coastal southerlies and alongshore surges of the west coast of north america evidence of mesoscale topographically trapped response to synoptic forcing abstract one of the most important warm season weather phenomena of the west coast of north america is the temporal transition from northerly to southerly flow within a few hundred kilometers offshore from the coastal mountains such wind shifts are often accompanied by cooler temperatures higher pressure and a change from nearly cloud free to low overcast conditions the more vigorous coastal transitions termed alongshore surges are characterized by an abrupt change in wind direction a sudden increase in wind speed to 15 m s 1 or more a precipitous temperature drop exceeding 10 c and a sharp rise in sea level pressure this paper presents two detailed case studies of topographically trapped coastal southerlies the strong surge event of 15 17 may 1985 and the far weaker case of 3 7 may 1982 it is shown that coastal southerlies and alongshore surges are controlled by the alongshore pressure gradients created by the synoptic scale flow at low levels and within approximately one rossby radius of th

bomb produced radiocarbon in the shell of the chambered nautilus rate of growth and age at maturity abstract the temporal pattern of bomb produced radiocarbon in the oceans provides a chronometer to estimate the rate of growth of marine organisms radiocarbon measurements by tandem accelerator mass spectrometry of samples from the septa and shell wall of a mature specimen of nautilus macromphalus reveal progressively increasing values in more recently formed shell material this pattern is similar to that recorded in a banded coral from surface waters of the great barrier reef australia however the pre bomb values of 14 c are lower in the nautilus than in the coral this offset is probably due to the difference in the respective habitat depths of the two animals taking this difference into account we have used the temporal pattern of 14 c in the coral as a point of reference to help interpret the pattern of 14 c in the nautilus according to our calculations the age of the specimen of n macromphalus is 10 12 years and the timing of septal formation ranges from 80 to 240 days septum

multidecadal oceanographic changes in the western pacific detected through high resolution bomb derived radiocarbon measurements on corals high resolution measurements of radiocarbon 14c in corals can be used to reconstruct past variability in ocean conditions here we report seasonal 14c changes in coral from ishigaki island japan and compare with previously reported data from palau and guam our data clearly indicate a significant increase in 14c from 1947 to 1998 related to atmospheric nuclear bomb testing the three early 14c spikes related to the atmospheric nuclear bomb tests in the us proving grounds at bikini and enewerak atoll conducted in 1954 1956 and 1958 were detected from the ishigaki coral after 1976 variability in the mindanao dome region related to north equatorial current nec bifurcation latitude migration affected the 14c difference between palau and guam whereas the difference between ishigaki and guam was not correlated with the bifurcation latitude the 14c difference between ishigaki and guam may be due to mesoscale eddies in the kuroshio area on the decadal scale the northward shift of nec bifurcation latitude after 1976 the year as known as pacific decadal oscillation regime shift from negative to positive was concurrent with the abundant westward propagating mesoscale eddies in the subtropical countercurrent region and stronger kuroshio transport off the east taiwan which may be represented by a smaller 14c difference between ishigaki and guam after 1976

oceanic cooling recorded in shells spanning the medieval climate anomaly in the subtropical eastern north atlantic ocean abstract the medieval climate anomaly mca 900 1300 ad was the most recent period of pre industrial climatic warming in the northern hemisphere and thus estimations of mca signals can illuminate possible impacts of anthropogenic climate change current high resolution mca climate signals are restricted to mid and high latitude regions which confounds inferences of how the mca impacted some global hemispheric climate mechanisms e g north atlantic oscillation nao to address this knowledge gap we estimate seasonally resolved sea surface temperatures ssts from the oxygen isotope composition 18o of serially sampled phorcus atratus shells from archaeological sites spanning the mca in the canary islands twelve archaeological and six modern p atratus shells were analyzed and archaeological shells were dated using carbonate target radiocarbon dating ssts were estimated using the published aragonite water equilibrium fractionation equation modern shells showed a mean sst of 20 0 1 5 c with a seasonal amplitude of 5 3 0 9 c archaeological shells exhibited a mean sst of 18 2 0 7 c with a mean seasonal amplitude of 5 5 1 0 c thus shells that span the mca in the canary islands recorded ssts that were significantly cooler than the modern p

numerical simulation of topographically forced mesoscale variability in a well mixed marine layer abstract a simple nonlinear numerical model of a well mixed marine layer is used to study topographically forced mesoscale variability off coastal california the model is used to simulate a persistent wind maximum observed near point conception during northwesterly winds the model also demonstrates the development of a coastally trapped kelvin wave and a marine layer eddy when the large scale forcing is suddenly reduced the model is a one layer two dimensional gridpoint model with idealized coastal topography the model assumes that potential temperature and wind are constant with height in the layer and that the layer is capped by an inversion effects of diabatic heating water vapor entrainment and spatial variations of potential temperature are neglected in order to focus on topographic effects the model solves for the two horizontal components of the marine layer wind and the marine layer height a comparison of the model results with observations taken near point conception during the 1983 o

water column hydrothermal plumes on the juan de fuca ridge hydrographic surveys on the juan de fuca ridge jdfr carried out from 1980 to 1987 show a complex pattern of sup 3 he and mn rich water column plumes produced by venting from several submarine hot spring areas in the vicinity of axial volcano at latitude 46 degree n distinct plumes were detected in 1980 1982 and 1983 with sup 3 he signatures up to delta sup 3 he 64 at approximately 1 500 m depth at distances of approximately 10 km from the seamount summit however the same plumes had no detectable thermal signature a paradox which is attributed to the high sup 3 he heat ratios and low salinities of the fluids venting within the caldera of axial volcano profiles directly over the seamount show hydrothermal sup 3 he in the water column up to 300 m above the caldera floor with the sup 3 he signal increasing with depth to very high and uniform ratios of delta sup 3 he 108 150 below the approximately 1 500 m caldera sill depth another apparent locus of hydrothermal input is helium basin a depression on the northeast flank of axial volcano which had delta sup 3 he 51 when first sampled in 1980 however subsequent hydrocasts into helium basin in 1982 and 1983 yielded lowermore helium enrichments suggesting either a decrease in hydrothermal input or flushing of the basin via a mixing event to the south of axial volcano high delta sup 3 he values of approximately 40 observed over the ridge axis at 45 degree 18 prime n and 45 degree 39 prime n indicate venting on this previously unexplored section of the ridge the water column plumes over the us geological survey vent site at approximately 44 degree 40 prime n on the southern jdfr have very high mn sup 3 he ratios of 4 600 mol cm sup 3 an apparently unique characteristic which can be used to distinguish these plumes from those originating at other jdfr vent fields less

