asynchronous behavior of outlet glaciers feeding godthabsfjord nuup kangerlua and the triggering of narsap sermia s retreat in sw greenland we thank w dryer and d podrasky for assistance with fieldwork and l kenefic for assisting with digitizing glacier front positions ch2 m hill polar services and air greenland provided logistics support the spot 5 images used for the 2008 dem were provided by the spirit program centre national d etudes spatiales france the digitalglobe worldview images used for the 2014 dem were obtained from p morin terminus positions were derived from landsat images courtesy of the u s geological survey funding was provided by the us national science foundation nsf office of polar programs opp grants nsf plr 0909552 and nsf plr 0909333 cassotto is supported by nasa under the earth and space science fellowship program grant nnx14al29h k k kjeldsen acknowledges support from the danish council research for independent research grant no dff 409000151 k kjaer is thanked for his support during the earlier phases of this study on ice weather stations are operated by geus denmark within the programme for monitoring of the greenland ice sheet promice j mortensen acknowledges support from iiknn greenland defrost project of the nordic centre of excellence program interaction between climate change and the cryosphere and the greenland ecosystem monitoring programme www g e m dk s rysgaard was funded by the canada excellence research chair programme additional funding was provided by the geophysical institute university of alaska fairbanks and greenland climate research centre scientific editor h fricker and reviewers h jiskoot and g cogley provided very constructive feedback that helped improve the paper

onset of recent rapid sea level rise in the western atlantic ocean a high resolution record of sea level change spanning the past 1000 years is derived from foraminiferal and chronological analyses of a 2 m thick salt marsh peat sequence at chezzetcook nova scotia canada former mean tide level positions are reconstructed with a precision of 0 055 m using a transfer function derived from distributions of modern salt marsh foraminifera our age model for the core section older than 300 years is based on 19 ams 14c ages and takes into account the individual probability distributions of calibrated radiocarbon ages the past 300 years is dated by pollen and the isotopes 206pb 207pb 210pb 137cs and 241am between ad 1000 and ad 1800 relative sea level rose at a mean rate of 17 cm per century apparent pre industrial rises of sea level dated at ad 1500 1550 and ad 1700 1800 cannot be clearly distinguished when radiocarbon age errors are taken into account furthermore they may be an artefact of fluctuations in atmospheric 14c production in the 19th century sea level rose at a mean rate of 1 6 mm yr between ad 1900 and ad 1920 sea level rise accelerated to the modern mean rate of 3 2 mm yr this acceleration corresponds in time with global temperature rise and may therefore be associated with recent global warming 2005 elsevier ltd all rights reserved

coupling instrumental and geological records of sea level change evidence from southern new england of an increase in the rate of sea level rise in the late 19th century 1 we construct a high resolution relative sea level record for the past 700 years by dating basal salt marsh peat samples above a glacial erratic in an eastern connecticut salt marsh to test whether or not the apparent recent acceleration in the rate of sea level rise slr is coeval with climate warming the data reveal an average slr rate of 1 0 0 2 mm year from about 1300 to 1850 a d coupling of the regional tide gauge data 1856 to present with this marsh based record indicates that the nearly three fold increase in the regional rate of slr to modern levels likely occurred in the later half of the 19th century thus the timing of the observed slr rate increase is coincident with the onset of climate warming indicating a possible link between historic slr increases and recent temperature increases

implications for sea level research of salt marsh and mudflat accretionary processes along paraglacial barrier coasts abstract paraglacial coastlines with dynamic coarse clastic barrier beaches are common in mid to high latitudes today and have been during the holocene sediments that have been deposited along these coastlines often in back barrier locations have been used to reconstruct relative sea level rsl movements and tendencies usually through the use of sea level index points derived frequently from salt marsh and mudflat deposits however the asymptotic relationship between minerogenic marsh mudflat accretion rates and time will produce regressive stratigraphies with a negative sea level tendency signature even within regimes of rising rsl the influence of gravel barriers on sedimentation will also tend to encourage regressive stratigraphies furthermore organogenic sediment production may release marsh accretion rates from the control of tidal inundation and result in succession to reed swamp despite rsl rise episodic minerogenic sediment supply to the marsh can trigger switches between marsh emergence and submergence which may result in stratigraphic sequences corresponding to negative and positive tendencies of rsl respectively although submergence may be prevented by organogenic sediment supply forcing by rsl rise may result in marsh emergence following initial submergence as a result of renewed accretion on the submerged marsh

the relationship between u s east coast sea level and the atlantic meridional overturning circulation a review scientific and societal interest in the relationship between the atlantic meridional overturning circulation amoc and u s east coast sea level has intensified over the past decade largely due to 1 projected and potentially ongoing enhancement of sea level rise associated with amoc weakening and 2 the potential for observations of u s east coast sea level to inform reconstructions of north atlantic circulation and climate these implications have inspired a wealth of model and observation based analyses here we review this research finding consistent support in numerical models for an antiphase relationship between amoc strength and dynamic sea level however simulations exhibit substantial along coast and intermodel differences in the amplitude of amoc associated dynamic sea level variability observational analyses focusing on shorter generally less than decadal timescales show robust relationships between some components of the north atlantic large scale circulation and coastal sea level variability but the causal relationships between different observational metrics amoc and sea level are often unclear we highlight the importance of existing and future research seeking to understand relationships between amoc and its component currents the role of ageostrophic processes near the coast and the interplay of local and remote forcing such research will help reconcile the results of different numerical simulations with each other and with observations inform the physical origins of covariability and reveal the sensitivity of scaling relationships to forcing timescale and model representation this information will in turn provide a more complete characterization of uncertainty in relevant relationships leading to more robust reconstructions and projections

observed fingerprint of a weakening atlantic ocean overturning circulation the atlantic meridional overturning circulation amoc a system of ocean currents in the north atlantic has a major impact on climate yet its evolution during the industrial era is poorly known owing to a lack of direct current measurements here we provide evidence for a weakening of the amoc by about 3 1 sverdrups around 15 per cent since the mid twentieth century this weakening is revealed by a characteristic spatial and seasonal sea surface temperature fingerprint consisting of a pattern of cooling in the subpolar atlantic ocean and warming in the gulf stream region and is calibrated through an ensemble of model simulations from the cmip5 project we find this fingerprint both in a high resolution climate model in response to increasing atmospheric carbon dioxide concentrations and in the temperature trends observed since the late nineteenth century the pattern can be explained by a slowdown in the amoc and reduced northward heat transport as well as an associated northward shift of the gulf stream comparisons with recent direct measurements from the rapid project and several other studies provide a consistent depiction of record low amoc values in recent years

partly pedogenic origin of magnetic variations in chinese loess quaternary sequences of interbedded aeolian silts loess and buried soils palaeosols potentially provide one of the best terrestrial records of past climates1 5 magnetic susceptibility variations in loess and palaeosol sequences from china are strongly correlated with climate induced fluctuations of oxygen isotope ratios in deep sea sediments2 4 6 8 as an explanation of this correlation it has been suggested that the recorded variations in magnetic susceptibility depend primarily on the degree of dilution by non magnetic bulk loess constituents of a uniform magnetic assemblage derived from remote but unknown sources6 8 it has also been suggested that such a model involving changes in the accumulation rate of loess superimposed on a constant flux of magnetic particles provides a relative geological timescale through the control of loess deposition by astronomically modulated climate fluctuations7 here we report a preliminary test of this model using rock magnetic properties especially sensitive to variations in magnetic grain size our results show that palaeosols are characterized by much finer magnetic grain size assemblages than are the intervening loess units this suggests that a simple model based on constant magnetic influx and dilution by variable amounts of non magnetic loess is inadequate our magnetic measurements establish the close comparability of the fine grained magnetic minerals in the palaeosol samples to those in contemporary soils and thus point to a partially pedogenic origin for the magnetic mineral assemblages in the palaeosols

scale considerations in using diatoms as indicators of sea level change lessons from alaska this paper assesses variations in quantitative reconstructions of late holocene relative sea level rsl change arising from using modern diatom datasets from different spatial scales applied to case studies from alaska we investigate the implications of model choice in transfer functions using local sub regional and regional scale modern training sets and produce recommendations on the creation and selection of modern datasets for reconstructing rsl change over holocene timescales in tidal marsh environments comparable with those in alaska we show that regional modern training sets perform best in terms of providing fossil samples with good modern analogues and in producing reconstructions that most closely match observations where these are available local training sets are frequently insufficient to provide fossil samples with good modern analogues and may over estimate the precision of rsl reconstructions this is particularly apparent when reconstructing rsl change for periods beyond the last century for reconstructing rsl change we recommend using regional modern training sets enhanced by local samples

