a flexible approach to assessing synchroneity of past events using bayesian reconstructions of sedimentation history the dating of depths in two or more cores is frequently followed by a study of the synchroneity or otherwise of events reflected in the cores the difficulties most frequently encountered are a determining precisely the depths associated with the events and b determining the ages associated with the depths there has been much progress in recent years in developing tools for the study of uncertainties in establishing chronologies this has not yet been matched by similar progress in modelling event depth relationships this paper proposes a simple and flexible approach showing how uncertain events can be married to uncertain chronologies difficulties in studying event depth age relationships typically involve a confounding of two different problems first what exactly do we mean by an event a point in history a single depth in the core corresponding to a single time or a depth time range sometimes event is in fact a shorthand for a space time process do the data reflect more than one type of event process this can reflect vagueness in definition second what are the sources and implications of the uncertainties here we illustrate the issues involved by examination of several features seen in north european holocene pollen records the alnus rise is regarded as a diachronous early holocene event in contrast the ulmus decline is widely seen as a near synchronous event in the mid holocene the third feature we examine is the interval between the ulmus decline and the first occurrence of cerealia type pollen the evidence for these events lies in cores of lake sediment from which are determined a the proportions of pollen at many depths and b radiocarbon age estimates from usually fewer depths for this illustration we focus on six sites we draw attention to a new and flexible method implemented in the free r software package bchron haslett j parnell a 2008 a simple monotone process with application to radiocarbon dated depth chronologies journal of the royal statistical society series c 57 4 399 418 for the establishment of the uncertainties surrounding the dating of samples in such cores we illustrate its flexibility by assessing the synchroneity of past events

regional patterns of sea level change related to interannual variability and multidecadal trends in the atlantic meridional overturning circulation some studies of ocean climate model experiments suggest that regional changes in dynamic sea level could provide a valuable indicator of trends in the strength of the atlantic meridional overturning circulation moc this paper describes the use of a sequence of global ocean ice model experiments to show that the diagnosed patterns of sea surface height ssh anomalies associated with changes in the moc in the north atlantic na depend critically on the time scales of interest model hindcast simulations for 1958 2004 reproduce the observed pattern of ssh variability with extrema occurring along the gulf stream gs and in the subpolar gyre spg but they also show that the pattern is primarily related to the wind driven variability of moc and gyre circulation on interannual time scales it is reflected also in the leading eof of ssh variability over the na ocean as described in previous studies the pattern however is not useful as a fingerprint of longer term changes in the moc as shown with a companion experiment a multidecadal gradual decline in the moc of 5 sv 1 sv 106 m3 s 1 over 5 decades induces a much broader basin scale ssh rise over the mid to high latitude na with amplitudes of 20 cm the detectability of such a trend is low along the gs since low frequency ssh changes are effectively masked here by strong variability on shorter time scales more favorable signal to noise ratios are found in the spg and the eastern na where a moc trend of 0 1 sv yr 1 would leave a significant imprint in ssh already after about 20 years

estimating tectonic uplift of the cape fear arch south eastern united states using reconstructions of holocene relative sea level we use relative sea level rsl reconstructions and a spatiotemporal statistical model to estimate the rate of uplift of the cape fear arch a mesozoic structural high during the last 4000 years we reconstructed rsl using 12 radiocarbon dated samples of basal salt marsh sediment preserved at elizabeth creek marsh on the cape fear river the new data show that rsl rose by 3m during the past 4 6 ka at an average rate of 0 67 0 12mm a 1 rsl reconstructions from other sites in southern north carolina which have rates of 0 91 0 10 to 0 84 0 24mm a 1 probably show p 0 9 higher rates of regional rsl rise for the same period while sites from northern south carolina which have rates of 0 72 0 17 to 0 80 0 21mm a 1 probably p 0 67 show the same we attribute the differences between elizabeth creek marsh and neighboring regions to uplift of the cape fear arch which we estimate to be 0 24 0 15mm a 1 uplift of the arch may be responsible for lower rates of 20 th century rsl rise recorded by the wilmington tide gauge relative to rates measured elsewhere along the us mid atlantic coast copyright 2014 john wiley sons ltd

seismicity patterns in the himalayan plate boundary and identification of the areas of high seismic potential abstract space time distribution of earthquakes along the himalayan plate boundary has been investigated with a view to discerning fluctuations in seismicity rates associated with great earthquakes the possibilities of epicentre migration and gaps in seismic activity data from 1800 to 1976 were considered this study shows that all great earthquakes m 8 0 were preceded by seismically quiescent periods of at least 19 years furthermore earthquake quiescence has also been recognised to follow the great earthquakes three possible trends of migration of epicentres of great earthquakes have been recognised 1 1 the first trend starts from the 1905 kangra earthquake the epicentres of subsequent earthquakes migrating eastwards along the plate boundary 2 2 the second trend of migration starts from the great nepal earthquake of 1833 associated with eastward migration 3 3 the third trend commences from the great assam earthquake of 1897 and shows a westward migration of earthquake epicentres the middle section of the himalayan convergent plate boundary 80 e to 90 e in general displays a relatively low level of seismicity as compared to the adjacent sections a remarkable decrease in seismicity following the year 1970 has been observed along a section of the himalaya which lies to the east of the rupture zone of the great 1905 kangra earthquake since 1970 the seismicity rate has also dropped in the region lying in between the rupture zones of the great assam earthquakes of 1897 and 1950 as has earlier been reported by khattri and wyss 1978 such decreases in the level of seismicity along active plate boundaries have been demonstrated to be indicative of building up of stresses leading to future great earthquakes mogi 1969 mccann et al 1979

intermediate depth earthquakes in a region of continental convergence south island new zealand it is rare to find earthquakes with depths greater than 30 km in continent continent collision zones because the mantle lithosphere is usually too hot to enable brittle failure however a handful of small intermediate depth earthquakes 30 97 km have been recorded in the continental collision region in central south island new zealand the earthquakes are not associated with subduction but all lie within or on the margins of thickened crust or uppermost mantle seismic high velocity anomalies the largest of the earthquakes has m l 4 0 corresponding to a rupture radius of between 100 and 800 m providing bounds on the upper limit to the rupture length over which brittle failure is taking place in the deep brittle plastic transition zone the earthquake sources may be controlled by large shear strain gradients associated with viscous deformation processes in addition to depressed geotherms

persistent solar influence on north atlantic climate during the holocene surface winds and surface ocean hydrography in the subpolar north atlantic appear to have been influenced by variations in solar output through the entire holocene the evidence comes from a close correlation between inferred changes in production rates of the cosmogenic nuclides carbon 14 and beryllium 10 and centennial to millennial time scale changes in proxies of drift ice measured in deep sea sediment cores a solar forcing mechanism therefore may underlie at least the holocene segment of the north atlantic9s 1500 year cycle the surface hydrographic changes may have affected production of north atlantic deep water potentially providing an additional mechanism for amplifying the solar signals and transmitting them globally

