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40. Chronology and Climate Forcing of the Last Four Interglacials
Frank Sirocko, Martin Claussen, Thomas Litt, Maria Fernanda Sa´nchez Gon˜i, Andre´ Berger, Tatjana Boettger, Markus Diehl, Ste´phanie Desprat, Barbara Delmonte, Detlev Degering, Manfred Frechen, Mebus A. Geyh, Matthias Groeger, Masa Kageyama, Frank Kaspar, Norbert Ku¨ hl, Claudia Kubatzki, Gerrit Lohmann, Marie-France Loutre, Ulrich Mu¨ ller, Bert Rein, Wilfried Rosendahl, Katy Roucoux, Denis-Didier Rousseau, Klemens Seelos, Mark Siddall, Denis Scholz, Christoph Spo¨tl, Brigitte Urban, Maryline Vautravers, Andrei Velichko, Stefan Wenzel, Martin Widmann and Bernd Wu¨ nnemann
The last four interglacials (intervals during suggestions for future research themes, which global ice volume was similar to, or which will need to be answered soon if the less than, that of our current warm stage) climate of the past is to be of use for the correspond to the warmest parts of the mar- prediction of climatic and environmental ine oxygen isotope stages MIS 5, 7, 9, 11. evolution in the future when the natural These interglacials followed the 100-kyr forcing of climate has to interact with the rhythm of eccentricity, but each had different human influence on the atmosphere and insolation regimes, different durations, dif- land surface. ferent ice volumes and different sea-level heights, but atmospheric greenhouse gas concentrations were similar and reached STATEMENTS BY FIRST AUTHORS values which, by and large, were close to OF RESEARCH ARTICLES those of the current interglacial (Holocene or MIS 1) before the industrial revolution Martin Claussen, University Hamburg and led to the artificial enrichment of the atmo- Max Planck Institute for Meteorology, Hamburg, sphere’s greenhouse gas concentrations via Germany the burning of fossil fuels. The Holocene is addressed in a few papers, but an intercom- (1. Introduction to Climate Forcing and Cli- parison of the ongoing interglacial with the mate Feedbacks) past interglacials is not the focus of this book. This final paper of the book will summar- 1. Commonly, climate is defined as statis- ize the evidence presented and discussed in tics (mean, variance, ...) of the atmo- the research articles. It is intended to be sphere. In climate physics, however, a comprehensible to the lay reader and thus wider definition has proven to be useful does not go into detail. Every paper is repre- in which climate is viewed as the state sented by a list of three statements which and statistics of the climate system which sum up the key findings. This is followed by encompasses the atmosphere, the ocean, a synthesis of the current state of knowledge the ice and the land including the living on each of the climatic warm intervals dis- world, i.e. the marine and terrestrial bio- cussed in the book. There is almost complete sphere as well as carbon and nutrient agreement on several themes, in particular cycles. on the subject of insolation forcing, while 2. Climate varies on all timescales, not only other topics, such as the correlation of because of changes in climate forcing, but sequences dated by different techniques, also because of internal dynamics and will need to be discussed and evaluated feedbacks between the components of further before a consensus is reached. At the climate system which are seemingly the end of this paper, we make some unrelated to variations in forcing. //FS/ELS/PAGINATION/ELSEVIER AMS/STPS/3B2/CH40-N2955.3D – 595 – [595–614/20] 30.10.2006 7:12PM
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3. Not all climate variations on timescales 3. It is likely that changes in insolation longer than 30 years are directly driven caused by changes in orbital parameters by oscillation forcing; some of these varia- trigger fast internal feedbacks such as the tions could arise because of the sluggish water vapour–temperature feedback and dynamics of the deep ocean or the ice the snow–albedo feedback. Some feed- sheets or because of a strongly nonlinear, backs, like the snow–albedo feedback, disproportional response of the climate amplify climate changes very rapidly system to subtle variations in forcing. once a certain threshold in the system is crossed. Initial changes are then further Andre´ Berger, Universite´ catholique de amplified by slower feedbacks such as Louvain, Belgium biogeochemical and biogeophysical feed- backs and finally, the isostatic response (2. Insolation During Interglacials) of the lithosphere to icesheet loading. 1. The spectrum of the long-term variations Andre´ Berger, Universite´ catholique de of daily insolation is dominated by pre- Louvain, Belgium cession everywhere over the Earth and for any day except close to the polar night. (4. Modelling the 100-kyr Cycle – An Exam- 2. The energy received by the Earth over a ple From LLN EMICs) given time slice during the year defined in terms of the longitude of the Sun (an 1. The LLN model is a model of intermedi- astronomical season for example) is a ate complexity which takes into account, function of obliquity only, the length of in a simplified way, the atmosphere, the such astronomical seasons being a func- hydrosphere, the cryosphere, the bio- tion of precession only. sphere, the lithosphere, their mutual 3. The amplitude of the variations of insola- interactions and internal feedbacks. tion (in particular during the intergla- Under the forcing of insolation and a cials) is a function of the amplitude of progressively decreasing atmospheric the variations of precession. CO2 concentration, it simulates the tran- sition between the 41-kyr and the 100-kyr Martin Claussen, University Hamburg, and worlds around 850 kyr. Max Planck Institute for Meteorology, Ham- 2. The model also simulates the spectrum of burg, Germany the northern hemisphere ice volume over the last 450 kyr, with the strongest period (3. A Survey of Hypotheses for the 100-kyr at 100 kyr. Cycle) 3. It fails to reproduce the reduced ampli- tude of the 100-kyr cycles before 450 kyr 1. Even some 160 years after first geological with cool interglacials and cold glacials. evidence, the ice-age riddle is not yet fully solved. However, we have some clues on Frank Sirocko, University of Mainz, Germany which elements should constitute a theory of Quaternary Earth system dynamics, (5. Introduction: Palaeoclimate Reconstruc- regarding concepts and model structure. tions and Dating) 2. It is certain that the ice-age riddle cannot be explained in terms of a single domi- 1. The beginning, end and duration of the nating process. Instead, a systems past interglacials do not appear to be approach involving a number of feed- synchronous all over the world, i.e. back processes and the nonlinear nature parts of the climate system have been of the climate system is expected to lead in an interglacial state for longer than to a solution. others. //FS/ELS/PAGINATION/ELSEVIER AMS/STPS/3B2/CH40-N2955.3D – 595 – [595–614/20] 30.10.2006 7:12PM
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2. Beginning and end of interglacials in the 1. The last nine interglacial periods differ low latitudes and in the Antarctic lead to not only in height and variability of sea respective changes on the northern level, but also in timing relative to north- hemisphere. ern summer insolation peaks. 3. Time-transgressive climate shifts are also 2. Sea levels during MIS 5e, 9c and 11 were strong over Europe, where the sea-surface close to or slightly higher than modern sea temperature (SST) changes of the North level but sea level during MIS 7 may have Atlantic drift were associated with a step- been slightly lower than present day. wise shift of the vegetation zones, at least 3. Some interglacials have a single peak at the end of the past interglacial, with close to modern sea level (MIS 5e, 9c) interglacial conditions persisting for and others have several (MIS 7), while longer in southern Europe than in the MIS 11 persisted with little variation for north. at least 30 kyr.
