atmospheric variability of methyl chloride during the last 300 years from an antarctic ice core and firn air measurements of methyl chloride ch3cl in antarctic polar ice and firn air are used to describe the variability of atmospheric ch3cl during the past 300 years firn air results from south pole and siple dome suggest that the atmospheric abundance of ch3cl increased by about 10 in the 50 years prior to 1990 ice core measurements from siple dome provide evidence for a cyclic natural variability on the order of 10 with a period of about 110 years in phase with the 20th century rise inferred from firn air thus the ch3cl increase measured in firn air may largely be a result of natural processes which may continue to affect the atmospheric ch3cl burden during the 21st century

permafrost and climate in europe monitoring and modelling thermal geomorphological and geotechnical responses we present a review of the changing state of european permafrost within a spatial zone that includes the continuous high latitude arctic permafrost of svalbard and the discontinuous high altitude mountain permafrost of iceland fennoscandia and the alps the paper focuses on methodological developments and data collection over the last decade or so including research associated with the continent scale network of instrumented permafrost boreholes established between 1998 and 2001 under the european union pace project data indicate recent warming trends with greatest warming at higher latitudes equally important are the impacts of shorter term extreme climatic events most immediately reflected in changes in active layer thickness a large number of complex variables including altitude topography insolation and snow distribution determine permafrost temperatures the development of regionally calibrated empirical statistical models and physically based process oriented models is described and it is shown that though more complex and data dependent process oriented approaches are better suited to estimating transient effects of climate change in complex mountain topography mapping and characterisation of permafrost depth and distribution requires integrated multiple geophysical approaches and recent advances are discussed we report on recent research into ground ice formation including ice segregation within bedrock and vein ice formation within ice wedge systems the potential impacts of climate change on rock weathering permafrost creep landslides rock falls debris flows and slow mass movements are also discussed recent engineering responses to the potentially damaging effects of climate warming are outlined and risk assessment strategies to minimise geological hazards are described we conclude that forecasting changes in hazard occurrence magnitude and frequency is likely to depend on process based modelling demanding improved understanding of geomorphological process response systems and their impacts on human activity

seeing the wood from the trees reconstructing past climates is important if we are to distinguish anthropogenic warming from natural variability in the climate system briffa and osborn 1 discuss a recent study by mann et al that has extended their northern hemisphere climatic reconstruction to a d 1000 and explain why there are large uncertainties in the reconstruction of medieval and earlier temperatures on large spatial scales thus although the 20th century was almost certainly the warmest of the millennium the amount of anthropogenic warming remains uncertain 1 http www sciencemag org cgi content full 284 5416 926

a 352 year record of summer temperature reconstruction in the western tianshan mountains china as deduced from tree ring density three robust tree ring density chronologies were developed for the western tianshan mountains of northwestern china the chronologies were significantly correlated and form a regional chronology gld the gld had significant and positive correlations with temperature of warm seasons based on this relationship the mean minimum temperatures of may to august were reconstructed using the gld chronology for the period ad 1657 to 2008 the temperature reconstruction exhibited temperature patterns on interannual to centennial timescales and showed that the end of the 20th century is the warmest period in the past 352 years the reconstructed temperature variation has a teleconnection with large scale atmospheric oceanic variability and captures long and broad scale regional climatic variations

subcentury scale variability in height increment and tree ring width chronologies of scots pine since ad 745 in northern fennoscandia height increment and tree ring width data of scots pine from northern fennoscandia were updated and their sample replication increased considerably standard chronologies as well as low frequency chronologies were built and compared during their common period in ad 745 2007 the two chronologies correlate significantly r 0 58 with each other and have several extreme years in common e g 1089 and 1601 the low frequency chronologies indicate four significant periods of above average growth and eight periods of below average growth which occur in both chronologies these include the early 20th century growth surges that occurred during 1917 1955 in height increment and during 1919 1961 in ring width in both chronologies this latest increasing trend unequivocally turns to a fall and comes to an end by the 1960s tree ring chronologies of scots pine from northern sweden and the khibiny low mountains region northwestern russia as well as from siberia show coincidence in the decadal to century scale with our chronologies

spatial and temporal patterns of variations in tree growth over the northeastern tibetan plateau during the period ad 1450 2001 we analyzed spatial and temporal growth variations of qilian junipers over the northeastern tibetan plateau tp during the period 1450 2001 by applying the empirical orthogonal function eof technique to seven moisture sensitive tree ring width chronologies the first three principal components together explain 78 21 of the total variance the first principal component pc1 accounts for 51 58 of the total variance and represents consistent tree growth variations in the northeastern tp the second eof mode reveals an opposite structure for the southern and northern parts of the northeastern tibetan plateau reflecting the effect of huge topography and associated atmospheric circulation on tree growth anomalies the third eof mode represents an opposite structure for the eastern and western parts of the northeastern tibetan plateau possibly indicating the influence of different branches of atmospheric circulation system in this area the eof analysis results of instrumental precipitation data resembl

spring temperatures in the far western nepal himalaya since ad 1640 reconstructed from picea smithiana tree ring widths we developed a new 422 year long tree ring width chronology spanning ad 1591 2012 from picea smithiana wall boiss in khaptad national park which is located in the far western nepalese himalaya seasonal correlation analysis revealed significant indirect relationship with spring temperature and lead to the reconstruction of march may average temperature for the past 373 years ad 1640 2012 the reconstruction was found significant based on validation statistics commonly used in tree ring based climate reconstruction furthermore it was validated through spatial correlation with gridded temperature data this temperature reconstruction identified several periods of warming and cooling the reconstruction did not show the significant pattern of cooling during the little ice age but there were few cold episodes recorded the spring temperature revealed relationship with different sea surface temperature index over the equatorial pacific ocean which showed linkages with climatic variability in a global scale

annual climate variability in the holocene interpreting the message of ancient trees abstract over vast areas of the world s landmasses where climate beats out a strong seasonal rhythm tree growth keeps unerring time in their rings trees record many climate melodies played in different places and different eras recent years have seen a consolidation and expansion of tree ring sample collections across the traditional research areas of north america and europe and the start of major developments in many new areas of eurasia south america and australasia from such collections are produced networks of precisely dated chronologies records of various aspects of tree growth registered continuously year by year across many centuries their sensitivities to different climate parameters are now translated into ever more detailed histories of temperature and moisture variability across expanding dimensions of time and space with their extensive coverage high temporal resolution and rigid dating control dendroclimatic reconstructions contribute significantly to our knowledge of late holocene climates most importantly on timescales ranging from 1 to 100 years in special areas of the world where trees live for thousands of years or where subfossil remnants of long dead specimens are preserved work building chronologies covering many millennia continues apace very recently trees have provided important new information about major modes of general circulation dynamics linked to the el nino southern oscillation and the north atlantic oscillation and about the effect of large volcanic eruptions as for assessing the significance of 20th century global warming the evidence from dendroclimatology in general supports the notion that the last 100 years have been unusually warm at least within a context of the last two millennia however this evidence should not be considered equivocal the activities of humans may well be impacting on the natural growth of trees in different ways making the task of isolating a clear climate message subtly difficult

geomorphic processes influence human settlement on two islands in the islands of four mountains alaska the islands of four mountains island group of the aleutian island arc is remote and difficult to access consequently little fieldwork has focused on geomorphic processes and their relationship to island morphology climatic change and human settlement we investigated glacial fluvial and slope processes on the morphologically different carlisle cleveland and tana volcanoes the islands were extensively glaciated at the last glacial maximum lgm and there is evidence for a neoglacial advance on the highly dissected tana volcano a large basin is likely the result of a pre lgm sector collapse and subsequent glacial erosion into weak hydrothermally altered rock valley and moraine morphology is also influenced by hydrothermal alteration on both tana and carlisle there are sediment fans composed dominantly of thick debris flow deposits mantled by 3 m of layered tephras fine grained alluvium and anthropogenic deposits debris flow deposition was favored during the unstable paraglacial landscape of the early holocene latest pleistocene the earliest direct archaeological evidence for settlement is 3 8 cal ka bp but soil geochemical evidence suggests that the islands were inhabited by 7 3 cal ka bp this discrepancy in the archaeological record may be explained by geomorphic processes including coastal erosion and unstable geomorphic surfaces

simulated relationships between regional temperatures and large scale circulation 125 kyr bp eemian and the preindustrial period to investigate relationships between large scale circulation and regional scale temperatures during the last eemian interglacial a simulation with a general circulation model gcm under orbital forcing conditions of 125 kyr bp is compared with a simulation forced with the late holocene preindustrial conditions consistent with previous gcm simulations for the eemian higher northern summer 2 m temperatures are found which are directly related to the different insolation differences in the mean circulation are evident such as for instance stronger northern winter westerlies toward europe which are associated with warmer temperatures in central and northeastern europe in the eemian simulation while the circulation variability analyzed by means of a principal component analysis of the sea level pressure slp field is very similar in both periods as a consequence of the differences in the mean circulation the simulated arctic oscillation ao temperature signal in the northern winter on interannual to multidecadal time scales is weaker during the eemian than today over large parts of the northern hemisphere correlations between the ao index and the central european temperature cet decrease by about 0 2 the winter and spring slp anomalies over the north atlantic european domain that are most strongly linearly linked to the cet cover a smaller area and are shifted westward over the north atlantic during the eemian however the strength of the connection between cet and these slp anomalies is similar in both simulations the simulated differences in the ao temperature signal and in the slp anomaly which is linearly linked to the cet suggest that during the eemian the link between the large scale circulation and temperaturesensitive proxy data from europe may differ from present day conditions and that this difference should be taken into account when inferring large scale climate from temperature sensitive proxy data

