equilibrium line altitude variations with latitude today and during the late wisconsin abstract present day and late wisconsin glacier equilibrium line altitudes ela were compared on a transect from patagonia along the coastal cordillera to alaska and a transect from mexico along the sierra madre rocky mountains to alaska late wisconsin ela s were determined from cirques occupied during the late wisconsin and present day ela from observations of active cirque glaciers the mean change in ela from the late wisconsin to the present was 735 m with a standard deviation of 120 m this indicates that the change in snowline altitude from the present to the late wisconsin was approximately uniform and not latitudinally dependent

the bering land bridge a moisture barrier to the dispersal of steppe tundra biota the bering land bridge blb connected the two principal arctic biological refugia western and eastern beringia during intervals of lowered sea level in the pleistocene fossil evidence from lowland blb organic deposits dating to the last glaciation indicates that this broad region was dominated by shrub tundra vegetation and had a mesic climate the dominant ecosystem in western beringia and the interior regions of eastern beringia was steppe tundra with herbaceous plant communities and arid climate although western and eastern beringia shared many species in common during the late pleistocene there were a number of species that were restricted to only one side of the blb among the vertebrate fauna the woolly rhinoceros was found only to the west of the blb north american camels bonnet horned musk oxen and some horse species were found only to the east of the land bridge these were all steppe tundra inhabitants adapted to grazing the same phenomenon can be seen in the insect faunas of the western and eastern beringia the steppe tundra beetle fauna of western beringia was dominated by weevils of the genus stephanocleonus a group that was virtually absent from eastern beringia the dry adapted weevils lepidophorus lineaticollis and vitavitus thulius were important members of steppe tundra communities in eastern beringia but were either absent or rare in western beringia the leaf beetles chrysolina arctica c brunnicornis bermani and galeruca interrupta circumdata were typical members of the pleistocene steppe tundra communities of western beringia but absent from eastern beringia on the other hand some steppe tundra adapted leaf beetles managed to occupy both sides of the blb such as phaedon armoraciae much of the blb remains unstudied but on biogeographic grounds it appears that there was some kind of biological filter that blocked the movements of some steppe tundra plants and animals across the blb

origin and causes of the mammoth steppe a story of cloud cover woolly mammal tooth pits buckles and inside out beringia to account for the vastness of the northern arid steppes during glacial episodes i propose the proximate key variable was simply frequent clear skies this hitherto under emphasized point is the hub which best explains many questions low maritime cloud cover best accounts for today s tundra and in a related way the cloudy polar front accounts for the whole of the taiga even during glacial maxima the proximity of the sea to the bering isthmus created intermittent maritime cloud cover this regional cloud cover produced an ecological interruption or buckle of the arid steppe belt while this beringian mesic buckle did not serve as an intercontinental ecological barrier to most steppe adapted species it does seem to have limited the distributions of woolly rhinos camels american kiangs short faced bears badgers and some others at the beginning of the holocene this narrow refugium seems to have been a source of some mesic adapted species which colonized westward into the now tundra vegetation of northern asia and eastward into northern north america this holocene expansion from a limited and regional pleistocene refugium created our present misconceptions about beringia the mid strait mesic ecological conditions were the exception to the more extensive arid adapted communities of the mammoth steppe 2000 published by elsevier science ltd all rights reserved

periglacial cirque analogs elevation trends of cryoplanation terraces in eastern beringia abstract cryoplanation terraces are large erosional landforms common in cold unglaciated mountainous environments terrace sequences are composed of alternating slope segments with gently sloping treads and steep rubble covered risers and culminate in extensive summit flats many unglaciated upland landscapes in eastern beringia are dominated by these landforms indirect evidence indicates that they evolve through locally intensified weathering and mass movement processes associated with late lying snowcover geospatial analysis involving nearly 700 cryoplanation terraces in eastern beringia demonstrates that their elevation rises from 175 to 350 masl on bering sea islands to median values 1200 m near the alaska canada border the regional trends of cryoplanation terrace elevation are nearly identical to those of wisconsinan cirques on several transects across alaska the consistency in the elevation trends of glacial cirques and cryoplanation terraces indicates close genetic links between the two classes of feature involving topographic position continentality gradients and the mass balance of localized snow accumulations cryoplanation terraces can be considered the periglacial analogs of glacial cirques and have greater potential as sources of paleoclimatic information than smaller periglacial features more sensitive to short term climate variations process oriented studies age determinations and high resolution mapping are needed before the paleoenvironmental potential of these landforms can be realized fully

on the relationship between sst gradients boundary layer winds and convergence over the tropical oceans a linear mixed layer model that skillfully reproduces observed surface winds and convergence over the tropicaloceans is used to examine the relative influenceof boundarylayer and free tropospheric processes on the distribution of climatological surface winds and convergence the semiempirical model assumes a subcloud layer momentum force balance between pressure gradients coriolis acceleration linearized friction and downward momentum mixing and it utilizes boundary conditions from the 40 yr ecmwf re analysis era 40 observed pressure gradients are linearly decomposed into boundary layer defined as the region below 850 hpa and free tropospheric components and the surface winds and convergence associated with these components are computed results show that surface zonal winds are predominantly associated with a combination of free tropospheric pressure gradients and downward momentum mixing whereas the distribution of convergence is primarily due to boundary layer temperature gradients which are closely related to sst gradients the authors conclude that the climatological distribution of boundary layer convergence is primarily a function of the pattern of sst gradients and is better regarded as a cause rather than a consequence of deep convection

the rodents from the late middle pleistocene hominid bearing site of j bel irhoud morocco and their chronological and paleoenvironmental implications abstract the rodents from the late middle pleistocene hominin bearing locality of j bel irhoud include the following species meriones shawii gerbillus grandis dipodillus campestris paraethomys ras lemniscomys barbarus mus cf spretus and eliomys sp we consider m shawii a living species as identical with the middle pleistocene meriones maghrebianus the mouse differs from the domestic mus musculus but does not clearly fit into mus spretus either the rare g grandis looks identical with the form from the middle pleistocene of thomas quarries which may suggest a rather early age for irhoud this is in agreement with the occurrence of paraethomys a genus unknown in the upper pleistocene of morocco but the absence of the arvicolid ellobius suggests that the site is younger than other middle pleistocene sites doukkala ii sidi abderrahmane d2 and irhoud derbala virage paleoecological indicators such as the taxonomic habitat spectrum or the relative abundances of gerbillinae and murinae suggest a less xeric environment than in many earlier and later sites diversity indices comparable to those of other middle pleistocene sites point to similarly favorable conditions before the major climatic crisis close to the middle upper pleistocene boundary that drastically reduced rodent diversity in north africa

