annual biogenic particle fluxes to the interior of the north atlantic ocean studied at 34 n 21 w and 48 n 21 w abstract in order to clarify the annual quality quantity and export processes of biogenic particles from the euphotic zone to the deep ocean interior an array of automated time series sediment traps were deployed for 1 year from 4 april 1989 to 17 april 1990 at 34 n 21 w and 48 n 21 w as part of the joint global ocean flux program jgofs north atlantic bloom experiment nabe three sediment traps with 13 time series sediment collectors were placed at both stations approximately 1 and 2 km below the surface and 0 7 km above the bottom they collected settling particles during 26 14 day intervals for 376 days with an 20 day hiatus in september october 1989 for changeover of the trap moorings the collection periods of the six traps were synchronized forming a spatio temporal matrix of 156 samples the annual mass flux at about 2 km deep during this experiment was 22 and 27 g m 2 y 1 at the 34 and 48 n stations consisting of biogenic particles with traceable quantities of lithogenic particle flux the spring particle bloom characterized by the sedimentation of particles relatively enriched by norg began in january at the 34 n station and in march at the 48 n station the bloom continued for 4 5 and 3 months and provided 62 and 50 of the annual biogenic particle mass flux at 2 km at the 34 and 48 n stations the surface bloom penetrated to the ocean interior within a few weeks with apparently accelerated settling speed at deeper layers the order of susceptibility of biogenic elements to mineralization while settling in the 0 7 1 km a b water column was from least to most resistant p norg corg si and ca the c n p ratio at 0 7 km a b was 154 18 1 at the 34 n station and 148 18 1 at the 48 n station

seasonal changes in planktonic foraminifera in the northwestern north pacific ocean sediment trap experiments from subarctic and subtropical gyres abstract upper ocean environments such as seawater temperature salinity thermal structure in the water column light intensity and food supply affect the assemblage of planktonic foraminifera since detailed information on planktonic foraminifera was not available for the northwestern north pacific we examined seasonal changes in fluxes and composition of planktonic foraminifera there data were collected by sediment traps deployed at three sites site 50n 50 01 n 165 02 e site knot 43 58 n 155 03 e and site 40n 39 60 n 165 00 e in this area in order to better understand the relationship between the foraminiferal assemblage and surface ocean environments although each planktonic foraminiferal species showed specific seasonal variations in flux some exhibited similar flux profiles in order to define these more accurately correlations among species were calculated and the foraminiferal species classified into four groups 1 group a subpolar species neogloboquadrina pachyderma globigerina quinqueloba globigerina bulloides and globigerinita glutinata 2 group b subtropical and tropical species globigerinoides ruber and globigerinoides sacculifer 3 group c post upwelling species neogloboquadrina dutertrei and 4 group d deep water species globorotalia scitula and globorotalia truncatulinoides the common environments for each period based on foraminiferal production and composition were observed among the three sites based upon predominant foraminiferal groups total foraminiferal fluxes tffs organic matter om fluxes and hydrographic conditions including sea surface temperatures sst and thermal structure the surface ocean environments in the northwestern north pacific could be generalized into five types type i is characterized by a dominance of group b with low tffs under high sst and type ii is marked by a high flux of group a on the other hand type iii shows low tffs and low om fluxes due to low insolation during winter type iv represents a high flux of group a and group d at site 40n under a well mixed surface ocean and type v is characterized by a prominent peak of group c under a developed thermocline a comparison of annual mean foraminifera fluxes at 50 n between the northwestern site 50n and the northeastern north pacific station papa during the normal cold mode demonstrated higher fluxes of foraminifera at site 50n due to higher nutrient concentrations the results also showed that g bulloides is not always a proxy for upwelling and that n pachyderma is not solely controlled by seawater temperature in the northwestern pacific where the surface water is enriched in nutrients the fluxes and composition of foraminifera suggest that similar ocean environments are expected in large areas of the northern north pacific from site knot to station papa during the warm mode which is affected by el nino events

seasonal stratification shell flux and oxygen isotope dynamics of left coiling n pachyderma and t quinqueloba in the western subpolar north atlantic blooms this annual population overturning is marked by a 0 7 increase in d 18 o in both species the shell flux of n pachyderma peaks during the spring bloom and in late summer when stratification is close to its minimum and maximum respectively both export periods contribute about equally and account for 95 of the total annual flux shell fluxes of t quinqueloba show only a single broad pulse in summer thus following the seasonal stratification cycle the d 18 oo fn pachyderma reflects temperatures just below the base of the seasonal sml without offset from isotopic equilibrium the d 18 op attern oft quinqueloba shows a nearly identical amplitude and correlates highly with the d 18 oo fn pachyderma therefore t quinqueloba also reflects temperature near the base of the sml but with a positive offset from isotopic equilibrium these offsets contrast with observations elsewhere and suggest a variable offset from equilibrium calcification for both species in the irminger sea the species consistently show a contrast in their flux timings their flux weighted dd 18 o will thus dominantly be determined by seasonal temperature differences at the base of the sml rather than by differences in their depth habitat consequently their sedimentary dd 18 o may be used to infer the seasonal contrast in temperature at the base of the sml citation jonkers l g j a brummer f j c peeters h m van aken and m f de jong 2010 seasonal stratification shell flux and oxygen isotope dynamics of left coiling n pachyderma and t quinqueloba in the western subpolar north atlantic paleoceanography 25 pa2204 doi 10 1029 2009pa001849

seasonal to interannual changes in planktonic foraminiferal assemblages in the northwestern north pacific sediment trap results encompassing a warm period related to el nino abstract planktonic foraminifera provide a record of the upper ocean environment through their species assemblage and individual tests to investigate the relationship between foraminifera and oceanographic conditions and the impact of el nino on foraminifera we analyzed foraminiferal fluxes and relative abundances by using sediment trap samples collected biweekly at three sites in the northwestern north pacific site 40n 39 60 n 165 00 e site knot 43 58 n 155 03 e and site 50n 50 01 n 165 02 e from 1998 2001 a period that included an el nino event based on foraminiferal production and assemblage composition we divided the sampling duration into several periods during which certain characteristic oceanographic properties were observed these sampling periods were classified into five types i v based upon four factors 1 the predominant foraminiferal group 2 total foraminiferal fluxes tffs 3 organic matter om fluxes and 4 hydrographic conditions which included sea surface temperature sst and thermal structure our results suggest that our observed seasonal changes in foraminifera were closely related to water mass properties in addition to sst if species compositions were the same then water mass properties were the most important factors affecting the seasonal variation of foraminiferal abundance in the northwestern north pacific although one of the major controlling factors for foraminiferal fluxes is food availability the controlling factors for each type types i v are different because of specific oceanographic situations such as phytoplankton blooms which result in an excess food supply for foraminifera at site knot high surface temperatures and weak winds related to an el nino period in 1998 would have caused a low nutrient supply and water column stratification and resulted in the relatively low fluxes of total foraminifera neogloboquadrina pachyderma and globigerina bulloides and high fluxes of neogloboquadrina dutertrei the impact of el nino on foraminifera was variable depending on the strength of the el nino event and site location however there were some instances of common annual foraminiferal patterns the patterns observed at sites 40n and knot in 1998 were similar to those observed off chile in 1997 1998 and in 1991 1992 respectively

