a penultimate glacial monsoon record from hulu cave and two phase glacial terminations oxygen isotope records of three stalagmites from hulu cave china extend the previous high resolution absolute dated hulu asian monsoon record from the last to the penultimate glacial and deglacial periods the penultimate glacial monsoon broadly follows orbitally induced insolation variations and is punctuated by at least 16 millennial scale events we confirm a weak monsoon interval between 135 5 1 0 and 129 0 1 0 ka prior to the abrupt increase in monsoon intensity at asian monsoon termination ii based on correlations with both marine ice rafted debris and atmospheric ch 4 records we demonstrate that most of marine termination ii the full rise in antarctic temperature and atmospheric co 2 and much of the rise in ch 4 occurred within the weak monsoon interval when the high northern latitudes were probably cold from these relationships and similar relationships observed for termination i we identify a two phase glacial termination process that was probably driven by orbital forcing in both hemispheres affecting the atmospheric hydrological cycle and combined with ice sheet dynamics

modulation of equatorial turbulence by a tropical instability wave 1 strong modulation of turbulent mixing by a westward propagating tropical instability wave tiw was observed in the stratified shear layer between the equatorial undercurrent euc and the surface mixed layer during october and november 2008 at 0 n 140 w the unique deep diurnal cycle mixing in the stratified layer beneath the equatorial cold tongue was observed where nighttime turbulent mixing was a factor of 10 greater than during daytime the turbulent kinetic energy dissipation rate e was 10 6 w kg 1 and the turbulent heat flux was 500 w m 2 at least 5 10 times greater than observed previously in the central equatorial pacific turbulence mixing varied significantly during the four distinct phases of the meridional flow associated with the tiw observations during the northward to southward transition recorded the largest values of reduced shear squared the thickest nighttime surface mixed layer the deepest penetration of the deep cycle turbulence and the largest turbulent heat flux and largest integrated e in the deep cycle layer dcl during steady southward flow the depth of the bases of the nighttime surface mixed layer and of the dcl were the shallowest a 50 m thick layer of strong turbulence was observed immediately above the euc core during the northward to southward and steady southward phases here the average e exceeded 10 6 w kg 1 the eddy diffusivity exceeded 10 3 m2 s 1 and the turbulent heat flux was 500 w m 2 to parameterize mixing in the central equatorial pacific accurately numerical models must simulate the enhancement of mixing associated with tiws and also the variability of mixing in different tiw phases

late pleistocene paleoclimate in the black hills of south dakota from isotope records in speleothems abstract two coeval speleothems from the black hills are used to investigate 18 o and 13 c variations within reed s cave and reconstruct climate during the wisconsin glacial period from 82 000 to 24 000 years ago variation in growth rates between the two speleothems reveals a strong control of hydrology and surface vegetation on isotopic variability and response of 18 o to climate high resolution 18 o and 13 c data show that local environmental conditions can produce an offset of 18 o values of up to 4 in coeval speleothems but still reveal important climate events the transition from warmer to cooler periods results in an increase in 18 o of calcite 18 o ct in sample rc2 while in sample rc20 another equilibrium deposit coeval to part of the rc2 record 18 o ct is offset from rc2 by between 0 and 3 5 and shows much higher frequency isotopic variation speleothem rc2 records interglacial glacial transitions and interstadial events that are also present in speleothems from north america and europe spectral analysis of the 18 o ct records for both speleothems reveals periodicity at 1000 to 2000 years similar to millennial scale variability seen in the north atlantic sediments and the greenland ice cores

the chronology of speleothem deposition in northern yukon and its relationships to permafrost in the northern yukon there is a significant group of limestone caves in an area that was not glaciated during the quaternary permafrost appears to have played an important role in restricting calcite speleothem deposition in the caves u th dating and stable isotopic studies indicate that the deposits form two distinct groups a first group younger than 350 ka and a second group older than the 350 ka bp limit of the conventional u th alpha spectrometric dating method two large samples from the second group yield sequences of magnetic declinations and inclinations with reversed and normal polarity perhaps from the tertiary the pollen content of five speleothems the modes of calcite deposition and stable isotopic analyses indicate that the speleothems were deposited under a cold regime it is suggested that the ancient speleothems were deposited at a time when permafrost was absent during the later tertiary or at the beginning of the quaternary period the establishment and maintenance of permafros

potential vorticity dynamics of tropical instability vortices abstracttropical instability vortices tivs in the equatorial pacific exhibit energetic horizontal and vertical circulation characterized by regions of high rossby number and low richardson number their strong anticyclonic vorticity and vertical shear can influence the broader scale circulation by driving lateral mixing and vertical exchange between the ocean surface and interior the authors use a set of nested high resolution simulations of the equatorial pacific with a finest grid size of 3 km to examine the vortex dynamics associated with tiv core water formation tiv cores are characterized by low values of the ertel potential vorticity pv as the relative vorticity is anticyclonic with magnitude comparable to the local coriolis parameter a study of the variation of pv and other scalars along lagrangian fluid parcel tracks entering the tivs shows that the low pv water in their cores is a mix of equatorial undercurrent euc water and north equatorial counter current necc water the euc water

elevated and variable values of 13c in speleothems in a british cave system 13c isotope variations in speleothems have been investigated for samples from the british isles where plants which use the hatch slack or c4 photosynthetic pathway are not present the range of 13c expected in speleothem carbonate formed in isotopic equilibrium with soil co2 derived from the overlying c3 vegetation should thus fall in the range 12 to 6 forty one actively growing speleothem samples from low discharge sites were analysed from stump cross caverns yorkshire england ten percent have 13c greater than 6 in addition a large range of 13c was observed 8 06 1 38 a 1 variability of 17 with adjacent samples having 13c differing by a maximum of 4 74 similar findings were obtained from a review of analyses of late quaternary speleothem samples from the british isles with 75 of flowstone samples and 57 of high flow stalagmite samples exhibiting elevated 13c three possible processes are proposed as possible causes of elevated 13c in speleothems firstly fractionation may occur between the stalactite and stalagmite due to evaporation or degassing secondly degassing of the groundwaters may have occurred within the aquifer before reaching the cave void allowing release of some co2 from the water whilst remaining saturated in calcium finally the elevated 13c may be due to short water residence times in the soil such that equilibrium between soil water and soil co2 is not reached evidence presented here demonstrates that any one of these mechanisms may be important in the karst areas of the british isles caution is needed before interpreting the 13c signal within speleothems in terms of palaeovegetation

