rossby waves mediate impacts of tropical oceans on west antarctic atmospheric circulation in austral winter recent studies link climate changearound antarctica to the sea surface temperature of tropical oceans with teleconnections from the pacific atlantic and indian oceans making different contributions to antarctic climate in this study the impacts of each ocean basin on the wintertime southern hemisphere circulation are identified by comparing simulation results using a comprehensive atmospheric model an idealized dynamical core model and a theoretical rossby wave model the results herein show that tropical atlantic ocean warming indian ocean warming and eastern pacific cooling are all able to deepen the amundsen sea low located adjacent to west antarctica while western pacific warming increases the pressure to the west of the international date line encompassing the ross sea and regions south of the tasman sea in austral winter these tropical ocean basins work together linearly to modulate the atmospheric circulation around west antarctica further analyses indicate that these teleconnections critically depend on stationary rossby wave dynamics and are thus sensitive to the background flow particularly the subtropical midlatitude jet nearthesejets wind shearis amplified which strengthens the generation of rossby waves on the other hand near the edges of the jets the meridional gradient of the absolute vorticity is also enhanced as a consequence of the rossby wave dispersion relationship the jet edge may reflect stationary rossby wave trains serving as a waveguide the simulation results not only identify the relative roles of each of the tropical ocean basins in the tropical antarctica teleconnection but also suggest that a deeper understanding of teleconnections requires a better estimation of the atmospheric jet structures

tonalite granodiorite suites as cotectic systems a review of experimental studies with applications to granitoid petrogenesis abstract granodiorites and tonalites granotonalites in this review paper form large batholiths at active continental margins and collisional orogens although the relation with subduction is obvious the mechanisms of magma generation remain among the most debated topics in earth sciences today the most outstanding features of these calc alkaline batholiths are summarized in this review the problem has been addressed by laboratory experiments along decades dispersed data from experimental studies are compiled here in order to give phase equilibria constraints of general application it is apparent from chemical data that major element compositional trends follow cotectic patterns whose composition is largely dependent on intensive variables the comparison between experiments and batholith chemical trends produces an empirical thermodynamic framework useful to understand in a first approach the origin and evolution of magmas forming granite batholiths a new projection scheme of rock compositions onto the pseudoternary plane defined by the fe mg anorthite orthoclase is given this can be taken as first approach to phase equilibria model of batholiths it has been revealed useful to distinguish processes controlled by increasing melting or decreasing crystallization magma temperature from processes controlled by assimilation or magma mixing the available experimental data although scarce can be used to tentatively depict phase equilibria in the projected pseudoternary f an or diagram although important limitations are imposed by the projective procedure phase equilibria relations in equilibrium with liquids can be drafted in the diagram the stability fields of mineral in areas close to the liquid are defined according to reported phase assemblages in the experimental studies of reference the diagram is robust to identify cotectic and non cotectic relations phase equilibrium constraints and rock textures have revealed that one of the most important parameter controlling phase equilibria in granite magmas is the initial water content typically calc alkaline granitoids from qtz diorite to granotonalite and granite have crystallized from strongly undersaturated water magmas low initial water contents w i in the range 1 2 wt h 2 o may account for residual saturated melt fractions as low as 0 1 0 2 for plutons emplaced at 400 mpa the water content of these residual melt fractions is enough to stabilize hydrous minerals namely hbl and bt as predicted by experiments the initial water content is a primary feature of the magma and it is directly related to the melting reaction and more precisely to the temperature of magma generation the study of compositional trends supports magma fractionation by crystal liquid separation as a relevant role as a first approach the pressure composition relations in the melts can be seen as a response to the composition of the solid saturating assemblage and particularly related to the ratio grt pl in the solid residue

intraseasonal oscillations in the global atmosphere part ii southern hemisphere abstract in part ii of this two part article we complete the systematic examination of oscillatory modes in the global atmosphere by studying 12 years of 500 mb geopotential heights in the southern hemisphere as in part i for the tropics and northern hemisphere extratropics the data were band pass filtered to focus on intraseasonal is phenomena and spatial eofs were obtained the leading principal components were subjected to singular spectrum analysis ssa in order to identify nonlinear is oscillations with high statistical confidence in the southern hemisphere the dominant mode has a period of 23 days with spatial patterns carried by the second and third winter eof of the is band it has a zonal wavenumber four structure the 40 day mode is second and dominated by wavenumbers three and four while a 16 day mode is too weak to separate its spatial behavior from the previous two the is dynamics in the southern hemisphere is more complex and dominated by shorter wavenumbers than the northern

multi pulse cotectic evolution and in situ fractionation of calc alkaline tonalite granodiorite rocks sierra de velasco batholith famatinian belt argentina abstract the study of a magmatic series composed of qtz diorites to granites of the south part of the sierra de velasco batholith famatinian arc in argentina reveals that most rocks follow a coherent cotectic trend which is comparable to a cotectic line of liquids cll traced from experimental liquid compositions of calc alkaline andesitic systems the identification of cotectic relationships is crucial to interpret the meaning of geochemical variation trends in terms of phase equilibria we show the contrast between typical cll trends defined by rocks of the palanche pluton and rocks departing from cll array which are interpreted as resulting from local processes of bulk assimilation of a pelitic host zircon u pb age determinations with shrimp support a coeval zircon crystallization record from of about 480 to 450 ma of samples plotting on the cll the absence of intrusive contacts between these coeval cotectic granites implies that they were fractionated in situ at the level of emplacement other younger pulses 442 5 ma also fall on the cll denoting that uniform processes of melting and fractionation were operative for at least 4 0 ma at the same locus at the active continental margin of gondwana during this protracted magmatic activity sporadic pulses of mafic magma were injected e g at 456 7 ma revealing a complex process of pulse amalgamation in the building up of the batholith these mafic magma pulses may have contributed to basification of the host granitoid by enclave dissolution at the low pressure of emplacement the reported geochemical trends as true cll together with observed textures and crystallization sequences point to a parental intermediate system of andesite composition sio 2 55 wt with a water content of about 2 5 wt h 2 o similar to those formed by sediment basalt subducted melanges a sublithospheric origin for the mafic precursor is proposed in agreement with prediction by recently published thermo mechanical modeling and experimental phase equilibria

petrochemistry and recrystallization history of granulite xenoliths from the pali aike volcanic field chile mafic granulite facies xenoliths found in the pleistocene recent alkali basalts of southern patagonia south america have an unfoliated granoblastic matrix with the mineral assemblage clinopyroxene orthopyroxene plagioclase or olivine or titanomagnetite wherever olivine and plagioclase are in close proximity to one another they are separated by symplectic intergrowths of pyroxenes and spinel two pyroxene geothermometry indicates that the granoblastic matrix phases equilibrated at approximately 900 degrees c the pyroxene spinel symplectites formed at 860 degrees c at which temperature the reaction boundary of olivine plagioclase to produce pyroxenes spinel occurs at 5 7 kbar the xenoliths are interpreted as fragments of a gabbroic pluton which exists at a depth of approximately 20 km in the crust this is consistent with suggestions that mafic igneous rocks comprise a large portion of the lower continental crust capture of the xenoliths in the host basalt must have resulted in extensive heating but the petrologic evidence of this event is restricted to heterogeneously distributed high temperature oxidation effects modified journal abstract

southern hemisphere circulation features associated with el nino southern oscillation events abstract composite seasonal mean and anomaly fields prepared from operational numerical analyses have been used to describe the southern hemisphere sh circulation features associated with el nino southern oscillation enso events the period of analyses available 1972 83 has limited the composites to include only three enso events the reliability and stability of the composites has been tested using multiple permutation methods and by comparison with the results obtained using a longer period 1950 79 of sh rawinsonde station data in the sh winter a weak equivalent barotropic wavetrain pattern of anomalies extends over australia and the south pacific ocean to south america this wavetrain pattern is quite variable in amplitude and location between enso events although it is more stable over the subtropical pacific in the sh summer the circulation anomalies are more zonally symmetric with increased height at low and high latitudes and decreased height in middle latitudes the circulation anoma

