persistent upwelling and front over the sulu ridge and their variations the persistent upwelling and front isolated over the sulu ridge are newly detected by a suite of satellite measurements and confirmed by historical cruise observations a three dimensional tide circulation coupled model is employed to investigate the dynamic mechanisms the intense vertical velocity shear induced by the vigorous internal tidal mixing is identified as the vital dynamic factor to trigger the upwelling and nutrient pumping through the strong tide topography interactions satellite observations indicate that the pronounced surface cooling and phytoplankton bloom are isolated over the sulu ridge throughout the year the steady front characterizes 10 20 km width and strength over 0 3 degrees c km near the southern edge the feature is further confirmed by the numerical simulation and in situ hydrological observation modeling experiment suggests that a quasi symmetrical vertical circulation bifurcation across the sulu ridge due to the asymmetry of tidal currents is the main mechanism to maintain the persistent upwelling and front moreover the local wind forcing plays an important regulating role in the seasonal and interannual variations the surface cooling and thermal front intensity reach the maximum in winter under the forcing of strong northeasterly monsoons due to prolonged el nino southern oscillation enso effects the surface cooling was significantly weakened during 1998 and 2010 summer further analysis indicates the fact that the southwesterly monsoon is weakened dramatically as part of the anticyclonic atmospheric circulation anomalies over the northwest pacific the latter results from the significant influence of tropical indian ocean capacitor effect associated with el nino southern oscillation

topex poseidon derived space time variations of the kuroshio current applications of a gravimetric geoid and wavelet analysis summary using topex poseidon t p altimeter data and a gravimetric geoid we derived 7 year time series of kuroshio s volume transport axis velocity width and axis locations northeast and southeast of taiwan for northeastern and southeastern taiwan the mean volume transports are 19 and 26 sv the mean widths are 112 and 96 km and the mean axis velocities are 50 and 82 cm s 1 respectively the t p derived volume transports agree well with in situ result drifter d21160 almost passes through the t p derived axes of the kuroshio the time series show intraseasonal semi annual annual and interannual variations but the frequency characteristics at the two locations are different owing to monsoon bottom topography and other factors wavelet analyses show that the amplitudes and phases of the frequency components vary with time a biennial component is found in almost all time series and may be excited by the tropical quasi biennial oscillation of the atmosphere the volume transport northeast of taiwan has a positive correlation 0 6 with enso with a 1 month lag and both the volume transport and velocity southeast of taiwan have a negative correlation 0 6 with enso with a 9 10 months lead

chemical and isotopic compositions of thermal springs fumaroles and bubbling gases at tacana volcano mexico guatemala implications for volcanic surveillance this study presents baseline data for future geochemical monitoring of the active tacana volcano hydrothermal system mexico guatemala seven groups of thermal springs related to a nw se oriented fault scarp cutting the summit area 4 100m a s l discharge at the northwest foot of the volcano 1 500 2 000m a s l another one on the southern ends of tacana la calera the near neutral ph from 5 8 to 6 9 thermal t from 25 7 c to 63 0 c hco3 so4 waters are thought to have formed by the absorption of a h2s so2 co2 enriched steam into a cl rich geothermal aquifer afterwards mixed by na hco3 enriched meteoric waters originating from the higher elevations of the volcano as stated by the isotopic composition d and 18o of meteoric and spring waters boiling temperature fumaroles 89 c at 3 600m a s l nw of the summit formed after the may 1986 phreatic explosion emit isotopically light vapour d and 18o as low as 128 and 19 9 respectively resulting from steam separation from the summit aquifer fumarolic as well as bubbling gases at five springs are co2 dominated the 13cco2 for all gases show typical magmatic values of 3 6 1 3 vs v pdb the large range in 3he 4he ratios for bubbling dissolved and fumarolic gases from 1 3 to 6 9 atmospheric 3he 4he ratio r a is ascribed to a different degree of near surface boiling processes inside a heterogeneous aquifer at the contact between the volcanic edifice and the crystalline basement 4he source tacana volcano offers a unique opportunity to give insight into shallow hydrothermal and deep magmatic processes affecting the co2 3he ratio of gases bubbling springs with lower gas water ratios show higher 3he 4he ratios and consequently lower co2 3he ratios e g zarco spring typical central american co2 3he and 3he 4he ratios are found for the fumarolic agua caliente and zarco gases 3 1 1 6 1010 and 6 0 0 9 r a respectively the l s 5 9 0 5 and l s m ratios 9 2 0 7 for the same gases are almost identical to the ones calculated for gases in el salvador suggesting an enhanced slab contribution as far as the northern extreme of the central american volcanic arc tacana

