enamel diagenesis at south african australopith sites implications for paleoecological reconstruction with trace elements abstract elemental ratio data from archaeological and paleontological bone have often been used for paleoecological reconstruction but recent studies have shown that even when solubility profiling techniques are employed in an attempt to recover biogenic signals bone is an unreliable material as a result there has been renewed interest in using enamel for such studies as it is known to be less susceptible to diagenesis nevertheless enamel is not immune from diagenetic processes and several studies have suggested that paleoecologically relevant elements may be altered in fossil enamel here we investigate sr ba zn and pb compositions of enamel from south african karstic cave sites in an effort to ascertain whether or not this material provides reliable paleoecological information we compared enamel data for mammals from three fossil sites aged 1 8 3 0 ma all of which are on dolomites with data from modern mammals living on dolomitic and granitic substrates sr ca and ba ca are about three times higher in enamel from modern mammals on granites than those living on dolomites stressing the need for geologically appropriate modern fossil comparisons after pretreatment with dilute acid we found no evidence of increased sr ca ba ca or pb ca in fossil enamel in contrast zn ca increased by over five times at one site makapansgat but much more subtly elsewhere ecological patterning in sr ca ba ca and sr ba ratios was also retained in fossil enamel this study suggests that sr ca ba ca and pb ca data likely preserve paleoecological information from these sites but also demonstrates that geologically similar sites can differ in the degree to which they impart certain elements zn in this case to fossils thus screening is probably necessary on a site by site basis lastly further investigation of elemental distributions in modern foodwebs is necessary before elemental ratio analysis can become a common tool for paleoecological reconstruction

oxygen isotopic composition of fossil horse tooth phosphate as a record of continental paleoclimate abstract oxygen isotopic elemental and x ray data are presented for a suite of 24 fossil horse teeth from nebraska ranging in age from 18 2 to 8 5 ma to test the use of 18o of enamel phosphate 18op04 as a quantitative record of continental climate modern equid teeth were analyzed to estimate a relationship between 8op04 and environment water multiple samples of seven different fossil species from burge quarry a 12 ma attritional fossil deposit indicate the diagenetic overprints exist but can be detected by decreased p concentration and increased crystallinity relative to modern enamel isotopic variation for the pristine samples from burge quarry is 1 5 1 n 9 which may represent the resolution of the procedure within a stratigraphic horizon there are no apparent correlations with body size hypsodonty or phylogeny a range of 7 0 in 18op04 occurs over the 10 m y interval a trend towards depleted 18op04 of about 4 corresponds to a depletion of up to 6 0 in 18o of precipitation between 18 2 and 8 5 ma but the range of variation of burge is large relative to the climate signal our results demonstrate that 18op04 should be useful in quantitatively reconstructing cenozoic continental paleoclimate on 106 year timescales isotopic variation due to taphonomic bias and the terrestrial rock record will likely obscure higher order climate signals

the life cycle of the northern hemisphere sudden stratospheric warmings motivated by recent evidence of strong stratospheric tropospheric coupling during the northern hemisphere winter this study examines the evolution of the atmospheric flow and wave fluxes at levels throughout the stratosphere and troposphere during the composite life cycle of a sudden stratospheric warming the composite comprises 39 major and minor warming events using 44 years of ncep ncar reanalysis data the incipient stage of the life cycle is characterized by preconditioning of the stratospheric zonal flow and anomalous quasistationary wavenumber 1 forcing in both the stratosphere and troposphere as the life cycle intensifies planetary wave driving gives rise to weakening of the stratospheric polar vortex and downward propagation of the attendant easterly wind and positive temperature anomalies when these anomalies reach the tropopause the life cycle is marked by momentum flux and mean meridional circulation anomalies at tropospheric levels that are consistent with the negative phase of the northern hemisphere annular mode the anomalous momentum fluxes are largest over the atlantic half of the hemisphere and are associated primarily with waves of wavenumber 3 and higher

high resolution trace element distributions and models of trace element diffusion in enamel of late neolithic early chalcolithic human molars from the rioja alavesa region north central spain help to separate biogenic from diagenetic trends abstract high resolution in situ trace element xrf maps and profiles were measured on the enamel exposed in cross sections through archaeological human permanent molars from seven late neolithic early chalcolithic funerary caves and megalithic graves of north central iberia changes in concentrations of fe zn and sr in inward direction into the enamel shed light on diagenetic and endogenous trace element concentrations in archaeological tooth enamel most of these profiles resemble sigmoid shaped leaching profiles suggesting that a combination of diffusion and advection processes govern the uptake of trace elements into the enamel from pore fluids on the outside of the tooth and in the more porous dentine the present study shows how diffusion advection da models can be fitted to these trace element profiles to explain changes in trace element concentrations that happen during diagenesis da models explain a major part of the variation observed in leaching profiles into the enamel and can be used to reconstruct endogenous trace element concentrations leaching times and leaching depth as well as trace element concentrations in ambient pore water during diagenesis models of trace element leaching together with trace element mapping reveal that fe zn and sr concentrations consistently increase during diagenesis regardless of the type of burial site i e funerary caves vs megalithic graves profiles of pb concentrations show much smaller concentration gradients causing da model fitting to be less accurate modelled leaching depths of 300 400 m warrant a careful approach when sampling for endogenous archaeological tooth enamel for trace element and stable isotope analysis results also show that it is possible to reconstruct endogenous trace element concentrations from these samples even without applying pretreatment procedures because leaching of trace elements into the enamel often remains limited to the outer 300 400 m of the enamel on archaeological timescales modelled leaching times are about ten times lower than the age of the samples suggesting that the rate of trace element leaching into tooth enamel slows down or even halts during the burial period

assessment of archaeological bone and dentine preservation from lazaret cave middle pleistocene in france chemical and structural changes in bones and dentine from cervus elaphus jaws during fossilization were studied by chemical analysis infrared spectroscopy ir and x ray diffraction xrd data were used to discuss the modifications of bones and dentine from the lazaret prehistoric cave nice france which is an important archeologic site of middle pleistocene age fossil bones and dentine mainly consisted of hydroxy carbonate apatite as the primary phase and of calcite as a secondary phase carbonation fluorination and recrystallization processes are shown as more important in bone and dentine than in tooth enamel a good correlation was found between the a cell parameter of apatite and its co3 and fluorine contents in the bones studied fluorine enrichment seems to be related to the permeability of the upper sedimentary levels lazaret fossil bones and dentine are less stable than enamels and their use for dating has to be taken with caution

the relative efficacy of fluvial and glacial erosion over modern to orogenic timescales it has been debated whether rivers or glaciers are more effective agents of erosion a global compilation of erosion rates reveals that both are capable of generating rates of erosion that match or exceed the highest rates of rock uplift since the late nineteenth century it has been debated whether rivers or glaciers are more effective agents of erosion1 the dramatic landscapes associated with glaciated terrain have often led to the argument that glaciers are more erosive than rivers and recent studies have documented the topographic signature of an ice controlled limit of mountain height known as the glacial buzz saw 2 3 here we present a new global compilation of erosion rates which questions the conventional view of glaciers and erosion in regions of rapid tectonic uplift erosion rates from rivers and glaciers both range from 1 to over 10 mm yr 1 indicating that both are capable of generating erosion rates matching or exceeding the highest rates of rock uplift moreover a comparison of erosion rates over timescales ranging from 101 to 107 years indicates that glacial erosion tends to decrease by one to two orders of magnitude over glacial cycles whereas fluvial erosion rates show no apparent dependence on time we conclude that tectonics controls rates of both fluvial and glacial erosion over millennial and longer timescales and that the highest rates of erosion 10 mm yr 1 generally result from a transient response to disturbance by volcanic eruptions climate change and modern agriculture

holocene optimum events inferred from subglacial sediments at tschierva glacier eastern swiss alps abstract this study investigates the subglacial sedimentary archive at tschierva glacier eastern swiss alps subfossil wood remains found at the retreating glacier tongue indicate that their emergence results from recent transport from an upvalley basin a confluence basin like structure was found to exist by georadar measurements underneath the present glacier in combination with high resolution age determinations based on dendrochronology and radiocarbon dating it is implied that a retreated tschierva glacier allowed vegetation growth and sediment accumulation in that basin three periods of glacier recession were detected which occurred around 9200 cal yr bp from 7450 to 6650 cal yr bp and from 6200 to 5650 cal yr bp these periods are called holocene optimum events hoe accordingly an equilibrium line rise 220 m compared to the reference period from 1960 to 1985 was inferred from digital elevation models of former glacier extents since glacier mass balance depends on summer june july august temperature and precipitation an equilibrium line altitude ela rise of 220 m implies a summer temperature increase of about 1 8 c assuming unchanged precipitation during the dated hoe alternative calculations point to probable temperature increase in a broad interval between 1 0 c taking into account a precipitation change of 250 mm a to 2 5 c with 250 mm a precipitation change supporting earlier paleotemperature estimates it is proposed that higher mean summer insolation caused a stronger seasonality during the mid holocene as compared to late holocene conditions

