pacific equatorial subsurface countercurrent velocity transport and potential vorticity concurrent shipboard adcp and ctd sections are used to calculate the mean velocity transport and potential vorticity fields associated with the pacific equatorial subsurface countercurrents sccs averaged in stream coordinates the core eastward velocity of the sccs is a factor of 2 higher than previously reported means but the estimated transports are unchanged the meridional profile of zonal velocity along isopycnals is sharply peaked and nearly linear on each flank of the current the sharp and strong reversal of relative vorticity over a distance of 20 km at the jet core sharpens the coincident potential vorticity front this front separates a region of very low homogeneous potential vorticity on the equatorward side from a homogeneous high potential vorticity region on the poleward side each potential vorticity pool extends well beyond the edges of the scc into regions of westward flow on the equatorward sides of the sccs this westward flow is the equatorial intermediate current in the western pacific but in the central and eastern parts of the basin it is off the equator in deep extensions of the south equatorial current in the central and eastern regions the net westward transport in an isopycnal layer between the sccs exceeds the combined eastward scc transport in that layer the net zonal transport between the scc cores is highly divergent in the east and convergent in the west this pattern together with downstream changes in scc density indicates that neither they nor the westward return flows are simple inertial recirculations strong diapycnal processes must be involved

pacific subtropical cell response to reduced equatorial dissipation abstract equatorial turbulent diffusivities resulting from breaking gravity waves may be more than a factor of 10 less than those in the midlatitudes a coupled general circulation model with a layered isopycnal coordinate ocean is used to assess pacific climate sensitivity to a latitudinally varying background diapycnal diffusivity with extremely low values near the equator the control experiments have a minimum upper ocean diffusivity of 10 5 m2 s 1 and are initialized from present day conditions the average depth of the 26 4 interface z26 4 in the pacific increases by 140 m after 500 yr of coupled model integration this corresponds to a warming trend in the upper ocean low equatorial diffusivities reduce the z26 4 bias by 30 isopycnal surfaces are elevated from the eastern boundary up to midlatitudes by cooling in the upper several hundred meters partially compensated by freshening entrainment of intermediate water masses from below 26 4 decreases by 1 5 sv 1 sv 106 m3 s 1 m

magnetic susceptibility of the rock matrix related to magnetic fabric studies non ferromagnetic minerals constitute what is called the rock matrix whose susceptibility k1 is directly accessible using only high magnetic fields measurements on minerals and a wide range of rock types show that k1 is mainly due to paramagnetism and hardly exceeds 10 3 si with an anisotropy degree p less than 1 35 different methods to estimate the role of the matrix component in low field susceptibility k and its anisotropy include petrological and chemical analysis evolution of p vs k low temperature studies and comparison of k with remanent magnetizations

on the boundary flow off brazil at 5 10 s and its connection to the interior tropical atlantic 1 within the context of the german clivar program an observational program in the western tropical atlantic with shipboard sections profiling floats and a moored array aims at studying the role of the shallow thermohaline subtropical cell stc in tropical subtropical interactions and the cold water transports underneath from 6 repeated shipboard profiling sections off brazil near 5 s a northward warm water transport above 1100 m of 25 0 4 4 sv is determined of which 13 4 2 7 sv occur in the thermocline layer supplying the equatorial undercurrent trajectories of 15 profiling floats released near the western boundary are presented that drift at shallow levels 200 m and 400 m and delineate the different stc branches for the southward flow of north atlantic deep water nadw a section mean transport of 31 7 9 2 sv was determined at 5 s however different from the steady nadw flow observed earlier along the topography north of the equator the nadw currents at 5 10 s are much more variable with long periods of northward counterflow along the topography

pathways and variability of the off equatorial undercurrents in the atlantic ocean the cold upwelling waters of the eastern tropical oceans not only interact with the atmospheric circulation via changing the sea surface temperatures but also influence the biological activity via affecting the nutrient and oxygen contents of the upwelling waters while the sources of the equatorial upwelling associated with the equatorial undercurrent euc have been studied extensively the relevance of the northern and southern off equatorial undercurrents neuc seuc for the off equatorial upwelling regions has remained unclear in this study we use output from a high resolution 1 12 model flame to investigate the mean pathways and variability of the off equatorial undercurrents oeucs in the atlantic in particular a calculation of lagrangian trajectories helps to gain insight into the source waters of the oeucs and their connection to the upwelling regions in the eastern tropical atlantic in the model solution the sources of both oeucs belong almost exclusively to the southern hemisphere the pathways of the source waters are found to be governed by strong recirculations between the different eastward and westward zonal currents because of intense eddy motions associated with the tropical instability wave activity whereas the seuc is predominantly fed through the recirculation in the ocean interior the neuc is also fed by a weak inflow from the western boundary current investigation of the fate of the neuc shows only a weak direct supply to the upwelling in the guinea dome and along the african coast but a significant contribution to the equatorial upwelling

the pacific subsurface countercurrents and an inertial model abstract the tsuchiya jets or subsurface countercurrents extend across the pacific ocean carrying 7 2 106 m3 s 1 eastward on each side of the equator mean meridional sections of potential temperature salinity neutral density anomaly and the square of buoyancy frequency are presented for the western central and eastern tropical pacific ocean these sections are used together with maps of depth and salinity on isopycnals as well as thickness between isopycnals to describe the evolution of the tsuchiya jets as they flow from west to east an inertial jet model is formulated in which conservation of the bernoulli function and potential vorticity combine with the eastward shoaling of the tropical pycnocline to dictate the jet structure this model jet is consistent with a number of features of the tsuchiya jets their roughly constant volume transports their advection of properties such as salinity and oxygen over long zonal distances their rapidity and narrowness their poleward shift from we

middepth circulation of the eastern tropical south pacific and its link to the oxygen minimum zone there is an incomplete description of the mid depth circulation and its link to the oxygen minimum zone omz in the eastern tropical south pacific subsurface currents of the omz in the eastern tropical south pacific are investigated with a focus at 400 m depth close to the core of the omz using several acoustic doppler current profiler sections recorded in january and february 2009 five profiling floats with oxygen sensors were deployed along 85 50 w in february 2009 with a drift depth at 400 m their spreading paths are compared with the model flow field from a 1 10 tropical pacific model tropac01 and the simple ocean data assimilation soda model overall the mean currents in the eastern tropical south pacific are weak so that eddy variability influences the flow and ultimately feed oxygen poor water to the omz the center of the omz is a stagnant area so that floats stay much longer in this region and can even reverse direction in one case of one float deployed at 8 s returned to the same location after 15 month on the northern side of the omz in the equatorial current system floats move rapidly to the west most current bands reported for the near surface layer exist also in the depth range of the omz a schematic circulation flow field for the omz core depth is derived which shows the northern part of the south pacific subtropical gyre south of the omz and the complicated zonal equatorial flow field north of the omz

subsurface connections in the eastern tropical pacific during la nina 1999 2001 and el nino 2002 2003 1 the subsurface connections between the equatorial current system ecs and the peru current system pcs between 1999 and 2005 are investigated with a primitive equation eddy resolving regional model that is forced with realistic atmospheric and lateral oceanic conditions specific attention is given to the 1999 2000 la nina and the 2002 2003 el nino the model s skill is assessed through a comparison with satellite derived sea level anomalies and in situ sea surface temperature time series the model reproduces fairly well the known dynamics of the region for climatological conditions and the numerical solution obtained for the particular 1999 2000 and 2002 2003 events presents patterns rather typical of cold and warm phases of el nino southern oscillation enso eulerian and lagrangian diagnoses are used to derive relevant information about the density and velocity vertical structures of the ecs and the pcs the transports of the major currents in the region are shown to differ a lot between the 1999 2000 la nina and the 2002 2003 el nino the equatorial subsurface currents transfer significantly more water into the eastern tropical pacific during la nina than during el nino whereas the peru chile undercurrent pcuc carries more water during el nino the equatorial subsurface currents and especially the primary southern subsurface countercurrent contribute to 80 of the pcuc transport during the 1999 2000 cold phase this ratio falls down to only 20 during the 2002 2003 warm phase

