did antarctic sea ice expansion cause glacial co2 decline 1 recently stephens and keeling 2000 have put forward an appealing theory for explaining the decrease in glacial atmospheric co2 they argue that a compact sea ice cover extending southward of 55 s trapped large amounts of co2 beneath the sea surface thus accounting for the lower atmospheric concentrations an atmosphere ocean box model in which sea ice area is prescribed allows them to simulate 80 of the co2 drawdown however glacial co2 levels can be attained in their model only when the fraction of ice covered area southward of the antarctic polar front rises to 99 100 we present simulations with a coupled sea ice upper ocean model indicating that ice area fractions so large might have not prevailed even under rather extreme glacial conditions the combination of our glacial ice coverage estimates with the ice area co2 relation derived by stephens and keeling suggests that co2 sequestration under sea ice could account for at most 15 50 of the total glacial co2 decline

the bering sea and paleoceanography abstract this paper serves as an introduction to the bering sea preceding the 14 contributed papers contained in this volume several parts of the paper are allocated for current reviews of the bering sea included in the review topics are geomorphology surface water circulation and the importance of the formation of intermediate waters representative results of previous paleoceanographic studies are also presented in particular focusing on spatial and temporal distributions of biosiliceous microfossils as well as isotopic analyses of carbon and nitrogen concerning changes in productivity and nutrients motivations behind the scientific expeditions conducted which resulted in the many papers included here are briefly discussed in order to illustrate the recent trend in paleoceanography in the bering sea and the adjacent regions brief summaries or highlights of each of the contributed papers are given in order to provide an overview of the volume

polycystine radiolarians in surface sediments from the bering sea green belt area and their ecological implication for paleoenvironmental reconstructions radiolarians in surface sediments along transects from the shelf edge along the slope into the deep basin of the northern bering sea are dominated by stylochlamydium venustum antarctissa sp 1 the spongodiscidae juvenile pseudodictyophimus gracilipes ceratospyris borealis the plagoniidae phormacantha group and plectacantha group siphocampe arachnea cycladophora davisiana and spongotrochus glacialis this dominance is most extreme on the shelf edge and slope where s venustum antarctissa sp 1 the spongodiscidae juvenile the plagoniidae and s glacialis have their highest relative abundance there is thus a close relation between radiolarian distribution and the high productivity of the bering sea green belt bsgb due to periodic sea ice melt the radiolarian depth distribution patterns indicate that some radiolarian species have specific ecological preferences s venustum the spongodiscidae juvenile and s glacialis live close to the surface water under relatively low temperature and low salinity conditions due to sea ice melting or melt water influx antarctissa sp 1 appears to dwell mainly in surface to subsurface waters but has not been recorded in trap samples of the bering sea the plagoniidae probably live in subsurface and intermediate waters s arachnea and c davisiana are intermediate to deep dwellers the close association of these radiolarians with the bsgb and specific water depths provides a valuable reference for paleoenvironmental reconstruction in the region

radiolarian responses of the central okhotsk sea to the global orbital and millennial scale climate oscillations over last 90 kyr abstract the study of total radiolarian content trc and species richness sr for radiolarian assemblage as well as absolute and relative abundance of cycladophora davisiana and abundance of other dominant taxa in the sediment core from the central okhotsk sea os over last 90 kyr with previously established age model position of millennial cycles of climatic changes and records of variations of various productivity proxies and activity of sea ices was carried out the trends of trc and sr in the radiolarian assemblage change synchronously on the orbital scale and are mainly determined by variations of paleoproductivity and input organic matter into the water column in turn the productivity of the os depends to a great extent on conditions of the sea ice formation and distribution and increases during the warmer mis 5a 3 and 1 with a shorter seasonal sea ice cover among various productivity proxies considered by us only ba bio reflects to the fullest extent the variations of trc and sr of radiolarians probably due to the fact that the accumulation of insoluble barite in sediment depends on degree of organic matter decomposition immediately within the water column and provision of more favorable for radiolarian food variations of trc of radiolarians and their sr on the millennial scale are also controlled by variations of productivity in the photic layer the millennial productivity minima associated with the cold greenland china stadials gs cs resulted in considerable sharp falls in trc and sr of radiolarians while subsequent increases in productivity during gi ci caused the smoother growth in trc and sr of radiolarians such a pattern of changes in the species richness and quantity of radiolarians in time is more similar to variations in 18o of stalagmite carbonates from the china caves than 18o of greenland ice core and probably is determined predominantly by variability of the winter monsoons in the east asia affecting the environment and ice cover of the os changes in absolute abundance aa of c davisiana on the orbital and millennial scales are closer related to changes in trc of radiolarians determined mainly by variations of the sea productivity changes in relative abundance ra of c davisiana in time are slightly different from variations in their absolute abundance as depend also on changes in percentage of other species in the assemblage

