Bernd Kromer - Academia.edu (original) (raw)
Papers by Bernd Kromer
The excavation of the Cyclope cave, situated on the deserted island of Youra in the Northern Spor... more The excavation of the Cyclope cave, situated on the deserted island of Youra in the Northern Sporades (39°22'N, 24°10'E), revealed material of marine and terrestrial origin in undisturbed layers, suitable for radiocarbon dating.
The Holocene, 2002
Tree-ring widths from 880 living, dry dead, and subfossil northern Swedish pines (Pinus sylvestri... more Tree-ring widths from 880 living, dry dead, and subfossil northern Swedish pines (Pinus sylvestris L.) have been assembled into a continuous and precisely dated chronology (the Torneträsk chronology ) covering the period 5407 bc to ad 1997. Biological trends in the data were removed with autoregressive standardization (ARS) to emphasize year-to-year variability, and with regional curve standardization (RCS) to emphasize variability on timescales from decades to centuries. The strong association with summer mean temperature (June-August) has enabled the production of a temperature reconstruction for the last 7400 years, providing information on natural summer-temperatur e variability on timescales from years to centuries. Numerous cold episodes, comparabl e in severity and duration to the severe summers of the seventeenth century, are shown throughout the last seven millennia. Particularly severe conditions suggested between 600 and 1 bc correspond to a known period of glacier expansion. The relatively warm conditions of the late twentieth century do not exceed those reconstructed for several earlier time intervals, although replication is relatively poor and con dence in the reconstructions is correspondingl y reduced in the pre-Christian period, particularly around 3000, 1600 and 330 bc. Despite the use of the RCS approac h in chronolog y construction, the 7400-yea r chronology does not express the full range of millennial-timescale temperature change in northern Sweden.
Quaternary Science Reviews, 2003
This paper reviews major results of the recent German research priority program ''Changes of the ... more 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. r
Quaternary Science Reviews, 2010
Quaternary Research, 2010
... After 45 ka, the Andean foreland and the western flank of the Cordillera Occidental were domi... more ... After 45 ka, the Andean foreland and the western flank of the Cordillera Occidental were dominated by ... ka BP a semi-desert environment was established in the study area in response to 150 ... period and well into the middle Holocene, the cacti and sparse grass vegetation of the ...
Quaternary International, 2007
Progress in Oceanography, 1995
... the Arctic Ocean PETER SCHLOSSER1'2, GERHARD BONISCH1, BERND KROMER3, H.... more ... the Arctic Ocean PETER SCHLOSSER1'2, GERHARD BONISCH1, BERND KROMER3, H. Huoo LOOSLI4, RENEDIKT BOHLER4, REINHOLD BAYER3, GEORGES ... Below the SML we find Lower Halocline Water (LHW) defined by JONES and ANDERSON (1986) as water with ...
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 1987
During the past ten years, AMS has become a powerful tool in radiocarbon dating. In some applicat... more During the past ten years, AMS has become a powerful tool in radiocarbon dating. In some applications, an overall accuracy comparable to that of conventional high precision low level counting is required. To achieve this accuracy, fractionation during sample preparation and measurement has to be constant. Comparison of series of 13C/'*C ratios measured with AMS and a conventional mass spectrometer indicates that systematic errors in the carbon isotope ratio measurements are in the order of 0.1 to 0.2%. With mg size samples prepared by catalytic reduction on iron, delivering beam currents of about 12 pA for at least 1 h, statistical uncertainties for 14C of 0.3% and a total error of 0.4 to 0.5% for the i4C/'*C ratio (including the calibration error and uncertainty in the background subtraction) for modem carbon has been obtained.
