a multiproxy approach to reconstructing sea surface conditions using coral skeleton geochemistry 1 we use elemental ratio mg ca sr ca u ca and ba ca and oxygen isotope data from a porites lutea coral head collected from offshore amedee island new caledonia 22 29 s 166 28 e to assess the degree to which changes in these geochemical variables reflect variations in sea surface conditions we have assessed the robustness of each geochemical proxy by comparing 25 years 1992 1968 of monthly geochemical variations with a local record of sea surface temperature sst and with the appropriate 1 by 1 grid box from a global gridded sst data set we conclude from our comparison that the most consistent proxies of monthly sst variations at this site are 18o r2 0 84 p 0001 and sr ca r2 0 84 p 0001 the fidelity of the coral based sr ca sst proxy was assessed via calibration verification exercises at new caledonia and rarotonga the paleoclimate accuracy of the coral sr ca sst technique is judged to be robust and the precision of the technique is estimated to be 0 3 0 5 2 based on the calibration verification exercise in contrast monthly variations in mg ca and u ca ratios are only moderately correlated with monthly sst variations r2 0 55 p 0001 for mg ca and r2 0 47 p 0001 the strength of the correlation between sst and mg ca and u ca varies as a function of time suggesting that variations in these ratios are not a simple function of sst variations this variability in goodness of fit between u ca sst and mg ca sst may ultimately limit the use of these ratios as coral paleothermometers averaging or stacking individual proxy sst records sr ca mg ca and u ca to generate a composite proxy sst record does not necessarily improve the proxy record if the signal to noise ratio in each proxy is highly variable for example stacking of sr ca mg ca u ca records at new caledonia produces a proxy sst time series that has greater standard error than the individual sr ca sst time series cf ordinary least squares standard error of 1 16 c versus 0 86 c ba ca variations have little correlation with sst sr ca mg ca or u ca variations at new caledonia in conclusion variations in oxygen isotopic composition of seawater calculated by removing the sr ca based temperature component of the 18o signal agree reasonably well with observed variations in sea surface salinity especially at the interannual timescale

eight centuries of north atlantic ocean atmosphere variability climate in the tropical north atlantic is controlled largely by variations in the strength of the trade winds the position of the intertropical convergence zone and sea surface temperatures a high resolution study of caribbean sediments provides a subdecadally resolved record of tropical upwelling and trade wind variability spanning the past 825 years these results confirm the importance of a decadal 12 to 13 year mode of atlantic variability believed to be driven by coupled tropical ocean atmosphere dynamics although a well defined interdecadal mode of variability does not appear to be characteristic of the tropical atlantic there is evidence that century scale variability is substantial the tropical atlantic may also have been involved in a major shift in northern hemisphere climate variability that took place about 700 years ago

seasonal clockwise gyration and tilt of the australian continent chasing the center of mass of the earth s system from gps and grace as atmosphere ocean ice and terrestrial water are redistributed the center of mass cm of the earth s system moves and the accompanying loading yields global surface deformation in australia when gps surface displacements were corrected for local mass change hydrology atmosphere and ocean with grace data the residual gps data reveal a peculiar seasonal mode of continental deformation during the southern summer the entire continent coherently shifts northwest by 1 mm and the southeastern part is uplifted while the northwestern part is subsided by 2 3 mm and the opposite patterns of deformation are observed during the southern winter such characteristic deformation could be understood to be a result of the earth s elastic response to globally averaged surface mass load generally heavier in europe during southern summer and in the south pacific ocean during southern winter it was found that such deformation is even larger than local hydrology induced loading effects in horizontal motion over australia a simple method of determining locations of the cm was developed by combining gps and grace data the latter being insensitive to the cm motion but sufficiently accurate to remove the local hydrologic and atmospheric effects in gps data the cm signals are pronounced over systematic errors in gps and grace data the cm coordinates estimated by inversion of the australian gps dataset and grace agree with the geocenter motions determined by satellite tracking analysis this study suggests an independent way of monitoring the cm motion entirely based on two distinct geodetic measurements of gps and grace

a potential bias in coral reconstruction of sea surface temperature 1 isotopic measurements in corals are used to reconstruct past sea surface temperature these reconstructions are based on calibration regression analyses using paired measurements of modern isotopic composition and sea surface temperature it is shown that error in these measurements of sea surface temperature can lead to substantial bias in reconstruction provided the variance of the measurement error is known or can be estimated a simple correction can eliminate this bias

a further study of the tropical western hemisphere warm pool abstract variability of the tropical western hemisphere warm pool whwp of water warmer than 28 5 c which extends seasonally over parts of the eastern north pacific the gulf of mexico the caribbean and the western tropical north atlantic tna was previously studied by wang and enfield using the da silva data from 1945 93 using additional datasets of the ncep ncar reanalysis field and the ncep sst from 1950 99 and the levitus climatological subsurface temperature the present paper confirms and extends the previous study of wang and enfield the whwp alternates with northern south america as the seasonal heating source for the walker and hadley circulations in the western hemisphere during the boreal winter a strong hadley cell emanates northward from the amazon heat source with subsidence over the subtropical north atlantic north of 20 n sustaining a strong north atlantic anticyclone and associated northeast ne trade winds over its southern limb in the tna this circulation including the ne

study of harmonic site position variations determined by very long baseline interferometry 1 position variations of 40 very long baseline interferometry vlbi stations at 32 tidal frequencies were obtained from analysis of 3 million measurements of group delays from 1980 to 2002 residual displacements after the removal of the effect of solid earth tides were studied the purpose of this study is to investigate a harmonic signal at any frequency where it is expected and to assess quantitatively whether the models of vertical and horizontal site position variations agree with the observations it was found that the estimates of station displacements are generally in good agreement with the ocean loading computed on the basis of ocean tide models for the main diurnal and semidiurnal tides moreover vlbi results allow us to discriminate between different ocean tide models however discrepancies between vlbi results and all models of ocean loading for k1 k2 and s2 tides exceed both the errors of the vlbi estimates and the errors of ocean loading displacements based on the reported formal uncertainties of ocean tide models it was found that there is a significant nontidal signal at diurnal and annual frequencies applying a model of hydrological loading reduces the variance of the residual vertical displacements at the annual frequency by 30 using an empirical model of harmonic site position variations in vlbi processing provides a better fit and improves the baseline length repeatability

body tides on a 3 d elastic earth toward a tidal tomography abstract the deformational and gravitational response of the earth to the tide generating potential has generally involved 1 d i e depth varying earth models progressive improvement in observational constraints on body tides generated from both ground and space based surveys suggests that an examination of the potential impact of lateral variations in earth structure is warranted we present a suite of predictions of the body tide response within the semi diurnal diurnal and long period tidal bands computed using a finite volume numerical code the calculations adopt 3 d density and elastic structure taken from seismic inferences and in a subset of the calculations dynamic topography on the surface and internal interfaces we find that perturbations in the radial displacement and surface gravity within the semi diurnal band reach 1 mm and 0 15 gal respectively the perturbations in the diurnal band are comparable to these values and within the long period band they are a factor of 3 5 smaller we also demonstrate that lateral variations in the elastic moduli which have been ignored in recent work contribute greater than 50 of the total perturbation the level of perturbation associated with 3 d structure exceeds the current observational uncertainty obtainable using space geodetic methods and this suggests the possibility of performing tidal tomographic inversions of such data

accuracy assessment of global barotropic ocean tide models the accuracy of state of the art global barotropic tide models is assessed using bottom pressure data coastal tide gauges satellite altimetry various geodetic data on antarctic ice shelves and independent tracked satellite orbit perturbations tide models under review include empirical purely hydrodynamic forward and assimilative dynamical i e constrained by observations ten dominant tidal constituents in the diurnal semidiurnal and quarter diurnal bands are considered since the last major model comparison project in 1997 models have improved markedly especially in shallow water regions and also in the deep ocean the root sum square differences between tide observations and the best models for eight major constituents are approximately 0 9 5 0 and 6 5 cm for pelagic shelf and coastal conditions respectively large intermodel discrepancies occur in high latitudes but testing in those regions is impeded by the paucity of high quality in situ tide records long wavelength components of models tested by analyzing satellite laser ranging measurements suggest that several models are comparably accurate for use in precise orbit determination but analyses of grace intersatellite ranging data show that all models are still imperfect on basin and subbasin scales especially near antarctica for the m2 constituent errors in purely hydrodynamic models are now almost comparable to the 1980 era schwiderski empirical solution indicating marked advancement in dynamical modeling assessing model accuracy using tidal currents remains problematic owing to uncertainties in in situ current meter estimates and the inability to isolate the barotropic mode velocity tests against both acoustic tomography and current meters do confirm that assimilative models perform better than purely hydrodynamic models

