teleseismic detection of a slow precursor to the great 1989 macquarie ridge earthquake low frequency spectra for the 1989 macquarie ridge earthquake magnitude 8 2 show an amplitude increase and a phase delay decrease below 6 millihertz that require a short term slow precursor this earthquake can be modeled as a compound event in which a fast rupturing ordinary earthquake was initiated by an episode of slow smooth deformation that began more than 100 seconds before the main shock the moment released in the slow precursor was large about 3 x 10 20 newton meters equivalent to an event of magnitude 7 6 the data are consistent with the precursor being generated in a region of the oceanic upper mantle below the main rupture

planktonic foraminiferal depth habitat and δ18o calibrations plankton tow results from the atlantic sector of the southern ocean varies by several orders of magnitude across a large gradient in sea surface temperature and other hydrographic features demonstrating high sensitivity of foraminiferal populations to regional differences in water properties the depth of maximum abundance for key species such as globigerina bulloides and neogloboquadrina pachyderma is not constant from station to station the pattern suggests that their abundance and shell chemistry are tied to density horizons or other conditions such as food availability that become more sharply defined with depth in the northern subantarctic the consistent observation of globorotalia inflata and globoratalia truncatulinoides as relatively deep dwelling species confirms their utility as indicators of upper thermocline properties in d 18 o all species are observed to be isotopically lighter than predicted from water properties but the species specific offset is fairly uniform at all stations these observations define the utility of multispecies d 18 o for reconstructing temperature and density stratification from past surface oceans index terms 4267 oceanography general paleoceanography 4572 oceanography physical upper ocean processes 4870 oceanography biological and chemical stable isotopes 3030 marine geology and geophysics micropaleontology keywords stratification d 18 o

oxygen isotopic composition of multiple species of planktonic foraminifera recorders of the modern photic zone temperature gradient abundances of 12 species of planktonic foraminifera collected in two plankton tows from the east tropical atlantic are compared to the chlorophyll content and the temperature of the sea water from which they were collected as expected from previous work in the tropics all dominant tropical species occur in greatest abundance within the photic zone many species occur in greatest abundances in the seasonal thermocline in association with the maximum chlorophyll concentration while a few algal symbiont bearing species occur in greatest abundance in the mixed layer the 18o measurements of planktonic foraminifera shells from core top sediment samples confirm the vertical stratification within the photic zone that is suggested by the relationship between hydrography and abundances found in the plankton tows and found in the statistical study by ravelo et al 1990 comparison between the measured 18o values of planktonic foraminifera with the predicted 18o profiles of the overlying water column at three core locations indicate that species abundances in the sediment record the seasonally integrated conditions of the photic zone and suggests that the abundance of a species in the sediment depends on whether the preferred ecological conditions of that species may be found within the photic zone of the overlying water column sometime during the year species which calcify below the photic zone have only trace relative abundances finally it appears that the total range of 18o values of the dominant species approximates the predicted annual 18o of calcite range in the upper 80 m of the water column

field examination of the oceanic carbonate ion effect on stable isotopes in planktonic foraminifera we determined the 18o and 13c of individual globigerinoides ruber and pulleniatina obliquiloculata from sediment traps located from 5 n to 12 s along 140 w in the pacific ocean to evaluate the effects of varying co3 on shell 18o and 13c variations in the offset between shell 13c and 13cdic 13cs dic are attributed to differences in co3 temperature and shell size between sample sites when 13cs dic of g ruber was corrected for variations in co3 using the experimental slope of bijma et al 1998 the residual 13cs dic was correlated with mixed layer temperature 0 10 0 04 c 1 the slope of this temperature effect is consistent with experimental results in p obliquiloculata 13cs dic and temperature were strongly anticorrelated 0 14 0 03 c 1 we are unable to separate the influences of co3 and temperature in this species without independent experimental data correcting for co3 variability on 18os of g ruber improves the accuracy of estimated sea surface temperatures

living planktic foraminifera in the central tropical pacific ocean articulating the equatorial cold tongue during la nina 1992 abstract in cold tongue conditions of august september 1992 living planktic foraminifera in the equatorial pacific tracked circulation featuresand phytoplankton abundance an equatorial assemblage associated with the cool and productive equatorial region contained g bulloides a species often associated with tropical coastal upwelling as well as the nonspinose herbivores g menardii g glutinata p obliquiloculata and n dutertrei previously associated with equatorial environments within surface subtropical waters poleward of 5 n and 5 s g sacculifer g ruber and g conglobatus dominated foraminiferal populations these species have successfully adapted to oligotrophic conditions by exploiting dinoflagellate endosymbionts high standing stocks of these species in equatorial regions suggest that they can also thrive within equatorial light levels and temperatures a deep southern assemblage dominated by nonspinose g conglomerata and g tumida and spinose g aequilateralis had a subsurface maximum at 80 200 m outside of active upwelling and outcropped to the surface at 1 s from el nino to cold tongue conditions equatorial fauna reflected higher primary productivity and an increase in the role of advection by the south equatorial current

variability in tropical thermocline nutrient chemistry on the glacial interglacial timescale abstract the organic carbon to calcite rain ratio in the tropical ocean may play a role in regulating global climate through its influence on co 2 draw down in the upper ocean the rain ratio may be altered by changes in the nutrient chemistry of the thermocline such changes in the tropical pacific are revealed by the carbon isotope values of thermocline dwelling planktonic foraminifera neogloboquadrina dutertrei the tropical pacific record over the last 30 kyr in the region south or along the equator which is fed by upwelling of deeper equatorial undercurrent water euc shows a carbon isotope signal distinct from any other in global mixed layer or benthic environments this unique record is consistent across the pacific unlike carbon isotope data from other basins and oceanic habitats the tropical pacific thermocline tracer shows last glacial values more positive than those of post glacial times the isotopic shift occurs in the early deglacial 20 17 kyr and leads to a deglacial carbon isotope minimum whose timing differs from that seen elsewhere the deglacial record of the pacific seems best interpreted as the progressive development of the modern nutrient rich thermocline under high nutrient low chlorophyll hnlc conditions the eastern tropical atlantic also has a unique glacial to modern carbon isotope record that is essentially opposite to that seen in the pacific strongly negative values in glacial times differ from those of the standard stratified ocean indicating higher nutrient concentrations a large shift to more positive values occurs rapidly at about 13 14 kyr this indicates a marked reduction in thermocline nutrients the implication is that nutrient flow to the tropics from the deep ocean via sub antarctic sources was stronger for the atlantic during the glacial but was weaker in the pacific transformation to modern conditions occurred in two steps at 17 18 and 13 14 kyr a timing that matches shifts in atmospheric co 2 concentrations and which would be compatible with driving those concentrations higher over deglacial time the mechanism could be an inherent difference in production regimes between the tropical pacific and atlantic

