magma mixing in the aleutian arc evidence from cognate inclusions and composite xenoliths abstract the complexity of igneous processes in the aleutian calc alkaline magma series can be inferred from study of xenolithic fragments composite xenoliths and cognate inclusions provide direct evidence for magma magma and wall rock magma mixing processes using distributions of cr in clinopyroxene compositional endmembers involved in mixing are identified within the xenoliths the basaltic mixing endmember is more mafic than calc alkaline lavas in the arc magma mixing and wall rock assimilation within calc alkaline basaltic to andesitic magmas is identified in phenocrystic assemblages as well as in xenoliths and appears to be a widespread phenomenon in aleutian calc alkaline magmas

equilibrium disequilibrium and nonequilibrium landforms in the landscape abstract landscapes are composed of a diversity of landforms that may be characterized as equilibrium disequilibrium or nonequilibrium equilibrium is a constant relation between input and output or form toward which a landform tends or around which it fluctuates in time because of recent environmental changes and long relaxation times however many landforms are not adjusted to present inputs disequilibrium landforms are those that tend toward equilibrium but have not had sufficient time to reach such a condition some landforms called nonequilibrium do not tend toward equilibrium even with relatively long periods of environmental stability but rather undergo frequent and large change in form nonequilibrium may be caused by high magnitude thresholds that cause low frequency weather events to dominate form positive feedbacks and or nonlinearities that result in deterministic chaos landscapes contain mixtures of equilibrium disequilibrium and nonequilibrium landforms and these types of landforms interact in geomorphic systems such as sediment cascades the three types of behavior may coexist in the same landscape and the outputs of such mixed geomorphic systems reflect the combined effects of equilibrium disequilibrium and nonequilibrium subsystems this classification provides a framework for analysis and modeling of complex landscapes

role of north tropical atlantic sst on the enso simulated using cmip3 and cmip5 models in this study role of north tropical atlantic nta sst on the enso variability is examined with cmip3 and cmip5 simulations it is found that most climate models involved in cmip3 and cmip5 successfully simulate the inverse relationship between nta sst during the boreal spring and the enso during the subsequent boreal winter the multi model ensemble mme results show the observed westward propagating signals related to nta sst from the atlantic to the pacific along the off equatorial pacific itcz however different from the observational argument the main mechanism for the nta to induce the enso is likely to be different in the mme while the observational result exhibits the nta induced off equatorial rossby waves play a more dominant role in leading the pacific signal the equatorial wind over the western pacific related to the nta induced kelvin wave is likely to be more crucial to lead the pacific variability in addition the amplitude of nta sst induced enso in the mme tends to be systematically weaker and the preference for the central pacific sst anomaly is also weak these weak signals are distinctly improved in a model that simulates two types of el nino events independently that the strength of the nta effect to the pacific can be affected by the seasonal distribution of climatological precipitation is also discussed additionally the strength of the nta effect tends to be stronger when the model simulates phase locking of enso reasonably

sea surface temperature in the north tropical atlantic as a trigger for el nino southern oscillation events the el nino southern oscillation in the pacific ocean influences temperature in other tropical ocean basins reanalysis data and model simulations suggest that temperature anomalies in the north tropical atlantic may also influence the development of la nina events

characteristics of atmospheric circulation over east asia associated with summer blocking the boreal summer blocking regions were defined using the reanalysis data over the three decades of 1981 2010 and the influence of the blocking on atmospheric circulation in east asia was examined the summer blocking occurred mostly in north europe ural region sea of okhotsk ok and northeastern pacific the summer blocking was the major mode in these four regions according to principal component analysis using 500 hpa geopotential heights among the four blocking regions ok blocking frequencies ok bfs showed negative and positive correlations with summer temperature and precipitation of northeast asia centered around the east sea sea of japan respectively in particular the ok bf had a statistically significant correlation coefficient of 0 54 with summer temperatures in the korean peninsula this indicates that the summer temperature and precipitation in this region were closely related to the ok blocking according to the composite analysis for the years of higher than average bf positive bf years the ok high became stronger and expanded while the north pacific high was weakened over the korean peninsula and japan and an anomalously deep trough was developed in the upper layer 200 hpa as the cool ok high expanded the temperature decreased over northeast asia centered around the east sea sea of japan and the lower level 850 hpa air converged cyclonically resulting in the increased precipitation which induced the divergence in the upper layer and thereby strengthened the jet stream thus the boreal summer ok blocking systematically influencing the area as the most dominant mode

indian ocean capacitor effect on indo western pacific climate during the summer following el nino significant climate anomalies persist through the summer june august after el nino dissipates in spring over the equatorial pacific they include the tropical indian ocean tio sea surface temperature sst warming increased tropical tropospheric temperature an anomalous anticyclone over the subtropical northwest pacific and increased mei yu baiu rainfall over east asia the cause of these lingering el nino effects during summer is investigated using observations and an atmospheric general circulation model gcm the results herein indicate that the tio warming acts like a capacitor anchoring atmospheric anomalies over the indo western pacific oceans it causes tropospheric temperature to increase by a moist adiabatic adjustment in deep convection emanating a baroclinic kelvin wave into the pacific in the northwest pacific this equatorial kelvin wave induces northeasterly surface wind anomalies and the resultant divergence in the subtropics triggers suppressed convection and the anomalous anticyclone the gcm results support this kelvin wave induced ekman divergence mechanism in response to a prescribed sst increase over the tio the model simulates the kelvin wave with low pressure on the equator as well as suppressed convection and the anomalous anticyclone over the subtropical northwest pacific an additional experiment further indicates that the north indian ocean warming is most important for the kelvin wave and northwest pacific anticyclone a result corroborated by observations these results have important implications for the predictability of indo western pacific summer climate the spatial distribution and magnitude of the tio warming rather than simply whether there is an el nino in the preceding winter affect summer climate anomalies over the indo western pacific and east asia

