lake banyoles northeastern spain a last glacial to holocene multi proxy study with regard to environmental variability and human occupation analyses of a 67 m long sediment core from lake banyoles northeastern spain have revealed evidence for the palaeoclimate history of the northern iberian peninsula investigations have included hi

organic carbon burial rate and the molybdenum proxy theoretical framework and application to cenomanian turonian oceanic anoxic event 2 1 in this study the controls on organic carbon burial and molybdenum accumulation in ancient strata are investigated through an integration of biogeochemical modeling and data analysis critical aspects of the study are employment of a biogeochemical model for organic matter degradation to explore the controls on pore water sulfide generation and authigenic molybdenum accumulation and use of accumulation rate data for mo oc caco3 fe and ti to reconstruct organic matter remineralization processes the model results form a conceptual framework for the interpretation of primary production estimates and geochemical burial fluxes calculated on the basis of a high resolution orbital timescale for the cenomanian turonian c t oceanic anoxic event 2 interval in the western interior basin the results of this study suggest that the strong correlation between source rock development and intervals of transgression in the geologic record such as the c t could reflect a confluence of biogeochemical processes within sediments that obviates the need for large magnitude changes in primary production levels or oceanographic conditions such as prolonged periods of stable water column stratification

vegetation changes and hydrological fluctuations in the central ebro basin ne spain since the late glacial period saline lake records abstract although the central ebro basin northeastern iberian peninsula is both the northernmost semi arid area in europe and one of the regions with the largest biodiversity it has been insufficiently studied in terms of past climate variability due to the scarcity of suitable sites for palaeoenvironmental analyses previous studies from ephemeral saline lakes in the area mainly based on palynological data show abrupt and rapid arid humid transitions throughout the last glacial cycle highlighting a complex palaeohydrological evolution new cores from two saline lakes la playa and la salineta in the los monegros area provide multi proxy records including sedimentology geochemistry and pollen indicators this study together with a detailed review of the main saline records from the central ebro basin enables us to reconstruct the main features of the palaeoclimate evolution during the last glacial cycle one of the main results of this study is the alternation of humid and dry phases as a characteristic of the climate evolution during the late glacial additionally the study suggests an important role of the increased flow from the pyrenean rivers during deglaciation in the hydrological balance of the central ebro basin the early holocene is the wettest period of the studied sequences contrasting with the aridity of the middle holocene interval which is frequently absent as a result of intense aeolian erosive processes the lack of archaeological remains associated with the middle holocene neolithic also supports increased aridity that would have impeded human settlements although anthropogenic activity partially masks the climate signal from the palynological data in the uppermost part of the studied sequences there is some sedimentological evidence for a climate change during the last 2000 yr resulting in a recovery of average saline lake levels in the central ebro basin

integrated gravity and seismic interpretation of duplex structures and imbricate thrust systems in the southeastern pyrenees ne spain abstract combined surface subsurface and gravity data were used to determine the deep structure of the thrust belt in the southeastern pyrenees the ripolles and la garrotxa areas are part of the cardona oil exploration permit hydrocarbons pervade the concession with numerous oil seeps abandoned oil wells and gas or condensate are in these two wells associated with the overthrust belt the source rocks the armancies formation upper cuisian lower lutetian consist of alternating layers of organic rich shales and thin limestones this formation outcrops in the cadi thrust sheet in the ripolles area the cadi unit overlies the serrat unit with a hanging wall ramp geometry as deduced from the serrat 1 well the structure of the garrotxa area is more complex it consists of a duplex structure folded by antiformal stack structures with basement rocks in their cores the northern boundary of these antiformal stacks represents an inversion of pre existent extensional faults the basement rocks involved in the structure represent shortcuts formed in the footwall of the extensional faults a negative anomaly is shown in these antiformal stacks these anomalies are interpreted as a combination of salt accumulation evaporites and sedimentary rocks under the antiformal stacks in the serrat 1 well the serrat unit is made up of a thick middle eocene evaporitic sequence but the gravity and seismic data evidence the presence of non evaporitic sedimentary rocks in the northern part of the serrat unit these sediments correspond to the footwall of the cadi series so the probable existence of the armancies formation in the serrat unit is a very good target for oil prospecting the existence of the previous extensional faults only in the garrotxa area determines the difference in the deep structure between the ripolles and garrotxa areas

lateglacial and late holocene environmental and vegetational change in salada mediana central ebro basin spain the salada mediana lacustrine sequence central ebro basin spain 41330 10an 0344 w 350 m a s l provides an example of the potential and limitations of saline lake records as palaeoclimate proxies in the semi arid mediterranean region sedimentary facies analyses chemical stratigraphy stable isotopes d18o and d13c of authigenic carbonates d13c values of bulk organic matter and pollen analyses from sediment cores provide paleohydrological and vegetation change reconstructions for the lateglacial and late holocene in the central ebro basin a preliminary chronology is based on 210pb and 14c ams dates the lacustrine sequence is composed of three sedimentary sections the lower section was deposited in a permanent saline to brackish lake this stage represents the most humid period in the record and it was accompanied by the expansion of temperate trees particularly corylus the middle section was deposited in an ephemeral playa lake complex frequent subaerial exposure conditions favour the colonisation of the playa lake oor by chenopodiaceae during a low water table period this interval re ects the most arid conditions in the salada mediana record including the current environment a secondary temperate tree expansion occurred after the maximum aridity period aquatic plants and cyanobacterial mats spread in the lake during periods of raised water tables this paleohydrological and vegetational evolution attests to large changes in e ective moisture during the lateglacial in the semi arid northeastern spain the abundance of corylus during the lateglacial indicates that refugia for temperate trees were located along the ebro valley during the last glacial maximum the holocene sediments in the salada mediana records have been eroded and the upper section represents deposition during the last few centuries 2000 elsevier science ltd and inqua all rights reserved

spatial and temporal variation of summer precipitation over the eastern tibetan plateau and the north atlantic oscillation abstract the interannual variability of summer precipitation over the eastern tibetan plateau etp was examined in relation to the northern hemisphere macroscale circulation patterns during the period 1961 90 summer precipitation data for 66 stations located above 2000 m msl are used in the analysis using principal component analysis it is found that the dominant spatial pattern of interannual variability of the summer precipitation is a seesaw structure between the southern and northern parts of etp correlation analysis shows that this pattern of precipitation anomalies is closely associated with the north atlantic oscillation nao further analysis based on midtropospheric geopotential height and wind data suggests the upstream zonal flow variation associated with the nao pattern as the major mechanism linking the regional precipitation fluctuation to macroscale circulation conditions during the summers of low nao index values the westerly winds between 40 and 50 n from the eastern atlantic to

volcanic stratigraphy of the quaternary la garrotxa volcanic field north east iberian peninsula this study was partially funded by the beca ciutat d olot and the european commission ft7 theme env 2011 1 3 3 1 grant 282759 vuelco

upstream subtropical signals preceding the asian summer monsoon circulation in this study the authors address several issues with respect to the antecedent signals of the large scale asian summer monsoon that were earlier identified by webster and yang in particular they revisit the changes in the subtropical upper tropospheric westerlies preceding the monsoon depict the detailed structure of the monsoon s antecedent signals and investigate the physical processes from the signals to the monsoon they also explore the teleconnection of these signals to various large scale climate phenomena and emphasize the importance of the upstream location of the signals relative to the tibetan plateau and the monsoon before a strong weak asian summer monsoon the 200 mb westerlies over subtropical asia are weak strong during the previous winter and spring a significant feature of these signals is represented by the variability of the middle east jet stream whose changes are linked to the arctic oscillation north atlantic oscillation el

holocene climatic changes in the western mediterranean from south east france to south east spain abstract holocene climatic changes along coastal regions from south east france to south east spain were studied using pollen ratios comparing modern pollen rain vegetation and climate along selected transects from the atlantic ocean to the mediterranean we obtained threshold values of two different ratios corresponding to the different climatic conditions along the transects these pollen ratios and threshold values were employed to characterize the holocene climatic changes from nine mediterranean coastal sites the results were compared with data from marine and continental pollen sequences distributed in the western mediterranean basin and with additional regional data independent of human activity lake level fluctuations alpine glacier advance and retreat chronology 14 c anomaly and cooling phases in eastern france and central europe the role of anthropogenic activities and climate on the changes in vegetation is discussed six major changes in vegetation cover were identified they correspond to aridification phases that occurred around 9500 9000 yr bp 10 900 9700 cal bp 7500 7000 yr bp 8400 7600 cal bp 4500 4000 yr bp 5300 4200 cal bp 3700 3300 yr bp 4300 3400 cal bp 2600 1900 yr bp 2850 1730 cal bp and 1300 1000 yr bp 1300 750 cal bp these arid episodes were regional responses to more global climatic changes and determined the changes in the vegetation cover humans undoubtedly enhanced the vegetation changes but none the less had to adapt to these new climatic conditions

dansgaard oeschger and heinrich event imprints in alboran sea paleotemperatures past sea surface temperature sst evolution in the alboran sea western mediterranean during the last 50 000 years has been inferred from the study of c37 alkenones in international marine global change studies md952043 core this record has a time resolution of 200 years allowing the study of millennial scale and even shorter climatic changes the observed sst curve displays characteristic sequences of extremely rapid warming and cooling events along the glacial period comparison of this alboran record with 18o from greenland ice greenland ice sheet project 2 core shows a strong parallelism between these sst oscillations and the dansgaard oeschger events five prominent cooling episodes standing out in the sst profile are accompanied by an anomalous high abundance of neogloboquadrina pachyderma sinistral which is confined to the duration of these cold intervals these features and the isotopic record reflect drastic changes in the surface hydrography of the alboran sea in association with heinrich events hl 5

climatic change on the iberian peninsula recorded in a 30 000 yr pollen record from lake banyoles the banyoles lacustrine sequence shows that the vegetational history of the northeastern iberian peninsula during the last 30 000 yr follows the north atlantic pattern of climatic oscillations the banyoles pollen diagram supported by two calibrated 14c dates and nine u th dates shows a clear interstadial event between 30 000 and 27 000 yr b p a pleniglacial period with minor oscillations that ended abruptly ca 14 420 410 yr b p and a late glacial sequence that records the classical stages described in northern europe the bolling allerod interstade the younger dryas event at 12 000 yr b p u series age and a short warming phase between the younger dryas and the last cold event dated at 11 000 yr b p u series age

geochronologies and environmental records of quaternary fluvial sequences in the guadalope basin northeast spain based on luminescence dating

