western pacific interannual variability associated with the el nino southern oscillation observations of sea surface temperature sst sea level pressure slp surface wind and outgoing longwave radiation olr show that the el nino southern oscillation enso displays western pacific anomaly patterns in addition to eastern pacific anomaly patterns during the warm phase of enso warm sst and low slp anomalies in the equatorial eastern pacific and low olr anomalies in the equatorial central pacific are accompanied by cold sst and high slp anomalies in the off equatorial western pacific and high olr anomalies in the off equatorial far western pacific also while the zonal wind anomalies over the equatorial central pacific are westerly those over the equatorial far western pacific are easterly the nearly out of phase behavior between the eastern and western tropical pacific is also observed during the cold phase of enso but with anomalies of opposite sign these western pacific interannual anomaly patterns are robust features of enso independent of data sets it is argued that equatorial easterly westerly wind anomalies over the far western pacific during the warm cold phase of enso are initiated by off equatorial western pacific cold warm sst anomalies and that these winds are important for the evolution of enso an atmosphere model is employed to demonstrate that small off equatorial western pacific cold warm sst anomalies compared to those in the east are sufficient to produce equatorial easterly westerly wind anomalies as observed over the far western pacific the coupled ocean atmosphere model of zebiak and cane is then modified to investigate the evolution of the western pacific interannual anomaly patterns in a coupled ocean atmosphere system by including a meridional structure to the subsurface temperature parameterization in the western pacific the modified model produces both western and eastern pacific interannual anomaly patterns

middle pleistocene climate and hydrological environment at the boxgrove hominin site west sussex uk from ostracod records the sediments of the slindon formation at the junction of the chalk south downs and the west sussex coastal plain as revealed and studied at boxgrove contain evidence for early middle pleistocene environments in southern england around half a million years ago the archaeological importance of the deposits is attested to by the recovery of stone and organic tools butchered fauna and fossil hominin remains we combine palaeoecological and geochemical analyses of ostracods from the coastal plain deposits to reconstruct the climate and environment at one period of the hominin occupation the stratigraphy of our study area is indicative of a terrestrial environment surrounding a small lake or pond ostracod assemblages from the sediments indicate that the ponds were shallow but permanent and fed by groundwater and springwater however the species alone cannot confirm that these ponds were completely fresh application of mutual climatic range mcr techniques shows that summer temperatures were similar to present day values and winter temperatures were probably colder whereas mean annual air temperature was similar to present or perhaps slightly cooler trace element and strontium isotope analyses of ostracods from the sediments support the conclusion that the ponds were fed largely by fresh groundwater derived from the chalk although there may have been a minor seawater input the carbon isotope ratios of the ostracod shells are consistent with a groundwater source although they also indicate that the dissolved inorganic carbon most likely did not reach equilibrium with atmospheric carbon dioxide suggesting that the ponds had short residence time the combination of palaeotemperature estimates with oxygen isotope values from ostracod shells allowed us to reconstruct the oxygen isotope ratio of the pond water which was close to the value of early middle pleistocene precipitation at this site values were similar to present day suggesting that there may have been a change in seasonality or precipitation source since the mean air temperatures might have been lower

characteristic patterns of variability of sea level pressure in the northern hemisphere abstract seasonal and annual mean sea level pressures for the northern hemisphere have been analyzed to determine the dominant modes of interannual and longer period variability using monthly sea level pressure analyses as revised by trenberth and paolino 1980 empirical orthogonal function eof analysis is used to reveal the modes which explain most of the variance for the period 1925 77 in winter kutzbach s 1970 eof 1 for january remains the dominant mode and a closely related pattern dominates all seasons and the annual means although there are differences in detail in each season the dominant mode is basically a high latitude zonal index type pattern with departures in pressure at high latitudes corresponding to anomalies of opposite sign in low latitudes eof 1 is linked to the north atlantic oscillation but the north south fluctuations in mass also occur in the pacific and to a lesser extent elsewhere time series associated with this pattern have highly significant spectral peaks at the

timing and thermochemical constraints on multi element mineralisation at the nori ra cu mo u prospect great bear magmatic zone northwest territories canada the timing of cu mo u mineralisation at the nori ra prospect in the paleoproterozoic great bear magmatic zone has been investigated using re os molybdenite and 40ar 39ar biotite geochronology the re os molybdenite ages presented are the first robust sulphide mineralisation ages derived from the great bear magmatic zone cu mo u mineralisation is hosted in early to syn deformational hydrothermal veins consisting of quartz and k feldspar or more commonly tourmaline biotite quartz k feldspar with associated wall rock alteration assemblages being predominantly biotite sulphide and oxide minerals consist of chalcopyrite molybdenite and uraninite with lesser pyrite and magnetite elevated light rare earth elements and tungsten concentrations associated with the cu mo u mineralisation have also been reported at the prospect by previous workers molybdenite and uraninite occur intimately in dravitic tourmaline growth zones and at grain margins attesting to their syngenetic nature with respect to hydrothermal veining two molybdenite separates yield re os model ages of 1 874 4 8 7 2 and 1 872 4 8 8 ma 2 with a weighted average model age of 1 873 4 6 1 ma 2 laser step heating of biotite from the marginal alteration of the wall rock adjacent to the veins yields a 40ar 39ar maximum cooling age of 1 875 8 ma mswd 3 8 2 indistinguishable from the re os molybdenite model age and a previously dated syn tectonic aplitic dyke in the region dravitic tourmaline hosts abundant primary liquid vapour solid bearing fluid inclusions analytical results indicate liquid vapour homogenisation at 260 c constraining the minimum temperature of mineralisation the solids which are possibly trapped did not homogenise with the liquid vapour by 400 c salinities in the inclusions are variable raman spectra identify that at least some of the solids are calcite and anhydrite raman spectra also confirm the vapour phases contain some co2 whereas clathrates or ch4 was not observed or detected quartz grains only host secondary fluid inclusions which fluoresce under ultraviolet light indicating trapped hydrocarbons we speculate that these resulted from phanerozoic fluid circulation through the proterozoic basement the collective interpretation of the age hydrothermal character and associated metals high temperature and variable salinity suggests that the nori ra cu mo u mineralisation can be linked with the earliest stages of plutonism in the great bear magmatic zone from a regional perspective the mineralisation may pre date the extensive multi element mineralisation now recognised as part of the iron oxide copper gold iocg spectrum of deposits as iocg provinces generally contain a variety of mineralisation styles we interpret this as the earliest phase of the extensive mineralising system

two regimes of the equatorial warm pool part i a simple tropical climate model abstract atmosphere ocean coupled processes responsible for generating and maintaining the equatorial warm pool were investigated using models of different complexities the primary focus was to answer the following question why is the observed warm pool concentrated around the maritime continent in this first of a two part series the solutions of a simple conceptual model that represents the tropical pacific and indian oceans interacting via the walker circulation are examined when the interbasin coupling is sufficiently strong surface wind convergence over the maritime continent associated with easterly trades over the pacific acts to generate the equatorial westerly over the indian ocean leading to a warm pool spontaneously emerging between the two ocean basins the conceptual model shows that tropical climate has two equilibria depending upon the ocean basin widths a single warm pool regime corresponding to the current climate and a split warm pool regime that accompanies warm pools created in

role of indian ocean warming in the development of philippine sea anticyclone during enso 1 the anomalous low level anticyclone near the philippines and suppressed convection over the western pacific associated with the mature warm phase of el nino southern oscillation enso have been suggested as important elements in the interaction between enso and the east asian monsoon we examined the causes of these anomalies in the circulation and convection using a newly developed linear baroclinic model that includes interactive moist processes of the cumulus convection and surface heat fluxes a conventional version of the linear model forced by prescribed heating indicates that the diabatic cooling due to suppressed convection over the maritime continent generates the philippine sea anticyclone from a series of the moist linear model experiments we found that the modest warming of the indian ocean in addition to the strong warming in the central eastern pacific and weak cooling in the western pacific is significant to suppress the convection over the maritime continent observed data also show a coincidence of the development between the philippine sea anticyclone indian ocean warming and the ascending motion over the indian ocean supporting the model results the above results indicate that the atmosphere ocean system in the indian ocean may be one of important factors to improve predictability of the east asian climate during enso

the initial value problem for tropical perturbations to a baroclinic atmosphere large scale wave propagation ideas have proved extremely valuable in interpreting real and model data these ideas have been developed in the context of barotropic models and here the extension to baroclinic atmospheres is investigated the dispersion of waves from an initial large scale tropical perturbation to a baroclinic basic flow is studied using a direct approach a 15 level spectral primitive equation model is integrated forward in time even in baroclinically unstable flows it is found that for a period normally of order 12 days the model yields what can be considered to be the direct response to the tropical perturbations after this time baroclinic instability dominates the basic flows are a resting atmosphere a climatological westerly an equatorial longitudinal modification to this and a 3 d climatological december february state for the perturbations used here equatorial kelvin waves play only a very small role the large scale equatorial rossby wave shows only small dispersion and tends to move with a doppler shifted phase speed which allows it to accumulate to the east of an equatorial maximum of 10 ms 1 or more rossby wavetrains propagate into the middle and high latitude westerly regions with the climatological flow perturbations in the indian ocean west pacific sector trigger a modal structure in the north pacific and wavetrain across north america very much as barotropic theory would suggest and similar to observed pacific north america pna patterns in such a flow the middle latitude waves tend to extend to the equator in the westerly regions of the east pacific and atlantic in agreement with observed behaviour

