spatio temporal structure of the pentadecadal variability over the north pacific abstract using a multi taper frequency domain singular value decomposition mtm svd a pentadecadal oscillation was detected in the winter spring sea level pressure slp field over the north pacific and surface air temperature in north america which was significant at the 95 confidence level the mtm svd captured the different slp and air temperature distributions between the winter and spring seasons in a consistent manner the pentadecadal slp signature in the spring season is centered nearer the west coast of north america than in the winter season this zonal displacement is consistent with the prominent springtime pentadecadal air temperature variability in mid latitude western north america a wavelet analysis of the pacific decadal oscillation index pdoi showed that the regime shifts in the 1920s 1940s and 1970s involved simultaneous phase reversals of the bidecadal and pentadecadal variations the two interdecadal variations are synchronized with one another such that a half period of the pentadecadal oscillation one epoch of an individual regime corresponds to one and half periods of the bidecadal oscillation these results are consistent with the wavelet analysis of the north pacific index npi similar resonance between the bidecadal and pentadecadal variations is evident in air temperatures over alaska the bidecadal and pentadecadal signals have different seasonality in these time series suggesting that although the two interdecadal variations arise from two different physical mechanisms they interact with each other the most distinct seasonal difference was observed in mid latitude western north america where the bidecadal variation prevails only in the winter season and the pentadecadal variation only in the spring season alaska air temperatures in the winter and winter spring of 1999 were the coldest since 1977 as were springtime air temperatures in mid latitude western north america in contrast to the warm anomalies that prevailed in this region during 1977 98 the npi and pdoi also exhibited an opposite polarity in 1999 to the respective regime mean polarities these anomalous conditions in winter and spring seasons of 1999 may signify a major regime shift in 1998 1999 in order to verify whether or not a regime shift did occur in 1998 1999 a careful examination of additional data in coming ten or so years will be necessary

millennial scale changes in sea surface temperature and ocean circulation in the northeast pacific 10 60 kyr bp 1 a new centennial scale mg ca temperature record from the california margin odp site 1017e reveals large millennial scale oscillations between 10 to 60 kyr this record indicates that sea surface temperature on the california margin warmed rapidly on the deglacial by 7 4 0 8 c and was preceded by a pre bolling temperature oscillation of 2 6 1 2 c millennial scale events of the last glacial episode were marked by sea surface temperature oscillations of between 3 and 7 c on the california margin and interstadials were associated with an increase in surface water salinity the data are consistent with evidence for a glacial southward shift in the polar jet stream and concomitant strengthening of the relatively cold fresh california current during stadial events the data also support previous hypotheses suggesting a tight coupling between the north atlantic and northeast pacific response to climate instability of the last glacial episode

salinity signature of the pacific decadal oscillation three sites in the north pacific have temperature and salinity observations in most months for several years before and after 1977 the gulf of alaska station 57 n 148 w showed a 2 c warming and a 0 6 freshening in salinity at 10 m depth in the 1980s compared to the 1970s ows papa 50 n 145 w and papa line station 7 49 1 n 132 4 w show warming of 0 6 c and 0 9 c with no major salinity change the decrease in density and increase in stratification in the gulf of alaska after 1977 corresponds primarily to a decrease in salinity in the upper 150 m we propose that while the pacific decadal oscillation has an east west character in temperature the salinity signature will have a nnw sse character similar to the pattern of interannual variability in precipitation

density inhomogeneities isostasy and flexural rigidity of the lithosphere in the transcaspian region the 3 d lithospheric density model for the southeastern part of the caspian sea and the transcaspian area practically coinciding with the territory of the turkmen republic has been constructed based on geophysical data and in accordance with the principle of isostasy from the model selected the anomalous density of the subcrustal layer between the moho discontinuity and the 100 km depth level is found to be 100 kg m3 under the tien shan 50 kg m3 under the kopet dag mountain area 80 kg m3 under the central region of the south caspian basin 50 kg m3 under the eastern part of the basin known as the west turkmenian depression and 45 kg m3 under the murgab depression significant disturbances of the local isostasy are determined both in the northern and central areas of the south caspian basin and also in the area of the kara bogaz swell of the turan platform and for the kopet dag foredeep indicating a high level of stresses in the lithosphere the shape of the turan plate determined by the seismic profiling is accounted for by elastic deformation resulting from the forces acting on the southern edge of the plate in the area of the turan plate kopet dag collision the elastic thickness of the turan plate is estimated as 25 5 km the results obtained seem to confirm the idea that the decomposition of the turan plate has taken place in the zone of the plates interaction and the decomposed material is situated under the kopet dag ridge we propose that the kara bogaz swell is supported by the mantle material upwelling whereas the subsidence of the adjacent part of the south caspian basin may be due to the downgoing mantle flow i e a small convection cell is suggested in that area

three dimensional gravity and magnetic modeling of crustal indentation and wedging in the western pyrenees cantabrian mountains 1 the complex crustal structure of the boundary zone between the iberian and european plates from the western pyrenees to the cantabrian mountains is probed by three dimensional 3 d gravity and magnetic modeling constrained by deep seismic profiles the 3 d modeling results support the presence of a continuous iberian crustal root and suggest that the geometry of the orogenic belt that formed in latest cretaceous tertiary times along the northern margin of iberia was conditioned by oblique structures separating areas characterized by different tectonic styles in the western pyrenees and the basque cantabrian basin a thick mesozoic basin presently incorporated to the pyrenean cantabrian belt the relatively narrow thinning of the crust inherited from the mesozoic rifting stage conditioned a structural style in which portions of the southward indenting european lower crust are interpreted to be back thrusted toward the north and uplifted to shallow depths promoting the appearance of significant potential field anomalies in the basque cantabrian basin the strongest aeromagnetic anomaly of the whole iberian mainland is superimposed on the eastern part of a well defined positive gravity anomaly similar in amplitude and wavelength to those located along the north pyrenean zone these observations suggest that the eastern part of the dense lower crustal causative body is strongly magnetized and may correspond to a gabbroic cumulate originated in the axis of the ancient mesozoic rift to the west tertiary compression affected the north iberian cantabrian passive continental margin whose geometry and inherited structures conditioned the formation of a double crustal delamination and the uplift of the cantabrian mountains