global charts of ocean tide loading effects global ocean tide loading charts of the radial displacement the potential divided by g gravity acceleration and the gravity effect have been computed using the 11 constituents m2 s2 n2 k2 k1 o1 p1 q1 mf mm ssa of schwiderski s tidal model these new charts have a resolution of 1 1 on the continents as well as on the oceanic area a description of farrell s convolution method to compute the loading effects is given and an estimate of the numerical errors leads to the conclusion that these global charts have a precision better than 2 5 independent of the accuracy of schwiderski s maps the current approximation of the loading effects by a proportionality relation with the local oceanic tides is also compared with farrell s convolution method departures of several centimeters systematically appear in particular over the continental shelves we then show that the maps of the oceanic tides deduced from satellite altimetry could be corrected for the loading effect by an iterative computational procedure based on our algorithm of farrell s convolution

climate change on the yucatan peninsula during the little ice age we studied a 5 1 m sediment core from aguada x caamal 20 36 6 n 89 42 9 w a small sinkhole lake in northwest yucatan mexico between 1400 and 1500 a d oxygen isotope ratios of ostracod and gastropod carbonate increased by an average of 2 2 and the benthic foraminifer ammonia beccarii parkinsoniana appeared in the sediment profile indicating a hydrologic change that included increased lake water salinity pollen from a core in nearby cenote san jose chulchaca showed a decrease in mesic forest taxa during the same period oxygen isotopes of shell carbonate in sediment cores from lakes chichancanab 19 53 0 n 88 46 0 w and salpeten 16 58 6 n 89 40 5 w to the south also increased in the mid 15th century but less so than in aguada x caamal climate change in the 15th century is also supported by historical accounts of cold and famine described in maya and aztec chronicles we conclude that climate became drier on the yucatan peninsula in the 15th century a d near the onset of the little ice age lia comparison of results from the yucatan peninsula with other circum caribbean paleoclimate records indicates a coherent climate response for this region at the beginning of the lia at that time sea surface temperatures cooled and aridity in the circum caribbean region increased

a coral sr ca calibration and replication study of two massive corals from the gulf of mexico abstract this study examined the variations in the ratio of strontium to calcium sr ca for two atlantic corals montastraea faveolata and siderastrea siderea from the dry tortugas national park centered on 24 7 n 82 8 w in the gulf of mexico cores from coral colonies in close proximity 10s of meters and with the same environmental conditions i e depth and water chemistry were micro sampled with approximately monthly resolution and the resulting sr ca variations were calibrated with local sea surface temperature sst records replication tests for coral sr ca variations found high agreement between intra colony variations and between individual colonies of s siderea a single m faveolata colony was sampled regression analysis of monthly variations in coral sr ca and local sst revealed significant correlation on monthly and inter annual timescales verification of the calibration on different timescales found coral sr ca sst reconstructions in s siderea were more accurate than those from m faveolata especially on inter annual timescales sr ca sst calibration equations for the two species are significantly different cf sr ca 0 042 sst 10 070 s siderea sr ca 0 027 sst 9 893 m faveolata mean linear extension for m faveolata is approximately twice that of s siderea 4 63 4 31 and 8 31 mm year 1 a1 f1 and b3 respectively however seasonal sr ca variability in m faveolata is less than s siderea 0 323 0 353 and 0 254 mmol mol 1 a1 f1 and b3 respectively the reduced slope for m faveolata is attributed to physical sampling issues associated with complex time skeletal structure of m faveolata i e a sampling effect and not a growth effect since the faster growing m faveolata has the reduced sr ca variability

anisotropic shear wave velocity structure of the earth s mantle a global model 1 we combine a new large data set of surface wave phase anomalies long period waveforms and body wave travel times to construct a three dimensional model of the anisotropic shear wave velocity in the earth s mantle our modeling approach is improved and more comprehensive compared to our earlier studies and involves the development and implementation of a new spherically symmetric reference model simultaneous inversion for velocity and anisotropy as well as discontinuity topographies and implementation of nonlinear crustal corrections for waveforms a comparison of our new three dimensional model s362ani with two other models derived from comparable data sets but using different techniques reveals persistent features 1 strong 200 km thick high velocity anomalies beneath cratons likely representing the continental lithosphere underlain by weaker fast anomalies extending below 250 km which may represent continental roots 2 weak velocity heterogeneity between 250 and 400 km depths 3 fast anomalies extending horizontally up to 2000 3000 km in the mantle transition zone beneath subduction zones 4 lack of strong long wavelength heterogeneity below 650 km suggesting inhibiting character of the upper mantle lower mantle boundary and 5 slow velocity superplumes beneath the pacific and africa the shear wave radial anisotropy is strongest at 120 km depth in particular beneath the central pacific lateral anisotropic variations appreciably improve the fit to data that are predominantly sensitive to the uppermost and lowermost mantle but not to the waveforms that control the transition zone and midmantle depths tradeoffs between lateral variations in velocity and anisotropy are negligible in the uppermost mantle but noticeable at the bottom of the mantle

late holocene changes in precipitation and hydrography recorded in marine sediments from the northeastern caribbean sea abstract we present a record of climate variability spanning the last 2000 years obtained from sediment cores retrieved south and west of puerto rico in the northeastern caribbean sea the records include lithological and mineral magnetic parameters as well as planktonic foraminifer data for chronostratigraphic control ams 14 c and 210 pb 137 cs measurements were made harmonic analysis of the values of the mineral magnetic parameters saturation isothermal remanent magnetization sirm anhysteric remanent magnetization divided by magnetic susceptibility arm and saturation isothermal remanent magnetization divided by magnetic susceptibility sirm indicate the existence of a 200 year long climate cycle in the northeastern caribbean during the last 2000 years the detected cycle may reflect changes in precipitation patterns over the low latitude north atlantic ocean and surrounding continental areas higher organic carbon contents appear in the sediments both off southern and western puerto rico before and at the onset of the little ice age around a d 1300 to 1500 this is indicative of increased run off and or enhanced surface productivity possibly associated with more intense wind induced upwelling major changes in the geochemical and mineral magnetic records around a d 850 1000 concur with changes in other records from the caribbean and north african regions indicating a shift toward a more humid climate over the low latitude north atlantic

typhoon induced ground deformation geodetic instruments now offer compelling sensitivity allowing to investigate how solid earth and surface processes interact by combining surface air pressure data nontidal sea level variations model and rainfall data we systematically analyze the volumetric deformation of the shallow crust at seven borehole strainmeters in taiwan induced by 31 tropical cyclones typhoons that made landfall to the island from 2004 to 2013 the typhoon s signature consists in a ground dilatation due to air pressure drop generally followed by a larger ground compression we show that this compression phase can be mostly explained by the mass loading of rainwater that falls on the ground and concentrates in the valleys towards the strainmeter sensitivity zone further our analysis shows that borehole strainmeters can help quantifying the amount of rainwater accumulating and flowing over a watershed during heavy rainfalls which is a useful constraint for building hydrological models

mid to late holocene changes in tropical atlantic temperature seasonality and interannual to multidecadal variability documented in southern caribbean corals proxy reconstructions of tropical atlantic sea surface temperature sst that extend beyond the period of instrumental observations have primarily focused on centennial to millennial variability rather than on seasonal to multidecadal variability here we present monthly resolved records of sr ca a proxy of sst from fossil annually banded diploria strigosa corals from bonaire southern caribbean sea the individual corals provide time windows of up to 68 years length and the total number of 295 years of record allows for assessing the natural range of seasonal to multidecadal sst variability in the western tropical atlantic during snapshots of the mid to late holocene comparable to modern climate the coral sr ca records reveal that mid to late holocene sst was characterised by clear seasonal cycles persistent quasi biennial and prominent interannual as well as inter to multidecadal scale variability however the magnitude of sst variations on these timescales has varied over the last 6 2 ka the coral records show increased seasonality during the mid holocene consistent with climatemodel simulations indicating that southern caribbean sst seasonality is induced by insolation changes on orbital timescales whereas internal dynamics of the climate system play an important role on shorter timescales interannual sst variability is linked to ocean atmosphere interactions of atlantic and pacific origin pronounced interannual variability in the western tropical atlantic is indicated by a 2 35 ka coral possibly related to a strengthening of the variability of the el nino southern oscillation throughout the holocene prominent inter to multidecadal sst variability is evident in the coral records and slightly more pronounced in the mid holocene we finally argue that our coral data provide a target for studying holocene climate variability on seasonal and interannual to multidecadal timescales when using further numerical models and high resolution proxy data

rapid analysis of high precision sr ca ratios in corals and other marine carbonates a method for rapid determination of high precision sr ca ratios in scleractinian corals is presented using an inductively coupled plasma atomic emission spectrophotometer samples are corrected for instrument drift using a reference solution similar to the approach used for analysis of stable isotopes using gas source mass spectrometry further correction for variation of the sr ca ratio with ca concentration is accomplished using internal standards the precision once all corrections have been made is better than 0 1 relative standard deviation 1 for samples of similar ca concentration and better than 0 2 for samples with variable ca concentrations this method increases the sample throughput by approximately a factor of 20 relative to thermal ionization mass spectrometry and significantly reduces instrument and per sample costs comparison of sr ca data for a coral from the galapagos islands with an instrumental temperature record shows excellent agreement and demonstrates the potential for application of this technique to samples of modern and fossil scleractinian corals and other marine carbonates including foraminifera

