early pleistocene climate changes in the central mediterranean region as inferred from integrated pollen and planktonic foraminiferal stable isotope analyses vegetation inherited from a pliocene subtropical climate evolved through obliquity oscillations and global cooling leading to modern conditions an integrated highly time resolved record of pollen and stable isotopes 18o and 13c of globigerina bulloides was obtained to understand vegetation responses to early pleistocene climate changes continental and marine responses are compared in the central mediterranean region with a particular consideration of environmental changes during anoxic events pollen data illustrate vegetation dynamics as follows 1 development of mesothermic elements warm and humid conditions 2 expansion of mid and high altitude elements cooler but still humid conditions and 3 strengthening of steppe and herb elements cooler and dry conditions these successions correlate with precession 18o variations recorded by globigerina bulloides define two cycles mis 43 40 related to obliquity at northern low to mid latitudes the pollen signal records temperature and wetness changes related to precession even during global climate changes induced by obliquity this may result in unexpected increasing wetness during glacial periods which has to be considered specific to the central and eastern mediterranean region lastly an analysis of anoxic events reveals that enhanced runoff is indicated by increasing frequency of the riparian trees liquidambar and zelkova

aspects of climate variability in the north atlantic sector discussion and relation to the greenland ice sheet project 2 high resolution isotopic signal this paper reviews aspects of climate variability in the north atlantic sector that may influence the seasonal to decadal scale isotopic signal in the greenland ice sheet project 2 gisp2 ice core interpretation of the isotopic signal and its spatial applicability at the seasonal level requires investigation into synoptic scale climatology we discuss possible climatic influences of 1 likely source regions of precipitation reaching the gisp2 site 2 the characteristics of cyclone activity over the north atlantic sector and 3 changes in major atmospheric features such as the mean sea level icelandic low and azores high pressure systems the north atlantic oscillation and the baffin trough next we evaluate correlations between the gisp2 deuterium isotopic signal and coastal temperatures with atmospheric pressure patterns thereby deriving climatic interpretations of the high resolution isotopic record the gisp2 site is influenced by both the icelandic low to the southeast and davis strait baffin bay storms to the southwest and west the north atlantic oscillation influences the gisp2 isotopic signal through the seesaw in winter temperatures between west greenland and northern europe agreement in excursion directions of gisp2 isotopes and east greenland and iceland temperature records is associated with different positions of the baffin trough in winter and also with anomalous 500 mbar net geostrophic flow linkages between isotopic excursion direction and atmospheric variability need to be explored further by comparison with additional seasonal data sets from other greenland ice cores

transition from a singly vergent to doubly vergent wedge in a young orogen the greater caucasus the greater caucasus mountains due to their youth 5 ma provide an opportunity for insight into the early stages of orogen development during continent continent collision however their recent tectonic evolution and first order architecture remain unclear here we investigate the evolution of the orogen by integrating new observations of the fluvial geomorphology and neotectonics of the range with prior work on seismicity geodetic strain bedrock geology and foreland basin structure we find that the range contains four zones along strike that differ in structural architecture topography and first order tectonic history in particular two south directed singly vergent zones at the western and eastern tips of the orogen are separated by both a central doubly vergent zone that is dominated by north directed deformation and an eastern doubly vergent zone in which south directed thrusting dominates we hypothesize that the along strike changes in vergence and locus of deformation reflects different stages in the development of a doubly vergent orogen with the tips of the range preserving an early singly vergent form and the center recording a more advanced orogen the differences between the two doubly vergent zones seem to be driven by the initial stages of collision between the structurally thickened crust of the greater and lesser caucasus orogens which initiated at 5 ma

gravity inferred crustal thickness of greenland abstract greenland s crust contains clues for understanding the dynamics of the earth s second largest ice sheet as well as the iceland hotspot over the past 100 ma however our knowledge of the sub ice crust is very limited due to the paucity of outcrops and seismic observations particularly in central greenland in order to augment these sparse constraints we modeled terrain and airborne free air gravity data which provide estimates for moho and related crustal thickness these estimates were obtained from the inversion of isostatically corrected terrain effects where the computed gravity effects of the terrain s rock water and ice components were subtracted from the terrain correlated free air anomalies the terrain correlated free air components were estimated from the correlation spectrum between the free air anomalies and the terrain s gravity effects which are assumed to reflect isostatic disturbances of the crustal terrain the results indicated an average crustal thickness of about 37 km for greenland with greater values by 5 10 km in the southern greenland archean blocks and caledonian foldbelt and comparably lower values in northern greenland the thinner crustal thickness estimates in the north are strongly correlated with the faster basal melt regions of the ice sheet and glaciers the crustal thickness map provides constraints for an improved interpretation of the iceland hotspot track in northern greenland at about 100 70 ma

the north atlantic oscillation and oceanic precipitation variability global north atlantic oscillation nao oceanic precipitation features in the latter half of the twentieth century are documented based on the intercomparison of multiple state of the art precipitation datasets and the analysis of the nao atmospheric circulation and sst anomalies most prominent precipitation anomalies occur over the ocean in the north atlantic where in winter a quadrupole like pattern is found with centers in the western tropical atlantic sub tropical atlantic high latitude eastern atlantic and over the labrador sea the extent of the sub tropical and high latitude center and the amount of explained variance over 50 are quite remarkable however the tropical atlantic center is probably the most intriguing feature of this pattern apparently linking the nao with itcz variability in summer the pattern is tripole like with centers in the eastern mediterranean sea the north sea baltic sea and in the sub polar atlantic in the eastern indian ocean the correlation is positive in winter and negative in summer with some link to enso variability the sensitivity of these patterns to the choice of the nao index is minor in winter while quite important in summer interannual nao precipitation anomalies have driven similar fresh water variations in these key regions in the sub tropical and high latitude atlantic in winter precipitation anomalies have been roughly 15 and 10 of climatology per unit change of the nao respectively decadal changes of the nao during the last 50 years have also influenced precipitation and fresh water flux at these time scales with values lower higher than usual in the high latitude eastern north atlantic labrador sea in the 1960s and the late 1970s and an opposite situation since the early 1980s in summer the north sea baltic region has been drier than usual during the period 1965 1975 when the nao was generally positive

40ar 39ar dating of the pre evaporitic messinian marine sequences of the melilla basin morocco a proposal for some biosedimentary events as isochrons around the alboran sea in the mediterranean region the melilla basin ne morocco represents a key area that recorded biosedimentary events and environmental changes relative to the pre evaporitic messinian times 40ar 39ar dating of volcanic tuffs interbedded all along the melilla messinian shelf carbonates and coeval basin deposits has been performed in order to date accurately three main pre evaporitic biosedimentary events the prograding bioclastic deposition and the oligospecific prograding porites coral reef buildings with coeval halimeda blooms both within the platform and the diatomite deposition basinward the new age data allow a precise chronological framework to be established for the pre evaporitic sequence of melilla basin demonstrating that diatomitic deposits are coeval with both prograding bioclastic and reefal units the prograding bioclastic carbonate unit related to boreal influences in coeval basinal diatomites began at least at 6 73 0 02 ma and ended at 6 46 0 03 ma the oligospecific prograding porites coral reefs and halimeda beds and coeval warm water diatomites began at least at 6 46 0 03 ma previous 40ar 39ar ages indicate that they ended prior to 6 0 0 1 ma both biosedimentological similarities and chronological accordance within several platforms and adjacent basins all around the alboran sea show that these main bioevents dated in melilla are synchronous over the alboran realm this accurate time scale for these pre evaporitic biosedimentary events 6 9 6 0 ma is in accordance with the most recent work on the latter period corresponding to the messinian salinity crisis

chronology of neogene and quaternary uplift and magmatism in the caucasus constraints from k ar dating of volcanism in armenia abstract the greater caucasus is one of earth s highest actively uplifting mountain ranges the adjoining caspian sea basin contains a substantial proportion of its hydrocarbon reserves like other parts of the former soviet union the neogene and quaternary chronology of these important regions has not previously been well defined it has thus been impossible to obtain reliable estimates for rates of processes such as uplift of the caucasus and sedimentation in the caspian sea previous studies have established the relative timings of events in the region using correlation schemes between volcanism glaciations and the stratigraphy of the caspian basin however a range of absolute chronologies has previously been proposed for these sediments and igneous rocks based mainly on different interpretations of their magnetostratigraphic records by k ar dating we determine the ages of volcanism at three localities in armenia as 1 1 0 8 and 0 8 ma using these data and other evidence we propose a revision to the chronology of this region in which a distinctive brief interval of normal magnetic polarity in the local sedimentary and volcanic magnetostratigraphic records is matched to the cobb mountain event in the global record rather than the olduvai event or an earlier subchron as had previously been thought we thus interpret a 1 5 ma timing for the start of volcanism in the lesser caucasus and also suggest a 1 2 ma timing for the late akchagyl transgression of the caspian sea a key event in the regional stratigraphy when this water body reached its greatest extent we tentatively correlate this transgression with the melting event following glaciation during stage 36 of the oxygen isotope timescale which was thus the first time during the pleistocene when eastern europe was covered by a lowland ice sheet time averaged since 1 ma the flanks of the eastern greater caucasus mountains are shown to have uplifted at 0 6 mm a 1 and the lesser caucasus at 0 3 mm a 1 we show that the rate and spatial scale of this uplift are too great to be the result of plate convergence and suggest instead that this uplift is caused by crustal thickening due to inward lower crustal flow to beneath these mountain ranges at the start of magmatism in both the greater and lesser caucasus the estimated crustal thickness was 45 km we thus suggest that this magmatism has been caused by heating of the mantle lithosphere due to earlier crustal thickening the temperature rise required to initiate magmatism being the same in both cases

