variability of el nino southern oscillation activity at millennial timescales during the holocene epoch the variability of el nino southern oscillation enso during the holocene epoch in particular on millennial timescales is poorly understood palaeoclimate studies have documented enso variability for selected intervals in the holocene but most records are either too short or insufficiently resolved to investigate variability on millennial scales1 2 3 here we present a record of sedimentation in laguna pallcacocha southern ecuador which is strongly influenced by enso variability and covers the past 12 000 years continuously we find that changes on a timescale of 2 8 years which we attribute to warm enso events become more frequent over the holocene until about 1 200 years ago and then decline towards the present periods of relatively high and low enso activity alternating at a timescale of about 2 000 years are superimposed on this long term trend we attribute the long term trend to orbitally induced changes in insolation and suggest internal enso dynamics as a possible cause of the millennial variability however the millennial oscillation will need to be confirmed in other enso proxy records

present day south american climate abstract this paper documents the main features of the climate and climate variability over south america on the basis of instrumental observations gathered during the 20th century it should provide a modern reference framework for paleoclimate research in south america targeting high resolution proxies over the past few centuries several datasets suitable for present day climate research are first described highlighting their advantages as well as their limitations we then provide a basic physical understanding of the mean annual cycle of the precipitation and atmospheric circulation over the continent and the adjacent oceans in particular the diversity of precipitation temperature and wind patterns is interpreted in terms of the long meridional extent of the continent and the disruption of the large scale circulation caused by the andes cordillera the contrasting oceanic boundary conditions and the landmass distribution similarly the intensity and timing of the interannual and interdecadal climatic fluctuations exhibit considerable geographical dependence as some regions are more influenced by large scale phenomena rooted in the tropical oceans while others are more influenced by high latitude phenomena the impact of these large scale phenomena over south america is documented by a regression analysis between selected atmospheric indices and the precipitation and temperature fields we have included a discussion on the seasonality and long term stability of such impacts and complemented our general description by an updated review of the literature on climate variability over specific regions

patagonian and southern south atlantic view of holocene climate abstract we present a comprehensive 10be chronology for holocene moraines in the lago argentino basin on the east side of the south patagonian icefield we focus on three different areas where prior studies show ample glacier moraine records exist because they were formed by outlet glaciers sensitive to climate change the 10be dated records are from the lago pearson herminita peninsula brazo upsala and lago frias areas which span a distance of almost 100 km adjacent to the modern icefield new 10be ages show that expanded glaciers and moraine building events occurred at least at 6120 390 n 13 4450 220 n 7 1450 or 1410 110 n 18 360 30 n 5 and 240 20 n 8 years ago furthermore other less well dated glacier expansions of the upsala glacier occurred between 1400 and 1000 and 2300 and 2000 years ago the most extensive glaciers occurred over the interval from 6100 to 4500 years ago and their margins over the last 600 years were well within and lower than those in the middle holocene the 10be ages agree with 14c limiting data for the glacier histories in this area we then link southern south american adjacent south atlantic and other southern hemisphere records to elucidate broader regional patterns of climate and their possible causes in the early holocene a far southward position of the westerly winds fostered warmth small patagonian glaciers and reduced sea ice coverage over the south atlantic although we infer a pronounced southward displacement of the westerlies during the early holocene these conditions did not occur throughout the southern mid high latitudes an important exception being over the southwest pacific sector subsequently a northward locus and or expansion of the winds over the patagonia south atlantic sector promoted the largest glaciers between 6100 and 4500 years ago and greatest sea ice coverage over the last few millennia the south patagonian icefield has experienced successive century scale advances superimposed on a long term net decrease in size our findings indicate that glaciers and sea ice in the patagonian south atlantic sector of the southern hemisphere did not achieve their largest holocene extents over the last millennium we conclude that a pattern of more extensive holocene ice prior to the last millennium is characteristic of the southern hemisphere middle latitudes which differs from the glacier history traditionally thought for the northern hemisphere

lichenometric dating using rhizocarpon subgenus rhizocarpon in the patagonian andes argentina abstract this study represents the first attempt to develop and apply lichenometric dating curves of rhizocarpon subgenus rhizocarpon for dating glacier fluctuations in the patagonian andes six glaciers were studied along the patagonian andes surfaces of known ages historical evidences and tree ring analyses were used as control sites to develop indirect lichenometric dating curves dating curves developed for the studied glaciers show the same general logarithmic form indicating that growth rate of subgenus rhizocarpon decreases over time the strong west east precipitation gradient across the andean cordillera introduces statistically significant differences in the growth curves with faster growth rates in the moist west sites than the drier eastern sites latitudinal difference among the studied glaciers does not appear to be a major factor regulating lichen growth rates therefore we developed two lichenometric curves for dating glacier fluctuations in wetter and drier sites in the patagonian andes during the past 450 yrs application of the developed curves to moraine dating allowed us to complement glacial chronologies previously obtained by tree ring analyses a first chronosequence for moraine formation in the torrecillas glacier 42 s is presented our findings confirm the utility of lichenometry to date deglaciated surfaces in the patagonian andes

the evolution of the patagonian ice sheet from 35 ka to the present day patice abstract we present patice a gis database of patagonian glacial geomorphology and recalibrated chronological data patice includes 58 823 landforms and 1 669 geochronological ages and extends from 38 s to 55 s in southern south america we use these data to generate new empirical reconstructions of the patagonian ice sheet pis and subsequent ice masses and ice dammed palaeolakes at 35 ka 30 ka 25 ka 20 ka 15 ka 13 ka synchronous with the antarctic cold reversal 10 ka 5 ka 0 2 ka and 2011 ad at 35 ka the pis covered of 492 6 x103 km2 had a sea level equivalent of 1 496 mm was 350 km wide and 2090 km long and was grounded on the pacific continental shelf edge outlet glacier lobes remained topographically confined and the largest generated the suites of subglacial streamlined bedforms characteristic of ice streams the pis reached its maximum extent by 33 28 ka from 38 s to 48 s and earlier around 47 ka from 48 s southwards net retreat from maximum positions began by 25 ka with ice marginal stabilisation then at 21 18 ka which was then followed by rapid irreversible deglaciation by 15 ka the pis had separated into disparate ice masses draining into large ice dammed lakes along the eastern margin which strongly influenced rates of recession glacial readvances or stabilisations occurred at least at 14 13 ka 11 ka 6 5 ka 2 1 ka and 0 5 0 2 ka we suggest that 20th century glacial recession a 1 is occurring faster than at any time documented during the holocene

atmospheric circulation changes and neoglacial conditions in the southern hemisphere mid latitudes insights from pmip2 simulations at 6 kyr glacial geologic studies in the southern hemisphere sh mid latitudes 40 54 s indicate renewed glacial activity in southern south america patagonia and new zealand s nz south island starting at 7 kyr the so called neoglaciation available data indicate that neoglacial advances in these regions occurred during a rising trend in atmospheric co2 and ch4 concentrations lower than present but increasing summer insolation and seasonality contrasts in this paper we examine the climatological context in which neoglaciations occurred through analysis of the complete paleoclimate modelling inter comparison project pmip2 database of simulations at 6 kyr for the sh we observe that the amplitude of the annual insolation cycle in the sh did not change significantly at 6 kyr compared to the pre industrial values the largest difference occurring in autumn mam negative anomalies and spring son positive anomalies the simulated changes in temperatures over the sh respond to the insolation changes with a 1 2 month delay over the oceans this results in a reduced amplitude of the annual cycle of temperature and precipitation over most continental regions except over patagonia and nz that show a slight increase in contrast large scale circulation features such as the low and upper level winds and the subtropical anticyclones show an amplified annual cycle as a direct response to the increased decreased insolation during the transitional seasons son mam in the annual mean there is a small but consistent equatorward shift of the latitude of maximum wind speed of 1 3 over the entire sh which results in a small increase of wind speed over the south pacific and atlantic oceans north of 50 s and a widespread decline south of 50 s pmip2 simulations for 6 kyr indicate that in the annual mean the sh mid latitudes were colder wetter and with stronger winds north of about 50 s these conditions are consistent with the observed neoglacial advances in the region as well as with terrestrial paleoclimate records from patagonia that indicate cooling and a multi millennial rising trend in southern westerly wind intensity starting at 7 8 kyr

