rossby waves in the tropical north pacific and their role in decadal thermocline variability abstract a band of enhanced thermocline variability at 10 15 n in the pacific found in nature also occurs in an ocean general circulation model forced with observed fluxes of momentum heat and freshwater over the period 1958 97 the variability in the model is primarily associated with long baroclinic rossby waves characterized by periods in the decadal range 7 10 yr the waves are forced by westward propagating ekman pumping anomalies east of the date line and propagate at a speed of 13 cm s 1 which is slower than the phase speed of the first mode unforced baroclinic waves 15 16 cm s 1 west of the date line the correlations between thermocline displacements and local ekman pumping are relatively small and the ocean signals have a phase speed of 20 cm s 1 very similar to the phase speed of the first baroclinic mode in the western half of the basin 18 20 cm s 1 the phase speeds of the ocean model signals have been estimated using cospectral analysis while the wkb approximation has been us

the utility of conductivity surveying and resistivity sounding in evaluating sand and gravel deposits and mapping drift sequences in northeast scotland abstract two types of ground geophysical survey using portable equipment capable of one man operation have been used with the aim of elucidating the thickness and extent of sources of potentially workable sand and gravel in northeast scotland vertical resistivity soundings have provided point data that allow extrapolation of the drift succession between exposures boreholes and trial pits lateral profiling of ground conductivity using a non contacting electromagnetic conductivity meter has proved to be of little use as an aid to conventional geological mapping in determining the position and extent of surface spreads of sand and gravel resistivity sounding using offset wenner apparatus in particular represents a rapid low cost method applicable by industry to the preliminary investigation of the thickness of sand and gravel at proposed extraction sites especially in areas where modern geological maps are not available or where ground disturbance has to be minimised

propagation and mechanism of decadal upper ocean variability in the north pacific n n two types of anomaly pathways associated with decadal thermocline variability in the north pacific ocean are identified on constant density surfaces isopycnals one westward and the other southwestward around the subtropical gyre a theory based on two baroclinic planetary wave modes in the thermocline is proposed to account for the observed variability pattern the variability along the westward wave path is ascribed to the non doppler shift ist mode and seems to be forced mainly by wind stress forcing the anomaly along the southwestward subduction path is associated with the advective nature of the 2nd mode and could be excited mainly by surface buoyancy anomalies this study may provide a dynamically unified three dimensional picture of decadal thermocline variability in the north pacific ocean

asymmetric impact of the north and south pacific on the equator in a coupled climate model 1 relative contributions of the north and south pacific to the equatorial ocean are estimated in a coupled climate model idealized experiments show that the south pacific contributes 30 50 more than the north pacific to the equatorial ocean temperature change because the warming in the north pacific can induce an additional cold rossby wave at around 20 n that tends to block the warm effect from the central north pacific while the south pacific influence can be easily convoyed to the equator through the interior pathway

influence of the indonesian throughflow on the circulation of pacific intermediate water abstract a 4 layer model is used to study intermediate water circulation in the pacific ocean solutions are forced by annual mean winds they are also driven by a prescribed inflow of water through the southwestern corner of the basin 12 sv sv 106 m3 s 1 and a compensating outflow in layers 1 2 and 3 through the western boundary just north of the equator this mass exchange simulates the pacific interocean circulation ioc in which intermediate water enters the south pacific and the same amount of upper water exits via the indonesian passages the water in each subsurface layer is formed by specific processes and hence can be interpreted as corresponding to a distinct water mass type the types are thermocline water generated by subtropical subduction layer 2 upper intermediate and lower thermocline water generated by midlatitude subduction in the north and south pacific npiw and spltw respectively layer 3 and lower intermediate water that corresponds to antarctic intermediate water

heat flow in the ozark plateau arkansas and missouri relationship to groundwater flow abstract heat flow values were calculated from direct measurements of temperature and thermal conductivity at thirteen sites in the arkansas missouri ozark plateau region these thirteen values are augmented by 101 estimates of heat flow based on thermal conductivity measurements and temperature gradients extrapolated from bottom hole temperatures the regional heat flow profile ranges from 9 mw m 2 to over 80 mw m 2 but at least two distinct thermal regimes have been identified seven new heat flow determinations are combined with three previously published values for the st francois mountains sfm a precambrian exposure of granitic and rhyolitic basement rocks average 47 mw m 2 radioactive heat production of 76 samples of the exposed rocks in the sfm averages 2 4 w m 2 and a typical continental basement contribution of 14 mw m 2 is implied conversely the sedimentary rock sequence of the plateau is characterized by an anomalously low heat flow averaging approximately 27 mw m 2 groundwater transmissivity values that are based on data from 153 wells in deep regional aquifers demonstrate an inverse relationship to the observed heat flow patterns the areas of high transmissivity that correspond to areas of low total heat flux suggest that the non conservative vertical heat flow within the ozark sedimentary sequence can be attributed to the effects of groundwater flow