radiolarian faunal provinces in surface sediments of the greenland iceland and norwegian gin seas the overall abundance and species composition of the polycystine and phaeodarian radiolaria have been determined in 63 surface sediment samples from the gin seas these results are compared to chemical and physical properties of the overlying water masses there are three abundance maxima in the distribution of radiolarian skeletal debris preserved in these surface sediments centered on the iceland plateau southern norwegian basin and northern norwegian basin the most commonly encountered species were a spumellarida actinomma boreale a leptoderma larcospira minor and phorticium clevei b nassellarida amphimelissa setosa artobotrys boreale lithomelissa setosa lithocampe platycephala pseudodictyophimus gracilipes cycladophora davisiana a ndlithomitra lineata based on factor analysis of the core top assemblages the radiolarian species were grouped into three associations factor 1 a polar and arctic water association dominated by amphimelissa setosa varimax factor score 5 269 high factor component values are found in the iceland plateau area and in a wedge just north of the iceland faeroe ridge factor 2 an atlantic water association dominated by pseudodictyophimus gracilipes 3 247 lithomelissa setosa 2 731 and actinomma boreale 1 851 high factor component values are found in the eastern part of the norwegian sea particularly in the area under the influence of the norwegian current and factor 3 an atlantic and arctic water mixed association dominated by lithocampe platycephala 3 251 lithomelissa setosa 2 176 actinomma leptoderma 1 994 and artobotrys boreale 1 504 high factor component values are found immediately to the east of the iceland plateau in correspondence to the deepest part of the norwegian basin the correlation coefficients obtained between seasonal sea surface temperature and factors 1 r 2 d 0 835 a nd 2 r 2 d 0 891 show a good fit whilst for factor 3 there was a less marked r 2 d 0 497 but still significant at the 5 confidence level correlation for fifth degree polynomial regression functions the factors correlated better with the summer than the winter sea surface temperatures however at 20 50 100 and 200 m depth the correlation became increasingly better particularly so for the winter situation the highest species richness for polycystine radiolarians 28 species was found in the warm atlantic domain the lowest 24 species was found in the colder arctic and polar domains whilst an area approximating the position of the arctic front had between 24 and 28 species 1998 elsevier science b v all rights reserved

rhizoplegma boreale radiolaria a tracer for mesoscale eddies from coastal areas 1 the impact of mesoscale eddies on the production of radiolarian species rhizoplegma boreale in the central subarctic pacific was investigated through analysis of sinking particle fluxes collected using sediment trap and altimetry data from satellite observations altimetry observations provided the locations of mesoscale eddies in time and space and indicated that mesoscale eddies propagating around sediment trap station sa were closely related to the high r boreale fluxes at the station the mesoscale eddies likely provided the deep sea region of the central subarctic pacific with coastal nutrient rich waters derived from the region around the aleutian islands and influenced the productivity of microzooplankton groups at station sa

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

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

fifteen year time series of radiolarian fluxes and environmental conditions in the bering sea and the central subarctic pacific 1990 2005 abstract in order to examine radiolarian fluxes and evaluate their relationships to environmental conditions a fifteen year long time series observation on radiolarian fluxes was conducted using sediment trap materials collected at the bering sea station ab 53 5 n 177 w and the central subarctic pacific station sa 49 n 174 w during 1990 2005 encountered radiolarian assemblages include 124 taxa at station ab and 110 taxa at station sa in general total radiolarian fluxes of the coarse fraction 63 m 1 mm at station ab mean 8 7 10 3 shells m 2 d 1 were greater than those observed at station sa mean 6 5 10 3 shells m 2 d 1 mainly due to the differences in physico chemical conditions i e mixed layer depth surface circulation nutrient concentrations etc out of 110 taxa thirty eight abundant radiolarian taxa were chosen for enumeration and further statistical treatment including the taxa with 1 annual mean occurrence as abundant radiolarian species display variable flux patterns during the study period an r mode cluster analysis was used to identify eight clusters at station ab and eleven clusters at station sa marked changes in the relative contribution of each of the clusters to the total radiolarian assemblages are apparent notably high flux maxima of total radiolarians were observed around 1990 1995 2000 2003 and 2004 the observed inter annual variations in the faunal assemblages in the bering sea and the central subarctic pacific were related to large scale climatic shift such as the arctic oscillation ao the negative correlation between the radiolarian assemblages including surface to subsurface dwellers and the ao index may suggest a significant influence by the intensity of surface water mixing and water mass exchanges

antarctic stratification and glacial co2 one way of accounting for lowered atmospheric carbon dioxide concentrations during pleistocene glacial periods is by invoking the antarctic stratification hypothesis which links the reduction in co2 to greater stratification of ocean surface waters around antarctica1 2 as discussed by sigman and boyle3 this hypothesis assumes that increased stratification in the antarctic zone fig 1 was associated with reduced upwelling of deep waters around antarctica thereby allowing co2 outgassing to be suppressed by biological production while also allowing biological production to decline which is consistent with antarctic sediment records4 we point out here however that the response of ocean eddies to increased antarctic stratification can be expected to increase rather than reduce the upwelling rate of deep waters around antarctica the stratification hypothesis may have difficulty in accommodating eddy feedbacks on upwelling within the constraints imposed by reconstructions of winds and antarctic zone productivity in glacial periods

