The first three stalagmites from the Bleßberg Cave (BB-1, BB-2, BB-3) grew during the last 10,000 years or so, the Holocene. By analysing stable isotopes and trace elements, various aspects of the past environmental and climatic conditions will be reconstructed. Although there are already first interesting published results, the investigation of these samples continues.
@misc{marwan2019lodz,
title = {Recurrence based entropies},
author = {Norbert Marwan and Kai Hauke Kraemer and Karolin Wiesner and Sebastian F. M. Breitenbach and Jens Leonhardt},
editor = {Fourth International Conference on Recent Advances in Nonlinear Mechanics, Łódz (Poland)},
year = {2019},
date = {2019-05-07},
abstract = {Many dynamical processes are considered to be of complex nature. To get a quantitative idea of the complexity, often the Shannon entropy of the value distribution of a measurement is used. Alternative entropy measures have been suggested using the recurrence plot (RP) approach. A RP is a matrix that represents the recurrences of states in the d-dimensional phase space. The RP can consist of small-scale structures, such as single points, diagonal and vertical lines, which characterize important dynamical properties of the system. Various entropy measures have been defined using different features of the RP or can be related to certain properties of the RP. Because of the different features that are used, some entropy measures represent different aspects of the analysed system and, thus, behave differently. This fact can lead to misunderstandings and difficulties in interpreting and understanding those measures. We discuss definitions, motivation and interpretation of some of those entropy measures, compare their differences and discuss some of the pitfalls when using them. },
note = {Fourth International Conference on Recent Advances in Nonlinear Mechanics, Łódz (Poland)},
keywords = {},
pubstate = {published},
tppubtype = {presentation}
}
Many dynamical processes are considered to be of complex nature. To get a quantitative idea of the complexity, often the Shannon entropy of the value distribution of a measurement is used. Alternative entropy measures have been suggested using the recurrence plot (RP) approach. A RP is a matrix that represents the recurrences of states in the d-dimensional phase space. The RP can consist of small-scale structures, such as single points, diagonal and vertical lines, which characterize important dynamical properties of the system. Various entropy measures have been defined using different features of the RP or can be related to certain properties of the RP. Because of the different features that are used, some entropy measures represent different aspects of the analysed system and, thus, behave differently. This fact can lead to misunderstandings and difficulties in interpreting and understanding those measures. We discuss definitions, motivation and interpretation of some of those entropy measures, compare their differences and discuss some of the pitfalls when using them.
@inproceedings{marwan2019,
title = {Recurrence based entropies},
author = {Norbert Marwan and Kai Hauke Kraemer and Karolin Wiesner and Sebastian F. M. Breitenbach and Jens Leonhardt},
url = {https://bbh.pik-potsdam.de/wp-content/uploads/2021/04/EGU2019-2817.pdf},
year = {2019},
date = {2019-04-08},
booktitle = {Geophysical Research Abstracts},
volume = {21},
pages = {EGU2019-2817},
abstract = {Dynamical processes in Earth sciences are often considered to be of complex nature. The term complexity is often used for processes that are either unpredictable (e.g. nonlinear dynamics), consist of many different components, or exhibit regime transitions (e.g. tipping points). To measure complexity, the Shannon entropy is often used.
Here we present various entropy measures that have been defined on the base of the recurrence plot. Because of the different features that are used, these entropy measures represent different aspects of the analysed system and, thus, behave differently. In the past, this fact has lead to difficulties in interpreting and understanding those measures. We summarize the definitions, the motivation and interpretation of these entropy measures, compare their differences and discuss some of the pitfalls when using them.
Finally, we illustrate their potential in an application on palaeoclimate time series. Using entropy measures, changes and transitions in the climate dynamics in the past can be identified and interpreted.},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}
Dynamical processes in Earth sciences are often considered to be of complex nature. The term complexity is often used for processes that are either unpredictable (e.g. nonlinear dynamics), consist of many different components, or exhibit regime transitions (e.g. tipping points). To measure complexity, the Shannon entropy is often used.
Here we present various entropy measures that have been defined on the base of the recurrence plot. Because of the different features that are used, these entropy measures represent different aspects of the analysed system and, thus, behave differently. In the past, this fact has lead to difficulties in interpreting and understanding those measures. We summarize the definitions, the motivation and interpretation of these entropy measures, compare their differences and discuss some of the pitfalls when using them.
Finally, we illustrate their potential in an application on palaeoclimate time series. Using entropy measures, changes and transitions in the climate dynamics in the past can be identified and interpreted.
At PIK, among other things, new methods are being developed that, on the one hand, can be used to investigate new aspects in palaeoclimate data, but on the other hand can also cope with the difficulties usually associated with palaeoclimate analyses – such as gaps in data series, uncertainties in the dating, or irregularities in the data sampling. Although this is basic research, it is also immediately applied to interesting questions.
In this example, a method was developed to determine the regularity of certain recurring pattern in the data. The technical terms here are “recurrence” and “entropy” (a measure of disorder). Methods that look for recurring patterns are used in various disciplines, not only in the geosciences, but also in medicine, mechanical engineering, finance, and so on. Besides finding abrupt changes, they are also used for comparing different data sets or for classification (e.g. for machine learning).
The newly developed method was applied to the carbon isotopeIsotopChemische Elemente können aus verschieden aufgebauten Atomen gebildet sein. Die Anzahl Protonen im Atomkern ist zwar dabei gleich, aber die Anzahl der Neutronen kann variieren. Man spricht dann von Isotopen, deren Massen kleine, aber messbare Unterschiede aufweisen. Der Atomkern des Sauerstoffs besteht z. B. aus 8 Protonen und in der Regel aus 8 Neutronen. Es gibt aber auch Sauerstoff, dessen Kerne aus 8 Protonen und 9 oder 10 Neutronen bestehen (neben selteneren, instabilen Sauerstoffisotopen). Um das zu kennzeichnen, gibt man zusätzlich zum chemischen Symbol noch die Massenzahl (Summe aus Protonen und Neutronen) an, also 16O, 17O oder 18O. Die unterschiedlichen Isotope verhalten sich zwar chemisch identisch, physikalisch aber - aufgrund ihres unterschiedlichen Gewichtes - leicht unterschiedlich. Damit stellen sie äusserst wertvolle Marker dar, die uns wichtige Hinweise zur Änderung des Klimas, der Umgebungsvegetation, Bodenaktivität und vielem mehr geben. data from BB-1 and BB-3 (for this purpose, the data from both stalagmites were combined into one long data series using a special procedure). Interestingly, there are regular differences during the influence of the maritime climate (Atlantic influence) and during the influence of the continental climate. During the Atlantic influence, the climate seems to have changed more regularly than during the dominant continental climate (this may be related to the regular change of cold events in the North Atlantic, so-called “Bond events”, or to the North Atlantic Oscillation). This could be used to extend our knowledge about the migration of the climate zone boundary, as known for the last 4,000 years (see Climate Zone Shift in central Europe), further into the past. Whenever the new measure indicates that there were more regular climate dynamics, the climate zone boundary was further east of the Bleßberg Cave.
