the corresponding tropospheric environments during downward extending and nondownward extending events of stratospheric northern annular mode anomalies abstractusing the ncep ncar reanalysis dataset this study classifies stratospheric northern annular mode nam anomalies during the negative or positive phase into two categories anomalies extendi

downward coupling between the stratosphere and troposphere the relative roles of wave and zonal mean processes abstract wave and zonal mean features of the downward dynamic coupling between the stratosphere and troposphere are compared by applying a time lagged singular value decomposition analysis to northern hemisphere height fields decomposed into zonal mean and its deviations it is found that both zonal and wave components contribute to the downward interaction with zonal wave 1 due to reflection dominating on the short time scale up to 12 days and the zonal mean due to wave mean flow interaction dominating on the longer time scale it is further shown that the two processes dominate during different years depending on the state of the stratosphere winters characterized by a basic state that is reflective for wave 1 show a strong relationship between stratospheric and tropospheric wave 1 fields when the stratosphere is leading and show no significant correlations in the zonal mean fields on the other hand winters characterized by a stratospheric state that does not reflect waves show a strong relat

a full glacial biota from southeastern iowa usa wisconsinan full glacial silts filling a swale exposed in conklin quarry johnson co iowa contain a large and diverse biota that includes pollen bryophytes vascular plant macrofossils small mammals molluscs and insects radiocarbon dates on wood from the top middle and bottom of the swale fill respectively were 16710 270 17 170 205 and 18090 190 yr bp the pollen diagram is dominated by picea spruce pinus pine and cyperaceae sedge and it records low pollen accumulation rates plant macrofossils include a number of tundra species along with picea and larix larch needles and small pieces of wood the insect fauna contains many species now confined to the forest tundra transition zone of northwestern yukon and alaska small mammals include the tundra indicators dicrostonyx collared lemming and probably microtus miurus singing vole together with boreal forest taxa the molluscs include extinct and relict species and show the widest range in present geographic distribution but rocky mountain and especially northern elements predominate in the swale fill all these lines of evidence lead to consistent palaeoclimato logical interpretation and palaeoecological reconstruction the dominant habitats represented by the biota and sedimentary environment collectively included open calcareous silty to sandy or gravelly upland sites minerotrophic fens wetlands pond or stream side clayey to sandy shores and shallow possibly ephemeral cold clear water ponds mean july temperatures were probably 11 to 13 c cooler than at present the biota indicates that a picea larix krummholz with extensive tundra openings was present in southeastern iowa between 18090 and 16710 yr bp

zonal mean dynamics of extended recoveries from stratospheric sudden warmings abstractthe recovery of the arctic polar vortex following stratospheric sudden warmings is found to take upward of 3 months in a particular subset of cases termed here polar night jet oscillation pjo events the anomalous zonal mean circulation above the pole during this recovery is characterized by a persistently warm lower stratosphere and above this a cold midstratosphere and anomalously high stratopause which descends as the event unfolds composites of these events in the canadian middle atmosphere model show the persistence of the lower stratospheric anomaly is a result of strongly suppressed wave driving and weak radiative cooling at these heights the upper stratospheric and lower mesospheric anomalies are driven immediately following the warming by anomalous planetary scale eddies following which anomalous parameterized nonorographic and orographic gravity waves play an important role these details are found to be robust for pjo events as opposed to sudden warmings in general in that ma

the selection of sites for paleovegetational studies the judicious selection of sites for paleovegetational and paleoclimatic studies permits paleoecologists to answer specific research questions that go beyond primary descriptions of past vegetation we present a model that describes the relationship between basin size and pollen source area and predicts the proportions of local extralocal and regional pollen sampled by lake basins of different size the distinctive sampling properties of lakes peats and small hollows can be exploited to provide details of pattern in paleovegetation so long as attention is given to the limitations and problems of these types of sites combinations of site types in a single study most fully exploit the information contained in sediments

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

a reconstruction of moorhead and emerson phase environments along the eastern margin of glacial lake agassiz rainy river basin northwestern ontario mapping of quaternary geology in the rainy river lowland northwestern ontario resulted in discovery of several fossil bearing localities organic remains are associated with both the moorhead and

quaternary forest associations in lowland tropical west africa terrestrial fossil pollen records are frequently used to reveal the response of vegetation to changes in both regional and global climate here we present a fossil pollen record from sediment cores extracted from lake bosumtwi west africa this record covers the last c 520 thousand years ka and represents the longest terrestrial pollen record from africa published to date the fossil pollen assemblages reveal dynamic vegetation change which can be broadly characterized as indicative of shifts between savannah and forest savannah formations are heavily dominated by grass poaceae pollen 55 typically associated with cyperaceae chenopodiaceae amaranthaceae and caryophyllaceae forest formations are palynologically more diverse than the savannah with the key taxa occurring in multiple forest zones being moraceae celtis uapaca macaranga and trema the fossil pollen data indicate that over the last c 520 ka the vegetation of lowland tropical west africa has mainly been savannah however six periods of forest expansion are evident which most likely correspond to global interglacial periods a comparison of the forest assemblage composition within each interglacial suggests that the holocene 11 0 ka forest occurred under the wettest climate while the forest which occurred at the time of marine isotope stage 7 probably occurred under the driest climate

a multi proxy geochemical investigation of the early paleocene danian continental palaeoclimate at the fontllonga 3 site south central pyrenees spain chronologically well constrained non marine deposits across the cretaceous tertiary boundary ktb are exceptionally rare the fontllonga section tremp formation south central pyrenees lleida spain constitutes one of these rare global records stable isotope 18oco3 and 13c analyses have been performed on the carbonate fraction of 29 samples from diverse skeletal micro remains charophyte gyrogonites gastropod shells ostracod valves and isolated skeletal remains of lepisosteids and pycnodonts from the earliest danian site fontllonga 3 a mean ba ca water palaeotemperature of 28 0 6 7 c has been obtained from the ganoine of 25 lepisosteid scales this mean palaeotemperature is comparable with the temperature tolerance range for extant relatives of fossil osteoglossiform fish found at fontllonga 3 which require a temperature range of 24 35 c mean annual temperature 27 30 c to survive using the temperature range provided by the ba ca palaeothermometer 21 3 34 7 c it is possible to determine 18owater values from the isotopic content of charophyte gyrogonites gastropod shells ostracod valves and fish remains mean 18oco3 5 00 0 21 18owater values of between 4 01 and 0 95 vsmow are calculated which when combined with la yb n versus la sm n plots are in good agreement with the sedimentary interpretation of the site as an estuarine environment based upon a comparison with modern day meteorical conditions these isotopic values are relatively high for subtropical freshwaters suggesting a low precipitation rate amount effect high evaporation rate and or long residence time when combined with other isotopic palaeobotanical and mineralogical studies carried out in the pyrenean and tethys realms this first geochemical study of an early paleocene site is consistent with there being a subtropical seasonally dry climate in the south central pyrenees at this time

re envisioning the structure of last glacial vegetation in new zealand using beetle fossils a series of 18 fossil beetle assemblages are used to reconstruct the paleoenvironment of the northwest west coast new zealand over the period of the last interstadial stadial transition ca 37 000 21 300 cal yr bp the samples were recovered from an in filled hollow within a dune field ca 9 km south west of westport 41 47 s 171 30 e this fossil beetle reconstruction is compared to an existing palynological reconstruction from the same site the beetle assemblages indicate an environment of marshy shrubland interspersed with closed canopy coastal vegetation prior to glacial onset and a mosaic of closed canopy patches and open tussock grassland during full glacial conditions these interpretations contrast with the palynologically based interpretation which indicates subalpine shrubland prior to glacial onset and widespread grassland with little woody vegetation during the period of maximum glacial cooling this study is consistent with other non pollen studies in new zealand and indicates that the palynological interpretation of the paleoenvironment of the westport region downplays the importance of closed canopy vegetation in the area during the transition from interstadial to full glacial stadial conditions it challenges the interpretation of open vegetation at low elevations during glacial periods from pollen studies copyright 2007 university of washington published by elsevier inc