Barbara Delmonte, DISAT, University Manfred Frechen, Leibniz Institute for Milano-Bicocca, Milano, Italy. Applied Geosciences (GGA-Institut) Hannover, Germany (6. Late Quaternary Interglacials in East Antarctica from Ice-Core Dust Records) (8. Uranium-Series Dating of Peat from Cen- tral and Northern Europe) 1. Aeolian dust records from deep East Ant- arctic ice cores preserve evidence for 1. Fen peat is suitable for uranium-series extremely low dust fluxes during the last dating under the asumption of complete five interglacials (10 to 25 times lower fractionation of uranium and thorium than in glacial periods). This is related during formation and no gain or loss of to reduced primary production and U and Th since the time of formation. mobilization of dust on the Southern 2. Uranium-series dating provides more Hemisphere continents, and to changes reliable and precise absolute dates of in atmospheric transport and the hydro- interstadial and interglacial peat layers logical cycle. The data show no evidence in Central Europe. Examples of uranium for pronounced cold events within the dates for MIS 5, 7 and 9 are: 91 2 kyr for last five interglacials (back to MIS 11.3). lignite (MIS 5c) from Zell in Switzerland,Æ 2. The Sr–Nd isotope fingerprint of aeolian 106 11 kyr for the fen peat (MIS 5e) dust in Antarctica suggests a dominant fromÆ Allt Odhar in Scotland, 214 8 kyr southern South American provenance for peat (MIS 7) from Groß-RohrheimÆ during Quaternary glacial times, but the in Germany and 317 14 kyr for fen first geochemical data for stage 5.5 and peat from Tottenhill QuarryÆ in Norfolk, the Holocene show significant differ- England. ences and opens up the possibility for 3. TIMS 230Th/U-dating results provide a different provenance mixing. chronological frame for terrestrial sedi- 3. Dust-size variability in the EPICA-Dome C ments such as fen peat, cave sinter and ice core suggests shorter transport time for travertine covering the past 500 000 dust or more direct air mass penetration to years. the site during interglacials with respect to cold periods. Denis Scholz, Heidelberger Akademie der Wissenschaften, Germany Mark Siddall, University of Bern, Switzerland (9. U-Redistribution in Fossil Reef Corals (7. Eustatic Sea Level During Past from Barbados, West Indies, and Sea-Level Interglacials) Reconstruction for MIS 6.5) //FS/ELS/PAGINATION/ELSEVIER AMS/STPS/3B2/CH40-N2955.3D – 595 – [595–614/20] 30.10.2006 7:12PM
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1. Postdepositional remobilisation produces interglacial sediments. The dated event is significantly wrong U-series ages of fossil the last optical bleaching of the sediment reef corals and may, therefore, have con- and the maximum determinable ages are sequences for the precise determination currently of the order of some hundred of the timing and duration of past inter- thousands of years, depending on sedi- glacials. ment properties and the luminescence 2. A small degree of U-redistribution can technique applied. A sufficiently long only be detected by analysis of a large exposure to sunlight prior to sedimentation number of samples but not by the con- is essential for correct age determination; ventional reliability criteria. an incomplete reset of the luminescence 3. MIS 6.5 sea level was between 50 11 signal will lead to age overestimation. and 47 11 m relative to the presentÀ Æ sea 2. Eemian deposits can be dated with ade- levelÀ fromÆ 176:1 2:8to168:9 1:4kyrBP. quate precision by conventional lumines- Æ Æ cence methods. These include multiple Bert Rein, Johannes Gutenberg-University, aliquot infrared stimulated (IRSL) techni- Mainz, Germany ques (using polymineral fine-grain and coarse-grain potassium feldpar samples) (10. Holocene and Eemian Varve Types of and, in some cases (of low radioactivity), Eifel Maar Lake Sediments) quartz optically stimulated luminescence (OSL) single-aliquot regeneration techni- 1. During the last interglacial, multicenten- ques. However, higher precision is nial periods of increased dust storm activ- reached by the infrared radiofluores- ity and aeolian dust deposition occurred cence method (IR-RF). Reliable lumines- at 126, 118 and 112 kyr BP. So far, no cence dating of older interglacials (MIS 7 evidence exists for comparable extreme, and 9) is only possible by the IR-RF multicentennial dry periods within the method. Holocene as observed in the deposits of 3. Dating of interglacial sediments requires, the last interglacial palaeolake. furthermore, the consideration of special 2. Besides the Younger Dryas sediments, dose rate-related problems: (i) the occur- which where deposited immediately rence of radioactive disequilibria and (ii) before the Holocene period, no indication layered sediments with varying radioiso- could be found for climatically induced tope content. In both cases, high analyti- dust storm activity during the Holocene. cal effort and model calculations are 3. The lithic maximum in the sediments of necessary to minimize the influence of the Little Ice Age (290–630 yr BP) does these sources of errors. not necessarily require a climatological explanation since it can be explained by anthropogenically induced soil erosion Stefan Wenzel, Schloß Monrepos, Neuwied, due to increasing population density Germany around the lake when medieval villages (12. Neanderthal Presence and Behaviour in on the surrounding plateau deserted. Central and Northwestern Europe During MIS 5e) Detlev Degering, Saxon Academy of Sciences, TU Freiberg, Germany 1. The majority of the few archaeological (11. Dating of Interglacial Sediments by sites of Central and Northwestern Eur- Luminescence Methods) ope which can be dated more precisely within MIS 5e are attributed to the first 1. Luminescence methods were successfully third of this interglacial (up to the applied in the age determination of Quercetum mixtum–Corylus phase). //FS/ELS/PAGINATION/ELSEVIER AMS/STPS/3B2/CH40-N2955.3D – 595 – [595–614/20] 30.10.2006 7:12PM
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2. So far, there is no evidence of hominid for the mechanisms underlying the cli- occupation in the Carpinus phase of the matic variability of the last interglacial. Eemian, and only a few archaeological sites are known from younger biozones Klemens Seelos, Johannes Gutenberg- of the Eemian. University, Mainz, Germany 3. In contrast to the rarity of archaeological (14. Aprupt Cooling Events at the Very End sites from the last two-thirds of the last of the Last Interglacial) interglacial, which could indicate a dete- rioration of living conditions, the early 1. The LEAP (late Eemian aridity pulse) Eemian sites and the sites solely attribu- is detectable in loess records of the Eifel ted to the Eemian evidence that the life- region and in the northern German ways of the Neanderthals living then record of Rederstall. differed little from those of their ances- 2. Taiga vegetation characterizes Rederstall tors and their successors occupying a in the first phase after the LEAP (after more open landscape: they hunted big 118 kyr) and develops gradually into game; they used a similar lithic technol- tundra after 115 kyr. At the same time, ogy, they practised long-distance trans- Carpinus-dominated temperate forest port of lithic artefacts (perhaps indicative spread in the Eifel region and in France, of social networks) and they performed and finally deteriorated at 111 kyr. symbolic behaviour. 