salinity driven thermocline transients in a wind and thermohaline forced isopycnic coordinate model of the north atlantic abstract an isopycnic coordinate oceanic circulation model formulated with the aim of simulating thermodynamically and mechanically driven flow in realistic basins is presented special emphasis is placed on the handling of diabatic surface processes and on thermocline ventilation the model performance is illustrated by a 30 year spinup run with coarse horizontal resolution 2 mesh in a domain with north atlantic topography extending from 10 to 60 n latitude the vertical structure encompasses 10 isopycnic layers in steps of 0 2 units capped by a thermodynamically active mixed layer from an initially isohaline state with isopycnals prescribed by zonally averaged climatology the model is forced by seasonally varying wind stress radiative and freshwater fluxes and by a thermal relaxation process at the surface after a mechanical spinup time of about 15 years a quasi stationary pattern of mean circulation and annual variability ensues characterized by pronounced subtropical mode water formation

flow structure and transport in the yucatan channel 1 the direct ocean current observations across the yucatan channel collected during the canek program allow the best description to date of the exchange between the caribbean sea and the gulf of mexico a net transport of 23 8 1 sv 1 sv 106m3s 1 95 confidence interval flowed through the yucatan channel from the caribbean sea into the gulf of mexico during the period between september 1999 and june 2000 this is about 20 percent less than the 30 sv accepted as the nominal transport of the florida current and less also than the 28 sv assumed for yucatan in closing the transport budgets for caribbean passages the discrepancy may be an imbalance due to fluctuations in the transports through other passages of the system especially the old bahama and northwest providence channels which remain poorly known our data corroborate the principal features of the flow through the yucatan channel the northerly surface yucatan current and its southerly under current off mexico and the southerly surface cuban counter current near cuba but previously unobserved mean currents are found to exist at depth especially on the eastern side of the channel fluctuations seen in the deep flows are related to volume anomalies over the gulf of mexico a transport through the yucatan channel smaller than previously thought has significant implications for the dynamics of the gulf of mexico and its modeling since this transport is the principal forcing of its circulation the circulation budgets in the western subtropical atlantic should be revised considering these new results

gulf of mexico circulation within a high resolution numerical simulation of the north atlantic ocean 1 the gulf of mexico circulation is examined from the results of a high resolution 1 12 north atlantic simulation using the miami isopycnic coordinate ocean model the motivation for this paper is twofold first we validate the model s performance in the gulf of mexico by comparing the model fields to past and recent observations and second given the good agreement with the observed gulf of mexico surface circulation and loop current variability we expand the discussion and analysis of the model circulation to areas that have not been extensively observed analyzed such as the vertical structure of the loop current and associated eddies especially the deep circulation below 1500 m the interval between successive model eddy sheddings is 3 to 15 months the eddy diameters range between 140 and 500 km the life span is about 1 year and the translational speeds are 2 3 km d 1 in good agreement with observations areas of high cyclonic eddy occurrence in the model are southwest of florida the loop current boundary and the western campeche bay area the cyclonic eddy diameters range between 50 and 375 km the orbital speeds range between 1 and 55 cm s 1 the translational speeds range between 0 5 and 14 km d 1 and the eddy life spans range between 1 and 3 months the vertical structure of the temperature and salinity of each modeled eddy from the moment it is shed until it disintegrates in the western gulf of mexico is in agreement with the few available observations below 1500 m deep cyclonic eddies are associated with the surface loop current anticyclones the eddy variability is consistent with rossby waves propagating westward and there is bottom intensification of the flow close to steep topography overall we show that this very high horizontal resolution isopycnic coordinate ocean model which is able to produce a quite realistic surface circulation for the north and equatorial atlantic is also able to reproduce well the smaller scale basin wide intricate dynamics such as the gulf of mexico variability

anticyclonic rings in the gulf of mexico abstract using the historical data set this study describes the anticyclonic rings that separated from the loop current in the eastern gulf of mexico six quasi synoptic data sets are used to describe the evolving circulation of the gulf of mexico from october 1966 to september 1967 showing the separation and movement into the western gulf of three anticyclonic rings the historical data are used to determine that these rings typically translate to the west at a mean speed of 2 1 km day 1 their length scale as defined by their rms radii is 183 km an estimate of ring life span as defined by an e folding time is one year within the context of the gulf s water property distributions these rings appear as warm salty bodies the heat and salt added by one of these rings after separation are estimated to be 7 109 j m 2 and 17 g cm 2 respectively the heat and salt added by one of these features play an important role in the heat and salt budget of the western gulf the latter indicates that about one r