palaeochannels of the balkh river northern afghanistan and human occupation since the bronze age period in 2002 the unexpected discovery of hellenistic architectural blocks buried in 8 m of alluvium found displaced in a former bed of the river of balkh brought about a programme of surveys and excavations under the aegis of the french archaeological mission in bactria the geoarchaeological side of the programme focused on the drawing of a regional geomorphological map then on the identification mapping and dating of the palaeochannels of the river of balkh we established the chronology of several fluvial channel generations by association with archaeological settlements of different eras bronze age bactro achaemenid period kushan period islamic period and with optically stimulated luminescence dating carried out on alluvium deposits the present riverbed leading up to aqcha was formed during the islamic period we suspect the primary agent of this change in the river channel to be tectonic activity and the activation of a blind fault crossing the floodplain we identified a northern bactro achaemenid aqueduct currently located in the desert area separating the plain of balkh from the amu darya

holocene glacier fluctuations in south america and antarctica abstract glacial geologic evidence indicates that glaciers throughout the andes and antarctica fluctuated during the holocene radiocarbon dating and other age determinations suggest that glaciers readvanced significantly only during the last 5 ka reaching positions from several 100 m to a few kilometres beyond their present limits in south america tenuous evidence from radiocarbon dates with dendrochronological data and environmental interpretations from pollen analyses indicate four main periods of neoglacial advance culminating 5000 4000 bp 3000 2000 bp 1300 1000 bp and 15th late 19th centuries smaller advances may have occurred at ca 8400 bp ca 7500 bp and ca 6300 bp the meagre data are consistent in indicating broad synchrony throughout the andes during the last 5 ka suggesting response to global climatic changes anomalies exist in patagonia where some tide water glaciers reached their maximal holocene limits recently this century the broad spectrum of differing antarctic environments produces interesting contrasts some local glaciers in the mcmurdo sound area of the east artarctic continent are more extensive now than during the global glacial maximum ca 18 ka bp when they were starved of precipitation consistent agreement among 14 radiocarbon dates from the south shetland islands indicates two main holocene glacier advances the most extensive 2 3 km peaking in the 12th century the other culminating in the 18th 19th century glaciers in south georgia reached their most advanced holocene limits before 2200 bp moraine fjord glacier which culminated as a 6 km advance between 1460 1700 radiocarbon bp may have lagged 400 650 years behind the climatic forcing because it could only advance in its deep water fjord by building a moraine bank smaller advances in south georgia culminated in the 17th 19th centuries and during the 1920s 30s there is no firm evidence of glacier advances before 3 ka bp in the southern ocean sub antarctic domain but broad synchrony in glacier advances during the last ca 3000 years appears to have occurred throughout the andes antarctic transect caution is required in the interpretation and correlation of moraines associated with calving glaciers and of those with poorly constrained dating

holocene glacier fluctuations a global overview of glacier advances and retreats grouped by regions and by millennia for the holocene is compiled from previous studies the reconstructions of glacier fluctuations are based on 1 mapping and dating moraines defined by 14 c tcn osl lichenometry and tree rings discontinuous records time series and 2 sediments from proglacial lakes and speleothems continuous records time series using 189 continuous and discontinuous time series the long term trends and centennial fluctuations of glaciers were compared to trends in the recession of northern and mountain tree lines and with orbital solar and volcanic studies to examine the likely forcing factors that drove the changes recorded a general trend of increasing glacier size from the earlyemid holocene to the late holocene in the extra tropical areas of the northern hemisphere nh is related to overall summer temperature forced by orbitally controlled insolation the glaciers in new zealand and in the tropical andes also appear to follow the orbital trend i e they were decreasing from the early holocene to the present in contrast glacier fluctuations in some monsoonal areas of asia and southern south america generally did not follow the orbital trends but fluctuated at a higher frequency possibly triggered by distinct teleconnections patterns during the neoglacial advances clustered at 4 4e4 2 ka 3 8e3 4 ka 3 3e2 8 ka 2 6 ka 2 3e2 1 ka 1 5e1 4 ka 1 2e1 0 ka 0 7e0 5 ka corresponding to general cooling periods in the north atlantic some of these episodes coincide with multidecadal periods of low solar activity but it is unclear what mechanism might link small changes in irradiance to widespread glacier fluctuations explosive volcanism may have played a role in some periods of glacier advances such as around 1 7e1 6 ka coinciding with the taupo volcanic eruption at 232 5 ce but the record of explosive volcanism is poorly known through the holocene the compilation of ages suggests that there is no single mechanism driving glacier fluctuations on a global scale multidecadal variations of solar and volcanic activity supported by positive feedbacks in the climate system may have played a critical role in holocene glaciation but further research on such linkages is needed the rate and the global character of glacier retreat in the 20th through early 21st centuries appears unusual in the context of holocene glaciation though the retreating glaciers in most parts of the northern hemisphere are still larger today than they were in the early and or mid holocene the current retreat

pleistocene glaciations of central asia results from 10be surface exposure ages of erratic boulders from the pamir tajikistan and the alay turkestan range kyrgyzstan abstract we have determined the timing of glaciations in the pamir tajikistan and the alay turkestan range kyrgyzstan using 10be surface exposure dating glacial advances in the area have occurred 93 136 60 80 40 55 27 25 22 20 19 17 16 15 15 13 and 11 9 cal ka bp all late pleistocene glaciers in the pamir and the alay turkestan ranges have been valley glaciers except for the most extended glaciers on the pamir plateau which have formed local piedmont glaciations in the eastern pamir these are characterized by ela depressions of 370 380 m thar 0 5 in the turkestan range and alay range ela depressions at the same time were 750 and 600 m respectively late pleistocene glacier advances all over western high asia were contemporaneous with climatic cold phases rather than monsoonal maxima their maximum extent and that of the western hemisphere ice sheets were asynchronous due to increasing aridity in the region over the course of the last glacial late pleistocene climate in central asia seems to have been influenced by the interplay of the westerly circulation and the siberian anticyclone some indirect monsoonal influence in the eastern pamir may be responsible for the existence of some of the lateglacial moraine stages in this area high altitude glaciers seem to have reached their maximum extent earlier mis 5 4 than low altitude glaciers first half of mis 3 possibly due to prolonged glacial aridity imparting with moisture advection onto high altitude sites inducing glacial retreat but prolonged cold during the same time imparting with glacier ablation at lower altitude sites inducing glacial advance