stable isotope analyses of carbonate complicated by nitrogen oxide contamination a delaware basin example abstract whole rock subsurface samples from the cherry canyon formation delaware basin were used to document the presence of a contaminant gas affecting the isotopic composition of acidified carbonate the whole rock material when reacted in purified phosphoric acid using the mccrea 1950 method produces a contaminant mass 46 gas nitrogen dioxide no2 this mass 46 gas contributes to the 18o 16o ratio mass 46 44 artificially enriching the 18o value and masking the true isotope signature of the co2 derived from the carbonate minerals acidified whole rock samples containing low carbonate 18o pdb values some greater than 30 conversely samples with higher carbonate 5 have 18o values ranging from 5 to 8 hence diluting the effects of the contaminant gas on the mass 46 44 ratio after purifying the co2 produced by the mccrea 1950 method with a reduction furnace all of the 18o values fall in the range of 0 to 12 regardless of carbonate content th 16c pdb values remain unchanged after reduction furnace purification indicating no effect on mass 45 44 ratio the inferred source of the contaminant no2 gas is from inorganic ammonium adsorbed to interlayer sites of alumina silicates such as illite and mica this source is supported by the detection of ammonium and clays in the whole rock material and the lack of correlation between percent organic carbon and 18o values influenced by no2 to eliminate the effect of the contaminant gas on 18o values we describe a simple procedure that removes the contaminant no2 gas yielding the true isotopic signal from the carbonate minerals in whole rock material

west greenland and global in situ 14c production rate calibrations the in situ cosmogenic nuclide 14 c is unique compared with other nuclides because of its short half life and when combined with longer lived isotopes e g 10 be in situ 14 c can be a powerful tool for deciphering recent and complex surface exposure histories like all in situ cosmogenic nuclides quantifying earth surface processes with in situ 14 c requires a well constrained in situ 14 c production rate we present a production rate calibration from an independently dated moraine in west greenland previously used as an in situ 10 be production rate calibration site the local in situ 14 c production rate is 22 8 1 4 atoms g 1 a 1 69 28un 50 76u w 350m asl and when scaled to sea level high latitude using time dependent lal stone scaling lm we calculate a spallation only in situ 14 c production rate of 12 0 0 9 atoms g 1 a 1 and a 14 c 10 be production rate ratio of 3 1 0 2 the west greenland in situ 14 c production rate is indistinguishable from the new zealand promontory point and scottish highlands in situ 14 c production rates when combined we calculate a global production rate of 12 1 0 5 atoms g 1 a 1 lm copyright 2014 john wiley sons ltd

deglaciation of coastal south western spitsbergen dated with in situ cosmogenic 10be and 14c measurements the svalbard barents ice sheet was predominantly a marine based ice sheet and reconstructing the timing and rate of its decay during the last deglaciation can inform predictions of future decay of marine based ice sheets e g west antarctica records of ice sheet change are now routinely built with cosmogenic surface exposure ages but in some regions this method is complicated by the presence of isotopic inheritance yielding artificially old and erroneous exposure ages here we present forty six 1025 be ages from bedrock n 38 and erratic boulders n 8 in southwestern spitsbergen that when paired with in situ 1427 c measurements n 5 constrain the timing of coastal deglaciation following the last glacial maximum 10be and 1428 c measurements from bedrock along a 400 m elevation transect reveal inheritance skewed 10be ages whereas 1429 c measurements constrain 400 m of ice sheet thinning and coastal deglaciation at 17 4 1 5 ka combined with three additional 10be dated coastal sites we show that the southwestern margin of the svalbard barents ice sheet retreated out of norwegian sea between 18 16 ka in situ 1432 c measurements can provide key chronological information on ice sheet response to the last termination in cases where measurements of long lived nuclides are compromised by isotopic inheritance

multicentury glacier fluctuations in the swiss alps during the holocene subfossil remains of wood and peat from six swiss glaciers found in proglacial fluvial sediments indicate that glaciers were smaller than the 1985 reference level and climatic conditions allowed vegetation growth in now glaciated basins an extended data set of swiss glacier recessions consisting of 143 radiocarbon dates is presented to improve the chronology of glacier fluctuations a comparison with other archives and dated glacier advances suggests 12 major recession periods occurring at 9850 9600 93008650 85508050 77007550 74506550 61505950 57005500 52004400 43003400 28002700 21501850 14001200 cal yr bp it is proposed that major glacier fluctuations occurred on a multicentennial scale with a changing pattern during the course of the holocene after the younger dryas glaciers receded to a smaller extent and prolonged recessions occurred repeatedly culminating around 7 cal kyr bp after a transition around 6 cal kyr bp weak fluctuations around the present level dominated after 3 6 cal kyr bp less frequent recessions interrupted the trend to advanced glaciers peaking with the prominent little ice age this trend is in line with a continuous decrease of summer insolation during the holocene

strengthening of the tropopause inversion layer during the 2009 sudden stratospheric warming a merra 2 study abstractthe behavior of the tropopause inversion layer til during the 2009 sudden stratospheric warming ssw is analyzed using nasa s modern era retrospective analysis for research and applications version 2 merra 2 and short term simulations with the merra 2 general circulation model consistent with previous studies it is found that static stability in a shallow layer above the polar tropopause sharply increases following the ssw leading to a strengthening of the high latitude til simultaneously the height of the thermal tropopause decreases by around 1 km similar behavior is also detected during other major ssw events between the years 2004 and 2013 using an ensemble of general circulation model forecasts initialized from merra 2 it is demonstrated that the primary cause of the strengthening of the til is an increased convergence of the vertical component of the stratospheric residual circulation in response to an ssw induced acceleration of the mean downward motion between 75 and 90 n

a mechanism to explain the variations of tropopause and tropopause inversion layer in the arctic region during a sudden stratospheric warming in 2009 the mechanism to explain the variations of tropopause and tropopause inversion layer til in the arctic region during a sudden stratospheric warming ssw in 2009 was studied with the modern era retrospective analysis for research and applications reanalysis data and gps constellation observing system for meteorology ionosphere and climate cosmic temperature data during the prominent ssw in 2009 the cyclonic system changed to the anticyclonic system due to the planetary wave with wave number 2 wave2 the gps cosmic temperature data showed that during the ssw in 2009 the tropopause height in the arctic decreased accompanied with the tropopause temperature increase and the til enhancement the variations of the tropopause and til were larger in higher latitudes a static stability analysis showed that the variations of the tropopause and til were associated with the variations of the residual circulation and the static stability due to the ssw larger static stability appeared in the upper stratosphere and moved downward to the narrow region just above the tropopause the descent of strong downward flow was faster in higher latitudes the static stability tendency analysis showed that the strong downward residual flow induced the static stability change in the stratosphere and around the tropopause the strong downwelling in the stratosphere was mainly induced by wave2 which led to the tropopause height and temperature changes due to the adiabatic heating around the tropopause a pair of downwelling above the tropopause and upwelling below the tropopause due to wave2 contributed to the enhancement of static stability in the til immediately after the ssw

ion probe measurement of rare earth elements in biogenic phosphates abstract the rare earth element ree distributions in individual fish teeth and conodonts have been measured by ion probe concentrations and la yb ratios show little variations except in the enamel which suggests that ree uptake from the sedimented biogenic debris takes place at the water sediment interface as an essentially quantitative process without fractionation late diagenetic disturbances remained of marginal importance hence ree in phosphatic debris might reflect the input from the overlying water column

a major stratospheric sudden warming event in january 2009 abstract the major stratospheric sudden warming ssw event of january 2009 is analyzed using the japan meteorological agency jma climate data assimilation system jcdas this ssw event is characterized by the extraordinary predominance of the planetary scale wave of zonal wavenumber 2 wave 2 the total amount of the upward eliassen palm ep flux for wave 2 was the strongest since the winter of 1978 79 it is found that the remarkable development of the upper troposphere ridge over alaska played important roles in the ssw in january 2009 during the first development stage the ridge excited wave packets upward as well as eastward over around alaska the eastward propagating packets intensified a trough over eastern siberia which led to the development of the planetary wave over eastern siberia during the second development stage the results of this study indicate that the pronounced wave 2 pattern observed in the stratosphere was brought about by accumulative effects of rather localized propagati

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

equatorial quasi biennial oscillation influence on northern winter extratropical circulation 1 this study investigated the holton tan relationship between the equatorial quasi biennial oscillation qbo and the polar vortex as seen in the era 40 reanalysis and era interim analysis 1980 2004 25 years data sets and in ensemble simulated data sets five members covering the period 1980 2004 125 years by using the meteorological research institute chemistry climate model mri ccm and focusing on the northern hemisphere winter the primary tools employed were composite differences in zonal wind temperature and eliassen palm ep fluxes although not many global circulation models can simulate the qbo realistically the mri ccm which includes the interaction between qbo dynamics and the ozone hence heating distribution reproduces a self generated qbo that is fairly realistic in agreement with the finding of previous studies our results revealed that the conventional holton tan explanation that the equatorial winds in the lower stratosphere act as a waveguide for midlatitude planetary wave propagation cannot explain the winter circulation in either the era 40 data or the simulation although the composite differences in zonal wind and temperature show a slight yet statistically significant holton tan effect i e the stratospheric polar vortex is weaker and more disturbed under easterly qbo conditions the ep flux diagnostics do not show more poleward propagation in the midlatitude stratosphere rather planetary waves propagate more equatorward as well as more upward during the easterly phase of the qbo

a chironomid based holocene summer air temperature reconstruction from the swiss alps we developed a quantitative chironomid july air temperature inference model based on surface sediments from 81 swiss lakes and applied it to the holocene subfossil chironomid record of hinterburgsee a small subalpine lake in the northern swiss alps present day mean july air temperature of 11 3 c after smoothing to reduce the high between sample variability of inferred temperatures the reconstruction indicates july air temperatures of 10 4 10 9 c at the end of the younger dryas of 11 9 12 8 c during the early and mid holocene 11500 4000 cal bp and slightly lower temperatures of 11 5 12 0 c during the late holocene 3500 1000 cal bp a warming trend inferred for the past millennium is most likely an artifact of human impact on hinterburgsee s chironomid fauna rather than a genuine temperature signal the most prominent climatological events during the holocene were two periods of lower temperatures at c 10700 10500 cal bp and 8200 7700 cal bp and an abrupt shift to a cooler late holocene cl