pacific thermocline bridge revisited abstract the coupling on decadal time scales of the mid latitude and tropical pacific via an oceanic bridge in the thermocline is investigated using ocean general circulation model hindcasts and a coupled ocean atmosphere model results indicate that in the tropics decadal anomalies of isopycnal depth are forced by ekman pumping and are largely independent of the arrival of subducted anomalies in the thermocline that originate in the mid latitudes of either hemisphere in the coupled model temperature anomalies on isopycnals show little coupling from the tropics to the northern hemisphere but are lag correlated between southern hemisphere mid and low latitudes however anomaly magnitudes on the equator are small these results suggest that the oceanic bridge to the northern hemisphere explains only a small part of the observed decadal variance in the equatorial pacific coupling to the southern mid latitudes via temperature anomalies on isopycnals remains an intriguing possibility

how different wind stress patterns affect the tropical subtropical circulations of the upper ocean abstract an oceanic gcm is used to investigate the response of the tropical and subtropical thermocline circulation and structure to different wind stress patterns although the subtropical winds do not affect the transport or the speed of the equatorial undercurrent significantly they do change the equatorial temperature field in the lower part of the equatorial thermocline significantly a weaker subtropical wind curl causes a cooling of the subsurface equatorial region and hence an intensification of the equatorial thermocline a weakening of the subtropical wind curl by a factor of 2 cools the equatorial lower thermocline water by 2 c

acquisition and processing of wide aperture ground penetrating radar data a 40 channel wide aperture ground penetrating radar gpr data set was recorded in a complicated fluvial aeolian environment in eastern canada the data were collected in the multichannel format usually associated with seismic reflection surveys and were input directly into a standard seismic processing sequence filtering static corrections common midpoint gathering velocity analysis normal and dip moveout corrections stacking and depth migration the results show significant improvements over single channel recordings in noise reduction and depth of penetration by stacking and in spatial positioning and reduction of diffraction artifacts by migration these characteristics increase the potential for reliable interpretation of structural and stratigraphic details thus without having to develop any new software gpr data processing technology is brought to the same level of capability flexibility and accessibility that is current in seismic exploration

origin of upper ocean warming and el nino change on decadal scales in the tropical pacific ocean the cause of decadal scale variability in the tropical pacific ocean such as that marked by the 1976 77 shift in the el nino southern oscillation1 2 3 4 5 6 7 is poorly understood unravelling the mechanism of the recent decade long warming in the tropical upper ocean is a particularly important challenge given the link to el nino variability but establishing the hypothesized interannual decadal oceanic connections between middle latitudes and tropics has proved elusive8 here we present observational evidence that pacific upper ocean warming and decadal changes in the el nino southern oscillation after 1976 may originate from decadal mid latitude variability in the middle 1970s the north pacific ocean is observed to have undergone a clear phase transition a see saw subsurface temperature anomaly pattern that rotates clockwise around the subtropical gyre at middle latitudes a subsurface warm anomaly formed in the early 1970s from subducted surface waters and penetrated through the subtropics and into the tropics thus perturbing the tropical thermocline and driving the formation of a warm surface water anomaly that may have influenced el nino in the 1980s the identification of this teleconnection of extratropical thermal anomalies to the tropics through a subsurface ocean bridge may enable improved prediction of decadal scale climate variability

interdecadal thermocline variability in the north pacific for 1958 97 a gcm simulation an ocean general circulation model is forced with the ncep reanalysis wind stress for 1958 97 to understand mechanisms of ocean subsurface variability with relatively high horizontal 1 83 18 and vertical 41 levels resolutions the model produces mode waters on a range of density surfaces in the western central and eastern north pacific in qualitative agreement with observations these mode waters appear as a thermostad or a region of weak stratification in the upper thermocline as they flow southward from their formation regions in the kuroshio and its extension in the model subsurface temperature variability in the central subtropical gyre reaches a maximum within the thermostad in contrast to what might be expected from the linear baroclinic rossby wave theory this variance maximum is associated with the longitudinal shift in the path of mode waters in particular deepened mixed layer and accelerated eastward currents in the kuroshio extension by wind changes in the mid 1970s act cooperatively to move the central mode waters toward the east causing large subsurface temperature anomalies besides the local maximum in the central north pacific subtropical gyre two additional maxima of the subsurface anomaly are identified in the northwestern and southern parts of the gyre respectively among these subsurface anomaly centers the one in the northwestern north pacific has a strong effect on the model sea surface temperature suggesting that the kuroshio and its extension are a key region to decadal interdecadal ocean atmosphere interaction finally possible effects of atmospheric thermal forcing are discussed

