reconstruction of past precipitation δ18o using tree ring cellulose δ18o and δ13c a calibration study near lac d annecy france abstract two sets of living oaks quercus r growing under different hydrological situations were sampled near lac d annecy france the stable isotope composition of the latewood cellulose was analysed in terms of oxygen and carbon isotopic composition for the period 1971 2001 and compared to the nearby monthly meteorological temperature relative humidity and isotopic composition of precipitation records a linear regression shows that 60 of the cellulose oxygen isotopic composition inter annual variations are due to changes in precipitation isotopic composition and relative humidity the small slope between cellulose versus precipitation oxygen isotopic composition suggests a significant contribution of local continental recycling and questions the common assumption that vapour oxygen isotopic composition is at equilibrium with precipitation isotopic composition in europe during the growing season finally the combined use of tree ring oxygen and carbon isotopic composition records enables to account for leaf water enrichment due to stomata stress and to provide a reconstruction r 2 0 64 of the summer precipitation isotopic composition

characterization of vertical mixing at a tidal front on georges bank studies of mixing were done at the northern flank of georges bank in the summer and autumn of 1988 two time series of the evolution and intensity of microstructure were examined over a tidal period in the context of tidal forcing and the evolution of the density and velocity field at the site from the ctd adcp and microstructure observations epsonde on georges bank several interesting features of the mixing processes were found high dissipation and diffusivity regions appear near the bottom of the bank turbulence near the bottom is highest in intensity and reaches farthest from the bottom at peak tidal flow and diminishes in intensity and vertical extent as the flow decreases the thickness of the bottom turbulent layer has its maximum value when the flow is strongest and the stratification is weakest characterization of the dissipation rate and turbulent diffusivities in respect to buoyancy frequency n current shear s richardson number ri and n2 was done dissipation and t showed little dependence on shear or n2 but decreased at larger ri t was found to be higher in regions of higher n2 and increased as n2 increased kt k and k were all highest near the bottom in excess of 10 2m2s 1 and decreased towards the surface there was little suggestion of a dependence of mixing efficiency on s2 ri or n2 but some indication that decreases with decreasing n2

zooplankton distributions and transport across the northeastern tidal front of georges bank tidal fronts are important sites of contact and mixing between zooplankton populations on and off georges bank in the northwest atlantic this study a component of the us globec program examined crossfrontal distributions of zooplankton especially the copepod calanus finmarchicus across the northeastern tidal front of georges bank relative to the tidal cycle frontal structure flow field and day night cycle a unique feature was a precisely executed sampling strategy designed to isolate spatial tidal and day night effects vertically stratified zooplankton sampling was done along tidally coordinated crossfrontal transects and during time series studies at specific locations zooplankton taxa differed in their spatial and vertical distributions relative to the front and the hydrographic structure of the water column there were significant associations between zooplankton assemblages and spatial location depth and water mass zooplankton distributions generally tracked water masses but usually showed crossbank abundance gradients consistent differences between day and night distributions were not apparent for most taxa meroplankton larvae of benthic animals were derived primarily from onbank populations the zooplankton community was advected with the tidal flow crossfrontal distributions characteristic of onbank and offbank flow regimes clearly differentiated tidal phases and interacted with the flow field and topography salinity a proxy for water mass and depth interacted in controlling vertical distributions as tidal forcing sloshed water masses up and down the bank slope some taxa followed isohalines through depth changes while other taxa maintained themselves within a relatively limited depth or salinity regime surface convergence and downwelling tidal upwelling of bottom water and mid depth tidal pumping influenced crossfrontal exchange

residual circulations due to bottom roughness variability under tidal flows abstract tidal flows over irregular bathymetry are known to produce residual circulation flows due to nonlinear interaction with gradients of depth using the depth averaged vorticity equations the generation of residual vorticity and residual flows due to variation of the frictional coefficient are examined the authors find that the contribution due to bottom roughness variations can be as large as that arising from gradients of depth and velocity specific cases are considered on the northern california shelf georges bank and the u s south atlantic bight the generation of residual vorticity is a strong function of the length scales at which roughness or depth vary length scales of bottom roughness variation are commonly within the range of greatest effect e g sand patchiness cobbly outcrops etc the site specific cases show that the bottom roughness variability can generate as much residual circulation as that expected from depth variability the implication for numerical modeling studies

influence of fracture system on the exploitation of building stones the case of the mondim de basto granite north portugal the most negative aspects in the exploitation of weathered granites as ornamental stones tend to be heterogenic coloration and fracturing therefore an accurate study is needed for a comprehensive evaluation of the granite resources during an exploration campaign this paper presents the results of the fracturing evaluation of a region located in north of portugal where the mondim de basto granite a stone with a high weathering degree is exploited the regional fracturing was evaluated from lineaments in aerial photos and then compared with local jointing in quarries the jointing in each quarry is characterized according to the strike and dip joint spacing and volumetric joint count two indices were proposed to facilitate the jointing comparison among quarries the joint space length ljs and joint set spacing sjs ljs is based on the sum of all the spacing values obtained perpendicularly to the strike direction sjs is computed based on the overall mean median spacing and on the number of joint sets observed in each quarry the most important joint sets in the subdivision of the rock mass were found not to be in accordance with the regional fracturing patterns highlighting the necessity of studying the fracturing at all scales

