the 1997 1998 oceanic el nino signal along the southeast and northeast pacific boundaries an altimetric view changes in the sea surface heights ssh and geostrophic currents along the eastern boundaries of the pacific north central and south america are examined during the 1997 1998 el nino using altimeter data and proxy winds these show that symmetric ssh signals left the equator and propagated into both hemispheres in two episodes with primary periods of high equatorial ssh during may july and october december 1997 these are the distant signals from the mid latitude perspective as the signals spread poleward in each hemisphere their loss of symmetry demonstrates the degree to which they were altered by topographic features local winds and or local currents the first four eofs are calculated for 2 d ssh fields in 10 wide strips along the eastern margins 60 n 60 s and extending out along the equator from the coast to 110 w these account for approximately 40 of the overall variability and represent the main features of the seasonal cycles and el nino interannual variability snapshots of the 2 d ssh fields depict the structure of the el nino signal at different phases of its evolution

a three dimensional model of the mean and seasonal circulation of the gulf of california 1 the mean and seasonal circulation of the gulf of california is simulated with a three dimensional numerical model forced by the pacific ocean through specifying the sea level the temperature and the salinity fields at its entrance at the sea surface the wind and the heat and freshwater fluxes are specified the model reproduces the observed mean and seasonal variability of sea level of heat and salt balances and the sea surface temperature sst climatology it also reproduces the general surface circulation of the northern gulf which consists of a seasonally reversing basin wide gyre it is found that tides and heat fluxes are both indispensable to reproduce the spatial structure and temporal evolution of the sst tides provide the mixing to upwell the cooler subsurface waters in the large islands area and the heating from the surface raises the sst the general circulation of the southern part of the gulf is due to the wind and the pacific forcing in the ekman layer two periods of anticyclonic circulation and one cyclonic per year occur below this layer two cyclonic periods develop in the northern part the tides play an important role in producing mean residual currents and both tides and winds compete against the pacific forcing to produce a cyclonic and anticyclonic circulation once a year contrary to conclusions of previous studies the thermohaline circulation is found to be unimportant in the gulf

seasonal gyres in the northern gulf of california abstract the circulation pattern in the northern gulf of california based on drifting buoys and hydrographic observations can be explained using the results of a linear two layer primitive equations model forced at the annual frequency by the pacific ocean wind stress and heat flux through the surface the modeled surface circulation consists of a cyclonic gyre from june to october and an anticyclonic gyre from december to april both located in the central region of the northern gulf of california which includes angel de la guarda island the maximum intensities of the gyres occur in august and february respectively with values of surface velocities of 65 cm s 1 in agreement with the observations and very low opposite velocities in the bottom layers may and november are transition months in which both gyres can be observed finally in june july or december january the growing gyre is still connected with the rest of the gulf of california through the narrows between tiburon island san este

isotopic and hydrochemistry spatial variation of sulfate for groundwater characterization in karstic aquifers the sierra gorda aquifer is one of the most extensive of southern spain the main groundwater discharge is produced at its northern boundary through several high flow springs in this study stable isotopes of dissolved sulfate 34s and 18o and groundwater chemistry were used to determine the origin of the sulfate and to characterize the groundwater flow we sampled the main springs as well as other minor outlets related to perched water tables in order to determine the different sources of so42 e g dissolution of evaporites atmospheric deposition etc the substantial difference in the amount of dissolved so42 between the springs located in its northwestern part 25 mg l and those elsewhere in the northern part 60 mg l suggests zones with separate groundwater flow systems a third group of springs far from the northeastern boundary of the permeable outcrops shows higher so42 content than the rest 125 mg l the isotopic range of sulfate 0 3 to 14 82 v ctd points to several sources including dissolution of triassic or miocene evaporites atmospheric deposition and decomposition of organic material in the soil among these the dissolution of triassic gypsum which overlies the saturated zone as a consequence of the folds and faults that deform the aquifer is the main source of so42 range from 12 79 to 14 82 v ctd this range is typical for triassic gypsum the higher karstification in the western sector together with important differences in the saturated thickness between the western and eastern sectors would also be due to the tectonic structure and could explain the difference in so42 contents in the water this singular arrangement may cause a higher residence time of groundwater in the eastern sector thus a higher contact time with triassic evaporitic rocks is inferred accordingly the stable isotopes of so42 are found to be a valuable tool for identifying areas with different flow systems in the saturated zone of karstic aquifers as well as for evaluating aspects such as the degree of karstification

