latest quaternary oceanographic changes in the okhotsk sea based on diatom records abstract the okhotsk sea is a locus of the north pacific intermediate water formation today the formation of the okhotsk intermediate water is linked with seasonal sea ice cover diatom records from the okhotsk sea show the following 1 during the last glacial maximum between 21 000 yr b p and 18 000 yr b p sea ice covered the western side of the sea throughout the whole year but the eastern part was open this permitted more efficient heat exchange with the atmosphere than waters and hence ventilation of the glacial okhotsk sea waters which in turn caused a greater extent of intermediate water formation through the bussol strait 2 the perennial sea ice cover extended northward and sea ice was present throughout the whole year over a great part of the sea except for the eastern part between 18 000 yr b p and 17 000 yr b p 3 the ice free area extended greatly to the south during the interval between 17 000 yr b p and 11 000 yr b p 4 there was no perennial ice cover over the whole sea and the ice free area that appeared as the seasonal ice area began to extend to the western part between 11 000 yr b p and 8 000 yr b p 5 after 8000 yr b p the ice free waters contracted to the present extent

reconstruction of surface water conditions in the central region of the okhotsk sea during the last 180 kyrs abstract core gc9a a 6 7 m long gravity core collected from the central region of the okhotsk sea during cruise yk0712 on r v yokosuka jamstec was used to reconstruct the changes in surface water conditions by measuring biogenic components biogenic opal caco3 total organic carbon and 15n of sediment organic matter of sediment samples the age of core gc9a was determined indirectly by graphic correlation comparing the b psychometric yellow blue chromaticness values with those of well dated core md01 2415 with complement to the tephra layer k3 50 ka the bottom age of core gc9a was estimated to be about 180 kyr therefore it provides the history of surface water conditions from mis 1 to mis 6 the biogenic opal caco3 and toc contents were high during the interglacial periods as expected indicating enhanced surface water production under warm climatic conditions this condition resulted from sufficient nutrient supply to the surface waters by active vertical mixing which was validated by low 15n values of the sediment organic matter in contrast surface water productivity was depressed during the colder glacial periods probably due to the expanded sea ice distribution and limited nutrient supply however the glacial sediments had moderately high 15n values indicating enhanced nitrate utilization resulting from the limited nutrient supply caused by strong stratification of the surface water high 15n values were also observed during the deglaciation which was attributed to the increased nitrate utilization during enhanced surface water productivity however the low 15n values during the glacial and deglacial periods may be attributed to the increased supply of terrestrial organic matter diatom production was primarily responsible for surface water paleoproductivity during the interglacial periods rather than coccolithophores however the succession of glacial to early deglacial coccolithophore production and late deglacial to interglacial diatom production was remarkable corresponding to the present day seasonal phytoplankton succession such an advanced coccolithophore production relative to diatom production might be attributed to the degree of nutrient availability associated with surface water conditions on the basis of variations in the 15n value finally the opal and toc contents decreased abruptly in conjunction with a gradual decrease in caco3 content from about 2 ka which seems to implicate a late holocene sudden decrease in paleoproductivity in the central region of the okhotsk sea according to the increase in 15n values during this interval nutrient availability appears to be poor which is likely attributed to the resumed strong stratification that occurred due to the southward shift of the aleutian low atmospheric pressure system

the paleoclimatic record provided by eolian deposition in the deep sea the geologic history of wind the mineral component of pelagic sediment is brought to the deep sea by transport in the wind extraction and analysis of this dust allows estimation of the past aridity of the eolian source region via flux determinations and of the intensity of the transporting winds from grain size data these two parameters the grain size and mass flux of dust vary independently there are three significant sources of modern dust eastern and central asia northwest africa and arabia all in the northern hemisphere as the rainfall associated with the intertropical convergence zone is an effective barrier to southerly transport of dust the northern hemisphere is an order of magnitude more dusty than is the southern an asymmetry that has characterized most of the cenozoic eolian flux data show that most of the northern hemisphere was more arid during glacial maxima with 3 to 5 times as much dust transported during glacial stages than during interglacials only northwestern south america varied in the opposite sense the periodicity of quaternary variation in both eolian flux and eolian grain size data is strongly influenced by the milankovitch cycles of orbital variability wind intensities vary on a shorter time scale than the general 100 kyr cycles of glaciation and general aridity eolian grain sizes display forcing at precessional 19 and 23 kyr tilt 41 kyr and at approximately 30 kyr periodicities as a result the generalization that winds are uniformly stronger during glacial times is not valid whole cenozoic records show that the largest change in dust flux an order of magnitude increase occurred in the northern hemisphere and reflects continental drying associated with the late pliocene onset of northern hemisphere glaciation southern hemisphere eolian records show no sign of paleoclimatic changes in the late pliocene the most important change in cenozoic atmospheric circulation was a severalfold reduction in wind intensity that occurred at the time of the paleocene eocene boundary before then latest cretaceous and paleocene winds were essentially as strong as those of the late cenozoic this shift appears to be one of several climatic responses to a change in the nature and amount of global heat transport at about 55 ma

eruption mechanism as inferred from geomagnetic changes with special attention to the 1989 1990 activity of aso volcano abstract geomagnetic changes associated with the volcanic activity of aso volcano were detected with a dense network of continuously recording proton precession magnetometers during the period from june 1989 to june 1990 magnetic date clearly indicate that changes in the magnetization within the volcano are most probably caused by temperature changes this activity can be divided into five stages which are characterized by magnetization and demagnetization of the volcano these magnetic changes with durations of a few months are definitely correlated with some typical volcanic events at the crater as well as the volcanic tremor activity the demagnetization stage appears when the vent is covered by a water pool or the volcanic activity is enhanced the magnetization stage follows the opening of a vent and several large explosions which make the vent permeable the source of magnetic changes lies at a depth of about 200 m below the crater rim in the southwestern part of the active crater magnetic moments responsible for observed magnetic changes at stages 1 2 and 4 are 3 4 5 2 and 2 2 wbm respectively the corresponding source volume is estimated as a single sphere of radius 40 50 m or a spherical shell of 100 m or so an effective mechanism of rapid heating cooling exists which is ascribed to the interaction of groundwater and superheated vapor i e a shallow hydrothermal system this hydrothermal system driven by the surface cap of the vent controls every feature of the eruptions at the final outlet of aso volcano

magnetic records of climate change sediments deposited on the sea floor on lake bottoms as well as on land as accumulations of windblown silt loess and as ancient soils paleosols formed in the loess possess many different properties that record past changes in climate geologically recoverable information on paleoclimate includes changes in global temperature as it may affect global ice volume and thus temperature of sea water net precipitation storm intensity wind speed and frequency as well as wind direction such information further contributes to interpretations about changes in oceanic and atmospheric circulation patterns as such the understanding of past climatic changes can provide baselines of natural climatic fluctuations as related to those that may be induced or influenced by human activities

evidence of sea ice driven terrigenous detritus accumulation and deep ventilation changes in the southern okhotsk sea during the last 180 ka abstract sediment core os03 1 retrieved from the akademia nauk rise in southern okhotsk sea was analyzed for the contents of rare earth elements rees and combined with carbon isotope 13c time series of benthic foraminifera to infer changes in terrigenous accumulation and bottom water ventilation on glacial interglacial timescales in the study area the age model of os03 1 was constructed by a combination of foraminifer 18o stratigraphy and 14c ams dating revealing that the 380 cm long core provides a window on climate change in the southern okhotsk sea since 180 ka a grain size controlled ree content shows strong glacial interglacial changes the cerium and europium anomalies vary from 0 89 to 1 32 and from 1 14 to 1 37 respectively the la yb n values range between 0 55 to 0 92 both results suggest a significant contribution of volcanic debris in the core sediments in addition the relationships between sm vs nd suggest main contribution origin from the amur river and sea ice during warm intervals and from the sea ice during cold intervals indicating that the sea ice played an important role in transporting terrigenous materials to the study site in the southern okhotsk sea during the last 180 ka the mass accumulation rates mar of rees are relatively higher during glacials and lower during interglacials with a peak accumulation during the early deglacial period we infer that an intensified mongolia high is responsible for the first order accumulation pattern of rees in the southern okhotsk sea by mediating the dynamic changes in sea ice extent furthermore six 13c minima are associated with intensified asian monsoon am precipitation and maximum mars of rees indicating that the dominance of barrier layer effects by high fresh water input through sea ice melting the maximum mar of rees during the marine isotope stage mis 5c coincides with the minimum of benthic foraminiferal 13c indicating a major interruption of ventilation in the bottom water in the okhotsk sea the major low ventilation event in the deep water of the okhotsk sea appears to be dampened by a cooling condition and a major blooming of surface productivity preceded the event

regionalized primary paleoproduction variability in the sea of okhotsk during late pleistocene and holocene abstract in order to reconstruct the history of primary paleoproductivity changes during the last 160 kyr in the okhotsk sea os the high resolution down core analyses of chlorin content were performed on 11 sediment cores obtained from various part of the studied area with wide ranged depths spatial and temporal distributions of the marine phytoplankton paleoproductivity depend on sea ice condition and nutrient supply the observed discrepancies among the reconstructed records allow us to separate out three main regions with specific environmental conditions during glacial stages the paleoproductivity was depressed and vice versa productivity in the central region is low comparing to other regions due to nutrient limitation increased paleoproductivity in the southeastern area was affected by influence of nutrient rich pacific waters

variations of okhotsk sea oxygen minimum zone comparison of foraminiferal and sedimentological records for latest mis 12 11c and latest mis 2 1 abstract benthic foraminiferal assemblage compositions foraminiferal and sedimentological proxies were analyzed in core md01 2415 from the northern slope of the okhotsk sea to compare variations of productivity and oxygen minimum zone omz intensity during the latest marine isotope stage mis 12 11c and latest mis 2 1 the benthic assemblages reveal close similarity between the two climatic cycles the absence of benthic assemblages during the latest mis 12 and the presence of the low productivity angulogerina angulosa assemblage during the latest mis 2 suggest the disappearance of the omz this regime was related to almost perennial ice cover with periods of active ice rafting during the latest mis 12 while it was attributed to prolonged seasonal ice cover low surface productivity and enhanced formation of well oxygenated water masses in the okhotsk sea during the latest mis 2 in deglacial times the omz gradually intensified as evidenced by the high productivity uvigerina akitaensis assemblage during the early termination t tv and early ti and the low oxygen tolerant bolivina spissa assemblage during the late tv and late ti the orbitally forced similar rises of the global sea level during tv and ti caused a large offshore supply of organic matter synchronously nutrients from the melting sea ice and shelf erosion promoted high surface mainly carbonate productivity as a result a high and sustained flux of particulate degraded and refractory organic matter enhanced oxygen consumption in bottom waters and sediments leading to the similar gradual omz intensifications the b spissa assemblage also points to expansion of oxygen depleted water mass from the north pacific into the okhotsk sea fostering the omz intensifications the phytodetritus related islandiella norcrossi assemblage indicates weakening of the omz during full interglacial times of mis 11c and mis 1 after stabilization of the global sea level nutrients were mainly delivered by regional upwelling and fluvial discharge favoring increased biogenic opal and carbonate production in the surface water similar to the present in this way moderate to high although less than deglacial and pulsed flux of predominantly particulate organic matter caused the weakening of the oxygen consumption and omz notably during mis 11c the benthic assemblage with the dominance of the taxa with dissolution resistant tests such as miliammina herzensteini karreriella baccata and martinottiella communis reflects carbonate dissolution events in sediments these events might have been resulted from an interruption of the local surface carbonate production and inflow of more carbonate corrosive water masses from the north pacific driven by a drawdown of the global ocean carbonate saturation