sinkholes in hypogene versus epigene karst systems illustrated with the hypogene gypsum karst of the sant miquel de campmajor valley ne spain abstract the garrotxa banyoles artesian aquifer system in ne spain includes zones with epigene and hypogene evaporite karst and sinkhole development the sinkhole fields related to hypogene evaporite dissolution are associated with the discharge zones of the aquifer where groundwater from a confined limestone rises traversing an overlying gypsum formation capped by thick marls this work analyses the sinkhole field developed in the sant miquel de campmajor valley smcv a discharge area of the aquifer where a cartographic inventory including 94 sinkholes has been produced sinkholes in this hypogene gypsum karst are mainly large caprock collapse sinkholes rooted in deep seated cavities generated by interstratal hypogene karstification as corroborated by an electrical resistivity imaging eri survey they show a non clustered distribution within the sinkhole field and the variations in size and density across the area are mainly controlled by the thickness of the marl caprock the magnitude and frequency relationships of the sinkholes can be modelled with a high goodness of fit with a log normal function like in other regions of the world however in this deep seated hypogene system the depressions show much larger dimensions potential differences between the sinkholes developed in hypogene and epigene karst environments are discussed including their distribution with respect to the groundwater flow system their spatial patterns and dimensions

global geologic context for rock types and surface alteration on mars petrologic interpretations of thermal emission spectra from mars orbiting spacecraft indicate the widespread occurrence of surfaces having basaltic and either andesitic or partly altered basalt compositions global concentration of ice rich mantle deposits and near surface ice at middle to high latitudes and their spatial correlation with andesitic or partly altered basalt materials favor the alteration hypothesis we propose the formation of these units through limited chemical weathering from basalt interactions with icy mantles deposited during periods of high obliquity alteration of sediments in the northern lowlands depocenter may have been enhanced by temporary standing bodies of water and ice

how the north atlantic multidecadal oscillation may have influenced the indian summer monsoon during the past two millennia 1 observations have indicated that the north atlantic sst variations have persistent effects on the indian summer monsoon rainfall at multidecadal and longer timescales the question of how such influences may have been achieved is addressed in this study using both instrumentation data of the 20th century and proxy records of the last 2000 years major results show that the north atlantic sst anomalies strongly affect the tibetan plateau surface temperature and heat sources the latter cause changes in the meridional temperature gradient between tibetan plateau and the tropical indian ocean through the thermal wind effect the meridional temperature gradient anomalies change the lower tropospheric zonal winds and the monsoon circulation and rainfall citation feng s and q hu 2008 how the north atlantic multidecadal oscillation may have influenced the indian summer monsoon during the past two millennia geophys res lett 35 l01707 doi 10 1029 2007gl032484

the holocene and upper pleistocene pollen record from padul granada spain a new study two borings were made at the site of padul granada pollen analysis of 200 spectra from two successive sequences 14 8 and 8 m deep enables a description of the vegetational and climatic history of this region the most southern one in europe from early wurmian times the chronology is supported by twenty one 14c dates original equivalents are found for the great european prewurm interstadials a markedly arid though thermically not extreme episode exactly equivalent to stage 4 of the marine isotopic stratigraphy closes this relatively temperate period the middle part of the last glacial shows climatic fluctuations that are poorly characterized as is often the case in europe for this period a long section very probably corresponding to the complete last pleniglacial does not show any climatic amelioration towards 15 000 yr b p a change in the diagram is noted that can only be interpreted as reflecting a larger expansion of a regional steppe cover this event also reported on three occasions in southeast france marks the beginning of the oldest dryas the climatic amelioration of ca 13 000 yr b p is far more pronounced here than anywhere else in europe whereas that at 10 000 yr b p is not so clearly marked this unexpected result may be accounted for by the fact that padul is the first continental site so far south and so near pleniglacial refuges to be known on the other hand this result is consistent with what is known from oceanic isotopic stratigraphy a quite new late glacial and holocene vegetational history is revealed characterized by the early appearance and dominance of quercus ilex oak forests of a southern type and the early occurrence of quercus suber and olea it is the first account of a complete history of the postglacial reafforestation in a region with a modern semi arid mediterranean climate from the palaeoclimatic point of view it shows that the hot and humid holocene optimum was attained slightly before 8000 yr b p and that the holocene climatic fluctuations were of but small amplitude

climatic and human influence on river systems and glacier fluctuations in southeast spain since the last glacial maximum abstract the semi desert environments of the mediterranean region are most sensitive to climatic changes and human land exploitation this paper is focused on the late pleistocene and holocene geomorphic evolution of southeast spain one of the driest regions in europe late pleistocene and holocene chronosequences of river terraces were established for the antas and aguas valleys respectively the deposition of up to four fluvial terraces during isotope stage 2 points to important erosion and accumulation processes at the end of late pleistocene in the vera basin in contrast to the stage 2 deposits the holocene terraces are composed of point bar deposits accumulated by meandering rivers with less sediment discharge according to the obtained 14c dating and extracted pottery fragments holocene terrace deposition occurred during the atlantic period early middle ages little ice age lia and the 20th century the most outstanding site in southern spain for studying holocene glacier shifts up to five end moraines is the veleta cirque in sierra nevada where the southernmost glacier of europe persisted during the little ice age the climate changes of the lia probably are recorded by two glacier fluctuations as indicated by 210pb dating and historical data the reconstruction of the evolution of the aguas and antas valleys stress that the aggradations of the lower terraces is mostly climate induced although during the last 500 years human interference in the landscape christian conquest mining boom of the 19th century etc may have played an important role to river dynamics

late glacial and post glacial deposits of the navamuno peatbog iberian central system chronology and paleoenvironmental implications abstract the navamuno peatbog sierra de bejar western spain is a 14 ha pseudo endorheic depression with boundaries defined by a lateral moraine of the cuerpo de hombre paleoglacier and fault line scarps on granite bedrock the stratigraphy of the navamuno peatbog system is characterized here using borehole data to a depth of 20 m an integrated interpretation from direct push coring dynamic probing boreholes and handheld auger drillings advances our knowledge of the navamuno polygenetic infill correlating this data with those obtained in other studies of the chronology and evolutionary sequence of the cuerpo de hombre paleoglacier has enabled us to establish the sequence of the hydrological system in the navamuno depression during the late pleistocene mis2 the depression was dammed by the cuerpo de hombre glacier and fed by its lateral meltwaters and was filled with glaciolacustrine deposits the onset of the holocene in navamuno is linked to a flat fluviotorrential plain with episodes of local shallow pond peat bog sedimentation this evolutionary sequence is congruent with the age model obtained from available radiocarbon dating obtaining 19 ages from 800 cal yr bp at depth 1 11 m to 16800 cal yr bp at depth 15 90 16 0 m finally the sedimentary record enabled interpretation of the environmental changes occurring in this zone during the late glacial from the older dryas to the younger dryas and postglacial holocene stages placing them within the paleoclimatic context of the iberian peninsula and mediterranean regions

circumglobal teleconnections the jet stream waveguide and the north atlantic oscillation abstract monthly and seasonally averaged upper tropospheric northern hemisphere winter fields are examined to determine whether the waveguiding effect of the time averaged tropospheric jets on low frequency disturbances that is predicted by theory does affect the behavior of these disturbances it is found that indeed disturbances in the vicinity of the mean jets particularly the jet that stretches across south asia are fundamentally different from those that reside in regions where the mean winds have weaker meridional gradients like the mid pacific patterns of variability in the jets tend to be smaller scale and to consist of zonally oriented chains of anomalies while variability in the mid pacific is composed of patterns with distinct meridional orientation because they are meridionally trapped and zonally elongated patterns associated with the jet stream waveguide connect activity at points that are much farther apart than do patterns in other regions of the globe within the south asian waveg

northern iberian abrupt climate change dynamics during the last glacial cycle a view from lacustrine sediments abstract we present a palaeoclimatic reconstruction of the last glacial cycle in iberia ca 120 000 11 600 cal yrs bp based on multi proxy reconstructions from lake sediments with robust chronologies and with a particular focus on abrupt climate changes the selected lake sequences provide an integrated approach from northern iberia exploring temperature conditions humidity variations and land sea comparisons during the most relevant climate transitions of the last glacial period thus we present evidence that demonstrates i cold but relatively humid conditions during the transition from mis 5 to mis 4 which prevailed until ca 60 000 cal yrs bp in northern iberia ii a general tendency towards greater aridity during mis 4 and mis 3 ca 60 000 to 23 500 cal yrs bp punctuated by abrupt climate changes related to heinrich events he iii a complex highly variable climate during mis 2 23 500 to 14 600 cal yrs bp with the mystery interval mi 18 500 to 14 600 cal yrs bp and not the global last glacial maximum lgm 23 000 to 19 000 cal yrs bp as the coldest and most arid period the last glacial transition starts in synchrony with greenland ice records at 14 600 cal yrs bp but the temperature increase was not so abrupt in the iberian records and the highest humidity was attained during the allerod gi 1a to gi 1c and not during the bolling gi 1e period the younger dryas event gs 1 is discernible in northern iberian lake records as a cold and dry interval although iberian vegetation records present a geographically variable signal for this interval perhaps related to vegetation resilience

heinrich events massive late pleistocene detritus layers of the north atlantic and their global climate imprint 1 millennial climate oscillations of the glacial interval are interrupted by extreme events the so called heinrich events of the north atlantic their near global footprint is a testament to coherent interactions among earth s atmosphere oceans and cryosphere on millennial timescales heinrich detritus appears to have been derived from the region around hudson strait it was deposited over approximately 500 250 years several mechanisms have been proposed for the origin of the layers binge purge cycle of the laurentide ice sheet jokulhlaup activity from a hudson bay lake and an ice shelf buildup collapse fed by hudson strait to determine the origin of the heinrich events i recommend 1 further studies of the timing and duration of the events 2 further sedimentology study near the hudson strait and 3 greater spatial and temporal resolution studies of the layers as well as their precursory intervals studies of previous glacial intervals may also provide important constraints

early holocene humidity patterns in the iberian peninsula reconstructed from lake pollen and speleothem records abstract comparison of selected well dated lacustrine speleothem and terrestrial pollen records spanning the holocene onset and the early holocene ca 11 7 8 cal kyrs bp in the iberian peninsula shows large hydrological fluctuations and landscape changes with a complex regional pattern in timing and intensity marine pollen records from alboran the mediterranean and off shore atlantic sites show a step wise increase in moisture and forest during this transition however available continental records point to two main patterns of spatial and temporal hydrological variability i atlantic influenced sites located at the northwestern areas enol sanabria lucenza prd 4 characterized by a gradual increase in humidity from the end of the younger dryas to the mid holocene similarly to most north atlantic records and ii continental and mediterranean influenced sites laguna grande villarquemado fuentillejo padul estanya banyoles salines with prolonged arid conditions of variable temporal extension after the younger dryas followed by an abrupt increase in moisture at 10 9 cal kyrs bp different local climate conditions influenced by topography or the variable sensitivity gradual versus threshold values of the proxies analyzed in each case are evaluated vegetation composition conifers versus mesothermophilous taxa and resilience would explain a subdued response of vegetation in central continental areas while in mediterranean sites insufficient summer moisture availability could not maintain high lake levels and promote mesophyte forest in contrast to atlantic influenced areas comparison with available climate models greenland ice cores north atlantic marine sequences and continental records from central and northern europe and the whole mediterranean region underlines the distinctive character of the hydrological changes occurred in inner iberia throughout the early holocene the persistent arid conditions might be explained by the intensification of the summer drought due to the high seasonality contrast at these latitudes caused by the orbital induced summer insolation maximum new records particularly from western and southernmost iberia and palaeoclimate models with higher spatial resolution would help to constrain these hypotheses

