the evolution of oceanic and atmospheric anomalies in the northeast pacific during the el nino and la nina events of 1995 2001 abstract from late 1995 through early 2001 three major interannual climate events occurred in the tropical pacific the 1995 97 la nina ln 1997 98 el nino en and 1998 2001 ln we analyze atmospheric and upper oceanic anomalies in the northeast pacific nep during these events and compare them to anomalies both elsewhere in the north and tropical pacific and to typical en and ln anomaly patterns the atmospheric and oceanic anomalies varied strongly on intraseasonal and interannual scales during the 1995 97 ln and 1997 98 en the northeast pacific was dominated by negative slp and cyclonic wind anomalies and by upper ocean temperature and sea surface height ssh anomalies the latter were positive along the north american west coast and in the nep thermal anomaly pool between hawaii vancouver island and baja california and negative in the central north pacific this atmospheric oceanic anomaly pattern is typical of en an eastward shift in the atmospheric teleconnection from east asia created en like anomalies in the nep during the 1995 97 ln well before the 1997 98 en had begun the persistence of negative sea level pressure slp and cyclonic wind anomalies in the nep during the 1997 98 en intensified pre existing upper oceanic anomalies atmospheric anomalies were shifted eastward during late 1996 early 1998 leading to a similar onshore shift of oceanic anomalies this produced exceptionally strong positive upper ocean temperature and ssh anomalies along the west coast during the 1997 98 en and explains the unusual coastal occurrences of several species of large pelagic warm water fishes the growth and eastward shift of these pre existing anomalies does not appear to have been linked to tropical pacific en anomalies until late 1997 when a clear atmospheric teleconnection between the two regions developed prior to this remote atmospheric impacts on the nep were primarily from east asia as the 1998 2001 ln developed nep anomalies began reversing toward the typical ln pattern this led to predominantly negative slp and cyclonic wind anomalies in the nep and upper ocean temperature and ssh anomalies that were mainly negative along the west coast and positive in the central north pacific the persistence of these anomalies into mid 2001 and a number of concurrent biological changes in the nep suggest that a decadal climate shift may have occurred in late 1998 during 1995 2001 nep oceanic anomalies tracked the overlying atmospheric anomalies as indicated by the maintenance of a characteristic spatial relationship between these anomalies in particular wind stress curl and ssh anomalies in the nep maintained an inverse relationship that strengthened and shifted eastward toward the west coast during late 1996 early 1998 this consistent relationship indicates that anomalous ekman transport driven by regional atmospheric forcing was an important contributor to temperature and ssh anomalies in the nep and ccs during the 1997 98 en other studies have shown that coastal propagations originating from the tropical pacific also may have contributed to coastal nep anomalies during this en our results indicate that at least some of this coastal anomaly signal may have been generated by regional atmospheric forcing within the nep

the ultimate undrained resistance of partially embedded pipelines on bottom pipelines for transporting oil and gas in deep water undergo significant changes in temperature and pressure during operating cycles which cause a tendency for lateral buckling prediction and control of this phenomenon are required for the safe design and operation of these pipelines however the soil response under combined vertical and lateral loading is a significant area of uncertainty and current practice relies on empirical expressions for the estimation of lateral pipe soil resistance this paper reports the results of finite element fe analyses of shallowly embedded pipelines under vertical and horizontal load these analyses have been compared with collapse loads calculated using the upper bound theorem of plasticity and are used to construct yield envelopes defining the limiting combinations of vertical and horizontal load the fe limiting loads were found to compare well with upper bound plasticity solutions and the internal soil displacements calculated in the fe analyses mat

settlements of shallow foundations on sand a method to evaluate settlements and rotations of rigid shallow foundations on sand under the combined action of inclined and eccentric loads is presented experimental results obtained on a model strip foundation are shown first next a mathematical model is formulated which is based on the hypotheses that a the foundation and the soil can be considered as a macro element for which the loadings act as generalized stress variables while the displacements and rotation of the foundation are the corresponding generalized strain variables and b the constitutive law of the macro element that is the relationship between generalized stress and strain rates is rigid plastic strain hardening with a non associated flow rule constitutive functions and parameters are determined by means of simple calibration tests predictions of the theory are then compared with experimental results in tests where loadings vary in a complex way up to foundation failure it is shown that experimental evidence is well matched