new empirical polyaxial criterion for rock strength abstract a new criterion is presented for prediction of intact rock and rock mass failure under polyaxial state of stresses a comprehensive database of the results of uniaxial triaxial and polyaxial tests on intact rock was utilized for evaluation of the new criterion and comparison of its accuracy with the most accurate and frequently used criteria analysis of 195 individual data groups of brittle failure in the form of 3 1 for twelve different rock types showed that the proposed criterion lead to determination coefficients higher than 0 99 in most cases it also gave the lower values of root mean squared errors relative to mohr coulomb and hoek brown criteria in fitting the normalized strength data for each rock type the criteria were used to fit a typical series of triaxial strength data including brittle and ductile behavior it showed that the new criterion can maintain its accuracy over a wider range of stresses in the absence of rock mass strength data applicability of the new criterion for rock mass was verified by fitting it to typical hoek brown failure envelopes regression analysis of the polyaxial strength data in the form of 3 2 1 for six rock types showed that the new criterion predict the strength more accurately than the modified wiebols cook and you criteria in all cases

palaeoceanographic implications of genetic variation in living north atlantic neogloboquadrina pachyderma the shells of the planktonic foraminifer neogloboquadrina pachyderma have become a classical tool for reconstructing glacial interglacial climate conditions in the north atlantic ocean1 2 3 palaeoceanographers utilize its left and right coiling variants which exhibit a distinctive reciprocal temperature and water mass related shift in faunal abundance both at present and in late quaternary sediments1 2 4 5 recently discovered cryptic genetic diversity in planktonic foraminifers6 7 8 now poses significant questions for these studies here we report genetic evidence demonstrating that the apparent single species shell based records of right coiling n pachyderma used in palaeoceanographic reconstructions contain an alternation in species as environmental factors change this is reflected in a species dependent incremental shift in right coiling n pachyderma shell calcite 18o between the last glacial maximum and full holocene conditions guided by the percentage dextral coiling ratio our findings enhance the use of 18o records of right coiling n pachyderma for future study they also highlight the need to genetically investigate other important morphospecies to refine their accuracy and reliability as palaeoceanographic proxies

reevaluation of the oxygen isotopic composition of planktonic foraminifera experimental results and revised paleotemperature equations cultured planktonic foraminifera orbulina universa symbiotic and globigerina bulloides nonsymbiotic are used to reexamine temperature 18o relationships at 15 25 c relationships for both species can be described by linear equations equations for o universa grown under low light ll and high light hl share a slope of 4 80 0 21 c 1 with a hl ll offset of 0 33 due to symbiont photosynthetic activity the effect of co32 on o universa is 0 002 mol 1 kg 1 and is insensitive to temperature for g bulloides ontogenetic effects produce size related trends in temperature 18o whereby larger shells are enriched in 18o relative to smaller specimens the o universa temperature 18o relationships are more accurate than previously published equations for describing plankton tow data our equations do not explain planktonic core top data with the same precision but provide a good fit to benthic cibicidoides data below 10 c temperature 18o relationships for g bulloides provide good agreement with field data for this species from the northeast pacific

monsoon influenced variations in plankton community structure and upper water column stratification in the western bay of bengal during the past 80 ky abstract to enhance our understanding of the forcing factors of marine biological community structure in the bay of bengal we studied proxies for biogenic carbonate and silicate production in the western bay of bengal and compared them with proxies for upper ocean stratification and strength of the indian summer monsoon ism specifically we investigated the record in a sediment core from the western bay of bengal that extended to approximately 80 ky before the present bp the records of globigerinoides ruber sensu stricto 18o minus neogloboquadrina dutertrei 18o 18or d were used to investigate changes in upper ocean stratification we reconstructed variations in mass accumulation rates mars of caco3 and biogenic silica bsi to discuss plankton community structure greater difference between globigerinoides ruber sensu stricto 18o and neogloboquadrina dutertrei 18o during the marine isotope stage mis 1 and 5a indicate intervals with less saline and more stratified conditions in contrast the relatively small difference between both planktic foraminiferal 18o during mis 2 and 4 indicates diminished stratification during these periods elevated carbonate production during mis 2 and 4 demonstrated by the increase in caco3 mar could have been driven by lower freshwater influx to the western bay of bengal resulting from lower ism precipitation and thus the increased mixing and upwelling of deep nitrate into the photic zone the relative increase in bsi mar during periods of high ism precipitation and decreased salinity of surface waters suggests a limited recovery in biological siliceous production under interglacial conditions possibly due to enhanced fluvial sio4 delivery to the ocean fluctuations of 18or d during mis 3 indicate that freshwater stratification was moderate and insufficient to restrict upwelling this might have induced moderate biogenic silica and carbonate productions during this period

mantle discontinuities and temperature under the north american continental keel a ubiquitous feature of upper mantle seismic velocity models has been the presence of high velocity keels beneath stable continental interiors1 2 3 4 5 uncertainty remains however regarding the maximum depth to which continental keels extend the degree to which they have cooled the mantle that surrounds them and their role in mantle flow here we investigate thermal anomalies across the eastern margin of the north american continental keel by imaging the seismic discontinuities at depths of 410 and 660 km with compressional to shear converted waves recorded by a 1 500 km long seismometer deployment in the eastern united states the thickness of the transition zone the region nominally between depths of 410 and 660 km and the depth to the 410 km discontinuity indicate that cold keel material and sub keel downwellings must be largely confined to the upper mantle and may impinge on the transition zone only in localized regions and with thermal anomalies of less than 150 k a 20 km depression of the 660 km discontinuity to the south of the westernmost stations coincides with a region of fast velocity in the deep transition zone2 and may be associated with the remnants of the subducted farallon plate1 2 4