greenland ice sheet mass balance reconstruction part i net snow accumulation 1600 2009 ice core data are combined with regional atmospheric climate model version 2 racmo2 output 1958 2010 to develop a reconstruction of greenland ice sheet net snow accumulation rate at g spanning the years 1600 2009 regression parameters from regional climate model rcm output regressed on 86 ice cores are used with available cores in a given year resulting in the reconstructed values each core site s residual variance is used to inversely weight the cores respective contributions the interannual amplitude of the reconstructed accumulation rate is damped by the regressions and is thus calibrated to match that of the rcm data uncertainty and significance of changes is measured using statistical models a 12 or 86 gt yr 21 increase in ice sheet accumulation rate is found from the end of the little ice age in 1840 to the last decade of the reconstruction this 1840 1996 trend is 30 higher than that of 1600 2009 suggesting an accelerating accumulation rate the correlation of at g with the average surface air temperature in the northern hemisphere satnht remains positive through time while the correlation of at g with local near surface air temperatures or north atlantic sea surface temperatures is inconsistent suggestinga hemispheric scale climateconnection an annualsensitivityof at g to satnhtof 6 8 k 21 or 51 gt k 21 is found the reconstuction at g correlates consistently highly with the north atlantic oscillation index however at the 11 yr time scale the sign of this correlation flips four times in the 1870 2005 period

stratigraphic analysis of upper cretaceous rocks in the mahajanga basin northwestern madagascar implications for ancient and modern faunas a discussion rogers et al 2000 presented new stratigraphic data on upper cretaceous sedimentary successions in the central mahajanga basin northwest madagascar the results of field studies by the mahajanga basin project team during the 1990s krause et al 1999 the authors focused on identifying and collecting late cretaceous fossils rogers et al 2000 and references therein and attempted to update the rock and time stratigraphy of part of the mahajanga basin in this discussion we wish to demonstrate that rogers et al 2000 provided first an incorrect lithostratigraphic picture second a nonrealistic account of the stratigraphic and depositional evolution of the succession and third only a partial reassessment of the chronostratigraphy of the basin s upper cretaceous deposits

short term variability in late holocene sea ice cover on the east greenland shelf and its driving mechanisms arctic sea ice is a critical component of the climate system as it influences the albedo heat moisture and gas exchange between ocean and atmosphere as well as the ocean s salinity an ideal location to study natural sea ice variability during pre industrial times is the east greenland shelf that underlies the east greenland current egc the main route of arctic sea ice and freshwaters from the arctic ocean into the northern north atlantic here we present a new high resolution biomarker record from the east greenland shelf 73 n which provides new insights into the sea ice variability and accompanying phytoplankton productivity over the past 5 2 kyr our ip25 based sea ice reconstructions and the inferred pip25 index do not reflect the wide spread late holocene neoglacial cooling trend that follows the decreasing solar insolation pattern which we relate to the strong influence of the polar egc on the east greenland shelf and interactions with the adjacent fjord throughout the studied time interval however our reconstructions reveal several oscillations with increasing decreasing sea ice concentrations that are linked to the known late holocene climate cold warm phases i e the roman warm period dark ages cold period medieval climate anomaly and little ice age the observed changes seem to be connected to general ocean atmosphere circulation changes possibly related to north atlantic oscillation and atlantic multidecadal oscillation regimes furthermore we identify a cyclicity of 73 74 years in sea ice algae and phytoplankton productivity over the last 1 2 kyr which may indicate a connection to atlantic multidecadal oscillation mechanisms

binary sources of loess on the chinese loess plateau revealed by u pb ages of zircon the age distribution of detrital zircon has been used to trace sediment sources existing datasets show great similarity of zircon ages between the loess on the chinese loess plateau clp and the sediments from the north tibetan plateau ntp implying that eolian dust is delivered from the ntp to the clp by westerly winds or via the yellow river however ntp dust can also be transported by northwesterly winds from the alxa arid lands aals where materials are received from both the ntp and the gobi altay mountains gams here we report u pb zircon ages for aals sands and ntp and clp loess the results show that the zircons in the aals are mixed from ntp and gams zircons ntp loess is mainly derived from local sources mixing of materials from the ntp and gams defines the zircon ages of the loess on the clp better than the pure ntp source no temporal and spatial heterogeneities of zircon ages have been observed for the loess on the clp which suggests that the well mixed materials in the aals likely have an eolian source

holocene thinning of the greenland ice sheet the nature of the response of the greenland ice sheet gis to climate change is a fundamental question in climate science but the details remain unclear during the holocene climate optimum 6 000 to 9 000 years ago for example many locations in the northern hemisphere showed unusual warmth yet changes in greenland appeared inconsistent vinther et al now standardize the previously disparate seeming ice core records of climate history on the gis during the holocene and find consistent evidence for a stronger climate optimum than was previously recognized together with elevation reduction and marginal ice sheet thinning the response of the greenland ice sheet gis to changes in climate remains uncertain during the holocene climatic optimum an unusually warm period from about 9 000 to 6 000 years ago changes in greenland appear inconsistent with the rest of the northern hemisphere here the greenland holocene temperature history and the evolution of gis surface elevation are extracted from four gis locations the results may resolve this disparity on entering an era of global warming the stability of the greenland ice sheet gis is an important concern1 especially in the light of new evidence of rapidly changing flow and melt conditions at the gis margins2 studying the response of the gis to past climatic change may help to advance our understanding of gis dynamics the previous interpretation of evidence from stable isotopes 18o in water from gis ice cores was that holocene climate variability on the gis differed spatially3 and that a consistent holocene climate optimum the unusually warm period from about 9 000 to 6 000 years ago found in many northern latitude palaeoclimate records4 did not exist here we extract both the greenland holocene temperature history and the evolution of gis surface elevation at four gis locations we achieve this by comparing 18o from gis ice cores3 5 with 18o from ice cores from small marginal icecaps contrary to the earlier interpretation of 18o evidence from ice cores3 6 our new temperature history reveals a pronounced holocene climatic optimum in greenland coinciding with maximum thinning near the gis margins our 18o based results are corroborated by the air content of ice cores a proxy for surface elevation7 state of the art ice sheet models are generally found to be underestimating the extent and changes in gis elevation and area our findings may help to improve the ability of models to reproduce the gis response to holocene climate

timing and climatic drivers for glaciation across semi arid western himalayan tibetan orogen abstract mapping and forty seven new 10 be ages help define the timing of glaciation in the ladakh and pangong ranges in northwest india five new local glacial stages are defined for the ladakh range from oldest to youngest these include the ladakh 4 glacial stage at 81 20 ka the ladakh 3 glacial stage not dated the ladakh 2 glacial stage at 22 3 ka the ladakh 1 glacial stage not dated and the ladakh cirque glacial stage at 1 8 0 4 ka three local glacial stages are defined for the pangong range which include the pangong 2 glacial stage at 85 15 ka the pangong 1 glacial stage at 40 3 ka and the pangong cirque glacial stage at 0 4 0 3 ka the new 10 be ages are combined with 645 recalculated 10 be ages from previous studies to develop the first regional framework of glaciation across the dryland regions of the greater himalaya transhimalaya pamir and tian shan at the western end of the himalayan tibetan orogen nineteen regional glacial stages are recognized that are termed semi arid western himalayan tibetan stages swhts these include swhts 9 at 311 32 ka swhts 7 at 234 44 ka tentative swhts 6 at 146 18 ka swhts 5e at 121 11 ka swhts 5a at 80 5 ka swhts 5a at 72 8 ka swhts 4 at 61 5 ka swhts 3 at 46 4 ka swhts 2f at 30 3 ka swhts 2e at 20 2 ka swhts 2d at 16 9 0 7 ka swhts 2c at 14 9 0 8 ka swhts 2b at 13 9 0 5 ka swhts 2a at 12 2 0 8 ka swhts 1e at 8 8 0 3 ka tentative swhts 1d at 6 9 0 2 ka tentative swhts 1c at 3 8 0 6 ka swhts 1b at 1 7 0 2 ka and swhts 1a at 0 4 0 1 ka regional glacial stages older than 21 ka are broadly correlated with strong monsoons swhts that are 21 ka or younger have smaller uncertainties and broadly correlate with global ice volume given by marine oxygen isotope stages and northern hemisphere climatic events oldest dryas older dryas younger dryas roman humid period and little ice age