palaeoenvironmental and cultural dynamics of the coast of malaga andalusia spain during the upper pleistocene and early holocene abstract the impact of late upper pleistocene climate change in the western mediterranean region has been mainly documented through marine records archaeological and geomorphological continental records now available for the coast of malaga complement these records for the second part of the last major glacial episode and the early stages of the holocene this paper provides an overview of the archaeological chronological and palaeoenvironmental data from the end of the middle palaeolithic period to the epipalaeolithic sequences from the two major sites nerja and bajondillo indicate a mosaic type response of ecosystems to the rapidly shifting conditions of the last glacial episode terrestrial mammals for example show no major variations from present day communities plant remains in contrast demonstrates the existence of localised refuge areas for species that would not otherwise have survived in the more widely prevailing climatic conditions of the time whereas remains of fish and secondarily birds demonstrate the existence of communities without any present day analogues combining mediterranean and boreal i e northern atlantic taxa from an archaeological standpoint the major cultural shift is the onset of marine fishing beginning in the solutrean this coincided with the end of the last glacial maximum lgm episode the faunal record also testifies to the rising importance of marine resources more generally although the data have not been used systematically to test the validity of the broad spectrum revolution bsr hypothesis the hints for it in the area seem compelling from the start of the solutrean onwards

diatom and vegetation responses to late glacial and early holocene climate changes at lake estanya southern pyrenees ne spain abstract we investigate lake estanya s diatom and pollen records from the late glacial lg to the early holocene eh in order to compare limnological and vegetation responses to common climate forcing the biotic changes recognized in this study largely agree with the hydrological evolution of the lake described previously for the same period the diatom record shows high sensitivity to fluctuations in both lake level and salinity concentration as a consequence of climate shifts in addition vegetation results indicate that the area could have played an important role as regional vegetation refuge shallow lake conditions during the last glacial maximum lgm were punctuated by relatively deeper freshwaters between 19 3 and 18 6 cal kyr bp and at 18 0 cal kyr bp as recorded by diatom shifts a subsequent increasing aridity trend coinciding with the mystery interval mi affected the diatom accumulation rates which dropped to its minimum values between 17 2 and 14 7 cal kyr bp particularly dry and cold conditions during the lgm and mi are supported by the largest values of steppic pollen taxa of the whole sequence which account for up to 40 however relatively high values of betula during the heinrich event 1 suggest a plausible regional vegetation refuge abrupt cooling and warming episodes within the lg triggered remarkable ecological threshold crossings in the diatom communities especially during the stadial interstadial episodes at this point the vegetation reflects the onset of warm conditions during the bolling allerod with the partial substitution of betula by marcescent and evergreen quercus which probably indicates the arrival of temperate taxa to the area and the likely migration of birch to higher altitudes the younger dryas stadial shows a complex ecological response diatoms are very poorly preserved but aquatic taxa reach their highest values an increase in marcescent quercus during this cold stage lends further support to the hypothesis that this is a regional vegetation refuge low lake levels recorded during the eh affected the development and preservation of diatom communities a delay in the onset of humid conditions for the eh is also supported by the vegetation composition characterized by the maximum expansion of juniperus

paleohydrological fluctuations and steppe vegetation during the last glacial maximum in the central ebro valley ne spain combined analysis of sedimentary facies geochemistry and pollen from lake sediment records and sedimentological and palynological studies from slope deposits allow the characterization of vegetation and lake level status during the last glacial lgm in the central ebro valley ne spain these records show the presence of phases of increased effective moisture while regional vegetation was dominated by steppe species the longest lake record comes from la salineta one of the saline lakes in the los monegros area the other lake sequence comes from a sinkhole in the gallego river floodplain the slope deposit from valmadrid is the only periglacial deposit found in the central ebro valley our data indicate that at least for some intervals during full glacial times when cold steppe vegetation dominated the region some lakes experienced more positive water balance than today and run off was also high the data are coherent with the hypothesis that at least for some periods the ice age climate of the western mediterranean was characterized by cold winters with relatively higher effective moisture precipitation minus evaporation ratio and summer droughts increased flow from the pyrenean rivers during the early deglaciation could also have played a significant role in the paleohydrological cycle in the central ebro valley however la salineta records also show evidence for arid periods during glacial times indicating the complex evolution of hydrology and moisture availability in the central ebro valley during the lgm

large scale flow and the long lasting blocking high over russia summer 2010 abstractseveral studies show that the anomalous long lasting russian heat wave during the summer of 2010 linked to a long persistent blocking high appears mainly as a result of natural atmospheric variability this study analyzes the large scale flow structure based on the ecmwf re analysis interim era interim data 1989 2010 the anomalous long lasting blocking high over western russia including the heat wave occurs as an overlay of a set of anticyclonic contributions on different time scales i a regime change in enso toward la nina modulates the quasi stationary wave structure in the boreal summer hemisphere supporting the eastern european blocking the polar arctic dipole mode is enhanced and shows a projection on the mean blocking high ii together with the quasi stationary wave anomaly the transient eddies maintain the long lasting blocking iii three different pathways of wave action are identified on the intermediate time scale 10 60 days one pathway commences over the eastern nort

impact of the atlantic multidecadal oscillation on north pacific climate variability 1 in this paper we found that the atlantic multidecadal oscillation amo can contribute to the pacific decadal oscillation pdo especially the component of the pdo that is linearly independent of el nino and the southern oscillation enso i e the north pacific multidecadal oscillation npmo and the associated pacific north america pna pattern using a hybrid version of the gfdl cm2 1 climate model we show that the amo provides a source of multidecadal variability to the north pacific and needs to be considered along with other forcings for north pacific climate change the lagged north pacific response to the north atlantic forcing is through atmospheric teleconnections and reinforced by oceanic dynamics and positive air sea feedback over the north pacific the results indicate that a north pacific regime shift opposite to the 1976 77 shift might occur now a decade after the switch of the observed amo to a positive phase around 1995 citation zhang r and t l delworth 2007 impact of the atlantic multidecadal oscillation on north pacific climate variability geophys res lett 34 l23708

palaeoecology of neanderthals during dansgaard oeschger cycles in northeastern iberia abric romani from regional to global scale abstract the sequence from abric romani has provided several palaeoecological studies this paper presents a synthesis of the results yielded by palynology including the data from the entire non excavated deposits and the data obtained through the study of large mammals micromammals herpetofauna and anthracology from the excavated layers the palaeobotanical studies show that the sequence is mainly related to pine forests and near or within these dominant forests there were smaller plant formations and or secondary species with a mediterranean and or atlantic character nevertheless continuous forest did not dominate the entire region the fauna occupying the territory indicate open spaces in which seasonal grasslands proliferated dry assemblages in sunny areas and humid ones in mountain shadows the non excavated archaeological layers correspond to mis 4 initially characterized by temperate and humid conditions and thereafter cool and humid until hs 6 and mis 3 afterwards at the beginning of the mis 3 the dansgaard oeschger cycles 1500 yr rapid and abrupt climatic changes occurred during the deposition of the archaeological levels o n m l k and j later these events were interrupted by a cold and dry phase between ca 49 and 47 ka bp which affected levels ja i and h culminating with hs 5 finally this cold episode was followed by the hengelo interstadial or do 12 characterized by a temperate and humid climate identified in levels e and d

solution collapse depressions and suspensates in the limnocrenic lake of banyoles ne spain a high resolution seismic reflection survey in the banyoles limnocrenic solution lake allowed penetration of dense suspensates occupying cone like bottom depressions of different size the depressions result from the dissolution and collapse of underlying eocene calcareous and gypsiferous materials over which lacustrine sediments of varying thicknesses have accumulated the suspensates occupying the depressions present three main types of seismic signatures stratified semistratified and transparent the densities of the suspensates and the water depths of their tops which fluctuate continuously vary from one depression to another the maximum seismically recorded suspensate thickness is 44 m morphological and structural features seismic characters and variable degrees of hydraulic activity point to the existence of different stages of maturity in the lake bottom depressions this work brings new insight on the dynamics and evolution of limnocrenic solution lakes

late quaternary deposition and facies model for karstic lake estanya north eastern spain lake estanya is a small 19 ha freshwater to brackish monomictic lake formed by the coalescence of two karstic sinkholes with maximum water depths of 12 and 20 m located in the pre pyrenean ranges north eastern spain the lake is hydrologically closed and the water balance is controlled mostly by groundwater input and evaporation three main modern depositional sub environments can be recognized as i a carbonate producing littoral platform ii a steep talus dominated by reworking of littoral sediments and mass wasting processes and iii an offshore distal area seasonally affected by anoxia with fine grained clastic sediment deposition a seismic survey identified up to 15 m thick sedimentary infill comprising i a basal unit seismically transparent and restricted to the depocentres of both sub basins ii an intermediate unit characterized by continuous high amplitude reflections and iii an upper unit with strong parallel reflectors several mass wasting deposits occur in both sub basins five sediment cores were analysed using sedimentological microscopic geochemical and physical techniques the chronological model for the sediment sequence is based on 17 accelerator mass spectrometry 14c dates five depositional environments were characterized by their respective sedimentary facies associations the depositional history of lake estanya during the last ca 21 kyr comprises five stages i a brackish shallow calcite producing lake during full glacial times 21 to 17 3 kyr bp ii a saline permanent relatively deep lake during the late glacial 17 3 to 11 6 kyr bp iii an ephemeral saline lake and saline mudflat complex during the transition to the holocene 11 6 to 9 4 kyr bp iv a saline lake with gypsum rich laminated facies and abundant microbial mats punctuated by periods of more frequent flooding episodes and clastic dominated deposition during the holocene 9 4 to 0 8 kyr bp and v a deep freshwater to brackish lake with high clastic input during the last 800 years climate driven hydrological fluctuations are the main internal control in the evolution of the lake during the last 21 kyr affecting water salinity lake level changes and water stratification however external factors such as karstic processes clastic input and the occurrence of mass flows are also significant the facies model defined for lake estanya is an essential tool for deciphering the main factors influencing lake deposition and to evaluate the most suitable proxies for lake level climate and environmental reconstructions and it is applicable to modern karstic lakes and to ancient lacustrine formations