regional weather prediction with a model combining terrain following and isentropic coordinates part i model description abstract a short range numerical prediction model which is part of a real time 3 h data assimilation and forecast system is described the distinguishing feature of the model is the use of terrain following coordinate surfaces in the lower troposphere combined with isentropic surfaces aloft such a hybrid coordinate system allows modeling of processes in a convectively unstable boundary layer while retaining tile advantages of coordinates in representing upper tropospheric frontal and jet stream structures the hybrid approach used in this model represents a in major departure from previous hybrid formulations in atmospheric models oven though it has been used for more than ten years in oceanic modeling part i of this two part paper contains a thorough description of the model and the results of validation experiments results of north american case studies wig be reported in part ii

inverse estuarine features of the upper gulf of california the upper gulf of california is the shallow depth 30 m tidal area at the head of the gulf of california it is an inverse estuary due to the high evaporation rate e 1 1 m year 1 and almost nil freshwater input from rainfall and the colorado river historical and recent hydrographic data show that the area is almost vertically well mixed throughout the year that the horizontal distribution of properties follows the bathymetry and that the hydrography has a strong annual modulation as in other negative estuaries the year round salinity increase toward the head causes the density to do likewise despite the seasonally reversing temperature gradient the pressure gradient thus formed leads to water mass formation and gravity currents speed 0 1 ms 1 both in winter and in summer in winter the high salinity water sinks beyond 200 m while in summer it only reaches a depth of 20 30 m the gravity currents appear to be modulated by the fortnightly tidal cycle with events in neap tides this phenomenon causes the presence at least during neap tides of slight stratification t 0 2

intraseasonal oscillations in sea level along the west coast of the americas abstract hourly observations of coastal sea level at stations from peru to british columbia are analyzed for low frequency content a space time contour plot of sea level from four years of data during the 1971 75 period shows the meridional structure of the seasonal cycle and interannual variability associated with the 1972 73 el nino oscillations with intraseasonal periods of 36 73 days are also evident coherent over alongshore distances of several thousand kilometers further investigation using spectral methods and empirical orthogonal function analysis in the frequency domain reveals in particular that intraseasonal sea level variability has a peak in spectral density along the coasts of south america central america and mexico with high coherence from near the equator tumaco 2 n north to central california 34 n and south to at least callao 12 s phase propagation north of the equator is poleward at 150 200 kilometers day atmospheric pressure alongshore wind stress and wind stress cu

tidal dissipation and stratification in the gulf of california the effect of tidal mixing upon the distribution of stratification and sea surface temperature sst in the gulf of california is studied by direct observation and by numerical modeling data from conductivity temperature depth surveys made in september and december of 1986 are used to describe the distribution of stratification and sst a vertically integrated finite differences numerical model was used to obtain the geographical distribution of available turbulent kinetic energy tke from the m2 tide the following three areas were found to be strongly affected by tidal mixing the shallow coastal area at the head of the gulf the shelf south of tiburon island and the area of the midgulf archipelago the first two are vertically well mixed and are therefore similar to other shelf sea frontal areas dissipation occurs all around the islands of the archipelago and the sills are foci of the most intense tidal dissipation stratification in this area was reduced with respect to the background but complete vertical mixing does not occur therefore the strong sst fronts that occur in this area do not mark the boundary between well mixed and stratified water the simpson hujiter criterion simpson and hunter 1974 for stratification and frontal position produced 2 75 crit 3 0 for the frontal position in the shallow northern gulf this value of crit is larger than in other shelf sea fronts which may be due to horizontal advection which is not included in the criterion we found that the effect of advection may be of the same order of magnitude as that of buoyancy flux in the area over the sills criti the available tke is not enough to produce complete mixing over the 400 m of water over the sills

