inter hemispheric asymmetry in the early pleistocene pacific warm pool the position of the southern boundary of the pacific warm pool is shown to have been stable since the early pleistocene based upon a planktic foraminiferal mg ca derived reconstruction of subtropical sea surface temperature in the coral sea this contrasts with previous reconstructions showing warm pool contraction from the north and east and means that the early pleistocene warm pool was more hemispherically asymmetric than its present configuration the latter was not established until 1ma supporting a strengthening of the northern hadley cell which was not replicated in its southern counterpart prior to the mid pleistocene transition copyright 2010 by the american geophysical union

analysis of local seismic waveforms from underground nuclear explosions forward modeling for effective source functions at pahute mesa in this study we use forward modeling of surface particle velocity data recorded within 15 km of underground nuclear explosions at pahute mesa in the nevada test site a plane layered velocity structure model is developed and effective source functions are obtained for six events with yields of 155 1300 kt kilotons recorded at ranges presumed to be well outside the zone of inelastic deformation we then use the effective source functions determined from well outside the elastic radius to compute synthetic seismograms for comparison with recordings within the spall zone prior to the onset of spall the comparison is good enabling us to estimate effective source functions for two additional events for which only recordings from the spall zone are available as surface zero is approached however the first half cycle of the observed velocity records includes an inflection which appears as a shoulder in acceleration records this suggests that in addition to the elastic arrival we are seeing secondary arrivals due to spall opening or inelastic shock wave propagation elastic wave propagation predicts the observed peak velocities well beyond a scaled slant range of about 175 m kt but overpredicts the first phase at closer ranges this limit of applicability of elastic wave propagation provides a useful estimate of the elastic radius for pahute mesa explosions yield scaling relations are determined using three events of known yield and these are then used to estimate yields for the eight pahute mesa explosions modeled in this study finally implications for the attenuation of teleseismic body waves are discussed

middle late pleistocene deep water circulation in the southwest subtropical pacific 1 the modern 13cdic distribution in southwest subtropical pacific deep waters is consistent with a regional mixing regime between water masses of open pacific ocean and tasman sea origin this mixing regime is reconstructed across the middle late pleistocene using a record of benthic foraminiferal 13c in a sediment core from the new caledonia trough the relative influence on the mixing regime from open pacific ocean deep waters is seen to be significantly reduced during glacial in comparison to interglacial stages over the past 1 1 ma the spatial 13c gradient in the southern ocean between deep waters entering the tasman sea and the open pacific ocean is shown to be consequently greater during glacial than interglacial stages but was generally reduced across the period of the middle pleistocene transition the existence of strong spatial chemical gradients in the glacial southern ocean limits its capacity to act as an enhanced sink for atmospheric carbon

a study of cleaning procedures used for foraminiferal mg ca paleothermometry the various cleaning steps required for preparation of foraminiferal samples for mg ca and sr ca analysis are evaluated for their relative importance and effects on measured elemental ratios it is shown that the removal of silicate contamination is the most important step for the measurement of mg ca ratios in an example bulk sample mg ca decreases from 10 5 to 2 5 mmol mol 1 during clay removal oxidation of organic material causes a lowering of sample mg ca in the order of 10 or approximately 1 c when converted to temperature use of dilute acid leaching to remove adsorbed contaminants causes partial dissolution of the sample carbonate and a corresponding decrease in mg ca reductive treatment also causes dissolution of the sample and a decrease in the mg ca ratio of up to 10 15 sample preparation for sr ca analysis does not require the same degree of rigor as is necessary for mg ca work the within run reproducibility of the method described here for g ruber in a core top sample from the arabian sea was 1 8 mean sample ratio was 4 72 mmol mol 1 when converted to temperature this becomes 28 0 2 c the equivalent result for sr ca was 0 5 mean ratio 1 44 mmol mol 1

sea surface temperature history of the low latitude western pacific during the last 5 3 million years abstract the late neogene was a time of cryosphere development in the northern hemisphere the present study was carried out to estimate the sea surface temperature sst change during this period based on the quantitative planktonic foraminiferal data of 8 dsdp sites in the western pacific target factor analysis has been applied to the conventional transfer function approach to overcome the no analog conditions caused by evolutionary faunal changes by applying this technique through a combination of time slice and time series studies the sst history of the last 5 3 ma has been reconstructed for the low latitude western pacific although the present data set is close to the statistical limits of factor analysis the clear presence of sensible variations in individual sst time series suggests the feasibility and reliability of this method in paleoceanographic studies the estimated sst curves display the general trend of the temperature fluctuations and reveal three major cool periods in the late neogene i e the early pliocene 4 7 3 5 ma the late pliocene 3 1 2 7 ma and the latest pliocene to early pleistocene 2 2 1 0 ma cool events are reflected in the increase of seasonality and meridional sst gradient in the subtropical area the latest pliocene to early pleistocene cooling is most important in the late neogene climatic evolution it differs from the previous cool events in its irreversible steplike change in sst which established the glacial climate characteristic of the late pleistocene the winter and summer sst decreased by 3 3 5 4 c and 1 0 2 1 c in the subtropics by 0 9 c and 0 6 c in the equatorial region and showed little or no cooling in the tropics moreover this cooling event occurred as a gradual sst decrease during 2 2 1 0 ma at the warmer subtropical sites while that at cooler subtropical site was an abrupt sst drop at 2 2 ma in contrast equatorial and tropical western pacific experienced only minor sst change in the entire late neogene in general subtropics was much more sensitive to climatic forcing than tropics and the cooling events were most extensive in the cooler subtropics the early pliocene cool periods can be correlated to the antarctic ice volume fluctuation and the latest pliocene early pleistocene cooling reflects the climatic evolution during the cryosphere development of the northern hemisphere

the loma prieta earthquake 1989 and earth strain tidal amplitudes an unsuccessful search for associated changes the loma prieta earthquake of 1989 pro vided an opportunity for a sensitive test of suggestions that earthquakes may be preceded by variations in earth tidal strain amplitudes such variations have been pro posed as providing an advantageous technique for detect ing precursory chkuges in elastic parameters in a seismo genic zone we have analyzed data from two borehole strainmeters continuously operating within 40 km of the epicenter and within about 10 km of the southern end of the rupture we are unable to identify any precursory changes in m2 and o 1 tidal amplitudes and estimate that any large scale changes in young s modulus must have been less than about 2 if these results apply gener ally we would conclude that variations in elastic material properties prior to earthquakes do not occur throughout substantial volumes of the subsequent hypocentral region

greatly expanded tropical warm pool and weakened hadley circulation in the early pliocene the pliocene warm interval has been difficult to explain we reconstructed the latitudinal distribution of sea surface temperature around 4 million years ago during the early pliocene our reconstruction shows that the meridional temperature gradient between the equator and subtropics was greatly reduced implying a vast poleward expansion of the ocean tropical warm pool corroborating evidence indicates that the pacific temperature contrast between the equator and 32 n has evolved from 2 c 4 million years ago to 8 c today the meridional warm pool expansion evidently had enormous impacts on the pliocene climate including a slowdown of the atmospheric hadley circulation and el nino like conditions in the equatorial region ultimately sustaining a climate state with weak tropical sea surface temperature gradients may require additional mechanisms of ocean heat uptake such as enhanced ocean vertical mixing

marine isotope stage 11 palaeoclimates palaeoenvironments and its role as an analogue for the current interglacial abstract interglacials of the quaternary period are currently the focus of a great deal of attention within the scientific community this is primarily because they play a vital role in distinguishing between natural and human climate change in the current interglacial and in understanding how the holocene would evolve in the absence of anthropogenic greenhouse warming in this respect marine isotope stage 11 mis 11 ca 410 000 yr bp is one of the key interglacial stages of the past 450 000 yr the pattern of insolation variability that occurs during mis 11 matches that which occurs in the holocene more closely than in any other warm stage of the past half a million years in addition there is now an extensive range of evidence for mis 11 palaeoclimates and palaeoenvironments from marine ice core lacustrine and terrestrial sequences the aim of this paper is to provide a comprehensive review of the current state of our understanding of mis 11 this is the first paper to provide a detailed review of mis 11 that incorporates the wide range of marine ice core long lacustrine and terrestrial records that have been generated over the last ten years since the last major overview crucially it is the first review of mis 11 that incorporates a detailed synthesis of the high resolution terrestrial sequences of western and central europe this paper therefore provides a holistic integration of a diverse range of proxies and archives to provide a detailed understanding of the expression of mis 11 in the earth system in particular the review focuses on 1 the climatic background of mis 11 2 the robustness of the identification of mis 11 in a diverse range of sequences 3 the climatic structure of mis 11 4 the magnitude of warmth that occurred in this warm stage 5 mis 11 sea level magnitude and variability 6 the duration of mis 11 7 evidence for abrupt climatic events within the interglacial of mis 11 and 8 precipitation patterns and trends during this interglacial the paper concludes by considering how useful mis 11 is as an analogue for holocene climates and compares it with other proposed analogues such as mis 19 with particular reference to the early anthropogenic hypothesis

aeolian processes and dune morphology in gale crater abstract datasets at resolutions many times greater than previously available were used to study aeolian features within gale crater high resolution thermal inertia data allowed for detailed particle size estimation with the data sufficient to resolve dunefields a wide range of grain sizes have now been identified in the gale crater dunefields ranging from medium to very coarse sand high resolution imaging science experiment hirise and themis vis data allowed for detailed analysis of the dune morphology and slip faces which shows that the dunes have responded to topographic influences on prevailing wind directions under a present day wind regime this result was corroborated by a regional mesoscale model for the crater under dust storm conditions the central mound and smaller scale crater floor topography has altered the prevailing wind regime and dune patterns aeolian activity has thus played and continues to play an important role in shaping many of the present surface features of gale crater the arrival of a future lander mission such as the mars science laboratory would be able to sample these surface features directly and add a wealth of data to the understanding of gale crater