quasi periodicity and global symmetries in interdecadal upper ocean temperature variability recent studies find interannual i e 3 to 7 year decadal i e 9 to 13 year and interdecadal i e 18 to 23 year periodicities and a trend dominating global sea surface temperature sst and sea level pressure slp variability over the past hundred years with the interdecadal signal dominating sub el nino southern oscillation enso frequencies we isolate interdecadal frequencies in sst and slp records by band passing with a window admitting 15 to 30 year periods from 1900 to 1989 the rms of interdecadal filtered sst and slp anomalies is largest in the extratropics and eastern boundaries first mode empirical orthogonal functions eofs explain about half the interdecadal variance in both variables with the tropical warm phase peaking near 1900 1920 1940 1960 and 1980 from 1955 to 1994 eof spatial patterns of interdecadal sst slp and 400m temperature t400 anomalies reveals global reflection symmetries about the equator and global translation symmetries between ocean basins with tropical and eastern ocean ssts warmer cooler than normal covarying with stronger weaker extratropical westerly winds cooler warmer ssts in western central subarctic and subantarctic frontal zones safzs stronger weaker subtropic and subarctic gyre circulations in north pacific and north atlantic oceans and warmer cooler basin and global average ssts of 0 1 c or so evolution of interdecadal variability from the tropical warm phase to the tropical cool phase is propagative also characterized by reflection and translation symmetries during the tropical warm phase cool sst anomalies along western central safzs are advected slowly eastward to the eastern boundaries and subsequently advected poleward and equatorward by the mean gyre circulation the latter conducting extratropical sst anomalies into the tropics a delayed action oscillation model is constructed that yields the quasiperiodicity of interdecadal variability in a manner consistent with these global symmetries in both pattern and evolution

southern hemisphere origins of the 1976 climate shift 1 observations from the tropical pacific ocean identify an abrupt climate shift in 1976 with surface temperatures changing from cooler than normal to warmer than normal in the span of about 1 year model results show that this climate shift originates with subsurface temperature anomalies in the south tropical pacific ocean which propagate first to the western boundary then northward to the equator and finally eastward along the equator to 140 w where they rise to the surface the results suggest that changes in the north pacific respond to changes in the tropical pacific

influence of extratropical thermal and wind forcings on equatorial thermocline in an ocean gcm the equatorial thermocline variability in the pacific in response to the extratropical thermal and wind forcings is investigated with an ocean general circulation model modular ocean model version 3 mom3 sensitivity experiments show that the extratropical wind forcing and thermal forcing contribute equally to the equatorial variability the wind induced response is attributed to the off equatorial wind within 30 8 of the equator the thermal induced response can be traced to higher latitudes the thermal forcing affects the equator mainly through the equatorward transport of the perturbation temperature by mean subduction flow the wind forcing affects the equator by changing the strength of meridional overturning circulations it is also found that the southern hemisphere contributes more to the equatorial variability than the northern hemisphere under both external forcings

propagation of north pacific interdecadal subsurface temperature anomalies in an ocean gcm propagation of subsurface north pacic inter decadal variations is investigated with an ocean general cir culation model forced by observed sea surface temperature anomalies subsurface temperature anomalies subducted in the central subtropical north pacic take a more westward pathway than a passive temperature tracer and reach the western boundary to the north of the bifurcation latitude this prevents them from extending into the equator on the boundary between the subtropical and the subarctic gyres on the other hand the upper 500 m heat content anomaly is found to propagate eastward as high vertical modes of rossby waves advectedbythemean eastward cur rent this notion is supported by a sign reversal in temper ature anomaly underneath

decadal variations in the subtropical cells and equatorial pacific sst 1 a mechanism for generating decadal sea surface temperature sst variability in the equatorial pacific is investigated using an ocean general circulation model forced by observed wind stress equatorial sst variability is governed by different ocean dynamics on interannual and decadal time scales at interannual time scales equatorial sst anomalies are mainly driven by equatorial winds at decadal time scales on the other hand they are forced both by equatorial winds and by off equatorial winds in the tropics while the contribution from midlatitude winds poleward of 25 is negligible trade wind variations in the off equatorial tropics force equatorial sst variability by spinning up and down the subtropical cells that transport cold water into the equatorial upwelling zone equatorial sst anomalies induced by this mechanism lag behind the response to local equatorial winds by about two years