corals record persistent multidecadal sst variability in the atlantic warm pool since 1775 ad 1 accurate low latitude sea surface temperature sst records that predate the instrumental era are needed to put recent warming in the context of natural climate variability and to evaluate the persistence of lower frequency climate variability prior to the instrumental era and the possible influence of anthropogenic climate change on this variability here we present a 235 year long sst reconstruction based on annual growth rates linear extension of three colonies of the atlantic coralsiderastrea sidereasampled at two sites on the northeastern yucatan peninsula mexico located within the atlantic warm pool awp awp ssts vary in concert the atlantic multidecadal oscillation amo a basin wide quasiperiodic 60 80 years oscillation of north atlantic ssts we demonstrate that the annual linear growth rates of all three coral colonies are significantly inversely correlated with sst we calibrate annual linear growth rates to sst between 1900 and 1960 ad the linear correlation coefficient over the calibration period is r 0 77 and 0 66 over the instrumental record 1860 2008 ad we apply our calibration to annual linear growth rates to extend the sst record to 1775 ad and show that multidecadal sst variability has been a persistent feature of the awp and likely of the north atlantic over this time period our results imply that tropical atlantic ssts remained within 1 c of modern values during the past 225 years consistent with a previous reconstruction based on coral growth rates and with most estimates based on the mg ca of planktonic foraminifera from marine sediments

a comparison of predicted and observed ocean tidal loading in alaska we investigate the elastic and anelastic response of the crust and upper mantle across alaska to mass loading by ocean tides gps inferred surface displacements recorded by the plate boundary observatory network are compared with predictions of deformation associated with the redistribution of ocean water due to the tides we process more than 5 yr of gps data from 131 stations using a kinematic precise point positioning algorithm and estimate tidal contributions using harmonic analysis we also forward calculate load induced surface displacements by convolving ocean tide models with load green s functions derived from spherically symmetric earth models we make the comparisons for dominant tidal harmonics in three frequency bands semidiurnal m diurnal o and fortnightly m f vector differences between predicted and observed ocean tidal loading otl displacements are predominantly sub mm in magnitude in all three frequency bands and spatial components across the network with larger residuals of up to several mm in some coastal areas accounting for the effects of anelastic dispersion in the upper mantle using estimates of q from standard earth models reduces the residuals for the m harmonic by an average of 0 1 0 2 mm across the network and by more than 1 mm at some individual stations for the relatively small m f tide the effects of anelastic dispersion 0 03 mm are undetectable within current measurement error incorporating a local ocean tide model for the northeastern pacific ocean reduces the m vertical residuals by an average of 0 2 mm with improvements of up to 5 mm at some coastal stations estimated rms observational uncertainties in the vertical component for the m and o tides are approximately 0 08 mm at the two sigma level 0 03 mm in the horizontal components and 0 21 mm for the m f harmonic 0 07 mm in the horizontal components for the m harmonic discrepancies between predicted and observed otl displacements exceed observational uncertainties by about one order of magnitude none of the ocean tide and earth model combinations is found to reduce the m residuals below the observational uncertainty and no single forward model provides a best fit to the observed displacements across all tidal harmonics and spatial components for the o harmonic discrepancies between predicted and observed displacements are generally several fold larger than the observational uncertainties for the m f harmonic the discrepancies are roughly within a factor of two of the observational uncertainties we find that discrepancies between predicted and observed otl displacements can be significantly reduced by removing a network uniform tidal harmonic displacement and that the remaining discrepancies exhibit some regional scale spatial coherency particularly for the m harmonic we suggest that the remaining discrepancies for the m o and m f tides cannot be fully explained by measurement error and instead convey information about deficiencies in ocean tide models and deviations from spherically symmetric earth structure

sst artifacts in coral proxy records produced by early marine diagenesis in a modern coral from rabaul papua new guinea 1 we investigated the effects of early marine diagenesis on the skeletal geochemistry of a porites coral collected live offshore of rabaul papua new guinea the lowermost 14 cm of the 1 9 m coral core contains physical evidence of alteration which is clearly visible in x radiograph sem and petrography images abrupt and significant increases in coral 18o and sr ca and decreases in coral mg ca occur at the transition from unaltered to altered skeleton all of which imply significant sst cooling if the altered nature of the coral skeleton went unrecognized screening for the effects of early marine diagenesis should become a standard procedure in coral climate studies

paleoclimate proxy perspective on caribbean climate since the year 1751 evidence of cooler temperatures and multidecadal variability 1 annually resolved coral 18o and sr ca records from southwestern puerto rico are used to investigate caribbean climate variability between 1751 and 2004 c e mean surface ocean temperatures in this region have increased steadily by about 2 c since the year 1751 with sr ca data indicating 2 1 0 8 c and 18o data indicating 2 7 0 5 c coral geochemical records from across the tropics demonstrate that regional variability is important for understanding climate variations at centennial time scales a strong multidecadal salinity signal in the oxygen isotope data correlates with observed multidecadal temperature variations in the northern hemisphere instrumental wind and precipitation data indicate that the most recent coral isotopic variations are caused by expansion and contraction of the steep regional salinity gradient forced by trade wind anomalies through meridional ekman transport the timing of the fluctuations suggests that the multidecadal scale wind and surface circulation anomalies might play a role in atlantic temperature variability and meridional overturning circulation but further work is needed to confirm this suggestion

normal mode and free air gravity constraints on lateral variations in velocity and density of earth s mantle with the use of a large collection of free oscillation data and additional constraints imposed by the free air gravity anomaly lateral variations in shear velocity compressional velocity and density within the mantle dynamic topography on the free surface and topography on the 660 km discontinuity and the core mantle boundary were determined the velocity models are consistent with existing models based on travel time and waveform inversions in the lowermost mantle near the core mantle boundary denser than average material is found beneath regions of upwellings centered on the pacific ocean and africa that are characterized by slow shear velocities these anomalies suggest the existence of compositional heterogeneity near the core mantle boundary

a satellite derived climatology of the itcz abstract this paper presents fundamental climatological characteristics of the intertropical convergence zone itcz in a simple concise manner using the highly reflective cloud hrc dataset this satellite derived dataset uses both visible and infrared observations to measure the frequency of occurrence of large scale convective systems over the global tropics at a 1 spatial resolution these dataset characteristics make the hrc particularly well suited for climatological analysis of the itcz because the dataset is based on estimates of organized deep convective cloud systems rather than observations of clouds as a whole and it provides the spatial resolution needed to identify thew large wale convective structures furthermore the dataset covers a time period extending nearly two decades which provides for a fairly robust climatology and the opportunity to examine seasonal and interannual variability of both the convection and the latitude of the itcz

comparison of equatorial pacific sea surface temperature variability and trends with sr ca records from multiple corals coral sr ca is widely used to reconstruct past ocean temperatures however some studies report different sr ca temperature relationships for conspecifics on the same reef with profound implications for interpretation of reconstructed temperatures we assess whether these differences are attributable to small scale oceanographic variability or vital effects associated with coral calcification and quantify the effect of intercolony differences on temperature estimates and uncertainties sr ca records from four massive porites colonies growing on the east and west sides of jarvis island central equatorial pacific were compared with in situ logger temperatures spanning 2002 2012 in general sr ca captured the occurrence of interannual sea surface temperature events but their amplitude was not consistently recorded by any of the corals no long term trend was identified in the instrumental data yet sr ca of one coral implied a statistically significant cooling trend while that of its neighbor implied a warming trend slopes of sr ca temperature regressions from the four different colonies were within error but offsets in mean sr ca rendered the regressions statistically distinct assuming that these relationships represent the full range of sr ca temperature calibrations in jarvis porites we assessed how well sr ca of a nonliving coral with an unknown sr ca temperature relationship can constrain past temperatures our results indicate that standard error of prediction methods underestimate the actual error as we could not reliably reconstruct the amplitude or frequency of el nino southern oscillation events as large as 2 c our results underscore the importance of characterizing the full range of temperature sr ca relationships at each study site to estimate true error

lunar tides in loch ness scotland 1 measurements have been made of the astronomical tide in loch ness scotland which is not directly connected to marine tides our measurements of the loch tide are so far as we know the first in a european lake where the tide originates primarily from ocean tide loading loch ness is a readily accessible lake and is in a region for which the neighboring ocean tides are large and described well by modern global ocean tide models the principal tidal constituent m2 was observed to have an amplitude of approximately 1 5 mm and to be in antiphase at each end of the loch these values are in close agreement with the theoretical combined effects of the direct gravitational tide body tide and the tilt effects due to ocean tide loading computed using green s functions based on conventional elastic earth models by analyzing over long periods for coherent tidal signals we are able to significantly improve the signal to noise ratio in the tilt values compared with values obtained by direct level differencing our tilt accuracy of better than 10 8 measured over 35 km demonstrates loch ness as one the world s longest and most accurate tiltmeters despite this unprecedented accuracy earth tidal models are still at least as accurate as our ability to measure them

nloadf a program for computing ocean tide loading the loading of the earth by the ocean tides produces several kinds of signals which can be measured by geodetic technique in order to compute these most accurately a combination of global and local models of the ocean tides may be needed the program nloadf convolves the green functions for loading with ocean tide models using a station centered grid with fixed dimensions making it easy to combine different ocean models without overlap in the convolution the program computes all the quantities of interest gravity displacement tilt and strain and includes the case where measurements are made beneath the surface of the ocean

