of soluble salts (up to 6·2wt-% dry). In addition, the porosity and permeability of the marls in Member I are high, enhancing water molecules and brine migration. Wetting and drying of the tomb surfaces in the past has affected solution, transportation and recrystallization of water soluble minerals, and has led to major destruction of wall paintings and ornamentations. This study shows that large amounts of salt minerals still remain in the wall rocks. Future humidity changes due to flash floods and tourists may favour salt crystallization in the ancient Egyptian monuments. The authors urge the authorities to undertake steps to prevent further destruction to save the magnificent cultural heritage found in the Thebes area.
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