calcic amphibole equilibria and a new amphibole plagioclase geothermometer there is currently a dearth of reliable thermobarometers for many hornblende and plagioclase bearing rocks such as granitoids and amphibolites a semi empirical thermodynamic evaluation of the available experimental data on amphibole plagioclase assemblages leads to a new thermometer based on the aliv content of amphibole coexisting with plagioclase in silica saturated rocks the principal exchange vector in amphiboles as a function of temperature in both the natural and experimental studies is left na square 1 right a left alsi 1 right t1 we have analysed the data using 3 different amphibole activity models to calibrate the thermometer reactions 1 edenite 4 quartz tremolite albite 1 2 pargasite 4 quartz hornblende albite 2 the equilibrium relation for both 1 and 2 leads to the proposed new thermometer t frac 0 677p 48 98 y 0 0429 0 008314 ln k and k left frac si 4 8 si right x ab plag where si is the number of atoms per formula unit in amphiboles with p in kbar and t in k the term y represents plagioclase non ideality rtln ab from darken s quadratic formalism dqf with y 0 for xab 0 5 and y 8 06 25 5 1 xab 2 for xab 0 5 the best fits to the data were obtained by assuming complete coupling between al on the t1 site and na in the a site of amphibole and the standard deviation of residuals in the fit is 38 c the thermometer is robust to ferric iron recalculation procedures from electron probe data and should yield temperatures of equilibration for hornblende plagioclase assemblages with uncertainties of around 75 c for rocks equilibrated at temperatures in the range 500 1100 c the thermometer should only be used in this temperature range and for assemblages with plagioclase less calcic than an92 and with amphiboles containing less than 7 8 si atoms pfu good results have been attained on natural examples from greenschist to granulite facies metamorphic rocks as well as from a variety of mafic to acid intrusive and extrusive igneous rocks our analysis shows that the pressure dependence is poorly constrained and the equilibria are not suitable for barometry

why is the bay of bengal less productive during summer monsoon compared to the arabian sea 1 the bay of bengal is traditionally considered to be a less productive basin compared to the arabian sea we explore the reasons for this in the central bay during summer copious rainfall and river water freshen the upper layers of the bay by 3 7 psu during summer and sst was warmer by 1 5 2 c than in the central arabian sea this leads to a strongly stratified surface layer the weaker winds over the bay are unable to erode the strongly stratified surface layer thereby restricting the turbulent wind driven vertical mixing to a shallow depth of 20 m this inhibits introduction of nutrients from below situated close to the mixed layer bottom into the upper layers while advection of nutrients rich water into the euphotic zone makes the arabian sea highly productive this process is unlikely in the bay of bengal

primary production in the arabian sea during the last 135 000 years abstract variations in primary productivity pp have been reconstructed in eutrophic mesotrophic and oligotrophic parts of the arabian sea over the past 135 000 years applying principal component analysis and transfer function to planktic foraminiferal assemblages temporal variation in paleoproductivity is most pronounced in the mesotrophic northern nast site and oligotrophic eastern east site arabian sea and comparatively weak in the western eutrophic geob 3011 1 site in the upwelling area off oman higher pp during interglacials 250 320 g c m 2 year 1 than during cold stages 210 270 g c m 2 year 1 at geob 3011 1 could have been caused by a strengthened upwelling during intensified summer monsoons and increased wind velocities at nast during interglacials pp is estimated to exceed 250 g c m 2 year 1 and during glacials to be as low as 140 180 g c m 2 year 1 these fluctuations may result from a 1 varying impact of filaments that are associated to the oman coastal upwelling and 2 from open ocean upwelling associated to the findlater jet at east highest productivity of about 380 g c m 2 year 1 is documented for the transition from isotope stage 5 to 4 we suggest that during isotope stages 2 4 5 2 the transition 5 4 and the end of stage 6 deep mixing of surface waters was caused by moderate to strong winter monsoons and induced an injection of nutrients into the euphotic layer leading to enhanced primary production the deepening of the mixed layer during these intervals is confirmed by an increased concentration of deep dwelling planktic foraminiferal species a high productivity event in stage 3 displayed by estimated pp values and by planktic foraminifera and radiolaria flux and accumulation rate likely resulted from a combination of intensified sw monsoons with moderate to strong ne monsoons differential response of globigerina bulloides globigerinita glutinata and mixed layer species to the availability of food is suited to subdivide productivity regimes on a temporal and spatial scale

seasonal variation of hydrographic and nutrient fields during the us jgofs arabian sea process study abstract between september 1994 and december 1995 the us jgofs arabian sea process experiment collected extensive high quality hydrographic data temperature salinity dissolved oxygen and nutrients during all seasons in the northern arabian sea an analysis of this unique data suite suggests the presence of many features that are described in the canonical literature but these new data provided the following insights 1 although the seasonal evolution of mixed layer depths was in general agreement with previous descriptions the deepest mixed layer depths in our data occurred during the late ne monsoon instead of the sw monsoon 2 the region exhibits considerable mesoscale variability resulting in extremely variable temperature salinity ts distributions in the upper 1000 db this mesoscale variability is readily observed in satellite imaging in the high resolution data taken by a companion onr funded project and in underway adcp data 3 the densest water reaching the sea surface during coastal upwelling appeared to have maximum offshore depths of 150 m and s close to the core value 25 for the saline arabian sea water asw but salinities in these upwelling waters were relatively low the densest water found at the sea surface during late ne monsoon conditions has s 24 8 and relatively high salinities suggesting that they are a source for the asw salinity maximum 4 persian gulf water pgw with a core of 26 6 forms a widespread salinity maximum despite the considerable extent of this feature persian gulf outflow water with a salinity 4 of 39 at its source can only be a minor contributor within the standard us jgofs sampling grid maximum salinities on this surface are 36 8 at stations near the gulf falling to values as low as 35 3 at the stations farthest removed from its influence even at our standard stations closest to the gulf n 1 and n 2 the high salinity low nutrient persian gulf water has only a modest direct effect on nutrient concentrations this pgw salinity maximum is associated with the suboxic portions of the arabian sea s oxygen minimum zone 5 the salinity maximum associated with red sea water rsw core 27 2 in the jgofs study region is clearly evident at the southermost sampling site at 10 n s 15 elsewhere this signal is weak or absent and salinity on the 27 2 surface tends to increase towards the persian gulf suggesting that the disappearance of this salinity maximum is due at least in part to the influence of the persian gulf outflow 6 inorganic nitrogen to phosphate ratios were lower frequently much lower than the standard redfield ratio of 15 1 16 1 by atoms at all times and all depths suggesting that inorganic nitrogen was more important than phosphate as a limiting nutrient for phytoplankton growth and that the effects of denitrification dominated the effects of nitrogen fixation 7 the water upwelling off the omani coast during the sw monsoon has inorganic nitrogen to silicate ratios that were higher 2 1 than the 1 1 ratio often assumed as the ratio of uptake during diatom growth 8 the temporal evolution of inorganic nitrogen to silicate ratios suggests major alteration by diatom uptake only during the late sw monsoon cruise tn050 in august september 1995 9 widespread moderate surface layer nutrient concentrations occurred during the late ne monsoon 10 a zone of high offshore nutrient concentrations was encountered during the sw monsoon but instead of being associated with offshore upwelling it may represent offshore advection from the coastal upwelling zone the influence of an eddy or both 11 although our data do not contradict previous suggestions that the volume of subtoxic water may be reduced the sw monsoon they suggest a weaker re oxygenation than indicated by some previous work similarly they do not confirm results suggesting that secondary nitrite maxima may be common in waters with oxygen concentrations 5 m

