The transition from the Late Glacial to the Early Holocene and its expression in moraine records of the Silvretta Massif

2021 ◽  
Author(s):  
Sandra M. Braumann ◽  
Joerg M. Schaefer ◽  
Stephanie M. Neuhuber ◽  
Markus Fiebig
Keyword(s):  
Roman Empire ◽  
Northern Hemisphere ◽  
Late Glacial ◽  
Climatic Conditions ◽  
Meridional Overturning Circulation ◽  
Early Holocene ◽  
Age Dating ◽  
Ice Age ◽  
Mountain Glaciers ◽  
Exposure Dating

<p>Mountain glaciers and their preserved moraine records provide important insights into periods when climate conditions favored glacier advance or stabilization. Comprehensive mapping of moraines in glacier forefields elucidates the <em>spatial distribution</em> of former ice margins. Numerical age dating of moraines, in turn, constrains the <em>timing </em>of moraine formation intervals. A combination of both methods allows reconstructing the evolution of mountain glaciers across time and space and links today’s alpine geomorphology with climate of the past.</p><p>Here, we present glacier reconstructions from two adjacent valleys in the northern Silvretta Massif (Austrian Alps). Both, the Jamtal and the Laraintal, exhibit multiple prominent moraine ridges outboard the Little Ice Age (LIA) moraine and inboard presumable Late Glacial ice margins. By applying <sup>10</sup>Be surface exposure dating to these moraines, we decipher the response of Silvretta glaciers to the transition from glacial to interglacial climatic conditions.</p><p>Pronounced double-ridge structures in lateral and terminal positions outside the LIA moraines were dated and yield landform ages of 11.3 ±0.8 kyrs (n=12) and 10.8 ±0.8 kyrs (n=9). This age pattern is consistent across both valleys and implies two significant moraine formation intervals during the earliest Holocene that overlap within uncertainties. Additional samples (n=6) were collected along presumable LIA ice margins. Four of them indeed produced LIA ages with three of them suggesting a culmination in the second half of the 18<sup>th</sup> century CE (mean age: 260 ±25 yrs). This result is in good agreement with <sup>10</sup>Be ages from a recent study at an adjacent site, which indicate a LIA advance around 260 ±30 yrs. The remaining two ages coincide with a phase of cooler temperatures and increased precipitation in Europe from the 4<sup>th</sup> to 6<sup>th</sup> century, a climate episode, which is often associated with the fall of the Roman Empire and with the migration period in Europe.</p><p>We interpret the sets of Early Holocene moraines as evidence of brief cold lapses, which punctuated the general warming trend at the beginning of the Holocene, with the Preboreal Oscillation (PBO; c. 11,300 to 11,150 cal BP) being the most prominent one. Moraine formation intervals during the Early Holocene have been reported in the wider Alpine region and at other places in the northern hemisphere (e.g. North America, Scandinavia, Greenland). Annual mean temperatures certainly differed at each of these places, but synchronous phases of glacier advances or stabilization are recorded across the northern hemisphere during the Early Holocene. We suggest that freshwater input into the Atlantic Ocean caused phases of temporary weakening of the Atlantic Meridional Overturning Circulation (AMOC), which lead to episodes of relative cooling in the northern hemisphere. This cooling phases are preserved in the Early Holocene moraine sets that we mapped and dated in the Silvretta region.</p>

scholarly journals How dry was the Younger Dryas? Evidence from a coupled <i>δ</i><sup>2</sup>H–<i>δ</i><sup>18</sup>O biomarker paleohygrometer applied to the Gemündener Maar sediments, Western Eifel, Germany

2019 ◽  
Vol 15 (2) ◽  
pp. 713-733 ◽  
Author(s):  
Johannes Hepp ◽  
Lorenz Wüthrich ◽  
Tobias Bromm ◽  
Marcel Bliedtner ◽  
Imke Kathrin Schäfer ◽  
...  
Keyword(s):  
Isotope Composition ◽  
Younger Dryas ◽  
Late Glacial ◽  
Climatic Conditions ◽  
Leaf Water ◽  
Early Holocene ◽  
Unexpected Finding ◽  
Temperature Dependent ◽  
The Past ◽  
Natural Climate