@proceedings{klose2023poster,
title = {Timing of Dansgaard-Oeschger events in Central Europe based on three precisely dated speleothems from Bleßberg Cave, Germany},
author = {J. Klose and D. Scholz and M. Weber and H. Vonhof and B. Plessen and S. Breitenbach and N. Marwan},
editor = {Summer School on Speleothem Sciences 2023, Sao Paulo},
url = {https://bbh.pik-potsdam.de/wp-content/uploads/2024/09/klose_SummerschoolSaoPaulo2023.pdf},
year = {2023},
date = {2023-08-07},
urldate = {2023-08-07},
abstract = {The last glacial period and especially Marine Isotope stage 3 (MIS 3, ca. 57 - 27 ka) was characterized by various climate oscillations (i.e., rapid increases in temperature, followed by a gradual cooling, the Dansgaard-Oeschger (D/O) events), which were first discovered in Greenland ice cores. Although their causes are still not fully understood, clear evidence for their supra-regional character was found in various climate records around the globe. However, European speleothem samples, which grew during MIS 3, are limited and mainly restricted to alpine regions, where glacier meltwater enabled speleothem growth, and to south/south-western parts of Europe characterised by a generally warmer climate. This led to the opinion that it was too cold and/or too dry in central Europe for speleothem growth. Here we present three speleothem (flowstone) records from Bleßberg Cave, Germany, which grew during MIS 3.
All flowstones show episodical growth patterns with distinctive, thin growth phases. Potential contamination deriving form detrital material deposited during hiatuses between individual growth phases, open-system behaviour around the hiatuses and the limited thickness of the growth layers are the biggest challenges during sampling for 230Th/U dating. By combination of different sampling techniques (i.e., laser ablation and micro-milling) in addition to the common approach of handheld drilling and due to the relatively high 238U concentration of the samples (approx. 0.4 – 1 µg/g), we were able to date even the thinnest growth layers (< 2 mm) of the Bleßberg flowstones with a very high precision (i.e., with 2σ-age uncertainties of a few hundred years or even lower).
The timing of the growth phases of the Bleßberg flowstones correlates with several D/O events recorded in the Greenland ice cores. This proves that at least some phases of MIS 3 had favourable climate conditions for speleothem growth in Central Europe. In addition, the analysis of the stable oxygen and carbon isotopes (δ18O and δ13C) for all three flowstones revealed several D/O events, which have not been recorded in any other speleothem from central Europe so far. This will enhance our understanding of climate variability during MIS 3 and specific D/O events in central Europe.},
howpublished = {Poster},
note = {Summer School on Speleothem Sciences 2023, Sao Paulo},
keywords = {},
pubstate = {published},
tppubtype = {proceedings}
}
The last glacial period and especially Marine IsotopeIsotopChemische Elemente können aus verschieden aufgebauten Atomen gebildet sein. Die Anzahl Protonen im Atomkern ist zwar dabei gleich, aber die Anzahl der Neutronen kann variieren. Man spricht dann von Isotopen, deren Massen kleine, aber messbare Unterschiede aufweisen. Der Atomkern des Sauerstoffs besteht z. B. aus 8 Protonen und in der Regel aus 8 Neutronen. Es gibt aber auch Sauerstoff, dessen Kerne aus 8 Protonen und 9 oder 10 Neutronen bestehen (neben selteneren, instabilen Sauerstoffisotopen). Um das zu kennzeichnen, gibt man zusätzlich zum chemischen Symbol noch die Massenzahl (Summe aus Protonen und Neutronen) an, also 16O, 17O oder 18O. Die unterschiedlichen Isotope verhalten sich zwar chemisch identisch, physikalisch aber - aufgrund ihres unterschiedlichen Gewichtes - leicht unterschiedlich. Damit stellen sie äusserst wertvolle Marker dar, die uns wichtige Hinweise zur Änderung des Klimas, der Umgebungsvegetation, Bodenaktivität und vielem mehr geben. stage 3 (MIS 3MIS 3"MIS" ist die Abkürzung für "marine isotope stage", übersetzt also "Isotopenstadium mariner Sedimente". Da sich beim Wechsel von Warm- zu Kaltzeiten (und umgekehrt) die Isotopenverhältnisse in den Kalkschalen kleiner Einzeller (Foraminiferen) auf dem Meeresboden ändern, werden diese zur Datierung herangezogen und lassen sich zur Eingruppierung verschiedener Klimazustände in der Vergangenheit nutzen. "MIS 3" bedeutet dabei eine kurzzeitige Warmphase (beginnend vor 57 Tausend Jahren) während der letzten Eiszeit., ca. 57 - 27 kaka BPMit "ka BP" sind "Tausend Jahre vor 1950" gemeint. Das "BP" steht für "before present", was in der Paläoklima-Wissenschaft als 1950 festgelegt wurde. "11.000 ka BP" bedeuted also 11 Tausend Jahre vor 1950, oder unter Verwendung unseres gewohnten Kalenders: 9050 v. Chr.) was characterized by various climate oscillations (i.e., rapid increases in temperature, followed by a gradual cooling, the Dansgaard-Oeschger (D/O) events), which were first discovered in Greenland ice cores. Although their causes are still not fully understood, clear evidence for their supra-regional character was found in various climate records around the globe. However, European speleothem samples, which grew during MIS 3, are limited and mainly restricted to alpine regions, where glacier meltwater enabled speleothem growth, and to south/south-western parts of Europe characterised by a generally warmer climate. This led to the opinion that it was too cold and/or too dry in central Europe for speleothem growth. Here we present three speleothem (flowstone) records from Bleßberg Cave, Germany, which grew during MIS 3.
All flowstones show episodical growth patterns with distinctive, thin growth phases. Potential contamination deriving form detrital material deposited during hiatuses between individual growth phases, open-system behaviour around the hiatuses and the limited thickness of the growth layers are the biggest challenges during sampling for 230Th/UU/Th-DatierungDie U/Th-Datierung ist eine sehr präzise radiometrische Altersbestimmung auf Basis der Uran-Thorium-Zerfallsreihe. Das Uran zerfällt mit bekannten Halbwertszeiten (245.500 Jahre) zum Tochterelement Thorium. Stalagmiten bauen bei ihrem Wachstum (fast) nur das wasserlösliche Uran ein, während das schlecht bewegliche Thorium zum größten Teil im Boden und Epikarst über der Höhle verbleibt. Das kann man nutzen, um die Zeit zu berechnen, die seit der Ausfällung der untersuchten Karbonatprobe vergangen ist. Moderne massenspektrometrische Verfahren erlauben Altersbestimmungen mit der U/Th-Methode bis zu 700.000 Jahren vor Heute. dating. By combination of different sampling techniques (i.e., laser ablation and micro-milling) in addition to the common approach of handheld drilling and due to the relatively high 238U concentration of the samples (approx. 0.4 – 1 µg/g), we were able to date even the thinnest growth layers (< 2 mm) of the Bleßberg flowstones with a very high precision (i.e., with 2σ-age uncertainties of a few hundred years or even lower).