early paleozoic accretionary orogenies in nw argentina growth of west gondwana abstract two early paleozoic orogenic cycles in the gondwana margin of nw argentina were driven by subduction and interrupted by collision of continental ribbons of laurentian affinity subduction started at the passive margin of gondwana possibly in response to the end of amalgamation of the supercontinent the passive margin was underlain by a hyper extended continent ocean transition and low angle subduction gave rise to a wide and hot fore arc region during the pampean orogenic cycle the arrival of the first continent ribbon ended the pampean cycle steepened the subduction further heating the fore arc and restarting arc magmatism after a magmatic lull 250 300 km trenchwards initiating the famatinian orogenic cycle this cycle started with a 30 ma long period of extension and marine sedimentation followed by the arrival of the second continent ribbon and inversion the back arc initiating a 20 ma long shortening event culminating with the shutting down of the arc this event gave rise to a 300 km wide low topography hot orogeny thus the many peculiarities of the two paleozoic orogens of nw argentina result from a subduction history that efficiently transferred heat to a 300 400 km wide belt of turbidite dominated sediments that was first part of the pampean fore arc and then part of the famatinian retroarc developed at the extended continental margin of gondwana the two orogenies with continued high heat flux lasted 110 ma giving rise to two calc alkaline arcs separated by a 300 km belt of high t low p migmatites and peraluminous granites formed by anatexis of sediments deposited on the passive margin as well as those deposited in the wide pampean fore arc these turbidite dominated sequences were metamorphosed and melted to form a continental crystalline basement and accreted to the cratonic margin adding 500 km of crystalline rocks to the margin of gondwana at the same time that a similar process was happening in eastern australia along the same continental margin interestingly this wide accretionary orogen has now become the region where the andean system developed a wide orogeny above flat slab subduction

a new method for identifying the pacific south american pattern and its influence on regional climate variability abstractthe pacific south american psa pattern is an important mode of climate variability in the mid to high southern latitudes it is widely recognized as the primary mechanism by which el nino southern oscillation enso influences the southeast pacific and southwest atlantic and in recent years has also been suggested as a mechanism by which longer term tropical sea surface temperature trends can influence the antarctic climate this study presents a novel methodology for objectively identifying the psa pattern by rotating the global coordinate system such that the equator a great circle traces the approximate path of the pattern the identification algorithm utilizes fourier analysis as opposed to a traditional empirical orthogonal function approach the climatology arising from the application of this method to era interim reanalysis data reveals that the psa pattern has a strong influence on temperature and precipitation variability over west antarctica and the antarctic peninsula and on sea i

temperature trends over the past five centuries reconstructed from borehole temperatures for an accurate assessment of the relative roles of natural variability and anthropogenic influence in the earth s climate reconstructions of past temperatures from the pre industrial as well as the industrial period are essential but instrumental records are typically available for no more than the past 150 years therefore reconstructions of pre industrial climate rely principally on traditional climate proxy records each with particular strengths and limitations in representing climatic variability subsurface temperatures comprise an independent archive of past surface temperature changes that is complementary to both the instrumental record and the climate proxies here we use present day temperatures in 616 boreholes from all continents except antarctica to reconstruct century long trends in temperatures over the past 500 years at global hemispheric and continental scales the results confirm the unusual warming of the twentieth century revealed by the instrumental record but suggest that the cumulative change over the past five centuries amounts to about 1 k exceeding recent estimates from conventional climate proxies the strength of temperature reconstructions from boreholes lies in the detection of long term trends complementary to conventional climate proxies but to obtain a complete picture of past warming the differences between the approaches need to be investigated in detail

the antarctic dipole and its predictability this study investigates the nature of interan nualvariability ofantarcticseaiceanditsrelationshipwith the tropical climate we nd that the dominant interan nual variance structure in the sea ice edge and surface air temperature elds is organized as a quasi stationary wave which we call the antarctic dipole adp it is charac terized by an out of phase relationship between the ice and temperature anomalies in the central eastern pacic and atlantic sectors of the antarctic the dipole consists of a strong standing mode and a weaker propagating motion within each basin s ice eld it has the same wavelength as the antarctic circumpolar wave acw and dominates the acw variance the dipole is clearly associated with tropical enso events it can be predicted with moderate skill using linear regression involving surface temperature two to four months ahead the prediction performs better in extreme warm cold years and best in la ni na years

the antarctic circumpolar wave its presence and interdecadal changes during the last 142 years abstractthe southern ocean so is the region of the world ocean bordering on antarctica over which significant exchanges between the atmosphere the ocean and the sea ice take place here the strong and nearly unhindered eastward flow of the antarctic circumpolar current plays an important role in mean global climate as it transmits climate anomalies around the hemisphere features of interannual variability have been observed to propagate eastward around the so with the circumpolar flow in the form of a system of coupled anomalies known as the antarctic circumpolar wave acw in the present study the 142 yr series of the twentieth century reanalysis version 2 dataset 850 hpa geopotential height sea level pressure sea surface temperature surface meridional wind and surface air temperature spanning from 1871 to 2012 is used to investigate the presence and variability of acws this examination shows for the first time the presence of the acw before the mid 1950s and interdecadal changes in i

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

teleconnections between tropical pacific sst anomalies and extratropical southern hemisphere climate abstractteleconnections from tropical pacific sea surface temperature sst anomalies to the high latitude southern hemisphere sh are examined using observations and reanalysis analysis of tropical pacific sst anomalies is conducted separately for the central pacific cp and eastern pacific ep regions during the austral cold season extratropical sh atmospheric rossby wave train patterns are observed in association with both ep and cp sst variability the primary difference between the patterns is the westward displacement of the cp related atmospheric anomalies consistent with the westward elongation of cp related convective sst required for upper level divergence and rossby wave generation consequently cp related patterns of sh sst antarctic sea ice and temperature anomalies also exhibit a westward displacement but otherwise the cold season extratropical sh teleconnections are largely similar during the warm season however extratropical sh teleconnections associated with tropical cp and

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

ground temperature histories for central and eastern canada from geothermal measurements little ice age signature deep borehole temperature profiles have been analyzed to determine ground temperature histories in central and eastern canada clear signs of a cold period between 1500 and 1800 a d corresponding to the little ice age have been found a warming trend after 1800 a d was detected throughout eastern and central canada temperature profiles from western ontario are consistent and were inverted simultaneously to yield a regional ground temperature history the recent warming appears to be correlated with the increase of atmospheric co2 reported for a greenland ice core

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

high sr y and la yb ratios the meaning of the adakitic signature abstract the name of adakite is used to describe a far too large group of rocks whose sole common feature is high sr y and la yb ratios however such a signature can be achieved via different processes melting of a high sr y and la yb source deep melting with abundant residual garnet fractional crystallization or afc or interactions of felsic melts with the mantle causing selective enrichment in lree and sr over hree a database of the compositions of adakitic rocks including high silica and low silica adakites martin h smithies r h rapp r p moyen j f champion d c 2005 an overview of adakite tonalite trondhjemite granodiorite ttg and sanukitoid relationships and some implications for crustal evolution lithos 79 1 2 1 24 continental adakites and archaean adakites was assembled geochemical modeling of the potential processes is used to interpret it and reveals that 1 the classical model of slab melting provides the best explanation for the genesis of high silica adakites 2 low silica adakites are explained by garnet present melting of an adakite metasomatized mantle i e at depths greater than 2 5 gpa 3 continental adakites is a term encompassing a huge range of rocks with a corresponding diversity of petrogenetic processes and most of them are different from both low and high silica adakites 4 archaean adakites show a bimodal composition range with some very high sr y examples similar to part of the ttg suite reflecting deep melting 2 0 gpa of a basaltic source with a relatively high sr y while lower sr y rocks formed by shallower 1 0 gpa melting of similar sources comparison with the archaean ttg suite highlights the heterogeneity of the ttgs whose composition spreads the whole combined range of hsa and archaean adakites pointing to a diversity of sources and processes contributing to the ttg suite