on the leading negative phase of major 2010 2014 tsunamis time series observations from instruments sited in the deep ocean and along coastal margins of the pacific during major tsunami events in the years since 2010 were systematically processed examination of these records during four events 2010 chile maule 2011 east japan tohoku 2012 haida gwaii and 2014 chile iquique show the prevalence of a small negative phase leading the first major positive tsunami wave a phase that is not typically reproduced by current modelling approaches we present leading negative phase signatures in examples from the more than 40 deep ocean bottom pressure and approximately 200 tide gauge records investigated for this study high sampling rate time series 15 s were given greater weight in our investigation than the more readily available 1 min series careful investigation of tsunami arrival at each deep ocean site highlights the role filtering techniques may play in misleading researchers or masking specific tsunami features such as the leading negative phase that is the basis of this study the main focus of this investigation is to characterise the scale and repeatability of the phenomenon in support of recent similar findings rather than to provide a definitive explanation as to the cause in general our findings are in good agreement with and support the theoretical results of watada et al j geophys res solid earth 119 4287 4310 2014

magnetic fabric and remanence analyses of cores from the u s continental margin and the vema channel abstract paleomagnetic analyses have been performed on 8 cc cubic samples from 20 gravity and piston cores 172 samples taken at the base of the u s continental margin in the region of a deep western boundary undercurrent dwbuc and from 28 gravity and piston cores 484 samples from the eastern flank on the vema channel downcore remanent magnetic rm and magnetic fabric measurements have been performed on these samples to examine the effects of depositional mechanisms on the magnetization of sediment at both sites vector diagrams after stepwise a f demagnetization to 50 mt for both suites of samples indicate variable rm stability above 8 10 cm depth below this depth samples exhibit a stable apparently primary rm after demagnetization to fields of 10 mt these results indicate that if the rm is to be used to orient these deep sea cores samples should be chosen from greater than 10 cm depth in core and demagnetized to at least 10 mt fabric analyses based on anisotropy of magnetic susceptibility ams measurements reveal primary sedimentary fabric in most cores from the u s continental margin but anomalous fabric below 40 80 cm depth in some vema channel cores this anomalous fabric is believed to be the result of soft sediment deformation at the site ams long axis alignments are essentially random for these vema channel cores under the dwbuc however the dominant fabric appears to be normal to the current flow direction while cores from outside the dwbuc exhibit a long axis ams alignment which parallels bottom contours the magnetic fabric parameter f s for core top samples on the eastern flank of the vema channel exhibits high values directly under fast flowing antarctic bottom water aabw and relatively low values under more sluggish water masses above aabw these f s results are consistent with those reported for earlier vema channel studies and for results from dwbuc core top samples

water mass and transport variability at 110 w in the equatorial pacific abstract an analysis of nine hydrographic sections collected in 1979 81 along 110 w in the equatorial pacific ocean is presented sections typically sampled the upper 500 m of the water column from 10 n to 3 s analysis concentrated on the repeated sections north of the equator examination of the variability of eastward transport indicates that the north equatorial countercurrent necc and the northern subsurface countercurrent nscc cannot be distinguished solely on the basis of water mass structure however using a potential density surface 25 0 as a current boundary we find that on average the nscc transports 13 7 106 m3 s 1 compared to only 8 3 106 m3 s 1 for the necc the nscc flow is sufficiently stable so that meridional surface dynamic height gradient remains a good index of zonal transport fluctuations variations in surface dynamic height observed in our data and in the eastropac data indicate a seasonal cycle to the surface topography with large values for the equatorial and coun

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

south equatorial undercurrent in the western to central tropical atlantic 1 the south equatorial undercurrent seuc in the western to central tropical atlantic is investigated by a combination of shallow floats with a few acoustically tracked shipboard current measurements and hydrography float trajectories show a well confined seuc revealing large standing meanders near its western origin transports determined from 31 sections across the seuc increase from 5 6 sv at 35 w near the western boundary to 10 2 sv 800 km farther east internal recirculations north and south of the seuc were indicated by the float trajectories and a weak transport reduction farther along its eastward progression is observed the deep part of the south equatorial current carries on both sides of the seuc interior water masses westward and supplies almost 5 sv to the seuc between 35 w and 28 w or about half of the seuc transport in the interior tropical atlantic

spectral analysis of tsunami waves separation of source and topography effects a new approach is proposed to separate the influence of source and topography in observed tsunami spectra and to reconstruct the initial source spectrum the method assumes a linear tide gauge response to external forcing and is based on comparative analysis of tsunami and background spectra evaluation of the ratio of tsunami to background spectra gives functional characteristics that are invariant of station location and dependent only on the source parameters three events the urup tsunami of december 22 1991 northwest pacific the hokkaido southwest okushiri tsunami of july 12 1993 sea of japan and the shikotan tsunami of october 4 1994 northwest pacific are used as examples of the proposed approach the source spectra reconstructed from the analysis of different tide gauges were found to be in good agreement with each other and with the seismological geodetic and field survey data

enso s impact on the gap wind regions of the eastern tropical pacific ocean abstractthe recently released ncep climate forecast system reanalysis cfsr is used to examine the response to enso in the northeast tropical pacific ocean netp during 1979 2009 the normally cool pacific sea surface temperatures ssts associated with wind jets through the gaps in the central american mountains at tehuantepec papagayo and panama are substantially warmer colder than the surrounding ocean during el nino la nina events ocean dynamics generate the enso related sst anomalies in the gap wind regions as the surface fluxes damp the ssts anomalies while the ekman heat transport is generally in quadrature with the anomalies the enso driven warming is associated with large scale deepening of the thermocline with the cold thermocline water at greater depths during el nino in the netp it is less likely to be vertically mixed to the surface particularly in the gap wind regions where the thermocline is normally very close to the surface the thermocline deepening is enhanced to the south

a comparison of different magnetic methods for determining the relative grain size of magnetite in natural materials some results from lake sediments abstract a new rapid method for identifying relative grain size variations in magnetic involves the parameter anhysteretic susceptibility arm i e specific arm obtained in a 1 oe steady field which is particularly sensitive to the single domain sd and small pseudo single domain psd grains of the finer magnetite fraction a second parameter low field susceptibility is relatively more sensitive to the coarser magnetite fraction larger psd and smaller multidomain md grains we can then obtain a measure of the ratio of coarse to fine grain magnetite for large numbers of samples by plotting arversus a simple idealized model based on sized magnetite samples is proposed to explain the use of the armversus plot for detecting relative grain size changes in the magnetic content of natural materials the sediments of three lakes that contain magnetite or a similar magnetic carrier and have a wide range of values of arm and are used to test the model the model is used to interpret the magnetic variations observed and the interpretations are supported by high field hysteresis measurements of the same sediments the combination of the high field hysteresis method of day et al 1 and the arm vs method is a powerful technique allowing the rapid identification of both the relative grain size and domain state for large numbers of samples containing magnetite the armvs method should be used as an intial means of identifying distinct groups of samples the high field hysteresis method should then be applied to a few representative samples from each group to confirm the initial interpretation

subthermocline and intermediate zonal currents in the tropical pacific ocean paths and vertical structure abstractthe mean subthermocline and intermediate zonal circulation in the tropical pacific is investigated using a compilation of shipboard adcp measurements and absolute geostrophic velocities constructed from a high resolution 0 2000 m argo climatology referenced to a 1000 m velocity field derived from argo float drifts this reference field is dominated by basinwide alternating zonal jets with a meridional wavelength of about 3 in regions where the sampling of sadcp data is sufficient the consistency between the two independent datasets is striking using the argo drift reference is crucial to capture the current structures two apparently distinct systems of alternating westward and eastward zonal jets are seen in both datasets equatorward of 10 a series of low latitude subthermocline currents llscs below the thermocline extending from about 200 to 800 m including the eastward tsuchiya jets and a series of low latitude intermediate currents llics extending from about 700 to at least 2000

