Jens Fohlmeister's research while affiliated with Bundesamt für Strahlenschutz, BfS and other places

Publications (96)

Article
Full-text available
Similarly to the effects of current climate change, the last deglaciation (Termination I) rapidly altered northern latitude temperatures and ice-sheet extent, as well as the Atlantic Meridional Overturning Circulation. However, it is still unclear how these changes propagated and impacted the central Mediterranean continental rainfall variability....
Article
Full-text available
The incorporation of water isotopologues into the hydrology of general circulation models (GCMs) facilitates the comparison between modeled and measured proxy data in paleoclimate archives. However, the variability and drivers of measured and modeled water isotopologues, as well as the diversity of their representation in different models, are not...
Preprint
Full-text available
Degassing of CO2 and precipitation of calcite to the surface of stalagmites can strongly impact isotope signals imprinted into the calcite of these speleothems. Here, we show that in all the variety of conditions occurring in nature only two distinct types of degassing exist. First, when a thin film of calcareous solution comes in contact to cave a...
Article
Full-text available
Degassing of CO 2 and precipitation of calcite to the surface of stalagmites can strongly impact isotope signals imprinted into the calcite of these speleothems. Here, we show that in all the variety of conditions occurring in nature only two distinct types of degassing exist. First, when a thin film of calcareous solution comes in contact to cave...
Preprint
Full-text available
The incorporation of water isotopologues into the hydrology of general circulation models (GCMs) facilitates the comparison between modelled and measured proxy data in paleoclimate archives. However, the variability and drivers of measured and modelled water isotopologues, and indeed the diversity of their representation in different models are not...
Article
Full-text available
Rapid and continuous analysis of radiocarbon (14C) concentration in carbonate samples at spatial resolution down to 100 µm has been made possible with the new LA-AMS (laser ablation accelerator mass spectrometry) technique. This novel approach can provide radiocarbon data at a spatial resolution similar to that of stable carbon (C) isotope measurem...
Conference Paper
The last deglaciation (Termination I, T-I) was the most recent global-scale climate transition. It involved a drastic temperature increase guiding massive melting of ice sheets, with a concurrent reorganization of inter- and intrahemispherical atmospheric and ocean circulation patterns. T-I lasted ~3.0 ka (ka = kiloyears before present) in Greenlan...
Preprint
Full-text available
The equilibrium oxygen isotope fractionation factor between calcite and water (18{\alpha}calcite/H2O) is an important quantity in stable isotope geochemistry and allows in principle to infer temperature variations from carbonate {\delta}18O if carbonate formation occurred in thermodynamic equilibrium. For this reason, many studies intended to deter...
Article
Full-text available
The Late Holocene was characterized by several centennial-scale climate oscillations including the Roman Warm Period, the Dark Ages Cold Period, the Medieval Warm Period and the Little Ice Age. The detection and investigation of such climate anomalies requires paleoclimate archives with an accurate chronology as well as a high temporal resolution....
Article
The equilibrium oxygen isotope fractionation factor between calcite and water (¹⁸αcalcite/H2O) is an important quantity in stable isotope geochemistry and allows in principle to infer temperature variations from carbonate δ¹⁸O if carbonate formation occurred in thermodynamic equilibrium. For this reason, many studies intended to determine the value...
Poster
Full-text available
In Europe, the scarcity of last glacial speleothem palaeoclimate/palaeoenvironmental records is attributable to the generally dry and cold climate that hampered soil bioproductivity, karst dissolution and carbonate deposition in caves. However, at southern Mediterranean latitudes, glacial climate was milder than in central or northern Europe and sp...
Article
Stalagmites are an extraordinarily powerful resource for the reconstruction of climatological palaeoseasonality. Here, we provide a review of different types of seasonality preserved by stalagmites and methods for extracting this information. A new drip classification scheme is introduced, which facilitates the identification of stalagmites fed by...
Preprint
Full-text available
Stalagmites are an extraordinarily powerful resource for the reconstruction of climatological palaeoseasonality. Here, we provide a comprehensive review of different types of seasonality preserved by stalagmites and methods for extracting this information. A new drip classification scheme is introduced, which facilitates the identification of stala...