snowline depression in the tropics during the last glaciation five primary methods have been used to reconstruct pleistocene snowlines or equilibrium line altitudes elas in the tropics 23 53n 23 53s during the last glaciation but each has inherent errors that limit the accuracy of the results additional potential errorsin determiningela depression involveestimates of modernsnowline altitude datingresolution topographicreconstructionof former glaciers orographic e ects the presence of rockfall debris on glaciers and calculation of regional ela gradients eustatic sea level lowering during the last glaciation is an additional factor in uencing estimates of ela depression ela in cases where modern snowline lies above a mountain summit only a minimum value for ela can be obtained at 12 tropical sites in africa the americas to 103s latitude and paci c islands estimates of average ela range from 440 to 1400m but most fall in the range of 800 1000m mean 1 900 135m in a regional study of ela depression in the southern tropical andes 8 223s an average ela of ca 920 250m has been reported based on the assumption that glacier mass balance was controlled solely by ablation season temperature and assuming a full glacial temperature lapse rate of 63c km depression of mean annual temperature in glaciated alpine areas was ca 5 4 0 83c if adjusted for a sea level fall of 120m at the glacial maximum this value is reduced to 4 7 0 83c the gure is based on the unlikely assumption that accumulation on alpine glaciers has been invariant nevertheless it is similar to values of temperaturedepresson 5 6 43c for the last glaciationobtainedfrom variousterrestrial sites but contrasts with tropical sea surface temperature estimates that are only 1 33c cooler than present 2001 elsevier science ltd all rights reserved

laser ablation u series analysis of fossil bones and teeth abstract over the past decade we have applied laser ablation icp mass spectrometry u series analysis to a large number of bones and teeth the method is fast and provides high resolution data of u series isotopes which give insights into the complexity of uranium migration into within and out of bones in this paper we present our laser ablation approach in detail from the experimental set up to data reduction and uranium diffusion modelling laser ablation analysis can now be applied with minimum damage complete diffusion data sets can be obtained by laser drilling which leaves a hole of around 200 m in diameter and 1 2 mm depth if the natural u diffusion follows a simple single stage process valuable age information can be obtained in other cases highly complex u migrations have been observed which make any age assessment impossible two examples from wadjak and callao illustrate the potential of nearly non destructive laser ablation u series analysis of human skeletal tissues the results demonstrate the physical presence of modern humans in south east asia at a time when our species just started to migrate into europe

glacial cirques as palaeoenvironmental indicators their potential and limitations abstract glacial cirques are armchair shaped erosional hollows typified by steep headwalls and often overdeepened floors they reflect former regions of glacier initiation and their distribution is therefore linked to palaeoclimate because of this association cirques can be analysed for the information they provide about past environments an approach that has a strong heritage and has seen resurgence over recent years this paper provides a critical assessment of what cirques can tell us about past environments and considers their reliability as palaeoenvironmental proxies specific focus is placed on information that can be obtained from consideration of cirque distribution aspect altitude and morphometry the paper highlights the fact that cirques potentially provide information about the style duration and intensity of former glaciation as well as information about past temperatures precipitation gradients cloud cover and wind directions in all cirques are considered a valuable source of palaeoenvironmental information if used judiciously particularly as they are ubiquitous within formerly glaciated mountain ranges globally thus making regional or even global scale studies possible furthermore cirques often occupy remote and inaccessible regions where other palaeoenvironmental proxies may be limited or lacking

hominid cave at thomas quarry i casablanca morocco recent findings and their context the thomas quarry i locality was made famous in 1969 with the discovery of a human half mandible in a cave in 1985 further investigations revealed the presence of a lower acheulean assemblage in lower units of the section from 1988 onwards modern controlled excavations took place within the framework of the franco moroccan co operative project casablanca acheulean artefacts a rich mammalian fauna and four hominid teeth have been excavated from the cave the faunal set indicates an open woodland environment carcasses were processed by carnivores but cut marks are absent which raises the question of any human role in the bone accumulations stone knapping was mainly oriented towards flake production and a few bifaces have been imported into the site laser ablation icp ms dating combining the esr and u series data for the modelling of the u uptake has given an us esr age of 501 76 ka for a human premolar while new osl measurements yielded an age of 420 34 ka for sediments immediately above the dated tooth and 391 32 ka below nevertheless biostratigraphy and lithostratigraphy point towards a greater antiquity

understanding controls on cirque floor altitudes insights from kamchatka abstract glacial cirques reflect former regions of glacier initiation and are therefore used as indicators of past climate one specific way in which palaeoclimatic information is obtained from cirques is by analysing their elevations on the assumption that cirque floor altitudes are a proxy for climatically controlled equilibrium line altitudes elas during former periods of small scale cirque type glaciation however specific controls on cirque altitudes are rarely assessed and the validity of using cirque floor altitudes as a source of palaeoclimatic information remains open to question in order to address this here we analyse the distribution of 3520 ice free cirques on the kamchatka peninsula eastern russia and assess various controls on their floor altitudes in addition we analyse controls on the mid altitudes of 503 modern glaciers currently identifiable on the peninsula and make comparisons with the cirque altitude data the main study findings are that cirque floor altitudes increase steeply inland from the pacific suggesting that moisture availability i e proximity to the coastline played a key role in regulating the altitudes at which former cirque forming glaciers were able to initiate other factors such as latitude aspect topography geology and neo tectonics seem to have played a limited but not insignificant role in regulating cirque floor altitudes though south facing cirques are typically higher than their north facing equivalents potentially reflecting the impact of prevailing wind directions from the sse and or variations in solar radiation on the altitudes at which former glaciers were able to initiate trends in glacier and cirque altitudes across the peninsula are typically comparable i e values typically rise from both the north and south inland from the pacific coastline and where glaciers cirques are south facing yet the relationship with latitude is stronger for modern glaciers and the relationship with distance to the coastline and to a lesser degree with aspect is notably weaker these differences suggest that former glacier initiation leading to cirque formation was largely regulated by moisture availability during winter months and the control this exerted on accumulation whilst the survival of modern glaciers is also strongly regulated by the variety of climatic and non climatic factors that control ablation as a result relationships between modern glacier mid altitudes and peninsula wide climatic trends are more difficult to identify than when cirque floor altitudes are considered i e cirque forming glaciers were likely in climatic equilibrium whereas modern glaciers may not be

temperature and precipitation climate at the equilibrium line altitude of glaciers expressed by the degree day factor for melting snow several authors relate accumulation or precipitation at the glacier equilibrium line altitude ela to summer mean temperature using exponential or power law functions i analyze the accumulation temperature relation at the ela with a degree day model using data from the 1992 paper by a ohmura and others the dataset includes estimates at the ela of winter balance and of winter balance plus summer precipitation which represent respectively low and high estimates of annual accumulation which is seldom measured the ohmura dataset only lists summer mean temperature but i recover monthly temperatures for the whole year for 66 of the glaciers by assuming sinusoidal temperature variation through the year and using annual temperature range from a gridded climatology monthly degree day sums are then estimated from monthly mean temperature and summed to give annual totals so degree day factors for melting snow at the ela are obtained the degree day factors fall close to those reported in the literature for glacier snowmelt with averages of 3 5 1 4 and 4 6 1 4 mm d 1 k 1 for low and high accumulation estimates on the 66 glaciers the degree day model gives a family of accumulation temperature curves that depend upon the annual temperature range representing the contrast between maritime and continental climates