orbital and suborbital environmental changes in the southern bering sea during the last 50 kyr abstract high resolution geochemical paleontological and lithological records of two sediment cores in the southern bering sea manifest regional environmental changes over the last 50 kyr on orbital and millennial time scales high ice rafted debris ird content and percentages of radiolarian species cycladophora davisiana ehrenberg during marine isotope stages miss 3 and 2 indicate active intermediate water ventilation driven by intensive winter sea ice formation in the southern bering sea although the total abundance of siliceous microfossils in glacial sediments is relatively low glacial productivity is higher than in the late holocene on the millennial time scale decreases in the abundance of calcareous and siliceous microfossils and in c davisiana at studied core may imply enhancement of sea ice influence synchronous with heinrich events h 5 to 2 changes in the 18o of fossil benthic and planktonic foraminifera during h 5 3 are inferred to be related to variability in ice sheet volume similar to the pattern from antarctica accompanied by glacioeustatic sea level fluctuations up to 20 30 m in amplitude the maximum benthic and planktonic 18o values in the studied cores occur during the lgm when sea level was at the lowest stand and sea bottom water temperature was around 0 4 c strong environmental changes during the heinrich event 1 and b a warming in the southern bering sea provide evidence of deglacial injection of very old water and the subsequent increase in productivity due to surface and intermediate water mixing from the lgm to the mid holocene the 18obenth foram changes corresponded to changes in the global deep water 18o and a rise in the deep water temperature to 1 0 c at 8 5 6 5 kyr bp the subsequent environmental changes in late holocene helped establishment of near modern day hydrological and environmental conditions featuring strong surface water stratification and weakened deep water ventilation

new northwest pacific radiolarian data as a tool to estimate past sea surface and intermediate water temperatures a new radiolarian data set for transfer function estimates of past sea surface temperature sst and intermediate water temperature was developed in this study for the northwestern pacific ocean covering a region from 1 to 50 n and 120 to 167 e we analyzed 87 sediments surface samples selected 30 species and or species group found in shallow water for estimating past summer sst and 17 species and or species group found in the intermediate water for estimating past intermediate water temperature since the intermediate water temperature changes greatly between 200 and 500 m our estimates provide values at 500 m because temperatures are relatively stable between 500 and 1000 m in this context we estimated past summer sst and intermediate water at 500 m temperature within an error margin of 0 9 and 1 2 c respectively a test of the accuracy of our transfer functions conducted on core samples provided by iodp expedition 346 site u1429 in the northern east china sea showed that the reconstructed summer ssts fluctuated between 17 2 and 26 5 c in selected late pleistocene sequences these temperatures corresponded to modern winter and summer sst respectively which highlights the ability of our new database to accurately reconstruct summer sst the reconstructed intermediate water temperature fluctuates between 3 and 8 c which corresponds to the observed temperature range at depths of 500 m at high and midlatitudes respectively

pleistocene mammals of mediterranean islands abstract this paper provides a synthesis and an integration of the current knowledge on pleistocene mammals from the main mediterranean islands new evidence enables us to consider faunal complexes paleobiodiversity degree of endemism and ways of dispersals into a chronological frame the balearic islands developed an endemic fauna from mainland ancestors spreading during the messinian sardinia and corsica have had a pliocene early pleistocene fauna spread from mainland during the messinian the arrivals after this time can be related to occasional spreading during the early pleistocene and early middle pleistocene sicily and malta acted as an archipelago made up of small islands since late middle pleistocene sicily has been a large island with frequent faunal exchanges with the mainland during early pleistocene and early middle pleistocene crete was an archipelago occasionally reached by mammals communications with the mainland have probably been easier since the late middle pleistocene cyprus has been completely isolated and developed a strongly endemic and impoverished fauna

radiolarian based transfer function for the estimation of sea surface temperatures in the southern ocean atlantic sector a new radiolarian based transfer function for sea surface temperature sst estimations has been developed from 23 taxa and taxa groups in 53 surface sediment samples recovered between 35 and 72 s in the atlantic sector of the southern ocean for the selection of taxa and taxa groups ecological information from water column studies was considered the transfer function allows the estimation of austral summer sst december march ranging between 1 and 18 c with a standard error of estimate of 1 2 c sst estimates from selected late pleistocene squences were sucessfully compared with independent paleotemperature estimates derived from a diatom transfer function this shows that radiolarians provide an excellent tool for paleotemperature reconstructions in pleistocene sediments of the southern ocean

spatial distribution pattern of living polycystine radiolarian taxa baseline study for paleoenvironmental reconstructions in the southern ocean atlantic sector the horizontal and vertical distribution of living polycystine radiolarian taxa was investigated at seven locations on a n s transect between the antarctic zone 54 s in the southern ocean and the subtropical zone 30 s in the southeastern south atlantic during austral autumn four to five depth intervals from 0 to 1000 m depth were sampled with 55 m mesh opening closing nets in combination with a hydrographic ctd survey a factor analysis for the delineation of specific assemblages and the relation between different taxa and taxa groups resulted in eight factors of which five represent surface and subsurface factors and three deep water factors the spatial distribution pattern of the factors shows that distinct radiolarian assemblages are closely related to water depth distribution of water masses hydrographic boundaries such as frontal systems and nutrients this documents that the distribution of individual radiolarian assemblages is controlled by specific hydrographic conditions and water depth and allows the definition and consolidation of the autecological demands these data are crucial for the paleoenvironmental interpretation of fossil polycystine radiolarian assemblages the comparison of living polycystine radiolarian taxa with those preserved in surface sediments shows general similarities this study includes the first documentation on the distribution of living cycladophora davisiana in circumpolar deep water and supports previous studies stating that c davisiana also lives in deep water masses

