cross season relation of the south china sea precipitation variability between winter and summer the present study reveals cross season connections of rainfall variability in the south china sea scs region between winter and summer rainfall anomalies over northern south china sea in boreal summer tend to be preceded by the same sign rainfall anomalies over southern south china sea in boreal winter denoted as in phase relation and succeeded by opposite sign rainfall anomalies over southern south china sea in the following winter denoted as out of phase relation analysis shows that the in phase relation from winter to summer occurs more often in el nino la nina decaying years and the out of phase relation from summer to winter appears more frequently in el nino la nina developing years in the summer during the el nino la nina decaying years cold warm and warm cold sea surface temperature sst anomalies develop in tropical central north pacific and the north indian ocean respectively forming an east west contrast pattern the in phase relation is associated with the influence of anomalous heating cooling over the equatorial central pacific during the mature phase of el nino la nina events that suppresses enhances precipitation over southern south china sea and the impact of the above east west sst anomaly pattern that reduces increases precipitation over northern south china sea during the following summer the impact of the east west contrast sst anomaly pattern is confirmed by numerical experiments with specified sst anomalies in the el nino la nina developing years regional air sea interactions induce cold warm sst anomalies in the equatorial western north pacific the out of phase relation is associated with a rossby wave type response to anomalous heating cooling over the equatorial central pacific during summer and the combined effect of warm cold sst anomalies in the equatorial central pacific and cold warm sst anomalies in the western north pacific during the mature phase of el nino la nina events

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

enhanced linkage between eurasian winter and spring dominant modes of atmospheric interannual variability since the early 1990s abstractthe present study reveals a marked enhancement in the relationship between eurasian winter and spring atmospheric interannual variability since the early 1990s specifically the dominant mode of winter eurasian 500 hpa geopotential height anomalies with same sign anomalies over southern europe and east asia and opposite sign anomalies over north central eurasia is largely maintained to the following spring after the early 1990s but not before the early 1990s the maintenance of the dominant atmospheric circulation anomaly pattern after the early 1990s is associated with a triple sea surface temperature sst anomaly pattern in the north atlantic that is sustained from winter to the subsequent spring this triple sst anomaly pattern triggers an atmospheric wave train over the north atlantic through eurasia during winter through spring atmospheric model experiments verify the role of the triple sst anomaly in maintaining the eurasian atmospheric circulation anomalies by contrast before the ea

shallow creep along the 1999 izmit earthquake rupture turkey from gps and high temporal resolution interferometric synthetic aperture radar data 2011 2017 characterizing the spatiotemporal evolution of creep is essential to constrain fault slip budget and understand creep mechanism studies based on interferometric synthetic aperture radar and global positioning system gps satellite observations until 2012 have shown that the central segment of the 17 august 1999 mw 7 4 izmit earthquake on the north anatolian fault began slipping aseismically following the event in the present study we combine new interferometric synthetic aperture radar time series based on terrasar x and sentinel 1a b radar images acquired over the period 2011 2017 with near field gps measurement campaigns performed every 6 months from 2014 to 2016 the mean velocity fields reveal that creep on the central segment of the 1999 izmit fault rupture continues to decay more than 19 years after the earthquake in overall agreement with models of postseismic afterslip decaying logarithmically with time for a long period of time along the fault section that experienced supershear velocity rupture during the izmit earthquake creep continues with a rate up to 8 mm year a significant transient accelerating creep is detected in december 2016 on the sentinel 1 time series near the maximum creep rate location associated with a total surface slip of 10 mm released in 1 month only additional analyses of the vertical velocity fields show a persistent subsidence on the hanging wall block of the golcuk normal fault that also ruptured during the izmit earthquake our results demonstrate that afterslip processes along the north anatolian fault east southeast of istanbul are more complex than previously proposed as they vary spatiotemporally along the fault

geochemical characterization of lithofacies and organic facies in cretaceous organic rich rocks from trinidad east venezuela basin abstract organic rich cretaceous sediments from southern trinidad show differences in hydrocarbon source potential which can be geochemically related to lithofacies and organic facies sediments which exhibit good to excellent potential for oil were deposited during the campanian through cenomanian in clastic starved environments as evidenced by the inverse relationship between hydrogen index and the parameters al2o3 toc and th u principal components analysis pca of combined toc rock eval major oxide and trace element data shows three lithofacies carbonate siliceous and clastic within samples exhibiting hydrocarbon source potential the highest petroleum potential is associated with the siliceous and carbonate lithofacies which consist of hemi pelagic sediments deposited under low oxygen conditions the clastic lithofacies have lower petroleum potential and represent nearshore sediments which have been transported to the continental slope via submarine canyons extractable saturated and aromatic hydrocarbon compositions vary with lithology pca of conventional biomarker and 2 and 3 ring aromatic hydrocarbon distributions shows that the carbonate lithofacies are characterized by an enrichment in steranes and dibenzothiophenes two organic facies can be recognized within the carbonate lithofacies that differ in their relative bundance of tricyclic terpanes gammacerane and bisnorhopane the siliceous lithofacies are characterized by an abundance of bisnorhopane 20r steranes and a slight enrichment in napthalenes relative to phenanthrenes the clastic lithofacies exhibit high hopane contents relative to steranes an enrichment in moretanes and 18 h oleanane and an enrichment in phenanthrenes relative to napthalenes

toward mapping surface deformation in three dimensions using insar 1 one of the limitations of deformation measurements made with interferometric synthetic aperture radar insar is that an interferogram only measures one component of the surface deformation in the satellite s line of sight we investigate strategies for mapping surface deformation in three dimensions by using multiple interferograms with different imaging geometries geometries for both current and future missions are evaluated and their abilities to resolve the displacement vector are compared the north component is always the most difficult to determine using data from near polar orbiting satellites however a satellite with an inclination of about 60 120 would enable all three components to be well resolved we attempt to resolve the 3d displacements for the 23 october 2002 nenana mountain alaska earthquake the north component s error is much larger than the signal but proxies for eastward and vertical motion can be determined if the north component is assumed negligible inversions of hypothetical coseismic interferograms demonstrate that earthquake model parameters can be well recovered from two interferograms acquired on ascending and descending tracks

surface displacements in the september 2005 afar rifting event from satellite image matching asymmetric uplift and faulting combining sub pixel analysis of spot4 images with insar measurements we generate 3d surface displacements for the september 2005 rifting event on the dabbahu segment in the afar valley the axis of rifting in the event is shifted to the east of the geomorphic rift the horizontal displacements reveal 6 m of extension and vertical displacements show asymmetric uplift of the flanks of the dike simple forward modelling indicates this asymmetry is due to the dike dipping 80 to the west towards the geomorphic rift the boundary between eastward and westward displacements aligns with the transition between uplift and subsidence on the east in the north part of the segment but on the west in the south normal faulting is not required on both sides of the instantaneous rift east dipping normal faulting on the west side of the instantaneous rift aligns with a west dipping normal fault in the topography

ground deformation before the 2015 eruptions of cotopaxi volcano detected by insar cotopaxi volcano started a period of volcanic unrest in april 2015 that led to a series of eruptions between august and november 2015 we use cosmo skymed interferometric synthetic aperture radar supported by continuous gps observations spanning the period of 2014 2016 to obtain time dependent ground deformation data over cotopaxi volcano related to the period of unrest and onset of eruptions we find evidence of precursory deformation with a maximum uplift on the western flank of 3 4 cm from april to august 2015 deformation is explained by an inclined sheet intrusion located a few km southwest of the summit with an opening volume of 6 8 106 m3 extending from a depth of 12 1 km and shallowing to 5 5 km below the summit that contributed to internal edifice growth the temporal coincidence of deformation prior to the eruptions potentially suggests that short term eruptions at cotopaxi are partly controlled by episodic edifice growth