Journal of Geophysical Research, 1996
In this paper we describe a recently developed technique to collect samples for atmospheric 222Rn... more In this paper we describe a recently developed technique to collect samples for atmospheric 222Rn measurements suited for deployment on (research) aircraft. Following a technical description of the sampler we present measurements from nine flights during the 1993 North Atlantic Regional Experiment (N•) intensive over the North Atlantic Ocean and over the continent in the vicinity of Nova Scotia and New Brunswick, Canada. Samples were taken both in the boundary layer and in the free troposphere up to about 5500 m (msl). Concentrations ranged from 0.01 to 1.66 Bq/m 3 in the free troposphere, with means of 1.66 and 0.52 Bq/m 3, respectively. Boundary layer 222Rn concentrations were strongly correlated with back trajectory origins continning the use of 222Rn as tracer for continental air masses. Samples collected in the marine boundary layer (MBL) were found to be significantly correlated with aerosol particle, NOy, and 03 concentrations reaffirming the utility of radon as a tracer of continental boundary layer air. Radon concentrations for the MBL samples were not found to be significantly correlated with transit times from the continent as estimated from back trajectory analysis implying that variations in the radon concentrations are dominated by factors other than radioactive decay. It is suggested that this factor is the height of the continental boundary layer into which the radon is emitted. On the basis of the radioactive decay we estimated apparent 222Rn ages for our samples and discuss the inherent difficulties in reliable age estimates. A comparison with hydrocarbon ratio age estimates for a highly polluted plume of air encountered during the campaign shows a similar age range for these samples and suggests that simultaneous measurements of species with different chemical and physical properties might allow narrowing the uncertainties in such ages estimates. 1Cooperative Institute for Marine and Atmospheric Studies, stable 2ø6pb. All of these daughters are chemically reactive charged ions and soon after production irreversibly associate with aerosol particles. Average emission rates of 222Rn over land are estimated to be about 0.7 to 1.3 atoms cm -2 s -1 [Wilkening and Clements, 1975; Sanak et al., 1978; Liu et al., 1984]. Emission from the oceans is 2 to 3 orders of magnitude lower [Broecker et al., 1967; Larson and Bressan, 1978].
Geophysical Research Letters, 2006
Geomorphology, 2005
Detailed geomorphological and chronological investigations of the NW-Namibian Amspoort Silt forma... more Detailed geomorphological and chronological investigations of the NW-Namibian Amspoort Silt formation show that the sediments are typical river-end deposits. This type of endoreic sediment, occuring only in desert margin areas, provides valuable information about the palaeo-environment. In the Hoanib valley, the fine-grained deposits have buried riverine trees. Radiocarbon dating of the wood and luminescence dating of the sediments allow a detailed reconstruction of the aggradation processes. Accumulation started~10 km downstream of Amspoort around the beginning of the 15th century and ended in the 19th century, some kilometres upstream of Amspoort. This upstream shift of sedimentation during the Little Ice Age was caused by gradually decreasing runoff resulting from aridification of the upper part of the Hoanib river catchment lying east of the Namib desert margin z1.200 m a.s.l.
Astronomy & Astrophysics, 2013
Aims. Miyake et al. (2012, Nature, 486, 240, henceforth M12) recently reported, based on 14 C dat... more Aims. Miyake et al. (2012, Nature, 486, 240, henceforth M12) recently reported, based on 14 C data, an extreme cosmic event in about AD775. Using a simple model, M12 claimed that the event was too strong to be caused by a solar flare within the standard theory. This implied a new paradigm of either an impossibly strong solar flare or a very strong cosmic ray event of unknown origin that occurred around AD775. However, as we show, the strength of the event was significantly overestimated by M12. Several subsequent works have attempted to find a possible exotic source for such an event, including a giant cometary impact upon the Sun or a gamma-ray burst, but they are all based on incorrect estimates by M12. We revisit this event with analysis of new datasets and consistent theoretical modelling. Methods. We verified the experimental result for the AD775 cosmic ray event using independent datasets including 10 Be series and newly measured 14 C annual data. We surveyed available historical chronicles for astronomical observations for the period around the AD770s to identify potential sightings of aurorae borealis and supernovae. We interpreted the 14 C measurements using an appropriate carbon cycle model. Results. We show that: (1) The reality of the AD775 event is confirmed by new measurements of 14 C in German oak; (2) by using an inappropriate carbon cycle model, M12 strongly overestimated the event's strength; (3) the revised magnitude of the event (the global 14 C production Q = (1.1−1.5) × 10 8 atoms/cm 2 ) is consistent with different independent datasets ( 14 C, 10 Be, 36 Cl) and can be associated with a strong, but not inexplicably strong, solar energetic particle event (or a sequence of events), and provides the first definite evidence for an event of this magnitude (the fluence >30 MeV was about 4.5 × 10 10 cm −2 ) in multiple datasets; (4) this interpretation is in agreement with increased auroral activity identified in historical chronicles. Conclusions. The results point to the likely solar origin of the event, which is now identified as the greatest solar event on a multimillennial time scale, placing a strong observational constraint on the theory of explosive energy releases on the Sun and cool stars.
