propagation and the vertical structure of the madden julian oscillation abstract the madden julian oscillation mjo dominates tropical variability on time scales of 30 70 days during the boreal winter spring it is manifested as an eastward propagating disturbance with a strong convective signature over the eastern hemisphere the space time structure of the mjo is described using the national centers for environmental prediction national center for atmospheric research reanalysis advanced very high resolution radiometer outgoing longwave radiation observed sea surface temperature and the climate prediction center merged analysis of precipitation empirical orthogonal function analysis is used to identify the convective signature of the mjo and regression is used to identify key relationships with the convection compared to analyzing successive years of data the selection of years of strong mjo activity results in a more robust lead lag structure and an increase in explained variance the mjo exhibits a rich vertical structure with low level moisture convergence bein

thermal properties and thermal structure in the deep water coalbed basin off the shimokita peninsula japan abstract heat transport properties are significant parameters that affect geothermal processes in deep sedimentary basins we measured the thermal properties of deep sediment core samples to a depth of approximately 2500 m below sea floor mbsf whereas most previous studies have only presented data 1 k 1 and calcite cemented sandstone siltstone exhibits the highest conductivity of approximately 3 wm 1 k 1 the other thermal properties are also influenced by the porosity and lithological contrast the correlation between thermal conductivity and porosity is explained by the mixed law model of the geometric mean the one dimensional temperature depth profile at site c0020 estimated from measured thermal conductivity reveals a regression of the thermal gradient with depth and the surface heat flow of 30 mwm 2 which is consistent with the heat flow data near this site was evaluated the obtained results suggest that the linear geothermal gradient estimated from the average thermal conductivity value at shallow sediment materials could overestimate the temperature at greater depths and underestimate the heat flow

speleothems in a wave cut notch cayman brac british west indies the integrated product of subaerial precipitation dissolution and microbes abstract a wave cut notch that is deeply incised into the vertical cliff faces of cayman brac is adorned with stalactites stalagmites and columns the prefix notch is applied to each type of speleothem in order to distinguish them from cave speleothems these speleothemic deposits must have formed since the highstand 125 000 years ago which was responsible for the development of the notch the laminated notch speleothems are formed largely of aragonite small and large crystals and calcite columnar fiber and grain coating mats along with minor amounts of dolomite a mg si precipitate kerolite gypsum and halite laminae typically the notch speleothems are the integrated product of precipitation and dissolution that was in some places microbially mediated interpretations based on their mineralogy and internal structures indicate that the composition of the formative waters must have temporally fluctuated with periods of precipitation being interrupted by periods of dissolution the microbes that formed the subaerial biofilms may have influenced some of these processes the aragonite calcite and kerolite probably formed as evaporation and loss of ca through precipitation progressively increased the mg ca and the si ca mg ratios the dolomite gypsum and halite probably formed during early diagenesis during the evaporation of seawater that percolated into the interiors of the notch speleothems

impact of air sea coupling on the madden julian oscillation in a general circulation model abstract the impact of air sea coupling on the dynamics of the tropical madden julian oscillation mjo is investigated with an atmospheric general circulation model gcm coupled to an ocean mixed layer model in the uncoupled gcm where climatological sea surface temperature sst is specified realistic space time spectra of near equatorial zonal wind and precipitation are produced with power concentrated at eastward wavenumbers 1 3 with periods of 35 90 days however the simulated mjo is roughly 50 stronger than observed largely resulting from enormous activity during northern summer furthermore during southern summer when the observed mjo is most dominant across the indian and western pacific oceans intraseasonal variance in the uncoupled model is overly concentrated to the north and east of australia with little activity extending into the equatorial indian ocean contrary to other recent modeling studies coupling did not alleviate either of these problems nor did it have any other apprecia