insolation values for the climate of the last 10 million years new values for the astronomical parameters of the earth s orbit and rotation eccentricity obliquity and precession are proposed for paleoclimatic research related to the late miocene the pliocene and the quaternary they have been obtained from a numerical solution of the lagrangian system of the planetary point masses and from an analytical solution of the poisson equations of the earth moon system the analytical expansion allows the direct determination of the main frequencies with their phase and amplitude numerical and analytical comparisons with the former astronomical solution ber78 are performed so that the accuracy and the interval of time over which the new solution is valid can be estimated the corresponding insolation values have also been computed this analysis leads to the conclusion that the new values are expected to be reliable over the last 5 ma in the time domain and at least over the last 10 ma in the frequency domain

the composition and evolution of the continental crust rare earth element evidence from sedimentary rocks the composition of the present day upper crust inferred from the uniformity of sedimentary rock r e e rare earth element patterns is close to that of granodiorite a revised andesite model is used to obtain total crustal composition the lower crust is the composition remaining assuming that the upper crust one third of the total is derived from intracrustal partial melting the upper crustal r e e pattern has pronounced eu depletion eu eu 0 64 the lower crustal pattern has eu enrichment eu eu 1 17 and the total crust has no eu anomaly relative to chondritic abundances the eu depletion in the upper crust is attributed to retention of eu in plagioclase in the lower crust because plagioclase is not stable below 40 km 10 kbar the anomaly is intracrustal in origin the archaean upper crust has a different r e e pattern to that of the present day upper crust being lower in total r e e and la yb ratios and lacking an eu anomaly these data are used to infer the archaean upper crustal composition which resembles that of the present day total crust except that ni and cr contents are higher the archaean crustal composition can be modelled by a mixture of tholeiites and tonalite trondhjemites the latter have steep light r e e enriched heavy r e e depleted patterns consistent with equilibration with garnet and hence probable mantle derivation there is little reason to suppose that the archaean lower crust was different in composition from the upper crust except locally where partial melting episodes occurred the r e e evidence is consistent with isotopic and geological evidence for a low continental growth rate in the early archaean a massive increase to about 70 of the total crust between about 3000 and 2500 ma b p and a slow increase until the present day the change from archaean to post archaean r e e patterns in the upper crust is not isochronous but is reflected in the sedimentary rock r e e patterns at differing times in different continents on the basis of a model composition for the mantle 36 of the potassium 30 of uranium 15 of lanthanum and 3 of ytterbium are concentrated in the present continental crust this enrichment is related to ionic size and valency differences from common mantle cations e g mg fe pre 3 9 ga b p crusts were obliterated by meteorite bombardment no geochemical evidence exists for primordial anorthositic sialic or mafic crusts

orbital scale changes of sea ice conditions of sea of okhotsk during the last glaciation and the holocene mis 4 mis 1 abstract in this paper 5 schemes for reconstructing the sea ice conditions in the sea of okhotsk the so during the last 74 kyr are presented these schemes were constructed based on calculations of the ice rafted debris ird fluxes in 16 sediment cores and the available published mineralogical data derkachev et al 2004 we obtained new data on the orbital scale changes of the ird fluxes in the studied area for the last four marine isotopic stages mis as a result the key areas of sea ice formation and general direction of sea ice drift and in turn dominate direction of geostrophic wind in the so were established for each of the investigated miss it allows us to suppose the positions of siberian high and aleutian low during the individual miss at that the sea ice was of predominantly seasonal for studied period except for the northwestern and western parts of sea where perennial sea ice fields were preserved over a period of several years during mis 2 the variations of sea ice conditions attest to a particular type of atmospheric pressure field prevailing over the so during individual miss the secondary sea ice drift directions points out that the predominant atmospheric pressure field during individual miss were inconstant except the mis 2

tides in the sea of okhotsk eight major tidal constituents in the sea of okhotsk have been investigated using a numerical solution of tidal equations on a 59 space grid the tides are dominated by the diurnal constituents diurnal tidal currents are enhanced in shelikhov bay and penzhinskaya guba at kashevarov bank in proximity to the kuril islands and at a few smaller locations the major energy sink for diurnal tides over 60 of the total energy is shelikhov bay and penzhinskaya guba the major portion of semidiurnal tide energy is dissipated in the northwestern region of the sea of okhotsk and in shelikhov bay and penzhinskaya guba nonlinear interactions of diurnal currents are investigated through k1 and o1 constituent behavior over kashevarov bank these interactions generate residual circulation of the order of 10 cm s 21 major oscillations at semidiurnal and fortnightly periods 13 66 days and higher harmonics of basic tidal periods the m2 tidal current caused by the nonlinear interaction of the diurnal constituents over kashevarov bank constitutes approximately a half of the total m2 tide current there the fortnightly current through nonlinear interactions also influences basic diurnal tidal currents by inducing fortnightly variations in the amplitude of these currents

evidence from diatom bound nitrogen isotopes for subarctic pacific stratification during the last ice age and a link to north pacific denitrification changes higher diatom bound d 15 n 70 wt lower opal content and 1200 ppm lower biogenic barium taken together and with constraints on sediment accumulation rate these results suggest a reduced supply of nitrate to the surface due to stronger stratification of the upper water column of the bering sea during glacial times with more complete nitrate consumption resulting from continued iron supply through atmospheric deposition this finding extends the body of evidence for a pervasive link between cold climates and polar ocean stratification in addition we hypothesize that more complete nutrient consumption in the glacial age subarctic pacific contributed to the previously observed ice age reduction in suboxia and denitrification in the eastern tropical north pacific by lowering the nutrient content of the intermediate depth water formed in the subpolar north pacific in the deglacial interval of the bering sea record two apparent peaks in export productivity are associated with maxima in diatom bound and bulk sediment d 15 n the high d 15 n in these intervals may have resulted from greater surface nutrient consumption during this period however the synchroneity of the deglacial peaks in the bering sea with similar bulk sediment d 15 n changes in the eastern pacific margin and the presence of sediment lamination within the bering sea during the deposition of the productivity peaks raise the possibility that both regional and local denitrification worked to raise the d 15 n of the nitrate feeding bering sea surface waters at these times

consistent relationship between global climate and surface nitrate utilization in the western subarctic pacific throughout the last 500 ka 1 the open subarctic pacific is at present a high nitrate low chlorophyll hnlc region where nitrate is perennially abundant at the surface theoretically the hnlc status of this region is subject to modification by ocean circulation and or micronutrient supply with implications for the effectiveness of the biological pump and hence carbon sequestration in the ocean interior records of biogenic detritus in sediments from throughout the subarctic pacific indicate that export production was generally lower during glacial maxima while nitrogen isotope measurements from the bering sea have shown that nitrate consumption there was more complete during the last glacial period than it is today here nitrogen isotopic analyses of bulk sediments 15nbulk from three deep water sites in the open subarctic pacific are evaluated in terms of regional nitrate isotopic composition and local relative nitrate utilization the eastern subarctic pacific 15nbulk record bears great similarity to 15nbulk records from the western margin of north america over the last glacial cycle suggesting that variability in the isotopic composition of subeuphotic zone nitrate the growth substrate is reasonably coherent throughout the northeast pacific and dominates at these sites however the two western subarctic pacific records which lie at the heart of the hnlc region display a different pattern implying that significant changes in local relative nitrate utilization overlie the regional background variability after a novel correction intended to remove the background signal associated with denitrification in the eastern tropical north pacific these nitrate utilization records are correlated with a benthic oxygen isotope stack reflecting global deep ocean temperature and ice volume r2 0 65 the correlation implies a strong link between global climate and subarctic pacific nitrate utilization with nearly complete nitrate consumption during glacial periods when export production was low

cycladophora davisiana abundances as a paleoceanographic and stratigraphic tool in high latitude siliciceous sediments abstract like the oxygen isotope curve the relative abundance curve for cycladophora davisiana hereafter c curve exhibits synchronous fluctuations between high latitude regions it was also thought that high abundances of c davisiana indicated glacial periods although numerous short c curves have been calibrated to oxygen isotope curves spanning the last 100 kyr only two longer c curves have been associated with oxygen isotopes spanning the last 0 425 myr in the southern ocean and 1 1 myr in the sea of okhotsk this lack of well established long c curve calibrations to the oxygen isotope curve decreases the reliability of the c curve for periods beyond 100 ka furthermore recent work indicates that high abundances of c davisiana do not necessary indicate glacial conditions this study sought to establish a long c davisiana curve by directly calibrating the c curve to oxygen isotope records measured from benthic foraminifera in the north pacific over the last 740 kyr to discuss the paleoceanographic significance of the c curve and to check the suitability of the c curve as a stratigraphic tool samples were obtained from core c9001c which was recovered at a water depth of 1180 m east of the shimokita peninsula in the tohoku region of japan the core contained a continuous stratigraphic succession down to marine isotope stage 18 740 ka abundance peaks exceeding 5 of the total radiolarian fauna were defined as davisiana event dae and a total of 20 daes were observed over the last 740 kyr the daes were generally near interglacial glacial period boundary whereas peaks in the radiolarian total abundance reflecting warm surface radiolarian productivity occur mainly within the interglacial intervals the daes appear to reflect hydrological and productivity events in the intermediate water masses of the studied site during climatic transition we correlated the occurrence of 20 daes in shimokita area with c curve davisiana events identified in previous studies the c curve fluctuations appear to be generally synchronized in the north pacific sea of okhotsk and southern ocean supporting the interpretation that daes are intermediate water changes possibly caused by ice cover fluctuations in high latitude regions on the background of the glacial interglacial cycling

pollen and radiolarian records from deep sea core rc14 103 climatic reconstructions of northeast japan and northwest pacific for the last 90 000 years using modern pollen and radiolarian distributions in sediments from the northwest pacific and seas adjacent to japan to interpret floral and faunal changes in core rc14 103 44 02 n 152 56 e we recognize two major responses of the biota of eastern hokkaido and the northwest pacific to climatic changes since the last interglaciation relatively stable glacial environments 80 000 20 000 yr b p were basically cold and wet 8 c and 1200 mm mean annual temperature and precipitation respectively supporting climax broadleaf deciduous forest with quercus and ulmus zelkova with surface waters in the northwest pacific characterized by warm 1 5 c winter and cold 10 4 14 3 c summer temperatures climatic evidence from rc14 103 shows a high degree of local and regional variation within the context of global climatic change correlative ocean and land records provide the detailed input necessary to assess local regional responses to variations in other key elements i e solar radiation monsoonal variations of the northeast asian climate system

satellite observations of the ice cover of the kuril basin region of the okhotsk sea and its relation to the regional oceanography for the period 1978 1982 this paper examines the nature of the sea ice which forms over the kuril basin of the okhotsk sea and describes the impact of this ice on the regional oceanography the paper compares the oceanographic behavior during the heavy ice season associated with the cold 1979 winter with the behavior during the lighter ice years of 1980 and 1982 examination of the oceanography in the okhotsk and the adjacent pacific shows that the early summer water column structure depends on the heat loss from the okhotsk during the preceding ice season the total amount of okhotsk ice formation and specifically the amount of ice formation in the kuril basin following the 1979 ice season the upper 200 300 m of the kuril basin waters were cooler less saline and richer in oxygen than for the other years this modification appears to be a process local to the kuril basin driven by eddy induced mixing local cooling and ice melting in the depths 300 1200 m the water modification is caused by the advection of water from the northern okhotsk for 1979 this deeper water is also less saline colder and richer in oxygen than for the lighter ice years the water modified in the okhotsk enters the adjacent north pacific through the bussol strait where for 1979 the adjacent waters are also cooler less saline and richer in oxygen down to a depth of 1000 m than for the lighter ice years

sediment core profiles of long chain n alkanes in the sea of okhotsk enhanced transport of terrestrial organic matter from the last deglaciation to the early holocene 1 terrestrial plant derived n alkanes c25 c35 w ere measured in three piston cores pc1 pc2 and pc4 in the sea of okhotsk covering the last 30 kyrs down core profiles of the n alkane concentrations and mass accumulation rates mar were characterized by deglacial maxima in particular cores pc2 and pc4 which were collected from the central and western sea of okhotsk respectively show a two step increase around the meltwater pulse events mwp 1a 14 5 13 5 kyr bp and 1b about 10 kyr bp this finding was interpreted by the outflow of terrestrial organic matter from the submerged land shelf to the sea of okhotsk through the east sakhalin current this study demonstrated that the sea level rise forced by global warming in the deglaciation period may have caused the enhanced transport of terrestrial organic matter in marginal seas index terms 3022 marine geology and geophysics marine sediments processes and transport 4267 oceanography general paleoceanography 1055 geochemistry organic geochemistry citation seki o k kawamura t nakatsuka k ohnishi m ikehara and m wakatsuchi sediment core profiles of long chain n alkanes in the sea of okhotsk enhanced transport of terrestrial organic matter from the last deglaciation to the early holocene geophys res lett 30 1 1001 doi 10 1029 2001gl014464 2003