the intraseasonal oscillation in eastern pacific sea levels how is it forced abstract daily sea level and surface winds at eastern pacific shore locations and equatorial islands together with gridded five day averages of 850 mb winds have been analyzed for the 1979 84 period to determine how the 40 60 day intraseasonal oscillation of eastern pacific sea levels is forced as described by spillane et al for 1971 75 the oscillation was also present in 1980 84 from callao peru to san francisco with maximum energy near 52 57 days and band limits of 43 and 65 days during 1980 84 there was no evidence for forcing of the large scale oscillation in the eastern pacific although a local contribution of forcing was superimposed on the remote signal at the california stations interannual fluctuations in amplitude were evident in the sea level time series consistent with those of the corresponding wind oscillation in the western equatorial pacific the oscillation was best developed in both variables in 1980 82 and became weak or nonexistent during the recovery phase of the 1982 83 e

factors which determine the hydrogeochemical behaviour of karstic springs a case study from the betic cordilleras spain the cabra alcaide karstic massif situated in the south of spain constitutes an important part of the so called natural park of the subbetic sierras this aquifer system is drained by various springs which supply a population of some 100 000 inhabitants the feed areas of these springs show very different characteristics with respect to their geological structure size of the drainage area thickness of the vadose zone elevation and degree of karstification in addition the carbonate rocks lie over a clayey substratum which contains large masses of intercalated evaporites due to these conditions the hydrochemical composition of the springs is relatively variable in this study a hydrogeochemical characterization of the aquifer in both space and time is undertaken and the factors that determine it are discussed to achieve this 19 monthly samples were taken from the 6 most significant springs of the hydrogeological system the commencement of sampling coincided with the transition from a period of several years of severe drought and a very wet two year period which amplified considerably the hydrochemical and hydrodynamic response of the springs to the recharge identification of hydrogeochemical processes was performed by studying hydrographs the temporal evolution of physico chemical parameters ionic ratios mainly mg ca and by means of simple and multivariate statistical analyses the saturation status was established using the wateqf program and the mass transfer was quantified using phreeqc with the exception of the epikarstic subsystem i e the zarza spring the majority of the results indicate that the aquifer exhibits a diffuse flow model in which piston flow phenomena are seen closely linked to the most intense precipitation along the direction of flow hydrochemical trends are seen as the water type changes from ca hco3 to ca mg hco3 at the same time enrichment in some ions derived from the dissolution of evaporitic minerals of the impermeable substratum and dedolomitization processes occur in this way almost 90 of the water samples were oversaturated in calcite the majority of cases being a consequence of the dissolution of the gypsum of the substratum only in the epikarstic springs can it be considered that the oversaturation in calcite is due to loss of co2 from the emerging groundwater it is concluded that hydrodynamic aspects together with hydrogeochemical characteristics need to be taken into account to correctly explain the hydrochemical evolution of the karstic springs moreover the use of both approaches permits a more accurate establishment of the degree of aquifer karstification which in turn needs to be known in order to assess its vulnerability to contamination and to protect recharge zones

effects of the 1997 1998 el nino on the exchange of the northern gulf of california 1 we analyze sea level and transports in the gulf of california from two large scale high resolution numerical models the naval research laboratory layered ocean model and the hybrid coordinate ocean model sea level from both models correlates well with sea surface height from a nearby topex track and subsurface pressure measured in the northern gulf during 1997 1998 an 8 year mean 1993 2000 section of the modeled meridional velocity at the mouth of the gulf is in good qualitative agreement with observations showing a localized near surface outflow on the baja california side the 8 year mean laterally integrated modeled near surface transport at the mouth of the gulf shows an opposite direction for both models during the 1997 1998 el nino however both models show a similar structure with increased inflow in the upper 100 m and an increased outflow in the underlying layer to about 500 m depth the modeled surface transport also shows increased inflow in the northern gulf the modeled incoming surface transport from both models during el nino is negatively correlated to near bottom currents measured at a sill in the northern gulf this measured near bottom current has previously been shown to constitute part of the strong localized incoming flow from the pacific ocean the negative correlation strongly suggests that the anomalous incoming surface flow at the mouth of the gulf inhibited the normal near surface outflow of the northern gulf of california water this in turn inhibited the normal deeper inflow entering the northern gulf from the pacific ocean these anomalies apparently increased the residence time of the waters in the northern gulf they are consistent with anomalously high near bottom salinities found during 1997 1998 hydrographic data for july 1997 also show an anomalous low salinity surface water which is most likely associated with advection of tropical waters from the pacific ocean