preliminary analysis of observations of the pinatubo volcanic plume with a polarization sensitive lidar a dual polarization lidar aboard the nasa electra aircraft was used in july 1991 to survey the stratospheric plume from the recent mt pinatubo eruption both depolarizing and non depolarizing volcanic layers were observed ranging from 17 to 26 km in altitude differences in the depolarization signatures of the layers indicates differences in the composition or physical state of the particles in the layers

three dimensional volcanic aerosol dispersal a comparison between multiangle imaging spectroradiometer misr data and numerical simulations 1 the three dimensional reconstruction of volcanic plumes is a central goal to enhance our understanding on dispersal processes in this paper we use data from the multiangle imaging spectroradiometer misr on board nasa s terra spacecraft combined with a stereo matching retrieval procedure we show the potential of misr in capturing important features of volcanic plumes like column height optical depth type and shape of the finest particles of two highly explosive eruptions occurring on mount etna in 2001 and 2002 this work tests how tephra dispersal models reconstruct the 3 d shape of volcanic clouds we compare misr data with fall3d an eulerian model for the transport and deposition of volcanic ash and aerosols coupled with the weather research and forecasting mesoscale meteorological model agreement between simulations and misr data is good regarding both events although it could be improved by increasing the accuracy of the meteorological data a better constraint on volcanological input parameters like the height of the eruptive column and improving our understanding of processes such as aggregation phenomena and volcanic cloud microphysics

intensive surveys of the azores front 1 tracers and dynamics the hypothesis that fronts are sites of active subduction is examined using density temperature salinity and horizontal velocity data from a trio of surveys of the azores front done in may 1991 and march 1992 these surveys were made using a seasoar equipped with a conductivity temperature depth profiler and a shipboard acoustic doppler current profiler the potential density and potential vorticity indicate that dense water from the north side of the front may be sliding down beneath the surface outcrop this apparently subducting isopycnal has a great deal of temperature and salinity variability horizontal velocity is nearly parallel to isopycnals indicating that the time rate of change and vertical advection must be small the thermal wind balance is observed to be valid especially in the region of the largest horizontal density gradients shear at the base of the mixed layer is likely due to near inertial motions the potential vorticity is dominated by the planetary vorticity except at the front where vertical shears the tilting term become large the tilting term acts to reduce the magnitude of the potential vorticity at the front in agreement with simple theoretical models the magnitude of the tilting term is similar to the total vorticity in the seasonal thermocline

zooplankton spatial distributions in coastal waters of the northern arabian sea august 1995 abstract the spatial distribution of zooplankton biomass was surveyed in coastal waters of the northern arabian sea during the 1995 southwest monsoon august on cruise mb 95 06 of the noaa ship malcolm baldrige vertical patterns of displacement volumes from a limited set of paired day night mocness tows suggest there was little diel vertical migration in the coastal waters off the southern arabian peninsula zooplankton biomass varied from 5 2 to 15 1 g dw m 2 178 517 mm c m 2 in the upper 200 300 m of omani coastal waters distributions of acoustic backscatter were mapped in eight daytime acoustic doppler current profiler transects in coastal waters off oman and somalia several transects contained maxima in acoustic backscatter that coincided with cool fresh surface features that were several tens of kilometers wide although there was considerable scatter in the relationship between acoustically determined biomass adb of zooplankton and surface temperature there was a trend of increased biomass in the cool surface temperatures of the omani upwelling zone acoustic transects crossed two filaments that extended seaward from upwelling centers off oman and somalia estimated zooplankton adb exported from the upwelling zones in the surface features was on the order of 300 kg dw s 1 the physical and biological characteristics of filaments maintain zooplankton associated with upwelling areas such as calanoides carinatus as they are advected offshore from coastal upwelling zones

characterization of the zooplankton community size composition and distribution in relation to hydrography in the japan east sea abstract the japan east sea jes may be thought of as a model or microcosm of larger oceanic systems where biogeographic boundaries juxtapose at highly dynamic boundaries the northern and southern portions of the jes are hydrographically and biologically distinct with the southern portion being more tropical oligotrophic and the northern portion being more boreal eutrophic regional zooplankton taxonomic and size compositions and abundance and the high resolution vertical distribution of plankton fluorescence and coincident hydrography were described using the video plankton recorder vpr equipped with high and low magnification cameras and environmental sensors and mounted on a vertically profiling towed vehicle in the upper 80 m of the jes during the summer of 1999 a survey was conducted over both the northern and southern regions including the subpolar front spf that spanned 10 12 of latitude and longitude and covered an along track distance of 7000 km plankton also were collected at 15 selected stations using a ring net for silhouette analysis of taxa and size distributional patterns in abundance liter of plankton taxa from the vpr were quantified at sea in real time identifying plankton automatically using a neural network classifier the most abundant taxa identified were copepods oithona spp calanus spp copepod nauplii protozoa and diatoms with copepods the dominant taxon the northern jes southern jes and north korean cold current were distinct based on based on temperature salinity properties the hydrography was complex and characterized by multiple mesoscale features including currents and the meandering of the spf different taxonomic and size compositions were observed in the three hydrographic regions the vertical distributions of copepods and fluorescence were associated with hydrographic structure especially at fronts plankton abundances varied with regional hydrographic region and environmental conditions although strong associations were not always observed the extremely dynamic nature of the jes may effectively mix the plankton and obscure strong gradients or differences between regions

integrated satellite observations of the 2001 eruption of mt cleveland alaska abstract satellite data were the primary source of information for the eruption of mt cleveland alaska on 19 february and 11 and 19 march 2001 multiple data sets were used pre syn and post eruption to mitigate the hazard and determine an eruption chronology the 19 february eruption was the largest of the three resulting in a volcanic cloud that formed an arc over 1000 km long moved to the ne across alaska and was tracked using satellite data over more than a 50 h period the volcanic cloud was concurrently detected on the goes avhrr and modis data at various times and their respective signals compared all three sensors detected a cloud that had a very similar shape and position but there were differences in their areal extent and internal structural detail goes data showed the largest volcanic cloud in terms of area probably due to its oblique geometry modis bands 31 and 32 which are comparable to goes and avhrr thermal infrared wavelengths were the least effective single channels at detecting the volcanic cloud of those investigated modis bands 28 29 31 and 32 modis bands 28 and 29 detected the largest volcanic clouds that could easily be distinguished from weather clouds of the split window data modis bands 29 minus band 32 detected the largest cloud but the band 31 minus band 32 data showed the volcanic cloud with the most internal structural detail the puff tracking model accurately tracked the movement and predicted the extent and shape of this complex cloud even into areas beyond satellite detection numerous thermal anomalies were also observed during the eruption on the twice daily avhrr data and the high spatial resolution landsat data the high resolution radarsat data showed that the avhrr thermal anomalies were due to lava and debris flow features and a newly formed fan along the west coast of the island field observations and images from a hand held forward looking infrared radiometer flir showed that the flow features were a a lava debris flows and a warm debris fan along the west coast real time satellite data were the primary tool used to monitor the eruption track changes and to mitigate hazards high resolution data even though coverage is infrequent were critical in helping to identify volcanic processes and to compile an eruption chronology