aspects of warm rings in the gulf of mexico various aspects of warm rings in the gulf of mexico were derived from satellite infrared data and ship of opportunity data after the warm rings separate from the loop current they move into the western gulf of mexico it was shown from 12 years of data 1973 through 1984 that there are three characteristic paths of movements of the rings a northern path a mid gulf path and a path that takes the rings into the southern extremities of the western gulf of mexico it was shown that all three paths eventually lead the ring to a region in the northwestern portion of the western gulf of mexico the area defined by 25 n to 28 n and 93 w to 96 w as the rings move from the eastern gulf to the western gulf the speed of the ring was observed to oscillate the oscillation is over a speed range from 1 to 8 km per day on the average and the period varies from 40 to 100 days the average speed of the ring was 5 km per day after the ring separates from the loop current the surface area of the ring decreases to about 55 percent of its initial size in approximately 150 days and to about 31 percent of its initial size in about 300 days

deep flows in the yucatan channel and their relation to changes in the loop current extension 1 the first attempt to establish a relation between the loop current extension and deep flows in yucatan channel was made by maul et al 1985 it was unsuccessful probably because of the low spatial resolution of their observations from september 8 1999 to june 17 2000 eight moorings with acoustic doppler current profilers current meters and thermometers were deployed across the yucatan channel the data from these arrays were used to compute time series of the transports below the level of the deepest isotherm observed in the florida straits as required by a simple box model that restricts deep exchanges with the gulf of mexico to the yucatan channel the surface extension of the loop current was inferred from 3 day advanced very high resolution radiometer imagery from october to may when temperature gradients were sufficient to map the warm water unambiguously the deep transports appear at first unrelated to the rate of change of the loop current extension but filtering the series with a 20 day running mean increases the correlation between the low pass series to 0 62 and up to 0 83 with a lag of 8 5 days with loop current changes leading the deep flows the cumulative deep transport a quantity that favors lower frequencies is very well related correlations 0 9 to the surface extension of the loop current also with a lag of about a week these lags are not statistically significant but suggest a timescale for internal adjustment processes in the gulf of mexico the empirical orthogonal function of the current best related to the area extension of the loop current represents a unidirectional flow across the entire deep section flowing either toward or from the gulf of mexico and includes a strong expression of the yucatan undercurrent

dynamics of agulhas retroflection and ring formation in a numerical model part ii energetics and ring formation abstract an energetics analysis of several numerical experiments on an idealized south atlantic indian ocean basin is presented the model used in the experiments is the quasi isopycnic coordinate model of bleck and boundra forced by wind and configured with two or three layers the region of focus is the most dynamically active one the agulhas current retroflection south of africa and the dynamical mechanisms associated with formation of agulhas rings are given special attention whether rings form in the model and their frequency depend on two primary factors the shape of africa and southward inertia baroclinicity in the overshooting agulhas the boundary condition on africa no slip free slip and horizontal resolution are also important experiments in which rings form exhibit considerably larger values of km to ke transfer than those in which no rings form in three of the experiments ring formation is studied in detail with the help of instantaneous top and bottom layer flow patterns and time se

relationships between the petrophysical properties density seismic velocity heat generation and mineralogical constitution the petrophysical properties density p compressional wave velocity v p and heat generation a exhibit considerable variation with rock type to characterize a given rock quantitatively a single parameter the cation fraction expressed by the k value has been found to be suited best 100 crystalline rocks have been sampled to cover the widest possible range in k value from silicic types like granophyres and granites through granodiorites tonalites diorites gabbros amphibolites hornblendites pyroxenites to ultrabasic rocks p k a and v p were determined experimentally the latter at 0 5 kbar 50 mpa the interrelations between these properties were established by regression analysis the relation k and v p k show a linear dependence whereas a k a and a v p follow exponential laws in a w m 3 12 20 230 5 k mole cm 3 in a 22 5 8 15 g cm 3 and in a 16 5 2 74 v p km s all correlation coefficients are better than 0 9

simulation of mesoscale variability in the gulf of mexico sensitivity studies comparison with observations and trapped wave propagation abstract a primitive equation gulf of mexico model was used to examine variability of the loop current lc and loop current eddies lce realistic results were obtained for a certain range of values of the horizontal mixing coefficient eddy paths were west and southwestward eddy propagation speeds from 3 to 5 km day 1 the ratio of minor to major eddy axes about 0 8 eddy shedding periods from 200 to 500 days eddy lifetimes from 100 to 200 days eddy sizes from 200 to 400 km and eddy swirl transports as fractions of the specified inflow of 30 sv were from 0 55 to 0 85 on the other hand the maximum vertical deepening of the 20 c isotherm was 15 to 50 less than that observed resulting in weaker near surface currents of about 0 65 m s 1 in comparison to observed values of 0 88 to 1 7 m s 1 a strong correlation between eddy shedding and decreasing or reversing lower layer below 750 m transport in the yucatan channel is found in the western gulf current variability is produced by eddy arriva