a numerical study on the formation of upwelling off northeast taiwan 1 we examined the spatial and temporal variations of upwelling off northeast taiwan using a fine resolution numerical model with realistic bathymetry the zonally running shelf break in the area deflects the kuroshio seaward and produces upwelling on its on shelf edge the upwelling in turn manifests a cold dome or a cyclonic eddy in depths below 150 m or so the upwelling and hence the cyclonic eddy exist year round above this depth the eddy waxes and wanes as the upper portion of the kuroshio migrates seaward and shoreward respectively the eddy event fluctuates in a wide range of timescales seasonally the occurrence heavily favors summer rather than winter because the mean kuroshio axis migrates seaward in summer intraseasonally the fluctuation contains two dominant periods centered at 70 days and 30 days local wind forcing and channeling by two local canyons do not affect the eddy statistics significantly

upper ocean currents around taiwan abstract current velocity measured by shipboard acoustic doppler current profiler sb adcp during 1991 2000 was used to study the upper ocean the composite and moored currents revealed a branch of the kuroshio that intruded steadily and persistently into the south china sea part of the intruded kuroshio flowed out of the south china sea through the northern luzon strait and re united with the main stream kuroshio the kuroshio had two velocity maximum cores southeast of taiwan but gradually combined into one as the kuroshio flowed north the kuroshio was deflected by the i lan ridge east of taiwan and the zonal running shelf break northeast of taiwan at the shelf break the kuroshio split with one branch intruding onto the shelf west of the luzon strait the kuroshio intruded into the south china sea some water flowed northward into the taiwan strait and re joined the kuroshio currents in the taiwan strait flowed primarily in a northward direction except for the southward current near the coast of mainland china north of the taiwan strait a branch of the northward flow followed the northern coast of taiwan to join the kuroshio the composite current varied consistently from season to season there was generally poor correlation between currents and local winds especially in the deep water regime remote forces were important in the currents around taiwan

volatiles and energy released by purace volcano total co2 output of purace volcano colombia was estimated on the basis of fluids discharged by fumaroles soil gases and dissolved carbon species in the aquifer the soil co2 emission was computed from a field survey of 512 points of co2 soil flux measurements at the main degassing areas of purace volcano the co2 flux from purace s plume was estimated using an indirect method that used the so2 plume flux and co2 so2 ratio of the main high temperature fumarole the total output of co2 was estimated at 1500 t day the main contribution of co2 comes from the plume summit degassing and from soil degassing that emit 673 and 812 t day respectively the contributions of summit and soil degassing areas are comparable indicating an intermediate degassing style partitioned between closed and open conduit systems the estimated water vapor discharge as derived from the chemical composition of the fumaroles the h2o co2 ratio and the so2 plume flux allowed calculation of the total thermal energy fumarolic soil degassing and aquifer released from the purace volcanic system this was 360 mw

topex poseidon observations of mesoscale eddies over the subtropical countercurrent kinematic characteristics of an anticyclonic eddy and a cyclonic eddy 1 relative dynamic heights and geostrophic fields were derived from topex poseidon altimetry data and then used to track mesoscale eddies over the subtropical countercurrent stcc the radii centers vorticities shearing deformation rates stretching deformation rates divergences and center velocities of all identified eddies over the stcc were determined using a model that assumes constant velocity gradients most eddies are concentrated in a zonal band near 22 n and there is an interannual variation in the number of eddies a case study was made for a cyclonic eddy and an anticyclonic eddy with time series of eddy kinematic parameters computed both eddies survive for 220 days and propagate westward along over 22 n 24 n to reach the kuroshio current east coast of taiwan where the eddies were dissipated and in turn affected the kuroshio current in many ways sea surface temperature data and drifter data confirm the existence of these two eddies the radii of both eddies vary and their shapes are mostly elliptical during propagation the anticyclonic eddy propagated almost westward with oscillating north south components and the mean speed is 8 3 km day the cyclonic eddy moved southwestward before reaching 130 e and then moved northwestward with a mean speed of 7 6 km day the propagations of these two eddies are basically consistent with the standard theory of eddy propagation but with larger speeds the propagating direction could be altered while passing steep bottom topography or merging with the other eddies index terms 4520 oceanography physical eddies and mesoscale processes 4576 oceanography physical western boundary currents 4512 oceanography physical currents 4594 oceanography physical instruments and techniques 4556 oceanography physical sea level variations

