relationships between loess and the silk road reflected by environmental change and its implications for human societies in the area of ancient panjikent central asia rich ancient societies of central asia developed on the basis of trade between east and west their existence was dependent on natural resources that favoured agriculture the branches of the silk road in central asia clearly coincide with loess areas where many settlements were erected based on the presence of fertile loess soil and water the aim of the study was to analyse the environmental factors that led to the growth and decline of one of the most important silk road loess towns ancient panjikent as an example of human and climatic impacts on landscape changes the town established in the fifth century quickly became one of the most important cities of sogdiana local loess material was used for the production of the sun dried bricks rapid population growth led to deforestation and consequently increased the intensity of erosion rates and reductions in cultivation area a period of drought near the end of the first millennium ad influenced the final abandonment of the ancient town and its relocation to the lower terrace of the zarafshan river a decline in natural and agricultural resources and subsequently climatic forces caused a decline in the number of cities in semiarid regions of central asia

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

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

evolution of cryoconite holes and their contribution to meltwater runoff from glaciers in the mcmurdo dry valleys antarctica cryoconite holes are water filled holes in the surface of a glacier caused by enhanced ice melt around trapped sediment measurements on the ablation zones of four glaciers intaylorvalley antarctica show that cryoconite holes cover about 4 6 of the ice surface they typically vary in diameter from 5 to 145 cm with depths ranging from 4 to 56 cm in some cases huge holes form with 5 m depths and 30 m diameters un like cryoconite holes elsewhere these have ice lids up to 36 cm thick and melt from within each spring about one half of the holes are connected to the near surface hydrologic system and the remainder are isolated the duration of isolation estimated from the chlor ide accumulation in hole waters commonly shows ages of several years with one hole of 10 years the cryoconite holes in the mcmurdo dryvalleys create a near surface hydro logic system tens of cm below the ice surface the glacier surface itself is generally frozen and dry comparison of water levels between holes a few meters apart shows independent cycles of water storage and release most likely local freeze thaw effects control water passage and therefore temporary storage rough calculations indicate that the holes gen erate at least 13 of the observed runoff on the one glacier measured this hydrologic system represents the transition between a melting ice cover with supraglacial streams and one entirely frozen and absent of water abstract cryoconite holes are water filled holes in the surface of a glacier caused by enhanced ice melt around trapped sediment measurements on the ablation zones of four glaciers intaylorvalley antarctica show that cryoconite holes cover about 4 6 of the ice surface they typically vary in diameter from 5 to 145 cm with depths ranging from 4 to 56 cm in some cases huge holes form with 5 m depths and 30 m diameters un like cryoconite holes elsewhere these have ice lids up to 36 cm thick and melt from within each spring about one half of the holes are connected to the near surface hydrologic system and the remainder are isolated the duration of isolation estimated from the chlor ide accumulation in hole waters commonly shows ages of several years with one hole of 10 years the cryoconite holes in the mcmurdo dryvalleys create a near surface hydro logic system tens of cm below the ice surface the glacier surface itself is generally frozen and dry comparison of water levels between holes a few meters apart shows independent cycles of water storage and release most likely local freeze thaw effects control water passage and therefore temporary storage rough calculations indicate that the holes gen erate at least 13 of the observed runoff on the one glacier measured this hydrologic system represents the transition between a melting ice cover with supraglacial streams and one entirely frozen and absent of water

temporal variations in physical and chemical features of cryoconite holes on canada glacier mcmurdo dry valleys antarctica cryoconite holes in the mcmurdo dry valleys are ice lidded thus isolating the pools of water from the atmosphere and from potential surface melt hourly measurements of ice and water temperature and water electrical conductivity ec were recorded to broadly characterize the physical and chemical changes on daily to seasonal timescales overall subsurface ice water temperatures were typically several degrees warmer than air temperatures underscoring the importance of subsurface solar heating at no time was surface melt observed and the holes melted from within detailed differences in the timing and magnitude of both temperature and ec variations during melt out and freezeup existed between holes despite short separation distances 1 m we attribute these differences to small scale changes in the optical characteristics of the ice and perhaps different efficiencies in hydrologic connections between holes the holes melt deepened quickly in the first half of the summer before slowing to a rate equal to the rate of surface ablation that kept hole depth constant for the remainder of the season the relatively constant ec of the hole waters during midsummer indicates that these holes were connected to a subsurface water system that flushed the holes with fresher meltwater the early and late season ecs are dominated by freeze thaw effects that concentrate dilute the solutes we speculate that high solute concentrations imply high nutrient concentrations in early summer that may help alleviate potential stresses caused by the production of new biomass after the winter freeze

high resolution monitoring reveals dissolved oxygen dynamics in an antarctic cryoconite hole this study presents the first high resolution dataset of dissolved oxygen do measurements in an ice lidded cryoconite hole on canada glacier mcmurdo dry valleys antarctica fibre optic do minisensors were installed in a cryoconite hole prior to seasonal internal melting and hydrological connection to the subsurface drainage system oxygen air saturation in the cryoconite hole typically ranged from 50 to 80 in broad agreement with previous single measurements indicating net respiration r this is consistent with results of simple incubation experiments performed in the field simultaneous time series for electrical conductivity water temperature and do over the four week study period provide information regarding the connectivity of cryoconite holes with the near surface drainage system the main driver of the observed variations in do is likely to be periodic melt freeze cycles we conclude that automated sensing techniques such as those described here when used in conjunction with physical measurements have great potential for high resolution monitoring of the factors that perturb biogeochemical processes in cryospheric surface aquatic ecosystems

biological processes on glacier and ice sheet surfaces glacial ice covers around 10 of the earth s continents a review of the literature suggests that microbes living on glaciers and ice sheets are an integral part of both the glacial environment and the earth s ecosystem

metabolic activity and diversity of cryoconites in the taylor valley antarctica 1 metabolic activity and biogeochemical diversity within cryoconites from the canada commonwealth howard and hughes glaciers in the mcmurdo dry valleys revealed the presence of a productive microbial refuge in this polar desert ecosystem fluorescent in situ hybridization showed a high percentage of cytophaga flavobacteria cells in cryoconite sediments 87 2 while b proteobacterial cells dominated the ice overlying the sediment layer 54 2 the biomass of bacterial cells in the sediments was also greater 4 82 mgc ml 1 than that in the overlying ice 0 18 mgc ml 1 and was related to bacterial productivity on the basis of thymidine incorporation which ranged from 36 ng cl 1 d 1 in the overlying ice to 3329 ng c l 1 d 1 in the sediment containing layers bacteria within both the sediments and overlying ice were able to actively incorporate and respire radio labeled glucose as well as 17 other dissolved organic carbon compounds the cryoconites in the taylor valley support an active diverse assemblage of organisms despite the fact that they may remain sealed from the atmosphere for decades given the density of the cryoconites in the dry valleys 4 6 of ablation zone surfaces flushing of the cryoconites during warm years could provide a vital nutrient and organic carbon source to the surrounding polar desert

tree ring recorded hydroclimatic change in tienshan mountains during the past 500 years abstract in central asia tree rings provide one of the best sources of paleoclimatological information however dendroclimatology has not been widely applied in the coniferous forests of central asia tree cores of picea schrenkiana from four sites in the hutubi river basin were developed into a 606 year tree ring width chronology the analyses showed that the tree ring width indices highly correlate with mean april may pdsi in the hutubi river basin mean april may pdsi of the hutubi river was reconstructed using the tree ring data with 41 5 of the variance explained the reconstructed series contains both high and low frequency climate signals our new pdsi reconstruction agrees reasonably well with the dry and wet periods previously estimated from tree rings in western tien shan the results reveal common climatic extremes over much of central asia spatial analysis shows that the pdsi reconstructions have strong common signals for the tien shan the first principal component of pdsi reconstructions in tien shan is significantly correlated with sea surface temperature in the eastern equatorial pacific ocean and atlantic ocean the linkages to the atlantic and pacific oceans suggest the connection of regional moisture variations to the asian monsoon and the westerlies