3. Loess and pollen records in the Eifel region and northern Germany show the Maria Fernanda Sa´nchez Gon˜ i, Universite´ first drastic and fast cooling, associated Bordeaux 1, France with widespread aridity, during the C24 cold event (111 kyr). (13. Introduction to Climate and Vegetation in Europe During MIS 5) Denis-Didier Rousseau, Universite´ Montpel- lier II, France 1. The complexity, both temporal leads and lags and geographical variability, of the (15. Estimates of Temperature and Precipi- nonlinear climatic signal in response to tation Variations During the Eemian Inter- insolation changes during the penulti- glacial: New Data From the Grande Pile mate deglaciation, last interglacial and Record (GP XXI)) last glacial inception is clearly shown by the collection of papers presented in this 1. We applied a new method on new pol- chapter. len data from Grande Pile, the inverse 2. Problems of nomenclature and stratigra- mode to the Biome4 vegetation model. phy for the last interglacial, reflecting the The method utilizes 13C, measured in history of the discipline, are on the way parallel to the pollen samples as a con- to being solved, although uncertainties in straint for the model. First the biomes the chronology of a number of MIS 5 and the 13Csimulatedbythemodel records require further investigation. are compared with the biome alloca- 3. Our scientific community should concen- tion of the pollen data. The 13Ctobe trate its efforts in accurately correlating simulated takes into account the degra- the available records. It is only through dation effect on the preserved organic this approach that we will be able to matter. document the climatic variability of MIS 2. This study highlights variation ranges of 5 in an integrated way, link the processes annual precipitation and/or temperature reflected in different parts of the Earth narrower using an inverse modelling system and propose reliable scenarios procedure with 13C than without. These //FS/ELS/PAGINATION/ELSEVIER AMS/STPS/3B2/CH40-N2955.3D – 595 – [595–614/20] 30.10.2006 7:12PM
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narrow ranges allow to reveal expected of vegetation during the Eemian Intergla- climatic trends that were noticed in mar- cial were similar in the Central and ine sediments but not precisely recon- Eastern Europe. structed on the continent. 2. We demonstrate the regional pattern of 3. The variations in temperature appear to vegetation in the Eemian and Early be related to SST oscillations in the North Weichselian. Mixed broad-leaved forests Atlantic region and are also in agreement in Central Europe included species that with the timing of ice-sheet build-up in characteristically require a certain ocea- the Northern Hemisphere. Seasonal nicity of climate (e.g. Ilex aquifolium, variations are also identified in the esti- Hedera helix and Taxus baccata). The parti- mated temperatures of the warmest and cipation of these plants decreased east- coldest months. ward. Of those species, only Tilia platyphyllos and Viscum album are found Norbert Ku¨ hl, University of Bonn, Germany in the Eemian pollen assemblages in the East European Plain. Plant communities (16. Quantitative Time-Series Reconstruc- also differed noticeably from west to east tions of Holsteinian and Eemian Tempera- during the cooler intervals at the begin- tures Using Botanical Data) ning and end of the interglacial, primar- ily in the proportion of broad-leaved 1. Reconstruction of Eemian and Holstei- species in zonal vegetation formations. nian temperatures shows uninterrupted 3. Significant contrasts in environmental interglacial conditions for both intervals. and climatic fluctuations mark the However, the Holsteinian seems to be Saalian/Eemian boundary (transition less stable than the Eemian with some from MIS 6 to MIS 5e). Two substages intra-interglacial coolings. of vegetation development can be 2. The course of temperature change within identified in the pollen diagram. Pine the Eemian and Holsteinian interglacial and spruce forest with shrubs occurred stages differs. Holsteinian January and in the earliest phase. Then open birch July temperatures were higher in the woodlands and steppe-like commu- later part of the interglacial, while the nities occupied the area. Vegetation Eemian had its temperature optimum dynamics at this boundary resemble during the early phase. those detected at the transition from 3. The temperature decline at the very end Weichselian to Holocene (Allerød and of the Holsteinian interglacial resembles Younger Dryas). in magnitude the decrease at the end of the Eemian. Reconstructions reveal a Tatjana Boettger, UFZ Centre for Environ- drop in mean January temperature by mental Research Leipzig-Halle, Germany 10–15C and in mean July temperature by about 3C. (18. Indications of Short-Term Climate Warming at the Very End of the Eemian in Terrestrial Records of Central and Eastern Andrei Velichko, Institute of Geography RAS, Europe) Moscow, Russia (17. Comparative Analysis of Vegetation 1. Geochemical and palynological investiga- and Climate Changes During the Eemian tions of lacustrine sediments from Central Interglacial in Central and Eastern Europe) and Eastern Europe document at least two warming events during the transition 1. As follows from comparison of pollen from the Eemian to the Early Weichselian data, the main phases in the evolution on a broad European transect. //FS/ELS/PAGINATION/ELSEVIER AMS/STPS/3B2/CH40-N2955.3D – 595 – [595–614/20] 30.10.2006 7:12PM
Chronology and Climate Forcing 603
2. The first pronounced warming phase 1. In the Gulf Stream area, eight periods can takes place towards the very end of be recognized between 108 and 134 kyr the Eemian. The second climatic ameli- related to changes in the intensity of oration was detected within the first summer stratification and late winter Weichselian Stadial (Herning). mixing. 3. Correlations between Eemian European 2. At the end of MIS 5e (122–116 kyr), win- terrestrial sequences and their possible ter SST are at their maximum while connection to the NGRIP record are summer SST start to decrease. Superim- discussed. Generally, it appears that posed on this trend, we found several warming phases towards the end of the high-frequency cooling events. last interglacial preceded the final transi- 3. Most of these small coolings are asso- tion to glacial conditions. ciated with lithics peaks testifying for ice- berg incursions in the subtropical area Ulrich Mu¨ ller, Johann Wolfgang Goethe during the last interglacial. University Frankfurt, Germany Bert Rein, Johannes Gutenberg University, (19. Vegetation Dynamics in Southern Mainz, Germany Germany During Marine Isotope Stage 5 ( 130 to 70 kyr Ago)) (21. Abrupt Changes of El Nin˜o Activity off Peru During Stage MIS 5e-d) 1. The Eemian interglacial in southern Germany is characterized by dense ther- 1. El Nin˜o activity sharply dropped during mophilous deciduous forests during the the last interglacial, as it did uring the early and middle part and coniferous middle of the Holocene when perihelion forests in the late part of the interglacial. occurred in late summer. However, dur- 2. The exact timing and persistence of ing MIS 5d, the strength of El Nin˜o activ- Eemian forests in southern Germany is a ity did not recover with more favourable matter of debate. Varve chronologies insolation conditions as was observed suggest a duration of Eemian forests during the late Holocene. from 126 to 115 kyr BP in northern 2. The strong El Nin˜o activity that was indi- Germany and from 127 to 109 kyr BP cated by the Zebiak and Cane ENSO in southern Italy. Possibly, Eemian for- model according to orbital forcing did ests existed in southern Germany from not occur in Peru at the beginning of the 126 to 110 kyr BP. last glaciation. The transition into a gla- 3. A comparison of vegetation reconstruc- cial world apparently changed critical tions across Europe points to a steepen- boundary conditions, which are linear- ing of meridional vegetation gradients ized around a current mean climatology during the declining stage ( 115 to in the ZC ENSO model. 109 kyr BP) of the last interglacial. Presumably, the steepening of vegetation Bernd Wu¨ nnemann, Freie Universita¨t Berlin, gradients was associated with a south- Germany ward displacement of the warm North (22. Interglacial and Glacial Fingerprints Atlantic current. from Lake Deposits in the Gobi Desert, NW China) Maryline Vautravers, University of Cambridge and British Antarctic Survey, 1. Hydrological changes in the Chinese Cambridge, UK Gobi Desert are strongly interlinked with (20. Subtropical NW Atlantic Surface Water climate dynamics on the Tibetan Plateau Variability During the Last Interglacial) during the last interglacial–glacial cycle //FS/ELS/PAGINATION/ELSEVIER AMS/STPS/3B2/CH40-N2955.3D – 595 – [595–614/20] 30.10.2006 7:12PM
