return of the coral reef hypothesis basin to shelf partitioning of caco3 and its effect on atmospheric co2 differences in the rate of coral reef carbonate deposition from the pleistocene to the holocene may account for the quaternary variation of atmospheric co sub 2 volumes of carbonate associated with holocene reefs require an average deposition rate of 2 0 times 10 sup 13 mol yr for the past 5 ka in light of combined riverine mid ocean ridge and ground water fluxes of calcium to the oceans of 2 3 times 10 sub 13 mol yr the current flux of calcium carbonate to pelagic sediments must be far below the pleistocene average of 1 2 times 10 sub 13 mol yr the authors suggest that sea level change shifts the locus of carbonate deposition from the deep sea to the shelves as the normal glacial interglacial pattern of deposition of quaternary global carbonates to assess the impact of these changes on atmospheric co sub 2 a simple numerical simulation of the global carbon cycle was developed atmospheric co sub 2 as well as calcite saturation depth and sediment responses to these carbonate deposition changes are examined atmospheric co sub 2 changes close to those observed in the vostok ice core approximately 80 ppm co sub 2 for the quaternary are observed as well as the approximate depth changes in percent carbonate of sediments measured in themore pacific ocean over the same time interval less

the role of caco3 compensation in the glacial to interglacial atmospheric co2 change the only viable explanations put forth to date for the glacial to interglacial change in atmospheric co2 content suggested from measurements of the co2 content of gas extracted from ice cores involve changes in the ocean s nutrient cycles any nutrient change capable of creating the 80 atm changes in atmosphere co2 pressure suggested by the ice core results also creates significant change in the deep ocean s co3 content evidence from deep sea sediments suggests that these co3 changes are compensated on the time scale of a few thousand years by reductions or increases in amount of caco3 accumulating in deep sea sediments this compensation process has two important consequences first it significantly increases the magnitude of the co2 change per unit of nutrient forcing second it causes a delay in the response of the atmospheric co2 change while the first of these consequences is a boon to those seeking to explain the co2 change the second may prove to be a curse the ice core co2 record shows no evidence of a significant lag between the co2 response and the polar warming in any case it is important that we improve our knowledge of the magnitude and timing of the caco3 preservation events which mark the close of episodes of glaciation and of the dissolution events which mark the onset of these episodes

extending the vostok ice core record of palaeoclimate to the penultimate glacial period the ice core record of local temperature dust accumulation and air composition at vostok station antarctica now extends back to the penultimate glacial period 140 200 kyr ago and the end of the preceding interglacial this yields a new glaciological timescale for the whole record which is consistent with ocean records temperatures at vostok appear to have been more uniformly cold in the penultimate glacial period than in the most recent one concentrations of co2 and ch4 correlate well with temperature throughout the record

atmospheric co2 content in the last 120 000 years the phosphate extraction model broecker 1982 has proposed that during the retreat of the wisconsin ice sheets atmospheric co2 increased because of the extraction of phosphorus from the ocean as sea level rose using a time dependent box model we examine the consequences of the phosphate extraction hypothesis over the last 120 000 years assuming that 18o change in core v28 238 is analogous to sea level variation the model takes into account the total co2 and alkalinity balance in the deep sea and in an upper reservoir consisting of the surface ocean and atmosphere which are assumed to be in equilibrium dissolution of deep sea calcium carbonate sediment is assumed to respond to the supply of particulate carbonate from the upper box and to the dissolved carbonate ion concentration of the deep sea assuming 1015 mole of phosphorus and 1017 mole of carbon were extracted during deglaciation the predicted increase in pco2 is 54 ppm variation of pco2 follows the ice volume forcing function with a 1000 yr lag which is the input residence time of water in the deep sea the accumulation supply minus dissolution of caco3 and the percent preservation accumulation over supply follow the derivative of the ice volume function both are similar to the solution index and percent fragments of core v28 238 in addition unusually good preservation is predicted during deglaciation due to carbon extraction if phosphorus but not carbon is assumed to be extracted the accumulation of caco3 varies little remaining near a value equivalent to the river input

invasion of anthropogenic co2 recorded in planktonic foraminifera from the northern gulf of aqaba the stable carbon isotopic composition of the planktonic foraminifera globigerinoides sacculifer and g ruber white and sedimentary organic matter from the northern gulf of aqaba have been investigated to estimate changes in 13cdic in surface waters during the last 1 000 years the high sedimentation rates at the core sites about 54 cm kyear provide high temporal resolution 10 years recent sediments at the top of the cores reflect conditions younger than 1950 the 13c records of the planktonic foraminifera from three multicores display similar trends showing a uniform and consistent pattern before the 1750s and a gradual decrease of approximately 0 63 over the last two centuries this decrease seems to track the decrease of 13cdic in surface waters which is mainly caused by the increase of anthropogenic input of 13c depleted co2 into the atmosphere similarly a trend towards lighter values of the carbon isotopic composition of sedimentary organic matter 13corg during the last 200 years supports the interpretation obtained from the planktonic foraminiferal 13c furthermore direct measurements of seawater show that 13c of the dissolved inorganic carbon dic in the northern gulf of aqaba has decreased by about 0 44 during the period 1979 2000 the average annual decrease is 0 021 which is similar to that observed globally the 13c values of planktonic foraminifera combined with organic matter 13c from marine sediments are good indicators for reconstructing past changes in atmospheric co2 concentrations from the northern gulf of aqaba

caspian sea level from topex poseidon altimetry level now falling tide gauge measurements recorded between 1978 and 1993 indicate that the caspian sea level csl has been rising at an average rate of 12 cm yr during this 15 yr time span decadal csl changes are currently attributed to changes in river runoff and effective evaporation we have analysed three and a half years from january 1993 through august 1996 of altimeter range data from the topex poseidon mission over the caspian sea to estimate temporal variations in the sea level we show that the caspian sea level was still rising at a rate of 18 9 0 5 cm yr between january 1993 and july 1995 and that the northwestern caspian in the area of the volga delta was rising faster by 3 cm yr than the middle and south caspian however by mid 1995 the csl started to drop abruptly a trend still observed in 1996 the average sea level decrease recorded from mid 1995 amounts to 24 8 1 4 cm yr

a 15 000 year paleoenvironmental record from meiji seamount far northwestern pacific late glacial and holocene hemipelagic sediments from meiji seamount in the far northwest pacific contain common to abundant planktonic and benthic foraminifera for ams 14c dating for stable isotope analysis and for interpreting paleoclimate change we present here chronostratigraphic faunal and geochemical results from a piston core which indicate that during glacial times as young as 14 000 yrs bp the northwest pacific sea surface salinity was at least as low as today effectively inhibiting convective overturn between 12 000 and 13 000 yrs ago after a major flux of ice rafting there is faunal and 18o evidence of an abrupt decrease in surface ocean salinity coincident with this event was an increase in biological productivity shown by higher fluxes of calcium carbonate organic carbon opal and greater abundances and lower 13o of the benthic foraminifera uvigerina oxygen isotope ratios in uvigerina and cibicidoides show step like decreases at about 13 000 14 000 11 000 10 000 and 6000 8000 yrs bp these events may be analogous to steps in the north atlantic 18o record during meltwater events if this interpretation is correct then the temperature and salinity history of the deep pacific lags that of the north atlantic by about 1000 yrs consistent with the transport time of deep water from the north atlantic to the north pacific

constraining outermost core velocity with smks waves smks waves m 2 3 4 seismic waves that travel as s waves in the mantle p waves in the core and reflect m 1 times on the underside of the core mantle boundary are well suited for constraining outermost core vp structure this is due to closeness of the mantle paths and also the shallow depth range these waves travel in the outermost core high quality digitized wwssn and canadian network recordings from a deep focus java sea event which sample the outer core beneath the northern pacific the artic and northwestern north america roughly th of the globe are utilized as an example to show the strength of smks waves to resolve outermost core structure s3ks s2ks and s4ks s3ks differential travel times were measured and compared to those from reflectivity synthetics created from core models of past studies constraints and uncertainties in outer core structure using smks are discussed for the event studied the prem core model with possibly a small vp decrease in the outermost 50 km of the core provides a good fit to the data