gas exchange and co2 flux in the tropical atlantic ocean determined from 222rn and pco2 measurements measurements of sup 222 rn vertical profiles and pco sub 2 in the surface water and the atmosphere were made simultaneously in the tropical atlantic ocean as part of the tto tas program the gas exchange rate or piston velocity was determined from the sup 222 rn profiles and the delta pco sub 2 between the surface ocean and the atmosphere was determined from the pco sub 2 measurements the net flux of co sub 2 across the sea air interface was calculated from these two data sets the piston velocity ranged from 1 4 to 6 9 m d and was correlated with wind speed the slope of piston velocity versus wind speed was estimated to be between 0 3 and 1 1 m d m s the delta pco sub 2 ranged from minus 35 mu atm at 15 degree n 55 degree w to 64 mu atm at 5 degree s 28 degree w with the zero delta pco sub 2 isopleth located at about 10 degree n the high delta pco sub 2 values can be explained by lateral advection of surface water from the east with heating and biological consumption of co sub 2 and alkalinity during transit the net flux of co sub 2 was into the ocean north of 10 degree n latitude with values reaching a maximum of 1 4 mol m sup minus 2 yr sup minus 1 at 15 degree n 50 degree w south of 10 degree n more the net flux was out of the ocean reaching a maximum value of 2 7 mol m sup minus 2 yr sup minus 1 at 8 degree s 28 degree w the average net flux from 10 degree n to 10 degree s was 1 3 mol m sup minus 2 yr sup minus 1 out of the ocean which is equivalent to 0 15 gigatons of carbon per year if the flux determined applied throughout the year 56 refs 16 figs 4 tabs ss less

constraints on explosive sources with spall from near source waveforms spall the tensile failure of a material due to high stress loading has been observed in a number of contained and surface explosions the phenomenon results in a repartition of the initial spherical explosion energy source yielding a second energy source which is cylindrical and delayed in time recent spall models by day et al 1983 demanding conservation of momentum have shown the phenomenon to have little contribution to 20 sec surface waves these models are extended to include the effect of the process on near source seismograms the spall model is constrained by observations within the nonlinear regime of the source which bound the mass momentum and timing of the process comparison of these forward models with the inverse vertical point force source inferred from seismic recordings of a bermed surface explosion yields excellent agreement the spall model developed from the contained explosion cheat is used to create synthetic seismograms comparisons of these waveforms with those from a mueller murphy contained explosion indicate that the waveform contribution from spall is similar in size to the spherical explosion waveform the complete synthetic composed of the spall and explosion contribution compares favorably with observational data from the cheat experiment in both amplitude and energy distribution

evolution of the eastern tropical pacific through plio pleistocene glaciation a tropical pacific climate state resembling that of a permanent el nino is hypothesized to have ended as a result of a reorganization of the ocean heat budget 3 million years ago a time when large ice sheets appeared in the high latitudes of the northern hemisphere we report a high resolution alkenone reconstruction of conditions in the heart of the eastern equatorial pacific eep cold tongue that reflects the combined influences of changes in the equatorial thermocline the properties of the thermocline s source waters atmospheric greenhouse gas content and orbital variations on sea surface temperature sst and biological productivity over the past 5 million years our data indicate that the intensification of northern hemisphere glaciation 3 million years ago did not interrupt an almost monotonic cooling of the eep during the plio pleistocene sst and productivity in the eastern tropical pacific varied in phase with global ice volume changes at a dominant 41 000 year obliquity frequency throughout this time changes in the southern hemisphere most likely modulated most of the changes observed

deep sea temperature and ice volume changes across the pliocene pleistocene climate transitions earth has undergone profound changes since the late pliocene which led to the development 2 7 million years ago ma and intensification 0 9 ma of large scale northern hemisphere ice sheets recorded as transitions in the benthic foraminiferal oxygen isotope 18ob record here we present an orbitally resolved record of deep ocean temperature derived from benthic foraminiferal magnesium calcium ratios from the north atlantic which shows that temperature variations are a substantial portion of the global 18ob signal the record shows two distinct cooling events associated with the late pliocene lpt 2 5 to 3 ma and mid pleistocene mpt 1 2 to 0 85 ma climate transitions whereas the lpt increase in ice volume is attributed directly to global cooling the shift to 100 000 year cycles at the mpt is more likely to be a response to an additional change in ice sheet dynamics

accuracy standardization and interlaboratory calibration standards for foraminiferal mg ca thermometry the use of liquid and solid standards for foraminiferal mg ca and sr ca determinations and interlaboratory calibration has been investigated preparation of single element standard solutions from primary solid standard material enables the preparation of mixed standard solutions with mg ca and sr ca ratios of known accuracy to better than 0 1 we also investigated commercial reference materials to determine whether existing carbonate standards could be used as reference material for mg ca determinations in foraminiferal calcite we propose that in the absence of a pure calcium carbonate standard certified for mg ca ecrm 752 1 a limestone crm containing mg ca within the range of typical foraminifera is a suitable solid standard for interlaboratory calibration replicate mg ca determinations showed that provided silicate phases are removed by centrifugation this material is homogenous within the precision of daily instrumental mg ca determinations over a range of sample weights from 10 to 1000 mg taken from two separate bottles of ecrm 752 1 results gave an average value of mg ca 3 75 mmol mol 0 015 s d 0 41 r s d on 118 determinations from the two bottles

an intensity ratio calibration method for the accurate determination of mg ca and sr ca of marine carbonates by icp aes an inductively coupled plasma atomic emission spectroscopy icp aes method for the accurate and precise simultaneous measurement of the mg ca and sr ca content of carbonates was established while a precision of 0 3 1 standard deviation sd is easily obtainable for both mg ca and sr ca analysis a ca matrix effect complicates achieving similar levels of accuracy with conventional calibration procedures an alternative ratio calibration procedure is proposed which overcomes the ca matrix effects and ensures the accuracy of the mg ca and sr ca analysis of marine carbonates to 0 3 almost an order of magnitude better than conventional calibration methods the longer term precision is 0 1 if the batch run average values are corrected for longer term drift the method is suitable for analysis of foraminiferal calcite and coral aragonite and can easily be adjusted for the analysis of other carbonates or microsamples

southeastern marginal west pacific warm pool sea surface and thermocline dynamics during the pleistocene 2 5 0 5 ma highlights re organization of the west pacific warm pool at 1 7 1 35 ma west pacific warm pool and south pacific convergence zone located further to the ne prior to 1 5 ma high amplitude variations at thermocline and deep thermocline depths after 1 5 ma west pacific warm pool thermocline dynamics linked to southern sourced mode waters abstract the internal development of the tropical west pacific warm pool and its interaction with high latitude ocean regions on geological timescales is only poorly constrained based on two newly recovered sediment cores from the southeastern margin of the west pacific warm pool northern and southern manihiki plateau we provide new aspects on the dynamically interacting ocean circulation at surface subsurface thermocline and deep thermocline levels during the pleistocene 2 5 0 5 ma notably the variability of thermocline and deep thermocline 150 400 m water depth foraminiferal mg ca based temperatures with up to 6 c amplitude variations exceeds those at shallower depths down to 120 m with only 2 3 c temperature variations a major gradual reorganization of the west pacific warm pool oceanography occurred during the transitional time period of 1 7 1 35 ma prior to 1 7 ma pronounced meridional and latitudinal gradients in sea surface to subsurface ocean properties point to the eastward displacement of the west pacific warm pool boundaries with the south pacific convergence zone being shifted further northeastward across manihiki plateau simultaneously the low amplitude variations of thermocline and deep thermocline temperatures refer to an overall deep and stable thermocline the meridional and zonal gradients in sea surface and subsurface ocean properties within the west pacific warm pool reveal a pronounced change after 1 5 ma leading to a more southward position of the warm south pacific convergence zone between 1 35 0 9 ma and 0 75 0 5 ma synchronous to the changes in the upper ocean the deeper water masses experienced high amplitude variations in temperature most prominently since 1 5 ma this and the dynamically changing thermocline were most likely associated to the impact of southern sourced mode waters which might have developed coincidently with the emergence of the east pacific cold tongue and high latitude sea surface cooling

shear wave velocity structure in the vicinity of the 2012 mw 7 8 haida gwaii earthquake from receiver function inversion abstract the thrust mechanism of the 2012 m w 7 8 haida gwaii earthquake suggests convergence across the transpressive pacific north america plate boundary in the region is accommodated by underthrusting with important consequences for seismic and tsunami hazard analysis this article investigates the crustal structure and extent of subduction beneath haida gwaii by nonlinear inversion of receiver function data processed from teleseismic recordings at five land based seismograph stations three of these stations were deployed since the 2012 earthquake to extend coverage to the southeast and have not been analyzed previously the inversions provide estimates of the shear wave velocity structure beneath much of moresby island results indicate a positive velocity contrast at approximately 18 26 km depth interpreted as a shallow continental moho a 12 17 km thick low shear wave velocity zone is also identified which increases in depth from 25 to 42 km along the direction of plate convergence which is interpreted as subducting oceanic material these results provide the first evidence that the subducting oceanic plate extends beneath the entirety of moresby island

middle pliocene sea surface temperatures a global reconstruction identification and analyses of pliocene marine microfossils from 64 globally distributed stratigraphic sequences have been used to produce a middle pliocene sea surface temperature reconstruction of the earth this reconstruction shows little or no change from current conditions in low latitude regions and significant warming of the ocean surface at mid and higher latitudes of both hemispheres this pattern of warming is consistent with terrestrial records and suggests a combination of enhanced meridional ocean heat transport and enhanced greenhouse effect were responsible for the middle pliocene warmth