thermal evolution and exhumation in obliquely convergent transpressive orogens most p t t path models to date have considered a linear erosion rate for exhumation from burial depth related to isostatic readjustment of crustal thickness a few have discussed extension enhanced exhumation erosional exhumation can only restore lower crustal rocks from the thickened mountain root to their previous original depth in the pre collisional crust one major assumption of all models to date is that the compressive forces responsible for crustal thickening cease before elevation and erosion begins however compression is often still active even if the crustal thickening has stopped further compression of the thickened and strongly deformed orogenic root is responsible for forceful exhumation extrusion of softened rocks upwards hence the rate of exhumation is related to the rate of convergence of colliding plates extrusional exhumation can elevate buried rocks to any depth depending on the action of fault shear systems in the extrusional exhumation models examined here the ascending rocks cool faster because they approach the zero temperature surface conditions more rapidly than by isostatic erosion the exhumation rate is also governed by the angle between the plate boundary and the displacement vector implying that the convergent plate boundaries are regarded as complex transpressive systems in which the degree of obliquity can be expressed by the ratio of pure to simple shear components a low ratio of pure simple shear typical for wrench dominated plate boundaries implies long distance horizontal transport from the buried position in the original orogen and longer periods during which metamorphic heating occurs a high ratio of pure simple shear characteristic for frontal like convergence implies a rapid exhumation without significant heating thus granulites barrovian type and blueschist facies metamorphism are characterised by increasing angle of obliquity 10 30 90 respectively the high temperature limit at low ratio of pure simple shear is the geotherm t and lies at temperatures that would commonly be taken to indicate that addition of mantle heat was required to generate hot geotherms and p t t paths wrench faulting over 100 s of kilometres at reasonable slow convergence rates could lead to extensive dehydration melting and granulite formation in large scale collisional orogens

characterizing swells in the southern pacific from seismic and infrasonic noise analyses a temporary network of 10 broad band seismic stations has been installed in french polynesia for the polynesian lithosphere and upper mantle experiment plume all the seismic stations were installed either on volcanic islands or on atolls of the various archipelagos of french polynesia in a manner which complements the geographic coverage provided by the regional permanent stations the primary aim of plume is to image the upper mantle structures related to plate motion and hotspot activity however because of its proximity to all sites the ocean is responsible for a high level of noise in the seismic data and we show that these data can also be used to analyse ocean wave activity the power spectral density psd analyses of the seismic data recorded in french polynesia show clear peaks in the 0 05 0 10 hz band periods between 10 and 20 s which corresponds to swell frequencies clear peaks in this frequency band are also observed in infrasonic data recorded on tahiti ground motion analysis shows that the swell related seismic noise srsn is linearly polarized in the horizontal plane and its amplitude decreases rapidly with the distance from the shore the microseismic and the infrasonic noise amplitudes show very similar variations from station to station and both are strongly correlated with the swell amplitudes predicted by the national oceanic and atmospheric administration noaa wind forced wavewatch models the swell direction can be estimated from srsn polarization analysis but this has to be done with care since for some cases the ground motions are strongly controlled by the islands anisometric shapes and by swell refraction processes we find cases however such as tahiti or roughly circular tuamotu atolls where the azimuth of the swell is in good agreement with the seismic estimates we therefore demonstrate that the srsn and the infrasonic signal observed in french polynesia can be used in such cases as a proxy for swell amplitude and azimuth from the continuous analysis of the data recorded in 2003 at the permanent seismic station pptl in tahiti transfer functions have been obtained this could provide a way to quantify the swell activity during the last two decades and therefore assist in the investigation of climate changes

western equatorial pacific planktic foraminiferal fluxes and assemblages during a la nina year 1999 abstract a correlation between foraminiferal community dynamics and environmental conditions may provide a basis for establishing paleoclimatic proxies we studied planktic foraminiferal shell fluxes and assemblages in samples collected in three time series sediment trap deployments in the western equatorial pacific under la nina conditions from january to november 1999 eleven species contributed about 90 of the total flux in all traps two sites mt1 mt3 in the western pacific warm pool region wpwp were characterized by common occurrences of the species globigerinoides ruber globigerinoides sacculifer globigerinoides tenellus and neogloboquadrina dutertrei site mt5 farther to the east in the equatorial upwelling region had common occurrences of globigerina bulloides globigerinita glutinata and pulleniatina obliquiloculata very high abundances of g bulloides and g glutinata at mt5 indicate that equatorial upwelling eu occurred during the 1999 la nina the two western sites have similar assemblage compositions but mt1 135 e has the highest fluxes up to 3800 tests m 2 day 1 whereas mt3 145 e has fluxes below 2200 tests m 2 day 1 relatively high fluxes up to 3000 tests m 2 day 1 occur at site mt5 176 e where upwelling occurred the differences in faunal composition in the wpwp and eu might be attributable to differences in the way in which nutrients are supplied to the phytoplankton large amounts of suspended material are supplied to the wpwp by advection of waters passing through the coastal region of an archipelago whereas upwelling of nutrient rich waters enhances primary production in the eu at the westernmost site in the wpwp a peak in the g bulloides flux coincided with southward flow of the new guinea coastal current ngcc in late february but the highest g ruber flux coincided with northward flow of this current in late may thus the differences in species dominance at this location may be caused by monsoon driven variability in the flow direction of the nggc

a slow seismic event recorded in pasadena a prominent long period wave with a duration of 2000 sec or longer was recorded with a very broadband system in pasadena on june 18 1988 this wave was not observed elsewhere and is considered of local origin the acceleration amplitude is 2 5 10 5 cm sec in the northwest direction with the vertical component less than 10 of the horizontal the horizontal acceleration can be interpreted as due to a tilt of the ground of 2 5 10 8 radians to the northwest a slowly propagating pressure wave with an amplitude of about 15 mbars could be the cause of the tilt however there were no reports suggesting such pressure changes a more likely cause is a slow tectonic event near pasadena the required magnitude of such a slow event is m w 0 2 and 4 for a distance of 0 1 1 and 10 km respectively this event could be part of a tectonic episode associated with the larger earthquakes which occurred in southern california around this time especially the december 3 1988 pasadena earthquake m l 4 9 which occurred six months later within 4 km of the pasadena station

oceanic conditions in the eastern equatorial pacific during the onset of enso in the holocene abstract records from south america show that modern enso el nino southern oscillation did not exist 7000 cal yr b p and has developed progressively since then there has been little information available on oceanic conditions in the eastern equatorial pacific eep to constrain explanations for enso onset we report quantitative observations on thermocline and mixed layer conditions in the eep during enso start up we found important changes in both the thermocline and the mixed layer indicating increased upwelling of cooler waters since 7000 cal yr b p this resulted from change in the source and or properties of waters supplying the equatorial undercurrent which feeds upwelling along the equator and the peru margin modeling shows that enso is sensitive to subsurface conditions in the eastern equatorial pacific and that the changes in the thermocline we observed were driven by extratropical processes giving these a role in conditioning the development of enso this is in contrast to models that call for control of equatorial pacific oceanography by tropical processes only these infer stronger upwelling and cooler surface waters for the eep during the mid holocene which is not supported by our results

