major features and forcing of high latitude northern hemisphere atmospheric circulation using a 110 000 year long glaciochemical series the greenland ice sheet project 2 glaciochemical series sodium potassium ammonium calcium magnesium sulfate nitrate and chloride provides a unique view of the chemistry of the atmosphere and the history of atmospheric circulation over both the high latitudes and mid low latitudes of the northern hemisphere interpretation of this record reveals a diverse array of environmental signatures that include the documentation of anthropogenically derived pollutants volcanic and biomass burning events storminess over marine surfaces continental aridity and biogenic source strength plus information related to the controls on both high and low frequency climate events of the last 110 000 years climate forcings investigated include changes in insolation of the order of the major orbital cycles that control the long term behavior of atmospheric circulation patterns through changes in ice volume sea level events such as the heinrich events massive discharges of icebergs first identified in the marine record that are found to operate on a 6100 year cycle due largely to the lagged response of ice sheets to changes in insolation and consequent glacier dynamics and rapid climate change events massive reorganizations of atmospheric circulation that are demonstrated to operate on 1450 year cycles changes in insolation and associated positive feedbacks related to ice sheets may assist in explaining favorable time periods and controls on the amplitude of massive rapid climate change events explanation for the exact timing and global synchroneity of these events is however more complicated preliminary evidence points to possible solar variability climate associations for these events and perhaps others that are embedded in our ice core derived atmospheric circulation records

impurity sources of f cl no3 and so4 2 in greenland and antarctic precipitation five polar impurity sources are proposed anthropogenic no3 and so42 in recent greenland but not antarctic snow marine aerosols the dominant cl source volcanic eruptions which produce detectable but variable peaks in so42 f and or cl concentrations biogenic sulfurous gases from soil and coastal waters the dominant source for so42 in nonvolcanic strata an unidentified source of background nitrate which is more active in the northern hemisphere and which displays a summer concentration maximum solar activity and supernova events do not modulate no3 concentrations in greenland snow

glaciochemistry of polar ice cores a review human activities have already modified the chemical composition of the natural atmosphere even in very remote regions of the world the study of chemical parameters stored in solid precipitation and accumulated on polar ice sheets over the last several hundred thousand years provides a unique tool for obtaining information on the composition of the preindustrial atmosphere and its natural variability over the past this paper deals with the chemistry of polar ice focused on the soluble mineral na nh4 k ca mg h f cl no3 so4 and h2o2 and organic methanesulfonate ch3so3 formate hcoo acetate ch3coo and formaldehyde hcho species and their interpretation in terms of past atmospheric composition aerosols and water soluble gaseous species we discuss ice core dating the difficulties connected with trace measurements and the significance of the ionic composition of snow we examine temporal from the last decades back to the last climatic cycle and spatial including examples from coastal as well as central areas of greenland and antarctica variations in the ionic budget of the precipitation and evaluate ice core studies in terms of the chemical composition of our past atmosphere we review 1 how greenland and antarctic ice cores that span the last few centuries have provided information on the impact of human activities and 2 how the chemistry of deep ice cores provides information on various past natural phenomena such as climatic variations glacial interglacial changes el nino volcanic eruptions and large boreal forest fires

imprint of large scale atmospheric transport patterns on sea salt records in northern greenland ice cores the decadal to interannual variability of sea salt aerosol concentrations in northern greenland ice cores is investigated and contrasted to meteorological reanalysis data over the time span 1959 1993 correlation analysis with average data on sea level pressure and geopotential height at the 500 mbar level identifies the eastern and northeastern pacific region as the most important center of action responsible for variations in sea salt aerosol export onto the greenland ice sheet which is related to the pacific north american teleconnection pattern the atlantic region however appears to be of secondary importance only correlation coefficients are highest during the first quarter of the year but also significant for annual pressure data explaining 20 of the sea salt variance in the ice cores furthermore higher storm activity in the pacific center of action as well as in the northern atlantic leads to higher sea salt concentrations in northern greenland explaining about 40 and 17 of the ice core variance a 30 increase during the nineteenth century in a 600 year sea salt record from northeastern greenland may be interpreted at least in part as an enhancement of sea salt export from the pacific region during that time

