late quaternary climate variability and vegetation response in ziro lake basin eastern himalaya a multiproxy approach abstract pollen phytolith and stable carbon isotopic records provide new insights into the palaeoenvironmental and palaeoclimatic changes in ziro lake basin sub himalayan arunachal pradesh india since pre lgm time phytoliths record a minor change in grass woodland cover and appear to be more sensitive than pollen grains to climate fluctuations both pollen and non pollen palynomorph data suggest prevalence of a dense c3 species dominated moist semi evergreen forest in the area until the lgm which shows conformity with 13c data the phytolith assemblage indicates an alteration in forest cover with expansion of c4 grasses during the lgm the study further indicates a climatic amelioration with intensification of south west monsoon during 10 2 3 8 ka and an expansion of forest cover after 3 8 ka there was a rising trend of dryness shrinkage in forest cover and a slight increase in c4 species while c3 plants dominated ecosystem variability also points towards a hydrological transformation in the area since pre lgm time application of coexistence approach on pollen data reveals that prior to the lgm the mean annual temperature and mean annual precipitation were approximately 19 3 0 001 c and 1925 15 mm respectively between 10 2 and 3 8 ka mat was about 19 4 0 5 c while map was 1901 41 3 mm between 3 8 and 1 2 ka and onwards a slight increase in mat 0 3c was observed with further decrease in map to 1861 33 4 mm during pre and post lgm times mat was more or less similar in the ziro lake basin which increased gradually after 3 8 ka and was 1 2 c higher than today prior to the lgm map was higher than the present day by 94 mm between 10 2 and 3 8 ka by 70 mm and since 3 8 ka onwards by 30 mm showing a tendency of gradual decline suggesting a consequent increase in dryness

methodology of the last climatic cycle reconstruction in france from pollen data abstract a numerical method has been devised to reconstruct the climate of the last climatic cycle from pollen data reliable annual reconstructions have been published recently for the two french long sequences of la grande pile and les echets covering the last 140 millennia this paper gives more details on the method used it proposes new reconstructions based on an extended modern pollen data base these reconstructions are consistent with the previous ones especially detailed information is obtained on the seasonal characteristics of climate computations of gcm on the climate variations from 125 kyr to 115 kyr b p are confirmed for western europe the insolation variations have induced at that time a decrease of seasonality accompanied by an increased cyclonic activity in winter this has been the beginning of the first ice growth after the last interglacial other glacier growth phases are detected at the end of substage 5c and particularly at the end of substage 5a

simulation of historic glacier variations with a simple climate glacier model glacier variations during the last few centuries have shown a marked coherence over the globe characteristic features are the maximum stand somewhere in the middle of the nineteenth century and the steady retreat afterwards with some minor interrruptions depending on the particular region in many papers qualitative statements have been made about the causes of these fluctuations lower temperatures associated with solar variability and or volcanic activity are the most popular explanations in particular the statistical relation between glacier activity and major volcanic eruptions appears to be strong in this paper an attempt is made to simulate recent glacier fluctations with a physics based model a simple climate model calculating perturbations of surface radiation balance and air temperature not necessarily in phase is coupled to a schematic time dependent glacier model the climate model is forced by volcanic activity greenland acidity and or lamb s dust veil index and greenhouse warming solar variability was not considered because its effect on climate has still not been demonstrated in a convincing way the output is translated into variations in equilibrium line altitude driving the glacier model the simulated variations in glacier length show good agreement with the observed record but the amplitude is too small this is improved when mass balance gradients are assumed to be larger in warmer climates compared to recently published modelling studies of particular glaciers in which series of local parameters e g tree ring width and temperature were used as forcing the present simulation is better this suggests that the radiation balance is a decisive factor with regard to glacier variations on longer time scales the model experiments lend support to the results of porter 1986 who concluded from a more qualitative study that a strong relation exists between periods of increased volcanic activity and glacier advances a comparison of some selected runs shows that according to the present model the greenhouse warming would be responsible for about 50 of the glacier retreat observed over the last 100 years

towards defining the transition in style and timing of quaternary glaciation between the monsoon influenced greater himalaya and the semi arid transhimalaya of northern india abstract to help delineate the transition in pattern and timing of glaciation between two contrasting regions lahul to the south and ladakh to the north moraines in the puga and karzok valleys of sanskrit in the transhimalaya of northern india were mapped and dated using cosmogenic 10 be in lahul late quaternary glaciation was extensive with total valley glacial systems being 100 km in extent whereas glaciation in ladakh has been comparatively restricted with glaciers advancing only 15 km from the contemporary glaciers during the last 200 ka in the puga valley glaciers advanced 15 km at 129 ka and 10 km at 46 ka 4 2 ka and 0 6 ka in the karzok valley glaciers advanced 1 km at 3 6 ka boulder exposure ages from a large moraine complex in karzok indicate a glacial advance at 80 ka of 4 km from the present ice margin the oldest moraine in karzok is 311 ka indicating that glaciers advanced 10 km from the present ice margin during or before marine isotope stage 9 the glacial chronology of the two valleys shows a lack of early holocene glaciation and generally asynchronous glaciation between them moraines in the puga and karzok valleys broadly correlate with previous studies in the zanskar range but the paucity of data for many of the glacial stages across the zanskar region makes the correlations tentative the lack of early holocene glaciation in the puga and karzok valleys is in stark contrast to many regions of the himalaya including lahul and the restricted glacial extent in zanskar is more similar to the style of glaciation in ladakh the similarity between the glacial records in the puga and karzok study areas suggests that the transition to lahul style glaciation is to the south of the karzok valley showing that this geographical transition is abrupt

climatic signal of ice melt features in southern greenland the stratigraphie record of melt features in intermediate depth polar ice cores has provided valuable data on past summer climate1 3 the thermal drilling technique used in previous studies precluded extending this record beyond a few hundred years recently however a 901 m deep ice core was mechanically drilled in southern greenland the excellent core quality and improved techniques for measuring melt features have resulted in an 2 200 yr record with consistently high quality data we report here that the temporal variations in melt feature abundance expressed as annual melt per cent amp provide proxy data on summer climate that can complement other records extending back thousands of years the amp profile indicates that relatively warm summers prevailed from about ad 950 until ad 1500 culminating in the thirteenth and fourteenth centuries the periods from about 300 to 150 bc ad 350 to 550 and ad 1550 to 1800 had relatively little summer melting

multiproxy summer and winter surface air temperature field reconstructions for southern south america covering the past centuries we statistically reconstruct austral summer winter surface air temperature fields back to ad 900 1706 using 22 20 annually resolved predictors from natural and human archives from southern south america ssa this represents the first regional scale climate field reconstruction for parts of the southern hemisphere at this high temporal resolution we apply three different recon struction techniques multivariate principal component regression composite plus scaling and regularized expectation maximization there is generally good

younger dryas and allerod summer temperatures at gerzensee switzerland inferred from fossil pollen and cladoceran assemblages linear and unimodal based inference models for mean summer temperatures partial least squares weighted averaging and weighted averaging partial least squares models were applied to a high resolution pollen and cladoceran stratigraphy from gerzensee switzerland the time window of investigation included the allerod the younger dryas and the preboreal characteristic major and minor oscillations in the oxygen isotope stratigraphy such as the gerzensee oscillation the onset and end of the younger dryas stadial and the preboreal oscillation were identified by isotope analysis of bulk sediment carbonates of the same core and were used as independent indicators for hemispheric or global scale climatic change in general the pollen inferred mean summer temperature reconstruction using all three inference models follows the oxygen isotope curve more closely than the cladoceran curve the cladoceran inferred reconstruction suggests generally warmer summers than the pollen based reconstructions which may be an effect of terrestrial vegetation not being in equilibrium with climate due to migrational lags during the late glacial and early holocene allerod summer temperatures range between 11 and 12 c based on pollen whereas the cladoceran inferred temperatures lie between 11 and 13 c pollen and cladocera inferred reconstructions both suggest a drop to 9 10 c at the beginning of the younger dryas although the allerod younger dryas transition lasted 150 160 years in the oxygen isotope stratigraphy the pollen inferred cooling took 180 190 years and the cladoceran inferred cooling lasted 250 260 years the pollen inferred summer temperature rise to 11 5 12 c at the transition from the younger dryas to the preboreal preceded the oxygen isotope signal by several decades whereas the cladoceran inferred warming lagged major discrepancies between the pollen and cladoceran inference models are observed for the preboreal where the cladoceran inference model suggests mean summer temperatures of up to 14 15 c both pollen and cladoceran inferred reconstructions suggest a cooling that may be related to the gerzensee oscillation but there is no evidence for a cooling synchronous with the preboreal oscillation as recorded in the oxygen isotope record for the gerzensee oscillation the inferred cooling was ca 1 and 0 5 c based on pollen and cladocera respectively which lies well within the inherent prediction errors of the inference models