can climate variations be inferred from tree ring parameters and stable isotopes from larix decidua juvenile effects budmoth outbreaks and divergence issue abstract larch wood has been used for centuries as a building material hence the study of the tree ring width the latewood maximal density and the oxygen and carbon isotope composition of the cellulose of this tree provides potential and valuable insights when reconstructing past climate variability we explore the qualities and limitations of these proxies focusing on a forest standing the nevache valley french alps the analysis of 15 trees demonstrates a small intra tree variability in comparison with the inter tree variability of 13c and 18o and shows that 6 trees at least must be pooled to make a population representative sample our results show no juvenile effect for 13c unlike tree ring width and density 13c and 18o are not altered by budmouth outbreaks these two parameters therefore appear well suited for climate reconstructions and depict a strong correlation with july august temperature and relative humidity the 18o of larch cellulose is also strongly linked with the previous winter december march oxygen isotopic composition of the precipitation this is consistent with a winter water recharge of soil and ground the past variations of july august maximum temperature and relative humidity were established using two different combinations of the isotopic ratios uncertainties on the reconstructions are estimated respectively at 1 4 c and 3 6 inter annual variations of temperature and relative humidity are well reproduced however the reconstructed july august temperature series diverges from the instrumental one being lower after ca 1990 the effects of the variation through time of the depth of source water and of the ecophysiological response of trees to rising co2 on the isotope composition are discussed as possible causes of divergence this divergence problem strongly questions the possibility of producing appropriate isotope based temperature calibration the relationships between isotopes and the july august relative humidity are more stationary than those with temperature this may reflect the first order control of the relative humidity on 13c via the stomatal conductance and its influence on the evaporative enrichment of the oxygen of the leaf water our study suggests that past variations of relative humidity in the french alps can be accurately estimated using the stable isotope composition of larch cellulose

evaluation of weathering resistance classes in clastic rocks on the example of polish sandstones the scope of the paper is an attempt at the identification of the weathering resistance classes within clastic rocks by means of analysis of capillary pressure saturation curves the porosimetric parameters corresponding to the cementing character and the grains mineralogical content are very important features of stone building materials because of the weathering processes the analysed rocks were polish sandstones and muddy sandstones used for building purposes collected from different geological units of poland i e sudety mts carpathian mts and holy cross mts the results indicate the usefulness of sandstone materials for building purposes they could also be used in conservation procedures and for the reconstruction of existing buildings and monuments basing on the parameterisation with the van genuchten function of cumulative capillary pressure saturation curves it was possible to distinguish four groups of the sampled rocks the lithological features and weathering sustainability within the groups are quite uniform what allow identifying the weathering resistance classes taking into account the complicated nature of all the factors influencing weathering processes it is supposed that the presented parameterisation could be a useful tool for weathering resistance classification of clastic rocks the classification could be useful in building industry and in conservation of historical stone monuments

comparison of stable carbon isotope ratios in the whole wood cellulose and lignin of oak tree rings abstract the stable carbon isotope ratios 13c of whole wood cellulose and acid insoluble lignin from annual latewood increments of quercus robur l from modern and sub fossil wood were measured and their potential use as palaeoenvironmental indicators examined the resulting time series demonstrate a very high degree of coherence with 13c of cellulose isotopically enriched by approximately 3 compared to 13c of lignin the 13c values of all three components are influenced by the climate of july and august modern whole wood retains the strongest climate signal perhaps because its composition is closest to that of leaf sugars in sub fossil wood there is no evidence that differential decay leads to fractionation of carbon within either cellulose or lignin but differential decay can alter the cellulose to lignin ratio

mid holocene warming in the northwest kola peninsula russia northern pine limit movement and stable isotope evidence a set of 40 subfossil scots pines pinus sylvestris l was sampled in small lakes beyond the modernpine limit in the northwest kola peninsula russia radiocarbon dating suggests that the pine exp

a numerical study of stratified tidal rectification over finite amplitude banks part ii georges bank abstract tidal rectification over a two dimensional finite amplitude symmetrical bank is studied using the blumberg and mellor primitive equation coastal ocean circulation model ecom si in the homogeneous case the nonlinear interaction of tidal currents with the variable bottom topography generates an along isobath residual circulation over the bank which tends to increase as either the slope or height of the bank is increased in the stratified case internal waves at tidal and higher frequencies are generated over the sloping sides of the bank tidal mixing occurs in the bottom boundary layer leading to horizontal tidal mixing fronts the resulting stratified tidal rectification associated with the tidal mixing front the generation of internal tides and the modification of internal friction due to stratification leads to a subsurface intensification of the along isobath residual current at the front and at the top of the bottom mixed layer over the slope and a cross bank double cell circulation