Archaeometry, 2005
ABSTRACT The paper presents proxies from an interdisciplinary geoarchaeological working group. Se... more ABSTRACT The paper presents proxies from an interdisciplinary geoarchaeological working group. Sediment analyses and geomorphological studies, radiocarbon ages of snail shells and luminescence dating of loess allow a preliminary chronology of the environmental evolution of the eastern Atacama desert, Nazca–Palpa region (southern Peru). Until now, typical desert loess was unknown from the arid western flank of the Andes (southern Peru). The loess points to periods of more humid conditions with open grasslands at the eastern Atacama desert margin in the early and middle Holocene. In the footzone of the Andes, aridification set in before the Paracas Culture (c. 800–200 bc) evolved, but the Cordillera Occidental remained semi-arid. A second push of increasing aridity started at the latest in the Middle Nazca Period (after ad 250). During this time, the Nazca settlement centres moved upstream through the river oasis, following the eastward-shifting desert margin. It is possible that culminating aridity after ad 600 caused the collapse of the Nazca civilization. During the Late Intermediate Period (ad 1000–1400), more humid conditions favoured the massive reoccupation of the eastern Atacama up to a distance of about 40 km from the Pacific coast. Since the 14th and 15th centuries, the Palpa region has again been part of the hyper-arid Atacama. The study shows that in the Nazca–Ica region, the deep cultural changes of Pre-Columbian civilizations were not caused by catastrophic run-off of El Niño events, but by a shifting eastern desert margin due to the changing monsoonal influence.
The prototype mini carbon dating system (MICADAS) at ETH Zurich has been in routine operation for... more The prototype mini carbon dating system (MICADAS) at ETH Zurich has been in routine operation for almost 2 yr. Because of its simple and compact layout, setting up a radiocarbon measurement is fast and the system runs very reliably over days or even weeks without retuning. The stability of the instrument is responsible for the good performance in highestprecision measurements where results of single samples can be reproduced within less than 2‰. The measurements are described and the performance of MICADAS is demonstrated on measured data.
Quaternary Science Reviews, 2001
Lateglacial and Holocene tree-ring chronologies are unique archives, which provide various inform... more Lateglacial and Holocene tree-ring chronologies are unique archives, which provide various information on past environments on a true annual time scale. Changes in ring-width can be related to past climate anomalies and dendrodated wood provides an ideal source for radiocarbon calibration. We present a 1051 year tree-ring chronology from the Lateglacial, built from subfossil Scots pines (Pinus sylvestris) that grew in di!erent regions of Central and Southern Europe. Through a series of high-precision radiocarbon measurements we obtained a #oating radiocarbon chronology, which allowed accurate wiggle-matching to the INTCAL98 calibration curve. The trees show a coherent pattern in ring-width variations throughout Central Europe, and extending into the Mediterranean, which indicates a strong external climatic factor, most probably temperature during the growing season. We identi"ed major growth events, which appear synchronous with events seen in isotopic and tracer signals in the Greenland ice cores and with changes in the strength of upwelling in the Cariaco Basin.
Nature, 1996
EXCELLENT preservation of wood and charcoal at archaeological sites in Anatolia has allowed the A... more EXCELLENT preservation of wood and charcoal at archaeological sites in Anatolia has allowed the Aegean Dendrochronology Project to build absolute and floating tree-ring sequences'. One such floating dendrochronology of 1,503 years includes samples relating to known rulers, sites and cultures of the ancient eastern Mediterranean. If this chronology could be dated precisely, many long-standing questions might be resolved. Here we report 18 high-precision '"C determinations which, when wiggle-matched to the radiocarbon calibration curve, provide a date within narrow limits. Inside this range, we can suggest the probable 780 absolute dating of the dendrochronology because of a remarkable growth anomaly in the seventeenth century BC, for which we propose a correlation with major growth anomalies at 16281
The atmospheric 14C level is governed by production rate changes, due to helio-magnetic and geoma... more The atmospheric 14C level is governed by production rate changes, due to helio-magnetic and geomagnetic variability, and by changes in the exchange rates between the major carbon reservoirs, i.e. deep ocean, ocean mixed layer and atmosphere. On decadal to century time scales the solar component is expected to dominate; yet, an oceanic contribution cannot be ruled out, especially if solar
We built a floating 1382-ring chronology based on pines recovered from alluvial deposits in Germa... more We built a floating 1382-ring chronology based on pines recovered from alluvial deposits in Germany, Switzerland and Northern Italy. It includes a tree buried in situ by the Laacher See eruption (LSE) providing already a strong constraint about the absolute age of the chronology. We performed high-precision 14C (+-25 years) analyses of decadal resolution samples. The end of the chronology
The excavation of the Cyclope cave, situated on the deserted island of Youra in the Northern Spor... more The excavation of the Cyclope cave, situated on the deserted island of Youra in the Northern Sporades (39°22'N, 24°10'E), revealed material of marine and terrestrial origin in undisturbed layers, suitable for radiocarbon dating.
