hydrographic conditions in the eastern pacific before during and after the 1982 83 el nino abstract between june 1981 and june 1984 a total of thirteen ctd sections were made across the equator along 85 w on some of these cruises additional sections were made along 5 s and 10 30 s between 85 w and the south american coast this sampling period covers the events that took place during the 1982 83 el nino these sections are used to describe the variability that took place before during and after this major event at the surface little evidence was found for a major southward flooding of warm low salinity water from north of the equator that has been observed during some previous el ninos major changes took place in the sub surface hydrographic structures the thermostad between 13 c and 16 c which is a prominent feature of the hydrography in this region disappeared early in 1983 and reappeared early in 1984 the vertical temperature gradient along the equator and along the coast which is usually quite variable with depth became much more uniform in early 1983 it regained its normal structure by early 1984 changes were not confined to the upper ocean but were evident over the whole depth interval sampled 1000m during november 1982 evidence was found for symmetric poleward spreading of the equatorial disturbance along the eastern boundary many of the changes that took place are consistent with linear models based on equatorial wave theory these observations presented a unique opportunity for observing the ocean response to a major interannual change in the wind forcing

a comparative study of suction stress between sand and silt under unsaturated conditions abstract the purpose of this study is to estimate and compare suction stress between sand and silt sampled from the coast of korea the water content and matric suction of sand joomunjin and silt saemangeum were first examined using an automated soil water characteristic curve swcc apparatus based on the axis translation technique swccs were then estimated from the test results using the van genuchten 1980 model at equal matric suction the corresponding water content of silt was higher than that of sand moreover the saturated water content and air entry value aev of silt were larger than those of sand using the fitting swcc parameters suction stress characteristic curves ssccs were estimated according to the method proposed by lu and likos 2006 the sscc behavior for sand and silt was different and significantly depended on the material properties particularly pore size and pore size distribution for sand the suction stress exhibited rapid variation with changes in matric suction but for silt the suction stress approached a constant value as the matric suction increased in addition when the matric suction was smaller than the aev of soil the suction stress was equal to the magnitude of the matric suction in contrast when the matric suction exceeded the aev of soil suction stress had a nonlinear shape with respect to the matric suction

circulation mixing and production of antarctic bottom water abstract the antarctic source of bottom water to the abyssal layer of the world ocean is examined as well as its large scale flow pattern and ultimate entrainment rate into the deep water above we make use of the available high quality station data in the southern ocean to construct bottom maps of neutral density and mean property maps including chlorofluorocarbon cfc for the abyssal layer underneath a selected neutral density surface the maximum density at the sill depth of drake passage is used to distinguish between the voluminous deep water mass that is a continuous component of the antarctic circumpolar current from the relatively denser bottom water originated along the antarctic continental margins based on water density antarctic bottom water aabw is defined here generically to include all volumes of non circumpolar water of antarctic origin over the shelf regime multiple localized sources of specific aabw types contribute to the abyssal layer of the adjacent antarctic basins characteristics of these dense bottom waters reflect closely those observed on the parent shelf water mass spreading paths of newly formed deep and bottom waters over the slope regime and their subsequent oceanic circulation patterns are analyzed on the basis of global property maps for the aabw layer interior mixing and interbasin exchanges of aabw are deduced from mean characteristic curves following the southern streamline of the antarctic circumpolar current outflow and mixing of aabw from the weddell sea to the argentine basin is depicted using density and cfc distributions of two zonal hydrographic lines recirculation and mixing of deep and bottom waters within the weddell gyre are also detailed using a meridional section along the greenwich meridian the strength of all localized sources of aabw combined is estimated by two independent approaches an estimate of the total production rate of aabw is calculated based on the oceanic cfc budget for the aabw layer offshore of the 2500 m isobath the sum of all downslope inputs of well ventilated bottom water types underneath the top isopycnal must account for the measured cfc content in the bottom layer the resulting total aabw production rate is about 8 sv which is a conservative figure that neglects the loss of cfc bearing waters across the top isopycnal in recent years whereas about 9 5 sv is calculated assuming a well mixed bottom layer making use of their transient nature cfc distributions at the top of the aabw layer indicate that more direct and rapid entrainment of cfc rich bottom waters below occurs over localized areas with relatively strong upwelling rates and enhanced vertical mixing a second more ad hoc but independent oceanic mass budget of the bottom layer is also constructed a typical basin wide rate of deep upwelling of 3 10 7 m s 1 requires 10 sv 1 sv 106 m3 s 1 of newly formed aabw to sink down the slope around antarctica we have also formulated a spatial distribution of deep upwelling on the isopycnal at the top of the aabw it is expressed as a combination of wind topographic and turbulent components which in turn are functions of the isopycnal depth bottom depth and bottom layer thickness this non uniform upwelling field yields about 12 sv of aabw exported across the top isopycnal fortuitously the overall average of upward speed at the top isopycnal 3 7 10 7 m s 1 compares well with previous estimates of deep upwelling in the northern basins a series of likely sites for strong vertical entrainment of aabw are clearly identified in the modeled distribution of deep upwelling consonant with the observed cfc distributions on the top isopycnal altogether regions with relatively high upwelling rates 5 10 7 m s 1 occupy only a quarter of the total areal extent of the top isopycnal but they account for as much as 45 of the total vertical transport