the geothermal regime of the northern yukon and mackenzie delta regions of northwest canada studies of two regional profiles temperature data from deep petroleum exploration wells and thermal conductivity estimates based on net rock analysis data have been used to make terrestrial heat flow estimates along two profiles across the sedimentary strata of the mackenzie delta northern yukon and offshore beaufort sea regions

estimates of terrestrial heat flow in offshore eastern canada from available bottom hole temperatures and conductivities estimated from lithologic descriptions heat flow estimates are calculated for 72 sites on the canadian atlantic shelf the resulting data suggest a pattern of low heat flow 055 mw m2 within the paleozoic basins in proximity to land areas and generally intermediate heat flow 60 80 mw m2 along the outer half of the continental shelf higher heat flows 90 mw m2 are estimated along the shelf edge in some areas e g the southwestern scotian shelf and the eastern newfoundland and labrador shelves radioactive heat generation in sediments that thicken seawards probably does not account for the observed increase in heat flow the possibility that higher heat flows in some areas may arise because of fluid movement from depth is suggested various other causes for the high heat flows e g tectonic or magmatic activity are considered less likely

biogenic β fabric features in the hard laminated crusts of the mersin and adana regions southern turkey and the role of soil organisms in the formation of the calcrete profiles abstract this paper describes fabric features and their distribution in the calcretes and emphasizes the role of soil organisms in the formation of the calcrete profiles quaternary calcretes are common in the mersin and adana provinces occurring as powdery nodular tubular fracture infill and various forms of crusts the stable isotope values indicate calcrete development under semi arid climatic conditions and a pedogenic origin biogenic or fabric constituents are abundant in the hard laminated crust these are the rhizoliths alveolar septal structures needle fiber calcites calcified filaments spherical calcite bodies microcodium and vadose calcrete pisoliths rhizoliths have mainly formed by the petrification of roots and often contain cellular cortex structures the alveolar septal structure comprises root voids separated by a micritic wall or a bundle of tangentially oriented calcite needles needle fiber calcite is common in the hard laminated crust as monocrystalline rods and polycrystalline needles monocrystalline rods are smooth and small

enso impact on kelvin waves and associated tropical convection abstractthe impact of el nino southern oscillation enso on atmospheric kelvin waves and associated tropical convection is investigated using the ecmwf re analysis noaa outgoing longwave radiation olr and the analysis technique introduced in a previous study it is found that the phase of enso has a substantial impact on kelvin waves and associated convection over the equatorial central eastern pacific el nino la nina events enhance suppress variability of the upper tropospheric kelvin wave and the associated convection there in both extended boreal winter and summer the mechanism of the impact is through changes in the enso related thermal conditions and the ambient flow in el nino years because of sst increase in the equatorial central eastern pacific variability of eastward moving convection which is mainly associated with kelvin waves intensifies in the region in addition owing to the weakening of the equatorial eastern pacific westerly duct in the upper troposphere in el nino years

centered composite analysis of variations associated with the madden julian oscillation abstract centered composite analysis is described and applied to gain a better understanding of the initial phases of the madden julian oscillation mjo centered composite analysis identifies the dates and central locations of key events the elements of the composite means are centered on these central locations before averages are calculated in this way much of the spatial fuzziness which is inherent in traditional composite analysis is removed the results for the mjo based on mjo filtered outgoing longwave radiation for the reference data and 40 yr ecmwf re analysis era 40 and ncep ncar reanalysis products for the composites show highly significant composites of unfiltered data for not only zero lag but also lags back to 20 days before the target events these composites identify propagating patterns of surface pressure upper and lower troposphere zonal winds surface temperature and 850 hpa specific humidity associated with mjo convective events in the indian ocean the propagation chara