late pleistocene continental climate and oceanic variability recorded in northwest pacific sediments core v21 146 provides a continuous record of northwest pacific pelagic sedimentation spanning the past 530 000 years downcore variations of 18o from benthic foraminiferal calcite were correlated to the specmap record to provide an age model for late pleistocene paleoclimatic and paleoceanographic variation fluxes of caco3 and eolian material have been determined by combining information about linear sedimentation rates bulk densities and component percentages the mass accumulation rate mar of caco3 varies from 58 to 1435 mg cm kyr 1 and exhibits the pacific ocean pattern of higher accumulation associated with glacial periods for the younger portion of the record however the pattern of caco3 accumulation appears to shift during the mid brunhes so that prior to 350 000 years ago it exhibits an opposite pattern of greater accumulation during interglacial periods the flux of eolian dust is a proxy measure of the source area aridity and correlates well to the loess soil stratigraphy in china dust fluxes range from 43 to 718 mg cm kyr 1 and are greater by a factor of about 4 during glacial times cross spectral analysis of the eolian flux and oxygen isotope records shows an inphase and coherent relationship at each of the major orbital periodicities of 100 41 and 19 kyr eolian grain sizes generally used as a proxy record of wind intensity range from 8 4 2 9 m to 6 2 13 6 m a change in grain size variability occurs near about 300 ka such that the older portion is characterized by lower frequency and higher amplitude fluctuations than the younger portion power spectra for the eolian grain size record show dominant peaks at 100 and 50 kyr and a broad 25 35 kyr peak but coherency to the oxygen isotope curve at only the 100 and 33 kyr periodicities the phase relationship for eccentricity between the eolian grain size and 18o records suggests that at the 100 kyr frequency the smallest grain sizes are associated with glacial conditions

characterization of airborne carbonate over a site near asian dust source regions during spring 2002 and its climatic and environmental significance 1 during spring 2002 three dust storm events were monitored by filter sampling in xi an near an asian dust source region of northwest china the carbonate co32 fraction was determined by sample acidification and thermal evolution the co32 accounted for 8 0 0 8 of particles with aerodynamic diameter 2 5 m pm2 5 during dust storms and 4 7 3 0 of pm2 5 between storms the ratios of calcium to carbonate carbon were consistent with those of calcite caco3 the 13c and 18o abundances in dust storm samples were 2 7 0 7 and 5 8 1 5 which differed from 8 3 1 9 for 13c and 10 8 2 0 for 18o during normal conditions the 13c is positively correlated with 18o values r 0 78 this first measurement of isotopic abundance in asian dust indicates the potential to quantify its contribution at distant locations using receptor models by increasing the alkalinity of ocean water in the pacific ocean and buffering the atmospheric acidity of east asia the large amounts of airborne co32 as high as 44 8 tg yr 1 entrained by asian dust may provide an important atmospheric alkaline carbon reservoir for large scale climatic and environmental changes

a study of the outermost liquid core using differential travel times of the sks skks and s3ks phases abstract differential travel times of sks skks and s3ks seismic phases are analysed to specify the structure of the outermost liquid core which is poorly sampled by the pkp waves currently used for core tomography the data are mainly broadband records at epicentral distances of 83 140 they have been selected to obtain a good global earth coverage skks sks and s3ks skks travel time residuals have been computed with respect to the mean earth model preliminary reference earth model prem and corrected for ellipticity the skks sks residuals plotted as a function of epicentral distance exhibit a general positive slope for distances greater than 105 with mean positive values of approximately 2 s at 120 130 c these features may be accounted for by slight perturbations in prem involving a 2 5 s velocity increase in the d layer at the base of the mantle and a small decrease in the p velocity in the upper 800 km of the liquid core the structure in the uppermost 100 km of the core is mainly constrained by the s3ks data a high velocity gradient followed by a low gradient is obtained immediately beneath the core mantle boundary this may suggest the existence of a thin low velocity layer at the top of the liquid core as a result of a possible accumulation of light elements beneath the core mantle boundary the skks sks residuals exhibit strong coherent regional variations whereas the s3ks skks residual variations remain small this indicates that the lateral heterogeneitics at the core side of the core mantle boundary if any are very small the simultaneous analysis of s3ks sks and skks sks residuals suggests a prevailing contribution of long wavelength heterogeneities in d

late quaternary variations in sea surface temperatures and their relationship to orbital forcing recorded in the southern ocean atlantic sector late quaternary summer sea surface temperatures ssts have been derived from radiolarian assemblages in the east atlantic sector of the southern ocean in the subantarctic and the polar frontal zone glacial ssts oxygen isotope stages 2 4 6 and 8 were 3 5 c cooler than today indicating northward displacements of the isotherms about 2 4 of latitudes during interglacials ssts almost reached modern levels oxygen isotope stages 7 and 9 or exceeded them by 2 3 c oxygen isotope stages 1 and 5 5 in the subantarctic atlantic ocean changes in sst and calcium carbonate content of the sediment precede variations in global ice volume in the range of the main milankovitch frequencies comparisons with the timing of north atlantic deep water nadw proxy records suggests that this early response in the subantarctic atlantic ocean is not triggered by the flux of nadw to the southern ocean

climatic change and caco3 preservation an 800 000 year bathymetric reconstruction from the central equatorial pacific ocean sixteen deep sea cores from the central equatorial pacific are used to reconstruct a continuous 800 000 year 800 kyr record of bathymetric variations in carbonate preservation as measured by calcium carbonate caco3 content the depth of the sedimentary lysocline has fluctuated markedly in conjunction with late pleistocene climate cycles while the carbonate critical depth ccrd which is the water depth where the sediments contain 10 caco3 has remained relatively constant as a result the depth of the lysocline controls the bathymetric position and thickness of the caco3 transition zone defined as the depth from the lysocline to the ccrd modern and interglacial aged sediments show poor caco3 preservation and thick caco3 transition zones glacial aged sediments show good preservation and deep thin zones due to the deepening of the lysocline detailed comparison of the caco3 preservation and oxygen isotope records from the central equatorial pacific confirms the observation that preservation maxima and minima tend to occur during the latter half of glacial and interglacial stages and on climate transitions rather than during the middle of climatic stages during the nine major glacial stages of the last 800 kyr the lysocline deepened by at least 400 to 800 m this deepening indicates an increase in the abyssal carbonate ion concentration co3 and a depression of the calcite saturation horizon best explained by the deeper presence of a more carbonate saturated water mass the bottom of the transition zone has remained at a relatively constant depth during the brunhes chron indicating a balance between caco3 sedimentation and dissolution in the deepest waters of the central equatorial pacific

late pleistocene paleoclimatology of the central equatorial pacific a quantitative record of eolian and carbonate deposition detailed records of vso 6i3c percentage and mass accumulation rate of caco and eolian percentage mass accumulation rate and grainsize generated for core rcl l 210 from the equatorial pacific reveal the timing of paleoclimatic events over the past 950 000 yr the caco percentage record shows the standard pacific correlation of high caco content with glacial periods but displays a marked change of character about 490 000 yr ago with older stages showing much less variability the carbonate mass flux record however does not show such a noticeable change sedimentation rates vary from about 0 5 to 3 0 cm l000 yr and during the past 490 000 yr sections with enhanced sedimentation rates correspond to periods of high caco percentage eolian mass accumulation rates an indication of the aridity of the source region are usually higher during glacial times eolian grainsize an indication of the intensity of atmospheric circulation generally fluctuates at a higher frequency than the loo ooo yr glacial cycle the mid brunhes climatic event centered at 300 000 yr ago appears as a 50 000 yr interval of low intensity and reduced variability of atmospheric circulation furthermore the nature of this entire record changes then with the younger portion indicating less variation in wind intensity than the older part of the record the late matuyama increase in amplitude of paleoclimatic signals begins 875 000 yr ago in the eolian record 25 000 yr before the 6i80 and caco percentage amplitude increases about

the effect of vertical nutrient redistribution on surface ocean δ13c processes that shift nutrients from mid to lower ocean depths may or may not increase the ocean s vertical carbon pump redistribution of 13c produced by these processes is compared in two box models a vertical three box ocean and a thirteen box ocean in the former there is no 13c fractionation laterally between surface waters and the ocean nutrient and 13c distributions are linearly correlated this correlation is not changed when these tracers become redistributed and if the model surface ocean is nutrient limited the surface 13c cannot change in the 13 box ocean there is a transfer of negative 13c from the cold surface water through the atmosphere into the warm ocean its 13c is therefore lower than it would be as a result of the carbon pump by itself if a middepth nutrient depletion occurs because of lower nutrients in antarctic waters the warm surface 13c increases if the vertical nutrient shift occurs because of ocean circulation or biological recycling changes the warm surface water 13c change depends on the ratio of its vertical co2 fluxes i e exchange of atmospheric co2 versus upwelling total co2 and net biological production if this ratio remains about the same then little change occurs in surface 13c and the 13c of pacific deep water decreases about 0 3 in this case no change in the average ocean 13c is required to explain observations from sediment data this would imply that the ice age land biota carbon mass was about the same as that of today the vertical co2 flux ratio could be an important consideration if greater wind driven upwelling is a factor in the nutrient redistribution