greenland ice core signal characteristics an expanded view of climate change the last millenium of earth history is of particular interest because it documents the environmental complexities of both natural variability and anthropogenic activity we have analyzed the major ions contained in the greenland ice sheet project 2 gisp 2 ice core from the present to 674 a d to yield an environmental reconstruction for this period that includes a description of nitrogen and sulfur cycling volcanic emissions sea salt and terrestrial influences we have adapted and extended mathematical procedures for extracting sporadic e g volcanic events secular trends and periodicities found in the data sets finally by not assuming that periodic components signals were stationary and by utilizing evolutionary spectral analysis we were able to reveal periodic processes in the climate system which change in frequency turn on and turn off with other climate transitions such as that between the little ice age and the medieval warm period

an ice core proxy for antarctic circumpolar zonal wind intensity using us national centers for environmental prediction us national center for atmospheric research re analysis data we investigate the relationships between crustal ion nssca 2 concentrations from three west antarctic ice cores namely siple dome sd itase00 1 it001 and itase01 5 it015 and primary components of the climate system namely air pressure geopotential height zonal u and meridional v wind strength linear correlation analyses between nssca 2 concentrations and both air pressure and wind fields for the period of overlap between records indicate that the sd nssca 2 variation is positively correlated with spring circumpolar zonal wind while it001 nssca 2 has a positive correlation with circumpolar zonal wind throughout the year r 0 3 p 0 01 intensified southern westerlies circulation is conducive to transport of more crustal aerosols to both sites further correlation analyses between nssca 2 concentrations from sd and it001 and atmospheric circulation suggest that the high inland plateau represented by core it001 is largely influenced by transport from the upper troposphere it015 nssca 2 is negatively correlated with westerly wind in october and november suggesting that stronger westerly circulation may weaken the transport of crustal species to it015 correlations of nssca 2 from the three ice cores with the antarctic oscillation index are consistent with results developed from the wind field investigation in addition calibration between nssca 2 concentration and the multivariate el nino southern oscillation enso index shows that crustal species transport to it001 is enhanced during strong enso events

blocking in the southern hemisphere abstract the focus of this paper is on the frequency and spatial distributions of blocking and persistent anomalies of geopotential height over the southern hemisphere the analysis is based upon daily height fields at 1000 and 500 mb for both summer and winter histogram frequency distributions of height anomalies and maps of the skewness and kurtosis have been computed blocking events are objectively defined by requiring a large positive anomaly to exist for 5 days or more composite flow and anomaly fields for several cases are presented and examined in detail the geographical distribution of the frequency of lame amplitude 150 gpm anomalies at 500 mb that persist for only 1 3 days is very similar to that of the high frequency band 2 8 day period variances that identity the storm tracks in the southern hemisphere the primary location for blocking in the southern hemisphere is in the new zealand sector and blocking occurs through a local enhancement of the climatological split in the mean westerli

evolution of the tropospheric split jet over the south pacific ocean during the 1986 89 enso cycle abstract a case study investigation into the meridional and horizontal circulation over the south pacific ocean is presented for the 1986 89 el nino southern oscillation enso cycle using the european centre for medium range weather forecasts ecmwf analyses annual average fields are created for the years before and after the 1987 minimum warm phase and 1989 maximum cold phase in the southern oscillation index the analyses reveal a shift in the split jet stream over the south pacific sector 180 120 w from a strong subtropical jet stj and weak polar front jet pfj during the warm phase to a weak stj and strong pfj during the cold phase analysis of the momentum budget reveals how the split jet in the upper troposphere over south pacific ocean evolved during the 1986 89 enso cycle during the warm phase the strong stj is associated with advection of the mean flow momentum flux from the australian sector which is approximately balanced by a large negative ageostrophic term the pfj is primaril

