the tidal spectrum underneath antarctic ice shelves a year long tidal record has been obtained from beneath the george vi ice shelf antarctica an unusual feature of the record is a significant response in tidal species 3 to 7 these harmonics are practically absent from records further north on the west coast of the antarctic peninsula but are present in all tidal height records from george vi sound a strong ter diurnal signal also exists in the tidal currents under the ice shelf nonlinearity also occurs in the tidal motion of the ronne and ekstrom ice shelves but has not been reported from the ross ice shelf the tidal dynamics of several antarctic ice shelves have therefore been modified by a region of strong nonlinear response to tidal forcing if nonlinear tides in the semidiurnal band are present on the ross ice shelf they could account for difficulties in modeling the area s weak semidiurnal tides an anelastic component in the deformation of the ice at the grounding line is tentatively proposed as the mechanism responsible the positioning of recording pressure sensors in pairs on the seafloor and at the ice shelf base will allow this hypothesis to be tested and also provide a value for the power dissipated by tidally induced flexure at the grounding line

impact of the equatorial atlantic on the el nino southern oscillation observations indicate that the atlantic zonal mode influences el nino southern oscillation enso in the pacific as already suggested in previous studies here we demonstrate for the first time using partial coupled experiments that the atlantic zonal mode indeed influences enso the partial coupling experiments are performed by forcing the coupled general circulation model echam5 mpi om with observed sea surface temperature sst in the tropical atlantic but with full air sea coupling allowed in the pacific and indian ocean the ensemble mean of a five member simulation reproduces the observational results well analysis of observations reanalysis and coupled model simulations all indicate the following mechanism sst anomalies associated with the atlantic zonal mode affect the walker circulation driving westward wind anomalies over the equatorial pacific during boreal summer the wind stress anomalies increase the east west thermocline slope and enhance the sst gradient across the pacific the bjerknes positive feedback acts to amplify these anomalies favouring the development of a la nina like anomalies the same mechanisms act for the cold phase of atlantic zonal mode but with opposite sign in contrast to previous studies the model shows that the influence on enso exists before 1970 furthermore no significant influence of the tropical atlantic on the indian monsoon precipitation is found in observation or model

anomalous warming in the indian ocean coincident with el nino the topex poseidon altimeter has provided further evidence that interannual warming occurs in the indian ocean with a frequency similar to that of el nino in the pacific and has yielded important clues to the dynamics driving the warming the signal is especially strong during the 1997 el nino the altimeter observes long waves which move westward from the southeastern indian ocean at about the same time as westwardly wind anomalies appear in the east central portion of the basin the sea level peaks in the southwestern indian ocean and causes a sea level variation signal that is a near mirror image of el nino in the eastern pacific sea surface temperature data also show a similar correlation an analysis of the altimeter data indicates significant variability in the indian ocean during the 1994 and 1997 el nino events at the first and second baroclinic rossby wave modes sea surface temperature and wind data suggest that the indian ocean warming has occurred during several previous el nino events particularly during the large events of 1982 and 1987 based on these observations it is suggested that the warming begins with wind forced rossby waves in the southeastern indian ocean associated with the southern oscillation similar to the forcing of kelvin waves which precede el nino in the pacific

tidal parameters for an inelastic earth abstract the gravimetric factors for an elliptical uniformly rotating earth are computed according to a new definition with respect to wahr s results and considering the mantle inelasticity the love numbers h and k are defined in the elliptical earth case to correspond to the love spherical definition they become latitude dependent the tidal parameters discussed in this paper are computed for an inelastic earth s mantle the numerical results show an increase of 0 4 of the gravimetric factors with respect to the wahr s values the love numbers h and k increase by 1 4 to 3 with respect to the elastic case

long wavelength s wave velocity structure throughout the mantle summary long wavelength s wave velocity anomalies are obtained for the entire mantle by inverting 6ooo long period 40 100s sh body waves and lo00 long period 100 500 s love waves in the shallow mantle the patterns of fast and slow velocity anomalies correlate well with age and tectonics in the depth range of 400 1000 km we find two antipodal fast velocity anomalies one in the western pacific and the other in south america they form a fairly strong i 2 anomaly moreover the 1 2 anomaly is the largest spherical harmonic component throughout the entire mantle except for in the layer of 1000 1300 km depth a fast velocity anomaly near the caribbean previously reported by several other investigators is found between the depths of 1000 and 1300km with diminishing amplitudes it can be traced to canada and the aleutians and may be related to old subducted slabs in the same depth interval similar size anomalies can be found in the middle of the pacific and in the indian ocean these could be checked by more detailed studies to judge the reliability of this study heterogeneity power has a peak at the surface and a secondary peak at the bottom of the mantle d consistent with the existence of chemical and or thermal boundary layers at the base of the mantle we also find a fast velocity anomaly which surrounds the pacific ocean this feature has been found by other researchers previously but its interpretation is difficult due to the trade off between velocity anomaly and core mantle boundary deformation