solute fluxes and geothermal potential of tacana volcano hydrothermal system mexico guatemala abstract solute and heat fluxes from thermal springs of tacana volcano are estimated by the chloride inventory method the thermal springs located at the northwestern slopes of the volcanic edifice at altitudes from 1500 to 2000 m above sea level discharge water enriched in hco 3 and so 4 up to 1 g kg 1 of each one with temperatures in the 25 63 c range there are two distinct groups of springs with a different chloride temperature correlation but with the same 87 sr 86 sr ratio 0 7046 0 0001 indicating the same wall rock composition for different aquifers each thermal spring feeds a thermal stream that flows into the main drainage of the area rio coatan the total observed chloride discharge from the thermal springs is estimated as 14 8 g s 1 and the total measured heat output of 9 5 mw considering a deep fluid temperature of 250 c calculated using na k geothermometer the corresponding advective heat transport from the deep reservoirs that feed these springs may be estimated as 26 mwt however the total chloride output measured in the main drainage coatan river is 4 times higher 59 g s 1 than the measured cl output of thermal springs this means that other undiscovered thermal springs exist in the area and that the natural heat output through thermal springs at tacana is significantly higher and depends on the cl content and temperatures of the unknown thermal water discharges if chloride concentration in these unknown springs does not exceed 540 mg l 1 the highest analyzed cl in tacana springs and the discharge temperature is 50 c then the natural heat output can be estimated at least as 22 mwt and the corresponding advective heat transport as 100 mwt

late pleistocene flank collapse triggered by dome growth at tacana volcano mexico guatemala and its relationship to the regional stress regime during late pleistocene time the extrusion of an andesitic dome at the summit of tacana volcano caused the collapse of its northwestern flank the stratocone collapse was nearly parallel to the min stress direction suggesting that failure was controlled by the regional stress field the event produced a debris avalanche that was channelized in the san rafael river and moved 8 km downstream the deposit covered a minimum area of 4 km2 had a volume of 0 8 0 5 km3 with an h l vertical drop to horizontal transport distance ratio of 0 35 defining a degree of mobility that is atypical for volcanic debris avalanches the flank failure undermined the summit dome leading to its collapse and the generation of a series of block and ash flows that were emplaced in quick succession and covered the avalanche surface the collapse event left a 600 m wide summit amphitheatre with a 30 degree opening to the northwest and 200 m thick debris that blocked the san rafael river remobilization of this material produced debris flows that eroded the primary deposits and cascaded into the coatan river after the collapse the activity of tacana continued with the emission of the agua zarca lava flow dated at 10 6 ka 40ar 39ar and pyroclastic surges dated at 10 610 330 315 yr bp 14c which provide a minimum age for the collapse event during the holocene tacana has been very active producing explosive and effusive eruptions that ended with the extrusion of two summit domes that today occupy the amphitheatre the 1950 and 1986 phreatic outbursts occurred along the pleistocene collapse scar currently 300 000 inhabitants live within a 35 km radius of tacana and could conceivably be impacted by future events of similar magnitude

upwelling in the taiwan strait during the summer monsoon detected by satellite and shipboard measurements the taiwan strait is located at the confluence of the east china sea and the south china sea in the west pacific ocean several upwelling zones in the taiwan strait are noted for their high fisheries production these upwelling zones have been studied in the past decade but we have no overall picture on the size and temporal changes of these upwelling zones due to only limited in situ observation over short periods of time the present paper investigates upwelling in the taiwan strait with satellite remote sensing data of noaa derived sea surface temperature sst and seawifs derived chlorophyll a chl a and shipboard measurements during summer 1998 results reveal five upwelling zones 1 coastal upwelling near pingtan island ptu 2 coastal upwelling between meizhou and xiaman mxu 3 big coastal upwelling near dongshan island dsu sometimes extending to offshore 4 small occasional upwelling near the penghu island phu and 5 an intensive upwelling in the taiwan bank tbu tbu was extensively studied over summer 1998 results showed that the tbu looks like a banana in shape in the southern edge of the taiwan bank it intensifies in its southeastern edge the size of tbu was about 2500 3000 km 2 with a mean value of 2796 km 2 the temperature difference between the upwelling and non upwelling areas was about 2 5 3 5 jc for early august with a mean value of 2 3 jc on july to october series of images indicated a short term variation of tbu and showed that high chl a concentrations up to 0 8 2 mg m 3 zones coincided with low sst 25 26 jc zones in terms of location time and shape these upwelling zones change with size and intensity center from time to time field measurements of water temperature salinity and chl a in 1998 are consistent with satellite measurements d 2002 elsevier science inc all rights reserved