landsliding in partially saturated materials 1 rainfall induced landslides are pervasive in hillslope environments around the world and among the most costly and deadly natural hazards however capturing their occurrence with scientific instrumentation in a natural setting is extremely rare the prevailing thinking on landslide initiation particularly for those landslides that occur under intense precipitation is that the failure surface is saturated and has positive pore water pressures acting on it most analytic methods used for landslide hazard assessment are based on the above perception and assume that the failure surface is located beneath a water table by monitoring the pore water and soil suction response to rainfall we observed shallow landslide occurrence under partially saturated conditions for the first time in a natural setting we show that the partially saturated shallow landslide at this site is predictable using measured soil suction and water content and a novel unified effective stress concept for partially saturated earth materials

co2 induced ocean warming of the antarctic continental shelf in an eddying global climate model national oceanic and atmospheric administration noaa cpo project na13oar4310128 national science foundation opp 1513411 university of arizona faculty startup funding university of arizona department of geosciences national aeronautics and space administration nasa nnx14al40g princeton environmental institute pei grand challenge initiative southern ocean carbon and climate observations and modeling soccom project under the national science foundation plr 1425989

on the role of coastal troughs in the circulation of warm circumpolar deep water on antarctic shelves abstractoceanic exchanges across the continental shelves of antarctica play an important role in biological systems and the mass balance of ice sheets the focus of this study is on the mechanisms responsible for the circulation of warm circumpolar deep water cdw within troughs running perpendicular to the continental shelf this is examined using process oriented numerical experiments with an eddy resolving 1 km 3d ocean model that includes a static and thermodynamically active ice shelf three mechanisms that create a significant onshore flow within the trough are identified 1 a deep onshore flow driven by the melt of the ice shelf 2 interaction between the longshore mean flow and the trough and 3 interaction between a rossby wave along the shelf break and the trough in each case the onshore flow is sufficient to maintain the warm temperatures underneath the ice shelf and basal melt rates of o 1 m yr 1 the third mechanism in particular reproduces several features revealed by moorings from m

warm ocean is eroding west antarctic ice sheet 1 satellite radar measurements show that ice shelves in pine island bay have thinned by up to 5 5 m yr 1 over the past decade the pattern of shelf thinning mirrors that of their grounded tributaries the pine island thwaites and smith glaciers and ocean currents on average 0 5 c warmer than freezing appear to be the source the synchronised imbalance of the inland glaciers is the result of reduced lateral and basal tractions at their termini and the drawdown of grounded ice shows that antarctica is more sensitive to changing climates than was previously considered

eastern equatorial pacific ocean t s variations with el nino 1 temperature salinity t s relationship variability in the pycnocline of the eastern equatorial pacific ocean nino3 region 5 s 5 n 150 w 90 w over the last two decades is investigated using observational data and model simulation a numerical model simulation using the mitgcm massachusetts institute of technology general circulation model suggests that during el nino years the water in the eastern equatorial pacific ocean becomes saltier by 0 1 to 0 2 and warmer by 0 5 to 1 c on density surfaces within the pycnocline this simulation is consistent with conductivity temperature depth ctd data collected mostly during tropical atmosphere ocean tao mooring maintenance cruises