rb sr and u pb geochronology and distribution of rock types in the precambrian basement of missouri and kansas most of what we know about basement rocks in kansas and missouri is derived from cores and cuttings from deep drilling these rocks may be divided into a northern terrane underlain by rocks consisting of abundant granite commonly showing cataclastic textures and by metavolcanic to metasedimentary rocks and a southern terrane underlain almost exclusively by rhyolitic flows and ash flow tuffs and epizonal granite plutons the northern terrane is interrupted in central kansas by mafic igneous rocks and flanking arkosic sedimentary rocks of the central north american rift system data from 63 rb sr whole rock analyses yield ages ranging from 1 153 to 1 748 m y but these are considered to represent only the minimum ages of the rocks ages derived from u pb analyses of suites of cogenetic zircons from 22 rock samples indicate that some rocks of the northern terrane were formed 1 610 to 1 650 m y ago these are apparently intruded by younger granite plutons formed 1 450 1 470 m y and 1 340 1 380 m y ago rocks of the southern terrane were formed 1 460 1 480 m y ago in the st francois mountains terrane of southeastern missouri and its buried equivalents but these are about 1 380 m y old in southwestern missouri and southern kansas rocks of the central north american rift system in kansas are assumed to be about 1 100 m y old by geophysical and drill hole extension to their outcrop in the lake superior region where they have been dated both the northern and southern terranes are notable for the great abundance of granitic rocks and the scarcity of intermediate to mafic igneous rocks quartzite is the most abundant metamorphic rock although the decrease in ages from north to south in the mid continent region suggests their sequential accretion at the edges of a pre existing continent the rock assemblages are not consistent with convergent plate margin suites of the andean type the great volumes of rhyolite and epizonal granite of the southern terrane may represent melting of thickened somewhat older crust following accretion at the continental margin major element chemical data are presented for basement rocks from kansas oklahoma and texas and these are compared with the compositions of similar rocks from the st francois mountains names and locations are given for wells from which samples were obtained

a simple model of the mass exchange between the subtropical and tropical ocean abstract a simple ventilated thermocline model is used to study the subtropical tropical mass exchange it is found that the water subducted in the western subtropical gyre recirculating window tends to recirculate within the subtropical gyre while the water subducted in the eastern part exchange window tends to penetrate equatorward the exchange window expands with an increased easterly wind or basin width on the southern boundary of the subtropical gyre but shrinks with an increased wind curl within the subtropical gyre furthermore the total exchange transport increases with the easterly wind or the width of the basin on the southern boundary of the subtropical gyre but it is independent of subtropical wind the ventilation mechanism is important in supporting the exchange transport for wind with realistic strength at the southern boundary the reduction of the exchange transport is about 15 30 of the ekman transport finally relative to the exchange transport in the interior of the ocean

heat flow in the gulf coastal plain forty four new heat flow values from panhandle florida southwestern georgia southern alabama mississippi and louisiana range from 13 mw m sup 2 0 3 hfu 1 hfu 1 mu cal cm sup 2 s sup 1 41 8 mw m sup 2 in florida and alabama to 88 mw m sup 2 2 1 hfu in northern louisiana in general the values depict the eastern gulf coastal plain as an area with low to normal continental heat flow that increases from east to west anomalously low heat flow 13 33 mw m sup 2 0 3 0 8 hfu characterizes northcentral florida southwestern georgia and southern alabama while in northern louisiana 13 measurement sites yield values ranging from 50 mw m sup 2 1 2 hfu to 88 mw m sup 2 2 1 hfu distinctive disruptions in the temperature depth profiles attributed to convective effects within aquifers are limited in magnitude and extent and do not alter the geothermal gradient computations the region of relatively high heat flux in northern louisiana is coincident with an area underlain by cenozoic alkalic igneous rocks of the monroe uplift and an abnormal concentration of radiogenic heat sources within that body is postulated as the cause of the thermal anomaly

discussion of the utility of conductivity surveying and resistivity sounding in evaluating sand and gravel deposits and mapping drift sequences in northeast scotland by c a auton

an application of ground penetrating radar to peat stratigraphy of ellice swamp southwestern ontario ground penetrating radar gpr has been applied to the mapping of stratigraphy and peat thickness of a large bog in southwestern ontario the gpr survey was undertaken in conjunction with a conventional coring survey and measurement of peat physical properties the results indicate that gpr responds to peat moisture content and bulk density which vary with stratigraphic changes in particular the acrotelm catotelm boundary and the basal clay are gpr reflectors the presence of gyttja above the clay is indicated by complex basal reflections ground penetrating radar is a viable alternative to an intensive coring survey for evaluating peat depth and extent

