holocene glacial activity and climatic variations in the swiss alps reconstructing a continuous record from proglacial lake sediments cores recovered from proglacial lake silvaplana swiss alps were investigated to examine the influence of holocene glaciers on lacustrine sedimentation during times of glacial activity in the catchment the sedimentation in the lake is dominated by the input of silt and clay sized material delivered by glacial meltwaters the deposition of fine grained material and the formation of varves reflect the existence of glaciers in the catchment and can therefore be used for the reconstruction of glacial history sedimentation rates are up to nine times higher in the varved than in the non varved sediments indicating significantly higher erosion rates under glaciated catchment conditions glacial varves were deposited in lake silvaplana during glacial retreat in the latest pleistocene and early holocene until 9400bp non varved deposits having a higher organic content and coarser grain sizes accumulated at lower rates when glacial activity was absent or negligible within the catchment between 9400 and 3300 bp

review and test of reproducibility of subdecadal resolution palaeoenvironmental reconstructions from microfossil assemblages abstract very high even annual resolution quantitative palaeoenvironmental reconstructions have been generated from microfossil assemblage data using transfer functions evidence of the utility of some of these reconstructions is given by the high correlations between the reconstructions and instrumental records such performance is despite several ecological and taphonomic issues that can become more problematic at subdecadal resolution than at multidecadal resolution this paper explores these timescale dependent issues and tests the reproducibility of the several of published reconstructions it demonstrates that the previously reported exceptionally good performance of several published chironomid based reconstructions is not reproducible

the medieval warm period the little ice age and simulated climatic variability the csiro mark 2 coupled global climatic model has been used to generate a 10 000 year simulation for present climatic conditions the model output has been analysed to identify sustained climatic fluctuations such as those attributed to the medieval warm period mwp and the little ice age lia since no external forcing was permitted during the model run all such fluctuations are attributed to naturally occurring climatic variability associated with the nonlinear processes inherent in the climatic system comparison of simulated climatic time series for different geographical locations highlighted the lack of synchronicity between these series the model was found to be able to simulate climatic extremes for selected observations for century timescales as well as identifying the associated spatial characteristics other examples of time series simulated by the model for the usa and eastern russia had similar characteristics to those attributed to the mwp and the lia but smaller amplitudes and clearly defined spatial patterns a search for the frequency of occurrence of specified surface temperature anomalies defined via duration and mean value revealed that these were primarily confined to polar regions and northern latitudes of europe asia and north america over the majority of the oceans and southern hemisphere such climatic fluctuations could not be sustained for reasons explained in the paper similarly sustained sea ice anomalies were mainly confined to the northern hemisphere an examination of mechanisms associated with the sustained climatic fluctuations failed to identify a role for the north atlantic oscillation the el nino southern oscillation or the pacific decadal oscillation it was therefore concluded that these fluctuations were generated by stochastic processes intrinsic to the nonlinear climatic system while a number of characteristics of the mwp and the lia could have been partially caused by natural processes within the climatic system the inability of the model to reproduce the observed hemispheric mean temperature anomalies associated with these events indicates that external forcing must have been involved essentially the unforced climatic system is unable to sustain the generation of long term climatic anomalies

alpine lacustrine varved record reveals summer temperature as main control of glacier fluctuations over the past 2250 years glacier fluctuations are a key indicator of changing climate their reconstruction beyond historical times unravels glacier variability and its forcing factors on long time scales which can considerably improve our understanding of the climate glacier relationship here we present a 2250 year long reconstruction of particle mass accumulation rates recorded in the lacustrine sediments of lake truebsee central swiss alps that are directly related to glacier extent thus reflecting a continuous record of fluctuations of the upstream located titlis glacier mass accumulation rate values show strong centennial to multi centennial fluctuations and reveal 12 well pronounced periods of enhanced values corresponding to times of maximum extent of the neighboring lower grindelwald glacier this result supports previous studies of proglacial lake sediments that documented high mass accumulation rate values during glacier advances the strong variability in the lake truebsee mass accumulation rate record thus represents a highly sensitive paleoclimatic archive which mirrors rapid and pronounced feedbacks of titlis glacier to climatic changes over the past 2250 years the comparison of our data with independent paleo temperature reconstructions from tree rings suggests that variations in mean summer temperature were the primary driving factor of fluctuations of titlis glacier also advances of titlis glacier occurred during the grand solar minima dalton maunder sporer wolf of the last millennium this relation of glacier extent with summer temperature reveals strong evidence that the mass balance of this alpine glacier is primarily controlled by the intensity of glacier melting during summer