anomalous crustal uplift and crustal structure in the matsushiro and the izu peninsula earthquake swarm regions abstract a close relation between the anomalous crustal uplift and the crustal structure has been revealed by a comparison between the precise crustal structure deduced from explosion seismology and the anomalous crustal uplift observed by the precise leveling survey in the matsushiro and the izu peninsula earthquake swarm regions that is the anomalous crustal uplift has occurred around the place where change in the crustal structure is present within a narrow zone these two examples imply the importance of information on crustal structure towards understanding the real cause of crustal movement

deep structure of the ocean continent transition in the southern iberia abyssal plain from seismic refraction profiles ocean drilling program legs 149 and 173 transect we present a wide angle seismic refraction study of an 80 40 km region of the southern iberia abyssal plain south of galicia bank an intersecting grid of two e w and four n s wide angle reflection refraction profiles is used to define variations of the basement velocity structure within this unusually wide ocean continent transition oct these structures can be systematically linked to variations in acoustic basement morphology and to results from ocean drilling program odp boreholes lateral changes in the velocity structure of the basement occur abruptly over distances of 20 km where complex variations may be found thinned upper continental crust 2 5 km thick with velocities of 5 0 6 6 km s is limited to a series of n s fault blocks immediately south of galicia bank this crust is underlain by a high velocity layer 7 3 7 9 km s of weakly serpentinized i e 0 25 peridotite which exists throughout the eastern part of the survey area basement within the oct appears to consist dominantly of a broad region of exposed upper mantle that has been serpentinized heterogeneously both vertically and horizontally in the southeast sector of our survey where basement topography deepens and becomes subdued continental fault blocks are absent instead basement contains an upper layer of more pervasively serpentinized i e 25 45 peridotite that is 2 km thick this layer is characterized by low velocity at the top of basement 4 2 km s that increases rapidly with depth and it probably corresponds to a seismically unreflective layer previously identified in reflection profiles to the south of our survey in the western section of our survey beneath a series of elevated basement ridges velocities are reduced within both the upper basement layer 3 5 6 0 km s and lower layer 6 4 7 5 km s these changes suggest that both upper and lower layers have become more highly serpentinized with values of 60 100 in the upper layer and 25 45 in the lower layer probably during the last stages of rifting and immediately before formation of oceanic crust a normal or slow spreading oceanic crustal structure is not found within the survey region thus it appears that the onset of seafloor spreading occurs in the region west of the peridotite ridge sampled at odp site 897 and east of the j magnetic anomaly

wide angle images of the mediterranean ridge backstop structure the mediterranean ridge is an accretionary wedge consisting of a large pile of tectonically deformed sediments in the past the mediterranean ridge has been interpreted as a prism related to hellenic subduction however geophysical evidence pasiphae cruise 1988 has indicated the presence of a high velocity body southward of the hellenic trench which was subsequently interpreted as an extended continental backstop during the recent imerse project coincident wide angle and normal incidence seismic data were collected over the ridge along the ne sw medriff corridor explora cruise 1994 the objectives of the imerse project were to acquire the seismic observations necessary for a high resolution structural model of the western mediterranean ridge including the structure of the newly interpreted continental backstop here we present the results of recent re modelling of two ship expanding spread seismic refraction data esp 8 and 9 recorded during the pasiphae cruise the modelling of these data has allowed an approximate constraint on the position of the juncture between the mediterranean accretionary complex and its buttress also presented are processing and modelling results of the recently acquired imerse wide angle data travel time modelling of these data has allowed the construction of six multi azimuth velocity depth models these models show the existence of high velocity material at depth p wave velocity 5 km s inferred to be extended backstop and constrain its southward extent all models show the presence of a messinian evaporite layer near the surface the evaporite layer is observed to vary in thickness from 0 to 2 0 km with the existence of local thickening and thinning due to depositional factors tectonism and salt dissolution in addition combined analysis of the wide angle velocity models with coincident seismic reflection and swath bathymetry data indicates that the geometry of the continental backstop varies laterally as a consequence of transform faulting possibly related to the southward rotation of the peloponnesus thrust sheet and backstop emplacement

basin evolution of the northern part of the northeast german basin insights from a 3d structural model abstract a 3d structural model for the entire southwestern baltic sea and the adjacent onshore areas was created with the purpose to analyse the structural framework and the sediment distribution in the area the model was compiled with information from several geological time isochore maps and digital depth maps from the area and consists of six post rotliegend successions the upper permian zechstein lower triassic middle triassic upper triassic jurassic cretaceous and cenozoic this structural model was the basis for a 3d backstripping approach considering salt flow as a consequence of spatially changing overburden load distribution isostatic rebound and sedimentary compaction for each backstripping step in order to reconstruct the subsidence history in the region this method allows determination of the amount of tectonic subsidence or uplifting as a consequence of the regional stress field acting on the basin and was followed by a correlation with periods of active salt movement in general the successions above the highly deformed zechstein evaporites reveal a thickening trend towards the gluckstadt graben which also experienced the highest amount of tectonic subsidence during the mesozoic and cenozoic two periods of accelerating salt movement in the area has been correlated with the e w directed extension during the late triassic early jurassic and later by the late cretaceous early cenozoic inversion suggesting that the regional stress field plays a key role in halokinesis the final part of this work dealt with a neotectonic forward modelling in an attempt to predict the future topography when the system is in a tectonic equilibrium the result reveals that many of the salt structures in the region are still active and that future coastline will run with a wnw ese trend arguing that the compressional stresses related to the alpine collision are the prime factor for the present day landscape evolution