The timing of the growth phases of the Bleßberg flowstones correlates with several D/O events recorded in the Greenland ice cores. This proves that at least some phases of MIS 3 had favourable climate conditions for speleothem growth in Central Europe. In addition, the analysis of the stable oxygen and carbon isotopes (δ18O and δ13C) for all three flowstones revealed several D/O events, which have not been recorded in any other speleothem from central Europe so far. This will enhance our understanding of climate variability during MIS 3 and specific D/O events in central Europe.
Klose, J.; Scholz, D.; Weber, M.; Vonhof, H.; Plessen, B.; Breitenbach, S.; Marwan, N.
Timing and progression of Dansgaard-Oeschger events in Central Europe based on three precisely dated speleothems from Bleßberg Cave, Germany Proceedings
@proceedings{klose2023,
title = {Timing and progression of Dansgaard-Oeschger events in Central Europe based on three precisely dated speleothems from Bleßberg Cave, Germany},
author = {J. Klose and D. Scholz and M. Weber and H. Vonhof and B. Plessen and S. Breitenbach and N. Marwan},
editor = {XXI INQUA Conference, Rome (Italy)},
year = {2023},
date = {2023-07-19},
urldate = {2023-07-19},
abstract = {Speleothems can be dated with unprecedented precision using U-series disequilibrium methods and provide numerous climate proxies, such as stable oxygen (δ18O) and carbon isotopes (δ13C) or trace elements, resulting in long, sometimes continuous climate proxy records. Therefore, speleothems have great potential for reconstruction of past climate variability during Marine Isotope Stage (MIS) 3 and precise determination of the timing and duration of Dansgaard-Oeschger (D/O) events. While first discovered in Greenland ice cores, various speleothem records around the globe provided clear evidence for the supra-regional character of the D/O events. However, MIS 3 speleothem records from Central Europe are very limited. Here we present three spleothem (flowstone) MIS 3 records from Bleßberg Cave, Germany.
All flowstones show episodic growth with distinctive, partially very thin (<2 mm) growth phases, interrupted by visible hiatuses consisting of detrital material. Precise and accurate 230Th/U dating of the individual growth phases is challenging due to potential detrital contamination from these layers. Combining different sampling and analytical techniques, we were able to date even the thinnest growth layers with very high precision, i.e., 2σ-age uncertainties of at most a few hundred years.
The timing of the growth phases aligns with several D/O events, which have not been recorded in other Central European speleothems yet. The δ18O and δ13C records of all three flowstones are highly correlated which suggests a dominant process influencing both isotope systems. Comparison with the Sr and Mg records provides evidence for a strong influence of Prior Calcite Precipitation (PCP) in the aquifer above and inside the cave on the stable isotope and trace element signals. In addition, all proxy records are interpreted as evidence for past changes in precipitation and vegetation density and document a clear trend from more humid climate during early MIS 3 (ca. 57 – 50 ka) to less humid conditions during mid and late MIS 3 (ca. 45 – 30 ka).
Our multi-proxy approach thus allows us not only to precisely determine the timing, duration, and progression of several D/O events, but also to deepen our general understanding of climate variability during MIS 3 in Central Europe.},
howpublished = {Poster},
note = {XXI INQUA Conference, Rome (Italy)},
keywords = {},
pubstate = {published},
tppubtype = {proceedings}
}
Speleothems can be dated with unprecedented precision using U-series disequilibrium methods and provide numerous climate proxiesProxyUmwelt- und Klimainformationen aus der Vergangenheit sind nicht direkt verfügbar, weil niemand da war, der diese messen und aufzeichnen konnte. Daher ist man darauf angewiesen, diese Informationen indirekt aus anderen Informationen abzuleiten, wie z. B. Baumringe, das Verhältnis von Sauerstoffisotopen, Spurenelementen, Mächtigkeit von Sedimentschichten usw. Diese Art von Daten nennt man Proxies, was aus dem englischen stammt und „Stellvertreter“ bedeutet., such as stable oxygen (δ18O) and carbon isotopes (δ13C) or trace elements, resulting in long, sometimes continuous climate proxyProxyUmwelt- und Klimainformationen aus der Vergangenheit sind nicht direkt verfügbar, weil niemand da war, der diese messen und aufzeichnen konnte. Daher ist man darauf angewiesen, diese Informationen indirekt aus anderen Informationen abzuleiten, wie z. B. Baumringe, das Verhältnis von Sauerstoffisotopen, Spurenelementen, Mächtigkeit von Sedimentschichten usw. Diese Art von Daten nennt man Proxies, was aus dem englischen stammt und „Stellvertreter“ bedeutet. records. Therefore, speleothems have great potential for reconstruction of past climate variability during Marine Isotope Stage (MISMIS"MIS" ist die Abkürzung für "marine isotope stage", übersetzt also "Isotopenstadium mariner Sedimente". Da sich beim Wechsel von Warm- zu Kaltzeiten (und umgekehrt) die Isotopenverhältnisse in den Kalkschalen kleiner Einzeller (Foraminiferen) auf dem Meeresboden ändern, werden diese zur Datierung herangezogen und lassen sich zur Eingruppierung verschiedener Klimazustände in der Vergangenheit nutzen. Die MIS werden rückwärts nummeriert (also größere Zahl = älter) und ungerade Zahlen stehen für Warmzeiten, gerade für Kaltzeiten.) 3 and precise determination of the timing and duration of Dansgaard-Oeschger (D/O) events. While first discovered in Greenland ice cores, various speleothem records around the globe provided clear evidence for the supra-regional character of the D/O events. However, MIS 3 speleothem records from Central Europe are very limited. Here we present three spleothem (flowstone) MIS 3 records from Bleßberg Cave, Germany.
All flowstones show episodic growth with distinctive, partially very thin (<2 mm) growth phases, interrupted by visible hiatuses consisting of detrital material. Precise and accurate 230Th/U dating of the individual growth phases is challenging due to potential detrital contamination from these layers. Combining different sampling and analytical techniques, we were able to date even the thinnest growth layers with very high precision, i.e., 2σ-age uncertainties of at most a few hundred years.
The timing of the growth phases aligns with several D/O events, which have not been recorded in other Central European speleothems yet. The δ18O and δ13C records of all three flowstones are highly correlated which suggests a dominant process influencing both isotope systems. Comparison with the Sr and Mg records provides evidence for a strong influence of Prior Calcite Precipitation (PCP) in the aquifer above and inside the cave on the stable isotope and trace element signals. In addition, all proxy records are interpreted as evidence for past changes in precipitation and vegetation density and document a clear trend from more humid climate during early MIS 3 (ca. 57 – 50 ka) to less humid conditions during mid and late MIS 3 (ca. 45 – 30 ka).