climate changes reconstructed from a glacial lake in high central asia over the past two millennia abstract climatic changes in arid central asia aca over the past two millennia have been widely concerned however less attention has been paid to those in the high central asia hca where the asian water tower nurtures the numerous oases by glacier and or snow melt here we present a new reconstruction of the temperature and precipitation change over the past two millennia based on grain size of a well dated glacial lake sediment core in the central of southern tianshan mountains the results show that the glacial lake catchment has experienced cold wet climate conditions during the dark age cold period 300 600 ad dacp and the little ice age 1300 1870 ad lia whereas warm dry conditions during the medieval warm period 700 1270 ad mwp integration of our results with those of previously published lake sediment records stalagmite 18o records ice core net accumulation rates tree ring based temperature reconstructions and mountain glacier activities suggest that there has a broadly similar hydroclimatic pattern over the hca areas on centennial time scale during the past two millennia comparison between hydroclimatic pattern of the hca and that of the aca areas suggests a prevailing warm dry and cold wet hydroclimatic pattern over the whole westerlies dominated central asia areas during the past two millennia we argue that the position and intensity of the westerlies which are closely related to the phase of the north atlantic oscillation nao and the strength of the siberian high pressure sh could have jointly modulated the late holocene central asia hydroclimatic changes

characterization of dissolved organic matter dom from glacial environments using total fluorescence spectroscopy and parallel factor analysis aquatic dissolved organic matter dom is a major reservoir of reduced organic carbon and has a significant influence on heterotrophic biological productivity and water quality in marine and freshwater environments although the forms and transformations of dom in temperate aquatic and soil environments have been studied extensively this is not the case for glacial environments in this study fluorescent excitation emission matrices eems parallel factor analysis parafac and cluster analysis were used to characterize the fluorescing components of dom in ice and water samples from supraglacial englacial subglacial and proglacial environments of seven glaciers in the canadian arctic norway and antarctica at least five significant fluorescent dom fractions were identified which accounted for 98 2 of the variance in the dataset these included four protein like components and one humic like component the predominantly proteinaceous character of dom from these glaciers is very different from the more humic character of dom described previously from lacustrine fluvial estuarine and marine environments dom from the sampled glaciers is broadly similar in character despite their geographically distinct locations different thermal regimes and inter and intra site differences in potential organic matter sources glacier ice samples had a relatively low ratio of humic like protein like fluorescence while meltwater samples had a higher ratio

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

dendroclimatic reconstruction of april may temperature fluctuations in the western himalaya of india since a d 1698 abstract ring width chronologies of himalayan cedar cedrus deodara d don g don himalayan pine pinus wallichianaa b jackson and himalayan spruce picea smithiana wall boiss from the western himalayan region india have been used to reconstruct mean april may temperature back to a d 1698 the reconstruction correlates significantly with the average april may instrumental temperature record r 0 62 1876 1988 and is characterized by annual to multiyear fluctuations the most striking feature of the present reconstruction is the absence of any warming trend in the 20th century relationships between the mean april may temperature for the western himalayan region indian summer monsoon rainfall and southern oscillation index indicate that the tree ring chronologies as surrogate temperature records will provide valuable data for climate change studies with regional and global perspectives

life at the freezing point microbial communities are known to exist in extremely hot environments such as hydrothermal vents but what about extremely cold regions in their research commentary psenner and sattler discuss results reported in the same issue by priscu et al in which a microbial assemblage was discovered in antarctic lake ice although this environment is marked by permanent ice cover pockets of liquid water can form during part of the year allowing active growth and reproduction of organisms

weakening climatic signal since mid 20th century in european larch tree ring chronologies at different altitudes from the adamello presanella massif italian alps abstract tree rings from temperature limited environments are highly sensitive climate proxies widely used to reconstruct past climate parameters for periods prior to the availability of instrumental data and to analyse the effect of recent global warming on tree growth an analysis of the climatic signal in five high elevation tree ring width chronologies of european larch larix decidua mill from the tops of five different glacial valleys in the italian central alps revealed that they contain a strong summer temperature signal and that tree ring growth is especially influenced by june temperatures however a moving correlation function analysis revealed a recent loss of the june temperature signal in the tree ring chronologies this signal reduction primarily involves the two lowest altitude chronologies it is probable that the observed increasing importance of late summer temperature for tree ring growth over the past 50 yr is an effect of the lengthening growing season and of the variations in the climate tree ring relationship over time all the chronologies considered especially those at the highest altitudes show an increasing negative influence of june precipitation on tree ring growth the climatic signal recorded in tree ring chronologies from the italian central alps varies over time and is also differentially influenced by climatic parameters according to site elevation

quantifying spatial and temporal trends in beach dune volumetric changes using spatial statistics abstract spatial statistics are generally underutilized in coastal geomorphology despite offering great potential for identifying and quantifying spatial temporal trends in landscape morphodynamics in particular local moran s i i provides a statistical framework for detecting clusters of significant change in an attribute e g surface erosion or deposition and quantifying how this changes over space and time this study analyzes and interprets spatial temporal patterns in sediment volume changes in a beach foredune transgressive dune complex following removal of invasive marram grass ammophila spp results are derived by detecting significant changes in post removal repeat dems derived from topographic surveys and airborne lidar the study site was separated into discrete linked geomorphic units beach foredune transgressive dune complex to facilitate sub landscape scale analysis of volumetric change and sediment budget responses difference surfaces derived from a pixel subtraction algorithm between interval dems and the lidar baseline dem were filtered using the local moran s i i method and two different spatial weights 1 5 and 5 m to detect statistically significant change moran s i i results were compared with those derived from a more spatially uniform statistical method that uses a simpler student s t distribution threshold for change detection morphodynamic patterns and volumetric estimates were similar between the uniform geostatistical method and moran s i i at a spatial weight of 5 m while the smaller spatial weight 1 5 m consistently indicated volumetric changes of less magnitude the larger 5 m spatial weight was most representative of broader site morphodynamics and spatial patterns while the smaller spatial weight provided volumetric changes consistent with field observations all methods showed foredune deflation immediately following removal with increased sediment volumes into the spring via deposition at the crest and on lobes in the lee despite erosion on the stoss slope and dune toe generally the foredune became wider by landward extension and the seaward slope recovered from erosion to a similar height and form to that of pre restoration despite remaining essentially free of vegetation

cryoconite hole thermodynamics energy sources governing the growth of cryoconite holes have been investigated by monitoring the meteorological balance at the surface of the manatee glacier british columbia the dimensions of 125 holes and the thermal conditions within them cryoconite holes are shown to be rough indicators of the energy balance at the glacier surface both atmospheric and biological energy sources operate thereby suggesting a genetic classification of holes with solar and biological end members

