an effect of dissolved nutrient concentrations on alkenone based temperature estimates the ratio of 37 carbon diunsaturated to diunsaturated and triunsaturated alkenones uk 37 produced by some haptophytes is widely used as a proxy for past sea surface temperatures however our isothermal culturing experiments with emiliania huxleyi clone ccmp372 show uk 37 values to also vary with nutrient availability and cell division rate these results provide a reasonable explanation for large isothermal variation in uk 37 values of single coccolithophorid strains grown in culture they also suggest that alkenone based estimates of past sea surface temperatures may have been influenced by dissolved nutrient concentrations as well as by temperature

japan sea oxygen isotope stratigraphy and global sea level changes for the last 50 000 years recorded in sediment cores from the oki ridge abstract we obtained twenty ams accelerator mass spectrometry radiocarbon dates 2 tephra layer chronologies and a planktonic foraminiferal 18 o stratigraphy for the last 50 000 years from japan sea cores from the oki ridge in this paper we report ams 14 c results that allow us to reconstruct a high resolution chronology of the cores and discuss millennial scale climate changes recorded in japan sea sediments the sedimentation rate for the site increased dramatically from the glacial stage to the holocene as a result of significant hydrological changes associated with deglaciation and global sea level rise a lighter 18 o anomaly for the planktonic foraminifers was found during the lgm last glacial maximum this shift corresponds to a freshening of the japan sea surface waters and is mainly due to a global sea level drop rather than anomalously warm ssts sea surface temperatures as previously reported our record combined with the global sea level data suggests that the lgm started about 30 kyr ago and that the salinity of the japan sea became fresher than at present the ssts during mis marine oxygen isotope stage 3 were relatively stable and global sea level was not lower than ca 80 m the surface water of the japan sea attained normal saline levels following the younger dryas cold event and reached the present day 18 o values 7 kyr ago

orbital scale stratigraphy and high resolution analysis of biogenic components and deep water oxygenation conditions in the japan sea during the last 640 kyr abstract paleoceanographic conditions in the japan sea changed drastically during the late quaternary in association with orbital and suborbital cycles and glacio eustatic sea level changes however few studies have examined long term sediment records older than 160 ka because of the lack of long and continuous cores and the difficulty in constructing high resolution age models in this study we first constructed an orbital scale stratigraphy of the sediments covering the last 640 kyr by comparing the specmap 18o curve and the 18o curve of planktonic foraminifera 18opf in the japan sea together with the combination zones of dominant planktonic foraminifera species then we reconstructed temporal variations in biogenic silica biosil and biogenic carbonate biocarb contents calculated from high resolution major element analysis data determined by an xrf microscanner in order to evaluate the deep water oxygenation conditions we also defined excess s as the difference between the content of s in the sediments and that for normal marine sediments calculated from the organic carbon content corg estimated from lightness l by assuming a total sulfur content stotal corg ratio of 0 36 and examined its variability biosil shows orbital scale variation and is generally low except during interglacial maxima when global sea level was high enough to allow a strong influx of the tsushima warm current biocarb shows orbital and suborbital scale variations and tends to be higher in dark layers deposited during glacial stages whereas the relationship is reversed during interglacial stages the low biocarb in dark layers deposited during interglacial stages is probably due to dissolution of biogenic carbonate caused by the increase in surface productivity as a result of the strong influx of nutrient rich east china sea coastal water and consequent increase in surface productivity and decomposition rate of organic matter in the intermediate water excess s tends to be higher in thicker dark layers deposited during glacial maxima when the sea level dropped below 90 m compared to adjacent light layers suggesting development of euxinic deep water conditions during these periods the results demonstrated the presence of orbital and suborbital scale variations in biosil and biocarb and their association with dark and light layers in the japan sea that reflect variations in the nature and strength of inflow through the tsushima strait controlled by both climatic and sea level changes whereas higher excess s reflects the development of euxinic deep water condition during glacial maxima in association with glacio eustatic sea level drops below 90 m during the last 640 kyr