Abstract. Causes of the Late Glacial to Early Holocene transition phase and particularly the Younger Dryas period, i.e. the major last cold spell in central Europe during the Late Glacial, are considered to be keys for understanding rapid natural climate change in the past. The sediments from maar lakes in the Eifel, Germany, have turned out to be valuable archives for recording such paleoenvironmental changes. For this study, we investigated a Late Glacial to Early Holocene sediment core that was retrieved from the Gemündener Maar in the Western Eifel, Germany. We analysed the hydrogen (δ2H) and oxygen (δ18O) stable isotope composition of leaf-wax-derived lipid biomarkers (n-alkanes C27 and C29) and a hemicellulose-derived sugar biomarker (arabinose), respectively. Both δ2Hn-alkane and δ18Osugar are suggested to reflect mainly leaf water of vegetation growing in the catchment of the Gemündener Maar. Leaf water reflects δ2H and δ18O of precipitation (primarily temperature-dependent) modified by evapotranspirative enrichment of leaf water due to transpiration. Based on the notion that the evapotranspirative enrichment depends primarily on relative humidity (RH), we apply a previously introduced “coupled δ2Hn-alkane–δ18Osugar paleohygrometer approach” to reconstruct the deuterium excess of leaf water and in turn Late Glacial–Early Holocene RH changes from our Gemündener Maar record. Our results do not provide evidence for overall markedly dry climatic conditions having prevailed during the Younger Dryas. Rather, a two-phasing of the Younger Dryas is supported, with moderate wet conditions at the Allerød level during the first half and drier conditions during the second half of the Younger Dryas. Moreover, our results suggest that the amplitude of RH changes during the Early Holocene was more pronounced than during the Younger Dryas. This included the occurrence of a “Preboreal Humid Phase”. One possible explanation for this unexpected finding could be that solar activity is a hitherto underestimated driver of central European RH changes in the past.

scholarly journals Holocene and ‘Little Ice Age’ glacial activity in the Marboré Cirque, Monte Perdido Massif, Central Spanish Pyrenees

The Holocene ◽  
2014 ◽  
Vol 24 (11) ◽  
pp. 1439-1452 ◽  
Author(s):  
José M García-Ruiz ◽  
David Palacios ◽  
Nuria de Andrés ◽  
Blas L Valero-Garcés ◽  
Juan I López-Moreno ◽  
...  
Keyword(s):  
Little Ice Age ◽  
18Th Century ◽  
Sediment Cores ◽  
Rock Avalanche ◽  
Late Glacial ◽  
Maunder Minimum ◽  
Ice Age ◽  
Massif Central ◽  
Exposure Dating ◽  
Glacial Expansion

The Marboré Cirque, which is located in the southern Central Pyrenees on the north face of the Monte Perdido Peak (42°40′0″N; 0.5°0″W; 3355 m), contains a wide variety of Holocene glacial and periglacial deposits, and those from the ‘Little Ice Age’ (‘LIA’) are particularly well developed. Based on geomorphological mapping, cosmogenic exposure dating and previous studies of lacustrine sediment cores, the different deposits were dated and a sequence of geomorphological and paleoenvironmental events was established as follows: (1) The Marboré Cirque was at least partially deglaciated before 12.7 kyr BP. (2) Some ice masses are likely to have persisted in the Early Holocene, although their moraines were destroyed by the advance of glaciers during the Mid Holocene and ‘LIA’. (3) A glacial expansion occurred during the Mid Holocene (5.1 ± 0.1 kyr), represented by a large push moraine that enclosed a unique ice mass at the foot of the Monte Perdido Massif. (4) A melting phase occurred at approximately 3.4 ± 0.2 and 2.5 ± 0.1 kyr (Bronze/Iron Ages) after one of the most important glacial advances of the Neoglacial period. (5) Another glacial expansion occurred during the Dark Age Cold Period (1.4–1.2 kyr), followed by a melting period during the Medieval Climate Anomaly. (6) The ‘LIA’ represented a clear stage of glacial expansion within the Marboré Cirque. Two different pulses of glaciation were detected, separated by a short retraction. The first pulse occurred most likely during the late 17th century or early 18th century (Maunder Minimum), whereas the second occurred between 1790 and ad 1830 (Dalton Minimum). A strong deglaciation process has affected the Marboré Cirque glaciers since the middle of the 19th century. (7) A large rock avalanche occurred during the Mid Holocene, leaving a chaotic deposit that was previously considered to be a Late Glacial moraine.