ocean atmosphere covariability in the western arabian sea abstract the western arabian sea exhibits strong spatial variability in sea surface temperature sst during the southwest monsoon with changes in sst that can exceed 5 c over 200 km exploration of satellite based and in situ data shows a strong connection between mesoscale sst features and changes in the atmospheric boundary layer the fundamental relationship is that of weak strong wind velocities overlying cold warm sst features there are also coherent changes in other near surface meteorological parameters such as the air sea temperature difference and relative humidity indicating changes in the stability of the planetary boundary layer over the mesoscale sst features these relationships are similar to those recently reported over the equatorial pacific tropical instability wave region this observed covariability of atmospheric boundary layer structure and sst results in variations of the surface heat and moisture fluxes latent heat flux is modified by changes in relative humidity principa

shear criteria in granite and migmatite deformed in the magmatic and solid states microstructural criteria for the determination of the sense of shear in rocks homogeneously deformed in the partially melted state are similar to those which apply to solid state deformation sense of shear determination is either direct deduced from the sense of rotation of markers or indirect involving the obliquity between the shear and foliation planes or between the successive foliations imprinted at different stages of progressive deformation this study is a by product of the detailed structural and microstructural investigation of a high grade metamorphic rock pile variscan vosges massif france which underwent subhorizontal shearing during partial melting and further solidification depending on the rock chemistry on the position in the pile and the relative timing of progressive deformation layered migmatites and homogeneous granites were variously deformed in the partially melted and solid states the sense of shear obtained from these rock types using the criteria presented here consistently gives a top to sw direction

volcanic ash plume identification using polarization lidar augustine eruption alaska 1 during mid january to early february 2006 a series of explosive eruptions occurred at the augustine volcanic island off the southern coast of alaska by early february a plume of volcanic ash was transported northward into the interior of alaska satellite imagery and puff volcanic ash transport model predictions confirm that the aerosol plume passed over a polarization lidar 0 694 m wavelength site at the arctic facility for atmospheric remote sensing at the university of alaska fairbanks for the first time lidar linear depolarization ratios of 0 10 0 15 were measured in a fresh tropospheric volcanic plume demonstrating that the nonspherical glass and mineral particles typical of volcanic eruptions generate strong laser depolarization thus polarization lidars can identify the volcanic ash plumes that pose a threat to jet air traffic from the ground aircraft or potentially from earth orbit

the upper ocean response to monsoonal forcing in the arabian sea seasonal and spatial variability abstract observations from four towed profiler surveys undertaken between december 1994 and october 1995 examine the seasonal and spatial variability of the upper ocean response to the monsoon cycle in the arabian sea although observed atmospheric forcing agrees well with modern climatologies cross basin patterns of mixed layer depth and water properties observed in 1994 1995 are not entirely consistent with an upper ocean response dominated by ekman pumping during the winter monsoon the mixed layer deepens dramatically with distance offshore surface cooling intensifies with offshore distance and a one dimensional response dominated by convective overturning could explain observed wintertime mixed layer depths except for waters associated with a filament extending offshore from the omani coast mixed layer depths and water properties show only modest cross basin contrasts during the southwest monsoon filament waters differ from surrounding mid basin waters having shallow mixed layers and water properties similar to those of waters upwelled near the omani coast in september following the southwest monsoon waters within 1000 km of the omani coast have cooled and freshened with marked changes in stratification extending well into the pycnocline estimates of ekman pumping and wind driven entrainment made using the southampton oceanographic center 1980 1995 surface flux and the levitus mixed layer climatologies indicate that during the southwest monsoon wind driven entrainment is considerably stronger than ekman pumping inshore of the windstress maximum ekman pumping partially counters wind driven entrainment while offshore the two processes act together to deepen the mixed layer as ekman pumping is too weak to counter wind driven mixed layer deepening inshore of the windstress maximum another mechanism must act to maintain the shallow mixed layers seen in our observations and in climatologies offshore advection of coastally upwelled water offers a mechanism for maintaining upper ocean stratification that is consistent with observed changes in upper ocean water properties ekman upwelling will modulate wind driven entrainment but these results indicate that the primary mechanisms acting inshore of the windstress maximum are wind driven mixing and horizontal advection

the vedrette di ries rieserferner plutonic complex petrological and geochemical data bearing on its genesis data on co sc rb sr th zr ta hf and ree contents are reported for tonalites granodiorites granites and one diorite from the alpine plutonic complex of vedrette di ries in the eastern alps co and sc range respectively between 19 6 1 2 ppm and 32 3 3 ppm showing a good negative correlation with the differentiation index d i rb values range between 61 197 ppm displaying a positive correlation with d i all the samples have variably fractionated light and heavy ree with lan smn 1 7 5 55 and tbn ybn 0 58 1 65 and no important europium anomalies on the basis of the hree fractionation two groups of rocks can be distinguished one showing higher tbn ybn values which range between 1 27 1 65 and are positively correlated with the d i and a second group with tbn ybn values less than unity which decrease with the differentiation the rocks with high tbn ybn ratio also display a positive sr versus d i variation whereas the samples with flat or upward concave hree patterns i e with tbn ybn 1 define negative sr versus d i trends th ta hf zr and lree show an overall tendecy to increase and then to decrease with the differentiation with a large scattering of values

theoretical study on volcanic plume hbox so _ 2 and ash retrievals using ground tir camera sensitivity analysis and retrieval procedure developments in this paper a sensitivity analysis and procedure development for volcanic plume sulfur dioxide and ash retrievals using ground thermal infrared camera have been carried out the semiconductor device camera considered as a reference has a spectral range of 8 14 m with noise equivalent temperature difference that is better than 100 mk at 300 k the camera will be used to monitor and assess the hazards of mt etna volcano to mitigate the risk and impact of volcanic eruptions on the civil society and transports a minimum number of filters have been selected for sulfur dioxide so2 and volcanic ash retrievals the sensitivity study has been carried out to determine the so2 and volcanic ash minimum concentration detectable by the system varying the camera geometry and the atmospheric profiles results show a meaningful sensitivity increase considering high instrument altitudes and low camera elevation angles for all geometry configurations and monthly profiles the sensitivity limit varies between 0 5 and 2 g m 2 for so2 columnar abundance and between 0 02 and 1 for ash optical depth two procedures to detect so2 and ash based on the least square fit method and on the brightness temperature difference btd algorithm respectively have also been proposed results show that high concentration of atmospheric water vapor columnar content significantly reduces the ash plume effect on the btd a water vapor correction procedure introduced improves the ash retrievals and the cloud discrimination in every season considering all the camera geometries