glacier surface area changes in sagarmatha national park nepal in the second half of the 20th century by comparison of historical maps we investigate variations in the surface area of glaciers in sagarmatha national park nepal during the second half of the 20th century through comparison of a map applicable to the late 1950s with the official map of nepal in the early 1990s the comparison reveals a slight overall decrease in glacier area by 4 9 from 403 9 to 384 6 km 2 a result which though potentially subject to errors arising from cartographic interpretation is in line with the area reductions found by other studies of asian glaciers we find that the areas of some individual glaciers the largest situated at higher altitudes increased during the study period this was most apparent for the glaciers oriented to the south with the increase occurring mainly in the glacier accumulation zones while the fronts tended to recede meanwhile the smaller glaciers situated lower and on steep basins experienced a reduction for the smaller glaciers the sections most affected by change were the accumulation zones and these glaciers showed a tendency for the front to advance in this region there is a lack of climate data for high altitudes nevertheless observations from stations situated around the park suggest that alongside temperature variations which are often considered the primary factor eliciting glacier response changes in precipitation play a significant role

from accumulation to discharge modification of stable isotopes during glacial and post glacial processes the isotopes of the water molecule tritium deuterium and oxygen 18 are considered to be ideal tracers of the water cycle an isobalance of accumulation and discharge from glaciated areas is therefore challenging in this article we review data from the alps concerning both the isotopic information of accumulated snow and ice and the relevant information of glacial discharge on a local to regional scale in the alps the seasonal distribution of accumulated snow is governed by small scale meteorology and exposition and distribution of cold and temperate glaciers from comparison with direct precipitation measurements it follows that uncontrolled erosive loss of parts of the seasonal mainly winter snow cover is more important for input output considerations of glacial discharge reconstruction of mean accumulation rates and palaeotemperatures by means of isotopes than occasional melting or even rainfall events the order of magnitude of the latter is controlled by laboratory and field experiments sublimation and evaporation turn out to be of minor influence if only the absolute values and not the deuterium excess the relationship of both stable isotopes deuterium and oxygen 18 is considered nevertheless during warming periods a pronounced increase of deuterium excess caused by intensive melting and evaporation may be used as an additional climate indicator the different isotopic signature of the seasonal snow cover old glacier ice and groundwater stored in the glacier bed enables a quantitative separation of the individual water components discharging at a given time of the day or the season although several detailed isotope studies are reported a complete isobalance from glaciated areas based on an interdisciplinary approach including hydrology and glaciology is still missing the hydroclimatic imprint of the discharge from glaciated areas remains even on a regional scale snowmelt shifts the more negative isotope values from winter precipitation to the summer months interannual climatic variability and changes in seasonal distribution of precipitation for instance reduced winter precipitation during the late 1980s are recorded by the stable isotopes in precipitation and discharge as well indicating that the modification of the isotopic information during glacial and post glacial processes does not override climatic trends

equilibrium line altitudes of the last glacial maximum for the himalaya and tibet an assessment and evaluation of results abstract contemporary equilibrium line altitudes elas for glaciers in the high mountains of the himalaya and tibet have considerable variation because the region is influenced by two major climatic systems the mid latitude westerlies and the south asian summer monsoon and glaciers are subject to strong topographic controls reconstructions of past elas based on the former extent of glaciers are numerous but were estimated using a variety of methods some of which are not appropriate for high altitude glaciers which are strongly influenced by topography and have extensive supraglacial debris cover furthermore few of the reconstructions have adequate chronological control because of the difficulty of dating glacial landforms in high altitude regions where organic matter for radiocarbon dating is sparse or absent cosmogenic radionuclide surface exposure and optically stimulated luminescence dating are providing data to define the timing of glaciation and these together with objective analysis of glacier dynamics may allow better estimates of ela changes in the future however there are currently only two regions the hunza valley and the khumbu himal which are sufficiently well dated to allow reconstructions of last glacial maximum glacier extent and hence elas these two regions cannot provide an adequate assessment of ela changes for the himalayan tibetan region

modern pollen climate calibration for southern south america abstract using the response surface technique a modern pollen climate calibration is presented for the mid latitudes in southern south america between latitudes 39 s and 44 s extending from the west coast in chile across the andes into the patagonian steppe region the climate parameters identified that relate to the present day pollen distribution of the nine most important pollen types nothofagus dombeyi type nothofagus obliqua type podocarpus weinmannia caldcluvia eucryphia type cupressaceae myrtaceae misodendrum and steppe types are summer precipitation summer and winter temperatures using the modern pollen climate data set three fossil pollen records mallin aguado and lago moreno east of the andes and caunahue west of the andes are interpreted in terms of these three seasonal climate parameters despite intervals of no analog fossil pollen assemblages the reconstruction shows similar climate trends on both sides of the andes during the last 21 000 cal yr bp 17 000 yr bp with summer precipitation as low or markedly lower than today prior to 17 000 cal yr bp 14 500 yr bp as high or higher than today between 15 000 and 12 500 cal yr bp 12 500 and 10 500 yr bp and again lower than today between 12 500 and 8000 cal yr bp 10 500 and 7200 yr bp summer and winter temperatures were low or high when summer precipitation was high or low

the coexistence approach a method for quantitative reconstructions of tertiary terrestrial palaeoclimate data using plant fossils abstract the coexistence approach is introduced as a method for quantitative terrestrial palaeoclimate reconstructions in the tertiary it is based on the assumption that tertiary plant taxa have similar climatic requirements to their nearest living relatives the aim of the coexistence approach is to find for a given fossil flora and a given climate parameter the climatic interval in which all nearest living relatives of the fossil flora can coexist for this purpose we have developed a data base climbot containing for over 800 tertiary plant taxa the nearest living relatives and their climatic requirements and an algorithm for analysis climst for all types of fossil floras the coexistence approach thus allows the rapid quantitative reconstruction of 10 different climate parameters including the mean annual temperature temperature of the warmest month temperature of the coldest month mean annual precipitation maximum monthly precipitation minimum monthly precipitation precipitation of the warmest month relative humidity potential evaporation as well as the ratio of mean annual precipitation over potential evaporation the reliability and resolution of the coexistence approach are tested with various techniques and proved to be reasonably good for instance the resolution with respect to the mean annual temperature can be up to 1 c applications to various modern and fossil floras are illustrated and the advantages and disadvantages of the coexistence approach are discussed

chironomid and pollen evidence for climate fluctuations during the last glacial termination in nw patagonia abstract we present chironomid and pollen records from the huelmo site 41 30 s nw patagonia to examine in detail the timing and structure of climate changes during the last glacial termination in the southern mid latitudes the chironomid record has the highest temporal and taxonomic resolution for this critical interval and constitutes the first account of midge faunas at the culmination of the last glacial maximum lgm for the region the chironomid record suggests cold and wet conditions during the lgm followed by deglacial warming between 17 6 and 16 8 cal kyr bp relatively warm conditions prevailed between 15 14 cal kyr bp followed by a reversal in trend with cooling pulses at 14 and 13 5 cal kyr bp and warming at the beginning of the holocene cool temperate conditions prevailed during the huelmo mascardi cold reversal hmcr which according to chironomid data exhibits a wet phase 13 5 12 8 cal kyr bp followed by a conspicuous drier phase 12 8 11 5 cal kyr bp the chironomid and pollen records from the huelmo site indicate step wise deglacial warming beginning at 17 6 cal kyr bp in agreement with other paleoclimate records from nw patagonia and isotopic signals from antarctic ice cores peak warmth during the last glacial termination was achieved by 14 5 cal kyr bp followed by a cooling trend that commenced during the antarctic cold reversal which later intensified and persisted during the hmcr 13 5 11 5 cal kyr bp we observe a shift toward drier conditions at 12 8 cal kyr bp superimposed upon the hmcr coeval with intense fire activity and vegetation disturbance during younger dryas time

beryllium 10 dating of mount everest moraines indicates a strong monsoon influence and glacial synchroneity throughout the himalaya moraine successions in glaciated valleys south of mount everest provide evidence for at least eight glacial advances during the late quaternary cosmogenic radionuclide crn surface exposure dating of moraine boulders defines the timing of each glacial advance and refines the previous glacial chronologies the crn data show that glaciation was most extensive during the early part of the last glacial marine oxygen isotype stage mis 3 and earlier but limited during mis 2 the global last glacial maximum and the holocene a previously assumed neoglacial advance is dated to 3 6 6 0 3 ka and the crn dates confirm a glacial advance ca 1 ka these results show that glaciations on the south side of everest were not synchronous with the advance of northern hemisphere ice sheets yet glaciations within the himalaya the world s highest mountain belt were synchronous during the late quaternary the existence of glacial advances during times of increased insolation suggests that enhanced moisture delivered by an active south asian summer monsoon is largely responsible for glacial advances in this part of the himalaya these data allow us to quantify the importance of global climate change and monsoon influence on glaciation in the himalaya