sea surface temperatures around the australian margin and indian ocean during the last glacial maximum abstract we present new last glacial maximum lgm sea surface temperature sst maps for the oceans around australia based on planktonic foraminifera assemblages to provide the most reliable sst estimates we use the modern analog technique the revised analog method and artificial neural networks in conjunction with an expanded modern core top database all three methods produce similar quality predictions and the root mean squared error of the consensus prediction the average of the three under cross validation is only 0 77 c we determine lgm sst using data from 165 cores most of which have good age control from oxygen isotope stratigraphy and radiocarbon dates the coldest sst occurred at 20 500 1400 cal yr bp predating the maximum in oxygen isotope records at 18 200 1500 cal yr bp during the lgm interval we observe cooling within the tropics of up to 4 c in the eastern indian ocean and mostly between 0 and 3 c elsewhere along the equator the high latitudes cooled by the greatest degree a maximum of 7 9 c in the southwest pacific ocean our maps improve substantially on previous attempts by making higher quality temperature estimates using more cores and improving age control

links between the onset of modern walker circulation and the mid pleistocene climate transition sea surface temperatures ssts reconstructed from ocean drilling program sites 806 and 849 in the western and eastern equatorial pacific provide a history of the strength of the walker circulation between 1 5 and 0 5 ma a progressive cooling in the eastern equatorial pacific is paralleled by intensification of the equatorial zonal sst gradient that began 1 17 ma prior to the expansion of global ice volume associated with the mid pleistocene climate transition the ssts in the eastern equatorial pacific and the zonal gradient reached modern values by 0 9 ma we propose that this onset and intensification of the modern walker circulation reduced heat flux but increased moisture transport to high latitudes leading to the development of more extensive ice sheets and the shift toward the 100 ka world

permanent el nino like conditions during the pliocene warm period during the warm early pliocene 4 5 to 3 0 million years ago the most recent interval with a climate warmer than today the eastern pacific thermocline was deep and the average west to east sea surface temperature difference across the equatorial pacific was only 1 5 0 9 c much like it is during a modern el nino event thus the modern strong sea surface temperature gradient across the equatorial pacific is not a stable and permanent feature sustained el nino like conditions including relatively weak zonal atmospheric walker circulation could be a consequence of and play an important role in determining global warmth

the effects of unconsolidated sediments upon the ground motion during local earthquakes abstract a vertical seismic array at the richmond field station on the margin of san francisco bay california has provided some excellent experimental data showing the effects of unconsolidated sediments on ground motion during local earthquakes the experiments are well controlled in that good estimates of the material properties of the sediments are available with the largest uncertainty being in the attenuation three components of acceleration have been recorded in bedrock below the sediments within the sediments and at the surface of the sediments from two local earthquakes the maximum accelerations at the surface are between 1 5 and 4 3 times those in the bedrock analytical calculations which assume vertically propagating waves and which are suitable for highly attenuating materials explain the major differences between the bedrock records and the surface records for both vertical and horizontal components maximum accelerations duration frequency content general character of the records and response spectra are all in approximate agreement some of the energy arriving late in the records can best be explained by surface waves propagating horizontally in the sediments

simulations of warm tropical conditions with application to middle pliocene atmospheres during the early and mid pliocene the period from 5 to 3 million years ago approximately the earth is believed to have been significantly warmer than it is today but the reasons for the higher temperatures are unclear this paper explores the impact of recent findings that suggest that at that time cold surface waters were absent from the tropical and subtropical oceanic upwelling zones el nino was in effect a perennial rather than intermittent phenomenon and sea surface temperatures in low latitudes were essentially independent of longitude when these conditions are specified as the lower boundary condition for an atmospheric gcm we find that the trade winds along the equator and hence the walker circulation collapse the low level stratus clouds in low latitudes diminish greatly thus reducing the albedo of the earth the atmospheric concentration of water vapor increases and enhanced latent heat release due to stronger evaporation warms up the tropical atmosphere particularly between 40 s and 20 n moreover teleconnection patterns from the pacific induce a warming over north america that is enhanced by surface albedo feedback a process that may have helped to maintain this region ice free before 3 ma the results presented here indicate that the suggested absence of cold surface waters from the tropical and subtropical oceanic upwelling zones could have contributed significantly to the pliocene warmth

source characteristics of two underground nuclear explosions summary broadband seismic waveform data recorded in the distance range of 1 11 km from two underground explosions detonated at pahute mesa of the nevada test site have been used to estimate the source time functions for the second order moment tensors of these events data were available from eight three component stations for the explosion harzer and from 11 stations for the explosion chancellor stable moment tensor estimates with a good signal to noise ratio were obtained in the frequency range of 0 2 5 0 hz the moment tensors are dominated by the diagonal elements but a significant asymmetry is present with vertical force couples being larger having additional low frequency energy in the 0 3 0 4 hz range and having a different time dependence in the 0 5 2 5s range than the horizontal force couples considerable evidence points to the possibility that this asymmetry is related to spall processes taking place in the depth interval between the explosion and the free surface when the isotropic parts of the moment tensors are interpreted as reduced displacement potentials the results are in reasonable agreement with theoretical and empirical models except that the characteristic times are about three times those predicted by published scaling relationships this difference is most likely due to the effects of spall but the fact that the explosions were detonated in unsaturated materials may also be a contributing factor

chemistry and texture of the rocks at rocknest gale crater evidence for sedimentary origin and diagenetic alteration a suite of eight rocks analyzed by the curiosity rover while it was stopped at the rocknest sand ripple shows the greatest chemical divergence of any potentially sedimentary rocks analyzed in the early part of the mission relative to average martian soil and to the stratigraphically lower units encountered as part of the yellowknife bay formation these rocks are significantly depleted in mgo with a mean of 1 3 wt and high in fe averaging over 20 wt feo t with values between 15 and 26 wt feo t the variable iron and low magnesium and rock texture make it unlikely that these are igneous rocks rock surface textures range from rough to smooth can be pitted or grooved and show various degrees of wind erosion some rocks display poorly defined layering while others seem to show possible fractures narrow vertical voids are present in rocknest 3 one of the rocks showing the strongest layering rocks in the vicinity of rocknest may have undergone some diagenesis similar to other rocks in the yellowknife bay formation as indicated by the presence of soluble calcium phases the most reasonable scenario is that fine grained sediments potentially a mixture of feldspar rich rocks from bradbury rise and normal martian soil were lithified together by an iron rich cement

in situ evaluation of air sea gas exchange parameterizations using novel conservative and volatile tracers measurements of air sea gas exchange rates are reported from two deliberate tracer experiments in the southern north sea during february 1992 and 1993 a conservative tracer spores of the bacterium bacillus globigii var niger was used for the first time in an in situ air sea gas exchange experiment this nonvolatile tracer is used to correct for dispersive dilution of the volatile tracers and allows three estimations of the transfer velocity for the same time period the first estimation of the power dependence of gas transfer on molecular diffusivity in the marine environment is reported this allows the impact of bubbles on estimates of the transfer velocity derived from changes in the helium sulphur hexafluoride ratio to be assessed data from earlier dual tracer experiments are reinterpreted and findings suggest that results from all dual tracer experiments are mutually consistent the complete data set is used to test published parameterizations of gas transfer with wind speed a gas ex change relationship that shows a dependence on wind speed intermediate between those ofliss and merlivat 1986 and wanninkhof 1992 is found to be optimal the dual tracer data are shown to be reasonably consistent with global estimates of gas exchange based on the uptake of natural and bomb derived radiocarbon the degree of scatter in the data when plotted against wind speed suggests that parameters not scaling with wind speed are also influencing gas exchange rates

implications of seawater mg ca variability for plio pleistocene tropical climate reconstruction abstract recent reconstructions of mg and ca concentrations of seawater indicate that seawater mg ca changed significantly over the last 5 million years ma tropical sea surface temperature sst records for the last 5 ma based on foraminiferal mg ca paleothermometry assume constant seawater mg ca these sst records suggest that average equatorial pacific ssts remained thermally stable from 5 to 2 ma after which significant cooling occurred only in the eastern equatorial pacific this study examines the implications of adjusting available equatorial pacific sst records based on mg ca paleothermometry to account for the inferred past variations of seawater mg ca the results suggest that both the cold and the warm regions of the equatorial pacific were much warmer during the early pliocene 30 31 c and that both regions experienced a marked cooling from 4 ma to 1 ma this new interpretation of foraminiferal mg ca creates a discrepancy with alkenone unsaturation based sst records from the eastern equatorial pacific which might be due to either overestimation of changes in past seawater mg ca or to factors affecting the interpretation of the u k 37 index the adjusted sst records are consistent with the hypothesis that higher levels of greenhouse gases maintained the warmth of the early pliocene

late pleistocene palaeocenography of the tasman sea implications for the dynamics of the warm pool in the western pacific quantitative analyses of planktonic foraminifera from 47 core top samples spatially distributed through the tasman sea and cores rc12 113 e36 23 dsdp sites 588 592 593 and odp site 828a from a n s transect supplemented with stable isotope analyses indicate that three planktonic foraminiferal assemblages defined by factor analysis on core top material correlated with three hydrographic modes defined on the basis of sea surface temperatures temperature profiles seasonal changes in temperature and mixed layer depth similar assemblages were found in down core material along the tasman sea transect that combined with semi quantitative analyses of foraminiferal assemblages provinces and the coiling ratio of globorotalia truncatulinoides allows reconstruction of the position of the tasman front or the subtropical divergence during the late brunhes chron the results indicate that the tasman front migrated from its present position at 30 s to 26 s during the last glacial maximum the northward migration of the tasman front may indicate a reduction in volume of the equatorial warm pool and or an increase in the strength of cool subtropical water masses the late pleistocene distribution of g truncatulinoides left coiling from appears to be related to the formation of subantarctic mode water thermostads this relationship may explain the evolutionary origin of this species in the southwest pacific at 2 4 ma simultaneously with the onset of late pliocene glaciations the past position of the subtropical convergence is reconstructed by means of coilingv directions in neogloboquadrina pachyderma the convergence apparently migrated slightly north of 43 s core e36 23 during glacial stages 6 10 and 12