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2. The Eemian interglacial stage between assume that periods of interglacial con- 129 and 119 kyr appears to have been a ditions necessarily resulted in forest period of positive water balance within vegetation everywhere for their whole the Gaxun Nur Basin as a result of warm duration. and moist climate conditions with enhanced summer monsoon moisture. Ste´phanie Desprat, Universite´ Bordeaux1, 3. The subsequent rapid increase of climate France instability with phases of colder and drier conditions coincides with strong (25. Climate Variability of the Last Five Iso- shrinkages of lake size and enhanced topic Interglacials: Direct Land–Sea–Ice aeolian transport, frequently influenced Correlation from the Multiproxy Analysis by the extra-tropical westerlies and the of North-western Iberian Margin Deep Sea winter monsoon. Cores)
1. The last five isotopic interglacials (MIS 1, Katy Roucoux, University of Leeds, UK 5, 7, 9 and 11) were investigated in (24. Fine Tuning the Land–Ocean Correla- NW Iberian margin deep-sea cores, using tion for the Late Middle Pleistocene of terrestrial (pollen) and marine (planktic Southern Europe) foraminifera, benthic and planktic fora- minifera oxygen isotopes) climatic 1. There are pronounced phase offsets indicators. between forested intervals in Portugal 2. This work shows that the climatic and marine isotope-defined warm inter- variability detected on the continent is vals. For example, MIS 7e lasts from 246 contemporaneously recorded in the to 229 kyr, while the forested interval ocean. Although minima and maxima associated with it lasts from 243.2 to of ice volume and marine and terrestrial 237 kyr. temperatures in the NW Iberian region 2. Forested intervals varied in length from appear synchronous, temperature changes one warm stage to the next, and correla- are not in phase with ice volume varia- tion of marine and terrestrial pollen tions. Particularly, substantial ice accumu- sequences indicates that this pattern lation at high latitudes, associated with the applies across southern Europe. In the glacial inception of these past interglacials, marine pollen record of MD01-2443, the generally lags NW Iberian temperature shortest forested period, at 3.5 kyr long, is decrease by some millennia. the Lisboa forest interval associated with 3. The comparison of the different marine MIS 9e, while the longest uninterrupted isotope stages highlights a common pat- forested period, at 10 kyr long, is the tern of climatic dynamics within these Cascais forest interval associated with isotopic interglacials, which is character- MIS 7c. ized by three major climatic cycles, 3. Forested intervals also varied in floristic related to orbital cyclicity, on which sub- character across southern Europe as a orbital climatic fluctuations are superim- result of local climatic, geological and posed. biogeographical factors. For example, it appears that while tree populations Mebus A. Geyh, Leibniz Research Institute of were replaced by Ericaceous heath in Geosciences, Hannover, Germany Portugal at the end of the forested inter- vals associated with MIS 7e and MIS 9e, (26. Palynological and Geochronological coniferous forest thrived elsewhere in Study of the Holsteinian/Hoxnian/Landos southern Europe. Hence, we cannot Interglacial) //FS/ELS/PAGINATION/ELSEVIER AMS/STPS/3B2/CH40-N2955.3D – 595 – [595–614/20] 30.10.2006 7:12PM
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1. Based on new TIMS 230Th/U dates from a change from a temperate forest to an two fen peat layers of the Holsteinian open boreal forest within centuries. reference site at Bossel, from several Holsteinian and non-Holsteinian profiles Brigitte Urban, University of Lu¨neburg, Germany in northern Germany as well as on re- evaluated numerical 230Th/U dates from (28. Interglacial Pollen Records from Scho¨- two sites with Hoxnian deposits in ningen, North Germany) England, the Holsteinian Interglacial has an 230Th/U age of about 320 kyr and 1. The complex Pleistocene sequence of the therefore is correlated with MIS 9. Scho¨ningen browncoal mine, Germany, 2. There is palynological evidence for a reli- contains six major cycles (I–VI) providing able correlation between precisely biostratigraphical evidence of four intergla- analysed Holsteinian and Hoxnian depos- cials (Holsteinian, Cycle I, Reinsdorf, Cycle its in Poland, Germany, England, SW- II, Scho¨ningen Cycle III, Eemian, Cycle V) Ireland and France. and a number of interstadials younger than 3. It became obvious that the Holsteinian the Elsterian glaciation and preceding the interglacial is correlated with the Holocene (Cycle VI) being tentatively cor- Landos interglacial rather than with the related with MIS 5, 7, 9 and 11 respectively. Praclaux interglacial. The latter belongs 2. The position of the Lower Palaeolithic to MIS 11 and is linked with the Rhume spruce throwing spears of Scho¨ningen interglacial. can be assigned to the ultimate and already cool and dry Reinsdorf intersta- dial B of Cycle II (MIS 9/8?), character- Markus Diehl, Johannes Gutenberg-University, ized by a pine-birch open forest. Mainz, Germany 3. MIS 7 and MIS 9 (tentatively correlated (27. A New Holsteinian Pollen Record from with the Scho¨ningen and Reinsdorf inter- the Dry Maar at Do¨ttingen (Eifel)) glacials, respectively) differ strongly in their moisture regime as shown by the 1. The Do¨ttingen pollen sequence is the first low presence of fir (Abies) in terminal Holsteinian pollen profile from middle- phases of the Reinsdorf and its total lack southern Germany. It represents a ‘low in the Scho¨ningen interglacial, pointing mountain range-type’ Holsteinian vegeta- to an increasing dryness of the forested tion succession, to correlate with that of periods (interglacials) following the the north German lowlands, but with dif- Holsteinian in northern Germany. ferent pollen percentage values, showing that the pine-birch dominance of the Wighart von Koenigswald, University of north German profiles cannot be seen as Bonn, Germany a overregional, typical Holsteinian signature. (29. Mammalian Faunas From the Intergla- 2. The first spike of pine-birch dominance cial Periods in Central Europe and Their (sometimes interpreted in Northern Stratigraphic Correlation) Germany as a cooling event) is also visible at Do¨ttingen, but is preceded by a 1. The MIS 5e, 7, and 9 can be distinguished volcanic ash layer. The Do¨ttingen sequence only vaguely by the mammalian fauna. thus points towards a causal connection Their diversity in insectivores and rodents between volcanic activity and the Holstei- is smaller than in the pre-Elsterian faunas. nian vegetation development. The only taxon showing an evolutionary 3. The transition of the Holsteinian to the trend is large vole Arvicola changing from subsequent cold stage is characterized by cantianus to terrestris at about the Eemian. //FS/ELS/PAGINATION/ELSEVIER AMS/STPS/3B2/CH40-N2955.3D – 595 – [595–614/20] 30.10.2006 7:12PM
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2. The multiple climatic changes during Climatically Sensitive High-Elevation Cave the middle and upper Pleistocene Site in the Alps) caused an almost complete exchange of the mammalian fauna. In each inter- 1. Changes in climate during MIS 5 to 7 glacial period, the Mammuthus assem- identified by speleothem growth periods blage adapted to the cold climate and oxygen isotope data are synchro- disappeared and the Elephas assemblage nous within the precision of the U/Th immigrated from the Mediterranean method with coral records of sea-level region. Most mammalian lineages do changes. not show a continuous evolution in 2. During MIS 7, the climate in the Alps was Central Europe. Immigration and local cooler, glaciers were larger and the tim- extinction is the normal pattern. berline was lower than during MIS 5e. 3. The occurrence of the exotic Hippopotamus Speleothem growth during MIS 7 com- amphibius, known in recent times only menced 236 kyr and ended 190 kyr from Africa, does not indicate very high ago. temperatures or during the Eemian, but 3. Full interglacial conditions during MIS 5e more likely a high maritime influence were reached 130 kyr ago and terminated with mild winters. 118–119 kyr ago.
