mesoscale features create hotspots of carbon uptake in the antarctic circumpolar current the influence of eddy structures on the seasonal depletion of dissolved inorganic carbon dic and carbon dioxide co2 disequilibrium was investigated during a trans atlantic crossing of the antarctic circumpolar current acc in austral summer 2012 the georgia basin downstream of the island of south georgia 54 55 s 36 38 w is a highly dynamic region due to the mesoscale activity associated with the flow of the subantarctic front saf and polar front pf satellite sea surface height and chlorophyll a anomalies revealed a cyclonic cold core that dominated the northern georgia basin that was formed from a large meander of the pf warmer waters influenced by the saf formed a smaller anticyclonic structure to the east of the basin both the cold core and warm core eddy structures were hotspots of carbon uptake relative to the rest of the acc section during austral summer this was most amplified in the cold core where greatest co2 undersaturation 78 atm and substantial surface ocean dic deficit 5 1 mol m 2 occurred in the presence of high wind speeds the cold core eddy acted as a strong sink for atmospheric co2 of 25 5 mmol m 2 day 1 waters of the warm core displayed characteristics of the polar frontal zone pfz with warmer upper ocean waters and enhanced co2 undersaturation 59 atm and depletion of dic 4 9mol m 2 a proposed mechanism for the enhanced carbon uptake across both eddy structures is based on the ekman eddy pumping theory i the cold core is seeded with productive high chlorophyll a waters from the antarctic zone and sustained biological productivity through upwelled nutrient supply that counteracts dic inputs from deep waters ii horizontal entrainment of low dic surface waters biological uptake from the pfz downwell within the warm core and cause relative dic depletion in the upper water column the observations suggest that the formation and northward propagation of cold core eddies in the region of the pf could project low dic waters towards the site of antarctic intermediate water formation and enhance co2 drawdown into the deep ocean

a scenario study of seismically induced landsliding in seattle using broadband synthetic seismograms abstract we demonstrate the value of utilizing broadband synthetic seismograms to assess regional seismically induced landslide hazard focusing on a case study of an m w 7 0 seattle fault earthquake in seattle washington we computed broadband synthetic seismograms that account for rupture directivity and 3d basin amplification we then adjusted the computed motions on a fine grid for 1d amplifications based on the site response of typical geologic profiles in seattle and used these time series ground motions to trigger shallow landsliding using the newmark method the inclusion of these effects was critical in determining the extent of landsliding triggered we found that for inertially triggered slope failures modeled by the newmark method the ground motions used to simulate landsliding must have broadband frequency content in order to capture the full slope displacement we applied commonly used simpler methods based on ground motion prediction equations for the same scenario and found that they predicted far fewer landslides if only the mean values were used but far more at the maximum range of the uncertainties highlighting the danger of using just the mean values for such methods our results indicate that landsliding triggered by a large seattle fault earthquake will be extensive and potentially devastating causing direct losses and impeding recovery the high impact of landsliding predicted by this simulation shows that this secondary effect of earthquakes should be studied with as much vigor as other earthquake effects online material high resolution maps of relative seismically induced landslide hazard for an m w 7 0 seattle fault earthquake for dry and saturated soil conditions

superimposed tectono metamorphic episodes of jurassic and eocene age in the jadeite uplift myanmar as revealed by 40ar 39ar dating abstract the myanmar jadeite uplift forms an important link between the indo burma range and the tagaung myitkyina belt two contrasting ages of jurassic 152 4 1 5 ma of glaucophane from blueschist and eocene 44 8 1 1 and 45 0 1 3 ma of phengitic muscovites from quartz schists in the uplift were yielded using 40 ar 39 ar dating the jurassic age of the glaucophane even older than the forming age of the jadeitite from recent relevant literatures and for the reason of possible excess argon involved is interpreted as the lower limit of the subduction age previous studies correlated this subduction with the woyla intra oceanic arc or the incertus arc to the west the eocene ages of phengitic muscovites are interpreted as the time of an intra continental shearing deformation event against the timing of hp lt metamorphism as previously suggested combined with other studies it is suggested that the tagaung myitkyina belt and the indo burma range belonged to a single belt which has been separated by the sagaing fault leaving the jadeite uplift straddling along the fault between the belt and the range we propose a rapid exhumation model for the myanmar jadeitite at 45 ma coeval with onset of the sagaing fault

the origin of jadeitite forming subduction zone fluids cl guided sims oxygen isotope and trace element evidence jadeitite a rare high p t rock is associated spatially with blueschist and or eclogite terranes scanning electron microscope sem and cathodoluminescence cl petrography of jadeitite samples from several major occurrences in burma myanmar guatemala japan kazakhstan and the u s a show that grains were deposited from s uids jadeite grain compositions indicate these s uid compositions changed with time cl imagery guided the acquisition of oxygen isotope and trace element analyses with the ion microprobe jadeite grains in each rock grew in cycles that began with red and or blue luminescent and ended with green luminescent zones the cl images were used to order the data into crystallization sequences these data and electron microprobe major element analyses document the association of green cl with increases in ca mg and cr 1 toward grain exteriors 2 in ne grained matrix around porphyroblasts 3 in shear zones that cut grains 4 in former open spaces now lled with jadeite or 5 in veins abundances of many trace elements are greater in green cl jadeitite compared with the red or blue cl zones some of these elements in particular li rb sr ti hf zr y and ree are unlikely to have been derived from serpentinite although crystal chemical effects may explain some of the trace element systematics e g preferential incorporation of ree into ca richer jadeite some kinetic control is suggested by sector zoned rhythmically zoned grains the oxygen isotope data suggest that jadeitite depositing s uids either had multiple sources or evolved in composition along their s ow paths or both

the modi taung nankwe gold district slate belt central myanmar mesothermal veins in a mesozoic orogen abstract the recently discovered quartz gold veins comprising the modi taung nankwe gold district in central myanmar are largely hosted by mudstones of the late palaeozoic slate belt mesozoic rocks of the paunglaung mawchi zone separate the slate belt from the shan scarp and shan plateau to the east at modi taung 5 km of exploration adits indicate that the veins within steeply dipping oblique reverse slip shear zones are displaced by movements along the shears intruded by late jurassic calc alkaline dykes and offset on conjugate cross faults drill intercepts show that mineralization extends vertically for more than 500 m coarse visible gold book and ribbon texture and stylolitic laminations and trace metal values are consistent with mineralization at mesothermal depths of several kilometres in the brittle ductile regime our field observations suggest that mineralization took place in the early jurassic following collision of myanmar on the passive western margin of a greater shan thai continental block with an oceanic arc on the overriding plate to the west collision generated intra continental thrusting in and east of the paunglaung mawchi zone metamorphism of plateau rocks thrust west beneath the slate belt to form the mogok metamorphics and ascent of mineralizing fluids expelled from dehydrating underthrust rocks reversal in orogenic polarity initiated late jurassic eastward subduction of oceanic crust beneath myanmar and generation of a magmatic arc with dykes cutting the quartz gold veins renewed east directed thrusting translated the slate belt over arc clastics and probably resulted in exhumation of the mogok metamorphics and offsets of the veins on conjugate faults young k ar rb 87 sr 86 and ar 40 ar 39 ages on the mogok metamorphic belt imply renewed tertiary uplift and possibly intrusion of mid tertiary or palaeogene granites

an anticyclonic circulation above the northwest georgia rise southern ocean data from a variety of sources reveal a warm core anticyclonic circulation above the northwest georgia rise nwgr an similar to2000 m high bathymetric feature north of south georgia the sense of the circulation is opposite to the general cyclonic flow in the georgia basin the circulation shows the characteristics of a stratified taylor column dimensional analysis shows that the local bathymetry and hydrography are conducive to the formation of such ers2 altimeter data show that the column whilst not fully permanent is nonetheless a recurring feature high concentrations of chlorophyll a are observed at the centre of the circulation indicating that the modulation of the physical environment has significant consequences for the local biogeochemical system via enhanced primary production enhanced chlorophyll a extends in a long plume from the nwgr along pathways indicated by drifters this passive redistribution may have consequences for the larger basin scale ecosystem

