seismic stability analysis of soil nail reinforced slope using kinematic approach of limit analysis prediction of the critical seismic yield acceleration coefficient and the seismic permanent displacement of soil nail reinforced slope under seismic loading has been playing an important role in helping design in the earthquake prone areas in this paper the seismic stability of soil nail reinforced slope is analyzed using the kinematic theorem of limit analysis the log spiral failure mechanism is considered and the corresponding analytical expressions are derived to calculate the critical seismic yield acceleration coefficient and the permanent displacement of slope subjected to earthquake loading a series of calculations are carried out to illustrate the influence of inertial force on the stability of a nail reinforced slope parametric studies indicate that the strength and geometry of slope as well as characteristic parameters of soil nail have a significant effect on the critical seismic yield acceleration coefficient and the permanent displacement of soil nail reinforced slope

five years of florida current structure and transport from the royal caribbean cruise ship explorer of the seas 1 using ship of opportunity platform explorer of the seas five years of full depth velocity data have been collected across the florida straits at 26 n between may 2001 and may 2006 the mean transport of the florida current was 31 0 4 0 sv this compares to a mean transport of 32 4 3 2 sv inferred from cable voltages at 27 n over the same period implying an average 1 4 sv transport into the straits through the northwest providence channel the climatological core of the florida current is 170 cms 1 and is positioned at 79 8 w about 10 km east of the shelf break the largest variability in velocity occurs over the shelf and shelf break and is likely related to shelf waves a secondary maximum occurs across much of the straits over the top 100 m of the water column and may be associated with wind events the annual cycle of florida current transports has a range of 4 7 sv with a maximum in may june july and a minimum in january the difference between the summer and winter current structure appears as a first baroclinic mode with zero crossing at 150 m the maximum difference is about 15 cms 1 at the surface and is centered just offshore of the mean current core on interannual timescales low pass filtered explorer and cable transports show similar downward trends between 2002 and 2005 but diverge over the last year or so of the record

recent wind driven variability in atlantic water mass distribution and meridional overturning circulation abstractinterannual variability in the volumetric water mass distribution within the north atlantic subtropical gyre is described in relation to variability in the atlantic meridional overturning circulation the relative roles of diabatic and adiabatic processes in the volume and heat budgets of the subtropical gyre are investigated by projecting data into temperature coordinates as volumes of water using an argo based climatology and an ocean state estimate ecco version 4 this highlights that variations in the subtropical gyre volume budget are predominantly set by transport divergence in the gyre a strong correlation between the volume anomaly due to transport divergence and the variability of both thermocline depth and ekman pumping over the gyre suggests that wind driven heave drives transport anomalies at the gyre boundaries this wind driven heaving contributes significantly to variations in the heat content of the gyre as do anomalies in the air sea fluxes the analysis presented suggests tha

toothpaste lava characteristics and origin of a lava structural type transitional between pahoehoe and aa toothpaste lava an important basalt structural type which illustrates the transition from pahoehoe to aa is particularly well displayed on the 1960 kapoho lava of kilauea volcano its transitional features stem from a viscosity higher than that of pahoehoe and a rate of flow slower than that of aa viscosity can be quantified by the limited settling of olivine phenocrysts and rate of flow by field observations related to the low angle slope on which the lava flowed much can be learned about the viscosity rheologic condition and flow velocity of lavas long after solidification by analyses of their structural characteristics and it is possible to make at least a semiquantitative assessment of the numerical values of these parameters

construction dynamics of a lava channel we use a kinematic gps and laser range finder survey of a 200 m long section of the muliwai a pele lava channel mauna ulu kilauea to examine the construction processes and flow dynamics responsible for the channel levee structure the levees comprise three packages the basal package comprises an 80 150 m wide a a flow in which a 2 m deep and 11 m wide channel became centred this is capped by a second package of thin 45 cm thick sheets of pahoehoe extending no more than 50 m from the channel the upper most package comprises localised a a overflows the channel itself contains two blockages located 130 m apart and composed of levee chunks veneered with overflow lava the channel was emplaced over 50 h spanning 30 may 2 june 1974 with the flow front arriving at our section 4 4 km from the vent 8 h after the eruption began the basal a a flow thickness yields effusion rates of 35 m3 s 1 for the opening phase with the initial flow advancing across the mapped section at 10 m min short lived overflows of fluid pahoehoe then built the levee cap increasing the apparent channel depth to 4 8 m there were at least six pulses at 90 420 m3 s 1 causing overflow of limited extent lasting no more than 5 min brim full flow conditions were thus extremely short lived during a dominant period of below bank flow flow depth was 2 m with an effusion rate of 35 m3 s 1 consistent with the mean output rate obtained from the total flow bulk volume of 23 54 m3 s 1 during pulses levee chunks were plucked and floated down channel to form blockages in a final low effusion rate phase lava ponded behind the lower blockage to form a syn channel pond that fed a a overflow after the end of the eruption the roofed over pond continued to drain through the lower blockage causing the roof to founder drainage emplaced inflated flows on the channel floor below the lower blockage for a further 10 h the complex processes involved in levee channel construction of this short lived case show that care must be taken when using channel dimensions to infer flow dynamics in our case the full channel depth is not exposed instead the channel floor morphology reflects late stage pond filling and drainage rather than true channel contained flow components of the compound levee relate to different flow regimes operating at different times during the eruption and associated with different effusion rates flow dynamics and time scales for example although high effusion rate brim full flow was maintained for a small fraction of the channel lifetime it emplaced a pile of pahoehoe overflow units that account for 60 of the total levee height we show how time varying volume flux is an important parameter in controlling channel construction dynamics because the complex history of lava delivery to a channel system is recorded by the final channel morphology time varying flow dynamics can be determined from the channel morphology developing methods for quantifying detailed flux histories for effusive events from the evidence in outcrop is therefore highly valuable we here achieve this by using high resolution spatial data for a channel system at kilauea this study not only indicates those physical and dynamic characteristics that are typical for basaltic lava flows on hawaiian volcanoes but also a methodology that can be widely applied to effusive basaltic eruptions

the significance of slab crusted lava flows for understanding controls on flow emplacement at mount etna sicily slab crusted flows on mount etna sicily are defined here as those whose crust has ridden on the flow core without significant disruption or deformation and have a high length to width ratio they typically erupt from ephemeral boccas as late stage products on dominantly aa flow fields such as that of the 1983 eruption on mount etna slab crusted flows tend to inflate mainly as they approach and after they reach the maximum length of slab crust formation the flow interior acting as a preferential pathway for injecting lava under a stable crust coalescence of vesicles under successive crusts causes separation between core and crust giving a new cooling surface within the flow on which ropy surfaces and occasionally aa textures of limited areal extent may develop slab crusted flows tend to form at ephemeral boccas together with other surface textural types including toes ropy pahoehoe sheets and aa flows this suggests that on etna slab crusted flows form from lava of the same rheological properties as both aa and pahoehoe textured flows they do not represent a transition between aa and pahoehoe as argued for toothpaste flows in hawaii we conclude that slab crusted flows on etna owe their morphology to a relatively high critical ratio of effusion rate to advance rate related to vent cross sectional area and the slope over which the flow forms

