implementation of a multivariate data assimilation scheme for isopycnic coordinate ocean models application to a 1993 1996 hindcast of the north atlantic ocean circulation 1 a 1993 1996 hindcast of the north atlantic circulation is presented and analyzed multivariate satellite observations sea surface height and sea surface temperature are assimilated into an isopycnic coordinate ocean model miami isopycnic coordinate ocean model micom using a reduced order kalman filter the seek filter the objective is to validate the assimilation system in hindcast mode before running a near real time exercise as part of the european diadem project the analysis scheme is upgraded to make the statistical parameterization as realistic as possible and this is shown to be particularly important as soon as a multivariate data set is used second the paper describes the modifications to the seek filter that are necessary to meet the requirements of a layered model and to benefit from the advantages of the isopycnic coordinate in particular the need for an initialization procedure is explained and this dynamical adjustment is shown to be more natural and robust in the context of the isopycnic coordinate the hindcast experiment is validated by comparisons with observations by studying innovation statistics and by comparing the results with independent observations expendable bathythermograph xbt profiles

towards a formal description of foraminiferal assemblage formation in shallow water environments qualitative and quantitative concepts the use of foraminifera in palaeoenvironmental reconstructions e g sea level may be complicated by processes such as infaunal test production taphonomic degradation and bioturbation which act to modify contemporary analogue surface assemblages during and subsequent to burial understanding the palaeoenvironmental significance of these processes is limited by the absence of a clear theoretical description of the mechanics of foraminiferal assemblage formation a conceptual framework is proposed which describes assemblage formation in terms of the balance of test inputs and losses within a volume of sediment undergoing burial through the upper sedimentary zones of test production taphonomic processes and bioturbation a corresponding mathematical model is described and shown to explain empirical dead test distributions in terms of empirically defined standing crops sedimentation and mixing rates together with model estimates of standing crop turnover and or taphonomic decay rates this approach provides a quantitative basis for understanding assemblage formation and for comparing assemblage forming processes between species environments and study sites rates of standing crop turnover and taphonomic loss are identified as the primary unknowns in the study of foraminiferal assemblage formation these multiple unknowns make interpretations of cored data ambiguous emphasising the need for a detailed and coherent framework of theory and assumptions for understanding the mechanics assemblage formation if interpretations are to be clear and conclusive

relative sea level rise and climate change over the last 1500 years we constructed a detailed relative sea level rise curve for the last 1500 years using a novel approach i e charting the rate of relative sea level rise using microfaunal and geochemical data from a coastal salt marsh sequence clinton ct usa the composition of benthic foraminiferal assemblages and the iron abundance in peats were used to describe shifts in marsh environment through time quantitatively the resulting sea level rise curve with age control from 14c dating and the onset of anthropogenic metal pollution shows strong increases in the rate of relative sea level rise during modern global warming since the late nineteenth century but not during the little climate optimum ad 1000 1300 there was virtually no rise in sea level during the little ice age ad 1400 1700 most of the relative sea level rise over the last 1200 years in clinton appears to have occurred during two warm episodes that jointly lasted less than 600 years changes from slow to fast rates of relative sea level rise apparently occurred over periods of only a few decades we suggest that changes in ocean circulation could contribute to the sudden increases in the rate of relative sea level rise along the northeastern usa seaboard relative sea level rise in that area is currently faster than the worldwide average which may result partially from an ocean surface effect caused by hydrodynamics our data show no unequivocal correlation between warm periods on a decaal to centennial time scale and accelerated sea level rise one period of acclerated sea level rise may have occurred between about ad 1200 and 1450 which was the transition for the little climate optimum to the little ice age i e a period of cooling at least in northwestern europe local changes in tidal range might also have contributed to this apparent increase in the rate of relative sea level however the second period of accelerated sea level rise occurred during the period of modern global warming that started at the end of the last century

global scale water masses meridional circulation and heat transport simulated with a global isopycnal ocean model abstract the goal of this study is to fill the gap in equilibrium solutions of the global scale water masses meridional circulation and heat transport with isopycnal ocean models to this end a global isopycnal ocean general circulation model is described and used in the present study a distinguishing feature of the isopycnal model is that it is formulated in the same parameter space boundary conditions and model configurations except the vertical coordinates are those of the gfdl model used by danabasoglu et al with an isopycnal depth diffusion parameterization of eddy induced tracer transport with the global isopycnal model the author repeated danabasoglu et al s coarse resolution simulation for a direct comparison for the same parameter values except lateral viscosity the isopycnal model is able to produce a larger northward heat transport in the northern hemisphere and a better latitudinal dependence of heat transport in the southern hemisphere than the gfdl model the model is also ab

a wind driven isopycnic coordinate model of the north and equatorial atlantic ocean 1 model development and supporting experiments numerical approximations to the dynamic equations are given which allow basin size ocean circulation models formulated in isopycnic coordinates to accommodate variable bottom topography and irregular coastlines emphasis is placed on computational economy through the use of a split explicit time integration scheme on the proper formulation of the advection and coriolis terms in the momentum equation in case of strongly varying layer thickness and on the correct estimation of the horizontal pressure gradient force in grid boxes truncated by steep bottom slopes the algorithms are tested in a series of two and three layer double gyre experiments in cases of steady forcing leading to a steady circulation we are able to reproduce the expected motionless final state in coordinate layers that are below the direct influence of the wind forcing this includes layers intersecting topographic obstacles a long term 25 30 year vacillation tentatively associated with the outcropping of isopycnals along the edge of the cyclonic gyre in a steadily forced model is documented the paper forms the basis for a subsequent study in which circulation features obtained in a realistic north atlantic setting will be discussed

a model study on internally generated variability in subtropical mode water formation internally generated variability in the subtropical gyre is studied as a possible mechanism for the observed interannual to decadal variability in subtropical mode water formation an isopycnic ocean model with idealized geometry and forcing which mimics the north atlantic subtropical gyre is used for this purpose the horizontal resolution is sufficiently high and the friction and diffusion sufficiently low for the flow to become barotropically and baroclinically unstable two modes of low frequency variability are found both modes consist of westward propagating thickness anomalies the anomalies have a first baroclinic modal structure with a maximum amplitude at the thermocline one mode has a timescale of 8 years and a basin wide spatial scale the other has a timescale of 4 5 years and a smaller spatial scale the modes appear to be damped when the diffusion is high in that case the 8 year mode can be excited by a spatially coherent stochastic wind stress the evolution of the modes is determined by an interaction between the mean flow and the low frequency variability itself the modes are instabilities of the mean flow determined by the basic stratification it appears that coupling to the atmosphere and a parameterization of surface mixing are necessary for the low frequency variability to appear in the mixed layer the coupling and surface mixing do not play a role in generating the modes it is concluded that these internally generated modes may play a role in the observed variability in mode water formation

shear wave velocity characteristics of geological units throughout tehran city iran abstract one simple way of accounting for site conditions in calculating seismic hazards is to use the shear wave velocity vs in the shallow subsurface to classify materials we used the average shear wave velocity to a depth of 30 m v s 30 to develop site categories for tehran this parameter can further be used for modifying a calculated ground motion to account for site conditions the national earthquake hazard reduction program nehrp classification was used to group sites into different classes our classification was based on v s 30 values measured in 188 seismic profiles and on the assumption of similar values for similar geological materials for each geological unit characteristics of shear wave velocity distribution including histograms of shear wave velocity and variation of vs versus depth were calculated and shown this study reveals that the v s 30 of the mountainous zones fall into categories a and b of nehrp site classification but in the tehran plain the northern alluvium tends to have v s 30 values which fall into range of category c of the nehrp site classification whereas those in the southern alluvium would be categorized as nehrp d

the roles of elevation and salinity as primary controls on living foraminiferal distributions cowpen marsh tees estuary uk abstract benthic foraminiferal assemblages in subrecent deposits are commonly used to reconstruct past sea level interpretations are generally made by comparison with either modern dead or total live plus dead assemblages in both cases there will have been post mortem changes that have differentially affected preservation it is therefore important to establish the primary ecological controls by analysis of the living assemblages we have determined the spatial and temporal variability of intertidal benthic foraminifera in the surface 0 1 cm sediments from a time series survey of 31 sampling stations at cowpen marsh for a period of 12 months we counted 112 067 live foraminifera assigned to 28 species the fauna was dominated by two agglutinated species jadammina macrescens and trochammina inflata on the high and middle marshes and three calcareous species elphidium williamsoni haynesina germanica and quinqueloculina spp on the low marsh and tidal flat the standing crop of the whole intertidal zone including the high middle low marsh and tidal flat habitats and the individual species varied both temporally and spatially the standing crop of the intertidal zone as a whole was greatest in the summer months and showed a positive correlation with elevation the standing crops of the high and middle marshes showed similar temporal variation with peaks in summer and autumn and a trough in winter the low marsh showed numerous peaks and troughs of standing crop during the year whereas the tidal flat showed a single peak in summer the standing crops of jadammina macrescens and trochammina inflata on the high and middle marshes peaked from april to may and august to october with troughs in winter these agglutinated species showed a strong correlation with elevation haynesina germanica peaked in may to august and november to january on the low marsh whereas on the tidal flat there was a single peak in july the standing crops of e williamsoni on the low marsh and tidal flat were relatively high in june and may and july respectively quinqueloculina spp peaked in may to july on the low marsh and july on the tidal flat the species was also found in the middle marsh from july to may and high marsh from september to november haynesina germanica showed a strong negative correlation with elevation whereas the other two dominant calcareous species demonstrated weak negative correlations with both elevation and salinity reconstructing former sea level depends primarily on the recognition of high and middle marsh assemblages and in this study these are shown to be strongly controlled by elevation rather than salinity caution may be needed in interpreting low marsh and tidal flat data as salinity plays a more important role here

buoyancy and mixed layer effects on the sea surface height response in an isopycnal model of the north pacific abstract an isopycnal model of the north pacific is used to demonstrate that the seasonal cycle of heating and cooling and the resulting mixed layer depth entrainment and detrainment cycle play a role in the propagation of wind driven rossby waves the model is forced by realistic winds and seasonal heat flux to examine the interaction of nearly annual wind driven rossby waves with the seasonal mixed layer cycle comparison among four model runs one adiabatic without diapycnal mixing or explicit mixed layer dynamics one diabatic with diapycnal mixing and explicit mixed layer dynamics one with the seasonal cycle of heating only and one with only variable winds suggests that mixed layer entrainment changes the structure of the response substantially particularly at midlatitudes specifically the mixed layer seasonal cycle works against ekman pumping in the forcing of first mode rossby waves between 17 and 28 n south of there the mixed layer seasonal cycle has little influence on the rossby waves