the response of glaciers to intrinsic climate variability observations and models of late holocene variations in the pacific northwest discriminating between glacier variations due to natural climate variability and those due to true climate change is crucial for the interpretation and attribution of past glacier changes and for the expectations of future changes we explore this issue for the well documented glaciers of mount baker in the cascades mountains of washington state usa using glacier histories glacier modeling weather data and numerical weather model output we find that natural variability alone is capable of producing kilometer scale excursions in glacier length on multi decadal and centennial timescales such changes are similar in magnitude to those attributed to a global little ice age the null hypothesis that no climate change is required to explain the glacier fluctuations in this setting cannot be rejected these results for mount baker glaciers are also consistent with an earlier study analyzing individual glaciers in scandinavia and the alps the principle that long timescale fluctuations of glacier length can be driven by short timescale fluctuations in climate reflects a robust and fundamental property of stochastically forced physical systems with memory it is very likely that this principle also applies to other alpine glaciers and that it therefore complicates interpretations of the relationship between glacier and climate history however the amplitude and timescale of the length fluctuations depends on the details of the particular glacier geometry and climatic setting and this remains largely unevaluated for most glaciers

onset of neoglaciation in the southern hemisphere a review of evidence documenting an early neoglacial mid holocene advance of mountain glaciers in south america and new zealand reveals that of 16 glaciers for which radiocarbon age control exists only two have associated dates that may approximate the culmination of an advance advances of the remaining glaciers are controlled only by minimum or maximum limiting ages additional dates for several new zealand glaciers are based on weathering rind measurements having large potential errors twelve of the glaciers now terminate or have terminated in lakes or in tidewater and are subject to instabilities associated with calving termini an extensive debris cover in the ablation zone of nearly half of the glaciers makes their moraine succession potentially suspect as a record of detailed climatic variation the two glaciers with seemingly reliable age control are located in valleys where large rock avalanches could affect glacier mass balance and lead to random advances or where rock avalanche deposits might easily be mistaken for moraines and tills the early neoglacial interval has been defined primarily based on this set of data the ages taken at face value suggest that the early neoglacial advance culminated between ca 5400 and 4900 cal yr ago ca 4600 4400 14c yr bp this chronology however should remain provisional until improved age control is obtained for a large population of glaciers based on closely bracketing radiocarbon dates and or an adequate number of cosmogenic isotope ages data from calving glaciers and those subject to rock avalanche activity should be avoided or assessed critically copyright 2000 john wiley sons ltd

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

micro dynamics and macro patterns exploring new archaeological data for the late holocene human water relationship in the murghab alluvial fan turkmenistan in this article we re visit hypotheses about the changing social and environmental landscapes in southern central asia during the late holocene specifically giving attention to the transitional period between the archaeologically defined late bronze early iron age second half of the 2nd millennium bc and the numerous documented changes in the archaeological and physio geographical record during this time we focus on the northeastern murghab alluvial fan turkmenistan as a window into this complex period and examine one aspect of human environmental dynamics there namely the relationship between the location of archaeological sites and mapped ancient watercourses palaeochannels through time our analysis incorporates nearly 400 new archaeological sites documented in the northeastern murghab since 2006 which have not previously been included in published models of settlement and or hydrological dynamics our findings suggest the periods of the late bronze age and early iron age yaz i demonstrate two distinct access to water practices which may correlate to different processes of socio territorial control being implemented while no single line of evidence can adequately disentangle the complex interconnected processes of environmental and social change our results lend themselves to integration with the current working knowledge of the local processes of socio environmental development in the murghab the results also fit more broadly within emerging discourse that recognizes the importance of micro scale processes and adaptation in eurasian prehistory

in situ cosmogenic 10be production rate at lago argentino patagonia implications for late glacial climate chronology abstract when calculated with the commonly accepted average northern hemisphere production rate 10 be dates of surface boulders on moraines in the lago argentino area of patagonia are younger than minimum limiting 14 c ages for the same landforms this disagreement could result from the lack of a regional 10 be production rate calibration site to assess this possibility we here present high precision measurements of 10 be in samples collected from surface boulders on the herminita and puerto bandera moraine complexes deposited alongside lago argentino on the eastern flank of the andes at 50 s in patagonia together with maximum and minimum limiting 14 c ages for the two moraine systems these measurements confine the local 10 be production rate to between 3 60 and 3 82 atoms g yr midpoint 3 71 0 11 atoms g yr when using a time dependent scaling method that incorporates a high resolution geomagnetic model this range includes upper and lower error bounds of acceptable production rates derived from both the herminita and the puerto bandera sites the upper limit of this range is more than 12 below the average northern hemisphere production rate as calculated using the same scaling method given in balco et al quat geochron 3 2008 174 195 other scaling models yield production rates with similarly large offsets from the balco et al 2008 rate on the other hand the range of acceptable production rate values determined from patagonia overlaps at 1 with and encompasses the production rate recently derived in macaulay valley in the southern alps of new zealand a putnam et al quat geochron 5 2010a 392 409 within uncertainties i e overlap at 1 sigma this patagonian production rate range also agrees with a recently determined production rate from low elevation sites in northeastern north america and northern norway when the macaulay production rate is used to calculate patagonian exposure dates 14 c and 10 be chronologies are mutually compatible for late glacial moraine systems both chronologies then indicate that outlet glaciers of the southern patagonian icefield achieved a late glacial maximum in the western reaches of lago argentino at 13 000 cal yr bp at the end of the antarctic cold reversal 14 500 12 900 cal yr bp outlet glaciers subsequently receded to near present day ice margins during the younger dryas stadial 12 900 11 700 cal yr bp this general retreat was interrupted about 12 200 cal yr bp when upsala glacier constructed an interlobate complex of moraine ridges on herminita peninsula mountain glaciers in patagonia and new zealand on both sides of the south pacific ocean exhibited a coherent pattern of late glacial ice margin fluctuations

contribution of the patagonia icefields of south america to sea level rise digital elevation models of the northern and southern patagonia icefields of south america generated from the 2000 shuttle radar topography mission were compared with earlier cartography to estimate the volume change of the largest 63 glaciers during the period 1968 1975 2000 these glaciers lost ice at a rate equivalent to a sea level rise of 0 042 0 002 millimeters per year in the more recent years 1995 2000 average ice thinning rates have more than doubled to an equivalent sea level rise of 0 105 0 011 millimeters per year the glaciers are thinning more quickly than can be explained by warmer air temperatures and decreased precipitation and their contribution to sea level per unit area is larger than that of alaska glaciers

high frequency holocene glacier fluctuations in new zealand differ from the northern signature understanding the timings of interhemispheric climate changes during the holocene along with their causes remains a major problem of climate science here we present a high resolution 10be chronology of glacier fluctuations in new zealand s southern alps over the past 7000 years including at least five events during the last millennium the extents of glacier advances decreased from the middle to the late holocene in contrast with the northern hemisphere pattern several glacier advances occurred in new zealand during classic northern warm periods these findings point to the importance of regional driving and or amplifying mechanisms we suggest that atmospheric circulation changes in the southwest pacific were one important factor in forcing high frequency holocene glacier fluctuations in new zealand

quaternary landscape evolution in the eastern hindu kush pakistan abstract the eastern hindu kush in northern pakistan is among the most dynamically active tectonic and geomorphic areas in the world during the quaternary valley fill sediments of great thickness have been deposited by glacial fluvial eolian and mass movement processes fluvial incision eroded these sediments and formed terraces their development was controlled by tectonic and climatic factors and therefore they record information about the quaternary landscape evolution and glaciations investigations included the mapping of landforms especially the terraces and sedimentological analyses on valley fill deposits this resulted in a classification with six main types of terraces morainic glaciofluvial fluvial lacustrine mass movement debris and fan terraces tectonic terraces were not recognized but tectonically influenced sediments have been found near the shyok suture zone this classification corresponds with results from the nearby karakoram two major late pleistocene glaciations are recognized during marine isotopic stage 3 mis 3 drosh glacial stage and in the mis 2 early holocene pret glacial stage moraines from the neoglacial shandur glacial stages i and ii and the little ice age barum glacial stage i are located near the contemporary glaciers during deglaciations huge terraces were formed the upper terrace or broz fan formation and the middle terrace or ayun fan formation between the drosh and pret glacial stages and the lower terrace or urghuch fan formation after the pret glacial stage the chronology presented in this paper shows that there was only limited glaciation in the eastern hindu kush during the global last glacial maximum lgm