Our multi-proxyProxyUmwelt- und Klimainformationen aus der Vergangenheit sind nicht direkt verfügbar, weil niemand da war, der diese messen und aufzeichnen konnte. Daher ist man darauf angewiesen, diese Informationen indirekt aus anderen Informationen abzuleiten, wie z. B. Baumringe, das Verhältnis von Sauerstoffisotopen, Spurenelementen, Mächtigkeit von Sedimentschichten usw. Diese Art von Daten nennt man Proxies, was aus dem englischen stammt und „Stellvertreter“ bedeutet. approach thus allows us not only to precisely determine the timing, duration, and progression of several D/O events, but also to deepen our general understanding of climate variability during MIS 3 in Central Europe.
@proceedings{klose2022,
title = {Timing of Dansgaard-Oeschger events in Central Europe based on three precisely dated speleothems from Bleßberg Cave, Germany},
author = {J. Klose and M. Weber and H. Vonhof and B. Plessen and S. Breitenbach and N. Marwan and D. Scholz},
editor = {KR9 in Innsbruck, 2022},
url = {https://bbh.pik-potsdam.de/wp-content/uploads/2024/09/klose_KR9-Innsbruck2022.pdf},
year = {2022},
date = {2022-07-19},
urldate = {2022-07-19},
abstract = {The last glacial period and especially Marine Isotope stage 3 (MIS 3, ca. 57 - 27 ka) was characterized by various climate oscillations (i.e., rapid increases in temperature, followed by a gradual cooling, the Dansgaard-Oeschger (D/O) events), which were first discovered in Greenland ice cores. Although their causes are still not fully understood, clear evidence for their supra-regional character was found in various climate records around the globe. However, European speleothem samples, which grew during MIS 3, are limited and mainly restricted to alpine regions, where glacier meltwater enabled speleothem growth, and to south/south-western parts of Europe characterised by a generally warmer climate. This led to the opinion that it was too cold and/or too dry in central Europe for speleothem growth. Here we present three speleothem (flowstone) records from Bleßberg Cave, Germany, which grew during MIS 3.
All flowstones show episodical growth patterns with distinctive, thin growth phases. Potential contamination deriving form detrital material deposited during hiatuses between individual growth phases, open-system behaviour around the hiatuses and the limited thickness of the growth layers are the biggest challenges during sampling for 230Th/U dating. By combination of different sampling techniques (i.e., laser ablation and micro-milling) in addition to the common approach of handheld drilling and due to the relatively high 238U concentration of the samples (approx. 0.4 – 1 µg/g), we were able to date even the thinnest growth layers (< 2 mm) of the Bleßberg flowstones with a very high precision (i.e., with 2σ-age uncertainties of a few hundred years or even lower).
The timing of the growth phases of the Bleßberg flowstones correlates with several D/O events recorded in the Greenland ice cores. This proves that at least some phases of MIS 3 had favourable climate conditions for speleothem growth in Central Europe. In addition, the analysis of the stable oxygen and carbon isotopes (δ18O and δ13C) for all three flowstones revealed several D/O events, which have not been recorded in any other speleothem from central Europe so far. This will enhance our understanding of climate variability during MIS 3 and specific D/O events in central Europe.},
howpublished = {Poster},
note = {KR9 Konferenz in Innsbruck},
keywords = {},
pubstate = {published},
tppubtype = {proceedings}
}
The last glacial period and especially Marine Isotope stage 3 (MIS 3, ca. 57 - 27 ka) was characterized by various climate oscillations (i.e., rapid increases in temperature, followed by a gradual cooling, the Dansgaard-Oeschger (D/O) events), which were first discovered in Greenland ice cores. Although their causes are still not fully understood, clear evidence for their supra-regional character was found in various climate records around the globe. However, European speleothem samples, which grew during MIS 3, are limited and mainly restricted to alpine regions, where glacier meltwater enabled speleothem growth, and to south/south-western parts of Europe characterised by a generally warmer climate. This led to the opinion that it was too cold and/or too dry in central Europe for speleothem growth. Here we present three speleothem (flowstone) records from Bleßberg Cave, Germany, which grew during MIS 3.
All flowstones show episodical growth patterns with distinctive, thin growth phases. Potential contamination deriving form detrital material deposited during hiatuses between individual growth phases, open-system behaviour around the hiatuses and the limited thickness of the growth layers are the biggest challenges during sampling for 230Th/U dating. By combination of different sampling techniques (i.e., laser ablation and micro-milling) in addition to the common approach of handheld drilling and due to the relatively high 238U concentration of the samples (approx. 0.4 – 1 µg/g), we were able to date even the thinnest growth layers (< 2 mm) of the Bleßberg flowstones with a very high precision (i.e., with 2σ-age uncertainties of a few hundred years or even lower).
The timing of the growth phases of the Bleßberg flowstones correlates with several D/O events recorded in the Greenland ice cores. This proves that at least some phases of MIS 3 had favourable climate conditions for speleothem growth in Central Europe. In addition, the analysis of the stable oxygen and carbon isotopes (δ18O and δ13C) for all three flowstones revealed several D/O events, which have not been recorded in any other speleothem from central Europe so far. This will enhance our understanding of climate variability during MIS 3 and specific D/O events in central Europe.
