Search results for "55"
showing 10 items of 2320 documents
Holocene land-cover reconstructions for studies on land cover-climate feedbacks
2010
The major objectives of this paper are: (1) to review the pros and cons of the scenarios of past anthropogenic land cover change (ALCC) developed during the last ten years, (2) to discuss issues related to pollen-based reconstruction of the past land-cover and introduce a new method, REVEALS (Regional Estimates of VEgetation Abundance from Large Sites), to infer long-term records of past land-cover from pollen data, (3) to present a new project (LANDCLIM: LAND cover – CLIMate interactions in NW Europe during the Holocene) currently underway, and show preliminary results of REVEALS reconstructions of the regional land-cover in the Czech Republic for five selected time windows of the Holocene…
Implementation of a comprehensive ice crystal formation parameterization for cirrus and mixed-phase clouds in the EMAC model (based on MESSy 2.53)
2018
A comprehensive ice nucleation parameterization has been implemented in the global chemistry-climate model EMAC to improve the representation of ice crystal number concentrations (ICNCs). The parameterization of Barahona and Nenes (2009, hereafter BN09) allows for the treatment of ice nucleation taking into account the competition for water vapour between homogeneous and heterogeneous nucleation in cirrus clouds. Furthermore, the influence of chemically heterogeneous, polydisperse aerosols is considered by applying one of the multiple ice nucleating particle parameterizations which are included in BN09 to compute the heterogeneously formed ice crystals. BN09 has been modified in order to co…
A sea surface temperature reconstruction for the southern Indian Ocean trade wind belt from corals in Rodrigues Island (19°S, 63°E)
2016
Abstract. The western Indian Ocean has been warming rapidly over recent decades, causing a greater number of extreme climatic events. It is therefore of paramount importance to improve our understanding of links between Indian Ocean sea surface temperature (SST) variability, climate change and sustainability of tropical coral reef ecosystems. Here we present monthly resolved coral Sr ∕ Ca records from two different locations from Rodrigues Island (63° E, 19° S) in the south-central Indian Ocean trade wind belt. We reconstruct SST based on a linear relationship with the Sr ∕ Ca proxy with records starting from 1781 and 1945, respectively. We assess relationships between the observed long-ter…
Large-scale, millennial-length temperature reconstructions from tree-rings
2018
Supported by the German Science Foundation, grants # Inst 247/665-1 FUGG and ES 161/9-1. SSG acknowledges support by the Alexander von Humboldt Foundation, KJA by US National Science Foundation grants AGS-1501856 and NSF AGS-1501834, and JL and LS by the Belmont Forum and JPI-Climate, Collaborative Research Action INTEGRATE. Over the past two decades, the dendroclimate community has produced various annually resolved, warm season temperature reconstructions for the extratropical Northern Hemisphere. Here we compare these tree-ring based reconstructions back to 831 CE and present a set of basic metrics to provide guidance for non-specialists on their interpretation and use. We specifically d…
Structural contacts in subduction complexes and their tectonic significance: the Late Palaeozoic coastal accretionary wedge of central Chile
2007
Understanding the contact between the very low-grade metagreywacke of the Eastern Series and high-pressure metamorphosed schist of the Western Series in the Late Palaeozoic accretionary wedge of central Chile is fundamental for the understanding of the evolution of ancient accretionary wedges. We show the progressive development of structures and finite strain from the least deformed rocks in the eastern part of the Eastern Series of the accretionary wedge to high-pressure schist of the Western Series at the Pacific coast. Upright chevron folds of sedimentary layering are associated with an axial-plane foliation, S1. As the F1 folds became slightly overturned to the west, S1 was folded abou…
Rapid climate change during the early Holocene in western Europe and Greenland
2006
Based on microfacies analyses of seasonally laminated varved sediments from lake Holzmaar, Germany, we report evidence of decadal-to century-scale climate variability during the early Holocene. The shifts in climate are documented in the thickness variations and changes in the composition of the varves in response to subtle shifts in limnological conditions. The close similarity between the Holzmaar varve record and the GRIP oxygen isotope record during 7.4-9.0 calendar (cal.) ka suggests that the high frequency climatic variations in both regions were controlled by the same mechanism. Our more detailed studies covering the central 409-yr period (∼7.846-8.255 cal. ka, encompassing the 8.2 …
Copper supply during the Final Neolithic at the Saint-Blaise/Bains des Dames site (Neuchâtel, Switzerland)
2009
The Saint-Blaise/Bains des Dames stratified site in Neuchâtel, Switzerland, contains several occupations that span the Late through Final Neolithic, including the Horgen, Lüscherz, and Auvernier-Cordé periods. As part of a study on prehistoric metallurgy in western Switzerland, we compare the lead isotope ratios (multicollector inductively coupled plasma mass spectrometer) and elemental compositions (instrumental neutron activation analysis) of the site's numerous copper finds to a database of corresponding measurements for copper ores throughout Europe. The results show a considerable variation in copper compositions present at the site, suggesting complex economic relationships and multip…
Volcanic climate forcing preceding the inception of the Younger Dryas: Implications for tracing the Laacher See eruption
2021
Climatic warming from the last glacial maximum to the current interglacial period was punctuated by a similar to 1300 years long cold period, commonly referred to as the Younger Dryas (YD). Several hypotheses have been proposed for the mechanism triggering the abrupt inception of the YD, including freshwater forcing, an extra-terrestrial impact, and aerosols from volcanic eruptions. Here, we use synchronised sulphate and sulphur records from both Greenland and Antarctic ice cores to reconstruct volcanic forcing between 13,200-12,800 a BPGICC05 (years before 1950 CE on the Greenland Ice Core Chronology 2005; GICC05). This continuous reconstruction of stratospheric sulphur injections highligh…
REWORKING OF FUSULINIDS AND CALCIPHAERIDS IN THE LERCARA FORMATION (SICILY, ITALY); GEOLOGICAL IMPLICATIONS
2004
Different fusulinids have been identified in the Lercara Formation (Sicily). They are: Reichelina sp., Schubertella paramelonica, Toriyamaia (?) sp., Neofusulinella lantenoisi, Yangchienia compressa, Rauserella staffi, Darvasites contractus, Chalaroschwagerina (Taiyuanella?) aff. davalensis, Levenella aff. evoluta, Pamirina darvasica, and Neoschwagerina ex gr. craticulifera. Small Permian foraminifers, as well as the calcispherid Asterosphaera pulchra also exist. The microfossils indicate reworking of different Permian stages, at different periods of time, and possibly also of the Mississippian (Early Carboniferous). All these resediments have been deposited within the Lercara Formation, a …
Timber Logging in Central Siberia is the Main Source for Recent Arctic Driftwood
2015
Abstract Recent findings indicated spruce from North America and larch from eastern Siberia to be the dominating tree species of Arctic driftwood throughout the Holocene. However, changes in source region forest and river characteristics, as well as ocean current dynamics and sea ice extent likely influence its spatiotemporal composition. Here, we present 2556 driftwood samples from Greenland, Iceland, Svalbard, and the Faroe Islands. A total of 498 out of 969 Pinus sylvestris ring width series were cross-dated at the catchment level against a network of Eurasian boreal reference chronologies. The central Siberian Yenisei and Angara Rivers account for 91% of all dated pines, with their oute…