the north atlantic oscillation signature in deuterium and deuterium excess signals in the greenland ice sheet project 2 ice core 1840 1970 the greenland ice sheet project 2 gisp2 core can enhance our understanding of the relationship between parameters measured in the ice in central greenland and variability in the ocean atmosphere and cryosphere of the north atlantic ocean and adjacent land masses seasonal summer winter to annual responses of d and deuterium excess isotopic signals in the gisp2 core to the seesaw in winter temperatures between west greenland and northern europe from a d 1840 to 1970 are investigated this seesaw represents extreme modes of the north atlantic oscillation which also influences sea surface temperatures ssts atmospheric pressures geostrophic wind strength and sea ice extents beyond the winter season temperature excursions inferred from the d record during seesaw extreme nao mode years move in the same direction as the west greenland side of the seesaw symmetry with the west greenland side of the seesaw suggests a possible mechanism for damping in the ice core record of the lowest decadal temperatures experienced in europe from a d 1500 to 1700 seasonal and annual deuterium excess excursions during seesaw years show negative correlation with d this suggests an isotopic response to a sst land temperature seesaw the isotopic record from gisp2 may therefore give information on both ice sheet and sea surface temperature variability cross plots of d and d show a tendency for data to be grouped according to the prevailing mode of the seesaw but do not provide unambiguous identification of individual seesaw years a combination of ice core and tree ring data sets may allow more confident identification of ga and gb extreme nao mode years prior to 1840

spatial variation in the influence of the north atlantic oscillation on precipitation across greenland 1 ice core derived accumulation records from greenland have been proposed as proxies for north atlantic oscillation nao reconstruction in a series of single site analyses accumulation records from ice cores drilled in western greenland were found to exhibit the strongest linear association with nao in this paper we expand on these findings by proposing a spatiotemporal statistical model to explore further the relationship between nao and the accumulation records from 35 firn and ice cores drilled in western and southern greenland in particular we propose a temporal extension of the bayesian spatially varying coefficient regression model which is fit using a markov chain monte carlo algorithm this model readily accommodates the irregular features of the data i e variation in record lengths and irregular spacing among ice core locations and the serial dependence within individual records using our statistical model we are able to exploit the spatial dependence structure of the derived accumulation nao relationship to explore the regional patterns in the strength of this relationship our findings support previous work that identified a region in western greenland where derived accumulation is most correlated with nao however we also identify a region further inland to the east and south where the estimated strength of the linear accumulation nao relationship is weaker but more certain than in the previously identified region thus our findings can be used to guide decisions regarding where to locate future drilling efforts in greenland by weighing the trade off between the potential strength of the accumulation nao relationship and its uncertainty

changes in vegetation and marine environments in the eastern mediterranean rhodes greece during the early and middle pleistocene pollen records marine faunal associations and stable isotope compositions of sediments from rhodes greece have been determined to track environmental changes in the eastern mediterranean during the early and middle pleistocene a detailed chronostratigraphic curve based on magnetostratigraphic data was obtained by correlating pollen spectra with the mediterranean oxygen isotopic curve of ocean drilling program site 975 five sedimentary sequences that correspond to marine oxygen isotope stage mis 31 27 and to mis 20 17 have been investigated in the confined tsampika microbasin high amplitude pinus variations confirm glacio eustatic changes deduced from changes in marine faunal associations and sedimentary depositional environments reflecting climatic cycles identified in the marine carbonate oxygen isotope record eight vegetation successions characterized by the dominance first of mesothermic elements then of mid and high altitude elements with pinus and ending with maxima in herb and steppe elements have been documented most of them were probably driven by changes in insolation occurring in high northern latitudes obliquity impact during the late early pleistocene and early middle pleistocene

pleistocene volcanism and the geomorphological record of the hrazdan valley central armenia linking landscape dynamics and the palaeolithic record abstract the southern caucasus lies at the intersection of africa the levant and eurasia and is thus a region of considerable interest in the study of pleistocene hominin population dynamics and behaviour while palaeolithic archaeological sites in the region such as dmanisi and nor geghi 1 attest to such palaeogeographic significance a greater understanding of the chronology and nature of climatic and geomorphic changes in the region is needed to fully understand hominin settlement dynamics the hrazdan river valley central armenia has the potential to offer such insights given its rich palaeolithic record and complex history of pleistocene infill as a result of alluvial lacustrine aeolian and volcanic processes we therefore present a stratigraphic framework for basin infill and hominin activity during the pleistocene based on extensive geomorphological and geological mapping published chronometric results 40ar 39ar and k ar and archaeological survey we demonstrate that the onset of pleistocene volcanism in the gegham range to the immediate east of the hrazdan valley occurred around 700 ka bp after which there were several phases of effusive eruption lasting until 200 ka interbedded with lava emplaced by these eruptions are alluvial and lacustrine sequences some with evidence of pedogenesis and several of which have yielded palaeolithic artefacts taken together these sequences suggest a cyclical model of infill whereby lava flow along the valley resulted in the blockage of the palaeo hrazdan river and lake formation in the lea of the lava dams breaching of these dams resulted in a shift to predominately fluvial deposition and the consequent development of floodplain soils hominin populations exploited the floodplains at times when the last of these phases coincided with interglacial and interstadial climates but they also occupied the surrounding valley sides during the same warm humid phases

high resolution magnetostratigraphy and radio isotope dating of early pleistocene lake sediments from southern armenia abstract the pleistocene geology of armenia is dominated by widespread occurrence of sediments recording recurring rapid and drastic changes of the environmental conditions during at least the last 2 million years these sediments predominantly diatomites contain a huge variety of various fossil remains allowing the reconstruction of flora fauna as well as the climatic conditions especially during dispersal of early man into eurasia 1 8 ma radio isotope dating of pumice levels as well as a detailed magnetostratigraphic study have been carried out in syunik province near the town of sisian southern armenia in order to establish a temporal correlation of all major outcrops of paleo lake sediments and to provide a timeframe for paleoenvironmental studies within this lake sediment succession a total of 455 oriented drill cores was sampled at six large and four short sections with a sampling resolution between 5 and 20 cm detailed paleomagnetic experiments reveal the presence of a characteristic remanent magnetization chrm pointing either to the north and down or south and up a positive reversal test suggests the primary character of this magnetization component combining the normal and reverse polarity directions results in an overall sample mean direction of d 354 8 i 51 5 with a fisherian precision parameter k of 14 6 and the associated 95 of 2 9 combining demagnetization data of 169 samples in addition ash layers were sampled for 40ar 39ar geochronology at five of the sections studied paleomagnetically and three additional small outcrops the resulting ages range between 1 31 ma and 1 08 ma with two samples yielding 1 65 and 1 90 ma the latter are characterized by extremely low abundances of radiogenic 40ar suggesting that the mineral system has not been closed since the time of eruption leading to substantial loss in ar integration of these radio isotope dates with the polarity data suggests that the normal polarities can be linked to the jaramillo subchron within the matuyama reversed polarity chron based on the longest interval of normal polarity identified at ashotavan 2 a lower limit for the sedimentation rate of 37 cm ky can be estimated therefore we infer the duration of lake sedimentation as 350 ky starting at 1 4 ma

structural geometries and magnitude of shortening in the eastern kura fold thrust belt azerbaijan implications for the development of the greater caucasus mountains 1 the greater caucasus are the northernmost extent of the arabia eurasia collision and are thought to represent the main locus of shortening within the central portion of the collision zone between 40 and 48 e recent work suggests that in detail since the plio pleistocene much of the shortening in the eastern portion of the caucasus system has been focused within the kura fold thrust belt along the southeastern margin of the greater caucasus here we present new field mapping and stratigraphic investigations of the eastern termination of the kura fold thrust belt in azerbaijan to better constrain the structural geometries magnitude of shortening and initiation age for this portion of the fold thrust belt our work suggests that this area of the fold thrust belt exhibits significant along strike variations in structural style and evolution and can effectively be divided into two distinct domains at 48 e the western domain is characterized by a subcritical median surface slope and isolated folds and thrusts propagating out of sequence whereas the eastern domain is dominated by a single duplex structure and a history of in sequence development in a critically tapered wedge we hypothesize that these variations result from changes in relative rates of syn tectonic sedimentation erosion and convergence velocity along strike we find that within the western domain the fold thrust belt has accommodated 12 km of total shortening an unconformity within the western domain brackets the initiation age of this portion of the fold thrust belt to between 1 8 and 0 88 ma yielding permissible average shortening rates of between 6 7 and 13 6 mm yr comparison of these average shortening rates to the geodetically measured shortening rate of 8 mm yr indicates that since initiation the fold thrust belt has accommodated 83 100 of convergence between the greater and lesser caucasus at this longitude

vegetation and climate changes during the late pliocene and early pleistocene in sw anatolia turkey abstract pollen analysis was done on lacustrine sedimentary sequences dated by micromammals as late pliocene early pleistocene that outcrop in two neogene graben basins from sw turkey this study shows vegetation changes from steppe like to more forested environments very similar to the cyclic oscillations related to late pleistocene glacial interglacial climate changes artemisia was abundant during cold arid periods indicating that this species was already widespread in this area during the latest pliocene and the beginning of the pleistocene a review of pollen records from anatolia agrees with this study suggesting that the spreading of this arid species occurred during a major climatic change the beginning of the first glaciations and probably a change in seasonality towards summer aridity artemisia temporarily disappeared from the region during warm wet periods and thus we suggest that glacial interglacial type oscillations already occurred in the area during the late pliocene early pleistocene