long term nivation rates cathedral massif northwestern british columbia cryoplanation terraces cts are large 3000 800 000 m2 erosional landforms found in upland periglacial environments two hypotheses for the formation of cts are supported in contemporary literatu

explaining the klasies pattern kua ethnoarchaeology the die kelders middle stone age archaeofauna long bone fragmentation and carnivore ravaging abstract the caves at klasies river mouth krm in the southern cape province south africa continue to play an important role in the study of human evolution and debates about the origins of modern humans as with most palaeolithic sites the behavioural interpretations offered for the middle stone age msa inhabitants of the krm caves are based in large part on the interpretation of fragmentary faunal remains from the main site or caves 1 1a 1b and 2 excavated in 1967 68 by singer wymer 1982 using zooarchaeological patterns detected in ethnoarchaeological data collected among kua foragers of the eastern kalahari central district botswana as well as in data collected from die kelders cave 1 layer 10 south africa we offer an alternative explanation for a provocative pattern of skeletal part representation discovered in the krm msa archaeofauna over 20 years ago by richard klein 1976 the klasies pattern is characterized by the underrepresentation of large bovid upper limb elements relative to more anatomically complete small bovids to date the pattern has been interpreted in three different ways each with strikingly different implications for middle stone age msa middle palaeolithic mp human behaviour understanding the nature of the pattern is not only important for reconstructing msa human behaviour at krm but it is also important for understanding how the conduct of zooarchaeological analyses can profoundly influence our reconstructions of the course of human behavioural evolution the kua ethnoarchaeological data and experimental case studies unambiguously connect to site formation histories to zooarchaeological patterns at die kelders cave 1 layer 10 the ethnoarchaeological expectations are expressed archaeologically in a context analytically relevant to krm overall by joining the kua and the die kelders data we show how uniformitarian actualistic approaches can be productively employed in zooarchaeological interpretation the klasies pattern is likely to be an artefact of a widespread taphonomic sequence followed by a particular style of analysis employed for practical reasons by many zooarchaeologists we suggest that the situation is common and likely to be seriously distorting inferences about many archaeofaunas around the world more generally we show how uniformitarian studies offer a coherent framework for developing methods and generating data useful in making behavioural inferences from faunal remains rather than a human behavioural signal in the krm archaeofauna the klasies pattern has more to do with the methods of zooarchaeology than with the behaviour of ancient people

late miocene early pliocene climatic evolution of the granada basin southern spain deduced from the paleoecology of the micromammal associations this paper analyses the relationship between the evolution of the late miocene and early pliocene rodent and insectivore assemblages from the granada basin southern spain and climate changes these climatic changes in terms of humidity and temperature fluctuations are inferred from variations of the relative abundances of taxons with definite ecological preferences there is a general tendency towards a temperature increase from the latest tortonian middle turolian to the messinian late turolian and towards a decrease from the mio pliocene boundary latest turolian earliest ruscinian to the end of the zanclean late ruscinian dry conditions predominate in the latest tortonian middle turolian at the beginning of the messinian late turolian there was a significant increase in humidity followed by an aridification throughout the end of the messinian and zanclean late turolian and ruscinian these climatic variations are in accordance with the sedimentary evolution of the basin and agree with the climatic interpretations inferred from the shallow marine carbonate sediments temperate tropical deposited in the marine basins of southeastern spain during the studied time interval

oldest human expansions in eurasia favouring and limiting factors 1 introductionon november 26e28 2008 an international conference wasorganised at the museum national d histoire naturelle paris france the topic was the oldest human expansions in eurasia under theaspect of the factors which could favour or limit the humansettlements while fossil human remains are scarce in eurasia lithicassemblages suggest at least two phases of human settlement or and techno cultural spread from africa to eurasia the rst one attested by mode 1 lithic industries is observed at dmanisi georgia at 1 8 ma in asia in china and pakistan around 2 ma and in europe for example in spain since 1 2e1 4 ma at orce atapuerca in italy monte poggiolo ca 1 ma pirro nord at least1 3 ma and in france pont de lavaud le vallonnet around 1 ma some dates in china and indonesia support the idea of earliersettlementsincontinentalandislandasiathanineurope whiletheoldest tool kit in africa dates to 2 6 ma kada gona ethiopia a second phase is marked by the appearance of new tools especially handaxes and cleavers these large tools do occur inafrica around 1 6e1 7 ma konso ethiopia kokiselei kenya andaround 1 4e1 2 ma in the middle east ubeidiya israel they areconsideredasthe rstindicatorsofacheuliantradition ormode2 consisting in shaping large tools on akes or blocks these toolsappear outside africa with different time lags according togeographical areas in asia the rst ones occur around 1 2 ma isampur india and then become more signi cant with anincreasing number of sites around 800 ka in eastern asia e china and south eastern asia ngebung java in western and southerneurope acheuliansitesonlyappeararound600e700ka asattestedbythe recent discoveriesin centreregion france la noira in chervalley and they become more numerous from 500 ka onwards inspain atapuerca galeria ambrona in italy visogliano castel diguido in northern and southern france somme river terraces caune de l arago in the european continent assemblages withbifaces characteristic of acheulian onlyoccurin a geographical areastretching from southern europe to great britain however theyare lacking in central europe and the rhine river is considered asa frontier but they do exist in the caucasus near the central asianborder while they are unknown further east in tadjikistan these two waves of populating probably include numerousarrivals and we do not know whether these arrivals led each timeto a permanentsettlement particularlyif the hominin groups weresmall and geographically dispersed this time lag between asia and europe regarding the peoplingphases and their consequences is debated today within the scien ti c community what could be the migratory paths from africa toboth asia and europe or from africa to asia then to europe whomoved homo antecessor homo heidelbergensis were there somecontacts between distinct human groups rather than shiftingpopulations these questions also concern the diffusion modalitiesof technical traditions and the effect of climatic and environmentalconditions on human movements the latter could explain chro nological lags and restriction of human settlements to some areasonly however it has to be kept in mind that convergencephenomena could also happen at a regional scale in the tool kits this may be the case for acheulian people the present state of knowledge on the earth s climatic storyduringthelasttwomillionyearsshowslocalphenomenacombinedto global changes for example increase of glaciations around800ka whenclimaticcyclesshiftedtothe100kaperiodicity astheeccentricity parameter of terrestrial orbit became more importantthan the obliquity of earth s axis earlier periodicity of 41 ka mis20 characterised by strong marine regression took place at thesame time as the matuyamaebrunhes geomagnetic inversion 780 ka and is considered as an accurate chronological marker recent results of various research teams contribute to builta more complete and precise picture of the past the betterknowledge of the palaeoenvironment allows a new appraisalregarding the spread of technical behaviours in relation to theenvironmental context highlighted by new issues concerningafrica some major questions were discussed during the conference 1 the geographical dispersal of each type of lithic industry 2 the chronological gaps in the hominin settlements in thevarious areas of eurasia 3 the periods when climatic or topographic variations had animportant role favouring or limiting the human expansion insome regions