tree ring reconstruction of late summer temperatures in northern sikkim eastern himalayas abstract the sikkim region of the himalayas is among one of the most highly sensitive hotspots to climate change due to its fragile mountainous environment and rapidly growing population which exert significant impacts on regional ecosystem factors including biodiversity and hydrology limited observational data coverage in space and time for the high altitude mountainous region impedes our understanding of climate change and its impact on the environment in this paper we develop a 437 year tree ring width index chronology of tsuga dumosa d don eichler in northern sikkim as a climate proxy the substantial dendroclimatic potential of this proxy is evidenced in various statistics computed from the tree ring chronology an analysis of the tree ring chronology indicates a strong negative relationship between late summer mean temperatures july august september jas and tree growth this relationship enables us to reconstruct the jas mean temperature over northern sikkim since 1705 c e the 304 year 1705 2008 c e reconstructed temperature series shows similar warm and cool epochs which have been observed in many other temperature reconstructions in the region and other proxy records of glacial fluctuations an overall steady decreasing trend in the regional surface temperature is observed since 1705 c e while an increasing trend with intermittent short and cool epochs are noticed from 1850 c e to the present prior to the observational period before 1901 c e cold conditions x 1 prevailed during 1816 1819 1831 1837 1856 1859 and 1884 1887 c e with extremely cold conditions x 2 occurring in 1816 1817 1832 1833 1857 1877 1884 and 1885 c e warm conditions x 1 prevailed during 1713 1735 and 1823 1827 c e with extremely warm x 2 conditions occurring in 1724 1823 1824 and 1825 c e global teleconnections of the reconstructed temperature variations indicate the important roles of the pacific decadal oscillation pdo el nino southern oscillation enso and volcanic eruptions as drivers of temperature variations in the sikkim region of the himalayas

foredunes and blowouts initiation geomorphology and dynamics this paper reviews the initiation dynamics geomorphology and evolution of incipient foredunes established foredunes and blowouts incipient foredunes may be initiated in a variety of ways leading to the formation of ramps terraces or ridges depending on progradation rates vegetation type and cover sediment transport rates and scale of erosional processes vegetation cover morphology growth rates and types combine with aerodynamic processes to determine dune and swale morphology established foredunes are classified into five morpho ecological types and the flow behaviour over two types is detailed a new model of foredune evolutionary paths at various possible time scales is presented blowout initiation dynamics and sediment transport and evolution is examined throughout the review the gaps in present understanding of dune processes and a range of ideas for new research possibilities are provided

sources and molecular composition of cryoconite organic matter from the athabasca glacier canadian rocky mountains cryoconite is a dark coloured dust like material found on the surfaces of glaciers cryoconite has received much interest recently because cryoconite holes which are produced by accelerated ice melt act as habitats for microbes on glacier surfaces to the best of our knowledge cyroconite organic matter com has not yet been chemically characterized at the molecular level in this study organic matter biomarkers and a host of nmr techniques were used to characterize com from the athabasca glacier in the canadian rocky mountains solvent extracts contained large quantities of fatty acids n alkanols n alkanes wax esters and sterols a large contribution of c23 c 25 and c27 relative to c29 and c31 n alkanes suggests that allochthonous com is mainly from lower order plants mosses lichens this is confirmed by the absence of lignin phenols after copper ii oxidation in extracts and nmr analyses of com solution state 1 h nmr reveals prominent signals from microbial components while solid state 13 c cp mas nmr analysis shows an atypically high alkyl o alkyl ratio suggesting that com is significantly different from organic matter found in nearby soils the nmr results suggest that com is dominated by microbially derived compounds which was confirmed by phospholipid fatty acid analysis revealing a significant microbial contribution primarily from bacteria with minor contributions from microeukaryotes both biomarker and nmr data suggest that com supports active microbial communities on the athabasca glacier given that such material is incorporated within the glacier in the accumulation zone or flushed by meltwaters into subglacial environments reworked com may provide nutrient sources for active microbial communities found within and under glaciers

aeolian sediment transport on a human altered foredune changes in wind speed and sediment transport are evaluated at a gap and adjacent crest of a 2 to 3 m high 40 m wide foredune built by sand fences and vegetation plantings on a wide nourished fine sand beach at ocean city new jersey anemometer masts cylindrical sand traps and erosion pins were placed on the beach and dune during two obliquely onshore wind events in february and march 2003 results reveal that 1 changes in the alongshore continuity of the beach and dune system can act as boundaries to aeolian transport when winds blow at an angle to the shoreline 2 oblique winds blowing across poorly vegetated patches in the dune increase the potential for creating an irregular crest elevation 3 transport rates and deflation rates can be greater within the foredune than on the beach if the dune surface is poorly vegetated and the beach has not had time to dry following tidal inundation 4 frozen ground does not prevent surface deflation and 5 remnant sand fences and fresh storm wrack have great local but temporary effect on transport rates temporal and spatial differences due to sand fences and wrack changes in sediment availability due to time dependent differences in surface moisture and frozen ground combined with complex topography and patchy vegetation make it difficult to specify cause effect relationships effects of individual roughness elements on the beach and dune on wind flow and sediment transport can be quantified at specific locations at the event scale but extrapolation of each event to longer temporal and spatial scales remains qualitative copyright 2006 john wiley sons ltd

understanding wind blown sand six vexations abstract the study of aeolian geomorphological systems over the last half century has advanced along several important fronts supported by developments in technologies and analytic methods and the evolution of modeling approaches remote sensing has led to a wealth of knowledge concerning the distribution and dynamics of dunes on earth and elsewhere and wind tunnels have elucidated the roles of aeolian processes in reshaping surfaces improvements in laboratory and field instrumentation allow measurement of aeolian sand transport systems at levels of detail unimaginable when the binghamton geomorphology symposium began we have seen for example the advent of large sophisticated field campaigns and advanced modeling approaches using cellular automata and computational fluid dynamics methods select avenues of development especially concerned with depositional environments are briefly summarized advances in many fields have not been matched with proportional advances in our ability to predict rates of sand transport in natural environments one of the most fundamental challenges at least eight commonly cited sand transport rate models do not agree with each other and do not replicate field observations even under near ideal conditions this review focuses on select reasons why that might be so and categorizes those reasons into six principal theoretical and empirical vexations that have made sand transport an intractable problem predicting rates of transport characterizing grain size characterizing fluid and sand densities estimating shear velocity predicting the threshold of motion including the effects of sand moisture content and understanding granular electrification the examination of potential sources of error in the rate of transport and threshold of motion models leads to a point by point consideration of our current assumptions and protocols or lack thereof the objective is to help us identify the hard targets and the soft targets for future research

surface glaciochemistry of taylor valley southern victoria land antarctica and its relationship to stream chemistry we have analysed a series of surface samples from the alpine glaciers of taylor valley southern victoria land antarctica for their geochemical composition this was done to better establish the role of glaciochemical variation on the chemical composition of meltwater streams emanating from the glaciers the chemistry of the snow and ice changes with proximity to the ocean and with elevation of the glacier surface the aeolian transport of dry valley dust as indicated by both chemical and particulate matter variations is a major process affecting the overall glacier chemistry and the chemistry of the meltwaters streams originating on the western edges of the glaciers are more impacted by the aeolian input as they are in the direct path of the major regional wind direction our data strongly suggest that the variation in stream geochemistry in taylor valley is a result in part of the differences in chemical composition of glacier melt copyright 2003 john wiley sons ltd