the variability of holocene climate change evidence from varved lake sediments varved sediments from a lake near the present forest prairie border in northwestern minnesota provide an annual record of climate change for the last 10 400 years climate sensitive mineral chemical and biological components show that the mid holocene dry interval between 8500 and 4000 years ago is asymmetrical and actually consists of two distinct drier pulses separated by a moister interval that lasted about 600 years cyclic fluctuations with periods of several hundred years were abrupt and persistent throughout the holocene and are most clearly recorded within the two drier pulses

the origin of fluoride rich groundwater in mizunami area japan mineralogy and geochemistry implications abstract the aim of this paper was to explore new factors that might be reasons for the occurrence of fluoride rich groundwater in the area around a construction site during the construction of two deep shafts of the mizunami underground research laboratory miu in mizunami city central japan a large quantity of groundwater with high fluoride concentration was charged into the shafts chemical investigation carried out during the excavation revealed that fluoride concentrations in the area around the miu site greatly exceeded those prescribed by japanese standards therefore the origin of fluoride ion was experimentally investigated samples were collected from the core of a deep borehole drilled in the study area the weathering and alteration levels of the collected granites varied greatly granitic powders were used to measure fluoride content in the granitic rock mass the fluoride content ranged between 200 and 1300 mg kg the powders were reacted with purified water for 80 days the results of water rock interaction showed granitic rock to be one of the main sources of fluoride rich groundwater in mizunami area fluoride concentrations in these solutions that were shaken for 80 days varied between 2 and 7 mg l this change may have occurred as a result of the spatial distribution of fluoride ions in the granite mass as evidenced by mineralogical analysis of fluoride content in several specimens x ray powder diffraction analysis of the rock before and after the water rock interaction tests manifested that the presence of fluorite mineral was relatively small compared to other minerals the degree of weathering and alteration might be an additional factor causing dissolution of fluoride rich minerals however it was difficult to interpret the change in fluorite composition by x ray diffraction analysis

gravity wave induced anomalous potential vorticity gradient generating planetary waves in the winter mesosphere abstractthis study shows that gravity wave gw forcing gwf plays a crucial role in the barotropic baroclinic instability that is frequently observed in the mesosphere and considered an origin of planetary waves pws such as quasi 2 day and quasi 4 day waves simulation data from a gw resolving general circulation model were analyzed focusing on the winter northern hemisphere where pws are active the unstable field is characterized by a significant potential vorticity pv maximum with an anomalous latitudinal gradient at higher latitudes that suddenly appears in the midlatitudes of the upper mesosphere this pv maximum is attributed to an enhanced static stability that develops through the following two processes 1 strong pws from the troposphere break in the middle stratosphere causing a poleward and downward shift of the westerly jet to higher latitudes and 2 strong gwf located above the jet simultaneously shifts and forms an upwelling in the midlatitudes causing a significant increase in

stratospheric control of planetary waves the effects of imposing at various altitudes in the stratosphere zonally symmetric circulation anomalies associated with a stratospheric sudden warming are investigated in a mechanistic circulation model a shift of the tropospheric jet is found even when the anomalies are imposed only above 2 hpa their influence is communicated downwards through the planetary wave field via three distinct mechanisms first a significant fraction of the amplification of the upward fluxes of wave activity prior to the central date of the warming is due to the coupled evolution of the stratospheric zonal mean state and the wave field throughout the column second a downward propagating region of localized wave mean flow interaction is active around the central date but does not penetrate the tropopause third there is deep vertically synchronous suppression of upward fluxes following the central date the magnitude of this suppression correlates with that of the tropospheric jet shift

the relation of a coastal environment to early diagenetic clinoptilolite zeolite formation new data from the late cretaceous european basin abstract clinoptilolite an authigenic mineral of the zeolite group is commonly considered as a product of rhyolitic volcanic glass transformation during diagenesis of carbonate pelagic hemipelagic sediments of cretaceous paleogene age another subordinate way of clinoptilolite formation that has been suggested in the literature is its precipitation during diagenetic transformation of carbonate sediments enriched with biogenic silica the observations concerning transformation of the latter into zeolite are scarce and mostly based on cretaceous pelagic hemipelagic and shallow marine deposits and post cretaceous sediments in which there was no volcanic material the mechanism of diagenetic clinoptilolite formation in volcanic free sediments as well as the role of the depositional setting in its precipitation is not well understood in carbonates of the nw part of the european basin west side of the ysogory dobrogea archipelago studied here the clinoptilolite is associated with opal ct from the dissolution of sponge spicules and a detrital clays are documented for the first time in a cretaceous coastal environment the carbonates were deposited in a coastal environment which was under the influence of weak currents delivering sponge spicules biogenic opal from the offshore zone and the terrestrial input was transported by rivers from a neighboring island the lush plant vegetation with numerous pteridophytes and conifers within a warm sub tropical or tropical and humid climate enhanced the terrestrial weathering of clays and feldspars this unique combination of elevated silica concentrations from sponge spicules dissolution and aluminum availability from terrestrial weathering of feldspars in a subtropical climate during the early diagenesis combined with alkalinity triggered by organic matter decomposition enhanced the clinoptilolite formation a few centimeters below the seabed the investigation demonstrates a novel route by which pore fluids enriched with silica and aluminum initiate clinoptilolite formation during the very early stage of diagenesis a few centimeters below the seafloor the clinoptilolite distribution in late cretaceous silica rich deposits with no volcanic input of the european basin is always associated with opal ct from sponge spicules and elevated terrestrial input clays taking into account the distinctive campanian maastrichtian sedimentation in the epicontinental european basin composed almost exclusively of pure pelagic carbonates the depositional settings in which the silica and aluminum were available in pore waters was restricted to the part of the basin influenced by terrestrial input this leads to the conclusion that clinoptilolite formation in volcanic free sediment is an indicator of not only enhanced sponge silica availability but also the close proximity of the source area

role of the quasi biennial oscillation in the downward extension of stratospheric northern annular mode anomalies using the jra 55 reanalysis datasets and radiosonde observations the impact of the quasi biennial oscillation qbo on the downward extension of stratospheric northern annular mode nam signals in its positive and negative phases positive and negative nam hereafter is examined the results show that the average number of days per month on which stratospheric negative nam signals extend downward into the troposphere is more than twice as large during the easterly phase of the qbo eqbo as those during the westerly phase of the qbo wqbo the increasing likelihood of downward extension of stratospheric negative nam signals during the eqbo is related to three factors enhanced upward wave 1 fluxes entering the stratosphere anomalous poleward wave fluxes below 100 hpa and eqbo induced residual circulation it is also revealed that the eqbo induced subtropical tropospheric easterly anomalies lead to positive height anomalies over the subtropical north atlantic which are amplified by transient eddies and maintained by convection these subtropical positive height anomalies further stimulate an anomalous wave train forcing subpolar positive height anomalies over the euro atlantic sector and enhancing wave 1 over the pacific the eqbo could also induce positive height anomalies in the tropical troposphere and these anomalies are related to convection and vertical motion the positive height anomalies can induce anomalous poleward propagating waves forcing negative height anomalies over the north pacific at mid high latitudes and the enhancing wave 1 fewer stratospheric positive nam signals extend downward into the troposphere during the eqbo than during the wqbo with mechanisms similar to those of negative nam