evidence of lateglacial and holocene climatic change and human impact in eastern anatolia high resolution pollen charcoal isotopic and geochemical records from the laminated sediments of lake van turkey annually laminated sediments from lake van spanning about 13000 varve years were sampled for stable isotopic geochemical pollen and charcoal analyses in order to find evidence of past regional climatic changes and human impact in the semi arid region of eastern anatolia turkey the lateglacial period was cold and dry with steppe vegetation and saline lake water during the younger dryas the lake level dropped dramatically and the vegetation turned to a semi desert geochemical and isotopic records indicate a strong increase in moisture at the onset of the holocene and artemisia chenopod steppes were partly replaced by grass steppe and pistachio scrub a delay of about 3000 years in the expansion of deciduous oak woodlands and high steppe fire frequencies suggest dry spring and summer weather during the early holocene at 8200 yr bp a shift in the regional climate regime facilitated the transport of more moisture into the interior areas of the taurus mountains and caused a change in the seasonal distribution of precipitation the steppe forests dominated by quercus advanced and reached their maximum extention at about 6200 yr bp all the proxy data indicate optimum climatic conditions low water salinity and high lake level between 6200 and 4000 yr bp after 4000 yr bp aridity increased again and the modern climatic situation was established human impact in the catchment of lake van started at 3800 yr bp and was intensified during the last 600 years

observational evidence of preferred flow regimes in the northern hemisphere winter stratosphere abstract ten yeah of stratosphere geopotential height data are analyzed in an attempt to determine whether there are preferred flow regimes in the northern hemisphere winter stratosphere the data are taken from stratospheric sounding units on board noaa satellites the probability density estimate of the amplitude of the wavenumber 1 10 mb height is found to be bimodal the density distribution is composed of a dominant large amplitude mode and a less frequent low amplitude mode when the wavenumber 1 10 mb height data are projected onto the phase plant defined by the 10 mb zonal mean winds and wavenumber 1 100 mb heights three preferred regimes are evident the small amplitude mode separates into a strong zonal wind weak wave regime and a weak zonal wind weak wave regime the large amplitude mode is an intermediate zonal wind strong wave regime transitions between the large amplitude regime and the weak zonal wind weak wave regime are found to be associated with major stratospheric warnings the clust

decadal scale autumn temperature reconstruction back to ad 1580 inferred from the varved sediments of lake silvaplana southeastern swiss alps a quantitative high resolution autumn september november temperature reconstruction for the southeastern swiss alps back to ad 1580 is presented here we used the annually resolved biogenic silic

recent warming in a 500 year palaeotemperature record from varved sediments upper soper lake baffin island canada laminated sediments from upper soper lake on southern baffin island provide a new 500 year record of temperature change in the arctic radiometric dating using 210pb and pu shows that the light and dark coloured laminae couplets are annually deposited varves dark laminae thickness is strongly correlated to average june temperature from kimmirut r 0 82 reflecting the influence of temperature on snowmelt and fluxes of runoff and suspended sediment this relationship allowed the construction of a palaeotemperature record that documents large amplitude interannual to decadal variability superimposed on distinct century scale trends including 2 c average warming and maximum temperatures during the 1900s similar patterns of change are seen in individual and regionally averaged palaeotemperature records from around the circum arctic upper soper lake records temperatures rates of change and variance during the twentieth century that are all anomal ously high within the context of the last 500 years and outside the observed range of natural variability comparisons of upper soper lake and arctic average palaeotemperature to proxy records of hypothesized forcing mechanisms suggest that the recent warming trend is mostly due to anthropogenic emissions of atmos pheric greenhouse gases the magnitude of the warming and decade scale variability throughout the records however indicate that natural forcing mechanisms such as changing solar irradiance and volcanic activity as well as positive feedbacks within the arctic environment also play an important role