norwegian fjord sediments reveal nao related winter temperature and precipitation changes of the past 2800 years abstract the north atlantic oscillation nao is the leading mode of atmospheric circulation variability in the north atlantic region associated shifts of storm tracks precipitation and temperature patterns affect energy supply and demand fisheries and agricultural as well as marine and terrestrial ecological dynamics long term nao records are crucial to better understand its response to climate forcing factors and assess predictability and shifts associated with ongoing climate change a recent study of instrumental time series revealed nao as main factor for a strong relation between winter temperature precipitation and river discharge in central norway over the past 50 years here we compare geochemical measurements with instrumental data and show that primary productivity recorded in central norwegian fjord sediments is sensitive to nao variability this observation is used to calibrate paleoproductivity changes to a 500 year reconstruction of winter nao luterbacher et al 2001 conditioned on a stationary relation between our climate proxy and the nao we establish a first high resolution nao proxy record nao tfj from marine sediments covering the past 2800 years the nao tfj shows distinct co variability with climate changes over greenland solar activity and northern hemisphere glacier dynamics as well as climatically associated paleo demographic trends the here presented climate record shows that fjord sediments provide crucial information for an improved understanding of the linkages between atmospheric circulation solar and oceanic forcing factors

north atlantic oscillation dynamics recorded in greenland ice cores carefully selected ice core data from greenland can be used to reconstruct an annual proxy north atlantic oscillation nao index this index for the past 350 years indicates that the nao is an intermittent climate oscillation with temporally active coherent and passive incoherent phases no indication for a single persistent multiannual nao frequency is found in active phases most of the energy is located in the frequency band with periods less than about 15 years in addition variability on time scales of 80 to 90 years has been observed since the mid 19th century

precipitation over greenland retrieved by a dynamic method and its relation to cyclonic activity abstract in order to calculate the vertical motion over some high mountain regions such as greenland an equation without the quasigeostrophic approximation in coordinates has been developed a dynamic method for retrieving precipitation over greenland is based on this equation the retrieved annual mean precipitation distribution for 1987 and 1988 is in very good agreement with the observed annual accumulation pattern over the greenland ice sheet the major weather system producing precipitation over greenland is the frontal cyclone based on the precipitation characteristics greenland can be divided into five subregions precipitation over the north coastal and central interior regions primarily occurs in summer for the three other subregions if the composite monthly mean sea level pressure charts for high and low monthly precipitation amounts are constructed a clear relationship between precipitation and cyclonic activity emerges if a mean cyclone exists in the labrador sea heavy precipita

thermobarometry of garnet clinopyroxene hornblende granulites from the kapuskasing structural zone amphibole mixing properties and standard state properties for the end members tremolite tschermakite pargasite ferrotremolite ferrotschermakite and ferropargasite have been refined through analysis of relevant phase equilibrium experiments coexisting cummingtonite hornblende pairs and natural mineral parageneses when merged with the mineral properties given by r g berman these amphibole properties allow the calculation of numerous equilibria suitable for thermobarometry in a wide range of bulk compositions at amphibolite to granulite metamorphic grades the method was applied to texturally equilibrated garnet pyroxene hornblende gneisses and compared both to results based on anhydrous assemblages and to those for garnet biotite gneisses from the kapuskasing structural zone thermometer resetting is apparent only in garnet biotite gneisses whereas touching garnet pyroxene pairs in mafic gneiss show little evidence of retrograde fe mg exchange computed metamorphic temperatures garnet clinopyrox

active faulting and natural hazards in armenia eastern turkey and northwestern iran active fault zones of armenia se turkey and nw iran present a diverse set of interrelated natural hazards three regional case studies in this cross border zone are examined to show how earthquakes interact with other hazards to increase the risk of natural disaster in northern armenia a combination of several natural and man made phenomena earthquakes landslides and unstable dams with toxic wastes along the pambak sevan sunik fault pssf zone lowers from 0 4 to 0 2 0 3g the maximum permissible level mpl of seismic hazard that may induce disastrous destruction and loss of life in the adjacent vanadzor depression in the ararat depression a large active fault bounded pull apart basin at the junction of borders of armenia turkey iran and azerbaijan an earthquake in 1840 was accompanied by an eruption of ararat volcano lahars landslides floods soil subsidence and liquefaction the case study demonstrates that natural hazards that are secondary with respect to earthquakes may considerably increase the damage and the casualties and increase the risk associated with the seismic impact the north tabriz gailatu fault system poses a high seismic hazard to the border areas of nw iran eastern turkey nakhichevan azerbaijan and southern armenia right lateral strike slip motions along the north tabriz fault have given rise to strong earthquakes which threaten the city of tabriz with its population of 1 2 million the examples illustrate how the concentration of natural hazards in active fault zones increases the risk associated with strong earthquakes in armenia eastern turkey and nw iran this generally occurs across the junctions of international borders hence the transboundary character of active faults requires transboundary cooperation in the study and mitigation of the natural risk

the diel cycle of water vapor in west greenland we present a study of the dynamics of small scale 100 km atmospheric circulation in west greenland which is dominated by interactions of marine and continental air masses water vapor concentration and isotopic ratios measured continuously over a 25 day period in kangerlussuaq greenland were used to monitor the convergence of easterly katabatic winds and westerly sea breezes that form a front between the dry isotopically depleted glacial air mass and the moist isotopically enriched marine air mass during the latter 16 days of the measurement period an interval with no large scale synoptic interference the inland penetration of the sea breeze controlled the largest day to day humidity and vapor isotopic variations kangerlussuaq experienced sea breezes in the afternoon on 9 days consistent with the long term average of such occurrences on 56 of days in july and august the inland position of the sea breeze front is controlled by the katabatic wind strength which is stronger during times of reduced cloud coverage and or higher pressure gradient between the coast and the greenland ice sheet the position and movement of the front will likely respond to changes in the general atmospheric circulation and regional radiation balance resulting from global warming which will in turn impact the local hydrological cycle and ecosystem processes

a late pleistocene long pollen record from lake urmia nw iran abstract a palynological study based on two 100 m long cores from lake urmia in northwestern iran provides a vegetation record spanning 200 ka the longest pollen record for the continental interior of the near east during both penultimate and last glaciations a steppe of artemisia and poaceae dominated the upland vegetation with a high proportion of chenopodiaceae in both upland and lowland saline ecosystems while juniperus and deciduous quercus trees were extremely rare and restricted to some refugia hippophae rhamnoides constituted an important phanerophyte particularly during the late last glacial period a pronounced expansion in ephedra shrub steppe occurred at the end of the penultimate late glacial period but was followed by extreme aridity that favoured an artemisia steppe very high lake levels registered by both pollen and sedimentary markers occurred during the middle of the last glaciation and late part of the penultimate glaciation the late glacial to early holocene transition is represented by a succession of hippophae ephedra betula pistacia and finally juniperus and quercus the last interglacial period eemian slightly warmer and moister than the holocene was followed by two interstadial phases similar in pattern to those recorded in the marine isotope record and southern european pollen sequences

precipitation over greenland and its relation to the north atlantic oscillation the equation method based on an equivalent isobaric geopotential height in coordinates has been used to retrieve the precipitation over greenland this approach is designed to accurately represent the topographic effects of the greenland ice sheet on atmospheric motion and precipitation the 11 year mean precipitation from 1985 to 1996 over all of greenland is 376 mm yr 1 which is close to the long term mean precipitation of 346 mm yr 1 estimated from glaciological data the precipitation over all of greenland shows that the largest value in 1986 is 472 mm yr 1 and the smallest value in 1995 is 309 mm yr 1 the major interannual variability of the atmospheric circulation in the north atlantic can be represented by the variation of the north atlantic oscillation nao index which is most pronounced during winter it is found that if the nao index increases the total precipitation over greenland decreases and vice versa the correlation coefficient between these two series for 1985 1995 is 0 75 the mean precipitation over southern greenland where the majority of precipitation falls is more closely related to the nao index in winter and their correlation coefficient is 0 80 this relationship can be understood from the composite maps of sea level pressure and greenland precipitation for the high and low index months during months of high nao index values the icelandic low is strong during months of low nao index values the monthly mean low is located to the southwest of greenland over the labrador sea precipitation amounts over the southeast coast of greenland are about 100 mm larger during the low nao index months than the high nao index months precipitation over all of greenland during the low nao index months is higher there are significant downward trends in annual precipitation from 1985 1995 for all of greenland and its southern and central west coastal regions amounting to about 3 per year

annual accumulation over recent centuries at four sites in central greenland 1 accurate accumulation records are fundamental to understanding mass balance of the greenland ice sheet ice cores can provide multicentury high resolution ground based point estimates of water accumulation in 2003 and 2004 four new ice cores were collected in the central western d4 and d5 and summit sandy and katie regions of greenland annual layer counting based on multiple glaciochemical parameters primarily hydrogen peroxide sea salt and dust proxies was used to date the ice cores resulting in annual dating the bottom depth ages for d4 d5 sandy and katie were estimated at 1738 1673 1844 and 1934 a d with mean annual accumulation rates of 41 4 35 2 22 4 and 22 4 cmweq yr 1 respectively these new records were in good agreement with previous accumulation maps and four previously published records from nearby multicentury ice cores spatial variability was quantified through an analysis of variance thereby allowing for more meaningful comparisons to atmospheric processes more regionally representative accumulation records were constructed for the central western and summit regions spanning recent centuries using a principle component analysis of both the new and previously reported ice core measurements these regional records exhibited 6 7 interannual variability 1 standard deviation of the mean and had lower spatial variability uncertainties than individual accumulation records correlations indicate that 20 of the variance in the central western region was explained by the north atlantic oscillation nao and suggests that an array of more northern ice cores may correlate more closely with nao