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

changes in detrital input ventilation and productivity in the central okhotsk sea during the marine isotope stage 5e penultimate interglacial period abstract by presenting benthic foraminifera isotope profiles and bulk geochemical composition of core sediments we offer a mutiproxy reconstruction of the central okhotsk sea oceanography between 130 to and 115 kyr related to the marine isotopic stage 5e mis 5e sediments from the site mr0604 pc7a have been compared with paleo sea surface temperatures and other records this multiparameter approach allowed to recognize three periods for mis 5e evolution characterized by variations in marine productivity and bottom oxygenation these variations have been ultimately associated with the production of okhotsk sea intermediate water and the presence or absence of nutrient contribution from the pacific deep water into central okhotsk sea aeolian input reconstructed by th sc ratio indicates higher values during the mis 6 and mis 5d compared with the mis 5e eu values indicate an input of detrital material from kurile islands and east kamchatka during the late mis 5e absent during the early mis 5e and glacial periods

responses of the okhotsk sea environment and sedimentology to global climate changes at the orbital and millennial scale during the last 350 kyr abstract we measured productivity proxies chlorin carbonate and organic carbon opal and biogenic ba content and lithophysical proxies magnetic susceptibility water content density and coarse sediment fraction in sediment of central okhotsk sea core pc 7r the age model covering the last 350 kyr of this core was constructed by correlating the dated series of relative paleointensity lows recognized in geomagnetic intensity records marine isotope stage mis boundaries determined in broad variations of the lithophysical and productivity proxies and tephrochronology the orbital changes of the lithophysical and productivity proxy stacks lag behind northern hemisphere summer radiation by approximately 6 3 and 5 9 kyr respectively this lag is consistent with a milankovich model of climate control by solar radiation through the northern ice sheet volume and sea surface and surrounding land responses which are fast compared with sedimentological evidence productivity proxies of the okhotsk sea also demonstrate 52 abrupt pronounced productivity minima associated with regional climate coolings during the last 350 kyr which present useful indicators of millennial scale climate changes in this marginal sea based on the postulated synchronicity of dansgaard oeschger cycles in the northern hemisphere and the established simultaneity of 11 okhotsk sea coolings in the last 77 kyr with abrupt severe cold events in the greenland ice core and north atlantic heinrich events all of these may be regarded as heinrich equivalent event anomalies the okhotsk sea events have their counterparts in the records of north atlantic sediments the greenland ice sheet east asia summer monsoon and the antarctic ice sheet probably the arctic oscillation was the main factor determining orbital and millennial climate oscillations in the high latitude northern hemisphere including the okhotsk sea region

environmental boundary conditions of cold water coral mound growth over the last 3 million years in the porcupine seabight northeast atlantic iodp expedition 307 made it for the first time possible to investigate the entire body of a cold water coral carbonate mound here we provide new insights into the long term history of challenger mound on the european continental margin off ireland this study is based on age determinations 230th u 87sr 86sr and geochemical signals mg li and ba ca measured in the scleractinian cold water coral lophelia pertusa from iodp site 1317 in the porcupine seabight the paleoceanographic reconstructions reveal that coral growth in the porcupine seabight was restricted to specific oceanographic conditions such as enhanced export of primary production and bottom water temperatures bwt between 8 10 c related to the water mass stratification of the mediterranean outflow water mow and eastern north atlantic water enaw the geochemical signals from the coral skeletons can be explained by the close interaction between cold water coral growth sea surface productivity and the surrounding water masses the boundary layer between mow and enaw enhanced sea surface productivity and the build up of a stable water mass stratification between enaw and mow caused enhanced nutrient supply at intermediate water depths and facilitated a steady mound growth between 3 0 2 1 ma with the decrease in sea surface productivity and related reduced export productivity the food supply was insufficient for rapid coral mound growth between 1 7 1 ma during the late pleistocene over the last 0 5 myr mound growth was restricted to interglacial periods during glacials the water mass boundary between enaw mow probably was below the mound summit and hence food supply was not sufficient for corals to grow

stacked 2 6 ma grain size record from the chinese loess based on five sections and correlation with the deep sea δ18o record 1 this study aims to establish a stacked climate record of the quaternary period from the chinese loess sequence and to address the forcing mechanisms for the regional climate history of the loess plateau by correlating the stacked record with a composite 18o record in deep sea sediments a total of 18 352 samples were obtained from five loess sections located at baoji lingtai jingchuan puxian and pingliang in the southern and middle loess plateau these yielded high resolution grain size records between section correlation of these shows that although small depositional hiatuses are present in places within a single section most parts of the sections display near continuous dust deposition throughout the quaternary the grain size records were tuned simultaneously to the theoretical variations in obliquity and precession of the earth s orbit the grain size records plotted on their orbital timescales were then averaged to form a stacked loess grain size time series termed the chiloparts record this resolves most of the orbital timescale paleoclimate events buried in the loess soil sequences of the southern and middle loess plateau and can be used as a regional archive of the pleistocene climate history in the loess plateau comparison of the chiloparts record with a composite marine 18o record shows that for the past 1 8 ma the loess paleosol record can be correlated almost cycle by cycle with the marine record several discrepancies in the climatic events between the two records have also been identified implying that regional forcing mechanisms may have played a part in the climatic evolution of the chinese loess plateau

pleistocene and holocene distribution of the radiolarian amphimelissa setosa cleve in the north pacific and north atlantic evidence for water mass movement abstract the radiolarian amphimelissa setosa is one of the prominent species of the pleistocene radiolarian assemblages in the sea of okhotsk below the marine isotope stage mis boundary 5 4 and it represents one of the most abundant radiolarian species in holocene and modern environments of the nordic seas we studied the a setosa distribution in six cores from the sea of okhotsk and established morphometric measurements on a setosa specimens from two cores of the sea of okhotsk and one core from the labrador sea we further compared our data with other available studies from the subarctic pacific the labrador sea the north atlantic the norwegian sea and the iceland greenland seas in order to discuss the possible settling of the species from the north pacific via the arctic ocean into the iceland greenland seas a setosa exhibits a stable abundant population in the sea of okhotsk during most of the last ca 0 7 m y and might repeatedly extend its population into the north atlantic through the arctic ocean during the pleistocene interglacial optima the species declines from the sea of okhotsk and from the subarctic pacific at the end of mis 5 its final documented settling into the north atlantic is during mis 5 when a setosa appears in low numbers in sediments of the labrador sea however reaching significant percentages at the boundary of mis 5 4 based on the available information we propose that a setosa could migrate from the north pacific into the arctic ocean during the interglacial optimum mis 5e and then through the channels of the canadian arctic archipelago into the baffin bay and labrador sea a further migration step of a setosa occurs at the boundary of mis 5 4 when a setosa migrated from the labrador sea into the north atlantic probably related to a southward expansion of cold waters at the end of the mis 5 during the warming at termination i a setosa moved from the north atlantic into the nordic seas the abundant occurrence of a setosa in sediments south of iceland the norwegian and north seas within the younger dryas period points to a marked cooling and a southward movement of polar water masses restricted to this time interval

world wide delivery of river sediment to the oceans new data and new estimates from old data show that rivers with large sediment loads annual discharges greater than about 15 times 10 6 tons contribute about 7 times 10 9 tons of suspended sediment to the ocean yearly extrapolating available data for all drainage basins the total suspended sediment delivered by all rivers to the oceans is about 13 5 times 10 9 tons annually bedload and flood discharges may account for an additional 1 2 times 10 9 tons about 70 of this total is derived from southern asia and the larger islands in the pacific and indian oceans where sediment yields are much greater than for other drainage basins

cadmium chemical tracer of deepwater paleoceanography the oceanic distribution of cadmium resembles that of phosphorus because the cadmium content of foraminiferal shells is governed by the cadmium content of seawater planktonic and benthic fossil shells can be used to infer nutrient distributions within ancient oceans empirical studies demonstrate that cadmium in benthic foraminiferal shells is related to the bottom water composition through a proportionality constant d 2 9 this constant is the same for each of the species studied cibicidoides wuellerstorfi cibicidoides kullenbergi nuttallides umbonifera and uvigerina spp downcore cadmium data from high quality pacific and atlantic sediment cores suggest that the cadmium inventory of the ocean did not change significantly between the most recent glacial maximum and the present hence changes in the cadmium content of fossils at a site directly reflect changes in nutrient distributions due to altered oceanic circulation patterns studies of cadmium in pleistocene sediments show that deep ocean circulation patterns were significantly different during the most recent glacial maximum in the western north atlantic ocean the nutrient content of waters from 2500 to 3500 m was twice as high during glacials as during interglacial periods signifying an increase in the proportion of waters of antarctic origin in this depth interval and a decrease but not a cessation in the flux of north atlantic deep waters through this depth range below 3500 m the nutrient increase was greater indicating a higher proportion of antarctic bottom water above 2500 m the nutrient content was lower during glacial periods than it has been during interglacial times the cd content of high latitude north atlantic and southern ocean surface waters does not show a significant glacial interglacial change which argues against theories for changes atmospheric carbon dioxide that require changes in high latitude nutrient concentrations

ice volume forcing of east asian winter monsoon variations in the past 800 000 years particle size measurements of some typical loess soil samples taken in different localities of the chinese loess plateau demonstrate that the grain size ratio of 10 m can be used as an indicator of variations in intensity of the east asian winter monsoon winds grain size curves of the baoji and weinan sections show that this proxy indicator is very sensitive to loess soil alterations analytical results also suggest that during soil forming periods eolian dust accumulation was still substantial and hence loess deposition can be regarded as a nearly continuous process during the quaternary period in this study we compared the baoji grain size time series with the specmap marine isotope record with the objective of elucidating the dynamic linkage between changes in global ice volume and the winter monsoon circulation both records show good agreement at both time and frequency domains in particular the winter monsoon variations are also dominated by a 100 000 yr period over the past 800 000 yr it is thus inferred that direct local insolation forcing could be less important in driving the east asian winter monsoon variability and alternatively variations in glacial age boundary conditions may have played a key role in modulating and pacing its strength and timing