long term tsunami data archive supports tsunami forecast warning research and mitigation in response to the 2004 indian ocean tsunami the united states began a careful review and strengthening of its programs aimed at reducing the consequences of tsunamis several reports and calls to action were drafted including the tsunami warning and education act public law 109 424 signed into law by the president in december 2006 noaa s national geophysical data center ngdc and co located world data center for geophysics and marine geology wdc gmg maintain a national and international tsunami data archive that fulfills part of the p l 109 424 the ngdc wdc gmg long term tsunami data archive has expanded from the original global historical event databases and damage photo collection to include tsunami deposits coastal water level data dart buoy data and high resolution coastal dems these data are used to validate models provide guidance to warning centers develop tsunami hazard assessments and educate the public about the risks from tsunamis in this paper we discuss current steps and future actions to be taken by ngdc wdc gmg to support tsunami hazard mitigation research to ultimately help save lives and improve the resiliency of coastal communities

quasi stationary north equatorial undercurrent jets across the tropical north pacific ocean 1 subthermocline circulation in the tropical north pacific ocean 2 n 30 n is investigated using profiling float temperature salinity data from the international argo and the origins of the kuroshio and mindanao current okmc projects three well defined eastward jets are detected beneath the wind driven westward flowing north equatorial current dubbed the north equatorial undercurrent neuc jets these subthermocline jets have a typical core velocity of 2 5 cms 1 and are spatially coherent from the western boundary to about 120 w across the north pacific basin centered around 9 n 13 n and 18 n in the western basin the neuc jet cores tend to migrate northward by 4 in the eastern basin vertically the cores of the southern central and northern neuc jets reside on the 26 9 27 2 and 27 3 surfaces respectively and they tend to shoal to lighter density surfaces by about 0 2 as the jets progress eastward

intermediate zonal jets in the tropical pacific ocean observed by argo floats abstractargo float data in the tropical pacific ocean during january 2003 august 2011 are analyzed to obtain lagrangian subsurface velocities at their parking depths maps of mean zonal velocities at 1000 and 1500 m are presented at both depths a series of alternating westward and eastward zonal jets with a meridional scale of 1 5 is seen at the basin scale from 10 s to 10 n these alternating jets with mean speeds about 5 cm s 1 are clearly present in the western and central parts of the basin but weaken and disappear approaching the eastern coast they are stronger in the southern hemisphere along the equator at both 1000 and 1500 m a westward jet is seen the jets closer to the equator are remarkably zonally coherent across the basin but the jets farther poleward appear broken in several segments in the western half of the basin the 1000 m zonal jets appear to slant slightly poleward from east to west at the western boundary in the south east of solomon islands and papua new guinea the al

inverse magnetic fabric in carbonate bearing rocks abstract the observation of a magnetic susceptibility ellipsoid whose maximum axis corresponds to the minimum axis of petrofabric pole of bedding or schistosity is referred to as an inverse magnetic fabric the investigation of the magnetic properties of some ferroan carbonate monocrystals and paramagnetic limestones demonstrates that c axis preferred orientation of paramagnetic carbonates results in a maximum susceptibility parallel to the flattening direction inverse magnetic fabrics due to magnetite are also encountered in weakly deformed limestones a mineralogical model based on the property of single domain grains to have a zero susceptibility parallel to their long axis is proposed however more complex cases are also encountered

upper and intermediate circulation in the western equatorial pacific ocean in october 1999 and april 2000 1 the upper and intermediate circulation 0 1200 m in the western equatorial pacific ocean is examined thanks to lowered acoustic doppler current profiler ladcp measurements carried out during two cruises in october 1999 and april 2000 several new features of the equatorial circulation are discussed it is shown that the secondary south subsurface countercurrent ssscc laying at 6 s 400 m depth had a deep extension at 165 e with a maximum core velocity around 5 s 1000 m furthermore the equatorial intermediate current eic and the lower eic leic displayed a strong temporal variability between 165 e and 180 as these two westward currents were replaced by eastward flow along the equator on the second cruise finally during the april 2000 cruise the zonal velocity profile carried out at the equator east of the gilbert island around 175 e broke into small vertical scales possibly reflecting topographic effect and or destabilization mechanism that leads to the formation of long zonal jet like structures

introduction to global tsunami science past and future volume ii twenty two papers on the study of tsunamis are included in volume ii of the pageoph topical issue global tsunami science past and future volume i of this topical issue was published as pageoph vol 173 no 12 2016 eds e l geist h m fritz a b rabinovich and y tanioka three papers in volume ii focus on details of the 2011 and 2016 tsunami generating earthquakes offshore of tohoku japan the next six papers describe important case studies and observations of recent and historical events four papers related to tsunami hazard assessment are followed by three papers on tsunami hydrodynamics and numerical modelling three papers discuss problems of tsunami warning and real time forecasting the final set of three papers importantly investigates tsunamis generated by non seismic sources volcanic explosions landslides and meteorological disturbances collectively this volume highlights contemporary trends in global tsunami research both fundamental and applied toward hazard assessment and mitigation

eastern pacific oxygen minimum zones supply paths and multidecadal changes the supply of oxygen rich water to the oxygen minimum zones omzs of the eastern north and south pacific via zonal tropical currents is investigated using shipboard acoustic doppler current profiler and hydrographic section data near the equator the equatorial undercurrent euc northern and southern subsurface countercurrents sccs and the northern and southern intermediate countercurrents iccs all carry water that is oxygen richer than adjacent westward flows thereby providing a net oxygen supply to the eastern pacific omzs the synoptic velocity weighted oxygen concentration difference between eastward and westward flows is typically 10 50 mol kg 1 subthermocline zonal oxygen fluxes reflect decreasing oxygen concentrations of the euc the sccs and the iccs as they flow eastward approximately 30 year time series in well sampled regions of the equatorial pacific show oxygen content decreasing as rapidly as 0 55 mol kg 1 yr 1 in the major oxygen supply paths of the omzs for a 200 700 m layer and similar trends for a density layer spanning roughly these depths this finding is in gross agreement with climate models which generally predict expanding omzs

the mean and annual cycle of upper layer temperature fields in relation to sverdrup dynamics within the gyres of the atlantic ocean using 28 years of expendable bathythermograph data 1967 1994 we describe the mean and annual cycle of the upper ocean temperature fields in the atlantic from 30 s to 50 n in the context of the basin scale wind driven gyres sverdrup stream function field which provide a framework for describing the oceanographic measurements we examine the circulation field implied by the temperature distributions which are used as a proxy for the field of mass similarities between the temperature and stream function fields increase with depth in the lower to subthermocline depths of the tropical and equatorial gyres the zonal currents form a closed circulation a southeastward boundary current is suggested near and below 150 m that provides closure for the tropical gyre and the equatorial gyre axis is southward of that suggested by the stream function field higher in the water column the north equatorial countercurrent necc may be a surface manifestation of the north equatorial undercurrent neuc where the latter can be interpreted as the southern limb of the tropical gyre because there are large vertical shears in the tropics the equatorial gyre is not clearly indicated in the vertically integrated temperature field but appears below about 200 m here the south equatorial undercurrent seuc can be interpreted as the eastward flowing northern limb of the equatorial gyre and is opposite in direction to the westward flowing south equatorial current above both the neuc and seuc are analagous to currents in the pacific that are governed by non sverdrup dynamics despite the shortcomings of the data the mean annual cycle appears to be relatively stable and we have discounted the possibility that in regions where it represents a significant percentage of the total variance it is changing slowly over the 28 years of record the wind forcing fields which undergo large meridional movements 5 6 of latitude during their annual cycle with some exceptions have essentially no counterpart in gyre movements between their seasonal extremes most of the variability associated with the annual cycle is confined to the upper 300 m greatest variability where ranges exceed 6 c occurs in the northwestern atlantic in late winter and early spring during this time of year south of the gulf stream and below about 100 m water temperatures exhibit a systematic phase lag with depth the next largest area of variability where ranges can also exceed 6 c resides in the tropical western basin between the equator and 10 n just below 100 m in the eastern basin ranges decrease and shoal additionally the phase fields are consistent with the intensification and relaxation of the tropical ridge trough system where the necc disappears in march in the west but the necc neuc complex is strongest in september