a comparison of mixed layer dynamics between the arabian sea and bay of bengal one dimensional model results 1 using a one dimensional turbulent closure model we investigate the physical mechanisms governing the seasonal evolution of mixed layer depth mld and sea surface temperature sst along two meridional sections 64 5 e and 88 5 e which are representative of the open ocean conditions of the arabian sea and the bay of bengal several perturbation experiments have been performed to isolate and judge exactly the relative importance of wind stress and buoyancy forcing to the evolution of mld and sst the wind stress forcing is found to be significant during the summer monsoon while buoyancy flux plays a significant role during the winter monsoon during the summer monsoon june september the mld in the arabian sea deepens to 80 m owing to strong wind driven vertical mixing but the weaker winds over the bay of bengal restrict the turbulent mixing to a shallow depth of 30 m as a result sst in the arabian sea bay of bengal decreases to 27 c remains high 29 c it is thus the asymmetry in the wind field that is responsible for the difference in mld and sst between the arabian sea and the bay of bengal during the winter monsoon november february the mld in the arabian sea penetrates to deeper than 80 m by convective vertical mixing because of strong negative buoyancy flux net heat loss but it is restricted to 40 50 m in the bay of bengal owing to reduced net heat loss from the ocean it is the asymmetry in the buoyancy forcing caused by the difference in latent heat flux that is responsible for the difference in mld and sst between the arabian sea and the bay of bengal the atmospheric parameter that controls this buoyancy difference is the difference in humidity between the two basins thus it is the differences in surface forcing rather than differences in the vertical salinity stratification that are key in explaining the observed and modeled differences between the arabian sea and bay of bengal

monitoring etna volcanic plumes using a scanning lidar in this paper we use data obtained from lidar measurements during an ash emission event on 15 november 2010 at mt etna in italy in order to evaluate the spatial distribution of volcanic ash in the atmosphere a scanning lidar system located at 7 km distance from the summit craters was directed toward the volcanic vents and moved in azimuth and elevation to analyse different volcanic plume sections during the measurements ash emission from the north east crater and high degassing from the bocca nuova crater were clearly visible from our analysis we were able to 1 evaluate the region affected by the volcanic plume presence 2 distinguish volcanic plumes containing spherical aerosols from those having non spherical ones and 3 estimate the frequency of volcanic ash emissions moreover the spatial distribution of ash mass concentration was evaluated with an uncertainty of about 50 we found that even during ash emission episodes characterised by low intensity like the 15 november 2010 event the region in proximity of the summit craters should be avoided by air traffic operations the ash concentration being greater than 4 10 3 g m3 the use of a scanning permanent lidar station may usefully monitor the volcanic activity and help to drastically reduce the risks to aviation operations during the frequent etna eruptions

nitrogen fixation rates in the eastern arabian sea abstract the arabian sea experiences bloom of the diazotroph trichodesmium during certain times of the year when optimal sea surface temperature and oligotrophic condition favour their growth we measured nitrogen fixation rates in the euphotic zone during one such event in the eastern arabian sea using 15 n 2 tracer gas dissolution method the measured rates varied between 0 8 and 225 mol n m 3 d 1 and were higher than those reported from most other oceanic regions the highest rates 1739 mol n m 2 d 1 0 10 m coincided with the growth phase of trichodesmium and led to low 15 n trichodesmium bloom nitrogen fixation rates were low 0 9 1 5 mol n m 3 d 1 due to episodic events of diazotroph bloom contribution of n 2 fixation to the total nitrogen pool may vary in space and time

physical mechanisms routing nutrients in the central red sea mesoscale eddies and boundary currents play a key role in the upper layer circulation of the red sea this study assesses the physical and biochemical characteristics of an eastern boundary current ebc and recurrent eddies in the central red sea crs using a combination of in situ and satellite observations hydrographic surveys in november 2013 autumn and in april 2014 spring in the crs 22 15 24 1 n included a total of 39 and 27 ctd stations respectively in addition high resolution hydrographic data were acquired in spring 2014 with a towed undulating vehicle scanfish in situ measurements of salinity temperature chlorophyll fluorescence colored dissolved organic matter cdom and dissolved nitrate phosphorous ratios reveal distinct water mass characteristics for the two periods an ebc observed in the upper 150 m of the water column during autumn transported low salinity and warm water from the south toward the crs patches of the low salinity water of southern origin tended to contain relatively high concentrations of chlorophyll and cdom the prominent dynamic feature observed in spring was a cyclonic anticyclonic eddy pair the cyclonic eddy was responsible for an upward nutrient flux into the euphotic zone higher chlorophyll and cdom concentrations and concomitant lower nitrate phosphorous ratios indicate the influence of the ebc in the crs at the end of the stratified summer period

improved prediction and tracking of volcanic ash clouds abstract during the past 30 years more than 100 airplanes have inadvertently flown through clouds of volcanic ash from erupting volcanoes such encounters have caused millions of dollars in damage to the aircraft and have endangered the lives of tens of thousands of passengers in a few severe cases total engine failure resulted when ash was ingested into turbines and coating turbine blades these incidents have prompted the establishment of cooperative efforts by the international civil aviation organization and the volcanological community to provide rapid notification of eruptive activity and to monitor and forecast the trajectories of ash clouds so that they can be avoided by air traffic ash cloud properties such as plume height ash concentration and three dimensional ash distribution have been monitored through non conventional remote sensing techniques that are under active development forecasting the trajectories of ash clouds has required the development of volcanic ash transport and dispersion models that can calculate the path of an ash cloud over the scale of a continent or a hemisphere volcanological inputs to these models such as plume height mass eruption rate eruption duration ash distribution with altitude and grain size distribution must be assigned in real time during an event often with limited observations databases and protocols are currently being developed that allow for rapid assignment of such source parameters in this paper we summarize how an interdisciplinary working group on eruption source parameters has been instigating research to improve upon the current understanding of volcanic ash cloud characterization and predictions improved predictions of ash cloud movement and air fall will aid in making better hazard assessments for aviation and for public health and air quality

reconstruction of indian monsoon variability over the past 230 000 years planktic foraminiferal evidence from the nw arabian sea open ocean upwelling area abstract we determined the faunal composition and total number of tests g of planktic foraminifera 125 m in core kh00 05 goa 6 near oman in order to decipher monsoon induced variability of oceanographic productivity in the open ocean upwelling area in the northwest arabian sea the core contains a continuous record of sedimentation over the last 230 kyr with the age model based on oxygen isotope and accelerator mass spectrometry 14c dates we focused on species globigerina bulloides and globigerinita glutinata typical for sw monsoonal upwelling and species typical for ne monsoon conditions neogloboquadrina incompta neogloboquadrina dutertrei globigerinoides ruber and globigerinoides sacculifer the changes in relative abundance of these monsoonal indicators suggest that the open ocean upwelling area was dominated by the sw monsoon during interglacial periods but by the ne monsoon during glacial periods increases in total test abundance during glacial periods confirmed that the ne monsoon rather than sw monsoon contributes largely to planktic foraminiferal productivity in this area we argue that three types of circumstances resulted in high productivity with nine high productivity events occurring at a 23 kyr frequency the first type caused high productivity events at 102 and 199 ka interglacial periods characterized by the dominance of upwelling species indicating high productivity during strong sw monsoons correlated with high july insolation at 45 n an exceptional high productivity event occurred at 37 ka during interglacial marine isotope stage mis 3 with contributions from both sw and ne monsoons the second type of high productivity event occurred at 61 147 and 175 ka during glacial periods characterized by dominance of ne monsoon species and correlated with low january insolation at 45 n in addition a high productivity event at 85 ka interglacial period also was induced by enhanced ne monsoons the last two high productivity events occurred during transitional periods from glacial to interglacial mis 6 5 5 and 2 1 were characterized by the replacement of ne monsoon species with upwelling species and corresponded to abrupt climate warming suggesting that they are related to both accelerated sw monsoon systems and reduced ne monsoon systems

