interannual enso and interdecadal enso like variability in the southern hemisphere tropospheric circulation abstract recent work has identified variability in the pacific ocean sst with a structure qualitatively similar to enso but at lower frequencies than enso zhang et al have documented the atmospheric circulation anomalies in the tropics and northern hemisphere that are associated with decadal enso like variability and compared these anomalies to those associated with the interannual enso cycle here the authors extend the study of zhang et al to the southern hemisphere using the national centers for environmental prediction national center for atmospheric research reanalysis data for 1958 96 consistent with previous studies the southern hemisphere circulation anomalies associated with enso display a teleconnection pattern from the central tropical pacific into the far southeastern pacific ocean comparatively larger circulation anomalies are found in the southern hemisphere associated with the decadal enso like variability though aloft the structure of the anomalies emphasizes the polar vortex wit

antarctic sea ice variability during 1958 1999 a simulation with a global ice ocean model 1 a hindcast simulation is carried out with a global ice ocean model driven by the national centers for environmental prediction ncep national center for atmospheric research ncar reanalysis daily surface air temperatures and winds in order to document the variability of the antarctic sea ice cover during 1958 1999 the model consists of an ocean general circulation model coupled to a thermodynamic dynamic sea ice model with viscous plastic rheology its horizontal resolution is of 1 5degrees x 1 5degrees both the mean state and variability of the antarctic ice pack over the satellite observing period are reasonably well reproduced by the model in particular from november 1978 to september 1998 the model produces an overall increasing trend in ice area defined as the total area of ice covered ocean of 11 400 2300 km 2 yr 1 which falls within the range of current uncertainty the model annual mean area averaged ice thickness displays no significant trend over 1958 1999 in contrast a retreat of the pack is simulated during the second half of the 1970s and the beginning of the 1980s leading to a loss of ice cover of roughly 0 5 x 10 6 km 2 between 1958 1976 and 1982 1999 the marked weakening of the antarctic semiannual oscillation that occurred since the mid to late 1970s seems to be partially responsible for this behavior part of the modeled decline might however be spurious and due to the 1979 change in the observing systems utilized in the ncep ncar reanalysis the simulation also reveals a pronounced decadal variability 8 10 years in both ice area and thickness locally the changes in ice thickness can reach 1 m during a particular cycle

decadal response of global circulation to southern ocean zonal wind stress perturbation abstract a substantial component of north atlantic deep water formation may be driven by westerly wind stress over the southern ocean variability of this wind stress on decadal time scales may lead to circulation variability far from the forcing region the hybrid coordinate ocean model hycom a numerical ocean model is used to investigate the spatial patterns and the time scales associated with such wind variability the evolution of circulation and density anomalies is observed by comparing one 80 yr simulation forced in part by relatively strong southern hemisphere westerlies with a simulation driven by climatological wind the volume transport anomaly takes about 10 yr to reach near full strength in the entire southern hemisphere however in the northern hemisphere it grows for the duration of the run the southern hemisphere indo pacific volume transport anomaly is about twice the strength of that found in the atlantic in the thermocline water exits the southern westerlies belt in a broad f