coccolithophore caco3 flux in the sea of okhotsk seasonality settling and alteration processes abstract coccolithophore fluxes were determined in the sea of okhotsk using samples from a 1 year experiment 12 august 1990 to 12 august 1991 with sediment traps at 258 and 1061 m depth a special study was made on coccolithus pelagicus using fragmentation and the degree of etching as indicators of transport mechanisms a corrosion index for c pelagicus is developed the coccolithophore flux pattern at 258 m depth was characterised by a strong seasonality with flux peaks during autumn 1990 late november to early december and spring 1991 march the assemblage consisted almost entirely of the two species c pelagicus and emiliania huxleyi during autumn coccolithophore transportation to 258 m depth mainly occurred within cylindrical fecal pellets and marine snow aggregates of silicoflagellates and through agglutination on tintinnids grazing caused severe fragmentation of coccoliths and disintegration of coccospheres marine snow aggregates contained many intact coccospheres of c pelagicus during spring coccolithophores were probably removed from the euphotic zone by the ballast effect of sinking diatoms the coccolithophore flux peak in spring occurred immediately after the ice had retreated from the trap station and the trapped assemblage included coccoliths of subtropical species these features indicate drifting from an ice free location to the south or east the coccolith and coccosphere flux at 1061 m was respectively 7 and 12 times lower than at 258 m depth and maximum fluxes were recorded 2 months later increasing carbonate dissolution from 258 to 1061 m depth is expressed in the coccolithophore caco 3 flux reduction of 82 and in the increasing percentage of etched coccoliths of coccolithus pelagicus from 32 to 90

the vertical distribution of radiolaria in the waters surrounding japan abstract geographic and vertical distribution patterns of living radiolaria are closely related to the characters of the water column we studied living radiolaria in samples collected at closely spaced depth intervals in the waters surrounding japan in order to understand their vertical distribution and its controlling factors such information is needed to reconstruct past vertical water mass structure the japanese islands are surrounded by the marginal japan sea and the north pacific ocean and from approximately 46 n to 26 n they thus extend across a large latitudinal range and are exposed to a similarly wide range of environmental conditions inducing the warm kuroshio tsushima and tsugaru currents and the cold oyashio current we performed plankton tows mesh size 63 mm from late may to early june 2002 at eight sites sampling the upper 200 m of the water column at seven depth intervals we recognized five radiolarian assemblages the upper surface assemblage 0 40 m the lower surface assemblage 40 80 m the surface assemblage 0 80 m the subsurface assemblage 80 200 m and the lower surface subsurface assemblage 40 200 m groups pseudodictyophimus gracilipes and tetrapyle octacantha juvenile show tropical submergence i e they live at the surface in high latitudes and at greater depth in low latitudes four taxa live at specific temperature and salinity acrosphaera spinosa larcopyle butschlii challengeron diodon and stichocorys seriata four taxa are associated with characteristic temperatures neosemantis distephanus arachnocorys umbellifura antarctissa sp 1 and saccospyris conithorax

a 350 ky radiolarian record off luderitz namibia evidence for changes in the upwelling regime abstract the study of radiolarian assemblages from core md 962086 provides new information on the variability in the upwelling intensity and origin of upwelled water masses over the past 350 ky in one of the major filamentous regions of the benguela upwelling system bus located off luderitz namibia the use of key radiolarian species to trace the source of upwelled waters and the use of a radiolarian based upwelling index uri to reconstruct the upwelling intensity represent the first use of radiolarians for paleoceanographic reconstructions in the bus these radiolarian based proxies indicate strongest upwelling during marine isotope stages mis 3 5 and 8 which compares well with other studies while during mis 3 and 8 the radiolarian based proxies indicate the influx of waters of southern ocean origin they also point to the increased influence of tropical waters during the lower portion of mis 5 during mis 2 4 and 6 the radiolarian assemblages indicate generally lower upwelling intensities although this signal is complicated by the increased occurrence of organic carbon in the sediments during these intervals during mis 2 there appears to be less of an input of southern ocean waters to the bus although during the also glacial mis 4 and 6 there is evidence for an increased influence of cold antarctic waters the comparison of the results from core md 962086 with other studies in the bus area indicates a non uniform pattern of upwelling intensity and advection of cold southern waters into this system during mis 2 weaker upwelling signaled by the radiolarian based proxy in mis 4 is in contrast to other studies that indicate higher productivity during this time period in general the data show that there is a strong spatiotemporal complexity in upwelling intensity in the bus and that the advection of water into it is not strongly tied to glacial interglacial variations in climate