differences in coastal subsidence in southern oregon usa during at least six prehistoric megathrust earthquakes abstract stratigraphic sedimentologic including ct 3d x ray tomography scans foraminiferal and radiocarbon analyses show that at least six of seven abrupt peat to mud contacts in cores from a tidal marsh at talbot creek south slough coos bay record sudden subsidence relative sea level rise during great megathrust earthquakes at the cascadia subduction zone data for one contact are insufficient to infer whether or not it records a great earthquake it may also have formed through local non seismic hydrographic processes to estimate the amount of subsidence marked by each contact we expanded a previous regional modern foraminiferal dataset to 174 samples from six oregon estuaries using a transfer function derived from the new dataset estimates of coseismic subsidence across the six earthquake contacts vary from 0 31 m to 0 75 m comparison of subsidence estimates for three contacts in adjacent cores shows within site differences of 0 10 m about half the 0 22 m error although some estimates may be minimums due to uncertain ecological preferences for balticammina pseudomacrescens in brackish environments and almost monospecific assemblages of miliammina fusca on tidal flats we also account for the influence of taphonomic processes such as infiltration of mud with mixed foraminiferal assemblages into peat on subsidence estimates comparisons of our subsidence estimates with values for correlative contacts at other oregon sites suggest that some of our estimates are minimums and that cascadia s megathrust earthquake ruptures have been heterogeneous over the past 3500 years

near field probabilistic seismic hazard analysis of metropolitan tehran using region specific directivity models ground motions are affected by directivity effects at near fault regions which result in low frequency cycle pulses at the beginning of the velocity time history the directivity features of near fault ground motions can lead to significant increase in the risk of earthquake induced damage on engineering structures the ordinary probabilistic seismic hazard analysis psha does not take into account such effects recent studies have thus proposed new frameworks to incorporate directivity effects in psha the objective of this study is to develop the seismic hazard mapping of tehran city according to near fault psha procedure for different return periods to this end the directivity models required in the modified psha were developed based on a database of the simulated ground motions the simulated database was used in this study because there are no recorded near fault data in the region to derive purely empirically based pulse prediction models the results show that the directivity effects can significantly affect the estimate of regional seismic hazard

a primitive equation ocean circulation model using a general vertical coordinate transformation 1 description and testing of the model the ocean general circulation model of the geophysical fluid dynamics laboratory has been modified to accommodate a generalized vertical coordinate transformation the model with a slightly modified transformation z h is applied to three simple test cases a clear improvement of barotropic and baroclinic topographic rossby waves has been achieved compared with the z coordinate model a somewhat more typical time independent problem for the overflow of dense water masses over a zonal ridge exhibits the potential benefits as well as the flaws of the new model vertically integrated mass transport is very sensitive to changes in bottom slope in regions where planetary and topographic are of comparable magnitudes this translates into large errors in the z model due to the crude approximation to the actual topography the deep flow in the z model does not follow the bottom exactly horizontal overshoots of dense water lead to convective mixing on the southern side of the ridge this can be a serious problem for modeling more realistic overflow situations with the z model increased diapycnal diffusion has been identified as the most serious problem with the terrain following coordinate system for this specific application

the spatial and vertical distribution of living stained benthic foraminifera from a tropical intertidal environment north queensland australia we investigated the distribution of living stained benthic foraminifera across a tropical intertidal shoreline adjacent to cocoa creek queensland australia for the purpose of better understanding the nature of test production and ultimately fossil assemblage development within such environments short cores up to 1 m were collected during the wet and dry season along an elevational gradient comprising non vegetated intertidal mudflat and higher intertidal mangrove forest environments the distribution of stained specimens can be broadly delineated into assemblages characterising upper mangrove 2 64 2 91 m above lowest astronomical tide lat and low mangrove mudflat 1 62 2 18 m above lat environments agglutinated species were generally limited to upper mangrove stations calcareous species occurred within all of the intertidal environments examined but differ in their composition between upper and lower intertidal settings upper mangrove faunas were characterised by the agglutinated species arenoparrella mexicana haplophragmoides wilberti miliammina fusca miliammina obliqua and trochammina inflata and the calcareous species helenina anderseni live stained assemblages at lower intertidal elevations were dominated by the calcareous species ammonia aoteana as well as rosalina spp elphidium oceanicum triloculina oblonga ammonia pustulosa and shackoinella globosa absolute densities of stained specimens were lowest within the low mangrove sediments 6 8 specimens per cm2 but higher within the upper mangrove 25 249 specimens per cm2 and mudflat 8 77 specimens per cm2 abundances within mudflat sediments varied seasonally being significantly larger in the wet season whereas those within mangrove zone sediments changed little through the year stained foraminifera were found to a maximum depth of 50 cm at cocoa creek extending to the greatest depth at the upper mangrove stations and were generally shallowest beneath the lower mangroves all stations had over 50 of their foraminiferal standing crop below the upper 1 cm although at most stations 10 of living specimens occurred within this layer comparison of this data with dead assemblages suggests that 1 abundances of stained specimens averaged over two sampling events reasonably approximate aggregate in situ test production and 2 a clear enrichment of infaunal species occurs within the mangrove the latter effect was less conspicuous on the mudflat due to high rates of mixing and assemblage time averaging which obscure the signal of test production within the dead assemblages in both cases the validity and stratigraphic resolution of surface assemblages for sea level and other palaeoenvironmental reconstructions is questionable

circulation characteristics in three eddy permitting models of the north atlantic a systematic intercomparison of three realistic eddy permitting models of the north atlantic circulation has been performed the models use different concepts for the discretization of the vertical coordinate namely geopotential levels isopycnal layers terrain following sigma coordinates respectively although these models were integrated under nearly identical conditions the resulting large scale model circulations show substantial differences the results demonstrate that the large scale thermohaline circulation is very sensitive to the model representation of certain localised processes in particular to the amount and water mass properties of the overflow across the greenland scotland region to the amount of mixing within a few hundred kilometers south of the sills and to several other processes at small or sub grid scales the different behaviour of the three models can to a large extent be explained as a consequence of the different model representation of these processes

a review of seismic geophysical testing in iran for building near surface velocity models abstract it has long been understood that the near surface structure of the earth affects several aspects of civil engineering practice particularly in seismic applications therefore the implementation of a competent subsurface exploration program not only addresses the need for comprehensive site characterization but also reduces the devastating consequences of seismic activities typical geotechnical practice for subsurface exploration has often relied on a combination of drilling in situ testing such as standard penetration testing and cone penetration testing and laboratory testing of field samples however geophysical techniques have been developed over the years to evaluate near surface velocity models as a proxy for subsurface stiffness in seismic applications in this regard seismic geophysical methods such as refraction reflection downhole and crosshole testing spectral analysis of surface waves sasw and multichannel analysis of surface waves masw have continued to receive increase

surface distributions of salt marsh foraminifera from connecticut usa modern analogues for high resolution sea level studies abstract salt marsh foraminifera are routinely used as sea level indicators since their vertical distribution is closely linked with elevation relative to the tidal frame the precise nature of these relationships is variable in time and space and the accuracy of sea level reconstructions depends upon the selection of appropriate modern analogues that reliably reflect past fauna environment associations the marshes of connecticut usa are sites of ongoing research seeking to produce high resolution records of sea level change yet little published data regarding their modern foraminiferal distributions exist this paper presents new surface foraminiferal data from three connecticut salt marshes and evaluates their suitability as modern analogues for past sea level changes the results indicate that significant intra and inter site variability between these marshes and those of neighbouring states exists as a consequence of this the extrapolation of fauna environment relationships developed from marshes with different hydrographic physiographic vegetative or climatic characteristics may produce erroneous reconstructions even when adjusted for variations in tidal range these errors are potentially greatest if single indicator species are used since the relative abundance of individual taxa does not vary consistently with elevation even in high marsh environments from the same site whilst cluster analysis demonstrates that foraminiferal assemblages from connecticut are vertically zoned with respect to mean high water mhw the composition elevation and height range of these zones is variable between sites this spatial heterogeneity results in reconstructions of relatively low and variable precision that restricts their utility in high resolution sea level research new studies seeking to distil decimetre scale changes in relative sea level will need to employ quantitative methods capable of combining multi site information to develop fauna environment relationships that capture this spatial variability reconstructions will be most precise when employing local foraminiferal distributions but may require the collection of additional modern analogue samples from other regions when the extant foraminiferal population of a site differs in composition from its sub fossil counterpart

a probabilistic procedure for scenario based seismic hazard maps of greater tehran abstract the seismic hazard assessment of tehran the capital of iran with a population of over 10 million is necessary in the decision making process for risk reduction the main objective of this paper is to present a procedure for obtaining maximum hazard maps in seismically active regions such as tehran with a history of destructive earthquakes but where the number of the instrumentally recorded large magnitude events is small the deterministic and probabilistic seismic hazard methods are two quantitative approaches with some practical limitations to overcome their limitations the bayesian statistics are used to estimate maximum earthquake magnitude by combining prior seismological information with the available limited data the bayesian approach is used to estimate maximum earthquakes corresponding to different individual ground motion scenarios at a specific hazard level the maximum hazard maps are obtained by merging different individual worst case ground motion scenarios at a specific hazard level the hazard analyses under different scenarios are conducted by the finite fault procedure which uses geological and seismological parameters for each seismic source the obtained results are in agreement with the observed intensities of historical earthquakes moreover the conventional approach of probabilistic seismic hazard analysis is presented to show the difference between the two procedures the findings provide information about the seismic design or retrofit of structures and infrastructures

shallow crustal structures of the tehran basin in iran resolved by ambient noise tomography in this study we present an application of the ambient noise tomography ant to study the near surface geological structures of the metropolitan tehran iran region short period fundamental mode rayleigh wave green s functions were estimated using cross correlations of the vertical component of the ambient noise from 2009 october to 2011 may using a variety of seismic sensors for example accelerometers and seismometers deployed in the tehran area standard common low frequency processing procedures were applied to the cross correlations and shorter time windows comprising 10 min segments were used in the processing step to enhance the time resolution of the signal in the frequency range of interest 1 10 s stacking was also conducted using the rms of the estimated empirical green s functions our results demonstrate that ambient seismic noise tomography is a viable technique at periods of 1 10 s in length even when different sensor types are present analysis of the empirical green s functions indicates that the dominant sources of ambient seismic noise originated from the same origin and no significant seasonal or spatial variations in the ambient noise sources were observed multiple filter analysis was used to extract the group velocities from the estimated empirical green s functions which were then inverted to image the spatially varying dispersion at periods of lengths between 1 and 7 s using tomographic inversion of the traveltimes estimated for each frequency the resulting group velocity maps show high correlations with known geological and tectonic features of the study region in general most of the tehran basin with certain exceptions could be clearly resolved with low group velocities whereas the mountain ranges were found to be correlated with high group velocities in the tehran basin for 2 and 3 s periods the low velocity zone deepens towards the south southwest which reflects thicker sediments in the southern part of the basin than in the north this feature has also been observed in other geological studies the vs models also show that bedrock depth varies between 400 and 1400 m from north to south within the tehran basin at longer periods main faults are associated with abrupt transitions between regions of high to low velocity anomalies in general our results indicate that ant can be a flexible and effective approach for studying near surface heterogeneity using short period surface wave data