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

bipolar changes in atmospheric circulation during the little ice age annually dated ice cores from siple dome west antarctica and central greenland indicate that meridional atmospheric circulation intensity increased in the polar south pacific and north atlantic at the beginning 1400 a d of the most recent holocene rapid climate change event the little ice age lia as deduced from chemical concentrations at these core sites the lia was characterized by substantial meridional circulation strength variability and this variability persists today despite strong evidence for an end to lia cooling thus increased late 20th century storm variability may be in part a result of the continuation of these climatic fluctuations

antarctic sea ice relationships with indices of the atmospheric circulation of the southern hemisphere a link between the antarctic sea ice extent and low frequency atmospheric variations particularly enso has been suggested by recent modeling and empirical studies this question is examined here using a high resolution by week by region data base of antarctic sea ice extent for the 1973 1982 period although of relatively short duration by northern hemisphere standards such a data base offers an opportunity rare in southern hemisphere climate studies the seaice variations are examined in the context of longer term indices of the large scale atmospheric circulation these are a southern oscillation index soi and an index of sea level pressure slp wavenumber one in the southern hemisphere extratropics the indices are updated through 1982 and their associations with regional scale pressure indices in the australia new zealand sector are also examined the 1973 1982 period is anomalous when compared with the period 1951 1972 correlation analysis of the monthly sea ice and circulation index values reveals that much of the apparent link between the ice and the soi suggested in previous studies arises from autocorrelations present in both data sets and the strong annual cycle of sea ice extent removing these effects from the data and re running the correlations reveals that most of the resulting significant associations between the ice and one or other of the circulation indices can probably be explained on the basis of chance in order to reconcile these findings with previous studies that show some strong ice circulation interactions on regional scales only those months in which significant correlations occur between both largescale circulation indices and the sea ice are examined further these occur preferentially in the ross and weddell sectors which constitute the regions contributing most to the variability of antarctic sea ice the analysis suggests that the sea ice extent changes lag the soi by several months but may precede changes in extratropical slp wavenumber one confirmation of these tentative regional ice extent circulation teleconnections necessarily awaits the forward extension of the high resolution sea ice data base beyond the 10 years available here

dust and sea salt variability in central east antarctica dome c over the last 45 kyrs and its implications for southern high latitude climate a detailed record of non sea salt calcium a proxy for dust and sea salt sodium a proxy for sea salt covering the last 45 kyr is presented it shows that in the first part of the transition from the last glacial period to the holocene 18 15 kyr bp the changes in dust flux mainly reflect changes at the dust source namely vegetation cover and local climate the changes in the later part of the transition 12 11 kyr bp are similar in extent to the changes seen in sea salt and most likely reflect a reorganization of the atmospheric circulation during the last glacial period considerable variation of dust but not of sea salt is observed pointing to climatic changes in patagonia the main dust source for dome c a comparison of the glacial records from dome c and taylor dome suggests that similar influences controlled aerosol input at both sites during this period

a 700 year record of atmospheric circulation developed from the law dome ice core east antarctica 1 a 700 year high resolution multivariate ice core record from dome summit south dss 66 46 s 112 48 e 1370 m law dome is used to investigate sea level pressure slp variability in the region of east antarctica empirical orthogonal function eof analysis reveals that the first eof ldeof1 of the combined glaciochemical oxygen isotope ratio and accumulation rate record from dss represents most of the variability in sea salt seen in the record ldeof1 is positively correlated at least 95 confidence level to instrumental june mean slp across most of east antarctica over the last 700 years ldeof1 levels at law dome were the highest during the nineteenth century suggesting an increase in intensification of winter circulation during this period the law dome dss oxygen isotope ratio series also indicates that the nineteenth century had the coldest winters of any century in the record in contrast ldeof1 levels were the lowest at law dome during the eighteenth century suggesting a significant shift in the patterns and or intensity of east antarctic atmospheric circulation between the eighteenth and the nineteenth centuries the ldeof1 sea salt record is characterized by significant decadal scale variability with a strong 25 year periodic structure

