discovery of early holocene wood and peat on the forefield of the pasterze glacier eastern alps austria during recent years a number of fragments of pinus cembra and larix decidua as well as peat were found in front of the tongue of the pasterze glacier in the eastern alps these were washed out by the stream from under the present ice the wood originates from trees which reached ages of upto 400 years or more radiocarbon dating shows them to come from the early holocene they indicate that between cal bc 8100 and cal bc 6900 the pasterze glacier was smaller than at present the pasterze glacier advanced around cal bc 6900 a lump of peat shows that around cal bc 6300 at the latest the pasterze glacier was again smaller than today the radiocarbon age of the fulvic acid fraction of thepeat suggests that growth could have continued until cal bc 5430 5080 further wood samples dated to around cal bc 4800 and cal bc 3800 show that at these times the pasterze glacier was smaller than at present the pasterze glacier had a relatively limited extent over long periods inthe early holocene thus mostly favou

major storm periods and climate forcing in the western mediterranean during the late holocene abstract big storm events represent a major risk for populations and infrastructures settled on coastal lowlands in the western mediterranean where human societies colonized and occupied the coastal areas since the ancient times the variability of storm activity for the past three millennia was investigated with a multi proxy sedimentological and geochemical study from a lagoonal sequence mappings of the geochemistry and magnetic susceptibility of detrital sources in the watershed of the lagoon and from the coastal barriers were undertaken in order to track the terrestrial or coastal marine origin of sediments deposited into the lagoon the multi proxy analysis shows that coarser material low magnetic susceptibility and high strontium content characterize the sedimentological signature of the paleostorm levels identified in the lagoonal sequence a comparison with north atlantic and western mediterranean paleoclimate proxies shows that the phases of high storm activity occurred during cold periods suggesting a climatically controlled mechanism for the occurrence of these storm periods besides an in phase storm activity pattern is found between the western mediterranean and northern europe spectral analyses performed on the sr content revealed a new 270 year solar driven pattern of storm cyclicity for the last 3000 years this 270 year cycle defines a succession of ten major storm periods sp with a mean duration of 96 54 yr periods of higher storm activity are recorded from 680 to 560 cal yr bc sp10 end of the iron age cold period from 140 to 820 cal yr ad sp7 to sp5 with a climax of storminess between 400 and 800 cal yr ad dark ages cold period and from 1230 to 1800 cal yr ad sp3 to sp1 little ice age periods of low storm activity occurred from 560 cal yr bc to 140 cal yr ad sp9 and sp8 roman warm period and from 820 to 1230 cal yr ad sp4 medieval warm period

palaeoflood and floodplain records from spain evidence for long term climate variability and environmental changes abstract palaeoflood chronologies from seven spanish river basins and floodplain aggradation chronologies from thirteen rivers are analysed these fluvial records were divided in to two sub sets namely atlantic 10 ka record and mediterranean 3 ka record river basins which represent distinct modern hydroclimatic conditions in atlantic basins floods result from intense widespread rainfalls associated with atlantic frontal systems transported by westerly airflow mediterranean river flooding is related to heavy rainfall induced by mesoscale convective systems mcss during autumn months evidence from radiocarbon dates in slackwater flood deposits shows six periods of flood clusters at 10 750 10 240 9550 9130 4820 4440 2865 2350 960 790 and 520 290 cal bp despite the different flood producing weather conditions in atlantic and mediterranean rivers the radiocarbon sample clusters overlap and indicate changes in large scale atmospheric circulation and climatic conditions in the iberian peninsula comparison with proxy records of mean temperature for the northern hemisphere demonstrates a relationship between the period of slackwater flood deposition and cold climatic phases e g the 2650 yr bp climatic event or ad 1590 1650 period of the little ice age radiocarbon dates from aggraded floodplain sediments were clustered at 2710 2320 2000 1830 and 910 500 cal bp the first cluster period is in phase with the timing of slackwater deposition whereas the third 910 500 cal bp occurs in between two periods of increased flood frequency as indicated by the palaeoflood and documentary flood records it is argued that the 910 500 cal bp floodplain aggradation period reflects the first post roman evidence of environmental change related to generalised land use changes at the catchment scale which produced high sediment load transported to overbank areas during high flows

persistent solar influence on north atlantic climate during the holocene surface winds and surface ocean hydrography in the subpolar north atlantic appear to have been influenced by variations in solar output through the entire holocene the evidence comes from a close correlation between inferred changes in production rates of the cosmogenic nuclides carbon 14 and beryllium 10 and centennial to millennial time scale changes in proxies of drift ice measured in deep sea sediment cores a solar forcing mechanism therefore may underlie at least the holocene segment of the north atlantic9s 1500 year cycle the surface hydrographic changes may have affected production of north atlantic deep water potentially providing an additional mechanism for amplifying the solar signals and transmitting them globally

holocene climate variability as reflected by mid european lake level fluctuations and its probable impact on prehistoric human settlements abstract a data set of 180 radiocarbon tree ring and archaeological dates obtained from sediment sequences of 26 lakes in the jura mountains the northern french pre alps and the swiss plateau was used to construct a holocene mid european lake level record the dates do not indicate a random distribution over the holocene but form clusters suggesting an alternation of lower and higher climatically driven lake level phases they provide evidence of a rather unstable holocene climate punctuated by 15 phases of higher lake level 11 250 11 050 10 300 10 000 9550 9150 8300 8050 7550 7250 6350 5900 5650 5200 4850 4800 4150 3950 3500 3100 2750 2350 1800 1700 1300 1100 750 650 cal bp and after 1394 ad a comparison of this mid european lake level record with the gisp2 polar circulation index pci record the north atlantic ice rafting debris ird events and the 14 c record suggests teleconnections in a complex cryosphere ocean atmosphere system correlations between the gisp2 pci the mid european lake level the north atlantic ird and the residual 14 c records suggest that changes in the solar activity played a major role in holocene climate oscillations over the north atlantic area

