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

impact of co2 geological sequestration on the nucleation of earthquakes 1 can co2 storage cause earthquakes what is the maximum possible earthquake magnitude resulting from co2 injection here as a theoretical case study we investigate these questions using coupled hydromechanical modeling with multiphase flow and seismological variables for quantifying earthquake magnitude and energy our simulations consider transient fluid flow and stress coupling and the evolution of fault properties we simulate co2 injection into a reservoir caprock system bounded by a subvertical normal fault subjected to different extensional stress regimes and over a range of initial fault permeability values for our assumed system and injection rate the simulation results show that sudden stress drop and fault slip primarily initiated along the fault portion intersecting the storage reservoir after a few months of injection when a sufficiently high reservoir pressure has been reached the size of the rupture area and consequently the earthquake magnitude and energy depends on initial horizontal to vertical stress ratio and fault permeability which strongly influences the size of the pressurized area and subsequent stress variations

on the three dimensional numerical modeling of the deep circulation around angel de la guarda island in the gulf of california a three dimensional nonlinear baroclinic model is used to model the circulation in the ballenas channel gulf of california mexico which was inferred from current meter observations over three sills that surround the area the suggested circulation consists of deep inflow that follows two paths the first one is a direct spill of water through san lorenzo sill into ballenas channel the second one a larger route that starts at san esteban sill then flows north of the island passing over tiburon and delfin basins and then turns to the south reaching the north ballenas channel sill and then spills into ballenas channel following the latter result a previous modeling effort to reproduce the circulation was partially obtained the long path was not reproduced and it was believed that finer horizontal resolution was needed in this work the bathymetric resolution was increased by a factor of three and the full path of this deep circulation is now obtained and corroborated

two overflows in the northern gulf of california 1 two overflows originating at sills in the northern gulf of california are marked by strong average downstream slopes of 17 and 4 near bottom stratification upstream of both sills is relatively strong but the near bottom water is very well mixed downstream of the sills the homogenization of a thick bottom layer downstream albeit close to the sills is indicative of very strong mixing waters in the downstream basins are well ventilated with relatively high oxygen concentrations these hydrographic patterns were observed during three different seasons time series of temperature salinity and potential density show that water flowing over the sills is essentially subsurface subtropical water from the pacific ocean the time series also indicate that water is nearly always denser at the sills compared to water in the downstream basins despite the two fold 800 m and more than three fold 1500 m increase in depth the long term more than a year average current at both sills is bottom intensified with maximum average speeds of 33 and 17 cm s there are also strong tidal currents at the sills although the subinertial currents near the bottom are quite persistent with nearly no flow reversals transports estimated exclusively with the mean flow are about 0 08 and 0 09 sv 1 sv 1 106 m3 s which agree well with previous estimates based on shorter time series and a lower vertical resolution these results indicate that the deep water at both downstream basins are renewed by these overflows which enter at sill depths 400 m and are capable of reaching the deepest part of both basins the overflows appear to be responsible for the main mechanisms that transform subsurface subtropical water into gulf of california water

a numerical investigation of the annual variability in the gulf of california the observations of sea level at the annual frequency in the gulf of california are reproduced both in amplitude and phase with a horizontal two dimensional linear two layer model the main forcing agents through which variability is explained are wind stress and the action of the pacific ocean which excites an internal wave in the mouth of the gulf the surface heating is shown to play a secondary role the response of the basin is qualitatively similar to that observed that is an energetic circulation in the upper layer cyclonic in summer and anticyclonic in winter compared to a weaker and opposite circulation in the bottom layer as well as a transversely averaged horizontal heat flux equal both in amplitude and phase to that calculated with historical hydrographic data the results of the simulation show that variability across the gulf is as important as the longitudinal variability

the effect of the seasonal variation of stratification on the circulation of the northern gulf of california abstract direct current measurements reveal that the circulation of the northern gulf of california in the annual timescale consists of a cyclonic basinwide gyre 0 35 m s 1 that lasts from june to september 4 months and an anticyclonic gyre 0 35 m s 1 lasting from november to april 6 months the transitions between regimes take about three weeks each the hypothesis that the difference in duration of the two circulation regimes is due to the seasonal variation of stratification of the water column is explored by simulations with a nonlinear two layer numerical model of circulation and thermodynamics that includes vertical mixing parameterized as an entrainment velocity the model results agree remarkably well with the observations considering its simplified vertical structure in addition the model predicts a net circulation consisting of an anticyclonic gyre of 0 05 m s 1 with a corresponding average concavity of the interface and a two layer exchange through the main channels of the arc