morphology and seismic stratigraphy of the inner continental shelf off nova scotia canada evidence for a 65 m lowstand between 11 650 and 11 250 c14 yr b p abstract nova scotia s position near the margin of large pleistocene ice sheets makes the scotian shelf region critical for evaluation of glaciation models and sea level change the sea floor of the inner scotian shelf was mapped using multibeam bathymetry a combination of conventional seismic and sonar techniques and sampling multibeam bathymetry provides an areal image of the sea floor combining this unique image with sub bottom seismic imaging the relationships between sea floor topography and the underlying strata were explored the inner continental shelf of nova scotia can be subdivided into five major terrain zones these are the 1 truncation zone 2 morainal zone 3 outcrop zone 4 basin zone and 5 scotian shelf end moraine complex the scotian shelf end moraine complex and basin zone are glacial depositional zones at the seaward edge of the inner shelf landward of these zones is a region of high relief bedrock with ridges and valleys largely devoid of surficial sediments extending from 80 to 120 m water depth outcrop zone this zone is interpreted as a relict bedrock surface preserved under frozen bed glacier conditions to the east of the outcrop zone in similar water depths are unmodified till ridges overlying bedrock morainal zone the truncation zone is a region of the inner shelf from 90 m to the present shoreline characterized by muted acoustic topography and planar erosional surfaces truncating bedrock and surficial sediments the truncation zone is subdivided into the valley subzone the transition subzone the platform subzone and the estuarine subzone the valley subzone is typified by sediment infilled valleys occurring in 75 to 90 m water depths these valleys contain seismic facies with a ponded style of deposition planed off at the sea floor or by erosional unconformities near the sea floor the transition subzone is marked by a relatively steep ramp and terraces the ramp at the type section extends from 75 to 65 m water depth the surface of the ramp can be either an erosional unconformity or a depositional surface formed by clinoform beds the 65 m former shoreline is interpreted as the top of the transition subzone ramp surface at one ramp locality clinoform beds form part of a progradational sequence called the sambro delta a mussel valve fragment mytilus edulis was obtained from a core in the foresets and radiocarbon dated an age of 11 650 110 yr b p was obtained adjusted for isotopic fractionation above 65 m the sea floor forms a low relief gently sloping erosional surface platform subzone estuarine deposits have been found above 50 m the new sea level curve constructed with the dated 65 m shoreline and recently published data is at variance with calculated rsl curves based on geophysical models primarily in the amplitudes and rates of rsl change reasons for the discrepancies may be late melting ice and regional variations in lithospheric strength and thickness

role of the enso indian ocean coupling on enso variability in a coupled gcm warming are only confined to the io and it has little impact on the tropical pacific during the boreal winter when the el nino is in its mature phase the anomalous warming extends eastward to cover the entire tropical io and the anomalous easterlies extend into the western pacific wp the anom alous easterlies in the wp generate oceanic upwelling kelvin waves which propagate eastward and accelerate the decay of the warm sst in the eastern pacific as a result the el nino is rapidly terminated and a la nina develops within one year from the el nino mature phase they concluded that the interaction between enso and the io may generate a biennial tendency for enso 4 the samples used for the composite analysis by kk06 are rather limited due to the relatively short length of the observational data in this study we intended to analyze a longer 200 yr data set obtained from the simulation of a sintex f scale interaction experiment frcgc cou pled gcm in order to verify the enso io feedback hypoth esis itturnsoutthatthefeedbackprocessbetweenensoand the io is quite plausible not only from observations but also from the state of the art coupled gcm

integrated micropalaeontological study ostracods and calcareous plankton of the langhian western hyblean successions sicily italy abstract four sections cropping out in the hyblean plateau se sicily were studied biostratigraphically and palaeoecologically the investigated succession was referred to the early late langhian on the basis of both the planktonic foraminifers lowermost part of the praeorbulina glomerosa sicana subzone lowermost part of the orbulina universa subzone and the calcareous nannofossils uppermost part of the mnn4a zone lowermost part of the mnn5b subzone all the biozonal markers were recorded and further significant events were identified the most remarkable ones are two paracmes of paragloborotalia siakensis within the p glomerosa sicana subzone and the distribution of helicosphaera waltrans which characterises the upper part of the mnn5a subzone the ostracod palaeoecological analysis indicated a progressive and gradual trend from thermospheric to psychrospheric conditions and probably a basin deepening from upper to lower epibathyal the flowing of deep atlantic waters into the basin is documented by the entry of the psychrospheric species agrenocythere hazelae within the upper part of the p glomerosa sicana subzone only in the late langhian however were typical psychrospheric conditions probably reached these data provide evidence that oceanic deep water masses reached the central mediterranean passing through both the western connections to the atlantic ocean and the african sicilian threshold during a great part of the langhian

synoptic analysis of the pacific north american teleconnection pattern in this study we use various diagnostic techniques to investigate the synoptic evolution of the pacific north american teleconnection pattern pna national center for environment prediction national center for atmospheric research reanalysis data are used these data cover the years 1948 2008 for the months of november march it is found that the positive pna is initiated by enhanced convection over the western tropical pacific and weakened convection over the tropical indian ocean the excitation of the negative pna exhibits opposite features for both phases the response to tropical convection excites a small amplitude pna about 8 12 days prior to the pattern attaining its maximum amplitude this is followed by slow steady growth for about 5 days after which driving by synoptic scale waves via their eddy vorticity flux together with stationary eddy advection lead to much more rapid growth and the establishment of the full pna for the positive pna the synoptic scale waves propagate eastward into the midlatitude northeastern pacific where they are observed to undergo cyclonic wave breaking for the negative pna the synoptic scale waves first amplify over the midlatitude northeastern pacific and then propagate equatorward into the subtropics where they undergo anticyclonic wave breaking once established for both phases the pna appears to be maintained through a positive feedback that involves a succession of wave breakings these results suggest that preconditioning may play an important role in the formation of the pna for the positive pna in its early development the strengthening and eastward extension of the subtropical jet result in an increase in the cyclonic shear and a decrease in the meridional potential vorticity gradient features that are known to favour cyclonic wave breaking for the negative pna opposite changes were observed for the background flow which favour equatorward wave propagation and anticyclonic wave breaking the role of optimal growth is also discussed our results also suggest that the pna is potentially predictable 1 2 weeks in advance copyright 2011 royal meteorological society

a moist linear baroclinic model coupled dynamical convective response to el nino a newly developed linear baroclinic model lbm and its application to the tropical enso teleconnection is described the model based on primitive equations linearized about the observed zonally varying basic state in northern winter involves linear schemes for the cumulus convection and surface sensible and latent heat fluxes referred to as the moist lbm this enables us to solve a steady state response of the coupled dynamical convective system to a given sst anomaly which is fairly different from the conventional dry lbm linear representation of the convection is acceptable for a realistic range of sst anomalies reproducing well the rossby wave train computed in the conventional lbm forced by a tropical heating the moist lbm is used to examine the formation mechanisms of an anomalous low level anticyclone near

interactive feedback between enso and the indian ocean abstract a feedback process of the indian ocean sst on enso is investigated by using observed data and atmospheric gcm it is suggested that warming in the indian ocean produces an easterly wind stress anomaly over indonesia and the western edge of the pacific during the mature phase of el nino the anomalous easterly wind in the western pacific during el nino helps a rapid termination of el nino and a fast transition to la nina by generating upwelling kelvin waves thus warming in the indian ocean which is a part of the el nino signal operates as a negative feedback mechanism to enso this indian ocean feedback appears to operate mostly for relatively strong el ninos and results in a la nina one year after the mature phase of the el nino this 1 yr period of phase transition implies a possible role of indian ocean enso coupling in the biennial tendency of the enso atmospheric gcm experiments show that indian ocean sst forcing is mostly responsible for the easterly wind anomalies in the western pacific

annular modes in the extratropical circulation part i month to month variability the leading modes of variability of the extratropical circulation in both hemispheres are characterized by deep zonally symmetric or annular structures with geopotential height perturbations of opposing signs in the polar cap region and in the surrounding zonal ring centered near 458 latitude the structure and dynamics of the southern hemisphere sh annular mode have been extensively documented whereas the existence of a northern hemisphere nh mode herein referred to as the arctic oscillation ao has only recently been recognized like the sh mode the ao can be defined as the leading empirical orthogonal function of the sea level pressure field or of the zonally symmetric geopotential height or zonal wind fields in this paper the structure and seasonality of the nh and sh modes are compared based on data from the national centers for environmental prediction national center for atmospheric research reanalysis and supplementary datasets the structures of the nh and sh annular modes are shown to be remarkably similar not only in the zonally averaged geopotential height and zonal wind fields but in the mean meridional circulations as well both exist year round in the troposphere but they amplify with height upward into the stratosphere during those seasons in which the strength of the zonal flow is conducive to strong planetary wave mean flow interaction midwinter in the nh and late spring in the sh during these active seasons the annular modes modulate the strength of the lagrangian mean circulation in the lower stratosphere total column ozone and tropopause height over mid and high latitudes and the strength of the trade winds of their respective hemispheres the nh mode also contains an embedded planetary wave signature with expressions in surface air temperature precipitation total column ozone and tropopause height it is argued that the horizontal temperature advection by the perturbed zonal mean zonal wind field in the lower troposphere is instrumental in forcing this pattern a companion paper documents the striking resemblance between the structure of the annular modes and observed climate trends over the past few decades