holocene glacier fluctuations a global overview of glacier advances and retreats grouped by regions and by millennia for the holocene is compiled from previous studies the reconstructions of glacier fluctuations are based on 1 mapping and dating moraines defined by 14 c tcn osl lichenometry and tree rings discontinuous records time series and 2 sediments from proglacial lakes and speleothems continuous records time series using 189 continuous and discontinuous time series the long term trends and centennial fluctuations of glaciers were compared to trends in the recession of northern and mountain tree lines and with orbital solar and volcanic studies to examine the likely forcing factors that drove the changes recorded a general trend of increasing glacier size from the earlyemid holocene to the late holocene in the extra tropical areas of the northern hemisphere nh is related to overall summer temperature forced by orbitally controlled insolation the glaciers in new zealand and in the tropical andes also appear to follow the orbital trend i e they were decreasing from the early holocene to the present in contrast glacier fluctuations in some monsoonal areas of asia and southern south america generally did not follow the orbital trends but fluctuated at a higher frequency possibly triggered by distinct teleconnections patterns during the neoglacial advances clustered at 4 4e4 2 ka 3 8e3 4 ka 3 3e2 8 ka 2 6 ka 2 3e2 1 ka 1 5e1 4 ka 1 2e1 0 ka 0 7e0 5 ka corresponding to general cooling periods in the north atlantic some of these episodes coincide with multidecadal periods of low solar activity but it is unclear what mechanism might link small changes in irradiance to widespread glacier fluctuations explosive volcanism may have played a role in some periods of glacier advances such as around 1 7e1 6 ka coinciding with the taupo volcanic eruption at 232 5 ce but the record of explosive volcanism is poorly known through the holocene the compilation of ages suggests that there is no single mechanism driving glacier fluctuations on a global scale multidecadal variations of solar and volcanic activity supported by positive feedbacks in the climate system may have played a critical role in holocene glaciation but further research on such linkages is needed the rate and the global character of glacier retreat in the 20th through early 21st centuries appears unusual in the context of holocene glaciation though the retreating glaciers in most parts of the northern hemisphere are still larger today than they were in the early and or mid holocene the current retreat

climatic change and contemporaneous land use phases north and south of the alps 2300 bc to 800 ad fluctuations in the 14c curve and subsequent gaps of archaeological findings at 800 650 and 400 100 bc in western and central europe may indicate major climate driven land abandonment phases to address this hypothesis radiocarbon dated sediments from four lakes in switzerland were studied palynologically pollen analysis indicates contemporaneous phases of forest clearances and of intensified land use at 1450 1250 bc 650 450 bc 50 bc 100 ad and around 700 ad these land use expansions coincided with periods of warm climate as recorded by the alpine dendroclimatic and greenland oxygen isotope records our results suggest that harvest yields would have increased synchronously over wide areas of central and southern europe during periods of warm and dry climate combined interpretation of palaeoecological and archaeological findings suggests that higher food production led to increased human populations positive long term trends in pollen values of cerealia and plantago lanceolata indicate that technical innovations during the bronze and iron age e g metal ploughs scythes hay production fertilising methods gradually increased agricultural productivity the successful adoption of yield increasing advances cannot be explained by climatic determinism alone combined with archaeological evidence our results suggest that despite considerable cycles of spatial and demographic reorganisation repeated land abandonments and expansions as well as large scale migrations and population decreases human societies were able to shift to lower subsistence levels without dramatic ruptures in material culture however our data imply that human societies were not able to compensate rapidly for harvest failures when climate deteriorated agriculture in marginal areas was abandoned and spontaneous reforestations took place on abandoned land south and north of the alps only when the climate changed again to drier and warmer conditions did a new wide spread phase of forest clearances and field extensions occur allowing the reoccupation of previously abandoned areas spatial distribution of cereal cultivation and growth requirements of cerealia species suggest that increases in precipitation were far more decisive in driving crop failures over central and southern europe than temperature decreases

buried paleoanthrosols of the bronze age agricultural terraces in the kislovodsk basin northern caucasus russia abstract the article is devoted to the impact of ancient agriculture on soils and landscapes of the kislovodsk basin on the basis of pedological and archaeological investigations we found that the population of the koban culture 1200 600 bc of the kislovodsk basin had a highly developed agriculture by the middle of the first millennium bc more than 60 70 over 120 km2 of the slope areas and interfluve plateaus at the heights between 900 and 1500 m a s l was terraced the strongest anthropogenic transformation of soils and landscapes in the region coincided with drastic changes in climatic conditions at the turn of subboreal to subatlantic periods as a result of increasing precipitation and cooling in the middle of the first millennium bc erosion processes became generally more active in the region of our study they were especially strong in consequence of the absence of meadow vegetation however the widespread distribution of terraces with horizontal surfaces prevented the formation of ravines on the slopes the soil and upper part of bedrock washed from the slope of the upper terraces was deposited on the surface of the underlying terrace as a result the bronze age anthrosols of the terraces were covered by thick layers of slope sediments the middle of the first millennium bc may be considered as a zero point of the current stage of soil formation in the kislovodsk basin the subsequent warming combined with a decrease of precipitation at the second half of the first millennium bc caused the stabilization of sedimentation and the beginning of the current stage of soil formation in the region