why does the ballenas channel have the coldest sst in the gulf of california 1 moored and hydrographic observations at the three most important sills in the northern gulf of california ngc are used to describe the circulation at the deepest san esteban se sill 600 m the mean along gulf flow is weak and outward toward the mouth of the gulf in the entire water column whereas the mean deep flow is inward and bottom intensified at the san lorenzo sl sill 400 m which controls the southern entrance to the ballenas channel bc however large tidal currents 1 m s during spring tides in the se sill drive a net inward bottom transport of 0 09 sv 1 sv 1 106 m3 s due to a tidal pumping process at the sl sill the net transport is also about 0 09 sv but here the mean flow contributes more than the tides and both are into the gulf at the northern bc sill which controls the northward entrance to the bc the mean near bottom flow is southward implying that the bottom water of this deep basin is renewed at both of its ends moreover the mean surface flow at both ends of the bc is out of the channel and hence the convergence at the bottom is compensated by a divergence at the surface generating a persistent upwelling 5 m day within the channel this circulation pattern primarily explains why the bc has the coldest sst and is one of the most biologically productive basins in the gulf of california

role of tides and mixing in the formation of an anticyclonic gyre in san pedro martir basin gulf of california abstract a three dimensional numerical model of the seasonal evolution of the hydrography and circulation of the gulf of california predicts a quasi permanent anticyclonic gyre in the central part of the gulf over san pedro martir basin spmb just south of the mid gulf archipelago a historical hydrographic data bank is used to search for evidence of the predicted gyre despite 363 useful profiles in 15 cruises from 1939 1996 sampling in the area of interest only allowed climatological average distributions of temperature and salinity to be obtained from which dynamic height and geostrophic currents were calculated the average distributions of temperature salinity and density all show a concave shape over spmb which translate into a dynamic height dome and therefore into and anticyclonic gyre vertical sections across and along the gulf axis of geostrophic velocity show that the gyre occupies most of the water column which is 800 m deep in the center of spmb experiments with the numerical model indicate that stratification is necessary and that the tidal currents are responsible for the formation of the gyre this occurs through nonlinear interactions friction and advection and vertical mixing mechanisms that are enhanced in spmb due to the proximity of the sills and channels of the midriff archipelago where internal tides are generated

correction to conjugate strike slip faulting along the bangong nujiang suture zone accommodates coeval east west extension and north south shortening in the interior of the tibetan plateau correction

lagrangian surface circulation in the gulf of california from a 3d numerical model the surface circulation of the gulf of california was studied from a lagrangian point of view using the results of a 3d numerical model the advection of particles whose depth is fixed was carried out for annual and monthly periods with 710 particles homogeneously distributed over the gulf an anticyclonic circulation was found at the northern region from october to may and in the central and southern regions during may and from october to november cyclonic circulation was found in the entire gulf from july to august this circulation pattern agrees with direct measurements of drifters in the northern region during the cyclonic period the particles from the central and southern regions travel to the northern basin where they are trapped by a gyre for more than a month on the other hand during the anticyclonic period the particles flow to the southern part of the gulf some particles escape to the pacific ocean and others remain in the gulf and return to the northern part during the cyclonic period the principal gyre that appears on the center of the northern gulf in both cyclonic and anticyclonic periods traps particles for more than 30 days in a radius of 50 km in the central and southern regions a trapping zone was found in the peninsula side where the particles travel less than 100 km in 30 days on the other hand over the continental coast there is a rapid transit zone the particles escape only during the anticyclonic period

seasonal surface connectivity in the gulf of california abstract a three dimensional numerical model is used to study seasonal connectivity in the gulf of california from the eulerian velocity fields of the model particle trajectories were calculated for the 12 months of the year using an advection diffusion scheme connectivity was quantified for twelve gulf provinces with different dynamic circulation characteristics being defined by the eulerian velocity field strong or weak coastal currents eddies and areas of mixing and exchange retention occurred for 9 12 months of the year in the upper gulf eddy and sonora regions of the northern gulf because of the gulf wide eddy circulation which implies high potential for the auto recruitment of larvae in this province high retention was also found on the peninsula side of the southern gulf in association with weaker residual currents again implying potential for self recruitment in contrast low retention was observed on the mainland side of the central and southern gulf from which particles are exported to many areas by the faster residual currents enhancing the potential for recruitment of distant coastal species empirical orthogonal function analyses revealed a strong annual and semiannual evolution in accordance with the strong seasonality of the gulf dynamics