long period lunar earth tides at the geographic south pole and recent models of ocean tides for many years the ocean tide models of schwiderski 1980 were the standards used by the earth tide community to interpret deviations of observed earth tides from predictions on the basis of earth models constructed by seismologists recently the topex poseidon altimeter mission provided new and improved information on pelagic ocean tides which led several research groups to generate new models of the major oceanic tides this in turn renewed our own interest in the observations of long period lunar tides at the geographic south pole that were reported many years ago with an attempt to interpret the deviation from predictions using the schwiderski models we used four different models of the fortnightly mf and monthly mm ocean tides to calculate their attraction and loading effects at the south pole and compared the results with the observed gravity tides in our earlier interpretation we did not realize that for long period ocean tides the so called greenwich phase does not refer to the phase of these tides at the latitude of greenwich but to the phase at the equator this resulted in a mistake in the relative phases of earth tide and ocean effect at the south pole for mf we now find that all models predict the phase lead of the observed versus theoretical tides within the formal uncertainties however the amplitude is still underpredicted by 1 5 2 per cent this could be due to several reasons instrument calibration errors in the body and or ocean tide models relaxation of the earth s elastic properties and the huge ice sheet of antarctica these possibilities are discussed for the mm tide the observed amplitude is well predicted within error however the uncertainties in the measurements are rather large

equatorial atlantic variability and its relation to mean state biases in cmip5 coupled general circulation model gcm simulations participating in the coupled model intercomparison project phase 5 cmip5 are analyzed with respect to their performance in the equatorial atlantic in terms of the mean state 29 out of 33 models examined continue to suffer from serious biases including an annual mean zonal equatorial sst gradient whose sign is opposite to observations westerly surface wind biases in boreal spring play an important role in the reversed sst gradient by deepening the thermocline in the eastern equatorial atlantic and thus reducing upwelling efficiency and sst cooling in the following months both magnitude and seasonal evolution of the biases are very similar to what was found previously for cmip3 models indicating that improvements have only been modest the weaker than observed equatorial easterlies are also simulated by atmospheric gcms forced with observed sst they are related to both continental convection and the latitudinal position of the intertropical convergence zone itcz particularly the latter has a strong influence on equatorial zonal winds in both the seasonal cycle and interannual variability the dependence of equatorial easterlies on itcz latitude shows a marked asymmetry from the equator to 15 n the equatorial easterlies intensify approximately linearly with itcz latitude when the itcz is south of the equator on the other hand the equatorial easterlies are uniformly weak despite serious mean state biases several models are able to capture some aspects of the equatorial mode of interannual sst variability including amplitude pattern phase locking to boreal summer and duration of events the latitudinal position of the boreal spring itcz through its influence on equatorial surface winds appears to play an important role in initiating warm events

enso influence on the atlantic nino revisited multi year versus single year enso events abstractthe influence of el nino southern oscillation enso on the atlantic nino over the past 113 years is investigated by comparing multi year and single year enso events multi year enso events

asymmetry in the duration of el nino and la nina abstract el nino and la nina are not a simple mirror image but exhibit significant differences in their spatial structure and seasonal evolution in particular sea surface temperature sst anomalies over the equatorial pacific cold tongue are larger in magnitude during el nino compared to la nina resulting in positive skewness of interannual sst variations the associated atmospheric deep convection anomalies are displaced eastward during el nino compared to la nina because of the nonlinear atmospheric response to sst in addition to these well known features an analysis of observational data for the past century shows that there is a robust asymmetry in the duration of el nino and la nina most el ninos and la ninas develop in late boreal spring summer when the climatological cold tongue is intensifying and they peak near the end of the calendar year after the mature phase el ninos tend to decay rapidly by next summer but many la ninas persist through the following year and often reintensify in