reconstruction of the sibinal pumice an andesitic plinian eruption at tacana volcanic complex mexico guatemala abstract the tacana volcanic complex located on the mexico guatemala border has had numerous small historical explosions the latest being a phreatic explosion in 1986 the stratigraphic record however suggests that much more voluminous eruptions have occurred in the past here we document one such eruption the sibinal pumice deposit which occurred ca 23 540 years b p the deposit consists of two pumice rich units 1 a lower stratified member sm that consists of at least seven normally graded fall layers interbedded with pyroclastic wet surge layers and 2 an upper massive member mm made up of a single fall deposit both members can reach up to 2 5 m in thickness and are separated by a single massive indurated yellowish pumice rich reworked layer sm was dispersed to the northeast n70 e with its 6 cm isopach covering an area of 275 km2 whereas mm was dispersed to the north n22 e with its 70 cm isopach covering an area of ca 330 km2 yellow vesicular pumice fragments light gray lithics and hydrothermally altered red and black dense lithics are abundant in both members although altered lithics are more abundant at the base of each reaching 15 vol pumice compositions range from basaltic to andesitic 48 61 wt sio2 anhydrous basis but are highly altered they contain plagioclase andesine labradorite augite hypersthene fe ti oxides and rare amphibole no compositional or mineralogical differences occur between the units indicating a common magma source during the same eruption the sibinal pumice eruption started with a weak pulsating column that reached at most 19 km in height ejecting 2 9 km3 of tephra 1 1 km3 dre at an average mass discharge rate of 4 7 107 kg s with repeated hydromagmatic explosions that generated wet surges down the slopes of the volcano the eruption ceased for a while during which rainfall generated a widespread lahar that eroded the top of sm the eruption began anew with a sustained and stable plinian column that ejected 4 6 km3 1 9 km3 dre of tephra at a mass discharge rate of 8 1 107 kg s the lack of any compositional differences in the magma suggests that the change in eruptive style was driven by influxes of external water provoking hydromagmatic explosions that cleared the conduit then the system changed to dry system and the eruption style changed from pulsating to stable plinian as the conduit became wider the mass discharge rate also increased

chemical geothermometry and geobarometry in hydrothermal aqueous solutions a theoretical investigation based on a mineral solution equilibrium model abstract the theoretical compositions of an aqueous solution in equilibrium with a mineral assemblage made up of low albite k feldspar either a ca al silicate or calcite clinochlore muscovite quartz anhydrite and fluorite under varying t pco2 mcl conditions of geothermal interest indicate that 1 1 the total so4 content as well as the na k k 2 mg and so 4 f 2 ratios are potential geothermometers 2 2 the total hco3 content as well as the k 2 ca ca mg hco 3 f and hco 3 2 so 4 ratios are potential pco2 indicators 3 3 the na k ca and mg total contents as well as the na 2 mg and na 2 ca ratios are mainly controlled by the total ionic salinity and are therefore hardly suitable as geoindicators a preliminary test of the equations involving total hco3 content as well as k 2 ca and hco 3 f ratios as pco2 indicators have provided satisfactory results

the domuyo volcanic system an enormous geothermal resource in argentine patagonia abstract a geochemical survey of the main thermal waters discharging in the southwestern part of the domuyo volcanic complex argentina where the latest volcanic activity dates to 0 11 ma has highlighted the extraordinarily high heat loss from this remote site in patagonia the thermal water discharges are mostly na cl in composition and have tds values up to 3 78 g l 1 el humazo a simple hydrogeochemical approach shows that 1 100 to 1 300 kg s 1 of boiling waters which have been affected by shallow steam separation flow into the main drainage of the area rio varvarco a dramatic increase of the most conservative species such as na cl and li from the rio varvarco from upstream to downstream was observed and related solely to the contribution of hydrothermal fluids the equilibrium temperatures of the discharging thermal fluids calculated on the basis of the na k mg geothermometer are between 190 c and 230 c if we refer to a liquid originally at 220 c enthalpy 944 j g 1 the thermal energy release can be estimated as high as 1 1 0 2 gw a value that is much higher than the natural release of heat in other important geothermal fields worldwide e g mutnovsky russia wairakei new zealand and lassen peak usa this value is the second highest measured advective heat flux from any hydrothermal system on earth after yellowstone

seasonal and interannual changes of the kuroshio intrusion onto the east china sea shelf an advanced artificial neural network classification algorithm is applied to 20 years of multisatellite geostrophic velocity data to study the kuroshio intrusion onto the southern shelf of the east china sea the results suggest that the on shelf intrusion may occur year round but winter intrusion events are more frequent than summer events both stronger intrusion which is closely correlated to surface heat flux gradient and weaker intrusion which is correlated to wind forcing occur during wintertime but the former dominates in late winter while the latter prevails in early winter there is a significant year to year variation of the winter on shelf intrusion although on shelf intrusion is the major characteristic of the region during wintertime seldom intrusion events have been identified in the winters of 1997 1998 and 2002 2003 two conditions are responsible for the cause of the nonintrusion events during the two nonintrusion winters the upstream kuroshio transport anomaly is insignificant the kuroshio is not weakened and no significant winter cooling off northeast taiwan thus the kuroshio tends to flow along the shelf break following the 200 m isobath and on shelf intrusion ceases those two nonintrusion events take place during the winters when both the nino 3 4 index and the pdo index are large and positive