recognition of cyclic and non cyclic environmental changes in the mediterranean pliocene a palynological approach the interval between 2 8 and 2 3 ma b p from the south italian singa section has been investigated for its dinoflagellate cyst and sporomorph contents in order to facilitate palaeoenvironmental interpretation the following curves are derived from the data the ratios sporomorphs dinoflagellate cysts protoperidinioid gonyaulacoid dinoflagellate cysts warm cold water indicating dinoflagellate cysts inner neritic oceanic dinoflagellate cysts outer neritic oceanic dinoflagellate cysts and the reworked dinoflagellate cysts per gram of sediment furthermore the already available 18o curve has been used calibration of changes in the sporomorph dinoflagellate ratio against the computed astronomical insolation curve leads to an improved age assessment for the section frequency analysis on the curves shows the 23 41 and 100 ka frequency components to be most important phase and amplitude differences between the filtered 23 41 and 100 ka frequency components are used for environmental interpretation the 23 ka frequency band is best explained by changes in runoff induced transport the 41 ka frequency components are classified in a group with short response time to orbital forcing and a group with longer response time those signals having a short response time are attributed to local precipitation induced changes in runoff those signals having a longer response time are mainly attributed to changes in global temperature and to a lesser extent to changes in global ice volume finally longer term cyclic and non cyclic changes are mainly attributed to temperature and sea level variation

a comparison of present sea level linear trends from tide gauge data and radiocarbon curves in eastern canada abstract a comparison is made of the results for determinations of vertical crustal movements by means of two independent sources of data widely used in geodesy and geology tide gauge sea level linear trends and gradients of radiocarbon curves as a reference the map of vertical crustal movements of canada is added which was computed using not only tide gauge data but also geodetic levelling data these results show similar trends computed by both techniques but an average value of 0 1 m century greater for the sea level trends the map of vertical crustal movements is in good agreement with the trends provided by the gradients of radiocarbon curves

interglacials of the last 800 000 years interglacials including the present holocene period are warm low land ice extent high sea level end members of glacial cycles based on a sea level definition we identify eleven interglacials in the last 800 000 years a result that is robust to alternative definitions data compilations suggest that despite spatial heterogeneity marine isotope stages mis 5e last interglacial and 11c 400 ka ago were globally strong warm while mis 13a 500 ka ago was cool at many locations a step change in strength of interglacials at 450 ka is apparent only in atmospheric co2 and in antarctic and deep ocean temperature the onset of an interglacial glacial termination seems to require a reducing precession parameter increasing northern hemisphere summer insolation but this condition alone is insufficient terminations involve rapid nonlinear reactions of ice volume co2 and temperature to external astronomical forcing the precise timing of events may be modulated by millennial scale climate change that can lead to a contrasting timing of maximum interglacial intensity in each hemisphere a variety of temporal trends is observed such that maxima in the main records are observed either early or late in different interglacials the end of an interglacial glacial inception is a slower process involving a global sequence of changes interglacials have been typically 10 30 ka long the combination of minimal reduction in northern summer insolation over the next few orbital cycles owing to low eccentricity and high atmospheric greenhouse gas concentrations implies that the next glacial inception is many tens of millennia in the future

the climate of the mis 13 interglacial according to hadcm3 the climate of the marine isotopic stage 13 mis 13 is explored in the fully coupled atmosphere ocean general circulation model the hadley centre coupled model version 3 hadcm3 it is found that the strong insolation forcing at the time imposed a strengthened land ocean thermal contrast resulting in an intensified summer monsoon over asia the addition of land ice over north america and eurasia results in a stationary wave feature across the eurasian continent this leads to a high pressure anomaly over the sea of japan with increased advection of warm moist air onto the chinese landmasses this in turn reinforces the east asian summer monsoon easm highlighting the counterintuitive notion that depending on the background insolation and its size ice can indeed contribute to strengthening the easm the modeling results support the geological record indication of a strong easm 500 000 years ago furthermore arctic oscillation el nino southern oscillation and indian ocean dipole like teleconnection features are discussed in the mis 13 environment it is shown that the change in the tropical pacific sea surface temperature has the potential to impact the north atlantic climate through an atmospheric bridge

new data from halifax harbour paleoenvironment and a new holocene sea level curve for the inner scotian shelf two vibracores collected from halifax harbour allow reevaluation of the early postglacial history and part of a new sea level curve for eastern nova scotia an acoustically distinct seismic unit fo

orbital and millennial antarctic climate variability over the past 800 000 years a high resolution deuterium profile is now available along the entire european project for ice coring in antarctica dome c ice core extending this climate record back to marine isotope stage 20 2 800 000 years ago experiments performed with an atmospheric general circulation model including water isotopes support its temperature interpretation we assessed the general correspondence between dansgaard oeschger events and their smoothed antarctic counterparts for this dome c record which reveals the presence of such features with similar amplitudes during previous glacial periods we suggest that the interplay between obliquity and precession accounts for the variable intensity of interglacial periods in ice core records

an 800 ky proxy record of climate from lake sediments of the zoige basin eastern tibetan plateau abstract we present the results of magnetic susceptibility geochemical and pollen analyses of a 120 m long core of lacustrine and fluvial sediments from the zoige basin eastern tibetan plateau palaeomagnetic dating indicates that the sediment sequence spans the last ca 800 ky the magnetic susceptibility record appears to be related to global ice volume over this period and this relationship is used to produce a tentative revised chronology for the sediment sequence the various climate proxies show a pattern of periodic variations over the last 800 ky bp the date of 500 ky bp is a significant boundary prior to this date the climate proxies show a pattern of more frequent variability after 500 ky bp the variations are of lower frequency and higher amplitude the results also indicate that marine oxygen isotope stage 13 was an unusually intense interglacial in the eastern tibetan plateau and chinese loess plateau areas

zonal circulations over the equatorial indian ocean abstract the ncep ncar 1958 97 upper air dataset and surface observations have been analyzed for evidence of zonal vertical circulations along the indian ocean equator and their role in climatic variability the long term mean upper tropospheric circulation is dominated in boreal winter by divergent outflow from the southern indian ocean northwestward into southern asia and in summer from southern asia southwestward into the southern hemisphere in boreal autumn only divergent easterlies blow from indonesia along the equator into an upper tropospheric convergence band over east africa and only then a closed zonal vertical circulation cell materializes along the indian ocean equator between the centers of ascending motion over indonesia and of subsidence over equatorial east africa and featuring westerlies in the lower layers the boreal autumn zonal vertical circulation varies interannually a regime of intense circulation features accelerated equatorial surface westerlies enhanced subsidence and d

the climate of north america and adjacent ocean waters ca 6 ka the climate of north america and the adjacent ocean at 6000 bp was estimated using five independent approaches using pollen data the terrestrial climate was estimated by the movement of ecozone boundaries and by the method of modern analogues both analyses indicate warmer temperatures in the western great lakes area and the northern great plains a model of sphagnum dominated peatland initiation when forced by canadian climate model 6 ka output projected a cooler and or wetter climate for continental western north america contrary to this a reconstruction of the distribution of sphagnum dominated peatlands in western canada indicates that they were located north of their modern distribution suggesting warmer and or drier conditions at 6000 bp this interpretation is strengthened by observations of lower lake levels at 6000 bp in western canada this drier climate may have been associated with warmer conditions as indicated by the quantitative climate reconstructions in general eastern north a

atmosphere ocean thermal coupling in the north atlantic a positive feedback in this article it is examined whether a positive atmosphere ocean feedback is found over the north atlantic through a series of general circulation model gcm experiments a 60 year integration of an atmospheric gcm agcm coupled with a 50 m deep motionless ocean was conducted the coupled run was compared with two uncoupled runs one with prescribed mid latitude climato logical sea surface temperatures ssts and the other with daily ssts derived from the coupled experiment the uncoupled atmosphere forces the slab ocean to obtain sst responses in these runs consistent with previous studies the coupled atmosphere ocean fields show interannual variances larger than those in the uncoupled runs due to reduction in the local thermal damping patterns of maximum atmosphere ocean covariability show the north atlantic oscillation nao and tripole sst anomalies both in the coupled and uncoupled fields indicating a dominant role of the atmosphere in generating the sst anomalies on the other hand analyses of the temporal variability in the three runs suggest an active role of sst anomalies in determining the polarity of the air sea coupled variability longer than the interannual time scale a combined analysis of forcing sst upper air height and the response sst anomalies in the uncoupled run identified that a patch of positive sst anomalies in the mid latitude band around 40 n effectively excite the positive phase of the nao which in turn reinforces the tripole sst anomalies this relationship was further confirmed by a nine member ensemble agcm experiment forced by the relevant sst anomalies since the forcing and response sst anomaly patterns bear some resemblance these results manifest positive feedback at work in the coupled atmosphere ocean patterns the processes responsible for this positive feedback were elaborated by a series of linear model experiments the local thermal adjustment of the atmosphere to the sst anomalies results in increased precipitation over the gulf stream region associated diabatic heating applied to a linear baroclinic model yields a positive height response to the east which highly influences the southern part of the nao this stationary response in turn induces a northward deflection in the storm track activity leading to an eddy vorticity feedback that tends to force the positive phase of the nao

marine dinocysts acritarchs and less well known npp tintinnids ostracod and foraminiferal linings copepod and worm remains

impact of ice sheet induced north atlantic oscillation on east asian summer monsoon during an interglacial 500 000 years ago marine isotope stage mis 13 an interglacial about 500 000 years ago is unique due to an exceptionally strong east asia summer monsoon easm occurring in a relatively cool climate with low greenhouse gas concentrations ghg this paper attempts to find one of the possible mechanisms for this seeming paradox simulations with an earth system model loveclim show that the presence of ice sheets over north america and eurasia during mis 13 induces a positive phase of the winter north atlantic oscillation nao like feature the ocean having a longer memory than the atmosphere the oceanic anomalies associated with nao persists until summer the signals of summer nao are transmitted to east asia to reinforce the monsoon there through the stationary waves excited at the asian jet entrance the geopotential height shows clearly a mid latitude wave train with positive anomalies over the eastern mediterranean caspian sea and the okhotsk sea and a negative anomaly over lake baikal this reinforces the effect of the high latitude wave train induced independently by the eurasian ice sheet topography as shown in previous study these features reinforce the meiyu front and enhance the precipitation over east asia the results obtained from loveclim are further confirmed by an atmospheric general circulation model arpege