changes of six selected glaciers in the tomor region tian shan central asia over the past 50 years using high resolution remote sensing images and field surveying as the major water resource of the tarim river glaciers in the tomor region have suffered major losses of ice in the last several decades based on topographic maps high resolution remote sensing image field survey data and previous studies changes of the six selected glaciers in the tomor region qingbingtan glacier no 72 qingbingtan glacier no 74 keqikekuzibayi glacier tomor glacier keqikar glacier and qiongtailan glacier over the past similar to 50 years were analyzed in this study analysis shows that all of the six glaciers showed continuous shrinkage the reduction rate of glacier no 72 terminus retreat of 41 m a 1 and area loss of 21 5 during 1964 2009 was higher than the others with a dramatically increased rate this dramatic ice thinning related glacier front retreat and area loss of the six glaciers suggests that glaciers in the tomor region might currently be suffering negative mass balance in response to the ongoing temperature rise differences in changes of the six glaciers are influenced by debris cover and other topographical factors c 2013 elsevier ltd and inqua all rights reserved

the supply and accumulation of silica in the marine environment rivers and submarine hydrothermal emanations supply 6 1 1014g sio2 yr to the marine environment approximately two thirds of the silica supplied to the marine environment can be accounted for in continental margin and deep sea deposits siliceous deep sea sediments located beneath the antarctic polar front convergence account for over a fourth 1 6 1014g sio2 yr of the silica supplied to the oceans deep sea sediment accumulation rates beneath the polar front are highest in the south atlantic with values as large as 53cm kyr during the last 18 000 yr siliceous sediments in the bering sea sea of okhotsk and subarctic north pacific accumulate 0 6 1014g sio2 yr or 10 of the dissolved silica input to the oceans the accumulation of biogenic silica in estuarine deposits removes a maximum of 0 8 1014g sio2 yr although estuarine silica versus salinity plots indicate extensive removal of riverine silica from surface waters the removal rates must be considered as maximum values because of dissolution of siliceous material in estuarine sediments and bottom waters siliceous sediments from continental margin upwelling areas e g gulf of california walvis bay or peru chile coast have the highest biogenic silica accumulation rates in the marine environment 69 g sio2 cm2 kyr despite the rapid accumulation of biogenic silica upwelling areas account for less than 5 of the silica supplied to the marine environment because they are confined laterally to such small areas

the environmental impact of the minoan eruption of santorini thera statistical analysis of palaeoecological data from golhisar southwest turkey eastwood w j tibby j roberts n birks h j b lamb h f 2002 the environmental impact of the minoan eruption of santorini thera statistical analysis of palaeoecological data from golhisar southwest turkey holocene 12 4 431 444

extensive glacial advances during the last glacial maximum near the eastern himalayan syntaxis abstract climatically the eastern himalaya are mainly controlled by the indian summer monsoon ism and important region for understanding the relationship between ism and glacial change this region is therefore useful for studies of the relation between glacial changes and ism using a geomorpho stratigraphic method combined with gis we investigated and mapped the outmost lateral frontal moraine of the most extensive glaciations that occurred in the basongcuo bsc catchment near the eastern himalayan syntaxis using optically stimulated luminescence osl and 10 be surface exposure dating technique we dated five boulders and 23 sediment samples the resultant osl and 10 be ages show that the region s glaciers were at their most extensive positions between 16 and 31 ka glacial coverage was 507 5 km 2 9 9 times greater than it is today 51 5 km 2 with an equilibrium line altitude ela depression of 690 m the rapidity with which the last glacial maximum lgm glacial advance and retreat occurred suggests that temperature was the dominant control on glacial change

response of chironomid assemblages to environmental change during the early late glacial at gerzensee switzerland prior to ca 14 660 yr bp during the early late glacial oldest dryas larval assemblages of chironomidae insecta diptera in gerzensee switzerland were dominated by cold stenothermic taxa as well as by taxa typical of subalpine lakes today this was the coldest period of the entire sequence after ca 14 660 yr bp in the late glacial interstadial bolling allerod a temperature increase is recorded by a sharp rise in the oxygen isotope ratio in lake marl and by an increase in the organic matter content of the sediments changes in the chironomid fauna then are consistent with rising temperatures this warming trend is interrupted between 14 070 and 13 940 yr bp coinciding with the gi 1d cold oscillation but the change in the chironomid assemblage is more consistent with a response to increasing lake depth and density of aquatic macrophytes than falling temperature a rise in cold adapted chironomid taxa between 13 840 and 13 710 yr bp suggests that summer air temperatures may have declined changes in the chironomid assemblage after 13 710 yr bp suggest a decline in submerged macrophytes coupled with a rise in lake productivity and summer temperature although the latter is not reflected in the oxygen isotope record this suggests that there may have been increasing seasonality during this period when summer temperatures were rising driven by rising summer insolation and winters becoming cooler which is largely reflected in the oxygen isotope record a decline in thermophilic chironomids and a rise in cold adapted taxa after 13 180 yr bp suggest a response to cooling at the beginning of the gerzensee oscillation

the climate of europe 6000 years ago palaeoclimates across europe for 6000 y bp were estimated from pollen data using the modern pollen analogue technique constrained with lake level data the constraint consists of restricting the set of modern pollen samples considered as analogues of the fossil samples to those locations where the implied change in annual precipitation minus evapotranspiration p e is consistent with the regional change in moisture balance as indicated by lakes an artificial neural network was used for the spatial interpolation of lake level changes to the pollen sites and for mapping palaeoclimate anomalies the climate variables reconstructed were mean temperature of the coldest month tc growing degree days above 5 c gdd moisture availability expressed as the ratio of actual to equilibrium evapotranspiration and p e the constraint improved the spatial coherency of the reconstructed palaeoclimate anomalies especially for p e the reconstructions indicate clear spatial and seasonal patterns of holocene climate change which can provide a quantitative benchmark for the evaluation of palaeoclimate model simulations winter temperatures tc were 1 3 k greater than present in the far n and ne of europe but 2 4 k less than present in the mediterranean region summer warmth gdd was greater than present in nw europe by 400 800 k day at the highest elevations and in the alps but 400 k day less than present at lower elevations in s europe p e was 50 250 mm less than present in nw europe and the alps but was 10 15 greater than present in s europe and p e was 50 200 mm greater than present in s and e europe

relationships between glacier and rock glacier in the maritime alps schiantala valley italy abstract in the schiantala valley of the maritime alps the relationship between a till like body and a contiguous rock glacier has been analyzed using geomorphologic geoelectric and ice petrographic methodologies dc resistivity tomographies undertaken in the till and in the rock glacier show the presence of buried massive ice and ice rich sediments respectively ice samples from a massive ice outcrop show spherical gas inclusions and equidimensional ice crystals that are randomly orientated confirming the typical petrographic characteristics of sedimentary ice the rock glacier formation began after a phase of glacier expansion about 2550 50 14c yr bp further ice advance during the little ice age lia overrode the rock glacier root and caused partial shrinkage of the pre existing permafrost finally during the 19th and 20th centuries the glacial surface became totally debris covered geomorphological and geophysical methods combined with analyses of ice structure and fabric can effectively interpret the genesis of landforms in an environment where glaciers and permafrost interact ice petrography proved especially useful for differentiating ice of past glaciers versus ice formed under permafrost conditions these two mechanisms of ice formation are common in the maritime alps where many sites of modern rock glaciers were formerly occupied by lia glaciers

on the thermal regime of an arctic valley glacier a study of white glacier axel heiberg island n w t canada from 1974 to 1981 a total of 32 bore holes was drilled on white glacier and vertical ice temperature profiles measured the data obtained allowed the construction of three longitudinal and four transverse profiles of the two dimensional temperature distributions thus an extensive layer of temperate or near temperate ice was discovered close to the bedrock in the lowest part of the glacier tongue it was also found that the temperature distribution cannot be in a steady state since there is a temperature minimum 100 150 m below the glacier surface in the accumulation area a simple numerical model calculation shows that this minimum can be mostly explained by the general climatic warming since 1880 the 10 m temperatures show diffuse relations to climatic conditions and balance zones a simple scheme for extrapolating surface temperatures is discussed

may september precipitation in the bhutan himalaya since 1743 as reconstructed from tree ring cellulose δ18o 1 we developed a 50 year tree ring 18o chronology for each of three tree species juniperus indica larix griffithii and picea spinulosa using a total of 12 trees four trees per species from the bhutan himalaya despite originating from different species sampled at two different altitudes the 18o chronologies are highly correlated with one another r 0 76 0 89 response analyses reveal that tree ring 18o values are controlled mainly by summer precipitation irrespective of species based on these results a robust 269 year 18o chronology was established to reconstruct the amount of may september precipitation based on data from four larch trees our tree ring 18o data show significant correlations with those from other regions of the himalaya and the tibetan plateau indicating that common signals related to monsoon activity are recorded in the data however at centennial timescales our data from bhutan show normal conditions during the 20th century whereas records from sites in western nepal and the southern eastern tibetan plateau show weakening trends in monsoon intensity during the last 100 200 years the weakening trends may be the result of a reduction in the meridional sea surface temperature gradient in the indian ocean during this time at continental scales the tree ring records show that areas more from ocean basins are particularly sensitive to reduced monsoon circulation correlation analyses suggest that the el nino southern oscillation enso plays an important role in modulating summer precipitation however the teleconnected relationship disappears during the period 1951 1970 coinciding with a negative phase of the pacific decadal oscillation pdo implying interdecadal modulation of the pdo on the influence of the enso on precipitation in bhutan