late wisconsin vegetational and climatic history at kylen lake northeastern minnesota abstract kylen lake located within the toimi drumlin field is critically positioned in relation to late wisconsin glacial advances for it lies between the areas covered by the superior and st louis glacial lobes between 12 000 and 16 000 yr b p the pollen and plant macrofossil record suggests the presence of open species rich tundra barrens from 13 600 to 15 850 yr b p small changes in percentages of artemisia pollen between 14 300 and 13 600 yr b p appear to be artifacts of pollen percentage data shrub tundra with dwarf birch willow and rhododendron lapponicum developed between 13 600 and 12 000 yr b p black and white spruce and tamarack then expanded to form a vegetation not dissimilar to that of the modern forest tundra ecotone of northern canada at 10 700 b p spruce and jack pine increased to form a mosaic dominated by jack pine and white spruce on dry sites and black spruce tamarack and deciduous trees such as elm and ash on moist fertile sites at 9250 yr b p red pine and paper birch became dominant to form a vegetation that may have resembled the dry northern forests of wisconsin today the diagram terminates at 8410 85 yr b p climatic interpretation of this vegetational succession suggests a progressive increase in temperature since 14 300 yr b p this unidirectional trend in climate contrasts with the glacial history of the area hypotheses are presented to explain this lack of correspondence between pollen stratigraphy and glacial history the preferred hypothesis is that the ice margin fluctuations were controlled primarily by changes in winter snow accumulation in the source area of the glacier whereas the vegetation and hence the pollen stratigraphy were controlled by climatic changes in front of the ice margin

analysis of the geochemical variability in lepisosteid scales from the fontllonga 3 site early danian tremp formation south central pyrenees spain implications for palaeoenvironmental studies rare earth element ree ba ca sr ca and 18opo4 analyses have been performed on the ganoine and isopedine of different types of isolated scales anterior middle posterior flank scales and dorsal body margin scales from juvenile lepisosteids from the fontllonga 3 site early danian tremp formation south central pyrenees spain with the aim of detecting the most suitable kind of scale to be used in palaeoclimate studies the ree flat shape patterns obtained in lepisosteid scales from fontllonga 3 are indicative of the absence of late stage diagenesis and recrystallization and have confirmed the identification of the palaeoenvironment where the fontllonga 3 lepisosteids inhabited to be that of an estuary the ba ca palaeothermometer shows that posterior flank scales record on average 4 52 c ganoine and 3 49 c isopedine higher temperatures when compared to middle flank scales which may be related to the fact that posterior flank scales grow preferentially during the warm season whilst middle flank scales which have the greatest number of layers of ganoine per unit of time and grow all year round record a greater amplitude with respect to palaeoenvironmental and palaeoclimatic variations temperature values obtained from anterior flank scales follow a pattern similar to that showed by middle flank scales whilst temperature values provided by dorsal scales resemble the pattern furnished by posterior flank scales the same relationship between scale position and temperature but to a lesser degree 1 48 c is also evident in the calculated 18opo4 temperatures the ba ca palaeothermometer was applied by considering ba ca ratios of the water for different types of environments and it has been found out that a ratio similar to that of marine waters yielded the best approximation to 18opo4 temperatures 29 82 3 76 c the mean ba ca temperature value obtained from the analysis of all the ganoine samples 26 96 5 72 c is also consistent with the temperature of the water in which extant relatives of osteoglossiform fish whose remains have been found in fontllonga 3 along with lepisosteid remains inhabit nowadays 24 40 c with mean values of 27 to 32 c the mean ba ca temperature values furnished by the isopedine are lower than that obtained on the ganoine which may be due to minor diagenetic alteration on account of these results it is recommended that a distinction should be made between different types of scales as this could provide information concerning the summer growth temperature posterior flank scales as well as the annual temperature range middle flank scales furthermore it is recommended that ganoine be used in all studies as it appears to be the most resistant tissue in lepisosteid scales to diagenetic alteration

holocene vegetation climate and history of a raised bog complex northern new zealand based on palynology plant macrofossils and tephrochronology a holocene history of vegetation climate and ombrogenous mire development is presented from pollen and plant macrofossil analyses of sediments at kopouatai bog a large raised restiad bog in northern new zealand tephra layers of established ages supplemented by numerous radiocarbon dates provide a secure chronology the earliest peats overlying last glacial sediments and dated at c 11700 radiocarbon years bp with extensive accumulation after c 10360 bp are dominated by pollen of warm temperate podocarp angiosperm forest indicating a moist mild early holocene climate the bog began as a series of small soligenous mires within lowland podocarp dominated swamp forest but was mostly oligotrophic by c 8500 bp peat accumulation rates have varied spatially and temporally averaging 0 9 mm yr 1 in central and southern areas the deposition of deltaic muds in the northern part of the bog accompanied a marine transgression c 6500 5000 bp while elsewhere an associated groundwater table rise result

last glacial pollen climate reconstructions from northland new zealand despite wide ranging interest in the vegetation and climate of northland new zealand during the last glacial cycle the region and timeframe lack quantitative climate reconstructions while land based pollen records have tended to be poorly dated and fragmentary the region is also important for geochronology due to the co occurrence of the rotoehu tephra a widely dispersed isochron near the current limits of radiocarbon dating and extensive subfossil wood remains of agathis australis with strong dendrochronological and dendroclimatological potential we present new pollen records and temperature reconstructions from three sites set in coastal dune belts from western mid northland 35 s all containing rotoehu tephra that collectively span the last 70 ka the phases and amplitude of temperature changes broadly align with those reported from elsewhere in new zealand and with marine isotope climate stratigraphic records including maximum temperature depression of 6 8 c during the last glacial maximum we argue that these climatic patterns are intimately linked to shifts in the southern westerly wind belt the northern margins of which extend to the region today correspondence between the northland temperature shifts and atmospheric co2 supports the model of ocean atmosphere co2 flux modulated by latitudinal migration of the southern westerlies copyright 2017 john wiley sons ltd

vegetation and climate in southern hemisphere mid latitudes since 210 ka new insights from marine and terrestrial pollen records from new zealand abstract paleo vegetation records developed from marine sedimentary sequences offer considerable potential for examining changes in terrestrial climate beyond the range of 14 c dating because they can be independently dated by 18 o stratigraphy here we present the first pollen record of vegetation from a marine core site in the tasman sea tan0513 14 42 18 s 169 53 e 110 km west of new zealand s south island an independent chronology provided by correlating the globigerina bulloides 18 o record at tan0513 14 to a global isotope stack shows that the record extends back to 210 ka glacial to interglacial changes in palynomorph content are characterised by shrub and podocarp broadleaf forest taxa respectively and are correlated with similar changes in the ca 150 kyr long terrestrial pollen record from okarito pakihi bog 110 km to the south southeast both records are placed on the same timescale by matching variations in dacrydium cupressinum and fuscospora between sites with a unique tie point provided by the ca 25 4 ka kawakawa tephra our southern hemisphere mid latitude vegetation records show forest extent is greatest during periods of low ice volume high mean annual sea surface temperature masst and anti phased with local insolation intensity however there are several features not attributable to changes in mean annual temperature first a fundamental change in forest composition occurred at termination ii tii with a loss of southern beech nothofagus from the study area second the amplitude of masst change through mis 5 is not reflected in corresponding changes in forest extent suggesting other feature s of regional climate seasonality frostiness ice cover exert important controls over vegetation patterns at these latitudes