fluctuations of the thermal fronts off northeastern taiwan 1 a high resolution sea surface temperature sst data derived from several satellites is used to investigate the variability of the thermal front off northeastern taiwan hidden by a dominant annual cycle the sst data cannot reveal the thermal front fluctuation in the form of hovmoller diagram an innovative methodology has been applied to the sst satellite imagery to derive the sst standardized index sstsi capable of revealing the frontal variability with multiple time scales principal component analysis shows that the sstsi variation consists mainly of two modes mode 1 represents a strong annual cycle related to the seasonal reversal of the monsoonal winds the temperature gradient is enhanced in winter and a cold dome is observed off northern taiwan in summer mode 2 is highly correlated with the upstream kuroshio variability the shoreward seaward migration of the thermal front takes place when the kuroshio transport weakens strengthens the results are consistent with transports estimated by tidal gauge measurements satellite altimeter based sea level anomaly and surface flow patterns derived from high frequency radars mode 2 is coherent with the kuroshio transport through the east taiwan channel at periods of 120 and 45 d with a time lag of 40 and 11 d respectively this 120 d fluctuation is due to the interaction between westward propagating eddies and the kuroshio east of taiwan while the 45 d signal arises from the kuroshio s self instability the interannual variations of the sst pattern in winter and summer are also discussed

multidecadal variations of the surface kuroshio between 1950s and 2000s and its impacts on surrounding waters based on the analyses of 59 year 1950 2008 surface geostrophic velocities the multidecadal changes of kuroshio from the eastern luzon to the southern japan are investigated result shows that the upstream kuroshio from the east of luzon to southern east china sea suffers much more obvious multidecadal changes except for the decade of 1980 the kuroshio east of luzon possesses a multidecadal tendency opposite to that east of taiwan besides 1980s the multidecadal change of kuroshio bordering taiwan is mainly governed by the eddy activity off the eastern taiwan while the wind stress curl plays a major role in the kuroshio in the east of luzon and in the luzon strait the wind stress induced ekman transport plays a secondary role in regulating the kuroshio east of luzon in addition the multidecadal fluctuation of kuroshio east of luzon also modulates the westward intrusion in the luzon strait instead the ekman transport dominated the whole upstream kuroshio area from the eastern luzon to the vicinity of taiwan during the exceptional decade of 1980 associated changes of water properties in the northern south china sea and southern east china sea are also ascribed to the multidecadal changes of surface kuroshio in the upstream area

chemical changes in spring waters at tacana volcano chiapas mexico a possible precursor of the may 1986 seismic crisis and phreatic explosion abstract local seismic activity consisting of sharp earthquakes accompanied by thunderous noise was reported starting in late december 1985 around tacana volcano 15 13 n 92 10 w portable seismic stations were established in the area by late january 1986 and sampling of the only known thermal spring on the volcano flanks started at the same time a marked increase in so42 concentration in the spring water preceded by two months the occurrence of a seismic swarm crisis and a small phreatic explosion a model involving a crystalline basement fractured by tectonic stresses is proposed to explain the chemical and seismic anomalies and the consequences on risk of volcanic activity are briefly discussed in terms of the observed behaviour

spatial and temporal variations of the kuroshio east of taiwan 1982 2005 a numerical study 1 a 1 8 east asian marginal seas model nested to a larger domain north pacific ocean model is implemented over a span of 24 years from 1982 to 2005 to investigate the spatial and temporal variations of the kuroshio east of taiwan between 22 and 25 n the mean state and variability of the kuroshio such as the two paths observed in the trajectories of surface drifters southeast of taiwan and the branching of the kuroshio northeast of taiwan are well reproduced by the model southeast of taiwan the kuroshio is mostly in the top 300 m in the inshore path but extends to 600 m in the offshore path northeast of taiwan the kuroshio follows the shelf edge in the east china sea but may branch along a path south of the ryukyu islands the latter path often meanders southward and a significant portion of the kuroshio transport may be diverted to this path the kuroshio extends from the coast to 123 123 5 e between 22 and 25 n with currents reaching a depth of 1000 m at some latitudes the kuroshio transports averaged over five sections east of taiwan are 28 4 5 0 sv and 32 7 4 4 sv with and without the contribution from the countercurrent respectively