late holocene teleconnections between tropical pacific climatic variability and precipitation in the western usa evidence from proxy records decadal to multidecadal fluctuations between drought and relatively more moist conditions are a defining characteristic of precipitation variability in the western usa in an attempt to better understand the forcing mechanisms responsible for producing this variability relationships between proxy indices of tropical climatic variability and precipitation related reconstructions in the western usa are examined the tropical proxies include the o record from the quelccaya ice cap southern subtropical andes and the lacustrine sedimentation record from laguna pallcacocha near equatorial andes the precipi tation related records are tree ring reconstructions of river flow drought severity and precipitation over the contiguo usa one new finding is a consistent relation between decadal variability in el ninno activity and precipitation related proxies through much of the western usa during the past 1200 years surpris ingly the proxy records do not show a systematic link between inferred el ninno activity and precipitation in the interior southwest usa a second new result is the existence of relationships at decadal to multidecadal timescales between fluctuations in quelccaya o precipitation related proxies from the western usa and proxy records from the pacific basin this finding links the quelccaya record to the transhemi spheric pacific decadal scale climatic variability documented from proxy records by villalba et al 2001 and suggests that similar changes in the large scale circulation changes accompany both the decadal and multidecadal signals a composite constructed using gridded proxy precipitation constructed on the basis of decadal scale fluctuations in inferred el ninno activity shows a pattern rather different to ninno based teleconnection maps for the instrumental record in the proxy based composite positive values cover much of the extreme western west central and southeastern usa with negative values in the central mis sissippi valley the interior southwest shows essentially no response a second composite based on multi decadal variability in quelccaya o shows a well developed dipole pattern across the western usa with opposing centres in the interior southwest and northwest it is suggested that this dipole pattern results from multidecadal variability in tropical pacific ssts and resulting changes in the strength of the northeast pacific high and the latitudinal distribution of cool season westerlies across the eastern north pacific and western usa

stiffness of soil geosynthetic composite under small displacements ii experimental evaluation abstractwhile most soil geosynthetic interaction models have focused on the characterization of failure conditions little emphasis has been placed on models and parameters suitable for characteriz

a reconstruction of the north atlantic oscillation using tree ring chronologies from north america and europe tree ring records six from eastern north america and four from northwestern europe are used to develop the first reconstruction of the winter north atlantic oscillation nao the reconstructed series spans the interval ad 1701 1980 and explains 41 of the variance in the nao over the ad 1874 1980 calibration period the reconstruction also captures the spectral properties of this index suggesting that the oscillatory character of the nao is a long term feature of the north atlantic climate system

temperature trends over the past five centuries reconstructed from borehole temperatures for an accurate assessment of the relative roles of natural variability and anthropogenic influence in the earth s climate reconstructions of past temperatures from the pre industrial as well as the industrial period are essential but instrumental records are typically available for no more than the past 150 years therefore reconstructions of pre industrial climate rely principally on traditional climate proxy records each with particular strengths and limitations in representing climatic variability subsurface temperatures comprise an independent archive of past surface temperature changes that is complementary to both the instrumental record and the climate proxies here we use present day temperatures in 616 boreholes from all continents except antarctica to reconstruct century long trends in temperatures over the past 500 years at global hemispheric and continental scales the results confirm the unusual warming of the twentieth century revealed by the instrumental record but suggest that the cumulative change over the past five centuries amounts to about 1 k exceeding recent estimates from conventional climate proxies the strength of temperature reconstructions from boreholes lies in the detection of long term trends complementary to conventional climate proxies but to obtain a complete picture of past warming the differences between the approaches need to be investigated in detail

comments on the paper of r n harris and d s chapman mid latitude 30 n 60 n climatic warming inferred by combining borehole temperatures with surface air temperatures harris and chapman 2001 hereafter hc2001 recently presented a comparison between ground temperature records temperature depth profiles measured in many boreholes and surface air temperature observations and reconstructions research such as theirs attempting to reconcile or compare climate proxies that have high temporal resolution with those that have much lower temporal resolution is important because it provides a way of assessing the fidelity with which the high resolution proxies capture multicentury climate variability briffa and osborn 1999 highlighted some potential difficulties at capturing such long time scale variations unfortunately the paper by hc2001 contains a conspicuous error that requires highlighting in order that their results can be re evaluated but also to prevent the error from propagating in the literature

a 2 326 year tree ring record of climate variability on the northeastern qinghai tibetan plateau 1 high resolution climate proxy records covering the last two millennia on the qinghai tibetan plateau are scarce yet essential to evaluation of the patterns synchroneity and spatial extent of past climatic changes including those in the medieval warm period mwp and the little ice age lia here we present a 2326 year tree ring chronology of sabina przewalskii kom for dulan area of northeastern qinghai tibetan plateau we find that the annual growth rings mainly reflect variations in regional spring precipitation the greatest change in spring precipitation during the last two millennia seems to occur in the second half of the 4th century the north atlantic mwp was accompanied by notable wet springs in the study region during a d 929 1031 with the peak occurring around a d 974 three intervals of dry springs occurred in the period of lia our tree ring data will facilitate intercontinental comparisons of large scale synoptic climate variability for the last two millennia

isotopic composition δ13c δ18o in wood and cellulose of siberian larch trees for early medieval and recent periods 1 we related tree ring width trw and isotopic composition 13c 18o of wood and cellulose from four larch trees larixcajanderi mayr to climate parameters the material was sampled in northeastern yakutia 70 n 148 e for the recent ad 1880 2004 and early medieval ad 900 1000 periods during the recent period june july and august air temperatures were positively correlated with 13c and 18o of wood and cellulose while july precipitation was negatively correlated furthermore the vapor pressure deficit vpd of july and august was significantly correlated with 13c of wood and cellulose but vpd had almost no influence on 18o comparative analyses between mean isotope values for the ad 900 1000 and ad 1880 2004 periods indicate similar ranges of climatic conditions with the exception of the period ad 1950 2004 while isotopic ratios in cellulose are reliably related to climatic variables during some periods those in whole wood showed even stronger relationships strong positive correlations between 18o of cellulose and greenland ice core gisp2 data were detected for the beginning of the medieval period r 0 86 p 0 05 indicating the reliability of isotope signals in tree rings for large scale reconstructions

1300 years of climatic history for western central asia inferred from tree rings more than 200 000 ring width measurements from 384 trees were obtained for 20 individual sites ranging from the lower to upper local timber lines in the northwest karakorum of pakistan and the southern tien shan of kirghizia samples were obtained predominantly from juniper species juniperus and were analysed to reconstruct regional climatic variation patterns in western central asia since ad 618 site distri bution represents diverse ecological conditions e g combinations of temperature and moisture stress within the karakorum and tien shan mountains permitting both intra montane and inter montane comparisons of chronologies three different types of chronologies ree ecting interannual decadal and centennial scale ring width variations were calculated a statistic skeleton plotting technique was used to identify ring width pointer years interannual a 101 year kernel e lter was used to identify decadal scale variations and for a subset of long lived trees the mean ring width of the entire single series was used to identify centennial trends after extracting and calibrating each of these three distinct wavelengths in ring width variation the results were combined into a comprehensive reconstruction ree ecting primarily temperature e uctuations in western central asia since ad 618 the nature and the temporally changing strength of the climatic signals of this reconstruction are discussed in detail a maximum latewood density record of pinus tienschanica from central tien shan was used as a predictor series to calibrate and validate tree ring width variation in so doing we link our results to the circumpolar maximum latewood density network briffa et al 1998a 1998b schweingruber and briffa 1996

borehole climate reconstructions spatial structure and hemispheric averages 1 ground surface temperature gst reconstructions determined from temperature profiles measured in terrestrial boreholes when averaged over the northern hemisphere estimate a surface warming of 1 k during the interval ad 1500 2000 other traditional proxy based estimates suggest less warming during the same interval mann et al 2003a have raised two issues with regard to borehole based reconstructions the first focuses on the need for spatial gridding and area weighting of the ensemble of borehole based gst reconstructions to yield an average hemispheric reconstruction the second asserts that application of optimal detection techniques show that the gst only weakly displays the spatial structure of the surface air temperature sat we demonstrate the consistency of gst warming estimates by showing that over a wide range of grid element area and occupancy weighting schemes the five century gst change falls in the range of 0 89 1 05 k we examine the subhemispheric spatial correlation of gst and sat trends at various spatial scales in the 5 degree grid employed for optimal detection we find that the majority of grid element means are determined from three or fewer boreholes a number that is insufficient to suppress site specific noise via ensemble averaging significant spatial correlation between sat and gst emerges in a 5 degree grid if low occupancy grid elements are excluded and also in a 30 degree grid in which grid element means are better determined through higher occupancy reconstructions assembled after excluding low occupancy grid elements show a five century gst change in the range of 1 02 1 06 k index terms 1645 global change solid earth 1699 global change general or miscellaneous 3309 meteorology and atmospheric dynamics climatology 1620 3322 meteorology and atmospheric dynamics land atmosphere interactions 3344 meteorology and atmospheric dynamics paleoclimatology keywords boreholes paleoclimate spatial analysis surface temperature