characterizing stratospheric polar vortex variability with computer vision techniques computer vision techniques are used to characterize the arctic stratospheric polar vortex in 38 years of reanalysis data such techniques are typically applied to analyses of digital images but they represent powerful tools that are more widely applicable basic techniques and considerations for geophysical applications are outlined herein segmentation descriptive and tracking algorithms are combined in the characterization and analysis of vortex evolution using algorithms for region tracking cave art package which was developed to comprehensively describe dynamical and geometrical evolution of polar vortices cave art can characterize and track multiple vortex regions through time providing an extensive suite of region moments and edge diagnostics for each cave art is valuable for identifying vortex splitting events including but not limited to previously cataloged vortex split sudden stratospheric warmings an algorithm for identifying such events detects 52 potential events between 1980 2017 of these 38 are subjectively classified as distinct split like events the algorithm based on cave art is also compared with moments based methods previously used to detect split events furthermore vortex edge averaged windspeeds from cave art are used to define extreme weak and strong polar vortex events over multiple vertical levels this allows characterization of their occurrence frequencies and extents in time and altitude weak and strong events show distinct signatures in cave art diagnostics in contrast to weak events strong vortices are more cylindrical and pole centered and less filamented than the climatological state these results from cave art exemplify the value of computer vision techniques for analysis of geophysical phenomena

postglacial palaeoecology of the subalpine forest grassland ecotone of southwestern alberta new insights on vegetation and climate change in the canadian rocky mountains and adjacent foothills postglacial vegetation change at the subalpine forest grassland ecotone in the foothills of southwestern alberta is reconstructed from fossil pollen plant macrofossils and fossil charcoal the fossils were obtained from the sediments of a small lake chronological control for the record is provided by tephra analysis and the 14c dating of terrestrial plant macrofossils the fossil record is compared with the results from similar studies at sites in the rocky mountains and foothills of alberta and british columbia the comparison of vegetation change at the upper and lower elevational limits of the subalpine forest provides a record of changes in temperature and aridity over the holocene at 10 000 yr b p the study site supported a shrub and herb dominated vegetation picea pinus abies forests were present at mid to high elevations in the mountains and in the northern foothills by this time the climate in the southern foothills was likely arid but not severely cold a relatively open picea and pinus forest was established in the study area between 9400 yr b p and 8000 yr b p fire activity in the region was at a postglacial maximum during this period the transition to forest suggests moister conditions by 8000 yr b p the importance of members of the chenopodiaceae amaranthaceae and typha latifolia increased suggesting an onset of arid conditions characterised by low and fluctuating water levels in lakes between 8000 yr b p and 5000 yr b p the picea and pinus contorta forest at the study site was largely replaced by grassland and pinus flexilis at high elevation sites treeline was located above its modern position during this period little vegetation change is recorded at sites in the northern foothills and at mid elevations at this time the vegetation change in the southern foothills and at high elevations suggests both an elevational and latitudinal displacement of vegetation zones during the mid holocene warm and arid conditions were prevalent in southwestern alberta picea glauca pinus contorta populus tremuloides forest has occupied the site since 5000 yr b p when cooler and moister conditions were established

the late quaternary environmental history of batorliget n e hungary abstract a sedimentary sequence extending back into the last glacial has been obtained from batorliget marsh in n e hungary reconstruction of the environmental history of the region using the techniques of pollen analysis molluscan analysis and geochemistry has revealed an important late quaternary refugium during the last glacial a refugium for temperate flora and fauna existed within a landscape dominated by coniferous forest predominantly made up of pinus and picea the lateglacial postglacial transition at 10 000 yr b p resulted in a dramatic shift from coniferous but also including betula woodland to deciduous woodland following the lateglacial postglacial transition a highly diverse woodland became established in the early postglacial accompanied by an equally diverse molluscan assemblage this diversity remained throughout the early postglacial although the types present within the woodland changed a number of times at c 7000 yr b p anthropogenic disturbance resulted in the destruction of the mixed forest and the development of agricultural land the importance of this region as a refugial area both in the lateglacial and early postglacial is discussed and the influence that it had on the postglacial development of the fauna and flora of northeastern hungary is reviewed

fluoride contamination of groundwater in parts of eastern india and a preliminary experimental study of fluoride adsorption by natural haematite iron ore and synthetic magnetite incidence of high fluoride f in groundwater 1 5 mg l in two tribal belts of eastern india one around chukru in the palamau district of jharkhand and the other around karlakot in the nuapada district of odisha has been studied the maximum concentration of f in groundwater from dug wells and tube wells is 10 30 mg l in chukru and 4 62 mg l in karlakot the groundwaters are mildly alkaline with ph ranges of 7 52 8 22 and 7 33 8 20 in chukru and karlakot respectively the f concentration is positively correlated with ph electrical conductivity and so4 2 in both areas the high f in groundwater resulted mainly from dissolution of biotite and fluorapatite in quartzofeldspathic gneiss the ionic dominance pattern in meq l is mostly in the order ca2 na mg2 k among cations and hco3 so4 2 f among anions in the karlakot groundwater preliminary adsorption experiments were conducted on natural haematite iron ore and synthetic magnetite to evaluate their potential for f removal from water effects of different parameters such as contact time ph adsorbent dose and initial f concentration on the adsorption capacity of these materials were investigated strong dependence of f removal on ph was observed for both the adsorbents with natural haematite iron ore the maximum f removal of 66 occurred at an initial ph of 3 2 for a solution with f concentration of 3 mg l adsorbent dose of 7 g l and overnight contact time the haematite iron ore was observed to increase the ph of the f solution adsorption equilibrium was not achieved with this adsorbent even after a contact time of 45 2 h in the case of synthetic magnetite 84 f removal was achieved after 2 min of contact time for a solution with f concentration of 6 mg l adsorbent dose of 10 g l and initial ph of 7 the results indicate high potential of both natural haematite iron ore and synthetic magnetite as adsorbents of f in water

us gulf coast vegetation dynamics during the latest palaeocene abstract pollen and spore floras from the bear creek section in western alabama us gulf coast record vegetation events from the lower to middle tuscahoma formation late palaeocene mid np9 sporomorphs are abundant and well preserved in these sediments and are used as a proxy to record vegetation change over time we present results from both palynofloral and clay mineral analyses in the interval approximately 0 4 0 1 my before the paleocene eocene thermal maximum petm a period of transient and intense global warming that had a profound effect on animal and plant groups in high latitudes an important factor that has a significant bearing on our understanding of turnover across the petm is that of climate environmental stability prior to the petm in terrestrial ecosystems palynological analysis with a between sample resolution of 4 10 5 yr clay mineral suites show the dominance of smectite and illite throughout the studied section with minor fluctuations in the abundance of kaolinite ranging from 2 to 10 that indicates a high seasonality of precipitation throughout our studied section the exact stratigraphic position of the petm is unknown on the us gulf coast but data from existing publications suggests there is little change in the vegetation type across the palaeocene eocene boundary with no major immigration or turnover events dinocysts are restricted in both diversity and occurrence but apectodinium homomorphum is present with 30 abundance throughout the studied section and provides some evidence that the apectodinium acme is not correlative with the petm at middle latitudes