brunt vaisala frequency and rossby radii in the south atlantic abstract brunt vaisala frequency profiles have been calculated in the south atlantic and neighboring regions on a 5 5 grid between 30 n and 70 s 70 w and 70 e using the annual mean temperature and salinity profiles computed by levitus from data available from the national oceanographic data center nodc these brunt vaisala frequency profiles are used in the computation of the first and second internal rossby deformation radii the external rossby radius is computed for reference these results compare very well with those of emery et at for the equatorial atlantic very small values of the radii are evidenced in the extreme south less than 10 km in the antarctic circumpolar current for the first internal mode high vertical variability in brunt vaisala frequency profiles is also observed at the center of the subtropical gyre this behavior is probably due to the lack of deep data in this region

tectonics and hp uhp metamorphism of northern tibet preface abstract this special issue has been prepared for the 8th international eclogite conference iec to be held in the qilian qaidam regions western china during august 2009 most papers in this issue summarize results of many current petrological geochemical geochronological and tectonic studies of both qilian pacific type and qaidam alpine type lithotectonic assemblages important new occurrences include the qilian lawsonite eclogites which required an extremely cold subduction of the early paleozoic oceanic lithosphere and the mixing of oceanic and supracrustal protoliths in the qaidam continental subduction channel these two early paleozoic sutures in northern tibet provide additional constraints on the regional tectonic evolution of paleo and neo tethys in south central asia

in situ la icp ms u pb dating of metavolcanics of norrbotten sweden records of extended geological histories in complex titanite grains in situ u pb dating of a variety of mineral phases is an important goal in petrology this study reports data chiefly from titanite but also from rutile and apatite obtained using the laser ablation la icp ms methodology on polished thick sections in order to retain as much petrologic information as possible and allowing trace element analyses from adjacent areas to the u pb analyses the samples analysed come from svecofennian intermediate to acid volcanic rocks of the porphyry group within the major iron ore province of norrbotten northern sweden where titanite is a common phase associated with the mineralisation using a laser beam of 30 45 m in diameter accurate and relatively precise 2 3 2 on 206pb 238u ratios data can be obtained on titanite similar precision on pb u ratios can be obtained in rutile but accuracy cannot be assessed because of the lack of well characterised standards however the data are a priori accurate as they are geologically reasonable apatite shows reverse discordance which could be explained by a number of scenarios however the 207pb 206pb ages are fairly precise 1 3 2 and the calculated age is geologically reasonable suggesting that the data may be accurate the titanite grains studied show complex internal structures rare earth element ree analysis by la icp ms demonstrates that the core and rim zones are distinct and supports a model for two stage evolution in two out of three samples with the rims in these samples being enriched in total ree and particularly in lree in one sample and displaying a positive y anomaly in contrast to the cores in situ u pb analysis reveals that core zones from all samples retain distinct older ages of c 2050 ma whereas the reworked rims have either distinct younger or strongly reset ages the older cores are interpreted as representing the first alteration metamorphism of the volcanic pile titanite rims record a u pb age of 1870 24 ma 2 at luossavaara and 1826 15 ma 2 at the smaller fe oxide apatite body at gruvberget in both cases the ages are consistent with previous age determinations from the fe oxide apatite deposits a sample from malmberget records a slightly different scenario where u pb ages spread along concordia from c 1920 to 1708 ma we attribute this pattern to metamorphic reworking of primary metasomatic titanite rutile ages from inclusions within the core of gruvberget titanite essentially mimic the ages obtained from the surrounding titanite and suggest that they have undergone the same history apatite inclusions within titanite at malmberget record a younger age of 1584 12 ma 2 which we attribute to later events known to have affected the area these data indicate that the porphyry group volcanics must be at least c 2050 ma in age in contrast to previous age determinations from zircon which suggested a deposition age of c 1960 to 1880 ma the large grain size of the titanites studied coupled with the ability for the first time to obtain in situ u pb ages from small areas has allowed probing of this hitherto unrecognised event smaller zircon grain size coupled with extremely saline hot pressurised high p t metasomatic fluids relating to regional magnetite apatite mineralisation in the period 1900 to 1800 ma may have resulted in resetting of zircon u pb systematics 2007 elsevier b v all rights reserved

zircon hf isotope signature of the depleted mantle in the myanmar jadeitite implications for mesozoic intra oceanic subduction between the eastern indian plate and the burmese platelet article i nfo this study systematically investigated the lu hf isotope signatures of zircons in jadeitite from the north myanmar which was formed from jadeite forming hydrothermal fluids and is always sourced in serpentinite as a mark for the subduction zone results show that the three group zircons have positive ehf t values group i zircons 163 2 3 3 ma have relatively higher 176 lu 177 hf ratios n0 0004 and the corresponding ehf t values range from 15 5 to 20 0 at t 163 ma in contrast group ii zircons 146 5 3 4 ma exhibit highly variable 176 lu 177 hf ratios from 0 000027 to 0 001398 but still have ehf t values of 15 6 to 18 5 at t 147 ma which resemble to those of the group i zircons the group iii zircon 122 2 4 8 ma has a 176 lu 177 hf ratio of 0 000578 and a ehf t value of 15 8 at t 122 ma such highly positive ehf t values for all jadeitite zircons indicate that they were derived from rapid reworking of the very juvenile crust therefore zircon in jadeitite can be used as a valuable mineral to constrain the age of serpentinization rodingitization and even the age of formation of ultramafic rock within ophiolites the results also suggest the presence of the mesozoic intra oceanic subduction within the indo burman range and further suggest that the hydrothermal fluids were derived from dehydration of seawater altered oceanic juvenile crust that had been hydrated during and or after the formation of the oceanic crust and additionally from serpentine minerals at greater depth consequently the fluids carry the hf isotope signature of the depleted mantle that can be later imparted to the jadeitite zircons

the unusual surface chlorophyll signatures of southern ocean eddies southern ocean mesoscale eddies play an important role in ocean circulation and biogeochemical cycling but their biological characteristics have not been well quantified at the basin scale to address this we combined a 15 year tracked eddy data set with satellite observations of ocean color sea surface temperature and autonomous profiling floats to quantify the surface and subsurface properties of eddies anomalies of surface temperature and chlorophyll were examined in eddy centric composite averages constructed from thousands of eddies normalized surface chlorophyll anomalies chlnorm vary seasonally and geographically cyclones typically show positive chlnorm while anticyclones have negative chlnorm the sign of chlnorm reverses during late summer and autumn for eddies between the subtropical and polar fronts the reversal is most obvious in the indian sector and we attribute this to a combination of eddy stirring deformation of surface gradients by the rotational velocity of an eddy and deeper winter mixing in anticyclones both chlnorm and sea surface temperature anomalies transition from dipole structures north of the subtropical front to monopole structures south of the subantarctic front sea surface temperature and chlnorm composites provide evidence for eddy trapping transporting of anomalies and eddy stirring this research provides a basin scale study of surface chlorophyll in southern ocean eddies and reveals counterintuitive biogeochemical signals

tectonics of the western margin of the shan plateau central myanmar implication for the india indochina oblique convergence since the oligocene abstract we present new data and interpretations on the neogene tectonics of the shan scarp area central myanmar and its relationship with the india indochina oblique convergence we describe ductile and brittle fabrics associated with the major features in this area the mogok metamorphic belt mmb the shan scarp and the sagaing fault from these data we identify a succession of two tectonic regimes first a dominant nnw sse trending extension marked by ductile stretching that characterizes the mmb and associated n70e brittle normal faults later from middle or upper miocene to the present these structures were cross cut by brittle right lateral faults among which the most important are the n20w transpressive shan scarp fault zone and the n s sagaing fault to explain this transition from a dominant transtensive to a transpressive stress regime that occurred during miocene we place our data within a larger geodynamic context we suggest that like the intraplate deformation in the indian ocean the end of spreading in the south china sea the opening of the andaman basin or the end of subduction within the indo burma range the change in the tectonic regime in central myanmar could be in response to a major miocene regional plate kinematic reorganization