moored observations of upper ocean response to the monsoons in the arabian sea during 1994 1995 the role of surface forcing in the semiannual evolution of the upper ocean temperature salinity and velocity fields in the arabian sea is examined to do so variability in the upper ocean in the central arabian sea was observed from an array of moorings deployed from october 1994 to october 1995 the northeast ne monsoon was characterized by moderate winds clear skies and dry air sea surface temperature sst dropped by 31c the ocean lost an average of 19 7 w m 2 and the mixed layer deepened by 100 m in response the southwest sw monsoon was accompanied by strong winds cloudy skies and moist air the ocean gained an average of 89 5 w m 2 but sst dropped by 5 51c and the mixed layer deepened to almost 80 m the response to the ne monsoon included daily cycling in the depth of the mixed layer in response to the diurnal cycle in the buoyancy forcing and a weak local wind driven response stronger windforcing during the sw monsoon dramatically reduced diurnal restratification and a clearer signal of local wind driven flow in the upper ocean was found the strongest velocity signal in the upper ocean however was the flow associated with mesoscale geostrophic features that passed slowly through the moored array dominating the current meter records in the first part of the ne monsoon and again in the latter part of the sw monsoon one dimensional heat and freshwater balances which held at other times through the year broke down during the passage of these features r 2002 published by elsevier science ltd

predicting regions susceptible to high concentrations of airborne volcanic ash in the north pacific region abstract airborne ash probability distribution aapd maps have been generated to show the distribution of airborne volcanic ash in the north pacific nopac region by simulating volcanic eruption clouds from 22 of the 100 most historically active volcanoes in the region the puff ash dispersion model was run daily using archived wind field data between 1994 1995 and 1997 2001 for low and high aircraft flight levels subsequent statistics are generated representing the distribution of simulated airborne ash at 6 and 24 h intervals defining the regions most likely to contain airborne ash and the direction and distance a volcanic ash cloud may propagate from a given volcano the aapd maps show the extent of ash from a given volcano can encompass all of alaska most of the north pacific ocean portions of northwestern north america regions as far south as 35 n regions over the western arctic ocean and portions of eastern russia in general low altitude atmospheric regions 3 8 km asl are more susceptible to airborne volcanic ash when compared to regions above 8 km asl due to the eruption characteristics of volcanoes in the north pacific and the region s atmospheric profile the results indicate that the paths of many nopac air traffic routes coincide with airborne ash distribution probability maxima the upper atmospheric region most likely to contain airborne ash is located off the eastern coast of the kamchatkan peninsula and is generally centered over the heavy air traffic flight corridor of the nopac although this paper focuses on the nopac region the technique can be directly applied to other regions characterized by active volcanism

dynamics of the indian ocean oxygen minimum zones abstract in the indian ocean mid depth oxygen minimum zones omzs occur in the arabian sea and the bay of bengal the lower part of the arabian sea omz asomz below 400 m intensifies northward across the basin in contrast its upper part above 400 m is located in the central eastern basin well east of the most productive regions along the western boundary the bay of bengal omz bbomz although strong is weaker than the asomz to investigate the processes that maintain the indian ocean omzs we obtain a suite of solutions to a coupled biological physical model its physical component is a variable density 6 1 2 layer model in which each layer corresponds to a distinct dynamical regime or water mass type its biological component has six compartments nutrients phytoplankton zooplankton two size classes of detritus and oxygen because the model grid is non eddy resolving 0 5 the biological model also includes a parameterization of enhanced mixing based on the eddy kinetic energy derived from satellite observations to explore further the impact of local processes on omzs we also obtain analytic solutions to a one dimensional simplified version of the biological model our control run is able to simulate basic features of the oxygen nutrient and phytoplankton fields throughout the indian ocean the model omzs result from a balance or lack thereof between a sink of oxygen by remineralization and subsurface oxygen sources due primarily to northward spreading of oxygenated water from the southern hemisphere with a contribution from persian gulf water in the northern arabian sea the northward intensification of the lower asomz results mostly from horizontal mixing since advection is weak in its depth range the eastward shift of the upper asomz is due primarily to enhanced advection and vertical eddy mixing in the western arabian sea which spread oxygenated waters both horizontally and vertically advection carries small detritus from the western boundary into the central eastern arabian sea where it provides an additional source of remineralization that drives the asomz to suboxic levels the model bbomz is weaker than the asomz because the bay lacks a remote source of detritus from the western boundary although detritus has a prominent annual cycle the model omzs do not because there is not enough time for significant remineralization to occur

melt enhanced deformation a major tectonic process convergent tectonics between continental crustal blocks result in deep burial and anatexis of supracrustal rocks anatectic and or mantle derived melts combine to form a melt weakened zone in the thickened lower crust the accumulation of melt eventually leads to crustal failure along melt lubricated shear zones rapid 1 mm yr vertical component movements of large crustal blocks result we refer to these crustal displacements as tectonic surges the melt lubricated shears are characterized by the close association of sheared country rocks with foliated or massive igneous sills and plutons rocks that formed at different crustal levels are juxtaposed across these shear zones one result of surges with large lateral component of movement is metamorphic inversion with high pressure and high temperature metamorphic rocks structurally over lower pressure and temperature assemblages large and rapid vertical surges may displace crust containing abundant melt and may result in high t p including granulite facies metamorphism and preservation of metamorphic textures caused by rapid decompression

understanding the arabian sea reflections on the 1994 1996 arabian sea expedition abstract the arabian sea expedition now five years past its field observations is at a stage when some of its dominant themes can be summarized of the large range of possible topics five are considered here 1 is the arabian sea a source or sink for carbon dioxide 2 is the arabian sea mother nature s iron experiment 3 do grazing zooplankton control carbon flux to the seabed 4 does the paleoceanographic record help us predict the ocean s response to climate change and 5 what are the predominant physical processes of the arabian sea a short history of each issue and results from the field work of 1994 1996 are presented

tectono magmatic evolution of sheeted plutonic bodies along the north giudicarie line northern italy tectonized slices of foliated quartz diorite quartz gabbro rocks are exposed along the north giudicarie line between dimaro and rumo western trentino region north east italy they show geochemical and mineralogical similarities with the north east corner of the adamello batholith presanella pluton and may be regarded as a northern apophysis lamella of adamello the intrusive bodies were emplaced within the adria crust at a relatively shallow depth approximately p text h text 2 text o equal to 3 kbar along a proto giudicarie line under transtensive conditions during late oligocene only near rumo has contact metamorphism on the austroalpine basement been observed whereas in other outcrops it has been tectonically removed by later movements along the giudicarie line in the samoclevolamella a magmatic flow texture which developed during the emplacement of a crystal mush at shallow depth is recorded by the preferred alignment of plagioclase and hornblende a solid state foliation outlined by quartz crystal aggregates green hornblende and biotite has been observed mostly in the rumolamella this indicates that a later ductile deformation which developed under decreasing temperatures overprinted the intrusive rocks this deformation probably reflects late oligocene strike slip movements along the tonale and giudicarie lines finally semi brittle to brittle deformation overprints the foliated igneouslamellae producing cataclasites and pseudotachylites sometimes these structures are subsequently cut by prehnite and epidote bearing veins during this event the intrusivelamellae were decoupled from their contact aureole and carried over the insubric flysch of the southern alps this last tectonic phase may be correlated to the upper miocene neo alpine transpressive event along the giudicarie line