woce section p1w in the sea of okhotsk 1 oceanographic data description we describe the results of a world ocean circulation experiment woce survey line p1w from the open pacific ocean through the bussol strait and across the sea of okhotsk observations are presented of distributions of temperature and salinity dissolved oxygen and nutrients and some derived quantities discussion centers on the distribution of the sea of okhotsk component of the north pacific intermediate water mass and its properties the sea of okhotsk has been suggested as the only location where deep convection may occur within the north pacific or its marginal seas our analysis suggests that the surface 26 85 has recently been ventilated and arguments might be made to suggest that ventilation has occurred to 27 05 this is discussed here but detailed evidence is covered in a companion paper analyzing cfc observations the okhotsk component of the north pacific intermediate water extends to substantially greater depths and densities and so some other process is needed to create the denser water mass

woce line p1w in the sea of okhotsk 2 cfcs and the formation rate of intermediate water from august 30 to september 21 1993 temperature salinity nutrient and cfc data were collected along a section starting in the pacific ocean near bussol strait in the kuril islands crossing the basin and shelf region of the sea of okhotsk and ending near the coastal town of okhotsk at the northwest corner of the sea of okhotsk world ocean circulation experiment woce line p1w water on the continental shelf had potential density as great as 27 0 with high cfc concentrations and low temperature and salinity the sea of okhotsk intermediate water soiw ranging from 26 8 to 27 4 had uniform water properties along isopycnal surfaces that were distinctly different from either the north pacific intermediate water npiw or the shelf water found at the same density since the soiw was colder and fresher than the npiw we postulate that soiw is formed by sinking plumes and diapycnal mixing shelf derived water sdw as dense as 27 0 is formed on the shelf during the winter by cooling and brine rejection during ice formation prevailing winds move the sdw off the shelf where it sinks to an equilibrium depth and subsequently mixes isopycnally with north pacific water npw flowing into the sea of okhotsk through the kuril islands the observations on the shelf suggest that sdw directly modifies soiw to 27 0 using potential temperature salinity s and cfc data we calibrated a simple box model to determine the input of sdw into the soiw model results required a minimum of 0 9 sv 1 sv 10 6 m 3 s 1 of sdw in the formation of soiw and produced a minimum export of 2 7 sv of soiw from the sea of okhotsk our minimum calculated export of soiw into the north pacific ocean makes the sea of okhotsk a significant source of the salinity minimum present in the npiw below 27 2 the box model failed because the cfc concentrations of the sdw were too high this suggests that sdw directly ventilates the soiw to a maximum of 27 2 the unique properties of the soiw below 27 2 must be the result of diapycnal mixing in the sea of okhotsk and isopycnal mixing with inflowing npw

late quaternary lake level changes of lake el gygytgyn ne siberia abstract lake el gygytgyn is situated in a 3 6 ma old impact crater in northeastern siberia presented here is a reconstruction of the quaternary lake level history as derived from sediment cores from the southern lake shelf there a cliff like bench 10 m below the modern water level has been investigated deep water sediments on the shelf indicate high lake levels during a warm mid pleistocene period one period with low lake level prior to marine oxygen isotope stage mis 3 has been identified followed by a period of high lake level 10 m above present in the course of mis 2 the lake level dropped to 10 m at the end of mis 2 the bench was formed and coarse beach sedimentation occurred subsequently the lake level rose rapidly to the holocene level changes in water level are likely linked to climate variability during relatively temperate periods the lake becomes free of ice in summer strong wave actions transport sediment parallel to the coast and towards the outlet where the material tends to accumulate resulting in lake level rise during cold periods the perennial lake ice cover hampers any wave activity and pebble transport keeping the outlet open and causing the lake level to drop

planktonic foraminifera in the western north pacific during the past 150 000 years comparison of modern and fossil assemblages abstract planktonic foraminiferal abundance variations in 186 deep sea piston core tops from the western north pacific were used to create a calibration set to characterize the present day kuroshio gyre system q mode factor analysis helped identify six faunal assemblages 93 variance related to modern water masses two tropical assemblages differing in relative dissolution three assemblages representing subtropical subpolar and transitional conditions and a gyre margin assemblage lying between the kuroshio current and the mainland of asia multivariate regression produced transfer functions relating observed summer august and winter february sea surface temperatures sst to the assemblages with standard errors of estimate of 1 5 c and 2 5 c respectively data from 24 piston cores was used to interpret variations of the kuroshio gyre system during the past 150 000 yr stratigraphic control is based on oxygen isotopic measurements the extinction of pink pigmented globigerinoides ruber at 120 000 b p coiling direction changes in neogloboquadrina pachyderma north of 30 n and dissolution variations between resistant and fragile taxa major dynamic changes in the circulation of the kuroshio gyre occurred during the last two glacial maxima at 15 20 000 b p isotopic stage 2 and at 140 150 000 b p isotopic stage 6 these intervals are characterized by 1 lowered sea levels which reduced flow into the sea of japan and sea of okh okhotsk 2 advance of the polar front from its modern position at about 42 n to 35 38 n 3 southward penetration of the oyashio current along the pacific coast of japan to tokyo 4 2 3 c lowered sst in tropical areas little or no change in subtropical areas and a 4 6 c decrease in transitional areas and 5 an overall decrease in carbonate dissolution relative to interglacial stages the maximum interglacial at 120 000 b p isotopic substage 5e shows a retreat of the polar front north of its modern position and an overall relative increase in interglacial carbonate dissolution that does not become severe until substage 5d

silicate weathering in anoxic marine sediments two sediment cores retrieved at the northern slope of sakhalin island sea of okhotsk were analyzed for biogenic opal organic carbon carbonate sulfur major element concentrations mineral contents and dissolved substances including nutrients sulfate methane major cations humic substances and total alkalinity down core trends in mineral abundance suggest that plagioclase feldspars and other reactive silicate phases olivine pyroxene volcanic ash are transformed into smectite in the methanogenic sediment sections the element ratios na al mg al and ca al in the solid phase decrease with sediment depth indicating a loss of mobile cations with depth and producing a significant down core increase in the chemical index of alteration pore waters separated from the sediment cores are highly enriched in dissolved magnesium total alkalinity humic substances and boron the high contents of dissolved organic carbon in the deeper methanogenic sediment sections 50 150 mg dm 3 may promote the dissolution of silicate phases through complexation of al3 and other structure building cations a non steady state transport reaction model was developed and applied to evaluate the down core trends observed in the solid and dissolved phases dissolved mg and total alkalinity were used to track the in situ rates of marine silicate weathering since thermodynamic equilibrium calculations showed that these tracers are not affected by ion exchange processes with sediment surfaces the modeling showed that silicate weathering is limited to the deeper methanogenic sediment section whereas reverse weathering was the dominant process in the overlying surface sediments depth integrated rates of marine silicate weathering in methanogenic sediments derived from the model 81 4 99 2 mmol co2 m 2 year 1 are lower than the marine weathering rates calculated from the solid phase data 198 245 mmol co2 m 2 year 1 suggesting a decrease in marine weathering over time the production of co2 through reverse weathering in surface sediments 4 22 15 0 mmol co2 m 2 year 1 is about one order of magnitude smaller than the weathering induced co2 consumption in the underlying sediments the evaluation of pore water data from other continental margin sites shows that silicate weathering is a common process in methanogenic sediments the global rate of co2 consumption through marine silicate weathering estimated here as 5 20 tmol co2 year 1 is as high as the global rate of continental silicate weathering

regional patterns of pleistocene ice rafted debris flux in the north pacific ird mass accumulation rate mar records are presented for deep sea drilling project site 580 and ocean drilling program sites 882 and 887 and are combined with results from previous ird mar studies to provide a synthesis of north pacific pleistocene ice rafting important regional differences in the ice rafting histories of the nw and ne pacific are highlighted by this synthesis and include 1 significant variations in ird fluxes across the north pacific which identify two major ird sources coastal alaska and coastal siberia kamchatka peninsula and 2 significant variations in the timing of ird supply across the north pacific particularly in response to global scale climatic forcing these regional differences indicate that local and regional controls on iceberg input transport and melting exert a major influence on ice rafting throughout the north pacific this suggests that a single generalized ice rafting record for the north pacific does not adequately describe the complexity of this basin s pleistocene history data used to calculate lsrs and ird mars for sites 380 882 and 887 are available on diskette or via anonymous ftp from kosmos agu org directory apend usemame anonymous password guest diskette may be ordered from american geophysical union 2000 florida avenue n w washington dc 20009 or by phone at 800 966 2481 15 00 payment must accompany order

on the relationship between atmospheric circulation and the fluctuations in the sea ice extents of the bering and okhotsk seas monthly and 3 day averaged nimbus 5 electrically scanning microwave radiometer sea ice data have been analyzed to document the fluctuations of the bering sea and sea of okhotsk ice covers for the four winters 1972 1973 through 1975 1976 on the short term seasonal and interannual time scales and to define those periods for which there is an out of phase relationship between the fluctuations of the two sea ice covers the sea ice fluctuations are shown to be related to changes in the position and intensity of quasi stationary high and low pressure systems associated with large scale standing wave patterns in the atmosphere through a comparison of the areal changes in ice cover with changes in the amplitude and phase of zonal harmonics 1 2 and 3 of the sea level pressure field on the seasonal time scale the sea level pressure for december the month of most rapid seasonal sea ice growth for both the bering and okhotsk seas is dominated by harmonic 2 which explains almost 60 of the total sea level pressure variance on average over the four winters the phase of harmonic 2 which is associated with the position of the aleutian low shifts from 156 e in 1972 1973 to 190 e in 1975 1976 thus providing a connection between the increasingly heavy bering sea ice cover over these four winters and the general circulation of the atmosphere on the short term episodes of midwinter bering sea ice retreat are generally preceded by or coincident with the breakdown of harmonic 1 and the intensification of harmonics 2 and 3 these episodes are also related to the coincidence of the phases of harmonics 2 and 3 with a mean position of 165 e this result is in excellent agreement with a study of the north pacific oscillation showing that the two modes of the oscillation are associated with the longitudinal position of the aleutian low it is suggested here that these two modes result from changes in the amplitudes and phases of atmospheric long waves 1 2 and 3 evidence is also presented indicating that the interaction of standing and transient components of wave 1 may play an important role in these fluctuations finally these results establish an observational connection relating climate dynamics to changes in ice covers in seasonal sea ice zones

sediment provenance variations in the southern okhotsk sea over the last 180 ka evidence from light and heavy minerals in this study we investigate light and heavy minerals in sediment core os03 1 located at the academy of sciences rise of the southern okhotsk sea to determine their distributions and sources over the last 180 ka thousand years the sediment mainly consists of terrigenous and volcanic detritus ubiquitous drop stones and volcanic detritus throughout the core and high detrital input suggest that sea ice driven by wind and kamchatka current was the main transport agent of detrital materials to the southern okhotsk sea the ternary diagram of heavy minerals hornblende hypersthene epidote shows an expansion of detritus provenance from the eastern in cold periods to the northeastern in warm intervals of the okhotsk sea it mainly relates to the shift of aleutian low combined with previous records accumulation rates of quartz indicated a maximum extent but not perennial sea ice coverage during the glacial periods