summer generation of the southern gulf of california eddy train 1 ocean color and sea surface temperature satellite observations show the existence of a series of anticyclonic eddies along the axis of the southern gulf of california sgoc to investigate the summer generation of these eddies a regional version of the hybrid coordinate ocean model hycom has been configured for the goc and has been nested inside the global model a suite of experiments using the nested goc model was developed and used to isolate the effects of the local wind and the effects of the oceanic remote forcing on the generation of the sgoc eddies the results indicate that the local wind is not essential for the generation of these eddies rather it is the oceanic remote forcing in the sgoc the monthly variability of the currents and sea surface height is mainly due to the deterministic near coastal poleward eastern boundary currents pebc the interaction of the pebc with the topographic irregularities the capes at topolobampo and cabo lobos and the ridges extending offshore from the entrance of the san lorenzo and sinaloa rivers generates the sgoc eddies the northward upper ocean transport induced by the pebc includes two maximums one in may june and the other in december during the summers of 1999 and 2004 the pebc were intensified by the arrival of equatorially originated downwelling coastally trapped waves ctws which contributed to the generation of the sgoc eddies the summer 2004 ctw increased the northward upper ocean transport by 2 sv this particular ctw was measured by several tide gauges located along the coast

surface heat flux in the northern gulf of california recent coastal meteorological data 1979 1986 are used to evaluate the seasonal cycle of surface heat fluxes in the northern gulf of california although net heat loss occurs from october to january the annual mean of the net surface heat flux was found to be into the sea 69 w m 2 near the coast and 83 w m 2 offshore with a mean evaporation rate 0 9 m yr 1 these results require an oceanic export of heat and salt out of the northern gulf to achieve a balance and imply that the annual mean thermohaline circulation must have an inflowing component at depth thus enriching the central and northern parts of the gulf these results differ from previous meteorological estimates which suggested a net surface heat loss but confirm those based on hydrographic data

lagrangian observations of the circulation in the northern gulf of california argos drifters deployed in the northern gulf of california in september 1995 showed the presence of a cyclonic gyre while a second deployment in march 1996 revealed an anticyclonic gyre a circulation pattern consisting of a seasonally reversing gyre had been proposed before on the basis of satellite images geostrophic calculations and numerical models but so far no direct observations have been made to test its existence in september the gyre was cyclonic baroclinic very well defined stable and strong its mean speed and rotation time were 0 3 m s21 and 7 days in march the gyre had the same mean speed but it was anticyclonic and displaced to the northwest of the summer position the march gyre has barotopic and baroclinic characteristics but the observed speeds are stronger than in numerical simulations these data and a data bank analysis suggest that the summer gyre is a persistent summer feature but the winter spring situation remains ill defined and requires further research

early cenozoic sedimentation in the hammerfest basin abstract using seismic stratigraphy combined with information from 24 wells a detailed history of the early cenozoic sedimentation of the hammerfest basin in the southwestern barents sea has been revealed during the early paleocene the hammerfest basin was subject to non deposition or minor erosion and sedimentation in the basin was initiated after a transgression in the mid paleocene coeval erosion on the basin margin ceased as the transgression gradually spread in the late paleocene and a south southwesterly sediment input from the loppa high to the hammerfest basin was initiated during the late paleocene the late paleocene early eocene environment was dominated by ssw directed progradation from the loppa high and westward progradation in the central part of the basin the early tertiary sedimentation of the hammerfest basin is speculated as mirroring reactivation of older fault regimes and transpression and transtension along the western margin during the latest phase of rifting and earliest phase of spreading in the norwegian greenland sea are indicated mid eocene to pliocene sediments have not been found in the hammerfest basin it seems however that sedimentation continued in the basin in post early eocene time during the oligocene and miocene accumulation and erosion alternated in the hammerfest basin the erosion increased during the late miocene and pliocene and culminated with the pleistocene glaciations