thermocline variability in different dynamic regions abstract the response of thermocline circulation to a variable wind forcing is investigated with quasigeostrophic models the physical mechanism responsible for the different variability features in various dynamic regions has been highlighted special attention is given to the role of density advection that is forced by wind driven currents in affecting baroclinic thermocline variability the strong density advection in the rhines young pool can effectively balance the variability induced by local ekman pumping resulting in weak baroclinic variability in the pool zone in contrast the lack of density advection in the shadow zone enables the local ekman pumping to force significant baroclinic variability there the variability in the barotropic field and the western boundary current system is also discussed

decadal variability of temperature at a depth of 400 meters in the north pacific ocean the gyre scale structure and evolution of decadal ocean thermocline variability in the north pacific is described by analyzing historical temperature data at a depth of 400 meters decadal thermocline anomalies are characterized by a distinct see saw pattern in the midlatitudes and subtropics that appears to circulate coherently in the north pacific basin with a period on the order of 20 years there are coherent spatial and temporal relationships between temperature anomalies around the subtropical gyre with phase differences at depth and at the sea surface suggesting that thermocline variability evolves independently of local sst anomalies in the subtropics subsurface anomalies can be seen to propagate all the way across the basin and thereby lead sst anomalies providing a possible phase transition mechanism for sst the basinwide anomaly pathways suggest a clockwise advection of subsurface temperature anomalies around the subtropical gyre an active role played by the mean geostrophic flow in decadal variability

upper ocean thermal variations in the north pacific during 1970 1991 abstract a newly available extensive compilation of upper ocean temperature profiles was used to study the vertical structure of thermal anomalies between the surface and 400 m depth in the north pacific during 1970 1991 a prominent decade long perturbation in climate occurred during this time period surface waters cooled by 1 c in the central and western north pacific and warmed by about the same amount along the west coast of north america from late 1976 to 1988 comparison with data from coads suggests that the relatively sparse sampling of the subsurface data is adequate for describing the climate anomaly the vertical structure of seasonal thermal anomalies in the central north pacific shows a series of cold pulses beginning in the fall of 1976 and continuing until late 1988 that appear to originate at the surface and descend with time into the main thermocline to at least 400 m depth individual cold events descend rapidly 100 m yr 1 superimposed upon a slower cooling 15 m yr 1 the inter

subduction of decadal north pacific temperature anomalies observations and dynamics abstract observations of oceanic temperature in the upper 400 m reveal decadal signals that propagate in the thermocline along lines of constant potential vorticity from the ventilation region in the central north pacific to approximately 18 n in the western pacific the propagation path and speed are well described by the geostrophic mean circulation and by a model of the ventilated thermocline the approximate southward speed of the thermal signal of 7 mm s 1 yields a transit time of approximately eight years the thermal anomalies appear to be forced by perturbations of the mixed layer heat budget in the subduction region of the central north pacific east of the date line a warm pulse was generated in the central north pacific by a series of mild winters from 1973 to 1976 and reached 18 n around 1982 after 1978 a succession of colder winters initiated a cold anomaly in the central north pacific that propagated along a similar path and with a similar speed as the warm anomaly then arrived in the west

structure and cycle of decadal variability of upper ocean temperature in the north pacific abstract yearly upper ocean in situ temperature anomaly data for the period 1961 90 are analyzed to reveal spatial structure and evolution of decadal variability in the north pacific ocean an eof analysis has been performed on individual temperature anomaly fields at upper ocean standard levels as well as simultaneously on the entire upper ocean data to depict the combined three dimensional structure in a coherent manner time evolution of anomaly fields is depicted by using a regression analysis the analyses detect the principal basin scale structure of decadal warm period dwp and decadal cold period dcp there is a well defined subsurface thermal anomaly pattern characterized by a prominent seesaw structure with opposite anomaly polarity between the midlatitude north pacific and the subtropical regions during a dwp a positive temperature anomaly is found in the central midlatitude upper ocean with the maximum at about 100 m depth this is accompanied by a corresponding negative anomaly in the

ground penetrating radar of northern lacustrine deltas ground penetrating radar gpr was used in several selected deltaic sedimentary environments to better understand subsurface stratigraphy and reconstruct former depositional environments the profiles provide high resolution continuous subsurface data on facies thickness and depths orientation of major sedimentary structures postdepositional failure planes and depth of peat deposits field experiments were carried out on six river deltas records from four of the deltas exhibit sedimentary facies a record from one delta shows a possible slump and records from another delta reveal the thickness and stratigraphic relationships of peat deposits the delta types are i sandy wave influenced ii sandy immature wave influenced steeper middle and lower shoreface iii sandy braided and iv gravelly fan foreset in areas of limited subsurface control stratigraphic logs from drill core cutbank exposure or geophysical logs radar profiles can provide big picture perspectives of the subsurface