geochemical and mineralogical characterization of sediments from lake futalaufquen 42 8 s andean patagonia to evaluate their potential as paleoclimatic proxies lake sediments are key archives for paleoenvironmental investigation as they provide continuous records of the depositional history of the lake and its watershed lake futalaufquen 42 8 s is an oligotrophic waterbody located in los alerces national park in the andes of northern patagonia south america a sedimentary sequence covering 1600 years was recovered to analyze the potential for paleoenvironmental reconstructions of the last millennia integration of different geochemical and mineralogical parameters and comparison with climatic reconstructions from other patagonian records give clues for the identification of a warm period around ad 800 1000 associated with the medieval climatic anomaly the high frequency of tephra layers beginning in the mid sixteenth century precludes identification of the little ice age recorded in northern patagonia as a cold period from the fourteenth to the eighteenth century furthermore the parameters analysed do not provide evidence of late twentieth century global warming however zn deposition a long distance atmospheric transport process of anthropogenic origin was identified during the last century

altitudinal dynamics of glacial lakes under changing climate in the hindu kush karakoram and himalaya ranges abstract the environmental challenges posed by global warming in the himalayan region include early and rapid melting of snow and glaciers creation of new lakes and expansion of old ones posing a high risk of glacial lakes outburst flood glof hazard for downstream communities according to various elevation ranges 3044 lakes were analyzed basinwide in the hindu kush karakoram himalaya hkh ranges of pakistan using multisensor remote sensing data of the 2001 2013 period an overall increase in glacial lakes was observed at various altitudinal ranges between 2500 and 5500 m out of which noticeable change by number was within the 4000 4500 m range the analysis carried out by glacial fed lakes and nonglacial fed lakes in different river basins indicated variable patterns depending on the geographic location in the hkh region the correlation analysis of parameters like lake area expansion rate and elevation was performed with 617 glacial lakes distributed in various river basins of the three hkh ranges lake area 2013 and elevation showed a negative relationship for all basins except hunza shigar and shyok the correlation between the expansion rate of lakes and elevation was on the positive side for swat gilgit shigar and shingo basins a situation that may be attributed to the variable altitudinal pattern of temperature and precipitation in order to explore such diverse patterns of lake behavior and relationship with influential factors in the hkh detailed studies based on using high resolution image data coupled with in situ information are a prerequisite although an increase in lake area observed below 3500 m would be favorable for water resource management but could be alarming in context of glacial flood hazards that need to be monitored critically on a long term basis

glacier and permafrost signals of 20th century warming currently available evidence of 20th century warming from glaciers and permafrost is briefly reviewed the signals are clear and strong warming of polar firn and permafrost and mass losses of glaciers at lower latitudes were most striking towards the middle of the century the easily observable length reduction of mountain glaciers confirms the global character of the evolution a probably intermittent reversal of the trend was observed in places after about 1950

late pleistocene glacial advances in the western tibet interior it has long been observed that the timing of glacial advances is asynchronous across the himalaya karakoram tibet plateau hktp but the climatic implications if any remain unclear resolving this question requires additional glacial chronologies from unique spatial and climatic regimes as well as an analysis of how glaciers within different regimes are likely to have responded to past climate changes this study presents a 10be 21ne chronology from the mawang kangri range of western tibet 34 n 80 e an arid high elevation site we identify advances at 123 83 and 56 kyr which agree reasonably well with sites in the immediate vicinity but are asynchronous relative to sites across the entire hktp and relative to sites in the western hktp to evaluate hktp wide asynchroneity we compile dated glacial chronologies and classify them by the approximate timing of their maximum recent advance this result shows a strong spatial clustering of young mis 1 2 relative to older mis 3 5 maximum advances further comparison with modern precipitation temperature and topographic data show that the pattern of hktp wide asynchroneity is broadly independent of topography and can potentially be explained by local responses to changes in temperature at either very warm wet or cold dry sites sites that receive intermediate amounts of precipitation are more ambiguous although spatial clustering of mis 1 2 vs mis 3 5 advances is suggestive of past variations in precipitation at these sites in western tibet no spatial or climatic correlation is observed with the timing of maximum glacial advances we suggest this could arise from mis interpretation of disparate boulder ages generated by a prolonged mis 3 4 glacial advance in the western hktp

glaciological investigations in the crete area central greenland a search for a new deep drilling site the results of the 1984 85 post gisp campaigns in central greenland are presented eight ice cores were obtained some spanning up to 360 years we present i geographical positions and elevations at the drill sites

a 11 000 yr palaeotemperature reconstruction from the southern boreal zone in finland abstract the ecotone between the boreo nemoral hemiboreal and the southern boreal vegetation zones constitutes the northern distributional limit of a number of thermophilous tree species in northern europe and is to a large extent controlled by climatic conditions we present a quantitative annual mean temperature reconstruction from a high resolution pollen stratigraphy in southern boreal finland using a pollen climate calibration model with a cross validated prediction error of 0 9 c our model reconstructs low but steadily rising annual mean temperature from 10 700 to 9000 cal yr bp at 8000 4500 cal yr bp reconstructed annual mean temperature reaches a period of highest values holocene thermal maximum with particularly high temperatures 2 0 1 5 c higher than at present at 8000 5800 cal yr bp from 4500 cal yr bp to the present day reconstructed annual mean temperature gradually decreases by ca 1 5 c comparison of present results with palaeotemperature records from the greenland ice cores notably with the northgrip 18 o record shows marked similarities suggesting parallel large scale holocene temperature trends between the north atlantic and north european regions the verification of the occurrence timing and nature of the short term temperature fluctuations during the holocene in the southern boreal zone in europe requires replicate high resolution climate reconstructions from the region

a transfer function model developed from an extensive surface pollen data set in northern china and its potential for palaeoclimate reconstructions a total of 237 surface soil pollen samples were collected from less disturbed zonal communities and a new surface pollen data set has been established in northern china pollen climate parameter transfer functions using weighted averaging regression and calibration partial least squares wa pls model as a tool to reconstruct past climate changes from pollen data were tested with this new surface pollen data set the results of cross validation showed that the method worked very well with precipitation r 0 94 r2jack 0 89 rmsepjack 69 mm the safe dynamic range of the reconstruction was 40 mm 800 mm and worked well with temperature tann r 0 84 r 2jack 0 71 rmsepjack 2 0 c the safe dynamic range of the reconstruction was 4 c 13 c mtwa r 0 79 r2jack 0 63 rmsepjack 2 5 c and the safe dynamic range of the reconstruction was 8 c 26 c indicating that the surface pollen data set and wa pls reconstruction technique in this paper have strong potential for palaeoclimatic reconstr

temporal evolution of sediment supply in lago puyehue southern chile during the last 600 yr and its climatic significance short term climate changes in southern chile are investigated by a multi proxy analysis of a 53 cm long sedimentary sequence selected among eight short cores retrieved in lago puyehue chile 40 s this core contains a 600 yr long undisturbed record of paleo precipitation changes two measurement methods for sediment density organic matter and biogenic silica contents are compared and the most appropriate techniques are selected together with aluminium and titanium concentrations grain size and geochemical properties of the organic matter these proxies are used to demonstrate paleo precipitation changes around 40 s increase of terrigenous particle supply between a d 1490 and a d 1700 suggests a humid period contemporaneously y 13 c data show increasing lake productivity in response to the high nutrient supply the a d 1700 1900 interval is characterized by a decreasing terrigenous supply and increasing y 13 c values interpreted as a drying period the magnetic susceptibility signal reflecting the terrigenous biogenic ratio demonstrates that similar variations occur in all the undisturbed sedimentary environments of lago puyehue the a d 1490 1700 wet period is associated with the onset of the european little ice age lia andinterpreted asits local signature this worksupports the fact that the liawasaglobal event not only restricted to thenorthern hemisphere d 2005 university of washington all rights reserved

responses of two branches of glacier no 1 to climate change from 1993 to 2005 tianshan china abstract clear understanding of how alpine glaciers respond to climate change is critical to accurately evaluate water resources and to retrieve climate information from the alpine glaciers however different glaciers may have different responses to climate change this study focuses on two branches of glacier no 1 at the head of urumqi river tianshan china these two branches west branch wb and east branch eb have experienced the same pattern of climate warming since their separation in 1993 however these glaciers have responded differently as observed by fieldwork and analysis of their annual mass balances lengths areas equilibrium line altitudes elas to illustrate the different responses of climate change increase in both temperature and precipitation the glacier length response time t rl and climate sensitivity c are calculated for the two branches the length response time and climate sensitivity are 1 89 y and 8 81 for the eb and 1 63 y and 5 92 for wb the different responses are interpreted to be controlled by glacial topographical features with larger slopes and smaller areas making the wb more sensitive to the recent climate warming