equilibrium line altitudes during the last glacial maximum across the brooks range alaska equilibrium line altitudes elas were estimated for 383 reconstructed glaciers across the brooks range northern alaska to investigate their regional pattern during the last glacial max imum lgm glacier outlines were delimited based on published field mapping and the original interpretations of aerial photographs glacier margins were digitised from 1 63 360 scale maps into a geographic information system gis with a digital elevation model on a 60 m grid elas were cal culated for each reconstructed glacier using the accumulation area ratio method aar 0 58 the analysis was restricted to relatively simple cirque and valley glaciers that deposited clearly identifi able lgm moraines and that did not merge with the complex transection glacier ice that filled most troughs of the range the glaciers used in this analysis had areas ranging from 0 14 to 120 km 2 their elas rose from 470 m a s l in the western brooks range to 1860 m a s l in the east over a distance of 1000 km the elas were fitted with a third order polynomial trend surface to model their distribution across the range and to investigate the source of local scale variations the trend surface lowers toward the west and south similar to previously derived trends based on glaciation thresholds in addition elas in the northeastern part of the range lower northward toward the beaufort sea which has not been reported as strongly in other studies modern glacier elas also lower toward the south west the depression of lgm elas from modern glacier elas is greatest in the central brooks range a maximum of 700 m and decreases to the east 200 m the regional pattern of lgm elas points to the primary source of moisture from the north pacific as it is today the unexpected trend of lgm elas in the northeast part of the range is supported by recent field mapping where anomalous ice distribution and elas reflect complicated lgm climate patterns and possibly late quaternary tectonism copyright 2005 john wiley sons ltd

surface temperature lapse rates over complex terrain lessons from the cascade mountains lapse rates of 3 9 5 2 c km 1 substantially smaller than the often assumed 6 5 c km 1 the data sets show similar seasonal and diurnal variability with lapse rates smallest 2 5 3 5 c km 1 in late summer minimum temperatures and largest 6 5 7 5 c km 1 in spring maximum temperatures geographic windward versus lee side differences in lapse rates are found to be substantial using a simple runoff model we show the appreciable implications of these results for hydrological modeling

tropical oceanic rainfall and sea surface temperature structure parsing causation from correlation in the mjo abstractbased upon on the findings of y li and r e carbone the association of tropical rainfall with sst structure is further explored with emphasis on the mjo passband analyses include the tropical indian ocean maritime continent and tropical western pacific regions the authors examine the anomalies of and correlations between sst structure the frequency of rainfall events and rainfall amount based on detailed examination of a 49 month time series all findings are statistical inferences and interpretations consistent with established theory the statistical inferences are broadly consistent with a pivotal role played by the convergent laplacian of sst together with an expected but somewhat indirect role of sst itself the main role of sst in the mjo passband appears limited to production of moist static energy which is highly correlated with cumulative precipitation yet bears a decidedly conditional relationship to the occurrence of rainfall if rain occurs then more rain is likely over

the role of cryptotephra in refining the chronology of late pleistocene human evolution and cultural change in north africa abstract sites in north africa hold key information for dating the presence of homo sapiens and the distribution of middle stone age msa middle palaeolithic mp and later stone age lsa cultural activity in the late pleistocene here we present new and review recently published tephrochronological evidence for five cave sites in north africa with long msa mp and lsa cultural sequences four tephra horizons have been identified at the haua fteah cyrenaica libya they include cryptotephra evidence for the campanian ignimbrite ci eruption dating to 39 ka that allows correlation with other palaeolithic sequences in the eastern mediterranean and as far north as russia cryptotephra have also been recorded from the moroccan sites of taforalt rhafas and dar es soltane 1 at taforalt the geochemical composition suggests a provenance in the azores while examples from sodmein egypt appear to derive from central anatolia and another unknown source in these latter examples chemical compositional data from relevant proximal volcanic centres is currently lacking so the identification of tephra in layers of known age and cultural association provides the first reliable age determinations for distal volcanic events and their geographical extent the future potential for tephrochronological research in north africa is also discussed

pleistocene glacial history of the southern ahklun mountains southwestern alaska soil development morphometric and radiocarbon constraints abstract four new ams 14 c ages glacial mapping and measurements of soil development loess thickness and moraine morphology constrain the age and extent of at least three quaternary advances by outlet lobes of an ice cap over the ahklun mountains of southwestern alaska the relative age data are from 107 sites correlated to 25 ice marginal positions in the kanektok goodnews togiak and kulukak river valleys and along the southeastern flank of the range radiocarbon ages provide minimum ages for six and a maximum age for one of the former ice margins soil and morphometric parameters subdivide the ice limits into three relative age groups one to three pre wisconsin advances probably middle pleistocene in age are represented by drift with relatively thick b horizons 60 5 cm with bt horizons thick loess caps 80 12 cm and broad moraines 135 134 m with gentle side slopes 7 5 an extensive early wisconsin sensu lato s l advance 39 9 ka and three associated stillstands or readvances are characterized by intermediate soil and morphometric parameters bw and weak bt horizons with thicknesses of 40 11 cm loess thicknesses of 69 46 cm crest widths of 38 13 m and slope angles of 14 4 the maximum late wisconsin advance 16 9 ka and two readvances or stillstands are associated with thin 20 5 cm weakly to moderately developed bw horizons thin loess caps 28 8 cm narrow crest widths 28 9 m and steep slope angles 18 3 the data confirm that early wisconsin glaciers in southeast beringia were much more extensive than late wisconsin glaciers which were apparently limited by availability of moisture

uplift and denudation of the central alaska range a case study in the use of apatite fission track thermochronology to determine absolute uplift parameters apatite fission track thermochronology aftt on granitic samples collected in the central alaska range in conjunction with geologic constraints from basins to the north nenana basin and south cook inlet of the range is used to constrain the timing amount rate and pattern of surface uplift rock uplift and denudation since the late miocene the conversion from a thermal frame of reference apatite fission track data to an absolute frame of reference with respect to mean sea level which requires constraining the paleoland surface elevation the paleomean annual temperature and the paleogeothermal gradient is evaluated and shown to be viable in the context of an exhumed apatite partial annealing zone paz apatite ages at denali mount mckinley range from 16 ma near the summit 6 km elevation to 4 ma at 2 km elevation a distinctive break in slope in the apatite age profile at an elevation of 4 5 km also marked by a change in confined track length distributions marks the base of an exhumed apatite paz rock uplift and denudation are greatest at denali decreasing southward away from the mckinley strand of the denali fault system as shown by progressively older apatite ages 7 35 ma from a suite of samples along the kahiltna glacier a correlative decrease in topography occurs southward from the fault the central alaska range lies within an arc defined by the denali fault with the highest peaks including denali concentrated at the arc apex patterns of rock uplift and denudation within the central alaska range mimic topography between early and late miocene and possibly earlier the central alaska range was most likely an area of relative tectonic and thermal stability rock uplift denudation and mean surface uplift of the denali region began by the late miocene 5 6 ma being 8 5 km 5 7 km and 2 8 km respectively at average rates of 1 5 km m y 1 km m y and 0 5 km m y the amount of rock uplift denudation and surface uplift decreases to 3 km 2 km and 1 km at little switzerland some 45 km south of the denali fault we conclude that the topographic and rock uplift patterns of the central alaska range the shape and proximity of the mckinley strand of the denali fault to these patterns the timing of the onset of rock uplift and denudation at 5 6 ma and a significant change in relative plate motion between north america and the pacific plates circa 5 6 ma are all inherently related