effects of sea level sea ice extent and nutrient availability on primary production at the umnak plateau bering sea iodp site u1339 during marine isotope stage mis 5 abstract this study investigates how primary production responded to changes in nutrient availability sea level and sea ice coverage at the umnak plateau during marine isotope stage mis 5 and parts of mis 4 and mis 6 the umnak plateau during mis 4 and mis 6 had low primary production resulting from extensive sea ice coverage that enhanced stratification and limited nutrient replenishment this nutrient limitation was relieved during the deglaciation going into mis 5 when previously exposed continental shelves were flooded and the eastern aleutian island passes were opened by an increase in sea level resulting in an increase in productivity opening and closing of the eastern aleutian island passes during the rest of mis 5 reflected fluctuations in sea level and likely affected nutrient sources and productivity at the umnak plateau nutrients during sea level lowstands were likely sourced by the aleutian north slope current whereas most of the sea level high stands throughout mis 5 had nitrogen sourced by an increase in nitrogen fixation and the assimilation of remineralized nitrogen which led to highly depleted nitrogen isotope values never before seen for the northern pacific higher sea level and productivity near the beginning of mis 5 likely reflected mis 5e however a discrepancy between two diatom productivity proxies suggests that changing environmental conditions stimulated a change in the dominant diatom species this highlights the complexities associated with productivity in the bering sea and emphasizes the need to continue studying how productivity and ecosystems changed during previous warm periods

astronomic timescale for the pliocene atlantic δ18o and dust flux records of ocean drilling program site 659 high resolution benthic oxygen isotope and dust flux records from ocean drilling program site 659 have been analyzed to extend the astronomically calibrated isotope timescale for the atlantic from 2 85 ma back to 5 ma spectral analysis of the 18o record indicates that the 41 kyr period of earth s orbital obliquity dominates the pliocene record this is shown to be true regardless of fundamental changes in the earth s climate during the pliocene however the cycles of sahelian aridity fluctuations indicate a shift in spectral character near 3 ma from the early pliocene to 3 ma the periodicities were dominantly precessional 19 and 23 kyr and remained strong until 1 5 ma subsequent to 3 ma the variance at the obliquity period 41 kyr increased the timescale tuned to precession suggests that the pliocene was longer than previously estimated by more than 0 5 m y

silicon diffusion in a natural quartz aggregate constraints on solution transfer diffusion creep abstract silicon bulk diffusion rates were determined in a fine grained 1 2 m diameter natural quartz aggregate novaculite from hot springs ar the diffusion experiments were done at 600 800 c and 150 mpa confining pressure hydrothermal and at 800 1100 c and 1 atm in a stream of dry n2 the technique employed an isotopic tracer 30si and standard step scan analysis using an ion microprobe sims the temperature dependence of silicon bulk diffusion in the novaculite is described by the arrhenius parameters d0 bulk 3 7 10 10 m2 s and q 137 18 kj mol and d0 bulk 6 2 10 9 m2 s and q 178 38 kj mol for the hydrothermal and dry experiments respectively at 800 c the silicon bulk diffusion rate at 150 mpa hydrothermal is about a factor of 10 greater than at 1 atm dry for an assumed effective grain boundary width of 2 nm the silicon grain boundary diffusion rates in novaculite are a factor of two to three less than oxygen diffusion rates for similar hydrothermal conditions and more than 12 orders of magnitude greater than anhydrous silicon volume diffusion rates extrapolated to the temperature of these experiments the results of this study provide valuable constraints on the role of diffusion accommodated deformation in quartz rich rocks

biogenic opal indicating less productive northwestern north pacific during the glacial ages 1 biogenic opal and ice rafted detritus ird data from sediments in the okhotsk sea and the neighboring north pacific revealed the remarkable reduction in opal production and southward advancement of sea ice covered area during the last glacial maximum resulting also southward shift of high biological productive area in the northwestern north pacific it implies that the substantial reduction in outflux of co2 to the atmosphere in northwestern north pacific and the pronounced increase in co2 sequestering in temperate north pacific this could be an additional co2 reduction mechanism of atmospheric co2 in the last glacial period

glacial age hydrography of the far northwest pacific ocean stable isotope data on benthic foraminifera from more than 30 cores on the northern emperor seamounts and in the okhotsk sea are synthesized in paleohydrographic profiles spanning the depth range 1000 4000 m holocene core top benthic foraminiferal 18o and 13c data are calibrated to modern hydrographic properties through measurements of 13c of co2 and 18o of seawater cibicidoides stable isotope ratios are close to the 13c and equilibrium 18o of seawater whereas uvigerina 18o and 13c are variably offset from cibicidoides glacial maximum 13c of cibicidoides displays a different vertical profile than that of the holocene when results are adjusted by 0 32 to account for the secular change in 13c during the last glacial maximum the data coincide with the modern seawater and foraminiferal curves deeper than 2 km however at shallower depths 13c gradually increases by as much as 1 above the modern value furthermore above 2 km the benthic 18o decreases by 0 5 these results are consistent with a benthic front at 2 km in the north pacific see herguera et al 1992 but they differ from interpretations based on trace metal data which indicate a source of nutrient depleted deep water during glaciation the isotopic data suggest that during glaciation there was a better ventilated watermass at intermediate depths in the far northwestern pacific it was relatively fresher than deep waters there and deep waters were as nutrient rich as today

the impact of the siberian high and aleutian low on the sea ice cover of the sea of okhotsk comparison of monthly averaged sea ice distributions in the sea of okhotsk with atmospheric pressure data during the four winters having passive microwave sea ice coverage from the nimbus 5 satellite 1973 76 revealed a strong apparent relationship between the extent of the sea ice cover and the influence of the siberian high atmospheric pressure system examination of data for the years 1978 86 having passive microwave coverage from the nimbus 7 satellite reveals that the strong correspondence found for 1973 76 between okhotsk sea ice extents and the siberian high was not maintained in the 1978 86 period a weaker correspondence continued however between the sea ice and the combined siberian high aleutian low system a siberian high aleutian low index was created and the correlation coefficient between that index and sea ice extents in the midwinter month of february is 0 97 for the 1973 76 period and 0 52 for the 1978 86 period primary reasons for the lack of a consistently strong monthly averaged ice atmosphere correspondence are the various oceanographic influences on the sea ice cover the failure of monthly averages to reflect fully the important shorter term interactions between the ice and the atmosphere and the fact that ice conditions in one month are influenced by ice conditions in previous months

millennial scale cycles in the bering sea during penultimate and last glacials their similarities and differences abstract the age model of the western bering sea core 85 kl was modified through correlation of new and earlier measured productivity proxies with the chinese interstadials described by 18 o records of hulu and sanbao caves and the relative paleointensity events in the studied core with those in the dated records resulted sequence of millennial scale bering sea interstadials recorded by abrupt productivity risings was established during the penultimate glacial consistently with the chinese interstadials and antarctica isotope maxima the pattern of the frequency and amplitude of the millennial productivity climate variability in the bering sea during the penultimate glacial resembles that initially depicted in the 18 o of chinese cave stalagmites and is quite similar to one of the dansgaard oeschger cycles during last glacial except for their terminations contrary to well pronounced interstadial a 1 during termination ti an interstadial b 1 over the tii has lower duration and therefore is weakly observed in antarctic temperature changes our results provide robust evidence that the bipolar seesaw mechanisms of millennial climate changes in the northern and southern hemispheres were similar during the last and penultimate glacials

mechanisms for the variation of sea ice extent in the northern hemisphere using daily sea ice data derived from satellite borne sensors and atmospheric data we examined processes controlling the variation of sea ice extent in the northern hemisphere the daily ice motion field was computed from imagery of the defense meteorological satellite program dmsp special sensor microwave imager ssm i for seven winters december to april from 1991 1992 to 1997 1998 by employing the maximum cross correlation method in order to examine mechanisms of the temporal variation of the ice extent we analyzed 50 specified lines across the daily ice edge although a high correlation between the ice motion and the geostrophic wind speed was observed in all the ice edge areas the degree for correlation between the speed of the ice edge displacement and the wind speed varied with region the degree for response of the ice edge speed to the wind speed largely depended upon that of the ice edge speed to the ice motion the following mechanisms controlling the variation of ice extent for regions in the northern hemisphere were anticipated in the barents sea bering sea and the sea of okhotsk the ice extent advances by wind driven ice advection and the daily scale variation of the ice extent were also controlled by the variation in wind speed in contrast the ice extent in the labrador sea and the greenland sea seemed to be considerably affected by oceanographic factors such as the location of the thermal front and was not related to the variation in wind speed the regional difference of the variation mechanism was also reflected in the interannual variation in maximum ice extent

dust sources and deposition during the last glacial maximum and current climate a comparison of model results with paleodata from ice cores and marine sediments mineral dust aerosols in the atmosphere have the potential to affect the global climate by influencing the radiative balance of the atmosphere and the supply of micronutrients to the ocean ice and marine sediment cores indicate that dust deposition from the atmosphere was at some locations 2 20 times greater during glacial periods raising the possibility that mineral aerosols might have contributed to climate change on glacial interglacial time scales to address this question we have used linked terrestrial biosphere dust source and atmospheric transport models to simulate the dust cycle in the atmosphere for current and last glacial maximum lgm climates we obtain a 2 5 fold higher dust loading in the entire atmosphere and a twenty fold higher loading in high latitudes in lgm relative to present comparisons to a compilation of atmospheric dust deposition flux estimates for lgm and present in marine sediment and ice cores show that the simulated flux ratios are broadly in agreement with observations differences suggest where further improvements in the simple dust model could be made the simulated increase in high latitude dustiness depends on the expansion of unvegetated areas especially in the high latitudes and in central asia caused by a combination of increased aridity and low atmospheric co2 the existence of these dust source areas at the lgm is supported by pollen data and loess distribution in the northern continents these results point to a role for vegetation feedbacks including climate effects and physiological effects of low co2 in modulating the atmospheric distribution of dust

on the seasonal sea ice cover of the sea of okhotsk free of ice 4 months of the year the sea of okhotsk begins to freeze over in a few coastal locations in november attains its maximum ice coverage usually in mid march and by june retains ice in only a few coastal regions this sequence is well recorded by satellite imagery from the electrically scanning microwave radiometer esmr on board nimbus 5 four years of esmr data reveal significant interannual variations in the maximum ice cover and in the smoothness of the growth and retreat periods of the years 1973 1976 the heaviest ice cover occurred in 1973 and the growth period most interrupted by temporary ice edge retreats was in 1974 comparison of the general features of the cycle of sea ice distribution with basic oceanographic factors shows that ice forms first in cold shallow low salinity waters and then seems to drift in a direction approximating the okhotsk kuril current system two basic patterns of ice edge positioning which occur frequently in the esmr data are identified as a rectangular structure and a wedge structure each of these is strongly correlated with the bathymetry of the region and with the known current system suggesting that convective depth and ocean currents play an important role in determining ice patterns certain major interannual variations in the ice extents are accounted for by interannual contrasts in the atmospheric pressure fields

atmospheric transport of iron and its deposition in the ocean the atmospheric transport of continental weathering products is responsible for much of the mineral material and fe entering the open ocean and is probably the dominant source of nutrient fe in the photic zone in regions where other nutrients are present in high concentrations the flux of fe from the atmosphere may be a limiting factor in primary productivity due to the larger source regions for dust north of the equator 8 times more atmospheric fe is deposited in the northern hemisphere than in the southern hemisphere the mineral aerosol and fe transport and deposition are highly variable due to the episodic nature of dust generation and its transport and deposition processes between 10 and 50 of the total atmospheric fe entering the world ocean appears to dissolve i e it will pass through a 0 4 m pore size filter rapidly when the mineral matter enters the ocean much of the atmospheric fe is present as fe ii apparently produced as a result of photochemical reduction reactions taking place during atmospheric transport this readily soluble fe ii should be available immediately for use as a nutrient by phytoplankton atmospheric transport from the continents is estimated to supply 3 times as much dissolved fe to the oceans as that delivered via rivers