distribution of chemical tracers in the eastern equatorial pacific during and after the 1982 1983 el nino southern oscillation event during april 1983 and march april 1984 two cruises were conducted in the central equatorial pacific to determine the effects of the el nino southern oscillation enso event on the sea air exchange of co2 measurements of total carbon dioxide pco2 total alkalinity freon 11 salinity temperature oxygen nutrients and wind and current velocities were made along three meridional transects 158 w april 1983 150 w march 1984 170 w april 1984 the cessation of upwelling during the enso event caused pco2 concentrations in surface waters to decrease to near saturation levels along the equator the calculated net flux of co2 across the sea air interface was essentially negligible in the eastern equatorial pacific during this period however when normal trade winds and consequent upwelling returned in late 1983 and early 1984 the equatorial region returned to a pco2 condition of highly supersaturated surface waters in the region between 8 n and 8 s along the 150 and 170 w transects the calculated post enso sea air flux of co2 exceeded 6 0 mmol co2 m 2d 1 the mean annual co2 flux in the equatorial pacific was estimated to be 0 02 gt of carbon during the 1982 1983 enso event as compared with 0 6 gt during 1984

sun ocean nuclear bombs and fossil fuels radiocarbon variations and implications for high resolution dating radiocarbon or 14c is a radiometric dating method ideally suited for providing a chronological framework in archaeology and geosciences for timescales spanning the last 50 000 years 14c is easily detectable in most common natural organic materials and has a half life 5 730 40 years relevant to these timescales 14c produced from large scale detonations of nuclear bombs between the 1950s and the early 1960s can be used for dating modern organic materials formed after the 1950s often these studies demand high resolution chronology to resolve ages within a few decades to less than a few years despite developments in modern high precision 14c analytical methods the applicability of 14c in high resolution chronology is limited by short term variations in atmospheric 14c in the past this article reviews the roles of the principal natural drivers e g solar magnetic activity and ocean circulation and the anthropogenic perturbations e g fossil fuel co2 and 14c from nuclear and thermonuclear bombs

oceanic penetration of excess co2 in a cross section between alaska and hawaii results from the recent co sub 2 dynamics cruise in the northeast north pacific ocean june july 1981 are presented the shipboard co sub 2 data indicate that the excess co sub 2 has penetrated to the deepest depth 1000 300 m near the subtropical front but to a shallower depth outside of the frontal zone in general the depth of penetration is several hundred meters shallower than in the northwest pacific

growth rate and potential climate record from a rhodolith using 14c accelerator mass spectrometry rhodoliths free living calcareous red algae create large and diverse habitats worldwide although these plants are abundant and ecologically important little is known about their growth rate we determined the growth rate for an individual rhodolith lithothamnium crassiusculum from the southern gulf of california through 14 c analysis using accelerator mass spectrometry ams to be 0 6 mm yr 21 this growth rate suggests large l crassiusculum which have been found with radii in excess of 6 cm may live over 100 yr declines in the d 14 c record associated with the large el nino events of 1957 1982 and 1992 indicate 14 c analysis may lead to identification of important climate events in the more distant past the ability to determine changes in past ocean circulation related to changes in past climatic conditions through ams 14 c analysis of rhodoliths would increase the geographic range of available climate records from the tropical oceans to the entire global ocean and potentially allow for the determination of past climate conditions from rhodoliths in fossil beds rhodoliths red nongeniculate calcareous algae occupy large areas of the world s oceans forming the basis of di verse and ecologically important communities bosence 1983 foster et al 1997 however little is known about the rate at which these communities develop their rate of re covery after natural or anthropogenic disturbances or their effects on the global carbon budget because some rhodo liths are long lived they also have the potential to provide information on past oceanic conditions as they grow these plants deposit calcium carbonate which should contain chemical and isotopic records reflecting environmental con ditions previous isotopic studies on coral and mollusks found that the amount of 14 c deposited as a part of the total carbon in biogenic carbonate records the 14 c concentration in the ocean water surrounding the organism e g druffel and linick 1978 nozaki et al 1978 druffel and suess 1983 this type of 14 c record should also be found in the carbonate of rhodoliths and can potentially be used as a re cord of climate variation rhodoliths are found in many locations and environ ments around the world ranging from polar deep water to tropical shallows bosence 1983 in the subtropical gulf

circulation of tritium in the pacific ocean abstract the input of bomb tritium into the high latitude northern hemisphere waters has demonstrated the spread of a tracer in three dimensions in the north pacific ocean subsurface tritium maxima in middle and low latitudes clearly show the importance of lateral mixing along isopycnals in the upper waters the tritium pattern as mapped on isopycnal surfaces puts definite time bounds on the exchange between the subtropical anticyclonic gyre of the north pacific and both the subarctic cyclonic gyre and the system of zonal flows in the equatorial region the penetration of bomb tritium to depths below 1000 m in the western north pacific ocean shows that these waters have been ventilated at least partially in the past 17 years of the post bomb era from the tritium pattern the upper waters of the north pacific can be divided into three regions a mixed layer that exchanges rapidly with the atmosphere a laterally ventilated intermediate region between the mixed layer and at most the winter outcrop isopy

modelling of time dependent behavior of the basal sliding surface of the aknes rockslide area in western norway abstract numerical modelling based on the finite difference code flac3d and the burger creep viscoplastic material model has been used for analysing time dependent behavior of the unstable rock slope at aknes in western norway the rockslide has an estimated volume of 43 million m3 with a basal sliding surface located 105 115 m below the surface displacement measurements by gps and reflector points which since 2004 have revealed average annual displacements in the order of 26 mm year in the central part of the sliding area have been used to calibrate the model the modelling shows that a set of parameters believed to represent the conditions of the slope at present time 3 intact rock in the sliding plane and surface conditions representing good surface conditions in the gsi system results in displacements which stabilise within a 100 year period however as the shear strength parameters are reduced according to 1 intact rock in the sliding layer and surface conditions representing fair surface conditions in the gsi system increased displacement and indications of failure at the toe of the slope are evident within the same time span

atmospheric14c changes resulting from fossil fuel co2 release and cosmic ray flux variability a high precision tree ring record of the atmospheric14c levels between 1820 and 1954 is presented good agreement is obtained between measured and model calculated 19th and 20th century atmospheric 14c levels when both fossil fuel co2 release and predicted natural variations in14c production are taken into account the best fit is obtained by using a diffusion model with an oceanic eddy diffusion coefficient of 3 cm2 s a co2 atmosphere ocean gas exchange rate of 21 moles m 2 yr 1 and biospheric residence time of 60 years for trees in the state of washington the measured 1949 1951 atmospheric 14c level was20 0 1 2 below the 1855 1864 level model calculations indicate that in 1950 industrial co2 emissions are responsible for at least 85 of the 14c decline whereas natural variability accounts for the remaining 15