precise comparisons of bottom pressure and altimetric ocean tides 1 a new set of pelagic tide determinations is constructed from seafloor pressure measurements obtained at 151 sites in the deep ocean to maximize precision of estimated tides only stations with long time series are used median time series length is 567 days geographical coverage is considerably improved by use of the international tsunami network but coverage in the indian ocean and south pacific is still weak as a tool for assessing global ocean tide models the data set is considerably more reliable than older data sets the root mean square difference with a recent altimetric tide model is approximately 5 mm for the m2 constituent precision is sufficiently high to allow secondary effects in altimetric and bottom pressure tide differences to be studied the atmospheric tide in bottom pressure is clearly detected at the s1 s2 and t2 frequencies the altimetric tide model is improved if satellite altimetry is corrected for crustal loading by the atmospheric tide models of the solid body tide can also be constrained the free core nutation effect in the k1 love number is easily detected but the overall estimates are not as accurate as a recent determination with very long baseline interferometry

variability in the mean latitude of the atlantic intertropical convergence zone as recorded by riverine input of sediments to the cariaco basin venezuela abstract changes in the strength and position of the intertropical convergence zone itcz are an important component of climate variability in the tropical atlantic the cariaco basin located on the northern margin of venezuela is sensitive to tropical atlantic climate change and its sediments provide a record of past itcz behavior today the cariaco basin experiences two distinct seasons that reflect the annual migration of the atlantic itcz between january and march when the itcz lies south of the equator northeasterly trade winds sit directly over cariaco basin and strong coastal upwelling and dry conditions dominate beginning in june july as the itcz moves north local rainfall reaches a maximum and the upwelling diminishes or disappears here we summarize new and previously published data on the river derived terrigenous fraction of cariaco basin sediments as well as comparisons to other paleoclimate records which together suggest a coherent climatologic response in the tropical atlantic triggered by a pattern of itcz migration that mimics the seasonal cycle during periods of cooler north atlantic ssts on time scales ranging from the little ice age to the younger dryas to the cold stadials of the last glacial decreased detrital delivery to cariaco basin from local rivers suggests a southward shift in the mean latitudinal position of the itcz during warm interstadials and periods of holocene and deglacial warmth northward shifts in itcz position and its belt of convective rainfall are inferred from increased detrital delivery to the basin whether the rapid shifts in itcz position and precipitation recorded by cariaco basin sediments and other regional records reflect a response to forcing originating in the high latitude atlantic or to forcing potentially sourced in the tropics is a key question yet to be fully answered

reproducibility of geochemical and climatic signals in the atlantic coral montastraea faveolata 1 monthly resolved 41 year long stable isotopic and elemental ratio time series were generated from two separate heads of montastraea faveolata from looe key florida to assess the fidelity of using geochemical variations in montastraea the dominant reef building coral of the atlantic to reconstruct sea surface environmental conditions at this site the stable isotope time series of the two corals replicate well mean values of 18o and 13c are indistinguishable between cores compare 0 70 versus 0 68 for 13c and 3 90 versus 3 94 for 18o mean values from the sr ca time series differ by 0 037 mmol mol which is outside of analytical error and indicates that nonenvironmental factors are influencing the coral sr ca records at looe key we have generated significant 18o sea surface temperature sst r 0 84 and sr ca sst r 0 86 calibration equations at looe key however these equations are different from previously published equations for montastraea variations in growth parameters or kinetic effects are not sufficient to explain either the observed differences in the mean offset between sr ca time series or the disagreement between previous calibrations and our calculated 18o sst and sr ca sst relationships calibration differences are most likely due to variations in seawater chemistry in the continentally influenced waters at looe key additional geochemical replication studies of montastraea are needed and should include multiple coral heads from open ocean localities complemented whenever possible by seawater chemistry determinations

a 2000 year record of caribbean and tropical north atlantic hydrographic variability 1 here we present near annually resolved oxygen isotope records from two species of planktic foraminifera from the cariaco basin that reflect sea surface temperature sst and intertropical convergence zone itcz precipitation related salinity variations over the caribbean and tropical north atlantic spanning the last 2000 years a strong broad spatial pattern of correlation exists between foraminiferal 18o and ssts over the period of instrumental overlap but the correlations weaken as they are extended back in time and instrumental sst records become discontinuous a long term trend in the globigerinoides ruber 18o record can be explained by two different but equally plausible scenarios first the increase in 18o may indicate that tropical summer fall ssts have cooled by as much as 2 c over the last 2000 years possibly as a result of a long term increase in upwelling intensity alternately comparisons to other studies of itcz and regional evaporation precipitation variability suggest that much of the 18o record is influenced by decadal to centennial scale variations in the mean annual position of the itcz and associated rainfall patterns similarities between the g bulloides 18o record and the 11 year sunspot cycle support prior studies that suggest solar variability plays a role in influencing the hydrologic balance of the circum caribbean

analysis of tidal signals in surface displacement measured by a dense continuous gps array abstract we analyze the tidal displacement signals for the eight major diurnal and semidiurnal tides from global positioning system gps measurements made at the western united states over the past 16 years with 1075 independent stations by careful examinations among inland versus coastal gps data we are able to demonstrate that estimated precisions down to the level of 0 1 mm horizontal and 0 3 mm vertical have been reached for the tidal signals and that at such precisions coherent spatial patterns are revealed in the residual tidal amplitudes and phases after the removal of a priori modeled effects of body tides and ocean tidal loading otl we demonstrate the facility of modern precise gps data in not only constraining the ocean tide models but more significantly in providing source data in terms of regional complex love numbers for geophysical inference of the heterogeneities of elastic and inelastic structures in the solid earth s deep interior on tidal timescales

accuracy of the international terrestrial reference frame origin and earth expansion the international terrestrial reference frame itrf is a fundamental datum for high precision orbit tracking navigation and global change monitoring accurately realizing and maintaining itrf origin at the mean earth system center of mass cm is critical to surface and spacecraft based geodetic measurements including those of sea level rise and its sources although itrf combines data from satellite laser ranging slr very long baseline interferometry vlbi global positioning system gps and doppler orbitography and radiopositioning integrated by satellite doris its origin is currently realized by the single technique of slr consequently it is difficult to independently evaluate the origin accuracy also whether the solid earth is expanding or shrinking has attracted persistent attention the expansion rate if any has not been accurately determined before due to insufficient data coverage on the earth s surface and the presence of other geophysical processes here we use multiple precise geodetic data sets and a simultaneous global estimation platform to determine that the itrf2008 origin is consistent with the mean cm at the level of 0 5 mm yr 1 and the mean radius of the earth is not changing to within 1 measurement uncertainty of 0 2 mm yr 1

joint inversion of rayleigh wave phase velocity and ellipticity using usarray constraining velocity and density structure in the upper crust rayleigh wave ellipticity or h v ratio observed on the surface is particularly sensitive to shallow earth structure in this study we jointly invert measurements of rayleigh wave h v ratio and phase velocity between 24 100 and 8 100 sec period respectively for crust and upper mantle structure beneath more than 1000 usarray stations covering the western united states upper crustal structure in particular is better constrained by the joint inversion compared to inversions based on phase velocities alone in addition to imaging vs structure we show that the joint inversion can be used to constrain vp vs and density in the upper crust new images of uppermost crustal structure 3 km depth are in excellent agreement with known surface features with pronounced low vs low density and high vp vs anomalies imaged in the locations of several major sedimentary basins including the williston powder river green river denver and san juan basins these results demonstrate not only the consistency of broadband h v ratios and phase velocity measurements but also that their complementary sensitivities have the potential to resolve density and vp vs variations

tidal observations on floating ice using a single gps receiver 1 we measure ocean tides as experienced by sea ice or ice shelves using a single gps receiver such a method allows for tidal measurements to be made with the same precision regardless of its distance from a gps base station since such a base station is not required single epoch observations are shown to be accurate to about 50 mm when compared with concurrent bottom pressure gauge bpg observations the differences between the gps and bpg observations are largely free from power at tidal frequencies furthermore harmonic tidal analyses show that these gps observations allow the correct determination of diurnal and semi diurnal tidal constituents meaning that observations of this type can be assimilated into numerical tide models

coral windows onto seasonal climate variability in the northern caribbean since 1479 mean surface ocean conditions in the caribbean were up to 2 c cooler than today at times during the little ice age the seasonal context for such mean state changes is important for determining the mechanisms involved we reconstructed surface ocean conditions in southwest puerto rico at approximately monthly resolution over eight 4 12 year periods during the last 520 years to test if the seasonal cycles of temperature or salinity varied with mean state we carried out paired analyses of sr ca and 18o for two coral cores the 18o data contained clear annual cycles and were significantly correlated to temperature during the 20th century calibration periods 1993 2004 and 1902 1912 r 0 73 the sr ca data contained high frequency noise that obscured the seasonal cycles although the centennial variability matched that of the coral 18o indicating a common forcing that is likely temperature the seasonal coral 18o amplitude averaged 0 60 0 17 with none of the periods significantly different from the most recent the simplest explanation is that the amplitudes of seasonal seawater 18o and temperature variations were not different from today previous work in the southern caribbean indicates that the intertropical convergence zone was shifted southward or weaker during the little ice age and we speculate about how this could occur with no apparent affect on seasonality in the northern caribbean