@incollection{breitenbach_bbh2022,
title = {Die Bleßberghöhle – ein Glücksfall für die Klimaforschung},
author = {Sebastian F. M. Breitenbach and Norbert Marwan},
editor = {Thüringer Höhlenverein, e. V.},
year = {2022},
date = {2022-02-22},
urldate = {2022-02-22},
booktitle = {Nächster Halt: Bleßberghöhle},
address = {Suhl},
abstract = {Höhlen stellen generell für die Wissenschaft ein wertvolles Archiv dar, aus dem vielfältige und interessante Erkenntnisse gewonnen werden können. So gehören sie inzwischen auch zu den bedeutendsten Klimaarchiven auf dem Festland (See- und Meeressedimente stellen andere wichtige Archive dar). Solange die Höhlensedimente und Sinter ungestört bleiben, können hydrologische und klimatische Bedingungen detailliert aufgezeichnet werden. Die Bleßberghöhle ist in diesem Zusammenhang ein ausgesprochener Glücksfall, da sie über viele Jahrtausende komplett verschlossen war und so vor äußeren Störungen bewahrt wurde. Sie ist in vielen Abschnitten mit verschiedensten Sinterformen geschmückt. Für die Rekonstruktion regionaler Klimaänderungen sind vor allem die Stalagmiten geeignet. Die wissenschaftliche Bearbeitung des aus der Bleßberghöhle gesammelten Materials ist ein langwieriger Prozess und noch lange nicht abgeschlossen. Zum gegenwärtigen Zeitpunkt können aber bereits erste interessante Aussagen gemacht werden, auf die wir hier nach einem kurzen allgemeinen Einblick in verschiedene Aspekte der Paläoklimaforschung eingehen wollen.},
keywords = {},
pubstate = {published},
tppubtype = {incollection}
}
Höhlen stellen generell für die Wissenschaft ein wertvolles Archiv dar, aus dem vielfältige und interessante Erkenntnisse gewonnen werden können. So gehören sie inzwischen auch zu den bedeutendsten Klimaarchiven auf dem Festland (See- und Meeressedimente stellen andere wichtige Archive dar). Solange die Höhlensedimente und Sinter ungestört bleiben, können hydrologische und klimatische Bedingungen detailliert aufgezeichnet werden. Die Bleßberghöhle ist in diesem Zusammenhang ein ausgesprochener Glücksfall, da sie über viele Jahrtausende komplett verschlossen war und so vor äußeren Störungen bewahrt wurde. Sie ist in vielen Abschnitten mit verschiedensten Sinterformen geschmückt. Für die Rekonstruktion regionaler Klimaänderungen sind vor allem die Stalagmiten geeignet. Die wissenschaftliche Bearbeitung des aus der Bleßberghöhle gesammelten Materials ist ein langwieriger Prozess und noch lange nicht abgeschlossen. Zum gegenwärtigen Zeitpunkt können aber bereits erste interessante Aussagen gemacht werden, auf die wir hier nach einem kurzen allgemeinen Einblick in verschiedene Aspekte der Paläoklimaforschung eingehen wollen.
@inproceedings{marwan2014,
title = {Recurrence properties as signatures for abrupt climate change},
author = {Norbert Marwan and Sebastian F. M. Breitenbach and Birgit Plessen and Denis Scholz and Jens Leonhardt
},
url = {https://bbh.pik-potsdam.de/wp-content/uploads/2021/04/EGU2014-8893.pdf},
year = {2014},
date = {2014-04-01},
booktitle = {Geophysical Research Abstracts},
volume = {16},
pages = {EGU2014-8893},
abstract = { The study of recurrence properties of dynamical systems has been shown to be very successful in characterising typical dynamical behaviour, finding regime transitions, or detecting couplings and synchronisations, even for short, noisy, and nonstationary data, as typical in Earth Sciences. Recurrence plots and their quantifications are powerful techniques for the investigation of recurrence and increasingly attract attention in recent years. We demonstrate the potential of the newly introduced extension of recurrence plot analysis by complex network measures for the detection of abrupt dynamical changes. This method is applied on a Holocene palaeoclimate data set from Central Europe derived from a stalagmite from Blessberg Cave, Thuringia, Germany. The stalagmite δ18O proxy record covers the middle to late Holocene (6000-400 years BP). Dating uncertainties are considered by an ensemble approach derived from the COPRA framework. Characteristic changes in the recurrence properties reflecting regular dynamics coincide well with the occurrence of the Bond events 1, 2, and 3. During Bond events the Central European climate variability appears more regular. The analysis presented here examplifies the potency of quantitative recurrence methods in detecting climatic events, which otherwise remain hidden in the raw proxy time series. },
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}
The study of recurrence properties of dynamical systems has been shown to be very successful in characterising typical dynamical behaviour, finding regime transitions, or detecting couplings and synchronisations, even for short, noisy, and nonstationary data, as typical in Earth Sciences. Recurrence plots and their quantifications are powerful techniques for the investigation of recurrence and increasingly attract attention in recent years. We demonstrate the potential of the newly introduced extension of recurrence plot analysis by complex network measures for the detection of abrupt dynamical changes. This method is applied on a Holocene palaeoclimate data set from Central Europe derived from a stalagmite from Blessberg Cave, Thuringia, Germany. The stalagmite δ18O proxy record covers the middle to late Holocene (6000-400 years BPka BPMit "ka BP" sind "Tausend Jahre vor 1950" gemeint. Das "BP" steht für "before present", was in der Paläoklima-Wissenschaft als 1950 festgelegt wurde. "11.000 ka BP" bedeuted also 11 Tausend Jahre vor 1950, oder unter Verwendung unseres gewohnten Kalenders: 9050 v. Chr.). Dating uncertainties are considered by an ensemble approach derived from the COPRA framework. Characteristic changes in the recurrence properties reflecting regular dynamics coincide well with the occurrence of the Bond events 1, 2, and 3. During Bond events the Central European climate variability appears more regular. The analysis presented here examplifies the potency of quantitative recurrence methods in detecting climatic events, which otherwise remain hidden in the raw proxy time series.
Among other things, new methods are being developed at PIK that, on the one hand, investigate new aspects in palaeoclimate data, but also cope with the difficulties usually associated with palaeoclimate analyses – such as gaps in the data, age uncertainties, or irregularities in the data sampling. While this is basic research, it is also immediately applied to interesting research questions.
One focus is the development and application of methods that specifically investigate recurring patterns. These methods are very successful for finding abrupt changes, but also for comparing different data sets, e.g., to detect mutual influences.
In one of our first analyses of the three stalagmites BB-1 to BB-3, we had looked at the oxygen isotopes of BB-1 with recurrence based methods. Thereby we had explicitly considered dating uncertainties. Due to the dating uncertainties there are small shifts of the time series along the x-axis. Therefore, within the uncertainties, different realizations of the course of the measured oxygen isotopes are possible.
Oxygen isotopes of BB-1. Due to the dating uncertainties, there are several possibilities when changes in this climate archive happened. The stalagmite grew from about 6,000 years ago to about 400 years ago.
The recurrence patterns are examined with a special analysis tool, the so-called “recurrence plot”. This can be used to plot times when similar states have occurred. The patterns seen in such a recurrence plot have a deeper meaning and can be further analyzed and quantified to find changes in the dynamics of the underlying process.
Recurrence plot of one realization of the measured oxygen isotopes in BB-1.
The numerical analysis of recurrence plots yields various results that shed light on different aspects of climate dynamics. Two such results are briefly presented here: on the one hand, the complexity of climate variability (“transitivityTransitivityEin Maß aus der Netzwerktheorie, welches quantifiziert, wie stark sich Zustände zu kleinen Gruppen zusammenfinden.”) and, on the other hand, how well such a climate signal would be predictable (“determinismDeterminismEin Maß aus der Wiederkehr-Analyse, welches beschreibt, wie gut sich die Veränderung eines Systems vorhersagen läßt.”). Both results show a general tendency towards greater complexity and lower predictability for younger ages. However, they also show short-lived increases to better predictability for certain time points, namely about 4,200, 2,800, and 1,400 years ago. It was precisely at these times that short-lived and rapid glaciations occurred in the North Atlantic, the so-called “Bond events.” Moreover, there are variations in the complexity of the climate signal (“transitivity”), but these variations are within the range of uncertainty (confidence interval), so we cannot really interpret them.