submerged early holocene coastal and terrestrial landforms on the inner shelves of atlantic canada coastal and terrestrial landforms that formed with lowered relative sea levels during the early postglacial period in atlantic canada were submerged during the holocene transgression however these landforms are seldom seen on sea floor imagery factors that contribute to their destruction include the brevity of sea level lowstands and high wave energy on shallow modern shelves we identify one situation within which preservation has been relatively good large coastal lakes that existed for many thousands of years before being connected to the ocean by rising sea level in the mid holocene we describe bedford basin near halifax nova scotia and deal more exhaustively with the bras d or lakes an inland sea in cape breton nova scotia the preservation of shore platforms barrier beaches and spits and fluvial systems was due to the rapid onset of the transgression and the relatively low wave energy in the subsequent marine phases the well preserved early holocene coastlines are highly favourable targets in the search for evidence of human occupation in the early to mid holocene

south asian summer monsoon and the eastern mediterranean climate the monsoon desert mechanism in cmip5 simulations abstractdry summers over the eastern mediterranean are characterized by strong descent anchored by long rossby waves which are forced by diabatic heating associated with summer monsoon rainfall over south asia the large scale teleconnection between rising and subsiding air masses is referred to as the monsoon desert mechanism this study evaluates the ability of the phase 5 of the coupled model intercomparison project cmip5 models in representing the physical processes involved in this mechanism an evaluation of statistics between summer climatologies of monsoon diabatic heating and that of vertical velocity over the eastern mediterranean suggests a linear relationship despite large spatial diversity in monsoon heating descent over the mediterranean is coherently located and realistic in intensity to measure the sensitivity of descent to the diversity in the horizontal and vertical distribution of monsoon heating a series of linear atmosphere model experiments are performed it is shown that col

teleconnections in the geopotential height field during the northern hemisphere winter abstract contemporaneous correlations between geopotential heights on a given pressure surface at widely separated points on earth referred to as teleconnections in this paper are studied in an attempt to identify and document recurrent spatial patterns which might be indicative of standing oscillations in the planetary waves during the northern hemisphere winter with time scales on the order of a month or longer a review of existing literature on the subject reveals the existence of at least four such patterns the north atlantic and north pacific oscillations identified by walker and bliss 1932 a zonally symmetric seesaw between sea level pressures in polar and temperature latitudes first noted by lorenz 1951 and what we will refer to as the pacific north american pattern which has been known to operational long range forecasters in this country since the 1950 s a data set consisting of nmc monthly mean sea level pressure and 500 mb height analyses for a 15 year period is used as a basis fo

a new gravity wave drag scheme incorporating anisotropic orography and low level wave breaking impact upon the climate of the uk meteorological office unified model a new anisotropic gravity wave drag parametrization scheme which represents high drag states modelled on hydraulic jump flow blocking and internal wave reflection theory including trapped lee waves is presented the scheme is shown to represent the breaking of waves over mountains better than previous schemes by comparison with mesoscale simulations of pyrex case studies extended simulations of the meteorological office unified model at climate resolution are presented showing the impact of the new scheme and a combination of the scheme with a new orographic roughness parametrization results show a changed distribution of surface gravity wave surface stress mostly due to mountain anisotropy and a greater tendency for lower troposphere wavc drag inclusion of the orographic roughness parametrization halves the gravity wave stress the combined effect of these schemes for climate integrations being a slight improvement to the tropospheric flow

late quaternary stratigraphy and paleoecology of northwest labrador sea abstract sedimentological study of 20 piston cores from the northwestern labrador sea shows that thin bedded distal turbidites are important constituents of the quaternary strata on the continental slope and rise sedimentation on the outer shelf ca 500 900 m is dominated by ice rafting and hemipelagic deposition detailed study of two outer shelf cores reveals a stratigraphic record extending to oxygen isotopic stage 9 studies of foraminifera and dinoflagellates show that subarctic surface waters penetrated into the northern labrador sea during the early middle glacial stages and pollen data indicate that northward advection of warm air masses occurred at the same time microfossil data indicate that late glacial stages were characterized by year around sea ice cover and arctic surface water and by the dominance of cold dry arctic air masses transitions from glacial to interglacial stages are marked by the presence of low salinity melt water these data support models which postulate that open water in the labrador sea played an important role in supplying moisture to laurentide and greenland ice sheets

pacific east asian teleconnection how does enso affect east asian climate observational evidence is presented to show a teleconnection between the central pacific and east asia during the extreme phases of enso cycles this pacific east asian teleconnection is confined to the lower troposphere the key system that bridges the warm cold events in the eastern pacific and the weak strong east asian winter monsoons is an anomalous lower tropospheric anticyclone cyclone located in the western north pacific the western north pacific wind anomalies develop rapidly in late fall of the year when a strong warm or cold event matures the anomalies persist until the following spring or early summer causing anomalously wet dry conditions along the east asian polar front stretching from southern china northeastward to the east of japan kuroshio extension using atmospheric general circulation and intermediate models the authors show that the anomalous philippine sea anticyclone results from a rossby wave response to suppressed convective heating which is induced by both the in situ ocean surface cooling and the subsidence forced remotely by the central pacific warming the development of the anticyclone is nearly concurrent with the enhancement of the local sea surface cooling both the anticyclone and the cooling region propagate slowly eastward the development and persistence of the teleconnection is primarily attributed to a positive thermodynamic feedback between the anticyclone and the sea surface cooling in the presence of mean northeasterly trades the rapid establishment of the philippine sea wind and sst anomalies implies the occurrence of extratropical tropical interactions through cold surge induced exchanges of surface buoyancy flux the central pacific warming plays an essential role in the development of the western pacific cooling and the wind anomalies by setting up a favorable environment for the anticyclone sst interaction and midlatitude tropical interaction in the western north pacific

tropical axisymmetric mode of variability in the atmospheric circulation dynamics as a neutral mode abstract there is an observational evidence that the variability in the global upper tropospheric flow fields on a monthly basis is dominated by a zonally uniform pattern symmetric about the equator this fluctuation is characterized by the zonal mean zonal wind anomaly having the same sign within the tropics and thus has been related to changes in the global atmospheric angular momentum in this paper the mechanism of this variability referred to as the tropical axisymmetric mode tam was investigated using the ncep ncar reanalysis an atmospheric general circulation model agcm and a linear baroclinic model an index of the tam defined by the leading principal component of the observed 300 hpa streamfunction anomalies shows quite significant correlation with the nino 3 sst anomalies consistent with a well known coherence between the angular momentum and el nino while this suggests that tam can be forced effectively by el nino events data analyses and an agcm experiment with climatological ss

calcareous plankton and the mid brunhes climate variability in the alboran sea odp site 977 abstract quantitative calcareous plankton analyses have been performed at the ocean drilling program site 977 in the alboran sea through the mid brunhes interval 300 540 ka the results evidence orbital suborbital and millennial scale climate variability which primary reflects temperature change the patterns of increase decrease of coccolithophore and planktonic foraminifera warm water taxa reproduce the stage and substage climate variability in the planktonic 18o in good agreement with other planktonic isotope records from mediterranean sea and atlantic ocean variable conditions characterized by alternating cool nutrient rich or warm and stable sea surface waters occurred during interglacial marine isotope stage mis 13 in response to high amplitude oscillations of insolation during obliquity maximum and to north africa monsoon strength influencing distribution of taxa mis 13a resulted warmer than mis 13c based on the higher abundances of warm water taxa they increase just after insolation maxima suggesting a primary response of calcareous plankton to precessional orbital control following short term warm mis 11e and more humid mis 11d phases a climate optimum lasting about 16 kyr is recognized during mis 11c when major tropical subtropical water arrival into the alboran sea occurred as evidenced by the presence of trilobatus sacculifer mis 11c records unstable climate condition that persisted up to the late mis 11 indicating multiple pulses of southward migrations of subpolar front following the full interglacial mis 11c warm and oligotrophic conditions occurred during mis 9 as during mis 11 especially in mis 9e although without a climate optimum reduced abundance of warm water taxa and decrease of globorotalia inflata highlight colder surface water conditions and decreased atlantic mediterranean water exchange during glacials especially during the prominent sea level low stand of mis 12 short term prominent peaks of the polar subpolar neogloboquadrina pachyderma and coccolithus pelagicus ssp pelagicus and additional key taxa preferring fresher and turbid water together with minima in total nannofossil accumulation rate and enhanced coccolith reworking sustain a correlation with the north atlantic heinrich type ht events ht1 ht1a ht3 ht4 6 thus documenting the sensitiveness of the alboran sea in recording european and laurentide ice sheet dynamics the comparable chronology of most of these cold spells in the available balearic and ionian calcareous plankton records highlights that atlantic melt water entering alboran basin through gibraltar strait may have reached the central mediterranean preserving some of its original polar signature