the east atlantic west russia ea wr teleconnection in the north atlantic climate impact and relation to rossby wave propagation large scale winter teleconnection of the east atlantic west russia ea wr over the atlantic and surrounding regions is examined in order to quantify its impacts on temperature and precipitation and identify the physical mechanisms responsible for its existence a rotated empirical orthogonal function analysis of the upper tropospheric monthly height field captures successfully the ea wr pattern and its interannual variation with the north atlantic oscillation nao as the first mode ea wr s climate impact extends from eastern north america to eurasia the positive negative ea wr produces positive negative temperature anomalies over the eastern us western europe and russia east of caspian sea with negative positive anomalies over eastern canada eastern europe including ural mountains northeastern africa and the middle east these anomalies are largely explained by lower tropospheric temperature advections positive negative precipitation anomalies are found over the mid latitude atlantic and central russia around 60 e where lower level cyclonic anticyclonic circulation anomaly is dominant eastern canada and western europe including the mediterranean region are characterized by negative positive precipitation anomalies the ea wr is found to be closely associated with rossby wave propagation wave activity fluxes show that it is strongly tied to large scale stationary waves furthermore a stationary wave model swm forced with vorticity transients in the mid latitude atlantic 40 n or diabatic heat source over the subtropical atlantic near the caribbean sea produces well organized ea wr like wave patterns respectively sensitivity tests with the swm indicate enhancement of ea wr like blocking over west of scandinavia when the mean state is modified to have a positive nao component that enhances upper level westerlies between 40 and 60 n

recent tectonics associated with the subduction collision of the d entrecasteaux zone in the central new hebrides abstract recent data from the new hebrides vanuatu subduction zone have enabled a morphological description and tectonic interpretation to be made of the complex plate contact between the d entrecasteaux zone and the west torres massif on the one hand and the old santo malekula block on the other between latitudes 14 30 and 17 s no trench occurs owing to the presence of the old rigid santo malekula block at the edge of the overriding plate the outer limit of plate contact describes a tortuous line westward of the projected line of the adjacent trenches this may be explained by local collision of the north d entrecasteaux ridge and the south d entrecasteaux chain with the west flank of santo this collision is compensated for by lateral plastic flow of the inner wall downward into the small basins which separate the d entrecasteaux zone ridges a process which may be explained by plastic plane strain theory the westward jump of the plate contact zone here may result from pieces of the north d entrecasteaux ridge being cut off and incorporated in the frontal arc a review of the geological evidence and the shallow seismicity of the central new hebrides shows that radiant horizontal stresses resulting from this collision have generated a specific compressive stress regime which influences the whole width of the arc the resultant deformation shows a close resemblance to a theoretical strain field produced by the indentation of a long narrow plastic body cf the arc by a rigid flat die cf the d entrecasteaux zone thus the central new hebrides block is both elastically bent under vertical stresses and plastically deformed and pushed eastwards by horizontal stresses recent uplift of the eastern chain can be explained by this model in contrast at the rear of both the northern and southern sections of the arc the tectonics are mainly controlled by a tensional stress regime the strong plate interaction due to the subduction of the d entrecasteaux zone is thought to be responsible for the compressive stress regime across the central new hebrides the same cause can be invoked to account for the tensional stress regime observed in north and south new hebrides rear arc regions

interannual and interdecadal variations of the east asian summer monsoon and tropical pacific ssts part i roles of the subtropical ridge the interannual relationship between the east asian summer monsoon and the tropical pacific ssts is studied using rainfall data in the yangtze river valley and the ncep reanalysis for 1951 96 the datasets are also partitioned into two periods 1951 77 and 1978 96 to study the interdecadal variations of this relationship a wet summer monsoon is preceded by a warm equatorial eastern pacific in the previous winter and followed by a cold equatorial eastern pacific in the following fall this relationship involves primarily the rainfall during the pre mei yu mei yu season may june but not the post mei yu season july august in a wet monsoon year the western north pacific subtropical ridge is stronger as a result of positive feedback that involves the anomalous hadley and walker circulations an atmospheric rossby wave response to the western pacific complementary cooling and the evaporation wind feedback this ridge extends farther to the west from the previous winter to the following fall resulting in an 850 hpa anomalous anticyclone near the southeast coast of china this anticyclone 1 blocks the pre mei yu and mei yu fronts from moving southward thereby extending the time that the fronts produce stationary rainfall 2 enhances the pressure gradient to its northwest resulting in a more intense front and 3 induces anomalous warming of the south china sea surface through increased downwelling which leads to a higher moisture supply to the rain area a positive feedback from the strong monsoon rainfall also appears to occur leading to an intensified anomalous anticyclone near the monsoon region this sst subtropical ridge monsoon rainfall relationship is observed in both the interannual timescale within each interdecadal period and in the interdecadal scale the sst anomalies sstas change sign in northern spring and resemble a tropospheric biennial oscillation tbo pattern during the first interdecadal period 1951 77 in the second interdecadal period 1978 96 the sign change occurs in northern fall and the tbo pattern in the equatorial eastern pacific sst is replaced by longer timescales this interdecadal variation of the monsoon sst relationship results from the interdecadal change of the background state of the coupled ocean atmosphere system this difference gives rise to the different degrees of importance of the feedback from the anomalous circulations near the monsoon region to the equatorial eastern pacific in a wet monsoon year the anomalous easterly winds south of the monsoon enhanced anomalous anticyclone start to propagate slowly eastward toward the eastern pacific in may and june apparently as a result of an atmosphere ocean coupled wave motion these anomalous easterlies carry with them a cooling effect on the ocean surface in 1951 77 this effect is insignificant as the equatorial eastern pacific sstas already change from warm to cold in northern spring probably as a result of negative feedback processes discussed in enso mechanisms in 1978 96 the equatorial eastern pacific has a warmer mean sst a stronger positive feedback between ssta and the walker circulation during a warm phase tends to keep the ssta warm until northern fall when the eastward propagating anomalous easterly winds reach the eastern pacific and reverse the ssta

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

the october 1980 earthquake sequence near the new hebrides four large earthquakes occurred in 1980 in a seismic gap near the loyalty islands in the new hebrides at 3 25 ut on october 24 an event with m s 6 7 initiated the sequence three events m s 6 7 7 2 and 6 5 followed on the next day we investigated this sequence by using the seismicity first motion and waveform data and long period surface waves the first motion data constrain one of each pair of nodal planes with this constraint inversion of rayleigh and love wave spectra at 256 seconds determines the other nodal plane the mechanisms of all four events are almost pure thrust on a plane dipping about 20 degrees east and striking parallel to the local strike of the new hebrides trench the first day aftershocks indicate an initial rupture zone of about 2 000 km which is consistent with the estimated seismic moment of 3 10 27 dyne cm during the next two days the aftershock activity expanded to an area of 10 000 to 20 000 km in the directions both along and perpendicular to the trench within 5 hours after the third and largest event the initial rupture zone had become mostly quiescent modeling of waveforms suggests a body wave moment of between 0 5 and 1 0 10 27 dyne cm and a source process time of 11 seconds this pattern suggests that the initial rupture zone represents a zone of increased strength i e an asperity and the stress change due to failure of this asperity subsequently migrated outward during the two year period before the main event seismicity in the initial rupture zone was very low except near the point where the first mainshock initiated a very tight clustering of activity occurred there this pattern indicates gradual stress concentration near the asperity which finally failed during the mainshock sequence