latest pleistocene and holocene glacial events in the colonia valley northern patagonia icefield southern chile the northern patagonia icefield npi is the primary glaciated terrain worldwide at its latitude 46 5 47 5 s and constraining its glacial history provides unique information for reconstructing southern hemisphere paleoclimate the colonia glacier is the largest outlet glacier draining the eastern npi ages were determined using dendrochronology lichenometry radiocarbon cosmogenic 10be and optically stimulated luminescence dated moraines in the colonia valley defined advances at 13 2 0 95 11 0 0 47 and 4 96 0 21 ka with the last being the first constraint on the onset of neoglaciation for the eastern npi from a directly dated landform dating in the tributary cachet valley which contains an ice dammed lake during periods of colonia glacier expansion defined an advance at ca 2 95 0 21 ka periods of advancement at 810 49 cal a bp and 245 13 cal a bp and retreat during the intervening periods recent colonia glacier thinning which began in the late 1800s opened a lower elevation outlet channel for lago cachet dos in ca 1960 our data provide the most comprehensive set of latest pleistocene and holocene ages for a single npi outlet glacier and expand previously developed npi glacial chronologies

equilibrium line altitudes along the andes during the last millennium paleoclimatic implications deciphering the climate changes that influenced the glacial fluctuations of the last millennium requires documenting the spatial and temporal patterns of these glacial events here we estimate the

trans pacific glacial response to the antarctic cold reversal in the southern mid latitudes abstract elucidating the timing and regional extent of abrupt climate events during the last glacial interglacial transition 18 11 5 ka is critical for identifying spatial patterns and mechanisms responsible for large magnitude climate events the record of climate change in the southern hemisphere during this time period however remains scarce and unevenly distributed we present new geomorphic chronological and equilibrium line altitude ela data from a climatically sensitive mountain glacier at monte san lorenzo 47 s central patagonia twenty four new cosmogenic 10be exposure ages from moraines provide a comprehensive glacial record in the mid latitudes of south america which constrain the timing spatial extent and magnitude of glacial fluctuations during the antarctic cold reversal acr 14 5 12 9 ka rio tranquilo glacier advanced and reached a maximum extent at 13 9 0 7 ka three additional inboard moraines afford statistically similar ages indicating repeated glacier expansions or marginal fluctuations over the acr our record represents the northernmost robust evidence of glacial fluctuations during the acr in southern south america documenting not only the timing of the acr maximum but also the sequence of glacier changes within this climate event based on ela reconstructions we estimate a cooling of 1 6 1 8 c at the peak of the acr the rio tranquilo record along with existing glacial reconstructions from new zealand 43 s and paleovegetation records from northwestern 41 s and central west 45 s patagonia suggest an uniform trans pacific glacier climate response to an acr trigger across the southern mid latitudes we posit that the equatorial migration of the southern westerly winds provides an adequate mechanism to propagate a common acr signal across the southern hemisphere

radiocarbon chronology of the late glacial puerto bandera moraines southern patagonian icefield argentina abstract we report radiocarbon dates that constrain the timing of the deposition of the late glacial puerto bandera moraine system alongside the western reaches of lago argentino adjacent to the southern patagonian icefield close maximum limiting radiocarbon ages n 11 for glacier advance into the outer moraines with a mean value of 11 100 60 14 c yrs bp 12 990 80 cal yrs bp were obtained from wood in deformation soft till exposed beneath flow and lodgment till in bahia del quemado on the northeast side of brazo norte north branch of western lago argentino other exposures of this basal deformation till in bahia del quemado reveal incorporated clasts of peat along with larger inclusions of deformed glaciofluvial and lacustrine deposits radiocarbon dates of wood included in these reworked peat clasts range from 11 450 45 14 c yrs bp to 13 450 150 14 c yrs bp 13 315 60 to 16 440 340 cal yrs bp the implication is that during this interval glacier fronts were situated inboard of the puerto bandera moraines with the peat clasts and larger proglacial deposits being eroded and then included in the basal till during the puerto bandera advance minimum limiting radiocarbon ages for ice retreat come from basal peat in cores sampled in spillways and depressions generated during abandonment of the puerto bandera moraines glacier recession and subsequent plant colonization were initiated close behind different frontal sectors of these moraines prior to 10 750 75 14 c yrs bp 12 660 70 cal yrs bp east of brazo rico 10 550 55 14 c yrs bp 12 490 80 cal yrs bp in peninsula avellaneda and 10 400 50 14 c yrs bp 12 280 110 cal yrs bp in bahia catalana in addition a radiocarbon date indicates that by 10 350 45 14 c yrs bp 12 220 110 cal yrs bp the brazo norte lobe or former upsala glacier had receded well up the northern branch of lago argentino to a position behind the herminita moraines furthermore glacier termini had receded to just outboard of the outer holocene moraines at lago frias and lago pearson anita prior to 10 400 40 14 c yrs bp 12 270 100 cal yrs bp and 9040 45 14 c yrs bp 10 210 50 cal yrs bp respectively the most extensive recession registered during the early holocene was in agassiz este valley where the upsala glacier had pulled back behind the outer holocene moraine reaching close to the present day glacier terminus before 8290 40 14 c yrs bp 9300 80 cal yrs bp the radiocarbon dated fluctuations of the lago argentino glacier in late glacial time given here are in accord with changes in ocean mixed layer properties predominately temperature derived from the isotopic record given here of odp core 1233 taken a short distance off shore of the chilean lake district it also matches recently published chronologies of late glacial moraines in the southern alps of new zealand on the opposite side of the pacific ocean from lago argentino finally the timing of the late glacial reversal of the lago argentino glacier fits the most recent chronology for the culmination of the antarctic cold reversal acr in the deuterium record of the epica dome c ice core from high on the east antarctic plateau therefore we conclude that the climate signature of the acr was widespread in both the ocean and the atmosphere over at least the southern quarter of the globe

latest pleistocene and holocene alpine glacier fluctuations in scandinavia abstract during the early holocene abrupt decadal to centennial scale climate variations caused significant glacier variations in norway increased freshwater inflow to the north atlantic and arctic oceans has been suggested as one of the most likely mechanisms to explain the abrupt and significant lateglacial and early holocene climatic events in nw europe the largest early holocene glacier readvances occurred 11 200 10 500 10 100 9700 9200 and 8400 8000 cal yr bp the studied norwegian glaciers apparently melted away at least once during the early mid holocene the period with the most contracted glaciers in scandinavia was between 6600 and 6000 cal yr bp subsequent to 6000 cal yr bp the glaciers started to advance and the most extensive glaciers existed at about 5600 4400 3300 2300 1600 cal yr bp and during the little ice age times with overall less glacier activity were apparently around 5000 4000 3000 2000 and 1200 cal yr bp it has been proposed that several glacier advances occurred in scandinavia including northern sweden at 8500 7900 7400 7200 6300 6100 5900 5800 5600 5300 5100 4800 4600 4200 3400 3200 3000 2800 2700 2000 1900 1600 1200 1000 and 700 200 cal yr bp glaciers in northern sweden probably reached their greatest little ice age extent between the 17th and the beginning of the 18th centuries evidence for early holocene glacier advances in northern scandinavia however has been questioned by more recent multi disciplinary studies the early to mid holocene glacier episodes in northern sweden may therefore be questioned most norwegian glaciers attained their maximum little ice age extent during the mid 18th century cumulative glacier length variations in southern norway based on marginal moraines dated by lichenometry and historic evidence show an overall retreat from the mid 18th century until the 1930s 40s subsequently most norwegian glaciers retreated significantly maritime outlet glaciers with short frontal time lags 15 20 years continued their retreat to the 1970s and 1980s however maritime glaciers started to advance as a response to higher winter accumulation during the first part of the 1990s after 2000 several of the observed glaciers have retreated remarkably fast annual frontal retreat 100 m mainly due to high summer temperatures the general glacier retreat during the early holocene and the neoglacial advances after 6000 cal yr bp are in line with orbital forcing due to the decrease of northern hemisphere summer solar insolation and the increase in winter insolation in addition regional weather modes such as the north atlantic oscillation nao and the arctic oscillation ao play a significant role with respect to decadal and multi decadal climate variability