coastal zone color scanner pigment concentrations in the southern ocean and relationships to geophysical surface features the spatial and seasonal distributions of phytoplankton pigment concentration over the entire southern ocean have been studied for the first time using the coastal zone color scanner historical data set from october 1978 through june 1986 enhanced pigment concentrations are observed between 35 s and 55 s throughout the year with such enhanced regions being more confined to the south in the austral summer and extending further north in the winter north and south of the polar front phytoplankton blooms 1 mg m3 are not uniformly distributed around the circumpolar region instead blooms appear to be located in regions of ice retreat or high melt areas such as the scotia sea and the ross sea in relatively shallow areas e g the patagonian and the new zealand shelves in some regions of ekman upwelling like the tasman sea and near areas of high eddy kinetic energy such as the agulhas retroflection among all features examined by regression analysis bathymetry appears to be the one most consistently correlated with pigments correlation coefficient being about 0 3 for the entire region the cause of negative correlation with bathymetry is unknown but is consistent with the observed abundance of iron in shallow areas in the antarctic region it is also consistent with resuspension of phytoplankton cells by wind induced mixing especially in shallow waters on the other hand in the deep ocean especially at latitudes 30 in average pigment concentration over the entire region during different seasons indicates possible influence of time dependent parameters

a 1400 year high resolution record of atmospheric circulation over the north atlantic and asia major ion series developed from new subannual scale sampling of an ice core from central greenland are calibrated with instrumental series of atmospheric sea level pressure recording major marine icelandic low and terrestrial siberian high atmospheric circulation systems to provide proxy records of atmospheric circulation over the past 1400 years examination of the proxy records reveals major changes in behaviour of these systems c ad 1400 multidecadal and centennial scale periodic components characterization of mean sea level pressure anomaly fields during the little ice age and the mediaeval warm period the potential role of solar forcing coupled ocean atmosphere associations and a perspective within which the characteristics of instrumental era climate can be assessed

seasonal variations of glaciochemical isotopic and stratigraphic properties in siple dome antarctica surface snow six snow pit records recovered from siple dome west antarctica during 1994 are used to study seasonal variations in chemical major ion and h 202 isotopic deuterium and physical stratigraphic properties during the 1988 94 period comparison of d measurements and satellite derived brightness temperature for the siple dome area suggests that most seasonal sd maxima occur within 4 weeks of each 1 january several other chemical species h 2o2 non sea salt nss so 4 2 methanesulfonic acid and no3 show coeval peaks with sd together providing an accurate method for identifying summer accumulation sea salt derived species generally peak during winter spring but episodic input is noted throughout some years no reliable seasonal signal is identified in species with continental sources nssca 2 nss mg 2 nh 4 or nsscl visible strata such as large depth hoar layers 5 cm are associated with summer accumulation and its metamorphosis but smaller hoar layers and crusts are more difficult to interpret a multi parameter approach is found to provide the most accurate dating of these snow pit records and is used to determine annual layer thicknesses at each site significant spatial accumulation variability exists on an annual basis but mean accumulation in the sampled 10 km 2 grid for the 1988 94 period is fairly uniform

characteristics of southern hemisphere blocking as determined from a time series of observational data a time series of 500 mb geopotential heights has been used to assess characteristics of southern hemisphere blocking a zonal index similar to the index used in an analogous study of northern hemisphere blocking has been used characteristics of blocking situations have been computed with a simple algorithm which has been programmed and are presented as statistics we found one preferred region for blocking action the australian new zealand region two other regions where blocks occur are the atlantic east of south america and the indian ocean south east of south africa the number of days with blocked flow is considerably less over the atlantic and the indian ocean than in the australian new zealand region the annual variation shows two maxima one peak value of 19 in april and one extended maximum of c 20 during june august in the australian new zealand region there is no clear indication of a seasonal variation in the atlantic and the indian ocean region investigation of individual blocking episodes reveals that the majority of the blocks have a mean eastward velocity although the longer they last the more of them are westward moving longlasting episodes are almost exclusively found in the australian region