north atlantic climate ocean variations and sea level in long island sound connecticut since 500 cal yr a d abstract a record of detrended mean high water mhw variations from hammock river marsh connecticut is extended from ca 850 to ca 500 cal yr a d and correlated with summer temperature reconstructions from northern fennoscandia and northern eurasia greenland ice sheet project 2 18 o and greenland ice core project borehole temperature variations from central greenland a sargasso sea sea surface temperature sst record and a proxy record for deep ocean flow south of iceland the records from northern fennoscandia eurasia and central greenland document century scale intervals of warming four and cooling three since ca a d 850 the mhw fluctuations lag behind these climate intervals by 0 100 yr with the two larger mhw rises corresponding to the two larger temperature increases this positive correlation suggests that surface air temperature sat is a dominant variable controlling sea level in the northwestern north atlantic since ca a d 850 the sst variations parallel the mhw fluctuations back to ca 950 cal yr a d a positive correlation is found also for sub century scale sat and mhw variations during the period a d 500 850 but this result is less firm mhw sst correlation over this time interval is not consistent

neoglacial history of robson glacier british columbia as glaciers in the canadian rockies recede glacier forefields continue to yield subfossil wood from sites overridden by these glaciers during the holocene robson glacier in british columbia forme

climate change record in subsurface temperatures a global perspective analyses of underground temperature measurements from 358 boreholes in eastern north america central europe southern africa and australia indicate that in the 20th century the average surface temperature of earth has increased by about 0 5 degreesc and that the 20th century has been the warmest of the past five centuries the subsurface temperatures also indicate that earth s mean surface temperature has increased by about 1 0 degreesc over the past five centuries the geothermal data offer an independent confirmation of the unusual character of 20th century climate that has emerged from recent multiproxy studies

improving a tree ring reconstruction from west central scandinavia 900 years of warm season temperatures dendroclimatological sampling of scots pine pinus sylvestris l has been made in the province of jamtland in the west central scandinavian mountains since the 1970s the tree ring width trw chronology spans several thousand years and has been used to reconstruct june august temperatures back to 1632 bc a maximum latewood density mxd dataset covering the period ad 1107 1827 with gap 1292 1315 was presented in the 1980s by fritz schweingruber here we combine these historical mxd data with recently collected mxd data covering ad 1292 2006 into a single reconstruction of april september temperatures for the period ad 1107 2006 regional curve standardization rcs provides more low frequency variability than non rcs and stronger correlation with local seasonal temperatures 51 variance explained the mxd chronology shows a stronger relationship with temperatures than the trw data but the two chronologies show similar multi decadal variations back to ad 1500 according to the mxd chronology the period since ad 1930 and around ad 1150 1200 were the warmest during the last 900 years due to large uncertainties in the early part of the combined mxd chronology it is not possible to conclude which period was the warmest more sampling of trees growing near the tree line is needed to further improve the mxd chronology

optimal surface temperature reconstructions using terrestrial borehole data 1 we derive an optimal northern hemisphere mean surface temperature reconstruction from terrestrial borehole temperature profiles spanning the past five centuries the pattern of borehole ground surface temperature gst reconstructions displays prominent discrepancies with instrumental surface air temperature sat estimates during the 20th century suggesting the presence of a considerable amount of noise and or bias in any underlying spatial sat signal the vast majority of variance in the borehole dataset is efficiently retained by its two leading eigenvectors a sizable share of the variance in the first eigenvector appears to be associated with non sat related bias in the borehole data a weak but detectable sat signal appears to be described by a combination of the first two eigenvectors exploiting this eigendecomposition application of optimal signal estimation methods yields a hemispheric borehole sat reconstruction that is largely consistent with instrumental data available in past centuries and is indistinguishable in its major features from several published long term temperature estimates based on both climate proxy data and model simulations

last millennium summer temperature variations in western europe based on proxy data we present a method of multiproxy reconstruction of the climate of europe during the last millennium the proxies used comprise long tree ring width series grape harvest dates greenland ice oxygen isotope series and temperature indices based on historical documents the proxies are calibrated using gridded april to september mean temperatures for western europe i e between 10 degrees w and 20 degrees e and between 35 degrees n and 55 degrees n they are calibrated also using the long instrumental summer temperature series of the marseilles observatory of longchamp which begins in the mid eighteenth century the method is a combination of an analogue technique which is able to deal with missing data an artificial neural network technique for an optimal non linear calibration and a bootstrap technique for calculating error bars on the reconstruction about 70 of the temperature variance is reconstructed the amplitude of the past temperature variations is particularly well reconstructed which is important when considering whether the recent temperature trend is or is not within the natural variability it appears that the temperature of the last decade of the twentieth century was reached only 14 times during the last millennium the reconstruction is discussed with respect to other multiproxy and borehole temperature reconstructions we conclude that a reconstruction such ours with a specific regional focus as opposed to the larger northern hemisphere is more reliable and is in better agreement with borehole results even allowing for the fact that only a part of the long term variance is reconstructed little ice age c ad 1560 1930 summers were 0 2 0 5 degrees c cooler than the 1961 1990 period borehole temperatures indicate a cooling of 0 4 degrees c which falls in the 95 confidence interval of our reconstructions

early summer temperature changes in the southern altai mountains of central asia during the past 300 years abstract june july mean temperature was reconstructed back to 1698 for the southern altai mountains in eastern central asia using four temperature series based on tree ring widths the reconstruction explains 48 of the variation in the observed temperature from 1962 to 2003 warm periods occurred during 1714 1732 1753 1776 1800 1840 1866 1886 1893 1911 and 1943 1969 while the periods of 1708 1713 1733 1752 1777 1799 1841 1865 1887 1892 1912 1942 and 1970 1993 were relatively cold power spectral and wavelet analyses demonstrated the existence of significant 50 14 2 8 and 2 5 year cycles of variability the results of a spatial correlation analysis suggested that this temperature reconstruction contains climatic signals for a large area of central asia after employing a 21 year low pass filter the coherence of the newly reconstructed series with a regional temperature reconstruction for central asia and also with a local temperature reconstruction for the zajsan lake area of east kazakhstan indicates that our temperature reconstruction captures broad scale regional climatic variations in the low frequency domain

paleoclimatic implication of buried peat layers in a subalpine snowpatch grassland on mt zarumori northern japan abstract we reconstruct the paleoclimatic background of buried peat layers formed around the 10th century which occur in a snowpatch grassland in a snowy mountain in northern japan in the snowpatch grassland peat accumulation is presently restricted by the presence of a summer snowpatch thus the buried peat layers imply that the summer snowpatch around the 10th century was smaller than it has been in recent times climatic control of the year to year variation of the present snowpatch was examined based on a snowpatch survey and analysis of meteorological data the observed snowpatch profiles suggested that winter wind speed played an important role in controlling summer snowpatch size the buried peat layers indicate not only warming in the melt season but also a possible weakened winter monsoon in the medieval warm period

direct transformation of tree ring measurements into palaeoclimate reconstructions in three dimensional space here we propose a new method for dendroclimatic reconstructions this direct reconstruction technique direct performs modelling of the age dependent association between climate and growth in thre

late quaternary linkage of sedimentary records to three astronomical rhythms and the asian monsoon inferred from a coastal borehole in the south bohai sea china abstract the bohai sea was formed by subsidence during the cenozoic some 2000 3000 m of fluvial lacustrine and marine sediments has been deposited in this basin previous studies focused mainly on the transgression history with little examination of orbital variation in relation to other areas within the asian monsoon domain here we present the late quaternary results of a new borehole in the south bohai sea optically stimulated luminescence and radiocarbon dating which provide concordant age estimates were employed to generate an initial chronology for the borehole after refining the chronology through astronomical tuning the results showed that 1 the grain size variation represents asian monsoon intensity which was dominated by both solar insolation major and global ice volume minor forcing 2 the magnetic susceptibility indicates river incision processes which were sensitive to orbital tilt with influence from solar insolation 3 the vegetation coverage responded to global ice volume coupled obliquity changes and that 4 neither external nor internal factors could dominate the paleoenvironmental evolution on orbital timescales in an independent way and they are both integrated in a complex pattern we conclude that three different astronomical rhythms have affected coastal evolution and that the sedimentary records in the south bohai sea china result from the nonlinear interaction and the complex response to driving processes

a 189 year tree ring record of drought for the dzungarian alatau arid central asia abstract mountain systems are the most important sources of water in arid central asia aca it is therefore essential to understand past cycles of droughts and pluvials and to explore how future cycles might influence the sustainable utilization of regional water resources the palmer drought severity index pdsi is a widely applied measure of dryness that can be reconstructed from tree rings here a schrenk spruce picea schrenkiana fisch et mey tree ring chronology was developed for the dzungarian alatau of aca correlation and response analysis indicated that the pdsi from previous july to current june was the principal factor limiting radial growth the chronology was used to reconstruct the pdsi of the past 189 years for the dzungarian alatau a calibration model for the period from 1950 to 2011 explains 42 6 or 41 7 after adjusting for the loss of degrees of freedom of the actual pdsi variance the reconstructed pdsi might be representative of drought conditions for most of aca because it captures severe drought events in the 1910s and 1940s that were widespread across aca the extreme drought years 1917 and 1945 are especially pronounced a decadal analysis shows that the five periods in which the pdsi trend increased were 1830 1840s 1880 1890s 1920 1930s 1950 1960s 1980 2000s the pdsi declined in the 1850 1870s the 1900 1910s the 1940s and the 1970s the pdsi in aca exhibited a notably long and rapid wetting from 1980 to 2005 but decreased after 2005 in fact there have been three especially dry years 2008 2014 and 2015 in the last 10 years meanwhile there was large power in the 2 1 year 2 9 year 4 1 year 5 5 year 9 5 year and 10 8 year short periods and in the 30 40 year long periods