Wilfried Rosendahl , Reiss-Engelhorn- Martin Claussen, University Hamburg and Museen, Mannheim, Germany. Max Planck Institute for Meteorology, (30. MIS 5 to MIS 8 – Numerically Dated Hamburg, Germany Palaeontological Cave Sites of Central Europe) (32. Climate System Models – A Brief Intro- duction) 1. The numerical dates (MIS 5 - MIS 8) now available for palaeontological cave sites 1. In climate physics, climate models are a in Central Europe (12 sites with 31 dated set of mathematical equations which are strata) do not allow a critical discussion derived from physical principles and of their faunal assemblages with regard which are used in a prognostic mode to to their ecological-climatic distribution, predict climate variations as function of with the exception of two sites. But even some external forcing or which are tuned these two sites are not without contra- to data to interpolate between sparse dicting faunal elements, and it remains data in time and space in a physically uncertain whether they represent glacial consistent manner. or interglacial faunas. 2. When comparing data and model results, it 2. In spite of all these problems, palaeonto- is important to realize that climate is logical cave sites represent a rich archive regarded as stochastic processes; therefore, that can deliver important contributions it is not possible to predict all climate varia- to the reconstruction of the Middle and tions such as the precise course of a glacial Upper Pleistocene palaeoclimate of Cen- interception in a deterministic way. tral Europe, provided many additional 3. Only the interpretation of past climate dates can be obtained to verify results variations by using mathematical climate obtained from other terrestrial archives. models, which are validated against palaeoclimate evidence, will lead to pic- Christoph Spo¨tl , Leopold-Franzens-Universita¨t ture of climate which is consistent with Innsbruck, Austria the physical understanding of our world. (31. The Last and the Penultimate Intergla- 4. In this chapter, models of different cial as Recorded by Speleothems From a complexity are used. In chapters 33, 34 //FS/ELS/PAGINATION/ELSEVIER AMS/STPS/3B2/CH40-N2955.3D – 595 – [595–614/20] 30.10.2006 7:12PM
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and 35, results of a comprehensive atmo- as used in the previous section) indicate sphere ocean model or even an that orbital forcing can change relation- atmosphere ocean–vegetation model (in ships between different climate variables. chapter 37) are discussed. In chapters 36, 2. Simulated temperature signals of multi- 38 and 39, models of intermediate com- decadal variations in the Arctic oscillation plexity are used which interactively simu- index are weaker in Europe and stronger late the dynamics of the atmosphere, the in Siberia during the Eemian compared to oceans, vegetation and ice sheets. the preindustrial period. 3. Simulated teleconnections between Frank Kaspar, Max Planck Institute for annual to decadal temperature variabil- Meteorology, Hamburg, Germany ity at different locations are related to the Arctic Oscillation temperature signal, (33. Simulations of the Eemian Interglacial and can be somewhat different in the and the Subsequent Glacial Inception with a Eemian and in the preindustrial period. Coupled Ocean-Atmosphere General Circu- lation Model) Gerrit Lohmann, Alfred Wegener Institute for Polar and Marine Research, Bremerhaven, 1. European seasonal patterns of pollen- Germany. based temperature reconstructions for the early Eemian (at 125 kyr) are in good (35. Orbital Forcing on Atmospheric agreement with simulation results of a Dynamics During the Last Interglacial and state-of-the-art coupled ocean atmosphere Glacial Inception) general circulation model (ECHO-G) which was driven by orbitally induced changes 1. Atmospheric dynamics plays an impor- in insolation. tant role on orbital timescales, e.g. the 2. When the same model is driven with modulation of the Icelandic Low. insolation patterns of the last glacial 2. The atmospheric teleconnections provide inception at 115 kyr, the significantly a bridge between low and high latitudes reduced summer insolation of the north- and transport the precessional forcing to ern latitudes leads to a distinct cooling of high latitudes. the northern hemisphere and the occur- 3. The related atmospheric circulation pat- rence of a perennial snow cover over terns induce nonuniform temperature parts of North America. anomalies which can have a greater 3. The snow cover initially occurs in the amplitude than those resulting from region of the Canadian Archipelago, direct solar insolation forcing. where cool southward winds from the 4. Transient simulations are performed Arctic prevail, and it is continuously using the coupled atmosphere–ocean– expanding into the continent during the sea ice general circulation model simulated period of several millennia. ECHO-G by applying a novel accelera- tion technique. Martin Widmann, GKSS Research Centre, Geesthacht, Germany, and University of Andre´ Berger, Universite´ catholique de Birmingham, UK Louvain, Belgium (34. Simulated Teleconnections During the (36. Interglacials as Simulated by MOBIDIC Eemian, the Last Glacial Inception and the and the LLN 2-D Climate Models) Preindustrial Period) 1. The LLN models succeed to reproduce 1. Simulations with a coupled atmosphere– the interglacials of the last 450 kyr as a ocean general circulation model (the same response to insolation and CO2 provided //FS/ELS/PAGINATION/ELSEVIER AMS/STPS/3B2/CH40-N2955.3D – 595 – [595–614/20] 30.10.2006 7:12PM
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feedbacks are correctly taken into (38. Mechanisms Leading to the Last Glacial account, in particular those related to Inception over North America: Results From water vapour, surface albedo and iso- the CLIMBER-GREMLINS Atmosphere- static rebound. Sensitivity analyses show Ocean-Vegetation-Northern Hemisphere Ice- that glacial–interglacial cycles cannot be Sheet Model) simulated under CO2 forcing alone. Using the insolation forcing alone, 1. The CLIMBER-GREMLINS model, in glacial–interglacial cycles are simulated which the atmosphere, the ocean, the vege- but only under low constant CO2 values tation and the northern hemisphere ice (under 230 ppmv). sheets and the interactions between those 2. Prediction for the next hundreds of thou- components are represented, simulates a sands of years leads to a very long inter- glacial inception over northern North glacial MIS 1. This length is similar to what America under the transient insolation was simulated for MIS 11. In both cases, and CO2 forcings of the period 126–106 kyr. these extremely long interglacials seem to 2. Glacial inception does not occur when be related to the very low eccentricity vegetation is fixed to its interglacial state value which prevails during these times, and is twice as slow, in terms of volume, the orbit of the Earth being almost circular. when the icesheet albedo feedback is not 3. In mid- and high latitudes during MIS 5e, taken into account. sea-surface temperature in summer starts 3. The role of the ocean and sea ice are more to decrease 11 kyr before the ice sheets ambiguous. A first experiment in which start to grow over the continents. the seasonal cycle of the ocean surface characteristics is fixed to its interglacial state shows that this yields a faster incep- Matthias Groeger, Max-Planck-Institut fu¨r tion than with an interactive ocean. On the Meteorologie, Hamburg, Germany other hand, when the Atlantic meridional (37. Vegetation – Climate Feedbacks in Tran- overturning circulation is forced to stop, sient Simulations Over the Last Interglacial this yields an even faster inception. (128 000–113 000 yr BP)) Claudia Kubatzki, Alfred Wegener Institute 1. During the Eemian, considerable changes for Polar- and Marine Research, Bremerhaven, in the land surface properties are simu- Germany lated with a coupled ocean atmosphere vegetation marine biogeochemistry (39. Modelling the End of an Interglacial model (ECHAM3.6 – LSG2 – LPJ – (MIS 1, 5, 7, 9, 11)) HAMOCC); among these the northward expansion of boreal forests, and the 1. The CLIMBER-SICOPOLIS model, which greening of the Sahara desert are the most describes the dynamics of atmosphere, pronounced ones. ocean, vegetation and northern hemi- 2. On land, the areas most sensitive to inso- spheric inland ice, simulates a glacial lation are the northern high latitudes and inception over northern North America the northern hemisphere monsoon belt. at about 117.5 kyr as a result of mainly 3. In these regions, vegetation feedbacks changes in precession (perihelion), obli- can amplify the insolation-forced climate quity as well as CO2 changes act as change by a factor of 2. amplifiers. 2. Glacial inception in North America at the Masa Kageyama, Laboratoire des Sciences du end of the Eemian might not have hap- Climat et de l’Environnement, Gif sur Yvette pened with vegetation and ocean surface Cedex, France remaining at their interglacial (Eemian) //FS/ELS/PAGINATION/ELSEVIER AMS/STPS/3B2/CH40-N2955.3D – 595 – [595–614/20] 30.10.2006 7:12PM
