variations of the east asian jet stream and asian pacific american winter climate anomalies in this study the authors apply the ncep ncar reanalysis and other observations to depict the association of the asian pacific american climate with the east asian jet stream eajs with an emphasis on boreal winter seasons and on interannual timescales they analyze the variations of the eajs and their relationships with el nino southern oscillation enso and extratropical north pacific sea surface temperature sst and assess the relative connections of the eajs and enso to the anomalies of atmospheric circulation surface temperature and precipitation in the asian pacific american region it is found that the eajs is coupled to a teleconnection pattern spanning the entire asian pacific american region with the strongest signals over east asia and the western pacific this pattern differs significantly from that associated with enso which influences the earth s climate extensively with a strongest impact on the climate over the central pacific and east a strong eajs is associated with an intensification of the weather and climate systems in asia and over the pacific such as deepening of the east asian trough and the aleutian low and strengthening of the east asian winter monsoon it is linked to colder and drier conditions in east asia and stronger convection over the tropical asia australia sector compared with enso the eajs seems to link to the climate signals of asia and the pacific more strongly an intensified eajs is also associated with anomalies of temperature and precipitation in north america due to the related changes in stationary wave patterns while the eajs does not strongly link to the tropical central eastern pacific sst it is significantly associated with the extratropical north pacific sst more specifically the second most dominant mode of the empirical orthogonal function analysis of the sst in addition a strong weak eajs seems to follow a large small meridional gradient of the western pacific sst associated with warming cooling in the tropics subtropics and cooling warming in the extratropics

can the southern hemisphere annular mode affect china winter monsoon 1 many previous studies suggested that the anomalous northern hemisphere annular mode nam and associated low boundary forcing e g snow cover greatly influence the china winter monsoon cwm variability on interannual to inter decadal timescales in this article it is found that the southern hemisphere annular mode sam also well correlates with the two observed cwm major modes which has not been revealed before note that the two cwm major modes are obtained by performing empirical orthogonal function eof analysis on winter surface air temperature at 160 gauge stations across china for the 1951 2006 period they explain around 70 of the total cwm variances thefirsteofmodeexhibitsahomogeneousspatialpatternwiththecorrespondingprincipal component displaying a significant inter decadal variation which reflects the warming trend in china during the past 56 years the second eof mode shows a meridional seesaw patternandisbasicallyassociatedwithsignificantinterannualvariations bothoftheleading modes are intimately associated with the simultaneous sam like hemispheric circulation anomalies moreover thesam likeanomaliessignalprecursoryconditionsforthefirstcwm mode in boreal autumn the relevant physical mechanisms by which anomalous autumn sam may affect the cwm are investigated with ncar community atmospheric model version 3 cam3 when sam is in a strong phase during boreal autumn the circumantarctic upper level jet stream displaces poleward and the corresponding surface wind speeds reduce in the region between 45s and 30s inducing a hemispheric scale warm sea surface temperature sst belt beneath such an anomalously warm sst belt persists through boreal winter and weakens the hadley cell the weakened hadley cell in boreal wintercorrespondstoanomaloussoutherliesprevailinginthelowertroposphereoverchina which favor a weak cwm the intimate linkage between the autumn sam and cwm may be instrumental for understanding interactions between the northern and southern hemisphere and can provide a way to predict the cwm variations

middle and late jurassic radiolarian palaeoecology versus carbon isotope stratigraphy abstract jurassic radiolarians are sensitive to palaeoclimatic palaeoceanographic changes recorded by the stable carbon isotope curve carbon isotopic variations have been linked to changes in ocean structure productivity and concentrations of greenhouse gases in the atmosphere in the middle upper jurassic terminilletto section of the umbria marche sabina apennines central italy well preserved radiolarians are present in a sequence of cherty limestones interbedded with platform derived carbonates the 13 c curve in the aalenian kimmeridgian interval indicates three main positive 13 c events in the lower bajocian late bathonian lower callovian and middle oxfordian the positive 13 c shifts are correlated to increases in visible chert in the outcrop and may represent periods of increased biological productivity of surface sea water spumellaria nassellaria ratios and the fluctuations of relative abundance of selected genera tend to correlate with 13 c and chert abundance values and seem to be related to episodes of high nutrient mobilisation from the base of the bajocian the radiolarian associations show a slight tendency towards diversification coincident with increasing 13 c values in the upper part of the middle bajocian last appearances prevail over first appearances associated with the peak of the 13 c event this may indicate maximum eutrophic conditions coincident with the late bathonian early callovian positive 13 c shift the radiolarian associations record a different trend with respect to the bajocian event when the 13 c values are increasing to a maximum radiolarian associations tend to be reduced in species diversity followed by a small diversification trend when the 13 c values are decreasing we speculate that during the callovian a more stressful palaeoenvironment due to high level of eutrophication is indicated by the combination of high productivity of biogenic silica and low carbonate input although varying preservational conditions may have influenced the observed trends in the radiolarian associations the good correlation between changes of sedimentation patterns radiolarian assemblages and 13 c positive anomalies open interesting avenues for further investigations concerning the palaeoecology of mesozoic radiolarians

the influence of climate hydrology and permafrost on holocene peat accumulation at 3500 m on the eastern qinghai tibetan plateau peatland of the eastern qinghai tibetan plateau lies at the convergence of the east asian and indian monsoon systems in eastern asia to understand the evolution of this peatland and its potential to provide new insights into the holocene evolution of the east asian monsoon a 6 m peat core was collected from the undisturbed central part of a peat deposit near hongyuan the age depth profile was determined using 16 14c ams age dates the peat analysed for a range of environmental variables including carbon nitrogen and hydrogen concentration bulk density 13c and the associated spring water analysed for hydrogen and oxygen isotopes the age depth profile of the recovered peat sequence covers the period from 9 6 to 0 3 kyr bp and is linear indicating that the conditions governing productivity and decay varied little over the holocene using changes in carbon density organic carbon content and its 13c cold dry periods of permafrost characterised by low density and impeded surface drainage were identified the low 18o and d values of the spring water emanating around the peat deposit down to 13 8 and 102 vsmow respectively with an inverse relationship between electrical conductivity and isotopic composition indicate precipitation under colder and drier conditions relative to the present day in view of the current annual mean air temperature of 1 c this suggests conditions in the past have been conducive to permafrost inferred periods of permafrost correspond to independently recognised cold periods in other holocene records from across china at 8 6 8 2 7 8 5 6 4 2 3 1 and 1 8 1 5 kyr bp the transition to a cold dry climate appears to be more rapid than the subsequent recovery and cold dry periods at hongyuan are of longer duration than equivalent cold dry periods over central and eastern china light dark banding peat on a scale of 15 30 years from 9 6 to 5 5 kyr bp may indicate a strong influence of decadal oscillations possibly the pacific decadal oscillation and a potential link between near simultaneous climatic changes in the northwest pacific enso movement of the intertropical convergence zone and the east asian monsoon

accelerated pacific plate movements and climatic changes on time scales of 102 103 years in the late quaternary a synthesis abstract sea level curves constructed for the japan region for the period 14 000 to 10 000 years b p reveal inconsistencies in sea level during the intervals 10 000 10 500 11 500 12 000 and 13 000 13 500 years b p these intervals correspond to episodes of global climatic deterioration and catastrophic volcanic activity in japan these inconsistencies are explained on the basis of field observation by geoidal change and reactivation of the pacific plate movements from a glacio eustatic sea level curve it is supposed that the reactivation of the pacific plate movements was induced by mass redistribution within the earth due to rapid melting of polar ice furthermore the rapid spreading within the ocean basins greatly increased upwelling and this change in the ocean circulation resulted in abrupt global climatic cooling similar phenomena are recognized after 8000 and 130 000 years b p