Fine laminated clastic deposits revealing the delay of the deglaciation timing in the High Tatras Mts. (Central Europe) to Early Holocene

2020 ◽  
Author(s):  
Dhavamani Ramachandran ◽  
Radovan Pipík ◽  
Timea Chamutiová ◽  
Lucia Žatková ◽  
Marina Vidhya ◽  
...  
Keyword(s):  
Central Europe ◽  
Late Glacial ◽  
Early Holocene ◽  
Age Dating ◽  
Tatra Mountains ◽  
East Central Europe ◽  
Tatra Mts ◽  
Cosmogenic Nuclide Dating ◽  
Late Glacial And Holocene ◽  
The Tatra Mountains

&lt;p&gt;The Tatra moraine relief and cosmogenic nuclide dating show glacier stabilizationand the maximum glacier extent in two phases,at26 &amp;#8211; 21 ka and at 18 ka followed by a gradual retreat and &amp;#160;a termination of the glaciation during the B&amp;#248;lling/Aller&amp;#248;d warming at 14.64 &amp;#8211;12.9 ka (Makos etal., 2014). A renewed glaciation within the Younger Dryas (12.9 &amp;#8211; 11.5 ka) formed smaller rock glaciers. This retreat was connected with the formation of the morainic, trough and cirque lakes and the beginning of light-grey silt sedimentation dated from 10ka to 16ka cal BP on the northern slopes of the Tatra Mountains and before 10ka cal BP on its southern slopes (Klapyta et al., 2016).&lt;/p&gt;&lt;p&gt;A new paleolimnic research led to a discovery of a cyclic fine laminated deposit in the four Tatra Mts. lakes. The laminae of thickness from 1 to 3 mm are built of couplets of light-coloured coarse detrital and fine dark-coloured laminae. Thicker light coloured laminae occasionally show a gradation ending in dark-coloured laminae. Laminae consist occasionally of low spherical angular grains of sand and gravel fractions, rarely up to size 10 mm which deformed underlying laminae. Light-coloured laminae are predominantly composed of quartz, followed by K-feldspar, plagioclase, mica, and clay-like particles. Dark-coloured laminae consist of clay-size clastic particles. These laminae were formed in cold, oxygen-rich, ultra-oligotrophic, slightly acid conditions in which the chironomids Pseudodiamesa nivosa and Micropsectra radialis-type dominated. We interpret these lamination as varves related to annual glacial melting. Once the valleys were ice-free, varve production stopped and a short deposition period of homogenous silt was replaced by gyttja. The radiometric C&lt;sup&gt;14&lt;/sup&gt; age dating shows the deglaciation in the Tatra Mts terminated at the beginning of the Early Holocene, around 10ka cal BP &amp;#8211; 9ka cal BP.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;The research was funded by APVV-15-0292 and the project Centre of Excellence for Integrated Research of the Earth's Geosphere, ITMS 26220120064.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;Klapyta P., Zasadni J., Pociask-Karteczka J., Gajda A., Franczak P., 2016. Late Glacial and Holocene Paleoenvironmental records in the Tatra Mountains, East-Central Europe, based on lake, peat bog and colluvial sedimentary data: A summary review. Quaternary International 415: 126-144.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;Makos M., Dzierzek J., Nitychoruk J., Zreda M., 2014. Timing of glacier advances and climate in the Tatra Mountains (Western Carpathians) during the Last Glacial Maximum. Quaternary Research 82: 1-13.&lt;/p&gt;

scholarly journals Late Glacial and Early Holocene human demographic responses to climatic and environmental change in Atlantic Iberia