regional seasonal and diurnal variations of extreme convection in the south asian region abstract temporal and spatial variations of convection in south asia are analyzed using eight years of tropical rainfall measuring mission trmm precipitation radar pr data and ncep reanalysis fields to identify the most extreme convective features three types of radar echo structures are defined deep convective cores contiguous 3d convective echo 40 dbz extending 10 km in height represent the most vertically penetrative convection wide convective cores contiguous convective 40 dbz echo over a horizontal area 1000 km2 indicate wide regions of intense multicellular convection and broad stratiform regions stratiform echo contiguous over an area 50 000 km2 mark the mesoscale convective systems that have developed the most robust stratiform regions the preferred locations of deep convective cores change markedly from india s east coast in the premonsoon to the western himalayan foothills in the monsoon they form preferentially in the evening and over land as near surface moist flow is cap

a 50 ka record of monsoonal variability in the darjeeling foothill region eastern himalayas abstract pollen phytoliths and 13 c signatures of soil organic matter from two fluvial sedimentary sequences of the darjeeling foothill region eastern himalayas are used to portray palaeoclimatic oscillations and their impact on regional plant communities over the last 50 ka quantitative palaeoclimate estimation using coexistence approach on pollen data and other proxies indicate significant oscillations in precipitation during the late part of mis 3 46 4 25 9 ka early and middle part of mis 2 25 9 15 6 ka and 5 4 to 3 5 ka middle to late mis 3 ca 46 4 31 ka was characterized by a comparatively low monsoonal activity and slightly higher temperature than that during ca 31 ka onwards simultaneous expansion of deciduous trees and chloridoid grasses also imply a drier and warmer phase between 31 and 22 3 ka late mis 3 to mid mis 2 higher precipitation and a slightly cooler temperature led to an increase in evergreen elements over deciduous taxa and wet loving panicoid grasses over dry loving chloridoid grasses than earlier after ca 22 3 ka shrinking of forest cover expansion of c4 chloridoid grasses asteraceae and cheno ams in the vegetation with lowering of temperature and precipitation characterized the onset of the lgm which continued till 18 3 ka end of the lgm is manifested by a restoration in the forest cover and in the temperature and precipitation regime later during 5 4 to 4 3 ka a strong monsoonal activity supported a dense moist evergreen forest cover that subsequently declined during 4 3 to 3 5 ka a further increase in deciduous elements and non arboreals might be a consequence of reduced precipitation and higher temperature during this phase a comparison between monsoonal rainfall mat and palaeoatmospheric co 2 with floral dynamics since last 50 ka indicates that these fluctuations in plant succession were mainly driven by monsoonal variations

climatic fluctuations in northern patagonia during the last 1000 years as inferred from tree ring records abstract millennium old alerce trees fitzroya cupressoides mol johnst have been used to develop a 1120 year reconstruction of the summer temperature departures for the andes of northern patagonia in argentina four main climatic episodes can be distinguished in this proxy paleoclimatic record the first a cold and moist interval from a d 900 to 1070 was followed by a warm dry period from a d 1080 to 1250 correlative with the medieval warm epoch of europe afterward a long cold moist period followed from a d 1270 to 1670 peaking around a d 1340 and 1650 these cold maxima are contemporaneous with two principal little ice age events registered in the northern hemisphere warmer conditions then resumed between a d 1720 and 1790 these episodes are supported by glaciological and palynological data in patagonia following a cold period in the early 1800s tree ring indices have oscillated around the long term mean except for a warmer period from a d 1850 to 1890 correlations between the rio alerce reconstruction and the regional weather stations indicate that the tree ring variations are correlated with a homogeneous summer weather pattern covering patagonia east of the andes from 38 to 50 s

the coexistence approach theoretical background and practical considerations of using plant fossils for climate quantification the coexistence approach was established by mosbrugger and utescher 1997 as a plant based method to reconstruct palaeoclimate by considering recent climatic distribution ranges of the nearest living relatives of each fossil taxon during its existence for over more than 15 years its basics have been tested and reviewed in comparison with other terrestrial and marine climate reconstruction techniques and climate modelling data however some controversies remain about its underlying data or its applicability in general in view of these controversies this paper discusses the power and limitations of the coexistence approach by summarising past results and new developments we give insights into the details and problems of each step of the application from the assignment of the fossil plant to the most suitable nearest living relative the crucial consideration of the usefulness of specific taxa towards their climatic values and the correct interpretation of the software based suggested palaeoclimatic intervals furthermore we reflect on the fundamental data integrated in the coexistence approach by explaining different concepts and usages of plant distribution information and the advantages and disadvantages of modern climatic maps additionally we elaborate on the importance of continually updating the information incorporated in the database due to new findings in e g palaeo botany meteorology and computer technology finally for a transparent and appropriate use we give certain guidelines for future applications and emphasize to users how to carefully consider and discuss their results we show the coexistence approach to be an adaptive method capable of yielding palaeoclimatic and palaeoenvironmental information through rime and space c 2014 elsevier b v all rights reserved

anthropogenic versus climatic control in a high resolution 1500 year chironomid stratigraphy from a southwestern greenland lake we performed a high resolution study of chironomid assemblages in a sediment core retrieved from lake igaliku in southern greenland the well dated core is located within the former norse eastern settlement and covered the last 1500 yr the comparison of chironomid stratigraphy pca axis scores with instrumental temperature data land use history and organic matter in the sediment over the last 140 yr suggested that the primary changes in chironomid fauna in 1988 2 yr were driven by the shift to modern agriculture in the catchment this unprecedented change in chironomid fauna was most likely triggered by a shift in in lake processes within the instrumental period subtle variations in the chironomid assemblages that occurred before 1988 2 yr were significantly correlated with summer temperatures even in times of traditional extensive sheep farming in the catchment the relevance of the chironomid derived climate signal over the last 1500 yr was supported by its good concordance with previous studies in west greenland and in the arctic the chironomid assemblage therefore appeared to be a valuable proxy for climate changes within the norse colony area synchronous changes in norse diet and chironomid reconstructed climate give new insights into the interplay of norse society with climate

chronology and climatic implications of late quaternary glaciations in the goriganga valley central himalaya india abstract goriganga valley which is located in the transition zone between the dry steppe of the tibetan plateau in the north and the sub humid himalayan climate in the south has preserved four events of glaciation with decreasing magnitude the oldest stage i glaciation is represented by a 12 5 km long discontinuous diamictite ridge which terminates north of rilkot 3100 m asl the stage ii glaciation is represented by sub rounded and partially eroded lateral moraines and terminates around martoli village 3240 m asl the stage iii and iv glacial moraines are sharp crested unstable and terminate proximal to the present day glacier at 3640 m asl and 3740 m asl respectively the stage ii moraines have been optically dated between 25 2 ka and 22 1 ka implying that glacier expanded during the global last glacial maximum lgm this is contrary to the suggestion that during last glacial maximum lgm glaciation was limited in extent due to weak indian summer monsoon ism in the monsoon dominated regions of the himalaya we ascribe the lgm glaciations to a combination of the lowered temperature and enhanced mid latitude westerlies following the lgm glaciation goriganga valley experienced two major pulses of deglaciation the older event is dated between 16 and 12 ka and is coeval with the initiation of the ism whereas the younger events 10 8 ka represent the early to mid holocene strengthened ism the stage iii and iv glaciations which terminated proximal to the modern glacier are speculated to occur during the mid holocene and little ice age lia respectively

signals of 20th century warming from the glaciers in the central italian alps the lombard alps in the central sector of the italian alps are one of the most intensively glacierized regions on the southern side of the chain about 113 km2 of ice cover all of the glaciers have been retreating since the beginning of the 20th century but the trend is not uniform since the 1950s there has been a drop in the percentage of retreat ing snouts and an increase in stationary and advancing snouts after 1985 the glaciers in the lombard alps began a new recession phase that is still going on this pattern is con sistent with temperature variations in lombardy in the 20th century according to data from sondrio station four alternating warming and cooling phases can be distinguished in 20th century warming the lombard glaciers well recorded the last three phases showing evident signs of the 1955 88 cold phase with a response time of about 20 years and may be considered good indicators of 20th century temperature trends

july mean temperature and annual precipitation trends during the holocene in the fennoscandian tree line area pollen based climate reconstructions july mean temperature and annual precipipation during the last 9900 cal yr bp were recon structed from pollen assemblages preserved in a sediment core from northern finland quantitative recon structions were performed using a modern pollen climate calibration model based on weighted averaging partial least squares regression the predictive ability of the model was evaluated against modern meteoro logical data using leave one out cross validation the prediction error for july mean temperature is c 1 0 c and for annual precipitation 340 mm the july mean temperatures during the earliest holocene were low c 1 1 0 c and annual precipitation was high c 600 800 mm between 8200 and 6700 cal yr bp july mean temperatures reached their maxima 12 5 13 0 c which are c 1 4 1 7 c higher than at present at the same time precipitation decreased during the late holocene july mean temperatures declined and the last 2000 years have been the coolest since the early holocene precipitation has slightly increased the spatial coherence between our results and of several other climate reconstructions from northern europe indicates that the holocene climate was strongly influenced by north atlantic oceanic and atmospheric circulation patterns we propose that the distinctly oceanic climate of the early holocene was due to enhanced westerly latitudinal airflow which was replaced at c 8200 cal yr bp by a more meridional flow pattern and by the development of predominantly anticyclonic summer conditions