northward and southward migrations of frontal zones during the past 40 kyr in the kuroshio oyashio transition area 1 the variation of sea surface temperature sst in the kuroshio oyashio transition area and the okhotsk sea during the last 40 kyr was estimated using long chain unsaturated alkyl ketones alkenones the temperature difference between the present and the last glacial period was about 5 6 c in the kuroshio oyashio transition area slightly larger than the 4 c previously reported moreover alkenones were not detected before 18 kyr b p in or near the okhotsk sea perhaps because of nearly year round sea ice expansion which would have prevented the growth of alkenone producers or because alkenones were less well preserved in surface sediments during the glacial period the northward and southward migrations of frontal zones were evaluated using differences in alkenone temperatures between stations located in the vicinity of the subarctic front saf subarctic boundary sab and kuroshio bifurcation front kbf all three frontal zones migrated southward during the glacial period compared with their present positions and their relative positions were different between the holocene and glacial periods in particular the distance between the saf and the sab was reduced during the glacial period compared with at present the northward and southward migration of the frontal zones may relate to both mid to low atmospheric circulation and polar atmospheric circulation

atmospheric dust loadings and their relationship to rapid oscillations of the asian winter monsoon climate two 250 kyr loess records abstract similar to records extracted from marine sediments paleoceanography 6 1991 349 rev geophys 32 1994 159 and ice cores nature 399 1999 429 estimates of dust inputs to the chinese loess plateau indicate that the dust fluxes during periods of extensive glaciation were higher than those in interglacial times catena 18 1991 125 quat res 41 1994 35 prior studies nature 375 1995 305 quat sci rev 18 1999 811 indicating that millennial scale oscillations of asian dust occurred during glacial times have raised questions about the conditions that govern the generation and transport of dust particularly those operating during the winter monsoon we present here atmospheric dust loadings reconstructed from two central loess plateau sections these extended our present day observations to cover the last two glacial cycles and thus provided a unique perspective on the relationships between asian dust and climate the reconstructed loadings indicate that higher and more variable dust concentrations occurred during glacials compared with interglacials and the high dust loadings frequently preceded decreases in winter sea surface temperature of the north pacific ocean during glacials a mechanism was proposed to explain how the thermal contrasts between the eurasian continent and the surrounding oceans induced by the high dust loadings could either trigger or modulate millennial scale variations in the winter monsoon climate and thus rapid transitions of glacial dust loadings

relationship of the tetra unsaturated c37 alkenone to salinity and temperature implications for paleoproxy applications 1 this study assesses the relationship to salinity and temperature of the levels of the tetra unsaturated 37 carbon methyl alkenone c37 4 in the surface ocean uk 37 a measure of the relative abundances of the c37 2 and the c37 3 alkenones has a well constrained linear relationship to temperature in the open ocean prahl and wakeham 1987 and is a well established technique for estimating past sea surface temperatures in the sediments e g muller et al 1998 unlike the di and tri unsaturated c37 alkenones the temperature response of the tetra unsaturated c37 alkenone is less certain sikes et al 1997 and recent work has suggested a relationship to salinity instead rosell mele 1998 schulz et al 2000 our study examined 106 surface water and sediment trap samples from the atlantic pacific and southern oceans to assess the relationship of the relative abundance of c37 4 to temperature and salinity we also examined the relative unsaturation of c37 2 and c37 3 the parameter uk 37 to the same parameters to place the c37 4 results in context uk 37 has a strong correlation to salinity in the atlantic but the relationship does not hold worldwide whereas uk 37 shows a strong linear relationship to temperatures in all ocean basins as shown in previous calibrations the salinity response in the atlantic does not confirm cause and effect and interpretation of the broader data set suggests any correlation is an artifact of the strong correlation of salinity to temperature in this basin implying salinity has no effect on the unsaturation of the c37 2 or c37 3 alkenones the c37 4 alkenone shows no discernable relationship to temperature or salinity across the several basins even when correlations are restricted to cooler temperatures where the tetra unsaturated alkenone would be expected to be present these results indicate that c37 4 alkenone levels in the open ocean do not reflect either salinity levels or temperature but respond most strongly to some other environmental variable perhaps changes in growth rate light or nutrient supply as suggested by culture studies