high frequency holocene glacier fluctuations in new zealand differ from the northern signature understanding the timings of interhemispheric climate changes during the holocene along with their causes remains a major problem of climate science here we present a high resolution 10be chronology of glacier fluctuations in new zealand s southern alps over the past 7000 years including at least five events during the last millennium the extents of glacier advances decreased from the middle to the late holocene in contrast with the northern hemisphere pattern several glacier advances occurred in new zealand during classic northern warm periods these findings point to the importance of regional driving and or amplifying mechanisms we suggest that atmospheric circulation changes in the southwest pacific were one important factor in forcing high frequency holocene glacier fluctuations in new zealand

late holocene environmental dynamics and climate variability in a mediterranean high mountain environment sierra nevada spain inferred from lake sediments and historical sources landscape dynamics in the periglacial belt of a high mountain mediterranean environment is a process of rapid evolution but complex reconstruction following this purpose in this paper we discuss data from two sources concerning the past evolution of the present day periglacial environment in the sierra nevada southern iberian peninsula mountain lake sediments and documentary sources la mosca lake sedimentary record provides information about the palaeocological evolution in the mulhacen cirque over the last three millennia while documentary sources enable us to reconstruct the landscape evolution in the high lands of this massif over the last eight centuries during the late holocene cold and wet phases have favoured the activity of geomorphic processes with ephemeral development of glaciers in the highest northern cirques abundance of late lying snow patches and a decrease of the vegetation cover in the highest catchments by contrast warm periods have been more conducive to geomorphic stabilit

6600 years of human and climate impacts on lake catchment and vegetation in the julian alps lake bohinj slovenia abstract mountain grazing and ore processing had a significant impact on the alpine environment in the last 5000 years but few studies have so far focused on environmental changes of the south eastern alps this study investigates the vegetation history and sedimentary processes in the catchment of lake bohinj julian alps slovenia where a 12 m long core was collected in the central part of the lake sediment in the early holocene section of the core was partially reworked due to a major seismic event dated to 6711 6523 yr cal bp rapuc et al 2018 therefore a detailed palaeoenvironmental reconstruction was performed only for the top 4 4 m of the core here the results of mineralogical sedimentological geochemical stable isotope 13c and 15n and pollen analysis are presented in order to better understand the impact of people agriculture grazing mining on the environment and climate human interactions over the last 6600 years the results of palynological research suggest that at ca 6000 yr cal bp lake bohinj was surrounded by mixed forest composed of picea abies deciduous quercus with fagus becoming dominant after ca 3300 yr cal bp in the bronze and especially the iron age 3500 2500 yr cal bp when the region was according to archaeological data densely populated clearing of forests due to agriculture livestock production and metallurgical activities was detected through cerealia type pollen plantago lanceolata and the decline of abies these activities probably triggered soil erosion recorded as increased sedimentation rates in the subsequent centuries human impact on the environment continued increased but it seems that the watershed was not destabilised again several periods of high terrigenous input were recorded at 6100 6000 5700 5550 5000 4600 3900 3700 3550 2300 2200 yr cal bp and could be associated with a mobilisation of river inflow from the eastern flysch bearing catchment due to river migration during periods of wetter climate these flood patterns match with periods of enhanced flood activity in the wider alpine region

application of inventory data for estimating characteristics of and regional climate change effects on mountain glaciers a pilot study with the european alps a parameterization scheme using simple algorithms for unmeasured glaciers is being applied to glacier inventory data to estimate the basic glaciological characteristics of the inventoried ice bodies and simulate potential climate change effects on mountain glaciers for past and potential climate scenarios glacier changes for assumed mass balance changes are calculated as step functions between steady state conditions for time intervals that approximately correspond to the characteristic dynamic response time a few decades of the glaciers in order to test the procedure a pilot study was carried out in the european alps where detailed glacier inventories had been compiled around the mid 1970s total glacier volume in the alps is estimated at about 130 km3 for the mid 1970s strongly negative mass balances are likely to have caused a loss of about 10 20 of this total volume during the decade 1980 90 backward calculation of glacier length changes using a mean annual mass balance of 0 25m w e a 1 since the end of the little ice age around 1850 ad gives considerable scatter but satisfactory overall results as compared with long term observations the total loss of alpine surface ice mass since 1850 can be estimated at about half the original value an acceleration of this development with annual mass losses of around 1 m a 1 or more as anticipated from ipcc scenario a for the coming century could eliminate major parts of the presently existing alpine ice volume within decades

glacial fluctuations since the medieval warm period at rothera point western antarctic peninsula at a global scale there is no evidence for synchronous multi decadal warm medieval warm period mwp or cold little ice age lia periods in the late holocene on the other hand there is go

anthropogenic and climatic impact on holocene sediment dynamics in se spain a review the climatic and anthropogenic control on holocene sediment dynamics was not well constrained for the western mediterranean basin the paucity of high resolution palaeoenvironmental records long hampered a detailed understanding of the human impact on erosion rates this paper analyses holocene sediment dynamics in the context of regional climatic conditions land cover and human occupation based on an extended compilation of recently published high resolution paleoenvironmental proxy data from both terrestrial and marine environments the palaeoenvironmental reconstruction identified four main aridification episodes a at 5600 4700 a4 4100 3400 a3 2800 2500 a2 and 1900 1300 1200 a1 cal bp most of the severe aridification phases were climatically induced not human driven and well correlated with a large dataset of paleoenvironmental records from the western mediterranean basin and north atlantic ocean the phases of enhanced aridity are generally associated with enhanced sediment dynamics independent of the intensity and type of human occupation in contrast wet climatic conditions are found to be associated with both high and low sediment dynamics dependent on the human impact on the environment the mid late phoenician phoenician ii republican rome civilizations and the christian reconquest are all associated with high human impact on the environment and high erosion rates are reported for the vera basin and ne spain despite the improved hydrological conditions human occupation is not necessarily associated with geomorphic instability as shown by the post argaric omeya and nazarene periods that are characterized by low erosion rates and geomorphic stability