recent changes in glacier area and volume within the southern canadian cordillera net changes in glacier area in the region 50 518 n 116 1258 w which includes the columbia and rocky mountains 1951 52 2001 and the coast mountains 1964 65 2002 were determined through a comparison of historic aerial photography and contemporary landsat 7 etm imagery the volumes of individual glaciers were estimated using an empirical volume area scaling relationship the area of glaciers in the coast mountains decreased by 120 10 km 2 or 5 of the initial ice covered area here the areas of glaciers in the columbia and rocky mountains decreased by 20 and 6k m 2 respectively corresponding to relative changes in total area of 5 and 15 the estimated total ice volume loss from the whole region was 13 3k m 3 in all parts of the study area the relative changes in area of individual glaciers showed considerable variability while the smallest glaciers remained essentially unchanged this suggests that local factors unique to individual glaciers largely determine their sensitivity to climatic change and that the very small glaciers are collectively less sensitive to such change

pollen response surface estimates of late quaternary changes in the moisture balance of the northeastern united states abstract quantitative estimates of late quaternary climate in the northeastern united states are reconstructed from fossil pollen data to evaluate changes in the regional moisture balance inferred from water level fluctuations we use environmental response surfaces to calibrate modern pollen data for 17 different taxa to an index of effective soil moisture and mean annual precipitation we apply these response surfaces to fossil pollen data from 60 sites in the region to reconstruct changes in soil moisture and mean annual precipitation at 3000 yr intervals from 12 000 yr b p to present the mapped reconstructions of soil moisture and mean annual precipitation illustrate how the regional moisture balance of the northeast may have changed over the last 12 000 yr in response to changing climate reconstructions of annual precipitation show a gradual increase from 30 below modern values at 12 000 yr b p to near modern values by 6000 yr b p and then remain relatively constant thereafter reconstructed changes in the index of effective soil moisture however show a pattern of near modern values at 12 000 6000 and 3000 yr b p with significantly lower values estimated for 9000 yr b p the time of maximum pine pollen abundances in the northeast this pattern of change is similar to the change in regional moisture balance inferred from stratigraphic records of water level fluctuations these results confirm previous interpretations based on records of water level fluctuations that conditions in the northeast were significantly drier during the early to middle holocene than at other times during the last 12 000 yr

cold firn and ice of high altitude glaciers in the alps measurements and distribution modelling the thermal regime of high altitude accumulation areas in the swiss alps was systematically investigated on the jungfraufirn bernese alps on the breithornplateau valais alps and on grenzgletscher valais alps in 1991 1992 and 1994 temperatures were measured in a deep hole 120 m deep and in several shallow holes 14 30 m deep whereas the wide neve of the jungfraufirn at 3400 3600 m a s l and the 3800 m high breithorn plateau seems to be predominantly temperate cold firn and ice temperatures were measured throughout on grenzgletscher 3900 4450 m a s l mean firn temperatures on grenzgletscher vary strongly and range between 3 and 14 c a comparison between the measured temperature profiles and a one dimensional heat conduction calculation shows that the release of latent heat by penetrating and refreezing meltwater decisively influences the thermal pattern of the firn pack a multiple linear regression model based on measured firn temperatures from the european alps and the parameters altitude and aspect yields aspect dependent lower boundaries for the occurrence of cold firn ranging between 3400 northerly aspects and 4150 m a s l southerly aspects a total of 120 glaciers with cold firn areas are found when applying the model to glacier inventory data from the european alps

last glacial maximum climate of the former soviet union and mongolia reconstructed from pollen and plant macrofossil data an improved concept of the best analogues method was used to reconstruct the last glacial maximum lgm climate from a set of botanical records from the former soviet union and mongolia terrestrial pollen and macrofossil taxa were grouped into broad classes plant functional types pfts defined by the ecological and climatic parameters used in the biome1 model pft scores were then calibrated in terms of modern climate using 1245 surface pollen spectra from eurasia and north america in contrast to individual taxa which exhibit great variability and may not be present in the palaeoassemblages even in suitable climates pfts are more characteristic of the vegetation types the modified method thus allows climate reconstruction at time intervals with partial direct analogues of modern vegetation e g the lgm at 18 kbp mean temperatures were 20 29 degrees c colder than today in winter and 5 11 degrees c colder in summer in european russia and ukraine sites from western georgia show negative but moderate temperature anomalies compared to today 8 11 degrees c in january and 5 7 degrees c in july lgm winters were 7 15 degrees c colder and summers were 1 7 degrees c colder in siberia and mongolia annual precipitation sums were 50 750 mm lower than today across northern eurasia suggesting a weakening of the atlantic and pacific influences reconstructed drought index shows much drier lgm conditions in northern and mid latitude russia but similar to or slightly wetter than today around the black sea and in mongolia suggesting compensation of precipitation losses by lower than present evaporation

deglaciation and landscape history around annapurna nepal based on 10be surface exposure dating abstract the high himalaya is a key area for tectonic geomorphological and climate studies because of its extreme relief and location at the transition zone between areas with abundant monsoonal precipitation and the arid semiarid tibetan plateau we present 10be surface exposure ages on 22 boulders from the annapurna area in nepal the ages improve understanding of the late quaternary landscape history and the geomorphological processes operating in this part of the himalaya although our study is reconnaissance in nature it highlights the importance of catastrophic events such as landslides and debris flows for denudation of high mountains holocene exposure ages for the dhampu chooya landslide 4 1 0 6 ka and for 600 m of alluviation in kali gandaki valley 2 1 0 6 ka for example indicate the frequent occurrence and extent of catastrophic events and their implications for natural hazards we also offer an explanation for the differences in late quaternary glacial chronologies at closely spaced study sites in the nepal himalaya topographically controlled and spatially variable precipitation in the himalaya determines the sensitivity of glaciers to changes in temperature and precipitation accordingly some glaciers advanced in phase with northern hemisphere ice sheets whereas others reached their maximum extent at times of increased monsoonal precipitation during marine isotope stage 3 and the early holocene

quantitative interpretation of fossil pollen spectra dissimilarity coefficients and the method of modern analogs abstract dissimilarity coefficients measure the difference between multivariate samples and provide a quantitative aid to the identification of modern analogs for fossil pollen samples how eight coefficients responded to differences among modern pollen samples from eastern north america was tested these coefficients represent three different classes 1 unweighted coefficients that are most strongly influenced by large valued pollen types 2 equal weight coefficients that weight all pollen types equally but can be too sensitive to variations among rare types and 3 signal0to noise coefficients that are intermediate in their weighting of pollen types the studies with modern pollen allowed definition of critical values for each coefficient which when not exceeded indicate that two pollen samples originate from the same vegetation region dissimilarity coefficients were used to compare modern and fossil pollen samples and modern samples so similar to fossil samples were found that most of three late quaternary pollen diagrams could be reconstructed by substituting modern samples for fossil samples when the coefficients indicated that the fossil spectra had no modern analogs then the reconstructed diagrams did not match all aspects of the originals no modern analogs existed for samples from before 9300 yr b p at kirchner marsh minnesota and from before 11 000 yr b p at wintergreen lake michigan but modern analogs existed for almost all holocene samples from these two sites and brandreth bog new york

climatic change in a high altitude alpine area suggested by the isotopic composition of cold basal glacier ice for the first time a cold ice cover of a summit in the central swiss alps has been sampled from the surface to the bed for determining its isotopic composition in d and 18o results of the analyses show a striking decrease of values with depth the value differences are greater than those explicable by a direct temperature effect but a substantial increase in melt water percolation through the firn since the formation of the deepest ice layer may explain the situation of this high altitude ice authors