mean three dimensional circulation in the northeast tropical pacific abstract historical xbt data are used to construct a mean climatology of the three dimensional geostrophic circulation in the northeast tropical pacific southwest of mexico and central america and are diagnosed based on linear dynamics forced with satellite scatterometer winds unlike the familiar central tropical pacific where the zonal scales are very large and the wind forcing nearly a function of latitude alone the north pacific east of about 120 w is strongly influenced by wind jets blowing through gaps in the central american cordillera the curl imposed by these wind jets imprints on the ocean producing a distinctive pattern of thermocline topography and geostrophic currents that are consistent with the sverdrup balance notably the weakening of the north equatorial countercurrent near 110 w is due to the wind forcing given the observed stratification and wind stress curl planetary vorticity conservation also determines the distribution of vertical velocity in the region with about 3 5 sv

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

origin and significance of complex authigenic carbonates in cretaceous black shales of the western alps abstract cretaceous black shales bearing complex authigenic carbonates are common in some penninic nappes of the western alps in this paper we discuss the petrography mineralogy chemistry and origin of a typical occurrence of these diagenetic carbonates in the pre senonian serenne zone of the embrunais ubaye area at least three types of carbonates with the following average compositions were identified by microprobe analyses mn fe rich dolomite ca1 02 mg 42 fe 24 mn 32 co3 2 ca rich rhodochrosite ca 30 mg1 2 fe 07 mn 51 co3 and mn mg rich siderite ca 07 mg 19 fe 54 mn 20 co3 these carbonates occur as lami ae nodules and layers petrographic results combined with x ray diffraction suggest that mn fe rich dolomite is a relatively early precipitate occurring as fine grained unevenly distributed cement which incorporates zones of less compacted shales its abundance relative to mn mg rich siderite increases towards the center of the diagenetic layers mn mg rich siderite is a late cement as suggested by large evenly distributed rhombs occurring in lower concentrations but with increasing abundance toward the margins relative to mn fe rich dolomite the presence of carich rhodochrosite could not be established with certainty as its 104 xrd peak is located in most samples in the shoulder of the dolomite peak compositional trends suggest equilibrium precipitation between ca ri h rhodochrosite and mn fe rich dolomite isotopic compositions of carbon and oxygen vary between 6 2 and 11 0 13cpdb and between 4 4 and 9 6 18opdb the oxygen being somewhat heavier for mn mg rich siderite 6 1 than for mn fe rich dolomite 8 8 the presence of iron in the authigenic carbonates and the carbon isotopic composition suggest that precipitation occured b low the lower limit of diffusion of sulfate from seawater after the onset of methane production absence of sulfate and high metal and co3 2 activities favored initial precipitation of mn fe rich dolomite which was followed by formation of mn mg rich siderite when an unknown value of fe mn mg ca activities was reached the metals were probably derived from hemipelagic metal rich sediments accumulated just above an oceanic crust the accumulation and preservation of high organic matter contents favored by episodes of an expanded oxygen minimum layer during the mid cretaceous may have promoted the mobilization of fe and mn and their incorporation into complex carbonates

on the dynamics of equatorial subsurface countercurrents abstract the equatorial subsurface countercurrents sscc are strong steady geostrophically balanced eastward flows situated below the high speed core of the equatorial undercurrent euc at 3 5 n and s the dynamics of these currents are explored using a continuously stratified vertically diffusive linear steady state ocean model forced by zonal winds with effectively no wind stress curl model results agree favorably with observations in that both euc and sscc like structures are generated a diagnosis of the model momentum vorticity and continuity balances at various depths and latitudes reveals that the sscc lie outside a vertically diffusive equatorial momentum boundary layer so that both components of velocity are geostrophically balanced they are however located at the poleward of a broader diffusive equatorial vorticity boundary layer within this boundary layer cyclonic vorticity associated with the euc diffuses to the level of the sscc where it is balanced by poleward advection of pla

marshrock formed by iron sulphide and siderite cementation in saltmarsh sediments the formation of authigenic sulphides and other iron minerals has proved interesting both in studies of palaeomagnetism1 and palaeosalinity reconstructions of pleistocene and older sediments2 3 iron sulphide and siderite cemented nodules concretions and layers are fairly common in the geological record4 6 but there is little evidence of their formation in modern environments accounts of authigenic iron minerals forming today in marine and brackish sediments generally refer only to micro concretions 10 500 m in size many of which have a framboidal texture3 7 8 i describe here macro concretions and cemented layers which are now forming within intertidal marsh sediments at warham norfolk uk parts of these marshes are only 30 yr old indicating how quickly early diagenetic cementation can occur siderite feco3 greigite fe3s4 and possibly mackinawite fes1 x are the main cementing agents the term marshrock is proposed for the cemented sediments by analogy with calcareous beachrock9 10 the formation of siderite monosulphide concretions in the warham sediments probably reflects a high reactive iron content and limited sulphate arising from rapid sedimentation and burial of organic matter during the early stages of marsh growth

direct measurements of upper ocean currents and water properties across the tropical pacific during the 1990s abstract meridional sections of upper ocean zonal currents potential temperature and salinity are estimated at ten longitudes from 143 e to 95 w using conductivity temperature depth and acoustic doppler current profiler data from 172 synoptic sections taken in the tropical pacific between 138 e and 86 w mostly in the 1990s data reduction is carried out in a potential isopycnal and mixed layer framework to preserve a sharp pycnocline a mixed layer water property extrema and velocity extrema mean zonal currents potential temperatures and salinities are produced at each longitude the seasonal cycles of these fields are also estimated as well as a simple el nino southern oscillation enso cycle zonal sections along the equator are also presented properties of the near equatorial zonal currents including transports temperatures and salinities are estimated separately from the synoptic sections the seasonal cycles of these quantities and their correlations with the southern oscillation index are investigated the work is distinguished from most existing literature in that direct estimates of zonal velocity are combined with contemporaneous temperature and salinity data allowing trans pacific estimates of near equatorial current transports and properties including those of the northern branch of the south equatorial current the new guinea coastal undercurrent and the equatorial undercurrent

upper ocean water masses and transports in the western tropical pacific 165 e abstract as part of the international toga program the orstom center in noumea new caledonia initiated in january 1984 a series of semi annual cruises along the 165 e meridian from 20 s to 10 n across the equatorial current system of the western pacific this paper presents an analysis of the first six hydrographic 0 1000 m and current 0 600 m sections a detailed description of typical january 1986 vertical structures of temperature salinity and zonal measured velocity is offered differences are noted with structures previously obtained in the tropical pacific compared to the central and eastern pacific the 165 e dataset evidences a much weaker equatorial upwelling and deeper surface isothermal layer and subsurface currents compared to the few western pacific measurements the two speed cores of the equatorial undercurrent euc previously reported at 100 and 200 m are not observed here special attention is given to the eastward equatorial jet 2 s 2 n 0 75 m measured in january 1985 wh