late holocene pelean style eruption at tacana volcano mexico and guatemala past present and future hazards tacana volcano located on the border between mexico and guatemala marks the northern extent of the central american volcanic chain composed of three volcanic structures it is a volcanic complex that has had periodic explosive eruptions for at least the past 40 k y the most recent major eruption occurred at the san antonio volcano the youngest volcanic edifice forming the complex about 1950 yr ago the pelean style eruption issued from the southwest part of the dome and swept a 30 sector with a hot block and ash flow that traveled about 14 km along the cahoacan ravine deposits from this event are well exposed around the town of mixcun and were therefore given the name of that town the mixcun flow deposit the mixcun flow deposit is in the channel facies a light gray massive thick 10 m matrix supported unit with dispersed lithic clasts of gravel to boulder size divisible in some sections into a variable number of flow units the overbank facies is represented by a thin 1 m massive matrix supported unit in both of these facies the deposit has disseminated charcoal fumarolic pipes and juvenile lithics with cooling joints the mixcun flow deposit contains clasts of 1 light gray dense andesite 2 dark gray glassy and banded andesite and 3 minor altered red andesite from the edifice set in a matrix of sand and silt the mixcun flow deposit covers an area of at least 25 km2 and has a minimum estimated volume of 0 12 km3 basaltic andesite inclusions 54 sio2 and various signs of disequilibrium in the mineral assemblage of the two pyroxene andesitic products 60 63 sio2 suggest that magma mixing may have triggered the eruption following deposition of the mixcun flow deposit andesitic to dacitic 62 64 sio2 lava flows were extruded and a dacitic dome 64 4 sio2 at the san antonio summit formed syn eruptive and posteruptive lahars flooded the main drainages of the cahoacan and izapa mixcun valleys in the area of the present city of tapachula population 250000 and the pre hispanic center of izapa three radiocarbon ages date this event between a d 25 and 72 range 1 38 b c a d 216 which correlates with a halt in construction at izapa hato phase of ca 50 b c a d 100 probably due to temporary abandonment of the city caused by lahars another similar event would produce extensive damage to the towns population of about 68 000 people now built upon the mixcun flow deposit the main summit of tacana volcano continues to show signs of fumarolic activity the most recent period of activity in 1985 1986 culminated in a minor phreatic explosion

preliminary paleomagnetic results from the triassic prida formation lower star peak group west central nevada and implications for latitudinal displacement paleomagnetic data were obtained from two oppositely dipping carbonate sections of the triassic prida formation lower star peak group in the humboldt range of west central nevada progressive demagnetization of the rocks indicated that the remanent magnetization consists of three or fewer vector components a characteristic component with the highest unblocking temperatures was most effectively isolated by low temperature 200 300 c thermal followed by progressive alternating field demagnetization the sections yield in situ mean directions that differ significantly but that have similar inclinations star canyon d 311 i 34 95 5 k 22 n 38 samples fossil hill d 281 i 33 95 2 k 2814 n 3 section means 154 samples the directions diverge upon simple structural correction from which we infer that at least one and probably both of the sections were remagnetized probably in latest middle to late jurassic time these data cannot be used to indicate significant southward translation of golconda allochthon rocks as inferred from magnetizations in underlying volcanic rocks the translation interpretation may require revision if magnetizations in the volcanic rocks are also secondary

sources fate and flux of riverine solutes in the southwest yellowstone plateau volcanic field usa abstract since the 1970s temporal variations of hydrothermal discharge and thermal output from the numerous hydrothermal features in the yellowstone plateau volcanic field ypvf have been studied by measuring the chloride flux in the major rivers in this study the sources fate and flux of solutes in the fall river and its major tributaries in southwest yellowstone national park were determined the considerable precipitation in southwest ypvf and high groundwater flow through quaternary rhyolites results in river solute fluxes that originate from shallow non thermal groundwater and deep thermal water specific conductance serves as a surrogate measure for thirteen riverine solute concentrations combining continuous 15 minute specific conductance and discharge data the annual chloride arsenic fluoride and silica fluxes from the fall river were determined to be 11 5 25 and 19 of the total flux exiting ypvf approximately 11 of the fall river chloride flux is from non thermal waters which is larger than the previous estimate of 4 to 6 furthermore a large proportion of fluoride and silica in the fall river are derived from water rock interaction in the shallow non thermal groundwater system and the non thermal weathering rate 30 2 t yr km2 is higher than other rivers draining the yellowstone caldera consequently 73 3 of the annual total dissolved solid flux in the fall river is from thermal sources synoptic sampling of river water and discharge measurements was performed during low flow conditions that allowed for the determination of solute sources and their downstream fate it was determined that chloride sodium arsenic rubidium lithium and boron are primarily 89 associated with thermal waters and the bechler river is the primary source of most hydrothermal solutes in the fall river but the major source of arsenic is boundary creek using the chloride inventory method the thermal water discharge from several thermal areas was also determined

