Thomas Litt

Correlation and synchronisation of Lateglacial continental sequences in northern central Europe based on annually laminated lacustrine sediments

Abstract The present study focusses on correlation and synchronisation of Weichselian Lateglacial varved lake sediments from western Germany (Meerfelder Maar, Eifel region), northern Germany (Hamelsee, Lower Saxony), central Poland (Lake Gości a z) and eastern Poland (Lake Perespilno) by using varve chronology, tephrochronology, palynostratigraphy and stable isotopes. Comparison of the several independent time scales shows that biotic and abiotic parameters respond abruptly and quasi-synchronously, within the errors of the different chronologies, during the Younger Dryas/Preboreal transition. Moreover, there is a consensus about the length of the Younger Dryas cold stage of 1100–1150 varve years. In the Allerod the prominent Laacher See tephra (12,880 varve years BP) can be used to fix floating varve chronologies. The relative duration of this biozone has been determined in Meerfelder Maar and Hamelsee at between 625 and 670 varve years. In the Meerfelder Maar a combination of continuous varve counting and biostratigraphy has been possible for the almost entire Lateglacial. The comparison between continental limnic sequences and Greenland ice-core records should be made on the basis of independent chronologies in both archives. It is more practicable to develop regional stratotypes on the continental regions instead of simply using ice cores as stratotypes for the Lateglacial for terrestrial European records. In this respect, annually laminated lacustrine sequences have a great potential.

High resolution sediment and vegetation responses to Younger Dryas climate change in varved lake sediments from Meerfelder Maar, Germany

Abstract This work focuses on a 1900-year section of varved sediments from Lake Meerfelder Maar (MFM) extending from the Late Allerod to the Preboreal. Varve counting provides the chronological framework and determines the length of Younger Dryas to 1025–1090 years. A strong relation between climate change, environment response and depositional processes has been found. In consequence, varve microfacies variations are a sensitive proxy for environment changes. These are reflected, for example, in erosion processes within the lake’s catchment (minerogenic input) and lake productivity (diatom blooms). The observed varve changes have been quantified by multiproxy analyses of physical and chemical sediment parameters with a resolution of between 8 and 40 years depending on sedimentation rate. In addition, high resolution palynological investigations provide the biostratigraphical subdivision based on changes in the vegetation occurring during the same time interval. Varve observations reveal that environment changes at the beginning and the end of the Younger Dryas occurred within 20–50 years. Furthermore, sediment and vegetation changes were synchronous. Within the actual precision of the MFM and GRIP chronologies (divergence of only a few decades) terrestrial responses in Western Europe occurred quasi-synchronous to temperature changes in Greenland.

Genetic consequences of glacial survival and postglacial colonization in Norway spruce: combined analysis of mitochondrial DNA and fossil pollen

Norway spruce (Picea abies [L.] Karst.) is a broadly distributed European conifer tree whose history has been intensively studied by means of fossil records to infer the location of full‐glacial refugia and the main routes of postglacial colonization. Here we use recently compiled fossil pollen data as a template to examine how past demographic events have influenced the species’ modern genetic diversity. Variation was assessed in the mitochondrial nad1 gene containing two minisatellite regions. Among the 369 populations (4876 trees) assayed, 28 mitochondrial variants were identified. The patterns of population subdivision superimposed on interpolated fossil pollen distributions indicate that survival in separate refugia and postglacial colonization has led to significant structuring of genetic variation in the southern range of the species. The populations in the northern range, on the other hand, showed a shallow genetic structure consistent with the fossil pollen data, suggesting that the vast northern range was colonized from a single refugium. Although the genetic diversity decreased away from the putative refugia, there were large differences between different colonization routes. In the Alps, the diversity decreased over short distances, probably as a result of population bottlenecks caused by the presence of competing tree species. In northern Europe, the diversity was maintained across large areas, corroborating fossil pollen data in suggesting that colonization took place at high population densities. The genetic diversity increased north of the Carpathians, probably as a result of admixture of expanding populations from two separate refugia.

Multiproxy climate reconstructions for the Eemian and Early Weichselian

Palaeobotanical, coleopteran and periglacial data from 106 sites across northwestern Europe have been analysed in order to reconstruct palaeoclimatic conditions during the Eemian and Early Weichselian. Three time slices in the Eemian and four in the Early Weichselian have been considered. In the Pinus–Quercetum mixtum–Corylus phase of the Eemian, summer temperatures were probably at their highest and the botanic evidence suggests a southeast to northwest gradient for both the warmest and coldest month. Coleoptera indicate that the summers in southern England were several degrees warmer than those of present day. The climate during theCarpinus–Picea phase was uniform and oceanic without obvious gradients. In the final time slice of the Eemian, the Pinus–Picea–Abies phase, temperatures of the warmest month seem to drop slightly with some indication of a shift towards a more boreal and suboceanic climate. The reconstruction of the palaeoclimate in the Herning Stadial and Rederstall Stadial is hampered by the limited number of sites, but botanical evidence suggests a gradient in temperature of the coldest month from east to west. Coleoptera from the Herning Stadial in central England and eastern Germany suggest similarly cold and continental climates. During the Brorup Interstadial and the Odderade Interstadial the botanical evidence suggests that the minimum mean July temperatures rose to 15–16°C but during the coldest month these temperatures show a gradient between −13°C in the east and −5°C in the west.