from the subtropics to the central equatorial pacific ocean neodymium isotopic composition and rare earth element concentration variations 1 neodymium isotopic compositions end and rare earth element ree concentrations were measured for filtered surface to deep waters 112 samples in the southern tropical pacific the relatively detailed picture of these tracer distributions allowed us to refine the areas where oceanic end variations occur end values increase for most of the water masses flowing from samoa to the solomon sea and in the papua new guinea png area as already observed furthermore water masses arriving from the eastern equatorial pacific 200 550 m depth also revealed radiogenic values possibly acquired in the vicinity of the south american coasts and galapagos islands these end variations affect the whole water column the most likely process causing such variations is boundary exchange between the numerous radiogenic slopes margins located in this area and seawater flowing past dissolution of atmospheric deposition and or diffuse streaming of volcanic ash are also suggested to explain the radiogenic end observed at the surface in the png area interestingly a positive europium eu anomaly characterizes the normalized ree patterns of most of the studied water masses this anomaly is consistent with the ree patterns of sediment and rock samples that are potential sources for the local waters such consistency reinforces the hypothesis that lithogenic sources play a major role in the oceanic ree budget thanks to boundary exchange the data set presented here is a good basis for further sampling that will be realized in the framework of the ongoing geotraces program www geotraces org

near coastal circulation in the northern humboldt current system from shipboard adcp data the near coastal circulation of the northern humboldt current system is described analyzing 8700 velocity profiles acquired by a shipboard acoustic doppler current profiler sadcp during 21 surveys realized between 2008 and 2012 along the peruvian coast this data set permits observation of i part of the peru coastal current and the peru oceanic current that flow equatorward in near surface layers close to the coast and farther than 150 km from the coast respectively ii the peru chile undercurrent pcuc flowing poleward in subsurface layers along the outer continental shelf and inner slope iii the near surfacing equatorial undercurrent renamed as ecuador peru coastal current that feeds the pcuc and iv a deep equatorward current referred to as the chile peru deep coastal current flowing below the pcuc a focus in the pcuc core layer shows that this current exhibits typical velocities of 5 10 cm s 1 the pcuc deepens with an increasing thickness poleward consistent with the alongshore conservation of potential vorticity the pcuc mass transport increases from 1 8 sv at 5 s to a maximum value of 5 2 sv at 15 s partly explained by the sverdrup balance the pcuc experiences relatively weak seasonal variability and the confluence of eddy like structures and coastal currents strongly complicates the circulation the pcuc intensity is also affected by the southward propagation of coastally trapped waves as revealed by a strong pcuc intensification in march 2010 coincident with the passage of a downwelling coastal wave associated with a weak el nino event

wind driven zonal jets in the south pacific ocean 1 zonal jets west of the large islands of the south pacific ocean are predicted by theory commonly seen in ocean models with sufficiently high resolution and are beginning to be observed these jets are often taken to reflect the blocking effect of the islands in the south equatorial current through island rule dynamics here it is shown that quasi permanent structures of the basin wide wind field imply the existence of jets formed independently of the islands evidence for the existence of the wind driven jets is found in climatological geostrophic currents the hydrographic structures that produce the jets occur well below the thermocline

zonal jets in the pacific ocean 1 the spatial and temporal properties of zonally coherent jet like structures found in high resolution ocean models is examined we focus on the pacific ocean we find the properties of the jets are not very sensitive to the model configuration distinct differences are found in the persistence and vertical structure of the jets poleward of 30 n and s compared with those in the tropics we make a quantitative comparison between the meridional scale of the jets and the rhines scale we find a local scaling applies in that the horizontal variation of the meridional scale of the jets is consistent with horizontal variations in the rhines scale

observing the galapagos euc interaction insights and challenges although sustained observations yield a description of the mean equatorial current system from the western pacific to the eastern terminus of the tropical atmosphere ocean tao array a comprehensive observational dataset suitable for describing the structure and pathways of the equatorial undercurrent euc east of 958w does not exist and therefore climate models are unconstrained in a region that plays acriticalroleinocean atmospherecoupling furthermore oceanmodelssuggestthattheinteractionbetween

equatorially trapped rossby waves in the presence of meridionally sheared baroclinic flow in the pacific ocean topex poseidon altimeter data are analyzed for the 8 5 year period november 1992 to may 2001 to investigate the sea surface height ssh and geostrophic velocity signatures of quasi annual equatorially trapped rossby waves in the pacific the latitudinal structures of ssh and both components of geostrophic velocity are found to be asymmetric about the equator across the entire pacific with larger amplitude north of the equator the westward phase speeds are estimated by several different methods to be in the range 0 5 0 6 m s 1 these observed characteristics are inconsistent with the classical theory for first vertical first meridional mode equatorially trapped rossby waves which predicts a phase speed of about 0 9 m s 1 with latitudinally symmetric structures of ssh and zonal velocity and antisymmetric structure of meridional velocity the observations are even less consistent with the latitudinal structures of ssh and geostrophic velocity components for other modes of the classical theory the latitudinal asymmetries deduced here have also been consistently observed in past analyses of subsurface thermal data and altimeter data and have been variously attributed to sampling errors in the observational data a superposition of multiple meridional rossby wave modes asymmetric forcing by the wind and forcing by cross equatorial southerly winds in the eastern pacific we propose a different mechanism to account for the observed asymmetric latitudinal structure of low frequency equatorial rossby waves from the free wave solutions of a simple 1 5 layer model it is shown that meridional shears in the mean equatorial current system significantly alter the potential vorticity gradient in the central and eastern tropical pacific the observed asymmetric structures of sea surface height and geostrophic velocity components are found to be a natural consequence of the shear modification of the potential vorticity gradient the mean currents also reduce the predicted westward phase speed of first meridional mode rossby waves improving consistency with the observations

anisotropy of magnetic susceptibility in the scaglia rossa pelagic limestone abstract during folding of the scaglia rossa limestone in umbria italy deformation was mainly accommodated by pressure solution cleavage fossils between the cleavage planes appear visibly undeformed yet the limestone possesses a weak magnetic fabric the maximum and intermediate principal axes of the magnetic anisotropy ellipsoid define a distinct magnetic foliation plane within which a weak concentration of the maximum axes forms a magnetic lineation neither of these features is of sedimentary origin results from a slumped outcrop where bedding and a cleavage induced by overburden compaction have different attitudes show that the magnetic foliation is caused by the compaction comparisons with field derived structural data suggest that the magnetic lineation was produced tectonically during deformation of the apennine fold belt

the influence of southern ocean winds on the north atlantic carbon sink observed and predicted increases in southern ocean winds are thought to upwell deep ocean carbon and increase atmospheric co2 however southern ocean dynamics affect biogeochemistry and circulation pathways on a global scale using idealized massachusetts institute of technology general circulation model mitgcm simulations we demonstrate that an increase in southern ocean winds reduces the carbon sink in the north atlantic subpolar gyre the increase in atmospheric co2 due to the reduction of the north atlantic carbon sink is shown to be of the same magnitude as the increase in atmospheric co2 due to southern ocean outgassing the mechanism can be described as follows the increase in southern ocean winds leads to an increase in upper ocean northward nutrient transport biological productivity is therefore enhanced in the tropics which alters the chemistry of the subthermocline waters that are ultimately upwelled in the subpolar gyre the results demonstrate the influence of southern ocean winds on the north atlantic carbon sink and show that the effect of southern ocean winds on atmospheric co2 is likely twice as large as previously thought in past present and future climates

grain size dependence of initial susceptibility and saturation magnetization related parameters of four natural magnetites in the psd md range summary initial susceptibility coercive force and several types of remanent coercive forces were measured on a set of artificial rock specimens containing grain size fractions of a natural magnetite and titanomagnetite both of which are optically homogeneous and a natural titanomagnetite and titanomaghemite both of which show exsolution phenomena it was found subsequently that the optically homogeneous titanomagnetite contains some submicroscopic fe rich inclusions these inclusions are magnetically screened in coarse grains only for the lower grain sizes studied they have an appreciable influence on the data the size of the fractions varied from 5 to 250 m the parameters and several parameter ratios are plotted as a function of grain size several of these parameters can be used as mineralogical and grain size indicators the varying degree of exsolution of the minerals is reflected in the gradients of the plots from plots of initial susceptibility versus grain size it is concluded that the shape of the grains does not play a dominant role in determining the change of this parameter with grain size variation of the various parameters with grain size is explained in terms of a gradual transition from large psd grains to md grains without there being any sharp transition for titanomagnetite x 0 55 the transition takes place at grain sizes that are about 15 m larger than for magnetite