role of grain size in phyllonitisation insights from mineralogy microstructures strain analyses and numerical modeling abstract brittle y and p planes exist in an exposure of greywacke in the garhwal lesser himalaya india although y planes are well developed throughout the p planes are prominent only in some parts domain a and not elsewhere domain b to investigate why the p planes developed selectively the following studies were undertaken 1 clay separated xrd analyses clinochlore and illite are present in both the domains 2 strain analyses by rf method it deduces strain magnitudes of 1 8 for the ductile deformed quartz grains from both the domains a and b 3 grain size analyses of quartz clasts domain a is mostly composed of finer grains area up to 40 000 m2 whereas domain b consists of a population of coarser grains area 45 000 m2 a 2d finite element modeling of linear elastic material was performed using comsol software to investigate the control of grain size variation on the generation brittle shear planes the results of numerical modeling corroborate the known fact that an increase in grain size reduces the elastic strain energy density a broader grain size distribution increases the effects of diffusion creep and resists the onset of dislocation creep thus rocks with coarser grain population domain b tend to resist the generation of shear fractures unlike their fine grained counterpart domain a

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

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

connectivity and larval dispersal along the oregon coast estimated by numerical simulations 1 connectivity and larval dispersal is explored off the oregon coast during the summer upwelling season of 2001 using numerical ocean circulation simulations the study region with strong wind driven currents and variable topography is modeled using the regional ocean modeling system roms forced by the coupled ocean atmosphere mesoscale prediction system a large number of passive particles as models of planktonic larvae are released daily for 120 days from 1 may to 28 august at depths of 1 7 15 20 50 and 75 m at every grid point shoreward of the 200 m isobath on average 32 km offshore the particles are transported by the three dimensional currents of the model simulation the competency time window for larval settlement is assumed to be in between days 15 and 35 after larvae are released larval settlement occurs at the shallowest location during the competency time window connectivity matrices reveal that some of the places of highest retention are similar to the proposed oregon marine reserve sites especially cape perpetua the heceta bank region has high probabilities as both a source and a destination for settled larvae larvae released in the heceta bank region often settle at higher latitudes than their release location there are strong correlations between the number of settled larvae shallower than the 50 m isobath and a 6 to 8 day running mean of the alongshore wind stress larvae are retained near the shore when the winds averaged over the previous 6 to 8 days are relaxed or downwelling favorable

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

surface dispersion in the gulf of california abstract surface dispersion is measured in the gulf of california by means of argos drifters released along this semi enclosed elongated basin first basic one particle statistics lagrangian scales absolute dispersion and diffusion coefficients are estimated along and across the gulf absolute dispersion shows a nearly ballistic regime during the lagrangian time scale t 2 where t is time during the subsequent 30 days absolute dispersion enters a random walk regime t along the gulf while being saturated across the basin due to the lateral boundaries secondly the analysis is extended to two particle statistics relative dispersion between pairs of drifters and finite scale lyapunov exponents fsle relative dispersion is nearly exponential in both directions during the first few days though evidence is not conclusive during the subsequent 30 days it grows as t 1 5 along the gulf while being saturated across the basin again it is shown that relative dispersion along the gulf is proportional to t 3 where t represents a shifted time that depends on the initial separation of the particles this form of the richardson regime is consistently measured for particles that are sufficiently separated 30 km or more the richardson regime is verified with the fsle for particle separations ranging from 30 to 140 km approximately the obtained dispersion properties are discussed in terms of the main circulation features within the basin such as mesoscale vortices that occupy the width of the gulf these structures might retain buoys during days or weeks thus preventing or delaying further displacements and therefore affecting the particle dispersion the vortices are also an important mechanism to translate particles across the gulf between the peninsula and the continent thus promoting the saturation of dispersion along this direction