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

variations in the difference between mean sea level measured either side of cape hatteras and their relation to the north atlantic oscillation we consider the extent to which the difference in mean sea level msl measured on the north american atlantic coast either side of cape hatteras varies as a consequence of dynamical changes in the ocean caused by fluctuations in the north atlantic oscillation nao from analysis of tide gauge data we know that changes in msl difference and nao index are correlated on decadal to century timescales enabling a scale factor of msl difference change per unit change in nao index to be estimated changes in trend in the nao index have been small during the past few centuries when measured using windows of order 60 120 years therefore if the same scale factor applies through this period of time the corresponding changes in trend in msl difference for the past few centuries should also have been small it is suggested thereby that the sea level records for recent centuries obtained from salt marshes adjusted for long term vertical land movements should have essentially the same nao driven trends south and north of cape hatteras only differing due to contributions from other processes such as changes in the meridional overturning circulation or geophysical fingerprints the salt marsh data evidently support this interpretation within their uncertainties for the past few centuries and perhaps even for the past millennium recommendations are made on how greater insight might be obtained by acquiring more measurements and by improved modelling of the sea level response to wind along the shelf

twentieth century global mean sea level rise is the whole greater than the sum of the parts confidence in projections of global mean sea level rise gmslr depends on an ability to account for gmslr during the twentieth century there are contributions from ocean thermal expansion mass loss from glaciers and ice sheets groundwater extraction and reservoir impoundment progress has been made toward solving the enigma of twentieth century gmslr which is that the observed gmslr has previously been found to exceed the sum of estimated contributions especially for the earlier decades the authors propose the following thermal expansion simulated by climate models may previously have been underestimated because of their not including volcanic forcing in their control state the rate of glacier mass loss was larger than previously estimated and was not smaller in the first half than in the second half of the century the greenland ice sheet could have made a positive contribution throughout the century and groundwater depletion and reservoir impoundment which are of opposite sign may have been approximately equal in magnitude it is possible to reconstruct the time series of gmslr from the quantified contributions apart from a constant residual term which is small enough to be explained as a long term contribution from the antarctic ice sheet the reconstructions account for the observation that the rate of gmslr was not much larger during the last 50 years than during the twentieth century as a whole despite the increasing anthropogenic forcing semiempirical methods for projecting gmslr depend on the existence of a relationship between global climate change and the rate of gmslr but the implication of the authors closure of the budget is that such a relationship is weak or absent during the twentieth century

late holocene salt marsh development under a regime of rapid relative sea level rise chezzetcook inlet nova scotia implications for the interpretation of palaeomarsh sequences pollen data illustrating a 2000 year record of salt marsh development have been obtained from a variety of outer estuarine settings in close proximity to the present gravel dominated coastal barriers at chezzetcook inlet nova scotia the relationship between the biostratigraphic and lithostratigraphic data and relative sea level movement is complex in the outer estuary temporal and spatial changes to the floral and sedimentological composition of the salt marsh reflect principally processes of estuarine and back barrier sedimentation that resulted in steep environmental gradients and the development of regressive marsh sediment complexes despite a relative sea level rise of up to 3 8 mm a during the late holocene our results contrast with those from the inner estuary at chezzetcook inlet where salt marsh has developed only over the last 200 years as a result of sediment inwash due to european land use and followed a prolonged episode approx 5000 years of tidal flat conditions this contrast high

prediction of some weathering trends of plutonic and volcanic rocks based on thermodynamic and kinetic considerations abstract the exposed crust consists mainly of plagioclase 35 quartz 20 k feldspar 11 volcanic glass 12 biotite 8 and muscovite 5 quartz is a resistate thus feldspars and glass represent approximately 75 percent of the labile minerals the weathering characteristics of these constituents are summarized in the context of thermodynamic mass balance and kinetic considerations experimentally determined release rate constants were used to predict the proportions of ca na and k released by feldspars of plutonic rocks granites to gabbros to weathering solutions the chemical weathering trends of the weathered residues calculated from the kinetic data conform closely to the initial trends observed in some recent weathering profiles demonstrating the accuracy of the predictions since the weathering of feldspars is controlled by processes that should not change through geological time the relative release rates of ca na and k from the feldspars of granitic rocks can be calculated for future and past episodes of continental weathering experimentally determined release rate constants are not available for a wide range of volcanic glass compositions but the limited data indicate that compositional trends are predictable in weathering profiles developed on volcanic rocks the kinetic data available for rhyolitic glasses accurately predict the initial weathering trends observed in a recent rhyolite weathering profile

anomalously weak labrador sea convection and atlantic overturning during the past 150 years the atlantic meridional overturning circulation amoc is a system of ocean currents that has an essential role in earth s climate redistributing heat and influencing the carbon cycle1 2 the amoc has been shown to be weakening in recent years 1 this decline may reflect decadal scale variability in convection in the labrador sea but short observational datasets preclude a longer term perspective on the modern state and variability of labrador sea convection and the amoc1 3 5 here we provide several lines of palaeo oceanographic evidence that labrador sea deep convection and the amoc have been anomalously weak over the past 150 years or so since the end of the little ice age lia approximately ad 1850 compared with the preceding 1 500 years our palaeoclimate reconstructions indicate that the transition occurred either as a predominantly abrupt shift towards the end of the lia or as a more gradual continued decline over the past 150 years this ambiguity probably arises from non amoc influences on the various proxies or from the different sensitivities of these proxies to individual components of the amoc we suggest that enhanced freshwater fluxes from the arctic and nordic seas towards the end of the lia sourced from melting glaciers and thickened sea ice that developed earlier in the lia weakened labrador sea convection and the amoc the lack of a subsequent recovery may have resulted from hysteresis or from twentieth century melting of the greenland ice sheet 6 our results suggest that recent decadal variability in labrador sea convection and the amoc has occurred during an atypical weak background state future work should aim to constrain the roles of internal climate variability and early anthropogenic forcing in the amoc weakening described here

plagioclase sub species in chinese loess deposits implications for dust source migration and past climate change plagioclase mineral sub species in the lingtai section in central chinese loess plateau are examined using mineral liberation analyzer techniques showing that loess and paleosol samples exhibit similar patterns in terms of plagioclase feldspar sub species content this suggests that both loess and paleosol units have preserved their primary ca bearing plagioclase compositions of loess source regions weighted average cao in ca bearing plagioclase lies within a narrow range and is equivalent to the average plagioclase composition for upper continental crust this fact supports the hypothesis that chinese loess deposits are the result of a thorough mixing of dust sources the sum of ca bearing plagioclase content exhibits a general increasing trend superimposed by glacial interglacial oscillations in combination with observed plagioclase data in the deserts the variations of ca bearing plagioclase minerals might be used as a proxy for dust source migration and climate changes in the loess source regions furthermore linear relationship between lithogenic magnetic susceptibility ms component input and contents of ca bearing plagioclase in loess units revises a ms proxy for reconstructing paleo monsoon precipitation history the revised ms and plagioclase sub species records help in understanding the mechanism of glaciation across northern tibetan plateau

spatial and glacial interglacial variations in provenance of the chinese loess plateau the chinese loess plateau clp covers an extensive area over 440 000 km2 and provides an unprecedented terrestrial record of neogene climate however it is still unclear whether the provenance of these loess deposits is uniform or contains spatial and temporal differences here this is addressed by comparing detrital zircon age spectra of typical loess and paleosol samples from three distant sites located at the western middle and southeastern parts of the clp our results reveal that the zircon age spectra not only change between loess and paleosol layers but also vary from the western to the eastern clp at least during the last glacial cycle the discrepancies of the zircon age spectra among different sites suggest that the loess provenance of clp is heterogeneous and spatially variable although it has been suggested that the mineralogical elemental and isotopic compositions of loess deposits on clp are highly homogenous spatially and in glacial interglacial cycles