cassini imaging of jupiter s atmosphere satellites and rings the cassini imaging science subsystem acquired about 26 000 images of the jupiter system as the spacecraft encountered the giant planet en route to saturn we report findings on jupiter s zonal winds convective storms low latitude upper troposphere polar stratosphere and northern aurora we also describe previously unseen emissions arising from io and europa in eclipse a giant volcanic plume over io s north pole disk resolved images of the satellite himalia circumstantial evidence for a causal relation between the satellites metis and adrastea and the main jovian ring and information on the nature of the ring particles

a framework for interpreting paleoclimatic variations in eastern beringia abstract paleoclimatic variations in a particular region can be viewed as the outcome of the superimposition of the effects of a number of large scale controls a framework for understanding paleoclimatic variations in a region can be established by considering the long term history of those controls jointly with climatic modeling results that illustrate how regional climates respond to changes of individual controls the relevant controls of late quaternary paleoclimatic variations in eastern beringia include 1 the size of the ice sheet which influences both atmospheric circulation and temperature 2 insolation which influences mainly temperature and seasonality 3 carbon dioxide concentration in the atmosphere which influences temperature and 4 feedbacks involving sea ice sea surface temperatures and snow cover which reinforce the insolation effects we review the results of a number of paleoclimatic experiments with general circulation models to illustrate the potential response of eastern beringia to the variations of these controls we then present a framework for understanding paleoclimatic variations in eastern beringia by describing the likely responses of the climate of this region to the known variations in the controls in addition we discuss key times during the quaternary when particular combinations of the controls give rise to natural experiments which lend themselves to the testing of particular hypotheses our understanding of the nature of climatic variations at high latitudes should increase through examination of paleoclimatic evidence that documents the response of the region at those key times

late cenozoic uplift of denali and its relation to relative plate motion and fault morphology apatite fission track analysis of samples that cover a 4 kilometer vertical section from the western flank of denali mount mckinley north america9s highest mountain suggests that the mountain massif was formed by rapid uplift 1 kilometer per million years beginning 6 million years ago ma uplift was a result of the morphology of the denali fault and a change in motion of the pacific plate with respect to north america at 5 ma which created opposing tangential vectors of relative movement along the fault and forced the intervening crustal blocks upward

late pleistocene glacial equilibrium line altitudes in the colorado front range a comparison of methods abstract six methods for approximating late pleistocene pinedale equilibrium line altitudes elas are compared for rapidity of data collection and error rmse from first order trend surfaces using the colorado front range trend surfaces computed from rapidly applied techniques such as glaciation threshold median altitude of small reconstructed glaciers and altitude of lowest cirque floors have relatively high rmses 97 186 m because they are subjectively derived and are based on small glaciers sensitive to microclimatic variability surfaces computed for accumulation area ratios aars and toe to headwall altitude ratios thars of large reconstructed glaciers show that an aar of 0 65 and a thar of 0 40 have the lowest rmses about 80 m and provide the same mean ela estimate about 3160 m as that of the more subjectively derived maximum altitudes of pinedale lateral moraines rmse 149 m second order trend surfaces demonstrate low elas in the latitudinal center of the front range perhaps due to higher winter accumulation there the mountains do not presently reach the ela for large glaciers and small front range cirque glaciers are not comparable to small glaciers existing during pinedale time therefore pleistocene ela depression and consequent temperature depression cannot reliably be ascertained from the calculated ela surfaces

the role of thermal stress fatigue in the breakdown of rock in cold regions abstract many geomorphological studies have ignored the role of thermal stress fatigue engineers have long maintained that thermal stress is an effective process physicists and the ceramics industry have provided a theoretical foundation to explain the nature and mode of operation of thermal breakdown recent geomorphological studies have shown the importance of thermal stress in cold regions by means of high frequency rock temperature data which can identify rates of temperature change in excess of 2 c min 1 the occurrence of weathered material in cold but dry regions can be explained by thermal stress shock differential radiation receipts on slopes of varying orientation and gradient can exert a very strong effect

explicitly simulated tropical convection over idealized warm pools 1 two dimensional cloud system resolving simulations of convection over idealized warm pools are conducted to examine the relationship between the spatial patterns of tropical convection and the sea surface temperature sst distributions results show that the most active convection resides near the edge of warm pools with a local minimum around the warmest center this finding might provide an interpretation for the observations that peak convection is commonly located several degrees of latitude off the maximum sst over some tropical oceans factors potentially affecting the convective patterns are explored through sensitivity experiments it is found that convection expands significantly and rainfall peaks are further displaced several hundred more kilometers away from the warmest water when the radiative cooling heating is applied homogeneously across the domain conversely when the wind induced surface flux variability is excluded convective activity is confined within a much narrower area of high ssts but the overall spatial pattern is largely retained moreover the surface friction exerts profound effects on the simulated convection and attendant large scale flow and is mostly responsible for the dual maximum precipitation and two cell circulation structure in the horizontal these results suggest that as well as the temperature pressure gradients resulting from the non uniform ssts other processes must be taken into consideration in the interpretation of observed tropical convection and circulation

the earliest occupation of north africa the moroccan perspective abstract the long sequence at casablanca covers the past 5 5 ma the oldest lithic assemblages are found in late lower pleistocene deposits ca 1 ma in unit l of thomas quarry 1 and consist of acheulean artefacts made from quartzite and flint the first human remains discovered in this area were found in younger middle pleistocene deposits and cover an important period of human evolution between homo erectus and modern homo they are associated with acheulean artefacts and rich faunal assemblages in caves littorina cave at sidi abderrahman caves at thomas quarries 1 and 3 the variability of acheulean assemblages is well documented following recent excavations in various sites around the well known locality of sidi abderrahman bears cave cap chatelier unit l and hominid cave at thomas quarry 1 rhino cave at oulad hamida quarry 1 sidi abderrahman extension and sidi al khadir open air sites the casablanca sequence offers useful data for comparison with those from other african areas where hominids appeared and developed and should thus be considered in the debate on the earliest occupation of europe