the effects of wind forcing and background mean currents on the latitudinal structure of equatorial rossby waves abstract the latitudinal structure of annual equatorial rossby waves in the tropical pacific ocean based on sea surface height ssh and thermocline depth observations is equatorially asymmetric which differs from the structure of the linear waves of classical theory that are often presumed to dominate the variability the nature of this asymmetry is such that the northern ssh maximum along 5 5 n is roughly 2 times that of the southern maximum along 6 5 s in addition the observed westward phase speeds are roughly 0 5 times the predicted speed of 90 cm s 1 and are also asymmetric with the northern phase speeds about 25 faster than the southern phase speeds one hypothesized mechanism for the observed annual equatorial rossby wave amplitude asymmetry is modification of the meridional structure by the asymmetric meridional shears associated with the equatorial current system another hypothesis is the asymmetry of the annually varying wind forcing which is stronger north of the equator a reduced g

lower mantle structure from scs s differential travel times knowledge of the spectrum of structure in the lower mantle is crucial to our understanding of the dynamical evolution of the earth and in principle can be inferred from the analysis of global seismic data sets the long wavelength compressional velocity structure has usually been constrained through tomographic inver sion of the isc catalogue of p wave travel times1 3 whereas shear velocity has been inferred from waveform modelling of long period shear waves4 6 the models that have been produced are similar in only the largest scale features7 and explain little of the variance of the raw data used in their construction thus there is a legitimate concern that the current generation of global scale models give only a crude approximation to the largest scale structure and that there may be significant aliasing of short wavelength heterogeneity here we use scs s differential travel times to demonstrate that the three dimensional structure of the lower mantle is indeed dominated by continental scale features particularly convincing is the fact that the features are apparent in the raw data and are not the product of a complicated modelling procedure

glacial to holocene changes in carbonate and clay sedimentation in the equatorial pacific ocean estimated from thorium 230 profiles uranium series nuclide concentrations have been measured on sediments from five box cores from an equatorial pacific transect 230thexcess activities show discontinuities at the holocene glacial boundary as dated by 14c the glacial sedimentation rates determined by 230th and 14c are 2 5 3 0 cm kyr the holocene rates from 230th are much lower than those dated by 14c 1 9 2 3 cm kyr because of carbonate dissolution 230th sedimentation fluxes exceed water column supply by factors of 1 2 1 8 in the holocene and 1 8 3 0 in the glacial sections a number of models have been applied to calculate carbonate dissolution rates the results show that carbonate dissolution rates in the holocene in g cm kyr equal 1 5 10 3 exp 1 4d where d is water depth in kilometers a point by point estimation of sediment fluxes through time show that clay accumulation rates in the area have been near constant at 0 1 0 2 g cm kyr over the past 20 kyr whereas carbonate accumulation rates have decreased dramatically from 0 6 1 0 g cm kyr in the glacial sections of the cores to 0 2 0 6 g cm kyr in the holocene the errors caused by the uncertainties in the age of the termination of the last glacial period have been investigated and results show that a range of 11 14 kyr leads to an error upper limit of about 30 in the estimation of caco3 dissolution rates the response time of caco3 and 230thex concentrations in the mixed layer of sediments due to an impulse of change in caco3 dissolution rate has also been discussed showing that the observed changes in carbonate dissolution may be explained in terms of a single or a continuous change depending upon the thickness of the mixed layer

multichannel analysis of shear wave splitting a multichannel analysis is introduced to constrain seismic anisotropy from the shear wave splitting of sks and skks this technique utilizes simultaneously a set of records coming from different azimuths the splitting intensity of sks waves measured by the amplitude of the transverse component depends on the angle between the back azimuth of the earthquake and the direction of the symmetry axis and on the delay time t between the two quasi shear waves it is shown that the splitting parameters can be determined from the azimuthal dependence of the splitting intensity which is given by the first right eigenvector of the matrix containing the transverse components of all the records alternatively the splitting intensity can be measured by projecting the transverse components on the radial components derivatives experiments on synthetic seismograms demonstrate that both approaches provide robust estimates of the splitting parameters however the projection approach gives measurements that are closer to the inputs and with smaller error bars which suggests that it should be preferred when the signal to noise ratio is low the new technique is applied to analyze shear wave splitting under stations bcao bangui central african republic and bdfb brasilia brazil the analysis of 75 seismograms recorded by station bcao gives a fast polarization direction in very close agreement with the present day motion direction of the african plate comparisons with the results of previous studies obtained with other techniques and smaller data sets suggest that some of the published measurements may be strongly biased the main limitation of the multichannel analysis is a good azimuthal distribution of the seismicity maps of the azimuthal coverage were determined and it is found that the most favorable regions to study anisotropy with sks waves are a latitudinal band that goes from south america to africa the eastern part of north america and india

cold surface ocean ventilation and its effect on atmospheric co2 the potential for greater air sea exchange rates in the northern atlantic to decrease atmospheric co sub 2 during the ice ages is examined using a simple model of the solubility pump this potential is shown to depend on whether the modern ocean s region of sinking cold water is requilibrating with atmospheric co sub 2 at a rate comparable to the poleward transport of warm surface water if this is the case it is possible that greater ice age polar ventilation may have produced as much as 60 of the decrease observed in ice cores in this scenario the cold surface water co sub 2 partial pressure does not covary with the atmosphere but instead would remain approximately constant 36 refs 8 figs 1 tab

on the late pleistocene ocean geochemistry and circulation a box model of the atmosphere and ocean was developed to investigate how geochemical distributions extant during the late pleistocene may have come about the model simulates the regional distribution of calcium carbonate dissolution as well as the chemical oceanography and atmospheric co2 13c and radiocarbon if the downward biological flux of particulate carbon increases by a factor of 2 to 3 in the antarctic and if this increase is combined with a relative increase of the atlantic sector antarctic bottom water aabw versus north atlantic deep water nadw source ratio from 1 3 to about 2 1 then the model predicts several changes that seem to be recorded in the sedimentary record as follows 1 a global redistribution of nutrients and 12c from the intermediate to deep water takes place with the atlantic intermediate water phosphate decreasing 0 6 mole kg 1 and the 13c increasing 0 3 to 0 5 2 the dissolved oxygen level of the deep sea is reduced from an average of about 180 to 70 mole kg 1 but the intermediate water oxygen declines only a small amount 3 the decrease in intermediate water nutrient concentration results in lower average organic carbon and calcium carbonate production in the warm surface ocean 4 the atmospheric co2 decreases by 90 to 110 ppm 5 initially a global increase in calcium carbonate dissolution occurs which is followed by a relaxation toward better preservation than exists for the present ocean in the model in this paper the reduction of nadw by itself does not produce these effects rather the nutrient decrease that does occur is found mostly in north pacific intermediate water and the model atmospheric co2 decrease is only 10 to 30 ppm it is observed that 92 of the atmospheric co2 change takes place according to a 200 year time constant in the model this corresponds to the response time of the upper ocean and atmosphere to a change in the stationary state atmospheric pco2 thus according to this model the time lag between the nutrient based cause and the atmospheric co2 response is not expected to be particularly large

