Abstracts / Quaternary International 279-280 (2012) 233–345336

BP in northern Iberia; ii) a general tendency towards greater aridity duringMIS 4 and MIS 3 (ca 60,000 to 23,500 cal yrs BP) punctuated by abruptclimate changes related to Heinrich Events (HE) and iii) a complex, highlyvariable climate during MIS 2 (23,500 to 14,600 cal yrs BP). The “MysteryInterval” (MI: 18,500 to 14,600 cal yrs BP) including HE1 and not the globalLast Glacial Maximum (LGM: 23,000 to 19,000 cal yrs BP) has beenrecorded as the coldest and most arid period. The last glacial transitionstarts in synchrony with Greenland ice records at 14,600 cal yrs BP but thetemperature increase was not so abrupt in the Iberian records and thehighest humidity was attained during the Allerød (GI-1a to GI-1c) and notduring the Bølling (GI-1e) period. The Younger Dryas event (GS-1) isdiscernible in northern Iberian lake records as a cold and dry interval,although Iberian vegetation records present a geographically variablesignal for this interval, perhaps related to vegetation resilience. Thisresearch provides an integrated view of the evolution of N IberianPeninsula during the last glacial cycle and emphasizes its peculiarities withrespect to other N Atlantic records.

INTERGLACIAL DIVERSITY RECONSTRUCTED FROM SPELEOTHEMRECORDS IN A CLIMATIC TRANSECT FROM THE ATLANTIC TO THEMEDITERRANEAN IBERIA

Ana Moreno. Pyrenean Institute of Ecology, SpainE-mail address: amoreno@ipe.csic.es

We present a compilation of U-Th chronologies from different speleothemscollected from caves located in northwestern (El Pindal, Calabrez in theCantabrian Range) to northeastern Spain (5 de Agosto, Pot au Feu, Seso,Esjamundo and Esteban Felipe in the Pyrenees, and Ortigosa and Molinoscaves in the Iberian Range). Selected caves are under the influence ofdifferent climates and located at diverse altitudes in order to detect theinfluence of local environmental situations on the speleothem growth.First chronologies indicate that all of the dated samples grow only duringinterglacials stages (MIS 11, 9, 7, 5 and Holocene) and stop during glacialones. Uncertainties in the U-Th results are mostly related to the generallylow U content and, for some samples, the high values of 232Th associated tothe detrital fraction. Speleothem growth is interpreted to represent waterrecharge into the unsaturated zone as a result of local positive precipita-tion/evaporation ratio above the cave, whereas simultaneous cease ofspeleothem growth in several caves points to aridification. In the highaltitude Pyrenean caves, speleothem formation could be also limited bythe extent of mountain glaciers and all year round permafrost. Stableisotopes (d18O and d13C) and trace elements (Mg/Ca, Sr/Ca, Ba/Ca) weremeasured along selected stalagmites to characterize the large diversityexisting among interglacials in terms of their intensity, duration andinternal variability. Evaluating whether similar hydrological patterns arefound in the studied interglacials, particularly if higher precipitation isassociated to cold or warm events and which source of precipitation wasdominant (Atlantic vs. Mediterranean), can serve as a reference for morerecent variability. We emphasize the results from El Pindal (Asturias) andMolinos (Teruel), where isotopes and trace element ratios respond to rapidclimate variability in synchrony with other regional terrestrial and marinepaleoclimate records.

MOISTURE FLUCTUATIONS RECONSTRUCTED FROM A COMPILATION OFPALEOCLIMATE ARCHIVES IN THE IBERIAN PENINSULA: IS THEREA COMMON PATTERN DURING THE MEDIEVAL CLIMATE ANOMALY?

Ana Moreno. Pyrenean Institute of Ecology, SpainE-mail address: amoreno@ipe.csic.es

Understanding the forcing mechanisms for the Medieval Climate Anomaly(MCA) requires the characterization of temperature and precipitationchanges in a higher number of sites located in different world areas. Mostof the studied lakes in the Iberian Peninsula (eg. Estanya, Taravilla, Basa dela Mora, Zoñar, Arreo, Montcortès) record shallower water levels andhigher chemical water concentrations, with predominance of scle-rophyllous Mediterranean vegetation, helyophytes and less deciduous treepollen content reflecting more arid conditions during the MCA (9th- mid14th century). Fluctuating, but generally more diluted waters and higherlake levels occurred during the Little Ice Age (LIA, 1350-1850 AD).