an empirical failure criterion for rocks and jointed rock masses abstract a new triaxial strength equation is proposed as fitting the available laboratory triaxial test data it is shown how the five triaxial parameters unconfined compressive tensile and shear strengths coefficient of friction and exponent in the triaxial equation can be inter related by three equations a relation between intact rock strength rock mass strength ratio and barton s rock quality 1974 is next developed based on geomechanical data for four longwall panels and in situ coal strength data this relation and the coefficient of internal friction from barton s classification are used in the three inter relations to evaluate the rest of the triaxial parameters for rock masses performance of the failure criterion is studied using practical cases of rock structures in coal and coal measure strata viz five longwall caving panels and four coal pillars

estimation of the catchment area of a sediment trap by means of current meters and foraminiferal tests abstract between june 1989 and july 1990 a mooring equipped with four current meters and one sediment trap was deployed in the fram strait 79 n from the material collected by the sediment trap two species of planktic foraminifera turborotalita quinqueloba and neogloboquadrina pachyderma were used to estimate the catchment area of the sediment trap for each species and size class the individual sinking velocity was used to determine the residence time in the water column the residence time is the major factor that determines the drift of the tests using current meter data trajectories were calculated to estimate the catchment area and the area of sedimentation the maximum distance the smallest tests have been transported while sinking from the surface 100 m to the sediment trap 1125 m is approximately 275 km with maximum trajectory lengths of up to 300 km depending mainly on the grain size of the tests the distances and trajectories have means lying between 25 and 50 km for n pachyderma and 50 and 100 km for t quinqueloba respectively considering the whole sampling period the estimated catchment areas are 23 900 km 2 for all n pachyderma tests and 33 300 km 2 for all t quinqueloba tests respectively the respective areas of sedimentation are estimated to range from 3400 km 2 to 3500 km 2

seasonal variation in the oxygen isotopic composition of different sized planktonic foraminifer neogloboquadrina pachyderma sinistral in the northwestern north pacific and implications for reconstruction of the paleoenvironment 1 the oxygen isotope value 18o of planktonic foraminifer shells is one of the most commonly used proxies to reconstruct the paleoenvironment neogloboquadrina pachyderma sinistral n pachyderma sin is a dominant foraminifer in subpolar and polar region that is used extensively for high latitude paleoreconstruction the present study examined seasonal variation in 18o of n pachyderma sin using sediment trap samples collected over 3 5 years in the northwestern north pacific ocean the vital offset value was about 1 which agrees with previous plankton tow studies large shell individuals 180 250 m secrete their shells in a shallower and warmer environment than small ones 125 180 m and the difference in 18o between shell size showed seasonal variation although large individuals calcify at a slower rate with slightly heavier 18o than small individuals differences between size classes mainly reflect different habitation in the water column and are related to seasonal changes in stratification during summer large individuals would calcify mainly at 25 35 m depth while small individuals calcify near the pycnocline at 45 m during winter both size classes calcify at or slightly above the weak pycnocline at 45 65 m thus the shell 18o could record the oceanographic environment around pycnocline depth and size specific differences in 18o reflect water column stratification the annual flux weighted 18o corresponded to non flux weighted mean 18o value due to the equal contribution of two flux peaks and differences between size classes also related to the stratification it suggests that fossil 18o data could represent the annual mean environment around pycnocline and past stratification

morphologic gradation and ecology in neogloboquadrina pachyderma and n dutertrei planktic foraminifera from core top sediments abstract an analysis of ecologic preferences of n pachyderma n dutertrei and morphologically intermediate forms is used for a test of coincidence of morphologic and ecologic gradation in modern neogloboquadrina relative abundances in 461 indian ocean and north atlantic surface sediment assemblages of planktic foraminifera 150 m climap data are plotted against annual means of physical parameters extracted for each core location sea surface temperature sea surface salinity the temperature at 200 m depth the vertical temperature gradient and the density contrast stratification between the sea surface and 200 m depth the intermediate forms can be considered as n pachyderma living under suboptimum conditions neogloboquadrina dutertrei consists of two populations one in tropical water masses and one in subtropical water masses near ocean margins morphologic gradation in neogloboquadrina does not reflect ecologic gradation two ecological groups exist in neogloboquadrina 1 n dutertrei tropical population and 2 n pachyderma the intermediate forms and n dutertrei subtropical ocean margin population a relative abundance minimum exists between these populations near the limit between tropical and subtropical water masses

strength of jointed rock masses jointed rock masses comprise interlocking angular par ticles or blocks of hard brittle material separated by discontinuity surfaces which may or may not be coated with weaker materials the strength of such rock masses depends on the strength of the intact pieces and on their freedom of movement which in turn depends on the number orientation spacing and shear strength of the discontinuities a complete understanding of this problem presents formidable theoretical and experi mental problems and hence simplifying assumptions are required in order to provide a reasonable basis for estimating the strength of jointed rock masses for engineering design purposes this paper summarizes some of the basic information upon which such simplifying assumptions can be made a simple empirical failure criterion is presented and its application in engineering design is illustrated by means of a number of practical examples des masses jointives de rochers comprennent des particules angulaires enchevetrees ou des

thermoelastic properties of ringwoodite fex mg1 x 2sio4 its relationship to the 520 km seismic discontinuity abstract we combine density functional theory dft within the local density approximation lda the quasiharmonic approximation qha and a model vibrational density of states vdos to calculate elastic moduli and sound velocities of fe x mg 1 x 2 sio 4 ringwoodite the most abundant mineral of the lower earth s transition zone tz comparison with experimental values at room temperature and high pressure or ambient pressure and high temperature shows good agreement with our first principles findings then we investigate the contrasts associated with the fe x mg 1 x 2 sio 4 transformation at pressures and temperatures relevant to the tz this information offers clearly defined reference values to advance the understanding of the nature of the 520 km seismic discontinuity