climate variability in the spanish pyrenees during the last 30 000 yr revealed by the el portalet sequence abstract palynological sedimentological and stable isotopic analyses of carbonates and organic matter performed on the el portalet sequence 1802 m a s l 42 48 00 n 0 23 52 w reflect the paleoclimatic evolution and vegetation history in the central western spanish pyrenees over the last 30 000 yr and provide a high resolution record for the late glacial period our results confirm previous observations that deglaciation occurred earlier in the pyrenees than in northern european and alpine sites and point to a glacial readvance from 22 500 to 18 000 cal yr bp coinciding with the global last glacial maximum the patterns shown by the new high resolution pollen data from this continental sequence chronologically constrained by 13 ams 14c dates seem to correlate with the rapid climate changes recorded in greenland ice cores during the last glacial interglacial transition abrupt events observed in northern latitudes heinrich events 3 to 1 oldest and older dryas stades intra allerod cold period and 8200 cal yr bp event were also identified for the first time in a lacustrine sequence from the central western pyrenees as cold and arid periods the coherent response of the vegetation and the lake system to abrupt climate changes implies an efficient translation of climate variability from the north atlantic to mid latitudes

active faulting in the western pyrenees france paleoseismic evidence for late holocene ruptures abstract we have identified a 50 km long active fault scarp called herewith the lourdes fault between the city of lourdes and arette village in the french pyrenees this region was affected by large and moderate earthquakes in 1660 io viii ix msk 64 in 1750 io viii msk 64 and in 1967 md 5 3 io viii msk 64 most earthquakes in this area are shallow and the few available focal mechanism solutions do not indicate a consistent pattern of active deformation field investigations in active tectonics indicate an east west trending and up to 50 m high fault scarp in average made of 3 contiguous linear fault sub segments to the north the fault controls quaternary basins and shows uplifted and tilted alluvial terraces deviated and abandoned stream channels of the southern block are likely due to the successive uplift of the northern block of the fault paleoseismic investigations coupled with geomorphic studies georadar prospecting and trenching along the fault scarp illustrate the cumulative fault movements during the late holocene trenches exhibit shear contacts with flexural slip faulting and thrust ruptures showing deformed alluvial units in buried channels 14c dating of alluvial and colluvial units indicates a consistent age bracket from two different trenches and shows that the most recent fault movements occurred between 4221 bc and 2918 bc fault parameters and paleoseismic results imply that the lourdes fault and related sub segments may produce a mw 6 5 to 7 1 earthquake fault parameters imply that the lourdes fault segment corresponds to a major seismic source in the western pyrenees that may generate earthquakes possibly larger than the 1660 historical event

neandertal extinction and the millennial scale climatic variability of ois 3 population models seeking climate as a triggering factor for the extinction of neandertals and the colonisation of europe by anatomically modern humans are contradictory due to uncertainties in the dating methods in the cultural attribution of archaeological layers and to the lack of terrestrial continuous and well dated palaeoclimatic sequences this is particularly the case for the iberian peninsula where neandertal populations seem to have survived later than in other regions of europe a review of the available palaeoclimatic evidence for ois3 of iberia reveals that this mainly consists of low resolution fragmentary ill dated and often ill interpreted records correlation between palaeoenvironmental sequences from two images pollen rich deep sea cores and archaeological data from western europe the electronic archive of the radiocarbon dates is available at qsr website http www elsevier nl locate quascirev indicates that aurignacian moderns colonised france and the north of iberia at the onset of the h4 event during this cold episode a probable contraction of neandertal populations is recorded in southern iberia where no aurignacian settlements are detected such a decline in population density is correlated with the particular desert steppe like environments made up of artemisia chenopodiaceae and ephedra characterising the h4 of this area while reducing the size of neandertal populations this inhospitable environment may have favoured their persistence in this region mainly exploiting herds of herbivores adapted to graminees rich grasslands the aurignacian moderns were probably not interested in colonising these arid mediterranean biotopes and did that only after the h4 event

behaviour and dynamics of a hydrothermal plume in lake banyoles catalonia ne spain a hydrothermal plume forms in lake banyoles ne spain as a result of convection above a springwater fed suspension cloud ponded on the lake floor the plume propagates upwards reaching a level of neutral buoyancy from where a turbidity current spreads out laterally two dimensional temperature and particle concentration measurements show the fate of the hydrothermal plume and its associated turbidity current and reveal its seasonal development silt particles transported by the plume have been used as tracers to determine the maximum and equilibrium heights of the plume when the lake is stratified the vertical transport of sediment is confined to the lake hypolimnion as the thermocline limits the vertical propagation of the plume in contrast when the lake water column is mixed the plume reaches the surface of the lake the field measurements have been compared with models for thermal convection from finite isolated sources measurements of the flow velocity at the source of the hydrothermal plume i e the rim current velocity indicate that cold hypolimnetic water is entrained by the plume sedimentation rates measured from sediment traps at the zone where the turbidity current develops vary between 10 and 25 g m 2 day 1 and result from continuous silt particle sedimentation from the turbidity current sedimentation rates in traps are higher for stations situated close to the source than those further away 5 g m 2 day 1 moreover the results demonstrate that double diffusive sedimentation from the turbidity current was dominant over grain by grain settling causing a mixed distribution of sediments in the region where the turbidity current spreads the deposition of silt particles could explain the occurrence of silt layers interbedded with biocalcarenites in the littoral zones of the lake and the stratigraphy identified by seismic profiles and cores taken from the lake floor

geomorphology and geochronology of sackung features uphill facing scarps in the central spanish pyrenees abstract the paper analyses uphill facing scarps and associated troughs developed in the oversteepened slopes of two neighbouring glacial valleys in the central spanish pyrenees previous studies of sackung landforms in the pyrenees have argued for deglacial unloading as the genetic mechanism but this causal and temporal relationship has not been proved due to the lack of chronological data the antislope scarps in the two studied locations vallibierna and estos are developed in palaeozoic metasedimentary rocks parallel to the contour lines and the structural grain occur in the intermediate sector of the hillslope and are up to 0 5 km long and several meters high a trench was excavated in a sackung trough fill in each of the valleys in order to gain information about their chronology and genesis charcoal from the lowermost unit in vallibierna provided an age of 5 9 cal ka for the sackung and extrapolation of the three dates obtained in estos indicates that the trough formed ca 7 6 7 8 cal ka deglaciation of the studied sectors of the valleys occurred between 16 and 13 ka the time lag of 5 ka suggests that glacial erosion and the subsequent debutressing of the oversteepened valley walls created slopes predisposed to sackung development but did not initiate the movement seismic shaking is proposed as a probable triggering factor this hypothesis although supported by the sudden deformation event recorded by a failure plane exposed in vallibierna trench and by the seismic and neotectonic activity of the area cannot be proved due to the lack of chronological information about paleoearthquakes

interpreting drivers of change in fluvial archives of the western mediterranean a critical view abstract fluvial archives in particular late glacial to holocene floodplain records may provide valuable information regarding past environmental conditions and stages of landscape evolution in view of the high significance of floodplain dynamics for the development of entire landscapes the number of studies that have been performed on floodplain sediments remains comparatively low especially regarding the western mediterranean region however one of the reasons could be seen in the high complexity and diversity of processes and factors that control and influence fluvial activity that often hampers a straightforward interpretation of floodplain dynamics therefore a basic demand on fluvial archive research is to address the complexity of the factors that control the characteristics of fluvial sequences in order to provide a robust basis for their interpretation as a starting point for discussion this paper aims to give an overview of fluvial dynamic patterns in the western mediterranean for the last 15 ka in order to examine their relevance for palaeoenvironmental reconstructions the basis for this is provided by previous investigations on four different river systems in spain and northern africa the results of which are herein synthesized in order to propose a regional late pleistocene and holocene fluvial history for the western mediterranean realm basic results are related to alluvial floodplain deposits and visible features within them such as alluvial soils incision marks and aggradation phenomena since fluvial systems are open systems we discuss our findings against the background of different influencing factors that could modify fluvial architecture and may restrict palaeoenvironmental reconstructions a more comprehensive interpretation focuses on signals that are common to each of the studied river systems in this respect we critically discuss the customary nature of cumulative probability functions for the identification of regional flooding episodes and point out the benefits of a stratigraphy supported approach for characterizing regional floodplain dynamics finally three alluvial soil formation periods were found in all settings a first phase after 15 ka ending with the younger dryas event a second one from 7 to 5 ka with a break between 6 5 and 5 5 ka and a third phase between 3 and 2 ka these soil formation periods were interrupted and framed by fluvial dynamic phases accompanied by channel aggradation floodplain deposition floodplain erosion and or river incision in particular after 5 ka around 1 6 and at 1 ka and during the little ice age lia floodplain aggradation affected river systems in iberia and northern africa as well a cautious assessment of these results and extensive comparisons with secondary archive information prompts us to relate the aggradation periods with climate forcing by means of a supra regional aridification that effected large areas of the western mediterranean in contrast the three mentioned soil formation periods can be linked with landscape stability most probably triggered by favorable climate conditions in the western mediterranean apart from these large scale patterns we discuss the reliability of information emerging from floodplain records against the background of individualistic river behavior and self organization regarding future work we want to emphasize the great potential of yet rarely applied system oriented approaches that also attach importance to sub catchment dynamics as a link between catchment slopes and the main river floodplain

circumglobal teleconnection in the northern hemisphere summer analysis of the 56 yr ncep ncar reanalysis data reveals a recurrent circumglobal teleconnection cgt pattern in the summertime midlatitude circulation of the northern hemisphere this pattern represents the second leading empirical orthogonal function of interannual variability of the uppertropospheric circulation the cgt having a zonal wavenumber 5 structure is primarily positioned within a waveguide that is associated with the westerly jet stream the spatial phases of cgt tend to lock to preferred longitudes the geographically phase locked patterns bear close similarity during june august and september but the pattern in july shows shorter wavelengths in the north pacific north america sector the cgt is accompanied by significant rainfall and surface air temperature anomalies in the continental regions of western europe european russia india east asia and north america this implies that the cgt may be a source of climate variability and predictability in the above mentioned midlatitude regions the cgt has significant correlations with the indian summer monsoon ism and el nino southern oscillation enso however in normal ism years the cgt enso correlation disappears on the other hand in the absence of el nino or la nina the cgt ism correlation remains significant it is suggested that the ism acts as a conductor connecting the cgt and enso when the interaction between the ism and enso is active enso may influence northern china via the ism and the cgt additionally the variability of the cgt has no significant association with the arctic oscillation and the variability of the western north pacific summer monsoon the circulation of the wave train shows a barotropic structure everywhere except the cell located to the northwest of india where a baroclinic circulation structure dominates two possible scenarios are proposed the abnormal ism may excite an anomalous west central asian high and downstream rossby wave train extending to the north pacific and north america on the other hand a wave train that is excited in the jet exit region of the north atlantic may affect the westcentral asian high and thus the intensity of the ism it is hypothesized that the interaction between the global wave train and the ism heat source may be instrumental in maintaining the boreal summer cgt