seasonal to interannual variations in the intensity and central position of the surface kuroshio east of taiwan 1 seasonal and interannual changes of surface kuroshio intensity and central position east of taiwan during 1993 2012 are investigated by quantitatively analyzing the satellite altimetry product the kuroshio moves inshore offshore off northeast of taiwan in winter summer whereas it has an offshore inshore path off southeast of taiwan in winter summer the seasonal change of heat flux over the east china sea shelf is found to cause the seasonality of the kuroshio central position off northeast of taiwan whereas the seasonal kuroshio movement off southeast of taiwan is found to be induced by the combined effect of the kuroshio changes through the luzon strait and the eastern luzon island in contrast to this y dependent path changes the kuroshio becomes weaker stronger as a whole east of taiwan in winter summer on the interannual time scales the kuroshio throughout the eastern coast of taiwan intensifies and has a concurrent offshore path during the periods of 1995 1997 and 2004 2007 the relative intensity of cyclonic eddies to anticyclonic eddies off eastern taiwan are found to contribute to these interannual kuroshio changes

summer upwelling and thermal fronts in the northwestern south china sea observational analysis of two mesoscale mapping surveys persistent coastal upwelling and upwelling induced thermal fronts in the northwestern south china sea are investigated using satellite measurements two intensive mesoscale mapping surveys and three bottom mounted adcps the results indicate that pronounced surface cooling and upwelling related fronts with a width of 20 50 km occur around hainan island and persist through the summer upwelling season driven by the prevailing southwesterly monsoon the subsurface cooling band is approximate to 6 degrees c colder than the water offshore of the east coast where the thermal gradients are generally more than 0 1 degrees c km the cold and nutrient rich coastal water is identified to be derived primarily from the deep water of the outer shelf at the same time the spatial structure of the upwelling and thermal front as well as the upwelling related coastal currents is significantly regulated by wind forcing a prominent lagged correlation between the moored temperature records and alongshore wind stress is detected in the east coast the correlation coefficient is 0 8 with the temperature lagging behind wind stress by 2 2 days indicating that the cooling band off the east coast is dominated mostly by the alongshore southwesterly monsoon during the upwelling season

climatology and seasonal variability of ocean fronts in the east china yellow and bohai seas from satellite sst data front detection and declouding algorithms developed at the uri have been applied to the 12 year 1985 1996 pathfinder sst data set to produce the first comprehensive objectively derived year round climatology of ocean thermal fronts in the eastern china seas from 24 n to 41 n ten fronts have been distinguished namely kuroshio zhejiang fujian jiangsu shandong peninsula bohai sea seohan bay kyunggi bay western and eastern chejudo south korean coastal front and yangtze bank ring front the fronts are seasonally persistent they emerge and disappear in the same seasons of different years the frontal pattern remains fairly stable from one year to another whereas individual fronts display different modes of seasonal variability

the kuroshio east of taiwan moored transport observations from the woce pcm 1 array observations from the woce pcm 1 moored current meter array east of taiwan for the period september 1994 to may 1996 are used to derive estimates of the kuroshio transport at the entrance to the east china sea three different methods of calculating the kuroshio transport are employed and compared these methods include 1 a direct method that uses conventional interpolation of the measured currents and extrapolation to the surface and bottom to estimate the current structure 2 a dynamic height method in which moored temperature measurements from moorings on opposite sides of the channel are used to estimate dynamic height differences across the current and spatially averaged baroclinic transport profiles and 3 an adjusted geostrophic method in which all moored temperature measurements within the array are used to estimate a relative geostrophic velocity field that is referenced and adjusted by the available direct current measurements the first two methods are largely independent and are shown to produce very similar transport results the latter two methods are particularly useful in situations where direct current measurements may have marginal resolution for accurate transport estimates these methods should be generally applicable in other settings and illustrate the benefits of including a dynamic height measuring capability as a backup for conventional direct transport calculations the mean transport of the kuroshio over the 20 month duration of the experiment ranges from 20 7 to 22 1 sv 1 sv 106 m3 s 1 for the three methods or within 1 3 sv of each other the overall mean transport for the kuroshio is estimated to be 21 5 sv with an uncertainty of 2 5 sv all methods show a similar range of variability of 10 sv with dominant timescales of several months fluctuations in the transport are shown to have a robust vertical structure with over 90 of the transport variance explained by a single vertical mode the moored transports are used to determine the relationship between kuroshio transport and sea level difference between taiwan and the southern ryukyu islands allowing for long term monitoring of the kuroshio inflow to the east china sea