glacier and lake level variations in west central europe over the last 3500 years on the basis of glacier and lake level records this paper attempts for the first time a comparison between high resolution palaeohydrological and palaeoglaciological data in west central europe over the past 3500 years a data set of tree ring width radiocarbon and archaeological data in addition to historical sources were used to reconstruct fluctuations of the great aletsch the gorner and the lower grindelwald glaciers in the swiss alps the three ice streams experienced nearly synchronous advances at c 1000 600 bc and ad 500 600 800 900 1100 1200 and 1300 1860 these glacier fluctuations show strong correspondence with lake level variations reconstructed in eastern france jura mountains and pre alps and on the swiss plateau this supports the hypothesis of climatically driven fluctuations historical data available for the period since ad 1550 reveal in detail various meteorological conditions behind the successive glacier advances however in agreement with the general trend shown by th

varve microfacies and varve preservation record of climate change and human impact for the last 6000 years at lake tiefer see ne germany the holocene sediment record of lake tiefer see exhibits striking alternations between well varved and non varved intervals here we present a high resolution multi proxy record for the past 6000

the cold event 8200 years ago documented in oxygen isotope records of precipitation in europe and greenland stable oxygen isotope ratios of ostracod valves in late glacial and holocene sediments of core as 92 5 from deep lake ammersee southern germany reflect variations of mean oxygen isotope ratios in past atmospheric precipitation the record reconfirms the strong similarity of climate evolution in europe and greenland during the last deglaciation for the first time in europe we find a 200 year long negative 18o excursion which is contemporaneous with the strongest negative 18o excursion in the greenland ice around 8 2 ky before present the 8 2 ky isotopic event on both sides of the north atlantic ocean is interpreted as a cold period most probably induced by a perturbation of the north atlantic thermohaline circulation we discuss two possible triggering mechanisms 1 weak forcing as proposed by alley et al and 2 forcing by a strong and sudden freshwater pulse from the collapse of the hudson ice dome

reduced solar activity as a trigger for the start of the younger dryas it is generally assumed that changes in ocean circulation forced the abrupt climate changes during the late pleistocene including the younger dryas event recently however it was proposed that variations in solar irradiance could have played a much more prominent role in forcing pleistocene climate changes furthermore two physical mechanisms were recently published that explain how relatively small changes in solar irradiance could have had a strong impact on the climate system we discuss the possibility that an abrupt reduction in solar irradiance triggered the start of the younger dryas and we argue that this is indeed supported by three observations 1 the abrupt and strong increase in residual c 14 at the start of the younger dryas that seems to be too sharp to be caused by ocean circulation changes alone 2 the younger dryas being part of an similar to 2500 year quasi cycle also found in the c 14 record that is supposedly of solar origin 3 the registration of the younger dryas in geological records in the tropics and the mid latitudes of the southern hemisphere moreover the proposed two physical mechanisms could possibly explain how the north atlantic thermohaline circulation was perturbed through an increase in precipitation together with iceberg influxes in addition the full magnitude of the younger dryas cooling as evidenced by terrestrial records in europe could be explained we conclude that a solar triggering of the younger dryas is a valid option that should be studied in detail with climate models c 2000 elsevier science ltd and inqua all rights reserved

1200 years of decadal scale variability of mediterranean vegetation and climate at pantelleria island italy a new sedimentary sequence from lago di venere on pantelleria island located in the strait of sicily between tunisia and sicily was recovered the lake is located in the coastal infra mediterranean vegetation belt at 2 m a s l pollen charcoal and sedimentological analyses are used to explore linkages among vegetation fire and climate at a decadal scale over the past 1200 years a dry period from ad 800 to 1000 that corresponds to the medieval warm period wmp is inferred from sedimentological analysis the high content of carbonate recorded in this period suggests a dry phase when the ratio of evaporation precipitation was high during this period the island was dominated by thermophilous and drought tolerant taxa such as quercus ilex olea pistacia and juniperus a marked shift in the sediment properties is recorded at ad 1000 when carbonate content became very low suggesting wetter conditions until ad 1850 1900 broadly this period coincides with the little ice age lia which was charact

reconstructing palaeoprecipitation from an active cave flowstone several drill cores were obtained from a laminated actively forming flowstone from a shallow cave in austria highly resolved petrographic and geochemical analyses combined with multi annual cave monitoring reveal a distinct sensitivity of flowstone growth and composition to late holocene meteoric precipitation the regular sub millimetre scale lamination consists of thicker translucent laminae and thinner organic inclusion rich laminae there is also a macroscopic millimetre scale banding of darker and lighter bands comprising several laminae stable isotope analyses of drill cores and modern calcite precipitates show a pronounced positive covariation of 13c and 18o values indicative of kinetic isotope effects comparing the isotope values with petrography shows gradual changes across several of the annual laminae i e changes of several per mille on a multi annual to decadal timescale the stable isotope and trace element composition as well as the flowstone petrography are mainly controlled by the variable drip water discharge controlling the water film thickness and water residence time on the flowstone surface and consequently the intensity of co2 degassing kinetic isotope enrichment and concomitant calcite precipitation drill core pfu6 provides an isotope record of the last ca 3000 years at near annual resolution a distinct phase of low c and o isotope values interpreted as increased discharge and hence higher meteoric precipitation occurred from ca 300 to 140 a b2k second half of the little ice age and another wet interval occurred around 700 a corresponding to reported medieval glacier advances the roman warm period was also dominated by relatively wet conditions although significant decadal variability prevailed increased precipitation further characterized the intervals from ca 2480 to 2430 and 2950 to 2770 a dry conditions persisted during the medieval climate anomaly although this trend towards reduced precipitation started earlier the highest c isotope values of the last 2 ka are recorded around 750 a and another dry phase is centred at 1480 a this new record shows that inter annual to decadal oscillations are a dominant mode of variation during the last 3 ka in the alps copyright 2011 john wiley sons ltd