multiple stable isotopes from oak trees in southwestern scotland and the potential for stable isotope dendroclimatology in maritime climatic regions across much of europe eurasia and n america there exist networks of long tree ring chronologies which under favourable circumstances may be used to provide a record of palaeoclimate information a proportion of these tree ring archives primarily those collected for archaeological dating purposes represent a significant and largely untapped palaeoenvironmental archive such records may be unsuitable for palaeoclimatic reconstruction based solely upon their physical characteristics ring width and density owing to weak or poorly expressed climatic forcing this is especially true of oak chronologies from maritime regions this study explores the potential for extracting a climate signal from such chronologies by comparing the stable isotope ratios of c h and o from the rings of common oak quercus robur trees in southwestern scotland with local and regional meteorological data summer growing season climate influences all three isotopes and the relationships identified are consistent with published empirical and mechanistic studies the climate signal appears strongest in o and weakest in h the c and o series in combination explain 31 of the variance in july august mean temperature measured locally and 26 when compared with a homogenised gridded dataset for the period ad1957 2002 over longer timescales the combination of c and o isotopes may also preserve a significant low frequency signal july august r 2 0 57 9 year running mean ad1879 1998 these findings demonstrate the potential of stable isotope dendroclimatology for investigating climatic change from oak chronologies in maritime regions 2008 published by elsevier b v

relative dispersion of surface drifters in a barrier reef region 1 the spreading of two clusters of satellite tracked surface drifters was quantified by relative dispersion and relative diffusivity the time derivative of relative dispersion in two regions of the southern great barrier reef gbr a low density reef matrix of complex topography and a shelf lagoon over flat bathymetry although based on a small data set averaged values of these parameters over a 12 day period with concurrent measurements for the two regions indicated that relative dispersion and diffusivity of drifter pairs were 182 and 52 times greater respectively along the reef matrix than found in the lagoon relative diffusivities in the southern gbr were anisotropic and varied largely in space and time within the spatial scales of 1 100 km and temporal scales of hours to 16 20 days they were considerably enhanced by high frequency tidal processes submesoscale processes 20 km were important in the southern gbr particularly in areas with complex topography where secondary circulations around the reefs and regions of steep bathymetry caused abrupt increase in dispersion although the dispersion was much higher along the reef matrix the presence of ring circulations around the islands and wake eddies in the lee of islands can act as trapping mechanisms to keep particles within the reef matrix retarding the loss to open water areas this provides an efficient physical mechanism for both enhancing larval connectivity between reefs and at the same time trapping larvae when in the vicinity of reefs

do tree ring δ13c series from pinus sylvestris in northern fennoscandia contain long term non climatic trends abstract non climatic trends in tree ring 13 c series are investigated using highly replicated pinus sylvestris 13 c series from finnish lapland the declining trend in stable carbon isotopes over the industrial period reflecting changes in the isotopic ratio of atmospheric co 2 is removed mathematically without recourse to statistical de trending regional curve standardisation rcs is then used to identify and remove the juvenile phase during which 13 c values increase the chronologies all show approximately 1 depletion in the juvenile phase with an average rise of 0 029 year 1 lasting for about 50 years after which trees of very different cambial age capture common variance over the same chronological period there is no evidence of long term age related trends and rcs provides an alternative to simply omitting the juvenile portion of the stable carbon isotope series thus allowing greater sample depth to be retained

near surface recirculation over georges bank satellite tracked drifters with drogues centered near surface 5 m and below the seasonal thermocline 50 m were launched during late winter and spring of 1988 and 1989 in the northern great south channel in the western gulf of maine to investigate the regional circulation as part of the south channel ocean productivity experiment scopex many of the near surface drifters became entrained in the clockwise gyre over georges bank and eight drifters made a total of 16 complete circuits around the bank during the stratified season the average recirculation period of these eight drifters was 48 days and the average drifter speed around the bank was 12 cm s 1 there is no clear evidence from the drifter data that the strength of the clockwise gyre over the bank increased with time during the stratified season on average these drifters i followed a relatively narrow path around the bank except over the eastern end of the bank where three preferred paths were observed ii moved fastest over the northern and southern flanks of the bank iii did not enter a core area of 3500 km2 centered at 41 17 n 68 00 w approximately 30 km southwest of the topographic center of the bank and iv stopped circling the bank by the end of november due in part to strong wind events that appeared to drive drifters off the bank curiously none of the near surface drifters moved from the southern flank of georges bank onto the new england shelf as might be expected from continuity of flow along the outer shelf instead the drifters that circled the bank tended to move off the bank along its southern flank none of the drifters with drogues centered at 50 m appeared to recirculate around georges bank

chaotic stirring in a tidal system an analysis of a two dimensional tidal model of the wadden sea reveals lagrangian chaos in the trajectories of water parcels the associated chaotic stirring results from the transverse intersection of the stable and unstable curves of hyperbolic fixed points in the lagrangian residual displacement field the tidal poincare map this tidal dispersion mechanism produces rapid water exchange along the channel axis and could be representative of many shallow tidal seas