winter climate anomalies in europe and their associated circulation at 500 hpa regional anomalies of the surface climate over europe are defined by a simultanous eof analysis of the normalized monthly mean sea level pressure temperature and precipitation fields of 100 winters december february 1887 1986 at 40 stations the monthly amplitudes of the first eof about 25 of the total variance are used as an index for the monthly winter climate anomaly they characterize a high low pressure cell over central europe associated with a positive negative temperature and precipitation anomaly over northern central southern europe as indicated by a northward southward shift of the tail end of the cross atlantic cyclone track these patterns resemble the phenomenological anticyclonic cyclonic grosswetter classification and the european blocking enhanced zonal flow regime the second eof is of similar magnitude and gives latitudinal corrections to these two basic flow regimes the joint probability distribution of both amplitudes shows a weak bimodality mainly associated with the first eof further insight into the underlying physical processes of the climate anomaly patterns in europe is obtained from the extended eliassen palm flux diagnostics of the barotropic transient eddy mean flow interaction hoskins et al 1983 and the stationary wave propagation plumb 1985 the diagnostics confined to the barotropic components and applied to the regression and the composite anomaly fields of the transient and stationary eddy flows of the 500 hpa geopotential 1946 87 north of 20 n leads to the following results 1 the bandpass filtered transient eddy variances of the 500 hpa geopotential show a shift of the cross atlantic storm track in high low pressure situations over europe the cross atlantic storm track intensity is enhanced reduced and its tail end is shifted northward remains zonal the north pacific storm track extends further less eastward and thus closer to the west coast of north america 2 the extreme high pressure system over europe tends to be supported by an anomalous transient eddy forcing of the mean flow stream function it enhances the zonal wind to its north and generates anticyclonic vorticity about 10 upstream from its center in the low pressure composite the anomalous cyclonic vorticity is generated reducing the zonal flow to its north 3 the occurrence lack of a strong eastward stationary wave activity flux over the atlantic is associated with the high low pressure situations over europe finally a positive feedback is conjectured between the stationary wavetrain modifying the tail end of the cross atlantic storm track and the transient eddies intensifying this anomaly

h4 abrupt event and late neanderthal presence in iberia heinrich event 4 h4 is well documented in the north atlantic ocean and the adjacent continents as a cooling event 39 000 yr before present bp to quantify the impact of this event with respect to climate and vegetation over the iberian peninsula we perform numerical experiments using a high resolution general circulation model forced by sea surface temperatures before and during h4 our model simulates an expansion of aridity over the peninsula during h4 a desertification of the south and a replacement of arboreal by herbaceous plants in the north all of which are in agreement with contemporaneous pollen sequences from marine cores located off the iberian peninsula our simulations demonstrate that the h4 marine event imprinted drastic changes over southern iberia which would not have favoured its occupation by anatomically modern humans therefore providing a plausible explanation for the delayed extinction of neanderthals in this region inferred from the archaeological record

strong continentality and effective moisture drove unforeseen vegetation dynamics since the last interglacial at inland mediterranean areas the villarquemado sequence in ne iberia abstract few continental palaeoenvironmental sedimentary sequences from southern europe are long enough to span the last interglacial period marine isotopic stage mis 5 the last glacial cycle mis 4 to 2 and the holocene el canizar de villarquemado north eastern iberian peninsula is an exceptional sedimentary lacustrine sequence spanning the last ca 135 000 years of environmental change in an area of inland iberia characterized by mediterranean climate with strong continentality we present a multiproxy study which combines palynological sedimentological and geochemical analyses framed by an independent robust chronology hydrological and climate evolutions were reconstructed by sedimentological and geochemical proxies development of wetlands and shallow carbonate lakes support relatively humid conditions during mis 6 till the onset of mis 4 and during the holocene palaeohydrological conditions were drier during mis 5 dominance of peat environments than during the holocene more frequent carbonate producing lakes sedimentological evidence indicates extremely arid conditions during mis 3 with greater activity of alluvial fans prograding into the basin sedimentary facies variability highlights a large environmental and hydrological variability during mis 2 and a rapid humidity response to the onset of the holocene compared to classic mediterranean sites we found novel pollen assemblages for the end of mis 6 and mis 5 indicating that the vegetation cover was essentially represented by sustained high proportions of continentality adapted taxa dominated by juniperus during the relatively humid conditions since mis 6 till the onset of mis 4 higher evapotranspiration in inland iberia would have increased during periods of higher seasonal insolation maxima impeding soil development and the usual mesophyte expansion during interglacials observed in other mediterranean areas four main periods of forest development occurred in villarquemado during mis 5e mis 5c mis 5a and the holocene secondary peaks occurred also during mis 3 during colder but still relatively humid mis 4 junipers and mediterranean taxa disappear but some mesophytes and cold tolerant species persisted and pinus became the dominant tree up to modern times pollen assemblages and geochemical data variability suggest a dominant control of seasonality and the impact of north atlantic dynamics both during mis 5 cold events c18 c24 and full glacial conditions he and d o interstadials at millennial scales steppe herbaceous assemblages dominated during the extremely arid conditions of mis 3 and pines and steppe taxa during glacial period mis 2 villarquemado sequence demonstrates that the resilient behaviour of conifers in continental areas of inland southern european regions is key to understand the glacial interglacial vegetation evolution and to evaluate scenarios for potential impacts of global change

climate palaeohydrology and land use change in the central iberian range over the last 1 6 kyr the la parra lake record a multiproxy study of a 7 m long sedimentary sequence from lake la parra 39 50 948 1 52 1014 m a s l supported by 11 14c ams and 210pb 137cs dates provides a robust high resolution hydrological and environmental variability record for the last 1600 years of the las torcas sinkhole complex in the central iberian range the succession of depositional environments in lake la parra sinkhole is controlled by both changes in the regional water table and by the balance between sedimentary input through ephemeral creeks and in lake production of carbonates and organic matter although synergetic links with climate are likely phases of increased sediment delivery to the lake at c ad 500 700 c ad 1000 ad 1450 1500 ad 1550 650 and since 1700 till recent times are driven primarily by human impact in the watershed prior to c ad 300 the sinkhole was dry then became a lake at the end of the roman period ad 350 when the doline was flooded and it has not dried out during the last 1600 years moderate

reconstructing the internal structure and long term evolution of hazardous sinkholes combining trenching electrical resistivity imaging eri and ground penetrating radar gpr abstract the approaches aimed at characterising specific damaging sinkholes have received limited attention compared with other ground instability phenomena e g landslides moreover the practicality of the trenching technique in combination with numerical dating and retro deformation analysis for sinkhole site investigations has been barely explored this work illustrates the advantages of combining geomorphic mapping electrical resistivity imaging eri ground penetrating radar gpr and trenching for sinkhole characterisation and shows how the trenching technique contributes to fill significant gaps that neither geomorphic nor geophysical methods can address two large sinkholes 200 m long related to the interstratal karstification of evaporites and generated by contrasting subsidence mechanisms sagging collapse were investigated in the fluvia valley ne spain although gpr data may provide high resolution information on subsidence related stratigraphic and structural features at shallow depth the profiles acquired in the investigated sites with 100 mhz shielded and 40 mhz unshielded antennae provided limited insight into the internal geometry of the sinkholes due to reduced signal penetration related to the presence of conductive clayey material the eri sections satisfactorily imaged the general geometry of the sagging and collapse subsidence structures up to depths higher than 100 m and clearly captured the basal contact of the low resistivity sinkhole fill in the sections with adequate layout and resolution the trenches despite their limited depth ca 5 m allowed us to obtain valuable objective information on several key aspects of the subsidence phenomenon 1 mechanisms deformation style and kinematics progressive versus episodic 2 limits of ground deformation 3 temporal evolution expansion versus contraction 4 chronology and timing of most recent deformation phase 5 rates of subsidence and sedimentation and 6 the role played by subsidence in the development of lacustrine environments and the associated sedimentation patterns

paleoproductivity variations related to climatic conditions in the alboran sea western mediterranean during the last glacial interglacial transition the diatom record the present study addresses the analysis of changes in marine primary productivity derived from climatic variability over the last 30 000 yr the study area is the alboran sea this is the westernmost basin of the mediterranean sea and was a very sensitive area to changes in sea levels and atmospheric configuration during the last glacial interglacial transition we report the results from four sediment cores recovered in both the western and eastern alboran basins this allowed us to monitor the w e evolution of the hydrological structures the study is mainly based on the diatom record although total organic carbon toc isotopes and uk 0 37 sst were also used to gain further information paleoceanographic conditions favoured high paleoproductivity rates during the last glacial maximum although this occurred at termination 1a and during the younger dryas event yd increasing towards the easternmost sites during these periods meteorological conditions with increased westerlies intensified the flow to the east driving an eastward migration of the western anticyclonic gyre a possible displacement of the north alboran upwelling system is also considered the major component of the diatom assemblage during the yd are the resting spores of leptocylindrus danicus which suggest the presence of cooler and less saline surface waters the opposite behaviour between planktonic and benthic proxies in addition to the high toc values allows us to infer a phase of reduced deep water renewal between 16 5 and 9 cal ky bp fresh water diatoms and opal phytoliths were used as indicators of aridity and humid land conditions respectively during the glacial period and until 14 cal ky bp we observed a gradual climatic deterioration accompanied by a loss of grass belts climatic conditions were warmer and moister during the bolling allerod while the yd was dry the re establishment of vegetation belts and replenishment of lakes was observed at 8 cal ky bp q 2001 elsevier science b v all rights reserved

mid holocene vegetation history and neolithic land use in the lake banyoles area girona spain abstract this paper focuses on high resolution analysis of pollen and sedimentology and botanical macro remains analysis in a core from lake banyoles girona spain the core sequence comprises a high resolution mid holocene ca 8 9 3 35 cal ka bp vegetation succession and sedimentological geochemical and geomorphological proxies are related to both climatic and anthropogenic causes deforestation processes affected natural vegetation development in the early neolithic 7 25 5 55 cal ka bp and late neolithic 5 17 3 71 cal ka bp in the context of broadleaf deciduous forest resilience against cooling and drying oscillations changes in sedimentation dynamics and in lake water level caused the emergence of dry land on the lake margin where riparian forest was established from 5 55 cal ka bp onwards the data show that in the context of an increasing aridification process neolithic land use played an important role in vegetation history and environmental evolution