a chironomid based holocene summer air temperature reconstruction from the swiss alps we developed a quantitative chironomid july air temperature inference model based on surface sediments from 81 swiss lakes and applied it to the holocene subfossil chironomid record of hinterburgsee a small subalpine lake in the northern swiss alps present day mean july air temperature of 11 3 c after smoothing to reduce the high between sample variability of inferred temperatures the reconstruction indicates july air temperatures of 10 4 10 9 c at the end of the younger dryas of 11 9 12 8 c during the early and mid holocene 11500 4000 cal bp and slightly lower temperatures of 11 5 12 0 c during the late holocene 3500 1000 cal bp a warming trend inferred for the past millennium is most likely an artifact of human impact on hinterburgsee s chironomid fauna rather than a genuine temperature signal the most prominent climatological events during the holocene were two periods of lower temperatures at c 10700 10500 cal bp and 8200 7700 cal bp and an abrupt shift to a cooler late holocene cl

an inverse approach to the course of the little ice age glacier advance and the following deglaciation at austerdalsisen eastern svartisen northern norway the course of the little ice age lia in scandinavia is characterized by large glacier advances that started at about ad 1300 and culminated at about ad 1750 the end of the lia is marked as an unprecedented and ongoing glacier retreat that accelerated from the early 20th century the course of the lia is here presented based on fluctuations of austerdalsisen the largest valley outlet glacier draining the austre svartisen ostisen ice cap nordland northern norway during the lia glacierization austerdalsisen separated into two branches and relative to the present glacier terminus a western valley glacier advanced more than 4 km whereas a se valley glacier advanced about 3 km at present meltwater from austerdalsisen drains towards se if the glacier obtains a critical magnitude however most of the meltwater is drained westwards across a higher overflow gap based on radiocarbon dated lake sediments distal proglacial glaciolacustrine glaciofluvial sediments and historical observations the c

high chemical weathering rates in first order granitic catchments induced by agricultural stress chemical erosion rates have been determined on two upland granitic catchments under agricultural pressure in brittany france intensive agriculture has been carried out for at least 30 years in this region the influence of geochemical processes related to agriculture on the chemistry of streamwaters is determined through a geochemical mass balance the elemental export fluxes from these two agricultural catchments are then compared with other catchments around the world the volume and concentrations of the precipitation are taken into account as well as the inputs of organic and chemical fertilizers groundwaters and streamwaters to estimate the relative influence on export fluxes and then evaluate the elemental fluxes released by weathering the relatively high si flux of about 1 8 0 9 kmol ha 1 yr 1 is directly attributed to the chemical weathering of soil and rock in the catchment system however the si flux remains comparable to values found in both small and large sized catchments under temperate and tropical conditions on the other hand extremely high fluxes of major cations ca na and mg are observed ranging from 4 2 2 6 to 8 0 4 9 kmol ha 1 yr 1 which can be attributed to chemical weathering these fluxes remain dramatically higher than those found in granitic catchments worldwide despite an integrated agriculture the soil acidification induced by fertilizer application leads mainly to a release of major cations from the system by processes of soil ion exchange leaching as well as weathering of soil and rock

changes in the relationship nao northern hemisphere temperature due to solar activity abstract the influence of the north atlantic oscillation nao on wintertime northern hemisphere temperature nht is investigated the results suggest that this relationship has different sign according to the phase of the solar cycle for solar maximum phases nao and nht are positively correlated a result assumed up to the moment but for solar minimum phases correlations are not significant or even negative this result is in agreement with the different extension of the nao for solar cycle phases kodera geophys res lett 29 2002 14557 14560 almost hemispheric for maximum phases and confined to the eastern atlantic for minimum phases

synchronous holocene climatic oscillations recorded on the swiss plateau and at timberline in the alps eight synchronous pre roman cold phases were found at 9600 9200 8600 8150 7550 6900 6600 6200 5350 4900 4600 4400 3500 3200 and 2600 2350 radiocarbon years bp by reconstructing past climate at two sites on the swiss plateau and at timberline in the alps the cooling events during the early and mid holocene represent temperature values similar to today and apparently the onset of cooling events represents a deviation from today s mean annual temperature of about 1 c and is triggered at a 1000 year periodicity at wallisellen langachermoos 440 m a former oligotrophic lake near zurich the correlation between sum mertime lake levels and the seed production of the amphi atlantic aquatic plantnajas flexilis was used to reconstruct lake levels over a 3000 year period during the first part of the holocene at lake seedorf on the western swiss plateau 609 m the sedimentological palynological and macrofossil record revealed fluctuations of lake levels for the complete holocene from lago basso in the