new empirical relationships among magnitude rupture length rupture width rupture area and surface displacement source parameters for historical earthquakes worldwide are compiled to develop a series of empirical relationships among moment magnitude m surface rupture length subsurface rupture length downdip rupture width rupture area and maximum and average displacement per event the resulting data base is a significant update of previous compilations and includes the additional source parameters of seismic moment moment magnitude subsurface rupture length downdip rupture width and average surface displacement each source parameter is classified as reliable or unreliable based on our evaluation of the accuracy of individual values only the reliable source parameters are used in the final analyses in comparing source parameters we note the following trends 1 generally the length of rupture at the surface is equal to 75 of the subsurface rupture length however the ratio of surface rupture length to subsurface rupture length increases with magnitude 2 the average surface displacement per event is about one half the maximum surface displacement per event and 3 the average subsurface displacement on the fault plane is less than the maximum surface displacement but more than the average surface displacement thus for most earthquakes in this data base slip on the fault plane at seismogenic depths is manifested by similar displacements at the surface log linear regressions between earthquake magnitude and surface rupture length subsurface rupture length and rupture area are especially well correlated showing standard deviations of 0 25 to 0 35 magnitude units most relationships are not statistically different at a 95 significance level as a function of the style of faulting thus we consider the regressions for all slip types to be appropriate for most applications regressions between magnitude and displacement magnitude and rupture width and between displacement and rupture length are less well correlated and have larger standard deviation than regressions between magnitude and length or area the large number of data points in most of these regressions and their statistical stability suggest that they are unlikely to change significantly in response to additional data separating the data according to extensional and compressional tectonic environments neither provides statistically different results nor improves the statistical significance of the regressions regressions for cases in which earthquake magnitude is either the independent or the dependent parameter can be used to estimate maximum earthquake magnitudes both for surface faults and for subsurface seismic sources such as blind faults and to estimate the expected surface displacement along a fault for a given size earthquake

mid holocene and last glacial maximum climate simulations with the ipsl model part ii model data comparisons the climates of the mid holocene mh 6 000 years ago and the last glacial maximum lgm 21 000 years ago have been extensively documented and as such have become targets for the evaluation of climate models for climate contexts very different from the present in part 1 of the present work we have studied the mh and lgm simulations performed with the last two versions of the ipsl model ipsl cm4 run for the pmip2 cmip3 coupled model intercomparion project projects and ipsl cm5a run for the most recent pmip3 cmip5 projets we have shown that not only are these models different in their simulations of the pi climate but also in their simulations of the climatic anomalies for the mh and lgm in the part 2 of this paper we first examine whether palaeo data can help discriminate between the model performances this is indeed the case for the african monsoon for the mh or for north america south of the laurentide ice sheet the south atlantic or the southern indian ocean for the lgm for the lgm off line vegetation modelling appears to offer good opportunities to distinguish climate model results because glacial vegetation proves to be very sensitive to even small differences in lgm climate for other cases such as the lgm north atlantic or the lgm equatorial pacific the large uncertainty on the sst reconstructions prevents model discrimination we have examined the use of other proxy data for model evaluation which has become possible with the inclusion of the biogeochemistry morel pisces in the ipsl cm5a model we show a broad agreement of the lgm pi export production changes with reconstructions these changes are related to the mixed layer depth in most regions and to sea ice variations in the high latitudes we have also modelled foraminifer abundances with the foramclim model and shown that the changes in foraminifer abundance in the equatorial pacific are mainly forced by changes in ssts hence confirming the sst foraminifer abundance relationship yet this is not the case in all regions in the north atlantic where food availability can have a strong impact of foraminifer abundances further work will be needed to exhaustively examine the role of factors other than climate in piloting changes in palaeo indicators

low frequency source characteristics of the great 1960 chilean earthquake the low frequency nature of the great 1960 chilean earthquake the earth s largest recorded event is characterized and a source model composed of three events with a combined seismic moment of 5 5 1023 n m and a duration of 1500 s is presented the results show conclusively that large scale slip which is only observed at low frequencies preceded the main shock complex amplitude measurements of normal mode data in the band 1 0 5 0 mhz recorded at eight vertical component stations comprise the data set in this band the earthquake source is assumed to be described by a line source propagating at a constant rupture velocity the data set is the basis for a sequence of least squares inversions to determine the seismic moment rupture velocity spatial slip distribution and the temporal slip function the data are best explained by a source model that begins 1150 s before the main shock with an event of moment 1 9 1023 n m and rise time of 300 s a main shock with moment of 3 2 1023 n m and for which most of the low frequency energy was released beginning about 50 s after the short period origin time and an event 350 s later with moment of 0 4 1023 n m the uncertainty in the moment estimate of the great 1960 chilean earthquake is about 50 and is due primarily to the probable range of fault plane dip which is not well constrained at this time

seasonal variability in the δ18o and δ13c of planktonic foraminifera from an upwelling environment sediment trap results from the san pedro basin southern california bight stable isotopic analyses 18o and 13crpar on four species of planktonic foraminifera collected from high resolution time series sediment trap sampling indicate that rapid and significant seasonal variability occurred in response to rapid changes in both the hydrographic environment and the isotopic composition of ambient seawater specimens were collected at a depth of 500 m for 28 consecutive 1 week periods in the san pedro basin within the southern california bight a region seasonally influenced by upwelling hydrographic monitoring of the study area revealed a 6 week period late april to mid june during which pulses of upwelling occurred causing significant increases in the oxygen isotopic composition of surrounding waters while decreasing the carbon isotopic composition analyses of globigerina bulloides orbulina universa neogloboquadrina dutertrei and neogloboquadrina pachyderma right coiling indicate that during the upwelling period these species live respectively at the surface in the surface mixed layer within the thermocline and below the thermocline globigerina bulloides ascends from well below the thermocline to the surface at the onset of upwelling and increases production to its maximum simultaneously as its morphology changes to less calcified open forms both n dutertrei and n pachyderma follow isothermal ranges migrating to shallower waters during upwelling and subsequently descending after upwelling ceases neogloboquadrina dutertrei appears to inhabit the region associated with both the thermocline base and chlorophyll maximum when it is most abundant following upwelling orbulina universa increases its depth habitat as solar irradiance increases but this species decreases in abundance during upwelling the 18o signal of o universa appears to be a useful indicator of seasonal temperature variations above the thermocline whereas the 18o of g bulloides documents near surface temperatures during upwelling the 13c signal of both n dutertrei and n pachyderma appears to record the 13c of equilibrium calcite for the regions of the thermocline and just below the thermocline respectively due to the relative preservation potentials of the four species analyzed only n dutertrei and n pachyderma are likely to be preserved in the sedimentary record in regions of oxygenated bottom waters thus an actual record of hydrographic conditions during upwelling as would be found in tests of g bulloides is not preserved instead conditions before n pachyderma and just after n dutertrei are more likely recorded

evaluation of automated flow through time resolved analysis of foraminifera for mg ca paleothermometry 1 the primary mg ca ratio of foraminiferal shells is a potentially valuable paleoproxy for sea surface temperature sst reconstructions however the reliable extraction of this ratio from sedimentary calcite assumes that we can overcome artifacts related to foraminiferal ecology and partial dissolution as well as contamination by secondary calcite and clay the standard batch method for mg ca analysis involves cracking sonicating and rinsing the tests to remove clay followed by chemical cleaning and finally acid digestion and single point measurement this laborious procedure often results in substantial loss of sample typically 30 60 we find that even the earliest steps of this procedure can fractionate mg from ca thus biasing the result toward a more variable and often anomalously low mg ca ratio moreover the more rigorous the cleaning the more calcite is lost and the more likely it becomes that any residual clay that has not been removed by physical cleaning will increase the ratio these potentially significant sources of error can be overcome with a flow through ft sequential leaching method that makes time and labor intensive pretreatments unnecessary when combined with time resolved analysis ft tra flow through performed with a gradually increasing and highly regulated acid strength produces continuous records of mg sr al and ca concentrations in the leachate sorted by dissolution susceptibility of the reacting material flow through separates secondary calcite from less susceptible biogenic calcite and clay and further resolves the biogenic component into primary and more resistant fractions ft tra reliably separates secondary calcite which is not representative of original life habitats from the more resistant biogenic calcite the desired signal and clay a contaminant of high mg ca which also contains al and further resolves the biogenic component into primary and more resistant fractions that may reflect habitat or other changes during ontogeny we find that the most susceptible fraction of biogenic calcite in surface dwelling foraminifera gives the most accurate value for sst and therefore best represents primary calcite sequential dissolution curves can be used to correct the primary mg ca ratio for clay if necessary however the temporal separation of calcite from clay in ft tra is so complete that this correction is typically 2 even in clay rich sediments unlike hands on batch methods that are difficult to reproduce exactly flow through lends itself to automation providing precise replication of treatment for every sample our automated flow through system can process 22 samples two system blanks and 48 mixed standards in 12 hours of unattended operation ft tra thus represents a faster cheaper and better way to determine mg ca ratios in foraminiferal calcite