effect of stratospheric sudden warming and vortex intensification on the tropospheric climate 1 the effect of stratospheric sudden warming ssw and vortex intensification vi on the tropospheric climate is examined through composite analysis of the observational data specifically examined in the present study is the eulerian meridional circulations associated with ssw and vi it is found that prominent signal in the troposphere tends to appear associated with the occurrence of ssw and vi the patterns created are very similar between ssw and vi except for the polarity in the high latitude region the pattern similar to the arctic oscillation ao is created before and after the occurrence of ssw and vi with changing polarities in the tropics convection tends to enhance in the southern hemisphere northern hemisphere tropics after the occurrence of ssw vi these signals are created through three prominent cells of the anomalous eulerian meridional circulation that extends from polar cap to the tropical southern hemisphere the mechanism for the formation of the cells associated with ssw and vi is also discussed

diffusion of rare earth elements in fish teeth from deep sea sediments the distribution of rare earth elements rees in biogenic phosphate phases in sediments such as the remains of fish teeth has been proposed as an indicator of the depositional environment in the water column recording for example palaeo redox conditions1 and isotope geochemical2 5 and hydrothermal6 7 processes enrichment of these phases in rees takes place only during early diagenesis8 9 for which reason the ree signal has often been assumed to represent the unfractionated record of ree distribution in the water column overlying the sediment surface1 4 5 10 here we report on studies of ree zoning in fish teeth from pacific sediments from which we extract a ree diffusion coefficient of 70 mm2 myr 1 this value suggests that diffusion of rees from sea water into the fish teeth before burial is too slow to produce the enrichments observed instead the ree distributions must derive from the surrounding sediment pore fluids the use of these distributions as palaeoceanographic indicators is therefore called into question

the expansion of c4 grasses and global change in the late miocene stable isotope evidence from the americas j3c values in paleosols and fossil teeth have been used to document the expansion of c plants in south asia africa and north america during the late miocene however the exact timing and rate of expansion of c vegetation is unclear outside the old world because of a lack of high resolution records we present a high resolution record from northwest argentina in which the s13c values of soil carbonate rise above a threshold of 8 0 suggesting the presence of c plants starting at 7 3 6 7 ma sr3c values of fossil teeth from well dated sections in south and north america display a concomitant increase of c plants in the diets of large herbivores these results show that the late miocene expansion of c plants was global but occurred at different rates in each region while it is has been suggested that declining pc0 levels during the late neogene caused c plant expansion climate change such as an increase in summer dominated rainfall regimes globally is an alternative explanation the 6 0 soil carbonate records from south asia east africa and now also northwest argentina all show an increase of at least 3 4 in the late neogene either the result of climate change or of greater evaporation in average grassland soils

erosion under climate and human pressures an alpine lake sediment perspective we review the scientific efforts over the last decades to reconstruct erosion from continuous alpine lake sediment records we focused both on methodological issues showing the growing importance of non destructive high resolution approaches xrf core scanner as well as progresses in the understanding of processes leading to the creation of an erosion signal in lakes we distinguish continuous records from event records both provide complementary information but need to be studied with different approaches continuous regionally relevant records proved to be particularly pertinent to document regional erosion patterns throughout the holocene in particular applying the source to sink approach event based approaches demonstrated and took advantage of the strong non linearity of sediment transport in high altitude catchment areas this led to flood frequency and intensity reconstructions highlighting the influence of climate change upon flood dynamics in the mountain the combination of different record types both in terms of location high vs low elevation sedimentology high vs low terrigenous contribution and significance local vs regional is one of the main outputs of this paper it allows the establishment of comprehensive histories of nw french alps erosion but also and consequently soil dynamics and hydrological patterns throughout the holocene we also discuss the influence of glacier dynamics one of the major agents of erosion in the alps a major feature is the growing human influence upon erosion at a local scale since at least the middle of the bronze age 3500 cal bp however and according to the regional record from lake bourget only few periods of rising erosion at local scales generated a regional record that can be discriminated from wetter climatic periods among them the period between 200 bce and 400 ad appeared to be marked by a generalised rise in human triggered erosion at local scales in the northern french alps this review highlights the importance of modern high resolution and interdisciplinary studies of lake sediments in order to better understand the complex relationships between humans climate and the earth system in general we strongly argue that regional integration of data is now required to move a step further such an integration is easier with cost and time effective methods as well as after a better definition of approaches and their limits this should lead to a stronger collaboration between paleo data producers and modellers in the near future

geology and palaeontology of the upper miocene toros menalla hominid locality chad all six known specimens of the early hominid sahelanthropus tchadensis come from toros menalla site 266 tm 266 a single locality in the djurab desert northern chad central africa here we present a preliminary analysis of the palaeontological and palaeoecological context of these finds the rich fauna from tm 266 includes a significant aquatic component such as fish crocodiles and amphibious mammals alongside animals associated with gallery forest and savannah such as primates rodents elephants equids and bovids the fauna suggests a biochronological age between 6 and 7 million years taken together with the sedimentological evidence the fauna suggests that s tchadensis lived close to a lake but not far from a sandy desert perhaps the oldest record of desert conditions in the neogene of northern central africa

the alps with little ice evidence for eight holocene phases of reduced glacier extent in the central swiss alps glacially deformed pieces of wood organic lake sediments and clasts of reworked peat have been collected in front of alpine glaciers since ad 1990 the palaeoglaciological interpretation of these organic materials is related to earlier phases of glacier recession surpassing that of today s shrunken glaciers and to tree growth and peat accumulation in the valleys now occupied by the glaciers glacial transport of the material is indicated by wood anatomy incorporated silt sand and gravel particles missing bark and deformed treerings a total of 65 samples have been radiocarbon dated so far and clusters of dates provide evidence of eight phases of glacier recession 9910 9550 9010 7980 7250 6500 6170 5950 5290 3870 3640 3360 2740 2620 and 1530 1170 calibrated years bp allowing for the timelag between climatic fluctuations glacier response and vegetation colonization these recession phases may lag behind climatic changes by 100 200 years

the stratospheric major warming of winter 1984 85 observations and dynamical inferences the evolution and dynamics of the major stratospheric warming of 1984 85 are described and discussed using synoptic maps of geopotential height and temperature fields of q vectors isentropic maps of ertel s potential vorticity and diagnostics based on zonal averaging and departures therefrom it is argued that the stratosphere cannot be regarded as being pre conditioned before the warming in the conventional sense of the term and that an important element of the warming was that the flow was highly asymmetric at the onset of the rapid breakdown of stratospheric westerlies nonlinear dynamics was involved as evidenced by an anticorrelation in time between the amplitudes of zonal waves 1 and 2 by the magnitude of a nonlinear term compared with those of linear terms in a governing equation and by the irreversible rearrangement of potential vorticity apparent loss of potential vorticity in the stratosphere is associated in part with differential advection of air in a vertically sheared flow salient features of the large scale flow in the troposphere during the stratospheric warming are noted

discovery of early holocene wood and peat on the forefield of the pasterze glacier eastern alps austria during recent years a number of fragments of pinus cembra and larix decidua as well as peat were found in front of the tongue of the pasterze glacier in the eastern alps these were washed out by the stream from under the present ice the wood originates from trees which reached ages of upto 400 years or more radiocarbon dating shows them to come from the early holocene they indicate that between cal bc 8100 and cal bc 6900 the pasterze glacier was smaller than at present the pasterze glacier advanced around cal bc 6900 a lump of peat shows that around cal bc 6300 at the latest the pasterze glacier was again smaller than today the radiocarbon age of the fulvic acid fraction of thepeat suggests that growth could have continued until cal bc 5430 5080 further wood samples dated to around cal bc 4800 and cal bc 3800 show that at these times the pasterze glacier was smaller than at present the pasterze glacier had a relatively limited extent over long periods inthe early holocene thus mostly favou

impact of relative sea level and rapid climate changes on the architecture and lithofacies of the holocene rhone subaqueous delta western mediterranean sea abstract the modern rhone delta in the gulf of lions nw mediterranean is a typical wave dominated delta that developed after the stabilization of relative sea level following the last deglacial sea level rise similar to most other deltas worldwide it displays several stacked parasequences and lobes that reflect the complex interaction between accommodation sediment supply and autogenic processes on the architecture of a wave dominated delta the interpretation of a large set of newly acquired very high resolution seismic and sedimentological data well constrained by 14c dates provides a refined three dimensional image of the detailed architecture seismic bounding surfaces sedimentary facies of the rhone subaqueous delta and allows us to propose a scenario for delta evolution during the last deglaciation and holocene the subaqueous delta consists of parasequence like depositional wedges a few metres to 20 30 m in thickness these wedges first back stepped inland toward the nw in response to combined global sea level rise and overall westward oceanic circulation at a time when sediment supply could not keep pace with rapid absolute eustatic sea level rise at the younger dryas preboreal transition more rapid sea level rise led to the formation of a major flooding surface equivalent to a wave ravinement surface after stabilization of global sea level in the mid holocene accommodation became the leading factor in controlling delta architecture an eastward shift of depocentres occurred probably favoured by higher subsidence rate within the thick messinian rhone valley fill the transition between transgressive backstepping geometry and regressive prograding geometry para sequences resulted in creation of a maximum flooding surface mfs that differs from a classical mfs described in the literature it consists of a coarse grained interval incorporating reworked shoreface material within a silty clay matrix this distinct lithofacies results from condensation erosion which appears as an important process even within supply dominated deltaic systems due to avulsion of distributaries the age of the mfs varies along strike between ca 7 8 and 5 6 kyr cal bp in relation to the position of depocentres and climatically controlled sediment supply the last rapid climate change of the holocene the little ice age 1250 1850 ad had a distinct stratigraphic influence on the architecture and lithofacies of the rhone subaqueous delta through the progradation of two deltaic lobes in response to changes in sediment supply linked to rapid climate changes and to anthropic factors the rhone delta evolved from wave dominated to fluvial dominated and then wave dominated again