on the inconsistent relationship between pacific and atlantic ninos the tropical atlantic wind response to el nino forcing is robust with weakened northeast trade winds north of the equator and strengthened southeast trade winds along and south of the equator however the relationship between sea surface temperature sst anomalies in the eastern equatorial pacific and atlantic is inconsistent with el nino events followed sometimes by warm and other times by cold boreal summer anomalies in the atlantic cold tongue region using observational data and a hindcast simulation of the nucleus for european modeling of the ocean nemo global model at 0 5 resolution nemo orca05 this inconsistent sst relationship is shown to be at least partly attributable to a delayed negative feedback in the tropical atlantic that is active in years with a warm or neutral response in the eastern equatorial atlantic in these years the boreal spring warming in the northern tropical atlantic that is a typical response to el nino is pronounced setting up a strong meridional sst gradient this leads to a negative wind stress curl anomaly to the north of the equator that generates downwelling rossby waves when these waves reach the western boundary they are reflected into downwelling equatorial kelvin waves that reach the cold tongue region in late boreal summer to counteract the initial cooling that is due to the boreal winter wind stress response to el nino in contrast this initial cooling persists or is amplified in years in which the boreal spring northern tropical atlantic warming is weak or absent either because of a positive north atlantic oscillation nao phase or an early termination of the pacific el nino event

observations of load tides at the south pole abstract the use of tidal observations to study the nearly diurnal free wobble mode of the earth is possible if oceanic effects in the tidal record are accurately removed we have analyzed vertical gravity data from the south pole to determine the amplitude and phase of the small daily and semidaily tides observed at the pole since these signals at the pole are most probably caused by oceanic tides our observations provide an excellent target for the oceanic models a comparison with the best models of the oceans now available indicates the need for improvement in measuring and modeling the southern oceans

a discussion of world wide measurements of tidal gravity with respect to oceanic interactions lithosphere heterogeneities earth s flattening and inertial forces abstract by the end of 1981 the international center of earth tides icet had collected and evaluated a considerable amount of data from 180 stations including those of the trans world profile which ensure for the first time a world wide distribution including the tropical areas and the southern hemisphere in 1979 80 new oceanic cotidal maps of high quality established by schwiderski became available these maps fit on land tidal gravity measurements quite successfully a new theoretical approach developed by wahr in 1981 has resulted in a set of theoretical formulae establishing the latitude dependence of the classical elastic amplitude factors for tidal deformations we calculate here for six tidal waves the correlations between the observed gravity variations and those resulting from a calculation based upon the schwiderski maps these correlations are highly significant after subtraction of these oceanic effects we calculate the latitude dependences of the experimentally determined amplitude factors which are found to fit wahr s theoretical formulae there remains however a serious discrepancy in the constant terms of the various formulae the effects of heterogeneities in the lithosphere on tidal deformations are also clearly identified

the heat flow from the continents the terrestrial heat flow is defined as the quantity of heat escaping per unit time from the earth s interior across each unit area of the earth s solid surface the quantity varies from place to place over the surface of the earth as well as with time throughout earth history the total heat being lost from the earth at a given time is the integral of the heat flow taken over the entire surface of earth the heat flow from the continents is therefore but a part of the larger picture of global heat loss indeed the lesser part when compared to the heat loss through the floor of the ocean basins pollack 1980 sclater et al 1980 davies 1980 this is so not only because of the lesser continental area but also because of the generally smaller heat flow found on the continents than in the ocean basins thus a full discussion of the thermal regime of the earth and the mechanisms by which it exhausts heat from the interior must center on the heat loss through the oceans a topic which lies beyond the scope of this review nonetheless because of the geological antiquity of at least some of their constituent terranes the continents provide the only direct evidence about the thermal tectonic and petrologic processes of the earth at times before the birth of any of the modem ocean basins some two hundred million years ago because inferences about earlier times are drawn wholly from materials now preserved in continents one must be cautious not to overgeneralize about global tectonothermal processes from observations confined to continents

a continuing discussion about the correlation of tidal gravity anomalies and heat flow densities on the basis of several objections rydelek et al phys earth planet inter 68 215 219 1991 hereafter noted rzh denied the existence of a correlation between residuals of tidal gravity r and heat flow h suggested by other workers to re examine the whole matter on safe grounds we previously revised and reanalysed all the original tidal data from 300 stations taking care of the rzh objections by eliminating what they considered as the important sources of errors in the data essentially calibration errors of the instruments in amplitude and phase using this new data base we meet here one by one the other criticisms not related to the original tidal measurements and show that most of them are not valid in particular those concerning oceanic load and attraction corrections the findings are as follows 1 no correlation between diurnal tide and semi diurnal tide residuals is normal 2 distance from the sea is not a valid criterion for elimination of several excellent stations 3 unexpected residues at the south pole are not due to imperfections of the cotidal schwiderski maps but to ice shelf tides not considered by rzh 4 the correlation of the tidal gravity residues with the age of tectonic provinces is proposed as an alternative to the correlation with heat flow the data used in 1991 having been corrected are recalculated for comparison with 1986 1991 statistics the correlation is confirmed with the same degree of probability also new tidal gravity data obtained since 1990 with nullified instruments as recommended by rzh in africa 31 stations and latin america 34 stations are included in new statistics which also confirm the correlation the global result obtained from 174 revised and new stations on all continents gives a correlation coefficient k 0 691 with a linear regression r 0 0201 h 57 0 063 0 0013 where r is in microgals and h is in mw m 2 as there is at present no practical or theoretical means to take into account the role of fluids lubrication and stress corrosion owing to deep seated saline waters or fluids in crustal processes such as tidal deformations such small tidal gravity anomalies cannot be correctly calculated the use of a correlation technique therefore remains the only way to treat unexplained residues even if this does not constitute an unequivocal proof other arguments have to be found to deny the existence of this correlation