prehistoric and colonial land use in the chihuahuan desert as inferred from pollen and sedimentary data from coahuila mexico abstract pollen along with context sedimentary data of two desert bottom sites in south coahuila mexico reconstruct holocene environment in the chihuahuan desert in relation to possible human influence on vegetation during the holocene examined pollen sites here derive from the margins and bottoms of the playa lake of the laguna mayran lm first at the reported site of cuota 4 lm4 archaeologically dated deposits of the initial spanish colonial period here are correlated with a xeric environment followed by an early modern mesic period of increased rainfall with wetland plants second at the reported site of coahuila highway 30 ch30 unconformable discontinuous deposits with intermittent representation of early middle and late holocene sedimentation are analyzed showing periodic changes in hydrology at ch30 possible cultivation based on cucurbitaceae pollen occurs in a defined wet phase dating to circa 1500 bp finally origins of pollen taphonomy at ch30 are defined by analog samples from the chihuahuan desert zone in the menchacas basin near cuatro cienegas are analyzed the pilot pollen analog study is based on inferred pollen recruitment mechanics in different sediments as well as moss pollsters in the menchacas basin in the chihuahuan desert in middle coahuila

impact of parametrized nonorographic gravity wave drag on stratosphere troposphere coupling in the northern and southern hemispheres the impact of parametrized nonorographic gravity wave drag nogwd on the stratosphere troposphere dynamical coupling in atmospheric models is relatively unexplored using the european centre for medium range weather forecasts integrated forecast system we find that changes in nogwd strength have a substantial impact on the tropospheric eddy driven jet edj in both hemispheres but the sense of the impact is opposite in the two hemispheres in the northern hemisphere the impact occurs via changes in the amplitude and persistence of stratospheric anomalies in the southern hemisphere sh it occurs instead via differences in the sensitivity of the edj to a given stratospheric anomaly arising from changes in the seasonal cycle leading up to the polar vortex breakdown increasing nogwd eliminates the springtime phase of the sh tropospheric semiannual oscillation sao resulting in a more equatorward annual mean edj and showing that the sao cannot be explained entirely from tropospheric mechanisms

variability of the polar night jet in the northern and southern hemispheres the spatial and temporal characteristics of the month to month variability of the polar night jet and its relationship with tropospheric circulation is investigated for both the northern and southern hemispheres the variabilities of the hemispheres have many common characteristics of the polar night jet oscillation pjo these common characteristics include the following 1 the anomalous zonal mean zonal winds shift poleward and downward 2 the anomalous polar temperatures propagate downward from the stratopause to the upper troposphere and 3 they are made through a wave mean flow interaction with mainly the planetary wave of zonal wave number one annular modes associated with the pjos appear in both hemispheres when the zones of maximum polar temperature anomaly descend to the lowermost stratosphere and upper troposphere the major difference in the pjos of the two hemispheres is found in their temporal characteristics in the southern hemisphere the phase of the pjo is closely locked to the annual cycle while in the northern hemisphere it exhibits quasiperiodic variability with its envelope controlled by the annual cycle the origin of the differences between the pjos is discussed based on the theory of the wave mean flow interaction

understanding the variation of stratosphere troposphere coupling during stratospheric northern annular mode events from a mass circulation perspective we revisit the various stratosphere troposphere coupling relation from the perspective of the meridional mass circulation we constructed 10 hpa northern annular mode nam phase composites to show the typical spatiotemporal evolution of circulation anomalies during the nam s life cycle our results indicate that there is large case to case difference in the temporal evolution and vertical profile of polar temperature anomalies during nam events which shows no strong dependence on the intensity and duration of nam events but agrees well with the variations of the three branches of mass circulation at 60 n the stratospheric poleward warm air branch st the poleward warm air branch in the upper troposphere wb and the equatorward cold air branch in the lower troposphere cb such correspondence is due to the dynamic heating and cooling anomalies associated with the redistribution of air masses by the anomalous meridional mass circulation in different isentropic layers the various relationship among the three mass circulation branches is attributed to anomalous wave activities the amplitude and westward tilt of waves are always stronger weaker throughout the stratosphere before after the peak time of negative nam events leading to a stronger weaker st before after the peak time variations in wb and cb are mostly dependent on wave variabilities in the mid to lower troposphere leading to variations in the timing of in or out of phase coupling of the st with the wb and cb and thus various thermostructure during nam events at a later stage of the negative nam events when the polar temperature becomes colder and the polar jet recovers the weakened baroclinic instability in the lower stratosphere provides favorable conditions for the strengthening of the wb and cb if wave activities strengthen in the troposphere during that period

the lincolnshire limestone hydrogeochemical evolution over a ten year period abstract in the lincolnshire jurassic limestone of britain a sequence of hydrogeochemical processes along a 28 km flow line was defined in 1969 these processes include solution redox and ion exchange reactions sulphate reduction and mixing with saline formation water resampling of the aquifer profile after 10 years has confirmed the overall sequence although downgradient increases in both sulphate and calcium together with changes in redox system can be recognised these changes are related to the migration of agrichemical pollutants and the results demonstrate that the aquifer must have a significant capacity for in situ nitrate reduction

dissolution of fluoride in groundwater a water rock interaction study fluoride rich groundwater is well known in granite aquifers in india and the world although its presence is necessary chances of health risk become high if the fluoride concentration is more than the permissible limit of 1 5 mg l world health organization who in drinking water fluoride mainly occurs in groundwater as a natural constituent results of a laboratory study on water rock interaction at normal temperature pressure and different chemical conditions indicate that the specific conductivity ph ca and hco3 are important chemical parameters for the dissolution of fluoride to groundwater from fluoride rich minerals e g fluorite experimental results indicate that an alkaline medium ph 7 6 to 8 6 high hco3 concentration ranging from 350 450 mg l and moderate specific conductivity ranging from 750 1 750 s cm are favourable for fluoride dissolution no significant correlation existed between fluoride and cahco3

the palynological record across the cretaceous tertiary boundary in differing palaeogeographical settings from the southern pyrenees spain north american and pacific spore pollen records show a major extinction event at the cretaceous tertiary k t boundary and abrupt changes are similarly found in many marine organisms world wide in contrast records from the old world reveal little evidence of terrestrial vegetational change across the boundary in order to improve the characterization of changes across the k t boundary palynological assemblages from two sections in the southern pyrenees have been evaluated the abundance and diversity of trilete fern spores are high in maastrichtian samples and show a statistically significant decrease during the danian the fern spike of low diversity spores found elsewhere is not recorded in the pyrenean region minor replacements of taxa across the k t boundary are also noted as well as an increase in inaperturate gymnosperm pollen in the danian comparing our two examined sections with one another reveals important differences in angiosperm pollen composition

applying plant functional types to construct biome maps from eastern north american pollen data comparisons with model results abstract global biome models like biome1 convert climate model simulations of past climates into biome distributions and thus facilitate comparison of both climate and biome model results with biomes estimate from paleoecological data we adapted a biomization method recently developed for european pollen data for use with pollen data in eastern north america and then compared its estimated biomes with those derived from applying biome1 to the climate simulations from the ncar ccm1 national center for atmospheric research community climate model version 1 for 6000 years ago 6 ka we first tested the biomization method by seeing how well the biomes inferred from modern pollen data match observed biomes we found that modifications to the method were necessary in part to account for physiological differences between north american and european taxa and in part to cope with our choice of using just 23 major pollen taxa our modifications significantly improved the match between observed modern biomes and pollen derived biomes as measured by the kappa statistic we tested our tuning of the biomization method by matching its inferred 6 ka biomes to biomes estimated from pollen data using the modern analog technique the degree of agreement at 6 ka is close to that for today showing that 1 the biomization method and modern analog technique when applied to the same pollen data produce consistent results and 2 the modifications made to the biomization method are robust back to 6 ka we then used the results of the biomization method to test the biome maps simulated by biome1 which derives biome distributions from observed climate values for today and from the climatic simulations of the ccm1 for 6 ka only a fair agreement is seen and significant offsets exist in the placement of biomes by biome1 for today biome1 simulates the boundary between the temperate deciduous and cool mixed forests to be too far south and the steppe forest boundary to be too far west these model biases are also evident in the simulations at 6 ka despite the fact that ccm1 simulates warmer than present temperatures in the central united states to the north however biome1 correctly simulates the cool mixed forest and taiga boundary at 6 ka as more northwestward than at present