north pacific dissolved inorganic carbon variations related to the pacific decadal oscillation we elucidated multiyear variations of sea surface dissolved inorganic carbon dic concentrations in the north pacific from 2002 to 2008 by using monthly dic maps derived from partial pressure co2 observations the pacific decadal oscillation pdo was related to an east west seesaw pattern in the north pacific dic anomaly field in the western north pacific dic concentrations were relatively high from mid 2002 to mid 2005 and low after late 2007 compared with climatological values and in the eastern north pacific the opposite change was observed changes of the forcing factors associated with the pdo could explain the dic east west seesaw pattern horizontal advection freshwater fluxes and vertical mixing in most regions co2 fluxes south of 40 n and biological production in the subarctic

eucrust 07 a new reference model for the european crust 1 we present a new digital model eucrust 07 for the crust of western and central europe and surroundings 35n 71n 25w 35e available results of seismic reflection refraction and receiver functions studies are assembled in an integrated model at a uniform grid 15 0 15 0 the model consists of three layers sediments and two layers of the crystalline crust besides depth to the boundaries we provide average p wave velocities in the upper and lower parts of the crystalline crust the new model demonstrates large differences in the moho depth compared to previous compilations over 10 km in some specific areas e g the baltic shield furthermore the velocity structure of the crust is much more heterogeneous than in previous maps eucrust 07 offers a starting point for numerical modeling of deeper structures by allowing correction for crustal effects beforehand and to resolve trade off with mantle heterogeneities citation tesauro m m k kaban and s a p l cloetingh 2008 eucrust 07 a new reference model for the european crust geophys res lett 35 l05313 doi 10 1029 2007gl032244

p wave tomography of the mantle under the alpine mediterranean area 1 we study the upper mantle p wave velocity structure below the euro mediterranean area down to 1000 km depth by seismic travel time tomography we invert summary residuals constructed with both regional and teleseismic first arrival data reported by the international seismological centre isc 1964 1995 introducing some alternative strategies in the travel time tomographic approach and a new scheme to correct teleseismic data for global mantle structure our high resolution model pm0 5 is parameterized with three dimensional 3 d linear splines on a grid of nodes with 0 5 spacing in both horizontal directions and 50 km vertical spacing we obtain about 26 root mean square rms reduction of residuals by inversion in addition to roughly 31 reduction after summary rays formation and selection sensitivity analyses are performed through several test inversions to explore the resolution characteristics of the model at different spatial scales the distribution of large scale fast anomalies suggests that two different stages of a convection process presently coexist in very close regions the mantle dynamics of western central europe is dominated by blockage of subducted slabs at the 660 km discontinuity and ponding of seismically fast material in the transition zone contrarily in the eastern mediterranean fast velocity material sinks into the lower mantle suggesting that the flow of the cold downwelling here is not blocked by the 660 km discontinuity on a smaller scale the existence of tears in the subducted slab lithospheric detachment all along both margins of the adriatic plate as proposed by some authors is not supported by our tomographic images

oceanic upper mantle structure from experimental scaling of vs and density at different depths summary isotropic shear wave velocities from the ekstrom dziewonski s20 global tomographic model and residual crust free gravity are used to determine density velocity relations for various mantle layers by inversion the residual gravity field was obtained by subtracting the crustal density inhomogeneities from the observed surface gravity the residual field is dominated by upper mantle signatures as the effect of dynamic topo graphy is also reduced from the gravity field before hand the gravity seismic inversion is almost independent of the viscosity distribution within the earth there exists a reliable correlation between residual gravity and shear wave velocities in the upper mantle under oceans but not under continents this result supports the idea that lateral density variations in the oceanic upper mantle are mostly driven by the temperature distribution while under the continents temperature and composition induced density anomalies are superimposed the inversion is therefore restricted to the oceanic area and was done by a least squares adjustment in the spatial domain the density velocity ratios obtained for the subcrustal layer down to 75 km and for the deep part of the oceanic upper mantle below 225 km are very close to the ones predicted from mineral physics analyses however for the oceanic layer from 75 to 225 km depth a significantly lower density velocity ratio is obtained this may be explained by a compositional layering dry partially depleted peridotite residuum underlain by damp fertile peridotite and separated by the g discontinuity at a depth of about 70 km for the mantle transition zone and for the lower mantle the results obtained are less reliable but relative minima in the density velocity ratio are found for the layers around the phase transition discontinuities and for the depth interval from about 900 to 1100 km applying the adjusted velocity to density relations to the seismic tomography model a mantle density distribution under the oceans is found which explains about 85 per cent of the longest wave crust free gravity field degrees 1 5 and 70 per cent of the overall field up to degree 20 which was the limit of this investigation

crustal structure of the ne rockall trough from wide angle seismic data modeling two wide angle seismic lines located in the northern rockall trough were acquired in may 2000 one line line e crosses the trough from the continental shelf off lewis to normal oceanic crust west of lousy bank in nw se direction the other line line d intersects with line e crosses the wyville thomson ridge in a sw ne direction and ends in the faeroe shetland basin sonobuoy data and expanding spread profiles acquired in the same area have been remodeled analysis of the seismic data using travel times and amplitudes reveals an up to 5 km thick sedimentary basin including an up to 1 5 km thick basaltic layer which is present in most of the trough further conclusions of this study are that the rockall trough is underlain by highly stretched continental crust of 13 km thickness the crust thickens to 24 km beneath lousy bank which is interpreted to be of continental nature beneath the hebrides continental shelf a three layer continental crust of 26 km is modeled an up to 12 km thick high velocity layer is observed underneath the ocean continent boundary and is interpreted as magmatic underplating resulting from excess volcanism during rifting no evidence for an underplate layer could be distinguished beneath the trough area modeling of the structure of the wyville thomson ridge revealed no existing igneous core of the ridge confirming existing theories that it is a compressional structure