estimates of dispersion from clustered drifter deployments on the southern flank of georges bank abstract data from 16 clustered drifter deployments are used to examine horizontal dispersion on the southern flank of georges bank the spreading rates of all clusters have an average of 1 6 km d 1 with a standard deviation of 1 8 km d 1 both effective and apparent diffusivities are calculated for each cluster their ranges e g 54 to 757 m 2 s 1 for effective diffusivity are related to differences in cluster size and proximity to the tidal mixing front cross bank convergence is documented for nearly 40 of the clusters this occurs especially for clusters with centroids within 10 km of the tidal mixing front location as deduced from conductivity temperature and depth transects ctd conducted concurrently with the cluster deployments estimates of turbulent dispersion distinct from shear effects are derived by the method of a okubo and c c ebbysmeyer 1976 determination of vorticity divergence and deformation rates from analysis of drogue observations deep sea research 23 349 352 the results reveal that the effects of horizontal shear are important in spreading of larger drifter clusters often the impact of shear is evidenced by the track of a lone drifter that separates from a cluster as it is entrained into the current of the shelf edge front or the tidal mixing front cluster dispersion is time dependent as evidenced by a significant modulation of cluster size at the m 2 tidal frequency this modulation is due to the spatial variation of tidal currents over the southern flank of georges bank and is closely reproduced by immersing drifter clusters into the flow field of a georges bank tidal model

evaluating the integrity of c and o isotopes in sub fossil wood from boreal lakes abstract extending climatic series back to the first millennium using isotopic tree ring chronologies in northern regions represents a challenge because trees seldom reach the adequate age fossil trees deposited in boreal lakes could serve such an endeavor provided that dating the tree ring series is possible and that the isotopic ratios of sub fossil wood are preserved from two boreal lakes in north eastern canada we collected segments of picea mariana black spruce stems with different degrees of wood textural preservation and covering the last millennium our main objectives are to assess the selection criteria for wood textures suitable for isotopic reconstruction and verify the reliability of sub fossil cellulose carbon and oxygen isotopic series for climatic reconstruction in boreal regions the isotopic differences between cellulose and lignin obtained for 48 ring pairs of a living tree 13cc l 3 7 0 3 18oc l 13 1 and 46 contemporaneous pairs from a sub fossil stem 3 5 0 3 and 12 9 0 9 in the same order are systematic and matching for the selection of all sub fossil samples we have visually identified three main classes of wood textures for which the degree of alteration is confirmed by secondary electron microscopy well preserved slightly altered and highly altered slightly altered stem segments have cellulose proportion showing a relative decrease reaching 35 but 13cc l and 18oc l values within the range of living trees non altered sub fossil stems covering the 14th and 11th centuries show systematic and coherent 13cc l 3 5 0 2 3 8 0 4 and 18oc l results 13 9 0 7 13 5 0 5 highly altered wood shows a decrease in both cellulose proportion and 18ocellulose values but apparently preserved 13c ratios this research shows that it is possible to visually identify the degree of wood preservation and preselect sub fossil segments holding reliable isotope ratios and to use sub fossil stems collected from boreal lake floors to reconstruct climate over the last millennia

georges bank residual circulation during weak and strong stratification periods prognostic numerical model results the seasonal extremes of the three dimensional residual circulation on georges bank are studied by numerically computing the circulation during weakly march april and strongly july august stratified periods the computations are performed using a prognostic i e including tidal time advection of the density field free surface nonlinear finite element model on realistic georges bank topography the dynamics considered result from the dominant m 2 tide baroclinic pressure gradients wind stress upstream boundary conditions and advanced turbulence closure comparison of these solutions with earlier diagnostic model results illustrates the importance of processes which could not be included in these earlier simulations such as density evolution and advanced turbulence closure in tidal time inclusion of nonlinear baroclinic effects improved treatment of other nonlinearities etc during the strongly stratified july august period the newly modeled processes intensify the residual circulation and result in recirculating transport on georges bank of 0 25 sv which is twice the diagnostic result the level of agreement between modeled and observed residual circulation improves very significantly for this period with the prognostic model predicting around bank currents as high as 46 cm s 1 in the frontal zone on the northeast peak analysis of the tidal time density and current structure in the frontal zone on the northeast peak indicates important tidal frequency dynamics and features which are supported by observational evidence during the weakly stratified march april period the dynamical impact of the newly modeled processes is small hence the prognostic and diagnostic models predict similar global structure with a recirculating transport on georges bank of 0 05 sv although there are local differences which result in the prognostic simulation agreeing more closely with the observed circulation

assessing tree ring carbon and oxygen stable isotopes for climate reconstruction in the canadian northeastern boreal forest abstract in this study we analyzed stable isotopes of oxygen 18o and carbon 13c of five black spruce picea mariana mill bsp trees growing in the quebec boreal forest we then produced the first dendroisotopic series covering the last two centuries 1800 2003 for this region where climatic records are particularly scarce and of short duration our aim was to evaluate the isotope sensitivity to climate and their potential as proxies for past climate conditions the 18o results show a strong coherence between all trees indicating that these values express a homogenous response at the site scale for the 13c series slight inter tree differences suggest the influence of micro site conditions isotopic values were compared to climatic data for the period 1944 2003 these statistical analyses indicate that the 13c and 18o ratios are directly influenced by summer maximum temperatures but also correlate with parameters that integrate temperatures and moisture status in all cases the climate effects on 13c values are weaker than the ones recorded by the 18o series moreover because the 18o and 13c values are sensitive to climatic variables that are linked and commonly associated in typical subarctic climate ambiances warm dry cold wet the patterns of their joint response show stronger correlations with climatic parameters then a temperature reconstruction was developed based on a regression model that calibrates the combined 13c and 18o series against summer maximum temperature tmaxjja the reconstructed summer temperatures indicates that the first half of the 19th century was the coldest period in the past 200 years and that a steadily change throughout milder conditions started in the early 1940 s these trends are consistent with other reconstructed values from independent proxies available for the same region this research confirms that c and o dendroisotopic series of black spruce trees in high latitudes can document adequately past climatic conditions