a review of modern coral δ18o and δ14c proxy records abstract this paper is a review of published modern coral 18 o and 14 c isotopic records that are at least 30 and 20 years long respectively the data are presented to show basin scale trends in both of these proxy records on decadal to centennial timescales the goal was to qualitatively integrate the general inter annual to centennial timescale variability revealed in these data as well as the statistical and modeling output results that have been produced using these coral records while many review papers typically include a representative subset of the data available this review aims to include as much of the available data as possible in general coral 18 o records show a long term warming and or freshening throughout the tropical oceans and agree with the noaa extended reconstruction sea surface temperature 2 ersst on decadal timescales in the western pacific it is most likely a freshening of the seawater 18 o that dominates the signal el nino southern oscillation enso variability dominates most 18 o records either by varying local seawater temperature or salinity depending on the regional oceanography climatology outside of the pacific enso affects seawater temperature and salinity via atmospheric or oceanic teleconnections post bomb coral 14 c records collectively show that the uptake of 14 c has been greatest in gyre water fed sites followed in descending order by western boundary current areas equatorial upwelling regions and eastern tropical pacific upwelling sites these surface water 14 c values indicate the proportion of surface water and or the residence time of water at the surface at a given location and can be used to model water mass mixing rates such models have only begun to be run and show that the amount of eastern pacific water entering the central south pacific increases during el ninos and that the indonesian throughflow is supplied year round by the north pacific comparing ocean circulation models with coral 14 c modelled circulation enables researchers to explore the mechanisms that drive seawater 14 c variability and fine tune their models in addition our comparison between the rate of coral 14 c increase between 1960 and 1970 and total anthropogenic co 2 uptake rates show general agreement demonstrating the value of coral records in understanding past carbon fluxes overall coral 18 o and 14 c proxy records represent natural archives of seawater conditions and are critical for studying the natural variability in local and regional patterns within and teleconnection patterns between the tropics extra tropics temperate and polar regions on intra annual to centennial timescales

radiocarbon in the weddell sea as observed in a deep sea coral and in krill radiocarbon measurements were performed on krill and coral samples collected from the weddell sea during iwsoe 80 these are the first radiocarbon measurements available from this area since 1973 these data reveal carbon 14 levels for weddell surface water and southern weddell shelf water these data indicate that the radiocarbon levels in surface waters in 1980 were the same or slightly lower than those present in 1973 in addition an unusually low 14c value for shelf water from coral at 500 m is evidence that warm deep water wdw may penetrate much further and more frequently onto the shelf region than had previously been expected

a shell derived time history of bomb 14c on georges bank and its labrador sea implications bomb produced radiocarbon has been used in the past as an important tracer of ocean circulation and as a valuable tool for calculating co2 air sea exchange however previous studies of the ocean s time varying bomb 14c record have been confined exclusively to analyzing banded corals and thus their application has been limited to the lower latitudes the first time history of bomb 14c from the high latitude north atlantic ocean is obtained from a 54 year old mollusc specimen bivalvia arctica islandica which was collected live from georges bank 41 n in 1990 the annual growth bands of its shell were analyzed for 14c using accelerator mass spectrometry producing a 14c time history from 1939 to 1990 the depleted condition of the georges bank bomb 14c signal relative to two coral derived north atlantic 14c time histories suggests a significant deepwater source for the waters on georges bank supported by previous work linking the origin of waters on georges bank to the labrador sea the 14c budget on georges bank is modeled as labrador sea water which largely becomes confined to the shelf and partially equilibrates with the atmosphere during a 1 year transit time from the labrador sea to georges bank this model is also used to estimate a time history of bomb 14c for the labrador sea prebomb 14c values calculated for the surface labrador sea suggest that a greater inventory of bomb 14c has accumulated here than has previously been reported however the estimated prebomb average 14c 70 6 for this period is nearly identical to the 70 previously calculated for the prebomb source of north atlantic deep water and is in agreement with transient tracers in the ocean subsurface tritium data from the central labrador sea deduced variations in the ventilation and or 14co2 uptake rates in the labrador sea correspond with observed changes in surface salinity of the labrador sea suggesting a reduction in deepwater formation during the late 1960s and 1970s

synoptic forcing of coastal trapped disturbances in the marine atmospheric boundary layer abstract motivated by recent observations along the west coast of the united states the authors investigate the generation and propagation of coastal trapped disturbances in the marine atmospheric boundary layer analytic solutions are obtained in a linear shallow water reduced gravity model of the flow subject to forcing by upper level pressure disturbances and dissipation in the form of wind stress at the sea surface it is found that unless the mean alongshore flow is to the south with speeds larger than the gravity wave phase speed a northward propagating coastal trapped response develops the superposition of cross shore propagating forcing and the northward propagating response in marine layer thickness can give rise to surface pressure ridges at the coast with both narrow and broad cross shore extent wind reversals associated with the disturbance lead the change in surface pressure at the coast the magnitude of the response increases for weaker inversion strength greater undisturbed marine l

structure of an atmospheric undular bore generated from colliding boundaries during cape abstract a case study of a sea breeze front originating from the east coast of florida colliding with a gust front moving toward the southeast is presented single and multi doppler radar analyses combined with serial balloon ascents suggest that the denser sea breeze flow undercut the cold pool behind the gust front and may have generated a westward propagating undular bore in addition another undular bore was generated by the collision and propagated eastward through the cape network the latter bore propagated upstream against the southeasterly flow behind the sea breeze front and was apparent as a narrow band 5 6 km wide of near zero radial velocities embedded within an overall flow that was positive as seen by the cp 4 doppler radar as the eastern bore propagated through the dual doppler lobe defined by the ncar cp 3 and cp 4 radars a detailed and unique wind synthesis revealed its three dimensional kinematic structure significant along bore variability was shown in the convergence and verti

radiocarbon variability in the western equatorial pacific inferred from a high resolution coral record from nauru island we have generated a high resolution coral delta sup 14 c record spanning the last 50 years to document the seasonal and interannual redistribution of surface waters in the western tropical pacific prebomb 1947 endash 1956 delta sup 14 c values average minus 63 per thousand and have a total range of 30 per thousand values begin to increase in 1957 reaching a maximum of 137 per thousand in mid 1983 large interannual variability of up to 80 per thousand closely follows the el ni tilde n o southern oscillation enso during each enso warm phase delta sup 14 c values begin to increase reflecting the reduction of low sup 14 c water upwelling in the east and the invasion of subtropical water into the western equatorial tropical pacific maximum delta sup 14 c values are in phase or lag the corresponding sea surface temperature maxima in the eastern tropical pacific whereas the rapid return to more negative delta sup 14 c is in phase with eastern pacific enso indices the highest amplitude excursions occur during the 1965 1966 and 1972 1973 events when the sup 14 c contrast is highest between the eastern pacific and subtropics the 1982 1983 el ni tilde n o although a larger enso event has a lower delta sup 14 c amplitude reflecting the penetration of bomb radiocarbon into the equatorial undercurrent and the reduced contrast in delta sup 14 c betweenmore thermocline and subtropical surface waters at that time this coral record demonstrates the potential for using similar radiocarbon time series for documenting variability in pacific shallow circulation over interannual and decadal timescales copyright 1998 american geophysical union less