assessment of slope stability and monitoring of a landslide in the koyulhisar settlement area sivas turkey the koyulhisar settlement area is located in the seismically active zone of kelkit valley the settlement area has been adversely affected by active landslides as a result of which some of the houses have been evacuated in this study areas within the koyulhisar settlement area where the landslides exist were delineated with a field mapping technique and active landslides were investigated by means of field observations drilling sampling field and laboratory testing and in situ monitoring using an inclinometer based on the field studies it is observed that a flyschoidal sequence of bedrock and colluvium consisting of clay and silt with some gravels comprise the main lithological units two areas affected by the landslides were identified one of the landslide areas is local and there were no adverse effects on the houses however the other one was investigated in detail due to its adverse effect on some important governmental buildings this is a slide with a non circular failure surface caused by the existence of the flyschoidal sequence that forms a resistant bedrock below the colluvium the inclinometer measurements reveal that the displacements are local and their velocities are generally less than 14 mm year indicating that the landslide is extremely slow in addition a high groundwater table with slow snow melt was observed as one of the major environmental parameters in the occurrence of the landslide nevertheless the slope stability analyses reveal that groundwater lowering alone is not an effective measure in increasing stability and therefore either reinforcement should be applied to the entire active landslide area or the area should be abandoned

changes across 66 w the caribbean sea and the western boundaries of the north atlantic subtropical gyre abstract a world ocean circulation experiment hydrographic program along with a global repeat hydrography program occupied sections along 66 w in the north west atlantic ocean in 2003 and 2012 hydrographic variables tracers and ladcp measurements were collected in situ this section together with the north american and south american coasts create a closed volume excluding any flow through the panama canal combining mass silica and ladcp information with constraints in an inverse box model we obtain a strong eastward flow of the gulf stream 100 1 4 6 sv in 2003 and 123 8 4 4 sv in 2012 and westward flows of the caribbean current 24 4 1 0 sv in 2003 and 24 2 1 1 sv in 2012 and deep western boundary current dwbc the dwbc carries the ventilated waters of the labrador sea and the nordic seas comparing the results of 2003 and 2012 an insignificant reduction is observed in the dwbc transport 17 3 2 9 sv and 15 0 2 5 sv for 2003 and 2012 respectively the net heat fluxes do not show major changes through the section during both cruises 0 23 0 08 pw in 2003 and 0 21 0 12 pw in 2012 in contrast freshwater fluxes present positive values in the dry season 0 24 sv in spring 2012 and negative values in the wet season 0 32 sv in fall 2003 the difference between both cruises may be due to seasonal variability in the area

volcanology and eruptive styles of barren island an active mafic stratovolcano in the andaman sea ne indian ocean barren island india is a relatively little studied little known active volcano in the andaman sea and the northernmost active volcano of the great indonesian arc the volcano is built of prehistoric possibly late pleistocene lava flows dominantly basalt and basaltic andesite with minor andesite intercalated with volcaniclastic deposits tuff breccias and ash beds deposited by pyroclastic falls and surges which are exposed along a roughly circular caldera wall there are indications of a complete phreatomagmatic tephra ring around the exposed base of the volcano a polygenetic cinder cone has existed at the centre of the caldera and produced basalt basaltic andesite aa and blocky aa lava flows as well as tephra during historic eruptions 1787 1832 and three recent eruptions 1991 1994 95 2005 06 the recent aa flows include a toothpaste aa flow with tilted and overturned crustal slabs carried atop an aa core as well as locally developed tumuli like elliptical uplifts having corrugated crusts based on various evidence we infer that it belongs to either the 1991 or the 1994 95 eruptions the volcano has recently 2008 begun yet another eruption so far only of tephra we make significantly different interpretations of several features of the volcano than previous workers this study of the volcanology and eruptive styles of the barren island volcano lays the ground for detailed geochemical isotopic and petrogenetic work and provides clues to what the volcano can be expected to do in the future

homogenization of potential vorticity in planetary gyres the mean circulation of planetary fluids tends to develop uniform potential vorticity q in regions where closed time mean streamlines or closed isolines of mean potential vorticity exist this state is established in statistically steady flows by geostrophic turbulence or by wave induced potential vorticity flux at the outer edge of the closed contours the expelled gradients of q are concentrated beyond this transition lies motionless fluid or a different flow regime in which the planetary gradient of q may be dominant the homogenized regions occur where direct forcing by external stress or heating within the closed isoline is negligible upon the potential density surface under consideration in the stably stratified ocean such regions are found at depths greater than those of direct wind induced stress or penetrative cooling in channel models of the atmosphere we again find constant q when mesoscale eddies cause the dominant potential vorticity flux in the real atmosphere the results here can apply only where internal heating is negligible the derivations given here build upon the prandtl batchelor theorem which applies to non rotating steady two dimensional flow supporting evidence is found in numerical circulation models and oceanic observations

the interaction of recirculation gyres and a deep boundary current abstractmotivated by the proximity of the northern recirculation gyre and the deep western boundary current in the north atlantic an idealized model is used to investigate how recirculation gyres

morphology and structure of the 1999 lava flows at mount cameroon volcano west africa and their bearing on the emplacement dynamics of volume limited flows the morphology and structure of the 1999 lava flows at mount cameroon volcano are documented and discussed in relation to local and source dynamics structures are analysed qualitatively and more detailed arguments are developed on the processes of levee formation and systematic links between flow dynamics and levee channel interface geometry the flows have clear channels bordered by four main types of levees initial accretionary rubble and overflow levees thermally immature pahoehoe lava units with overflow drapes define the proximal zone whereas rubble and accretionary levees are common in the distal region bordering thermally mature aa clinker or blocky aa flow channels pressure ridges squeeze ups and pahoehoe ropes are the prevalent compressive structures standlines displayed on clinkery breccias are interpreted to represent levee channel interactions in response to changing flow levels these data complement previous knowledge on lava flow morphology thus far dominated by etnean and hawaiian examples

two decades of the atlantic meridional overturning circulation anatomy variations extremes prediction and overcoming its limitations the zonally integratedmeridional volumetransport in the north atlantic atlantic meridionaloverturning circulation amoc is described in a 19 yr long ocean state estimate one consistent with a diverse global dataset apart from a weak increasing trend at high northern latitudes the amoc appears statistically stable over the last 19yr with fluctuations indistinguishable from those of a stationary gaussian stochastic process this characterization makes it possible to study using highly developed tools extreme values predictability and the statistical significance ofapparenttrends gaussianbehaviorisconsistentwith the central limittheorem for a process arising from numerous independent disturbances in this case generators include internal instabilities changes in wind and buoyancy forcing fields boundary waves the gulf stream and deep western boundary current transports the interior fraction in sverdrup balance and all similar phenomena arriving as summation effects from long distances and times as a zonal integral through the sum of the large variety of physical processes in the three dimensional ocean circulation understanding of the amoc if it is of central climate importance requires breaking it down into its unintegrated components over the entire basin

north atlantic barotropic vorticity balances in numerical models abstractnumerical simulations are conducted across model platforms and resolutions with a focus on the north atlantic barotropic vorticity diagnostics confirm that the subtropical gyre is characterized by an inviscid balance primarily between the applied wind stress curl and bottom pressure torque in an area integrated budget over the gulf stream the northward return flow is balanced by bottom pressure torque these integrated budgets are shown to be consistent across model platforms and resolution suggesting that these balances are robust two of the simulations at 100 and 10 km resolutions produce a more northerly separating gulf stream but obtain the correct integrated vorticity balances in these simulations viscous torque is nonnegligible on smaller scales indicating that the separation is linked to the details of the local dynamics these results are shown to be consistent with a scale analysis argument that suggests that the biharmonic viscous torque in particular is upsetting the inviscid