teleconnections in the geopotential height field during the northern hemisphere winter abstract contemporaneous correlations between geopotential heights on a given pressure surface at widely separated points on earth referred to as teleconnections in this paper are studied in an attempt to identify and document recurrent spatial patterns which might be indicative of standing oscillations in the planetary waves during the northern hemisphere winter with time scales on the order of a month or longer a review of existing literature on the subject reveals the existence of at least four such patterns the north atlantic and north pacific oscillations identified by walker and bliss 1932 a zonally symmetric seesaw between sea level pressures in polar and temperature latitudes first noted by lorenz 1951 and what we will refer to as the pacific north american pattern which has been known to operational long range forecasters in this country since the 1950 s a data set consisting of nmc monthly mean sea level pressure and 500 mb height analyses for a 15 year period is used as a basis fo

assessment of potential seismic hazard and site effect in antakya hatay province se turkey antakya city is at risk because of strong earthquakes occurring in the area and different soil conditions that can produce variation of the ground motion amplification microzonation of cities provides a basis for site specific hazard analysis in urban settlements in particular seismic microzonation can be provided by means of detailed seismic assessment of the area including earthquake recordings and geological studies in this paper we propose a preliminary microzonation map for the city of antakya based on the variation of the dominant periods and shear velocities of the sediments covering the area the periods are retrieved from microtremor measurements conducted at 69 sites using the horizontal to vertical spectral ratio technique the results of microtremor analysis were compared with data obtained from refraction microtremor remi measurements at four profiles crossing the studied area according to the classification of dominant periods antakya city can be divided into five zones probably prone to different levels of seismic hazard the shorter natural periods are in inner antakya and both the sides of asi river i e northern and southern parts the eastern and western parts of antakya have maximum dominant periods the vs30 values were calculated by using the remi method along the profiles antakya city has vs30 values in the range of category c of the national earthquake hazard reduction programme site classification

sea surface temperature anomalies planetary waves and air sea feedback in the middle latitudes the mechanisms that contribute to the generation and damping of large scale mid latitude sea surface temperature sst anomalies are discussed the sst anomalies reflect primarily the response of the upper ocean to the changes in air sea fluxes that are associated with daily weather fluctuations heat flux forcing is dominant in the lower middle latitudes while wind driven entrainment may be most effective in the high latitudes advection by anomalous ekman current is generally less important and ekman pumping is negligible the sst anomalies decay in part because of entrainment effects associated with mixed layer deepening and oceanic mixing and in part because of heat exchanges with the atmosphere the three approaches commonly used to model the evolution of sst anomalies are reviewed case studies based on monthly or seasonal anomaly maps of the large scale sst and atmospheric anomalies numerical simulations with one dimensional mixed layer models and stochastic forcing models we stress the similarities in the different approaches and discuss their main advantages and limitations the response of the atmosphere to mid latitude sst anomalies is considered first we discuss the poorly known relationship between sst anomalies and diabatic heating using a crude assumption for the air sea coupling we consider a two layer quasi geostrophic channel model and discuss the stationary wave response to sst anomaly forcing and the resulting air sea feedback it is found that the back interaction of the sst anomalies onto the atmosphere causes a weak sst anomaly damping at large scales and a strong one at small scales the air sea coupling should also act as an eastward propagator for the sst anomalies the response of more realistic linear wave models to prescribed diabatic heating is then reviewed and it is suggested that realistic mid latitude sst anomalies have a weak influence on the atmospheric circulation corresponding to changes in the geopotential height of 10 30 m at most this order of magnitude is consistent with the results of general circulation model experiments and with the limited climate predictability associated with mid latitude sst anomalies

microhabitats of salt marsh foraminifera st catherines island georgia usa abstract salt marsh foraminifera of st catherines island georgia occupy a range of epibenthic to deep infaunal to 30 cm micro habitats freshly collected specimens of arenoparrella mexicana from 27 to 30 cm below the marsh surface extruded pseudopodial nets and actively collected foreign material about the aperture salt marsh foraminifera may be primarily epibenthic 0 1 cm epibenthic to intermediate infaunal 0 10 cm or deep infaunal 0 30 cm most of the twelve commonly occurring species in st catherines island marshes are epibenthic to intermediate infaunal species distributional patterns differ with regard to maximum depth of infaunal occurrences infaunal microhabitat utilization in different marsh zones and environments and the presence or absence of subsurface population maxima selective preservation impacts both calcareous and agglutinated foraminifera intense bioturbation primarily by halophytes and decapod crustaceans may contribute to the deep infaunal occurrences of foraminifera in these environments

microfacies characteristics of a tropical mangrove fringed shoreline cleveland bay queensland australia sedimentary and taphonomic controls on mangrove facies development mangrove ecosystems strongly influence the sedimentology and geomorphology of contemporary intertidal environments and are known to have occupied similar ecological niches at least as far back as the early cenozoic given this it is remarkable how few records of mangrove occurrence have been reported in the geologic record here a microfacies approach is adopted to examine the characteristics of a contemporary mangrove colonized intertidal succession along an active prograding shoreline in north queensland australia and compared with a proximal mid late holocene preserved intertidal succession this enables a comparison of microfacies development and preservation potential in like for like depositional environments over short temporal and spatial scales in the contemporary intertidal system active shoreline progradation has produced a highly gradational shallowing upward succession mid to low intertidal substrates characterized by an abundant and diverse bioclast especially molluscan fauna and a rich calcareous foraminiferal assemblage are overlain by organic rich upper intertidal mangrove facies characterized by abundant organic material especially wood and bark fragments and a distinct fauna of agglutinated foraminifera the major sedimentary effects of mangrove progradation are to introduce substantial amounts of organic matter into the substrate effectively overprinting the mudflat facies to mix and re texture due to root network development and infaunal bioturbation the sediment substrate and to modify the depth ranges over which infaunal molluscs and foraminifera occur variations in the relative abundance of constituents permit however the clear delineation of mangrove and intertidal mudflat facies whilst an essentially similar facies succession is identifiable in the sub recent many of the diagnostic facies constituents are either not preserved or are present in far lower abundances than in the modern in particular the inferred mangrove units contain far less organic material most wood and root material is absent are essentially devoid of bioclastic material and contain a depauperate agglutinated foraminiferal fauna the primary drivers of this are 1 loss of calcareous foraminifera and bioclasts due to carbonate dissolution 2 loss of agglutinated foraminifera due primarily to biological fiddler crab test degradation and mineralization of their organic binding agents and 3 aerobic and anaerobic degradation of organic material consequently actual criteria for identifying the presence of a former mangrove in this succession are limited such poor preservation even within sub recent mangrove deposits suggest that the longer term preservation potential of key diagnostic criteria is likely to be extremely poor within similar terrigenoclastic dominated organically enriched successions thus whilst mangroves significantly modify and re texture intertidal substrates use may often need to be made of sparsely preserved faunal or floral remains or traces interpreted in the context of the broader intertidal depositional succession to infer the presence of mangrove colonized substrates in the rock record

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

eddy subduction in a model of the subtropical gyre abstract subduction is the process by which fluid transfers from the mixed layer to the interior of the ocean south of the gulf stream extension 18 mode water is formed in a region of high subduction rates in this region there is high mesoscale eddy activity in the present study the role of eddies in modifying the large scale subduction into mode water is investigated an eddy resolving isopycnic ocean model with mixed layer physics included and coupled to an atmospheric anomaly model is used for this purpose the geometry and forcing of the model are idealized annual mean subduction rates into mode water up to 200 m yr 1 are found south of the gulf stream extension the eddy contribution to the annual subduction is estimated by comparing the annual mean subduction rates obtained from monthly mean quantities with the total subduction rates i e eddy plus mean contributions the latter are determined by integrating the detrainment rates over the period when fluid is irreversibly detrained eddy

the ecology of living stained deep sea benthic foraminifera from the sulu sea the distribution of living rose bengal stained deep sea benthic foraminifera was determined in the upper 20 cm of sediments of eight soutar box cores taken from two depth transects 510 4515 m in the thermospheric 10 c sulu sea despite the uniformity of bottom water temperatures salinities and dissolved oxygen levels below 1000 m significant faunal differences exist at different depths in the low oxygen 1 25 ml l below 1000 m basin the shallowest site 510 m is dominated 10 of the calcareous fauna by cibicidoides uvigerina 150 m and bolivina 63 m while siphonina is codominant with cibicidoides and uvigerina in the 1005 m core the 2000 m cores are dominated by cibicidoides gyroidinoides and oridorsalis while cibicidoides bradyi and oridorsalis umbonatus dominate the 3000 and 4000 m cores infaunal assemblages of valvulineria mexicana are found in the sediments of the 4515 m core relatively low bottom water oxygen values do not necessarily yield typical low oxygen taxa such as bolivina uvigerina chilostomella bulimina and globobulimina changes in the abundances of these taxa in fossil assemblages have been used as indicators of changes in ancient bottom water oxygen levels but may instead reflect organic carbon contents of the sediments an examination of the vertical distributions of foraminiferal assemblages from the 63 m and 150 m fractions reveals that taxa have microhabitat preferences similar to those observed in other regions taxa found in the upper 0 to 1 cm interval epifaunal include cibicidoides wuellerstorfi and hoeglundina elegans while taxa such as chilostomella and globobulimina reach maximum abundances in subsurface sediments and have infaunal microhabitat preferences cibicidoides bradyi and o umbonatus live in sediment depths from 0 to 4 cm and have transitional preferences with both epifaunal and infaunal occurrences intrageneric differences in test morphologies including pore distribution rounded peripheries and variable spire height are observed in cibicidoides and gyroidinoides and are suggested to be related to microhabitat preferences vertical distributions of a number of taxa found in both the 63 to 150 m and 150 m fractions are similar suggesting that juveniles and adults live under similar microhabitat conditions ontogenetic changes in microhabitat preferences of most species are not observed in this study and therefore would not be expected to account for isotopic vital effects reported for some taxa in previous studies