surf zone diffusivity on a rip channeled beach absolute and relative diffusivity are measured on a rip channeled beach using 30 position tracking drifters released in clusters 4 12 drifters deployed on 7 days with different wave forcing and tidal elevations at sand city monterey bay california diffusivity and dispersion were found to be larger on days with rip current flow patterns and larger waves rip currents cause material to diffuse quickly for t 0 9 two independent methods are used to measure the small scale turbulent diffusion contribution kxy which are found significantly correlated r2 0 95 with each other and calculated surf zone wave breaking induced turbulent eddy viscosity here kxy is small relative to the total dispersion ke kxy 3 30 indicating that the shear flow is the primary mechanism responsible for dispersion in a rip current system

stable carbon isotopes from tornetrask northern sweden provide a millennial length reconstruction of summer sunshine and its relationship to arctic circulation this paper presents results from the first 1100 years of a long stable carbon isotope chronology currently in development from scots pine pinus sylvestris l trees growing in the tornetrask region of northern sweden the isotope record currently comprises a total of 74 trees with a mean annual replication of 12 thereby enabling it to be compared directly with other tree ring based palaeoclimate reconstructions from this region in developing the reconstruction several key topics in isotope dendroclimatology chronology construction replication co2 adjustment and age trends were addressed the resulting carbon isotope series is calibrated against instrumental data from the closest meteorological station at abisko ad1913 2008 to provide a record of june august sunshine for northern fennoscandia this parameter is closely linked to the direct control of assimilation rate photosynthetically active radiation par and the indirect measures mean july august temperature and percent cloud cover the coupled response of summer sunshine and temperature in this region permits a multiparameter comparison with a local reconstruction of past temperature variability based upon tree growth proxies to explore the stability of this coupling through time several periods are identified where the temperature x ray density and sunshine stable carbon isotope ratio records diverge the most significant and sustained of these occur between c ad1200 1380 and c ad1550 1780 providing evidence for a cool sunny two phase little ice age whilst summer sunshine reconstructed for the 20th century is significantly different from the mean of the last 1100 years p 0 01 so it is the 17th 18th and to a lesser extent the 13th centuries rather than the early medival period that appear anomalous when viewed within the context of the last 1100 years the observed departures between temperature and sunshine are interpreted as indicating a change in large scale circulation associated with a southward migration of the polar front such a change affecting the northern annular mode arctic oscillation would result in more stable anticyclonic conditions cool bright summers over northern fennoscandia thus providing a testable mechanism for the development of a multi phase time transgressive little ice age across europe

the influence of the characteristics of quartz and mineral deterioration on the strength of granitic dimensional stones it is important to have a thorough knowledge of the petrographic characteristics of rocks to evaluate and understand their mechanical behavior this paper deals with the influence of the texture and the mineral characteristics of nine portuguese granites employed as dimensional stones this study evaluates different mineral characteristics such as mineral deterioration grain size quartz fissuration and the contacts between quartz and others mineral groups the main differences in the studied granites were identified clarifying the relationship between the petrographic characteristics the consequences on their respective mechanical behavior were subsequently evaluated the physical and textural characteristics of quartz in the studied granites have proven to be very important for understanding the behavior of granitic rocks under compressive stress uniaxial compressive strength values are not proportional to the quartz feldspar ratio or quartz content and there is a tendency for strength to decrease with the increase in quartz this could be related to the increase in quartz quartz contacts and the decrease in the rock capacity for accommodating the deformation

stable carbon and hydrogen isotope ratios of subfossil oaks in southern germany methodology and application to a composite record for the holocene the d ad values exist for the time interval 6470 bc to ad 905 not all records have the same time resolution and not all of them were prepared in the same way for isotope analysis however investigations on the influence of the preparation technique on the isotope values and on the isotope composition of different wood compartments latewood and earlywood respectively allowed us to homogenize the records the comparison of d values of wood with different cambial ages showed that hydrogen isotoperatios were affected by growth tre

last millennium northern hemisphere summer temperatures from tree rings part i the long term context abstract large scale millennial length northern hemisphere nh temperature reconstructions have been progressively improved over the last 20 years as new datasets have been developed this paper and its companion part ii anchukaitis et al in prep details the latest tree ring tr based nh land air temperature reconstruction from a temporal and spatial perspective this work is the first product of a consortium called n trend n orthern hemisphere tre e ring n etwork d evelopment which brings together dendroclimatologists to identify a collective strategy for improving large scale summer temperature reconstructions the new reconstruction n trend2015 utilises 54 records a significant expansion compared with previous tr studies and yields an improved reconstruction with stronger statistical calibration metrics n trend2015 is relatively insensitive to the compositing method and spatial weighting used and validation metrics indicate that the new record portrays reasonable coherence with large scale summer temperatures and is robust at all time scales from 918 to 2004 where at least 3 tr records exist from each major continental mass n trend2015 indicates a longer and warmer medieval period 900 1170 than portrayed by previous tr nh reconstructions and by the cmip5 model ensemble but with better overall agreement between records for the last 600 years future dendroclimatic projects should focus on developing new long records from data sparse regions such as north america and eastern eurasia as well as ensuring the measurement of parameters related to latewood density to complement ring width records which can improve local based calibration substantially