the onset of convection in the madden julian oscillation abstract an observational study of the onset of convection in the madden julian oscillation mjo was performed composites of radiosonde data from the comprehensive aerological reference data set were constructed for an ensemble of tropical stations located in the indian ocean maritime continent and western pacific ocean the composites suggest that for the off equatorial stations used in this study the mjo period may be set by the buildup and discharge of the low level moist static energy this result supports the discharge recharge hypothesis of blade and hartmann mjo events appear to begin when the off equatorial atmosphere has been destabilized through a combination of low level moist static energy buildup and concurrent drying of the middle troposphere by subsidence in the wake of the previous cycle of mjo convection the low level moist static energy buildup is controlled by a corresponding increase in low level moisture the increase in low level moisture is not caused by the 1000 mb convergen

deep subpermafrost thermal regime in the mackenzie delta basin northern canada analysis from petroleum bottom hole temperature data in our studies of the thermal regime of sediments of the young mackenzie delta in the southeastern part of the beaufort mackenzie basin of northern canada we used thermal data from the base of the permafrost layer together with temperature data from petroleum wells by analyzing bottom hole temperature bht data we found that the percentage correction i e the percentage difference between bht and equilibrium temperature is less than 10 with 67 probability for times exceeding 10 hours after circulation ended regardless of circulation time no correlation exists between the percentage correction and depths for the bht data theoretical temperature depth profiles were constructed from the individual heat flow q q q and q q values q is error of estimate of q the interval thermal conductivities and a permafrost base temperature of 0 c estimates of q were based on the maximum bhts from depths 2 7 km the measured and corrected bht values for depths less than 1 5 km lie outside the rang

oxygen and carbon stable isotope composition of authigenic carbonates in loess sequences from the carpathian margin and podolia as a palaeoclimatic record abstract samples were collected from the outcrops situated in the north and east of the carpathian margin in the transition zone between the area of loess covers of eastern and western europe the chosen localities include two zones of temperate climate with slightly different prevailing wind directions these loess palaeosol sequences formed and develop in different time intervals early quaternary epoch podolia ukraine and late quaternary epoch carpathian foothills poland the isotopic analysis was carried out on many types of authigenic soil carbonates including nodules rhizoliths rhizocretions calcified root cells and bioclasts the carbon isotopic compositions 13 c of different types vary markedly these differences seem to be more important than the variations within one type of carbonate at a particular section the 13 c values for authigenic carbonate cements rhizoliths rhizocretions and nodules vary in a narrow range from about 11 to 8 suggesting that calcite cements were precipitated under roughly similar conditions with a considerable supply of co 2 derived from biomineralization of organic matter predominantly from c 3 plants the 18 o record of the calcite cements within the upper quaternary deposits exhibits relatively slight variability suggesting that 18 o values in soil water were homogeneous the significant depletion of 13 c as well as 18 o in calcite from calcified root cells 12 and 7 respectively and to a lesser extent from calcitic globules with respect to calcite cements points to different environments of formation the morphology of calcite crystals replacing root cells and their carbon and oxygen isotopic composition indicate that they may precipitate inside the root cells from fluids with organic compounds in general the temperature reconstructions yield an average mat about 11 c for the upper quaternary sediments deposited during mis 2 the estimated mat for sediments of mis 3 5 range from 12 to 14 c mean annual temperatures estimated for the lower quaternary of podolia fall in the range from 9 to 11 c with two single minimums about 7 c probably corresponding to short lived environmental changes the mat curve throughout the lower part of lower quaternary is more variable and shows several local shifts up to 3 c