near equatorial ctd observations at 85 w in october 1982 ctd data collected about the equator along 85 w between october 8 and 12 1982 are used to investigate stratification changes in the upper 1 km associated with the 1982 83 el nino with respect to the thermal field observed in november 1981 virtually the entire section exhibited downward displacements in the upper kilometer of the water column observed displacements at the depth of the mean thermocline were large 150 m and relatively symmetric about the equator displacements around 1 km depth were near zero this stratification change appears to have been produced by a zonal convergence of mass at temperatures above 15 c with divergence below least square modal decompositions of the vertical displaced profiles revealed significant contributions from modes 1 and 2 with meridional structure consistent with kelvin waves the observations thus support current theories that relate el nino onset in the eastern pacific to anomalous wind forcing in the west

response of a residual soil slope to rainfall rainfall induced landslides are a common problem in residual soil slopes of the tropics it is widely known that rainfall induced slope failures are mainly caused by infiltration of rainwater howe

eastern pacific ocean circulation near the onset of the 1982 1983 el nino over a 1 month period october 5 to november 6 1982 during the initial stages of the 1982 1983 el nino hydrographic and velocity profiling measurements were made in the eastern equatorial pacific by two research vessels track lines approximated a square centered near the galapagos islands with approximately meridional sections at 95 w and 85 w and nearly zonal sections at about 5 n and 5 s water mass characteristics and estimated currents of these sections are discussed sea surface temperature nearly everywhere was warmer than 25 c an anomaly of 2 c 3 c the equatorial thermocline represented by the 20 c isotherm was depressed by nearly 50 m at 85 w and more than 100 m at 95 w relative to a historical mean profile across 95 w estimated geostrophic relative to 500 dbar and directly measured near equatorial velocity profiles indicated significant eastward surface flow the south equatorial current south of the equator had disappeared estimated warm water transport t 24 5 kg m 3 indicated an influx into the region which was approximately that required to balance the observed low frequency sea level change at the galapagos islands temperature and salinity properties as well as the transport estimates indicated that this warm water came predominantly from the west

field hydrological monitoring of a sloping shallow pyroclastic deposit many mountainous areas in campania southern italy are characterized by steep slopes covered by unsaturated volcanic deposits shallow landslides are frequently triggered by intense and persistent

the termination of the equatorial undercurrent in the eastern pacific abstract the termination of the equatorial undercurrent euc in the eastern tropical pacific has been studied through analysis of the historical hydrographic station data in the region bounded by 5 n 10 s 80 w and 100 w three distinctive hydrographic features associated with the euc are used along with dynamic topography to trace the mean path of the euc and to investigate aspects of its seasonal variation these features are 1 the 13 c thermostad 2 the high salinity core and 3 the high dissolved oxygen concentration tongue the thermostad is thickest just south of the equator to the west of the galapagos islands with a decreasing maximum extending southeast to the coast of south america near 7 s the thermostad is poorly developed in the mean near the equator east of the galapagos islands this pattern appears to be produced by convergence of eastward flow in the euc and in the southern subsurface countercurrent as the euc flows southeastward from the galapagos this interpretation is supported by the geostrophic flow calculated from the mean dynamic topography the isolated high salinity core is found to the south of the equator and is traced all the way to the coast of south america the high oxygen tongue associated with the euc splits at the galapagos with the southward projecting branch disappearing rapidly as an identifiable feature the other branch of the tongue continues around the islands to the north and along the equator to the coast of ecuador some evidence of recirculation of euc water in the south equatorial current is seen to the northwest of the galapagos a strong seasonal pulsation of the euc affects these features in a consistent way with the pulse occurring first west of the galapagos and later along the coast the thermostad first reaches maximum development and then a pronounced downwelling of the thermocline occurs rapidly leading to minimum thermostad extent associated wtih this downwelling is an eastward protruding high salinity tongue near the equator which is later seen as an isolated core along the coast at 4 s and 6 s pressure gradients along the equator and the coast inferred from dynamic topography suggest that this pulse is associated with an increase in the flow of the euc and ultimately the peru chile undercurrent the pressure gradient reversal along the equator occurs prior to the annual wind reversal suggesting that remote forcing plays a role in the seasonal pulse of the euc in the eastern pacific