influence of diurnal heating on stratification and residual circulation of georges bank 1 the influence of the diurnal heat flux on summer stratification and residual circulation over georges bank was examined using a three dimensional primitive equation numerical circulation model for a given spatially uniform and time varying heat flux the model results show that the surface water is heated much faster on the southern flank than on the northern flank and much faster in the stratified region than in the mixed region heating significantly strengthens the tidal mixing front and intensifies the frontward convergence near the surface as seasonal stratification develops the location of the tidal mixing front gradually shifts on bank on the southern flank while remaining almost unchanged on the northern flank response of the tidal currents to the diurnal variation in the heat flux varies across georges bank it changes periodically with tidal cycles on the southern flank but is locked to the phase of the eastward tidal current on the northern flank this phase lock feature directly contributes to the intensification of the along bank residual current jet on the northern flank diagnostic analysis suggests that this intensification is mainly caused by the heat enhanced cross bank momentum flux modelcomputed variations of near surface temperature and residual currents are in good agreement with satellite derived sea surface temperature data and drifter measurements index terms 4219 oceanography general continental shelf processes 4227 oceanography general diurnal seasonal and annual cycles 4255 oceanography general numerical modeling 4279 oceanography general upwelling and convergences 4528 oceanography physical fronts and jets keywords heat flux tidal mixing front residual current stratification frontward convergence

age related trends in subfossil tree ring δ13c data abstract long stable isotope chronologies are increasingly constructed from tree rings averaging the mean chronologies necessitates that the contributing series contain no age related trends therefore any set of dendroisotope data needs to be tested for age dependency in isotope values before the chronology is compared with climate or other environmental records such age trends are common to tree ring width and density data but corresponding evidence on stable isotope records is yet relatively limited moreover there is contrasting evidence suggesting that while a number of dendroisotope datasets appear to portray no age related trends such trends may be found in different regions and tree species here we analyze a collection of 182 subfossil tree ring 13c series from a species pinus sylvestris and a region northern fennoscandia where previous investigations have found no support for age related trends beyond the juvenile effect in the tree ring 13c data our 13c dataset benefits from a large sample size of analysed tree rings representing a wide range of calendar years 5630 bc through ad 1930 formed under varying climate conditions our results indicate that the tree ring 13c series do contain age related trends throughout the trees lifespan this age dependence corresponded to an ascending linear change of ca 0 4 per 100 years illustrating the mean 13c curve as a function of trees biological age demonstrated that the age dependence may alternatively be modelled with non linear trends with varying curvature there were also time variant changes in the 13c trend curvature of subfossil tree ring data increasing and diminishing age trend curvatures coincided with palaeoecological indications of denser and thinner pine populations respectively over the study period overall our results highlight the hardships of detecting age related trends in dendroisotope data in comparison to records of tree ring widths and densities the possibility that age related trends are present in dendroisotope data in regions and tree species where such trends may not yet have been detected is underlined

progress in isotope dendroclimatology numerous studies have demonstrated the potential of stableisotopes in tree rings for quantitative terrestrial palaeoclimaticreconstruction ramesh et al 1986 heaton 1999 switsur andwaterhouse 1998 mccarroll and loader 2004 2005 but the earlywidespread application of isotope dendroclimatology has been hin dered by laborious technical procedures that have until recently prevented wider application of this technique and severely con strained progress developments in mass spectrometry preston andowens 1985 barrie et al 1995 filot et al 2006 leuenberger andfilot 2007 and sample preparation techniques leavitt and danzer 1993 loader et al 1997 brendel et al 2000 schulze et al 2004 rinneet al 2005 gaudinskiet al 2005 haverevolutionisedthe eldand enabled development of stable isotope chronologies with aheightened degree of replication gagen et al 2007 and temporalrange treydteetal 2006 thatwaspreviouslynotpracticalandrarelyobserved in any other proxy record outside of dendroclimatology these and associated advances are re ected in the dramatic increasein the number and diversity of isotope tree ring papers presented atrecent international conferences the thirty isotope tree ring paperspresented at the recent 7th international conference on dendrochro nology beijing 11 17june2006 aretrulyinstarkcontrasttothetwodelivered at the 2nd international workshop on global dendroclima tology 1980 long 1982 wigley 1982 in this volume the progressand advances in isotope dendroclimatology are critically reviewed inthe context of the initial work and aspirations of the early pioneers inthis eld and new directions and methodologies are explored dendroclimatology is an established eld of palaeoclimatologyused in its scienti c form since the early 20th century however theapplication of stable isotope techniques to dendroclimatology is morerecent conceptually the seed was planted when urey 1947 statedthat it seems probable that plant carbon compounds synthesised atdifferent temperatures may contain varying amounts of c