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

revisiting the earthquake sources in the himalaya perspectives on past seismicity abstract the 2500 km long himalaya plate boundary experienced three great earthquakes during the past century but none of them generated any surface rupture the segments between the 1905 1934 and the 1897 1950 sources known as the central and assam seismic gaps respectively have long been considered holding potential for future great earthquakes this paper addresses two issues concerning earthquakes along the himalaya plate boundary one the absence of surface rupture associated with the great earthquakes vis a vis the purported large slip observed from paleoseismological investigations and two the current understanding of the status of the seismic gaps in the central himalaya and assam in view of the paleoseismological and historical data being gathered we suggest that the ruptures of earthquakes nucleating on the basal detachment are likely to be restricted by the crustal ramps and thus generate no surface ruptures whereas those originating on the faults within the wedges promote upward propagation of rupture and displacement as observed during the 2005 kashmir earthquake that showed a peak offset of 7 m the occasional reactivation of these thrust systems within the duplex zone may also be responsible for the observed temporal and spatial clustering of earthquakes in the himalaya observations presented in this paper suggest that the last major earthquake in the central himalaya occurred during ad 1119 1292 rather than in 1505 as suggested in some previous studies and thus the gap in the plate boundary events is real as for the northwestern himalaya seismically generated sedimentary features identified in the 1950 source region are generally younger than ad 1400 and evidence for older events is sketchy the 1897 shillong earthquake is not a decollement event and its predecessor is probably 1000 years old compared to the central himalaya the assam gap is a corridor of low seismicity between two tectonically independent seismogenic source zones that cannot be considered as a seismic gap in the conventional sense

holocene sea level variability from chesapeake bay tidal marshes usa we reconstructed the last 10 000 years of holocene relative sea level rise rslr from sediment core records near chesapeake bay eastern united states including new marsh records from the potomac

earthquake frequency distribution and the mechanics of faulting the level of intraplate seismicity in japan generally shows a positive correlation with the density of quaternary faulting in southwest japan where intraplate seismicity is concentrated on land rates of seismic moment release m 0 are similar when calculated from either the 400 year historical record of seismicity or geologically determined slip rates of quaternary faults a data set of 18 earthquakes with seismic moments m0 ranging from 0 01 to 3 1027 dyn cm shows a relationship between rupture lengthl and m0 log m0 23 5 1 94 log l when seismic moment on each quaternary fault is assumed to occur in discrete events every t m0 m 0g years where m0 is estimated for a rupture extended over the entire fault length and m 0g is proportional to the slip rate of each quaternary fault the moment frequency distribution of earthquakes log n a b log m0 predicted from the geologic record is virtually identical to that seen with the 400 year record of seismicity in contrast if it is assumed that earthquakes on each fault occur according to the gutenberg richter relation we obtain poor agreement with the observed seismicity thus while regional seismicity satisfies the relation log n a b log m0 or equivalently log n a b log m where m is magnitude it appears that seismicity on individual faults does not this further implies that the primary factor that leads to the magnitude frequency distribution in regional seismicity studies is the relative distribution of the slip rates and lengths of preexisting faults

reassessing transfer function performance in sea level reconstruction based on benthic salt marsh foraminifera from the atlantic coast of ne north america abstract the need to increase the number and distribution of sea level records spanning the last few hundred years has led to particular interest in developing high precision geologically based sea level reconstructions that capture decimetre and multi decadal scale changes transfer functions for tide level are statistical tools that quantify the vertical relationship between inter tidal microfossils and elevation within the tidal frame and their use in sea level reconstruction is growing in popularity whilst a range of sampling strategies dataset qualities and underlying statistical models have been used in transfer function development all variants share the common requirement of accurately extracting precise species elevation relationships from surface data and reliably applying these to fossil assemblages to infer past conditions we present surface foraminiferal data from six transects sampled at three sites spanning a large latitudinal range extending from newfoundland canada to north carolina usa these data demonstrate that significant spatial differences exist within the high marsh foraminiferal assemblages commonly used to reconstruct past relative sea level rsl we standardise these data to account for inter site differences in tidal range using several variants of the standardised water level index swli of horton et al 1999b and show that the best performance is achieved by using the highest occurrence of foraminifera as the upper tidal datum level the standardised surface foraminiferal data are used to develop a suite of foraminiferal transfer functions for tide level which are then applied to fossil assemblages from two sediment cores to reconstruct palaeomarsh surface elevation we highlight the manner in which species elevation relationships are extracted and modified during transfer function development and the impacts that choices in dataset composition and transfer function type have on the resulting reconstructions our results graphically illustrate the importance of these choices and the impacts of temporal and spatial variability in foraminiferal distributions none of which are adequately represented or discernible from the standard summary statistics of performance that commonly accompany transfer function reconstructions we conclude that a more explicit treatment of the transfer function development process is required to support the growing body of precise rsl reconstructions that are now appearing in the literature to that end we make the following four recommendations for a framework to assist in transfer function development that will allow better record inter comparison and minimise the potential for producing precise but ultimately inaccurate reconstructions 1 sampling for surface data should focus on capturing complete species response curves rather than simply compiling modern analogues for fossil material 2 the similarity between the surface assemblages used to produce transfer functions and the fossil assemblages to which they are applied should be better quantified using a range of statistical approaches and must accompany any reconstruction 3 where modern analogues are lacking in local surface assemblages data from additional sites should be added with selection based on fulfilling the requirements of the previous two recommendations the manner in which individual species optima are combined to produce a composite optimum and the extent to which this provides a reasonable representation of the surface data should also be documented 4 the application of wa pls component 2 and higher cannot be justified solely on the grounds of increased performance measures e g r2jack and rmsep and if applied the pattern of optima updates should be used to highlight species that may distort reconstructions

geological characteristics and spatial distribution of paleo inlet channels beneath the outer banks barrier islands north carolina usa abstract nearly 200 km of high resolution ground penetrating radar gpr data were acquired along the outer banks barrier island system of north carolina usa gpr data combined with lithofacies and biofacies data reveal multiple depositional facies including inlet channel flood tide delta overwash peat and inner shelf previously undocumented paleo inlet channels constitute a significant portion of the shallow geologic framework between oregon inlet and cape hatteras gpr data reveal the complex stratigraphy associated with multiple sequences of cut and fill within inlet channels two types of paleochannels non migrating and migrating were classified based on geometry and fill patterns sediments and foraminifera collected from vibracores were correlated to gpr data to define the regional shallow stratigraphic framework channel fill facies are characterized by clinoform packages sometimes bounded by erosional surfaces indicating variable sediment transport directions from the ocean and sound sides channels are incised into older flood tide delta deposits corresponding to older inlet activity when barriers existed further seaward flood tide delta deposits are capped with marsh peat and overwash units migrating inlet facies occur under the widest portions of the island whereas narrow portions of the island are underlain by the non migrating inlet facies or flood tide delta overwash facies this geologic geomorphic relationship is attributed to the successional stage of island evolution during transgression and sediment transport processes associated with the different inlet types the radar facies lithofacies and biofacies provide a comprehensive dataset that will permit more precise identification of barrier island facies in the geologic record

quantifying the contribution of sediment compaction to late holocene salt marsh sea level reconstructions north carolina usa abstract salt marsh sediments provide accurate and precise reconstructions of late holocene relative sea level changes however compaction of salt marsh stratigraphies can cause post depositional lowering pdl of the samples used to reconstruct sea level creating an estimation of former sea level that is too low and a rate of rise that is too great we estimated the contribution of compaction to late holocene sea level trends reconstructed at tump point north carolina usa we used a geotechnical model that was empirically calibrated by performing tests on surface sediments from modern depositional environments analogous to those encountered in the sediment core the model generated depth specific estimates of pdl allowing samples to be returned to their depositional altitudes after removing an estimate of land level change error in variables changepoint analysis of the decompacted and original sea level reconstructions identified three trends compaction did not generate artificial sea level trends and cannot be invoked as a causal mechanism for the features in the tump point record the maximum relative contribution of compaction to reconstructed sea level change was 12 the decompacted sea level record shows 1 71 mm yr 1 of rise since ad 1845

the little ice age and medieval warm period in the sargasso sea sea surface temperature sst salinity and flux of terrigenous material oscillated on millennial time scales in the pleistocene north atlantic but there are few records of holocene variability because of high rates of sediment accumulation holocene oscillations are well documented in the northern sargasso sea results from a radiocarbondated box core show that sst was approximately 1 degree c cooler than today approximately 400 years ago the little ice age and 1700 years ago and approximately 1 degree c warmer than today 1000 years ago the medieval warm period thus at least some of the warming since the little ice age appears to be part of a natural oscillation 39 refs 4 figs 1 tab

can long term variability in the gulf stream transport be inferred from sea level recent studies by sturges and collaborators suggest a simple but powerful technique to estimate climatic changes in the transport of the gulf stream from the difference between the oceanic sea level calculated with a simple wind driven rossby wave model and the observed coastal sea level the hypothesis behind this technique is tested using 40 years of data 1950 to 1989 obtained from a three dimensional atlantic ocean model forced by observed surface data the analysis shows that variations in sea level difference between the ocean and the coast are indeed coherent with variations of the gulf stream transport for periods shorter than 1 year or longer than 4 5 years the results obtained from the three dimensional model confirm the findings of the simple rossby wave model that decadal climatic changes in the gulf stream transport vary considerably with latitude