numerical analysis on influence of principal parameters of topography on hillslope instability in a small catchment this study was conducted to identify the influence of three principal parameters constituting topography slope inclination soil depth and slope length on hillslope instability in a small catchment known as higashifukubegawa of shikoku island western japan the typhoon rainfall of 19 20 october 2004 was significant in causing a total of seven slope failures in the catchment though other rainfall events of various intensities in the same year did not cause failure to understand the influence of the three principal parameters numerical modeling of seepage and slope stability was performed in slope profiles constructed by varying the three parameters across their permissible range prepared from the seven slope failures of higashifukubegawa in geostudio geostudio tutorials includes student edition lessons geo slope international ltd calgary 2005 v 4 the change in porewater pressure and slope mass weight due to variation in values of principal parameters was used to interpret the change in factor of safety or instability the results showed that 1 instability increases with increase in the values of all three selected parameters across their range in higashifukubegawa with remarkable decreasing trend in factors of safety 2 slope inclination and soil depth were observed to affect instability through change in both unsaturated zone moisture content and mobilizing force of slope mass 3 but with slope length the unsaturated zone moisture content was not found to change considerably which implies that the instability due to slope length is mainly governed by change in slope mass weight overall this study has dealt in great detail with how hillslope instability changes with principal parameters of topography under the same simulating conditions of hydrological and geo mechanical parameters

southern acc front to the northeast of south georgia pathways characteristics and fluxes 1 in december 2000 we conducted high resolution hydrographic and towed undulator transects across the south georgia shelf and into the deep waters of the georgia basin the southern antarctic circumpolar current front saccf was observed flowing northwestward close to the base of the slope at 53 7 s with a second manifestation around 53 4 s having flow in the reverse direction both crossings had a significant barotropic component aligned with the flow the region of the saccf was characterized by large scale undulations of properties on horizontal scales of 5 10 km similar to the local internal rossby radius we observe a distinct surface temperature gradient associated with the saccf in the vicinity of south georgia and demonstrate the usefulness of this by tracing the course of the front around the island with advanced very high resolution radiometer data a distinct northward deflection of the front to the north of south georgia is probably due to topographic steering by the north georgia rise the signature of the saccf is pronounced in the circumpolar deep water with strong isopycnal interleaving indicative of cross frontal mixing the salinity of the weddell sea deep water is marginally higher between the two manifestations of the saccf reflecting the different pathways from its source regions in the weddell sea remarkably strong vertical gradients of potential temperature and salinity exist in the bottom 100 m of the water column at depths of around 3500 m because of the vertical juxtaposition of waters that have taken different routes around the northeast georgia rise

potential for landsliding dependence on hyetograph characteristics 1 this paper examines the effect of hyetograph shape on the potential for landsliding in soil mantled landscapes an existing pore pressure response model iverson 2000 is used to study the effects of unsteady rainfall infiltration in hillslopes and the effect of slope and convergent topography is expressed using a steady state model of slope parallel subsurface flow slope stability is assessed using an infinite slope analysis this theoretical framework is coupled with simple hyetograph models and to intensity duration frequency functions to determine the return period of landslide triggering rainfall results also show that hyetographs with a peak at the end of a rainfall event have a stronger destabilizing effect than hyetographs with a constant rainfall or with a peak at the beginning of a storm thus the variability of hyetograph shapes adds uncertainty to the assessment of landsliding triggered by rainfall

titanite bearing omphacitite from the jade tract myanmar interpretation from mineral and trace element compositions abstract jadeitite is a rare rock composed predominantly of jadeite which typically occurs in association with tectonic blocks of high pressure low temperature metabasaltic rocks such as eclogite or blueschist often as a matrix in exhumed serpentinite melanges omphacitite are far less common occurring together with jadeitite such as those in the jade tract of hpakan area in myanmar the omphacitite in this locality is mostly composed of omphacite and jadeite with minor titanite ilmenite epidote and zircon the jadeite formed after omphacite shows a lower jd content than that in the neighboring white jadeitite the omphacite shows significant variation in jd content and is associated with aegirine augite both rocks show relatively linear and upslope pattern from lree to hree and a slight enrichment of ba th u zr and hf relative to chondrites in the absence of eu anomaly the titanite occurs in two groups one as discrete islands replacing ilmenite and the other as precipitation within jadeite veinlet titanite grains show convex patterns from lree to hree and depletion of sr zr and hf with no eu anomaly chemical characteristics of the titanite and ilmenite alteration around titanite suggest that the omphacitite is of secondary origin likely derived from pyroxenite through the replacement of pyroxene by jadeite based on the previous findings of jadeitization of chromitite serpentine and rodingite it is suggested that protoliths such as plagiogranite or gabbro trapped within serpentinite melange might have undergone jadeitization

a simplified physically based coupled rainfall threshold model for triggering landslides abstract a number of rainfall threshold models for triggering landslides have been developed in either empirical or physical manner the objective of an empirical rainfall threshold model is to establish a relationship between rainfall intensity and duration which is a line on a log log diagram although the mechanism of the relationship following the power law is not yet well understood the sufficiency of rainfall and landslide data is also a significant concern for empirical models a simplified physically based rainfall threshold model is developed by coupling the mohr coulomb law and darcy s law based on the assumptions that the slope has an infinite length and that discrete water diffusion is physically based the power law mechanism for the relationship between rainfall intensity and duration for the initiation of a landslide is investigated using this physically based model the rainfall threshold calculated with the model shows that the threshold follows the power law for short rainfall durations whereas it gradually tends towards a constant value for long rainfall durations case studies have shown that a plausible threshold for regions that lack sufficient landslide and rainfall data can be obtained via the model the model is also applied to cases which occurred in regions geologically typical of fujian province southeast china the landslide distribution predicted by our model accords with the interpretation of high resolution satellite imagery and this suggests that the proposed physically based model also effectively determines rainfall thresholds for triggering regional landslides

assessment of rainfall induced shallow landslide susceptibility using a gis based probabilistic approach abstract this study proposes a probabilistic analysis method to assess shallow landslide susceptibility over an extensive area by integrating an infinite slope model with gis geographic information system and monte carlo simulation taking into consideration the inherent uncertainty and variability in input parameters the mechanical parameters of soil materials such as cohesion and friction angle used in the infinite slope analysis have been identified as the major source of uncertainty because of their spatial variability therefore these parameters were considered as random variables in this probabilistic landslide analysis to properly account for the uncertainty in input parameters the probabilistic analysis method used was monte carlo simulation the process was carried out in a gis based environment because gis has effective spatial data processing capacity over broad areas in addition the hydrogeological model was coupled with the infinite slope model to evaluate increases in pore water pressure caused by rainfall the proposed approach was applied to a practical example to evaluate its feasibility the landslide inventory map and the spatial database for input parameters were constructed in a grid based gis environment and a probabilistic analysis was implemented using monte carlo simulation to evaluate the performance of the model the results of the probabilistic landslide susceptibility analysis were compared with the landslide inventory the probabilistic approach demonstrated good predictive performance when compared with the landslide occurrence location in addition deterministic analysis was carried out using fixed single input data for comparison with the results from the proposed approach in this comparison the probabilistic analysis showed better performance than the deterministic analysis in addition the results showed that proper consideration and understanding of uncertainties play an important role in accurately predicting shallow landslide susceptibility

influence of hydraulic properties on physically modelling slope stability and the definition of rainfall thresholds for shallow landslides abstract physically based models are recognized as a good tool for slope stability analysis and have been implemented for the definition of rainfall thresholds for landslides in this study a methodology for estimating rainfall intensity and duration thresholds for shallow sliding failure using the physical model trigrs was implemented in a tropical mountainous basin of the valle de aburra colombia the variation of pressure head and factor of safety during different rainfall events and hydraulic conditions is studied for specific grid cells steady state and a maximum pressure head were reached for each grid cell regardless of the different rainfall intensities and hydraulic conductivities simulated but the time in which this condition is reached depends on these variables and occurs faster for steeper slopes the influence of hydraulic properties on the stability results and the position of the rainfall intensity and duration thresholds were studied with parametric analysis very low values of saturated hydraulic conductivity do not allow rainfall intensity and duration thresholds to be developed the rainfall threshold position also has a greater variation with respect to the parameters of the soil water retention curve and the initial infiltration rate or long term background rainfall rate for low values of saturated hydraulic conductivity