glacial interglacial changes in central tropical pacific surface seawater property gradients much uncertainty exists about the state of the oceanic and atmospheric circulation in the tropical pacific over the last glacial cycle studies have been hampered by the fact that sediment cores suitable for study were concentrated in the western and eastern parts of the tropical pacific with little information from the central tropical pacific here we present information from a suite of sediment cores collected from the line islands ridge in the central tropical pacific which show sedimentation rates and stratigraphies suitable for paleoceanographic investigations based on the radiocarbon and oxygen isotope measurements on the planktonic foraminifera globigerinoides ruber we construct preliminary age models for selected cores and show that the gradient in the oxygen isotope ratio of g ruber between the equator and 8 n is enhanced during glacial stages relative to interglacial stages this stronger gradient could reflect enhanced equatorial cooling perhaps reflecting a stronger walker circulation or an enhanced salinity gradient perhaps reflecting increased rainfall in the central tropical pacific

alkenones and multiproxy strategies in paleoceanographic studies 1 we assess multiproxy strategies involving alkenone based and other paleoceanographic indicators in an effort to define uncertainties and to advance understanding of past oceanic and climatic changes looking to the future we recommend a parallel strategy of applying proxies to the geologic record while continuously seeking refinements in methods and understanding of mechanisms that control each proxy a multiproxy strategy increases confidence in results and provides oceanographic context for more effective interpretation of processes a combination of proxies allows derivation of additional properties such as upper ocean paleosalinity or paleo pco2 for a more complete view of the oceanographic and climate mechanisms involved in changing earth s environment

planktonic foraminifera calcareous nannoplankton and ascidian variations during the last 25 kyr in the southwestern atlantic a paleoproductivity signature micropaleontological and geochemical analyses from western south atlantic core san 76 off southeast brazil revealed changes in stable isotope values and in the assemblages of calcareous nannoplankton and planktonic foraminifera during the past 25 kyr that point to significant paleoceanographic and climatic changes leading to an increase in productivity during the last deglaciation the enhanced surface productivity was clearly indicated by increased relative abundances of the planktonic foraminifera globigerina bulloides and neogloboquadrina dutertrei and the decreased values of 13 c in planktonic foraminiferal tests a coeval shoaling of the nutricline and thermocline was indicated by decreased relative abundances of the calcareous nannoplankton florisphaera profunda and an increased relative abundance of the planktonic foraminifera globorotalia truncatulinoides right coiling we speculate that these changes are related to n s shifts of the atlantic intertropical convergence zone itcz a significant increase in the cd ca ratio and decrease in 13 c values in the benthic foraminifer hoeglundina elegans along with a significant increase in the relative abundance of ascidian spicules during the deglaciation suggest that benthic communities in this area strongly benefited from increased surface water productivity 2007 elsevier b v all rights reserved

seasonal changes in the isotopic composition of planktonic foraminifera collected in panama basin sediment traps abstract isotopic analyses have been made on five species of planktonic foraminifera collected in two deployments of parflux mark ii time series sediment traps in the panama basin the automated sampling system on the traps provided 4 one month samples from 29 july to 16 november 1979 and 6 two month samples from december 1979 to november 1980 the 18o values of globigerinoides ruber and globigerinoides sacculifer in this region are primarily affected by a low salinity surface layer that forms during the early winter these species each show a 1 total range in 18o the 18o values of the colder water species globorotalia menardii neogloboquadrina dutertrei and globorotalia theyeri show smaller seasonal changes in 18o the 13c values of g ruber and g sacculifer exhibit small seasonal changes 0 35 and 0 4 respectively despite large seasonal changes in surface water productivity the colder water species exhibit only slightly larger changes in 13c up to 0 55 throughout the year all colder water species exhibit minimum or near minimum 13c values during february and march which is the period of maximum upwelling and primary productivity seasonal variations in the flux of foraminifera in the water column at this location will have only a small effect on the isotopic composition of the sediment assemblage extreme values of 18o and 13c do not occur during the periods which are associated with the high flux of foraminiferal tests

no analog planktonic foraminiferal faunas in the glacial southern south china sea implications for the magnitude of glacial cooling in the western pacific warm pool sea surface temperature sst estimates in the sediment core md01 2390 based on planktonic foraminiferal species abundances using five different transfer function techniques suggest nearly unchanged or unusually higher temperatures in the tropical southern south china sea scs during the last glacial maximum lgm relative to modern temperatures these results are in contrast to substantial cooling of 2 5 c inferred by geochemical uk 37 mg ca ratios and terrestrial proxies from the western tropical pacific region using multivariate statistics we show that the glacial southern scs harboured unique planktonic foraminiferal assemblages that have no modern analogs analyses of faunal variation through the core reveal that planktonic foraminiferal assemblages responded to temperature changes inferred from mg ca data but that this signal is subdued by superimposed variations in the relative abundance of pulleniatina obliquiloculata and neogloboquadrina pachyderma dextral these species occur in glacial samples at proportions that are not observed in the calibration data set the glacial high abundance of n pachyderma dextral are interpreted to reflect a seasonal winter inflow of cold surface water from the northeast via the bashi strait due to the combined effects of an intensified winter monsoon a southward shift of the polar front and the eastward migration of the kuroshio current in contrast processes controlling the high relative abundances of p obliquiloculata during the lgm may be unique to the southern scs we propose a scenario involving a stronger winter mixing or enhanced upwelling due to an intensified winter monsoon that prevented shallow dwelling warm indicators to establish larger populations during the lgm our results indicate that a no analog behaviour of planktonic foraminifera faunas is responsible for the warm glacial conditions in this part of the western pacific warm pool as implied by foraminiferal transfer functions and that a more significant surface cooling in the region as implied by terrestrial and geochemical mg ca ratios alkenone unsaturation index marine proxies is a more likely scenario