response of the overturning circulation to high latitude fresh water perturbations in the north atlantic studies have suggested that sea ice cover east and west of greenland fluctuates out of phase as a part of the atlantic decadal climate variability and greater changes are possible under global warming conditions in this study the response of the atlantic meridional overturning circulation moc to the distribution of surface fresh water flux is explored using a global isopycnal ocean model an arctic ice related fresh water flux of 0 1 sv entering the nordic seas is shown to reduce the maximum overturning by 1 to 2 sv 106 m3 s 1 a further decrease of 3 to 5 sv in the moc is observed when the fresh water flux is shifted from the fram strait to the southern baffin bay area surprisingly the salinity in much of the upper nordic seas actually increases when the arctic fresh water source is the strongest there as a result of enhanced global overturning it reflects the great influence of labrador sea convection on this model s moc by applying a weaker surface fresh water transport perturbation 0 02 sv on the baffin bay area and therefore perturbing the labrador sea water lsw formation we have also investigated the interaction between the overflows across the greenland scotland ridge and the lsw and find that with the same surface forcing conditions in the nordic seas volume transport of the overflows weakens when the lsw formation intensifies

simulation of north atlantic decadal multidecadal winter sst anomalies driven by basin scale atmospheric circulation anomalies the north atlantic winter sea surface temperature anomaly tsa response to anomalous surface atmospheric circulation anomalies that vary over decadal and short term inter decadal periods is simulated for 1950 through 1992 anomalous ocean variability is driven by adding monthly coads derived anomalous fields of vector wind stress and wind speed to the climatological annual cycle forcing a simple model is derived relating winter tsa to the integrated atmospheric forcing present earlier in time that is responsible for its existence the basinscale structure of forced winter tsa patterns depends on the structure of the atmospheric forcing along with regional differences in the dominant mixed layer processes that generate tsa for example when the atmospheric subtropical high and subpolar low pressure systems are simultaneously strong enhanced flow around and baroclinic adjustments within the subtropical gyre results in anomalously warm water in the gulf stream region off the u s east coast at the same time however the open ocean generally cools because the westerlies and trades are anomalously strong by analyzing tsa variability not driven by the atmosphere an anomalously cold decade is identified characterized by rapid onset and termination that both occur within one year the onset during 1968 coincides with the appearance of the great salinity anomaly while the termination during 1977 coincides with an abrupt northern hemisphere climate shift that is particularly evident in the pacific

coastal circulations driven by river outflow in a variable density 1 layer model a variable density 1 layer model is used to investigate the dynamics of the fresher water plumes generated by river outflow solutions are found in a north south channel and the transport mr and salinity sr of the outflow are specified as boundary conditions along a 25 km wide segment of the western boundary in most cases the river water discharges into a preexisting oceanic mixed layer with thickness h1 when mr is sufficiently low plumes remain coastally trapped immediately after the outflow is switched on a coastal kelvin wave is excited at the river mouth that establishes a southward current of oceanic water along the right hand coast in contrast all the river water first bends to the left as it exits the river mouth and the resulting plume advances northward along the left hand coast at the plume nose some of the fresher water reverses direction and this water together with some oceanic water flows southward on either side of the offshore density front between the fresher and salty waters two processes cause this upstream movement geostrophic adjustment generates the southward frontal current and kelvin wave propagation from the nose thins the layer within the plume thereby establishing the northward geostrophic coastal jet when mr is sufficiently high coastally trapped plumes no longer exist if the rossby number of the outflow is also large enough the river water flows directly offshore and only a portion of it recirculates to form a northward propagating coastal plume the angle at which the outflow leaves the river mouth becomes more southward as mr and sr increase and as h1 decreases the strength of the northward propagating plume is weakened as h1 decreases and sr increases when h1 0 so that there is no ambient oceanic layer there is no northward plume at all likewise the plume is weakened when the model includes entrainment a process that acts to prevent the layer thickness from thinning appreciably

mixed layer thermocline interaction in a three dimensional isopycnic coordinate model abstract the annual buildup and obliteration of the seasonal thermocline and the associated ventilation of the permanent thermocline in a wind and thermally driven ocean basin are simulated numerically the model developed for this purpose is a combination of a single layer model of the oceanic mixed layer based on a simple closure of the turbulence kinetic energy equation and a three dimensional isopycnic coordinate model of the stratified oceanic interior the joint model set in a rectangular ocean basin is forced by annually varying wind stress and radiative plus turbulent heal fluxes approximating zonnaly averaged conditions over the north atlantic special emphasis is placed on the description of the mixed layer detrainment process which requires distributing mixed layer water of continuously variable density among constant density interior layers the truncation errors associated with this process are found to be numerically tolerable the quasi lagrangian character of the model s vertical coo

reconstructing relative sea level change using uk salt marsh foraminifera abstract the position of past sea levels can be reconstructed using a series of sea level index points that possess information on age location altitude and a quantified vertical relationship with a former tidal frame the indicative meaning whilst these points fix the altitude of relative sea level at one instant in time they provide no information on its variation between them here a foraminiferal transfer function is used to reconstruct changes in water depth from fossil assemblages preserved within salt marsh sediments the transfer function performs reliably in the high marsh zone where agglutinated foraminiferal species are dominant in lower marsh environments where calcareous species are prevalent postmortem test dissolution alters the fossil assemblages and leaves them without modern analogues to circumvent this problem a new transfer function based on agglutinated foraminifera and utilising preserved test linings is developed this new transfer function significantly reduces the number of samples without modern analogues but at the expense of diminished sensitivity in the low marsh environment additionally the transfer function is used to establish a series of sea level index points that place observed lateral shifts in depositional environment into a vertical and temporal context the combination of age altitude and high resolution water level reconstructions offers the potential to obtain more detailed and reliable records of relative sea level change from salt marsh sediments

a rotated eigenanalysis of the correlation between 700 mb heights and sea surface temperatures in the pacific and atlantic abstract associations between pacific and atlantic sea surface temperature sst and the 700 mb circulation were studied using 30 years 1949 78 of gridded monthly data the monthly data were grouped into four nonstandard seasons for the analysis the linear correlation between the two fields sst and 700 mb heights was analyzed by finding the eigenvalue solution of the mean product matrix of the cross correlations this technique introduced by prohaska was modified through the use of a varimax rotation the result is a set of pairs of patterns one pattern for each medium which explains part of the linear correlation between the two fields the number of significant modes pairs was determined by a monte carlo simulation one well known atmospheric teleconnections pattern referred to as the pacific north american pna pattern by wallace and gutzler was found in all seasons however seasonal differences were noted during the warm season the pna pattern manifests itself as the great plains g

field experiments on bioturbation in salt marshes bombay hook national wildlife refuge smyrna de usa implications for sea level studies the suitability of marsh sites for sea level studies was examined based on field experiments along a transect from low to high marsh bead distributions were determined both seasonally and after 7 years seasonal sediment mixing was greatest in the low marsh and in the late spring and early summer when biological activity is greatest however after an initial interval of relatively intense reworking the bead concentrations reached an approximate equilibrium profile characteristic of each marsh environment as reflected by the profiles obtained after 7 years mixed layer thickness is greatest 10 cm in the intermediate and low marsh and burial rates are rapid 3 7 11 1 mm yr 1 moreover burial rates are comparable to or even surpass longer term 30 to 150 yr radiotracer derived sediment accumulation rates and rates of local and regional sea level rise 4 mm yr 1 therefore sediment accumulation rates appear to reflect primarily sediment resuspension redeposition within the system due to bioturbation thus bioturbation may be critical to the ability of marshes to keep pace with sea level while seemingly precluding the use of low marsh for high resolution sea level studies copyright 2008 john wiley sons ltd

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

a site conditions map for california based on geology and shear wave velocity one simple way of accounting for site conditions in calculating seismic hazards is to use the shear wave velocity in the shallow subsurface to classify materials the average shear wave velocity to 30 m v 30s has been used to develop site categories that can be used for modifying a calculated ground motion to account for site conditions we have prepared a site category map of california by first classifying the geologic units shown on 1 250 000 scale geologic maps our classification of geologic units is based on v 30s measured in 556 profiles and geological similarities between units for which we have v s data and the vast majority of units for which we have no data we then digitized the geologic boundaries from those maps that separated units with different site classifications v s data for california shows that several widespread geologic units have ranges of v 30s values that cross the boundaries between nehrp ubc site categories the franciscan complex has v 30s values across ubc categories b and c with a mean value near the boundary between those two categories older alluvium and late tertiary bedrock have v 30s values that range from about 300 to about 450 m sec across the boundary between categories c and d to accommodate these units we have created intermediate categories which we informally call bc and cd geologic units that have or are interpreted to have v 30s values near the boundary of the ubc categories are placed in these intermediate units in testing our map against the available v 30s measurements we have found that 74 of the measured v 30s values fall within the range assigned to the v s category where they fall on the map this ratio is quite good considering the inherent problems in plotting site specific data on a regional map and the variability of physical properties in geologic units we have also calculated the mean and distribution of v 30s for each of our map units and prepared composite profiles showing the variation of v s in the upper 100 m from the available v s data these data show that the map categories that we have defined based on geologic units have different v s properties that can be taken into account in calculating seismic hazards

an earthquake history derived from stratigraphic and microfossil evidence of relative sea level change at coos bay southern coastal oregon much of the uncertainty in determining the number and magnitude of past great earthquakes in the cascadia subduction zone of western north america stems from difficulties in using estuarine stratigraphy to infer the size and rate of late holocene relative sea level changes a sequence of interbedded peaty and muddy intertidal sediment beneath a small protected tidal marsh in a narrow inlet of coos bay oregon records ten rapid to instantaneous rises in relative sea level each rise is marked by a contact that records an upward transition from peaty to muddy sediment but only two contacts dating from about 1700 and 2300 yr ago show the site wide extent and abrupt changes in lithology and foraminiferal and diatom assemblages that can be used to infer at least half a meter of sudden coseismic subsidence although the characteristics of a third gradual contact do not differ from those of some contacts produced by nonseismic processes regional correlation with other similar sequences and high precision 14 c dating suggest that the third contact records a great plate boundary earthquake about 300 yr ago a fourth contact formed too slowly to have been caused by coseismic subsidence because lithologic and microfossil data are not sufficient to distinguish a coseismic from a nonseismic origin for the other six peat mud contacts we cannot determine earthquake recurrence intervals at this site similar uncertainties in great earthquake recurrence and magnitude prevail at similar sites elsewhere in the cascadia subduction zone except those with sequences showing changes in fossils indicative of 1 m of sudden subsidence sand sheets deposited by tsunamis or liquefaction features