reconstructing the subsurface ocean decadal variability using surface nudging in a perfect model framework initialising the ocean internal variability for decadal predictability studies is a new area of research and a variety of ad hoc methods are currently proposed in this study we explore how nudging with sea surface temperature sst and salinity sss can reconstruct the three dimensional variability of the ocean in a perfect model framework this approach builds on the hypothesis that oceanic processes themselves will transport the surface information into the ocean interior as seen in ocean only simulations five nudged simulations are designed to reconstruct a 150 years target simulation defined as a portion of a long control simulation the nudged simulations differ by the variables restored to sst or sst sss and by the area where the nudging is applied the strength of the heat flux feedback is diagnosed from observations and the restoring coefficients for sss use the same time scale we observed that this choice prevents spurious convection at high latitudes and near sea ice border when nudging both sst and sss in the tropics nudging the sst is enough to reconstruct the tropical atmosphere circulation and the associated dynamical and thermodynamical impacts on the underlying ocean in the tropical pacific ocean the profiles for temperature show a significant correlation from the surface down to 2 000 m due to dynamical adjustment of the isopycnals at mid to high latitudes sss nudging is required to reconstruct both the temperature and the salinity below the seasonal thermocline this is particularly true in the north atlantic where adding sss nudging enables to reconstruct the deep convection regions of the target by initiating a previously documented 20 year cycle of the model the sst sss nudging is also able to reproduce most of the amoc variations a key source of decadal predictability reconstruction at depth does not significantly improve with amount of time spent nudging and the efficiency of the surface nudging rather depends on the period events considered the joint sst sss nudging applied everywhere is the most efficient approach it ensures that the right water masses are formed at the right surface density the subsequent circulation subduction and deep convection further transporting them at depth the results of this study underline the potential key role of sss for decadal predictability and further make the case for sustained large scale observations of this field

onshore offshore structure of the juan de fuca plate in northern cascadia from bayesian receiver function inversion abstract this study applies bayesian inversion to receiver functions rfs to estimate local shear wave velocity v s structure of the juan de fuca jdf plate beneath the northern cascadia subduction zone csz offshore and onshore vancouver island british columbia canada we use passive seismic data recorded on neptune northeast pacific time series undersea networked experiments canada ocean bottom seismometers obss on temporary autonomous keck foundation obss and on two land based seismometers on vancouver island that are part of the canadian national seismograph network cnsn three component broadband recordings of large distant 30 100 earthquakes are used to compute rfs dominated by locally generated p to s converted waves these are subsequently inverted using a nonlinear bayesian approach that yields optimal profiles of v s v p compressional wave velocity and strike and dip angles as well as quantitative uncertainty estimates for these parameters the introduction of neptune canada helps fill a gap in offshore seismic monitoring results from obs stations indicate a thin oceanic crust at the jdf ridge which thickens to 10 km at the continental slope where sediment thickness also increases to 5 km at ozb a coastal station a 6 8 km thick two part low velocity zone lvz is imaged at 19 km depth an lvz of similar thickness is also observed 34 km beneath pgc a south central vancouver island station the thickness of the lvz imaged at these two land based stations indicates that the oceanic sediments are not subducted but are scraped off the jdf plate and accreted to the north american plate determining these v s models at various stages of the csz provides a more detailed image of the subducting plate and therefore contributes valuable new information useful for seismic hazard analysis

measurements and interpretations of tilt strain gauges in seismically active areas abstract an overview of different aspects of deformation measurements is given an introduction to the general theory of point crustal deformations with an application to the stress strain relations at the earth surface is made the instrumentation used in crustal deformation measurements is briefly explained emphasizing different constructions of tilt and strainmeters the problems connected with the housing of the instruments i e the cavity and topography effects and with the ambient noise factors as the hydrological and pressure effects are discussed the last part of the paper is concerned with the relation between deformation measurements and seismic events both from a theoretical and observational standpoint a number of examples are shown that report on pre co and post seismic and the secular term deformation in different areas of the world

low high latitude interaction forcing on the evolution of the 400 kyr cycle in east asian winter monsoon records during the last 2 8 myr abstract variability of the east asian winter monsoon eawm stronger during glacials and weaker during interglacials has been tightly linked to the wax and wane of the northern hemisphere ice sheets nhis via the siberian high over the last 2 8 million years myr however the long eccentricity cycle ca 400 kyr in the eawm record from the late pliocene to early pleistocene 2 8 1 2 ma could not be linked to nhis changes which lacked the long eccentricity cycle in the pleistocene here we present the first low latitude eawm record of the last 2 8 myr using surface and subsurface temperature difference from the northern south china sea to evaluate interactions between tropical ocean and eawm changes the results show that the eawm variability displayed significant 400 kyr cycle between 2 8 ma and 1 2 ma with weak strong eawm during high low earth orbital eccentricity state a super el nino southern oscillation enso proxy record calculated using west east equatorial pacific sea surface temperature differences revealed 400 kyr cycles throughout the last 2 8 myr with warm phase during high eccentricity state thus we propose that super enso mean state strongly modulated the eawm strength through remote forcing to generate the 400 kyr cycle between 2 8 ma and 1 2 ma while low nhis volume was not sufficient to dominate the eawm variation as it did over the last 0 9 myr with 100 kyr cycles in dominance

modeling near field and teleseismic observations from the amchitka test site during the amchitka testing program recordings were made of the near field ground velocity for events milrow and cannikin these records exhibited a p arrival a feature associated with near field pp and a developing rayleigh wave in this investigation simple models were found which match the complete seismograms they simultaneously predict the amplitude wave shape timing and periodicity of both the body waves and the surface waves models for both the amchitka crustal structure and the source time functions were developed the crustal model is similar to previous models in its average properties so travel time constraints are still satisfied small modifications have been made to match the waveform data the events on amchitka can apparently be represented as isotropic point sources with the types of simple source time histories predicted by classical yield scaling laws a source model for event longshot was developed on the basis of the yield scaling laws since no near field records are available for it the source models were tested by comparing the teleseismic body waveforms they predict with observations short period p waves long period p waves and long period ps waves were considered the short period p waves provided the best constraint to match them it was necessary both to develop a model for teleseismic pp since it arrives later than the near field model would predict and to estimate the average value of t the milrow and cannikin teleseismic short period p waves indicate that the average effective t for teleseismic ray paths from amchitka is 0 9 s the scatter about this value however is very substantial the accuracy of the scaling laws was tested by comparing synthetics for longshot to teleseismic observations the predicted amplitudes and wave shapes fall within the scatter in the observations though again this scatter is substantial

role of tropics in changing the response to milankovich forcing some three million years ago appeared in regions that today have intense oceanic upwelling the eastern equatorial pacific and the coastal zones of southwestern africa and california there was furthermore a significant change in the earth s response to milankovich forcing obliquity signals became large but those associated with precession and eccentricity remained the same the latter change in the earth s response can be explained by hypothesizing that the global cooling during the cenozoic affected the thermal structure of the ocean it caused a gradual shoaling of the thermocline around 3 ma the thermocline was sufficiently shallow for the winds to bring cold water from below the thermocline to the surface in certain upwelling regions this brought into play feedbacks involving

relative importance of meridional and zonal sea surface temperature gradients for the onset of the ice ages and pliocene pleistocene climate evolution sst gradients and ice ages

variations in the western pacific warm pool across the mid pleistocene evidence from oxygen isotopes and coccoliths in the west philippine sea abstract we present planktonic foraminifera oxygen isotope and florisphaera profunda abundance data from the international marine global change study program images core md06 3050 which was collected in the west philippine sea on the margin of the western pacific warm pool wpwp our records reveal marked changes in the upper water structure in the kuroshio source region as early as 1 5 ma continuing through the mid pleistocene climate transition mpt these changes are evidenced by reconstructions of the thermocline based on planktonic foraminiferal oxygen isotope differences and the nutricline based on the relative abundance of the coccolithophore species florisphaera profunda in the kuroshio source region the evolution of the thermocline nutricline featured three prominent phases 1 phase i 1 5 1 1 ma which was characterized by low amplitude variations in a shallow thermocline 2 phase ii 1 1 0 8 ma which was characterized by high amplitude variations in a relatively shallow thermocline nutricline and 3 phase iii 0 8 0 5 ma which was characterized by low amplitude variations in a deep thermocline nutricline combined with the zonal sea surface temperature gradient in the tropical pacific the evolution of the upper water structure can be linked to tropical climatic changes across the mpt including the intensification of atmospheric circulation and a gradual cessation of the long term el nino like state the upper water structure of the wpwp was asymmetric before 0 8 ma with a shallow thermocline nutricline along the northern margin and a deep thermocline nutricline in the center of the wpwp and south china sea scs the modern wpwp was established by approximately 0 8 ma and the upper water structure has changed synchronously as a whole since that time a comparison of the 18 o values derived from globigerinoides ruber tests from the md06 3050 core with those from other cores in the western pacific suggests that the lower glacial interglacial g ruber 18 o values in md06 3050 before 0 8 ma could be related to the enhancement of the wpwp and to changes in atmospheric circulation patterns