holocene glacier fluctuations in patagonia are modulated by summer insolation intensity and paced by southern annular mode like variability abstract alpine glaciers are sensitive indicators of changes in climate and their ubiquity in mountainous regions make them valuable proxies for terrestrial climate reconstructions worldwide however the timing and extent of glacier change across the south american mid latitudes through the holocene are still poorly constrained relative to their counterparts in the northern hemisphere here we report a new 10be surface exposure based chronology of moraines recording a series of progressively less extensive glacier advances of glaciar torre argentina 49 3 s 73 0 w since the last glacial maximum with expansions culminating at 17 600 900 13 500 500 9700 400 6900 200 6100 300 4500 200 and 530 60 yr bp the declining magnitude of holocene glacier expansions parallels a gradual rise in local summer insolation intensity during the holocene while individual advances occurred during inferred negative southern annular mode sam like states at centennial to millennial timescales these observations suggest that i summer insolation intensity modulated antiphased trends in glacier extent in the polar hemispheres during the holocene and that ii centennial scale sam like temperature and precipitation anomalies paced glacier fluctuations throughout patagonia given the persistence of the inferred sam like anomalies throughout the holocene the modern measured trend towards positive sam index conditions could mark the onset of a fundamental shift in the climate of the southern hemisphere midlatitudes that warrants consideration in projections of future climate

glacier expansion in southern patagonia throughout the antarctic cold reversal resolving debated climate changes in the southern middle latitudes and potential teleconnections between southern temperate and polar latitudes during the last glacial interglacial transition is required to help understand the cause of the termination of ice ages outlet glaciers of the patagonian ice fields are primarily sensitive to atmospheric temperature and also precipitation thus former ice margins record the extent and timing of past climate changes 38 10 be exposure ages from moraines show that outlet glaciers in torres del paine 51 s south patagonia chile advanced during the time of the antarctic cold reversal acr ca 14 6 12 8 ka reaching a maximum extent by 14 200 560 yr ago the evidence here indicates that the south patagonian ice field was responding to late glacial climate change distinctly earlier than the onset of the european younger dryas stadial ca 12 9 ka major glacier recession and deglaciation in the torres del paine region occurred by 12 5 ka and thus early in the younger dryas we provide direct evidence for extensive ice in patagonia at the very start of the acr that agrees with atmospheric and marine records from the southern ocean and antarctica atmospheric conditions responsible for the early late glacial expansion at torres del paine resulted from a climate reorganization that prompted a northern migration of the south westerly wind belt to the latitude of torres del paine at the onset of the acr chronozone

modes of climate variability synthesis and review of proxy based reconstructions through the holocene abstract modes of climate variability affect global and regional climates on different spatio temporal scales and they have important impacts on human activities and ecosystems as these modes are a useful tool for simplifying the understanding of the climate system it is crucial that we gain improved knowledge of their long term past evolution and interactions over time to contextualise their present and future behaviour we review the literature focused on proxy based reconstructions of modes of climate variability during the holocene i e the last 11 7 thousand years with a special emphasis on i proxy based reconstruction methods ii available proxy based reconstructions of the main modes of variability i e el nino southern oscillation pacific decadal variability atlantic multidecadal variability the north atlantic oscillation the southern annular mode and the indian ocean dipole iii major interactions between these modes and iv external forcing mechanisms related to the evolution of these modes this review shows that modes of variability can be reconstructed using proxy based records from a wide range of natural archives but these reconstructions are scarce beyond the last millennium partly due to the lack of robust chronologies with reduced dating uncertainties technical issues related to proxy calibration and difficulty elucidating their stationary impact or not on regional climates over time while for each mode the available reconstructions tend to agree at mutidecadal timescales they show notable disagreement on shorter timescales beyond the instrumental period the reviewed evidence suggests that the intrinsic variability of modes can be modulated by external forcing such as orbital solar volcanic and anthropogenic forcing the review also highlights some modes experience higher variability over the instrumental period which is partly ascribed to anthropogenic forcing these features stress the paramount importance of further studying their past variations using long climate proxy records for the progress of climate science

reconstructing climate from glaciers glaciers offer the potential to reconstruct past climate over timescales from decades to millennia they are found on nearly every continent and at the last glacial maximum glaciers were larger in all regions on earth the physics of glacier climate interaction are relatively well understood and glacier models can be used to reconstruct past climate from geological evidence of past glacier extent this can lead to significant insights regarding past present and future climate for example glacier modeling has demonstrated that the near ubiquitous global pattern of glacier retreat during the last few centuries resulted from a global scale climate warming of 1 c consistent with instrumental data and climate proxy records climate reconstructions from glaciers have also demonstrated that the tropics were colder at the last glacial maximum than was originally inferred from sea surface temperature reconstructions future efforts to reconstruct climate from glaciers may provide new constraints on climat

reconstruction of mid holocene sedimentary environments in the central part of the thessaloniki plain greece based on microfaunal identification magnetic susceptibility and grain size analyses abstract the study aims to estimate the relative contributions of the two drainage basins of the aliakmon and axios rivers which since the mid holocene have been responsible for building the largest deltaic area in greece sediments from five cores located in the central part of the thessaloniki plain have been studied for their environmental changes using paleontological and sedimentological methods chronostratigraphical evidence was obtained from 14 c ams dating of marine shells peat and organic sediment samples during the holocene marine transgression this large coastal plain was a shallow marine bay reaching approx 35 km inland circa the 4th millennium bc from which the sea subsequently regressed to the east around the middle of the 3rd millennium bc strong fluvial deposition of aliakmon to the east and of axios to the north occurred and was responsible of a gradual change to lagoonal and limnic environmental conditions around the 5th century bc a freshwater lake occupied the westernmost part of the plain microfaunal identification together with magnetic susceptibility measurements and grain size analysis reveal three main environments of sediment deposition that reflect combinations of both concentrated and dispersed sources of magnetic source minerals using remote sensing and a combination of spectral bands landsat tm imagery we identify former fluvial levees and a freshwater lake and give a spatial interpretation of the rivers influences in building this deltaic complex the mechanisms of edification of the plain as well as the roles played by aliakmon and axios sedimentation are described