molecular characterization of dissolved organic matter associated with the greenland ice sheet abstract subsurface microbial oxidation of overridden soils and vegetation beneath glaciers and ice sheets may affect global carbon budgets on glacial interglacial timescales the likelihood and magnitude of this process depends on the chemical nature and reactivity of the subglacial organic carbon stores we examined the composition of carbon pools associated with different regions of the greenland ice sheet subglacial supraglacial proglacial in order to elucidate the type of dissolved organic matter dom present in the subglacial discharge over a melt season electrospray ionization esi fourier transform ion cyclotron resonance ft icr mass spectrometry coupled to multivariate statistics permitted unprecedented molecular level characterization of this material and revealed that carbon pools associated with discrete glacial regions are comprised of different compound classes specifically a larger proportion of protein like compounds were observed in the supraglacial samples and in the early melt season spring subglacial discharge in contrast the late melt season summer subglacial discharge contained a greater fraction of lignin like and other material presumably derived from underlying vegetation and soil these results suggest 1 that the majority of supraglacial dom originates from autochthonous microbial processes on the ice sheet surface 2 that the subglacial dom contains allochthonous carbon derived from overridden soils and vegetation as well as autochthonous carbon derived from in situ microbial metabolism and 3 that the relative contribution of allochthonous and autochthonous material in subglacial discharge varies during the melt season these conclusions are consistent with the hypothesis that given sufficient time e g overwinter storage resident subglacial microbial communities may oxidize terrestrial material beneath the greenland ice sheet

carbon fluxes through bacterial communities on glacier surfaces there is very little information about the activity of microbial communities on the surface of glaciers though there is an increasing body of evidence to show that they strongly influence the biogeochemistry of these habitats we measured bacterial abundance and production in cryoconite holes on arctic antarctic and alpine glaciers in order to estimate the role of heterotrophic bacteria within the carbon budget of glacial ecosystems our results demonstrate an active bacterial community on the surface of glaciers with doubling times that vary from a few hours to hundreds of days depending on the glacier and position water or sediments within the cryoconite hole however bacterial production is only 2 3 of the published literature values of community respiration from similar habitats indicating that other types of microbes e g eukaryotic organisms may also play a role in the c cycle of glaciers we estimate that only up to 7 of the organic c in cryoconite sediments is utilized by the heterotrophic bacterial community annually suggesting that the surface of glaciers can accumulate organic carbon and that this c may be important for biogeochemical activity downstream to adjacent ecosystems

peat δ13ccelluose signified moisture variations over the past 2200 years in the southern altai mountains northwestern china abstract a 2200 year moisture history of the southern altai mountains i e chinese altai was established based on peat 13ccelluose data obtained at yushenkule yskl peat generally speaking the moisture record from yskl peat exhibits a cool wet dacp dark age cold period from 500 to 800 ce a warm dry mwp medieval warm period from 800 to 1200 ce a cool wet lia little ice age from 1200 to 1900 ce and a warm dry cwp current warm period since 1900 ce but rwp roman warm period from prior to 100 ce to 500 ce is an exception i e warm wet if the heat water combinations within those major temperature change events are further examined the warm dry cool wet generalization collapses the comparisons between the variations in the peat 13ccelluose based moisture obtained from yskl peat and the variations of reconstructed climatic variables in the referenced sequences suggest that the moisture variations in the altai mountains have been basically controlled by the precipitation that was primarily modulated by the nao variations

cryoconite on a glacier on the north eastern tibetan plateau light absorbing impurities albedo and enhanced melting cryoconite is a dark coloured granular sediment that contains biological and mineralogical components and it plays a pivotal role in geochemistry carbon cycling and glacier mass balance in this work we collected cryoconite samples from laohugou glacier no 12 lhg on the north eastern tibetan plateau during the summer of 2015 and measured the spectral albedo to explore the impacts of this sediment on surface ablation the ice melting differences between the cryoconite free removed ice and the intact layers were compared the results showed that the mean concentrations of black carbon bc organic carbon oc and total iron fe in the lhg cryoconite were 1 28 11 18 and 39 94 mg g 1 respectively bc was found to play a stronger role in solar light adsorption than oc and free fe in addition ice covered by cryoconite exhibited the lowest mean reflectance i e 1 and free fe bc and oc were estimated to contribute 1 01 0 99 and 0 76 cm d 1 respectively this study provides important insights for understanding the role of cryoconite in the glacier mass balance of the northern tibetan plateau

limnological conditions in subglacial lake vostok antarctica subglacial lake vostok is located 4 km beneath the surface of the east antarctic ice sheet and has been isolated from the atmosphere for 15 million yr concerns for environmental protection have prevented direct sampling of the lake water thus far however an ice core has been retrieved from above the lake in which the bottom 85 m represents lake water that has accreted i e frozen to the bottom of the ice sheet we measured selected constituents within the accretion ice core to predict geomicrobiological conditions within the surface

winter precipitation changes during the medieval climate anomaly and the little ice age in arid central asia abstract the strength of the north atlantic oscillation nao is considered to be the main driver of climate changes over the european and western asian continents throughout the last millennium for example the predominantly warm medieval climate anomaly mca and the following cold period of the little ice age lia over europe have been associated with long lasting phases with a positive and negative nao index its climatic imprint is especially pronounced in european winter seasons however little is known about the influence of nao with respect to its eastern extent over the eurasian continent here we present speleothem records 13c 18o and sr ca from the southern rim of fergana basin central asia revealing annually resolved past climate variations during the last millennium the age control of the stalagmite relies on radiocarbon dating as large amounts of detrital material inhibit accurate 230th dating present day calcification of the stalagmite is most effective during spring when the cave atmosphere and elevated water supply by snow melting and high amount of spring precipitation provide optimal conditions seasonal precipitation variations cause changes of the stable isotope and sr ca compositions the simultaneous changes in these geochemical proxies however give also evidence for fractionation processes in the cave by disentangling both processes we demonstrate that the amount of winter precipitation during the mca was generally higher than during the lia which is in line with climatic changes linked to the nao index but opposite to the higher mountain records of central asia several events of strongly reduced winter precipitation are observed during the lia in central asia these dry winter events can be related to phases of a strong negative nao index and all results reveal that winter precipitation over the central eurasian continent is tightly linked to atmospheric nao modes by the westerly wind systems

a blue ice ecosystem on the margins of the east antarctic ice sheet freezing temperatures desiccation and high levels of solar radiation make the surface of the antarctic ice sheet one of earth s harshest habitats however our study in the vestfold hills area of east antarctica shows that favourable conditions for microbial production become established just beneath the surface of blue ice areas which collectively cover about 2 of the ice sheet periphery their translucent wind polished surface allows solar heating to create meltwater in a greenhouse type environment at depths of up to 1m melting is intensified around dark debris particles or cryoconite where we found microbiological activity to be greatest rates of photosynthesis average 2060 ngc g cryoconite 1 d 1 were adapted to low light intensities 10 of surface irradiance values and most likely dominated by cyanobacteria and chloroplastida a heterotrophic bacterial community was also found to be active within the cryoconite although average bacterial growth rates 5 7 ngc g cryoconite 1 d 1 were far lower than average community respiration 1870 ng c g cryoconite 1 d 1 the majority of the respired carbon was most likely associated with the autotrophs and several protists therefore blue ice areas constitute oases for microbial life around the periphery of earth s coldest ice sheet

the influence of coarse woody debris on gravel beach geomorphology abstract coarse woody debris cwd is an important component of fluvial systems affecting in channel hydrology and sediment storage which in turn controls channel geometry and evolution the role of coarse woody debris in coastal geomorphology is an emerging research field and this study investigates its role on mixed sand and gravel beach systems a case study approach is used whereby two field areas in wellington new zealand each with two distinct beaches with differing wood accumulations were investigated through field surveying it is found that on gravel beaches cwd is most important during storm events where it causes the berm crests to be 0 5 1 0 m higher than on unwooded beaches as well as making the beachface twice as steep during calm periods the berm appears to be inactive as non storm waves can only rework the lower beachface a review of the literature indicates that on sandy beaches cwd is most important in the post storm recovery of beach systems the same wave event that causes beach erosion also deposits the cwd during calm periods the woody material is a trap for sand being transported along the beachface and therefore aids in re establishing foredune systems the differing sediment composition between sandy and gravelly beaches drives their morphological response to storm events and in turn determines how cwd interacts with the beach profile