cryogenic cave calcite from several central european caves age carbon and oxygen isotopes and a genetic model abstract cryogenic cave calcite ccc formed by segregation of solutes during water freezing was found in three central european caves this calcite type forms accumulations of loose calcite grains on cave floor the calcite grains are of highly variable crystal morphology and of sizes ranging from less than 1 mm to over 1 cm the most typical feature is their accumulation as loose uncemented crystals u series dating indicates the formation of ccc in the studied caves during several climatic oscillations of the weichselian between 61 and 36 ka bp in the chelsiowa jama jaskinia jaworznicka cave system in poland between 34 and 26 ka bp in the buml cave in the czech republic and between 26 and 21 ka bp in the stratenska jasky a cave system slovakia at the time of ccc formation the studied caves were lying in a periglacial zone detailed c and o stable isotope study of ccc samples revealed that slow water freezing under isotope equilibrium was the dominant formational process in the studied polish and czech caves significantly higher 13 c values of ccc in the stratenska jasky a cave indicate either water freezing in a more opened system with continuous co 2 escape rayleigh fractional separation or participation of another co 2 source the model of slow water freezing under isotope equilibrium is supported by isolated character of the caves having limited ventilation in contrast modern cryogenic cave calcite powders sampled directly on the ice surface of two recently iced caves in slovakia with high ventilation showed much higher 18 o and 13 c data similar to cryogenic calcites obtained in experimental rapid water freezing

start of the last interglacial period at 135 ka evidence from a high alpine speleothem a detailed study of growth periods of a flowstone from spannagel cave in the zillertal alps austria at 2500 m above sea level a site highly sensitive to climate changes offers unprecedented new insights into pleistocene climate change in central europe flowstone sample spa 52 has a high u content to 116 ppm analyses of this sample reveal that episodes of calcite deposition started at 204 3 ka 135 1 2 ka and 122 ka suggesting that at these times the mean air temperature at this high alpine site was within 1 5 c of the present day condition the beginning of growth at 135 ka corresponds to the ending of the last glaciation and is concordant with a midpoint age for the penultimate deglaciation at 135 2 5 ka as deduced from the absolutely dated oxygen isotope curve in sediments from the bahamas as well as with recent coral evidence from barbados indicating a high sea level already by 135 8 0 8 ka this set of data supports evidence against northern hemisphere forcing of termination ii because the insolation maximum is at 127 ka

generation mechanism of tropical instability waves in the equatorial pacific ocean abstracttropical instability waves tiws are prominent features in the equatorial pacific propagating westward at a speed of 0 5 m s 1 with a wavelength of 1000 km in this study we show that

an analysis of tropical instability waves in a numerical model of the pacific ocean 2 generation and energetics of the waves this work was supported by the department of com merce noaa under grant na56gp0026 one of the au thors sm was partially supported by a nasa global change fellowship ngt 30288 another author ab was supported by a ucar postdoctoral fellowship

vegetation response to rapid climate change in central europe during the past 140 000 yr based on evidence from the furamoos pollen record the response of central european vegetation to rapid climate change during the late quaternary period eemian to holocene is assessed by data from the new pollen record of furamoos southwestern germany this record represents the longest late quaternary pollen record north of the alps as currently known its high degree of completeness allows detailed correlations with greenland ice cores and sea surface temperature records from the north atlantic our data show that if climate deteriorations were not long or severe enough to extirpate refugia of arboreal taxa north of the alps such as during marine oxygen isotope stage mis 5 i e wurm stadial a stadial b and stadial c reforestation with the onset of warmer conditions in central europe occurred on a centennial scale if arboreal taxa became completely extinct north of the alps such as during mis 4 i e wurm stadial d several thousand years were necessary for the reimmigration from refugia situated in regions south of the alps thus dansgaard oeschger interstades dois 24 to 20 and 15 to 11 are expressed in central european pollen records whereas dois 19 to 16 are not recorded due to migration lags

dynamics on seasonal variability of eke associated with tiws in the eastern equatorial pacific ocean abstractenergetic mesoscale eddies vortices associated with tropical instability waves tiws exist in the eastern equatorial pacific ocean between 0 and 8 n this study examines the seasonal va

calcite fabrics growth mechanisms and environments of formation in speleothems from the italian alps and southwestern ireland five fabrics were identified in alpine and irish caves on the basis of morphological and microstructural characteristics and re lated to growth mechanisms and growth environment columnar and fibrous fabrics grow when speleothems are continuously wet and from fluids at near equilibrium conditions low supersaturation sicc 0 35 through the screw dislocation mechanism the highly defective microcrystalline fabrics form at the same supersaturation range as co lumnar fabric but under variable discharge and the presence of growth inhibitors dendritic fabrics which have the highest density of crystal defects develop in disequilibrium conditions high supersaturation un der periodic very low flow regime periods that result in prolonged out gassing cave calcareous tufa forms in disequilibrium conditions only the calcite crystals of fabrics formed at low supersaturation seem to precipitate near isotopic equilibrium conditions

internal waves and mixing in the upper equatorial pacific ocean microstructure measurements in the equatorial pacific at 140 w in late 1984 show a pronounced diurnal variation in both high frequency internal wave energy and kinetic energy dissipation rate observations indicated that after sunset internal waves presumably generated by convective overturns in the mixed layer propagate downward and increase turbulence levels in the pycnocline it is proposed that large mixed layer eddies in the south equatorial current interact with the large shear caused by the equatorial undercurrent to generate a westward going anisotropic wave field the momentum transport in the radiated wave field results in a drag force on the equatorial mean flow field the observed mean wind stress at 140 w during tropic heat i which is twice as large as the annual mean wind is closer to the estimated radiation stress 10 4 m2 s 2 at the base of the mixed layer 30 m than to the estimated turbulent stress 10 5 m2 s 2 a wave dissipation model based on the observed turbulent kinetic energy dissipation rate is introduced in order to estimate the wave momentum flux divergence in the stratified region above the undercurrent core the model predicts that most of the downward wave momentum flux penetrates through the undercurrent core it is hypothesized that when the wind stress is strong the equatorial pacific ocean responds by generating a westward traveling internal wave field which transports much of the surface wind stress below the actively mixing surface layer