timing and style of late quaternary glaciation in the eastern hindu kush chitral northern pakistan a review and revision of the glacial chronology based on new optically stimulated luminescence dating abstract glacial landforms and sediments provide evidence for two late quaternary major glaciations in the eastern hindu kush new optically stimulated luminescence osl dating was undertaken to define the timing of these glaciations and associated sediment deposition the drosh glacial was defined by osl dating to have occurred during marine isotopic stage 3 producing an extensive valley glaciation that extended to an altitude of 1300 m above sea level asl in the main valley with an equilibrium line altitude ela depression of 1200 m the pret glacial produced a valley glaciation that extended to an altitude of 1670 m asl in the main valley with an ela depression of 1000 m the new osl dating suggests that this glacial stage probably represents several glacial advances that occurred during the latter part of the last glacial moraines representing two minor glacial advances the shandur and barum glacial stages were also recognized near the contemporary glaciers these probably formed during the middle late holocene and little ice age respectively this study and comparisons with adjacent regions suggest that there was limited glaciation during the global last glacial maximum lgm in the hindu kush deglaciation in the mountain ranges of the himalayas and the consequent meltwater discharge into the adjacent seas was negligible immediately after the global lgm and it was therefore of minor importance as a forcing factor for global climate change during the end of the last glacial cycle however our studies show that glaciation and particularly deglaciation is important in controlling the deposition of thick valley fills and the landscape evolution of the high mountain environments

holocene glacier history of the lago argentino basin southern patagonian icefield abstract we present new geomorphic stratigraphic and chronologic data for holocene glacier fluctuations in the lago argentino basin on the eastern side of the southern patagonian andes chronologic control is based on 14c and surface exposure 10be dating after the lateglacial maximum at 13 000 cal yrs bp the large ice lobes that filled the eastern reaches of lago argentino retreated and separated into individual outlet glaciers this recession was interrupted only by a stillstand or minor readvance at 12 200 cal yrs bp the eight largest of these individual outlet glaciers are from north to south upsala agassiz onelli spegazzini mayo ameghino perito moreno and grande formerly frias holocene recession of upsala glacier exposed brazo cristina more than 10 115 100 cal yrs bp and reached inboard of the holocene moraines in agassiz este valley by 9205 85 cal yrs bp ice remained in an inboard position until 7730 50 cal yrs bp several subsequent glacier readvances are well documented for the upsala and frias glaciers the upsala glacier readvanced at least seven times the first being a relatively minor expansion documented only in stratigraphic sections between 7730 50 and 7210 45 cal yrs bp the most extensive holocene advances of upsala glacier resulted in the deposition of the pearson 1 moraines and related landforms which are divided into three systems the pearson 1a advance occurred about 6000 5000 cal yrs bp and was followed by the slightly less extensive pearson 1b and 1c advances dated to 2500 2000 and 1500 1100 cal yrs bp respectively subsequent advances of upsala glacier resulted in deposition of the pearson 2 moraines and corresponding landforms also separated into three systems pearson 2a 2b and 2c constructed respectively at 700 400 and

anomalous molybdenum isotope trends in upper pennsylvanian euxinic facies significance for use of δ98mo as a global marine redox proxy abstract the use of molybdenum isotope data 98mo from organic rich shales to draw inferences concerning marine paleoredox conditions at a global scale is predicated upon the assumptions of 1 a residence time of mo in seawater much greater than the ocean mixing time and 2 quantitative removal of mo from a strongly euxinic h2s aq 11 m water column to the sediment thus preserving the seawater 98mo signature in this study we analyze mo isotopic variation in the hushpuckney shale a 73 cm thick unit representing the late transgressive to early regressive stages of a glacio eustatic cyclothem swope formation deposited in the late pennsylvanian midcontinent sea lpms of north america the hushpuckney can be subdivided into four stratigraphic zones of distinctive geochemical character zones i and iii which accumulated under weakly euxinic conditions acquired relatively high 98mo values 0 9 to 1 1 whereas zone ii which accumulated under intensely euxinic conditions acquired lower 98mo values 0 6 zone iv which accumulated under suboxic conditions in the water column acquired the heaviest 98mo values 1 1 to 1 8 these results contrast with the pattern of redox 98mo covariation in modern marine environments in which the heaviest 98mo values are found in the most intensely euxinic facies we evaluate three different hypotheses to account for the mo isotopic patterns of the hushpuckney shale one hypothesis seawater freshwater mixing is rejected owing to isotopic mass balance considerations a second hypothesis is a local control on 98mo by water column redox cycling of mn with particulate mn oxyhydroxides adsorbing isotopically light mo and transferring it to the sediment a process that was most active during deposition of zone ii the significance of this scenario is that euxinic black shales may not reliably record global seawater 98mo in areas where a mn particulate shuttle is operative a third hypothesis is based on rapid secular variation of the mo isotope composition of late pennsylvanian global seawater in order to account for 98mo trends within the hushpuckney shale seawater 98mo must have varied by 1 2 at a 100 kyr timescale which would have been possible only if the residence time of mo in late pennsylvanian seawater was

the anatomy of long term warming since 15 ka in new zealand based on net glacier snowline rise the timing and magnitude of postglacial climatic changes around the globe provide insights into the underlying drivers of natural climate change using geomorphologic mapping of moraines 10 be surface exposure dating snowline reconstructions and numerical modeling we quantified glacier behavior during late glacial 15 11 5 ka and holocene the past 11 5 k y time in the ben ohau range new zealand glaciers were more extensive during the antarctic cold reversal acr than subsequently and the margins underwent a punctuated net withdrawal over the holocene numerical modeling experiments that achieve the best fit to the moraines suggest that air temperature during the acr was between 1 8 c and 2 6 c cooler than today with similar 20 prescribed precipitation after the acr a net snowline rise of 100 m through the younger dryas stadial 12 9 11 7 ka was succeeded by a further long term or net rise of 100 m between 11 k y and 500 yr ago glacier snowline records in new zealand show generally coherent late glacial and holocene climate trends however the paleoclimate record in the southwest pacific region shows important differences from that in the northern hemisphere

early and mid holocene age for the tempanos moraines laguna san rafael patagonian chile data about the nature and timing of holocene events from the southern hemisphere especially in southern south america are required to provide insight into the extent and nature of past climate change in a region where land based records are restricted here we present the first use of single grain optically stimulated luminescence osl dating of a moraine sequence recording glacial advance along the western side of the patagonian icefields dates from the tempanos moraines at laguna san rafael lsr show that the san rafael glacier srg advanced to maximum holocene positions during the period 9 3 to 9 7 ka and at 5 7 ka outwash lying beneath the moraine in its northern portion dated to 7 7 ka indicates that the glacier front was also advanced at this time since these advances span both the regional early holocene warm dry phase 11 5 ka to 7 8 ka and the subsequent cooling and rise in precipitation in the mid late holocene since 6 6 ka we infer that the advances of the srg are not simply climate driven but that the glacier has also probably responded strongly to non climatic stimuli such as internal ice dynamics and the transition between calving and non calving many westwards flowing glaciers in patagonia were probably calving during much of the late pleistocene and holocene so we conclude that establishing robust glacial chronologies where climatic and non climatic factors cannot be distinguished is likely to remain a challenge