european lakes as palaeohydrological and palaeoclimatic indicators abstract lakes in temperate regions have fluctuated in size on annual to millenial time scales changes in water level or depth can be reconstructed by applying geomorphic sedimentological and biostratigraphic methods to transects of sediment cores this systematic field based approach has been used at a number of sites in europe it is illustrated by reconstructions of water level changes in lakes from southern sweden these lakes have shown broadly synchronous changes during the holocene such synchronous changes in water levels at several sites in a region reflect climatic changes inferences about the mechanism of the climatic change depend on identifying both synchronous changes within a region and differences in the direction magnitude and timing of lake level changes between regions continental compilations of lake level data are therefore necessary detailed studies are not available from enough sites but the interpretation of already existing stratigraphic and biostratigraphic data in terms of lake level changes has greatly increased the number of sites available for a continental scale synthesis in europe this eclectic literature based approach is illustrated with examples from southern europe lakes in the mediterranean region were high around the glacial maximum and again somtime during the first half of the holocene in the western mediterranean the peak of late glacial aridity occurred at 15 000 16 000 bp and the lakes were already high again by 12 000 bp in the east maximum late glacial aridity occurred between 13 000 and 11 000 bp and there was a gradual return to wetter climates during the early holocene such that 9000 bp was more arid than 6000 bp most lakes in the mediterranean region were high at 6000 bp the transition to arid conditions after 5000 bp occurred abruptly in the west and more gradually in the east the lakes of southern sweden indicate drier climates in the early holocene ca 9000 bp more effective moisture between 8000 and 6000 bp increased aridity between 5500 and 3500 bp and increased effective moisture again during the last 3000 years the history of lake level changes in southern sweden and the mediterranean region can be partially explained in terms of changes in the direct effects of insolation and in the strength and position of the westerlies and of the subtropical high pressure cell during the late quaternary

reconstruction and palaeoclimatic interpretation of mid holocene vegetation and lake level changes at saint jorioz lake annecy french pre alps pollen and sediment analyses were used to reconstruct vegetation and lake level changes over the mid holocene period at saint jorioz lake annecy northern french pre alps episodes of forest clearings point to neolithic cultural activities in the northern french pre alps from c 6500 cal bp in agreement with other pollen and macrofossils records from eastern switzerland and the jura mountains the lake level record shows rises atc 8300 8200 6400 5900 and after 5730 cal bp the rise at c 8300 8200 cal bp shows a tripartition lower water levels developed before 8300 8200 and 6665 cal bp at c 6050 and 5730 cal bp rises at c 8300 8200 6400 5900 and after 5730 cal bp can be related to the 8200 yr event and north atlantic ice rafted debris ird events occurring at c 6200 5800 and 5500 cal bp respectively using a model based on pollen and lake level data the palaeoenvironmental changes reconstructed at saint jorioz were translated into quantitative climate parameters the results suggest that rises in lake level coincided with increasing annual precipitation runoff and available moisture and decreasing mean summer temperature and shortening of the growing season probably as a result of alternate southward northward displacements of the atlantic westerly jet at saint jorioz the period around the 8200 yr event corresponded to a c 2 5degreesc summer temperature cooling and a c 130 mm p e precipitation evaporation increase in agreement with other european and marine palaeoclimate records a c 4degreesc summer temperature cooling and a rise in annual precipitation by c 175 mm are reconstructed at c 5900 cal bp and after 5730 cal bp i e close to the time of the north atlantic ird events dated at 5800 and 5500 cal bp and are to be tested by further investigations a general trend toward temperature cooling and precipitation increase appears over the period documented by the sediment sequence of saint jorioz possibly related to an orbitally induced reduction of summer insolation

solar influences on holocene climatic changes illustrated by correlations between past lake level fluctuations and the atmospheric 14c record chronological correlations established at different time scales among the lake level fluctuations in the jura and french subalpine ranges glacier movements in the swiss and austrian alps and the atmospheric 14c record during the last 7 millennia show coincidences between lake level rises glacier advances and high 14c production and vice versa these correspondences suggest that the short term 14c variations may be an empirical indicator of holocene palaeoclimates and argue for possible origins of holocene climatic oscillations 1 the varying solar activity refers to secular climatic oscillations and to major climatic deteriorations showing a ca 2300 yr periodicity 2 a question is raised about a relationship between the earth s magnetic field and climate first the weak strength periods of the earth s dipole magnetic field between 3800 and ca 2500 b c coincide with higher climate variability and vice versa second the ca 2300 yr periods revealed by the 14c record and also by the major climatic deteriorations re corded in jurassian lakes ca 1500 a d ca 800 b c and ca 3500 b c coincide with the ca 2300 yr periods revealed by the earth s nondipole geomagnetic field the present warming induced by anthropogenic factors should be intensified during the next few centuries by natural factors of climate evolution

the 8 2 kyr bp event simulated by a global atmosphere sea ice ocean model seven freshwater perturbation experiments were performed with a global atmosphere sea ice ocean model to study the mechanism behind the 8 2 kyr bp holocene cooling event these experiments differed in initial state and duration of the applied freshwater pulse while the amount of freshwater was kept constant 4 67x10 14 m 3 one of the scenarios with freshwater added to the labrador sea at a rate of 0 75 sv during 20 years resulted in weakening of the north atlantic thermohaline circulation during 320 years and surface cooling varying from 1 to 5 degreesc over adjacent continents this result is consistent with proxy data suggesting that a meltwater induced weakening of the thermohaline circulation caused the event moreover our results indicate that the time scale of the meltwater release and the initial state are important as both have a strong effect on the magnitude and duration of the produced model response