changes in the relationship between northeast china summer temperature and enso 1 northeast china nec summer temperature tends to be lower higher than normal in el nino la nina developing years during 1950s through mid 1970s the relationship between the nec summer temperature and el nino southern oscillation enso is weakened or even becomes opposite in 1980s and 1990s the present study documents this interdecadal change and investigates plausible reasons for this change before the late 1970s enso affects the nec summer temperature through modulating the south asian heating and consequently the midlatitude asian circulation after the late 1970s the connection between enso and the indian summer monsoon and that between the south asian heating and the midlatitude asian circulation have been weakened this leads to a weakening of enso impacts on the nec summer temperature it is found that the nec summer temperature variations are closely related to the north atlantic sea surface temperature sst and circulation changes in 1980s and 1990s in particular a tripole north atlantic sst anomaly pattern in boreal spring is a good precursory for the nec summer temperature anomalies the nec summer temperature displays a negative correlation with the summer sst surrounding the maritime continent in 1980s and 1990s in many years the tropical north pacific and the north atlantic sst anomalies can contribute in concert to the midlatitude asian circulation changes and the nec summer temperature anomalies these effects overcome those of the central and eastern equatorial pacific sst anomalies leading to a same sign relationship between the nec summer temperature and the central and eastern equatorial pacific sst anomalies

what leads to persisting surface air temperature anomalies from winter to following spring over mid to high latitude eurasia abstractsurface air temperature sat anomalies tend to persist from winter to following spring over the mid high latitudes of eurasia the present study compares two distinct cases of eurasian sat

recent interdecadal shift in the relationship between northeast china s winter precipitation and the north atlantic and indian oceans this study documents an interdecadal change in the interannual relationship between northeast china s winter precipitation necwp and the sea surface temperature sst in the north atlantic and indian oceans in the 1990s it is revealed that the necwp shows a significant simultaneous correlation with the sst anomalies in the north atlantic sst atlantic tropical indian ocean sst indian during 1996 2013 1961 1990 generally the necwp anomaly is concurrent with apparent eurasian wave pattern during 1961 1990 whereas anomalous okhotsk high and east asia trough during 1996 2013 it is found that before the 1990s the warming sst anomalies in the tropical indian ocean could stimulate the eurasian wave pattern via inducing significant anomalous upper level convergence over the northern europe which tends to favor a positive necwp anomaly during 1996 2013 the sst indian necwp connection is disrupted instead the north atlantic tri polar sst anomaly pattern exerts a dominant impact on the necwp through triggering a stationary rossby wave that originates from the north atlantic and propagates eastward to northeast asia and further modulates the okhotsk high and east asia trough further analyses indicate that the weakened connection between the tropical sst indian anomalies and the northern ferrell circulation likely contributes to the weakening of the necwp sst indian relationship after the 1990s however the eastward shift and the enlarged anomalous magnitudes of the north atlantic oscillation might favor the strengthening of the necwp sst atlantic relationship after the mid 1990s it is therefore suggested that the strengthened variability of the sst atlantic anomalies after the 1990s might partially contribute to the intensification of the interannual variability of the necwp

pressure solution in carbonate source rocks and its control on petroleum generation and migration abstract based on detailed geochemical and petrographic studies of conventional cores of a triassic age carbonate source rock formation from three well sites at increasing maturity stages it is shown that the effects of carbonate diagenesis especially pressure solution during relatively shallow burial stages exercise major controls on the processes of petroleum generation and migration during deeper burial pressure solution leads to an internal redistribution of organic matter within this source rock formation in the form of local concentrations as solution seams and stylolites they provide very favourable conditions for effective petroleum generation and migration due to their internal structure and composition three dimensional arrangement of kerogen surrounded by carbonate cemented rims as tight seals the geochemical and petrographic effects of petroleum generation and expulsion are documented e g the expulsion of petroleum occurred as a separate phase fluid at high efficiencies 60 80 for the normal and isoprenoid alkanes and was facilitated by fractures presumably resulting from pore fluid overpressuring a five stage conceptual model is proposed to explain how the effects of pressure solution achieved during relatively shallow burial stages exercised controls on the extent and efficiency of petroleum generation and expulsion during deeper burial stages

interdecadal changes in the relationship between southern china winter spring precipitation and enso winter spring precipitation in southern china tends to be higher lower than normal in el nino la nina years during 1953 1973 the relationship between the southern china winter spring precipitation and el nino southern oscillation enso is weakened during 1974 1994 during 1953 1973 above normal southern china rainfall corresponds to warmer sea surface temperature sst in the equatorial central pacific there are two anomalous vertical circulations with ascent over the equatorial central pacific and ascent over southern china and a common branch of descent over the western north pacific that is accompanied by an anomalous lower level anticyclone during 1974 1994 above normal southern china rainfall corresponds to warmer sst in eastern south indian ocean and cooler sst in western south indian ocean two anomalous vertical circulations act to link southern china rainfall and eastern south indian ocean sst anomalies with ascent over eastern south indian ocean and southern china and a common branch of descent over the western north pacific present analysis shows that south indian ocean sst anomalies can contribute to southern china winter spring precipitation variability independently the observed change in the relationship between southern china winter spring rainfall and enso is likely related to the increased sst variability in eastern south indian ocean and the modulation of the pacific decadal oscillation

geochemical and carbon isotopic studies of crude oil destruction bitumen precipitation and sulfate reduction in the deep smackover formation abstract crude oil generated by the lower smackover source facies migrated to upper smackover reservoirs where slow thermal cracking of crude oil resulted in the formation of gas condensate and late solid bitumen ultimately only pyrobitumen methane and nonhydrocarbon gases including hydrogen sulfide persist in the deepest smackover reservoirs the carbon isotopic compositions of crude oils became heavier during crude oil destruction the carbon isotopic compositions of asphaltenes nso compounds and saturated hydrocarbons in late solid bitumen and the lower smackover source facies became isotopically lighter during crude oil destruction it is suggested that some isotopically light components from crude oils were incorporated in late solid bitumen by reactions involving thermochemical sulfate reduction thermochemical sulfate reduction and crude oil destruction occurred over a long span of geologic time at temperatures in the 120 150 c range

slip distribution of the 2015 lefkada earthquake and its implications for fault segmentation this work was partially supported by the uk natural environmental research council nerc through ne k011006 1 ne p008828 1 and the centre for the observation and modelling of earthquakes volcanoes and tectonics comet ga 13 m 031 http comet nerc ac uk

evidence for vertical movement of fluids gulf coast sedimentary basin sediments between 10 and 15 km thick have prograded approximately 400 km into the small oceanic basin which formed along the southern margin of north america subsequent to early mesozoic rifting redistribution of mass during burial diagenesis and the chemistry of present day formation waters in jurassic through pleistocene formations document local kilometer scale and in cases basin scale vertical fluid transport within the sedimentary wedge fluid flow is in part driven by porosity reduction which takes place by both physical and chemical processes during burial vertical and horizontal transport also occurs as the result of thermally and salinity generated buoyancy effects input of fluids into the sedimentary wedge from the underlying crust is predicted but not documented

formation of immature asphalt from organic rich carbonate rocks i geochemical correlation abstract the formation of low maturity asphaltic oils immature asphalts from carbonate source rocks was investigated the senonian bituminous rocks sbr in israel are organic rich carbonate rocks that were deposited in a high productivity environment and they are part of a sedimentary sequence that also contains cherts and phosphorites the sbr were studied in different basins and the samples are from outcrops and three deep drillholes the bitumen contents of the rocks are exceptionally high up to 700 mg g c org and immature asphalts are found to be associated with them geochemical analysis indicates that the bitumens are indigenous to the host sbr and the associated asphalts are bitumens that have migrated a short distance with negligible chemical fractionation the high heteroatom content of the kerogens up to 30 in the sbr is suggested as a possible cause of the generation of asphaltic oils in an early stage of maturation

the origins of petroleum in the northern gulf of mexico abstract the distribution and chemistry of oils in the northern gulf of mexico and the adjacent onshore can be explained by multiple sources fades variations maturation and post generation alteration genetic families include jurassic smackover flexure trend upper cretaceous and paleogene oils smackover oils have high sulfur contents pristane phytane ratios c 35 c 34 hopane ratios 1 0 and c 30 c 29 hopane ratios usuall 1 0 flexure trend oils are similar and contain abundant extended hopanes high sulfur contents and v ni v 0 5 these oils are inferred to be sourced in upper jurassic lower cretaceous strata upper cretaceous oils contain a distinctive suite of tricyclic and nonhopanoid triterpanes oleanane is low or absent paleogene oils can be recognized by the presence of 18 h oleanane and a lack of extended hopanes these oils occur from south texas to southern and offshore louisiana two subfamilies can be recognized based on the relative abundance of triterpanes and steranes these oils have a presumed paleogene source mixing of oil types is quite prevalent at the geographic boundaries of oil types the initial control on the distribution of oil and gas in the northern gulf of mexico is provided by the areal extent of source rocks secondary control is due to cenozoic deposition which provides the thermal stress to generate as well as destroy oil salt tectonics provide conduits for migrating fluids to escape the zone of thermal destruction mesozoic source strata again become important in the deep gulf of mexico where cenozoic sediments thin