The Holocene, 2002
Tree-ring widths from 880 living, dry dead, and subfossil northern Swedish pines (Pinus sylvestri... more Tree-ring widths from 880 living, dry dead, and subfossil northern Swedish pines (Pinus sylvestris L.) have been assembled into a continuous and precisely dated chronology (the Torneträsk chronology ) covering the period 5407 bc to ad 1997. Biological trends in the data were removed with autoregressive standardization (ARS) to emphasize year-to-year variability, and with regional curve standardization (RCS) to emphasize variability on timescales from decades to centuries. The strong association with summer mean temperature (June-August) has enabled the production of a temperature reconstruction for the last 7400 years, providing information on natural summer-temperatur e variability on timescales from years to centuries. Numerous cold episodes, comparabl e in severity and duration to the severe summers of the seventeenth century, are shown throughout the last seven millennia. Particularly severe conditions suggested between 600 and 1 bc correspond to a known period of glacier expansion. The relatively warm conditions of the late twentieth century do not exceed those reconstructed for several earlier time intervals, although replication is relatively poor and con dence in the reconstructions is correspondingl y reduced in the pre-Christian period, particularly around 3000, 1600 and 330 bc. Despite the use of the RCS approac h in chronolog y construction, the 7400-yea r chronology does not express the full range of millennial-timescale temperature change in northern Sweden.
Quaternary Science Reviews, 2003
This paper reviews major results of the recent German research priority program ''Changes of the ... more 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. r
Quaternary Science Reviews, 2010
Quaternary Research, 2010
... After 45 ka, the Andean foreland and the western flank of the Cordillera Occidental were domi... more ... After 45 ka, the Andean foreland and the western flank of the Cordillera Occidental were dominated by ... ka BP a semi-desert environment was established in the study area in response to 150 ... period and well into the middle Holocene, the cacti and sparse grass vegetation of the ...
Quaternary International, 2007
Progress in Oceanography, 1995
... the Arctic Ocean PETER SCHLOSSER1'2, GERHARD BONISCH1, BERND KROMER3, H.... more ... the Arctic Ocean PETER SCHLOSSER1'2, GERHARD BONISCH1, BERND KROMER3, H. Huoo LOOSLI4, RENEDIKT BOHLER4, REINHOLD BAYER3, GEORGES ... Below the SML we find Lower Halocline Water (LHW) defined by JONES and ANDERSON (1986) as water with ...
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 1987
During the past ten years, AMS has become a powerful tool in radiocarbon dating. In some applicat... more During the past ten years, AMS has become a powerful tool in radiocarbon dating. In some applications, an overall accuracy comparable to that of conventional high precision low level counting is required. To achieve this accuracy, fractionation during sample preparation and measurement has to be constant. Comparison of series of 13C/'*C ratios measured with AMS and a conventional mass spectrometer indicates that systematic errors in the carbon isotope ratio measurements are in the order of 0.1 to 0.2%. With mg size samples prepared by catalytic reduction on iron, delivering beam currents of about 12 pA for at least 1 h, statistical uncertainties for 14C of 0.3% and a total error of 0.4 to 0.5% for the i4C/'*C ratio (including the calibration error and uncertainty in the background subtraction) for modem carbon has been obtained.