analyses on variations in the unsaturated characteristics of a mine waste dump slope during rainfall field measurement units and a system were constructed and installed in a waste dump slope at the imgi mine to investigate and analyze the variations in the unsaturated characteristics of the soil the field instrumentation system was composed of a data acquisition system a solar system and measuring sensors the rainfall matric suction and volumetric water contents were continuously measured from the units in the instrumented site and analyzed with the soil water characteristic curve swcc estimated from laboratory experiments the variations in matric suction and volumetric water content were primarily affected by the rainfall intensity at the surface of the slope the largest increase and decrease in the changes in matric suction and volumetric water content were observed during the wetting and drying processes respectively the matric suction and volumetric water content measured from the instrumented area were compared with the swccs obtained from the laboratory test and the measured data were located between the drying and wetting paths the drying and wetting paths obtained from the laboratory test are regarded as primary drying and wetting curves respectively therefore the measured data can be defined as scanning curves which are located between primary drying and wetting curves the variations in matric suction according to volumetric water content were dependent on depth and a wide range of variations was observed at shallow depths it was confirmed that the unsaturated soil near the ground surface has the sensitive reaction induced by the infiltration and evaporation in nature

different magnitudes of projected subsurface ocean warming around greenland and antarctica accurate projections of global sea level rise require information of future ocean warming in the vicinity of the large ice sheets an analysis of 19 climate model projections suggests that subsurface ocean warming near both polar ice sheets will be substantial with the potential to lead to significant increases in ice mass loss

steep slope monitoring in unsaturated pyroclastic soils based on monitoring results the paper describes the hydrological response of a steep hillslope covered by unsaturated pyroclastic soils the instrumented site is located just beside an area which experienced a catastrophic flowslide two years prior to the survey monitoring involved rainfall and matric suction measured at different locations and depths investigations focused on the hydrological response of the slope so as to model the effects of rainfall and then predict the onset of slope failure triggered by critical rainfall

role of tides on the formation of the antarctic slope front at the weddell scotia confluence the structure of the antarctic slope front asf and the associated antarctic slope current asc on the scotia sea side of the weddell scotia confluence wsc is described using data from a hydrographic survey and three 1 year long moorings across the continental slope the asc in this region flows westward along isobaths with an annual mean speed of 0 2 m s 1 with time variability dominated by the k1 and o1 tidal diurnal constituents a narrowband oscillation with 2 week period attributable to the spring neap tidal cycle and seasonal variability realistic and idealized high resolution numerical simulations are used to determine the contribution of tides to the structure of the asf and the speed of the asc two simulations forced by realistic atmospheric forcing and boundary conditions integrated with and without tidal forcing show that tidal forcing is essential to reproduce the measured asf asc cross slope structure the time variability at our moorings and the reduced stratification within the wsc two idealized simulations run with tide only forcing one with a homogeneous ocean and the other with initial vertical stratification that is laterally homogeneous show that tides can generate the asc and asf through volume flux convergence along the slope initiated by effects including the lagrangian component of tidal rectification and mixing at the seabed and in the stratified ocean interior climate models that exclude the effects of tides will not correctly represent the asf and asc or their influence on the injection of intermediate and dense waters from the wsc to the deep ocean

melting of ice shelves and the mass balance of antarctica we calculate the present ice budget for antarctica from measurements of accumulation minus iceberg calving run off and in situ melting beneath the floating ice shelves the resulting negative mass balance of 469 gt year 1 differs substantially from other recent estimates but some components are subject to high temporal variability and budget uncertainties of 20 50 annual accumulation from an earlier review is adjusted to include the antarctic peninsula for a total of 2144 gt year 1 an iceberg production rate of 2016 gt year 1 is obtained from the volume of large icebergs calculated from satellite images since 1978 and from the results of an international iceberg census project ice shelf melting of 544 gt year 1 is derived from physical and geochemical observations of meltwater outflow glaciological field studies and modeling of the sub ice ocean circulation the highest melt rates occur near ice fronts and deep within sub ice cavities run off from the ice sheet surface and from beneath the grounded ice is taken to be 53 gt year 1 less than half of the negative mass balance need come from the grounded ice to account for the unattributed 0 45 mm year 1 in the ipcc best estimate of the recent global sea level rise