hydrological variability in southeastern patagonia and explosive volcanic activity in the southern andean cordillera during oxygen isotope stage 3 and the holocene inferred from lake sediments of laguna potrok aike argentina abstract seismic reflection studies in the maar lake laguna potrok aike 51 58 s 70 23 w revealed an erosional unconformity associated with a sub aquatic lake level terrace at a water depth of 30m radiocarbon dated multi proxy sediment studies of a piston core from this location indicate that the sediment below this discontinuity has an age of 45kyr bp oxygen isotope stage 3 and was deposited during an interval of high lake level in comparison to the holocene section geochemical indicators of this older part of the record either point towards a different sediment source or to a different transport mechanism for oxygen isotope stage 3 sediments holocene sedimentation started again before 6790cal yr bp providing a sediment record of hydrological variability until the present geochemical and isotopic data indicate a fluctuating lake level until 5310cal yr bp during the late holocene the lake level shows a receding tendency nevertheless the lake level did not drop below the 30m terrace to create another unconformity the geochemical characterization of volcanic ashes reveals evidence for previously unknown explosive activity of the reclus and mt burney volcanoes during oxygen isotope stage 3

a test of uranium series dating of fossil tooth enamel results from tournal cave france abstract a series of well preserved mammal bones and horse teeth was analyzed from archaeological levels of tournal cave magdalenian aurignacian and mousterain to test the hypothesis that well crystallized enamel behaves more as a closed system than does whole bone the isotopic composition of bones and tooth enamels from this deposit meet criteria for confidence and gave no reasons to suspect contamination or open system behavior two samples for which231pa could be analyzed showed internal concordance with the respective230th ages in spite of the favourable isotopic criteria however comparison of the u series ages of the bones and the tooth enamel with stratigraphic position and14c control indicated the dates were not meaningful in general both bones and tooth enamels gave ages too young although some were clearly too old neither group showed any systematic increase of age with stratigraphic depth tooth enamel therefore shows no advantage over bone for u series dating for this site in tournal cave both bones and enamel are apparently open to u which is probably cycling as a consequences of post depositional groundwater movement

sea surface temperature during the quaternary at odp sites 976 and 975 western mediterranean abstract based on the relative abundances of the planktonic foraminifera species found in quaternary samples from odp sites 976 alboran sea and 975 menorca rise and using a modern analog technique winter and summer sea surface temperatures were estimated frequency distributions of temperatures are asymmetrical more so at odp site 976 where there is a greater abundance of samples from the warm part of the temperature range during the quaternary there is a general tendency for temperatures to fall with an overall diminution of 1 c for the winters and of more than 2 c for the summers overall mean temperatures and those of the biostratigraphic intervals identified are higher at odp site 975 than at 976 when differences are statistically significant the q1 interval i e the oldest in the quaternary is colder than the upl i e terminal pliocene and the q2 interval the q3 interval is also colder than the q2 interval and the q4 interval i e the most recent interval differences between intervals general trends and the asymmetries of frequency distributions cannot be explained as linear responses to insolation the stratigraphic series from odp site 976 was dated by correlating the relative maxima and minima of the summer temperature series with those of insolation during the month of july at 65 n it was found that 26 2 of the variance of the time series of temperatures was concentrated in the harmonics related to precession and obliquity while 19 was located in those related to eccentricity there are indications of the need to add lags and leads to the age of temperature spikes with respect to insolation but such delays and leads cannot be quantified precisely

arctic sea ice patterns driven by the asian summer monsoon abstractthe fluctuation of arctic sea ice concentration sic has been associated with changes in ocean circulation ecology and northern hemisphere climate prediction of sea ice melting patterns is of great societal interest but such prediction remains difficult because the factors controlling year to year sea ice variability remain unresolved distinct monsoon arctic teleconnections modulate summer arctic sic largely by changing wind forced sea ice transport east asian monsoon rainfall produces a northward propagating meridional rossby wave train extending into the siberian arctic the indian summer monsoon excites an eastward propagating circumglobal teleconnection along the subtropical jet reaching the north atlantic before bifurcating into the arctic the remote asian monsoon variations induce a dominant dipole sea ice melt pattern in which the north atlantic european arctic contrasts with the siberian north american arctic the monsoon related sea ice variations are complementary and comparable

abrupt changes in the asian southwest monsoon during the holocene and their links to the north atlantic ocean during the last ice age the indian ocean southwest monsoon exhibited abrupt changes that were closely correlated with millennial scale climate events in the north atlantic region1 2 3 suggesting a mechanistic link in the holocene epoch which had a more stable climate the amplitude of abrupt changes in north atlantic climate was much smaller and it has been unclear whether these changes are related to monsoon variability here we present a continuous record of centennial scale monsoon variability throughout the holocene from rapidly accumulating and minimally bioturbated sediments in the anoxic arabian sea our monsoon proxy record reveals several intervals of weak summer monsoon that coincide with cold periods documented in the north atlantic region4 including the most recent climate changes from the medieval warm period to the little ice age and then to the present we therefore suggest that the link between north atlantic climate and the asian monsoon is a persistent aspect of global climate

hydrological extremes in the aksu tarim river basin mid latitude dynamics analyses of precipitation 1961 2010 from 39 meteorological stations in the tarim river basin revealed a trend from dryer towards wetter conditions induced by an increase of the number of wet extremes a first 1961 1986 and second 1987 2010 period are the basis for a dynamical analysis of changing drought and wetness extremes which are closely related to cyclonic activity over the european continent and circulation anomalies in the northern hemisphere mid latitudes wave train cyclone tracks water flux and potential vorticity pv front analysis of the wet and dry months show the following result 1 the extreme wet and dry cases in winter and summer are characterized by distinguished wave train patterns upstream of the tarim river basin all wave trains originate in the atlantic european sector pointing towards wave train dynamics as one possible mechanism underlying the connection patterns observed 2 the selected extreme cases show that exceptional precipitation events can be connected to characteristic cyclone tracks and a pv front in the upper troposphere even if cyclone tracks never cross the tarim basin extremely wet winters are characterized by cyclone tracks close to the western and northern boundary of the tarim basin whereas during extremely dry winters such cyclone tracks are absent wet summers are characterized by long lived cyclonic anomalies at the north western corner of the tarim river basin see also 3 during dry summers such anomalies are absent 3 on a more local level the hydrological extreme events are linked to special dynamical structures of the upper tropospheric pv front in winter strong extreme precipitation is connected to a strong non linear wave development or a wave breaking event over the tarim river basin together with non linear wave development moisture and precipitation areas are advected towards the tarim river basin in dry winters the upper tropospheric pv front is much more zonally oriented and wave breaking is less frequent strong precipitation events are connected to strong breaking events and to the formation of long lived nearly stationary cyclones over or north of the tarim river basin during extremely wet summer months

the influence of subaquatic springs in lacustrine sedimentation origin and paleoenvironmental significance of homogenites in karstic lake banyoles ne spain abstract banyoles 42 08 n 2 45 e is the largest and deepest lake of karstic tectonic origin in the iberian peninsula the lake comprises two basins and six sub circularly shaped sub basins fed by subaquatic springs periods of intense groundwater inflow in the deepest sub basins lead to the fluidization and re suspension of previously deposited sediments and subsequent settling forming homogenite deposits on the southern basin intermediate platforms the multiproxy analysis of sediment cores combined with high resolution seismic stratigraphy 3 5 khz pinger and multi frequency chirp surveys allows a precise reconstruction of depositional environments and related hydrological variability and groundwater inflow during the last ca 7 6 cal kyr bp according to the age model based on 137cs 210pb and ams 14c dating homogenite deposition occurred between 7 2 and 5 5 cal kyr bp stopped during the middle holocene 5 5 2 8 cal kyr bp and greatly increased during the last two millennia with a total of 17 homogenite layers individually up to 75 cm thick the onset of this unique sedimentation mode at ca 3 cal kyr bp coincides with an increase in lake level evidenced by the onlapping of fine grained distal sediments over coarser massive carbonate rich littoral deposits a detailed multidisciplinary study of the homogenites sedimentology physical properties high resolution elemental geochemistry mineral composition grain size organic matter content and sem combined with seismic stratigraphy demonstrates that the fluidization events triggering the formation of the homogenites were caused by higher and more intense local groundwater inflow related to increased rainfall during the late holocene and likely intensified by land use changes during the last millennium

high resolution saline lake sediments as enhanced tools for relating proxy paleolake records to recent climatic data series abstract lake level in an endorheic saline lake in southern europe has been inferred for the last 105 years 1889 1994 at an annual level of resolution using two independent methods first ordination analyses factor analysis fa correspondence analysis ca and detrended correspondence analysis dca have been used to point out the mineral successions of the sedimentary record these successions are evidenced by the arch disposition of both samples and mineral phases in the plane defined by the first two eigenvectors calculated by these analyses these temporal evolutions are the same as those obtained during the drying and refilling phases of saline lakes relay indices ri were obtained from distances to the first two eigenvectors which accurately reconstructed the lake level evolution during this period second an inferred lake level series was obtained using a multivariate time series model from the average maximum temperatures and total rainfall six main drought periods were found which coincided with known droughts in the area a high level of agreement was found between the two reconstructions which offered the possibility of directly extending the instrumental record back into the past therefore climatic changes could be reconstructed from saline lakes provided that an accurate chronological control of sedimentary processes is available

interpreting transient carbonate compensation depth changes by marine sediment core modeling 1 with the advent of computationally fast intermediate complexity models of earth s climate and carbon cycle the marine record can be interpreted much more directly than before specifically the mechanistic simulation of deep sea sediment cores provides an important step in bridging the model data divide here i use this methodology to help interpret the excursion in carbonate compensation depth ccd during the paleoceneeocene thermal maximum that is recorded in cores recovered from walvis ridge in the south atlantic by explicitly simulating the expected geological record of a massive co2 release in an earth system model i show how reduction in the intensity of subsurface mixing of the sediment by benthic animals substantially magnifies the recorded shoaling of the ccd conversely to quantify correctly the carbon release consistent with the observed ccd changes one must account for any bioturbational changes a reduction in sediment mixing intensity also appears to be important to reproducing the sharpness of the contact between carbonate rich late paleocene sediments and the overlying early eocene clay layer at walvis ridge assuming a relatively rapid approximately 1 ka duration co2 release further helps to account for some of the paleoceanographic observations finally interbasin differences in bioturbational regime help resolve some of the observed disparity in carbonate preservation between walvis ridge and sites outside of the atlantic although changes in ocean ventilation and circulation are also likely to play a critical role in this

hydrological extremes in the aksu tarim river basin climatology and regime shift precipitation data between 1961 and 2010 from 39 meteorological stations in the tarim river basin are analyzed to classify and investigate hydrological drought and wetness conditions by using the standardized precipitation index spi the leading time and spatial variability of hydrological drought has been investigated by applying a principal component analysis and varimax rotation to the spi on a time scale of 24 months the results suggest that the western basin is characterized by a clear tendency towards wetter conditions after the middle of the 1980s which results from an increase in the number of wet extremes and can be considered as a regime shift subdividing the period of analysis into two parts 1961 1986 and 1987 2010 this change can be clearly seen in a shift of the probability distribution function of precipitation events composite analyses of monthly mean geopotential height fields and wind fields of the era 40 data set show that enhanced wetness in the tarim river basin after the middle of 1980s is closely related to cyclonic anomalies on the european continent and circulation anomalies over mid latitude of the northern hemisphere further correlation analysis between the principal components of spi and large circulation indices shows that hydrological extremes in the tarim river basin correlate with indices related to the polar vortex and subtropical high