a sea level rise curve from guilford connecticut usa abstract high resolution stratigraphic studies based on sediment chemistry lithology macroflora and benthic foraminiferal assemblages in three peat cores from coastal salt marshes at guilford connecticut show that coastal marshes are ephemeral environments marsh wide environmental variations were common and century long episodes of relative submergence alternated with emergence despite about 2 m of relative sea level rise rslr in connecticut over the last 1500 years the marshes have expanded both landwards and seawards and marsh accretion has been outpaced only marginally by rslr we used radiocarbon dating and the level of anthropogenic markers metal pollution as dated with 210 pb in the cores for age control for most of the last 1000 years the rate of rslr was between 1 3 and 1 8 mm yr but over the last 300 400 years it increased to 2 9 3 3 mm yr and has been faster than the accretion rate especially in the middle marsh the net submergence rate or submergence index ratio of the rate of rslr and marsh accretion rate averaged about 1 15 over the last 1000 years and increased to about 1 5 over the last 200 years the rate of rslr was very sluggish during the early part of the little ice age but we found a slightly higher rate during the little climate optimum this excursion is close to the noise level however the most significant observation is that rslr increased strongly around a d 1650 the onset of this acceleration falls in the middle to end of the little ice age and thus preceded the period of modern global warming that started late last century and that has been tentatively correlated with anthropogenic emissions of greenhouse gases

surface ocean density gradients during the last glacial maximum we have compiled published planktonic foraminiferal oxygen isotope values from the tropical to subtropical atlantic and pacific for the late holocene and last glacial maximum lgm we interpret the spatial distribution of 18o values in terms of meridional density gradients in the lgm surface ocean and discuss implications on tropical ocean thermocline structure in both oceans glacial 18o values display a pattern of interhemispheric asymmetry evidenced by increasingly higher glacial 18o values toward northern latitudes the 18o derived density estimates suggest that the northern subtropical surface ocean density was higher during the lgm than today which has significant implications on lgm thermocline ventilation in the atlantic steeper density gradients in the northern subtropics during the lgm are consistent with a more compressed subtropical gyre and thermocline water formation farther south than today in the pacific the steeper density gradients suggest a significant reduction in freshwater fluxes to the northern tropical and subtropical regions which raises the possibility of a more significant component of northern hemisphere source waters to the tropical pacific thermocline these predictions could be tested with numerical ocean models that assess the structure of the tropical thermocline in the glacial ocean

intertidal substrate modification as a result of mangrove planting impacts of introduced mangrove species on sediment microfacies characteristics a programme of mangrove planting has been undertaken around the island of rodrigues sw indian ocean since the mid 1980 s involving the introduction of the species rhizophora mucronata we examined three coastal embayment sites baie diamant anse goeland and anse pansia in which planting has been undertaken over different time periods within the past 20 years planting has met with variable success in the different sites probably due to variations in fluvial and groundwater influence at two sites baie diamant first planted in 1990 and anse pansia first planted in 1995 ecological data indicates that the mangroves are becoming well established and sedimentary evidence suggests that relatively rapid modification of intertidal substrates has occurred this is evident in the form of significant increases in sediment organic matter content especially fibrous organic matter and an increase in the accumulation of sediment fines inside the mangroves a strong correlation exists between the magnitude and depth of substrate modification and mangrove forest density especially root and sapling density at the third site anse goeland first planted in 2001 mangrove establishment has not been successful many of the seedlings have died and no secondary colonisation has occurred sediment substrates show no deviation from background levels in terms of organic content or weight fines content and we find no evidence for mangrove planting influencing sediment substrates despite evidence for the development of a distinctive mangrove facies at baie diamant and anse pansia there is however no evidence as yet for a marked change in substrate geochemistry such as would be demonstrated by evidence of active bioclast dissolution a common process in many natural mature mangrove substrates we infer this to be a function of the present relative immaturity of the still developing mangrove substrates but may also be a function of the apparent paucity of burrowing crabs which play an important role in nutrient cycling and sediment geochemistry thus whilst the mangroves in some of the study sites are reaching a stage where they are producing distinctive sedimentary facies the systems appear to be in a state of progressive sedimentary and diagenetic modification as the floral and infaunal components of the mangroves continue to develop

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

living foraminifera and total populations in salt marsh peat cores kelsey marsh clinton ct and the great marshes barnstable ma common species of intertidal agglutinated benthic foraminifera in salt marshes in massachusetts and connecticut live predominantly at the marsh surface and in the topmost sediment o 2 5 cm but a considerable part of the fauna lives at depths of 2 5 15 cm few specimens are alive at depths of 15 25 cm with rare individuals alive between 25 50 cm in the sediments specimens living between the sediment surface and 25 cm deep occur in all marsh settings whereas specimens living deeper than 25 cm are restricted to cores from the lower and middle marsh and have an irregular distribution with depth lower and middle marsh areas are bioturbated by metazoa suggesting that living specimens reach these depths at least in part by bioturbation high marsh sediments in new england consist of very dense mats of spa m paleens or distichlis spicatu roots and are not bioturbated by metazoa in this marsh region bioturbation by plant roots and vertical fluid motion may play a role in moving the foraminifera into the sediment the depth distribution of living specimens varies with species living specimens of trochammina injluta consistently occur at the deepest levels this suggests that species have differential rates of survival in the sediment possibly because of differential adaptation to severe dysoxia to anoxia or because of differing food preferences there is no simple correlation between depth in core and faunal diversity absolute abundance and species composition of the assemblages it is therefore possible to derive a signal of fauna1 changes and thus the environmental changes that may have caused them from the complex fauna1 signal of fossil assemblages 0 1998 elsevier science b v all rights reserved

saltmarsh foraminifera in the subarctic white sea thrive in summer endure in winter abstract abundance and diversity of intertidal benthic foraminifera decreases towards the poles well studied in the temperate zone saltmarsh foraminiferal assemblages have only recently received attention at higher latitudes we report modern foraminifera including the taxonomy abundance and zonation from a pristine saltmarsh in the subarctic white sea northern europe we sampled 10 stations surface sediment two replicates from two high tide flats covered with lush halophytic plants nine foraminiferal species found exhibited distinct vertical zonation confined to certain elevation levels the high marsh assemblage comprised arenaceous balticammina pseudomacrescens trochammina inflata jadammina macrescens and monothalamous ovammina opaca this is the northernmost location where the first two species have been encountered alive the low marsh assemblage was dominated by miliammina fusca and elphidium williamsoni summer abundances of live foraminifera were surprisingly higher than on other subarctic saltmarshes studied mostly 100 500 and up to 3000 per 10 cm in winter under a 40 cm of ice the abundances were only 15 20 ind 10 cm but the species richness was the same unlike summer specimens of calcareous foraminifera which are always brightly colored winter elphidium williamsoni all had bleak colorless cytoplasm suggesting they discard kleptoplasts and abandon algal diet we conclude that the insulating blanket of fast ice which hardly moves on saltmarshes prevents elimination of foraminifera in the harshness of winter whereas the intense continental heating in summer lets them thrive on white sea saltmarshes the composition of foraminiferal assemblages under local climatic conditions may thus deviate substantially from the latitudinal trend

extratropical large scale air sea interaction in a coupled and uncoupled ocean atmosphere model spatial patterns of mid latitude large scale ocean atmosphere interaction on monthly to seasonal time scales have been observed to exhibit a similar structure in both the north pacific and north atlantic basins these patterns have been interpreted as a generic oceanic response to surface wind anomalies whereby the anomalous winds give rise to corresponding anomalous regions of surface heat flux and consequent oceanic cooling this mechanistic concept is investigated in this study using numerical models of a global atmosphere and a mid latitude ocean basin nominally the atlantic the models were run in both coupled and uncoupled mode model output was used to generate multi year time series of monthly mean fields empirical orthogonal function eof and singular value decomposition svd analyses were then used to obtain the principal patterns of variability in heat flux air temperature wind speed and sea surface temperature sst and to determine the relationships among these variables svd analysis indicates that the turbulent heat flux from the ocean to the atmosphere is primarily controlled by the surface scalar wind speed and to a lesser extent by air temperature and sst the principal patterns of air sea interaction are closely analogous to those found in observational data in the atmosphere the pattern consists of a simultaneous strengthening or weakening of the mid latitude westerlies and the easterly trades in the ocean there is cooling warming under the anomalously strong weak westerlies and trade winds with a weaker warming cooling in the region separating the westerly and easterly wind regimes these patterns occur in both coupled and uncoupled models and the primary influence of the coupling is in localizing the interaction patterns the oceanic patterns can be explained by the principal patterns of surface heat flux and the attendant warming or cooling of the ocean mixed layer

effects of the mixed layer time variability on kinematic subduction rate diagnostics abstract an eddy resolving primitive equation general circulation model is used to estimate water mass subduction rates in the north atlantic ocean subtropical gyre the diagnostics are based on the instantaneous kinematic approach which allows the calculation of the annual rate of water mass subduction at a given density range following isopycnal outcrop positions over the annual cycle it is shown that water mass subduction is effected rapidly 1 2 months as the mixed layer depth decreases in spring consistent with stommel s hypothesis and occurs mostly over the area of deep late winter mixed layers 150 m across the central north atlantic in the density range 26 27 2 annual subduction rates o 100 200 m yr 1 are found south and east of the gulf stream extension in the density range of subtropical mode waters from roughly 26 2 to 26 6 in the northeastern part of the subtropical gyre annual subduction rates are somewhat larger o 250 m yr 1 from a density of about 26 9 east of the nort

benthic foraminifera assemblages as bottom environmental indicators posiet bay sea of japan abstract benthic foraminiferal fauna patterns have been investigated as possible indicators of the various morphological features interpreted as the expression of slightly different environmental conditions within a ria bay eighty grab top samples from the posiet bay and twenty littoral stations were examined concerning the distribution of benthic foraminifera in different bottom environments in one of the largest ria bays of the western japan sea altogether 51 species of benthic foraminifera belonging to 32 genera were determined from the bay bottom sediments the zones of high productivity and diversity shannon diversity are established the distribution of agglutinated and carbonate forms reflects mainly river input agglutinated foraminifera dominate within brackish shallow closed and semi open inlets calcareous species dominate within the inshore part of open inlets and seaward part of the bay the combination of the species composition an information function shannon diversity and population density are used to characterize modern bottom environments based on benthic foraminifera four faunal assemblages were identified by q mode cluster analysis the first assemblage dominated by eggerella advena is present from 7 to 40 m and is associated with temperatures of 9 7 16 9 c that are typical for semi open inlet environments with silt substrate a second assemblage dominated by trochammina inflata occurs in closed inlets at depths up to 21 m and is associated with temperatures of 12 9 17 5 c a brackish environment and muddy substrate the third cribroelphidium asterenium assemblage represents a semi open marine environment the fourth assemblage dominated by c etigoense is present to a depth of 18 m within an open shallow inlet this assemblage with the highest species diversity is associated with bottom temperatures of 10 18 c and a sandy substrate the difference in the benthic foraminiferal assemblages at similar depths in posiet bay is the result of different hydrologic regimes in closed semi open and open environments littoral benthic foraminiferal assemblages are different from bottom ones regional environmental conditions can be recognized as deviations from the depth bottom temperature range river influx and coastal configuration features