a new extraction technique and production rate estimate for in situ cosmogenic 14c in quartz the potential of in situ cosmogenic 14c in situ 14c for surficial process studies is widely recognized yet a reliable means of isolating it has proved difficult to develop we present here a new method for extracting in situ 14c from quartz that overcomes difficulties encountered with earlier techniques yielding more reliable production rate estimates comparison of 14c thermal release patterns from surficial and deeply shielded quartz samples lifton 1997 demonstrated that contaminant 14c is released at or below 500 c and that 14c released between 500 and 1500 c is essentially all in situ produced the new technique builds on this key result using resistance heating of samples in the presence of a lithium metaborate libo2 flux and collection of all evolved carbon as co2 between 500 c and 1100 to 1200 c our improved method has four distinct advantages over other extraction methods 1 we can identify and quantitatively eliminate atmospheric organic 14c contamination 2 we can identify the in situ 14c component unambiguously without assumptions of 14co 14co2 production proportions within the rock or equilibria on extraction 3 in situ 14c is reliably extracted from quartz at lower temperatures and in less time than earlier methods and 4 blank 14c levels are consistently low 2 3 0 1 105 14c atoms 1 our new extraction procedures should thus enable researchers to use in situ 14c in diverse applications without reservation we developed our new procedures using samples of wave cut quartzite benches from the well dated bonneville 17 4 0 3 cal ky and provo 16 8 0 3 cal ky shorelines of pleistocene lake bonneville utah and from underlying deeply shielded locations in situ 14c was extracted from quartz separated from 2 bonneville shoreline samples 6 aliquots and 1 provo shoreline sample 2 aliquots results demonstrate that our new procedures can effectively isolate the in situ 14c fraction with replicate analytical precision better than 2 1 n 5 while remaining consistent with earlier results this level of precision and accuracy is comparable to or exceeds those currently obtainable with in situ cosmogenic 10be 26al 3he 21ne and 36cl resulting weighted mean in situ 14c site production rates for the bonneville and provo shorelines are 52 9 1 7 14c atoms g sio2 y and 48 7 2 8 14c atoms g sio2 y 1 respectively consistent with earlier production rate estimates current and previously published in situ 14c site production rate estimates were then scaled to sea level and high geomagnetic latitude using the latitude altitude scaling models of lal 1991 and dunai 2000 results indicate that both models yield sea level high latitude production rates consistent with independent estimates our new in situ 14c data yield integrated late quaternary production rate estimates at sea level and high latitude of 15 1 0 5 14c atoms g sio2 y using the lal 1991 model and 15 8 0 5 14c atoms g sio2 y with that of dunai 2000 until significant uncertainties in these models are addressed however we prefer the value from the widely used lal 1991 model as our best estimate of the integrated late quaternary production rate for in situ 14c

modulations in the planetary wave field induced by upward propagating rossby wave packets prior to stratospheric sudden warming events a case study a diagnostic framework is introduced in which anomalous zonally averaged rossby wave activity injection into the stratosphere is decomposed into a contribution solely from zonally confined upward propagating rossby wave packets and another from interaction of the wave packets with the climatological planetary waves to pinpoint the tropospheric sources of the wave packets a particular form of wave activity flux is evaluated for the associated circulation anomalies the framework is applied to reanalysis data for the period prior to a stratospheric sudden warming ssw event in january 2006 which was associated with two successive events of above normal wave activity injection from the troposphere in the earlier event a pair of wave packets that emanated from tropospheric anomalies over the north pacific and over europe enhanced the upward wave activity injection which was augmented further by their interaction with the climatological planetary wave in contrast in the later period a wave packet that emanated from an anticyclonic anomaly over the north atlantic is found to be the primary contributor to the enhanced planetary wave activity injection while its interaction with the climatological planetary wave contributed negatively the predominant importance of the sole contribution from a single wave packet is also found in a major ssw event observed over antarctica in september 2002 these results indicate that the diagnostic framework presented in this study is a useful tool for understanding the interaction between anomalies associated with zonally confined wave packets and climatological mean planetary waves in the study of stratosphere troposphere dynamical coupling copyright 2009 royal meteorological society

planetary scale wave activity as a source of varying tropospheric response to stratospheric sudden warming events a case study 1 stratospheric sudden warming ssw events are typically but not always accompanied by negative northern annular mode anomalies in the troposphere however large uncertainties remain as to which dynamical processes are responsible for those anomalies in order to highlight sources of variability in stratosphere troposphere coupling among ssw events we present a case study of three selected events and show detailed transformed eulerian mean diagnostics for momentum changes in the stratosphere and troposphere in the course of those events our results suggest that planetary scale waves especially the zonal wave number 2 component may play an important role not only for the onset of tropospheric anomalies in response to ssw events but also for introducing variability in the vertical coupling i e whether the tropospheric circulation anomalies lag lead or occur simultaneous to the weakening of the vortex particularly the meridional propagation of those waves in the upper troposphere could be an important factor that determines whether ssw events lag or lead tropospheric anomalies

a 16 ma record of paleodiet using carbon and oxygen isotopes in fossil teeth from pakistan abstract the siwalik sequence of northern pakistan contains a 16 ma record of paleosol carbonate and fossil teeth from which a record of paleovegetation can potentially be reconstructed and compared the carbon isotopic composition of paleosol carbonate and organic matter from siwalik strata reflects a major paleoecological change on the floodplains of major rivers beginning7 3 ma ago by 6 ma c 3 dominated plant communities probably composed of mostly trees and shrubs were displaced by nearly continuous c 4 grassland we find that the carbon isotopic ratios in herbivore tooth enamel reflect this dramatic ecologic shift carbonate in enamel older than 7 ma averages 11 in 13 c pdb consistent with a largely c 3 diet enamel from the plio pieistocene averages 1 9 in 13 c similar to the value displayed by modern c 4 grazers analysis of post burial carbonate cements and the concordance with isotopic evidence from paleosols argues strongly against major isotopic alteration of the enamel while coexisting bone may have been altered early in burial this study confirms that enamel apatite is useful for paleodietary reconstruction much further back in the geologic record than was previously thought

crystallinity and diagenesis of sedimentary apatites the crystallinity of sedimentary apatites was determined by fourier transform infrared spectroscopy ft ir using the splitting of a triply degenerate antisymmetric bending vibration of orthophosphate the crystallinity indices of recent marine apatites are low 3 0 3 6 while those of onland ancient apatites are high 4 5 7 8 indicating post depositional recrystallization the infrared spectra reveal that recrystallization is associated with a decrease in carbonate content substituting for po43 and an increase in fluoride order within the apatite structure the relationship between the crystallinity index and po43 18o suggests alteration of the primary isotopic composition by exchange reactions between po43 oxygens and surrounding waters the monterey samples have a large range of crystallinity index that reflects a set of complex and highly variable diagenetic conditions this demonstrates the use of ft ir criteria for differentiating between pristine and altered apatites and as a consequence for relating geochemical markers to formation or diagenetic environments it is suggested that only those samples that have low crystallinity indices c i 3 8 should be considered as pristine apatite spectra of fish remains indicate that differences in rare earth element ree patterns correspond to variations in crystallinity carbonate content and f order in the apatite lattice the fact that crystallinity is not correlated with geologic age suggests that environmental factors such as accumulation rate and pore water chemistry govern the recrystallization process in general sr content decreases and 18op exhibits high variability with increasing crystallinity

sediment evacuation and glacial erosion rates at a small alpine glacier 1 glacial erosion is known to be driven by sliding which occurs in brief episodes in the melt season what is not known is how well this sliding history is reflected in the sediment output from a glacier and to what degree temporary sediment storage in the glacier smoothes the history of sediment production we document sediment evacuation rates for three seasons at bench glacier a small temperate alpine glacier in the chugach range of alaska two lines of evidence suggest that subglacial sediment storage is small strong hysteresis in the relationship between sediment and water discharge argues for sediment exhaustion from the subglacial system on seasonal and flood event timescales uplift of the glacier surface during periods of enhanced basal motion reflects intimate contact of the glacier sole with up glacier inclined stoss slopes of bedrock bumps sediment evacuation rates at bench glacier should therefore closely track glacial erosion rates over annual timescales much of the sediment emerges in a major pulse that closely follows the termination of enhanced sliding each year suggesting that the conduits and well connected cavities that allowed removal of englacial water to terminate sliding also promoted efficient transport of sediment this small glacier efficiently modifies the landscape lowering its bed by 1 2 mm yr while sliding only 1 2 m yr our sparse measurements of instantaneous bed load discharge average 41 of concurrent suspended sediment discharge assuming that half of the suspended load derives from abrasion of subglacially quarried clasts roughly two thirds of the sediment evacuated can be attributed to quarrying

major ice sheet change in the weddell sea sector of west antarctica over the last 5 000 years until recently little was known about the weddell sea sector of the west antarctic ice sheet in the last 10 years a variety of expeditions and numerical modelling experiments have improved knowledge of its glaciology glacial geology and tectonic setting two of the sector s largest ice streams rest on a steep reverse sloping bed yet despite being vulnerable to change satellite observations show contemporary stability there is clear evidence for major ice sheet reconfiguration in the last few thousand years however knowing precisely how the ice sheet has changed in the past and when would allow us to better understand whether it is now at risk two competing hypotheses have been established for this glacial history in one the ice sheet retreated and thinned progressively from its last glacial maximum position retreat stopped at or very near the present position in the late holocene alternatively in the late holocene the ice sheet retreated significantly upstream of the present grounding line and then advanced to the present location due to glacial isostatic adjustment and ice shelf and ice rise buttressing both hypotheses point to data and theory in their support yet neither has been unequivocally tested or falsified here we review geophysical evidence to determine how each hypothesis has been formed where there are inconsistencies in the respective glacial histories how they may be tested or reconciled and what new evidence is required to reach a common model for the late holocene ice sheet history of the weddell sea sector of west antarctica

