Abstracts / Quaternary International 279-280 (2012) 9–120 43

and feedback mechanisms of our present climate system. During the lastinterglacial period (MIS5e/Eemian), for instance, overall climatic condi-tions were comparable to the Holocene, but with higher temperaturesthan during the Holocene. While this pattern seems consistent in marineand terrestrial records within the mid-northern latitudes, proxy recordsfrom the polar North would suggest rather cold surfacewaters for MIS5e. Asimilar, but even more extreme, picture emerges when studying the cross-latitudinal surface ocean temperature patterns of the interglacial peaks ofMIS9 and 11. Although recognized as very prominent interglacials inAntarctic ice cores as well as in the North Atlantic, little of that oceanwarmth is found in the polar North during these latter two interglacials,independent of their different durations.Because of the importance of overturning processes in the polar North forthe global ocean circulation, it appears as if the hydrological system of theArctic is the likely candidate to influence the efficiency of the interglacial”North Atlantic Heat Pump” thereby not only causing intra-interglacialclimate perturbations such as known from historical times, but affectingthe interglacial period on awhole. Moreover, our observed contrasts in themeridional ocean heat flux during past interglaciations have further-reaching implications also for a climatic evaluation of the present time. It isindicated that certain factors of the Arctic climate system, that is the highlydynamical interaction between sea ice, atmosphere and ocean, playa crucial role for both interglacial regionality as well as for climate changeon a more global scale.

STUDYING THE ROLE OF DIRECT RADIATIVE FORCING OF AEOLIAN DUSTDURING GLACIAL-INTERGLACIAL CLIMATE CHANGES WITH AN EARTHSYSTEM MODEL OF INTERMEDIATE COMPLEXITY

Eva Bauer. PIK, GermanyE-mail address: Eva.Bauer@pik-potsdam.de

Reconstructed dust deposition fluxes of mineral dust show considerablevariations during glacial-interglacial climate changes of the Quaternary. Itis believed that increased arid and semi-arid areas, stronger winds andreduced precipitation are causal for larger fluxes of dust emission and dustdeposition in glacial than in interglacial periods. Associated with theclimate-driven dust cycle are different feedback processes of variablestrength which can influence the climate on orbital time scales between 20and 100 kyr. We focus on the question whether and under whichcircumstances the direct radiative forcing of atmospheric dust can affectglacial-interglacial climate changes. The determination of the dust radia-tive forcing depends crucially on space-time distributions of dust, opticalproperties of dust aerosols, and on environmental conditions as surfacealbedo and cloudiness. In an attempt to account for these dependencies,we performed sensitivity experiments for the last 420 kyr with theCLIMBER-2 model and the recently developed aeolian dust cycle model.CLIMBER-2 is an Earth system model of intermediate complexity, satis-factorily tested for glacial-interglacial climate changes. The dust cyclemodel, incorporated into the CLIMBER-2 model, simulates the space-timedistributions of atmospheric dust load and dust deposition in closeagreement with data. By using a realistic range of optical parameters,model experiments show that amplitude and sign of the radiative forcingat the top of the atmosphere are highly sensitive to absorption and scat-tering properties of dust aerosols. Subsequent applications of the directradiative forcing in sensitivity experiments with consistent climatic envi-ronments suggest that the dust radiative forcing has the potential toinfluence glacial-interglacial climate shifts.