connections between the pacific ocean tropics and midlatitudes on decadal timescales abstract connections between the tropical and midlatitude pacific on decadal timescales are examined using a 137 yr run of a fully coupled ocean atmosphere general circulation model it is shown that the model does a credible job of simulating both enso scale and decadal scale variability and that there are statistically significant correlations between the midlatitudes and tropics on decadal timescales three physical mechanisms linking the regions are examined 1 oceanic advection along isopycnal surfaces from the midlatitude subduction regions to the tropics 2 coastally trapped or kelvin wave propagation between the tropics and midlatitudes and 3 near simultaneous communication between the regions affected by changes in the atmosphere it is found that communication via the atmosphere explains the strongest correlations found in the model further evidence is presented that is consistent with the idea that midlatitude sea surface temperature anomalies drive changes in the trade wind system that a

major proterozoic basement features of the eastern midcontinent of north america revealed by recent cocorp profiling cocorp profiling in the eastern midcontinent of north america has 1 traced an extensive sequence of precambrian layered rocks beneath southern illinois indiana and western ohio 2 detected a broad zone of east dipping basement reflectors associated with the grenville front beneath western ohio and 3 discovered a wide region of west dipping reflectors penetrating most of the crust beneath eastern ohio the precambrian layered assemblage may be as much as 11 km thick beneath southern illinois extends at least 170 km in an east west direction and contains several strong reflectors that have a lateral continuity of 80 km or more industry seismic data indicate that the layering is extensive in a north south direction as well possible explanations for the layering include the silicic igneous rocks of the ca 1 48 ga eastern granite rhyolite province which are penetrated by basement drill holes throughout the region perhaps intermixed or underlain by mafic igneous or sedimentary rocks the 40 50 km wide zone of strong east dipping 25 30 reflectors beneath west central ohio corresponds to the position of the grenville front as determined from potential field and drill hole data these dipping reflectors in the upper and middle crust are interpreted to result from ductile deformation zones mylonites like those exposed at the grenville front in canada and imaged on the glimpce seismic reflection lines in lake huron both the cocorp and glimpce lines show a remarkably similar reflection geometry despite the more than 500 km separating the two profiles easternmost ohio appears to be underlain by pronounced west dipping 40 reflectors in the middle and lower crust which are also interpreted as marking a region of pervasive ductile deformation 80 km or more in width analogy with similar reflection packages elsewhere suggests that these reflections may mark a major collision zone the west dipping reflectors may be correlative with similar reflectors imaged on another cocorp survey in northern alabama the correlations suggested by these new results though tentative imply that the eastern midcontinent is composed of a relatively simple assemblage of crustal blocks

ocean mixed layer processes in the pacific decadal oscillation in coupled general circulation models it is investigated how the pacific decadal oscillation pdo is simulated differently among various coupled general circulation models cgcms and how it is related to the heat budget of the simulated ocean mixed layer which includes the surface heat flux and ocean heat transport for this purpose the dataset of the climate of the 20th century experiment 20c3m from nine cgcms reported to ipcc s ar4 are used while the mri and miroc models are examined in detail detailed analyses of these two cgcms reveal that the pdo is mainly affected by ocean heat transport rather than surface heat flux in particular in the mri model which has a larger contribution of ocean heat transport to the heat budget it is found that the ocean heat transport due to ekman advection versus geostrophic advection contributes differently to the pdo in the western and central north pacific specifically the strength of pdo tends to be larger for cgcms with a larger ocean heat transport in the region