impacts of different types of el nino and la nina on northern tropical atlantic sea surface temperature the present study investigates the dependence of the northern tropical atlantic nta sea surface temperature sst response to el nino and la nina events on the decay time and amplitude of tropical pacific sst anomalies it is found that the nta sst response to la nina events displays a notable difference between late and early decaying events similar to that in response to el nino events but with a weaker signal latent heat flux is a dominant term in the nta sst change in preceding winter early spring in both el nino and la nina events and in the difference of the nta sst anomaly between late and early decaying el nino and la nina events the zonal and meridional advections have an opposite effect on the nta sst warming in late decaying el nino events although the warming in the nta region is similar in late decaying moderate and strong el nino events the distribution of the sst anomalies in the mid latitude north atlantic ocean shows a notable difference between the two types of late decaying el nino events the sst anomalies also display difference in the early decaying weak and moderate el nino events surface heat flux differences are largely attributed to wind differences

northeast china summer temperature and north atlantic sst a previous study revealed a close relationship between interannual variations ofnortheast china nec summer temperature and a tripole sea surface temperature sst anomaly pattern in the north atlantic in preceding spring the present study investigatesthe change in the above relationship and the plausible causes for the change a tripole sstindex is defined with its positive value corresponding to positive sst anomalies in thetropics and midlatitudes and negative sst anomalies in the subtropics the tripole sstanomaly pattern has a weak correlation with nec summer temperature during the 1950sthrough the mid 1970s in sharp contrast to the 1980s and 1990s this change is related tothe difference in the persistence of the tripole sst pattern before the late 1970s thetripole sst pattern weakened from spring to summer and thus the spring north atlantictripole sst pattern had a weak connection with nec summer temperature on thecontrary after the late 1970s the tripole sst pattern displayed a tendency of persistencefrom spring to summer contributing to circulation changes that affected nec summertemperature there are two factors for the persistence of the tripole sst pattern fromspring to summer one is the north atlantic air sea interaction and the other is thepersistence of sst anomalies in the eastern equatorial pacific during the decay ofel nino southern oscillation enso it is shown that the north atlantic sst anomaliescan have an impact on nec summer temperature independent of enso

thrust faulting and 3d ground deformation of the 3 july 2015 mw 6 4 pishan china earthquake from sentinel 1a radar interferometry abstract boosted by the launch of sentinel 1a radar satellite from the european space agency esa we now have the opportunity of fast full and multiple coverage of the land based deformation field of earthquakes here we use the data to investigate a strong earthquake struck pishan western china on july 3 2015 the earthquake fault is blind and no ground break features are found on site thus synthetic aperture radar sar data give full play to its technical advantage for the recovery of coseismic deformation field by using the sentinel 1a radar data in the interferometric wide swath mode we obtain 3 tracks of insar data over the struck region and resolve the 3d ground deformation generated by the earthquake then the line of sight los insar data are inverted for the slip distribution of the seismogenic fault the final model shows that the earthquake is completely blind with pure thrust motion the maximum slip is 0 48 m at a depth of 7 km consistent with the depth estimate from seismic reflection data in particular the inverted model is also compatible with a south dipping fault ramp among a group of fault interfaces detected by the seismic reflection profile over the region the seismic moment obtained equals to a mw 6 4 earthquake the pishan earthquake ruptured the frontal part of the thrust ramps under the slik anticline and unloaded the coulomb stress of them however it may have loaded stress to the back thrust above the thrust ramps by 1 4 bar and promoted it for future failure moreover the stress loading on the west side of the earthquake fault is much larger than that on the east side indicating a higher risk for failure to the west of the zepu fault

individual and combined influences of enso and the indian ocean dipole on the indian summer monsoon the relative influences of the enso and indian ocean dipole iod events on the indian summer rainfall were studied using observational data and an atmospheric general circulation model agcm the composite analysis of rainfall anomalies demonstrates that the iod while significantly influencing the indian summer monsoon rainfall also significantly reduces the impact of enso on the indian summer rainfall whenever these events with the same phase co occur the agcm experiments have shown that during an el nino event the walker circulation over the tropical indo pacific region is modulated a low level anomalous divergence center over the western pacific and an anomalous convergence zone over the equatorial indian ocean are induced furthermore an anomalous zone of convergence over the myanmar and south china regions is induced during an el nino event these zones of anomalous convergence are complemented by anomalous divergence over the indian region causing anomalous subsidence and weakened rainfall when a strong positive iod event simultaneously occurs with el nino the latter s influence on the indian monsoon is reduced by both poles of the iod through the following mechanism an anomalous divergence center as compared to the summers when an el nino alone occurs is introduced in the eastern tropical indian ocean from this center the anomalous divergent flow crosses the equator and this air while weakening the el nino induced divergence over the western pacific also leads to convergence over the indian monsoon region this results in the reduction of the enso induced subsidence and the related rainfall deficit over the eastern flank of the indian monsoon trough region and adjoining regions to the east on the other hand over the western part of the tropical indian ocean sector part of the anomalous ascending motion from the warm pole of the positive iod event subsides just to the north of the equator moves northward ascends and causes surplus rainfall this reduces the enso induced rainfall deficit over western india the western part of the monsoon trough and parts of pakistan the agcm experiments also demonstrate that positive iod events amplify the enso induced dryness over the indonesian region

asian jet waveguide and a downstream extension of the north atlantic oscillation abstract anomalous atmospheric fields associated with the north atlantic oscillation nao are analyzed on interannual and intraseasonal time scales in order to examine the extent to which the nao is a regional phenomenon analyses on the interannual time scale reveal that the nao signal is relatively confined to the euro atlantic sector in december while it extends toward east asia and the north pacific in february the difference is most clearly seen in the meridional wind anomaly which shows a wave train along the asian jet collocated with an anomalous vorticity source near the jet entrance diagnoses using a linear barotropic model indicate that this wave train is interpreted as quasi stationary rossby waves trapped on the asian jet waveguide and effectively excited by the anomalous upper level convergence over the mediterranean sea it is found that when the nao accompanies the mediterranean convergence mc anomaly most frequently seen in february the nao indeed has a much wider horizontal str

dominant modes of interannual variability in eurasian surface air temperature during boreal spring abstractthis study investigates interannual variations of surface air temperature sat over mid and high latitudes of eurasia during boreal spring and their association with snow atmospheric circulation and sea surface temperature sst changes the leading mode of spring sat variations is featured by same sign anomalies over most regions the second mode features a tripole anomaly pattern with anomalies over the central part opposite to those over the eastern and western parts of eurasia a diagnosis of surface heat flux anomalies suggests that snow change contributes partly to sat anomalies in several regions mainly by modulating surface shortwave radiation but cannot explain sat changes in other regions atmospheric circulation anomalies play an important role in spring sat variability via wind induced heat advection and cloud induced surface radiation changes positive sat anomalies are associated with anomalous westerly winds from the north atlantic ocean or with anomalous anticyclone and souther

ice velocity determined using conventional and multiple aperture insar abstract we combine conventional interferometric synthetic aperture radar insar and multiple aperture insar mai to determine the ice surface velocity on the langjokull and hofsjokull ice caps in iceland in 1994 this approach allows the velocity of the 20 principal ice cap outlet glaciers to be fully resolved we show that mai leads to displacement estimates of finer resolution 15 versus 150 m and superior precision 5 versus 15 cm to those afforded by the alternative technique of speckle tracking using sar data acquired in ascending and descending orbits we show that ice flows within 15 of the direction of maximum surface slope across 66 of the ice caps it is therefore possible to determine ice displacement over the majority of the ice caps using a single sar image pair thereby reducing errors associated with temporal fluctuations in ice flow