latest pleistocene and holocene glacier variations in the european alps in the alps climatic conditions reflected in glacier and rock glacier activity in the earliest holocene show a strong affinity to conditions in the latest pleistocene younger dryas glacier advances in the alps related to younger dryas cooling led to the deposition of egesen stadial moraines egesen stadial moraines can be divided into three or in some cases even more phases sub stadials moraines of the earliest and most extended advance the egesen maximum stabilized at 12 2 1 0 ka based on 10be exposure dating at the schonferwall tyrol austria and the julier pass outer moraine switzerland final stabilization of moraines at the end of the egesen stadial was at 11 3 0 9 ka as shown by 10be data from four sites across the alps from west to east the sites are piano del praiet northwestern italy grosser aletschgletscher central switzerland julier pass inner moraine eastern switzerland and val viola northeastern italy there is excellent agreement of the 10be ages from the four sites in the earliest holocene glaciers in the northernmost mountain ranges advanced at around 10 8 1 1 ka as shown by 10be data from the kartell site northern tyrol austria in more sheltered drier regions rock glacier activity dominated as shown for example at julier pass and larstig valley tyrol austria new 10be dates presented here for two rock glaciers in larstig valley indicate final stabilization no later than 10 5 0 8 ka based on this data we conclude the earliest holocene between 11 6 and about 10 5 ka was still strongly affected by the cold climatic conditions of the younger dryas and the preboreal oscillation with the intervening warming phase having had the effect of rapid downwasting of egesen glaciers at or slightly before 10 5 ka rapid shrinkage of glaciers to a size smaller than their late 20th century size reflects markedly warmer and possibly also drier climate between about 10 5 ka and 3 3 ka conditions in the alps were not conducive to significant glacier expansion except possibly during rare brief intervals past tree line data from kaunertal tyrol austria in concert with radiocarbon and dendrochronologically dated wood fragments found recently in the glacier forefields in both the swiss and austrian alps points to long periods during the holocene when glaciers were smaller than they were during the late 20th century equilibrium line altitudes ela were about 200 m higher than they are today and about 300 m higher in comparison to little ice age lia elas the larstig rock glacier site we dated with 10be is the type area for a postulated mid holocene cold period called the larstig oscillation presumed age about 7 0 ka our data point to final stabilization of those rock glaciers in the earliest holocene and not in the middle holocene the combined data indicate there was no time window in the middle holocene long enough for rock glaciers of the size and at the elevation of the larstig site to have formed during the short infrequent cold oscillations between 10 5 and 3 3 ka small glaciers less than several km2 may have advanced to close to their lia dimensions overall the cold periods were just too short for large glaciers to advance after 3 3 ka climate conditions became generally colder and warm periods were brief and less frequent large glaciers for example grosser aletschgletscher advanced markedly at 3 0 2 6 ka around 600 ad and during the lia glaciers in the alps attained their lia maximum extents in the 14th 17th and 19th centuries with most reaching their greatest lia extent in the final 1850 1860 ad advance

earliest holocene south greenland ice sheet retreat within its late holocene extent early holocene summer warmth drove dramatic greenland ice sheet gis retreat subsequent insolation driven cooling caused gis margin readvance to late holocene maxima from which ice margins are now retreating we use 10be surface exposure ages from four locations between 69 4 n and 61 2 n to date when in the early holocene south to west gis margins retreated to within these late holocene maximum extents we find that this occurred at 11 1 0 2 ka to 10 6 0 5 ka in south greenland significantly earlier than previous estimates and 6 8 0 1 ka to 7 9 0 1 ka in southwest to west greenland consistent with existing 10be ages at least in south greenland these 10be ages likely provide a minimum constraint for when on a multicentury timescale summer temperatures after the last deglaciation warmed above late holocene temperatures in the early holocene current south greenland ice margin retreat suggests that south greenland may have now warmed to or above earliest holocene summer temperatures

the interconnected global climate system a review of tropical polar teleconnections abstractthis paper summarizes advances in research on tropical polar teleconnections made roughly over the last decade elucidating el nino southern oscillation enso impacts on high latitudes has remained an important focus along different lines of inquiry tropical to polar connections have also been discovered at the intra seasonal timescale associated with madden julian oscillations mjo on the timescale of decades changes in mjo phases can result in temperature and sea ice changes in the polar regions of both hemispheres moreover the long term changes in sst of the western tropical pacific tropical atlantic and north atlantic ocean have been linked to the rapid winter warming around the antarctic peninsula while sst changes in the central tropical pacific have been linked to the warming in west antarctica rossby wave trains emanating from the tropics remain the key mechanism for tropical and polar teleconnections from intraseasonal to decadal timescales enso related tropical sst anomal

holocene thermal maximum in the western arctic 0 180 w the spatio temporal pattern of peak holocene warmth holocene thermal maximum htm is traced over 140 sites across the western hemisphere of the arctic 0 180 w north of 60 n paleoclimate inferences based on a wide variety of proxy indicators provide clear evidence for warmer than present conditions at 120 of these sites at the 16 terrestrial sites where quantitative estimates have been obtained local htm temperatures primarily summer estimates were on average 1 6 0 8 c higher than present approximate average of the 20th century but the warming was time transgressive across the western arctic as the precession driven summer insolation anomaly peaked 12 10 ka thousands of calendar years ago warming was concentrated in northwest north america while cool conditions lingered in the northeast alaska and northwest canada experienced the htm between ca 11 and 9 ka about 4000 yr prior to the htm in northeast canada the delayed warming in quebec and labrador was linked to the residual laurentide ice sheet which chilled the region through its impact on surface energy balance and ocean circulation the lingering ice also attests to the inherent asymmetry of atmospheric and oceanic circulation that predisposes the region to glaciation and modulates the pattern of climatic change the spatial asymmetry of warming during the htm resembles the pattern of warming observed in the arctic over the last several decades although the two warmings are described at different temporal scales and the htm was additionally affected by the residual laurentide ice the similarities suggest there might be a preferred mode of variability in the atmospheric circulation that generates a recurrent pattern of warming under positive radiative forcing unlike the htm however future warming will not be counterbalanced by the cooling effect of a residual north american ice sheet

holocene glacier culminations in the western alps and their hemispheric relevance the natural variability of holocene climate defi nes the baseline to assess ongoing climate change greenland ice core records indicate warming superimposed by abrupt climate oscillations in the early holocene followed by a general cooling trend throughout the middle and late holocene that culminated during the little ice age lia tropical precipitation changes correlate with these patterns throughout the holocene here we use mountain glaciers in the european alps to reconstruct the regional holocene climate evolution and to test for a link between mid latitude north atlantic and tropical climate our precise 10 be chronology from tsidjiore nouve glacier western swiss alps indicates a glacier culmination during the earliest holocene 11 4 k y ago likely related to the preboreal oscillation based on our data no holocene glacier advance of similar amplitude occurred until 3 8 k y ago when the glacier reached lia limits the 10 be ages between 500 and 170 yr correspond to the lia while the youngest 10 be ages overlap with the historically recorded post lia glacier positions integrating our data with existing records we propose a hemispheric climate link between the alps north atlantic temperature and tropical precipitation patterns for the holocene supporting the concept of a pervasive climate driver these fi ndings from northern mid latitudes are consistent with the hypothesis formulated for the tropics that the earth s thermal equator responding to north atlantic temperature changes might have migrated southward throughout the holocene reaching the southern turning point toward the end of the lia

pedosedimentary and climatic reconstruction of the last interglacial and early glacial loess paleosol sequence in south tadzhikistan abstract the thick loess paleosol sequences in tadzhikistan which indirectly record the environmental changes from the upper pliocene to the present day have been extensively described from a chronostratigraphical and archaeological point of view the genesis of the soil sedimentary complexes and their implications for palaeoenvironmental reconstruction in tadzhikistan however have been considered only relatively recently bronger a winter r derevjanko o aldag s 1993 loess paleosol sequences in tadjikistan as a palaeoclimatic record of the quaternary in central asia quaternary proceedings 4 69 81 lomov s p tursina t v zhou l p 1996 magnetic susceptibility of soils micromorphology and possible reconstructions of climate in soil micromorphology studies in soil diversity diagnostics dynamics 10th international working meeting on soil micromorphology moscow russia july 8 13 1996 p 145 the pedocomplex of last interglacial and early glacial age oxygen isotope stage 5 in the tagidjar and darai kalon sections near the town of khovaling is represented by three major stages of soil formation the soil characteristics have been micromorphologically analysed the distinction between primary and secondary carbonates is of major importance to understand the soil forming processes the relative distribution of needle fibre calcite nfc micritic infillings m hypocoatings chc coarse calcitic grains ccg and calcified root cells crc provides detailed insights into the environmental conditions prior during and following pedogenesis the abundance of coprolitic aggregates ca and pupal chambers gives a clear indication of the rate of biological activity which prevailed during the last two soil forming stages void pseudomorphs after gypsum crystals gypsum pseudomorphs are frequently observed beneath the cca horizons of the paleosols using the present day climate and soilscape as a reference base the obtained pedosedimentary events detected in the tadzhikistan sections provide a detailed palaeoenvironmental record indeed glacial and interglacial climates and soils respond to contemporaneous climatic schemes and soil forming processes which are still active in the region today the amount and the seasonal variability of precipitation mostly are at the origin of the variable soils formed during glacial and interglacial ages