a study of the interaction of the north atlantic oscillation with ocean circulation observed patterns of wind stress curl and air sea heat flux associated with the north atlantic oscillation nao are used to discuss the response of ocean gyres and thermohaline circulation to nao forcing and their possible feedback on the nao the observations motivate and are interpreted in the framework of a simple mathematical model that couples ekman layers ocean gyres and thermohaline circulation to the atmospheric jet stream meridional shifts in the zero wind stress curl line are invoked to drive anomalies in ocean gyres and north south dipoles in air sea flux drive anomalous thermohaline circulation both gyres and thermohaline circulation play a role in modulating sea surface temperature anomalies and hence through air sea interaction the overlying jet stream the model which can be expressed in the form of a delayed oscillator with ocean gyres and or thermohaline circulation providing the delay identifies key nondimensional parameters that control whether the ocean responds passively to nao forcing or actively couples it suggests that both thermohaline circulation and ocean gyres can play a role in coupled interactions on decadal timescales

the use of bomb spike calibration and high precision ams 14c analyses to date salt marsh sediments deposited during the past three centuries abstract a combination of bomb spike calibration and conventional calibration of ams 14c dating has been used to determine a detailed age depth model for a 1 m sediment section collected from a salt marsh in poole harbour southern england these data were compared with the chronology obtained from 210pb analysis and 137cs age markers we report post bomb values of over 1 46 f14c 146 modern 14c and both the rising and falling limbs of the atmospheric bomb spike are identified five pre bomb samples were analysed using multi target high precision 2 ams analysis and after the replicates were combined the one sigma uncertainty was as low as 9 14c yr on some ages these data and an additional three normal precision pre bomb 14c samples were calibrated using calib 5 0 and the chronology constrained using the prior knowledge of independent age markers obtained from the analysis of pollen and spheroidal carbonaceous particle scps no agreement was found between the 14c bomb spike dates and the crs 210pb chronology modelled for this sequence in addition poor agreement was found between the signal of the 1960s weapons test fallout indicated by the 14c bomb spike dates and the timing suggested by the 137cs data this disagreement is attributed to the influence of the local discharge of 137cs from the former ukaea site at winfrith we use our new chronology to confirm the existence of an acceleration in sedimentation rates in poole harbour during the last 100 yr previously reported for this site by long et al long a j scaife r g edwards r j 1999 pine pollen in intertidal sediments from poole harbour uk implications for late holocene sediment accretion rates and sea level rise quaternary international 55 3 16 and conclude that bomb spike 14c calibration dating may offer a more robust alternative to the use of 210pb chronologies for dating sediment deposition in salt marsh environments in addition we demonstrate how the use of high precision ams analysis has the potential for reducing some of the uncertainties involved in the high resolution dating of recent salt marsh sediments

assessing sea level data from connecticut usa using a foraminiferal transfer function for tide level concerns surrounding possible future climate change sea level rise and their potential impacts on coastal environments have stimulated research seeking to elucidate the relationship between ocean levels and climate at the sub century scale the need for increasingly precise reconstructions of relative sea level change has in turn driven the development of new methodologies capable of resolving fine scale variability within salt marsh sedimentary sequences the use of salt marsh foraminifera as precise indicators of past tide levels has played a central role in this process and is exemplified by a number of detailed studies conducted in connecticut usa in this paper we apply the most recent methodological advance in the reconstruction of relative sea levels using salt marsh foraminifera we develop a foraminiferal transfer function for tide level derived from the modern foraminiferal distributions of four connecticut salt marshes in contrast to existing approaches that employ site specific interpolations of local vertical foraminiferal assemblage zones this transfer function can provide objective quantitative and reproducible estimates of palaeomarsh surface elevation with explicitly stated error terms for marshes throughout connecticut irrespective of differences in tidal range we demonstrate the foraminiferal transfer function approach by employing it to reconstruct changes in palaeomarsh surface elevation from three cores recovered from hammock river marsh connecticut the resulting reconstructions which are precise to f0 09 m are tested using an independent dataset from the neighbouring state of maine and are used to assess a pivotal record of mean high water mhw change from this site we conclude that the transfer function reconstructions show good general agreement with previous records of palaeomarsh surface elevation but with the advantages of quantified error terms and a transparent reproducible methodology this replicability will assist in the comparison or combination of local records of mhw change to infer large scale regional sea level variations d 2003 elsevier b v all rights reserved

rapid sea level rise in the gulf of maine usa since ad 1800 two sea level records from salt marshes in coastal maine are derived from foraminiferal analyses and ams 14 c 210 pb 137 cs and pollen chronology both records cover the period from ad 800 until the present and show corresponding patterns of sea level change when corrected for trends which could accommodate millennial scale isostatic adjustments the records provide a detailed sea level chronology for the last few centuries and thus link the instrumental tide gauge record with the long term geological record of sea level change results show that sea level was relatively stable between ad 800 and 1300 and reached a lowstand around ad 1800 which was preceded by an oscillation in the eighteenth century since ad 1800 sea levels in the gulf of maine have risen by 0 3 0 4 m the onset of this rise corresponds with regional climatic warming and could be interpreted as thermal expansion of the gulf of maine and north atlantic sea surface sea level rise possibly slowed temporarily during the mid nineteenth century but twentieth century rates are unprecedented in the last millennium and correspond with hemispheric warming

does the mid atlantic united states sea level acceleration hot spot reflect ocean dynamic variability 1 to test a hypothesized faster than global sea level acceleration along the mid atlantic united states i construct a gaussian process model that decomposes tide gauge data into short term variability and longer term trends and into globally coherent regionally coherent and local components while tide gauge records indicate a faster than global increase in the rate of mid atlantic u s sea level rise beginning 1975 this acceleration could reflect either the start of a long term trend or ocean dynamic variability the acceleration will need to continue for 2 decades before the rate of increase of the sea level difference between the mid atlantic and southeastern u s can be judged as very likely unprecedented by 20th century standards however the difference is correlated with the atlantic multidecadal oscillation north atlantic oscillation and gulf stream north wall indices all of which are currently within the range of past variability

high arctic holocene temperature record from the agassiz ice cap and greenland ice sheet evolution we present a revised and extended high arctic air temperature reconstruction from a single proxy that spans the past 12 000 y up to 2009 ce our reconstruction from the agassiz ice cap ellesmere island canada indicates an earlier and warmer holocene thermal maximum with early holocene temperatures that are 4 5 c warmer compared with a previous reconstruction and regularly exceed contemporary values for a period of 3 000 y our results show that air temperatures in this region are now at their warmest in the past 6 800 7 800 y and that the recent rate of temperature change is unprecedented over the entire holocene the warmer early holocene inferred from the agassiz ice core leads to an estimated 1 km of ice thinning in northwest greenland during the early holocene using the camp century ice core ice modeling results show that this large thinning is consistent with our air temperature reconstruction the modeling results also demonstrate the broader significance of the enhanced warming with a retreat of the northern ice margin behind its present position in the mid holocene and a 25 increase in total greenland ice sheet mass loss 1 4 m sea level equivalent during the last deglaciation both of which have implications for interpreting geodetic measurements of land uplift and gravity changes in northern greenland

a simple model of the decadal response of the ocean to stochastic wind forcing abstract a simple linear model is used to estimate the decadal response of the extratropical ocean to wind stress forcing assuming a flat bottom a mean state at rest and no dissipation the barotropic fields are governed by a time dependent sverdrup balance the baroclinic ones by the long rossby wave equation the ocean is bounded by a coast in the east and a radiation condition is used in the west at each frequency the baroclinic response consists of a forced response plus a rossby wave generated at the eastern boundary for zonally independent forcing the response propagates westward at twice the rossby phase speed the wind stress is assumed to be stochastic with a white frequency spectrum so the model represents the continuous excitation of the ocean interior by the weather fluctuations the model predicts the shape and level of the frequency spectra of the oceanic pressure field and their variation with longitude and latitude the baroclinic response is spread over a continuum of frequencies