monsoons and the dynamics of deserts the existence of subtropical deserts such as the sahara has often been attributed to the annual mean zonal mean hadley circulation which shows strong descent in the subtropics however the zonal mean hadley circulation shows considerable evolution over the course of the year with very strong subtropical descent during winter but practically no zonal mean subtropical descent during summer when rainfall over the eastern sahara and the mediterranean is least charney 1975 proposed a biosphere albedo feedback mechanism whereby local anthropogenic effects related to over grazing could affect the radiative balance enhancing summertime diabatic descent and leading to desertification of the subtropics in general the present study which uses an idealized model suggests a monsoon desert mechanism for desertification whereby remote diabatic heating in the asian monsoon region can induce a rossby wave pattern to the west integral with the rossby wave solution is a warm thermal structure that interacts with air on the southern flank of the mid latitude westerlies causing it to descend this adiabatic descent is localized over the eastern sahara and mediterranean and over the kyzylkum desert to the south east of the aral sea by the mountains of north africa and south west asia trajectories indicate that the monsoon desert mechanism does not represent a simple walker type overturning cell instead the descending air is seen to be mainly of mid latitude origin it is speculated that the monsoon forced adiabatic descent may result in clear air and therefore a local diabatic enhancement which effectively doubles the strength of descent with this mechanism desertification can be forced by remote changes in monsoon strength rather than by local effects this conclusion is supported by the observed dramatic strengthening of descent over the mediterranean and east sahara during the onset of the asian monsoon and on the longer timescale by relating prehistoric lake levels to milankovitch monsoon forcing the latter may help to explain the perceived discrepancies between the palaeoclimate of the eastern sahara and the strength of a tropic wide monsoon the monsoon desert mechanism may not be confined to the asian monsoon alone and the existence of other monsoon climate regions over the globe may in a similar way explain the observed summertime strengthening of the oceanic sub tropical anticyclones and the existence of western continental deserts and mediterranean type climate regions

source model for the mw 6 7 23 october 2002 nenana mountain earthquake alaska from insar 1 the 23 october 2002 nenana mountain earthquake mw 6 7 occurred on the denali fault alaska to the west of the mw 7 9 denali earthquake that ruptured the same fault 11 days later we used 6 interferograms constructed using radar images from the canadian radarsat 1 and european ers 2 satellites to determine the coseismic surface deformation and a source model data were acquired on ascending and descending satellite passes with incidence angles between 23 and 45 degrees and time intervals of 72 days or less modeling the event as dislocations in an elastic half space suggests that there was nearly 0 9 m of right lateral strike slip motion at depth on a near vertical fault and that the maximum slip in the top 4 km of crust was less than 0 2 m the nenana mountain earthquake increased the coulomb stress at the future hypocenter of the 3 november 2002 denali earthquake by 30 60 kpa

radar interferometry and its application to changes in the earth s surface geophysical applications of radar interferometry to measure changes in the earth s surface have exploded in the early 1990s this new geodetic technique calculates the interference pattern caused by the difference in phase between two images acquired by a spaceborne synthetic aperture radar at two distinct times the resulting interferogram is a contour map of the change in distance between the ground and the radar instrument these maps provide an unsurpassed spatial sampling density 100 pixels km 2 a competitive precision 1 cm and a useful observation cadence 1 pass month 1 they record movements in the crust perturbations in the atmosphere dielectric modifications in the soil and relief in the topography they are also sensitive to technical effects such as relative variations in the radar s trajectory or variations in its frequency standard we describe how all these phenomena contribute to an interferogram then a practical summary explains the techniques for calculating and manipulating interferograms from various radar instruments including the four satellites currently in orbit ers 1 ers 2 jers 1 and radarsat the next chapter suggests some guidelines for interpreting an interferogram as a geophysical measurement respecting the limits of the technique assessing its uncertainty recognizing artifacts and discriminating different types of signal we then review the geophysical applications published to date most of which study deformation related to earthquakes volcanoes and glaciers using ers 1 data we also show examples of monitoring natural hazards and environmental alterations related to landslides subsidence and agriculture in addition we consider subtler geophysical signals such as postseismic relaxation tidal loading of coastal areas and interseismic strain accumulation we conclude with our perspectives on the future of radar interferometry the objective of the review is for the reader to develop the physical understanding necessary to calculate an interferogram and the geophysical intuition necessary to interpret it

interseismic coupling and refined earthquake potential on the hayward calaveras fault zone interseismic strain accumulation and fault creep is usually estimated from gps and alignment arrays data which provide precise but spatially sparse measurements here we use interferometric synthetic aperture radar to resolve the interseismic deformation associated with the hayward and calaveras faults hf and cf in the east san francisco bay area the large 1992 2011 sar data set permits evaluation of short and long wavelength deformation larger than 2 mm yr without alignment of the velocity field to a gps based model our time series approach in which the interferogram selection is based on the spatial coherence enables deformation mapping in vegetated areas and leads to refined estimates of along fault surface creep rates creep rates vary from 0 2 mm yr on the northern cf to 14 2 mm yr on the central cf south of the hf surface junction we estimate the long term slip rates by inverting the long wavelength deformation and the distribution of shallow slip due to creep by inverting the remaining velocity field this distribution of slip reveals the locations of locked and slowly creeping patches with potential for a m6 8 0 3 on the hf near san leandro a m6 6 0 2 on the northern cf near dublin a m6 5 0 1 on the hf south of fremont and a m6 2 0 2 on the central cf near morgan hill with cascading multisegment ruptures the hf rupturing from berkeley to the cf junction could produce a m6 9 0 1 the northern cf a m6 6 0 1 the central cf a m6 9 0 2 from the junction to gilroy and a joint rupture of the hf and central cf could produce a m7 1 0 1

deformation during the 12 november 1999 duzce turkey earthquake from gps and insar data only 87 days after the mw 7 5 17 august 1999 izmit earthquake the duzce earthquake ruptured a ca 40 km long adjoining strand of the north anatolian fault naf system to the east we used displacements of 50 global positioning system gps sites together with interferometric synthetic aperture radar insar range change data spanning the event to estimate the geometry and slip distribution of the coseismic rupture postseismic deformation transients from the duzce earth quake and the preceding i zmit event that are included in some of the measurements are corrected for using dislocation models fit to gps data spanning the various time periods nonlinear inversions for fault geometry indicate that the rupture occurred on a ca 54 north dipping oblique normal right lateral fault distributed slip inver sions indicate maximum strike slip near the center of the duzce fault close to the earthquake hypocenter slip magnitude and depth of faulting decrease to the west and east of the hypocenter both gps and insar data suggest that normal slip is restricted to the shallow portion of the rupture the duzce earthquake had the highest slip to rupture length ratio of any historic earthquake along the naf

observed positive feedback between the nao and the north atlantic ssta tripole 1 ncep ncar reanalysis data from 1948 to 2001 are used to examine the relationship between the north atlantic oscillation nao and the north atlantic sea surface temperature anomaly ssta tripole it is demonstrated that the atmospheric anomalies associated with nao produce tripole like sea surface temperature sst anomalies in turn the ssta tripole produces nao like atmospheric anomalies therefore a positive feedback between the nao and the ssta tripole is suggested the results are statistically significant they clarify prior uncertainties associated with the relationship between the nao and the north atlantic ssta tripole

impacts of early autumn arctic sea ice concentration on subsequent spring eurasian surface air temperature variations this study reveals a close relation between autumn arctic sea ice change sic in the laptev sea eastern siberian sea beaufort sea and subsequent spring eurasian surface air temperature sat variation specifically more less sic over the above regions in early autumn generally correspond to sat warming cooling over the mid high latitudes of eurasia during subsequent spring early autumn arctic sic affects spring eurasian sat via modulating spring arctic oscillation ao associated atmospheric changes the meridional temperature gradient over the mid high latitudes decreases following the arctic sea ice loss this results in deceleration of prevailing westerly winds over the mid latitudes of the troposphere which leads to increase in the upward propagation of planetary waves and associated eliassen palm flux convergence in the stratosphere over the mid high latitudes thereby westerly winds in the stratosphere are reduced and the polar vortex is weakened through the wave mean flow interaction and downward propagation of zonal wind anomalies a negative spring ao pattern is formed in the troposphere which favors sat cooling over eurasia the observed autumn arctic sic spring eurasian sat connection is reproduced in the historical simulation 1850 2005 of the flexible global ocean atmosphere land system model spectral version 2 fgoals s2 the fgoals s2 also simulates the close connection between autumn sic and subsequent spring ao further analysis suggests that the prediction skill of the spring eurasian sat was enhanced when taking the autumn arctic sic signal into account

gas souring by thermochemical sulfate reduction at 140 c discussion 814 the subject of the article gas souring by thermochemical sulfate reduction at 140 c by worden et al 1995 is closely related to our recent research we examined the origin of h2s and other organic sulfur compounds osc in produced gas from gas condensate filled stari gradac field in the drava depression in croatia based on results of numerous conventional and specific analyses of reservoir rocks gas condensate and formation water and data from fluid composition monitoring over a long period of time we concluded that sulfur compounds in the stari gradac reservoir permian triassic depths greater than 3700 m were formed by thermochemical reduction mechanism of sulfate rock anhydrite in the presence of