a near inertial internal wave spectrum for the sargasso sea in late summer abstract independent estimates of the frequency wavenumber spectrum of near inertial waves for the sargasso sea in late summer were made using 8 time series of horizontal velocity from a single moored vertical array and 58 vertical profiles of horizontal velocity from a horizontal array of expendable velocity profilers the profiler data were analyzed to produce an internal wave frequency wavenumber spectrum with sufficient resolution to resolve the details of the inertial peak and compute the vertical energy flux comparison with the lower resolution spectrum from the moored array shows qualitative agreement the differences are most likely due to biases in both techniques and to intermittency of the internal wave field these data reveal a marked asymmetry of the near inertial internal wave field with a net downward enemy flux of 0 12 0 12 ergs cm 2 s 1 the downward propagating waves have more energy a larger horizontal scale and a lower frequency than the upward propagating waves the magnitude of t

northern arabian sea variability from topex poseidon altimetry data an extension of the us jgofs onr shipboard adcp study abstract sea level anomalies sla derived from the topex poseidon t p altimetry and inferred geostrophic currents within the northern arabian sea were examined for the period from march 1993 through november 1996 the primary objective of this study was to confirm and extend our understanding of the upper ocean mesoscale variability observed in the shipboard acoustic doppler current profiler adcp data collected during the us jgofs onr arabian sea expedition september 1994 january 1996 the accuracy of the t p altimetry data 3 cm rms results in an uncertainty in the altimeter derived velocities comparable to the adcp measurement error thus the t p data provide a reasonable method for extending studies of the mesoscale dynamics for the region comparison of the t p derived geostrophic velocities with concurrent adcp data showed good correlation with an r 2 between 0 7 and 0 9 and rms differences of 10 cm s 1 the t p data confirm both the overall spatial and seasonal current patterns observed by the adcp the monsoonally averaged rms sea level anomalies indicate a high degree of intraseasonal variation due to the generation of squirts jets and eddies all along the coast the variability of which increases in both intensity and areal extent during the southwest monsoon the sla data indicate a much reduced degree of variability over the shelf the sla derived eddy kinetic energy eke fields are consistent with those derived earlier from the adcp data in both distribution and magnitude there is a large increase in eke to the west and southwest and to a lesser extent to the south and a large area of relatively reduced eddy activity over much of the eastern and northern arabian sea the area of reduced eddy activity coincides with the location of the most intense portions of the oxygen minimum zone found in the northern arabian sea the spatial scales of the eddies responsible for the eke distribution over the study area range between 200 and 500 km in the nearshore region decreasing to 100 200 km offshore while there is significant energy variability in annual and semi annual time scales a substantial portion of the energy is found between 50 and 120 days and the relative importance of this frequency band increases offshore spectra indicate a distinct break in the frequency content of the eddy field at about 15 n with little energy at less than annual periods south of this latitude

mesoscale eddies coastal upwelling and the upper ocean heat budget in the arabian sea estimation of the terms in the upper ocean heat budget from a moored array in the central arabian sea shows periods when a rough balance between the temperature trend and the horizontal advection of heat exists altimetry and sea surface temperature imagery are used to demonstrate that these episodes of strong horizontal advection are associated with mesoscale features during the wintertime northeast ne monsoon these are capped off mesoscale eddy features generated during the previous summertime southwest sw monsoon and have little horizontal transport of heat within the mixed layer during the sw monsoon the major contribution is strong offshore export of coastally upwelled water in a filament with a strong surface presence temperature and salinity properties from the moored array and a seasoar survey during the formation of the coastal filament confirm the offshore transport of the upwelled water mass to the site of the moored array more than 600 km offshore estimates of the filament section heat flux are several percent of the total estimated heat flux due to upwelling along the arabian peninsula and remote sensing data show that similar mesoscale variability along the coast is enhanced during the sw monsoon this points to the importance of mesoscale modulated transports in not only the observed heat budget at the moored array but in the overall upper ocean heat budget in the arabian sea

upper ocean currents in the northern arabian sea from shipboard adcp measurements collected during the 1994 1996 u s jgofs and onr programs abstract a large upper ocean velocity data set was obtained using a shipboard acoustic doppler current profiler adcp on seventeen rv t g thompson cruises during the jgofs and onr expedition to the northern arabian sea from september 1994 through january 1996 seven of the cruises followed a large area survey track centered over the arabian basin four cruises conducted seasoar surveys on either side of the findlater jet axis and six cruises were for the deployment and maintenance of moored instrumentation together providing some 380 cruise days and 96 000 track kilometers of coverage the adcp data extended over the upper 250 400 m of the water column depending upon the temporal spatial distributions of acoustic scatterers the velocity data revealed several items that differed significantly from the historical perspective maximum current magnitudes in this area varied from more than 1 m s 1 along the arabian coast to 10 20 cm s 1 well offshore perhaps the most important result was the complete dominance of the velocity field by eddies that had offshore correlation length scales of roughly 100 km a spectral peak at around 300 km and kinetic energies that ranged from 70 to more than 90 of the total kinetic energy the total kinetic energy was highest within about 300 km of the shore and decreased significantly in magnitude and vertical extent offshore within the coastal region the temporal variability was such that currents of 50 cm s 1 or more could completely reverse within a two week period seemingly independent of any local atmospheric forcing mean and seasonal velocities also differed from historical results there was a large anti cyclonic feature located for most of the year south of ras ash shabatat 58 e which intensified during the southwest monsoon there was a strong jet like current off ras al hadd 22 n which also intensified during the southwest monsoon although itflowed southwestward against the wind in contrast to the historical ship drift data which indicated that the surface currents followed the monsoonal winds the adcp data over the upper 200 400 m was highly variable with overall seasonal means that were often directed against the wind except within 100 200 km of the arabian coast the mean currents were generally toward the southwest with a mean transport in the upper 150 m between the coast and 10 n of approximately 9 10 6 m 3 s 1

spring evolution of arabian sea high in the indian ocean the seasonal formation of a large anticyclonic circulation pattern southern arabian sea high sah appears in the southern arabian sea during the northeast monsoon sah is studied on the basis of the recent observations that include the world ocean circulation experiment woce tropical ocean global atmosphere toga experiment drifting buoys along with topex ers 2 satellite altimeter data in conjunction with the climatological hydrography observations the sah forms west of the laccadive high lh first appears in january and grows rapidly in situ to form a well developed anticyclonic eddy extending across the southern arabian sea by march the center of the eddy is 65 e 5 n the sah is bounded by a strong eastward current to the north and a weak southward flow between 65 and 70 e which separates sah from the lh the westward flowing north equatorial current nec is on the southern flank a strong northward flow along 55 e during january and february marks the western boundary sah propagates westward as a rossby wave between march and april the arrival of sah in the western boundary in april is accompanied by intensification of current along the coast of somalia in may part of the sah has subsequently moved northward to form an anticyclonic eddy with an apparent center 13 n 53 e in the vicinity of the gulf of aden gulf of aden eddy gae the gae extends horizontally nearly 600 km along 13 and is vertically extended down through the upper main thermocline to 250 m comparisons of hydrography buoy and altimetry reveal a good agreement in eddy size location and time of appearance of the gae

