Irene Schimmelpfennig

Holocene glacier culminations in the Western Alps and their hemispheric relevance

The natural variability of Holocene climate defi nes the baseline to assess ongoing climate change. Greenland ice-core records indicate warming superimposed by abrupt climate oscillations in the early Holocene, followed by a general cooling trend throughout the middle and late Holocene that culminated during the Little Ice Age (LIA). Tropical precipitation changes correlate with these patterns throughout the Holocene. Here we use mountain glaciers in the European Alps to reconstruct the regional Holocene climate evolution and to test for a link between mid-latitude, North Atlantic, and tropical climate. Our precise 10 Be chronology from Tsidjiore Nouve Glacier, western Swiss Alps, indicates a glacier culmination during the earliest Holocene ~11.4 k.y. ago, likely related to the Preboreal Oscillation. Based on our data, no Holocene glacier advance of similar amplitude occurred until ~3.8 k.y. ago, when the glacier reached LIA limits. The 10 Be ages between 500 and 170 yr correspond to the LIA, while the youngest 10 Be ages overlap with the historically recorded post-LIA glacier positions. Integrating our data with existing records, we propose a hemispheric climate link between the Alps, North Atlantic temperature, and tropical precipitation patterns for the Holocene, supporting the concept of a pervasive climate driver. These fi ndings from northern mid-latitudes are consistent with the hypothesis formulated for the tropics that the Earth’s thermal equator, responding to North Atlantic temperature changes, might have migrated southward throughout the Holocene, reaching the southern turning point toward the end of the LIA.

Geomorphologic and paleoclimatic evidence of Holocene glaciation on Mount Olympus, Greece

This study investigates the possibility of Holocene glaciation on Mount Olympus (Greece) with a respective local temperature–precipitation equilibrium line altitude (TP-ELA) at c. 2200 m a.s.l., based on geomorphologic and paleoclimatic evidence. At present, the local TP-ELA is situated above the mountain’s summit (c. 2918 m a.s.l.), but permanent snowfields and ice bodies survive within Megala Kazania cirque between c. 2400 and c. 2300 m a.s.l., because of the cirque’s maritime setting that results from its close proximity (c. 18 km) to the Aegean Sea and of the local topographical controls. The snow and ice bodies occupied a considerably larger area and attained a stabilization phase between AD 1960 and 1980, also manifested from aerial photographs, a period characterized by increased winter precipitation (Pw) with subsequent TP-ELA depression to c. 2410 m a.s.l. Mid- to late-20th-century Pw and TP-ELA variations exhibit negative correlations with the winter North Atlantic Oscillation index (NAOw) at annual and multidecadal (30 years) timescales. Late Holocene (AD 1680–1860) reconstructed summer mean temperatures were lower by Ts < 1.1°C in relation to the reference period between AD 1960 and 1980 and were also superimposed to negative NAOw phases, thus bracketing this time interval as a favorable one to glacial formation and/or advance. Millennial-scale annual precipitation reconstructions at the hypothesized TP-ELA (c. 2200 m a.s.l.) point the period between 8 and 4 kyr BP as another glacier-friendly candidate. The mid-Holocene rather simplistic sequence of potential glacial advance phase was disturbed by short-lived cold climatic deteriorations, well-documented over the northern Aegean region that may partly explain the multicrested shape of the highest (c. 2200 m a.s.l.) morainic complex of Megala Kazania cirque.

Paradoxical cold conditions during the medieval climate anomaly in the Western Arctic

In the Northern Hemisphere, most mountain glaciers experienced their largest extent in the last millennium during the Little Ice Age (1450 to 1850 CE, LIA), a period marked by colder hemispheric temperatures than the Medieval Climate Anomaly (950 to 1250 CE, MCA), a period which coincided with glacier retreat. Here, we present a new moraine chronology based on 36Cl surface exposure dating from Lyngmarksbræen glacier, West Greenland. Consistent with other glaciers in the western Arctic, Lyngmarksbræen glacier experienced several advances during the last millennium, the first one at the end of the MCA, in ~1200 CE, was of similar amplitude to two other advances during the LIA. In the absence of any significant changes in accumulation records from South Greenland ice cores, we attribute this expansion to multi-decadal summer cooling likely driven by volcanic and/or solar forcing, and associated regional sea-ice feedbacks. Such regional multi-decadal cold conditions at the end of the MCA are neither resolved in temperature reconstructions from other parts of the Northern Hemisphere, nor captured in last millennium climate simulations.