north pacific freshwater events linked to changes in glacial ocean circulation there is compelling evidence that episodic deposition of large volumes of freshwater into the oceans strongly influenced global ocean circulation and climate variability during glacial periods1 2 in the north atlantic region episodes of massive freshwater discharge to the north atlantic ocean were related to distinct cold periods known as heinrich stadials1 3 by contrast the freshwater history of the north pacific region remains unclear giving rise to persistent debates about the existence and possible magnitude of climate links between the north pacific and north atlantic oceans during heinrich stadials4 5 here we find that there was a strong connection between changes in north atlantic circulation during heinrich stadials and injections of freshwater from the north american cordilleran ice sheet to the northeastern north pacific our record of diatom 18o a measure of the ratio of the stable oxygen isotopes 18o and 16o over the past 50 000 years shows a decrease in surface seawater 18o of two to three per thousand corresponding to a decline in salinity of roughly two to four practical salinity units this coincided with enhanced deposition of ice rafted debris and a slight cooling of the sea surface in the northeastern north pacific during heinrich stadials 1 and 4 but not during heinrich stadial 3 furthermore results from our isotope enabled model6 suggest that warming of the eastern equatorial pacific during heinrich stadials was crucial for transmitting the north atlantic signal to the northeastern north pacific where the associated subsurface warming resulted in a discernible freshwater discharge from the cordilleran ice sheet during heinrich stadials 1 and 4 however enhanced background cooling across the northern high latitudes during heinrich stadial 3 the coldest period in the past 50 000 years7 prevented subsurface warming of the northeastern north pacific and thus increased freshwater discharge from the cordilleran ice sheet in combination our results show that nonlinear ocean atmosphere background interactions played a complex role in the dynamics linking the freshwater discharge responses of the north atlantic and north pacific during glacial periods

oxygen isotope composition of living neogloboquadrina pachyderma sin in the arctic ocean data from the nansen basin of the arctic ocean are used to investigate the habitat and conditions under which the polar planktic foraminifer neogloboquadrina pachyderma sin calcifies the vertical distribution of 18o values of net sampled speciments together with their abundances and proportion of calcification are compared with 18o values from both water samples and foraminiferal tests from core top sediments within the nansen basin the average depth of habitat of n pachyderma sin changes from about 150 m in the southern part to about 80 m in the northern the average depth of calcification however in both regimes varies between 100 and 200 m water depth 18o data from net sampled n pachyderma sin are directly reflected in the core top sediment data but compared to equilibrium calcite 18o values derived from measurements of the ambient water a consistent offset of about 1 over all depth intervals is observed while in the southern part of the nansen basin advection through fram strait of planktic foraminifers from further south may play a role the data from the northern part of the nansen basin give clear evidence that the observed offset in 18o values is caused by a vital effect of n pachyderma sin

the morphotypes of neogloboquadrina pachyderma isotopic signature and distribution patterns in the canadian arctic archipelago and adjacent regions abstract neogloboquadrina pachyderma represents a key planktonic foraminifera species in the boreal atlantic and has been extensively used as a paleoceanographic tool in polar to subpolar environments the species shows an intraspecific morphological variability displaying at least 5 different morphotypes previously documented from northern and southern oceans the present work focuses on the distribution of these morphotypes in modern surface sediment samples from the canadian arctic archipelago caa our results obtained for the first time for this area show the prevalence of morphotypes 1 2 and 3 abundance on average 19 48 and 22 respectively two types of assemblages were observed in the inner and outer parts of the northwest passages on the basis of the abundance and diversity of morphotypes their geographical and vertical positions regarding the water depth in the caa argue for a strong influence of water mass stratification on morphotype distribution the detailed morphometric study of test morphology together with sem imagery provides a way to re evaluate and complete previous classifications of n pachyderma morphotypes this morphological approach is supported by stable isotope analyses that document a link between 18o and 13c and morphotype mean sizes this relationship is interpreted as indicative of water column position with large morphotypes living in relatively shallower but also fresher colder and more productive waters compared to small morphotypes the former interpretation is further supported by the increased pore concentration in larger morphotypes which is tentatively interpreted as a strategy to increase buoyancy and to adapt to lower salinity consequently we propose that a coupled approach of using morphology and stable isotopes may constitute an improved tool for oceanographic reconstructions particularly water column stratification when used with n pachyderma assemblages furthermore the additional morphometric criteria defined in the current work are the basis of a useful and updated identification key for n pachyderma morphotypes

living neogloboquadrina pachyderma sin and its distribution in the sediments from oman and somalia upwelling areas abstract microfaunal analysis of plankton nets collected offshore oman yemen and sediment traps offshore somalia shows that neogloboquadrina pachyderma sin is abundant during the sw monsoon upwelling the sediment traps recorded the highest flux 136 specimens m 2 day 1 and the highest relative frequency 3 55 of the total foraminifera assemblage of the species during this period during the intermonsoon it became less abundant and decreased in size and only very few n pachyderma sin were found in the water column during the ne monsoon sediment trap and recent sediment data collected along a downslope transect off somalia show that the species frequency decreases offshore the highest concentrations of n pachyderma sin in plankton nets off oman yemen were found at a depth of 300 500 m however the oxygen isotope compositions of n pachyderma sin at the depth of 300 500 m and from the surface 8 m are identical and also similar to that of globigerina bulloides which reflects properties of the upper 25 m of the water column the carbon isotope values are relatively consistent within the studied samples from both areas except for the specimens from the surface water samples offshore oman yemen the data show that the 18o ratio of n pachyderma sin is in equilibrium with the ambient water while the 13c values are at least 0 8 lower we infer that n pachyderma sin in the arabian sea reproduces grows and calcifies in the upper 25 m of the water column but possibly descends into deeper waters later during its life cycle

using the pietruszczak mroz anisotropic failure criterion to model the strength of stratified rocks abstract the strength of stratified rocks is closely related to their inherent structural anisotropy which cannot be accurately represented by the isotropic failure criteria in this study the pietruszczak mroz pm anisotropic failure criterion was used to describe the directional dependency of strength of stratified rocks in the meridian plane the frictional coefficient was established by incorporating an anisotropic variable defined as a joint invariant of fabric and stress tensors in the deviatoric plane the anisotropic failure surface was characterized by a smooth shape function of lode s angle the material parameters for the failure criterion can be determined using the triaxial test the pm anisotropic criterion was utilized to predict the anisotropic strength of specific stratified rocks analysis of the experimental data validated the assertion that pm anisotropic criterion has excellent ability to model the anisotropic strength features of stratified rocks

scattered wave imaging of the lithosphere asthenosphere boundary several recent studies have imaged discontinuities interpreted as the lithosphere asthenosphere boundary using receiver function methods these are exciting results since this boundary is fundamental and yet relatively elusive its location is not well imaged nor are its properties well understood the receiver function method provides high depth resolution and the multitude of studies using this method have increased lateral resolution a better global understanding of the location and nature of the boundary is developing which ultimately will have implications for mantle dynamics and planetary evolution however these new results do not all form a clear and consistent picture and in some cases introduce new complexities and questions some apparent contradictions may represent unmodeled earth structure overall interpretation and synthesis requires careful consideration of the approaches and sensitivities of individual studies