estimation of the refractive index of volcanic ash from satellite infrared sounder data abstract we investigated the spectral refractive indices ris of volcanic ash materials in the wavenumber range of 700 1100 cm 1 using satellite infrared sounder measurements and radiative transfer calculations the ash ris of 10 ash clouds from eight volcanoes were evaluated bezymianny on 2 september 2012 chaiten on 3 may 2008 kelut on 14 february 2014 kirishimayama on 27 january 2011 kliuchevskoi on 30 june 2007 and 18 october 2013 puyehue cordon caulle on 5 june 2011 sangeang api on 31 may 2014 and sheveluch on 28 october 2010 and 18 september 2012 we elaborated on a dataset of volcanic ash measurements made by the atmospheric infrared sounder airs onboard the aqua satellite the measured brightness temperatures in the ash cloud data revealed silicate absorption features at around 10 m by applying atmospheric profiles from results of a global data assimilation system and using ash cloud properties ash optical depth effective radius and ash cloud height as parameters for radiative transfer calculations least squares analyses for the observed and calculated brightness temperatures were conducted using airs channels in the wavenumber range of 700 1100 cm 1 except for the o3 absorption channels in the range of 980 1070 cm 1 using the ris for typical volcanic rocks in the ascending order of sio2 content basalt andesite and rhyolite a mixture of basalt and rhyolite and a mixture of andesite and rhyolite for the ash material were considered the volume fraction of the mixture was used as a retrieval parameter and as the ash cloud parameter using the estimated ash cloud parameters as fixed values and under the assumption that the ri from the estimated volume fraction had some accuracy in the wavenumber ranges of 850 980 cm 1 and 1070 1100 cm 1 the ri imaginary part of each eruptive ash cloud captured by airs was then determined from iterative calculations at wavenumbers between 750 cm 1 and 980 cm 1 in the wavenumber range of 850 980 cm 1 the observed brightness temperatures could be approximately simulated using the reported ris from pollack toon and khare 1973 for andesite basalt and rhyolite and their combinations furthermore some estimated ris were consistent with the reported rock types of the volcanoes which had been previously classified by compositional analyses in the literature our analysis also identified weak absorptions around 750 850 cm 1 which could not be reproduced by the reported ris these weak absorptions were likely due to si o and or al o vibrations which have been proposed in reports from previous laboratory experiments for some silicate glass samples our results suggest that the detailed ri of volcanic ash can be determined from an analysis of satellite infrared sounder data the ri of the ash material estimated from satellite infrared sounder data can be used to improve the ash retrieval algorithms of other satellite measurements furthermore an ri retrieved by sounder measurements may provide diagnostic information regarding volcanic activity from comparisons with the ash ris from past eruptions

young alpine dykes south of the tauern window austria a k ar and sr isotope study fortyfive new k ar ages and sr isotope data on amphiboles biotites clinopyroxenes and whole rock samples from subvolcanic dykes south of the tauern window establish that alkalibasaltic dykes were intruded 30 m y ago and shoshonitic volcanism occured between 30 and 24 m y ago two calc alkaline rocks of high potassium composition yielded ages of 40 and 26 m y resp a spread which may or may not be real calc alkaline dykes with medium and low potassium contain excess argon and are hence undatable alkalibasaltic dykes have 87sr 86sr ratios of 0 7056 0 7070 shoshonitic rocks 0 7075 0 7133 potassium rich calc alkaline dykes 0 7077 0 7100 87sr 86sr of all other calc alkaline rocks scatter between 0 7074 and 0 7150 sr data indicate that dykes studied do not represent closed sr systems but that sr characteristics result from selective strontium assimilation en route to surface primary sr isotopic ratios of alkalibasaltic dykes point to an origin of these rocks in enriched sub continental upper mantle the source region of shoshonitic and high potassium calcalkaline rocks could have 87sr 86sr around 0 707 which is assigned to the input of a component rich in alkalies lree and lil elements genetic relationships with other tertiary magmatites of similar geotectonic position are explained in terms of plate tectonic models of the eastern alps

a review of criteria for the identification of magmatic and tectonic foliations in granitoids abstract foliations in granitoids can form by magmatic flow submagmatic flow high temperature solid state deformation and moderate to low temperature solid state deformation a review of previous work suggests that no single criterion can consistently distinguish foliations in granitoids formed by flow during ascent diapiric emplacement and expansion emplacement during regional deformation or regional deformation post dating emplacement however a magmatic origin is favoured for foliations defined by the alignment of igneous commonly euhedral minerals particularly where the foliation is parallel to internal or external pluton contacts foliations formed during expansion or ballooning of diapirs may be strictly magmatic in origin although some studies suggest that solid state deformation also may occur if so we would hope to find evidence of deformation of crystal melt systems and that the solid state deformation occurred at high temperatures the inference of syntectonic foliations is most convincing where magmatic and high temperature solid state foliations are subparallel these foliations are continuous with regionally developed foliations in the wall rocks synkinematic porphyroblasts are present in the wallrocks and igneous minerals have the same age as metamorphic minerals associated with the regional cleavage a strictly tectonic origin for foliations in granitoids is favoured when the foliation is defined by metamorphic minerals no alignment of igneous minerals occurs the foliation is locally at high angles to pluton wallrock contacts and the foliation is continuous with a regionally developed cleavage

the response of the surface circulation of the arabian sea to monsoonal forcing abstracttwo decades of drifter and satellite data allow the authors to describe the seasonal evolution of the surface circulation of the arabian sea which reverses annually with the indian monsoon winds this study finds several features that advance current understanding most significantly northward flow appears along the length of the western boundary together with a weak anticyclone at 6 n a precursor to the great whirl as early as march or april one or two months before the southwest monsoon winds this circulation is driven by planetary waves which are initiated by wind curl forcing during the previous southwest monsoon leading the authors to speculate that there is an oceanic mechanism through which one monsoon may precondition the next second the authors find that the eastward south equatorial counter current secc is present year round fed by the northward east african coastal current eacc during the southwest monsoon the eacc overshoots the equator and splits feeding both northwa

variations in apparent mixing efficiency in the north atlantic central water abstract microstructure data from the north atlantic tracer release experiment natre are presented providing detailed profiles of the thermal variance in the upper 360 m of the canary basin for the fall and spring seasons the osborn cox model is used to compute the diffusivity kt the diffusivity for the depth range 240 340 m is found to be 1 0 0 04 10 5 m2 s 1 in the fall and 2 2 0 1 10 5 m2 s 1 in the spring in good agreement with dye inferred diffusivities at similar depths measured turbulent kinetic energy tke dissipation rates were found to be contaminated by hydrodynamic noise so the osborn dissipation method was not used to compute k however data segments for which the tke dissipation rate e was large enough to be unaffected by noise were used to compute the apparent mixing efficiency d the computed d values are used to investigate variations in apparent mixing efficiency with respect to density ratio r and turbulence reynolds number e n2 in an attempt to eluci

mesoscale dynamics in the arabian sea and a focus on the great whirl life cycle a numerical investigation using roms the great whirl gw is a persistent anticyclonic mesoscale eddy that is observed seasonally in the arabian sea during a period embedding the 3 months of the southwest monsoon june july august at a quasi steady location its dynamics remain unclear despite it being one of the largest coherent vortices in the world ocean realistic regional numerical experiments using roms are performed to investigate the life cycle of the gw which is not well resolved by sparse available in situ measurements in the region using a set of sensitivity experiments and an accurate temporal characterization of the eddy properties including position radius depth and vorticity we i confirm the role of basin scale downwelling rossby waves in the gw generation ii clarify the role of the monsoonal strong anticyclonic wind in its maintenance and barotropization and iii suggest a connection between basin scale rossby wave dynamics and gw collapse