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

the application of intertidal foraminifera to reconstruct coastal subsidence during the giant cascadia earthquake of ad 1700 in oregon usa abstract changes in species assemblages of intertidal foraminifera can be used to estimate the amount of earthquake related subsidence during plate boundary earthquakes at the cascadia subduction zone the accuracy and precision of foraminiferal methods in paleoenvironmental reconstruction is underpinned by the relations between contemporary taxa and their environment which are used to calibrate fossil foraminiferal assemblages in sediment sequences a contemporary training set of surface sediment samples from five intertidal marshes along the oregon coast was used to determine foraminiferal distributions and prevailing environmental control s along elevational transects dominant taxa include balticammina pseudomacrescens trochamminita irregularis haplophragmoides wilberti trochammina inflata jadammina macrescens and miliammina fusca unconstrained cluster analysis and detrended correspondence analysis was used to identify two elevation dependent faunal zones faunal zone i upland high marsh middle marsh dominated by balticammina pseudomacrescens haplophragmoides wilberti and trochammina inflata and faunal zone ii low marsh and tidal flat dominated by miliammina fusca site specific differences in assemblages at three marshes enabled further subdivision of faunal zone i zone ia is based on one or more of balticammina pseudomacrescens trochammina inflata trochamminita irregularis and haplophragmoides sp and zone ib on jadammina macrescens haplophragmoides sp trochammina inflata and miliammina fusca canonical correspondence analysis cca and partial cca of the training set from the nehalem river marsh transect was used to infer that the zonation of foraminifera is elevation dependent 39 of explained variance a transfer function was developed to reconstruct sudden changes in relative sea level during plate boundary earthquakes in oregon the results indicate a robust performance of the transfer function r jack 2 0 82 with the error estimate rmsep jack 0 20 m comparable to local and regional transfer functions from other temperate marshes to illustrate the potential of the technique the transfer function was applied to reconstruct subsidence during the ad 1700 earthquake using at alsea bay oregon the reconstruction 0 18 0 20 m is less than half the subsidence estimate of nelson et al 2008 great earthquake palogeoesy and tsunamis of the past 2000 years at alsea bay central oregon coast usa quaternary science reviews 27 747 768 using their foraminiferal transfer function perhaps because of differences in taxonomy and the species relationship to elevation

seismotectonics of the 20 october 1991 uttarkashi earthquake in garhwal himalaya north india the 20 october 1991 uttarkashi earthquake killed over a thousand people and caused extensive damage to property in the garhwal himalaya region the body wave magnitude of the earthquake was 6 6 and the fault plane solution indicates reverse faulting the hypocenrre was located at a focal depth of about 12 km between the chail and jutogh thrusts but movement propagated southward along the jamak gangori fault jgf and dunda fault df which are developed as blind faults related to the growing uttarkashi antiform

distribution of modern salt marsh foraminifera in the albemarle pamlico estuarine system of north carolina usa implications for sea level research abstract we described the distributions of foraminifera from ten physiographically distinct salt marshes in the albemarle pamlico estuarine system north carolina using 193 surface samples we defined elevation dependent ecological zones at individual sites using cluster analysis and detrended correspondence analysis additionally seven principal biozones of salt marsh foraminifera were identified that have distinctive spatial distributions reflecting a pattern of salinity regimes caused by the current configuration of barrier island inlets high salinity sites along the southern outer banks are associated with sub tidal calcareous assemblages low marshes dominated by miliammina fusca and high marsh environments defined by haplophragmoides wilberti trochammina inflata and arenoparrella mexicana in contrast lower salinity marshes have ammobaculites spp in sub tidal settings miliammina fusca dominated low marshes and high marsh settings characterized by jadammina macrescens spatial variation of foraminiferal populations and the potential for biozones to migrate in response to changing inlet configuration and salinity suggests that datasets of modern salt marsh foraminifera from multiple environments would be appropriate for reconstructing holocene relative sea level in north carolina

barrier island response to late holocene climate events north carolina usa the outer banks barrier islands of north carolina usa contain a geologic record of inlet activity that extends from ca 2200 cal yr bp to the present and can be used as a proxy for storm activity optically stimulated luminescence osl dating 26 samples of inlet fill and flood tide delta deposits recognized in cores and geophysical data provides the basis for understanding the chronology of storm impacts and comparison to other paleoclimate proxy data osl ages of historical inlet fill compare favorably to historical documentation of inlet activity providing confidence in the technique comparison suggests that the medieval warm period mwp and little ice age lia were both characterized by elevated storm conditions as indicated by much greater inlet activity relative to today given present understanding of atmospheric circulation patterns and sea surface temperatures during the mwp and lia we suggest that increased inlet activity during the mwp responded to intensified hurricane impacts while elevated inlet activity during the lia was in response to increased nor easter activity a general decrease in storminess at mid latitudes in the north atlantic over the last 300 yr has allowed the system to evolve into a more continuous barrier with few inlets

contrasting records of sea level change in the eastern and western north atlantic during the last 300 years we present a new 300 year sea level reconstruction from a salt marsh on the isle of wight central english channel uk that we compare to other salt marsh and long tide gauge records to examine spatial and temporal variability in sea level change in the north atlantic our new reconstruction identifies an overall rise in relative sea level rsl of c 0 30 m since the start of the eighteenth century at a rate of 0 9 0 3 mmyr 1 error in variables changepoint analysis indicates that there is no statistically significant deviation from a constant rate within the dataset the reconstruction is broadly comparable to other tide gauge and salt marsh records from the european atlantic demonstrating coherence in sea level in this region over the last 150 300 years in contrast we identify significant differences in the rate and timing of rsl with records from the east coast of north america the absence of a strong late 19th early 20th century rsl acceleration contrasts with that recorded in salt marsh sediments along the eastern usa coastline in particular in a well dated and precise sea level reconstruction from north carolina this suggests that this part of the north carolina sea level record represents a regionally specific sea level acceleration this is significant because the north carolina record has been used as if it were globally representative within semi empirical parameterisations of past and future sea level change we conclude that regional scale differences of sea level change highlight the value of using several regionally representative rsl records when calibrating and testing semi empirical models of sea level against palaeo records this is because by using records that potentially over estimate sea level rise in the past such models risk over estimating sea level rise in the future