three dimensional connectivity in the gulf of california based on a numerical model abstract quantifying connectivity is useful for understanding the exchange and trapping of some tracers such as fish larvae and nutrients in the gulf of california connectivity studies have been limited to certain periods and regions the current study investigated the connectivity among 17 areas defined by the presence of eddies and weak or strong flows as obtained from a three dimensional non linear baroclinic model the particles were released into the water column and advected for 28 days using an advection diffusion scheme the results revealed a seasonal connectivity pattern in the northern region particle trapping was greater during the cyclonic circulation period june to september compared with the anticyclonic period november to march this high retention was due to both the presence of a cyclonic eddy in the central portion of the region and the intense northwestward flow off the coast of sonora retentions were low for the large island region due to the intense exchange between the northern and southern regions east of angel de la guarda island the transport occurred predominantly towards the northwest due to the nearly permanent deep flow in that direction and to a branching of the surface flow among the large islands during the anticyclonic period and the northwestward low during the cyclonic period in the peninsular and central areas of the southern region retentions were high due to weak flows and the presence of eddies respectively the greatest retention and low dispersion of particles in practically all of the provinces were recorded during the transition periods of the circulation

sediment transport patterns inferred from grain size trends and trace metal dispersion near the santa rosalia mining district gulf of california abstract the transport of continental materials of natural and or anthropic origin as well as their dispersion and final deposition in marine environments can be inferred from the analysis of the textural tendencies of sediments the exploitation of copper ore since the 19th century in the santa rosalia mining district has caused the accumulation of potentially toxic elements ptes in sediments off the western coast of the gulf of california however after several decades of mining little is known about the mobilization and final destination of these ptes in the present work the net sedimentary transport and dispersion of cu and zn is inferred in front of the mining district of santa rosalia at the western margin of the gulf of california net sedimentary transport is dominantly towards the southeast with a change towards the east of the port of santa rosalia the spatial distribution of cu and zn showed the same pattern as the net sediment transport which suggests that the dispersion of ptes is controlled by the textural tendencies of the sediments and their transport corroborated by hydrodynamic models of the marine currents at the western margin of the gulf of california

v pull apart microstructures a new shear sense indicator abstract granitoids deformed in a low grade shear zone show conspicuous development of asymmetric pull apart microstructures in feldspars characterized by v shaped gaps between the separated fragments v pull aparts they occur beside active shear planes and result from rigid body rotation of one fragment relative to the other the shear sense in the adjacent flow surface can be easily determined through the asymmetry normally shown by v pull aparts where the fracture wall at a lower angle to the shear plane indicates which fragment has rotated synthetically to the adjacent shearing another diagnostic feature is the foliation deflection that occurs adjacent to the rotated fragment the v shaped gaps are infilled by recrystallized quartz mica aggregates showing quartz c axis patterns indicative of strong participation of crystal plastic processes in these domains evidence of crack seal by precipitation c axes parallel to the direction of separation have also been found the rigid body rotation indicated by these microstructures worked as a mechanism of removal of protruding porphyroclast edges enabling the smoothing of the shear planes rigid body rotation should operate in circumstances where other mechanisms such as dissolution or crystal plasticity did not succeed in eliminating undulations along the shear planes

tidal current ellipses in a three dimensional baroclinic numerical model of the gulf of california using a numerical model of the circulation of the gulf of california a description of the tidal ellipses parameters is given the best modeled constituents are those of the semidiurnal band while those of the diurnal band are underestimated in general tidal ellipse semimajor axes for the diurnal and semidiurnal bands increase from south to north with a maximum in the archipelago area the annual and semiannual components are largest in the southern part the eccentricity of the internal tide is larger than the barotropic tide but in general the currents are mostly rectilinear with no preferred sense of rotation it is found that the barotropic currents are more energetic than the baroclinic currents the most energetic component is the barotropic m2 component followed by the ssa s2 and sa harmonics for the internal currents the energy levels of the m2 ssa and sa harmonics are about the same and are much larger than the rest of the constituents

seasonal evolution of the geostrophic circulation in the northern gulf of california abstract an improved description of the seasonal variability of the geostrophic circulation in the northern gulf of california is obtained from a historical hydrographic database larger than in previous studies the evolution of the geostrophic circulation consists of a cyclonic summer period an anticyclonic winter period and two transition periods the cyclonic summer period lasts from june to september four months and is characterized by a strongly baroclinic cyclonic gyre which dominates the circulation the anticyclonic winter period starts in november and persists until april six months the anticyclonic geostrophic circulation is less robust than that in summer the transition periods take of the order of one month occurring around october and april may and are characterized by the simultaneous presence of both types of gyres empirical orthogonal function analysis shows a strong seasonal signal in the dynamic height for the first mode 97 2 of the total variance whose spatial structure is a closed gyre which oscillates between cyclonic during the summer months and anticyclonic the rest of the year the results strengthen and extend those from previous work based on analysis of hydrographic data on limited direct observations on satellite image analysis and on numerical modelling