a salinity related occurrence of a novel alkenone and alkenoate in late pleistocene sediments from the japan sea abstract the novel alkenoate ethyl tetratriacontadienoate c34 2ee has been found in late quaternary sediments of the japan sea by using gas chromatography mass spectrometry gc ms it accompanied hexatriacontadien 3 one c36 2ek previously found in black sea sediments a linear relationship between c36 2ek and c34 2ee concentrations points to both compounds being derived from the same source most likely a specific haptophyte the relative abundance of c34 2ee in total alkenones and alkenoates was significantly higher during the last glacial maximum when the 18o in planktonic foraminifera was anomalously light strongly suggesting that c34 2ee is associated with low salinity environments as samples with abundant c34 2ee also possessed anomalously high u 37 k values low salinity may have an ecological or physiological influence on both the unsaturation and carbon chain length of alkenones and alkenoates

variability of the path of the kuroshio ocean current over the past 25 000 years the kuroshio current is the strong northwestern component of the subtropical north pacific ocean gyre and advects a large amount of heat from the tropics to northern mid latitudes the kuroshio has bimodal stationary flow patterns with small and large meander paths east of central japan1 2 which switch on annual and decadal timescales3 4 these switches seem to be caused by changes in current velocity and volume transport of the north equatorial current that are associated with variations in the trade wind intensity in the eastern equatorial north pacific ocean5 6 here we present alkenone derived sea surface temperature records at multicentennial resolution from sediment cores from the nishishichitou ridge off central japan these 25 000 year records show that the kuroshio path has also fluctuated on millennial timescales this variability resembles that of the subtropical high pressure of the north pacific reconstructed from terrestrial pollen distributions water levels in north american lakes and marine micropalaeontological records7 together these data indicate that climate variability off central japan over the past 25 000 years may be part of a circum pacific phenomenon reflecting the rate of subtropical surface circulation in the north pacific ocean

millennial scale fluctuations in seasonal sea ice and deep water formation in the japan sea during the late quaternary abstract the east asian winter monsoon is characterized by cold dry air blowing from the siberian high to the surrounding lows this cold wind cools the surface water along the russian coast of the japan sea modern oceanographic observations indicate that sea ice formation along this coast during an extremely cold winter is an important process for deep water formation thus formation of both seasonal sea ice and deep water masses in the japan sea are closely related to the east asian winter monsoon two sediment cores were analyzed to reconstruct the history of sea ice expansion and deep water formation seasonal sea ice history was reconstructed from the occurrence of ice rafted debris ird in a core from the northeastern japan sea whereas the deep water ventilation history was estimated on the basis of records of a deep dwelling radiolarian species cycladophora davisiana in a core from the southwestern japan sea in the records of sea ice expansion and deep water ventilation for the last 160 ky clear fluctuations on a millennial timescale were observed during marine oxygen isotope stages 3 5 some of the peaks in sea ice formation and c davisiana abundance occurred contemporaneously indicating strong surface cooling along the russian coast by a strong winter monsoon decoupling of the two records might have occurred because of surface water stratification caused by the freshening of surface water in relation to high precipitation in summer synchronicity of high ird peaks with north atlantic heinrich events suggests that high latitude climate changes related to the bond cycle also occurred in the asian monsoon region on shorter timescales ird occurrence was not clearly related to dansgaard oeschger cycles which are revealed in the alternating dark and light layers in the late quaternary japan sea sediments therefore during the studied period strong east asian winter monsoons did not have a simple see saw like relationship with strong summer monsoons