late holocene moisture balance inferred from diatom and lake sediment records in western mongolia the valley of the great lakes in western mongolia is a unique ecosystem comprising a wide variety of terrestrial and aquatic habitats relatively little is known about the long term climate history

aeolian sand transport and deposition patterns within a large woody debris matrix fronting a foredune abstract sediment transport pathways and resulting erosion deposition patterns across beach foredune systems can be complex although a great deal is known about the effects of wind fetch surface moisture topographic forcing and vegetation cover the role of large woody debris lwd as a control on sediment redistribution across beaches is relatively understudied pieces of lwd act as non porous roughness elements that induce secondary flow circulation thereby creating unique sedimentation patterns that differ markedly from those over a flat beach large accumulations of lwd collectively have a bulk porosity that provides substantial sand trapping volume yet no studies to date have quantified the effect of lwd on aeolian sand transport results from a field study on a macrotidal beach on calvert island british columbia canada show that the lwd matrix alters the character of the turbulent boundary layer in a way that reduces sediment flux by 99 sand is trapped within the lwd matrix thereby interrupting sediment delivery from the nearshore to the foredune as such lwd has the potential to modulate rates of foredune recovery growth and evolution the relative importance of this effect depends on the density and arrangement of lwd as a fundamental control on aeolian sediment transport as well as on the magnitude and frequency of events that erode the beach periodically and re organize the lwd matrix

comparative analysis of morphological mineralogical and spectral properties of cryoconite in jakobshavn isbrae greenland and canada glacier antarctica we report the results of a comparative analysis focusing on grain size mineralogical composition and spectral reflectance values 400 2500nm of cryoconite samples collected from jakobshavn isbrae west greenland and canada glacier mcmurdo dry valleys antarctica the samples from the greenland site were composed of small particles clumped into larger rounded agglomerates while those from the site in antarctica contained fragments of different sizes and shapes mineralogical analysis indicates that the samples from jakobshavn isbrae contained a higher percentage of quartz and albite whereas those from canada glacier contained a higher percentage of amphibole augite and biotite spectral measurements confirmed the primary role of organic material in reducing the reflectance over the measured spectrum the reflectance of the samples from the antarctic site remained low after the removal of organic matter because of the higher concentration of minerals with low reflectance the reflectance of dried cryoconite samples in the visible region was relatively low e g between 0 1 and 0 4 favouring increased absorbed solar radiation despite high reflectance values in the shortwave infrared region the effect of the presence of cryoconite is negligible at infrared wavelengths where ice reflectance is low

vegetation history fire history and lake development recorded for 6300 years by pollen charcoal loss on ignition and chironomids at a small lake in southern kyrgyzstan alay range central asia analyses of pollen microscopic charcoal loss on ignition loi and chironomids in the sediment of the small sub alpine lake kichikol 2541 m a s l 39 59 n 73 33 e alay range kyrgyzstan provide new data to reconstruct the vegetational and lacustrine history during the past 6300 years from 6300 5100 calibrated 14c years bp cal yr bp semi deserts with chenopodiaceae and ephedra and rather open juniperus stands persisted around the lake at 5100 4000 cal yr bp dense juniperus forest established around 4000 cal yr bp the forest retreated and was probably restricted to north facing slopes as is the case today changes in the hydrology of kichikol are inferred from lithological properties pollen of aquatic plants and remains of aquatic invertebrates the lacustrine development of kichikol suggests a step wise increase in humidity during the mid and late holocene with major shifts recorded at 5000 and 4000 cal yr bp at the beginning of the record kichikol was a very shallow possibly temporary pond an initial rise in water table is registered at c 5000 cal yr bp followed by a second rise to near present levels at c 4000 cal yr bp these hydrological shifts could be related to an increase of westerly moisture transport from the mediterranean region as a consequence of a late holocene weakening of the central asian high and indian monsoon systems moderate human impact in the region is recorded after 2100 cal yr bp as indicated by pollen of plantago lanceolata type and a slight increase of charcoal accumulation rates considering the general course of climate as well as human impact we conclude that the present forest composition is natural or quasi natural

annual to decadal morphodynamics of the foredune system at greenwich dunes prince edward island canada the purpose of this study was to quantify relationships between season sediment availability sediment transport pathways and beach foredune morphology at greenwich dunes pei this was done for periods ranging from a few days to multiple decades using erosion pins bedframe measurements annual surveys and digital photogrammetry using historical aerial photographs the relative significance of seasonal annual processes versus response of the foredune system to broader geomorphic controls e g relative sea level rise storms etc was also assessed the data show that there are clear seasonal differences in the patterns of sand supply from the beach to the foredune at greenwich and that there are differences in sediment supply to the foredune between the east and west reaches of the study area resulting in ongoing differences in foredune morphology they also demonstrate that models that incorporate wind climate alone or even models that include other factors like beach moisture would not be able to predict the amount of sediment movement from the beach to the foredune in this environment unless there were some way to parameterize system morphology especially the presence or absence of a dune ramp finally the data suggest that the foredune can migrate landward while maintaining its form via transfers of sediment from the stoss slope over the crest and onto the lee slope although the rate of foredune development or recovery after disturbance changes over time due to morphological feedback the overall decadal evolution of the foredune system at greenwich is consistent with and supports the davidson arnott 2005 conceptual model of dune transgression under rising sea level copyright 2012 john wiley sons ltd

airflow and aeolian sediment transport patterns within a coastal trough blowout during lateral wind conditions blowouts are depressions that occur on coastal dunes deserts and grasslands the absence of vegetation in blowouts permits high speed winds to entrain and remove sediment whereas much research has examined patterns of wind flow and sediment transport on the stoss slopes and lee of sand dunes no study has yet investigated the connections between secondary air flow structures and sediment transport in a blowout where zones of streamline compression expansion and steering are less clearly delineated in this study we investigated the variability of sediment flux and its relation to near surface wind speed and turbulence within a trough blowout during wind flow that was oblique to the axis of the blowout wind flow was measured using six three dimensional 3d ultrasonic anemometers while sediment flux by eight sand traps all operating at 25 hz results demonstrated that sediment flux rates were highly variable throughout the blowout deflation basin even over short distances 0 5 m where flow was steadiest flux was greatest consequently the highest rates of sediment transport were recorded on the erosional wall crest where flow was compressed and accelerated the strength of correlation between sediment flux and wind parameter improved with an increase in averaging interval from 10 seconds to 1 minute at an interval of 10 seconds however wind speed correlated best with flux at seven of eight traps whereas at an interval of one minute turbulent kinetic energy tke provided the best correlation with flux at six of the eight traps correlation between sediment flux and wind parameters was best in the centre of the blowout and poorest on the erosional wall crest the evidence from this paper suggests for the first time that tke may be a better predictor of sediment transport at minute scale averaging intervals particularly over landforms where wind flow is highly turbulent