petrology of tholeiitic lavas from tanna island new hebrides importance of cumulative processes in island arc magmatism tanna one of the southernmost islands of the new hebrides volcanic arc is made of late pliocene to recent island arc tholeiitic basalts and andesites with sio2 contents ranging from 45 to 57 these lavas are highly porphyritic 30 50 in volume phenocrysts of plagioclase are the most abundant together with olivine and clinopyroxene the groundmass contain plagioclase augite olivine magnetite and glass pigeonite tridymite sanidine and rarely biotite may also occur the olivines and clinopyroxenes show an iron enrichment from the cores of phenocrysts to their rims and the groundmass crystals but their compositional variations are not correlated with the mg fe ratio of bulk host rocks the most fe rich compositions being found in mg rich lavas plagioclase compositions range from an95 to an60 in the basalts and an60 to an50 in the andesites but within each group they are not correlated with sio2 or na2o contents of host lavas consequently the bulk major element compositions of tanna volcanic rocks cannot be considered as primarily controlled by crystal separation from successive liquids the oxyde sio2 variations diagrams and the modal compositions and mineral chemistry show that crystal accumulation is the predominant mechanism accounting for bulk rock compositions however this does not exclude fractional crystallization the variation of the calculated groundmass mineralogy strongly suggest the occurrence of crystal removal mainly clinopyroxene and magnetite

mechanisms of an extraordinary east asian summer monsoon event in july 2011 previous studies have demonstrated that the strong east asian summer monsoon results mainly from the westward intensification of the north pacific subtropical high npsh or equivalently the enhancement of the western north pacific subtropical high however during early july in 2011 a strong southerly or southeasterly moist flow gave rise to a large amount of precipitation over southwestern japan and korea and anomalous dry conditions over central china because of the extraordinary intensification of the npsh to the north the formation of the anomalous high that occurred to the east of central japan during early july is very rare and its physical mechanisms are investigated in this study the regressed circulation anomalies and wave activity flux vectors for july 2011 and data from the previous 32 years show that two teleconnection patterns due to rossby wave trains are the most important mechanisms rossby wave propagation from the eastern north atlantic and western europe to east asia following the north eurasian jet and east asian jet in the upper level and northward propagation of rossby waves forced by diabatic heating over the western north pacific wnp region in the lower level this simultaneous forcing of a significant negative phase of the summertime north atlantic oscillation in the higher latitudes and enhanced diabatic heating over the subtropical wnp is found to be the cause of the abnormal development of the anomalous high to the east of central japan resulting in extremely wet conditions in korea and southern japan and dry conditions in southern china

impact of the atlantic warm pool on the summer climate of the western hemisphere abstract the atlantic warm pool awp is a large body of warm water that comprises the gulf of mexico the caribbean sea and the western tropical north atlantic located to its northeastern side is the north atlantic subtropical high nash which produces the tropical easterly trade winds the easterly trade winds carry moisture from the tropical north atlantic into the caribbean sea where the flow intensifies forming the caribbean low level jet cllj the cllj then splits into two branches one turning northward and connecting with the great plains low level jet gpllj and the other continuing westward across central america into the eastern north pacific the easterly cllj and its westward moisture transport are maximized in the summer and winter whereas they are minimized in the fall and spring this semiannual feature results from the semiannual variation of sea level pressure in the caribbean region owing to the westward extension and eastward retreat of the nash the ncar community atmospher

geological evidence bearing on the miocene to recent structural evolution of the new hebrides arc abstract the new hebrides archipelago is a complex reversed arc system that can be divided into four major volcanic provinces the western belt is an early to middle miocene extinct volcanic arc that as a result of polarity reversal is now incorporated into the frontal arc of the present day configuration the eastern belt initially received detritus in the early middle miocene from a tholeiitic arc complex but in the mio pliocene became the locus of a more calc alkaline arc volcanism volcanic activity then ceased in the eastern belt but is well represented as a third and largely submerged marginal province through the pliocene into the early pleistocene the present volcanic line the central chain is essentially a continuation of the marginal province volcanism into recent times initial tectonic events in the new hebrides arc were associated with the regional disruption in the middle miocene of an east facing system with consequent termination of western belt arc volcanism the western belt remained as a landmass during the lowermost late miocene but subsided following a late miocene renewal of island arc volcanism to the east this latest phase was coeval with initial expansion of the north fiji basin and marked the advent of the new hebrides as a westwards migrating reversed arc system during arc migration there were apparent hiatuses in island arc volcanism the most notable being a middle pliocene to late pleistocene period of quiescence in the central sector tectonism in the early pleistocene recent raised the fore arc brought about rifting and extension to the rear and concentrated volcanism along the presently active central chain

geochemistry of basalts from central and southern new hebrides arc implication for their source rock composition abstract the basaltic rocks from the central and southern islands of the new hebrides aneityum tanna erromango efate emae tongoa and epi have geochemical features typical of island arc volcanics they are enriched in lile and depleted in zr hf nb and ta compared to n type morb the rocks were derived from a similar upper mantle source as n type morb but with a higher degree of partial melting in addition their source was enriched in lile k rb sr ba and lree probably by migrating hydrous fluids released during the dehydration of the subducted oceanic slab the basalts from futuna island which is located farther from the trench display characteristics typical of calc alkaline rocks the futuna basalts were generated from a different lile enriched upper mantle source it seems that this upper mantle source was modified by interaction with partial melts from the subducted oceanic lithosphere

iron ore mining promotes iron enrichment in sediments of the gualaxo do norte river basin minas gerais state brazil the objective of the present study is to assess the influence of iron ore mining on fe concentrations in fluvial sediments of the gualaxo do norte river basin minas gerais state brazil initially background values were determined for fe by means of the boxplot representation the iterative 2 technique and the calculated distribution function using geochemical data obtained for alluvial terraces geochronologic analyses in carbonaceous materials attested for the proposed background values after that chemical analyses of active drainage sediments collected along the entire basin were carried out and a geochemical map of the study area was prepared the mean background value for fe is relatively high 8 2 wt when compared to the fe concentration in the earth s crust 5 6 wt such background value is strongly associated with the geological characteristics of the region it was observed that most of the high fe concentrations were detected in active sediments collected in the main river of the basin and not in its tributaries this suggests that fe enrichment is not only linked to the local geology but also to possible increase resulting from accidental leakage of iron ore mining tailings from containment dams and lakes upstream it is suggested that measures that help stop or minimize such impact be adopted the large capacity of fe to adsorb and form complexes with toxic metals implicates in environmental hazards that may not be restricted only to the gualaxo do norte river basin but may affect the other basins downstream