pliocene paleoclimatic reconstruction using dinoflagellate cysts comparison of methods the application of quantitative and semiquantitative methods to assemblage data from dinoflagellate cysts shows potential for interpreting past environments both in terms of paleotemperature estimates and in recognizing water masses and circulation patterns estimates of winter sea surface temperature wsst were produced by using the impagidinium index ii method and by applying a winter temperature transfer function tfw estimates of summer sea surface temperature ssst were produced by using a summer temperature transfer function tfs two methods based on a temperature distribution chart act and actpo and a method based on the ratio of gonyaulacoid protoperidinioid specimens g p wsst estimates from the ii and tfw methods are in close agreement except where impagidinium species are sparse ssst estimates from tfs are more variable the value of the g p ratio for the pliocene data in this paper is limited by the apparent sparsity of protoperidinioids which results in monotonous ssst estimates of 14 26 c the act methods show two biases for the pliocene data set taxonomic substitution may force matches yielding incorrect temperature estimates and the method is highly sensitive to the end points of species distributions dinocyst assemblage data were applied to reconstruct pliocene sea surface temperatures between 3 5 2 5 ma from dsdp hole 552a and odp holes 646b and 642b which are presently located beneath cold and cool temperate waters north of 56 n our initial results suggest that at 3 0 ma wssts were a few degrees c warmer than the present and that there was a somewhat reduced north south temperature gradient for all three sites it is likely that sssts were also warmer but by an unknown perhaps large amount past oceanic circulation in the north atlantic was probably different from the present

tropical atlantic sea surface temperature variability and its relation to el nino southern oscillation past analyses of tropical atlantic sea surface temperature variability have suggested a dipole behavior between the northern and southern tropics across the intertropical convergence zone itcz by analyzing an improved 43 year 1950 1992 record of sst smith et al 1996 and other data derived from the comprehensive ocean atmosphere data set coads it is shown that the regions north and south of the itcz are statistically independent of each other at the seasonal to interannual timescales dominating the data confirming the conclusions of houghton and tourre 1992 some dipole behavior does develop weakly during the boreal spring season when there is a tendency for sst anomaly west of angola to be opposite of that in the tropical north atlantic it is further shown that tropical atlantic sst variability is corre lated with pacific e1 nifio southern oscillation enso variability in several regions the ma jor region affected is the north atlantic area of ne trades west of 40ow along 10on 20on and extending into the caribbean there about 50 80 of the anomalous sst variability is associ ated with the pacific enso with atlantic warmings occurring 4 5 months after the mature phases of pacific warm events an analysis of local surface flux fields derived from coads data shows that the enso related atlantic warmings occur as a result of reductions in the surface ne trade wind speeds which in turn reduce latent and sensible heat losses over the region in ques tion as well as cooling due to entrainment this enso connection is best developed during the boreal spring following the most frequent season of maximum enso anomalies in the pacific a region of secondary covariability with enso occurs along the northern edge of the mean itcz position and appears to be associated with northward migrations of the itcz when the north at lantic warmings occur although easterly winds are intensified in the western equatorial atlantic in response to pacific warm events they do not produce strong local changes in sst contrary to expectations from studies based on equatorial dynamics these teleconnected wind anomalies do not give rise to significant correlations of sst in the gulf of guinea with the pacific enso as the teleconnection sequence matures strong se trades at low southern latitudes follow the de velopment of the north atlantic sst anomaly and precede by several months the appearance of weak negative sst anomalies off angola and stronger positive anomalies extending eastward from southern brazil along 15o 30os

formation of albitite hosted uranium within iocg systems the southern breccia great bear magmatic zone northwest territories canada uranium and polymetallic u mineralization hosted within brecciated albitites occurs one kilometer south of the magnetite rich au co bi cu nico deposit in the southern great bear magmatic zone gbmz canada concentrations up to 1 wt u are distributed throughout a 3 by 0 5 km albitization corridor defined as the southern breccia zone two distinct u mineralization events are observed primary uraninite precipitated with or without pyrite chalcopyrite molybdenite within magnetite ilmenite biotite k feldspar altered breccias during high temperature potassic iron alteration subsequently pitchblende precipitated in earthy hematite specular hematite chlorite veins associated with a low temperature iron magnesium alteration the uraninite bearing mineralization postdates sodic albite and more localized high temperature potassic iron biotite magnetite k feldspar alteration yet predates potassic k feldspar boron tourmaline and potassic iron magnesium hematite k feldspar chlorite alteration the southern breccia zone shares attributes of the valhalla australia and lagoa real brazil albitite hosted u deposits but contains greater iron oxide contents and lower contents of riebeckite and carbonates potassium ni and th are also enriched whereas zr and sr are depleted with respect to the aforementioned albitite hosted u deposits field relationships geochemical signatures and available u pb dates on pre syn and post mineralization intrusions place the development of the southern breccia and the nico deposit as part of a single iron oxide alkali altered ioaa system in addition this case example illustrates that albitite hosted u deposits can form in albitization zones that predate base and precious metal ore zones in a single ioaa system and become traps for u and multiple metals once the tectonic regime favors fluid mixing and oxidation reduction reactions

precession and glacial cycle controls of monsoon precipitation isotope changes over east asia during the pleistocene abstract precipitation isotope reconstructions derived from speleothems and plant waxes are important archives for understanding hydroclimate dynamics their climatic significance in east asia however remains controversial here we present terrestrial plant wax stable hydrogen isotope dwax records over periods covering the last four interglacials and glacial terminations from sediment cores recovered from the northern south china sea scs as an archive of regionally integrated precipitation isotope changes in southeast china combined with previous precipitation isotope reconstructions from china we find that the scs dwax and southwest central china stalagmite 18 o records show relatively enriched and depleted isotopic values respectively during interglacial peaks but relatively similar isotopic variations during most sub interglacials and glacial periods over the past 430 thousand years during interglacial peaks strong summer insolation should have intensified the convection intensity the isotopic fractionation along moisture trajectories and the seasonality which are all in favor of causing isotopically depleted rainfall over the east asian monsoon regime these effects in combination with a relatively high proportion of indian ocean versus pacific sourced moisture influx should have resulted in strongly depleted precipitation isotopes stalagmite 18 o over most parts of china however southeast china should have been affected by a relatively low ratio of indian ocean versus pacific sourced moisture influx which dominated over effects yielding depleted precipitation isotopes and led to enriched precipitation isotopes dwax it is thus concluded that glacial boundary conditions and insolation forcing are the two most important factors for causing regional differences in precipitation isotope compositions over subtropical east asia on orbital timescales

climate soil model reveals causes of differences between marine isotope stage 5e and 13 paleosols over the last decades numerous studies have used the loess paleosol sequences in china to reconstruct the east asian climate and to investigate their linkage with global climate change the paleosols embedded in the loess developed during warm periods and contain valuable information on climate and vegetation under warm conditions however because soil formation is controlled by multiple factors it is not straightforward to obtain a pure climate signal based on soil property analyses this leads often to debates and questions here for the first time we use a soil formation model together with a climate model to identify the main factors that control the paleosol formation a case study has been performed on paleosols in the chinese loess plateau of the last interglacial marine isotope stage mis 5e and the interglacial at ca 500 kyr b p mis 13 our results show that although the peak warmth and peak summer monsoon precipitation are stronger during mis 5e the soil formation is stronger during mis 13 which is supported by field evidence this is mainly due to larger accumulative precipitation surplus weaker dust deposition and longer interglacial duration during mis 13 our results provide a new interpretation of the climate signal recorded by the paleosols and an explanation for the seeming paradox that strongly developed soils formed during relatively weak interglacials they also highlight the necessity to include proxy modeling in paleoclimate studies

ice marginal depositional responses to readvance episodes in the late devensian deglaciation of the isle of man abstract remapping of the quaternary geology of the isle of man and consequent revision of the stratigraphic succession identifies three glacigenic formations each separated by a major unconformity the oldest formation the shellag represents an extensive ice advance beyond the island limits to the last glacial maximum lgm the overlying formation the orrisdale represents a major readvance episode during retreat from the lgm and is associated with the construction of the bride moraine and the deposition of extensive proglacial subaqeous sediment examination of the sedimentology and micropalaeontology of these sediments indicates that the water body was most likely lacustrine and not marine application of sequence stratigraphy to the overlying jurby formation identifies evidence for three further phases of readvance each off lapping one another into the margin of the lake basin via a complex system of ice contact subaqueous fans and outwash fan deltas the jurby formation is dated by organic sediments overlying it as older than 18 5 14 4 kyr bp and provides an ice marginal correlative for heinrich event 1 readvance limits identified 50 km to the west in eastern ireland

modeling the contribution of m2 tidal amplification to the holocene rise of mean high water in the gulf of maine and the bay of fundy abstract increase in the m2 principal lunar semi diurnal component of the tidal range is an important contributor to the postglacial rise of the high tide level in the gulf of maine and the bay of fundy in addition to relative sea level rise the increase occurred as the shape of this semi enclosed embayment changed with sea level rise and its natural period approached resonance with the m2 tide a three dimensional tide model 3dens predicts the following m2 tidal ranges averaged for the gulf of maine bay of fundy as a percentage of the present range 54 59 at 7000 yrs b p 73 at 5000 yrs b p 78 at 4000 yrs b p 85 at 3000 yrs b p 94 at 2000 yrs b p and 98 at 1000 yrs b p with a predicted sea level rise of 0 15 0 90 m by the year 2100 m2 tidal range may increase 0 3 1 9