palaeohydrology of kangerlussuaq sondre stromfjord west greenland during the last 8000 years major fluctuations of hydroclimate in west greenland are recorded in paleoshoreline terraces that encircle several lakes near kangerlussuaq greenland 67 01 n 50 40 w geomorphic and stratigraphic analyses were used to construct a lake level curve for hunde so a large closed basin lake in this region changes in lake volume associated with lake level fluctuations were cal culated and a water balance model was used to determine the primary factors influencing lake volume and the changes in those factors necessary to affect reconstructed lake level change sensitivity tests suggest that mean annual precipitation and the relative proportion of summer versus winter precipitation are the primary climate drivers of lake level change temperature effects are less important unless coupled with changes in one of the other variables two pluvial periods occurred centered around 4600 and 2000 cal yr bp with mean annual precipitation estimated at 130 mm and 70 mm higher than modern respectively in contrast a low stand prior to 6070 cal yr bp with water levels as much as 18 m below modern was a result of summer temperatures 2 3 above modern coupled with a 14 day increase in the length of the iceoff period and a reduction in mean annual precipitation of 80 mm relative to modern

modeled variations of precipitation over the greenland ice sheet abstract a parameterization of the synoptic activity at 500 hpa and a simple orographic scheme are used to model the spatial and temporal variations of precipitation over the greenland ice sheet for 1963 88 from analyzed geopotential height fields produced by the national meteorological center nmc model coefficients are fitted to observed accumulation data primarily from the summit area of the ice sheet all major spatial characteristics of the observed accumulation distribution are reproduced apart from the orographic accumulation maximum over the northwestern coastal slopes the modeled time averaged total precipitation amount over greenland is within the range of values determined by other investigators from surface based observations a realistic degree of interannual variability in precipitation is also simulated a downward trend in simulated ice sheet precipitation over the 26 years is found this is supported by a number of lines of evidence it matches the accumulation trends during this peri

southeast greenland winter precipitation strongly linked to the icelandic low position abstractgreenland s largest precipitation flux occurs in its southeast se region during the winter controlled primarily by easterly winds and frequent cyclogenesis in the north atlantic several

mediterranean quaternary sapropels an immediate response of the african monsoon to variation of insolation abstract in the subsurface of the east mediterranean sea eleven discrete basin wide organic rich black sapropels were deposited during the last 465 000 years they are dated by oxygen isotopic chronostratigraphy the most recent sapropel has been shown to be the consequence of heavy nile river summer floods due to increased monsoonal summer precipitation over ethiopia and not of scandinavian ice sheet meltwater influx into the east mediterranean sea as was previously believed while most sapropels were deposited during interglacials two thick sapropels formed during glacial periods as shown by their position in the oxygen isotopic stratigraphy and by their pollen record in core rc9 181 the new evidence presented here is that the sapropel sequence in this core including the two glacial sapropels correlates on a one to one basis with the highest values of an index of insolation on top of the atmosphere the concept of this index derives from an analysis of the african monsoon process the index variation is computed for the last 465 000 years from the caloric northern summer insolation in the tropical latitudes controlled by variations of the earth s orbital parameters it is conjectured that this index might be linked through the climate system to the monsoonal precipitation which in africa produces the nile river summer flood

holocene climatic changes in greenland different deuterium excess signals at greenland ice core project grip and northgrip 1 water stable isotope measurements d and 18o have been conducted on the holocene part of two deep greenland ice cores greenland ice core project grip and northgrip located 320 km apart these combined measurements provide the first two continuous greenland holocene deuterium excess profiles d d 8 18o a parameter strongly influenced by changes in moisture sources we discuss here temporal and regional fluctuations of the deuterium excess within central to north greenland with a mean temporal resolution of 4 years although grip and northgrip exhibit similar annual mean surface temperatures and 18o levels a significant offset of modern deuterium excess is observed between the two sites we attribute this offset to a different mix of modern moisture sources pointing to regional scale differences in moisture advection toward greenland the common long term deuterium excess holocene increasing trend is probably related to the increased relative contribution of low latitude moisture to greenland snowfall in response to the change in the earth obliquity as symmetrically observed in antarctica three abrupt declines punctuate the grip excess record 8 2 4 5 and 0 35 ka bp suggesting associated reorganizations of the northern high latitudes hydrological cycle the 8 2 ka bp event is characterized by 1 a rapid cooling followed by a progressive warming and 2 a deuterium excess cooling restricted to grip therefore totally different from rapid events during glacial times by contrast the northgrip deuterium excess record is more stable we propose that a slightly larger proportion of moisture supplied by local storm tracks to grip induces an isotopic compensation mechanism between simultaneous site and source temperature coolings resulting in a rather temperature insensitive 18o profile together with well marked deuterium excess amplitudes northgrip 18o seems less biased by isotopic processes and should provide a more reliable past temperature record

late cenozoic deformation in the south caspian region effects of a rigid basement block within a collision zone abstract active deformation in the south caspian region demonstrates the enormous variation in kinematics and structural style generated where a rigid basement block lies within a collision zone rigid basement to the south caspian basin moves with a westward component relative both to stable eurasia and iran and is beginning to subduct at its northern and western margins this motion is oblique to the approximately north south arabia eurasia convergence and causes oblique shortening to the south and northeast of the south caspian basin thrusting in the alborz and kopet dagh is accompanied by range parallel strike slip faults which are respectively left and right lateral there are also arcuate fold and thrust belts in the region for two principal reasons firstly weaker regions deform and wrap around the rigid block this occurs at the curved transition zone between the alborz and talysh ranges where thrust traces are concave towards the foreland secondly a curved fold and thrust belt can link a deformation zone created by movement of the basement block to one created by the regional convergence west to east thrusts in the eastern talysh represent underthrusting of the south caspian basement but pass via an arcuate fan of fold trains into ssw directed thrusts in the eastern greater caucasus which accommodates part of the arabia eurasia convergence each part of the south caspian region contains one or more detachment levels which vary dependent on the pre pliocene geology buckle folds in the south caspian basin are detached from older rocks on thick mid tertiary mudrocks whereas thrust sheets in the eastern greater caucasus detach on mesozoic horizons in the future the south caspian basement may be largely eliminated by subduction leading to a situation similar to archaean greenstone belts of interthrust mafic and sedimentary slices surrounded by the roots of mountain ranges constructed from continental crust

the impact of cloud cover on the net radiation budget of the greenland ice sheet energy balancemodelsdrivenbyradiationandturbulentheatfluxeshave beenwidelyappliedto predictingtheresponse ofthegreenland ice sheetto climatechange however a lackof knowledge of the temporal and spatial distribution of cloudamount and type has necessitated the use of parameterizations or statistical models of cloud cover this deficiency results in large uncertainties in both shortwave and longwave radiation fluxes stereo matching of nadir and forward viewalongtrack scanning radiometer 2 atsr 2 image pairs has been shown to be a reliable method of retrieving cloud top height and further cloud properties can be derived from thermal imagery allowing classification into cloud type a1year cloud record for a transect across southern greenland derived from stereo matching is presented here and comparisons are made with climate re analysis data and ground observations the cloud cover data were used in a simple radiative transfer model and the impact of clouds on the net radiation fluxes was found to be considerable different cloud scenarios produced up to 40wm 2 difference in net radiation balance in theablationzone wherethealbedoislowerandmost variable thesensitivity to cloud cover fraction was less marked but the higher spatial resolution of the atsr 2 cloud record was reflected by a much more varied trend in radiation balance whether the net radiation balance increases or decreases with increased cloud cover was foundto be a function of the cloud amount andtype and also the surface albedo the sensitivity of the model to a 5 change in cloud amount was found to be comparable to a1k change in temperature this clearlydemonstratestheimportanceofreliable quantitativeclouddatainmass balanceand otherglaciological studies

modeled precipitation variability over the greenland ice sheet on the basis of the evaluation of recent greenland precipitation studies some of the deficiencies in the modeled precipitation are probably related to the topographic data employed in modeling in this paper the modern digital elevation data of ekholm 1996 is used if the horizontal pressure gradient force in coordinates is separated into its irrotational and rotational parts which are expressed by the equivalent geopotential and geo stream function respectively the topographic effect on the precipitation can be accurately modeled the equivalent geopotential and geo stream function are implemented in a fully consistent manner in the generalized equation in this paper a simplified large scale condensation without evaporation of condensate is also used these improvements are combined to yield an improved dynamic method two aspects of the precipitation distribution are refined by the improved dynamic method one is the 10 cm yr 1 contour near summit greenland and the other is a relative large precipitation area centered near the point 70 n 49 w extensive comparisons are made between the retrieved precipitation and the observed annual accumulation time series from 11 ice core sites on the ice sheet the modeled precipitation from the original method must use sealers to have a high degree of interannual correspondence between the measured accumulation and the retrieved precipitation but the retrieved precipitation from the improved method increases at all ice core sites and a good correspondence is obtained without any sealer being required the spatial average of multiyear mean error e j is 11 5 cm yr 1 for the modeled precipitation from the improved method while that for p from era 15 is 14 5 cm yr 1 the total mean error em is 3 0 cm yr 1 for the improved method while em for the p from era 15 is 4 0 cm yr 1 these two errors show that the precipitation modeled by the improved method is better than the p from era 15 thus the distribution of precipitation over the 11 sites retrieved by the improved dynamic method is considerably refined large downward trends in annual amounts are present in the precipitation retrieved by the improved dynamic method for all of greenland and its southern and central west coastal regions the modeled precipitation from the improved dynamic method and observed accumulation from ice cores are all in agreement with the thomas et al 1999 result that the southern greenland ice sheet above 2000 m is approximately in balance it also shows that local thickening and thinning areas of the ice sheet derived by airborne laser altimetry from 1993 to 1999 over the entire greenland above 2000 m krabill et al 2000 are approximately consistent with precipitation change retrieved by the improved dynamic method