late holocene sea level changes in eastern quebec and potential drivers abstract late holocene sea level changes can be reconstructed from salt marsh sediments with decimetre scale precision and decadal scale resolution these records of relative sea level changes comprise the net sea level contributions from mechanisms that act across local regional and global scales recent efforts help to constrain the relative significance of these mechanisms that include sediment dynamics and isostasy which cause relative sea level changes via vertical land motion ocean atmosphere processes that influence regional scale ocean mass redistribution and ocean cryosphere and steric interactions that drive global scale ocean volume changes there remains a paucity of high resolution late holocene sea level data from eastern canada this precludes an interrogation of the mechanisms that define sea level changes over recent centuries and millennia in a region sensitive to oceanic atlantic multidecadal variability atlantic meridional overturning circulation atmospheric north atlantic oscillation arctic oscillation and cryospheric ice mass balance changes we present new relative sea level data that span the past three millennia from baie des chaleurs in the gulf of st lawrence generated using salt marsh foraminifera supported with plant macrofossil analyses the accompanying chronology is based on radiocarbon and radionuclide analyses which are independently verified using trace metal and microcharcoal records relative sea level has risen at a mean rate of 0 93 1 25 mm yr 1 over the past 1500 years residual structure within the reconstruction internal variability has contributed up to an additional 0 61 0 46 mm yr 1 of short lived rsl rise prior to 1800 ce following a sea level low stand during the little ice age acceleration in relative sea level rise is identified between 1800 and 1900 ce within the estimates of internal variability and from 1950 ce to present in both the secular and residual trends phases of relative sea level changes in the gulf of st lawrence are concomitant with periods of glacier mass loss following the little ice age phase periods of the north atlantic oscillation and the atlantic meridional overturning circulation and northern hemisphere warming quantifying the individual effects of these different mechanisms is important for understanding how ocean atmosphere processes redistribute ocean mass upon larger scale background ocean volume changes

high resolution numerical modeling of tides in the western atlantic gulf of mexico and caribbean sea during the holocene 1 tidal constituents and datums are computed on a high resolution grid of the northwestern atlantic ocean including the gulf of mexico and the caribbean sea a global model is used to determine tidal parameters on a grid with a nominal resolution of 800 800 the global model includes self attraction and loading drag in shallow marginal seas and internal tide drag in the deep ocean simulations are performed at 1000 year intervals during the holocene 10 000 calibrated years before present 10 ka in combination with changes in bathymetry and coastline location derived from a glacial isostatic adjustment model the global model results are then used to force a regional barotropic tidal model the regional model uses an unstructured finite element grid with very high resolution at the coastline the model results reveal significant variations in tidal constituent amplitudes throughout the holocene in the northwestern atlantic semi diurnal components show a strong amplification at around 9 ka while in the gulf of mexico the response is much more muted variations in diurnal tidal parameters are found to be less significant than semi diurnal parameters throughout the model domain changes in tidal range of great relevance to changes in relative sea level rsl are also investigated throughout the holocene the overall structure is similar to the patterns observed in the m2 tide with peak increases of 200 300 relative to present day being observed along the east coast of the united states from 9 to 8 ka finally the high spatial resolution of the regional model allows for the investigation of tidal changes at spatial scales e g individual bays much smaller than in previous studies

global sea level rise and glacial isostatic adjustment an analysis of data from the east coast of north america the fact that modern rates of secular sea level change recorded on tide gauges are significantly contaminated by the ongoing influence of glacial isostatic adjustment is now well known peltier 1986 1988 peltier and tushingham 1989 the east coast of the continental united states is uniquely monitored both by a dense network of such tide gauge installations and by a similarly dense coverage of 14 c dated relative sea level histories extending several millennia into the past in this letter we employ the latter data which primarily record the glacial isostatic submergence of this coast to decontaminate the tide gauge records of this influence the perhaps climate related signal so revealed is much more uniform spatially than either of the individual data sets and when averaged along the coast yields a rate of relative sea level rise of 1 94 0 6 mm yr 1 furthermore comparisons of the 14 c data from along the coast with the predictions of global models of the glacial isostatic adjustment process are shown to provide key insights into the design of a best theoretical model that may be employed for decontamination of the global tide gauge data set to more clearly reveal the climate related signal

gulf stream density structure and transport during the past millennium the gulf stream transports approximately 31 sv 1 sv 10 6 m 3 s 1 of water and 1 3 10 15 w of heat into the north atlantic ocean the possibility of abrupt changes in gulf stream heat transport is one of the key uncertainties in predictions of climate change for the coming centuries given the limited length of the instrumental record our knowledge of gulf stream behaviour on long timescales must rely heavily on information from geologic archives here we use foraminifera from a suite of high resolution sediment cores in the florida straits to show that the cross current density gradient and vertical current shear of the gulf stream were systematically lower during the little ice age ad 1200 to 1850 we also estimate that little ice age volume transport was ten per cent weaker than today s the timing of reduced flow is consistent with temperature minima in several palaeoclimate records implying that diminished oceanic heat transport may have contributed to little ice age cooling in the north atlantic the interval of low flow also coincides with anomalously high gulf stream surface salinity suggesting a tight linkage between the atlantic ocean circulation and hydrologic cycle during the past millennium

the antarctica component of postglacial rebound model ice 6g_c vm5a based on gps positioning exposure age dating of ice thicknesses and relative sea level histories

the status of central seismic gap a perspective based on the spatial and temporal aspects of the large himalayan earthquakes abstract the central himalaya considered as a prominent seismic gap is generally believed to be the most vulnerable segment due for a great plate boundary earthquake m 8 two significant historical earthquakes are known to have occurred in this region in ad 1505 and 1803 interpreted by some workers as great earthquakes occurrences of these events question the validity of central himalaya being a seismic gap here we analyze the macroseismal data from the central himalaya and the gangetic plains and suggest that neither of these earthquakes can be qualified as a plate boundary type event and the size of at least the 1803 does not exceed mw 7 7 our studies further indicate that the central himalayan frontal thrusts may be undergoing a quiescence of 1000 years in terms of generation of great earthquakes assuming a steady elastic strain accumulation due to plate convergence and its simple translation as periodic great earthquakes such long quiescence may appear intriguing we suggest that the long term quiescence and the spatial and temporal clustering that characterize the distribution of large earthquakes in the himalaya is a manifestation of the tectonic deformation associated with a highly evolved fold and thrust belt our analyses also indicate that the large moderate earthquakes are mostly concentrated on higher level thrusts these structures probably accommodate most of the seismogenic slip in the himalaya and the rest of the strain could possibly be expended on passive folding consequently great earthquakes m 8 are relatively infrequent as in the case of central himalaya apparently leading to long periods of quiescence

reducing time scale uncertainty for the devonian by integrating astrochronology and bayesian statistics dealing with uncertainties is inherent to the scientific process in the process of building geologic time scales the reported uncertainties are at least as important as the estimates of the numerical ages currently all time scales for the devonian are based on conventional age depth models constructed by linear or cubic interpolation between different dated positions unfortunately such models tend to produce overoptimistic confidence intervals in this study we apply bayesian statistics to the devonian time scale to better incorporate stratigraphic and radioisotopic uncertainty this approach yields a devonian time scale characterized by increasing uncertainty with growing stratigraphic distance from a radioisotopically dated sample this feature is absent from the geologic time scale 2012 therefore that time scale is overoptimistic we further constrain the obtained time scale by incorporating astrochronological duration estimates for the givetian and frasnian stages the combination of radioisotopic dating and astrochronology results in a reduction of the uncertainty on the numerical age of the stage boundaries concerned by several million years for example we estimate the age of the frasnian famennian boundary at 373 9 1 4 ma

evolution of a salt marsh in the southeastern north sea region anthropogenic and natural forcing abstract salt marsh sediments of the southeastern north sea provide an archive to unravel the influences of coastal management and natural processes such as storm tide deposition on salt marsh development we present a record of salt marsh evolution during the past century from the bay of tumlau northwestern germany based on fossil foraminiferal assemblages and sedimentological data after diking the hinterland of the bay of tumlau in 1935 ce and commencing marsh management the environment at the study site changed from a tidal flat to a salt marsh salt marsh sediment accretion is influenced by recurrent dredging events as indicated by layers rich in calcareous tidal flat foraminifera and redeposition of siliciclastic particles from the surrounding tidal flats during storm tides the latter fostered the establishment of a typical salt marsh foraminiferal fauna dominated by the agglutinating species entzia macrescens storm tide layers have a lighter sediment color and commonly a more negatively skewed grain size distribution with variable sorting the observed long term coarsening of the salt marsh sediment likely reflects the landward progression of the vertical erosional cliff and the depletion of fine grained sediment particles in the tidal flats under the influence of sea level rise supra tidal conditions resulting from natural protection measures and abandonment of dredging are indicated by the occurrence of balticammina pseudomacrescens around 2001 ce this species is adapted to only occasional submergence during storm tides the recent increase in elevation is accompanied by establishment of high marsh vegetation and characterized by a present height of the marsh surface 50 cm above mean high water springs during the past sixty years average sediment accretion rates decreased from 18 to 11 mm yr 1 reflecting the maturing of the salt marsh these rates clearly outpace the recent mean sea level rise in the southern north sea demonstrating that the regional salt marshes are still resilient to sea level rise