extreme hydrochemical conditions in natural microcosms entombed within antarctic ice cryoconite holes are near vertical tubes that form in the surface of glaciers when solar heated debris melts into the ice those that form in the mcmurdo dry valleys of antarctica are distinctive in that they have ice lids and are closed to the atmosphere for periods of years to decades photoautotrophs and heterotrophs grow within this closed environment perturbing the poorly buffered water chemistry yet maintaining the potential for photosynthesis microbial excretion and decomposition of organic matter produces dissolved organic carbon doc dissolved inorganic carbon ratios of 1 2 much of the dissolved nitrogen pool 80 100 exists as dissolved organic nitrogen don the don doc ratio is 1 11 mol mol typical of organic particulate material at the earth s surface the combination of photoautotrophy heterotrophy and weak chemical buffering within these microcosms promotes values of ph pco2 o2 saturation and percentage total dissolved nitrogen as don that reach 10 99 10 7 6 atm 160 and 100 respectively which are a unique combination among the surface waters on earth these ice sealed cryoconite holes could be important analogues of refugia on snowball earth and other icy planets

quantifying sand storage capacity of large woody debris on beaches using lidar abstract the sedimentological role of large woody debris lwd on beaches is understudied and is relevant for the morphodynamics of sandy high energy beach dune systems of the northeast pacific ocean on the west coast of canada this debris consists largely of historical escape logs from the coastal logging industry in areas with competent wind regimes lwd can trap appreciable amounts of windblown sand in the backshore which can alter beach foredune sediment budgets and initiate incipient dune formation as this additional store of sediment must be reworked first during high water events it provides an important buffer that reduces erosion of established foredunes this study examines the morphology and sand storage capacity of three backshore lwd deposits of varying morphologies on northeastern graham island haida gwaii queen charlotte islands british columbia canada a new method was developed using coincident high spatial resolution lidar data and digital orthophotographs to derive dems for distinct ground cover classes sand lwd these dems were then used to quantify relative storage capacities of lwd and sand in the backshore significant amounts of sand are stored within and around lwd on beaches in the study region existing storage quantities above hhwmt range from 9 19 10 4 to 1 39 10 5 kg m 1 beach width or 1 14 to 1 60 m storage depth the same lwd deposits have a further potential storage capacity ranging from 1 04 to 1 70 10 4 kg m 1 beach width or 0 21 to 0 28 m depth the relative storage capacity of these features is reflected in the backshore morphology of each site with sediment transport further into the backshore dependent upon the morphology and relative in filling of the log debris jam with this additional sediment storage log debris could enhance development of large incipient dunes in the backshore thereby buffering against increasing storminess and gradual sea level rise in the region as the use of precise lidar data is increasing in geomorphic research the development of a verifiable methodology for estimating beach dune storage volumes is timely

in situ quantification of supraglacial cryoconite morphodynamics using time lapse imaging an example from svalbard there is growing recognition of the significance of biologically active supraglacial dust cryoconite for glacial mass balance and ecology nonetheless the processes controlling the distribution transport and fate of cryoconite particles in the glacial system remain somewhat poorly understood here using a 216 hour time series of plot scale 0 04 m 2 images we quantify the small scale dynamics of cryoconite on longyearbreen svalbard we show significant fluctuations in the apparent cryoconite area and dispersion of cryoconite over the plot within the 9 day period of observations however the net movement of cryoconite across the ice surface averaged only 5 3 mm d 1 high resolution measurements of cryoconite granule motion showed constant random motion but weak correlation with meteorological forcing factors and no directional trends for individual particle movement the high resolution time series data suggest that there is no significant net transport of dispersed cryoconite material across glacier surfaces the areal coverage and motion of particles within and between cryoconite holes appears to be a product of differential melting leading to changes in plot scale microtopography local meltwater flow dynamics and weather dependent events these subtle processes of cryoconite redistribution may be significant for supraglacial albedo and have bearing on the surface energy balance at the glacier scale

comparison of cryoconite organic matter composition from arctic and antarctic glaciers at the molecular level abstract glacier surfaces are reservoirs that contain organic and inorganic debris referred to as cryoconite solar heating of this material results in the formation of water filled depressions that are colonized by a variety of microbes and are hypothesized to play a role in carbon cycling in glacier ecosystems recent studies on cryoconite deposits have focused on their contribution to carbon fluxes to determine whether they are a net source or sink for atmospheric co 2 to better understand carbon cycling in these unique ecosystems the molecular constituents of cryoconite organic matter com require further elucidation com samples from four glaciers were analyzed by targeted extraction of plant and microbial derived biomarkers in conjunction with non targeted nmr experiments to determine the com composition and potential sources several molecular proxies were applied to assess com degradation and microbial activity using samples from greenland the canadian arctic and antarctica com from canadian john evans glacier and greenlandic leverett glacier locations was more chemically heterogeneous than that from the antarctic likely due to inputs from higher plants mosses and sphagnum as suggested by the solvent extractable alkyl lipids and sterols and the detection of lignin and sphagnum derived phenols after cupric oxide chemolysis solid state 13 c nuclear magnetic resonance nmr experiments highlighted the bulk chemical functional groups of com allowing for a general assessment of its degradation stage from the alkyl o alkyl proxy whereas solution state 1 h nmr highlighted both microbial and plant contributions to base soluble extracts from these com samples the dominance of 1 h nmr signals from microbial protein peptides in base soluble extracts of com from antarctica joyce glacier and garwood glacier phospholipid fatty acid plfa biomarker detection and the absence of plant derived biomarkers in both the solvent and cupric oxide extracts suggests that this com is dominated by microbial derived material these results indicate that com carbon composition is dependent on the local glacier environment which may have a profound impact on carbon cycling and sequestration on glacier surfaces

high frequency sediment transport responses on a vegetated foredune wind flow and sand transport intensity were measured on the seaward slope of a vegetated foredune during a 16 h storm using an array of sonic anemometers and wenglor laser particle counters the foredune had a compound seaward slope with a wave cut scarp about 0 5 m high separating the upper vegetated portion from the lower dune ramp which was bare of vegetation wind direction veered from obliquely offshore at the start of the event to obliquely onshore during the storm peak and finally to directly onshore during the final 2 h as wind speed dropped to below threshold sand transport was initially inhibited by a brief period of rain at the start of the event but as the surface dried and wind speed increased sand transport was initiated over the entire seaward slope transport intensity was quite variable both temporally and spatially on the upper slope as a result of fluctuating wind speed and direction but overall magnitudes were similar over the whole length ten minute average transport intensity correlates strongly with mean wind speed measured at the dune crest and there is also strong correlation between instantaneous wind speed and transport intensity measured at the same locations when the data are smoothed with a 10 s running mean transport on the beach for onshore winds is decoupled from that on the seaward slope above the small scarp when the wind angle is highly oblique but for wind angles 45 from shore perpendicular some sand is transported onto the lower slope copyright 2012 john wiley sons ltd

analysis of coastal dune dynamics shoreline position and large woody debris at wickaninnish bay pacific rim national park british columbia large woody debris lwd and colonizing vegetation alter the sediment budgets and stability of coastal dune systems in british columbia lwd on beaches consists largely of historical escape logs f

temperature covariance in tree ring reconstructions and model simulations over the past millennium spatial covariance in the simulated temperature evolution over the past millennium has been reported to exceed that of multiproxy based reconstructions here we use tree ring based temperature reco