lateglacial environmental and climatic changes at the maloja pass central swiss alps as recorded by chironomids and pollen abstract chironomids and pollen were studied in a radiocarbon dated sediment sequence obtained from a former lake near the maloja pass in the central swiss alps 1865 m a s l to reconstruct the lateglacial environment pollen assemblages imply a vegetation development around the maloja pass from shrub tundra at the beginning of the allerod to coniferous forest during the early holocene with a lowering of the timberline during the younger dryas chironomid assemblages are characterized by several abrupt shifts in dominant taxa through the lateglacial the occurrence of taxa able to survive hypoxia in the second part of the allerod and during the preboreal and their disappearance at the onset of the younger dryas cold phase suggest summer thermal stratification and unfavourable hypolimnetic oxygen conditions in the palaeo lake during the warmer periods of the lateglacial interstadial and early holocene mean july air temperatures were reconstructed using a chironomid temperature transfer function from the alpine region the pattern of reconstructed temperature changes agrees well with the greenland 18 o record and other lateglacial temperature inferences from central europe the inferred july temperatures of ca 10 0 c during most of the allerod were slightly lower than modern values 10 8 c and increased up to ca 11 7 c i e above present day values at the end of the allerod the first part of the younger dryas was colder ca 8 8 c than the second part ca 9 8 c during most of the preboreal the temperatures persisted within the limits of 13 5 14 5 c i e ca 3 c above present day values the amplitudes of temperature changes at the allerod younger dryas preboreal transitions were ca 3 5 4 0 c the temperature reconstruction also shows three short lived cooling events of ca 1 5 2 0 c which may be attributed to the centennial scale greenland interstadial events gi 1d and gi 1b and the preboreal oscillation

evolution of nao and amo strength and cyclicity derived from a 3 ka varve thickness record from iceland abstract a 3000 year varve thickness record from hvitarvatn a glacier dominated lake in central iceland preserves inter annual variations in the delivery of glacially eroded sediment to the lake the first order low frequency trend in varve thickness reflects increased glacial erosion through the late holocene reaching a peak during the little ice age lia superimposed on this trend are large inter annual to decadal fluctuations in varve thickness that we suggest reflect variability in climate parameters that determine the efficiency of the fluvial transport system to deliver glacially eroded sediment to the lake each year we use spectral analysis to test whether regular high frequency cyclicity in varve thickness exists in the 3 ka record after removing the low frequency variability spectral analyses from three sediment cores recovered from the lake show essentially the same periods of 2 8 3 4 13 35 40 and 85 93 for the overlapping 900 year period additionally cycles of 55 130 and 290 years are found in the spectrum for the 3000 year record that do not show up in the spectra for the shorter cores some of these cycles show similar variability to those of the north atlantic oscillation nao and atlantic multidecadal oscillation amo this relationship is supported by a significant correlation between varve thickness and both the nao precipitation and amo summer temperature indices over the 180 year instrumental period nao cyclicities 2 15 years are weakly expressed in the first half of the record increase between 600 and 1000 ad decrease in strength during medieval time and are most strongly expressed between 1300 ad and the early 20th century amo cyclicities 50 to 130 years are also relatively weak in the first half of the record becoming quite strong between 600 and 1000 ad and again between 1100 and 1500 ad but are essentially absent through the peak of the lia between 1500 and 1900 ad a time when strong cyclicities of about 35 years appear

reconstructions of late holocene paleofloods and glacier length changes in the upper engadine switzerland ca 1450 bc ad 420 article i nfo article history the relationship between summer autumn floods in central europe and climate warming is poorly con strained by available instrumental historical proxy and model data to investigate this relationship a complete record of paleofloods regional glacier length changes and associated climate phases and regional glacier advances and retreats and associated climate transitions are derived from the varved sediments of lake silva plana ca 1450bc ad420 upperengadine switzerland incombination theserecordsprovideinsightintothe behavior of floods i e frequency under a wide range of climate conditions eighty five paleofloods are identified from turbidites in the sediments of lake silvaplana regional glacier length changes and associated cool and or wet and warm and or dry climate phases are inferred from centennial anomalies in the square root of low pass lp filtered mass accumulation rates marlp