Quantitative analysis of recurrence patterns in oxygen isotope measurements of BB-1.
@incollection{breitenbach_bbh2022,
title = {Die Bleßberghöhle – ein Glücksfall für die Klimaforschung},
author = {Sebastian F. M. Breitenbach and Norbert Marwan},
editor = {Thüringer Höhlenverein, e. V.},
year = {2022},
date = {2022-02-22},
urldate = {2022-02-22},
booktitle = {Nächster Halt: Bleßberghöhle},
address = {Suhl},
abstract = {Höhlen stellen generell für die Wissenschaft ein wertvolles Archiv dar, aus dem vielfältige und interessante Erkenntnisse gewonnen werden können. So gehören sie inzwischen auch zu den bedeutendsten Klimaarchiven auf dem Festland (See- und Meeressedimente stellen andere wichtige Archive dar). Solange die Höhlensedimente und Sinter ungestört bleiben, können hydrologische und klimatische Bedingungen detailliert aufgezeichnet werden. Die Bleßberghöhle ist in diesem Zusammenhang ein ausgesprochener Glücksfall, da sie über viele Jahrtausende komplett verschlossen war und so vor äußeren Störungen bewahrt wurde. Sie ist in vielen Abschnitten mit verschiedensten Sinterformen geschmückt. Für die Rekonstruktion regionaler Klimaänderungen sind vor allem die Stalagmiten geeignet. Die wissenschaftliche Bearbeitung des aus der Bleßberghöhle gesammelten Materials ist ein langwieriger Prozess und noch lange nicht abgeschlossen. Zum gegenwärtigen Zeitpunkt können aber bereits erste interessante Aussagen gemacht werden, auf die wir hier nach einem kurzen allgemeinen Einblick in verschiedene Aspekte der Paläoklimaforschung eingehen wollen.},
keywords = {},
pubstate = {published},
tppubtype = {incollection}
}
Höhlen stellen generell für die Wissenschaft ein wertvolles Archiv dar, aus dem vielfältige und interessante Erkenntnisse gewonnen werden können. So gehören sie inzwischen auch zu den bedeutendsten Klimaarchiven auf dem Festland (See- und Meeressedimente stellen andere wichtige Archive dar). Solange die Höhlensedimente und Sinter ungestört bleiben, können hydrologische und klimatische Bedingungen detailliert aufgezeichnet werden. Die Bleßberghöhle ist in diesem Zusammenhang ein ausgesprochener Glücksfall, da sie über viele Jahrtausende komplett verschlossen war und so vor äußeren Störungen bewahrt wurde. Sie ist in vielen Abschnitten mit verschiedensten Sinterformen geschmückt. Für die Rekonstruktion regionaler Klimaänderungen sind vor allem die Stalagmiten geeignet. Die wissenschaftliche Bearbeitung des aus der Bleßberghöhle gesammelten Materials ist ein langwieriger Prozess und noch lange nicht abgeschlossen. Zum gegenwärtigen Zeitpunkt können aber bereits erste interessante Aussagen gemacht werden, auf die wir hier nach einem kurzen allgemeinen Einblick in verschiedene Aspekte der Paläoklimaforschung eingehen wollen.
@article{breitenbach2019,
title = {Holocene interaction of maritime and continental climate in Central Europe: New speleothem evidence from Central Germany},
author = {Sebastian F. M. Breitenbach and Birgit Plessen and Sarah Waltgenbach and Rik Tjallingii and Jens Leonhardt and Klaus-Peter Jochum and Hanno Meyer and Bedartha Goswami and Norbert Marwan and Denis Scholz},
doi = {10.1016/j.gloplacha.2019.03.007},
year = {2019},
date = {2019-00-00},
journal = {Global and Planetary Change},
volume = {176},
pages = {144–161},
abstract = {Central European climate is strongly influenced by North Atlantic (Westerlies) and Siberian High circulation patterns, which govern precipitation and temperature dynamics and induce heterogeneous climatic conditions, with distinct boundaries between climate zones. These climate boundaries are not stationary and shift geographically, depending on long-term atmospheric conditions. So far, little is known about past shifts of these climate boundaries and the local to regional environmental response prior to the instrumental era.
High resolution multi-proxy data (stable oxygen and carbon isotope ratios, S/Ca and Sr/Ca) from two Holocene stalagmites from Bleßberg Cave (Thuringia) are used here to differentiate local and pan-regional environmental and climatic conditions Central Germany through the Holocene. Carbon isotope and S/Ca and Sr/Ca ratios inform us on local Holocene environmental changes in and around the cave, while δ18O (when combined with independent records) serves as proxy for (pan-)regional atmospheric conditions.
The stable carbon isotope record suggests repeated changes in vegetation density (open vs. dense forest), and increasing forest cover in the late Holocene. Concurrently, decreasing S/Ca values indicate more effective sulfur retention in better developed soils, with a stabilization in the mid-Holocene. This goes in hand with changes in effective summer infiltration, reflected in the Sr/Ca profile. Highest Sr/Ca values between 4 ka and 1 ka BP indicate intensified prior calcite precipitation resulting from reduced effective moisture supply.
The region of Bleßberg Cave is sensitive to shifts of the boundary between maritime (Cfb) and continental (Dfb) climate and ideally suited to reconstruct past meridional shifts of this divide. We combined the Bleßberg Cave δ18O time series with δ18O data from Bunker Cave (western Germany) and a North Atlantic Oscillation (NAO) record from lake SS1220 (SW Greenland) to reconstruct the mean position of the Cfb-Dfb climate boundary. We further estimate the dynamic interplay of the North Atlantic Oscillation and the Siberian High and their influence on Central European climate. Repeated shifts of the Cfb-Dfb boundary over the last 4000 years might explain previously observed discrepancies between proxy records from Europe. Detailed correlation analyses reveal multi-centennial scale alternations of maritime and continental climate and, concurrently, waning and waxing influences of Siberian High and NAO on Central Europe.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Central European climate is strongly influenced by North Atlantic (Westerlies) and Siberian High circulation patterns, which govern precipitation and temperature dynamics and induce heterogeneous climatic conditions, with distinct boundaries between climate zones. These climate boundaries are not stationary and shift geographically, depending on long-term atmospheric conditions. So far, little is known about past shifts of these climate boundaries and the local to regional environmental response prior to the instrumental era.