the retention of primary oxygen isotope compositions of fossil elephant skeletal phosphate fossil elephant remains from sediments of plio pleistocene age in the vicinity of lake turkana kenya provide insights into the ability of the phosphate oxygen system to preserve original 18o values 18op in the depositional environment individual fossil specimens exhibit systematic variations in the 18op values of their various tooth and bone components differences in 18op values between these skeletal components can be as high as 3 6 despite the fact that equivalent phases for individual modern elephants have 18op values which vary by less than 0 6 xrd traces of the different skeletal phases of modern and fossil samples also infer differential preservation of primary apatite crystallinities among the various fossil phases fossil samples of dentine cementum and bone have x ray spectra with sharper and more intense peaks compared to their modern counterparts but little change in crystallinity is observed for fossil enamel samples a model based on the premise that the enamel phase preserves primary isotope signatures and that the accompanying skeletal phases are partially re equilibrated with the fluids associated with the microbial decomposition of the elephant s carcass is consistent with the features of the 18op dataset this isotopic evidence in conjunction with the physical and chemical attributes of enamel has led us to postulate that enamel could be preserving primary isotope signatures while other skeletal components are affected to varying degrees by alteration processes in the burial environment

persistent positive north atlantic oscillation mode dominated the medieval climate anomaly the medieval climate anomaly mca was the most recent pre industrial era warm interval of european climate yet its driving mechanisms remain uncertain we present here a 947 year long multidecadal north atlantic oscillation nao reconstruction and find a persistent positive nao during the mca supplementary reconstructions based on climate model results and proxy data indicate a clear shift to weaker nao conditions into the little ice age lia globally distributed proxy data suggest that this nao shift is one aspect of a global mca lia climate transition that probably was coupled to prevailing la nina like conditions amplified by an intensified atlantic meridional overturning circulation during the mca

extraordinary features of the planetary wave propagation during the boreal winter 2013 2014 and the zonal wave number two predominance observational features of the winter 2013 2014 are investigated using of the japanese 55 year reanalysis jra 55 data this winter can be characterized by the continuous predominance of planetary waves of zonal wavenumber two wn2 that did not cause major sudden stratospheric warming ssw events it is found that the vertical component of the eliassen palm flux of wn2 for the winter 2013 2014 is almost equal to the highest value of the winter 2008 2009 the longitudinal distribution of vertical components of plumb wave activity flux wafz for this winter shows marked downward propagation around 100 w and upward propagation around 60 e both of which are the strongest of their type among the 56 winters since 1958 1959 the convergence of wave packets propagating from around 60 e contributes to the development and continuance of the quasi barotropic aleutian high which is associated with the extension of negative extended refractive index ks region the extension of negative ks region is related to the convergence or reflection of the wave packets emanating from tropospheric blocking highs developing in the north pacific ocean the development and continuance of the quasi barotropic aleutian high is considered to be one of plausible reasons for the lack of major ssws in the winter 2013 2014 in addition to these results we revealed the significant contribution of smaller scale waves with a zonal wavenumber of three or more to the structure of localized wave packet propagation in the stratosphere

a statistical analysis of the propagating quasi 16 day waves at high latitudes and their response to sudden stratospheric warmings from 2005 to 2018

glacier and lake level variations in west central europe over the last 3500 years on the basis of glacier and lake level records this paper attempts for the first time a comparison between high resolution palaeohydrological and palaeoglaciological data in west central europe over the past 3500 years a data set of tree ring width radiocarbon and archaeological data in addition to historical sources were used to reconstruct fluctuations of the great aletsch the gorner and the lower grindelwald glaciers in the swiss alps the three ice streams experienced nearly synchronous advances at c 1000 600 bc and ad 500 600 800 900 1100 1200 and 1300 1860 these glacier fluctuations show strong correspondence with lake level variations reconstructed in eastern france jura mountains and pre alps and on the swiss plateau this supports the hypothesis of climatically driven fluctuations historical data available for the period since ad 1550 reveal in detail various meteorological conditions behind the successive glacier advances however in agreement with the general trend shown by th

diagenesis in prehistoric bone problems and solutions abstract post depositional chemical alteration or diagenesis in prehistoric human bone is the major problem in the use of trace element analyses for dietary reconstruction following a review of recent studies of diagenesis we discuss means for evaluating post depositional chemical change in bone and for removing such contaminants three different procedures are described which reflect current efforts to evaluate and reduce the effects of diagenesis these include 1 mechanical cleaning 2 chemical cleaning through acid washing and 3 washing with a reducing agent these procedures usually remove major contaminants leaving significant potential of trace element analyses for the investigation of past diet

holocene temperature variations at a high altitude site in the eastern alps a chironomid record from schwarzsee ob solden austria few well dated quantitative holocene temperature reconstructions exist from high altitude sites in the central eastern alps here we present a chironomid based quantitative reconstruction of mean july air temperatures tjuly throughout the holocene for a remote high mountain lake schwarzsee ob solden situated above the treeline at 2796 m a s l in the austrian alps applying a chironomid temperature inference model developed from lakes of the alpine region to a high resolution chironomid record from the lake provides evidence for early holocene ca 10000 8600 cal yr bp tjuly of up to 8 5 c i e 4 c above the modern 1977 2006 mean july temperature the reconstruction reveals the so called 8 2 ka cold event centered at ca 8250 8000 cal yr bp with temperatures ca 3 c below the early holocene thermal maximum rather warm ca 6 c and productive conditions prevailed during ca 7900 4500 cal yr bp the chironomid record suggests a climate transition between ca 5200 and 4500 cal yr bp to cooler tjuly a distinct cooling trend is evident from ca 4500 until ca 2500 cal yr bp thereafter the study site experienced its coldest conditions around 4 c or less throughout the rest of the holocene with the exception of the warming trend during the late 20th century beside other factors the northern hemisphere summer insolation seems to be the major driving force for the long term trends in tjuly at high altitudes in the eastern alps due to the extreme location of the lake and the limited temperature range represented by the applied calibration data set the chironomid based temperature reconstruction fails to track phases of the late holocene climatic history with tjuly cooler than 4 c further chironomid based palaeoclimate model and down core studies are required to address this problem provide more realistic tjuly estimates from undisturbed high altitude lakes in the alps and extract a reliable regional temperature signal

ice cap erosion patterns from bedrock 10be and 26al southeastern tibetan plateau quantifying glacial erosion contributes to our understanding of landscape evolution and topographic relief production in high altitude and high latitude areas combining in situ be 10 and al 26 ana

analysis of multiple cosmogenic nuclides constrains laurentide ice sheet history and process on mt mansfield vermont s highest peak abstract constraining glacial history and process on mt mansfield the highest peak in vermont 1339 m a s l provides insight into how the laurentide ice sheet shaped the underlying landscape when latest pleistocene ice retreated and how upland and lowland glacial histories relate here we quantify in situ cosmogenic 10be in 20 bedrock and boulder surfaces as well as in situ cosmogenic 14c in three of those surfaces to assess subglacial erosion and exposure history isotopic concentrations indicate that mt mansfield s lower elevations 400 1200 m a s l were deeply eroded by at least several meters during the last glaciation and then deglaciated rapidly 10be ages across this elevation span are indistinguishable and average 13 9 0 6 ka n 15 suggesting that 800 m of ice thinning occurred within at most about a millennium conversely the higher elevations 1200 m a s l preserve a more complex geomorphic history mt mansfield s summit surfaces contain 10be from previous periods of exposure indicating that the mountaintop landscapes were likely preserved beneath cold based weakly erosive glacial ice exposure ages from the shorter lived isotope 14c are younger 9 7 and 11 7 ka suggesting that mt mansfield s summit was covered until the early holocene perhaps by snowfields ice carapaces and or till our findings in context of previous work suggest that thinning laurentide ice flowed through the valleys for at most hundreds of years following deglaciation of the uplands but that the summit remained shielded by ice or sediment for millennia after the valleys became ice free

strontium increases and crystallinity changes in taphonomic and archaeological bone bone strontium levels and hydroxyapatite crystal sizes increased with time in two exposed wildebeest skeletons the strontium increases could not be removed by sequential washing according to the method of sillen a 1986 biogenic and diagenetic srca in plio pleistocene fossils of the omo shungura formation paleobiology12 311 323 human subfossil bone recovered archaeologically also showed evidence of extensive diagenetic reworking that resulted in crystal growth and elevated strontium levels the increase in bone strontium content was independent of nonapatitic contaminating crystal phases

holocene glacial activity and climatic variations in the swiss alps reconstructing a continuous record from proglacial lake sediments cores recovered from proglacial lake silvaplana swiss alps were investigated to examine the influence of holocene glaciers on lacustrine sedimentation during times of glacial activity in the catchment the sedimentation in the lake is dominated by the input of silt and clay sized material delivered by glacial meltwaters the deposition of fine grained material and the formation of varves reflect the existence of glaciers in the catchment and can therefore be used for the reconstruction of glacial history sedimentation rates are up to nine times higher in the varved than in the non varved sediments indicating significantly higher erosion rates under glaciated catchment conditions glacial varves were deposited in lake silvaplana during glacial retreat in the latest pleistocene and early holocene until 9400bp non varved deposits having a higher organic content and coarser grain sizes accumulated at lower rates when glacial activity was absent or negligible within the catchment between 9400 and 3300 bp