Journal of Geophysical Research, 1996
In this paper we describe a recently developed technique to collect samples for atmospheric 222Rn... more In this paper we describe a recently developed technique to collect samples for atmospheric 222Rn measurements suited for deployment on (research) aircraft. Following a technical description of the sampler we present measurements from nine flights during the 1993 North Atlantic Regional Experiment (N•) intensive over the North Atlantic Ocean and over the continent in the vicinity of Nova Scotia and New Brunswick, Canada. Samples were taken both in the boundary layer and in the free troposphere up to about 5500 m (msl). Concentrations ranged from 0.01 to 1.66 Bq/m 3 in the free troposphere, with means of 1.66 and 0.52 Bq/m 3, respectively. Boundary layer 222Rn concentrations were strongly correlated with back trajectory origins continning the use of 222Rn as tracer for continental air masses. Samples collected in the marine boundary layer (MBL) were found to be significantly correlated with aerosol particle, NOy, and 03 concentrations reaffirming the utility of radon as a tracer of continental boundary layer air. Radon concentrations for the MBL samples were not found to be significantly correlated with transit times from the continent as estimated from back trajectory analysis implying that variations in the radon concentrations are dominated by factors other than radioactive decay. It is suggested that this factor is the height of the continental boundary layer into which the radon is emitted. On the basis of the radioactive decay we estimated apparent 222Rn ages for our samples and discuss the inherent difficulties in reliable age estimates. A comparison with hydrocarbon ratio age estimates for a highly polluted plume of air encountered during the campaign shows a similar age range for these samples and suggests that simultaneous measurements of species with different chemical and physical properties might allow narrowing the uncertainties in such ages estimates. 1Cooperative Institute for Marine and Atmospheric Studies, stable 2ø6pb. All of these daughters are chemically reactive charged ions and soon after production irreversibly associate with aerosol particles. Average emission rates of 222Rn over land are estimated to be about 0.7 to 1.3 atoms cm -2 s -1 [Wilkening and Clements, 1975; Sanak et al., 1978; Liu et al., 1984]. Emission from the oceans is 2 to 3 orders of magnitude lower [Broecker et al., 1967; Larson and Bressan, 1978].
Geophysical Research Letters, 2006
Geomorphology, 2005
Detailed geomorphological and chronological investigations of the NW-Namibian Amspoort Silt forma... more Detailed geomorphological and chronological investigations of the NW-Namibian Amspoort Silt formation show that the sediments are typical river-end deposits. This type of endoreic sediment, occuring only in desert margin areas, provides valuable information about the palaeo-environment. In the Hoanib valley, the fine-grained deposits have buried riverine trees. Radiocarbon dating of the wood and luminescence dating of the sediments allow a detailed reconstruction of the aggradation processes. Accumulation started~10 km downstream of Amspoort around the beginning of the 15th century and ended in the 19th century, some kilometres upstream of Amspoort. This upstream shift of sedimentation during the Little Ice Age was caused by gradually decreasing runoff resulting from aridification of the upper part of the Hoanib river catchment lying east of the Namib desert margin z1.200 m a.s.l.
Astronomy & Astrophysics, 2013
Aims. Miyake et al. (2012, Nature, 486, 240, henceforth M12) recently reported, based on 14 C dat... more Aims. Miyake et al. (2012, Nature, 486, 240, henceforth M12) recently reported, based on 14 C data, an extreme cosmic event in about AD775. Using a simple model, M12 claimed that the event was too strong to be caused by a solar flare within the standard theory. This implied a new paradigm of either an impossibly strong solar flare or a very strong cosmic ray event of unknown origin that occurred around AD775. However, as we show, the strength of the event was significantly overestimated by M12. Several subsequent works have attempted to find a possible exotic source for such an event, including a giant cometary impact upon the Sun or a gamma-ray burst, but they are all based on incorrect estimates by M12. We revisit this event with analysis of new datasets and consistent theoretical modelling. Methods. We verified the experimental result for the AD775 cosmic ray event using independent datasets including 10 Be series and newly measured 14 C annual data. We surveyed available historical chronicles for astronomical observations for the period around the AD770s to identify potential sightings of aurorae borealis and supernovae. We interpreted the 14 C measurements using an appropriate carbon cycle model. Results. We show that: (1) The reality of the AD775 event is confirmed by new measurements of 14 C in German oak; (2) by using an inappropriate carbon cycle model, M12 strongly overestimated the event's strength; (3) the revised magnitude of the event (the global 14 C production Q = (1.1−1.5) × 10 8 atoms/cm 2 ) is consistent with different independent datasets ( 14 C, 10 Be, 36 Cl) and can be associated with a strong, but not inexplicably strong, solar energetic particle event (or a sequence of events), and provides the first definite evidence for an event of this magnitude (the fluence >30 MeV was about 4.5 × 10 10 cm −2 ) in multiple datasets; (4) this interpretation is in agreement with increased auroral activity identified in historical chronicles. Conclusions. The results point to the likely solar origin of the event, which is now identified as the greatest solar event on a multimillennial time scale, placing a strong observational constraint on the theory of explosive energy releases on the Sun and cool stars.