2020 ◽  
Vol 376 (1816) ◽  
pp. 20190724 ◽  
Author(s):  
T. Rowan McLaughlin ◽  
Magdalena Gómez-Puche ◽  
João Cascalheira ◽  
Nuno Bicho ◽  
Javier Fernández-López de Pablo
Keyword(s):  
Population Growth ◽  
Quantitative Methods ◽  
Late Glacial ◽  
Climatic Conditions ◽  
Early Holocene ◽  
Food Sources ◽  
Resource Base ◽  
Temporal Models ◽  
Spatio Temporal ◽  
Successive Generations

Successive generations of hunter–gatherers of the Late Glacial and Early Holocene in Iberia had to contend with rapidly changing environments and climatic conditions. This constrained their economic resources and capacity for demographic growth. The Atlantic façade of Iberia was occupied throughout these times and witnessed very significant environmental transformations. Archaeology offers a perspective on how past human population ecologies changed in response to this scenario. Archaeological radiocarbon data are used here to reconstruct demographics of the region over the long term. We introduce various quantitative methods that allow us to develop palaeodemographic and spatio-temporal models of population growth and density, and compare our results to independent records of palaeoenvironmental and palaeodietary change, and growth rates derived from skeletal data. Our results demonstrate that late glacial population growth was stifled by the Younger Dryas stadial, but populations grew in size and density during the Early to Middle Holocene transition. This growth was fuelled in part by an increased dependence on marine and estuarine food sources, demonstrating how the environment was linked to demographic change via the resource base, and ultimately the carrying capacity of the environment. This article is part of the theme issue ‘Cross-disciplinary approaches to prehistoric demography’.

Last Glacial Maximum to near present 10Be chronology of the Universidad glacier fluctuations in the Subtropical Chilean Andes (34° S): paleoclimate implications  

2021 ◽  
Author(s):  
Hans Fernández ◽  
Juan-Luis García ◽  
Samuel U. Nussbaumer ◽  
Alessa Geiger ◽  
Isabelle Gärtner-Roer ◽  
...  
Keyword(s):  
Last Glacial Maximum ◽  
Late Glacial ◽  
Glacial Maximum ◽  
Ice Age ◽  
Climate History ◽  
Last Glacial ◽  
Exposure Dating ◽  
Glacier Fluctuations ◽  
History Of ◽  
The Last Glacial

&lt;p&gt;The geochronological and geomorphological reconstruction of glacier fluctuations is required to assess the timing and structure of climate changes of the last glacial cycle in the subtropical Andes of Chile. The scarcity of data in this region limits the knowledge related to the timing of glacial landscape changes during this long-term period. To provide a new framework to better understand the climate history of the semiarid Andes of Chile, we have reconstructed the glacial history of the Universidad glacier (34&amp;#176; S).&lt;/p&gt;&lt;p&gt;Our mapping shows the existence of four moraine belts (UNI I to UNI IV, from outer to inner) that are spatially unequally distributed along the 13 km of the valley between ~2500 and ~1400 m a.s.l. We applied &lt;sup&gt;10&lt;/sup&gt;Be cosmogenic surface exposure dating to 26 granodioritic boulders on moraines and determined the age of the associated glacial advances. UNI I moraine represents the distal glacier advance between 20.8&amp;#177;0.8 and 17.8&amp;#177;0.8 kyr ago (number of &lt;sup&gt;10&lt;/sup&gt;Be samples = 11). Other two significative glacier advances terminated one and four km up-valley from the UNI I moraine, respectively, formed 16.1&amp;#177;0.9 kyr (n=1) (UNI II) and 14.6&amp;#177;1 to 10&amp;#177;0.5 kyr ago (n=3) (UNI III). A sequence of six distinct and smaller moraine ridges has been identified in the proglacial area. They are part of last significative glacier advances labeled as UNI IV. The four distal ridges have been dated to between 645-150 years ago (n=11), while the most proximal moraines coincide with mid-20&lt;sup&gt;th&lt;/sup&gt; century and 1997 aerial photographs.&lt;/p&gt;&lt;p&gt;The results indicate that the Universidad glacier advanced during the Last Glacial Maximum (LGM) (UNI I). Deglaciation was punctuated by glacier readvances during the Late Glacial when the UNI II and UNI III moraines were deposited. Finally, UNI IV moraine shows six glacier fluctuations developed between the 14th and 20&lt;sup&gt;th&lt;/sup&gt; centuries.&lt;/p&gt;&lt;p&gt;Our data suggest that the glacier advances by the Universidad glacier were triggered by intensified southern westerly winds bringing colder and wetter conditions to subtropical latitudes in the SE Pacific. Moreover, our data indicate that more or less in-phase Late-Glacial advances along the tropical and extratropical Andes occurred. We discuss different climate forcings that explain these glacier changes. Finally, we illustrate the influence of the &amp;#8220;Little Ice Age&amp;#8221; in the Semiarid Andes.&lt;/p&gt;