alpine subglacial hydrology abstract the size and shape of subglacial flow pathways exert a strong influence over the pressure and speed at which meltwaters are routed through glaciers these characteristics in turn influence glacier sliding velocity and the quantity and quality of bulk meltwaters discharging from glaciers in this paper we summarise four empirical research approaches that have been developed to improve our understanding of the subglacial hydrology of predominantly temperate based alpine glaciers investigations of bulk meltwater discharge and chemistry tracer studies proglacial bedrock investigations and borehole investigations as a result of linking these studies to conceptual or numerical models three arborescent and four non arborescent or distributed subglacial drainage configurations are described these drainage networks may be neither spatially nor temporally persistent but may compete with and replace each other on a seasonal basis a qualitative model of the temporal and spatial evolution of a typical alpine subglacial drainage system is advanced on the basis of research conducted at haut glacier d arolla switzerland

warm period growth of travertine during the last interglaciation in southern germany abstract late quaternary travertine at two sites near stuttgart formed entirely during interglacial periods the travertine contains structures from growth induced by bacteria and such structures have been dated by 230th u mass spectrometry the resulting ages from both sites imply growth episodes of short duration with growth rates up to 5 mm yr 1 at 99 800 1300 yr b p 2 n 8 and 105 900 1300 yr b p 2 n 7 these episodes were likely part of marine isotope stage mis 5 3 deposition of silt interrupted travertine growth at one of the sites 105 000 yr b p likely correlatives of this silt are the st germain i b stade recorded in the grand pile peat bog and a cold episode 1000 yr long recorded by 18o values in the grip ice core travertine also formed during stage 5 5 115 000 yr and during the early holocene we found no evidence for travertine accumulation in stages 2 3 4 and 5 1 at both sites the sr u ratio and the initial 234u 238u activity ratio resemble those of modern spring water however the sites differ in the chemical composition of spring water and in stratigraphic sequence of travertine accumulation

sea land oxygen isotopic relationships from planktonic foraminifera and speleothems in the eastern mediterranean region and their implication for paleorainfall during interglacial intervals the oxygen and carbon stable isotope compositions of cave speleothems provide a powerful method for understanding continental climate change here we examine the question of the regionality of this isotopic record and its linkage with the marine isotopic record in the eastern mediterranean em region the study presents a new accurately dated 250 kyr 18o and 13c record determined from speleothems of the peqiin cave northern israel its comparison with the continuous 185 kyr isotopic record of the soreq cave speleothems from central israel reveals striking similarities thus a strong regional climatic signal brought about by variations in temperature and rainfall amount is reflected in both cave records low 18o minima in the peqiin profile for the last 250 to 185 kyr period interglacial marine isotopic stage 7 match the timing of sapropels 9 to 7 and are indicative of high rainfall in the em region at these times the combined soreq and peqiin 18o record for the last 250 kyr excellently matches the published globigerinoides ruber g ruber marine 18o record for the em sea with the isotopic compositional difference g ruber speleothems remaining relatively constant at 5 6 0 7 thus establishing for the first time a robust exploitable link between the land and the marine isotopic records the correspondence of low 18o speleothem values and high cave water stands with low g ruber 18o values during interglacial sapropel events indicates that these periods were characterized by enhanced rainfall in the em land and sea regions by use of sea surface temperatures derived from alkenone data as a proxy for land temperatures at the soreq cave we calculate the paleorainfall 18o values and its amounts maximum rainfall and lowest temperature conditions occurred at the beginning of the sapropel events and were followed by decrease in rainfall and increase in temperatures leading to arid conditions the record for the last 7000 yr shows a trend toward increasing aridity and agrees well with climatic and archeological data from north africa and the middle east

on isc pp and pp data and their use in delay time tomography of the caribbean region summary a major problem in p delay time tomography is the inhomogeneous sampling of mantle structure by the p wave ray paths resulting in low resolution in images of large regions of the upper mantle incorporation of pp and pp phases can improve the quality and reliability of tomographic images because they 1 sample earth structure not ordinarily sampled by direct p phases 2 add rays that are oblique to rays of direct phases which is especially important where the latter sample mantle structure in selected directions and 3 pp data better constrain the earthquake focal depths pp traveltimes have often been used in combination with p data in differential traveltime studies we show that the assumptions and approximations necessary for this approach are problematic and that they can be avoided when the p pp and p data are used in tomographic inversion we investigated the applicability of pp and pp delay times to the tomographic study of the aspherical mantle structure below the caribbean region the success of the application of data of the later arriving reflected waves depends critically on the quality of these data we examined possible sources of error in the isc pp and pp data and assessed the contribution to the delay times used in this study for the caribbean region analyses of the isc pp and pp delay times do not reveal biases due to effects of pp waveform distortions the asymmetry of the reflections or due to misidentifications of phases that reflect at a surface other than that assumed the noise level of pp and pp data is high with respect to data of the direct p wave this is accommodated by weighting with the inverse of the variance of the data of each of the three phases the independent information that is revealed from the pp and pp data results in modifications of tomographic images based solely on p data these modifications are important if the tomographic images are being used to understand the geodynamical history of convergent margins in the caribbean region we investigated the effect of adding data of later arriving phases to the isc p data with sensitivity tests we inverted synthetic delay times to which we added gaussian noise with a standard error typical for the data of the three seismic phases these tests demonstrate that the image resolution of shallow mantle structure is enhanced significantly by the incorporation of later arriving phases due to the absence of seismicity below 200 km the resolution improved less at deeper levels below the caribbean region in some poorly constrained parts of the solution the test results even indicate an apparent decrease of resolution this is explained by changes in the rate of convergence of the inversion algorithm in mantle regions where the effective sampling of structure improved by the addition of pp and pp wave ray paths the convergence was speeded up at the expense of the convergence rate in regions where fewer or no pp or pp wave ray paths were added a shortcoming of the resolution tests used in our study is that some specific problems of reported delay times are not reflected in synthetic data we observe that isc delay times of later arriving phases are not necessarily consistent with the reported hypocentral parameters as most isc reported earthquake locations are computed from direct p wave data for the pp data the inconsistency with event location not only results in a decrease of focal depths during relocation but in a bias of the imaged velocity perturbations as well this property of reported data is not modelled in resolution tests