excitation of rainfall over the tropical western pacific abstractthe authors have examined 4 years of satellite derived sst and rainfall data in anticipation of a relationship between sst structure and the excitation of convective rainfall the results exhibit a strong excitation signal consistent with the presence of mesoscale sst gradients in about 75 of approximately 10 000 rainfall onset events rainfall onset events occur at locations with enhanced horizontal convergence as inferred by the laplacian of sst on scales of order 100 km the daily sst field exhibits multiscale patchiness spanning a 2 c range the signal is disproportionately large at ssts that are 0 25 c above the mean near 29 5 c disproportionately weak for sst 28 8 c and proportionately neutral for sst 30 3 c the calculations suggest that a characteristic strength of this lower boundary forcing 3 10 5 s 1 is approximately one order of magnitude stronger than the mean regional background forcing 3 10 6 s 1 the periphery of warm oceanic patches exhibits both convergent an

marine resources exploitation by palaeolithic hunter fisher gatherers and neolithic tribal societies in the historical region of the strait of gibraltar this work has been financially supported by the benzu project spanish ministry of culture and ceuta government158 08 pv benzu cv the project dges har2008 06477 c03 02 the aecid hispanic moroccan projects pci a 2893 05 a 6317 06 and a 010823 07 and junta de andalucia project p07 hum 03015 authors are grateful to carol and paul beven and ana durante for their editorial assistance and to the anonymous referees for their helpful suggestions also we are grateful to ivan briz and marco madella for the corrections and suggestions

percussion marks on bone surfaces as a new diagnostic of hominid behaviour since stone tool cut marks and carnivore tooth marks were first described systematically on plio pleistocene archaeological bone1 2 bone surface modification has played a prominent role in interpreting early archaeological site formation and hominid behaviour3 15 here we introduce a new class of bone surface modification which we call percussion marks percussion marks were produced during experimental breakage of marrow bones and occur as pits or grooves impressed on a bone s surface by natural protrusions on the granitic hammerstone and anvil used although percussion marks can superficially mimic carnivore tooth marks they nonetheless are closely associated with hammerstone impact notches and show consistent micromorphological features which distinguish them from tooth marks and other classes of bone surface modification given indications of prehistoric hammer stone breakage of marrow bones1 7 an awareness of percussion marks is critical for accurately identifying the biological agents of bone modification at archaeological sites and provides a new diagnostic of carcass processing by hominids

influence of ocean surface conditions on atmospheric vertical thermodynamic structure and deep convection abstract the authors analyze the influence of sea surface temperature sst and surface wind divergence on atmospheric thermodynamic structure and the resulting effects on the occurrence of deep convection using national meteorological center radiosonde data and international satellite cloud climatology program data for july 1983 july 1985 the onset of deep convection requires not only the existence of positive convective available potential energy cape but also an unstable planetary boundary layer pbl a stable pbl is observed to suppress deep convection even when cape is positive variations of sst have a major effect on cape but surface wind divergence can also affect deep convection by changing the lapse rate in the lower troposphere and humidity in the pbl specifically when sst 28 c cape is always positive and surface wind divergence does not qualitatively change the buoyancy profile above the pbl strong surface wind divergence however stabilizes the pbl so as to suppress the initiation

equilibrium line altitudes and paleoenvironment in the merchants bay area baffin island n w t canada the fiordlands south of merchants bay contain an extensive well preserved moraine record of a late foxe advance of local valley glaciers this has allowed accurate reconstruction of former glacier margins and computation of former equilibrium line altitudes elas by a variety of methods statistical comparison of three methods maximum lateral moraine elevation median elevation and accumulation area ratio aar shows that different techniques can give different results for the same glaciers lateral moraines gave estimates that were too low probably due to post glacial erosion or to non deposition median elevations and the aar method produced statistically similar results but only for glaciers of simple geometry the median elevation method fails to take into account variations in valley morphology and glaciological parameters and so is not reliable in all situations the aar method is supported by empirical evidence and is the best of the three methods for estimating former elas analysis of trend surfaces of present and late foxe elas shows changes in elevation and orientation through time due to changing environmental factors present elas are strongly influenced by local factors southerly storm tracks and warm maritime conditions paleo elas do not show this influence suggesting that davis strait may have been ice covered during the late foxe stade and that storm tracks were from the north

do periglacial landscapes evolve under periglacial conditions polar and alpine periglacial areas are traditionally regarded as necessarily submitted to very efficient frost driven processes that control the holocene and ongoing geomorphic activity during the last decade the validity of this academic view has been increasingly questioned among the international scientific community the search for the real past and present processes responsible for landform evolution in cold nonglaciated areas is based mainly on more and more refined monitoring protocols relying upon sophisticated equipment to assess the representativeness and significance of monitoring data collected in restricted sites it appears necessary however to widen the perspective by adopting a twofold multiscale approach as proposed in the present paper 1 in space by integrating various scales from the general slope system to the bioclimatic nanoenvironment and 2 in time by taking into account the landscape history from tertiary inherited features to recent process changes induced by the contemporary warming reintegrating the historical approach should help both to place the ongoing processes within a succession and or combination of interoperating processes and to avoid misinterpretations of features considered wrongly as emblematic of frost action overall both the historical and monitoring approaches tend to reduce the geomorphic efficiency of frost derived processes instead the role of noncold related processes such as chemical thermal biogenic and rainfall induced ones is being emphasized of special interest would be an interdisciplinary discussion between geomorphologists and various disciplines of biological sciences including biochemistry and ecology studying processes of primary successions

age and development of active cryoplanation terraces in the alpine permafrost zone at svartkampan jotunheimen southern norway schmidt hammer exposure age dating shd of boulders on cryoplanation terrace treads and associated bedrock cliff faces revealed holocene ages ranging from 0 825 to 8890 1185 yr the cliffs were significantly younger than the inner treads which tended to be younger than the outer treads radiocarbon dates from the regolith of 3854 to 4821 cal yr bp 2 range indicated maximum rates of cliff recession of 0 1 mm year which suggests the onset of terrace formation prior to the last glacial maximum age angularity and size of clasts together with planation across bedrock structures and the seepage of groundwater from the cliff foot all support a process based conceptual model of cryoplanation terrace development in which frost weathering leads to parallel cliff recession and hence terrace extension the availability of groundwater during autumn freeze back is viewed as critical for frost wedging and or the growth of segregation ice during prolonged winter frost penetration permafrost promotes cryoplanation by providing an impermeable frost table beneath the active layer focusing groundwater flow and supplying water for sediment transport by solifluction across the tread snowbeds are considered an effect rather than a cause of cryoplanation terraces and cryoplanation is seen as distinct from nivation

interannual variability of western north pacific sst anomalies and its impact on north pacific and north america in this study the interannual variability of sea surface temperature sst and its atmospheric teleconnection over the western north pacific wnp toward the north pacific north america during boreal winter are investigated first we defined the wnp mode as the first empirical orthogonal function eof mode of sst anomalies over the wnp region 100 165 e 0 35 n of which the principle component time series are significantly correlated with several well known climate modes such as the warm pool mode which is the second eof mode of the tropical to north pacific sst anomalies north pacific oscillation npo north pacific gyre oscillation npgo and central pacific cp el nino at 95 confidence level but not correlated with the eastern pacific ep el nino the warm phase of the wnp mode sea surface warming is initiated by anomalous southerly winds through reduction of wind speed with the background of northerly mean winds over the wnp during boreal winter i e reduced evaporative cooling meanwhile the atmospheric response to the sst warming pattern and its diabatic heating further enhance the southerly wind anomaly referred to the wind evaporation sst wes feedback thus the wnp mode is developed and maintained through winter until spring when the northerly mean wind disappears furthermore it is also known that anomalous upper level divergence associated with wnp mode leads to the npo like structure over the north pacific and the east west pressure contrast pattern over the north america through rossby wave propagation impacting the climate over the north pacific and north america