The extent, timing and palaeoclimatic significance of Late-glacial and Holocene snowpatches and glaciers in the Marrakech High Atlas, Morocco

2021 ◽  
Author(s):  
Benjamin Bell ◽  
Philip Hughes ◽  
William Fletcher ◽  
Roger Braithwaite ◽  
Henk Cornelissen ◽  
...  
Keyword(s):  
Little Ice Age ◽  
Late Glacial ◽  
Ice Age ◽  
High Atlas ◽  
The Holocene ◽  
Exposure Dating ◽  
Ground Water Recharge ◽  
Late Glacial And Holocene ◽  
High Level ◽  
Snow And Ice

&lt;p&gt;Pleistocene glaciers were extensive in the Marrakech High Atlas, Morocco. Today, semi-permanent snowpatches survive in topoclimatic settings and there is evidence of niche glaciers as recently as the Little Ice Age and early 20&lt;sup&gt;th&lt;/sup&gt; Century. However, little is known about the state of permanent snow and niche glaciers through the Holocene. One hypothesis is that Little Ice Age glaciers were the largest snow and ice masses since the end of the Late-glacial (Younger Dryas 12.9-11.7 ka). Another possibility is that snow and ice expanded to similar or greater extents at other points in the Holocene.&lt;/p&gt;&lt;p&gt;To test these hypotheses, moraine boulders have been sampled on moraine successions in the highest parts of the High Atlas, including moraine successions in front of the n&amp;#233;v&amp;#233; permanent below the north-facing cliffs of Tazaghart (3890 m a.s.l.), a semi-permanent snowpatch that survives many summers today. This site is bounded by prominent moraine ridges with no soil development and no lichens on surface boulders. Several other high-level sites have been targeted and over 40 samples are currently being processed for &lt;sup&gt;10&lt;/sup&gt;Be and &lt;sup&gt;36&lt;/sup&gt;Cl exposure dating. Establishing the relative difference in extent and altitude of Late-glacial and the most recent glaciers in the High Atlas is important for understanding landscape and climate evolution in high mountain areas in the subtropics (31&amp;#186;N).&lt;/p&gt;&lt;p&gt;The dated geomorphological records for late-lying snow and glaciers will be compared to high-resolution &lt;sup&gt;14&lt;/sup&gt;C dated continuous parasequences from sediment cores from marshes at the Yagour Plateau and Ouka&amp;#239;meden, both high-level sites in the High Atlas (~2700 m a.s.l.). The proximity of these sites (5-30 km, respectively) from the snowpatch/glacier sites will provide an important independent record of environmental change, spanning the Late-glacial and Holocene. This geomorphological record of former glaciers and snowpatches (moraines and pronival ramparts) is inherently fragmentary in time and the continuous core records from these alpine marshes will provide crucial insights into changing moisture conditions over time, which at these altitudes are closely related to the extent and volume of snowpack.&lt;/p&gt;&lt;p&gt;The climates associated with perennial snow cover and niche glaciers, and the associated annual snowpack melt, will be quantified using degree-day modelling. This allows melt rates to be predicted and this can be compared against observed modern climate in the High Atlas region. This involves interrogation of existing meteorological datasets from across the High Atlas and the development of algorithms for interpolation and extrapolation to ungauged higher altitudes.&lt;/p&gt;&lt;p&gt;Changes in the nature of the cryosphere through time in the High Atlas Mountains is crucial for understanding human activity and socioeconomic development in the wider region. Today, snowmelt from the High Atlas represents the most important ground water recharge used for a wide variety of purposes. Understanding changes in snow conditions, and as a consequence the behaviour of niche glaciers, in the High Atlas through the Holocene has important implications not only for water supply for humans but also for biological refugia and the evolution of cold-adapted flora and fauna.&lt;/p&gt;