geodynamic regimes of subduction under an active margin effects of rheological weakening by fluids and melts the dynamics of subduction under an active margin are analysed by using a 2d coupled petrological thermomechanical numerical model of an oceanic continental subduction system the model includes spontaneous slab bending dehydration of the subducted crust aqueous fluid transport partial melting of both crustal and mantle rocks as well as melt extraction processes resulting in magmatic arc crust growth based on our models the following five geodynamic regimes of subduction which may potentially form at active margins are identified i stable subduction with no backarc spreading centre and without plumes in the mantle wedge ii retreating subduction with a focused backarc spreading centre and without plumes iii retreating subduction with distributed intra arc extension and trans lithospheric sedimentary plumes iv advancing subduction with underplating laterally extending sub lithospheric plumes and v stable to advancing subduction with stationary laterally limited sub lithospheric plumes transitions between these different regimes are mainly caused by the concurrence of rheological weakening effects of i aqueous fluids percolating from the subducting slab into the mantle wedge and ii melts propagating from the partially molten areas formed in the mantle wedge towards the surface the aqueous fluids mainly affect the forearc region strong fluid related weakening promotes plate decoupling and reduces subduction drag and thus results in stacking of sediments in the accretion prism in contrast reduced weakening by fluids results in strong coupling of the plates and leads to advancing collision like subduction with enhanced subduction erosion thickening of the overriding plate and large sedimentary plumes in the mantle wedge are the consequences on the other hand melts extracted from the hot regions above the slab rheologically weaken the lithosphere below the arc which thus controls overriding plate extension and shortening strong rheological weakening by melts in combination with weak plate coupling trigger retreating subduction with a pronounced backarc spreading centre also weakening of the continental lithosphere by melts extracted from trans lithospheric sedimentary plumes generate a weak channel through which these structures may be emplaced into subarc crust if there is insufficient melt related weakening plumes cannot ascend but extend horizontally and thus underplate the lithosphere

ordovician back arc foreland and ocloyic thrust belt development on the western gondwana margin as a response to precordillera terrane accretion 1 the famatina belt southern central andes records a circa 470 m y shortening episode ocloyic orogeny affecting the peri gondwanan back arc basin in response to the accretion of the precordillera terrane collision created distinct features across and along the margin some of which persisted into the present andean structure from east to west the ocloyic deformation is recorded across the telescoped region of famatina represented by 1 an east vergent fold thrust belt evftb involving a major angular unconformity between early and middle ordovician rocks 2 a highly deformed volcano sedimentary belt and 3 an east vergent ductile shear zone affecting famatinian granites axis attitudes of ordovician refolded anticlines in the evftb show west east tectonic transport in agreement with kinematics of ocloyic high strain belts indicating shortening orthogonal to the present pacific margin eastward displacement of the ordovician volcanic arc at 27 s latitude together with a documented sinistral slip zone across the proto andean margin suggests tectonic indentation

austral spring southern hemisphere circulation and temperature changes and links to the spcz abstractsignificant austral spring trends have previously been observed in west antarctica and antarctic peninsula temperatures and in atmospheric circulation across the southern pacific and atlantic here physical mechanisms for the observed trends are investigated through analysis of monthly circulation and temperatures from the era interim dataset and outgoing longwave radiation olr data the negative pressure trend over the south pacific during spring is strongest in september while the positive pressure trend over the south atlantic is strongest in october pressure trends in november are generally nonsignificant the authors demonstrate that a significant september trend toward increased convection reduced olr in the poleward portion of the south pacific convergence zone spcz is statistically related to rossby wave like circulation changes across the southern oceans the wave response is strongest over the south pacific in september and propagates eastward to the south atlantic in october o

comparing and contrasting the behaviour of arctic and antarctic sea ice over the 35 year period 1979 2013 we examine the evolution of sea ice extent sie over both polar regions for 35 years from november 1978 to december 2013 as well as for the global total ice arctic plus antarctic our examination confirms the ongoing loss of arctic sea ice and we find significant p 0 001 negative trends in all months seasons and in the annual mean the greatest rate of decrease occurs in september and corresponds to a loss of 3 x 10 6 km 2 over 35 years the antarctic shows positive trends in all seasons and for the annual mean p 0 01 with summer attaining a reduced significance p 0 10 based on our longer record which includes the remarkable year 2013 the positive antarctic ice trends can no longer be considered small and the positive trend in the annual mean of 15 29 3 85 x 10 3 km 2 a 1 is almost one third of the magnitude of the arctic annual mean decrease the global annual mean sie series exhibits a trend of 35 29 5 75 x 10 3 km 2 a 1 p

dominant covarying climate signals in the southern ocean and antarctic sea ice influence during the last three decades abstracta composite dataset comprising geopotential height sea surface temperature zonal and meridional surface winds precipitation cloud cover surface air temperature latent plus sensible heat fluxes and sea ice concentration has been investigated with the aim of revealing the dominant time scales of variability from 1982 to 2013 three covarying climate signals associated with variations in the sea ice distribution around antarctica have been detected through the application of the multiple taper method with singular value decomposition mtm svd features of the established patterns of variation over the southern hemisphere extratropics have been identified in each of these three climate signals in the form of coupled or individual oscillations the climate patterns considered here are the southern annular mode sam the pacific south american psa teleconnection the semiannual oscillation sao and the zonal wavenumber 3 zw3 mode it is shown that most of the sea ice temporal variance i

modeling the land surface boundary in climate models as a composite of independent vegetation stands an efficient strategy for modeling the land surface boundary in general circulation models gcms is presented which accounts for the effects of vegetation on surface energy fluxes and allows for an arbitrary number of vegetation types to coexist in a grid square the gcm grid square is depicted as a mosaic of vegetation tiles with each tile consisting of a single vegetation type the energy balance equation for each tile follows closely that of a single vegetation version of the simple biosphere sib model of sellers et al 1986 but is simplified enough to be written in penman monteith form each tile in the square is coupled independently to the gcm atmosphere and tiles affect each other only through the atmosphere this coupling strategy differs conceptually from that of models such as sib that assume a homogeneous mixture of vegetation types within a gcm grid square a quantitative comparison of the two strategies is presented

atmospheric patterns over the antarctic peninsula abstractusing clustering analysis for the sea level pressure field of the era interim reanalysis between 1979 and 2016 five synoptic pressure patterns have been obtained for the drake area and antarctic peninsula ap region 45 75 s 20 120 w and the resulting daily series has been made available to the scientific community the five patterns have been named according to their most important features as follows low over the weddell sea lws low over the amundsen and bellingshausen seas lab low over the drake passage ldp zonal flow over the drake passage zdp and ridge over the antarctic peninsula rap each atmospheric pattern is described after analyzing its development and evolution a frequency analysis shows that the five atmospheric patterns present a similar annual frequency but a large seasonal variability the transitions from one pattern to another tend to follow a cycle in which synoptic atmospheric waves are displaced eastward by a quarter wavelength four of the five atmosphe

surface heat flux histories from geothermal data inferences from inversion past changes in the earth s surface energy balance propagate into the subsurface and appear as perturbations of the subsurface thermal regime a singular value decomposition inversion svd scheme has been used to reconstruct surface heat flux histories shfh from the heat flux anomalies detected in the subsurface synthetic data tests yield results in agreement with analytical expressions inversion of a temperature log from central canada is used to illustrate this procedure results show that reconstruction of shfh is possible with existing data application of this method to the existing geothermal data base should permit a quantification of the energy balance at the earth s surface for the past few centuries

circulation regimes and low frequency oscillations in the south pacific sector abstract the characteristics of subseasonal circulation variability over the south pacific are examined using 10 day lowpass filtered 700 hpa geopotential height ncep ncar reanalysis data the extent to which the variability in each season is characterized by recurrent geographically fixed circulation regimes and or oscillatory behavior is determined two methods of analysis a k means cluster analysis and a cross validated gaussian mixture model both indicate three to four geographically fixed circulation regimes in austral fall winter and to some extent spring the spatial regime structures are found to be quite similar in each season they resemble the so called pacific south american psa patterns discussed in previous studies and often referred to as psa 1 and psa 2 oscillatory behavior is investigated using singular spectrum analysis this identifies a predominantly stationary wave with a period of about 40 days and a spatial structure similar to psa 1 it is most pronounced in winter and spr

timing and rate of granulite facies metamorphism and cooling from multi mineral chronology on migmatitic gneisses sierras de la huerta and valle fertil nw argentina abstract migmatitic paragneisses of the valle fertil la huerta ranges at the western margin of the sierras pampeanas are composed of garnet cordierite plagioclase biotite quartz bearing units that experienced peak metamorphic conditions of ca 800 c at 6 7 kbar based on petrological studies pseudosection modeling and petrographic observations an anticlockwise p t path with a small pressure increment is proposed rare earth element la icp ms patterns acquired from rutile bearing garnets suggest a single stage of garnet growth at high t at pressures above the ilmenite rutile transition u pb dating of zircon rims from the migmatites indicates two distinct metamorphic u pb ages of 525 9 ma and 478 9 ma the older age is suggested to record an amphibolite facies event of the pampean orogeny the younger metamorphic age is contemporary with igneous zircons from metatonalites and pegmatites that yield 478 4 ma we suggest that the prograde high t metamorphic famatinian event is associated with the emplacement of large magmatic bodies in which large scale magmatic activity gave rise to an increased geothermal gradient of about 35 c km sm nd garnet ages of 447 3 ma indicate a time span of around 30 ma for which temperatures above the garnet closure temperature prevailed using u pb sm nd and rb sr isotope systems a cooling rate of 3 to 6 c myr is inferred