first evidence of widespread active methane seepage in the southern ocean off the sub antarctic island of south georgia an extensive submarine cold seep area was discovered on the northern shelf of south georgia during r v polarstern cruise ant xxix 4 in spring 2013 hydroacoustic surveys documented the presence of 133 gas bubble emissions which were restricted to glacially formed fjords and troughs video based sea floor observations confirmed the sea floor origin of the gas emissions and spatially related microbial mats effective methane transport from these emissions into the hydrosphere was proven by relative enrichments of dissolved methane in near bottom waters stable carbon isotopic signatures pointed to a predominant microbial methane formation presumably based on high organic matter sedimentation in this region although known from many continental margins in the world s oceans this is the first report of an active area of methane seepage in the southern ocean our finding of substantial methane emission related to a trough and fjord system a topographical setting that exists commonly in glacially affected areas opens up the possibility that methane seepage is a more widespread phenomenon in polar and sub polar regions than previously thought

a tale of three islands downstream natural iron fertilization in the southern ocean iron limitation of primary productivity prevails across much of the southern ocean but there are exceptions in particular the phytoplankton blooms associated with the kerguelen plateau crozet islands and south georgia these blooms occur annually fertilized by iron and nutrient rich shelf waters that are transported downstream from the islands here we use a highresolution 1 12 ocean general circulation model and lagrangian particle tracking to investigate whether inter annual variability in the potential lateral advection of iron could explain the inter annual variability in the spatial extent of the blooms comparison with ocean color data 1998 to 2007 suggests that iron fertilization via advection can explain the extent of each island s annual bloom but only the inter annual variability of the crozet bloom the area that could potentially be fertilized by iron from kerguelen was much larger than the bloom suggesting that there is another primary limiting factor potentially silicate that controls the inter annual variability of bloom spatial extent for south georgia there are differences in the year to year timing of advection and consequently fertilization but no clear explanation of the inter annual variability observed in the bloom s spatial extent has been identified the model results suggest that the kerguelen and crozet blooms are terminated by nutrient exhaustion probably iron and or silicate whereas the deepening of the mixed layer in winter terminates the south georgia bloom therefore iron fertilization via lateral advection alone can explain the annual variability of the crozet bloom but not fully that of the kerguelen and south georgia blooms this article is protected by copyright all rights reserved

high resolution modelling of the shelf and open ocean adjacent to south georgia southern ocean abstract the marine ecosystem on the shelf and open ocean adjacent to south georgia is extraordinarily rich with a history of commercial exploitation although much progress has been made attempts at modelling and hence better understanding this system have consistently been hampered by the poor representation of key physical processes in global or regional ocean general circulation models here we present the development of a high resolution 3d hydrodynamic model of the south georgia shelf and the adjacent open ocean including a novel method for prescribing freshwater fluxes the ability of the model to reproduce the observed oceanography of the region is quantified by comparisons with data from tide gauges at south georgia with satellite derived sea surface temperatures and with an extensive ctd dataset collected during january april 1995 predicted cotidal charts for the diurnal tides o1 and k1 show a periodic amplification in both the current and elevation fields at the shelf edge suggesting the presence of a diurnally forced continental shelf wave this could have important implications for processes such as larval transport and retention the comparison with ctd data reveals mean and root mean square errors in temperature salinity of 0 27 c 0 07 and 0 64 c 0 23 respectively vertical profiles of potential temperature and salinity on the shelf agree acceptably well with observations but there is a tendency for the model to under predict the density contrast between surface and bottom waters the main limitation on model accuracy is found to be the large scale forcing releasing a passive tracer into the model transport and retention pathways are identified including a prevalence for tracer export from the shelf to the west of south georgia and a transport pathway linking south georgia and shag rocks significantly the model suggests this to be a unidirectional link from south georgia to shag rocks with possible significance for fisheries management the implications of these results in the context of the south georgia ecosystem are discussed briefly demonstrating the usefulness of this new tool for interdisciplinary studies of the region

ion microprobe zircon u pb age and geochemistry of the myanmar jadeitite combined geochemistry and geochronology of the myanmar jadeitite were determined bulk rock trace element compositions display u shaped ree patterns with pronounced positive eu anomalies the total ree abundances are very low less than half chondritic and the high field strength elements and some large ion lithophile elements are moderately enriched these features indicate a metasomatic origin there are three groups of zircons with different interior characteristics cathodoluminescence mineral inclusions chemical compositions and sensitive high resolution ion microprobe u pb ages group i zircons with a mean age of 163 2 3 3 ma mostly have distinct oscillatory zoning highest u and th contents and na free mg rich mineral inclusions and thus indicate an igneous formation of oceanic crust or hydrothermal serpentinization and or rodingitization event in the middle jurassic group ii zircons with a mean age of 146 5 3 4 ma have bright luminescence without oscillatory zoning and include jadeite and jadeitic pyroxene inclusions suggesting that formation of the myanmar jadeitites as well as subduction of the eastern indian oceanic plate occurred in the late jurassic group iii zircons have an age of 122 2 4 8 ma which represents a later unknown thermal event discovery of the middle jurassic zircons provides geochronological constraint on the tectonic evolution of the eastern indo burman range

transient deterministic shallow landslide modeling requirements for susceptibility and hazard assessments in a gis framework abstract application of transient deterministic shallow landslide models over broad regions for hazard and susceptibility assessments requires information on rainfall topography and the distribution and properties of hillside materials we survey techniques for generating the spatial and temporal input data for such models and present an example using a transient deterministic model that combines an analytic solution to assess the pore pressure response to rainfall infiltration with an infinite slope stability calculation pore pressures and factors of safety are computed on a cell by cell basis and can be displayed or manipulated in a grid based gis input data are high resolution 1 8 m topographic information derived from lidar data and simple descriptions of initial pore pressure distribution and boundary conditions for a study area north of seattle washington rainfall information is taken from a previously defined empirical rainfall intensity duration threshold and material strength and hydraulic properties were measured both in the field and laboratory results are tested by comparison with a shallow landslide inventory comparison of results with those from static infinite slope stability analyses assuming fixed water table heights shows that the spatial prediction of shallow landslide susceptibility is improved using the transient analyses moreover results can be depicted in terms of the rainfall intensity and duration known to trigger shallow landslides in the study area

weddell sea phytoplankton blooms modulated by sea ice variability and polynya formation author s vonberg lauren prend channing j campbell ethan c mazloff matthew r talley lynne d gille sarah t

the effect of titanite and other hfse rich mineral ti bearing andradite zircon eudialyte fractionation on the geochemical evolution of silicate melts abstract we present trace element data for hfse rich minerals titanite eudialyte ti bearing andradite zircon from plutonic rocks of the eocene tamazeght complex high atlas mountains morocco in most lithologies significant amounts of titanite are present and as such titanite fractionation played a major role in the evolution of the hfse budget of the whole complex by combining our data with published titanite melt partition coefficients we explore the effects of titanite fractionation on the evolution of geochemical parameters zr hf nb ta la lu and th u ratios during differentiation of silicate melts in detail based upon this we further discuss the genetic relationships between the various rock types present in the tamazeght complex and show that the above mentioned element ratios can potentially be useful for distinguishing geochemically distinct melt reservoirs within a given plutonic rock suite zircon eudialyte and ti bearing andradite are generally rare or are restricted to localized rock units despite their scarcity each of them can have a significant effect upon the hfse budget in their evolving magmas here we derive first estimations of eudialyte melt partition coefficients for ree application of these data to eudialyte bearing rocks of the ilimaussaq complex south greenland and comparing the results to published estimations for the parental melts of these rocks yields consistent results and demonstrates the reliability of our estimations