a synthetic pollen record of the eastern mediterranean sapropels of the last 1 ma implications for the time scale and formation of sapropels abstract the quaternary climate of southern europe south italy and greece is investigated by pollen analysis of the sapropels which were deposited in the deep eastern mediterranean sea during the last 1 million year ma the time scale of core kc01b in the ionian sea has been established by tuning its oxygen isotopic record to the ice volume model of imbrie and imbrie 1980 for the last 250 000 year 250 ka the previous pollen studies and astronomical tuning have been confirmed sapropels were deposited under a large range of mediterranean climates fully interglacial fully glacial and intermediary as revealed mainly by the balance between the respective pollen abundances of oak quercus and sage brush artemisia the high value of the oak reveals the warm and wet climate of an interglacial and the high value of the sage brush the dry and cold climate of a glacial whereas the mediterranean climate is directly related to the variation of the high latitude ice sheets the deposition of sapropels is not so in contrast with the wide climatic range sapropels were deposited only when summer insolation in the low latitudes reached its highest peaks however between 250 ka and 1 ma that stable pattern is not yet established only six sapropels are observed many expected ones do not appear even as ghosts signalled by peaks of barium abundance that remain after the post deposition oxidation of organic matter the pattern of sapropel formation in stable and direct relationship to highest insolation does not seem to apply for five of those sapropels neither climate extremes are observed they mainly formed during intermediary types of mediterranean climate in contrast one sapropel and one ghost relates to a relatively low peak of insolation and its climate is of a unique composite type not seen later this might suggest an unsuspected more complex pattern linking the formation of mediterranean sapropels to the astronomical configuration

recent ice sheet growth in the interior of greenland a continuous data set of greenland ice sheet altimeter height from european remote sensing satellites ers 1 and ers 2 1992 to 2003 has been analyzed an increase of 6 4 0 2 centimeters per year cm year is found in the vast interior areas above 1500 meters in contrast to previous reports of high elevation balance below 1500 meters the elevation change rate is 2 0 0 9 cm year in qualitative agreement with reported thinning in the ice sheet margins averaged over the study area the increase is 5 4 0 2 cm year or 60 cm over 11 years or 54 cm when corrected for isostatic uplift winter elevation changes are shown to be linked to the north atlantic oscillation

early pleistocene climate cycles in continental deposits of the lesser caucasus of armenia inferred from palynology magnetostratigraphy and 40ar 39ar dating plio pleistocene diatomitic sequences in the shamb paleo lake south armenia lesser caucasus offer a rare opportunity to give new insights on the paleo climate of western asia we present an integrated palynological 40ar 39ar geochronologic and magnetostratigraphic study for the most complete section in the sedimentary deposits of the shamb paleo lake 40ar 39ar dating of two volcaniclastic layers provided ages of 1 24 0 03 and 1 16 0 02 ma 2 magnetostratigraphic data show that the entire shamb section is of reversed polarity which combined with 40ar 39ar dating suggests that the entire section correlates with part of the matuyama period 1 785 1 070 ma pollen assemblages and macroremains diversity clearly show an alternation of glacial and interglacial phases age calibrations and accumulation rate extrapolation allow a direct correlation of climate changes with the global isotopic curve and show that the shamb section probably ranges from approximately 1 300 to 1 080 ma marine isotopic stages 40 to 31 the vegetation of the lesser caucasus developed in a mosaic pattern in a pleistocene continental mostly arid climate comparable to the present day climate the observed vegetation changes record a dominant climate response to the obliquity orbital parameter but the influence of precession could not be established from the shamb data pollen and macroflora both indicate that glacial periods were cold and dry and that interglacials were warm with local humidity the early pleistocene climatic model for western asia is thus similar to the climatic model for the mediterranean area

greenland ice sheet high elevation balance and peripheral thinning aircraft laser altimeter surveys over northern greenland in 1994 and 1999 have been coupled with previously reported data from southern greenland to analyze the recent mass balance of the greenland ice sheet above 2000 meters elevation the ice sheet is in balance on average but has some regions of local thickening or thinning thinning predominates at lower elevations with rates exceeding 1 meter per year close to the coast interpolation of our results between flight lines indicates a net loss of about 51 cubic kilometers of ice per year from the entire ice sheet sufficient to raise sea level by 0 13 millimeter per year approximately 7 of the observed rise

mid pleistocene revolution and the eccentricity myth the mid pleistocene revolution mpr is the term used to describe the transition between 41 ka and 100 ka glacial interglacial cycles which occurred about one million years ago despite eccentricity having by far the weakest influence on insolation received at the earth s surface of any of the orbital parameters it is often assumed to be the primary driver of the post mpr 100 ka climate cycles the traditional solution to this is to call for a highly nonlinear response by the global climate system to eccentricity this eccentricity myth is a simplified view of the relationship between global climate and orbital forcing and is in part due to an artefact of spectral analysis our aim here is to clarify the often confused role of eccentricity and review current theories of the mpr we suggest that the post mpr 100 ka glacial interglacial cycles are more closely linked to precession with the saw toothed climate cycles being defined by every four or five precessional cycle because control over the number of precessional cycles involved is determined by eccentricity eccentricity at most paces rather than drives the system if true then one must also question whether the mpr itself defined by an abrupt change in spectral characteristics is not also somewhat misconceived

the north atlantic oscillation and its imprint on precipitation and ice accumulation in greenland interannual to decadal fluctuations in net precipitation and ice accumulation are examined over greenland it is shown that in western greenland these fluctuations are correlated with the north atlantic oscillation the analysis is based on two complementary data sources a highly resolved net precipitation and accumulation history over 15 years derived form the reanalysis data of the european centre for medium range weather forecasts and a composite ice accumulation record representative for the western part of central greenland it is suggested that western greenland snow accumulation is a good proxy for the nao index with the potential for the reconstruction of a long time series

vegetation fire and climate history of the lesser caucasus a new holocene record from zarishat fen armenia vegetation fire and climate history are investigated in the 10 000 year record of zarishat fen located today in the steppe grasslands of armenia near east pollen based climate quantification provides a reconstruction of seasonal parameters the development of in situ water dependant plants and of forests at lower altitude at 8200 cal a bp echoes the shift from an arid and cold annual precipitation pann 452mm mean temperature of the coldest month mtco 11 1uc early holocene to a more humid and warmer pann 721mm mtco 6 8uc mid late holocene this marks the onset of lower seasonality in particular more effective precipitation brought during late spring by the westerlies paralleling the mediterranean precipitation pattern precipitation in the near east and central asia decreased during the mid late holocene in favour of higher seasonality controlled in winter spring by the siberian high fire history and sedge based fen development record drier phases at approximately 6400 5300 4900 3000 2200 1500 and 400 cal a bp which resemble the precipitation pattern of the south western mediterranean and contrast with the holocene pattern in the south central and south eastern mediterranean regions arid phases in armenia are believed to be related to multi centennial scale variation of westerly activity north atlantic oscillation like copyright 2013 john wiley sons ltd

quaternary volcano lacustrine patterns and palaeobotanical data in southern armenia the morphogenetic evolution of the lesser caucasus has been strongly influenced by plio quaternary volcanic and tectonic events and pleistocene glaciations fluvio lacustrine environments indicated by diatomaceous deposits prevailed in the syunik region of southern armenia during the pliocene and pleistocene the pleistocene diatomaceous deposits studied contain leaf impressions and pollen allowing local palaeoclimatic reconstructions the chronology of morphogenetic events has been determined by 17 radiometric dates k ar ar ar u th palaeomagnetic investigations and is placed in a spatial context by a detailed geomorphological map and a 24 km geological transect of the vorotan valley the main area studied before 1 21 ma tectonic movements antecedents of the lower part of the vorotan valley generated extensive lake formations with diatomaceous deposits from 993 ka volcanic eruptions produced lava flows that covered the fluvio lacustrine accumulations during marine isotopic stages 12 6 and 4 glaciers and fluvio glacial deposits were probably present overall the principal uplands and valleys of southern armenia at 53 68 ka mis 3 12 6 ka 10 78 ka and 4 14 ka mis 1 the development of travertines on some slopes and in some valleys highlights temperate and humid climatic phases palaeobotanical studies of leaf and pollen floras show that the vegetation changed several times from forested to steppic phases in response to the climate oscillations of the lower pleistocene this work proposes a first morphogenic and palaeoclimatic reconstruction from the lower pleistocene to the postglacial period when the first settlements of the population in the lesser caucasus were influenced by tectono volcanic events lake level changes and glacialeinterglacial oscillations forced by the obliquity orbital parameter 41 ky cycles