upper eocene to middle miocene ostracode faunas and paleo oceanography of the north coastal belt jamaica west indies the ostracode fauna of the montpelier group upper eocene middle miocene exposed in the western part of the north coastal belt of jamaica contains representatives of three paleo environments allochthonous shelf and littoral species characterized by abraded carapaces and eye tubercles and a diverse group of archibenthal slope forms are present throughout species restricted to the world ocean psychrosphere 1000 m notably bradleya dictyon australoecia tipica agrenocythere hazelae and macrocypris spp first occur in sediments of earliest miocene age planktonic foraminiferal zone n4 their presence establishes a minimum age for the entry into the cayman trench of frigid 8 10 c water masses drawn from the atlantic thermohaline stratification upper eocene and oligocene assemblages are dominated by smooth blind genera such as krithe messinella and bythocypris and lived in lower thermospheric conditions 10 c at or near the base of the thermocline 700 900 m during the early miocene downfaulting of the north island slope of jamaica in response to southward tilting of the nicaraguan rise brought the montpelier depositional site into contact with progressively deeper and colder water masses this subsidence culminated in the late early miocene faunas of this age contain large numbers of bradleya dictyon agrenocythere hazelae macrocypris sp 1 bairdia oarion and bairdoppilata cassida they suggest paleodepths of 1500 2000 m and the local presence of a 3 4 water mass tentatively identified as the north atlantic deep water if this interpretation is correct then the maximum sill depth and water mass configuration of the miocene cayman trench have persisted to the present middle miocene assemblages indicate a return to paleodepths of 1000 1500 m heralding the pronounced upper miocene to mid pleistocene tectonism which elevated montpelier strata above sea level an alternative view attributes the miocene ostracode succession in the montpelier to episodes in the development of the atlantic circulation as recognized in the northeast atlantic montpelier deposition took place either on a broad step intervening between the northern edge of the clarendon platform and the abyssal basins of the cayman trench or on a tertiary analog of the existing north island slope these results have emphasized the value of detailed taxonomic and morphologic studies of deep sea ostracodes in geohistorical reconstruction

on the relationship between indian ocean sea surface temperature and the transition from el nino to la nina the relationship between indian ocean sea surface temperature and the transition of el nino events into either la nina or el nino southern oscillation neutral conditions is examined in both observations and the retrospective ensemble hindcasts of the national center for environmental prediction climate forecast system the southern indian ocean is shown to demonstrate a particularly robust and consistent relationship with the evolution of these transitions these associations are described and a physical mechanism involving air sea interaction in the indian and western pacific oceans is proposed observations suggest that easterly surface wind anomalies in the western pacific ocean are associated with the emergence of la nina during boreal summer and fall here it is shown that these winds are significantly correlated to southern indian ocean sea surface temperature in the preceding spring that is characterized by a large scale zonal dipole of cool and warm anomalies in the southwestern and southeastern indian oceans respectively these associations are particularly pronounced for strong el nino conditions during the dissipation of which a pronounced wavetrain like atmospheric pattern accompanies sea surface temperature anomalies in the southern indian ocean together the circulation and sea surface temperature anomalies increase the meridional cross equatorial temperature gradient in the western indian ocean and mute intraseasonal variability while strengthening surface equatorial easterly winds in the indo pacific warm pool collectively these anomalies favor subsequent la nina development on the basis of these observed associations a predictive model that demonstrates skill in anticipating the nature of el nino transitions involving the southern indian ocean asian monsoon and el nino southern oscillation is proposed in the national center for environmental prediction climate forecast system the relationships described above are simulated both consistently and realistically despite model weaknesses further bolstering a key role of southern indian ocean and predictive relationship comparison of fully coupled and sea surface temperature forced simulations suggests a key role for air sea interaction in the observed associations moreover it is demonstrated that coupled simulations of el nino southern oscillation may benefit substantially from improved representation of indian ocean variability and indo pacific interaction

possible link of an exceptionally strong east asian summer monsoon to a la nina like condition during the interglacial mis 13 abstract previous studies from the central and eastern chinese loess plateau clp showed that the s5 1 paleosol which corresponding to marine isotope stage mis 13 was the strongest developed during the last million years suggesting extremely strong east asian summer monsoon easm however evidence shows that regional diversity exists in the relative intensity of the s5 1 soil formation in this study we first verify systematically the s5 1 soil development across the whole clp by using numerous loess records we then examine the spatial variation of the magnetic susceptibility of different loess paleosol sections to identify the spatial change of the easm intensity during mis 13 we also compare the loess records with other monsoon records in china our results show that in central clp s5 1 is indeed the strongest developed as suggested by previous studies whereas in the western clp it is weakly developed and the s4 paleosol developed during mis 11 is the strongest as compared to mis 11 the northern front of the easm during mis 13 didn t penetrate into western clp but was located more northerly and eastward based on sea surface temperature records in the tropical pacific we suggest that the temporal and spatial abnormal variation of the easm during mis 13 could be related to a strong la nina or la nina like climate condition under such condition the western pacific subtropical high wpsh becomes weaker and retreats more northeastward leading to more precipitation in the mid east region of northern china but less rainfall in the western inland

the coads sea level pressure signal a near global el nino composite and time series view 1946 1993 abstract using coads data for the period 1946 1993 the near global sea level pressure slp patterns associated with interannual variability and the climatological seasonal march are discussed a particular focus concerns the patterns associated with the two years before and after the south american sea surface temperatures rise el nino the ten el nino events in this record are composited and the robustness of the features of this composite is tested many features of the composite are quite robust they occur during most el nino events and are infrequent during non el nino periods the most robust feature is an area of negative slp anomaly slpa in the eastern equatorial pacific during year 0 of the composite this feature exceeds significance thresholds during every el nino year and never during non el nino years it correlates better with central pacific sst variability than does the soi a west central north pacific positive slpa occurring late in year 0 and lasting into the spring of year

the influence of atmospheric convection on the interaction between the indian ocean and enso abstractin recent years it has been proposed that a negative positive indian ocean dipole iod in boreal autumn favors an el nino la nina at a lead time of 15 months observational analysis suggests that a negative iod might be accompanied by easterly anomalies over the western pacific such easterlies can enhance the western pacific warm water volume thus favoring el nino development from the following boreal spring onward however a gill model response to a negative iod forcing would lead to nearly zero winds over the western pacific the authors hypothesize that a negative iod or even a cool western indian ocean alone leads to low level air convergence and hence enhanced convectional heating over the maritime continent which in turn amplifies the wind convergence so as to cause easterly winds over the western pacific this hypothesis is tested by coupling an idealized indian ocean model and a convective feedback model over the maritime continent to the zebiak cane model it is found that for a

holocene history of bedford basin nova scotia foraminifera dinoflagellate and pollen records three piston cores from bedford basin a silled coastal inlet provide the basis for a micropaleontological study of postglacial to recent sediments five faunal units four foraminiferal one arcellacean are found in core 79 11 a surface assemblage followed by deep estuarine marginal marine transition and freshwater arcellacean assemblages the other cores contain only expanded marine sequences the top of the transition zone in core 79 11 has a c 14 age of 5830 230 years bp indicating a rise in sea level of at least 20 m the sill depth during the holocene four dinoflagellate assemblage zones are found in core 79 11 the first o centrocarpum b tepikiense is typical of a silled basin with marine water of near normal salinity the second p conicoides cyst c indicates a temperate marine environment with strong fluvial influence marginal marine the third p limbatum is dominated by freshwater cysts and the fourth dinocyst sp a is dominated by subarctic brackish water cysts fo

palynological records of red tide producing species in canada past trends and implications for the future abstract increases in red tides and other harmful algal blooms habs during the past 50 yr on both the atlantic and pacific coasts of canada suggest that global scale factors such as climate change and increased international shipping trade are the driving forces because the historical record is too short to understand the long term dynamics of habs the holocene history of harmful phytoplankton species was examined using ultra high resolution studies annual to decadal scale of dinoflagellate cysts as a proxy for red tide production paleoecological transfer functions were then applied to the cyst assemblage data to determine correlations with changes in sea surface temperature and salinity pacific records were obtained from varved marine sediments in saanich inlet british columbia and in the santa barbara basin off california comparison of annual cyst production and historical plankton data provides cyst theca ratios from which the magnitude of past bloom size can be evaluated the 10 500 yr pacific record clearly shows that the largest blooms correspond to cysts of protoceratium reticulatum and gonyaulax spinifera during the early holocene sporadic blooms of potentially toxic alexandrium spp lingulodinium polyedrum and gymnodinium spp also occurred from ca 7000 to 5000 yr bp and more frequently from ca 2000 to 3000 yr bp individual holocene blooms were up to 10 times larger than in the historical record but they almost always occurred sequentially without overlap of red tide species in pre historical times the bloom cycles started and stopped abruptly in 10 yr or less and they persisted for about 100 1000 yr in contrast the variability and near concurrence of species blooms in the modern past 60 yr record is unmatched in the past and suggests disequilibrium of the natural ecosystem structure atlantic records from la have and emerald basins on the scotian shelf are less precise because bioturbation limits time resolution to ca 25 yr however cyst abundances of cf alexandrium protoceratium reticulatum gonyaulax spinifera and lingulodinium polyedrum were also an order of magnitude larger in the early holocene where they correspond to a summer sea surface warming of 2 5 c lesser peaks also appear during the past 2000 yr where they apparently correspond to a slight increase in winter temperature there is no evidence of much lower salinity that would support stronger stratification the similarity of pre industrial age cyst records of red tide histories in the oceanographically different pacific and atlantic regions of canada indicates that climate change including surface temperature and storminess is the main driving force stimulating blooms this implies that habs will reoccur regardless of efforts to limit spreading however reduced pollution may decrease the hab diversity thereby stabilizing the population dynamics and increasing the predictability of bloom occurrences