Article
Full-text available
Characterizing the temporal uncertainty in palaeoclimate records is crucial for analysing past climate change, correlating climate events between records, assessing climate periodicities, identifying potential triggers and evaluating climate model simulations. The first global compilation of speleothem isotope records by the SISAL (Speleothem Isoto...
Data
Data supporting Comas-Bru et al., 2020 (ESSD): https://doi.org/10.5194/essd-12-2579-2020
Preprint
Full-text available
A novel technique making use of laser ablation coupled online to accelerator mass spectrometry (LA-AMS) allows analyzing the radiocarbon (14C) concentration in carbonate samples continuously at high spatial resolution within very short analysis times. This new technique can provide radiocarbon data similar to the spatial resolution of stable carbon...
Preprint
The most pronounced climate anomaly of the Holocene was the 8.2 ka cooling event. We present new 230Th/U-ages as well as high-resolution stable isotope and trace element data from three stalagmitesfrom two different cave systems in Germany, which provide important information about the structure and climate variability of the 8.2 ka event in centra...
Article
The most pronounced climate anomaly of the Holocene was the 8.2 ka cooling event. We present new ²³⁰Th/U-ages as well as high-resolution stable isotope and trace element data from three stalagmites from two different cave systems in Germany, which provide important information about the structure and climate variability of the 8.2 ka event in centr...
Conference Paper
Full-text available
High-resolution records of lake-level changes are crucial to elucidate the impact of local and global climatic changes in lacustrine basins. The Late Quaternary evolution of the Dead Sea has been characterized by substantial variability apparently linked with global climatic changes, beign subject of many research e orts since decades. Previous stu...
Preprint
The climatic controls on the stable carbon isotopic composition (d13C) of speleothem carbonate are less often discussed in the scientific literature in contrast to the frequently used stable oxygen isotopes. Various local processes influence speleothem d13C values and confident and detailed interpretations of this proxy are often complex. A better...
Article
The climatic controls on the stable carbon isotopic composition (δ¹³C) of speleothem carbonate are less often discussed in the scientific literature in contrast to the frequently used stable oxygen isotopes. Various local processes influence speleothem δ¹³C values and confident and detailed interpretations of this proxy are often complex. A better...
Preprint
Full-text available
Abstract. Characterising the temporal uncertainty in palaeoclimate records is crucial for analysing past climate change, for correlating climate events between records, for assessing climate periodicities, identifying potential triggers, and to evaluate climate model simulations. The first global compilation of speleothem isotope records by the SIS...
Article
Full-text available
In this study, the dead carbon fraction (DCF) variations in stalagmite M1-5 from Socotra Island in the western Arabian Sea were investigated through a new set of high-precision U-series and radiocarbon (14C) dates. The data reveal an extreme case of very high and also climate-dependent DCF. For M1-5, an average DCF of 56.2±3.4 % is observed between...
Article
Full-text available
In this study, the dead carbon fraction (DCF) variations in stalagmite M1-5 from Socotra Island in the western Arabian Sea were investigated through a new set of high-precision U-series and radiocarbon (¹⁴C) dates. The data reveal an extreme case of very high and also climate dependent DCF values. For M1-5 an average DCF of 56.2 ± 3.4 % is observed...
Article
Full-text available
Although quantitative isotope data from speleothems has been used to evaluate isotope-enabled model simulations, currently no consensus exists regarding the most appropriate methodology through which to achieve this. A number of modelling groups will be running isotope-enabled palaeoclimate simulations in the framework of the Coupled Model Intercom...
Article
The ‘bomb-pulse’ method is a chronological approach to further constrain the age of speleothems that grew between 1950 CE – present. Establishing dependable chronological constraints is crucial for modern calibration studies of speleothems to instrumental climate records, which provides the basis for paleoclimate interpretations. However, a large u...
Poster
Paleoclimate interpretations based on variations in stable-isotope ratios of carbon (δ13C) are still underrepresented in speleothem-based studies, owing mainly to the complexities and uncertainties associated with the precise controls on δ13C with respect to climatic and local conditions. Interpretations of δ18O of speleothem calcite form the found...