sea level pressure variability around antarctica since a d 1750 inferred from subantarctic tree ring records a tree ring chronology network recently developed from the subantarctic forests provides an opportunity to study long term climatic variability at higher latitudes in the southern hemisphere fifty long 1911 1985 homogeneous records of monthly mean sea level pressure mslp from the southern latitudes 15 65 s were intercorrelated on a seasonal basis to establish the most consistent long term trans polar teleconnections during this century variations in summer mslp between the south america antarctic peninsula and the new zealand sectors of the southern ocean are significantly correlated in a negative sense r 0 53 p 0 001 climatically sensitive chronologies from tierra del fuego 54 55 and new zealand 39 47 were used to develop verifiable reconstructions of summer november to february mslp for both sectors of the southern ocean these reconstructions which explain between 37 and 43 of the instrumentally recorded pressure variance indicate that inverse trends in mslp from diametrically opposite sides of antarctica have prevailed during the past two centuries however the strength of this relationship varies over time differences in normalized mslp between the new zealand and the south america antarctic peninsula sectors were used to develop a summer trans polar index stpi which represents an index of sea level pressure wavenumber one in the southern hemisphere higher latitudes tree ring based reconstructions of stpi show significant differences in large scale atmospheric circulation between the nineteenth and the twentieth centuries predominantly negative stpi values during the nineteenth century are consistent with more cyclonic activity and lower summer temperatures in the new zealand sector during the 1800s in contrast cyclonic activity appears to have been stronger in the mid twentieth than previously for the south american sector of the southern ocean recent variations in mslp in both regions are seen as part of the long term dynamics of the atmosphere connecting opposite sides of antarctica a detailed analysis of the mslp and stpi reconstructions in the time and frequency domains indicates that much of the interannual variability is principally confined to frequency bands with a period around 3 3 3 6 y cross spectral analysis between the stpi reconstruction and the southern oscillation index suggests that teleconnections between the tropical ocean and extra tropical mslp variations may be influencing climate fluctuations at southern latitudes

copper and noble metal enrichments across the lithosphere asthenosphere boundary of mantle diapirs evidence from the lanzo lherzolite massif

the behaviour of platinum group elements during partial melting crystal fractionation and sulphide segregation an example from the cape smith fold belt northern quebec abstract the behaviour of the pt group elements pge during both normal igneous processes and during the formation of pge deposits is poorly understood this is in part because of the limited data set available for nonmineralized rocks accordingly pge concentrations have been determined in komatiitic basalts associated with ni cu sulphide deposits rich in pge from the proterozoic cape smith fold belt of northern quebec the lavas have been divided into olivine phyric pyroxene phyric and plagioclase phyric on the basis of the phenocrysts present olivine phyric lavas have mg s greater than 0 66 and are thought to be primary partial melts the bulk partition coefficients of the pge during partial melting calculated from the average of olivine phyric basalts are 6 2 0 6 and 0 2 for ir rh pt and pd respectively which indicates a decrease in compatibility of the pge in this order the pyroxene and plagioclase phyric lavas are thought to have formed from the olivine phyric lavas by crystal fractionation of olivine and chromite in the pyroxene phyric lavas and olivine chromite and pyroxene in the plagioclase phyric lavas ir shows a strong positive correlation with mg cr and ni and this is attributed to ir having partitioned into olivine or chromite if olivine chromite and clinopyroxene were the only phases to have crystallized then pd should have behaved as an incompatible element however it does not correlate with the lithophile incompatible elements it does however correlate with rh and pt this is interpreted to suggest that rh pt and pd were controlled by sulphide segregation the removal of a small amount of sulphide along with the olivine and chromite during crystal fractionation could have resulted in the mildly compatible behavior exhibited by rh pt and pd the composition of the sulphides in the sulphide deposits may be modelled by assuming that the silicate magma from which they segregated was similar in composition to the spinifex textured komatiites containing 15 mgo

a zonal wave 3 index for the southern hemisphere 1 in this study 500 hpa geopotential heights from the ncar ncep reanalysis are used to calculate an index describing the spatial and temporal characteristics of zonal wave three zw3 in the high latitude southern hemisphere atmosphere the index spans the period 1958 2001 wavelet analysis of the index shows the strong interannual variation which is characteristic of zw3 and also reveals significant high amplitude decadal scale variation this interannual variation takes the form of marked fluctuation in sign and magnitude of the index it appears to occur when there are rapid changes from strongly meridional to strongly zonal flow or vice versa initial indications are that some of this variability may be associated with enso events

relationships between low frequency variability in the southern hemisphere and sea surface temperature anomalies abstract long term trends and interannual variations of circulation anomalies in the southern hemisphere are examined using the national centers for environmental prediction national center for atmospheric research reanalysis from 1949 to 1998 the changes in planetary circulation regimes are linked to global sea surface temperature anomalies sstas empirical orthogonal function eof analysis was performed on 500 hpa height anomalies the leading mode eof1 shows a strong zonal symmetry with a phase reversal between height anomalies in high and midlatitudes apart from zonal symmetry a zonal wavenumber 3 is evident with three centers located in three southern oceans in the low frequency band with fluctuations longer than 60 months eof1 is associated with the second rotated eof mode of sstas with positive loadings over three southern oceans and negative loadings in the north pacific and the north atlantic the next two modes are the pacific south american psa patterns they depict wave 3 patterns in