statistical characterization of arctic polar night jet oscillation events abstracta novel diagnostic tool is presented based on polar cap temperature anomalies for visualizing daily variability of the arctic stratospheric polar vortex over multiple decades this visualization illustrates the ubiquity of extended time scale recoveries from stratospheric sudden warmings termed here polar night jet oscillation pjo events these are characterized by an anomalously warm polar lower stratosphere that persists for several months following the initial warming a cold anomaly forms in the middle stratosphere as does an anomalously high stratopause both of which descend while the lower stratospheric anomaly persists these events are characterized in four datasets microwave limb sounder mls temperature observations the 40 yr ecmwf re analysis era 40 and modern era retrospective analysis for research and applications merra reanalyses and an ensemble of three 150 yr simulations from the canadian middle atmosphere model the statistics of pjo events in the model are found t

sensitivity of the brewer dobson circulation and polar vortex variability to parameterized nonorographic gravity wave drag in a high resolution atmospheric model abstractthe role of parametrized nonorographic gravity wave drag nogwd and its seasonal interaction with the resolved wave drag in the stratosphere has been extensively studied in low resolution coarser than 1 9 2 5 climate models but is comparatively unexplored in higher resolution models using the european centre for medium range weather forecasts integrated forecast system at 0 7 0 7 resolution the wave drivers of the brewer dobson circulation are diagnosed and the circulation sensitivity to the nogw launch flux is explored nogws are found to account for nearly 20 of the lowerstratospheric southern hemisphere sh polar cap downwelling and for less than 10 of the lower stratospheric tropical upwelling and northern hemisphere nh polar cap downwelling despite these relatively small numbers there are complex interactions between nogwd and resolved wave drag in both polar regions seasonal cycle analysis reveals a temporal offset in the resolved and parametrized wave interaction the n

dynamics of the northern annular mode at weekly time scales abstractrapid onsets of positive and negative tropospheric northern annular mode nam events during boreal winters are studied using era interim datasets the nam anomalies first appear in the north pacific from low frequency rossby wave propagation initiated by anomalous convection in the western tropical pacific around 2 weeks before the peak of the events for negative nam the enhanced convection leads to a zonal acceleration of the pacific jet while for positive nam the reduced convection leads to a poleward deviated jet in its exit region the north atlantic anomalies which correspond to north atlantic oscillation nao anomalies are formed in close connection with the north pacific anomalies via downstream propagation of low frequency planetary scale and high frequency synoptic waves the latter playing a major role during the last onset week prior to positive nam the generation of synoptic waves in the north pacific and their downstream propagation is strong the poleward deviated pacific j

sequential palynological changes across the composite cretaceous tertiary k t boundary claystone and contiguous strata western canada and montana u s a the boundary claystone in the western canada basin is composed of three intimately associated layers with a regional distribution a basal brownish grey hackly claystone a middle brownish black sa

depositional settings and palynofacies assemblages of the upper triassic fluviodeltaic mungaroo formation northern carnarvon basin western australia

paleoecology of the late campanian early maastrichtian fossil lagerstatte of lo hueco cuenca spain palynological insights abstract detailed palynological analyses of the late campanian early maastrichtian fossil lagerstatte of lo hueco have been undertaken the recovered assemblages particularly rich in angiosperm taxa included freshwater palynomorphs spores and pollen grains related to swamp or local wetland vegetation the palynofloras of the site revealed different micro environments the main differences among them may be related to water availability within a coastal environment the overwhelming presence of pollen grains especially emmapollis spp but also sparganiaceaepollenites spp herein described and related to typhaceae distinguishes the assemblages of lo hueco from the other late cretaceous european palynofloras accordingly this site may represent the oldest wetland vegetation under stressful conditions showing such modern plant community characteristics

a new look at stratospheric sudden warmings part iii polar vortex evolution and vertical structure the evolution of the arctic polar vortex during observed major midwinter stratospheric sudden warmings ssws is investigated for the period 1957 2002 using 40 yr european centre for medium range weather forecasts ecmwf re analysis era 40 ertel s potential vorticity pv and temperature fields timelag composites of vertically weighted pv calculated relative to the ssw onset time are derived for both vortex displacement ssws and vortex splitting ssws by averaging over the 15 recorded displacement and 13 splitting events the evolving vertical structure of the polar vortex during a typical ssw of each type is clearly illustrated by plotting an isosurface of the composite pv field and is shown to be very close to that observed during representative individual events results are verified by comparison with an elliptical diagnostic vortex moment technique for both types of ssw little variation is found between individual events in the orientation of the developing vortex relative to the underlying topography that is the location of the vortex during ssws of each type is largely fixed in relation to the earth s surface during each type of ssw the vortex is found to have a distinctive vertical structure vortex splitting events are typically barotropic with the vortex split occurring near simultaneously over a large altitude range 20 40 km in the majority of cases of the two daughter vortices formed it is the siberian vortex that dominates over its canadian counterpart in contrast displacement events are characterized by a very clear baroclinic structure the vortex tilts significantly westward with height so that the top and bottom of the vortex are separated by nearly 1808 longitude before the upper vortex is sheared away and destroyed

comparing and contrasting extreme stratospheric events including their coupling to the tropospheric circulation recent work has emphasized the importance of stratosphere troposphere coupling associated with extreme values of the polar vortex strength and stratospheric planetary wave heat flux during northern hemisphere winter here using era interim reanalysis data the evolution of the two types of events are compared the life cycle of total anomaly plus climatology positive negative heat flux events are associated with vertically deep high latitude planetary wave structures and exhibit largely equal but opposite signed impacts including a net deceleration acceleration of the polar vortex due to ep flux convergence divergence and an equatorward poleward tropospheric jet shift in the north atlantic the tropospheric wave pattern is westward propagating high latitude stratospheric vertical zonal wind shear plays a key role during both events a comparison of the stratospheric events reveals that planetary wave events contribute to the development of vortex events in particular total negative heat flux events precede strong vortex events showing that strong vortex events represent true dynamical events involving significant wave mean flow interaction coupling with the north atlantic jet occurs preceding vortex events when wave 1 dominates the total eddy heat flux in the lower stratosphere since interference with wave 2 makes the impacts less clear the tropospheric impacts in the north atlantic associated with planetary wave events are found to be comparable if not larger than those following vortex events

pollen representation source area and basin size toward a unified theory of pollen analysis abstract the concepts of pollen source area and of production and dispersal biases in pollen representation are quantified by means of a simple theoretical model source areas and relative pollen representation are shown to depend on basin size according to functions that describe the amount of pollen remaining airborne at increasing distances from single pollen sources the form of these functions is determined by physical processes standard formulas for elevated sources do not apply but the integrated form of sutton s equation for particle dispersal from a ground level source gives useful approximations applicable to pollen transport over a forest canopy simulations using this equation yielded source areas that increased realistically with basin size showed substantial differences between source areas for pollen grains with different deposition velocities and predicted that lighter pollen grains should become better represented with increasing basin size all of these predictions are qualitatively consistent with present knowledge of the characteristics of pollen assemblages in different depositional environments the model further allows parameters that can be estimated by statistical calibration methods to be predicted from underlying physical quantities this extension suggests procedures for testing the theory with quantitative data on surface pollen and forest composition preliminary results showed reasonable agreement between estimated and predicted values of dispersal indices for the most abundant taxa in pollen spectra from the northern midwestern united states