effects of bond crushing on the settlements of shallow foundations on soft rocks the paper presents a model capable of describing the behaviour of shallow foundations on soft rocks when subjected to eccentric loading the model is based on the concept of a macroelement according to this concept the foundation and the subsoil can be seen as a unique volume element a mathematical relationship is established that links the force and moment acting on the foundation and the corresponding displacement and rotation as if they were generalised stresses and strains respectively this relationship is based on the theory of hardening plasticity with two hardening variables both functions of the permanent generalised strains it is assumed that the second of such variables connected to the action of intergranular bonds monotonically decreases as strains progress and bonds crush it is shown that the model can reproduce quite well the observed displacement and rotation of a model circular foundation on a layer of calcarenite a parametric study also highlights that the model can in prin

seasonal cross shelf flow structure upwelling relaxation and the alongshelf pressure gradient in the northern california current system abstractmoored observations are used to investigate the seasonal change in vertical structure of the cross shelf circulation at a midshelf location in the northern california current system a streamwise normal coordinate system is employed to eliminate meander and eddy induced biases in the cross shelf flow that are unaccounted for with an alternative commonly applied approach the resulting flow structure develops an organized pattern midway through the upwelling season in particular under upwelling favorable conditions an onshore return layer occurs just beneath the offshore surface flow and a third offshore directed layer exists at depth that does not appear to satisfy ekman dynamics to within 9 m of the bottom both subsurface layers strengthen in time over the upwelling season mechanisms to explain the mean structure are evaluated and it is suggested that the timing of the development and strengthening of both the interior onshore return flow and the offshore near bottom layer are consisten

combined loading of spudcan foundations on clay laboratory tests recent research has shown that work hardening plasticity theory provides a suitable framework for interpreting and predicting the load displacement behaviour of rigid shallow foundations under combined vertical moment and horizontal loading most previous work has however been restricted to footings on granular soils this paper describes a series of laboratory tests conducted at unit gravity using a small circular footing and specimens of reconstituted kaolin the results indicate that work hardening plasticity concepts can also be applied to the modelling of shallow foundation behaviour on undrained clay the footing shape chosen for the experiments is representative of the spudcan foundations which support the legs of jack up drilling platforms a novel testing apparatus allows independent control of the vertical rotational and horizontal footing displacements within a single vertical plane tests conducted at constant vertical penetration are used to investigate the shape and size of the combine

inverse analysis based interpretation of sand behavior from triaxial compression tests subjected to full end restraint current laboratory testing often imposes or assumes uniform stress and strain distribution in a specimen for convenient data reduction to interpret soil behavior this paper presents an inverse analysis framework self learning simulations selfsim to interpret the drained behavior of sand from triaxial compression tests with fully frictional loading platens the frictional platens result in significant bulging of and nonuniform stresses and strains within sand specimens selfsim treats the specimen as a boundary value problem bvp and extracts these nonuniform stresses and strains from within each specimen using external load and displacement measurements the extracted behavior shows significant principal stress rotation variation of intermediate principal stress and nonuniform volume change throughout the specimen mobilized friction angles are interpreted on the two dimensional slip surface associated with the mohr coulomb failure criterion on the octahedral plane associated with the drucker pra

anomalously warm july 2005 in the northern california current historical context and the significance of cumulative wind stress 1 in the northern california current the onset of the 2005 upwelling season was five weeks later than usual and well established upwelling with a cold surface signature did not occur until about seven weeks after this as part of the joint us canada pacific hake survey from 14 16 july 2005 we occupied the newport hydrographic line at 44 65 n from the oregon coast to 83 km offshore instead of the cold surface layer expected in july we observed anomalously warm water for example 10 m temperature at the shelf station nh 5 was the warmest ever recorded in july at this location 6 2 c above average with observations back to 1961 we explore the pivotal role played by cumulative time integrated wind forcing in the development of upwelling in both 2005 and previous years we find that 80 of july surface layer 0 30 m interannual temperature variance can be explained by cumulative upwelling index from the spring transition