role of the gulf stream and kuroshio oyashio systems in large scale atmosphere ocean interaction a review abstract ocean atmosphere interaction over the northern hemisphere western boundary current wbc regions i e the gulf stream kuroshio oyashio and their extensions is reviewed with an emphasis on their role in basin scale climate variability sst anomalies exhibit considerable variance on interannual to decadal time scales in these regions low frequency sst variability is primarily driven by basin scale wind stress curl variability via the oceanic rossby wave adjustment of the gyre scale circulation that modulates the latitude and strength of the wbc related oceanic fronts rectification of the variability by mesoscale eddies reemergence of the anomalies from the preceding winter and tropical remote forcing also play important roles in driving and maintaining the low frequency variability in these regions in the gulf stream region interaction with the deep western boundary current also likely influences the low frequency variability surface heat fluxes damp the low frequency sst anomalies ove

topographic coupling of the atlantic overturning and gyre circulations abstractthe vorticity dynamics associated with the mean and time varying gyre and overturning circulations of the atlantic ocean are examined in a realistic ocean model hindcast simulation of the late twentieth century abyssal flow interaction with sloping bottom bathymetry gives rise to the bottom pressure torque bpt term of the vertically integrated vorticity equation the dominance of this term in the closure of the barotropic gyre circulation noted in previous studies is corroborated here for both non eddy resolving and eddy resolving versions of the parallel ocean program pop model this study shows that bpt is also a dominant term in the vorticity balance of the atlantic meridional overturning circulation amoc and therefore represents a key dynamical link between the overturning and gyre streamfunctions the interannual variability of the atlantic circulation over the last several decades viewed in terms of time varying integral vorticity balances demonstrates the fundamental role played by

a multi methodological re evaluation of the volcanic events during the 1580 ce and 1808 eruptions at sao jorge island azores archipelago portugal abstract among all eruptions that took place on the azores archipelago since the portuguese settlement in the xvi century those of 1580 and 1808 in the island of sao jorge were unusual the magma erupted in 1580 ascended from at least 23 km and ponded at a minimum depth of 16 km here residual magma fractionated mafic phases and plagioclase during 228 years before erupted again in 1808 magma emission occurred from numerous fissures active at the same time and opening for several kilometres following a local tectonic trend hydro volcanic outbursts and hot rock fall over steep slopes caused casualties and injuries and lava flows and heavy tephra fallout affected the local economy despite of all these dramatic consequences the memory of these eruptions is almost vanished representative geosites and morphological landforms if not hindered by lush vegetation have been reshaped by diffuse quarries and reworked to recover croplands and pastures aiming at a better comprehension of the multiple hazards associated with volcanic eruptions at sao jorge island we retraced the volcanic events of these two eruptions by matching our re interpretation of historic reports with field data and photogrammetry and with fluid inclusions petrography and geochemical data of erupted products

dynamically and observationally constrained estimates of water mass distributions and ages in the global ocean abstracta data constrained ocean circulation model is used to characterize the distribution of water masses and their ages in the global ocean the model is constrained by the time averaged temperature salinity and radiocarbon distributions in the ocean as well as independent estimates of the mean sea surface height and sea surface heat and freshwater fluxes the data constrained model suggests that the interior ocean is ventilated primarily by water masses forming in the southern ocean southern ocean waters including those waters forming in the antarctic and subantarctic regions make up about 55 of the interior ocean volume and an even larger percentage of the deep ocean volume in the deep north pacific the ratio of southern ocean to north atlantic waters is almost 3 1 approximately 65 of interior ocean waters make first contact with the atmosphere in the southern ocean further emphasizing the central role played by the southern ocean in the regulation of the earth s climate results of the a

construction of the adjoint mit ocean general circulation model and application to atlantic heat transport sensitivity we first describe the principles and practical considerations behind the computer generation of the adjoint to the massachusetts institute of technology ocean general circulation model gcm using r giering s software tool tangent linear and adjoint model compiler tamc the tamc s recipe for fortran line by line generation of adjoint code is explained by interpreting an adjoint model strictly as the operator that gives the sensitivity of the output of a model to its input then the sensitivity of 1993 annual mean heat transport across 29on in the atlantic to the hydrography on january 1 1993 is calculated from a global solution of the gcm the kinematic sensitivity to initial temperature variations is isolated showing how the latter would influence heat transport if they did not affect the density and hence the flow over 1 year the heat transport at 29on is influenced kinematically from regions up to 20 o upstream in the western boundary current and up to 5 o upstream in the interior in contrast the dynamical influences of initial temperature and salinity perturbations spread from as far as the rim of the labrador sea to the 29on section along the western boundary the sensitivities calculated with the adjoint compare excellently to those from a perturbation calculation with the dynamical model perturbations in initial interior salinity influence meridional overturning and heat transport when they have propagated to the western boundary and can thus influence the integrated east west density difference our results support the notion that boundary monitoring of meridional mass and heat transports is feasible

vorticity balance in coarse resolution global ocean simulations abstract the vorticity budget of the vertically integrated circulation from two global ocean simulations is analyzed using a horizontal spacing of 2 2 in longitude latitude the two simulations differ in their initial hydrographic conditions and surface wind and buoyancy forcing the constrained simulation obtains optimal initial condition and surface forcing through assimilating observational data using the model s adjoint whereas the unconstrained simulation uses levitus climatological conditions for initialization and is driven by ncep ncar reanalysis forcing plus restoring to the monthly surface temperature and salinity climatological conditions the goal is to examine the dynamics that sets the time mean circulation and to understand the differences between the constrained and unconstrained simulations it is found that similar to eddy permitting simulations the bottom pressure torque bpt in coarse resolution models plays an important role in the western boundary currents and in the souther

mercury s caloris basin continuity between the interior and exterior plains the smooth plains on the floor of mercury s caloris basin and those almost entirely surrounding it beyond its rim are usually accepted to be younger than the rim materials and to be lava flows rather than impact melt high resolution imaging shows that the emplacement of interior and exterior plains was concurrent with evidence of both inward and outward flow while they were being emplaced the caloris rim is breached in two places by continuous smooth plains that seamlessly connect interior and exterior plains the gross scale spectral and compositional distinctiveness of interior and exterior plains is blurred on a scale of several tens of kilometers which could reflect interfingering of flow units less than a few hundred kilometers long that tapped melt sources of different composition and or depth inside and outside the basin followed by local mixing of regolith flows occurring both inside and outside the basin should be included in estimates of the total erupted volume

textural characterization of the pāhoeho a a transition in hawaiian basalt p hoehoe and a are the most common surface morphologies in basaltic lava flows yet no predictive models exist to link physical parameters of flow emplacement to changes in their surface textures and rheological properties we have characterized changes of vesicularity vesicle deformation and crystallinity across the p hoehoe a transition as preserved in two different eruptions a brief high velocity effusion of lava from k lauea volcano on 1 february 1996 and a small breakout from an ephemeral vent within a larger channel produced during the 1868 eruption of mauna loa this allowed us to compare conditions leading to the p hoehoe a transition for both open channel flow k lauea 1996 and reactivation of lava from an ephemeral vent mauna loa 1868 textural changes across the transition include a decrease in vesicularity and vesicle number density b increase in microlite crystallinity and crystal number density and c increase in vesicle deformation the results support past qualitative descriptions of the transition and highlight the importance of plagioclase crystallinity in controlling lava rheology and surface morphology