climatic implications of macro and microfossil assemblages from late pleistocene deposits in northern new zealand twenty two plant species were identified from leaves fruits or flowers and 41 taxa from pollen present in a macrofossil leaf layer in a peat swamp formed on pleistocene dunes on the aupouri peninsula in northern new zealand eight genera of gymnosperms are represented with the exception of lagarostrobos colensoi all tree species abundant as macrofossils are also common as pollen macrofossils enabled the on site flora to be compared with the regional flora represented by the pollen rain studies on leaf decomposition rates indicate bias toward sclerophyllous species in the macrofossils identification to species level and treering data from preserved kauri logs allow quantitative comparisons with similar extant communities current climatic conditions at those analogue sites are cooler 2 to 3 c cloudier 11 and much wetter 85 than those currently prevailing on the aupouri peninsula dendrochronological results also suggest that the far north of new zealand had a cooler cloudier and wetter climate at the time the fossil leaf assemblage was formed radiocarbon dates from possibly contaminated samples suggest that a diverse mixed gymnosperm angiosperm forest dominated by kauri agathis australis was present about or sometime before 41 00034 000 yr b p when the leaf layer was formed similar temperature reductions have been postulated for this period in new zealand by other authors

european charophyte evolution across the cretaceous paleogene boundary abstract the cretaceous paleogene k pg boundary has traditionally been considered a key moment in charophyte evolution marked by the extinction of two important mesozoic families the porocharaceae and the clavatoraceae and a major turnover within the characeae however new data presented here suggest that one species of the european porocharaceae based on gyrogonites and one species of the clavatoraceae based on thalli persisted into the basal danian in addition a taxonomic revision of the characeae coupled with an updated biostratigraphy shows that this family underwent a step wise extinction during the latest cretaceous with only a small number of species becoming extinct at the k pg boundary as a result changes in charophyte floras around the k pg boundary in europe cannot be considered to represent a major turnover in charophyte evolution its effects were more comparable to a normal stage boundary event rather than to a major erathem boundary one similar disappearance patterns at the k pg boundary have also been recorded in other taxa including fish and amphibians showing that aquatic freshwater biotas may somehow be resilient to catastrophic events such as those that occurred during the k pg crisis

forest or no forest implications of the vegetation record for climatic stability in western beringia during oxygen isotope stage 3 abstract two conflicting stratigraphic schemes describe the siberian karginskii interstade oxygen isotope stage 3 equivalent as having 1 relatively stable climate with environments more similar to the full glaciation or 2 variable climate with landscapes that more closely approximate contemporary ones new data from continuous lake cores and a nearly continuous section from western beringia wb suggest that both schemes are valid herb dominated communities possibly with isolated populations of larix characterized northern wb with only a slight shift from relatively warm to cool summers during the mid interstade in contrast herb and shrub tundra steppe forest tundra and modern larix forest occurred at various times in areas of southern wb suggesting greater climatic instability a thermal optimum is evident in the south during the mid interstade with modern vegetation in southeastern wb and larix forest tundra in the southwest variations in pinus pumila pollen indicate summer warm winter dry and summer warm winter wet conditions in southeastern wb these fluctuations contrast to other areas of wb where summers and probably winters were consistently arid although the interstade presents a unique interval within the late pleistocene paleodata and paleoclimatic models suggest that changes in marine conditions including sea level were likely key drivers in the regional climate history

magnetostratigraphy and biostratigraphy of cretaceous tertiary continental deposits ager basin province of lerida spain abstract at fontllonga northeast spain province of lerida a nearly continuous outcrop covers the stratigraphic interval from the maastrichtian to the thanetian in continental deposits magnetostratigraphy of the section was determined from 72 samples the magnetic polarity sequence was satisfactorily correlated with chrons 32r to 26r top of lower maastrichtian to lower thanetian chron 29r in which the k t boundary occurs is unambiguously recognizable considering the biostratigraphic data charophyte ostracod palynomorph the k t boundary occurs in the uppermost part of the microchara cristata subzone which includes late cretaceous and early palaeocene species this subzone is interpreted as an interval of crisis following the late maastrichtian extinctions and preceeding the palaeocene radiation no ir rich horizon has been yet found in this section the stratigraphic position of the last dinosaur remains found in the chron 31n interval leaves open the question of a causal link between the extinction of cretaceous reptiles and the k t event

geomedical assessment of an area having high fluoride groundwater in southeastern turkey the high fluoride concentration in groundwater has been yet determined in two villages sarim and karatas of western anliurfa turkey where it is the only source of drinking water to assess medical and hydrogeological dimensions of this problem principally including fluoride concentrations as well as electrical conductivity temperature and ph values were measured in groundwater wells of 65 villages including these two villages on site and a dental examination was performed on 451 children the fluoride concentrations in the groundwater of four villages determined as greater than 1 20 mg l causing dental fluorosis among children of these villages results revealed that dental fluorosis cases can develop even at low fluoride levels finally the prepared geomedical map demonstrated that medical and hydrogeological evidences were compatible with each other

sedimentologic and palynologic records of the last deglaciation and holocene from ballston lake new york continuous pollen and sediment records from two 8 5 m long cores document late pleistocene and holocene sedimentation and vegetation change in the ballston lake basin eastern new york state pebbles at the base of both cores and the geomorphology of the watershed reflect the presence of the mohawk river in the basin prior to 12 900 70 cal yr b p ballston lake formed at the onset of the younger dryas yd by an avulsion of the mohawk river the transition from clay to gyttja with low magnetic susceptibility ms low bulk density and high organic carbon indicates rapid warming and increased lake productivity beginning 11 020 cal yr b p ms measurements reveal that the influx of magnetic particles associated with pre holocene clastic sedimentation ceased after 10 780 cal yr b p the pollen record is subdivided into six zones bl1 12 920 to 11 020 cal yr b p is dominated by boreal forest pollen bl2 11 020 to 10 780 cal yr b p by pine pinus forest pollen bl3 10 780 to 5290 cal yr b p by hemlock tsuga and mixed hardwood pollen bl4 5290 to 2680 cal yr b p by mixed hardwood pollen bl5a 2680 cal yr b p to 1030 cal yr b p by conifer and mixed hardwood pollen and bl5b 1030 cal b p to present by increasing ragweed ambrosia pollen a 62 decrease in spruce picea pollen in 320 cal years during bl1 reflects rapid warming at the end of the yd holocene pollen zones record more subtle climatic shifts than occurred at the end of the yd one of the largest changes in the holocene pollen spectra began 5300 cal yr b p and is characterized by a marked decline in hemlock pollen this has been noted in other pollen records from the region and may record preferential selection of hemlock by a pathogen or parasites