a new data bank for tidal gravity measurements db 92 abstract tidal gravity parameters are now available in 352 permanent or temporary stations all over the world previous tentative interpretations of these data were made on the basis of a data bank created in 1980 1982 which contained all available results without any discrimination which could have appeared as arbitrary these interpretations were criticized on the basis of the different qualities of instruments null instruments or not data calibration and necessary corrections for ocean continent interactions as we agree that a careful re examination of the basic data is needed before any geophysical discussion we have built this new data bank which contains only those 211 stations where rigid control of every step in the observations calibrations and reduction could be made either because the original data are stored in the world data center c or because the published results give enough information to permit checks and revisions as a result the scattering in the tidal parameters is reduced by a factor of 2 with respect to the previous data while the mean values of the amplitude factors of the two main waves o 1 diurnal m 2 semi diurnal calculated continent by continent agree with the best available earth model it is expected that this new data bank will be used for renewed discussions of the results

the impacts of inter el nino variability on the tropical atlantic and northeast brazil climate abstractin this study observations and numerical simulations are used to investigate how different el nino events affect the development of sst anomalies in the atlantic and how this relates to the brazilian northeast ne precipitation the results show that different types of el nino have different impacts on the sst anomalies of the equatorial and tropical south atlantic but a similar sst response in the tropical north atlantic strong and long weak and short el ninos with the main heating source located in the eastern central pacific generate cold warm anomalies in the cold tongue and benguela upwelling regions during boreal winter and spring when the sst anomalies in the eastern equatorial and tropical south atlantic are cold warm the meridional sst gradient across the equator is positive negative and the itcz is not allowed allowed to move southward during the boreal spring as a consequence the precipitation is below above the average over the ne thus strong and long weak and s

testing recent global ocean tide models with loading gravimetric data as soon as altimetric data from topex poseidon satellite were available several ocean tide models were able to be constructed by different teams in response to the scientific community request here we present a complement to a first comparison study made with ten tidal models llubes and mazzega 1996 we use five more models of which some are updated versions computed using longer time series of altimetric data the loading tide effects predicted by these models are compared to a data base of 228 gravimetric stations provided by the international center for earth tides melchior 1994 global statistical tests provide us with the relative performances of the models merging the five new models with the ten previous models allows us to make more general conclusions csr3 0 eanes 1994 remains the best of the fifteen models for the m2 constituent standard deviation of 0 425 gal for the o1 constituent schwiderski schwiderski 1980 with a standard deviation of 0 298 gal gives the best results when considering only regional subsets of gravimetric data no ocean tide model systematically performs better than any other

towards a detailed knowledge of the world ocean tides the example of the kerguelen plateau a zoom view of a solution of the m2 tide computed over the whole indian ocean and focusing on the kerguelen plateau is presented to illustrate the extent of detail and accuracy which can be expected from solutions produced by a global ocean tide model based on finite element methods developed by the authors the characteristics of the m2 tide as revealed by this solution are in good agreement with the observations available around kerguelen island and explain the phase differences of more than 40 degrees observed between the two sides of the western part of this island which until now has been unexplained for the m2 tide this results from the presence of a one node axisymetric standing wave with a real amphidromic point on the north western side of the plateau which is due to the combination of two waves one coming directly from the ocean to the west and the other propagating counterclockwise on the shelf around the island

multiple causes of interannual sea surface temperature variability in the equatorial atlantic ocean the tropical atlantic ocean shows sea surface temperature variability on interannual timescales observational and model data suggest that some of this variability can be attributed to the advection of anomalously warm northern subtropical waters toward the equator