High resolution multi-proxyProxyUmwelt- und Klimainformationen aus der Vergangenheit sind nicht direkt verfügbar, weil niemand da war, der diese messen und aufzeichnen konnte. Daher ist man darauf angewiesen, diese Informationen indirekt aus anderen Informationen abzuleiten, wie z. B. Baumringe, das Verhältnis von Sauerstoffisotopen, Spurenelementen, Mächtigkeit von Sedimentschichten usw. Diese Art von Daten nennt man Proxies, was aus dem englischen stammt und „Stellvertreter“ bedeutet. data (stable oxygen and carbon isotopeIsotopChemische Elemente können aus verschieden aufgebauten Atomen gebildet sein. Die Anzahl Protonen im Atomkern ist zwar dabei gleich, aber die Anzahl der Neutronen kann variieren. Man spricht dann von Isotopen, deren Massen kleine, aber messbare Unterschiede aufweisen. Der Atomkern des Sauerstoffs besteht z. B. aus 8 Protonen und in der Regel aus 8 Neutronen. Es gibt aber auch Sauerstoff, dessen Kerne aus 8 Protonen und 9 oder 10 Neutronen bestehen (neben selteneren, instabilen Sauerstoffisotopen). Um das zu kennzeichnen, gibt man zusätzlich zum chemischen Symbol noch die Massenzahl (Summe aus Protonen und Neutronen) an, also 16O, 17O oder 18O. Die unterschiedlichen Isotope verhalten sich zwar chemisch identisch, physikalisch aber - aufgrund ihres unterschiedlichen Gewichtes - leicht unterschiedlich. Damit stellen sie äusserst wertvolle Marker dar, die uns wichtige Hinweise zur Änderung des Klimas, der Umgebungsvegetation, Bodenaktivität und vielem mehr geben. ratios, S/Ca and Sr/Ca) from two Holocene stalagmites from Bleßberg Cave (Thuringia) are used here to differentiate local and pan-regional environmental and climatic conditions Central Germany through the Holocene. Carbon isotope and S/Ca and Sr/Ca ratios inform us on local Holocene environmental changes in and around the cave, while δ18O (when combined with independent records) serves as proxyProxyUmwelt- und Klimainformationen aus der Vergangenheit sind nicht direkt verfügbar, weil niemand da war, der diese messen und aufzeichnen konnte. Daher ist man darauf angewiesen, diese Informationen indirekt aus anderen Informationen abzuleiten, wie z. B. Baumringe, das Verhältnis von Sauerstoffisotopen, Spurenelementen, Mächtigkeit von Sedimentschichten usw. Diese Art von Daten nennt man Proxies, was aus dem englischen stammt und „Stellvertreter“ bedeutet. for (pan-)regional atmospheric conditions.
The stable carbon isotope record suggests repeated changes in vegetation density (open vs. dense forest), and increasing forest cover in the late Holocene. Concurrently, decreasing S/Ca values indicate more effective sulfur retention in better developed soils, with a stabilization in the mid-Holocene. This goes in hand with changes in effective summer infiltration, reflected in the Sr/Ca profile. Highest Sr/Ca values between 4 kaka BPMit "ka BP" sind "Tausend Jahre vor 1950" gemeint. Das "BP" steht für "before present", was in der Paläoklima-Wissenschaft als 1950 festgelegt wurde. "11.000 ka BP" bedeuted also 11 Tausend Jahre vor 1950, oder unter Verwendung unseres gewohnten Kalenders: 9050 v. Chr. and 1 ka BPka BPMit "ka BP" sind "Tausend Jahre vor 1950" gemeint. Das "BP" steht für "before present", was in der Paläoklima-Wissenschaft als 1950 festgelegt wurde. "11.000 ka BP" bedeuted also 11 Tausend Jahre vor 1950, oder unter Verwendung unseres gewohnten Kalenders: 9050 v. Chr. indicate intensified prior calcite precipitation resulting from reduced effective moisture supply.
The region of Bleßberg Cave is sensitive to shifts of the boundary between maritime (Cfb) and continental (Dfb) climate and ideally suited to reconstruct past meridional shifts of this divide. We combined the Bleßberg Cave δ18O time series with δ18O data from Bunker Cave (western Germany) and a North Atlantic Oscillation (NAO) record from lake SS1220 (SW Greenland) to reconstruct the mean position of the Cfb-Dfb climate boundary. We further estimate the dynamic interplay of the North Atlantic Oscillation and the Siberian High and their influence on Central European climate. Repeated shifts of the Cfb-Dfb boundary over the last 4000 years might explain previously observed discrepancies between proxy records from Europe. Detailed correlation analyses reveal multi-centennial scale alternations of maritime and continental climate and, concurrently, waning and waxing influences of Siberian High and NAO on Central Europe.
@inproceedings{breitenbach2016,
title = {A multi-proxy reconstruction of Holocene climate change from Blessberg Cave, Germany},
author = {Sebastian F. M. Breitenbach and Birgit Plessen and Sarah Wenz and Jens Leonhardt and Rik Tjallingii and Denis Scholz and Klaus-Peter Jochum and Norbert Marwan},
url = {https://bbh.pik-potsdam.de/wp-content/uploads/2021/05/Breitenbach_poster_EGU_2016.pdf},
year = {2016},
date = {2016-04-01},
booktitle = {Geophysical Research Abstracts},
volume = {18},
pages = {EGU2016-14213},
abstract = {Although Holocene climate dynamics were relatively stable compared to glacial conditions, climatic changes had significant impact on ecosystems and human society on various timescales (Mayewski et al. 2004, Donges et al. 2015, Tan et al. 2015). Precious few high-resolution records on Holocene temperature and precipitation conditions in Central Europe are available (e.g., von Grafenstein et al. 1999, Fohlmeister et al. 2012).
Here we present a speleothem-based reconstruction of past climate dynamics from Blessberg Cave, Thuringia, central Germany. Three calcitic stalagmites were recovered when the cave was discovered during tunneling operations in 2008. Samples BB-1, -2 and -3 were precisely dated by the 230Th/U-method, with errors between 10 and 160 years (2σ). The combined record covers large parts of the Holocene (10 – 0.4 ka BP). δ13C and δ18O were analysed at 100 μm resolution. To gain additional insights in infiltration conditions, Sr/Ca and S/Ca were measured on BB-1 and BB-3 using an Röntgenanalytik Eagle XXL μXRF scanner.
Differences to other central European records (e.g., von Grafenstein et al. 1999, Fohlmeister et al. 2012) suggest complex interaction between multiple factors influencing speleothem δ18O in Blessberg Cave. Furthermore, no clear influence of the North Atlantic Oscillation on our proxies is found. However, a link across the N Atlantic realm is indicated by a centennial-scale correlation between Blessberg δ18O values and minerogenic input into lake SS1220 in Greenland over the last 5 ka (Olsen et al. 2012). In addition, recurrence analysis indicates an imprint of Atlantic Bond events on Blessberg δ18O values (Marwan et al. 2014), corroborating the suggested link with high northern latitudes. Larger runoff into the Greenland lake seems to be associated with lower δ18O, higher δ13C and S/Ca ratios, as well as lower Sr/Ca ratios in Blessberg Cave speleothems. This might be linked to lower local temperature and/or changes in precipitation seasonality. Opposing millennial scale trends with lowering S/Ca ratios and δ13C values but increasing Sr/Ca ratios calls for more than one controlling factor. Most likely, δ13C decreased through the Holocene due to afforestation, which in turn might have increased sulphate retention in the thickening soil cover (Frisia et al. 2005) and limited sulphur flux into the cave. Alternatively, marine sulfur flux could have diminished with winter wind intensities. However, additional data is required to clarify this hypothesis. A positive Sr/Ca trend through the Holocene might result from increasing prior calcite precipitation induced by a negative moisture balance in summer.},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}
Although Holocene climate dynamics were relatively stable compared to glacial conditions, climatic changes had significant impact on ecosystems and human society on various timescales (Mayewski et al. 2004, Donges et al. 2015, Tan et al. 2015). Precious few high-resolution records on Holocene temperature and precipitation conditions in Central Europe are available (e.g., von Grafenstein et al. 1999, Fohlmeister et al. 2012).