a barotropic vorticity budget for the subtropical north atlantic based on observations abstractto ground truth the large scale dynamical balance of the north atlantic subtropical gyre with observations a barotropic vorticity budget is constructed in the ecco state estimate and compa

uav based remote sensing surveys of lava flow fields a case study from etna s 1974 channel fed lava flows during an eruption time scales of topographic change are fast and involve vertical and planimetric evolution of millimeters to meters as the event progresses repeat production of high spatial resolution terrain models of lava flow fields over time scales of a few hours is thus a high value capability in tracking the buildup of the deposit among the wide range of terrestrial and aerial methods available to collect such topographic data the use of an unmanned aerial vehicle uav as an acquisition platform together with structure from motion sfm photogrammetry has become especially useful this approach allows high frequency production of centimeter scale terrain models over kilometer scale areas including dangerous and inaccessible zones with low cost and minimal hazard to personnel this study presents the application of such an integrated uav sfm method to generate a high spatial resolution digital terrain model and orthomosaic of mount etna s january february 1974 lava flow field the sfm method applied to images acquired using a uav platform enabled the extraction of a very high spatial resolution 20 cm digital elevation model and the generation of a 3 cm orthomosaic covering an area of 1 35 km2 this spatial resolution enabled us to analyze the morphology of sub meter scale features such as folds blocks and cracks over kilometer scale areas the 3 cm orthomosaic allowed us to further push the analysis to centimeter scale grain size distribution of the lava surface using these data we define three types of crust structure and relate them to positions within a channel fed a flow system these crust structures are i flow parallel shear lines ii raft zones and iii folded zones flow parallel shear lines are found at the channel edges and are 2 m wide and 0 25 m deep zones running along the levee base and in which cracking is intense they result from intense shearing between the moving channel lava and the static levee lava in zones where initial levees are just beginning to form these subtle features are the only marker that delimits the moving lava from the stagnant marginal lava rafts generally form as the system changes from a stable to a transitional channel regime over this 170 m long zone the channel broadens from 8 to 70 m and rafts are characterized by topographically higher and poorly cracked areas surrounded by lower heavily cracked areas we interpret the rafts as forming due to breakup of crust zones previously moving in a coherent manner in the narrow proximal channel reach folded zones involve arcuate cross flow ridges with their apexes pointing down flow where ridges have relatively small clasts and depressions are of coarser grained breccia our folds have wavelengths of 10 m and amplitudes of 1 m are found towards the flow front down flow of the raft zones and are associated with piling up of lava behind a static or slowly moving flow front the very high spatial resolution topographic data available from uav sfm allow us to resolve surfaces where roughness has a vertical and horizontal scale of variation that is less than 1 m this is the case over p hoehoe and a flow surfaces and thus allows us to explore those new structures that are only apparent in the sub metric data moreover during future eruptions the possibility to acquire such information in near real time will allow a prompt analysis of developing lava flow fields and structures therein such as developing lava channel systems so as to contribute to timely hazard assessment modeling and projections

cooling and crystallization of lava in open channels and the transition of pāhoehoe lava to a ā samples collected from a lava channel active at kilauea volcano during may 1997 are used to con strain rates of lava cooling and crystallization during early stages of flow lava erupted at near liquidus tem peratures f1150 7c cooled and crystallized rapidly in upper parts of the channel glass geothermometry indi cates cooling by 12 14 7c over the first 2 km of trans port at flow velocities of 1 2 m s this translates to cooling rates of 22 50 7c h cooling rates this high can be explained by radiative cooling of a well stirred flow consistent with observations of non steady flow in proximal regions of the channel crystallization of plag ioclase and pyroxene microlites occurred in response to cooling with crystallization rates of 20 50 per hour crystallization proceeded primarily by nucleation of new crystals and nucleation rates of f10 4 cm 3 s are similar to those measured in the 1984 open channel flow from mauna loa volcano there is no evidence for the large nucleation delays commonly assumed for plagioclase crystallization in basaltic melts possibly a reflection of enhanced nucleation due to stirring of the flow the transition of the flow surface morphology from pahoehoe to a aoccurred at a distance of 1 9 km from the vent at this point the flow was thermally stratified with an interior temperature of f1137 7c and crystallinity of f15 and a flow surface tempera ture of f1100 7c and crystallinity of f45 a afor mation initiated along channel margins where crust was continuously disrupted and involved tearing and clotting of the flow surface both observations suggest that the transition involved crossing of a rheological threshold we suggest this threshold to be the develop ment of a lava yield strength sufficient to prevent vis cous flow of lava at the channel margin we use this concept to propose that a aformation in open chan nels requires both sufficiently high strain rates for con tinued disruption of surface crusts and sufficient groundmass crystallinity to generate a yield strength equivalent to the imposed stress in hawai i where lava is typically microlite poor on eruption these combined requirements help to explain two common observations on a aformation a a aflow fields are generated when effusion rates are high thus promoting crustal disruption and b under most eruption conditions lava issues from the vent as pahoehoe and changes to a aonly after flowing some distance thus permitting sufficient crystallization

pulsed inflation of pahoehoe lava flows implications for flood basalt emplacement abstract dilated fractures in hawaiian pahoehoe lava flows contain three zones that show the kinematics of inflation the upper columnar zone forms through thermal contraction prior to inflation the middle planar zone reflects inflation induced tension and the lower banded zone contains evidence of brittle and ductile deformation the formation of the lower banded zone requires varying strain rates during fracture propagation and is best explained by a model where small pulses of lava inject beneath the cooled flow crust through a network of preferred pathways we demonstrate via simple models of pipe flow that this inflation mechanism is incapable of producing areally extensive continental flood basalts on earth although it may explain related features on large martian volcanoes

a global analysis of sverdrup balance using absolute geostrophic velocities from argo using observations from the argo array of profiling floats the large scale circulation of the upper 2000 decibars db of the global ocean is computed for the period from december 2004 to november 2010 the geostrophic velocity relative to a reference level of 900db is estimated from temperature and salinity profiles and the absolute geostrophic velocity at the reference level is estimated from the trajectory data provided by the floats combining the two gives the absolute geostrophic velocity on 29 pressure surfaces spanning the upper 2000db of the global ocean these velocities together with satellite observations of wind stress are thenusedtoevaluatesverdrupbalance thesimplecanonicaltheoryrelatingmeridionalgeostrophictransport to wind forcing observed transports agree well with predictions based on the wind field over large areas primarily in the tropics and subtropics elsewhere especially at higher latitudes and in boundary regions sverdrup balance does not accurately describe meridional geostrophic transports possibly due to the increased importance of the barotropic flow nonlinear dynamics and topographic influence thus while it provides an effective framework for understanding the zero order wind driven circulation in much of the global ocean sverdrup balance should not be regarded as axiomatic