the representation of the south tropical atlantic teleconnection to the indian ocean in the ar4 coupled models a series of recent papers showed that sea surface temperature sst anomalies in the south equatorial tropical atlantic modulate the interannual variability of the african and indian monsoon rainfall physically this teleconnection can be explained by a simple gill matsuno mechanism in this work the output from five different models chosen within the cmip3 coupled model intercomparison project version 3 ensemble of coupled general circulation models cgcms are analyzed to investigate how state of the art cgcms represent the impact of the south tropical atlantic sta ssts on the indian and african region using a correlation regression technique it is found that four out of the five models display a teleconnection between sta and indian region which is generally weaker than in the observations but in agreement in the rainfall field pattern this teleconnection is also noticeable in the ensemble mean of the five models over africa however the significant changes in rainfall displayed in the observation are properly caught by only one of the cgcms additionally none of the models reproduces the symmetric upper level wind response around the equator seen over the indian ocean in the observations and all have significant biases also in the surface pressure field response to the tropical atlantic ssts nonetheless the sta response particularly over the southern hemisphere is indicative of the gill matsuno type mechanism identified in previous studies using idealized experiments with atmospheric gcms and observational data with a suite of atmospheric only gcm integrations it is shown that the differences in amplitude and pattern are not only due to the strong biases and reduced variabilities of the cgcms over the tropical atlantic but they are also caused by the different physical parameterizations used in models

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

the origin of reversed geochemical zoning in the northern new hebrides volcanic arc integration of petrographic and geochemical data on each island in the banks group northern vanuatu new hebrides has revealed a decrease in k2o and related incompatible elements across the islands away from the new hebrides trench the correlation with depth to the benioff zone is therefore the reverse of that typically found in island arcs ree evidence and source modelling indicates that this variation represents a progressive depletion in lree hree in the upper mantle laterally away from the trench and a progressive increase in partial melting of the source in the same direction these variations in chemistry are attributed to an earlier west dipping miocene subduction system and the variation in degree of partial melting to the location of the islands with respect to the active back arc basin an enrichment of the upper mantle in the miocene is ascribed to the ascent of hydrous fluids enriched in incompatible elements from the west dipping benioff zone and subsequent reaction with the overlying upper mantle the model thus envisages approximately contemporaneous development of the central chain volcanoes and the backarc basin in the late pliocene with partial melting of hydrous laterally zoned upper mantle resulting from the convective thermal regime associated with the rifting apart of the back arc basin the role of the present subduction regime in magma generation is considered to be very limited

an introduction to the sangihe arc volcanism accompanying arc arc collision in the molucca sea indonesia in the molucca sea region of northeastern indonesia the sangihe and halmahera arcs are presently in the process of colliding the earth s only example of a collision between facing volcanic arcs the collision event is more advanced in the northern molucca sea where back arc thrusting occurs along the cotobato and philippine trenches and volcanic centers are inactive and dissected this paper describes the sangihe arc the western arc of the collision the sangihe are is approximately 500 km in length extending from the ne tip of sulawesi to mindanao philippines the arc comprises over 25 quaternary volcanic centers the eight presently active volcanoes being confined to the southern half of the arc the active volcanic front lies 100 110 km above the top of the west dipping benioff zone and volcanoes extend up to 70 km behind the front thereby defining a volcanic arc overlying earthquakes 100 to 180 km deep rock types range from basalt to rhyolite andesites are dominant pyroxene andesites are common on sulawesi and at or near the volcanic front from ruang to buhias pahepa and buang to mamanuk hornblende andesites are common at the volcanic front between mahengetang and sangihe island and in centers located well behind the volcanic front tholeiitic th suites defined on the basis of relative degrees of iron enrichment are confined to the southern volcanic front lack hornblende are low k k55 1 05 have low rb zr ratios 0 10 0 17 low ba y ratios 3 4 4 9 low rb cs ratios 8 14 and have the highest 87sr 86sr ratios 0 7039 0 7042 calcalkaline ca suites occur throughout the arc are low to high k k55 0 6 2 0 have variable rb zr ratios 0 15 0 65 and ba y ratios 4 2 12 4 high rb cs ratios 14 82 and low 87sr 86sr ratios 0 7035 0 7040 zr and y distribution coefficients are lower in th suites dzr 0 0 dy 0 2 0 5 than in ca suites dzr 0 0 0 8 dy 0 3 1 2 ti initially increases with increasing sio2 in some th suites while decreasing with sio2 in all ca suites with the exception of bukide ti zr 138 ti zr ratios of basalts exceed 100 only in th suites 76 130 lil element contents and lil hfs element ratios increase 2 to 3 times across the are away from the volcanic front and 2 to 3 times from south to north along the arc 87sr 86sr ratios decrease away from the volcanic front the south to north increase in lil element contents and lil hfs element ratios without corresponding changes in sr isotopic compositions are interpreted as resulting from decreasing degrees of partial melting northward this reflects the gradual cessation of volcanism in the north due to collision

mineralogical and geochemical indicators of the polygenetic nature of terra rossa in istria croatia abstract terra rossa in istria is situated on the jurassic cretaceous paleogene carbonate plain and is considered a polygenetic reddish soil which bears typical terra rossa fe oxide characteristics e g fe d and fe d fe t the difference in particle size mineralogy and geochemistry observed between terra rossa and the insoluble residue of limestones and dolomites clearly indicates that the additions of external materials might have diminished the influence of insoluble residue of limestones and dolomites as the primary parent material of terra rossa in istria terra rossa is clay and silty clay composed of quartz plagioclase k feldspar micaceous clay minerals illitic material and mica kaolinites kl d and kl chlorite vermiculite low charge vermiculite or high charge smectite mixed layer clay minerals other than illitic material hematite goethite and xrd amorphous inorganic compound calcite dolomite and boehmite are sporadically present and are of local importance kaolinites and illitic material are dominant clay mineral phases in the clay fraction of all terra rossa from istria kaolinite which does not form intercalation compounds with dimethylsulfoxide dmso is the dominant mineral phase in fine clay and is considered predominantly authigenic rather then inherited from parent materials neither the content and particle size distribution nor the bulk and clay mineralogy of the insoluble residue of limestone and dolomite support development of terra rossa entirely by dissolution of carbonate rock if terra rossa has developed only from the insoluble residue of limestone and dolomite its clay content due to weathering should be higher than that in the insoluble residues which is not the case plagioclase was found only in one insoluble residue while all terra rossa samples contain this mineral moreover insoluble residues do not contain vermiculite which was observed in small amounts in clay fraction of all terra rossa samples na 2 o k 2 o 100 zr nb and zr ti 1000 ratios in the majority of terra rossa samples are much higher than in the insoluble residue of limestones and dolomites which also supports external material influence in the genesis of terra rossa materials other than the insoluble residue of limestones and dolomites which might have contributed to terra rossa are loess sediments whose deposition was very important recurrent process in istria probably since the early middle pleistocene and flysch sediments which extended much more southwards from its present position analyses performed indicate that both loess older than that of the upper pleistocene age and flysch might have contributed in the genesis of terra rossa