horizontal and vertical distributions of planktic foraminifera in the subarctic pacific abstract observations of the horizontal and vertical distributions of modern planktic foraminifera facilitate formation of ecological and geochemical inferences derived from the study of foraminiferal shells in this study we used plankton tows to collect planktic foraminifera at nine sites distributed longitudinally throughout the subarctic pacific a total of nine planktic foraminiferal species were identified the horizontal distributions of the foraminiferal assemblages could be assigned to four regions characteristics of the foraminiferal assemblages and the horizontal distributions of their shell sizes appeared to be influenced by the sea surface structure within each water mass the vertical distributions of globigerina bulloides and globigerina quinqueloba were associated with the depth of the pycnocline those of neogloboquadrina pachyderma and neogloboquadrina incompta were different and appeared to reflect a significant difference of optimum habitat temperatures based on the vertical distribution of shell sizes we found evidence of vertical migrations during shell growth of g bulloides and n incompta this information about the distribution of modern planktic foraminifera will facilitate reconstruction of past oceanographic conditions based on geochemical proxies in the subarctic pacific

seasonal mg ca variability of n pachyderma s and g bulloides implications for seawater temperature reconstruction given the importance of high latitude areas in the ocean climate system there is need for a paleothermometer that is reliable at low temperatures here we assess the applicability of the mg ca temperature proxy in colder waters 5 10 c by comparing for the first time the seasonal mg ca and 18o cycles of n pachyderma s and g bulloides using a sediment trap time series from the northern north atlantic while both species show indistinguishable seasonal 18o patterns that clearly track the near surface temperature cycle their mg ca are very different g bulloides mg ca is high 2 0 3 1 mmol mol but varies in concert with the seasonal temperature cycle the mg ca of n pachyderma s on the other hand is low 1 1 1 5 mmol mol and shows only a very weak seasonal cycle the 18o patterns indicate that both species calcify in the same depth zone consequently depth habitat differences cannot explain the contrasting mg ca patterns the elevated mg ca in pristine g bulloides might be due to the presence of high mg phases that are not preserved in fossil shells the contrasting absence of a seasonal trend in the mg ca of n pachyderma s confirms other studies where calcification temperatures were less well constrained the reason for this absence is not fully known but may include species specific vital effects the very different seasonal patterns of both species mg ca underscore the importance of parameters other than temperature in controlling planktonic foraminiferal mg ca our results therefore lend further caution in the interpretation of mg ca temperature reconstructions from high northern latitudes

paired δ18o signals of neogloboquadrina pachyderma s and turborotalita quinqueloba show thermal stratification structure in nordic seas abstract the vertical density gradients in the nordic seas are crucial for the preconditioning of the surface water to thermohaline sinking in winter these gradients can be reconstructed from paired oxygen isotope data in tests of different species of planktonic foraminifera the isotopic signatures of which represent different calcification depths in the water column comparison of 18 o values from foraminiferal tests in plankton hauls sediment traps and nearby core top samples with the calculated 18 o calcite profile of the water column revealed species specific 18 o vital effects and the role of bioturbational admixture of subfossil specimens into the surface sediment on the basis of core top samples obtained along a west east transect across various hydrographic regions of the nordic seas 18 o values of turborotalita quinqueloba document apparent calcification depths within the pycnocline at 25 75 m water depth the isotopic signatures of neogloboquadrina pachyderma s reflect water masses near and well below the pycnocline between 70 and 250 m off norway where the atlantic inflow leads to thermal stratification here temperatures in the calcification depth of n pachyderma s differ from sea surface temperature by approximately 2 5 c in contrast n pachyderma s calcifies very close to the sea surface 20 50 m in the arctic domain of the western nordic seas however further west n pachyderma s prefers somewhat deeper more saline water at 70 130 m well below the halocline that confines the low saline east greenland current this implies that the 18 o values of n pachyderma s do not fully reflect the freshwater proportion in surface water and that any reconstruction of past meltwater plumes based on 18 o is too conservative because it overestimates sea surface salinity minimum 18 o differences n pachyderma s and t quinqueloba may serve as proxy for sea regions with dominant haline and absent thermal stratification whereas thermal stratification leads to 18 o differences of 0 4 to 1 5

deglacial development of sub sea surface temperature and salinity in the subarctic northwest pacific implications for upper ocean stratification based on models and proxy data it has been proposed that salinity driven stratification weakened in the subarctic north pacific during the last deglaciation which potentially contributed to the deglacial rise in atmospheric carbon dioxide we present high resolution subsurface temperature tmg ca and subsurface salinity approximating 18oivc sw records across the last 20 000 years from the subarctic north pacific and its marginal seas derived from combined stable oxygen isotopes and mg ca ratios of the planktonic foraminiferal species neogloboquadrina pachyderma sin our results indicate regionally differing changes of subsurface conditions during the heinrich stadial 1 and the younger dryas cold phases our sites were subject to reduced thermal stratification brine rejection due to sea ice formation and increased advection of low salinity water from the alaskan stream in contrast the bolling allerod warm phase was characterized by strengthened thermal stratification stronger sea ice melting and influence of surface waters that were less diluted by the alaskan stream from direct comparison with alkenone based sea surface temperature estimates sstuk 37 we suggest deglacial thermocline changes that were closely related to changes in seasonal contrasts and stratification of the mixed layer the modern upper ocean conditions seem to have developed only since the early holocene

stable oxygen and carbon isotopes in planktonic foraminifera neogloboquadrina pachyderma in the arctic ocean an overview of published and new surface sediment data abstract a summary study on oxygen and carbon stable isotopes in planktonic foraminifera from arctic ocean floor appeared in marine geology 20 years ago spielhagen and erlenkeuser 1994 we revisit this topic with a wealth of new data focused on the western amerasian arctic a spotlight in the current climatic and oceanic change neogloboquadrina pachyderma the most abundant polar planktonic foraminiferal species is an important tool for reconstructing surface subsurface water changes in the arctic our new data on n pachyderma 150 250 m from the surface sediments show 18 o and 13 c values of 18 o and 13 c are both influenced by complex water sources water column structure and foraminiferal depth habitat the observed distribution of n pachyderma stable isotopes confirms a shallow habitat of this species in the sea ice covered central arctic especially in the canada basin probably in relation to the shallow chlorophyll maximum the associated light n pachyderma 18 o reflects the long term storage of fresh water at the shelf break a deeper dwelling of n pachyderma with heavier 18 o is supported by a more extensive photic zone and nutrient availability air sea exchange plays an important role in 13 c distribution and is consistent with heavy n pachyderma 13 c in the perennially ice covered central arctic ocean light 13 c composition at the shelf break is additionally influenced by shelf bottom waters enriched in isotopically light remineralized terrestrial carbon distribution of foraminiferal 13 c on the chukchi shelf reflects primary production patterns in the area