long chain alkenones in qinghai lake sediments abstract long chain methyl and ethyl alkenones c 37 c 40 containing two to four double bonds have been detected in sediments from qinghai lake china this is the first report of the alkenones in lake sediments deposited under a variety of salinity conditions where the lake has not encountered any marine incursions the presence of the alkenones suggests the presence of prymnesiophyceae in the lake which may have reached the lake via eolian transportation or seabirds sediment samples from the more saline areas of the lake contained higher concentrations of the more highly unsaturated compounds widespread use of these compounds as paleotemperature indicators in marine sediments introduces the possibility of extrapolating this approach to lacustrine environments if appropriate calibrations can be undertaken

cretaceous paleogene tectonics of the pelagonian zone inferences from skopelos island greece we have investigated subduction exhumation processes in the pelagonian zone exposed on the northern sporades islands aegean sea related to successive episodes of ocean continent and continent continent convergence through integrating multiscale structural analysis metamorphic petrology and white mica 40ar 39ar dating two major progressive phases of ductile deformation are documented which are related to distinct episodes of tectonic burial and exhumation of the pelagonian continental margin which was facing the neotethys vardar ocean review of existing data sets from neighboring regions shows that both deformation phases can be correlated along strike up to the dinarides the first phase of tectonic burial and exhumation d1 is characterized by nw se tectonic transport greenschist facies metamorphism and early cretaceous 105 135ma 40ar 39 ar white mica single fusion ages d1 is correlated with the initial closure of the vardar ocean by top to the w to nw ophiolite obduction and the underthrusting of the pelagonian margin below the oceanic upper plate underthrusting was followed by exhumation and the deposition of late cretaceous paleogene sediments the second phase of burial and exhumation d2 is characterized by ne sw tectonic transport greenschist to blueschist facies metamorphism and latest cretaceous early eocene 40ar 39 ar white mica ages of s2 fabrics top to the sw shearing is correlated with the tectonic burial of the pelagonian zone below the eurasian continent rhodopia while top to the ne shearing is attributed to subsequent extensional exhumation d2 fabrics record low grade p t conditions suggesting that the decoupled cover formations exposed on skopelos were incorporated in an accretionary wedge that formed above the subducting pelagonian basement during paleogene times

high resolution record of northern hemisphere climate extending into the last interglacial period high resolution record of northern hemisphere climate extending into the last interglacial period

physiological impacts on alkenone paleothermometry we conducted isothermal 15 c batch culture experiments with the coccolithophorid emiliania huxleyi strain nepcc 55a to evaluate the extent to which nutrient and light stress contribute to variability in the alkenone unsaturation index u37k alkenone content and composition were constant throughout exponential growth in both experiments when nutrients nitrate and orthophosphate were replete stationary phase nutrient starved cells continued to produce alkenones amassing concentrations alk 3 times higher than those dividing exponentially 1 5 2 pg cell 1 and the u37k of excess alkenone dropped by 0 11 units in contrast 5 days of continuous darkness resulted in a 75 decrease in cellular alk and a significant u37k increase 0 11 units given an established 0 034 unit c response for exponentially growing cells of this strain the observed range of u37k variability at 15 c corresponds to an uncertainty of 3 2 c in predicted growth temperature this level of variability matches that of the global u37k annual mean sea surface temperature calibration for surface marine sediments begging the question what is the physiological condition of alkenone producing cells exported to marine sediments comparison of our laboratory results for a strain of e huxleyi isolated from the subarctic pacific ocean with depth profiles for alkenones in surface waters from two contrasting sites in the northeast pacific ocean suggests that the answer to this question depends on the ocean regime considered a possibility with significant bearing on how stratigraphic u37k records in marine sediments are to be interpreted paleoceanographically