acoustic measures of partial gas saturation in tight sandstones the acoustic properties of tight sandstones are very sensitive to partial gas water saturation measurements at 5 khz show that compressional velocity drops sharply with undersaturation extensional and shear losses at 5 khz are large in both fully and partially saturated sands the shear loss qs 1 declines linearly with increasing gas content the extensional loss qe 1 peaks at 0 80 water saturation q 1 is frequency dependent the attenuation is well explained by hydrodynamic relaxation in the grain contacts the measurements indicate velocity dispersions consistent with this mechanism ultrasonic velocities at 500 khz are roughly 10 25 higher than acoustic velocities at 5 khz the ultrasonic velocities exhibit a weak dependence on saturation frame moduli are unrelaxed at these frequencies

atmosphere sea ice low frequency variability with a simple model of the southern hemisphere summary a simple primitive equation general circulation model sgcm is used as a representation of an aquaplanet with no orography to model constant southern hemisphere winter conditions the statistical signie cance of the decadal and quasi biennial variability is erst assessed in a long time sgcm run by means of a frequencydomain statistical decomposition the modelled long wave atmospheric pattern is then associated with the observed southern hemisphere annular mode as suggested by previous studies using the same sgcm a simple linear relationship between the low level wind and the ice velocity is then introduced into the sgcm to investigate the feedbacks between the sea ice cover and the baroclinic waves the zonal mean state reached by the sea ice cover in a long coupled run a few hundred years exhibits characteristics similar to the observations investigation of the low frequency variability in the coupled simulation leads to the following results 1 statistically signie cant variability is observed on interdecadal decadal interannual and quasi biennial time scales 2 interdecadal decadal and quasi biennial signals are associated with the atmospheric annular mode that forces changes in the northward extent of the sea ice cover at all southern ocean longitudes 3 the interannual signal 3 6 year period exhibits spatio temporal patterns and propagation speed similar to the wellknown antarctic circumpolar wave

interannual variations in the southern hemisphere winter circumpolar vortex relationships with the semiannual oscillation abstract several studies of southern hemisphere circulation report changes in the late 1970s and 1980s through the mid and high latitudes that are associated with a weakening in the semiannual oscillation sao of sea level pressure and geopotential height this weakening is thought to reflect changes in the amplitude of zonal wavenumber 3 a deepening of the subantarctic trough intensification of subtropical ridging and an increase in the strength of the westerlies these conclusions suggest an equatorial expansion of the circumpolar vortex in high latitudes and a poleward contraction of the vortex in the midlatitudes the goal of this study is to examine the size and spatial variation of the southern hemisphere circumpolar vortex in winter for evidence of such change the size of the 500 hpa vortex was calculated for the mid and high latitudes in 5 longitude sectors from both the national centers for environmental prediction national center for atmospheric research ncep ncar reanalysis dataset 1

wetting of mantle olivine by sulfide melt implications for re os ratios in mantle peridotite and late stage core formation this study investigates the effects of variations in the relative fugacities of oxygen and sulfur on the wetting of mantle olivine by molten sulfide experiments were performed on mixtures of san carlos olivine and synthetic fes at 1 bar and 1350 c crucibles were fabricated from san carlos olivine and the fugacities of oxygen and sulfur were controlled by mixing co2 co and so2 gases experimental conditions ranged from logfo2 7 9 to 10 3 and from logfs2 1 5 to 2 5 our experimental results demonstrate that at a given temperature and pressure the olivine sulfide melt dihedral angle is controlled by the concentration of o dissolved in an anion rich melt trace amounts of o dissolve in sulfide melt at fo2 conditions near the iron wustite oxygen buffer and the dihedral angle is 90 at fo2 conditions near the fayalite magnetite quartz oxygen buffer the concentration of dissolved o is near 9 wt and the dihedral angle is 52 allowing small amounts of sulfide melt to form an interconnected network in olivine rich rocks and to migrate via porous flow these results indicate that sulfide melt is likely to be mobile at current upper mantle fo2 and fs2 conditions in mantle peridotite the addition or removal of sulfide melt by porous flow will variably fractionate re os u pb and th pb ratios because os and pb are more chalcophile than re u and th the re os ratio of the peridotite is especially sensitive to this process the mobility of sulfide melt at oxidizing conditions implies that the addition of oxidized chondritic material during the later stages of the accretion of the earth may have facilitated the segregation of core forming material by porous flow if temperatures were in excess of the sulfide solidus