distinct modes of east asian winter monsoon documented by a southern red sea coral record the large scale boreal winter climatic patterns associated with interannual variability in a coral oxygen isotope 18o record from the southern red sea covering most of the last century are investigated from the early 1930s to the early 1960s the winter coral 18o record reflecting temperature and salinity variations in southern red sea surface waters is associated with global or large scale sea surface temperature sst and 850 mb geopotential height z850 anomalies which project on the corresponding patterns associated with the el nino southern oscillation enso in contrast since the early 1960s the winter coral 18o record is related to a z850 pattern that reflects the enso independent part of the east asian winter monsoon eawm which includes the siberian high the east asian through and the east asian upper tropospheric jet our results indicate a weakening of the enso control on interannual temperature salinity variations in southern red sea surface waters in the early 1960s due to the warming of the indian ocean and suggest that information about the nonstationarity in the relationship between enso and two distinct modes of eawm can be documented in southern red sea coral 18o records

modelled atmospheric response to changes in northern hemisphere snow cover the surface boundary conditions are altered in a numerical simulation of january climate by prescribing a higher and b lower than average snow extent over northern hemisphere land masses the anomalies in snow cover are shown to have quite a strong impact on the mean climatic state associated with an increase in the areal extent of the snow there is a significant reduction in temperature throughout the lower troposphere there are also large increases in sea level pressure over most land areas significant responses in the mass field are also seen at 500 hpa where reductions in atmospheric thickness lead to significant negative anomalies in the height field responses are also seen non locally over both the north pacific and north atlantic basins the impact of increased snow on cyclone tracks is also examined a reduction in cyclones is noted over both continents and over the western sectors of both ocean basins over the north atlantic basin this reduction extends across over europe significantly weakening the storm track in the north pacific cyclone density is reduced in the west while in the east there is actually a strengthening of the storm tracks there are corresponding changes in the genesis of cyclones in both of these regions the change in cyclogenesis intensity and density is demonstrated to be associated with changes in baroclinicity between the two experiments the anomalous snow boundary conditions lead to significant changes in the meridional temperature gradients over both ocean basins which impact on the baroclinic zones

interannual variability of the seesaw mode of the interface between the indian and east asian summer monsoons the relation between the seesaw mode of the interface between the indian summer monsoon and east asian summer monsoon iie and the south china sea summer monsoon trough scssmt and the indian summer monsoon trough ismt is investigated using two atmospheric reanalyses together with outgoing longwave radiation sea surface temperature sst and gridded precipitation datasets canonical correlation analysis combined with empirical orthogonal functions correlation and composite analysis are employed results indicate that a stronger ismt and scssmt resulting from colder sst over the tropical indian ocean and tropical east central pacific cause the iie to deviate from its normal position in an anticlockwise direction with a node at around 22 n this leads to heavier than normal summer rainfall over the north central indian subcontinent and south china sea but weaker than normal from the low and middle reaches of the yangtze river and south korea to central japan a weaker ismt and scssmt resulting from warmer sst over the tropical indian ocean and tropical east central pacific causes the iie to deviate from its normal position in a clockwise direction and the anomalous summer rainfall pattern is the opposite of that for the stronger troughs further analysis indicates that the scssmt plays a crucial role in the evolution of the iie seesaw mode the latitudinal difference between the imst and scssmt may be one of the most important reasons for the formation of the iie seesaw mode

asynchronous variation in the east asian winter monsoon during the holocene the east asian winter monsoon eawm is one of the most active components of the global climate system climate anomalies associated with the eawm differ between extratropical and tropical regions due to the eawm s meridional extent spatial differences in the eawm variability on centennial and millennial time scales during the holocene have not been well understood this study describes holocene spatiotemporal features of the eawm based on comparisons of proxy records and climate simulations the analysis specifically compared four proxy records located throughout china to assess the eawm s spatial variability during the holocene these records indicate a stronger eawm during the early holocene than that during the late holocene the eawm also shows a rapid asynchronous decline from northwestern to southeastern china the eawm declined in northwestern china from 10 to 7 5 ka b p whereas the decline did not occur in southern china and the eastern tibetan plateau until 6 4 5 ka b p coupled equilibrium and transient simulations of climate evolution during the holocene indicate that the decline of the eawm from 10 to 7 5 ka b p was probably caused by melting of northern hemisphere nh ice sheets and enhanced atlantic meridional overturning circulation amoc the decline of the eawm from 6 to 4 5 ka b p over the eastern tibetan plateau and southern china is related to an abrupt increase in sea surface temperatures ssts of the tropical western indian ocean we therefore argue that the regional shift in eawm intensity was probably related to a distinguishing response to high latitude nh ice sheets and amoc and low latitude tropical ssts forcings

the influence of shelf sea fronts on winter monsoon over east china sea strong sea surface temperature fronts in open seas are known to affect the atmosphere shelf sea fronts in winter have comparable strengths yet their impacts on winds have not been studied in january of 2012 a persistent narrow band of cloud stretching 600 1 000 km was observed along the front of east china sea ecs numerical and analytical models show that the cloud was formed atop a recirculating cell induced by the front and more generally that plumes of low and high pressures emanate and spread far from fronts consistent with the theory observations show that in ecs at inter annual time scales strong fronts co vary with on shelf convergent wind strong northeasterly monsoon and alongshelf alignment of clouds with low clouds near the coast and higher clouds offshore our results suggest that shelf sea fronts are potentially an important dynamic determinant of climate variability of east asia

silica secreting biota and mass extinctions survival patterns and processes abstract high survival and at least regional blooms of siliceous marine groups with coeval retreat of calcareous organisms is known from the frasnian famennian radiolarians silicisponges and end cretaceous diatoms radiolarians mass extinctions a strictly actualistic approach to the palaeoecology of silica secreting biota is of limited significance especially for silica enriched and oligotrophic palaeozoic epeiric seas and in particular during biotic turnovers adaptation among silica secreting marine plankton has led toward more efficient utilization of shrinking dissolved silica resources within surface waters of cenozoic oceans as shown by both radiolarians and diatoms this biosiliceous signal during the major biotic crises is mostly explained by a large scale increase in volcano hydrothermal activity during major plate boundary re arrangements triggering global ecosystem perturbations the cumulative stimulus favoured siliceous versus calcareous biota growth deposition and preservation because of 1 a higher rate of input of silica and other nutrients promoting eutrophication pulses 2 a punctuated or reversed greenhouse climatic effect episodically coupled with 3 vigorous oceanic circulation due to a variety of volcanogenic upwellings and turnovers siliceous communities adapted to more eutrophic conditions have thrived in the stressed niches on the other hand expanding anoxia and nutrification may lead to a stepwise loss of deep water niches and consequent selective decline of more specialized oligotrophic radiolarians and other pelagic biota by contrast siliceous faunas experienced severe non selective losses during the end permian mass extinction recorded as a chert gap thus the greatest environmental disaster of the phanerozoic was driven by a unique set of killing factors extremely effective for radiolarian productivity e g due to the combination of a drastic volcanic winter with expanding superanoxia

increased summer rainfall in northwest australia linked to southern indian ocean climate variability 1 although annual rainfall over most of australia has followed a continuously decreasing trend over the past 6 decades i e 1948 2007 summer rainfall in northwest australia nwa has followed a pronounced increasing trend with a significant linear trend of 2 65 mm yr this study investigates the causes of increasing rainfall over nwa and focuses on influences originating in the middle to high latitudes i e southern indian ocean climate variability our results indicate that variations in summer rainfall over nwa are related to the concurrent strength of the mascarene high in years with a strong mascarene high in the lower troposphere the cyclonic vorticity over nwa is enhanced and more moisture is transported into nwa simultaneously an anomalous vertical closed circulation forms with an ascending branch over nwa and subsidence over the region occupied by the mascarene high as for the upper troposphere the mascarene high is related to a teleconnection wave train from the southern indian ocean to nwa which in turn influences the circulation over nwa this setting is favorable for enhanced rainfall over nwa analysis of the cause of variations in the mascarene high indicates that underlying external forcing of the high by for example sea surface temperature sst has intensified possibly due to the influence of the southern annular mode sam during the preceding spring this mechanism was further examined using numerical experiments we believe that the strengthening of the mascarene high which is caused by the enhanced sst gradient within the southern indian ocean associated with the preceding upward sam has had a significant influence on the increase in summer rainfall over nwa