enso like interdecadal variability 1900 93 a number of recent studies have reported an enso like eof mode in the global sea surface temperature sst field whose time variability is marked by an abrupt change toward a warmer tropical eastern pacific and a colder extratropical central north pacific in 1976 77 the present study compares this pattern with the structure of the interannual variability associated with the enso cycle and documents its time history back to 1900 the analysis is primarily based on the leading eofs of the sst anomaly and anomaly deviation fields in various domains and the associated expansion coefficient or principal component time series which are used to construct global regression maps of sst sea level pressure slp and a number of related variables the use of anomaly deviations i e departures of local sst anomalies from the concurrent global mean sst anomaly reduces the influence of global mean sst trends upon the structure of the eofs and their expansion coefficient time series an important auxiliary time series used in this study is a southern oscillation index based on marine surface observations by means of several different analysis techniques the time variability of the leading eof of the global sst field is separated into two components one identified with the enso cycle related variability on the interannual timescale and the other a linearly independent residual comprising all the interdecadal variability in the record the two components exhibit rather similar spatial signatures in the global sst slp and wind stress fields the sst signature in the residual variability is less equatorially confined in the eastern pacific and it is relatively more prominent over the extratropical north pacific the corresponding slp signature is also stronger over the extratropical north pacific and its counterpart in the cold season 500 mb height field more closely resembles the pna pattern the amplitude time series of the enso like pattern in the residual variability reflects the above mentioned shift in 1976 77 as well as a number of other prominent features including a shift of opposite polarity during the 1940s

petrography micromorphology and genesis of holocene pedogenic calcrete in al jabal al akhdar sultanate of oman abstract holocene pedogenic calcrete nodules occur within quaternary terra rossa soil that fills shallow phytokarst cavities in the permian triassic carbonate sequence of al jabal al akhdar in the sultanate of oman they are preferentially clustered around plant roots and are almost wholly formed of calcite holocene pedogenic calcrete nodules developed within a mediterranean like climate that is characterized by intermittent wet and dry seasons petrographic examination revealed that the host terra rossa soil is partially calcitized and that the calcrete nodules consist of smaller coalesced diffused and or discrete granular nodules the latter consist of several types of rhizoliths floating in a groundmass formed of micrite and microspar as well as spar to a lesser extent several textures of calcrete groundmass are recognized the most common is partially neomorphosed micrite three types of rhizoliths are recognized root moulds root casts and petrified calcified root tissues the latter were developed by mimic replacement of the tissue cells by cytomorphic calcite sem investigation of the calcite forming the calcrete nodules revealed that it consists of closely stacked sheets formed of calcareous nanoglobules agglutinated by eps and entombed calcareous microbial fossils which indicate a biogenic origin the calcareous nature of the bedrock climatic conditions and prevalence of biological activities of microorganisms associated with the plant root system in the host soil have significantly controlled the development and texture of these nodules the relative abundance of scalenohedral calcite within the calcrete groundmass is attributed to the impact of mg ions and organic compounds it has been concluded that the studied pedogenic calcrete is a type of freshwater terrestrial thrombolitic microbialite this study may help improve the understanding of the palaeoenvironmental conditions of analogue fossil calcretes

the 1985 86 intraseasonal oscillation and the role of the extratropics abstract an intraseasonal oscillation that occurred in the 1985 86 northern winter is documented in this study the tropical convection of this event is dominated by the mixture of a standing oscillation over the maritime continent and an eastward moving feature from the indian ocean into the central pacific the time evolution of the upper tropospheric circulation patterns instead of propagating eastward along the equator as suggested in the existing composites of the intraseasonal oscillation is characterized by a series of wave patterns in the northern hemisphere and does not complete the cycle around the globe the familiar moist kelvin wave explanation for the intraseasonal oscillation receives little support from diagnosis of this event using zonal wind height field streamfunction and potential vorticity only in the lower troposphere near the date line is the convincing evidence for its existence found a scenario for the intraseasonal oscillation which is suggested by the analysis includes

modulation of hurricane activity in the gulf of mexico by the madden julian oscillation the madden julian oscillation mjo is a large scale episodic modulation of tropical winds and precipitation that travels eastward from asia to america with a characteristic repeat time of 30 to 60 days here it is shown that when mjo wind anomalies in the lower troposphere of the eastern pacific are westerly gulf of mexico and western caribbean hurricane genesis is four times more likely than when the mjo winds are easterly accurate predictions of the mjo may lead to improved long range forecasts of tropical cyclone activity