large changes in seasonal sea ice distribution and productivity in the sea of okhotsk during the deglaciations changes in the surface environment of the central sea of okhotsk were reconstructed using tex86 paleothermometry facilitated by the bit index in order to investigate paleoenvironmental changes during the glacial interglacial cycles the core top tex86 derived temperature is the same as the present day summer sea surface temperature sst suggesting that tex86 records seasonal rather than annually averaged ssts in this region the tex86 record reveals 3 c lower summer sst during glacial maxima than during interglacial periods and significant warming during the deglaciations 15 10 ka and 136 130 ka this is consistent with previous inferences of more expanded and persistent seasonal sea ice during the glacial periods than the present day and its substantial retreat during the deglaciation timing of the deglacial warming also coincided with a distinct increase in coccolithophorid productivity suggesting a causal relationship between sea surface warming and coccolithophorid blooms during the deglaciations the relationship could reflect an increase in the supply of fresh and warm water from the amur river during deglaciation which significantly impacted hydrology by facilitating sea surface stratification which in turn promoted production of coccolithophids

characteristics and ages of tephra layers in the central okhotsk sea over the last 350 kyr abstract a sequence of 9 ash layers tephra found in the middle late pleistocene and holocene sediments of the central okhotsk sea was established on the basis of glass chemical composition and refractive indices grain size distributions and heavy mineral assemblages five tephras were also characterized by rare earth element distributions volcanic sources and ages of the identified tephra were estimated based on pre existing marine sediment core chronostratigraphy and correlation between these marine tephra deposits with geochemically similar terrestrial deposits on the kamchatka peninsula and adjacent kurile islands areal distributions and approximate eruptive volumes of pyroclastic material were also estimated for some of these tephras

environmental change in the sea of okhotsk during the last 1 1 million years on the basis of two sedimentary records from the central sea of okhotsk we reconstruct the closely coupled glacial interglacial changes in terrigenous flux marine productivity and sea ice coverage over the past 1 1 myr the correspondance of our sedimentary records to the china loess grain size record china loess particle timescale chiloparts suggests that environmental changes in both the sea of okhotsk area and in se asia were closely related via the siberian atmospheric high pressure cell during full glacial times our records point to a strong siberian high causing northerly wind directions the extension of the sea ice cover and a reduced amur river discharge deglacial maxima of terrigenous flux were succeeded by or synchronous to high productivity events marine productivity was strengthened during glacial terminations because of an effective nutrient utilization at times of enhanced water column stratification and high nutrient supply from fluvial runoff and sea ice thawing during interglacials se monsoonal winds prevailed analogous to today s summer situation of a pronounced mongolian heat low and a strong hawaiian high strong freshwater discharge induced by high precipitation rates in the amur drainage area and a seasonally reduced and mobile sea ice cover favored marine productivity although being considerably lower than during the terminations and a lowered flux of ice rafted detritus

late quaternary changes of the oxygen conditions in the bottom and intermediate waters on the western kamchatka continental slope the sea of okhotsk microfossil data on the foraminifers and radiolarians in the sediment core komex lv28 44 3 the kamchatka slope in the eastern sea of okhotsk exhibit the changes in the water oxygen conditions during the last 146 ky the paleoenvironmental proxies are the radiolarian species cycladophora davisiana as indicator of the upper intermediate water ventilation and the benthic planktonic foraminifers as indicators of the bioproductivity and bottom water oxygenation in case of sediment core lv28 44 3 the bottom water represents the lower intermediate one so that conclusions on paleoenvironments are applicable for the most range of the local intermediate water the well oxygenated intermediate and near bottom waters existed in the area of study during the penultimate glaciation of mis 6 early weichselian initiation of the last glaciation within mis 5b d and last glacial stages of mis 3 2 the intervals of the short low o2 bottom events with suboxic conditions dissolved o2 in water 0 3 1 2 ml l occur during the last interglacial mis 5e eemian stage 125 to 113 ka and during the last deglaciation 17 5 to 6 5 ka eemian low o2 bottom events are associated with the high bioproductivity of the subsurface water but poor ventilation on the upper intermediate depths the low o2 bottom events during the last deglaciation occurred at the high bioproductivity of the subsurface water and active ventilation on the upper intermediate depths

satellite passive microwave studies of the sea of okhotsk ice cover and its relation to oceanic processes 1978 1982 this paper describes the use of the nimbus 7 scanning multichannel microwave radiometer smmr satellite data to study the ice cover in the sea of okhotsk during the four winters of 1978 1982 the ice concentration estimates obtained from smmr are used to study two different polynyas one over the kashevarova bank and the other over the northwest continental shelf for the kashevarova polynya this study shows that the polynya which may be related to the upwelling observed in historic summer cruises occurs directly over the bank for the continental shelf which because of strong offshore winds and cold temperatures is a region of high ice production the polynya areas are combined with heat flux estimates from weather station data to yield the production rates of ice salt and dense shelf water as a previous study by kitani 1973 shows the mixing of this dense shelf water with pacific water yields a water mass unique to the okhotsk which is the layer of cold low salinity intermediate water between depths of 150 and 800 m from our calculations we estimate that the dense shelf water is produced at an annual rate of about 0 5 sv and that the intermediate water is produced at a rate of 1 2 sv which yields a renewal time for this layer of 10 40 years

sea surface temperature changes in the okhotsk sea and adjacent north pacific during the last glacial maximum and deglaciation abstract we estimated sea surface temperatures ssts in the western okhotsk sea during the last glacial maximum lgm and the last glacial termination from measurements of the alkenone unsaturation index u k 37 the t etra e ther inde x of tetraethers consisting of 86 carbon atoms tex 86 and tex 86 l in piston core sediments which reveal the climate response of this region to different types of forcings tex 86 l is a modification of tex 86 proposed for high latitude ocean regions the tex 86 l derived temperatures were not different from the alkenone derived temperatures from the same and nearby sediment samples during the lgm alkenone derived temperatures in the okhotsk sea were relatively warm these and similarly warm alkenone derived temperatures found at many other sites in the western north pacific may reflect a shift in the season of biomarker production from early summer and autumn to mid summer during the lgm as a result of the expansion of the season of sea ice cover empirical orthogonal function eof analysis of alkenone derived temperatures at 14 sites from the north pacific suggested substantial cooling between 20 and 14 cal kyr bp during the deglaciation at 11 of the sites including 4 sites in the okhotsk sea this dominant eof mode suggests either an overall seasonal bias in alkenone derived temperatures or potential shifts in the haptophyseae production season the second eof mode of variability indicated a deglacial warming trend punctuated by millennial scale cold events associated with reorganizations of the atlantic meridional overturning circulation the sst pattern corresponding to this eof mode is indicative of millennial scale meridional shifts of the axis of the westerly jet which may have affected heat transport across the kuroshio reconstructed temperature changes in particular in the okhotsk sea provide insight into the conditions that modulated the ventilation history of intermediate waters in the north pacific

neodymium isotopic variations in north pacific modern silicate sediment and the insignificance of detrital ree contributions to seawater the neodymium isotopic composition of the silicate fraction of holocene pelagic sediments from the north pacific define two provinces a central north pacific province characterized by unradiogenic and remarkably homogeneous end 10 2 0 5 and a narrow circum pacific marginal province characterized by more radiogenic and variable end 4 2 3 8 the silicate fraction in the central north pacific is exclusively eolian based on prevailing wind patterns meteorological data and neodymium isotopic data the only significant sediment source is chinese loess leaching experiments on chinese loess confirm that leachable nd is isotopically indistinguishable from bulk and residual silicate nd silicates in the circum north pacific marginal province comprise eolian loess volcanic ash and hemipelagic sediments derived from volcanic arcs a compilation of pacific seawater and mn nodule end data shows no clear spatial variation except for a general decrease from surface to deep waters from 3 to 4 and slightly lower end in bottom waters along the western north pacific due to the incursion of antarctic bottom water the relative homogeneity of bottom water end which contrasts sharply with the distinctive variation in sediment end plus the large difference between the average end of bottom waters and the central north pacific eolian silicates 4 vs 10 suggests that any contribution of ree to seawater from eolian materials is insignificant furthermore leaching of ree from eolian particles as they sink though the water column must be insignificant because nd in shallow waters is more radiogenic than nd in deeper waters that there is no contrast in the nd isotopic composition of bottom waters that overlie the central and marginal sediment provinces suggests that the ash and hemipelagic sediments derived from pacific rim volcanic arcs also contribute minimal ree to seawater the elimination of eolian ash and hemipelagic sediments leaves only near shore riverine particulates as a possibly significant particulate source of ree to seawater

a multiproxy study of past environmental changes in the sea of okhotsk during the last 1 5 ma abstract long chain diols have been detected in a wide range of environments and have been used to reconstruct past environmental changes however only a few long term records exist to date here we reconstructed past environmental changes in the central sea of okhotsk over the last 1 5 million years covering the mid pleistocene transition mpt sea surface temperatures sst reconstructed using the long chain diol index ldi reflects glacial interglacial changes however when compared with other organic paleothermometers uk 37 and texl86 the ldi sst is lower during interglacials and similar or higher during glacials possibly suggesting a shift of diol production season during interglacials the ldi sst does not change in periodicity around the mpt as observed for the texl86 likely due to this seasonal shift diatom productivity as recorded by 1 14 diols and biogenic opal content increased during the main deglaciations with a succession from proboscia diatoms to diatoms with a more heavily silicified shell confirming that primary productivity in the central sea of okhotsk is driven by sea ice progress and retreat in contrast to the ldi sst the 1 14 diols record shows a change in periodicity around the mpt from 41 to 100 kyr cycle suggesting an influence of orbital parameters on diatom productivity in the central sea of okhotsk the relative amount of c32 1 15 diol fc32 1 15 a proxy for riverine input correlates with sea level change with more riverine derived material reaching the core site when the amur river mouth is closer at lower sea levels in agreement fc32 1 15 shows a change in periodicity during the mpt with the appearance of a 100 kyr cycle our results show that the long chain diols can provide important paleoceanographic information in subpolar environments over long time scales but that temperature reconstructions can be severely impacted by changes in seasonality

deglacial variability in okhotsk sea intermediate water ventilation and biogeochemistry implications for north pacific nutrient supply and productivity highlights multi proxy multi site reconstruction of okhotsk sea palaeo productivity and mid depth ventilation changes from 8 to 18 ka link between hinterland river discharge and downstream okhotsk sea intermediate water osiw ventilation nutrient signatures surplus fe si oh 4 export in osiw during bolling allerod to pelagic pacific supported transient nutrient replete conditions subarctic and subtropical pacific gyres disconnected during bolling allerod with restricted osiw flow to lower latitudes deglacial osiw export and mid depth pacific biogeochemistry modulate millennial scale regional co2 source sink conditions the modern north pacific plays a critical role in marine biogeochemical cycles as an oceanic sink of co2 and by bearing some of the most productive and least oxygenated waters of the world ocean the capacity to sequester co2 is limited by efficient nutrient supply to the mixed layer particularly from deeper water masses in the pacific s subarctic and marginal seas the region is in addition only weakly ventilated by north pacific intermediate water npiw which receives its characteristics from okhotsk sea intermediate water osiw here we present reconstructions of intermediate water ventilation and productivity variations in the okhotsk sea that cover the last glacial termination between eight and 18 ka based on a set of high resolution sediment cores from sites directly downstream of osiw formation in a multi proxy approach we use total organic carbon toc chlorin biogenic opal and caco3 concentrations as indicators for biological productivity c n ratios and xrf scanning derived elemental ratios si k and fe k as well as chlorophycean algae counts document changes in amur freshwater and sediment discharge that condition the osiw stable carbon isotopes of epi and shallow endobenthic foraminifera in combination with 14c analyses of benthic and planktic foraminifera imply decreases in osiw oxygenation during deglacial warm phases from c 14 7 to 13 ka bolling allerod and c 11 4 to 9 ka preboreal no concomitant decreases in okhotsk sea benthic planktic ventilation ages are observed in contrast to nearby but southerly locations on the japan continental margin we attribute okhotsk sea mid depth oxygenation decreases in times of enhanced organic matter supply to maxima in remineralization within osiw in line with multi proxy evidence for maxima in primary productivity and supply of organic matter sedimentary c n and fe k ratios indicate more effective entrainment of nutrients into osiw and thus an increased nutrient load of osiw during deglacial warm periods correlation of palynological and sedimentological evidence from our sites with hinterland reference records suggests that millennial scale changes in osiw oxygen and nutrient concentrations were largely influenced by fluvial freshwater runoff maxima from the amur caused by a deglacial northeastward propagation of the east asian summer monsoon that increased precipitation and temperatures in conjunction with melting of permafrost in the amur catchment area we suggest that osiw ventilation minima and the high lateral supply of nutrients and organic matter during the allerod and preboreal are mechanistically linked to concurrent maxima in nutrient utilization and biological productivity in the subpolar northwest pacific in this scenario increased export of nutrients from the okhotsk sea during deglacial warm phases supported subarctic pacific shifts from generally fe limiting conditions to transient nutrient replete regimes through enhanced advection of mid depth nutrient and fe rich osiw into the upper ocean this mechanism may have moderated the role of the subarctic pacific in the deglacial co2 rise on millennial timescales by combining the upwelling of old carbon rich waters with a transient delivery of mid depth derived bio available fe and silicate