el nino flavors and their simulated impacts on atmospheric circulation in the high southern latitudes abstracttwo el nino flavors have been defined based on whether warm sea surface temperature sst anomalies are located in the central or eastern tropical pacific cp or ep this study further characterizes the impacts on atmospheric circulation in the high latitudes of the southern hemisphere associated with these types of el nino events though a series of numerical simulations using the national center for atmospheric research community atmosphere model cam comparing results with the interim ecmwf re analysis era interim cam simulates well the known changes to blocking over australia and a southward shift in the subtropical jet stream across the eastern pacific basin during cp events more importantly for the high southern latitudes cam simulates a westward shift in upper level divergence in the tropical pacific which causes the pacific south american stationary wave pattern to shift toward the west across the entire south pacific these changes to the rossby wave source region impact the south

tropical pacific sst drivers of recent antarctic sea ice trends abstracta strengthening of the amundsen sea low from 1979 to 2013 has been shown to largely explain the observed increase in antarctic sea ice concentration in the eastern ross sea and decrease in the bellingshausen sea here it is shown that while these changes are not generally seen in freely running coupled climate model simulations they are reproduced in simulations of two independent coupled climate models one constrained by observed sea surface temperature anomalies in the tropical pacific and the other by observed surface wind stress in the tropics this analysis confirms previous results and strengthens the conclusion that the phase change in the interdecadal pacific oscillation from positive to negative over 1979 2013 contributed to the observed strengthening of the amundsen sea low and the associated pattern of antarctic sea ice change during this period new support for this conclusion is provided by simulated trends in spatial patterns of sea ice concentrations that are similar to those obse

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

the origins of granulites a metamorphic perspective although many recent reviews emphasize a uniformity in granulite pressure temperature p t conditions and paths granulites in reality preserve a spectrum of important petrogenetic features which indicate diversity in their modes of formation a thorough survey of over 90 granulite terranes or occurrences reveals that over 50 of them record p t conditions outside the 7 5 1 kbar and 800 50 c average granulite regime preferred by many authors in particular an increasing number of very high temperature 900 1000 c terranes are being recognized both on the basis of distinctive mineral assemblages and geothermobarometry petrogenetic grid and geothermobarometric approaches to the determination and interpretation of p t histories are both evaluated within the context of reaction textures to demonstrate that the large range in p t conditions is indeed real and that both near isothermal decompression itd and near isobaric cooling ibc p t paths are important amphibolite granulite transitions promoted by the passage of co 2 rich fluids as observed in southern india and sri lanka are exceptional and not representative of fluid related processes in the majority of terranes it is considered on the contrary that fluid absent conditions are typical of most granulites at or near the time of their recorded thermal maxima itd granulites are interpreted to have formed in crust thickened by collision with magmatic additions being an important extra heat source erosion alone is not however considered to be the dominant post collisional thinning process instead the itd paths are generated during more rapid thinning 1 2 mm yr exposure related to tectonic exhumation during moderate rate or waning extension ibc granulites may have formed in a variety of settings those which show anticlockwise p t histories are interpreted to have formed in and beneath areas of voluminous magmatic accretion with or without additional crustal extension ibc granulites at shallow levels very rapid 5 mm yr extensional thinning subsequent to collision it is suggested that the preservation of ibc paths rather than itd paths in many granulites is primarily related to the rate and timescale of extensional thinning of thickened crust and that hybrid itd to ibc paths should also be observed most ibc granulites and probably many itd granulites have not been exposed at the earth s surface as a result of the tectonic episodes which produced them but have resided in the middle and lower crust for long periods of time 100 2000 ma following these events the eventual exhumation of most granulite terranes only occur through their incorporation in later tectonic and magmatic events unrelated to their formation

tropical connections to climatic change in the extratropical southern hemisphere the role of atlantic sst trends abstractthe austral spring relationships between sea surface temperature sst trends and the southern hemisphere sh extratropical atmospheric circulation are investigated using an atmospheric general circulation model agcm a suite of simulations are analyzed wherein the agcm is forced by underlying sst conditions in which recent trends are constrained to individual ocean basins pacific indian and atlantic allowing the impact of each region to be assessed in isolation when forced with observed global sst the model broadly replicates the spatial pattern of extratropical sh geopotential height trends seen in reanalyses however when forcing by each ocean basin separately similar structures arise only when atlantic sst trends are included it is further shown that teleconnections from the atlantic are associated with perturbations to the zonal walker circulation and the corresponding intensification of the local hadley cell the impact of which results in the development of atmospheric rossby w

identifying rossby wave trains and quantifying their properties a novel method is introduced to automatically identify upper level rossby wave trains and to objectively diagnose their properties based on the envelope of the upper tropospheric meridional wind represented in a hovmoller diagram the algorithm identifies individual rossby wave trains as objects these depend to some extent on user defined parameters the utility of the method is demonstrated in two areas of application first the skill of a particular numerical weather prediction model is analysed for a specific case of a long lived rossby wave train for this purpose a novel diagnostic is designed based on a hovmoller diagram of the rossby wave train objects that contains forecast data with the same lead time throughout the diagram automatically calculated properties of the different forecast rossby wave trains are compared second the climatological behaviour of rossby wave train objects is investigated in long time series from reanalysis data there are preferred regions for the generation and the decay of rossby wave trains and these regions show significant differences for rossby wave trains of different minimum lifetimes in addition there are substantial differences between the seasons

teleconnections between the tropical pacific and the amundsen bellinghausens sea role of the el nino southern oscillation 1 tropical pacific high southern latitude teleconnections are shown to be caused by rossby wave dynamics and are sensitive to the exact pattern of sea surface temperature sst anomalies forcing anomalous ascent further the signal becomes obscured by local natural variability at higher southern latitudes here it is shown that a rossby wave with a source in the tropical pacific can explain the general pattern of teleconnection found during the southern winter upper level divergence associated with deep convection in the tropical pacific plays a major role in the generation of these rossby waves sst anomalies associated with el nino southern oscillation force the tropical deep convection however the relationship between deep convection and sst anomalies is complex and modeling experiments show that in areas of large scale subsidence positive sst anomalies would have to be larger than any observed anomalies 4 c before they have any effect on the vertical motion large variations are observed between the high latitude response to el nino with apparently similar tropical forcings this makes accurate prediction of the high latitude response to tropical change difficult ensemble gcm runs show that variations due to the natural variation of the zonal flow in the southern hemisphere can swamp the signal resulting from changes in the rossby wave source region

the influence of the large scale atmospheric circulation on antarctic sea ice during ice advance and retreat seasons antarctic sea ice a key component of the southern hemisphere climate system is influenced by several large scale modes of the atmospheric circulation antarctic sea ice variability is spatially heterogeneous and links between the atmospheric circulation modes and the sea ice variability are unclear using the observed sea ice concentration data this research isolates distinct regions of sea ice variability around antarctica and determines the advance and retreat periods for each of them the latter are then statistically linked with the observed geopotential height data to determine the atmospheric circulation pattern associated with the variability in the sea ice for each period and region the results clarify which circulation mechanism is of primary importance to sea ice variability during critical periods of the ice lifecycle in the different regions around antarctica and have potential for making estimates of past sea ice extent using the observed geopotential height data

tropical forcing of circumpolar deep water inflow and outlet glacier thinning in the amundsen sea embayment west antarctica outlet glaciers draining the antarctic ice sheet into the amundsen sea embayment ase have accelerated in recent decades most likely as a result of increased melting of their ice shelf termini by warm circumpolar deep water cdw an ocean model forced with climate reanalysis data shows that beginning in the early 1990s an increase in westerly wind stress near the continental shelf edge drove an increase in cdw inflow onto the shelf the change in local wind stress occurred predominantly in fall and early winter associated with anomalous high sea level pressure slp to the north of the ase and an increase in sea surface temperature sst in the central tropical pacific the slp change is associated with geopotential height anomalies in the middle and upper troposphere characteristic of a stationary rossby wave response to tropical sst forcing rather than with changes in the zonally symmetric circulation tropical pacific warming similar to that of the 1990s occurred in the 1940s and thus is a candidate for initiating the current period of ase glacier retreat