a reexamination of the mechanism of the semiannual oscillation in the southern hemisphere the local pressure changes associated with the twice annual contraction intensification and expansion weakening of the circumpolar trough of low pressure around antarctica termed the semiannual oscillation sao was the dominant signal in the annual cycle at mid and high southern latitudes before 1979 the mechanism as shown by van loon 1967 arises from diverent response to the surface heat budget over the polar continent and the midlatitude ocean it has subsequently been shown that in most years since 1979 the sao has weakened considerably evidence is presented here from surface temperature data 500 mb temperatures from a station pair and zonal mean 500 mb temperatures from the ncar ncep reanalyses to show that a warming trend since 1979 has not been evenly distributed through the year at each latitude thus an anomalous change in the temperature gradient between 50 s and 65 s with peaks in roughly may and november has modulated the mechanism that produces the sao with its peaks in march and september consequently the magnitude of the sao has decreased in the more recent period

comments on the ronda peridotite garnet spinel and plagioclase lherzolite facies and the p t trajectories of a high temperature mantle intrusion by m obata j petrology 21 533 72 1980

the influence of atmospheric zonal wave three on antarctic sea ice variability 1 the study examines the relationship between atmospheric zonal wave three and antarctic sea ice variability using an index of zonal wave three and sea ice concentration the net sensible heat flux and the surface air temperature are used to explain the apparent atmosphere sea ice interaction the results show that zonal wave three forces an alternating pattern of equatorward colder and poleward warmer flow which influences the temperature difference between the atmosphere and the ocean the net sensible heat flux is positive ocean heat loss is greater and sea ice growth and expansion is greater in regions of colder air the reverse is true in regions of warmer air this influence of zonal wave three on sea ice concentration appears greatest in the southern fall and early winter it is most clearly seen in the ross and weddell seas outflows and off the amery iceshelf

seasonal zonal asymmetries in the southern annular mode and their impact on regional temperature anomalies abstractthe southern hemisphere annular mode sam is the dominant mode of climate variability in the extratropical southern hemisphere representing variations in pressure and the corresponding changes to the circumpolar zonal flow it is typically thought of as an annular or ringlike structure however on seasonal time scales the zonal symmetry observed in the sam in monthly or annual mean data is much less marked this study further examines the seasonal changes in the sam structure and explores temperature signals across the southern hemisphere that are strongly tied to the asymmetric sam structure the sam asymmetries are most marked in the pacific sector and in austral winter and spring related to changes in the jet entrance and exit regions poleward of 30 s depending on the season the asymmetric sam structure explains over 25 of the variance in the overall sam structure and has strong connections with enso or zonal wavenumber 3 in austral summer and autumn the sam has been becoming more zona

spatial variability of sea level pressure and 500 mb height anomalies over the southern hemisphere abstract the spatial variability of mean sea level pressure slp and 500 mb height anomalies over the southern hemisphere during summer djf and winter jja is determined using eigenvector analysis based on daily synoptic maps from 1972 to 1979 the patterns of spatial distribution of pressure and height anomalies are further verified and examined by means of station data and the eigenvectors are compared between the seasons and to those found for the northern hemisphere the first eigenvector shows that midlatitude anomalies of slp and 500 mb height are of an opposite sign to those found over and around antarctica the pattern is highly barotropic and suggests strengthening and weakening of the zonal wind in alternating latitude belts the 500 mb height differences are calculated for five midlatitude to antarctic station pairs using data from the late 1950 s onward these latitudinal height differences are also used to describe the association between the hemispheric westerlies and the southern oscil