3d effects of permeability and strength anisotropy on the stability of weakly cemented rock slopes subjected to rainfall infiltration abstract weakly cemented sedimentary rocks with pronounced stratification exhibit permeability and strength anisotropy the influence of permeability and strength anisotropy on the groundwater flow and slope stability depends on the orientation of the bedding planes the stability of slopes with different orientations of bedding planes under rainfall infiltration was evaluated in this study using three dimensional finite element modeling the groundwater table and pore water pressure in slopes before and after rainfall were simulated and the calculated pore pressure corresponding to the initial and highest groundwater tables was used for slope stability analyses the results showed that in comparison with gently dipping bedding planes a slope with steeply dipping bedding planes exhibits a greater rise of the groundwater table and a greater increase of pore pressure leading to a larger reduction in the factor of safety also a shorter time is required to reach the highest groundwater table and the maximum pore pressure at a certain position in consideration of the anisotropic behavior and the groundwater table rise during rainfall unfavorable conditions were identified for the slope stability the four unfavorable conditions where the bedding planes and the slope face approximately strike in the same direction are 1 the daylight condition of the bedding planes 2 the coincidence of the bedding planes and the slope face and 3 steep bedding planes dipping out or 4 into the slope slopes with the unfavorable orientations of bedding planes need additional attention in order to ensure a safe land development in the mountainous areas

evidence of kelvin waves in california s marine layer and related eddy generation abstract evidence suggests that an internal solitary kelvin wave exists in the marine layer along california the marine layer is lifted over the central coast by a weak cyclonic circulation this bump initially 850 m high moves to the north along the coast at 6 m s 1 the undisturbed layer depth is 100 200 m thick the crest height of the wave decreases to 500 m farther north winds under the raised marine layer are southerly the leading edge of the wave is easily followed by satellite as the thickened marine layer is marked by overcast stratus a greatly curved offshore leading edge indicates that nonlinear effects are important offshore scale in the overcast is about 300 km in the south and 50 km in the north surface pressure gradient alongshore is closely related to the marine layer depth the surface wind shifts when the leading and trailing edge of the wave passes northerly wave progression ceases at the sharp bend formed by cape mendocino at this time a vortex is formed in the marine laye

a 250 year decadally resolved radiocarbon time history in the gulf of maine reveals a hydrographic regime shift at the end of the little ice age

reproducibility of geochemical and climatic signals in the atlantic coral montastraea faveolata 1 monthly resolved 41 year long stable isotopic and elemental ratio time series were generated from two separate heads of montastraea faveolata from looe key florida to assess the fidelity of using geochemical variations in montastraea the dominant reef building coral of the atlantic to reconstruct sea surface environmental conditions at this site the stable isotope time series of the two corals replicate well mean values of 18o and 13c are indistinguishable between cores compare 0 70 versus 0 68 for 13c and 3 90 versus 3 94 for 18o mean values from the sr ca time series differ by 0 037 mmol mol which is outside of analytical error and indicates that nonenvironmental factors are influencing the coral sr ca records at looe key we have generated significant 18o sea surface temperature sst r 0 84 and sr ca sst r 0 86 calibration equations at looe key however these equations are different from previously published equations for montastraea variations in growth parameters or kinetic effects are not sufficient to explain either the observed differences in the mean offset between sr ca time series or the disagreement between previous calibrations and our calculated 18o sst and sr ca sst relationships calibration differences are most likely due to variations in seawater chemistry in the continentally influenced waters at looe key additional geochemical replication studies of montastraea are needed and should include multiple coral heads from open ocean localities complemented whenever possible by seawater chemistry determinations

response of the summer marine layer flow to an extreme california coastal bend abstract a summer wind speed maximum extending more than 200 km occurs over water around point conception california the most extreme bend along the u s west coast the following several causes were investigated for this wind speed maximum 1 synoptic conditions 2 marine layer hydraulic flow effects 3 diurnal variations 4 mountain leeside downslope flow 5 sea surface temperature structure and 6 island influence synoptic conditions set the general wind speed around point conception and these winds are classified as strong moderate or weak the strong wind condition extends about point conception reaching well offshore toward the southwest and the highest speeds are within 20 km to the south moderate wind cases do not extend as far offshore and they have a moderate maximum wind speed that occurs over a smaller area in the western mouth of the santa barbara channel the weak wind speed case consists of light and variable winds about point conception each category occurs about one third

decade time scale variability of ventilation in the north atlantic high precision measurements of bomb radiocarbon in banded corals the first high precision radiocarbon measurements for the upper ocean are presented for banded corals from two sites in the north atlantic ocean the striking dissimilarities between the post 1950 records at bermuda in the sargasso sea and the florida straits in the gulf stream illustrate the different mixing processes in the upper ocean at each site convective overturn associated with 18 degree water formation during late winter in the northern sargasso sea facilitates storage of considerable quantities of bomb radiocarbon at depth which accounts for the damping of the 14c signal at bermuda during the 1960s a multibox isopycnal mixing model is used to estimate the ventilation rate of the upper 700 m of the water column in the sargasso sea from 1950 to 1983 an inverse model is used that is the water mass renewal rate was calculated for the post bomb period in order to satisfy the bomb radiocarbon time history in the corals sea water radiocarbon measurements made during the geosecs 1972 1973 and transient tracers in the ocean 1980 1981 surveys are used to constrain the subsurface radiocarbon values calculated by the model results show that the rate of water mass renewal in the sargasso sea was high during 1963 1964 decreased during the late 1960s and remained low during most of the 1970s the 14c derived record of water mass renewal precedes by about 4 years that derived from isopycnal salinity in the sargasso sea jenkins 1982 illustrating that the coral 14c record is controlled to a large extent by changes in ocean circulation rather than by atmospheric exchange of co2

observations and analysis of the 10 11 june 1994 coastally trapped disturbance abstract a coastally trapped disturbance ctd characterized by southerly flow at the surface on 10 11 june 1994 was observed from the california bight to bodega bay during a field experiment along the california coast north south approximates the coast parallel direction data from a special observational network of wind profilers radio acoustic sounding systems special surface data balloon ascents and a research aircraft were used with satellite and synoptic data to explore both the ctd structure and the regional scale changes before the event the disruption of the climatological northerly flow along the central california coast which preconditioned the area for the development of a ctd began with the eastward movement of a surface high into washington and oregon and the amplification of a thermal low in northern california as with most ctds in the region this occurred over the 2 3 days preceding the ctd s initiation these large scale changes caused westward advection of warm continental