climate variability in west antarctica derived from annual accumulation rate records from itase firn ice cores thirteen annually resolved accumulation rate records covering the last 200 years from the pine island thwaites and ross drainage systems and the south pole are used to examine climate variability over west antarctica accumulation is controlled spatially by the topography of the ice sheet and temporally by changes in moisture transport and cyclonic activity a comparison of mean accumulation since 1970 at each site to the long term mean indicates an increase in accumulation for sites located in the western sector of the pine island thwaites drainage system accumulation is negatively associated with the southern oscillation index soi for sites near the ice divide and periods of sustained negative soi 1940 42 1991 95 correspond to above mean accumulation at most sites correlations of the accumulation rate records with sea level pressure slp and the soi suggest that accumulation near the ice divide and in the ross drainage system may be associated with the mid latitudes the post 1970 increase in accumulation coupled with strong slp accumulation rate correlations near the coast suggests recent intensification of cyclonic activity in the pine island thwaites drainage system

an antarctic circumpolar wave in surface pressure wind temperature and sea ice extent the southern ocean is the only oceanic domain encircling the globe it contains the strong eastward flow of the antarctic circumpolar current and is the unifying link for exchanges of water masses at all depths between the world s major ocean basins1 as these exchanges are an important control on mean global climate the southern ocean is expected to play an important role in transmitting climate anomalies around the globe interannual variability has been often observed at high southern latitudes and observations of sea ice extent suggest that such features propagate eastwards around the southern ocean2 3 here we use data from a variety of observational techniques to identify significant interannual variations in the atmospheric pressure at sea level wind stress sea surface temperature and sea ice extent over the southern ocean these anomalies propagate eastward with the circumpolar flow with a period of 4 5 years and taking 8 10 years to encircle the pole this system of coupled anomalies which we call the antarctic circumpolar wave is likely to play an important role in climate regulation and dynamics both within and beyond the southern ocean

complexity of holocene climate as reconstructed from a greenland ice core glaciochemical time series developed from summit greenland indicate that the chemical composition of the atmosphere was dynamic during the holocene epoch concentrations of sea salt and terrestrial dusts increased in summit snow during the periods 0 to 600 2400 to 3100 5000 to 6100 7800 to 8800 and more than 11 300 years ago the most recent increase and also the most abrupt coincides with the little ice age these changes imply that either the north polar vortex expanded or the meridional air flow intensified during these periods and that temperatures in the mid to high northern latitudes were potentially the coldest since the younger dryas event

a climatology of anticyclones and blocking for the southern hemisphere abstract an automated procedure for locating and tracking high pressure centers is applied to 10 years of twice daily ecmwf analyses during 1980 89 to survey the behavior of anticyclones in the southern hemisphere anticyclones are concentrated in the 25 45 s band with preferred regions consistent with previous studies except in the new zealand nz south pacific sector where a double occurrence maximum noted in earlier studies was only weakly evident marked interannual variability was found in this region with the poleward branch of maximum occurrence south of 50 s present in only 3 out of 10 years mean central pressure maximized about 10 south of the time averaged ridge with highest values in winter anticyclones poleward of 50 s involve an anomalous breakdown of the westerlies with mean central pressures there 20 30 hpa higher than climatology highs tend to form and intensify in western regions of ocean basins and weaken and dissipate in the east of these oceans regions southeast of australi