new age estimates for the palaeolithic assemblages and pleistocene succession of casablanca morocco marine and aeolian quaternary sediments from casablanca morocco were dated using the optically stimulated luminescence osl signal of quartz grains these sediments form part of an extensive succession spanning the pleistocene and contain a rich faunal and archaeological record including an acheulian lithic assemblage from before the brunhes matayama boundary and a homo erectus jaw from younger cave deposits sediment samples from the sites of reddad ben ali oulad j mel sidi abderhamane and thomas quarries have been dated in order to assess the upper limits of osl the revision of previously measured mammalian tooth enamel electron spin resonance esr dates from the grotte des rhinoceros oulad hamida quarry 1 incorporating updated environmental dose rate measurements and attenuation calculations also provide chronological constraint for the archaeological material preserved at thomas quarries several osl age estimates extend back to around 500 000 years with a single sample providing an osl age close to 1 ma in magnetically reversed sediments these luminescence dates are some of the oldest determined and their reliability is assessed using both internal criteria based on stratigraphic consistency and external lithostratigraphic morphostratigraphic and independent chronological constraints for most samples good internal agreement is observed using single aliquot regenerative dose osl measurements while multiple aliquot additive dose measurements generally have poorer resolution and consistency novel slow component and component resolved osl approaches applied to four samples provide significantly enhanced dating precision and an examination of the degree of signal zeroing at deposition a comparison of the osl age estimates with the updated esr dates and one u series date demonstrate that this method has great potential for providing reliable age estimates for sediments of this antiquity we consider the cause of some slight age inversion observed at thomas quarries and provide recommendations for further luminescence dating within this succession

in situ u series dating by laser ablation multi collector icpms new prospects for quaternary geochronology the capabilities and potential applications of in situ dating of quaternary materials using laser ablation mc icpms are explored 234 u 238 u and 230 th 234 u can be measured with precision sufficient for dating at a spatial resolution of 100mm or better in samples that contain as a little as 1 ppm uranium moreover u and th concentrations and u series isotope ratios can be continuously profiled to determine changes in age that occur with sample growth e g in speleothems these capabilities additionally permit the dating of bones teeth and possibly molluscs which are subject to post mortem open system behaviour of useries isotopes and can be employed to elucidate processes of u series migration during weathering and diagenesis a drawback of laser ablation mc icpms is that it cannot in general provide u series age estimates with the high precision and accuracy of conventional tims or solution mc icpms methods however sample preparation is straightforward the amount of sample consumed negligible and it can be used to rapidly characterise or screen and select samples from which more precise and accurate dates can be obtained using conventional methods given further instrumental developments and the establishment of suitable matrix matched standards for carbonates and other materials we foresee that laser ablation mc icpms will play an increasingly important role in quaternary dating research r 2005 published by elsevier ltd

cosmogenic 10be and 36cl geochronology of cryoplanation terraces in the alaskan yukon tanana upland cryoplanation terraces are prominent but enigmatic landforms found in present and past periglacial environments geomorphologists have debated for more than a century over processes involved in the formation of these elevated step like bedrock features presented here are the first numerical surface exposure ages and scarp retreat rates from cryoplanation terraces in the yukon tanana upland ytu in alaska part of unglaciated eastern beringia obtained from terrestrial cosmogenic nuclides tcn in surface boulders ages comprise six 10be tcn ages from two terrace treads near eagle summit and six 36 cl ages from two treads on mt fairplay based on these exposure ages scarps at both locations were last actively eroding from 49 to 22 4 ka both locations exhibit time transgressive development particularly near scarp tread junctions boulder exposure ages and distances between sampled boulder locations were used to estimate scarp retreat rates of 0 11 to 0 56 cm yr these numerical exposure ages presented here demonstrate that the cryoplanation terraces in the ytu are diachronous surfaces actively eroding during multiple cold intervals with these results hypotheses for cryoplanation terrace formation are discussed and evaluated for the ytu including those based on geologic structure nivation and the influence of permafrost

a simple model of climatological rainfall and vertical motion patterns over the tropical oceans abstract a simple model is developed that predicts climatological rainfall vertical motion and diabatic heating profiles over the tropical oceans given the sea surface temperature sst using statistical relationships deduced from the 40 yr ecmwf re analysis era 40 the model allows for two modes of variability in the vertical motion profiles a shallow mode responsible for all boundary layer convergence between 850 hpa and the surface and a deep mode with no boundary layer convergence the model is based on the argument expressed in the authors companion paper that boundary layer convergence can be usefully viewed as a forcing on deep convection not just a result thereof the shallow mode is either specified from satellite observations or modeled using a simple mixed layer model that has sst as well as 850 hpa geopotential height winds and temperature as boundary conditions the deep mode amplitude is empirically shown to be proportional to a simple measure of conditional instability in conve

trends in upper level cloud cover and surface divergence over the tropical indo pacific ocean between 1952 and 1997 1 this study investigates the spatial pattern of linear trends in surface observed upper level combined midlevel and high level cloud cover precipitation and surface divergence over the tropical indo pacific ocean during 1952 1997 cloud values were obtained from the extended edited cloud report archive eecra precipitation values were obtained from the hulme climate research unit data set and surface divergence was alternatively calculated from wind reported by comprehensive ocean atmosphere data set and from wind derived from smith and reynolds extended reconstructed sea level pressure data between 1952 and 1997 upper level cloud cover increased by about 4 sky cover over the central equatorial south pacific and decreased by about 4 6 sky cover over the adjacent subtropics the western pacific and the equatorial indian ocean trends in precipitation and surface convergence are usually positive where upper level cover trends are positive and negative where they are negative consistency between time series of upper level cloud cover reported by eecra and the international satellite cloud climatology project isccp during 1984 1997 for various subregions provides further confirmation that the surface observed upper cloud trends are real estimated radiative effects of surface observed cloud cover anomalies are also well correlated with all sky radiation flux anomalies reported by the earth radiation budget satellite in most areas contrastingly eecra and isccp low level cloud cover regional time series exhibit little correspondence and eecra low level cloud cover trends are uniformly positive across the tropical indo pacific with no apparent relationship to changes in surface divergence although the spatial pattern of upper level cloud trends resembles that associated with el nino the trends are approximately three times larger than those predicted by a linear relationship to sea surface temperature in the nino3 4 region