glacier dynamics during a phase of late quaternary warming in patagonia reconstructed from sediment landform associations abstract the geomorphological record in glaciated landscapes can provide important information for the study of the response of glaciers to rapid climate change this study presents a new reconstruction of the glacial history of the northern monte san lorenzo ice cap southern south america during a period of accelerated warming and deglaciation following the antarctic cold reversal 14 5 12 8 ka we present a detailed geomorphological map of the valleys to the north of monte san lorenzo sediment landform assemblages identified include lateral and terminal moraine ridges flutes deltas ice contact fans palaeoshorelines kame terraces and outwash plains we map 14 primary ice limits 7 of which are newly identified and 7 of which are from previous studies mapped here in greater detail we devise landsystem models to formalise and document spatial and temporal changes in glacial processes and environments our new geomorphological mapping and landsystem reconstructions provide an important insight into the response of temperate patagonian glaciers to rapidly warming climate

air ground temperature coupling and subsurface propagation of annual temperature signals 1 borehole based reconstructions of ground surface temperature gst have been widely used as indicators of paleoclimate these reconstructions assume that heat transport within the subsurface is conductive climatic interpretations of gst reconstructions also assume that gst is strongly coupled to surface air temperature sat on timescales of decades and longer we examine these two assumptions using records of sat and subsurface temperature time series from fargo north dakota prague czech republic cape henlopen state park delaware and cape hatteras national seashore north carolina the characteristics of downward propagating annual temperature signals at each site clearly indicate that heat transport can be described as one dimensional conduction in a homogeneous medium extrapolations of subsurface observations to the ground surface yield estimates of annual gst signals and allow comparisons to annual sat signals all annual gst signals are modestly attenuated and negligibly phase shifted relative to sat the four sites collectively demonstrate that differences between annual gst and sat signals arise in both summer and winter seasons in amounts dependent on the climatic setting of each site index terms 1645 global change solid earth 1875 hydrology unsaturated zone 3322 meteorology and atmospheric dynamics land atmosphere interactions 3344 meteorology and atmospheric dynamics paleoclimatology 3367 meteorology and atmospheric dynamics theoretical modeling keywords heat transport air ground termperature coupling paleoclimate

hydraulic back flood model for the archaeological stratigraphy of the connecticut river alluvial lowland central connecticut usa abstract state mandated archaeological investigations associated with urban renewal in downtown hartford led to the development of a mechanistic model for holocene floodplain sedimentation in central connecticut our model is based on historic flood hydrometeorology and geomorphologic mapping the lithologic magnetic pollen and archaeological stratigraphy exposed in sixteen deep boreholes and 24 hydraulic push cores the chronology provided by sixteen ams radiocarbon ages and diagnostic historic artifacts ranging from 10 030 cal bp to the present we conclude that the alluvial stratigraphy in this part of the lowland resulted from bottom up changes in hydraulic ponding at a bedrock outlet rather than from top down responses of the watershed to changes in climate vegetation or human activity our model provides a geologically based time space framework for the distribution of known archaeological sites and carries implications for future research

influence of various forcings on global climate in historical times using a coupled atmosphere ocean general circulation model the results of a simulation of the climate of the last five centuries with a state of the art coupled atmosphere ocean general circulation model are presented the model has been driven with most relevant forcings both natural solar variability volcanic aerosol and anthropogenic greenhouse gases sulphate aerosol land use changes in contrast to previous gcm studies we have taken into account the latitudinal dependence of volcanic aerosol and the changing land cover for a period covering several centuries we find a clear signature of large volcanic eruptions in the simulated temperature record the model is able to simulate individual extreme events such as the year without a summer 1816 warm periods in the early seventeenth century and the second half of eighteenth century occur in periods of increased solar irradiation strong warming is simulated after 1850 in particular over land going along with an increase of the positive north atlantic oscillation nao phase consistent circulation anomalies are simulated in multidecadal means with similarity to observed and reconstructed anomalies for example during the late seventeenth and early eighteenth century the model is able to reproduce some of the observed or reconstructed regional patterns we find that cooling around 1700 and at the end of the eighteenth century is less than in other studies due to the relatively small variations in solar activity and the relatively modest volcanic forcing applied here these cooling events are not restricted to europe and north america but cover most of the northern hemisphere colder than average conditions for example during the late seventeenth and early eighteenth centuries go along with a decrease in pressure difference between low and high latitudes and a decrease of the north atlantic oscillation this favours positive sea ice anomalies east of greenland and around iceland leading to widespread negative temperature anomalies over europe we also find characteristic blocking patterns over western europe in particular during autumn which contribute to the advection of cold air

reconstructing 800 years of summer temperatures in scotland from tree rings this study presents a summer temperature reconstruction using scots pine tree ring chronologies for scotland allowing the placement of current regional temperature changes in a longer term context living tree chronologies were extended using subfossil samples extracted from nearshore lake sediments resulting in a composite chronology 800 years in length the north cairngorms ncairn reconstruction was developed from a set of composite blue intensity high pass and ring width low pass filtered chronologies with a range of detrending and disturbance correction procedures calibration against july august mean temperature explains 56 4 of the instrumental data variance over 1866 2009 and is well verified spatial correlations reveal strong coherence with temperatures over the british isles parts of western europe southern scandinavia and northern parts of the iberian peninsula ncairn suggests that the recent summer time warming in scotland is likely not unique when compared to multi decadal warm periods observed in the 1300s 1500s and 1730s although trends before the mid sixteenth century should be interpreted with some caution due to greater uncertainty prominent cold periods were identified from the sixteenth century until the early 1800s agreeing with the so called little ice age observed in other tree ring reconstructions from europe with the 1690s identified as the coldest decade in the record the reconstruction shows a significant cooling response 1 year following volcanic eruptions although this result is sensitive to the datasets used to identify such events in fact the extreme cold and warm years observed in ncairn appear more related to internal forcing of the summer north atlantic oscillation

twentieth century trends in tree ring stable isotopes δ13c and δ18o of larix sibirica under dry conditions in the forest steppe in siberia 1 tree ring width density and ratio of stable isotopes 13c 12c and 18o 16o in wood and cellulose were determined for larch larix sibirica ledeb growing under water deficit conditions in the forest steppe zone in central siberia 54 24 n 89 57 e for the period 1850 2005 dendroclimatic analysis of the chronologies indicated precipitation to be the most important factor determining indicated parameters precipitation of june is significantly correlated with tree ring width and maximum density r 0 36 and 0 43 p 0 05 respectively relations of 13c and 18o to precipitation are similar but the most important month is july r 0 47 p 0 05 for 13c r 0 29 p 0 05 for 18o further 18o is positively related to the mean temperatures of july r 0 30 p 0 05 carbon and oxygen isotope ratios in wood and cellulose showed strong negative trends for the last 100 years the reason for this decrease could be the observed shift of the beginning of the vegetation period to earlier dates up to 1 week in spring and the increased use of precipitation water stored in the soil from october of the previous year although other explanations cannot be excluded in particular the physiological effect of increasing atmospheric co2 also responsible for lower 13c values thus an earlier start of the vegetation period could lead to tree ring formation during a period with higher water availability resulting in stronger isotopic fractionation and 13c depletion also reflected in a higher earlywood to latewood ratio at the same time highly 18o depleted water from october precipitation of the previous year is absorbed the incorporation of this isotopically lighter water during photosynthesis is reflected in the wood and cellulose of tree rings

reply to comment by t j osborn and k r briffa on mid latitude 30 60 n climatic warming inferred by combining borehole temperatures with surface air temperatures 1 we thank osborn and briffa 2002 for their comment regarding our use of the climatic reconstruction of overpeck et al 1997 we harris and chapman 2001 had taken a proxy arctic wide summer weighted annual temperature reconstruction overpeck et al 1997 given in dimensionless sigma units i e normalized deviation from the 1901 1960 proxy mean in units of standard deviation of the new series for the period 1901 1960 and represented the reconstruction in our figure 3 and table 1 in terms of dimensional temperature units c 2 while figure 3 of overpeck et al 1997 is given in dimensionless units the text refers twice to dimensional temperature change in the arctic in both instances the 19th to 20th century warming averaged about 1 5 c across the arctic overpeck et al p 1252 half of the post 1840 warming about 0 75 c took place from 1840 to 1920 overpeck et al p 1253 the magnitude of the changes cited in dimensional temperature c match the change in dimensionless units because the earth is a lowpass filter and borehole temperature reconstructions are sensitive to long term variations we felt that the long term variations in the arctic temperature were adequately represented the calibration of the overpeck et al 1997 proxy temperature reconstruction given by briffa et al 2001 suggests that this is not the case the calibrated reconstruction does not indicate greater warming than other northern hemispheric reconstructions and thus the latitudinal amplification of surface warming in the northern hemisphere now appears illusory 3 the comparison of calibrated climatic reconstructions shown in figure 1 osborn and briffa 2002 illustrates results from two kinds of analysis each yielding a different climate change parameter the proxy reconstructions briffa et al 2001 are calibrated into temperature space by comparison with observed april september surface air temperature sat averaged over all land areas north of 20 n and for the period 1881 1960 temperature anomalies are plotted relative to the 1961 90 mean the pomsat model of harris and chapman 1997 2001 combines borehole temperatures for long term baseline temperature information with co located sat information for highresolution 20th century temperature change the hybrid reconstruction is referenced to the 1961 1990 mean annual rather than spring summer temperature we emphasize that the magnitude of temperature change determined with this method is the same as that determined from the borehole temperatures alone and thus does not represent a calibration in the sense used with proxy methods 4 these temperature reconstructions whether proxy or sgt see also huang et al 2000 show that the 20th century exhibits unusual warming relative to the previous three or four centuries the other major observation that remains if the arctic reconstruction is not an outlier of northern hemisphere reconstructions is that surface ground temperatures sgt histories inferred from borehole temperatures clearly suggest greater warming since the 18th and 17th centuries than do proxy reconstructions this discrepancy see harris and chapman 2001 for some possible explanations needs to be resolved before the potential of combining borehole temperatures with highresolution proxy indicators of climate change can be fully realized