a biomarker approach for assessing marine and terrigenous inputs to the sediments of sea of okhotsk for the last 27 000 years abstract a sediment core taken from the sea of okhotsk which is located in the western north pacific rim with an extensive seasonal sea ice cover was investigated for lipid class compounds total organic carbon total nitrogen and 13 c of bulk organic matter to reconstruct changes in sedimentary regimes of marine and terrestrial organic matter over the last 27 kyrs higher molecular weight n alkanes fatty acids and fatty alcohols showed an increase in terrigenous inputs in glacial and to a greater extent in early deglacial periods the enhanced terrestrial input in the deglaciation stages has for the first time been found and never been reported in the open ocean biomarker profiles together with the coarse grain size distribution in nearby sediment cores suggested that sea ice rafting was the main transport mechanism of continental material to the okhotsk sea sediments however the ice rafting inputs have been weakened from 14 kyrs bp to the holocene probably due to a rapid reduction of the sea ice cover and continental shelf erosion profiles of c 37 alkenones phytol and brassicasterol as well as temporal variation in calcium carbonate and organic carbon contents indicated that the marine inputs were enhanced during the deglaciation the enhanced marine inputs were likely caused by an intensification of the primary production induced by a possibly increased nutrient supply from the continental shelves in early deglaciation and by the deglacial retreat of the sea ice cover at 14 kyrs bp this study demonstrates that biomarkers in the marginal marine sediments had recorded changes in the biogeochemical processes in the sea of okhotsk over the last 27 kyrs which may be significantly affected by changes in the okhotsk water exchange processes such as sea ice activity and sea ice transport of terrigenous materials

paleoceanography of the last 500 kyrs in the central okhotsk sea based on geochemistry abstract analyses of geochemical constituents organic carbon nitrogen calcium carbonate and biogenic opal on core yk07 12 pc3b core pc3b provided detailed and useful information in biological productivity and paleoceanographic changes which occurred in the central okhotsk sea during the last 500 kyrs an age model for core pc3b was established based on changes in benthic foraminiferal 18 o the trend in organic carbon oc content represented the temporal change that can be correlated with the 18 o curve in core pc3b high during the interglacial periods mis 1 5 9 11 and 13 the trend in caco 3 content represented is similar to the trend seen in the oc content the high correlation between oc and caco 3 contents indicates an increase in coccolithophorid productivity during the early deglaciations the comparison between the changes in caco 3 and biogenic opal indicates that the dominant phytoplankton group was coccolithophorids during the early deglaciations which was subsequently replaced by diatoms during the late deglaciations it appears that such a temporal phytoplankton succession was caused by an increase in dissolved silicon supply to the euphotic layer possibly associated with a change in surface hydrography that subsequently caused an upward expansion of the intermediate layer such ecological changes probably played an important role in the uptake of atmospheric co 2

penultimate and last glacial oceanographic variations in the bering sea on millennial timescales links to north atlantic climate we present high resolution multi proxy records from a marine sediment core so201 2 85kl from the western bering sea to assess orbital and millennial scale paleoceanographic conditions during two last glacial intervals including both terminations based on changes in foraminiferal assemblages grain size content and previously published toc and d13c records we reconstruct variations in sea surface biological productivity intermediate water oxygenation and sea ice conditions during the last 180 kyr our data demonstrate remarkable differences between the penultimate mis 6 and last mis 4 2 glacial relatively high sea surface bioproductivity and reduced sea ice cover are reconstructed for the penultimate glacial interval whereas low bioproductivity and expanded sea ice cover appear to be typical for the last glacial millennial scale changes in intermediate water ventilation are inferred from faunal records for the middle part of the penultimate glacial high amplitude environmental variability during the penultimate glacial time in the bering sea resembles the well known dansgaard oeschger oscillations and roughly corresponds to similar rapid climatic fluctuations found in north atlantic records the termination ii and i intervals display a similar succession of high bioproductivity events being more pronounced during the penultimate glacial interglacial transition probably due to the different orbital configuration during the late phase of termination ii two short intervals characterized by high sea surface bioproductivity and low oxygen content of bottom waters resemble the bolling and allerod warmings whereas an episode with low bioproductivity occurs in between similar to the older dryas our results provide support for a close circumpolar coupling between high latitude environments on millennial timescales at least since the penultimate glacial

okhotsk sea ice coverage and kamchatka glaciation over the last 350ka evidence from ice rafted debris and planktonic δ18o high resolution records of ice rafted debris ird and oxygen isotope records spanning an e w trending transect across the okhotsk sea unravel the marine and terrestrial cryogenic history of ne siberia over the last 350 kyr ird predominantly dispersed basin wide by sea ice shows lowest fluxes during interglacial periods implying a reduced and seasonal sea ice coverage highest ird accumulation rates are observed during glacial and deglacial periods with a more extended but highly dynamic ice cover although being rather synchronous ird fluxes are on average higher in the western okhotsk sea than in the eastern part pointing to a persistent but mobile particle supplying sea ice cover even during full glacial conditions presumably less dense in the eastern parts mis 6 is exceptional in this respect asynchronous fluxes of ird which vary spatially reflect rapid paleoclimatic and paleo glaciomarine changes ird accumulation rates were by factor 2 3 higher during mis 6 as compared to the last glacial maximum and the ird depositional center shifted from the western okhotsk sea early mis 6 toward kamchatka late mis 6 synchronous to a distinct change in the ird mineral composition both the characteristic composition of late mis 6 ird originating from the sredinny mountain range of kamchatka and their significantly enhanced accumulation rates refer to intensified iceberg dispersal across the eastern part of the okhotsk sea at 138 ka 135 ka 129 ka and 128 ka bp this scenario affords the presence of extended mountain glaciers protruding down to sea level on the western side of kamchatka anomalously light planktonic stable oxygen isotopes during mis 6 3 termination ii and mis 5 5 5 4 suggest significant freshwater supply related to the westward drainage of kamchatka glaciers the intensified kamchatka glaciation observed during late mis 6 was repeated during mis 3 iceberg discharges into the eastern okhotsk sea are observed at 60 ka 51 ka 42 ka 38 ka 36 ka and 31 ka and may partly correspond to n atlantic heinrich events

geomagnetic relative paleointensity chronostratigraphy of sediment cores from the okhotsk sea abstract we conducted a paleomagnetic study of three piston cores from the central okhotsk sea to enable inter core correlation and age estimation using relative paleointensity of the geomagnetic field which can provide the basis for paleoceanographic studies in this area the cores are composed of diatom bearing dark olive gray silty clay magnetic overprints were generally removed by alternating field demagnetization of up to 10 mt magnetic properties reveal no evidence of reductive diagenesis or magnetite dissolution the anhysteretic remanent magnetization arm was used as a normalizer for relative paleointensity estimations because there is a smaller coherence between normalized intensity and the arm than with saturation isothermal remanent magnetization sirm depths of the three cores were converted to ages by correlating relative paleointensity variations with those from ocean drilling program site 983 which was selected as a target curve because of its higher resolution than the widely used sint 800 paleointensity stack the age at the bottom of the cores is estimated to be between 360 and 540 ka inter core correlation using relative paleointensity variations reveals that changes in magnetic properties such as magnetic susceptibility and magnetic mineral grain size are not synchronous between the northernmost site and the southern two sites despite their close proximity which indicates regional differences in paleoenvironmental variations associated with glacial interglacial changes nevertheless relative paleointensity variations among the three cores are mutually consistent and agree with other published paleointensity curves which indicates that our paleointensity records are not influenced significantly by lithological changes

analysis and modelling of gravity and piston coring based on soil mechanics the effects of gravity and piston corers on the dimensional accuracy of marine sediment cores is analysed using principles of soil mechanics a model for the coring process is built around the feedback that arises and develops between the core barrel and the sampled sediment this model for sediment response is applied to different hypothetical coring scenarios which are then compared to real examples providing insights into the specific effects of each sampling method and the development of these effects down core four cores from a single location on the iberian margin are found to contain stratigraphically intact successions that differ in length by a factor of up to 2 7 due solely to the different effects of each coring method these dimensional discrepancies are attributed to the combined effects of over sampling in the upper portions of the piston cores due to cable rebound causing upward piston acceleration and under sampling dominant in the basal portions of the open barrel gravity type cores it is suggested that heavier piston corers deployed on longer lighter cables are prone to greater over sampling ratios over longer stratigraphic intervals due to the increased likelihood and extent of cable rebound cable rebound may also give rise to double penetration of gravity corers resulting in repeated stratigraphic intervals knowledge of the dimensional accuracy of marine sediment cores is essential to an evaluation of past sedimentation rates and hence interpretations of past depositional processes it is therefore essential that we recognise the sampling effects of each coring method and their variability down core lest coring artefacts be interpreted as sedimentary signals different core types may be more suited to different palaeoceanographic investigations hence failing the development of a practical cable deployed recoilless piston corer a combination of a variety of core types will permit the best acquisition of the in situ stratigraphic truth our results suggest that a large diameter dc 20 30 cm square barrel gravity corer for the top 10 12 m combined with a cylindrical piston corer below 10 m may provide the least deformed material

a record of past ocean atmosphere radiocarbon differences from the northeast pacific a record of the 14c age differences between atmosphere and the mixed layer of the northeast pacific ocean was obtained from 58 radiocarbon measurements on shells and associated wood from coastal sediments in british columbia this series of mixed layer reservoir ages spans the holocene and extends into the period of the younger dryas cold event in the north atlantic and surrounding regions the data reflect the extent of upwelling in the northeast pacific and thus constrain models of carbon cycling and ocean circulation most of the reservoir ages are only slightly less than than the present preindustrial value of about 800 years and may be identical when probable sampling errors are taken into account either the north pacific reached a state close to its present mode of circulation at or before the end of the younger dryas or a different circulation fortuitously produced a similar reservoir age our results support the hypothesis that slow changes in atmospheric radiocarbon concentrations over the holocene arose from 14c production rate changes data corresponding to a radiocarbon age of around 6400 years b p give a reservoir age of 1200 years if this result is confirmed it indicates a much greater variability for the holocene ocean circulation than was previously believed possible