3d gravity modeling of the triassic salt diapirs of the cubeta alavesa northern spain abstract up to now subsurface information permitted the delineation of the top of the triassic salt all throughout the cantabro navarro domain although little was known on the location and geometry of its base and thus on the estimation of the total salt thickness a 3d gravity inversion scheme combined with a 3d analytic method has been conducted to map out the geometry of the main salt structures of the basin the gravity modeling results have been constrained by well log information and available geological and reflection seismic data the combined 3d scheme integrated with available geological and geophysical data has allowed us to obtain the geometry of the main diapirs that characterize the central and marginal regions of the basin from our interpretation the salinas de anana diapir has almost vertical flanks and can be divided into two different parts one of them forming a lateral overhang of the main body the salinas de oro diapir has near vertical flanks and a main axis in the n s direction also the anomaly is rather more extensive than the outcrop of the diapir which implies an important expansion of non outcropping salt in this area like the hoz sobron diapir the salinas de ollo diapir is long and narrow stretching in the nw se direction which includes three important highs plus an intense zone of salt migration the estella and alloz diapirs crop out individually in spite of being connected at depth also two non outcropping salt domes have been detected to the south of atauri that like the estella diapir are related to the thrust front we point out the gravity signature of the murguia diapir which shows an intense gravity high probably due to the presence of high density rocks in the cap rock or more probably due to the existence of triassic volcanites of ophitic texture pinched off into the diapir

deep structure of the armorican basin bay of biscay a review of norgasis seismic reflection and refraction data the bay of biscay is bounded to the north by the north biscay margin which comprises the western approaches and armorican segments in the 1970s and 1980s most researchers considered this margin typical of a non volcanic passive margin it is characterized by a striking succession of tilted blocks beneath which occurs the s reflector and the continent ocean boundary is abrupt this paper examines the armorican segment and is based on a study of all early seismic profiles together with new multichannel reflection and refraction seismic data norgasis cruise an important result is the discovery of a 80 km wide ocean continent transition zone that coincides with the armorican basin a deep sedimentary basin it is characterized by a high velocity lower crustal layer 7 4 7 5 km s 1 overlain by sediments the other results are 1 the main crustal thinning occurs exclusively under the narrow continental slope 2 the tilted blocks and the s reflector are observed only at the base of the continental slope in the narrow domain called the neck area 3 the north biscay ridge is a large oceanic plateau present only off the nw armorican margin rather than a long ridge elongated off the whole north biscay margin

mid depth freshening in the north pacific subtropical gyre observed along the jma repeat and woce hydrographic sections 1 we report a freshening at mid depth in the north pacific subtropical gyre by using long term repeat hydrographic data along the 137 e section and one time hydrographic data along the world ocean circulation experiment hydrographic program whp p2 and p3 sections north of 15 n along the 137 e section we estimated a linear freshening trend of 0 0015 yr between the main thermocline and the salinity minimum layer of the north pacific intermediate water mainly caused by isopycnal surface deepening due to warming and by westward shifts of the salinity minimum tongue due to strengthening of the subtropical gyre furthermore along the whp p2 section the linear freshening trend could be classified into several groups according to longitude such spatial differences in the freshening trend seem to reflect differences in the formation processes and mid depth pathways of the salinity minimum waters

low frequency pycnocline depth variability at ocean weather station p in the northeast pacific abstract low frequency variability of the depth of the main pycnocline at ocean weather station p and over the northeast pacific is examined in terms of the one dimensional response to local ekman pumping according to the hasselmann stochastic climate model the model is forced with monthly wind stress curl anomalies derived from the national centers for environmental prediction reanalysis for the period 1948 2000 an empirical orthogonal function analysis shows that the leading mode of the response bears the signature of the pacific inter decadal oscillation pdo and that the associated principal component captures the regime shift of 1976 77 the correlation is 0 77 between annually averaged pycnocline displacement anomalies hindcast from the model and anomalies in the depth of the main pycnocline at station p 50 n 215 e observed over a 43 yr period the comparison indicates that variability in the depth of the upper layer on interannual to interdecadal timescales at station p occurs largely as

steric sea level change in the northern seas abstract ocean temperature and salinity data over the period 1950 2000 in the northern seas defined here as the north atlantic ocean north of 50 n north pacific ocean north of 40 n and arctic oceans are combined to diagnose the steric i e density contribution to sea level variation the individual contributions to steric height from temperature thermosteric height and salinity halosteric height are also analyzed it is found that during 1950 2000 steric height rose over the study s domain mostly as a result of halosteric increases i e freshening over a shorter time period late 1960s to early 1990s during which climate indices changed dramatically steric height gradients near the nordic seas minimum were reduced by 18 32 it is speculated that this may be associated with a local slowing of both the meridional overturning circulation and the southward flow through fram strait however steric height increases in the north pacific ocean during this time imply a possible accelerati