exchange of carbon with biological apatite abstract the validity of using carbon isotopes in biological apatite from bone for dietary studies has been questioned because of diagenetic alterations and supposed exchange of carbon from the burial environment laboratory and natural experiments have been devised to test the integrity of carbon isotope ratios in biological apatite with respect to isotopic exchange of carbon with natural waters the laboratory experiment subjected a sample of bone to a synthetic groundwater whose carbon isotopic composition had been adjusted to 9750 analyses indicate that simple carbonates exchanged rapidly with the groundwater but that the actual biological apatite exchanged very little if any of its carbon even with 2 years exposure the natural experiment involved analysis of mammoth and mastodon teeth that had been submerged in sea water for 11 000 years with proper cleaning the original dietary signals were well preserved despite the long exposure to oceanic dissolved carbonate of much different isotopic composition these experiments suggest that properly cleaned biological apatite is an appropriate analytical phase for dietary studies on bone or teeth as old as 10 000 years

the rhone glacier was smaller than today for most of the holocene we present the development and application of the novel in situ cosmogenic 14 c 10 be chronometer to recently exposed proglacial bedrock of the rhone glacier switzerland results show that during the holocene the glacier was smaller than today for 6500 2000 yr and larger than today for 4500 2000 yr this pattern is consistent with limited data from other techniques for glaciers in the alps and scandinavia but in contrast to glaciers from the southern alps of new zealand emphasizing the high sensitivity of large mountain glaciers to small climate changes the 14 c 10 be chronometer also shows that abrasion rates beneath the rhone glacier increased with ice speed

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

geographical dependence observed in blocking high influence on the stratospheric variability through enhancement and suppression of upward planetary wave propagation abstractprevious studies have suggested the importance of blocking high bh development for the occurrence of stratospheric sudden warming ssw while there is a recent study that failed to identify their statistical linkage through composite analysis applied to high amplitude anticyclonic anomaly events observed around every grid point over the extratropical northern hemisphere the present study reveals a distinct geographical dependence of bh influence on the upward propagation of planetary waves pws into the stratosphere tropospheric bhs that develop over the euro atlantic sector tend to enhance upward pw propagation leading to the warming in the polar stratosphere and in some cases to major ssw events in contrast the upward pw propagation tends to be suppressed by bhs developing over the western pacific and the far east resulting in the polar stratospheric cooling this dependence is found to arise mainly from the sensitivity of the interference between the climatological pws and upward p

a new record of a scelidotheriine ground sloth xenarthra mylodontidae from central brazil quaternary cave stratigraphy taxonomy and stable isotopes abstract an upper fourth molariform of a scelidotheriine ground sloth is reported from carneiro cave which is located in the karstic region of serra da mesa goias in this limestone cave the tooth was found at the base of a depositional sequence associated with a 2 m thick debris flows deposit which is covered by the lowest carbonate crust dated at approximately 200 000 yr bp detailed morphological description stable isotope data and stratigraphic context are provided this represents the first megafauna record for this region of central brazil where this record is found in direct association with a diverse microvertebrate fauna

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

trace element and isotopic aspects of predator prey relationships in terrestrial foodwebs abstract strontium calcium ratio sr ca and stable carbon isotope ratio 13c 12c analyses of bone and enamel apatites may be used for reconstructing predator prey relationships in vertebrate fossil assemblages the approach is based on the rationale that 13c 12c in predator apatite closely resemble those of their prey while sr ca is predictably reduced in specific predator prey pairs as an example we compare the relationship of the extant leopard panthera pardus and its preferred prey in modern foodwebs with the relationship of fossil leopards from the member 1 fossil faunal assemblage at swartkrans cave and their likely prey the results suggest that swartkrans member i leopards depended heavily on papio baboons with some lesser contribution from hyrax procavia sp the approach has considerable potential for elucidating the preferred prey of extinct predators such as sabertooth cats

on the three dimensional propagation of stationary waves abstract a locally applicable nonzonally averaged conservation relation is derived for quasi geostrophic stationary waves on a zonal flow a generalization of the eliassen palm relation the flux which appears in this relation constitutes it is argued a useful diagnostic of the three dimensional propagation of stationary wave activity this is illustrated by application to a simple theoretical model of a forced rossby wave train and to a northern hemisphere winter climatology results of the latter procedure suggest that the major forcing of the stationary wave field derives from the orographic effects of the tibetan plateau and from nonorographic effects diabatic heating and or interaction with transient eddies in the western north atlantic and north pacific oceans and siberia no evidence is found in the data for wave trains of tropical origin forcing by the orographic effects of the rocky mountains seems to be of secondary importance

tests for diagenesis in tooth enamel esr dating signals and carbonate contents abstract we have tested whether tooth enamel might be altered during burial by focusing on the carbonate content and electron spin resonance esr signals used for dating since oxidized carbon atoms co 2 or co 3 moieties in the apatite lattice give rise to the esr dating signal as a function of absorbed radiation dose inward or outward carbonate mobility would induce changes in the radiation sensitivity of the esr dating signal we used manometry and fourier transform infra red spectroscopy to study carbonate in 11 fossil and five modern tooth enamels from horse cow hippopotamus rhinoceros and mammoth we have shown that ungulate tooth enamel exhibits a narrow range of both carbonate content 4 5 to 5 1 wt and esr signal intensity at 300 gy radiation dose these characteristics are true both for modern and most fossil samples ranging in age up to several hundred thousand years old evidence for possible diagenesis was found only for two samples consisting of fragments of enamel which exhibited anomalous high and low carbonate contents and esr signal sizes

the amplification of height wave 1 in january 1979 a characteristic precondition for the major warming in february abstract the development in time and space of the planetary scale height waves 1 and 2 and of the mean zonal flow is described for the winter 1978 79 it is concluded that this winter supports earlier observational results the anomalous amplification of height wave 1 in the stratosphere concurrent with a distinct minimum of height wave 2 is a characteristic precondition for the development of a major warming if later the breakdown itself concurs with the development of height wave 2 the amplification of height wave 1 before is needed insofar as it changes the zonal flow i e displaces the stratospheric jet poleward to favor propagation of height wave 2

extracting a climate signal from 169 glacier records i constructed a temperature history for different parts of the world from 169 glacier length records using a first order theory of glacier dynamics i related changes in glacier length to changes in temperature the derived temperature histories are fully independent of proxy and instrumental data used in earlier reconstructions moderate global warming started in the middle of the 19th century the reconstructed warming in the first half of the 20th century is 0 5 kelvin this warming was notably coherent over the globe the warming signals from glaciers at low and high elevations appear to be very similar

coupling between mesosphere and ionosphere over beijing through semidiurnal tides during the 2009 sudden stratospheric warming 1 sudden stratospheric warming ssw in the winter of 2008 2009 is the strongest recorded ssw event the enhancement in semidiurnal variation of ionospheric tec total electron content with phase shift forward is shown during 22 to 27 january 2009 based on the tec observations in beijing 40 30 n 116 19 e geographic 39 73 n dip latitude we focus on finding the reason for the tec variation winds observed by an all sky meteor radar in the same observatory are used to study mesospheric variation the semidiurnal solar tide in the mesosphere starts to increase before the ssw and maintains oscillation with period 16 20 days during the ssw the semidiurnal lunar tides in tec and wind start to increase on 17 and 15 january respectively although the semidiurnal lunar tide in tec over beijing almost dies out on 1 february that over equatorial ionospheric anomaly crest does not vanish until 15 february when lunar tide in wind tends to be very weak the maximum of lunar tide in wind appears on 2 february at 96 km with amplitudes of 15 m s and 21 m s for zonal and meridional winds the phase comparison shows that lunar tides in tec and zonal wind reach their maxima at almost the same time which is 2 4 h lag behind the meridional wind the coupling between the mesosphere and ionosphere contributes to the semidiurnal variation of tec through both solar and semidiurnal lunar tides the enhancement in semidiurnal lunar tide is responsible for the tec peak shift forward during the ssw

influence of a glacial buzzsaw on the height and morphology of the cascade range in central washington state usa abstract analysis of climatic and topographic evidence from the cascade range of washington state indicates that glacial erosion limits the height and controls the morphology of this range glacial erosion linked to long term spatial gradients in the ela created a tilted planar zone of 373 cirques across the central part of the range peaks and ridges now rise 600 m above this zone hypsometric analysis of the region shows that the proportion of land area above the cirques drops sharply and mean slopes 30 indicate that the areas above the cirques may be at or near threshold steepness the mean plus 1 relief of individual cirque basins 570 m corresponds to the 600 m envelope above which peaks rarely rise the summit altitudes are set by a combination of higher rates of glacial and paraglacial erosion above the ela and enhanced hillslope processes due to the creation of steep topography on the high precipitation western flank of the cascades the dominance of glacial and hillslope erosion at altitudes at and above the ela may explain the lack of a correspondence between stream power erosion models and measured exhumation rates from apatite u th he thermochronometry

reply to the comment on implications of diagenesis for the isotopic analysis of upper miocene large mammalian herbivore tooth enamel from chad by l jacques n ogle i moussa r kalin p vignaud m brunet and h bocherens palaeogeography palaeoclimatology palaeoecology 266 2008 200 210 n their comment to our recent paper jacques et al 2008 zazzo et al 2009 this issue provide a correction regarding some technical features of one of the isotopic mass spectrometers used in our comparative study it appears that the system used to purify co2 in saskatoon was a dual inlet di and not a continuous flow cf as mistakenly stated as this system was considered as reliable as the other cf used in the comparative study zazzo et al 2009 this issue infer that the isotopic ratios previously measured on heavily contaminated material from a late miocene chadian site toros menalla tm with another di are reliable as well our reply will re evaluate the comparison between cf and di systems in the light of the correction for the system used in saskatoon and discuss the claim that previous isotopic measurements made on chadian material reflect biogenic signatures and were not affected by oxide contamination