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

holocene periodicity in north atlantic climate and deep ocean flow south of iceland climate fluctuations during the past millennium are relatively well documented1 on a longer timescale there is growing evidence of millennial scale variability of holocene climate at periodicities of 2 500 and 950 years possibly caused by changes in solar flux 2 3 and 1 500 years maybe related to an internal oscillation of the climate system 4 5 6 but the involvement of deep water masses in these holocene climate changes has yet to be established here we use sediment grain size data from the iceland basin to reconstruct past changes in the speed of deep water flow the study site is under the influence of iceland scotland overflow water isow the flow of which is an important component of the thermohaline circulation that modulates european climate flow changes coincide with some known climate events the little ice age and the mediaeval warm period and extend over the entire holocene epoch with aquasi periodicity of 1 500 years the grain size data indicate afaster isow flow when the climate of northern europe is warmer however a second mode of operation is observed in the early holocene when warm climate intervals are associated with slower isow flow at that time the melting remnant of land based glacial age ice may have provided a sufficient source of fresh water to the ocean to reduce isow flow south of iceland

extended late holocene relative sea level histories for north carolina usa abstract we produced 3000 year long relative sea level rsl histories for two sites in north carolina usa using foraminifera preserved in new and existing cores of dated salt marsh sediment at cedar island rsl rose by 2 4 m during the past 3000 years compared to 3 3 m at roanoke island this spatial difference arises primarily from differential gia that caused late holocene rsl rise to be 0 1 0 2 mm yr faster at roanoke island than at cedar island however a non linear difference in rsl between the two study regions particularly from 0 ce to 1250 ce indicates that additional local to regional scale processes drove centennial scale rsl change in north carolina therefore the cedar island and roanoke island records should be considered as independent of one another between site differences on sub millennial timescales cannot be adequately explained by non stationary tides sediment compaction or local sediment dynamics we propose that a period of accelerating rsl rise from 600 ce to 1100 ce that is present at roanoke island and other sites north of cape hatteras at least as far as connecticut but absent at cedar island and other sites south of cape hatteras at least as far as northeastern florida is a local to regional scale effect of dynamic ocean and or atmospheric circulation

inverted barometer contributions to recent sea level changes along the northeast coast of north america regional sea level sl changes reflect dynamic and isostatic ocean effects recent works have interpreted accelerated and extreme sl changes along the northeast coast of north america primarily in terms of dynamic changes however dedicated study of isostatic changes related to surface atmospheric pressure loading the inverted barometer ib effect has been lacking this investigation uses five different atmospheric pressure products to analyze the influence of the ib effect on annual mean sl from tide gauge records the ib effect explains 25 of interannual sl variance and accounts for 50 of the magnitude of a recent extreme event of sl rise along atlantic canada and new england estimated ib effects also amount to 10 30 of recent multidecadal sl accelerations over the mid atlantic bight and southern new england these findings reiterate the need for careful estimation and removal of isostatic effects for studies of dynamic sl

stable carbon isotopes as potential sea level indicators in salt marshes north carolina usa we compared the use of 13c values and c n ratios from salt marsh sediments to reconstruct relative sea level rsl with an established approach using foraminifera analysis of bulk organic sediment and plant samples collected along transects at two sites in north carolina usa demonstrates that sediment 13c values can be used to distinguish between spartina alterniflora dominated low marsh c photosynthetic pathway 13c values from 17 6 to 16 1 and juncus roemerianus dominated high marsh c 3 photosynthetic pathway 13c values from 28 2 to 21 8 environments juncus roemerianus plants undergo little decompositional change in 13c average 0 8 although there is a clear difference between spartina alterniflora tissue and bulk organic sediments approximately 4 c n ratios on bulk organic sediment from freshwater upland and salt marsh environments converge during early diagenesis rendering them of little use in reconstructing rsl the utility of 13c values as a sea level indicator is limited by the elevational range of c4 plants making it difficult to recognize salt marsh subenvironments and improve the precision of rsl reconstructions furthermore juncus roemerianus dominated high marsh and freshwater upland sediments cannot be adequately distinguished with 13c values

the kumaun and garwhal lesser himalaya india part 1 structure and stratigraphy our understanding of the geologic evolution of the himalaya remains incomplete particularly in regard to structural and geochronologic details of the proterozoic paleozoic lesser himalayan sequence we conducted an integrated field mapping geochronological study and geochemical analysis of the lesser himalayan sequence strata in the kumaun and garwhal himalaya of nw india 78 00 80 30 e structural observations reveal a systematic change in deformation styles from lower to higher structural levels in the main central thrust footwall in the south and at lower structural levels the main central thrust footwall is characterized by parallel folding and sparse development of axial cleavage quartz microstructures indicate that deformation occurred at temperatures below 350 c in contrast in the north and at higher structural levels close to the main central thrust deformation is characterized by replacement of original bedding the development of penetrative cleavage and schistosity locally folds are tight in places isoclinal and overturned the corresponding quartz microstructures indicate that deformation occurred above 350 c dating of detrital zircons from lesser himalayan sequence metasedimentary units and igneous zircons from schistose gneisses throughout the lesser himalayan sequence allow refinements to the stratigraphic framework first unlike has been observed in western nepal immediately west of our study area u pb zircon dating suggests the absence of paleoproterozoic strata in the ramgarh thrust hanging wall this suggests that the thrust cuts upsection laterally along strike second u pb detrital zircon dating suggests that metasedimentary strata in the ramgarh thrust hanging wall are correlative with basal units of the outer lesser himalayan sequence removing the necessity that the ramgarh thrust hanging wall was allochthonous with respect to its footwall lesser himalayan sequence units schistose gneisses with u pb ages of ca 1850 ma are older than lesser himalayan sequence units in the area suggesting that they are thrust emplaced lesser himalayan sequence basement we conclude that the ramgarh thrust is an out of sequence thrust postdating a folding event in its footwall the earlier proposal that neoproterozoic cambrian lesser himalayan sequence strata are the southern extension of the tethyan himalayan sequence requires that the tons thrust which separates the distal and proximal facies of the lesser himalayan sequence be a major south directed structure with a slip magnitude of 50 100 km

annual sea level changes on the north american northeast coast influence of local winds and barotropic motions abstractunderstanding the relationship between coastal sea level and the variable ocean circulation is crucial for interpreting tide gauge records and projecting sea level rise in this study annual sea level records adjusted for the inverted barometer effect from tide gauges along the north american northeast coast over 1980 2010 are compared to a set of data assimilating ocean reanalysis products as well as a global barotropic model solution forced with wind stress and barometric pressure correspondence between models and data depends strongly on model and location at sites north of cape hatteras the barotropic model shows as much if not more skill than ocean reanalyses explaining about 50 of the variance in the adjusted annual tide gauge sea level records additional numerical experiments show that annual sea level changes along this coast from the barotropic model are driven by local wind stress over the continental shelf and slope this result is interpreted in the light of a simple dynamic