turbulence and internal waves at the equator part i statistics from towed thermistors and a microstructure profiler abstract high correlations between turbulent dissipation rates and high wavenumber internal waves and the high values of turbulent dissipation associated with internal wave activity suggest that internal waves are the main direct source of mixing in the thermocline above the core of the equatorial undercurrent an extensive dataset obtained using a microstructure profiler and thermistor chain towed along the equator was analyzed to examine the correspondence between turbulent mixing and high wavenumber internal waves in the low richardson number ri thermocline below the mixed layer but above the core of the equatorial undercurrent and when winds were moderate and steadily westward it was found that the spectrum of vertical isotherm displacement was dominated by a narrow wavenumber band corresponding to 150 250 m zonal wavelength of internal waves both turbulence and internal waves varied diurnally hourly averaged values of turbulent dissipation rate and wave potential energy were greater by a

on some possible interactions between internal waves and sea ice in the marginal ice zone the ice edges of the world ocean are generally the site at times when winds are blowing off the ice of regularly spaced surface bands of ice floes these bands have size scales of the order of 1 10 km and their long axes are oriented approximately normal to the wind direction available oceanic temperature and salinity data from the bering and greenland sea ice edge regions suggest that these ice bands are commonly underlain by a two layered density structure which is maintained by net melting along the ice edges linear internal wave theory is applied to these data to compute first mode interfacial wave phase speeds a simple analytical model is developed that demonstrates the feasibility of generation of such interfacial internal waves by the stress discontinuity due to off ice winds blowing over either a stationary or a moving ice edge it is qualitatively shown that the computed internal wave phase speeds and wavelengths are under many conditions compatible with the speeds and spacings of the surface ice bands this compatibility suggests in turn that coupling between internal waves and ice bands may commonly occur some possible implications of the generation and presence of these internal waves upon other ice edge processes such as air sea heat and momentum transfer are qualitatively discussed

constraints on the miocene landscape evolution of the eastern alps from the kalkspitze region niedere tauern austria abstract in order to unravel aspects of the miocene landscape evolution of the eastern european alps we present geomorphic and isotopic data from the western niedere tauern region austria the region is critical for such interpretations because it is one of the few regions along the topographic axis of the eastern alps where the highest peaks up to 2500 m a s l are dominated by limestone as such the region contains a record of miocene landscape forming events that survived the pleistocene glaciations not preserved elsewhere in the central eastern alps this record includes karst caves karstified planation surfaces and crystalline fluvial pebbles augenstein formation preserved on planation surfaces and in karst caves caves in the region occur in three distinct levels that correlate with well known cave levels in the northern calcareous alps although they are somewhat higher in the niedere tauern in part these cave elevations also correlate with three planation surfaces and knickpoints of major streams draining the region testifying their pre glacial origin we report details of a karst cave durchgangshohle from the highest cave level located at 2340 m a s l in this cave allochthonous fluvial gravels are present overgrown by speleothems one speleothem yielded an early middle pleistocene u pb age 682 17 ka we regard this as a minimum age for the erosion of the fluvial cave deposits during marine isotope stages 17 or 16 carbon and oxygen isotope data of these speleothems imply a climate that is consistent with this interpretation cosmogenic 21 ne data of fluvial quartz clasts collected from the surface on plateaus of the northern calcareous alps suggest minimum exposure durations of 115 and 262 ka they probably reflect successive exposure since removal of the sediment cover of the oligocene augenstein formation during the pleistocene while our geochronological data fail to record aspects of the earlier miocene uplift history they are consistent with the overall geomorphic history inferred from the geomorphic markers this suggests that the niedere tauern share a common uplift history with the northern calcareous aps and implies a moderate south north topographic gradient that has been maintained since the miocene

on pp and ss reflection point anomalies reflection point residuals of pp and ss waves obtained from the residuals of pp p and ss s with respect to the j b tables are shown to be in need of corrections recent velocity models of the earth s mantle predict residuals that differ considerably amongst themselves and from the j b tables before useful reflection point residuals can be determined by this method a reference model has to approximate closely the actual velocity distribution of the earth between the source and receiver lateral variations layering in velocity and scattering in the vicinity of the reflection point of short period pp also contribute large uncertainties in defining the reflection points of pp and its precursors all of the foregoing problems suggest that interpretations of pp and ss wave residuals in terms of structure near the symmetric reflections points as far as they have been determined up to now are subject to serious errors

buoyant gravity currents released from tropical instability waves abstracttwo extremely sharp fronts with changes in sea surface temperature 0 4 c over lateral distances of 1 m were observed in the equatorial pacific at 0 140 w and at 0 75 n 110 w in both c

paleoclimate implications of mass spectrometric dating of a british flowstone the timing of growth phases in a cave flowstone from yorkshire england has been precisely dated by thermal ionization mass spectrometric 238u 234u 230th dating six growth periods of both short duration and fast growth rate are separated by nondepositional hiatuses the ages of these phases were determined to be 128 8 2 7 103 1 1 8 84 7 1 2 57 9 1 5 49 6 1 3 and 36 9 0 8 ka there is a remarkably good correlation between the periods of active speleothem growth and the timing of solar insolation maxima derived from orbital parameters which has not previously been reported speleothem growth theory and evidence from other terrestrial paleoclimate records suggest that episodic rapid growth phases at the insolation maxima are most likely to be caused by changes in either precipitation intensity or volume which caused switching in the routing of water flow in the unsaturated zone above the cave such a result provides new evidence of the importance of variations in solar insolation for terrestrial paleoclimate and offers the potential for derivation of a paleowetness index from speleothem growth

sea surface cooling at the equator by subsurface mixing in tropical instability waves changes in the sea surface temperature of equatorial waters have critical effects on the large scale atmospheric circulation shipboard measurements of turbulence kinetic energy dissipation rate indicate that seasonal surface cooling in the central equatorial pacific may be largely caused by mixing induced by tropical instability waves

internal wave generation by ice floes moving in stratified water results from a laboratory study a series of tests has been conducted to investigate the increased ice water drag exhibited by ice floes in two layer salinity stratified water scaled model tests are used to quantify the additional drag due to internal wave creation at the fresh water salt water interface this additional drag is shown to have a peak value five times the drag in similar unstratified conditions and to have a strong dependence on a few well defined nondimensional parameters describing the ice and water characteristics

distinct 17 and 33 day tropical instability waves in subsurface observations abstract tropical instability waves tiws within a half degree of the equator in the pacific ocean have been consistently observed in meridional velocity with periods of around 20 days on the other hand near 5 n tiws have been observed in sea surface height ssh thermocline depth and velocity to have periods near 30 days tropical atmosphere ocean tao project moored equatorial velocity and temperature time series are used to investigate the spatial and temporal structure of tiws during 3 years of la nina conditions from 1998 through 2001 along 140 w where the tiw temperature and velocity variabilities are at their maxima these variabilities include two distinct tiws with periods of 17 and 33 days rather than one broadbanded process as predicted by modeling studies the 17 day tiw variability is shown to occur not only in meridional velocity at the equator but also in subsurface temperature at 2 n and 2 s while the 33 day tiw variability is observed primarily in subsurface temperature at 5