a deep seismic crustal transect from the ne iberian peninsula to the western mediterranean the crustal structure of the transition from the ne iberian peninsula to the western mediterranean is characterized by large scale variations related to its successive compressional and extensional cenozoic tectonics the spanish esci spanish acronym for seismic studies of the iberian crust program recorded 450 km of deep vertical reflection profiles on land and at sea to complete a first crustal transect from the pyrenees to the south balearic basin highly energetic north dipping reflections imaged by combining the etude continentale et oceanique par reflexion et refraction sismique ecors and esci land profiles mark a crustal thickening toward the pyrenees the reflective band becomes horizontal beneath the catalan coastal ranges and the moho is found at 11s no evidence of crustal thinning affecting the iberian mainland is observed the transition to the mediterranean basin is constrained by complementary onshore offshore recordings forward modeling combined with multichannel processing of the wide angle data set shows that a strong thinning of the continental crust by a factor of 2 over a distance of 50 km affects both the catalan and balearic flanks of the valencia trough this thinning affects mainly the deep crust characterized by low velocities of 6 4 6 5 km s suggesting a removal of part of the lower crust during the rifting processes velocities of 7 8 7 9 km s are interpreted in the uppermost mantle with no evidence of underplating the moho appears as a marked discontinuity throughout the transect the nw part of the balearic promontory is characterized by a thick and reflective crust from 12 to 30 km depth an intensely fracturated evaporitic sequence is seen for 100 km along the south balearic basin the seismic images of the continent ocean transition are disturbed by these prominent sediments however the deep reflectivity suggests a crustal thinning moho at 6 7 s to be related to the middle miocene present extensional tectonics

crustal structure in the carpatho pannonian region insights from three dimensional gravity modelling and their geodynamic significance a three dimensional gravity modelling of the carpatho pannonian region was carried out to get a better image of the moho boundary and the most prominent intra crustal density heterogeneities at first only the major density boundaries were considered the bottom of the tertiary basin fill the moho discontinuity and the lithosphere to asthenosphere boundary density contrasts were represented by relative densities the improved density model shows a transitional unit of high density at the base of the crust along the teisseyre tornquist zone in the western carpathians an extensive relatively low density unit was inferred in mid crustal levels the border zone between the southern carpathians and the transylvanian basin is characterized by a sharp step like contact of the two crustal units the moho configuration reveals important information on the tectonic evolution of the region zones of continental collision are represented by thick moho roots eastern alps eastern carpathians transpressional orogenic segments however are different in the western carpathians the moho is a flat surface in the dinarides a medium moho root is observed the southern carpathians are characterized by a thick crustal root the differences are explained with the presence or absence of subductible oceanic crust along the carpathians during the extrusion of pannonian blocks

refraction seismic investigations of the northern massif central france abstract new refraction seismic data have been obtained in the northern french massif central seven shots were recorded simultaneously on two parallel nnw sse i e perpendicular to the surface structures oriented profiles allowing for inline and fan interpretations the results of a 2d interpretation reveal a large scale updoming of the moho of about 2 km compared to average western europe corresponding to the cenozoic uplift of the massif central local crustal thinning of up to 20 is restricted to the cenozoic grabens as seen at the surface beneath the volcanic area of cantal one of the largest cenozoic european shield volcanoes which was active in miocene to recent times significant crustal thickening of 2 3 km is observed velocities in the upper mantle are generally in the range of 7 9 8 1 km s beneath the limagne graben and surrounding undisturbed areas underneath the volcanic area of cezallier however velocity is reduced to about 7 7 km s corresponding to the area of crustal thickening therefore the low velocity in this zone is explained by the remainders of cooling magma chambers and heating by ascending hot plume material the cenozoic tectonic evolution of the massif central has affected crust and upper mantle in different ways oligocene rifting corresponds well to local crustal thinning but no correlation is detected to velocities of the upper mantle in contrast the volanic event occurring since miocene times is related to upper mantle velocity reduction and crustal thickening due to underplating

anomalous crustal uplift in the northeastern part of the izu peninsula central honshu japan abstract in the northeastern part of the izu peninsula near the northern boundary of the philippine sea plate crustal subsidence extending for several tens of years and intermittent anomalous crustal uplift extending over about 10 years have occurred alternately it seems likely that the strain energy in the northeastern part of the izu peninsula has been released mainly in the form of the intermittent aseismic crustal uplift

the velocity structure of the sediments in the southern rockall basin results from new wide angle seismic modelling abstract travel time modelling of first and second arrivals have been used to produce p wave velocity models of the sedimentary structure on three new wide angle reflection refraction profiles from the irish sector of the rockall basin the models indicate a sedimentary succession that is typically 4 5 km thick and reaches a maximum thickness of 7 km the sediments are typically horizontal within the basin centre but display significant structural complexities towards the margins where sediment depocentres and large fault blocks are interpreted up to seven layers with velocities ranging from 1 8 to 5 2 km s 1 have been resolved within which three distinct seismic packages have been identified an upper package interpreted as oligocene and neogene in age is approximately 1 5 km thick and confined within the rockall basin pinching out onto the basin margins this overlies a structurally complex middle package ca 1 5 km thick confined predominantly within the basinal areas which is interpreted as being of cretaceous to early tertiary age a regionally extensive lower package up to 4 km thick is interpreted as being of probable late palaeozoic to jurassic age the new data provide a much clearer picture than was hitherto available of the entire sedimentary succession in the basins that underlie the rockall trough they show a significant variability in thickness of the various sedimentary layers and in particular illustrate a marked topographic irregularity at the base of the sedimentary succession

the application of vhf measurements to earthquake prediction the use of very high frequency measurements applied to the detection of the variation in dielectric constant as a precursor to earthquakes is examined it is concluded that such a technique is feasible and that the installation of source and sensor in separate deep boreholes provides a suitable environment for this type of study the boreholes could also be used for a considerable range of other types of instrumentation