petrology of matthew and hunter volcanoes south new hebrides island arc southwest pacific abstract matthew and hunter the two southernmost active volcanoes of the new hebrides island arc southwest pacific differ markedly from the other mainly tholeiitic quaternary volcanoes of this arc geodynamically related to the new hebrides subduction zone they also lie close to the southern limb of the active expanding ridge of the north fiji basin both volcanoes are made up of acid medium k calcalkaline orogenic andesites containing a variety of inclusions pyroxene and gabbroic cumulates as well as doleritic cognate inclusions this paper presents the first systematic petrographic and chemical study of these volcanics and their inclusions trace element geochemistry and rare earth element modelling suggest that the two volcanoes developed from successive batches of similar parental magmas originating from limited partial fusion of garnet peridotite in the mantle wedge various degrees of fractional crystallization of these batches led to the formation of three volcanic suites hunter little fractionated west matthew moderately fractionated and east matthew highly fractionated moreover on matthew island no correlation exists between the degree of fractionation and the eruptive chronology the youngest edifice west matthew being less evolved than the older one east matthew

structure and dynamics of a springtime atmospheric wave train over the north atlantic and eurasia the leading pattern of boreal spring 250 hpa meridional wind anomalies over the north atlantic and mid high latitude eurasia displays an obvious wave train the present study documents the structure energy source relation to the north atlantic sea surface temperature sst and impacts on eurasian climate of this wave train during 1948 2018 this atmospheric wave train has a barotropic vertical structure with five major centers of action lying over subtropics and mid latitudes of the north atlantic northern europe central eurasia and east asia respectively this spring wave train can efficiently extract available potential energy from the basic mean flow the baroclinic energy conversion process and positive interaction between synoptic scale eddies and the mean flow both play important roles in generating and maintaining this wave train the north atlantic horseshoe like nah sst anomaly contributes to the persistence of the wave train via a positive air sea interaction specifically the nah sst anomaly induces a rossby wave type atmospheric response which in turn maintains the nah sst anomaly pattern via modulating surface heat fluxes this spring atmospheric wave train has significant impacts on eurasian surface air temperature sat and rainfall during the positive phase of the wave train pronounced sat warming appears over central eurasia and cooling occurs over west europe and eastern eurasia in addition above normal rainfall appears over most parts of europe and around the lake baikal accompanied by below normal rainfall to east of the caspian sea and over central asia

signatures of divergence and self organization in soils and weathering profiles abstract complex system behaviors such as self organization are difficult to address in geology system evolution often cannot be directly observed and in geology models and theory must be reconciled with field evidence however self organization can be addressed within the historical interpretive paradigm by applying a measure of the degree of self organization of geologic features using standard interpretive methods to determine the nature of changes and determining whether those changes result in an increase or decrease in organization in this way stable non self organizing convergent development can be distinguished from unstable chaotic self organizing divergent development kolmogorov entropy k entropy was used as a measure of the self organization of soil profiles in eastern north carolina in general the profiles are low in k entropy indicating a generally high level of predictability and information in the vertical arrangement of pedogenetic horizons as a broad generality the study p

mineralogy of erromango lavas new hebrides evidence of an early stage of fractionation in island arc basalts abstract the orogenic volcanic rocks of erromango island are divided into a quaternary theoleiitic group and an older pliocene one showing calc alkalic affinity the microprobe mineralogy of these lavas agrees with this geochemical distinction and indicates a marked iron enrichment trend in the recent tholeiitic lavas whereas titanomagnetite occurs as early formed phenocrysts al cr mg rich only in pliocene basalts some ni and mg rich olivine phenocrysts fo88 and unusual chemically zoned clinopyroxene megacrysts are described from pliocene basic lavas and interpreted as deep fractionated minerals the large compositional range of these latter diopside core to augite rim through salite intermediate zone leads us to discuss the physical conditions and the corresponding cation substitutions prevailing during their formation diopside cores crystallized at depths of about 20 km from a relatively primitive melt the formation of salite is considered to be the result of concomitant fractionation of mg rich phases and increase of f o 2 an early stage of fractionation of cr bearing diopside ni bearing olivine would account for the typical cr and ni depletion of erromango lavas

the termination of the southern new hebrides subduction zone southwestern pacific abstract recent data bathymetric map and petrological investigations as well as reappraisal of local seismological events for more than 20 years allow us to present a new geodynamic interpretation of the southern new hebrides subduction zone a multidisciplinary approach to this complex area where transform movements relay subduction process clearly shows the interrelationships between intermediate seismicity lithospheric plates tectonics and volcanic activity according to our model two hinge zones tearing the downgoing slab along directions which parallel the convergence vector n70 e reasonably account for most seismological and petrological data from the region the approach of the loyalty islands ridge towards the trench and its increasing influence on the subduction regime is beginning to complicate this scheme