coexisting retrograde jadeite and omphacite in a jadeite bearing lawsonite eclogite from the motagua fault zone guatemala coexisting jadeite and omphacite were found as retrograde minerals in a jadeite bearing lawsonite eclogite from the motagua fault zone guatemala the lawsonite eclogite is characterized by the occurrence of garnet porphyroblasts up to 2 5 cm in size and the eclogite facies parageneses almandine rich garnet impure jadeite lawsonite rutile quartz garnet contains inclusions of impure jadeite phengite ferroglaucophane chlorite lawsonite rutile ilmenite and quartz textural relations and parageneses and compositions of minerals indicate that the lawsonite eclogite experienced two stages of metamorphism prograde eclogite facies stage m 1 and retrograde stage m 2 the impure jadeite jd i of the m 1 eclogite facies occurs in both the matrix and as inclusions in garnet and contains considerable amounts of augite and aegirine components jd 6 1 7 5 aug 1 6 2 4 ae 0 1 8 it is partly recrystallized to retrograde m 2 jadeite jd ii jd 7 4 8 7 aug 9 1 6 ae 0 1 1 and omphacite jd 4 2 5 0 aug 3 6 4 6 ae 7 1 6 some of these two sodic pyroxenes may have crystallized from fluids both m 2 jadeite and omphacite show textural equilibrium and are believed to have grown concurrently based on the observed compositions and the phase relations of sodic pyroxenes from carpenter 1980 the m 1 impure jadeite jd i may have had a disordered c2 c symmetry at t ca 450 c and p ca 1 8 2 4 gpa and was subsequently crystallized into jadeite jd ii plus ordered p2 n omphacite during retrogression with infiltration of fluids at t ca 300 c and p ca 0 7 gpa m 2 the extreme low t conditions during retrogression may have prevented reaction between eclogitic jadeite and adjacent minerals instead eclogitic impure jadeite plus fluid has recrystallized into the retrograde jadeite omphacite pair with a wide compositional gap

very low solubility of rutile in h2o at high pressure and temperature and its implications for ti mobility in subduction zones the solubility of rutile in h2o has been measured at 1000 1100 c 1 2 gpa the data indicate that solubility is very low over the investigated range with a maximum of 4 7 millimol kg h2o at 1100 c 2 gpa the data were fit with the equation log m ti 4 892 10470 t 0 1923 p where m ti is ti molality t is in kelvins and p in gpa when compared to previous results the new data indicate substantially lower solubility opposite pressure dependence and thermodynamic properties of the reaction rutile tio2 aq that are now consistent with other oxide hydrolysis reactions calculations of ti transport during mantle metasomatism by h2o in subduction zone environments predict much lower ti mobility at all conditions these results offer strong support for models of ti retention in eclogites during slab devolatilization and require that examples of significant ti mass transfer be explained by complexing agents in solution most likely aluminosilicate complexes

two high pressure low temperature serpentinite matrix melange belts motagua fault zone guatemala a record of aptian and maastrichtian collisions left lateral motion along the north american caribbean plate boundary has juxta posed two high pressure low temperature hp lt belts from separate cretaceous colli sions these two belts have quite different ages and different suites of high pressure as semblages yet they both contain jadeitite a relatively rare rock type this part of the plate boundary zone follows the motagua river valley in guatemala where it separates the maya block north american plate from the chortis block caribbean plate on both sides of the bounding motagua fault tectonic slices of serpentinite matrix melange host the hp lt rocks south of the fault the melange slices contain eclogite lawsonite eclogite glaucophane eclogite and blueschist blocks north of the fault the melange slices contain omphacite metabasite albitite and garnet amphibolite blocks but lack intact eclogite in addition to the dissimilar rock assemblages 40 ar 39 ar geochronology of phen gitic micas yields 77 65 ma for northern and 125 113 ma for southern blocks these data suggest that the southern belt formed during early cretaceous aptian northeastward dipping subduction of the farallon plate and collision of the chortis block with western mexico the block was then displaced southeastward along this suture in contrast the northern belt records subduction related to the maastrichtian collision of an extension of the chortis block perhaps the nicaraguan rise with the maya block

carbon cycling fed by methane seepage at the shallow cumberland bay south georgia sub antarctic recent studies have suggested that the marine contribution of methane from shallow regions and melting marine terminating glaciers may have been underestimated here we report on methane sources and potential sinks associated with methane seeps in cumberland bay south georgia s largest fjord system the average organic carbon content in the upper 8 m of the sediment is around 0 65 wt this observation combined with parasound data suggest that the methane gas accumulations probably originate from peat bearing sediments currently located several tens of meters below the seafloor only one of our cores indicates upward advection instead most of the methane is transported via diffusion sulfate and methane flux estimates indicate that a large fraction of methane is consumed by anaerobic oxidation of methane aom carbon cycling at the sulfate methane transition smt results in a marked fractionation of the 13c ch4 from an estimated source value of 65 to a value as low as 96 just below the smt methane concentrations in sediments are high especially close to the seepage sites 40 mm however concentrations in the water column are relatively low max 58 nm and can be observed only close to the seafloor methane is trapped in the lowermost water mass however measured microbial oxidation rates reveal very low activity with an average turnover of 3 1 years we therefore infer that methane must be transported out of the bay in the bottom water layer a mean sea air flux of only 0 005 nm m2 s confirms that almost no methane reaches the atmosphere

modeling landslide recurrence in seattle washington usa abstract to manage the hazard associated with shallow landslides decision makers need an understanding of where and when landslides may occur a variety of approaches have been used to estimate the hazard from shallow rainfall triggered landslides such as empirical rainfall threshold methods or probabilistic methods based on historical records the wide availability of geographic information systems gis and digital topographic data has led to the development of analytic methods for landslide hazard estimation that couple steady state hydrological models with slope stability calculations because these methods typically neglect the transient effects of infiltration on slope stability results cannot be linked with historical or forecasted rainfall sequences estimates of the frequency of conditions likely to cause landslides are critical for quantitative risk and hazard assessments we present results to demonstrate how a transient infiltration model coupled with an infinite slope stability calculation may be used to assess shallow landslide frequency in the city of seattle washington usa a module called crf critical rainfall for estimating deterministic rainfall thresholds has been integrated in the trigrs transient rainfall infiltration and grid based slope stability model that combines a transient one dimensional analytic solution for pore pressure response to rainfall infiltration with an infinite slope stability calculation input data for the extended model include topographic slope colluvial thickness initial water table depth material properties and rainfall durations this approach is combined with a statistical treatment of rainfall using a gev general extreme value probabilistic distribution to produce maps showing the shallow landslide recurrence induced on a spatially distributed basis as a function of rainfall duration and hillslope characteristics

geochemical and u pb age constraints on the occurrence of polygenetic titanites in uhp metagranite in the dabie orogen abstract relict magmatic titanite was identified in the core of a few titanite grains with the overgrown rim of metamorphic titanite in uhp metagranite in the dabie orogen la icpms u pb dating gave neoproterozoic ages for the magmatic titanite but triassic ages for the metamorphic titanite the magmatic and metamorphic titanites are clearly distinct by differences in petrological and geochemical compositions the magmatic titanite occurs as residual cores that show bright bse the presence of allanite and quartz inclusions low contents of cao al2o3 and tio2 but high contents of fe2o3 and mgo in trace elements the magmatic titanite exhibits high ree and hfse contents distinctly negative eu anomalies with flat mree hree patterns and high th u ratios in contrast the metamorphic titanite occurs as rims and grains of homogeneously dark bse that contain inclusions of epidote quartz k feldspar rutile biotite and phengite and have relatively high contents of cao al2o3 and tio2 but low contents of fe2o3 and mgo and relatively low ree and hfse contents slightly negative eu anomalies with hree depletion relative to mree and low th u ratios the zr in titanite thermometry yields 727 to 877 c at 0 5 to 1 0 gpa for the magmatic titanite and 729 to 870 c at 1 5 to 2 0 gpa for the metamorphic titanite the neoproterozoic u pb chronometric system of magmatic titanite survived the triassic continental subduction zone hp uhp metamorphism this suggests a relatively high closure temperature of 800 c for the titanite u pb system the metamorphic titanite is principally a product of retrograde metamorphism during decompression exhumation at the transition from hp eclogite facies to amphibolite facies therefore titanite holds a great potential to geochronological and petrogenetic studies of continental subduction zone metamorphic rocks