calibration and application of b ca cd ca and δ11b in neogloboquadrina pachyderma sinistral to constrain co2 uptake in the subpolar north atlantic during the last deglaciation the north atlantic and norwegian sea are prominent sinks of atmospheric co 2 today but their roles in the past remain poorly constrained in this study we attempt to use b ca and 11 b ratios in the planktonic foraminifera neogloboquadrina pachyderma sinistral variety to reconstruct subsurface water ph and pco 2 changes in the polar north atlantic during the last deglaciation comparison of core top results with nearby hydrographic data shows that b ca in n pachyderma s is mainly controlled by seawater b oh 4 hco 3 with a roughly constant partition coefficient k d b ca caco 3 b oh 4 hco 3 seawater of 1 48 0 15 10 3 2 and 11 b in this species is offset below 11 b of the borate in seawater by 3 38 0 71 2 these values represent our best estimates with the sparse available hydrographic data close to our core tops more culturing and sediment trap work is needed to improve our understanding of boron incorporation into n pachyderma s application of a constant k d of 1 48 10 3 to high resolution n pachyderma s b ca records from two adjacent cores off iceland shows that subsurface pco 2 at the habitat depth of n pachyderma s 50 m generally followed the atmospheric co 2 trend but with negative offsets of 10 50 ppmv during 19 10 ka these b ca based reconstructions are supported by independent estimates from low resolution 11 b measurements in the same cores we also calibrate and apply cd ca in n pachyderma s to reconstruct nutrient levels for the same down cores like today s north atlantic past subsurface pco 2 variability off iceland was significantly correlated with nutrient changes that might be linked to surface nutrient utilization and mixing within the upper water column because surface pco 2 at 0 m water depth is always lower than at deeper depths and if the application of a constant kd is valid our results suggest that the polar north atlantic has remained a co 2 sink during the calcification seasons of n pachyderma s over the last deglaciation

carbon isotopes and habitat of polar planktic foraminifera in the okhotsk sea the carbonate ion effect under natural conditions the upper 500 or 1000 m of the water column in the okhotsk sea was sampled for living planktic foraminifera the polar species neogloboquadrina pachyderma sinistral strongly dominates the foraminiferal assemblage the subpolar to temperate species globigerina bulloides accounts for 10 25 other species account for up to 3 only the shell 18o and 13c values of the species n pachyderma sin are compared to water 18o values and 13c values of dissolved inorganic carbon dic the strong gradient in 18o composition and temperature in the upper water column is reflected in the 18o of n pachyderma sin relative to the values expected for inorganic calcite precipitated under equilibrium conditions n pachyderma sin displays a vital effect of about 1 in 18o the 13c composition of n pachyderma sin is about constant with water depth and the reflection of 13cdic in the foraminiferal shell seems to be masked by other effects most foraminifera are found above or slightly below the thermocline and can be assumed to calcify in the upper 200 m of the water column the gradient of 13cdic extends well below this depth therefore the lack of correlation can partly be attributed to this fact the remaining discrepancy between 13c of n pachyderma sin and 13cdic correlates with the carbonate ion concentration in the water column this leads to the conclusion that the carbonate ion effect cie which has been derived from culturing experiments for other species spero et al 1997 nature 390 497 500 is found here under natural conditions when the magnitude of the cie derived for g bulloides is applied to n pachyderma sin cie corrected 13c of n pachyderma sin is a direct reflection of 13cdic in the water column with a constant offset of 1 2

size dependent isotopic composition of planktic foraminifers from chukchi sea vs nw atlantic sediments implications for the holocene paleoceanography of the western arctic abstract in arctic and sub arctic seas shell growth and or secondary calcite overgrowth of neogloboquadrina pachyderma left coiled npl occur along the pycnocline and their 13c and 18o values are size and weight dependent however whereas the npl 18o data from the nw atlantic indicate near equilibrium conditions with ambient waters and a positive relationship between shell weight and 18o content assemblages from box cored sediments of the chukchi sea western arctic are depleted by 2 with respect to equilibrium values with modern conditions and depict a negative relationship between shell weight and its 18o value 0 15 0 03 g on vpdb scale a similar feature is also depicted by the dextral form of n pachyderma npd we associate the reverse shell size or weight vs 18o relationship to the reverse temperature gradient observed along the thermocline between the surface cold and dilute water layer and the underlying near 3 c warmer saline north atlantic water mass the analysis of two late to post glacial sedimentary sequences from the chukchi sea indicates that such a water mass stratification with a reverse thermocline persisted throughout the holocene thus reflecting an early onset of the modern like linkage between the arctic ocean and the north atlantic moreover lower 18o values in both npl and npd together with larger 18o gradients between the different shell sizes at ca 9 7 ka bp suggest 3 c higher temperatures in the upper north atlantic water mass in comparison with the present approximately 1 c at the study site thus likely a higher inflow rate of this water mass during the early holocene

isotope paleontology growth and composition of extant calcareous species abstract isotope paleontology uses the isotopic composition of fossil remains of organisms to make inferences about the physical surroundings of growth of the organisms especially temperature and to obtain clues about life history and modes of growth in calcareous fossils oxygen isotopes are mainly used in the former and carbon isotopes in the latter however since physical surroundings and organism response are intimately associated both types of information are contained in each of the isotopic signals to explore the potential of isotope paleontology and to provide a basis for reconstruction a broad range of extant organisms has been studied taking the pioneering work of epstein and associates as a starting point results are summarized for a representative sampling of these studies with emphasis on work at the laboratories of the authors from the mid seventies to the present the organisms considered are nannoplankton benthic algae planktonic and benthic deep sea foraminifera larger foraminifera sponges corals bryozoans polychaetes arthropods bivalves gastropods cephalopods and vertebrates fish otoliths the survey broadly suggests that regarding oxygen isotopes materials tend to be precipitated close to equilibrium with the surrounding seawater as postulated by urey and that for carbon isotopes disequilibrium is the rule life spans growth rates differential seasonal growth and age of reproductive activity can be extracted under favorable circumstances from individual shells and skeletal parts in detail the interpretation of isotope records of individual shells is quite complicated and simple models will fail to give satisfactory results in many or most cases