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state, i.e. the feedback of the changing appear to respond to orbital forcing ear- Earth’s surface on climate is needed lier than the north. (compare with 38). 3. Cold events at the end of the interglacial MIS 5 can be reproduced, by the introduction of freshwater disturbances into the model 1. The last interglacial MIS 5 began earlier North Atlantic. than 135 kyr in the low latitudes with a humid phase in Equatorial Africa, i.e. at a Synthesis on the chronology and forcing of time when the seasonal contrast between climate change during the last interglacials spring and fall insolation was at a max- imum, which is a condition favourable 1. There is clear evidence that insolation for strong El Nin˜o, which apparently changes are the primary driver of past increased suddenly in strength at the climate variations. The 100-kyr rhythm end of the MIS 6 ice age. of eccentricity dominates the occurrence 2. Sea level began rising also around of past interglacials, but it is still not 135 kyr, leading to Termination II with fully understood why interglacials have the main transgression during the time occurred even at times when insolation of strong increase of northern summer on the northern hemisphere was quite insolation. The first well-dated evidence low in absolute terms (for example, of interglacial conditions in central during MIS 11). Presumably, it is not Europe come from speleothems in the the amplitude of insolation, but the Spannagel cave at 130 kyr, which impli- change of the amplitude, which drives cates that the mean annual temperature the climate system to cross some in the Alps were on a modern level well thresholds. before the northern insolation maximum 2. Some model studies indicate that preces- at 127 kyr. This is consistent with spe- sion is the main driver of glacial inception. leothem data from Italy, where the onset 3. North Atlantic SST patterns, mainly a of the last interglacial has recently been function of deep-water formation in the determined at 129 1 kyr. This date Æ far north Atlantic, are an important should be the beginning of the Eemian mechanism for the temperature and sensu stricto on the continent, but this availability of moisture in central Europe. date is in conflict with a marine age 4. Also changes in vegetation cover, mainly model which places the beginning of the a shift in Artic tree line, and changes Eemian sensu stricto at 126 kyr 2, estab- Æ in ocean dynamics appear to amplify lished on botanical grounds in a marine glacial–interglacial climate changes. In core off Portugal. some models, a glacial inception does 3. The Eemian, sensu strictu (Zagwijn, not occur if vegetation is set to interglacial 1961), is characterized by a typical suc- values. cession of pollen zones (E1/E2: Betula– 5. Ice melting (Termination) and ice accu- Pinus forest, E3: Quercetum mixtum, mulation (glacial inception), primarily E4: Quercus–Corylus forest, E5: Carpinus controlled by 100 000-year insolation forest, E6: Picea–Abies forest), which can changes, occurred in the high latitudes be correlated across Europe and has a of the northern hemisphere and were duration of about 10 000 years according synchronous by definition. What did not to varve counts in northern Germany and occur simultaneously was the response in the Eifel. of the different regions in the world to 4. A direct correlation between pollen and these insolation changes. The southern marine proxies conducted on Iberian hemisphere and low-latitude regions margin deep-sea cores indicates that a //FS/ELS/PAGINATION/ELSEVIER AMS/STPS/3B2/CH40-N2955.3D – 595 – [595–614/20] 30.10.2006 7:12PM
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time lag exists between ice volume 8. About 118 kyr is identified by several decay/growth and forest development model experiments with ice-sheet in Europe during the last interglacial dynamics as the time when snow cover sensu strict,: (1) the minimum in ice in North America became perennial and volume is reached at 128 kyr, 2000 years the ice sheet over North America began before the onset of the Eemian forest. (2) to expand significantly. The cause for The substantial accumulation of ice in the perennial snow and expansion of high northern latitudes (MIS5e/MIS5d ice sheets is most likely a threshold in transition) occurs at 115 kyr, i.e. 5000 the insolation regime, with summer years before the demise of the temperate insolation being no more sufficient to and conifer forests in Iberia, France and melt the snow in the northern Arctic of the Eifel. The 11 000-year duration of the North America. The further increase in Eemian in northern European latitudes ice-sheet extent is caused by a positive above 50N suggests that tundra vegeta- feedback, i.e. further cooling over the tion expanded during the first 5000 years snow and ice with a high albedo and of MIS 5d when forest still occupied growing ice sheets with higher and southern latitudes. cooler surfaces. 5. Earth models of intermediate complexity 9. During the entire length of MIS5 (EMIC) indicate that the shift in Arctic (132–74 kyr), seven episodes of ice raft- tree line played a major role in the last ing, C19 to C25, occurred in the mid- glacial inception, mainly via the albedo latitude North Atlantic related not only changes around 122–120 kyr. Pollen data to periods of maximum ice volume but are in agreement with this prediction as also to episodes of ice-sheet growth and they identify a replacement of the tempe- decay. The beginning of the substantial rate forest by conifers at 52N as early as ice-sheet growth, MIS5e/MIS5d transi- 120 kyr. This suggests a southward dis- tion (115 kyr), is associated with a 2–3C placement of the boreal vegetation belt of reduction in surface water temperature around 10 by comparison to its location and labelled C26 event, but no ice-rafted (60N–70N) at the beginning of the detritus have been recorded. Eemian. 10. The Laurentian ice sheet became first 6. There are no indications of abrupt cooling unstable at around 112 kyr (C25 event), during the Eemian sensu stricto. Air tem- and the surface water of the mid-North perature reconstructions for central Eur- Atlantic experienced a widespread sub- ope based on botanical fossils reveal a stantial cooling by at 6-7 C. slight summer cooling (2C/10 kyr) and 11. Major icebergs surged for the first time a little stronger winter cooling (3C/ not before 110 kyr (C24), i.e. after a 10 kyr) for the Eemian sensu stricto. How- growth period of 8000 years, which ever, climatic reconstructions from a new would be enough time to reach a height pollen dataset of La Gande Pile using an of more than 1 km. This pronounced inverse modelling procedure with 13Cto cold event coincides, based on the direct constrain pollen data-derived estimations correlation between marine proxies and would identify substantial climatic pollen, with the Me´lisey I steppic period changes within the Eemian. on land. 7. Stalagmite growth at Spannagel termi- 12. Sea-level drop was about 50 m between nates at 118–119 kyr, which leaves us the last glacial inception around 118 kyr with a time of about 10 000–12 000 and C24, corroborating the build-up of a years at which annual temperature in massive ice sheet. the Alps were quite similar to modern 13. CO2 was still at an interglacial level conditions. during these first seven millennia of //FS/ELS/PAGINATION/ELSEVIER AMS/STPS/3B2/CH40-N2955.3D – 595 – [595–614/20] 30.10.2006 7:12PM