geochemistry of micas from the finero spinel lherzolite italian alps the finero lherzolite is distinct amongst the tectonically emplaced slices of mantle in the ivrea zone italian alps for its abundant coarse phlogopite an average composition sio2 39 9 tio2 0 97 al2o3 16 0 cr2o3 1 16 feo 2 73 mgo 24 5 nio 0 16 bao 0 31 na2o 0 58 k2o 8 7 rb2o 0 056 cl 0 03 f 0 10 wt is similar in fe cr ni ba and f cl to primary textured micas from coarse garnet lherzolite xenoliths from s africa but is higher in ti na rb and al and lower in halogens the distinct values of ti and fe for five specimens of finero peridotites demonstrate local spatial variation the overall ranges of tio2 0 5 1 7 and feo 2 3 3 6 fall within the range for secondary textured micas in peridotite xenoliths from s africa the finero micas are lower in both k rb and k ba than the primary and secondary micas from s africa and their mean values of k rb 110 220 and k ba 15 39 are lower than for almost all bulk rocks but fit well with the ranges of 109 180 and 12 49 for the high k lavas of the roman region

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

decadal variation of the annual cycle in the australian dataset abstract during the 1970s and 1980s elements of the atmospheric circulation over the southern hemisphere changed markedly from their state in the two previous decades the change was evident in the zonal asymmetry especially in the zonal harmonic wave 3 at higher latitudes and in the semiannual wave in pressure and wind the semiannual wave changed in the same sense in all three southern oceans but by the largest amount in the south pacific ocean the second harmonic in a 12 month series by which we describe the semiannual wave dominates the shape of the long term mean annual curve of sea level pressure in mid and high latitudes this harmonic weakened during the period and its midlatitude peak disappeared in the south pacific ocean as part of the low frequency changes during the 18 years from 1972 to 1988 the central pressure in the subantarctic trough fell the trough moved northward and the subtropical ridge moved south the meridional movement of the trough and the ridge and the concurrent

decadal change in the south tropical pacific in a global assimilation analysis using an ocean general circulation model that incorporates data assimilation we show that the northward flowing portion of the subtropical gyre in the south pacific undergoes a well defined decadal variation the maximum variability of ocean temperature is located at around 10 degrees s and is largest in the western side of the basin with a vertical extension of up to 1000 m the anomalous temperature shows a rapid warm to cold transition in the late 1970s with a peak to peak value of more than 1 degrees c coupled with this change is a strengthened circulation in the northern portion of the subtropical gyre further analysis indicates that the decadal change in the south tropical pacific is linked to increased ekman suction induced by enhanced cyclonic wind stress curl in the region

platinum group element distribution in subcontinental mantle evidence from the ivrea zone italy and the betic rifean cordillera spain and morocco the six platinum group elements pge s os ir ru rh pt and pd and au were analyzed by instrumental neutron activation analysis after nickel sulfide fire assay in peridotites and dyke rocks from the orogenic ultramafic massifs of the ivrea zone in the italian western alps baldissero balmuccia finero and the betico rifean cordillera in southern spain and northern morocco ronda beni bousera the peridotites are considered as variably depleted and reenriched low lithosphere whereas the dyke rocks represent polybaric derivatives of basaltic melts pyroxenites and gabbros most coming from the underlying asthenosphere the peridotites have total pge content in the range 8 6 54 7 ppb while mantle normalized patterns generally grade from nearly flat and pge rich in less depleted lherzolites to negative and pge poor in residual harzburgites and dunites dyke rocks have total pge s in the range 5 4 250 ppb and positive mantle normalized patterns negative anomalies of ir pt are frequently ob