influence of the tropics on the southern annular mode abstractperturbations in the southern annular mode sam are shown to be significantly correlated with sst anomalies in the central tropical pacific during austral winter and sst anomalies in the eastern tropical pacific during austral summer the sam signature in the pacific sector resembles a tropically forced rossby wave train the so called pacific south american pattern while the signature in the indian ocean sector is a zonally elongated meridional dipole thus the sam contains strong zonally asymmetric variability and tends to behave differently in the eastern and western hemispheres with internal dynamics prevailing in the indian ocean sector and the forced response to tropical sst anomalies exerting a strong influence in the pacific sector the tropically forced component of the sam in the pacific sector is related to a geographically fixed active rossby wave source to the east of australia within the core of the subtropical jet in addition to the well documented positive trend in summer the

the impacts of el nino on the observed sea ice budget of west antarctica we assess the impact of el nino induced wind changes on seasonal west antarctic sea ice concentrations using reanalysis data and sea ice observations a novel ice budget analysis reveals that in autumn a previously identified east west dipole of sea ice concentration anomalies is formed by dynamic and thermodynamic processes in response to el nino generated circulation changes the dipole features decreased increased concentration in the ross sea amundsen and bellingshausen seas thermodynamic processes and feedback make a substantial contribution to ice anomalies in all seasons the eastward propagation of this anomaly is partly driven by mean sea ice drift rather than anomalous winds our results demonstrate that linkages between sea ice anomalies and atmospheric variability are highly nonlocal in space and time therefore we assert that caution should be applied when interpreting the results of studies that attribute sea ice changes without accounting for such temporally and spatially remote linkages

surface heat flux histories from inversion of geothermal data energy balance at the earth s surface past changes in the earth s surface energy balance propagate into the subsurface and appear as perturbations of the subsurface thermal regime this paper presents a singular value decomposition inversion method used to reconstruct surface heat flux histories shfh from the heat flux anomalies detected in the shallow subsurface synthetic tests were used to assess the robustness of the inversion procedure it was found that data noise can have a significant effect on the stability of the shfh inferred from inversion this translates in shfhs having lower temporal resolution than ground surface temperature histories gsths obtained from the same data but the long term trends are robust results are encouraging for temperature data noise levels typically encountered in field measurements synthetic data tests yield results in agreement with analytical expressions derived from gsths for the same parameterization temperature depth profiles from canada s geothermal database were used to illustrate the inversion procedure individual temperature profile inversions are shown as examples all 112 temperature logs in the database were used to obtain a mean heat flux history for the region results indicate that the ground heat flux has increased an average of 24 mw m 2 over the last 200 years in canada application of this method to the existing global geothermal data base should allow for a quantification of the global energy balance at the earth s surface for the past few centuries and may be useful for land surface models

dynamical causes for incipient magma chambers above slabs using a regional upper mantle model with an unprecedented spatial resolution of 100 m we have investigated at multiple resolutions the character of incipient magma chambers forming under oceanic arcs the magma chambers are formed from wave like structures propagating upward along descending slabs and consist of compositionally buoyant hydrated partially molten subducted crustal and mantle material these wave structures are 300 500 c colder than the mantle wedge and may have an upward velocity of 1 m yr inverted temperature structures and transitory bimodal magmatism are plausible consequences of finger like penetration of relatively cold hydrated material of the incipient magma chambers into the hot mantle wedge apart from forming and periodic feeding of the magma chambers cold waves may also transport upward thousands of cubic kilometers of subducted material and may cause the rapid exhumation of ultrahigh pressure rocks along slabs

simultaneous inversion of borehole temperature data for determination of ground surface temperature history summary recent variations of the ground surface temperature recorded in the earth s subsurface can be inverted from borehole temperature data the resolution of the inversion of borehole temperature logs is poor even when the noise level is low this report concerns the potential improvement in the resolution of ground surface temperature history when temperature logs from several boreholes are inverted simultaneously for an inversion algorithm based on singular value decomposition the singular values obtained for simultaneous inversion of several boreholes do not decrease as rapidly as the singular values for a single borehole with the same value of the cut off or of the damping parameter more eigenvectors remain in the solution and give higher resolution for several boreholes than for one tests conducted with synthetic data for 15 boreholes show that the improvement in resolution is real but not spectacular these tests indicate that borehole temperature logs should have approximately the same sampling interval temperature profiles over different depth ranges can be inverted if the reference heat flows and ground temperatures are included in the parameters determined by the inversion tests also show that no consistent ground temperature history gth is obtained when inverting data from boreholes that have experienced different surfacetemperature variations simultaneous inversion can be applied to 1 obtain a local gth for a single site with several boreholes having identical surface conditions or 2 obtain regional averages with data from different sites that have experienced the same variations in ground temperature temperature profiles measured in four boreholes near belleterre in eastern canada appear to have recorded the same perturbation inversion of the temperature data from individual boreholes yields similar but not identical gths the gth obtained by simultaneous inversion of these four boreholes indicates a cool period with minimum temperatures at ca 1800 ad followed by warming above the reference level it is consistent with other analyses indicating recent warming in eastern canada

metagabbros of the gangdese arc root south tibet implications for the growth of continental crust abstract the gangdese batholith of the southern tibet is regarded as a principal component of the pre himalayan collision andean type continental margin however the gangdese arc root remains poorly understood because most of previous studies concentrated on granitoids from the middle and upper crust of the arc in this paper we report new petrochemical and geochronological characteristics of metagabbros occurred as a part of the late cretaceous lilong batholith in the eastern gangdese arc the gabbros with protolith ages of 82 95 ma underwent slightly late 68 77 ma granulite facies metamorphism and nearly coeval anatexis typical of lower arc crusts the metagabbros and diorites of the lilong batholith show geochemical features of juvenile crust in continental magmatic arcs and an original magmatic differentiation trend with gabbros formed as the cumulates whereas diorites as the crystalline products of evolved magmas the lilong batholith forms an arc crustal section with a possible thickness of 20 30 km and may have an overall andesitic composition providing a support for the andesite model of continental crust growth

definition of antarctic oscillation index following walker s work about his thmous three oscillations published during the 1920 30s many papers were written about atmospheric oscillations a iburth atmospheric oscillation in the middle and high southern latitudes was lbund and nanted the grotarctic oscillation ao a refiers to a large scale alternation of atmospheric mass between the mid latitudes and high latitudes surthce pressure in order to understand the spatial structure of sea level pressure variation in detail empirical orthogonal fitnction analysis is applied an objective index of the antarctic oscillation index aoi is defined as the diffierence of zonal mean sea level pressure between 40os and 65os the aoi has the potential tbr clarifying climate regimes in the southern hemisphere similar to how the na and the npo has been used in the northern hemisphere were there other oscillation s besides nao npo and s especially in the southern hemisphere it had been supposed that there might be other atmospheric oscillation s in the high southern latitudes although as early as in the first quarter of this century walker 1928 had stated that just as in the north atlantic there is a pressure opposition between the azores and iceland there is an opposition between the high pressure belt across chile and the argentine on the one hand and the low pressure area of weddell sea and the bellingshausen sea on the other the scarcity of data in the southern hemisphere hindered the search tbr new oscillation s during the last two decades more comprehensive data over the southern hemisphere became available and more analyses were carried out see kidson 1975 rogers and van loon 1982 mo and l 7 ite 1985 2 4o 1986 connolley 1997 gong and wang 1998 a tburth atmospheric oscillation in the middle and high southern latitudes was tbund and nanted as the antarctic oscillation a wang 1992 gong and wang 1998 the term ao relrs to a large scale alternation of atmospheric mass between the mid latitude sur hce pressure

statistics and dynamics of persistent anomalies abstract persistent anomalies with recurrent spatial patterns play an important role in the atmosphere s low frequency variability we establish a connection between statistical and dynamical methods of description and prediction of persistent anomalies this is done by computing and analyzing the empirical orthogonal functions eofs in a simple deterministic model on the one hand and in southern hemisphere geopotential heights on the other the dynamical model is governed by the fully nonlinear equivalent barotropic vorticity equation on the sphere with simplified forcing dissipation and topography model solutions exhibit persistent anomalies identifiable with blocked zonal and wave train anomalies in northern hemisphere atmospheric data flow structures similar to the patterns above occur as high variance eofs of this nonlinear model the southern hemisphere data we analyze consist in gridded daily maps of 500 mb heights from june 1972 to july 1983 two types of persistent anomalies appear in t