a census of north brazil current rings observed from topex poseidon altimetry 1992 1998 six years of topex poseidon altimeter data are used to investigate the formation of rings and eddies shed by the north brazil current upper layer thickness maps were used to identify 34 of these features formed in the north brazil current retroflection region an average of more than 5 rings and eddies per year the ensemble of ring trajectories closely parallels the 500 m isobath and one out of six rings penetrate into the caribbean sea through the southern lesser antilles the rest of the rings and eddies follow a northern trajectory past barbados once they reach 58w their estimated mean translation speed is 14 km day and their mean length scale is approximately 100 km our results suggest that the formation rate of nbc rings and eddies is nearly twice that previously thought and that they may account for more than 1 3 of the interhemispheric transport within the atlantic meridional overturning cell

current meter observations on the continental slope at two sites in the eastern gulf of mexico abstract current meter observations obtained at two sites on the continental slope of the eastern gulf of mexico at nominal positions of 29 n 88 w the mobile site and 27 5 n 85 5 w the tampa site are presented data were collected at three levels at mobile 90 190 and 980 m from july 1977 through august 1978 and at four levels at tampa 150 250 550 and 950 m from june 1978 through june 1979 at 90 and 190 m the flow at mobile was on the average to the east sustained periods of flow to the west were observed during the summer 1977 and spring 1978 during the periods of eastward flow the wind was generally out of the north and during the periods of westward flow the wind was out of the east the flow at the top meter at tampa was on the average to the west in the same direction as the average wind at both sites the motions are perturbed by events associated with the loop current these events make it difficult to define any seasonal variability in the upper layers the flow at the bottom m

forecasting scale dependent dispersion from spills in heterogeneous aquifers abstract existing theories of flow and contaminant transport in aquifers are either based on monte carlo simulations or small perturbation solutions of the governing stochastic partial differential equations which limit the applications to cases of small variances in the physical parameters in this article scale dependent models to predict mean contaminant concentration from point sources well injection and non point sources ground surface spills in heterogeneous aquifers are developed and tested a general analytic technique the neumann expansion is used in the solution of the equations this method does not require the assumptions of small perturbation logarithmic transformations or a specific probability law in the random quantities in addition aquifer parameters such as the mean pore velocity are functionally defined in terms of the underlying groundwater flow problem and field measurable aquifer hydrogeologic properties such as mean transmissivity mean hydraulic gradient mean porosity and aquifer thickness comparison with theoretical models and verification with field tracer tests at the borden aquifer indicated that the proposed models reproduced the enhanced longitudinal dispersion as a function of distance reported in the literature

a simple method to determine heat production from gamma ray logs abstract usually the radiogenic heat production is determined from the potassium k uranium u and thorium th content and the rock density by using the formula by rybach 1986 in boreholes the k u and th content can be taken from the natural gamma spectrometry tool ngs measurements and the rock density from the litho density tool ldt measurements in this paper a simple method is presented to determine heat production from normal gamma ray logs which are readily available from a vast number of boreholes this method is based on a linear relationship between the gamma ray gr and the heat production a for a wide variety of lithologies extending from granite through gneiss carbonate and amphibolite to basaltic rocks it is shown that this relation is valid in the range 0 350 api and 0 03 7 w m3 respectively with an error lower than 10 reliable information of the radiogenic heat production for the use in thermal modelling now can be derived quickly using only standard gr api readings

land air boundary environment as recorded by the18o 16o and13c 12c isotope ratios in the shells of land snails abstract a yearly cycle of carbon and oxygen isotope composition of shells of the israeli land snailxeropicta vestalis is presented the18o 16o values indicate that the snails use water from the land air boundary zone the18o 16o ratio of the shells is in isotopic equilibrium with the water condensate from the vapour during the winter months during the summer months a contribution to the above water from soil water migrating upwards due to evaporation is noticeable the 13c values indicate that as in marine molluscs the carbon isotopic composition in land snails is controlled mainly by the aqueous carbonate compound which is in equilibrium with the land air boundary co2

the problem of heat flow density determination from inaccurate data abstract we present an inverse method for processing rough data from oil wells in order to evaluate the heat flow density assuming that the evaluations of temperatures and thermal resistivities present gaussian uncertainties we give formulas for computing the optimal value of the heat flow density and its standard deviation a synthetic example using likely assumptions on various uncertainties leads to the prediction that a standard deviation of about 10 mw m 2 could apply to heat flow estimates from oil well data for typical situations