test of theoretical solid earth and ocean gravity tides summary data from three superconducting gravimeters at four different locations are analysed for agreement with theoretical computations of gravity tides and of the influence of ocean tides on gravity the absolute value of the measured tide is determined by an independent absolute calibration of the gravimeters the method differs from previous tests of tide theories in that it compares the entire predicted time series rather than specific harmonic constituents in this way it is possible to test the solid earth and ocean tide effects independently we find that the ratios of observed to predicted solid earth tides at different locations are the same within an uncertainty of about ko 2 per cent however the magnitude of the tides deduced by the absolute calibration of the gravimeters is 0 6 per cent larger than the theoretical solid earth tide we point out that an accurate determination of the solid earth tide in this way provides a direct comparison between the gravitational constant g at laboratory scales and at the distance to the moon

tropical atlantic sea surface temperature variability and its relation to el nino southern oscillation past analyses of tropical atlantic sea surface temperature variability have suggested a dipole behavior between the northern and southern tropics across the intertropical convergence zone itcz by analyzing an improved 43 year 1950 1992 record of sst smith et al 1996 and other data derived from the comprehensive ocean atmosphere data set coads it is shown that the regions north and south of the itcz are statistically independent of each other at the seasonal to interannual timescales dominating the data confirming the conclusions of houghton and tourre 1992 some dipole behavior does develop weakly during the boreal spring season when there is a tendency for sst anomaly west of angola to be opposite of that in the tropical north atlantic it is further shown that tropical atlantic sst variability is corre lated with pacific e1 nifio southern oscillation enso variability in several regions the ma jor region affected is the north atlantic area of ne trades west of 40ow along 10on 20on and extending into the caribbean there about 50 80 of the anomalous sst variability is associ ated with the pacific enso with atlantic warmings occurring 4 5 months after the mature phases of pacific warm events an analysis of local surface flux fields derived from coads data shows that the enso related atlantic warmings occur as a result of reductions in the surface ne trade wind speeds which in turn reduce latent and sensible heat losses over the region in ques tion as well as cooling due to entrainment this enso connection is best developed during the boreal spring following the most frequent season of maximum enso anomalies in the pacific a region of secondary covariability with enso occurs along the northern edge of the mean itcz position and appears to be associated with northward migrations of the itcz when the north at lantic warmings occur although easterly winds are intensified in the western equatorial atlantic in response to pacific warm events they do not produce strong local changes in sst contrary to expectations from studies based on equatorial dynamics these teleconnected wind anomalies do not give rise to significant correlations of sst in the gulf of guinea with the pacific enso as the teleconnection sequence matures strong se trades at low southern latitudes follow the de velopment of the north atlantic sst anomaly and precede by several months the appearance of weak negative sst anomalies off angola and stronger positive anomalies extending eastward from southern brazil along 15o 30os

european tidal gravity an improved agreement between observations and models tidal gravity observations were made at 5 sites in europe using improved lacoste and romberg et gravimeters special attention was paid to improving the accuracy of determining both the amplitude and phase in tidal gravity measurements the measuring screws of the gravimeters were calibrated on the well established short range vertical gravity calibration lines at hannover frg for m sub 2 and o sub 1 it is shown that there is a very significant improvement in the agreement between observations and models compared to previous european tidal gravity measurements for o sub 1 the ocean tide loading and attraction is very small in europe and these observations verify that the dehant wahr anelastic body tide gravimetric factor is accurate to within 0 2 there is no dependence upon lateral changes of earth structure at least within the accuracy of these measurements

ocean load tides at the south pole a validation of recent ocean tide models small diurnal and semidiurnal gravity tides are seen at the south pole because of the loading by and attraction of the ocean tides these data provide a check on the quality of ocean tide models especially in the southernmost ocean which has historically been the most lacking in tidal data ocean tide models developed in the 1980 s did not predict the gravity tides at this location very well recently developed models based on the topex poseidon altimetric data and improved hydrodynamical modeling agree much better with the observations provided that the tides beneath the ice shelves are included the level of agreement at this remote location suggests that loads from very local tides aside the new generation of ocean tide models can predict the loading tides to very high accuracy