eddy induced carbon transport across the antarctic circumpolar current the implications of a mesoscale eddy for relevant properties of the southern ocean carbon cycle are examined with in situ observations we explored carbon properties inside a large 190 km diameter cyclonic eddy that detached from the subantarctic front saf south of tasmania in march 2016 based on remote sensing the eddy was present for 2 months in the subantarctic zone saz an important region of oceanic carbon dioxide co2 uptake throughout the annual cycle and carbon subduction i e where mode and intermediate waters form before it was reabsorbed into the saf the eddy was sampled during the middle of its life 1 month after it spawned comparatively the eddy was 3 c colder 0 5 practical salinity unit fresher and less biologically productive than surrounding saz waters the eddy was also richer in dissolved inorganic carbon dic and had lower saturation states of aragonite and calcite than the surrounding saz waters as a consequence it was a strong source of co2 to the atmosphere with fluxes up to 25 mmol c m 2 d 1 compared to the saf waters from which it originated dic concentration in the eddy was 20 mol kg 1 lower indicating lateral mixing small scale recirculation or eddy stirring with lower dic saz waters by the time the eddy was observed as they are commonly spawned from the antarctic circumpolar current and as 50 of them decay in the saz the rest being reabsorbed by the saf n these types of eddies may represent a significant south north transport pathway for carbon across the acc and may alter the carbon properties of saz waters

an advanced process based distributed model for the investigation of rainfall induced landslides the effect of process representation and boundary conditions extreme rainfall events are the major driver of shallow landslide occurrences in mountainous and steep terrain regions around the world subsurface hydrology has a dominant role on the initiation of rainfall induced shallow landslides since changes in the soil water content affect significantly the soil shear strength rainfall infiltration produces an increase of soil water potential which is followed by a rapid drop in apparent cohesion especially on steep slopes of shallow soils this loss of shear strength can lead to failure even in unsaturated conditions before positive water pressures are developed we present hydrolisthisis a process based model fully distributed in space with fine time resolution in order to investigate the interactions between surface and subsurface hydrology and shallow landslides initiation fundamental elements of the approach are the dependence of shear strength on the three dimensional 3 d field of soil water potential as well as the temporal evolution of soil water potential during the wetting and drying phases specifically 3 d variably saturated flow conditions including soil hydraulic hysteresis and preferential flow phenomena are simulated for the subsurface flow coupled with a surface runoff routine based on the kinematic wave approximation the geotechnical component of the model is based on a multidimensional limit equilibrium analysis which takes into account the basic principles of unsaturated soil mechanics a series of numerical simulations were carried out with various boundary conditions and using different hydrological and geotechnical components boundary conditions in terms of distributed soil depth were generated using both empirical and process based models the effect of including preferential flow and soil hydraulic hysteresis was tested together with the replacement of the infinite slope assumption with the multidimensional limit equilibrium analysis the results show that boundary conditions play a crucial role in the model performance and that the introduced hydrological preferential flow and soil hydraulic hysteresis and geotechnical components multidimensional limit equilibrium analysis significantly improve predictive capabilities in the presented case study

vertical flow in the southern ocean estimated from individual moorings abstractthis study demonstrates that oceanic vertical velocities can be estimated from individual mooring measurements even for nonstationary flow this result is obtained under three assumptions i weak diffusion peclet number 1 ii weak friction reynolds number 1 and iii small inertial terms rossby number 1 the theoretical framework is applied to a set of four moorings located in the southern ocean for this site the diagnosed vertical velocities are highly variable in time their standard deviation being one to two orders of magnitude greater than their mean the time averaged vertical velocities are demonstrated to be largely induced by geostrophic flow and can be estimated from the time averaged density and horizontal velocities this suggests that local time mean vertical velocities are primarily forced by the time mean ocean dynamics rather than by for example transient eddies or internal waves it is also shown that in the context of these four moorings the time mean ver

the eclogite garnetite transformation in the morb h2o system abstract to decipher phase relations of oceanic crust in the coldest slab at the mantle transition zone multi anvil experiments were conducted in the morb h 2 o system at pressures of 10 19 gpa and temperatures of 700 1500 c garnet and stishovite were recognized in all run charges above 15 gpa garnet drastically increases nasi na 2 msi 5 o 12 component m ca mg fe 2 jadeite occurs instead of omphacite na k hollandite containing 7 mol naalsi 3 o 8 and ca perovskite with 60 mol catio 3 were observed at p 17 gpa with decomposition of omphacite and increase of modal ratio of garnet there is a sharp increase of density at 440 km the density increase due to appearance of ca perovskite at 570 km is estimated approximately 100 km shallower than that of previous estimation

europium redox equilibria in aqueous solution thermochemical data and recent advances in theoretical aqueous solution chemistry enable prediction of the relative stabilities of aqueous eu2 and eu3 over a wide range of temperatures and pressures at low temperatures near earth surface conditions the aqueous geochemistry of europium should be dominated by the trivalent state except possibly in the most reducing alkaline pore waters of anoxic marine sediments however at temperatures greater than about 250 c and elevated pressures divalent europium should predominate even with significant amounts of complexing trivalent europium is not stable at elevated temperatures and pressures consequently under most hydrothermal and metamorphic conditions europium in aqueous solution should be divalent at intermediate temperatures around 100 c significant activities of both eu2 and eu3 and related complexes can occur in aqueous solutions depending on the oxidation state and the ph of the solutions and the activities of potential ligands such as sulfate carbonate and chloride the predicted stability of divalent europium in aqueous solution at elevated temperatures is consistent with the large positive europium anomalies in rare earth element patterns of high temperature barites of hydrothermal and metamorphic origin reported by guichard et al 5 and with the observed depletion of europium as a result of high temperature sericitization of feldspar bearing assemblages discovered by alderton et al 1 it is suggested that significant fractionation of europium relative to the other rare earth elements may take place during high temperature hydrothermal alteration processes such as in the mid oceanic ridge systems because of the expected stability of divalent europium during these processes

the spatial distribution of particulate organic carbon and microorganisms on seamounts of the south west indian ridge abstract 1 the ecology and biogeochemistry of oceanic seamounts is not very well understood and explored pelagic ecosystems above the summits and flanks of seamounts have been observed to show different biological or biogeochemical properties to off seamount areas such as enhanced chlorophyll concentrations a phenomenon referred to as the seamount effect in addition seamount biogeography has been hypothesised to be similar to islands where community structure differences in multiple organisms have been shown to change between seamounts and across frontal systems we used elemental analysis to measure particulate organic carbon poc and flow cytometry to estimate abundance of microorganisms from above four seamounts coral melville middle of what and atlantis along the southwest indian ridge swir from latitude 32 6 s to 41 3 s longitude 57 1 e to 42 7 e samples were collected from the surface to the bottom using a ctd fitted with optical sensors poc was predicted from models created from in situ transmission optical data cp the high resolution predicted poc in the euphotic zone showed a heterogeneous distribution both above individual and between seamounts the shallow penetration of two of the seamounts displayed an effect on the poc concentration in the euphotic zone depleting the layer around the summit the transmission data showed higher concentrations of particles towards the surface caused by primary production and near to the seabed probably resulting from re suspension of sediments the poc concentrations and microbial abundance were positively correlated to cp and fluctuated with particle abundance with microorganisms accounting for 50 of the observed poc based on non metric multidimensional scaling it is clear that the microbial clusters strongly indicate three separate biological regimes associated with northeastern central and southwestern zones of the section of the swir that was sampled this biological zonation is associated with physical oceanographic boundaries represented by the subtropical and subantarctic fronts forming three distinct biogeographical regions