island arc magmatism in relation to the evolution of the crust and mantle abstract one aspect of the evolution of the earth s mantle is the development through geologic time of the continental crust a popular hypothesis is that the earth s crust has developed through the magmatic events associated with plate movements a two stage melting process involving generation of ocean ridge basalts followed by subduction and partial remelting of the oceanic lithosphere to form andesitic suites has been invoked as the major continental crust forming magmatic cycle however there is chemical and isotopic evidence for the composition of continental crust and arcs that is in conflict with the broad consequences predicted by this hypothesis the average composition of the upper continental crust has been fairly readily determined as granodioritic but the composition of the lower crust is less certain seismological and petrological evidence suggest that a substantial portion of the lower crust is basaltic in character therefore it cannot be concluded that the bulk average crust corresponds to andesite again the rock type most frequently collected in many arcs is andesite but the conclusion that the whole arc pile is of this composition is illogical and not supported by much field and petrologic evidence the peripheral accretion of arcs to continents is well documented for post palaeozoic epochs so that the nature of arc magma sources is critically relevant to the processes of continental crustal growth a large body of data on arc magmas can be explained by the hypothesis that the superjacent upper mantle wedge rather than the subducted lithosphere itself is the major source of arc erupted melts for many oceanic arcs isotopic evidence 87 sr 86 sr 143 nd 144 nd rules out the possibility that they constitute appropriate bulk crustal additions for the development of continents continental crustal growth may therefore either have changed in essential chemical isotopic character since the cambrian or arc magmas derived from chondritic type or lil enriched sources may be the only volumetrically significant additions to continental crust

spring arctic oscillation east asian summer monsoon connection through circulation changes over the western north pacific in the present study the links between spring arctic oscillation ao and east asian summer monsoon easm was investigated with focus on the importance of the north pacific atmospheric circulation and sea surface temperature sst to reduce the statistical uncertainty we analyzed high pass filtered data with the inter annual time scales and excluded the el nino southern oscillation signals in the climate fields using a linear fitting method the significant relationship between spring ao and easm are supported by the changes of multi monsoon components including monsoon indices precipitation and three dimensional atmospheric circulations following a stronger positive spring ao an anomalous cyclonic circulation at 850 hpa appears in southeastern asia and the western north pacific in summer with the easterly anomalies spanning from the pacific to asian continent along 25 n 30 n and the westerly anomalies south of 15 n at the same time the summer western north pacific subtropical high becomes weaker consistently the positive precipitation anomalies are developed over a broad region south of 30 n stretching from southern china to the western pacific and the negative precipitation anomalies appear in the lower valley of the yangtze river and southern japan the anomalous cyclone in the western north pacific persisting from spring to summer plays a key role in modulating easm and monsoon precipitation by a positive air sea feedback mechanism during spring the ao associated atmospheric circulation change produces warmer ssts between 150 e 180 near the equator the anomalous sensible and latent heating in turn intensifies the cyclone through a gill type response of the atmosphere through this positive feedback the tropical atmosphere and sst patterns sustain their strength from spring to summer that consequently modifies the monsoon trough and the western north pacific subtropical high and eventually the easm precipitation moreover the sst response to ao circulation is supported by the numerical simulations of an ocean model and the anomalous atmospheric circulation over the western north pacific is also reproduced by the dedicated numerical simulations using the coupled atmosphere ocean model the observation evidence and numerical simulations suggest the spring ao can impact the easm via triggering tropical air sea feedback over the western north pacific

equilibrium scale and inheritance in geomorphology abstract of the many equilibrium terms that have been proposed only two are needed dynamic equilibrium in the original sense of g k gilbert 1877 and steady state the former refers to the relationship between the process components of a system the latter to the system as a whole the tendency towards establishing a dynamic equilibrium is inherent in all natural systems that contain negative feedbacks between processes capable of compensating each other in geomorphology equilibrium tendencies of the mass budget are more relevant than those of the energy budget the validity of the equilibrium concept is discussed at several scales from a slope point to entire slopes drainage basins and mountain ranges the effects of eksystemic changes vary depending upon the length of the intervals between such changes in comparison to the length of the required relaxation times this relationship also applies to the influence of inherited forms patterns and materials that have become components of present day systems

possible mechanisms for the coupling between late spring sea surface temperature anomalies over tropical atlantic and east asian summer monsoon the relationship between the preceding late spring sea surface temperature sst over the tropical atlantic and the east asian summer monsoon easm is investigated based on the observational data and coupled model intercomparison project phase 5 cmip5 historical simulations the results show that warm cold tropical atlantic sst tasst during may tends to be followed by a strong weak easm with positive negative precipitation anomalies over the subtropical frontal area evidence is also provided that the atmospheric teleconnections propagating in both east and west directions are the key mechanisms linking the easm with the preceding may tasst that is the warm tasst anomaly during late spring can persist through the subsequent summer which in turn induces the gill type rossby wave response in the eastern pacific exciting the westward relay of the atlantic signal as well as the eastward propagation of the rossby wave along the jet stream furthermore the westward eastward propagating teleconnection signal may induce the anomalous anticyclone in the lower troposphere over the philippine sea anomalous tropospheric anticyclone with barotropic structure over the okhotsk sea the anomalous anticyclonic circulation over the philippine sea okhotsk sea brings warm and humid cold air to higher latitudes lower latitudes these two different types of air mass merge over the baiu meiyu changma region causing the enhanced subtropical frontal rainfall to support the observational findings cmip5 historical simulations are also utilized most state of the art cmip5 models can simulate this relationship between may tasst and the easm

geochemical background in soils a linear process domain an example from istria croatia definition of geochemical background in exploration and environmental geochemistry has always been regarded as contingent upon scale and investigated locality but mostly under assumption that hosts of processes that produce the data more or less conform individually to gaussian law of central tendencies recently understanding of pedogenesis as synergetic process being characterized by non linear dynamics renders thermodynamic approach directly applicable in assessment of geochemical thresholds with concepts of linearity and normality set alongside in solving the problems of soil geochemistry seen from this perspective the work is an attempt to relate conceptual fundamentals of non linear dynamical theory to basic statistical methods in order to elucidate the nature and origins of element subpopulations hidden in the original geochemical data from the soils of istrian peninsula western croatia to this purpose the two major groups of soils were selected for analysis depending on the type of bedrock as one of the main soil forming factors geochemical data were subjected to the trimming procedure by which the outliers were removed from the total data collective and attributed to non linear causes precluding simple cause and effect relationships as the sine qua non of gaussian distribution geochemical background is then defined as the normal range of data of the remaining trimmed dataset indicating the thermodynamic branch of the specific soil processes as opposed to outliers being described as dissipative structures