investigating the base of the mantle using differential travel times abstract several techniques using differential seismic travel times to map lateral structure in the lowermost mantle are discussed results are shown for recent studies involving the established techniques of core reflected phases scs s and pcp p and diffracted phase profiles sdiff and new techniques involving the differential times of both core transmitted and core diffracted phases pkp pdiff and sdiff sks skks are described the recent databases of digital seismograms have allowed for a study of d velocities in the eastern hemisphere using scs s and sscs ss differential times from the many western pacific earthquakes the result is an image at a resolution of a few hundred kilometers of a slow velocity anomaly of 2500 km width beneath micronesia 2 relative to the preliminary reference earth model prem that is surrounded on three sides by fast d rock that is 3 faster than prem a study using the differential arrivals of core diffracted s waves sdiff from digital records is providing information about long wavelength variations in d shear velocities though the rigorous earthquake station geometry requirements limit the study to particular regions of the globe another study is using over 40 000 pcp p differential travel times as reported to the international seismological centre to map global p velocities at the base of the mantle and it shows that global coverage of the core mantle boundary cmb is very poor though there are some regions northern asia northern pacific central america with enough data sampling to allow a quantification of average d p velocities with a total robust range of 4 lateral variation they cover only a small portion of the total cmb as a means of increasing our understanding of the long wavelength variations of seismic velocities a description is given of two techniques that will take advantage of totally different sets of earthquake station geometries from the core reflected phase studies in the distance range from 120 to beyond 165 the differential times of pkp and pdiff can be used to map long wavelength d p velocities these two phases are very different in shape and frequency content so the differential times are found by a waveform cross correlation with reflectivity synthetic counterparts in the distance range from 105 to beyond 135 the differential times of sdiff sks and skks can be examined simultaneously to test models of velocity structure above and below the cmb also through comparison with synthetic counterparts

how well do we utilize global seismicity abstract this article describes a method for quantifying the ability to record teleseismic phases at particular epicentral distance ranges given the geographical history of global seismicity with the use of geographical sampling maps we identify the regions of the earth that are best suited to record the greatest numbers of earthquakes at particular distances since seismic studies of the earth9s interior use teleseismic phases that have unique ranges this information can be useful in the planning of future permanent and temporary deployments of seismometers deployment of ocean bottom seismometers would be required for recording large numbers of earthquakes in the 40 to 80 range corresponding to phases like scs and pcp and in the 140 to 170 range important for investigations of the pkp branches an examination of existing analog and digital networks shows that they do either better or worse than a hypothetical grid of evenly spaced seismometers depending upon the distance range examined the use of temporary deployments of seismometers perhaps even in the oceans may be the best way to significantly sample poorly examined regions of the earth9s interior

late quaternary caco3 stratigraphy of the eastern equatorial pacific four patterns of caco3 abundance occur in cores retrieved from the eastern equatorial pacific during the venture 01 expedition core locations lie along a north south transect at 110 w underneath the different currents of the equatorial current system and along an east west transect from 110 to 90 w at approximately 3 s underneath the south equatorial current the classic or central equatorial pacific pattern of caco3 abundance maxima associated with glacial stages as defined by the 18o record characterizes only a small portion of the area studied in the area where the peru current turns west to join the south equatorial current the carbonate record is characterized by a broad low centered on interglacial carbonate stage b 3 approximately stage 5 in 18o stratigraphy overlying a broad mid brunhes maximum low amplitude variations in caco3 percentages are superimposed on this pattern this pattern extends westward in a long wavelength pattern in which the b 3 carbonate low becomes decreasingly pronounced away from the equator the fourth pattern observed north of 10 n is erratic and may be only local in extent

extraterrestrial 3 he as a tracer of marine sediment transport and accumulation the deposition rate of deep sea sediments and their focused redeposition by deep sea currents can be evaluated from analyses of sedimentary 230th with a temporal resolution limited only by bioturbation6 7 10 11 230th is produced uniformly throughout the ocean by radioactive decay of dissolved 234u and is removed sufficiently fast by sorption onto sinking particles to act as a constant flux tracer of sedimentation rates but the half life of 230th 75 kyr limits its use for this purpose to the past 200 250 kyr here we explore the use of extraterrestrial 3he from interplanetary dust particles1 4 idps as a constant flux proxy that is free from this limitation a comparison of 3he with 230th in two cores from the equatorial pacific ocean indicates that the variability in the mean flux of idps over the past 200 kyr is less than 75 but in contrast to this relatively constant rate of supply of 3he to the deep sea the local burial rates of 3he and 230th have varied by a factor of five over the past 450 and 200 kyr respect ively we interpret this variability as reflecting sediment focusing with a temporal pattern that suggests regular cycles of climate driven reorganization of near bottom currents in the deep pacific ocean

the calcite lysocline as a constraint on glacial interglacial low latitude production changes we investigate the response of the calcite lysocline to changes in the export production of the low latitude surface ocean the combined equatorial tropical and subtropical regions we employ different caco3 throughput schemes in a time dependent ocean carbon cycle model to separate the caco3 production lysocline balance from the other components of the model response and to estimate the effect of dissolution driven by organic matter decomposition in surface sediments with this model we carry out three experiments based on previous hypotheses for the cause of glacial interglacial atmospheric co2 variations 1 a simple increase in low latitude production 2 a decrease in its caco3 organic carbon rain ratio and 3 an increase in the depth of organic carbon regeneration none of these changes when taken alone can lower atmospheric co2 to glacial levels without violating observations of the glacial lysocline depth if a low latitude production increase were accompanied by a decrease in the caco3 organic carbon rain ratio then these simultaneous changes could lower atmospheric co2 to observed glacial levels without causing a significant change in the ocean average depth of the lysocline however even with these simultaneous changes the required increase in production is 50 or more of the modern rate of production

from oxisols to spodosols and histosols evolution of the soil mantles in the rio negro basin amazonia abstract the upper rio negro basin under a constantly humid equatorial climate is a low altitude peneplain of more than 165 000 km 2 prevailing soils are oxisols and spodosols and their distribution is usually related to the lithology of the parent materials spodosols being generally associated with sandy deposits after exploratory surveys in this extensive region six major soil geomorphic units have been identified in which selected toposequences have been studied by means of micromorphological chemical and mineralogical analyses detailed field analysis of the horizonation of the soil mantle has been carried out in three sequences consisting of oxisols ultisols and spodosols results show that sharp transitions within distances of less than one hundred meters separate the oxisols from the spodosols however the arrangement of the horizons in the soil mantle and similarities in micromorphological features chemical composition and mineral components between the adjacent horizons are evidences that genetic relationships link contiguous profiles the authors propose an alternative explanation for this soil distribution based on the lateral transformation of oxisols and ultisols into spodosols and on the lateral evolution of the giant spodosols into histosols peat and waterlogged ultisols interpretative models of landscape evolution as consequence of soil evolution are thus proposed

characterization of complex fluvial systems using remote sensing of spatial and temporal water level variations in the amazon congo and brahmaputra rivers the surface water and ocean topography swot satellite mission will provide global space based estimates of water elevation its temporal change and its spatial slope in fluvial environments as well as across lakes reservoirs wetlands and floodplains this paper illustrates the utility of existing remote sensing measurements of water temporal changes and spatial slope to characterize two complex fluvial environments first repeat pass interferometric sar measurements from the japanese earth resources satellite are used to compare and contrast floodplain processes in the amazon and congo river basins measurements of temporal water level changes over the two areas reveal clearly different hydraulic processes at work the amazon is highly interconnected by floodplain channels resulting in complex flow patterns in contrast the congo does not show similar floodplain channels and the flow patterns are not well defined and have diffuse boundaries during inundation the amazon floodplain often shows sharp hydraulic changes across floodplain channels the congo however does not show similar sharp changes during either infilling or evacuation second shuttle radar topography mission measurements of water elevation are used to derive water slope over the braided brahmaputra river system in combination with in situ bathymetry measurements water elevation and slope allow one to calculate discharge estimates within 2 3 accuracy these two studies illustrate the utility of satellite based measurements of water elevation for characterizing complex fluvial environments and highlight the potential of swot measurements for fluvial hydrology copyright 2010 john wiley sons ltd

a 135 000 year vostok specmap common temporal framework the object of the present study is to introduce a means of comparing the vostok and marine chronologies our strategy has been to use the 18o of atmospheric o2 denoted 18oatm from the vostok ice core as a proxy for the 18o of seawater denoted 18osw our underlying premise in using 18oatm as a proxy for 18osw is that past variations in 18osw an indicator of continental ice volume have been transmitted to the atmospheric o2 reservoir by photosynthesizing organisms in the surface waters of the world s oceans we compare our record of 18oatm to the 18osw record which has been developed from studies of the isotopic composition of biogenic calcite 18oforam in deep sea cores we have tied our 18oatm record from vostok to the specmap timescale throughout the last 135 kyr by correlating 18oatm with a 18osw record from v19 30 results of the correlation indicate that 77 of the variance is shared between these two records we observed differences between the 18oatm and the 18osw records during the coldest periods which indicate that there have been subtle changes in the factors which regulate 18oatm other than 18osw our use of 18oatm as a proxy for 18osw must therefore be considered tentative especially during these periods by correlating 18oatm with 18osw we provide a common temporal framework for comparing phase relationships between atmospheric records from ice cores and oceanographic records constructed from deep sea cores our correlated age depth relation for the vostok core should not be considered an absolute vostok timescale we consider it to be the preferred timescale for comparing vostok climate records with marine climate records which have been placed on the specmap timescale we have examined the fidelity of this common temporal framework by comparing sea surface temperature sst records from sediment cores with an antarctic temperature record from the vostok ice core we have demonstrated that when the southern ocean sst and antarctic temperature records are compared on this common temporal framework they show a high degree of similarity we interpret this result as supporting our use of the common temporal framework for comparing other climate records from the vostok ice core with any climate record that has been correlated into the specmap chronology