three dimensional simulation of earthquakes on the los angeles fault system we have used a 3d finite difference method to simulate ground motion from elastodynamic propagating ruptures with constant slip on faults in the metropolitan area of los angeles california simulations are carried out for hypothetical m 6 75 earthquakes on the palos verdes and elysian park faults and for comparison an approximation to the 17 january 1994 m 6 7 northridge earthquake the dominant subsurface features of this area are the deep sedimentary los angeles basin and the smaller and shallower san fernando basin simulated ground motions are restricted to the frequency range 0 0 to 0 4 hz ground motion time histories show that in general sites associated with the largest particle velocities and cumulative kinetic energies are located 1 in the epicentral area 2 above the deepest parts of the basins and 3 near the steepest edges of the los angeles basin we find maximum particle velocities for the palos verdes elysian park and northridge simulations of 0 44 0 67 and 0 58 m sec respectively in each case both the directivity of the rupture and the lower impedance of the basins significantly amplify the ground motion although the gross radiation pattern from these ruptures is observable the 3d basin structure distorts the wave field and becomes a source for edge generated waves signal durations at some basin sites last beyond 90 sec due to love waves and refracted s waves that propagate into the sediments from the basin edges compared with the palos verdes event the durations are generally smaller for the elysian park earthquake due to a smaller amount of love waves generated at the basin edges a simple approximation to the northridge earthquake reproduces the overall spatial pattern of the long period particle velocities successfully predicts the timing of late arriving waves and matches the peak velocities with discrepancies generally less than a factor of 2 however for localized areas immediately north and south of the santa monica mountains the computed ground motion underpredicts the observed horizontal peak velocities but matches the vertical ones the pattern of simulated total cumulative kinetic energies is similar to that for the damage intensities observed near the epicenter of the northridge event while the northridge earthquake caused damage in the los angeles area the 3d simulations show that earthquakes with the same magnitude on the palos verdes or elysian park faults produce more severe ground shaking in the los angeles basin

the environmental setting and microfauna of the oligohaline timsah pond israel the last remnant of the kabara swamps abstract enot timsah is a spring fed wetland ecosystem at the foot of the carmel mountain a relict of the much larger holocene kabara swamps at the northern outlet of the yarqon tanninim mountain aquifer this groundwater surface water interaction zone supports a unique living foraminiferal and ostracod fauna sampling of water and sediment was carried out approximately monthly in 2002 3 as part of a study of the species richness and history of this distinctive ecosystem enot timsah is nearly isothermal 23 98 0 4 c and oligohaline with total dissolved solids tds of 3 213 118 5 mg l the water column is transparent and highly oligotrophic with very low phosphate concentration living ostracods and rose bengal stained benthic foraminifera occur in low numbers a monospecific population of the ostracod cyprideis torosa lives at the surface with a reproductive peak in april 2002 foraminifera occur throughout the topmost 0 4 cm extreme oligotrophy of this ecosystem means that there is a low flux of phytoplankton limiting abundance of surface dwelling ostracods and foraminifera microbial decomposition of vascular plant debris was the food source for infaunal foraminifera the low salinity means that living conditions are marginal explaining low numerical abundance of foraminifera however foraminiferal diversity is exceptionally high at enot timsah compared with other oligohaline environments with 15 living benthic taxa and three additional species found in the dead assemblage the living assemblage is composed of cosmopolitan agglutinants known to live in brackish environments together with some calcareous hyaline and miliolid taxa the exceptional foraminiferal diversity is attributed to four factors the very stable conditions of salinity and temperature the high ca2 and hco3 concentrations derived from the karstic aquifer promoting mineralization of calcareous tests the maturity of the kabara ecosystem dating from the early holocene and the repetitive reintroduction of cosmopolitan brackish foraminifera by avian transport increased numbers of living foraminifera with abnormal morphologies testify to stress conditions dead foraminifera are more abundant than living ones with agglutinated foraminifera dominating the living assemblage and calcareous forms dominating the dead assemblage this taphonomic reversal is attributed to microbial decomposition of organic cement of the agglutinants while the calcareous forms are resistant to dissolution because of the high ca2 and hco3 of the aquifer derived spring waters the holocene fossil record of the predecessors of the kabara swamps therefore represents an estimated 10 40 of the information found in the living foraminiferal assemblage at timsah

a review of the ecological and taphonomic controls on foraminiferal assemblage development in intertidal environments intertidal foraminifera from surface sediments are commonly used as a high resolution indicator of sea level change the integrity of this approach is based upon the assumption that surface assemblages are similar in composition to their buried fossil counterparts this assumption may in some cases be inappropriate due to subsurface or infaunal production and taphonomic alteration here we review the current understanding of foraminiferal production and taphonomic loss in intertidal environments and examine the extent to which these processes can affect the development of foraminiferal assemblages in intertidal environments as a sediment layer undergoes burial dead tests are added at a rate proportionate to the standing crop at that depth as a consequence test accumulation within the layer is proportionate to the depth integrated standing crop depending on the nature of its vertical living distribution the upper 1 cm of sediment may therefore not adequately characterise a given species total input instead a comparison of each species contribution to the entire depth integrated living community may offer a better a priori estimate of relative input to the sediment column this provides an improved base line for identifying true taphonomic trends downcore the potential for infauna to create discrepancies between surface and subsurface assemblages may be minimised however where 1 reproduction is concentrated near to the sediment surface transforming an apparent infaunal standing crop into an effective epifaunal production 2 the living fauna is composed similarly at all depths of production and or 3 intense bioturbation homogenises the upper sediment layers the likely decline in the intensity of taphonomic processes with depth may mean that the foraminiferal production from different depths may not experience taphonomic processes uniformly consequently in addition to their possible gradual enrichment due to subsurface production infaunal species may be preferentially preserved by virtue of their production closer to the base of the taphonomically active zone additionally homogenisation of the sediment column by reworking may mix temporally and perhaps environmentally distinct faunas affecting the stratigraphic integrity of the sediment deposit the most important taphonomic processes in intertidal environments are those associated with early diagenesis while the organic cements of agglutinated taxa may be directly oxidised the associated changes in the saturation state of porewaters with respect to calcium carbonate may affect calcareous species the type of diagenetic reaction operating within the sediment provides a quantitative control on agglutinated test degradation but a largely qualitative control on calcareous preservation in addition calcareous test preservation is dependent upon the rate with which organic matter is supplied while agglutinated test preservation is independent of organic matter concentrations although the specific morphological pathways of test degradation for calcareous species are well understood the stages under which agglutinated tests are lost are less clear the combined but varying influences of production infaunal and species composition taphonomic processes and bioturbation may create complex pathways in the transition from live to dead to fossil assemblages understanding the extent to which infauna taphonomic loss and sediment reworking affect assemblage development in different intertidal environments is essential in order to interpret the fossil record

distributions of salt marsh foraminifera along the coast of sw california usa implications for sea level reconstructions abstract salt marsh foraminifera are frequently used around the world as proxies in paleoenvironmental studies of sea level change quantitative reconstructions of sea level change use transfer functions which are based on the vertical zonation of salt marsh foraminifera with respect to the tidal frame this paper explores for the first time the environmental factors that control the foraminiferal assemblages in southern california marshes using modern surface samples 1 cm thick from two marshes seal beach and tijuana estuary the dead foraminiferal assemblages demonstrate distinct zonation across the salt marsh surfaces which is primarily related to elevation other variables less important than elevation such as o2 temperature salinity and ph additionally control the distribution pattern of these assemblages the tidal flat and low marshes are characterized by high abundances of miliammina fusca and calcareous species the middle marsh is dominated by jadammina macrescens and trochammina inflata while the high marsh zone is dominated by trochamminita irregularis miliammina petila j macrescens and t inflata regression modelling was used for the development of a sea level transfer function based on a combined training set of surface samples from the two study sites the performance of the weighted average partial least squares wa pls transfer function suggests a robust relationship between the observed and estimated elevations r2jack 0 72 and is capable of predicting former sea levels to a precision of 0 09 m our results can be used for future paleoenvironmental reconstructions along the southern california coast an area that has experienced changes in sea level in the past and will be affected by future sea level rise coupled with climate and anthropogenic changes resulting in wide impacts on the natural coastal habitats in this region

the response of quasigeostrophic oceanic vortices to tropical cyclone forcing abstractthe response of quasigeostrophic qg oceanic vortices to tropical cyclone tc forcing is investigated using an isopycnic ocean model idealized oceanic currents and wind fields derived from observational data acquired during hurricane katrina are used to initialize this model it is found that the upwelling response is a function of the curl of wind driven acceleration of oceanic mixed layer oml currents rather than a function of the wind stress curl upwelling downwelling regimes prevail under the tc s eye as it translates over cyclonic anticyclonic qg vortices oml cooling of 1 c occurs over anticyclones because of the combined effects of downwelling instantaneous turbulent entrainment over the deep warm water column weak stratification and vertical dispersion of near inertial energy by contrast oml cooling of 4 c occurs over cyclones due to the combined effects of upwelling instantaneous turbulent entrainment over regions of tight vertical thermal gradients strong stratificati

tropical instability vortices in the atlantic ocean 1 this paper examines the physical characteristics and dynamics of atlantic tropical instability vortices based on observational data from 1997 to 2000 and a high resolution numerical model simulation most prominent during boreal summer the vortices are characterized by 400 km spatial scales westward translation at 0 40 cm s 1 anticyclonic circumferential velocities of 30 110 cm s 1 and sstanomalies that decrease from 2 ci n midbasin to 0 5 c or less near the western boundary in contrast the sea level anomalies grow as the vortices progress westward reaching maximum amplitudes of 14 cm near 40 w the large circumferential velocities leading to relative vorticities of 4 10 6 s 1 and rossby numbers of 0 5 indicate that centrifugal effects may play an important role in the vortices vorticity balance we address the vortices vertical structure and vorticity dynamics by examination of a high resolution numerical model there is a reasonably good agreement between the model and observations simulated vortices are confined mostly to the mixed layer which increases westward in depth from 30 to 100 m near the western boundary in the eastern basin potential vorticity within the vortices is not conserved but decreases because of wind stress forcing in contrast in the western basin decreases in potential vorticity are due mostly to the vortices acquisition of southern hemisphere water we estimate an annualized cross equatorial transport of up to 1 2 sv associated with the vortices which is eventually contributed to the north brazil current system index terms 4231 oceanography general equatorial oceanography 4520 oceanography physical eddies and mesoscale processes 4528 oceanography physical fronts and jets keywords tropics instability atlantic