a new look for the southern hemisphere jet stream a new jet stream description defined as the geostrophic streamline of maximum average velocity is proposed an objective algorithm for detecting and tracking the jet has been developed tested and applied to the ncep ncar 200 hpa geopotential height in the southern hemisphere for the period 1958 2002 the results show the variability of the double character of the southern hemisphere jet with a marked seasonality during the warm season a single jet can be found around 40 s while autumn and winter are characterized by a clear double jet structure with a strong and dominant subtropical jet located around 30 s and a polar front jet progressively displaced toward southern latitudes and reaching 60 s by the end of the cold season in general a trend toward slower subtropical jets and stronger polar front jets has been detected during the study period the southern annular mode appears as a main modulator of the latitude and strength of the polar front jet influencing to a minor extent its subtropical counterpart the enso cycle strongly modifies the latitude and specially the strength of the subtropical jet affecting its preferred wavenumber as well nevertheless the effect of this oscillation seems fairly restricted in the pacific thus limiting the ability of this jet to drive the el nino teleconnections along the southern hemisphere the consistency of the results when compared with previous jet climatologies suggests that the new approach is a reliable jet tracking method thus providing a new tool to analyze climatic variability at hemispheric scales

multidecadal and interannual changes of stationary rossby waves changes in stationary rossby waves srw are connected to regional climate change and the propagation of these waves has a large influence on the evolution and development of the general circulation since the late 1970s and early 1980s many studies have noted a major shift in the structure of large scale circulation occurring in both hemispheres this paper explores the changes in the srw pattern and their propagation associated with these climate shifts first multidecadal changes in srw activity are examined using ncep ncar reanalysis data for two periods 1948 1978 and 1979 2000 for comparison of these two periods the zonal wind srw kinetic energy pattern along the waveguide and stationary wavenumber ks are analysed the results showed that in the northern hemisphere nh the srw propagation is favoured in the asian jet stream ajs waveguide ks 7 in the period 1979 2000 mainly in the east asia region there are indications that this could be associated with the pacific decadal oscillation warm phase a favoured srw propagation also occurs in the north atlantic subtropical jet nasj waveguide ks 5 region in the latter period and could be linked with positive north atlantic oscillation in the southern hemisphere sh a favoured srw propagation in the polar jet waveguide ks 4 region is observed in the latter period and this could be associated indirectly with tropical sea surface temperature fluctuations the interannual changes in the srw propagation during stronger el nino and la nina events which occurred from 1948 to 2000 are then examined the results showed that during stronger el nino events in nh the srw propagation in the ajs mainly in the east asia region and in the nasj waveguides ks 7 5 respectively is reduced on the other hand in sh the srw propagation in australian and polar waveguides ks 7 4 respectively is favoured copyright 2011 royal meteorological society

a comparison of southern hemisphere circulation statistics based on gfdl and australian analyses abstract two sets of observed atmospheric circulation statistics for the southern hemisphere sh are compared the first set was compiled at the geophysical fluid dynamics laboratory gfdl and consists of global objective analyses of circulation statistics accumulated at individual rawinsonde stations for the period may 1963 april 1973 the second set was obtained from daily hemispheric numerical analyses prepared operationally at the world meteorological centre melbourne australia for the period september 1972 august 1982 this study extends the earlier comparison of circulation statistics from station based and from numerical analysis based methods by lau and oort for the northern hemisphere to the southern hemisphere the domain used for the comparison is a 5 5 latitude longitude grid from 10 to 90 s and seven pressure levels from 1000 to 100 mb the circulation statistics examined include i ten year averages of the monthly mean fields measures of the mean circulation ii ten year averag

experimental study of the solubility of platinum and iridium in basic silicate melts implications for the differentiation of platinum group elements during magmatic processes this study presents evidence for the dissolution of two platinum group elements pge s pt and ir in silicate melts of basic composition in the absence of any associated fluid phase the dissolution of these pge s is attributed to the formation of a complex ion in which the noble metal is uncharged an increase in oxygen fugacity in equilibrium with the melt brings about a considerable decrease in ir solubility in this way we can explain the early enrichment in ir group pge s ipge s ir ru os observed during the crystallization of ultrabasic cumulates by contrast however pt remains soluble in the melt an increase in the fs2 results in a pronounced increase in the solubility of pt in the silicate melt the sulfur saturation which leads to the precipitation of the base metal sulfides bms s also brings about the fixation of pt group pge s ppge s pt pd rh which are dissolved in bms s this accounts for the presence of ppge s in the nickel sulfide horizons of stratiform deposits the occurrence of platiniferous fe crystallizing with chromite in alaskan type complexes at oxygen fugacities of 10 6 bar can be explained by the low activity of fe in fe pt alloys such alloys have been formed in our laboratory at such fo2