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the new ice age (118–111 kyr), indicating MIS 7.3 and MIS 7.1. Generally, the mag- that the global carbon cycle responded nitude of the different climatic changes of to changing insolation later than the MIS 7 is large and mirrored by the volume atmosphere or even later than the ice- of ice in concert with the large amplitude sheets in their initial growth phase. of insolation variations which charac- 14. Vegetation around the Mediterranean, terizes this stage. MIS 7.4 shows similar France and into the Eifel region showed climatic conditions as the previous glacial: a continuation of almost interglacial icecaps were particularly developed and conditions from 118 to 111 kyr. Vegeta- related with the coldest and driest climate tion in northern Europe at this time was on the continent and the lowest sea sur- already cold adapted. face temperatures of MIS 7. 15. The major vegetation change in the 2. The equivalent of MIS 7 in continental Mediterranean and also in the Eifel European is well developed in southern region occurred during C24, when the European long sequences from the Velay late interglacial forest changed abruptly region (Massif Central, France), Valle di to tundra in central Europe, to steppe in Castiglione (Italy) and Tenagi Phillipon western Europe between 50N and 40N (Greece). This stage is characterized by and to a semidesert in the Mediterra- three warm phases interrupted by nean region. stadials. It is interesting to note that none 16. Severe cold and aridity is most likely the of these warm intervals in the Massif effect of severe SST lowering during Central (named as Bouchet interstadials C24 over the North Atlantic, caused by 1–3) reach the climatic state of a fully a spread of icebergs and a cold melt- developed interglacial (such as in MIS water lid that inhibited deep-water for- 5e or 9e and 11c), while they did in mation and advection of warm waters sequences from Greece and Italy. from the Carribean via the North Atlan- 3. There is no direct link between the north- tic drift (Gulf Stream). central European terrestrial records and 17. The final successive minor cold episode the marine isotope stages. In addition, of MIS 5 was the C21 event (86 kyr), the correlation with long continental Me´lisey II on land, which was also char- sequences in southern Europe is under acterized by massive ice discharges. C24 debate caused by uncertainties of absolute and C21 were coincident with the most dating older than the last interglacial. extreme glacial events MIS 5d and MIS 4. There is some evidence in north-central 5b, respectively. Icebergs did not reach Europe of at least one warm event that the southern latitudes below 40N could be correlative with the warm inter- during any of these seven events. vals of MIS 7: the Do¨mnitz warm stage in northeastern Germany, the possibly synonymous Wacken warm stage in MIS 7 northwestern Germany and the Rein- 1. Similar to MIS 5, a direct link between sdorf and Scho¨ningen warm stages. terrestrial pollen and marine benthic/ These warm phases are not separated by planktic foraminifera as well as oxygen glacial sediments and are situated strati- isotopes has been obtained only in W Iber- graphically above the Holsteinian, and ian margin deep-sea cores for MIS 7 and before the first Saalian ice advance. for older interglacial stages. In this region, the first warm period during MIS 7 was MIS 9 only half the length of the Eemian and does not appear substantially warmer 1. New 230Th/U datings based on peat than the successive ones occurring during deposits from the type section of the //FS/ELS/PAGINATION/ELSEVIER AMS/STPS/3B2/CH40-N2955.3D – 595 – [595–614/20] 30.10.2006 7:12PM
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Holsteinian stage at Bossel (near Ham- chronology. The first forested phase of burg, Germany) indicate an age of about MIS 9 lasted 12 000 years in NW Iberia, 310–330 kyr BP which would correspond France and Greece but only at around to MIS 9 (and therefore to the Landos 3600 years in southwestern Iberia due to interglacial in the Massif Central). the occurrence of a dry cold event parti- 2. The INQUA Subcommission on Eur- cularly affecting the forest in this region. opean Quaternary Stratigraphy defined the lower boundary of the Holsteinian MIS 11 and earlier interglacials as the transition from subarctic (still late Elsterian) to boreal conditions and the 1. MIS 11 is an exceptional interglacial com- upper boundary as the transition from plex. Weak changes in insolation during boreal to subarctic (Saalian) conditions. this stage are surprisingly associated with 3. The interglacial vegetation development substantial climatic and greenhouse gas reconstructed by palynological data is variations. The duration of its first warm very similar throughout north-central period, 30 000 years, is much longer Europe and begins with a pine-birch for- than the succeeding interglacial periods. est. The immigration of thermophilous For instance, direct correlation between trees including alder, oak, elm, lime, marine and terrestrial signals indicates esh, yew and hazel occurred more or less that this warm period is twice as long as simultaneously. The early expansion of the Eemian in the Iberian Peninsula. spruce is remarkable. Hornbeam and fir 2. The continental equivalent of the MIS 11 immigrated during the course of the in central Europe could be the Rhume interglacial. Particulary characteristic of interglacial documented at Bilshausen the Holsteinian Stage in north-central where 27 000 varve years have been Europe is the appearance of Pterocarya counted. The pollen record shows that and Azolla filiculuides. this interglacial stage was climatically 4. The first half of the Holsteinian is charac- unstable. Several fast climatic deteriora- terized by temperatures somewhat lower tions are documented. than today. In the second half, the recon- 3. If this dating is correct, the consequence structed mean temperatures are higher would be that the Cromerian Complex than today, in particular the July tempera- terminated with MIS 11. This would be in ture. In addition, the Holsteinian seems to agreement with the 230Th/U datings of the be less stable than the present interglacial Holsteinian-type section above the Elster- (Holocene) or the last interglacial (Eemian) ian stage, but contradicts the often-used with some intra-interglacial coolings. The correlation of MIS 11 to be the Holsteinian. magnitude of the main cooling in the mid- 4. The ‘Cromerian Complex’ stage of the Holsteinian is reconstructed as approxi- Netherlands is defined by the recognition mately 5CforJanuarytemperature.No of at least four warm temperate (Waar- great change is reconstructed for July tem- denburg, Westerhoven, Rosmalen and perature during this episode. Noordbergum interglacials) and three 5. The duration of the Holsteinian in central (unnamed) cold substages indicating the Europe is estimated as about 15 000– climatic complexity of this time interval. 16 000 years, based on varve counts at 5. The Early–Middle Pleistocene boundary, Munster-Breloh. the begin of the Cromerian Complex, is 6. This duration disagrees with the new linked to the Brunhes–Matuyama evidence from the multiproxy study of palaeomagnetic boundary which has Iberian margin records, allowing the been recognized within the first Cromer- establishment of the timing of botanical ian interglacial (Waardenburg) at 780 kyr events through the benthic isotopic (MIS 19). //FS/ELS/PAGINATION/ELSEVIER AMS/STPS/3B2/CH40-N2955.3D – 595 – [595–614/20] 30.10.2006 7:12PM