variability of unusual distributions of alkenones in the surface waters of the nordic seas 1 samples of filtered particulate organic matter pom were obtained during the summers of 1999 and 2000 from the surface waters of the nordic seas to monitor the spatial distribution of long chain alkenones the aim of the study was to appraise existing alkenone based climatic proxies in northern high latitudes unusually high percentages of the tetraunsaturated alkenone were measured in the polar waters of the east greenland current with c37 4 of up to 77 in 80 of sea ice cover values of percent c37 4 across the nordic seas showed a strong association with water mass type analysis of coccoliths in filters indicated that calcified emiliania huxleyi could not be discounted as the biological precursor of alkenones in all the water masses a combined data set of 69 samples of pom revealed a stronger correlation of percent c37 4 to sea surface salinity sss r2 0 72 than to sea surface temperature sst r2 0 50 values of percent c37 4 in sea surface pom were much higher than those in surficial sediments of the northern north atlantic to explain the discrepancy in sedimentary and surface water column percent c37 4 we propose that the alkenone contents in surface sediments underlying arctic and polar waters are a combination of autochthonous and allochthonous inputs of alkenones our results show that percent c37 4 can be used to reconstruct the relative extension of arctic polar water masses in the north atlantic however the results prevent confirmation of percent c37 4 as a paleo sss proxy in the nordic seas given its multivariate nature in our data set and the decoupling between its range of values in surface waters and sediments

surface water changes recorded in late quaternary marine sediments of the ulleung basin east sea japan sea abstract in order to reconstruct past sea surface temperature sst and salinity sss in the east sea japan sea this study investigated the oxygen isotopic composition of the planktonic foraminifer globigerina bulloides and the degree of unsaturation of alkenones in bulk sediments of core ty99pc18 recovered from the southeastern part of the ulleung basin east sea between 11 and 15 cal kyr bp the surface waters were 2 4 c cooler than today the surface salinity was 12 lower during 14 15 cal kyr bp than today then increased after 14 cal kyr bp but remained lower during 11 14 cal kyr bp than present values between 14 and 15 cal kyr bp the northern east china sea surface waters were likely to be greatly diluted by fresh water discharge from land and coastal waters would have flowed into the east sea through the korea strait during 11 14 cal kyr bp the southern input waters most likely changed from fresh water influenced coastal water to open ocean water the increased salinity probably enhanced active deep water convection at that time during 7 11 cal kyr bp the surface waters were warmer 1 c and more saline 1 3 than today indicating that the warm and saline kuroshio current became stronger and that one of its branches flowed into the east sea during this time interval the cold 2 c and less saline waters 1 at 3 6 cal kyr bp may indicate a suppression of the kuroshio current the sst and sss values are close to the present values at about 3 cal kyr bp suggesting that the physiological conditions of the east sea approached that of the present at this time

sea level surface salinity of the japan sea and the younger dryas event in the northwestern pacific ocean abstract the japan sea was profoundly different during glacial times than today available 18 o evidence indicates that sea surface salinity was lower by several per mil this probably increased the stability of the water column and caused anoxic sedimentary conditions in the deep sea as shown by the absence of benthic microfossils and the presence of laminated sediment these changes are likely related to the effects of late quaternary sea level change on the shallow sills ca 130 m across which the japan sea exchanges with the open ocean the hwang he yellow river has previously been implicated as the source of fresh water to the japan sea during glaciation but the possible roles of the amur river and excess precipitation over evaporation must also be considered ambiguous radiocarbon chronologies for the latest quaternary of japan sea cores do not adequately constrain the timing of salinity lowering previous studies have suggested that lowest sea surface salinity was achieved 27 000 to 20 000 14 c yr b p however if global sea level fall restricted exchange with the open ocean circulation then lowest salinity in the japan sea may have occurred as recently as 15 000 to 20 000 yr ago when sea level was lowest if this alternative is correct then as sea level abruptly rose about 12 000 yr ago relatively fresh water must have been discharged to the open pacific this might have affected the dynamics of outflow local faunal and floral expression of the polar front and stable isotope ratios in foraminifera these environmental changes could be misinterpreted as evidence for the cooling of younger dryas age which has not been identified in nearby terrestrial records