vertical distribution and isotopic fractionation of living planktonic foraminifera from the panama basin a model1 2 which explains the vertical and seasonal distribution of planktonic foraminifera was developed using data from the western north atlantic and is comprised of three tenets 1 the conditions in the photic zone upper 80 100 m exclusively dictate planktonic foraminifera species composition and abundance throughout the water column 2 species are vertically stratified within the photic zone according to their temperature preference depth distribution according to temperature preference has been proposed by several authors3 based on isotope analyses of sediments due to seasonal temperature variations seasonal variations in the 18o composition of seawater and species specific isotope fractionation rigorous proof of this hypothesis cannot be provided from sediment analyses alone 3 the chlorophyll maximum is a major food source zone which is preferentially exploited by foraminifera our data from the panama basin which are presented here are confirmation of this model the panama basin in the eastern equatorial pacific which has a shallow and steep thermocline was sampled for living planktonic foraminifera a multiple opening closing net and environmental sensing system mocness 4 was used to collect 13 sets of eight vertically stratified oblique samples we report here the quantitative distribution and stable isotopic composition of planktonic foraminifera from four mocness tows taken over 5 days during august 1979 rv knorr cruise 73 at 5 20 n 8 50 w each tow consisted of eight samples which integrated 12 5 m intervals from 0 to 100 m for moc 126 25 m intervals from 0 to 200 m for moc 127 100 150 m intervals from 0 to 1 000 m on moc 128 and 250 m intervals from 0 to 2 000 m on moc 131

teleseismic search for slow precursors to large earthquakes some large earthquakes display low frequency seismic anomalies that are best explained by episodes of slow smooth deformation immediately before their high frequency origin times analysis of the low frequency spectra of 107 shallow focus earthquakes revealed 20 events that had slow precursors 95 percent confidence level 19 were slow earthquakes associated with the ocean ridge transform system and 1 was a slow earthquake on an intracontinental transform fault in the east african rift system these anomalous earthquakes appear to be compound events each comprising one or more ordinary fast ruptures in the shallow seismogenic zone initiated by a precursory slow event in the adjacent or subjacent lithosphere

new magnetobiostratigraphic chronology and paleoceanographic changes across the oligocene miocene boundary at dsdp site 516 rio grande rise sw atlantic new magnetobiostratigraphic data for the late oligocene through early miocene at deep sea drilling project dsdp hole 516f provide a significantly revised age model which permits reevaluation of developments that led to the mi 1 glacial event at the oligocene miocene boundary our new high resolution paleomagnetic study which is supported by quantitative calcareous nannofossil and planktonic foraminiferal analyses significantly refines previous age models for oligocene miocene sediments from dsdp hole 516f with ages that are systematically younger than those previously determined in some parts of the oligocene the discrepancy with previous studies exceeds 450 kyr based on this new age model we infer a progressive increase in sedimentation rate and paleoproductivity between circa 23 9 ma and circa 22 9 ma with the highest rate coinciding with the mi 1 glacial event at the oligocene miocene boundary this productivity increase would have resulted in higher rates of carbon burial and in turn a drawdown of atmospheric co2 immediately afterward an abrupt decrease in sedimentation rate and paleoproductivity suggests that the mi 1 deglaciation was associated with decreased carbon input into the ocean elevated sedimentation rates are also documented at 24 5 ma coincident with the oi2d glacioeustatic event the presence of volcanic material within the sediments during these glacial events is interpreted to have resulted from redeposition of sediment scoured from nearby sites on the rio grande rise due to transient variations in bottom water flow patterns

paleoenvironmental conditions for the development of calcareous nannofossil acme during the late miocene in the eastern equatorial pacific repeated monospecific coccolithophore dominance intervals acmes of specimens belonging to the noelaerhabdaceae family including the genus reticulofenestra and modern descendants emiliania and gephyrocapsa occurred during the neogene such acme was recognized during the late miocene 8 6 ma at a time of a major reorganization of nannofossil assemblages resulting in a worldwide temporary disappearance of larger forms of the genus reticulofenestra r pseudoumbilicus and the gradual recovery and dominance of its smaller forms 5 m in this study we present a multiproxy investigation of late miocene sediments from the east equatorial pacific integrated ocean drilling program site u1338 where small reticulofenestrid type placoliths with a closed central area known as small dictyococcites spp 3 m formed an acme we report on oxygen and carbon stable isotope records of multispecies planktic calcite and alkenone derived sea surface temperature our data indicate that during this 100 kyr long acme the east equatorial pacific thermocline remained deep and stable local surface stratification state fails to explain this acme and thus contradicts the model based hypothesis of a southern ocean high latitude nutrient control of the surface waters in the east equatorial pacific instead our findings suggest that external forcing such as an extended period of low eccentricity may have created favorable conditions for the small dictyococcites spp growth

sub milankovitch cycles in periplatform carbonates from the early pliocene great bahama bank high resolution bulk sediment magnetic susceptibility and aragonite content and 18o records from two different planktonic foraminifera species were analyzed in an early pliocene core interval from the straits of florida ocean drilling program site 1006 the 18o record of the shallow dwelling foraminifera g sacculifer and the aragonite content are dominated by sub milankovitch variability in contrast magnetic susceptibility and the 18o record of the deeper dwelling foraminifera g menardii show precession cycles the relationship between the aragonite and the paleoproxy data suggests that the export of sediment from the adjacent great bahama bank was triggered directly by atmospheric processes rather than by sea level change we propose a climate mechanism that bears similarities with the semiannual cycle component of eastern equatorial pacific sea surface temperatures under present day conditions

multispecies approach to reconstructing eastern equatorial pacific thermocline hydrography during the past 360 kyr 1 stable isotope data from eastern equatorial pacific eep core tr163 19 2 15 n 90 57 w 2348 m are presented for the surface dwelling foraminifers globigerinoides ruber and g sacculifer and thermocline dwelling globorotalia menardii and neogloboquadrina dutertrei using species specific normalization factors derived from experimental and plankton tow data we reconstruct a 360 kyr record of water column hydrography across the past three glacial cycles we demonstrate that g ruber maintains a mixed layer habitat throughout the entire record while g sacculifer records a mixture of thermocline and mixed layer conditions and g menardii and n dutertrei record thermocline properties we conclude that g sacculifer is not appropriate for paleoceanographic applications in regions with steep vertical hydrographic gradients results suggest that this region of the eep had a thicker mixed layer and deeper 13cdic boundary between the surface and equatorial undercurrent during the last two glacial periods a shift in n dutertrei and g sacculifer geochemistry prior to 185 kyr suggests water column structure and chemocline gradients changed possibly due to a shift in the position of the undercurrent relative to this site the timing and magnitude of glacial interglacial 13c variations between species indicates that near surface carbon chemistry is controlled by changes in productivity atmospheric circulation and advected intermediate water sources north of the antarctic polar front these results demonstrate that when properly calibrated for species differences multispecies geochemical data sets can be invaluable for reconstructing water column structure and properties in the past