correlation of the magnetic susceptibility stratigraphy of chinese loess and the marine oxygen isotope record chronological and palaeoclimatic implications abstract the thick deposits of wind blown silt of the loess plateau in central china constitute arguably the most important terrestrial record of the late pliocene and pleistocene climate magnetic susceptibility stratigraphy has proven extremely useful for quantifying the palaeoclimatic record of chinese loess with intervals of high magnetic susceptibility corresponding to warm humid interglacials and intervals of low susceptibility to cooler drier glacials several workers have noted that the magnetic susceptibility stratigraphy strongly resembles the marine oxygen isotope record for which a high resolution chronology is available from tuning to the frequencies of earth orbital parameters attempts have been made to correlate the two records statistically and we use this approach to generate a new magnetic susceptibility time series for the central chinese loess plateau our results suggest that the two records are sufficiently similar over the interval ca 0 1 5 my bp for this approach to yield a useful age model for loess accumulation spectral analysis of the resulting magnetic susceptibility time series clearly shows that the growth of 100 ky variance which occurs in the marine oxygen isotope record after about 1 my bp also occurs synchronously in the magnetic susceptibility record reinforcing recent suggestions of a strong linkage between the high latitude northern hemisphere and the asian climate we also show that a significant improvement in the strength of the loess magnetic susceptibility marine oxygen isotope correlation occurs after about 1 5 my bp which corresponds to a significant increase in the rate of sediment accumulation across the loess plateau

terminus driven retreat of a major southwest greenland tidewater glacier during the early 19th century insights from glacier reconstructions and numerical modelling tidewater glaciers in greenland experienced widespread retreat during the last century information on their behaviour prior to this is often poorly constrained due to lack of observations while determining the drivers prior to instrumental records is also problematic here we present a record of the dynamics of kangiata nunaata sermia kns southwest greenland from its little ice age maximum liamax to 1859 the period before continuous air temperature observations began at nuuk in 1866 using glacial geomorphology historical accounts photographs and gis analyses we provide evidence kns was at its liamax by 1761 had retreated by 5 km by 1808 and a further 7 km by 1859 this predates retreat at jakobshavn isbrae by 43 113 years demonstrating the asynchroneity of tidewater glacier terminus response following the lia we use a one dimensional flowband model to determine the relative sensitivity of kns to atmospheric and oceanic climate forcing results demonstrate that terminus forcing rather than surface mass balance drove the retreat modelled glacier sensitivity to submarine melt rates is also insufficient to explain the retreat observed however moderate increases in crevasse water depth driving an increase in calving are capable of causing terminus retreat of the observed magnitude and timing

relative sea level change in connecticut usa during the last 2200 yrs we produced a relative sea level rsl reconstruction from connecticut usa spanning the last 2200 yrs that is free from the influence of sediment compaction the reconstruction used a suite of vertically and laterally ordered sediment samples 2 cm above bedrock that were collected by excavating a trench along an evenly sloped bedrock surface paleomarsh elevation was reconstructed using a regional scale transfer function trained on the modern distribution of foraminifera on long island sound salt marshes and supported by bulk sediment 13c measurements the history of sediment accumulation was estimated using an age elevation model constrained by radiocarbon dates and recognition of pollution horizons of known age the rsl reconstruction was combined with regional tide gauge measurements spanning the last 150 yrs before being quantitatively analyzed using an error in variables integrated gaussian process model to identify sea level trends with formal and appropriate treatment of uncertainty and the temporal distribution of data rsl rise was stable 1 mm yr from 200 bce to 1000 ce slowed to a minimum rate of rise 0 41 mm yr at 1400 ce and then accelerated continuously to reach a current rate of 3 2 mm yr which is the fastest century scale rate of the last 2200 yrs change point analysis identified that modern rates of rise in connecticut began at 1850 1886 ce this timing is synchronous with changes recorded at other sites on the u s atlantic coast and is likely the local expression of a global sea level change earlier sea level trends show coherence north of cape hatteras that are contrasted with southern sites this pattern may represent centennial scale variability in the position and or strength of the gulf stream comparison of the new record to three existing and reanalyzed rsl reconstructions from the same site developed using sediment cores indicates that compaction is unlikely to significantly distort rsl reconstructions produced from shallow 2 3 m thick sequences of salt marsh peat

modeling the contribution of m2 tidal amplification to the holocene rise of mean high water in the gulf of maine and the bay of fundy abstract increase in the m2 principal lunar semi diurnal component of the tidal range is an important contributor to the postglacial rise of the high tide level in the gulf of maine and the bay of fundy in addition to relative sea level rise the increase occurred as the shape of this semi enclosed embayment changed with sea level rise and its natural period approached resonance with the m2 tide a three dimensional tide model 3dens predicts the following m2 tidal ranges averaged for the gulf of maine bay of fundy as a percentage of the present range 54 59 at 7000 yrs b p 73 at 5000 yrs b p 78 at 4000 yrs b p 85 at 3000 yrs b p 94 at 2000 yrs b p and 98 at 1000 yrs b p with a predicted sea level rise of 0 15 0 90 m by the year 2100 m2 tidal range may increase 0 3 1 9

middle and late holocene sea level changes in eastern maine reconstructed from foraminiferal saltmarsh stratigraphy and ams 14c dates on basal peat abstract a relative sea level history is reconstructed for machiasport maine spanning the past 6000 calendar years and combining two different methods the first method establishes the long term 10 3 yr trend of sea level rise by dating the base of the holocene saltmarsh peat overlying a pleistocene substrate the second method uses detailed analyses of the foraminiferal stratigraphy of two saltmarsh peat cores to quantify fluctuations superimposed on the long term trend the indicative meaning of the peat the height at which the peat was deposited relative to mean tide level is calculated by a transfer function based on vertical distributions of modern foraminiferal assemblages the chronology is determined from ams 14 c dates on saltmarsh plant fragments embedded in the peat the combination of the two different approaches produces a high resolution replicable sea level record which takes into account the autocompaction of the peat sequence long term mean rates of sea level rise corrected for changes in tidal range are 0 75 mm yr between 6000 and 1500 cal yr b p and 0 43 mm yr during the past 1500 years the foraminiferal stratigraphy reveals several low amplitude fluctuations during a relatively stable period between 1100 and 400 cal yr b p and a sea level rise of 0 5 m during the past 300 years

late holocene sea and land level change on the u s southeastern atlantic coast abstract late holocene relative sea level rsl reconstructions can be used to estimate rates of land level subsidence or uplift change and therefore to modify global sea level projections for regional conditions these reconstructions also provide the long term benchmark against which modern trends are compared and an opportunity to understand the response of sea level to past climate variability to address a spatial absence of late holocene data in florida and georgia we reconstructed 1 3 m of rsl rise in northeastern florida usa during the past 2600 years using plant remains and foraminifera in a dated core of high salt marsh sediment the reconstruction was fused with tide gauge data from nearby fernandina beach which measured 1 91 0 26 mm year of rsl rise since 1900 ce the average rate of rsl rise prior to 1800 ce was 0 41 0 08 mm year assuming negligible change in global mean sea level from meltwater input removal and thermal expansion contraction this sea level history approximates net land level subsidence and geoid change principally from glacio isostatic adjustment historic rates of rise commenced at 1850 1890 ce and it is virtually certain p 0 99 that the average rate of 20th century rsl rise in northeastern florida was faster than during any of the preceding 26 centuries the linearity of rsl rise in florida is in contrast to the variability reconstructed at sites further north on the u s atlantic coast and may suggest a role for ocean dynamic effects in explaining these more variable rsl reconstructions comparison of the difference between reconstructed rates of late holocene rsl rise and historic trends measured by tide gauges indicates that 20th century sea level trends along the u s atlantic coast were not dominated by the characteristic spatial fingerprint of melting of the greenland ice sheet

stratigraphic analysis of upper cretaceous rocks in the mahajanga basin northwestern madagascar implications for ancient and modern faunas abstract upper cretaceous strata of the mahajanga basin northwestern madagascar yield some of the most significant and exquisitely preserved vertebrate fossils known from gondwana the sedimentology of these strata and their stratigraphic relations have been the focus of renewed geological investigations during the course of five expeditions since 1993 we here designate stratotypes and formalize the terrestrial maevarano formation with three new members masorobe anembalemba miadana and the overlying marine berivotra formation the maevarano formation accumulated on a broad semiarid alluvial plain bounded to the southeast by crystalline highlands and to the northwest by the mozambique channel the berivotra formation was deposited in an open marine setting that evolved from a clastic to a carbonate dominated shelf resulting in deposition of the overlying betsiboka limestone of danian age new stratigraphic data clearly indicate that the maevarano formation correlates at least in part with the