dynamics of viscous backflow from a model fracture network hydraulic fracturing for production of oil and gas from shale formations releases fluid waste by products that must be managed carefully to avoid significant harm to human health and the environment these fluids are presumed to result from a variety of fracture relaxation processes and are commonly referred to as flowback and produced water depending primarily on the time scale of their appearance here a model is presented for investigating the dynamics of backflows caused by the elastic relaxation of a pre strained medium namely a single fracture and two model fracture network systems a single bifurcated channel and its generalization for n bifurcated fracture generations early and late time asymptotic solutions are obtained for the model problems and agree well with numerical solutions in the late time period the fracture apertures and backflow rates exhibit a time dependence of t 1 3 and t 4 3 respectively in addition the pressure distributions collapse to universal curves when scaled by the maximum pressure in the system which we calculate as a function of n the pressure gradient along the network is steepest near the outlet while the bulk of the network serves as a reservoir fracture networks with larger n are less efficient at evicting fluids manifested through a longer time required for a given fractional reduction of the initial volume the developed framework may be useful for informing engineering design and environmental regulations

subduction zones an introduction to comparative subductology abstract the subduction model for trench arc back arc systems was deduced more or less as a logical consequence of sea floor spreading many features in these systems such as thrust type inter plate earthquakes and deep earthquakes along wadati benioff zones are readily explained by the subduction model but other features such as extensional spreading and high heat flow in back arc regions and arc volcanism are difficult to explain an approach to solve these problems may be to recognize the existence of the two basically different modes of subduction one chilean type causing a compressional stress regime in the arc and back arc regions the other mariana type causing a tensional stress regime implications of the two types of the mode of subduction for some tectonic problems such as vertical movement and sediment accretion at trenches are discussed with special reference to the results of recent dsdp active margin drilling in discussing the possible causes of the two modes it is suggested that the large scale thermal and stress regimes in the back arc areas may not be the direct products of simple subduction but of some additional factors involving much greater energy such as mantle flow associated with the motion of major plates finally the possible great importance of various types of collision accretion and erosion at subduction zones is emphasized

crustal movements and geodynamics in fennoscandia abstract morner n a 1981 crustal movements and geodynamics in fennoscandia in p vyskocil r green and h malzer editors recent crustal movements 1979 tectonophysics 71 241 251 the fennoscandian shield the classical area of glacial isostasy has been subjected to a complex sequence of motions throughout the late cenozoic still the geometry of the areas deformed has been roughly the same an asthenosphere of low viscosity 1020 1021 poises and a lithosphere of high flexural rigidity are established the present uplift represents an other mechanism than the rapid glacial isostatic readjustment of the low viscosity asthenosphere and seems to originate from mesospheric motions at around 1900 1910 there was a distinct geodynamic change which seems to be controlled by changes in the earth s rate of rotation the postglacial uplift of fennoscandia is found to be associated with intensive neotectonism faulting fracturing and seismicity

distinct modes of the east asian winter monsoon two distinct modes of the east asian winter monsoon eawm have been identified and they correspond to real and imaginary parts of the leading mode of the eawm respectively analyses of these modes used the national centers for environment prediction ncep and national center for atmospheric research ncar monthly mean reanalysis datasets for the period 1968 2003 as well as the southern oscillation index soi north atlantic oscillation index and eastern equatorial pacific sea surface temperature sst data results were obtained by resolving a complex hermite matrix derived from 850 hpa anomalous wind fields and determining the resulting modes associations with several climate variables the first distinct mode m1 is characterized by an anomalous meridional wind pattern over east asia and the western north pacific mode m1 is closely related to several features of the atmospheric circulation including the siberian high east asian trough east asian upper tropospheric jet and local hadley circulation over east asia thus m1 reflects the traditional eawm pattern revealed in previous studies the second distinct eawm mode m2 which was not identified previously displays dominant zonal wind anomalies over the same area mode m2 exhibits a closer relation than m1 to sea level pressure anomalies over the northwestern pacific southeast of japan and with the soi and equatorial eastern pacific sst unlike m1 m2 does not show coherent relationships with the siberian high east asian trough and east asian upper tropospheric jet since atmospheric circulation anomalies relevant to m2 exhibit a quasibarotropic structure its existence cannot simply be attributed to differential land sea heating el nino events tend to occur in the negative phase of m1 and the positive phase of m2 both corresponding to a weakened eawm the arctic oscillation does not appear to impact the eawm on interannual time scales although the spatial patterns for the two modes are very different the two distinct modes are complementary with the leading eawm mode being a linear combination of the two the results herein therefore demonstrate that a single eawm index may be inappropriate for investigating and predicting the eawm

gravity currents with residual trapping motivated by geological carbon dioxide co 2 storage we present a vertical equilibrium sharp interface model for the migration of immiscible gravity currents with constant residual trapping in a two dimensional confined aquifer the residual acts as a loss term that reduces the current volume continuously in the limit of a horizontal aquifer the interface shape is self similar at early and at late times the spreading of the current and the decay of its volume are governed by power laws at early times the exponent of the scaling law is independent of the residual but at late times it decreases with increasing loss owing to the self similar nature of the current the volume does not become zero and the current continues to spread in the hyperbolic limit the leading edge of the current is given by a rarefaction and the trailing edge by a shock in the presence of residual trapping the current volume is reduced to zero in finite time expressions for the up dip migration distance and the final migration time are obtained comparison with numerical results shows that the hyperbolic limit is a good approximation for currents with large mobility ratios even far from the hyperbolic limit in gently sloping aquifers the current evolution is divided into an initial near parabolic stage with power law decrease of volume and a later near hyperbolic stage characterized by a rapid decay of the plume volume our results suggest that the efficient residual trapping in dipping aquifers may allow co 2 storage in aquifers lacking structural closure if co 2 is injected far enough from the outcrop of the aquifer

effects of northern and southern components of the east asian winter monsoon variability on sst changes in the western north pacific the present study investigates the impacts of the two components of the east asian winter monsoon eawm variability on sea surface temperature sst changes in the western north pacific when the eawm is stronger than normal significant negative sst anomalies form in the east asian marginal seas and subtropical western north pacific and persist from winter to the following spring it is found that winter spring sst anomalies in the yellow sea and the japan sea have a close association with the northern component of the eawm variability whereas the southern component has a large impact on sst changes in subtropical western north pacific the two components induce sst anomalies through both surface heat flux and oceanic advection changes the surface latent heat flux is predominantly responsible for sst changes the oceanic advection has a secondary contribution to the sst change in subtropical western north pacific associated with the northern component and in the japan sea associated with the southern component the surface latent heat flux anomalies associated with the northern component are induced through changes in both wind speed and sea air humidity difference and those associated with the southern component are induced mainly through changes in sea air humidity difference north of 20 n the sst anomalies induced by the northern component are mostly independent of el nino southern oscillation enso while enso has a large effect on the sst anomalies in open oceanic regions the southern component has a dominant contribution independent of enso to the sst anomalies in the marginal seas

radiolarian palaeoecology and radiolarites is the present the key to the past abstract radiolarian productivity pulses and related radiolarite deposition are phenomena difficult to understand from an exclusively actualistic viewpoint evolutionary selection pressure among silica secreting marine plankton both radiolarians and diatoms has led toward more economic usage of rapidly shrinking nutrient resources including dissolved silica of the photic zone in the late cenozoic oceans and in particular a substantial modification of oceanic cycle by the diatom explosive radiation even if there is a proved link between biomineralization and dissolved silica loading among the phytoplankton only the relative independence of modern siliceous planktic biotas from the available silica pool reflects mainly their progressive physiological specialisation during evolutionary history oceanic chemistry and productivity as well as patterns of circulation upwelling have changed radically during the phanerozoic radiolarites apparently represent an anachronistic facies as exemplified by their long lived and ocean wide distribution in palaeo pacific and hitherto highlighted actualistic models of localized intra oceanic wind driven upwelling loci are of largely questionable applicability in addition to plate drift hypersiliceous domains and intervals are explainable mostly by a large scale volcano hydrothermal activity during major plate boundary reconfigurations which in many ways favoured siliceous biotas acme and their skeletal remains accumulation and preservation factors tied to rapid voluminous submarine eruptions such as thermal buoyant megaplumes and basin overturns offer a viable alternative for traditional climatic circulation scenarios in case of hypersiliceous high productivity events irrelevant to greenhouse to icehouse climatic change the evolving carbon and silica cycles were coupled through the greenhouse effect and enhanced chemical weathering volcano hydrothermal and tectonic uplift events related mostly to extensive rifting and or accelerated oceanic spreading were the endogenous driving force that created this perturbation of the exogenous system the present biogeochemical cycle is representative only for the overall silica depleted post eocene oceanic ecosystems which broadly correlates with a major expansion of diatoms groups extremely efficient in silica removal and closely linking the silica budget with phosphorus and nitrogen cycles thus an orthodox uniformitarian approach to biosiliceous sedimentation based on a silica starved vigorous ocean is of limited significance when applied to the pre neogene settings especially in the peculiar planktic habitats of epeiric seas as well as during biotic crises marked by strong geotectonic overprint the major turnovers in marine siliceous biota composition in particular after the end permian radiolarite gap may have been coupled with discernible changes in an increasing biological control on the long term oceanic silica cycling punctuated equilibrium the evolutionary turnovers have induced a stepdown decrease of dissolved silica levels through the phanerozoic contemporaneously with the general secular trend of upward scaling of nutrient related ecological processes and increased effectiveness of resource utilization