Here we present a speleothem-based reconstruction of past climate dynamics from Blessberg Cave, Thuringia, central Germany. Three calcitic stalagmites were recovered when the cave was discovered during tunneling operations in 2008. Samples BB-1, -2 and -3 were precisely dated by the 230Th/UU/Th-DatierungDie U/Th-Datierung ist eine sehr präzise radiometrische Altersbestimmung auf Basis der Uran-Thorium-Zerfallsreihe. Das Uran zerfällt mit bekannten Halbwertszeiten (245.500 Jahre) zum Tochterelement Thorium. Stalagmiten bauen bei ihrem Wachstum (fast) nur das wasserlösliche Uran ein, während das schlecht bewegliche Thorium zum größten Teil im Boden und Epikarst über der Höhle verbleibt. Das kann man nutzen, um die Zeit zu berechnen, die seit der Ausfällung der untersuchten Karbonatprobe vergangen ist. Moderne massenspektrometrische Verfahren erlauben Altersbestimmungen mit der U/Th-Methode bis zu 700.000 Jahren vor Heute.-method, with errors between 10 and 160 years (2σ). The combined record covers large parts of the Holocene (10 – 0.4 ka BP). δ13C and δ18O were analysed at 100 μm resolution. To gain additional insights in infiltration conditions, Sr/Ca and S/Ca were measured on BB-1 and BB-3 using an Röntgenanalytik Eagle XXL μXRF scanner.
Differences to other central European records (e.g., von Grafenstein et al. 1999, Fohlmeister et al. 2012) suggest complex interaction between multiple factors influencing speleothem δ18O in Blessberg Cave. Furthermore, no clear influence of the North Atlantic Oscillation on our proxiesProxyUmwelt- und Klimainformationen aus der Vergangenheit sind nicht direkt verfügbar, weil niemand da war, der diese messen und aufzeichnen konnte. Daher ist man darauf angewiesen, diese Informationen indirekt aus anderen Informationen abzuleiten, wie z. B. Baumringe, das Verhältnis von Sauerstoffisotopen, Spurenelementen, Mächtigkeit von Sedimentschichten usw. Diese Art von Daten nennt man Proxies, was aus dem englischen stammt und „Stellvertreter“ bedeutet. is found. However, a link across the N Atlantic realm is indicated by a centennial-scale correlation between Blessberg δ18O values and minerogenic input into lake SS1220 in Greenland over the last 5 ka (Olsen et al. 2012). In addition, recurrence analysis indicates an imprint of Atlantic Bond events on Blessberg δ18O values (Marwan et al. 2014), corroborating the suggested link with high northern latitudes. Larger runoff into the Greenland lake seems to be associated with lower δ18O, higher δ13C and S/Ca ratios, as well as lower Sr/Ca ratios in Blessberg Cave speleothems. This might be linked to lower local temperature and/or changes in precipitation seasonality. Opposing millennial scale trends with lowering S/Ca ratios and δ13C values but increasing Sr/Ca ratios calls for more than one controlling factor. Most likely, δ13C decreased through the Holocene due to afforestation, which in turn might have increased sulphate retention in the thickening soil cover (Frisia et al. 2005) and limited sulphur flux into the cave. Alternatively, marine sulfur flux could have diminished with winter wind intensities. However, additional data is required to clarify this hypothesis. A positive Sr/Ca trend through the Holocene might result from increasing prior calcite precipitation induced by a negative moisture balance in summer.
The three stalagmites BB-1 to BB-3 were geochemically investigated by GFZ Potsdam, Ruhr-Uni Bochum, PIK Potsdam, Uni Mainz and Northumbria University.
The dating was done at the University of Mainz. Stalagmite BB-1 grew 5,600 to 600 years ago, BB-2 6,200 to 3,700 years ago, and BB-3 (although the shortest) 11,200 to 5,300 years ago. At GFZ, carbon and oxygen isotopes (δ13C and δ18O) were measured in over 1,000 samples in BB-1, and about 400 and 540 samples each in BB-2 and BB-3. In parallel, the distribution of various elements was measured by X-ray analysis. Age modelling and statistical analysis were carried out at Ruhr-Uni Bochum, PIK Potsdam and Northumbria University.
In the age models of stalagmites BB-1 and BB-3, abrupt changes from slow to fast growth are evident at about 5,900 BC and from fast to more slow growth at about 2,600 BC.
Age models of stalagmites BB-1 and BB-3. Changes in growth rates at around 6,200 BC and between 5,900 and 2,600 BC can clearly be seen, for which climatic changes are responsible.
The temporal changes in isotope ratios were compared with palaeoclimate data from the Bunker Cave in North Rhine-Westphalia and from Greenland.
Isotope ratios in stalagmites BB-1 and BB-3 (combined). The longer-term trends probably reflect a change in solar influence. The short-term climate cooling around 6,200 BC is clearly visible in the isotope ratios. The abrupt drop in δ18O values around 900 to 1,200 AD coincides with the Medieval Warm Period.
This comparison allows an estimation of the spatial distribution of the influence of the maritime, humid and warm Atlantic climate in Central Europe. The Blessberg cave is located at the border between the influence of the Atlantic climate and the continental, drier and colder climate from the east. From the alternation between stronger similarities and greater differences in the regional climate at the Blessberg Cave and the Bunker Cave it can be determined when the climate zone boundary was east or west of the Bleßberg Cave, i.e. when the Atlantic, wetter and warmer climate and when the colder and drier continental climate prevailed over the Bleßberg Cave. This analysis could be carried out back to about 4,000 years ago (i.e. about 2050 BC). Before this time, due to the lack of data from Greenland, it is not yet possible to make conclusions regarding the location of the climate zone boundary, but at least around this time the Bleßberg Cave was probably under the influence of the Atlantic climate. Around 1850 BC it then changed to a continental climate (in the late Aunjetitz culture, known from the Nebra sky disc). Between 950 and 850 BC, the Atlantic influence became more dominant again (towards the end of the Urnfield Culture).
Shift of the climate zone boundary (dashed) to the east with hypothetical course (dotted) at the time of the Urnfield Culture (BU – Bunker Cave, BBH – Blessberg Cave).