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

synthetic aperture radar interferometry to measure earth s surface topography and its deformation synthetic aperture radar interferometry insar from earth orbiting spacecraft provides a new tool to map global topography and deformation of the earth s surface radar images taken from slightly different viewing directions allow the construction of digital elevation models of meter scale accuracy these data sets aid in the analysis and interpretation of tectonic and volcanic landscapes if the earth s surface deformed between two radar image acquisitions a map of the surface dis placement with tens of meters resolution and subcentimeter accuracy can be con structed this review gives a basic overview of insar for earth scientists and presents a selection of geologic applications that demonstrate the unique capabilities of insar for mapping the topography and deformation of the earth

the interrelationship between temperature changes in the free atmosphere and sea surface temperature changes fields of sea surface temperature anomalies from the global ocean surface temperature atlas gosta and microwave sounding measurements msu of temperature in the troposphere are examined separately and together for the 1979 1988 period global correlation patterns of both sets of fields are investigated at a range of leads and lags up to 6 months and exhibit a wide range of correlation structure there are regions such as the tropical eastern pacific where sea surface temperature anomalies persist for several months and are associated with local air temperature anomalies in this particular example about 0 7 c air temperature change is associated with a 1 0 c sea temperature change by contrast some ocean regions and many atmospheric regions mostly in middle and high latitude show only local spatial correlations that disappear completely in a month or two the most persistent and extensive spatial correlation patterns are quite different for the sea and the air in the sea the butterfly pattern of the pacific is the most important and reverses sign between the eastern equatorial pacific and the western pacific and subtropics in the warm phase the temperature anomalies associated with this pattern are similar to the correlation pattern for the atmosphere the main correlation pattern is an equatorial belt with no sign changes in the tropics this pattern is linked to the oceanic el nino mode in the warm phase the temperature anomalies show peak values on both sides of the equator in the eastern and central pacific based mainly on the results from the spatial patterns certain regions are selected for intercomparison of time series in the tropical eastern pacific the sea leads the air by about a month while in the gulf stream and kuroshio regions the sequence is reversed

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

james limestone northeastern gulf of mexico refound opportunity in a lower cretaceous trend recent offshore exploratory success has focused industry interest on porous lower cretaceous carbonates of the james limestone in the eastern gulf of mexico the current offshore play targets the interior james platform trend in the viosca knoll and mobile areas south of mississippi and alabama where water depths are 30 60 m 98 197 ft james reservoirs in this area consist mainly of patch reef debris halos and interior platform grainstone facies at drilling depths of 4358 4632 m 14 300 15 200 ft these facies comprise a belt parallel to but up to 25 km 15 5 mi behind updip from the james shelf margin diagenetic alteration including dolomitization and dissolution of original calcite grains and cement cause porosities of 8 19 and permeabilities in the range of 20 30 md to date seven fields have been discovered individual wells in these fields have been completed at rates ranging from 10 39 mmcfgd and have produced as much as 15 9 bcf in less than 3 yr the new play represents an extension into the offshore of scattered older production in the james that occurs from east texas to southern mississippi when combined with the onshore part of the play the new success in the james suggests that significant regional potential still exists in many areas of the northern and northeastern gulf scott l montgomery is a petroleum consultant and author he received his b a degree in english from knox college in 1973 and his m s degree in geological sciences from cornell university in 1978 he is widely published in the geosciences and since 1996 has been principal author of the e p notes series in the aapg bulletin his other publications include seven books on topics in petroleum geology science education and the history of science plus articles and monographs related to frontier plays new technologies field studies and reservoir characterization andrew j petty is currently a geologist with the minerals management service mms in new orleans louisiana he joined the mms in 1979 where he worked in the rate control section served as the corpus christi district geologist and is now with the regional analysis unit andy received his b s degree in geology from stephen f austin state university in 1973 and his m s degree in geology from the university of texas at el paso in 1975 paul j post is a geologist with the minerals management service mms in new orleans louisiana he has more than 30 years of diverse exploration experience in an array of united states and international basins with major and independent companies as a consultant and with mms his primary technical expertise is in regional synthesis new venture play development and prospect evaluation basin analysis basin modeling economic analysis and risk assessment paul has a b s degree in geology from virginia polytechnic institute

migration of crude oil from the smackover source rock to jurassic and cretaceous reservoirs of the northern gulf rim abstract migration of distinctive crude oils from the upper jurassic smackover source rock across the northern gulf rim began at various times during the cretaceous regional source rock differences resulted in two compositional subfamilies of smackover crude oils type i crude oils in upper smackover reservoirs of east texas arkansas louisiana and mississippi reflect an origin from algal derived kerogen deposited in an anoxic environment type ii crude oils in upper smackover reservoirs of alabama and florida reflected an origin from kerogen preserved in a less anoxic environment with a terrestrial component comparison of molecular and carbon isotopic compositions of crude oils suggests that vertical migration of type i smackover crude oils charged many overlying upper jurassic lower cretaceous and upper cretaceous reservoirs some lateral migration to cretaceous reservoirs north of the updip limit of the smackover formation also occurred both type i smackover crude oils and geochemically dissimilar cretaceous sourced oils are found in upper cretaceous tuscaloosa and woodbine reservoirs because of impermeable barriers to migration especially in alabama vertical migration of type ii crude oils was less significant

the signature of enso in global temperature and precipitation fields derived from the microwave sounding unit abstract global temperature anomalies associated with enso are investigated making use of a 13 year record of gridded temperature and precipitation data from the microwave sounding unit msu the warm phase of the enso cycle during this period was characterized by an overall warming of the tropical troposphere superimposed upon a distinctive equatorially symmetric dumbbell shaped pattern straddling the equator near 140 w accompanied by negative anomalies along the equator over the western pacific by means of singular value decomposition svd analysis it is shown that this pattern fluctuated in phase with the displacements of convective activity over the equatorial pacific as reflected in the anomalies in outgoing longwave radiation olr and msu precipitation fields fluctuations in mean tropical tropospheric temperature lagged the olr anomalies and the related temperature pattern by about 3 months the same dumbbell shaped pattern was evident with reversed polarity in the lower stratosphere tog

distribution of hydrocarbon source potential in the jurassic smackover formation abstract there are regionally consistent differences in source potential between the upper and lower members of the smackover formation measurements of total organic carbon and visual kerogen assessments indicate that the lower smackover has source potential for crude oil from texas to florida source potential is largely restricted to the laminated lime mudstone facies of the lower smackover where deposition occurred in a subtidal environment that was anoxic and probably hypersaline algal derived amorphous kerogen is concentrated in laminations of depositional origin carbonate diagenesis during burial enhanced source potential by further concentrating kerogen along stylolites we suggest that the efficiency of hydrocarbon expulsion has been enhanced by depositional and diagenetic factors that concentrate source rock kerogen along conduits for fluid movement the upper smackover serves mainly as a reservoir rock and other jurassic formations lack source potential

relative contribution of enso and east asian winter monsoon to the south china sea sst anomalies during enso decaying years present study investigates respective contributions of el nino southern oscillation enso and east asian winter monsoon eawm to two periods of sea surface temperature sst anomalies in the south china sea scs one subsequent to the enso mature phase and the other in the following summer during 1982 2010 it is found that the sst anomalies in the first period are related to the eawm and the enso impact independent of eawm is weak which differs from previous studies the sst anomalies in the second period are mainly due to the enso effect a heat budget analysis shows that changes in shortwave radiation and wind related surface latent heat flux as well as horizontal advections are the processes leading to the eawm related sst anomalies in the first period the enso related sst anomalies in the second period are contributed by shortwave radiation and latent heat flux anomalies as well as meridional advection and vertical upwelling processes near the southeast coast of indochina peninsula the enso contribution to the scs sst anomalies in the first period is larger before than after the late 1970s this is attributed to an earlier development of enso events that is followed by larger equatorial central and eastern pacific sst anomalies in boreal summer and subsequently larger north indian ocean sst anomalies around october consequently anomalous surface anticyclone over the scs is stronger leading to larger surface heat flux anomalies and thus a larger sst increase around october before than after the late 1970s