scholarly journals Climate change and evolving human diversity in Europe during the last glacial

2004 ◽  
Vol 359 (1442) ◽  
pp. 243-254 ◽  
Author(s):  
Clive Gamble ◽  
William Davies ◽  
Paul Pettitt ◽  
Martin Richards
Keyword(s):  
Climate Change ◽  
Climatic Factors ◽  
Habitat Preferences ◽  
Late Glacial ◽  
Climatic Conditions ◽  
Population History ◽  
Ice Age ◽  
Oxygen Isotope Stage ◽  
Last Glacial ◽  
The Last Glacial

A link between climate change and human evolution during the Pleistocene has often been assumed but rarely tested. At the macro–evolutionary level Foley showed for hominids that extinction, rather than speciation, correlates with environmental change as recorded in the deep sea record. Our aim is to examine this finding at a smaller scale and with high–resolution environmental and archaeological archives. Our interest is in changing patterns of human dispersal under shifting Pleistocene climates during the last glacial period in Europe. Selecting this time frame and region allows us to observe how two hominid taxa, Neanderthals and Crô–Magnons, adapted to climatic conditions during oxygen isotope stage 3. These taxa are representative of two hominid adaptive radiations, termed terrestrial and aquatic , which exhibited different habitat preferences but similar tolerances to climatic factors. Their response to changing ecological conditions was predicated upon their ability to extend their societies in space and time. We examine this difference further using a database of all available radiocarbon determinations from western Europe in the late glacial. These data act as proxies for population history, and in particular the expansion and contraction of regional populations as climate changed rapidly. Independent assessment of these processes is obtained from the genetic history of Europeans. The results indicate that climate affects population contraction rather than expansion. We discuss the consequences for genetic and cultural diversity which led to the legacy of the Ice Age: a single hominid species, globally distributed.

scholarly journals Early Holocene cold snaps and their expression in the moraine record of the Eastern European Alps

2021 ◽  
Author(s):  
Sandra M. Braumann ◽  
Joerg M. Schaefer ◽  
Stephanie M. Neuhuber ◽  
Christopher Lüthgens ◽  
Alan J. Hidy ◽  
...  
Keyword(s):  
Climate Change ◽  
Arctic Region ◽  
Climate System ◽  
Early Holocene ◽  
Ice Age ◽  
The Arctic ◽  
European Alps ◽  
Eastern European ◽  
Exposure Dating ◽  
The Past