Environmental response to climatic and volcanic events in central Europe during the Weichselian Lateglacial

This paper reviews major results of the recent German research priority program “Changes of the geo-biosphere during the last 15,000 years”, a contribution to PAGES focussing on changes of the geo-biosphere during the Weichselian Lateglacial. Different continental archives such as annually laminated lacustrine sediments, floodplain sediments, and speleothems were used to reconstruct environmental response to climatic changes and the Laacher See eruption event at ca 12,900 cal BP. Special emphasis is paid to establish a reliable time control using varve counting, high-precision radiocarbon dating of tree-ring series, and AMS radiocarbon dating of terrestrial plant macrofossils recovered from lacustrine sediments to correlate and synchronize large-scale environmental changes and events in central Europe.

Climate Change during and after the Roman Empire: Reconstructing the Past from Scientific and Historical Evidence

Growing scientific evidence from modern climate science is loaded with implications for the environmental history of the Roman Empire and its successor societies. The written and archaeological evidence, although richer than commonly realized, is unevenly distributed over time and space. A first synthesis of what the written records and multiple natural archives (multi-proxy data) indicate about climate change and variability across western Eurasia from c. 100 b.c. to 800 a.d. confirms that the Roman Empire rose during a period of stable and favorable climatic conditions, which deteriorated during the Empires third-century crisis. A second, briefer period of favorable conditions coincided with the Empires recovery in the fourth century; regional differences in climate conditions parallel the diverging fates of the eastern and western Empires in subsequent centuries. Climate conditions beyond the Empires boundaries also played an important role by affecting food production in the Nile valley, and by encouraging two major migrations and invasions of pastoral peoples from Central Asia.

A model‐data comparison of European temperatures in the Eemian interglacial

Compared to the wide range of different models used for the analysis of the climate system, GCMs have the most complex representation of the atmospheric physical processes. We have chosen the ECHO-G model as a state-ofthe-art OA-GCM to simulate the climatic conditions at 125 kyr BP by adapting the orbital parameters and greenhouse gas concentrations. [4] For terrestrial palaeoclimate reconstructions, the use of botanical fossils is well-established, because vegetation is in close relation to climate. Mainly pollen can be found in large numbers in suitable sediments, and macro remains add valuable information for important climate indicator species. For the reconstructions, recently developed botanical � � � � � � � � � � � � � � � � � � � � � ��

Climate during the Eemian in north-central Europe - A critical review of the palaeobotanical and stable isotope data from central Germany

This paper reviews the evidence from terrestrial palaeoenvironmental records in north-central Europe and, in particular, central Germany, which relates to the controversial proposition that there were strong climate oscillations during the last interglacial (oxygen isotope substage 5e). In contrast to the evidence from the GRIP ice core at Summit, Greenland, and a recent palaeoclimate reconstruction based on the pollen profile from Bispingen, Germany, the evaluation of the palaeobotanical and the stable isotope data presented here strongly suggests relatively stable temperature for most of the Eemian and with instability confined to the beginning and end of the interglacial. High amplitude temperature variations can be seen in both the Early Weichselian pollen and isotope records. It is argued that this pattern of climate development is applicable to most of continental north-central Europe.

Climate and the Late Bronze Collapse: New Evidence from the Southern Levant

Abstract A core drilled from the Sea of Galilee was subjected to high resolution pollen analysis for the Bronze and Iron Ages. The detailed pollen diagram (sample/~40 yrs) was used to reconstruct past climate changes and human impact on the vegetation of the Mediterranean zone of the southern Levant. The chronological framework is based on radiocarbon dating of short-lived terrestrial organic material. The results indicate that the driest event throughout the Bronze and Iron Ages occurred ~1250–1100 BCE—at the end of the Late Bronze Age. This arid phase was identified based on a significant decrease in Mediterranean tree values, denoting a reduction in precipitation and the shrinkage of the Mediterranean forest/maquis. The Late Bronze dry event was followed by dramatic recovery in the Iron I, evident in the increased percentages of both Mediterranean trees and cultivated olive trees. Archaeology indicates that the crisis in the eastern Mediterranean at the end of the Late Bronze Age took place during the same period—from the mid- 13th century to ca. 1100 BCE. In the Levant the crisis years are represented by destruction of a large number of urban centres, shrinkage of other major sites, hoarding activities and changes in settlement patterns. Textual evidence from several places in the Ancient Near East attests to drought and famine starting in the mid-13th and continuing until the second half of the 12th century. All this helps to better understand the ‘Crisis Years’ in the eastern Mediterranean at the end of the Late Bronze Age and the quick settlement recovery in the Iron I, especially in the highlands of the Levant.

Stable climatic conditions in central Germany during the last interglacial

Stable isotopic data from the high-resolution limnic sequence in the opencast mine at Grobern (central Germany) confirm the relatively stable climate of the last interglacial deduced from pollen analyses. After significant warming during the transition from the Saalian to the Eemian, stable warm climatic conditions set in once the climatic optimum was reached in the course of biozones E4 to E5. From the middle of biozone E6b, a gradual temperature decrease can be observed, reaching a minimum at the start of biozone E7. The division of the early Weichselian glacial in central Germany into two stadials (Herning, Rederstall) and two interstadials (Brorup, Odderade) is also documented by the findings. Copyright