dense bottom layers in the scotia sea southern ocean creation lifespan and destruction the lower limb of the atlantic overturning circulation is renewed by dense waters from the southern ocean a substantial portion of which flow through the scotia sea we report dense bottom layers here with gradients in temperature and salinity comparable to those seen near the surface of the southern ocean these are overlain by layers with much weaker stratification and are caused by episodic overflows of dense waters across the south scotia ridge and topographic trapping within deep trenches one such layer was found to be at least 3 4 years older than the water immediately above the estimated vertical diffusivity to which this layer was subject is substantially less than the strong basin average deep mixing reported previously we conjecture that a vertical mixing in the scotia sea is strongly spatially inhomogeneous and b the flushing of these layers like their formation is related to overflow events and hence also strongly episodic

the pliocene paradox mechanisms for a permanent el nino during the early pliocene 5 to 3 million years ago globally averaged temperatures were substantially higher than they are today even though the external factors that determine climate were essentially the same in the tropics el nino was continual or permanent rather than intermittent the appearance of northern continental glaciers and of cold surface waters in oceanic upwelling zones in low latitudes both coastal and equatorial signaled the termination of those warm climate conditions and the end of permanent el nino this led to the amplification of obliquity but not precession cycles in equatorial sea surface temperatures and in global ice volume with the former leading the latter by several thousand years a possible explanation is that the gradual shoaling of the oceanic thermocline reached a threshold around 3 million years ago when the winds started bringing cold waters to the surface in low latitudes this introduced feedbacks involving ocean atmosphere interactions that along with ice albedo feedbacks amplified obliquity cycles a future melting of glaciers changes in the hydrological cycle and a deepening of the thermocline could restore the warm conditions of the early pliocene

methyl bromide cycling in a warm core eddy of the north atlantic ocean 1 we conducted a detailed investigation of the evolution of methyl bromide concentrations degradation rates and ventilation rates for 26 days in a naturally contained warm core eddy of the north atlantic ocean this is the first study of the oceanic cycling of methyl bromide in a natural contained system with a complete suite of supporting measurements of physical and chemical variables methyl bromide concentrations in the mixed layer ranged from 2 3 to 4 2 nmol m 3 degradation rates ranged from 0 1 to 0 9 nmol m 3 d 1 net sea to air exchange rates ranged from 0 to 0 5 nmol m 3 d 1 and net loss rates through the thermocline were less than 0 1 nmol m 3 d 1 from a mass balance for methyl bromide in the mixed layer we calculated production rates ranging from 0 1 to 1 3 nmol m 3 d 1 the median of this range 0 48 nmol m 3 d 1 is higher than the 0 15 nmol m 3 d 1 necessary to maintain the reported global oceanic emission of 56 gg yr 1 this is reasonable because our study area was supersaturated in methyl bromide whereas the ocean as a whole is undersaturated

a geophysical geological transect of the silent canyon caldera complex pahute mesa nevada revision of lithological logs for boreholes penetrating the volcanic center at pahute mesa nevada has led to a thorough review of the volcanic stratigraphy and geologic structure we have combined this review with a compilation of old and newly acquired gravity and seismic travel time data producing a unified interpretation along a northwest to southeast profile the analysis supports a new interpretation of the silent canyon caldera complex the caldera is found to be more asymmetric than previously suggested with the southeastern boundary formed by linear high angle normal faults and a more gently sloping northwestern boundary the total thickness of volcanic units within the caldera complex does not appear to exceed 5 km the shallow structure at pahute mesa could have a profound effect on the seismic response for regional and teleseismic signals from this nuclear test site the silent canyon caldera complex is actually a set of nested calderas first filled by thick 1 km postcaldera lavas and subsequently buried by outflow sheets of the timber mountain caldera to the south thick postcaldera lavas filled a half graben structure formed west of the west greeley fault dropping the tops of the youngest caldera forming units to depths in excess of 2 km therefore the western boundary of the caldera complex is poorly defined east of the west greeley fault two overlapping calderas are defined and stratigraphic data suggest the presence of even older calderas the youngest caldera the calc alkaline area 20 caldera is well defined from drill hole data the area 20 caldera overlaps the 13 6 ma peralkaline grouse canyon caldera which is less well defined but apparently collapsed in trap door style along the almendro fault for both these calderas collapse continued after the main caldera forming eruption concurrent with the accumulation of thick 1 km lavas within the peripheral collapse zones the geophysical interpretation indicates that the major structural boundary of the caldera complex corresponds to the nne trending scrugham peak and almendro faults which offset the pre tertiary contact more than 1 km but have less than 200 m offset in rocks of 11 ma age drill hole data show that offsets along these faults increase systematically within older up to 15 ma units which are commonly rotated eastward in a style similar to units at the surface abrupt changes in the subsurface thickness of the caldera forming units occur across the faults indicating that these linear features served as caldera boundaries

ml m0 as a regional seismic discriminant the m b m s ratio determined by teleseismic observations has proven to be an effective discriminant for explosive sources tend to be significantly richer in short period energy than are earthquakes unfortunately this method is limited by the detection threshold of teleseismic surface waves however recent advances in instrumentation allowing low amplitude surface wave measurements coupled with new analytical techniques make it feasible to use regional waveform data to determine the long period source excitation level of low magnitude events we propose using the ratio of m l local magnitude to m 0 scalar seismic moment as an analogous regional discriminant we applied this criterion to a data set of 299 earthquakes and 178 explosions and found that this ratio seems to be diagnostic of source type for a given m 0 the m l of an explosion is more than 0 5 magnitude units larger than that of an earthquake this separation of populations with respect to source type can be attributed to the fact that m l is a short period 1 hz energy measurement whereas seismic moment is determined from long period body wave phases period 4 s and surface waves 10 to 40 sec using regional stations with sources 200 to 600 km away the effective threshold for magnitude measurements for this discriminant is found to be m l 3 1 for earthquakes and m l 3 6 for explosions this method does require the determination of regional crustal models and path calibrations from master events or by other means

surface waves from underground explosions with spall analysis of elastic and nonlinear source models anomalous surface wave observations from underground explosions have been widely attributed to the phenomenon of spall i e the detachment and subsequent slapdown of near surface layers in response to explosion induced tensile stresses we argue on the basis of a simple equivalent force model that while spall can enhance explosion surface waves at very short periods it cannot contribute significantly to the teleseismic surface waves radiated by underground explosions at periods exceeding about 10 sec previous theoretical results to the contrary are in error having been based on source models which do not conserve momentum a nonlinear two dimensional axisymmetric finite difference simulation of a buried explosion in granite further supports the conclusion that spall cannot contribute to long period surface waves the simulation exhibits extensive spall nonetheless predicted fundamental mode rayleigh wave spectra are nearly identical to those obtained from a spherically symmetric simulation which does not include spall at periods exceeding about 10 sec at shorter periods the two dimensional simulation predicts some rayleigh wave enhancement compared to the one dimensional simulation the maximum enhancement about a factor of 2 occurs at a period of approximately 2 5 sec synthetic long period rayleigh wave seismograms at 3000 km range show no perceptible phase or amplitude anomalies due to spall these results are in excellent agreement with the predictions of our equivalent force model

calibration of mg ca thermometry in planktonic foraminifera from a sediment trap time series 1 paired mg ca and 18o measurements on planktonic foraminiferal species g ruber white g ruber pink g sacculifer g conglobatus g aequilateralis o universa n dutertrei p obliquiloculata g inflata g truncatulinoides g hirsuta and g crassaformis from a 6 year sediment trap time series in the sargasso sea were used to define the sensitivity of foraminiferal mg ca to calcification temperature habitat depths and calcification temperatures were estimated from comparison of 18o of foraminifera with equilibrium calcite based on historical temperature and salinity data when considered together mg ca mmol mol of all species except two show a significant r 0 93 relationship with temperature t c of the form mg ca 0 38 0 02 exp 0 090 0 003 t equivalent to a 9 0 0 3 change in mg ca for a 1 c change in temperature small differences exist in calibrations between species and between different size fractions of the same species o universa and g aequilateralis have higher mg ca than other species and in general data can be best described with the same temperature sensitivity for all species and pre exponential constants in the sequence o universa g aequilateralis g bulloides g ruber g sacculifer other species this approach gives an accuracy of 1 2 c in the estimation of calcification temperature the 9 sensitivity to temperature is similar to published studies from culture and core top calibrations but differences exist from some literature values of pre exponential constants different cleaning methodologies and artefacts of core top dissolution are probably implicated and perhaps environmental factors yet understood planktonic foraminiferal mg ca temperature estimates can be used for reconstructing surface temperatures and mixed and thermocline temperatures using g ruber pink g ruber white g sacculifer n dutertrei p obliquiloculata etc the existence of a single mg thermometry equation is valuable for extinct species although use of species specific equations will where statistically significant provide more accurate evaluation of mg ca paleotemperature