Abstract. Glaciers preserve climate variations in their geological and geomorphological records, which makes them prime candidates for climate reconstructions. Investigating the glacier-climate system over the past millennia is particularly relevant because, first, the amplitude and frequency of natural climate variability during the Holocene provides the climatic context against which modern, human-induced climate change must be assessed. Second, the transition from the last glacial to the current interglacial promises important insights into the climate system during warming, which is of particular interest with respect to ongoing climate change. Evidence of stable ice margin positions that record cooling during the past 12 ka are preserved in two glaciated valleys of the Silvretta Massif in the Eastern European Alps, the Jamtal (JAM) and the Laraintal (LAR). We mapped and dated moraines in these catchments including historical ridges using Beryllium-10 Surface Exposure Dating (10Be SED) techniques, and correlate resulting moraine formation intervals with climate proxy records to evaluate the spatial and temporal scale of these cold phases. The new geochronologies indicate two moraine formation intervals (MFI) during the Early Holocene (EH): 10.8 ± 0.7 ka (n = 9) and 11.2 ± 0.8 ka (n = 12). Boulder ages along historical moraines (n = 6) imply at least two glacier advances during the Little Ice Age (LIA; c. 1250–1850 CE), around 1300 CE and in the second half of the 18th century. An earlier advance to the same position may have occurred around 500 CE. The Jamtal and Laraintal moraine chronologies provide evidence that millennial scale EH warming was superimposed by centennial scale cooling. The timing of EH moraine formation is contemporaneous with brief temperature drops identified in local and regional paleoproxy records, most prominently with the Preboreal Oscillation (PBO), and is consistent with moraine deposition in other catchments in the European Alps, and in the Arctic region. This consistency points to cooling beyond the local scale and therefore a regional or even hemispheric climate driver. Freshwater input sourced from the Laurentide Ice Sheet (LIS), which changed circulation patterns in the North Atlantic, is a plausible explanation for EH cooling and moraine formation in the Nordic region and in Europe.

scholarly journals How dry was the Younger Dryas? Evidence from a coupled δ<sup>2</sup>H-δ<sup>18</sup>O biomarker paleohygrometer, applied to the Lake Gemündener Maar sediments, Western Eifel, Germany

2018 ◽  
Author(s):  
Johannes Hepp ◽  
Lorenz Wüthrich ◽  
Tobias Bromm ◽  
Marcel Bliedtner ◽  
Imke Kathrin Schäfer ◽  
...  
Keyword(s):  
Isotope Composition ◽  
Younger Dryas ◽  
Vegetation Period ◽  
Late Glacial ◽  
Climatic Conditions ◽  
Leaf Water ◽  
Early Holocene ◽  
Air Humidity ◽  
Relative Air Humidity ◽  
Natural Climate

Abstract. The Late Glacial to Early Holocene transition phase and particularly the Younger Dryas period, i.e. the major last cold spell in Central Europe during the Late Glacial, are considered crucial for understanding rapid natural climate change in the past. The sediments from Maar lakes in the Eifel, Germany, have turned out to be valuable archives for recording such paleoenvironmental changes. For this study, we investigated a Late Glacial to Early Holocene sediment core that was retrieved from Lake Gemündener Maar in the Western Eifel, Germany. We analysed the hydrogen (δ2H) and oxygen (δ18O) stable isotope composition of leaf wax-derived lipid biomarkers (n-alkanes C27 and C29) and hemicellulose-derived sugar biomarkers (arabinose), respectively. Both δ2H and δ18O are suggested to reflect mainly leaf water of vegetation growing in the catchment of the Gemündener Maar. This enables the coupling of the results via a δ2H-δ18O biomarker paleohygrometer approach and allows calculating past relative air humidity values, which is the major advantage of the applied approach. Fundamental was the finding that the isotopic enrichment of leaf water due to evapotranspiration depends mainly on relative humidity. We hence use the coupled δ2H-δ18O biomarker approach to reconstruct the deuterium-excess of leaf water and in turn relative air humidity values corresponding to the vegetation period and daytime (RHdv). Most importantly, the results of the coupled δ2H-δ18O biomarker paleohygrometer approach (i) support a two-phasing of the Younger Dryas, i.e. a relative wet phase (on Allerød level) followed by a drier Younger Dryas ending, (ii) do not corroborate overall drier climatic conditions characterising the Younger Dryas or a two-phasing with regard to a first dry and cold Younger Dryas phase followed by a warmer period along with increasing precipitation amounts, and (iii) suggest that the amplitude of RHdv changes during the Early Holocene was more pronounced compared to the Younger Dryas. One possible driver for the unexpected Lake Gemündener Maar RHdv variations could be the solar activity.

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