cascading trend of early paleozoic marine radiations paused by late ordovician extinctions the greatest relative changes in marine biodiversity accumulation occurred during the early paleozoic the precision of temporal constraints on these changes is crude hampering our understanding of their timing duration and links to causal mechanisms we match fossil occurrence data to their lithostratigraphical ranges in the paleobiology database and correlate this inferred taxon range to a constructed set of biostratigraphically defined high resolution time slices in addition we apply capture recapture modeling approaches to calculate a biodiversity curve that also considers taphonomy and sampling biases with four times better resolution of previous estimates our method reveals a stepwise biodiversity increase with distinct cambrian and ordovician radiation events that are clearly separated by a 50 million year long period of slow biodiversity accumulation the ordovician radiation is confined to a 15 million year phase after which the late ordovician extinctions lowered generic richness and further delayed a biodiversity rebound by at least 35 million years based on a first differences approach on potential abiotic drivers controlling richness we find an overall correlation with oxygen levels with temperature also exhibiting a coordinated trend once equatorial sea surface temperatures fell to present day levels during the middle ordovician darriwilian age contrary to the traditional view of the late ordovician extinctions our study suggests a protracted crisis interval linked to intense volcanism during the middle late ordovician katian age as richness levels did not return to prior levels during the silurian a time of continental amalgamation we further argue that plate tectonics exerted an overarching control on biodiversity accumulation

an overlooked feature of tropical climate inter pacific atlantic variability 1 both the tropical pacific and atlantic host an equatorial mode of interannual variability called the pacific el nino and the atlantic nino respectively although the pacific el nino does not correlate with the atlantic nino anomalous warming or cooling of the two equatorial oceans can form an inter pacific atlantic sea surface temperature sst gradient variability that induces surface zonal wind anomalies over equatorial south america and over some regions of both ocean basins the zonal wind anomalies act to bridge the interaction of the two ocean basins reinforcing the inter pacific atlantic sst gradient through atmospheric walker circulations and oceanic dynamics thus a positive feedback seems to exist for climate variability of the tropical pacific atlantic oceans and atmosphere system in which the inter basin sst gradient is coupled to the overlying atmospheric wind rainfall responds to the inter pacific atlantic sst gradient by showing an anti symmetric configuration between the two equatorial oceans suggesting that rainfall is sensitive to the equatorial inter basin sst gradient regardless of which ocean is anomalously warm or cold

lag relationships involving tropical sea surface temperatures abstract a long historical record 100 years of monthly sea surface temperature anomalies from the comprehensive ocean atmosphere data set was used to examined the lag relationships between different locations in the global tropics application of complex principal component cpc analysis revealed that the leading mode captures enso related quasi cyclical warming and cooling in the tropical pacific ocean the dominant features of this mode indicate that sst anomalies in the eastern pacific lead those of the central pacific however a somewhat weaker aspect of this mode also indicates that sst anomalies in the tropical indian and western tropical north atlantic oceans vary roughly in concert with each other but lag behind those in the central and eastern pacific the stability of these lag relationships is indicated by the fact that the leading mode is quite similar in three different 30 year time periods in order to further examine these relationships some simple indexes were formed as the average ov

correlation of tidal gravity and heat flow in eastern north america abstract an apparent correlation of tidal gravity and heat flow can be examined using data from ten sites in eastern north america a trend is clearly evident on the plot of m2 tidal gravity residuals and estimated heat flow values with a linear regression slope of 0 043 gal m 2 mw 1 and a multiple correlation coefficient of 0 79 the mean deviation of points from the linear regression line is 0 2 gal similar plots for the o1 k1 and s2 harmonics reveal positively sloping trends but multiple correlation coefficients smaller than 0 06 indicate that little significance can be attached to these apparent trends the o1 k1 and s2 tidal gravity residuals as well as the n2 residuals are not determined accurately enough to verify the trend found for the stronger m2 harmonic the well known linear relationship between heat flow and heat production within the eastern north american heat flow province has been interpreted to indicate significant upper crustal influence on spatial variations in heat flow therefore a correlation of tidal gravity with heat flow implies a measurable upper crustal tidal response

heat production and seismic velocity of crustal rocks heat production of the continental crust can be determined from the seismic velocity structure there is however a significant scatter in the determination partly caused by the quality of geothermal data and partly by the fact that seismic velocity and radiogenic heat production are not uniquely related to each other by the chemical composition of rocks

numerical simulations of the ross sea tides tidal currents below the floating ross ice shelf are reconstructed by using a numerical tidal model they are predominantly diurnal achieve maximum strength in regions near where the ice shelf runs aground and are significantly enhanced by topographic rossby wave propagation along the ice front a comparison with observations of the vertical motion of the ice shelf surface indicates that the model reproduces the diurnal tidal characteristics within 20 similar agreement for the relatively weak semi diurnal tides was not obtained and this calls attention to possible errors of the open boundary forcing obtained from global ocean tidal simulations and to possible errors in mapping zones of ice shelf grounding air sea contact below the ice shelf is eliminated by the thick ice cover the dominant sub ice shelf circulation may thus be tidally induced a preliminary assessment of sub ice shelf conditions based on the numerical tidal simulations suggests that 1 strong barotropic circulation is driven along the ice front and 2 tidal fronts may form in the sub ice shelf cavity where the water column is thin and where the buoyancy input is weak