toothpaste lava from the barren island volcano andaman sea abstract toothpaste lava is a basaltic lava flow type transitional between pahoehoe and aa and has been described from paricutin kilauea and etna volcanoes here we describe a spectacular example of toothpaste lava forming part of a recent possibly 1994 95 aa flow on the active volcano of barren island andaman sea this flow of subalkalic basalt shows abundant squeeze ups of viscous toothpasate lava near its entry into the sea the squeeze ups are sheets and slabs up to several meters across and tens of centimeters thick extruded from boccas they are often prominently curved have striated upper surfaces with close spaced en echelon linear ridges and grooves broad wave like undulations perpendicular to the striations and sometimes clefts textural geochemical and sr nd isotopic data on the squeeze ups and the exposed aa flow core indicate very crystal rich viscous and isotopically very homogeneous lava we envisage that a greatly reduced speed of this viscous flow at the coastline possibly aided by a shallowing of the basal slope led to lateral spreading of the flow which caused tension in its upper parts this with continued albeit dwindling lava supply at the back led to widespread tearing of the flow surface and extrusion of the squeeze ups the larger slabs while extruding in a plastic condition curved under their own weight whereas their surfaces experienced brittle deformation forming the en echelon grooves the extruded detached and rotated sheets and slabs were carried forward for some distance atop the very slowly advancing aa core before the flow solidified

lidar derived surface roughness signatures of basaltic lava types at the muliwai a pele lava channel mauna ulu hawai i we used light detection and ranging lidar data to calculate roughness patterns homogeneity mean roughness and entropy for five lava types at two different resolutions 1 5 and 0 1 m pixel we found that end member types a and p hoehoe are separable with 95 confidence at both scales indicating that roughness patterns are well suited for analyzing types of lava intermediate lavas were also explored and we found that slabby p hoehoe is separable from the other end members using 1 5 m pixel data but not in the 0 1 m pixel analysis this suggests that the conversion from p hoehoe to slabby p hoehoe is a meter scale process and the finer roughness characteristics of p hoehoe such as ropes and toes are not significantly affected furthermore we introduce the ratio frac ent hom derived from lava roughness as a proxy for assessing local lava flow rate from topographic data high entropy and low homogeneity regions correlate with high flow rate while low entropy and high homogeneity regions correlate with low flow rate we suggest that this relationship is not directional rather it is apparent through roughness differences of the associated lava type emplaced at the high and low rates respectively

assessment of slope stability in ankara clay a case study along e90 highway some slope instability problems exist in ankara clay along e90 highway the purpose of this paper is to determine the mineralogical and geotechnical properties of soils and to investigate the causes and mechanisms of three rotational landslides along a section of the highway in order to accomplish these tasks field studies laboratory testing back analyses and limit equilibrium and finite difference analyses were performed the landslides are formed within a soil consisting of clay and silt with a little sand and gravel slope stability analyses indicate that long term stability of already failed slopes is critical the failures are progressive showing strain softening behavior with full saturation broken irrigation pipes existing near the landslides are found to be the main cause of sliding maintenance of the pipes surface drainage removal and replacement of the failed slided material are considered to be economical and practical solutions for the remediation of the slides

vertical heat flux in the ocean estimates from observations and from a coupled general circulation model the net heat uptake by the ocean in a changing climate involves small imbalances between the advective and diffusive processes that transport heat vertically generally it is necessary to rely on global climate models to study these processes in detail in the present study it is shown that a key component of the vertical heat flux namely that associated with the large scale mean vertical circulation can be diagnosed over extra tropical regions from global observational data sets this component is estimated based on the vertical velocity obtained from the geostrophic vorticity balance combined with estimates of absolute geostrophic flow results are compared with the output of a non eddy resolving coupled atmosphere ocean general circulation model reasonable agreement is found in the latitudinal distribution of the vertical heat flux as well as in the area integrated flux below about 250 m depth the correspondence with the coupled model deteriorates sharply at depths shallower than 250 m due to the omission of equatorial regions from the calculation the vertical heat flux due to the mean circulation is found to be dominated globally by the downward contribution from the southern hemisphere in particular the southern ocean this is driven by the ekman vertical velocity which induces an upward transport of seawater that is cold relative to the horizontal average at a given depth the results indicate that the dominant characteristics of the vertical transport of heat due to the mean circulation can be inferred from simple linear vorticity dynamics over much of the ocean

topographic control of basin and channel flows the role of bottom pressure torques and friction the topographical control of western boundary currents within a basin and zonal jets in a channel is investigated in terms of the potential vorticity pv and barotropic vorticity bv the curl of the depth integrated velocity budgets using isopycnic adiabatic wind driven experiments along the western boundary the wind driven transport is returned across latitude lines by the bottom pressure torque while friction is only important in altering the pv within an isopycnic layer and in allowing a closed circulation these contrasting balances constrain the geometry of the flow through integral relationships for the bv and pv for both homogenous and stratified basins with sloping sidewalls the northward subtropical jet separates from the western wall and has opposing frictional torques on either side of the jet which cancel in a zonal integral for bv but alter the pv within a layer streamline in a channel with partial topographic barriers the bottom pressure torque is again important in returning wind driven flows along western boundaries and in transferring bv from neighboring wind driven gyres into a zonal jet the depth integrated flow steered by topography controls where the bottom friction alters the pv which can lead to different pv states being attained for separate subbasins along a channel

is the north atlantic in sverdrup balance abstract evidence for the widespread assumption that sverdrup balance describes the dynamics of the north atlantic subtropical gyre is reviewed critically if the balance were to hold up to the edge of the gulf stream system then there is a serious conflict with existing estimates of the net meridional flux of heat if a recirculation region near the stream is excluded then one loses numerical agreement between a geostrophic calculation of the interior mass flux and the opposite gulf stream transport our conclusion is that while the linear vorticity balance may well apply over much of the north atlantic subtropical gyre there is little evidence supporting the special version called sverdrup balance even in the relatively quiescent region east of the mid atlantic ridge to the contrary simple order of magnitude estimates suggest that it is just as likely that the flows are dominated by bottom induced vertical velocities as they are directly driven by the wind stress curl

why western boundary currents in realistic oceans are inviscid a link between form stress and bottom pressure torques it is shown that wind stress curl is balanced by bottom pressure torque in a zonal integral over any strip wide enough to smooth out the effect of nonlinear terms typically about 3 of latitude the derivation is completely general as long as the zonal wind stress is balanced by form stress at each latitude as is known to be the case in the ocean this implies that viscous torques are not important in western boundary currents their place being taken by bottom pressure torques the prediction is confirmed in the context of a global eddy permitting numerical ocean model this link between form stress and bottom pressure torques makes it easier to consider southern ocean dynamics and subtropical gyre dynamics in the same conceptual framework with topographic interactions being important in both cases

the canary basin contribution to the seasonal cycle of the atlantic meridional overturning circulation at 26 n this study examines the seasonal cycle of the atlantic meridional overturning circulation amoc and its eastern boundary contributions the cycle has a magnitude of 6 sv as measured by the rapid mocha wbts project array at 26 n which is driven largely by the eastern boundary the eastern boundary variations are explored in the context of the regional circulation around the canary islands there is a 3 month lag between maximum wind forcing and the largest eastern boundary transports which is explained in terms of a model for rossby wave generated at the eastern boundary two dynamic processes take place through the lanzarote passage lp in fall the recirculation of the canary current and the northward flow of the intermediate poleward undercurrent in contrast during the remaining seasons the transport through the lp is southward due to the canary upwelling current these processes are linked to the seasonal cycle of the amoc