quantitative summer temperature reconstruction derived from a combined biogenic si and chironomid record from varved sediments of lake silvaplana south eastern swiss alps back to ad 1177 abstract high resolution quantitative temperature records are needed for placing the recent warming into the context of long term natural climate variability in this study we present a quantitative high resolution 9 year summer june august temperature reconstruction back to ad 1177 for the south eastern swiss alps this region is a good predictor for summer temperatures in large parts of western and central europe our reconstruction is based on a combination of the high frequency component of annually resolved biogenic silica bsi flux data and the low frequency component of decadal chironomid inferred temperatures from annually laminated well dated sediments varves from proglacial lake silvaplana eastern swiss alps for the calibration period ad 1760 1949 we assess systematically the effects of six different regression methods type i regressions inverse regression ir inverse prediction ip generalised least squares gls type ii regressions major axis ma ranged major axis rma and standard major axis sma with regard to the predicted amplitude and the calibration statistics such as root mean square error of prediction rmsep reduction of error re and coefficient of efficiency ce we found a trade off in the regression model choice between a good representation of the amplitude and good calibration statistics the band pass filtered bsi flux record is in close agreement both in the structure and the amplitude with two fully independent reconstructions spanning back to ad 1500 and ad 1177 respectively all known pulses of negative volcanic forcing are represented as cold anomalies in the bsi flux record volcanic pulses combined with low solar activity sporer and maunder minimum are seen as particularly cold episodes around ad 1460 and ad 1690 the combined chironomid and bsi flux temperature record rmsep 0 57 c is in good agreement with the glacier history of the alps the warmest ad 1190 and coldest decades 17th century 1680 1700 of our reconstruction coincide with the largest anomalies in the alpine tree ring based reconstruction both records show in the decadal variability an amplitude of 2 8 c between ad 1180 and 1950 which is substantially higher than the amplitude of hemispheric reconstructions our record suggests that the current decade is slightly warmer than the warmest decade in the pre industrial time of the past 800 years

a 600 years warm season temperature record from varved sediments of lago plomo northern patagonia chile 47 s abstract high resolution records of calibrated proxy data for the past millennium are fundamental to place current changes into the context of pre industrial natural forced and unforced variability although the need for regional spatially explicit comprehensive reconstructions is widely recognized the proxy data sources are still scarce particularly for the southern hemisphere and especially for south america we present a 600 year long warm season temperature record from varved sediments of lago plomo a proglacial lake of the northern patagonian ice field in southern chile 46 59 s 72 52 w 203 m a s l the thickness of the bright summer sediment layer relative to the dark winter layer measured as total brightness reflectance 400 730 nm is calibrated against warm season sondjf temperature 1900 2009 r 0 58 p aut 0 056 re 0 52 ce 0 15 rmsep 0 28 c five year triangular filtered data in lago plomo warm summer temperatures lead to enhanced glacier melt and suspended sediment transport which results in thicker light summer layers and to brighter sediments although patagonia shows pronounced regional differences in decadal temperature trends and variability the 600 years temperature reconstruction from lago plomo compares favourably with other regional continental temperature records but also emphasizes significant regional differences for which no data and information existed so far these regional differences seem to be real as they are also reflected in modern climate data sets 1900 2010 the reconstruction shows pronounced subdecadal multidecadal variability with cold phases during parts of the little ice age 16th and 18th centuries and in the beginning of the 20th century the most prominent warm phase is the 19th century which is as warm as the second half of the 20th century the exceptional summer warmth ad 1780 1810 is also found in other archives of northern patagonia and central chile our record shows the delayed 20th century warming in the southern hemisphere the comparison between winter precipitation and summer temperature inter seasonal coupling from lago plomo reveals alternating phases with parallel and contrasting decadal trends of winter precipitation and summer temperature positive and negative running correlations r winter pp summer tt this observation from the sediment proxy data is also confirmed by two sets of reanalysis data for the 20th century reanalysis data show that phases with negative correlations between winter precipitation and summer temperature e g dry winters and warm summers at lago plomo are characteristic for periods when circumpolar westerly flow is displaced southward and enhanced around 60 s