modeling leakage pathways in subsurface formations fluid drainage through multiple fractures in porous media insights from hele shaw cell experiments abstract arresting the recent observed warming of the earth s climate is a challenge requiring the reduction of anthropogenic emissions of carbon dioxide one option for reducing emissions into the atmosphere is to capture and sequester the released carbon dioxide in geological formations however potential geological storage first requires a risk assessment of carbon dioxide escaping to overlying layers and back to the atmosphere through leakage pathways in the formation this in turn requires an understanding of fluid flow through the leakage pathways in this study the effect of leakage pathways on the flow of a gravity current was investigated using an analogue system a hele shaw cell fluid was introduced through the top edge of the cell and flowed out through one or more holes in its impermeable base the height of the accumulated fluid above the base of the cell at various points along its length and the outflow rate of fluid through the holes was measured this measurement was conducted with varying conditions of the location number and strength of source as well as the location and number of holes at steady state the fluid motion was in accordance with darcy s law for horizontal flow in a long thin current in another set of experiments in which inflow was stopped and the fluid was allowed to drain out of a single open hole the outflow rate was in accordance with darcy s law for one dimensional flow in the vertical direction until the fluid height above the hole fell below a certain limit this threshold height was found to be 1 3 cm which was similar in magnitude to the length of the hole a time series of photographs tracked the flow of colored dye the photographs demonstrated that at steady state the fluid traveled for some distance beyond the hole before draining through it this implies that contaminants may be transported in a formation even beyond an outlet before finally draining out through it the photographs also documented the shape of the interface between the newly introduced dye and the ambient fluid in the cell these shapes were found to be different in a cell placed horizontally versus one placed on an incline suggesting that the geometry and flow conditions in a formation affecting the transport of an injected fluid these findings may be used as a basis for predicting behavior of a fluid injected into a fractured formation in the subsurface

palaeoceanography of organic rich rocks of the loma chumico formation of costa rica late cretaceous eastern pacific the late cretaceous late cenomanian campanian loma chumico formation consists of laminated to massive bedded siliceous shales cherts ash fall tuffs volcanic glass beds and volcaniclastic sandstones the loma chumico formation is at least 630 m thick core data in the tempisque basin and can be subdivided in the subsurface into organic rich and organic lean total organic carbon 1 facies rock eval total organic carbon toc data show that toc in the organic rich facies averages 15 5 with values as high as 33 inorganic geochemical petrological and sedimentological analyses indicate that all the lithologies of the loma chumico formation were deposited in middle shelf to outer slope environments adjacent to an active subaerial island arc the organic geochemistry and palaeontology of the loma chumico formation help constrain the factors that controlled biological productivity in the region during the late cretaceous biomarkers identified in organic rich facies by gas chromatography mass spectrometry gc ms show a high abundance of total steranes relative to hopanes in the morote 1 core indicating algal dominated organic input the hopane to sterane ratio of the extract from the manzanillo 1 core indicates a relatively high bacterial component to the organic matter upwelling and extrusive volcanism were the most important factors that controlled nutrient supply including silica flux and biological productivity within the loma chumico formation depositional system episodic radiolarian dinoflagellate or diatom blooms instigated by rapid infusions of volcanogenic silica may have resulted in expansion of the oxygen minimum zone omz enhancing the preservation of organic matter productivity appears to have been uniform even during deposition of the organic lean facies the findings of this study suggest that ocean wide anoxia in the eastern pacific was unlikely during the late cretaceous high toc contents of organic rich radiolarites from central caribbean deep sea drilling project dsdp sites may be related to upwelling produced in the eastern pacific by convergence of the easterly trade winds eastern pacific equatorial upwelling zone or may be part of a more complex pacific atlantic ocean interaction the end of deposition of organic rich rocks began near the end of the latest santonian earliest campanian in the central caribbean and costa rica palaeoceanographic models suggest that improved circulation and ventilation of bottom waters due to early opening of the north atlantic south atlantic seaway may explain this observation this may represent the influx of a previously unrecognized source of colder oxygenated intermediate bottom water proto antarctic intermediate water into the late cretaceous central atlantic and eastern pacific oceans

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

buoyant dispersal of co2 during geological storage carbon capture and storage is currently the only technology that may allow significant reductions in co2 emissions from large point sources seismic images of geological co2 storage show the rise of co2 is influenced by horizontal shales the buoyant co2 spreads beneath impermeable barriers until a gap allows its upward migration the large number and small scale of these barriers makes the prediction of the co2 migration path and hence the magnitude of co2 trapping very challenging we show that steady buoyancy dominated flows in complex geometries can be modeled as a cascade of flux partitioning events this approach allows the analysis of two dimensional plume dispersal from a horizontal injection well we show that the plume spreads laterally with height y above the source according to y h 1 2 l where l is the width of the shales and h is their vertical separation the fluid volume below successive shale layers and therefore the magnitude of trapped co2 increase as y h 5 4 above the source so that every additional layer of barriers traps more co2 than the one below upscaling small scale flow barriers by reducing the vertical permeability common in numerical simulations of co2 storage does not capture the dispersion and trapping of the co2 plume by the flow barriers

pollen and oxygen isotope analyses on late and post glacial sediments of the tourbiere de chirens dauphine france the sequence of vegetation phases in the late glacial was studied in a sediment section from the bog tourbiere de chirens by means of pollen analysis 18o16o ratios of samples of lacustrine marl obtained from the same profile reflect variations of 18o16o in precipitation and thus provide an additional independent paleoclimatic record the observed 18o16o variations agree well with the climatic history as deduced from pollen analysis the climatic transition from the oldest dryas to the bolling period sensu lato as well as the beginning and end of the younger dryas cold phase is marked by abrupt changes in the 18o16o ratio which were observed also in other regions of the alps these drastic climatic changes probably took place simultaneously over large areas of central europe and occurred within short time spans

decadal change of the spring snow depth over the tibetan plateau the associated circulation and influence on the east asian summer monsoon abstract the decadal change in the spring snow depth over the tibetan plateau and impact on the east asian summer monsoon are investigated using station observations of snow depth data and the ncep ncar reanalysis for 1962 93 during spring march april both the domain averaged snow depth index sdi and the first principal component of the empirical orthogonal function eof analysis exhibit a sharp increase in snow depth after the late 1970s which is accompanied by excessive precipitation and land surface cooling the correlation between sdi and precipitation shows a coherent remote teleconnection from the tibetan plateau northern india to western asia it is found that the increased snow depth over the plateau after the mid 1970s is concurrent with a deeper india burma trough an intensified subtropical westerly jet as well as enhanced ascending motion over the tibetan plateau additional factors for the excessive snowfall include more moisture supply associated with the intensification of the south