the messinian of the nijar basin se spain sedimentation depositional environments and paleogeographic evolution abstract the reconstruction of the depositional events related to the messinian salinity crisis msc of the mediterranean is generally hampered by an incomplete stratal record in the circum mediterranean basins the sediments of the northern part of the nijar basin however provide an excellent and continuous record of late messinian sediments because features of severe erosion are lacking especially the successions of the deeper part of the basin had sufficient accommodation space to warrant ongoing deposition and may thus serve as a testing ground for existing hypotheses regarding the msc conformable contacts with the overlying pliocene and good correlation possibilities with the adjacent astronomically dated messinian of the sorbas basin provide the necessary age constraints the main body of evaporites in the nijar basin yesares formation has been affected by local dissolution and erosion prior to deposition of the latest messinian lago mare facies pelitic float breccias show textures indicating flowage and or mass transport and include slumped and slided stratal packets due to foundering of the mixed evaporitic clastic margin increased runoff of meteoric waters probably played an important role as these packet slides are perfectly sealed by the hyposaline lago mare strata field observations show that marginal sediments commonly classified as the terminal carbonate complex tcc are a lateral equivalent of the basinal yesares evaporites the latest messinian deposits feos formation are characterized by a sedimentary cyclicity related to fluctuating base levels consisting of chalky marly laminitic strata alternating with continental coarser clastic intervals despite considerable w e facies changes and indications for discrete tectonic events a persistent sequential pattern of eight lago mare cycles is present which are interpreted as precession controlled variations in regional climate instead of one major desiccation event in the latest messinian the repeatedly fluctuating water levels of the lago mare episode may have been the cause of the widespread vigorous erosion and canyon cutting in the lower evaporites abrupt non erosional contacts with the normal marine pliocene take place above the continental interval of the last lago mare cycle indicating that flooding took place during a period of lowered water levels the paleogeographic configuration of the nijar sorbas and vera basins has changed considerably during the messinian separation of the formerly interconnected basins is thought to have started in the late yesares times by tectonic uplift of the basement complexes in the latest messinian of the nijar basin two different coarse clastic supply areas can be distinguished which point to the partial emergence of the sierra cabrera and the cabo de gata block and activity of the sierra alhamilla and carboneras faults concerning the overall regional tectonic activity tectonics were probably also instrumental for the restoration of the atlantic gateway in the basal pliocene

sea level pressure variability in the amundsen sea region inferred from a west antarctic glaciochemical record using european center for medium range weather forecasts ecmwf numerical operational analyses sea ice extent records and station pressure data we investigate the influence of sea level pressure variability in the amundsen sea region on a west antarctic siple dome glaciochemical record empirical orthogonal function analysis of the high resolution siple dome multivariate ice core chemical time series record sdeof1 documents lower tropospheric transport of sea salt aerosols to the site during 1985 1994 the sdeof1 record of high low aerosol transport corresponds to anomalously low high sea level pressure slp in the amundsen sea region spatial correlation patterns between ecmwf monthly slp fields and the annual sdeof1 record suggest that a majority of sea salt aerosol is transported to siple dome during spring september october and november analysis of zonal and meridional wind fields supports the slp sdeof1 correlation and suggests the sdeof1 record is sensitive to changes in regional circulation strength no relationship is found between sea ice extent and the sdeof1 record for the period 1973 1994 to investigate the sdeof1 record prior to ecmwf coverage a spring transpolar index stpi is created using normalized slp records from the new zealand and south america antarctic peninsula sectors and is significantly correlated at least 95 c l with the sdeof1 record on an annual r 5 0 32 p 0 001 and interannual 3 years r 5 0 51 p 0 001 basis dominant periodicities 3 3 and 7 1 years in the annual sdeof1 record 1890 1994 a d suggest that a portion of the recorded interannual variability may be related tropical extratropical enso teleconnections changes in the periodic structure of the full 850 1994 a d siple dome record suggests a shift in slp forcing during the little ice age 1400 1900 a d interval