the response of the earth to tidal body forces described by second and third degree spherical harmonics as derived from a 12 year series of measurements with the superconducting gravimeter gwr t3 in brussels abstract a 12 year tidal gravity registration performed in brussels with a gwr superconducting gravimeter allows us to separate six tidal components derived from the third degree lunar potential from those derived from the classical second degree luni solar potential 39 components with which they differ in frequency by the lunar perigee period 8 847 year four ter diurnal waves are also separated such a separation appears necessary as the results show a non negligible residue on the third degree frequency wave m 1 lunar day period owing to an amplification of the corresponding oceanic component in the north atlantic ocean the other third degree components also differ slightly from the theoretical model amplitudes a correct determination of the free core nutation resonance acting on the 1 diurnal solar wave is discussed in relation to atmospheric pressure gravitational effects and climatological disturbances the zonal fortnightly tide mf is also deduced with precision but its comparison with the theoretical model raises a problem

upper mantle properties of the tuscan tyrrhenian area a framework for its recent tectonic evolution abstract within the alpine mediterranean deformational system several interesting features in the physical properties of the upper mantle have been recognized through the regional analysis of surface wave dispersion a large upper mantle anomaly uma here called the tuscan uma has been identified in the area northeast of corsica which includes part of the northern tyrrhenian sea and part of the north central apennines this anomalous upper mantle area together with the upper mantle characteristics of the tyrrhenian sea located further to the south provides a natural framework for comprehensive interpretation of the large data set of geological and geophysical observations such as land and marine geology volcanism gravity magnetic data seismic data and seismology deep temperatures and surface heat flow

el nino modoki and its possible teleconnection 1 using observed data sets mainly for the period 1979 2005 we find that anomalous warming events different from conventional el nino events occur in the central equatorial pacific this unique warming in the central equatorial pacific associated with a horseshoe pattern is flanked by a colder sea surface temperature anomaly ssta on both sides along the equator empirical orthogonal function eof analysis of monthly tropical pacific ssta shows that these events are represented by the second mode that explains 12 of the variance since a majority of such events are not part of el nino evolution the phenomenon is named as el nino modoki pseudo el nino modoki is a classical japanese word which means a similar but different thing the el nino modoki involves ocean atmosphere coupled processes which include a unique tripolar sea level pressure pattern during the evolution analogous to the southern oscillation in the case of el nino hence the total entity is named as el nino southern oscillation enso modoki the enso modoki events significantly influence the temperature and precipitation over many parts of the globe depending on the season the impacts over regions such as the far east including japan new zealand western coast of united states etc are opposite to those of the conventional enso the difference maps between the two periods of 1979 2004 and 1958 1978 for various oceanic atmospheric variables suggest that the recent weakening of equatorial easterlies related to weakened zonal sea surface temperature gradient led to more flattening of the thermocline this appears to be a cause of more frequent and persistent occurrence of the enso modoki event during recent decades

the response method applied to the analysis of superconducting gravimeter data abstract the response method a technique used in ocean tide analysis to separate linear and nonlinear components is applied to the analysis of superconducting gravimeter data a response analysis is shown to be capable of resolving small non tidal signals of a few nanogal amplitude arbitrarily close in frequency to large amplitude tidal signals a synthetic example in which a small signal is injected into a spectrally rich tidal signal is used to demonstrate how the method is applied and its advantages compared to a conventional analysis the technique is also applied to the analysis of degree 3 diurnal and semi diurnal tides in short records the degree 3 waves are easily separated and a reasonable ocean loading effect for these waves is recovered despite the fact the open ocean tide is only a few mm in amplitude finally a response analysis is used to separate gravitational tides from the radiation tides at coincident frequencies in both the diurnal and semi diurnal bands

seasonal influence of enso on the atlantic itcz and equatorial south america 1 in late boreal spring especially may a strong relationship exists in observations among precipitation anomalies over equatorial south america and the atlantic intertropical convergence zone itcz and eastern equatorial pacific and central equatorial atlantic sea surface temperature anomalies ssta a chain of correlations of equatorial pacific ssta western equatorial atlantic wind stress wea equatorial atlantic ssta sea surface height and precipitation supports a causal chain in which el nino southern oscillation enso induces wea stress anomalies which in turn affect atlantic equatorial ocean dynamics these correlations show strong seasonality apparently arising within the atmospheric links of the chain this pathway and the influence of equatorial atlantic ssta on south american rainfall in may appear independent of that of the northern tropical atlantic brazil s nordeste is affected by the northern tropical atlantic the equatorial influence lies further to the north over the eastern amazon and the guiana highlands