alkenones and alkenes in surface waters and sediments of the southern ocean implications for paleotemperature estimation in polar regions abstract the concentration of c37 c39 long chain alkenones and alkenes were determined in surface water and surface sediment samples from the subpolar waters of the southern ocean distributions of these compounds were similar in both sample sets indicating little differential degradation between or within compound classes the relative amounts of the tri to tetra unsaturated c37 alkenones increased with increasing temperature for temperatures below 6 c similar to the di and tri unsaturated c37 alkenones the c37 di tri and tetra unsaturated methyl alkenones are used in paleotemperature calculations via the u37k and the u37k ratios in these datasets the relative abundances of the c37 2 and the c37 3 alkenones as a proportion of the total c37 alkenones were opposite and strongly related to temperature the latter with more scatter but the abundance of the c37 4 alkenone showed no relationship with temperature the original definition of u37k includes the abundance of 37 4 in both the numerator and denominator and thus it is perhaps not surprising that there is considerable scatter in the values obtained for u37k at low temperatures of the two we suggest that u37k is the better parameter for use in paleotemperature estimations even in cold locations u37k values in the sediments fall on virtually the same regression line obtained for the water column samples of sikes and volkman 1993 indicating that their calibration is suitable for use in southern ocean sediments the comparison of water column data with sedimentary temperature estimates suggests that the alkenone distributions are dominated by contributions from the summer when the biomass of emiliania huxleyi and presumably flux to the sediment is expected to be high

sea surface temperature fronts in the east japan sea and temporal variations 1 the spatial pattern of sea surface temperature sst fronts and its seasonality are presented for the entire east japan sea they are based on semi monthly sea surface temperature sst gradient maps constructed from declouded sst images over the period 1990 1995 fronts in the east sea can be assigned to the subpolar front spf in its central sea areas and to other fronts along the continental shelves it is observed for the first time that the spf located mostly along about 40 n between 132 3 e and 138 e bifurcates at both its eastern and western ends the spatial structure of the spf shows strong seasonality associated with temporal variations of a warm eddy off the east coast of korea surface cooling due to siberian cold air south of vladivostok and bifurcation of the tsushima warm current west of the tsugaru strait we have also observed an isolated frontal zone trapped by a seamount in the northeastern part of the japan basin

organic walled microfossils of possible dinoflagellate affinity from the lower permian of sonora northwest mexico abstract shallow water carbonates from the lower permian of sonora northwest mexico have yielded small organic walled microfossils that show several features characteristic of dinoflagellates the oldest unequivocal dinoflagellate fossils however presently known come from the middle triassic earlier reports of microfossils with possible dinoflagellate affinity from the paleozoic and neoproterozoic together with dinoflagellate specific biomarkers found in early cambrian rocks and molecular phylogenetic analyses suggest the presence of an intermediate stage of evolution or protodinoflagellate group in pre mesozoic times

alkenone temperature estimates for the east sea during the last 190 000 years abstract the late quaternary records of alkenone based sea surface temperature sst from a core located in the western margin of the east sea japan sea showed that the estimated temperature fluctuated greatly the variability being consistent with orbital scale global climate records during the period of marine isotope stage mis 6 the alkenone temperatures were low 7 10 c whereas during mis 5 5 the temperature increased rapidly up to 21 c during the entire period of mis 5 the temperature decreased from 21 c to 13 c then the temperature fluctuated between 10 c and 15 c during miss 4 and 3 after that it continued to fluctuate between 15 c and 17 c variation in the east sea sst is considered to be closely related to changes in the east asian monsoon system and seawater transport by the tsushima warm current the glacial surface cooling could be associated with the strong winter monsoon and or weakened summer monsoon in east asia during the glacial period when the sea level was low the influx of warm water was restricted and this might have enhanced the lowering of the surface temperature these conditions most likely caused significant changes in surface water circulation a basin scale cyclonic gyre might have occurred in the east sea without the development of the subpolar front during the interglacial period the surface warming seems to be related to the intensified summer monsoon system the high stand of the sea level and climate change most likely caused the development of cyclonic and anti cyclonic gyres in the north and south respectively and the subpolar front in the central part of the sea