chronology of late quaternary glaciation and landform evolution in the upper dhauliganga valley trans himalaya uttarakhand india abstract detailed field mapping of glacial and paraglacial landforms supported by optical and radiocarbon dating is used to reconstruct the history of late quaternary glaciation and landform evolution in the trans himalayan region of the upper dhauliganga valley the study identifies four events of glaciations with decreasing magnitude which are termed as purvi kamet stage ia pks ia pks ib pks ii pks iii and pks iv respectively the oldest pks ia and ib are assigned the marine isotopic stgae 3 mis 3 the pks ii to the last glacial maximum mis 2 pks iii dated to 7 9 0 7 ka and the pks iv is dated to 3 4 0 3 ka and 1 9 0 2 ka respectively the largest valley glaciations viz the pks ia occurred during the strengthened summer monsoon corresponding to the mis 3 following this the recessional moraines pks ib represent the gradual decline in summer monsoon towards the later part of mis 3 the valley responded to the global last glacial maximum lgm which is represented by the pks ii moraine implying the influence of strengthened mid latitude westerlies during the lgm the post lgm deglaciation was associated with the onset of summer monsoon and is represented by the deposition of four distinct outwash gravel terraces the early holocene pks iii glaciation occurred around 7 9 0 7 ka and broadly coincides with the early holocene cooling event 8 2 ka this was followed by the deposition of stratified scree deposits and the alluvial fan between 5 5 ka and 3 ka during the mid to late holocene aridity this was followed by marginal re advancement of the valley glacier viz pks iv during the late holocene cool and moist climate although glaciers respond to a combination of temperature and precipitation changes however during the holocene it seems that temperature played a major role in driving the glaciation

tephrochronology of recent events in the andean range northern patagonia spatial distribution and provenance of lacustrine ash layers in the nahuel huapi national park tephrochronology is a powerful tool for dating sedimentary sequences especially in patagonia where a large number of active volcanoes have produced frequent historical eruptions short lacustrine sedimentary sequences were extracted from the lakes moreno oeste and ton cek nahuel huapi national park seventeen volcanic ash layers were identified in both cores 210 pb and 137 cs were used for dating techniques and historical volcanic records were employed for correlation white pumice and glass shards from the tephras were characterised by measuring major and trace element contents by instrumental neutron activation analysis two volcanic sources the cordon caulle and the calbuco volcanoes were recognised as the prevailing systems that impacted the area in the past 800 1000 a the calbuco volcano was mainly responsible for the nine tephras identified in the lake ton cek sequence four of these nine tephras also contained material from the cordon caulle complex and could be interpreted as composite tephras or possible reworked ones the calbuco volcano showed predominant influences in the lake moreno oeste sequence six of the eight tephras identified in such a sequence were from the calbuco volcano and three of these six contained material from the cordon caulle complex the other two were from the cordon caulle complex with contributions from the calbuco volcano in one of them these findings show that the high frequency of volcanic events in the study region demands an accurate characterisation of the products generated by each source as well as an evaluation of their spatial distribution to obtain a consistent framework for dating recent environmental changes copyright 2010 john wiley sons ltd supporting information can be found in the online version of this article

late pleistocene snowline fluctuations at nevado coropuna 15 s southern peruvian andes deposits preserved on peaks in the southern peruvian andes are evidence for past glacial fluctuations and therefore serve as a record of both the timing and magnitude of past climate change moraines corresponding to the last major expansion of ice on nevado coropuna date to 20 25 ka during the last glacial maximum we reconstructed the snowline at coropuna for this period using a combined geomorphic numeric approach to provide a first order estimate of the magnitude of late pleistocene climate change our reconstructions show that snowline was approximately 550 770m lower during the last glacial maximum than during the late holocene maximum which ended in the 19 th century and 750m lower than today while these values are similar to data from nearby nevado solimana reconstructions from the neighbouring peak of nevado firura reveal a smaller snowline depression suggesting the glacial response to climate forcing in the tropics is strongly influenced by non climatic factors these data constitute some of the first directly dated palaeo snowline data from the arid tropics and suggest that the magnitude of the last glaciation in at least parts of the tropical andes was similar to late pleistocene events at higher latitudes copyright 2011 john wiley sons ltd

quantitative multiproxy assessment of long term patterns of holocene environmental change from a small lake near abisko northern sweden quantitative reconstructions are made of holocene changes in climatic and environmental conditions from analyses of pollen chironomids and diatoms in identical stratigraphic levels of a sediment c

late quaternary climatic change in france estimated from multivariate pollen time series abstract in regions like southern france where usual analytical techniques are unsatisfactory due to the heavy influence of human activity and the existence of a complex climate the quantitative reconstruction of climate from pollen is particularly difficult that is why an original method has been performed the first step of the method based on best analogs estimation and multiple regression is to calculate a relationship between climate monthly temperature and precipitation and modern pollen spectra for data from 182 sites the result is called the analog climate the second step of the method an original combination of canonical correlation and principal components analyses extracts the common information from several fossil pollen sequences to produce a so called paleobioclimate this step removes the effects of local differences in the vegetation among nearby sites and also reduces the effects of human disturbance in the third step the signals obtained from the first two steps are merged by kalman filter into a final reconstruction where the noise is reduced by around 37 the results presented with a 95 confidence level suggest that the pleni wurm was 7 to 13 c colder than present and had 20 to 60 less precipitation than today this large confidence takes into account the climatic diversity of the region at 13 000 yr b p the climate reached the modern level of precipitation but the temperature was just less than present the subsequent decrease of precipitation is less important than that of temperature this fact may explain the advance of alpine glaciers during the younger dryas preboreal warming was abrupt 3 to 4 c per 500 yr and precipitation increased more slowly

response of chironomid assemblages to east asian summer monsoon precipitation variability in northern china since the last deglaciation we investigate chironomid assemblages in a sediment core from gonghai lake which is located on the east asian summer monsoon easm boundary in northern china to quantify easm variability during the past 13 5 ka bp six significantly different chironomid assemblage zones indicate that maximum precipitation and water depth occurred in the mid holocene 8270 2700 cal a bp and the minimum period was the past 1250 years a modern dataset of 44 lakes near gonghai lake was sampled to calibrate the response of chironomid assemblages to precipitation our results demonstrate that mean annual precipitation is the most significant environmental variable influencing modern chironomid assemblages in this monsoonal region maximum easm precipitation in the mid holocene indicated by chironomid assemblages in the monsoon fringe contrasts with the early holocene easm maximum suggested by stalagmite delta o 18 data from southern china but is consistent with other evidence our findings are compatible with the proposal that the stalagmite delta o 18 variations in southern china may not reliably reflect the evolution of easm since the last deglaciation copyright c 2016 john wiley sons ltd

the dynamics of chironomid assemblages and vegetation during the late quaternary at laguna facil chonos archipelago southern chile abstract we compare high resolution pollen and chironomid records from the last 15 000 yr in laguna facil southern chile major vegetation and chironomid changes are recorded between ca 14 900 and 14 700 cal yr bp during the lateglacial changes in the chironomid stratigraphy lag behind changes in the pollen stratigraphy suggesting that the chironomids are responding to changes in the tree canopy or in soil chemistry brought about by vegetational development at about 7200 cal yr bp there is a change in the chironomid stratigraphy in advance of changes in the vegetation this suggests that the response is to regional climatic change the relatively close correlation of the chironomid and pollen stratigraphies with changes in charcoal concentrations also implicates the importance of fire and or vulcanism in influencing the dynamics of forest and limnological systems there is no clear evidence of cooling during the younger dryas chronozone in laguna facil

chironomids as indicators of natural and human impacts in a 700 yr record from the northern patagonian andes abstract chironomid communities were studied in a sediment core collected from lake moreno oeste located in nahuel huapi national park a major change in midge assemblages occurred at ad 1760 which was characterized by a decrease of cold taxa including polypedilum sp 2 and dicrotendipes and an increase of warm taxa including apsectrotanypus and polypedilum sp 1 these taxa are likely related to climatic conditions concurrent with the end of a cold period at ad 1500 1700 and the beginning of a drying climate at ad 1740 1900 in northern patagonia coarse tephra layers had low midge diversity however they did not disrupt the climatic trend as the community recovered rapidly after the event since ad 1910 after the increase in suburban housing fish introduction and the construction of a road there was an increase in the relative abundances of taxa typically associated with the littoral zone such as parapsectrocladius riethia apsectrotanypus and some tanytarsini morphotypes the main change in the chironomid community appears to be associated with long term climate change at the beginning of the 20th century other site specific environmental factors catchment change and fish introduction altered the chironomid assemblages making it more difficult to understand the relative importance of each driver of assemblage change

the use of hypsometry to indicate long term stability and response of valley glaciers to changes in mass transfer a simple equation is derived relating the net mass balance and hypsometric curves of a steady state valley glacier it is used to examine how valley shape is linked to disparate extents and responses of glaciers subjected to similar climatic conditions examples are given which show that area based indices e g aar for estimating the equilibrium line altitude ela may be subject to a substantial built in variance because they implicitly rely upon similarity of glacier shape and regimen over a region if accurate topographic maps are available the equation may be used to infer the regimen of modern glaciers in the form of a dimensionless ratio of net mass balance gradients alternatively if similar information is available concerning regional glacier regimen disparate extents and responses may be collectively utilized to estimate values of ela or to infer climatic influence taking glacier hypsometry into account