holocene climate variability in the western mediterranean region from a deepwater sediment record 1 the detailed analysis of the international marine past global changes study core md99 2343 recovered from a sediment drift at 2391 m water depth north of the island of minorca illustrates the effects of climate variability on thermohaline circulation in the western mediterranean during the last 12 kyr geochemical ratios associated with terrigenous input resulted in the identification of four phases representing different climatic and deepwater overturning conditions in the western mediterranean basin during the holocene superimposed on the general trend eight centennial to millennial scale abrupt events appear consistently in both grain size and geochemical records which supports the occurrence of episodes of deepwater overturning reinforcement in the western mediterranean basin the observed periodicity for these abrupt events is in agreement with the previously defined holocene cooling events of the north atlantic region thus supporting a strong atlanticmediterranean climatic link at high frequency time intervals during the last 12 kyr the rapid response of the mediterranean thermohaline circulation to climate change in the north atlantic stresses the importance of atmospheric teleconnections in transferring climate variability from high latitudes to midlatitudes

lacustrine carbonates of iberian karst lakes sources processes and depositional environments abstract carbonates are the main components of iberian quaternary lake sediments in this review we summarize the main processes controlling carbonate deposition in extant iberian lakes located in mesozoic and tertiary carbonate dominated regions and formed through karstic activity during the late quaternary the lakes relatively small 1 ha to 118 ha and relatively shallow zmax 11 to 40 m provide examples of the large variability of sedimentary facies depositional environments and carbonate sources hydrology is dominated by groundwater inflow except those directly connected to the fluvial drainage nine lakes have been selected for this review and the main facies in palustrine littoral and profundal environments described and interpreted clastic carbonates occur in all iberian lakes due to the carbonate composition of the bedrocks surface formations and soils of the watersheds low temperatures and dilute meteoric waters seem responsible for the low carbonate content of sediments in high elevation lakes in the glaciated terrains in the pyrenees and the cantabrian mountains clastic carbonates are dominant in small karst lakes with functional inlets where sediment infill is dominated by fining upward sequences deposited during flood events re working of littoral carbonates is common in shallow environments and during low lake level stages in most lakes endogenic carbonate production occurs in two settings i littoral platforms dominated by chara and charophyte meadows and ii epilimnetic zone as biologically mediated calcite precipitates continuous preservation of varves since the mid holocene only occurs in one of the deeper lakes montcortes lake up to 30 m where calcite laminae textures massive fining upward and coarsening upward reflect seasonal changes in limnological conditions however varves have been formed and preserved in most of the lakes during short periods associated with increased water depth and more frequent meromictic conditions most iberian lakes are in a mature stage and karstic processes are not very active an outstanding example of a lake with intense karstic activity is banyoles lake where increased spring discharge after long rainy periods causes large remobilization and re suspension of the sediments accumulated in the deepest areas leading to the deposition of thick homogeneous layers homogeinites the iberian karst lake sequences underline the large variability of facies carbonate sources and depositional environments in small lake systems they illustrate how lake types evolve through the existence of a lake basin at centennial or even smaller time scales hydrology is the paramount control on facies and depositional environment patterns distribution and lake evolution and consequently a lake classification is proposed based on hydrology and sediment input a correct interpretation of carbonate sources and depositional history is a key for using lake sequences as archives of past global changes

late pleistocene loess and their paleosols in the granada basin southern spain abstract the granada basin contains several sites that include late pleistocene loess about seventy samples of fossil soils and sediments in six representative soil sequences were studied using palaeopedological methods the results form a basis for a regional pedostratigraphy and a high resolution indicator of changing climate during the last interglacial glacial cycle in the western mediterranean ten fossil soils of different ages show some similarity to the middle european loess stratigraphy it is thus inferred that there was a regular climatic sequence in this region during the late pleistocene with sedimentation during dry stadials and soil formation during wetter interstadials even in the sub humid to semi arid parts of southern spain

the taravilla lake and tufa deposits central iberian range spain as palaeohydrological and palaeoclimatic indicators 21 pages 8 figures 3 tables available online oct 13 2007 issue title lake systems sedimentary archives of climate change and tectonics egu general assembly

the record of hydroclimatic changes in the sediments of a kettle hole in a young glacial landscape north central poland abstract multidisciplinary research on the bottom sediments of a kettle hole at the retno site the brodnica lake district north central poland provided some information about changes in hydroclimatic conditions in the late glacial and the holocene detailed analysis sedimentological palynological macroremains geochemical and radiocarbon dating helped to identify 6 stages in the development of the depression in the village of gaj near retno lake with 11 phases of hydroclimatic conditions sediments of the retno profile with a total thickness of 6 72 m reflected individual natural stages in the development of the depression from a lake to a peat bog most of the environmental changes were gradual a sequence of late glacial and early holocene lacustrine sediments mainly gyttja occurred in the floor of the profile the upper 4 10 m consisted of paludal deposits peat of transitional and raised bogs divided at a depth of 1 56 1 54 m b g l by a thin layer of clay dated late subboreal early subatlantic the presence of this layer indicates a sudden change in the environmental conditions associated with a water level rise at that time denudation processes started within the drainage basin probably induced by human activity the important effects related to contemporary anthropopressure included desiccation of the peat bog muck formation in the uppermost 10 cm layer and elevated trophic conditions resulting in a change of the vegetation cover

on the pacific decadal oscillation and the atlantic multidecadal oscillation might they be related 1 the nature of the pacific decadal oscillation pdo is investigated based upon analyses of sea surface temperature observations over the last century the pdo is suggested to be comprised of a 20 year quasi periodic oscillation and a lower frequency component with a characteristic timescale of 60 years the 20 year quasi periodic oscillation is clearly identified as a phase locked signal at the eastern boundary of the pacific basin which could be interpreted as the signature of an ocean basin mode we demonstrate that the 60 year component of the pdo is strongly time lag correlated with the atlantic multidecadal oscillation amo on this timescale the amo is shown to lead the pdo by approximately 13 years or to lag the pdo by 17 years this relation suggests that the amo and the 60 year component of the pdo are signatures of the same oscillation cycle

low frequency variability of the indian monsoon enso relationship and the tropical atlantic the weakening of the 1980s and 1990s abstract the indian monsoon el nino southern oscillation enso relationship according to which a drier than normal monsoon season precedes peak el nino conditions weakened significantly during the last two decades of the twentieth century in this work an ensemble of integrations of an atmospheric general circulation model agcm coupled to an ocean model in the indian basin and forced with observed sea surface temperatures ssts elsewhere is used to investigate the causes of such a weakening the observed interdecadal variability of the enso monsoon relationship during the period 1950 99 is realistically simulated by the model and a dominant portion of the variability is associated with changes in the tropical atlantic ssts in boreal summer in correspondence to enso the tropical atlantic ssts display negative anomalies south of the equator in the last quarter of the twentieth century and weakly positive anomalies in the previous period those anomalies in turn produce heating anomalies which excit

a physical mechanism for north atlantic sst influence on the indian summer monsoon a link between the atlantic multidecadal oscillation amo and multidecadal variability of the indian summer monsoon rainfall is unraveled and a long sought physical mechanism linking atlantic climate and monsoon has been identified the amo produces persistent weakening strengthening of the meridional gradient of tropospheric temperature tt by setting up negative positive tt anomaly over eurasia during northern late summer autumn resulting in early late withdrawal of the south west monsoon and persistent decrease increase of seasonal monsoon rainfall on inter annual time scales strong north atlantic oscillation nao or north annular mode nam influences the monsoon by producing similar tt anomaly over eurasia the amo achieves the interdecadal modulation of the monsoon by modulating the frequency of occurrence of strong nao nam events this mechanism also provides a basis for explaining the observed teleconnection between north atlantic temperature and the asian monsoon in paleoclimatic proxies citation goswami b n m s madhusoodanan c p neema and d sengupta 2006 a physical mechanism for north atlantic sst influence on the indian summer monsoon

summer atmospheric bridging between europe and east asia influences on drought and wetness on the tibetan plateau abstract based on the era 40 reanalysis data dryness and wetness over the tibetan plateau are categorized according to the monthly standardized precipitation index the atmospheric features associated with severe and extreme dryness and wetness reveal two cross eurasia wave trains the scandinavia east asia wave train and the mediterranean east asia wave train severe and extreme dryness is associated with an anomalous cyclone over south and southeast asia which directs the moisture supply from the arabian sea the bay of bengal and the south china sea directly eastward towards the western pacific thus bypassing the tibetan plateau this cyclone anomaly constitutes part of the scandinavia east asia wave train which is sustained by the divergence and convergence of the anomalous transient eddy heat transport associated with a more southwest northeast oriented north atlantic storm track and a northward shift of the polar front jet in the north atlantic in contrast severe and extreme wetness over the tibetan plateau is associated with a more zonally elongated north atlantic storm track wave trains excited from there have a high probability to reach the mediterranean region and to propagate eastward following the subtropical westerly jet this mediterranean east asia wave train generates anticyclonic anomalies around the tibetan plateau and east china which bring more moisture supply from the arabian sea the south china sea and the western pacific towards the tibetan plateau and enhance the moisture convergence there this paper demonstrates how atmospheric bridging processes affect regional climate variability under present day climatic conditions which are also relevant for understanding past climates

paleoparasitological investigations on the neolithic lakeside settlement of la draga lake banyoles spain paleoparasitological analyses were conducted on samples from the neolithic lakeside settlement of la draga in spain 5320 4980 bc conventional microscopic analysis revealed the presence of tapewo

rossby wave propagation and teleconnection patterns in the austral winter abstract observational evidence of and theoretical support for the northern and southern hemisphere teleconnection patterns in the austral southern hemisphere winter are examined through an upper troposphere streamfunction teleconnectivity map and time lag cross correlation analysis using ecmwf initialized analysis 2oo hpa winds for the 11 june august periods from 1979 to 1989 as was previously found for the northern hemisphere winter the regions of strong teleconnectivity particularly in the winter hemisphere tend to he oriented in the zonal direction and coincide with the location of the major jet streams although equatorward propagation from the northern and southern hemispheres is observed little evidence of cross equatorial propagation has been found for comparison the response of a barotropic model linearized about a climatological 300 hpa june august time mean flow to localized forcing is determined it is found that the activity tends to be trapped inside each of the southern hemisphere