three dimensional analysis of a deep seated landslide in central taiwan the unstable slope which is located at lushan central taiwan slid when heavy rainfall occurred in recent decades posing a threat to a nearby village slope stability analysis in three dimensions is more realistic and can advance comprehension of the sliding mechanism the landslides caused by two heavy rainfall events are simulated in sequence using finite element modeling the three dimensional 3d modeling is established according to the data of extensive investigations including field reconnaissance borehole drilling laboratory experimentation and monitoring of groundwater tables and displacements in particular it requires skills for the generation of a sliding surface and the division of the 3d model the difference in lithology and a joint set initiated the instability of the slope forming the fractures on the slope the sliding surface with greatest depth over 100 m has not yet extended to the lower slope resulting in greater displacements on the upper and middle slopes than those on the lower slope the 3d numerical modeling not only reasonably simulates the displacements induced by the rainfall events but also enables 3d visualization and details of the sliding mechanism also it is capable of revealing the features that cannot be explained in a 2d analysis

deep seated gravitational slope deformation in lushan taiwan transformation from cleavage controlled to weakened rockmass controlled deformation abstract the northern slope in lushan nsl in central taiwan is recognized as a large deep seated gravitational slope deformation dsgsd in anisotropic slate and is often activated by typhoons and heavy rainfall however a recent southward movement of the dsgsd was apparently not caused by translational sliding along the eastward dipping cleavage in the nsl because the regional attitudes of the cleavages in the nsl moderately vary and no major fault has been observed in the field the deformed cleavages with their random dips indicate that the deformation of the rockmass was caused by older mass movements in addition ancient progressive erosion of the nsl toe by the talowan river which passes through the eastern side of the slope induced deep large scale mass movement toward the east based on detailed core recognition measurements including the cleavage dips log q values and inclinometer measurements we identified five geometrical styles and geotechnical zones of the deformed rockmasses for characterization of the evolution of the nsl dsgsd with regard to the spatial distributions of old mass movements and recent transformations curves obtained from recent inclinometer measurements suggested two deformation behaviors namely specific sliding and progressive deformation the underlying rockmass with overturned and flexural folding in cleavages at the slope toe have baffled a recent southward advancement of the dsgsd consequently the deep specific sliding surface close to the basal disintegrated rockmass at the center of the nsl was transformed into progressive deformation which mostly occurred in the overturned rockmass at the toe based on our observations we propose the following relationship between the p wave velocity vp km s and log qc where qc is a normalized q as an empirical model for slate in taiwan vp 0 6 log qc 4 0 this empirical model might be suitable for the low uniaxial compressive strength slate in the lushan area and could be used for the quantitative evaluation of the geotechnical zone of the dsgsd of the nsl

gaining insight into clipperton s lagoon hydrology using tritium historical descriptions of the clipperton lagoon appear to converge on the fact that it became isolated from the surrounding ocean around 1858 since then because of the high precipitation rate which largely exceeds evaporation in this region of the eastern tropical pacific a brackish lens has formed on top of the saline oceanic waters in 1980 literature data show that the thickness of this water body was reaching 14 m during the 2005 etienne s clipperton expedition we collected lagoon water on two vertical profiles salinity 18 o and tritium analyses were performed on these samples with the objective of gaining further insight into the lagoon hydrology and age of the deep waters the upper 15 m were characterized by low salinities 5 4 0 2 and 18 o and tritium values typical of local precipitation at depth waters had salinity and 18 o similar to oceanic surface waters but with low tritium concentrations hence pointing to quite isolated waters representing a remnant of marine waters when the lagoon was still communicating with the ocean at lagoon closure the excess of precipitation over evaporation raised the lagoon level thus creating a hydraulic pressure head which favored salt expulsion through the permeable walls of the atoll a simple geohydrological modeling of this salt expulsion process based on darcy s law describes reasonably well the time evolution of the brackish lens tritium is used to discuss the main physical processes potentially involved in the slow ventilation of the halocline and deep saline layer including vertical diffusion sinking of salty surface water intrusions and deep horizontal exchange through fissures in the limestone these different mechanisms give reasonable results which are all compatible with available salinity and isotopic data 18 o and tritium and therefore are all plausible candidates unfortunately the lack of a detailed description of the vertical tritium profile in the halocline between 15 m and 20 m precludes any further quantification of their respective role in the ventilation process

radiocarbon in annual coral rings from the eastern tropical pacific ocean sixty radiocarbon measurements were performed on aragonite from annually banded corals collected from three sites in the galapagos islands preanthropogenic 14c values of coral that grew around a d 1930 averaged 70 this is substantially lower than average values previously reported 51 for corals from florida and belize in the western north atlantic ocean a decrease of 6 was noticed in coral that grew from 1930 to 1954 this decrease could be interpreted as a suess effect in surface ocean water the 100 increase in 14c for coral that grew from 1954 to 1973 is the result of bomb produced 14c that was introduced to the surface ocean waters the 14c levels in corals that grew during el nino years were considerably higher than those for normal years these higher values are attributed to the absence of up welling at the equator during el nino events

eastern north atlantic deep sea corals tracing upper intermediate water δ14c during the holocene abstract paired 230th u and 14c dating were performed on deep sea corals lophelia pertusa and madrepora oculata from the northeastern north atlantic at 730 m bsl to investigate past changes of the thermohaline circulation these were estimated using the 14c value of the upper intermediate waters based on the 14c ages of the top and base of each coral where possible and the 230th u dating the reliability of these estimates was checked by dating two very young corals of the species l pertusa one of these corals collected alive in 1999 ad gave a 230th u age of 1995 4 ad after correction for non radiogenic 230th another coral the top of which dated to 1969 6 ad recorded the atmospheric 14c 12c increase due to the nuclear tests in the early 1960s the calculated 14c values from these two corals agree with those measured at geosecs station 23 in 1972 1973 ostlund et al earth planet sci lett 23 1974 69 86 and 1991 1992 nydal and gisfelos radiocarbon 38 1996 389 406 this together with the 100 aragonite content and the 234u and 230th 232th values of all the dated corals indicates that none of the corals behaved as open systems with respect to their u series nuclides and that they closely represent the water mass properties in which they lived the pre anthropogenic 14c value of the north atlantic intermediate waters was estimated at 69 4 the reservoir age varies from 400 years to 600 years and this variation is due to atmospheric 14c 12c changes a reservoir age of 610 80 years close to the pre anthropogenic value was determined from one coral dated at 10 430 120 cal yr bp when the global sea level was approximately at 35 m bard et al nature 382 1996 241 244 this suggests a modern like pattern of the oceanic circulation prevailed in the northeast atlantic ocean at this time although the deglaciation was not completely achieved