Archaeometry, 2005
ABSTRACT The paper presents proxies from an interdisciplinary geoarchaeological working group. Se... more ABSTRACT The paper presents proxies from an interdisciplinary geoarchaeological working group. Sediment analyses and geomorphological studies, radiocarbon ages of snail shells and luminescence dating of loess allow a preliminary chronology of the environmental evolution of the eastern Atacama desert, Nazca–Palpa region (southern Peru). Until now, typical desert loess was unknown from the arid western flank of the Andes (southern Peru). The loess points to periods of more humid conditions with open grasslands at the eastern Atacama desert margin in the early and middle Holocene. In the footzone of the Andes, aridification set in before the Paracas Culture (c. 800–200 bc) evolved, but the Cordillera Occidental remained semi-arid. A second push of increasing aridity started at the latest in the Middle Nazca Period (after ad 250). During this time, the Nazca settlement centres moved upstream through the river oasis, following the eastward-shifting desert margin. It is possible that culminating aridity after ad 600 caused the collapse of the Nazca civilization. During the Late Intermediate Period (ad 1000–1400), more humid conditions favoured the massive reoccupation of the eastern Atacama up to a distance of about 40 km from the Pacific coast. Since the 14th and 15th centuries, the Palpa region has again been part of the hyper-arid Atacama. The study shows that in the Nazca–Ica region, the deep cultural changes of Pre-Columbian civilizations were not caused by catastrophic run-off of El Niño events, but by a shifting eastern desert margin due to the changing monsoonal influence.
The prototype mini carbon dating system (MICADAS) at ETH Zurich has been in routine operation for... more The prototype mini carbon dating system (MICADAS) at ETH Zurich has been in routine operation for almost 2 yr. Because of its simple and compact layout, setting up a radiocarbon measurement is fast and the system runs very reliably over days or even weeks without retuning. The stability of the instrument is responsible for the good performance in highestprecision measurements where results of single samples can be reproduced within less than 2‰. The measurements are described and the performance of MICADAS is demonstrated on measured data.
Quaternary Science Reviews, 2001
Lateglacial and Holocene tree-ring chronologies are unique archives, which provide various inform... more Lateglacial and Holocene tree-ring chronologies are unique archives, which provide various information on past environments on a true annual time scale. Changes in ring-width can be related to past climate anomalies and dendrodated wood provides an ideal source for radiocarbon calibration. We present a 1051 year tree-ring chronology from the Lateglacial, built from subfossil Scots pines (Pinus sylvestris) that grew in di!erent regions of Central and Southern Europe. Through a series of high-precision radiocarbon measurements we obtained a #oating radiocarbon chronology, which allowed accurate wiggle-matching to the INTCAL98 calibration curve. The trees show a coherent pattern in ring-width variations throughout Central Europe, and extending into the Mediterranean, which indicates a strong external climatic factor, most probably temperature during the growing season. We identi"ed major growth events, which appear synchronous with events seen in isotopic and tracer signals in the Greenland ice cores and with changes in the strength of upwelling in the Cariaco Basin.
Nature, 1996
EXCELLENT preservation of wood and charcoal at archaeological sites in Anatolia has allowed the A... more EXCELLENT preservation of wood and charcoal at archaeological sites in Anatolia has allowed the Aegean Dendrochronology Project to build absolute and floating tree-ring sequences'. One such floating dendrochronology of 1,503 years includes samples relating to known rulers, sites and cultures of the ancient eastern Mediterranean. If this chronology could be dated precisely, many long-standing questions might be resolved. Here we report 18 high-precision '"C determinations which, when wiggle-matched to the radiocarbon calibration curve, provide a date within narrow limits. Inside this range, we can suggest the probable 780 absolute dating of the dendrochronology because of a remarkable growth anomaly in the seventeenth century BC, for which we propose a correlation with major growth anomalies at 16281
The atmospheric 14C level is governed by production rate changes, due to helio-magnetic and geoma... more The atmospheric 14C level is governed by production rate changes, due to helio-magnetic and geomagnetic variability, and by changes in the exchange rates between the major carbon reservoirs, i.e. deep ocean, ocean mixed layer and atmosphere. On decadal to century time scales the solar component is expected to dominate; yet, an oceanic contribution cannot be ruled out, especially if solar
We built a floating 1382-ring chronology based on pines recovered from alluvial deposits in Germa... more We built a floating 1382-ring chronology based on pines recovered from alluvial deposits in Germany, Switzerland and Northern Italy. It includes a tree buried in situ by the Laacher See eruption (LSE) providing already a strong constraint about the absolute age of the chronology. We performed high-precision 14C (+-25 years) analyses of decadal resolution samples. The end of the chronology