a novel approach to diagnosing southern hemisphere planetary wave activity and its influence on regional climate variability abstractsouthern hemisphere mid to upper tropospheric planetary wave activity is characterized by the superposition of two zonally oriented quasi stationary waveforms zonal wavenumber 1 zw1 and zonal wavenumber 3 zw3 previous studies have tended to consider these waveforms in isolation and with the exception of those studies relating to sea ice little is known about their impact on regional climate variability a novel approach is taken to quantifying the combined influence of zw1 and zw3 using the strength of the hemispheric meridional flow as a proxy for zonal wave activity the methodology adapts the wave envelope construct routinely used in the identification of synoptic scale rossby wave packets and improves on existing approaches by allowing for variations in both wave phase and amplitude while zw1 and zw3 are both prominent features of the climatological circulation the defining feature of highly meridional hemispheric states is an enhancement of the zw3 component composites of the mea

the relationship of pacific deep tropical convection to the winter and springtime extratropical atmospheric circulation of the south pacific in el nino events during some el nino events rossby wave trains rwt are observed to strongly modulate the seasonal atmospheric circulation of the south pacific extratropics in the austral winter and spring here it is shown that seasonally intensified deep tropical convection is confined to the pacific intertropical convergence zone itcz close to the dateline in those events with strong rwt modulation but not in other cases in other cases deep convection either withdraws from the itcz or the itcz strongly interacts with the south pacific convergence zone spcz lying at 5 10degreess in both cases this points to a weakening of the local tropical hadley circulation that may be crucial for rossby wave generation it is also found that the expected rwt response in the high latitudes can fail to occur even when sst in the central tropical pacific are very high

determination of the fluid absent solidus and supersolidus phase relationships of morb derived amphibolites in the range 4 14 kbar experiments on a morb mid ocean ridge basalt derived amphibolite have been conducted in order to determine fluid absent solidus and supersolidus phase relationships the solidus has been determined in the range 4 14 kbar by using the incremental heating technique tested against classical procedures peritectic clinopyroxene was produced below 10 kbar and epidote was the stable peritectic phase at pressures greater than 10 kbar for temperatures near the solidus garnet was the peritectic phase for temperatures above 800 c and pressures of 10 to 14 kbar the shape of the solidus was similar to previous estimations but the temperature interval between the high and low pressure regions was strongly reduced with these new estimations the possibilities for melting of the oceanic crust at p below 10 kbar are increased and consequently the number of tectonic scenarios needed for magma generation from amphibolite sources is enlarged in the absence of free water the solidus in the pressure region above 10 kbar is at higher t than previous estimations

the pacific south american modes and tropical convection during the southern hemisphere winter abstract atmospheric circulation features and convection patterns associated with two leading low frequency modes in the southern hemisphere sh are examined in multiyear global reanalyses produced by ncep ncar and nasa dao the two leading modes referred to as the pacific south american psa modes are represented by the first two eof patterns the two patterns are in quadrature with each other and are dominated by wavenumber 3 in midlatitudes with large amplitudes in the pacific south american sector in the pacific anomalies in the subtropics and in the midlatitudes are opposite in phase taken together the two psa modes represent the intraseasonal oscillation in the sh with periods of roughly 40 days the evolution of the psa modes shows a coherent eastward propagation a composite analysis was conducted to study the evolution of tropical convection and the corresponding circulation changes associated with the psa modes outgoing longwave radiation olr anomaly composites during the mature phase

generation of tonalitic and dioritic magmas by coupled partial melting of gabbroic and metasedimentary rocks within the deep crust of the famatinian magmatic arc argentina the source regions of dioritic and tonalitic magmas have been identified in a deep crustal section of the famatinian arc sierras pampeanas of western argentina the source zones of intermediate igneous rocks are located at the transition between a gabbro dominated mafic unit and a tonalite dominated intermediate unit in the upper levels of the mafic unit mafic magmas intruded into metasedimentary wall rocks crystallized mainly as amphibole gabbronorite and caused the partial melting of the surrounding metasediments in turn the leucogranitic melts sourced from the metasedimentary rocks intruded into the newly crystallized but still hot mafic layers and catalysed the process of partial melting of the gabbroic plutonic rocks the gabbroic rocks became mafic migmatites comprising amphibole rich pyroxene bearing mesosomes and leucotonalitic veins significantly most of the mafic migmatites have isotopic compositions sr sr t 50 7063 and end t 1 4 0 94 to 2 24 similar to those of the gabbroic rocks and distinct from those of their complementary leucotonalitic veins sr sr t 1 4 0 7075 0 7126 and end t 5 2 65 providing evidence for the idea that melting of the mafic rocks was triggered by the intrusion of leucogranitic anatectic melts sr sr t 1 4 0 715 and end t 1 4 6 21 mass balance calculations show that the model reaction plagioclase amphibole leucogranitic melt leucotonalitic melt clinopyroxene orthopyroxene can better explain the partial melting of the gabbroic rocks based on field observations we argue that the coalescence of leucotonalitic veins in the mafic migmatites led to breakdown of the solid matrix to form melt dominated leucotonalitic pools however the leucotonalitic veins that crystallized before leaving behind the mafic migmatitic rock are chemically elemental and isotopic more evolved than the dioritic and tonalitic rocks we envisage that once detached from their source region the leucotonalitic magmas were able to react commingle and mix with entrained fragments of both mafic and metasedimentary rocks this process gave rise to melts that became tonalitic and dioritic magmas this study concludes that the generation of intermediate magmas is a multistage process with three critical steps 1 influx and emplacement of hydrous mafic magmas into a deep crust containing metasedimentary country rocks 2 physically and chemically coupled melting of mafic and metasedimentary rocks leading to the formation of a leucotonalitic vein and dyke system that coalesces to form leucotonalitic or tonalitic magma bodies 3 retrogression of the leucotonalitic magmas by partially assimilating entrained fragments of their mafic and metasedimentary precursors the dimensions of the

el nino modoki and its possible teleconnection 1 using observed data sets mainly for the period 1979 2005 we find that anomalous warming events different from conventional el nino events occur in the central equatorial pacific this unique warming in the central equatorial pacific associated with a horseshoe pattern is flanked by a colder sea surface temperature anomaly ssta on both sides along the equator empirical orthogonal function eof analysis of monthly tropical pacific ssta shows that these events are represented by the second mode that explains 12 of the variance since a majority of such events are not part of el nino evolution the phenomenon is named as el nino modoki pseudo el nino modoki is a classical japanese word which means a similar but different thing the el nino modoki involves ocean atmosphere coupled processes which include a unique tripolar sea level pressure pattern during the evolution analogous to the southern oscillation in the case of el nino hence the total entity is named as el nino southern oscillation enso modoki the enso modoki events significantly influence the temperature and precipitation over many parts of the globe depending on the season the impacts over regions such as the far east including japan new zealand western coast of united states etc are opposite to those of the conventional enso the difference maps between the two periods of 1979 2004 and 1958 1978 for various oceanic atmospheric variables suggest that the recent weakening of equatorial easterlies related to weakened zonal sea surface temperature gradient led to more flattening of the thermocline this appears to be a cause of more frequent and persistent occurrence of the enso modoki event during recent decades

a geothermal climate change observatory first year results from emigrant pass in northwest utah temperature depth profiles measured in boreholes contain a temporal record of past changes in surface ground temperature and provide valuable constraints on climatic variations over the last few centuries however the linkage between ground temperature and meteorological variables including air temperature is imperfectly known to understand that linkage better and to document in detail how the surface ground temperature changes propagate into the subsurface where they are later measured in temperature depth logs in boreholes we have designed and installed a geothermal climate change observatory installed in arid northwest utah our emigrant pass observatory epo consists of an array of thermistor strings in the subsurface and a meteorological station at the borehole collar results from our first complete annual cycle november 1 1993 though october 31 1994 are presented ground and air temperatures generally track each other but with important time varying offsets the mean surface ground temperatures for the period are 11 3 c on the granite outcrop and 9 5 c for the partially shaded regolith site mean air temperature at a 2 m mast height above the ground is 8 8 c the ground air temperature differences are variable on timescales from days to seasons largely governed by level of absorbed solar radiation marginal precipitation 8 6 mm and ephemeral snow cover did not significantly disturb the ground air temperature difference during the year monitored instrumental measurement of air temperature has nonrandom sampling biases that present problems for observing long term changes the calculation of average annual air temperature at epo decreases by 0 34 k as the sampling rate of air temperature is decreased from 60 s to every 12 hours the attenuation and phase lag of thermal waves with depth confirm that heat conduction theory adequately describes the transient temperature field at this site and yield in situ estimates of thermal diffusivity a quantity needed to reconstruct surface ground temperature histories thermal diffusivity for the granite and regolith is 0 88 10 6 m2 s 1 and 0 45 10 6 m2 s 1 respectively energy flux calculations for the emigrant pass observatory site suggest that a geothermal climate change observatory has the capability of detecting a century scale energy perturbation that is one part in a million of the instantaneous flux