converging gravity currents over a permeable substrate we study the propagation of viscous gravity currents along a thin permeable substrate where slow vertical drainage is allowed from the boundary in particular we report the effect of this vertical fluid drainage on the second kind self similar solutions for the shape of the fluid fluid interface in three contexts i viscous axisymmetric gravity currents converging towards the centre of a cylindrical container ii viscous gravity currents moving towards the origin in a horizontal hele shaw channel with a power law varying gap thickness in the horizontal direction and iii viscous gravity currents propagating towards the origin of a porous medium with horizontal permeability and porosity gradients in power law forms for each of these cases with vertical leakage we identify a regime diagram that characterizes whether the front reaches the origin or not in particular when the front does not reach the origin we calculate the final location of the front we have also conducted laboratory experiments with a cylindrical lock gate to generate a converging viscous gravity current where vertical fluid drainage is allowed from various perforated horizontal substrates the time dependent position of the propagating front is captured from the experiments and the front position is found to agree well with the theoretical and numerical predictions when surface tension effects can be neglected

a synoptic climatology of episodic subseasonal retractions of the pacific jet abstracttwenty eight years of ncep ncar reanalysis data are employed in a composite analysis of the structure and evolution of the large scale circulation associated with rapid subseasonal westward retractions of the northern hemisphere pacific jet nineteen pacific jet retractions are identified in the dataset the salient characteristics of these transitions are presented emphasizing the structure and evolution of anomalies in the zonal wind upper tropospheric geopotential height sea level pressure slp and tropopause potential vorticity pv the composite analysis demonstrates that as the jet retracts a transition from a dominant negative anomaly to a dominant positive anomaly across the north pacific in both the 500 hpa geopotential height and slp fields occurs in 10 days the resulting anticyclonic anomalies are sprawling and intense with slp anomalies of nearly 20 hpa and 500 hpa geopotential height anomalies of more than 200 m the vertical superposition of these upper and lower level an

interannual variations of the dominant modes of east asian winter monsoon and possible links to arctic sea ice two dominant modes of the winter temperature over east asia a northern mode and a southern mode and their links with arctic climate conditions are analyzed the relationships of the two modes with arctic sea ice are different the northern mode is closely linked to variations in sea ice of the arctic barents laptev sea in previous autumn and most of the arctic in concurrent winter the southern mode seems independent from the arctic sea ice variations but is associated with sea surface temperature sst anomalies in the equatorial central eastern pacific results suggest an effect of arctic sea ice variation on the northern mode and an influence of tropical sst anomalies on the southern mode reduced sea ice over the arctic increases 1000 500 hpa thickness over the high latitudes of eurasian continent which reduces the meridional thickness gradient between the middle and high latitudes and thus weakens the extratropical upper level zonal wind the weakened zonal wind provides a favorable dynamic condition for the development of a high latitude ridge around the ural mountain reduced arctic sea ice also tends to enhance the siberian high through both thermodynamic and dynamic processes the above atmospheric circulation patterns provide a favorable condition for the intrusion of cold air to northern east asia

similarity solutions for fluid injection into confined aquifers fluid injection into the deep subsurface such as injection of carbon dioxide co 2 into deep saline aquifers often involves two fluid flow in confined geological formations similarity solutions may be derived for these problems by assuming that a sharp interface separates the two fluids by imposing a suitable no flow condition along both the top and bottom boundaries and by including an explicit solution for the pressure distribution in both fluids when the injected fluid is less dense and less viscous than the resident fluid as is the case for co 2 injection into a resident brine gravity override produces a fluid flow system that is captured well by the similarity solutions the similarity solutions may be extended to include slight miscibility between the two fluids as well as compressibility in both of the fluid phases the solutions provide the location of the interface between the two fluids as well as drying fronts that develop within the injected fluid applications to cases of supercritical co 2 injection into deep saline aquifers demonstrate the utility of the solutions and comparisons to solutions from full numerical simulations show the ability to predict the system behaviour

circumglobal teleconnection in the northern hemisphere summer analysis of the 56 yr ncep ncar reanalysis data reveals a recurrent circumglobal teleconnection cgt pattern in the summertime midlatitude circulation of the northern hemisphere this pattern represents the second leading empirical orthogonal function of interannual variability of the uppertropospheric circulation the cgt having a zonal wavenumber 5 structure is primarily positioned within a waveguide that is associated with the westerly jet stream the spatial phases of cgt tend to lock to preferred longitudes the geographically phase locked patterns bear close similarity during june august and september but the pattern in july shows shorter wavelengths in the north pacific north america sector the cgt is accompanied by significant rainfall and surface air temperature anomalies in the continental regions of western europe european russia india east asia and north america this implies that the cgt may be a source of climate variability and predictability in the above mentioned midlatitude regions the cgt has significant correlations with the indian summer monsoon ism and el nino southern oscillation enso however in normal ism years the cgt enso correlation disappears on the other hand in the absence of el nino or la nina the cgt ism correlation remains significant it is suggested that the ism acts as a conductor connecting the cgt and enso when the interaction between the ism and enso is active enso may influence northern china via the ism and the cgt additionally the variability of the cgt has no significant association with the arctic oscillation and the variability of the western north pacific summer monsoon the circulation of the wave train shows a barotropic structure everywhere except the cell located to the northwest of india where a baroclinic circulation structure dominates two possible scenarios are proposed the abnormal ism may excite an anomalous west central asian high and downstream rossby wave train extending to the north pacific and north america on the other hand a wave train that is excited in the jet exit region of the north atlantic may affect the westcentral asian high and thus the intensity of the ism it is hypothesized that the interaction between the global wave train and the ism heat source may be instrumental in maintaining the boreal summer cgt

tectonic processes in papua new guinea and past productivity in the eastern equatorial pacific ocean phytoplankton growth in the eastern equatorial pacific ocean today accounts for about half of the new production the fraction of primary production fuelled by externally supplied nutrients in the global ocean the recent demonstration that an inadequate supply of iron limits primary production in this region1 supports earlier speculation that in the past fluctuations in the atmospheric deposition of iron bearing dust may have driven large changes in productivity2 but we argue here that only small 2 nm increases in the iron concentration in source waters of the upwelling equatorial undercurrent are needed to fuel intense diatom production across the entire eastern equatorial pacific ocean episodic increases in iron concentrations of this magnitude or larger were probably frequent in the past because a large component of the undercurrent originates in the convergent island arc region of papua new guinea which has experienced intensive volcanic erosional and seismic activity over the past 16 million years cycles of plankton productivity recorded in eastern equatorial pacific sediments may therefore reflect the influence of tectonic processes in the papua new guinea region superimposed on the effects of global climate forcing

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 role of nutrient availability in bioerosion consequences to carbonate buildups abstract zooxanthellate organisms which are among the major carbonate producers on coral reefs are highly adapted to nutrient deficient conditions and tend to be outcompeted by filamentous or fleshy algae if nutrients are abundant reef dwelling bioeroding organisms on the other hand seem to increase in abundance with increasing availability of nutrient and food resources maximum rates of calcium carbonate production in a reef system are comparable in magnitude to maximum rates of bioerosion the dynamic interplay between accretion destruction of coral reefs is therefore likely to be strongly influenced by nutrient availability nutrient availability may also influence development of carbonate facies in reef systems that develop in oligotrophic waters skeletal sands and framework should dominate carbonate buildups in systems that develop in mesotrophic waters enhanced bioerosion should reduce much of the skeletal material to carbonate muds increasing the prevalence of mud rich facies eutrophic conditions should result in bioeroded hardgrounds and carbonate depositional hiatuses when carbonate accumulation rates fail to equal or exceed rates of local relative sea level rise reefs drown bored and lithified pavements with crusts of ferromanganese oxides phosphates or glauconite often separate shallow reef from overlying deeper water deposits nondeposition bioerosion and evidence for low redox potentials at the sediment water interface all implicate excess nutrient availability as a factor in reef drowning some carbonate depositional hiatuses and bioerosional surfaces are local phenomena evidence of responses to local increases in nutrient availability resulting from submergence of soils runoff or topographic upwelling others appear to reflect regional or worldwide events because many carbonate producing organisms have life history strategies specialized to nutrient deficient conditions they are unable to compete when nutrients become plentiful events that triggered ocean turnover or sharp increases in the rate of deep ocean circulation would have increased sea surface nutrient availability worldwide such eutrophication could have caused widespread extinctions in reef communities because eutrophication promotes bioerosion details of the fossil records of those events are probably lost in bioerosional hiatuses