sandstone degradation an experimental study of accelerated weathering the investigated rock material belongs to the group of upper cretaceous quader sandstones which are very important construction stones in poland and germany the mineral composition of the rocks is relatively uniform they are quartzose sandstones the most important feature is their good workability and comparatively high weathering resistance still regardless of the apparent resemblance the observations carried on buildings and monuments show differences in weathering processes the undertaken test was an attempt to verify the proposed before rock classification performed on the basis of parameterization of porosimetric cumulative intrusion volume curves the aim of the experiment was the evaluation of the sandstone petrography including the structure texture and porosity of the rock influence on the weathering process the modelling of accelerated weathering was conducted in chamber for ageing acceleration where some weather circumstances were simulated insolation rain and frost as the result of the weathering experiment it could be stated that the dominant mechanism of the sandstones deterioration was granular disintegration and weight loss as a consequence of sample destruction the most important factor influencing rock deterioration is rock texture especially the character of grain contacts the effective porosity is a requisite of potential for the stone to take in and hold water and hence of resistance to weathering in case of silica cemented sandstones the deciding criterion influencing weathering resistance is pore structure in case of sandstones with clay cement the most important is mineral composition of the rock

short lived juvenile effects observed in stable carbon and oxygen isotopes of uk oak trees and historic building timbers abstract stable carbon 13 c and oxygen 18 o isotope ratios were measured on the latewood cellulose of individual oak quercus robur l q petraea liebl samples from living trees and historic building timbers this represents the type of material available to produce long tree ring chronologies for north western europe including the uk and ireland results from the juvenile rings those located closest to the pith were compared with results from equivalent sections representing the same calendar years from independent master isotope chronologies that do not contain any juvenile wood allowing any juvenile offsets and trends to be separated from those caused by environmental change oak timbers from archaeological sources are often relatively short pinus sp would severely constrain the material available for chronology construction the aim of this study was to determine the magnitude and duration of juvenile effects including the detection of trends offsets and their influence upon signal strength the results show clearly that juvenile effects for oak from central england are very small and short lived and that removing merely the first five rings closest to the pith is sufficient to avoid them this result greatly increases the potential for building long and well replicated stable isotope chronologies using archived oak samples from historic building timbers allowing high resolution climate reconstructions to be produced for the highly populated regions where oak is abundant and which are currently under represented in regional palaeoclimate reconstructions

riparian influences on carbon isotopic composition of tree rings in the slave river delta northwest territories canada abstract tree ring cores from two white spruce picea glauca trees at each of three sites within the slave river delta northwest territories canada were separated processed for cellulose and analyzed for their carbon isotope composition the three carbon isotope 13 c cellulose time series collectively covering the time period from 1689 to 2003 were statistically correlated with average historical monthly climate grid temperature and precipitation for the period 1901 2000 the results suggest that the trees from all three sites show a distinct trend towards more enriched 13 c cellulose values with time implying more stressful environmental conditions possibly related to the overall 20th century drying of the slave river delta anthropogenic impacts of heavy logging and the construction of a large upstream dam may also be present in the 13 c cellulose time series the main focus of the study relates to the different nature of the three riparian sites the 13 c cellulose values of the trees from the two sites 50 m from the river at higher elevation suggest a relationship with moisture deficit stress mds emanating from hydroclimate effects during the non growing and growing seasons the 13 c cellulose values from a site adjacent to the river at lower elevation however suggest that these same effects can manifest as moisture excess stress mes on the trees the relationships between these two types of moisture stress and the 13 c cellulose values of the trees from the sites with obvious riparian differences are discussed in detail

tree ring stable carbon isotope based may july temperature reconstruction over nanwutai china for the past century and its record of 20th century warming growth anomaly of trees in some regions was detected under current episode of rapid warming thisraises a dilemma for temperature reconstructions by using tree ring width which is believed to be themost important proxy on inter annual temperature reconstruction during the past millenniums here weemployed the tree ring d13c to reconstruct temperature variations for exploring their potential oncapturing signals of rapid warming and to test how its difference with the tree ring width basedreconstruction in this study the mean mayejuly temperature tmej was reconstructed over the pastcentury by tree ring d13c of chinese pine trees growing in the nanwutai region the explained varianceof the reconstruction was 43 3 42 1 after adjusting the degrees of freedom compared to a ring widthtemperature reconstruction mayejuly from the same site the tree ring d13c based temperaturereconstruction offered two distinct advantages 1 it captured a wider range of temperature variability i e at least mayejuly even over a longer part of the year januaryeseptember and 2 the reconstructionpreserved more low frequency climate information than that of ring width did the 20th century warming was well represented in the nanwutai tree ring d13c temperature reconstruction which implied that stable carbon isotope of tree rings potentially represents temperaturevariations during historical episodes of rapid warming a spatial correlation analysis showed that ourtemperature reconstruction represented climate variations over the entire loess plateau in north centralchina significant positive correlations p 0 1 were found between the temperature reconstruction andenso as well as ssts in the pacific and indian oceans the reconstruction showed the periodicities of22 78 4 16 3 45e3 97 and 2 04e2 83 year quasi cycles at a 95 confidence level our results suggestedthat temperature variability in the nanwutai region may be linked to pacific and indian ocean sstvariations and solar activity less