rapid climate change from north andean lake fuquene pollen records driven by obliquity implications for a basin wide biostratigraphic zonation for the last 284 ka this paper compares a new super high resolution pollen record from a central location in lake fuquene 4 n with 3 pollen records from marginal sites from the same lake basin located at 2540 m elevation in the eastern cordillera of colombia we harmonized the pollen sum of all records and provided previously published records of climate change with an improved age model using a new approach for long continental pollen records we dissociated from subjective curve matching and applied a more objective procedure including radiocarbon ages cyclostratigraphy and orbital tuning using the new 284 ka long fuquene basin composite record fq bc as the backbone groot et al 2011 we showed that a common 9 m cycle in the arboreal pollen percentage ap records reflects obliquity forcing and drives vegetational and climatic change the ap records were tuned to the 41 kyr component filtered from standard benthic 18o lr04 record changes in sediment supply to the lake are reflected in concert by the four records making frequency analysis in the depth domain an adequate method to compare records from the same basin we calibrated the original 14c ages and used where necessary biostratigraphic correlation i e for records shorter than one obliquity cycle pollen records from the periphery of the lake showed changes in the abundance of alnus and weinmannia forests more clearly while centrally located record fq 9c shows a more integrated signal of regional vegetation change the revised age models show that core fq 2 reflects the last 44 ka and composite record fq 7c the last 85 5 ka marginally located core fq 3 has an age of 133 ka at 32 m core depth and the lowermost 11 m of sediments appear of older but unknown age the longest record fq bc shows 60 yr resolution over the period of 284 27 ka all pollen records are in support of a common regional vegetation development leading to a robust reconstruction of long series of submillennial climate oscillations reflecting dansgaard oeschger do cycles reconstructed climate variability in the tropical andes since marine isotope stage mis 8 compares well with ngrip 18o based epica dome c d based and the mediterranean sea surface temperature record md01 2443 44 uk 37 based underpinning the global significance of the climate record from this tropical andean lake a basin wide biostratigraphy is presented and we concluded although with varying robustness that each core is representative of regional vegetational and climatic change

do split and displacement sudden stratospheric warmings have different annular mode signatures sudden stratospheric warmings ssws contribute to intraseasonal tropospheric forecasting skill due to their surface impacts recent studies suggest these impacts depend upon whether the polar vortex splits or is displaced during the ssw we analyse the annular mode signatures of ssws in a 1000 year ipsl cm5a lr simulation although small differences in the mean surface northern annular mode nam index following splits and displacements are found the sign is not consistent for two independent ssw algorithms and over 50 events are required to distinguish the responses we use the winter time correlation between extratropical lower stratospheric wind anomalies and the surface nam index as a metric for two way stratosphere troposphere coupling and find that the differences between splits and displacements and between classification methodologies can be simply understood in terms of their mean stratospheric wind anomalies predictability studies should therefore focus on understanding the factors that determine the persistence of these anomalies following ssws

downward propagating temperature anomalies in the preconditioned polar stratosphere abstract dynamical links of the northern hemisphere stratosphere and troposphere are studied with an emphasis on whether stratospheric changes have a direct effect on tropospheric weather and climate in particular downward propagation of stratospheric anomalies of polar temperature in the winter spring season is examined based upon 22 years of ncep ncar reanalysis data it is found that the polar stratosphere is sometimes preconditioned which allows a warm anomaly to propagate from the upper stratosphere to the troposphere and sometimes it prohibits downward propagation the arctic oscillation ao is more clearly seen in the former case to understand what dynamical conditions dictate the stratospheric property of downward propagation the upper stratospheric warming episodes with very large anomalies such as stratospheric sudden warming are selected and divided into two categories according to their downward propagating features eliassen palm e p diagnostics and wave propagation theories are u

tracing the north atlantic decadal scale climate variability in a late holocene pollen record from southern siberia abstract this paper presents a new palynological record from a 146 cm long finely laminated sediment core obtained in 2009 from the deep water meromictic lake shira 54 30 38 n 90 12 09 e ca 353 m a s l situated in the khakassian steppe region of southern siberia between the rivers ob and yenisei the area is rich in lakes and represents an exceptionally well preserved sequence of bronze and iron age archeological cultures little is known about the changes in vegetation and climate of the region during the holocene the palynological analysis of the core allows us to partly fill up this gap in current knowledge the record of pollen and non pollen palynomorphs presented here covers the past 2450 year interval with an average resolution of 22 years the results obtained support the interpretation that the late holocene vegetation changes around lake shira are mainly associated with large scale atmospheric circulation processes controlling the regional water balance rather than with human activities an attempt to trace human impact in the pollen assemblages provides no clear evidence for anthropogenic activity except for the last few decades since ca 1955 though the region has a long history of mobile pastoralists for explanation of decadal scale changes in the regional vegetation cover the artemisia chenopodiaceae a c pollen ratio proved to be a reliable indicator of effective moisture availability using available fossil and published instrumental data our study suggests a link between the north atlantic warmer colder temperatures and higher lower atmospheric precipitation or moisture availability in southern siberia at multi decadal to centennial scales

palynology after y2k understanding the source area of pollen in sediments pollen grains preserved in lake and bog sediment provide a record of past vegetation that has been an important source of information about climate and land cover during the quaternary period yet from the beginning questions have been raised about the source area of pollen in sediment interpretation has been hampered by the lack of well developed theory treating the relationship between the spatial distribution of trees on the landscape and the percentages of pollen in sediment within the past decade however new theory models and empirical data show how heterogeneous vegetation is represented by pollen the distinction between local and regional pollen is explained by the prentice sugita dispersal deposition models which predict how the ratio of regional to local pollen changes with lake size sugita s model simulating a landscape with heterogeneous vegetation predicts the size of the relevant source area the area of vegetation reflected in between lake variations in pollen loading while demo

case studies of the mesospheric response to recent minor major and extended stratospheric warmings 1 we have studied the mesospheric response to two recent stratospheric warmings by performing short term forecasts at medium 1 5 and high 0 5 spatial resolution under different gravity wave drag gwd scenarios we validated our models with our high altitude analysis that extends from 0 to 90 km for the minor warming of january 2008 reduced upper level orographic gwd weakened the downward residual circulation and cooled the mesosphere parameterized nonorographic gwd increased the simulated mesospheric cooling for the prolonged major warming of 2006 heavily attenuated orographic gwd led to pronounced cooling near 50 km during the extended phase of this event an unusually strong westerly polar vortex reformed in the lower mesosphere which allowed westward propagating nonorographic gravity waves to reach the mesosphere and break with net westward accelerations of over 50 m s 1 d 1 this in turn forced a strong residual circulation yielding descent velocities over 2 cm s 1 between 65 n and 85 n consistent with previous reports of enhanced downward transport of trace constituents the resulting adiabatic heating as evidenced by the unusually vertically displaced stratopause at 80 km is likely a direct consequence of this enhanced gravity wave driven descent high resolution simulations without parameterized gwd were closer to the analysis than medium resolution simulations with parameterized orographic gwd only but still did not fully simulate the mesospheric thermal response specifically the 80 km temperature enhancement was still underestimated in these simulations this suggests that higher spatial resolution is needed to adequately resolve extratropical gravity wave momentum fluxes

predicting the downward and surface influence of the february 2018 and january 2019 sudden stratospheric warming events in subseasonal to seasonal s2s models using the real time predictions from 11 models this study analyzes the prediction of the downward propagation and surface impact of the 2018 and 2019 sudden stratospheric warmings ssws these two ssws differed both in their morphology types 2018 split 2019 displacement followed by split and magnitudes the former being stronger with a large sample size 2 200 of multimodel ensemble forecasts it is revealed that the strength of the ssw is more important than the vortex morphology in determining the magnitude of its downward impact with strong ssws more likely to propagate downward than weak ssws therefore based on the probabilistic forecasts the observed strong ssw in february 2018 was more likely to have a downward and surface impact than the january 2019 ssw the relationship between the 10 hpa dominant wave number and the 100 hpa polar cap height or the northern annular mode is weak implying that the dominant wave number might not be the primary factor determining the downward propagation of ssws in the two analyzed cases hence the high polar cap height or negative northern annular mode response in the lower stratosphere and troposphere following the february 2018 ssw is mainly attributed to its strong intensity rather than the split morphology further the 2 m temperature anomaly pattern following the january 2019 ssw is not forecasted due to its weak downward propagation whereas the 2 m temperature in north eurasia middle east south china and eastern united states could be forecasted for the downward propagating february 2018 ssw however regional rainfall anomalies are poorly forecasted both in a deterministic and probabilistic sense for both ssws