how stable are twentieth century calibration models a high resolution summer temperature reconstruction for the eastern swiss alps back to ad 1580 derived from proglacial varved sediments we found a significant positive correlation between local summer air temperature may september and the annual sediment mass accumulation rate mar in lake silvaplana 46 n 9 e 1800 m a s l during the twentieth century r 0 69 p 0 001 for decadal smoothed series sediment trap data 2001 2005 confirm this relation with exceptionally high particle yields during the hottest summer of the last 140 years in 2003 on this base we developed a decadal scale summer temperature reconstruction back to ad 1580 surprisingly the comparison of our reconstruction with two other independent regional summer temperature reconstructions based on tree rings and documentary data revealed a significant negative correlation for the pre 1900 data ie late little ice age this demonstrates that the correlation between mar and summer temperature is not stable in time and the actualistic principle does not apply in this case we suggest that different climatic regimes modern little ice age lead to changing state conditions in the catchment and thus to considerably different sediment transport mechanisms therefore we calibrated our mar data with gridded early instrumental temperature series from ad 1760 1880 r 0 48 p 0 01 for decadal smoothed series to properly reconstruct the late lia climatic conditions we found exceptionally low temperatures between ad 1580 and 1610 0 75 c below twentieth century mean and during the late maunder minimum from ad 1680 to 1710 0 5 c below twentieth century mean in general summer temperatures did not experience major negative departures from the twentieth century mean during the late little ice age this compares well with the two existing independent regional reconstructions suggesting that the lia in the alps was mainly a phenomenon of the cold season

maturity of nearby faults influences seismic hazard from hydraulic fracturing understanding the causes of human induced earthquakes is paramount to reducing societal risk we investigated five cases of seismicity associated with hydraulic fracturing hf in ohio since 2013 that because of their isolation from other injection activities provide an ideal setting for studying the relations between high pressure injection and earthquakes our analysis revealed two distinct groups i deeper earthquakes in the precambrian basement with larger magnitudes m 2 b values 1 5 and few post shut in earthquakes based on geologic history laboratory experiments and fault modeling we interpret the deep seismicity as slip on more mature faults in older crystalline rocks and the shallow seismicity as slip on immature faults in younger sedimentary rocks this suggests that hf inducing deeper seismicity may pose higher seismic hazards wells inducing deeper seismicity produced more water than wells with shallow seismicity indicating more extensive hydrologic connections outside the target formation consistent with pore pressure diffusion influencing seismicity however for both groups the 2 to 3 h between onset of hf and seismicity is too short for typical fluid pressure diffusion rates across distances of 1 km and argues for poroelastic stress transfer also having a primary influence on seismicity

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

model study of the spatial distribution of the energy and mass balance of morteratschgletscher switzerland to investigate the spatial distribution of the energy and mass balance fluxes of a glacier a two dimensional mass balance model was developed and applied to morteratschgletscher switzerland the model is driven by meteorological input from four synoptic weather stations located in the vicinity of morteratschgletscher the model results were compared to observations made on the glacier the calculated mean specific mass balance is 0 47 m w e for 1999 and 0 23 m w e for 2000 net shortwave radiation shows a minimum at around 3350 m a s l due to the effects of shading slope aspect reflection from the slopes and obstruction of the sky ignoring these effects results in a 37 increase in the annual incoming shortwave radiation on the glacier causing 0 34 m w e more ablation a 1 c change in the air temperature results in a shift of 0 67 m w e in the mean specific mass balance while altering the precipitation by 10 causes a change of 0 17 m w e