manganese iron and sulphur cycling on the pakistan margin abstract benthic biogeochemical processes in the oceans oxygen minimum zones omzs are of global significance yet they remain poorly defined here sedimentary manganese iron and sulphur cycling are studied at sites above within and below the omz on the pakistan margin of the arabian sea before and immediately after the southwest monsoon mechanisms and rates of sedimentary mn fe and s cycling demonstrated down slope variation according to the position of the omz no significant seasonal change was evident except at one station on the upper margin where bottom waters became hypoxic during the late to post monsoon sampling due to the shoaling of the upper omz boundary within the omz mn 4 reduction within the water column limited supply of reactive mn to the underlying sediments the majority of reactive mn reaching the sedimentary environment is reduced abiotically via reaction with fe 2 sediments within the omz act as a source of mn 2 to the overlying water below the omz mn 2 is re oxidised within the water column and is deposited on the surface of the underlying sediments manganese is then reduced microbially and re oxidised within the oxygenated surface sediments uniform surface sediment fe al ratios across the margin suggest that fe 3 reduction is lacking within the water column omz in contrast fe is actively cycled within the sediments with fe 3 reduction occurring via dissimilatory pathways an absence of potential fe 2 oxidants within the omz results in an efflux of fe 2 from the sediments to the water column below the omz greater oxidant availability ensures that fe is retained within the sediments measured sulphate reduction rates at all sites across the margin were surprisingly low 0 0 45 mmol m 2 d 1 relative to rates observed on other omz margins the abundance of fe oxides in the sedimentary environment appears to suppress sulphate reduction

puff a high resolution volcanic ash tracking model this paper presents a volcanic ash tracking model referred to as puff the model was developed to simulate the movement of airborne ash in near real time following an eruption for the purposes of hazard warning the model tracks particles through a lagrangian formulation of advection fallout and turbulent diffusion using a random walk technique three recent eruption events are simulated using archived data avhrr images from these events are used for comparison and to validate model results

opening of the kuril basin deduced from the magmatic history of central hokkaido north japan abstract the kuril basin is a fan shaped back arc basin in the northwestern pacific rim the basin is separated by the kuril arc from the pacific ocean to the southeast and is bounded by the subsided okhotomorsk block to the north and by the late eocene to early miocene hidaka magmatic arc to the west the clastic sediments constituting the late cretaceous to early eocene proto kuril arc which underlies the modern kuril arc were transported from the okhotomorsk block between them the kuril basin now intervenes this suggests that the kuril basin had not opened and that the proto kuril arc had been located in the southern margin of the okhotomorsk block at least until early eocene time it also indicates that the kuril basin was not entrapped by the proto or modern kuril arc the tertiary hidaka magmatic arc in central hokkaido was formed along a n s trending subduction zone where the pacific plate was subducting beneath the eurasian plate therefore the kuril basin was not yet present on the east of central hokkaido during the period when the hidaka magmatism was taking place based on the fact that the hidaka arc magmatism ceased at 17 16 ma and coevally along its n s trending extension it is suggested that the kuril basin opened just after 16 ma by the southward retreat of the proto kuril arc trench system in central hokkaido an extensional stress regime during the middle miocene is inferred from the occurrence of a type magmatism and graben like sedimentary basins this stress field can be attributed to subsidence of the pacific slab covered by the retreated proto kuril arc during the opening of the kuril basin the occurrence of an undeformed and horizontal sedimentary cover on the rugged basement of the kuril basin is consistent with rather rapid opening at 16 15 ma during the middle miocene the kuril basin and japan basin were formed by a similar process i e rotation and oceanward retreat of an arc trench system opening of the two back arc basins along different plate boundaries i e the pacific north american boundary for the kuril basin and the pacific eurasian boundary for the japan basin may have been caused by the migration of a hot region across the overriding plate boundary

strain partitioning in the helvetic thrust belt of eastern switzerland from the leading edge to the internal zone abstract the strain and strain partitioning in the helvetic thrust belt are analysed in order to determine their variation across the belt from the external thin skinned portion to the internal thick skinned portion and in order to begin the detailed mechanical analysis of the entire fold and thrust belt coarse grained limestones of jurassic and cretaceous age were chosen for analysis because they can be traced from the external to the internal zones the strain within a bed is partitioned into three components transgranular pressure solution microfaults veins twinning granular and intragranular exclusive of twinning crystal plasticity associated with recrystallization transgranular strain was very important in the early history of the helvetic nappes giving way to twinning at a later stage under tectonic burial twinning strain was early in the infrahelvetic complex giving way to intracrystalline deformation at the later stage of burial the transition from transgranular to intragranular dominated strain occurred at a vitrinite reflectance value of 3 5 significantly below the greenschist grade of metamorphism in a large scale fold at the leading edge of the helvetic nappes transgranular strains were associated with the buckling stage of the fold and twinning occurred during fold tightening in more internal parts of the helvetic nappes twinning strains are also late with regard to transgranular strains but here their pattern corresponds to the regional finite strain pattern in the internal zone the infrahelvetic complex twinning seems to have been an early event and records an initial layer parallel shortening followed by regional internal deformation with intragranular strains

nd sr isotopic and geochemical characteristics of the southern adamello northern italy intrusives implications for crustal versus mantle origin among the periadriatic tertiary calc alkaline intrusions in northern italy the adamello batholith displays the most convincing evidence for a mafic parentage this is particularly the case for the southern adamello where minor ultramafic to gabbroic bodies form the margins of several distinct and dominantly tonalitic plutons isotopic analyses are presented for the val fredda and blumone ultramafic gabbroic to tonalitic leucoquartzdioritic suites for the more felsic rock types of the spatially predominant re di castello group as well as for a lamprophyre this dike of picrobasaltic composition is thought to represent the parental magma field relations and a large body of petrographic geochemical and mineral chemical data point to a cogenetic origin for all of these rocks and to magmatic differentiation with fractional crystallization and accumulation as the main evolutionary mechanism this is compatible with the isotopic results for the blumone series and the mafic rocks of val fredda with end 3 8 to 1 5 and esr 9 1 to 4 6 a common parental magma similar to the lamprophyre end 3 1 esr 4 4 also seems plausible the isotopically homogeneous felsic lithologies of val fredda end 0 1 to 0 3 esr 2 9 to 0 7 structurally intimately associated with their mafic counterpart indicate crustal contamination incurred prior to their differentiation for the re di castello group progressing crustal affinity of isotopic compositions end of 1 9 to 4 9 and esr of 16 5 to 40 9 with chemical differentiation implies large scale interaction with a granitoid crustal component attempts at quantifying this process reveal individual characteristics and evolution for each pluton the data indicate extraction of this component from a source in the lower crust with time integrated low rb sr esr approximating 50 and en close to 6 corresponding to a 1000 ma crustal residence age if a two stage evolution is assumed formation of a gabbroic reservoir from the above parental melt would require uptake of some 4 12 wt of granitoid component by combined assimilation fractional crystallization whereas subsequent evolution to tonalitic compositions would necessitate admixing of 40 70 wt of granitoid partial melt assimilation thus mainly occurs during evolution from gabbroic to tonalitic compositions when the mafic magma is ponded near the mantle crust boundary and where homogenization prior to resuming buoyant ascent is assured precise locations and more detailed petrography of the samples is available with entire article on microfiche order from american geophysical union 2000 florida avenue n w washington dc 20009 document 91b 002 2 50 payment must accompany order