seasonal change in foraminiferal production in the western equatorial pacific warm pool evidence from sediment trap experiments seasonal changes in the flux of individual planktonic foraminifera in the deep ocean have been studied in the western equatorial pacific warm pool using material collected by sediment traps over a period of 1 yr 1991 1992 mean total foraminiferal fluxes tffs were 171 and 97 shells m 2 day 1 at sites n1 2 59 8 n 135 01 5 e and n2 4 07 5 n 136 16 6 e respectively the seasonal change in tffs was much higher than for organic matter om and carbonate fluxes the major species of planktonic foraminifera were pulleniatina obliquiloculata neogloboquadrina dutertrei globigerinoides sacculifer globigerinella aequilateralis and globigerinoides ruber symbiont bearing species and n dutertrei were predominant in the western equatorial pacific warm pool comparison between the warm pool and upwelling deep sea research ii 43 1996 1257 mar micropaleontology 33 1998 157 indicates that the foraminiferal assemblage trapped at the western equatorial pacific warm pool was comparable with the south equatorial and subtropical assemblages during a plankton tow study conducted at 140 w in 1992 it suggests that fairly oligotrophic conditions prevailed in the western equatorial pacific warm pool in association with terrestrial nutrient inputs or temporary mixing by wind bursts the om flux was more positively correlated with the 63 m carbonate fraction mainly composed of coccoliths r 0 87 and biogenic opal which suggests that om fluxes were more affected by phytoplankton productivity although food availability is generally important for foraminiferal production tffs were poorly correlated with om fluxes at sites n1 and n2 which is partly attributed to the significant influence of symbiont photosynthesis the 18o values of p obliquiloculata and n dutertrei showed maxima in association with high om fluxes during period 2 from august to october and period 4 from late december to april at site n1 reflecting thickening of the mixed layer following wind bursts g sacculifer showed a lunar reproduction cycle when between july and october carbonate production was more predominant than biogenic opal production a similar profile was evident for g ruber orbulina universa and g aequilateralis these four species are generally predominant at low latitudes therefore the lunar reproduction cycle may significantly affect the fluctuation in carbonate production in the equatorial ocean

episodic aseismic earthquake precursors shallow earthquakes are generally believed to be brittle fractures in a stressed medium with rupture velocity at a speed close to that for shear waves we know however that the earth allows failure over a wide range of timescales creep events occur on the san andreas fault system and for some earthquakes the high speed rupture is accompanied by a slower process1 5 here we report on episodic slow events which occurred before the japan sea earthquake of magnitude 7 7 on 26 may 1983 a sacks evertson borehole strain meter6 90 km from the earthquake recorded about 100 aseismic strain events in a five month period before and immediately following the earthquake none has been detected after the large aftershocks the observed signals are consistent with a precursory redistribution of stress through aseismic slip on a deep extension of the main shock fault plane such episodic aseismic events may provide a mechanism for relatively rapid stress concentration before earthquakes

the influence of salinity on mg ca in planktic foraminifers evidence from cultures core top sediments and complementary δ18o the mg ca ratio in foraminiferal calcite is one of the principal proxies used for paleoceanographic temperature reconstructions but recent core top sediment observations suggest that salinity may exert a significant secondary control on planktic foraminifers this study compiles new and published laboratory culture experiment data from the planktic foraminifers orbulina universa globigerinoides sacculifer and globigerinoides ruber in which salinity was varied but temperature ph and light were held constant combining new data with results from previous culture studies yields a mg ca sensitivity to salinity of 4 4 2 3 4 7 1 2 and 3 3 1 7 per salinity unit 95 confidence respectively for the three foraminifer species studied here comparison of these sensitivities with core top data suggests that the much larger sensitivity 27 4 per salinity unit derived from atlantic core top sediments in previous studies is not a direct effect of salinity rather we suggest that the dissolution correction often applied to mg ca data can lead to significant overestimation of temperatures we are able to reconcile culture calibrations with core top observations by combining evidence for seasonal occurrence and latitude specific habitat depth preferences with corresponding variations in physico chemical environmental parameters although both mg ca and 18o yield temperature estimates that fall within the bounds of hydrographic observations discrepancies between the two proxies highlight unresolved challenges with the use of paired mg ca and 18o analyses to reconstruct paleo salinity patterns across ocean basins the first step towards resolving these challenges requires a better spatially and seasonally resolved 18osw archive than is currently available nonetheless site specific reconstructions of salinity change through time may be valid

the holocene pulleniatina minimum event revisited geochemical and faunal evidence from the okinawa trough and upper reaches of the kuroshio current abstract the holocene pulleniatina minimum event pme is characterized by a very low abundance of the planktonic foraminifer pulleniatina obliquiloculata between 4 5 and 3 ka the pme occurs widely in the okinawa trough and the south china sea and can be correlated throughout this area it has been related to variability in the kuroshio current to further explore the nature of the pme we studied cores obtained from the southern okinawa trough and the upper reaches of the kuroshio current faunal census data indicate that all cores record the pme between 4 5 and 3 ka the relative abundance of neogloboquadrina dutertrei is negatively correlated to that of p obliquiloculata in the southern okinawa trough but not in the sites at the upper reaches mg ca and 18 o measurements on globigerinoides ruber shells from the southern okinawa trough indicate that there was no change in sea surface temperature or sea surface salinity during the pme the vertical structure of the water column as reconstructed by multispecies 18 o and 13 c profiles shows no consistent anomalies in the southern okinawa trough and western philippine sea during the pme these observations suggest that 1 the pme was not restricted to marginal seas but widespread in the western north pacific 2 the high abundance of n dutertrei during the pme in the okinawa trough may be a result of higher food availability in the absence of p obliquiloculata 3 no distinctive consistent anomalies in the paleoceanographic proxies are associated with the pme implying there were no changes in hydrography and productivity the absence of a linkage between faunal variation and paleoceanographic proxies indicates that we do not yet understand what causes changes in planktonic foraminiferal assemblages this lack of understanding implies that we cannot always trust fauna based paleothermometry at millennial timescales

a convergent instability wave front in the central tropical pacific abstract a narrow front encountered at 2 1 n 140 w was characterized by high productivity and a 2 c temperature drop satellite sea surface temperature sst imagery showed this front to extend over 400 km from just north of the equator to 5 n along the western leading edge of a tropical instability wave cold cusp during 3 days of observations the front propagated westward at 64 cm s 1 while oriented sw ne water velocities and densities around the front were measured using a shipboard acoustic doppler current profiler and hydrographic stations these data showed warm fresh northern water moving southward at speeds of up to 50 cm s 1 to encounter cold salty equatorial water moving northward at up to 40 cm s 1 both slabs were embedded in the south equatorial current here a uniform 100 m deep westward flow of 90 cm s 1 at their meeting a net convergence of 30 cm s 1 across the 1 km wide front drove intense downselling of up to 0 9 cm s 1 both t s relations and velocity fields indicate that cold water subducted beneath the warmer water and continued northward to beyond 3 n deepening to 120 m for analysis the data were gridded in a co ordinate system centered on the front and moving with it the dynamics near the front consisted of a balance between pressure gradient and non linear advection the coriolis force was smaller and associated mostly with the broader scale flow thus the front itself was not geostrophic but rather the leading edge of a density driven flow that can be accurately modeled as a dissipative lock exchange the subduction released potential energy at the rate of 5290 230 w m 1 of front length comparable to previous estimates of large scale energy conversion nevertheless the kinetic energy gain by the larger scale instability was only 840 31 w m 1 implying that the rest of the energy was lost to the large scale flow turbulent dissination as derived from the rate of mixing accounted for only 500 300 w m 1 of this loss on the full 100 km scale of the layered flow the coriolis force became important the orientation of the surface front and the angle of the interface s northward deepening produced a pressure gradient that balanced the meridional flow geostrophically