the lower atmosphere over the gulf of california automated meteorological observations at coastal and island stations instrumented aircraft flights and coastal soundings were made between july 1983 and june 1985 to define the variations of the lower atmosphere over the northern half of the gulf of california during the two important climatic seasons the mid latitude winter and the subtropical summer a marine layer is well defined over water during both seasons but dissipates within a few kilometers inland the winter large scale pressure field is dominated by the great basin high over the southwestern united states modulated by upper level synoptic activity it causes 3 to 6 days events of northwesterly winds 8 12 m s 1 directed along the gulf s axis which are coherent over basin scales and bring cool dry desert air over the gulf the vertical scale of these winds is 700 1000 m over land on the western side of the gulf close to the height of the baja california mountains but only 100 400 m over water defined by the wintertime inversion cross gulf winds related to topographic effects during upper level trough passages over baja california are particularly intense in the northwestern portion of the gulf the winter marine layer is defined by a 1 to 4 5 c temperature inversion and a dew point temperature of 6 11 c a moisture content of 6 8 g kg 1 weak subsidence reduces dew point values to 4 c above the inversion winter winds above the marine layer are coherent 0 8 across the width of the gulf the summer large scale pressure field is dominated by a thermal low over the southwestern united states and drives weak 2 5 m s 1 southeasterly winds also directed primarily along the gulf which are less spatially uniform than winter winds air temperature and moisture content are rather constant and topographic effects are absent the summer marine layer is on the order of 200 300 m thick with dew point temperatures of 26 28 c 21 24 g kg 1 and capped by a weak temperature inversion 1 2 c over water aloft the dew point temperature is 17 21 c and winds are weak and uncorrelated across the width of the gulf during june and early july 1984 four week long pulses of southeasterly winds 10 m s 1 support the existence reported previously of moisture surges from the gulf into the sonoran desert a dynamical analysis of subdiurnal motions shows that the cross gulf momentum balance is geostrophic the along gulf balance is ageostrophic with the along gulf pressure gradient opposed by friction at the surface these results are consistent with a scale analysis of the equations of motion in the marine layer over the gulf of california

equatorial kelvin wave influences may reach the bering sea during 2002 to 2005 1 the time history of sea surface height ssh anomaly data from the topex and jason 1 altimeters is examined along the equator and northward following the west coast of the americas along track topex and jason 1 altimeter data are put into an alongshore offshore coordinate system and then smoothed this procedure increases the degrees of freedom in individual estimates of long wavelength coastally trapped waves ctws during times when both satellites are available 2002 2005 equatorially trapped kelvin waves are detected during the 2002 2003 el nino these kelvin waves excite ctws that travel northward along the west coast of the americas while ctws associated with the 2002 2003 equatorial kelvin waves are not always discernible along the entire coast correlations of the coastal and equatorial ssh over the entire period of topex and jason 1 overlap show a clear phase progression this phase progression implies remote influence of equatorial kelvin waves that may reach as far north as the bering sea during the weak to moderate el nino events that occurred from 2002 to 2005