quaternary glaciation of gurla mandhata naimon anyi abstract the quaternary glaciation of gurla mandhata naimona nyi an impressive isolated dome shaped massif situated in a remote region of southern tibet was examined using glacial geomorphic methods and dated using 10 be terrestrial cosmogenic nuclides the oldest moraines representing an expanded ice cap that stretched 5 km into the foreland of the gurla mandhata massif likely formed during marine isotope stage mis 10 or an earlier glacial cycle another glacial expansion of coalescing piedmont type occurred during the early part of the last glacial cycle or the penultimate glacial cycle after which glaciers became restricted to entrenched valley types impressive latero frontal moraines at the mouths of most valleys date to the early part of the last glacial cycle and mis 3 a succession of six sets of moraines within the valleys and up to the contemporary glaciers show that glaciers advanced during the lateglacial early holocene neoglacial and possibly little ice age the change of style of glaciation throughout the latter part of the quaternary from expanded ice caps to deeply entrenched valley glaciers might reflect 1 climatic controls with reduced moisture supply to the region over time and or 2 tectonic controls reflecting increase basin subsidence due to detachment faulting and enhanced valley incision

a modern pollen climate dataset from the darjeeling area eastern himalaya assessing its potential for past climate reconstruction abstract relying on the ability of pollen assemblages to differentiate among elevationally stratified vegetation zones we assess the potential of a modern pollen climate dataset from the darjeeling area eastern himalaya in past climate reconstructions the dataset includes 73 surface samples from 25 sites collected from a c 130 3600 m a s l elevation gradient along a horizontal distance of c 150 km and 124 terrestrial pollen taxa which are analysed with respect to various climatic and environmental variables such as mean annual temperature mat mean annual precipitation map mean temperature of coldest quarter mtcq mean temperature of warmest quarter mtwq mean precipitation of driest quarter mpdq mean precipitation of wettest quarter mpwq aet actual evapotranspiration and mi moisture index to check the reliability of the modern pollen climate relationships different ordination methods are employed and subsequently tested with huisman olff fresco hof models a series of pollen climate parameter transfer functions using weighted averaging regression and calibration partial least squares wa pls models are developed to reconstruct past climate changes from modern pollen data and have been cross validated results indicate that three of the environmental variables i e mtcq mpdq and mi have strong potential for past climate reconstruction based on the available surface pollen dataset the potential of the present modern pollen climate relationship for regional quantitative paleoclimate reconstruction is further tested on a late quaternary fossil pollen profile from the darjeeling foothill region with previously reconstructed and quantified climate the good agreement with existing data allows for new insights in the hydroclimatic conditions during the last glacial maxima lgm with winter temperature being the dominant controlling factor for glacial changes during the lgm in the eastern himalaya

response of chironomidae to environmental disturbances in a high mountain lake in patagonia during the last millennium through the last millennium patagonia has been affected by changing climate conditions and successive volcanic eruptions lake toncek is a high altitude lake in the southern volcanic zone in the northern patagonian andes we documented the responses of the subfossil chironomid community to the effects of successive volcanic and different conditions in a sedimentary sequence from this lake comprising the last 900 years the community composition and structure abundance diversity and richness and the development of morphological anomalies in the chironomid mouthparts were evaluated throughout the core both climatic conditions and volcanism affected the chironomid community differentially the chironomid community changed following short term climate change patterns being affecting not only by temperature changes but also by variations in the regional precipitation regime decreases in abundance and diversity were only observed in coarse volcanic layers in these samples we recorded a high percentage of damaged chironomid mouthparts caused by mechanical wear breakage or abrasion possibly due to the increase of mineral particles our results represent important baseline data about the responses of chironomid communities to environmental disturbances in high altitude lakes over long time frames

timing of multiple late quaternary glaciations in the hunza valley karakoram mountains northern pakistan defined by cosmogenic radionuclide dating of moraines moraines and associated landforms in the upper hunza valley karakoram mountains northern pakistan provide an excellent record of multiple glaciations during the late quaternary glaciers advanced at least eight times by using 10 be and 26 al surface exposure dating on moraine boulders and scoured bedrock we determined the timing of glaciation for four of these glacial advances ca 54 7 43 2 ka borit jheel glacial stage ca 25 7 21 8 ka ghulkin i glacial stage ca 18 4 15 3 ka ghulkin ii glacial stage and ca 10 8 9 0 ka batura glacial stage for two of the older advances the yunz and shanoz glacial stages our data set a limit of 60 ka although at present the uncertainties in dating make it impossible to describe unequivocally the climate processes controlling glaciations in the hunza valley the results suggest that precipitation changes related to oscillations in the southwest asian monsoonal system combine with cooling that is broadly associated with heinrich events to cause glacial advances in this region

glacier fluctuations in extratropical south america during the past 1000 years article i nfo this paper presents an updated extensive review of glacier fluctuations during the past 1000 years in the extratropical andes of south america between ca 17 and 55 s given the variety of environmental conditions and evidence available for glacier fluctuations across this wide latitudinal range regional accounts are given for the desert andes 17 31 s the andes of central chile and argentina 31 36 s and the north 36 45 s and south 45 55 s patagonian andes the techniques dating limitations and interpretations of the glacier records along this transect are also discussed information on glacier fluctuations in the desert andes is limited to the 20th century documentation on past glacier variations is more abundant in the central chilean argentinean andes but the number of chronologies dealing with glacier fluctuations prior to the 1900s is also limited most records indicate that glaciers were generally more extensive prior to the 20th century with dates of maximum expansion ranging from the 16th to the 19th centuries the number and extent of glaciers increase significantly in the patagonian region where the evidence available for dating glacier variations during the past centuries is more abundant and the dating control for glacier events is generally better than in the northern parts of the study area for some patagonian glaciers maximum little ice age lia or post lia advances have been precisely dated by dendro geomorphological determinations or in situ measurements however for most sites the evidence available is still preliminary and there is considerable variability in the extent and timing of events related to the maximum lia expansion identified in most areas between the 16th and 19th centuries evidence is starting to appear at a growing number of sites for glacier advances during the first half of the past millennium these events were generally less extensive than the lia maximum pulses despite the occurrence of several post lia readvances over the past 100 110 years most areas in the andes of extratropical south america have experienced a general pattern of glacier recession and significant ice mass losses the differences in the glacier histories observed at local and regional scales probably reflect the inherent limitations associated with the glacier records and or the dating techniques used in each case together with the varying dominance of precipitation temperature and other climatic and non climatic factors on glacier mass balance and glacier dynamics these differences indicate that the late holocene glacier history of southern south america is more complex than commonly assumed the evidence discussed in this study highlights not only the immense potential for glaciological studies of this region but also a significant need for an increased number of detailed well dated records of glacier fluctuations

southern westerly winds submit to the enso regime a multiproxy paleohydrology record from lake dobson tasmania abstract the el nino southern oscillation enso and southern westerly winds sww profoundly influence synoptic scale climate in the southern hemisphere although many studies have invoked either phenomenon to explain trends in proxy data few have demonstrated the transition from a climate dominated by sww flow to one controlled by el nino activity which is postulated to have occurred after 5 cal ka bp in the mid latitudes of the southern hemisphere tasmania southeast australia is ideally situated to detect changes in both of these climatic controls currently el nino and la nina events result in drier and wetter conditions island wide respectively with the greatest impact in the north further tasmania houses north south trending mountain ranges near its western coast as a result areas west of the mountains exhibit a positive correlation between sww flow and precipitation while eastern regions possess either no or a negative relationship here we present data from chironomid remains charcoal and geochemical proxies to investigate the paleohydrological history of lake dobson a site located in mount field national park tasmania the proxies revealed three broad periods 1 an early holocene 11 5 8 3 cal kyr bp characterised by generally high rainfall the occurrence of irregular fires and elevated charcoal influx at 11 4 and 10 2 cal ka bp conditions compatible with attenuated sww flow over the site 2 an ambiguous mid holocene 8 3 5 cal kyr bp that marks the transition from a sww to enso dominated climate and 3 a relatively dry and stable late holocene 5 cal kyr bp to present that is consistent with the onset of a climate controlled by enso activity i e characterised by a more mean el nino climate state the proxy record of lake dobson highlights the teleconnections between the equatorial pacific and southern australasia

holocene climate reconstructions from the fennoscandian tree line area based on pollen data from toskaljavri due to its location on the eastern north atlantic seaboard the fennoscandian tree line area is an ideal area to use biological proxies to assess the relative roles of the scandinavian ice sheet and of oceanic atmospheric and astronomic forcings on regional climate history here we report pollen based july mean temperature tjul and annual precipitation pann reconstructions from a sediment core from a high altitude tree line lake in northwestern finland the reconstructions suggest that at 9600 8300 cal yr b p tjul values were low but steadily rising while pann was high the period of warmest summers with tjul values ca 1 8 1 6 c higher than at present occurred at ca 8000 6500 cal yr b p since then climate has become gradually cooler tjul values during the medieval warm period ca 1400 1000 cal yr b p were ca 0 8 c higher that at present but decreased rapidly to the low little ice age levels at 800 cal yr b p we compare these results with an earlier pollen based climate reconstruction from the same region the reconstructions indicate a similar general holocene tjul pattern with lower values in the reconstruction from the high altitude lake however most of the small scale variations are not synchronous suggesting that they may represent noise rather than signal in our data c 2002 university of washington