integrated high precision analyses of holocene relative sea level changes lessons from the coast of maine a suite of salt marsh peat samples from four sites along the coast of maine wells phippsburg gouldsboro and machiasport has been analyzed using high precision techniques to determine local relative sea level trends and to evaluate proposed along coast warping a spatially variable set of relative sea level records in maine would have important implications for geophysical models that predict the response of the lithosphere during deglaciation and postglacial isostatic relaxation the amplification of m sub 2 tidal range in the gulf of maine and the bay of fundy during the holocene is modeled and applied to the mean high water data yielding best estimate envelopes of mean tide level change for each location average long term thousands of years mean tide level rise did not exceed approx 2 mm yr at any time during the late holocene at wells phippsburg and machiasport between 4 5 and 3 ka calibrated cal the apparent rate of rise at gouldsboro was higher than at any other site studied this along coast variation in the rate of mean tide level rise may reflect time of deglaciation neotectonics or differential isostatic adjustments a slight acceleration of mean tide level rise has occurred during the past millennium in gouldsboro and machiasport if 12 m downwarping inmore easternmost maine occurred as suggested in other publications it must have happened prior to 5 7 ka cal 84 refs 13 figs 8 tabs less

zr rb ratio in the chinese loess sequences and its implication for changes in the east asian winter monsoon strength abstract the long term dust accumulation sequences on the chinese loess plateau clp provide a valuable opportunity to study the evolution of east asian winter monsoon strength grain size of bulk samples of loess deposits though widely used is a modified measure of the strength of winter monsoon wind due to modification by post depositional weathering and pedogenesis this study proposes a new and reliable geochemical climate proxy that records the variability of the east asian winter monsoon on the clp six loess paleosol sections on the plateau were selected for measuring concentrations of the trace elements zr and rb as well as grain size variations of the zr rb ratio in all the sections encompassing the last 130 ka display a generally similar pattern to that of mean grain size of bulk samples mgsb though a positive correlation exists between the zr rb ratio and mgsb the correlation coefficient decreases in southern and eastern sections where intense pedogenesis occurred in the relatively warm and humid climates long term zr rb variation in the lingtai section exhibits amplitudes and frequencies similar to those in mgsb and the mean grain size of quartz particles mgsq accepted as a more reliable proxy than mgsb in the upper loess paleosol sequence over the past 2 6 ma however for the underlying red clay formation in the interval from about 7 2 6 ma b p the mgsb record is relatively stable whereas both the zr rb ratio and mgsq show distinct variability and display amplitudes similar to those observed in the overlying loess paleosol sequence these results demonstrate that the zr rb ratio reflects original eolian grain size and may serve as a reliable index of the strength of east asian winter monsoon winds

relative sea level trends in new york city during the past 1500 years new york city nyc is threatened by 21st century relative sea level rsl rise because it will experience a trend that exceeds the global mean and has high concentrations of low lying infrastructure and socioeconomic activity to provide a long term context for anticipated trends we reconstructed rsl change during the past 1500 years using a core of salt marsh sediment from pelham bay in the bronx foraminifera and bulk sediment 13c values were used as sea level indicators the history of sediment accumulation was established by radiocarbon dating and recognition of pollution and land use trends of known age in down core elemental isotopic and pollen profiles the reconstruction was generated within a bayesian hierarchical model to accommodate multiple proxies and to provide a unified statistical framework for quantifying uncertainty we show that rsl in nyc rose by 1 70 m since 575 ce including 0 38 m since 1850 ce the rate of rsl rise increased markedly at 1812 1913 ce from 1 0 to 2 5 mm y

forcing of recent decadal variability in the equatorial and north indian ocean recent decadal sea surface height ssh variability across the equatorial and north indian ocean enio north of 5 s is spatially coherent and related to a reversal in basin scale upper ocean temperature trends analysis of ocean and forcing fields from a data assimilating ocean synthesis eccov4 suggests that two equally important mechanisms of wind driven heat redistribution within the indian ocean account for a majority of the decadal variability the first is the cross equatorial cell cec forced by zonal wind stress curl at the equator the wind stress curl variability relates to the strength and position of the mascarene high which is influenced by the phase of the indian ocean subtropical dipole the second mechanism is deep 700 m upwelling related to zonal wind stress at the equator that causes deep cross equatorial overturning due to the unique geometry of the basin the cec acts to cool the upper ocean throughout most of the first decade of satellite altimetry while the deep upwelling delays and then amplifies the effect of the cec on ssh during the subsequent decade reversals in the forcing anomalies drive warming of the upper ocean and increasing ssh with the effect of the deep upwelling leading the cec this article is protected by copyright all rights reserved

relative sea level change in greenland during the last 700 yrs and ice sheet response to the little ice age this paper presents new evidence regarding relative sea level rsl changes and vertical land motions at three sites in greenland since 1300 a d a time interval that spans the later part of the medieval climate anomaly mca and the little ice age lia we observe rsl rise at two sites in central west greenland from c 0 80 0 20 m at c 1300 a d to c 0 20 m 0 25 m at c 1600 a d after which rsl slowed and then stabilised at a third site in south greenland we observe rsl rise from c 1 40 0 20 m at c 1400 a d until c 1750 a d after which rsl slowed and was stable during at least the latter part of the 20th century the c 1600 a d rsl slow down seen at the two former sites is surprising because it occurs during the lia when one might expect the ice sheet to be gaining mass and causing rsl to rise we interpret this rsl slowdown to indicate a period of enhanced regional mass loss from central west greenland since c 1600 a d and propose two hypotheses for this loss first a reduction in precipitation during cold and dry conditions and second higher air temperatures and increased peripheral surface melt of the ice sheet from this date onwards the latter hypothesis is compatible with a well established temperature seesaw between western greenland and northern europe and potentially a previously identified shift from a positive to generally more negative nao conditions around 1400 to 1600 a d our study shows how rsl data from greenland can provide constraints on the timing of ice sheet fluctuations in the last millennium and challenges the notion that during cold periods in northern europe the ice sheet in west greenland gained mass

gulf stream s induced sea level rise and variability along the u s mid atlantic coast 1 recent studies indicate that the rates of sea level rise slr along the u s mid atlantic coast have accelerated in recent decades possibly due to a slowdown of the atlantic meridional overturning circulation amoc and its upper branch the gulf stream gs we analyzed the gs elevation gradient obtained from altimeter data the florida current transport obtained from cable measurements the north atlantic oscillation nao index and coastal sea level obtained from 10 tide gauge stations in the chesapeake bay and the mid atlantic coast an empirical mode decomposition hilbert huang transformation emd hht method was used to separate long term trends from oscillating modes the coastal sea level variations were found to be strongly influenced by variations in the gs on timescales ranging from a few months to decades it appears that the gs has shifted from a 6 8 year oscillation cycle to a continuous weakening trend since about 2004 and that this trend may be responsible for recent acceleration in local slr the correlation between long term changes in the coastal sea level and changes in the gs strength was extremely high r 0 85 with more than 99 99 confidence that the correlation is not zero the impact of the gs on slr rates over the past decade seems to be larger in the southern portion of the mid atlantic bight near cape hatteras and is reduced northward along the coast the study suggests that regional coastal sea level rise projections due to climate change must take into account the impact of spatial changes in ocean dynamics

a 17 yr record of sediment accretion in the salt marshes of maine usa abstract marker horizons of brick dust were established in 1986 in 26 salt marshes along the coast of maine usa in 2003 we measured the sediment accumulation rates for the 17 year period in 11 relocated sites and obtained results varying from 1 4 to 4 2 mm yr the mean accretion rate for all marshes was 2 8 mm yr accretion rates measured from 1986 to 2003 were comparable to those measured at the sites in 1987 and 1990 indicating that marsh accretion rates are similar on annual and decadal time scales inorganic material was found to be the primary constituent of maine salt marsh sediments several marshes show clear evidence of transgression since 1986 in the form of landward moving plant zones or encroachment of mudflat onto salt marsh indications for regressive changes were not observed marsh sediment accumulation rates are generally higher than mean rates of relative sea level rise indicating that most salt marshes are currently keeping pace with sea level rise however if relative sea level rise were to exceed rates of 4 mm yr many salt marshes in maine may not survive