the surface expression of radiocarbon anomalies near baja california during deglaciation abstract periods of declining atmospheric radiocarbon activity 14 c during the heinrich 1 17 8 14 6 ka and younger dryas 12 8 11 5 ka stadials of the last deglaciation coincide with intervals of rising atmospheric co2 as well as evidence of 14c depleted carbon at intermediate ocean depths near baja california mexico and in the arabian sea the latter has been interpreted as the signature of aged carbon emerging through the intermediate ocean to the atmosphere from a previously isolated deep ocean reservoir here we report measurements from near baja california that enable us to reconstruct the 14 c of surface waters as recorded by three different species of planktonic foraminifera we find that surface ocean 14 c recorded by planktonic foraminifera was anomalously low relative to the coeval atmosphere during previously documented periods of low benthic 14 c consistent with upwelling and subsequent mixing and or partial atmospheric equilibration of the intermediate depth benthic signal we also propose an oceanographic explanation for observed 14 c differences between individual planktonic species during deglaciation at this location based on seasonal growth habitats and a seasonal change in the source of coastal upwelling waters from northern in the spring to southern in late summer as the shelf trapped poleward california undercurrent strengthens an analysis of the contemporary hydrography and planktic habitat preferences suggests that g bulloides and g sacculifer record primarily springtime conditions off baja california when the local influence of waters sourced from the surface of the north pacific is greatest this is supported by the strong resemblance of the 14 c of those species and a recent record of planktic 14 c from the northeast pacific during deglaciation lower 14 c recorded by the late summer species g ruber suggests that locally upwelling waters carried 14c depleted carbon that was proximately sourced from equatorial subsurface waters entrained by the california undercurrent together with the benthic record these observations are consistent with transport of an anomalous 14c depletion signal carried primarily by antarctic intermediate water from an ultimate source in the southern ocean

annual reversal of the equatorial intermediate current in the pacific observations and model diagnostics abstract a large reversal of zonal transport below the thermocline was observed over a period of 6 months in the western pacific ocean between 2 s and the equator from 26 2 sv 1 sv 106 m3 s 1 eastward in october 1999 to 28 6 sv westward in april 2000 to document this reversal and assess its origin an unprecedented collection of adcp observations of zonal currents 2004 06 together with a realistic ogcm simulation of the tropical pacific was analyzed the results of this study indicate that this reversal is the signature of intense annual variability in the subsurface zonal circulation at the equator at the level of the equatorial intermediate current eic and the lower equatorial intermediate current l eic in this study the eic and the l eic are both shown to reverse seasonally to eastward currents in boreal spring and winter for the l eic over a large depth range extending from 300 m to at least 1200 m the peak to peak amplitude of the annual cycle of subthermocline zonal currents at

magnetic anisotropy in the trenton limestone results of a new technique anisotropy of anhysteretic susceptibility a new method for determining magnetic anisotropy using anhysteric remanence susceptibility is described the magnetic fabric of a collection of trenton limestone specimens has been determined using this method as well as by conventional anisotropy of magnetic susceptibility the results demonstrate the usefulness of the new method for finding the magnetic fabric of rock units such as the trenton in which the bulk magnetic susceptibilities are low a model is proposed to explain the observed foliated and lineated fabric as a consequence of overburden compaction and regional horizontal stresses the original fabric is inferred to have been isotropic the anisotropy resides in secondary magnetite of late paleozoic age it is argued that the observed magnetic fabric must therefore be alleghenian or younger in age our method has the potential to determine paleostress directions in carbonates elsewhere provided our assumptions are correct

anomalous magnetic properties in rocks containing the mineral siderite paleomagnetic implications sampling and magnetic measurement of a 1 m bed in a new road cut of the upper cretaceous austin chalk northeastern texas has yielded anomalous magnetic results initial measurement of the anisotropy of magnetic susceptibility ams indicated unusually high anisotropies and low bulk susceptibilities characteristic of a magnetocrystalline anisotropy which might be expected for siderite feco3 natural remanent moments nrm for these samples were low 1 10 4 a m2 and directions were typical for samples which had acquired a normal geomagnetic field overprint at the site periodic remeasurement of the nrm yielded an increase in moment for some samples and periodic reversals of rm in a direction parallel or antiparallel to the ambient field in the laboratory isothermal remanent moments of these samples saturates at low induction values 200 mt ams remeasurement over a period of weeks to months revealed a general decrease in the anisotropy magnitudes an increase in susceptibility and a change in principal axis orientations these data were compared with heating oxidation experiments on austin chalk siderite ore and clastic sediments with siderite cements all of these results are consistent with the x ray diffraction and mossbauer data which indicate the presence of siderite in the austin chalk samples the mossbauer spectra of the samples obtained at room temperature and 78 k indicate the presence of approximately 80 pyrite 10 siderite and 10 of a clay component possibly chlorite when only the iron bearing mineral components are considered after sampling exposure to the air and subsequent oxidation in the laboratory the siderite in austin chalk samples appears to have altered to fe2o3 maghemite or fe3o4 magnetite increasing the magnetic moment and changing the nrm and ams directions in the samples the continuing changes appear to reflect a conversion from the less stable fe2o3 to fe2o3 hematite or oxidation of fe3o4 to fe2o3 we infer from our study that oxidation of siderite bearing limestone e g during the formation of unconformities or due to low magnitude tectonic events may produce a very stable secondary magnetic moment in the rock such changes may be very important when interpreting paleomagnetic data from limestones

iron sources and dissolved particulate interactions in the seawater of the western equatorial pacific iron isotope perspectives this work presents iron isotope data in the western equatorial pacific marine aerosols and top core margin sediments display a slightly heavy fe isotopic composition 56 fe of 0 33 0 11 2sd and 0 14 0 07 respectively samples reflecting the influence of papua new guinea runoff sepik river and rabaul volcano water are characterized by crustal values in seawater fe is mainly supplied in the particulate form and is found with a 56 fe between a0 49 and 0 34 0 07 the particulate fe seems to be brought mainly by runoff and transported across continental shelves and slopes aerosols are suspected to enrich the surface vitiaz strait waters while hydrothermal activity likely enriched new ireland waters dissolved fe isotopic ratios are found between a0 03 and 0 53 0 07 they are almost systematically heavier than the corresponding particulate fe and the difference between the signature of both phases is similar for most samples with 56 fe dfe pfe 0 27 0 25 2sd this is interpreted as an equilibrium isotopic fractionation revealing exchange fluxes between both phases the dissolved phase being heavier than the particles suggests that the exchanges result in a net nonreductive release of dissolved fe this process seems to be locally significantly more intense than fe reductive dissolution documented along reducing margins it may therefore constitute a very significant iron source to the ocean thereby influencing the actual estimation of the iron residence time and sinks the underlying processes could also apply to other elements