a comparison of decadal climate oscillations in the north atlantic detected in observations and a coupled gcm abstract decadal climate variations in the atlantic ocean found in observational fields and a coupled general circulation model cgcm are investigated in particular physical processes responsible for the phase reversal are compared observed and modeled decadal variations have dominant periodicities around 12 3 and 9 9 yr respectively both variations show similar spatial features sea surface temperature sst anomalies in the western subtropical atlantic sandwiched by those with opposite sign to the north and south and a dipole of sea level pressure anomalies which resemble the north atlantic oscillation their temporal evolutions are however different from each other suggestive of different dynamics of the oscillation in the observations sst and surface layer 0 100 m temperature anomalies move eastward from the subtropical western atlantic to the european coast along the gulf stream northward propagation of sst anomalies are also found along the western boundaries including the gulf of me

observed relationship of spring and summer east asian rainfall with winter and spring eurasian snow abstract this study investigates the relationship between spring and summer rainfall in east asia and the preceding winter and spring snow cover depth over eurasia using station rainfall observations satellite observed snow cover satellite derived snow water equivalent and station observations of the number of days of snow cover and snow depth correlation analysis shows that snow depth anomalies can persist from winter to spring whereas snow cover anomalies cannot in most regions of eurasia locally snow cover and snow depth anomalies in february are not related in most regions to the north of 50 n but those anomalies in april display consistent year to year variations the results suggest that the winter snow cover cannot properly represent all the effects of snow and it is necessary to separate the winter and spring snow cover in addressing the snow monsoon relationship spring snow cover in western siberia is positively correlated with spring rainfall in southern china the circulation anomalies

sterane and triterpane patterns as diagnostic tools in the mapping of oils condensates and source rocks of the gulf of mexico region abstract four hundred and eighty one gulf of mexico oils and condensates can be subdivided into nine major families based on their sterane m z 217 218 and triterpane m z 191 177 biomarker mass chromatogram patterns these families are 1 carbonate sourced oils reservoired in jurassic cretaceous reservoirs onshore and plio pleistocene reservoirs offshore 2 austin chalk reservoired oils 3 tuscaloosa oils 4 wilcox reservoired oils la 5 south texas palaeogene reservoired oils 6 mississippi delta oils 7 post mature oils of uncertain affinities 8 migration contaminated oils showing attributes of a mixing of immature and post mature sources and 9 oils and condensates lacking biomarkers each oil family is concentrated in specific age defined producing trends ranging in age from jurassic to pleistocene for tertiary reservoirs these producing trends shift geographically with time in a manner analogous to the clockwise migrating cenozoic depocenter model for the northern gulf of mexico at least six ages of marine source rock deposition may be implicated in the genesis of these oils 1 the kimmeridgian oxfordian including smackover and norphlet formations 2 the aptian including pine island bexar and sunniland formations 3 the albian paluxy formation 4 the cenomanian turonian including eagle ford and tuscaloosa formations 5 the coniacian santonian eagle ford and austin chalk and 6 the palaeocene wilcox midway sparta formations the jurassic and cretaceous source rocks correspond to described oceanic anoxic events of probable global significance this paper will concentrate on describing the biomarker patterns of the oils and postulated source rocks but due to reasons of space isotopic elemental and other data will only be briefly discussed

the influence of boreal spring arctic oscillation on the subsequent winter enso in cmip5 models this study examines the influence of boreal spring arctic oscillation ao on the subsequent winter el nino southern oscillation enso using 15 climate model outputs from the coupled model intercomparison project phase 5 cmip5 results show that out of the 15 cmip5 models ccsm4 and cnrm cm5 can well reproduce the significant ao enso connection these two models capture the observed spring ao related anomalous cyclone anticyclone over the subtropical western central north pacific and westerly easterly winds over the tropical western central pacific in contrast the spring ao related anomalous circulation over the subtropical north pacific is insignificant in the other 13 models and the simulations in these models cannot capture the significant influence of the spring ao on enso further analyses indicate that the performance of the cmip5 simulations in reproducing the ao enso connection is related to the ability in simulating the spring north pacific synoptic eddy intensity and the spring ao s pacific component strong synoptic scale eddy intensity results in a strong synoptic eddy feedback on the mean flow leading to strong cyclonic circulation anomalies over the subtropical north pacific which contributes to a significant ao enso connection in addition a strong spring ao s pacific component and associated easterly wind anomalies to its south may provide more favorable conditions for the development of spring ao related cyclonic circulation anomalies over the subtropical north pacific

on the role of sea surface temperature gradients in forcing low level winds and convergence in the tropics abstract we examine the importance of pressure gradients due to surface temperature gradients to low level p 700 mb flow and convergence in the tropics over time scales 1 month the latter plays a crucial role in determining the distribution of cumulonimbus convection and rainfall our approach is to consider a simple one layer model of the trade cumulus boundary layer wherein surface temperature gradients are mixed vertically consistent with ecmwf analyzed data the top of the layer is taken at 700 mb the influence from higher levels is intentionally suppressed by setting horizontal pressure gradients and frictional stresses to zero at the top of the layer horizontal convergence within the layer is taken up by cumulonimbus mass flux however the development of the cumulonimbus mass flux is associated with a short relaxation time o hr roughly the development time for such convection during this short time horizontal convergence acts to redistribute mass so as to reduce horizontal pressur

enrichment of diamondoids and 13c in condensate from hudson canyon us atlantic abstract gas condensate migrated vertically to upper jurassic and lower cretaceous reservoir rocks in the hudson canyon hc area of the baltimore canyon trough us atlantic condensate samples are enriched in diamondoids 4742 4774 ppm and 13c 13c 23 7 to 24 6 pdb several lines of evidence suggest that the main source rock is within the middle to lower jurassic section of hudson canyon condensates from hudson canyon are similar to condensates generated by the upper jurassic smackover formation of the us gulf coast a laminated lime mudstone with shale facies the petrologic fabric of the lime mudstone favors early generation of diamondoids hydrogen rich kerogen and clay catalysts are concentrated within thin laminations of depositional origin separated by thicker barren carbonate layers

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

fault slip distribution of the 1999 mw 7 1 hector mine california earthquake estimated from satellite radar and gps measurements we use a combination of satellite radar and gps data to estimate the slip distribution of the 1999 m w 7 1 hector mine earthquake a right lateral strikeslip earthquake that occurred on a northwest southeast striking fault in the southern california mojave desert the data include synthetic aperture radar interferograms insar from both ascending and descending orbits radar amplitude image offset fields sario for both ascending and descending azimuth directions and campaign gps observations from 55 stations provided by agnew et al 2002 we model the fault with nine segments derived from the field mapped fault rupture the sario data and aftershock locations we first estimate the dip of each fault segment as well as a single constant strike slip component across each segment resulting in an average dip of 83 to the northeast and slip of up to 5 6 m then we fix the optimal fault segment dip discretize the fault segments into 1 5 km 1 5 km patches and solve for the variable slip distribution using a nonnegative least squares method that includes an appropriate degree of smoothing our preferred solution has both right lateral strike slip and reverse faulting the estimated geodetic moment is 5 93 10 19 n m m w 7 1 similar to seismological estimates indicating that there are insignificant interseismic and postseismic deformation signals in the data we find strike slip displacements of up to 6 0 m and reverse faulting of up to 1 6 m with the maximum slip located just northwest of the epicenter most of the slip is concentrated northwest and south of the epicenter little slip is found on the northeastern branch of the fault the sario data and our modeling indicate that the amount and extent of surface fault rupture were underestimated in the field