identification of a precambrian rift through missouri by digital image processing of geophysical and geological data digital free air and bouguer gravity anomaly images have been constructed from approximately 287 000 station readings for the region bordered by 25 49 n latitude and 80 110 w longitude the technique used to interpolate between station locations was based on a two dimensional spatial filter where the average of the anomaly values located within the filter area was computed the images contain as many as 256 contours values in byte variable so that subtle anomaly patterns can be identified and traced with much greater certainty than on most contour maps a newly discovered feature in the midcontinent is a gravity low that begins at a break in the midcontinent gravity high in se nebraska extends across missouri in a nw se direction and intersects the mississippi valley graben to form the pascola arch the anomaly varies from 120 to 160 km in width extends about 700 km and is best expressed in southern missouri where it has a bouguer amplitude of approximately 34 mgal the magnitude of the anomaly cannot be explained on the basis of a thickened section of paleozoic sedimentary rock the gravity data and the sparse seismic refraction data for the region are consistent with an increased crustal thickness beneath the gravity low some of the discrete positive magnetic anomalies in missouri are located along the borders of the gravity low digitally enhanced thermal infrared images from the heat capacity mapping mission show a distinct alignment of linear structures with the gravity feature the linear features in some cases correspond to mapped high angle normal faults to drape folds over relief within the precambrian basement and in some cases to extensions of mapped structures the gravity anomaly also cuts across the major precambrian boundary in se missouri marking the change from older sheared granites and metasedimentary rocks to younger granites and rhyolites given the cumulative evidence the gravity anomaly is probably the present expression of a failed arm of a rifting event perhaps one associated with the spreading that led to or preceded formation of the granite and rhyolite terrain of southern missouri

thermocline forced by annual and decadal surface temperature variation abstract a two layer thermocline model is modified by adding an essentially passive mixed layer above it the surface temperature variation is simulated by a moving outcrop line it is found that in contrast to a surface wind stress a surface temperature variation causes strong variability in the ventilated zone through subducted water while it affects the shadow zone little two types of buoyancy forced solution are found when the outcrop line moves slowly the solutions are nonentrainment solutions for these solutions the surface beat flux is mainly balanced by the horizontal advection in the permanent thermocline the mixed layer never entrains the time mean thermocline is close to the steady thermocline with the time mean outcrop line when the outcrop line moves southward rapidly during the cooling season the solutions become entrainment solutions now deep vertical convection must occur because the horizontal advection in the permanent thermocline is no longer strong enough to balance the s

structure and evolution of interannual variability of the tropical pacific upper ocean temperature n n yearly in situ temperature anomaly data for the period 1961 1990 are analyzed to reveal the dominant structure and evolution of interannual variability of the tropical pacific upper ocean we use multivariate empirical orthogonal function eof analyses to detect the principal three dimensional structure related to el nino there are well defined subsurface thermal patterns characterized by a prominent sea saw structure with opposite anomaly polarity in the equatorial and off equatorial tropical north pacific regions during an el nino year a positive temperature anomaly is found in the e astern and central tropical upper ocean this is accompanied by a corresponding negative anomaly at subsurface depths in the west with a maximum at 100 150 m off the equator unlike sea surface temperature whose variations are confined largely to the east with one dominant polarity temperature variations at 50 200 m depths have a dipole pattern with out of phase oscillations in the central equatorial pacific and in the western tropical north pacific a reverse pattern of these anomalies is observed during a la nina year evolution between el nino and la nina involves a significant zonal transfer of anomaly phase across the equatorial basin as well as across the off equatorial tropical north pacific showing consistent and coherent variations from west to east from subsurface to sea surface and from on the equator to off the equator this phase propagation is more evident at subsurface depths than that at the sea surface suggesting a continual movement of anomaly pattern in succession eastward along the equator and westward off the equator of the tropical north pacific with spatial inhomogeneities of zonal propagation in longitude our analyses present evidence of the manner in which temperature anomalies evolve at subsurface ocean depths in the tropical pacific thus providing an observational basis for evaluating theoretical studies and model simulations the dynamical implication of these results is also discussed

calderas in the precambrian terrane of the st francois mountains southeastern missouri precambrian igneous rocks in the st francois mountains of southeastern missouri consist of silicic volcanic rocks mostly ash flow tuff which crop out mostly in the western and southwestern part of the region and epizonal granitic plutons which are mostly exposed in the northeastern part of the area these relations suggest that the exposures in the northeast are of a somewhat deeper part of the crust and that rocks there are now exposed because of west southwesterly tilting and beveling by erosion in the eastern st francois mountains the occurrence of a thick rhyolitic ash flow tuff grassy mountain ignimbrite and its distribution relative to a large high silica pluton butler hill granite suggest that the ash flow is the principal eruptive material of a caldera the butler hill caldera and that butler hill granite is the frozen magma chamber that was originally beneath it structural relations indicate that butler hill granite was emplaced into the volcanic rocks of the caldera during resurgent doming four small low silica plutons silvermine stono knoblick and slabtown granites are distributed peripherally to the butler hill granite and are interpreted as ring plutons emplaced along the ring fracture of the caldera or along arcuate intracaldera faults after resurgent doming and emplacement of butler hill granite more than 3 km of silicic volcanic rocks occupy a basinal structure in the western st francois mountains these rocks lie with angular unconformity upon up domed older rocks of the butler hill caldera along an arcuate zone of megabreccia and disturbed structure on the western margin of the older caldera this feature is interpreted as the topographic wall of a second caldera which lies to the west the occurrence of the thick taum sauk rhyolite stratigraphically about 3 km higher than the rocks involved in the megabreccias may indicate that there was yet another caldera formed in this western part of the st francois mountains