arctic oscillation or north atlantic oscillation abstract the definition and interpretation of the arctic oscillation ao are examined and compared with those of the north atlantic oscillation nao it is shown that the nao reflects the correlations between the surface pressure variability at its centers of action whereas this is not the case for the ao the nao pattern can be identified in a physically consistent way in principal component analysis applied to various fields in the euro atlantic region a similar identification is found in the pacific region for the pacific north american pna pattern but no such identification is found here for the ao the ao does reflect the tendency for the zonal winds at 35 and 55 n to anticorrelate in both the atlantic and pacific regions associated with the nao and pna because climatological features in the two ocean basins are at different latitudes the zonally symmetric nature of the ao does not mean that it represents a simple modulation of the circumpolar flow an increase in the ao or nao implies stro

a comparison of observed and theoretical postglacial relative sea level in atlantic canada two extreme models of late wisconsinan ice cover in atlantic canada and the northeastern u s a are shown to produce postglacial relative sea level curves that bracket existing field observations at six sites throughout the region this suggests that the true late wisconsinan ice distribution is probably intermediate to the two contrasting reconstructions proposed both ice models predict the existence of four relative sea level zones an innermost zone closest to the centre of glaciation in which relative sea level falls continuously throughout postglacial time an outermost zone in which it rises continuously and two transitional zones in which it first falls and then rises in varying proportions according to the distance from the ice margin the distinctive forms of the relative sea level curves are probably representative of each of the zones and are unlikely to be significantly perturbed even by large local ice readvances they therefore establish patterns with which future field data are expected to conform the form that the geological record of relative sea level change is likely to take within each zone is discussed and promising settings for the collection of new data are proposed the common practice of separating relative sea level into an isostatic and a eustatic component is analysed and shown to be incorrect as usually applied the practice is also shown to be unnecessary because the models discussed in this paper predict changes in relative sea level that can be compared directly with the observations

impacts of extremely asymmetrical polar ice sheets on the east asian summer monsoon during the mis 13 interglacial abstract marine isotope stage mis 13 500 ka ago was a relatively weak interglacial according to the benthic 18o and antarctic ice core records however proxy records from the northern hemisphere indicate that mis 13 was at least as warm as or even warmer than more recent interglacials with an extremely strong summer monsoon and possible melting of the greenland ice sheet in this study assuming an asymmetric hemispheric climate we investigate the response of the east asian summer monsoon to various greenland and antarctic ice sheet sizes using a set of sensitivity experiments with the hadcm3 model through factor separation analysis results show that with no greenland ice sheet and a large antarctic ice sheet there is an enhancement of summer monsoon precipitation in the east asian monsoon region of up to 7 in agreement with the direction of change from proxy reconstructions for china this enhancement is associated with a stronger land sea thermal contrast more water vapor transport to east asia and a northward shift of the intertropical convergence zone the response to the greenland ice sheet removal is related to thermodynamic and topographical effects that influence the east asian monsoon through an orographically induced wave train the response to the larger antarctic ice sheet involves stronger upwelling of circumpolar deep water in the southern ocean melts the sea ice leading to a warmer sst this warming propagates to the north affecting the east asian summer monsoon

high resolution holocene palynological record from the scotian shelf abstract because of their location at the confluence of polar and subtropical airmasses and near a transition zone between the cold labrador current and the gulf stream the atlantic provinces experience some of the most dynamic climate conditions in canada major climate changes occurred during the holocene as shown by pollen records from lakes but previous paleoceanographic studies based on low resolution proxy data records do not show major changes during the past 8000 years therefore the holocene history of canada s atlantic region was examined using a high resolution palynological record from the scotian shelf la have basin sea surface conditions were reconstructed using proxy data from dinoflagellate cysts and paleobioclimatic transfer functions ocean atmosphere interactions are determined by onshore offshore correlation of marine and pollen records from nova scotia results show a succession of major paleoceanographic events sea surface temperatures sst february and august up to 5 c higher than today s average and slightly higher salinity are reconstructed between 10 5 and 8 5 ka the last pulse of meltwater from the residual ice sheet affected the shelf waters between 8 5 and 6 5 ka by lowering the sst in february and the salinity most previous studies failed to record this event since 6 5 ka august temperature generally remained around today s value while february temperature was generally 2 c above it except for recurring colder and lower salinity intervals these cold intervals have a recurrence of about 1000 years a slight cooling of summer sst is recorded in the last 500 years comparison with climatic reconstructions from nova scotia pollen records shows a difference in timing between ocean and atmosphere the onset of the climatic optimum hypsithermal in nova scotia lags by about 2000 years until 8 ka relative to the ocean but it lasted longer the neoglacial cooling in atlantic canada however started earlier 2 ka than the late holocene ocean cooling la have basin s holocene paleoceanography presents some differences from most other studies from the region 1 the hypsithermal started earlier 2 the last pulse of meltwater is recorded 3 the last 6500 years are punctuated by colder intervals increased productivity and blooms of toxic algae in the early holocene are probably due to a combination of factors increased nutrients and a greater stability of the water column because of meltwaters higher sst and increased upwelling or storm activity

latest pleistocene holocene paleoceanographic trends on the continental margin of eastern canada foraminiferal dinoflagellate and pollen evidence micropaleontological studies were made of cores from four shelf basins on the eastern canadian margin emerald and canso basins on the scotian shelf 44 46 n notre dame channel newfoundland shelf 50 n and cartwright saddle labrador shelf 55 events were correlated using a combination of14c dates and pollen stratigraphies surface and bottom water changes were compared on the basis of dinoflagellates and benthic foraminifera respectively the results indicate significant paleoceanographic shifts along a north south gradient both prior to and during the holocene distinct late pleistocene holocene paleoceanographic events were distinguished in the emerald canso and notre dame basins these events are less obvious in cartwright saddle which is in deeper water and further off shore pleistocene glaciomarine sediments in all basins contain a fauna dominated byelphidium excavatum f clavata dinoflagellates and pollen are rare or absent the widespreadelphidium fauna probably reflects turbid glacial meltwater and or a permanent ice shelf cover from 20 000 10 000 yrs bp the notre dame core also penetrates older sediment with an outer labrador current fauna which may represent a late wisconsinian interstade at about 23 000 yrs bp from 7 000 10 000 yrs bp a cold water fauna occurred which is similar to modern outer labrador current faunas from about 5000 7000 yrs bp a warm interval is indicated by a relatively warm water calcareous benthonic foraminiferal fauna and increased representation of typical gulf stream dinoflagellates the most recent change occurred in the last 2000 years with an abrupt cooling associated with stronger flow of the arctic inner labrador current this cooling event is marked by an increase in arctic dinoflagellates and by an exclusively agglutinated benthonic foraminiferal fauna at two sites canso and notre dame these holocene paleoceanographic changes are not clearly seen in the benthic fauna of the deep northern basin cartwright saddle although dinoflagellate data at this site indicate that surface water changes have occurred that are similar to those found in shallower basins shifts in the zonal position of the gulf stream and changes in the relative mass transports of the west greenland and labrador currents are mechanisms which may account for the paleoceanographic events the glacial interstadial glacial sequence recorded in the notre dame channel in conjunction with other theories on glacial triggering mechanisms provides biostratigraphic evidence which suggests the onset of a glacial stage in the near future

late holocene changes in sea level and environment on eastern cape breton island nova scotia canada the late holocene history of a coastal basin in otter harbour on the great bras d or of cape breton island nova scotia was reconstructed using micro and macrofossils the pollen stratigraphy shows a decrease in oak and pine pollen percentages around 4000 bp while tsuga pollen reaches a maximum over the last 1000 years genera of the mixed hardwood forest have declined while boreal genera have increased suggesting climatic cooling in the region human influence from 400 bp to the present is evidenced by increased pteridophyte spores and pollen of rumex gramineae and ambrosia siliceous microfossils indicate that sea level in the great bras d or rose over the last 4000 years to 1 5 m below present level at 950 bp this rate of sea level rise 16 cm per century falls within the regional range of relative sea level rise in the maritimes of 10 30 cm per century for the last several thousand years however this long term rate in the maritimes is less than the rate of 30 35 cm per century determined from

a geological interpretation of seasat sar imagery of jamaica spaceborne radar imagery obtained from seasat allows an unobscured large scale view of jamaica that can be used for geological interpretation we have mapped lineaments and textures visible in these images and compared them with the known geology of the tertiary karst limestones covering the central and western parts of the island some of these radar textures correlate with lithological units while others follow tectonically controlled zones or structural blocks mapping of radar lineaments has led to the recognition of three new aspects of jamaican faults 1 a major through going ne sw fault system termed here the vere annotto lineament 2 a series of curving scissor faults in the central part of the island and 3 the related observation that the dominant nnw sse tectonic fabric of the central part of the island takes the form of an elongate sigmoid in plan view during most of the neogene jamaica has been part of an active zone of left lateral transform motion between the caribbean and north am

muted climate variations in continental siberia during the mid pleistocene epoch the large difference in carbon and oxygen isotope data from the marine record between marine oxygen isotope stage 12 mis 12 and mis 11 spanning the interval between about 480 and 380 kyr ago has been interpreted as a transition between an extremely cold glacial period and an unusually warm interglacial period with consequences for global ice volume sea level and the global carbon cycle1 2 3 4 the extent of the change is intriguing because orbital forcing is predicted to have been relatively weak at that time5 here we analyse a continuous sediment record from lake baikal siberia which reveals a virtually continuous interglacial diatom assemblage a stable littoral benthic diatom assemblage and lithogenic sediments with interglacial characteristics for the period from mis 15a to mis 11 from about 580 to 380 kyr ago from these data we infer significantly weaker climate contrasts between mis 12 and 11 than during more recent glacial interglacial transitions in the late pleistocene epoch about 130 to 10 kyr ago for the period from mis 15a to mis 11 we also infer an apparent lack of extensive mountain glaciation