a centennial scale variability of tropical north atlantic surface hydrography during the late holocene abstract sea surface temperature sst and sea surface salinity sss fluctuations in the northeastern caribbean have been reconstructed through the last 2000 yr using an artificial neural network and 18 o analyses of planktonic foraminifera a warmer period prevailed in the ne caribbean from ad 700 950 which may reflect the occurrence of stronger and or more frequent el nino events a 2 c cooling of winter ssts from ad 1400 to 1550 coincides with the occurrence of reduced solar output the sporer event episodes of lower ssss with marked minima at the onsets of the dark ages in europe ad 500 600 and little ice age ad 1400 are cyclically recurrent at intervals of 200 400 yr and coincide with drier periods in mexico this may indicate that the tropical atlantic evaporation precipitation budget and ssss are affected by a centennial scale modulation involving the freshwater export import from into the atlantic ocean coeval changes recorded in the deep north atlantic circulation indicate that low latitude sss anomalies may be advected polewards by the north atlantic current system thus affecting deep ocean convection and strength of the thermohaline circulation

high resolution palaeoclimatology of the last millennium a review of current status and future prospects this review of late holocene palaeoclimatology represents the results from a pages clivar intersection panel meeting that took place in june 2006 the review is in three parts the principal high resolution proxy disciplines trees corals ice cores and documentary evidence emphasizing current issues in their use for climate reconstruction the various approaches that have been adopted to combine multiple climate proxy records to provide estimates of past annual to decadal timescale northern hemisphere surface temperatures and other climate variables such as large scale circulation indices and the forcing histories used in climate model simulations of the past millennium we discuss the need to develop a framework through which current and new approaches to interpreting these proxy data may be rigorously assessed using pseudo proxies derived from climate model runs where the answer is known the article concludes with a list of recommendations first more raw proxy data are required from the diverse disciplines and from more locations as well as replication for all proxy sources of the basic raw measurements to improve absolute dating and to better distinguish the proxy climate signal from noise second more effort is required to improve the understanding of what individual proxies respond to supported by more site measurements and process studies these activities should also be mindful of the correlation structure of instrumental data indicating which adjacent proxy records ought to be in agreement and which not third large scale climate reconstructions should be attempted using a wide variety of techniques emphasizing those for which quantified errors can be estimated at specified timescales fourth a greater use of climate model simulations is needed to guide the choice of reconstruction techniques the pseudo proxy concept and possibly help determine where given limited resources future sampling should be concentrated

sea surface temperature and salinity reconstruction from coral geochemical tracers massive scleractinian corals secrete an aragonitic skeleton which incorporates a large array of chemical tracers corals present several advantages for palaeoclimate research they grow continuously and can live up to 1000 years they are easy to date and they can be sampled at high resolution weekly to monthly resolution both live and fossil corals can be collected in the field in the past two decades significant efforts have been made to identify robust tracers of sea surface temperature sst and salinity sss in corals to date sr ca and 18o are considered to be the most reliable sst tracers although changes in seawater 18o can significantly alter sst reconstructed from coralline 18o because these variations in seawater 18o can be linked to sss changes this initial problem can in fact be turned into an advantage and provide us with an sss tracer the sst component in the coral 18o signal can either be evaluated through sr ca measurements or in some case simply filtered out however there is still much uncertainty concerning the exact mode of incorporation of trace elements and stable isotopes into the coral skeleton the effects of growth rate light intensity feeding habits ph and water chemistry are still poorly documented a review of the strength and weaknesses of sr ca and 18o is presented together with some examples of sst and sss reconstructions other potential sst tracers are also reviewed it is expected that the ability to grow corals in aquarium under controlled conditions and that the development of sophisticated analytical techniques at the micrometric level should help us understand better the robustness of each tracers and the factors controlling their incorporation in coral aragonite

troposphere mapping functions for gps and very long baseline interferometry from european centre for medium range weather forecasts operational analysis data 1 in the analyses of geodetic very long baseline interferometry vlbi and gps data the analytic form used for mapping of the atmosphere delay from zenith to the line of site is most often a three parameter continued fraction in 1 sin elevation using the 40 years reanalysis era 40 data of the european centre for medium range weather forecasts for the year 2001 the b and c coefficients of the continued fraction form for the hydrostatic mapping functions have been redetermined unlike previous mapping functions based on data from numerical weather models isobaric mapping functions niell 2000 and vienna mapping functions vmf boehm and schuh 2004 the new c coefficients are dependent on the day of the year and unlike the niell mapping functions niell 1996 they are no longer symmetric with respect to the equator apart from the opposite phase for the two hemispheres compared to vmf this causes an effect on the vlbi or gps station heights that is constant and as large as 2 mm at the equator and that varies seasonally between 4 mm and 0 mm at the poles the updated vmf based on these new coefficients and called vmf1 hereinafter yields slightly better baseline length repeatabilities for vlbi data the hydrostatic and wet mapping functions are applied in various combinations with different kinds of a priori zenith delays in the analyses of all vlbi international vlbi service for geodesy and astrometry ivs r1 and ivs r4 24 hour sessions of 2002 and 2003 the investigations concentrate on baseline length repeatabilities as well as on absolute changes of station heights

annual to interannual temperature variability in the caribbean during the maunder sunspot minimum we reconstruct caribbean seawater temperatures from sclerosponge sr ca ratios using a specimen of ceratoporella nicholsoni that grew at 20 m below sea level in a reef cave at jamaica we sample the time interval from 1620 to 1745 a d with almost monthly resolution this interval includes the maunder sunspot minimum one of the coldest periods of the little ice age reconstructed annual temperature amplitudes are on the order of about 1 c the mean growth rate calculated from the annual sr ca variations corresponds perfectly with u th based growth rates we find that the interannual climate variability is determined by el nino southern oscillation and by a decadal signal most likely originating from the tropical north atlantic on a multidecadal timescale the maunder minimum is characterized by a 1 2 c cooling and reduced amplitudes of the interannual and decadal temperature variations

effects of unmodelled tidal displacements in gps and glonass coordinate time series this study demonstrates the effect of unmodelled sub daily tidal displacement on glonass globalnaya navigatsionnaya sputnikovaya sistema coordinate time series in comparison with gps global positioning system more than two propagated periodic signals appear in gps and glonass coordinate time series in the presence of an unmodelled m2 o1 tidal displacements the propagation mechanism of stewart et al 2005 explains well most of the periodic signals at a fortnightly period an unmodeled m2 tidal displacement propagates into two long period signals at 13 6x x is a positive integer and 14 76 days for gps while only a significant propagated periodic signal at 14 76 day is discernible for glonass similarly significant propagated periodic signals at 13 6x and 14 19 days for gps and only at 14 19 day for glonass are evident as a result of an unmodeled o1 tidal displacement however an unmodeled mf long period results in a strong power of similar magnitude at 13 6x day 13 66 day for both gps and glonass solutions the appearance of different periodic signals but as a result of the same unmodelled tidal displacement is attributed to the different ground repeat periods of the constellations which is one of the factors of the propagation mechanism from stewart et al 2005 the latter explains the reason why the 13 6x day fortnightly is present only for gps solutions comparing the powers of the m2 aliased periodic signals at 13 6x day and 14 76 day from a stacked spectra over all stations the amplitude of the former is larger than the latter by an order of magnitude the results of this study may infer that the 13 6x day periodic signal in gps gnss global navigation satellite system derived products of the igs international gnss service is a joint contribution of the propagation of unmodelled sub daily tidal displacements and errors at longer periods with the former appearing to contribute more we also demonstrated that significant reduction of the propagated periodic signals can be achieved from combined system solutions

ocean tide loading displacements in western europe 1 validation of kinematic gps estimates gps has been extensively used to estimate tidal ground displacements but the accuracy of this has not been systematically verified using more than 20 sites distributed across western europe we show that postprocessed kinematic precise point positioning gps with appropriately tuned process noise constraints is capable of recovering synthetic tidal displacements inserted into real data with a typical accuracy of 0 2 mm depending on the time series noise the kinematic method does not result in erroneous propagation of signals from one coordinate component to another or to the simultaneously estimated tropospheric delay parameters it is robust to the likely effects of day to day equipment and reference frame changes and to outages in the data a minimum data span of 4 years with at least 70 availability is recommended finally we show that the method of reducing apparent coordinate time series noise by constraining the tropospheric delay to values previously estimated in static batch gps analysis in fact results in the suppression of true tidal signals using our kinematic gps analysis approach periodic displacements can be reliably observed at the 0 2 mm level which is suitable for the testing and refinement of ocean tide and solid earth response models