emplacement and inflation of pahoehoe sheet flows observations and measurements of active lava flows on kilauea volcano hawaii inflated pahoehoe sheet flows have a distinctive horizontal upper surface which can be several hundred meters across and are bounded by steep monoclinal uplifts the inflated sheet flows we studied ranged from 1 to 5 m in thickness but initially propagated as thin sheets of fluid pahoehoe lava generally 20 30 cm thick individual lobes originated at outbreaks from the inflated front of a prior sheet flow lobe and initially moved rapidly away from their source velocities slowed greatly within hours due to radial spreading and to depletion of lava stored within the source flow as the outward flow velocity decreases cooling promotes rapid crustal growth at first the crust behaves plastically as pahoehoe toes form after the crust attains a thickness of 2 5 cm it behaves more rigidly and develops enough strength to retain incoming lava thus increasing the hydrostatic head at the flow front the increased hydrostatic pressure is distributed evenly through the liquid lava core of the flow resulting in uniform uplift of the entire sheet flow lobe initial uplift rates are rapid flows thicken to 1 m in 1 2 hours but rates decline sharply as crustal thickness increases and as outbreaks occur from the margins of the inflating lobe one flow reached a final thickness of nearly 4 m after 350 hr inflation data define power law curves whereas crustal cooling follows square root of time relationships the combination of data can be used to construct simple models of inflated sheet flows as the flow advances preferred pathways develop in the older portions of the liquid cored flow these pathways can evolve into lavatube systems within a few weeks formation of lava tubes results in highly efficient delivery of lava at velocities of several kilometers per hour to a flow front that may be moving 1 2 orders of magnitude slower if advance of the sheet flow is terminated the tube remains filled with lava that crystallizes in situ rather than draining to form the cave like lava tubes commonly associated with pahoehoe flows inflated sheet flows from kilauea and mauna loa are morphologically similar to some thick icelandic and submarine sheet flows suggesting a similar mechanism of emplacement the planar sheet like geometry of flood basalt flows may also result from inflation of sequentially emplaced flow lobes rather than nearly instantaneous emplacement as literal floods of lava

interpretations of the jebar term abstract in diagnostic calculations of the ocean s circulation the so called jebar joint effect of baroclinicity and relief term may induce a significant depth average current field as has been noted in the oceanographic literature here we present two consistent interpretations of this term in the equation governing the vorticity of the depth averaged current a topographic vortex stretching term proportional to the dot product of depth averaged velocity and the depth gradient arises we show that jebar corrects this term by removing the contribution of the geostrophic flow referenced to the bottom which cannot generate topographic vortex stretching in the evolution equation for the vorticity of the depth integrated flow a bottom torque term is present we show that the jfbar term discussed above enters here as a contribution to the bottom torque emphasizing the role of jebar as a forcing term we also show that when a diagnostic calculation is formulated completely in terms of the transport str

structure and origin by injection of lava under surface crust of tumuli lava rises lava rise pits and lava inflation clefts in hawaii tumuli are positive topographic features that are common on hawaiian pahoehoe lava flow fields particularly on shallow slopes and 75 measured examples are presented here to document the size range tumuli form by up tilting of crustal plates without any crustal shortening and are thus distinguished from pressure ridges which are up buckled by laterally directed pressure the axial or star like systems of deep clefts that characterize tumuli are defined here as lava inflation clefts their tips advanced into red hot lava and they widened as uplift proceeded and while the lava crust was thickening flat surfaced uplifts formed like tumuli by injection of lava under a surface crust were previously called pressure plateaus but lava rise is proposed instead the pits that abound among lava rises previously attributed to collapse or subsidence are generally formed because the lava around them rose and the name lava rise pit is proposed unique examples of tumuli and lava rises from which lava drained out under a surface crust 1 5 to 2 5 m thick are described from kilauea caldera these examples show that in tumuli and lava rises the crust floats on considerable bodies of fluid lava and is able to do so because of its higher vesicle content the fluid lava loses many of its gas bubbles during residence beneath the crust the bulk densities of samples from tumuli show a general downward increase the form of the density profile is consistent with the relationship that for any given crustal thickness the density of fluid lava closely matched the average density of that crust suggesting that the lava was stably density stratified it is inferred that stable stratification was regulated by out flows of the more vesicular lava fractions loss of bubbles through the lava inflation clefts and entry of injected lava at its level of neutral buoyancy below the uppermost meter the downward decrease in vesicularity closely conforms with that expected by compression of a uniform mass of gas per unit mass of lava

lava field evolution and emplacement dynamics of the 2014 2015 basaltic fissure eruption at holuhraun iceland abstract the 6 month long eruption at holuhraun august 2014 february 2015 in the bar arbunga vei ivotn volcanic system was the largest effusive eruption in iceland since the 1783 1784 ce laki eruption the lava flow field covered 84 km2 and has an estimated bulk i e including vesicles volume of 1 44 km3 the eruption had an average discharge rate of 90 m3 s making it the longest effusive eruption in modern times to sustain such high average flux the first phase of the eruption august 31 2014 to mid october 2014 had a discharge rate of 350 to 100 m3 s and was typified by lava transport via open channels and the formation of four lava flows no 1 4 which were emplaced side by side the eruption began on a 1 8 km long fissure feeding partly incandescent sheets of slabby p hoehoe up to 500 m wide by the following day the lava transport got confined to open channels and the dominant lava morphology changed to rubbly p hoehoe and a the latter became the dominating morphology of lava flows no 1 8 the second phase of the eruption mid october to end november had a discharge of 100 50 m3 s during this time the lava transport system changed via the formation of a 19 km2 of the flow field the primary lava morphology from this phase was spiny p hoehoe which superimposed on the a lava flows no 1 3 and extended the entire length of the flow field i e 17 km this made the 2014 2015 holuhraun a paired flow field where both lava morphologies had similar length we suggest that the similar length is a consequence of the p hoehoe is fed from the tube system utilizing the existing a lava channels and thereby are controlled by the initial length of the a flows

what sets the mean transport through drake passage twelve experiments with two coarse resolutions of a global ocean model using a variety of surface forcings are analyzed to address the question of what sets the mean transport through drake passage seven of the experiments do not have an active sea ice model but the remaining five do previous theories have suggested that the drake passage transport is governed by the cape horn sverdrup transport or alternatively is proportional to the square root of the meridional ekman transport at the latitude of drake passage the results presented here do not support either of these theories the drake passage transport depends quite strongly on the isopycnal diffusivity parameter in the model and less strongly on the background vertical diffusivity and horizontal viscosity parameters however when the magnitudes of these parameters are fixed the results show a very strong correlation between drake passage transport and both the strength of the meridional ekman transport at the latitude of drake passage and the thermohaline circulation off the antarctic shelf the relationships are monotonic but not linear the best estimate is that the meridional ekman transport drives 100 sv of drake passage transport while the remaining 30 sv are driven by the global thermohaline circulation