relationship between ural siberian blocking and the east asian winter monsoon in relation to the arctic oscillation and the el nino southern oscillation this study attempts to assess the possible linkage between ural siberian blocking and the east asian winter monsoon eawm during the boreal winter the dominance of blocking thermally enhances cold advection downstream the frequent occurrence of ural siberian blocking potentially promotes a cold eawm and vice versa the seasonal blocking activity can be regarded as the combined effect of the arctic oscillation ao and the el nino southern oscillation enso weakened strengthened meridional flow in the positive negative phase of the ao is unfavorable favorable for the formation of blocking highs because the ao shows a close relationship with the north atlantic oscillation nao its teleconnection with ural siberian blocking may exist in the form of an eastward propagating wave train be that as it may the wave train signal across east asia may be disturbed by the external effect of a strong enso event which probably enhances weakens the westerlies near siberia in its warm cold phase consequently the blocking eawm relationship is stronger weaker when the ao and enso are in phase out of phase if both ao and enso attain the positive negative phase the siberian high tends to be weaker stronger and the temperature tends to be higher lower in east asia with less more ural siberian blocking on the other hand if they are out of phase they are not strongly linked to the intensity of the siberian high and the blocking activity over ural siberia is unclear

are undiscovered hydrothermal vents in the southern red sea the main source of silica and helium 3 for the red sea deep water geochemical ocean sections study geosecs indian ocean expedition data show that silica and 3he in the red sea deep water are linearly correlated suggesting a common hydrothermal source silica sections for the red sea from the geosecs and mer rouge merou expeditions show a strong vertical silica maximum centered at 500 to 600 m depth the merou sections which have higher horizontal resolution than the geosecs sections suggest that the primary silica source lies in the south at that depth the interpretation is that the large scale silica and 3he distributions are due to the dispersal in the red sea deep water of warm or hot hydrothermal vent waters associated with the seafloor spreading center of the southern red sea the helium and silica rich hot brines of the central red sea probably cannot provide the large fluxes of silica or 3he required to maintain the inventory of either of these deep water properties in steady state the hypothesis of a common hydrothermal source for silica and 3he can most readily be tested by measurements of the germanium silicon ratio in red sea deep water

pacific east asian teleconnection part ii how the philippine sea anomalous anticyclone is established during el nino development the anomalous philippine sea anticyclone psac conveys impacts of el nino to east asian climate during the mature and decay of an el nino from the winter to ensuing summer it is shown that the anomalous psac forms in fall about one season prior to the peak el nino its strength increases with the el nino intensity and its sign reverses during a la nina the psac formation concurs with abnormal deepening of the east asian trough and with increasing number of northward recurvature of tropical storms in the western pacific the psac establishment is abrupt coupling with a swing from a wet to dry phase of an intraseasonal oscillation iso and often concurrent with early retreat of the east asian summer monsoon the iso becomes inactive after psac establishment the development of the psac is attributed to combined effects of the remote el nino forcing tropical extratropical interaction and monsoon ocean interaction the developing el nino induces off equatorial as cending rossby wave responses and land surface cooling in northeast asia both deepen the east asian trough in fall and induces vigorous tropical extratropical exchange of air mass and heat which enhances the cold air outbreak and initiation of the psac through exciting descending rossby waves the el nino induced indonesian subsidence generates low level anticyclonic vorticity over south asia which is advected by mean monsoon westerly instigating the anomalous psac the iso interacting with the underlying ocean plays a critical role in the abrupt establishment of psac the wind evaporation entrainment feedback tends to amplify suppress iso before after winter northeasterly monsoon commences suggesting the roles of atmosphere ocean inter action and the seasonal march of background winds in changing the philippine sea iso intensity and maintaining psac

on the association between spring arctic sea ice concentration and chinese summer rainfall 1 a statistical relationship between spring arctic sea ice concentration sic and chinese summer rainfall is identified using singular value decomposition svd results show that decreased increased spring sic in the arctic ocean and the greenland sea corresponds to increased decreased summer rainfall in northeast china and central china between the yangtze river and the yellow river 28 36 n and decreased increased rainfall in south china corresponding summer 500 hpa height anomalies show a eurasian wave train structure which originates in northern europe and extends southeastwards to northeast china and a south north dipole structure over east asia south to lake baikal such a spatial distribution of 500 hpa height anomalies and corresponding summer rainfall anomalies cannot be entirely attributed to the impact of east asian summer monsoon easm variability the spring arctic sic provides a complementary precursor for chinese summer rainfall variability the combined impacts of both spring arctic sic and eurasian snow cover on the eurasian wave train may explain their statistical linkage

an intensity index for the east asian winter monsoon the thermal contrast betweenthe asian continentand the adjacent oceans is the primary aspect of the east asian winter monsoon eawm that can be well represented in the sea level pressure slp field based on this consideration a new slp based index measuring the intensity of the eawm is proposed by explicitly taking into account both the east west and the north south pressure gradients around east asia the new index can delineate the eawm related circulation anomalies well including the deepened shallow midtropospheric east asian trough sharpened and accelerated widened and decelerated upper tropospheric east asian jet stream and enhanced weakened lower tropospheric northerly winds in strong weak eawm winters compared with previous indices the new index has a very good performance describing the winter mean surface air temperature variations over east asia especially for the extreme warm or cold winters the index is strongly correlated with several atmospheric teleconnections including the arctic oscillation theeurasianpattern andthenorthpacificoscillation westernpacificpattern implyingthepossible internal dynamics of the eawm variability meanwhile the indexis significantly linked to el ni oscillation enso and the sea surface temperature sst over the tropical indian ocean moreover the sst anomalies over the tropical indian ocean are more closely related to the index than enso as an independent predictor this adds further knowledge to the prediction potentials of the eawm apart from enso the predictability of the index is high in the hindcasts of the centre national de recherches m cnrm model from development of a european multimodel ensemble system for seasonal to interannual prediction demeter hence it would be a good choice to use this index for the monitoring prediction and research of the eawm

distinguishing interannual variations of the northern and southern modes of the east asian winter monsoon abstractthe east asian winter monsoon eawm related climate anomalies have shown large year to year variations in both the intensity and the meridional extent the present study distinguishes the interannual variations of the low latitude and mid to high latitude components of the eawm to gain a better understanding of the characteristics and factors for the eawm variability through composite analysis based on two indices representing the northern and southern components modes of the eawm variability the present study clearly reveals features unique to the northern and southern mode the northern mode is associated with changes in the mid to high latitude circulation systems including the siberian high the aleutian low the east asian trough and the east asian westerly jet stream whereas the southern mode is closely related to circulation changes over the global tropics the north atlantic and north america a strong northern mode is accompanied by positive negative and positive surface temp

in phase transition from the winter monsoon to the summer monsoon over east asia role of the indian ocean 1 analysis of observations shows that the weak east asian winter monsoon eawm to weak east asian summer monsoon easm transitions mainly occur in el nino decaying years whereas strong eawm denoting stronger northerly winds along east asian coast to strong easm denoting less precipitation along the meiyu baiu rainband transitions all occur in non el nino southern oscillation enso years during the period 1979 2009 this new finding implies that enso is not indispensable to the in phase eawm to the easm transitions the present study reveals an important role of the indian ocean in the strong eawm to strong easm transitions and proposes a possible mechanism for these transitions a strong eawm induces more precipitation over the maritime continent and the associated anomalous heating excites a gill matsuno type pattern in the tropics the resultant wind and cloud changes enhance latent heat flux and reduce downward shortwave radiation over the northwestern indian ocean in winter which leads to sst cooling the cold sst anomalies persist to summer and excite an anomalous cyclone over the subtropical western north pacific leading to a strong easm the above processes also operate in the weak eawm to weak easm transitions during which el nino impacts dominate but with additional contributions from the eawm the results of observational analysis are confirmed by numerical experiments with a coupled model