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

application of stable carbon isotopes for reconstructing salt marsh floral zones and relative sea level new jersey usa we investigated use of 13c in bulk organic sediment to define the botanical origin of samples preserved in coastal sediment as a means to reconstruct relative sea level in new jersey usa modern transects at three sites demonstrated that low and high salt marsh floral zones dominated by c4 species spartina alterniflora and spartina patens were associated with sediment 13c values between 18 9 and 15 8 and occurred from mean tide level mtl to mean higher high water mhhw brackish transitional settings vegetated by phragmites australis with iva fructescens and typha sp c3 species and freshwater upland samples c3 species were characterized by bulk sediment 13c values of 27 0 to 22 0 and existed above mhhw parallel transects at one site suggested that intra site variability was not discernible the utility of 13c values for reconstructing relative sea level in new jersey is limited by an inability to differentiate between brackish sediments related to sea level and freshwater upland samples to facilitate this distinction in a 4 4 m core we used a multi proxy approach 13c values with presence or absence of agglutinated foraminifera to recognize indicative meanings for four sample types sediment with 13c values greater than 18 9 was derived from a vegetated salt marsh and formed between mtl and mhhw sediment with 13c values less than 22 0 and containing agglutinated foraminifera formed in a brackish transitional zone between mhhw and highest astronomical tide hat this is the narrowest elevational range of the four sample types and most precise sea level indicator sediment with 13c values less than 22 0 and lacking foraminifera can only constrain the upper bound of former sea level samples with intermediate values 22 0 to 18 9 formed between mtl and hat using these indicative meanings and radiocarbon dates we suggest that a transition from brackish to salt marsh 13c values recorded in the core took approximately 350 years from 1800 to 1450 cal a bp

tectonic influences on late holocene relative sea levels from the central eastern adriatic coast of croatia 2018 elsevier ltd differential tectonic activity is a key factor responsible for variable relative sea level rsl changes during the late holocene in the adriatic here we compare reconstructions of rsl from the central eastern adriatic coast of croatia with ice 7g na vm7 glacial isostatic model rsl predictions to assess underlying driving mechanisms of rsl change during the past 2700 years local standardized published sea level index points n 23 were combined with a new salt marsh rsl reconstruction and tide gauge measurements we enumerated fossil foraminifera from a short salt marsh sediment core constrained vertically by modern foraminiferal distributions and temporally by radiometric analyses providing sub century resolution within a bayesian age depth framework we modelled changes in rsl using an errors in variables integrated gaussian process eiv igp model with full consideration of the available uncertainty previously established index points show rsl rising from 1 48 m at 715 bce to 1 05 m by 100 ce at 0 52 mm yr 0 82 1 87 mm yr between 500 and 1000 ce rsl was 0 7 m below present rising to 0 25 m at 1700 ce rsl rise decreased to a minimum rate of 0 13 mm yr 0 37 0 64 mm yr at 1450 ce the salt marsh reconstruction shows rsl rose 0 28 m since the early 18th century at an average rate of 0 95 mm yr magnitudes and rates of rsl change during the twentieth century are concurrent with long term tide gauge measurements with a rise of 1 1 mm yr predictions of rsl from the ice 7g na vm7 glacial isostatic model 0 25 m at 715 bce are consistently higher than the reconstruction 1 48 m at 715 bce during the late holocene suggesting a subsidence rate of 0 45 0 6 mm yr the new salt marsh reconstruction and regional index points coupled with glacial isostatic and statistical models estimate the magnitude and rate of rsl change and subsidence caused by the adriatic tectonic framework

timing and magnitude of recent accelerated sea level rise north carolina united states we provide records of relative sea level since a d 1500 from two salt marshes in north carolina to complement existing tide gauge records and to determine when recent rates of accelerated sea level rise commenced reconstructions were developed using foraminifera based transfer functions and composite chronologies which were validated against regional twentieth century tide gauge records the measured rate of relative sea level rise in north carolina during the twentieth century was 3 0 3 3 mm a consisting of a background rate of 1 mm a plus an abrupt increase of 2 2 mm a which began between a d 1879 and 1915 this acceleration is broadly synchronous with other studies from the atlantic coast the magnitude of the acceleration at both sites is larger than at sites farther north along the u s and canadian atlantic coast and may be indicative of a latitudinal trend

on the robustness of predictions of sea level fingerprints summary the rapid melting of the earth s ice reservoirs will produce geographically distinct patterns of sea level change that have come to be known as sea level fingerprints a basic gravitationally self consistent theory for computing these patterns appeared in the 1970s however recent highly discrepant fingerprint calculations have led to suggestions that the algorithms and or theoretical implementation adopted in many previous predictions is not robust we present a suite of numerical predictions including benchmark comparisons with analytic results that counter this argument and demonstrate the accuracy of most published predictions moreover we show that small differences apparent in calculations published by some groups can be accounted for by subtle differences in the underlying physics the paper concludes with two sensitivity analyses 1 we present the first ever calculation of sea level fingerprints on earth models with 3 d variations in elastic structure and density and conclude that this added complexity has a negligible effect on the predictions 2 we compare fingerprints of polar ice sheet mass flux computed under the very common assumption of a uniform melt distribution to fingerprints calculated using melt geometries constrained by analysing recent trends in grace gravity data predictions in the near field of the ice sheets are sensitive to the assumed melt geometry however this sensitivity also extends to the far field particularly in the case of antarctic mass changes because of the strong dependence of the rotational feedback signal on the melt geometry we conclude that inferences of ice sheet mass flux based on modern sea level constraints should consider these more realistic melt geometries

quantitative interpretation of fossil pollen spectra dissimilarity coefficients and the method of modern analogs abstract dissimilarity coefficients measure the difference between multivariate samples and provide a quantitative aid to the identification of modern analogs for fossil pollen samples how eight coefficients responded to differences among modern pollen samples from eastern north america was tested these coefficients represent three different classes 1 unweighted coefficients that are most strongly influenced by large valued pollen types 2 equal weight coefficients that weight all pollen types equally but can be too sensitive to variations among rare types and 3 signal0to noise coefficients that are intermediate in their weighting of pollen types the studies with modern pollen allowed definition of critical values for each coefficient which when not exceeded indicate that two pollen samples originate from the same vegetation region dissimilarity coefficients were used to compare modern and fossil pollen samples and modern samples so similar to fossil samples were found that most of three late quaternary pollen diagrams could be reconstructed by substituting modern samples for fossil samples when the coefficients indicated that the fossil spectra had no modern analogs then the reconstructed diagrams did not match all aspects of the originals no modern analogs existed for samples from before 9300 yr b p at kirchner marsh minnesota and from before 11 000 yr b p at wintergreen lake michigan but modern analogs existed for almost all holocene samples from these two sites and brandreth bog new york

a review of statistical chronology models for high resolution proxy based holocene palaeoenvironmental reconstruction abstract in this paper we explain the background workings and results obtained from three recently developed statistical age depth models implemented in freely available general purpose software packages bpeat oxcal and bchron these models aim to reconstruct the sedimentation rate in a single core typically lake peat or ocean given a limited number of scientific date estimates usually radiocarbon and fixed depths most importantly they provide a suitably qualified estimate of the uncertainty in the age depth chronology and thus can be used in a variety of applications we perform a large data driven study of the three models and discuss their general utility in chronology construction for palaeoenvironmental research