radiolarians in the sea of okhotsk and their ecological implication for paleoenvironmental reconstructions to assess the relationship of radiolarian production species distribution in water and surface sediment to water mass characteristics biological productivity and export regimes in the sea of okhotsk sok we accomplished a quantitative analysis of radiolarian assemblages obtained from 35 surface sediment samples and 115 plankton samples recording the radiolarian depth distribution in the upper 1000 m of the water column at 23 locations this study augments the knowledge on the autecological demands of radiolarians dwelling in a specific hydrographic and biological environment and extracts new information on the significance of radiolarians for the assessment of past oceanographic and climatic development in high latitudes highest radiolarian accumulation rates and seasonal radiolarian standing stocks are encountered in the western part of the sok close to sakhalin marking the environmental conditions in this area as most favorable for radiolarian production maximum standing stocks occur during summer indicating that the radiolarian signal preserved in the sediment record is mainly produced during this season when the mesopelagic biomass is at highest activity we identified seven radiolarian species and groups related to specific water mass characteristics depth habitats and productivity regimes of those dictyophimus hirundo and cycladophora davisiana are most prominent in the sea of okhotsk intermediate water 200 1000 m the latter representing an indicator of the occurrence of cold and well ventilated intermediate deep water and enhanced export of organic matter from a highly productive ocean surface while antarctissa sp 1 is typically related to the cold water sea of okhotsk dicothermal layer sodl ranging between 50 and 150 m water depth the surface waters above the sodl affected by strong seasonal variability are inhabited predominantly by taxa belonging to the spongodiscidae having a broad environmental tolerance taxa only found in the sediment record show that the plankton study did not cover all assemblages occurring in the modern sok this accounts for an assemblage restricted to the western kurile basin and apparently related to environmental conditions influenced by north pacific and japan sea waters other important taxa include species of the plagoniidae group representing the most prominent contributors to the sok plankton and surface sediments these radiolarians show a more opportunistic occurrence and are indicative of high nutrient supply in a hydrographic environment characterized by pronounced stratification enhancing heterotrophic activity and phytodetritus export r 2005 elsevier ltd all rights reserved

impact of shallow living radiolarian flux variations on north atlantic cycladophora davisiana percentages abstract the cause of high cycladophora davisiana percentages a deep living maximum abundance 200 m radiolarian species in high latitude 45 late pleistocene deep sea sediments has been much debated in this paper we show that in four subpolar north atlantic cores these late pleistocene high percentages 20 result more from a reduction of other radiolarian flux predominantly shallow living species c davisiana flux relative to holocene flux these findings are similar to those reported from the north pacific hays et al 2013 in both oceans the late pleistocene to holocene shallow living species flux increase is larger than the concomitant decrease of c davisiana flux similarly high c davisiana percentages 20 found today in okhotsk sea holocene sediments kruglikova 1975 robertson 1975 morley and hays 1983 result from low radiolarian concentrations in the overlying dicothermal layer 20 150 m where year round temperatures are near 0 c it is likely that the high c davisiana percentages in north atlantic late pleistocene sediments were caused by a similar overlying stratification that had important biological consequences for radiolarians and other plankton a more significant time transgressive increase in shallow and others radiolarian assemblage flux occurs initially in the southernmost core in mid holocene ultimately recorded at the northernmost site during the late holocene here flux of the deep assemblage and c davisiana also increases

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

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

distribution of polycystine radiolarians in the northern south china sea in september 2005 we studied the distribution of polycystine radiolarians in the northern south china sea scs in september 2005 in order to document the relation between radiolarian assemblages and environmental parameters vertical plankton tows were collected at depth intervals from 0 to 250 m at thirteen stations using a closing net 62 pm mesh the highest abundance of polycystine radiolarians generally occurred at depths of 0 75 m i e above the chlorophyll a maximum and thermocline in contrast the maximum polycystine abundance occurred below the chlorophyll a maximum at station e105 75 150 m possibly as a result of down welling of warm waters and the maximum fell within the chlorophyll a maximum at station e702 as a result of upwelling of intermediate cold waters during our sampling period the southwestern monsoon caused upwelling in the northern scs the taiwan bank region as shown by the high abundance of tetrapyle octacantha acanthodesimia vinculata cladococcus cervicoris octopyle octospinosa spongaster tetras streblacantha circumtexta and spongotrochus glacialis the patterns of distribution and the abundances of the species botryocyrtis scutum pterocorys hertwigii collosphaera tuberosa and didymocyrtis tetrathalamus tetrathalamus suggested that western equatorial pacific waters did not yet influence the region at the time of sampling the first two species were dominant in the northern scs during our sampling the species cornutella profunda and cyrtopera laguncula were rare at depths of 150 250 m in the tropical region of the scs and assemblages in northern and southern scs were very similar the relative abundance of b scutum and p hertwigii is an indicator for seasonal changes in monsoonal circulation c 2008 elsevier b v all rights reserved

recent variability in the pacific western subarctic boundary currents and sea of okhotsk abstract the objective of this research is to describe physical processes which are the cause of the recent variability of the pacific western subarctic waters rapid thermohaline changes have occurred within the oyashio and kamchatka current during the last decade this variability has included a warming of the kamchatka current warm intermediate layer but a cooling and freshening of the upper layer in the oyashio and sea of okhotsk the example presented here uses data obtained during the canada russia inpoc and woce projects as well as the new russian studies with high resolution station grid the possible physical mechanism that generated the upper layer freshening during the thermohaline transition is examined major components of the fresh water budget of the okhotsk sea are considered in order to describe the dramatic changes in salinity which have recently occurred in the pacific subarctic significant changes in precipitation and other fresh water inputs are demonstrated it is suggested that upper layer of the oyashio and kamchatka current became cooler and fresher because of the export of cold fresher waters from the bering and okhotsk seas these waters from the marginal seas have cooled the bottom of the halocline reducing evaporation and acting as a feedback that has kept the upper layer of the western subarctic boundary currents fresh it is also shown that the outflow of the cold sea of okhotsk water has changed its path during this recent thermohaline transition