little ice age fluctuations of small glaciers in the monte fitz roy and lago del desierto areas south patagonian andes argentina abstract current knowledge about late holocene glacier fluctuations in the south patagonian andes is mainly based on evidence from large outlet glaciers of the north and south patagonian icefields and few data exist for the smaller glaciers elsewhere in the region here we provide dendrogeomorphological evidence for little ice age lia and post lia activity for five small glaciers near the northeast margin of the south patagonian icefield the study sites include glaciar torre and piedras blancas in the monte fitz roy area and three adjacent glaciers near lago del desierto at these sites the lia maximum position was identified by massive moraines with mature trees dating to the late 1500s early 1600s several older moraines were observed beyond these limits but could not be precisely dated relatively synchronous advances occurred at most glaciers in the early 1700s and were dated using living trees and in situ subfossil material all glaciers show three to five subsequent advances mostly concentrated between the mid 19th and early 20th centuries estimates based on landsat tm imagery indicate these glaciers lost between 15 and 46 of their lia areas by 1984 and a further 5 18 by 2005 with the smallest glaciers showing the greatest proportional loss paired comparisons of contemporary and the earliest known photography for the glaciers in the fitz roy area confirm this mass loss these results provide important new information on the glacier history of this area but additional more precisely dated records are needed from many more sites before we can fully elucidate the complex late holocene glacial history of this region

scaling time integrated in situ cosmogenic nuclide production rates using a continuous geomagnetic model abstract spatial and temporal variations in earth s magnetic field affect the corresponding time integrated distribution of in situ cosmogenic nuclide cn production rates these effects can be quantified by the effective vertical cutoff rigidity r c a measure of the energy required for primary cosmic rays to penetrate the geomagnetic field and interact with the atmosphere at a given location recent cn production rate scaling models are based on atmospheric cosmic ray measurements parameterized using r c estimates derived from detailed modern geomagnetic field representations which include both dipole and non dipole field contributions however published methods for quantifying time integrated geomagnetic effects on cn production rate scaling rely on various geocentric dipolar approximations to r c driven by separate records of paleomagnetic pole position and paleointensity therefore applying dipolar paleomagnetic records spanning millennial time scales which explicitly ignore past non dipole effects to scaling models derived using modern geomagnetic field representations may lead to systematic errors in any calculated results a recently published continuous geomagnetic model covering the last 7 kyr cals7k 2 m korte and c g constable continuous geomagnetic field models for the past 7 millennia 2 cals7k 2005 geochem geophys geosyst 6 q02h16 doi 10 1029 2004gc000801 may allow reduction of such errors by bridging the gap between detailed modern geomagnetic and simplified paleomagnetic models we have developed a new model framework describing temporal and spatial variation in r c for 0 7 ka and earlier based on cals7k 2 which explicitly accounts for non dipole field effects while attempting to mitigate systematic scaling biases scaling factors derived using the new r c framework predict significant longitudinal variability in time integrated cn production while predictions using dipolar geomagnetic approximations do not one can test these predictions using in situ cosmogenic 14 c in situ 14 c in quartz due to its short half life 5 73 kyr 14 c attains secular equilibrium between production and decay after approximately 25 kyr of exposure at which point its measured concentration is only a function of its integrated average production rate initial in situ 14 c results from samples at secular equilibrium from 38 n and 3 5 km in tibet and eastern california are consistent with the longitudinal variability predicted by the new framework

sensitivities of the equilibrium line altitude to temperature and precipitation changes along the andes abstract equilibrium line altitudes elas of alpine glaciers are sensitive indicators of climate change and have been commonly used to reconstruct paleoclimates at different temporal and spatial scales however accurate interpretations of ela fluctuations rely on a quantitative understanding of the sensitivity of elas to changes in climate we applied a full surface energy and mass balance model to quantify ela sensitivity to temperature and precipitation changes across the range of climate conditions found in the andes model results show that ela response has a strong spatial variability across the glaciated regions of south america this spatial variability correlates with the distribution of the present day mean climate conditions observed along the andes we find that elas respond linearly to changes in temperature with the magnitude of the response being prescribed by the local lapse rates ela sensitivities to precipitation changes are nearly linear and are inversely correlated with the emissivity of the atmosphere temperature sensitivities are greatest in the inner tropics precipitation becomes more important in the subtropics and northernmost mid latitudes these results can be considered an important step towards developing a framework for understanding past episodes of glacial fluctuations and ultimately for predicting glacier response to future climate changes

large scale control on the patagonian climate abstractpatagonia located in southern south america is a vast and remote region holding a rich variety of past environmental records but a small number of meteorological stations precipitation over this region is mostly produced by disturbances embedded in the westerly flow and is strongly modified by the austral andes uplift on the windward side leads to hyperhumid conditions along the pacific coast and the western slope of the andes in contrast downslope subsidence dries the eastern plains leading to arid highly evaporative conditions the authors investigate the dependence of patagonia s local climate precipitation and near surface air temperature year to year variability on large scale circulation anomalies using results from a 30 yr long high resolution numerical simulation variations of the low level zonal wind account for a large fraction of the rainfall variability at synoptic and interannual time scales zonal wind also controls the amplitude of the air temperature annual cycle by changi

loess chronology of the middle and upper pleistocene in tadjikistan the loess paleosol sequences of central asia are continuous terrestrial records of the quaternary period and enable detailed comparison with paleoclimatic archives such as marine and ice core records in order to reconstruct regional and global paleoclimatic and paleoecological development during the past 130 000 years thermoluminescence tl and infrared stimulated luminescence irsl dating methods are applied to the extensively studied loess paleosol sequence of the section at darai kalon chashmanigar tadjikistan in order to determine a more accurate chronological framework and climatostratigraphic reconstruction for the last interglacial glacial cycle luminescence dating suggests that the loess above the first pedocomplex from the top pc1 accumulated during the last glacial period a high accumulation rate of up to 1 20 m per 1000 years was determined for the last glacial loess especially for the uppermost 5 8 m pc1 formed during the last interglacial period oxygen isotope stage 5 the loess between pc1 and pc2 is designated to be of penultimate glacial deposition age infrared stimulated luminescence and tl age estimates are in agreement to 80 000 years before present bp indicating a long distance transport of the aeolian dust prior to deposition the upper numerical age limit range is between 300 000 and 450 000 years however reliable dating of the loess older than 130 000 years is not possible due to age scatter between samples and an inadequate increase of paleodose with depth this high resolution dating study underlines the importance of the section at darai kalon and indicates that it is one of the most continuous loess paleosol records of the northern hemisphere the chronological results are particularly important for the reconstruction of the human evolution in central asia suggesting much older age estimates than previously obtained for most of the archeological key sites associated with pc5 and pc4 in tadjikistan