correlation between incompetent beds and slope deformation at badong town in the three gorges reservoir china badong town is a new immigration area in the three gorges reservoir china which is built on many giant deep seated landslides in this region the slope deformation is very severe and it is strongly correlated with the incompetent beds which are distributed widely in the rock mass in this paper two giant deep seated translational rock landslides used as study cases are huangtupo landslide and zhaoshuling landslide firstly the composition materials structures and deformation characteristics of the two landslides are analyzed then the position structure mineral composition and the formation mechanism of the incompetent beds are studied in detail finally based on the comparison of the position mineral and structure between incompetent beds and sliding zones of the landslides the correlations between incompetent beds and giant landslide are discussed the results indicate that 13 large incompetent beds exist in the middle triassic badong formation strata which can be divided into three types as weak interlayers crushed beds and groundwater corrosion zones the dominant minerals in the incompetent beds are illite chlorite quartz and calcite the contents of the clay minerals in different positions are quite distinct and the maximum difference of clay content exceeds 70 in addition it is found that the contents of minerals in incompetent beds are similar to the slide zones of the landslides the initial deformation of slopes normally developed along the incompetent beds which induced subsequent shear displacement easily under the effect of gravity the deep slip zones were generated mainly along the incompetent beds and the failure mode evolved from creep to integral slide gradually the results can provide an important reference for the mechanism analysis and prevention of landslides in badong town

sea surface mixed layer during the 10 11 june 1994 california coastally trapped event abstract a midlevel coastally trapped atmospheric event occurred along the california coast 10 11 june 1994 this feature reversed the surface wind field along the coast in a northerly phase progression along the central california coast the winds at the coastal stations reverse before the corresponding coastal buoy offshore then followed hours later by passage of the leading edge of an overcast stratus cloud the sea surface temperature was much colder in the narrow strip along the coast the cloud characteristics may be accounted for by a sea surface mixed layer ssml model beginning with the wind reversal and growing with the square root of time heat is lost from the ssml to the sea surface a cloud forms when the air temperature at the top of the ssml is equal to the dewpoint it is suggested that a bore develops on the top of the ssml increasing the thickness of the ssml and the progression speed of the cloud to 8 m s 1 there is evidence that an undular bore with a leading cloud develops in t

the marine layer off northern california an example of supercritical channel flow abstract during the spring and summer northerly winds driven by the north pacific high pressure system are prevalent over the northern california continental shelf only interrupted for periods of a few days when weak or southerly winds occur in the course of the coastal ocean dynamics experiment code fixed station and observations were made to describe the temporal and spatial structure of the lower atmosphere and their relation to the strong upwelling of coastal waters in a region extending up to 40 km offshore and 100 km along the coast these observations suggest that atmospheric conditions during the spring and summer usually fall into one of three categories the surface wind can be everywhere weak pattern 1 it can blow at large speeds in a uniform pattern pattern 2 or finally the structure of the northerly surface wind can be complex with large changes in the wind speed and corresponding changes in the surface pressure over short spatial scales pattern 3 the latter pattern which o

transport of north pacific 137cs labeled waters to the south eastern atlantic ocean abstract during the reoccupation of the woce transect a10 at 30 s by the beagle2003 cruise the shots project partners collected a large number of samples for the analysis of isotopic tracers 137cs was mostly deposited on the oceans surface during the late 1950s and early 1960s after the atmospheric detonation of large nuclear devices which mostly occurred in the northern hemisphere the development of advanced radioanalytical and counting techniques allowed to obtain for the first time in this region a zonal section of 137cs water concentrations where little information existed before thus constituting an important benchmark for further studies 137cs concentrations in the upper waters 0 1000 m of the south eastern atlantic ocean are similar to those observed in the south western indian ocean suggesting transport of 137cs labeled waters by the agulhas current to the benguela current region in contrast bomb radiocarbon data do not show this feature indicating the usefulness of 137cs as a radiotracer of water mass transport from the indian to the south atlantic ocean

carbon isotope records from extant caribbean and south pacific sponges evolution of δ13c in surface water dic stable isotope records of demosponges from the caribbean and coral sea are described for the purpose of studying the influence of fossil fuel co2 on the carbon isotopic composition of dissolved inorganic carbon dic in surface water the slow growing sponges precipitate calcium carbonate in isotopic equilibrium with ambient sea water and are used to detect changes in 13cdic from pre industrial times early 19th century to the present we observed similar shapes and ranges in 13c curves measured on caribbean specimens collected from water depths of 25 84 and 91 m as well as a specimen collected in shallow waters off new caledonia the records reveal a highly significant correlation with atmospheric 13cco2 13cdic values for caribbean and coral sea surface waters were calculated using the 13c sponge records while 13c of atmospheric co2 decreased by about 1 4 from the early 19th century to 1990 13cdic of caribbean and coral sea surface waters decreased by 0 9 0 2 and 0 7 0 3 respectively no isotopic equilibrium between surface water dic and atmospheric co2 was observed either during the pre industrial steady state or during the last 100 years the lower amount of depletion in the surface water 13cdic with respect to the atmospheric anthropogenic signal is explained by the dilution of the surface waters by biologically altered subsurface water dic the lower 13c decrease in the coral sea points to a stronger influence of the subsurface water source compared to the caribbean

model test on rainfall induced loess mudstone interfacial landslides in qingshuihe china loess mudstone interfacial landslide is one of the most prominent landslide hazards that occurred in soil rock contacting zones in the world a semi similar material physical model test was conducted to investigate the startup conditions and sliding mechanism of rainfall induced loess mudstone interfacial landslides based on the landslides which occurred in qingshuihe county inner mongolia autonomous region china when rainwater infiltrates downward along loess strata and gradually gathers near the interface the soil strata near the interface are softened causing frictional constraint reduction the mudstone strata serve as an aquifuge between underlying mudstone and overlying loess strata due to different permeability coefficients as rainfall continues the softened zone is expanded and gradually developed into fluidization ultimately leading to interfacial landslide this instability process is studied and reproduced experimentally through a self designed physical model test in this paper the model test results indicate that startup conditions of interfacial landslides are related to rainfall intensity and duration as well as thickness of overlying loess strata this study also indicates that the more the impact is from the rock at the back of the slope the more likely an interfacial landslide is to occur but this is not a decisive factor to induce the interfacial landslide the gradient of slope is also a potential factor to induce interfacial landslide when the gradient exceeds 24 the cutting layer landslide is likely to occur because impact of gravity is greater than that of interface friction resistance this study exploring startup conditions and the sliding mechanism of rainfall induced loess mudstone interfacial landslides provides a scientific guidance for the prevention monitoring early warning and control for geologic landslide hazards