hydrographic variability west of the galapagos islands during the 1982 1983 el nino abstract nine hydrographic temperature salinity and in some cases oxygen and four zonal velocity sections near the equator along 95 w in 1980 1984 are presented and discussed perturbations associated with the 1982 1983 el nino form the locus for the discussion this event was sampled by sections in november 1982 and in march may november and december 1983 the upper ocean response in november 1982 was a downward displacement of isotherms above 400m on the equator the equatorial undercurrent euc was deep and strong for this season the vertical displacement perturbations extended to at least 5 s and were more uniform with depth off the equator in may 1983 the largest vertical displacements were observed the euc was replaced by a westward jet at about 75m and the equatorial 13 c water thermostad has disappeared local estimates of the zonal pressure gradient suggest that between 110 w and 95 w this slope had reversed in may 1983 and was at least in part responsible for the observed westward jet local winds were westerly and forced the observed eastward surface current by november 1983 surface conditions were fairly normal however the deeper stratification remained anomalous the equatorial 13 c water thermostad was still missing the vertical profile of vertical displacements from a mean suggested a complicated vertical structure near the equator in april 1984 conditions had returned to near normal

upper equatorial pacific ocean current and salinity variability during the 1996 1998 el nino la nina cycle the recent el nino la nina cycle exhibited striking patterns of current and salinity variability in the upper equatorial pacific ocean this evolution is described from mid 1996 through 1998 using a remarkable data set of 35 meridional conductivity temperature depth ctd acoustic doppler current profiler adcp sections along with buoy data the sections nominally from 8 s to 8 n between 165 e and 95 w were occupied over the course of 27 months a wide range of current variability was sampled with currents that appeared or disappeared some time during the cycle including an equatorially trapped eastward surface current the equatorial undercurrent the northern branch of the south equatorial current and the north equatorial countercurrent basin wide interannual changes in upper ocean and pycnocline zonal transports were as large as 64 32 106 m3 s 1 changes in the salinity structure included a deep and fresh mixed layer in the central equatorial pacific that built up during the el nino and was then disrupted by upwelled salty water with the onset of la nina a very fresh mixed layer observed in the eastern equatorial pacific late in the el nino and a reduction in the strength of the meridional equatorial salinity gradient within the pycnocline to one third of the usual value during the el nino finally the zonal transports above the thermocline from 5 s to 5 n were well correlated with the rate of change of warm water volume west of the individual ctd adcp sections

correlation of current and sea level in the eastern equatorial pacific abstract upper ocean current and temperature records from neat 0 110 w are compared with galapagos island sea level measurements 0 3 s 91 28 w for the period march 1980 to july 1981 low frequency periods greater than 30 days near surface zonal currents 20 and 50 m were well correlated with local wind but deeper currents 100 and 150 m and sea level were not response to the local wind was studied in terms of linear dynamics periods where zonal acceleration was in phase with zonal wind stress were found however overall these two series were uncorrelated the direct relation of low frequency wind stress and surface current rather than acceleration suggests a quasi equilibrium response on these time scales the response at deeper levels was investigated by comparing the zonal transport per unit width vertically averaged zonal velocity in the upper 200 m with sea level these series were significantly correlated with 95 confidence at a lag of 10 5 d indicating eastward phase propagation

monitored and simulated variations in matric suction during rainfall in a residual soil slope this research combines field laboratory and numerical investigations to estimate the development of a wetting front within a 1 2 m residual soil mantle on a steep forested slope during rainfall events the field monitored variations in matric suction due to rain water infiltration during various events revealed that the maximum infiltration rate was much higher when the wetting front resided in the upper 20 cm of soil compared to the case when the wetting front advanced to depths 20 cm laboratory investigations on soil hydraulic properties i e soil water characteristic curve and hydraulic conductivity were useful to establish the parameters of a multilayer finite element model for one dimensional vertical infiltration these parameters were subsequently calibrated by matching the predicted and field measured transient pore water pressure responses during actual rainstorms with irregular rainfall patterns the calibrated simulation model was used to assess the migration of the wetting front under uniform rainfall with different intensities based on the numerical results a hyperbolic equation was developed to predict the duration of uniform rainfall required for the propagation of wetting front to a certain depth for a given rainfall intensity the proposed equation was subsequently tested against field monitored advancements of the wetting front during real rainstorms with variable rainfall intensity

recent dramatic thinning of largest west antarctic ice stream triggered by oceans a growing body of observational data suggests that pine island glacier pig is changing on decadal or shorter timescales these changes may have far reaching consequences for the future of the west antarctic ice sheet wais and global sea levels because of pig s role as the ice sheet s primary drainage portal we test the hypothesis that these changes are triggered by the adjoining ocean specifically we employ an advanced numerical ice flow model to simulate the effects of perturbations at the grounding line on pig s dynamics the speed at which these changes are propagated upstream implies a tight coupling between ice sheet interior and surrounding ocean