implications of diagenesis for the isotopic analysis of upper miocene large mammalian herbivore tooth enamel from chad high resolution chemical and textural investigation of upper miocene mammalian tooth enamel from chad using electron microprobe and scanning electron microscope techniques provide direct evidence of extensive diagenetic alteration when compared with some modern and contemporaneous fossil specimens chemical and textural changes in chadian fossil enamel during fossilization include large amounts of secondary fe si mn and al bearing oxides both as coarse precipitation in cracks and permeating the apatite high fluorine contamination i e apatite alteration ca p cl na and mg depletion and sulphur contamination such diagenetic contamination significantly affects the oxygen and carbon isotope analysis of carbonate in apatite altering the delta o 18 and delta c 13 biogenic signals towards more positive values isotopic alteration is however greater for oxygen than for carbon indeed isotopic analysis of the heavily oxide and s contaminated chadian fossil tooth enamel samples on a classical dual inlet multiprep system versus three continuous flow irms mass spectrometers show great differences in both the delta o 18 and delta c 13 values while the multiprep dual inlet approach provides carbon and oxygen isotopic results that are indubitably altered and generally inconsistent with any biological values isotopic analysis on continuous flow systems which automatically filter out contaminating gases allow to attain or at least greatly approach primary isotopic signals some of the chadian fossil enamel samples analysed in this work come from the very important upper miocene tm266 fossil locality that yielded sahelanthropus tchadensis a k a toumai the oldest member of the hominid clade known so far at this site as in others a few or no other environmental proxies than isotopic analysis of biomaterials are available for palaeoenvironmental and palaeoecological reconstructions therefore to obtain reliable environmental information from the time of this ancient hominid recovering uncontaminated biogenic isotopic signals is crucial and from these results it is now technically possible c 2008 elsevier b v all rights reserved

the timing of glacier advances in the northern european alps based on surface exposure dating with cosmogenic 10be 26al 36cl and 21ne

a model of fossil tooth and bone diagenesis implications for paleodiet reconstruction from stable isotopes abstract diagenesis of structural carbonate in biogenic apatite in the postmortem environment is modeled as a process of water mineral interaction both closed and open system model calculations suggest that 13 c of structural carbonate in biogenic apatite is much more resistant to diagenetic modification than 18 o apatite structural carbonate retains an original 13 c signal in closed system diagenesis for open systems 13 c of biogenic apatite with very low porosity such as tooth enamel can survive most diagenesis and retain a primary isotopic signature on the hand 18 o of structural carbonate in biogenic apatite may not be a reliable indicator of the original isotopic ratios except in a diagenetic system with low temperature and very low water biomineral ratio application of the model to teeth and carbonate cement in sediments from the badlands south dakota illustrates that 13 c values of enamel samples preserve the original signal whereas 13 c values of dentine represent varying extents of diagenesis 18 o values of fossil teeth may record an early or late part of their water biomineral interaction history during diagenesis

diagenesis and the reconstruction of paleoenvironments a method to restore original δ18o values of carbonate and phosphate from fossil tooth enamel abstract intra tooth 18 o variations within the carbonate 18 oc and phosphate 18 op components of tooth apatite were measured for miocene and pliocene hypsodont mammals from afghanistan greece and chad in order to evaluate the resistance of enamel to diagenetic alteration application of water apatite interaction models suggest that the different kinetic behaviours of the phosphate water and carbonate water systems can be used to detect subtle oxygen isotope disequilibria in fossil enamel when intra individual variations are considered selective alteration of the oxygen isotope composition from the carbonate component of afghan and greek enamels suggests inorganic isotopic exchange processes microbially induced isotopic exchange for phosphate is demonstrated for the first time in enamel samples from chad in association with extensive recrystallization in chad 18 op values were derived from partial isotopic exchange with fossil groundwater during early diagenesis mass balance calculations using average carbonate content in enamel as a proxy for recrystallization and the lowest 18 op value of dentine as a proxy for the isotopic composition of the diagenetic fluid indicate that diagenesis can alter 18 op by as much as 3 in some enamel samples this diagenetic alteration is also responsible for a decrease in intra individual variations of up to 1 in affected specimens the effects of diagenesis on 18 op values of fossil enamel are not systematic however and can only be estimated if sequential 18 op and 18 oc analyses are performed on fossil enamel and dentine reconstruction of large temporal or spatial scale paleoclimates based on 18 op analyses from mammalian teeth cannot be considered valid if enamel has been affected by bacterial activity or if the data cannot be corrected for diagenetic effects

the unusual midwinter warming in the southern hemisphere stratosphere 2002 a comparison to northern hemisphere phenomena a strong midwinter warming occurred in the southern hemisphere sh stratosphere in september 2002 based on experiences from the northern hemisphere nh this event can be defined as a major warming with a breakdown of the polar vortex in midwinter which has never been detected so far in the sh since observations began at the earliest in the 1940s minor midwinter warmings occasionally occurred in the sh but a strong interannual variability as is present in winter and spring in the nh has been explicitly associated with the spring reversals a detailed analysis of this winter reveals the dominant role of eastward traveling waves and their interaction with quasi stationary planetary waves forced in the troposphere such wave forcing finally leading to the sudden breakdown of the vortex is a familiar feature of the northern winter stratosphere therefore the unusual development of this antarctic winter is described in the context of more than 50 arctic winters concentrating on winters with similar wave perturbations the relevance of preconditioning of major warmings by traveling and quasi stationary planetary waves is discussed for both hemispheres

holocene glacier fluctuations of flatebreen and winter precipitation changes in the jostedalsbreen region western norvay based on glaciolacustrine sediment records the history of holocene glacier variations of flatebreen an independent glacier close to the sw part of the jostedalsbreen ice cap has been reconstructed from lacustrine sediments in the proglacial lake jarbuvatnet the sedimentary succession shows evidence of three maini episodes of holocene glacier expansion the first is recorded in the basal part of the core up to 370 cm according to the age depth relationship in the sediment core based on 12 ams radiocarbon dates this glacier expansion episode terminated about 10200 cal yr bp the second major glacier phase lasted from 8400 to 8100 cal yr bp while the third was initiated around 4000 cal yr bp and has continued up to the present at 43 cm in the core the medium silt content increases significantly accompanied by a minor increase in the sand content this textural change is interpreted as the first time that the tenninus of flatebreen extended inlto an upstream lake at 1083 m a s l the age model suggests that this event took place around

what kind of stratospheric sudden warming propagates to the troposphere 1 the factors affecting the downward propagation of stratospheric sudden warming ssw events to the troposphere are studied through composite analysis of 45 year reanalysis data from the european centre for medium range weather forecasts during the growth stage of ssw events that propagate into the troposphere exhibit enhanced upward flux of the wavenumber 2 wave while events that do not propagate downward display reduced wavenumber 2 flux in both events upward flux of the wavenumber 1 wave is enhanced but the enhancement is stronger in the non propagating event the composite for propagating events reveals a negative eurasian pattern of horizontal geopotential anomalies in the troposphere during the growth stage and a negative arctic oscillation pattern following the event while non propagating events are preceded by a positive eurasian pattern in both types of event the tropospheric anomalies are generated mainly by tropospheric planetary wave forcing prior to the emergence of ssw

rossby wave propagation into the northern hemisphere stratosphere the role of zonal phase speed sudden stratospheric warming ssw events are to a dominant part induced by upward propagating planetary waves while theory predicts that the zonal phase speed of a tropospheric wave forcing a ects wave propagation into the stratosphere its relevance for ssw events has so far not been considered this study shows in a linear wave diagnostic and in reanalysis data that phase speeds tend eastward as waves propagate upward indicating that the stratosphere preselects eastward phase speeds for propagation especially for zonal wave number 2 this also a ects ssw events split ssw events tend to be preceded by anomalously eastward zonal phase speeds zonal phase speed may indeed explain part of the increased wave ux observed during the preconditioning of ssw events as for example for the record 2009 ssw event

ionospheric current system during sudden stratospheric warming events 1 this paper describes ionospheric current systems associated with the counter electrojet during sudden stratospheric warming ssw events in the northern winter months of 2001 2002 and 2002 2003 magnetic data from 20 stations in the east asian region covering both the northern hemisphere and the southern hemisphere are analyzed additional current systems that are superposed on the normal sq current system and related to the counter electrojet during the ssw events show a global semidiurnal current pattern which shifts to later local times approximately by 0 8 hour day the results indicate that abnormally large lunar tidal winds played a main role to produce the additional current system and counter electrojet during the ssw events

distribution and inferred age of exfoliation joints in the aar granite of the central swiss alps and relationship to quaternary landscape evolution abstract exfoliation joints are well known natural fractures limited to near the ground surface relatively few details however are known about their distribution and age in the swiss alps exfoliation joints follow the landscape surface at the time of their formation the age of the associated landscape feature then provides a maximum age of exfoliation joints while landscape forms can change through time exfoliation joints preserve elements of former landscape morphologies by their undisturbed orientations the grimsel region of the central alps is well suited for analyzing the impact of erosional episodes and accompanying stress changes on exfoliation joint formation in granitic rocks mapping above and below ground revealed that exfoliation joints are widespread and occur between valley bottoms and mountain crests within glacial inner and hanging u shaped trough valleys glacial cirques and steep mountain crests and predominantly fluvial landforms gently inclined linear slopes above the inner trough valleys narrow inner valley gorges and steep v shaped side gullies based primarily on their geometric properties at the ground surface three exfoliation joint types were distinguished in our study area 1 closely spaced