enhanced aridity and atmospheric high pressure stability over the western mediterranean during the north atlantic cold events of the past 50 k y multiproxy paleoenvironmental records pollen and planktonic isotope from ocean drilling program site 976 alboran sea document rapid ocean and climate variations during the last glacial that follow the dansgaard oeschger climate oscillations seen in the greenland ice core records thus suggesting a close link of the mediterranean climate swings with north atlantic climates continental conditions rapidly oscillated through cold arid and warm wet conditions in the course of stadial interstadial climate jumps at the time of heinrich events i e maximum meltwater flux to the north atlantic western mediterranean marine microflora and microfauna show rapid cooling correlated with increasing continental dryness enhanced aridity conceivably points to prolonged wintertime stability of atmospheric high pressure systems over the southwestern mediterranean in conjunction with cooling of the north atlantic

impact of iceberg melting on mediterranean thermohaline circulation during heinrich events down core samples of planktonic and benthic foraminifera were analyzed for oxygen and carbon isotopes in international marine past global changes study images core md99 2343 in order to study the interactions between climate change in the northern hemisphere and the western mediterranean thermohaline circulation at times of heinrich events he our results confirm the antiphase correlation between enhanced north atlantic deep water formation and low ventilation in the mediterranean however this study reveals that this antiphase relationship in deepwater formation between the north atlantic and mediterranean was interrupted during times of he when the injection of large volumes of water from melting icebergs reached the entrance to the mediterranean these events which lasted less than 1000 years are represented by pronounced decreases in both planktonic d18o and benthic d13c signals lower salinities of mediterranean surface water resulted in a slowdown of western mediterranean deepwater overturn even though cold sea surface temperatures and drier climate should have resulted in enhanced deepwater formation

palaeoenvironmental forcing during the middle upper palaeolithic transition in central western portugal article i nfo geoarchaeological analysis of the middle and upper palaeolithic record preserved in cave rock shelter and open air sites in the northern sector of the meso cenozoic of the western iberian peninsula margin portugal reveals several disconformities erosive unconformities hiatuses and surface stabilization phases a recurrent disconformity dated to ca 29 500 32 000 cal yr bp in the time range of heinrich event 3 must correspond to a main erosive event related to the impacts of climate change on the landscape including a reduction in vegetation cover and altered precipitation patterns with the consequent accelerated down cutting by stream systems slope reactivation and endokarstic reorganisation causing the erosion of sediments and soils accumulated in cave rock shelter and open air sites these processes create a preservation bias that may explain why early upper palaeolithic finds in primary deposition context remains exceptional in the carbonate areas of central western portugal and possibly elsewhere in the other places of iberia the impact of such site formation processes must therefore be duly considered in interpretations of the current patchy and scarce archaeological record of the middle upper palaeolithic transition in south western

high resolution x ray fluorescence core scanning analysis of les echets france sedimentary sequence new insights from chemical proxies the les echets sediment sequence has recently been the subject of a high resolution multi proxy study which revealed shifts in lake productivity linked to greenland stadials and interstadials over the last 40 ka wohlfarth et al 2008 rapid ecosystem response to abrupt climate changes during the last glacial period in western europe 40 16 ka geology 36 407 410 here we present new elemental data for this sequence as acquired using an x ray fluorescence core scanning system which provides in situ high resolution continuous multi element analyses it was found that the strength of associations between the studied elements ti rb k zr si ca sr mn and fe varied over time with changes in lake status which are ultimately driven by changes in climate increases in fine grained detrital input as indicated by ti rb k and zr rb overlap with independently established periods of lower lake productivity and are interpreted to represent more arid conditions several of these arid periods are coincident with low diatom concentrations and the timing of heinrich events h4 h3 and h2 the duration of the environmental impacts linked to the h events varied by proxy with elemental data ti and zr rb estimating shorter events than the diatom data periods of lower detrital input and coarser grain sizes agreed in time with periods of higher lake productivity the elemental data provide new insights into hydrological changes and related sediment processes within the catchment and highlight the need for multi element and multi proxy approaches when reconstructing climate change using lacustrine sediment sequences copyright 2011 john wiley sons ltd

saharan dust transport and high latitude glacial climatic variability the alboran sea record millennial to submillennial marine oscillations that are linked with the north atlantic s heinrich events and dansgaard oeschger cycles have been reported recently from the alboran sea revealing a close ocean atmosphere coupling in the mediterranean region we present a high resolution record of lithogenic fraction variability along images core md 95 2043 from the alboran sea that we use to infer fluctuations of fluvial and eolian inputs to the core site during periods of rapid climate change between 28 000 and 48 000 cal yr b p comparison with geochemical and pollen records from the same core enables end member compositions to be determined and to document fluctuations of fluvial and eolian inputs on millennial and faster timescales our data document increases in northward saharan dust transports during periods of strengthened atmospheric circulation in high northern latitudes from this we derive two atmospheric scenarios which are linked with the intensity of meridional atmospheric pressure gradients in the north atlantic region

did pyrenean glaciers dance to the beat of global climatic events evidence from the wurmian sequence stratigraphy of an ice dammed palaeolake depocentre in andorra the ice marginal depositional sequence of la massana provides a chronostratigraphic benchmark for reconstructing the wurmian glacial evolution of the valira catchment in andorra se pyrenees the sedimentary record of andorra confirms the asynchronous chronology of glacier fluctuations in different parts of the pyrenean mountain range a major ice recession occurred at the end of marine isotope stage mis 4 high magnitude valley glacier fluctuations during mis 3 constitute another important finding major readvances occurred toward the end of mis 3 whereas mis 2 in particular the global last glacial maximum or lgm featured sharp contrasts in ice recession rates between pyrenean valleys substantial distances separated mis 4 glacier fronts the wurmian maximum ice extent or mie from those reached during the global lgm in contrast to situations in the eastern pyrenees where wurmian mie and global lgm ice fronts nearly coincided overall the valira glaciers reveal patterns that are more similar to those recorded elsewhere in the western and central pyrenees than in the eastern pyrenees the rapid fluctuations recorded by andorran glaciers during the second half of the wurm also suggest a response to global forcing events such as heinrich events in the north atlantic

calibration and application of marine sedimentary physical properties using a multi sensor core logger abstract we examined geophysical data from a multi sensor core logger mscl a logging device providing continuous measurements of gamma ray attenuation p wave travel time and magnetic susceptibility on marine sediment cores in the first part we focused on the gamma ray system and compared two different calibration methods from the gamma ray attenuation we calculated densities and porosities by incorporating mass weighted attenuation coefficients the application of an iteration method reduces the error of the density and porosity estimates compared to grape data in addition we derived equations to calculate water content and dry bulk density from gamma ray attenuation measurements comparison with physical properties determined on discrete samples revealed a very good correlation of both data sets r 0 99 this correlation is valid for sediments from substantially different geological settings e g turbidites hemipelagic muds and opal rich sediments in the second part we applied our data to marine geological questions for sediments from the antarctic polar frontal zone there is indication that the content of biogenic opal can be assessed using a correlation of density and p wave velocity for sediments from the bengal fan the relationship between the mscl acoustic impedance the product of density and p wave velocity and the grain size distribution in discrete samples can be used to predict clay and sand silt ratios for sediment cores from the shelf and upper continental slope

late glacial early holocene vegetation and environmental changes in the western iberian central system inferred from a key site the navamuno record bejar range spain abstract a new record from a long sediment core s3 in navamuno 1505 m asl western iberian central system provides the reconstruction of the vegetation history and environmental changes in the region between 15 6 and 10 6 ka cal bp namely during the late glacial and the early holocene using a multiproxy analysis pollen based vegetation and climate reconstruction sedimentary macrocharcoals loss on ignition magnetic susceptibility and x ray fluorescence xrf measurements the results are then compared with other sequences from the iberian central system and the whole iberian peninsula in order to better understand the past dynamics of the main forest constituents the pollen record shows a shift from open pine forests 15 6 14 7 ka cal bp oldest dryas to mixed open pine birch woodlands 14 7 14 0 ka cal bp bolling woodlands were succeeded by a steppe like landscape until 13 4 ka cal bp older dryas which was replaced again by high mountain pine forests and riparian woodlands 13 4 12 6 ka cal bp allerod a great development of cold steppe grasslands linked to the decline of birch woodlands is documented 12 6 11 7 ka cal bp younger dryas the early holocene 11 7 10 6 ka cal bp was characterized by a progressive reforestation of the study area by pine and birch forests in the highlands and oak woods in the lowlands temperate tree taxa carpinus betulus castanea sativa corylus avellana fraxinus juglans tilia and ulmus were also common but likely at lower elevations pollen of fagus sylvatica was already recorded during the late glacial and the early holocene the marked increasing local fire activity during the warmer and wetter allerod oscillation could be related to a rise in tree cover supporting the climatically driven character of these fires nevertheless the strong increase in fire activity during the younger dryas would probably be related to growing tree and shrub mortality as well as to the wet dry biphasic structure of this stadial the standard modern analogue technique has been also applied to the navamuno sequence to provide quantitative climate estimations for the late glacial and the early holocene periods this record is one of the few continental archives that show the climatic trend between the late glacial and the early holocene in central iberia agreeing with many other regional records from the western mediterranean

abrupt climatic changes during the last glaciation based on pollen analysis of the abric romani catalonia spain the abric romani continental pollen record provides evidence of abrupt climate variations during the last glaciation the pollen record reveals a pattern of high frequency variations similar to that in ice cores as shown by oxygen isotopes or dust content analyses of 14 travertine samples yield coherent u series ages in correct stratigraphic order ranging from 40 000 to 70 000 yr according to changes in the composition and structure of the vegetation five paleoclimatic phases have been differentiated the oldest ranging from 70 200 to 65 500 yr ago records thermophilous taxa which correspond to the last warm events of isotopic stage 5 the next phase from 65 500 to 56 800 yr records a cold humid climate that correlates with isotope stage 4 during the third phase from 56 800 to 49 500 yr relatively warm and cold events alternate the fourth phase from 49 500 to 46 200 yr records a cold dry climate the fifth phase ranging from 46 200 to 40 800 yr records a milder phase that is similar in appearance to the beginning of the holocene

karstification without carbonic acid bedrock dissolution by gypsum driven dedolomitization aggressive karstification can take place where dolomite and gypsum are in contact with the same aquifer gypsum dissolution drives the precipitation of calcite thus consuming carbonate ions released by dolomite lake banyoles in northeastern spain is a karst lake supplied by sublacustrine springs and karstic collapse is occurring in the immediate vicinity of the lake lake water is dominated by mg ca and so 4 hco 3 and is supersaturated with calcite that is actively accumulating in lake sediments water chemistry sulfur isotope composition local stratigraphy and mass balance modelling suggest that the primary karst forming process at at lake banyoles is dedolomitization of basement rocks driven by gypsum dissolution karstification takes place along the subsurface contact between the gypsiferous beuda formation and the dolomitic perafita formation this process is here recognized for the first time to cause karstification on a large scale this is significant because it proceeds without the addition of soil generated carbonic acid gypsum driven dedolomitization may be responsible for other karstic systems heretofore attributed to soil generated carbonic acid