role of the tropical atlantic sea surface temperature in the decadal change of the summer north atlantic oscillation 1 recent observational studies have shown that the southern center of the summer north atlantic oscillation snao shifted eastward after the late 1970s in this study this phenomenon and its causes are further explored it is found that the decadal spatial shift of the snao southern center is related to the decadal variability of the tropical atlantic sea surface temperature tasst in the past half century the tasst experienced an abrupt change around the late 1970s with a rapid warming in the recent 2 decades thus in the period after the late 1970s when the tasst is relatively warmer the tasst released more energy into the atmosphere then stimulated strong convection over the tropical atlantic and further excited anomalous wave like patterns this strengthened the circulation in the region of the mediterranean sea namely the east part of the snao southern center consequently leading to an eastward shift of the snao southern center meanwhile in the period before the late 1970s when the tasst is relatively cooler the tasst released less energy into the atmosphere so its impact on the overlying atmosphere was significantly weakened and confined to the lower level atmosphere of the tropical atlantic thus the tasst possibly did not influence the variability of the snao southern center and the snao pattern exhibited a traditional distribution with two centers over the north atlantic

high na dacite from the jean charcot trough vanuatu southwest pacific abstract rifting that produced the jean charcot trough jct in the vanuatu back arc region commenced 2 3 ma leading to sio 2 bimodal magmatism in the northern half of the trough dacite with high na 2 o 6 0 and low k 2 o zr rb 10 nb rb 0 5 y rb 2 0 nb la 0 5 and ba zr but are quite different to lavas from the active vanuatu volcanic arc the dacites are compositionally close to oceanic plagiogranite produced during fractional crystallization of an n morb basaltic magma and mass balance calculations show that they may be similarly derived from the associated basalts we show that jct basalts are derived from a mantle source compositionally very close to that beneath the central spreading axis of the nfb with minimal contamination by a subduction component westward injection of diapiritic source mantle similar to that of the nfb back arc basin basalts may have caused rifting of the jct during incipient back arc rifting high na k felsic magmas may have evolved from parental low k basalts via side wall crystallization within a large lower crustal magma chamber

impacts of the atlantic multidecadal oscillation on the relationship of the spring arctic oscillation and the following east asian summer monsoon abstractprevious studies indicated that spring arctic oscillation ao can influence the following east asian summer monsoon easm this study reveals that the atlantic multidecadal oscillation a

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

nonlinear dynamical systems in geomorphology revolution or evolution abstract geomorphic systems typically exhibit complex apparently random behaviors and patterns in both spatial and temporal domains this complexity can arise from the cumulative impacts of individual process response mechanisms which are far too numerous to be accounted for in individual detail or due to multiple controls over process response relationships which operate over a range of spatial and temporal scales stochastic complexity nonlinear dynamical systems nds theory which includes specific techniques and concepts such as chaos dissipative structures bifurcation and catastrophe theory and fractals shows that extreme complexity can also arise due to the nonlinear dynamics and couplings of relatively simple systems represented by relatively small equation systems deterministic complexity while emphasis in earth science has been largely on stochastic complexity geomorphologists have long recognized the presence of deterministic complexity as well recent developments in the study of nonlinear dynamical systems have implications for the ability to make reliable long term predictions and therefore applications of nds in geomorphology may be revolutionary to some extent however virtually all the basic conceptual underpinnings of nds theory can be mapped onto existing and even traditional theoretical concepts in geomorphology in this sense the use of nds concepts in understanding earth surface processes and landforms is evolutionary the link between traditional and nds based concepts is illustrated by analyzing a generalized geomorphic mass flux system it is shown that the system is in most cases unstable consistent with chaos or deterministic complexity however the three attractor states of the system correspond exactly to the states of aggradation degradation and steady state

spatial distribution and mechanisms of earthquakes in the southern new hebrides arc from a temporary land and ocean bottom seismic network and from worldwide observations in 1977 a wide aperture seismic network of land and ocean bottom stations obs was operated for 6 weeks in the southern new hebrides island arc data on the spatial distribution and mechanisms of small events recorded by this local network were integrated with worldwide observations of moderate to large size new hebrides earthquakes of the past 17 years to study the structure and deformational processes in the new hebrides subduction zone surprisingly small differences less than about 10 km were found between the locations of shallow and intermediate depth earthquakes as located by the temporary local network and by the international seismological centre using worldwide stations analysis of the p wave travel time data from the obs station closest to the trench shows limited evidence for a high velocity zone about 5 higher than the surrounding mantle associated with the descending plate the thrust zone between the descending and upper plates is defined mainly by the spatial distribution and focal mechanisms of moderate to large size events and their aftershocks but it is not very well defined by the spatial distribution of small size events located in this study shallow seismic activity located beneath the trench and beneath the interplate thrust zone indicates a lower limit of about 40 km for the thickness of the seismically active part of the descending plate beneath the thrust zone focal mechanisms of moderate to large size earthquakes located within the upper plate and geological observations on the islands suggest that the upper plate in the region of erromango and tanna is divided into a series of blocks that are differentially uplifted along mainly nw se striking faults during the obs experiment several shallow events were well located beneath the coriolis trough a riftlike feature located to the east of the volcanic arc well determined depths of these events are between 11 and 22 km the well located intermediate depth events define a 20 km thick benioff zone that has a dip of about 70 the spatial distribution of events within the descending slab is very strongly clustered in a persistent pattern that is seen in both the short term sample of small events determined by the local network and the long term sample of locations based on worldwide data several focal mechanisms of moderate to large size intermediate depth events show components of lateral extension along the strike of the arc and some show components of lateral compression both of which could be interpreted as the result of a lateral bending of the descending plate in the part of the southern new hebrides arc where the trench begins to curve around to the east

dynamics of the extratropical response to a tropical atlantic sst anomaly abstract previous atmospheric general circulation model agcm experiments revealed that atmospheric responses to a tropical atlantic sea surface temperature anomaly ssta were asymmetric with respect to the sign of the ssta a positive ssta produced a south north dipole in geopotential heights much like the north atlantic oscillation nao while a negative ssta yielded an eastward propagating wave train with the northern lobe of the nao absent here these height responses are decomposed into components that are symmetric or antisymmetric with respect to the sign of the ssta the symmetric or notionally linear component is a nearly south north dipole projecting on the nao while the antisymmetric or notionally nonlinear component is a different dipole experiments with a diagnostic linear baroclinic model lbm suggest that both components are maintained primarily by transient eddy forcing dynamical mechanisms for the formation of the two components are explored using the lbm and a nonlinear baro

on the vertical drift of ionospheric f layer during disturbance time results from ionosondes the morphology of low latitude ionosphere is greatly affected by the zonal electric field especially at disturbance time in this study historical data from two low latitude ionosondes located at haikou and chongqing china are used to study the disturbance vertical drift properties of ionospheric f layer during the initial and main phases of 50 intense storms the disturbance drift from an empirical model is used as an indicator to denote the e x b disturbance magnitude it is found that the drifts both at the base and at the peak height are increased in magnitude when the disturbance becomes stronger for the same disturbance ionospheric vertical drifts at the base height are comparable with those at the peak height over haikou but they are larger than the latter over chongqing both drifts being smaller than those at the magnetic equator the drifts are larger in daytime than in nighttime but no rule is found on their seasonal dependence this indicates that low latitude storm time ionospheric vertical drift of the ionospheric layer exhibits both consistent and individual properties at different locations