suspended sediment transport in the seine estuary france effect of man made modifications on estuary shelf sedimentology abstract man made modifications of the seine estuary have produced large geometric changes with important hydrographic and sedimentological consequences affecting estuary shelf interrelationships the estuary once had shallow meandering ebb and flood tidal channels and broad tidal flats today after 130 years of landfill marsh reclamation jettying and dredging there is only a narrow deep jettied channel extending to the sea most of the tidal flats and marshes have been filled these modifications have concentrated river discharge and ebb flow into a narrow jettied channel which in turn has produced a seaward migration of the salt intrusion and the turbidity maximum as the estuary volume was reduced river flow dilution was also reduced and its mean residence time in the estuary was shortened at the same time sedimentation and landfill have reduced the area available for sedimentation of fluvial sediments this change has amplified seaward transport of fluvial suspended sediment and increased the size of shelf mud zones off the estuary mouth man has thus changed the geologic role of the estuary from a sink for fluvial and marine sediment to a source of fluvial sediment for the shelf

ocean tide loading displacements in western europe 2 gps observed anelastic dispersion in the asthenosphere gps observed vertical ocean tide loading displacements show in cornwall southwest england and in brittany northwest france discrepancies of 2 3 mm with predicted values based on the isotropic preliminary reference earth model for the main tidal harmonic m2 yet in central europe the agreement is better than 0 5 mm by comparison of ocean tide models and validation with tide gauge observations we demonstrate that the uncertainties in the former are too small to cause this disagreement furthermore we find that different local models of the crust and different global elastic reference models derived from seismological observations can only reduce the observed discrepancies to 1 2 mm which still exceeds the gps observational uncertainty of 0 2 0 4 mm it is customary to use the elastic properties of the earth as given by seismic models previously there has been insufficient evidence to determine how to modify these properties during the transformation from seismic to tidal frequencies to account for possible anelastic dispersion in the asthenosphere and so this effect has been ignored if we include this effect then our discrepancies reduce further to 0 2 0 4 mm this value is of the same order as the sum of the remaining errors due to uncertainties in the ocean tide models and in the gps observations themselves this research provides evidence in western europe of a reduction of around 8 10 of the seismic shear modulus in the asthenosphere at tidal frequencies in addition we find that the asthenosphere absorption band frequencies can be represented by a constant quality factor q

an 8 century tropical atlantic sst record from the cariaco basin baseline variability twentieth century warming and atlantic hurricane frequency 1 we present the first direct comparison and calibration of a downcore foraminiferal mg ca record to historical instrumental sea surface temperature sst mg ca measured on the planktic foraminifer globigerina bulloides from a cariaco basin sediment core strongly correlate with spring march may instrumental ssts between a d 1870 and 1990 a mg ca sst equation is derived and a paleo sst record is presented spanning the last 8 centuries an interval that includes the end of the medieval warm period and the little ice age the long term record displays a surprising amount of variability the temperature swings are not necessarily related to local upwelling variability but instead represent wider conditions in the caribbean and western tropical atlantic the mg ca sst record also captures the decadal and multidecadal variability observed in records of global land and sea surface temperature anomalies and atlantic tropical storm and hurricane frequency over the late nineteenth and twentieth centuries a divergence between the sst proxy record and atlantic storm frequency around 1970 appears to reflect a fundamental change in atlantic hurricane behavior noted in historical data on average twentieth century temperatures are not the warmest in the entire record but they do show the largest increase in magnitude and fastest rate of sst change over the last 800 a

twentieth century warming of the tropical atlantic captured by sr u paleothermometry coral skeletons are valuable archives of past ocean conditions however interpretation of coral paleotemperature records is confounded by uncertainties associated with single element ratio thermometers including sr ca a new approach sr u uses u ca to constrain the influence of rayleigh fractionation on sr ca decarlo et al 2016 here we build on the initial pacific porites sr u calibration to include multiple atlantic and pacific coral genera from multiple coral reef locations spanning a temperature range of 23 15 30 12 c accounting for the wintertime growth cessation of one bermuda coral we show that sr u is strongly correlated with the average water temperature at each location r2 0 91 p 0 001 n 19 we applied the multi species spatial calibration between sr u and temperature to reconstruct a 96 year long temperature record at mona island puerto rico using a coral not included in the calibration average sr u derived temperature for the period 1900 1996 is within 0 12 c of the average instrumental temperature at this site and captures the 20th century warming trend of 0 06 c per decade sr u also captures the timing of multi year variability but with higher amplitude than implied by the instrumental data mean sr u temperatures and patterns of multi year variability were replicated in a second coral in the same grid box conversely sr ca records from the same two corals were inconsistent with each other and failed to capture absolute sea temperatures timing of multi year variability or the 20th century warming trend our results suggest that coral sr u paleothermometry is a promising new tool for reconstruction of past ocean temperatures

a high resolution calibration of sr ca thermometry using the caribbean coral montastraea annularis 1 a relationship has been established between the sr ca ratio in the skeleton of the scleractinian coral montastraea annularis and sea surface water temperature in south florida in order to obtain this correlation specimens of montastraea annularis were transplanted to a site at a local reef where every two to three months throughout a 2 year period the corals were stained with alizarin red s and where water temperature which annually ranges between 20 and 30 c was continually monitored at the end of the experimental period the coral skeleton was sampled at a rate of 50 samples per year each sample corresponding to only around 20 g of calcium carbonate for the 2 5 year period the sr ca ratio exhibited excellent correlation in the first year r2 0 83 sr ca mmol mol 10 11 0 0452 sst c but a rather poorer correlation in the second year r2 0 68 sr ca mmol mol 10 09 0 0406 sst c averaging the data into monthly values for year 1 we determined a relationship of sr ca mmol mol 10 165 0 0471 sst c on the basis of the excellent correlation between temperature and sr ca we feel that this relationship is the most accurate discrepancies in the second year are suggested to arise from slight sampling errors relative to the stain lines

seasonal changes in sea surface temperature and salinity during the little ice age in the caribbean sea deduced from mg ca and 18o 16o ratios in corals abstract the oxygen isotopic composition 18 o of coral skeletons reflects a combination of sea surface temperature sst and the 18 o of seawater which is related to sea surface salinity sss in contrast the magnesium calcium mg ca ratio of a coral skeleton reflects sst independent of salinity by using the relationships among coral mg ca ratios coral 18 o seawater 18 o and sst it is possible to determine past sst and sss uniquely such determinations were made and calibrated using the mg ca ratio and the 18 o of the modern part of a 3 m long coral core montastrea faveolata collected from the southwest coast of puerto rico in the caribbean sea where both sst and sss changes seasonally and the seawater 18 o measured at the coral site our results yielded three relationships coral mg ca sst 18 o coral 18 o water sst and 18 o water sss with these calibration equations seasonal changes in sst and sss during the little ice age lia in the caribbean sea were reconstructed the 18 o and mg ca ratio of the coral skeleton between 1699 and 1703 suggests that the sst during the lia was approximately 2 c cooler than present with the sss showing greater seasonal changes as well these results are in good agreement with climate based reconstruction from corals based on oxygen isotopes although the possibility of some uncertainty remain in our estimation including long term decadal scale trends in climate

interpreting sea surface temperature from strontium calcium ratios in montastrea corals link with growth rate and implications for proxy reconstructions 1 we analyzed strontium calcium ratios sr ca in four colonies of the atlantic coral genus montastrea with growth rates ranging from 2 3 to 12 6 mm a 1 derived sr ca sea surface temperature sst calibrations exhibit significant differences among the four colonies that cannot be explained by variations in sst or seawater sr ca for a single coral sr ca ratio of 8 8 mmol mol 1 the four calibrations predict ssts ranging from 24 0 to 30 9 c we find that differences in the sr ca sst relationships are correlated systematically with the average annual extension rate ext of each colony such that sr ca mmol mol 1 11 82 0 13 0 058 0 004 ext mm a 1 0 092 0 005 sst c this observation is consistent with previous reports of a link between coral sr ca and growth rate verification of our growth dependent sr ca sst calibration using a coral excluded from the calibration reconstructs the mean and seasonal amplitude of the actual recorded sst to within 0 3 c applying a traditional nongrowth dependent sr ca sst calibration derived from a modern montastrea to the sr ca ratios of a conspecific coral that grew during the early little ice age lia 400 years b p suggests that caribbean ssts were 5 c cooler than today conversely application of our growth dependent sr ca sst calibration to sr ca ratios derived from the lia coral indicates that ssts during the 5 year period analyzed were within error 1 4 c of modern values

sr ca ratios and oxygen isotopes from sclerosponges temperature history of the caribbean mixed layer and thermocline during the little ice age we investigate aragonitic skeletons of the caribbean sclerosponge ceratoporella nicholsoni from jamaica 20 m below sea level mbsl and pedro bank 125 mbsl we use d18o and sr ca ratios as temperature proxies to reconstruct the caribbean mixed layer and thermocline temperature history since 1400 a d with a decadal time resolution our age models are based on u th dating and locating of the radiocarbon bomb spike the modern temperature difference between the two sites is used to tentatively calibrate the c nicholsoni sr ca thermometer the resulting calibration points to a temperature sensitivity of sr ca in c nicholsoni aragonite of about 0 1 mmol mol k our sr ca records reveal a pronounced warming from the early 19th to the late 20th century both at 20 and 125 mbsl two temperature minima in the shallow water record during the late 17th and early 19th century correspond to the maunder and dalton sunspot minima respectively another major cooling occurred in the late 16th century and is not correlatable with a sunspot minimum the temperature contrast between the two sites decreased from the 14th century to a minimum in the late 17th century and subsequently increased to modern values in the early 19th century this is interpreted as a long term deepening and subsequent shoaling of the caribbean thermocline the major trends of the sr ca records are reproduced in both specimens but hardly reflected in the d18o records