alteration of enamel carbonate environments during fossilization an understanding of enamel diagenesis is necessary to ensure sound isotopic palaeodietary and palaeoenvironmental reconstructions although carbon isotope signals of browsing and grazing herbivores remain distinct in enamel even after millions of years subtle alteration of isotopic signatures does occur to better understand this change we analysed modern and fossil enamel from a number of south african sites using fourier transform infra red spectroscopy our results indicate that while there is little evidence of increased crystallinity in fossil enamel there is a small but significant change in the proportion of carbonate ions occupying hydroxyl and phosphate sites this seems to occur early in the process of fossilization after which there is no noticeable change it is also important to note that the degree of alteration varies significantly within and between sites we suggest that this change results from one or some combination of three mechanisms exogenous carbonate incorporation endogenous carbonate loss and endogenous carbonate reorganization determining which mechanism s contribute to this alteration is important because all three are likely to affect biogenic carbon isotope ratios differently ftir spectroscopy promises to increase our knowledge of diagenesis and in so doing should improve our palaeodietary and palaeoenvironmental reconstructions

the last glaciation of bear peninsula central amundsen sea embayment of antarctica constraints on timing and duration revealed by in situ cosmogenic 14c and 10be dating abstract ice streams in the pine island thwaites region of west antarctica currently dominate contributions to sea level rise from the antarctic ice sheet predictions of future ice mass loss from this area rely on physical models that are validated with geological constraints on past extent thickness and timing of ice cover however terrestrial records of ice sheet history from the region remain sparse resulting in significant model uncertainties we report glacial geological evidence for the duration and timing of the last glaciation of hunt bluff in the central amundsen sea embayment a multi nuclide approach was used measuring cosmogenic 10be and in situ 14c in bedrock surfaces and a perched erratic cobble bedrock 10be ages 118 144 ka reflect multiple periods of exposure and ice cover not continuous exposure since the last interglacial as had previously been hypothesized in situ 14c dating suggests that the last glaciation of hunt bluff did not start until 21 1 5 8 ka probably during the last glacial maximum and finished by 9 6 0 9 ka at the same time as ice sheet retreat from the continental shelf was complete thickening of ice at hunt bluff most likely post dated the maximum extent of grounded ice on the outer continental shelf flow re organisation provides a possible explanation for this with the date for onset of ice cover at hunt bluff providing a minimum age for the timing of convergence of the dotson and getz tributaries to form a single palaeo ice stream this is the first time that timing of onset of ice cover has been constrained in the amundsen sea embayment

early diagenetic evolution of bone phosphate an x ray diffractometry analysis abstract a new crystallinity index ci based on the x ray powder diffractometric pattern of fossil bone carbonate hydroxylapatite is defined this ci value provides a semi quantitative way to estimate the diagenetic changes in archaeological and palaeontological bone phosphate the studied samples are 71 human bones from the french merovingian cemetery of saint linaire 1200 1700 bp 37 human bones from two necropoleis in niger 1000 5000 bp two cave bear bones from aldene cave southern france around 70 000 bp five bones of miocene mammals and 14 bones of mesozoic reptiles the main results are that 1 there is no correlation between the increase in the ci and the age of the sample even in one given locality 2 the ci seems to be related to the taphonomical conditions in archaeological and fossil bones 3 an increase in the ci is correlated with a loss in organic matter in one archaeological site but the quality of preservation of organic matter in fossil bones does not depend on the changes in the ci 4 the correlation between the increase in the ci and the decrease of co3amount in bones from the niger necropolies suggests a possible mechanism for the increase in crystallinity the changes of crystallinity reflect early diagenetic changes and depend on the burial environments

a new greenland ice core chronology for the last glacial termination 1 we present a new common stratigraphic timescale for the north greenland ice core project ngrip and grip ice cores the timescale covers the period 7 9 14 8 kyr before present and includes the bolling allerod younger dryas and early holocene periods we use a combination of new and previously published data the most prominent being new high resolution continuous flow analysis cfa impurity records from the ngrip ice core several investigators have identified and counted annual layers using a multiparameter approach and the maximum counting error is estimated to be up to 2 in the holocene part and about 3 for the older parts these counting error estimates reflect the number of annual layers that were hard to interpret but not a possible bias in the set of rules used for annual layer identification as the grip and ngrip ice cores are not optimal for annual layer counting in the middle and late holocene the timescale is tied to a prominent volcanic event inside the 8 2 kyr cold event recently dated in the dye 3 ice core to 8236 years before a d 2000 b2k with a maximum counting error of 47 years the new timescale dates the younger dryas preboreal transition to 11 703 b2k which is 100 150 years older than according to the present grip and ngrip timescales the age of the transition matches the gisp2 timescale within a few years but viewed over the entire 7 9 14 8 kyr section there are significant differences between the new timescale and the gisp2 timescale the transition from the glacial into the bolling interstadial is dated to 14 692 b2k the presented timescale is a part of a new greenland ice core chronology common to the dye 3 grip and ngrip ice cores named the greenland ice core chronology 2005 gicc05 the annual layer thicknesses are observed to be log normally distributed with good approximation and compared to the early holocene the mean accumulation rates in the younger dryas and bolling periods are found to be 47 2 and 88 2 respectively

lower stratospheric rossby wave trains in the southern hemisphere a case study for late winter of 1997 behaviour of quasi stationary circulation anomalies observed in the lower stratosphere of the extratropical southern hemisphere during austral late winter of 1997 is studied the anomalies are defined as daily low pass filtered departures from the circulation varying slowly with the seasonal cycle a wave activity flux and refractive index for stationary rossby waves are utilized in the analysis each of which is defined locally for the zonally varying westerlies subseasonal fluctuations in the lower stratosphere were often associated with zonally confined wave trains emanating upward from localized quasi stationary anomalies in the troposphere including blocking ridges the three dimensional propagation of the waves was found sensitive to the structure of a local waveguide upward injection of rossby wave activity into the stratosphere tended to occur slightly upstream or just beneath of a lower stratospheric waveguide associated with the developed polar night jet pnj which led to the subsequent formation of a well defined wave train downstream along that jet the distribution of the lower stratospheric subseasonal variability thus exhibits significant zonal asymmetries reflecting those in the pnj structure and the distribution of tropospheric disturbances seasonal evolution of the pnj and that of the tropospheric intraseasonal variability substantially modulated the lower stratospheric activity of subseasonal fluctuations copyright 2004 royal meteorological society

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

diagenetic evolution and experimental heating of bone phosphate abstract fresh bone samples have been experimentally heated with monitoring of the evolution of several parameters the comparison of these results with a large suite of measurements performed on archaeological and fossil bones gave valuable clues about some possible mechanisms of the diagenetic evolution of bone crystallinity the main conclusions of this comparison are that 1 bone organic matter protects the mineral phase and thus needs to be significantly altered before crystallographic changes occur and 2 loss of structural carbonate may be a key factor in the increase of bone crystallinity the crystallinity of carbonate hydroxylapatite seems to monitor the degree to diagenetic evolution and thus may be used to detect diagenetic alteration of biogenic paleoenvironmental signals in archaeological and fossil bones independently of their age

improved discrimination of subglacial and periglacial erosion using 10be concentration measurements in subglacial and supraglacial sediment load of the bossons glacier mont blanc massif france deciphering the complex interplays between climate uplift and erosion is not straightforward and estimating present day erosion rates can provide useful insights glaciers are thought to be powerful erosional agents but most published glacial erosion rates combine periglacial subglacial and proglacial erosion processes within a glaciated catchment sediments found in subglacial streams originate either from glacial erosion of substratum or from the rock walls above the glacier that contribute to the supraglacial load terrestrial cosmogenic nuclides tcn are produced by interactions between cosmic ray particles and element targets at the surface of the earth but their concentration becomes negligible under 15 m of ice measuring tcn concentrations in quartz sand sampled in subglacial streams and in supraglacial channels is statistically compliant with stochastic processes e g rockfalls and may be used to discriminate subglacial and periglacial erosion results for two subglacial streams of the bossons glacier mont blanc massif france show that the proportion of sediments originating from glacially eroded bedrock is not constant it varies from 50 to 90 n 6 the difference between the two streams is probably linked to the presence or absence of supraglacial channels and sinkholes which are common features of alpine glaciers therefore most of the published mean catchment glacial erosion rates should not be directly interpreted as subglacial erosion rates in the case of catchments with efficient periglacial erosion and particularly rockfalls the proportion of sediments in the subglacial stream originating from the supraglacial load could be considerable and the subglacial erosion rate overestimated here we estimate warm based subglacial and periglacial erosion rates to be of the same order of magnitude 0 39 0 33 and 0 29 0 17 mm a 1 respectively

late glacial and holocene glacier fluctuations in north island new zealand abstract geological records of past glacier extent can yield important constraints on the timing and magnitude of pre historic climate change here we present a cosmogenic 3he moraine chronology from mt ruapehu in central north island new zealand that records fluctuations of new zealand s northernmost glaciers over the last 14 000 years in the mangaehuehu glacier catchment exposure ages and geomorphic observations at our most distal moraine site relative to the current glacier margin show that glacial retreat during the last glacial termination was interrupted by one or more readvances between 14 and 11 ka further up valley moraine boulders deposited at 4 5 ka indicate that glaciers were more extensive during the mid holocene than at any later time the youngest exposure ages in our study 150 450 years constrain the formation of moraines situated within 500 m from the present day mangaehuehu glacier terminus these ages are in agreement with historic sources that show the glacier close to these moraine limits approximately 100 years ago overall our data show that glaciers on mt ruapehu retreated c 3 km since 14 ka in response to a net rise in the local equlibrium line altitude of c 400 m the magnitude of post industrial snowline rise and glacier retreat on mt ruapehu is also consistent with instrumental temperature data that record approximately 0 9 c of warming during the 20th century