river loads and modern denudation of the alps a review this paper presents the first comprehensive analysis of sediment and dissolved load across an entire mountain range we investigate patterns and rates of modern denudation of the european alps based on a compilation of data about river loads and reservoir sedimentation from 202 drainage basins that are between ca 1 to 10 000 km2 large the study basins cover about 50 of the total area of the alps modern glaciated basins have the highest sediment yields of up to 7000 t km 2 a 1 which are on average 5 to 10 times higher than in non glaciated basins likewise sediment yield and glacial cover are positively correlated instead relief is a relatively weak predictor of sediment yield the strong glacial impact in the correlations is due to glacier recession since the 19th century as well as due to glacial conditioning during repeated quaternary glaciations which have produced the strong transient state of the alpine landscape we suggest that this is the major cause for ca 3 fold enhanced denudation of the western compared to the eastern alps chemical denudation rates are highest in the external alps dominated by carbonate sedimentary rocks where they make up about one third of total denudation the high rates cannot be explained without anhydrite dissolution we estimated that only 45 of the sediments mobilized in headwaters are exported out off the alps most sediments being trapped in artificial reservoirs the total amount of sediment annually trapped within the alps equates to 43 mt when corrected for sediment storage we obtain an area weighted mean total denudation rate for the alps of about 0 32 mm a 1 the pre dam rate might be as high as 0 42 mm a 1 in total ca 35 plus 23 mt of mass are exported each year out of the alps as solids and solutes respectively these rates are not enough to out pace modern rock uplift nevertheless pattern of sediment yield across the alps coincides roughly with the intensity of glacial conditioning and modern rock uplift supporting the hypothesis of an erosion driven uplift of the alps

high resolution chironomid inferred temperature history since ad 1580 from varved lake silvaplana switzerland comparison with local and regional reconstructions chironomids were used to reconstruct mean july air temperatures between c ad 1580 and 2001 at lake silvaplana a varved lake located in the engadine eastern swiss alps the goal of this study was to reconstruct temperature changes at near annual resolution and validate the reconstruction by comparison with records based on early instrumental data documentary proxy evidence dendrochronology geochemical biogenic silica bsi and mineralogical data quartz mica ratios at local and regional scales warmer than the climate normal ad 1961 1990 mean july air temperatures were inferred between c ad 1610 and 1662 ad 1710 and 1740 ad 1790 and 1866 ad 1940 and 1960 and ad 1990 and 2001 colder than the climate normal july air temperatures were reconstructed between c ad 1662 and 1710 ad 1740 and 1790 ad 1866 and 1919 and ad 1970 and 1990 the 420 year chironomid inferred mean july air temperature record was significantly p 0 01 related to june september jjas temperatures reconstructed from e

quantifying human induced eutrophication in swiss mountain lakes since ad 1800 using diatoms sedimentary diatom assemblages from three lakes in the southeastern swiss alps were analysed at high temporal resolution since ad 1800 altered land use patterns increasing population and exploitation through tourism are clearly reflected in annually laminated sediments of lej da san murezzan lake st moritz and lej da silvaplauna lake silvaplana diatom assemblages originally dominated by cyclotella taxa are replaced by taxa indicating higher total phosphorus tp concentrations such as asterionella formosa fragilaria crotonensis and stephanodiscus parvus in lej da la tscheppa located well above the treeline in a catchment that was hardly exposed to human impact cyclotella comensis prevails throughout the entire sediment sequence quantitative estimates of past tp concentrations were inferred using a newly developed regional diatom tp inference model based on 119 modern samples in lej da la tscheppa diatoms imply stable low tp concentrations 10 g l which can be considered as natural background concentration elevated tp levels are inferred for lej da san murezzan max 60 g l since ad 1910 and for lej da silvaplauna max 40 g l since ad 1950 corroborated by changes in sedimentary biogenic silica concentration and organic carbon content since ad 1970 improved waste water management led to a considerable reduction in tp loading in lej da silvaplauna and lej da san murezzan