seismic evidence for a 920 km discontinuity in the mantle analysis of hundreds of seismograms from a seismic array in the japanese islands reveals a seismic discontinuity at a depth of about 920 km in the mantle beneath the tonga subduction zone this discontinuity is also evident beneath subduction zones in the japan and flores seas the discontinuity probably represents either a change in mantle chemical composition or the signature of the subducted slab s garnet layer

seasonal variations in planktonic foraminiferal flux and oxygen isotopic composition in the western north pacific implications for paleoceanographic reconstruction abstract the oxygen isotopic composition 18o of planktonic foraminiferal shells in seafloor sediment provides information on past surface oceanography knowledge of seasonal and depth habitat as well as the 18o disequilibrium vital effect is essential to constrain the interpretation of sedimentary 18o here we present a 1 year time series of planktonic foraminiferal shell fluxes and 18o from a sediment trap moored in the northwestern margin of the north pacific the vital effect and calcification depth for four species were estimated by comparing shell 18o and the predicted values of equilibrium calcite calculated from temperature and estimated 18o in seawater six major species neogloboquadrina incompta neogloboquadrina dutertrei neogloboquadrina pachyderma globigerina quinqueloba globigerina bulloides and globorotalia scitula constituted 97 of the total foraminiferal flux most major species showed large fluxes in june and december corresponding to periods of the development and disruption of the seasonal thermocline implying the importance of nutrient injection and or circulation for foraminiferal fluxes additional peaks in n dutertrei and n pachyderma were observed in august the seasonal successions of foraminiferal fluxes corresponded to surface ocean stratification conditions and food availability which are closely related to circulation of local currents vital effect estimations suggest that shells calcified in equilibrium for g bulloides and n pachyderma sinistral s and with a 0 7 offset for n dutertrei dextral d a 1 0 offset for n incompta d and a 0 3 offset for n pachyderma d the calculation of flux weighted 18o values reveals that the sedimentary 18o values of g bulloides n dutertrei d and n incompta d reflect surface temperature in winter season and those of n pachyderma s and n pachyderma d reflect summer and annual mean subsurface temperature respectively the shallow calcification depths for the four species suggest that 18o between different species 18o in the western north pacific does not work for reconstructing past stratification conditions unlike in other regions rather the 18o between n pachyderma s and g bulloides n dutertrei d or n incompta d may be a more suitable proxy for past seasonality

seasonal patterns of shell flux δ18o and δ13c of small and large n pachyderma s and g bulloides in the subpolar north atlantic past water column stratification can be assessed through comparison of the delta o 18 of different planktonic foraminiferal species the underlying assumption is that different species form their shells simultaneously but at different depths in the water column we evaluate this assumption using a sediment trap time series of neogloboquadrina pachyderma s and globigerina bulloides from the nw north atlantic we determined fluxes delta o 18 and delta c 13 of shells from two size fractions to assess size related effects on shell chemistry and to better constrain the underlying causes of isotopic differences between foraminifera in deep sea sediments our data indicate that in the subpolar north atlantic differences in the seasonality of the shell flux and not in depth habitat or test size determine the interspecies delta delta o 18 n pachyderma s preferentially forms from early spring to late summer whereas the flux of g bulloides peaks later in the season and is sustained until autumn likewise seasonality influences large and small specimens differently with large shells settling earlier in the season the similarity of the seasonal delta o 18 patterns between the two species indicates that they calcify in an overlapping depth zone close to the surface however their delta c 13 patterns are markedly different 1 parts per thousand both species have a seasonally variable offset from delta c 13 dic that appears to be governed primarily by temperature with larger offsets associated with higher temperatures the variable offset from delta c 13 dic implies that seasonality of the flux affects the fossil delta c 13 signal which has implications for reconstruction of the past oceanic carbon cycle citation jonkers l s van heuven r zahn and f j c peeters 2013 seasonal patterns of shell flux delta o 18 and delta c 13 of small and large n pachyderma s and g bulloides in the subpolar north atlantic paleoceanography 28 164 174 doi 10 1002 palo 20018

deep dwelling planktonic foraminifera of the northeastern pacific ocean reveal environmental control of oxygen and carbon isotopic disequilibria abstract we assess the utility of four species of living planktonic foraminifera as tracers of thermocline and intermediate water masses in the northern pacific ocean based on their water column distribution and shell isotopic composition assuming oxygen isotopic equilibria with the water column we infer apparent calcification depths this allows an estimate of apparent carbon isotopic disequilibria we then relax the assumption of oxygen isotopic equilibrium to examine habitat effects on kinetic disequilibrium processes in the california current left coiling neogloboquadrina pachyderma and globigerina calida calcify in the upper thermocline globorotalia scitula resides within the shallow salinity minumum potential density 25 1 26 7 while globoquadrina hexagona is associated with the deeper north pacific intermediate water 26 7 26 9 apparent carbon isotopic disequilibria corrected for oxygen isotopic disequilibria range from 1 0 1 9 in these asymbiotic species the carbon isotopic disequilibrium can be modeled as a single exponential function of temperature or a logarithmic function of potential food supply we infer that carbon isotopic disequilibrium increases with metabolic rate related to temperature and or food supply kinetic processes of oxygen and carbon isotopic disequilibria yields reasonable depth habitats if the slope of the oxygen carbon isotopic shift is about 0 35 consistent with culture data our finding of a link between environment metabolism and isotopic disequilibrium observed in oceanic settings suggests the potential to better reconstruct the structure and biological processes of the upper water column from geologic data

seismic shear wave reflectivity structure of the mantle beneath northeast china and the northwest pacific 1 using multiple scs reverberations we examine the mantle reflectivity structure beneath northeast china and the northwest pacific we find several upper mantle discontinuities including a melt layer with a mean thickness of 64 km atop the 410 km discontinuity present on both sides of the subducting slab near the nankai trench the transition zone contains a split 520 km discontinuity in several paths and tomographic images show stagnant slabs at this depth we believe that this may be slab related based on experimental work a negative reflector is found in one path beneath the northeast china craton at a depth of 598 km mid mantle reflectors are found in all of our paths and are present throughout a wide depth range 750 1600 km