surface circulation in the gulf of california in summer from surface drifters and satellite images 2004 2006 surface drifters released in the gulf of california between june 2004 and august 2006 are used to describe the surface circulation in late spring and summer in the june to september mean there was a poleward coastal current on the shelf and slope of the mainland side of the gulf with mean speed 0 3 m s it reached the northern gulf and joined the cyclonic circulation typical of this zone in summer in the western half of the southern gulf the drifters presented recirculating currents that are due to mesoscale eddies that appear to dominate the surface circulation in summer in june 2004 the coastal current presented an enhancement event with mean speed around 0 60 m s and maximum 0 80 m s it took 20 days for a particular drifter to travel the 1000 km from the gulf entrance to the head this strengthening of the coastal current was apparent in chlorophyll a and sst satellite images the drifters following closely the intrusion of warm chlorophyll poor surface water from outside the gulf the drifters and the satellite images suggest that the current enhancement event lasted less than a month this mesoscale event was linked with a mesoscale remote forcing in the tropical pacific coast and with a mesoscale local forcing of the wind these events seem to occur every year and are probably important in carrying organisms and properties from the entrance to the whole length of the gulf

water mass formation in the gulf of california the gulf of california is a long narrow marginal sea lying between the baja california peninsula and the mainland of mexico air sea fluxes of heat and moisture in the gulf are enhanced because of geographical isolation from the pacific provided by the mountainous baja california peninsula in the northern gulf annual evaporation rates are about 1 m y 1 unlike most evaporative basins however the gulf gains heat from the atmosphere at an annual average rate of 20 to 80 w m 2 bray 1988 given the unusual air sea forcing of the gulf what form or forms should water mass formation take the annual moisture loss and heat gain require that high salinity surface water be transported downward to an intermediate depth and that cold fresh inflow be transported upward to an intermediate depth this is accomplished through several mechanisms 1 winter convection this occurs only in a limited geographical region the wagner basin of the far northern gulf except in el nino southern oscillation years when convection appears to be more widespread 2 dispersion of convected water in small eddylike features this occurs within a large scale southward transport possibly driven by the large scale density gradient associated with atmospheric fluxes 3 an anticyclonic circulation in the northern gulf this is found south of the convection region and transports high salinity water off the shallow shelves and to substantial depths where it may mix with water of central gulf origin 4 tidal mixing most of the energy available for mixing in the northern gulf derives from the tides in particular tidal mixing over the sill in the island region is responsible for the substantial reduction in salinity of northern gulf waters as they enter the central gulf

altimeter derived surface circulation in the large scale ne pacific gyres part 2 1997 1998 el nino anomalies abstract changes in the sea surface heights ssh and geostrophic transports in the ne pacific are examined during the 1997 1998 el nino using altimeter data sea level pressure slp fields proxy winds and satellite sea surface temperature sst most of the signal occurs along the boundaries of the basin from panama to the alaska peninsula changes in the ssh and alongshore transports along the boundaries are caused both by propagation of signals from the south stronger between the equator and the gulf of california and by local and basin scale winds stronger between the pacific northwest and the alaska peninsula two periods of high ssh occur at the equator may july 1997 and october 1997 january 1998 the first coastal ssh signal moved quickly polewards to approximately 24 n in early june then stalled and moved farther north during transient events in july september large scale wind forcing combined with the equatorial signals during the second period of high equatorial ssh fall 1997 to move the high ssh and poleward transports quickly around the alaska gyre a connection between the boundary currents and the interior north pacific developed as part of the large scale response to the basin scale winds after changes in the boundaries decreases in anomalies of ssh and poleward transports began in january 1998 south of 40 n and in february 1998 farther north

modeling the seasonal and interannual variability of the northern gulf of california salinity 1 the 7 years 2003 2009 of output from a regional version of the hybrid coordinate ocean model hycom nested in global hycom are used to study the seasonal and interannual variability of the salinity in the northern gulf of california ngoc previous studies illustrate that the ngoc is characterized by an annual evaporation of 0 9 m yr this evaporation generates high sea surface salinity sss water which reaches a maxima in the ngoc 37 and decreases to 35 toward the entrance of the gulf of california the ngoc surface water is interannually modulated by fluctuations in evaporation and by fluctuations in the low salinity water transported into the region by poleward eastern boundary currents the fluctuations in the transport of low salinity water are linked to the arrival of equatorially originated coastally trapped waves the crucial role of the transport of low salinity water for the interannual variability of sss is illustrated by the 2006 and 2008 fall seasons which include the lowest simulated salinity of the period 2003 2009 the lowest salinity in 2006 and 2008 cannot be explained solely by evaporation because 2006 was characterized by the largest evaporation of the period 2003 2009 however the presence of the lowest salinity environment can be attributed to the evaporation in conjunction with the largest upper ocean transport of low salinity water carried to the ngoc by the 2006 and 2008 coastally trapped waves intensified poleward eastern boundary currents