cenozoic metamorphism along the shan scarp myanmar evidences for ductile shear along the sagaing fault or the northward migration of the eastern himalayan syntaxis the mogok metamorphic belt exposed along the n s trending shan scarp and sagaing fault in the eastern part of myanmar has been regarded as paleozoic to precambrian for a long time new observations in the shan scarp area close to the sagaing fault from thaton in the south to mandalay in the north allowed us to collect samples of high grade metamorphic and intrusive rocks that have been analyzed by 40ar 39ar step heating method the 13 samples we analyzed provide oligocene to lower miocene ages for this metamorphism oriented thin sections and field observations suggest that this metamorphism was caused by a nnw sse to n s ductile extension therefore we suggest that this metamorphism is not directly related to the sagaing fault but could be instead related to the northward migration of the eastern himalayan syntaxis characterized by crustal thinning resulting from the india asia oblique collision

a probabilistic approach for landslide hazard analysis abstract we present a general framework for probabilistic landslide hazard analysis with respect to other quantitative hazard assessment approaches this probabilistic landslide hazard analysis has the advantage to provide hazard curves and maps and to be applicable to all typologies of landslides if necessary accounting for both their onset and transit probability the method quantifies for a given slope location the exceedance probability of being affected by a landslide with a specific local intensity within a reference time interval i e the hazard curve under the common assumption that landslides behave as a poisson process hazard maps are calculated reducing the hazard curve to single values by choosing a fixed probability of exceedance following standards or regulation requirements the method is based on the assessment of a landslide onset frequency a runout frequency for long runout landslides and the local definition of landslide intensity which can be expressed through different parameters according to landslide typology for long runout landslides the runout and spatially varying intensity and uncertainty are considered hazard curves and maps play a fundamental role in the design and dimensioning of mitigation structures in land planning and in the definition of risk and hazard management policies starting from the general framework we apply the methodology for rockfall hazard analysis and we test it in an area affected by the christchurch 2011 earthquake new zealand which triggered a large number of rockfalls killing five people

origin of titanite in metarodingite from the zagros thrust zone iraq three types of metamorphic titanite have been noted in a metarodingite pod within the tectonized and serpentinized peridotite portion of the penjwin ophiolite sequence within the iraqi zagros thrust zone iztz northeastern iraq type i metamorphic titanite occurs as subhedral to anhedral fine grained disseminated crystals within chlorite that was formed during chloritization of biotite as a result of low temperature t 330 340 c ocean floor metamorphism or rodingitization of plagiogranite under a reducing environment it is characterized by intermediate al2o3 avg 3 61 wt high feot avg 0 89 wt and intermediate tio2 avg 34 7 wt type ii metamorphic titanite occurs as a thin rim around ilmenite and has high al2o3 avg 4 8 wt intermediate feot avg 0 6 wt and low tio2 avg 33 7 wt it represents a reaction product between grossular and ilmenite which resulted from an oxidizing high pressure high temperature p 1 4 1 6 gpa and t 750 c metamorphic event involving plagiogranite type iii metamorphic titanite occurs as very coarse highly fractured grains up to 0 5 mm with inclusions of ilmenite and surrounded by albitic plagioclase analcime and chlorite this titanite is characterized by low al2o3 avg 1 23 wt low feot avg 0 30 wt and high tio2 avg 36 98 wt it formed during extensive titanitization of ilmenite by a reaction with ca plagioclase during moderate pressure and temperature p 1 6 gpa and t 750 c conditions as a result of albitization of ca plagioclase in plagiogranite

on the interannual variability of ocean temperatures around south georgia southern ocean forcing by el nino southern oscillation and the southern annular mode abstract the ocean around south georgia in the southwest atlantic sector of the southern ocean is highly productive with large stocks of antarctic krill supporting extensive colonies of marine and land based predators the operation of this ecosystem is strongly influenced by physical forcings and the role of the el nino southern oscillation enso phenomenon has been highlighted previously here we examine in detail the transmission of enso signals to south georgia and investigate other sources of interannual variability enso variability generates anomalies in sea surface temperature sst across the south pacific via atmospheric teleconnections these anomalies are advected toward south georgia within the antarctic circumpolar current acc and previous studies have focussed on long period advection order of 2 3 years from the southwest pacific we observe here however that the region close to the antarctic peninsula in the southeast pacific is especially susceptible to enso forcing via anomalous meridional winds this induces sst anomalies that are advected to south georgia on a much more rapid timescale order 5 6 months the phasing of these teleconnections is such that anomalies that reach the southeast pacific from farther west tend to be reinforced here by air sea ice interaction we also find an important role for the southern annular mode sam in determining sst variability at south georgia this is a circumpolar mode of climate variability and thus can readily influence local sst at south georgia directly the sam is however not perfectly zonally symmetric and like enso has a particular impact on meridional winds in the southeast pacific the average timescale for sam influence on south georgia sst is shorter than that of enso since it includes a stronger component of direct local forcing the south georgia ecosystem is not self sustaining with import of krill from breeding and nursery grounds upstream in the acc being important we speculate here that these varying meridional winds close to the antarctic peninsula play a direct role in promoting restricting the injection of shelf waters and the krill therein into the acc following which anomalies in krill density would be advected toward south georgia this offers a dynamical mechanism that might contribute to interannual changes in biological communities at south georgia in addition to existing theories both sam and enso have shown long period changes in recent decades with enso exhibiting a higher preponderance of el nino events compared with la nina events and the sam showing a marked trend toward a higher index state such long period behaviour is likely to induce changes in the south georgia ecosystem via their impacts on advection and sst for which an understanding of the physical mechanisms elucidated here will be key to unravelling

comparing the performance of trigrs and tivass in spatial and temporal prediction of rainfall induced shallow landslides this study compares the performance of transient rainfall infiltration and grid based regional slope stability trigrs model and time variant slope stability tivass model in the prediction of rainfall induced shallow landslides trigrs employs one dimensional 1 d subsurface flow to simulate the infiltration rate whereas a three dimensional 3 d model is utilized in tivass the former has been widely used in landslide modeling while the latter was developed only recently both programs are used for the spatiotemporal prediction of shallow landslides caused by rainfall this study uses the july 2011 landslide event that occurred in mt umyeon seoul korea for validation the performance of the two programs is evaluated by comparison with data of the actual landslides in both location and timing by using a landslide ratio for each factor of safety class text lr text class index which was developed for addressing point like landslide locations moreover the influence of surface flow on landslide initiation is assessed the results show that the shallow landslides predicted by the two models are highly consistent with those of the observed sliding sites although the performance of tivass is slightly better overland flow affects the buildup of the pressure head and reduces the slope stability although this influence was not significant in this case a slight increase in the predicted unstable area from 19 30 to 19 93 was recorded when the overland flow was considered it is concluded that both models are suitable for application in the study area however although it is a well established model requiring less input data and shorter run times trigrs produces less accurate results

nested strike slip duplexes and other evidence for late cretaceous palaeogene transpressional tectonics before and during india eurasia collision in thailand myanmar and malaysia the late cretaceous palaeogene structural and tectonic events in the northern region of sundaland represent a poorly known but potentially important orogenic development in se asia extensive late cretaceous s type granites extending from malaysia through thailand to myanmar have long been used to infer an episode of crustal thickening an inference supported by the presence of late cretaceous eocene ophiolites in myanmar however structural evidence for a well developed associated fold and thrust belt has been lacking apatite and zircon fission track studies of thailand indicate a broad regional uplift from about 80 ma to 40 ma suggesting an episode of crustal thickening but the uplift amount is modest and not that expected for a major fold and thrust belt left lateral motion on major nw se trending strike slip fault zones mae ping and three pagodas faults in myanmar and thailand has been attributed to himalayan tibetan escape tectonics this paper demonstrates that the fault zones are considerably more complicated than just nw se trends they are a network of branching faults with important north south trends as well as nw se trends they form large scale nested strike slip duplex structures and affect a region over 1000 km long and up to 250 km wide this diffuse branching network of strike slip fault trends may represent a substantial late cretaceous palaeogene transpressional belt himalayan escape tectonics represent later increments of deformation with both oligocene sinistral and late oligocene recent dextral reactivation