a frost buzzsaw mechanism for erosion of the eastern southern alps new zealand article in the southern alps new zealand large gradients in precipitation b 1t o 12 m year 1 and rock uplift b 1t o 10 mm year 1 produce distinct post glacial geomorphic domains in which landslide driven sediment production dominates in the wet rapid uplift western region and rockfall controls erosion in the drier low uplift eastern region because the western region accounts for b25 of the active orogen the dynamics of erosion in the extensive eastern region are of equal importance in estimating the relative balance of uplift and erosion across the southern alps here we assess the efficacy of frost cracking as the primary rockfall mechanism in the eastern southern alps using air photo and topographic analysis of scree slopes cosmogenic radionuclide dating of headwalls paleo climate data and a numerical model of headwall temperature currently active scree slopes occur at a relatively uniform mean elevation 1450 m and their distribution is independent of hillslope aspect and rock type consistent with the notion that frost cracking which is maximized between 3 and 8 c may control rockfall erosion headwall erosion rates of 0 3 to 0 9 mm year 1 measured using in situ 10 be and 26 al in the cragieburn range confirm that rockfall erosion is active in the late holocene at rates that roughly balance rock uplift models of the predicted depth of frost activity are consistent with the scale of fractures and scree blocks in our field sites also vegetated paleo scree slopes are ubiquitous at elevations lower than active scree slopes consistent with the notion that lower temperatures during the last glacial advance induced pervasive rockfall erosion due to frost cracking our modeling suggests temporally averaged peak frost cracking intensity occurs at 2300 m a s l the approximate elevation of the highest peaks in the central southern alps suggesting that the height of these peaks may be limited by a frost buzzsaw

unusual distributions of long chain alkenones and tetrahymanol from the highly alkaline lake van turkey long chain c37 to c40 alkenones with di tri and tetra unsaturation are very abundant in sediment trap material and holocene to late pleistocene core samples from the earth s largest soda lake lake van turkey thus the known distribution range of these typical biomarkers for haptophyte microalgae is extended to highly alkaline environments the observed unsaturation patterns differ strikingly from those found in open marine haptophytes and sediments by an enhanced relative abundance of the tetra unsaturated compounds especially the c37 4 methyl ketone their preponderance is suggested to be a facies marker pattern for lacustrine and marginal marine areas of sedimentation using published u37k calibrations no reliable absolute temperatures were obtained for the lake van samples accordingly marine sea surface temperature determinations based on long chain alkenones should be applied with caution when a contribution of these compounds from coastal or nonmarine sources can not be excluded the presence of tetrahymanol and gammacer 3 one in the lake van materials is attributed to organic matter contributions of ciliates the relative abundance of long chain alkenones and of tetrahymanol gammacer 3 one is considered to reflect changes in the environmental conditions in particular in the hydrological setting we suggest that times of pronounced stagnation are recognised by very high tetrahymanol gammacer 3 one concentrations together with drastically increased stanol stenol ratios and intervals of enhanced convection or of high freshwater input are characterised by high alkenone contributions

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

interhemispheric appraisal of the value of alkenone indices as temperature and salinity proxies in high latitude locations alkenone sediment data from the nordic seas and north atlantic are compared to those from sikes et al 1997 for the southern ocean to evaluate further uk37 and uk37 as proxies to estimate cold temperatures 10 c and the effect of salinity and temperature in the relative abundance of 37 4 to the total abundance of c37 alkenones 37 4 uk37 and uk37 are found to be equally viable as proxies but there are significant regional differences in their cold temperature dependence the measurement of 37 4 in cores from the north atlantic region can be used to identify situations when uk37 is not a reliable paleothermometer variations in salinity are probably responsible for changes in the sedimentary record of 37 4 and a preliminary calibration has been obtained for 37 4 f salinity this new relationship should be further confirmed through field or laboratory experiments but it paves the way to derive a molecular proxy to reconstruct paleosalinity in surface waters