behavior and analysis of stabilizing piles installed in a cut slope during heavy rainfall abstract in this study the behavior of stabilizing piles installed in a cut slope is investigated using a field measurement system and analyzed considering the infiltration depth of environmental rainfall two cut slopes located on an express highway construction site in donghae korea were selected for this study landslides with some tension cracks were found in the upper part of these cut slopes during the cutting process as the primary method of slope enforcement four rows of stabilizing piles were created and a series of field monitoring systems was installed to measure the movements of the stabilizing piles and the slope according to the field monitoring results the deflection of the stabilizing piles and the deformation of the slope were significantly affected by heavy rainfall lumb s theory 1975 was used to calculate the depth of the wetting front for the case in which the rainfall intensity is equivalent to the coefficient of permeability of the soil a slope stability analysis was performed and the calculated depth of the wetting front and the measured groundwater level were considered in this analysis the behavior of the stabilizing piles was calculated by the slopile program ver 3 0 which was used to analyze and design the slope and the piles the expected deflections of the piles obtained from the analysis are similar to measured deflections therefore the rainfall intensity can be used to calculate the depth of the wetting front and this analysis technique very effectively calculates the slope stability and the behavior of stabilizing piles

bedmap a new ice thickness and subglacial topographic model of antarctica measurements of ice thickness on the antarctic ice sheet collected during surveys undertaken over the past 50 years have been brought together into a single database from these data a seamless suite of digital topographic models have been compiled for antarctica and its surrounding ocean this includes grids of ice sheet thickness over the grounded ice sheet and ice shelves water column thickness beneath the floating ice shelves bed elevation beneath the grounded ice sheet and bathymetry to 60 s including the sub ice shelf cavities these grids are consistent with a recent high resolution surface elevation model of antarctica while the digital models have a nominal spatial resolution of 5 km such high resolution is justified by the original data density only over a few parts of the ice sheet the suite does however provide an unparalleled vision of the geosphere beneath the ice sheet and a more reliable basis for ice sheet modeling than earlier maps the total volume of the antarctic ice sheet calculated from the bedmap grid is 25 4 million km3 and the total sea level equivalent derived from the amount of ice contained within the grounded ice sheet is 57 m comprising 52 m from the east antarctic ice sheet and 5 m from the west antarctic ice sheet slightly less than earlier estimates the gridded data sets can be obtained from the authors

variability in the eastern equatorial pacific ocean during 1986 1988 we examine variability in the eastern equatorial pacific during 1986 1988 using conductivity temperature depth data velocity and temperature data from equatorial moorings between 110 w and 140 w and wind data from a basin scale zonal array of islands and moorings between 110 w and 165 e the period studied coincides with the el nino southern oscillation enso event of 1986 1987 and a subsequent cold event in 1988 weak warm sea surface temperature anomalies first appeared in the eastern equatorial pacific in mid 1986 and increased to 1 c in september november 1986 in association with a 30 cm s 1 weakening of the south equatorial current and a 20 to 40 m depression of the thermocline these warm anomalies lasted until early 1988 after which a large scale shoaling of the thermocline led to sea surface temperatures more than 3 c colder than climatology year to year fluctuations in the eastern pacific were related primarily to zonal wind variations in the central and western pacific westerly wind stress anomalies of 0 02 0 05 n m 2 were observed between 140 w and 165 e from the latter half of 1986 until the end of 1987 these were replaced by easterly wind anomalies of similar magnitude between 157 w and 165 e in 1988 energetic intraseasonal fluctuations with periods of 2 3 months were also prominent in zonal current temperature and dynamic height time series these fluctuations propagate eastward at approximately first baroclinic mode kelvin wave phase speeds and are forced west of the date line by episodes of westerly winds extrema in several oceanic variables occurred in association with these waves though their precise dynamical link to the enso cycle is unclear from our data sea surface temperature and thermocline depth anomalies at 0 110 w were less pronounced during the 1986 87 enso than during the 1982 1983 enso the equatorial undercurrent though weaker than normal in early 1987 did not disappear as it did in early 1983

on the cause of eastern equatorial pacific ocean t s variations associated with el nino the nature of observed variations in temperature salinity t s relationship between el nino and non el nino years in the pycnocline of the eastern equatorial pacific ocean nino3 region 5 deg s 5 deg n 150 deg w 90 deg w is investigated using an ocean general circulation model the origin of the subject water mass is identified using the adjoint of a simulated passive tracer the higher salinity during el nino is attributed to larger convergence of saltier water from the southern hemisphere and smaller convergence of fresher water from the northern hemisphere