prediction of rainfall induced shallow landslides in the loess plateau yan an china using the trigrs model in this work a transient rainfall infiltration and grid based regional slope stability model trigrs was implemented in a case study of yan an city northwest china in this area widespread shallow landslides were triggered by the 12 july 2013 exceptional rainstorm event a high resolution dem soil parameters from in situ and laboratory measurements water table depths the maximum depth of precipitation infiltration and rain gauge corrected precipitation of the event were used as inputs in the trigrs model shallow landslides triggered on the same day were used to evaluate the modeling results the summarized results are as follows i the characteristics and distribution of thirty five shallow landslides triggered by the 12 july 2013 rainfall event were identified in the study area and all were classified as shallow landslides with the maximum depth area and volume less than 3 m 200 m2 and 1000 m3 respectively ii four intermediate factor of safety fs maps were generated using the trigrs model to represent the scenarios 6 12 18 and 24 hours after the storm event the area with fs 1 increased with the rainfall duration the percentage of the area with fs 1 was 0 2 3 3 3 8 and 5 1 for the four stages respectively twenty four hours after the rainstorm trigrs predicted that 1255 grid cells failed which is consistent with the field data iii trigrs generated more satisfactory results at a given precipitation threshold than sinmap which is ideal for landslide hazard zoning for land use planning at the regional scale comparison results showed that trigrs is more useful for landslide prediction for a certain precipitation threshold also in the regional scale iv analysis of the responses of loess slope prone to slope failure after different precipitation scenarios revealed that loess slopes are particularly sensitive to extended periods of heavy precipitation copyright 2016 john wiley sons ltd

physical and biogeochemical controls on the variability in surface ph and calcium carbonate saturation states in the atlantic sectors of the arctic and southern oceans polar oceans are particularly vulnerable to ocean acidification due to their low temperatures and reduced buffering capacity and are expected to experience extensive low ph conditions and reduced carbonate mineral saturations states in the near future however the impact of anthropogenic co2 on ph and will vary regionally between and across the arctic and southern oceans here we investigate the carbonate chemistry in the atlantic sector of two polar oceans the nordic seas and barents sea in the arctic ocean and the scotia and weddell seas in the southern ocean to determine the physical and biogeochemical processes that control surface ph and high resolution observations showed large gradients in surface ph 0 10 to 0 30 and aragonite saturation state ar 0 2 to 1 0 over small spatial scales and these were particularly strong in sea ice covered areas up to 0 45 in ph and 2 0 in ar in the arctic sea ice melt facilitated bloom initiation in light limited and iron replete dfe 0 2 nm regions such as the fram strait resulting in high ph 8 45 and ar 3 0 along the sea ice edge in contrast accumulation of dissolved inorganic carbon derived from organic carbon mineralisation under the ice resulted in low ph 8 05 and ar 1 1 in areas where thick ice persisted in the southern ocean sea ice retreat resulted in bloom formation only where terrestrial inputs supplied sufficient iron dfe 0 2 nm such as in the vicinity of the south sandwich islands where enhanced ph 8 3 and ar 2 3 were primarily due to biological production in contrast in the adjacent weddell sea weak biological uptake of co2 due to low iron concentrations dfe 0 2 nm resulted in low ph 8 1 and ar 1 6 the large spatial variability in both polar oceans highlights the need for spatially resolved surface data of carbonate chemistry variables but also nutrients including iron in order to accurately elucidate the large gradients experienced by marine organisms and to understand their response to increased co2 in the future

a hybrid feature selection algorithm integrating an extreme learning machine for landslide susceptibility modeling of mt woomyeon south korea abstract an ever increasing trend of extreme rainfall events in south korea owing to climate change is causing shallow landslides and debris flows in mountains that cover 70 of the total land area of the nation these catastrophic gravity driven processes cost the government several billion krw south korean won in losses in addition to fatalities every year the most common type of landslide observed is the shallow landslide which occurs at 1 3 m depth and may mobilize into more catastrophic flow type landslides hence to predict potential landslide areas susceptibility maps are developed in a geographical information system gis environment utilizing available morphological hydrological geotechnical and geological data landslide susceptibility models were developed using 163 landslide points and an equal number of nonlandslide points in mt woomyeon seoul and 23 landslide conditioning factors however because not all of the factors contribute to the determination of the spatial probability for landslide initiation and a simple filter or wrapper based approach is not efficient in identifying all of the relevant features a feedback loop based hybrid algorithm was implemented in conjunction with a learning scheme called an extreme learning machine which is based on a single layer feed forward network validation of the constructed susceptibility model was conducted using a testing set of landslide inventory data through a prediction rate curve the model selected 13 relevant conditioning factors out of the initial 23 and the resulting susceptibility map shows a success rate of 85 and a prediction rate of 89 45 indicating a good performance in contrast to the low success and prediction rate of 69 19 and 56 19 respectively as obtained using a wrapper technique

calibrated seismic imaging of eddy dominated warm water transport across the bellingshausen sea southern ocean seismic reflection images of thermohaline circulation from the bellingshausen sea adjacent to the west antarctica peninsula were acquired during february 2015 this survey shows that bright reflectivity occurs throughout the upper 300 m by calibrating these seismic images with coeval hydrographic measurements intrusion of warm water features onto the continental shelf at marguerite and belgica troughs is identified and characterized these features have distinctive lens shaped patterns of reflectivity with lengths of 0 75 11 00 km and thicknesses of 100 150 m suggesting that they are small mesoscale to submesoscale eddies abundant eddies are observed along a transect that crosses belgica trough near alexander island drift a large of order urn x wiley 21699275 media jgrc22803 jgrc22803 math 0001 km3 bowl like feature that may represent an anticyclonic taylor column is imaged on a pair of orthogonal images a modified iterative procedure is used to convert seismic imagery into maps of temperature that enable the number and size of eddies being transported onto the shelf to be quantified finally analysis of prestack shot records suggests that these eddies are advecting southward at speeds of urn x wiley 21699275 media jgrc22803 jgrc22803 math 0002 m s 1 consistent with limited legacy hydrographic measurements concentration of observed eddies south of the southern antarctic circumpolar current front implies they represent both a dominant and a long lived mechanism of warm water transport especially across belgica trough our observations suggest that previous estimates of eddy frequency may have been underestimated by up to 1 order of magnitude which has significant implications for calculations of ice mass loss on the shelf of the west antarctic peninsula

antarctic circumpolar current frontal system in the south atlantic monitoring using merged argo and animal borne sensor data 1 we describe large scale features of the antarctic circumpolar current acc in the atlantic part of the southern ocean by merging argo data and data obtained by novel animal borne ctd sensors twenty one of these ctd satellite relay data loggers ctd srdls were attached to southern elephant seals mirounga leonina on south georgia the merged data yield unified gridded hydrogaphic fields with high temporal and spatial resolution enabling the determination of features absent in each of the data sets separately the structure and variability of the frontal field revealed by this data set were compared with those in daily quarter degree optimally interpolated sea surface temperature fields and fields of weekly gridded sea level anomaly in general the frontal positions derived using our data set are in agreement with previous work especially where the pathways are constrained by topography e g at the north scotia ridge and the south scotia ridge however with the improved temporal and spacial resolution provided by the ctd srdls we were able to observe some novel features all frontal positions are more variable than previously indicated across the scotia sea and west of the mid atlantic ridge on seasonal time scales the merged data set shows the temporal variability of the southern acc front saccf north of south georgia and in its position east of the island where the saccf lies further north than has been suggested in previous work in addition the subantarctic front crosses the mid atlantic ridge about 400 km further north when compared to previous work

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