indices of el nino evolution abstract to characterize the nature of el nino southern oscillation enso sea surface temperature sst anomalies in different regions of the pacific have been used an optimal characterization of both the distinct character and the evolution of each el nino or la nina event is suggested that requires at least two indices i sst anomalies in the nino 3 4 region referred to as n3 4 and ii a new index termed here the trans nino index tni which is given by the difference in normalized anomalies of sst between nino 1 2 and nino 4 regions the first index can be thought of as the mean sst throughout the equatorial pacific east of the date line and the second index is the gradient in sst across the same region consequently they are approximately orthogonal tni leads n3 4 by 3 to 12 months prior to the climate shift in 1976 77 and also follows n3 4 but with opposite sign 3 to 12 months later however after 1976 77 the sign of the tni leads and lags are reversed

the antarctic circumpolar wave in a coupled ocean atmosphere gcm abstract a phenomenon called the antarctic circumpolar wave acw suggested earlier from fragmentary observational evidence has been simulated realistically in an extended integration of a max planck institute coupled general circulation model the acw both in the observations and in the model constitutes a mode of the coupled ocean atmosphere sea ice system that inhabits the high latitudes of the southern hemisphere it is characterized by anomalies of such climate variables as sea surface temperature sea level pressure meridional wind and sea ice that exhibit intricate and evolving spatial phase relations to each other the simulated acw signal in the ocean propagates eastward over most of the high latitude southern ocean mainly advected along in the antarctic circumpolar current on average it completes a circuit entirely around the southern ocean but is strongly dissipated in the south atlantic and in the southern indian ocean just marginally maintaining statistical significance in these areas

the generation of global rotational flow by steady idealized tropical divergence abstract tropical convective heating is balanced on the large scale by the adiabatic cooling of ascent the horizontal divergence of the wind above this heating may be viewed as driving the upper tropospheric rotational wind field a vorticity equation model is used to diagnose this relationship it is shown that because of the advection of vorticity by the divergent component of the flow the rossby wave source can be very different from the simple fd source often used in particular an equatorial region of divergence situated in easterly winds can lead to a rossby wave source in the subtropical westerlies where it is extremely effective this part of the source can be relatively insensitive to the longitudinal position of the equatorial divergence a divergence field which is asymmetric about the equator can lead to a quite symmetric rossby wave source for a steady frictionless flow the rossby wave source averaged over regions within closed streamfunction or absolute vorticity contours is under cert

fractionation and incipient self granulitization during deep crust emplacement of lower ordovician valle fertil batholith at the gondwana active margin of south america abstract large granite batholiths were emplaced at the gondwana active margin during lower ordovician in south america these have contributed to crustal growth by net addition of silicic rocks to the continental crust new u pb shrimp zircon age determinations together with thermobarometric and geochemical data yield that batholith magma intrusion is the responsible of heating and self granulitization of early gabbro pulses partially molten granulitic gabbros which appear as either early intruded into the metasedimentary host or as large inclusions within the batholith forming qtz diorites contain opx bearing trondhjemitic leucosomes surrounding hbl opx pl mafic mesosomes forming typical agmatitic structures hornblende plagioclase equilibria applied to mineral pairs of granoblastic aggregates in textural equilibrium of metagabbro mesosomes yield temperatures in the range 850 910 c for core to core pairs and in the range 1000 1075 c for rim to rim pairs at pressures of about 0 7 gpa shrimp zircon age revealed that the whole batholith was emplaced over a narrow time interval of 20 ma from 465 to 485 ma with most ages clustered at about 470 ma the age of metagabbros is 473 7 ma for older zircons and 454 4 for younger zircons these ages are almost coincident within error with the age of host migmatites 477 5 ma and those of batholith intrusion of 476 9 ma and 475 3 ma for qtz diorites and 475 5 ma for granites zircon overgrowths of these intrusive rocks yield sages clustered around 450 ma revealing a protracted thermal history more complex than previously believed the geochemical study reveals that qtz diorites tonalites and granodiorites form a continuous trend produced by magmatic fractionation from a parental dioritic magma a weak adakitic tendency with sr y 15 in several samples implies the presence of grt in the source or magma chamber at a minimum pressure of 1 0 gpa higher than the depth of emplacement at 0 7 gpa the high temperature of magma emplacement which induced the incipient self granulitization of early magmatic pulses together with the cotectic like fractionation linking coeval qtz diorites tonalites and granodiorites is compatible with fractionation at the lower crust of a deep generated infracrustal sublithospheric intermediate magma

timing constraints on building an intermediate plutonic arc crustal section u pb zircon geochronology of the sierra valle fertil la huerta famatinian arc argentina 1 the sierra valle fertil range in northwestern argentina exposes a tilted crustal section through the ordovician famatinian arc from 25 km to shallow crustal paleodepths fourteen new u pb zircon crystallization ages of magmatic rocks from sierra valle fertil area show that this section of the arc was built over a short time interval during the ordovician between 485 and 465 ma zircon rim ages demonstrate that high grade metamorphism and migmatization were synchronous with magmatic emplacement inherited ages in some of the plutonic rocks as well as detrital zircons in the metasedimentary framework suggest that the famatinian arc was emplaced into a thick miogeoclinal cover to the thinned margin of the proto south american continent in the ordovician which represents a part of gondwana docking of the precordilleran terrane outboard of proto south america led to the cessation of arc magmatism in the valle fertil area and preservation of the arc in its early stages after 60 myr of subduction during the pampean and famatinian magmatic stages our age data from the sierra valle fertil indicate that wet mafic magmas were emplaced into the section at a rate typical for modern island arcs 30 km3 km 1 myr 1 the production of intermediate to felsic magmas in the upper plate was a result of partial melting of the metasedimentary framework and hybridization with mantle derived melts and resulted in the generation of tonalites granodiorites and granites in the upper crust at a rate of 100 km3 km 1 myr 1 similar to major magmatic flare ups in the mature arcs of north american cordillera the sierra valle fertil arc section is a type example of an immature cordilleran arc before major crustal thickening and crustal overturn takes place in the upper plate the famatinian arc section may also be an equivalent to the crustal architecture of more mature modern island arcs such as parts of the aleutians caribbean and japan

temperature change on the antarctic peninsula linked to the tropical pacific abstractsignificant summer warming over the eastern antarctic peninsula in the last 50 years has been attributed to a strengthening of the circumpolar westerlies widely believed to be anthropogenic in origin on the western side of the peninsula significant warming has occurred mainly in austral winter and has been attributed to the reduction of sea ice the authors show that austral fall is the only season in which spatially extensive warming has occurred on the antarctic peninsula this is accompanied by a significant reduction of sea ice cover off the west coast in winter and spring warming is mainly observed on the west side of the peninsula the most important large scale forcing of the significant widespread warming trend in fall is the extratropical rossby wave train associated with tropical pacific sea surface temperature anomalies winter and spring warming on the western peninsula reflects the persistence of sea ice anomalies arising from the tropically forced atmospheric circulation changes

hot orogens tectonic switching and creation of continental crust many granulite terrains were too hot to have formed during continental collision rather along with many high grade metamorphic terrains that typify continental crust most formed in accretionary orogens during tectonic switching when prolonged lithospheric extension was interrupted by intermittent transient contraction based on modern and ancient examples tectonic switching occurs when slab retreat induces upper plate extension causing arc splitting formation of microcontinent slivers and backarc basins then intermittent arrival of buoyant oceanic plateaus induces transient flat subduction or slab flip and crustal thickening during slab retreat basaltic magmas produced from decompressed asthenosphere advect into the extending orogen causing granulite facies metamorphism and granite generation but subsequent thickening during flat subduction cools the region thickening is focused in the thermally softened backarc region and if sediment filled a hot short lived 10 m y narrow 50 100 km orogenic belt forms such thickening is often misleadingly ascribed to arc or microcontinent collision once slab retreat mode is reestablished lithospheric extension recommences and a new arc backarc system forms generally outboard arrival of another plateau will reverse the procedure and another short lived hot orogen will form within the orogenic system cycles of tectonic switching efficiently produce continental crust