stiffness of soil geosynthetic composite under small displacements i model development abstractwhile significant emphasis has been placed on the quantification of soil geosynthetic properties under failure conditions studies of properties that are suitable for characterizing this in

low frequency temperature variations from a northern tree ring density network we describe new reconstructions of northern extratropical summer temperatures for nine subcontinental scale regions and a composite series representing quasi northern hemisphere temperature change over the last 600 years these series are based on tree ring density data that have been processed using a novel statistical technique age band decomposition designed to preserve greater long timescale variability than in previous analyses we provide time dependent and timescale dependent uncertainty estimates for all of the reconstructions the new regional estimates are generally cooler in almost all precalibration periods compared to estimates obtained using earlier processing methods particularly during the 17th century one exception is the reconstruction for northern siberia where 15th century summers are now estimated to be warmer than those observed in the 20th century in producing a new northern hemisphere series we demonstrate the sensitivity of the results to the methodology used once the number of regions with data and the reliability of each regional series begins to decrease we compare our new hemisphere series to other published large regional temperature histories most of which lie within the 1 confidence band of our estimates over most of the last 600 years the 20th century is clearly shown by all of the palaeoseries composites to be the warmest during this period

large ground warming in the canadian arctic inferred from inversions of temperature logs abstract the simultaneous functional space inversion applied for the first time to the set of precise temperature logs from 61 wells located between 60 and 82 n in northern canada shows evidence of large ground surface temperature gst warming these results include highest latitude locations of the well temperature profiles known in the northern hemisphere there is strong evidence that gst warming started in the late 18th century and lasted until the 20th century simultaneous inversion of all well temperature data suggests that the cumulative ground surface temperature change over the past five centuries amounts to about 2 c significantly exceeding recent estimates from conventional climate proxies this large gst warming is also present in other circumpolar locations in the northern hemisphere

holocene palaeoenvironmental record preserved in a paraglacial alluvial fan sunwapta pass jasper national park alberta canada abstract the soil stratigraphy of a 1 5 m section in the distal portion of a paraglacial alluvial fan in sunwapta pass jasper national park has been examined as part of a long term investigation into holocene palaeoenvironments of the area the section is complex and its characteristics are a result of both episodic sediment inputs and pedogenesis a series of sediments comprising debris flows and aeolian material including three discrete tephra layers mazama st helens yn bridge river underlie the present day soil multiple criteria including stratigraphy radiocarbon dates glass shard morphology and electron microprobe analysis of glass and titanomagnetite composition confirmed the identity of the tephras most fan development occurred before deposition of mazama tephra pedogenesis has been active on the fan throughout the holocene soils have formed between phases of sediment deposition during periods of greater relative site stability soil horizonation is best developed where tephric material has influenced soil chemistry and clay mineralogy leading to the formation of brunisols the sequence of events inferred from the icefield fan s stratigraphy accord well with the holocene palaeoenvironmental history inferred from other sites in the canadian rockies

age and nature of paraglacial debris cones along the margins of the san rafael glacier chilean patagonia this study employs sedimentological indices and lichenometric dating on the lichen species plac opsis patagonica to investigate the nature and age of debris cones which have accumulated at the margins of the downwasting san rafael glacier in chilean patagonia these cones appear to have accumulated by the resedimentation of glacigenic deposits by debris flows with debris movement starting in the early 1980s cone activity follows a pattern of intense initial activity and sediment mobilisation followed by increased stability and colonization by vegetation three of the four cones had stabilized within 15 years of sediment movement initiation these features may be seen as being conditioned by glacial activity with second order controls provided by the local climate and sediment supply the cones have accumulated in a paraglacial environment

improved understanding of geogrid response to pullout loading insights from three dimensional finite element analysis soil reinforcement has rapidly become one of the most common soil improvement techniques used in geotechnical engineering understanding the behavior of a geogrid under pullout loading is essential

detection of volcanic solar and greenhouse gas signals in paleo reconstructions of northern hemispheric temperature 1 we apply a multiple regression method to estimate the response to anthropogenic and natural climate forcings simultaneously from a number of paleo reconstructions of northern hemispheric average temperature these long records 600 to 1000 years provide a unique opportunity to distinguish between different external influences on climate the response to volcanic forcing is reliably detected in all reconstructions and the simulated temperature response to volcanic eruptions compares favorably with observations the response to solar forcing is detected in hemispheric mean data only over some periods in some records and appears weak although most records can be used only to the middle of the 20th century the temperature response to co2 can be detected by this time in most records

sea surface temperature and salinity variability at bermuda during the end of the little ice age 1 we use geochemical and isotope measurements on a 225 year old brain coral diploria labyrinthiformis from the south shore of bermuda 64 w 32 n to construct a record of decadal to centennial scale climate variability the coral was collected alive and annual density bands visible in x radiographs delineate cold and warm seasons allowing for precise dating coral skeletons incorporate strontium sr and calcium ca in relative proportions inversely to the sea surface temperature sst in which the skeleton is secreted previous studies on this and other coral colonies from this region document the ability to reconstruct mean annual and wintertime sst using sr ca measurements goodkin et al 2007 2005 the coral based records of sst for the past 2 centuries show abrupt shifts at both decadal and centennial timescales and suggest that sst at the end of the little ice age between 1840 and 1860 was 1 5 0 4 c colder than today 1990s coral reconstructed sst has a greater magnitude change than does a gridded instrumental sst record from this region this may result from several physical processes including high rates of mesoscale eddy propagation in this region oxygen isotope values 18o of the coral skeleton reflect changes in both temperature and the 18o of seawater ow where ow is proportional to sea surface salinity sss we show in this study that mean annual and wintertime 18o of the carbonate oc are correlated to both sst and sss but a robust quantitative measure of sss is not found with present calibration data in combination however the sr ca and oc qualitatively reconstruct lower salinities at the end of the little ice age relative to modern day temperature changes agree with other records from the bermuda region radiative and atmospheric forcing may explain some of the sst variability but the scales of implied changes in sst and sss indicate large scale ocean circulation impacts as well

nd isotope signature of holocene baltic mn fe precipitates as monitor of climate change during the little ice age neodymium nd isotope profiles were analyzed on two baltic mn fe precipitates 99 2 and tl1 from shallow water 20 m of the mecklenburg bay the age range of these mn fe precipitates determined by 226raex ba dating reaches from recent growth back to 4300 and 1000 yr bp respectively over this time range the nd isotope composition varies from end 0 13 1 to 17 5 in the selected baltic precipitates indicating substantial changes in the nd isotope composition of the baltic sea the lowest end values were recorded during the time interval of the little ice age lia ad 1350 to 1850 these minimum values indicate either an increase of the input of less radiogenic nd from scandinavian archean proterozoic sources end about 22 to the baltic sea or a decrease of the input of more radiogenic nd from continental european sources end about 12 and or north sea water end about 10 variations of both erosive continental input and north sea inflow may indicate a direct response of the nd isotope signal in the baltic sea to climate changes during the lia and be related to cyclic shifts in the atmospheric circulation triggered by the north atlantic oscillation nao another aspect that possibly influenced the input of trace elements and nd isotopes into the baltic sea is the population development in the circum baltic area during the lia the lowest end values also correspond to the medieval demographic crises that led to a significant decrease of agricultural activity and farmland the reduction of soil erosion and enhanced regrowth of natural vegetation may have changed the amount and proportions of dissolved and suspended particulate matter transported into the baltic sea by rivers which in turn may have resulted in a change of the nd isotope composition of baltic sea water

last millennium northern hemisphere summer temperatures from tree rings part i the long term context abstract large scale millennial length northern hemisphere nh temperature reconstructions have been progressively improved over the last 20 years as new datasets have been developed this paper and its companion part ii anchukaitis et al in prep details the latest tree ring tr based nh land air temperature reconstruction from a temporal and spatial perspective this work is the first product of a consortium called n trend n orthern hemisphere tre e ring n etwork d evelopment which brings together dendroclimatologists to identify a collective strategy for improving large scale summer temperature reconstructions the new reconstruction n trend2015 utilises 54 records a significant expansion compared with previous tr studies and yields an improved reconstruction with stronger statistical calibration metrics n trend2015 is relatively insensitive to the compositing method and spatial weighting used and validation metrics indicate that the new record portrays reasonable coherence with large scale summer temperatures and is robust at all time scales from 918 to 2004 where at least 3 tr records exist from each major continental mass n trend2015 indicates a longer and warmer medieval period 900 1170 than portrayed by previous tr nh reconstructions and by the cmip5 model ensemble but with better overall agreement between records for the last 600 years future dendroclimatic projects should focus on developing new long records from data sparse regions such as north america and eastern eurasia as well as ensuring the measurement of parameters related to latewood density to complement ring width records which can improve local based calibration substantially