near surface horizontal convergence and dispersion near the tidal mixing front on northeastern georges bank abstract horizontal dispersion and convergence are evaluated from near surface drifter data collected during the summer and autumn of 1988 and summer of 1989 in the vicinity of the tidal mixing front on northeastern georges bank the effective horizontal diffusivity coefficient k e estimated from the relative motion of the drifters over the duration of the cluster tracking increases as the cluster length scale with a range from approximately 100 to 450 m 2 s 1 for length scales of approximately 5 to 58 km at length scales k e is near zero with many negative estimates indicative of convergence at length scales 20 km k e increases in magnitude and scatter above 30 km length scales k e is typically between 200 400 m 2 s 1 the dispersion as a function of length scale is compared to published estimates using apparent diffusivities which are adjusted for the finite size of the drifter cluster at release georges bank shows lower apparent diffusivities at length scales 20 km the latter are believed to be principally due to the large horizontal gradients in the seasonal flow field although other processes perhaps associated with the large tidal currents may also contribute at the shorter length scales the low dispersion is due to convergent processes examples of convergence at different locations and under different wind and stratification conditions are presented convergence near the tidal mixing front tends to occur under light wind conditions and was observed in both seasons and in both years during two intense southwestward windstorms drifters also converged in the bank s vertically well mixed zone apparently due to a combination of spatially varying ekman depth and topographic effects

influence of earlywood latewood size and isotope differences on long term tree ring δ13c trends abstract inter annual 13 c values of cellulose in two chinese pine trees pinus tabulaeformis carr exhibit a long term decline of more than 2 for the period of 1896 to 1990 ad this decline is much larger than the decrease in atmospheric 13 c caused by industrialization since 1850 ad here we present evidence that long term trends of 13 c 12 c in tree rings also reflect ecophysiological effects superimposed on the anthropogenic trend these effects are associated with the decreasing increasing productivity of earlywood or latewood associated with the changing growth history of the tree theoretical calculations show that long term decreases in the 13 c 12 c ratios in tree rings may be enhanced or reduced by these ecophysiological effects depending on the pattern of seasonal differences in tree ring 13 c values based on seasonal 13 c analyses the influence of these effects on 13 c values for one of these trees hl02 has been removed the corrected data are in agreement with the observed size and timing of the 13 c decline in atmospheric co 2 this study suggests that long term tree ring 13 c data used to infer the anthropogenic impact on atmospheric co 2 carbon isotope compositions may be improved by correcting for possible ecophysiological effects using measurement of latewood and earlywood ring widths and seasonally resolved isotopic analysis removal of growth effects may also benefit the assessment of long term changes in the water use efficiency in response to increasing atmospheric co 2 concentrations

recent observations of the mean circulation on georges bank abstract a clockwise circulation around georges bank was measured by means of moored current meters aircraft tracked surface drifters and satellite tracked drifters drogued at 10 m the strongest flow was in a narrow jetlike current 30 cm s 1 along the northern flank of the bank the flow of shelf water on the southern flank was westward 10 cm s 1 toward the middle atlantic bight some of this water flowed northward through the eastern side of great south channel and recirculated around georges bank the satellite tracked drifters and the moored observations indicate that the circulation around the bank was not completely closed and considerable variability occurs in the trajectory of an individual water particle

mid and late holocene tree population density changes in northern fennoscandia derived by a new method using megafossil pines and their tree ring series changes in tree density are estimated for the northern forest limit region of finnish lapland over the past seven and a half millennia this is done using dendrochronologically dated scots pine megafossils and their tree ring series direct and indirect estimates of past tree density are derived from chronology sample size css and growth trend modelling gtm respectively the latter is a new method where the past levels of growth competition the influence of nearby trees are extracted from the behaviour of growth trends in cross dated tree ring series trends that are expected to be driven by tree density control two records constructed from the same original data set but by different means independently correlate significantly both records show a tree density maximum around 3000 1750 bc indicating relative warmth during that time another positive tree density anomaly occurred in accordance with the medieval warm period preceding the thinning at the forest limit due to the little ice age copyright 2005 john wiley sons ltd

circulation hydrographic structure and mixing at tidal fronts the view from georges bank and discussion the steep slope on the northern side of georges bank and its location in the fundy maine tidal system result in a persistent summertime frontal system comprising a tidal mixing front and a stratified tide topography interaction at the bank edge recent field studies have provided a high resolution description of the circulation hydrographic structure and mixing in the region frontal features include an along front residual jet a surface convergence zone regular variations in frontal structure and position over the tidal period and tidal modulation cycle large amplitude internal waves and strong spatial and temporal variations in small scale turbulence the observations suggest that the magnitude of cross front and vertical exchange in frontal regions can be site specific depending on the relative importance of the underlying physical processes

stable isotope coherence in the earlywood and latewood of tree line conifers abstract annually resolved and replicated tree ring stable isotope series have the potential to reconstruct growing season environmental parameters over multi millennial timescales as this archive may require only minimal statistical detrending it has the potential to preserve a large portion of low frequency climate signals to date many studies have utilised only the latewood portion of the tree ring in an attempt to minimize carry over effects from previous year reserves and maximise the annual nature of the climate signal preserved however the old trees from tree line locations necessary to build long chronologies often display narrow ring widths