(Un)Resolved contradictions in the Late Pleistocene glacial chronology of the Southern Carpathians - new samples and recalculated cosmogenic radionuclide age estimates

Application of cosmogenic nuclides in the study of Quaternary glaciations has increased rapidly during the last decade owing to the previous absence of direct dating methods of glacial landforms and sediments. Although several hundred publications have already been released on exposure age dating of glacial landforms worldwide, very few studies targeted the Carpathians so far (Kuhlemann et al, 2013a; Makos et al., 2014; Reuther et al, 2004, 2007; Rinterknecht et al. 2012). There are many unresolved or contradictory issues regarding the glacial chronology of the Romanian Carpathians. Recently, some attempts have been made to develop an improved temporal framework for the glaciations of the region using cosmogenic 10 Be dating (Reuther et al. 2004, 2007, Kuhlemann et al. 2013a). However, these studies made the picture even more confusing because the local last glacial maximum, for instance, apparently occurred in asynchronous timing compared to each other and also to other dated glacial events in Europe (Hughes et al, 2013). This situation is even more interesting if we take into account that the local glacial maximum tends to agree with the global LGM derived from the Eastern Balkans (Kuhlemann et al. 2013b), while the penultimate glaciation seems to significantly overtake the LGM advance over the Western Balkans (Hughes et al. 2011). The primary candidate reasons to resolve these discrepancies are methodological, e.g. insufficient number of samples (one sample/landform) ignoring geological scatter of the data and the application of different half-lives, production rates and scaling schemes during the calculation of exposure ages. Systematic methodological uncertainties in computing exposure ages from measured nuclide concentrations have a significant impact on the conclusions concerning correlations of exposure-dated glacier chronologies with millennial scale climate changes (Balco, 2011). The changes in glacial timing generated by only using the most recent constants for the exposure age calculations has not been considered in the most recent review on the timing of the LGM (Hughes et al., 2013). Main objective of our study is to utilize the potential offered by the cosmogenic in situ produced 10 Be dating to disentangle the contradictions in the available Southern Carpathian Late Pleistocene glacial chronology (Kuhlemann et al, 2013a; Reuther et al, 2004, 2007). We recalculate 10 Be data published by Reuther et al. (2007) in accordance with the new half-life and production rate of 10 Be. Besides, a new sample set has been collected to establish a precise chronological framework supported by in-situ exposure dating of several additional moraine generations.

Determining erosion rates in Allchar (Macedonia) to revive the lorandite neutrino experiment

205Tl in the lorandite (TiAsS2) mine of Allchar (Majdan, FYR Macedonia) is transformed to 205Pb by cosmic ray reactions with muons and neutrinos. At depths of more than 300 m, muogenic production would be sufficiently low for the 4.3 Ma old lorandite deposit to be used as a natural neutrino detector. Unfortunately, the Allchar deposit currently sits at a depth of only 120 m below the surface, apparently making the lorandite experiment technically infeasible. We here present 25 erosion rate estimates for the Allchar area using in situ produced cosmogenic 36Cl in carbonates and 10Be in alluvial quartz. The new measurements suggest long-term erosion rates of 100–120 m Ma−1 in the silicate lithologies that are found at the higher elevations of the Majdanksa River valley, and 200–280 m Ma−1 in the underlying marbles and dolomites. These values indicate that the lorandite deposit has spent most of its existence at depths of more than 400 m, sufficient for the neutrinogenic 205Pb component to dominate the muon contribution. Our results suggest that this unique particle physics experiment is theoretically feasible and merits further development.