tree ring derived temperature records in the central loess plateau china using tree ring widths of pinus tabulaeformis carr trees mean temperatures from february to september were reconstructed for the kongtong mountain during the past 283 years the reconstruction could explain 43 7 of temperature variance during the calibration period from 1951 to 2004 it displays similar patterns to several temperature reconstructions in the loess plateau it corresponds well with the temperature regimes in hokkaido japan indicating that both regions have similar warm and cold intervals the high correlation between the reconstruction and the cru climatic research unit of university of east anglia uk ts3 temperature datasets showed that the temperature reconstruction could be representative of large scale climate change over northern china in addition the pacific decadal oscillation pdo affected temperature variations of northern china and even hokkaido to a certain extent

using discriminant function analysis to identify holocene tephras based on magnetite composition a case study from the sunwapta pass area jasper national park the magnetite composition from three sets of samples of mazama st helens set y and bridge river tephras from jasper and banff national parks are used to test whether discriminant function analysis can unambiguously distinguish these tephras the multivariate method is found to be very sensitive to the change in reference samples st helens set y tephra is clearly distinguished however discrimination between mazama and bridge river tephras is less distinct a set of unknown tephras from the sunwapta pass area was used to test the classification schemes unknown tephras are assigned to different tephra types depending on which reference tephra set is used in the discriminant function analysis

high resolution reconstruction of wetness dynamics in a southern boreal raised bog finland during the late holocene a quantitative approach a high resolution plant macrofossil analysis was applied to investigate wetness dynamics in a southern finnish boreal bog kontolanrahka during the last 5000 years the chronological control and the age depth model were based on 40 ams radiocarbon dates pollen analysis provided information on regional scale vegetation changes macrofossil analysis revealed prominent changes in vegetation assemblages during the late holocene indicating fluctuations in water table the reconstruction suggests that at the coring point which nowadays is a relatively wet lawn habitat type has repeatedly varied between transient communities similar to those currently represented in dry hummocks very wet lawns and even hollows in order to quantify historical changes in water table generalized additive models gam were used to investigate the current relationships between surface plant species and water table depth modern water table measurements and a survey of associated plant communities along moisture gradients prov

vegetation climate and lake changes over the last 7000 years at the boreal treeline in north central siberia abstract palaeoecological investigations in the larch forest tundra ecotone in northern siberia have the potential to reveal holocene environmental variations which likely have consequences for global climate change because of the strong high latitude feedback mechanisms a sediment core collected from a small lake radius 100 m was used to reconstruct the development of the lake and its catchment as well as vegetation and summer temperatures over the last 7100 calibrated years a multi proxy approach was taken including pollen and sedimentological analyses our data indicate a gradual replacement of open larch forests by tundra with scattered single trees as found today in the vicinity of the lake an overall trend of cooling summer temperature from a 2 c warmer than present mid holocene summer temperatures until the establishment of modern conditions around 3000 years ago is reconstructed based on a regional pollen climate transfer function the inference of regional vegetation changes was compared to local changes in the lake s catchment an initial small water depression occurred from 7100 to 6500 cal years bp afterwards a small lake formed and deepened probably due to thermokarst processes although the general trends of local and regional environmental change match the lake catchment changes show higher variability furthermore changes in the lake catchment slightly precede those in the regional vegetation both proxies highlight that marked environmental changes occurred in the siberian forest tundra ecotone over the course of the holocene

a strategy to improve the contribution of coral data to high resolution paleoclimatology abstract various geochemical tracers measured in massive coral skeletons have the potential to compliment other sources of high resolution proxy climate information e g tree rings ice cores by providing paleoclimatic data from shallow water tropical ocean regions twenty previously published coral records 19 18o and one sr ca series between 54 and 346 years in length were examined for their local and larger scale relationships el nino southern oscillation with climate series were examined in a consistent manner over the same time periods and relationships were tested for stability through time the results demonstrate a spectrum of climatic interpretation ranging from 1 no significant relationship of the coral record with either local or larger scale climate variables 2 significant relationship of the coral record with climate but the relationship is not stable through time and 3 the coral record shows a significant and temporally stable relationship with climate which explains a significant and useful proportion of climate variance it is concluded that reliance to date on analyzing only one long coral core from a site has prevented identification of coral records or parts of coral records where non climatic factors are dominating the geochemical signal various factors may cause these non climatic signals to dominate more process studies into how corals of particular species with various growth rates and from various environmental settings incorporate geochemical tracers into their skeleton are required to understand exactly what is being measured in addition it is recommended that some level of replication ideally three separate corals of geochemical tracers will ensure accurate dating of the record identification of periods when non climatic factors dominate and thus enhance the reliability of the paleoclimatic record such an approach will allow the rich archive of environmental information contained in massive coral skeletons to make a significant contribution to high resolution paleoclimatology and improve our understanding of the nature and causes of past climate variability

holocene landscape evolution of a nivation hollow on gassan volcano northern japan abstract this paper describes the results of detailed surveys for the landscape systems landforms vegetation topsoils and snow cover duration of a nivation hollow in northern japan and discusses their evolution in the holocene epoch the nivation hollow studied consists of three concentric zones whose landscapes and historical development are different the outermost zone where snow disappears early is covered with dwarfed trees sasa kurilensis subalpine bamboo thicket and snowbed grasses fossil solifluction lobes and drainage channels are common in this zone slope stabilization and vegetation establishment penetration and settlement of vegetation on slopes followed by pedogenesis occurred after 12 350 cal bp in the middle zone slopes are mostly covered with snowbed plants and turf banked terraces and minor slumps are observed this zone experienced slope stabilization and vegetation establishment followed by pedogenesis after 4870 cal bp the innermost zone overlaps with the snow induced bare ground in the centre of the nivation hollow basin active geomorphic processes operate here and traces of surficial wash and rills are abundant humic soils are not present in this zone these differences in landscape development of the nivation hollow may reflect the temporal changes in the timings of snow disappearance associated with the holocene climatic variabilities

sensitivity of tree growth to a high co2 environment consequences for interpreting the characteristics of fossil woods from ancient greenhouse worlds abstract long term carbon cycle models and independent proxies indicate that the atmospheric co 2 concentration was substantially higher in the mesozoic and early tertiary than now the responses of tree growth to a high co 2 environment must therefore be understood if present day relationships between climate and tree growth are to be used with confidence for palaeoclimate reconstructions from mesozoic and tertiary fossil woods a brief review of experimental data shows that stimulation of leaf photosynthesis suppression of plant respiration and lower transpiration rates under elevated co 2 500 700 ppm can reduce the ratio of wood basal area to tree height but increase total basal area growth in wood by 20 25 to assess the consequences of these plant co 2 responses for tree growth during ancient greenhouse episodes we developed a mathematical model explicitly incorporating the physiological mechanisms underpinning the observed co 2 effects application of this model to predict the height of coniferous forests in the late jurassic 150 ma and mid cretaceous 100 ma indicated maximum heights in the mid latitudes of over 60 m and 40 60 m respectively corresponding wood growths of these forests expressed as basal area growth rates were 1 5 2 5 cm 2 and 0 75 1 75 cm 2 sapwood m 2 ground area yr 1 values exceeding those of modern conifers in warm temperate sites these results were highly sensitive to the concentration of atmospheric co 2 and this co 2 sensitivity depended strongly on climate consequently direct application of present day growth climate relationships to fossil woods may be inappropriate for the mesozoic and tertiary however models that explicitly consider the mechanisms of plant co 2 responses may provide a useful method for accounting for this co 2 sensitivity allowing more secure palaeoclimate reconstructions from material of this age

scale dependent reconstruction of the nao index a method is presented to reconstruct decadal variations of the north atlantic oscillation nao the spectral characteristics of the nao on time scales of decades and longer are of particular interest for the understanding of north atlantic ocean atmosphere interactions the reconstruction is based on a transfer model calibration that uses bandpass filtered time series the maximum overlap discrete wavelet transform modwt is applied for decomposing the time series variance into different time scales a total of 43 proxies including greenland ice cores and european tree ring chronologies are selected and regionally grouped providing four independent reconstructions for the period 1700 1978 the mean reconstruction agrees well with two recently published reconstructions during most of the time period however there are considerable differences in the earliest part before 1750 running correlations between the reconstructions indicate that time dependent relations exist among the different nao reconstructions the results suggest that the geographical distribution of proxies strongly affects the reconstruction and could explain some of the apparent discrepancies among the reconstructions recently published in literature in the early eighteenth century external forcing solar volcanic seems to mask the nao signature within the proxies

instrument and tree ring based estimates of the antarctic oscillation abstract an estimate of the strength of the austral summer antarctic oscillation using station sea level pressure records for the period 1878 2000 is presented the first to the authors knowledge the reconstruction was obtained by relating the antarctic oscillation aao intensity derived from ncep ncar reanalysis data to the leading principal components of station records using multiple regression analysis particular effort has been made to fit the model in a way that is robust to the questionable trends in the ncep ncar data in the southern hemisphere the trends in the reconstruction are derived from the station data not from the ncep data cross validation with the ncep data and comparison with other analyses of the aao over the late instrumental period give confidence that this station based reconstruction can be regarded as trustworthy with regard to the whole reconstruction period some unquantifiable uncertainty stems from potential instability of the statistical relationships to extend this