turbulence variability at the equator in the central pacific at the beginning of the 1991 1993 el nino a 38 day 5990 cast microstructure study on the equator performed during the onset of the 1991 1993 el nino shows the effect on small scale activity at 140 w of an equatorial kelvin wave by using two ships data were taken continuously from november 4 to december 12 1991 near the national oceanic and atmospheric administration pacific marine environmental laboratory mooring at o n 140 w the ships occupied the station sequentially with a 3 5 day overlap for intercalibration variability in currents was observed on tidal periods and periods of 4 days presumably equatorially trapped internal gravity waves 8 days cause unknown 20 days tropical instability waves and longer kelvin waves variation in water structure occurred most prominently on the timescale of kelvin waves the diurnal cycle typical of that location was observed nocturnal deepening of the surface mixed layer was accompanied by a deep cycle bursts of turbulence penetrating into the stratified region below the nighttime mixed layer during the observational period one kelvin wave trough and one crest passed through the site changes accompanying the phase change in the kelvin wave included a reversal of the near surface current a deepening of the thermocline and a change of water mass changes in small scale activity included a tenfold decrease of the thermal dissipation rate and a fourfold decrease of the rate of heat transport downward from the mixed layer the nighttime mixed layer deepened from 30 to 60 m the thickness of the stratified region in which nocturnal turbulence bursts occurred the deep cycle region thinned from 40 to 20 m because it was confined between the bottom of the nighttime mixed layer and the low shear region near the core of the undercurrent the decrease in downward heat flux observed at this passage of the downwelling kelvin wave front could explain the rapid sea surface temperature sst increase seen at el nino onsets the magnitude of the change in vertical flux is similar to the magnitude of the change in horizontal advection this process would produce a warmer sst much more quickly than could the advection of warm waters eastward

speleothems and paleoglaciers abstract ice and speleothems are widely regarded as mutually exclusive as the presence of liquid water is a fundamental prerequisite for speleothem deposition here we show that speleothems may form in caves overlain by a glacier as long as the temperature in the cave is above freezing and the conduits are not completely flooded by melt water carbonate dissolution is accomplished via sulfide oxidation and the resultant speleothems show high 13c values approaching and locally exceeding those of the parent host rock lack of soil derived biogenic c the 18o values reflect the isotopic composition of the melt water percolating into the karst fissure network and carry an atmospheric temperature signal which is distinctly lower than those of speleothems formed during periods when soil and vegetation were present above the cave these subglacial speleothems provide a means of identifying and dating the former presence of warm based paleoglaciers and allow us to place some constraints on paleotemperature changes

reconstruction of temperature in the central alps during the past 2000 yr from a δ18o stalagmite record the precisely dated isotopic composition of a stalagmite from spannagel cave in the central alps is translated into a highly resolved record of temperature at high elevation during the past 2000 yr temperature maxima during the medieval warm period between 800 and 1300 ad are in average about 1 7 8c higher than the minima in the little ice age and similar to present day values the high correlation of this record to d 14 c suggests that solar variability was a major driver of climate in central europe during the past 2 millennia d 2005 elsevier b v all rights reserved

factors that affect the amplitude of el nino in global coupled climate models historically el nino like events simulated in global coupled climate models have had reduced amplitude compared to observations here el nino like phenomena are compared in ten sensitivity experiments using two recent global coupled models these models have various combinations of horizontal and vertical ocean resolution ocean physics and atmospheric model resolution it is demonstrated that the lower the value of the ocean background vertical diffusivity the greater the amplitude of el nino variability which is related primarily to a sharper equatorial thermocline among models with low background vertical diffusivity stronger equatorial zonal wind stress is associated with relatively higher amplitude el nino variability along with more realistic east west sea surface temperature sst gradient along the equator the sst seasonal cycle in the eastern tropical pacific has too much of a semiannual component with a double intertropical convergence zone itcz in all experiments and thus does not affect nor is it affected by the amplitude of el nino variability systematic errors affecting the spatial variability of el nino in the experiments are characterized by the eastern equatorial pacific cold tongue regime extending too far westward into the warm pool the time scales of interannual variability as represented by time series of nino3 ssts show significant power in the 3 4 year enso band and 2 2 5 year tropospheric biennial oscillation tbo band in the model experiments the tbo periods in the models agree well with the observations while the enso periods are near the short end of the range of 3 6 years observed during the period 1950 94 the close association between interannual variability of equatorial eastern pacific ssts and large scale sst patterns is represented by significant correlations between nino3 time series and the pc time series of the first eofs of near global ssts in the models and observations

comparison of the climate during marine isotope stage 9 and 11 inferred from a speleothem isotope record from northern norway abstract a stalagmite from northern norway is dated with 12 thermal ionization mass spectrometry u th dates and at least four separate growth periods are identified that correspond with marine isotope stages 9 11 13 and probably 15 the calcite is tested for isotopic equilibrium with the hendy test oxygen isotope measurements on 231 subsamples on a vertical transect are used as a paleotemperature proxy the detailed isotopic record from mis 9 show apparent similarities to a holocene record from the same cave both in the climatic evolution and the overall temperatures both show temperature oscillations changing from high frequency low amplitude cycles in the beginning of the interglacial period to lower frequency higher amplitude cycles in the later part of the interglacial period the isotope record from mis 11 shows a distinct isotopic event toward heavier values the isotopic record together with the porous humus rich calcite are interpreted as indicating a warmer than present interglacial period with several episodes of heavy rainfall

timing and progression of the last interglacial derived from a high alpine stalagmite 1 u th dating and oxygen isotope analysis of a stalagmite from spannagel cave in the austrian alps provides information about the timing and progression of the last interglacial climate we determined two distinct growth intervals warm climate from 130 7 thousand years ka before the present to 130 0 ka and from 125 7 ka to 118 2 ka the latter containing two periods of ceased stalagmite growth colder climate at around 123 8 ka and 120 5 ka high resolution 18o analysis of stalagmite spa 50 reveals a clear regular cyclic pattern with periods of 197 109 and 21 years which are likely to be related to the suess gleissberg and hale cycles respectively indicating that eemian climate in the alps was forced by the sun