sea level change during the last 2500 years in new jersey usa relative sea level changes during the last w2500 years in new jersey usa were reconstructed to test if late holocene sea level was stable or included persistent and distinctive phases of variability foraminifera and bulk sediment d 13 c values were combined to reconstruct paleomarsh elevation with decimeter precision from sequences of salt marsh sediment at two sites using a multi proxy approach the additional paleoenvironmental information provided by bulk sediment d 13 c values reduced vertical uncertainty in the sea level reconstruction by about one third of that estimated from foraminifera alone using a transfer function the history of sediment deposition was constrained by a composite chronology an ageedepth model developed for each core enabled reconstruction of sea level with multi decadal resolution following correction for land level change 1 4 mm yr four successive and sustained multi centennial sea level trends were objectively identified and quantified 95 confidence interval using error in variables change point analysis to account for age and sea level uncertainties from at least 500 bc to 250 ad sea level fell at 0 11 mm yr the second period saw sea level rise at 0 62 mm yr from 250 ad to 733 ad between 733 ad and 1850 ad sea level fell at 0 12 mm yr the reconstructed rate of sea level rise since w1850 ad was 3 1 mm yr and represents the most rapid period of change for at least 2500 years this trend began between 1830 ad and 1873 ad since this change point reconstructed sea level rise is in agreement with regional tide gauge records and exceeds the global average estimate for the 20th century these positive and negative departures from background rates demonstrate that the late holocene sea level was not stable in new jersey

mean sea level variability along the northeast american atlantic coast and the roles of the wind and the overturning circulation the variability in mean sea level msl during 1950 2009 along the northeast american atlantic coast north of cape hatteras has been studied using data from tide gauges and satellite altimetry and information from the liverpool hadley centre lhc ocean model thereby providing new insights into the spatial and temporal scales of the variability although a relationship between sea level and the overturning circulation can be identified an increase of approximately 1 5 cm in msl for a decrease of 1 sv in overturning transport it is the effect of the nearshore wind forcing on the shelf that is found to dominate the interannual sea level variability in particular winds are found to be capable of producing low frequency changes in msl accelerations in a narrow coastal band comparable to those observed by the tide gauges evidence is presented supporting the idea of a common mode of spatially coherent low frequency msl variability both to the north and south of cape hatteras and throughout the northwest atlantic which is associated with large spatial scale density changes from year to year

climatic implications of the s5 paleosol complex on the southernmost chinese loess plateau the s5 is the most prominent paleosol unit in the chinese loess plateau and is distinguished by its great thickness dark color and well developed clay coatings previous studies led to the proposal that the s5 developed under much warmer and wetter conditions than at present implying a climatic optimum however the s5 is a paleosol complex corresponding in time to a period of weak glacial interglacial oscillations as recorded by marine oxygen isotope stages 15 through 13 to understand the character of this climatic interval two profiles of the paleosol s5 in the guanzhong basin were studied with most of the emphasis being placed on the uppermost and best developed pedon s5 i grain size mineralogical and chemical data indicate that the major pedogenic processes experienced by the s5 i included complete decalcification and mechanical translocation of fine particles chemical alteration of silicate minerals has been weak stable carbon isotope analyses of organic matter showed that c4 plant remains are abundant throughout the profiles these results suggest that grasslands dominated the paleovegetation during s5 i development the prominent development of the s5 paleosol complex may reflect a prolonged period of pedogenesis in contrast to previous reports paleoclimatic conditions perhaps even drier than at present are implied by the data for the s5 profiles the relative strength of the glacial interglacial oscillation in this region related to the east asian monsoon was similar to that indicated for global climate during s5 time

oceanic control of sea level rise patterns along the east coast of the united states 1 along the eastern seaboard of the u s from florida to maine sea level rise slr shows notable patterns and significant deviation from the global mean which have been attributed to land subsidence consistent with several recent studies we analyze various observation and modeling data and find that ocean dynamics is also an important factor in explaining these coastal slr patterns despite a southward shift since the 1990s an overall northward shift of the gulf stream during the twentieth century contributed to the faster slr in the mid atlantic region north carolina to new jersey in response to the 21st century climatic forcing the rise fall of the dynamic sea level north south of cape hatteras is mainly induced by the significant decline of ocean density contrast across the gulf stream this baroclinic process is the likely cause of the recent switch of the coastal slr to a pattern with faster slower rates north south of cape hatteras citation yin j and p b goddard 2013 oceanic control of sea level rise patterns along the east coast of the united states geophys res lett 40 doi 10 1002 2013gl057992

isotopic record of lead pollution in lake sediments from the northeastern united states abstract although it is common knowledge that pb concentrations have increased in lake sediments in the northeastern united states over the last 150 years the processes responsible have been the subject of debate in this study differences in lead isotopic compositions and concentrations in sediment from large lakes lake erie ontario and michigan and small ones deep lake and lake andrus are used to infer temporal changes in the source s of anthropogenic pb in the great lakes region a natural background component of pb is present in sediment deposited prior to 1860 in lake erie and the other lakes as indicated from low pb concentrations and uniform lead isotopic compositions changes in isotopic ratios of lake sediment reflect differing sources of anthropogenic pb superimposed on the natural component such as regional deforestation from 1860 1890 followed by coal combustion and ore smelting through 1930 combustion of leaded gasoline was the dominant anthropogenic pb source to the atmosphere and by inference to lake sediment from 1930 1980 temporal changes in lead isotopic compositions in lake sediment suggest that the source of the pb used in gasoline additives gradually changed from 1930 to present the best example is a distinct shift in lead isotopic ratios in lake sediment deposited after 1970 which corresponds to increased pb production from the viburnum trend deposits in missouri present in all lakes except ontario however the changes in lead isotopic compositions are much less variable than and do not parallel those calculated on the basis of annual united states mine production and imports rather anthropogenic recycling of pb as well as natural mixing processes during emission transport and deposition of pb in lake sediment control most of the variation in lead isotope ratios differences in lead isotopic ratios in lake michigan erie and deep lake sediment preserve regional differences in lead isotopic ratios from u s and canadian sources first noted in aerosols by sturges and barrie 1987 more localized sources of pb such as point discharges are needed to explain the results from lake ontario and andrus

ocean gyre circulation changes associated with the north atlantic oscillation abstract observational evidence is presented for interannual to interdecadal variability in the intensity of the north atlantic gyre circulation related to the atmospheric north atlantic oscillation nao patterns a two point baroclinic pressure difference between the subtropical and subpolar gyre centers an oceanic analogue to the much used sea level pressure slp based atmospheric nao indices is constructed from time series of potential energy anomaly pea derived from hydrographic measurements in the labrador basin and at station s near bermuda representing the upper 2000 db eastward baroclinic mass transport between the two centers the transport index indicates a gulf stream and north atlantic current that gradually weakened during the low nao period of the 1960s and then intensified in the subsequent 25 years of persistently high nao to a record peak in the 1990s the peak to peak amplitude difference was 15 20 megatons per second mt s 1 with a 43 yr mean of about 60 mt s 1 a change of 25 33

quaternary glaciation of the bailang river valley qilian shan abstract the qilian shan on the northeast margin of the qinghai tibetan plateau is weakly influenced by the asian monsoon until recently the quaternary glacial geology of this region has been poorly understood this paper describes a sequence of quaternary glacial deposits in the upper reaches of the bailang river using electron spin resonance esr thermoluminescence tl and radiocarbon dating tills loess buried soils and landforms were dated the oldest till was dated 463 ka bp by esr a younger till and its outwash terrace were dated to 135 and 130 ka bp the loess on this outwash terrace was dated to 141 7 11 4 ka bp at its base and 43 7 3 5 ka bp in its central part by tl dating a buried soil on a younger till was dated at 6920 78 ka bp using 14c the glacial landforms and these dating results show that glacial advances occurred during the little ice age the neoglacial mis 2 4 mis 6 and mis 12 glaciation during mis 12 implies that the qilian mountains were rising coevally with the qinghai tibetan plateau and were probably at a sufficient elevation for glaciation since at least 463 ka bp