the subduction of young lithosphere studies using a variety of techniques of the subduction beneath western south america and the southwest honshu kyushu region of japan indicate that volcano free segments occur where the subducted and continental lithospheres remain in contact without intervening asthenosphere the subduction is initiated at normal dip angles but the plate deforms at some depth 100 km under central peru to travel horizontally immediately beneath continental lithosphere the most plausible reason for this geometry is that the subducted plate is buoyant a model is developed constrained by age of the plate bathymetry and heat flow estimates of the density of oceanic plates as a function of age show that younger ocean floor may be less dense than the asthenosphere into which it subducts if the high density tranformation of crustal basalt to eclogite is retarded by low temperatures the plate can remain buoyant to considerable depth for long periods of time heat flow data from western south america are consistent with this model

el nino variability in simple ocean data assimilation soda 1871 2008 1 a new ocean reanalysis that covers the period from 1871 to 2008 is used to explore the time evolving characteristics of el nino the new reanalysis assimilates all available hydrographic and sea surface temperature data into a model of the global ocean forced with surface boundary conditions from an atmospheric reanalysis that also covers the period from 1871 through 2008 using traditional measures of el nino our reanalysis shows that the timing of el nino events is in agreement with sea surface temperature reconstructions but el nino in the reanalysis is stronger particularly from 1871 to 1920 a new index based on the first moment of the temperature anomaly is introduced the new index is used to characterize the strength and location of el nino events and has the advantage that it is independent of the location of el nino using the new index el nino in the reanalysis shows prominent decadal variability of strength but relatively little long term trend el nino events were strong in the last part of the 19th century and first part of the 20th century and again in the latter part of the 20th century with weak el nino events in the middle of the 20th century the location of el nino also varies considerably ranging from the western to the eastern pacific near the coast of south america however the null hypothesis that the location of el nino can be represented as a random distribution about a central longitude of about 140 w cannot be rejected

on the atlantic pacific ninos connection a multidecadal modulated mode atlantic and pacific el nino are the leading tropical oceanic variability phenomena at interannual timescales recent studies have demonstrated how the atlantic nino is able to influence on the dynamical processes triggering the development of the pacific la nina and vice versa however the stationarity of this interbasin connection is still controversial here we show for the first time that the atlantic pacific ninos connection takes place at particular decades coinciding with negative phases of the atlantic multidecadal oscillation amo during these decades the atlantic pacific connection appears as the leading coupled covariability mode between tropical atlantic and pacific interannual variability the mode is defined by a predictor field the summer atlantic sea surface temperature sst and a set of predictand fields which represent a chain of atmospheric and oceanic mechanisms to generate the pacific el nino phenomenon alteration of the walker circulation surface winds in western pacific oceanic kelvin wave propagating eastward and impacting on the eastern thermocline and changes in the pacific sst by internal bjerknes feedback we suggest that the multidecadal component of the atlantic acts as a switch for el nino prediction during certain decades putting forward the amo as the modulator acting through changes in the equatorial atlantic convection and the equatorial pacific sst variability these results could have a major relevance for the decadal prediction systems

anisotropy of the african continent inferred from surface waves abstract a no block regionalization is performed over the african continent to retrieve simultaneously local surface wave velocities and the 2 azimuthal variation of rayleigh waves the geographical distribution of phase and group velocities shows general agreement with global models but with enhanced lateral resolution a correlation with surface tectonics is found even at long periods low velocities occur in the tectonically active regions and high velocities in the shield areas the azimuthal anisotropy analysis results in a general north south fastest direction for rayleigh waves which could be correlated with the african plate s absolute motion the amplitude is of the order of 2 an isotropic inversion with data corrected for effects of surficial layers is performed very slight differences appear between the corrected and uncorrected results lateral heterogeneities of rayleigh and love waves are then inverted simultaneously with the 2 azimuthal terms of rayleigh waves by vectorial tomography to retrieve the 3d structures of s wave velocity and anisotropy throughout the african continent good correlation between low velocities and small anisotropies is found and their location at depth suggests an origin for african hotspots

tidal gravity heat flow and the upper crust abstract tidal gravity anomalies appear to vary linearly with terrestrial heat flow the linear relationship between heat flow and heat production within an individual heat flow province indicated that variations in heat flow depend on the distribution of heat sources situated in the upper crust this implied a measurable upper crustal effect on the tidal response of the earth