reconstruction of holocene precipitation patterns in europe using pollen and lake level data abstract lake level data can be used to refine palaeoclimate reconstructions based on pollen data this approach is illustrated for the european holocene estimates of p pet precipitation minus potential evapotranspiration were first inferred from modern pollen analogues the pollen based estimates were then compared with the status of lakes within a 5 radius analogues with p pet anomalies inconsistent with the lake level changes were rejected the constrained sets of analogues were used to estimate continental scale patterns of annual mean temperature and annual precipitation at 3000 yr intervals estimated temperature anomalies differed only slightly from the unconstrained reconstructions estimated precipitation anomalies however showed improved spatial coherence and increased regional contrast and were occasionally reversed in sign the effect of the constraint was to impose a rational selection among almost equally similar modern pollen analogues with similar temperatures but widely varying moisture regimes the resulting maps showed clear spatially coherent patterns of change in precipitation as well as temperature suitable for comparison with climate model results further improvement of these maps will become possible as a more extensive coverage of lake level data is obtained

uranium isotopic evidence for the origin of the bahariya iron deposits egypt abstract the economic iron ore deposits of egypt are located at bahariya oasis in the lower middle eocene limestone the main iron minerals are goethite hematite siderite pyrite and jarosite manganese minerals are pyrolusite and manganite gangue minerals are barite glauconite gibbsite alunite quartz halite kaolinite illite smectite palygorskite and halloysite geochemical comparison between the ore and the nubia sandstone showed that the ore is depleted in the residual elements al ti v and ni and enriched in the mobile elements fe mn zn ba and u which indicates that the bahariya iron ore is not a lateritic deposit despite the deep weathering in this area on the other hand the nubia sandstone showed depletion in the mobile elements which demonstrates the leaching process in the nubia aquifer the presence of such indicator minerals as jarosite alunite glauconite gibbsite palygorskite and halloysite indicate that the ore was deposited under strong acidic conditions in fresh water isotopic analyses of the uranium in the amorphous and crystalline phases of the ore in the country rocks and dissolved in the nubia aquifer water all support the conclusion that u and fe were precipitated together from warm ascending groundwater u and fe display strong co variation in the ore and the 234u 238u activity ratio of the newly precipitated u in the country rock and the leached component of u in the groundwater are identical there is only slightly more uranium in the amorphous phase than in the crystalline and only a slightly lower 234u 238u activity ratio suggesting that the iron in the two phases have a similar origin comparison of the excess 234u in the water and in the total ore leads to the conclusion that the precipitation of the u and by inference the iron occurred within the last million years however that both precipitation and leaching of u have occurred over the last 300 000 years is evidenced by the extreme 230th 234u disequilibria observed in some of the samples some of the amorphous depositional events have been very recent perhaps within the last 10 000 years

lake sediment based paleoseismology limitations and perspectives from the swiss alps abstract in regions with moderate seismicity and large intervals between strong earthquakes paleoseismological archives that exceed the historical and instrumental timescale are needed to establish reliable estimates of earthquake recurrence for long return periods in several regions lake sediments have shown to be suitable for paleoseismological studies by causally linking characteristic sedimentological features to historic earthquakes studies on single lakes however do neither allow determining the paleoepicentre nor the paleomagnitude for the potential paleoearthquakes here we compile using shaking induced mass movements and micro deformations summarized as sedimentary event deposits seds the sedimentary paleoseismic record of 11 lakes from switzerland over the last 10 000 years the large dating uncertainty attributed to such deposits up to 250 years does not allow us to conclusively test for one large earthquake hypothesis when comparing the different lake records and therefore represents one of the major limitations of this approach instead using a new approach of exploring the normalized frequency of occurrence averaged over a larger area the compiled dataset reveals striking periods of enhanced occurrence of seds in the studied lakes during several phases of the past 10 000 years centered at 9700 6500 and during the last 4000 cal yr bp moreover we use a calibrated intensity attenuation relation in order to model scenarios of possible epicentral areas and ranges of magnitudes of paleoearthquakes we differentiate two cases i a single earthquake scenario if seds occur simultaneously in various studied lakes or ii a multi earthquake scenario if seds in the studied lakes cluster within a time interval the modelled scenarios allow us to propose maximally possible magnitudes of large paleoearthquakes constituting an important input for seismic hazard assessment in the swiss alps

geomorphological evidence for fluvial change during the roman period in the lower rhone valley southern france abstract the hydrological and geomorphological dynamics of the lower rhone river southern france are studied during the roman period 2nd 1st centuries bc 2nd 3rd centuries ad the crossing of archaeological and radiocarbon dating methods allow to study events at a pluridecadal to centennial scale from the avignon town to the delta the 15 sites where roman fluvial dynamics were recorded show higher flooding frequencies higher energy levels during floods rises in the marshes or groundwater levels and or active morphological dynamics such as channel migrations from 1st century bc to 1st 2nd centuries ad with respect to the encircling periods although this fluvial change does not reach the amplitude of great climatic events such as the little ice age in the rhone valley we show that it is also perceived in other parts of the catchment and could have a climatic origin however this event is not recorded in the immediate mediterranean environment of the lower rhone so that the rhone appears to efficiently transmit a foreign climatic change

extraordinary flood events and the response to monsoonal climatic change during the last 3000 years along the middle yangtze river valley china abstract well dated long term flood data series is very important in studying of hydrological response to past climatic change along the mainstream of the yangtze river five palaeoflood events recorded by slackwater deposits were identified by the sedimentological criteria and analytical results a detailed chronological framework of palaeoflood events during the late holocene was established by optically stimulated luminescence dating in combination with anthropogenic remains and with pedo stratigraphic correlations with well dated holocene loess soil profiles within the middle yangtze river basin the five palaeoflood events were dated to 2 43 0 18 ka 1 82 0 17 ka 0 94 0 07 ka 0 72 0 06 ka and 0 59 0 05 ka respectively these results are consistent with geological records at other palaeoflood sites and historical flood records along the middle yangtze river valley a regional synthesis of the palaeoflood chronology over the last 3000 years was compiled along the middle yangtze river extraordinary flood events generally seem to be correlated with late holocene climatic variability i e neoglacial cooling roman warm period dark ages cold period medieval climate anomaly and little ice age the high resolution climatic proxies from stalagmites of the dongge cave and heshang cave ice cores of the grip the total solar irradiance variations and sunspot number and enso activities suggest that these hydroclimatic events are possibly related to the weaker asia summer monsoon and the cooling climatic events as well as the stronger enso activities during the late holocene in the yangtze river valley these results provide insights into the response of hydroclimatic system to global change in the large rivers of asia