slope stability analysis under unsaturated conditions case studies of rainfall induced failure of cut slopes abstract we present two case studies of rainfall induced failure of engineered slopes the traditional limit equilibrium and finite element methods are expanded to unsaturated conditions using a generalized effective stress framework because effective stress is represented by the suction stress characteristic curve sscc and the sscc and the soil water retention curve swrc have been unified with the same set of hydromechanical parameters the expanded framework requires only three hydromechanical parameters in addition to those used for saturated slope stability analysis using recorded rainfall measured shear strength parameters and the swrc and site geology transient slope stability analyses are conducted to reconstruct the failure events we find that despite differences in slope geometry hydromechanical properties shear strength and rainfall history the actual failure occurred when the simulated factor of safety approaches its minimum below 1 0 it is shown that the hydromechanical framework under the suction stress based effective stress can reconcile the observed timing of failure

rapid subsurface warming and circulation changes of antarctic coastal waters by poleward shifting winds the southern hemisphere westerly winds have been strengthening and shifting poleward since the 1950s this wind trend is projected to persist under continued anthropogenic forcing but the impact of the changing winds on antarctic coastal heat distribution remains poorly understood here we show that a poleward wind shift at the latitudes of the antarctic peninsula can produce an intense warming of subsurface coastal waters that exceeds 2 c at 200 700 m depth the model simulated warming results from a rapid advective heat flux induced by weakened near shore ekman pumping and is associated with weakened coastal currents this analysis shows that anthropogenically induced wind changes can dramatically increase the temperature of ocean water at ice sheet grounding lines and at the base of floating ice shelves around antarctica with potentially significant ramifications for global sea level rise

eddy driven exchange between the open ocean and a sub ice shelf cavity the exchange between the open ocean and sub ice shelf cavities is important to both water mass transformations and ice shelf melting here we use a high resolution 500 m numerical model to investigate to which degree eddies produced by frontal instability at the edge of a polynya are capable of transporting dense high salinity shelf water hssw underneath an ice shelf the applied surface buoyancy flux and ice shelf geometry is based on ronne ice shelf in the southern weddell sea an area of intense wintertime sea ice production where a flow of hssw into the cavity has been observed results show that eddies are able to enter the cavity at the southwestern corner of the polynya where an anticyclonic rim current intersects the ice shelf front the size and time scale of simulated eddies are in agreement with observations close to the ronne ice front the properties and strength of the inflow are sensitive to the prescribed total ice production flushing the ice shelf cavity at a rate of 0 2 0 4 106 m3 s 1 depending on polynya size and magnitude of surface buoyancy flux eddy driven hssw transport into the cavity is reduced by about 50 if the model grid resolution is decreased to 2 5 km and eddies are not properly resolved

a model study of circumpolar deep water on the west antarctic peninsula and ross sea continental shelves abstract transport of relatively warm nutrient rich circumpolar deep water cdw onto continental shelves around antarctica has important effects on physical and biological processes however the characteristics of the cdw along the shelf break as well as what happens to it once it has been advected onto the continental shelf differ spatially in the present study high resolution 4 5 km regional models of the ross sea and the west antarctic peninsula coastal ocean are used to compare differences in cdw transport the models compared very well with observations from both regions examining the fluxes not only of heat but also of a simulated dye representing cdw shows that in both cases cdw crosses the shelf break in specific locations primarily determined by the bathymetry but eventually floods much of the shelf the frequency of intrusions in marguerite trough was ca 2 3 per month similar to recent mooring observations a significant correlation between the along shelf break wind stress and the cross shelf break dye flux through marguerite trough was observed suggesting that intrusions are at least partially related to short duration wind events the primary difference between the cdw intrusions on the ross and west antarctic peninsula shelves is that there is more vigorous mixing of the cdw with the surface waters in the ross sea especially in the west where high salinity shelf water is created the models show that the cdw moving across the antarctic peninsula continental shelf towards the base of the ice shelves not only is warmer initially and travels a shorter distance than that advected towards the base of the ross ice shelf but it is also subjected to less vertical mixing with surface waters which conserves the heat available to be advected under the ice shelves this difference in vertical mixing also likely leads to differences in the supply of nutrients from the cdw into the upper water column and thus modulates the impacts on surface biogeochemical processes