dem simulations of transverse pipe soil interaction on sand realistic modelling of transverse i e vertical and lateral pipe soil interaction plays an important role in predicting the behaviour of untrenched offshore pipelines that are designed to undergo

assessment of numerical procedures for determining shallow foundation failure envelopes the failure envelope approach is commonly used to assess the capacity of shallow foundations under combined loading but there is limited published work that compares the performance of various num

the effect of alongcoast advection on pacific northwest shelf and slope water properties in relation to upwelling variability the northern california current system experiences highly variable seasonal upwelling in addition to larger basin scale variability both of which can significantly affect its water chemistry salinity and temperature fields from a 7 year roms hindcast model of this region 43 n 50 n along with extensive particle tracking were used to study interannual variability in water properties over both the upper slope and the midshelf bottom variation in slope water properties was an order of magnitude smaller than on the shelf furthermore the primary relationship between temperature and salinity anomalies in midshelf bottom water consisted of variation in density cold salty versus warm fresh nearly orthogonal to the anomalies along density levels cold fresh versus warm salty observed on the upper slope these midshelf anomalies were well explained r2 0 6 by the combination of interannual variability in local and remote alongshore wind stress and depth of the california undercurrent cuc core lagrangian analysis of upper slope and midshelf bottom water shows that both are affected simultaneously by large scale alongcoast advection of water through the northern and southern boundaries the amplitude of anomalies in bottom oxygen and dissolved inorganic carbon dic on the shelf associated with upwelling variability are larger than those associated with typical variation in alongcoast advection and are comparable to observed anomalies in this region however a large northern intrusion event in 2004 illustrates that particular large scale alongcoast advection anomalies can be just as effective as upwelling variability in changing shelf water properties on the interannual scale

preface to special section on enhanced subarctic influence in the california current 2002 1 this special section discusses a rare phenomenon strong enhancement of subarctic influence in the california current system in the summer of 2002 this cold fresh anomaly in the upper halocline was more extreme than any prior observation though historical records extend back for several decades the subarctic anomaly extended more than 1500 km along the u s west coast from 49 n to 33 n it brought high nutrient waters into the coastal upwelling zone off oregon and northern california and produced exceptionally high chlorophyll concentrations inner shelf oxygen concentrations were very high near the surface and very low near the bottom the presence of this subarctic water mass was associated with anomalous southward currents detected by three different methods by satellite tracked drifters a mid shelf mooring and by satellite altimetry large scale wind forcing over the northeastern pacific during the previous winter and spring seems to be responsible for these anomalies

a systematic framework for formulating convex failure envelopes in multiple loading dimensions the failure envelope approach is widely used to assess the ultimate capacity of shallow foundations for combined loading and to develop foundation macro element models failure envelopes are typic

numerical investigation of bearing capacity of spudcan foundations in clay overlying sand under combined loading abstractthe evaluation of the foundation capacity under combined vertical horizontal and moment loading is an essential element of the site specific assessment that ensures mobile jackup rigs are

subthermocline eddies over the washington continental slope as observed by seagliders 2003 09 abstractin the california current system subthermocline lenslike anticyclonic eddies generated within the california undercurrent cu are one mechanism for lateral transport of the warm saline waters of the cu garfield et al established the name cuddies for eddies of this type and hypothesized that they account for a significant fraction of the offshore transport of cu water this study presents observations of subthermocline eddies collected from a time series of seaglider surveys in the northern california current system gliders made 46 crossings of subthermocline anticyclones and 17 crossings of subthermocline cyclones over 5 5 yr close inspection grouped these into 20 distinct anticyclones and 10 distinct cyclones water properties at the core of anticyclonic eddies were similar to those in the core of the cu over the continental slope these anticyclones are examples of cuddies anticyclonic cyclonic eddies had average radii of 20 4 20 6 km peak azimuthal current speeds of 0 25 0 23