ocean circulation and atmospheric co2 changes coupled use of models and paleoceanographic data we have perturbed a simple model of oceanic circulation in a series of sensitivity tests to determine how circulation changes associated with the last glacial maximum could affect observable or potentially observable paleoceanographic parameters ultimately we want to use such paleoceanographic data to construct models of glacial ocean circulation we have found that the different circulation patterns that we imposed in our sensitivity tests have dramatically different responses for the distribution of po4 o2 and 13c contents of the oceans they also produce different levels of low latitude productivity by comparing the coupled responses of several of these paleoceanographic parameters to the responses from the sensitivity tests it is possible to constrain the possible glacial circulation scenarios to a relatively small number we give as one example a case where intermediate turnover is significantly higher than the present and deep ocean turnover has dropped in addition exchange of waters between the intermediate and high latitude surface ocean is much lower the result of this scenario is an atmosphere with 60 ppm lower atmospheric co2 low latitudes with about 40 higher productivity and a change in the planktic benthic 13c contrast of about 0 3 when we compare our model to other independent paleoceanographic data we find that the major point of disagreement is in the distribution of surface water 13c in the antarctic region we believe that somewhat more complex box models which take open system effects into account will resolve this discrepancy

chemical accumulation variations under the peru current during the past 130 000 years the titanium to aluminum ratio in core v19 29 is correlated with aluminosilicate accumulation rates this correlation may be due to pleistocene eolian transport fluctuations which alter the mean grain size of sedimented eolian material the relation between aluminum accumulation rate and ti al established from accumulation rates integrated over 11 000 50 000 year intervals can be inverted to compute a high resolution record of aluminosilicate and calcium carbonate accumulation rates over the past 130 000 years carbonate accumulation rates are closely related to the oxygen isotope record in the core with a phase lag and damping constant that is compatible with the response time shown to be only 6000 years of calcium carbonate in the ocean carbonate sedimentation at this site responds to several processes independently correlated with climatic change the relative importance of these processes for carbonate sedimentation at this site can be constrained by the record in this core and other lines of evidence 15 of the increased carbonate deposition at this site during glacial periods may be due to diminished nadw north atlantic deep water formation 10 is due to carbonate productivity decreases in the north atlantic 25 may be due to a diminished shallow sea carbonate sink and the residual 50 must be due to a local productivity increase these assignments are consistent with observations on carbonate paleoceanography in the north atlantic aluminosilicate accumulation rate variations correlate with the record of eolian quartz deposition near northwest africa and in a general way with the climatic record but in detail the record differs substantially from the oxygen isotope record and may provide independent evidence on the nature of climate dynamics

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

the imprint of anthropogenic co2 in the arctic ocean evidence from planktic δ13c data from watercolumn and sediment surfaces 13c values of n pachyderma sin from the water column and from core top sediments are compared in order to determine the 13c decrease caused by the addition of anthropogenic co2 to the atmosphere this effect which is referred to as the surface ocean suess effect is estimated to be about 0 9 0 2 within the arctic ocean halocline waters and to about 0 6 0 1 in the atlantic derived waters of the southern nansen basin this means that the area where the arctic ocean halocline waters are formed the arctic shelf regions are relatively well ventilated with respect to co2 nevertheless 13c of dissolved inorganic carbon 13cdic in the arctic ocean halocline waters is far from isotopic equilibrium absolute values of 13c of n pachyderma sin covary with the surface ocean suess effect and we interprete changes in both parameters as a reflection of the degree of ventilation of the waters on the shelf sea measurements of 13c of n pachyderma sin in the arctic ocean from plankton tows reveal a vital effect of about 2 significantly different from other published values a first order estimate of the total anthropogenic carbon inventory shows that despite of its permanent sea ice cover the arctic ocean with 2 of the global ocean area is responsible for about 4 6 of the global ocean s co2 uptake

paleoclimatic significance of eolian carbonates supplied to the japan sea during the last glacial maximum laminated sediments deposited under anoxic bottom waters in the japan sea during the last glacial maximum lgm contain extremely well preserved calcareous microfossils and eolian carbonates the radiocarbon age difference between bulk sediment and monospecific planktonic foraminifera in discrete laminae from a core in the southern japan sea implies that 40 of the total carbonates in the sediments at the lgm are of eolian origin extrapolation of this result yields a rate of supply of eolian carbonates of 2800 tons d 1 to the entire japan sea during the lgm the climatic significance of this flux potentially lies in its broader geographic extension particularly in the interaction of the carbonate bearing dust with shallow corrosive north pacific waters and with rain in the atmosphere by increasing the alkalinity of such waters and by enhancing the biological pump the dust flux could have increased co2 absorption by both the ocean and rain during the lgm

production and accumulation of calcium carbonate in the ocean budget of a nonsteady state present day production of caco3 in tne world ocean is calculated to be about 5 billion tons bt per year of which about 3 bt accumulate in sediments the other 40 is dissolved nearly half of the carbonate sediment accumulates on reefs banks and tropical shelves and consists largely of metastable aragonite and magnesian calcite deep sea carbonates predominantly calcitic coccoliths and planktonic foraminifera have orders of magnitude lower productivity and accumulation rates than shallow water carbonates but they cover orders of magnitude larger basin area twice as much calcium is removed from the oceans by present day carbonate accumulation as is estimated to be brought in by rivers and hydrothermal activity 1 6 bt suggesting that outputs have been overestimated or inputs underestimated that one or more other inputs have not been identified and or that the oceans are not presently in steady state one missing calcium source might be groundwater although its present day input is probably much smaller than that of rivers if as seems likely caco3 accumulation presently exceeds terrestial and hydrothermal input this imbalance presumably is offset by decreased accumulation and increased input during lowered sea level shallow water accumulation decreases by an order of magnitude with a 100 m drop in sea level while groundwater influx increases because of heightened piezometric head and the diagenesis of metastable aragonite and magnesian calcite from subaerially exposed shallow water carbonates

reconstructing past particle fluxes in the tropical atlantic ocean using a research strategy analogous to modern sediment trap studies sediment accumulation patterns on submarine rises can be interpreted in terms of past ocean chemistry and circulation we have followed this research strategy to reconstruct the history of surface water productivity and deep water chemistry and circulation in the eastern equatorial atlantic sierra leone rise and western equatorial atlantic ceara rise during the last glacial maximum 18 000 b p on shallow sections of these rises at depths with little carbonate particle degradation we assume that the accumulation of skeletal carbonate approximates the carbonate production rate in surface water during the last glacial maximum the rate of carbonate productivity was lower in the eastern atlantic than it is today while the western atlantic exhibited no glacial interglacial difference in carbonate productivity based on the difference in carbonate accumulation rates between shallow and deep cores on the rises we observed greater dissolution in both basins during the last glaciation the eastern atlantic always had a lower rate of dissolution than the western atlantic despite having deep water with a lower 13c during the last glacial maximum organic carbon accumulation in the eastern atlantic increased with depth in the water column during the last glaciation suggesting that there was a bathymetric decrease in dissolved oxygen concentration at that time these observations are consistent with a glacial decrease in the production rate of northern source deep water during the last glaciation at that time the mixing zone between northern source and southern source deep water migrated to the north in the atlantic resulting in a greater proportion of corrosive southern source deep water in the western atlantic and entering the eastern atlantic through low latitude fracture zones today the ratio of northern and southern components entering the eastern atlantic is about 4 1 based on 13c and carbonate accumulation our best estimate of this ratio during the last glaciation is 1 1