magnetostratigraphy and tephrochronology of the upper quaternary sediments in the okhotsk sea implication of terrigenous volcanogenic and biogenic matter supply seven lithological units alternating between horizons enriched in biogenic opal diatoms and carbonate foraminifera and units composed largely of terrigenous sediment with very low biogenic admixture were distinguished in a series of late quaternary sediment cores from the sea of okhotsk sediments were characterised using on board visual description smear slides analyses grain size composition and magnetic susceptibility ms records five tephra marker layers identified as ko tr k2 k3 and k4 were distinguished using petrological mineralogical and geochemical analyses age models were developed by comparing lithological units tephra stratigraphy and ms records with oxygen isotope curves and with records of biogenic caco3 opal content and sediment grain size composition in three ams radiocarbon dated okhotsk cores this chronological framework allowed us to investigate climate control over the sedimentation regime and productivity and to clarify the formation times of the lithological and tephra units the data show that sediment ms variations in the south eastern area of the glacial okhotsk sea arose primarily from volcanic material input the sedimentation in all other parts of the sea was mainly controlled by the supply of terrigenous material the cores show a tight correlation between ms sediment grain size and climate change in the okhotsk sea coarse sediments with a high ms were accumulated during the cold period oxygen isotope stages mis 2 4 6 fine sediments with a low ice rafted debris ird content and ms were formed in the warm isotope stages according to the oxygen isotope stratigraphy and radiocarbon data the ko tr k2 k3 and k4 tephra were deposited at 7 7 8 0 26 0 kyr bp in mis 4 about 60 70 kyr ago and near mis 5 4 respectively comparison of tephra mineralogy petrology spatial distributions and ages with the history of kurile kamchatka volcanism allows us to identify likely candidates for the tephra source eruptions the combined use of ms records tephrochronology and lithological unit sequences provides a detailed basis for okhotsk sea sediment stratigraphy

coherent response of antarctic intermediate water and atlantic meridional overturning circulation during the last deglaciation reconciling contrasting neodymium isotope reconstructions from the tropical atlantic antarctic intermediate water aaiw plays important roles in the global climate system and the global ocean nutrient and carbon cycles however it is unclear how aaiw responds to global climate changes in particular neodymium isotopic composition end reconstructions from different locations from the tropical atlantic have led to a debate on the relationship between northward penetration of aaiw into the tropical atlantic and the atlantic meridional overturning circulation amoc variability during the last deglaciation we resolve this controversy by studying the transient oceanic evolution during the last deglaciation using a neodymium enabled ocean model our results suggest a coherent response of aaiw and amoc when amoc weakens the northward penetration and transport of aaiw decreases while its depth and thickness increase our study highlights that as part of the return flow of the north atlantic deep water nadw the northward penetration of aaiw in the atlantic is determined predominately by amoc intensity moreover the inconsistency among different tropical atlantic end reconstructions is reconciled by considering their corresponding core locations and depths which were influenced by different water masses in the past the very radiogenic water from the bottom of the gulf of mexico and the caribbean sea which was previously overlooked in the interpretations of deglacial end variability can be transported to shallow layers during active amoc and modulates end in the tropical atlantic changes in the aaiw core depth must also be considered thus interpretation of end reconstructions from the tropical atlantic is more complicated than suggested in previous studies

surface nitrate utilization in the bering sea since 180 ka bp insight from sedimentary nitrogen isotopes we present high resolution records of sedimentary nitrogen 15nbulk and carbon isotope ratios 13cbulk from piston core so201 2 85kl located in the western bering sea the records reflect changes in surface nitrate utilization and terrestrial organic matter contribution in submillennial resolution that span the last 180 kyr the 15nbulk record is characterized by a minimum during the penultimate interglacial indicating low nitrate utilization 62 80 despite the relatively high export production inferred from opal concentrations along with a significant reduction in the terrestrial organic matter fraction mterr this suggests that the consumption of the nitrate pool at our site was incomplete and even more reduced than today 84 15nbulk increases from marine isotope stage mis 5 4 and culminates during the last glacial maximum which indicates that nitrate utilization in the bering sea was raised during cold intervals mis 5 4 5 2 4 and almost complete during mis 3 and 2 93 100 this is in agreement with previous hypotheses suggesting that stronger glacial stratification reduced the nutrient supply from the subeuphotic zone thereby increasing the iron to nutrient ratio and therefore the nitrate utilization in the mixed surface layer large variations in 15nbulk were also recorded from 180 to 130 ka bp mis 6 indicating a potential link to insolation and sea level forcing and its related feedbacks millennial scale oscillations were observed in 15nbulk and 13cbulk that might be related to greenland interstadials

barium accumulation in the atlantic sector of the southern ocean results from 190 000 year records extensive investigations of sedimentary barium were performed in the southern south atlantic in order to assess the reliability of the barium signal in antarctic sediments as a proxy for paleoproductivity maximum accumulation rates of excess barium were calculated for the antarctic zone south of the polar front where silica accumulates at high rates the correspondence between barium and opal supports the applicability of barium as a proxy for productivity within the antarctic zone north of today s average sea ice maximum interglacial vertical rain rates of excess barium are high with a maximum occurring during the last deglaciation and early holocene and during oxygen isotope chronozone 5 5 during these periods the maximum silica accumulation was supposedly located south of the polar front glacial paleoproductivity instead was low within the antarctic zone north of the polar front significantly higher barium accumulation occurs during glacial times the vertical rain rates however are as high as in the glacial antarctic zone therefore there was no evidence for an increased productivity in the glacial southern ocean

glacial to deglacial ventilation and productivity changes in the southern okhotsk sea abstract as a source region of north pacific intermediate water the okhotsk sea plays an important role in the ventilation of the north pacific to understand the detailed oceanographic changes in this marginal sea since the last glaciation we studied decadal to centennial scale proxy records from new sediment cores from the southwestern okhotsk sea glacial to holocene 14 c records of benthic foraminiferal shells suggested enhanced ventilation in the okhotsk sea during the early deglacial period between 18 and 15 ka corresponding to heinrich event 1 although the 14 c reconstruction has considerable uncertainties the okhotsk sea may have acted as a source for vigorous ventilation of the subarctic pacific during this period caco 3 preservation events appear to be better explained by the ventilation history of the okhotsk sea than by coccolithophores and foraminifera production caco 3 preservation started to improve during 18 to 15 ka and pronounced peaks in the caco 3 content corresponded to the bolling allerod 15 to 13 ka and preboreal 11 5 to 10 ka warm periods diatom and coccolithophore productivity remained low in the okhotsk sea throughout the glacial to deglacial periods different from the situation in the open subarctic pacific where high productivity was observed during the bolling allerod period after the preboreal period biogenic opal gradually increased and 15 n decreased in the southern okhotsk sea suggesting that productivity was enhanced by a relaxation of the nitrate limitation

tephra layers of in the quaternary deposits of the sea of okhotsk distribution composition age and volcanic sources the fullest summary on composition age and distribution of 23 tephra layers detected and investigated in the okhotsk sea pleistocene holocene deposits is presented seven tephra layers are surely identified with powerful explosive eruptions of volcanoes of kamchatka kurile and japanese islands for them the areas of ash falls including which weren t revealed earlier on the land are specified and established it is estimated that explosive eruptions of volcanoes of the kamchatka sredinny range were the sources for three tephra layers complex investigations of morphological mineralogical and chemical composition of tephras including composition of rare and earth rare elements electron microprobe analysis and laser ablation method la icp ms have been made for all studied layers they were a basis for tephrostratigraphic correlation of the regional deposits promoting to specification of stages of volcanic explosive activity in this region

bubble induced porewater mixing a 3 d model for deep porewater irrigation porewater data from vent sites of the northeastern shelf off sakhalin island sea of okhotsk exhibit bottom water concentrations down to a sediment depth of up to 300 cm below this depth solute concentrations rapidly change due to methanogenesis and anaerobic methane oxidation amo the profile shapes suggest an irrigation like process that mixes on a meter scale at these sites active gas emanation into the overlying water column and near surface gas hydrates are commonly observed we propose that methane gas bubbles rise through the soft surface sediments and cause mixing of the porewater mathematically the bubble induced irrigation can be described by eddy diffusion enhancing the diffusive transport of solutes by several orders of magnitude a 3 d numerical transport reaction model was developed to investigate the parameters defining the mixing process such as bubble rise velocity tube size tube distribution in the sediment and ebullition frequency model consistency with the field data requires eddy diffusivities 1 105 cm2 a tube densities of 4 tubes m2 equivalent to a tube spacing of 40 cm active gas seepage for more than a few weeks or months and moderate to low diagenetic reaction rates of solutes the corresponding methane gas fluxes that are predicted from the results of the model realizations range from 1 103 5 105 l m2 a due to bubble mixing solute fluxes in these sediments are increased by a factor of 3 and the maximum amo rate by a factor of 7

stable isotope and lithologic evidence of late glacial and holocene oceanography of the northwestern pacific and its marginal seas abstract stable isotopes geochemical lithological and micropaleontological results from cores from the far northwest fnw pacific and the okhotsk and bering seas are used to reconstruct the regional environment for the last glaciation the deglacial transition and the holocene 18 o records of planktonic foraminifera of the region show two light shifts during deglacial time provoked by the freshening of the surface water and climate warming these north pacific terminal events t1anp and t1bnp with ages of 12 500 and 9300 yr b p respectively occur almost simultaneously with two episodes of accelerated glacier melting around the north atlantic along with the isotopic shifts the caco 3 content in regional sediments increased abruptly 1a and 1b carbonate peaks probably due to changes of productivity and pore water chemistry of surface sediments organic matter and opal concentration increased during the transition between t1anp and t1bnp events in the sediments of the fnw pacific and the southern part of the bering sea and opal content increased in the holocene in the bering and okhotsk seas 13 c records of cores from the okhotsk and bering seas and the fnw pacific do not contradict the hypothesis of increased intermediate water formation in the region during glaciation during deglaciation accumulation of the coarse terrigenous component decreased in sediments of the bering sea and the fnw pacific before the t1anp event probably as a result of rising sea level and opening of the bering strait

controls on deglacial changes in biogenic fluxes in the north pacific ocean the subarctic north pacific ocean holds a large co2 reservoir that is currently isolated from the atmosphere by a low salinity layer it has recently been hypothesized that the reorganization of these high co2 waters may have played a crucial role in the degassing of carbon dioxide to the atmosphere during the last deglaciation this reorganization would leave some imprint on paleo productivity records here we present 230th normalized biogenic fluxes from an intermediate depth sediment core in the northwest pacific rc10 196 54 7 n 177 1 e 1007 m and place them within the context of a synthesis of previously published biogenic flux data from 49 deep sea cores north of 20 n ranging from 420 to 3968 m water depth the 230th normalized opal carbonate and organic carbon fluxes from rc10 196 peak approximately 13 000 calendar years bp during the bolling allerod b a period our data synthesis suggests that biogenic fluxes were in general lowest during the last glacial period increased somewhat in the northwest pacific during heinrich event 1 and reached a maximum across the entire north pacific during the b a period we evaluate several mechanisms as possible drivers of deglacial change in biogenic fluxes in the north pacific including changes in preservation sediment focusing sea ice extent iron inputs stratification and circulation shifts initiated in the north atlantic and north pacific our analysis suggests that while micronutrient sources likely contributed to some of the observed changes the heterogeneity in timing of glaciogenic retreat and sea level make these mechanisms unlikely causes of region wide contemporaneous peaks in export production we argue that paleoobservations are most consistent with ventilation increases in both the north pacific during h1 and north atlantic during b a being the primary drivers of increases in biogenic flux during the deglaciation as respectively they were likely to bring nutrients to the surface via increased vertical mixing and shoaling of the global thermocline