Additionally, recent coastal and marine sediments from offshore Galiciaand Tagus prodelta point to warmer SST and drier (less runoff) conditionsduring the MCA versus the LIA (Abrantes et al., 2005; Lebreiro et al., 2006).In the Mediterranean side, first results from MINMC06-2 core north ofMinorca, point to weaker westerlies during the MCA, a situation coherentwith a positive North Atlantic Oscillation (NAO) index. Recently, theclimate signal for the MCA in the North Atlantic-European region has beensuggested as a consequence of more persistent positive phase of the NAO(Trouet et al., 2009). That situation would produce warm and wet condi-tions in northern-central Europe but warm and arid climate in the Medi-terranean region. Thus, a dry climate during the MCA in the IberianPeninsula is coherent with a persistent positive phase of the NAO, char-acterized by less river discharge offshore Lisbon, lower lake levels in thenortheast and southwest Iberia, less flood events in the Tagus basin andless intense westerly winds offshore Minorca Island. Analyses in progressand a more detailed comparison of records will clarify the internal struc-ture and spatial coherence of the main phases of environmental changewithin the MCA in the Iberian Peninsula.

THERMOKARST LAKES AND ALASSES IN ICE-RICH PERMAFROST OF THELENA DELTA REGION

Anne Morgenstern. Alfred Wegener Institute for Polar and Marine Rese,GermanyE-mail address: Anne.Morgenstern@awi.de

In the late Pleistocene ice-rich deposits (Ice Complex) of northern Yakutia,Siberia, distinctive periglacial landscapes have been formed since theBoelling/Alleroed - early Holocene. Thermokarst lakes and thermokarstdepressions (alasses) alternate with ice-rich Yedoma uplands. Recentstudies on modern thermokarst activity have focused on thermokarstlakes, e. g. by using large scale change detection of thermokarst lake area,but rarely addressed alasses. However, the effect of thermokarst devel-opment on landscape changes and carbon cycling varies depending onwhether it takes place on undisturbed plain surfaces or in alasses of oldergeneration thermokarst. Newly developing thermokarst lakes on Yedomauplands have a stronger transformative impact on permafrost sediments,landscape character, and environmental processes than thermokarst lakesin existing alasses. Taliks forming underneath thermokarst lakes onYedoma uplands allow for the activation of physical and biochemicalprocesses in the Ice Complex sediments altering their structure andcomposition that had been conserved for thousands of years. The sedi-ments in existing alasses, however, have already been reworked duringpast talik formation and refreezing and do not represent the characteristicsof the very ice-rich permafrost of the surrounding Yedoma uplands as theycontain less ice and labile carbon.We investigate different stages of thermokarst development in the ice-richpermafrost of the north Siberian Lena River delta regarding theirmorphometry and spatial distribution with respect to relief position andcryolithological context and deduce the potential extent of future ther-mokarst evolution in the study area.

THE EFFECTS OF CLIMATE CHANGE ON HYDROLOGICAL ENVIRONMENT:THEIR QUANTITATIVE AND QUALITATIVE CONSEQUENCES

Kazuki Mori. Nihon University, JapanE-mail address: kzmori@chs.nihon-u.ac.jp

Climate change as induced by anthropogenic greenhouse gas has latelybecome the centre of wide interest. The impacts of global warming onhydrological environment in terms of both quantity and quality are,however, left for further accumulation of observation data. In the presentpaper, secular changes in the components of annual water balanceincluding precipitation, evapotranspiration and runoff were investigatedover the last 120 years in the meso-spatial scale watersheds in Japan.Smoothed trend curve on long-term changes in the difference betweenannual values of precipitation and potential evapotranspiration has tendedto decrease since the first half of the 1970s. The average annual runoff ratiofor each year has also shown a tendency to decrease during the last fewdecades. The notable characteristics of current frequency-magnitudedistributions in annual precipitation are both a reduction of intervals of