depth related radiolarian assemblage in the water column and surface sediments of the japan sea plankton tows and surface sediments from the japan sea a marginal sea of the northwestern pacific were examined to study the depth distribution of modern radiolarians the depth distribution patterns between the living assemblage in the water column and the thanatocoenose in surface sediments are similar to each other indicating that the depth related assemblage in sediments is closely related to the living depths of major species four clear restrictions of many species to discrete depth zones are recognized in the water column from the surface down to 2000 m 1 upper subsurface water species which are abundant from 40 to 120 m larcopyle butschlii juvenile form spirocyrtis subscalaris spongodiscus resurgens and lipmanella virchowii 2 lower subsurface water species which are abundant from 40 to 300 m larcopyle butschlii adult form ceratocyrtis histricosa and spongotrochus glacialis 3 intermediate water species which have population maxima from 160 to 300 m ceratospyris borealis and 4 deep water species which have maxima between 1000 and 2000 m cycladophora davisiana and actinomma boreale only a few specimens of a boreale were found in the water column ranging from 1000 to 2000 m depth although this is a dominant species in surface sediments from depths below 2000 m of which the dominance increases with water depth a boreale may live mainly in the bottom water cycladophora davisiana and a boreale which characterize the japan sea deep assemblage are naturally shallow or intermediate dwellers in other oceans on the other hand the typical deep dwellers e g cornutella profunda cyrtopera languncula and peripyramis circumtexta of other oceans have not been found in the japan sea such a peculiar deep assemblage is a result of the deep circulation system in the japan sea and the shallow depths of the sills around it

oceanographic conditions associated with high abundances of the radiolarian cycladophora davisiana abstract the cosmopolitan radiolarian cycladophora davisiana usually comprises less than 5 of the radiolarian fauna in holocene sediments in recent sediments from the sea of okhotsk however this species frequently represents more than 20 of the radiolarian assemblage at times during the late pleistocene abundances of this species in excess of 40 are recorded in marine sediments from high latitude oceans 40 of both hemispheres the sea of okhotsk apparently represents a modern analogue of climatic and oceanographic conditions that existed throughout large portions of high latitude oceans at times during the late pleistocene the near surface water structure of the sea of okhotsk is characterized by a low salinity surface layer with a strong temperature minimum near its base the low surface salinities are responsible for maintaining near freezing subsurface temperatures as well as establishing relatively stable temperatures and salinities at depths below the temperature minimum this water structure is produced at least in part by intense freezing of sea ice in winter with subsequent summer melting the physical characteristics of the upper water column affect the abundance and activity of shallow dwelling flora and fauna while providing a stable subsurface environment for deeper dwelling fauna

orbital and millennial scale changes of radiolarian assemblages during the last 220 kyrs in the japan sea abstract significant abundance changes of seven radiolarian species during the last 220 kyrs in the japan sea are reported herein based on three sediment cores during the interglacial periods warm water species the tetrapyle octacantha group and warmer high nutrient water species lithomelissa setosa occurred commonly which may indicate inflows of the tsushima warm current on the other hand cold water species such as ceratospyris borealis and stylochlamydium venustum dominated the assemblage during the glacial periods when the japan sea was mostly isolated from the adjacent seas due to lower eustatic sea level however at glacial maxima the habitat of s venustum was strongly limited due to low salinity surface waters the abundance of the deep water species cycladophora davisiana seems to have changed significantly possibly related to the intrusion of oxygen and organic materials into deeper waters higher abundances of this species in mis marine isotope stage 1 mis 3 and mis 5c resulted from well ventilated deep water and high organic flux while its low abundance during the glacial maxima and mis 5e was probably caused by oxygen poor deep water millennial scale variations of c davisiana abundance show high abundance at the transition intervals from interstadial to stadial periods of the dansgaard oeschger cycles the disappearance events of lychnocanoma nipponica sakaii and amphimelissa setosa were recognized at 54 ka and 85 ka respectively both of these events in the japan sea can be correlated with those in the north pacific bering sea and sea of okhotsk

an early holocene peak occurrence and recent distribution of rhizoplegma boreale radiolaria a biomarker in the norwegian sea abstract several sediment cores in the norwegian sea reveal in the early preboreal abundance peaks of up to 14 of rhizoplegma boreale cleve these peaks generally coincide with a transition from cold to warm water radiolarian assemblages and a high number of diatom valves chaetoceros sp indicating highly productive surface waters the r boreale peak represents an ecological event caused by an influx of north atlantic water and can potentially be used as a chrono stratigraphic marker within the eastern part of the norwegian sea in core hm 79 6 2 the r boreale peak reaches 9 2 and is found between two 14 c dated ash layers we estimated the age of the r boreale peak to be 9880 55 yr bp by linear interpolation between datum points the characteristic stratigraphical distribution of r boreale was used to establish a better age model for the studied section rhizoplegma boreale has been mapped in surface sediment samples from the iceland sea the norwegian sea and the norwegian fjords an oceanic form with six and a neritic form with eight radial spines were found in these areas recent distribution of rhizoplegma boreale is mainly confined to the nordic seas greenland iceland and norwegian seas the north pacific including the bering sea and sea of okhotsk and in the southern ocean the highest occurrence of r boreale is found in areas with high primary production and mixing of water masses