a re examination of the three most prominent holocene tephra deposits in western canada bridge river mount st helens yn and mazama abstract volcanic ash deposits tephra in western canada are instrumental in providing independent chronologic control for many archaeological and paleoenvironmental sites in alberta tephra are a key chronologic tool in a region where radiocarbon dates are often unreliable because of the prevalence of carbonate rich bedrock and other old carbon sources such as coal however many studies using tephra for age control particularly archaeological projects identify tephra simply through field characteristics or light microscopy in both alberta and british columbia many radiocarbon dates that were used to date key tephra deposits were bulk conventional ages on peat and lake sediments which are not always reliable these factors have led to uncertainty in the age and number of bridge river and mount st helens msh set y tephra present in the region and incomplete distribution maps new major element geochemical analyses from archaeological and sedimentary sites across south central alberta complemented by new analyses of tephra from british columbia and saskatchewan refine the distribution of the bridge river msh yn and mazama tephra new geochemical data radiocarbon dates and a detailed overview of proximal msh set y stratigraphy and geochemistry show that only one msh layer yn is present in this region rather than two msh set y tephra as previously suggested additionally re assessment of age data combined with new geochemical analyses confirm that there is also only one bridge river tephra a bayesian modelled age estimate is determined for msh yn based on new ams dates on the tephra and vetted existing conventional ages providing a revised age estimate for msh yn of 3805 3535 cal bp mean of 3660 cal bp

multidecadal variability of atmospheric methane 1000 1800 c e 1 we present a new high precision high resolution record of atmospheric methane from the west antarctic ice sheet wais divide ice core covering 1000 1800 c e a time period known as the late preindustrial holocene lpih the results are consistent with previous measurements from the law dome ice core the only other high resolution record of methane for this time period and confirm most of the observed variability multidecadal variability in methane concentrations throughout the lpih is weakly correlated or uncorrelated with reconstructions of temperature and precipitation from a variety of geographic regions correlations with temperature are dominated by changes in northern hemisphere high latitude temperatures between 1400 and 1600 c e during the onset of the little ice age times of war and plague when large population losses could have reduced anthropogenic emissions are coincident with short periods of decreasing global methane concentrations

variation of early summer and annual temperature in east taymir and putoran siberia over the last two millennia inferred from tree rings regional tree ring chronology with extension 2209 years from 212 b c till 1996 a d was built for east taymir and putoran according to wood of living trees well preserved remains of dead trees and subfossil wood from alluvial bank deposits by the cross dating method in addition the floating tree ring width chronology for the period of holocene optimum 3300 2600 b c was built with extention 685 years and supported by several radiocarbon dates high values of synchrony and correlation of individual tree ring series show a prevailing effect of one external factor on radial tree growth change in the studied region of the siberian subarctic it was established that the main factors of growth variability are the early summer and annual temperature which explain up to 70 of tree growth rate variability cyclic components stable for two millennia were revealed at analysis of the tree ring chronology double secular 180 years secular 78 90 years and intrasecular 44 28 11 and 6 7 6 9 years variations models for reconstruction of the early summer and annual air temperature were obtained according to tree ring variability temperature dynamics in the eastern part of taymir for the last two millenia agree well with temperature variations in the northern hemisphere obtained according to other indirect sources the warming of the middle of the twentieth century is not extraordinary the warming at the end of the first and beginning of the second millennia medieval warm period was longer in time and closer in amplitude

applications of stalagmite laminae to paleoclimate reconstructions comparison with dendrochronology climatology abstract laminated stalagmites observed in either ultra violet or visible light or recognized via trace elements are now widely recognized as a common deposition form annually laminated stalagmites should be expected in caves which have an overlying climate that has a strong seasonality similar climate zones to where trees grow with distinct annual rings continuous laminated stalagmite chronologies up to several thousand years should be expected where some mixing of stored water occurs such stalagmites can be used to reconstruct climate particularly through variations in lamina width such climate records would be relatively damped by mixing of event water with stored groundwater constraining the amount of high frequency climate signals contained in the stalagmite but relatively long continuous lamina sequences permit the preservation of low frequency centennial scale climate signals this contrasts with numerous tree ring climate records which are frequently limited in preserving multi centennial trends due to the necessary removal of age related noise from relatively short tree segments laminated stalagmites and tree rings should therefore to some degree provide complementary climate information appropriate methods for compiling stalagmite layer chronologies and climatologies are presented

a numerical approach toward the classification of magnetites from tephra in southern alberta high titanium glass encased magnetites associated with intermixed tephras in upper subalpine soils in banff national park are shown to be characteristic of mazama tephra and of regional significance similar magnetites occur in a mazama layer above a paleosol at fish creek alberta and within a sample of mazama ash ua 396 from windy point alberta detailed sampling and analysis of the fish creek tephra indicate that the magnetites do not represent a separate eruptive event or an older ashfall cluster analysis of glass encased magnetites from reference samples of mazama st helens y and bridge river ashes revealed composite grouping of mazama and bridge river magnetites and separate and strong groupings of high tio2 magnetites discriminant analysis identifies mgo tio2 and al2o3 as the most significant chemical discriminants between the various ashes discriminant function analysis identifies the high titanium magnetites as mazama in type and successfully classifies 96 of the tephra derived magnet

late quaternary vegetation history of wilcox pass jasper national park alberta five pollen zones are recognized in a radiocarbon and tephra dated core from an alpine site at an elevation of ca 2355 masl in wilcox pass jasper national park and record late quaternary vegetation history the two lower zones underlie material dated at 9600 305 yr b p gx 8785 and record early postglacial vegetation the basal zone wp1 containing an artemisia dominated assemblage represents tundra vegetation after deglaciation in zone wp2 arboreal pollen mainly diploxylon pine becomes dominant and represents a lodgepole pine forest the pollen assemblage of zone wp3 which initially contains large amounts of haploxylon pine as well as picea and abies pollen shows a transition from a forest with large amounts of whitebarkpine to vegetation resembling present day subalpine forest during this phase temperatures were probably warmer than present zone wp4 beginning after the influx of mazama tephra 6800 yr b p to the site records an expansion of the subalpine forest to higher elevations with a warmer climate in zone wp5 beginning about 2800 yr b p values of the main arboreal components fluctuate indicating cooler temperatures and less favourable environmental conditions probably associated with neoglacial ice advances the environmental trends observed from this record accord with those from other vegetation records in the canadian rockies

global surface temperatures over the past two millennia 1 we present reconstructions of northern and southern hemisphere mean surface temperature over the past two millennia based on high resolution proxy temperature data which retain millennial scale variability these reconstructions indicate that late 20th century warmth is unprecedented for at least roughly the past two millennia for the northern hemisphere conclusions for the southern hemisphere and global mean temperature are limited by the sparseness of available proxy data in the southern hemisphere at present

revised 14c age for st helens y tephra at tonquin pass british columbia the age of a mount st helens set y tephra at tonquin pass british columbia previously assumed to be 4300 years bp is revised to ca 3400 years bp based on bracketing 14c dates of 3140 70 beta 13558 and 3680 80 years bp beta 13559 the implications of this revision for tephrostratigraphy of this area are discussed

strain distribution within geosynthetic reinforced slopes geosynthetic reinforced slopes are conventionally designed using methods based on limit equilibrium in order to estimate the factor of safety against internal stability using these methods the distribution of the reinforcement peak tensile forces with height must be assumed a linear distribution of reinforcement peak tension with height with zero tension at the crest and maximum peak tension at the toe of the structure has often been assumed although this assumption may be appropriate for the design of vertical geosynthetic reinforced walls little evidence has been collected so far justifying this distribution for the design of geosynthetic reinforced slopes a combination of centrifuge testing and digital image analysis is undertaken in order to obtain the strain distribution within geosynthetic reinforced slopes under prefailure conditions specifically digital image analysis techniques are used to determine the displacement distribution along reinforcement layers in reduced scale models subjected to increasing g levels a sigmoid function was useful to fit raw displacement data and estimate the strain distribution along reinforcement layers analysis of reinforcement strain results shows that the location of the reinforcement maximum peak strain does not occur near the toe of the structure but was located approximately at midheight of the reinforced slopes at the point along the critical failure surface directly below the crest of the slope the pattern of reinforcement peak strain with height obtained for prefailure conditions is similar to that obtained for failure conditions the estimated factor of safety is found to be a good indicator of the magnitude of the reinforcement maximum peak strain for geosynthetic reinforced slopes built with different configurations

the temperature of europe during the holocene reconstructed from pollen data we present the first area average time series reconstructions of warmest month coldest month and mean annual surface air temperatures across europe during the last 12 000 years these series are based on quantitative pollen climate reconstructions from over 500 pollen sites assimilated using an innovative four dimensional gridding procedure this approach combines three dimensional spatial gridding with a fourth dimension represented by time allowing data from irregular time series to be focussed onto a regular time step we provide six regional reconstructed temperature time series as well as summary time series for the whole of europe the results suggest major spatial and seasonal differences in holocene temperature trends within a remarkably balanced regional and annual energy budget the traditional mid holocene thermal maximum is observed only over northern europe and principally during the summer this warming was balanced by a mid holocene cooling over southern europe whilst central europe occupied an intermediary position changes in annual mean temperatures for europe as a whole suggest an almost linear increase in thermal budget up to 7800 bp followed by stable conditions for the remainder of the holocene this early holocene warming and later equilibrium has been mainly modulated by increasing winter temperatures in the west which have continued to rise at a progressively decreasing rate up to the present day