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

coupled nitrate nitrogen and oxygen isotopes and organic matter remineralization in the southern and pacific oceans 1 the difference between nitrate 15n and 18o or 15 18 is sensitive to organic matter remineralization and tracks the modification of nitrate as it passes from the deep pacific ocean through the southern ocean surface and into the intermediate depth pacific circumpolar deep water cdw is upwelled with a nitrate 15 18 of 3 0 and appears unaltered by nitrate assimilation in the antarctic surface however within subantarctic mode water samw the primary conduit of deep sea nutrients to the lower latitudes nitrate 15n and 18o are both higher than cdw while nitrate 15 18 is as low as 1 5 the lower samw nitrate 15 18 results from the production of low 15n organic matter during partial assimilation of the surface nitrate pool followed by its sinking and remineralization back to nitrate lowering the 15n of thermocline nitrate more than its 18o as samw flows toward the lower latitudes nitrate 15 18 is expected and observed to increase because complete surface ocean nitrate consumption produces sinking nitrogen with a 15n similar to that of the nitrate supplied from below such that remineralization lowers the 18o of nitrate but not its 15n nitrate 15 18 is also used to estimate a surprisingly high low latitude sinking nitrogen 15n of 9 0 suggesting a major effect of 14no3 loss by tropical denitrification on middepth nitrate basin wide the remineralization of this high sinking nitrogen 15n increases nitrate 15 18 as deep as the southward moving pacific deep water which supplies cdw this relatively high 15 18 is then lowered to the observed cdw value by the remineralization of southern ocean sinking nitrogen with a low 15n

microstructural analysis and origin of lineations in the magnetic fabric of some alpine slates abstract the anisotropy of magnetic susceptibility was measured in 266 samples taken from 23 sites throughout the jurassic sequence of the dauphinois zone french alps four main areas were investigated showing evolution from slightly to highly deformed rocks in a thrusting regime the orientation and shape of the ellipsoid of the magnetic fabric exhibit a good qualitative correlation with structural field observations as shown by comparative lineation maps however the interpretation of the magnetic data in terms of orientation and intensity of deformation is complicated by the interaction of different planar and linear structural elements and by the variable mineralogical origin of the magnetic fabric magnetite and phyllosilicates both contribute in varying degrees to the magnetic fabric

southern ocean contributions to the eastern equatorial pacific heat content during the holocene abstract temperature reconstructions from a shallow core 375 m from the peru margin are used to test the influence of subantarctic mode water samw on the eastern equatorial pacific eep thermostad and thus the effect of southern high latitude climate on interior ocean heat content ohc temperature estimates based on mg ca measurements of planktonic and benthic foraminifera neogloboquadrina dutertrei and uvigerina spp respectively show higher temperatures in the early holocene a cooling of 2 by 8 kyr b p and after relatively stable temperatures to the present the temperature signal is similar in direction and timing to a rather robust holocene climate signal from the southern high latitudes suggesting it originated there and was advected to the core site in the eep based on the n dutertrei and uvigerina mg ca temperature and 13c records we conclude that samw acted as a conduit transporting the southern high latitude climate to the interior of the equatorial pacific we propose that the early holocene warmth is related to a southward migration of the subtropical front which enhanced the influence of warm subtropical water in the region of samw formation and was then transported to the eep thermostad the early holocene warmth recorded in the eep thermostad has a muted sea surface temperature expression indicating this mechanism is important for sequestering heat in the ocean interior

equatorial pacific thermostad response to el nino el ninos are characterized by a shift of warm surface water from the western to eastern equatorial pacific due to weakening of easterly trade winds this shift is associated with the pycnocline or thermocline the large vertical density gradient beneath the surface mixed layer shoaling in the west and deepening in the east inducing a redistribution of ocean heat with global impacts here the response of the pacific equatorial thermostad a layer of low vertical stratification below the pycnocline to el nino is investigated using a monthly argo float climatology and argo float deep velocity data a mean seasonal cycle trend and time lagged linear response to the nino3 4 index are fit by least squares to temperature and salinity at each gridpoint as well as to deep float velocities omitting the trend the results of these fits are used to characterize the response of physical properties in the thermostad including layer thickness and velocity to el nino by comparing the mean properties following neutral conditions nino3 4 0 c versus those following a moderate el nino nino3 4 1 c following an el nino a strengthening of the westward flowing equatorial intermediate current of about 2 7 106 m3 s 1 shifts about 97 1012 m3 of thermostad water from the east to the west allowing conservation of volume within the thermostad as the pycnocline above deepens in the east and shoals in the west this transport and volume change imply a 14 month time scale consistent with el nino this article is protected by copyright all rights reserved

calcite fabrics in a natural shear environment the helvetic nappes of western switzerland the aim of this contribution is to describe and interpret the crystallographic orientations and microstructures of calcite in the upper jurassic limestones of the helvetic nappes between the mont blanc and aar massifs over a distance along strike of about 180 km the c axis preferred orientation pattern which could be inferred is regionally very constant the c axis point maxima are everywhere subperpendicular to the regional strike of the chain there is an obliquity between the orientation of the macroscopically dominant cleavage and the microscopically visible long axes of individual grains the c axis maxima in most specimens are parallel to the axis of shortening of the microscopic grain shape fabric this fabric geometry indicates either continuous shear deformation or alternatively a two stage deformation history the obliquity of the grain shape fabric may be due to the fact that the flattening plane of the individual grains reflects only the last increment of a continuous shear process or it may represent a later finite deformation which has led to the formation of a regionally developed second cleavage there is a systematic relationship between the direction of these late shear movements and the main overthrust direction as given by the finite strain pattern this suggests that the microfabric of the rocks was acquired during a progressive rotation with time of the main overthrust direction the observed pattern of preferred orientation has been correlated by several authors with intracrystalline deformation mechanisms a combination of slip on r and twinning on e however the e twinning observed in the specimens investigated is younger than the development of the crystallographic fabric a new method for stress determination from e twinning is proposed

three dimensional dynamics of the subsurface countercurrents and equatorial thermostad part i formulation of the problem and generic properties a fully three dimensional primitive equation simulation is performed to reunite the local equatorial dynamics of the subsurface countercurrents sccs and thermostad with the large scale tropical ventilated ocean dynamics it captures i the main characteristics of the equatorial thermostad the sccs location and their eastward evolution and the potential vorticity budget with its equatorial homogenization to zero values and ii the largescale meridional shoaling of the thermocline equatorward it supports the idea that the two dimensional hadley cell mechanism proposed by marin et al is a candidate able to operate in a fully three dimensional ocean the main difference between the 2d hadley cell mechanism and the oceanic 3d case is that for the 3d case the large scale meridional velocity at zeroth order is geostrophic while the cell mechanism is a next order smallscale mechanism a detailed budget of the zonal momentum equation is provided for the ageostrophic dynamics at work in the sccs the mean meridional advection and the coriolis term dominate discounting the possibility that lateral eddies play a major role for the sccs creation a 3 layer idealized ventilation model calibrated to the three dimensional simulation parameters is able not only to capture the tropical density structure but also to isolate the main controlling factors leading to the triggering of the equatorial secondary cells with its associated jet and thermostad namely the shoaling of the equatorial thermocline because of low potential vorticity injection at distant subduction latitudes it is also shown that equatorial recirculation gyres play a quantitative role that may be of the same order of magnitude as ventilation from higher latitudes

challenges in defining tsunami wave heights the national oceanic and atmospheric administration noaa national centers for environmental information ncei and co located world data service for geophysics maintain the global tsunami archive consisting of the historical tsunami database imagery and raw and processed water level data the historical tsunami database incorporates where available maximum wave heights for each coastal tide gauge and deep ocean buoy that recorded a tsunami signal these data are important because they are used for tsunami hazard assessment model calibration validation and forecast and warning there have been ongoing discussions in the tsunami community about the correct way to measure and report these wave heights it is important to understand how these measurements might vary depending on how the data were processed and the definition of maximum wave height on september 16 2015 an 8 3 m w earthquake located 48 km west of illapel chile generated a tsunami that was observed all over the pacific region we processed the time series water level data for 57 coastal tide gauges that recorded this tsunami and compared the maximum wave heights determined from different definitions we also compared the maximum wave heights from the ncei processed data with the heights reported by the noaa tsunami warning centers we found that in the near field different methods of determining the maximum tsunami wave heights could result in large differences due to possible instrumental clipping we also found that the maximum peak is usually larger than the maximum amplitude peak to trough but the differences for the majority of the stations were 20 cm for this event the maximum tsunami wave heights determined by either definition maximum peak or amplitude would have validated the forecasts issued by the noaa tsunami warning centers since there is currently only one field in the ncei historical tsunami database to store the maximum tsunami wave height for each tide gauge and deep ocean buoy ncei will consider adding an additional field for the maximum peak measurement