density structure of the lithosphere in the southwestern united states and its tectonic significance we calculate a density model of the lithosphere of the southwestern united states through an integrated analysis of gravity seismic refraction drill hole and geological data deviations from the average upper mantle density are as much as 3 a comparison with tomographic images of seismic velocities indicates that a substantial part 50 of these density variations is due to changes in composition rather than temperature pronounced mass deficits are found in the upper mantle under the basin and range province and the northern part of the california coast ranges and adjacent ocean the density structure of the northern and central southern sierra nevada is remarkably different the central southern part is anomalous and is characterized by a relatively light crust underlain by a higher density upper mantle that may be associated with a cold stalled subducted plate high densities are also determined within the uppermost mantle beneath the central transverse ranges and adjoining continental slope the average density of the crystalline crust under the great valley and western sierra nevada is estimated to be up to 200 kg m 3 higher than the regional average consistent with tectonic models for the obduction of oceanic crust and uppermost mantle in this region

lithospheric structure beneath trans carpathian transect from precambrian platform to pannonian basin celebration 2000 seismic profile cel05 1 in 2000 a consortium of european and north american institutions completed a huge active source seismic experiment focused on central europe the central european lithospheric experiment based on refraction or celebration 2000 this experiment primarily consisted of a network of seismic refraction profiles that extended from the east european craton along and across the trans european suture zone region in poland to the bohemian massif and through the carpathians and eastern alps to the pannonian basin the longest profile cel05 1420 km is the focus of this paper the resulting two dimensional tomographic and ray tracing models show strong variations in crustal and lower lithospheric structure clear crustal thickening from the pannonian basin 24 25 km thick to the trans european suture zone region 50 km together with the configuration of the lower lithospheric reflectors suggests northward subduction of mantle underlying carpathian pannonian plate under the european plate this however conflicts with strong geological evidence for southward subduction and we present three tectonic models that are to not totally mutually exclusive to explain the lithospheric structure of the area 1 northward old subduction of the pannonian lithosphere under the east european craton in the jurassic lower cretaceous 2 a collisional zone containing a crocodile structure where carpatho pannonian upper crust is obducting over the crystalline crust of the east european craton and the carpathian pannonian mantle lithosphere is underthrusting cratonic lower crust and 3 lithosphere thinning due to the effects of neogene extension and heating with the slab associated with young subduction southward in the miocene having been either detached and or rolled back to the east in the last case the northwestward dipping in the lithosphere can be interpreted as being due to isotherms that could represent the lithosphere asthenosphere boundary in the pannonian region

three dimensional flexural modelling of the ebro basin ne iberia summary the ebro basin the southern foreland basin of the pyrenees has undergone a complex evolution in which apart from the pyrenees the iberian range and the catalan coastal ranges have played an important role both as sediment sources and as basin confining structures the deflected basement underlying the ebro basin dips north suggesting a lithospheric scale control on the structure of this basin this is compatible with the results of subsidence analyses which show that the study area is not in a local mode of isostatic compensation in order better to understand the mechanisms that led to the present configuration of the ebro basin and particularly the relevance of the various kinds of un loading e g surrounding fold and thrust belts basin topography subsurface loads we carried out a 3 d kinematic modelling study that accounts for the flexural state of the lithosphere subjected to various loads applied at its lateral boundaries and the sedimentary fill of the basin we also included the effect of neogene extensional tectonics along the eastern basin margin which is related to the opening of the valencia trough we show the suitability of the 3 d lithospheric scale flexural modelling approach to the study of ne iberia modelling results point to a relatively strong lithosphere in this area with values of effective elastic thickness ranging from 10 to 35 km in the ebro basin increasing towards the pyrenees we also find that the topographic tectonic load itself is insufficient to explain the observed basement deflection thus an extra subsurface load beneath the pyrenees corresponding to the underthrusted iberian lithosphere is required the effect of lithospheric stretching in the valencia trough on the ebro basin is appreciable only in its eastern part where the lithosphere was uplifted this had considerable repercussions on the sedimentary and erosional regime of the ebro basin we have analysed the link between the stretching related tectonically uplifted areas and the erosional patterns observed onshore northeast iberia

insight into the structure of the upper rhine graben and its basement from a new compilation of bouguer gravity abstract a compilation of gravity data from the upper rhine graben urg is presented that includes all the main data sources from its german and french parts this data is used to show that the urg consists of at least two arc shaped and asymmetric rift units that tectonically are the basic building blocks of the graben in this sense the urg does not differ from other continental rifts such as the african rifts this division should replace the now classical geomorphologic division of the urg into three segments based on their different trends moreover the gravity suggests that the faults in the central and southern segments are continuous and have the same trend appearing to respond as a single kinematic unit changes in the gravity field in the graben are shown to reflect not only the structure of the graben but also the highly variable composition of the basement in this respect the urg is quite different from some other tertiary continental rifts where possible changes in the composition of the basement are mostly masked in the gravity field by the effect of the overlying low density sediments this characteristic is used to study the extent of some of the main basement units that underlie the graben

interdecadal variations in the alaska gyre abstract climatic dynamic topography variations in the alaska gyre during the period 1968 1990 are described with an objective analysis of more than 12000 std and xbt stations and coads wind stress data interannual dynamic height and sst variations were correlated and were consistent with recently described large scale climatic shifts in the north pacific the gyre was cantered more to the east circulation appeared stronger and sst was lower during the early to mid 1970s than during the 1980s the aleutian low np and pna indices intensified during the interim but the response did not appear as a gyre spinup instead the associated wind stress anomalies forced a slowly varying dynamic height anomaly across the eastern and northern part of the gyre through ekman convergence which had the effect of displacing the gyre s low somewhat to the wsw in the 1980s the wind curl spectrum was white and the slow oceanic response was modelled as stochastic forced climate variability with a simple first order m