pleistocene sea surface temperature evolution early cooling delayed glacial intensification and implications for the mid pleistocene climate transition the mid pleistocene climate transition mpt is defined by the emergence of high amplitude quasi 100 ka glacial interglacial cycles from a prior regime of more subtle 41 ka cycles this change in periodicity and amplitude cannot be explained by a change in external astronomical forcing here we review and integrate published records of sea surface temperatures ssts to assess whether a common global expression of the mpt in the surface ocean can be recognized and examine our findings in light of mechanisms proposed to explain climate system reorganization across the mpt we show that glacial interglacial variability in ssts is superimposed upon a longer term cooling trend in oceanographic systems spanning the low to high latitudes regional variability exists in the timing of the onset and magnitude of cooling but in most cases a long term cooling trend begins or intensifies from 1 2 ma marine isotope stage mis 35 34 the sst cooling accompanies a long term trend towards higher global ice volume as recorded in benthic foraminifera 18o but predates a step like increase in 18o at 0 9 ma mis 24 22 that is argued to reflect expansion of continental ice sheets the strongest expression of pleistocene cooling is found during glacial stages whereas minor or negligible trends in interglacial temperatures are identified however pronounced cooling during both glacial and interglacial maxima is evident at 0 9 ma alongside the long term sst cooling trends quasi 100 ka cycles begin to emerge in both the sst and 18o records at 1 2 ma and become dominant with the expansion of the ice sheets at 0 9 ma we show that the intensified glacial stage cooling is accompanied by evolving pco2 abyssal ocean ventilation atmospheric circulation and or dust inputs to the southern ocean these changes in diverse environmental parameters suggest that glacial climate boundary conditions evolved across the mpt in turn these modified boundary conditions may have altered climate sensitivity to orbital forcing by placing pre existing ice sheets closer to some threshold of climate ice sheet response

velocity structure of silent canyon caldera nevada test site abstract a laterally averaged one dimensional p and s wave velocity structure is obtained for silent canyon caldera located beneath pahute mesa at the nevada test site the velocity models are derived from a linearized damped least squares travel time inversion for slowness gradient perturbations a total of 72 p and 20 s wave travel times generated from 13 different explosions obtained at locations above the caldera are used in the inversion the structure is modeled using linear velocity gradients in a series of horizontal layers the inversion produces a model in which velocity for p waves increases from 1 5 km sec at the surface to 4 5 km sec at 2 3 km depth and from 1 0 km sec at the surface to 2 3 km sec at 2 0 km depth for s waves the p and s wave models produce travel time residuals which are typically less than 0 1 and 0 2 sec respectively which is within observational error in an attempt to estimate the degree of lateral velocity variations over which the one dimensional model averages waveform data collected above the caldera are examined for indications of a laterally heterogeneous structure

interpretation of gravity data in a complex volcano tectonic setting southwestern nevada this regional gravity study based on an irregular 2 km data grid was conducted during the past few years at yucca mountain southern nye county nevada as part of a program to locate a suitable repository for high level nuclear waste about 100 surface rock samples three borehole gamma gamma logs and one borehole gravity study provide excellent density control a nearly linear increase in density of 0 26 g cm3 per kilometer of depth is indicated in the thick tuff sequences that underlie the mountain isostatic and 2 0 g cm3 bouguer corrections were applied to the observed gravity values to remove regional gradients and topographic effects respectively the bare mountain gravity high with an isostatic anomaly maximum of 48 mgal is connected with a greater gravity high over the funeral mountains to the southwest together these highs result from a continuous block of dense metamorphosed precambrian and paleozoic rocks that stretches across much of the walker lane from the east edge of death valley to bare mountain the calico hills gravity high appears more likely to originate from a northeast trending buried ridge of paleozoic rocks that extends southwestward beneath busted butte 5 km southeast of the proposed repository where two and three dimensional modeling indicates that the pre cenozoic rocks lie less than 1000 m beneath the surface tuff at least 4000 m thick fills a large steep sided depression in the pretuff rocks beneath yucca mountain and crater flat the gravity low and the thick tuff section lie within a large collapse area that includes the crater flat timber mountain silent canyon caldera complexes gravity lows in crater flat itself are interpreted to coincide with the source areas of the prow pass member the bullfrog member and the tram member of the crater flat tuff these source areas add nearly 350 km2 to the previously recognized extent of the local caldera complexes southward extension of the broad gravity low associated with crater flat into the amargosa desert is evidence for sector graben type collapse segments related to the formation of the timber mountain caldera and superimposed on the other volcanic and extensional structures within crater flat

intracaldera volcanic activity toledo caldera and embayment jemez mountains new mexico the toledo caldera was formed at 1 47 0 06 ma during the catastrophic eruption of the lower member bandelier tuff the caldera was obscured at 1 12 0 03 ma during eruption of the equally voluminous upper member of the bandelier tuff that led to formation of the valles caldera earlier workers interpreted a 9 km diameter embayment located ne of the valles caldera toledo embayment to be a remnant of the toledo caldera drill hole data and new k ar dates of toledo intracaldera domes redefine the position of toledo caldera nearly coincident with and of the same dimensions as the younger valles caldera the toledo embayment may be of tectonic origin or a small tschicoma volcanic center caldera this interpretation is consistent with distribution of the lower member of the bandelier tuff and with several other field and drilling related observations explosive activity associated with cerro toledo rhyolite domes is recorded in tuff deposits located between the lower and upper members of the bandelier tuff on the northeast flank of the jemez mountains recorded in the tuff deposits are seven cycles of explosive activity most cycles consist of phreatomagmatic tuffs that grade upward into plinian pumice beds a separate deposit of the same age and consisting of pyroclastic surges and flows is associated with rabbit mountain located on the southeast rim of the valles toledo caldera complex these are the surface expression of what may be a thicker more voluminous intracaldera tuff sequence the combined deposits of the lower and upper members of the bandelier tuff toledo and valles intracaldera sediments tuffs and dome lavas form what we interpret to be a wedge shaped caldera fill this sequence is confirmed by deep drill holes and gravity surveys this fill accumulated in depressions formed during precaldera rifting and episodes of caldera collapse we interpret the toledo valles caldera complex to be a pair of nearly coincident trapdoor calderas with the hinge on the west side and thick caldera fill in the east

evidence for variations of mechanical properties in the friuli seismic area abstract tidal strains of the earth were extracted from three horizontal strainmeter records 1979 1986 in the friuli seismic area by the filter method the areal strain factor ignoring the tidal loading effects shows that its time variation is significant their amplitudes in 1986 are about 50 of those in 1979 the modifications of mechanical properties estimated in terms of the local shear and bulk modulus variations were obtained considering the envelope of the tidal strain signals the seismic wave velocity determined by the simultaneous inversion of the arrival time data of the local seismometric network displayed comparable changes a major change both in the seismic velocities and the elastic parameters started in march 1982 which was about 11 months before an earthquake of magnitude 4 1 the largest event from 1979 to 1986 which occurred within the seismic network on feb 10 1983

decomposition of seismic moment tensors for underground nuclear explosions generally the decomposition of a seismic moment tensor is not unique however to favorably view the characteristics of a certain seismic source one must decompose a seismic moment tensor into parts according to assumptions about the properties of the seismic source different from natural earthquakes in which the shear dislocation component plays a predominant role in the source process and the seismic moment tensor can be separated into an isotropic component a double couple and a compensated linear vector dipole clvd underground nuclear explosions have three major components in their source process i e the explosion the tensional spalling and the tectonic strain release associated with the explosion in such a situation the conventional moment tensor decomposition for earthquakes is not convenient to estimate the yield of the explosion and to characterize the tectonic strain release in this paper an alternative decomposition scheme is proposed to deal with the moment tensor of underground nuclear explosions which might benefit the approach to study the tectonic strain release induced by underground nuclear detonations

initial intensification of east asian winter monsoon at about 2 75 ma as seen in the chinese eolian loess red clay deposit 1 the loess paleosol red clay sequence in the chinese loess plateau provides a record of the evolution of atmospheric circulation and monsoon climate over east asia during the last 7 8 ma detailed analyses of the baishui and jingchuan sections show that the grain size of eolian loess increased abruptly at about 2 75 ma which is accompanied with a reversal of depositional pattern from the red clay to loess paleosol deposits suggesting that the dust transporting circulation was reorganized this is the earliest clear expression of the east asian winter monsoon intensification at the pliocene pleistocene climate transition coincident with the initiation of major northern hemisphere glaciation over the eurasian arctic and northeast asia implying that at the early stage of the pliocene pleistocene global cooling the east asian winter monsoon circulation had been closely linked with the build up of ice sheet and climate changes over the high latitudes of northern hemisphere the intensified winter monsoon winds would have in turn acted as an important positive feedback in strengthening global cooling by increasing albedo and dust loading

simultaneous inversion of velocity structures and hypocentral locations application to the friuli seismic area ne italy a layeredp ands wave velocity model is obtained for the friuli seismic area using the arrival time data ofp ands waves from local earthquakes a damped least squares method is applied in the inversion

single foraminifera mg ca analyses of past glacial interglacial temperatures derived from g ruber sensu stricto and sensu lato morphotypes abstract the ratio of magnesium to calcium mg ca in foraminiferal shells is commonly used as a proxy for past ocean temperature recent advances in elemental analyses now enable single specimen measurements of planktic foraminifera and thus can provide information on past seasonal and interannual variability owing to the near monthly lifespan of foraminifera in this study we explore the temperature variance recorded by mg ca in tests of foraminifera globigerinoides ruber a planktic species that occurs throughout the year in tropical waters using la icp ms we characterize mg ca variability in single specimens of two morphotypes of g ruber picked from a sediment core retrieved offshore new caledonia we provide an estimate of the range of calcification temperatures for these morphotypes during five interglacial glacial cycles over the last 1 55 ma first we find significant and systematic differences between the morphotypes and second the temperature difference between morphotypes does not remain constant through time our results highlight a progressive increase in surface water temperatures during interglacials and a progressive decrease in glacial subsurface water temperatures these changes in surface and subsurface temperatures potentially highlight a change in the stratification of the water column over the mid pleistocene transition we conclude that single specimen mg ca on foraminiferal morphotypes can offer unique perspectives on paleoenvironmental reconstructions