winter water masses and nutrients in the northern gulf of california hydrographic data salinity temperature o2 po4 no3 and sio2 collected in the northern gulf of california between february 27 and march 3 1988 reveal that bottom water formation took place that winter north of 30 5 n salinity increased with depth from 35 30 practical salinity units psu at the surface to 35 57 psu at the bottom of the 200 m deep wagner basin below 25 m temperature was almost homogeneous at 15 c 0 4 c with some inversions the ts diagrams and the distribution of dissolved oxygen and nutrients suggest that the most likely origin of this bottom water is the shallow coastal region 2 2 m nitrate 22 m and silicate 35 m indicate the presence of oceanic water from guaymas basin probably subsurface subtropical water the boundary between the two regimes was 18 km wide with clearly defined bottom fronts and intrusions at all depths of the several late winter hydrographic data sets available only that from march 1973 presents a similar distribution of high salinity bottom water therefore interannual variability not necessarily el nino southern oscillation enso related can have a profound effect on vertical convection which can occur both in enso and non enso years an important and as yet unexplained difference between the two data sets is that there was more gulf of california water in the northern gulf of california in 1973 than in 1988

circulation at the entrance of the gulf of california from satellite altimeter and hydrographic observations 1 the surface circulation around the entrance to the gulf of california is described from satellite altimetry supported by 10 conductivity temperature depth ctd surveys the sea surface height calculated from the 1 4 world ocean database 2001 climatology plus the archiving validation and interpretation of satellite oceanographic altimeter data october 1992 to january 2008 were rms adjusted to the dynamic height calculated from ctd data the 27 0 kg m 3 isopycnal provided the optimum reference in the mean the surface circulation shows a branch of the california current heading landward toward the gulf of california entrance where it splits into two subbranches these are separated by a cyclonic circulation attached to the coast south of cabo corrientes this feature is produced by sverdrup dynamics and is the first observational indication that the mexican coastal current is generated locally by the wind stress curl as previously suggested by numerical models the global variance of the surface circulation can be separated into seasonal explained variance 35 interannual explained variance 35 and mesoscale explained variance 30 components the seasonal signal which shows the interplay of the poleward mexican coastal current and the equatorward branch of the california current can be explained by a long rossby wave model forced by the annual wind and by radiation from the coast the interannual component is dominated by the el nino southern oscillation which induces in the gulf entrance an anticyclonic cyclonic circulation during el nino la nina this circulation includes a poleward flowing branch during el nino parallel to the pacific coast of the baja california peninsula the mesoscale variability is caused by intense eddy activity

hydrogeochemistry and possible sulfate sources in karst groundwater in chongqing china groundwater from karst subterranean streams is among the world s most important sources of drinking water supplies and the hydrochemical characteristics of karst water are affected by both natural environment and people therefore the study of karst groundwater hydrochemistry and its solutes sources is very important to ensure the normal function of life support systems this paper focused on the major ion chemistry and sulfate isotope of karst groundwater in chongqing for tracing the sulfate sources and related hydrochemical processes hydrochemical types of karst groundwater in chongqing were mainly of the ca hco3 type or ca mg hco3 type however some hydrochemical types were the k na ca so4 type g25 site or ca hco3 so4 type g26 and g14 sites indicating that the hydrochemistry of these sites may be strongly influenced by anthropogenic activities or unique geological characteristics the 34s so42 of collected karst groundwater sample fell into a range of 6 8 to 21 5 with a mean value of 5 6 in dolomite aquifer the 34s so42 value ranges from 4 3 to 11 0 and in limestone aquifer it ranged from 6 8 to 21 5 the groundwater samples from different land use types showed distinctive 34s so42 value the 34s so42 value of groundwater samples had range of 6 8 to 16 7 mean 4 0 n 11 in cultivated land areas 1 5 21 5 mean 7 2 n 20 in forested land areas and 4 3 to 0 8 mean 1 7 n 2 in coalmine areas the 34s so42 values of groundwater samples collected from factory area and town area were 2 2 and 9 9 respectively according to the 34s information of potential sulfate sources this paper discussed the possible sulfate sources of collected karst groundwater samples in chongqing the variations of both 34s and 1 so42 values of the groundwater samples indicated that the atmospheric acid deposition aad dissolution of gypsum gd oxidation of sulfide mineral os or anthropogenic inputs sf sewage or fertilizer contributed to sulfate in karst groundwater the influence of oxidation of sulfide mineral atmospheric acid deposit and anthropogenic inputs to groundwater in chongqing karst areas was much widespread for protecting sustaining and utilizing the groundwater resources the sewage possibly originating from urban mine or industrial area must be controlled and treated and the use of fertilizer should be limited