A SYNTHESIS OF REGIONAL BIOMES AND EVOLUTION OF SOUTHERNBRAZIL LANDSCAPE DURING THE LATE QUATERNARY, ON THE BASISOF PALEOPALYNOLOGY

Soraia Bauermann. Ulbra, BrazilE-mail address: soraia.bauermann@ulbra.br

Neotropical vegetational formations are considered ecosystems with high-diversity endemism. However, little is known about their developmentand the reasons behind such varied and abundant flora. Palynology hasa unique role in obtaining and understanding the factors that the lead tosuch biodiversity. In southern Brazil, Rio Grande do Sul state, is

a transitional zone between a variety of very peculiar floras. This work ispart of a long term effort to obtain a historical account of the formation ofthese bioms in southern Brazil to understand their development and highdiversity. Additionally, we aim to clarify relations between vegetation andpast environmental processes, and how they resulted in today's ecologicalpatterns. Palynological data indicates that during the Pleistocene, at 42 ka,the regional vegetation was composed by grasslands. The modern vege-tation started during the Holocene, when the Araucaria forests of thehighlands, and the humid forests vegetation of the coastal lowlandsdeveloped. In the Pampa biome, tree growth in form of gallery foresthappened only during late Holocene times. However, expansion of theseforests was interrupted by the intensive agricultural activities originatedby the arrival of European colonizers. The pollen records from differentsites obtained reflect that climatic changes affected southern Brazil, sincethe cold polar fronts were more intense and frequent during the Pleisto-cene and attenuated after the mid-Holocene.

RECENT PALYNOLOGICAL ASSEMBLAGES IN SURFACE SEDIMENTS OFTHE BIOMES FROM SOUTHERNMOST BRAZIL

Soraia Bauermann. Ulbra, BrazilE-mail address: soraia.bauermann@ulbra.br

Southernmost Brazil is covered by large grassland areas known as “CamposSulinos” and smaller areas of forests, both are highly diverse naturalecosystems. These ecosystems belong to the Brazilian bioms “Pampa” and“Mata Atlantica”, which include large extensions of Uruguay andArgentina. The Pampa biome constitutes one of the richest regions inPoaceae of the world, and contains a mixture of micro- and megathermalspecies, with dominance of the latter. The "Mata Atlantica" biome occupiesthe northern part of Rio Grande do Sul state (RS), and holds one of theecosystems with the highest diversity. Unfortunately, very little is knownabout the origin of this biological diversity. Paleoecological studies wereperformed on surface samples from sites located along a southwest tonortheast transect in southernmost Brazil. The results document severalpollen assemblages, representing marked differences in the pollen rangebetween vegetational formations of the same biome. Additionally, thepalynomorph preservation is different in each one of these formations,reflecting different taphonomical signatures. The importance of some ofthe taxa involved in these biomes, relies on their vegetation specificity, asis the case of Lupinus rubriflorus, endemic in highland Campos of the MataAtlântica, and whose pollen indicates well preserved fields with dry,stony and uncovered soils. Other taxa, as Prosopis and Aspidospermaquebracho-blanco, are characteristic of the "Pampa" (Savana EstépicaParque) formation, with pollen grains represented in the pollen spectrum,and dominated by Prosopis. These observations will surely help makemore precise reconstructions of vegetation communities as interpretedfrom palynological assemblages recovered from Quaternary deposits inthe region.

BOG PINES, TRACK WAYS AND MAN – THE INFLUENCE OF CLIMATECHANGE ON NEOLITHIC SETTLEMENTS IN THE DUEMMER AREA(NORTHWEST GERMANY)

Andreas Bauerochse. Lower Saxony State Service for Cultural Heritage,GermanyE-mail address: a.bauerochse@gmx.net

The influence of climate change on landscape variation and population isa major topic in modern peatland archaeology. In this context, tree ringanalysis, combined with archaeological findings and palynological on-siteinvestigations, has been carried out in the Duemmer area; one of thelargest peatland areas in Germany.Until the end of the Neolithic period, the Duemmer basin was character-ized by large swamps and fens, riddled with mineral islands, settled byindividuals living during the Mesolithic and Neolithic periods. Numerouswooden track ways and other artefacts, as well as pollen of anthropogenicindicators, prove man’s activity and reflect the dynamics of the landscape.At the beginning of the 3rd millennium BC, large peatland areas in thebasin were covered by pine forest. Climate changes at the beginning of the3rd millennium BC led to landscape alterations. Wetter conditions