radiolarians under the seasonally sea ice covered conditions in the okhotsk sea flux and their implications for paleoceanography abstract four time series sediment traps at two stations and three piston cores from the okhotsk sea were quantitatively examined for coarse sized radiolarian shells 63 m traps were deployed at 300 m and 1550 m at station m4 53 01 n 145 30 e and at 300 m and 700 m at station m6 49 30 n 146 28 e during august 1998 through may 2000 the chronologies of the piston cores were established applying 18 o and paleomagnetic intensity variations they provide records extending back to marine isotope stage mis 5 51 the modern and past changes in radiolarian assemblages are associated with environmental and productivity changes radiolarian fluxes in the sediment traps exhibited significant summer to autumn flux peaks with suppressed values during the winter when sea ice covered the sea surface at the trap sites total radiolarian accumulation rate rar variations in each core tended to correspond to glacial interglacial cycles and increased during the last deglaciation in particular the temporal rar variation in core xp98 pc1 off kamchatka showed a similar trend with the climatic changes expressed by 18 o values during the glacial interglacial cycles for the last 125 kyr regional differences were also apparent rars showed extremely low values during 12 40 kyr and 63 70 kyr in core xp98 pc2 central okhotsk sea indicating the enhanced sea ice impact the sea ice coverage might have continued for a significant part of the year during the intervals since radiolarians did not appear to increase even during the summer to autumn rar variations in core xp98 pc4 off sakhalin showed higher values than xp98 pc2 during mis 2 and 4 thus in eastern sakhalin around site xp98 pc4 sea ice coverage might have been seasonal but not perennial even during mis 2 and 4 among the radiolarian taxa cycladophora davisiana was the most abundant species at the lower traps and in all cores the fluxes of c davisiana at lower traps showed much higher values than those of upper traps and also showed similar temporal patterns with the fluxes of aluminum and terrigenous materials therefore c davisiana fluxes may be associated with terrigenous organic materials increased nutrient supply from the continental shelves presumably transported by seasonal sea ice and released by sea ice melting might be mainly responsible for the high production of c davisiana in the okhotsk sea especially during the last deglaciation

a new coastal water radiolarian assemblage recovered from sediment samples from the antarctic ocean abstract the study of circum antarctic sediment samples from south of 60 s reveals the presence of a distinctive coastal assemblage in shallow waters around antarctica this assemblage consists primarily of just two species rhizoplegma boreale cleve and phormacantha hystrix cleve plectacantha oikiskos jorgensen group this assemblage resembles assemblages from norwegian fjords in both its taxonomic composition and low diversity it is distinguished from the typical open ocean antarctic assemblage with its high diversity the distribution of the coastal assemblage appears to be determined mainly by water depth or proximity to the coastline rather than temperature

polycystine radiolarians in surface sediments in the arctic ocean basins and marginal seas abstract the polycystine radiolarian faunas in the arctic ocean including the adjacent arctic seas have been studied in more than 377 surface samples the deep basins in the arctic ocean have revealed 31 polycystine radiolarian species 11 spumellarians and 20 nassellarians the polycystine radiolarian fauna in the southern norwegian sea was introduced from the north atlantic ocean ca 13 400 yr bp the shallow low arctic marginal sea sediments iceland barents and chukchi seas have a strong dominance of cannobotryidae 79 77 and 74 respectively while the deep arctic ocean basins nansen amundsen and makarov basins have a dominance of actinommidae 90 70 and 75 respectively the arctic polycystine radiolarian faunas have a strong affinity with the norwegian sea fauna which supplies the arctic ocean with faunal elements that can live thrive and reproduce there in the chukchi sea the pacific faunal influence is obvious 41 species but none of the pacific species are found in any abundance in the amerasian basin no radiolarian species was found to be endemic to the arctic ocean except for a morphotype of actinomma l leptoderma with a round inner sphere this species is a possible endemic candidate for the arctic ocean eight species are to be found in all of the central arctic basins and can therefore be referred to as circumpolar species actinomma leptoderma leptoderma a l leptoderma with round middle sphere a l longispina a boreale spongotrochus glacialis pseudodictyophimus platycephalus cycladophora davisiana and tholospyris gephyristes while amphimelissa setosa probably is the only true arctic radiolarian species