development of tumuli in the medial portion of the 1983 aa flow field mount etna sicily a number of tumuli formed on the aa dominated lava fan complex which developed in the medial zone of the 1983 flow field of mount etna during the later stages of the eruption this complex flow field formed on shallow sloping ground below a scarp between 1900 and 1700 m asl a major tube system fed a branching tube network in the fan complex numerous tumuli and break outs of lava formed in the fan three main types of tumulus are identified 1 focal tumuli which are formed from the break up and uplift of old thick lava crust and themselves become sustained sites for the distribution of lava both as flows and within distributary tubes these focal tumuli are significant centres associated with major tubes 2 satellite tumuli which are typically elongate whale back shaped features that branch out from focal tumuli these satellite tumuli were initially lava flows erupted from a focal tumulus the crust of the flow slowed or came to a halt and the rigid crust became uplifted and fractured forming a dome shaped ridge feature these satellite tumuli continued to be fed from the focal tumulus and became sites of lava emission with numerous break outs 3 distributary tumuli formed on the fan associated with short lived break outs from tubes and are relatively simple structures formed from limited effusion of toey lobes and pahoehoe lava the major tumuli on the fan complex show distinct dilation fractures the fracture surfaces provide good exposure of the crust and three distinct zones are recognised an upper zone showing columnar jointing a middle zone consisting of planar fracture surfaces and a basal zone with distinctive banded planar fracture surfaces showing evidence of both brittle and ductile formation using these data a model is proposed for tumulus growth field analysis of the fan complex shows how it was fed by a branching tube system leading to flow thickening formation of tumuli and numerous ephemeral boccas

sverdrup and nonlinear dynamics of the pacific equatorial currents abstract the sverdrup circulation in the tropical pacific is constructed from satellite scatterometer winds compared with measured ocean currents and diagnosed in an ocean gcm previous depictions of the sverdrup circulation near the equator have shown only weak vertically integrated flows here it is shown that the actual transports are not weak this discrepancy could be due either to inaccuracies in the wind forcing or to sverdrup dynamics being too simple in this region scatterometer winds show a strip of positive curl along the sst front north of the equator in the eastern pacific that is due to wind speed changes induced by the front including that additional element of curl forcing greatly improves the realism of the sverdrup representation but the magnitudes of the equatorial transport are still too small by a factor of about 2 although the nonlinear advective and friction terms are small in the model momentum balance they are o 1 in the vorticity balance especially because their meridi

effect of slope on development of pahoehoe flow fields evidence from mount etna abstract we describe and compare two types of pahoehoe on mount etna one similar to an hawaiian inflated flow field consisting of tumuli lava rises and lava rise pits and the other a coalescing complex of rootless centres of ephemeral boccas fed from lava tubes and superimposed on an initial a a flow field the former we define as a primary pahoehoe field that results from relatively slow advance rate of lava over an almost horizontal surface the latter is a result of an eruption of long enough duration to allow tube formation over a substantial portion of the flow field over steeper slopes at breaks in slope in the underlying topography centres of ephemeral boccas develop giving rise to low effusion rate pahoehoe lavas covering the original channelled a a surface these we refer to as secondary pahoehoe flow fields

examining rhyolite lava flow dynamics through photo based 3d reconstructions of the 2011 2012 lava flowfield at cordon caulle chile during the 2011 2012 eruption at cordon caulle chile an extensive rhyolitic flowfield was created in excess of 0 5 km3 in volume affording a unique opportunity to characterise rhyolitic lava advance in 2012 and 2013 we acquired approximately 2500 digital photographs of active flowfronts on the north and east of the flowfield these images were processed into three dimensional point clouds using structure from motion and multi view stereo sfm mvs freeware from which digital elevation models were derived sequential elevation models separated by intervals of three hours six days and one year were used to reconstruct spatial distributions of lava velocity and depth and estimate rheological parameters three dimensional reconstructions of flowfronts indicate that lateral extension of the rubbly a like flowfield was accompanied by vertical inflation which differed both spatially and temporally as a function of the underlying topography and localised supply of lava beneath the cooled upper carapace compressive processes also drove the formation of extensive surface ridges across the flowfield continued evolution of the flowfield resulted in the development of a compound flowfield morphology fed by iterative emplacement of breakout lobes the thermal evolution of flow units was modelled using a one dimensional finite difference method which indicated prolonged residence of magma above its glass transition across the flowfield we compare the estimated apparent viscosity 1 21 4 03 1010 pa s of a breakout lobe based on its advance rate over a known slope with plausible lava viscosities from published non arrhenian temperature viscosity models and accounting for crystallinity 50 vol there is an excellent correspondence between viscosity estimates when the lava temperature is taken to be magmatic despite the breakout being located 3 km from the vent and advancing approximately nine months after vent effusion ceased this indicates the remarkably effective insulation of the lava flow interior providing scope for significant evolution of rhyolitic flow fields long after effusive activity has ceased

ocean response to low frequency wind forcing with application to the seasonal variation in the florida straits gulf stream transport abstract the linear response of a two layer ocean model to a periodic wind stress curl in the presence of bottom photography has been invesrigated for periods much less than the time taken for the wind generated baroclinic rossby waves to pass over the topography i e short periods the ocean response is primarily that for a homogenous ocean and thus strongly modified by topography for periods much longer than this time i e long periods the rossby waves compensate for the effect of topography and the non topographic sverdrup balance holds at intermediate periods the phase and amplitude of the transport variations over topography can be understood in terms of a non equilibrium baroclinic response forcing the barotropic mode over topography with relatively little feedback from the barotropic mode a the bottom topography therefore imposes a low pass filter on the transport variations for the atlantic at 25 n the long period limit is of the order of years to decades depending on the location of the wind stress variability so at annual period the non topographic sverdrup balance is not applicable variations in transport can be forced by a wind stress over varying topography and by the passage of a coastal baroclinic kelvin wave over topography at short periods including the annual the effect of strong bottom topography is similar to that of an island it was found that both with and without associated bottom topography a north south island acts as a spatial filter such that wind stress forcing of larger north south scale to the east of the island contributes proportionately more to transport variations to the west of the island than forcing of smaller north south scale

on the midlatitude circulation in a high resolution model of the north atlantic this paper describes and establishes the dynamical mechanisms responsible for the large scale time mean midlatitude circulation in a high resolution model of the north atlantic basin the model solution is compared with recently proposed transport schemes and interpretations of the dynamical balances operating in the sub tropical gyre in particular the question of the degree to which sverdrup balance holds for the subtropical gyre is addressed at 25 n thermohaline driven bottom flows cause strong local departures from the sverdrup solution for the vertically integrated meridional mass transport but these nearly integrate to zero across the interior of the basin in the northwestern region of the subtropical gyre in the vicinity of the gulf stream higher order dynamics become important and linear vorticity dynamics is unable to explain the model s vertically integrated transport in the subpolar gyre the model transport bears little resemblance to the sverdrup prediction and higher order dynamics are important across the entire longitudinal extent of the basin the sensitivity of the model transport amplitudes patterns and dynamical balances are estimated by examining the solutions under a range of parameter choices and for four different wind stress forcing specifications taking into account a deficit of 7 10 sv sv 106 m3 s 1 in the contribution of the model thermohaline circulation to the meridional transports at 25 n the wind stress climatology of isemer and hasse appears to yield too strong of a circulation while that derived from the ncar community climate model yields too weak of a circulation the hellerman and rosenstein and ecmwf climatologies result in wind driven transports close to observational estimates at 25 n the range between cases for the annual mean southward transport in the interior above 1000 m is 14 sv which is 40 70 of the mean transport itself there is little sensitivity to the model closure parameters at this latitude at 55 n in the subpolar gyre there is little sensitivity of the model solution to the choice of either closure parameters or wind climatology despite large differences in the sverdrup transports implied by the different wind stress datasets large year to year variability of the meridional transport east of the bahamas makes it difficult to provide robust estimates of the sensitivity of the antilles and deep western boundary current systems to forcing and parameter changes