geodetic observations of postseismic creep in the decade after the 1999 izmit earthquake turkey implications for a shallow slip deficit the relationship between aseismic slip and tectonic loading is important for understanding both the pattern of strain accumulation along a fault and its ability to generate large earthquakes we investigate the spatial distribution and temporal evolution of aseismic creep on the western north anatolian fault naf using time series analysis of envisat interferometric synthetic aperture radar insar data covering the full extent of the 1999 izmit and duzce earthquake ruptures and spanning 2002 2010 discontinuities in the line of sight velocity across the fault imply that fault creep reaches the earth s surface at an average fault parallel rate of 5 mm yr along an 80 km section of the naf by combining insar and published gps velocities we are able to extract the vertical and east west components of motion and show that the adapazari basin is subsiding at a rate of 6 mm yr vertical motions have biased previous estimates of creep in this region the displacement time series close to the fault is consistent with an afterslip model based on rate and state friction which predicts a rapid deceleration in fault creep rate after the izmit earthquake to a near steady state 5 mm yr after 5 years projecting our model 200 years into the future we find that the cumulative displacement of 1 1 3 m is insufficient to account for the shallow coseismic slip deficit observed in previous studies distributed off fault deformation in the shallow crust or transient episodes of faster slip are likely required to release some of the long term strain during the earthquake cycle

global climate variations connected with sea surface temperature anomalies in the eastern equatorial pacific ocean for the 1958 73 period abstract the sea surface temperature anomalies in the eastern equatorial pacific ocean are shown to demarcate a key region new 130 w for observed variations in the global general circulation various techniques are used to describe global conditions during warm and cold sea surface conditions in the key region based on a global 15 year set of surface and upper air analyses earlier work is confirmed that during warm episodes 1 the westerly jets in both hemispheres are strengthened and 2 some of the semi permanent circulation features such as the intertropical convergence zone the subtropical high over the western and central pacific and the aleutian low increase in strength and vice versa for cold episodes the time series of monthly mean atmospheric temperature averaged over the entire man of the northern hemisphere is found to be highly correlated with the sea surface temperature anomalies in the key region the highest correlation of r 0 65 is found when the atmosphere lags the ocean by 6 m

the ratios of dibenzothiophene to phenanthrene and pristane to phytane as indicators of depositional environment and lithology of petroleum source rocks abstract the ratio of dibenzothiophene to phenanthrene and the ratio of pristane to phytane when coupled together provide a novel and convenient way to infer crude oil source rock depositional environments and lithologies such knowledge can significantly assist in identifying the source formation s in a basin thereby providing valuable guidance for further exploration the ability to infer this information from analysis of a crude oil is especially valuable as frequently the earliest samples in a new area may be shows and or drill stem test samples from exploratory wells which are characteristically drilled on structural highs stratigraphically remote from the source formation s a cross plot of dibenzothiophene phenanthrene versus the pristane phytane ratios measured on seventy five crude oils from forty one known source rocks ranging in age from ordovician to miocene consistently classified the oils into the following environment lithology groups marine carbonate marine carbonate mixed and lacustrine sulfate rich lacustrine sulfate poor marine and lacustrine shale and fluvial deltaic carbonaceous shale and coal the dibenzothiophene phenanthrene ratio alone is an excellent indicator of source rock lithology with carbonates having ratios 1 and shales having ratios the dibenzothiophene to phenanthrene and the pristane to phytane ratios can also be used to classify source rock paleodepositional environments the classification scheme is based on the premise that these ratios reflect the different eh ph regimes resulting from the significant microbiological and chemical processes occurring during deposition and early diagenesis of sediments the dibenzothiophene phenanthrene ratio assesses the availability of reduced sulfur for incorporation into organic matter and the pristane phytane ratio assesses the redox conditions within the depositional environment interpretation of these ratios has been aided by quantitative biomarker analysis and by carbon isotope data for pristane and phytane obtained by gas chromatography isotope ratio mass spectrometry

migration of hydrocarbons in carbonate source rocks of the stasfurt member ca2 of the permian zechstein borehole aue 1 germany the role of solution seams abstract the effects of petroleum migration from carbonate source rocks through preferential expulsion of hydrocarbons from stylolites is investigated this type of expulsion is associated with compositional fractionation saturated hydrocarbons and nso compounds are expelled preferentially pristane and phytane show higher relative expulsion efficiencies than n c 17 and n c 18 alkanes aromatic hydrocarbons especially trimethylnaphthalenes are fractionated by the expulsion processes triterpanes and steranes are not fractionated by expulsion from solution seams and could be valuable tools for oil source rock correlation in carbonate rocks

the complete 3 d surface displacement field in the epicentral area of the 1999 mw7 1 hector mine earthquake california from space geodetic observations we use interferometric synthetic aperture radar insar data to derive continuous maps for three orthogonal components of the co seismic surface displacement field due to the 1999 m w7 1 hector mine earthquake in southern california vertical and horizontal displacements are both predominantly antisymmetric with respect to the fault plane consistent with predictions of linear elastic models of deformation for a strike slip fault some deviations from symmetry apparent in the surface displacement data may result from complexity in the fault geometry

impact of the atlantic multidecadal oscillation on the asian summer monsoon 1 the impact of the atlantic multidecadal oscillation amo on the asian summer monsoon is investigated using a coupled atmosphere ocean global general circulation model by imposing the amo associated sea surface temperature anomalies in the atlantic as boundary forcing and allowing atmosphere ocean interactions outside the atlantic the positive amo phase characterized by anomalous warm north atlantic and cold south atlantic leads to strong southeast and east asian summer monsoons and late withdrawal of the indian summer monsoon these changes of monsoons are mainly through coupled atmosphere ocean feedbacks in the western pacific and indian oceans and tropospheric temperature changes over eurasia in response to the imposed forcing in the atlantic the results are in agreement with the observed climate changes in china corresponded to the amo phases they suggest a non local mechanism for the asian summer monsoon variability and provide an alternative view to understanding its interdecadal variation during the twentieth century citation lu r b dong and h ding 2006 impact of the atlantic multidecadal oscillation on the asian summer monsoon geophys res lett 33 l24701 doi 10 1029 2006gl027655

impacts of enso on multi scale variations in sediment discharge from the pearl river to the south china sea abstract sediment load delivered by rivers is an important terrestrial factor in the evolution and productivity of coastal ecosystems and coastal morphology as the strongest interannual climate signal the el nino southern oscillation enso is closely related to variations in the hydrological cycle at global and regional scales however the influence of enso on temporal variations in sediment discharge is poorly understood in this paper we examine periodic variations in sediment discharge to the south china sea from the pearl river since the 1950s using wavelet transform analysis wt furthermore we apply cross wavelet spectrum xwt and wavelet coherence wtc to investigate the linkages between enso and sediment variability the wt results revealed that periodic oscillations in sediment discharge in the pearl river occurred annually 1 yr before the 2000s interannually 2 8 yr from 1960 2002 and decadally 10 16 yr from 1975 1995 these periodic variations in the sediment load series had common spectrum power with the water discharge and precipitation series indicating an important climatic control the xwt and wtc results revealed significant impacts of enso on precipitation water discharge and sediment load at interannual time scales of 2 4 6 yr from 1960 2002 with a shift of patterns of enso on sediment variability after the 1970s in addition an in phase relation between sediment discharge and enso at time scales of 10 16 yr from 1975 1995 was detected indicating that variations at decadal scales could be related to other climatic teleconnections such as the pacific decadal oscillation compared with the spectrum structures of periodic variations in precipitation and water discharge and their relationship with enso there was a loss of energy in the sediment load at annual time scales after 2002 that can be attributed to dam construction in the river basin our study provides perspectives on the connections between enso and sediment variability at different time scales which is of practical and scientific importance for forecasting global hydrological processes and for river management

interdecadal changes in the relationship between interannual variations of spring north atlantic sst and eurasian surface air temperature abstractthis study investigates interdecadal changes in the relationship between interannual variations of boreal spring sea surface temperature sst in the north atlantic and surface air temperature sat over the mid to high latitudes of eurasia during 1948 2014 analyses show that the connection between the spring north atlantic tripole sst anomaly pattern and the eurasian sat anomalies has experienced marked interdecadal shifts around the early 1970s and mid 1990s the connection is strong during 1954 72 and 1996 2014 but weak during 1973 91 a diagnosis indicates that interdecadal changes in the connection between the north atlantic sst and eurasian sat variations are associated with changes in atmospheric circulation anomalies over eurasia induced by the north atlantic tripole sst anomaly pattern further analyses suggest that changes in atmospheric circulation anomalies over eurasia are related to changes in the position of atmospheric heating anomalies over the north atlantic which may be due to