drainage of a horizontal boussinesq aquifer with a power law hydraulic conductivity profile 1 solutions to the boussinesq equation describing drainage into a fully penetrating channel have been used for aquifer characterization two analytical solutions exist for early and late time drainage from a saturated homogeneous and horizontal aquifer following instantaneous drawdown the solutions for discharge q can be expressed as dq dt aq b where a is constant and b takes on the value 3 and 3 2 for early and late time respectively though many factors can contribute to departures from the two predictions we explore the effect of having permeability decrease with depth as it is known that many natural soils exhibit this characteristic we derive a new set of analytical solutions to the boussinesq equation for k oc z n where k is the saturated hydraulic conductivity z is the height above an impermeable base and n is a constant the solutions reveal that in early time b retains the value of 3 regardless of the value of n while in late time b ranges from 3 2 to 2 as n varies from 0 to oo similar to discharge water table height h in late time can be expressed as dh dt ch d where d 2 for constant k and d oo as n in theory inclusion of a power law k profile does not complicate aquifer parameter estimation because n can be solved for when fitting b to the late time data whereas previously b was assumed to be 3 2 however if either early or late time data are missing there is an additional unknown under appropriate conditions water table height measurements can be used to solve for an unknown parameter

short term planetary scale interactions over the tropics and midlatitudes during northern winter part i contrasts between active and inactive periods abstract objectively analyzed 200 mb winds of four winters are used to study the short term several days teleconnections between planetary scale circulation components over the monsoon region the composited structures suggest that during very active northeasterly monsoon surge periods the midlatitude and tropical circulation components vary in a coherent way the jet streak and local hadley circulation over east asia the divergent flow over the maritime continent and the equatorial walker circulations over the pacific and indian oceans all strengthen steadily while the secondary jet streak over west asia weakens during inactive break periods the midlatitude circulation components all exhibit reversed changes while the variations in the tropics are less coherent although still showing reversed tendencies the results basically verify the short term teleconnection model proposed by chang and lau 1980 but more complex processes in the acceleration of the midlatitude jet streaks are indicated

multiple factors in the origin of the cretaceous tertiary boundary the role of environmental stress and deccan trap volcanism a review of the scenarios for the cretaceous tertiary k t boundary event is presented and a coherent hypothesis for the origin of the event is formulated many scientists now accept that the event was caused by a meteorite impact at chicxulub in the yucatan peninsula mexico our investigations show that the oceans were already stressed by the end of the late cretaceous as a result of the long term drop in atmospheric co2 the long term drop in sea level and the frequent development of oceanic anoxia extinction of some marine species was already occurring several million years prior to the k t boundary the biota were therefore susceptible to change the eruption of the deccan traps which began at 66 2 ma coincides with the k t boundary events it erupted huge quantities of h2so4 hcl co2 dust and soot into the atmosphere and led to a significant drop in sea level and marked changes in ocean temperature the result was a major reduction in oceanic productivity and the creation of an almost dead ocean the volcanism lasted almost 0 7 m y extinction of biological species was graded and appeared to correlate with the main eruptive events elements such as ir were incorporated into the volcanic ash possibly on soot particles this horizon accumulated under anoxic conditions in local depressions and became the marker horizon for the k t boundary an oxidation front penetrated this horizon leading to the redistribution of elements the eruption of the deccan traps is the largest volcanic event since the permian triassic event at 245 ma it followed a period of 36 m y in which the earth s magnetic field failed to reverse instabilities in the mantle are thought to be responsible for this eruption and therefore for the k t event we therefore believe that the k t event can be explained in terms of the effects of the deccan volcanism on an already stressed biosphere the meteorite impact at chicxulub took place after the onset of deccan volcanism it probably played a regional rather than a global role in the k t extinctions

another look at interannual to interdecadal variations of the east asian winter monsoon the northern and southern temperature modes abstract this study investigates the causes of interannual to interdecadal variability of the east asian ea 0 60 n 100 140 e winter monsoon eawm over the past 50 yr 1957 2006 the winter mean surface air temperature variations are dominated by two distinct principal modes that together account for 74 of the total temperature variance the two modes have notably different circulation structures and sources of variability the northern mode characterized by a westward shift of the ea major trough and enhanced surface pressure over central siberia represents a cold winter in the northern ea resulting from cold air intrusion from central siberia the southern mode on the other hand features a deepening ea trough and increased surface pressure over mongolia representing a cold winter south of 40 n resulting from cold air intrusion from western mongolia the cold northern mode is preceded by excessive autumn snow covers over southern siberia mongolia whereas the cold southern mode is preceded b

holocene tectonism in eastern asia and geoidal changes abstract there have been eight major tectonic movements along the east margins of asia during the holocene they are correlated with intervals of volcanic eruptions in japan and glacio eustatic falls which are believed to be worldwide at the same time the tectonic activities migrate from south to north the facts suggest that geoidal changes occurred at times of global cooling furthermore it is thought that the geoidal changes and the tectonic movements induced abrupt climatic cooling on a worldwide basis

enso and east asian winter monsoon relationship modulation associated with the anomalous northwest pacific anticyclone using observational datasets and numerical model experiments the mechanism on the slowly varying change in the relationship between the el nino southern oscillation enso and the east asian winter monsoon eawm is investigated the decadal window 11 15 and 21 year moving correlations show a significant change in the boreal wintertime enso eawm relationship between two sub periods of 1976 1992 and 1997 2013 such recent change in enso eawm relationship is mainly attributed to the changes in the intensity and zonal location of the anomalous lower tropospheric northwest pacific anticyclone nwp ac nwp ac commonly develops near the region of the philippine sea during the enso s peak phase and plays an important role of bridging the tropical convection and mid latitude teleconnection on one hand the intensity of the nwp ac is influenced by the interdecadal variation in a linkage between enso and the indian ocean sea surface temperature sst variability referring that a strong connection between the pacific and indian oceans results in the strengthening of nwp ac response to enso on the other hand the zonal displacement of the nwp ac is associated with the pacific decadal oscillation pdo and the atlantic multidecadal oscillation amo that is the tropical pacific mean state i e zonal sst gradient between climatologically warm western pacific and cold eastern pacific strengthened by either the negative pdo phase or the positive amo phase drives the anomalous enso induced convection to be shifted to the west with this westward shift the zonal center of the nwp ac also migrates westward over the philippine islands and exerts stronger connection between enso and eawm in contrast the relaxed zonal sst contrast associated with either the positive pdo phase or the negative amo phase tends to exhibit weaker enso eawm relationship via both of eastward shifted zonal centers of the anomalous enso induced convection and the nwp ac finally a series of the numerical experiments conducted by an atmospheric general circulation model supports the observational findings

fluid drainage from the edge of a porous reservoir we report theoretical and experimental studies to describe buoyancy driven fluid drainage from a porous medium for configurations where the fluid drains from an edge we first study homogeneous porous systems to investigate the influence of heterogeneities we consider the case where the permeability varies transverse to the flow direction exemplified by a v shaped hele shaw cell finally we analyse a model where both the permeability and the porosity vary transverse to the flow direction in each case a self similar solution for the shape of these gravity currents is found and a power law behaviour in time is derived for the mass remaining in the system laboratory experiments are conducted in homogeneous and v shaped hele shaw cells and the measured profile shapes and the mass remaining in the cells agree well with our model predictions our study provides new insights into drainage processes such as may occur in a variety of natural and industrial activities including the geological storage of carbon dioxide

late cretaceous and paroxysmal cretaceous tertiary extinctions the various geological signatures at cretaceous tertiary time including iridium and other associated elements microspherules and shock deformation features are compatible with the suggestion that the transition is marked by a period of intense volcanism the volatile emissions from this volcanism would lead to acid rain reduction in the alkalinity and ph of the surface ocean global atmospheric temperature changes and ozone layer depletion these environmental effects coupled with those related to the major sea level regression of the late cretaceous provide the framework for an explanation of the selective nature of the observed extinction record