spatial distribution and controlling factors of planktonic foraminifera in the modern western pacific abstract studies of the spatial distribution of living planktonic foraminifera in modern water columns are still lacking in the western pacific in this study 40 plankton tows at 8 stations were conducted focusing on the terminus of the north equatorial current nec and its two bifurcated branches in the western pacific the results show that planktonic foraminifera were in high abundance around the kuroshio current kc source region and the mindanao current mc system but in low abundance in the nec the planktonic foraminiferal assemblage was dominated by g sacculifer and g ruber with relative abundances of 44 0 and 27 3 respectively according to a cluster analysis of the results of seven stations the stations can be divided into three groups namely group nec group kc and group mc which displayed different features of planktonic foraminiferal assemblages the low abundance of planktonic foraminifera that characterized the nec stations may be induced by the thick mixed layer and deep thermocline nutricline in this region however stations in the kc region which also had thick mixed layers and deep thermoclines showed higher abundances of planktonic foraminifera than the nec stations this result was probably caused by the higher terrigenous input the planktonic foraminifera show the highest abundance at the mc stations which may be the result of existing upwelling conditions

late quaternary course changes of the kuroshio current in the ryukyu arc region northwestern pacific ocean the existence of a land bridge connecting the central southern ryukyu arc to taiwan during the last glacial stage oxygen isotope stages 2 to 4 and its postglacial disappearance are demonstrated by variations in the planktic 18o values and the frequency of pulleniatina in 11 piston cores from the okinawa trough region the upward increase in the pulleniatina group in the cores signals the progressive inflow of the kuroshio current into the okinawa trough area because this group is characteristic of the kuroshio current as revealed here by planktic foraminiferal distribution using 56 surface sediment samples collected from the whole area of this region the ryukyu taiwan land bridge caused eastward deflection of the kuroshio current at the southern end of the ryukyu arc a pulleniatina minimum event in the period from 4500 to 3000 yr b p is recognized in 10 cores from the okinawa trough and one from the northern ryukyu trench slope in contrast to the lgm the decline of pulleniatina in this event was not ascribed to cyclic climate changes such as worldwide cooling but to the formation of a barrier between taiwan and the southern okinawa arc however this regional event influences largely on the holocene climate of japan and its adjacent seas

beginnings of earthquakes in the mexican subduction zone on strong motion accelerograms abstract the guerrero mexico accelerograph network has recorded at short distances earthquakes with magnitudes from 3 0 to 8 1 in this article the initial 3 5 sec of the p waves on the vertical component are compared in addition to unfiltered accelerograms several causal bandpass filters are applied we do not see significant differences in either original or filtered records between the initial e g 0 5 sec seismograms of moderate and large earthquakes in the original and 2 to 5 hz passband the main differences among events with magnitudes over about 4 5 is in the duration of shaking the initial ground motions of all the large events have very small amplitudes which gradually get larger at lower frequencies seismograms of the largest events show a complex series of multiple pulses assumed related to failure of numerous asperities in our lowest frequency band 0 2 to 0 5 hz most of the large events that we examined begin with rupture of asperities that are not necessarily larger and are sometimes smaller than the asperities that fail during smaller events the observations are consistent with a model of faulting in which the largest asperities are located at random on the eventual fault plane and fail when the rupture front propagating from the hypocenter reaches them this allows the largest asperities to occasionally be at the hypocenter and to fail immediately but for a large fault it is more likely that they will be located elsewhere and fail later

enso related decadal scale climate variability from the indo pacific warm pool the el nino southern oscillation enso is a climatic phenomenon that affects socio economical welfare in vast areas in the world a continuous record of holocene enso related climate variability of the indo pacific warm pool ipwp is constructed on the basis of stable oxygen isotopes in shells of planktic foraminifera from a sediment core in the western pacific ocean at the centennial scale variations in the stable oxygen isotope signal delta o 18 are thought be a representation of enso variability although an imprint of local conditions cannot be entirely excluded the record for the early holocene 10 3 6 ka bp shows in comparison with the mid to late holocene small amplitude variations in the delta o 18 record of up to 0 3 parts per thousand indicating relatively stable and warm sea surface conditions the mid to late holocene 6 2 ka bp exemplified higher variability in delta o 18 and thus in oceanic ipwp conditions climatically we interpret this change 5 5 4 2 ka bp as a phenomenon induced by variability in frequency and or intensity changes of el nino in the period 4 2 2 ka bp we identified several periods centred on 1 9 2 1 2 7 3 3 3 7 and 4 2 ka bp with in general heavy 6180 values during these periods the ipwp was relocated to a more eastward position enhancing the susceptibility for el nino like conditions at the core site over the last 2000 yr precipitation increased in the area as a response to an increase in asian monsoon strength resulting in a freshening of the surface waters this study corroborates previous findings that the present day enso activity started around 5 5 ka bp c 2006 elsevier b v all rights reserved

planktonic foraminifers as tracers of ocean currents in the eastern south atlantic the standing stock of planktonic foraminifers collected at 16 stations by multinet plankton tow has been examined in five discrete depth intervals 0 25 m 25 50 m 50 100 m 100 150 m and 150 300 m the assemblages document the status of populations in the surface and subsurface waters of the southeast atlantic during february march 1988 standing crops document hydrographic conditions in the coastal and geostrophic branch of the benguela current the angola current the tropical cyclonic gyre and the south equatorial current standing stocks are highest when primary production is intermediate very high primary production reduces foraminiferal crops significantly eleven species occur abundantly average 10 of the total standing stock a few species g glutinata g quinqueloba g clarkei are abundant at each station whereas the occurrence of other species g ruber g sacculifer g scitula g menardii g crassaformis n incompta n dutertrei is spatially restricted g ruber g rubescens and g glutinata are abundant in high salinity surface water also g ruber is abundant within the equatorial undercurrent water when this water is brought to the surface high concentrations of n incompta and g bulloides are observed in the angola benguela front when nutrient concentration is moderately elevated in surface and subsurface water upper part of the thermocline g crassaformis becomes abundant in the subsurface water of the angola benguela front this species is restricted to lower oxygenated subsurface water and traces incursions of water transported by the angola current g menardii is considered as an indicator for the equatorial undercurrent below the mixed layer whereas g scitula most probably points to an admixture of water transported by the northward flowing benguela current high abundances of g quinqueloba g clarkei in the surface and subsurface waters reflect favorable nutrient conditions like those present in the geostrophic benguela current and in the equatorial divergence zone g falconensis n dutertrei and g siphonifera appear to trace the southern equatorial current

seasonal succession vertical distribution and dissolution of planktonic foraminifera along the subarctic front implications for paleoceanographic reconstruction in the northwestern pacific abstract the regional spatial and depth distribution of planktonic foraminifera were studied through sediment trap observations at two stations stations wct 5 about 41 n 150 e and wct 6 about 42 n 155 e along the subarctic front in the northwestern pacific ocean the sediment traps were moored at 1000 and 4500 m depths at station wct 5 and 1091 2051 and 4871 m depths at station wct 6 the samples were collected from 17 august 1998 to 10 august 1999 at station wct 5 and from 15 august 1999 to 6 august 2000 at wct 6 at station wct 5 two distinct annual periods of increased total foraminiferal and species production were evident the period of highest production was in autumn with a secondary period in early summer at station wct 6 high total foraminiferal shell fluxes occurred in april may and september october the april may spring bloom of planktonic foraminifera apparently began each year as the sea surface temperature sst increased after winter and the decrease of thickness of the mixed water layer during june july in every year following the cessation of bloom the most common foraminiferal species in the study region were globigerina quinqueloba neogloboquadrina pachyderma neogloboquadrina dutertrei neogloboquadrina incompta globigerinita glutinata globigerina bulloides globigerina falconensis globorotalia theyeri globorotalia scitula and globigerinella calida foraminiferal fluxes displayed a distinct seasonality at all trap depths at both stations at station wct 5 in 1998 1999 foraminiferal species were scarce in the surface water during spring and summer and the dominant foraminiferal species were most productive during winter and autumn at station wct 6 the dominant foraminiferal species were most productive during late winter to spring and all species showed a peak in middle spring may a comparison of seasonal patterns of dominant foraminiferal species between the northwestern and northeastern pacific demonstrated that foraminiferal productivity was a good proxy for sea surface temperature and mixing of water column significant dissolution of foraminiferal tests was evident in the deepwater column and was used to estimate the foraminiferal lysocline depth 4500 m in the northeastern pacific basin