measured radiogenic heat production in sediments from continental margin of eastern north america implications for petroleum generation measurements of radiogenic heat production are presented for most of the major sedimentary formations beneath the rifted continental margin off nova scotia canada the measurements were made on 32 samples from 14 deep exploratory wells drilled in the area the results show that heat production ranges from about 1 8 to 0 3 w m 3 and varies with lithology the effect of this radiogenic heat production is to increase the heat flow and the temperatures within the sediments by up to 15 and 30 6 f 17 c respectively these temperature changes will increase the rate of organic maturation so that for example oil generation should occur 10 to 30 ma earlier in jurassic sediments than if those sediments exhibited no heat production it is noted ho ever that other thermal properties of the sediments must be studied before predictions of organic maturation and the timing of oil generation can be considered reliable the results presented here show that radiogenic heat production in sediments is an important parameter in making reliable predictions of their thermal maturity and thus should be included in future studies of thermal models for sedimentary basins

frictional moisture convergence in a composite life cycle of the madden julian oscillation abstract a composite life cycle of the madden julian oscillation mjo is constructed using an index based on the first two eofs of the bandpass filtered 20 80 days 850 mb zonal wind averaged from 5 n to 5 s every 2 5 around the equator precipitation 1000 mb convergence 850 mb wind and 200 mb wind are composited for the period 1979 95 water vapor integrated from the surface to 300 mb is composited for the period 1988 92 frictional moisture convergence at the equator is shown to play an important role in the life cycle of the madden julian oscillation mjo regions of boundary layer convergence foster growth of positive water vapor anomalies to the east of convection this convergence coincides with 850 mb easterly wind anomalies as is consistent with kelvin wave dynamics drying of the atmosphere occurs rapidly after the passage of convection with the onset of 850 mb westerly perturbations possible mechanisms for this drying include boundary layer divergence and subsidence or horizontal advect

the structure and diagenesis of rhizoliths from cayman brac british west indies abstract rhizoliths from the pleistocene ironshore formation are formed of a brown micrite core surrounded by sediment that is well cemented with 1 calcite rhomb chains 2 isolated calcite rhombs 3 calcified spherical bodies 4 types i and ii calcified epilithic and chasmolithic filaments and 5 grain coating calcite needle mats the friable host sediment has significantly less cement and lacks the grain coating calcite needle mats and type ii calcified filaments of the rhizoliths the sediment however contains calcite needles and a cryptocrystalline cement which do not occur in the rhizolith the contrast in the amount and type of cement between the rhizoliths and the encasing sediment points to the significant role that plants can play in carbonate diagenesis not only do the plant roots act as conduits for water of varying composition they also provide sites at which algae fungi and bacteria thrive these microorganisms serve to promote diagenesis in the rhizoliths the occurrence of the sediments in a coastal setting means that they are subjected to many different types of water ranging from freshwater to saltwater such variability along with the associated changes in the water chemistry may be responsible for the considerable variation in the cement associated with the rhizoliths

intraseasonal behavior of clouds temperature and motion in the tropics abstract the spectral character of tropical convection is investigated in an 11 yr record of outgoing longwave radiation from the advanced very high resolution radiometer to identify interaction with the tropical circulation along the equator in the eastern hemisphere the space time spectrum of convection possesses a broad peak at wave numbers 1 3 and eastward periods of 35 95 days significantly broader than the dynamical signal of the madden julian oscillation mjo this quasi discrete convective signal is associated with a large scale anomaly that propagates across and modulates time mean or climatological convection over the equatorial indian ocean and western pacific outside that region the convective signal is small even though under amplified conditions coherence can be found east of the date line and in the subtropics having a zonal scale of approximately wavenumber 2 anomalous convection propagates eastward at some 5 m s 1 and suppresses as well as reinforces climatological convection