isotopic composition of sulfate as a tracer of natural and anthropogenic influences on groundwater geochemistry in an urban sandstone aquifer birmingham uk abstract development and management of urban groundwater resources is limited in practice by a lack of knowledge of the nature distribution and sources of groundwater contamination in an urban aquifer that may have had complex land use and abstraction history sulfate is associated with many of the solute sources to urban groundwater and in this study the use of dual isotope 18o and 34s fingerprinting of so 4 2 in groundwater to assess the contribution of different sources to urban groundwater is investigated groundwater 70 locations and surface water samples from the city of birmingham on the triassic sherwood sandstone aquifer have been analyzed for inorganic chemical and so 4 2 isotopic composition isotopic compositions of so 4 2 associated with various solute sources have also been determined sulfate derived from pyrite oxidation during recharge through quaternary drift deposits is characteristically depleted in 18o and 34s compared to other sources and is ubiquitous in unconfined zone groundwater though the contribution from this source has increased markedly following draw down induced by abstraction from the aquifer in unpolluted groundwaters other so 4 2 sources are dissolution of evaporite minerals confined zone and rainfall unconfined zone unfortunately so 4 2 isotopic composition cannot distinguish between made ground i e artificial man made ground usually demolition waste and sewage sources of so 4 2 which constitute the major contributions to so 4 2 in polluted urban groundwater at most sites contributions of so 4 2 from spilt industrial acids do have a distinctive isotopic composition seen at many metal working and former metal working sites estimates of solute contributions derived from these sources derived in this way provide a useful check on the calibration of aquifer and pollutant flux recharge models for urban groundwater

curved fold and thrust accretion during the extrusion of a synorogenic viscous allochthonous sheet the estepa range external zones western betic cordillera spain 1 new structural borehole and time domain electromagnetic data allow us to reconstruct the 3 d geometry of the estepa range external zones of the western betic cordillera which constitutes an isolated curved fold and thrust range made up of jurassic shallow marine carbonates and cretaceous to paleocene marls and marly limestones contraction and rising load linked to the accretion of the subbetic nappe enhanced the expulsion of triassic evaporites and overpressured clays during the early and middle miocene finally forming part of a highly deformed melange unit this plastic extrusion favored the disconnection of external and middle subbetic blocks including the sierra de estepa range there deformation is characterized by northwest vergent curved folds and thrusts associated with ne sw frontal ramps and nw se lateral transfer faults that segmented the folds active between 18 and 12 ma at a local scale curvature was achieved under a nearly uniform nw wnw transport direction suggesting a primary arc type friction variation across the heterogeneous detached plastic basal triassic unit mainly controlled the curvature and segmentation of the fold systems transport direction is consistent with previously published slip data from the internal subbetic and the campo de gibraltar units after the late serravallian accretion slowed down and a shallow marine unit deposited unconformably placed over the main thrust and folds the sequence of deformation and emplacement of these ranges is interpreted as a continuous process linked to the early miocene e continental collision of the iberian margin thin continental crust and subduction of the flysch trough oceanic crust beneath the alboran continental domain