new reconstruction of antarctic near surface temperatures multidecadal trends and reliability of global reanalyses a reconstruction of antarctic monthly mean near surface temperatures spanning 1958 2012 is presented itsprimarygoalistotakeadvantageofarecentlyrevisedkeytemperaturerecordfromwestantarctica byrd to shed further light on multidecadal temperature changes in this region the spatial interpolation relies on a kriging technique aided by spatiotemporal temperature covariances derived from three global reanalyses the european centre for medium range weather forecasts ecmwf interim re analysis erainterim modern era retrospective analysis for research and applications merra and climate forecast system reanalysis cfsr for 1958 2012 the reconstruction yields statistically significant annual warming in the antarctic peninsula and virtually all of west antarctica but no significant temperature change in east antarctica importantly the warming is of comparable magnitude both in central west antarctica and in most of the peninsula rather than concentrated either in one or the other region as previousreconstructions have suggested the transantarctic mountains act for the temperature trends as a clear dividing line between east and west antarctica reflecting the topographic constraint on warm air advection from the amundsen sea basin the reconstruction also serves to highlight spurious changes in the 1979 2009 time series of the three reanalyses that reduces the reliability of their trends illustrating a longstanding issue in high southern latitudes the study concludes with an examination of the influence of the southern annular mode sam on antarctic temperature trends the results herein suggest that the trend of the sam toward its positive phase in austral summer and fall since the 1950s has had a statistically significant cooling effect not only in east antarctica as already well documented and but also only in fall in west antarctica

interhemispheric propagation of stationary rossby waves in a horizontally nonuniform background flow abstractsignificant interhemispheric teleconnections are identified that span the tropical easterlies in the boreal summer 300 hpa streamfunction such as the north africa antarctic naa and the north pacific south america npsa patterns these patterns are not supported by traditional wave theory since stationary waves in a basic state without meridional wind would be trapped in the easterlies to describe the interhemispheric responses more realistically two dimensional spherical rossby wave theory in a horizontally nonuniform basic state is considered conditions sufficient for the existence of one propagating wave are obtained and the meridional group velocity of the wave is shown to have the same direction as the meridional basic wind at the traditional critical latitude it is concluded that stationary waves with a specific wavelength can propagate across the easterlies from south north to north south via southerly northerly flows hence energy transport by stationary waves on a horizont

south pacific circulation changes and their connection to the tropics and regional antarctic warming in austral spring 1979 2012 after 1979 statistically significant warming in antarctica is only observed in austral spring september november son across west antarctica and the antarctic peninsula while previous work has linked this warming to reductions in sea ice cover we note that a substantial 30 60 portion of the warming is related to changes in the son atmospheric circulation in particular western antarctic peninsula warming is consistent with increasing pressure in the south atlantic while western west antarctica warming is tied to a deepening of the amundsen sea low near the eastern ross sea while both of these circulation changes are associated with increased warm northerly flow toward the antarctic continent they are connected with different aspects of tropical variability the increase in pressure in the south atlantic is associated with a trend toward more la nina like conditions in the tropical pacific and an associated rossby wave train in contrast the deepening of the amundsen sea low is more strongly tied to a shift in the pacific decadal oscillation pdo toward its negative phase since the 1990s compared to typical la nina events the recent negative pdo events display a different tropical forcing which drives a rossby wave train that propagates more meridionally across the south pacific culminating in the eastern ross sea rather than in the south atlantic the results suggest multiple independent forcing mechanisms governing the son pressure trends and associated antarctic peninsula and west antarctica warming after 1979 which partially cancel each other out in the amundsen sea and portions of eastern west antarctica

blocking over the south pacific and rossby wave propagation abstract atmospheric blocking events over the south pacific are investigated using a 39 yr record of 500 hpa height fields from the ncep ncar reanalysis dataset the analysis extends earlier work using a 16 yr record and confirms that the occurrence of blocking over the southeast pacific is strongly modulated by the enso cycle during austral spring and summer comparison of results at 500 hpa with the 300 hpa meridional wind component showed that blocking events are associated with large scale wave trains lying across the south pacific from the region of australia to southern south america similar wave trains are evident in both hemispheres in singular value decomposition analyses between 300 hpa meridional wind components and tropical pacific outgoing longwave radiation olr anomalies the hypothesis that the divergence associated with tropical olr anomalies forces an extratropical wave response that results in enhanced blocking over the southeast pacific was tested using a linearized barotropic vorti

paleoproterozoic tectonic history of the cerbat mountains northwestern arizona implications for crustal assembly in the southwestern united states structural mapping metamorphic analysis and u pb geochronology from the cerbat mountains of northwestern arizona place new constraints on the tectonic significance and timing of the boundary between the mojave and yavapai proterozoic crustal provinces in the southwestern united states the cerbat mountains are the easternmost range that exhibits wholly mojave pb isotopic signatures yet their paleoproterozoic structural history is strikingly similar to that of the yavapai province two pervasive deformational events are recognized in the cerbat mountains d1 fabrics are well preserved in the northern cerbat mountains and are characterized by a north northwest striking moderately northeast dipping foliation s1 that is axial planar to macroscopic recumbent folds that we interpret to be west to southwest vergent similar structures have been documented locally in the yavapai province d1 is bracketed between 1740 and 1721 ma in the cerbat mountains on the basis of u pb zircon ages of the big wash granite 1737 4 3 ma and the diana and chloride granites 1719 1 2 and 1721 2 4 ma respectively d2 fabrics dominate the central and southern cerbat mountains and include a subvertical northeast striking foliation that truncates and transposes s1 d2 is bracketed between 1721 and 1682 ma on the basis of u pb ages of the diana and chloride granites and post d2 granite dikes in the eastern cerbat mountains 1682 5 2 4 ma the structural style orientation and timing of d1 and d2 fabrics in the cerbat mountains are identical to those of the yavapai province supracrustal rocks within the cerbat mountains were subjected to two periods of metamorphism that correspond temporally to the two periods of deformation the early phase occurred at 675 725 c and 5 6 kilobars the later phase occurred at 650 700 c and 3 5 4 5 kilobars we propose that the mojave and yavapai provinces were sutured together between ca 1740 and 1720 ma during regional d1 deformation collisional orogenesis in the eastern mojave province may have resulted in the tectonic burial of rocks in the cerbat mountains to depths of 20 km d2 between 1720 and 1682 ma corresponds to the widespread yavapai orogeny and is interpreted to record accretion of the amalgamated mojave yavapai terrane to proterozoic terranes that are now located in colorado

heat flow density values and paleoclimate determined from stochastic inversion of four temperature depth profiles from the superior province of the canadian shield abstract it has long been recognized that terrestrial heat flow density observations from boreholes may be biased due to non steady surface temperature conditions this calls for paleoclimatic corrections which have conventionally been obtained by solving a forward problem based on the equation of heat conduction and models of the surface temperature history and the thermal properties structure while computationally convenient the forward method fails 1 1 to provide a stringent quantitative representation of all available data with confidence limits 2 2 to extract all available information in an optimum manner 3 3 to provide confidence limits on the parameters of interest a stochastic inverse method which overcomes these shortcomings is described the method treats the surface temperature history the thermal conductivity structure and the background heat flow as unknowns which have been constrained a priori with soft bounds the bounds ensure numerical stability and prevent unrealistic solutions when the a priori hypothesis is safe the technique is applied to geothermal data from four 600 m deep boreholes in the superior province of the canadian shield the examples show how it is possible to constrain simultaneously the recent surface temperature history and the steady state background heat flow from shallow geothermal data and furthermore show how uncertainty about the average ground temperature during the wisconsin glaciation may be taken into account

ground temperature histories in eastern and central canada from geothermal measurements evidence of climatic change abstract inverse and direct methods have been used to analyze a large number of borehole temperature logs in order to infer past climatic changes results indicate a warming of 1 2 c in eastern and central canada during the past 150 years a period of cooling between 500 and 200 years before present corresponding to the time of the little ice age has also been identified in the same areas a regional ground temperature history is estimated for eastern and central canada from the simultaneous inversion of several temperature logs the inferred temperature changes appear correlated with the concentration of atmospheric carbon dioxide as reported from a greenland ice core and agree with existing meteorological and dendrochronological records for the area