amount of subsidence during a late holocene earthquake evidence from fossil tidal marsh foraminifera at vancouver island west coast of canada abstract fossil foraminifera in intertidal deposits beneath a marsh near tofino on west central vancouver island british columbia provide a basis for estimating the amount of subsidence during a large earthquake less than 400 years ago we compared the fossil foraminiferal assemblages with present day assemblages along a surveyed transect across the marsh and we estimated paleo elevation by means of both subjective and quantitative methods the comparisons suggest that the site subsided at least 0 2 m and perhaps more than 1 m during the earthquake most of the subsidence was tectonic for the deposits rest on a pleistocene substrate unlikely to have compacted much when shaken soon after the earthquake the land began to rebound tectonically most of the 0 2 1 m of recorded subsidence was recovered during deposition of the first 6 cm of sediment above the buried marsh surface probably within a few decades after the earthquake because of the speed at which the land rebounded some recovery may have occurred before the first post earthquake sediments were deposited if so the actual amount of subsidence is larger than the foraminiferal data indicate

shallow s wave well logs as an indicator of past strong shaking from earthquakes on the newport inglewood fault numerical calculations assuming linear elasticity by bose et al 2014 indicate that an m w 7 75 earthquake on the newport inglewood fault would cause 5 m s of horizontal peak ground velocity pgv within the los angeles basin however the dynamic strain from this event would take much of the uppermost few hundred meters of basin rock beyond its frictional elastic limit stiff quartz rich beds within the basin are fragile geological features that would fail and crack before the rest of the clay rich rock mass repeated cracking would reduce the shear modulus of the quartz rich beds to the level that cracking barely occurred during strong events when interpreted in this way data from such stiff beds near the los angeles international airport indicate past pgv of 1 6 m s comparable with near field records from the strike slip 2002 denali and 1992 landers earthquakes numerical calculations capable of representing nonlinear failure within shallow bedded rocks are warranted online material digital rosrine s wave borehole logs

burrows and trails produced by quinqueloculina impressa reuss a benthic foraminifer in fine grained sediment the benthic foraminifer quinqueloculina impressa reuss was buried in various types of sediment in order to assess its capability for producing sediment disturbances and thus ichnofossils silts and silty clays showed distinct burrows fine sands did not two types of burrows were produced fairly straight vertical burrows from 4 cm below the water sediment interface to within 1 cm of the sediment surface and a horizontal and vertical maze like burrow system in the top centimetre of the sediment individuals moving on the sediment surface also produced visible trails when the sediments were dried the burrows were always destroyed in some cases the surface trails were preserved we propose that the vertical burrows are escape structures and that the horizontal and vertical maze like structures are living burrows ichnofossils similar to the escape structures and surface structures have been described presence of these ichnofossils indicates a low energy sedimentary environment and a lack of macrofaunal bioturbation the presence of escape structures may indicate a pulsatory pattern of sedimentation

radial anisotropy in the upper crust beneath the tehran basin and surrounding regions radial anisotropy is characterized by rayleigh love wave discrepancy indicating crustal past and ongoing deformation for this study data from 1075 micro earthquakes were collected based on recordings by 36 stations between 2004 and 2016 and after using data selection criteria 375 events were used to calculate radial anisotropy in the tehran region more than 1908 and 1705 source station rayleigh and love wave group velocity dispersion curves were respectively measured in the period band of 0 6 3 0 s furthermore the tomographic inversion method was carried out to obtain group velocity maps for each period individually next a damped least square iterative process was performed using a 3 5 3 5 km geographic grid size to calculate both vsv and vsh models horizontal and vertical spatial extents of the radial anisotropy beneath the tehran region are revealed as maps of anisotropy as a percentage furthermore the average value of the radial anisotropy as a function of depth indicates three sharp anomalies including 1 relatively negative within a depth range from subsurface to 1 5 km 2 relatively positive anomaly within a depth range from 2 0 to 4 0 km and 3 an approximately isotropic half space for a depth greater than 4 0 km in general the redeposition of former sediments near fault systems geological and tectonic setting features are correlated with radial anisotropy anomalies at various depths as shown in the horizontal maps in the radial anisotropy profiles sedimentary thickness varies from 500 to 1500 m for southward transects and it is constant for the eastward transect these profiles clearly indicate the edges of three different tectonic settings

variability of intertidal foraminiferal assemblages in a salt marsh oregon usa we studied 18 sampling stations along a transect to investigate the similarity between live rose bengal stained foraminiferal populations and dead assemblages their small scale spatial variations and the distribution of infaunal foraminifera in a salt marsh toms creek marsh at the upper end of the south slough arm of the coos bay estuary oregon usa we aimed to test to what extent taphonomic processes small scale variability and infaunal distribution influence the accuracy of sea level reconstructions based on intertidal foraminifera cluster analyses have shown that dead assemblages occur in distinct zones with respect to elevation a prerequisite for using foraminifera as sea level indicators our nonparametric multivariate analysis of variance showed that small scale spatial variability has only a small influence on live rose bengal stained populations and dead assemblages the dissimilarity was higher however between live rose bengal stained populations in the middle marsh we observed early diagenetic dissolution of calcareous tests in the dead assemblages if comparable post depositional processes and similar minor spatial variability also characterize fossil assemblages then dead assemblage are the best modern analogs for paleoenvironmental reconstructions the toms creek tidal flat and low marsh vascular plant zones are dominated by miliammina fusca the middle marsh is dominated by balticammina pseudomacrescens and trochammina inflata and the high marsh and upland marsh transition zone are dominated by trochamminita irregularis analysis of infaunal foraminifera showed that most living specimens are found in the surface sediments and the majority of live rose bengal stained infaunal specimens are restricted to the upper 10 cm but living individuals are found to depths of 50 cm the dominant infaunal specimens are similar to those in the corresponding surface samples and no species have been found living solely infaunally the total numbers of infaunal foraminifera are small compared to the total numbers of dead specimens in the surface samples this suggests that surface samples adequately represent the modern intertidal environment in toms creek

foraminiferal biofacies across mangrove mudflat environments at cocoa creek north queensland australia contemporary and relict subsurface intertidal foraminiferal dead assemblages were collected from a site near to cocoa creek north queensland australia and analysed for the purpose of understanding fossil assemblage development and preservation a marked dichotomy was identified between dead foraminiferal assemblages within mangrove sediments and those within adjacent mudflat sediments mangrove assemblages were almost exclusively represented by agglutinated species mainly arenoparrella mexicana haplophragmoides wilberti milliammina fusca m obliqua trochammina inflata while calcareous species dominated the mudflat mainly ammonia aoteana pararotalia venusta parrellina hispidula surface and subsurface test abundances were also an order of magnitude greater within mudflat sediments 1000 3000 tests per cm3 than in the sediments beneath the mangroves 100 300 tests per cm3 statistically significant differences in the abundance of calcareous and agglutinated tests between wet and dry seasons within the mangrove suggest that tests are systematically lost from this part of the system on an annual basis a model of assemblage formation under shoreface progradation is presented which makes a direct link between surface assemblages post depositional processes and the composition and environmental resolution of the fossil assemblages entering the stratigraphic record assemblages within the mangrove undergo rapid taphonomic loss and are then overprinted during burial by the deep infaunal communities associated with the prograding higher elevation environments as such much of the eventual mangrove sequence is represented entirely by assemblages produced relatively recently within an upper mangrove environment and therefore cannot be differentiated according to elevation at the time of deposition in addition organic enrichment of upper mudflat deposits by mangrove roots which occurs during progradation results in the dissolution of calcareous tests from an 40 cm thick stratigraphic interval it is argued that in order to reliably recognise the changes to foraminiferal assemblages which occur during burial assemblages must be compared with respect to stratigraphy rather than reflexively downcore

mode water variability in a model of the subtropical gyre response to anomalous forcing abstract the response of mode water formation to typical atmospheric forcing anomalies is studied as a possible mechanism for generating the observed interannual to decadal variability in mode water an isopycnal model of the north atlantic subtropical gyre coupled to a mixed layer model is used for this purpose geometry and forcing are idealized the control run shows that mode water is a well ventilated water mass formation rates up to 200 m yr 1 are found at the outcrop of the mode water layer in a series of experiments the sensitivity to the position of the anomalous forcing and to the timescale of the forcing is examined the anomalous forcing has a dipole pattern that mimics the spatial structure of the north atlantic oscillation anomalous cooling induces a positive thickness anomaly in the mode water layer at the center of the gyre and a negative anomaly at the eastern side of the gyre the response to anomalous heat flux forcing appears to be sensitive to the position of the forcing anomaly

adaptation of an isopycnic coordinate ocean model for the study of circulation beneath ice shelves abstract much of the antarctic coastline comprises large floating ice shelves beneath which waters from the open ocean circulate the interaction of the seawater with the base of these ice shelves has a bearing both on the rate at which antarctic bottom water is formed and on the mass balance of the ice sheet an isopycnic coordinate ocean general circulation model has been modified so as to allow the incorporation of a floating ice shelf as an upper boundary to the model domain the modified code admits the introduction of an arbitrary surface pressure field and includes new algorithms for the diagnosis of entrainment into and detrainment from the surface mixed layer special care is needed in handling the cases where the mixed layer and isopycnic interior layers interact with surface and basal topography the modified model is described in detail and then applied to an idealized ice shelf ocean geometry simple tests with zero surface buoyancy forcing indicate that the introduction of the static s

foraminiferal microhabitats in a high marsh consequences for reconstructing past sea levels abstract the foraminiferal faunas of the high marsh of plougoumelen in the western part of the gulf of morbihan on the french atlantic coast have been studied in three successive sample sets taken in weekly intervals in april 2001 each sampling day four cores have been taken in different marsh environments with or without vegetation in order to determine the microhabitat of the major species and the eventual influence of a vegetation cover physico chemical parameters have been surveyed during each sampling day the foraminiferal faunas are similar to other faunas described from temperate salt marshes we have distinguished three groups of taxa with different microhabitats a jadammina macrescens is found in comparable numbers down to about 9 cm depth b shallow infaunal taxa such as miliammina fusca and trochammina inflata and c deep infaunal taxa such as haplophragmoides wilberti and arenoparrella mexicana although these deep infaunal taxa have to cope with low oxygen concentrations or even anoxia life at depth in the sediment appears to provide ecological advantages our survey of the physico chemical parameters shows an extreme variability at the surface in comparison with much more stable conditions deeper in the sediment these more stable conditions demanding smaller tolerance ranges for several parameters temperature salinity water content appear to be advantageous to deep infaunal taxa for the species j macrescens the microhabitat depth appears to be controlled by the water content of the sediment that strongly fluctuates in function of the meteorological conditions during dry periods when the water content of the sediment is lower j macrescens displays a much shallower microhabitat than during more humid periods at the sediment surface the presence of vegetation appears to have a positive influence on the density of the foraminiferal faunas by providing a shelter to desiccation during low tide or more prolonged dry periods important differences exist between the live faunas found in the uppermost centimetre of the sediment and those of the total 9 cm deep sediment cores therefore data inventories of living faunas based on the superficial centimetre alone can not be used as a basis for paleo environmental reconstructions without correction for these microhabitat effects