a strengthened influence of enso on august high temperature extremes over the southern yangtze river valley since the late 1980s abstractthe present study investigates the decadal change in the relationship between china high temperature extremes htes and el nino southern oscillation enso it is found that the relationship between the august htes in the southern yangtze river valley syrv and enso has strengthened since the late 1980s before the late 1980s the relationship is weak whereas after the late 1980s the august hot day numbers in the syrv region tend to be more than normal during el nino decaying years during 1988 2008 el nino induced august warm sst anomalies are mainly located in the eastern tropical and north indian ocean as a response to the north indian ocean warming the south asia high extends eastward and the syrv is overlain by upper level easterly anomalies the cold horizontal temperature advection induced by upper level easterly anomalies leads to anomalous descent which is conducive to the occurrence of htes through adiabatic warming during 1966 86 el nino induced august warm sst anomalies are

change in the contribution of spring snow cover and remote oceans to summer air temperature anomaly over northeast china around 1990 sea surface temperature sst snow cover and soil moisture anomalies are factors for climate variability over land regions the present study found that the relationship between in situ spring snow cover and northeast china summer surface temperature variations is not steady it is significant during mid 1970s through late 1980s but weak during the 1990s and 2000s this interdecadal change in the spring snow cover summer temperature relationship is found to relate to the effects of sst anomalies in the tropical indian ocean and western pacific regions during the recent decades these sst anomalies induce a meridional circulation pattern along the east asian coast the remote sst forcing induced circulation and precipitation anomalies overcome local snow cover induced soil moisture anomalies and thus disrupt the spring snow cover summer temperature connection during the recent decades the present study indicated that both the north atlantic sst anomaly pattern and local spring snow cover anomalies contribute to northeast china summer temperature variations during mid 1970s through late 1980s during the 1990s and 2000s the influence of the north atlantic sst anomalies is weakened and the sst anomaly in the tropical indo western pacific region is a major player in northeast china summer temperature variations

some optical characteristics of solid bitumen in visual kerogen preparations solid bitumen probably derived from liquid hydrocarbon can be identified in visual kerogen strewn slides or palynology slides this kind of material may have been previously identified as amorphous or structured kerogen organic matter in most petroleum source rocks is too dispersed to be studied in situ therefore it is isolated from the mineral matrix and concentrated to make strewn slides for optical study both insoluble and soluble bitumen may be observed in visual kerogen slides when no solvent extraction is used during sample preparation examination of a series of samples prepared both as thin sections and visual kerogen strewn slides led to the observation of solid bitumen in the strewn slides when an organic petrographer sees solid bitumen particles in visual kerogen slides they may be classified as either woody herbaceous coaly or most often amorphous kerogen types thompson and dembicki 1986 describe four kinds of amorphous kerogens optically and relate them to source rock hydrocarbon generating potential a fifth kind of amorphous kerogen is documented in this paper this material appears through the microscope as thin smooth brown flakes in transmitted light with a white to grey color in reflected light some of the particles appear to have the structure of the space between mineral grains where they form at this time it is not possible to identify the exact mode of origin of this material such as thermal alteration of oil gas deasphalting of oils or water washing and biodegradation of oils however the homogenous flowed appearance implies a liquid hydrocarbon origin therefore it is suggested that this kind of kerogen be called solid bitumen the petrographic documentation of solid bitumen in visual kerogen strewn slides can be very meaningful to organic geochemists and geologists because it may indicate that liquid hydrocarbons have been generated in or migrated through the rock interval of interest further study is needed to optically characterize the various stages of maturation of solid bitumen in visual kerogen preparations

source parameters of the 1 october 1995 dinar turkey earthquake from sar interferometry and seismic bodywave modelling abstract the 1 october 1995 m s 6 1 dinar earthquake ruptured a 10 km section of the nw se dinar civril fault there are discrepancies between the published source parameters from seismic data with seismic moments in disagreement by over a factor of two we use both sar interferometry and seismic bodywave modelling to determine earthquake source parameters an interferogram generated from ers 1 2 sar imagery spanning the event and separated by 5 months is used to derive source parameters by a downhill simplex inversion with multiple monte carlo restarts we model the displacements in the satellite line of sight initially using uniform slip on a rectangular dislocation in an elastic half space the resultant model fault plane agrees in strike and location with the observed surface break but systematic residuals exist in the line of sight deformation field resulting in a r m s residual of 20 mm in the interferogram the residuals are reduced if the depth distribution of slip is allowed to vary spatially in four segments along a continuous fault plane our best fitting solution with a r m s misfit of 8 mm reveals two distinct areas of slip on the fault plane strike 145 dip 49 rake 270 a main rupture slipping by 1 44 m between depths of 1 and 8 km becoming deeper to the se and matching the observed surface rupture and an along strike continuation to the nw of the same fault plane but between depths of 8 and 13 km and not associated with a surface break the total geodetic moment 4 5 0 1 10 18 nm is more than twice as large as published seismic moments based on the inversion of p waveforms alone but close to the harvard cmt moment 4 7 10 18 nm we use sh waveforms in addition to the p waves used previously to determine an alternative seismic source mechanism sh waves constrain the depth to be shallower than solutions based on p waves alone agreeing with the depths from the interferometric inversion and resulting in a larger moment 3 1 0 4 10 18 nm than the previous bodywave estimates 2 2 1 10 18 nm the cmt moment reduces in magnitude to a similar size 3 3 10 18 nm if the centroid depth and fault dip are constrained to the values determined from bodywave modelling and interferometry thus the geodetic moment is 40 bigger than the moment determined from seismology

interdecadal changes in the major modes of asian australian monsoon variability strengthening relationship with enso since the late 1970s abstract the present paper develops an integral view of the year to year variability across the entire asian australian monsoon a am system which covers one third of the global tropics between 40 and 160 e using season reliant empirical orthogonal function s eof analysis the authors identified two major modes of variability for the period 1956 2004 the first exhibits a prominent biennial tendency and concurs with the turnabout of el nino southern oscillation enso providing a new perspective of the seasonally evolving spatiotemporal structure for tropospheric biennial oscillation the second mode leads enso by one year the remote el nino forcing the monsoon warm pool ocean interaction and the influence of the annual cycle are three fundamental factors for understanding the behavior of the first mode the monsoon ocean interaction is characterized by a positive feedback between the off equatorial convectively coupled rossby waves and the underlying sea surface temperature sst dipole anoma

on the weakening relationship between the indian monsoon and enso analysis of the 140 year historical record suggests that the inverse relationship between the el nino southern oscillation enso and the indian summer monsoon weak monsoon arising from warm enso event has broken down in recent decades two possible reasons emerge from the analyses a southeastward shift in the walker circulation anomalies associated with enso events may lead to a reduced subsidence over the indian region thus favoring normal monsoon conditions additionally increased surface temperatures over eurasia in winter and spring which are a part of the midlatitude continental warming trend may favor the enhanced land ocean thermal gradient conducive to a strong monsoon these observations raise the possibility that the eurasian warming in recent decades helps to sustain the monsoon rainfall at a normal level despite strong enso events

monitoring an effusive eruption at piton de la fournaise using radar and thermal infrared remote sensing data insights into the october 2010 eruption and its lava flows

biomarkers and carbon isotopes of oils in the jurassic smackover trend of the gulf coast states u s a abstract the geochemistry of 25 oils from 23 fields in alabama and the mississippi and louisiana arkansas jurassic salt basins was evaluated results show that the oils were generated by a carbonate source rock which was deposited under highly anoxic conditions and which contains mainly marine derived organic matter the mississippi and louisiana arkansas oils are geochemically similar indicating similar depositional environments for the source although the alabama oils were also derived from a carbonate source rock they are dissimilar to the mississippi and louisiana arkansas oils terpane biomarkers suggest that in addition to marine derived organic matter the source for the alabama oils had an organic input from a more near shore paralic environment i e with a component of terrestrially derived kerogen within each area the oils are similar therefore the norphlet and upper smackover oils in alabama share a common source and the upper smackover cotton valley and some of the lower tuscaloosa oils where production is from faulted structures in mississippi also share a common source maturities of the oils in the three areas vary from low in the updip mississippi salt basin high in the louisiana arkansas salt basin to very high in portions of alabama based on the maturity of oils in mississippi oil generation and migration commenced during the cretaceous when the source was at modest levels of thermal maturity oils migrated relatively short distances into nearby reservoir rocks some oils reached high maturities in the reservoirs resulting in abundant late forming bitumen and pyrobitumen deposition in pore spaces