interdecadal variability of the pacific ocean model response to observed heat flux and wind stress anomalies variability of the pacific ocean is examined in numerical simulations with an ocean general circulation model forced by observed anomalies of surface heat flux wind stress and turbulent kinetic energy tke over the period 1970 88 the model captures the 1976 77 winter time climate shift in sea surface temperature as well as its monthly seasonal and longer term variability as evidenced in regional time series and empirical orthogonal function analyses examination of the surface mixed layer heat budget reveals that the 1976 77 shift was caused by a unique concurrance of sustained heat flux input anomalies and very strong horizontal advection anomalies during a multi month period preceding the shift in both the central pacific region where cooling occurred and the california coastal region where warming occurred in the central pacific the warm conditions preceding and the cold conditions following the shift tend to be maintained by anomalous vertical mixing due to increases in the atmospheric momentum flux tke input into the mixed layer which deepens in the model after the shift from the early 1970s to the late 1970s and 1980s since the ocean model does not contain feedback to the atmosphere and it succeeds in capturing the major features of the 1976 77 shift it appears that the midlatitude part of the shift was driven by the atmosphere although effects of midlatitude ocean atmosphere feedback are still possible the surface mixed layer heat budget also reveals that in the central pacific the effects of heat flux input and vertical mixing anomalies are comparable in amplitude while horizontal advection anomalies are roughly half that size in the california coastal region in contrast where wind variability is much weaker than in the central pacific horizontal advection and vertical mixing effects on the mixed layer heat budget are only one quarter the size of typical heat flux input anomalies

evolution of subduction planetary waves with application to north pacific decadal thermocline variability abstract the evolution of decadal subduction temperature anomalies in the subtropical north pacific is studied using a simple and a complex ocean model it is found that the amplitude of the temperature anomaly decays faster than a passive tracer by about 30 50 the faster decay is caused by the divergence of group velocity of the subduction planetary wave which is contributed to significantly by the divergent sverdrup flow in the subtropical gyre the temperature anomaly also seems to propagate southward slower than the passive tracer or mean ventilation flow this occurs because the mean potential vorticity gradient in the ventilated zone is directed eastward the associated general beta effect produces a northward propagation for the temperature anomaly partially canceling the southward advection by the ventilation flow

crustal heterogeneities and the thermal structure of the continental crust the observed linear relationship between surface heat flow q0 and the radiogenic heat production of near surface rocks a0 discovered almost two decades ago has been a primary tool used to infer the distribution of heat production in the continental crust recent evidence on the nature of compositional heterogeneities in the continental crust has led us to reexamine the q0 a0 relationship and the likely implications for the thermal structure of the lower continental crust numerical simulations of crustal thermal models indicate that some interpretations derived from this relation may be flawed in particular the length scale determined from the q0 a0 function normally thought to describe the depth distribution of crustal heat sources is significantly affected by the horizontal scale of crustal heterogeneity as a consequence most estimates of lower crustal heat flow and lower crustal temperatures obtained using heat flow data with the q0 a0 relationship are overestimates this overestimation is proportionally largest in areas of low mantle heat flux such as cratons where basal heat flux may be overestimated by more than a factor of two

half precessional cycle of thermocline temperature in the western equatorial pacific and its bihemispheric dynamics the el nino southern oscillation enso which is tightly coupled to the equatorial thermocline in the pacific is the dominant source of interannual climate variability but its long term evolution in response to climate change remains highly uncertain this study uses mg ca in planktonic foraminiferal shells to reconstruct sea surface and thermocline water temperatures sst and twt for the past 142 ky in a western equatorial pacific wep core md01 2386 unlike the dominant 100 ky glacial interglacial cycle recorded by sst and 18o which echoes the pattern seen in other wep sites the upper ocean thermal gradient shows a clear half precessional 9 4 ky or 12 7 ky cycle as indicated by the reconstructed and simulated temperature t and 18o differences between the surface and thermocline waters this phenomenon is attributed to the interplay of subtropical to tropical thermocline anomalies forced by the antiphased meridional insolation gradients in the two hemispheres at the precessional band in particular the twt shows greater variability than sst and dominates the t changes which couple with the west east sst difference in the equatorial pacific at the half precessional band implying a decisive role of the tropical thermocline in orbital scale climate change