impact of vertical mixing induced by small vertical scale structures above and within the equatorial thermocline on the tropical pacific in a cgcm oceanic vertical mixing is known to influence the state of the equatorial ocean which affects the climate system including the amplitude of el nino southern oscillation enso recent measurements of ocean currents at high vertical resolution capture numerous small vertical scale structures svss within and above the equatorial thermocline that contribute significantly to vertical mixing but which are not sufficiently resolved by coarse resolution ocean models we investigate the impact of the vertical mixing induced by the svss on the mean state and interannual variability in the tropical pacific by using a coupled general circulation model the vertical mixing induced by the svss is represented as an elevated vertical diffusivity from the surface down to the 20 c isotherm depth a proxy for the depth of the thermocline we investigate different forms for the elevated mixing it is found that the svs induced mixing strongly affect the mean state of the ocean leading to a warming of sea surface temperature sst and associated deepening and sharpening of the thermocline in the eastern equatorial pacific we find that the sst warming induced by the elevated mixing is further strengthened through the bjerknes feedback and sst shortwave flux feedback we also find a reduction in the number of large amplitude enso events and in certain cases an increase in the skewness of enso

palaeo climate reconstruction from stable isotope variations in speleothems a review abstract speleothems are now regarded as valuable archives of climatic conditions on the continents offering a number of advantages relative to other continental climate proxy recorders such as lake sediments and peat cores they are ideal materials for precise u series dating yielding ages in calendar years thereby circumventing the radiocarbon calibration problems associated with most other continental records stable isotope studies in speleothems have shifted away from attempting to provide palaeo temperature reconstructions to the attainable goal of providing precise estimates for the timing and duration of major o isotope defined climatic events characterised by high signal to noise ratios e g glacial interglacial transitions dansgaard oeschger oscillations the 8200 year event unlike the marine records speleothem data sets are not tuned and their independent chronology offers opportunities to critically assess leads and lags in the climate system that in turn can provide important insights into forcing and feedback mechanisms improved procedures for the extraction and measurement of stable isotope ratios in fluid inclusions trapped in speleothems are likely to provide in the near future a much enhanced basis for the quantitative interpretation of o isotope ratios in speleothem calcite the latter developments open up once again the tantalising prospect of palaeo temperature estimates but more importantly perhaps provide a direct test for a new generation of general circulation models whose hydrological cycles will incorporate the water isotopes the literature is reviewed briefly to provide for the reader a sense of the current state of the art and to provide some pointers for future research directions

downward lee wave radiation from tropical instability waves in the central equatorial pacific ocean a possible energy pathway to turbulent mixing turbulent mixing in the equatorial pacific ocean is an important process that controls diapycnal heat transport and hence affects the air sea interactions and global climate it is recently shown that in the eastern equatorial pacific strong mixing is induced in the thermocline by enhanced vertical shear associated with tropical instability waves tiws which propagate westward along the equator at a speed of 0 5 m s 1 with a wavelength of 1000 km in this study using a high resolution ocean general circulation model we show that the tiws can play an important role in inducing turbulent mixing in the thermocline also in the central equatorial pacific although the thermocline is too deep to be directly affected by the vertical shear of the tiws the front of the tiw is clearly manifested as a narrow strip of strong convergence of horizontal surface flow from which area downward and westward propagating internal waves are intermittently emanated these internal waves can be interpreted as lee waves generated by the surface flow convergence zone which acts like an inverted obstacle moving along the stratified ocean surface by inducing downward flow the associated downward energy flux below the surface mixed layer increases as the tiw structure becomes deeper toward the central equatorial pacific so that the energy pathway to turbulent mixing in the thermocline can be created the downward energy flux integrated over the entire equatorial pacific and averaged during january 2011 amounts to 8 1 gw occupying a significant fraction of the energy input to the tiws

a precisely dated climate record for the last 9 kyr from three high alpine stalagmites spannagel cave austria 1 here we use the 18o time series of three stalagmites from the high alpine spannagel cave austria which grew in small distance from each other to construct a precisely dated continuous 18o curve for the last 9 kyr comnispa this speleothem record is not influenced by effects of kinetic isotope fractionation due to the low temperatures in the cave thus the variations in 18o can be interpreted in terms of past climate change comnispa exhibits several oscillations within the holocene and their timing and duration is in agreement with that documented by other alpine archives

tropical instability wave kinematics observations from the tropical instability wave experiment the kinematics of planetary waves originating from instability of the nearsurface equatorial currents are reported on using velocity measurements from an array of acoustic doppler current profilers deployed in the equatorial pacific during the tropical instability wave experiment a distinctive wave season was observed from august to december 1990 with wave energy confined primarily above the core of the equatorial undercurrent particle motions in the horizontal plane are described by eccentric ellipses oriented toward the north but tilting into the cyclonic shear of the south equatorial current the tilt is maximum near the surface just north of the equator and decreases to the south and with depth the distribution of wave variance is narrowband in both frequency and zonal wavenumber with central period zonal wavelength and westward directed phase propagation estimated to be 500 hours 1060 km and 59 cm s 1 respectively neither the meridional nor the vertical wavenumber component is statistically different from zero these results generally agree with previous findings on tropical instability waves from the atlantic and pacific oceans and in the undersampled arena of geophysical measurements they provide an example where statistical inference is supported by an ensemble of independent measurements

mapping of upper mantle structure from differential pp p travel time residuals abstract p and pp travel time residuals have been collected from 23 quarters of the regional catalog of earthquakes of the international seismological centre isc the difference in travel time residuals between pp and p are used as an indicator of the p delay time near the pp reflection point global maps of these differential travel time residuals are used to study lateral heterogeneity in the crust and upper mantle two of the regions studied have mean differential travel time residuals significantly different at greater than the 95 confidence level from the global mean of the differential travel time residuals in the central pacific southeast of hawaii differential pp p travel time residuals of 3 8 0 36 s are observed these observations imply an average p delay time of 1 1 0 38 s average p delay times of 0 67 0 20 s are observed beneath the tibetan plateau and the western portion of the people s republic of china these travel time variations basically agree in location and sign with the surface wave results of tanimoto and anderson