the impact of tropical western pacific convection on the north pacific atmospheric circulation during the boreal winter in this study we investigate the impact of atmospheric convection over the western tropical pacific 100 145 e 0 20 n on the boreal winter north pacific atmosphere flow by analyzing national center for environmental prediction reanalysis 1 extended reconstructed sea surface temperature and global precipitation climatology project data the western tropical pacific convection is not only the main energy source driving the local hadley and walker circulations but it also significantly influences north pacific circulation by modifying a mid latitude jet stream through the connection with the local hadley circulation on the one hand this strong convection leads to a northward expansion of local hadley cells simultaneous with a northward movement of the western north pacific jet because of the close correlation between the jet and hadley circulation boundaries on the other hand this strong convection also intensifies tropical pacific walker circulation which reduces the eastern pacific sea surface temperature resembling a la nina state through the enhanced equatorial upwelling the cooling of the eastern tropical pacific has an inter tropical convergence zone located further north thus the local hadley circulation moves northward as a result the jet axis over the eastern north pacific which also corresponds to the boundary of the local hadley circulation moves to higher latitude consequently this northward movement of the jet axis over the north pacific is reflected as a northwest southeast dipole sea level pressure slp pattern the composite analysis of slp over the north pacific against the omega pa s at 500 hpa over the western tropical pacific actually reveals that this northwest southeast dipole structure is attributed to the intensified tropical western pacific convection which pushes the pacific jet to the north finally we also analyzed south pacific for the austral winter as did previously to north pacific and found that the results were consistent

small mammals from marine isotope stage 5 at klasies river south africa reconstructing the local palaeoenvironment abstract klasies river a significant middle stone age msa site preserves remains of anatomically modern humans and a 21 m sequence of human habitation that shows use of sophisticated lithic technology and systematic exploitation of marine and terrestrial resources in this paper micromammals recovered from the lower msa sequence msa i and msa ii at klasies river main site have been analysed to provide proxy data for palaeoenvironmental reconstruction small mammals recovered from 183 separate layers ensure a detailed record of local climate and vegetation during marine isotope stage mis 5 taphonomic analyses indicate that avian predators accumulated the micromammals analysis of post depositional processes has provided information on intra site variability and utilisation the palaeoenvironmental reconstruction shows changes in rainfall seasonality within mis 5 there was transient movement towards more aseasonal rainfall and significant alterations in the vegetation composition from mis 5e to mis 5a our study adds new insights to palaeoenvironmental conditions on the cape coast during mis 5

enhanced bedrock weathering in association with late lying snowpatches evidence from livingston island antarctica an indication of the extent of weathering on different aspects of rock outcrops on livingston island antarctica was obtained by means of a schmidt hammer a cone indenter and measurement of weathering rind thickness results show that weathering particularly chemical weathering is enhanced on the lee side of outcrops where snow accumulates as a result of prolonged wetting by the melting snow rock moisture and temperature data indicate that the south facing snow accumulation side of obstacles have high rock moisture levels and maintain relatively high temperatures whilst chemical weathering is greater on the leeward side of outcrops mechanical processes are greater on the windward side the presence of late lying snow thus appears to exert a strong influence on weathering

low and high frequency climate variability in eastern beringia during the past 25 000 yearsthis article is one of a series of papers published in this special issue on the theme polar climate stability network we present new temperature and precipitation reconstructions for the past 25 000 cal years bp from across eastern beringia based on a network of pollen diagrams an updated modern pollen calibration database and an improved methodology using the modern analogue technique mat time series show july temperatures were around 4 c lower during full glacial and january temperatures were about 2 c lower than present annual temperatures rose beginning around 16 000 cal years bp reaching a maximum around 12 000 cal year bp the warming was more rapid in southern beringia annual precipitation varied by 250 mm during the past 25 000 cal years bp maps of reconstructed precipitation patterns show increasingly drier conditions since 12 000 cal years bp that vary regionally suggesting holocene atmospheric circulation changes at multiple time and space scales orbitally forced seasonality changes during the late glacial and early holocene resulted in reversed seasonal temperature reconstructions due to me

late pleistocene mountain glaciation in alaska key chronologies moraine sequences of mountain glaciers can be used to infer spatial and temporal patterns of climate change across the globe alaska is an accessible high latitude location in the northern hemisphere and contains a rich record of alpine glaciation here we highlight the key chronologies from three mountain ranges in alaska that reveal the timing and spatial extent of late pleistocene glaciation and pay particular attention to age of the penultimate glaciation the most extensive glacier advance of the last glaciation occurred prior to the last global glacial maximum cosmogenic exposure ages from moraine boulders in three sites spanning 800km indicate that this penultimateadvancemostlikelyculminatedduringmarineisotopestage mis 4orearlymis3 during mis 2 more limited glacier expansion generated multiple moraines that span from prior to the global last glacial maximum lgm through the lateglacial period glaciers retreated from their terminal positions ca 27 25ka in arctic alaska and ca 22 19ka in southern alaska moraines in at least two ranges date to 12 11ka indicating a glacial advance during the younger dryas period reconstructed equilibrium line altitudes of both penultimate and mis 2 glaciers were lowered only 300 600m much less than elsewhere in the americas alaska is documented to have been more arid during mis 2 perhaps due in large part to the exposure of the bering chukchi platform during eustatic sea level lowering the restricted ice extent is also consistent with the output of climate models that simulate a lack of significant summer cooling copyright 2008 john wiley sons ltd

late quaternary paleoclimate of western alaska inferred from fossil chironomids and its relation to vegetation histories abstract fossil chironomidae assemblages with a few chaoboridae and ceratopogonidae from zagoskin and burial lakes in western alaska provide quantitative reconstructions of mean july air temperatures for periods of the late middle wisconsin 39 000 34 000 cal yr b p to the present inferred temperatures are compared with previously analyzed pollen data from each site summarized here by indirect ordination paleotemperature trends reveal substantial differences in the timing of climatic warming following the late wisconsin at each site although chronological uncertainty exists zagoskin lake shows early warming beginning at about 21 000 cal yr b p whereas warming at burial lake begins 4000 years later summer climates during the last glacial maximum lgm were on average 3 5 c below the modern temperatures at each site major shifts in vegetation occurred from 19 000 to 10 000 cal yr b p at zagoskin lake and from 17 000 to 10 000 cal yr b p at burial lake vegetation shifts followed climatic warming when temperatures neared modern values both sites provide evidence of an early postglacial thermal maximum at 12 300 cal yr b p these chironomid records combined with other insect based climatic reconstructions from beringia indicate that during the lgm 1 greater continentality likely influenced regions adjacent to the bering land bridge and 2 summer climates were at times not dominated by severe cold

enhanced boulder weathering under late lying snowpatches a schmidt test hammer was employed to assess the aggregate surface hardness of samples of boulders dug out from under late lying snowpatches at sites in switzerland scotland and norway the results were compared with an equivalent set of readings made on boulders at nearby snow free control sites the results in every case reveal that the aggregate surface hardness of boulders buried by late lying snow is significantly less at the 0 001 level than that of boulders at the corresponding control sites this result indicates that late lying snow significantly enhances rock weathering probably because boulder and rock surfaces are exposed to prolonged wetting by percolating meltwater under late lying snowbeds