Article
Three small stalagmites from Zoolithencave (southern Germany) show visible laminae, which consist of a clear and a brownish, pigmented layer pair. This potentially provides the opportunity to construct precise chronologies by counting annual laminae. The growth period of the three stalagmites was constrained by the ¹⁴ C bomb peak in the youngest pa...
Article
Speleothems, secondary cave carbonates, are important tools for climate reconstruction, especially as they often can be very precisely dated with the UTh method. If the U-Th method fails, dating becomes difficult, and often results in abandonment of samples and study sites. Radiocarbon dating is the only other radiometric dating technique applicabl...
Poster
Full-text available
Speleothem records have been successfully calibrated against instrumental data, e.g., using stable oxygen isotope or annual growth lamina data considered as reliable recorders of air temperature or precipitation amount. We present the first high-resolution trace element (Mg/Ca, Sr/Ca, Ba/Ca) record providing the potential for quantitative climate r...
Article
Marine Isotope Stage 3 (MIS 3, 57–27 ka) was characterised by numerous rapid climate oscillations (i.e., Dansgaard-Oeschger (D/O-) events), which are reflected in various climate archives. So far, MIS 3 speleothem records from central Europe have mainly been restricted to caves located beneath temperate Alpine glaciers or close to the Atlantic Ocea...
Chapter
Central Asia is located at the confluence of the large-scale atmospheric circulation systems of the dominant Siberian High and the Midlatitude Westerlies, and partly the Indian Monsoon. However, the number of Holocene climate records is still low in most parts of this region and insufficient to allow detailed discussion and comparisons to disentang...
Article
The precise determination of the stable C and O isotope fractionation between water and calcite (CC) and water and aragonite (AR) is of special interest for climate reconstructions, e.g. paleotemperatures. Previous studies reported results from both laboratory and field experiments, but their results are only partly consistent. Here we present C an...
Article
Here we present high-resolution δ 18 O records obtained from speleothems collected in the eastern Bolivian Andes. The stable isotope records are related to the regional-to large-scale atmospheric circulation over South America and allow interpreting changes in δ 18 O during the last 1400 yr as a function of changes in precipitation regimes over the...
Article
Numerous charcoal accumulations discovered in the submerged Chan Hol cave near Tulum, Quintana Roo, Mexico, have been 14C‐dated revealing ages between 8110 ± 28 14C a BP (9122–8999 cal a BP) and 7177 ± 27 14C a BP (8027–7951 cal a BP). These charcoal concentrations, interpreted here as ancient illumination sites, provide strong evidence that the Ch...
Article
Full-text available
Radiocarbon Dating of a Speleothem Record of Paleoclimate for Angkor, Cambodia – Corrigendum - Quan Hua, Duncan Cook, Jens Fohlmeister, Dan Penny, Paul Bishop, Solomon Buckman
Article
Dating the transport/deposition time of supratidal coarse-clast deposits is difficult, limiting their value for inferring frequency-magnitude patterns of high-energy wave events. On Bonaire (Leeward Antilles, Caribbean), these deposits form prominent landforms, and transport by one or several Holocene tsunamis is assumed at least for the largest cl...
Article
The strength of the North Atlantic Oscillation (NAO) is considered to be the main driver of climate changes over the European and western Asian continents throughout the last millennium. For example, the predominantly warm Medieval Climate Anomaly (MCA) and the following cold period of the Little Ice Age (LIA) over Europe have been associated with...
Article
Full-text available
We report the chronological construction for the top portion of a speleothem, PC1, from southern Cambodia with the aim of reconstructing a continuous high-resolution climate record covering the fluorescence and decline of the medieval Khmer kingdom and its capital at Angkor (~9th–15th centuries AD). Earlier attempts to date PC1 by the standard U-Th...
Article
The northern edge of the western central Tien Shan range is bounded by the Issyk-Ata fault situated south of Bishkek, the capital of Kyrgyzstan. Contraction in this thick-skinned orogen occurs with low-strain accumulation and long earthquake recurrence intervals. In the nineteenth to twentieth centuries, a sequence of large earthquakes with magnitu...