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

how to measure the strength of the east asian summer monsoon defining the intensity of the east asian summer monsoon easm has been extremely controversial this paper elaborates on the meanings of 25 existing easm indices in terms of two observed major modes of interannual variation in the precipitation and circulation anomalies for the 1979 2006 period the existing indices can be classified into five categories the east west thermal contrast north south thermal contrast shear vorticity of zonal winds southwesterly monsoon and south china sea monsoon the last four types of indices reflect various aspects of the leading mode of interannual variability of the easm rainfall and circulations which correspond to the decaying el nino while the first category reflects the second mode that corresponds to the developing el nino the authors recommend that the easm strength can be represented by the principal component of the leading mode of the interannual variability which provides a unified index for the majority of the existing indices this new index is extremely robust captures a large portion 50 of the total variance of the precipitation and three dimensional circulation and has unique advantages over all the existing indices the authors also recommend a simple index the reversed wang and fan index which is nearly identical to the leading principal component of the easm and greatly facilitates real time monitoring the proposed index highlights the significance of the mei yu baiu changma rainfall in gauging the strength of the easm the mei yu which is produced in the primary rain bearing system the east asian ea subtropical front better represents the variability of the easm circulation system this new index reverses the traditional chinese meaning of a strong easm which corresponds to a deficient mei yu that is associated with an abnormal northward extension of southerly over northern china the new definition is consistent with the meaning used in other monsoon regions worldwide where abundant rainfall within the major local rain bearing monsoon system is considered to be a strong monsoon

geochemistry of istrian lower palaeogene bauxites is it relevant to the extent of subaerial exposure during cretaceous times abstract investigation of the origin and occurrence of istrian lower palaeogene bauxites discussed in this work relies on adoption of the recent perspectives on development of the collision induced diachronous discontinuity surface in the istrian part of the adriatic dinaric carbonate platform this process related to the forebulge uplift at the latest stages of alpine orogenesis is amply recorded in the geochemical signature of contemporaneous bauxites in order to elucidate the patterns of bauxite formation a discriminant function model based on the compositional data analysis major and trace elements is constructed providing the solid ground for separation of the bauxite groups deposited in the subaerially exposed istrian palaeoenvironment complete distinction between the four a priori defined istrian lower palaeogene bauxite groups achieved by the analysis demonstrates the highest degree of efficiency in characterizing environmental conditions marked by the unique suite of geochemical variables compositions

progressive and regressive pedogenesis and complex soil evolution abstract the simultaneous operation of regressive and progressive pedogenetic pathways raises the possibility that soil evolution may exhibit patterns far richer and more complex than increasing development over time this possibility is explored via a numerical model incorporating the relative rates of progressive and regressive pedogenesis and feedbacks between these rates and the degree of soil development this model may exhibit deterministic chaos and sensitive dependence on initial conditions with realistic parameter values variations in profile development in a region of the north carolina coastal plain where soil forming factors are relatively constant is consistent with deterministic chaos chaotic soil evolution suggests that soil development may reflect the interplay between progressive and regressive soil forming processes in addition to or instead of the age of a surface or deposit the former may produce a state of development which is unique to a particular time sensitively dependent on the unknown initial conditions and not simply related to age soils and their genetic signatures as indicators of relative ages and quaternary environments may need to be reinterpreted in this light

on the mechanism of tectonic transport in zones of oblique subduction abstract many cases of oblique subduction are known throughout the world today and many more must have existed in the past in at least one modern case sumatra the over riding plate has responded to oblique subduction by forming a strike slip fault that traverses the magmatic arc and displaces its leading edge in the direction of the transverse component of oblique convergence conditions favoring this sort of tectonic response are shown to be 1 1 a high angle of oblique convergence 2 2 a low angle of subduction and 3 3 relative thermal softening of the magmatic arc this mechanism may have been responsible in part for northward transport of western cordilleran magmatic arc and subduction zone rocks in the late cretaceous and earliest tertiary it also may help to explain evidence of southward transport and left lateral shear in northern mexico and the caribbean region in pre jurassic time

nonlinear dynamics and the evolution of relief abstract theories of landscape evolution and available field evidence suggest that topographic relief may increase decrease or remain relatively constant over time the trend depends on the relative balance between endogenic and exogenic forces and or the spatial scale a straightforward mathematical argument shows that when relief generally decreases over time or remains constant landscape evolution is stable and non chaotic chaotic unstable topographic evolution produces divergence where initial elevation differences and subsequent perturbations generally increase over time this leads to or at least towards a conceptual model of landscape evolution this model based on nonlinear dynamical systems nds theory recognizes 10 modes five stable and five chaotic of topographic evolution together these modes can accommodate existing theories and models of landscape evolution no mode can persist indefinitely over geologic time implying that landscapes inevitably undergo phases of increasing and decreasing relief these phases may be quite long because the model can accommodate any observed trend in relief evolution it is not falsifiable and is therefore not proposed as a theory the nds model does have implications with respect to the preservation of planar surfaces the next step is to develop a testable hypothesis

impact of the indian ocean sst basin mode on the asian summer monsoon 1 following an el nino event a basin wide warming takes place over the tropical indian ocean peaks in late boreal winter and early spring and persists through boreal summer our observational analysis suggests that this indian ocean warming induces robust climatic anomalies in the summer indo west pacific region prolonging the el nino s influence after tropical east pacific sea surface temperature has returned to normal in response to the indian ocean warming precipitation increases over most of the basin forcing a matsuno gill pattern in the upper troposphere with a strengthened south asian high near the ground the southwest monsoon intensifies over the arabian sea and weakens over the south china and philippine seas an anomalous anticyclonic circulation forms over the subtropical northwest pacific collocated with negative precipitation anomalies all these anomaly patterns are reproduced in a coupled model simulation initialized with a warming in the tropical indian ocean mixed layer indicating that the indian ocean warming is not just a passive response to el nino but important for summer climate variability in the indo west pacific region the implications for seasonal prediction are discussed