holocene glacier chronologies are high resolution global and inter hemispheric comparisons possible in the context of reconstruction of holocene glacier chronologies there has been a clear tendency during the past few decades towards imprecise use of the term high resolution furthermore it seems to be increasingly assumed that recently developed terrestrial cosmogenic nuclide dating tcnd is replacing earlier dating methods although recent glaciological knowledge clearly reveals the futility of oversimplified global and inter hemispheric correlation on the basis of few key sites such comparisons are widely attempted stimulated by the example of a recently published article relating to the southern alps of new zealand schaefer et al 2009 science 324 622 625 we highlight some related potential problems with the interpretation of holocene glacier chronologies in particular we consider 1 that the term high resolution should be applied only to decadal scale resolution or better and therefore not to tcnd based chronologies 2 that discontinuous moraine chronologies should not be ter

varve formation and the climatic record in an alpine proglacial lake calibrating annually laminated sediments against hydrological and meteorological data processes leading to the formation of varves in proglacial oeschinensee switzerland are investigated the aim is to calibrate annually laminated sediments of the last three decades against hydrological and meteorological instrumental data results from water samples and sediment traps show that the suspended sediment in the lake is mainly distributed by underflows during the time of the largest sediment input from may to mid august this leads to the deposition of the basal silt layers of the varves settling of fine grained suspension from interflows dominates sedimentation between august and october forming the final layer of fine grained material at the end of the annual deposition cycle the median grain size at the top of the varves is always below 5 m and thus defines the varve boundaries varve thickness is a function of the annual discharge of suspended load from the catchment this is supported by evidence from hydrological and meteorological data compiled for a glaciated catchment loetschen

thousand years of climate change reconstructed from chironomid subfossils preserved in varved lake silvaplana engadine switzerland abstract fossil chironomids non biting midges from varved lake silvaplana switzerland were used to reconstruct climate mean july air temperatures during the last millennium at the beginning of the record corresponding to the last part of the medieval climate anomaly mca here the period between ca 1032 and 1262 ad the chironomid inferred mean july air temperatures were 1 c warmer p

holocene glacier variations in central jotunheimen southern norway based on distal glaciolacustrine sediment cores abstract sediment cores from two glacier fed lakes are used to reconstruct a continuous record of glacier variations since about 10 000 cal bp in the smorstabbtinden massif of central jotunheimen southern norway particular attention is paid to the century to millennial scale pre little ice age glacial signal based on an estimated temporal resolution of 55 and 25 yr cm 1 for bovertunsvatnet and dalsvatnet respectively visible lithostratigraphic variations organic content loss on ignition calcium carbonate content magnetic susceptibility and grain size fractions especially the fine silt are used as proxy indicators of glacier presence and extent in the lake catchments following deglaciation the early holocene was characterized by generally small glaciers until a major advance the finse event peaking at approximately 8200 cal bp from 7900 to at least 5300 cal bp glaciers appear to have been absent from central jotunheimen there is evidence of glacier expansion between about 2400 and 1600 cal bp the bovertun i event and between about 1400 and 800 cal bp the bovertun ii event before reduced glacier extent during the mediaeval warm period finally the most extensive neoglacial maximum occurred during the little ice age after 500 cal bp in addition to providing a record of the broad pattern of climatically forced holocene glacier variations periodicities at 110 140 200 285 and about 500 yr have been identified uncertainties remain concerning the precise timing of events glacierization and deglacierization detection thresholds a possible mid to late holocene 5300 2500 cal bp neoglacial build up of small glaciers and shorter term decadal to century scale variations in glacier size for which more proximal sites are required

downward propagating temperature anomalies in the preconditioned polar stratosphere abstract dynamical links of the northern hemisphere stratosphere and troposphere are studied with an emphasis on whether stratospheric changes have a direct effect on tropospheric weather and climate in particular downward propagation of stratospheric anomalies of polar temperature in the winter spring season is examined based upon 22 years of ncep ncar reanalysis data it is found that the polar stratosphere is sometimes preconditioned which allows a warm anomaly to propagate from the upper stratosphere to the troposphere and sometimes it prohibits downward propagation the arctic oscillation ao is more clearly seen in the former case to understand what dynamical conditions dictate the stratospheric property of downward propagation the upper stratospheric warming episodes with very large anomalies such as stratospheric sudden warming are selected and divided into two categories according to their downward propagating features eliassen palm e p diagnostics and wave propagation theories are u