Data
Stable isotope (δ13O, δ18O) measurements of the CH-7 stalagmite from Chan Hol cave. (DOCX)
Article
Full-text available
Preceramic human skeletal remains preserved in submerged caves near Tulum in the Mexican state of Quintana Roo, Mexico, reveal conflicting results regarding ¹⁴C dating. Here we use U-series techniques for dating a stalagmite overgrowing the pelvis of a human skeleton discovered in the submerged Chan Hol cave. The oldest closed system U/Th age comes...
Presentation
Full-text available
The evaluation of thrust paleoearthquakes and associated fault scarps is often hampered by the size of their cumulative fault scarps and interaction with sedimentary processes during interseismic periods. This is especially true if these events occur in areas undergoing low strain accumulation with long recurrence intervals. Furthermore, the earthq...
Article
Precisely-dated stalagmites are increasingly important archives for the reconstruction of terrestrial paleoclimate at very high temporal resolution. In-depth understanding of local conditions at the cave site and of the processes driving stalagmite deposition is of paramount importance for interpreting proxy signals incorporated in stalagmite carbo...
Article
The North Atlantic Oscillation is the dominant atmospheric pressure mode in the North Atlantic region and affects winter temperature and precipitation in the Mediterranean, northwest Europe, Greenland, and Asia. The index that describes the sea-level pressure difference between Iceland and the Azores is correlated with a dipole precipitation patter...
Article
Full-text available
A new instrumental setup, combining laser ablation (LA) with accelerator mass spectrometry (AMS), has been investigated for the online radiocarbon ((14)C) analysis of carbonate records. Samples were placed in an in-house designed LA-cell and CO2 gas was produced by ablation using a 193 nm ArF excimer laser. The (14)C/(12)C abundance ratio of the ga...
Article
Robust chronologies are crucial for the correct interpretation of climate proxy records and for detailed reconstructions of palaeoclimate. Stalagmites have garnered strong interest as recorders of past climate in part due to their amenability to U-series dating. However, many stalagmites are not dateable using this technique due to low 238U and/or...
Article
Full-text available
An arrangement of three stalagmites from Zoolithencave (southern Germany) was analysed for different types of annual laminae using both microscopic and geochemical methods. The speleothems show visible laminae (consisting of a clear and a brownish, pigmented layer pair) as well as fluorescent and elemental laminae. The age of the speleothems was co...
Article
Extreme, abrupt Northern Hemisphere climate oscillations during the last glacial cycle (140,000 years ago to present) were modulated by changes in ocean circulation and atmospheric forcing. However, the variability of the Atlantic meridional overturning circulation (AMOC), which has a role in controlling heat transport from low to high latitudes an...
Conference Paper
Full-text available
The subsurface of the Mexican state of Quintana Roo, located on the northeastern Yucatán peninsula, hosts one of the largest underwater cave systems in the world. Interconnected caves formed within thick-bedded shallow water carbonate bedrock of Mio-, Plio-and Pleistocene age (Weidie, 1985). The cave system is located only a few kilometers away fro...
Conference Paper
Full-text available
The subsurface of the Mexican state of Quintana Roo, located on the northeastern Yucatan peninsula, is known to house one of the largest underwater cave systems in the world. Sinkholes, regionally known as cenotes, and several levels of interconnected caves reach to >150 m depth and formed within thick-bedded shallow water carbonate bedrock of Mio-...
Article
Full-text available
A 350-year-long, well-dated δ(18)O stalagmite record from the summer rainfall region in South Africa is positively correlated with regional air surface temperatures at interannual time scales. The coldest period documented in this record occurred between 1690 and 1740, slightly lagging the Maunder Minimum (1645-1710). A temperature reconstruction,...
Article
We present an update (COMNISPA II) of a precisely dated, high-resolution speleothem δ18O record from the Austrian Alps. COMNISPA II consists of five stalagmites from Spannagel Cave, which have comparable δ18O values within periods of simultaneous growth and show similar δ18O variations on centennial to millennial timescales. This allows combining t...
Conference Paper
Full-text available
The North Atlantic Oscillation (NAO) has a major impact on Northern Hemisphere winter climate. Trouet et al. (2009) reconstructed the NAO for the last millennium based on a Moroccan tree ring PDSI (Palmer Drought Severity Index) reconstruction and a Scottish speleothem record. More recently, Olsen et al. (2012) extended the NAO record back to 5.2 k...