cyclonic eddies in the eastern gulf of mexico abstract cold domed cyclonic eddies juxtaposed to the cyclonic shear side of the gulf loop current are observed in simultaneously obtained hydrographic current meter mooring and satellite infrared data the cyclones are initially observed in the satellite data as cold perturbations on the northern extreme of the current and grow either into a cold tongue or a quasi stable meander off the dry tortugas florida areal shipboard surveys show closed isopleths of temperature and salinity and surface geostrophic current speeds relative to 1000 db are in excess of 100 cm s 1 the diameter of the cold domes varied from 80 to 120 km separation of large anticyclonic rings is always observed to be preceded by cyclonic eddies in the transition zone between campeche bank and the west florida shelf but only on the eastern side not every cyclonic eddy off dry tortups is associated with the separation of an anticyclonic ring some are eroded away by the florida current but they have never been observed in 10 years

modelling the variability of heat flow due to the random thermal conductivity of the crust summary analytical solutions for the mean heat flow and its error bounds have been obtained by solving the steady state heat conduction equation following a stochastic analytical approach incorporating gaussian uncertainties in the thermal conductivity this study on the uncertainty analysis to quantify the variability in the heat flow along with its associated error statistics has been applied to the latur earthquake region of the indian shield results obtained show that the mean heat flow and its error bounds are highly dependent on the random components of the thermal conductivity such as its coefficient of variability and its correlation length scale hence the study can be used to quantify the error statistics in the heat flow field for any given region

stochastic modeling of the thermal structure to decipher the lithospheric thickness application to dharwar craton a wide range of speculation regarding lithospheric thermal thickness in a region calls for quantifying the uncertainties associated with model parameters in this paper we present an attempt to decipher it by solving the differential equations governing the heat transfer through the lithosphere adequately quantifying the temperature field is very important since it is highly dependent on the controlling thermal parameters thermal conductivity is modeled as a random parameter with a known mean value and correlation structure we compute the temperatures in the crust and lithospheric mantle along with their error bounds using an analytical solution to the steady state heat equation and the adomian method of decomposition we apply these solutions in the archean dharwar craton which is divided into western dharwar craton wdc and eastern dharwar craton edc we obtain a moho temperature estimate of 304 58 c in wdc whilst in edc it is 375 74 c for a 20 coefficient of variability in thermal conductivity the range of lithospheric thickness obtained for wdc is 150 280 km and 110 160 km for the edc these values are in agreement with other geophysical and geological findings in the region the thermal lithosphere obtained from this study is based on the mantle solidus and the surface wave seismological studies considering radial anisotropy reveal that the lithosphere is characterized by higher shear wave velocities and decrease at the lithosphere asthenosphere boundary average shear velocity model for two different cratonic blocks edc and wdc is used to show the lab thickness for the eastern and western dharwar craton the two independent studies show a correlation in the lithospheric thickness

a model for temperature variations in sedimentary basins due to random radiogenic heat sources summary the thermal structure of a sedimentary basin is controlled by its thermal conductivity its boundary conditions water flow rate of sedimentation and erosion and radiogenic heat sources the radiogenic heat production in the sediments is known to vary over several orders of magnitude with the lowest values in evaporites and carbonates and the highest values in black shales due to a paucity of information available on the existing heat sources this parameter can be represented with a known mean value and a gaussian correlation structure rather than a deterministic function in this paper the 1 d steady state thermal structure in a sedimentary basin has been modelled in a stochastic framework with a random radiogenic heat source and analytical expressions for the first two moments of the temperature field have been obtained a synthetic example has been examined to quantify the error bounds on the temperature field due to uncertainties in the radiogenic heat sources

effects of random horizontal variations in radiogenic heat source distribution on its relationship with heat flow lateral conduction resulting from variations in the radiogenic heat generation is known to modify the heat flow heat generation relation and to bias the evaluation of thickness of radiogenic heat sources in this paper a statistical approach is used to account for a random horizontal variation in radiogenic heat sources whereas their vertical variation is simulated by simple models relationships between spectral densities and autocorrelation functions of heat generation and heat flow are obtained when the horizontal scale length of heat generation distribution is not much larger than the vertical one lateral heat conduction modifies drastically the statistical properties of heat flow distribution and the apparent thickness obtained from the heat flow heat generation plot is highly reduced the procedure is applied to a set of actual heat flow and heat generation data recorded over new hampshire u s a heat production data and especially heat flow data are affected by different types of noise and errors which can be analyzed through their autocorrelation functions the depth scale of heat generation deduced empirically does not seem to have much relation with any geophysical dimension

aspects of the behavior of cold perturbations in the eastern gulf of mexico a case study abstract between 2 march and 13 may 1983 while using in situ and satellite data three cold perturbations were observed off the west florida shelf these perturbations moved southward along the boundary of the loop current at speeds of about 4 to 10 km day 1 geostrophic current and current meter data indicated a cyclonic circulation associated with the cold perturbations the geostrophic current indicated northward flow on the west side of the warm filaments that formed on the shoreward side of the cold perturbation and weak southward flow on the east side however the current meter data only gave indications of northward flow in the filaments the current meter array may not have been able to discriminate the entire flow pattern in the filaments