diagenesis in pleistocene 80 to 500 ka corals from the ironshore formation implications for paleoclimate reconstruction abstract fossil corals provide a unique opportunity for paleoclimate research because they can be dated and they incorporate climate controlled seawater proxies into their aragonitic skeletons during growth coral skeletons however can only produce reliable environmental information if they have not been diagenetically altered an issue that becomes increasingly probable as the age of the corals increase although commonly used analytical techniques such as thin section scanning electron microscopy and x ray diffraction can highlight obvious mineralogical changes subtle changes in the trace element and isotopic composition of the skeletons may not be evident this premise is assessed by examining orbicella annularis and montastrea cavernosa corals from the pleistocene ironshore formation units a f on grand cayman 80 500 ka to determine the diagenetic effects on both physical and chemical properties of corals in the ironshore formation the corals in units a and c were altered in a semi open diagenetic system by seawater diluted by meteoric water which resulted in chemical diagenesis that changed the elemental and isotopic composition of the corals even though their aragonitic skeletons show no obvious signs of change in contrast the limestones in unit b have been pervasively recrystallized in an open diagenetic system by meteoric waters that caused both chemical and physical changes the corals in units d to f however underwent minimal diagenesis and show no evidence of alteration for altered corals from the ironshore formation elevated mg ca and low sr ca ratios provide evidence of subtle chemical diagenetic changes even in corals that have retained their primary aragonitic skeleton thus corals that are formed of 95 wt aragonite show no evidence of cementation and have mg ca ratios 8 0 mmol mol 1 18o values 5 7 and 13c values 3 0 are ideal candidates for paleoclimate reconstruction adoption of these criteria shows that the corals from units d to f can be used to calculate sea surface temperatures sst whereas those from units a to c cannot be used for this purpose the calculated sst and the corresponding temperature profiles derived from the corals in units d to f are consistent with global sst reconstructions during the pleistocene unit d corals record an overall increase in sst which is consistent with elevated temperatures associated with marine isotope stage mis 5e whereas units e and f record overall cooling which is consistent with the end of the peak interglacials of mis 5c and 5a respectively

the tidal displacement field at earth s surface determined using global gps observations 1 we investigate the 3 d tidal displacement field on earth s surface recorded globally by 456 continuous global positioning system gps stations of igs spanning 1996 2011 for eight principal diurnal and semidiurnal tidal constituents in phase and quadrature amplitudes of the residual tidal displacements after removal of an a priori body tide model are estimated using the precise point positioning ppp technique on the daily gps data the resultant daily estimates are combined to derive final estimates for each tide at each station the results are compared with the predictions of eight recent global ocean tide models separately for coastal 307 and inland 149 stations we show that gps can provide tidal displacement estimates accurate to the level of 0 12 mm horizontal and 0 24 mm vertical for the lunar only constituents m2 n2 o1 and q1 and less favorably for solar related tidal constituents s2 k2 k1 and p1 although improved by ambiguity resolution most recent ocean tide models fit the gps estimates equally well on the global scale but do not agree well between them in certain coastal areas especially for the vertical displacements suggesting the existence of model uncertainties near shallow seas the tidal residuals for the inland stations after removing both body tides and ocean tidal loading otl furthermore show clear continental scale spatial coherence implying deficiencies of the a priori body tide modeling in catching lateral heterogeneity in elastic as well as inelastic properties in the earth s deep interior we assert that the gps tidal displacement estimates now achieve sufficient accuracy to potentially provide constraints on the earth s structure

tidal gravity and ocean tide loading in europe b the results are presented from tidal gravity measurements at five sites in europe using lacoste and romberg et gravimeters improvements that we have made to the accuracies of these gravimeters are discussed it is shown that the standard calibration of the international center for earth tides used for worldwide tidal gravity profiles is 1 2 per cent too high the m2 and o1 observations are compared with model calculations of the earth s body tide and ocean tide loading and it is shown that there is a very significant improvement in the agreement between observations and models compared to that obtained with previous tidal gravity measurements for o1 where the ocean tide loading and attraction in central europe is only 0 4 per cent of the body tide our measurements verify that the dehant wahr anelastic body tide model gravimetric factor is accurate to 0 2 per cent it is also shown that the effects of lateral heterogeneities in earth structure on tidal gravity are too small to explain the large anomalies in previously published tidal gravity amplitudes the observations clearly show the importance of conserving tidal mass in the schwiderski ocean tide model for sites in central europe the m2 and o1 observations and the models are in agreement at the 0 1 gal 10 9 m s 2 level and tidal corrections to this accuracy can now be made to absolute gravity measurements

temporal and spatial variations in suspended matter in continental shelf and slope waters off the north eastern united states seston in waters of georges bank originates primarily from biological production and from resuspension of bottom sediments the concentrations of suspended matter observed on the central shoals are more influenced by storms than by seasonal changes winter storms produce highest concentrations of non combustible material throughout the water column and summer storms appear to increase biological production by mixing additional nutrients into the photic zone on the south east flank of the bank in water depths between 80 and 200 in the concentrations of total suspended matter and non combustible material show little variation compared with the central shoals and storm effects are far less noticeable highest concentrations 15 mg 1 1 of suspended matter occur in bottom waters south of nantucket island after winter storms and appear to be primarily resuspended bottom sediment resuspended sediment is also common in near bottom waters of the south western gulf of maine and occasionally near the intersection of the shelf slope water mass front and the bottom seasonal variations were observed in the distribution and species composition of phytoplankton coccoliths are predominant on the central bank during the winter but during the spring and summer they are concentrated on the eastern flank at deeper depths

caribbean sea surface temperatures two to three degrees cooler than present during the little ice age we determined the seasonal environmental conditions during the little ice age lia by interpreting isotope proxies in the coral skeleton of montastrea faveolata from the northeast caribbean the oxygen isotope composition was determined for three time intervals during the lia 1700 1705 1780 1785 1810 1815 thought to correspond to the coldest intervals the period 1984 1989 was used to represent modern calibration conditions we determined that ssts from the lia intervals are nearly 2 3 c cooler than present lia cooling in the caribbean may have resulted from regional oceanic and atmospheric circulation differences especially in winter we propose that a trough of cold air from the north atlantic may have extended farther south than present into the northern caribbean although there are indications from pacific corals that seasonality was greater during the lia this does not seem to be the case for the caribbean

consideration of tidal variations in the geocenter on satellite altimeter observations of ocean tides tidal geocenter motion has been previously ignored when developing ocean tide models from satellite altimetry accounting for tidal geocenter motion is necessary because the best orbit determinations for altimetric satellites position sea surface heights relative to the center of mass of the total earth system including the ocean tides but the ocean tides are presumed relative to the earth s crust and thus are effectively relative to the center of figure by accounting for this effect we find improved agreement between an altimeter based ocean tide model and bottom pressure recorder observations the variance of differences between these two observations is reduced by 31 and 43 for the two tidal constituents with the largest contributions to geocenter variations o1 and k1 respectively with this accommodation the predicted contribution from altimeter based ocean tide models to geocenter variations is amplified by 15 22 providing improved agreement with observations especially for the k1 component

probing asthenospheric density temperature and elastic moduli below the western united states periodic ocean tides continually provide a cyclic load on earth s surface the response to which can be exploited to provide new insights into earth s interior structure we used geodetic observations of surface displacements induced by ocean tidal loads to constrain a depth dependent model for the crust and uppermost mantle that provides independent estimates of density and elastic moduli below the western united states and nearby offshore regions our observations require strong gradients in both density and elastic shear moduli at the top and bottom of the asthenosphere but no discrete structural discontinuity at a depth of 220 kilometers the model indicates that the asthenosphere has a low density anomaly of 50 kilograms per cubic meter a temperature anomaly of 300 c can simultaneously explain this density anomaly and inferred colocated minima in elastic moduli