the structure of the core mantle boundary from diffracted waves diffracted p and s waves pd sd traveling around the core mantle boundary cmb of the earth give us information about the velocity structure and therefore the thermochemistry of d the base of the earth s mantle by examining pd and sdarrivals we determined the apparent ray parameter for different regions at the base of the mantle by comparing the data slownesses to those found from reflectivity synthetic seismograms we were able to quantify d average velocities using these averaged velocities with a thermochemical modeling of lower mantle minerals using a birch mumaghan equation of state we have been able to make chemical and physical inferences as to the causes of lateral variations at the cmb examinations found significant lateral heterogeneity at the base of the mantle amounting to 4 for both p and s velocities these velocities did not always vary in parallel and the poisson ratio varied regionally by almost 6 the most unusual region of the cmb found was under indonesia where velocities 3 slower than the preliminary reference earth models were found adjacent to a region of faster than average velocities these regions currently correspond to areas of core up welling and down welling respectively found by voorhies 1986 which if mostly held in place by core mantle coupling might cause a flux of heat and iron into the mantle making the anomaly both thermally and chemically derived at the cmb under the northern pacific rim the fastest shear velocities were found but the same region yielded slower than average p velocities while the presence of fast shear velocities here would support the idea that we are seeing the cold dregs of mantle convection perhaps continuing down from the north pacific subduction zones the presence of slow p velocities suggests additional complications our thermochemical modeling suggests that the d poisson ratio is very sensitive to variations in the silicate oxide ratio and that a decrease in the amount of perovskite relative to magnesiowustite may play an important role in this region

modeling the response of the oceanic si inventory to perturbation and consequences for atmospheric co2 1 it has been suggested that much of the observed glacial interglacial variability in the atmospheric mixing ratio of co2 xco2 could potentially be driven by a perturbation of the marine si cycle to date only relatively simple steady state analysis has been made of this hypothesis in this study we develop a description of the ocean carbon cycle incorporating novel descriptions for the recycling of si both within the water column and in deep sea sediments a high degree of computational efficiency enables model integrations over multiple glacial interglacial cycles driven by a time varying input of dissolved si to the ocean due to the long time constant 23 ka of atmospheric xco2 response to perturbation in si supply and the highly nonlinear nature of opal preservation in deep sea sediments we find that reduction in the deposition rate of aeolian silicates at the surface ocean can explain little 3 ppm of the rapid 90 ppm rise in atmospheric xco2 observed at glacial termination however increased si supply has the potential to make an important contribution to the decline in atmospheric xco2 associated with the much slower transition from interglacial to full glacial conditions

the δ13c of equatorial atlantic surface waters implications for ice age pco2 levels carbon isotopic records of nutrient depleted surface water place constraints on the past fertility of the oceans and on past atmospheric pco2 levels the best records of nutrient depleted 13c are obtained from planktonic foraminifera living in the thick mixed layers of the western equatorial and tropical atlantic ocean we have produced a composite stacked globigerinoides sacculifer 13c record from the equatorial atlantic which exhibits significant spectral power at the 100 000 and 41 000 year milankovitch periods but no power at the 23 000 year period similar to the record presented by shackleton and pisias 1985 surface deep ocean 13c produced with the g sacculifer record leads the 18o ice volume record however the glacial interglacial amplitudes of 13c differ between our record and shackleton and pisias 1985 record although large changes in 13c occur in the equatorial atlantic during early stages of the last three glacial cycles surface deep 13c at glacial maxima 18o stage 2 late stage 6 and late stage 8 was only about 0 2 greater than during the subsequent interglacial our results imply that nutrient driven pco2 changes account for about one third of the pco2 decrease observed in ice cores and consequently 13c should not be used as a proxy pco2 index enough variance in the ice core pco2 records remains to be explained that conclusions about pco2 and ice volume phase relationships should also be reexamined as much as 40 ppm pco2 change still has not been accounted for by models of past physics and chemistry of the ocean

modeling the calcite lysocline a numerical model of calcite dissolution in contact with sediment pore water is used to predict the depth and shape of the calcite lysocline in the deep sea model results are compared with lysocline data from 13 regions in the atlantic pacific and indian oceans the model lysocline shape is sensitive to the calcite dissolution rate constant the calcite organic carbon and refractory material rain rates and the rates of oxic versus anoxic organic carbon degradation in the sediment the model is able to reproduce the observed lysocline within the constraints of the sediment trap and calcite accumulation data using a calcite dissolution rate constant of 30 100 d 1 a molar ratio of organic carbon to calcite rain rates of 0 5 1 0 and an initial caco3 fraction of 90 excluding organic carbon this rate constant is consistent with microelectrode results presented by archer et al 1989 the model predicts that 30 50 of the calcite rain to the sea floor at the saturation horizon dissolves in response to organic carbon respiration consistent with previous modeling studies the range in the best fit value of the organic inorganic carbon rain rates arises from model sensitivity to uncertainty in the rate of anoxic carbon degradation in the sediment and in the rain rate of refractory material rather than from scatter in the data lysocline data from the western equatorial atlantic are anomalous to the rest of the data this anomaly may be explained by high rates of refractory material sedimentation from the amazon river

the evolution of deep ocean chemistry and respired carbon in the eastern equatorial pacific over the last deglaciation the authors acknowledge funding by the spanish ministry of economy industry and competitiveness through grants ctm2009 08849 acdc project and ctm2012 32017 manifest project by generalitat de catalunya through grant 2014sgr1029 marine biogeochemistry and global change research group and by nerc grant ne l006421 1 isabel cacho thanks the icrea academia program from the generalitat de catalunya

surface water dynamics in the amazon basin application of satellite radar altimetry 1 satellite radar altimetry has the ability to monitor variations in surface water height stage for large wetlands rivers and associated floodplains a clear advantage is the provision of data where traditional gauges are absent as part of an international program a complete altimetric analysis of the amazon basin is being undertaken here an updated and more rigorous evaluation of the topex poseidon t p data set is presented for the first 7 5 years of the mission with an initial study group of 230 targets height variability at many ungauged locations can be observed for 30 50 the range reflecting the clarity of the variations in lieu of instrument limitations an assessment of the instrument performance confirms that the minimum river width attainable is 1 km in the presence of some inundated floodplain this constraint does allow observation of the main stem solimoes amazon and the larger tributaries but rugged terrain in the vicinity of the target additionally places severe limitations on data retrieval first order validation exercises with the deduced 1992 1999 time series of stage fluctuations reveal accuracies ranging from tens of centimeters to several meters mean 1 1 m rms altimetric water levels in the solimoes and amazon are particularly well defined with amplitudes 13 m and variations in peak level timing from may to july the water surface gradient of the main stem is found to vary both spatially and temporally with values ranging from 1 5 cm km downstream to 4 0 cm km for more upstream reaches in agreement with ground based estimates the seasonal variability of the gradients reveals that the hysteresis characteristic of the flood wave varies along the main stem and the derived altimetric velocity of this flood wave is estimated to be 0 35 m s overall the altimetric results demonstrate that the t p mission is successfully monitoring the transient flood waves of this continental scale river basin

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

the role of vertical chemical fractionation in controlling late quaternary atmospheric carbon dioxide the 30 decrease in atmospheric carbon dioxide during glacial maxima must be driven by some change in the chemical circulation of the ocean here a new model for late quaternary co2 variability is presented which resolves some problems occurring in previous models including the timing of carbon dioxide response and changes in the oxygen content of the deep ocean the primary driving factor in this model is a rearrangement of chemical distributions in the ocean whereby labile nutrients and metabolic co2 are concentrated in deep waters rather than in intermediate waters as observed in the modern ocean this new bottom heavy chemical structure does not affect atmospheric carbon dioxide directly instead co2 induced acidity lowers the deep ocean carbonate ion concentration and temporarily increases carbonate dissolution rates oceanic alkalinity then rises until the deep ocean carbonate ion is restored to its steady state value the resulting increase in oceanic alkalinity draws co2 out of the atmosphere into the ocean alkalinity and atmospheric co2 lag several thousand years behind the change in oceanic chemical structure this delayed response is determined by the limited rate of continental weathering and deep ocean carbonate dissolution relative to the oceanic alkalinity inventory it is proposed that characteristic deglacial and preglacial states of the ocean are leading factors driving glacial interglacial climate changes this concept reinterprets the carbon isotope contrast between surface water and deep waters 13c p b as due to a shift of light metabolic carbon from intermediate waters into deep waters the process is illustrated here by a simple equilibrium five box ocean model the observed intermediate depth nutrient depletion is not sufficient in itself to determine which of several possible mechanisms are operating and some mechanisms are not as effective in changing atmospheric co2 as others the largest response is seen from deepening the regeneration cycle of organic carbon the least response is seen from converting north atlantic deep water into intermediate water