recent large scale changes in the extratropical southern hemisphere atmospheric circulation abstract the zonal anomalies in the 500 hpa geopotential height field of the southern hemisphere are examined using the national centers for environmental prediction national center for atmospheric research reanalyses 1958 96 the zonal anomalies were constructed by removing the zonal mean from each grid point and principal components analysis was performed on the resulting spatial anomalies the principal components of the leading eof of the seasons march april may mam to september october november son indicate that a change has occurred in the extratropical large scale atmospheric circulation of the southern hemisphere it is estimated to have begun after 1975 and is limited to the southern late fall winter and early spring the elements of this change are a deeper pacific trough and higher indian ocean ridge at subtropical latitudes at higher latitudes the ridge over the pacific strengthened and shifted east while troughing occurred in the southwest atlantic weddell sea region consistent wi

tree ring based reconstructions of northern patagonia precipitation since ad 1600 long term reconstructions 400 years of seasonal and annual precipitation variations were developed for northern patagonia east of the andes using a new set of 16 tree ring width chronologies from austrocedrus chilensis d don endl reconstructions which capture between 41 and 50 of the precipitation variance show that the twentieth century contains the most extreme long periods of wetness and dryness in the past 400 years since about ad 1910 the reconstructions are also characterized by an increase in interannual variability and one of the highest rates of extreme events within the last 400 years a prominent oscillation on the order of 2 2 1 years in length has been identified in the reconstructions using spectral analysis quasi biennial oscillations have been shown to be very marked in some circulation indices of the southern hemisphere although significant oscillations within the preferred frequency domain of el nino southern oscillation enso are present in the reconstructions no clear trod consistent responses to enso have been observed correlations of reconstructions with mean sea level pressure around south america for the interval ad 1912 1984 reveal the influence of subtropical and high latitude features of the atmospheric circulation on precipitation variations in northern patagonia droughts result from an intensification of the subtropical pacific anticyclone off the chilean coast and the deepness of the circum antarctic trough over the south orkney antarctic peninsula sector mean sea level pressure reconstructions for the south atlantic sector of the southern oceans were used to evaluate the temporal stability of the relationships between northern patagonia precipitation and high latitude climatic variations since ad 1750 the influence of high latitude circulation on precipitation appears to be more significant during the twentieth century which in turn may respond to an intensification of wavenumbers 3 on the mean planetary wave structure over the southern hemisphere recent increase of precipitation variability in northern patagonia may reflect stronger interactions between middle and high latitude atmospheric circulation in the southern hemisphere during the twentieth century

partitioning of palladium iridium platinum and gold between sulfide liquid and basalt melt at 1200 c abstract iron nickel monosulfide and basalt glass containing trace amounts of pge equilibrated at 1200 c and fo 2 10 9 2 close to the wustite magnetite buffer and fs 2 10 0 9 have been analyzed for noble metals by radiochemical and instrumental neutron activation analysis the average contents of pge in coexisting fe ni sulfide and basalt glass respectively are pd 50 ppm and 0 5 ppb ir 50 ppm and 0 5 ppb pt 100 ppm and 10 ppb and au 0 7 ppm and 0 8 ppb the sulfide liquid silicate melt partition coefficients d values for the noble metals are 9 7 10 4 for pd 1 0 7 10 5 for ir 9 6 10 3 for pt and 1 0 9 10 3 for au the noble metals are strongly partitioned into sulfide liquid but the affinity of pd and ir for sulfide liquid is about 50 times greater than that of pt and about 500 times greater than that of au the d values indicate that equilibrium partitioning between immiscible sulfide liquid and basalt magma would result in fractionation of the noble metals which differs significantly from that generally observed in nature