the sensitivity of surface mass loading displacement response to perturbations in the elastic structure of the crust and mantle surface mass loads generate a rich spectrum of deformation responses in the solid earth that might be exploited to probe the material properties of the crust and mantle here we present a detailed examination of load induced surface displacements and their sensitivities to systematic perturbations in elastic earth structure we compute love numbers and displacement load green s functions lgfs by integrating the equations of motion for spheroidal deformation of a radially heterogeneous and self gravitating earth sensitivity kernels are derived for individual love numbers numerically using finite differences and quasi analytically using calculus of variations we then generate sensitivity kernels for displacement lgfs by systematically perturbing the preliminary reference earth model we find that displacement lgfs are most sensitive to elastic structural perturbations within 500 km depth from the surface and for short source receiver distances for separate perturbations to the shear modulus bulk modulus and density within the crust and mantle the sensitivity kernels exhibit unique patterns consistent with the possibility to constrain the parameters independently given a spatially distributed set of sufficiently accurate loading response observations the sensitivity to density structure however is generally weak in comparison to elastic structure we also examine the sensitivity of surface displacements caused by m 2 ocean tidal loading otl to systematic perturbations in the elastic moduli and density since otl induced surface displacements are load and site dependent we focus on high resolution profiles across iceland as a case study the sensitivity kernels constitute a key element in the formulation of the inverse problem with application to geodetic tomography

southward migration of the intertropical convergence zone through the holocene titanium and iron concentration data from the anoxic cariaco basin off the venezuelan coast can be used to infer variations in the hydrological cycle over northern south america during the past 14 000 years with subdecadal resolution following a dry younger dryas a period of increased precipitation and riverine discharge occurred during the holocene thermal maximum since approximately 5400 years ago a trend toward drier conditions is evident from the data with high amplitude fluctuations and precipitation minima during the time interval 3800 to 2800 years ago and during the little ice age these regional changes in precipitation are best explained by shifts in the mean latitude of the atlantic intertropical convergence zone itcz potentially driven by pacific based climate variability the cariaco basin record exhibits strong correlations with climate records from distant regions including the high latitude northern hemisphere providing evidence for global teleconnections among regional climates

volcano monitoring using gps developing data analysis strategies based on the june 2007 kīlauea volcano intrusion and eruption 1 the global positioning system gps is one of the most common techniques and the current state of the art used to monitor volcano deformation in addition to slow several centimeters per year displacement rates gps can be used to study eruptions and intrusions that result in much larger tens of centimeters over hours days displacements it is challenging to resolve precise positions using gps at subdaily time intervals because of error sources such as multipath and atmospheric refraction in this paper the impact of errors due to multipath and atmospheric refraction at subdaily periods is examined using data from the gps network on k lauea volcano hawai i methods for filtering position estimates to enhance precision are both simulated and tested on data collected during the june 2007 intrusion and eruption comparisons with tiltmeter records show that gps instruments can precisely recover the timing of the activity

sediment transport in a microtidal estuary matanzas river florida u s a abstract tidal channels and shoals at the mouth of the matanzas river are the site of considerable sediment transport rates and patterns of transport were determined using fluorescent dyed sediment tracers which were introduced on three intertidal locations temporal sampling after introduction was at the surface and by coring transport rates and patterns were examined for both quartz and shell hash fragments in the distinctly bimodal sediment wave activity and time velocity asymmetry of currents produced a net landward sediment transport over the channel margin bar and flood delta the combination of time velocity asymmetry and deflection of currents by the ebb shield causes landward transport over the flood delta ebb transport of sediment dominates in the south flood channel minimum sediment transport rates vary with morphology currents and grain size parameters but these rates average 15 20 m over one tidal cycle wave activity enhances transport of shell hash vertical variation in tracer concentration consistently decreases with depth depth of disturbance values are typically 10 15 cm on the channel margin bar but are variable elsewhere being controlled by type and height of bedforms

a new test of earth tide models in central europe new improved ocean tide models allow a corresponding improvement in ocean tide loading computations during recent years various groups have made more accurate tidal gravity observations in central europe using gravimeters carefully calibrated on various calibration lines this progress with tidal gravity measurements and ocean loading corrections now allows a more comprehensive test of body tide models than was possible previously it is shown that the o1 and m2 gravimetric factors corrected using the latest ocean tide models are very consistent between the sites despite the different instruments and gravity calibration lines that have been used these observations allow constraints to be put on the anelasticity of the earth at tidal frequencies the corrected gravimetric factors are consistent with recent model results for both the elastic prem model and with 0 09 for an anelastic prem model with the q for dissipation in shear varying as frequency to the power

insights into sea surface temperatures from the cayman islands from corals over the last 540 years abstract seven large corals orbicella annularis and montastrea cavernosa from grand cayman and cayman brac which grew between 1474 to 1512 ce and 1815 to 2014 ce are characterized by growth banding that reflects bi annual growth periods some of these growth bands however include micro scale bands that reflect sub annual growth phases paleotemperatures derived from the oxygen isotope composition of these corals indicate that sea surface temperature sst between 1474 to 1512 ce and 1815 to 2014 ce ranged from 18 to 34 c and included four main periods of temperature change with smaller scale warm or cool intervals superimposed on these periods cool period 1 1474 to 1512 ce coincided with decreased temperatures that existed in the northern hemisphere during the little ice age lia ca 1450 1850 ce cool period 2 1815 to 1924 ce coincided with a caribbean wide reduction in temperatures that was probably related to the final phase of the lia warm period 1 1924 to 2006 ce is characterized by an overall increase in sst consistent with the pronounced global warming since the 1970 s modern period 1 2006 2014 ce is characterized by temperatures that fluctuate around 28 5 c the current average water temperature for grand cayman the overall 3 c 0 96 c increase in sst since 1815 ce derived from the cayman corals is consistent with the caribbean and global temperature increases since the 1850 s smaller scale deviations in the cayman temperature profiles from the general caribbean global temperature trends probably reflect local factors such as increased storm and or cold air front frequencies a reduction in the size and or intensity of the atlantic warm pool shifts in the phase of the atlantic multidecadal oscillation and or weakening of the cayman basin current

dating earthquakes with high precision thorium 230 ages of very young corals mass spectrometric techniques have recently yielded significant increases in precision and sensitivity over previous methods for measuring 230 th abundance in corals to assess the accuracy of 230 th ages three corals from vanuatu whose ages were known from counting annual growth bands were analyzed for each sample the date of growth determined by 230 th analysis a d 1969 3 1932 5 and1806 5 2 uncertainties based on analytical error was indistinguishable from the date determined by counting bands a d 1971 1973 1935 1937 and 1804 1810 indicating that the 230 th dates are accurate 230 th dates were also determined for two adjacent emerged heads from santo is vanuatu which were thought to have died when they were raised above sea level during coseismic uplift the dates a d 1864 4 1866 4 were the same indicating that the heads died at the same time and consistent with the idea that they were killed by coseismic emergence around a d 1865 the difference between this date and the date of the only major historically documented earthquake that caused uplift a d 1973 m s 7 5 suggests a seismic recurrence interval of108 4y for santo analogous emerged corals from malekula is vanuatu yielded 230 th dates that were similar to each other a d 1729 3 1718 5 and are inferred to have died during coseismic emergence around a d 1729 in conjunction with the date of the only large historically documented earthquake that caused uplift a d 1965 m s 7 5 the recurrence interval for malekula is236 3y if similar emerged corals can be found this appraoch may be extended back in time and to other localities because it appears that such features can now be dated both accurately and precisely

sediment exchanges between the seine estuary and its adjacent shelf the study of sediment dynamics within the seine estuary and its adjacent shelf permits some conclusions regarding sediment exchanges in this coastal zone on the shelf sediment transport is directed toward the seine estuary and contributes to the infilling of the estuary by marine sands and muds these were originally derived from land carried to the shelf at times of lower sea level and subsequently transported shoreward by dominant tidal and wave induced currents in the estuarine section tidal processes form a turbidity maximum both by inducing strong bed resuspension and by trapping fluvial and marine sediments due to flood current predominance occasionally this turbid zone extends seaward during periods of river floods and sediment is redispersed onto the shelf this phenomenon has been amplified by man made modifications of the estuarine morphology however currents patterns tend to retard the natural seaward escape of fluvial material mainly due to dredging operations at the present time thus man has changed the natural role of the estuary from a sink to a source of fluvial sediments for the shelf a tentative sedimentary budget is proposed taking into account the various sources of material and the complexity of sediment dynamics

the role of non uniform roughness in the formation of sand ribbons abstract sand ribbons typically are shallow water sedimentary features characterized as thin elongate bands of sand overlying a coarser lag sediment which is exposed between them the ribbons are oriented along the direction of the dominant current and are formed by a secondary circulation pattern that includes a small component of the boundary shear stress directed toward the center of the sand ribbons a perturbation expansion coupled with flume experiments indicates that this circulation pattern is linked to differences in the bottom roughness between the sand ribbons and the adjacent coarser strips the non uniform turbulence field arising from this roughness distribution drives a secondary helical flow the expansion indicates that there is a preferred ratio of sand ribbon spacing to water depth 4 1 for unstratified channel flow conditions the secondary flow pattern forces the downstream flow to readjust so that the boundary shear stress over the smooth sand strips is considerably smaller than the mean stress this serves to retard the movement of sand through such a system

comparisons of measured and predicted sediment transport rates in tidal currents abstract this paper describes bedload transport measurements in a large scale sedimentary system on the british continental shelf steady flow sediment transport theories are applied to oscillatory tidal currents and various equations are compared with measured transport rates from tracer dispersion experiments the effects of waves on both measured and predicted rates are briefly considered and the predicted directions of sediment movement compared with those inferred from sedimentological data