the role of ocean atmosphere reorganizations in glacial cycles abstract a case is made that glacial to interglacial transitions involve major reorganizations of the ocean atmosphere system such reorganizations constitute jumps between stable modes of operation which cause changes in the greenhouse gas content and albedo of the atmosphere only in this way can the rapidity of glacial terminations the hemispheric synchroneity and symmetry of mountain glaciation and the large polar air temperature and dustiness variations be accounted for if these reorganizations are driven in some fashion by orbitally induced seasonal insolation changes then the connection between insolation and climate is most likely through impacts of fresh water transport on the ocean s salinity distribution

seismic anisotropy beneath stable continental interiors a robust knowledge of seismic anisotropy beneath the continents is essential to our understanding of plate tectonic theory as anisotropy provides a unique constraint on the character of past and present deformation in the lithosphere and sublithospheric mantle this review paper summarizes the range of techniques currently available to image seismic anisotropy with passive source seismic data and addresses current issues surrounding the observation and interpretation of continental seismic anisotropy to this end we present case studies for four regions where seismic anisotropy has been extensively investigated in recent years eastern north america the canadian shield australia and southern africa based on this full suite of results we infer that stable continental regions generally contain seismic anisotropy that is clearly located within both the lithosphere and the sublithospheric mantle usually to depths of at least 200 km and perhaps more an implication of these results is that tectonic plates are at most only partially coupled to the underlying mantle the results from these case studies also demonstrate that while remarkable progress in seismic anisotropy imaging has been achieved in recent years it is clear that much more work will be required to adequately understand the origin of continental seismic anisotropy we suggest that a more robust characterization of anisotropic parameters can only be achieved by integrating complementary seismic datasets and by incorporating constraints from key related datasets from mineral physics magnetotellurics gravity and geodesy

is there a component of pleistocene co2 change associated with carbonate dissolution cycles the only processes which could have decreased atmospheric co2 during glacial climates without appreciably changing the carbon isotope distribution in the sea appear to be 1 dissolved calcium carbonate input to the ocean e g coral reef buildup and erosion 2 the ocean solubility pump due to changes in surface temperature or air sea exchange or 3 decreased biological production of calcium carbonate it is assumed here that one of these mechanisms caused part of the atmospheric co2 changes recorded in the 200 kyr long vostok ice core two residual co2 records are generated by scaling the 13c difference between planktonic and benthic foraminifera in marine sediment cores to 82 ppm co2 per 1 increase in 13c and subtracting from this the measured co2 concentration in the ice core both residual co2 records exhibit two broad maximums between about 20 50 ka and 140 200 ka indicating that during these times about 40 ppm of the co2 decrease from interglacial levels cannot be explained by the interaction of the ocean s biological and vertical mixing cycles the shape of the residual co2 curve is similar qualitatively to the variation of calcium carbonate in central equatorial pacific sediments during this time period which would imply that changes in dissolved carbonate input to the ocean contributed the added component of co2 change however recent models of atmospheric co2 change in response to changing alkaline input to the ocean exhibit about a 25 to 35 ppm decrease per 1013 mol yr 1 increase in dissolved caco3 input if compensation for the changing input is occurring mostly within an area of about 40 106 km below the lysocline in the indo pacific the change in carbonate accumulation rate corresponding to a 40 ppm co2 change would be a minimum of 3 mg cm 2 yr 1 this can be compared to glacial increases of 0 5 to 1 0 mg cm 2 yr 1 during the last 200 kyr in central equatorial pacific sediments thus the added glacial accumulation of carbonate does not seem to match quantitatively with the 40 ppm amplitude of the residual co2 signal leading one to suspect that solubility plays a greater role than expected on the basis of a 2 c cooler surface ocean

carbonate variations in the northeast pacific during the late quaternary quaternary glacial interglacial changes in the carbonate compensation depth ccd have been determined from core suites in three regions of the ne pacific the cores have sedimentation rates ranging from 1 6 to 16 cm kyr based on oxygen isotope radiocarbon and or carbonate stratigraphies carbonate values are higher in glacial than interglacial times and generally follow a pattern similar to that of the central equatorial pacific the sediment s carbonate profiles can be readily intercorrelated allowing the construction of a regional carbonate stratigraphy the extent of carbonate preservation is very sensitive to small changes in water depth but does not depend on geographic location a depth transect of cores off northern california and oregon provides a detailed record of glacial interglacial shifts in the ccd through time during the late holocene intensified carbonate dissolution at 7 ka is coincident with shifts in continental climatic indicators and may suggest the onset of the modern upwelling regime along the nw u s margin during the last 45 ka the ccd has migrated more than 1800 m between glacial and interglacial times although carbonate patterns are similar to those in the equatorial pacific the amplitude of the carbonate fluctuations is much greater in the northeast pacific this suggests that regional mechanisms such as glacial deepwater formation or enhanced dissolution due to interglacial noncarbonate productivity related to coastal upwelling may modulate carbon cycling

equatorial pacific calcite preservation cycles production or dissolution in the equatorial pacific ocean the depth and shape of the calcite lysocline appears to have changed significantly in response to climate forcing farrell and prell 1989 taking the farrell and prell record at face value the lysocline apparently became steeper during each of the last eight glacial stages also the accumulation rate of calcite during the last glacial maximum was 2 4 times higher than it was during the previous interglacial arrhenius 1952 1988 broecker 1971 farrell 1991 a numerical model for calcite dissolution in sediment is used to interpret these observations the model was validated by comparison with observations from the present day ocean these results are presented elsewhere if the lysocline fluctuations in the equatorial pacific are primarily a dissolution record then changes in the glacial pacific co3 of 20 40 m can be inferred here i offer the alternative explanation that cycles in equatorial production are responsible for the observations higher rates of calcite and organic carbon rain to the sediment in the equatorial region would have depressed the calcite lysocline and increased the calcite accumulation rate as observed a twofold increase in glacial production appears to be adequate to explain the observations but a precise determination is prevented by uncertainties in some of the model parameters

field test of an inexpensive small broadband ocean bottom seismograph we conducted tests of a three component broadband ocean bottom seismograph obs including side by side comparisons with the broadband global seismic network u s national seismic network station hkt at hockley texas and a 28 day deployment in the gulf of mexico our goals were to evaluate seismometer performance and determine whether our seafloor deployment strategy allows useful earthquake data to be collected the seismometer generally performed well but showed unexpectedly high intrinsic noise at frequencies above 1 hz and produced occasional spikes that were confined to a single component at a given time we identified 32 earthquakes from the gulf of mexico data only five additional events were observed at the nearby highly sensitive station hkt on land while noise levels were higher throughout the 0 01 20 hz frequency band in the gulf of mexico compared with hkt site amplification effects in the gulf were only significant at frequencies above 1 hz and power in most earthquake signals peaked at frequencies below 0 1 hz nearly coinciding with a minimum in background noise we found the seismometer and obs package encouraging for far regional and teleseismic studies given the low cost of the obs and inexpensive means for deployment and recovery but less encouraging for detecting and locating small magnitude local and near regional events manuscript received 23 october 2001

estimating reach averaged discharge for the river severn from measurements of river water surface elevation and slope summary an algorithm is presented that calculates a best estimate of river bathymetry roughness coefficient and discharge based on input measurements of river water surface elevation h and slope s using the metropolis algorithm in a bayesian markov chain monte carlo scheme providing an inverse solution to the diffusive approximation to the shallow water equations this algorithm has potential application to river h and s measurements from the forthcoming surface water and ocean topography swot satellite mission the algorithm was tested using in situ data as a proxy for satellite measurements along a 22 4 km reach of the river severn uk first the algorithm was run with gage measurements of h and s during a small in bank event in june 2007 second the algorithm was run with measurements of h and s estimated from four remote sensing images during a major out of bank flood event in july 2007 river width was assumed to be known for both events algorithm derived estimates of river bathymetry were validated using in situ measurements and estimates of roughness coefficient were compared to those used in an operational hydraulic model algorithm derived estimates of river discharge were evaluated using gaged discharge for the in bank event when lateral inflows from smaller tributaries were assumed to be known the method provided an accurate discharge estimate 10 rmse when lateral inflows were assumed unknown discharge rmse increased to 36 finally if just one of the three river reaches was assumed to be have known bathymetry solutions for bathymetry roughness and discharge for all three reaches were accurately retrieved with a corresponding discharge rmse of 15 6 for the out of bank flood event the lateral inflows were unknown and the final discharge rmse was 19 these results suggest that it should be possible to estimate river discharge via swot observations of river water surface elevation slope and width