competition between ocean carbon pumps in simulations with varying southern hemisphere westerly wind forcing we analyse the impact of migration and strength of southern hemisphere westerly winds on the ocean carbon cycle in a systematic sensitivity study with the university of victoria earth system climate model we find that changes in the biological pump are mainly driven by changes in ocean residence times while changes in export production are negligible changes in the biological and physical pumps are always of opposite sign with the physical pump being dominant for southward shifts and the biological pump being dominant for northward shifts furthermore changes in the pacific ocean carbon budget dictate the overall changes in global marine and atmospheric carbon overall atmospheric hbox co 2 increases and delta 14 hbox c decreases for northward shifts or a strengthening in wind forcing the opposite is true for a southward shift or a weakening in wind forcing combining forcings shift and intensity change results in a combination of their impacts with the direction of the shift being the first order forcing the terrestrial carbon reservoir absorbs releases 50 70 of the net oceanic carbon loss increase counterbalancing the effect on atmospheric hbox co 2

first estimates of the principal directions of strains compared to those of stresses in seismic friuli ne italy three cambridge wire strainmeters and a pair of horizontal pendulum tiltmeters operate since 1978 in a cave in the northern friuli seismic area straightforward considerations based on the principles of continuum mechanics permit a first estimate of the secular and seasonal variations of the cave strain rate tensor under the assumption of homogeneous constant volume strain together with an analysis of the effects on the tensor components of particular tiltmeter installation sites with respect to the orientation of both the strainmeters plane and the principal axes

constraint on the penultimate glacial maximum northern hemisphere ice topography 140 kyrs bp abstract the penultimate glacial maximum pgm 140 kyrs bp is known to be the most extensive glaciation on record that occurred during the last 400 kyrs over eurasia we used a coupled atmosphere ocean sea ice land model to simulate the climate of the pgm accounting for a reconstruction of the large pgm eurasian ice sheet due to uncertainties in the pgm laurentide ice sheet topography two simulations with different ice sheet topographies over north america large as for the last glacial maximum lgm and small as for 13 kyrs bp are performed results show that the simulated pgm glacial maximum climates are of comparable magnitude with previous simulations of the lgm in both cases assuming a small laurentide ice sheet instead of the lgm one in our pgm simulations results in a shift in the planetary waves this causes an increase in storm track activity over the north atlantic as well as higher temperatures and precipitation rates over north america north atlantic and over the eurasian ice sheet in addition it induces a negative temperature anomaly over east siberia yielding a thick snow cover which seems to be in agreement with data from recent arctic campaigns suggesting that an ice cap developed over beringia during the pgm all together the changes in large scale circulation and regional climate simulated using a small laurentide ice sheet match the proxies well based on our findings we suggest that the laurentide ice sheet might have been smaller during the pgm than during the lgm in turn also implying a larger eurasian ice sheet than during the lgm which is supported by various geological evidence of the pgm

el nino like pattern in ice age tropical pacific sea surface temperature sea surface temperatures ssts in the cold tongue of the eastern equatorial pacific exert powerful controls on global atmospheric circulation patterns we examined climate variability in this region from the last glacial maximum lgm to the present using a sst record reconstructed from magnesium calcium ratios in foraminifera from sea floor sediments near the galapagos islands cold tongue sst varied coherently with precession induced changes in seasonality during the past 30 000 years observed lgm cooling of just 1 2 c implies a relaxation of tropical temperature gradients weakened hadley and walker circulation southward shift of the intertropical convergence zone and a persistent el nino like pattern in the tropical pacific this is contrasted with mid holocene cooling suggestive of a la nina like pattern with enhanced sst gradients and strengthened trade winds our results support a potent role for altered tropical pacific sst gradients in global climate variations

the mid pleistocene transition in the subtropical southwest pacific 1 reconstructions of subtropical southwest pacific climate variability over the pleistocene were derived from coupled planktic foraminiferal 18o mg ca measurements taken from a southern coral sea sediment core a clear shift from 40 kyr to 100 kyr modes of reconstructed glacial interglacial sea surface temperature sst variability is seen over the mid pleistocene transition and these fluctuations are shown to have remained coherent with the orbital obliquity cycle across the transition the likely origin of this strong obliquity signal in subtropical southwest pacific sst is shown to be the southern high latitudes and comparison with existing sst reconstructions from the equatorial pacific is consistent with the communication of the signal occurring principally by greenhouse gas forcing in contrast to the sst reconstruction regional hydrological cycle variability based on the calculated local component of 18osw change does not show significant coherence with obliquity after 1000 ka the decoupling of the sst and hydrological cycle responses over the mid pleistocene transition allows constraints to be placed on the evolution and extent of orbitally paced fluctuations within the coupled low latitude ocean atmosphere system

methyl bromide loss rates in surface waters of the north atlantic ocean caribbean sea and eastern pacific ocean 8 45 n the first order loss rate constant of methyl bromide was measured in surface seawater samples from the north atlantic ocean caribbean sea and coastal eastern pacific ocean during may july 1998 a stable isotope incubation technique was used 13 1 which consisted of spiking seawater samples with ch3br and follow ng the loss rate of the isotopically labeled spike with gas chromatography and isotope dilution mass spectrometry the analysis of both filtered and unfiltered aliquots of seawater provides insight into the relative importance of chemical and particle related presumably biological degradation pathways over the entire cruise first order total degradation rate constants ranged from 0 03 0 40 day on average higher rate constants were observed during the last part of the cruise in the caribbean sea mean 0 34 day and coastal pacific waters 0 31 day than in the earlier passage through the north atlantic ocean 0 18 day legs 1 and 3 in the warm waters of the caribbean sea and the pacific total degradation rate constants were controlled primarily by chemical losses 0 30 and 0 25 day respectively in the colder atlantic waters the average chemical loss rate constant was lower 0 11 day z and biological losses constituted a significant fraction of the total loss rate constant 35 chemical loss rate constants varied strongly with water temperature in good agreement with previous determinations of the rate constant for methyl bromide removal from seawater due to chloride substitution and hydrolysis biological losses were detected in most of the water samples analyzed suggesting that the biological capability to degrade methyl bromide is ubiquitous in the oceans rate constants for biological removal exhibited no apparent relationship to seawater temperature salinity chlorophyll or bacterial counts

hydrological variability in the western tropical pacific over the past 700 kyr and its linkage to northern hemisphere climatic change abstract el nino southern oscillation enso events and latitudinal shifts of the intertropical convergence zone itcz cause large scale hydrologic changes in the western tropical pacific wtp however there is still a debate on the role of enso and itcz shifts on the hydroclimate in the wtp and their linkage to northern hemisphere climate change on glacial interglacial timescales for that reason we present ice volume corrected seawater 18o 18osw ice a proxy for salinity and sea surface temperature sst records from images core md06 3047b recovered from the northern wtp to investigate the hydroclimate in the wtp during the last 700 kyr planktic foraminifera globigerinoides ruber based mg ca sst and 18osw ice records reveal distinct glacial interglacial variations the 18osw ice record shows that our study site is characterized by fresher conditions and thus higher precipitation during glacials than during interglacials our results are in good agreement with numerical model simulations which also suggest a glacial freshening in the northern wtp a glacial freshening of the wtp is most likely related to a substantial weakening of the atlantic meridional overturning circulation amoc and or exposure of the maritime continent due to sea level changes which resulted in an enhanced pacific walker circulation and or southward shift of the itcz in addition sst records from the wtp and the eastern tropical pacific etp suggest an enhanced tropical pacific zonal sst gradient and thus la nina like conditions which may have contributed to fresher conditions in the wtp during glacial periods besides our rainfall record is in antiphase to the chinese speleothem 18o records supporting the idea of an opposing trend in precipitation changes between the wtp and east asia on orbital timescales

constraining foraminiferal calcification depths in the western pacific warm pool highlights first apparent calcification depth assessment of living foraminifera in the se wpwp deep surface mixed layer causes deep apparent calcification depths deep dwelling g hexagonus traces nutrient conditions in equatorial water masses abstract insight into past changes of upper ocean stratification circulation and nutrient signatures rely on our knowledge of the apparent calcification depth acd and ecology of planktonic foraminifera which serve as archives for paleoceanographic relevant geochemical signals the acd of different species varies strongly between ocean basins but also regionally we constrained foraminiferal acds in the western pacific warm pool manihiki plateau by comparing stable oxygen and carbon isotopes 18ocalite 13ccalcite as well as mg ca ratios from living planktonic foraminifera to in situ physical and chemical water mass properties temperature salinity 18oseawater 13cdic our analyses point to globigerinoides ruber as the shallowest dweller followed by globigerinoides sacculifer neogloboquadrina dutertrei pulleniatina obliquiloculata and globorotaloides hexagonus inhabiting increasing greater depths these findings are consistent with other ocean basins however absolute acds differ from other studies the uppermost mixed layer species g ruber and g sacculifer denote mean calcification depths of 95 m and 120 m respectively these western pacific acds are much deeper than in most other studies and most likely relate to the thick surface mixed layer and the deep chlorophyll maximum in this region our results indicate that n dutertrei appears to be influenced by mixing waters from the pacific equatorial divergence while p obliquiloculata with an acd of 160 m is more suitable for thermocline reconstructions acds of g hexagonus reveal a deep calcification depth of 450 m in oxygen depleted but nutrient rich water masses consistent to other studies as the 13c of g hexagonus is in near equilibrium with ambient seawater we suggest this species is suitable for tracing nutrient conditions in equatorial water masses originating in extra topical regions