water flow through temperate glaciers understanding water movement through a glacier is fundamental to several critical issues in glaci ology including glacier dynamics glacier induced floods and the prediction of runoff from glacierized drainage basins to this end we have synthesized a conceptual model of water movement through a temper ate glacier from the surface to the outlet stream pro cesses that regulate the rate and distribution of water input at the glacier surface and that regulate water movement from the surface to the bed play important but commonly neglected roles in glacier hydrology where a glacier is covered by a layer of porous perme able firn the accumulation zone the flux of water to the glacier interior varies slowly because the firn tempo rarily stores water and thereby smooths out variations in the supply rate in the firn free ablation zone in con trast the flux of water into the glacier depends directly on the rate of surface melt or rainfall and therefore varies greatly in time water moves from the surface to the bed through an upward branching arborescent net work consisting of both steeply inclined conduits formed by the enlargement of intergranular veins and gently inclined conduits spawned by water flow along the bottoms of near surface fractures crevasses engla cial drainage conduits deliver water to the glacier bed at a limited number of points probably a long distance downglacier of where water enters the glacier englacial conduits supplied from the accumulation zone are quasi steady state features that convey the slowly varying water flux delivered via the firn their size adjusts so that they are usually full of water and flow is pressurized in contrast water flow in englacial conduits supplied from the ablation area is pressurized only near times of peak daily flow or during rainstorms flow is otherwise in an open channel configuration the subglacial drainage system typically consists of several elements that are distinct both morphologically and hydrologically an up glacier branching arborescent network of channels in cised into the basal ice conveys water rapidly much of the water flux to the bed probably enters directly into the arborescent channel network which covers only a small fraction of the glacier bed more extensive spatially is a nonarborescent network which commonly includes cav ities gaps between the glacier sole and bed channels incised into the bed and a layer of permeable sediment the nonarborescent network conveys water slowly and is usually poorly connected to the arborescent system the arborescent channel network largely collapses during winter but reforms in the spring as the first flush of meltwater to the bed destabilizes the cavities within the nonarborescent network the volume of water stored by a glacier varies diurnally and seasonally small temper ate alpine glaciers seem to attain a maximum seasonal water storage of 200 mm of water averaged over the area of the glacier bed with daily fluctuations of as much as 20 30 mm the likely storage capacity of subglacial cavities is insufficient to account for estimated stored water volumes so most water storage may actually occur englacially stored water may also be released abruptly and catastrophically in the form of outburst floods

a modeling study of the impact of tropical instability waves on the heat budget of the eastern equatorial pacific a numerical simulation is used to investigate the mixed layer heat balance of the tropical pacific ocean including the equatorial cold tongue and the region of vortices associated with tropical instability waves tiws the study is motivated by a need to quantify the effects that tiws have on the climatological heat budget of the cold tongue mixed layer there has been some discrepancy between observations indicating very large equatorward heat transport by tiws and models that disagree on the full three dimensional budget validation of the model reveals that the tiw induced circulation patterns are realistic but may have amplitudes about 15 weaker than those in the observations the sst budget within tropical instabilities is first examined in a frame of reference moving with the associated tropical instability vortices tivs zonal advection of temperature anomalies and meridional advection of temperature by current anomalies dominate horizontal advection these effects strongly heat the cold cusps and slightly cool the downwelling areas located at the leading edge of the vortices cooling by vertical mixing is structured at the vortex scale and almost compensates for horizontal advective heating in the cold cusps in contrast to some previous studies tiw induced vertical advection is found to be negligible in the sst budget cooling by this term is only significant below the mixed layer the effect of tiws on the climatological heat budget is then investigated for the region bounded by 2 s 6 n 160 90 w where instabilities are most active tiwinduced horizontal advection leads to a warming of 0 84 c month 1 which is of the same order as the 0 77 c month 1 warming effect of atmospheric fluxes while the mean currents and vertical mixing cool the upper ocean by 0 59 c month 1 and 1 06 c month 1 respectively the cooling effect of tiw induced vertical advection is also negligible in the long term surface layer heat budget and only becomes significant below the mixed layer the results above and in particular the absence of cancellation between horizontal and vertical tiw induced eddy advection are robust in three other sensitivity experiments involving different mixing parameterizations and increased vertical resolution

holocene forcing of the indian monsoon recorded in a stalagmite from southern oman a high resolution oxygen isotope record from a thorium uranium dated stalagmite from southern oman reflects variations in the amount of monsoon precipitation for the periods from 10 3 to 2 7 and 1 4 to 0 4 thousand years before the present ky b p between 10 3 and 8 ky b p decadal to centennial variations in monsoon precipitation are in phase with temperature fluctuations recorded in greenland ice cores indicating that early holocene monsoon intensity is largely controlled by glacial boundary conditions after approximately 8 ky b p monsoon precipitation decreases gradually in response to changing northern hemisphere summer solar insolation with decadal to multidecadal variations in monsoon precipitation being linked to solar activity

stalagmite from the austrian alps reveals dansgaard oeschger events during isotope stage 3 implications for the absolute chronology of greenland ice cores a mass spectrometric uranium series dated stalagmite from the central alps of austria provides unprecedented new insights into high altitude climate change during the peak of isotope stage 3 the stalagmite formed continuously between 57 and 46 kyr before present a series of hendy tests demonstrates that the outer parts of the sample show a progressive increase of both stable c and o isotope values no such covariant increase was detected within the axial zone this in conjunction with other observations suggests that the continuous stable oxygen isotope profile obtained from the axial zone of the stalagmite largely reflects the unaltered isotopic composition of the cave drip water the n 18 o record shows events of high n 18 o values that correlate remarkably with interstadials 15 a and b 14 and 12 identified in the greenland ice cores interstadial 15b started rapidly at 55 6 kyr and lasted v300 yr only interstadial 15a peaked 54 9 kyr ago and was even of shorter duration v100 yr and interstadial 14 commenced 54 2 kyr ago and lasted v3000 yr this stalagmite thus represents one of the first terrestrial archives outside the high latitudes which record precisely dated dansgaard oeschger d o events during isotope stage 3 provided that rapid d o warmings occurred synchronously in greenland and the european alps the new data provide an independent tool to improve the grip and gisp2 chronologies 2002 elsevier science b v all rights reserved