changes in the distribution of δ13c of deep water σco2 between the last glaciation and the holocene carbon isotopic measurements on the benthic foraminiferal genus cibicidoides document that mean deep ocean 13c values were 0 46 lower during the last glacial maximum than during the late holocene the geographic distribution of 13c was altered by changes in the production rate of nutrient depleted deep water in the north atlantic during the late holocene north atlantic deep water with high 13c values and low nutrient values can be found throughout the atlantic ocean and its effects can be traced into the southern ocean where it mixes with recirculated pacific deep water during the glaciation decreased production of north atlantic deep water allowed southern ocean deep water to penetrate farther into the north atlantic and across low latitude fracture zones into the eastern atlantic mean southern ocean 13c values during the glaciation are lower than both north atlantic and pacific 13c values suggesting that production of nutrient depleted water occurred in both oceans during the glaciation enriched 13c values in shallow cores within the atlantic ocean indicate the existence of a nutrient depleted water mass above 2000 m in this ocean

tomographic filtering of geodynamic models implications for model interpretation and large scale mantle structure 1 the resolution operator r is a critical accompaniment to tomographic models of the mantle r facilitates the comparison between conceptual three dimensional velocity models and tomographic models because it can filter these theoretical models to the spatial resolution of the tomographic model we compute r for the tomographic model s20rts ritsema et al 1999 2004 and two companion models that are based on the same data but derived with different norm damping values the three models explain within measurement uncertainty s sks and s skks travel times equally well to demonstrate how artifacts distort tomographic images and complicate model interpretation we apply r to 1 a thermochemical and 2 an isochemical model of convection in the mantle that feature different patterns of shear velocity heterogeneity in the deep mantle if we assume that shear velocity heterogeneity is caused by temperature variations only r suppresses short wavelength structures removes strong velocity gradients and introduces artificial stretching and tilting of velocity anomalies temperature anomalies in the thermochemical model resemble the spatial extent of low seismic velocity anomalies and the shear velocity spectrum in the d region better than the isochemical model however the thermochemical model overpredicts the amplitude of shear velocity variation and places the african and pacific anomalies imperfectly we suspect that inaccurate velocity scaling laws and uncertain initial conditions control these mismatches extensive hypothesis testing is required to identify successful models

rating curves and estimation of average water depth at the upper negro river based on satellite altimeter data and modeled discharges summary the objective of this study is to derive the stage discharge relationship for 21 virtual gauge stations located at the upper negro river amazon basin brazil a virtual station can be defined as any crossing of water body surface i e large rivers by radar altimeter satellite tracks rating curve parameters are estimated by fitting with a power law the temporal series of water surface altitude derived from satellite measurements and the discharge discharges are calculated using progum a flow routing model based on the muskingum cunge m c approach considering a diffusion cum dynamic wave propagation leon j g bonnet m p cauhope m calmant s seyler f submitted for publication distributed water flow estimates of the upper negro river using a muskingum cunge routing model based on altimetric spatial data j hydrol among these parameters is the height of effective zero flow measured from the wgs84 ellipsoid used as reference it is shown that the height of effective zero flow is a good proxy of the mean water depth from which bottom slope of the reaches can be computed and manning roughness coefficients can be evaluated mean absolute difference lower than 1 1 m between estimated equivalent water depth and measured water depth indicates the good reliability of the method employed we computed the free surface water slope from envisat altimetry data for dry and rainy seasons these profiles are in good agreement with the bottom profile derived from the aforementioned water depths also the corresponding manning coefficients are consistent with the admitted ranges for natural channels with important flows superficial width 30 5 m chow v t 1959 open channel hydraulics mcgraw hill new york and irregular section

late quaternary caco3 production and preservation in the southern ocean implications for oceanic and atmospheric carbon cycling recent geochemical models invoke ocean alkalinity changes particularly in the surface southern ocean to explain glacial age pco2 reduction in such models alkalinity increases in glacial periods are driven by reductions in north atlantic deep water nadw supply which lead to increases in deep water nutrients and dissolution of carbonate sediments and to increased alkalinity of circumpolar deep water upwelling in the surface southern ocean we use cores from the southeast indian ridge and from the deep cape basin in the south atlantic to show that carbonate dissolution was enhanced during glacial stages in areas now bathed by circumpolar deep water this suggests that deep southern ocean carbonate ion concentrations were lower in glacial stages than in interglacials rather than higher as suggested by the polar alkalinity model broecker and peng 1989 our observations show that changes in southern ocean caco3 preservation are coherent with changes in the relative flux of nadw suggesting that southern ocean carbonate chemistry is closely linked to changes in deepwater circulation the pattern of enhanced dissolution in glacials is consistent with a reduction in the supply of nutrient depleted water nadw to the southern ocean and with an increase of nutrients in deep water masses carbonate mass accumulation rates on the southeast indian ridge 3200 3800 m and in relatively shallow cores 3000 m from the kerguelen plateau and the south pacific were significantly reduced during glacial stages by about 50 the reduced carbonate mass accumulation rates and enhanced dissolution during glacials may be partly due to decreases in caco3 corg flux ratios acting as another mechanism which would raise the alkalinity of southern ocean surface waters the polar alkalinity model assumes that the ratio of organic carbon to carbonate production on surface alkalinity is constant even if overall productivity in the southern ocean were held constant a decrease in the caco3 corg ratio would result in increased alkalinity and reduced pco2 in southern ocean surface waters during glacials this ecologically driven surface alkalinity change may enhance deepwater mediated changes in alkalinity and amplify rapid changes in pco2

a 150 000 year climatic record from antarctic ice during much of the quaternary the earth s climate has undergone drastic changes most notably successive glacial and interglacial episodes the past 150 kyr includes such a climatic cycle the last interglacial the last glacial and the present holocene interglacial a new climatic time series for this period has been obtained using 18 o data from an antarctic ice core

increase of atmospheric co2 during deglaciation constraints on the coral reef hypothesis from patterns of deposition 1 the coral reef hypothesis asserts that carbonate production on newly flooded shelves contributes importantly to the rise of atmospheric carbon dioxide during deglaciation we seek to constrain the timing and strength of such carbon dioxide flux by re assessing reef and platform distribution in the world ocean the pattern of reef growth that emerges suggests that emission of co 2 resulting from carbonate production was important particularly during the late stages of deglaciation the effect peaked during the early holocene and presumably contributed to the warming in the climatic optimum

sediment focusing in the central equatorial pacific ocean at four sites in the central equatorial pacific ocean the flux of extraterrestrial he determined using the excess 230th profiling method is 8 10 13 cm stp cm 2 ka 1 this supply rate is constant to within 30 at these same sites however the burial rate of he determined using chronostratigraphic accumulation rates varies by more than a factor of 3 the lowest burial rates which occur north of the equator at 1 n 139 w are lower than the global average rate of supply of extraterrestrial he by 20 and indicate that sediment winnowing may have occurred the highest burial rates which are recorded at the equator and at 2 s are higher than the rate of supply of extraterrestrial he by 100 and these provide evidence for sediment focusing by analyzing several proxies measured in core pc72 sediments spanning the past 450 kyr we demonstrate that periods of maximum burial rates of 230th he 10be ti and barite with a maximum peak to trough amplitude of a factor of 6 take place systematically during glacial time however the ratio of any one proxy to another is constant to within 30 over the entire length of the records given that each proxy represents a different source 234u decay in seawater interplanetary dust upper atmosphere continental dust or upper ocean our preferred interpretation for the covariation is that the climate related changes in burial rates are driven by changes in sediment focusing

benthic foraminiferal δ13c and accumulation rates of organic carbon uvigerina peregrina group and cibicidoides wuellerstorfi the glacial to interglacial 13c records of the benthic foraminifera cibicidoides wuellerstorfi and the uvigerina peregrina group from deep sea cores cannot be adjusted by a generally valid constant the 13c values of the u peregrina group largely correlate with the accumulation rates of organic carbon suggesting a local habitat effect those of c wuellerstorfi vary independently with respect to the carbon flux and record fluctuations in the 13c of the ambient bottom water isotopic composition