porothermoelastic effect on wellbore stability in transversely isotropic medium subjected to local thermal non equilibrium abstract provided that the hydraulic boundary conditions at the wellbore wall are identified as permeable pbc and impermeable impbc and that the assumption of plane strain holds the present paper formulates a newly porothermoelastic analytical solution which is based on the thermodynamic principles in laplace space domain for inclined borehole the adopted linear porothermoelastic model embodies the transient heat transfer process in the presence of local thermal non equilibrium ltne during the derivation the solution is available for the cases where the wellbore axis of inclined wellbore is perpendicular to the isotropic plane of the low permeable transversely isotropic porous medium under non hydrostatic stress field condition the wellbore problem is decomposed into axisymmetric and deviatoric loading cases the numerical results of the time dependent distributions of field variables are obtained by virtue of performing the inversion technique for laplace transforms an integrated geomechanical wellbore stability model is proposed which is not only comprised by the abovementioned new porothermoelastic solution but also associated with the theoretical derivations of strength criteria to evaluate the rock to shear failure which include mogi coulomb criterion and single weak plane criterion when a horizontal borehole is drilled along the direction of in the minimum horizontal in situ stress the numerical comparative analyses in the present paper examine the combined influence of material anisotropy and thermal effect which embody in the ltne and local thermal equilibrium lte models on the thermally induced pore pressure stresses and the shear and tensile failure regions around the wellbore

seasonal variability of δ18o and δ13c of planktic foraminifera in the bering sea and central subarctic pacific during 1990 2000 we evaluated a 10 year time series of 18o and 13c records from three planktic foraminifers neogloboquadrina pachyderma globigerina umbilicata and globigerinita glutinata in the bering sea and central subarctic pacific with a focus on their responses to environmental changes foraminiferal 18o followed the equilibrium equation for inorganic calcite with species specific equilibrium offsets ranging from nearly zero 0 02 for n pachyderma and 0 01 for g umbilicata to 0 16 g glutinata equilibrium offsets in our sediment trap samples were smaller than those from plankton tow studies implying that foraminiferal 18o was modified by encrustation during settling habitat calcification depths varied from 35 55 m n pachyderma and g umbilicata or 25 45 m g glutinata during warm stratified seasons to around 100 m during winter when the mixed layer depth increases unlike 18o foraminiferal 13c showed species specific responses to environmental changes we found a dependency of 13c in g umbilicata on co32 concentrations in ambient seawater that agreed reasonably well with published laboratory results suggesting that 13c of g umbilicata is subject to vital effects in contrast 13c of n pachyderma and g glutinata are likely affected by other species specific biological activities seasonal flux patterns reveal that fossil records of n pachyderma and g glutinata represent annual mean conditions whereas that of g umbilicata most likely indicates those of a specific season because none of these three taxa was abundant from december to february their fossil records likely do not reflect isotope signals from cold seasons

δ18o seasonality of planktonic foraminifera from southern ocean sediment traps latitudinal gradients and implications for paleoclimate reconstructions abstract the oxygen isotopic record obtained from globigerina bulloides globorotalia inflata and neogloboquadrina pachyderma s was analysed for 5 sediment traps moored in the southern ocean and southwest pacific the traps extend from subtropical to the polar frontal environments providing the first analysis of seasonal foraminiferal 18 o records from these latitudes comparison between the foraminiferal records and various equations for predicted 18 o of calcite reveals that the predicted 18 o is best captured by the equations of epstein et al 1953 epstein s buchsbaum r lowenstam h a urey h c 1953 revised carbonate water isotopic temperature scale geological society of america bulletin 64 1315 1326 and kim and o neil 1997 kim s t o neil j r 1997 equilibrium and non equilibrium oxygen isotope effects in synthetic carbonates geochimica et cosmochimica acta 61 3461 3475 the epstein equation shows a constant offset from the 18 o of g bulloides and n pachyderma s across the full range of latitudes the seasonal range in 18 o values for these two species implies a near surface habitat across all sites while g inflata most likely dwells at 50 m depth a significant finding in this study was that offsets from predicted 18 o for g bulloides do not correlate to changes in the carbonate ion concentration this suggests that co 3 2 in and of itself may not capture the full range of carbonate chemistry conditions in the marine system this sediment trap deployment also reveals distinct seasonal flux patterns for each species comparison between flux weighted isotopic values calculated from the sediment traps and the isotopic composition of nearby surface sediments indicates that the sedimentary records retain this seasonal imprint at the 51 s site g bulloides has a spring flux peak while n pachyderma s is dominated by summer production the imprint of these differing seasonal production patterns on the flux weighted 18 o values results in more depleted 18 o for n pachyderma s than for g bulloides interpretations of n pachyderma s isotopic composition as a record of subsurface conditions may therefore need to be refined with implications for interpretation of depleted glacial 13 c for this species sigman boyle 2000 sigman d m boyle e a 2000 glacial interglacial variations in atmospheric carbon dioxide nature 407 859 869

oxygen isotope ecology of recent planktic foraminifera at the central walvis ridge se atlantic 1 above the walvis ridge in the se atlantic ocean we collected living plantkic foraminifera from the upper water column using depth stratified plantkon tows the oxygen isotope composition 18oc in shells of foraminifera and shell concentration profiles show seasonal and depth habitats of individual species the tow results are compared with the average annual deposition 18oc from sediment traps and the interannual average 18oc of fossil specimens in top sediments at the same site the species globigerinita glutinata best reflects the austral winter spring sea surface temperature sst its 18oc signal in top sediments remains pristine in contrast tow results also show that globigerinoides ruber continues to calcify below the surface mixed layer sml i e down to the deep chlorophyll maximum dcm hence its 18oc signature of exported specimens reflects the sst only when sml incorporates the dcm deep tow and sediment trap results show that both globorotalia truncatulinoides and globorotalia inflata record the temperature between 150 and 350 m depending on the season and the shell size however for all fossil taxa in sediments apart from globigerinita glutinata we observe a positive 18oc shift with respect to the sediment trap and plankton tow values likely related to the interannual flux changes and deep encrustation

high temperature anomalies oceanward of subducting slabs at the 410 km discontinuity abstract our p wave whole mantle tomography revealed a low velocity region oceanward of the northern honshu slab of the pacific plate at depths around the 410 km seismic discontinuity resolution tests and scrutiny of the traveltime residuals for the ray paths passing through the low velocity region indicate that this anomaly is a resolvable feature and not an artifact due to the strong slab anomalies the existence of the slow anomalies is also supported by the analysis of the p wave records from the j array a large aperture seismic array in japan for a bonin earthquake the p arrivals to northern honshu at epicentral distances of 13 20 are strongly triplicated because of the 410 km discontinuity the later arrivals along the retrograde branch where ray paths pass through the low velocity region are anomalously slow comparison of the observed and synthetic waveforms indicates not only slow anomalies but also depression of the 410 km discontinuity this depression represents the direct evidence for the low velocity zone of primarily thermal origin an excess temperature of 200 k and the associated fractional melt of less than 1 can explain both the results of the tomographic and waveform analyses