vegetation response to obliquity and precession forcing during the mid pleistocene transition in western mediterranean region odp site 976 abstract the odp leg 161 site 976 alboran sea is a deep sea section sampled at a water depth of 1108 m in the western mediterranean sea pollen analysis provides a vegetation and climate record of the mid pleistocene transition mpt roughly one million years ago the age model tied to biostratigraphic events was revised by aligning the pollen climate index pci to mediterranean kc01b and global lr04 oxygen isotope records the studied time slice spans the interval 1 09 ma mis 31 to 0 90 ma mis 23 across this interval past phytogeography of nowadays extinct taxa which were rare allows a successful application of the modern analogues technique mat to quantitative climate reconstructions for the mpt five long term obliquity related vegetation successions o1 to o5 and eight short term precession related vegetation successions p1 to p8 are observed within the studied interval these vegetation successions regardless of their duration show the same pattern the progressive replacement of temperate trees by mountainous taxa and then by herbs and steppe maxima precession related successions correspond therefore to as dramatic vegetation changes as those driven by obliquity including a final steppe phase under deteriorated climate conditions wavelet analysis of the pci record shows that the western mediterranean experienced a shift at 1 01 ma from precession dominated frequencies 1 05 1 01 ma to obliquity dominated frequencies 1 01 0 9 ma there is therefore an apparent discrepancy between wavelet analysis results and vegetation dynamic analysis which suggests that obliquity and precession are recorded throughout the entire studied interval this discrepancy could result from the fact that the pci record sums somehow similar vegetation changes wet to dry occurring at different periodicities such a complex vegetation dynamics is mathematically rendered through a single parameter i e principal component which does not successfully catch the subtle combinations of variability occurring at two close periodicities furthermore the pollen inferred early pleistocene vegetation dynamic and climate of the western mediterranean region does not show a decrease of the obliquity response relative to the precession response at the onset of the mpt

a freshwater jet on the east greenland shelf in august 1997 rrs discovery cruise 230 world ocean circulation experiment woce section a25 ran a hydrographic section into cape farewell on the southern tip of greenland the closest approach to the shore was 2 nm in a water depth of 160 m over the east greenland shelf analysis of the hydrographic data conductivity temperature depth ctd vessel mounted acoustic doppler current profiler and thermosalinograph has revealed a current flowing southwestward 15 km wide 100 m deep and centered 10 km offshore we believe it to be driven by meltwater runoff from greenland this feature which we call the east greenland coastal current egcc carries a little less than 1 sv 106 m3 s 1 with peak current speeds of 1 m s 1 at the surface the center of the egcc lies on a salinity front with maximum salinity contrast 4 practical salinity units psu between coast and shelf break and between surface and bottom a spot value of freshwater transport is 0 06 sv 1800 km3 yr 1 which is equivalent to 30 of the arctic freshwater gain the presence of the egcc and its continuity up the east greenland coast as far as denmark strait is confirmed in satellite sea surface temperature images and surface drifter tracks we estimate the sensitivity of its freshwater flux to changes in melt season mean surface air temperature to be 25 per 1 c

early diagenetic greigite as a recorder of the palaeomagnetic signal in miocene pliocene sedimentary rocks of the carpathian foredeep romania summary during the miocene pliocene the carpathian region represented the westernmost part of the so called eastern paratethys a palaeobioprovince that covered central and eastern europe as well as parts of southwest asia previous palaeomagnetic investigations provide a highresolution magnetochronology for the sedimentary sequences of the carpathian foredeep and indicate a marked transition in magnetic carriers from iron oxides to iron sulphides in chron c3r here we demonstrate using detailed rock magnetic investigations and scanning electron microscope sem analyses that the major magnetic iron sulphide mineral is greigite fe3s4 thermomagnetic runs indicate an irreversible decrease in magnetization with increasing temperature up to 400 c and sem observations indicate octahedral grain morphologies and fe s ratios that are indicative of greigite hysteresis loops have rectangular shapes which are typical of single domain behaviour with coercivity and coercivity of remanence at values of bc 35 45 mt and bcr 52 67 mt respectively first order reversal curve diagrams have contours that close around single domain peaks with bc values of 45 90 mt isothermal remanent magnetization component analysis reveals a small dispersion for the greigite component dispersion parameter dp 0 15 log units indicating a narrow grain size distribution a positive fold test inclination shallowing and two positive reversal tests are additional arguments for the syn depositional formation of this greigite we thus argue that most of the greigite was formed under early diagenetic conditions that is within 1000 yr of deposition of the sediment in this setting and that it thus can be considered as a reliable recorder of the palaeomagnetic signal in this situation the appearance of greigite during chron c3r between 6 0 and 5 5 ma in the carpathian foredeep is most likely related to regional tectonic and or climatic events that reshaped the basin configuration and changed the palaeoenvironmental conditions

fossil fruit identification by sem investigations a tool for palaeoenvironmental reconstruction of dmanisi site georgia abstract archaeological excavations and multidisciplinary studies at the site of dmanisi lesser caucasus georgia have provided an assemblage of lithic artefacts and numerous palaeontological and human remains in a volcano sedimentary context dating to the early lower pleistocene the sieving of archaeological sediments from dmanisi also yielded mineralised botanical macro remains that were analysed according to a particular protocol the use of scanning electron microscopy sem allowed the comparison between fossil fruit remains and modern specimens leading to a precise identification of the earlier seed remains recognised by this method belonging to several taxa from the boraginaceae family as well as to the genus celtis l of the ulmaceae family the ecological requirements of these taxa suggest the presence of xeric conditions a result that is in accordance with data obtained by faunal and stratigraphic studies

on the mid pleistocene transition to 100 kyr glacial cycles and the asymmetry between glaciation and deglaciation times 1 a mechanism is proposed for the mid pleistocene transition from a dominant periodicity of 41 kyr to 100 kyr in glacial oscillations the same mechanism is shown to also explain the asymmetry between the long glaciation and short deglaciation phases of each cycle since that transition versus the symmetry of the 41 kyr oscillations prior to the transition these features arise naturally within the framework of the sea ice switch glacial cycle mechanism of gildor and tziperman 2000 as a result of the gradual cooling of the deep ocean during the pleistocene this cooling results in a change of the relation between atmospheric temperature and the rates of accumulation and ablation of continentals ice sheets it is this latter change that leads to the activation of the sea ice switch and therefore to the initiation of the 100 kyr oscillations the gradual glaciation and rapid deglaciations during these oscillations occur because the mean value of the ice sheet ablation is not far from the maximum rate of snow accumulation during warm periods this proximity of mean ablation and maximum accumulation rates is shown to be also a consequence of the mid pleistocene gradual cooling of the deep ocean index terms 3344 meteorology and atmospheric dynamics paleoclimatology 1620 global change climate dynamics 3309 1640 global change remote sensing 4267 oceanography general paleoceanography keywords climate dynamics glacial cycles mid pleistocene transition 100 kyr 41 kyr

the lacustrine deposits of fornaci di ranica late early pleistocene italian pre alps stratigraphy palaeoenvironment and geological evolution an interdisciplinary investigation of the pleistocene clay succession of fornaci di ranica italian pre alps aimed to reconstruct the palaeoenvironmental history and its chronostratigraphic position and to consider the implications for the quaternary evolution of the southern alpine borderland near the early middle pleistocene transition a detailed survey of quaternary deposits in boreholes and exposed sections provided a complete record of the basin the most complete core was analyzed for palynology and magnetic properties plant macrofossils were obtained by flotation pollen and spectrometric analysis allowed a precise stratigraphic placement of a moose antler and braincase kept in museum collections the basin originated from fluviatile obstruction of a tributary valley cut into bedrock the basal deposits formed as a terrestrial hydromorphic soil under a dense tsuga forest zone rnc 1 the overlying palustrine gyttja shows a marked forest withdrawal with a climatic signature zone rnc 3 followed by a re establishment of mixed conifer forests zones rnc 4 6 the occurrences of pollen of cold adapted taxa saxifraga oppositifolia type saxifraga stellaris type larix are the oldest so far known south of the alps and suggest that mean summer temperature was near or even below the thermic tree limit high herb diversity partially represented by tall forbs characterizes this zone a further increase of the water table can be assumed in zones rnc 4 and rnc 5 since pollen of aquatic plants increases the find of larix decidua l cones demonstrates the existence of the european larch in the early pleistocene of the alps previously not identified at the species level after the serio river had reached the maximum quaternary aggradation the lake was rapidly filled up with turbiditic sediments the identification of cervalces latifrons johnson 1874 by azzaroli palaeantogr italica 71 1979 48 was confirmed pollen spectra obtained from clay fragments preserved in the braincase allowed us to constrain the stratigraphic position of these fossil remains in the lower palustrine portion of the sequence pollen and moose palaeoecology corroborate the reconstruction of a boreal landscape the succession of fornaci di ranica is attributed to the late early pleistocene on the basis of the following elements i the occurrence of an acme pollen zone of tsuga with carya and pterocarya ii the low representation of cedrus iii the biochronology of cervalces latifrons iv normal fossil magnetic polarity interpreted as part of the jaramillo subchron on the basis of correlations with other studied sections from the same region and finally v indications from the regional geological evolution the basin deposits spanned the final stage of a temperate period and the subsequent transition to a cold phase during the jaramillo subchron or the cobb cryptochron the basin originated by fluvioglacial aggradation triggered by glaciation in the northern part of the serio river catchement the lake succession may represent an episode of marked increase of polar ice volume related to mis 36 30 or 28 the correlation with the leffe sequence also suggests that cold climate conditions inferred for pollen zone rnc 3 did not occur earlier in the early pleistocene of this region

relationship of late quaternary tectonics and volcanism in the khanarassar active fault zone the armenian upland the syunik rhombus like structure in the khanarassar active dextral fault zone of armenia is a typical pull apart basin formed between terminal parts of two adjacent en echelon fault segments some component of subsidence associated with the faults of the structure is found between the en echelon segments nevertheless the dextral component continues to be predominant even on the boundaries of the pull apart basin the late pleistocene and holocene lava volcanoes of the basin are also associated with those faults that have a component of extension the relative ages of fault displacements and volcanic eruptions have been identified by the mutual correlation of lavas moraines and topographic features and by archaeological and radiocarbon dating according to the interpretation of rupturing and volcanism major earthquakes and volcanic eruptions appear inter related and three pulses of such activity during the earlier and middle holocene have been identified