1738 years of mongolian temperature variability inferred from a tree ring width chronology of siberian pine 1738 years ad 262 1999 of temperature variability are inferred from tree ring widths of siberian pine at solongotyn davaa sol dav a timberline 2420 m site in mongolia this chronology can account for 33 of the temperature variance from 1882 1993 the warmest conditions over the past millennium are during the 20th century the 1999 ring width has the highest index value over the past millennium both warmer and colder intervals are inferred during the medieval warm epoch the most severe cold occurred in the 19th century unusual cold and frost in ad 536 545 coincide with extremes in other proxies and historical accounts confirming a widespread catastrophic event trends resemble those of other eurasian paleoseries and hemispheric scale reconstructions over the past millennium more chronologies such as sol dav are essential to improve coverage in the uncertain earlier centuries of these reconstructions and their estimates of natural variability relative to recent anthropogenic change

modeling ocean heat content changes during the last millennium 1 observational studies show a significant increase in ocean heat content over the last half century herein we estimate heat content changes during the last millennium with a climate model whose forcing terms have been best fit to surface proxy data the model simulates the observed late 20th century ocean heat content increase and a comparable little ice age minimum when glacial advances are factored in these results imply a sea level fall after the middle ages that is consistent with some geologic data the present ocean heat content increase can be traced back to the mid 19th century with a near linear rate of change during the 20th century

august temperature variability in the southeastern tibetan plateau since ad 1385 inferred from tree rings long term high resolution climate proxies are essential for understanding climate variability on the tibetan plateau tp where few long term climate records are available in this paper we describe a summer august temperature reconstruction over the period 1385 2002 based on a tree ring width chronology of balfour spruce picea likiangensis var balfouriana on the southeastern tp created using the regional curve standardization method the reconstruction explains 44 7 of the variance in the instrumental temperature records during the calibration period 1962 2002 and captures temperature variability over a broad region of the tp warmer than average augusts were found during the periods 1446 1494 1509 1522 1553 1567 1797 1812 1845 1905 and 1918 2002 cooler than average augusts occurred from 1385 1416 1426 1445 1495 1508 1523 1552 1568 1686 1695 1718 1725 1796 1813 1844 and 1906 1917 a warming trend in the 20th century was unprecedented during the past six centuries the reconstruction closely matched other tree ring summer temperature reconstructions from neighboring regions as well as patterns from ice core delta 18 o data and fluctuated in synchrony with northern hemisphere temperature reconstructions c 2011 elsevier b v all rights reserved

reconstructed summer temperature in the northern rocky mountains wilderness usa ring widths from whitebark pine pinus albicaulis englem and subalpine larch larix lyallii parl collected at three high elevation sites were used to develop tree growth chronologies to reconstruct summer temperature anomalies a step wise multiple regression procedure was used to screen potential predictor variables to generate a transfer function capable of skillfully reconstructing summer temperature the resulting regression model explained approximately 38 of the adjusted variance in the instrumental temperature record the fidelity of the reconstruction was verified using product mean and sign tests both of which suggested significant predictive power in the reconstructions p 0 05 reduction of error re and coefficient of efficiency ce measures were both positive indicating the reconstruction contained useful climate information cool periods often coincided with reduced solar activity and or periods of increased volcanic activity differences between this reconstruction and others encompassing a broader geographic scale highlight the importance of developing local reconstructions of climate variability particularly when used in conjunction with ecological data sets that describe the occurrence of fires or insect epidemics mixed and divergent climate response relationships were evident in the whitebark pine chronologies and suggest subalpine larch may be a more useful species than whitebark pine to target for the development of temperature reconstructions in this region

a combined study of radar facies lithofacies and three dimensional architecture of an alpine alluvial fan illgraben fan switzerland alluvial fans serve as useful archives that record the history of depositional and erosional processes in mountainous regions and thus can reveal the environmental controls that influenced their development economically they play an important role as groundwater reservoirs as well as host rocks for hydrocarbons in deeply buried systems the interpretation of these archives and the evaluation of their reservoir architecture however are problematic because marked heterogeneity in the distribution of sedimentary facies makes correlation difficult this problem is compounded because the accumulated sedimentary deposits of modern unconsolidated fan systems tend to be poorly exposed and few such systems have been the focus of investigation using high resolution subsurface analytical techniques to overcome this limitation of standard outcrop analogue studies a geophysical survey of an alpine alluvial fan was performed using ground penetrating radar to devise a scaled three dimensional subsurface model radar facies were classified and calibrated to lithofacies within a fan system that provided outcropping walls and these were used to derive a three dimensional model of the sedimentary architecture and identify evolutionary fan stages the illgraben fan in the swiss alps was selected as a case study and a network of ca 60 km sections of ground penetrating radar was surveyed seven radar facies types could be distinguished which were grouped into debris flow deposits and stream flow deposits assemblages of these radar facies types show three depositional units which are separated by continuous fan wide reflectors they were interpreted as palaeo surfaces corresponding to episodes of sediment starvation that affected the entire fan an overall upward decline in the proportion of debris flow deposits from ca 50 to 15 and a corresponding increase in stream flow deposits were identified the uppermost depositional unit is bounded at its base by a significant incision surface up to 700 m wide which was subsequently filled up mostly by stream flow deposits the pronounced palaeo surfaces and depositional trends suggest that allocyclic controls governed the evolution of the illgraben fan making this fan a valuable archive from which to reconstruct past sediment fluxes and environmental change in the alps the results of the integrated outcrop geophysical approach encourage similar future studies on fans to retrieve their depositional history as well as their potential reservoir properties

precipitation reconstruction from hailar pine pinus sylvestris var mongolica tree rings in the hailar region inner mongolia china back to 1865 ad article precipitation is the major limiting factor for the radial growth of hailar pine pinus sylvestris var mongolica i n the hailar northeast china herein the amount of precipitation from the previous july to current june was chosen for reconstruction from 1865 to 2003 ad this reconstruction accounts for 51 of the variance in the instrumental precipitation data during the 1952 2003 period the reconstruction reveals the precipitation fluctuation history over the last 139 years some severe drought events lasting for more than 3 years are displayed in theseries such as 1905 1909 1926 1929 asevere drought event in central northern china with tremendous losses of human lives and 1968 1970 extreme wet events are 1867 1870 1932 1934 1939 1941 and 1955 1957 on the decadal scale there are two dry periods with precipitation lower than the mean of 1865 2003 1888 1929 and 1963 1975 and two wet intervals more than the mean 1930 1962 and 1976 2003 drought events or dry intervals correspond to weak and wet events to strong east asian summer monsoon easm the reconstructed precipitation can be well compared with the baiyinaobao ortindag sand land in eastern inner mongolia and northeastern mongolia rainfall series derived from tree rings the four curves show similar variation related to weak strong easm a power spectrum analysis shows that there are 7 67 and 7 08 year quasi periodicities which may be associated with enso activity

a matter of divergence tracking recent warming at hemispheric scales using tree ring data 1 no current tree ring tr based reconstruction of extratropical northern hemisphere enh temperatures that extends into the 1990s captures the full range of late 20th century warming observed in the instrumental record over recent decades a divergence between cooler reconstructed and warmer instrumental large scale temperatures is observed we hypothesize that this problem is partly related to the fact that some of the constituent chronologies used for previous reconstructions show divergence against local temperatures in the recent period in this study we compiled tr data and published local regional reconstructions that show no divergence against local temperatures these data have not been included in other large scale temperature reconstructions utilizing this data set we developed a new completely independent reconstruction of enh annual temperatures 1750 2000 this record is not meant to replace existing reconstructions but allows some degree of independent validation of these earlier studies as well as demonstrating that tr data can better model recent warming at large scales when careful selection of constituent chronologies is made at the local scale although the new series tracks the increase in enh annual temperatures over the last few decades better than any existing reconstruction it still slightly under predicts values in the post 1988 period we finally discuss possible reasons why it is so difficult to model post mid 1980s warming provide some possible alternative approaches with regards to the instrumental target and detail several recommendations that should be followed in future large scale reconstruction attempts that may result in more robust temperature estimates

fennoscandia revisited a spatially improved tree ring reconstruction of summer temperatures for the last 900 years despite the spatially homogenous summer temperature pattern in fennoscandia there are large spreads among the many existing reconstructions resulting in an uncertainty in the timing and amplitude of past changes also there has been a general bias towards northernmost fennoscandia in an attempt to provide a more spatially coherent view of summer june august jja temperature variability within the last millennium we utilized seven density and three blue intensity scots pine pinus sylvestris l chronologies collected from the altitudinal scandinavian mountains and latitudinal northernmost part treeline to attain a jja temperature signal as strong as possible as well as preserving multicentury scale variability we used a new tree ring parameter where the earlywood information is removed from the maximum density and blue intensity and a modified signal free standardization method two skilful reconstructions for the period 1100 2006 ce were made one regional reconstruction based on an average of the chronologies and one field gridded reconstruction the new reconstructions were shown to have much improved spatial representations compared to those based on data from only northern sites thus making it more valid for the whole region an examination of some of the forcings of jja mean temperatures in the region shows an association with sea surface temperature over the eastern north atlantic but also the subpolar and subtropical gyres moreover using superposed epoch analysis a significant cooling in the year following a volcanic eruption was noted and for the largest explosive eruptions the effect could remain for up to 4 years this new improved reconstruction provides a mean to reinforce our understanding of forcings on summer temperatures in the north european sector