the signature of el nino off oregon 1982 1983 national science foundation through grants oce 8026131 oce 8405232 oce 8014943 and oce 8315014

displacements of footings on sand under eccentric and inclined loads results of an investigation of the response of footings on sand under eccentric and inclined loads are presented apparatus was constructed that could simultaneously apply loads to footings at any eccentricity and inclination without imposing restraints on the footing displacements the experimental results are interpreted compared with published data and a method for predicting vertical and horizontal displacements and rotations of loaded footings on sand developed at low load levels the analysis generates the elastic half space solution which is then augmented to provide the complete nonlinear response of the footing in addition interaction diagrams between the vertical loads horizontal loads and moments that cause failure of the footing are presented key words footing sands eccentric loading inclined loading displacement rotation bearing capacity

a rheological model for the description of boulder impacts on granular strata this paper considers the mechanics of rock boulders impacting on granular strata the study is aimed at improving the numerical methods devoted both to describing boulder trajectories along slopes and designing preventive structures in mountain regions the problem is analysed by using a simplified approach inspired by the lumped mass method this is based on a the macro element concept b the definition of generalised stresses and displacements and c delayed plasticity theory both vertical and inclined impacts on horizontal strata and vertical impacts on inclined slopes are discussed the numerical results are obtained by using a finite difference numerical discretisation to integrate over time a coupled system of two dimensional differential equations most of the input data requested by the model are basic and geotechnically meaningful and comparison of the numerical results with the experimental data seems to be quite promising

flow and mixing in juan de fuca canyon washington we report breaking internal lee waves strong mixing and hydraulic control associated with wind driven up canyon flow in juan de fuca canyon washington unlike the flow above the canyon rim which shows a tidal modulation typical on continental shelves the flow within the canyon is persistently up canyon during our observations with isopycnals tilted consistent with a geostrophic cross canyon momentum balance as the flow encounters a sill near the canyon entrance at the shelf break it accelerates significantly and undergoes elevated mixing on the upstream and downstream sides of the sill on the downstream side a strong lee wave response is seen with displacements of o 100 m and overturns tens of meters high the resulting diffusivity is o 10 2 m2 s 1 sufficient to substantially modify coastal water masses as they transit the canyon and enter the salish sea estuarine system

pipe soil interaction model incorporating large lateral displacements in calcareous sand the use of the plasticity theory offers an attractive framework to encapsulate the behavior of a pipe and the underlying soil in terminology consistent with pipeline structural analysis models that express the pipe soil behavior purely in terms of the loads on a segment of pipe and the corresponding displacements have been suggested although verification with geotechnical centrifuge experiments has been limited to relatively small lateral displacements i e less than two pipe diameters over larger movements the berms that build up alongside the pipe affect the load displacement behavior with existing strain hardening plasticity models incapable of simulating this transition this technical note provides experimental evidence of pipe soil behavior for lateral displacements for up to five diameters it further presents observations from 20 centrifuge experiments of a prototype 1 m diameter pipe in calcareous sand the results are used to validate the modification of a pipe soil model to include the

a numerical modeling study of the upwelling source waters along the oregon coast during 2005 abstract regional ocean circulation along the oregon coast is studied numerically for forcing fields derived from year 2005 and climatological mean conditions the primary object is to study directly the lagrangian pathways by which fluid arrives in the oregon upwelling zone roughly half of the upwelling fluid is found to arrive in the regional domain from alongshelf source points primarily north but also south of the oregon upwelling zone while the other half ultimately arrives from points offshore and west of the zone for both the year 2005 and the climatological simulations different regimes of dominant alongshelf source waters are found with cape blanco being a dividing point for northern versus southern sources and with the water parcels coming primarily from depths below 100 m for the offshore sources most upwelling fluid originates from depths between 150 and 250 m during 2005 but from within the upper 150 m for the climatological simulations in both cases there are specific regions alon