a three dimensional insight into the mackenzie basin canada implications for the thermal history and hydrocarbon generation potential of tertiary deltaic sequences the stratal architecture of the mackenzie basin was reconstructed based on seismic and well data and used to define a three dimensional model to reconstruct the so far poorly known thermal and maturation history of the basin to correctly account for the complex tectonic history of the mackenzie basin episodes of uplift and erosion were implemented based on interpretations of original depositional surfaces our results indicate that the combined effects of basin inversion and low surface temperatures inhibited maturation from the late miocene forward in all except the most deeply buried parts of the basin this explains why upper eocene and younger deposits are mostly immature despite their burial to more than 5000 m 16 400 ft the specific history of the basin is shown to control the time intervals of potential hydrocarbon generation predictions of transformation ratios using a variety of published kinetics to account for source rock kinetic variability indicate that potential generation from paleocene and older strata occurred mainly before the late oligocene the generation from eocene strata however occurred mainly during the miocene and therefore is interpreted to be a source for oligocene and younger gas rich reservoirs these findings contribute to a better understanding of hydrocarbon systems in the mackenzie basin and are the basis for future studies of hydrocarbon migration and accumulation

a model for the boreal summer intraseasonal oscillation abstract the tropical intraseasonal oscillation iso exhibits pronounced seasonality the boreal summer iso is more complex than its winter counterpart due to the coexistence of equatorial eastward off equatorial westward and northward propagating low frequency modes and their interactions based on observational evidence and results obtained from numerical experiments a mechanism is proposed for the boreal summer iso in which the northern hemisphere summer monsoon nhsm circulation and moist static energy distribution play essential roles with a climatological july mean basic state the life cycle of model low frequency waves consists of four processes an equatorial eastward propagation of a coupled kelvin rossby wave packet an emanation of moist rossby waves in the western pacific a westward propagation and amplification of the rossby waves in south asian monsoon regions and a reinitiation of the equatorial disturbances over the central indian ocean the life cycle spans about one month and p

geothermal gradients and heat flow in the beaufort mackenzie basin arctic canada thermal gradients have been calculated and heat flow estimates made for 34 petroleum exploration wells along four regional profiles crossing the mesozoic cenozoic beaufort mackenzie basin of northern canada the geothermal gradients vary from 22 mkm 1 to 44 mkm 1 four sets of possible thermal conductivity values were used to calculate a range of heat flow values for each well generally low heat flow is observed in wells within the deeper portions of the basin and higher heat flow values occur in wells along the aklavik arch complex which forms the southeastern margin of the basin

eastern cordilleran foldbelt of northern canada its structural geometry and hydrocarbon potential the eastern cordilleran foldbelt of northern canada embraces that part of the foreland thrust and foldbelt north of lat 60 n including the continental shelf of southern beaufort sea the sedimentary succession there lies with pronounced unconformity on continental crust presumably crystalline rocks of the hudsonian 1 750 ma basement and ranges in thickness from an estimated 4 mi 7 km along the eastern margin of the foldbelt to more than 12 mi 20 km in the interior regional and interregional unconformities divide the succession into five discrete tectono stratigraphic sequences ranging in age from proterozoic helikian to holocene these sequences are termed from oldest to youngest inuvikian rapitanian franklinian ellesmerian and brookian the region is characterized by bundles of en echelon folds cut by two major fault systems the richardson fault array bordering the foreland and the kaltag fault zone transecting the foldbelt late cretaceous and tertiary horizontal contraction with concomitant vertical thickening of the supracrustal wedge is roughly one fourth that of the eastern cordillera of southern canada potential hydrocarbon traps in paleozoic and mesozoic rocks of the northern cordillera commonly occur within these en echelon fold bundles thus their locations are predictable because they are arranged systematically right and left hand en echelon in the cenozoic succession of the arctic coastal plain and continental shelf however closures are arranged only crudely en echelon current estimates of the combined oil and gas resources of the eastern cordilleran foldbelt of northern canada and the adjacent interior platform are about 10 billion bbl of oil and 123 tcf of natural gas with the preponderance of resources being confined to the upper cretaceous and tertiary brookian sequence