continental crust under the southern porcupine seabight west of ireland abstract two new seismic refraction wide angle reflection profiles demonstrate that the crust beneath the southern porcupine seabight out to water depths in excess of 4000 m is of continental type they also reveal the rifted margin of the porcupine basin on its eastern side crustal thickness under the seabight inclusive of sediments which are up to 6 km thick decreases from 23 km in the east to about 10 km at a sharp continent ocean transition in the west

the crustal structure of the rockall trough differential stretching without underplating the crustal structure along the axis of the rockall trough in the north atlantic has been studied along a 600 km refraction wide angle reflection transect containing three lines each 200 to 250 km long using explosives and ocean bottom seismometers one dimensional inversions of each section were made using the p method and forward modeling of the observed travel times in the next stage travel times and amplitudes were modeled using ray tracing techniques through two dimensional heterogeneous structures the results indicate that there are three sedimentary layers with velocities ranging from 2 km s to 4 5 km s the whole sedimentary section is up to 6 km thick and interpreted as late paleozoic to tertiary in age a two layer continental crust 5 to 7 km thick occurs along the length of the profile the upper crust 6 0 6 3 km s is circa 2 km thick and the lower crust 6 6 6 9 km s is circa 3 km thick a moho transition zone approximately 1 km thick lies at the base of the crust velocities in this transition zone increase from 6 9 km s up to 7 8 km s along the profile the underlying upper mantle has a laterally variable velocity between 7 6 and 7 8 km s unstretched crust onshore in ireland comprises a three layered crust with each layer approximately 10 km thick and a moho transition zone which is about 3 km thick the two upper layers in the onshore region are interpreted as corresponding to the upper crust in the rockall trough and indicate a stretching factor of 8 10 the velocity pattern in the lower crust in the rockall trough and under ireland are similar suggesting significantly less stretching 2 3 the differential stretching model is supported by the presence of the moho transition zone which is stretched by a similar factor to the lower crust the bulk stretching factor for the crust as a whole is in the range of 4 6 if this represents the lithospheric stretching factor significant underplating would be expected however if the stretching factor for the lower crust in the differential stretching model is more representative of overall lithospheric stretching little or no underplating is predicted the velocity patterns observed in the rockall trough indicate the absence of any significant underplating at the base of the crust such as that observed at the continental margin west of the hatton basin

the hatton basin and continental margin crustal structure from wide angle seismic and gravity data results from a wide angle seismic and gravity study between the rockall bank and the iceland basin in the north atlantic are presented crustal and sedimentary structures are resolved in the hatton basin and across the hatton continental margin hcm east of magnetic anomaly 24 the structure of the oceanic crust west of the anomaly is also determined gravity data support the seismic model in areas of good seismic coverage and are used to control the model where the wide angle seismic data are poor a two layer sedimentary sequence is present both in the hatton basin and across the continental margin the lower layer with p wave velocity of about 4 km s is interpreted as pre eocene synrift sediments and is up to 3 5 km thick a younger and thinner 1 2 5 km postrift sequence with a velocity of about 2 km s defines a strong velocity contrast which suggests an erosional unconformity surface the sedimentary structure is distinctly different from that in the rockall trough where a third intermediate layer vp 3 km s occurs the three layer crust characterized by two intracrustal reflections pip1 and pip2 varies from 30 km thick under the rockall bank to about 15 km below the hatton basin where it is stretched by a factor of 2 relative to onshore ireland the crust is thinnest below the hatton bank where the presence of a single intracrustal reflection indicates that the lower crustal layer thins to below the seismic resolution limit below the hcm a region of thick lower crust with anomalously high velocity vp 7 2 km s is resolved by the seismic and gravity data it is connected west of anomaly 24 to a region of oceanic crust which is thicker than in the iceland basin these relationships between the thick lower crust below the hcm and the oceanic crust in the iceland basin are interpreted as evidence for magmatic underplating consistent with previous models for the hcm the inferred unconformity surface between the synrift and postrift layers may be due to regional uplift driven by upwelling of hot asthenosphere before anomaly 24 early eocene time

geodynamic evidence for a chemically depleted continental tectosphere the tectosphere namely the portions of earth s mantle lying below cratons has a thermochemical structure that differs from average suboceanic mantle the tectosphere is thought to be depleted in its basaltic components and to have an intrinsic buoyancy that balances the mass increase associated with its colder temperature relative to suboceanic mantle inversions of a large set of geodynamic data related to mantle convection using tomography based mantle flow models indicate that the tectosphere is chemically depleted and relatively cold to 250 kilometers depth below earth s surface the approximate equilibrium between thermal and chemical buoyancy contributes to cratonic stability over geological time

deep structure of the voring margin the transition from a continental shield to a young oceanic lithosphere the present day lithospheric structure across the norwegian margin in the voring region is presented the voring margin is characterized by the presence of large volume of magmatic underplating thick mesozoic basins and prominent crustal thinning results from recent deep seismic experiments in the voring basin and voring marginal high and 3 d gravity modelling have been implemented in a regional 2 d lithospheric transect that runs from the norwegian caledonian belt to the oceanic domain crossing the transition between the precambrian fennoscandian baltic shield and the cenozoic northern north atlantic oceanic lithosphere the modelling approach integrates elevation gravity geoid and heat flow data under the assumptions of thermal steady state and local isostasy the results confirm and refine the major trends of the crustal geometry which is characterized by a moho depth varying from about 45 km beneath the caledonian thrusts to 30 km beneath the trondelag platform to 20 14 km beneath the voring basin and to 13 km in the oceanic domain the lithosphere thins from the norwegian caledonian belt 190 km thick to the oceanic domain 60 km in a stepwise manner reflecting the progressive seawards migration of lithospheric deformation since the paleozoic our lithospheric thickness results are different from those predicted by post rift lithospheric cooling models in the oceanic domain observed residual bathymetry 600 m is interpreted as the remaining effect of a deep seated thermal perturbation during the upper cretaceous which would also produce a heat flow anomaly of 15 mw m 2 alternatively residual bathymetry can be interpreted in the absence of thermal anomalies as produced by depletion of the sublithospheric mantle extending down to 130 230 km depth depending on the density contrast 10 30 kg m 3