quantitative reconstruction of younger dryas to mid holocene paleoclimates at le locle swiss jura using pollen and lake level data abstract pollen and lake level data from le locle in the swiss jura were used to quantitatively reconstruct climatic parameters for the younger dryas event and the first half of the holocene period the younger dryas cold event at le locle was characterized by i a general trend toward a slight increase in summer temperature and a decrease in annual precipitation and ii a marked drying phase at ca 11 900 cal yr b p that occurred between two wetter ones further phases of major deficit in moisture occured at ca 11 500 cal yr b p younger dryas holocene transition 10 800 cal yr b p 8700 cal yr b p and 6500 cal yr b p climatic parameters reconstructed here suggest that phases of higher lake level developing at ca 12 500 12 000 11 750 11 600 11 200 10 900 synchronous with the preboreal oscillation 10 400 8900 8400 8300 possibly related to the 8200 yr event and 7800 7000 cal yr b p coincided with an increase in annual precipitation a decrease in summer temperature and a shorter growing season conversely periods of low lake level corresponded to a decrease in annual precipitation an increase in summer temperature and a longer growing season this general pattern could have resulted from alternate southward northward displacements of the atlantic westerly jet

holocene fluctuations of lake levels in the french jura and sub alpine ranges and their implications for past general circulation patterns temperature and precipitation variations reflected in lake level fluctuations in the french jura and pre alps during the last nine millennia are qualitatively assessed by reference to 1 climatic oscillations reconstructed in the alps and 2 modern processes behind alpine tree limit variations the summer season and mainly the late summer appears to have a deterministic impact on the holocene environment correlations between palaeoclimatic proxy data recorded in the north atlantic area from high and middle latitudes and climatic dynamics illustrated by the little ice age and the recent warming suggest 1 the existence of climatic oscillations due to varying solar activity superimposed on larger plurimillennial climatic trends and 2 that these minor climatic phases correspond with two main types of general circulation pattern alternating over western europe during the last six millennia the climatic deteriorations correspond with cooling at high latitudes inducing a stronger thermal grad

the alps with little ice evidence for eight holocene phases of reduced glacier extent in the central swiss alps glacially deformed pieces of wood organic lake sediments and clasts of reworked peat have been collected in front of alpine glaciers since ad 1990 the palaeoglaciological interpretation of these organic materials is related to earlier phases of glacier recession surpassing that of today s shrunken glaciers and to tree growth and peat accumulation in the valleys now occupied by the glaciers glacial transport of the material is indicated by wood anatomy incorporated silt sand and gravel particles missing bark and deformed treerings a total of 65 samples have been radiocarbon dated so far and clusters of dates provide evidence of eight phases of glacier recession 9910 9550 9010 7980 7250 6500 6170 5950 5290 3870 3640 3360 2740 2620 and 1530 1170 calibrated years bp allowing for the timelag between climatic fluctuations glacier response and vegetation colonization these recession phases may lag behind climatic changes by 100 200 years

holocene river activity analysing 14c dated fluvial and colluvial sediments from germany records of fluvial dynamics in response to long term changes of climate and land use impacts are rare therefore cumulative probability functions cpfs of 401 14c ages originating from german rivers and hillslopes were compiled to reconstruct phases of increased geomorphic activity and stability during the holocene an improved analytical method is suggested to normalise cpfs and eliminated the effects of wiggles of the calibration curve and the young age bias nine periods of activity are identified peaking at 7050 6250 5525 3690 2250 1350 820 325 bc and since 875 ad and are compared with climatic palaeohydrological and human impact proxy data until 2250 bc events of geomorphic activity are mainly coupled to wetter and or cooler climatic phases due to growing population and intensive agricultural activities during the bronze age the increased geomorphologic activity between 1300 and 820 bc cannot unequivocally be related to climate since 875 ad the growing population density is considered as the major external forcing differential geomorphic activity of hillslopes and floodplains suggest that the hillslope channel coupling during the holocene is mainly controlled by human impact with a strong increased coupling after 1500 bc

is a regional flood signal reproducible from lake sediments the evolution of flood activity with global warming remains uncertain to better assess flood climate relationships lake sediments are increasingly being investigated because they could provide regional flood histories long enough to cover past climate changes however site specific sedimentary processes may bias flood reconstructions the aim of this article is to investigate these effects through the reconstruction of two distinct flood records from independent neighbouring sedimentary basins of the same lake lake allos in the mediterranean french alps i e under the same climate conditions understanding of sedimentary processes is crucial in order to adapt the sampling strategy and the flood intensity proxy to each sedimentary system and thereby reconstruct a complete and reliable flood history thanks to this detailed approach the main trends of the regional flood variability can be reproduced i e periods of high flood frequency ranges of flood frequency values and timing of the most intense events in detail some differences appeared associated to the various stream capacities to erode and transport flood sediments to the lake system implying variable sensitivity of sedimentary systems in recording floods comparing regional flood records based on independent sedimentary systems from similar environments could thus be a complementary approach to assessing past flood intensity such an approach could open particularly interesting perspectives because reconstructing the long term evolution of flood intensity is a key challenge in the geosciences