a new upper level circulation index for the east asian summer monsoon variability the east asian summer monsoon easm andits variability involvecirculationsystems in both the tropicsand midlatitudes as well as in both the lower and upper troposphere considering this fact a new easm index newi is proposed based on 200 hpa zonal wind which takes into account wind anomalies in the southern about 58n middle about 208n and northern areas about 358n of east asia the newi can capture the interannual easm related climate anomalies and the interdecadal variability well compared to previous indices thenewishowsabetterperformanceindescribingprecipitationandairtemperaturevariationsovereastasia it can also show distinct climate anomalous features in early and late summer the newi is tightly associated with the east asian pacific or the pacific japan teleconnection suggesting a possible role of internal dynamics in the easm variability meanwhile the newi is significantly linked to el nino southern oscillation and tropical indian ocean sea surface temperature anomalies furthermore the newi is highly predictable in the ensembles models indicating its advantage for operational prediction of the easm the physical mechanism of the easm variability as represented by the newi is also explicit both warm advection anomalies of temperaturebyanomalouswesterlywindsandtheadvectionofanomalouspositiverelativevorticitybynortherly basic winds cause anomalous ascending motion over the mei yu changma baiu rainfall area and vice versa over the south china sea area hence this newi would be a good choice to study monitor and predict the easm

leakage from gravity currents in a porous medium part 2 a line sink we consider the propagation of a buoyancy driven gravity current in a porous medium bounded by a horizontal impermeable boundary the current is fed by a constant flux injected at a point and leaks through a line sink at a distance from the injection point this is an idealized model of how a fault in a cap rock might compromise the geological sequestration of carbon dioxide the temporal evolution of the efficiency of storage defined as the instantaneous ratio of the rate at which fluid is stored without leaking to the rate at which it is injected is of particular interest we show that the efficiency of storage decays like t 2 5 for times t that are long compared with the time taken for the current to reach the fault this algebraic decay is in contrast to the case of leakage through a circular sink neufeld et al j fluid mech vol 2010 where the efficiency of storage decays more slowly like 1 ln t the implications of the predicted decay in the efficiency of storage are discussed in the context of geological sequestration of carbon dioxide using parameter values typical of the demonstration project at sleipner norway we show that the efficiency of storage should remain greater than 90 on a time scale of millennia provided that there are no significant faults in the cap rock within about 12 km of the injection site

the cretaceous tertiary boundary event in ecuador reduced biotic effects due to eastern boundary current setting a multidisciplinary study of a new cretaceous tertiary k t boundary section near guayaquil ecuador reveals an unusually cool water low diversity planktic foraminiferal fauna and a high diversity radiolarian fauna similar to those found in southern high latitude k t sequences despite the fact that this section was deposited near the cretaceous equator the k t boundary is located by planktic foraminifera within a narrow interval bounded by last appearances of tropical cretaceous species and first appearances of tertiary species including parvularugoglobigerina eugubina as in southern high latitudes there is no major mass extinction of either planktic foraminifera or radiolarians at this level a major radiolarian faunal discontinuity occurs some 6 m higher in the section within foraminiferal zone plc some 300 500 kyr after the k t event 13c values from bulk carbonates show both high and low latitude characteristics similarly to low latitudes there is a 3 negative 13c excursion at the k t boundary which is generally interpreted as a major decrease in primary productivity but unlike the low latitudes recovery occurs within a few thousand years as compared with 300 500 kyr and suggests rapid nutrient influx from the antarctic region via a current similar to the humboldt current today similarly to high latitude k t sequences a negative 13c shift occurs in the early danian zone plb about 300 kyr after the k t boundary sedimentologic and mineralogic data indicate a late maastrichtian with relatively low biogenic quartz and high carbonate followed by increasing biogenic quartz 50 and decreasing carbonate 5 during the early danian this suggests intensified atmospheric and oceanic circulation and upwelling off ecuador during the early danian the k t transition is marked by increased volcanic activity continental erosion and terrigenous influx but this also occurs in the early danian zone at the p1ap1b zonal transition and is thus not unique to the k t boundary we suggest that the catastrophic biotic effects normally observed at the k t boundary in low latitudes are greatly reduced or absent in the eastern equatorial pacific because this region was dominated then as now by upwelling and current transport of nutrient rich waters from the antarctic ocean as a result the biotic patterns are characteristic of southern high latitudes whereas the 13c pattern combines ameliorated low latitude effects with predominantly high latitude trends

inter decadal changes in the east asian summer monsoon and associations with sea surface temperature anomaly in the south indian ocean previous studies have revealed inter decadal changes in the east asian summer monsoon easm that occurred around the late 1970s and early 1990s respectively the present study compares characteristics of these two changes and analyzes plausible influences of the south indian ocean sio sea surface temperature sst change the two changes share pronounced common features characterized by an equivalent barotropic circulation anomaly over northern east asia and a meridional vertical overturning circulation over the tropical region meanwhile they display some distinct characteristics especially over the tropics the circumfluent anomalies are more robust for the first change than for the second one related amplitude asymmetry is partly attributed to a weakening trend in the easm moreover sst change in the sio featuring a decadal warming since the 1980s and a cooling after 1993 may contribute to both of these inter decadal changes cold sst anomaly induces anomalous mid tropospheric descent over the western sio and ascent extending from the eastern sio to western australia and over the equatorial indian ocean the accompanying upper tropospheric divergent flows from western australia and equatorial indian ocean to the philippines lead to anomalous descent and an anomalous lower tropospheric anticyclone over the south china sea philippines warm sst anomaly induces opposite changes in above regions the possible influence of sst anomaly in the sio is further confirmed by numerical experiments

the influence of capillary effects on the drainage of a viscous gravity current into a deep porous medium the drainage of a viscous gravity current into a deep porous medium driven by both the gravitational and capillary forces is considered in two steps we first study the one dimensional case where a layer of fluid drains vertically into an infinitely deep porous medium we determine a transition from the capillary driven regime to the gravity driven regime as time proceeds second we solve the coupled spreading and drainage problem there are no self similar solutions of the problem for the entire time period so asymptotic analyses are developed for the height depth and front location in both the early time and the late time periods in addition we present numerical results of the governing partial differential equations which agree well with the self similar solutions in the appropriate asymptotic limits

combined effect of el nino southern oscillation and pacific decadal oscillation on the east asian winter monsoon using long term observational data and numerical model experiments the combined effect of the el nino southern oscillation enso and pacific decadal oscillation pdo on the variability of the east asian winter monsoon is examined in the observations it is found that when the enso and pdo are in phase combinations i e el nino positive pdo phase and la nina negative pdo phase a negative relationship between enso and east asian winter monsoon is significantly intensified in other words when el nino la nina occurs with positive negative pdo phase anomalous warm cold temperatures are dominant over the east asian winter continent on the other hand there are no significant temperature anomalies when the enso and pdo are out of phase combinations i e el nino negative pdo phase and la nina positive pdo phase further analyses indicate that the anticyclone over the western north pacific including the east asian marginal seas plays an essential role in modulating the intensity of the east asian winter monsoon under the changes of enso pdo phase relationship long lasting high pressure and warm sea surface temperature anomalies during the late fall winter and following spring over the western north pacific which appear as the el nino occurs with positive pdo phase can lead to a weakened east asian winter monsoon by transporting warm and wet conditions into the east asian continent through the southerly wind anomalies along the western flank of the anomalous high pressure and vice versa as the la nina occurs with negative pdo phase in contrast the anomalous high pressure over the western north pacific does not show a prominent change under the out of phase combinations of enso and pdo numerical model experiments confirm the observational results accompanying dominant warm temperature anomalies over east asia via strong anticyclonic circulation anomalies near the philippine sea as the el nino occurs with positive pdo phase whereas such warming is weakened as the el nino occurs with negative pdo phase this result supports the argument that the changes in the east asian winter monsoon intensity with enso are largely affected by the strength of the anticyclone over the western north pacific which significantly changes according to the enso pdo phase relationship

patterns of asian winter climate variability and links to arctic sea ice abstractthis paper describes two dominant patterns of asian winter climate variability the siberian high sh pattern and the asia arctic aa pattern the former depicts atmospheric variability closely associated with the intensity of the siberian high and the latter characterizes the teleconnection pattern of atmospheric variability between asia and the arctic which is distinct from the arctic oscillation ao the aa pattern plays more important roles in regulating winter precipitation and the 850 hpa meridional wind component over east asia than the sh pattern which controls surface air temperature variability over east asia in the arctic ocean and its marginal seas sea ice loss in both autumn and winter could bring the positive phase of the sh pattern or cause the negative phase of the aa pattern the latter corresponds to a weakened east asian winter monsoon eawm and enhanced winter precipitation in the midlatitudes of the asian continent and east asia for the sh pattern sea ice loss in the