late holocene sea level changes and isostatic crustal movements in atlantic canada abstract it has long been recognised that sea levels along the shores of atlantic canada have been rising rapidly during the holocene in response to isostatic crustal movements new sea level data for the bay of fundy coast of southern new brunswick little dipper harbour and the atlantic coast of nova scotia chezzetcook inlet show that late holocene average rates of sea level rise in these areas have been 1 0 and 2 5 m per 1000 yr respectively numerical model calculations suggest that the high rates of sea level rise are due to crustal subsidence produced by the combined effects of laurentide ice loading forebulge collapse and ocean loading of the scotian shelf although ice loading is the dominant contributor to the regional sea level pattern ocean loading is also important contributing up to 40 of the total crustal subsidence in some areas tide gauges record rates of sea level rise during the 20th century that are 0 7 1 9 mm yr higher than late holocene trends with the highest residuals occurring in the bay of fundy

sea level changes in iceland and the influence of the north atlantic oscillation during the last half millennium abstract we present a new diatom based sea level reconstruction for iceland spanning the last 500 years and investigate the possible mechanisms driving the sea level changes a sea level reconstruction from near the icelandic low pressure system is important as it can improve understanding of ocean atmosphere forcing on north atlantic sea level variability over multi decadal to centennial timescales our reconstruction is from vi arholmi salt marsh in snaefellsnes in western iceland a site from where we previously obtained a 2000 yr record based upon less precise sea level indicators salt marsh foraminifera the 20th century part of our record is corroborated by tide gauge data from reykjavik overall the new reconstruction shows ca 0 6 m rise of relative sea level during the last four centuries of which ca 0 2 m occurred during the 20th century low amplitude and high frequency sea level variability is super imposed on the pre industrial long term rising trend of 0 65 m per 1000 years most of the relative sea level rise occurred in three distinct periods ad 1620 1650 ad 1780 1850 and ad 1950 2000 with maximum rates of 3 2 mm yr during the latter two of these periods maximum rates were achieved at the end of large shifts from negative to positive of the winter north atlantic oscillation nao index as reconstructed from proxy data instrumental data demonstrate that a strong and sustained positive nao a deep icelandic low generates setup on the west coast of iceland resulting in rising sea levels there is no strong evidence that the periods of rapid sea level rise were caused by ocean mass changes glacial isostatic adjustment or regional steric change we suggest that wind forcing plays an important role in causing regional scale coastal sea level variability in the north atlantic not only on multi annual timescales but also on multi decadal to centennial timescales

holocene sea level database for the atlantic coast of the united states we have constructed a database of holocene relative sea level rsl observations for the atlantic coast of the united states the database contains 492 index points which locate the position of rsl in time and space and 344 limiting dates which constrain the minimum or maximum limit of former sea level the majority of the index points in the database are from 6 ka bp to present with only 7 older than 6 ka bp spatially index points are distributed between maine and south carolina but there is an absence of data from georgia and the atlantic coast of florida the database is sub divided into 16 regions based on the distance from the former laurentide ice sheet and are classified depending upon their susceptibility to compaction the index points and limiting data demonstrate that rsl did not exceed present 0 m during the holocene except potentially in regions 1 and 2 eastern maine and southern maine rates of rsl change were highest during the early holocene and have decreased over time due to the diminishing response of the earth s mantle to glacial isostatic adjustment and reduction of ice equivalent meltwater input along the atlantic coast of the united states the linear rate of rsl rise prior to 4 ka bp ranged from 0 5 to 4 5 mm a 1 compared to 0 6 1 8 mm a 1 from 4 ka bp to ad 1900 the database suggests minimal 0 3 mm yr changes in these rates of rsl rise during the late holocene deglaciation of the laurentide ice sheet caused the spatial variability captured by the database the maximum rate of late holocene and ongoing rsl rise occurred in mid atlantic regions new jersey and inner delaware because of collapse of the peripheral forebulge

arctic holocene glacier fluctuations reconstructed from lake sediments at mitrahalvoya spitsbergen the arctic region has experienced a significantly larger warming during the last decades compared to the rest of the world and model simulations indicate a continued amplification of future global warming in the polar regions a better understanding of natural climate variability in the arctic is much needed to provide a better context for the observed warming trend by utilising proxy data it is possible to obtain palaeoclimatic records beyond the range of instrumental observations which increase our understanding of long term arctic climate change here a continuous record of past changes in equilibriumline altitude ela has been reconstructed for the alpine glacier karlbreen located on the northwest coast of spitsbergen 79 n based on sediment analyses from a distal glacier fed lake a multivariate statistical analysis suggests that the concentration of geochemical elements ti si and k in the lake sediments together with the physical parameter dry bulk density dbd reflect changes in the amount of inorganic detrital input to klosa which is closely linked to the size and ela of the upstream glacier karlbreen a linear regression model based on historically documented glacier extents was used to calculate continuous ela changes back to 3500 cal yr bp from about 9200 to 3500 cal yr bp the sedimentary record indicates that karlbreen was very small or had completely melted away karlbreen was probably close to its maximum holocene extent several times during the neoglacial first around 1700 cal yr bp then later at 225 and 135 cal yr bp an ice cored moraine system in front of karlbreen extends well into the main basin of klosa and it is difficult to explain how this moraine could have formed without disturbing the sedimentary record in the lake e g through slumping events the sedimentary record in klosa is continuous and undisturbed over the past 6700 years suggesting that the outermost moraine formed prior to this time and that it most likely survived the holocene thermal maximum on svalbard

neotectonic history of eastern maine evaluated from historic sea level data and 14c dates on salt marsh peats we constructed a local relative sea level curve for eastern maine from 14 c dates on salt marsh peats to evaluate potential holocene neotectonic activity this sea level chronology indicates that contrary to suggestions made previously low elevations of late glacial shoreline features in eastern maine are not related to neotectonic activity during the past 5 ka a comparison between seismicity and tide gauge records leads to the conclusion that there is no relation between seismic activity and contemporary subsidence of eastern coastal maine we propose that eastern maine has not been affected by anomalous subsidence during at least the past 5 ka

origin of spatial variation in us east coast sea level trends during 1900 2017 identifying the causes of historical trends in relative sea level the height of the sea surface relative to earth s crust is a prerequisite for predicting future changes rates of change along the eastern coast of the usa the us east coast during the past century were spatially variable and relative sea level rose faster along the mid atlantic bight than along the south atlantic bight and the gulf of maine past studies suggest that earth s ongoing response to the last deglaciation1 5 surface redistribution of ice and water5 9 and changes in ocean circulation9 13 contributed considerably to this large scale spatial pattern here we analyse instrumental data14 15 and proxy reconstructions4 12 using probabilistic methods16 18 to show that vertical motions of earth s crust exerted the dominant control on regional spatial differences in relative sea level trends along the us east coast during 1900 2017 explaining most of the large scale spatial variance rates of coastal subsidence caused by ongoing relaxation of the peripheral forebulge associated with the last deglaciation are strongest near north carolina maryland and virginia such structure indicates that earth s elastic lithosphere is thicker than has been assumed in other models19 22 we also find a substantial coastal gradient in relative sea level trends over this period that is unrelated to deglaciation and suggests contributions from twentieth century redistribution of ice and water our results indicate that the majority of large scale spatial variation in long term rates of relative sea level rise on the us east coast is due to geological processes that will persist at similar rates for centuries vertical motions of earth s crust had the greatest effect on regional spatial differences in relative sea level trends along the eastern coast of the usa during 1900 2017 explaining most of the large scale spatial variance in regional rates of sea level rise

using foraminiferal transfer functions to produce high resolution sea level records from salt marsh deposits maine usa quantitative analyses of foraminiferal distributions along the coast of maine are used to provide transfer functions for reconstruction of sea level changes from fossil foraminiferal assemblages the indicative meaning of fossil assemblages is most accurately predicted by a training set that incorporates live and dead foraminifera and that uses flooding duration not height as the predictor variable sea level records are produced for two sites in maine usa a middle marsh site in scarboro and a high marsh site in machiasport these records offer temporal resolution of five to seven years and span the past century they are compared with instrumental data from a nearby tidal station to assess their accuracy strong correlations are found between the geologic records and the observational data in particular between the foraminiferal record from machiasport and the tide gauge record from eastport r2 0 83 p 0 005 thus a foraminifera based transfer function approach offers great potential for reso