interannual variations of snow accumulation on the greenland ice sheet 1985 1996 new observations versus model predictions newly measured time series of net water equivalent accumulation from ice cores are reported for 11 sites located near the 2000 m contour of the greenland ice sheet many of these sites are located in regions where accumulation has not been previously measured we compared these new time series of annual accumulation with previously reported modeled precipitation covering the same time range because ice core accumulation records include both regional and local accumulation components we used adjacent ice core records at six multiple core sites to estimate the local component and extrapolated these results to the five single core sites we investigated the impact of this short scale spatial variability in accumulation on statistical comparisons between the observed accumulation and model precipitation although sealers were required to match the 12 year mean modeled precipitation to the mean observed accumulation a high degree of correspondence between observed interannual accumulation and scaled modeled precipitation was found at 7 of 11 locations the need for scaling and the low correspondence between model simulations and observations at some sites clearly indicate that model improvements are needed although very encouraging a more spatially distributed array of ice core accumulation measurements spanning the same time period as the precipitation modeling is necessary for continued model improvement and validation in agreement with earlier studies the large temporal variability in snow accumulation predicted by modeling and confirmed by ice cores indicates that the ice sheet elevation varies by tens of centimeters from year to year simply because of changing accumulation

atmospheric circulation and cyclone frequency variations linked to the primary modes of greenland snow accumulation 1 data from 34 greenland firn cores extending from 1982 to 1996 are used to identify spatial accumulation variability patterns and their associated atmospheric circulation and cyclone frequencies the first principal component representing west central greenland accumulation is correlated to nao variability having increased southwesterly northeasterly flow over that area during high low accumulation winters the flow is linked to a relative increase in cyclone activity on the west central region of the ice sheet during high accumulation periods the second principal component represents accumulation over southeastern greenland where strong westerly flow leads to high accumulation and an increase in lee cyclones on the east and southeast coast the study provides evidence that increased cyclone activity occurs over or immediately adjacent to areas experiencing anomalously high accumulation and it is important to distinguish lee cyclones from icelandic cyclones as they produce opposite precipitation effects over the ice sheet

vegetation changes during the late early pleistocene at montalbano jonico province of matera southern italy based on pollen analysis pollen analysis of the early pleistocene montalbano jonico section in southern italy reveals cyclic changes driven by climate and eustasy as illustrated by mesothermic vs steppe elements for climate and pinus vs caryophyllaceae amaranthaceae chenopodiaceae and ephedra for eustasy these results are directly compared with oxygen isotope data on globigerina bulloides constrained within a biostratigraphic framework based on nannofossils and foraminifers facilitating a new age calibration for the section marine isotopic stages 37 to 23 1 250 0 900 ma are recorded and compared with global and mediterranean oxygen isotope curves high frequency changes in pollen are related to the mediterranean curve globigerinoides ruber from odp site 967 and superimposed the lr04 stack curve during the early pleistocene pollen recorded global and regional climate changes related to obliquity and precession respectively and regional tectonic evolution precession forcing was caused by mediterranean wetness related to precession the intensified precession effect over climatic cycles that is expected during the middle pleistocene transition is not recorded in the montalbano jonico interval a vegetation changes

climate driven fluctuations in freshwater flux to sermilik fjord east greenland during the last 4000 years the freshwater runoff from the glaciated and snow covered sermilik fjord catchment se greenland was estimated at annual resolution for the period 1900 2008 and at decadal resolution for the past four millennia our simulations were forced with available meteorological station data 1900 2008 and greenland ice core estimated temperature data 1899 bc ad 1980 from dye3 and gisp2 time series of estimated ice discharge 2000 2009 for the three major outlet glaciers helheim fenris and midgard indicate that 53 74 of the ice discharge variations could be explained by variations in areally averaged glacier terminus surface supraglacial runoff based on these data and together with calculated subglacial geothermal and frictional melting as well as net precipitation for the fjord area the sermilik fjord freshwater flux was deduced for the period 1900 2008 our simulations indicated that during the last century surface freshwater runoff has equaled 13 of the sermilik fjord average freshwater flux of 33

grain boundary graphite in kapuskasing gneisses and implications for lower crustal conductivity surface electromagnetic measurements commonly reveal that the intermediate and lower continental crust has an appreciable electrical conductivity much higher than that found for laboratory analogues of deep crustal rocks or for upper crustal rocks either formed at shallow depths or uplifted from deeper levels conducting films at grain boundaries are thought to play an important part in enhancing deep crustal conductivity with brines and graphite being the main candidates1 at present however there is a lack of direct evidence for such films frost et al 2 have reported an enhancement in conductivity of igneous lower crustal rocks from the la ramie complex apparently owing to the presence of graphite films but the possible role of brines was not clear from this work here we present a study of the grain surface composition of metamorphic and one igneous rocks exhumed from 20 km depth by the kapuskasing uplift of the canadian shield3 we expect these samples to be representative of metamorphic and igneous rocks of the deep archaean crust auger spectroscopy provides evidence for graphite films at grain boundaries which can account for the present electrical signature of the kapuskasing crust4 6 we also detect traces of chlorine sulphur and iron which suggest that brines and solid conductors other than graphite may have helped to enhance the conductivity but their abundance suggests at best a minor role relative to graphite

assessment of greenland albedo variability from the advanced very high resolution radiometer polar pathfinder data set the advanced very high resolution radiometer polar pathfinder app data set is used to examine the variability of the surface albedo over greenland analysis of the app albedo record from 1981 to 1998 show anomalously low albedo during 1995 and 1998 over most of the ice sheet as compared with the other years the low albedo encountered during these years suggests that the ice sheet experienced considerable melt in 1995 and 1998 particularly near the western margin of the ice sheet conversely anomalously high albedos were found in 1992 as a result of colder temperatures and hence less melt following the eruption of mount pinatubo the relationship between the annual north atlantic oscillation nao index and the mean summer albedo from all the stations reveals a positive correlation of 0 44 and a positive correlation of 0 55 for the southern part of the ice sheet therefore variations in the mean summer albedo over greenland can in part be explained by variations in the nao such that during periods of intensification of the normal mode of the nao the mean summer albedo is above normal trend analysis reveals an overall downward trend in surface albedo from 1981 to 1998 which agrees with recent trends in melt and precipitation however the trend was found not to be statistically significant but rather influenced by the low albedo in recent years

glacial interglacial cycles in arid regions of northern eurasia abstract considering evolution of arid environments in northern eurasia through the glaciation interglacial cycle the author adheres to the opinion as stated by i p gerasimov according to the latter pluvial stages in arid regions correspond to glaciations in the arcto boreal zone while xerothermal stages are synchronous to interglacials there are new paleofloristic evidence obtained in support of this opinion in particular it has been inferred from pollen spectra that during pluvial stages boreal flora including forest species penetrated into the caspian lowland turanian plain and to the black sea coast i e the regions of dry steppes and deserts at present at the xerothermal stages the typical steppe and desert landscapes of arid zone were restored

evaluation of recent precipitation studies for greenland ice sheet the retrieval of an accurate spatial and temporal record of contemporary greenland precipitation is a uniquely challenging task because of the extreme variability in both atmospheric processes and the resulting precipitation distribution over relatively small spatial scales a comparison of precipitation data sets composed of monthly mean values from recent studies shows a convergence on the general features of the long term spatial patterns but substantial disagreement on the temporal variability both regionally and for all of greenland there is general agreement on a long term greenland average of about 35 cm yr 1 and on long term values for regional scales although differences for outlying data sets exceed 50 of the observed glaciological estimate for particular regions a fundamental problem is the inadequate topographic representation of greenland in the numerical analyses nearly all of the data sets are overly dry for high elevation areas as seen from comparisons with glaciological observations from summit the east central region of greenland is found to be particularly susceptible to the temporal discontinuities in data sets which employ operational analyses in contrast there is strong agreement among all methods on the temporal variability for the west central region over a 15 year period from the comparison it is concluded that none of the data sets is able to capture all of the regional scale features in general however the deficiencies of each data set are readily identifiable from comparison and evaluation in the context of circulation features agreement among the methods on particular regions and timescales gives increased confidence in drawing conclusions related to aspects of greenland s precipitation climatology in particular an enhanced precipitation retrieval method is found to be less susceptible to data artifacts than other methods using operational analyses in the north anomalously high precipitation is associated with cyclonic development near the fram strait for west central greenland the close agreement among methods is related to the dominant contribution of the mean circulation

a comparison of quasigeostrophic and nonquasigeostrophic vertical motions for a model simulated rapidly intensifying marine extratropical cyclone abstract large scale departures from quasigeostrophic vertical motions are diagnosed for a model simulation of the qe ii storm 9 11 september 1978 the simulation was performed by the limited area mesoscale prediction system lamps initialized at 1200 utc 9 september 1978 the model cyclone intensified from a central pressure of 1003 mb to 976 mb in 24 h considerably short of the 59 mb 24 h 1 observed deepening but reasonable in comparison to other model simulations of this storm this diagnosis centers on a hydrostatic generalized omega equation which scales to the quasigeostiophic omega equation for small rossby number vertical motions were computed both from this generalized omega equation and the quasigeostrophic omega equation in order to examine the importance of nonquasigeostrophic effects the high correlation of vertical motions from a control experiment using most of the terms in the generalized omega equation with the vertical motions predicted by the model establishes the validity o