controls on the stratigraphic framework and paleoenvironmental change within a holocene estuarine system pamlico sound north carolina usa abstract this study examines the holocene stratigraphic record and paleoenvironmental evolution of a large estuarine system at high temporal and spatial resolution in the context of changing climate sea level and hydrodynamics new data are used to examine two time periods of increased marine influence within pamlico sound in northeastern north carolina interpreted to be the result of extensive barrier island segmentation synchronous with periods of rapid climate change during the late holocene the study reveals the controls on the stratigraphic development and the highly dynamic character of the coastal system in response to climate and sea level change as it interacts with paleotopography these findings can be used to inform projections of future environmental changes estuarine waters occupied paleovalleys in the pamlico sound region as early as ca 7500 cal bp and pleistocene interfluves separated the paleovalleys from the atlantic ocean until ca 5500 cal bp when they were flooded by rising sealevel forming the broad shallow pamlico sound initial barrier islands and shoals likely formed sometime between 5500 and 5000 cal bp providing the geomorphic setting for continued estuarine conditions behind the barriers at ca 4000 cal bp an increase in marine influence and sand content is detected in multiple cores and is correlated to seismic data within the pamlico sound basin this change is interpreted to be the result of increased segmentation of barrier islands thus a greater number of inlets or wider inlets which is consistent with a rapid transgression seen in other areas of the u s east coast the segmentation may have been partially facilitated by a rapid increase in lagoonal area and tidal prism by overtopping of interfluves greater barrier island continuity is evident from 3500 to 1200 cal bp as indicated by muddy deposits with low brackish estuarine foraminiferal assemblages at ca 1200 cal bp seismic sedimentological and micropaleontological data suggest an increase in wave and current energy and marine influence throughout southeastern pamlico sound these changes are interpreted to represent extensive segmentation of the barrier islands during the medieval climate anomaly mca since ca 500 cal bp the pamlico sound system has returned to a more restricted state as inlets have closed currently only three major inlets segment the outer banks the barrier island system fronting pamlico sound but warming climate and increasing rates of sea level rise suggest that another episode of barrier island segmentation began about a half century ago and appears that it may extend into the near future

characterizing the main himalayan thrust in the garhwal himalaya india with receiver function ccp stacking abstract we use common conversion point ccp stacking of ps receiver functions to image the crustal structure and moho of the garhwal himalaya of india our seismic array of 21 broadband seismometers spanned the himalayan thrust wedge at 79 80 e between the main frontal thrust and the south tibet detachment in 2005 2006 our ccp image shows the main himalayan thrust mht the detachment at the base of the himalayan thrust wedge with a flat ramp flat geometry seismic impedance contrasts inferred from geologic cross sections in garhwal imply a negative impedance contrast velocity decreasing downward for the upper flat located beneath the lower himalaya and a positive impedance contrast velocity increasing downward for the ramp located beneath the surface trace of the munsiari thrust or mct i at the lower flat located beneath the higher himalaya spatially coincident measurements of very high electrical conductivities require the presence of free fluids and we infer a negative impedance contrast on the mht caused by ponding of these fluids beneath the detachment our seismic image indicates that the upper flat of the mht is 10 km below sea level and dips north at 2 connecting to a mid crustal ramp which is 10 km high and dips at 16 the lower flat is 20 25 km below sea level and dips at 4 the main central thrust mct appears as a negative impedance contrast dipping at 16 the moho is nearly horizontal at 35 45 km depth beneath the sub himalaya and lower himalaya deepening to 50 km or more beneath the higher himalaya this depth is 10 25 km shallower than in the nw indian himalaya and 5 10 km shallower than in central nepal requiring significant along strike variations in crustal thickness the observed thickness of subducted indian crust in garwhal is 20 28 km

slowing of the atlantic meridional overturning circulation at 25 n the atlantic meridional overturning circulation carries warm upper waters into far northern latitudes and returns cold deep waters southward across the equator its heat transport makes a substantial contribution to the moderate climate of maritime and continental europe and any slowdown in the overturning circulation would have profound implications for climate change a transatlantic section along latitude 25 n has been used as a baseline for estimating the overturning circulation and associated heat transport here we analyse a new 25 n transatlantic section and compare it with four previous sections taken over the past five decades the comparison suggests that the atlantic meridional overturning circulation has slowed by about 30 per cent between 1957 and 2004 whereas the northward transport in the gulf stream across 25 n has remained nearly constant the slowing is evident both in a 50 per cent larger southward moving mid ocean recirculation of thermocline waters and also in a 50 per cent decrease in the southward transport of lower north atlantic deep water between 3 000 and 5 000 m in depth in 2004 more of the northward gulf stream flow was recirculating back southward in the thermocline within the subtropical gyre and less was returning southward at depth

the relative utility of foraminifera and diatoms for reconstructing late holocene sea level change in north carolina usa abstract foraminifera and diatoms preserved in salt marsh sediments have been used to produce high resolution records of holocene relative sea level rsl change to determine which of these microfossil groups is most appropriate for this purpose we investigated their relative utility from salt marshes in north carolina usa regional scale transfer functions were developed using foraminifera diatoms and a combination of both multi proxy from three salt marshes oregon inlet currituck barrier island and pea island we evaluated each approach on the basis of transfer function performance foraminifera diatoms and multi proxy based transfer functions all demonstrated a strong relationship between observed and predicted elevations r 2 jack 0 74 and rmsep 210 pb and 14 c based chronology and we were able to reconcile this with tide gauge records

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

glacial isostatic adjustment and the anomalous tide gauge record of eastern north america sea level variations as recorded by the global network of tide gauges represent a rich data set for studying a wide range of natural and anthropogenic phenomena such as the sea level rise induced by possible global warming for this purpose long term sea level trends must be corrected for the contaminating effects of continuing glacial isostatic adjustment1 5 gia the numerical correction procedure has for sites on the east coast of north america yielded a set of highly anomalous sea level rates characterized by systematic geographical trends2 4 5 we demonstrate that these trends are a consequence of inadequacies in the previous standard numerical prediction for gia in particular we find that the well known trends in the gia corrected tide gauge rates are eliminated if the lower mantle viscosity of the earth model used in the gia prediction is increased this result obviates the need to explain the anomalous trend as a manifestation of gulf stream ocean circulation4 or neotectonic processes2

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

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

revised age of proximal deposits in the zagros foreland basin and implications for cenozoic evolution of the high zagros the regionally extensive coarse grained bakhtiyari formation represents the youngest synorogenic fill in the zagros foreland basin of iran the bakhtiyari is present throughout the zagros fold thrust belt and consists of conglomerate with subordinate sandstone and marl the formation is up to 3000 m thick and was deposited in foredeep and wedge top depocenters flanked by fold thrust structures although the bakhtiyari concordantly overlies miocene deposits in foreland regions an angular unconformity above tilted paleozoic to miocene rocks is expressed in the hinterland high zagros the bakhtiyari formation has been widely considered to be a regional sheet of pliocene pleistocene conglomerate deposited during and after major late miocene pliocene shortening it is further believed that rapid fold growth and bakhtiyari deposition commenced simultaneously across the fold thrust belt with limited migration from hinterland ne to foreland sw thus the bakhtiyari is generally interpreted as an unmistakable time indicator for shortening and surface uplift across the zagros however new structural and stratigraphic data show that the most proximal bakhtiyari exposures in the high zagros south of shahr kord were deposited during the early miocene and probably oligocene in this locality a coarse grained bakhtiyari succession several hundred meters thick contains gray marl limestone and sandstone with diagnostic marine pelecypod gastropod coral and coralline algae fossils foraminiferal and palynological species indicate deposition during early miocene time however the lower miocene marine interval lies in angular unconformity above 150 m of bakhtiyari conglomerate that in turn unconformably caps an oligocene marine sequence these relationships attest to syndepositional deformation and suggest that the oldest bakhtiyari conglomerate could be oligocene in age the new age information constrains the timing of initial foreland basin development and proximal bakhtiyari deposition in the zagros hinterland these findings reveal that structural evolution of the high zagros was underway by early miocene and probably oligocene time earlier than commonly envisioned the age of the bakhtiyari formation in the high zagros contrasts significantly with the pliocene quaternary bakhtiyari deposits near the modern deformation front suggesting a long term 20 myr advance of deformation toward the foreland