impact of mesoscale eddies on kuroshio intrusion variability northeast of taiwan abundant mesoscale eddies propagate to the east of taiwan and affect the kuroshio current and its onshore intrusion northeast of taiwan but the dynamical process of how eddy activities modulate the kuroshio intrusion is still unclear in this study in situ ocean velocity observations drifter trajectories tide gauge measurements satellite sea surface height data and assimilative hybrid coordinate ocean model hycom reanalysis outputs were used to analyze a cyclonic eddy induced large kuroshio onshore intrusion during late autumn 2008 along with nine anticyclonic eddy events and seven cyclonic eddy events extracted from long term hycom reanalysis outputs the variability of the eddy induced intrusion were quantified the impacts of the cyclonic eddy and the anticyclonic eddy were opposite under the impact of cyclonic anticyclonic eddy the total onshore intrusion between 122 e and 124 e across the 200 m isobaths was decreased increased by 15 7 7 3 while the onshore intrusion west of 122 6 e and the northeastward current on the outer shelf was increased decreased by 30 6 4 7 and 31 10 1 respectively the arrival of cyclonic anticyclonic eddy brought positive negative potential vorticity pv flux and modulated the local ocean vertical stratification which weakened enhanced the cross slope pv gradient and the shelf slope constraint on the upper layer current therefore favored inhibited the kuroshio onshore intrusion this article is protected by copyright all rights reserved

interannual modulation of the pacific decadal oscillation pdo on the low latitude western north pacific to investigate the interannual variability in the northwestern pacific an empirical mode decomposition emd was applied to 17 year absolute dynamic topography adt data west of luzon island the philippines the mean sea surface height in this area is an appropriate index for the kuroshio intrusion into the south china sea scs significant interannual fluctuations were extracted by the emd the interannual variability was strongly correlated with the pacific decadal oscillation pdo index but not the el nino southern oscillation enso this indicated the potential impact of the pdo on the circulation in the area in the warm phase of the pdo positive index a southerly anomalous wind off the philippines causes a northward shift of the north equatorial current bifurcation latitude necbl this leads to a weakened kuroshio off luzon favoring kuroshio intrusion into the scs the northward migration of the necbl also results in a weakened kuroshio off southeast taiwan and a larger kuroshio transport off northeast taiwan the abundant westward propagating eddies impinging on the kuroshio in the subtropical countercurrent region increases this transport although the enso has little effect on monsoonal winds during the warm pdo phase it has a strong impact on the monsoon and meridional migration of the necbl during the cold phase of the pdo therefore necbl variations only show a close correspondence with the enso during the cold pdo phase because the influence of the enso is not stationary the impact of the pdo should be taken into account when examining interannual variability in the low latitude western north pacific

effects of kuroshio intrusions on the atmosphere northeast of taiwan island the kuroshio loses bathymetric support off northeast taiwan island causing large variability in its path the resultant covariability of sea surface temperature sst and the lower atmosphere is investigated using satellite observations in winter and spring off northeast taiwan island the intrusions of warm kuroshio water onto the continental shelf cause a large increase in local sst intensify the northeasterly monsoonal winds and lead to the increases in water vapor and rainfall key to this air sea interaction is the existence of anomalous heat advection by the kuroshio intrusions the kuroshio intrusions are partly due to westward propagating ocean eddies east of taiwan island with a lead time of 3 weeks hinting at the possibility of improved weather prediction near northeast taiwan island by considering ocean variability east of taiwan island

symmetrical and segmented variation of physical and geochemical characteristics of the central american volcanic front abstract the regional variation of physical and geochemical characteristics of central american volcanoes occurs in two fundamentally different patterns the first pattern is symmetrical about nicaragua crustal thickness silica contents of mafic lavas and volcanic edifice heights are lowest in nicaragua and increase smoothly toward costa rica to the south and guatemala to the north magma density is maximum in nicaragua and decreases smoothly outward the regional variation in crustal thickness is just enough so that magma densities calculated at appropriate moho pressures are the same at the base of the crust throughout the region this is consistent with magma ponding at the base of the crust the bulk compositions of central american basalts show the same symmetrical variation suites of nicaraguan basalts plotted in pseudo ternary cmas projections indicate large olivine and plagioclase primary phase volumes toward costa rica and guatemala the olivine and plagioclase fields inferred from suites of basaltic lavas are smaller which is consistent with fractionation at increasing depth the second pattern is the segmentation of the volcanic front and the plate margin in general the segmentation strongly affects the spacing and size of volcanic centers at segment boundaries volcanic centers are generally small and unusually widely spaced toward segment interiors volcano spacing and size increase systematically the lil element contents of lavas strongly reflect this pattern for lavas with similar silica contents the larger the volcano the higher the lil element contents the relationships between segmentation volcano spacing and volcano size are compatible with diapiric rise of magma accumulated in narrow ribbons near the upper surface of the underthrust slab the relationship between volcano volume and lil element content is qualitatively in agreement with an open system fractionation model