generation of internal waves by sea ice observations in the greenland sea marginal ice zone suggest that when strong stratification occurs near the surface momentum flux into the internal wave field of the upper ocean can be a major component of the force balance that governs ice drift since energy is radiated away by the internal waves turbulent mixing and heat flux are also affected we investigate the downward flux of momentum and energy by internal waves in an ice covered ocean with an idealized model comprising a mixed layer overlying a deep uniformly stratified layer a buoyancy jump separates the mixed layer from the pycnocline drag from a single wave number component of the under ice roughness spectrum is derived as the product of a drag coefficient based on ice speed under ice roughness wave number and amplitude and uniform stratification to the ice ocean interface times an attenuation factor that depends additionally on mixed layer depth and the buoyancy jump at the base of the mixed layer the model is extended to a plausible spectrum of under ice roughness by integration over wave number space internal wave effects are parameterized in terms of the drag coefficient from the integrated spectrum and incorporated into an upper ocean turbulence model model calculations show that plausible values for the peak wave number of the idealized spectrum and roughness variance can account for 1 decreased ice velocity relative to the wind 2 decreased heat exchange coefficient between the ice and ocean and 3 lack of mixed layer deepening all of which were observed during the last week of the 1984 marginal ice zone experiment

high precision constraints on timing of alpine warm periods during the middle to late pleistocene using speleothem growth periods a long standing problem in the reconstruction of warm climate periods during the late quaternary is the difficulty of determining absolute ages for undisturbed terrestrial climate archives speleothems offer an important source of information about the timing and duration of middle and late pleistocene warm phases a flowstone from the high elevation spannagel cave zillertal alps austria provides a new absolutely dated climate record which includes the most prominent warm phases between 260 and 50 ka before present new data from the penultimate interglacial improve our knowledge about the timing and progression of warm periods in the alps corresponding to marine isotope stages 7 and 8 speleothem growth phases were identified from 261 to 249 from 236 to 229 and from 200 to 192 ka an early onset of the last interglacial is corroborated by a growth phase commencing at 136 7f2 8 ka and the youngest section of the flowstone provides further evidence for an alpine climate during time intervals corresponding to marine isotope stages 5a and 3 sufficiently warm to allow speleothems to grow the high resolution stable isotope profile taken along the growth axis of the flowstone provides information about the hydrological conditions during the growth phases d 2005 elsevier b v all rights reserved

impact of explosive cyclones on the deep ocean in the north pacific using an eddy resolving ocean general circulation model the oceanic response to explosive cyclones over the north pacific in winter is investigated using eddy resolving 34 year hindcast simulation of a quasi global ocean its response appears as a horizontal divergence of the surface layer above 60 m depth and upward flow that reaches 2000 m depth a case study of a typical explosive cyclone using hourly outputs from january 2011 shows that the explosive cyclone induces horizontal divergence within the surface mixed layer and upward flow that reaches 6000 m depths the flow causes oceanic internal waves and temperature cooling because of the vertical advection in the deep ocean the interannual variability of explosive cyclone activity in january affects the amplitude of the vertical motion and the daily scale temperature variations in the deep ocean

chronology and paleoenvironment of marine isotope stage 3 from two high elevation speleothems austrian alps abstract a new high resolution stable isotope record from the alpine kleegruben cave 2165 m central alps is presented this record largely duplicates a previously reported speleothem record from this site high precision u series thermal ionization mass spectrometry dates constrain the growth history of this new sample 56 48 ka to the marine isotope stage mis 3 both stalagmites reveal highly similar variations in o isotopes that can be directly compared to o isotope variability associated with dansgaard oeschger interstadials recorded in the greenland ice cores greenland interstadials gis based on the new record we refine our previous age assignments of the gis during this time interval i e gis 15b at 55 7 ka gis 15a at 55 3 ka onset mid point of the prominent gis 14 at 54 5 yr and onset of gis 12 at 48 ka the overall uncertainties associated with these ages are 0 1 0 3 ka the timing of these dansgaard oeschger interstadials is within 0 2 ka of the newly proposed grip sfcp04 timescale the age data for both kleegruben stalagmites demonstrate that liquid water was at least seasonally present in the shallow sub surface allowing calcite precipitation to continue even during stadials of mis 3 given the present day low temperature 2 4 c we propose that these unusual speleothems formed in a karst system overlain by a warm based glacier

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

precise dating of dansgaard oeschger climate oscillations in western europe from stalagmite data the signature of dansgaard oeschger events millennial scale abrupt climate oscillations during the last glacial period is well established in ice cores and marine records but the effects of such events in continental settings are not as clear and their absolute chronology is uncertain beyond the limit of 14 c dating and annual layer counting for marine records and ice cores respectively here we present carbon and oxygen isotope records from a stalagmite collected in southwest france which have been precisely dated using 234u 230th ratios we find rapid climate oscillations coincident with the established dansgaard oeschger events between 83 000 and 32 000 years ago in both isotope records the oxygen isotope signature is similar to a record from soreq cave israel and deep sea records indicating the large spatial scale of the climate oscillations the signal in the carbon isotopes gives evidence of drastic and rapid vegetation changes in western europe an important site in human cultural evolution we also find evidence for a long phase of extremely cold climate in southwest france between 61 2 0 6 and 67 4 0 9 kyr ago

glacier response in the european alps to heinrich event 1 cooling the gschnitz stadial the gschnitz stadial was a period of regionally extensive glacier advance in the european alps that lies temporally between the breakdown of the last glacial maximum piedmont lobes and the beginning of the bolling warm interval moraines of the gschnitz stadial are found in medium to small catchments are steep walled and blocky and reflect a snowline lowering of 650 700 m in comparison to the little ice age reference snowline 10 be surface exposure dating of boulders from the moraine at the type locality at trins gschnitz valley tyrol austria shows that it stabilised no later than 15 400 1400 yr ago the overall morphological situation and the long reaction time of the glacier suggest that the climatic downturn lasted about 500 300 yr indicating that the gschnitz cold period began approximately 15 900 1400 yr ago if not somewhat earlier this is consistent with published radiocarbon dates that imply that the stadial occurred sometime between 15 400 14 c yr bp 18 020 19 100 cal yr and 13 250 14 c yr bp 15 360 16 015 cal yr a palaeoclimatic interpretation of the gschnitz glacier based on a simple glacier flow model and statistical glacier climate models shows that precipitation was about one third of modern day precipitation and summer temperatures were about 10 k lower than today in comparison during the younger dryas precipitation in this area was only about 10 less and ts summer temperature was only 3 5 4 k lower than modern values based on the age of the moraine and the cold and dry climate at that time we suggest that the gschnitz stadial was the response of alpine glaciers to cooling of the north atlantic ocean associated with heinrich event 1 copyright 2005 john wiley sons ltd