exploring seasonal accumulation bias in a west central greenland ice core with observed and reanalyzed data the seasonality of accumulation in west central greenland is investigated to determine whether a summer bias exists in a multi century ice core recovered from crawford point cp such a bias would negatively affect the ice core s potential for reconstructing the history of winter circulation patterns including the north atlantic oscillation an automatic weather station aws installed at the cp site in 1995 records sub daily surface heights and affords a unique opportunity to assess the seasonal distribution of accumulation and test the performance of five gridded reanalysis datasets and a regional climate model simulated accumulation compares remarkably well with in situ measurements from both the aws and cp ice core demonstrating their potential to accurately represent accumulation in this region seasonal accumulation exhibits no summer maximum indicating that any concurrent precipitation maximum is likely offset by melt and or sublimation effects the lack of a strong seasonal accumulation bias implies that the cp ice core is well suited for future investigations of the history of winter circulation patterns

recent greenland accumulation estimated from regional climate model simulations and ice core analysis the accumulation defined as precipitation minus evaporation over greenland has been simulated with the high resolution limited area regional climate model hirham4 applied over an arctic integration domain this simulation is compared with a revised estimate of annual accumulation rate distribution over greenland taking into account information from a new set of ice core analyses based on surface sample collections from the north greenland traverse the region with accumulation rates below 150 mm yr21 in central northwest greenland is much larger than previously assumed and extends about 500 km farther to the south it is demonstrated that good agreement between modeled and observed regional precipitation and accumulation patterns exists particularly concerning the location and the values of very low accumulation in the middle of greenland the accumulation rates in the northern part of greenland are reduced in comparison to previous estimates these minima are connected with a prevailing blocking high over the greenland ice sheet and katabatic wind systems preventing humidity transports to central greenland the model reasonably represents the synoptic situations that lead to precipitation maxima of precipitation and accumulation occur at the southwestern and southeastern coasts of greenland and are connected with cyclonic activity and the main storm tracks around greenland the central region of the greenland ice sheet acts as a blocking barrier on moving weather systems and prohibits cyclones moving from west to east across this region and thus prevents moisture transports

late pliocene northern hemisphere glaciations the continental and marine responses in the central mediterranean abstract detailed pollen analyses and oxygen isotope records of three foraminiferal species globigerina bulloides uvigerina peregrina and cibicides pachyderma from the semaforo and vrica composite sections crotone southern italy have been compared to the global climatic changes depicted by late pliocene early pleistocene foraminiferal 18o records of site 607 in the north atlantic and hole 653a in the tyrrhenian basin west mediterranean major overturns in the mid altitude vegetation are shown near isotopic stages 82 60 58 and 50 at about 2 03 ma 1 6 ma and 1 37 ma according to the raymo et al 1989 and ruddiman et al 1989 timescales at the same dates glacial 18o maxima either became higher or display step increases in the western mediterranean or in the open ocean as well this suggests that size increases of northern hemisphere ice sheets were the driving factor for regional or local marine and continental environmental changes within the mediterranean basin near isotopic stages 62 60 close to the conventional plio pleistocene boundary the climatic conditions severed enough within the mediterranean basin to modify the continental environment as depicted by a sudden increase of artemisia percentages while the first significant southward migration of the north polar front may have been recorded by an influx of left coiling neogloboquadrina pachyderma in the central mediterranean it also appears that boreal guests entered the mediterranean during phases of 18o enrichment of foraminiferal calcite there does not seem to be any discrepancy between the climatic concept of the pliocene pleistocene boundary and its chronostratigraphic definition

calculation and application of clinopyroxene garnet plagioclase quartz geobarometers recently published thermodynamic and experimental data in a variety of chemical systems have been evaluated to derive gibbs free energies for hedenbergite and pyrope these were used to calculate the geobarometric equilibria

the 1958 2009 greenland ice sheet surface melt and the mid tropospheric atmospheric circulation in order to assess the impact of the mid tropospheric circulation over the greenland ice sheet gris on surface melt as simulated by the regional climate model mar an automatic circulation type classification ctc based on 500 hpa geopotential height from reanalyses is developed general circulation correlates significantly with the surface melt anomalies for the summers in the period 1958 2009 the record surface melt events observed during the summers of 2007 2009 are linked to the exceptional persistence of atmospheric circulations favouring warm air advection the ctc emphasizes that summer 500 hpa circulation patterns have changed since the beginning of the 2000s this process is partly responsible for the recent warming observed over the gris

substantial thinning of a major east greenland outlet glacier aircraft laser altimeter surveys in 1993 and 1998 over kangerdlugssuaq glacier in east greenland reveal thinning over the 5 year interim of several meters for all surveyed areas within 70 km of the seaward ice front rising to 50 meters in the final 5 km such rapid thinning is best explained by increased discharge velocities and associated creep thinning most probably caused by enhanced lubrication of the glacier bed the calving ice front over the past decade has occupied approximately the same location as in 1966 velocity estimates for 1995 96 are about the same as those for 1966 and 1988 but significantly less than for 1999 suggesting that major thinning began after 1995

the last 1 35 million years at tenaghi philippon revised chronostratigraphy and long term vegetation trends abstract in addition to being of interest to ancient greek and roman historians the site of philippi ne greece has long been noted in quaternary circles for providing the longest continuous european pollen record spanning the last one million years here the original age model is re evaluated and a new marine terrestrial correlation is proposed an astronomical calibration procedure based on a correspondence between changes in certain vegetation elements and march and june perihelion configurations suggests that the base of the sequence extends back to 1 35 million years ago the revised chronological framework for the tenaghi philippon sequence provides an opportunity to examine the long term behaviour of individual taxa and vegetation trends within the context of global climate changes comparisons reveal a close correspondence between the terrestrial and marine records in terms of orbital and suborbital variability however joint time frequency analysis of the arboreal pollen record shows that the obliquity and eccentricity precession signals persist into the 100 kyr and 41 kyr worlds respectively suggesting the operation of additional climate mechanisms that are independent of high latitude glacial interglacial effects unlike ice core and marine sequences no change in the magnitude of interglacial tree population expansions is observed after the mid brunhes event instead the tenaghi philippon record suggests a major shift in the vegetational composition of interglacials after mis 16 with the establishment of forests of reduced diversity and a modern appearance

new precipitation and accumulation maps for greenland annual total precipitation and the annual accumulation on the greenland ice sheet are evaluated and presented in two maps the maps are based on accumulation measurements of 25 1 pits and cores obtained from the upper accumulation zone and precipitation measurements made at 35 meteorological stations in the coastal region to construct the accumulation map the annual precipitation was split into solid and liquid precipitation components annual total precipitation exceeding 2500 mm w e occurs on the southeastern tip of greenland while the minimum precipitation is estimated to occur on the northeastern slope of the ice sheet the mean annual precipitation for all of greenland is 340 mm w e the largest annual accumulation of about 1500 mm w e is found on the glaciers in the southeastern corner of greenland while the smallest accumulation is found on the northeastern slope of the ice sheet west of danmarkshavn the mean accumulation on the greenland ice sheet is estimated at 310 mm w e the regional difference in accumulation is examined with respect to the 850 hpa m bar level circulation the present surface topography is found to play an important role in determining regional accumulation on the ice sheet

detailed jaramillo field reversals recorded in lake sediments from armenia lower mantle influence on the magnetic field revisited abstract while it is well established that the earth s magnetic field is generated by a self sustaining dynamo that reversed its polarity at irregular intervals in the geological past the very mechanisms causing field reversals remain obscure paleomagnetic reconstructions of polarity transitions have been essential for physically constraining the underlying mechanisms in terms of time scale but thus far remain ambiguous with regard to the transitional field geometry here we present new paleomagnetic records from a rapidly deposited lacustrine sediment sequence with extraordinarily stable paleomagnetic signals which has captured in unprecedented detail the bottom reverse to normal r n and top normal to reverse n r transitions of the jaramillo subchron at 1 072 ma and at 0 988 ma the obtained virtual geomagnetic pole vgp path indicates an oscillatory transitional field behavior with four abrupt transequatorial precursory jumps across the pacific the distribution of vgp positions indicates regions of preferred occurrence our results are in agreement with previously proposed bands of transitional vgp occurrence over the americas and australia northwest pacific additionally our vgp positions seem to avoid large low shear velocity provinces llsvps above the core mantle boundary cmb thus our data supports the idea that the transitional field geometry is controlled by heat flux heterogeneities at the cmb linked to llsvps

atmospheric circulation variability associated with shallow core seasonal isotopic extremes near summit greenland seasonal back diffused 18o time series reconstructed for nine shallow firn cores from the greenland summit for 1959 1987 are evaluated in terms of 1 their spatial and temporal variability and 2 their association to the atmospheric circulation rotated principal component analysis evaluates spatial and temporal patterns of organization in the back diffused 18o ice core time series mean sea level pressure and 500 hpa height fields are obtained for winter and summer seasons that fall in the isotopically warmest and coldest thirds of the seasonal data the winter back diffused 18o data indicate that some degree of longitudinal separation takes place between isotopic records from western and eastern greenland in agreement with coastal station climatic data temporal variability is linked with statistical significance to the variability of the atmospheric circulation over the denmark strait as well as over the norwegian and barents seas the north atlantic oscillation nao and the mean icelandic low in the denmark strait affect isotopic variability over the cores west of the ice divide just as they have been shown to prominently affect west coast air temperature records isotopic variability at some ice cores east of the divide is influenced by pressure variability over the norwegian and barents seas although statistical significance is lower the nao appears insignificant in summer isotopic variability as the circulation in that season is very much localized and dominated by either ridging warm cases or troughs cold cases over eastern greenland and the arctic ocean results suggest that long term winter 18o variability can potentially be linked to climate variation over europe especially from the mediterranean basin northward to about 55 n and as far east as central siberia