intrabasin comparison of surface radiocarbon levels in the indian ocean between coral records and three dimensional global ocean models 1 oceanic uptake and transport of bomb produced radiocarbon is used as a diagnostic in global ocean models to test parameterizations of mixing and air sea gas exchange between the ocean and atmosphere a model s ability to simulate bomb produced 14c is also a good indicator of its ability to predict uptake of anthropogenic co2 we have conducted a model data comparison of surface radiocarbon time series from coral records from the coasts of kenya and sumatra and a suite of dynamical three dimensional ocean models that were included in the second phase of the ocean carbon cycle model intercomparison project the coral records comprise the first intrabasin record of surface water 14c variability in the equatorial indian ocean and provide an independent evaluation of model performance differing treatments of lateral subgrid scale mixing in different models appear to be less important than other unknown factors in explaining differences in results between the models those models that include a dynamic vertical mixing scheme appear to be more capable of matching observed coral radiocarbon time series however among models with the same parameterization of lateral subgrid scale mixing there is a large degree of variation suggesting that at both sites factors such as resolution topography physical forcing and horizontal advection are more important than mixing parameterization in explaining intermodel differences none of the models reproduce the time lag in the rate of bomb 14c response between the kenya and sumatra coral sites future efforts are needed to improve model simulation of radiocarbon in surface waters in the equatorial indian ocean

on the radiocarbon record in banded corals exchange parameters and net transport of 14co2 between atmosphere and surface ocean we have made radiocarbon measurements of banded hermatypic corals from florida belize and the galapagos islands interpretation is presented here of these previously reported results these measurements represent the 14c 12c ratios in dissolved inorganic carbon dioc in the surface ocean waters of the gulf stream and the peru current at the time of coral ring formation a depletion in radiocarbon concentration was observed in coral rings that grew from a d 1900 1952 it was caused by dilution of existing 14c levels with dead co2 from fossil fuel burning the suess effect or se the observed depletion of radiocarbon was greater in corals from the gulf stream 11 than in corals from the peru current 6 a similar trend was observed in the distribution of bomb produced 14c in corals that had grown during the years following a d 1952 the concentration of bomb produced radiocarbon was much higher in corals from temperate regions florida belize hawaiian islands than in corals from tropical regions galapagos islands and canton island a linear relationship appears to exist between the preanthropogenic 14c values and the se values measured in the individual corals because the 14c in corals is derived from two different carbon reservoirs 1 the atmosphere and 2 the subsurface ocean a linear relationship is also observed between the preanthropogenic 14c values and the concentration of bomb produced 14c in the individual corals during a d 1973 the apparent radiocarbon ages of the surface waters in temperate and tropical oceans during the preanthropogenic period range from about 280 to 520 years b p 40 to 69 at all investigated locations it is likely that waters at subsurface depths have the same apparent radiocarbon age of about 670 years b p from the change of oceanic 14c in the surface ocean during post bomb times the approximate annual rate of net input of 14co2 to the ocean waters is calculated to be about 8 of the prevailing 14c difference between atmosphere and ocean from this input and from preanthropogenic 14c values found at each location it can be seen that vertical mixing of water in the peru current is about 3 times greater than that in the gulf stream

a record of past ocean atmosphere radiocarbon differences from the northeast pacific a record of the 14c age differences between atmosphere and the mixed layer of the northeast pacific ocean was obtained from 58 radiocarbon measurements on shells and associated wood from coastal sediments in british columbia this series of mixed layer reservoir ages spans the holocene and extends into the period of the younger dryas cold event in the north atlantic and surrounding regions the data reflect the extent of upwelling in the northeast pacific and thus constrain models of carbon cycling and ocean circulation most of the reservoir ages are only slightly less than than the present preindustrial value of about 800 years and may be identical when probable sampling errors are taken into account either the north pacific reached a state close to its present mode of circulation at or before the end of the younger dryas or a different circulation fortuitously produced a similar reservoir age our results support the hypothesis that slow changes in atmospheric radiocarbon concentrations over the holocene arose from 14c production rate changes data corresponding to a radiocarbon age of around 6400 years b p give a reservoir age of 1200 years if this result is confirmed it indicates a much greater variability for the holocene ocean circulation than was previously believed possible

the transfer of bomb radiocarbon and anthropogenic lead to the deep north atlantic ocean observed from a deep sea coral abstract deep ocean c 14 pb concentrations and pb isotopes were reconstructed from a deep sea coral enallopsammia rostrata from 1410 m depth off of bermuda our high resolution time series is created from closely spaced radial cross sections with samples taken from the center of concentric coral growth bands that we show to be the oldest portion of the section prebomb radiocarbon ages from the coral demonstrate that the vertical growth rate of the coral is linear and the age of the coral is estimated to be 560 630 yr old based on the growth rate using this age model to reconstruct c 14 in deep seawater we first detect bomb radiocarbon at the coral growth site around 1980 and show that c 14 increased from 80 1 average 1930 1979 to a plateau at 39 3 1999 2001 pb ca of the coral ranges between 1 1 4 5 nmol mol during the 16th and 17th centuries and pb isotope ratios 206pb 207pb 1 21 208pb 207pb 2 495 in this period agree with pre anthropogenic values found in the pelagic sediments of the north atlantic ocean basin coral pb ca is slightly elevated to 6 2 0 9 nmol mol between the 1740s and the 1850s and then increases to 25 1 0 2 nmol mol in the 1990s the increase in coral pb ca is accompanied by a decrease in coral 206pb 207pb and 208pb 207pb indicating that the increase was caused by the infiltration of anthropogenic pb to the coral growth site comparing our data to the surface coral c 14 and pb records from bermuda reveals a time scale of tracer transport from the surface ocean to the coral growth site some characteristic features e g the bomb derived c 14 increase appear in the deep ocean approximately 25 yr later than the surface but the overall increase of c 14 and pb in the deep ocean is smaller and slower than the surface showing the importance of mixing during the transport of these tracers

the morning glory of the gulf of carpentaria an atmospheric undular bore abstract this paper presents the results of a field expedition mounted in late september early october 1979 to investigate the structure and origin of the morning glory of the gulf of carpentaria in northern australia the morning glory is a line wind squall accompanied by a pressure jump and often by a long roll cloud or series of such clouds it frequently occurs in the early morning especially in october in the gulf area a light aircraft fitted with a temperature and humidity probe was flown in two glories to determine their thermodynamic structure and wind fields wore obtained principally by tracking pilot balloons using the double theodolite method data also were obtained from a network of surface stations recording wind velocity and pressure installed at locations across cape york peninsula which is believed to be the area of genesis the morning glory is identified as an internal undular bore propagating on the nocturnal and or maritime inversion its origin appears to lie frequently