variations in the radiolarian assemblages in the bering sea since pliocene and their implications for paleoceanography radiolarian assemblages were analyzed using samples from the iodp site u1340 to reconstruct the paleoceanographic conditions in the bering sea based on the characteristic faunal changes the radiolarian evolution at site u1340 was divided into four major intervals from stages i to iv with stage iv divided into substages iva and ivb the radiolarians in each stage recorded significant paleoenvironmental conditions in general the bering sea was governed by an ocean ecological environment with stable warm and saline surface water during stage i 4 15 myr to 3 91 myr the environment in the bering sea fluctuated strongly during stage 11 3 91 myr to 2 75 myr and was controlled by the cold water masses and sea ices during stage iii 2 75 myr to 1 07 myr with the gradual development of cold and well ventilated intermediate water stage iva 1 07 myr to 0 47 myr was a transitional period characterized by the enhanced formation of cold subsurface and intermediate water as well as of the oxygen rich deep water during stage ivb after 0 47 myr the bering sea was mainly characterized by enhanced warmth during interglacial episodes and well developed water layers that were generally comparable to those of the modern bering sea these conditions indicated that the vertical water mass structure of the modern bering sea began to form since 0 47 ma every stage boundary in the studied core was marked by notable changes in the radiolarian assemblages these changes corresponded to the climatic cooling event at similar to 3 91 ma the intensification of northern hemisphere glaciation at similar to 2 75 ma the beginning of the middle pleistocene transition at similar to 1 07 ma and the low latitude radiolarian ecology event at similar to 0 47 ma in addition the relative abundance pattern of cycladophora davisiana indicates that the bering sea was the main source of the past north pacific intermediate water at ca 0 85 ma mis22 ca 0 63 ma mis16 and ca 0 18 ma mis6 just as it was during the last glacial maximum c 2014 elsevier b v all rights reserved

plankton in the norwegian greenland sea from living communities to sediment assemblages an actualistic approach a synoptic study is carried out to reconstruct the development of the plankton community in the late quaternary in the norwegian greenland sea it comprises quantitative analyses of coccolithophores dinoflagellate cysts diatoms and radiolarians an actualistic approach is applied to evaluate the different fossil records of these plankton groups the preliminary results of the current investigation are reported here

variability of cloud vertical structure during astex observed from a combination of rawinsonde radar ceilometer and satellite the macroscale cloud vertical structure cvs including cloud base and top heights and layer thickness and characteristics of multilayered clouds is studied at porto santo island during the atlantic stratocumulus transition experiment astex by using rawinsonde radar ceilometer and satellite data the comparisons of cvs parameters obtained from four different approaches show that 1 by using the method developed by wang and rossow rawinsonde observations raob s can sample all low clouds and determine their boundaries accurately but oversample low clouds by about 10 mistaking clear moist layers for clouds 2 cloud base heights less than 200 m in the radar data are ambiguous but can be replaced by the values measured by ceilometer and 3 the practical limit on the accuracy of marine boundary layer cloud top heights retrieved from satellites appears to be about 150 300 m mainly due to errors in specifying the atmospheric temperature and humidity in the inversion layer above the cloud the vertical distribution of clouds at porto santo during astex is dominated by low clouds below 3 km a cloud free layer between 3 and 4 km and 20 high clouds with a peak occurrence around 7 8 km low clouds have mean base and top heights of 1 0 km and 1 4 km respectively and occur as single layers 90 of the time for double layered low clouds the tops of the uppermost layers and the bases of the lowermost layers have similar distributions as those of single layered clouds the temporal variations of low clouds during astex are apparently dominated by advecting mesoscale 20 200 km horizontal variations coherent time variations are predominately synoptic timescale 4 5 6 8 days and diurnal variability on the diurnal timescale all cloud properties show maxima in the early morning around 0530 lst decreasing to minima in the late afternoon diurnal variations appear to be altered when high clouds are present above low clouds the general characteristics of cvs in three astex and the first isccp regional experiment fire87 regions derived from a 20 yr rawinsonde dataset are also presented the results suggest that cvs characteristics obtained from data collected at porto santo during astex june 1992 are not representative of other marine stratiform cloud regions

a high resolution opal and radiolarian record from the subpolar north atlantic during the mid pleistocene transition 1069 779ka palaeoceanographic implications abstract a high resolution record of radiolarian assemblages from site u1314 was studied to reconstruct hydrographic and climatic changes in the north atlantic ocean during the mid pleistocene transition period 1069 779 ka besides the faunal record absolute accumulation of radiolarians and total biogenic opal are used to determine changes in surface water productivity results show that the north atlantic arctic front shifted back and forth repeatedly at a glacial interglacial timescale bringing the site under the influence of both cold arctic glacial and much warmer atlantic interglacial waters during glacial intervals and ice rafted debris ird events the deep dwelling taxon cycladophora davisiana was the greatest contributor of the radiolarian assemblage suggesting cold surface conditions melt water discharge and changes in deep and intermediate circulation interglacial intervals were characterized by abundant shallow dwelling taxa like pseudodyctiophimus gracilipes and lithomelissa setosa increased opal accumulation and higher radiolarian diversities indicating a northward flow of warm atlantic surface waters to the site u1314 area a marked change in the structure of the radiolarian assemblage occurred after mis 22 860 ka with large taxa differences between warm and cold periods probably in response to changing ocean conditions due to the higher amplitude of glacial interglacial changes as the dominant periodicity of high latitude climate oscillations shifted from 41 kyr to 100 kyr thus we conclude that the radiolarian assemblage from the north atlantic have changed drastically along with variations in ocean circulation in response to orbital and millennial scale climatic variations that occurred in the early and mid pleistocene