the effect of quaternary alluvium on strong ground motion in the coyote lake california earthquake of 1979 abstract the effect of alluvium on strong ground motion can be seen by comparing two strong motion records of the coyote lake california earthquake of 6 august 1979 m l 5 9 one record at a site on franciscan bedrock had a peak horizontal acceleration of 0 13 g and a peak horizontal velocity of 10 cm sec the other at a site 2 km distant on 180 meters of quaternary alluvium overlying franciscan had values of 0 26 g and 32 cm sec amplifications by factors of 2 and 3 horizontal motions computed at the alluvial site for a linear plane layered model based on measured p and s velocities show reasonably good agreement in shape with the observed motions but the observed peak amplitudes are greater by a factor of about 1 25 in acceleration and 1 8 in velocity about 15 per cent of the discrepancy in acceleration and 20 per cent in velocity can be attributed to the difference in source distance the remainder may represent focusing by refraction at a bedrock surface concave upward there is no clear evidence of nonlinear soil response fourier spectral ratios between motions observed on bedrock and alluvium show good agreement with ratios predicted from the linear model in particular the observed frequency of the fundamental peak in the amplification spectrum agrees with the computed value indicating that no significant nonlinearity occurs in the secant shear modulus computations show that nonlinear models are compatible with the data if values of the coefficient of dynamic shear strength in terms of vertical effective stress are in the range of 0 5 to 1 0 or greater the data illustrate that site amplification may be less a matter of resonance involving reinforcing multiple reflections and more the simple effect of the low near surface velocity application of traditional seismological theory leads to the conclusion that the site amplification for peak horizontal velocity is approximately proportional to the reciprocal of the square root of the product of density and shear wave velocity

seismically damaged regolith as self organized fragile geological feature 1 the s wave velocity in the shallow subsurface within seismically active regions self organizes so that typical strong dynamic shear stresses marginally exceed the coulomb elastic limit the dynamic velocity from major strike slip faults yields simple dimensional relations the near field velocity pulse is essentially a love wave the dynamic shear strain is the ratio of the measured particle velocity over the deep s wave velocity the shallow dynamic shear stress is this quantity times the local shear modulus the dynamic shear traction on fault parallel vertical planes is finite at the free surface coulomb failure occurs on favorably oriented fractures and internally in intact rock i obtain the equilibrium shear modulus by starting a sequence of earthquakes with intact stiff rock extending all the way to the surface the imposed dynamic shear strain in stiff rock causes coulomb failure at shallow depths and leaves cracks in it wake cracked rock is more compliant than the original intact rock cracked rock is also weaker in friction but shear modulus changes have a larger effect each subsequent event causes additional shallow cracking until the rock becomes compliant enough that it just reaches coulomb failure over a shallow depth range of tens to hundreds of meters further events maintain the material at the shear modulus as a function where it just fails the formalism provided in the paper yields reasonable representation of the s wave velocity in exhumed sediments near cajon pass and the san fernando valley of california a general conclusion is that shallow rocks in seismically active areas just become nonlinear during typical shaking this process causes transient changes in s wave velocity but not strong nonlinear attenuation of seismic waves wave amplitudes significantly larger than typical ones would strongly attenuate and strongly damage the rock

eddy induced heat transport in a coupled ocean atmospheric anomaly model the midlatitude meridional heat transport in the ocean can be partitioned into a transport by the mean flow and an eddy transport this heat transport has been studied in several ocean only models surprisingly it was found that eddy resolving and coarse resolution models have similar total heat transport this is caused by a compensation mechanism in which poleward eddy transport is counterbalanced by an eddy induced meridional circulation recently it was shown that this compensation depends on details of the atmospheric forcing and in fact only occurs for weak thermal coupling where thermal coupling is defined as the rate of change of the surface heat flux with respect to the sea surface temperature sst the thermal coupling varies with the spatial scale of the sst anomaly to study the actual strength of this coupling on the eddy length scale the authors have coupled an isopycnic ocean model with embedded mixed layer to an atmospheric anomaly model by comparing coarse resolution and eddy resolving simulations it is found that 1 the thermal coupling is strong on the eddy length scale and 2 the aforementioned compensation does not occur consequences for the temperature boundary condition in ocean only models the gent and mcwilliams eddy parameterization and climate modeling are discussed

on the role of the azores current in the ventilation of the north atlantic ocean three high resolution ocean circulation models of the north atlantic differing chiefly in their description of the vertical coordinate are used to examine the ventilation of the north atlantic subtropical gyre all the models produce mode waters of realistic densities in the sargasso sea and the european basin but have azores currents of differing strengths which are categorised as strong of realistic transport intermediate and weak these differences have a critical impact upon the ventilation of the gyre most importantly the strong azores current forms an effective barrier to the southward ventilation of eastern north atlantic water from the northern european basin initially driving it southwestwards into the central gyre before turning it back eastwards again in a general cyclonic circulation north of the current the intermediate and weak azores currents instead allow the southward ventilation of this water mass near the european and african coasts the situation in nature appears to be intermediate between these two cases with the azores current acting as a partial block the study also raises the possibility of the azores current forming an advective connection between the sargasso sea mode waters in the western basin and modes of similar densities found in the eastern basin on the southern side of the current although there are high levels of variability in the extent of these lighter modes in the eastern basin in nature this postulate is supported by a number of observational studies in addition the present study also provides some support for the local production of madeira mode water in the eastern basin associated with retroflecting current branches on the southern side of the azores current overall the azores current is therefore likely to have a critical impact upon the ventilation of the subtropical gyre over a large area rather than just locally affecting the potential vorticity and density structure of the upper ocean between subtropical latitudes and the northern european basin the study also contributes to an ongoing community effort to assess the realism of our current generation of ocean models

spatial patterns of atmosphere ocean interaction in the northern winter abstract the variability of monthly mean sea surface temperature sst anomalies over the extratropical north atlantic and pacific and its relation to atmospheric circulation anomalies over the northern hemisphere during wintertime is investigated by applying eigenvector analysis to a 39 year dataset and correlating the time series of the resulting expansion coefficients with the hemispheric 500 mb height and sea level pressure fields in agreement with previous studies the simultaneous correlation between the tone series of the expansion coefficient of the first empirical orthogonal function eof 1 of north pacific sea surface temperature sst and the hemispheric 500 mb height field resembles the pacific north american pattern and the corresponding pattern for atlantic sst resembles the north atlantic oscillation in the vicinity of the conters of action of thew patterns the sst fluctuations associated with these modes explain on the order of half the variance of 500 mb height and slightly less of

shallow crustal radial anisotropy beneath the tehran basin of iran from seismic ambient noise tomography abstract we studied the shear wave velocity structure and radial anisotropy beneath the tehran basin by analyzing the rayleigh wave and love wave empirical green s functions obtained from cross correlation of seismic ambient noise approximately 199 inter station rayleigh and love wave empirical green s functions with sufficient signal to noise ratios extracted from 30 stations with various sensor types were used for phase velocity dispersion analysis of periods ranging from 1 to 7 s using an image transformation analysis technique dispersion curves extracted from the phase velocity maps were inverted based on non linear damped least squares inversion method to obtain a quasi 3d model of crustal shear wave velocities the data used in this study provide an unprecedented opportunity to resolve the spatial distribution of radial anisotropy within the uppermost crust beneath the tehran basin the quasi 3d shear wave velocity model obtained in this analysis delineates several distinct low and high velocity zones that are generally separated by geological boundaries high shear velocity zones are located primarily around the mountain ranges and extend to depths of 2 0 km while the low shear velocity zone is located near regions with sedimentary layers in the shallow subsurface our results indicate strong radial anisotropy with negative magnitude vsv vsh primarily associated with thick sedimentary deposits reflecting vertical alignment of cracks with increasing depth the magnitude of the radial anisotropy shifts from predominantly negative less than 10 to predominantly positive greater than 5 our results show a distinct change in radial anisotropy between the uppermost sedimentary layer and the bedrock

a modelling and observational study of the relationship between sea surface temperature in the north west atlantic and the atmospheric general circulation results from four pairs of 50 day wintertime integrations of the meteorological office s 5 level general circulation model with warm and cold sea surface temperature s s t anomalies of about 3 k in the northwest atlantic are described difference fields between the warm and cold integrations are statistically significant at the 1 level with positive geopotential height over the central north atlantic and weaker negative height over europe the storm track over the atlantic is displaced from its normal position results from four further pairs of integrations with halved s s t anomalies are also described the response is approximately linear with systematic differences in 500 mb geopotential height over the atlantic parts of which are just significant at the 10 level with half the full s s t anomaly overall however the model s response is weaker than could be obtained with tropical s s t anomalies of the same magnitude results from the model integrations are compared with results from an observational study of the relationship between wintertime s s t in the north west atlantic and mean sea level pressure and 500mb height two independent 30 year periods were chosen for study thus minimizing the influence of long term trends in s s t over the atlantic and europe the model results compared well with the observations with s s t data lagging the atmosphere by one month the observational study appears to show that the s s t anomalies are initially forced by perturbations in the atmospheric circulation with s s t data leading the atmosphere by one month results show that atmospheric and s s t anomalies are most persistent in the period october to december throughout the winter these lagged relationships are much weaker and not statistically significant diagnostics of e vector divergence from the gcm experiments are used to suggest that anomalous baroclinic wave activity over the atlantic is important as a momentum forcing for the anomalous time mean flow pattern on the other hand the role of thermal forcing provided by anomalous diabatic heating and transient eddy heat flux convergence may be important to substantiate this statement a simple linear steadystate two layer model of the response to extratropical thermal forcing is described with a suitable basic state flow and a mid tropospheric heat source given mainly by the transient eddy heat flux convergence the response is shown to be equivalent barotropic with a downstream ridge and ascent over the thermal source conversely results from an ocean mixed layer model are discussed which suggest that warm s s t anomalies could be maintained by a positive surface pressure perturbation positioned downstream of the anomaly through anomalous northward advection of warm ocean water by ekman drift currents this northward advection would balance the sensible and latent heat loss into the atmosphere over the s s t anomaly hence it is possible that some positive ocean atmosphere feedback may account for the persistence of such atmospheric and oceanic anomalies

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