variability of the northeast atlantic sea surface δ14c and marine reservoir age and the north atlantic oscillation nao abstract we compiled new 14 c analyses of mollusc shells bivalves and gastropods of known age from the collection of the museum national d histoire naturelle de paris and previously published data to investigate changes in the sea surface 14 c and reservoir age in the northeast atlantic sector nea between 1823 and 1952 ad the mollusc shells are mainly located off the atlantic margin between 45 n and 60 n downstream of the north atlantic current nac we show that the temporal variability of the nea 14 c is independent of the mollusc species depth habitat diet and latitudinal distribution the quasi null difference between mollusc 14 c and the marine model indicate that the mollusc 14 c reflects the 14 c values of open marine conditions between 1823 and 1850 ad the pre anthropogenic mean of 14 c is 45 5 corresponding to a reservoir age of 380 60 years and a r value of 7 50 years in agreement with previous estimates the 14 c values show a significant long term decrease of 12 from 1823 to 1952 ad attributed to changes in 14 c production between 1823 and 1900 ad and the suess effect between 1900 and 1952 ad between 1885 and 1950 ad 14 c fluctuations of 10 up to 18 occurred in the northeast atlantic corresponding to reservoir age variations of 90 years up to 170 years these fluctuations are very similar to changes of 14 c in the southern norwegian sea spectral analyses of the nea 14 c exhibit quasi periodic cycles of about 7 4 years almost equivalent to the quasi periodic cycles of the winter index of the north atlantic oscillation nao with a period around 6 5 years we find that changes of nea 14 c cannot be attributed to changes in river runoff or the precipitation evaporation budget the 14 c lows or high reservoir ages correspond to the more intense phase of the winter nao with a time lag of 1 3 years such a time lag may reflect the eastward transit time of upstream changes originating in the labrador sea then entrained within the nac along with the subpolar gyre into the northeast atlantic sector during these events we estimate that about 70 of the total transport in the nac was due to water originating in the labrador sea

slope creep behavior observations and simulations rock slopes undergoing long term effects of weathering and gravity may gradually deform or creep downslope leading to geological structures such as bending bucking fracturing or even progressive failure this study uses geomechanics based numerical modeling to qualitatively explain the cause and evolution of slope creep behavior constitutive models used include the creep mohr coulomb and anisotropic models the last two models are used with the strength reduction in calculation first the results of field investigation around a landslide site occurring in slate are present the causes and modes of creep structures observed on slopes and underground are studied second the study investigates the influences of slope topography and anisotropy orientations on slope creep behavior finally progressive failure of slopes with different shapes is examined the simulated results show that the bending type of structures develops near slope surfaces and the buckling type of structures is associated with the deformation or slides of a slope the creep pattern varies with the orientation and position of an original planar structure the shear zone involves a joint or fracture along which displacement has taken place moreover creep behavior is more significant on slopes with greater height and inclination as well as on steeper portions whether on concave or convex slopes in addition with the same topographic conditions consequent slopes with coinciding cleavage and obsequent slopes with steep cleavage result in greater creep behavior without the effects of anisotropic cleavage concave and straight slopes develop failure surfaces from the crowns downwards whereas convex slopes develop failure surfaces from the toes upwards

observations of entry and exit of potential vorticity at the sea surface abstract although potential vorticity pv is central to many theories of the oceanic circulation the entry exit of pv at the sea surface has not been thoroughly discussed from an observational perspective after clarifying the notion of pv entry and exit and the mechanisms responsible for it a climatology of this quantity for the northern hemisphere is presented it is found that surface pv loss over western boundary current regions and their interior extension is a robust feature over the north pacific and atlantic basins at high latitudes mechanical and diabatic effects act in concert in the north atlantic to drive the net pv exit in the pacific however these effects oppose each other and the net entry exit of pv is more uncertain at low latitudes surface winds are found to be particularly important in setting the surface pv exit in the pacific equatorward of the intertropical convergence zone

september 2005 rain induced catastrophic rockslides on slopes affected by deep seated gravitational deformations kyushu southern japan river rejuvenation forms convex slope breaks that can destabilize nearby slopes leading to gravitational deformation and in some cases catastrophic sliding of the slopes during heavy rainstorms such landslides were induced by typhoon 0514 which passed to the west of kyushu island japan on 6 september 2005 five large catastrophic rockslides occurred aligning along convex slope breaks 150 to 300 m above the present river bed of the mimi river the slope breaks are inferred to have been formed by rejuvenation of the river geological and geomorphological investigation revealed that these slides occurred in sandstone and mudstone of the cretaceous shimanto group and were preceded by slope deformation which generated gravitational folds and faults that appeared as scarplets at the tops of the deformed areas the slopes seem to have been in critical condition just before catastrophic failure which was triggered by the rainstorm

an organic tracer for surface ocean radiocarbon the 14c of surface water dissolved inorganic carbon dic in the southern california bight was compared to 14c as recorded by the sterols in santa monica and santa barbara basin sediments all of the c26 c27 c28 and c29 sterols as well as dinosterol had 14c concentrations equal to surface water dic indicating that all of the major sterols were derived from phytoplanktonic production there is no detectable terrestrial component their tracer capability was confirmed by comparing the bomb 14c derived change in surface water 14cdic with the change in 14csterol the prebomb 14cdic was 82 and prebomb sterols averaged 75 19 the 14c value in 1996 was 71 eighteen measurements representing eight different sterols from the sediment water interface of both santa monica and santa barbara basins averaged 62 23 when three of these values were eliminated because of suspected contamination the remaining data averaged 71 12 the entire compound class could serve as an excellent proxy for the 14c concentration of ocean surface waters

a basinwide estimate of vertical mixing in the upper pycnocline spreading of bomb tritium in the north pacific ocean abstract the vertical diffusivity kv in the upper half kilometer of the north pacific subtropical pycnocline is estimated from observations of the spreading rate of anthropogenic tritium the calculation is based on approximately 300 ocean tritium profiles made since tritium was introduced to the atmosphere via bomb testing in the 1960s the data coverage does not permit detailed mapping of tritium penetration especially in the sparsely sampled western pacific for this reason and to minimize advective effects the spreading rate is averaged within the closed streamlines of the subtropical gyre spanning 5 n to 40 n the result kv 1 5 0 7 10 5 m2 s 1 is consistent with inferences from microstructure and purposefully released tracer measurements in the north atlantic confirming that the spatially averaged rate of mixing in the upper pycnocline is substantially lower than the canonical munk estimate for the lower pycnocline

empirical estimation of rock mass modulus the deformation modulus of a rock mass is an important input parameter in any analysis of rock mass behaviour that includes deformations field tests to determine this parameter directly are time consuming expensive and the reliability of the results of these tests is sometimes questionable consequently several authors have proposed empirical relationships for estimating the value of rock mass deformation modulus on the basis of classification schemes these relationships are reviewed and their limitations are discussed based on data from a large number of in situ measurements from china and taiwan a new relationship based upon a sigmoid function is proposed the properties of the intact rock as well as the effects of disturbance due to blast damage and or stress relaxation are also included in this new relationship