testing the effects of tropical temperature productivity and mixed layer depth on foraminiferal transfer functions statistical transfer functions relate living planktonic foraminiferal species of the central equatorial pacific to measured sea surface temperature integrated primary productivity and mixed layer depth the faunal estimates successfully reconstruct latitudinal patterns observed in both warm el nino february march 1992 and cool la nina august september 1992 seasonal settings predictions of mixed layer depth appear to be unbiased by temperature or productivity in our data set but tend to underestimate deep mixed layers interactions between productivity and temperature perhaps through their common influence on respiration and growth rates bias foraminiferal transfer functions for both properties paleoceanographic estimates may be improved by accounting for such biological processes that translate the environment into a faunal response preserved in the geologic record

the morning glory wave of southern california a pulse like disturbance traveling across the los angeles basin was observed on 12 october 2001 with seismographs of the trinet network this wave had a period of about 1000 s and a propagation speed of about 10 m s much slower than seismic waves the seismograph data were compared with barograph data and a good correlation was found so the wave was determined to be atmospheric in origin it had amplitude of about 1 mbar but it was not known what process could produce such a wave since the initial finding we have inspected all the trinet barograph and seismograph data for a period of two and a half years from january 2000 to august 2002 and found four more similar events each of the events has amplitude between 0 8 and 1 3 mbar a period between 700 and 1400 s and a propagation speed between 5 and 25 m s we conclude that these waves are internal gravity waves trapped in a stable layer formed by a temperature inversion some of these waves have large amplitudes and develop into solitary waves nonlinear internal gravity waves similar to the spectacular morning glory wave observed in australia we call these waves the la morning glory waves the la morning glory wave is probably excited by either stormy weather winds such as the santa ana winds or large teleseismic events the morning glory wave could contribute to the recently reported excitation of the background free oscillations of the earth additionally because of its large amplitude it could have important implications for aviation safety as was suggested earlier for the morning glory waves in australia

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

a perpetually running enso in the pliocene abstract difficulties remain with theoretical explanations of the apparent reduced zonal sea surface temperature gradient in the tropical pacific of the pliocene one favored hypothesis is that it was a permanent el nino state with the warm phase of enso remaining fixed over millions of years here an alternative is suggested that there was a perpetually running enso with a shorter return time than is observed today and that the apparently reduced zonal gradient is an alias rectification of a high frequency signal governed by the growth patterns of the foraminifera used to provide proxy temperatures the hypothesis is probably testable in the modern ocean with comparatively modest measurements of foraminifera behavior in time

time dependent inversion study of the slow thrust event in the nankai trough subduction zone southwestern japan we estimate time variation of interplate coupling between the subducting philippine sea and the overriding continental plates along the western part of the nankai trough japan during the period between 1996 and 1999 after subtracting annual components and average annual velocities deviation from steady crustal deformation in the shikoku and kyushu islands is examined around 15 gps stations facing the bungo channel detected the following three stage ground displacements of up to 3 cm in 1997 with a duration of 1 year 1 increased displacement rate associated with the 1996 hyuga nada earthquakes 2 an increasingly rapid anomalous period of deformation from june 1997 to the end of 1997 and 3 a slowdown period and return to normal rates of deformation after the end of 1997 linearized least squares locate the slip area of this slow event near the plate boundary beneath the bungo channel the estimated slip is opposite the motion of the philippine sea plate these results support the hypothesis that the observed anomalous caistal deformation is due to a rebound process of the philippine sea plate time dependent inversion analysis shows the following slip history during the initial period of increased displacement rate a visible slip area is resolved beneath the coastal area of southwestern shikoku in the next stage of accelerated displacements the slip area expanded southwestward to the bungo channel beginning around june 1997 when postseismic slip of the 1996 hyuga nada earthquakes almost ended after this accelerated period the estimated thrust slip ends with time

reconstructing past ocean ph depth profiles measurement of boron isotope compositions in species of planktonic foraminifera that calcified their tests at different depths in the water column are used to reconstruct the ph profile of the upper water column of the tropical ocean results for five time windows from the middle miocene to the late pleistocene indicate ph depth profiles similar to that of the modern ocean in this area which suggests that this method may greatly aid in our understanding of the global carbon cycle

spatial and temporal variability of surface water in the kuroshio source region pacific ocean over the past 21 000 years evidence from planktonic foraminifera abstract the kuroshio current is the major western boundary current of the north pacific ocean and has had a large impact on surface water character and climate change in the northwestern pacific region the kuroshio current becomes a distinctive surface flow in the ryukyu arc region after diverging from the north equatorial current and passing through the okinawa trough therefore the ryukyu arc area can be called the kuroshio source region we reconstructed post 21 ka time space changes in surface water masses in the ryukyu arc region using 15 piston cores which were dated by planktonic 18 o stratigraphy and ams 14 c ages our analysis utilized spatial and temporal changes in planktonic foraminiferal assemblages which were classified into the kuroshio subtropical coastal and cold water groups on the basis of modern faunal distributions in the study region these results indicate that the kuroshio current and adjacent surface water masses experienced major changes during 1 the last glacial maximum lgm and 2 the so called pulleniatina minimum event pme from 4 500 to 3 000 yr bp the kuroshio lgm event corresponds to severe global cooling and is marked by decreases in planktonic 18 o values and estimated sea surface temperature sst with the dominance of the cold water group of planktonic foraminifera cooling within the kuroshio source region was enhanced during the lgm event because the kuroshio current was forced eastward due to the formation of a land bridge between taiwan and the southern ryukyu arc which prohibited its flow into the okinawa trough except for the severe reduction and disappearance of the pulleniatina group no clear cooling signal was identified during the pme based on 18 o values estimated sst values and variations in the composition of planktonic foraminiferal faunas the pme assemblages are marked by high abundances of neogloboquadrina dutertrei a distinctive kuroshio type species along with other species assigned to the coastal and central water groups subtle ecological differences exist between pulleniatina obliquiloculata and n dutertrei i e p obliquiloculata exhibits lower rates of reproduction under conditions of lower primary productivity in the central equatorial pacific ocean el nino like conditions in the equatorial pacific ocean result in lower rates of surface transport in the kuroshio current in turn this response triggers lower rates of primary productivity in central equatorial surface waters as well as in the upstream kuroshio source region ultimately resulting in a lower abundance of p obliquiloculata thus we interpret the pme as a possible proxy signal of el nino like conditions and enhancement of the el nino southern oscillation climate system after the pme in the tropical and sub tropical pacific ocean