vegetation and sedimentation on coastal foredunes on a timescale of years to decades vegetated foredunes may show various modes of morphological development vegetation is one of the factors that determine the sedimentation pattern and thus morphology on the foredune in turn the vegetation pattern may be controlled by the sedimentation pattern although these effects have been quantified for short timescales there is relatively little information on the interaction between vegetation and sedimentation for timescales of over a year for the island of ameland the netherlands elevation measurements and aerial photographs between 2002 and 2012 were used to derive changes in elevation and vegetation patterns on a year to year basis this was done for a range of stable to accreting foredunes sedimentation increases from the beach to a maximum halfway up the seaward slope of the foredune and then decreases again when going landward this trend is further modified by the vegetation s spatial pattern on a timescale of years there is no correlation between the density of vegetation cover and the amount of accretion however by accounting for the gradual depletion of the sand load over the foredune a relationship can be defined between vegetation cover and its trapping efficiency foredune vegetation spreads mainly by lateral expansion of existing patches no strong effect was found of the sedimentation balance on the expansion of vegetation it is suggested that other growth limiting factors are of similar importance masking any possible dependency of vegetation growth on sand accretion

laser induced fluorescence emission life from lake fryxell antarctica cryoconites laser induced fluorescence emission life images were obtained in situ from a 27 cm long ice core at lake fryxell antarctica the excitation was accomplished with a simple 532 nm green laser pen light and the fluorescence images were captured with a small compact digital camera the targets for the experiment were mm scale cryoconite assemblages found in the ice covers of this perennially frozen antarctic lake the fluorescence response originates from photo pigments in cyanobacteria dominated cryoconite assemblages with phycoerythrin pe exhibiting the optimal target cross section this inexpensive low mass low energy method avoids manipulation of the in situ habitat and individual target organisms and does not disturb the microbial community or the surrounding ice matrix we establish the correlation between fluorescence intensity and pe concentration we show that cryoconite fluorescence response does not appear to decrease with depth in the ice cover in agreement with similar findings at lake untersee a perennially ice covered lake in dronning maud land antarctica optical reflection and refraction events at the air ice interface can complicate quantitative estimates of total pigment concentrations laser targeting of a single mm scale cryoconite can result in multiple neighboring excitation events secondary to reflection and refraction phenomena in the multiple air ice interface of the bubbles surrounding the primary target

aeolian flux of biotic and abiotic material in taylor valley antarctica abstract we studied patterns and mechanisms controlling wind driven flux of soils and associated organic matter in taylor valley antarctica over a 10 year period using passive aeolian traps and dynamic mass erosion particle counters deployment of the particle counters near meteorological stations allowed us to compare the magnitude of soil flux with data on prevailing wind particulate organic c n and p measurements on transported sediment allowed us to examine connectivity of wind dispersed organic matter among landscape units most sediment entrainment occurred within 20 cm of the soil surface during saltation bursts that occupied 1 sediment movement was highest in the up valley reaches of taylor valley and transport was down valley towards mcmurdo sound the general paucity of biological organic matter production throughout the mcmurdo dry valleys in concert with low fluvial transport makes aeolian distribution or organic c n and p an important factor in the distribution of organic matter throughout this polar desert ecosystem and increases connectivity among the ecosystem components

contrasting sea surface temperature of summer and winter monsoon variability in the northern arabian sea over the last 25 ka abstract the seasonal monsoon cycle with winds from the southwest sw in summer and from the northeast ne in winter strongly impacts on modern regional sea surface temperature sst patterns in the arabian sea northern indian ocean to reconstruct the temporal and spatial variation in the dynamically coupled winter and summer monsoon strength over the last 25 ka we analyzed alkenone derived sst variations in one sediment core from the northwestern arabian sea that is influenced by the summer monsoon sst affected by upwelling processes and in one core from the northeastern arabian sea where sst is mainly governed by the winter monsoon no upwelling comparison of the sst records reveals an antagonistic relationship of summer and winter monsoon strength throughout the late deglaciation and the holocene upwelling along the arabian peninsula associated with peak sw monsoonal wind strength was strongest during the early holocene climate optimum between 11 and 8 ka and coincided with the northernmost position of the intertropical convergence zone itcz marked by maximum precipitation over northern oman the sw monsoon weakened over the middle to late holocene while the ne monsoon gained strength this different evolution was caused by the southward displacement of the itcz throughout the holocene superimposed over the long term trend are variations in northeast monsoon wind strength at time scales of centuries that were synchronous with late holocene climate variations recorded on the asian continent and in the high latitude northern hemisphere their likely driving forces are insolation changes associated with sunspot cycles enhanced by feedback mechanisms e g land sea thermal contrast they enforced centennial scale fluctuations in wind strength and temperature in the northern arabian sea monsoon system

coastline orientation aeolian sediment transport and foredune and dunefield dynamics of mocambique beach southern brazil abstract this paper examines the role of coastline orientation on foredune and dunefield development at mocambique beach southern brazil the beach displays significant alongshore variations in exposure to the prevailing winds and waves grain size beach surfzone morphodynamic type foredune volume and type and dimensions of the holocene dune systems two wind analyses and calculation of aeolian drift potentials were carried out one based on 1 year of wind record and another based on a record of 34 years monthly topographic surveys of beach and foredunes on 5 profiles along mocambique beach were conducted over one year to obtain data on beach mobility and width aeolian sediment transport and foredune development southerly winds dominate and aeolian sediment supply is minimal in the south moderate in the central portion and high in the northern portion of the embayment the relationship between actual sediment supply foredune building and potential sediment supply is relatively poor over one year due to factors such as beach type and mobility beach moisture levels rainfall storm surge and wave scarping the intermediate term 34 year record indicates a strong relationship between foredune size and volume winds and shoreline orientation foredune volume is minimum in the southern part of the beach and greatest in the northern part of the beach the holocene barrier and dunefield development also reflects the long term control of shoreline orientation and increasing longshore gradient in exposure to southerly winds for the last 6000 7000 years a small foredune developed in the southern portion parabolics and small transgressive dunes in the central portion and a large scale transgressive dunefield in the northern portion

evolution of a foredune and backshore river complex on a high energy drift aligned beach abstract this paper examines the multi decadal evolution of a foredune and backshore river complex on a wave dominated drift aligned coast at wickaninnish bay on southwestern vancouver island british columbia canada local shoreline positions are generally prograding seaward as fast as 1 46 m a 1 in response to rapid regional tectonic uplift and positive onshore sediment budgets the northern end of the foredune system has extended rapidly alongshore in response to net northward littoral drift despite these net accretional responses the beach dune system experiences relatively frequent return interval 1 53 years erosive events when total water levels exceed a local erosional threshold elevation of 5 5 m above regional chart datum geomorphic recovery of the beach dune system from erosive events is usually rapid i e within a year by way of high onshore sand transport and aeolian delivery to the upper beach this response is complicated locally however by the influence of a backshore river that alters spatial temporal patterns of both intertidal and supratidal erosion and deposition historic landscape changes and rates of shoreline positional change are derived from several years of aerial photography 1973 1996 2007 2009 2012 using the usgs digital shoreline analysis system dsas significant volumetric changes are also estimated from aerial lidar derived dems in 2005 2009 and 2012 and related morphodynamics are interpreted using a statistically constrained geomorphic change detection method results suggest that supratidal bar development overwash deposition and aeolian deposition on a low lying supratidal platform combined with alongshore extension of the foredune complex is forcing sandhill creek to migrate northward in the direction of beach drift in response the river actively erodes 1 24 m a 1 a bluff system landward of the channel which generates substantial sediment volumes 0 137 m3 m 2 a 1 that feed a large intertidal braided channel and delta system these local responses provide context for a conceptual model of the evolution of a wave dominated drift aligned beach foredune system that interacts with a backshore river this model may provide useful information to local park managers as erosion and sedimentation hazards threaten visitor safety and park infrastructure