the effects of tectonic release on short period p waves from nts explosions the first cycle ab amplitude of teleseismic short period p waves from underground nuclear explosions at pahute mesa nts show a systematic azimuthal amplitude pattern that can possibly be explained by tectonic release the amplitudes vary by a factor of three with diminished amplitudes being recorded at azimuths around n25 e this azimuthal pattern has a strong sin 2 component and is observed to varying degrees for 25 pahute mesa events but not for events at other sites within the nts events that are known to have large tectonic release have more pronounced sin 2 amplitude variations a synthesis of long period body and surface wave investigations of tectonic release for pahute mesa events shows that in general the nonisotropic radiation is equivalent to nearly vertical right lateral strike slip faulting trending from n20 w to due north long period p waves at upper mantle distances demonstrate that there is a significant high frequency component to the tectonic release using the long period constraints on orientation moment and frequency content of the tectonic release the expected short period p wave effects are predicted for models in which the downgoing p wave from the explosion triggers tectonic release within a few kilometers below the shot point a factor of 2 5 amplitude variation with azimuth is predicted for the short period ab amplitudes with the lowest amplitudes expected near n25 e rather subtle azimuthal variations in the waveforms are expected particularly for downward propagating ruptures which is consistent with the absence of strong variations in the data the occurrence of the azimuthal pattern albeit with varying strength for all of the pahute mesa events suggests a tectonic release model in which the shatterzone surrounding the explosion cavity is extended preferentially downward by driving a distributed network of faults and joints underlying the mesa several kilometers beneath the surface in this model all events could have a component of tectonic release which would reflect the regional stress regime although there may be slight spatial and temporal variations in the tectonic release contribution some events may trigger slip on larger throughgoing faults as well while it is shown that tectonic release can affect teleseismic short period signals significantly and may contribute to the pahute mesa amplitude pattern other possible explanations are considered

sea surface temperature differences between the western equatorial pacific and northern south china sea since the pliocene and their paleoclimatic implications 1 alkenone sea surface temperatures ssts in the northern south china sea scs were reconstructed for the last 3 8 ma the sst difference between the western equatorial pacific and northern scs was then estimated showing a general increase since 2 8 ma three features of the sst gradient evolution were prominent 1 low values 2 c in the late pliocene 2 increased values during the late pliocene early pleistocene from 1 to 4 c and 3 high values 4 c by the end of the early pleistocene these features were also shown in zonal sst gradient across equatorial pacific implying an intimate relationship of the meridional hadley and east asian monsoon circulations with the zonal walker circulation moreover the sst gradient records displayed some characters unique to the equatorial pacific and not found in benthic 18o record suggesting that zonal tropical climate change could spread into higher latitude by interactions with meridional circulations

evidence of tectonic release from underground nuclear explosions in long period s waves the sh waves from 21 underground nuclear explosions at pahute mesa nts were used to investigate tectonic release the equivalent double couple representation of the tectonic release which was constrained by waveform modeling and the polarity of sp is very similar for all the explosions the average orientation is a right lateral strike slip fault trending n15 w seismic moments were determined on the basis of comparisons with two western united states strike slip earthquakes benham has the largest tectonic release moment 5 6 10 24 dyne cm and stilton 0 1 10 24 dyne cm the smallest of the events studied in general the seismic moments increase with the size of the explosion but the location of the explosion relative to previous explosions can strongly affect the tectonic release the pahute mesa events can be separated into two populations 1 events which are well separated 4 km from previous explosions and 2 those events which are close 4 km to previous explosions those events which are close to previous explosions show a marked decrease in tectonic release a least squares fit of seismic moment to event size as determined from the world wide average ab amplitude shows that the two populations are approximately parallel but offset the fact that the trends remain separated even at small yields e g pipkin and scotch suggests that for pahute mesa there is not a threshold for tectonic release since spatial position gives the best separation of high and low tectonic release events a volume model is favored for the source mechanism the preferred model is motion on a system of faults and joints

a 5 million year comparison of mg ca and alkenone paleothermometers geochemical sea surface temperature sst proxies such as the magnesium to calcium ratio mg ca in foraminifera and the alkenone unsaturation index uk 37 are becoming widely used in pre pleistocene climate records this study quantitatively compares previously published mg ca and uk 37 data from ocean drilling program odp site 847 in the eastern equatorial pacific to assess the utility of these proxies to reconstruct tropical sst over the last 5 ma foraminiferal mg ca sst calibrations that include a dissolution correction are most appropriate at this location because they provide sst estimates for the youngest sample that are close to modern mean annual sst the long term trends in the two records are remarkably similar and confirm a 3 5 c cooling trend from the early pliocene warm period to the late pleistocene noted in previous work absolute temperature estimates are similar for both proxies when errors in the dissolution correction used to estimate sst from mg ca are taken into account comparing the two sst records at odp site 847 to other records in the region shows that the eastern equatorial pacific was 2 4 c warmer during the early pliocene compared to today

two dimensional array measurements of near source ground accelerations abstract two dimensional array measurements of near source accelerations have been conducted 6 km from the 5 6 m l explosion colwick at pahute mesa nevada test site the three component nine station array measured 400 m across with interstation spacing of 100 m wavenumber spectra and beam forming stacking were used to measure apparent velocities and directions of propagation of acceleration waveforms the robustness of individual station accelerograms was measured with frequency domain coherency estimates and cross correlation functions the dependence of interstation coherency upon station spacing and frequency band was also examined wave propagation in pahute mesa can be characterized by p sv and sh wave motion in a horizontally homogeneous medium for frequencies below 5 hz strong incoherent scattered signals are present above 5 hz on all components the fraction of scattered energy can be estimated and treated as signal generated noise a strong sh pulse was observed to propagate across the array measured phase velocity arrival time and direction of propagation require cogeneration of sh with p sv energy by the explosion colwick weaker and more diffuse transverse acceleration signals arrive coincident with the p wave and during the time prior to s these arrivals are interpreted as forward scattered energy from the p wave the small array permitted a refinement of the horizontally averaged s wave velocity model for pahute mesa the mesa is characterized by a low velocity layer 600 m thick above the water table with a steep velocity gradient immediately below the coherency measurements indicate the upper 1 km or more of pahute mesa is heterogeneous at scale lengths less than 1 km

movement of the intertropical convergence zone during the mid pleistocene transition and the response of atmospheric and surface ocean circulations in the central equatorial pacific this paper investigates the causes of a brief but prominent cooling episode 1 1 0 8 ma that occurred in the equatorial upwelling region of the atlantic and pacific during the mid pleistocene transition mpt using temporal changes in dust provenance regional hydrology and surface productivity recorded in a deep sea sediment core from the central equatorial pacific the 87sr 86sr and nd values of the inorganic silicate fraction indicate deposition of dust from australia and central south america before 0 8 ma but a gradual increase in asian dust deposition after 0 8 ma the change in dust provenance was accompanied by an increased dust flux and a decrease in surface productivity and salinity these changes can be explained by the southward movement of the intertropical convergence zone itcz and north equatorial counter current necc and the direct influence of these features on the site after 0 8 ma our results together with previously published atlantic data suggest the northward position of the itcz between 1 1 and 0 9 ma and the southward position thereafter the meridional movement of the itcz is in phase with the cooling and warming trend in upwelling regions in the equatorial pacific and atlantic which suggests strengthening of southeast trades relative to its northern counterpart between 1 1 and 0 9 ma as a plausible cause of this brief cooling event the southward movement of the itcz from 0 9 to 0 8 ma indicates more significant cooling in the northern hemisphere nh than in the southern hemisphere which is supportive of the interpretation that the nh ice sheet expanded significantly and stabilized after 0 9 ma

oceanic distributions and emissions of short lived halocarbons 1 using data from seven cruises over a 10 year span we report marine boundary layer mixing ratios i e dry mole fractions as pmol mol 1 or ppt degrees of surface seawater saturation and air sea fluxes of three short lived halocarbons that are significant in tropospheric and potentially stratospheric chemistry chbr3 c h2br2 and ch3i were all highly supersaturated almost everywhere all the time highest saturations of the two polybrominated gases were observed in coastal waters and areas of upwelling such as those near the equator and along ocean fronts ch3i distributions reflected the different chemistry and cycling of this gas in both the water and the atmosphere seasonal variations in fluxes were apparent where cruises overlapped and were consistent among oceans undersaturations of these gases were noted at some locations in the southern ocean owing to mixing of surface and subsurface waters not necessarily biological or chemical sinks the pacific ocean appears to be a much stronger source of chbr3 to the marine boundary layer than the atlantic the high supersaturations fluxes and marine boundary layer mixing ratios in the tropics are consistent with the suggestion that tropical convection could deliver some portion of these gases and their breakdown products to the upper troposphere and lower stratosphere

long and middle term behaviour of the tilt and strain variations in the decade following the 1976 friuli earthquake in ne italy tilt and strainmeter data collected in the friuli seismic area between 1977 and 1985 have been analyzed to study the stress strain field and or the elastic parameter variations in the area after the strong 1976 seismic event

the mid pleistocene climate transition onset of 100 ka cycle lags ice volume build up by 280 ka the mid pleistocene climate transition mpt is the complex climatic change which brought the late pleistocene ice ages we explore the mpt in the time and frequency domains by new methods of time series analysis high resolution oxygen isotope records reveal that the ice volume related increase in 18o mean amplitude 0 29 0 05 1 transition midpoint 922 12 ka duration 40 9 ka significantly preceded the abrupt increase in the amplitude of the 100 ka cycle at 641 9 ka this finding can be quantitatively simulated using a simple ice bedrock model in which due to the additional ice the calving threshold is exceeded the simulated calving events prior to 650 ka are separated by 77 ka whereas after 650 ka they occur pseudo periodically with a mean period of nearly 100 ka the cause for the delay of the 100 ka calving cycle was not a slow bedrock relaxation rather the coincidental combination of insolation existing ice mass and bedrock depression