effect of scaling and regression on reconstructed temperature amplitude for the past millennium 1 examination of large scale millennial long temperature reconstructions reveals a wide range of datasets and methods used for calibration proxy time series are commonly calibrated against overlapping instrumental records representing different seasons northern hemisphere latitudinal bands and including or excluding sea surface temperature data methodological differences include using scaling or regression the calibration time period and smoothing data before calibration we find that these various approaches alone can result in differences in the reconstructed temperature amplitude of about 0 5 c this magnitude is equivalent to the mean annual temperature change for the northern hemisphere reported in the last ipcc report for the 1000 1998 period a more precise assessment of absolute reconstructed temperature amplitudes is necessary to help quantify the relative influences of forcing mechanisms in climate models

a 1052 year tree ring proxy for alpine summer temperatures a june august alpine temperature proxy series is developed back to ad 951 using 1 527 ring width measurements from living trees and relict wood the reconstruction is composed of larch data from four alpine valleys in switzerland and pine data from the western austrian alps these regions are situated in high elevation alpine environments where a spatially homogenous summer temperature signal exists in an attempt to capture the full frequency range of summer temperatures over the past millennium from inter annual to multi centennial scales the regional curve standardization technique is applied to the ring width measurements correlations of 0 65 and 0 86 after decadal smoothing with high elevation meteorological stations since 1864 indicate an optimal response of the rcs chronology to june august mean temperatures the proxy record reveals warm conditions from before ad 1000 into the thirteenth century followed by a prolonged cool period reaching minimum values in the 1820s and a warming trend into the twentieth century this latter trend and the higher frequency variations compare well with the actual high elevation temperature record the new central alpine proxy suggests that summer temperatures during the last decade are unprecedented over the past millennium it also reveals significant similarities at inter decadal to multi centennial frequencies with large scale temperature reconstructions however deviating during certain periods from h h lamb s european north atlantic temperature history

annually dated late weichselian continental paleoclimate record from the eifel germany a record extending back to 23 220 calendar yr b p was obtained from varved sediments from lake holzmaar germany by applying multiple dating methods and interlake comparison with meerfelder maar variations in the weichselian inorganic carbon content resulting from intensified eolian activities coincide with proxy parameters of dust accumulation in greenland the timing for the end of the last glacial maximum at holzmaar agrees with the greenland ice sheet project gisp2 data but suggests dating discrepancies with the greenland ice core project data grip assuming that periods of maximum dust deposition in the eifel and greenland coincide with ice advances in northeastern germany the holzmaar record provides a means of dating three late weichselian terminal moraines

mineralogy based quantitative precipitation and temperature reconstructions from annually laminated lake sediments swiss alps since ad 1580 1 we present quantitative autumn summer and annual precipitation and summer temperature reconstructions from proglacial annually laminated lake silvaplana eastern swiss alps back to ad 1580 we used x ray diffraction peak intensity ratios of minerals in the sediment layers quartz qz plagioclase pl amphibole am mica mi that are diagnostic for different source areas and hydrometeorological transport processes in the catchment xrd data were calibrated with meteorological data ad 1800 1864 1950 and revealed significant correlations mi pl with son precipitation r 0 56 p 0 05 and mjjas precipitation r 0 66 p 0 01 qz mi with mjjas temperature r 0 72 p 0 01 and qz am with annual precipitation r 0 54 p 0 05 geological catchment settings and hydro meteorological processes provide deterministic explanations for the correlations our summer temperature reconstruction reproduces the typical features of past climate variability known from independent data sets the precipitation reconstructions show a lia climate moister than today exceptionally wet periods in our reconstruction coincide with regional glacier advances citation trachsel m u eggenberger m grosjean a blass and m sturm 2008 mineralogy based quantitative precipitation and temperature reconstructions from annually laminated lake sediments swiss alps since ad 1580 geophys res lett 35 l13707 doi 10 1029 2008gl034121