observations of decadal time scale salinity changes in the subtropical thermocline of the north pacific ocean abstract data from argo floats indicate that significant salinity changes have occurred in the north pacific thermocline relative to data collected in the previous two decades including observations obtained as part of the woce hydrographic program such a salinity decrease on both isopyncals and isobars implies a freshening scenario in the near surface source region of this water mass the frequently repeated meridional section p16 supports this inference the subsurface salinity freshening likely began in the early 1990s strengthened through 1997 and continued into the 2000s the surface salinity freshening had commenced by 1984 and continued through the first decade of the 21st century the spatial distribution of salinity change on the density surface 25 5 is examined through comparisons of argo and most of the north pacific woce sections 1985 1994 and between argo and the hydrobase climatology largely composed of data from the late 1970s through the mid 1980s both comparisons show a large scale basin wide decrease in subsurface salinity through the argo time period used in this analysis 2003 2006 the salinity difference is maximum in the northeast area and spreads southward and westward approximately following geostrophic streamlines

seismic evidence of alpine crustal thickening and wedging from the western pyrenees to the cantabrian mountains north iberia 1 the alpine collision between the iberian and european plates resulted in a complex crustal structure beneath the northern iberian peninsula as revealed from a new set of seismic refraction wide angle reflection profiles the study area is characterized by two major e w ranges the cantabrian mountains and the pyrenees which are relayed to the south by the iberian chain important variations in crustal thickness and velocity distribution are found in a 560 km long e w transect in contrast to the typical 30 to 32 km thick european variscan crust of the western end of the profile a continuous alpine crustal root is evidenced from the cantabrian mountains to the central pyrenees with a moho depth of 46 48 km locally rising to 40 km depth in between beneath the basque cantabrian basin another outstanding feature is the inferred presence of high velocities of 6 40 6 75 km s at midcrustal depths which can be associated with portions of a lower crustal wedge from the northern european domain indenting the southern iberian crust during the alpine stage of compression this indentation produces the delamination of the iberian crust with northward underthrusting of its lower half and the consequent crustal thickening the indenting wedge has a discontinuous presence along the longitudinal section as it was controlled and or affected by n s to ne sw structures further evidence of the northward subduction of the iberian plate is provided by another profile toward the aquitaine basin while a n s profile across the iberian chain reveals an alpine midcrustal thickening beneath this belt with moho depths of 42 km

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

contemporary plate motion and crustal deformation the measurement of relative plate velocities during the past few years is a signal accomplishment in earth science leading to refinement of the precepts of steady motion of plate interiors and cyclic deformation along plate margins regrettably deformation premonitory to an earthquake has yet to be detected with confidence delineation of the spatial and temporal buildup of strain between earthquakes however has put limits on models of the earthquake cycle a diverse set of fault structures and crustal rheologic conditions can explain the pattern of surface strain accumulation and release along strike slip faults in contrast the geometry of thrusts and normal faults revealed by earthquake deformation has been found to differ markedly from expectations geodetic observations have proved vital to monitor the ascent of magma through the earth s crust and to predict volcanic eruptions at the earth s surface episodic vertical and horizontal deformation in southern california remains a subject of dispute if anything it is less certain than it once seemed

an integrated gravity model for europe s crust and upper mantle we present an integrated gravity model of the european lithosphere based on an analysis of a number of new data sets leading to a much higher resolution than provided by previous models first of all a recent crustal model eucrust 07 is used to quantify the crustal contribution to the observed gravity field and to identify the effect of mantle heterogeneity the new gravity field model is based on a combination of satellite champ and grace and terrestrial data we also use these data sets to estimate residual mantle gravity anomalies and residual topography reflecting the effect of mantle density variations induced by temperature and compositional heterogeneity the separation of these effects is vital for a proper assessment of mantle structure and evolution in addition we utilize a new tomographic model for p and s velocity anomalies beneath europe which is a priori corrected for crustal structure using eucrust 07 the seismic velocity anomalies were subsequently converted into temperature anomalies using a mineral physics approach we estimate the effect of temperature variations on the gravity field and subtract it from the total mantle field the residual fields point to an important role of compositional density anomalies in the upper mantle a number of key features of the compositional density distribution so far invisible in seismic tomography data are detected for the first time

oscillations in land surface hydrological cycle abstract hydrological cycle is the perpetual movement of water throughout the various component of the global earth s system focusing on the land surface component of this cycle the determination of the succession of dry and humid periods is of high importance with respect to water resources management but also with respect to global geochemical cycles this knowledge requires a specified estimation of recent fluctuations of the land surface cycle at continental and global scales our approach leans towards a new estimation of freshwater discharge to oceans from 1875 to 1994 as recently proposed by labat et al labat d godderis y probst jl guyot jl 2004 evidence for global runoff increase related to climate warming advances in water resources 631 642 wavelet analyses of the annual freshwater discharge time series reveal an intermittent multiannual variability 4 to 8 y 14 to 16 y and 20 to 25 y fluctuations and a persistent multidecadal 30 to 40 y variability continent by continent reasonable relationships between land water cycle oscillations and climate forcing such as enso nao or sea surface temperature are proposed even though if such relationships or correlations remain very complex the high intermittency of interannual oscillations and the existence of persistent multidecadal fluctuations make prediction difficult for medium term variability of droughts and high flows but lead to a more optimistic diagnostic for long term fluctuations prediction