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

spatial variability of late holocene and 20th century sea level rise along the atlantic coast of the united states accurate estimates of global sea level rise in the pre satellite era provide a context for 21 st century sea level predictions but the use of tide gauge records is complicated by the contributions from changes in land level due to glacial isostatic adjustment gia we have constructed a rigorous quality controlled database of late holocene sea level indices from the u s atlantic coast exhibiting subsidence rates of 0 8 mm a 1 in maine increasing to rates of 1 7 mm a 1 in delaware and a return to rates 0 9 mm a 1 in the carolinas this pattern can be attributed to ongoing gia due to the demise of the laurentide ice sheet our data allow us to defi ne the geometry of the associated collapsing proglacial forebulge with a level of resolution unmatched by any other currently available method the corresponding rates of relative sea level rise serve as background rates on which future sea level rise must be superimposed we further employ the geological data to remove the gia component from tide gauge records to estimate a mean 20 th century sea level rise rate for the u s atlantic coast of 1 8 0 2 mm a 1 similar to the global average however we fia distinct spatial trend in the rate of 20 th century sea level rise increasing from maine to south carolina this is the fi rst evidence of this phenomenon from observational data alone we suggest this may be related to the melting of the greenland ice sheet and or ocean steric effects

signature of the atlantic meridional overturning circulation in sea level along the east coast of north america in this letter we examine the relationship between the north atlantic meridional overturning circulation moc and sea level sl along the east coast of north america in the eddy permitting ocean model occam we find a distinctive topography following pattern of sl variability in the western north atlantic that is closely linked with the changing strength of the moc with a 2 cm drop in sl along the us east coast corresponding to a 1sv increase in the moc we find a similar pattern of sl variability in the altimetry record and show that this meridionally coherent sl mode dominates interannual sl variability at tide gauges along the north american east coast between 40 50n hence we conclude that north american coastal sea level may indeed be a useful indicator of moc variability on interannual timescales allowing an observationally based estimate of the likely range of interannual moc fluctuations to be determined citation bingham r j and c w hughes 2009 signature of the atlantic meridional overturning circulation in sea level along the east coast of north america geophys res lett 36 l02603 doi 10 1029 2008gl036215

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

on the driving processes of the atlantic meridional overturning circulation because of its relevance for the global climate the atlantic meridional overturning circulation amoc has been a major research focus for many years yet the question of which physical mechanisms ultimately drive the amoc in the sense of providing its energy supply remains a matter of controversy here we review both observational data and model results concerning the two main candidates vertical mixing processes in the ocean s interior and wind induced ekman upwelling in the southern ocean in distinction to the energy source we also discuss the role of surface heat and freshwater fluxes which influence the volume transport of the meridional overturning circulation and shape its spatial circulation pattern without actually supplying energy to the overturning itself in steady state we conclude that both wind driven upwelling and vertical mixing are likely contributing to driving the observed circulation to quantify their respective contributions future research needs to address some open questions which we outline

gyre scale atmospheric pressure variations and their relation to 19th and 20th century sea level rise 1 most of the long tide gauge records in the north atlantic and north pacific commonly used to estimate global sea level rise and acceleration display a marked difference in behavior in the late 1800 s early 1900 s compared to the latter half of the 20th century the rates of sea level rise tend to be lower in the 19th compared to 20th century we show this behavior may be related to long term gyre scale surface pressure variations similar to those associated with the northern annular mode as sea level pressure increases decreases at decadal and longer timescales at the centers of the subtropical atmospheric gyres sea level trends along the eastern margins in each ocean basin decrease increase this is not an isostatic response the scaling between local surface pressure and sea level at interannual and longer timescales is 3 to 6 times greater than expected by that mechanism rather it appears to be the result of large possibly gyre scale changes in ocean circulation some evidence is also presented indicating slow 2 cm sec westward propagation of sea level changes in the atlantic from the west coast of europe to the east coast of the u s which produce the decadal variability seen there

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

global glacial isostasy and the surface of the ice age earth the ice 5g vm2 model and grace abstract the 100 kyr quasiperiodic variation of continental ice cover which has been a persistent feature of climate system evolution throughout the most recent 900 kyr of earth history has occurred as a consequence of changes in the seasonal insolation regime forced by the influence of gravitational n body effects in the solar system on the geometry of earth s orbit around the sun the impacts of the changing surface ice load upon both earth s shape and gravitational field as well as upon sea level history have come to be measurable using a variety of geological and geophysical techniques these observations are invertible to obtain useful information on both the internal viscoelastic structure of the solid earth and on the detailed spatiotemporal characteristics of glaciation history this review focuses upon the most recent advances that have been achieved in each of these areas advances that have proven to be central to the construction of the refined model of the global process of glacial isos

relative sea level change in newfoundland canada during the past 3000 years abstract several processes contributing to coastal relative sea level rsl change in the north atlantic ocean are observed and or predicted to have distinctive spatial expressions that vary by latitude to expand the latitudinal range of rsl records spanning the past 3000 years and the likelihood of recognizing the characteristic fingerprints of these processes we reconstructed rsl at two sites big river and placentia in newfoundland from salt marsh sediment bayesian transfer functions established the height of former sea level from preserved assemblages of foraminifera and testate amoebae age depth models constrained by radiocarbon dates and chronohorizons estimated the timing of sediment deposition during the past 3000 years rsl rose by 3 0 m at big river and by 1 5 m at placentia a locally calibrated geotechnical model showed that post depositional lowering through sediment compaction was minimal to isolate and quantify contributions to rsl from global regional linear regional non linear and local scale processes we decomposed the new reconstructions and those in an expanded global database using a spatio temporal statistical model the global component confirms that 20th century sea level rise occurred at the fastest century scale rate in over 3000 years p 0 999 distinguishing the contributions from local and regional non linear processes is made challenging by a sparse network of reconstructions however only a small contribution from local scale processes is necessary to reconcile rsl reconstructions and modeled rsl trends we identified three latitudinally organized groups of sites that share coherent regional non linear trends and indicate that dynamic redistribution of ocean mass by currents and or winds was likely an important driver of sea level change in the north atlantic ocean during the past 3000 years

intensity magnitude location and attenuation in india for felt earthquakes since 1762 a comprehensive consistently interpreted new catalog of felt intensities for india martin and szeliga 2010 this issue includes intensities for 570 earth quakes instrumental magnitudes and locations are available for 100 of these events we use the intensity values for 29 of the instrumentally recorded events to develop new intensity versus attenuation relations for the indian subcontinent and the himalayan region we then use these relations to determine the locations and mag nitudes of 234 historical events using the method of bakun and wentworth 1997 for the remaining 336 events intensity distributions are too sparse to determine mag nitude or location we evaluate magnitude and location accuracy of newly located events by comparing the instrumental with the intensity derived location for 29 cali bration events for which more than 15 intensity observations are available with few exceptions most intensity derived locations lie within a fault length of the instrumen tally determined location for events in which the azimuthal distribution of intensities is limited we conclude that the formal error bounds from the regression of bakun and wentworth 1997 do not reflect the true uncertainties we also find that the regression underestimates the uncertainties of the location and magnitude of the 1819 allah bund earthquake for which a location has been inferred from mapped surface deformation comparing our inferred attenuation relations to those developed for other regions we find that attenuation for himalayan events is comparable to intensity attenuation in california bakun and wentworth 1997 while intensity attenuation for cratonic events is higher than intensity attenuation reported for central eastern north america bakun et al 2003 further we present evidence that intensities of intraplate earth quakes have a nonlinear dependence on magnitude such that attenuation relations based largely on small to moderate earthquakes may significantly overestimate the magnitudes of historical earthquakes