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6. The above discussion shows that the cor- dated with dates published. If there are relation of interglacial pollen for all older other interglacials/interstadials with a interglacials than MIS 5 between north- pollen succession similar to the Eemian, central Europe and southwestern Europe correlation of records on biostratigraphical is still uncertiain because there are no grounds can lead to misinterpretations. established chronozones and few abso- Thus, as many as possible interglacial lute dates, but also because of biogeogra- pollen records should be dated by U/Th phical reasons. Based on the long or advanced luminescence techniques to continental sequence from the Massif assure that the classical Eemian pollen Central, a correlation of the Praclaux sequence in central Europe is a pattern interglacial (MIS 11) and the Holsteinian indeed typical only of MIS 5e. appeared to establish, now several . Radiometric ages for past interglacial authors argue, on the basis of U/Th dates sediments have large analytical errors that the Holsteinian represents MIS 9, and and cannot be precise enough to correlate for a synchronization between the last any sediment section by absolute dating. Cromerian interglacial (Bilshausen) with Thus, we will always depend on biostra- MIS 11 including the Praclaux interglacial. tigraphy or event correlation. Event cor- relation is done at the moment mostly relative to North Atlantic cold events, Open questions and recommendations for but this works reliably only if the records future research are long enough and reach from MIS 5e at The majority of the open questions concern least into MIS5c and show the structure of problems of dating. In the following, we will the C21–C26 events clearly. We need summarize the background for these pro- independent marker layers, probably blems and try to recommend steps towards from tephra and dust, which allow to cor- solving these gaps in our knowledge on past relate terrestrial records independently interglacials. from the marine and ice core chronology. . The time-transgressive development of . U/Th dates from stalagmites match in vegetation succession and local/regio- general the chronology derived from orbi- nal/overregional patterns across Europe tally tuned marine records; in detail, how- complicate a detailed correlation of ever, dates from terrestrial sites in central records by biostratigraphy and palynol- Europe show differences up to 4000 years ogy only. The successful analysis of the for the beginning and end of the last inter- terrestrial vegetation in marine records glacial in comparison with the marine off Iberia was a big step forward for the records off Portugal tuned to the SPEC- land–ocean correlation in southern Eur- MAP timescale and coral 230Th/U age. ope. Comparable records to link the vege- Whether this reflects uncertainties in the tation development of Central and 230Th/U dating or the SPECMAP chron- Northern Europe to the North Atlantic ology, or whether these offsets are related SST are still missing. to time-transgressive behaviour of vege- . There are at the moment only two varve tation zones across Europe, cannot be counted records for the Eemian; these are finally decided yet. Thus, there is an from Northern Germany and the Eifel urgent need for a precise correlation of region. None of these records is comple- speleothem dates to the marine chronol- tely varved and undisturbed. In Northern ogy and terrestrial pollen sites. Germany, only about 4000 individual . There are many sites across Europe with varve laminae have been counted, in the pollen sequences of the Eemian type. Very Eifel, 12 000 varves were counted. There is few of these sites have been absolutely an urgent demand for cores totally //FS/ELS/PAGINATION/ELSEVIER AMS/STPS/3B2/CH40-N2955.3D – 595 – [595–614/20] 30.10.2006 7:12PM
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undisturbed and also varve counted from continents after the melting of the large the late MIS 6 and well into MIS 5d. glacial icesheets. This process was quanti- . There is only one varve counted core for fied for Scandinavia, but it is hardly the Holsteinian (MIS 9 or MIS 11) and one understood for ocean islands, where the varve counted core for the Rhume inter- isostatic adjustment is caused by the chan- glacial (MIS 11 or Cromerian). No varve ging sea level. Thus, glacio-hydro-isostatic counted record is available for MIS 7 or modelling is an important target for link- any older interglacial. ing the land and ocean records worldwide. . U/Th dates from peat is a rather newly . Interpretation of palaeorecords by using developed dating method, but distin- climate models is still a problem, because guishing MIS9 (320 kyr) from MIS 11 climate models provide information on (420 kyr) is at the limit of the applicability average over a large area, whereas most of this method, and it can be problematic palaeorecords contain mainly local infor- to proove that a respective site is a closed mation. First attempts to bridge this gap system for uranium. in scale are underway, but it has not been . There is general agreement that insolation feasible to apply these so-called down- is the prime forcing mechanism of past scaling or data nudging methods to interglacials. The character and exact long-term climate simulations. value of the threshold at which a glacial . Most climate system models which include terminates and develops into an intergla- ice-sheet dynamics are able to reproduce a cial is, however, not determined yet. This glacial inception. A termination of a glacial is particularly difficult because the inter- or the beginning of an interglacial has not action between changes in insolation, ice- yet been successfully simulated. sheet stability, sea-level change, continen- . Most climate system models show a tal vegetation and albedo, atmospheric strong sensitivity to shifts in vegetation dust and greenhouse gas concentration zones, or biomes, in the sense that if is a complex process which lasts over sev- biome dynamics is missing, a glacial eral millennia with abrupt events interca- inception does not occur or is greatly lated. Final interpretation from data has diminished in the model. not yet been possible, mainly because the . The role of biome dynamics as an ampli- records from different geoarchives (ice, fier of glacial inception seems to be a land and ocean) cannot be plotted on a robust result in climate system models, commonly agreed timescale for past inter- the role of ocean dynamics, in particular glacials. Accordingly, we have avoided to the meridional overturning circulation is plot all results from this final synthesis into less clear. Climate system models yield one big figure. At least the 4000-year offset ambiguous results. between the marine and speleothem . Most climate system models do not yet chronologies has to be explained before include all components of the climate sys- this can be tried with some faith for the tem. In particular, the biogeochemical last interglacial. The most reliable cycles are often not explicitly simulated. approach would probably be a detailed Instead, concentration of greenhouse parallel study of cave speleothems and gases, mineral dust and other biogeochem- ocean terrace corals, both dated by the ical substances is prescribed from data in same U/Th technique, in comparison with most models. Hence, the course of atmo- Ar/Ar-dated and varve counted records spheric CO2 concentrations during inter- from laminated lakes. glacials is still an unresolved riddle. . The reconstruction of past sea level from corals is, however, hampered by the unknown isostatic changes of the 6.2. DATA APPENDIX (CD-ROM)