geomorphological analysis and classification of foredune ridges based on terrestrial laser scanning tls technology abstract along the north adriatic sea coast italy vulnerability to climate change is further aggravated by anthropogenic influences such as strong subsidence rate due to deep groundwater and gas abstraction tourism and industry impacts in this context conservation and restoration of coastal sand dunes become extremely important especially because of their importance in terms of natural coastal defense this paper proposes an innovative geomorphological approach based on terrestrial laser scanning tls which allows us to measure and monitor morphometric dune evolution with high precision and details several tls surveys were performed along the ravenna coast adriatic sea italy and the resulting digital elevation models dems were analyzed in order to classify the foredune ridges in three geomorphological sub zones the topographic areal and volumetric variations over time of geomorphological units were calculated by gis tools in order to identify seasonal trends or particular pattern meteo marine climate conditions were also analyzed and principal component analysis pca was performed to correlate changes in morphology with meteo marine forcing factors highlighting the ones that most influence dune evolution and dynamics

late holocene temperature fluctuations on the tibetan plateau abstract proxy data of palaeoclimate like ice cores tree rings and lake sediments document aspects of climate changes on the tibetan plateau during the last 2000 years the results show that the tibetan plateau experienced climatic episodes such as the warm intervals during ad 800 1100 and 1150 1400 the little ice age between ad 1400 and 1900 and an earlier cold period between the 4th and 6th centuries in addition temperatures varied from region to region across the plateau a warm period from ad 800 to 1100 in the northeastern tibetan plateau was contemporaneous with cooling in the southern tibetan plateau which experienced warming between ad 1150 and 1400 large scale trends in the temperature history from the northeastern tibetan plateau resemble those in eastern china more than the trends from the southern plateau the most notable similarities between the temperature variations of the tibetan plateau and eastern china are cold phases during ad 1100 1150 1500 1550 1650 1700 and 1800 1850

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

airflow and sand transport variations within a backshore parabolic dune plain complex ne graham island british columbia canada onshore aeolian sand transport beyond the beach and foredune is often overlooked in the morphodynamics and sediment budgets of sandy coastal systems this study provides detailed measurements of airflow sand transport via saltation and modified suspension vegetation density and surface elevation changes over an extensive 325 30 m swath of a backshore foredune parabolic dune plain complex near surface 30 cm wind speeds on the backshore ranged from 4 3 to 7 3 m s 1 gusting to 14 0 m s 1 oblique onshore flow is steered alongshore near the incipient foredune then landward into a trough blowout where streamline compression flow acceleration to 1 8 times the incident speed and increasing steadiness occur highest saltation rates occur in steady topographically accelerated flow within the blowout as such the blowout acts as a conduit to channel flow and sand through the foredune into the foredune plain beyond the blowout flow expands vegetation roughness increases and flow decelerates over the foredune plain localized flow steering and acceleration to 1 6 times the incident speed occurs followed by a drop to 40 of incident flow speed in a densely vegetated zone upwind of an active parabolic dune at 250 m from the foredune sediment properties reflect variations in near surface flow and transport processes well sorted fine skewed backshore sands become more poorly sorted and coarse skewed in the blowout due to winnowing of fines sorting improves and sands become fine skewed over the foredune plain toward the parabolic dune due to grainfall of finer sands winnowed from the beach and foredune during the fall winter season significant amounts of sand up to 110 kg m 2 are transported via modified suspension and deposited as grainfall up to 300 m landward of the foredune no distinct trend in grainfall was found although most fell on the depositional lobe of the blowout and at 200 m near an isolated active parabolic dune grainfall amounts may reflect several transporting events over the measurement period and the transport process is likely via localized modified suspension from the crest of the foredune and other compound dune features in the foredune plain this evidence suggests that the process of grainfall delivery though often overlooked in coastal research may be a key process in maintaining active dunes hundreds of metres from the shoreline in a densely vegetated foredune plain the effectiveness of this process is controlled by seasonal changes in vegetation cover and wind strength as well as shorter term e g tidally controlled variations in sand availability from the beach

a tree ring based precipitation reconstruction for the baluntai region on the southern slope of the central tien shan mountains china since a d 1464 abstract july june precipitation has been reconstructed back to a d 1464 for the baluntai region on the southern slope of the central tien shan mountains china using the picea schrenkiana tree ring width the reconstruction explains the variance of 51 in the observed precipitation from 1959 to 2005 by employing a 21 year moving average to the reconstruction nine periods with above average reconstructed precipitation comprised 1474 1503 1550 1577 1588 1619 1658 1713 1790 1812 1833 1867 1890 1907 1923 1944 and 1988 1995 eight periods with below average reconstruction consisted of 1504 1549 1578 1587 1620 1657 1714 1789 1813 1832 1868 1889 1908 1922 and 1945 1987 the wet dry periods of the reconstructed precipitation correspond well with other reconstructions some droughts in the historical documents are also precisely captured in the reconstruction precipitation variations for the southern slope of the central tien shan mountains are roughly synchronous with that of the northern slope in the recent 300 year power spectral and wavelet analysis demonstrated the existence of significant 100 y 60 y 50 y 16 y 10 y and 2 y cycles of variability

evaluation of glycerol dialkyl glycerol tetraether proxies for reconstruction of the paleo environment on the qinghai tibetan plateau the uplift of the qinghai tibetan plateau has a great effect on local and global climate changes here we report the late holocene climate change in the northern plateau by using a 3490 year sediment core record from kusai lake glycerol dialkyl glycerol tetraethers gdgts collected from the core were examined in combination with other paleo environmental proxies the reconstructed mean annual air temperatures maat using branched gdgt membrane lipids of certain bacteria proxies are higher than the measured maat but much closer to measured summer air temperatures suggesting a possibility of a bias of the reconstructed maat towards summer temperatures the ph values derived from a branched gdgt proxy show a negative correlation with toc a lake productivity indicator in arid regions furthermore both cbt ph and toc show temporal cyclic changes which suggest that the branched gdgt derived ph index may be useful in reconstructing paleo ph values in a lacustrine system lastly the composition of isoprenoid gdgts membrane lipids of archaea shows a major shift around 1400 bp which is in line with a large increase in sediment soluble salts at this time but lags behind the onset of salt mineral precipitation by 600 yr suggesting that change in archaeal community composition and salt mineral precipitation may require different threshold values of salinity the results of this study demonstrate that useful paleo climatic and paleo environmental information can be extracted from the gdgts preserved in lake sediments

early holocene to present palaeoenvironmental shifts and short climate events from the tropical wetland and lake sediments kukkal lake southern india geochemistry and palynology the kukkal basin tamil nadu india receives most of its rain from the southwest monsoon swm a sediment core from kukkal lake preserves a continuous sediment record from the early holocene to p

patterns of sand transport on vegetated foredunes the aeolian development of coastal foredunes is studied at two sites along the dutch coast amounts of sand transport are measured in cross sections over the foredunes and changes in surface height are monitored sand transport decreases rapidly landward of the vegetation boundary near the dunefoot changes in surface roughness and topography generate turbulence and upward flow causing a small part of the sand to be transported in suspension patterns of transport are found to be closely related to air flow which in turn is related to topography and vegetation density with steeper topography the amounts of sand transported landward from the dunefoot increase if vegetation density is low during oblique onshore winds most of the sand accumulates at the dune front during perpendicular onshore winds a large proportion of the sand is deposited landward of the slope when deflection of flow occurs landward transport of sand is interrupted