a diagnostic and modeling study of the monthly mean wintertime anomalies appearing in a 100 year gcm experiment abstract the nature of simulated atmospheric variability on monthly time scales has been investigated by analyzing the output from a 100 year integration of a spectral gcm with rhomboidal wavenumber 15 truncation in this experiment the seasonally varying climatological sea surface temperature was prescribed throughout the world oceans the principal modes of variability in the model experiment were identified by applying a rotated empirical orthogonal function eof analysis to the northern hemisphere monthly averaged 515 mb geopotential height for the winter season november through march the individual leading spatial modes are similar to the observed north south dipoles over the north atlantic and north pacific as well as wavelike patterns in the pacific north american and northern asian sectors quasigeostrophic geopotential tendencies forced by synoptic scale 2 5 6 day eddy vorticity and heat fluxes were computed for those months when the individual eof modes are particularly active the comp

sediment accumulation in low sedimentation wave dominated glaciated inlets abstract many fjords situated in lowland areas of resistant bedrock are characterized by a comparatively low fluvial sediment flux and are often dominated by wave processes several such fjords in eastern canada are used as examples to develop a generalized sediment distribution model physiographically the fjords can be subdivided into nearshore platforms basin slopes and basin floors where there has been marine transgression the principal sediment source is shoreline erosion of glacial till in areas of crustal rebound late glacial and early holocene muds deposited on highs are eroded as they come within the zone of wave erosion with the falling sea level storm waves resuspend fine grained sediment in water depths of many tens of metres and produce near bottom turbid water zones within basins fine sand and silt settle out rapidly leading to the deposition of graded beds on the basin floors residual sand and gravel accumulate on the near shore platforms while silt and mud prograde over or are advected beyond basin slopes burying older basin fill sediment

large scale dynamics of the meiyu baiu rainband environmental forcing by the westerly jet abstract meiyu baiu is the major rainy season from central china to japan brought by a zonally elongated rainband from june to mid july large scale characteristics and environmental forcing of this important phenomenon are investigated based on a reanalysis dataset the meiyu baiu rainband is accompanied by a trough of sea level pressure horizontal shears and sharp moisture gradients near the surface a westerly jet tilted northward with height and large northeastward moisture transport from the south the analysis here reveals the westerly jet as an important culprit for meiyu baiu along the rainband mean ascending motion corresponds well with a band of warm horizontal temperature advection in the midtroposphere throughout summer this adiabatic induction of upward motion originates from the advection of warm air by the westerlies from the eastern flank of the tibetan plateau the ascending motion both induces convection and is enhanced by the resultant condensational heating the westerly jet anch

dynamical and boundary forcing characteristics of regional components of the asian summer monsoon abstract in this paper the authors present a description of the internal dynamics and boundary forcing characteristics of two major subcomponents of the asian summer monsoon asm that is the south asian monsoon sam and the east southeast asian monsoon eam the description is based on a new monsoon climate paradigm in which the variability of asm is considered as the outcome of the interplay of a fast and an intermediate monsoon subsystem under the influence of slow external forcings two sets of regional monsoon indices derived from dynamically consistent rainfall and wind data are used in this study results show that the internal dynamics of sam are representative of a classical monsoon system in which the anomalous circulation is governed by rossby wave dynamics where anomalous vorticity induced by an off equatorial heat source is balanced by the advection of planetary vorticity on the other hand the internal dynamics of eam are characterized by a hybrid monsoon system featuring m

a new sea level curve from nova scotia evidence for a rapid acceleration of sea level rise in the late mid holocene a new late holocene sea level curve is presented from the atlantic coast of nova scotia contrary to earlier data from the same area this curve starts at 4400 sidereal years before present bp and shows a rapid acceleration between 4400 and 3800 bp which coincides with a similar acceleration already reported from the northumberland strait nova scotia and an oscillation observed in south carolina comparing the two nova scotia curves suggests that the acceleration lasts just over 1000 years and has a vertical extent of 10 m one puzzling fact is that the 10 m vertical extent in nova scotia is 8 m more than the same event measured in south carolina and it cannot be accounted for simply by postglacial isostatic depression since that occurs on a much longer time scale a closer examination of most of the sea level curves from northeastern north america reveals that either the record is missing from this interval or it is inconsistent we suggest that this acceleration is part of a global response that c

postglacial stratigraphy and sea level change in southwestern new brunswick cores from small basins in southwestern new brunswick above present sea level but below the former marine limit were examined for microfaunal changes indicating a transition from marine to freshwater conditions carbon 14 dates of those transition points add to and strengthen a previous sea level curve from the area the oldest date places sea level at about 75 m above present at 16 000 years bp dates from the lower lakes 10 m appear to be anomalously old and it is suggested that after 12 000 years bp erosion became a factor in marine areas this erosion may be related to the overall breakup of ice in the north atlantic and may explain why few dates younger than 12 000 years bp are found in raised marine deposits of new brunswick and maine

el nino impacts on precipitation in the western north pacific east asian sector abstract in this study the western north pacific east asian wnp ea rainfall anomaly induced by the strong el nino in 1982 83 1991 92 and 1997 98 and its association with the mean state are examined over the northern part of the wnp ea region north of 20 n which is dominated by southwest northeast tilting frontal systems positive rainfall anomalies from the fall before the el nino peak phase year 0 to the first wet period after the peak phase year 1 are affected by low and midlevel horizontal moisture convergence anomalies induced by low level anticyclonic circulation anomalies over the wnp region that are associated with el nino over the southern part of the wnp ea region south of 20 n which is dominated by tropical convection positive precipitation anomalies in the first and second wet periods of year 0 and negative precipitation anomalies from the fall of year 0 to the second wet period of year 1 are associated with the variation of the net energy into the atmosphere which is main

pleistocene precipitation balance in the amazon basin recorded in deep sea sediments abstract terrigenous sediments from ceara rise in the western tropical atlantic ocean record pleistocene amazon basin climate variability iron oxides and oxyhydroxides in this region originate mainly from chemically leached amazon lowland soils concentrations of goethite and hematite in the terrigenous fraction consistently peak during transitions from glacial to interglacial periods suggesting an increased proportion of erosive products derived from the amazon lowlands compared to the physically weathered highlands lowland amazon basin precipitation changes monitored by the percentage of goethite relative to total iron oxides lead ice age extremes with maximum aridity during ice growth and maximum precipitation during ice melt rapid climate changes over the amazon basin may reflect shifts in the position of the intertropical convergence zone forced by northern hemisphere insolation at precessional 1 23 000 yr 1 and obliquity 1 41 000 yr 1 frequencies variance in the orbital eccentricity bands 1 100 000 and 1 413 000 yr 1 may be explained by nonlinear amplification of insolation forcing at precessional frequencies the early response of amazon precipitation to insolation ahead of high latitude ice volume 18o at all orbital frequencies suggests that tropical aridity is part of the chain of events leading to ice ages rather than a response to glacier oscillations

origins of biases in cmip5 models simulating northwest pacific summertime atmospheric circulation anomalies during the decaying phase of enso abstractpresent study documents the biases of summertime northwest pacific nwp atmospheric circulation anomalies during the decaying phase of enso and investigates their plausible reasons in 32 coupled model intercomparison project phase 5 models based on an inter model empirical orthogonal function eof analysis of el nino southern oscillation enso related 850hpa wind anomalies the dominant modes of biases are extracted the first eof mode explaining 21 3 of total inter model variance is characterized by a cyclone over the nwp indicating a weaker nwp anticyclone the cyclone appears to be a rossby wave response to unrealistic equatorial western pacific wp sea surface temperature sst anomalies related to excessive equatorial pacific cold tongue in the models on one hand the cold sst biases increase the mean zonal sst gradient which further intensifies warm zonal advection favoring the development and persistence of equatorial wp sst anomalies on the other hand they reduce the anomalou

variations in surface water mass conditions in the norwegian sea evidence from holocene coccolith and dinoflagellate cyst assemblages coccolith and dinoflagellate cyst assemblages have been investigated in five sediment cores from the norwegian sea and fram strait both fossil groups are characterized by similar patterns of composition the assemblages contain high proportions of single species the coccolith flora is of low diversity and consists almost entirely of coccolithus pelagicus and emiliania huxleyi the dinoflagellate cysts are generally dominated by operculodinium centrocarpum and nematosphaeropsis labyrinthus other species especially bitectatodinium tepikiense peridinium faeroense and impagidinium pallidum sometimes contribute considerably to the assemblages based on the abundance of the assemblages and the ratio change between the dominating species it has been possible to establish three intervals of distinct major changes in surface water mass conditions sparse occurrences of coccoliths and dinoflagellate cysts have been observed before 10 000 yrs b p indicating harsh environmental conditions with a distinct influence of meltwater and temporarily very slight inflow of atlantic water the modern surface water circulation pattern was reinitiated during termination ib the assemblages suggest slightly cooler and probably less saline surface water conditions than are present today until 7500 yrs b p solar insolation may have caused a first temperature peak which is responsible for the early holocene productivity maximum a considerable change in the composition of dinocyst and coccolith assemblages occurs corresponding approximately to the onset of the holocene climatic optimum this change was most probably linked to an almost synchronous reorganization of the hydrographic properties in the entire north atlantic realm after the ice sheets had vanished since 6000 yrs b p the norwegian current with its modern oceanographic and ecological properties has been fully established