constraining foraminiferal calcification depths in the western pacific warm pool highlights first apparent calcification depth assessment of living foraminifera in the se wpwp deep surface mixed layer causes deep apparent calcification depths deep dwelling g hexagonus traces nutrient conditions in equatorial water masses abstract insight into past changes of upper ocean stratification circulation and nutrient signatures rely on our knowledge of the apparent calcification depth acd and ecology of planktonic foraminifera which serve as archives for paleoceanographic relevant geochemical signals the acd of different species varies strongly between ocean basins but also regionally we constrained foraminiferal acds in the western pacific warm pool manihiki plateau by comparing stable oxygen and carbon isotopes 18ocalite 13ccalcite as well as mg ca ratios from living planktonic foraminifera to in situ physical and chemical water mass properties temperature salinity 18oseawater 13cdic our analyses point to globigerinoides ruber as the shallowest dweller followed by globigerinoides sacculifer neogloboquadrina dutertrei pulleniatina obliquiloculata and globorotaloides hexagonus inhabiting increasing greater depths these findings are consistent with other ocean basins however absolute acds differ from other studies the uppermost mixed layer species g ruber and g sacculifer denote mean calcification depths of 95 m and 120 m respectively these western pacific acds are much deeper than in most other studies and most likely relate to the thick surface mixed layer and the deep chlorophyll maximum in this region our results indicate that n dutertrei appears to be influenced by mixing waters from the pacific equatorial divergence while p obliquiloculata with an acd of 160 m is more suitable for thermocline reconstructions acds of g hexagonus reveal a deep calcification depth of 450 m in oxygen depleted but nutrient rich water masses consistent to other studies as the 13c of g hexagonus is in near equilibrium with ambient seawater we suggest this species is suitable for tracing nutrient conditions in equatorial water masses originating in extra topical regions

metamorphic control of the magnetic mineralogy of black shales in the swiss alps toward the use of magnetic isogrades abstract the magnetic susceptibility of the helvetic jurassic black shales sampled around the aar and gothard massifs in the swiss alps is due to iron bearing silicates magnetite or pyrrhotite it exhibits a clear correlation with the alpine metamorphism from zeolite to amphibolite facies it firstly decreases due to the breakdown of original magnetite then sharply increases when pyrite is transformed into magnetic pyrrhotite using numerous field measurements of the susceptibility it was possible to carry out a fast and precise mapping of the pyrrhotite in isograde which appears to correspond closely to the stilpnomelane out isograde the matrix susceptibility obtained by means of high field measurements with a cryogenic magnetometer is due to iron bearing silicates and shows only smooth variations with metamorphism both monoclinic and hexagonal pyrrhotites are observed in the high grade area

observed tracer fields structuration by middepth zonal jets in the tropical pacific abstractthe middepth ocean circulation in the tropical pacific is dominated by sets of alternating eastward and westward jets the origin and transport properties of these flow features remain in m

on the evolution of the thermocline and subthermocline eastward currents in the equatorial atlantic 1 eastward currents in the thermocline and subthermocline layers of the tropical atlantic ocean are described using observations obtained during two boreal summer cruises covering the whole equatorial basin the analysis focuses on the eastward evolution of zonal currents in the thermocline and sub thermocline the equatorial undercurrent is not found close to the african coast in boreal summer 2000 maybe because of interannual variability as observed in the pacific the south and north equatorial undercurrents are shown to shift poleward from west to east and the two cruises indicate that the north equatorial undercurrent does not enter the gulf of guinea the south and north intermediate countercurrents are variable with longitude and contrarily to the observations in the eastern equatorial pacific are not found in the east of the guinea basin

on the pathways of the equatorial subsurface currents in the eastern equatorial pacific and their contributions to the peru chile undercurrent 1 theconnections between theequatorial currentsystem andtheperu currentsystem in the eastern tropical pacific etp are examined with a primitive equations eddy resolving regional model the quasi equilibrium solutions reproduce three eastward equatorial subsurface currents of interest the equatorial undercurrent euc located between 1 n and 1 s the primary southern subsurface countercurrent psscc between 3 and 4 s and farther south the secondary southern subsurface countercurrent ssscc between 7 and 8 s using a lagrangian tracking procedure the fate of these currents in the etp and their contribution to the peru chile undercurrent pcuc are studied lagrangian diagnostics show that for the most part the euc water contributes to westward flows including the south equatorial current and deeper flows below it and strikingly only a very little fraction feeds the pcuc while a significant part of both ssccs contribute substantially mesoscale eddies are shown to exert an effect on these connections in addition about 30 of the pcuc is fed by the three subsurface equatorial flows euc psscc ssscc the remaining part of the pcuc comes from an alongshore recirculation associated with flows below it and from the southern part of the domain south of 9 s

real time assessment of the 16 september 2015 chile tsunami and implications for near field forecast the magnitude 8 3 earthquake in central chile on 16 september 2015 and the resulting tsunami severely affected the region with 15 deaths onemi in monitoreo por sismo de mayor intensidad in spanish available at http www onemi cl alerta se declara alerta roja por sismo de mayor intensidad y alarma de tsunami 2015 over one million evacuated and flooding in nearby coastal cities we present our real time assessment of the 2015 chile tsunami using the short term inundation forecasting for tsunamis system and post event analyses with local community models in chile we evaluate three real time tsunami sources which were inverted at the time that the first quarter half and full wave passed the first tsunameter dart 32402 located approximately 580 km north northwest of the epicenter respectively measurement comparisons from 26 deep ocean tsunameters and 38 coastal tide stations show that good model accuracies are achieved for all three sources particularly for the local sites that recorded the most destructive waves the study highlights the forecast speed time and accuracy dependence and their implications for the local forecast capability our analyses suggest that the tsunami s main origination area is about 100 200 km long and 100 km wide to the north of the earthquake epicenter along the trench and the total estimated tsunami wave energy is 7 9 1013 j with 13 uncertainty the study provides important guidelines for the earliest reliable estimate of tsunami energy and local forecasts they can be obtained with the first quarter wave of tsunameter recording these results are also confirmed by a forecast analysis of the 2011 japan tsunami furthermore we find that the first half wave tsunameter data are sufficient to accurately forecast the 2015 chile tsunami due to the specific orientation between the nearest tsunameter and the source the study also suggests expanding the operational use of the local community models in real time and demonstrates the applicability of the model results for all clear evaluations search and rescue operations and near real time mitigation planning in both near and far fields

the magnetic fabric of surficial deep sea sediments in the hebble area nova scotian continental rise flood r d kent d v shot a n and hall f r 1985 the magnetic fabric of surficial deep sea sediments in the hebble area nova scotian continental rise in a r m nowell and c d hollister editors deep ocean sediment transport preliminary results of the high energy benthic boundary layer experiment mar geol 66 149 167 the anisotropy of magnetic susceptibility ams of surficial sediments in the hebble area depth 4820 m nova scotian continental rise has been measured to study the fabric of these sediments and to relate the sediment fabric to depositional conditions previous investigators have established that strong but variable bottom currents are important agents in redistributing bottom sediments in the area we observe that the upper 1 5 cm of the sediments has a primary fabric dominantly foliar with horizontal bedding created by bottom current activity while sediments deeper than 2 5 cm have a predominantly secondary fabric due to bioturbation the magnitude of the ams signal in these sediments is generally low making it difficult to measure some of the fabric elements especially the direction of the lineated fabric in the upper 1 5 cm magnetic grains are predominantly oriented parallel to the regional bathymetric contours but there is also a significant grouping of alignments perpendicular to the contours primary fabrics are observed in a few of the samples from the bioturbated sediments with the magnetic grains oriented parallel to the contours some of the variability observed between box cores in the magnetic fabric may reflect the variability of depositional conditions within the region an analysis of the magnitude of the ams fabric suggests that the parameter fs often used to denote bottom current fabrics is strongly dependent on the total anisotropy and only weakly dependent on the lineated nature of the fabric both primary and secondary fabrics can have relatively large f s values thus f s does not appear sufficient for delineating bottom current activity in the deep sea