global ocean circulation during 1992 1997 estimated from ocean observations and a general circulation model 1 a three dimensional oceanic state is estimated for the period 1992 1997 as it results from combining large scale ocean data sets with a general circulation model at the cost of increased computational load the estimation assimilation method is chosen specifically so that the resulting state estimate is consistent with the model equations having no artificial sources or sinks to bring the model into close agreement with observations its initial temperature and salinity conditions are permitted to change as are the time dependent surface fluxes of momentum heat and freshwater resulting changes of these control vectors are largely consistent with accepted uncertainties in the hydrographic climatology and meteorological analyses the assimilation procedure is able to correct for many of the traditional shortcomings of the flow field by changing the surface boundary conditions changes in the resulting flow field are predominantly on the gyre scale and affect many features that are often poorly simulated in traditional numerical simulations such as the strengths of the gulf stream and its extension the azores current and the anticyclonic circulation associated with the labrador sea tests of the results and their consistency with prior error assumptions show that the constrained model has moved considerably closer to the observations imposed as constraints but has also moved closer to independent data from the world ocean circulation experiment not used in the assimilation procedure in some regions where the comparisons remain indeterminate not enough ocean observations are available and it is difficult to ascribe the residuals to either the model or the observations although problems remain a useful first solution to the global time dependent ocean state estimation problem has been found the estimates will continue to improve through the evolution of numerical models computer power increases more data and more efficient estimation methods

geotechnical assessment of a landslide along a natural gas pipeline for possible remediations karacabey turkey a new natural gas pipeline with a 0 90 m diameter is under construction to provide a gas connection between turkey and greece as well as to create a gas ring for southern europe the new pipeline route lies next to an existing small diameter gas pipeline broken by a landslide that occurred in february 2006 near karacabey bursa although the existing pipeline has been temporarily repaired either the pipeline route should be relocated or the landslide should be stabilized the geological survey conducted in the study area reveals that relocation is not feasible due to the existence of other landslides in close vicinity to the site in order to investigate the causes of the landslide and to suggest possible remedial measures geotechnical investigations including surface geological mapping trial pitting drilling with field tests inclinometer measurements laboratory testing and limit equilibrium analyses were conducted the investigation revealed that the unconsolidated clayey soil slid on claystone along a non circular failure surface based on the gathered data possible remedial measures including partial removal of landslide material and construction of toe buttresses slope flattening lowering the pipeline and surface drainage systems were evaluated these are suggested to prevent the reactivation of the landslide and thus to establish a safe route for both the existing and the new pipelines

the relation of meridional pressure gradients to north atlantic deep water volume transport in an ocean general circulation model we use a coarse resolution ocean general circulation model to study the relation between meridional pressure and density gradients in the southern ocean and north atlantic and the atlantic meridional overturning circulation in several experiments we artificially modify the meridional density gradients by applying different magnitudes of the gent mcwilliams isopycnal eddy diffusion coefficients in the southern ocean and in the north atlantic and investigate the response of the simulated atlantic meridional overturning to such changes the simulations are carried out close to the limit of no diapycnal mixing with a very small explicit vertical diffusivity and a tracer advection scheme with very low implicit diffusivities our results reveal that changes in eddy diffusivities in the north atlantic affect the maximum of the atlantic meridional overturning but not the outflow of north atlantic deep water into the southern ocean in contrast changes in eddy diffusivities in the southern ocean affect both the south atlantic outflow of north atlantic deep water and the maximum of the atlantic meridional overturning results from these experiments are used to investigate the relation between meridional pressure gradients and the components of the atlantic meridional overturning pressure gradients and overturning are found to be linearly related we show that in our simulations zonally averaged deep pressure gradients are very weak between 20 s and about 30 n and that between 30 n and 60 n the zonally averaged pressure grows approximately linearly with latitude this pressure difference balances a westward geostrophic flow at 30 40 n that feeds the southbound deep atlantic western boundary current we extend our analysis to a large variety of experiments in which surface freshwater forcing vertical mixing and winds are modified in all experiments the pycnocline depth assumed to be the relevant vertical scale for the northward volume transport in the atlantic is found to be approximately constant at least within the coarse vertical resolution of the model the model behaviour hence cannot directly be related to conceptual models in which changes in the pycnocline depth determine the strength of atlantic meridional flow and seems conceptually closer to stommel s box model in all our simulations the atlantic overturning seems to be mainly driven by southern ocean westerlies however the actual strength of the atlantic meridional overturning is not determined solely by the southern ocean wind stress but as well by the density pressure gradients created between the deep water formation regions in the north atlantic and the inflow outflow region in the south atlantic

characteristics of the atlantic storm track eddy activity and its relation with the north atlantic oscillation abstract this study focuses on feedbacks of the high frequency eddy activity onto the quasi stationary circulation particularly with regard to the north atlantic oscillation nao the methodology consists of analyzing ncep ncar reanalysis data and sensitivity runs from a high resolution nonhydrostatic regional model consistent with recent studies results show that the jet displacement characteristic of the nao phenomenon depends strongly on the dynamics of the synoptic scale waves and the way they break positive and negative phases of the nao are closely related to anticyclonic and cyclonic wave breaking respectively indeed the high frequency momentum flux whose sign is directly related to the type of wave breaking is correlated with the nao index over the atlantic the peak of the momentum flux signal precedes that of the nao by a few days suggesting that wave breaking is triggering nao events two examples illustrate the significant impact of single storms in particular those occurring in the e

the evolution of lava flows from ephemeral vents at mount etna insights from vesicle distribution and morphological studies abstract lava flow units from ephemeral vents at mount etna are characterized by a cross flow subdivision into zones with different surface morphology symmetrically distributed with respect to the centerline of the flow these zones are 1 a central zone cp zone with a relatively smooth surface near the vent 2 a lateral zone lp zone covered by a carpet of clinkers overlying the massive lava body and 3 a lateral levee zone ll zone in many cases the cp and lp zones are separated by an inward dipping groove and the cp zone is from some decimeters up to more than 1 m thicker than the adjacent lp zone in sections perpendicular to the flow direction the vesicles corresponding with the cp zone are systematically distributed in a ring like region and are characterized by a sub elliptical shape with their minor axes along a direction radial to the center of such region vesicles corresponding with the lp zone are still elliptical and their major axes tend to be parallel to the nearest cooling surface vesicularity is the lowest at the center of the ring like region where vesicles approach a spherical shape in the upper part of the ring like region vesicle accumulation and coalescence below the crust produces one or more gas rich layers which act as levels of preferential detachment for the formation of lava tubes the observed morphological characteristics and reconstructed vesicle distribution patterns are consistent with a radial distribution of velocity within the lava flow unit and suggest the existence of an inner plug flow region where the velocity gradient is zero a simple evolution scheme is proposed in which a lava flow unit from ephemeral vent invariably evolves to a lava tube through the downward migration of the plug flow region the progressive reduction of the cross flow section due to cooling produces a pressure increase within the flowing lava body and the thickening of the active central portion of the lava flow unit in order to satisfy mass conservation